U.S. patent application number 09/829853 was filed with the patent office on 2001-10-18 for hinge mechanism for variable displacement compressor.
Invention is credited to Kayukawa, Hiroaki, Tomita, Masanobu, Yamada, Kiyohiro.
Application Number | 20010029837 09/829853 |
Document ID | / |
Family ID | 18626548 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010029837 |
Kind Code |
A1 |
Kayukawa, Hiroaki ; et
al. |
October 18, 2001 |
Hinge mechanism for variable displacement compressor
Abstract
By changing the inclination of a cam plate, the stroke of a
piston is changed to change the discharge displacement a of
compressor. A hinge mechanism is positioned between a rotating
support and the cam plate. The hinge mechanism includes a guide
pin, and the guide pin transfers the rotational motion of the
rotating support to the cam plate and permits inclination of the
cam plate. At least a part of the guide pin is hollow.
Inventors: |
Kayukawa, Hiroaki;
(Kariya-shi, JP) ; Yamada, Kiyohiro; (Kariya-shi,
JP) ; Tomita, Masanobu; (Kariya-shi, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
345 Park Avenue
New York
NY
10154
US
|
Family ID: |
18626548 |
Appl. No.: |
09/829853 |
Filed: |
April 10, 2001 |
Current U.S.
Class: |
92/71 |
Current CPC
Class: |
F04B 27/1072
20130101 |
Class at
Publication: |
92/71 |
International
Class: |
F01B 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 17, 2000 |
JP |
2000-114806 |
Claims
1. A variable displacement compressor comprising: a housing
including a cylinder bore; a piston accommodated in the cylinder
bore; a drive shaft supported by the housing; a rotating support
integrally fixed to the drive shaft; a cam plate connected to the
piston for converting rotational motion of the drive shaft to
reciprocation of the piston, wherein the cam plate inclines with
respect to the drive shaft, and wherein the stroke of the piston
changes to vary the discharge displacement of the compressor when
the inclination of the cam plate changes; and a hinge mechanism
positioned between the rotating support and the cam plate, wherein
the hinge mechanism includes a guide pin for transferring rotation
of the rotating support to the cam plate and for permitting the
inclination of the cam plate, wherein a part of the guide pin is
hollow.
2. The compressor according to claim 1, wherein the hinge mechanism
includes a supporting arm extending from the rotating support
toward the cam plate and a guide portion provided in the support
arm, the guide pin comprising: a shaft portion, which is fixed to
the cam plate, and a spherical portion, which has a larger diameter
than the shaft portion and is provided on the shaft portion,
wherein the spherical portion engages the guide portion, and at
least a part of the spherical portion is hollow.
3. The compressor according to claim 2, wherein the guide pin has a
hollow chamber that is open on the outer periphery of the spherical
portion, wherein the hollow chamber extends substantially to the
center of the spherical portion.
4. The compressor according to claim 2, wherein the guide pin has a
hollow chamber that is open on the outer periphery of the spherical
portion, wherein the hollow chamber extends to the shaft
portion.
5. The compressor according to claim 2, wherein a part of the shaft
portion is embedded in the cam plate, and a part of the shaft
portion is exposed from the cam plate, and wherein the guide pin
has a hollow chamber that is open on the outer surface of the
spherical portion, wherein the hollow chamber extends within the
entire exposed portion of the shaft portion.
6. The compressor according to claim 1, wherein the hinge mechanism
comprises: a swing arm extending from the cam plate toward the
rotating support; a supporting arm on the rotating support; a guide
hole formed in one of the swing arm and the supporting arm; and a
mounting hole formed in the other of the swing arm and the
supporting arm, wherein the guide pin is located within the guide
hole and the mounting hole.
7. The compressor according to claim 6, wherein the guide hole is
formed in the supporting arm and the mounting hole is formed in the
swing arm.
8. The compressor according to claim 7, wherein the swing arm is a
first swing arm and the mounting hole is a first mounting hole, and
the compressor further comprises a second swing arm and a
corresponding second mounting hole, the first and second swing arms
being arranged on opposite sides of the supporting arm, wherein the
first mounting hole is coaxial with the second mounting hole, and
end portions of the pin, which extend between the swing arms and
the supporting arm, are solid.
9. The compressor according to claim 1, wherein the guide pin is
manufactured by forging.
