U.S. patent application number 11/137672 was filed with the patent office on 2005-12-01 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 | 20050265853 11/137672 |
Document ID | / |
Family ID | 34936403 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050265853 |
Kind Code |
A1 |
Hirota, Hisatoshi |
December 1, 2005 |
Control valve for variable displacement compressor
Abstract
To provide a control valve for a variable displacement
compressor, which is simple in construction and excellent in
controllability. Between a port for introducing refrigerant at
discharge pressure Pd1 delivered from a discharge chamber and a
port for allowing refrigerant at discharge pressure Pd2 to flow out
at a controlled flow rate, there are provided a main valve the
valve lift of which is varied according to the flow rate of
refrigerant passing therethrough, and a solenoid valve that uses a
valve element of the main valve as a variable valve seat and
supplies to the crankcase the refrigerant at pressure Pc the flow
rate of which is controlled according to the size of a gap formed
between the variable valve seat and the hollow cylindrical valve
element. The main valve not only senses the flow rate but also
serves as the valve seat of the solenoid valve, and the solenoid
valve controls the small flow rate of refrigerant supplied to the
crankcase. Therefore, the control valve is simple in construction,
and capable of performing stable flow rate control.
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: |
34936403 |
Appl. No.: |
11/137672 |
Filed: |
May 26, 2005 |
Current U.S.
Class: |
417/222.2 ;
417/222.1; 417/269 |
Current CPC
Class: |
F04B 2027/1813 20130101;
F04B 2027/1854 20130101; F04B 49/225 20130101; F04B 2027/1895
20130101; F04B 2027/1872 20130101; F04B 27/1804 20130101 |
Class at
Publication: |
417/222.2 ;
417/222.1; 417/269 |
International
Class: |
F04B 001/12; F04B
001/26 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2004 |
JP |
2004-162122 |
Jul 2, 2004 |
JP |
2004-196230 |
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 set to a first valve lift a lift amount of which is dependent on
a flow rate of refrigerant passing therethrough which is discharged
from a discharge chamber of the compressor; and a solenoid valve
that is set to a second valve lift by an external signal, and
controls a flow rate of refrigerant to be allowed to flow from the
discharge chamber to a crankcase according to an amount of change
in the first valve lift relative to the second valve lift set
thereto.
2. 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 valve seat formed in a refrigerant passage communicating
between a first port to be connected to a discharge chamber of the
compressor and a second port to be connected to an outlet port of
the compressor, and a valve element that is disposed at a location
downstream of the valve seat, in a state urged in a valve-closing
direction such that the valve element can be moved to and away from
the valve seat; and a solenoid valve that is disposed coaxially
with the main valve, and has a hollow cylindrical body having a
hollow portion, one open end opening in the first port, and another
open end opening in a third port to be connected to a crankcase of
the compressor, the hollow cylindrical body being urged along a
same axis as that of the main valve, the valve element of the main
valve being regarded as a movable valve seat or a movable valve
element and forming a valve portion in cooperation with the hollow
cylindrical body.
3. The control valve according to claim 2, wherein the valve
element of the main valve is configured such that the valve element
has an axially extending piston inserted in a through hole axially
formed therethrough, and is movable axially back and forth using
the piston as a guide, the valve portion of the solenoid valve
being a slide valve configured such that the one end of the hollow
cylindrical body is disposed in a manner removably insertable into
the through hole.
4. The control valve according to claim 2, wherein the valve
element of the main valve is configured such that a hollow
cylindrical valve element having a same diameter as the hollow
cylindrical body is fitted in a through hole axially formed through
the valve element, and the hollow cylindrical valve element is held
in an axially recessed guide in a manner movable axially back and
forth, whereby the valve element of the main valve is movable
axially back and forth, the valve portion of the solenoid valve
comprising a hollow cylindrical movable valve seat having a
funnel-like shape formed by expanding the one open end of the
hollow cylindrical body opening in the first port, and the hollow
cylindrical valve element fitted on the valve element of the main
valve.
5. The control valve according to claim 2, wherein the valve
element of the main valve is configured such that the valve element
has an axially extending piston inserted in a through hole axially
formed therethrough, and is movable axially back and forth using
the piston as a guide, the valve portion of the solenoid valve
being a poppet valve configured such that a frustoconical valve
element having a frustoconical shape at one end of the hollow
cylindrical body is disposed such that the frustoconical valve
element can be moved to and away from a rim of the through
hole.
