U.S. patent application number 11/205119 was filed with the patent office on 2006-02-23 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 | 20060039799 11/205119 |
Document ID | / |
Family ID | 35447475 |
Filed Date | 2006-02-23 |
United States Patent
Application |
20060039799 |
Kind Code |
A1 |
Hirota; Hisatoshi |
February 23, 2006 |
Control valve for variable displacement compressor
Abstract
To provide a control valve for a variable displacement
compressor, which is capable of promptly restoring the compressor
to a predetermined discharge capacity even when the rotational
speed of an engine is rapidly changed. In a valve section for
controlling the flow rate of refrigerant flowing from a discharge
chamber into a crankcase of a variable displacement compressor, a
pressure-sensing section is provided in a high-pressure port that
receives discharge pressure. In the pressure-sensing section, when
a pressure-sensing piston which is larger in pressure-receiving
area than a valve element receives a change in discharge pressure
caused by a rapid change in rotational speed of the engine,
differential pressure is produced between discharge pressure Pd and
pressure in a pressure-adjusting chamber, which temporarily
produces a force for axially moving the piston. This force is
transmitted to the valve element via a shaft, to thereby accelerate
the opening/closing motion of the valve element caused by the
differential pressure between discharge pressure and suction
pressure, whereby the compressor is promptly restored to a
predetermined discharge capacity.
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.
Tokyo
JP
|
Family ID: |
35447475 |
Appl. No.: |
11/205119 |
Filed: |
August 17, 2005 |
Current U.S.
Class: |
417/222.2 ;
417/269 |
Current CPC
Class: |
F04B 2027/1854 20130101;
F04B 2027/1859 20130101; F04B 2027/1827 20130101; F04B 27/1804
20130101; F04B 2027/185 20130101; F04B 2027/1813 20130101 |
Class at
Publication: |
417/222.2 ;
417/269 |
International
Class: |
F04B 1/26 20060101
F04B001/26; F04B 27/08 20060101 F04B027/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 19, 2004 |
JP |
2004-239162 |
Oct 1, 2004 |
JP |
2004-289520 |
Claims
1. A control valve for a variable displacement compressor, which is
configured to sense differential pressure between discharge
pressure in a discharge chamber of the compressor and suction
pressure in a suction chamber of the compressor, and control a flow
rate of refrigerant allowed to flow from the discharge chamber into
a crankcase to thereby change a discharge capacity of the
refrigerant, comprising: a pressure-sensing section that senses a
change in pressure caused by a rapid change in a rotational speed
of the compressor and accelerates a motion of a valve section in a
valve-opening/closing direction performed in response to the change
in pressure.
2. The control valve according to claim 1, wherein the
pressure-sensing section comprises a pressure-sensing piston that
is disposed in a high-pressure port through which the discharge
pressure is introduced, for receiving the discharge pressure at a
pressure-receiving area larger than that of a valve element of the
valve section, and a shaft that transmits an axial motion caused by
differential pressure between the discharge pressure received by
the pressure-sensing piston and pressure in a pressure-adjusting
chamber closed by the pressure-sensing piston, through a valve hole
to the valve element.
3. The control valve according to claim 2, wherein the shaft is
formed integrally with the valve element that receives the
discharge pressure at one end face thereof, and a piston rod that
receives the suction pressure at an end face thereof opposite to
the one end face.
4. The control valve according to claim 2, wherein the
pressure-sensing piston has flow rate-adjusting means for adjusting
an amount of leakage of the refrigerant between the high-pressure
port and the pressure-adjusting chamber.
5. The control valve according to claim 4, wherein the flow
rate-adjusting means is a C-shaped ring that is disposed on a
sliding surface of the pressure-sensing piston, and has a shape cut
out over a circumferential length corresponding to the amount of
leakage, the C-shaped ring being made of a material which is low in
sliding resistance.
6. The control valve according to claim 1, wherein the
pressure-sensing section has a pressure-sensing piston that is
disposed in a medium-pressure port from which control pressure
controlled by the valve section is delivered into the crankcase,
and receives the control pressure at a pressure-receiving area
larger than that of the valve element, and wherein the
pressure-sensing piston transmits an axial motion caused by
differential pressure between the control pressure received by the
pressure-sensing piston and pressure in the pressure-adjusting
chamber closed by the pressure-sensing piston, to the valve
element.
7. The control valve according to claim 1, wherein the
pressure-sensing section has a pressure-sensing piston that is
disposed in a low-pressure port into which the suction pressure is
introduced, and receives the suction pressure at a
pressure-receiving area larger than that of the valve element, and
wherein the pressure-sensing piston transmits an axial motion
caused by differential pressure between the suction pressure
received by the pressure-sensing piston and pressure in the
pressure-adjusting chamber closed by the pressure-sensing piston,
to the valve element.
8. The control valve according to claim 2, wherein the
pressure-sensing section has sensitivity-switching means for making
a force that the pressure-sensing piston exerts on the valve
element larger when the discharge pressure has rapidly increased
than when the discharge pressure has rapidly decreased.
9. The control valve according to claim 8, wherein the
sensitivity-switching means is a check valve disposed in a passage
formed through the pressure-sensing piston for communication
between a side toward the high-pressure port and the
pressure-adjusting chamber, for blocking flow of refrigerant from
the side toward the high-pressure port to the pressure-adjusting
chamber, and allowing flow of the refrigerant from the
pressure-adjusting chamber to the side toward the high-pressure
port.
10. The control valve according to claim 8, wherein the
sensitivity-switching means is a check valve that has a film-like
valve element disposed such that the film-like valve element blocks
a gap formed around an outer periphery of the pressure-sensing
piston from a side toward the high-pressure port, for blocking flow
of the refrigerant from the side toward the high-pressure port to
the pressure-adjusting chamber via the gap, and allowing flow of
the refrigerant from the pressure-adjusting chamber to the side
toward the high-pressure port.
