U.S. patent application number 10/918420 was filed with the patent office on 2005-03-10 for capacity control valve for variable displacement compressor.
This patent application is currently assigned to TGK CO., LTD.. Invention is credited to Hirota, Hisatoshi, Kajiwara, Morimitsu, Yoshihiro, Ryosuke.
Application Number | 20050053474 10/918420 |
Document ID | / |
Family ID | 34137993 |
Filed Date | 2005-03-10 |
United States Patent
Application |
20050053474 |
Kind Code |
A1 |
Hirota, Hisatoshi ; et
al. |
March 10, 2005 |
Capacity control valve for variable displacement compressor
Abstract
To provide a capacity control valve for a variable displacement
compressor of a Pd-Ps differential pressure-controlled type, which
suppresses overshooting of the differential pressure between the
discharge pressure Pd and the suction pressure Ps which can occur
when the differential pressure is changed in response to a stepwise
change in the solenoid current. The capacity control valve includes
a valve section having a Pd-Pc valve for control of the flow rate
of refrigerant flowing from a discharge chamber to a crankcase and
a Pc-Ps valve for control of the flow rate of refrigerant flowing
from the crankcase to a suction chamber operating in a manner
interlocked with the Pd-Pc valve. A spool valve element is provided
on a valve element of the Pc-Ps valve, whereby in a stroke region
where the Pd-Pc valve is toward the fully-closed position,
refrigerant is allowed to pass through the clearance between the
spool valve element and the valve hole of the Pc-Ps valve, to cause
the Pc-Ps valve to have a characteristic that the opening area
thereof does not change in response to a change in stroke. This
makes it possible to suppress sharp changes in the pressure Pc in
the crankcase due to the existence of the clearance, even if the
solenoid current is stepwise sharply changed.
Inventors: |
Hirota, Hisatoshi; (Tokyo,
JP) ; Kajiwara, Morimitsu; (Tokyo, JP) ;
Yoshihiro, Ryosuke; (Tokyo, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW
SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
TGK CO., LTD.
Tokyo
JP
|
Family ID: |
34137993 |
Appl. No.: |
10/918420 |
Filed: |
August 16, 2004 |
Current U.S.
Class: |
417/222.2 ;
417/222.1; 417/269 |
Current CPC
Class: |
F04B 27/1804 20130101;
F04B 2027/1831 20130101; F04B 2027/1877 20130101; F04B 2027/1854
20130101; F04B 2027/1827 20130101; F04B 2027/1813 20130101 |
Class at
Publication: |
417/222.2 ;
417/269; 417/222.1 |
International
Class: |
F04B 001/26; F04B
001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 4, 2003 |
JP |
2003-312369 |
Sep 25, 2003 |
JP |
2003-332652 |
Claims
What is claimed is:
1. A capacity control valve for a variable displacement compressor,
for controlling pressure in a crankcase to thereby vary discharging
capacity of the variable displacement compressor such that
differential pressure between pressure in a suction chamber and
pressure in a discharge chamber is held at a predetermined
differential pressure, comprising: a first control valve for
controlling a flow rate of refrigerant flowing into the crankcase
from the discharge chamber; a second control valve for controlling
a flow rate of refrigerant flowing out of the crankcase into the
suction chamber, the second control valve having flow
rate-restricting means operable to provide an opening area which
does not change in the case where the second control valve is moved
more than a predetermined value of stroke amount when the second
control valve is moved in an opening area-increasing direction in a
manner interlocked with operation of the first control valve; and a
solenoid section for applying a solenoid force corresponding to the
predetermined differential pressure to the first control valve and
the second control valve.
2. The capacity control valve according to claim 1, wherein the
flow rate-restricting means comprises a spool valve element
provided on a valve element of the second control valve to form a
clearance between the spool valve element and a valve hole such
that an opening area of the clearance does not change.
3. The capacity control valve according to claim 1, wherein the
flow rate-restricting means is an orifice provided on a downstream
side of the second control valve.
