U.S. patent application number 10/405303 was filed with the patent office on 2003-10-09 for proportional pressure control valve.
Invention is credited to Harms, Louis C., Liberfarb, Zilek.
Application Number | 20030188788 10/405303 |
Document ID | / |
Family ID | 27364589 |
Filed Date | 2003-10-09 |
United States Patent
Application |
20030188788 |
Kind Code |
A1 |
Harms, Louis C. ; et
al. |
October 9, 2003 |
Proportional pressure control valve
Abstract
The technical field of the invention generally concerns
electronically controlled hydraulic valves adapted for use in
electro-hydraulically controlled automotive transmissions. The
proportional pressure control valve 20 includes a hollow cage 42
pierced by cage tank ports 52, cage clutch ports 54, and by cage
pump ports 56. The cage pump ports 56 receive fluid from a pump.
The cage clutch ports 54 supply fluid to a hydraulic actuator, such
as that for an automotive clutch. The cage clutch ports 54 supply
the fluid at a pressure that is proportional to an electrical
control signal applied to a solenoid coil 252 of the valve 20. The
cage tank ports 52 return fluid from the valve 20 to a tank from
which the fluid circulates back to the pump. Located in the cage 42
is a main spool 112 that is movable laterally relative to the cage
42 for controlling a flow of hydraulic fluid between the cage
clutch ports 54 and either the cage pump ports 56 or the cage tank
ports 52. An electro-magnetically operated pilot valve regulates a
control pressure of fluid applied to a control pressure surface 138
at one end of the main spool 112. A feedback pressure passage 126,
having a feedback restriction orifice 128, couples the pressure of
fluid in the cage clutch ports 54 to a feedback pressure surface
114 at the opposite end of the spool. The feedback restriction
orifice 128 restrains the rate at which fluid may flow between the
cage clutch ports 54 and the feedback pressure surface 114. One
embodiment of the valve 20 includes a pressure spike suppression
check valve 504 for relieving any abnormally high pressure that
occurs in the cage clutch ports 54.
Inventors: |
Harms, Louis C.; (Evanston,
IL) ; Liberfarb, Zilek; (Morton Grove, IL) |
Correspondence
Address: |
Roper & Quigg
Suite 1000
200 South Michigan Avenue
Chicago
IL
60604
US
|
Family ID: |
27364589 |
Appl. No.: |
10/405303 |
Filed: |
April 2, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10405303 |
Apr 2, 2003 |
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10086005 |
Feb 28, 2002 |
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6571828 |
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10086005 |
Feb 28, 2002 |
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09912825 |
Jul 25, 2001 |
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6405746 |
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09912825 |
Jul 25, 2001 |
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09667093 |
Sep 21, 2000 |
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6286535 |
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09667093 |
Sep 21, 2000 |
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08960971 |
Oct 30, 1997 |
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08960971 |
Oct 30, 1997 |
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08598285 |
Feb 8, 1996 |
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5836335 |
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08598285 |
Feb 8, 1996 |
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08426647 |
Apr 21, 1995 |
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08426647 |
Apr 21, 1995 |
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08034188 |
Mar 22, 1993 |
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08034188 |
Mar 22, 1993 |
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07747131 |
Aug 19, 1991 |
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Current U.S.
Class: |
137/625.64 ;
137/625.61 |
Current CPC
Class: |
F15B 2211/513 20130101;
F16H 61/0251 20130101; Y10T 137/86614 20150401; F15B 2211/526
20130101; F15B 13/0433 20130101; F16H 2061/0258 20130101; Y10T
137/0396 20150401; F15B 13/0402 20130101; Y10T 137/87241 20150401;
Y10T 137/8659 20150401; F15B 2211/575 20130101; G05D 16/2024
20190101 |
Class at
Publication: |
137/625.64 ;
137/625.61 |
International
Class: |
F15B 013/043 |
Claims
What is claimed is:
1. A proportional pressure control valve comprising: a hollow cage
that includes a wall pierced by a pump port that is adapted for
receiving fluid from a pump at a pressure provided by the pump, the
wall also being pierced by a clutch port that is adapted for
supplying pressurized fluid to a hydraulic actuator, and the wall
also being pierced by a tank port that is adapted for supplying
fluid to a tank; a main spool adapted to be positioned within said
hollow cage in which location said main spool is moveable relative
to said cage for controlling a flow of fluid passing between the
clutch port in said cage and either the pump port or the tank port
in said cage, said main spool including a control pressure surface
to which pressure may be applied for urging said main spool to move
within said cage to a position in which said main spool allows a
flow of fluid to pass between the pump port and the clutch port,
said main spool also including a feedback pressure surface to which
pressure may be applied for urging said main spool to move within
said cage to a position in which said main spool allows a flow of
fluid to pass between the clutch port and the tank port; a control
pressure chamber located within said cage for receiving fluid under
pressure and applying the pressure of the fluid to the control
pressure surface of said main spool; an electromagnetically
operated pilot valve means for supplying a regulated pressure of
fluid to said control pressure chamber responsive to an electrical
control signal; a feedback pressure chamber located within said
cage for receiving fluid at a pressure and coupling the pressure of
the fluid to the feedback pressure surface of said main spool; and
a clutch port pressure feedback passage for coupling the pressure
of fluid within the clutch port in said cage to said feedback
pressure chamber, said clutch port pressure feedback passage
including a feedback restriction orifice for restraining the rate
at which fluid may flow between the clutch port in said cage and
said feedback pressure chamber.
2. The proportional pressure control valve of claim 1 further
comprising pressure spike suppression means for relieving any
abnormally high pressure that occurs in the clutch port.
3. The proportional pressure control valve of claim 2 wherein said
pressure spike suppression means includes a check valve for
allowing fluid to flow from the clutch port to the tank port if an
abnormally high pressure occurs in the clutch port.
4. The proportional pressure control valve of claim 3 wherein the
check valve of the pressure spike suppression means is mounted
within said main spool.
5. The proportional pressure control valve of claim 2 wherein the
pressure spike suppression means further includes a spike
suppression orifice between said control pressure chamber and said
pressure spike suppression means for restraining the rate at which
fluid may flow between said control pressure chamber and said
pressure spike suppression means.
6. The proportional pressure control valve of claim 1 further
comprising a pilot valve supply passage for supplying a control
pressure flow of fluid from the pump port to said control pressure
chamber; said control pressure chamber having a control pressure
chamber outlet through which fluid flows from said control pressure
chamber; said electromagnetically operated pilot valve means
restraining the rate at which fluid flows from said pilot valve
supply passage into said control pressure chamber, and thereby
regulating the pressure of the fluid within said control pressure
chamber.
7. The proportional pressure control valve of claim 6 further
comprising a control pressure flow return passage for directing the
fluid that flows out of said control pressure chamber through the
control pressure chamber outlet to the tank port of the valve.
8. The proportional pressure control valve of claim 1 further
comprising a pilot valve supply passage for supplying a control
pressure flow of fluid from the pump port to said control pressure
chamber, said pilot valve supply passage including a control flow
restriction orifice for restraining the flow rate of the control
pressure flow of fluid; said control pressure chamber having a
control pressure chamber outlet through which fluid flows from said
control pressure chamber; said electromagnetically operated pilot
valve means restraining the rate at which fluid flows from said
control pressure chamber through the control pressure chamber
outlet, and thereby regulating the pressure of the fluid within
said control pressure chamber.
9. The proportional pressure control valve of claim 8 further
comprising a control pressure flow return passage for conducting
the fluid that flows out of said control pressure chamber through
the control pressure chamber outlet to the tank port of the
valve.
10. The proportional pressure control valve of claim 1 further
comprising a pilot valve supply passage for supplying a control
pressure flow of fluid from the pump port to said control pressure
chamber; said control pressure chamber having a control pressure
chamber outlet through which fluid flows from said control pressure
chamber; said electromagnetically operated pilot valve means both
restraining the rate at which fluid flows from said pilot valve
supply passage into said control pressure chamber and restraining
the rate at which fluid flows from said control pressure chamber
through the control pressure chamber outlet, and thereby regulating
the pressure of the fluid within said control pressure chamber.
11. The proportional pressure control valve of claim 10 further
comprising a control pressure flow return passage for directing the
fluid that flows out of said control pressure chamber through the
control pressure chamber outlet to the tank port of the valve.
12. The proportional pressure control valve of claim 2 further
comprising a pilot valve supply passage for supplying a control
pressure flow of fluid from the pump port to said control pressure
chamber; said control pressure chamber having a control pressure
chamber outlet through which fluid flows from said control pressure
chamber; said electromagnetically operated pilot valve means
restraining the rate at which fluid flows from said pilot valve
supply passage into said control pressure chamber, and thereby
regulating the pressure of the fluid within said control pressure
chamber.
13. The proportional pressure control valve of claim 12 further
comprising a control pressure flow return passage for directing the
fluid that flows out of said control pressure chamber through the
control pressure chamber outlet to the tank port of the valve.
14. The proportional pressure control valve of claim 2 further
comprising a pilot valve supply passage for supplying a control
pressure flow of fluid from the pump port to said control pressure
chamber, said pilot valve supply passage including a control flow
restriction orifice for restraining the flow rate of the control
pressure flow of fluid; said control pressure chamber having a
control pressure chamber outlet through which fluid flows from said
control pressure chamber; said electromagnetically operated pilot
valve means restraining the rate at which fluid flows from said
control pressure chamber through the control pressure chamber
outlet, and thereby regulating the pressure of the fluid within
said control pressure chamber.
15. The proportional pressure control valve of claim 14 further
comprising a control pressure flow return passage for directing the
fluid that flows out of said control pressure chamber through the
control pressure chamber outlet to the tank port of the valve.
16. The proportional pressure control valve of claim 2 further
comprising a pilot valve supply passage for supplying a control
pressure flow of fluid from the pump port to said control pressure
chamber; said control pressure chamber having a control pressure
chamber outlet through which fluid flows from said control pressure
chamber; said electromagnetically operated pilot valve means both
restraining the rate at which fluid flows from said pilot valve
supply passage into said control pressure chamber and restraining
the rate at which fluid flows from said control pressure chamber
through the control pressure chamber outlet, and thereby regulating
the pressure of the fluid within said control pressure chamber.
17. The proportional pressure control valve of claim 16 further
comprising a control pressure flow return passage for directing the
fluid that flows out of said control pressure chamber through the
control pressure chamber outlet to the tank port of the valve.
