U.S. patent application number 11/649923 was filed with the patent office on 2007-07-12 for control valve for variable displacement compressor.
This patent application is currently assigned to TGK CO., LTD.. Invention is credited to Hisatoshi Hirota.
Application Number | 20070157648 11/649923 |
Document ID | / |
Family ID | 37897416 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070157648 |
Kind Code |
A1 |
Hirota; Hisatoshi |
July 12, 2007 |
Control valve for variable displacement compressor
Abstract
In a control valve for a variable displacement compressor, for
controlling the discharge flow rate of refrigerant to be constant,
to dispense with a check valve in a refrigerant outlet port of the
compressor. The control valve includes a first control valve that
controls the passage cross-sectional area of a refrigerant passage
through which refrigerant passes from a discharge chamber of the
compressor to a refrigerant outlet port thereof, and a second
control valve that controls the flow rate of refrigerant allowed to
flow from the discharge chamber to a crankcase such that a
differential pressure (Pdh-Pdl) across the first control valve
generated by the refrigerant passing therethrough becomes constant.
The control valve is configured such that when a solenoid section
is not energized, a first valve element is engaged with a piston to
forcibly fully open the second control valve. The piston has an
outer diameter equal to the inner diameter of a second valve seat,
so that the discharge pressure Pdl on a refrigerant outlet port
side is inhibited from adversely affecting the fully-opening
operation of the second control valve, to thereby maintain the
fully-closed state of the first control valve. This makes it
possible to dispense with a check valve conventionally provided in
the refrigerant outlet port.
Inventors: |
Hirota; Hisatoshi; (Tokyo,
JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
TGK CO., LTD.
Hachioji-shi
JP
|
Family ID: |
37897416 |
Appl. No.: |
11/649923 |
Filed: |
January 5, 2007 |
Current U.S.
Class: |
62/228.1 |
Current CPC
Class: |
F04B 2027/1854 20130101;
F04B 27/1804 20130101; F04B 2205/05 20130101; F04B 2027/185
20130101; F04B 2027/1845 20130101; F04B 2027/1827 20130101 |
Class at
Publication: |
62/228.1 |
International
Class: |
F25B 49/00 20060101
F25B049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 12, 2006 |
JP |
2006-004395 |
Feb 16, 2006 |
JP |
2006-039365 |
Sep 4, 2006 |
JP |
2006-238904 |
Claims
1. A control valve for a variable displacement compressor,
including a first control valve that controls a flow rate of
refrigerant which said first control valve allows to flow from a
discharge chamber of the compressor to a refrigerant outlet port of
the compressor, a second control valve that controls a flow rate of
refrigerant which said second control valve allows to flow from the
discharge chamber into a crankcase of the compressor based on a
differential pressure across said first control valve, to change a
displacement of the compressor, to thereby control the flow rate of
the refrigerant allowed to flow by said first control valve to be
constant, and a solenoid section that sets the flow rate of
refrigerant which said first control valve is to allow to flow,
wherein the control valve is made insensitive to pressure on a
downstream side of said first control valve, and when said solenoid
section is in a non-energized state, said first control valve is in
a fully closed state, and said second control valve is in a fully
open state, said second control valve is forcibly held in the fully
open state even when the pressure on the downstream side of said
first control valve is equal to or higher than pressure on an
upstream side of said first control valve.
2. The control valve according to claim 1, wherein: said first
control valve has a first valve element that has a lift position
thereof set according to an urging force of said solenoid section
and is urged in a valve-closing direction against the urging force
of said solenoid section; said second control valve has a
differential pressure-sensing section that has a same
pressure-receiving area as a pressure-receiving area of part of
said first valve element, which receives the pressure on the
downstream side of said first control valve when said first valve
element is in a closed position, and senses a differential pressure
between the pressure on the upstream side of said first control
valve and the pressure on the downstream side of said first control
valve, which are generated across said first control valve, and a
second valve element that is held by said differential
pressure-sensing section; and upon transition of said solenoid
section from a control state in which said solenoid section sets
said first control valve to a non-energized state, said first valve
element being shifted to a fully closed position by the urging
force engages with said differential pressure-sensing section which
has been away from said first valve element during the control
state, to cause said second valve element to shift to a fully open
position.
3. The control valve according to claim 2, wherein said second
control valve, said first control valve, and said solenoid section
are arranged along a same axis in order, wherein said first control
valve has a first port formed on a side toward said solenoid
section, for introducing refrigerant from the discharge chamber, a
second port formed on a side toward said second control valve, for
discharging refrigerant into the refrigerant outlet port, a first
valve seat provided between said first port and said second port,
and said first valve element disposed on a downstream side of said
first valve seat in a manner movable to and away from said first
valve seat, and said second control valve has a third port
separated from said second port by said differential
pressure-sensing section, for introducing refrigerant from the
discharge chamber, a fourth port formed on a side opposite from
said first control valve and along an axis thereof, for discharging
refrigerant into the crankcase, said differential pressure-sensing
section urged in a valve-closing direction, a second valve seat
disposed in said fourth port, and said second valve element
disposed on an upstream side of said second valve seat and held by
said differential pressure-sensing section in a manner movable to
and away from said second valve seat.
4. The control valve according to claim 3, wherein said first
control valve has a guide slidably disposed along an axis of said
first valve element within a space communicating with said first
port and connected to said first valve element via a valve hole,
for guiding an axial motion of said first valve element, and a
spring disposed between said guide and said first valve seat, for
urging said first valve element in the valve-closing direction.
5. The control valve according to claim 4, wherein said guide has a
same pressure-receiving area as a pressure-receiving area of part
of said first valve element, which receives the pressure on the
upstream side of said first control valve when said first valve
element is in the closed position, and receives the pressure on the
upstream side of said first control valve in a valve-closing
direction of said first control valve.
6. The control valve according to claim 5, wherein said first valve
element is slidably disposed along an axis of said first control
valve within a space communicating with said second port.
7. The control valve according to claim 5, wherein said first valve
element and said guide connected thereto have a refrigerant passage
axially formed therethrough, and a check valve for closing said
refrigerant passage when pressure in said refrigerant passage on a
side toward said second port has become higher than pressure in
said refrigerant passage on a side toward said solenoid
section.
8. The control valve according to claim 6, wherein said first valve
element and said guide connected thereto have a refrigerant passage
axially formed therethrough, and a valve that engages with said
differential pressure-sensing section to thereby close said
refrigerant passage when said first valve element forcibly shifts
said second valve element to a fully open position.
9. The control valve according to claim 4, wherein said guide is
provided with an intercommunicating hole for making pressure in
said solenoid section equal to the pressure on the upstream side of
said first control valve.
10. The control valve according to claim 3, wherein said second
control valve has a piston as said differential pressure-sensing
section for receiving pressure from said second port and pressure
from said third port at axially opposite ends thereof to operate
according to a differential pressure between the pressures, and a
spring urging said piston in the valve closing direction.
11. The control valve according to claim 10, wherein said spring is
disposed between said piston and said first valve element.
12. The control valve according to claim 10, wherein said second
control valve has a film-like seal ring which is disposed on at
least one of open ends of a clearance where the clearance formed
between said piston and a body that axially movably holds said
piston opens toward said second port and said third port, for
sealing the clearance by the pressure from said second port or said
third port.
13. The control valve according to claim 12, wherein said second
control valve has a valve element base portion-accommodating
portion formed in an end face of said piston, opposed to said
second valve seat, and a base portion of said second valve element
is accommodated in said valve element base portion-accommodating
portion in a state urged in the valve-closing direction and in a
manner prevented from coming off.
14. The control valve according to claim 3, wherein said second
control valve has a bellows that has axially opposite ends thereof
tightly connected to said differential pressure-sensing section
holding said second valve element, and a body that axially movably
accommodates said differential pressure-sensing section, said
bellows being capable of axially extending and contracting while
sealing said third port from said second port.
15. The control valve according to claim 3, wherein said second
control valve has a diaphragm as said differential pressure-sensing
section, which is disposed between said second port and said third
port in a manner sealing said second port from said third port, for
receiving pressure from said second port and pressure from said
third port at axially opposite surfaces thereof to cause said
second valve element to operate by a differential pressure between
the pressures.
16. The control valve according to claim 15, wherein said diaphragm
is tightly connected to a body in a state in which an outer
periphery thereof is sandwiched between a first ring and a second
ring, a central portion thereof being sandwiched between a center
disk and a flange portion integrally formed with said second valve
element having a hollow cylindrical shape, said diaphragm being
fixed to a shaft fitted thereon in a manner axially extending
therethrough, together with said center disk and said flange
portion.
17. The control valve according to claim 16, wherein said diaphragm
is configured such that a pressure-receiving area thereof for
receiving pressure when the pressure in said third port is higher
than the pressure in said second port is equal to a
pressure-receiving area of said first valve element for receiving
the pressure from said second port when said first control valve is
in a closed state.