4. The capacity control valve according to claim 1, comprising a
passage communicating between a space connected to the crankcase
and an inside of the solenoid section, and wherein the second
control valve causes the pressure in the crankcase introduced via
the passage into the solenoid section to be received by a valve
element thereof in a valve-opening direction, to thereby cancel out
the pressure in the crankcase received by the valve element in a
valve-closing direction.
5. The capacity control valve according to claim 4, wherein a
pressure-receiving area of the second control valve obtained by
subtracting an area where the pressure in the crankcase is received
via the solenoid section from an opening area of a valve hole of
the second control valve is set equal to an opening area of a valve
hole of the first control valve.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY
[0001] This application claims priority of Japanese Application
No.2003-312369 filed on Sep. 4, 2003 and entitled "CAPACITY CONTROL
VALVE FOR VARIABLE DISPLACEMENT COMPRESSOR" and No. 2003-332652
filed on Sep. 25, 2003, entitled "CAPACITY CONTROL VALVE FOR
VARIABLE DISPLACEMENT COMPRESSOR".
BACKGROUND OF THE INVENTION
[0002] (1) Field of the Invention
[0003] The present invention relates to a capacity control valve
for a variable displacement compressor, and more particularly to a
capacity control valve for use in a variable displacement
compressor that compresses a refrigerant gas in a refrigeration
cycle of an automotive air conditioner.
[0004] (2) Description of the Related Art
[0005] A compressor used for compressing refrigerant in a
refrigeration cycle of an automotive air conditioner is driven by
an engine, which makes it impossible to perform rotational speed
control of the compressor. To overcome the inconvenience, a
variable displacement compressor which is capable of changing
displacement of compressed refrigerant is employed so as to obtain
adequate refrigerating capacity without being constrained by the
rotational speed of the engine.
[0006] In such a variable displacement compressor, compression
pistons are connected to a wobble plate fitted on a shaft driven by
the engine for rotation, and the angle of the wobble plate is
changed to change the stroke of the pistons for changing the
discharge amount of the refrigerant, i.e. the displacement of the
compressor.
[0007] The angle of the wobble plate is continuously changed by
introducing part of the compressed refrigerant into an airtight
crankcase and changing the pressure Pc in the crankcase, thereby
changing the balance between pressures applied to the opposite ends
of each piston.
[0008] The pressure Pc in the crankcase of the variable
displacement compressor can be changed by forming refrigerant
passages, respectively, between a discharge chamber and the
crankcase of the compressor and between the crankcase and a suction
chamber of the same, and thereby controlling the flow rate of
refrigerant flowing from the discharge chamber into the suction
chamber via the crankcase at respective locations upstream and
downstream of the crankcase. More specifically, a capacity control
valve is provided in one of the passages between the discharge
chamber and the crankcase and between the crankcase and the suction
chamber, and an orifice is provided in the other of the passages,
whereby control is provided such that the capacity control valve
allows or blocks the communication via the associated refrigerant
passage, so as to control the pressure Pc in the crankcase.
[0009] Further, a capacity control valve is also known which
comprises two control valves disposed in respective refrigerant
passages between a discharge chamber and a crankcase and between
the crankcase and a suction chamber, such that they operate in a
manner interlocked with each other (see e.g. Japanese Unexamined
Patent Publication (Kokai) No. 2003-35269 (Paragraph numbers [0023]
to [0034], FIG. 2)). The capacity control valve for a variable
displacement compressor described in Japanese Unexamined Patent
Publication (Kokai) No. 2003-35269 controls the discharging
capacity of the compressor such that the differential pressure
(Pd-Ps) between the discharge pressure Pd and the suction pressure
Ps of the compressor is held a predetermined value, and comprises a
first control valve (hereinafter also referred to as "the Pd-Pc
valve") for high pressure which controls the flow rate of
refrigerant flowing from the discharge chamber into the crankcase,
a second control valve (hereinafter also referred to as "the Pc-Ps
valve") for low pressure which controls the flow rate of
refrigerant flowing from the crankcase into the suction chamber in
a manner interlocked with operation of the Pd-Pc valve, and a
solenoid which is capable of externally setting a predetermined
differential pressure (Pd-Ps) between the discharge pressure Pd and
the suction pressure Ps by a current value.