6. The control valve according to claim 2, wherein the valve
element of the main valve comprises a hollow cylindrical skirt
slidably disposed in a valve hole of the main valve and having a
slit forming a passage in the main valve, and a hollow cylindrical
portion forming a valve seat of the solenoid valve, the skirt and
the hollow cylindrical portion being coaxially arranged and formed
integrally with each other, the valve portion of the solenoid valve
being a poppet valve configured such that a frustoconical portion
formed at one end of the hollow cylindrical body is disposed such
that the frustoconical portion can be moved to and away from the
hollow cylindrical portion.
7. The control valve according to claim 6, wherein the slit formed
in the skirt is varied in opening width thereof in a direction in
which the valve element of the main valve is lifted.
8. The control valve according to claim 2, wherein the hollow
cylindrical body has closed opposite ends and a side provided with
holes opening into the first port and the third port, and wherein
the valve element of the main valve is configured such that the
valve element has the hollow cylindrical body inserted in a through
hole axially formed therethrough, and is movable axially back and
forth using the hollow cylindrical body as a guide, the valve
portion of the solenoid valve being a slide valve formed by the
open end opening into the first port and the valve element of the
main valve.
9. The control valve according to claim 2, wherein the hollow
cylindrical body is held by a body accommodating the main valve and
the solenoid valve or by a core of the solenoid provided in the
body, in a manner movable axially back and forth, an end of the
hollow cylindrical body on a side opposite from the main valve
being fixed to a plunger of the solenoid.
10. The control valve according to claim 2, wherein the hollow
cylindrical body is held by a body accommodating the main body and
the solenoid valve or by a core of the solenoid provided in the
body, in a manner movable axially back and forth, an end of the
hollow cylindrical body on a side opposite from the main valve
being in abutment with a shaft fixed to a plunger of the
solenoid.
11. The control valve according to claim 2, wherein the main valve
includes damper means for suppressing a sudden motion of the valve
element responsive to a sudden change in pressure of refrigerant
supplied from the discharge chamber.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY
[0001] This application claims priority of Japanese Application No.
2004-162122 filed on May 31, 2004 and entitled "CONTROL VALVE FOR
VARIABLE DISPLACEMENT COMPRESSOR" and No. 2004-196230 filed on Jul.
2, 2004, entitled "CONTROL VALVE FOR VARIABLE DISPLACEMENT
COMPRESSOR".
BACKGROUND OF THE INVENTION
[0002] (1) Field of the Invention
[0003] The present invention relates to a control valve for a
variable displacement compressor, and more particularly to a
control valve for a variable displacement compressor, which is
mounted 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 between
the discharge port of refrigerant and the crankcase or between the
crankcase and the suction port of refrigerant. This control valve
provides control such that communication 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
includes a variable orifice 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 variable
orifice becomes equal to a predetermined value. By holding the
differential pressure across the variable orifice set to a certain
flow passage 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 flow passage area of the refrigerant
passage, a solenoid section that sets the flow passage area
according to a change 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 flow passage area.
Therefore, this control valve suffers from the problems that it is
not easy to change the large flow passage area by the solenoid
section, and the overall construction thereof is complicated.
SUMMARY OF THE INVENTION
[0012] 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 is simple in construction
and excellent in controllability.
[0013] 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 set to
a first valve lift a lift amount of which is dependent on a flow
rate of refrigerant passing therethrough which is discharged from a
discharge chamber of the compressor, and a solenoid valve that is
set to a second valve lift by an external signal, and controls a
flow rate of refrigerant to be allowed to flow from the discharge
chamber to a crankcase according to an amount of change in the
first valve lift relative to the second valve lift set thereto.
[0014] The above and other objects, features and advantages of the
present invention will become apparent from the following
description when taken in conjunction with the accompanying
drawings which illustrate preferred embodiments of the present
invention by way of example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a cross-sectional view of a conceptual
configuration of a variable displacement compressor.
[0016] 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.
[0017] FIG. 3 is a cross-sectional view showing details of the
control valve according to the first embodiment, in a balanced
state during energization.
[0018] FIG. 4 is a cross-sectional view showing details of a
control valve according to a second embodiment, in a balanced state
during energization.