18. The control valve according to claim 17, wherein said diaphragm
is configured such that an inner diameter of said second ring is
made smaller than an inner diameter of said first ring, and an
outer diameter of said flange portion is made smaller than an outer
diameter of said center disk, whereby a pressure-receiving area of
said diaphragm for receiving pressure when the pressure in said
second port is higher than the pressure in said third port is made
smaller than the pressure-receiving area for receiving pressure
when the pressure from said third port is higher than the pressure
from said second port.
19. The control valve according to claim 2, wherein said second
control valve, said first control valve, and said solenoid section
are arranged along a same axis in order, and wherein said first
control valve has a first port formed on a side toward said
solenoid section, for discharging refrigerant into the refrigerant
outlet port, a second port formed on a side toward said second
control valve, for introducing refrigerant from the discharge
chamber, a first valve seat disposed between said first port and
said second port, and said first valve element disposed on an
upstream side of said first valve seat in a manner movable to and
away from said first valve seat, and wherein said second control
valve has a third port formed on a side opposite from said first
control valve and along an axis thereof, for discharging
refrigerant introduced into said second port into the crankcase, a
hollow cylindrical body that has said first valve seat fixed to an
inside thereof and is axially movably disposed in a state urged in
the valve-closing direction, forming said differential
pressure-sensing section, and a second valve element integrally
formed with said hollow cylindrical body, for opening and closing
said third port.
20. The control valve according to claim 19, wherein said first
control valve includes a piston slidably disposed along an axis of
said first valve element within a space communicating with said
first port, and connected to said first valve element via a valve
hole, for guiding an axial motion of said first valve element, and
a spring disposed between said piston and a body accommodating said
piston, for urging said first valve element in a valve-closing
direction.
21. The control valve according to claim 20, wherein said piston is
configured to have a same outer diameter as that of said hollow
cylindrical body of said second control valve, to thereby inhibit
said piston from sensing the pressure on the downstream side of
said first control valve when said first valve element is in the
closed position.
22. The control valve according to claim 20, wherein said first
valve element and said piston connected thereto have a refrigerant
passage axially formed therethrough for causing pressure of the
refrigerant introduced into said second port to be received by an
end face toward said solenoid section via said refrigerant
passage.
23. The control valve according to claim 22, wherein when a shaft
of said solenoid section urges said first valve element, said
refrigerant passage is closed by said shaft.
24. The control valve according to claim 2, wherein said second
control valve, said first control valve, and said solenoid section
are arranged along a same axis in order, and wherein said first
control valve has a first port formed on a side toward said
solenoid section, for discharging refrigerant into the refrigerant
outlet port, a second port formed on a side toward said second
control valve, for introducing refrigerant from the discharge
chamber, a first valve seat disposed between said first port and
said second port, and said first valve element disposed on an
upstream side of said first valve seat in a manner movable to and
away from said first valve seat, and wherein said second control
valve has a third port for discharging refrigerant into the
crankcase, a fourth port formed on a side opposite from said first
control valve and along an axis thereof, for introducing
refrigerant from the discharge chamber, a hollow cylindrical body
disposed within a space communicating with said second port and
having said first valve seat rigidly fixed to an inside thereof in
a state urged in the valve-closing direction, forming said
differential pressure-sensing section, a second valve seat provided
in said fourth port, and a second valve element that is disposed
such that one end thereof is opposed to said second valve seat, and
the other end thereof is urged in the valve closing direction with
respect to said first valve element, for thereby being engaged with
said hollow cylindrical body, and is movable to and away from said
second valve seat.
25. The control valve according to claim 24, wherein said first
control valve includes a piston slidably disposed along an axis of
said first valve element within a space communicating with said
first port, and connected to said first valve element via a valve
hole, for guiding an axial motion of said first valve element, and
a spring disposed between said piston and a body accommodating said
piston, for urging said first valve element in the valve-closing
direction, and wherein said first valve element has a refrigerant
passage axially formed therethrough which is closed by a shaft of
said solenoid section when said shaft urges said first valve
element.
26. The control valve according to claim 25, wherein said piston is
configured such that a portion thereof receiving the pressure at
said first port in the valve-closing direction has a same outer
diameter as that of said hollow cylindrical body of said second
control valve, to thereby inhibit said piston from sensing the
pressure on the downstream side of said first control valve when
said first valve element is in the closed position.
Description
CROSS-REFERENCE TO RELATED APPLICATION, IF ANY
[0001] This application claims priority of Japanese Application No.
2006-004395 filed on Jan. 12, 2006, entitled "Control Valve For
Variable Displacement Compressor", No. 2006-039365 filed on Feb.
16, 2006, entitled "Control Valve For Variable Displacement
Compressor", and No. 2006-238904 filed on Sep. 4, 2006, entitled
"Control Valve For Variable Displacement Compressor".
BACKGROUND OF THE INVENTION
[0002] (1) Field of the Invention
[0003] The present invention relates to a control valve for a
variable displacement compressor, and more particularly to a
control valve for a variable displacement compressor, for
controlling a flow of refrigerant discharged from the compressor to
a constant flow rate.
[0004] (2) Description of the Related Art
[0005] As a compressor used in the refrigeration cycle of an
automotive air conditioner, for compressing refrigerant, a variable
displacement compressor capable of varying the volume (discharge
amount) of refrigerant is employed so as to obtain an adequate
cooling capacity without being constrained by the rotational speed
of an engine which is the drive source of the compressor. In such a
variable displacement compressor, pistons that reciprocate in
parallel with a rotational shaft driven by the engine for rotation
are connected to a wobble plate (swash plate) fitted on the
rotational shaft, and by rotating the wobble plate while varying
the inclination angle thereof within a crankcase, the stroke of the
pistons is varied to control the capacity of the compressor, that
is, the discharge amount of refrigerant.
[0006] In order to change the inclination angle of the wobble
plate, the balance of pressures acting on the both sides of each
piston connected to the wobble plate is changed by introducing part
of compressed refrigerant into a hermetically closed crankcase to
cause a change in the pressure in the crankcase.
[0007] In general, pressure in the crankcase is changed by
controlling a control valve for the compressor provided in a
passage communicating between the discharge chamber and the
crankcase such that communication through the control valve is
allowed or blocked. Now, when the control valve is set to a
predetermined valve lift, if the rotational speed of the engine
increases, pressure introduced from the discharge chamber into the
crankcase increases to make the inclination angle of the wobble
plate close to an angle perpendicular to the rotational shaft,
whereby the volume of compressible refrigerant is controlled to be
small. Inversely, when the rotational speed of the engine lowers,
pressure introduced into the crankcase decreases whereby the volume
of compressible refrigerant is controlled to be large. Thus, the
variable displacement compressor is controlled such that the volume
of discharged refrigerant is not varied irrespective of the
rotational speed of the engine.
[0008] As methods for controlling the displacement of a variable
displacement compressor using a control valve therefor, it is
generally known, for example, to cause suction pressure Ps in the
suction chamber to be held constant, and to cause the differential
pressure between the suction pressure Ps in the suction chamber and
a discharge pressure Pd in the discharge chamber to be held
constant. It is also known to cause the flow rate of refrigerant
discharged from the compressor to become constant (see e.g.
Japanese Unexamined Patent Publication No. 2001-107854 (Paragraph
Nos. [0035] to [0036], and FIG. 3)).
[0009] According to this control valve for a variable displacement
compressor, disclosed in Japanese Unexamined Patent Publication No.
2001-107854, the differential pressure between two pressure
monitoring points is detected by sensors to thereby indirectly
grasp the flow rate of refrigerant drawn into the suction chamber,
and the control valve controls the flow rate of refrigerant
introduced from the discharge chamber into the crankcase such that
the flow rate of refrigerant drawn into the suction chamber becomes
constant, whereby the flow rate of refrigerant discharged from the
compressor is controlled to be constant.
[0010] In contrast, a control valve for a variable displacement
compressor is also known which dispenses with the sensors for
detecting the differential pressure between two pressure monitoring
points (see e.g. Japanese Unexamined Patent Publication No.
2004-116349 (Paragraph Nos. [0102] to [0108], and FIG. 12)). This
control valve comprises a first control valve that controls the
flow rate of refrigerant allowed to flow from a discharge chamber
of the compressor to a refrigerant outlet port of the compressor, a
second control valve that senses the differential pressure across
the first control valve using a diaphragm thereof and controls the
flow rate of refrigerant allowed to flow from the discharge chamber
into a crankcase of the compressor based on the differential
pressure, to change the displacement of the compressor, to thereby
control the flow rate of refrigerant which the first control valve
allows to flow to be constant, and a solenoid section that sets the
flow rate of refrigerant to be allowed to flow by the first control
valve, all of which are arranged along the same axis. According to
this control valve, the first control valve forms a variable
orifice that has its passage area of a refrigerant passage set by
the solenoid section according to changes in external conditions,
and the second control valve senses the differential pressure
across the variable orifice, and controls pressure in the crankcase
such that the differential pressure becomes equal to a
predetermined value. As a result, the differential pressure across
the variable orifice set to a certain passage area is held at the
predetermined value, whereby the flow rate of refrigerant
discharged from the compressor is controlled to be constant.