11. The control valve according to claim 8, wherein the
sensitivity-switching means is constructed by forming an outer
periphery of the pressure-sensing piston into a tapered shape such
that a flow passage cross-sectional area of a gap formed around the
outer periphery of the pressure-sensing piston progressively
increases from the side toward the high-pressure port to the
pressure-adjusting chamber.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY
[0001] This application claims priority of Japanese Application No.
2004-239162 filed on Aug. 19, 2004 and entitled "CONTROL VALVE FOR
VARIABLE DISPLACEMENT COMPRESSOR" and No. 2004-289520 filed on Oct.
1, 2004, 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, which is
mounted on a variable displacement compressor as a component of a
refrigeration cycle of an automotive air conditioner, for control
of the discharge capacity of the compressor by the differential
pressure between discharge pressure and suction pressure.
[0004] (2) Description of the Related Art
[0005] A compressor used in the refrigeration cycle of an
automotive air conditioner, for compressing refrigerant, uses an
engine as a drive source, and hence is incapable of performing
rotational speed control. To eliminate the inconvenience, a
variable displacement compressor capable of varying the compression
capacity of refrigerant is employed so as to obtain an adequate
cooling capacity without being constrained by the rotational speed
of the engine.
[0006] In such a variable displacement compressor, a wobble plate
fitted on a shaft driven by the engine for rotation has compression
pistons connected thereto, and by varying the inclination angle of
the wobble plate, the stroke of the pistons is varied to vary the
discharge amount of refrigerant.
[0007] The inclination angle of the wobble plate is continuously
changed by introducing part of compressed refrigerant into a
hermetically closed crankcase, and causing a change in the pressure
of the introduced refrigerant, thereby changing the balance of
pressures acting on the opposite sides of each piston.
[0008] A control valve for a variable displacement compressor is
known (see e.g. Japanese Unexamined Patent Publication (Kokai) No.
2001-132650 (Paragraph numbers [0043] to [0045], FIG. 4)) which is
disposed between a discharge chamber and a crankcase of the
compressor, or between the crankcase and a suction chamber of the
compressor, for adjusting pressure in the crankcase by changing the
flow rate of refrigerant introduced from the discharge chamber into
the crankcase, or changing the flow rate of refrigerant delivered
from the crankcase to the suction chamber.
[0009] The control valve described in Japanese Unexamined Patent
Publication (Kokai) No. 2001-132650 is configured such that it has
a valve section disposed in a refrigerant passage between the
discharge chamber and the crankcase of the compressor when it is
mounted in the compressor, and a path is formed along which
refrigerant flows from the discharge chamber to the suction chamber
of the compressor via an orifice provided between the crankcase and
the suction chamber. The control valve has the valve section which
comprises a valve element that receives discharge pressure Pd in
the valve-opening direction, and a piston rod that is integrally
formed with the valve element on a rear side of the valve element
and has approximately the same diameter as that of a valve hole,
and is configured such that an end face of the piston rod receives
suction pressure Ps and the load of a solenoid for setting the
discharge capacity of the compressor by an external signal, in the
valve-closing direction. Therefore, in this control valve, the
discharge pressure Pd and the suction pressure Ps are received by
the opposite ends of the valve element and piston rod, both having
the same effective pressure-receiving area, and hence the
differential pressure (Pd-Ps) between the discharge pressure Pd and
the suction pressure Ps causes the valve element to perform an
opening/closing operation to thereby control the flow rate of
refrigerant flowing from the discharge chamber into the
crankcase.
[0010] For example, as the rotational speed of the compressor
increases with an increase in the rotational speed of the engine to
cause an increase in the discharge capacity of the compressor, the
discharge pressure Pd increases and the suction pressure Ps
decreases to increase the differential pressure (Pd-Ps). This
increases the valve lift of the valve section which operates
depending on the differential pressure (Pd-Ps), so that the control
valve increases the flow rate of refrigerant being introduced into
the crankcase to increase pressure Pc in the crankcase, which
decreases the discharge capacity of the compressor, thereby
decreasing the differential pressure (Pd-Ps). In short, the control
valve controls the flow rate of refrigerant being introduced into
the crankcase such that the differential pressure (Pd-Ps) between
the discharge pressure Pd and the suction pressure Ps is held at a
predetermined value. The predetermined value of the differential
pressure can be set from outside by a value of electric current
supplied to the solenoid.
[0011] In the control valve for the variable displacement
compressor that operates based on the differential pressure (Pd-Ps)
between the discharge pressure Pd and the suction pressure Ps, when
the rotational speed of the engine has changed to change the
rotational speed of the compressor, causing a change in the
discharge capacity of the compressor, the pressure Pc in the
crankcase is adjusted after the differential pressure (Pd-Ps) is
changed due to the change in the discharge capacity of the
compressor. Therefore, when the engine is in a transient period in
which the rotational speed of the engine has rapidly changed, the
discharge capacity of the compressor can be temporarily largely
changed due to low responsiveness of the compressor. This
inconvenience can be eliminated by improving the sensitivity of the
control valve.
[0012] However, the control valve for the variable displacement
compressor, which operates based on the differential pressure
(Pd-Ps), has a structure in which the load of the solenoid is
applied to the piston rod in a manner against the high discharge
pressure Pd which the valve element receives, and hence the method
of increasing sensitivity by increasing the pressure-receiving area
is impractical since the load of the solenoid has to be increased,
which makes the solenoid very large in size.
SUMMARY OF THE INVENTION
[0013] The present invention has been made in view of the problem,
and an object thereof is to provide a control valve for a variable
displacement compressor, which is capable of promptly restoring the
compressor to a predetermined discharge capacity even when the
rotational speed of an engine has rapidly changed.
[0014] To solve the above problem, the present invention provides a
control valve for a variable displacement compressor, which is
configured to sense differential pressure between discharge
pressure in a discharge chamber of the compressor and suction
pressure in a suction chamber of the compressor, and control a flow
rate of refrigerant allowed to flow from the discharge chamber into
a crankcase to thereby change a discharge capacity of the
refrigerant, comprising a pressure-sensing section that senses a
change in pressure caused by a rapid change in a rotational speed
of the compressor and accelerates a motion of a valve section in a
valve-opening/closing direction performed in response to the change
in pressure.