10. The compressor according to claim 2, wherein the distal end
portion of the spherical portion is truncated.
11. A guide pin used in a compressor, the compressor comprising: a
housing including a cylinder bore; a piston accommodated in the
cylinder bore; a drive shaft supported by the housing; a rotating
support integrally fixed to the drive shaft; a cam plate connected
to the piston for converting the rotational motion of the drive
shaft to reciprocation of the piston, wherein the cam plate
inclines with respect to the drive shaft, and wherein the stroke of
the piston changes to vary the discharge displacement of the
compressor when the inclination of the cam plate changes; a hinge
mechanism positioned between the rotating support and the cam
plate, wherein the hinge mechanism includes a guide pin for
transferring rotation of the rotating support to the cam plate and
for permitting the inclination of the cam plate, wherein a part of
the guide pin is hollow.
12. The guide pin according to claim 11, wherein the hinge
mechanism includes a supporting arm extending from the rotating
support toward the cam plate and a guide portion provided in the
support arm, the guide pin comprising: a shaft portion, which is
fixed to the cam plate, and a spherical portion, which has a larger
diameter than the shaft portion and is provided on the shaft
portion, wherein the spherical portion engages the guide portion,
and at least a part of the spherical portion is hollow.
13. The guide pin according to claim 12, wherein the guide pin has
a hollow chamber that is open on the outer periphery of the
spherical portion, wherein the hollow chamber extends substantially
to the center of the spherical portion.
14. The guide pin according to claim 12, wherein the guide pin has
a hollow chamber that is open on the outer periphery of the
spherical portion, wherein the hollow chamber extends to the shaft
portion.
15. The guide pin according to claim 12, wherein a part of the
shaft portion is embedded in the cam plate, and a part of the shaft
portion is exposed from the cam plate, and wherein the guide pin
has a hollow chamber that is open on the outer surface of the
spherical portion, wherein the hollow chamber extends within the
entire exposed portion of the shaft portion.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a hinge mechanism in a
variable displacement compressor suitable for vehicle
air-conditioners and a guide pin used in such a hinge
mechanism.
[0002] A typical variable displacement compressor includes a
housing, which includes a cylinder block, and a drive shaft, which
is supported by the housing. In the cylinder block, a plurality of
bores are formed to surround the drive shaft, and a piston is
located in each bore. A swash plate is driven by on the drive shaft
through a special hinge mechanism such that the swash plate rotates
integrally with the drive shaft and inclines with respect to the
drive shaft. When the inclination of the swash plate changes, the
swash plate slides along the surface of the drive shaft in the
axial direction.
[0003] Each piston is connected to the outer periphery of the swash
plate. Rotation of the drive shaft is converted to reciprocating
movement of the pistons, and suction and compression are performed
in each of the cylinder bores. By controlling the pressure in a
crank chamber, in which the swash plate is located, the inclination
angle of the swash plate is controlled, and the stroke of the
pistons and the discharge displacement are changed accordingly.
[0004] FIG. 9 shows one example of a hinge mechanism between a
swash plate and a drive shaft. The mechanism of FIG. 9 is from
Japanese Unexamined Patent Publication No. Hei 11-93833. To a drive
shaft 61 is fixed to a rotor 63 in a crank chamber 62, and a pair
of support arms 64 projects from the rotor 63. Guide holes 65 are
formed in the support arms 64, respectively.
[0005] In the crank chamber 62, a swash plate 66 is supported by
the drive shaft 61. To limit the weight of the swash plate 66 and
to prevent burning of a shoe 69, the swash plate 66 includes an
aluminum based swash plate body 67 and an iron based swash plate
guide 68. The swash plate body 67 is press fitted into the swash
plate guide 68. The swash plate body 67 is connected to the pistons
70 via the shoes 69, which slide on the periphery of the swash
plate body 67.
[0006] A pair of guide pins 71 extend from the swash plate 68. Each
guide pins 71 includes a spherical portion 71a, which is received
by one of the guide holes 65. The support arms 64, the guide holes
65 and the guide pins 71 form a hinge mechanism. When the pressure
in the crank chamber 62 is changed, the inclination angle of the
swash plate 66 is changed so that the stroke of the piston 70 is
changed while the top dead center position of each piston 23 does
not substantially change.