18. In a proportional pressure control valve that includes: a
hollow cage a wall pierced by a pump port that is adapted for
receiving hydraulic fluid from a pump at a pressure established by
the pump, the wall also being pierced by a clutch port that is
adapted for supplying pressurized hydraulic fluid to a hydraulic
actuator, and the wall also being pierced by a tank port that is
adapted for supplying hydraulic fluid to a tank; a main spool
adapted to fit within the cage in which location the main spool is
moveable relative to the cage for controlling a flow of hydraulic
fluid passing between the clutch port in the cage and either the
pump port or the tank port in the cage, the main spool including a
control pressure surface to which pressure may be applied for
urging the main spool to move within the cage to a position in
which the main spool allows a flow of hydraulic fluid to pass
between the pump port and the clutch port, the main spool also
including a feedback pressure surface to which pressure may be
applied for urging the main spool to move within the cage to a
position in which the main spool allows a flow of hydraulic fluid
to pass between the clutch port and the tank port; a control
pressure chamber located within the cage for receiving fluid under
pressure and applying the pressure of the fluid to the control
pressure surface of the main spool; an electromagnetically operated
pilot valve for supplying a regulated pressure of fluid to the
control pressure chamber responsive to an electrical control
signal; a feedback pressure chamber located within the cage for
receiving fluid at a pressure and coupling the pressure of the
fluid to the feedback pressure surface of the main spool; and a
clutch port pressure feedback passage for coupling the pressure of
hydraulic fluid within the clutch port in the cage to the feedback
pressure chamber; the improvement comprising: a feedback
restriction orifice located in the clutch port pressure feedback
passage for restraining the rate at which fluid may flow between
the clutch port in the cage and the feedback pressure chamber.
19. The proportional pressure control valve of claim 18 further
comprising pressure spike suppression means for relieving any
abnormally high pressure that occurs in the clutch port if a flow
of hydraulic fluid through the clutch port is interrupted.
20. The proportional pressure control valve of claim 19 wherein
said pressure spike suppression means includes a check valve for
allowing hydraulic fluid to flow from the clutch port to the tank
port if an abnormally high pressure occurs in the clutch port.
21. The proportional pressure control valve of claim 20 wherein the
check valve of the pressure spike suppression means is mounted
within said main spool.
22. The proportional pressure control valve of claim 19 wherein the
pressure spike suppression means further includes a spike
suppression orifice between said control pressure chamber and said
pressure spike suppression means for restraining the rate at which
fluid may flow between said control pressure chamber and said
pressure spike suppression means.
23. The proportional pressure control valve of claim 19 further
comprising a pilot valve supply passage for supplying a control
pressure flow of hydraulic fluid from the pump port to said control
pressure chamber; said control pressure chamber having a control
pressure chamber outlet through which fluid flows from said control
pressure chamber; said electromagnetically operated pilot valve
means restraining the rate at which fluid flows from said pilot
valve supply passage into said control pressure chamber, and
thereby regulates the pressure of the fluid within said control
pressure chamber.
24. The proportional pressure control valve of claim 23 further
comprising a control pressure flow return passage for directing the
fluid that flows out of said control pressure chamber through the
control pressure chamber outlet to the tank port of the valve.
25. The proportional pressure control valve of claim 19 further
comprising a pilot valve supply passage for supplying a control
pressure flow of hydraulic fluid from the pump port to said control
pressure chamber, said pilot valve supply passage including a
control flow restriction orifice for restraining the flow rate of
the control pressure flow of hydraulic fluid; said control pressure
chamber having a control pressure chamber outlet through which
fluid flows from said control pressure chamber; said
electromagnetically operated pilot valve means restraining the rate
at which fluid flows from said control pressure chamber through the
control pressure chamber outlet, and thereby regulates the pressure
of the fluid within said control pressure chamber.
26. The proportional pressure control valve of claim 25 further
comprising a control pressure flow return passage for conducting
the fluid that flows out of said control pressure chamber through
the control pressure chamber outlet to the tank port of the
valve.
27. The proportional pressure control valve of claim 19 further
comprising a pilot valve supply passage for supplying a control
pressure flow of hydraulic fluid from the pump port to said control
pressure chamber; said control pressure chamber having a control
pressure chamber outlet through which fluid flows from said control
pressure chamber; is said electromagnetically operated pilot valve
means both restraining the rate at which fluid flows from said
pilot valve supply passage into said control pressure chamber and
restraining the rate at which fluid flows from said control
pressure chamber through the control pressure chamber outlet, and
thereby regulates the pressure of the fluid within said control
pressure chamber.
28. The proportional pressure control valve of claim 27 further
comprising a control pressure flow return passage for conducting
the fluid that flows out of said control pressure chamber through
the control pressure chamber outlet to the tank port of the
valve.
29. The proportional pressure control valve of claim 18 further
comprising a pilot valve supply passage for supplying a control
pressure flow of hydraulic fluid from the pump port to said control
pressure chamber; said control pressure chamber having a control
pressure chamber outlet through which fluid flows from said control
pressure chamber; said electromagnetically operated pilot valve
means restraining the rate at which fluid flows from said pilot
valve supply passage into said control pressure chamber, and
thereby regulates the pressure of the fluid within said control
pressure chamber.
30. The proportional pressure control valve of claim 29 further
comprising a control pressure flow return passage for conducting
the fluid that flows out of said control pressure chamber through
the control pressure chamber outlet to the tank port of the
valve.
31. The proportional pressure control valve of claim 18 further
comprising a pilot valve supply passage for supplying a control
pressure flow of hydraulic fluid from the pump port to said control
pressure chamber, said pilot valve supply passage including a
control flow restriction orifice for restraining the flow rate of
the control pressure flow of hydraulic fluid; said control pressure
chamber having a control pressure chamber outlet through which
fluid flows from said control pressure chamber; said
electromagnetically operated pilot valve means restraining the rate
at which fluid flows from said control pressure chamber through the
control pressure chamber outlet, and thereby regulates the pressure
of the fluid within said control pressure chamber.
32. The proportional pressure control valve of claim 31 further
comprising a control pressure flow return passage for conducting
the fluid that flows out of said control pressure chamber through
the control pressure chamber outlet to the tank port of the
valve.
33. The proportional pressure control valve of claim 18 further
comprising a pilot valve supply passage for supplying a control
pressure flow of hydraulic fluid from the pump port to said control
pressure chamber; said control pressure chamber having a control
pressure chamber outlet through which fluid flows from said control
pressure chamber; said electromagnetically operated pilot valve
means both restraining the rate at which fluid flows from said
pilot valve supply passage into said control pressure chamber and
restraining the rate at which fluid flows from said control
pressure chamber through the control pressure chamber outlet, and
thereby regulates the pressure of the fluid within said control
pressure chamber.
34. The proportional pressure control valve of claim 33 further
comprising a control pressure flow return passage for conducting
the fluid that flows out of said control pressure chamber through
the control pressure chamber outlet to the tank port of the
valve.
35. A method for operating a proportional pressure control valve
comprising the steps of: supplying pressurized fluid to a pump port
formed through a wall of a hollow cage; supplying a regulated
control pressure of fluid to a control pressure chamber within the
cage which control pressure is regulated by an electrical control
signal applied to the proportional pressure control valve, the
control pressure chamber including a control pressure surface
located on a main spool, the main spool positioned within the
hollow cage and being moveable therein, said control pressure
applied to the control pressure surface urging the main spool to
move relative to the cage to a position in which the main spool
allows a flow of fluid to pass between the pump port in the wall of
the cage to a clutch port also formed through the wall of the cage
while simultaneously obstructing any flow of fluid between the
clutch port and a tank port also formed through the wall of the
cage; supplying a feedback pressure of fluid from the clutch port
to a feedback pressure chamber within the cage, the feedback
pressure chamber including a feedback pressure surface on the main
spool, said feedback pressure applied to the feedback pressure
surface urging the main spool to move relative to the cage to a
position in which the main spool obstructs any flow of fluid
between the pump port and the clutch port while simultaneously
allowing a flow of fluid to pass between the clutch port and the
tank port; and restraining the rate at which fluid may flow between
the clutch port in the cage and the feedback pressure chamber.
36. The method for operating a proportional pressure control valve
of claim 35 further comprising the step of relieving any abnormally
high pressure that occurs in the clutch port.
37. The method for operating a proportional pressure control valve
of claim 36 wherein the abnormally high pressure is relieved by
venting fluid from the clutch port to the tank port.
38. The method for operating a proportional pressure control valve
of claim 35 wherein said regulated control pressure of fluid that
is supplied to the control pressure chamber is generated by
supplying a control pressure flow of fluid from the pump port to
the control pressure chamber at a flow rate that is regulated in
response to the electrical control signal applied to the
proportional pressure control valve, and by allowing the fluid to
flow out of the control pressure chamber at a restrained flow
rate.
39. The method for operating a proportional pressure control valve
of claim 35 wherein said regulated control pressure of fluid that
is supplied to the control pressure chamber is generated by
supplying a control pressure flow of fluid from the pump port to
the control pressure chamber at a restrained flow rate, and by
allowing the fluid to flow out of the control pressure chamber at a
rate that is regulated in response to the electrical control signal
applied to the proportional pressure control valve.
40. The method for operating a proportional pressure control valve
of claim 35 wherein said regulated control pressure of fluid that
is supplied to the control pressure chamber is generated by
supplying a control pressure flow of fluid from the pump port to
the control pressure chamber at a flow rate that is regulated in
response to the electrical control signal applied to the
proportional pressure control valve, and by allowing the fluid to
flow out of the control pressure chamber at a rate that is also
regulated in response to the electrical control signal.
41. The method for operating a proportional pressure control valve
of claim 36 wherein said regulated control pressure of fluid that
is supplied to the control pressure chamber is generated by
supplying a control pressure flow of fluid from the pump port to
the control pressure chamber at a flow rate that is regulated in
response to the electrical control signal applied to the
proportional pressure control valve, and by allowing the fluid to
flow out of the control pressure chamber at a restrained flow
rate.
42. The method for operating a proportional pressure control valve
of claim 36 wherein said regulated control pressure of fluid that
is supplied to the control pressure chamber is generated by
supplying a control pressure flow of fluid from the pump port to
the control pressure chamber at a restrained flow rate, and by
allowing the fluid to flow out of the control pressure chamber at a
rate that is regulated in response to the electrical control signal
applied to the proportional pressure control valve.
43. The method for operating a proportional pressure control valve
of claim 36 wherein said regulated control pressure of fluid that
is supplied to the control pressure chamber is generated by
supplying a control pressure flow of fluid from the pump port to
the control pressure chamber at a flow rate that is regulated in
response to the electrical control signal applied to the
proportional pressure control valve, and by allowing the fluid to
flow out of the control pressure chamber at a rate that is also
regulated in response to the electrical control signal.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to the technical
field of hydraulic control devices and, more particularly, to
electrically controlled hydraulic valves.
