U.S. patent application number 11/148300 was filed with the patent office on 2005-12-15 for control valve for variable displacement compressor.
This patent application is currently assigned to TGK CO., LTD.. Invention is credited to Hirota, Hisatoshi.
Application Number | 20050276700 11/148300 |
Document ID | / |
Family ID | 34937224 |
Filed Date | 2005-12-15 |
United States Patent
Application |
20050276700 |
Kind Code |
A1 |
Hirota, Hisatoshi |
December 15, 2005 |
Control valve for variable displacement compressor
Abstract
To provide a control valve for a variable displacement
compressor, which can be realized with a simple construction, while
being equipped with the function of a check valve to be disposed at
an outlet port of the compressor. The control valve for a variable
displacement compressor includes a main valve that sets a
cross-sectional area-fixed passage in which the passage
cross-sectional area thereof is substantially constant when
refrigerant flows between a discharge chamber and an outlet port of
the compressor, and closes the cross-sectional area-fixed passage
due to inversion of the magnitudes of pressure across the
cross-sectional area-fixed passage when the compressor is not in
operation, a pilot valve that controls the flow rate of refrigerant
flowing from the discharge chamber to a crankcase in a manner
interlocked with the differential pressure across the
cross-sectional area-fixed passage received by the main valve, and
a solenoid that is capable of setting a valve lift of the pilot
valve by an external signal. The pilot valve controls the flow rate
of refrigerant allowed to flow into the crankcase so as to make
constant the differential pressure across the cross-sectional
area-fixed passage, to thereby provide control such that the flow
rate of refrigerant allowed to flow to the outlet port of the
compressor is constant.
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: |
34937224 |
Appl. No.: |
11/148300 |
Filed: |
June 9, 2005 |
Current U.S.
Class: |
417/222.2 ;
417/222.1 |
Current CPC
Class: |
F04B 49/225 20130101;
F04B 2027/1854 20130101; F04B 2027/1895 20130101; F04B 27/1804
20130101; F04B 2027/1872 20130101; F04B 2027/1813 20130101; F04B
2027/1827 20130101 |
Class at
Publication: |
417/222.2 ;
417/222.1 |
International
Class: |
F04B 001/26 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 2004 |
JP |
2004-174154 |
Claims
What is claimed is:
1. A control valve for a variable displacement compressor, for
providing control such that a flow rate of refrigerant discharged
from the compressor becomes constant, comprising: a main valve that
is disposed in a first refrigerant passage formed between a first
port communicating with a discharge chamber of the compressor and a
second port communicating with an outlet port of the compressor,
such that the main valve is lifted in a valve-opening direction to
set the first refrigerant passage to a cross-sectional area-fixed
passage having a predetermined passage cross-sectional area in
response to a flow of refrigerant from the first port to the second
port, and closed when a flow rate of the flow of refrigerant is
slight or zero; a pilot valve that is disposed into a second
refrigerant passage formed between the first port and a third port
communicating with a crankcase of the compressor, for controlling a
flow rate of refrigerant flowing from the first port to the third
port according to a differential pressure across the
cross-sectional area-fixed passage; and a solenoid that sets the
pilot valve to a predetermined valve lift by an external
signal.
2. The control valve according to claim 1, wherein the main valve
and the pilot valve are lifted in a same lifting direction and
arranged on a same axis, and the pilot valve senses the
differential pressure generated across the cross-sectional
area-fixed passage, based on a change in a flow rate of refrigerant
flowing through the main valve, to thereby directly control a lift
of the pilot valve.
3. The control valve according to claim 2, wherein the solenoid is
arranged on the same axis as the main valve and the pilot valve,
and holds the pilot valve in a fully-open state when the solenoid
is not energized.
4. A control valve for a variable displacement compressor, for
providing control such that a flow rate of refrigerant discharged
from the compressor becomes constant, comprising: a main valve that
has a main valve seat formed in a refrigerant passage communicating
between a first port connected to a discharge chamber of the
compressor and a second port connected to an outlet port of the
compressor, and a main valve element that is disposed at a location
downstream of the main valve seat, in a state urged in a
valve-closing direction such that the main valve element is movable
to and away from the main valve seat, and is lifted from the main
valve seat in response to a flow of refrigerant from the first port
to the second port, for setting the first refrigerant passage to a
cross-sectional area-fixed passage having a predetermined passage
cross-sectional area; a pilot valve that has a valve seat formed in
a second refrigerant passage communicating between the first port
and a third port connected to a crankcase of the compressor, and a
valve element disposed at a location upstream of the valve seat in
a state urged in a valve-opening direction such that the valve
element is movable to and away from the valve seat, and at the same
time operates in a manner interlocked with the main valve element
when the main valve is set to the cross-sectional area-fixed
passage, the pilot valve being arranged on a same axis as the main
valve; and a solenoid disposed on a same axis as the main valve and
the pilot valve, for setting the pilot valve to a predetermined
valve lift by an external signal.
5. The control valve according to claim 4, wherein the valve
element of the pilot valve is formed integrally with a shaft
extending through a through hole formed in the main valve element
of the main valve, the shaft having a stopper member that stops the
main valve element when the main valve element is lifted from the
main valve seat in response to the flow of refrigerant from the
first port to the second port, to thereby set the main valve to the
cross-sectional area-fixed passage.
6. The control valve according to claim 5, wherein the valve
element of the pilot valve, the shaft, and a drive shaft of the
solenoid are formed integrally with each other.