[0010] FIG. 7 is a diagram showing characteristics of the
conventional capacity control valve, and FIG. 8 is a diagram
showing characteristics of the variable displacement compressor
using the conventional capacity control valve.
[0011] The capacity control valve equipped with the two control
valves for high pressure and low pressure has the characteristics,
as shown in FIG. 7, that when the Pd-Pc valve is changed from its
closed state in an opening area-increasing direction, the Pc-Ps
valve is changed from its fully-open state in an opening
area-decreasing direction in a manner interlocked with the
operation of the Pd-Pc valve, and that inversely when the Pd-Pc
valve is changed from its fully-open state in an opening
area-decreasing direction, the Pc-Ps valve is changed from its
closed state in an opening area-increasing direction in a manner
interlocked with the operation of the Pd-Pc valve.
[0012] In such a capacity control valve, when the stroke position
is changed according to the value of electric current supplied to
the solenoid, the respective opening areas of the Pd-Pc valve and
the Pc-Ps valve are changed in opposite directions, which increases
the amount of change in the pressure Pc in the crankcase with
respect to the same amount of change in the stroke compared with a
case where the orifice having fixed opening area is provided
between the discharge chamber and the crankcase or between the
crankcase and the suction chamber of the compressor, which makes it
possible to promptly change the variable displacement of the
compressor.
[0013] However, the variable displacement compressor using the
conventional capacity control valve, characteristics of which are
illustrated in FIG. 8, suffers from the problem that when the
current (solenoid current) supplied to the solenoid is stepwise
changed, the pressure Pc in the crankcase is largely changed
according to a change in the solenoid current, which causes a large
change in the differential pressure (Pd-Ps) between the discharge
pressure Pd and the suction pressure Ps, which is to be controlled,
causing a large overshoot, so that torque consumed by the
compressor is largely changed only at the moment in time at which
the solenoid current is changed, resulting in large variation in
load on the engine.
[0014] More specifically, when the solenoid current is stepwise
increased as illustrated in FIG. 8, the Pd-Pc valve is changed in
the valve-closing direction and the Pc-Ps valve is changed in the
valve-opening direction, which causes a too rapid drop in the
pressure Pc in the crankcase, so that the pressure Pc in the
crankcase once undergoes a sharp drop and then changes such that it
settles in the predetermined pressure. The variable displacement
compressor has its discharging capacity excessively increased in
response to the sharp drop in the pressure Pc in the crankcase,
which results in a sharp increase in the torque consumed by the
compressor and causes an overshoot.
SUMMARY OF THE INVENTION
[0015] The present invention has been made in view of the
above-described points, and an object thereof is to provide a
capacity control valve for a variable displacement compressor,
which suppresses a overshoot which can occur when the differential
pressure between the discharge pressure and the suction pressure is
changed in response to a stepwise change in the solenoid
current.
[0016] To solve the above problem, the present invention provides a
capacity control valve for a variable displacement compressor, for
controlling pressure in a crankcase to thereby vary discharging
capacity of the variable displacement compressor such that
differential pressure between pressure in a suction chamber and
pressure in a discharge chamber is held at a predetermined
differential pressure, comprising a first control valve for
controlling a flow rate of refrigerant flowing into the crankcase
from the discharge chamber, a second control valve for controlling
a flow rate of refrigerant flowing out of the crankcase into the
suction chamber, the second control valve having flow
rate-restricting means operable to provide an opening area which
does not change in the case where the second control valve is moved
more than a predetermined value of stroke amount when the second
control valve is moved in an opening area-increasing direction in a
manner interlocked with operation of the first control valve, and a
solenoid section for applying a solenoid force corresponding to the
predetermined differential pressure to the first control valve and
the second control valve.
[0017] 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
[0018] FIG. 1 is a central longitudinal cross-sectional view
showing a capacity control valve according to a first embodiment of
the present invention.
[0019] FIG. 2 is a diagram showing characteristics of the capacity
control valve according to the first embodiment.
[0020] FIG. 3 is a diagram showing characteristics of a variable
displacement compressor using the capacity control valve according
to the first embodiment.
[0021] FIG. 4 is a central longitudinal cross-sectional view
showing a capacity control valve according to a second embodiment
of the present invention.