[0011] In the conventional control valve disclosed in the
above-described Japanese Unexamined Patent Publication No.
2004-116349, when the compressor stops its operation, its
capability of compressing and discharging refrigerant is suddenly
lost to invert the relationship in pressure between the discharge
chamber that has been at high pressure and the refrigerant outlet
port located downstream of the first control valve. This acts not
to control the second control valve to the minimum displacement
side but to control the same to the maximum displacement side. To
solve this problem, the conventional control valve is configured
assuming that a check valve is provided at the refrigerant outlet
port so as to prevent the first control vale from being adversely
affected by the pressure at the refrigerant outlet port upon
stoppage of the compressor. Therefore, the variable displacement
compressor using the conventional control valve suffers from the
problem of increased manufacturing costs due to the necessity of
provision of the check valve.
SUMMARY OF THE INVENTION
[0012] The present invention has been made in view of the above
problems, and an object thereof is to provide a control valve for a
variable displacement compressor, which is of a type that controls
the flow rate of discharged refrigerant, without requiring a check
valve to be provided at a refrigerant outlet port of the
compressor.
[0013] To solve the above problem, the present invention provides a
control valve for a variable displacement compressor, including a
first control valve that controls a flow rate of refrigerant which
the first control valve allows to flow from a discharge chamber of
the compressor to a refrigerant outlet port of the compressor, a
second control valve that controls a flow rate of refrigerant which
the second control valve allows to flow from the discharge chamber
into a crankcase of the compressor based on a differential pressure
across the first control valve, to change a displacement of the
compressor, to thereby control the flow rate of the refrigerant
allowed to flow by the first control valve to be constant, and a
solenoid section that sets the flow rate of refrigerant which the
first control valve is to allow to flow, wherein the control valve
is made insensitive to pressure on a downstream side of the first
control valve, and when the solenoid section is in a non-energized
state, the first control valve is in a fully closed state, and the
second control valve is in a fully open state, the second control
valve is forcibly held in the fully open state even when the
pressure on the downstream side of the first control valve is equal
to or higher than pressure on an upstream side of the first control
valve.
[0014] The above and other objects, features and advantages of the
present invention will become apparent from the following
description when taken in conjunction with the accompanying
drawings which illustrate preferred embodiments of the present
invention by way of example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a central longitudinal cross-sectional view of the
whole construction of a control valve for a variable displacement
compressor, according to a first embodiment.
[0016] FIG. 2 is a partial enlarged cross-sectional view of the
construction of a valve section of the control valve according to
the first embodiment.
[0017] FIG. 3 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a second embodiment.
[0018] FIG. 4 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a third embodiment.
[0019] FIG. 5 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a fourth embodiment.
[0020] FIG. 6 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a fifth embodiment.
[0021] FIG. 7 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a sixth embodiment.
[0022] FIG. 8 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a seventh embodiment.
[0023] FIG. 9 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to an eighth embodiment.
[0024] FIGS. 10A to 10C are views for explaining characteristics of
a diaphragm, in which FIG. 10A shows a state in which no
differential pressure is applied to the diaphragm, FIG. 10B shows a
state in which the diaphragm is displaced by a differential
pressure, and FIG. 10C shows a state in which the differential
pressure is applied to the displaced diaphragm in a direction
opposite to the direction of the displacement.
[0025] FIGS. 11A to 11C are explanatory views showing the
construction of a differential pressure-sensing section of the
control valve according to the eighth embodiment, in which FIG. 11A
shows a case where pressure in a discharge chamber of the
compressor is higher than pressure in a refrigerant outlet port of
the compressor, and FIG. 11B shows a case where the pressure in the
discharge chamber is lower than the pressure in the refrigerant
outlet port.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Hereinafter, embodiments of the present invention will be
described in detail with reference to the drawings.
[0027] FIG. 1 is a central longitudinal cross-sectional view of the
whole construction of a control valve for a variable displacement
compressor, according to a first embodiment of the present
invention. FIG. 2 is a partial enlarged cross-sectional view
showing the construction of a valve section of the control valve
according to the first embodiment.
[0028] The control valve 10 for a variable displacement compressor
comprises a first control valve 10A that controls a passage
cross-sectional area of a refrigerant passage through which
high-pressure refrigerant flows from a discharge chamber of the
compressor to a refrigerant outlet port thereof, a second control
valve 10B that controls the flow rate of refrigerant to be supplied
from the discharge chamber to a crankcase of the compressor, and a
solenoid section 10C that sets the passage cross-sectional area of
the refrigerant passage of the first control valve 10A, all of
which are arranged on the same axis.
[0029] The first control valve 10A and the second control valve 10B
have a first body 11 and a second body 12 press-fitted into the
first body 11. The first body 11 and the second body 12 are
provided with a port 13, a port 14, and a port 15. When the control
valve 10 is mounted in the compressor, the port 13, the port 14,
and the port 15 are communicated respectively with the discharge
chamber of the compressor, for introducing refrigerant at discharge
pressure Pdh into the first control valve 10A, with the refrigerant
outlet port of the compressor, for discharging refrigerant at
discharge pressure Pdl from the first control valve 10A, and with
the discharge chamber of the compressor, for introducing
refrigerant at discharge pressure Pdh2 into the second control
valve 10B. The second body 12 has foremost end formed with a port
16 that is communicated with the crankcase of the compressor, for
discharging refrigerant at pressure Pc from the second control
valve 10B.
[0030] Although the control valve 10 can be applied to a variable
displacement compressor configured such that when the control valve
10 is mounted therein, the port 13 at the discharge pressure Pdh
and the port 15 at the discharge pressure Pdh2 both communicate
with the discharge chamber thereof, it is preferable that the
control valve 10 is applied to a variable displacement compressor
configured such that the port 13 at the discharge pressure Pdh is
directly communicated with the discharge chamber, and the port 15
at the discharge pressure Pdh2 is communicated with an outlet port
of an oil separator disposed on the downstream side of the
discharge chamber. This enables the second control valve 10B to
return compressor lubricating oil, contained in refrigerant in a
large amount, while controlling pressure Pc in the crankcase.
[0031] The first control valve 10A has a passage axially formed
through the second body 12 such that the passage communicates
between the port 13 at the discharge pressure Pdh and the port 14
at the discharge pressure Pdl. A first valve seat 17 is rigidly
press-fitted in the passage, and a first valve element 18 is
disposed on the downstream side of the first valve seat 17 in a
manner movable to and away from the first valve seat 17.
[0032] The first valve element 18 has a hollow cylindrical portion
integrally formed in a manner axially extending through a valve
hole, and a guide 19 is rigidly press-fitted in the hollow
cylindrical portion. The guide 19 is urged by a spring 20 in the
valve-closing direction of the first control valve 10A. The guide
19 is configured such that a portion thereof in sliding contact
with an inner wall of the first body 11 has an outer diameter equal
to the inner diameter of the first valve seat 17, whereby the
discharge pressure Pdh introduced into the port 13 equally acts on
the first valve element 18 and the guide 19 in respective opposite
directions to prevent the discharge pressure Pdh from adversely
affecting the control operation of the first control valve 10A.
[0033] The guide 19 has a refrigerant passage axially extending
therethrough, and is provided with a check valve 21 for opening and
closing the refrigerant passage. The check valve 21 has a valve
element 22, e.g. made of rubber, disposed on a low-pressure side of
the refrigerant passage formed in the guide 19, that is, on the
side communicating with the port 14 at the discharge pressure Pdl
via the first valve element 18, and a leaf spring 23 for axially
movably holding the valve element 22. In a neutral state of the
valve element 22 in which no pressure acts thereon, the valve
element 22 is held at a position where the refrigerant passage is
slightly open, by the leaf spring 23.
[0034] The second control valve 10B has a second valve seat 31 that
is press-fitted into the foremost end of the second body 12, which
has the port 16 formed therethrough in the axial direction, and a
second valve element 32 disposed on the upstream side of the second
valve seat 31 in a manner movable to and away from the second valve
seat 31 such that the second valve element 32 opens and closes the
port 16 on the upstream side. The second valve element 32 is
axially movably held by the second body 12, and is mounted on the
piston 33 forming a differential pressure-sensing section. More
specifically, the piston 33 is configured such that it has a valve
element base portion-accommodating portion 34 recessed in a surface
thereof opposed to the second valve seat 31, for having a spring 35
and a base portion of the second valve element 32 arranged in the
accommodating portion 34, and an open end of the accommodating
portion 34 is swaged to prevent the second valve element 32 from
being pushed out by the spring 35. This makes it possible to soften
impact of collision which is caused between the second valve
element 32 and the second valve seat 31 when the second control
valve 10B is fully closed quickly.
