U.S. patent application number 11/187441 was filed with the patent office on 2005-11-17 for control valve for variable displacement compressor.
This patent application is currently assigned to ZEXEL VALEO CLIMATE CONTROL CORPORATION. Invention is credited to Irie, Kazuhiro, Kawamura, Yuji, Kowada, Kazutaka, Muta, Shunji, Sato, Yoshie.
Application Number | 20050254961 11/187441 |
Document ID | / |
Family ID | 32767372 |
Filed Date | 2005-11-17 |
United States Patent
Application |
20050254961 |
Kind Code |
A1 |
Kawamura, Yuji ; et
al. |
November 17, 2005 |
Control valve for variable displacement compressor
Abstract
In order to reduce the amount of refrigerant circulating within
a variable displacement compressor to thereby improve compression
efficiency, a control valve is configured to comprise a ball valve
for controlling the flow rate of refrigerant flowing from a
discharge chamber to a crankcase, a spool valve for controlling the
flow rate of refrigerant flowing from the crankcase to a suction
chamber, a diaphragm for sensing suction pressure, and a solenoid
for setting the suction pressure, wherein the spool valve starts
flow rate control after the ball valve is fully closed or nearly
fully closed, and the ball valve starts flow rate control after the
valve lift of the spool valve is minimized or nearly minimized. As
a result, a region is almost eliminated in which the ball valve and
the spool valve are both open simultaneously during switching of
flow rate control between the ball valve and the spool valve, which
makes it possible to minimize the flow rate of the refrigerant
circulating within the compressor without contributing to a
refrigerating operation, to thereby improve the efficiency of the
compressor.
Inventors: |
Kawamura, Yuji; (Saitama,
JP) ; Kowada, Kazutaka; (Saitama, JP) ; Irie,
Kazuhiro; (Saitama, JP) ; Muta, Shunji;
(Saitama, JP) ; Sato, Yoshie; (Saitama,
JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW
SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
ZEXEL VALEO CLIMATE CONTROL
CORPORATION
Saitama
JP
|
Family ID: |
32767372 |
Appl. No.: |
11/187441 |
Filed: |
July 20, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11187441 |
Jul 20, 2005 |
|
|
|
PCT/JP04/00505 |
Jan 21, 2004 |
|
|
|
Current U.S.
Class: |
417/222.2 ;
417/222.1; 417/269 |
Current CPC
Class: |
F04B 2027/1831 20130101;
F04B 27/1804 20130101; F04B 2027/1827 20130101; F04B 2027/1859
20130101; F04B 2027/1854 20130101; F04B 2027/1813 20130101 |
Class at
Publication: |
417/222.2 ;
417/222.1; 417/269 |
International
Class: |
F04B 001/26; F04B
001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 22, 2003 |
JP |
2003-013890 |
Claims
What is claimed is:
1. A control valve for a variable displacement compressor, which is
capable of controlling pressure in a crankcase to thereby change a
discharge amount of refrigerant, comprising: a first valve that is
disposed between a discharge chamber and the crankcase of the
compressor, for controlling a flow rate of refrigerant flowing from
the discharge chamber to the crankcase; a second valve that is
disposed between the crankcase and a suction chamber of the
compressor, for controlling a flow rate of refrigerant flowing from
the crankcase to the suction chamber to a predetermined minimum
rate when the first valve is controlling the flow rate of the
refrigerant flowing from the discharge chamber to the crankcase,
and for controlling the flow rate of the refrigerant flowing from
the crankcase to the suction chamber when the first valve is fully
closed or nearly fully closed; and a pressure-sensing section that
senses suction pressure in the suction chamber, for changing a lift
amount of the first valve and a lift amount of the second
valve.
2. The control valve according to claim 1, wherein the second valve
has a clearance set between a diameter of a valve hole and a
diameter of a valve element inserted into the valve hole when the
first valve is controlling the flow rate of the refrigerant flowing
from the discharge chamber to the crankcase, the clearance being
provided with a fixed orifice function for controlling the flow
rate of the refrigerant flowing from the crankcase to the suction
chamber to the predetermined minimum rate.
3. The control valve according to claim 1, comprising a shaft
extending through the valve hole of the second valve coaxially with
the valve hole, for transmitting an opening/closing operation of
the second valve to the first valve.