BACKGROUND OF THE INVENTION
[0002] Automobiles, trucks, tractors, earth-moving vehicles, and
many other different types of vehicles (hereinafter collectively
referred to as automotive vehicles) frequently include an internal
combustion engine for powering their movement across the earth's
surface. An automotive vehicle also includes a drive train for
transmitting energy produced by the internal combustion engine into
movement of the wheels, drive tracks or similar means by which the
vehicle is driven across the earth's surface. To effectively
accommodate the power characteristics of the internal combustion
engine to the load of the vehicle that it must drive at various
speeds over varying terrain, an automotive vehicle's drive train
usually includes one or more transmissions. Each transmission in an
automotive vehicle includes a transmission power input shaft that
receives energy from the internal combustion engine's power output
shaft, and a transmission power output shaft for transmitting the
engine's energy onto the means for driving the vehicle across the
earth's surface. Each transmission in an automotive vehicle also
includes sets of gears, each one of which, when selected for
coupling the transmission's power input shaft to its power output
shaft, provides a different speed ratio between the rotation rates,
respectively, of the transmission's power input and power output
shafts.
[0003] To facilitate selecting a particular gear ratio and for
smoothly accelerating an automotive vehicle from a stationary
start, its drive train usually includes a clutch located between
the automotive vehicle's internal combustion engine and its
transmission(s). This clutch selectively couples the internal
combustion engine's power output shaft to the transmission's power
input shaft. In one position of the clutch, it completely decouples
the engine's power output shaft from the transmission's power input
shaft. In another position, the clutch of an automotive vehicle
provides a tight coupling between the internal combustion engine's
power output shaft and the transmission's power input shaft. In
this tightly coupled state, the internal combustion engine's power
output shaft and the transmission's power input shaft rotate at the
same speed. However, most clutches for automotive vehicles
operating in this tightly coupled state are capable of passing only
some maximum amount of torque from the internal combustion engine
to the transmission without slippage occurring in the clutch. If a
torque greater than this maximum amount is supplied to the clutch
in its tightly coupled state, slippage occurs within the clutch
that allows the power output shaft of the internal combustion
engine to rotate at a speed different from that of the
transmission's power input shaft.
[0004] Between these two extremes of clutch operation, either of
being decoupled or of being tightly coupled, the design of most
clutches used in automotive vehicles permit progressively varying
the tightness of coupling between the engine's power output shaft
and the transmission's power input shaft. In intermediate states
between these two extremes, the clutch will transmit an amount of
torque to the transmission without slippage that is less than the
maximum amount that it will transmit when tightly coupled.
Controllably coupling differing amounts of torque from the internal
combustion engine to the means for driving the vehicle across the
earth's surface permits smoothly accelerating an automotive vehicle
into motion. Controllably coupling different amounts of torque from
the internal combustion engine to the means for driving the vehicle
through the clutch is also useful, particularly for heavy
industrial vehicles such as trucks, tractors and the like when
shifting the transmission smoothly from a set of gears having one
ratio to another set having a different ratio.
[0005] Historically, a driver of an automotive vehicle usually
operated its clutch through a direct mechanical linkage between the
clutch and a clutch pedal located in the vehicle's passenger
compartment near the driver. In some instances, a closed hydraulic
system for operating the clutch by pressure on the clutch pedal
replaces the direct mechanical linkage. More recently, to provide
automatic electronic control of gear ratio selection, particularly
in automotive vehicle's that include a microprocessor, it has
become desireable to control clutch operation by means of an
electrical signal rather than by the driver pressing on a clutch
pedal. While some designs for clutches are known that permit an
electrical current to directly effect coupling and uncoupling of
the clutch, such clutches generally consume, and must therefore
also dissipate, a significant amount of electrical power. Thus,
even with microprocessor controlled operation of an automotive
vehicle's transmission, it still appears desirable to continue
controlling clutch operation indirectly by converting a control
electrical signal from the microprocessor into a more powerful
mechanical driving force for directly operating a conventional
clutch.
[0006] In pursuing this indirect electronic control of automotive
vehicle clutches, some automotive vehicle manufacturers have chosen
to employ electro-hydraulic transmissions having hydraulically
operated clutches. In such electro-hydraulic transmissions, a
hydraulic pump supplies pressurized hydraulic fluid for energizing
a hydraulic actuator, for example a piston or a bellows, that
directly operates the clutch. In one design for such a clutch,
springs hold the clutch in its disengaged position and a carefully
controlled pressure of the hydraulic fluid from the pump overcomes
the springs' force to effect engagement of the clutch. When the
hydraulic pressure is removed from this clutch, the springs once
again move the clutch into its disengaged state. By using the
spring pressure to effect clutch disengagement and hydraulic
pressure to effect clutch engagement, the clutch inherently
disconnects the engine from the transmission when the engine is not
running to power the hydraulic fluid pump. Furthermore, this method
of operating an electro-hydraulic clutch inherently avoids creating
a hazardous condition if the hydraulic fluid pump fails. With such
an electro-hydraulically operated clutch, smoothly accelerating the
vehicle into motion and smoothly shifting transmission gear ratios
require a hydraulic valve that controls the pressure of the
hydraulic fluid supplied to the clutch precisely in response to
changing values of the controlling electrical signal.
[0007] U.S. Pat. No. 4,996,195 entitled "Transmission Pressure
Regulator" issued on Oct. 30, 1990 to Ralph P. McCabe ("the McCabe
patent") and discloses a valve for controlling the pressure of a
fluid medium that is adapted for use in a control system such as
that of an automatic transmission of an automotive vehicle.
[0008] The valve disclosed in the McCabe patent includes a
cylindrically shaped, elongated, hollow aperture means or cage.
Formed through the wall of the cage toward one end is a first set
of apertures or ports. This first set of ports receives a supply
pressure of hydraulic fluid, apparently from a pump (not depicted
or described in the text or drawings of the McCabe patent). A
second set of apertures or ports also passes through the wall of
the aperture means or cage. The second set of ports is displaced
laterally from the first set of ports along the length of the cage
and located near the middle of the length of the cage. The
hydraulic fluid in the second set of ports has a control pressure
and, apparently, is supplied to the automatic transmission (not
depicted or described in the McCabe patent). A third set of
apertures or ports is formed in the wall of the cage. The third set
of ports is displaced laterally along the length of the cage from
both the first and second sets of ports and is located near the end
of the cage furthest from the first set. The hydraulic fluid in
this third set of ports has a sump or tank pressure, and appears to
return from the valve to a tank (not depicted or described in the
McCabe patent).
[0009] The inner surface of the cage is formed in the shape of a
right, circular cylinder and receives a snugly fitting main spool.
The spool is much shorter than the cage and can, therefore, move
laterally back and forth within the cage while remaining totally
enclosed therein. A broad trough encircles the outer surface of the
spool about its mid-section to establish a first chamber between
the outer surface of the spool and the inner surface of the cage.
The width of this trough along the length of the spool permits the
first chamber to couple immediately adjacent pairs of sets of ports
to each other while not simultaneously coupling all three sets of
ports to each other. As depicted in FIGS. 1 and 2 of the McCabe
patent, when the spool is fully displaced toward the right, the
first chamber couples the second set of apertures, i.e., the clutch
ports, to the third set of apertures, i.e., the tank ports.
Alternatively, when the spool is fully displaced toward the left,
the first chamber couples the first set of apertures, i.e., the
pump ports, to the second set of apertures, i.e., the clutch ports.
Thus, precisely controlled motion of the main spool laterally
within the cage couples the set of clutch ports either to the set
of pump ports or to the set of tank ports, and, as described in the
McCabe patent, can thereby control the hydraulic fluid pressure in
the clutch ports.
[0010] As depicted in FIGS. 1 and 2 of the McCabe patent, the outer
surface of the spool is also encircled by a narrow trough located
near its left end. This narrow trough establishes a second chamber
between the outer surface of the spool and the inner surface of the
cage. The second chamber appears to be always open to a flow of
hydraulic fluid from the pump through the pump ports through the
wall of the cage.
[0011] Located in the interior of the spool disclosed in the McCabe
patent is a hollow first internal passage. The formation of this
passage in the spool establishes a cup-shaped cavity that is open
toward the right end of the spool and closed at the spool's left
end. A passage, formed through the wall of the spool, connects this
cup-shaped cavity to the second chamber. From FIGS. 1 and 2 of the
McCabe patent, it appears that the first internal passage in the
spool always receives a flow of hydraulic fluid from the pump
through the pump ports in the cage and the second chamber
regardless of the lateral position of the spool along the length of
the cage.
[0012] The spool disclosed in the McCabe patent also includes a
second internal passage that pierces both the wall of the broad
trough and the left end surface of the spool. This second internal
passage couples the pressure of hydraulic fluid in the first
chamber to a second cavity located at the left end of the spool
between the spool and an end cap. The end cap closes the end of the
cage to the left of the spool and seals the second cavity so that
fluid may enter and leave it only through the second internal
passage. Because the second cavity opens only into the second
internal passage, the pressure within this second cavity always
equals the pressure of fluid within the first chamber. The end cap
also compresses a first coil spring between its inner surface and
the left hand surface of the spool. In the absence of any other
force on the spool, this first coil spring urges the spool toward
the right end of the cage as depicted in FIGS. 1 and 2 of the
McCabe patent.
[0013] An annularly shaped poppet valve plate is located
immediately to the right of the spool as depicted in FIGS. 1 and 2
of the McCabe patent, and partially obscures the right hand end of
the cylindrically shaped interior of the cage. The full pressure of
hydraulic fluid applied by the pump to the pump ports forces
hydraulic fluid through the pump ports in the wall of the cage, the
second chamber, and the first internal passage in the spool to the
side of the poppet plate immediately adjacent to the right hand end
of the spool. A second coil spring is compressed between the spool
and the poppet plate at the right end of the spool and, according
to the text of the McCabe patent, applies a force to the spool that
is smaller than that applied by the first coil spring at the left
end of the spool.
[0014] Located to the right of the poppet plate is a movable
armature that is surrounded by a solenoid coil. An electrical
current flowing through the coil applies a magnetic force to the
armature. In the valve depicted in FIG. 1 of the McCabe patent,
this electromagnetic force on the armature urges it to move
laterally toward the left which tends to close the opening in the
center of the annularly shaped poppet valve.
[0015] According to the text of the McCabe patent, closure of the
poppet valve increases the pressure of the hydraulic fluid at the
right end of the spool adjacent to the poppet plate. With the spool
urged to the right end of the cage by the first coil spring, an
increase in hydraulic fluid pressure on the right end of the spool
urges it to move laterally to the left away from the poppet plate.
Movement of the spool to the left causes the first chamber to move
laterally away from the tank ports toward the pump ports. Lateral
movement of the first chamber over the pump ports permits hydraulic
fluid to flow from the pump ports to the clutch ports thereby
increasing the pressure of the hydraulic fluid in the clutch ports.