[0019] FIG. 5 is a cross-sectional view showing details of a
control valve according to a third embodiment, in a balanced state
during energization.
[0020] FIG. 6 is a cross-sectional view showing details of a
control valve according to a fourth embodiment, in a balanced state
during energization.
[0021] FIG. 7 is a cross-sectional view showing details of a
control valve according to a fifth embodiment, in a balanced state
during energization.
[0022] FIG. 8 is a cross-sectional view showing details of a
control valve according to a sixth embodiment, in a balanced state
during energization.
[0023] FIG. 9 is a cross-sectional view showing details of a
control valve according to a seventh embodiment, in a balanced
state during energization.
[0024] FIG. 10 is a cross-sectional view showing details of a
control valve according to an eighth embodiment, in a balanced
state during energization.
[0025] FIGS. 11A, 11B are views showing a main valve of the control
valve according to the eighth embodiment, wherein FIG. 11A is side
view of the main valve, and FIG. 11B is a cross-sectional view
taken on line A-A of FIG. 11A.
[0026] FIG. 12 is a diagram showing changes in the flow rate of
refrigerant occurring in response to electric current supplied to
the solenoid.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] 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 of a fixed
flow rate control type in which the flow rate of discharged
refrigerant is controlled to be constant, by way of example.
[0028] FIG. 1 is a cross-sectional view of a conceptual
configuration of a variable displacement compressor.
[0029] The variable displacement compressor includes a hermetically
formed crankcase 1, which contain a rotating shaft 2 rotatably
supported therein. One end of the rotating shaft 2 extends via a
sealed bearing device to the outside of the crankcase 1, and a
pulley 3 having a drive force transmitted 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 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 relieve valve 8,
respectively. 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.
[0030] 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 the 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.
[0031] 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. Then, each piston 6
connected to the outer peripheral part of the wobble plate 4
performs 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.
[0032] The control valve 11 detects a flow rate of refrigerant sent
from the discharge chamber 10 to the condenser 13, and introduces
the refrigerant into the crankcase 1 at a flow rate dependent on
the detected flow rate, 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, when the
rotational speed of the engine increases, the suction pressure Ps
lowers, and the discharge pressure Pd1 rises. If this increases the
flow rate of refrigerant sent from the discharge chamber 10 to the
condenser 13 via the control valve 11, the flow rate of refrigerant
introduced into the crankcase 1 is also increased, 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 becomes 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.
[0033] 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 is decreased, whereby the
flow rate of refrigerant introduced into the crankcase 1 is also
decreased 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.
[0034] Now, a description will be given of examples of the
construction of the control valve for a variable displacement
compressor.
[0035] 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
non-energization. FIG. 3 is a cross-sectional view showing details
of the control valve according to the first embodiment, in a
balanced state during energization.
[0036] The control valve 11 has a main valve 20 and a solenoid
valve 21 actuated by solenoid, which are accommodated in a body 22.
The body 22 is formed with three ports 23, 24, and 25. When the
control valve 11 is mounted in the variable displacement
compressor, the port 23 is communicated with the discharge chamber
10 to introduce refrigerant at discharge pressure Pd1. The port 24
is communicated with the outlet port of the compressor to deliver
refrigerant at discharge pressure Pd2. The port 25 is communicated
with the crankcase 1 to deliver refrigerant at the controlled
pressure Pc.
[0037] The body 22 has an upper portion thereof, as viewed in FIG.
2, formed with a refrigerant passage 26 extending therethrough to
communicate between the port 23 and the port 24, and in the
refrigerant passage 26, a valve seat 27 of the main valve 20 is
formed integrally with the body 22. On a downstream side of the
valve seat 27, a valve element 28 is disposed in a manner opposed
to the valve seat 27 such that the valve element 28 is movable to
and away from the valve seat 27. This valve element 28 has a
through hole extending therethrough along the axis of the body 22,
and a piston 30 hanging from a holder 29 capped on an upper end of
the body 22, as viewed in FIG. 2, is inserted in the through hole,
whereby the piston 30 holds the valve element 28 in a manner
movable axially back and forth. Between the valve element 28 and
the holder 29, the spring 31 is interposed to urge the valve
element 28 in a valve-closing direction, whereby the main valve 20
has a check valve structure.