7. The control valve according to claim 5, wherein the shaft has a
protrusion that protrudes radially outward, and closes the through
hole of the main valve element when the main valve is closed.
8. The control valve according to claim 5, wherein the valve
element of the pilot valve has a guide integrally formed therewith,
the guide being formed by axially extending the valve element such
that a periphery of the guide is in sliding contact with an inner
wall of a valve hole of the pilot valve.
9. The control valve according to claim 4, wherein the main valve
element of the main valve has an extended portion that is always
positioned within a valve hole of the main valve, and wherein the
cross-sectional area-fixed passage which the main valve element is
to set is defined between an outer peripheral surface of the
extended portion and an inner peripheral surface of a valve hole of
the main valve.
10. The control valve according to claim 4, wherein the main valve
element of the main valve has a skirt axially slidable in a valve
hole of the main valve, the skirt being formed with a slit to
thereby form the cross-sectional area-fixed passage which the main
valve element is to set.
11. The control valve according to claim 4, wherein the main valve
element of the main valve defines the cross-sectional area-fixed
passage which the main valve element is to set, between an outer
peripheral surface thereof and an inner peripheral surface of a
cylinder accommodating the main valve element.
12. The control valve according to claim 4, wherein the pilot valve
is a poppet valve disposed such that the poppet valve is movable to
and away from the valve seat.
13. The control valve according to claim 4, wherein the pilot valve
is a slide valve having a valve hole into which the valve element
can be inserted or from which the valve element can be removed.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY
[0001] This application claims priority of Japanese Application No.
2004-174154 filed on Jun. 11, 2004 and 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 in the compressor and capable of providing control such
that a flow rate of refrigerant discharged therefrom becomes
constant.
[0004] (2) Description of the Related Art
[0005] A compressor used in a 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 refrigerant capacity (the discharge
amount 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
(swash plate) fitted on a shaft driven by the engine for rotation
has pistons connected thereto, and is rotated within a crankcase
while varying the inclination angle thereof, whereby the stroke of
the pistons is varied to vary the capacity of the compressor, i.e.
the discharge amount of refrigerant.
[0007] To change the inclination angle of the wobble plate, part of
compressed refrigerant is introduced into the hermetically closed
crankcase to cause a change in the pressure in the crankcase,
whereby the balance of pressures acting on the opposite sides of
each piston connected to the wobble plate is changed to
continuously change the inclination angle of the wobble plate.
[0008] The pressure in the crankcase is changed by a control valve
for a variable displacement compressor, which is disposed in a
refrigerant passage extending between the refrigerant discharge
chamber and the crankcase or a refrigerant passage extending
between the crankcase and the suction chamber. This control valve
provides control such that the communication through the
refrigerant passages is allowed or blocked so as to maintain the
differential pressure thereacross at a predetermined value, and
more particularly, the differential pressure can be set to the
predetermined value by externally changing a value of control
current supplied to the control valve. With this configuration,
when the rotational speed of the engine rises, the pressure
introduced into the crankcase is increased to reduce the volume of
refrigerant that can be compressed, whereas when the rotational
speed of the engine lowers, the pressure introduced into the
crankcase is reduced to increase the volume of refrigerant that can
be compressed, whereby the amount of refrigerant discharged from
the compressor is maintained constant.
[0009] One known method of controlling the capacity of such a
variable displacement compressor uses a control valve therefor,
which provides control such that the flow rate of refrigerant
discharged from the compressor becomes constant (see e.g. Japanese
Unexamined Patent Publication (Kokai) No. 2004-116349).
[0010] This control valve for a variable displacement compressor,
which provides control such that the flow rate of refrigerant
flowing through the compressor becomes constant, includes a
cross-sectional area variable passage which is capable of changing
the passage area of a refrigerant passage through which flows the
refrigerant discharged from the compressor, using a solenoid by an
external signal supplied thereto, and controls the flow rate of
refrigerant introduced from the discharge chamber into the
crankcase such that the differential pressure across the
cross-sectional area variable passage becomes equal to a
predetermined value. By holding the differential pressure across
the cross-sectional area variable passage set to a certain passage
cross-sectional area, at the predetermined value, the flow rate of
refrigerant passing through the variable orifice is controlled to
be constant.
[0011] However, the conventional control valve for a variable
displacement compressor is configured such that it includes a first
control valve that varies the passage cross-sectional area of the
refrigerant passage, a solenoid section that sets the passage
cross-sectional area according to changes in external conditions,
and a second control valve that senses the differential pressure
occurring across the first control valve and controls the pressure
in the crankcase such that the differential pressure becomes equal
to the predetermined value, and the first control valve through
which high-pressure refrigerant is allowed to pass is controlled by
the solenoid section to thereby directly change the passage
cross-sectional area. Therefore, this control valve suffers from
the problems that it is not easy to change the large passage
cross-sectional area by the solenoid section, and the overall
construction of the control valve is complicated.
[0012] Further, in the variable displacement compressor, there
occurs a large differential pressure between during operation and
during stoppage of operation, and when the compressor is changed
from an operating state into a non-operating state, pressure
corresponding to the differential pressure is returned to the
discharge chamber instantaneously. Therefore, when the operation is
resumed, the compressor starts compression of refrigerant from its
state without the differential pressure, which degrades operating
efficiency. To prevent refrigerant discharged from the compressor
from returning during stoppage of operation, a check valve is
disposed on the outlet port of the compressor. This has been a
factor increasing the cost of the compressor.