[0022] FIG. 5 is a central longitudinal cross-sectional view
showing a capacity control valve according to a third embodiment of
the present invention.
[0023] FIG. 6 is a central longitudinal cross-sectional view
showing a capacity control valve according to a fourth embodiment
of the present invention.
[0024] FIG. 7 is a diagram showing characteristics of a
conventional capacity control valve.
[0025] FIG. 8 is a diagram showing characteristics of a variable
displacement compressor using the conventional capacity control
valve.
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
showing a capacity control valve according to a first embodiment of
the invention, FIG. 2 a diagram showing characteristics of the
capacity control valve according to the first embodiment, and FIG.
3 a diagram showing characteristics of a variable displacement
compressor using the capacity control valve according to the first
embodiment.
[0028] The capacity control valve is formed by a valve section 1
and a solenoid section 2. The valve section 1 includes a body 3
having an opening in the top thereof, and a plug 4 is fitted in the
opening. The plug 4 has a hole axially extending therethrough, with
an opening in the upper end thereof as viewed in FIG. 1 forming a
port 5 for receiving refrigerant at discharge pressure Pd from a
discharge chamber of the variable displacement compressor, and a
lower end thereof as viewed in FIG. 1 forming a valve seat 6. In
opposed relation to the valve seat 6, a ball valve element 7 is
disposed in a manner movable to and away therefrom. Space within
which the ball valve element 7 is disposed communicates with the
crankcase of the variable displacement compressor via a port 8
formed in the body 3. Therefore, the ball valve element 7 and the
valve seat 6 forms a Pd-Pc valve (first control valve) that
controls the flow rate of refrigerant at the discharge pressure Pd
to thereby fill the crankcase with refrigerant at pressure Pc.
[0029] The body 3 is also provided with a port 9 which communicates
with a suction chamber of the variable displacement compressor, and
a valve seat 10 is integrally formed with the body 3 in a passage
between the port 8 and the port 9. A valve element 11 which holds
the ball valve element 7 of the Pd-Pc valve is disposed in opposed
relation to the valve seat 10 in a manner movable to and away
therefrom. Interposed between the valve element 11 and the plug 4
is a spring 12 for urging the ball valve element 7 in the
valve-opening direction and the valve element 11 in the
valve-closing direction. The valve element 11 and the valve seat 10
form a Pc-Ps valve (second control valve) which controls the flow
rate of refrigerant at pressure Pc in the crankcase to fill the
suction chamber with refrigerant at suction pressure Ps.
[0030] The capacity control valve is characterized in that it
includes a spool valve structure whose opening area does not change
in a region in which the Pd-Pc valve is toward the fully-closed
position. To realize the structure, a spool valve element 11a
disposed within a valve hole of the Pc-Ps valve is integrally
formed with the valve element 11 in an end face thereof opposed to
the valve seat 10. Therefore, this Pc-Ps valve forms a spool valve
in which in a stroke region where the valve element 11 is moved
axially to start opening the Pd-Pc valve, the opening area of the
Pc-Ps valve defined by a clearance between the spool valve element
11a and the valve hole does not change, but in a stroke region in
which the Pd-Pc valve is toward the fully-open position, the
opening area between the valve element 11 and the valve seat 10
changes. The clearance which does not change its opening area forms
flow rate-restricting means of the present invention.
[0031] Further, the body 3 has a strainer 13 capped on the upper
end thereof as viewed in FIG. 1, and the port 9 is provided with a
passage 14 for transmitting the suction pressure Ps to the inside
of the solenoid 2. It should be noted that in the valve section 1,
the Pc-Ps valve is formed such that the diameter of the valve hole
thereof is larger than that of the valve hole of the Pd-Pc valve,
thereby enabling refrigerant to instantly flow at a large flow
rate.
[0032] The solenoid section 2 has a core 15 disposed in the center
thereof which has an upper end thereof screwed into a lower end of
the body 3, and a yoke 16 is arranged in a manner enclosing the
core 15, with an upper end thereof screwed into the body 3. A
sleeve 17 is disposed inward of the yoke 16, and a hollow
cylindrical holder 18 is provided on the lower ends of the yoke 16
and the sleeve 17 as viewed in FIG. 1. The holder 18 has an
adjustment screw 19 screwed into an opening thereof.