[0038] The solenoid valve 21 uses the valve element 28 of the main
valve 20 as a movable valve seat, and has a hollow cylindrical
valve element 32 that can be inserted in and removed from a valve
hole defined by the through hole formed in the valve element 28 and
forms a slide valve in cooperation with the movable valve seat
provided by the valve element 28. The valve lift of the hollow
cylindrical valve element 32 is controlled by solenoid. The hollow
cylindrical valve element 32 is held in the body 22 in a manner
movable axially back and forth.
[0039] The solenoid has a bottomed sleeve 33 having an open end
thereof hermetically fixed to the body 22, and a core 34 is fitted
in the opening of the bottomed sleeve 33. The core 34 has a through
hole formed therethrough for having the hollow cylindrical valve
element 32 loosely fitted therein along the axis thereof. A plunger
35 is disposed within the bottomed sleeve 33 in a manner movable to
and away from the core 34, and is urged by a spring 36 in a
direction away from the core 34. Fitted in the plunger 35 is a
lower end of the hollow cylindrical valve element 32, as viewed in
FIG. 2, which is held by the body 22. A coil 37 is
circumferentially provided outside the bottomed sleeve 33, and
surrounded by a yoke 38 integrally formed with the body 22. The
yoke 38 has an annular plate 39 fitted in a lower end thereof, as
viewed in FIG. 2, between the yoke 38 and the plunger 35, for
forming a magnetic circuit.
[0040] The hollow cylindrical valve element 32 is provided with a
hole 40 at a location corresponding to the port 25, whereby the
port 23 through which refrigerant at discharge pressure Pd1 is
introduced and the port 25 communicating with the crankcase 1 are
communicated via a gap between the valve element 28 of the main
valve 20 and the hollow cylindrical valve element 32 and a hollow
part of the hollow cylindrical valve element 32. The hollow
cylindrical valve element 32 is provided with a pressure-equalizing
hole 41 in the vicinity of a portion thereof fitted in the plunger
35, for communication between the inside of the bottomed sleeve 33
and the port 25, to thereby cause the pressure Pc to equally act on
the opposite ends of the hollow cylindrical valve element 32 in the
direction of motion thereof, whereby the pressure Pc never
influences the control operation of the solenoid 21.
[0041] In the control valve 11 constructed as above, as shown in
FIG. 2, when the solenoid is not energized, the main valve 20 is
fully closed by having the valve element 28 seated on the valve
seat 27 by the spring 31, and the solenoid valve 21 is fully open
since the plunger 35 is urged by the spring 36 in the direction
away from the core 34, and the hollow cylindrical valve element 32
fixed to the plunger 35 is moved away from the valve element 28 as
the variable valve seat associated therewith.
[0042] Therefore, in this state, when the drive force is
transmitted from the engine to the rotating shaft 2 to cause
rotation thereof, in the compressor, the wobble plate 4 provided on
the rotating shaft 2 performs wobbling motion while rotating. The
wobbling motion of the wobble plate 4 causes the reciprocating
motion of the pistons 6 connected to the peripheral part of the
wobble plate 4, whereby the refrigerant in the suction chamber 9 is
drawn into the cylinder 5 to be compressed therein, and the
compressed refrigerant is discharged into the discharge chamber 10.
At this time, since the main valve 20 is in the fully closed state,
the refrigerant discharged into the discharge chamber 10 passes
through the solenoid valve 21 in the fully open state, and flows to
the port 25 via the hollow part of the hollow cylindrical valve
element 32 and the hole 40, to be introduced into the crankcase 1.
This places the compressor in the minimum capacity operating state.
The force of the spring 31 acting on the main valve 20 in the
valve-closing direction is set to be somewhat larger than the force
generated by the discharge pressure Pd1 in the valve-opening
direction when the compressor is operating with the minimum
capacity, and hence the closed state of the main valve 20 is
maintained.