SUMMARY OF THE INVENTION
[0013] The present invention has been made in view of these
problems, and an object thereof is to provide a control valve for a
variable displacement compressor, which can be realized with a
simple construction, while being equipped with the function of a
check valve to be disposed at an outlet port of the compressor.
[0014] To solve the above problem, the present invention provides a
control valve for a variable displacement compressor, for providing
control such that a flow rate of refrigerant discharged from the
compressor becomes constant, comprising a main valve that is
disposed in a first refrigerant passage formed between a first port
communicating with a discharge chamber of the compressor and a
second port communicating with an outlet port of the compressor,
such that the main valve is lifted in a valve-opening direction to
set the first refrigerant passage to a cross-sectional area-fixed
passage having a predetermined passage cross-sectional area in
response to a flow of refrigerant from the first port to the second
port, and closed when a flow rate of the flow of refrigerant is
slight or zero, a pilot valve that is disposed into a second
refrigerant passage formed between the first port and a third port
communicating with a crankcase of the compressor, for controlling a
flow rate of refrigerant flowing from the first port to the third
port according to a differential pressure across the
cross-sectional area-fixed passage, and a solenoid that sets the
pilot valve to a predetermined valve lift by an external
signal.
[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 cross-sectional view of a conceptual
configuration of a variable displacement compressor.
[0017] FIG. 2 is a cross-sectional view showing details of a
control valve for a variable displacement compressor, according to
a first embodiment of the present invention, in a state during
deenergization.
[0018] FIG. 3 is a cross-sectional view showing the control valve
according to the first embodiment, in a state where the compressor
is controlled to its maximum capacity.
[0019] FIG. 4 is a cross-sectional view showing the control valve
according to the first embodiment, in a state where the compressor
is subjected to variable displacement control.
[0020] FIG. 5 is a cross-sectional view showing the control valve
according to the first embodiment, in a state where the compressor
is controlled to its minimum capacity.
[0021] FIG. 6 is a cross-sectional view showing details of a
control valve according to a second embodiment, in a state during
deenergization.
[0022] FIG. 7 is a cross-sectional view showing details of a
control valve according to a third embodiment, in a state during
deenergization.
[0023] FIG. 8 is a cross-sectional view showing a control valve
according to a fourth embodiment, in a state where the compressor
is subjected to variable displacement control.
[0024] FIG. 9 is a cross-sectional view showing a control valve
according to a fifth embodiment, in a state where the compressor is
subjected to variable displacement control.
[0025] FIG. 10 is a cross-sectional view showing a control valve
according to a sixth embodiment, in a state where the compressor is
subjected to variable displacement control.
[0026] FIG. 11 is a cross-sectional view showing a control valve
according to a seventh embodiment, in a state where the compressor
is subjected to variable displacement control.
[0027] FIG. 12 is an expanded cross-sectional view showing a main
valve element used in a main valve of the control valve for a
variable displacement compressor, according to the seventh
embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Hereafter, embodiments of the present invention will be
described in detail with reference to the drawings showing control
valves applied to a variable displacement compressor for a
clutchless type in which the variable displacement compressor is
directly connected to an engine for an automotive vehicle, and for
a fixed flow rate control type in which the flow rate of discharged
refrigerant is controlled to be constant, by way of example.
[0029] FIG. 1 is a cross-sectional view of a conceptual
configuration of a variable displacement compressor.
[0030] The variable displacement compressor includes a hermetically
formed crankcase 1, which contains a rotating shaft 2 rotatably
supported therein. One end of the rotating shaft 2 extends via a
shaft seal device, not shown, to the outside of the crankcase 1,
and a pulley 3 transmitted a drive force from an engine for an
automotive vehicle is fixed to the one end of the rotating shaft 2.
The rotating shaft 2 has a wobble plate 4 fitted thereon such that
the inclination angle of the wobble plate 4 can be varied. Around
the axis of the rotating shaft 2, there are arranged a plurality of
cylinders 5 (one of which is shown in FIG. 1). Each cylinder 5 has
a piston 6 disposed therein, for converting the rotating and
wobbling motion of the wobble plate 4 into reciprocating motion.
The cylinder 5 is connected to a suction chamber 9 and a discharge
chamber 10 via a suction relief valve 7 and a discharge relief
valve 8. A control valve 11 for a variable displacement compressor
is provided between the discharge chamber 10 and an outlet port
formed to communicate therewith and between the discharge chamber
10 and the crankcase 1, and an orifice 12 is provided between the
crankcase 1 and the suction chamber 9.
[0031] In the variable displacement compressor, the outlet port
formed to communicate with the discharge chamber 10 is connected
via a high-pressure refrigerant conduit line to a condenser 13,
from which piping extends to an inlet port formed to communicate
with the suction chamber 9 via an expansion valve 14, an evaporator
15, and a low-pressure refrigerant conduit line, whereby a
refrigeration cycle as a closed circuit is formed.
