U.S. patent application number 11/891514 was filed with the patent office on 2008-10-09 for displacement control valve for variable displacement compressor.
Invention is credited to Motoaki Okuda, Junya Suzuki, Hiromi Ueda, Naoya Yokomachi.
Application Number | 20080247883 11/891514 |
Document ID | / |
Family ID | 38792098 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080247883 |
Kind Code |
A1 |
Yokomachi; Naoya ; et
al. |
October 9, 2008 |
Displacement control valve for variable displacement compressor
Abstract
A displacement control valve for a variable displacement
compressor has a control passage, a valve hole formed in the
control passage, a first shaft portion including a valve body, and
a connecting portion connected to the end portion of the valve
body. The control passage is connected to a crank chamber for
controlling the pressure in the crank chamber for adjusting the
discharge displacement of the compressor. The valve body is formed
at an end portion of the first shaft portion to open and close the
valve hole. The connecting portion connected to the end portion of
the valve body is disposed into the valve hole, and a
circumferential surface of the connecting portion has a curved
surface so as to be flared out at an end of the connecting
portion.
Inventors: |
Yokomachi; Naoya;
(Kariya-shi, JP) ; Suzuki; Junya; (Kariya-shi,
JP) ; Okuda; Motoaki; (Kariya-shi, JP) ; Ueda;
Hiromi; (Kariya-shi, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
3 WORLD FINANCIAL CENTER
NEW YORK
NY
10281-2101
US
|
Family ID: |
38792098 |
Appl. No.: |
11/891514 |
Filed: |
August 9, 2007 |
Current U.S.
Class: |
417/218 |
Current CPC
Class: |
F04B 2027/185 20130101;
F04B 2205/05 20130101; F04B 2027/1827 20130101; F04B 27/1804
20130101; F04B 2027/1854 20130101; F04B 2027/1813 20130101; F04B
2205/08 20130101 |
Class at
Publication: |
417/218 |
International
Class: |
F04B 49/00 20060101
F04B049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2006 |
JP |
P2006-217622 |
Claims
1. A displacement control valve for a variable displacement
compressor that adjusts the discharge displacement by controlling
the pressure in a crank chamber, the displacement control valve
comprising: a control passage connected to the crank chamber for
controlling the pressure in the crank chamber; a valve hole formed
in the control passage; a first shaft portion including a valve
body at an end portion thereof to open and close the valve hole;
and a connecting portion connected to the end portion of the valve
body, so that the connecting portion is disposed into the valve
hole, wherein a circumferential surface of the connecting portion
has a curved surface so as to be flared out at an end of the
connecting portion adjacent to the valve body.
2. The displacement control valve for a variable displacement
compressor according to claim 1, wherein the curved surface is
formed with an arc.
3. The displacement control valve for a variable displacement
compressor according to claim 1, wherein the curved surface is
connected to a circumferential edge of the end portion of the valve
body.
4. The displacement control valve for a variable displacement
compressor according to claim 1, wherein a valve seat is formed
around the valve hole, wherein the valve body has a plane end
surface adjacent to the connecting portion, wherein the plane end
surface of the valve body makes contact with the valve seat to
close the valve hole.
5. The displacement control valve for a variable displacement
compressor according to claim 1 further comprising a second shaft
portion connected to the connecting portion.
6. The displacement control valve for a variable displacement
compressor according to claim 5, wherein a diameter of an end of
the connecting portion adjacent to the valve body is larger than a
diameter of an end of the connecting portion adjacent to the second
shaft portion.
7. The displacement control valve for a variable displacement
compressor according to claim 5, wherein a step is formed by the
connecting portion and the second shaft portion.
8. The displacement control valve for a variable displacement
compressor according to claim 5 further comprising a pressure
sensing mechanism for moving the valve body.
9. The displacement control valve for a variable displacement
compressor according to claim 1 further comprising a solenoid for
moving the valve body.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a displacement control
valve of a variable displacement compressor which is used in a
vehicle air conditioner.
[0002] Generally, a variable displacement compressor (hereinafter
referred to as "compressor") is known as a compressor for use in a
vehicle air conditioner, which variably controls the displacement.
In this type of compressor, a swash plate is accommodated in a
crank chamber and is inclinable with respect to a drive shaft. As
the pressure in the crank chamber increases, the inclination of the
swash plate approaches to be perpendicular to the axis of the drive
shaft (the inclination angle of the swash plate decreases). As the
pressure in the crank chamber decreases, the swash plate is
inclined so that the inclination of the swash plate approaches to
the axis of the drive shaft (the inclination angle of the swash
plate increases). The compressor has a plurarity of pistons, and
the stroke of the pistons changes in accordance with the
inclination angle of the swash plate. For example, when the
pressure in the crank chamber is high and the inclination angle of
the swash plate is small, the stroke of the piston is short. When
the pressure in the crank chamber is low and the inclination angle
of the swash plate is large, the stroke of the pistons is long. As
the stroke of the pistons decreases, the displacement of the
compressor decreases. As the stroke of the pistons increases, the
displacement of the compressor increases.
[0003] Japanese Unexamined Patent Application Publication (KOKAI)
No. 9-268973, or, the corresponding U.S. Pat. No. 5,890,876
discloses a displacement control valve 49 for a compressor. The
displacement control valve 49 has a valve housing 61 and a solenoid
62 joined thereto. A valve chamber 63 is defined by the valve
housing 61 and the solenoid 62, and is connected to a discharge
chamber 38. A valve body 64 is arranged in the valve chamber 63 to
open and close a valve hole 66. The valve hole 66 is connected to a
crank chamber 15.
[0004] The displacement control valve 49 has a pressure sensing
chamber 68 which is connected to a suction passage 32 and provided
a bellows 70 therein. The bellows 70 is connected to the valve body
64 by a rod 72 which has a large diameter portion 72a and a small
diameter portion 72b. The large-diameter portion 72a extends
through and slides with respect to a guide hole 71. The
small-diameter portion 72b extends through the valve hole 66. The
small-diameter portion 72b is connected to a top end 64a of the
valve body 64 by a tapered portion 73. The diameter of the tapered
portion 73 increases toward the valve body 64.