4. The control valve according to claim 3, wherein the shaft has a
joining part joined to the valve element, formed such that the
joining part has a frustconical shape.
5. The control valve according to claim 3, wherein the shaft has an
end thereof in contact with a valve element of the first valve,
formed such that the end has a spool shape.
6. The control valve according to claim 3, wherein the shaft can be
brought into contact with and left the valve element of the first
valve.
7. The control valve according to claim 3, wherein a clearance set
between a diameter of an end of the shaft in contact with the valve
element of the first valve and a diameter of a valve hole of the
first valve is provided with a fixed orifice function for
controlling the flow rate of the refrigerant flowing from the
discharge chamber to the crankcase to the predetermined minimum
rate.
8. The control valve according to claim 1, wherein the first valve
is a spool valve.
9. The control valve according to claim 1, comprising a fixed
orifice that is formed in parallel with the second valve, for
controlling the flow rate of the refrigerant flowing from the
crankcase to the suction chamber to the predetermined minimum rate
when the first valve is controlling the flow rate of the
refrigerant flowing from the discharge chamber to the
crankcase.
10. The control valve according to claim 1, comprising a
pressure-setting section that applies urging load to the
pressure-sensing section to set a pressure control point of the
control valve.
11. The control valve according to claim 10, wherein the
pressure-setting section is a solenoid that sets the pressure
control point by applying the urging load in response to an
external signal.
12. The control valve according to claim 10, wherein the
pressure-setting section is a spring that sets the pressure control
point by a spring force.
Description
[0001] This application is a continuing application, filed under 35
U.S.C. .sctn.111(a), of International Application
PCT/JP2004/000505, filed Jan. 21, 2004.
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 used in a
refrigeration cycle of an automotive air conditioner.
[0004] 2. Description of the Related Art
[0005] The rotational speed of an engine as a drive source of an
automotive air conditioner is not constant, and hence the air
conditioner is required to be controlled such that refrigerating
power thereof is held constant regardless of the engine rotational
speed. To meet this requirement, a swash plate variable
displacement compressor capable of changing the discharge amount of
refrigerant is generally used in an automotive air conditioner. In
the variable displacement compressor, a swash plate disposed within
a crankcase such that the inclination angle thereof can be changed
is driven by the rotation of a rotating shaft, for performing
wobbling motion, and the wobbling motion causes a plurality of
pistons to perform reciprocating motion in a direction parallel to
the rotating shaft, whereby refrigerant is drawn, compressed, and
then discharged. In doing this, the inclination angle of the swash
plate is varied by changing the pressure in the crankcase, whereby
the stroke of the pistons is changed for changing the discharge
amount of the refrigerant.
[0006] In general, the control valve is disposed in a refrigerant
passage communicating between a discharge chamber and a crankcase,
and controls the flow rate of refrigerant introduced at discharge
pressure Pd from the discharge chamber into the crankcase, to
thereby control pressure Pc within the crankcase. The refrigerant
introduced into the crankcase is drawn into the suction chamber via
a fixed orifice. In this control valve, suction pressure Ps in the
suction chamber is sensed e.g. by a pressure-sensing member, such
as a diaphragm, and the flow rate of the refrigerant introduced
into the crankcase is controlled such that the suction pressure Ps
is maintained at a constant level.
[0007] On the other hand, it is also conventional to dispose a
control valve in a refrigerant passage communicating between the
crankcase and the suction chamber, and provide a fixed orifice
between the discharge chamber and the crankcase, so as to control
the flow rate of the refrigerant drawn from the crankcase.
[0008] In either of the variable displacement compressors using
these two types of control valves, the fixed orifice having an
invariable flow passage area is interposed in the passage from the
discharge chamber to the crankcase or the passage from the
crankcase to the suction chamber in series with the passage.
Consequently, in the variable displacement compressor using one of
the above-described control valves, increased amount of refrigerant
circulates therein, which inevitably causes degradation of
compression efficiency.
[0009] There has also been proposed a control valve having two
valves disposed, respectively, in the refrigerant passage
communicating between the discharge chamber and the crankcase and
the refrigerant passage communicating between the crankcase and the
suction chamber, such that the two valves operate in a manner
interlocked with each other, so as to simultaneously control the
flow rate of the refrigerant introduced into the crankcase and the
flow rate of the refrigerant drawn from the crankcase (e.g. in
Japanese Unexamined Patent Publication (Kokai) NO. S58-158382, FIG.