[0033] The core 15 has a through hole formed in the center thereof,
and a shaft 20 is disposed in a manner extending through the
through hole. This shaft 20 has one end thereof supported in a
through hole formed in the body 3, and the other end thereof
supported in a recess formed in the adjustment screw 19. The shaft
20 has a shaft 21 integrally formed therewith at the one end
thereof, which is reduced in diameter and inserted into the valve
element 11 for centering the valve element 11 and the ball valve
element 7 held thereby. The shaft 20 has the same diameter as that
of the valve hole of the Pd-Pc valve, whereby a pressure-receiving
area of the ball valve element 7 where the discharge pressure Pd is
received and a pressure-receiving area of the lower end of the
shaft 20 as viewed in FIG. 1 where the suction pressure Ps
introduced into the solenoid section 2 via the passage 14 is
received are equal to each other.
[0034] The solenoid section 2 further includes a plunger 22 fixed
to the shaft 20 at a location between the core 15 and the
adjustment screw 19, a spring 23 disposed between the core 15 and
the plunger 22, a spring 24 disposed between the plunger 22 and the
adjustment screw 19, and a coil 25 disposed between the sleeve 17
and the yoke 16. The coil 25 is electrically connected to a harness
27 extending out of the solenoid section 2 via a water-proof
coupler 26.
[0035] In the capacity control valve having the Pd-Pc valve and the
Pc-Ps valve, described above, when the solenoid current is not
supplied to the coil 25 of the solenoid section 2, such as when an
automotive air conditioner is not in operation or when
refrigerating load is the minimum, the plunger 22 is urged by the
spring 23 in a direction away from the core 15, and the ball valve
element 7 and the valve element 11 are urged by the spring 12 in a
direction toward the solenoid section 2, which places the Pd-Pc
valve for high pressure in the fully-open position and the Pc-Ps
valve for low pressure in the fully-closed position. If the
discharge pressure Pd is introduced at this time from the discharge
chamber of the compressor, the discharge pressure Pd is introduced
into the crankcase via the Pd-Pc valve. Since the refrigerant
passage extending from the crankcase to the suction chamber is
closed by the Pc-Ps valve, so that the pressure Pc in the crankcase
becomes closer to the discharge pressure Pd, minimizing the
differential pressure between the pressures applied to the opposite
end faces of each piston of the compressor. This places the wobble
plate at an inclination angle which minimizes the stroke of the
piston, whereby the compressor is controlled to the minimum
displacement operation.
[0036] Now, as the solenoid current supplied to the coil 25 of the
solenoid section 2 increases, the plunger 22 is attracted by the
core 15 to be moved upward as viewed in FIG. 1, and the shaft 20
fixed to the plunger 22 as well is moved upward as viewed in FIG.
1. Therefore, the capacity control valve has the characteristics,
as shown in FIG. 2, that the opening area of the Pd-Pc valve is
changed in a decreasing direction from the maximum since the ball
valve element 7 is moved toward the valve seat 6, while the opening
area of the Pc-Ps valve is changed in an increasing direction from
zero since the valve element 11 is moved in a direction away from
the valve seat 10. Accordingly, the pressure Pc in the crankcase
progressively decreases, so that the variable displacement
compressor is controlled to operation with displacement dependent
on the solenoid current.
[0037] When the solenoid current continues to be increased, the
opening area of the Pd-Pc valve continues to be decreased but the
increase in the opening area of the Pc-Ps valve stops at a time
point the opening area between the valve element 11 and the valve
seat 10 becomes larger than the opening area defined by the
clearance between spool valve element 11a and the valve hole of the
Pc-Ps valve. Thereafter, even if the solenoid current is increased,
the Pc-Ps valve has a flat characteristic that the opening area
thereof does not change relative to the travel or stroke amount of
the valve element since the opening area of this valve is
restricted by the opening area between the spool valve element 11a
and the valve hole.