[0043] When predetermined control current is supplied to the coil
37 of the solenoid, the plunger 35 of the solenoid valve 21 is
attracted to the core 34, and as shown in FIG. 3, the hollow
cylindrical vale element 32 is lifted to a position where the
attractive force of the solenoid and the urging force of the spring
36 are balanced, and stopped thereat. At this time, the valve
element 28 of the main valve 20 still remains seated in the valve
seat 27, as shown in FIG. 2, and hence the hollow cylindrical valve
element 32 of the solenoid valve 21 is inserted into the valve hole
formed in the valve element 28, whereby the solenoid valve 21 is
momentarily fully closed. This prevents introduction of refrigerant
into the crankcase 1, which causes prompt transition of the
compressor to its maximum capacity operating state, to increase the
discharge capacity Pd1 drastically. The discharge pressure Pd1
causes the valve element 28 of the main valve 20 to be lifted
against the urging force of the spring 31, whereby the valve
element 28 of the main valve 20 is lifted to a lift amount
dependent on the flow rate of refrigerant. At this time, the hollow
cylindrical valve element 32 of the solenoid valve 21 is removed
from the valve hole formed in the valve element 28 to open the
solenoid valve 21, whereby the refrigerant is allowed to flow
through a gap between the hollow cylindrical valve element 32 and
the valve element 28 into the crankcase 1 at a flow rate dependent
on the size of the offset between these, whereby the compressor
performs transition to a state of operation with the predetermined
capacity.
[0044] Here, if the rotational speed of the engine increases, the
suction pressure Ps lowers, and the discharge pressure Pd1 rises.
This increases the flow rate of refrigerant delivered from the
discharge chamber 10, and accordingly, the valve element 28 of the
main valve 20 is further lifted to increase the flow passage area
of the main valve 20, which is about to cause an increase in the
flow rate of refrigerant discharged from the compressor. The
further lift of the valve element 28 increases the offset between
the hollow cylindrical valve element 32 of the solenoid valve 21
and the valve element 28 as the movable valve seat associated
therewith to increase the flow rate of refrigerant introduced into
the crankcase 1 to thereby increase the pressure Pc in the
crankcase 1. Therefore, the compressor acts in the direction of
reducing its capacity, and is thus controlled such that the flow
rate of discharged refrigerant is reduced.
[0045] Inversely, when the rotational speed of the engine lowers,
the flow rate of refrigerant delivered from the discharge chamber
10 decreases to also reduce the flow rate of refrigerant introduced
into the crankcase 1, whereby the pressure Pc in the crankcase 1
lowers, so that the compressor acts in the direction of increasing
the discharge capacity.
[0046] Thus, the control valve 11 constantly acts such that it
takes a balanced position as shown in FIG. 3, whereby even if the
flow rate of refrigerant discharged from the compressor is about to
change due to a change in the rotational speed of the engine, the
compressor is controlled in the direction of decreasing the flow
rate of refrigerant discharged from the compressor. As a result,
the flow rate of refrigerant discharged from the compressor is
controlled to be constant.
[0047] FIG. 4 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 balanced state
during energization. It should be noted that component elements in
FIG. 4 identical or similar to those shown in FIGS. 2 and 3 are
designated by identical reference numerals, and detailed
description thereof is omitted.
[0048] 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 solenoid valve 21 is
modified. More specifically, the solenoid valve 21 comprises a
hollow cylindrical movable valve seat 52 held in a body 22 in a
manner movable axially back and forth, and a hollow cylindrical
valve element 54 having the same diameter as that of the hollow
cylindrical movable valve seat 52, held on a guide 53 hanging from
the holder 29 in a manner movable back and forth along the axis of
the body 22, and at the same time, fixed to the valve element 28,
and is configured such that the hollow cylindrical movable valve
seat 52 is actuated by the shaft 55 fixed to the plunger 35. One
end of the hollow cylindrical movable valve seat 52, which is
opposed to the hollow cylindrical valve element 54, is expanded in
a funnel-like fashion to form a valve seat face, and a hole 56 is
formed at a location where the port 25 is formed, whereby a hollow
part of the hollow cylindrical movable valve seat 52 is
communicated with the port 25 communicating with the crankcase
1.
[0049] As to the main valve 20, the valve element 28 thereof is
rigidly fitted on the hollow cylindrical valve element 54, and the
hollow cylindrical valve element 54 is fitted in the guide 53,
whereby the valve element 28 is held in a manner movable axially
back and forth.
[0050] In this control valve 51 as well, when a predetermined
control current is supplied to the coil 37 of the solenoid, the
solenoid valve 21 is stopped at a point where the attractive force
of the solenoid and the force of the spring 36 are balanced,
whereby the hollow cylindrical movable valve seat 52 is set to a
valve lift corresponding to a discharge flow rate as a target. This
causes the main valve 20 to be lifted according to a flow rate of
refrigerant discharged from the discharge chamber 10 of the
compressor, and the flow rate is eventually controlled such that it
is set to a flow rate of refrigerant set by the solenoid valve
21.