3). With this configuration, the control valve provides control
such that when the flow rate of refrigerant in one of the
refrigerant passage communicating between the discharge chamber and
the crankcase and the refrigerant passage communicating between the
crankcase and the suction chamber is increased, the flow rate of
refrigerant in the other is reduced. This makes it possible to
reduce the flow rate of refrigerant circulating in the variable
displacement compressor, and hence construct a variable
displacement compressor which is higher in compression efficiency
than those using the control valves configured as described
hereinbefore.
[0010] Further, there has been proposed a control valve having two
valves disposed, respectively, in the refrigerant passage
communicating between the discharge chamber and the crankcase and
the refrigerant passage communicating between the crankcase and the
suction chamber, such that the two valves operate in a manner
interlocked with each other to hold one of the refrigerant passages
in a closed state when the other passage is open in a controlled
state (e.g. in Japanese Unexamined Patent Publication (Kokai) No.
S64-41680, FIG. 2). According to this control valve, when the flow
rate of refrigerant in one of the refrigerant passages is being
controlled, the other refrigerant passage is closed, so that
refrigerant circulating in the variable displacement compressor can
be further reduced.
[0011] However, in the former control valve described in Japanese
Unexamined Patent Publication (Kokai) No. S58-158382, in which the
valves are disposed on the respective inlet and outlet sides of the
crankcase, one of the two valves operated in an interlocked manner
closes as the other opens, and hence there inevitably occurs a
region where the two valves are both open. Consequently, the flow
rate of refrigerant circulating in the compressor can only be
reduced to a limited degree, which makes it impossible to obtain
sufficiently improved compression efficiency.
[0012] On the other hand, in the latter control valve described in
Japanese Unexamined Patent Publication (Kokai) No. S64-41680, in
which while one of the valves is open, the other is held closed,
when the suction pressure becomes not higher than a first set
pressure, the refrigerant passage (outlet side) between the
crankcase and the suction chamber is fully closed, and hence the
pressure in the crankcase sensitively reacts to a slight change in
the valve in the refrigerant passage (inlet side) between the
discharge chamber and the crankcase. As a consequence, when the
pressure in the crankcase rises excessively, gaseous refrigerant
compressed in the crankcase cannot be reduced by changing the valve
lift of the valve on the inlet side, and not until the suction
pressure spontaneously becomes higher than a second set pressure
with decrease in the displacement of the compressor to open the
outlet-side refrigerant passage, does the pressure in the crankcase
fall. Then, the displacement of the compressor increases with
decrease in the pressure in the crankcase, and the suction pressure
becomes not higher than the first set pressure. Thereafter, a
so-called hunting phenomenon occurs in which the above-described
cycle is repeated. As described above, the latter control valve
cannot ensure stable controllability.
SUMMARY OF THE INVENTION
[0013] The present invention has been made in view of the above
points, and an object thereof is to provide a control valve for a
variable displacement compressor, which is capable of reducing the
amount of refrigerant circulating within the compressor to thereby
improve compression efficiency, while ensuring stable
controllability.
[0014] To solve the above problems, the present invention provides
a control valve for a variable displacement compressor, which is
capable of controlling pressure in a crankcase to thereby change a
discharge amount of refrigerant, comprising a first valve that is
disposed between a discharge chamber and the crankcase of the
compressor, for controlling a flow rate of refrigerant flowing from
the discharge chamber to the crankcase, a second valve that is
disposed between the crankcase and a suction chamber of the
compressor, for controlling a flow rate of refrigerant flowing from
the crankcase to the suction chamber to a predetermined minimum
rate when the first valve is controlling the flow rate of the
refrigerant flowing from the discharge chamber to the crankcase,
and for controlling the flow rate of the refrigerant flowing from
the crankcase to the suction chamber when the first valve is fully
closed or nearly fully closed, and a pressure-sensing section that
senses suction pressure in the suction chamber, for changing a lift
amount of the first valve and a lift amount of the second
valve.
[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 conceptual view showing the arrangement of a
control valve for a variable displacement compressor, according to
the present invention.
