U.S. patent application number 11/213902 was filed with the patent office on 2006-03-02 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 | 20060045758 11/213902 |
Document ID | / |
Family ID | 35457145 |
Filed Date | 2006-03-02 |
United States Patent
Application |
20060045758 |
Kind Code |
A1 |
Hirota; Hisatoshi |
March 2, 2006 |
Control valve for variable displacement compressor
Abstract
To provide a control valve for a variable displacement
compressor, which is capable of promptly restoring a
high-sensitivity variable displacement compressor to a
predetermined discharge capacity without causing hunting even when
the rotational speed of the compressor is rapidly changed. A valve
section controls the flow rate of refrigerant flowing from a
discharge chamber to a crankcase, based on the differential
pressure between discharge pressure and suction pressure. A
pressure-sensing section is provided in a high-pressure port, and
when a pressure-sensing piston having a pressure-receiving area
larger than that of a valve element is exposed to a rapid change in
the discharge pressure, the differential pressure generated between
the discharge pressure and pressure in a pressure-adjusting chamber
acts on the valve element in a direction opposite to a
valve-opening/closing direction, to thereby temporarily make slower
the motion of the valve element which is to be opened or closed by
the differential pressure between the discharge pressure and the
suction pressure. This makes it possible to promptly restore a
high-sensitivity variable displacement compressor to a
predetermined discharge capacity without hunting.
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: |
35457145 |
Appl. No.: |
11/213902 |
Filed: |
August 30, 2005 |
Current U.S.
Class: |
417/222.2 ;
417/212 |
Current CPC
Class: |
F04B 27/1804 20130101;
F04B 2027/1813 20130101; F04B 2027/1859 20130101; F04B 2027/1854
20130101; F04B 2027/1827 20130101 |
Class at
Publication: |
417/222.2 ;
417/212 |
International
Class: |
F04B 49/00 20060101
F04B049/00; F04B 1/26 20060101 F04B001/26 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2004 |
JP |
2004-251287 |
Jan 28, 2005 |
JP |
2005-021518 |
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 makes a motion of a valve section in a
valve-opening/closing direction slower by a value proportional to a
degree of 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, and a
shaft that transmits an axial motion generated by differential
pressure between the discharge pressure and pressure in a
pressure-adjusting chamber closed by the pressure-sensing piston
which are received 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 section further comprises sensitivity-switching
means for making a force which the pressure-sensing piston causes
to act on the valve element via the shaft smaller when the
discharge pressure is rapidly increased than when the discharge
pressure is rapidly decreased.
5. The control valve according to claim 4, 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 allowing flow of refrigerant from
the side toward the high-pressure port to the pressure-adjusting
chamber, and blocking flow of the refrigerant from the
pressure-adjusting chamber to the side toward the high-pressure
port.
6. The control valve according to claim 4, wherein the
sensitivity-switching means is a check valve provided in a passage
that is formed through a member defining the pressure-adjusting
chamber together with the pressure-sensing piston such that the
passage communicates between a side receiving the discharge
pressure and the pressure-adjusting chamber, for blocking flow of
refrigerant from the side receiving the discharge pressure to the
pressure-adjusting chamber, and allowing the refrigerant to flow
from the pressure-adjusting chamber to the side receiving the
discharge pressure.
7. The control valve according to claim 4, wherein the
sensitivity-switching means is formed by forming an outer periphery
of the pressure-sensing piston into a tapered shape such that a gap
formed as a passage along the outer periphery of the
pressure-sensing piston is progressively decreased in
cross-sectional area from the side toward the high-pressure port to
the pressure-adjusting chamber.
8. The control valve according to claim 1, wherein the
pressure-sensing section has a pressure-sensing -piston disposed in
a medium-pressure port through which control pressure controlled by
the valve section is delivered into the crankcase, for receiving
the control pressure at a pressure-receiving area larger than that
of a valve element, and wherein the pressure-sensing piston is
configured to transmit an axial motion caused by differential
pressure between the control pressure and pressure in a
pressure-adjusting chamber closed by the pressure-sensing piston
which are received by the pressure-sensing piston, to the valve
element.