[0035] Further, the piston 33 is urged in the valve-closing
direction of the second control valve 10B by a spring 37 disposed
between the piston 33 and a spring-receiving portion 36 rigidly
press-fitted into the second body 12 from the side toward the port
14. The spring 37 is set to a spring force smaller than that of the
spring 20 urging the first control valve 10A in the valve-closing
direction. Furthermore, the piston 33 is integrally formed with an
extended portion 38 extended therefrom toward the solenoid section
10c into the first valve element 18. A washer 39 is fixed to an end
of the extended portion 38 by swaging. The washer 39 is brought
into engagement with a stepped portion formed on the first valve
element 18. Thus, when the first control valve 10A is fully closed,
the piston 33 is forcibly pulled by the first valve element 18 in
the valve-opening direction of the second control valve 10B, and
hence the second control valve 10B can be held in the fully open
state. Further, the piston 33 is configured to have an outer
diameter equal to the inner diameter of the first valve seat 17
such that when the piston 33 is engaged with the first valve
element 18, the piston 33 is prevented from being adversely
affected by the discharge pressure Pdl.
[0036] Furthermore, the second control valve 10B has film-like seal
rings 40 and 41 formed e.g. of rubber for sealing clearances
between the piston 33 and the second body 12 by pressures in the
ports 14 and 15. The seal rings 40 and 41 are arranged between a
stepped portion of the second body 12 and the spring-receiving
portion 36 and between a stepped portion of the second body 12 and
the second valve seat 31, respectively.
[0037] The solenoid section 10c has a core 51 rigidly press-fitted
into a central opening of the first body 11. The core 51 is fitted
into an opening of a bottomed sleeve 52 in a manner blocking the
opening. The bottomed sleeve 52 contains a plunger 53, a shaft 54
axially extending through the core 51 and rigidly fixed to the
plunger 53, an adjustment member 55 disposed on a bottom of the
bottomed sleeve 52 for axially plastically deforming the bottom,
thereby adjusting spring loads, a spring 56 disposed between the
core 51 and the plunger 53, and a spring 57 disposed between the
plunger 53 and the adjustment member 55. The shaft 54 is axially
movably held by the core 51 and the plunger 53, with a free end
thereof extending into the guide 19. When the solenoid section 10c
is energized, the free end is brought into abutment with an
intercommunicating plate 24 fitted on a side of the guide 19
opposite from a side where the check valve 21 is disposed for the
refrigerant passage formed in the guide 19, for urging the first
valve element 18 in the valve-opening direction of the first
control valve 10A. Arranged around the outer periphery of the
bottomed sleeve 52 are a coil 58 and a yoke 59.
[0038] On the outer peripheries of the first body 11 and the second
body 12, there are circumferentially provided an O ring 61 for
sealing between the port 13 and the port 14, an O ring 62 for
sealing between the port 14 and the port 15, an O ring 63 for
sealing between the port 15 and the port 16, and an O ring 64 for
sealing between the port 13 and the atmosphere, when the control
valve 10 is mounted in the compressor.
[0039] In the control valve 10 configured as above, when the
compressor is driven for rotation by the driving force of the
engine, the compressor draws refrigerant from a suction chamber for
compression, and discharges the compressed refrigerant.
[0040] At this time, when the solenoid section 10C is not
energized, as shown in FIG. 1, the first control valve 10A is
forcibly fully closed by the urging force of the spring 20, and the
second control valve 10B is fully open since the piston 33 is
pulled in the valve-opening direction against the urging force of
the spring 37 by the first valve element 18. Therefore, since all
the refrigerant discharged from the discharge chamber is introduced
into the crankcase via the second control valve 10B, the compressor
is in the minimum displacement operation state. As described above,
when the solenoid section 10C is not energized, the compressor is
in the minimum displacement operation state, so that the control
valve 10 can be applied to a variable displacement compressor which
does not necessitate an electromagnetic clutch for performing
On-Off control of transmission of the driving force between the
compressor and the engine for driving the compressor for
rotation.
[0041] Now, when the compressor is started, control current is
supplied to the solenoid section 10C. As the control current
increases, the plunger 53 is pulled by the core 51, whereby the
first valve element 18 is pushed upward by the shaft 54, as viewed
in FIG. 1. In accordance with the upward motion of the first valve
element 18, the piston 33 of the second control valve 10B, engaged
with the first valve element 18, is also pushed upward, as viewed
in FIG. 1, by the spring 37, until the second valve element 32 is
seated on the second valve seat 31 to fully close the second
control valve 10B. As a result, since all the refrigerant
discharged from the discharge chamber ceases to be introduced into
the crankcase, the compressor is now shifting to the maximum
displacement operation.
[0042] When the control current is further increased, the first
valve element 18 continues to be lifted, but in the second control
valve 10B, which has been shifting in the valve-closing direction
along with the lift of the first valve element 18, the motion of
the piston 33 is stopped by the second valve element 32 being
seated on the second valve seat 31, and therefore the first valve
element 18 is disengaged from the piston 33.
[0043] After that, when the control current is held at a
predetermined value, the first valve element 18 is stopped at a
position where the urging force of the solenoid section 10C
corresponding to the predetermined value and the urging force of
the spring 20 against the solenoid force are balanced. The position
where the first valve element 18 is stopped does not change until
the value of the control current is changed. As described above,
the first valve element 18 is stopped after being lifted from the
first valve seat 17, whereby the first control valve 10A is set to
a predetermined passage cross-sectional area with respect to the
refrigerant passage thereof, to allow refrigerant at the discharge
pressure Pdh, introduced into the port 13, to flow through the
refrigerant passage having the predetermined passage
cross-sectional area, so that refrigerant at the discharge pressure
Pdl is discharged from the port 14.
[0044] When refrigerant flows through the first control valve 10A,
a predetermined differential pressure (Pdh-Pdl=.DELTA.P) is
generated across the first control valve 10A. Since the discharge
pressure Pdh2 of refrigerant supplied to the port 15 of the second
control valve 10B is approximately equal to the discharge pressure
Pdh of refrigerant supplied to the port 13 of the first control
valve 10A, the differential pressure .DELTA.P generated across the
first control valve 10A can be sensed by the piston 33.
[0045] Up to this time point, the compressor has been operating
toward its maximum displacement operation, so that the discharge
pressure Pdh presently increases, and the flow rate of refrigerant
passing through the first control valve 10A also increases. When
the flow rate of refrigerant becomes larger than a predetermined
value, an urging force in the valve-opening direction, caused by
application of the differential pressure
(Pdh2-Pdl.apprxeq..DELTA.P) to the piston 33, comes to overcome the
urging force of the spring 37, causing the second valve element 32
to be moved away from the second valve seat 31 to open the second
control valve 10B. This causes refrigerant discharged from the
discharge chamber to be introduced into the crankcase, which starts
the variable displacement of the compressor.
[0046] After that, when the flow rate of refrigerant passing
through the first control valve 10A increases to increase the
differential pressure A P across the first control valve 10A, the
piston 33 senses a change in the differential pressure to further
open the second control valve 10B, and controls the compressor in a
direction of decreasing the displacement thereof. Further, when the
flow rate of refrigerant flowing through the first control valve
10A decreases to decrease the differential pressure .DELTA.P across
the first control valve 10A, the piston 33 senses a change in the
differential pressure to cause the second control valve 10B to
shift in the valve-closing direction, and controls the compressor
in a direction of increasing the displacement thereof.
[0047] At this time, although in the second control valve 10B,
refrigerant at the discharge pressure Pdh2, supplied from the port
15, is about to leak into the port 14 via the clearance between the
piston 33 and the second body 12, the leakage of the refrigerant is
sealed by the seal ring 41 pressurized for deformation by the
discharge pressure Pdh2. Further, although refrigerant at the
discharge pressure Pdh, supplied from the port 13, leaks into the
guide 19 via a portion where the guide 19 and the first body 11 are
in sliding contact with each other, and leaks further into the port
14 via the check valve 21, this slight leakage is negligible since
the leakage does not adversely affect the operations of the control
valve 10 and the compressor.
[0048] As described above, the piston 33 of the second control
valve 10B senses the differential pressure A P across the first
control valve 10A, which is generated by refrigerant passing
through the first control valve 10A set to the predetermined
passage cross-sectional area, and the second control valve 10B
controls the flow rate of refrigerant supplied to the crankcase
such that the differential pressure A P is held constant. This
enables the control valve 10 to control the compressor such that
refrigerant is discharged at a flow rate corresponding to control
current supplied to the solenoid section 10C.
[0049] Next, operation for stopping the control valve 10 in the
above control state will be described hereinafter.
[0050] When the supply of the control current to the solenoid
section 10C is suddenly stopped so as to stop the compressor, the
solenoid force which has set the lift amount of the first control
valve 10A is lost, whereby the first control valve 10A is
instantaneously fully closed by the urging force of the spring 20.
This allows the first valve element 18 to pull the piston 33
downward, as viewed in FIG. 1, to thereby fully close the second
control valve 10B forcibly. This causes the compressor to shift to
the minimum displacement operation.