[0017] FIG. 2 is an enlarged fragmentary view useful in explaining
the control valve set to a first opening/closing timing.
[0018] FIG. 3 is a diagram showing characteristics of the control
valve set to the first opening/closing timing.
[0019] FIG. 4 is an enlarged fragmentary view useful in explaining
the control valve set to a second opening/closing timing.
[0020] FIG. 5 is a diagram showing characteristics of the control
valve set to the second opening/closing timing.
[0021] FIG. 6 is an enlarged fragmentary view useful in explaining
the control valve set to a third opening/closing timing.
[0022] FIG. 7 is a diagram showing characteristics of the control
valve set to the third opening/closing timing.
[0023] FIG. 8 is an enlarged fragmentary view useful in explaining
a control valve in which a fixed orifice is formed in each of an
inlet side and an outlet side.
[0024] FIG. 9 is a diagram showing characteristics of the control
valve set to a fourth opening/closing timing.
[0025] FIG. 10 is a conceptual view showing a control valve in
which a fixed orifice is formed in each of an inlet side and an
outlet side.
[0026] FIG. 11 is a diagram showing characteristics of the control
valve set to a fifth opening/closing timing.
[0027] FIG. 12 is a conceptual view showing the arrangement of a
mechanical control valve for a variable displacement
compressor.
[0028] FIG. 13 is a conceptual view showing the arrangement of a
mechanical control valve for a variable displacement
compressor.
[0029] FIG. 14 is a conceptual view showing the arrangement of a
control valve for a variable displacement compressor, in which the
fixed orifice function of a second valve is provided
independently.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] The present invention will now be described in detail with
reference to the accompanying drawings showing preferred
embodiments thereof.
[0031] FIG. 1 is a conceptual view showing the arrangement of a
control valve for a variable displacement compressor, according to
the present invention.
[0032] The control valve for a variable displacement compressor,
according to the present invention has a ball valve 11 forming a
first valve, a spool valve 12 forming a second valve, a diaphragm
13 forming a pressure-sensing section, and a solenoid 14 forming a
pressure-setting section, which are arranged in the mentioned
order.
[0033] The ball valve 11 introduces refrigerant discharged at
discharge pressure Pd from a discharge chamber of the variable
displacement compressor, and controls the flow rate of the
introduced refrigerant to supply the refrigerant at pressure Pc1 to
a crankcase. The spool valve 12 introduces refrigerant delivered at
pressure Pc2 from the crankcase, and controls the flow rate of the
introduced refrigerant to supply the pressure to a suction chamber
of the compressor in a manner interlocked with operation of the
ball valve 11. The diaphragm 13 receives suction pressure Ps from
the suction chamber, and when the suction pressure becomes lower
than a predetermined suction pressure setting point, the diaphragm
13 displaces the ball valve 11 and the spool valve 12 to increase
pressure in the crankcase. With increase in the pressure in the
crankcase, the displacement of the compressor is reduced. As a
consequence, the suction pressure of an air conditioner is
controlled to a level in the vicinity of the predetermined suction
pressure setting point. The solenoid 14 applies urging load to the
diaphragm 13 to set the suction pressure setting point. The urging
load is set according to the value of an electric current
externally supplied.
[0034] The spool valve 12 comprises a valve seat 15 and a valve
element 16 removably inserted into a valve hole. Between the valve
seat 15 and the valve element 16, there is formed a predetermined
clearance 17. This clearance 17 forms a fixed orifice with an
invariable flow passage area between the crankcase and the suction
chamber when the valve element 16 is inserted into the valve hole.
The clearance 17 is determined depending on the stability of the
swash plate of the compressor. The valve element 16 is integrally
formed with a shaft 18 for driving the ball valve 11. The valve
element 16 and the shaft 18 are joined to each other by a joining
part 19 having a frustoconical shape with a taper in cross
section.
[0035] The spool valve 12 can be freely modified according to
characteristics, such as hunting, controllability, and stability,
of the variable displacement compressor such that the spool valve
12 has a different opening/closing timing from that of the ball
valve 11 interlocking with operation of the spool valve 12. The
change in the opening/closing timing of the spool valve 12 can be
easily achieved by changing the distance between an end of the
valve element 16 as a boundary to the joining part 19 and a forward
end of the shaft 18 in contact with a valve element 20 of the ball
valve 11 to thereby axially shift a position where the end of the
valve element 16 is held in a fully-closed state of the ball valve
11.