[0038] When the capacity control valve is controlled by the supply
of the predetermined solenoid current, the Pd-Pc valve and the
Pc-Ps valve are controlled to respective stroke positions dependent
on the solenoid current. At this time, when the differential
pressure between the discharge pressure Pd received by the ball
valve element 7 and the suction pressure Ps received by the shaft
20 varies due to a change in the rotational speed of the engine,
i.e. the rotational speed of the compressor, the capacity control
valve changes the travel or stroke amount of the valve elements of
the Pd-Pc valve and the Pc-Ps valve to vary the displacement of the
compressor, thereby providing control such that the differential
pressure between the discharge pressure Pd and the suction pressure
Ps is held at a predetermined differential pressure set by the
solenoid current.
[0039] As described above, the Pc-Ps valve is caused to have the
flat characteristic that the opening area thereof does not change
in a region where the opening area of the Pd-Pc valve is small,
whereby when the solenoid current is changed stepwise, the pressure
Pc in the crankcase does not largely change relative to the change
in the solenoid current, as shown in FIG. 3. If the solenoid
current is increased e.g. stepwise in a region where the opening
area of the Pc-Ps valve changes, the ratio of change in opening
area in a opening direction of the Pc-Ps valve with respect to a
stroke amount is larger than that of change in opening area in a
closing direction of the Pd-Pc valve with respect to the same
stroke amount, so that the pressure Pc in the crankcase is about to
be sharply decreased, but the range of this change is restricted by
the flat characteristic of the Pc-Ps valve so that overshooting of
the pressure Pc in the crankcase is prevented. As a result,
overshooting of the differential pressure (Pd-Ps) between the
discharge pressure Pd and the suction pressure Ps does not occur,
either, which reduces variation in torque consumed by the
compressor and hence reduces variation in load on the engine.
[0040] Similarly, if the solenoid current is increased e.g.
stepwise in a region where the opening area of the Pc-Ps valve does
not change, the Pc-Ps valve does not undergo a change relative to a
stroke amount even though the Pd-Pc valve undergoes a change in the
valve-closing direction relative to the same stroke amount, which
reduces the range of variation in the pressure Pc in the crankcase.
Therefore, the pressure Pc in the crankcase, the differential
pressure (Pd-Ps) between the discharge pressure Pd and the suction
pressure Ps, and torque consumed by the compressor are reduced,
which makes it possible to reduce variation in load on the engine.
Of course, even when the solenoid current is stepwise decreased,
occurrence of the overshooting can be suppressed in the same
manner.
[0041] FIG. 4 is a central longitudinal cross-sectional view
showing a capacity control valve according to a second embodiment
of the invention. In FIG. 4, component elements identical to those
in FIG. 1 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0042] Although the capacity control valve according to the first
embodiment attains the flat characteristic of the Pc-Ps valve by
the spool valve structure, the capacity control valve according to
the second embodiment attains the same by providing an orifice 28
as flow rate-restricting means whose opening area does not
change.
[0043] That is, the Pc-Ps valve has a valve element 11 whose
surface opposed to the valve seat 10 is formed to have a tapered
shape, and the orifice 28 is provided between the downstream side
of the valve element 11, and the port 9 and the passage 14. The
orifice 28 is disposed in series with the Pc-Ps valve, and
therefore, when the opening area of the Pc-Ps valve becomes larger
than the opening area of the orifice 28, even if the valve element
11 of the Pc-Ps valve further travels in a direction of increasing
the opening area thereof, the opening area of the Pc-Ps valve is
limited by the orifice 28 whose opening area does not change, and
hence this capacity control valve has the same characteristics as
shown in FIG. 2. Therefore, the capacity control valve according to
the second embodiment operates in the same manner as the capacity
control valve according to the first embodiment, and therefore
reduces undesired variations in the pressure Pc in the crankcase,
the differential pressure (Pd-Ps) between the discharge pressure Pd
and the suction pressure Ps, and torque consumed by the variable
displacement compressor, thereby making it possible to decrease
variation in load on the engine.
[0044] FIG. 5 is a central longitudinal cross-sectional view
showing a capacity control valve according to a third embodiment of
the invention. In FIG. 5, component elements identical to those in
FIG. 1 are designated by identical reference numerals, and detailed
description thereof is omitted.