[0051] When the compressor shifts to the minimum displacement
operation, the discharge pressure Pdh from the compressor quickly
decreases, but the discharge pressure Pdl at the refrigerant outlet
port of the compressor progressively decreases since the first
valve element 18 is in the fully-closed state. Therefore, the
discharge pressure Pdl sometimes becomes higher than the discharge
pressure Pdh immediately after stoppage of the control current to
the solenoid section 10C. In this case, the first control valve 10A
is held in the fully-closed state since the discharge pressure Pdl
acts on the first valve element 18 and the check valve 21 in the
valve-closing directions, while the second control valve 10B is
held in the fully-open state without being caused to operate by the
discharge pressure Pdl since the piston 33 and the first valve
element 18 engaged with the piston 33 have the same
pressure-receiving area. At this time, leakage of refrigerant from
the port 14 to the port 15 via the clearance between the second
body 12 and the piston 33 is sealed by the seal ring 40.
[0052] As described hereinbefore, even when the discharge pressure
Pdl on the refrigerant outlet port side of the compressor becomes
equal to or higher than the discharge pressure Pdh on the discharge
chamber side of the compressor, the first control valve 10A can be
held in the fully-closed state, which enables the first control
valve 10A to act similarly to the check valve conventionally
provided in the refrigerant outlet port of the compressor, and the
second control valve 10B can be held in the fully-open state, which
enables the compressor to positively shift to the minimum
displacement operation state. This means that the check valve
conventionally provided in the refrigerant outlet port of the
compressor is dispensed with.
[0053] FIG. 3 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a second embodiment. In FIG. 3, component
elements which have functions identical to or equivalent to those
of the component elements appearing in FIG. 1, are designated by
identical reference numerals, and detailed description thereof is
omitted.
[0054] The control valve 70 according to the second embodiment is
distinguished from the control valve 10 according to the first
embodiment in that it is not equipped with the check valve 21
formed on the guide 19.
[0055] More specifically, in a first control valve 70A of the
control valve 70, the guide 19 connected to the first valve element
18 for operation in unison therewith comprises a hollow cylindrical
portion having a closed end, and a sliding portion which is
integrally formed with the hollow cylindrical portion, and radially
outwardly extends from an open end of the hollow cylindrical
portion such that an outer peripheral surface of the extended
portion slides on the inner wall surface of the first body 11. The
shaft 54 of a solenoid section 70C extends into the hollow
cylindrical portion for abutment with the closed end of the hollow
cylindrical portion. Further, the guide 19 has an
intercommunicating hole 19a formed in a side of the hollow
cylindrical portion such that pressure in the solenoid section 70C
always becomes equal to the discharge pressure Pdh on the upstream
side of the first control valve 70A. The other features of
configuration of the control valve 70 according to the second
embodiment are the same as those of the control valve 10 according
to the first embodiment.
[0056] In the control valve 70 configured as above, first, when the
solenoid section 70C is not energized, as shown in FIG. 3, the
first control valve 70A is fully closed by the urging force of the
spring 20, and a second control valve 70B is fully open since the
first valve element 18 of the first control valve 70A forcibly
pulls the piston 33 that senses a differential pressure across the
first control valve 70A, in the valve-opening direction. This
allows the discharge chamber and the crankcase to communicate with
each other via the second control valve 70B, and hence the
compressor is in the minimum displacement operation state.
[0057] Then, when control current is supplied to the solenoid
section 70C, as the control current increases, the shaft 54 of the
solenoid section 70C lifts the first valve element 18 of the first
control valve 70A, whereby the first control valve 70A starts to be
opened, and the second control valve 70B starts to shift in the
valve-closing direction in an interlocked manner. After that, when
the second control valve 70B is closed, the compressor is placed in
the maximum displacement operation state. After the second control
valve 70B is closed, the first control valve 70A is positioned in a
lift position corresponding to the control current, and is set to a
passage cross-sectional area corresponding to the control current,
without being interlocked with the second control valve 70B.
[0058] When the compressor shifts to the maximum displacement
operation state, the flow rate of refrigerant passing through the
first control valve 70A increases. When the differential pressure
across the first control valve 70A becomes equal to or larger than
a predetermined value, the piston 33 that senses the differential
pressure acts to open the second control valve 70B to make the
displacement of the compressor variable.
[0059] If the solenoid section 70C is deenergized when the control
valve 70 is in the control state, the first control valve 70A is
fully closed instantaneously by the spring 20, and the second
control valve 70B is constrained and forcibly fully opened during
transition of the first control valve 70A to the fully-closed
state. This sharply decreases the discharge pressure Pdh in the
discharge chamber while progressively decreasing the discharge
pressure Pdl at the refrigerant outlet port of the compressor, to
thereby invert the relationship between the discharge pressure Pdh
and the discharge pressure Pdl. However, the first valve element 18
and the piston 33 integrally engaged with each other have the same
pressure-receiving area, and are insensitive to the discharge
pressure Pdl, so that even if the discharge pressure Pdl becomes
higher than the discharge pressure Pdh, the fully-closed state of
the first control valve 70A and the fully-open state of the second
control valve 70B are maintained.
[0060] FIG. 4 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a third embodiment. In FIG. 4, component
elements which have functions identical to or equivalent to those
of the component elements appearing in FIGS. 1 and 3, are
designated by identical reference numerals, and detailed
description thereof is omitted.
[0061] The control valve 80 according to the third embodiment is
distinguished from the control valves 10 and 70 according to the
first and second embodiments in that its construction is simplified
by forming the two ports 13 and 15 through which refrigerant from
the discharge chamber is introduced, into a common port.
[0062] More specifically, in the control valve 80, a first control
valve 80A thereof has the first valve element 18 disposed on the
upstream side of the first valve seat 17. The first valve element
18 has a through hole axially formed therethrough, and a hollow
cylindrical portion 81 extending via a valve hole is rigidly
press-fitted into the through hole. The hollow cylindrical portion
81 is integrally formed with a piston 82 axially slidably disposed
within the first body 11. A hollow part of the hollow cylindrical
portion 81 extends into the piston 82 such that the hollow part
communicates with a side opposite to the side where the hollow
cylindrical portion 81 is formed, and the hollow part extending
through the piston 82 forms a refrigerant passage 83 through which
the discharge pressure Pdh is introduced into the solenoid section
80C. Further, the piston 82 is urged in the valve-closing direction
of the first control valve 80A by the spring 20 disposed between
the piston 82 and an end face of the second body 12. Furthermore,
the piston 82 is configured such that it has a large outer diameter
on the side toward a second control valve 80B, whereby the first
control valve 80A has a valve structure in which when the urging
force of the spring 20 exceeds the urging force of the solenoid
section 80C, the clearance between the first body 11 and the piston
82 is sealed.
[0063] In the second control valve 80B, the port 16 is formed in
the center of a foremost end of the second body 12, and an inner
open end of the port 16 forms a second valve seat. The second valve
element 32 is disposed in a manner movable to and away from the
second valve seat. The second valve element 32 is integrally formed
with a hollow cylindrical body 84 axially slidably disposed within
the second body 12. The hollow cylindrical body 84 has the same
outer diameter as that of the piston 82 of the first control valve
80A, and at the same time is formed with a plurality of
intercommunicating holes. Further, the hollow cylindrical body 84
has the first valve seat 17 of the first control valve 80A rigidly
press-fitted into the inside thereof. Disposed between the first
valve seat 17 and the piston 82 is the spring 37 for urging the
hollow cylindrical body 84 in the valve-closing direction of the
second control valve 80B.
[0064] In the control valve 80 configured as above, first, when the
solenoid section 80C is not energized, as shown in FIG. 4, the
first control valve 80A is fully closed by the urging force of the
spring 37 since the first valve seat 17 has the first valve element
18 brought into abutment therewith, while in the second control
valve 80B, the second valve element 32 integrally formed with the
hollow cylindrical body 84 is held in a fully-open position since
the first valve seat 17 rigidly fixed to the hollow cylindrical
body 84 has the first valve element 18 brought into abutment
therewith by the spring 37. This allows the discharge chamber and
the crankcase to communicate with each other via the second control
valve 80B, and hence the compressor is in the minimum displacement
operation state.
[0065] Then, when control current is supplied to the solenoid
section 80C, as the control current increases, the shaft 54 of the
solenoid section 80C pushes the piston 82 of the first control
valve 80A upward, as viewed in FIG. 4, whereby the movable parts of
the first control valve 80A and the second control valve 80B move
in unison in the valve-closing direction of the second control
valve 80B. After that, when the second valve element 32 is seated
on the second valve seat to close the second control valve 80B, the
compressor shifts to the maximum displacement operation state.
Then, when the piston 82 is pushed in the valve-closing direction
of the second control valve 80B, the first valve element 18 is
progressively lifted from the first valve seat 17 to progressively
open the first control valve 80A. Subsequently, the first valve
element 18 stops at a lift position corresponding to the control
current, and the first control valve 80A is set to a passage
cross-sectional area corresponding to the control current.