[0036] In the ball valve 11, as the shaft 18 moves rightward as
viewed in FIG. 1, the valve element 20 moves in a valve-opening
direction, and the maximum valve lift of the ball valve 11 is
limited by abutment of a stepped part 21 of the shaft 18 against a
stepped part 22 of a body.
[0037] FIG. 2 is an enlarged fragmentary view useful in explaining
the control valve set to a first opening/closing timing, and FIG. 3
is a diagram showing characteristics of the control valve set to
the first opening/closing timing.
[0038] The first opening/closing timing is set such that the
opening/closing timing of the ball valve 11 and that of the spool
valve 12 coincide with each other, and more specifically such that
when the ball valve 11 is fully closed, the end of the valve
element 16 of the spool valve 12 is aligned with a solenoid-side
open end face of the valve seat 15.
[0039] With this configuration, the characteristics exhibited by
the control valve when the valve element 16 of the spool valve 12
is axially moved are as shown in FIG. 3. In FIG. 3, the abscissa
represents a stroke of the shaft 18, and the origin represents a
state where the stepped part 21 of the shaft 18 is in abutment with
the stepped part 22 of the body and at a position closest to the
ball valve side (or a deenergized state of the solenoid). The
ordinate in FIG. 3 represents the opening area of the ball valve 11
and that of the spool valve 12. A line indicated by Pd-Pc
represents changes in the opening area of the ball valve 11, while
a line indicated by Pc-Ps represents changes in the opening area of
the spool valve 12.
[0040] In the first opening/closing timing, as long as the ball
valve 11 is open, the spool valve 12 has an opening area
corresponding to the clearance 17, and operates as the fixed
orifice. When the shaft 18 moves toward the solenoid 14 and reaches
a position s1, the valve element 20 of the ball valve 11 is seated
to fully close the ball valve 11. When the shaft 18 further moves
toward the solenoid 14, the forward end of the shaft 18 moves away
from the valve element 20 of the ball valve 11, whereby the ball
valve 11 is held in its fully-closed state, and the spool valve 12
starts opening from the state operating as the fixed orifice to
increase its opening area in accordance with increase in the stroke
of the shaft 18. When the ball valve 11 is in its fully-closed
state, compressed refrigerant cannot flow into the crankcase via
the control valve, but a slight amount of blowby gas leaks into the
crankcase through a gap between a piston for drawing and
compressing refrigerant and a cylinder having the piston slidably
received therein, which makes it possible to control pressure Pc
(=Pc1=Pc2) within the crankcase.
[0041] FIG. 4 is an enlarged fragmentary view useful in explaining
the control valve set to a second opening/closing timing, and FIG.
5 is a diagram showing characteristics of the control valve set to
the second opening/closing timing.
[0042] The second opening/closing timing is set such that the
opening timing of the spool valve 12 is retarded with respect to
the closing timing of the ball valve 11, and hence in the second
opening/closing timing, when the ball valve 11 is fully closed, the
spool valve 12 is still in its closed state (fixed orifice state).
To this end, the distance between the ball valve-side end of the
valve element 16 and the forward end of the shaft in contact with
the valve element 20 of the ball valve 11 is made shorter by a
distance "a" than in the first opening/closing timing such that
when the ball valve 11 is closed, the ball valve-side end of the
valve element 16 of the spool valve 12 is positioned within the
valve hole.
[0043] With this configuration, in the second opening/closing
timing, as shown in FIG. 5, as the shaft 18 moves toward the
solenoid 14, first, the ball valve 11 is fully closed when the
shaft 18 reaches the position s1. At this time, the spool valve 12
has the opening area corresponding to the clearance 17. Then, when
the shaft 18 further moves toward the solenoid 14 and reaches a
position s2, the spool valve 12 starts opening.
[0044] FIG. 6 is an enlarged fragmentary view useful in explaining
the control valve set to a third opening/closing timing, and FIG. 7
is a diagram showing characteristics of the control valve set to
the third opening/closing timing.