[0032] In the variable displacement compressor constructed as
above, as the rotating shaft 2 to which the drive force is
transmitted from the engine is rotated, the wobble plate 4 fitted
on the rotating shaft 2 wobbles while rotating. This causes each
piston 6 connected to the outer peripheral part of the wobble plate
4 to perform reciprocating motion in a direction parallel to the
axis of the rotating shaft 2, whereby refrigerant at suction
pressure Ps in the suction chamber 9 is drawn into the associated
cylinder 5 and compressed therein, and the compressed refrigerant
at discharge: pressure Pd1 is discharged into the discharge chamber
10. At this time, high-pressure refrigerant in the discharge
chamber 10 is decompressed to discharge pressure Pd2 when passing
through the control valve 11, and delivered from the outlet port to
the condenser 13. Part of the high-pressure refrigerant is
introduced into the crankcase 1 via the control valve 11. This
causes the pressure Pc in the crankcase 1 to rise, whereby the
inclination angle of the wobble plate 4 is set such that the bottom
dead center of the piston 6 is brought to a position where the
pressure in the cylinder 5 and the pressure Pc in the crankcase 1
are balanced. Thereafter, the refrigerant introduced into the
crankcase 1 is returned to the suction chamber 9 via the orifice
12.
[0033] The control valve 11 detects the differential pressure
(Pd1-Pd2) which is generated across a refrigerant passage having a
predetermined cross-sectional area set thereto when refrigerant
delivered from the discharge chamber 10 passes through the
refrigerant passage, and introduces the refrigerant into the
crankcase 1 at a flow rate dependent on the detected differential
pressure, thereby providing control such that the flow rate of the
refrigerant sent from the discharge chamber 10 to the condenser 13
becomes constant. More specifically, as the rotational speed of the
engine increases, the suction pressure Ps lowers, and the discharge
pressure Pd1 rises. When this increases the flow rate of
refrigerant sent from the discharge chamber 10 to the condenser 13
via the control valve 11, thereby increasing the differential
pressure (Pd1-Pd2) across the control valve, the flow rate of
refrigerant introduced into the crankcase 1 also increases, whereby
the pressure Pc in the crankcase 1 increases. Accordingly, in the
variable displacement compressor, the wobble plate 4 is inclined in
such a direction as will cause the wobble plate 4 to become at
right angles to the rotating shaft 2 to decrease the stroke of the
pistons 6, which acts on the compression capacity of the cylinders
5 in a reducing direction to reduce the discharge flow rate of
refrigerant. Thus, even when the flow rate of discharged
refrigerant is about to increase due to an increase in the
rotational speed of the engine, the control valve 11 increases the
flow rate of refrigerant introduced into the crankcase 1 according
to the increase in the flow rate of refrigerant, whereby the
pressure Pc in the crankcase 1 is increased to reduce the discharge
capacity. Therefore, the flow rate of refrigerant discharged from
the compressor is controlled to be constant.
[0034] Inversely, when the rotational speed of the engine lowers,
the flow rate of refrigerant sent from the discharge chamber 10 to
the condenser 13 via the control valve 11 decreases to decrease the
differential pressure (Pd1-Pd2) across the control valve 11,
whereby the flow rate of refrigerant introduced into the crankcase
1 also decreases to lower the pressure Pc in the crankcase 1. As a
result, the discharge flow rate of refrigerant is increased whereby
the flow rate of discharged refrigerant is controlled to be
constant.
[0035] Next, a description will be given of examples of the
construction of the control valve for a variable displacement
compressor.
[0036] FIG. 2 is a cross-sectional view showing details of a
control valve for a variable displacement compressor, according to
a first embodiment of the present invention, in a state during
deenergization.
[0037] The control valve 11 has a main valve 20, a pilot valve 21,
and a solenoid 22, and is accommodated in a body 23 in a manner
such that the main valve 20, the pilot valve 21, and the solenoid
22 are arranged on the same axis. The body 23 is provided with
three ports 24, 25 and 26 which form refrigerant outlets and an
inlet of the main valve 20 and the pilot valve 21. When the control
valve 11 is mounted in the variable displacement compressor, the
port 24 communicates with the discharge chamber 10 for introduction
of refrigerant at discharge pressure Pd1. The port 25 communicates
with the outlet port of the compressor for delivery of refrigerant
at discharge pressure Pd2. The port 26 communicates with the
crankcase 1 of the compressor for delivery of refrigerant at the
controlled pressure Pc.
[0038] The body 23 has a refrigerant passage 27 formed therein to
communicate between the port 24 and the port 25 One end of the
refrigerant passage 27 toward the port 25 forms a main valve seat
28 of the main valve 20, using the refrigerant passage 27 as a
valve hole of the main valve seat 28. On the downstream side of the
valve seat 28, a main valve element 29 is disposed in a manner
opposed to the main valve seat 28 such that the main valve element
29 is movable to and away from the main valve seat 28. Disposed in
a space communicating with the port 25 is a spring 30 having a weak
spring force for urging the main valve element 29 in a
valve-closing direction, whereby the main valve 20 is configured to
have a check valve structure.
[0039] Furthers, the body 23 has a refrigerant passage 31 formed
therein to communicate between the port 24 and the port 26. One end
of the refrigerant passage 31 toward the port 24 forms a valve seat
32 of the pilot valve 21, using the refrigerant passage 31 as a
valve hole of the valve seat 32. On the upstream side of the valve
seat 32, a valve element 33 is disposed in a manner opposed to the
valve seat 32 such that the valve element 33 is movable to and away
from the valve seat 32, thereby forming a poppet valve. A spring 34
is disposed in a space communicating with the port 24, for urging
the valve element 33 in a valve-opening direction.