[0015] 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
[0016] FIG. 1 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a first embodiment of the present
invention.
[0017] FIG. 2 is a diagram useful in explaining operation of the
control valve, in the case where the rotational speed of the
compressor is rapidly increased.
[0018] FIG. 3 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a second embodiment of the present
invention.
[0019] FIG. 4 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a third embodiment of the present
invention.
[0020] FIG. 5 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a fourth embodiment of the present
invention.
[0021] FIG. 6 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a fifth embodiment of the present
invention.
[0022] FIG. 7 is a central longitudinal cross-sectional view
showing a configuration of a control valve for a variable
displacement compressor, according to a sixth embodiment of the
present invention.
[0023] FIG. 8 is an enlarged fragmentary central longitudinal
cross-sectional view showing details of essential parts of a
control valve for a variable displacement compressor, according to
a seventh embodiment of the present invention.
[0024] FIG. 9 is an enlarged fragmentary central longitudinal
cross-sectional view showing details of essential parts of a
control valve for a variable displacement compressor, according to
an eighth embodiment of the present invention.
[0025] FIG. 10 is an enlarged fragmentary central longitudinal
cross-sectional view of the control valve according to the eighth
embodiment in an operative state in which the discharge pressure of
the compressor has rapidly decreased.
[0026] FIG. 11 is an enlarged fragmentary central longitudinal
cross-sectional view showing a control valve for a variable
displacement compressor, according to a ninth embodiment of the
present invention, in states in which the discharge pressure has
rapidly increased and in which the discharge pressure has rapidly
decreased.
[0027] FIG. 12 is an enlarged fragmentary central longitudinal
cross-sectional view showing details of essential parts of a
control valve for a variable displacement compressor, according to
a tenth embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Hereinafter, embodiments of the present invention will be
described in detail with reference to the drawings.
[0029] FIG. 1 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a first embodiment of the present
invention.
[0030] The control valve 11 comprises a pressure-sensing section 12
that senses a rapid change in discharge pressure Pd, a valve
section 13 that senses the differential pressure (Pd-Ps) between
the discharge pressure Pd and suction pressure Ps to control the
flow rate of refrigerant allowed to flow from a discharge chamber
into a crankcase, and a solenoid 14 that is capable of setting a
predetermined value to which the differential pressure (Pd-Ps) is
to be controlled by the control valve, from outside, these sections
being arranged on the same axis.
[0031] The pressure-sensing section 12 and the valve section 13
have a first body 15, and a second body 16 into which the first
body 15 is press-fitted. The first body 15 has a cylinder 17 that
has an open upper end, as viewed in FIG. 1, and the open end
defines a high-pressure port 18 communicating with the discharge
chamber when the control valve 11 is mounted in the variable
displacement compressor. A pressure-sensing piston 19 is disposed
within the cylinder 17 in a manner movable axially back and forth,
and the pressure-sensing piston 19 is urged downward, as viewed in
FIG. 1, by a spring 21 disposed between the pressure-sensing piston
19 and a stopper 20 fixed to an upper end of the first body 15. The
cylinder 17 has a hole formed in the center of a bottom thereof,
and a hollow cylindrical valve seat-forming member 22 is
press-fitted in the hole. The valve seat-forming member 22 has an
upper part thereof inserted into a cylinder formed in an center of
a lower end the pressure-sensing piston 19, as viewed in FIG. 1, in
a recessed manner, thereby defining a pressure-adjusting chamber 23
having an annular space, together with the first body 15 and the
pressure-sensing piston 19. The pressure-sensing piston 19 is
formed with a through hole which communicates between the cylinder
formed in the pressure-sensing piston 19 in a recessed manner and
the high-pressure port 18, whereby the high-pressure port 18
communicates with a passage axially extending through the valve
seat-forming member 22, i.e. a valve hole, via the through hole of
the pressure-sensing piston 19. Further, the pressure-sensing
piston 19 has one end of a shaft 24 fixed thereto, the shaft 24
extending through the valve hole defined by the valve seat-forming
member 22.
[0032] The valve seat-forming member 22 has a lower end, as viewed
in FIG. 1, which forms a valve seat, and a valve element 25 is
disposed in a manner opposed to the valve seat such that the valve
element 25 can open and close the valve hole. The valve element 25
is formed integrally with a piston rod 26, and the piston rod 26 is
held by the second body 16 in a manner movable axially back and
forth. The piston rod 26 is formed such that it has an outer
diameter equal to the inner diameter of the valve hole of the valve
seat-forming member 22. The valve element 25 is in abutment with
the other end of the shaft 24 which is disposed within the valve
hole of the valve seat-forming member 22 and urged downward by the
spring 21, as viewed in FIG. 1. Further, the piston rod 26 is urged
by a spring 27 in a direction in which the valve element 25 is
moved away from the valve seat-forming member 22. It should be
noted that a space where the valve element 25 is disposed
communicates with a medium-pressure port 28 for supplying pressure
Pc to the crankcase of the compressor when the control valve 11 is
mounted in the compressor, and a space where the spring 27 is
disposed communicates with a low-pressure port 29 for receiving the
suction pressure Ps from a suction chamber.
[0033] The second body 16 has a hole formed in the center of a
lower part thereof, as viewed in FIG. 1. The rim of an opening of a
bottomed sleeve 30 is tightly connected to the hole. The bottomed
sleeve 30 has a core 31 and a plunger 32 of the solenoid 14
arranged therein. The core 31 is fixed to the hole of the second
body 16 and the bottomed sleeve 30 by press-fitting. The plunger 32
is axially slidably disposed in the bottomed sleeve 30, and fixed
to one end of a shaft 33 disposed in a manner axially extending
through the core 31. Further, the plunger 32 is urged toward the
core 31 by a spring 34 such that the other end of the shaft 33 is
brought into abutment with a lower end face of the piston rod 26,
as viewed in FIG. 1. Disposed around the outer periphery of the
bottomed sleeve 30 is a coil 35, and a harness 36 for supplying
electric current to the coil 35 is led to the outside of the
solenoid 14.