9. The control valve according to claim 8, wherein the
pressure-sensing section further comprises sensitivity-switching
means for making a force which the pressure-sensing piston causes
to act on the valve element smaller when the control pressure is
rapidly increased than when the control pressure is rapidly
decreased.
10. The control valve according to claim 9, wherein the
sensitivity-switching means is a check valve provided in a passage
that is formed through the pressure-sensing piston such that the
passage communicates between a side toward the medium-pressure port
and the pressure-adjusting chamber, for allowing refrigerant to
flow from the side toward the medium-pressure port to the
pressure-adjusting chamber, and blocking flow of the refrigerant
from the pressure-adjusting chamber to the side toward the
medium-pressure port.
11. The control valve according to claim 1, wherein the
pressure-sensing section has a pressure-sensing piston disposed in
a low-pressure port through which the suction pressure is
introduced, for receiving the suction pressure at a
pressure-receiving area larger than that of a valve element, and
wherein the pressure-sensing piston is configured to transmit an
axial motion caused by differential pressure between the suction
pressure and pressure in a pressure-adjusting chamber closed by the
pressure-sensing piston which are received by the pressure-sensing
piston, to the valve element.
12. The control valve according to claim 11, wherein the
pressure-sensing section further comprises sensitivity-switching
means for making a force which the pressure-sensing piston causes
to act on the valve element larger when the suction pressure is
rapidly increased than when the suction pressure is rapidly
decreased.
13. The control valve according to claim 12, wherein the
sensitivity-switching means is a check valve disposed in a passage
that is formed through the pressure-sensing piston such that the
passage communicates between a side toward the low-pressure port
and the pressure-adjusting chamber, for allowing refrigerant to
flow from the side toward the low-pressure port to the
pressure-adjusting chamber, and blocking flow of the refrigerant
from the pressure-adjusting chamber to the side toward the
low-pressure port.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY
[0001] This application claims priority of Japanese Application No.
2004-251287 filed on Aug. 31, 2004 and entitled "CONTROL VALVE FOR
VARIABLE DISPLACEMENT COMPRESSOR" and No. 2005-021518 filed on Jan.
28, 2005, 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 above compressor controlled by the control valve, a
change in the rotational speed of the engine changes the rotational
speed of the compressor to change the discharge capacity of the
compressor. This change in the discharge capacity changes the
differential pressure (Pd-Ps) to change the pressure Pc in the
crankcase, whereby the inclination angle of the wobble plate is
changed to vary the discharge capacity between the maximum and
minimum capacities. For example, when the differential pressure
(Pd-Ps) is zero as at the start of the compressor, the compressor
operates with the maximum capacity, and when the differential
pressure (Pd-Ps) reaches a certain value, the capacity starts to be
varied. However, each individual variable displacement compressor
has a character of its own, and the differential pressure (Pc-Ps)
between the pressure Pc in the crankcase and the suction pressure
Ps at the start of varying the discharge capacity has a range of
values varying depending on the compressor. This is caused by the
difference in mobility of the wobble plate, that is, the difference
in sensitivity between compressors.
[0012] However, a high-sensitivity variable displacement compressor
suffers from the problem of reacting sensitively to rapid changes
in the discharge pressure Pd and the suction pressure Ps caused by
a sudden change in the rotational speed of the engine, resulting in
hunting.
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 controlling the
variable displacement compressor having high sensitivity stably
without causing hunting, even when a rapid change in pressure is
caused by a sudden change in the rotational speed of the
engine.
[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 makes a motion of a valve section in a
valve-opening/closing direction slower by a value proportional to a
degree of 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
schematically showing a control valve for a variable displacement
compressor, according to a sixth embodiment of the present
invention.
[0023] FIG. 8 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a seventh embodiment of the present
invention.
[0024] FIG. 9 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to an eighth embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] Hereinafter, embodiments of the present invention will be
described in detail with reference to the drawings.
[0026] 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.
[0027] 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.