[0066] When the compressor shifts to the maximum displacement
operation state, the flow rate of refrigerant passing through the
first control valve 80A increases to generate a differential
pressure across the first control valve 80A. This differential
pressure is received by the cross-sectional areas of the first
valve seat 17 and the hollow cylindrical body 84 forming a
differential pressure-sensing section. When the differential
pressure becomes equal to or larger than a predetermined value, the
first valve seat 17 and the hollow cylindrical body 84, which sense
the differential pressure, act to open the second control valve 80B
to make the displacement of the compressor variable.
[0067] Now, when the discharge pressure Pdh increases while the
compressor is being controlled at a predetermined displacement, the
second control valve 80B operates in the valve-opening direction to
control the capacity in a direction of decreasing the same, whereas
when the discharge pressure Pdh decreases, the second control valve
80B operates in the valve-closing direction to control the capacity
in a direction of increasing the same. At this time, although the
first control valve 80A as well changes in accordance with the
change in the discharge pressure Pdh, the displacement of the
compressor is determined depending on the control balance between
the first control valve 80A and the second control valve 80B, and
is substantially set to a predetermined displacement.
[0068] If the solenoid section 80C is suddenly deenergized when the
control valve 80 is in the control state, the first control valve
80A is fully closed instantaneously by the spring 20, and the
second control valve 80B is constrained and forcibly fully opened
during transition of the first control valve 80A to the
fully-closed state. This sharply decreases the discharge pressure
Pdh in the discharge chamber while progressively decreasing the
discharge pressure Pdl in the refrigerant outlet port of the
compressor, so that the discharge pressure Pdl at the refrigerant
outlet port presently becomes higher than the discharge pressure
Pdh in the discharge chamber. However, the pressure-receiving area
at which the first valve seat 17, the first valve element 18, and
the hollow cylindrical body 84, which are integrally engaged with
each other, receive the discharge pressure Pdl in the upward
direction, as viewed in FIG. 4, is the same as the
pressure-receiving area at which the piston 33 receives the
discharge pressure Pdl in the downward direction, as viewed in FIG.
4, so that the control valve 80 has a structure insensitive to the
discharge pressure Pdl. Accordingly, even if the discharge pressure
Pdl becomes higher than the discharge pressure Pdh, the
fully-closed state of the first control valve 80A and the
fully-open state of the second control valve 80B are
maintained.
[0069] FIG. 5 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a fourth embodiment. In FIG. 5, component
elements which have functions identical to or equivalent to those
of the component elements appearing in FIG. 4, are designated by
identical reference numerals, and detailed description thereof is
omitted.
[0070] The control valve 90 according to the fourth embodiment is
distinguished from the control valve 80 according to the third
embodiment in that the control valve 90 is improved in speed at
which it returns again to the control state after suddenly
transitioning from the control state to the stopped state.
[0071] More specifically, in the control valve 90, the first valve
element 18 and the hollow cylindrical portion 81 are integrally
formed with each other, and the refrigerant passage 83 is linearly
axially formed therethrough. The hollow cylindrical portion 81 is
fixed to the piston 82 in a manner extending therethrough, and an
open end of the refrigerant passage 83 on the side toward a
solenoid section 90C is opened and closed by an end face of the
shaft 54. With this configuration, the control valve 90 has a valve
structure in which when the solenoid section 90C is not energized
as shown in FIG. 5, the port 13 through which the discharge
pressure Pdh is introduced, and the inside of the solenoid section
90C are communicated with each other, whereas when the solenoid
section 90C is energized, the communication between the port 13
through which the discharge pressure Pdh is introduced, and the
inside of the solenoid section 90C is blocked.
[0072] In the construction described above, the basic operation of
the control valve 90 is the same as that of the FIG. 4 control
valve 80 according to the third embodiment. However, when the
solenoid section 90C is energized immediately after the control
valve 90 has suddenly shifted or transitioned from the control
state to the stopped state, to return again to the control state,
the shaft 54 lifts the first valve element 18 while closing the
open end of the hollow cylindrical portion 81. When the first valve
element 18 is lifted even in a slight degree, the piston 82 as well
is lifted accordingly, to open the clearance between the piston 82
and the first body 11, and refrigerant at still high discharge
pressure Pdl is introduced into a space formed between the piston
82 and the solenoid section 90C. This causes an urging force for
causing a first control valve 90A to operate in the valve-opening
direction to act on the piston 82, which helps the solenoid section
90C cause the first control valve 90A to operate in the
valve-opening direction. This shortens a time period required for
fully opening a second control valve 90B, and makes it possible for
the control valve 90 to return to its original control state
sooner.
[0073] FIG. 6 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a fifth embodiment. In FIG. 6, component
elements which have functions identical to or equivalent to those
of the component elements appearing in FIGS. 1 and 5, are
designated by identical reference numerals, and detailed
description thereof is omitted.
[0074] In the control valve 100 according to the fifth embodiment,
the structure of the control valve 90 according to the fourth
embodiment is applied to the control valve 10 according to the
first embodiment, which has the ports 13 and 15 formed
independently of each other for introducing refrigerant into the
first control valve 10A and the second control valve 10B,
respectively, and further the control valve 90 according to the
fourth embodiment is improved in that the pressure Pc in the
crankcase acts on the second control valve 90B in the valve-opening
direction.
[0075] More specifically, in the control valve 100, the second
valve seat 31 forming the port 15 for introducing the discharge
pressure Pdh2 is formed on the foremost end of the second body 12,
and the second valve element 32 is axially movably supported by the
second body 12 in a manner opposed to the second valve seat 31. An
end of the second valve element 32 on the side toward a solenoid
section 100C extends up to a chamber of the port 13 into which the
discharge pressure Pdh is introduced, and an engaging portion 101
held by a closing portion of the hollow cylindrical body 84 of the
first control valve 100A is rigidly press-fitted into the end of
the second valve element 32. Disposed between the engaging portion
101 and the first valve element 18 is the spring 35 for urging the
second valve element 32 in the valve-closing direction. Further, an
end face of the engaging portion 101 on a side opposite from a side
receiving the spring 35 is tapered such that when the second valve
element 32 is seated on the second valve seat 31, the clearance
between the second valve element 32 and the second body 12
supporting the second valve element 32 can be closed.
[0076] In the control valve 100 configured as above, operation
thereof is substantially the same as that of the control valve 90
according to the fourth embodiment. However, a second control valve
100B is configured such that the discharge pressure Pdh and the
discharge pressure Pdh2, which are approximately equal to each
other, are applied to axially opposite ends of the second valve
element 32, respectively. This allows the control valve 100 to
perform control operation in response to a differential pressure
between the pressures that are applied to the first valve seat 17
and the hollow cylindrical body 84 from axially opposite sides,
without being adversely affected by the pressure Pc from the
crankcase.
[0077] FIG. 7 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a sixth embodiment. In FIG. 7, component
elements which have functions identical to or equivalent to those
of the component elements appearing in FIG. 1 are designated by
identical reference numerals, and detailed description thereof is
omitted.
[0078] In the control valve 110 according to the sixth embodiment,
although its first control valve 110A and solenoid section 110C
have quite the same constructions as the constructions of those of
the control valve 10 according to the first embodiment, a second
control valve 110B has a construction different from that of the
second control valve 10B.
[0079] More specifically, in the second control valve 110B of the
control valve 110, the differential pressure-sensing section is
formed by a valve element-holding portion 111 that holds the second
valve element 32, and a bellows 112 that has axially opposite ends
thereof tightly connected to an upper end, as viewed in FIG. 7, of
the valve element-holding portion 111 and an upper end, as viewed
in FIG. 7, of the spring-receiving portion 36, respectively, such
that the bellows 112 can axially extend and contract. In this
differential pressure-sensing section as well, similarly to the
piston 33 of the second control valve 10B, the valve
element-holding portion 111 causes the second valve element 32 to
axially move according to a differential pressure between the
discharge pressure Pdh2 and the discharge pressure Pdl, whereby the
valve lift of the second control valve 110B can be adjusted.
Further, since the bellows 112 partitions between the port 15 at
the discharge pressure Pdh2 and the port 14 at the discharge
pressure Pdl, it is possible to completely prevent leakage of
refrigerant from being caused by the differential pressure between
the pressures Pdh2 and Pdl. This construction of the second control
valve 110B makes it possible to dispense with the seal rings 40 and
41 used in the second control valve 10B.
[0080] In the control valve 110 constructed as above, operation
thereof is the same as that of the control valve 10 according to
the first embodiment, and detailed description thereof is
omitted.
[0081] FIG. 8 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to a seventh embodiment. In FIG. 8, component
elements which have functions identical to or equivalent to those
of the component elements appearing in FIG. 3 are designated by
identical reference numerals, and detailed description thereof is
omitted.