[0007] Essentially, two types of moments, that is, a moment due to
centrifugal force and a moment generated based on mutual
relationships between the internal pressures of the cylinder bores
and the pressure (crank pressure Pc) in the crank chamber 62, act
on the swash plate 66, and the inclination angle of the swash plate
66 is determined based on the balance of the moments. The mass of
the guide pin 71, which form the hinge mechanism, influences the
moment due to centrifugal force and acts to increase the
inclination angle of the swash plate 66.
[0008] In consideration of the centrifugal force moment, an xyz
coordinate system is used in FIG. 9. A vibration axis of the swash
plate 66 is represented by z, and the axis of the drive shaft 61,
which is perpendicular to the vibration axis z, is represented by
y. An axis that is perpendicular to both the y and z axes is
represented by x. The point of intersection of the axes is shown by
an origin 0. In such a right-angled coordinate system (x, y, z),
the centrifugal force moment is obtained by multiplying the product
of inertia Ixy of the swash plate 66 with respect to the xz plane
and the yz plane by the square of the angular velocity with respect
to the drive shaft 61 (refer to U.S. Pat. No. 5,573,379, which is
incorporated herein by reference). Here the product of inertia Ixy
is expressed by Ixy=.intg.fxy dm. The dm represents mass of a
minute component which forms the swash plate.
[0009] Therefore, the larger the mass of the guide pin 71 is, the
greater the influence on the moment during high velocity rotation
is. Thus, to decrease the inclination angle of the swash plate 66
during high speed velocity, a high crank pressure Pc is necessary.
As a result, hunting may occur in the control of the crank
pressure, and wear of a sealing member that seals the drive shaft
61 is more likely to occur. Further, in a clutchless type
compressor, the power consumption during minimum displacement
operation is increased.
[0010] When the swash plate 67 is made of an aluminum-based metal
and is fitted into an iron based guide 68, the distance from the
plane of the swash plate body 67 to the spherical portion 71a of
the guide pin 71 in the axial direction increases by about 20%
compared to a compressor where the entire swash plate 66 is formed
of an iron-based metal, to ensure the press-fit strength of the
swash plate 66. As a result, the influence of the moment
increases.
BRIEF SUMMARY OF THE INVENTION
[0011] The present invention has been made in consideration of the
above-described problems. An object of the present invention is to
provide a hinge mechanism of a variable displacement compressor
capable of reducing pressure in a crank chamber which is necessary
for changing displacement at a high speed rotation, capable of
suppressing the occurrence of hunting and capable of reducing the
power dissipation in a clutchless type compressor, and a guide pin
suitable for the hinge mechanism.
[0012] To achieve the foregoing and other objectives and in
accordance with the purpose of the present invention, a variable
displacement compressor is provided. The compressor includes a
housing including a cylinder bore, a piston accommodated in the
cylinder bore, a drive shaft supported by the housing, a rotating
support integrally fixed to the drive shaft, a cam plate and a
hinge mechanism. The cam plate is connected to the piston for
converting rotational motion of the drive shaft to reciprocation of
the piston. The cam plate inclines with respect to the drive shaft.
The stroke of the piston changes to vary the discharge displacement
of the compressor when the inclination of the cam plate changes.
The hinge mechanism is positioned between the rotating support and
the cam plate. The hinge mechanism includes a guide pin for
transferring rotation of the rotating support to the cam plate and
for permitting the inclination of the cam plate, wherein a part of
the guide pin is hollow.
[0013] 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 SEVERAL VIEWS OF THE DRAWING
[0014] 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:
[0015] FIG. 1 is a cross-sectional view of a first embodiment of
the present invention;
[0016] FIGS. 2(a), 2(b), and 2(c) are cross-sectional views of
various guide pins;
[0017] FIGS. 3(a) and 3(b) are schematic cross-sectional views
illustrating swash plates;
[0018] FIG. 4 is a graph showing a relationship between an
inclination angle of the swash plate and moment;
[0019] FIG. 5 is a partial cross-sectional view showing a hinge
mechanism of a second embodiment;
[0020] FIG. 6 is a partial plan view of the hinge mechanism of FIG.