[0028] A body 15 containing the pressure-sensing section 12 and the
valve section 13 has an upper part thereof, as views in FIG. 1,
formed with a cylinder 16, and an upper end thereof formed with an
opening closed by a lid 17. A high-pressure port 18 which
communicates with the discharge chamber when the control valve 11
is mounted in the variable displacement compressor is formed in the
body at a location below the cylinder 16, as viewed in FIG. 1. A
pressure-sensing piston 19 is disposed within the cylinder 16 in a
manner movable axially back and forth, and a space for a
pressure-adjusting chamber 20 is defined in an upper portion of the
cylinder 16, together with the body 15 and the lid 17. The
pressure-adjusting chamber 20 is configured to communicate with the
high-pressure port 18 via a predetermined clearance between the
cylinder 16 and the pressure-sensing piston 19. The cylinder 16 has
a hole formed in the center of a bottom thereof, and a hollow
cylindrical valve seat-forming member 21 is press-fitted in the
hole. The valve seat-forming member 21 has a passage, i.e. a valve
hole axially extending therethrough, and a lower end, as viewed in
FIG. 1, which forms a valve seat of the valve section 13. Further,
a shaft 22 extends through the valve hole formed through the valve
seat-forming member 21, and one end of the shaft 22 is fixed to the
pressure-sensing piston 19.
[0029] A valve element 23 is disposed in a manner opposed to the
valve seat formed by the valve seat-forming member 21 such that it
can open and close the valve hole. The valve element 23 is
integrally formed with the shaft 22 having one end thereof fixed to
the pressure-sensing piston 19 and a piston rod 24 held by the body
15 in a manner movable axially back and forth. The piston rod 24 is
formed such that it has an outer diameter equal to the inner
diameter of the valve hole of the valve seat-forming member 21.
Further, the piston rod 24 is urged by a spring 25 in a direction
in which the valve element 23 is moved away from the valve
seat-forming member 21. It should be noted that a space where the
valve element 23 is disposed communicates with a medium-pressure
port 26 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 25 is disposed communicates with a
low-pressure port 27 for receiving the suction pressure Ps from a
suction chamber.
[0030] The body 15 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 28 is tightly connected to the hole. The bottomed sleeve 28
has a core 29 and a plunger 30 of the solenoid 14 arranged therein.
The core 29 is fixed to the hole in the center of the lower part of
the body 15 and the bottomed sleeve 28 by press-fitting. The
plunger 30 is axially slidably disposed in the bottomed sleeve 28,
and fixed to one end of a shaft 31 disposed in a manner axially
extending through the core 29. Further, the plunger 30 is urged
toward the core 29 by a spring 32 such that the other end of the
shaft 31 is brought into abutment with a lower end face of the
piston rod 24, as viewed in FIG. 1. Disposed around the outer
periphery of the bottomed sleeve 28 is a coil 33, and a harness 34
for supplying electric current to the coil 33 is led to the outside
of the solenoid 14.
[0031] In the control valve 11 constructed as above, the spring 25
urging the piston rod 24 of the valve section 13 toward the
solenoid 14 is set to have a larger spring load than that of the
spring 32 urging the shaft 31 of the solenoid 14 toward the valve
section 13. Therefore, when the solenoid 14 is deenergized, the
valve element 23 of the valve section 13 is away from the valve
seat-forming member 21, 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 26 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.
[0032] When an automotive air conditioner is started or when the
cooling load is maximum, the value of electric control current
supplied to the solenoid 14 is maximum. At this time, the plunger
30 is attracted with the maximum attractive force by the core 29,
so that the piston rod 24 of the valve section 13 is pushed by the
shaft 31 fixed to the plunger 30, in the valve-closing direction
against the urging force of the spring 25, whereby the valve
element 23 is seated on the valve seat-forming member 21 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.
[0033] Now, when the value of electric current supplied to the
solenoid 14 is set to a predetermined value, the valve element 23
is stopped at a valve lift position where the load of the spring 25
urging the valve element 23 in the valve-opening direction, the
load of the solenoid 14 urging the valve element 23 in the
valve-closing direction, the discharge pressure Pd which the valve
element 23 receives in the valve-opening direction, and the suction
pressure Ps which the valve element 23 receives in the
valve-closing direction are balanced.