[0082] The control valve 120 according to the seventh embodiment is
distinguished from the control valve 70 according to the second
embodiment in that it has a simpler construction. More
specifically, in a first control valve 120A of the control valve
120, respective both ends of the first valve element 18 and the
guide 19 connected thereto are in sliding contact with the
respective inner walls of the first body 11 and the second body 12
such that the first valve element 18 and the guide 19 can axially
move in a stable state. Further, the guide 19 has a communication
hole 121 formed through a portion close to a portion with which the
shaft 54 of a solenoid section 120C is in abutment.
[0083] A second control valve 120B includes the piston 33 that
senses the differential pressure between the discharge pressure
Pdh2 at the port 15 and the discharge pressure Pdl at the port 14,
and a shaft 122 fixed to the piston 33. One end of the shaft 122
forms the second valve element 32 of the second control valve 120B,
while the other end thereof forms an engaging portion with which
the first valve element 18 of the first control valve 120A is
engaged when the solenoid section 120C is not energized, and
cooperates with the first valve element 18 to form a valve element
of a valve that opens and closes a refrigerant passage axially
formed through the centers of the first valve element 18 and the
guide 19. Further, the spring 37 urging the piston 33 in the
valve-closing direction of the second control valve 120B is
disposed between the seal ring 40 and the first valve element 18 of
the first control valve 120A. Although the spring 37 should urge
the piston 33 with respect to the second body 12, it is configured
to urge the piston 33 with respect to the first valve element 18 so
as to reduce a spring load and simplify the construction.
[0084] According to the control valve 120, when the solenoid
section 120C is not energized, the spring 20 pushes the first valve
element 18 downward, as viewed in FIG. 8, to fully close the first
control valve 120A, and the first valve element 18 pulls the shaft
122 downward, as viewed in FIG. 8, to fully open the second control
valve 120B. At this time, since the first valve element 18 and the
engaging portion of the shaft 122 are tightly engaged with each
other, the refrigerant passage formed through the centers of the
first valve element 18 and the guide 19 is closed, and refrigerant
at the discharge pressure Pdh leaks through where the guide 19 and
the first body 11 are in sliding contact with each other, so that
pressure in the solenoid section 120C is close to the discharge
pressure Pdh.
[0085] When the solenoid section 120C is energized, the shaft 54
pushes the first valve element 18 upward, as viewed in FIG. 8, via
the guide 19 to open the first control valve 120A. The piston 33 as
well is pushed upward, as viewed in FIG. 8, by the spring 37 in a
manner interlocked with the pushing of the first valve element 18
upward, and when the second valve element 32 is seated, the second
control valve 120B is fully closed. When the first valve element 18
is further pushed upward, the shaft 122 tightly engaged with the
first valve element 18 comes to be away from the first valve
element 18, so that the refrigerant passage formed through the
centers of the first valve element 18 and the guide 19 is opened,
and the solenoid section 120C communicates with the port 14 to make
the pressure therein equal to the discharge pressure Pdl.
[0086] When supply of the control current to the solenoid section
120C is suddenly stopped from the control state in which the first
valve element 18 is lifted to a predetermined value by the control
current supplied to the solenoid 120C, the first control valve 120A
is fully closed, and the second control valve 120B is fully opened,
while fully closing the refrigerant passage formed in the centers
of the first valve element 18 and the guide 19. This causes the
compressor to shift to the minimum displacement operation state,
whereby the discharge pressures Pdh and Pdh2 on the discharge
chamber side are sharply decreased, and the discharge pressure Pdl
in the solenoid section 120C leaks into the port 13 through where
the guide 19 and the first body 11 are in sliding contact with each
other, to make the discharge pressure Pdl close to the discharge
pressures Pdh sharply decreased. As a result, the discharge
pressures Pdh and Pdh2, which have been sharply decreased to become
approximately equal to each other, are applied to the axially
opposite ends of the movable part of the guide 19, the first valve
element 18, and the piston 33, which are made integral with each
other, and therefore the fully-closed state of the first control
valve 120A and the fully-open state of the second control valve
120B are maintained almost only by the load of the spring 20.
[0087] FIG. 9 is a central longitudinal cross-sectional view of the
construction of a control valve for a variable displacement
compressor, according to an eighth embodiment. FIGS. 10A to 10C are
views useful in explaining characteristics of a diaphragm, in which
FIG. 10A shows a state in which no differential pressure is applied
to the diaphragm, FIG. 10B shows a state in which the diaphragm is
displaced by a differential pressure, and FIG. 10C shows a state in
which the differential pressure is applied to the displaced
diaphragm in a direction opposite to the direction of the
displacement. FIGS. 11A and 11B are explanatory views showing the
construction of a differential pressure-sensing section of the
control valve according to the eighth embodiment, in which FIG. 11A
shows a case where pressure in the discharge chamber of the
compressor is higher than pressure in the refrigerant outlet port
of the compressor, and FIG. 11B shows a case where the pressure in
the discharge chamber is lower than the pressure in the refrigerant
outlet port. In FIG. 9 and FIGS. 11A and 11B, component elements
which have functions identical to or equivalent to those of the
component elements appearing in FIG. 8 are designated by identical
reference numerals, and detailed description thereof is
omitted.
[0088] The control valve 130 according to the eighth embodiment is
constructed by lower-cost component parts in place of the high-cost
bellows 112 used in the control valve 110 according to the sixth
embodiment, and high-cost cut parts used in the control valve 120
according to the seventh embodiment.
[0089] More specifically, in the control valve 130, almost all the
component elements of a first control valve 130A and a second
control valve 130B are pressed parts formed by pressing pipes, and
the pressed parts are assembled by press-fitting or swaging.
[0090] In the first control valve 130A, a first body 131 having an
end thereof inwardly bent is fixed to a solenoid section 130C by
swaging the foremost end of the core 51 protruding from the yoke
59, and a second body 132 and a third body 133 having one end
forming the first valve seat 17 are rigidly press-fitted into the
first body 131. The third body 133 has the guide 19, which has a
shape of a bell, axially slidably disposed therein, and a
bell-shaped shaft-receiving portion 134 having the communication
hole 121 is press-fitted into the guide 19. The guide 19 has the
first valve element 18 externally fitted on one end thereof on the
side toward the second control valve 130B, and is urged in the
valve-closing direction by the spring 20 disposed between the other
end thereof and a protrusion formed on the inside of the body
133.
[0091] The second body 132 has an open end provided with a
diaphragm 135 made of polyimide for sealing between the port 15 at
the discharge pressure Pdh2 and the port 14 at the discharge
pressure Pdl, and sensing the differential pressure between the
discharge pressure Pdh2 and the discharge pressure Pdl. The
diaphragm 135 has an outer peripheral portion thereof sandwiched
between a first ring 136 and a second ring 137, and a central
portion thereof sandwiched between a center disk 138 and a flange
portion 139. The first ring 136 and the second ring 137 are fixed
to the second body 132 together with a fourth body 140 by swaging
open ends of the second body 132, in a state sandwiching the
diaphragm 135 therebetween. On the other hand, the center disk 138
and the flange portion 139 are fixed to each other in a state
sandwiching the diaphragm 135 therebetween, by press-fitting a
shaft 141 into a central portion of the center disk 138 and the
hollow cylindrical second valve element 32 of the second control
valve 130B, integrally formed with the flange portion 139. It
should be noted that portions of the first and second rings 136 and
137, sandwiching the outer peripheral portion and the central
portion of the diaphragm 135, are configured such that the inner
diameter of the first ring 136 is set to be larger than the inner
diameter of the second ring 137, and the outer diameter of the
center disk 138 is set to be larger than the outer diameter of the
flange portion 139. Further, the first ring 136 has a stepped
portion, and a portion thereof extending from the stepped portion
forms a stopper 142 for restricting the displacement of the
diaphragm 135.
[0092] A cup-shaped fifth body 143 is press-fitted into the fourth
body 140. The fifth body 143 has a valve hole of the second control
valve 130B formed in the center of its bottom, and an opening of
the valve hole forms the port 16 leading to the crankcase. The
shaft 141 extends through the valve hole of the second control
valve 130B, and a spring-receiving portion 144 is externally fitted
on a foremost end of the shaft 141. Interposed between the bottom
of the fifth body 143 and the spring-receiving portion 144 is the
spring 37 for urging the second valve element 32 in the
valve-closing direction.
[0093] According to the control valve 130 described above, when the
solenoid section 130C is not energized, the spring 20 pushes the
guide 19 downward, as viewed in FIG. 9, to fully close the first
control valve 130A, and at the same time the guide 19 pulls the
shaft 141 downward, as viewed in FIG. 9, until the center disk 138
is brought into abutment with the stopper 142, to fully open the
second control valve 130B. At this time, since the guide 19 and the
shaft 141 are tightly engaged with each other, and refrigerant at
the discharge pressure Pdh leaks into the first body 131 through
where the guide 19 and the third body 133 are in sliding contact
with each other, so that pressure in the solenoid section 130C is
close to the discharge pressure Pdh.