[0034] In the control valve 11 constructed as above, the spring 27
urging the piston rod 26 of the valve section 13 toward the
solenoid 14 is set to have a larger spring load than that of the
spring 34 urging the shaft 33 of the solenoid 14 toward the valve
section 13. Therefore, when the solenoid 14 is not energized, the
valve element 25 of the valve section 13 is away from the valve
seat-forming member 22, and hence the valve section 13 is held in
the fully open state. At this time, high-pressure refrigerant at
the discharge pressure Pd, which has been introduced from the
discharge chamber of the compressor to the high-pressure port 18,
passes through the valve section 13 in the fully open state, and
flows from the medium-pressure port 28 into the crankcase. This
makes the pressure Pc in the crankcase close to the discharge
pressure Pd, whereby the compressor is caused to operate with the
minimum discharge capacity.
[0035] When an automotive air conditioner is started or when the
cooling load is maximum, the value of electric current supplied to
the solenoid 14 is maximum. At this time, the plunger 32 is
attracted with the maximum attractive force by the core 31, so that
the piston rod 26 of the valve section 13 is pushed by the shaft 33
fixed to the plunger 32, in the valve-closing direction against the
urging force of the spring 27, whereby the valve element 25 is
seated on the valve seat-forming member 22 to place the valve
section 13 in the fully closed state. At this time, the
high-pressure refrigerant at the discharge pressure Pd, introduced
into the high-pressure port 18, is blocked by the valve section 13
in the fully closed state, which makes the pressure Pc in the
crankcase close to the suction pressure Ps, whereby the compressor
is caused to operate with the maximum discharge capacity.
[0036] Now, when the value of electric current supplied to the
solenoid 14 is set to a predetermined value, the valve element 25
is stopped at a valve lift position where the loads of the springs
21 and 27 urging the valve element 25 in the valve-opening
direction, the load of the solenoid 14 urging the valve element 25
in the valve-closing direction, the discharge pressure Pd which the
valve element 25 receives in the valve-opening direction, and the
suction pressure Ps which the valve element 25 receives in the
valve-closing direction are balanced.
[0037] In the above balanced state, when the rotational speed of
the compressor is increased e.g. by an increase in the rotational
speed of the engine, to increase the discharge capacity of the
compressor, the discharge pressure Pd increases and the suction
pressure Ps decreases so that the differential pressure (Pd-Ps)
increases to cause a force in the valve-opening direction to act on
the valve element 25 and the piston rod 26, whereby the valve
element 25 is lifted, thereby allowing refrigerant to flow from the
discharge chamber into the crankcase at an increased flow rate. As
a result, the pressure Pc in the crankcase is increased to cause
the compressor to operate in a direction in which the discharge
capacity thereof is reduced, whereby the differential pressure
(Pd-Ps) is controlled to the predetermined value set by the
solenoid 14. When the rotational speed of the engine has decreased,
the control valve operates oppositely to the above, whereby the
compressor is controlled such that the differential pressure
(Pd-Ps) becomes equal to the predetermined value set by the
solenoid 14.
[0038] As described above, when the rotational speed of the
compressor is being gently changed as in the case where an
automotive vehicle is cruising at an approximately constant speed,
the pressure-sensing section 12 is insensitive, and performs the
same operation as that of the conventional control valve for a
variable displacement compressor. Next, a description will be given
of operation of the control valve 11 in the case where the
rotational speed of the compressor is rapidly changed by a rapid
change in the rotational speed of the engine as in the case where
the automotive vehicle has been rapidly accelerated or
decelerated.
[0039] FIG. 2 is a diagram useful in explaining operation of the
control valve for a variable displacement compressor, in the case
where the rotational speed of the compressor is rapidly
increased.
[0040] When the compressor is stably operating e.g. at a rotational
speed of 800 rpm, if the rotational speed has been increased up to
a rotational speed of 2000 rpm, the valve lift is increased due to
a rise in the discharge pressure Pd and a drop in the suction
pressure Ps, and as a result, the control valve 11 tends to
increase the pressure Pc in the crankcase, as indicated by broken
lines in FIG. 2. At this time, the pressure-sensing section 12
receives the discharge pressure Pd, which has rapidly increased, at
the pressure-sensing piston 19 having a larger pressure-receiving
area than that of the valve element 25. On the other hand, in the
pressure-adjusting chamber 23, pressure Pd(av), which is average
pressure of the discharge pressure Pd before it has rapidly
increased, is maintained, and hence the differential pressure
(Pd-Pd(av)) generates a force which acts on the pressure-sensing
piston 19 in a direction in which the pressure-sensing piston 19 is
moved toward the valve section 13. This force is applied to the
valve element 25 via the shaft 24, and hence in addition to the
rapidly increased discharge pressure Pd, the differential pressure
(Pd-Pd(av)) of the pressure-sensing section 12 is additionally
applied to the valve element 25. As a result, as indicated by solid
lines in FIG. 2, the valve lift is increased more promptly, so that
the control valve 11 causes the pressure Pc in the crankcase to
increase more promptly. After that, in the pressure-sensing section
12, the rapidly increased discharge pressure Pd is promptly
introduced into the pressure-adjusting chamber 23 via the clearance
between the cylinder 17 and the pressure-sensing piston 19 and the
clearance between the pressure-sensing piston 19 and the valve
seat-forming member 22, whereby the differential pressure
(Pd-Pd(av)) becomes equal to zero. At this time, the function of
the pressure-sensing section 12 has been lost. This means that the
pressure-sensing section 12 has the function of a derivative
element for sensing a rapid increase in the discharge pressure Pd,
and temporarily accelerating the motion of the valve section 13 in
the valve-opening direction. This enables the control valve 11 to
promptly restore the compressor to the predetermined discharge
capacity.