[0034] 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 23 and the piston rod 24, whereby the valve
element 23 is lifted from the balanced position, 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.
[0035] 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 suddenly accelerated or
decelerated.
[0036] 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.
[0037] 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, whereby the control valve 11 increases the pressure Pc
in the crankcase. At this time, in the compressor with higher
sensitivity, as indicated by broken lines in FIG. 2, overshoots of
the valve lift, the discharge pressure Pd, the pressure Pc in the
crankcase, and the suction pressure Ps tend to occur, causing a
hunting phenomenon.
[0038] When the overshoots occur, the pressure-sensing section 12
receives the discharge pressure Pd, which has rapidly increased, at
the pressure-sensing piston 19 having a sufficiently larger
pressure-receiving area than that of the valve element 23. In
contrast, in the pressure-adjusting chamber 20, 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 valve
element 23 is moved away from the valve section 13. This force is
transmitted to the valve element 23 via the shaft 22, a force
obtained by subtracting the differential pressure (Pd-Pd(av))
acting on the pressure-sensing section 12 from the rapidly
increased discharge pressure Pd is applied to the valve element 23.
As a result, as indicated by solid lines in FIG. 2, the valve lift
is increased more slowly, so that the control valve 11 causes the
pressure Pc in the crankcase to increase more slowly. After that,
in the pressure-sensing section 12, the rapidly increased discharge
pressure Pd is promptly introduced into the pressure-adjusting
chamber 20 via the clearance between the cylinder 16 and the
pressure-sensing piston 19, 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 sensing a rapid
increase in the discharge pressure Pd, and temporarily making the
motion of the valve section 13 in the valve-opening direction
slower by a value proportional to the degree of the change in
pressure. This enables the control valve 11 to promptly restore the
compressor to the predetermined discharge capacity without causing
any hunting.
[0039] 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 serves as a
force for moving the pressure-sensing piston 19 toward the valve
section 13. Therefore, the differential pressure (Pd-Pd(av) serves
as a force for temporarily urging the valve element 23, which is
about to move in the valve-closing direction, in the valve-opening
direction. Thus, also when the rotational speed of the compressor
is rapidly decreased, 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.
[0040] In the control valve constructed as above, the
pressure-sensing piston 19 may be provided with flow rate-adjusting
means, such as a piston ring, which has a portion circumferentially
cut off to a predetermined length, to adjust the size of a passage
via which refrigerant flows into or out of the pressure-adjusting
chamber 20 to thereby control the characteristics of the
pressure-sensing section 12.
[0041] 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.
[0042] As is distinct from the control valve 11 according to the
first embodiment which is 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 11a according to the second
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.
[0043] To this end, in the control valve 11a according to the
second embodiment, the pressure-sensing section 12 is disposed in a
space communicating with the medium-pressure port 26, and the
pressure-sensing piston 19 that receives the pressure Pc is fixed
to the piston rod 24 integrally formed with the valve element 23.
The valve seat-forming member 21 has a flange portion that is
fitted in an opening formed in an upper end of the body 15, as
viewed in FIG. 3. The pressure-sensing piston 19 is loosely fitted
in the body 15 at a location below the valve seat-forming member 21
in a manner movable axially back and forth, and an annular space of
the pressure-adjusting chamber 20 is defined by the body 15 and the
flange portion of the valve seat-forming member 21. Further, the
pressure-sensing piston 19 has a recess formed in the center of an
upper part thereof, and the recess is formed with a communication
hole such that the recess communicates with the space communicating
with the medium-pressure port 26 via the communication hole.
[0044] When the control valve 11a constructed as above is
controlling the compressor at 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 23 and the piston rod 24
increases, whereby the valve lift is about to increase. 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 23, a
force is generated, which acts on the pressure-sensing piston 19 in
a direction for temporarily moving the same upward, as viewed in
FIG. 3, and the force causes the piston rod 24 fixed to the
pressure-sensing piston 19 to act in the valve-closing direction.