[0094] When the solenoid section 130C is energized, the shaft 54
pushes the first valve element 18 upward, as viewed in FIG. 9 via
the guide 19, to open the first control valve 130A. The shaft 141
as well is pulled upward, as viewed in FIG. 9, by the spring 37 in
a manner interlocked with the pushing of the first valve element 18
upward, and when the second valve element 32 is seated, the second
control valve 130B is fully closed. When the first valve element 18
is further pushed upward, the shaft 141 tightly engaged with the
guide 19 comes to be away from the guide 19, so that the solenoid
section 130C communicates with the port 14 via a hole in the center
of the guide 19, through which the shaft 141 extends, and the
communication hole 121 of the shaft-receiving portion 134, whereby
pressure in the solenoid section 130C becomes equal to the
discharge pressure Pdl.
[0095] After that, when control current is held at a predetermined
value, the first valve element 18 is stopped at a position where
the urging force of the solenoid section 130C corresponding to the
predetermined value and the urging force of the spring 20 against
the solenoid force are balanced. The first valve element 18 is
lifted from the first valve seat 17 and is stopped, whereby the
first control valve 130A is set as to a refrigerant passage thereof
such that the refrigerant passage has a predetermined passage
cross-sectional area, so that refrigerant at the discharge pressure
Pdh, introduced into the port 13, is allowed to flow through the
refrigerant passage having the predetermined passage
cross-sectional area, and refrigerant at the discharge pressure Pdl
is discharged from the port 14 into the refrigerant outlet port of
the compressor. When refrigerant flows through the first control
valve 130A, a predetermined differential pressure .DELTA.P is
generated across the first control valve 130A. Since the discharge
pressure Pdh2 is approximately equal to the discharge pressure Pdh,
the differential pressure .DELTA.P generated across the first
control valve 130A is sensed by the diaphragm 135. The diaphragm
135 drives the second valve element 32 that moves in unison
therewith, whereby it controls the flow rate of refrigerant
supplied via the second control valve 130B to the crankcase. Thus,
the control valve 130 provides control such that the compressor
discharges refrigerant at a flow rate corresponding to the control
current supplied to the solenoid section 130C.
[0096] When the supply of the control current to the solenoid
section 130C is suddenly stopped from the control state in which
the first valve element 18 is lifted to a predetermined value by
the control current supplied to the solenoid 130C, the first
control valve 130A is fully closed, and the second control valve
130B is fully opened, while closing the hole in the center of the
guide 19. This causes the compressor to shift to the minimum
displacement operation state, whereby the discharge pressures Pdh
and Pdh2 on the discharge chamber side are sharply decreased, and
the discharge pressure Pdl in the solenoid section 130C leaks into
the port 13 through the guide 19 and the first body 11 are in
sliding contact with each other, to make the discharge pressure Pdl
close to the discharge pressures Pdh sharply decreased. As a
result, the discharge pressure Pdl progressively decreased is
applied to the guide 19 from the side toward the port 14, whereas
the discharge pressures Pdh sharply decreased is applied to the
inside of the guide 19, and hence the differential pressure
therebetween and the load of the spring 20 maintains the
fully-closed state of the first control valve 130A and the
fully-open state of the second control valve 130B.
[0097] Now, when attention is paid to the differential
pressure-sensing section, it is known that an effective
pressure-receiving area of the diaphragm 135 is changed according
to the stroke of the displacement thereof. As shown in FIG. 10A,
the effective pressure-receiving area of the diaphragm 135 depends
on the area of a circle a diameter (effective diameter b) of which
is the distance between the centers of curvature circles a of
respective corrugated portions. Here, when pressure P1 applied from
above, as viewed in the figures, becomes larger than pressure P2
applied from below, as viewed in the same, a central portion of the
diaphragm 135 is displaced downward, as viewed in FIG. 10B. At this
time, since an inner peripheral portion of each corrugated portion
is also displaced together with the central portion, the curvature
of the corrugated portion is increased, and the center of the
curvature moves inward, whereby the effective diameter becomes an
effective diameter b1 smaller than the effective diameter b, to
decrease the effective pressure-receiving area. Here, as shown in
FIG. 10C, when the pressure P2 becomes larger than the pressure P1
in the state in which the central portion of the diaphragm 135 is
displaced, the corrugated portion alone expands to swell toward the
pressure P1, which causes the center of the curvature to move
outward such that the effective diameter becomes an effective
diameter b2 larger than the effective diameter b, to increase the
effective pressure-receiving area.
[0098] This situation corresponds to a case where the supply of the
control current to the solenoid section 130C is suddenly stopped to
make the discharge pressure Pdl on the downstream side of the first
control valve 130A higher than the discharge pressure Pdh2 on the
upstream side thereof. In such a case, the second valve element 32
that moves in unison with the diaphragm 135 is caused to act in the
valve-closing direction by the differential pressure between the
discharge pressure Pdl and the discharge pressure Pdh2. More
specifically, when the solenoid section 130C is deenergized, the
second control valve 130B is fully opened by the load of the spring
20, but immediately after that, when the discharge pressure Pdl
becomes higher than the discharge pressure Pdh2, the diaphragm 135
responsive to the differential pressure acts on the second control
valve 130B in the valve-closing direction. Therefore, particularly
when the differential pressure is large, it is impossible to
maintain the fully-closed state of the first control valve 130A and
the fully-open state of the second control valve 130B.
[0099] In contrast, the control valve 130 is configured such that
when the discharge pressure Pdl becomes higher than the discharge
pressure Pdh2, the force that acts on the second control valve 130B
in the valve-closing direction is inhibited from being increased.
To this end, it is only required that an effective diameter c2 of
the diaphragm 135 obtained when the discharge pressure Pdl is
higher than the discharge pressure Pdh2 is made smaller than an
effective diameter c1 of the diaphragm 135 obtained when the
discharge pressure Pdh2 is higher than the discharge pressure Pdl.
This is realized, as shown in FIGS. 11A and 11B in an enlarged
form, by making the respective inner diameters of the first and
second rings 136 and 137 which sandwich the respective surfaces of
the diaphragm 135, different from each other, and making the
respective outer diameters of the center disk 138 and the flange
portion 139 which also sandwich the respective surfaces of the
diaphragm 135, different from each other. More specifically, the
inner diameter of the stepped portion of the first ring 136 is set
to be larger than that of the second ring 137, and at the same time
the outer diameter of the center disk 138 is set to be larger than
that of the flange portion 139. However, the effective diameter c1
is set to be equal to the inner diameter of the first valve seat of
the first control valve 130A such that when the first control valve
130A is in the closed state, the diaphragm 135 has the same
pressure-receiving area as the pressure-receiving area of the first
valve element 18 for receiving the discharge pressure Pdl. It
should be noted that the distance between the inner periphery of
the first ring 136 and the outer periphery of the center disk 138
is set to be equal to the distance between the inner periphery of
the second ring 137 and the outer periphery of the flange portion
139.
[0100] As a result, when Pdl<Pdh2 holds, as shown in FIG. 11A,
the corrugated portion of the diaphragm 135 is defined by the
center disk 138 having a larger outer diameter and the first ring
136 having a larger inner diameter, and the effective
pressure-receiving area of the diaphragm 135 at this time is
determined by the effective diameter c1. On the other hand, when
Pdl>Pdh2 holds, as shown in FIG. 11B, the corrugated portion of
the diaphragm 135 is defined by the flange portion 139 having a
smaller outer diameter and the second ring 137 having a smaller
inner diameter, and the effective pressure-receiving area of the
diaphragm 135 at this time is determined by the effective diameter
c2. As described above, when deenergization of the solenoid section
130C causes transition from the state in which the discharge
pressure Pdl is lower than the discharge pressure Pdh2 to the state
in which the discharge pressure Pdl is higher than the discharge
pressure Pdh2, the effective pressure-receiving area of the
diaphragm 135 is changed to be made smaller, whereby it is possible
to reduce the force caused to act on the second control valve 130B
in the valve-closing direction by the differential pressure, which
makes it possible to smoothly perform a stopping operation of the
automotive air conditioner.
[0101] Since the control valve for a variable displacement
compressor, according to the present invention, is configured such
that it is insensitive to pressure on the downstream side of the
first control valve, pressure at the refrigerant outlet port is
prevented from acting on the second control valve in the direction
of increasing the displacement of the compressor even when the
pressure at the refrigerant outlet port becomes higher than the
pressure in the discharge chamber. This makes it possible to
dispense with the check valve conventionally provided at the
refrigerant outlet port of the compressor, which is advantageous in
that it is possible to reduce the costs of the compressor.
[0102] The foregoing is considered as illustrative only of the
principles of the present invention. Further, since numerous
modifications and changes will readily occur to those skilled in
the art, it is not desired to limit the invention to the exact
construction and applications shown and described, and accordingly,
all suitable modification and equivalents may be regarded as
falling within the scope of the invention in the appended claims
and their equivalents.
* * * * *