5;
[0021] FIGS. 7(a) and 7(b) are cross-sectional views showing other
embodiments of guide pins used in the compressor of the first
embodiment, and FIG. 7(c) is a perspective view of another
embodiment of a guide pin;
[0022] FIG. 8(a) is a cross-sectional view showing another
embodiment of a guide pin used in a compressor of the second
embodiment, and FIG. 8(b) is a perspective view showing a guide pin
of still another embodiment; and
[0023] FIG. 9 is a partial cross-sectional view of a prior art
variable displacement compressor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] A variable displacement compressor of a vehicle
air-conditioner of a first embodiment of the invention will be
described with reference to FIGS. 1, 2, and 3.
[0025] As shown in FIG. 1, a compressor 10 includes a cylinder
block 11, a front housing member 12, which is fixed to the front
end of the cylinder block 11, and a rear housing member 14, which
is fixed to the rear end of the cylinder block 11 through a valve
plate 13. The housing members 12, 14, the valve plate 13 and the
cylinder block 11 are secured to each other with a plurality of
bolts 10a (only one shown). A crank chamber 15 is defined between
the cylinder block 11 and the front housing member 12.
[0026] A drive shaft 16 is supported in the cylinder block 11 and
the front housing member 12 with bearings. A lug plate 17 is fixed
to the drive shaft 16 in the crank chamber 15. The lug plate 17
transmits thrust to an internal wall surface of the front housing
member 12 through a thrust bearing 18.
[0027] A swash plate 19, or cam plate, includes an aluminum-based
swash plate body 20 and an iron-based swash plate guide 21, and the
swash plate body 20 is press fitted into the swash plate guide 21.
Thus, burning between the swash plate 19 and an iron-based shoe 23a
is inhibited. Also, the weight of the swash plate 19 is limited.
The swash plate guide 21 is provided with a through hole 21a, and
the drive shaft 16 passes through the through hole 21a. A hinge
mechanism 22 is located between the lug plate 17 and the swash
plate 19. Therefore, the swash plate 19 rotates in synchronization
with the lug plate 17 and the drive shaft 16, and the swash plate
19 can incline with respect to the drive shaft 16 while sliding on
the drive shaft 16 in the axial direction.
[0028] The swash plate 21 includes a counterweight 21b at a
location that is opposite to the hinge mechanism 22 with respect to
the drive shaft 16. Between the lug plate 17 and the swash plate
guide 21 a spring 16a is fitted around the drive shaft 16. The
spring 16a urges the swash plate 19 toward the cylinder block 11,
that is, in the direction in which the inclination angle
decreases.
[0029] A plurality of cylinder bores 11a (only one shown in FIG. 1)
is provided in the cylinder block 11 such that the bores 11a are
positioned at equal angular intervals. A single-headed piston 23 is
fitted in each of the cylinder bores 11a. The front openings of the
cylinder bores 11a are closed by the valve plate 13, and a
compressor chamber 11b is defined in each cylinder bore 11a. The
volume of the compressor 11b varies depending on the position of
the corresponding piston 23. Each piston 23 is connected to the
periphery of the swash plate 19 through a pair of the shoes 23a.
Accordingly, the rotational motion of the swash plate 19, which is
produced by the rotation of the drive shaft 16, is converted to
reciprocating motion of the pistons 23.
[0030] The drive shaft 16 is connected to an engine 25 through a
power transmission mechanism 24. The power transmission mechanism
24 may be a clutch mechanism (for example, an electromagnetic
clutch), which connects and disconnects power transmission and is
externally controlled. Alternatively, the power transmission
mechanism 24 may be a clutchless (for example, the combination of a
belt and a pulley). The present embodiment has a clutchless type
power transmission mechanism 24.
[0031] A suction chamber 26 and a substantially annular discharge
chamber 27, which surrounds the suction chamber 26, are defined in
the rear housing member 14. In the valve plate 13, a suction port
28, a suction valve 29, which opens and closes the suction port 28,
a discharge port 30, and a discharge valve 31, which opens and
closes the discharge port 30, are formed in correspondence with
each cylinder bore 11a. The suction chamber 26 and the discharge
chamber 27 are connected to each other by an external refrigerant
circuit 32.
[0032] The cylinder block 11, the valve plate 13 and the rear
housing member 14 are provided with an air-supply passage 33, which
connects the crank chamber 15 and the discharge chamber 27, and a
bleed passage 34, which connects the crank chamber 15 and the
suction chamber 26. A control valve 35 is installed on the way of
the supply passage 33. The control valve 35 is similar to the
control valve disclosed in Japanese Unexamined Patent Publication
No. Hei 9-268973, and includes a bellows, which moves in response
to changes in the suction pressure, a solenoid, which produces
electromagnetic force, and a valve mechanism, which controls the
degree of opening of the supply passage 33 according to the
displacement of the bellows and the electromagnetic force of the
solenoid. The parts of the control valve 35 are not shown.