[0041] Although the above description has been given of the
operation of the control valve 11 in the case of the rotational
speed of the compressor being rapidly increased, the control valve
11 operates similarly when the rotational speed of the compressor
is rapidly decreased. More specifically, when the rotational speed
of the compressor is rapidly decreased, the differential pressure
(Pd(av)-Pd) acting on the pressure-sensing section 12 causes the
pressure-sensing piston 19 to move away from the valve section 13,
and hence the urging force of the spring 21 urging the valve
element 25 in the valve-opening direction via the pressure-sensing
piston 19 and the shaft 24 is weakened, which causes the valve
element 25 to move in the valve-closing direction. After all, when
the rotational speed of the compressor is rapidly decreased as
well, the control valve 11 operates in a quite an opposite way
compared with the case of the rotational speed of the compressor
being rapidly increased.
[0042] However, when the rotational speed of the variable
displacement compressor is rapidly changed, the shaft 24 sometimes
moves away from the valve element 25, depending on the setting of
the spring 21. In such a case, the speed of motion of the valve
element 25 in the valve-closing direction is made slower, so that
the valve-opening characteristic of the control valve becomes an
asymmetric one in which the valve opens differently between when
the rotational speed of the compressor is rapidly increased and
when the same is rapidly decreased. In this case, when the
rotational speed of the compressor is rapidly increased as when the
automotive vehicle is rapidly accelerated, if the discharge
capacity of the compressor is not promptly decreased, the load of
the compressor applied to the engine becomes more significant to
the engine, whereas in the opposite case, even if the discharge
capacity of the compressor is not promptly increased, the load of
the compressor applied to the engine only decreases the speed of
the automotive vehicle, and hence there is no problem even if the
valve opening characteristic is asymmetric.
[0043] FIG. 3 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a second embodiment. In FIG. 3, component
elements having functions identical or equivalent to those of the
component elements shown in FIG. 1 are designated by identical
reference numerals, and detailed description thereof is
omitted.
[0044] As is distinct from the control valve 11 according to the
first embodiment, in the control valve 11a according to the second
embodiment, the shaft 24 of the pressure-sensing section 12, the
valve element 25 of the valve section 13, and the piston rod 26 are
formed integrally with each other, and the spring 21 urging the
pressure-sensing piston 19 toward the valve section 13 is
eliminated. That is, in the pressure-sensing section 12 and the
valve section 13 of this control valve 11a, the shaft 24, the valve
element 25, and the piston rod 26 are formed integrally with each
other, and the shaft 24 is fixed to the pressure-sensing piston
19.
[0045] With this arrangement, the control valve 11a is capable of
directly exerting influence of the pressure-sensing section 12 on
the valve section 13 in both the cases where the rotational speed
of the compressor has rapidly increased and where the same has
rapidly decreased. That is, when the rotational speed of the
compressor is rapidly increased, the control valve 11a operates in
quite the same way as the control valve 11 according to the first
embodiment, but when the rotational speed of the compressor is
rapidly decreased, the pressure-sensing piston 19 of the
pressure-sensing section 12 is capable of directly actuating the
shaft 24, the valve element 25, and the piston rod 26 which are
integrally formed with each other, in the direction of closing the
valve section 13. Therefore, the control valve 11a is suitable when
the valve-opening characteristic is desired to be made symmetric
between when the rotational speed of the compressor is rapidly
increased and when the same is rapidly decreased.
[0046] FIG. 4 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a third embodiment of the present
invention. In FIG. 4, component elements having functions identical
or equivalent to those of the component elements shown in FIG. 1
are designated by identical reference numerals, and detailed
description thereof is omitted.
[0047] As is distinct from the control valve 11a according to the
second embodiment, in the control valve 11b according to the third
embodiment comprises flow rate-adjusting means for adjusting the
amount of leakage of refrigerant flowing into or out of the
pressure-adjusting chamber 23, at a location between the cylinder
17 of the pressure-sensing section 12 and the pressure-sensing
piston 19 and between the pressure-sensing piston 19 and the valve
seat-forming member 22. That is, in the control valve 11b according
to the third embodiment, the pressure-sensing piston 19 and the
valve seat-forming member 22 have outer peripheries thereof formed
with grooves, respectively, and sealing members 37 and 38, such as
piston rings, are disposed in the respective grooves. The sealing
members 37 and 38 have the shape of a C-shaped ring which is
circumferentially partially cut out, and is made of a material low
in sliding resistance, such as polytetrafluoroethylene.
[0048] As described above, in the pressure-sensing piston 12, the
sealing members 37 and 38 are arranged between the cylinder 17 and
the pressure-sensing piston 19 and between the pressure-sensing
piston 19 and the valve seat-forming member 22, and the
circumferential length of each of cut-off portions of the members
37 and 38 are adjusted, whereby the flow rate of refrigerant
flowing from the high-pressure port 18 into the pressure-adjusting
chamber 23 or the flow rate of refrigerant flowing out from the
pressure-adjusting chamber 23 to the high-pressure port 18 can be
adjusted. This makes it possible to adjust the rise and fall
characteristics of the valve lift.
[0049] FIG. 5 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a fourth embodiment of the present
invention. In FIG. 5, component elements having functions identical
or equivalent to those of the component elements shown in FIG. 1
are designated by identical reference numerals, and detailed
description thereof is omitted.
[0050] As is distinct from the control valves 11, 11a, and 11b
according to the first to third embodiments which are configured to
sense a rapid change in the discharge pressure Pd for control of
the valve lift of the valve section 13, the control valve 11c
according to the fourth embodiment is configured to sense a rapid
change in pressure Pc supplied to the crankcase for control of the
valve lift of the valve section 13.