Therefore, the force acting on the pressure-sensing piston 19 in
the valve-closing direction acts on the valve element 23, which is
about to be moved in the valve-opening direction by the increased
differential pressure (Pd-Ps), in an opposite direction to the
direction of movement or lift of the valve element 23, and hence
the valve lift is slowly increased, and the discharge pressure Pd
and the pressure Pc in the crankcase are also slowly increased in
accordance with the slow increase in the valve lift. In a short
time, when the pressure in the pressure-adjusting chamber 20
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 return to their original states
without causing overshoots. Of course, similarly, also when the
rotational speed of the compressor is rapidly decreased, the
control valve 11a operates slowly to thereby make it possible to
promptly restore the compressor to the predetermined discharge
capacity.
[0045] 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.
[0046] As is distinct from the control valve 11 according to the
first embodiment which is 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 configured to sense a rapid change in
the pressure Pc supplied to the crankcase for control of the valve
lift of the valve section 13, the control valve 11b according to
the third embodiment is configured to sense a rapid change in
suction pressure Ps for control of the valve lift of the valve
section 13.
[0047] To this end, in the control valve 11b, the pressure-sensing
piston 19 is disposed in a manner blocking a space having the
spring 25 disposed therein and communicating with the low-pressure
port 27 and a space communicating with the solenoid 14, and the
pressure-sensing piston 19 is fixed to the piston rod 24 integrally
formed with the valve element 23. Therefore, in the control valve
11b, a space defined by the body 15, the pressure-sensing piston
19, the piston rod 24, the core 29, and the shaft 31 forms the
pressure-adjusting chamber 20.
[0048] When the control valve 11b constructed as above is
controlling the compressor at 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 23 and the piston rod 24
increases, whereby the valve lift increases. This causes the
suction pressure Ps to rapidly decrease. 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 23, a force is generated which acts on the pressure-sensing
piston 19 in a direction in which the same is moved upward, as
viewed in FIG. 4, and the force causes the piston rod 24 fixed to
the pressure-sensing piston 19 to act in the valve-closing
direction. The force of the pressure-sensing piston 19 in the
valve-closing direction acts on the valve element 23, in an
opposite direction to the direction of lift of the valve element
23, and hence the valve lift is slowly increased, to cause the
discharge pressure Pd and the pressure Pc in the crankcase to also
slowly increase. In a short time, when the pressure in the
pressure-adjusting chamber 20 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 return to
their original states without causing overshoots. Of course,
similarly, also when the rotational speed of the compressor is
rapidly decreased, the control valve 11b operates slowly to thereby
make it possible to promptly restore the compressor to the
predetermined discharge capacity.
[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 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 11c according to the
fourth embodiment, the pressure-sensing section 12 does not sense a
rapid change in the discharge pressure Pd in the increasing
direction but sensitively senses a rapid change in the discharge
pressure Pd in the decreasing direction for control of the valve
lift of the valve section 13.
[0051] More specifically, in the control valve 11c, the
pressure-sensing piston 19 as a component of the pressure-sensing
section 12 is provided with a check valve mechanism
(sensitivity-switching means) 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 20, disposing a ball-shaped valve
element 41 in a large-diameter passage toward the
pressure-adjusting chamber 20, and holding a leaf spring 42 in an
open end of the passage toward the pressure-adjusting chamber 20 so
as to prevent the valve element 41 from being removed into the
pressure-adjusting chamber 20.
[0052] When the control valve 11c 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 immediately opened by
the differential pressure between the discharge pressure Pd and the
pressure in the pressure-adjusting chamber 20, to thereby reduce
the differential pressure to zero. As a result, the
pressure-sensing section 12 is placed in an insensitive state, so
that the valve section 13 acts rapidly in the valve-opening
direction in a manner sensitively responsive to the rapid increase
in the discharge pressure Pd, 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.