[0005] When the valve hole 66 is opened, the refrigerant gas in the
discharge chamber 38 flows into the crank chamber 15. When the
valve hole 66 is closed by the valve body 64, the refrigerant is
not introduced from the discharge chamber 38 to the crank chamber
15.
[0006] When the solenoid 62 is excited and the valve body 64 is
moved in the direction to close the valve hole 66, the amount of
the refrigerant which flows from the discharge chamber 38 to the
crank chamber 15 is decreased so that the pressure in the crank
chamber 15 decreases and the inclination angle of a swash plate 22
increases. When the solenoid 62 is not excited and the valve body
64 is moved away from the valve hole 66, the amount of the
refrigerant from the discharge chamber 38 to the crank chamber 15
is increased so that the pressure in the crank chamber 15 increases
and the inclination angle of the swash plate 22 decreases. Since
the tapered portion 73 is formed at the top end 64a of the valve
body 64, and the diameter of the tapered portion 73 adjacent to the
top end 64a is larger than the diameter of the tapered portion 73
adjacent to the rod 72, the cross-sectional area of the flow path
of the valve hole 66 varies gradually in accordance with the
movement of the tapered portion 73, when the valve body 64 opens
and closes the valve hole 66. Thus, due to opening and closing of
the displacement control valve 49, rapid start and stop of the
supply of the highly-pressurized refrigerant into the crank chamber
15 may be prevented.
[0007] In the Japanese Unexamined Patent Application Publication
No. 9-268973, the cross-sectional area of the flow path through
which the refrigerant flows varies discontinuously at a connecting
part of the tapered portion 73 and the top end 64a of the valve
body 64, and a continuous flow rate control and the stable control
may not be accomplished. For example, in a graph shown in FIG. 8,
the movement distance of the valve body 64 is indicated by a
horizontal axis, and the cross-sectional area in the flow path is
indicated by a vertical axis. A characteristic of the conventional
art is shown by a characteristic curve indicated by a graph G0,
which connects points A, B, C, and D. The characteristic curve G0
is discontinuous at the point B and C. The cross-sectional area of
the flow path varies discontinuously in accordance with the
movement distance of the valve body 64. Especially at the
neighborhood of the point B which corresponds to a beginning of the
displacement control, the graph G0 varies discontinuously. The
point B corresponds to the discontinuous connecting part of the top
end 64a of the valve body 64 and the larger-diameter side of the
tapered portion 73. The point C corresponds to the discontinuous
connecting part of the small-diameter portion 72b of the tapered
portion 73 and the smaller-diameter side of the pressure sensing
rod 72. Thus, at the neighborhood of the point B and C, the
continuous flow rate control and thereby a target displacement may
not be accomplished.
[0008] The present invention which is made in view of the above
problems is directed to a displacement control valve for a variable
displacement compressor which has a continuous flow rate control
and an improved stability in control.
SUMMARY OF THE INVENTION
[0009] An aspect in accordance with the present invention provides
a displacement control valve for a variable displacement
compressor. The displacement control valve has a control passage, a
valve hole formed in the control passage, a first shaft portion
including a valve body, and a connecting portion connected to the
end portion of the valve body. The control passage is connected to
a crank chamber for controlling the pressure in the crank chamber
for adjusting the discharge displacement of the compressor. The
valve body is formed at an end portion of the first shaft portion
to open and close the valve hole. The connecting portion connected
to the end portion of the valve body is disposed into the valve
hole, and a circumferential surface of the connecting portion has a
curved surface so as to be flared out at an end of the connecting
portion.
[0010] Other aspects and advantages of the invention will become
apparent from the following description, taken in conjunction with
the accompanying drawings, illustrating by way of example the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The features of the present invention that are believed to
be novel are set forth with particularity in the appended claims.
The invention together with objects and advantages thereof, may
best be understood by reference to the following, description of
the presently preferred embodiments together with the accompanying
drawings in which:
[0012] FIG. 1 is a longitudinal cross-sectional view schematically
showing a compressor according to a first embodiment;
[0013] FIG. 2 is a longitudinal cross-sectional view schematically
showing a displacement control valve according to the first
embodiment;
[0014] FIG. 3 is a partial sectional view showing a connecting
portion of the displacement control valve according to the first
embodiment;
[0015] FIG. 4 is a graph for specifying the shape of the connecting
portion according to the first embodiment, a second embodiment, and
a third embodiments;
[0016] FIG. 5A is a partial sectional view for explaining operation
of the displacement control valve according to the first
embodiment, when the displacement control valve starts to be
opened;
[0017] FIG. 5B is a partial sectional view for explaining operation
of the displacement control valve according to the first
embodiment, when the displacement control valve is fully
opened;
[0018] FIG. 6 is a partial sectional view showing a connecting
portion of the displacement control valve according to the second
embodiment;
[0019] FIG. 7 is a partial sectional view showing a connecting
portion of the displacement control valve according to the third
embodiment; and
[0020] FIG. 8 is a graph for specifying a shape of a connecting
portion according to a conventional art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] The following will describe a displacement control valve for
a variable displacement compressor (hereinafter referred to as
"displacement control valve) of a first preferred embodiment
according to the present invention with reference to FIGS. 1
through 5. Referring to FIG. 1, a variable displacement compressor
10 (hereinafter referred to as "compressor") includes a housing,
which forms its configuration. The housing 11 includes a cylinder
block 12 having a plurarity of cylinder bores 12a formed therein, a
front housing 13 which is joined to the front end (left side in
FIG. 1) of the cylinder block 12, and a rear housing 14 which is
joined to the rear end (right side in FIG. 1) of the cylinder block
12. A bolt 15 is passed through the front housing 13, the cylinder
block 12 and the rear housing 14 to tighten those components in the
axial direction of the bolt 15, so that those components are
integrally fixed to form the housing 11.