[0045] The third opening/closing timing is configured such that the
opening timing of the spool valve 12 is advanced with respect to
the closing timing of the ball valve 11. To this end, the distance
between the ball valve-side end of the valve element 16 and the
forward end of the shaft in contact with the valve element 20 of
the ball valve 11 is made longer by a distance "b" than in the
first opening/closing timing whereby when the ball valve 11 is
closed, the ball valve-side end of the valve element 16 of the
spool valve 12 is positioned closer to the solenoid 14 than the
valve seat 15.
[0046] With this configuration, in the third opening/closing
timing, as shown in FIG. 7, as the shaft 18 moves toward the
solenoid 14, first, the spool valve 12 starts opening when the
shaft 18 reaches a position s1, and then when the shaft 18 reaches
a position s2, the ball valve 11 is fully closed.
[0047] FIG. 8 is an enlarged fragmentary view useful in explaining
a control valve in which a fixed orifice is formed in each of an
inlet side and an outlet side, and FIG. 9 is a diagram showing
characteristics of the control valve set to a fourth
opening/closing timing. It should be noted that component elements
in FIG. 8 identical to those in FIG. 1 are designated by identical
reference numerals.
[0048] This control valve is configured such that the fixed
orifices are formed on the respective inlet and outlet sides of the
crankcase. In the control valve, the forward end of the shaft 18 in
contact with the valve element 20 of the ball valve 11 is formed
into a spool shape, and a clearance 24 is formed between the outer
periphery of a contact end part 23 of the shaft 18 and the inner
wall of the valve hole. When the ball valve 11 is in the vicinity
of its fully-closed position, the clearance 24 is formed within the
valve hole to form a fixed orifice with an invariable flow passage
area between a compression chamber and the crankcase. The fixed
orifice is provided for stably maintaining the flow rate of
refrigerant introduced from the discharge chamber into the
crankcase in a region where refrigerant is introduced into the
crankcase by blowby gas, and the flow rate of refrigerant
discharged from the crankcase is controlled by the spool valve 12.
The distance between the rear end (diameter reduction start
position) of the contact end part 23 and the seated position of the
valve element 20 is set to a distance "c". Further, in the present
example, the distance "d" between the end of the valve element 16
of the spool valve 12 and a valve closing start position of the
spool valve 12 is set such that it becomes equal in value to the
distance "c" when the ball valve 11 is fully closed with the valve
element 20 thereof held in contact with the contact end part
23.
[0049] The control valve set as above has the following
characteristics: As shown in FIG. 9, first, when the solenoid is
not energized, the stepped part 21 of the shaft 18 is in contact
with the stepped part 22 of the body, and hence the ball valve 11
is in its fully-open state, and the spool valve 12 is in the fixed
orifice state.
[0050] With an increase in electric current for energizing the
solenoid, the ball valve 11 turns from the fully-open state in the
direction of reducing its opening area, whereas the spool valve 12
maintains its fixed orifice state. Then, when the shaft moves to a
position s1, the rear end of the contact end part 23 reaches the
seated position of the valve element 20, and the spool valve 12
reaches a valve opening start position at which it starts to get
out of the fixed orifice state. When the shaft 18 further moves
from the position s1, the rear end of the contact end part 23
enters the valve hole, whereby the ball valve 11 enters its fixed
orifice state, and the spool valve 12 changes from its fixed
orifice state in the direction of increasing its opening area.
[0051] Thereafter, the fixed orifice state of the ball valve 11 is
maintained until the opening area of the ball valve 11 becomes
smaller than that of the fixed orifice, and finally the ball valve
11 is seated to be fully closed.
[0052] Although in the above example, the distance "c" and the
distance "d" are set to the same value, the distance "d" may be
increased or decreased according to the characteristics of the
variable displacement compressor to thereby easily change the
opening/closing timing of the spool valve 12.
[0053] FIG. 10 is a conceptual view showing the arrangement of a
control valve in which a fixed orifice is formed in each of the
inlet side and the outlet side, and FIG. 11 is a diagram showing
characteristics of the control valve set to a fifth opening/closing
timing. It should be noted that component elements in FIG. 10
identical to those in FIG. 1 are designated by identical reference
numerals.