[0033] When the pressure in the suction chamber 26 is a
predetermined value or less, the bellows are displaced so that the
supply passage 33 is opened, and when the pressure in the suction
chamber 26 is a predetermined value or more, the supply passage 33
is held in a closed state. The discharge displacement of the
compressor is adjusted by controlling the pressure (crank pressure)
Pc in the crank chamber with the control valve 35. That is, when
the pressure in the suction chamber 26 is relatively low, the
degree of opening of the control valve 35 is increased so that the
crank pressure Pc is increased. Accordingly, the inclination angle
(angle formed by a plane perpendicular to the drive shaft 16 and
the swash plate 19) of the swash plate 19 is decreased so that the
stroke of each piston 23 is decreased and the discharge
displacement is reduced. On the other hand, when the pressure in
the suction chamber 26 is relatively high, the degree of opening of
the control valve 35 is decreased so that the crank pressure Pc is
lowered. Accordingly, the inclination angle of the swash plate 19
is increased so that the stroke of each piston 23 is increased and
the discharge displacement is increased.
[0034] Next, the hinge mechanism 22 will be described in further
detail. The hinge mechanism 22 has two supporting arms 36 (only one
is shown), which extend from a rear surface of the lug plate 17, a
guide hole 37 formed in each of the supporting arms 36, and two
guide pins 38, which are fixed to the swash plate 19. Each guide
hole 37 is cylindrical. The guide pins 38 are parallel, and an
imaginary plane that includes the axis of the drive shaft 16 lies
between the pins 38. One pin 38 corresponds to each supporting arm
36. The guide pins 38 are identical in shape and size, and are
symmetrical with respect to the previously mentioned imaginary
plane.
[0035] Each of the guide pins 38 includes a shaft portion 38a
attached to the swash plate 19 and a spherical portion 38b formed
at the distal end of the shaft portion 38a. The spherical portions
38b engage the guide holes 37. Each spherical portion 38b has a
larger outer diameter than the shaft portion 38a, and the distal
end of each spherical portion 38b is truncated along a plane. At
least a portion of each spherical portion 38b is hollow. Each guide
pin 38 is forged by use of, for example, a header or a former.
[0036] A hollow chamber 38c in each guide pin 38 is opened at the
distal end of the spherical portion 38b. The shape of the hollow
chamber 38c can be appropriately selected. For example, any one of
many shapes such as a first shape, in which the hollow chamber 38c
extends to approximately the center of the spherical portion 38b as
shown in FIG. 2(a), a second shape, in which the hollow chamber 38c
extends to the shaft portion 38a as shown in FIG. 2(b), and a third
shape, in which the hollow chamber 38c extends to the vicinity of
the location where the shaft portion 38a joins with the swash plate
guide 21 as shown in FIG. 2(c), can be selected. The masses of the
guide pins 38 shown in FIGS. 2(a), 2(b) and 2(c) decreases as
indicated by the following inequality: FIG. 2(a)>FIG.
2(b)>FIG. 2(c).
[0037] The shape of the swash plate 19 is like that of the swash
plate disclosed in Japanese Unexamined Patent Publication, No. Hei
7-293429 (U.S. Pat. No. 5,573,379). FIGS. 3(a) and 3(b) employ an
xyz coordinate system. Additionally, a vibration axis of the swash
plate 19 is represented by S. The axis of the drive shaft 16, is
represented by y. A z-axis is perpendicular to the plane of the
sheet of FIG. 3(a) and is parallel to the vibration axis S. An
x-axis is perpendicular to both the y and z axes. A point of
intersection the x, y and z axes is defined as an origin point O.
When the inclination angle of the swash plate 19 starts rotation at
an angular portion of zero degrees as shown in FIG. 4, the product
of inertia Ixy of the swash plate 19 with respect to the xy plane
and the yz plane generates moment M in a direction such that the
displacement is increased (the direction in which the inclination
angle of the swash plate 19 is increased).
[0038] The operation of the compressor is as follows.