[0053] Inversely, if the discharge pressure Pd has rapidly
decreased, the check valve mechanism provided in the
pressure-sensing piston 19 is closed by the differential pressure
between the rapidly-lowered discharge pressure Pd and pressure
Pd(av) in the pressure-adjusting chamber 20, which is average
pressure of the discharge pressure Pd before it has rapidly
decreased, so that the pressure-sensing piston 19 having a larger
pressure-receiving area than that of the valve element 23
sensitively detects the change in the rapidly-lowered discharge
pressure Pd. Although the valve element 23 attempts to act in the
valve-closing direction in response to the rapid decrease in the
discharge pressure Pd, since the pressure-sensing piston 19
instantaneously acts in the valve-opening direction in response to
the rapid change in the discharge pressure Pd, the valve element 23
is made slower in its action in the valve-closing direction. This
means that the control valve 11c 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 an excessive 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 an excessive
response to a rapid change in the discharge pressure Pd in the
decreasing direction. This prevents occurrence of a hunting
phenomenon.
[0054] 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 identical to those shown
in FIG. 5 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0055] As is distinct from the control valve 11c according to the
fourth embodiment in which the check valve mechanism of the
pressure-sensing section 12 is provided in the pressure-sensing
piston 19, and the valve element of the check valve is formed by a
ball-shaped valve, in the control valve 11d according to the fifth
embodiment, the check valve mechanism of the pressure-sensing
section 12 is provided in the lid 17, and the valve element of the
check valve is formed by a poppet valve.
[0056] More specifically, in the control valve 11d, the check valve
mechanism provided in the pressure-sensing section 12 is formed by
forming a passage with a stepped portion in the lid 17 of the
pressure-sensing section 12 so as to communicate between a space
for receiving the discharge pressure Pd and the pressure-adjusting
chamber 20, disposing a valve element 41 in the form of a mushroom
in a large-diameter passage toward the pressure-adjusting chamber
20, fixedly engaging the leaf spring 42 in an open end of the
passage toward the pressure-adjusting chamber 20 such that the
valve element 41 is prevented from being removed into the
pressure-adjusting chamber 20, and further disposing a sprig 43
having a small load for urging the pressure-sensing piston 19 in a
direction away from the lid 17 between the lid 17 and the
pressure-sensing piston 19.
[0057] The operation of the control valve lid including the
pressure-sensing section 12 constructed as above is the same as the
operation of the control valve 11c according to the fourth
embodiment. It should be noted that although in the fifth
embodiment, the check valve mechanism is provided in the lid 17 of
the pressure-sensing section 12, it may be provided in the body 15
isolating the pressure-adjusting chamber 20 from a side exposed to
the discharge pressure Pd.
[0058] FIG. 7 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to a sixth embodiment of the present
invention. In FIG. 7, component elements identical to those shown
in FIG. 6 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0059] As is distinct from the control valves 11c and 11d according
to the fourth and fifth embodiments which have the check valve
mechanism, the control valve 11e according to the sixth 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.
[0060] More specifically, in the control valve 11e, 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 20, 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
progressively increases from the side toward the high-pressure port
18 to the pressure-adjusting chamber 20. 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 in
the pressure-adjusting chamber 20, as viewed in FIG. 7, and is
progressively increased in passage cross-sectional area from the
restriction to a space communicating with the high-pressure port
18. Assuming that the cross-sectional area of the refrigerant
passage is hugely expanded on the high-pressure port side of the
restriction, and refrigerant flows from the restriction into the
hugely-expanded portion, a contracted flow is produced there.
Insofar as the differential pressure between pressure in the
high-pressure port 18 and pressure in the pressure-adjusting
chamber 20 is the same, the pressure-sensing section 12 has a
characteristic that the flow rate of refrigerant is smaller when
refrigerant in the pressure-adjusting chamber 20 flows to the
high-pressure port 18 after being abruptly restricted in flow by
the restriction than when refrigerant in the high-pressure port 18
flows into the pressure-adjusting chamber 20 through the
restriction after being progressively restricted in flow.