[0051] To this end, in the control valve 11c according to the
fourth embodiment, the pressure-sensing section 12 is disposed
between the valve section 13 and the solenoid 14, and the
pressure-sensing piston 19 that receives the pressure Pc is fixed
to the piston rod 26 integrally formed with the valve element 25.
Then, in the pressure-adjusting chamber 23 having an annular shape,
which is defined by the first body 15 having the cylinder 17 formed
in an end face thereof toward the valve section 13, and the
pressure-sensing piston 19, there is disposed a spring 39 for
urging the piston rod 26 in the valve-opening direction via the
pressure-sensing piston 19 against the discharge pressure Pd.
[0052] When the control valve 11c constructed as above is
controlling the compressor to a predetermined valve lift, if the
discharge pressure Pd rapidly increases and the suction pressure Ps
rapidly decreases, the differential pressure (Pd-Ps) between the
opposite ends of the valve element 25 and the piston rod 26
increases, whereby the valve lift is increased. This causes the
pressure Pc on the downstream side of the valve section 13 as well
to rapidly increase. At this time, since the pressure-sensing
piston 19 of the pressure-sensing section 12 has a sufficiently
larger pressure-receiving area than that of the valve element 25, a
force is generated which causes the pressure-sensing piston 19 to
further move in a direction away from the valve section 13, and the
force causes the piston rod 26 fixed to the pressure-sensing piston
19 to act in the valve-opening direction. Therefore, the force of
the pressure-sensing piston 19 acting in the valve-opening
direction is additionally applied to the valve element 25, and
thereby causes the valve lift to promptly increase, and hence the
discharge pressure Pd and the pressure Pc in the crankcase to
sharply increase. In a short time, when the pressure in the
pressure-adjusting chamber 23 becomes equal to the pressure Pc in
the crankcase, the discharge pressure Pd, the pressure Pc in the
crankcase, the suction pressure Ps, and the valve lift promptly
returns to their original states. Of course, also when the
rotational speed of the compressor is rapidly decreased, the
control valve 11c operates promptly, similarly to the above, to
thereby make it possible to promptly restore the compressor to the
predetermined discharge capacity.
[0053] FIG. 6 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a fifth embodiment of the present
invention. In FIG. 6, component elements having functions identical
or equivalent to those of the component elements shown in FIG. 1
are designated by identical reference numerals, and detailed
description thereof is omitted.
[0054] As is distinct from the control valves 11, 11a, and 11b
according to the first to third embodiments which are configured to
sense a rapid change in the discharge pressure Pd for control of
the valve lift of the valve section 13, and the control valve 11c
according to the fourth embodiment which is configured to sense a
rapid change in pressure Pc supplied to the crankcase for control
of the valve lift of the valve section 13, the control valve 11d
according to the fifth embodiment is configured to sense a rapid
change in suction pressure Ps for control of the valve lift of the
valve section 13.
[0055] To this end, in the control valve 11d, the cylinder 17 is
formed in an end face, toward the solenoid 14, of the first body 15
holding the piston rod 26, and in the cylinder 17, there is
disposed the pressure-sensing piston 19 which is fixed to the
piston rod 26 integrally formed with the valve element 25. Then, in
the pressure-adjusting chamber 23 having an annular shape, there is
disposed a spring 27 urging the piston rod 26 in the valve-opening
direction via the pressure-sensing piston 19.
[0056] When the control valve 11d constructed as above is
controlling the compressor to a predetermined valve lift, if the
discharge pressure Pd rapidly increases, and the suction pressure
Ps rapidly decreases, the differential pressure (Pd-Ps) between the
opposite ends of the valve element 25 and the piston rod 26
increases, whereby the valve lift is increased. At this time, since
the pressure-sensing piston 19 of the pressure-sensing section 12
has a sufficiently larger pressure-receiving area than that of the
valve element 25, a force is generated which causes the
pressure-sensing piston 19 to further move in a direction away from
the valve section 13, and the force causes the piston rod 26 fixed
to the pressure-sensing piston 19 to act in the valve-opening
direction. Therefore, the force of the pressure-sensing piston 19
acting in the valve-opening direction is additionally applied to
the valve element 25, and thereby causes the valve lift to promptly
increase, and hence the pressure Pc in the crankcase to sharply
increase, to thereby promptly cause the discharge capacity of the
compressor to change in the decreasing direction. In a short time,
when the pressure in the pressure-adjusting chamber 23 becomes
equal to the suction pressure Ps, the discharge pressure Pd, the
pressure Pc in the crankcase, the suction pressure Ps, and the
valve lift promptly returns to their original states. Of course,
also when the rotational speed of the compressor is rapidly
decreased, the control valve 11c operates promptly, similarly to
the above, to thereby make it possible to promptly restore the
compressor to the predetermined discharge capacity.
[0057] FIG. 7 is a central longitudinal cross-sectional view
showing a configuration of a control valve for a variable
displacement compressor, according to a sixth embodiment of the
present invention. In FIG. 7, component elements having functions
identical or equivalent to those of the component elements shown in
FIG. 1 are designated by identical reference numerals, and detailed
description thereof is omitted.
[0058] As is distinct from the control valve 11 according to the
first embodiment in which the pressure-sensing section 12 senses
rapid changes in the discharge pressure Pd in an increasing
direction and a decreasing direction for control of the valve lift
of the valve section 13, in the control valve 11e according to the
sixth embodiment, the pressure-sensing section 12 sensitively
senses a rapid change in the discharge pressure Pd in the
increasing direction but insensitively senses a rapid change in the
discharge pressure Pd in the decreasing direction for control of
the valve lift of the valve section 13, and a main passage for
high-pressure refrigerant does not extend through the
pressure-sensing section 12.