[0022] The front housing 13 has a crank chamber 16 defined therein,
whose rear end is closed by the cylinder block 12. A drive shaft 17
is rotatably supported by a radial bearing 18 provided in the front
housing 13 and a radial bearing 19 provided in the cylinder block
12 so as to extend through the vicinity of the center of the crank
chamber 16. A sealing mechanism 20 is provided in front of the
radial bearing 18 which supports the front part of the drive shaft
17 so as to keep in slide contact with the circumferential surface
of the drive shaft 17. The sealing mechanism 20 has a lip seal
member and the like to prevent refrigerant in the crank chamber 16
from leaking through a clearance between the front housing 13 and
the drive shaft 17. The front end of the drive shaft 17 is
connected to an external drive source (not shown) through a power
transmission mechanism (not shown) so that the drive shaft 17 is
rotated by the external drive source.
[0023] A lug plate 21 is fixedly mounted on the drive shaft 17 in
the crank chamber 16 so as to integrally rotate with the drive
shaft 17. A swash plate 23 which constitutes a displacement
changing mechanism 22 is supported by the drive shaft 17 in the
rear side of the lug plate 21 so as to slide along and incline
relative to the axial direction of the drive shaft 17. A hinge
mechanism 24 is interposed between the swash plate 23 and the lug
plate 21. The swash plate 23 is connected to the lug plate 21
through the hinge mechanism 24 so as to synchronously rotate with
and incline relative to the lug plate 21 and the drive shaft
17.
[0024] A coil spring 25 is wound around the drive shaft 17 between
the lug plate 21 and the swash plate 23. A cylindrical body 26 is
slidably fitted on the drive shaft 17, and is urged by the coil
spring 25 rearward. The swash plate 23 is continuously urged
rearward through the cylindrical body 26 urged by the coil spring
25. That is, the swash plate 23 is urged continuously in a
direction to decrease the inclination angle of the swash plate 23.
It is noted that an inclination angle of the swash plate 23
represents an angle formed by a plane perpendicular to the drive
shaft 17 and the plane of the swash plate 23. A stopper 23a
protrudes from the front surface of the swash plate 23. The maximum
inclination angle of the swash plate 23 is regulated by the contact
between the lug plate 21 and the stopper 23a as shown in FIG. 1. A
retaining ring 27 is fitted on the drive shaft 17 in the rear side
of the swash plate 23, and a coil spring 28 is wound around the
drive shaft 17 in front of the retaining ring 27. The minimum
inclination angle of the swash plate 23 is regulated by the contact
between the swash plate 23 and the front end of the coil spring 28.
In FIG. 1, the swash plate 23 indicated by a solid line is at a
position of the maximum inclination angle, and the swash plate 23
indicated by a phantom line is at a position of the minimum
inclination angle.
[0025] A single-headed piston 29 is disposed in each cylinder bore
12a of the cylinder block 12 respectively so as to reciprocate
therein. A compression chamber 31 is defined by each cylinder bore
12a and each head of the piston 29. A neck portion of the piston 29
engages with the periphery of the swash plate 23 through a pair of
shoes 30. As the swash plate 23 is rotated with the drive shaft 17,
the rotation of the swash plate 23 is converted to the
reciprocation movement of each piston 29 through shoes 30. As shown
in FIG. 1, the front end of the rear housing 14 is joined to the
rear end of the cylinder block 12. A suction chamber 38 is defined
at the center of the rear housing 14. A discharge chamber 39 is
defined at the periphery of the rear housing 14. The discharge
chamber 39 is separated from the suction chamber 38 by a partition
wall 14a.
[0026] A valve plate 32, valve body forming plates 33, 34, and a
retainer 35 are interposed between the cylinder block 12 and the
rear housing 14. The valve plate 32 forms a compression chamber 31
in each cylinder bore 12a together with each piston 29. Suction
ports 36 and discharge ports 37 are formed in the valve plate 32.
Each suction port 36 corresponds to one of the cylinder bore 12a to
communicate the cylinder bore 12a to the suction chamber 38. Each
discharge port 37 corresponds to one of the cylinder bore 12a to
communicate the cylinder bore 12a to the discharge chamber 39. The
valve body forming plate 33, has suction valves (not shown). Each
suction valve corresponds, to one of the suction ports 36 and is
interposed between the suction chamber 38 and the corresponding
compression chamber 31. The valve body forming plate 34 has reed
type discharge valves 34a. Each discharge valve 34a corresponds to
one of the discharge ports 37 and is interposed between the
discharge port 37 and the discharge chamber 39. The retainer
regulates the maximum opening degree of each discharge valve
34a.
[0027] While the piston 29 moves from its top dead center to its
bottom center, the refrigerant in the suction chamber 38 is
introduced into the compression chamber 31 through the suction port
36 and the suction valve (not shown). While the piston 29 moves
from its bottom dead center to its top dead center, the refrigerant
introduced into the compression chamber 31 is compressed to a
predetermined pressure and then discharged to the discharge chamber
39 through the discharge port 37 and the discharge valve 34a. The
inclination angle of the swash plate 23 is determined by a moment
caused by the pressure of the refrigerant, and the like. The moment
caused by the pressure of the refrigerant is the moment generated
on the basis of the correlation between the pressure in each
compression chamber 31 and the pressure in the crank chamber 16
which is applied to the back surface of each piston 29. The moment
is applied to the swash plate 23 in the direction to increase or to
decrease the inclination angle in accordance with fluctuation of
the pressure in the crank chamber 16. In the compressor 10 of this
embodiment, a control valve which is described after, controls the
pressure in the crank chamber 16, and varies the moment caused by
the pressure of the refrigerant appropriately, so that the
inclination angle of the swash plate 23 is set at an optional angle
between the minimum inclination angle and the maximum inclination
angle.