Increased pressure of the hydraulic fluid in the clutch ports is
coupled via the second internal passage to the second cavity
thereby increasing the pressure of the hydraulic fluid in the
second cavity at the left end of the spool. An increasing pressure
in the second cavity urges the spool to halt its lateral movement
to the left away from the poppet plate and urges it to begin moving
back to the right toward the poppet plate. According to the text of
the McCabe patent, "the spool . . . will move axially in relation
to the poppet plate . . . until the sum of the forces on the spool
are in equilibrium." The text of the McCabe patent also states that
the second coil spring compressed between the poppet plate and the
spool acts to reduce lateral oscillation of the spool due to
changes in the pressure of hydraulic fluid at opposite ends of the
spool. Thus, according to the McCabe patent, the combination of the
poppet valve at the right end of the spool with the second internal
passage in the spool and the second cavity at the left end of the
spool along with the second coil spring, precisely controls the
movement of the main spool laterally within the cage to adjust the
pressure in the clutch ports.
[0016] Based upon the preceding description of the operation of the
valve depicted in FIG. 1 of the McCabe patent, that valve may be
characterized as a normally closed valve that couples the clutch
ports to the tank ports when no current flows through the coil.
Conversely, the valve depicted in FIG. 2 of the McCabe patent
includes a spring which biases the poppet valve closed, and a
magnetic field generated by an electric current flowing through the
coil urges the armature to move toward the right thereby opening
the poppet valve. According to the text of the McCabe patent, the
hydraulic pressure applied to the right end of the spool of the
valve depicted in FIG. 2 when no current flows through the coil
causes the spool to move to the left thereby causing the first
chamber to couple the clutch ports to the pump ports. Thus the
valve embodiment depicted in FIG. 2 of the McCabe patent may be
characterized as a normally open valve that couples the clutch
ports to the pump ports when no current flows through the coil.
[0017] The text of the McCabe patent appears to lack an explanation
of how closing and opening of the poppet valve depicted in the
drawings of the patent may increase or decrease the pressure of
hydraulic fluid present at the right end of the spool adjacent to
the annularly shaped poppet plate. Accordingly, it appears that the
valve disclosed in the McCabe patent may be commercially
impractical for its intended purpose of controlling the pressure of
hydraulic fluid in an automatic transmission of an automotive
vehicle.
[0018] U.S. Pat. No. 4,996,195 entitled "Pilot-Operated Valve With
Load Pressure Feedback" issued on May 3, 1988 to Kenneth J. Stoss
and Richard A Felland ("the Stoss et al. patent", discloses a
pilot-operated electro-hydraulic valve adapted for use in
controlling a transmission of an automotive vehicle. The valve
disclosed in the Stoss et al. patent includes an
electro-magnetically controlled pilot valve that controls the
operation of the valve's main spool. A pilot feedback passage
couples the pressure of hydraulic fluid in the load or clutch port
of the valve to a feedback chamber at one end of the pilot valve.
The Stoss et al. patent discloses that a pilot feedback passage
coupling the clutch port to the feedback chamber preferably
includes a filtered orifice. The Stoss et al. patent appears to
omit an explanation of the function provided by the filtered
orifice.
[0019] Neither the McCabe patent nor the Stoss et al. patent
disclose or solve a problem that occurs in the operation of
clutches in electro-hydraulic transmissions known as spiking.
Spiking is a phenomenon that results from abruptly halting fluid
flow through a hydraulic system. Fluid flowing through a hydraulic
system has two types of energy. Those two different types of energy
are potential energy and kinetic energy. Potential energy is energy
that is present due to the pressure of hydraulic fluid. Kinetic
energy is energy that is present due to the flow of fluid through
the hydraulic system.
[0020] When a clutch, or any other hydraulically operated device
that is moving in response to a flow of hydraulic fluid reaches the
mechanical limit of its travel, the hydraulic fluid flow through
the system stops abruptly. This abrupt stopping of hydraulic fluid
flow converts the fluid's kinetic energy into potential energy
thereby producing a sudden and abnormal increase, or spike, in the
pressure of the hydraulic fluid. Under appropriate circumstances,
this pressure spike may be heard audibly as a disturbing or
alarming noise, and the pressure increase may be so severe that it
causes failure of the hydraulic system.
SUMMARY OF THE INVENTION
[0021] The present invention provides a commercially practical
electrically energized, hydraulic proportional pressure control
valve for use in electro-hydraulic transmissions having
hydraulically operated clutches.
[0022] An object of the present invention is to provide a fully
operable electrically energized, hydraulic proportional pressure
control valve for use in electro-hydraulic transmissions.
[0023] Another object of the present invention is to provide an
electrically energized, hydraulic proportional pressure control
valve that controls the pressure in its clutch port precisely in
response to changing values of the controlling electrical
signal.
[0024] Yet another object of the present invention is to provide an
electrically energized, hydraulic proportional pressure control
valve that relieves the abnormally high hydraulic fluid pressure
spike that occurs when a flow of hydraulic fluid through the valve
stops abruptly.
[0025] Another object of the present invention is to provide an
electrically energized, hydraulic proportional pressure control
valve that reduces the abnormally high hydraulic fluid pressure
spike that occurs when a flow of hydraulic fluid through the valve
stops abruptly.
[0026] Another object of the present invention is to provide a
simpler electrically energized, hydraulic proportional pressure
control valve.
[0027] Another object of the present invention is to provide a more
easily manufactured electrically energized, hydraulic proportional
pressure control valve.
[0028] Another object of the present invention is to provide a more
economical electrically energized, hydraulic proportional pressure
control valve.
[0029] Another object of the present invention is to provide an
electrically energized, proportional pressure control valve that,
when used in conjunction with a clutch, provides improved and
smooth engagement and disengagement of a load through precise
control of fluid pressures within a hydraulic system.
[0030] A further object of the present invention is to provide an
electrically energized, proportional pressure control valve that
has an improved pilot valve section allowing precise control of
fluid pressures within a hydraulic system.
[0031] Another object of the invention is to provide an
electrically energized, proportional pressure control valve that
has an improved ball type pilot valve section which allows precise
control of fluid pressures within a hydraulic system and
substantially reduces the cost of such a valve.
[0032] A further object of the invention is to provide an
electronically energized, proportional pressure control valve that
includes improved feedback means to dampen oscillation within the
valve.
[0033] Briefly a proportional pressure control valve in accordance
with the present invention includes a hollow cage having a wall
that is pierced by a pump port, by a clutch port, and by a tank
port. The pump port receives hydraulic fluid from a pump at a
pressure provided by the pump. The clutch port is adapted for
supplying pressurized hydraulic fluid to a hydraulic actuator at a
pressure that is controlled by the proportional pressure control
valve. The tank port of the cage returns hydraulic fluid from the
proportional pressure control valve to a tank from which the fluid
circulates back to the pump.
[0034] The proportional pressure control valve also includes a main
spool adapted to fit snugly within the cage. Contained within the
cage, the main spool is movable along the length of the cage for
controlling a flow of hydraulic fluid passing between the clutch
port and either the pump port or the tank port.
[0035] An electromagnetically operated pilot valve regulates a
control pressure of hydraulic fluid that is present in a control
pressure chamber of the proportional pressure control valve. The
pressure of the fluid in the control pressure chamber is applied to
a control pressure surface of the main spool. Pressure applied to
the control pressure surface urges the main spool to move along the
length of the cage to a position in which it allows hydraulic fluid
to flow between the pump port and the clutch port. When disposed in
such a position, the main spool obstructs any flow of hydraulic
fluid between the clutch port and the tank port.
[0036] A feedback pressure passage couples the pressure of
hydraulic fluid in the clutch port of the proportional pressure
control valve to a feedback pressure chamber. The feedback pressure
chamber applies the pressure of hydraulic fluid in the clutch port
to a feedback surface of the main spool. Pressure applied to the
feedback pressure surface of the main spool urges the main spool to
move within the cage to a position in which it allows a flow of
hydraulic fluid to pass between the clutch port and the tank port.
When disposed in such a position, the main spool obstructs any flow
of hydraulic fluid between the pump port and the clutch port. The
feedback pressure passage includes a feedback restriction orifice
for restraining the rate at which fluid may flow between the clutch
port and the feedback pressure chamber.
[0037] An embodiment of the proportional pressure control valve of
the present invention includes a pressure spike suppression check
valve for relieving any abnormally high pressure that occurs in the
clutch port of the cage. Such an abnormally high pressure may occur
if a flow of hydraulic fluid through the clutch port stops
abruptly. In the preferred form of this embodiment, the check valve
allows hydraulic fluid to flow from the cage clutch port to the
cage tank port when an abnormally high pressure occurs in the
clutch port. A spike suppression orifice may also be included to
restrain the rate at which fluid may flow through the check
valve.
[0038] These and other features, objects and advantages will be
understood or apparent to those of ordinary skill in the art from
the following detailed description of the preferred embodiment as
illustrated in the various drawing figures.
BRIEF DESCRIPTION OF DRAWINGS
[0039] FIG. 1, made up of FIGS. 1A and 1B, is an exploded,
cross-sectional plan view of a normally closed proportional
pressure control valve constructed in accordance with the present
invention that is adapted for control by an analog electrical
control signal;
[0040] FIG. 2 is a cross-sectional plan view of the assembled
proportional pressure control valve depicted in FIG. 1;
[0041] FIG. 3 is a plan view of a plunger included in the
proportional pressure control valve depicted in FIGS. 1 and 2 taken
along the line 3-3 in FIG. 1;
[0042] FIGS. 4A through 4D are cross-sectional plan views of a
portion of the assembled proportional pressure control valve of
FIGS. 1 and 2 illustrating motion of the main spool relative to the
cage;
[0043] FIG. 5, made up of FIGS. 5A and 5B, is an exploded,
cross-sectional plan view of a normally open proportional pressure
control valve in accordance with the present invention that is
adapted for control by a digital electrical control signal;
[0044] FIG. 6 is a cross-sectional plan view of the assembled
proportional pressure control valve depicted in FIG. 5;
[0045] FIG. 7, made up of FIGS. 7A and 7B, is an exploded,
cross-sectional plan view of a normally closed proportional
pressure control valve in accordance with the present invention
that is adapted for control by a digital electrical control
signal;
[0046] FIG. 8 is a cross-sectional plan view of the assembled
proportional pressure control valve depicted in FIG. 7; and
[0047] FIG. 9 is a cross-sectional plan view of a spool in
accordance with the present invention including a pressure spike
suppression check valve for relieving any abnormally high pressure
that occurs in the clutch port of the cage;
DETAILED DESCRIPTION OF THE INVENTION
[0048] FIG. 2 depicts a cross-sectional plan view of a normally
closed proportional pressure control valve referred to by the
general reference character 20. FIG. 1, made up of FIGS. 1A and 1B,
is an exploded, cross-sectional plan view depicting the various
parts included in the proportional pressure control valve 20. The
same reference characters are used to identify the same part of the
proportional pressure control valve 20 both in FIG. 1 and in FIG.
2.