[0059] More specifically, in the control valve 11e, the
pressure-sensing piston 19 as a component of the pressure-sensing
section 12 is provided with a check valve mechanism for switching
sensitivity between when a rapid change occurs in the discharge
pressure Pd in the increasing direction and when a rapid change
occurs in the same in the decreasing direction. The check valve
mechanism is formed by forming a passage with a stepped portion in
the pressure-sensing piston 19 for communication between the
high-pressure port 18 and the pressure-adjusting chamber 23, and
disposing a ball-shaped valve element 40 in a large-diameter
passage toward the high-pressure port 18. The pressure-sensing
piston 19 is urged by a leaf spring 42 engaged with the open end of
the cylinder-forming member 41 which is formed integrally with the
valve seat-forming member 22 in a manner accommodating the
pressure-sensing piston 19, such that the pressure-sensing piston
19 is brought into contact with the shaft 24 that transmits the
motion of the pressure-sensing section 12 to the valve element 25
of the valve section 13. The leaf spring 42 also servers to prevent
the valve element 40 of the check valve mechanism from being
removed from a large-diameter passage in which it is disposed. The
shaft 24 is held by the cylinder-forming member 41 with a
predetermined clearance therefrom, in a manner movable axially back
and forth. Further, the valve hole of the valve seat-forming member
22 directly opens into the high-pressure port 18. Moreover, the
first body 15 has a strainer 43 attached thereto such that the
strainer 43 covers the high-pressure port 18 including the
pressure-sensing section 12.
[0060] When the control valve 11e constructed as above is
controlling the compressor at a predetermined valve lift, if the
discharge pressure Pd rapidly increases, the check valve mechanism
provided in the pressure-sensing piston 19 is closed, so that the
pressure-sensing piston 19 having a larger pressure-receiving area
than that of the valve element 25 senses a change in the discharge
pressure Pd which has rapidly increased, to cause the valve section
13 to rapidly operate in the valve-opening direction, thereby
causing the pressure Pc in the crankcase to rise more promptly such
that the discharge capacity of the compressor is promptly
controlled in the decreasing direction. Inversely, if the discharge
pressure Pd has rapidly decreased, the check valve mechanism
provided in the pressure-sensing piston 19 is opened by the
differential pressure between the rapidly-lowered discharge
pressure Pd and pressure in the pressure-adjusting chamber 23, so
that the pressure-sensing piston 19 becomes only little sensitive
to a change in the rapidly-lowered discharge pressure Pd. This
means that the control valve 11e has asymmetric valve-opening
characteristics that it has a high sensitivity to a rapid change in
the discharge pressure Pd in the increasing direction, whereas it
has a low sensitivity to a rapid change in the discharge pressure
Pd in the decreasing direction. Therefore, e.g. even if the
compressor performs a transient response to a rapid change in the
discharge pressure Pd in the increasing direction to cause the
discharge pressure Pd to rapidly change in the decreasing
direction, the compressor is prevented from performing a transient
response to a rapid change in the discharge pressure Pd in the
decreasing direction. This prevents occurrence of a hunting
phenomenon.
[0061] FIG. 8 is an enlarged fragmentary central longitudinal
cross-sectional view showing details of essential parts of a
control valve for a variable displacement compressor, according to
a seventh embodiment of the present invention. In FIG. 8, component
elements identical to those shown in FIG. 7 are designated by
identical reference numerals, and detailed description thereof is
omitted.
[0062] As is distinct from the control valve 11e according to the
sixth embodiment in which the check valve mechanism of the
pressure-sensing section 12 is formed using a ball-shaped valve, in
the control valve 11f according to the seventh embodiment, the
check valve mechanism of the pressure-sensing section 12 is formed
using a poppet valve.
[0063] More specifically, in the control valve 11f, the check valve
mechanism provided in the pressure-sensing section 12 is formed by
disposing a valve element 40a in the form of a mushroom in a
large-diameter passage toward the high-pressure port 18, which is
formed in the pressure-sensing piston 19 such that the passage
communicates between the high-pressure port 18 and the
pressure-adjusting chamber 23, and urging the valve element 40a in
the valve-closing direction using a spring 44 which is low in load.
The operation of the control valve 11f including the
pressure-sensing section 12, constructed as above, is the same as
the operation of the control valve 11e according to the sixth
embodiment.
[0064] FIG. 9 is an enlarged fragmentary central longitudinal
cross-sectional view showing details of essential parts of a
control valve for a variable displacement compressor, according to
an eighth embodiment of the present invention. FIG. 10 is an
enlarged fragmentary central longitudinal cross-sectional view of
the control valve according to the eighth embodiment in an
operative state in which the discharge pressure of the compressor
has rapidly decreased. In FIGS. 9 and 10, component elements
identical to those shown in FIG. 8 are designated by identical
reference numerals, and detailed description thereof is
omitted.
[0065] As is distinct from the control valve 11f according to the
seventh embodiment in which the check valve mechanism of the
pressure-sensing section 12 is formed using a poppet valve, in the
control valve 11g according to the eighth embodiment, the check
valve mechanism is formed using a reed valve.
[0066] More specifically, in this control valve 11g, the check
valve mechanism provided in the pressure-sensing section 12 has a
through hole formed through the pressure-sensing piston 19 such
that the through hole communicates between the high-pressure port
18 and the pressure-adjusting chamber 23, and a valve element 40b
is provided such that the valve element 40b opens and closes the
through hole at an end face of the pressure-sensing piston 19
toward the high-pressure port 18. The valve element 40b comprises a
film-like part which is capable of easily bending in response to
the differential pressure between discharge pressure Pd in the
high-pressure port 18 and pressure in the pressure-adjusting
chamber 23, and a base part fixed to the pressure-sensing piston
19, which are integrally formed of rubber or a flexible resin. The
valve element 40b has the base portion thereof fitted in a fixing
through hole formed through the pressure-sensing piston 19, and a
portion of the film-like part close to the base part is retained by
the leaf spring 42, whereby the valve element 40b is fixed to the
pressure-sensing piston 19.
