U.S. patent application number 10/080023 was filed with the patent office on 2003-09-04 for solenoid operated hydraulic control valve.
Invention is credited to Lou, Zheng David.
Application Number | 20030164193 10/080023 |
Document ID | / |
Family ID | 23150544 |
Filed Date | 2003-09-04 |
United States Patent
Application |
20030164193 |
Kind Code |
A1 |
Lou, Zheng David |
September 4, 2003 |
Solenoid operated hydraulic control valve
Abstract
A pressure control valve with a hydraulic system of an automatic
transmission for a motor vehicle includes a valve body defining a
control chamber, fluid ports communicating with the control
chamber, and a valve spool having spaced pressure control lands
located in the control chamber, the valve spool urged by a
compression spring in an opposite direction from an electromagnetic
force developed on the spool when a solenoid is energized. In one
embodiment a control land is formed with a pressure feedback
orifice that communicates a control port with a feedback chamber.
The valve spool can be formed with different sized control lands.
The feedback orifice is substantially insensitive to fluid
temperature variation.
Inventors: |
Lou, Zheng David; (Plymouth,
MI) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60611
US
|
Family ID: |
23150544 |
Appl. No.: |
10/080023 |
Filed: |
February 21, 2002 |
Current U.S.
Class: |
137/625.65 |
Current CPC
Class: |
F16H 2061/0253 20130101;
F16K 31/0613 20130101; G05D 16/2024 20190101; Y10T 137/86622
20150401; F16H 61/0251 20130101 |
Class at
Publication: |
137/625.65 |
International
Class: |
F15B 013/044 |
Claims
I claim:
1. A solenoid-operated valve assembly for an automatic transmission
of a motor vehicle, comprising: a valve body having a control
chamber, mutually spaced first, second and third ports
communicating with the control chamber; a valve spool supported for
movement along the control chamber, including a shank, a first land
adapted to open and close the first port, the first land having a
feedback chamber and a feedback orifice connecting the feedback
chamber and second port, and a second land located at an opposite
end of the shank from the first land and adapted to open and close
the third port; and a spring urging the valve spool to move along
the control chamber; and a solenoid assembly having an armature
axially displaceable in response to an electric signal supplied to
a coil, the armature urging the valve spool to move along the
control chamber.
2. The valve assembly of claim 1 further comprising: a source of
low pressure; wherein the valve body further includes a scaling
orifice connecting the feedback chamber and the source of low
pressure.
3. The valve assembly of claim 1 wherein the length of the feedback
orifice is relatively short.
4. The valve assembly of claim 1 wherein the first land and second
land have substantially equal diameters.
5. The valve assembly of claim 1 wherein the first land has a
larger diameter than the diameter of the second land.
6. The valve assembly of claim 1 wherein the first port is adapted
for connection to a source of supply pressure, the third port is
adapted for connection to a source of low pressure, and the second
port is adapted to produce control pressure achieved by balancing
supply flow from the first port, vent flow to the third port, and
control flow to and from the load.
7. A solenoid-operated valve assembly for an automatic transmission
of a motor vehicle, comprising: a valve body having a control
chamber, first, second and third ports spaced mutually along, and
communicating with the control chamber; a valve spool located
within the control chamber, including a shank, a first land adapted
to open and close the first port &and having a first end and
second end, a second land located at a opposite end of the shank
and adapted to open and close the third port, the second land
having a larger diameter than the diameter of the first land; a
damping orifice facing the first end, communicating the control
chamber adjacent the first end and a source of low pressure fluid;
a spring urging the valve spool to move along the control chamber;
and a solenoid assembly having an armature axially displaceable in
response to an electric signal supplied to a coil, the armature
urging the valve spool to move along the control chamber.
8. The valve assembly of claim 7 wherein the first control land
includes a control edge located at a radially outer surface of the
first land at the second end, and a radial step defining an annular
surface extending radially between the shank and control edge, and
wherein the feedback passage is directed radially and axially from
the bore to the annular surface.