[0061] When the rotational speed of the compressor is rapidly
increased to thereby rapidly increase the discharge pressure Pd.
refrigerant is about to flow from a side toward the high-pressure
port 18 into the pressure-adjusting chamber 20 through the gap
between the outer periphery of the pressure-sensing piston 19 and
the body 15, by the difference in pressure between the increased
pressure in the high-pressure port 18 and the pressure in the
pressure-adjusting chamber 20 before it is increased. Inversely,
when the rotational speed of the compressor is rapidly decreased to
rapidly lower the discharge pressure Pd, refrigerant is about to
flow from the pressure-adjusting chamber 20 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
around the outer periphery of the pressure-sensing piston 19
between when the discharge pressure Pd has rapidly increased and
when the same has rapidly decreased. When the discharge pressure Pd
has rapidly increased, it takes a short time for the pressure in
the pressure-adjusting chamber 20 to become equal to the discharge
pressure Pd rapidly increased, whereas when the discharge pressure
Pd has rapidly decreased, it takes a longer time for the pressure
in the pressure-adjusting chamber 20 to become equal to the
discharge pressure Pd rapidly decreased. A force which the
pressure-sensing piston 19 exerts on the valve element 23 of the
valve section 13 in the valve-closing direction when the discharge
pressure Pd has rapidly increased is smaller than a force which the
pressure-sensing piston 19 exerts on the valve element 23 in the
valve-opening direction when the discharge pressure Pd has rapidly
decreased, so that when the discharge pressure Pd has rapidly
increased, the pressure-sensing section 12 becomes less sensitive,
whereby the sensitivity of the valve section 13 is not much
lowered. On the other hand, during a transition period over which
the discharge pressure Pd rapidly decreases, the pressure-sensing
piston 19 is easy to move in the valve-opening direction, and hence
the pressure-sensing section 12 becomes more sensitive. Since the
differential pressure between the discharge pressure Pd and the
suction pressure Ps becomes smaller, a force that is about to cause
the valve section 13 to operate in the valve-closing direction is
instantaneously canceled by a force that is about to cause the
pressure-sensing section 12 to operate in the valve-opening
direction, the movement of the valve element 23 of the valve
section 13 in the valve-closing direction is suppressed. As a
result, the valve section 13 is inhibited from performing an
excessive response in the direction in which the discharge pressure
Pd is rapidly decreased. This prevents a high-sensitivity
compressor from causing a hunting phenomenon due to a rapid change
in the discharge pressure Pd.
[0062] FIG. 8 is a central longitudinal cross-sectional view
schematically showing 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. 3 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0063] As is distinct from the control valve 11a according to the
second embodiment in which the pressure-sensing section 12 senses
rapid changes in the pressure Pc supplied to the crankcase in an
increasing direction and a decreasing direction of the pressure Pc
for control of the valve lift of the valve section 13, in the
control valve 11f according to the seventh embodiment, the
pressure-sensing section 12 does not sense a rapid change in the
pressure Pc supplied to the crankcase in the increasing direction
but sensitively detects only a rapid change in the pressure Pc in
the decreasing direction for control of the valve lift of the valve
section 13.
[0064] More specifically, in the control valve 11f, 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 pressure Pc
supplied to the crankcase 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 medium-pressure port 26 and the pressure-adjusting chamber 20,
disposing the ball-shaped valve element 41 in a large-diameter
passage toward the pressure-adjusting chamber 20, and fitting a
stopper 44 in an open end of the passage toward the
pressure-adjusting chamber 20 such that the valve element 41 is
prevented from being removed into the pressure-adjusting chamber
20.
[0065] When the control valve 11f constructed as above is
controlling the compressor at a predetermined valve lift, if a
rapid increase in the discharge pressure Pd causes the valve
section 13 to operate in the valve-opening direction to thereby
rapidly increase the pressure Pc supplied to the crankcase, the
check valve mechanism provided in the pressure-sensing piston 19 is
immediately opened by the differential pressure between the
pressure Pc in the crankcase and the pressure in the
pressure-adjusting chamber 20. Therefore, since the
pressure-sensing section 12 does not adversely affect the operation
of the valve section 13, the valve section 13 promptly operates in
the valve-opening direction in response to the rapid increase in
the pressure Pc to increase the pressure Pc in the crankcase more
promptly, thereby promptly controlling the discharge capacity of
the compressor in the decreasing direction.