[0054] In this control valve, a valve disposed between the
compressor and the crankcase and a valve disposed between the
crankcase and the suction chamber are implemented by respective
spool valves 11a and 12. The valve element 16 of the spool valve
12, the shaft 18, and a valve element 20a of the spool valve 11a
are integrally formed with each other. The valve element 20a is
smaller in diameter than the shaft 18 supported by the body, and
the clearance 24 is formed between the valve element 20a and the
inner wall of the valve hole. Further, a portion between the valve
element 20a and the shaft 18 is reduced in diameter to have a spool
shape. The distance between the rear end (diameter reduction start
position) of the valve element 20a and a valve closing start
position where the valve element 20a enters the valve hole is set
such that it becomes equal to a distance "e" when the spool valve
12 is in a valve closing start position.
[0055] The control valve set as above has the following
characteristics: As shown in FIG. 11, first, when the solenoid is
not energized, the stepped part 21 of the shaft 18 is in contact
with the stepped part 22 of the body, and hence the spool valve 11a
is in its fully-open state, and the spool valve 12 is fully closed
and in its fixed orifice state.
[0056] With an increase in electric current for energizing the
solenoid, the rear end of the valve element 20a of the spool valve
11a approaches the valve hole and changes from its fully-open state
in the direction of reducing its opening area, whereas the spool
valve 12 maintains its fixed orifice state. Then, when the shaft 18
moves to a position s1, the spool valve 11a reaches the valve
closing start position, and the spool valve 12 reaches a valve
opening start position at which it starts to get out of its fixed
orifice state. When the shaft 18 further moves from the position
s1, the valve element 20a enters the valve hole, whereby the spool
valve 11a enters its fixed orifice state, and the spool valve 12
changes from its fixed orifice state in the direction of increasing
its opening area.
[0057] In the above embodiments, the electric control valves are
described which use, as means for setting the suction pressure Ps
in the suction chamber, the solenoid that enables a set point
(pressure control point) thereof to be freely set by external
electric control current. Next, mechanical control valves will be
describe in which the suction pressure Ps is set to a fixed
value.
[0058] FIG. 12 is a conceptual view showing the arrangement of a
mechanical control valve for a variable displacement compressor. It
should be noted that component elements in FIG. 12 identical to
those in FIG. 1 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0059] This control valve has the ball valve 11 forming the first
valve, the spool valve 12 forming the second valve, the diaphragm
13 forming the pressure-sensing section, and a spring 25 forming a
pressure-setting section, which are arranged in the mentioned
order.
[0060] This control valve is also configured such that as long as
the ball valve 11 is variably controlling its opening area, the
spool valve 12 functions as a fixed orifice, and when the ball
valve 11 is in its fully-closed state, the spool valve 12 variably
controls its opening area. Of course, the opening/closing timing of
the spool valve 12 is set to one of the above described first to
third opening/closing timings in accordance with the
characteristics of the variable displacement compressor.
[0061] The diaphragm 13 has a disk 26 provided on a spring-side
surface thereof, and the spring 25 urges the diaphragm 13 toward
the spool valve 12 via the disk 26. The spring 25 is adjusted to
have a spring load corresponding to a predetermined suction
pressure control point. Therefore, when the suction pressure Ps
received from the suction chamber becomes lower than the suction
pressure control point, the diaphragm 13 urges the ball valve 11
and the spool valve 12 such that the pressure in the crankcase is
increased, whereby the control valve controls the displacement of
the variable displacement compressor to thereby control suction
pressure in the air conditioner to a level in the vicinity of the
predetermined suction pressure control point.
[0062] Of course, the present control valve can also be configured
as a control valve set to the fourth opening/closing timing, by
forming the contact end part 23 at the end of the shaft 18 to form
the fixed orifice shown in FIG. 8 and thereby forming the fixed
orifices on the respective refrigerant inlet and outlet sides of
the crankcase.
[0063] FIG. 13 is a conceptual view showing the arrangement of a
mechanical control valve for a variable displacement compressor. It
should be noted that component elements in FIG. 13 identical to
those in FIGS. 1 and 10 are designated by identical reference
numerals, and detailed description thereof is omitted.
[0064] This control valve has the spool valve 11a forming the first
valve, the spool valve 12 forming the second valve, the diaphragm
13 forming the pressure-sensing section, and the spring 25 forming
the pressure-setting section, which are arranged in the mentioned
order.