9. The valve assembly of claim 7 wherein the first port is adapted
for connection to a source of supply pressure, the third port is
adapted for connection to a source of low pressure, and the second
port is adapted to produce control pressure achieved by balancing
supply flow from the first port, vent flow to the third port, and
control flow to and from the load.
10. The valve assembly of claim 9, wherein the source of fluid at
low pressure is a volume of fluid contained apart from the valve
assembly.
11. The valve assembly of claim 9, wherein the source of fluid at
low pressure is a volume of fluid contained apart from the valve
assembly.
12. A solenoid-operated valve assembly for an automatic
transmission of a motor vehicle, comprising: a valve body having a
bore, mutually spaced first, second and third ports communicating
with the bore; a valve spool supported for movement along the bore,
including a shank, a first land adapted to open and close the first
port and having an axial bore extending partially along the first
land from the first end thereof toward the second end, a feedback
orifice in the first land communicating the second port and said
axial bore in the first land, said feedback orifice being
substantially shorter in length and smaller in diameter than said
axial bore in the first land; the first control land including a
control edge located at a radially outer surface of the first land
at the second end, and a radial step defining an annular surface
extending radially between the shank and control edge, and wherein
the second feedback orifice extends from the bore to the annular
surface; a spring urging the valve spool o move along the control
chamber; and a solenoid assembly having an armature axially
displaceable in response to an electric signal supplied to a coil,
the armature urging the valve spool to move along the control
chamber.
13. The valve assembly of claim 12 further comprising: a source of
low pressure; wherein the valve body further includes a scaling
orifice connecting the feedback chamber and the source of low
pressure.
14. The valve assembly of claim 12 wherein the first land and
second land have substantially equal diameters.
15. The valve assembly of claim 12 wherein the first land has a
larger diameter than the diameter of the second land.
16. The valve assembly of claim 12 wherein the first port is
adapted for connection to a source of supply pressure, the third
port is adapted for connection to a source of low pressure, and the
second port is adapted to produce control pressure achieved by
balancing supply flow from the first port, vent flow to the third
port, and control flow to and from the load.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a pressure control device for
controlling the pressure of hydraulic fluid in the control system
of an automatic transmission for a motor vehicle. More
particularly, the invention pertains to a solenoid-operated
pressure control valve.
[0003] 2. Description of the Prior Art
[0004] SAE Technical Paper 960430 describes a hydraulic control
valve for use with a solenoid, the valve having two control lands
of equal diameter and a long feedback orifice that passes through a
control land and a major portion of the spool shank length. That
valve is moderately stable due to viscous damping through the
feedback orifice. However, it exhibits slow low-temperature
response. Furthermore it is difficult and expensive to manufacture,
particularly because of the long feedback passage.
[0005] U.S. Pat. Nos. 4,678,893 and 5,513,673 describe hydraulic
control valves for use with a solenoid, each valve having three
control lands of equal diameter and long orifices extending through
the valve body. The valves are stable due to the presence of
positive hydrodynamic damping; however, they are expensive to
manufacture and require a large lateral package space.
[0006] U.S. Pat. No. 5,615,860 describes a hydraulic control valve
for use with a solenoid, the valve having two control lands of
unequal diameter. Damping occurs in the electrical solenoid. The
valve is simple and compact, but it is unstable because damping is
not reliable. Also it is possible that hydraulic fluid may not be
continuously available for hydraulic damping.
SUMMARY OF THE INVENTION
[0007] It is an object of this invention to provide an improved
variable force solenoid-operated valve. The valve is stable and
provides inertia damping, either through a short feedback orifice
that passes through a land, or through a short damping orifice
located at the pressure end. In either case, the valve is easy to
manufacture, compact, and stable. It has good response time at low
temperature.