[0051] FIG. 5 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 balanced state
during energization. It should be noted that component elements in
FIG. 5 identical or similar to those shown in FIGS. 2 and 3 are
designated by identical reference numerals, and detailed
description thereof is omitted.
[0052] The control valve 61 according to the third embodiment is
distinguished from the control valve 11 according to the first
embodiment in that the structure for holding the valve element 28
of the main valve 20 in a manner movable axially back and forth is
modified and at the same time the pressure acting on the hollow
cylindrical valve element is changed. More specifically, the core
34 of the solenoid is extended upward, as viewed in FIG. 5, to the
location of the port 23 where the refrigerant at discharge pressure
Pd1 is introduced, and a hollow cylindrical valve element 62 is
held by the core 34 in a manner movable back and forth along the
axis thereof. This hollow cylindrical valve element 62 has the
plunger 35 of the solenoid fixed to a lower end thereof, as viewed
in FIG. 5, and a plug 63 fitted in an upper end thereof, as viewed
in FIG. 5, and is urged by the spring 64 downward, as viewed in
FIG. 5.
[0053] The hollow cylindrical valve element 62 has the valve
element 28 of the main valve 20 fitted thereon in the vicinity of
the upper end thereof and the valve element 28 is movable back and
forth using the hollow cylindrical valve element 62 as the guide
along the axis thereof. The hollow cylindrical valve element 62 is
provided with a hole 65 such that the hole 65 cooperates with the
valve element 28 of the main valve 20 to form a valve portion of
the solenoid valve 21, and is further provided with a hole 66 at a
location where the port 25 is formed.
[0054] The core 34 of the solenoid is provided with a
pressure-equalizing hole 67 in parallel with the hole for holding
the hollow cylindrical valve element 62, such that the discharge
pressure Pd1 is introduced into the bottomed sleeve 33 of the
solenoid. With this configuration, the hollow cylindrical valve
element 62 receives the discharge pressure Pd1 in an upward
direction and the discharge pressure Pd2 in a downward direction,
as viewed in FIG. 5. The differential pressure across the valve
element 28 is very small compared with the discharge pressure Pd1,
and hence substantially the same pressure acts on the opposite ends
of the hollow cylindrical valve element 62 in the direction of
motions thereof, which prevent the control operation of the
solenoid valve 21 from being adversely affected.
[0055] Similarly to the control valves 11 and 51 according to the
first and second embodiments, the control valve 61 also controls
the compressor such that the flow rate of refrigerant delivered
from the discharge chamber 10 becomes constant.
[0056] FIG. 6 is a cross-sectional view showing details of a
control valve for a variable displacement compressor, according to
a fourth embodiment of the present invention, in a balanced state
during energization. It should be noted that component elements in
FIG. 6 identical or similar to those shown in FIG. 5 are designated
by identical reference numerals, and detailed description thereof
is omitted.
[0057] The control valve 71 according to the fourth embodiment is
distinguished from the control valve 61 according to the third
embodiment in that a part of the solenoid for driving its valve
element is divided.
[0058] A hollow cylindrical valve element 72 supported on the core
34 has a plug 73 inserted in a portion of a hollow part thereof
downward, as viewed in FIG. 6, of a location where the port 25 is
formed, and fixed thereat, whereby the port 25 and the bottomed
sleeve 33 are fluidically separated from each other. Disposed
between the plug 73 and the plunger 35 is a shaft 74, and one end
of the shaft 74 is in abutment with the plug 73, and the other end
of the same is fitted in the plunger 35. This causes axial motion
of the plunger 35 to be transmitted to the hollow cylindrical valve
element 72 via the shaft 74 and the plug 73.
[0059] This control valve 71 as well controls the flow rate of
refrigerant allowed to flow into the crankcase 1 according to the
lift of the main valve 20, thereby controlling the compressor such
that the discharge flow rate of refrigerant becomes constant.
[0060] FIG. 7 is a cross-sectional view showing details of a
control valve for a variable displacement compressor, according to
a fifth embodiment of the present invention, in a balanced state
during energization. It should be noted that component elements in
FIG. 7 identical or similar to those shown in FIG. 6 are designated
by identical reference numerals, and detailed description thereof
is omitted.