[0028] An external refrigerant circuit will be described. The
suction chamber 38 is connected to an external refrigerant circuit
42 through a suction passage 40 formed in the rear housing 14, and
the refrigerant in the external refrigerant circuit 42 is supplied
to the suction chamber 38 through the suction passage 40. In this
embodiment, a suction pressure region includes the suction chamber
38 and the suction passage 40. The discharge chamber 39 is
connected to the external refrigerant circuit 42 through a
discharge passage 41 formed in the rear housing 14, and the
refrigerant in the discharge chamber 39 is discharged to the
external refrigerant circuit 42. The external refrigerant circuit
42 includes a condenser 43, an expansion valve 44, and a heat
exchanger 45. The condenser 43 absorbs heat from the refrigerant,
and the heat exchanger 45 transmits heat to the refrigerant.
[0029] The expansion valve 44 is a temperature sensing type
automatic expansion valve for controlling the flow rate of the
refrigerant in accordance with the temperature fluctuation of the
refrigerant at an outlet of the heat exchanger 43. A throttle 46 is
provided on the downstream side of the discharge passage 41 and on
the upstream side of the heat exchanger 43 in the external
refrigerant circuit 42. In this embodiment, an upstream circuit 42a
is defined by a part of the external refrigerant circuit 42 between
the discharge passage 41 and the throttle 46, and a downstream
circuit 42b is defined by a part of the external refrigerant
circuit 42 between the throttle 46 and the heat exchanger 43. A
discharge pressure region includes the discharge chamber 39, the
upstream circuit 42a, and the downstream circuit 42b in this
embodiment.
[0030] As shown in FIG. 1, a displacement control valve 50 is
provided in the rear housing 14 to supply the refrigerant in the
discharge pressure region to the crank chamber 16. As shown in FIG.
2 the displacement control valve 50 includes a valve housing 51, a
solenoid 66, a rod 70 including a valve body 72, and a pressure
sensing mechanism 62 as main parts. The valve housing 51 is
substantially cylindrical shape and has a plurarity of chambers
therein. The solenoid is connected to the valve housing 51. The rod
70 including the valve body 72 serves as a reciprocation body, and
moves in one direction by the exciting force of the solenoid 66,
and moves in the opposite direction by the pressure sensing
mechanism 62.
[0031] A pressure sensing chamber 52 is defined in the valve
housing 51 adjacent to a first end, or a upper end (upper side of
FIG. 1). An end wall member 58 is fitted at the upper end of the
pressure sensing chamber 52. The pressure sensing chamber 52
accommodates the pressure sensing mechanism 62 therein. The
pressure sensing mechanism 62 has a bellows 63 which divides the
pressure sensing chamber 52 into the low-pressure chamber 52a and a
high-pressure chamber 52b. A fixed end, or the upper end of the
bellows 63 is fixed to the end wall member 58. The high-pressure
chamber 52b is defined inside the bellows 63. The low-pressure
chamber 52a is defined outside the bellows 63.
[0032] A valve chamber 53 is defined next to the pressure sensing
chamber 52. The valve chamber 53 is separated from the pressure
sensing chamber 52 by a partition wall 51a. The partition wall 51a
has a valve hole 54 therethrough and a valve seat 54a around the
valve hole 54 on the side of the valve chamber 53. The valve
housing 51 has a first communication port 55 as a first port and a
second communication port 57 as a second port. The first
communication port 55 connects the low-pressure chamber 52a of the
pressure sensing chamber 52 to the downstream circuit 42b. The
second communication port 57 connects the valve chamber 53 to the
crank chamber 16.
[0033] A supply passage as a control passage is formed in the valve
housing 51. A valve hole 54 is formed in the control passage. The
control passage communicates the first communication port 55 to the
second communication port 57 through the valve hole 54. That is,
the supply passage is constituted between the first communication
port 55 and the second communication port 57, and includes the
low-pressure chamber 52a which is part of the pressure sensing
chamber 52, the valve chamber 53, and the valve hole 54. The first
communication port 55 is connected to the downstream circuit 42b
through a first communication passage 59. The second communication
port 57 is connected to the crank chamber 16 through a second
communication passage 61. The pressure in the discharge chamber 39
and the upstream circuit 42a is high, and the pressure in the
downstream circuit 42b, the crank chamber 16, and the suction
chamber 38 is decreased in this order. It is noted that when the
compressor 10 is operated at the maximum displacement, the pressure
in the suction chamber 38 and the crank chamber 16 is substantially
equal.
[0034] In the pressure sensing chamber 52, a movable member 64 is
connected on a movable end, or the lower end of the bellows 63. The
high-pressure chamber 52b is defined inside the bellows 63, and the
low-pressure chamber 52a is defined outside the bellows 63. A third
communication port 56 is formed in the end wall member 58 and
connects the high-pressure chamber 52b to the upstream circuit 42a
through a third communication passage 60. The pressure difference
between the low-pressure chamber 52a and the high-pressure chamber
52b gives a force to the movable member 64 in the direction to
extend the bellows 63. Accordingly, when, the pressure difference
between the low-pressure chamber 52a and the high-pressure chamber
52b exists, the force in a direction to extend the bellows 63 is
given to the movable member 64.
[0035] The solenoid 66 is connected to a lower end (lower side of
FIG. 1) of the valve housing 51 adjacent to the valve chamber 53.
The solenoid 66 has a fixed core 67 which faces the valve chamber
53, and the fixed core closes the lower end of the valve housing
51. The solenoid 66 has a movable core 68 and an electromagnetic
coil 69. The movable core 68 faces the fixed core 67. The
electromagnetic coil 69 is formed so as to surround the fixed core
67 and the movable core 68. The fixed core 67 has a through hole
67a formed through the center thereof, and the through hole 67a has
a larger diameter than the valve hole 54. The axial center of the
through hole 67a is coaxial with that of the valve hole 54. The
fixed core 67 attracts the movable core 68 when electric current is
supplied to the electromagnetic coil 69 to excite the
electromagnetic coil 69. The solenoid 66 is controlled by a current
supply control (a duty control) based on a duty ratio of a control
unit (not shown).