[0065] The spool valve 11a is identical in construction to that
shown in FIG. 10. Therefore, the present control valve has the
characteristic of the fifth opening/closing timing shown in FIG.
11.
[0066] Also in this control valve, the suction pressure Ps is
received from the suction chamber to change the lift amount of each
of the spool valves 11a and 12, and the pressure in the crankcase
is controlled such that the suction pressure Ps is held constant as
a consequence.
[0067] FIG. 14 is a conceptual view showing the arrangement of a
control valve for a variable displacement compressor, in which the
fixed orifice function of the second valve is provided
independently. It should be noted that component elements in FIG.
14 identical to those in FIG. 1 are designated by identical
reference numerals, and detailed description thereof is
omitted.
[0068] The present control valve is distinguished from the control
valve shown in FIG. 1, in which the clearance 17 formed between the
valve element 16 of the spool valve 12 and the inner wall of the
valve hole provides the fixed orifice function, in that a fixed
orifice 27 having an opening area equivalent to that formed by the
clearance 17 is formed in the body. In this case, the clearance 17
formed between the valve element 16 of the spool valve 12 and the
inner wall of the valve hole is minimized. As a result, when the
refrigerant passage between the crankcase and the suction chamber
is narrowed by the spool valve 12, refrigerant is caused to flow
through the fixed orifice 27 larger in diameter, and prevented from
flowing through the clearance 17 which is small. This provides an
advantageous effect that a change in the flow rate of refrigerant
due to deposition of sludge contained in the refrigerant can be
reduced.
[0069] More specifically, assuming that the clearance 17 between
the valve element 16 of the spool valve 12 and the inner wall of
the valve hole is e.g. 0.1 mm, the fixed orifice 27 having an
opening area equivalent to the clearance 17 is a through hole with
a diameter of 1 mm, and sludge deposited on the valve element 16 or
the inner wall of the valve hole, or on the inner wall of the fixed
orifice 27 has grown e.g. to a thickness of 0.1 mm, the clearance
17 is almost clogged with the sludge, whereas the diameter of the
fixed orifice 27 is reduced only to 0.8 mm, which makes smaller the
change in the flow rate of refrigerant due to deposition of sludge.
Further, since refrigerant mainly flows through the fixed orifice
27 which is easier for refrigerant to flow through, the amount of
refrigerant flowing through the narrow clearance 17 is small, which
makes it difficult for sludge to deposit.
[0070] Although the arrangement in which the fixed orifice 27 is
formed in parallel with the spool valve 12 forming the second valve
is described based on an example of application thereof to the
control valve of a type having the solenoid 14 shown in FIG. 1, it
can also be applied to the mechanical control valves shown in FIGS.
12 and 13.
[0071] As described above, according to the present invention, the
control valve is configured to comprise the first valve for
controlling the flow rate of refrigerant flowing from the discharge
chamber to the crankcase, the second valve for controlling the flow
rate of refrigerant flowing from the crankcase to the suction
chamber, the pressure-sensing section for sensing suction pressure,
and the pressure-setting section for setting the suction pressure,
wherein the second valve starts flow rate control after the first
valve is fully closed or nearly fully closed, and the first valve
starts flow rate control after the valve lift of the second valve
is minimum or nearly minimum. As a result, a region is eliminated
in which the first and second valves are both open simultaneously
during switching of control between the first valve and the second
valve, which makes it possible to minimize the flow rate of
refrigerant flowing from the discharge chamber to the crankcase and
further from the crankcase to the suction chamber, i.e. the flow
rate of refrigerant circulating within the variable displacement
compressor without contributing to a refrigerating operation, to
thereby improve the efficiency of the compressor. Further, since
the second valve is equipped with the fixed orifice function for
reducing the flow rate of refrigerant flowing from the crankcase to
the suction chamber to a predetermined minimum flow rate, it is
possible to stably adjust the pressure in the crankcase to thereby
provide excellent controllability.
[0072] The foregoing is considered as illustrative only of the
principles of the present invention. Further, since numerous
modifications and changes will readily occur to those skilled in
the art, it is not desired to limit the invention to the exact
construction and applications shown and described, and accordingly,
all suitable modifications and equivalents may be regarded as
falling within the scope of the invention in the appended claims
and their equivalents.
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