[0049] The proportional pressure control valve 20 includes a body
22. Formed in the center of the body 22, symmetrically about a
center line 24 that appears only in FIG. 1, is a
cylindrically-shaped cavity 26. Surrounding the cavity 26 is a body
wall 28 that is pierced by a body tank port 32 and a body clutch
port 34. During normal operation of the proportional pressure
control valve 20, the pressure of hydraulic fluid in the body tank
port 32 is very low because the body tank port 32 connects to an
unpressurized hydraulic fluid reservoir (not depicted in any of the
FIGs.).
[0050] The cavity 26 is formed to receive a cylindrically-shaped,
elongated, hollow cage 42 having a cylindrically-shaped cage wall
44. Formed through the cage wall 44, toward one end of the cage 42,
is a set of cage tank ports 52. Displaced laterally along the
length of the cage 42 from the cage tank ports 52 and located
approximately about the middle of the cage 42 is a set of cage
clutch ports 54 that pass through the cage wall 44. Displaced even
further laterally along the length of the cage 42 from the cage
tank ports 52 than the cage clutch ports 54 is a set of cage pump
ports 56 that also pass through the cage wall 44. The cage wall 44
between the cage tank ports 52 and the cage clutch ports 54
includes a pair of raised lands 62 that encircle the cage 42. The
lands 62 establish a U-shaped trough 64 that also encircles the
cage 42 and receives an encircling O-ring 66. Similarly, the cage
wall 44 between the cage clutch ports 54 and the cage pump ports 56
includes another pair of raised lands 72 that encircle the cage 42.
The lands 72 establish another U-shaped trough 74 that encircles
the cage 42 and receives another encircling O-ring 76.
[0051] When the cage 42 is inserted into the cavity 26 in the body
22, the surface of the cavity 26 receives the raised outer surface
of the lands 62 and 72, and the O-rings 66 and 76 seal between the
surface of the cavity 26 and the outer surface of the cage wall 44.
With the cage 42 disposed in this position within the body 22, the
surface of the cavity 26 and the outer surface of the cage wall 44
between immediately adjacent lands 62 and 72 established a hollow,
annularly-shaped clutch outlet chamber 82 that encircles the cage
42. Hydraulic fluid, that is applied to a hydraulic actuator (not
depicted in any of the FIGs.), flows between the cage clutch ports
54 and the body clutch port 34 through the clutch outlet chamber
82. On the opposite side of the lands 72 from the clutch outlet
chamber 82, the surface of the cavity 26 and the outer surface of
the cage wall 44 establish a hollow, annularly-shaped pump inlet
chamber 84 that also encircles the cage 42. The pump inlet chamber
84 receives pressurized hydraulic fluid from a pump (not depicted
in any of the FIGs.) and supplies it to the interior of the cage 42
through the cage pump ports 56.
[0052] A cup-shaped plug 92 fits snugly within the interior surface
of the cage wall 44 at the end of the cage 42 nearest the cage pump
ports 56. A U-shaped trough 94 encircles the plug 92 and receives
an O-ring 96. The O-ring 96 seals between the inner surface of the
cage wall 44 and the outer surface of the plug 92. The inner
surface of the cage wall 44 immediately adjacent to the plug 92
includes a U-shaped groove 102. The groove 102 receives a snap ring
104 that mechanically retains the plug 92 within the cage 42.
Secured in this location, the plug 92 closes the interior surface
of the cage 42 between the plug 92 and the cage pump ports 56
formed through the cage wall 44. Received within the cage 42
abutting the plug 92 is a coil spring 108.
[0053] The inner surface of the cage wall 44 is formed in the shape
of a right, circular cylinder to receive a snugly fitting main
spool 112. While the length of the main spool 112 is shorter than
that of the cage 42, the main spool 112 nevertheless abuts the end
of the coil spring 108 furthest from the plug 92 to compress the
coil spring 108 between the plug 92 and a feedback pressure surface
114 of the main spool 112. The pressure of the coil spring 108
against the feedback pressure surface 114 urges the main spool 112
to move laterally along the length of the cage 42 away from the
plug 92.
[0054] When the main spool 112 is properly disposed within the cage
42, the plug 92, the feedback pressure surface 114 of the main
spool 112, and the interior surface of the cage wall 44 between the
plug 92 and the feedback pressure surface 114 establish a feedback
pressure chamber 118. In addition to the coil spring 108, any
hydraulic fluid pressure within the feedback pressure chamber 118
also urges the main spool 112 to move laterally along the length of
the cage 42 away from the plug 92.
[0055] A broad, U-shaped trough 122 encircles the outer surface of
the main spool 112 about its mid-section. When the main spool 112
is properly disposed within the cage 42, the outer surface of the
main spool 112 formed by the trough 122 and the inner surface of
the cage wall 44 establish a hollow, annularly-shaped valving
chamber 124 that encircles the main spool 112. A sufficiently large
lateral movement of the main spool 112 toward the plug 92 allows
hydraulic fluid to flow through valving chamber 124 between the
cage pump ports 56 and the cage clutch ports 54 while the outer
surface of the main spool 112 simultaneously obscures the cage tank
ports 52 thereby obstructing hydraulic fluid flow through the cage
tank ports 52. Alternatively, a sufficiently large lateral movement
of the main spool 112 away from the plug 92 allows hydraulic fluid
to flow through the valving chamber 124 between the cage clutch
ports 54 and the cage tank ports 52 while the outer surface of the
main spool 112 simultaneously blocks any substantial flow of
hydraulic fluid between the cage pump ports 56 and the cage clutch
ports 54. Thus, controlled movement of the main spool 112 laterally
along the length of the cage 42 couples the cage clutch ports 54
either to the cage pump ports 56 or to the cage tank ports 52.
[0056] A feedback pressure passage 126 is formed into the end of
the main spool 112 adjacent to the coil spring 108 and the plug 92.
A feedback restriction orifice 128, formed at the end of the
feedback pressure passage 126 furthest from the coil spring 108 and
the plug 92, passes through the surface of the trough 122 thereby
coupling the feedback pressure passage 126 to valving chamber 124.
Because the cage clutch ports 54 always open into the valving
chamber 124, the feedback pressure passage 126 continuously couples
the pressure of hydraulic fluid in the cage clutch ports 54 through
the main spool 112 to establish a feedback pressure for the
hydraulic fluid within the feedback pressure chamber 118. The
feedback restriction orifice 128 in the feedback pressure passage
126 restrains the rate at which hydraulic fluid may flow between
the valving chamber 124 and the feedback pressure chamber 118. The
feedback restriction office 128 is sized dependant upon flow rate
of fluid within the system as well as the size of the main spool
112 to provide acceptable overshoot spike suppression and
operational stability of the system. To accomplish these intended
purposes, feedback restriction orifice 128 is approximately about
0.020" to about 0.040" in diameter.
[0057] The outer surface of the main spool 112 between the trough
122 and the feedback pressure surface 114 is also encircled by a
narrow trough 132. This narrow trough 132 establishes a hollow,
annularly-shaped pilot valve supply chamber 134 encircling the main
spool 112 between the outer surface of the main spool 112 and the
inner surface of the cage wall 44. Regardless of the lateral
position of the main spool 112 along the length of the cage 42, the
pilot valve supply chamber 134 is always open to a flow of
hydraulic fluid from the pump through the cage pump ports 56 in the
cage wall 44. One end of a pilot valve supply passage 136, formed
through the interior of the main spool 112, is open to the trough
132 while the other end of the pilot valve supply passage 136
passes through a control pressure surface 138 on the outer surface
of the main spool 112 furthest from the coil spring 108 and the
plug 92. In the proportional pressure control valve 20 depicted in
FIGS. 1 and 2, the pilot valve supply passage 136 immediately
adjacent to the control pressure surface 138 receives a screen 142
and is threaded to receive a threaded control flow restriction
orifice 144. The control flow restriction orifice 144 restrains the
flow rate of a control pressure flow of hydraulic fluid that passes
from the cage pump ports 56 through the trough 132, the pilot valve
supply passage 136, and through the control pressure surface 138 of
the main spool 112. The screen 142 catches particles in the
hydraulic fluid to hinder blockage of the control flow restriction
orifice 144 by such particles.
[0058] An annularly-shaped stop 152 fits snugly within the interior
surface of the cage wall 44 at the end of the cage 42 nearest the
cage tank ports 52. A U-shaped trough 154 encircles the stop 152
and receives an O-ring 156. The O-ring 156 seals between the inner
surface of the cage wall 44 and the outer surface of the stop 152.
When the main spool 112 is properly disposed within the cage 42,
the stop 152, the control flow restriction orifice 144, the control
pressure surface 138 of the main spool 112, and the interior
surface of the cage wall 44 between the stop 152 and the control
pressure surface 138 establish a control pressure chamber 158. The
pressure of hydraulic fluid within the control pressure chamber 158
urges the main spool 112 to move laterally along the length of the
cage 42 away from the stop 152 toward the plug 92.
[0059] Passing through the middle of the stop 152 is a hollow
control pressure chamber outlet passage 162. Formed on the edge of
the control pressure chamber outlet passage 162 furthest from the
control pressure surface 138 of the main spool 112 is a beveled
valve seat 164.
[0060] Formed on the outer surface of the cage wall 44 surrounding
the stop 152 are threads 172 adapted to mate with threads 174
formed on the interior surface of an annularly-shaped adaptor 176
of a tube assembly 178. Formed on the outer surface of the adaptor
176 are threads 182 adapted to mate with threads 184 formed at one
end of the cavity 26 formed in the body 22. A U-shaped trough 186
encircles the adaptor 176 immediately adjacent to the threads 182
and receives an encircling O-ring 188. The O-ring 188 seals between
the outer surface of the adaptor 176 and the surface of the cavity
26 in the body 22. With the adaptor 176 disposed in this position
within the body 22 and mated with the cage 42, the surface of the
cavity 26, the end surface of the adaptor 176, the outer surface of
the cage wall 44 and the land 72 nearest to the adaptor 176
establish a hollow, annularly-shaped tank outlet chamber 192
encircling the cage 42. Hydraulic fluid flowing to the tank flows
between the cage tank ports 52 and the body tank port 32 through
the tank outlet chamber 192.
[0061] A pair of control pressure flow return ports 194 pass
through the adaptor 176 at the end of the threads 174 and 182
immediately adjacent to the trough 186 and the O-ring 188. A pair
of elongated control pressure flow return slots 196 extend across
the threads 182 from the control pressure flow return ports 194
away from the trough 186 and the O-ring 188. The control pressure
flow return ports 194 and the control pressure flow return slots
196 provide a passage by which the control pressure flow of
hydraulic fluid, that flows out of the control pressure chamber 158
through the control pressure chamber outlet passage 162, returns to
the body tank port 32 and the cage tank ports 52, and thence to the
tank.