[0008] The valve provides the ability to operate with these
advantages at a low magnitude of load spring force and low
electromagnetic force. The output pressure produced by the valve
has been demonstrated to be predictable and stable over time and
over a large range of line pressure.
[0009] In realizing these objects and advantages a
solenoid-operated valve assembly for an automatic transmission of a
motor vehicle includes a valve body having a control chamber,
first, second and third ports spaced mutually along, and
communicating with the control chamber; a valve spool located
within the control chamber including a shank, a first land adapted
to open and close the first port; a feedback orifice connecting a
feedback chamber and the second port, and a second land located at
an opposite end of the shank and adapted to open and close the
third port; a spring urging the valve spool to move along the
control chamber; and a solenoid assembly having an armature axially
displaceable in response to an electric signal supplied to a coil,
the armature urging the valve spool to move along the control
chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a partial cross sectional view through a pressure
control valve according to the invention.
[0011] FIG. 2 is a cross section showing a variation of the control
valve portion of the assembly of FIG. 1.
[0012] FIG. 3 is a cross section of another embodiment of the
control valve portion of the assembly of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] Referring first to FIG. 1, a magnetically operated pressure
control assembly 10 includes a solenoid portion 12 and a control
valve portion 14. The solenoid includes housing 16, in which a
magnetic coil member 18 carrying a coil 20 and a magnetic armature
25 are located. Coil 20 has an electrical connection 24 that
extends outward from housing 16 and is adapted for connection to a
source of electric power.
[0014] A valve body 26, attached to housing 16, is provided with an
inlet passage or supply port 28, through which hydraulic fluid from
a supply source, such as a pressure regulator valve, is carried to
a central chamber 30 of the valve; a vent passage or port 32,
through which chamber 30 is alternately opened and closed to a low
pressure sump or vent; and a control or outlet passage or port 34,
through which hydraulic fluid is connected to a hydraulic system or
load.
[0015] In order to adjust the pressure in control port 34, and the
stream of fluid supplied to the load, a valve spool 36 moves
axially along the axis of chamber 30 in response to various
pressure forces applied to the spool, the force of spring 46, and
electromagnetic force applied by a push rod 38 to the spool from
magnetic armature 25.
[0016] Push rod 38 is press-fitted inside the magnetic armature 25
and is centered radially by a diaphragm spring 40, which is clamped
at its periphery on the inner wall of housing 16. The center of
diaphragm spring 40 is secured longitudinally between a head 42 of
the push rod and a hub 44 of a sealing diaphragm 22. Push rod 38 is
supported and guided for sliding movement in a bearing sleeve
located at its end that is opposite spool 36. Armature 25 is urged
leftward by compression spring 46. Diaphragm spring 40 and sealing
diaphragm 22 exert minimum force, if any, in the axial
direction
[0017] Spool 36 is formed with a first control land 48 and a second
control land 50, each land having a control edge for opening and
closing ports 28, 32 respectively, as the spool moves axially
within chamber 30. Control land 48 is formed with a central bore 52
that extends partially along the length of the land and
communicates with control port 34 through a short feedback orifice
54. The diameter of land 48 can be greater than that of land 50 if
a lower spring preload and lower electromagnetic force are
desired.
[0018] Hydraulic fluid is supplied to the control valve 14
preferably from a source of regulated line pressure through port
28. The fluid pressure produced by valve 14 is communicated through
port 34 to a load or hydraulic system, such as a control and
actuation system for an automatic transmission. In the alternate
embodiment of the invention shown in FIG. 2, the space 55 of
chamber 30 located at the left-hand end of control land 48 is
connected through an orifice 56 to a source of low pressure such as
a transmission fluid sump.
[0019] If coil 20 is energized, armature 25 and push rod 38 move
rightward toward a pole piece (not shown). The force of compression
spring 46 applies to spool 36 a force directed leftward.