[0039] With rotation of the drive shaft 16, the swash plate 19
rotates, and the rotation of the swash plate 19 is converted to
reciprocating motion of each piston 23 through the shoes 23a. As a
result, in the compressor chamber 11b, suction, compression and
discharge of refrigerant are sequentially repeated. Refrigerant
supplied from the external refrigerant circuit 32 to the suction
chamber 26 is drawn into the compressor 11b through the suction
port 28. After the refrigerant is compressed, it is discharged to
the discharge chamber 27 through the discharge port 30. The
refrigerant discharged to the discharge chamber 27 enters the
external refrigerant circuit 32 via the discharge hole.
[0040] The degree of opening of the control valve 35 is adjusted
according to the cooling load. When the cooling load is high and
the pressure in the suction chamber 26 is high, the opening degree
of the control valve 35 is reduced, and the pressure (crank
pressure Pc) in the crank chamber 15 is decreased as a result,
which increases the inclination angle of the swash plate 19. The
stroke of each piston 23 is increased accordingly, and the
compressor 10 operates with a large displacement. On the other
hand, when the cooling load is low and the pressure in the suction
chamber 26 is low, the opening degree of the control valve 35 is
increased and the pressure (crank pressure Pc) in the crank chamber
15 is increased so that the inclination angle of the swash plate 19
is decreased. As a result, the stroke of the piston 23 is
decreased, and the compressor 10 operates with a small
displacement.
[0041] The moment that is generated based on the relationship
between the internal pressure of the cylinder bores and the crank
pressure Pc, the moment due to centrifugal force, and the force of
the spring 16a act on the swash plate 19, and the inclination angle
of the swash plate 19 is determined based on the equilibrium of
these components.
[0042] The moment that is generated by rotation of the swash plate
19 (the moment due to centrifugal force) is the product of inertia
Ixy of the swash plate 19 with respect to the xz plane and the yz
plane in the right-angled coordinate system (x, y, z) multiplied by
the square of the angular velocity .omega. of the drive shaft
16.
[0043] As shown in FIG. 3(a), y axis coincides with the axis of the
drive shaft 16, the z axis is parallel to the vibration shaft S,
and the x axis is perpendicular to the y axis and the z axis. When
the upward direction of the x axis is positive and the front
direction of the y axis is also positive, the product of inertia
Ixy of the swash plate is expressed by Ixy=.intg.fxy dm. Here, dm
is the minute mass of the swash plate 19 including the guide pin.
Therefore, even if the outer diameter, number and arrangement of
the pistons 23, the outer diameter of the swash plate 19, the outer
shape of the guide pin 38, and the rotational speed (angular
velocity .omega.) are constant, the moment due to the rotation
varies depending on the distance L between the center of the
spherical portion 38b of the guide pin 38 and the xz plane.
[0044] When the swash plate 19 is formed by press fitting the iron
based metallic swash plate guide 21 into the aluminum based
metallic swash plate body 20, to produce a large press-fit area,
the distance L is increased by about 20%, as shown in FIG. 3(a), as
compared with the swash plate 19 shown in FIG. 3(b), which is an
entirely iron-based swash plate. As a result, even if the shapes of
the guide pins 38 are the same, the product of inertia Ixy of the
swash plate 19 of FIG. 3(a) is significantly increased compared
with the swash plate 19 of FIG. 3(b).
[0045] The moment M that is generated by rotation of the swash
plate 19 in the vicinity of the minimum inclination angle acts to
increase the inclination angle of the swash plate 19. Thus, when
the product of inertia Ixy is large, the influence is greater at a
high rotation speeds. Therefore, to reduce the inclination angle of
the swash plate 19, high crank pressure Pc is required. Even if the
mass of the guide pins 38 is the same as, the product of inertia
Ixy of the guide pins 38 becomes large when the mass of the portion
spaced apart from the xy plane, the distal end portion of the guide
pin 38 is larger.
[0046] On the contrary, in this embodiment, since the hollow
chambers 38c are formed so that the masses of the front spherical
portions 38b of the guide pins 38 are decreased, even if the mass
of the guide pins 38 are the same, the product of inertia Ixy is
smaller than that of a swash plate lacking the hollow chambers 38c.