[0040] The valve element 33 has a hollow cylindrical shape, and is
integrally formed with a drive shaft 35 of the solenoid 22. The
drive shaft 35 is disposed in a manner extending through a through
hole axially formed in the main valve element 29 of the main valve
20, whereby the main valve element 29 of the main valve 20 is
axially movably held on the drive shaft 35. Further, the drive
shaft 35 has a stop ring 36 fitted thereon as a stopper member.
When the main valve element 29 of the main valve 20 is lifted in a
direction away from the main vale seat 28, the main valve element
29 is stopped by the stop ring 36 so as to set the main valve 20 to
a cross-sectional area-fixed passage having a predetermined
cross-sectional area. The stop ring 36 is disposed at an
approximately intermediate position in the range of the stroke of
the drive shaft 35 to be exhibited when the pilot valve 21 is
within a control range. The location of the stop ring 36 is set
such that the main valve element 29 is stopped by the stop ring 36
at such a lift position that the main valve 20 has the
predetermined cross-sectional area. As a result, when the control
valve 11 is performing control, in the main valve 20, the passage
cross-sectional area defined by a gap between the main vale seat 28
and the main valve element 29 is held approximately constant. This
is because when the pilot valve 21 is performing a control
operation, a change in the passage cross-sectional area of the main
valve 20 with respect to the stroke of the valve element 33 is very
small, so that it is possible to consider that the passage
cross-sectional area of the main valve 20 is substantially
constant. Thus, when refrigerant is flowing through the main valve
20, the main valve element 29 of the main valve 20 is stopped by
the stop ring 36 such that the main valve element 29 moves in
unison with the valve element 33 of the pilot valve 21. Therefore,
a change in the flow rate of refrigerant flowing through the main
valve 20 having a passage cross-sectional area set to be
substantially constant causes a change in the differential pressure
across the main vale 20, and the main valve element 29 of the main
valve 20 senses the change in the differential pressure to axially
displace itself. The displacement of the main valve element 29 sets
the axial displacement of the valve element 33 of the pilot valve
21.
[0041] The solenoid 22 has a bottomed sleeve 37 having an open end
thereof hermetically fixed to the body 23, and a core 38 is fitted
in the opening of the bottomed sleeve 37. The core 38 has a through
hole formed therethrough along the axis thereof, and axially
movably holds the drive shaft 35. A plunger 39 is disposed within
the bottomed sleeve 37 in a manner movable to and away from the
core 38. Fitted in the plunger 39 is an upper end of the drive
shaft 35, as viewed in FIG. 2, which is held by the core 38, and
the plunger 39 is urged by the spring 34 of the pilot valve 21 via
the drive shaft 35 in a direction away from the core 38. A coil 40
is circumferentially provided outside the bottomed sleeve 37, and
surrounded by a yoke 41 integrally formed with the body 23. The
yoke 41 has an annular plate 42 fitted in an upper end thereof, as
viewed in. FIG. 2, between the yoke 41 and the plunger 39, for
forming a magnetic circuit.
[0042] Further, the drive shaft 35 which has a hollow structure,
and the upper end thereof, as viewed in FIG. 2, fitted in the
plunger 39, has a hole 43 formed in a lateral side thereof such
that the inside of the bottomed sleeve 37 closed by the core 38 and
the refrigerant passage 31 on the downstream side of the pilot
valve 21 communicate with each other. This causes the pressure Pc
to equally act on the axially opposite ends of the valve element 33
and the drive shaft 35, respectively, thereby enabling the solenoid
22 to control the pilot valve 21 without being adversely affected
by the pressure Pc.
[0043] In the control valve 11 constructed as above, when the
solenoid 22 is in a deenergized state in which no control current
is supplied to the solenoid 22 by an external signal supplied
thereto, in other words, when the automotive air conditioner is in
a non-operating state, the main valve 20 is fully closed by having
the main valve element 29 seated on the main valve seat 28 by the
urging force of the spring 30, and the pilot valve 21 is fully open
since the valve element 33 is urged by the spring 34 in the
valve-opening direction. Therefore, all the refrigerant discharged
from the compressor driven by the engine is always introduced into
the crankcase 1 via the pilot valve 21, which places the compressor
in the minimum capacity operating state. In the minimum capacity
operation, the flow rate of refrigerant discharged from the
compressor is very small, so that the discharge pressure Pd1 is
small and not large enough to push open the main valve element 29
of the main valve 20 against the urging force of the spring 30.
[0044] Further, the FIG. 2 showing the state of the control valve
11 during deenergization also shows a state of the automotive air
conditioner immediately after the air conditioner is changed from
an operating state into the non-operating state. More specifically,
when the automotive air conditioner is in operation, and the
solenoid 22 is energized, the plunger 39 of the solenoid 22 is
attracted to the core 38, whereby the drive shaft 35 is pushed
downward, as viewed in the figure, to place the pilot valve 21 in
the fully closed state or in a state where the valve lift thereof
is controlled. Therefore, the compressor is operating in a variable
displacement region, and hence refrigerant at discharge pressure
Pd1, delivered from the discharge chamber 10, is introduced into
the port 24 of the control valve 11. At this time, in the main
valve 20, the main valve element 29 is lifted from the main valve
seat 28 by the discharge pressure Pd1, and refrigerant decompressed
to discharge pressure Pd2 is delivered from the port 25. In this
state, when the automotive air conditioner stops its operation, the
discharge pressure Pd1 sharply decreases to invert the relationship
between the discharge pressure Pd1 at the port 24 and the discharge
pressure Pd2 at the port 25, and the refrigerant at discharge
pressure Pd2, having been sent from the port 25, is about to flow
upstream, but, as shown in FIG. 2, the main valve 20 is fully
closed by the discharge pressure Pd2, thereby enabling the
refrigerant at the port 25 to maintain the high discharge pressure
Pd2. Therefore, when the automotive air conditioner is started
again, a rise time required until the discharge pressure Pd1
recovers to the maintained high discharge pressure Pd2 is
shortened.