[0067] In the control valve 11g having the pressure-sensing section
12 constructed as described above, when the rotational speed of the
compressor is gently being changed, and when the rotational speed
of the compressor is rapidly increased to increase the discharge
pressure Pd, the check valve mechanism of the pressure-sensing
section 12 is closed as shown in FIG. 9. On the other hand, when
the rotational speed of the compressor is rapidly decreased to
rapidly decrease the discharge pressure Pd, the check valve
mechanism of the pressure-sensing section 12 is opened by the
differential pressure between the discharge pressure Pd and the
pressure in the pressure-adjusting chamber 23, as shown in FIG.
10.
[0068] FIG. 11 is an enlarged fragmentary central longitudinal
cross-sectional view showing a control valve for a variable
displacement compressor, according to a ninth embodiment of the
present invention, in states in which the discharge pressure has
rapidly increased and in which the discharge pressure has rapidly
decreased. In FIG. 11, component elements identical to those shown
in FIGS. 9 and 10 are designated by identical reference numerals,
and detailed description thereof is omitted.
[0069] The control valve 11h according to the ninth embodiment is
distinguished from the control valve 11g according to the eighth
embodiment, in that the check valve mechanism formed using a reed
valve is differently configured.
[0070] More specifically, in this control valve 11h, the check
valve mechanism provided in the pressure-sensing section 12 has a
valve hole formed by a gap formed around the outer periphery of the
pressure-sensing piston 19, and a valve element 40c disposed such
that the valve element 40c blocks the valve hole from an end toward
the high-pressure port 18, with a central portion of the valve
element 40c being held by the leaf spring 42 and the
pressure-sensing piston 19 in a sandwiched manner. The valve
element 40c may be formed by a circular film made of rubber or a
flexible resin.
[0071] When the rotational speed of the compressor is gently being
changed, and when the rotational speed of the compressor is rapidly
increased to increase the discharge pressure Pd, the valve element
40c of the check valve mechanism is brought into intimate contact
with upper end faces of the pressure-sensing piston 19 and the
cylinder in a manner extending over a gap around the outer
periphery of the pressure-sensing piston 19 to close the check
valve mechanism, as shown in the left half of FIG. 11. On the other
hand, when the rotational speed of the compressor is rapidly
decreased to rapidly decrease the discharge pressure Pd, the valve
element 40c of the check valve mechanism is bent upward due to the
differential pressure between the discharge pressure Pd and the
pressure in the pressure-adjusting chamber 23, to open the check
valve mechanism, as shown in the right half of FIG. 11.
[0072] FIG. 12 is an enlarged fragmentary central longitudinal
cross-sectional view showing details of essential parts of a
control valve for a variable displacement compressor, according to
a tenth embodiment of the present invention. In FIG. 12, component
elements identical to those shown in FIG. 11 are designated by
identical reference numerals, and detailed description thereof is
omitted.
[0073] As is distinct from the control valves 11e to 11h according
to the sixth to ninth embodiments which have the check valve
mechanism, the control valve 11i according to the tenth embodiment
includes a sensitivity-switching mechanism which is capable of
switching sensitivity between when the discharge pressure Pd
rapidly increases and when the same rapidly decreases.
[0074] More specifically, in the control valve 11i, the
sensitivity-switching mechanism provided in the pressure-sensing
section 12 switches ease of flow of refrigerant flowing into or out
of the pressure-adjusting chamber 23, and the outer peripheral
shape of the pressure-sensing piston 19 is formed into a tapered
shape in which the outer diameter of the pressure-sensing piston 19
progressively decreases from the side toward the high-pressure port
18 to the pressure-adjusting chamber 23. Therefore, a gap between
the outer periphery of the pressure-sensing piston 19 and the body
15 provides a narrowest restriction at an upper end of the gap, as
viewed in FIG. 12, and is progressively increased in passage
cross-sectional area from the restriction to the pressure-adjusting
chamber 23. Assuming that the cross-sectional area of the
refrigerant passage is suddenly expanded on the high-pressure port
18 side of the restriction, and refrigerant flows from the
restriction into the suddenly-expanded portion, a contracted flow
is produced there. The pressure-sensing section 12 has a
characteristic that insofar as the differential pressure between
pressure in the high-pressure port 18 and pressure in the
pressure-adjusting chamber 23 is the same, the flow rate of
refrigerant is smaller when refrigerant having entered the
high-pressure port 18 passes through a restriction after being
suddenly restricted in flow than when refrigerant in the
pressure-adjusting chamber 23 passes through the restriction after
being progressively restricted in flow.
[0075] When the rotational speed of the compressor is rapidly
increased to thereby rapidly increase the discharge pressure Pd,
refrigerant is about to flow from the side toward the high-pressure
port 18 into the pressure-adjusting chamber 23 through the gap
between the outer periphery of the pressure-sensing piston 19 and
the body 15. Inversely, when the rotational speed of the compressor
is rapidly decreased to rapidly decrease the discharge pressure Pd,
refrigerant is about to flow from the pressure-adjusting chamber 23
toward the high-pressure port 18 through the gap around the outer
periphery of the pressure-sensing piston 19. In this regard, there
is a difference in the flow rate of refrigerant flowing through the
gap between when the discharge pressure Pd has rapidly increased
and when the same has rapidly decreased. Therefore, a force which
the pressure-sensing piston 19 exerts on the valve element 25 of
the valve section 13 in the valve-opening direction when the
discharge pressure Pd has rapidly increased can be made larger than
a force which the pressure-sensing piston 19 exerts on the valve
element 25 of the valve section 13 in the valve-closing direction
when the discharge pressure Pd has rapidly decreased.
[0076] The control valve for a variable displacement compressor,
according to the present invention, is configured such that when
the compressor undergoes a rapid change in the rotational speed
thereof, the pressure-sensing section senses a change in pressure
caused by the rapid change in the rotational speed of the
compressor and accelerates the motion of the valve section in the
valve-opening/closing direction performed in response to the change
in pressure. This is advantageous in that the sensitivity of the
control valve can be enhanced only when the compressor undergoes a
rapid change in the rotational speed thereof.
[0077] 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.
* * * * *