[0061] As is distinct from the control valve 71 according to the
fourth embodiment in which the pressure introduced into the
solenoid is the discharge pressure Pd1 upstream of the valve
element 20, in the control valve 81 according to the fifth
embodiment, the pressure is set to the discharge pressure Pd2
downstream of the main valve 20.
[0062] To introduce the discharge pressure Pd2 into the bottomed
sleeve 33 of the solenoid, the body 22 is provided with a
pressure-equalizing hole 82, and the core 34 is provided with a
pressure-equalizing hole 83 such that the pressure-equalizing hole
83 communicates with the pressure-equalizing hole 82. This causes
the same discharge pressure Pd2 to act on the opposite ends of the
hollow cylindrical valve element 72 in the directions of motion
thereof, which prevents discharge pressure Pd2 from adversely
affecting the control operation of the solenoid valve 21.
[0063] FIG. 8 is a cross-sectional view showing details of a
control valve for a variable displacement compressor, according to
a sixth embodiment of the present invention, in a balanced state
during energization. It should be noted that component elements in
FIG. 8 identical or similar to those shown in FIG. 4 are designated
by identical reference numerals, and detailed description thereof
is omitted.
[0064] The control valve 91 according to the sixth embodiment is
distinguished from the control valve 51 according to the second
embodiment in that damper means is added to the main valve 20. More
specifically, the valve element 20 has a valve element 92 having a
cup shape, and the valve element 92 is held within a cylinder 93
recessed inside the holder 29 in a manner movable axially back and
forth. The hollow cylindrical valve element 54 of the solenoid
valve 21 fixed to the valve element 92 of the main valve 20 is also
held within the guide 53 hanging from the holder 29 in a manner
movable back and forth along the axis thereof. The upper opening of
the holder 29 is closed by a plate 94, whereby a space defined
between the inside of the valve element 92 of the main valve 20 and
the outside of the hollow cylindrical valve element 54 of the
solenoid valve 21, where the spring 31 is accommodated, forms an
approximately hermetically closed chamber.
[0065] Now, when the discharge pressure Pd1 introduced into the
port 23 is suddenly changed, the valve element 92 of the main valve
20 is about to be fluctuated due to a sudden change in the received
pressure, but a progressive increase or decrease of the volume of
the hermetically closed chamber absorbs the sudden change in the
received pressure, whereby the valve element 92 is prevented from
being suddenly fluctuated, whereby the vibrating noise generated by
fluctuating motion of the valve element 92 can be reduced.
[0066] FIG. 9 is a cross-sectional view showing details of a
control valve for a variable displacement compressor, according to
a seventh embodiment of the present invention, in a balanced state
during energization. It should be noted that component elements in
FIG. 9 identical or similar to those shown in FIGS. 2 and 3 are
designated by identical reference numerals, and detailed
description thereof is omitted.
[0067] As is distinct from the control valve 11 according to the
first embodiment in which the solenoid valve 21 is implemented by a
slide valve, in the control valve 101 according to the seventh
embodiment, the solenoid valve 21 is implemented by a poppet
valve.
[0068] More specifically, in the control valve 101, the hollow
cylindrical valve element 32 has a frustoconical valve element 95
fitted on the upper end thereof, as viewed in FIG. 9, thereby
forming a valve portion of the solenoid valve 21. The valve element
95 has a through hole extending axially therethrough and having the
same inner diameter as that of the hollow cylindrical valve element
32, and is capable of moving to and away from the rim of the
through hole formed in the valve element 28 of the main valve 20 in
a manner interlocked to the axial motion of the hollow cylindrical
valve element 32. This causes the valve element 95 to be closely
seated on the valve seat formed on the valve element 28 of the main
valve 20, which makes it possible to reduce leakage of refrigerant
from the solenoid valve 21.
[0069] FIG. 10 is a cross-sectional view showing details of a
control valve for a variable displacement compressor, according to
an eighth embodiment of the present invention, in a balanced state
during energization, and FIGS. 11A and 11B are views showing a main
valve of the control valve according to the eighth embodiment,
wherein FIG. 11A is side view of the main valve, and FIG. 11B is a
cross-sectional view taken on line A-A of FIG. 11A. FIG. 12 is a
diagram showing changes in the flow rate of refrigerant occurring
in response to electric current supplied to the solenoid. It should
be noted that component elements in FIG. 10 identical or similar to
those shown in FIG. 8 are designated by identical reference
numerals, and detailed description thereof is omitted.