[0020] Under steady state conditions, spool 36 is balanced
primarily by three major forces: the leftward force from
compression spring 46 (F.sub.spring), the rightward electromagnetic
force from coil 20 & armature 25 assembly (F.sub.em), and the
rightward net fluid pressure force on the spool. The spring and
electromagnetic forces are applied to spool 36 through push rod 38.
The fluid pressure force is substantially equal to the product of
control pressure (P.sub.control) times the cross section area of
land 50 (A.sub.50). Therefore, one has the following approximate
mathematical relation under steady state condition:
P.sub.control.apprxeq.(F.sub.spring-F.sub.em)/A.sub.50
[0021] Control pressure is thus controlled by electromagnetic force
F.sub.em. Both spring and magnetic forces are generally designed to
be substantially constant with respect to the spool movement. If
the maximum electromagnetic force is equal to the spring pre-load,
then control pressure varies between its maximum and zero when the
coil is deenergized and energized, respectively. A full range of
inversely-proportional control can be achieved between the two
extreme states. It should be noted, as shown in the above force
balance equation, that the control pressure is a function of the
cross section area of land 50 instead of that of land 48. Without
adversely affecting the spring pre-load and the peak magnetic
force, one can design a bigger land 48 to accommodate larger flow
demand and provide more space for a proper location of orifice 54
on end surface 60.
[0022] Whenever the current to coil 20 and thus the electromagnetic
force are changed, there will be a momentary force unbalance on
spool 36. Spool 36 will be forced to a new position, changing the
relative size of the openings at the ports and thus the fluid flows
rate from port 28 to port 34 and from port 34 to port 32, thereby
producing a new control pressure value to balance spool 36. For
example when the coil current is increased, the momentary force
increment will pull spool 36 rightward, closing fluid flow from
supply port 28 to control port 34 and opening fluid flow from
control port 34 to vent port 32. This spool movement reduces
control pressure and thus decreases the pressure force that will
roughly balance out the electromagnetic force rise.
[0023] Feedback damping orifice 54 communicates control pressure to
the left end of land 48 through bore 52, thereby offering
resistance or damping to spool movement. For example when spool 36
is pulled rightward by an increased electromagnetic force, there
will be a momentary pressure imbalance across damping orifice, the
pressure at the left-hand end of land 48 being lower than control
pressure at the right-hand end because of a vacuum effect caused by
the flow restriction through damping orifice 54. This vacuum causes
a reduction in net pressure force, which tends to resist the
rightward movement of spool 36. The flow through orifice 54 is
proportional to the axial displacement velocity of spool 36 if one
ignores fluid compressibility and leakage through the annular
clearance around the outside diameter of land 48.
[0024] Orifice 54 is relatively short, the pressure drop and
damping is substantially independent of fluid viscosity and
therefore is substantially independent of temperature. In other
designs with long orifices, damping is predominantly achieved
through laminar fluid flow, which causes too much pressure drop and
thus extremely slow response at cold temperatures.
[0025] In hydraulic valve design, it is known that at each metering
port there is a steady state flow force, or steady state
hydrodynamic force, which tends to resist the valve from opening
the port. In the case of the metering port between supply port 28
and control port 34, the steady state hydrodynamic force tends to
move spool 36 rightward. The source of this force is the well-known
Bernoulli effect: the hydrostatic pressure drops when the velocity
increases along a fluid stream. Because of continuity, the velocity
is the highest and thus the hydrostatic pressure is the lowest at
the radially outer edge of surface 60 (see FIG. 2), which is
located at the right-hand end of land 48. The hydrostatic pressure
on surface 60 is approximately equal to hydrostatic control
pressure at the radially inner corner where surface 60 and the
spool shank meet. This non-uniform pressure distribution results in
a leftward pressure force reduction on surface 60 and thus a net
rightward force increase on spool 36. This net force affects the
overall force balance on spool 36 and thus control pressure
produced by the valve. According to the Bernoulli effect, the
hydrostatic pressure distribution along surface 60 and thus valve
control pressure are influenced by fluid velocity distribution,
which in turn is a function of pressure at supply port 28 and load
flow or flow demand. The control pressure from an ideal pressure
regulating valve should be a function of input current or
electromagnetic force only.