[0045] Next, a description will be given of the operation of the
control valve 11 in the state where the compressor is in the
variable displacement region.
[0046] FIG. 3 is a cross-sectional view showing the control valve
according to the first embodiment, in a state where the compressor
is controlled to its maximum capacity. FIG. 4 is a cross-sectional
view showing the control valve according to the first embodiment,
in a state where the compressor is subjected to variable
displacement control. FIG. 5 is a cross-sectional view showing the
control valve according to the first embodiment, in a state where
the compressor is controlled to its minimum capacity.
[0047] When the automotive air conditioner starts its operation,
the control valve 11 controls the compressor to its maximum
capacity. That is, control current corresponding to the maximum
capacity is supplied to the solenoid 22. As a result, the plunger
39 is attracted to the core 38, and moved downward, as viewed in
FIG. 3, to thereby seat the valve element 33 integrally formed with
the drive shaft 35 on the valve seat 32 to fully close the pilot
valve 21.
[0048] This causes the flow rate of refrigerant introduced into the
crankcase 1 to be reduced to zero, whereby the compressor starts
its maximum capacity operation. Refrigerant at discharge pressure
Pd1, delivered from the discharge chamber 10, is introduced into
the port 24, lifts the main valve element 29 of the main valve 20
from the main valve seat 28, passes through a gap (passage having a
constant cross-sectional area) between the main valve element 29
and the main valve seat 28 produced by the lift of the main valve
element 29, and is delivered from the port 25 while being
decompressed to discharge pressure Pd2. At this time, the main
valve element 29 of the main valve 20 is stopped by the stop ring
36 fitted on the drive shaft 35, and the passage cross-sectional
area formed by the gap between the main valve element 29 and the
main valve seat 28 is fixed.
[0049] When cooling load on the automotive air conditioner
decreases, control current dependent on the cooling load is
supplied to the solenoid 22 of the control valve 11. This causes
the plunger 39 to be moved by the urging force of the spring 34 in
the direction away from the core 38, and in accordance with the
movement of the plunger 39, the pilot valve 21 is set to a valve
lift dependent on the control current, as shown in FIG. 4. The
pilot valve 21 decompresses refrigerant introduced into the port 24
at discharge pressure Pd1, to the pressure Pc, and supplies the
refrigerant from the port 26 to the crankcase 1 at a flow rate
dependent on the valve lift.
[0050] Now, when the discharge capacity of the compressor is
increased e.g. due to an increase in the rotational speed of the
engine, the discharge pressure Pd1 increases to increase the
differential pressure (Pd1-Pd2) across the main valve 20, whereby a
force to push open the main valve element 29 of the main valve 20
is increased and about to further lift the main valve element 29.
When the main valve element 29 is lifted, the valve element 33 of
the pilot valve 21, formed integrally with the drive shaft 35
stopping the main valve 29 is also lifted in a manner interlocked
with the lift of the main valve element 29. This increases the flow
rate of refrigerant supplied to the crankcase 1, so that the
compressor operates in a direction of reducing the discharge
capacity thereof to lower the discharge pressure Pd1 to thereby
restore the differential pressure across the main valve 20 to its
original state. Inversely, when the discharge capacity of the
compressor decreases e.g. due to a decrease in the rotational speed
of the engine, the compressor operates in a direction of increasing
the discharge capacity thereof to restore the differential pressure
across the main valve 20 to its original state. As a result, the
control valve 11 operates to provide control such that refrigerant
is discharged from the compressor at a constant flow rate.
[0051] When the cooling load on the automotive air conditioner
becomes sufficiently low, the control current dependent on the
sufficiently low cooling load is supplied to the solenoid 22 of the
control valve 11. As shown in FIG. 5, this causes the solenoid 22
to set the valve lift of the pilot valve 21 to the maximum or its
vicinity, to thereby set the flow rate of refrigerant supplied from
the port 26 to the crankcase 1 to the maximum or its vicinity. As a
result, the compressor is controlled to the minimum discharge
capacity or its vicinity.
[0052] FIG. 6 is a cross-sectional view showing details of a
control valve for a variable displacement compressor, according to
a second embodiment of the present invention, in a state during
deenergization. It should be noted that component elements in FIG.
6 identical to those shown in FIGS. 2 to 5 are designated by
identical reference numerals, and detailed description thereof is
omitted.
[0053] The control valve 51 according to the second embodiment is
distinguished from the control valve 11 according to the first
embodiment in that the structure of the drive shaft 35 of the
solenoid 22 is modified. More specifically, in the control valve
51, the solenoid 22 has a first drive shaft 52 having one end
thereof fitted in the plunger 39, and the other end thereof
slidably held by a cylinder formed in the core 38. The core 38 also
holds a hollow cylindrical second drive shaft 53 integrally formed
with the valve element 33 of the pilot valve 21, in a manner
movable axially back and forth. The solenoid 22, the main valve 20,
and the pilot valve 21 are capable of performing their
predetermined functions only provided that they are arranged on the
same axis. However, by dividing a drive portion of the solenoid 22
into the first drive shaft 52 and the second drive shaft 53, as
described above, the solenoid 22 can at least tolerate misalignment
of the main valve 20 and the pilot valve 21 from the axis, to some
extent.