[0062] Projecting outward from the side of the annularly-shaped
adaptor 176 opposite to the threads 174 and 182 is a hollow tube
202 included in the tube assembly 178. The tube 202 is rigidly
attached to the adaptor 176 and sealed to it. Also rigidly attached
and sealed to the tube 202 at its end furthest from the adaptor 176
is an annularly-shaped threaded tube plug 204 also included in the
tube assembly 178.
[0063] Received within the adaptor 176 and positioned at the end of
the tube 202 nearest the adaptor 176 is an elongated,
annularly-shaped pole piece 212. A raised land 214 encircles the
outer surface of the pole piece 212. When the adaptor 176 is
threaded onto the cage 42, the adaptor 176 presses the land 214
against the stop 152. Thus, threading the adaptor 176 onto the cage
42 forces the stop 152 into the cage 42 and holds it there. An
annularly-shaped recess 216 is formed into the end of the pole
piece 212 immediately adjacent to the stop 152. A pair of elongated
slots 218 are formed along the entire length of the pole piece 212
and across the land 214 to open into the recess 216. The recess 216
and the ends of the slots 218 crossing the land 214 also form part
of the passage by which the control pressure flow of hydraulic
fluid, that flows out of the control pressure chamber 158 through
the control pressure chamber outlet passage 162, returns to the
body tank port 32 and cage tank ports 52, and thence to the tank.
The slots 218 allow hydraulic fluid to flow past the pole piece 212
and fill the length of the tube 202 extending outward from the
adaptor 176.
[0064] Formed through the middle of the pole piece 212 is an
elongated, cylindrically-shaped pin passage 222. An elongated pin
224 fits loosely within the pin passage 222 and slides freely back
and forth within the length of the pin passage 222. The end of the
pin passage 222 immediately adjacent to the recess 216 is formed
with an enlarged diameter to provide a valve ball retaining chamber
226. The valve ball retaining chamber 226 receives a loosely
fitting valve ball 228 that is free to move back and forth along
the length of the valve ball retaining chamber 226. Within the
proportional pressure control valve 20, the valve ball retaining
chamber 226 supports the valve ball 228 in a position in which the
pin 224 may urge the valve ball 228 into sealing engagement with
the valve seat 164 of the stop 152.
[0065] Loosely received within the tube 202 of the tube assembly
178 between the pole piece 212 and the threaded tube plug 204 is a
plunger 232. The plunger 232 is free to move back and forth within
the tube 202 between the pole piece 212 and the threaded tube plug
204. The end of the plunger 232 nearest the pole piece 212 contacts
the end of the pin 224 that extends out of the pole piece 212
furthest from the valve ball 228. A spring cavity 234 is formed
into the end of the plunger 232 nearest the threaded tube plug 204
to receive a light, minimum pressure coil spring 236. A partially
threaded, central passage 238, that passes longitudinally through
the middle of the threaded tube plug 204, receives the end of the
spring 236 that projects out of the end of the plunger 232. As
illustrated in the plan view of FIG. 3, the outer surface of the
plunger 232 parallel to the center line 24 is not formed in the
shape of a full right circular cylinder. Rather, portions of the
outer surface of the plunger 232 parallel to the center line 24 are
formed by planar surfaces 240.
[0066] A preload adjusting screw 242 threads into the central
passage 238 and contacts the end of the spring 236 within the
central passage 238. Threading the preload adjusting screw 242 into
the central passage 238 of the threaded tube plug 204 presses the
spring 236 into the spring cavity 234 of the plunger 232. This
force on the plunger 232 urges it into contact with the immediately
adjacent end of the pin 224 whose far end contacts the valve ball
228. This force applied to the valve ball 228 by the preload
adjusting screw 242 urges the valve ball 228 into a sealing contact
with the valve seat 164 of the stop 152.
[0067] A U-shaped trough 244 encircles the end of the preload
adjusting screw 242 nearest the spring 236 and receives an O-ring
246. The O-ring 246 seals between the threaded tube plug 204 and
the preload adjusting screw 242 to close the end of the tube
assembly 178 furthest from the body 22. Because the tube assembly
178 is formed as a sealed unit, because the O-ring 246 seals
between the preload adjusting screw 242 and the threaded tube plug
204, and because the O-ring 188 seals between the adaptor 176 and
the body 22, hydraulic fluid normally enters the proportional
pressure control valve 20 only through the pump inlet chamber 84
and normally leaves the proportional pressure control valve 20 only
through the body tank port 32 and the body clutch port 34.
[0068] The proportional pressure control valve 20 also includes an
annularly-shaped solenoid coil 252 that loosely encircles the tube
202 of the tube assembly 178 immediately adjacent to the adaptor
176. An annularly-shaped spacer 254 also loosely encircles the tube
202 of the tube assembly 178 on side of the solenoid coil 252
furthest from the adaptor 176. A flux ring 253 is located between
the coil shell and the adaptor 176 to enhance magnetic flux between
the coil and the adaptor. A nut 256 threads onto the threaded tube
plug 204 to contact the spacer 254 thereby urging it along the
length of the tube assembly 178 toward the adaptor 176. Thus, force
from the nut 256 holds the solenoid coil 252 in contact with the
adaptor 176. The solenoid coil 252 includes a pair of electrically
conductive leads 258. Applying an electrical control signal to the
leads 258 produces a magnetic field within the tube 202 of the tube
assembly 178. This magnetic field applies a force that pushes the
plunger 232 along the length of the tube 202 toward the valve ball
228. Thus, in addition to the coil spring 236, an electric current
flowing through the solenoid coil 252 also applies a force to the
valve ball 228 that urges it into a sealing contact with the valve
seat 164 of the stop 152.
[0069] With no electric current passing through the solenoid coil
252 of the proportional pressure control valve 20 depicted in FIGS.
1 and 2, the pressure of the hydraulic fluid supplied by the pump
to the pump inlet chamber 84 is transmitted substantially
undiminished to the control flow restriction orifice 144 retained
in the main spool 112. The control pressure flow of hydraulic fluid
passing through the control flow restriction orifice 144 fills the
control pressure chamber 158 and flows out of the control pressure
chamber 158 through the control pressure chamber outlet passage
162. This control pressure flow of fluid through the control
pressure chamber outlet passage 162 impinges upon the valve ball
228 urging it away from the valve seat 164 on the stop 152. The
pressure applied to the plunger 232 by the spring 236 applies only
a light force urging the valve ball 228 back toward the valve seat
164. Therefore, when no electrical current passes through the
solenoid coil 252, it requires only a low pressure for fluid within
the control pressure chamber 158 to overcome the force applied to
the valve ball 228 by the coil spring 236 and to push the valve
ball 228 away from the stop 152.
[0070] With the valve ball 228 thus displaced away from the valve
seat 164 against only the force applied by the spring 236, the
control flow restriction orifice 144 located within the main spool
112 restrains the flow rate of the control pressure flow of
hydraulic fluid passing through the pilot valve supply passage 136
to a low value. The resistance to this low rate of fluid flow past
the valve ball 228 and through the control pressure flow return
passage to the cage tank ports 52 provides a backup pressure that
is sufficiently low such that little force is applied by the fluid
in the control pressure chamber 158 to the control pressure surface
138 of the main spool 112. Therefore, the force applied to the
feedback pressure surface 114 of the main spool 112 by the coil
spring 108 within the feedback pressure chamber 118 pushes the main
spool 112 toward the stop 152.
[0071] In the proportional pressure control valve 20 depicted in
FIGS. 1 and 2, varying the pressure applied to the plunger 232 by
the spring 236 adjusts the hydraulic fluid pressure present in the
cage clutch ports 54 of the cage 42 to a predetermined pressure
valve. This is accomplished by turning the preload adjusting screw
242 within the threaded tube plug 204.
[0072] The coil spring 236, the central passage 238 in the plug 204
and the adjustable screw 242 may be eliminated in applications
where back-up pressure is not required or is undesirable. Such an
arrangement is illustrated in FIG. 6 and described below.
[0073] When the control pressure surface 138 of the main spool 112
is located immediately adjacent to the stop 152, the main spool 112
spool blocks substantially all fluid flow through the cage pump
ports 56 to the cage clutch ports 54 while the valving chamber 124
allows fluid to flow freely from the cage clutch ports 54 to the
cage tank ports 52. Because the valving chamber 124 couples the
cage clutch ports 54 to the cage tank ports 52, substantially the
same low pressure of hydraulic fluid is present both in the body
tank port 32 and in the body clutch port 34.
[0074] Applying an electrical control signal to the leads 258
increases the force pushing the plunger 232 toward the stop 152.
This increased force on the plunger 232 is applied by the pin 224
to the valve ball 228. The force from the plunger 232 urges the
valve ball 228 toward the valve seat 164 thereby reducing the
control pressure flow of fluid out of the control pressure chamber
outlet passage 162 and increasing the pressure of fluid within the
control pressure chamber 158. The increased fluid pressure within
the control pressure chamber 158 presses against the control
pressure surface 138, overcomes the force applied to the main spool
112 by the coil spring 108 located in the feedback pressure chamber
118, and moves the main spool 112 away from the stop 152 toward the
plug 92 as illustrated in FIGS. 4A through 4D. Movement of the main
spool 112 away from the stop 152 first causes the outer surface of
the main spool 112 to occlude the cage tank ports 52 and then
allows the valving chamber 124 to couple the cage clutch ports 54
to the cage pump ports 56. Coupling of the cage clutch ports 54 to
the cage pump ports 56 increases the pressure of hydraulic fluid
within the body clutch port 34.
[0075] The increased pressure of fluid in the body clutch port 34
is coupled through the cage clutch ports 54, the valving chamber
124, feedback restriction orifice 128, and the feedback pressure
passage 126 to the feedback pressure chamber 118. The pressure of
fluid in the feedback pressure chamber 118 presses against the
feedback pressure surface 114 of the main spool 112 to oppose the
force applied to the control pressure surface 138 of the main spool
112 by the fluid in the control pressure chamber 158. When the
forces applied to these opposite ends of the main spool 112 become
equal the main spool 112 stops moving within the cage 42 and the
proportional pressure control valve 20 maintains a constant fluid
pressure within the body clutch port 34. Any inequality between the
forces applied simultaneously to the control pressure surface 138
and to the feedback pressure surface 114 of the main spool 112
cause the main spool 112 to move laterally within the cage 42. In
response to such unequal forces, the main spool 112 moves away from
the end receiving the larger force and toward the end receiving the
lesser force. Because the feedback restriction orifice 128
restrains the rate at which hydraulic fluid may flow from the
valving chamber 124 to the feedback pressure chamber 118, it
dampens out possible oscillation of the main spool 112 within the
cage 42. Operated in this manner, the solenoid coil 252, the
plunger 232, the pin 224, the valve ball 228, the stop 152, and the
control flow restriction orifice 144 provide an electromagnetically
operated pilot valve for supplying a regulated pressure of fluid to
the control pressure chamber 158 responsive to an electrical
control signal.