[0045] Compared with the capacity control valve according to the
first embodiment shown in FIG. 1, the capacity control valve
according to the third embodiment is configured such that the
operation of the Pc-Ps valve is not adversely affected by the
pressure Pc in the crankcase.
[0046] More specifically, the capacity control valve is provided
with a passage 14 which causes a space between the Pd-Pc valve and
the Pc-Ps valve, which is connected to the crankcase via the port
8, to communicate with the inside of the solenoid section, whereby
the pressure Pc in the crankcase is transmitted to the inside of
the solenoid section 2. This causes the valve element 11 of the
Pc-Ps valve to receive the pressure Pc in the crankcase in the
valve-closing direction, and receive the pressure Pc in the
crankcase introduced via the passage 14 into the solenoid section
2, via the shaft 20 in the valve-opening direction. Therefore, the
pressure Pc in the crankcase received by the valve element 11 in
the opposite directions is cancelled off, so that even when the
pressure Pc in the crankcase is changed, the change in the pressure
does not adversely affect the operation of the Pc-Ps valve.
[0047] It should be noted that the pressure received by the valve
element 11 of the Pc-Ps valve in the valve-opening direction is the
sum of the pressure Pc in the crankcase received from the solenoid
section 2 and the suction pressure Ps. At this time, the area where
the pressure Pc in the crankcase is received is equal to the
cross-sectional area of the shaft 20, and the area where the
suction pressure Ps is received is equal to an area obtained by
subtracting the cross-sectional area of the shaft 20 from the
opening area of the valve hole of the Pc-Ps valve, and at the same
time, equal to the area where the discharge pressure Pd is received
by the Pd-Pc valve, i.e. the opening area of the valve hole of the
Pd-Pc valve.
[0048] The capacity control valve according to the third embodiment
also has the valve characteristic shown in FIG. 2, similarly to the
capacity control valves according to the first and second
embodiments, so that when the solenoid current is stepwise changed,
the clearance between the spool valve element 11a and the valve
hole restricts the flow rate of refrigerant which is about to be
stepwise changed, whereby an undesired variation in the pressure Pc
in the crankcase is suppressed. As a result, undesired variations
in the differential pressure (Pd-Ps) between the discharge pressure
Pd and the suction pressure Ps and torque consumed by the variable
displacement compressor are reduced, which makes it possible to
reduce variation in load on the engine.
[0049] FIG. 6 is a central longitudinal cross-sectional view
showing a capacity control valve according to a fourth embodiment
of the invention. In FIG. 6, component elements identical to those
in FIG. 4 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0050] Compared with the capacity control valve according to the
second embodiment shown in FIG. 4, the capacity control valve
according to the fourth embodiment is configured such that the
operation of the Pc-Ps valve thereof is not adversely affected by
the pressure Pc in the crankcase.
[0051] More specifically, the capacity control valve is provided
with a passage 14 which causes space between the Pd-Pc valve and
the Pc-Ps valve connected to the crankcase via the port 8 to
communicate with the inside of the solenoid section, whereby
similarly to the capacity control valve according to the third
embodiment, the pressure Pc in the crankcase is transmitted to the
inside of the solenoid section 2. This causes the pressure Pc in
the crankcase received by the valve element 11 in the opposite
directions to be cancelled off, so that even when the pressure Pc
in the crankcase is varied, the change in the pressure does not
adversely affect the operation of the Pc-Ps valve. The capacity
control valve according to the fourth embodiment also operates
similarly to the capacity control valves according to the first to
third embodiments to provide the same advantageous effects.
[0052] Due to provision of the flow rate-restricting means in the
second control valve, the capacity control valve for a variable
displacement compressor according to the present invention is
capable of suppressing overshooting of the pressure in the
crankcase, which can occur when the solenoid current is stepwise
changed. This makes it possible to reduce undesired variation in
the differential pressure to be controlled, and undesired variation
in torque consumed by the compressor. As a result, it is possible
to reduce variation in load on the engine that drives the
compressor.
[0053] 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 modifications and equivalents may be regarded as
falling within the scope of the invention in the appended claims
and their equivalents.
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