[0036] The rod 70 will now be described. In the first embodiment,
the rod 70 is disposed in the valve housing 51, and includes a
first shaft portion 71 whose end portion serves as the valve body
72. The first shaft portion 71 has a round-bar shape. The first
shaft portion 71 is surrounded by the solenoid 66, and a part of
the first shaft portion 71 is disposed in the valve chamber 53. The
first shaft portion 71 has a larger diameter than the valve hole
54. In this embodiment, most of the first shaft portion 71 is
located in the through hole 67a of the fixed core 67 so as to slide
along the through hole 67a of the fixed core 67. The lower end of
the first shaft portion 71 adjacent to the solenoid 66 is connected
to the movable core 68. Since the diameter of the first shaft
portion 71 is set larger than that of the valve hole 54, the upper
end of the first shaft portion 71 adjacent to the valve hole 54
serves as the valve body 72. That is, when the first shaft portion
71 which includes the valve body 72 is in contact with the
partition wall 51a which faces the valve chamber 53, the valve hole
54 is closed. When the contact between the first shaft portion 71
and the partition wall 51a is released, the valve hole 54 is
opened.
[0037] A spring receiving body 73 is mounted on the first shaft
portion 71 and located in the valve chamber 53. The spring
receiving body 73 has a flange. A coil spring 74 is interposed
between the spring receiving body 73 and the partition wall 51a.
When the exciting force of the electromagnetic coil 69 is not
applied to the movable core 68, the coil spring 74 moves the rod 70
toward the solenoid 66. That is, the coil spring 74 urges the first
shaft portion 71 in the direction to move the movable core 68 away
from the fixed core 67 through the spring receiving body 73. A
connecting portion 76 connects the end portion of the first shaft
portion 71 and a second shaft portion. The second shaft portion 75
is a round-bar shape, and is coaxial with the first shaft portion
71. The second shaft portion 75 has a sufficiently smaller diameter
than the valve hole 54 and extends through the valve hole 54 to be
connected to the pressure sensing mechanism 62. A clearance with an
annular cross section formed by the valve hole 54 and the rod 70
(the second shaft portion 75 or the connecting portion 76)
constitutes a flow path, when the valve body 72 opens the valve
hole 54. The flow path forms a part of the control passage.
[0038] The connecting portion 76 will now be described. As shown in
FIG. 3, the lower end (lower side of FIG. 3) of the connecting
portion 76 is connected to the first shaft portion 71, or the end
portion of the valve body 72, and the upper end of the connecting
portion 76 is connected to the second shaft portion 75. The
connecting portion 76 is integrally formed with the first shaft
portion 71 and the second shaft portion 75 to constitute a part of
the rod 70. The connecting portion 76 is disposed into the valve
hole 54 so that the vicinity of the axial center of the connecting
portion 76 protrudes into the valve hole 54 at the upper end
portion of the valve body 72. That is, the connecting portion 76
protrudes into the valve hole 54 from a plane end surface 72a of
the valve body 72, and is coaxial with the rod 70. The
configuration of the connecting portion 76 has a shape to be flared
out at the lower end of the connecting portion 76 adjacent to the
valve body 72, and the circumferential surface of the connecting
portion 76 is formed with an arc-shaped curved surface 76a which
connects the plane end surface 72a of the valve body 72 and the
second shaft portion 75 in a round chambered manner. In other
words, the cross-section of the connecting portion 76 cut along a
longitudinal axis of the rod 70 has an arc-shaped curve on both
sides of the axis so as to be flared out at the lower end of the
connecting portion 76 adjacent to the valve body 72.
[0039] The diameter of the lower end of the connecting portion 76
adjacent to the first shaft portion 71 is indicated as R1. In other
words, the diameter R1 is the diameter of the lower end of the
connecting portion 76 adjacent to the plane end surface 72a of the
valve body 72. The diameter R1 is set smaller than the outside
diameter of the valve body 72, and substantially equal to the
inside diameter of the valve hole 54. The diameter of the upper end
of the connecting portion 76 adjacent to the second shaft portion
75 is indicated as R2. The diameter R2 is substantially equal to
the diameter of the second shaft portion 75. That is, the diameter
of the connecting portion 76 decreases from the end portion of the
valve body 72 toward the second shaft portion 75, and the
circumferential surface of the connecting portion 76 is formed as
an arc-shaped curved surface 76a which connects the plane end
surface 72a of the valve body 72 and the circumferential surface of
the second shaft portion 75. Thus, the end portion of the valve
body 72 and the second shaft portion 75 are connected by the
continuous curved surface. The plane end surface 72a of the valve
body 72 adjacent to the connecting portion 76 closes the valve hole
54 by making contact with the valve seat 54a.
[0040] FIG. 4 is a graph for specifying the shape of the connecting
portion 76 of the first embodiment. The movement distance of the
valve body 72 indicated by a horizontal axis, and the
cross-sectional area in the flow path is indicated by a vertical
axis, and the shape of the connecting portion 76 is specified by a
characteristic curve indicated by a graph G1, or a solid line. That
is, the graph G1 is divided into three areas J1, J2, J3, which are
indicated in ascending order of the movement distance, and the area
J1 is the nearest to the origin (point A). In the area J1,
Immediately after the opening of the valve 50, the cross-sectional
area of the flow path increases rapidly in accordance with the
increase of the movement distance of the valve body 72. In the area
J2, the cross-sectional area of the flow path increases slightly
gradually in accordance with the increase of the movement distance
of the valve body 72. In the area J3, the cross-sectional area of
the flow path has reached at the maximum value and maintains the
value constantly. The characteristic curve of the graph G1 shows a
continuous curve at the boundary points from the area J1 to the
area J2, and from the area J2 to the area J3. That enables a
continuous flow control even around the boundary points.