[0054] The second drive shaft 53 has a groove 54 formed in an outer
periphery of a part thereof, which is held by the core 38. The
groove 54 has a function of preventing high-pressure refrigerant at
discharge pressure Pd2 from leaking through a clearance between the
second drive shaft 53 and the core 38 into the inside of the
bottomed sleeve 37, in which pressure is made equal to the pressure
Pc at the port 26 via the hollow part of the second drive shaft
53.
[0055] Further, the second drive shaft 53 holds the main valve
element 29 of the main valve 20 in a manner movable axially back
and forth. Therefore, when the relationship between the discharge
pressure Pd1 and the discharge pressure Pd2 which was lower than
the discharge pressure Pd1 is inverted, as in the case of
immediately after the automotive air conditioner has stopped its
operation, and the main valve 20 is functioning as a check valve,
refrigerant at pressure Pd2 sometimes leaks from a clearance
between the second drive shaft 53 and the main valve element 29,
and flows upstream. To eliminate this inconvenience, the second
drive shaft 53 has a protrusion 55 integrally formed therewith such
that it extends radially outward and a face thereof opposed to the
main valve element 29 has a tapered shape. The protrusion 55 is
configured such that it can also be used as a stopper for receiving
the spring 34 urging the second drive shaft 53 toward the first
drive shaft 52. Therefore, when the main valve element 29 is seated
on the main valve seat 28 by the discharge pressure Pd2 to close
the main valve 20, since the second drive shaft 53 is urged upward,
as viewed in FIG. 6, by the spring 34, the protrusion 55 functions
as a stop valve which is brought into abutment with the main valve
element 29 for closing the clearance between the second drive shaft
53 and the main valve element 29.
[0056] FIG. 7 is a cross-sectional view showing details of a
control valve for a variable displacement compressor, according to
a third embodiment of the present invention, in a state during
deenergization. It should be noted that component elements in FIG.
7 identical to those shown in FIG. 6 are designated by identical
reference numerals, and detailed description thereof is
omitted.
[0057] The control valve 61 according to the third embodiment is
distinguished from the control valve 51 according to the second
embodiment in that operations of the main valve 20 and the pilot
valve 21, including the second drive shaft 53, are made more
stables. More specifically, in the control valve 61, guides 62 are
integrally formed with the valve element 33 of the pilot valve 21
in a manner axially extended from the valve element 33. The guides
62 provided three in total are arranged around a
pressure-equalizing hole formed through the foremost end of the
valve element 33 such that an outer peripheral portion of each
guide 62 is in sliding contact with the inner wall of a valve hole
of the pilot valve 21. As a result, the second drive shaft 53 has
one end thereof held by the core 38, and the other end thereof held
by the valve hole of the pilot valve 21, which enables the main
valve element 29 of the main valve 20 and the valve element 33 of
the pilot valve 21 to operate while maintaining the coaxial status,
even if lateral load is applied thereto by the flow of
high-pressure refrigerant.
[0058] FIG. 8 is a cross-sectional view showing a control valve for
a variable displacement compressor, according to a fourth
embodiment of the present invention, in a state where the
compressor is subjected to variable displacement control. It should
be noted that component elements in FIG. 8 identical to those shown
in FIGS. 2 to 5 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0059] The control valve 71 according to the fourth embodiment is
distinguished from the control valve 11 according to the first
embodiment in that the structure of the pilot valve 21 is modified.
More specifically, in the control valve 71, the drive shaft 35 and
the valve element 33 of the pilot valve 21 are formed by a pipe
having a straight shape, and the outer diameter of the pipe is
formed to be close to the inner diameter of the valve hole of the
pilot valve 21 such that the valve element 33 can be inserted in
and removed from the valve hole of the pilot valve 21. This enables
the pilot valve 21 to function as a slide valve. When the
compressor is controlled to the maximum capacity, as in the case of
the automotive air conditioner having been started, the pilot valve
21 is fully closed by having the valve element 33 inserted into its
valve hole. Further, when the compressor is subjected to variable
displacement control, the pilot valve 21 is set to a predetermined
valve lift by having the valve element 33 removed from its valve
hole.
[0060] FIG. 9 is a cross-sectional view showing a control valve for
a variable displacement compressor, according to a fifth embodiment
of the present invention, in a state where the compressor is
subjected to variable displacement control. It should be noted that
component elements in FIG. 9 identical to those shown in FIGS. 2 to
5 are designated by identical reference numerals, and detailed
description thereof is omitted.
[0061] As is distinct from the control valve 11 according to the
first embodiment in which when the valve lift of the pilot valve 21
is controlled by the solenoid 22, the valve lift of the main valve
20 is more or less changed to slightly change the passage
cross-sectional area of the main valve 20, in the control valve 81
according to the fifth embodiment, the passage cross-sectional area
of the main valve 20 is completely fixed to be constant. More
specifically, in the control valve 81, the main valve element 29 of
the main valve 20 has a concentrically shaped extended portion 82
which is integrally formed therewith such that the extended portion
82 is always partially positioned in the valve hole, whereby
between the outer peripheral surface of the extended portion 82 of
the main valve element 29 and the inner peripheral surface of the
valve hole, there is formed a passage which has a cross-sectional
area unchangeable with respect to a change in the stroke of the
main valve element 29 along the axis thereof. Therefore, during
variable displacement control of the compressor, the main valve 20
functions as a cross-sectional area-fixed passage which is
unchangeable in cross-sectional area, and when the magnitude of
pressure of refrigerant is inverted across the main valve 20 as in
the case of immediately after the automotive air conditioner has
stopped its operation, the main valve 20 functions as a check
valve.