[0076] Changing the electrical control signal so an electrical
current no longer flows through the solenoid coil 252 again permits
the fluid pressure from the cage pump ports 56 to overcome the
force applied to the valve ball 228 and move it away from the valve
seat 164 on the stop 152. Moving the valve ball 228 away from the
valve seat 164 reduces the force applied to the control pressure
surface 138 of the main spool 112 by fluid pressure within the
control pressure chamber 158. With a lesser force being applied to
the control pressure surface 138, both the force applied to the
feedback pressure surface 114 by the coil spring 108 and any
residual pressure in the feedback pressure chamber 118 urge the
spool to move back toward the stop 152.
[0077] Applying different levels of electrical control signals
provides different solenoid forces and therefore different
pressures in the control chamber and the clutch in proportion to
electric signals. This type of signal control makes proportional
pressure control and corresponding clutch torque control
possible.
[0078] FIG. 6 depicts a cross-sectional plan view of a proportional
pressure control valve referred to by the general reference
character 310. FIG. 5, made up of FIGS. 5A and 5B, is an exploded,
cross-sectional plan view depicting the various parts included in
the proportional pressure control valve 310. Those elements
depicted in FIGS. 5 and 6 that are common to the proportional
pressure control valve 20 depicted in FIGS. 1 and 2 carry the same
reference numeral distinguished by a prime ("'") designation. The
same reference characters are used to identify the same part of the
proportional pressure control valve 310 both in FIG. 5 and in FIG.
6. The proportional pressure control valve 310 depicted in FIGS. 5
and 6 is a normally open valve.
[0079] The interior of the main spool 112' of the proportional
pressure control valve 310 differs from that of the proportional
pressure control valve 20. Formed through the entire length of the
interior of the main spool 112' is a right circular
cylindrically-shaped seat spool passage 322. When assembled into
the proportional pressure control valve 310, the seat spool passage
322 of the main spool 112' receives a rod-shaped seat spool 324
having a length that is greater than that of the main spool 112'.
The end of the seat spool 324 extending outward beyond the feedback
pressure surface 114' of the main spool 112' contacts the inner
surface of the plug 92 and is surrounded by the coil spring 108'.
Thus, in the proportional pressure control valve 310 the coil
spring 108' presses against the feedback pressure surface 114' of
the main spool 112' and not against the seat spool 324.
[0080] The outer surface of the seat spool 324 enclosed within the
main spool 112' near its feedback pressure surface 114' is
encircled by a trough 326. The trough 326 establishes a hollow,
annularly-shaped pilot valve supply coupling chamber 328 encircling
the seat spool 324 between the, outer surface of the seat spool 324
and the surface of the seat spool passage 322. The pilot valve
supply coupling chamber 328 forms part of the pilot valve supply
passage 136' to couple the portion of the pilot valve supply
passage 136' passing through the main spool 112' to the portion of
the pilot valve supply passage 136' passing through the interior of
the seat spool 324. Thus, as in the proportional pressure control
valve 20, the pilot valve supply passage 136' of the proportional
pressure control valve 310 is always open to a flow of hydraulic
fluid from the pump through the cage pump ports 56' in the cage
wall 44'.
[0081] Formed on the edge of the pilot valve supply passage 136'
passing through the seat spool 324 that extends outward through the
control pressure surface 138' of the main spool 112' is a beveled
valve seat 332. In the assembled proportional pressure control
valve 310, a valve ball 336 is juxtaposed with the valve seat 332
of the seat spool 324. The digital control signal proportional
pressure control valve 310 depicted in FIGS. 5 and 6 omits, the
screen 142 and the control flow restriction orifice 144 included in
the proportional pressure control valve 20 depicted in FIGS. 1 and
2.
[0082] The tube assembly 178' of the proportional pressure control
valve 310 differs from the tube assembly 178 of the proportional
pressure control valve 20 by substituting a solid tube plug 342 for
the annularly-shaped threaded tube plug 204.
[0083] The proportional pressure control valve 310 omits the coil
spring 236" included in the proportional pressure control valve 20.
Accordingly, the plunger 232' of the digital normally open
proportional pressure control valve 310 lacks the spring cavity 234
that is included in the plunger 232 of the analog normally closed
proportional pressure control valve 20.
[0084] In the assembled proportional pressure control valve 310, a
long pin 346 and a short pin 348 extend outward coaxially from the
plunger 232' through the interior of the pole piece 212' toward the
seat spool 324. The long pin 346 is preferably made from a
non-magnetic material such as stainless steel or the like. To
resist wear at the point of contact between the short pin 348 and
the valve ball 336, the short pin 348 is preferably made from a
material such as hardened steel or a material having similar wear
resistant properties. The end of the short pin 348 furthest from
the plunger 232' and nearest to the seat spool 324 is formed with a
smaller diameter which allows it to enter freely into the control
pressure chamber outlet passage 162' of the stop 152'. As may be
appreciated by those skolled in the art, this same two-piece pin
configuration may be utilized in the system illustrated on FIG. 2
and previously described above.
[0085] While in the proportional pressure control valve 20 the
diameter of the control pressure chamber outlet passage 162 in the
stop 152 has a uniform diameter throughout its entire length, the
diameter of the control pressure chamber outlet passage 162' of the
stop 152' in the proportional pressure control valve 310 has an
enlarged diameter immediately adjacent to the valve seat 332 of the
seat spool 324. The enlarged diameter of the control pressure
chamber outlet passage 162' immediately adjacent to the valve seat
332 provides a valve ball retaining chamber 354 analogous to the
valve ball retaining chamber 226 in the pole piece 212 of the
proportional pressure control valve 20. A U-shaped slot 356 extends
across the face of the stop 152' immediately adjacent to the main
spool 112' and the seat spool 324. The slot 356 forms a portion of
the control pressure chamber 158' that permits hydraulic fluid to
flow into and out of that portion of the control pressure chamber
158' adjacent to the control pressure surface 138' of the main
spool 112'. The diameter of the control pressure chamber outlet
passage 162' on the opposite side of the stop 152' from the valve
ball retaining chamber 354 that is adjacent to the pole piece 212'
is also enlarged to permit hydraulic fluid to flow freely about the
short pin 348 on its way to the body tank port 32' and cage tank
ports 52', and thence to the tank.
[0086] Because the proportional pressure control valve 310 omits
the coil spring 236" included in the proportional pressure control
valve 20, unless an electrical current flows through the solenoid
coil 252' there is no force urging the plunger 232' away from the
solid tube plug 342 toward the valve ball 336. Therefore, when no
electrical current flows through the solenoid coil 252', the force
of the hydraulic fluid impinging on the valve ball 336 urges it
away from the valve seat 332 of the seat spool 324 toward the
interior of the stop 152' and the narrowest portion of the control
pressure chamber outlet passage 162'. In this location, the valve
ball 336 seals the control pressure chamber outlet passage 162' and
hydraulic fluid at the full pressure supplied by the pump fills the
control pressure chamber 158'. The presence of hydraulic fluid
within the control pressure chamber 158' at the full pressure
supplied by the pump causes the main spool 112' to move
longitudinally within the cage 42 thereby coupling the cage pump
ports 56' to the cage clutch ports 54' to supply hydraulic fluid at
the full pressure supplied by the pump to the body clutch port
34'.
[0087] The magnetic field resulting from the application of a PWM
electrical signal to the solenoid coil 252' pushes the plunger 232'
away from the solid tube plug 342 toward the valve ball 336. The
combined long pin 346 and short pin 348 transmit this movement of
the plunger 232' to the valve ball 336 pushing it toward the valve
seat 332 of the seat spool 324. Movement of the valve ball 336
toward the valve seat 332 simultaneously allows hydraulic fluid to
flow from the control pressure chamber 158' into the control
pressure chamber outlet passage 162' and restricts the flow of
hydraulic fluid through the pilot valve supply passage 136' in the
seat spool 324 into the control pressure chamber 158'. Thus, a PWM
electrical signal applied to the solenoid coil 252' reduces the
pressure of the hydraulic fluid in the control pressure chamber
158' thereby causing longitudinal movement of the main spool 112'
within the cage 42' that reduces the pressure of hydraulic fluid
within the body clutch port 34'. Operated in this manner, the
solenoid coil 252', the plunger 232', the pins 346 and 348, the
valve ball 336, the stop 152', and the seat spool 324 provide an
electromagnetically operated pilot valve for supplying a regulated
pressure of fluid to the control pressure chamber 158' responsive
to an electrical control signal.
[0088] FIG. 8 depicts a cross-sectional plan view of a proportional
pressure control valve referred to by the general reference
character 410. FIG. 7, made up of FIGS. 7A and 7B, is an exploded,
cross-sectional plan view depicting the various parts included in
the proportional pressure control valve 410. Those elements
depicted in FIGS. 7 and 8 that are common to the proportional
pressure control valve 20 depicted in FIGS. 1 and 2 or to the
proportional pressure control valve 310 depicted in FIGS. 5 and 6
carry the same reference numeral distinguished by a double prime
(""") designation. The same reference characters are used to
identify the same part of the proportional pressure control valve
410 both in FIG. 7 and in FIG. 8. The proportional pressure control
valve 410 depicted in FIGS. 7 and 8 is a normally closed valve that
is adapted for control by a digital pulse width modulated ("PWM")
electrical control signal.
[0089] The tube 202" of the proportional pressure control valve 410
is shorter than the tube 202 of the tube assemblies 178 and 178' of
the proportional pressure control valves 20 and 310. Because of the
shorter tube 202", the proportional pressure control valve 410
omits the spacer 254. The solid tube plug 342" of the proportional
pressure control valve 410 extends further into the tube 202" than
the tube plug 342 of the proportional pressure control valve 310
and functions as a pole piece for the proportional pressure control
valve 410. Formed into the end of the solid tube plug 342" nearest
to the adaptor 176" is a plug spring cavity 412. In the assembled
proportional pressure control valve 410, the plug spring cavity 412
receives one end of the coil spring 236". The other end of the
spring 236" is received into the spring cavity 234" formed into the
plunger 232" of the proportional pressure control valve 410
immediately adjacent to the solid tube plug 342".
[0090] Projecting outward from the end of the plunger 232" furthest
from the spring cavity 234" is a protrusion 422. A pin cavity 424,
formed into the protrusion 422, receives a pin 426. The outer
surface of the plunger 232" parallel to the center line 24" is not
formed in the shape of a full right circular cylinder. Rather, the
shape of the outer surface of the plunger 232" parallel to the
center line 24" is similar to that of the plunger 232 as depicted
in FIG. 3.