Further, the moment M based on the rotation of the swash plate 19
is smaller than the moment Mo of a conventional swash plate, as
shown in FIG. 4. Thus, the crank pressure Pc necessary for changing
the inclination angle of the swash plate 19 is reduced. When the
crank pressure Pc necessary for changing the inclination angle is
high, the inclination angle is likely to shift by a slight
variation in the compression load and hunting is likely to occur
even if adjusted to a predetermined inclination angle. However,
when the crank pressure Pc necessary for changing the inclination
angle is reduced, hunting is less likely to occur. This can be
understood from the fact that the rate of change in the moment M
with respect to the inclination angle of the swash plate 19 is
smaller than that of the moment Mo of the swash plate provided with
conventional guide pins of FIG. 4. Reducing the mass of the guide
pins 38 permits the mass of the counterweight 21b to be reduced,
and contributes to reducing the rate of change of the rotating
moment M of the swash plate 19.
[0047] This embodiment has the following effects.
[0048] (1) At least a part of the guide pin 38 is hollow. Thus, the
product of inertia of a portion of the guide pin 38 that influences
the rotational moment rotation of the drive shaft 16 and the swash
plate 19 is decreased. As a result, the crank pressure Pc that is
necessary for changing the displacement of a compressor can be
reduced at a high rotation speeds, and hunting can be inhibitted.
Further, in a clutchless type compressor, even if the vehicle
air-conditioner is off, the power of engine is transferred to the
compressor. However, at the time the inclination angle of the swash
plate 19 approaches zero degree so that power dissipation can be
decreased. Further, when a check valve is provided downstream of
the discharge port of the compressor, the valve opening pressure
can be reduced and performance is consequently improved.
[0049] (2) The spherical portion 38b of the guide pin 38 and the
guide hole 37 of the supporting arm 36 form the hinge mechanism 22.
Therefore, sliding of the swash plate 19 on the drive shaft 16 is
smoothly guided by forming the guide hole 37 in a simple
cylindrical shape or the like.
[0050] (3) When the guide pins 38 are hollowed out, the mass that
has the greatest influence on the product of inertia Ixy is
removed. Since the distal end of the pin 38 has a greater effect
than the proximal end, the distal end is hollowed out.
[0051] (4) The hollow chamber 38c is opened at the distal end.
Thus, by changing the depth of the hollow chamber 38c, the product
of inertia Ixy can be easily changed. Further, machining of the
hollow chamber 38c is relatively simple.
[0052] (5) The distal ends of the spherical portions 38b of the
guide pins 38 are truncated. Accordingly, the product of inertia
Ixy is reduced, as compared with a conventional guide pin having a
full spherical end.
[0053] (6) The guide pin is formed by forging. Therefore, the guide
pin is stronger than a pin in which the hollow chamber 38c of the
guide pin 38 is formed by a cutting operation. In addition, if the
guide pin is manufactured by a header or a former, productivity is
higher.
[0054] (7) The swash plate 19 is made of an aluminum based metallic
swash plate body 20 and an iron based metallic swash plate guide
21. Therefore, the entire swash plate 19 is lighter than an
iron-based swash plate 19.
[0055] (8) The swash plate 19 is directly supported on the drive
shaft 16 by the wall of the through hole 21a. Thus, since it is not
necessary to provide a sleeve on the drive shaft 16 and a pivot
shaft that connects the swash plate to the sleeve, the number of
parts is low.
[0056] A second embodiment of the present invention will be
described with reference to FIGS. 5 and 6. In the second
embodiment, the hinge mechanism 22 is different from that of the
first embodiment. Otherwise, the second embodiment is basically the
same as the first embodiment. Therefore, parts that are the same
are denoted by the same reference numerals, and only the
differences will be explained.
[0057] As shown in FIG. 5, a sleeve 39 is fitted on the drive shaft
16 and is permitted to slide on the drive shaft 16. A swash plate
guide 21 is pivotally supported by a pair of supporting shafts 40
(only one shown) to the sleeve 39. The supporting shafts 40 extend
perpendicular to the drive shaft 16.
[0058] The hinge mechanism 22 includes two swing arms 41 that
extend from the swash plate guide 21 toward the lug plate 17. A
supporting arm 42 extends from on the lug plate 17, and a guide pin
43 connects the swing arms 41 to the supporting arm 42. The swing
arms 41 surrounds the supporting arm 42 as shown in FIG. 6. A guide
hole 44 is formed in the supporting arm 42. Each of the swing arms
41 has a mounting hole 45, the axes of which are parallel to the
supporting shaft 40. The guide pin 43 is press fitted into the
mounting holes 45 and fitted into the guide hole 44.