[0062] FIG. 10 is a cross-sectional view showing a control valve
for a variable displacement compressor, according to a sixth
embodiment of the present invention, in a state where the
compressor is subjected to variable displacement control. It should
be noted that component elements in FIG. 10 identical to those
shown in FIG. 9 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0063] As is distinct from the control valve 81 according to the
fifth embodiment in which the cross-sectional area-fixed passage of
the main valve 20 is formed on the upstream side of the main valve
seat 28, in the control valve 91 according to the sixth embodiment,
the cross-sectional area-fixed passage of the main valve 20 is
formed on the downstream side of the main valve seat 28. More
specifically, in the control valve 91, the main valve element 29 of
the main valve 20 is formed to have an axially long shape, and is
configured such that a passage having a predetermined
cross-sectional area is formed between the outer peripheral surface
of the main valve element 29 and the inner peripheral surface of a
cylinder containing the same. As a result, in the main valve 20,
refrigerant having passed through a gap between the main valve
element 29 and the main valve seat 28 passes through the
cross-sectional area-fixed passage having a predetermined
cross-sectional area.
[0064] FIG. 11 is a cross-sectional view showing a control valve
for a variable displacement compressor, according to a seventh
embodiment of the present invention, in a state where the
compressor is subjected to variable displacement control. FIG. 12
is a fragmentary expanded cross-sectional view of a main valve
element used in a main valve of the control valve according to the
seventh embodiment. It should be noted that component elements in
FIG. 11 identical to those shown in FIG. 9 are designated by
identical reference numerals, and detailed description thereof is
omitted.
[0065] As is distinct from the control valve 81 according to the
fifth embodiment in which the cross-sectional area-fixed passage of
the main valve 20 is formed between the outer peripheral surface of
the extended portion 82 of the main valve element 29 and the inner
peripheral surface of the valve hole, in the control valve 101
according to the seventh embodiment, the cross-sectional area-fixed
passage is formed by a slit 103 formed in a skirt 102 of the main
valve element 29. More specifically, in the control valve 101, the
main valve element 29 of the main valve 20 is integrally formed
with the skirt 102 which is axially slidable in the valve hole, and
the slit 103 is formed in the skirt 102, whereby a passage is
formed the cross-sectional area which is not changeable with
respect to the change in the stroke of the main valve element 29
along the axis thereof. The main valve element 29 illustrated in
FIG. 12, by way of example, has one slit 103 formed in the hollow
cylindrical skirt 102 extended downward from a tapered face via
which the main valve element 29 is seated on the main valve seat
28, at a location downward of the seating position of the main
valve element 29, as viewed in FIG. 12. Of course, there may be
formed a plurality of slits 103 along the circumference of the
skirt 102.
[0066] Since the skirt 102 integrally formed with the main valve
element 29 of the main valve 20 is axially slidably fitted in the
valve hole of the main valve 20, the main valve element 29 having
the above-described shape is not wobbled and the passage
cross-sectional area defined by the slit 103 is not changed even
slightly even if lateral load is applied to the main valve element
29 by the flow of high-pressure refrigerant. Further, the main
valve element 29 has a function of a bearing supporting the drive
shaft 35 disposed in a manner extending therethrough, and hence is
capable of holding the valve element 33 of the pilot valve 21 on
the same axis as that of the valve seat 32 of the pilot valve
21.
[0067] Although the present invention is described in detail
heretofore based on the preferred embodiments thereof, it is by no
means limited to the specific forms thereof. For example, in the
above-described first to sixth embodiments, the solenoid for
control of the pilot valve 21 is disposed on a side of the main
valve 20 opposite to a side thereof where the pilot valve 21 is
disposed, this is not limitative, but of course the solenoid may be
disposed on a side of the pilot valve 21 opposite to a side thereof
where the main valve 20 is disposed.
[0068] The control valve for a variable displacement compressor,
according to the present invention, is configured such that the
solenoid does not control the main valve to change the passage
cross-sectional area of a refrigerant passage, but sets the valve
lift of the pilot valve having a smaller valve section than that of
the main valve. This makes it possible to provide a stable flow
rate control. Further, the main valve and the pilot valve are
configured to operate in a manner interlocked with each other,
which is advantageous in that the flow rate control can be realized
by a very simple construction.
[0069] Further, in the variable displacement compressor, there
occurs a large differential pressure between during operation and
during stoppage of operation, and when the compressor is changed
from an operating state into a non-operating state, pressure
corresponding to the differential pressure is returned to the
discharge chamber at a dash. To prevent this, a check valve has
been conventionally disposed at an outlet port of the compressor.
In the control valve according to the present invention, the main
valve has a check valve structure in which it is lifted only
depending on the flow rate of refrigerant flowing in one direction
toward the outlet port. This is advantageous in that it is possible
to dispense with the check valve disposed at the outlet port, and
thereby reduce the cost of the compressor.
[0070] 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.
* * * * *