[0026] Another advantage of orifice 54 in this application is its
potential for line pressure compensation. The exact hydrostatic
pressure value in feedback chamber 55 depends on the location of
orifice 54 on end surface 60. If the opening is located on surface
60 between its radially outer edge and radially inner corner, the
hydrostatic pressure in feedback chamber 55 will be less than the
hydrostatic control pressure, thereby reducing the rightward fluid
pressure force. A pressure force compensation is achieved if the
rightward pressure force reduction in feedback chamber 55 is equal
in magnitude to the leftward pressure force reduction on end
surface 60.
[0027] In addition, the combination of bore 52 and short feedback
orifice 54 is easier to manufacture than a combination that
includes a long axial passage extending along land 48 to the center
of the shank portion of spool 36 and a radial passage communicating
with such a long axial passage.
[0028] In the alternate embodiment of the present invention shown
in FIG. 2, one can add a scaling orifice 56 at the left-hand end of
feedback chamber 55 to reduce the steady state pressure in chamber
55, thereby allowing the valve to operate with lower magnitudes of
spring and electromagnetic forces.
[0029] The valve of FIG. 3 creates at the end volume 55 a dynamic
pressure to resist movement of the spool. The valve body 26' is
formed with a control chamber 30'. A valve spool 36' has a control
land 50' having a larger diameter than the diameter of control land
48'. In addition, damping orifice 62 connects the end volume 55
within chamber 30', located at the left-hand end of spool 36 to an
oil reservoir 64. Under steady state conditions, the differential
pressure force on the faces 60, 66 of the control lands resulting
from the pressure in outlet passage 34 is balanced against the net
force produced by spring 46 and the electromagnetic force.
[0030] If the variable force solenoid is not always immersed in
hydraulic fluid, the oil reservoir 64 is necessary to assure that
volume 55 is filled with fluid. Orifice 62 is large enough to avoid
causing a substantial steady state back pressure in volume 55 due
to the leak flow path from supply port 28 and through the clearance
between chamber 30' and land 48'. This leak flow tends to fill
volume 55.
[0031] The presence of the damping orifice 62 at the end of land
48' produces a valve having substantially stable dynamic pressure
and improved low temperature performance. The valve is easy to
manufacture, yet is simple and compact.
[0032] Preferably, the diameter of the orifice 54 is 0.6-1.1 mm.
Orifice 54, whose length is preferably no more than 3.0 mm, is
relatively short in order to produce turbulent flow, so that the
valve is less sensitive to temperature effects, such as the
viscosity variation of the transmission fluid, than is laminar
flow. Preferably the diameter of lands 48 and 50 is 3.0-6.0 mm. In
the case where land 48 is larger than land 50, the diameter of land
48 can be as large as 10.0 mm. The diameter of land 48' is
preferably 3.0-10.0 mm, and the diameter of land 50' is preferably
4.0-10.5 mm.
[0033] In the valve of FIG. 3, orifice 62 creates a flow
restriction, but the restriction preferably will not permit the
steady state pressure in volume 55 to be large enough to upset the
force balance on the spool. The flow restriction is great enough,
however, to resist unstable, oscillatory spool movement. Orifice 62
need not be centered on the axis of the spool. Both the end volume
55 and oil reservoir 64 can be filled with fluid leaking between
supply port 28 through the gap between valve body 26' and the outer
diameter of control land 48'.
[0034] Although the form of the invention shown and described here
constitutes the preferred embodiment of the invention, it is not
intended to illustrate all possible forms of the invention. Words
used here are words of description rather than of limitation.
Various changes in the form of the invention may be made without
departing from the spirit and scope of the invention as
disclosed.
* * * * *