[0041] Accordingly, in a predetermined range of the movement
distance of the valve body 72, the graph G1 is a smooth curve which
shows the relation between the cross-sectional area of the flow
path and the movement distance of the valve body 72, thereby
enables a continuous flow control. That is when the movement
distance of the valve body 72 is determined, the cross-sectional
area of the flow path is unambiguously determined, and the flow
rate flowing through the flow path is determined. For reference, a
graph G0 in FIG. 4 shows characteristics of a conventional art and
is indicated as a dotted line which connects points A, B C and D.
The graph G0 shows a discontinuous curve at the points B and C.
[0042] Operation of the displacement control valve of the present
embodiment will now be described with reference to FIGS. 5A and 5B.
As external heat load such as temperature in a vehicle compartment
rises, the solenoid 66 is excited by electric current supplied
thereto. Accordingly the movable core 68 is moved to the fixed core
67, and the rod 70 is moved in the direction toward the pressure
sensing mechanism 61. On the other hand, urging force is applied to
the bellows 63 of the pressure sensing mechanism 62 in accordance
with the pressure difference between the upstream circuit 42a and
the downstream circuit 42b. The moving direction of the rod 70 is
determined by the balance of the urging force of the bellows 63,
the urging force of the coil spring 74, and the exciting force of
the solenoid 66. As the exciting force of the solenoid 66 becomes
greater to the urging forces of the bellows 63 and the coil spring
74, the rod 70 is moved in the direction to open the valve hole 54
(downward in FIG. 5).
[0043] FIG. 5A shows a state of the displacement control valve 50
which is transited from a closed state to a opened state to perform
the displacement control. When the rod 70 is moved in the direction
to open the valve hole 54, the valve body 72 is moved apart from
the valve hole 54. That is, the plane end surface 72a of the valve
body 72 is spaced away from the valve seat 54a. Thus, the
displacement control valve 50 is transited from the closed state to
the opened state. Immediately after the opening of the valve hole
54, the cross-sectional area of the flow path is determined by a
distance between the plane end surface 72a of the valve body 72 and
the valve seat 54a. When the distance between the plane end surface
72a and the valve seat 54a increases, the cross-sectional area of
the flow path increases substantially linearly (shown by the area
J1 in FIG. 4). When the rod 70 moves further in the direction to
open the valve hole 54, the cross-sectional area of the flow path
is determined by the positional relation between the arc-curved
surface 76a of the connecting portion 76 and the valve hole 54.
Thus, the cross-sectional area of the flow path increases slightly
gradually in accordance with the movement distance of the valve
body 72 (shown by the area J2 in FIG. 4).
[0044] The plane end surface 72a of the valve body 72 and the
arc-curved surface 76a of the connecting portion 76 are connected
with a continuous surface so that the cross-sectional area of the
flow path changes smoothly as shown by the smooth curve around the
boundary point from the area J1 to the area J2 in FIG. 4. When the
rod 70 moves and the connecting portion 76 is out of the valve hole
54, the cross-sectional area of the flow path, which is determined
by the valve hole 54 and the second shaft portion 75, becomes the
maximum, and the refrigerant flows sufficiently through the valve
hole 54 (shown by the area J3 in FIG. 4). The arc-curved surface
76a of the connecting portion 76 and the circumferential surface of
the second shaft portion 75 are formed to be connected with a
continuous surface so that the cross-sectional area of the flow
path changes smoothly as shown by the smooth curve around the
boundary point from the area J2 to the area J3 in FIG. 4.
[0045] As the valve hole 54 is opened, part of the refrigerant with
high pressure in the downstream circuit 42b flows through the first
communication passage 59 and first communication port 55 into the
low-pressure chamber 52a in the pressure sensing chamber 52. The
refrigerant in the low-pressure chamber 52a flows through the flow
path formed by the valve body 72 and the valve hole 54 into the
valve chamber 53. Then the refrigerant flows through the second
communication port 57 and the second communication passage 61 into
the crank chamber 16. The inclination angle of the swash plate 23
is determined by the pressure in the crank chamber 16. Since the
refrigerant with high pressure is supplied to the crank chamber 16,
the pressure in the crank chamber 16 increases and the inclination
angle of the swash plate 23 decreases.
[0046] The opening and closing of the valve hole 54 by the valve
body 72 is determined by the balance between the exciting force of
the solenoid 66, the urging force of the coil spring 74 and the
pressure sensing mechanism 62. When the movement distance of the
valve body 72 is determined, the cross-sectional area of the flow
path is unambiguously determined, and the flow rate of the
refrigerant is determined accordingly. The pressure in the crank
chamber 16 is determined by the flow rate of the refrigerant
supplied to the crank chamber 16 so that the inclination angle of
the swash plate 23 is determined. In a determined range of the
movement distance of the valve body 72, the change of the
cross-sectional area of the flow path in accordance with movement
distance of the valve body 72 draws a smooth and continuous curve
(graph G1 in FIG. 4), and the flow rate control can be continuous
and smooth.
[0047] As external heat load such as temperature in a vehicle
compartment decreases, the current to the solenoid 66 decreases. In
FIG. 5B the displacement control valve 50 is in a state that the
movable core 68 is the farthest from the fixed core 67. At the
time, the solenoid 66 is not excited, and the rod 70 is moved
toward the solenoid 66 by the urging force of the coil spring 74
and the pressure sensing mechanism 62. Thus the movement distance
of the valve body 72 is the maximum. The connecting portion 76 of
the valve body 72 is out of the valve hole 54, and the
cross-sectional area of the flow path is maximum, which is
determined by the valve hole 54 and the second shaft portion 75.
Since the refrigerant is supplied to the crank chamber 16 through
the flow path with the maximum cross-sectional area, the pressure
in the crank chamber 16 becomes maximum, and the inclination angle
of the swash plate 23 becomes minimum accordingly so that the
compressor 10 is operated at the minimum displacement.