[0091] There are only two substantial differences between stop 152"
of the normally closed proportional pressure control valve 410 and
the stop 152' of the normally open proportional pressure control
valve 310. Because the proportional pressure control valve 410
omits the pole piece 212' included in the proportional pressure
control valve 310, the width of the stop 152" between the cage 42"
and the adaptor 176" is greater than that of the stop 152'. Thus,
in the assembled proportional pressure control valve 410, the
adaptor 176" contacts the stop 152" and directly forces it into the
cage 42" and holds it there. Also because the proportional pressure
control valve 410 lacks the pole piece 212', a U-shaped slot 432 is
formed across the face of the stop 152" immediately adjacent to the
plunger 232". The slot 432 forms a portion of the passage by which
hydraulic fluid, that flows out of the control pressure chamber
158" through the control pressure chamber outlet passage 162",
returns to the body tank port 32" and cage tank ports 52", and
thence to the tank.
[0092] The coil spring 236 included in the proportional pressure
control valve 410 applies sufficient force to the valve ball 336"
through the plunger 232" and the pin 426 that, in the absence of an
electric current flowing through the solenoid coil 252", the valve
ball 336" seals the pilot valve supply passage 136" thereby
preventing hydraulic fluid from entering into and pressurizing the
control pressure chamber 158". As explained previously, the absence
of any pressure on the hydraulic fluid in the control pressure
chamber 158" causes the proportional pressure control valve 410 to
block all fluid flow from the pump inlet chamber 84" to the body
clutch port 34" and relieves all pressure from the hydraulic fluid
in the body clutch port 34".
[0093] Application of a PWM signal to the solenoid coil 252" of the
proportional pressure control valve 410 overcomes the force applied
to the plunger 232" by the spring 236" and pulls the plunger 232"
away from the valve ball 336" toward the solid tube plug 342".
Pulling the plunger 232" toward the solid tube plug 342" releases
the force urging the valve ball 336" into the valve seat 332" of
the seat spool 324". The force of the hydraulic fluid impinging on
the valve ball 336" urges it away from the valve seat 332" of the
seat spool 324" toward the interior of the stop 152". Thus spaced
apart from the valve seat 332", the valve ball 336" allows
hydraulic fluid to flow into and raise the pressure of hydraulic
fluid within the control pressure chamber 158". The pressurized
hydraulic fluid within the control pressure chamber 158" causes the
main spool 112" to move laterally along the length of the cage 42"
and to couple the cage pump ports 56" to the cage clutch ports 54"
thereby supplying hydraulic fluid to the body clutch port 34".
Operated in this manner, the solenoid coil 252", the plunger 232",
the pin 426, the valve ball 336", the stop 152", and the seat spool
324" provide an electromagnetically operated pilot valve for
supplying a regulated pressure of fluid to the control pressure
chamber 158" responsive to an electrical control signal.
[0094] A normally open proportional pressure control valve adapted
for control by an analog electrical control signal may be
constructed by substituting certain elements from the normally
closed proportional pressure control valve 410 for elements of the
normally closed proportional pressure control valve 20. Such a
normally open proportional pressure control valve may be assembled
by incorporating the tube assembly 178", the spring 236", and a
plunger 232" that lacks the protrusion 422 of the proportional
pressure control valve 410 for the corresponding elements of the
proportional pressure control valve 20. The stop 152 of such an
analog normally open valve must also be modified from that included
in the proportional pressure control valve 20 by making it thicker
so the adaptor 176 of the tube assembly 178 may force the stop 152
into the cage 42, and by providing structures that will support the
valve ball 228 at the valve seat 164 analogous to the valve ball
retaining chamber 226 in the pole piece 212. The stop 152 must also
be modified to provide a passage by which hydraulic fluid, that
flows out of the control pressure chamber 158 through the control
pressure chamber outlet passage 162, may return to the body tank
port 32 and cage tank ports 52.
[0095] In such a modified valve, if no current flows through the
solenoid coil 252, the force of the spring 236" urges the valve
ball 228 into sealing relationship with the valve seat 164 thereby
pressurizing the hydraulic fluid within the control pressure
chamber 158. Supplying an analog electrical control current to the
solenoid coil 252 of such a modified valve applies a magnetic field
to the plunger 232" that overcomes the force of the spring 236 and
pulls the plunger 232" away from the valve ball 228 thereby
relieving the pressure of hydraulic fluid within the control
pressure chamber 158. Operated in this manner, the solenoid coil
252", the plunger 232", the pin 426, the valve ball 228, the
modified stop 152, and the control flow restriction orifice 144
provide an electromagnetically operated pilot valve responsive to
an analog current for supplying a regulated pressure of fluid to
the control pressure chamber 158 responsive to an electrical
control signal.
[0096] Referring now to FIG. 9, depicted there is a cross-sectional
plan view of a main spool 502 in accordance with the present
invention that also includes a pressure spike suppression check
valve 504. Those elements depicted in FIG. 9 that are common to the
main spool 112 of the proportional pressure control valve 20
depicted in FIGS. 1 and 2 carry the same reference numeral
distinguished by a triple prime ("'"") designation.
[0097] The main spool 502 includes a narrow U-shaped trough 512
formed into the outer surface of the main spool 502 between the
control pressure surface 138'" of the main spool 502 and the trough
122'" that establishes the hollow, annularly-shaped valving chamber
124'". The trough 512 establishes a hollow, annularly-shaped
pressure spike pilot chamber 514 encircling the main spool 502
between its outer surface and the inner surface of the cage 42'"
(not illustrated in FIG. 9). The pressure spike pilot chamber 514
is always open to the cage tank ports 52'" (not illustrated in FIG.
9). A pressure spike pilot valve cavity 518 extending between the
trough 122'" and the control pressure surface 138'" opens into the
pressure spike pilot chamber 514. The pressure spike pilot valve
cavity 518 is open to the valving chamber 124'" through the surface
of the trough 122'". Threads formed at the end of the pressure
spike pilot valve cavity 518 adjacent to the control pressure
surface 138'" receive a threaded plug 522. The pressure spike
suppression check valve 504 fits snugly within the pressure spike
pilot valve cavity 518 to normally block any flow among the valving
chamber 124'", the control pressure chamber 158'" and the pressure
spike pilot chamber 514 due to the pressure difference between the
control pressure chamber 158 and valving chamber 124 and a spring
524 located between pressure spike suppression check valve 504 and
the pressure spike pilot orifice 522. Spring 524 provides a biasing
force to prevent unwated oscillation of pressure spike suppression
check valve 504.
[0098] If a clutch, or any other hydraulically operated device,
reaches the mechanical limit of its travel and hydraulic fluid flow
through the cage clutch ports 54'" stops abruptly, the fluid
pressure on the side of the pressure spike suppression check valve
504 open to the valving chamber 124'" rises abruptly. The pressure
spike suppression check valve 504 is constructed such that when the
pressure of the hydraulic fluid on the side open to the valving
chamber 124' exceeds the pressure of the hydraulic fluid applied to
the other side of the valve 504, the valve 504 opens to permit
fluid to flow between the valving chamber 124'" and the pressure
spike pilot chamber 514. Since the pressure spike pilot chamber 514
is always open to the cage tank ports 52'", fluid flows from the
valving chamber 124'" to the cage tank ports 52 to relieve the
abnormally high pressure within the cage clutch ports 54'". When
the pressure applied to the pressure spike suppression check valve
504 from the trough 122'" once again equals or becomes less than
the pressure applied to the valve 504 from the control pressure
surface 138'", the pressure spike suppression check valve 504 once
again closes to prevent fluid from flowing between the valving
chamber 124'" and the pressure spike pilot chamber 514.
INDUSTRIAL APPLICABILITY
[0099] While the disclosed embodiment describes certain preferred
locations for various passages in the valve such as the pilot valve
supply passage 136 supplying hydraulic fluid from the cage pump
ports 56 to the pilot valve, and the feedback pressure passage 126
from the valving chamber 124 to the feedback pressure chamber 118,
those passages need not necessarily be located exactly as described
above. For example, the pilot valve supply passage 136 could be
formed through the body 22 and the adaptor 176 rather than through
the main spool 112 in the proportional pressure control valve 20,
or through the combined main spool 112' and the seat spool 324 in
the proportional pressure control valve 310. Analogously, the
feedback pressure passage 126 need not be formed through the main
spool 112. Rather, the feedback pressure passage 126 could be
formed through the cage wall 44. Similarly, the pressure spike
pilot valve cavity 518 could be formed through the cage wall 44'"
and the pressure spike suppression check valve 504 be located in
the cage 42'" rather than in the main spool 502.
[0100] Comparatively large passages in the pilot valve of the
proportional pressure control valves 310 and 410 adapted for use
with a PWM control signal permit omission of the screen 142
included in valves adapted for control by an analog signal. If
particles in the hydraulic fluid cause blockage of the passages in
the valves 310 or 410, then a screen, similar to the screen 142
included in the proportional pressure control valve 20, may be
suitably incorporated into either the main spool or the seat spool
of the valves 310 or 410.
[0101] While the solenoid coil 252 of the proportional pressure
control valves adapted for control by an analog signal, a pulse
width modulated ("PWM") signal and the like, it may be desirable to
use this valve as a solenoid on-off valve provided a small amount
of bleeding flow is acceptable. Such an on-off valve assures the
benefits of using a small inexpensive coil to control comparatively
large flow.
[0102] In distinction to the valves 20 and 310, the valve 410, when
used in the proportional control mode, requires a pluse width
modulated ("PWM") driver with a "peak-and-hold" means to develop
sufficient magnetic forces to overcome the force provided by the
compressed coil spring which otherwise cannot be overcome at lesser
values of current. It has been determined that a usable pulse width
modulation frequency range will be approximately from about 50 Hz
to about 500 Hz.
[0103] While the body 22 has been described in connection with the
preferred embodiment of the invention, the body 22 is not essential
to the functioning of the valve. Rather, as described above, the
body 22 merely provides a mechanical housing for the cage 42 and
for joining the cage 42 respectively with the pump, the tank and
the clutch. Thus, a valve in accordance with the present invention
need not include the body 22. Rather, other structures, such as the
case that mechanically encloses the transmission for an automotive
vehicle, could itself directly incorporate the structure and
provide the function of the body 22 as described above.
[0104] While the present invention has been described for use in
hydraulic transmissions, its usefulness in other hydraulic systems
will be understood by those skilled in the art of hydraulic
systems. Such uses may include but are not limited to hydraulic
braking systems, hydraulic lifting systems and such similar
hydraulic systems using proportional control valves.
[0105] Although the present invention has been described in terms
of the presently preferred embodiment, it is to be understood that
such disclosure is purely illustrative and is not to be interpreted
as limiting. Consequently, without departing from the spirit and
scope of the invention, various alterations, modifications, and/or
alternative applications of the invention will, no doubt, be
suggested to those skilled in the art after having read the
preceding disclosure. Accordingly, it is intended that the
following claims be interpreted as encompassing all alterations,
modifications, or alternative applications as fall within the true
spirit and scope of the invention.
* * * * *