[0066] Inversely, if the pressure Pc supplied to the crankcase has
rapidly decreased, the pressure Pc in the medium-pressure port 26
becomes lower than pressure Pc(av) in the pressure-adjusting
chamber 20, which is average pressure of the pressure Pc before it
has rapidly decreased, whereby the check valve mechanism provided
in the pressure-sensing piston 19 is closed. As a result, the
pressure-sensing piston 19 having a larger pressure-receiving area
than that of the valve element 23 sensitively detects the rapid
decrease in the pressure Pc, and the differential pressure between
the discharge pressure Pd and the suction pressure Ps becomes
smaller, so that the operation of the valve section 13 in the
valve-closing direction is instantaneously suppressed by the
pressure-sensing section 12 sensitively acting in the valve-opening
direction.
[0067] With this arrangement, the control valve 11f is provided
with asymmetric valve-opening characteristics that it has a high
sensitivity to a rapid change in the pressure Pc supplied to the
crankcase in the increasing direction, whereas it has a low
sensitivity to a rapid change in the pressure Pc in the decreasing
direction. This prevents occurrence of the hunting of the control
even if the pressure Pc is rapidly changed due to the rapid change
in the discharge pressure Pd.
[0068] FIG. 9 is a central longitudinal cross-sectional view
schematically showing a control valve for a variable displacement
compressor, according to an eighth embodiment of the present
invention. In FIG. 9, component elements identical to those shown
in FIG. 4 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0069] As is distinct from the control valve 11b according to the
third embodiment in which the pressure-sensing section 12 senses
rapid changes in the suction pressure Ps in an increasing direction
and a decreasing direction for control of the valve lift of the
valve section 13, in the control valve 11g according to the eighth
embodiment, the pressure-sensing section 12 does not sense a rapid
change in the suction pressure Ps in the decreasing direction but
sensitively detects only a rapid change in the suction pressure Ps
in the increasing direction for control of the valve lift of the
valve section 13.
[0070] More specifically, in the control valve 11g, 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 suction
pressure Ps 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
low-pressure port 27 and the pressure-adjusting chamber 20,
disposing the ball-shaped valve element 41 in a large-diameter
passage toward the low-pressure port 27, and fitting the stopper 44
in an open end of the passage toward the low-pressure port 27 such
that the valve element 41 is prevented from being removed into the
space communicating with the low-pressure port 27.
[0071] When the control valve 11g constructed as above is
controlling the compressor at a predetermined valve lift, if a
rapid increase in the discharge pressure Pd causes a rapid decrease
in the suction pressure Ps, the check valve mechanism provided in
the pressure-sensing piston 19 is immediately opened by the
differential pressure between the suction pressure Ps and the
pressure in the pressure-adjusting chamber 20. Therefore, the
pressure-sensing section 12 does not adversely affect the operation
of the valve section 13, so that the valve section 13 operates
promptly in the valve-opening direction in response to the rapid
increase in the discharge pressure Pd to increase the pressure Pc
in the crankcase more promptly, and promptly controls the
compressor in a direction in which the discharge capacity thereof
decreases.
[0072] Inversely, if a rapid decrease in the discharge pressure Pd
causes a rapid increase in the suction pressure Ps, the suction
pressure Ps in the low-pressure port 27 becomes higher than
pressure Ps(av) in the pressure-adjusting chamber 20, which is
average pressure of the suction pressure Ps before it has rapidly
increased, so that the check valve mechanism provided in the
pressure-sensing piston 19 is closed. As a result, the
pressure-sensing piston 19 sensitively detects the rapid increase
in the suction pressure Ps, and the operation of the valve section
13 in the valve-closing direction is instantaneously suppressed by
the pressure-sensing section 12 which sensitively acts in the
valve-opening direction.
[0073] With this arrangement, the control valve 11g is provided
with asymmetric valve-opening characteristics that it has a high
sensitivity to a rapid change in the suction pressure Ps in the
decreasing direction, and it has a low sensitivity to a rapid
change in the pressure Pc in the increasing direction. This
prevents occurrence of hunting.
[0074] 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 makes the motion of the valve section in a
valve-opening/closing direction slower by a value proportional to
the degree of the change in pressure. This enables the control
valve to perform stable displacement control without any hunting
even when the high-sensitivity compressor experiences a rapid
change in the rotational speed thereof.
[0075] 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.
* * * * *