[0048] When the displacement control valve 50 of the compressor 10
is transited from the opened state to the closed state, the rod 70
is moved in the direction to close the valve hole 54 (upward in
FIG. 5), and part of the connecting portion 76 is inserted into the
valve hole 54 so as to decrease the cross-sectional area in
accordance with the position of the arc-curved surface 76a. In this
case, the state of the displacement control valve 50 is transited
from the long movement distance state of the valve body 72 to the
short movement distance state thereby decreasing the
cross-sectional area of the flow path. The operation of the control
valve 50 transited from the opened state to the closed state is the
reverse operation of the transition from the closed state to the
opened state, and the explanation is omitted.
[0049] When the valve body 72 of the rod 70 is moved in the
direction to close the valve hole 54 and the cross-sectional area
of the flow path decreases, the flow rate of the refrigerant which
passes through the flow path decreases, and the refrigerant which
is introduced into the crank chamber 16 decreases accordingly. Thus
the pressure in the crank chamber 16 decreases, and the inclination
angle of the swash plate 23 increases so as to increase the
displacement of the compressor 10. When the cross-sectional area of
the flow path is zero, that is, when the plane end surface 72a of
the valve body 72 is in contact with the valve seat 54a and the
movement distance of the valve body 72 is zero, the valve hole 54
is closed completely and the refrigerant is not supplied to the
crank chamber 16. Accordingly, the pressure in the crank chamber 16
is minimum, and the inclination angle of the swash plate 23 is
maximum so as to operate the compressor at the maximum
displacement. Because of the sealing performance by the contact
between the plane end surface 72a and the valve seat 54a, the
refrigerant with high pressure does not leak into the crank chamber
16 through the valve hole 54.
[0050] The displacement control valve 50 of the present embodiment
has the following advantageous effects.
(1) The end portion of the valve body 72 has the connecting portion
76 protruding into the valve hole 54, and the configuration of the
connecting portion 76 has a curved surface which protrudes at the
vicinity of the axial center of the valve body 72. In other words,
the end portion of the valve body 72 and the cylindrical second
shaft portion 75 which is connected adjacent to the valve body 72
is connected with an arc-shaped curve. Thus, the cross-sectional
area of the flow path changes smoothly and continuously, when the
valve body 72 is moved with respect to the valve hole 54. Thus, the
displacement control valve 50 according to the present embodiment
eliminates the discontinuity of the change in the cross-sectional
area of the flow path in accordance with the movement distance of
the valve body 72, which is shown in the conventional art.
Accordingly, the continuous flow rate control can be accomplished,
and the control stability is improved. (2) The connecting portion
76 is formed with the arc-shaped curved surface 76a which connects
the plane end surface 72a of the vale body 72 and the cylindrical
second shaft portion 75 adjacent to the valve body 72. Accordingly,
the displacement control valve 50 is easily manufactured, and the
manufacturing processes can be decreased. Further, the connecting
portion 76 does not require a long axial length so that the
movement distance of the valve body 72 can be set shorter and the
displacement control valve 50 can be downsized. (3) The valve hole
54 is closed when the plane end surface 72a of the valve body 72 is
in contact with the valve seat 54a. In the closed state, the
sealing performance is reliably accomplished between the valve body
72 and the valve hole 54. That prevents the refrigerant with high
pressure from leaking into the crank chamber 16.
[0051] A displacement control valve according to the second
embodiment of the present invention will now be described with
reference to FIGS. 4 and 6. Since most part of the displacement
control valve of the second embodiment is common or similar to the
displacement control valve 50 of the first embodiment, the common
or similar reference numerals of the first embodiment are applied
to those of the second embodiment, and the explanations are
omitted.
[0052] As shown in FIG. 6, a displacement control valve 80 has a
first shaft portion 82 with a valve body 83 at the end portion
thereof, and a second shaft portion 85. The second embodiment
differs in the shape of a connecting portion 86 formed at the end
portion of the valve body 83 from the connecting portion 76 of the
first embodiment. The connecting portion 86 has a diameter R3
adjacent to the first shaft portion 82, or adjacent to the end
portion of the valve body 83 with which the connecting portion is
formed. The diameter R3 of the connecting portion 86 is equal to
the outside diameter of the valve body 83. The connecting portion
86 has a diameter adjacent to the second shaft portion 85 indicated
as R2, which is equal to the diameter of the second shaft portion
75 of the first embodiment. That is, the connecting portion 86
rises from a circumferential edge of the end portion of the valve
body 83, and decreases its diameter toward the second shaft portion
85. The configuration or the circumferential surface of the
connecting portion 86 is formed with an arc-shaped curved surface
86a which connects the circumferential edge of the end portion of
the valve body 83 and the circumferential surface of the second
shaft portion 85. Thus, the valve hole 54 is closed when the
arc-shaped curved surface 86a of the connecting portion 86 is in
contact with an inner circumferential edge of the valve seat 54a,
that is, the corner formed by the valve seat 54 and the valve hole
54.
[0053] FIG. 4 shows a graph G2 with a characteristic curve as a
chain line for specifying the shape of the connecting portion 86.
In the characteristic curve shown by the graph G2, the
cross-sectional area of the flow path varies gradually and linearly
from the origin (point A) in accordance with the movement distance
of the valve body 83. Compared to the graph G1 of the first
embodiment, the inclination of the curve at the beginning of the
valve opening is gradual. Around the boundary point to the
maximum-opened state is a continuous curve, and that enables the
continuous flow rate control around the boundary point.
[0054] The displacement control valve of the present invention has
the following effects in addition to the effects (1) and (2) of the
first embodiment.
(4) The connecting portion 86 rises from the circumferential edge
of the end portion of the valve body 83, and the diameter of the
connecting portion 86 decreases toward the second shaft portion 85.
The circumferential surface of the connecting portion 86 is formed
with an arc-shaped curve which connects the circumferential edge of
the end portion of the valve body 83 and the circumferential
surface of the second shaft portion 85. When the valve hole 54
starts to be opened, the cross-sectional area of the flow path
varies gradually in accordance with the movement distance of the
valve body 83 so that the stability of the flow rate control is
improved.