[0059] The guide hole 44 is elongated so that, even if the
inclination angle of the swash plate is changed, the top dead
center position, of the pistons 23 do not substantially change.
That is, the guide hole 44 extends so that the closer the guide
hole 44 is to the swash plate 19, the further it is from the drive
shaft 16. The guide pin 43 is a hollow cylinder.
[0060] In the hinge mechanism 22 of this embodiment, as the guide
pin 43 moves along the guide hole 44, the swash plate 19 is rotated
integrally with the lug plate 17 and the sliding and inclining
movements of the swash plate 19 on the drive shaft 16 are
guided.
[0061] Therefore, this embodiment has the following effects in
addition to the effects (1) to (7) described in the first
embodiment.
[0062] (9) The guide pin 43, which is part of the hinge mechanism
22, moves along the guide hole 44, and the sliding motion and
inclination of the swash plate 19 are guided. Therefore, the guide
pin 43 can have a simple linear shape, which further simplifies
manufacturing.
[0063] (10) The guide hole 44 is formed in the supporting arm 42,
and mounting holes 45 are formed in the swing arms 41. Therefore,
the structure of the swash plate 19 is simple as compared to a
swash plate where the guide hole 44 is formed in the swing arm
41.
[0064] The second embodiment is not limited to the structure
described above, and may be constructed as follows for example.
[0065] In a construction in which the spherical guide pin 38 is
used, as in the first embodiment, the hollow chamber 38c of the
guide pin 38 may be formed in the shaft 38a of the guide pin 38, as
shown in FIGS. 7(a) and 7(b). Alternatively, a hollow chamber 38c
may be formed in the guide pin 38 and a slit 38d may be formed in
the shaft portion 38a, as shown in FIG. 7(c). In this case, the
outer diameter tolerance of the shaft portion 38a may be
increased.
[0066] In the second embodiment, the guide pin 43 may be formed
such that a partition is formed in the hollow portion 43a as shown
in FIG. 8(a). Alternatively, the ends of the pin 43 may be formed
by solid bodies, as shown in FIG. 8(b), instead of the simple pipe
shape of FIG. 5. The force on the guide pin 43 acts strongly on the
ends of the guide pin 43. However, when the ends of the guide pin
43 are solid, the strength of the guide pin 43 is improved.
[0067] In the first embodiment, the swash plate 19 may be pivotally
connected to a sleeve 39 that is fitted on the drive shaft 16, as
in the second embodiment, through the supporting shafts 40.
Alternatively, in the second embodiment, the swash plate 19 may be
supported on the drive shaft 16 as in the first embodiment. In
addition, a spherical sleeve may be fitted on the drive shaft 16,
and the swash plate 19 may be pivotally supported on the outer
surface of the spherical sleeve.
[0068] The hinge mechanisms of FIG. 1 and 6 have two joints. That
is, two pins 38 couple with two holes 37 in FIG. 1, and two arms 41
form joints in FIG. 6. Alternatively, each hinge may have just one
joint. However, two sets are preferable from the viewpoints of
rotational balance and stability in the driving power
transmission.
[0069] The swash plate 19 may be made of only one kind of metal,
such as an iron based metal or the like. In this case, a press-fit
margin is not needed, and the distance between the guide pin 38 and
the xz plane can be decreased. Accordingly, the product of inertia
Ixy can be further decreased by forming the guide pin 38 in a
hollow shape. When the material of the swash plate 19 is the same
as that of the shoe 23a, a surface treatment (for example, aluminum
spray coating) for the prevention of burning is applied to the
sliding face of the shoe 23a.
[0070] In the hinge mechanism 22 of the second embodiment, the
guide hole 44 may be formed in the swing arm 41, and the mounting
holes 45 may be formed in the supporting arm 42.
[0071] The guide pin 38 may be manufactured by cutting or
casting.
[0072] The present invention may be applied to a wobble type
variable displacement compressor.
[0073] It should be apparent to those skilled in the art that the
present invention may be embodied in many other specific forms
without departing from the spirit or scope of the invention.
Particularly, it should be understood that the invention may be
embodied in the following forms.
[0074] 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 and equivalence of the appended claims.
* * * * *