[0070] The control valve 111 according to the eighth embodiment is
distinguished from the control valves 11, 51, 61, 71, 81, 91, and
101 according to the first to seventh embodiments, in that the
structure of the main valve 20 is modified.
[0071] More specifically, the main valve 20 includes a valve
element 112 that can be moved to and away from the valve seat 27
formed in the refrigerant passage 26, and the valve element 112 is
integrally formed with a hollow cylindrical skirt 113 which is
extended therefrom into a valve hole of the main valve 20 and is
slidably disposed therein, and a hollow cylindrical portion 115 the
lower end of which forms a valve seat 114 of the solenoid valve 21,
which are arranged on the same axis. Inserted into the hollow
cylindrical portion 115 is a guide 116 hanging from the holder 29.
The solenoid valve 21 has a hollow cylindrical valve element 117
held in the body 22 in a manner axially movable to and from the
valve seat 114, and the hollow cylindrical valve element 117 is
provided with a valve hole 118 so as to cause the hollow part of
the valve element 117 to communicate with the port 25. An upper end
of the hollow cylindrical vale element 117 on a side opposed to the
valve seat 114 is formed to have a frustoconical shape, and makes
up a poppet valve in cooperation with the valve seat 114.
[0072] The valve element 112 of the main valve 20 is configured, as
shown in FIG. 11, to have a tapered portion 119 such that the vale
element 112 is closely seated on the valve seat 27, so as to
maintain a sufficient closed state when the main valve 20 functions
as a check valve. The skirt 113 formed integrally with the valve
element 112 has at least one slit 120 in a circumferential
direction. The slit 120 is formed by cutting the skirt 113 along
the axis of the main valve 20, and forms a flow passage
area-variable refrigerant passage of the main valve 20, the opening
area of which is changed according to the lift amount.
[0073] The valve element 112 of the main valve 20 is configured
such that the opening width of the slit 120 is reduced as it is
closer to the tapered portion 119. With this configuration, when
the valve element 112 starts to open from the fully-closed state in
which it is seated on the valve seat 27, it is possible to modify
the rate of change in the opening area with respect to the amount
of motion of the valve element 112. Therefore, in this control
valve 111, as shown in FIG. 12, the change in the flow rate
relative to electric current supplied to the solenoid is not
linear, when the valve seat 27 is positioned in a region where the
opening width of the slit 120 is changing after the valve element
112 has started to be lifted, an increase in the flow rate
responsive to an increase in electric current is small, and the
change in the flow rate relative to the electric current is
proportional when the valve element 27 is positioned in a region
where the opening width of the slit 120 is constant.
[0074] Although described in detail based on the preferred
embodiments heretofore, the present invention is by no means
limited to the specific forms thereof. For example, in the
illustrated examples, the control valve is disposed in a
discharge-side refrigerant passage of the variable displacement
compressor to control the flow rate of refrigerant introduced into
the crankcase 1, this is not limitative, but the control valve may
be disposed in a suction-side refrigerant passage, and the main
valve senses the flow rate of refrigerant flowing through the
suction-side refrigerant passage, to control the flow rate of
refrigerant flowing from the crankcase 1 out into the suction
chamber.
[0075] The control valve for a variable displacement compressor,
according to the present invention, comprises the main valve and
the solenoid valve having a valve portion which is commonly used as
part of the main valve. Therefore, the control valve is
advantageous in that it can be realized by a very simple
construction, and a stable flow rate control is possible since the
solenoid valve performs actuation control of the valve portion
smaller than the main valve.
[0076] 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 an operation stoppage state, pressure
corresponding to the differential pressure is returned to the
discharge chamber at a dash. To prevent this, a check valve is
disposed at an outlet port of the compressor. In the control valve
according to the present invention, the main valve is formed by a
check valve structure in which it is lifted by the flow rate of
refrigerant flowing in one direction. 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.
[0077] The foregoing is considered as illustrative only of the
principles of the present invention. Further, since numerous
modifications and changes will readily occur to those skilled in
the art, it is not desired to limit the invention to the exact
construction and applications shown and described, and accordingly,
all suitable modifications and equivalents may be regarded as
falling within the scope of the invention in the appended claims
and their equivalents.
* * * * *