[0055] A displacement control valve according to the third
embodiment of the present invention will now be described with
reference to FIGS. 4 and 7. Since most part of the displacement
control valve of the third embodiment is common or similar to the
displacement control valve 50 of the first embodiment, the common
or similar reference numerals of the first embodiment are applied
to those of the third embodiment, and the explanations of these
structures are omitted.
As shown in FIG. 7, a displacement control valve 90 has a first
shaft portion 92 with a valve body 93 formed at the end portion
thereof and a second shaft portion 94. The third embodiment differs
in the shape of a connecting portion 95 formed at the end portion
of the valve body 93 from the connecting portion 76 of the first
embodiment. R1 indicates a diameter of the connecting portion 95
adjacent to the first shaft portion 92, or a diameter of the
connecting portion 95 adjacent to the plane end surface of the
valve body 93. The diameter R1 is smaller than an outside diameter
of the valve body 93, and is substantially equal to the inside
diameter of the valve hole 54. R2 indicates a diameter of the
connecting portion 95 adjacent to the second shaft portion 94. R4
indicates a diameter of the second shaft portion 94. The diameter
R2 is set larger than the diameter R4. That is, a step 96 is formed
by the connecting portion 95 and the second shaft portion 94. The
diameter of the connecting portion 95 decreases from the end
portion of the valve body 93 toward the second shaft portion 94,
and the circumferential surface of the connecting portion 95 is
formed with an arc-shaped curved surface 95a which connects a plane
end surface 93a of the valve body 93 and the step 96 at the end
portion of the second shaft portion 94. The valve seat 54a is
formed around the valve hole 54 in the partition wall 51a adjacent
to the valve chamber 53, and the valve hole 54 is closed when the
plane end surface 93a of the valve body 93 is in contact with the
valve seat 54a.
[0056] FIG. 4 shows a graph G3 with a characteristic curve shown as
a two-dot chain line for specifying the shape of the connecting
portion 95. The characteristic curve of the graph G3 has the same
characteristics as the graph G1 in the areas J1 and J2. That is,
the cross-sectional area of the flow path varies gradually in
accordance with the movement distance of the valve body 93 in the
areas J1 and J2. In the area J3, the cross-sectional area has
reached at the maximum, as shown by a line between points E and
F.
[0057] The displacement control valve of the present invention has
the following effects in addition to the effects (1), (2) and (3)
of the first embodiment.
(5) The connecting portion 95 is formed with an arc-curved surface
95a which connects the plane end surface 93a of the valve body 93
and the second shaft portion 94, and the step 96 is formed by the
arc-curved surface 95a and the second shaft portion 94.
Accordingly, the outside diameter R4 of the second shaft portion 94
is set smaller than the diameter R2 of the arc-curved surface 95a
adjacent to the second shaft portion 94. The maximum area of the
cross-sectional area of the flow path which is determined by the
inside diameter of the valve hole 54 and the outside diameter of
the second shaft portion 94 can be increased, and the flow rate of
the refrigerant at the fully-opened state can be increased so that
the displacement of the compressor 10 is rapidly decreased to the
minimum displacement.
[0058] The present invention is not limited to the first through
the third embodiments, but may be variously modified within the
scope of the invention. For example, the above embodiments may be
modified as follows.
[0059] In each embodiments, the displacement control valve has the
pressure sensing mechanism which senses the pressure difference
between the upstream circuit and the downstream circuit of the
discharge pressure region. That is, the pressure sensing mechanism
is a type which senses the pressure difference caused by the flow
rate. However, the present invention may be applicable to a
displacement control valve with a pressure sensing mechanism which
senses a pressure difference between a suction pressure region and
a discharge pressure region. Alternatively, the present invention
may also be applicable to a displacement control valve with a
pressure sensing mechanism which senses a pressure difference
between a discharge pressure region and a control pressure region,
or a pressure difference based on a suction pressure region. In the
above-described cases, it is preferable that a refrigerant passage
or a chamber which is required may be added to the displacement
control valve in accordance with the arrangement of a pressure
sensing chamber and a valve chamber. The present invention may be
applicable to a displacement control valve which is located in a
control passage which connects a crank chamber and a suction
chamber to adjust the opening degree of the control passage.
[0060] In each of the embodiments, the throttle is provided in the
external refrigerant circuit to divide the external refrigerant
circuit into the upstream circuit and the downstream circuit. A
throttle may be provided in a discharge passage and pressure in a
discharge chamber or pressure at an upstream side of the throttle
may be introduced into a high-pressure chamber in a displacement
control valve, and pressure at an downstream side of the throttle
or pressure in a discharge pressure region in the external
refrigerant circuit is introduced into a low-pressure chamber in
the displacement control valve.
[0061] In each of the embodiments, the refrigerant in the discharge
pressure region is introduced into the crank chamber and is shut
from the crank chamber by the displacement control valve. The
present invention may be applicable to a three-way valve which has
a passage from a discharge pressure region to the crank
chamber.
[0062] In each of the embodiments, the type of the refrigerant is
not specified. Fluorocarbon-based gas or carbon dioxide is for
example preferably used. The refrigerant may be gas or liquid.
[0063] The step of the third embodiment may be provided at the
connecting portion of the connecting portion 86 and the second
shaft portion 85 in the second embodiment. In this case, the
maximum cross-sectional area of the flow path can be increased.
[0064] According to the first and the third embodiment, the
diameter R1 of the connecting portion 76, 95 adjacent to the plane
end surface 72a, 93a of the valve body 72, 93 is set smaller than
the outside diameter of the valve body 72, 93 and substantially
equal to the inside diameter of the valve hole 54. The diameter R1
may be set smaller than the Inside diameter of the valve hole 54.
In this case, the axial length of the connecting portion can be
shortened and the movement distance of the rod can be set further
shorter.
[0065] Therefore, the present examples and embodiments are to be
considered as illustrative and not restrictive, and the invention
is not to be limited to the details given herein but may be
modified within the scope of the appended claims.
* * * * *