EP1275846B1

EP1275846B1 - Hinge for a swash plate

Info

Publication number: EP1275846B1
Application number: EP20020013643
Authority: EP
Inventors: Hiroshi Zexel Valeo Climate Control Corpo. Kanai
Original assignee: Zexel Valeo Climate Control Corp
Current assignee: Valeo Thermal Systems Japan Corp
Priority date: 2001-07-11
Filing date: 2002-06-19
Publication date: 2006-08-16
Anticipated expiration: 2022-06-19
Also published as: JP2003021055A; DE60213927D1; DE60213927T2; EP1275846A2; EP1275846A3

Description

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to a variable capacity compressor such as a variable capacity swash plate compressor in which delivery quantity is changed according to the inclination angle of a swash plate with respect to a plane perpendicular to a shaft on which the swash plate is mounted, and more particularly to a variable capacity compressor using CO₂ as refrigerant.

Description of the Prior Art

FIGS. 5 and 6 show a conventional variable capacity swash plate compressor using CO₂ (carbon dioxide).
FIG. 5 shows the compressor with a swash plate thereof at a minimum inclination angle with respect to a plane perpendicular to a shaft, while FIG. 6 shows the same with the swash plate thereof at a maximum inclination angle with respect to the plane perpendicular to the shaft. Further, FIG. 7 is a graph useful in explaining how a Y coordinate value of the center O of a moment acting on the swash plate in a tilting direction changes with respect to an angle of the inclination of the swash plate with respect to the plane perpendicular to the shaft (hereinafter also referred to as "the swash plate angle"). In the figure, curves A, B represent changes in the Y coordinate value in the embodiments of the present invention, described hereinafter, while a curve C represents changes in the same in the prior art.
The conventional variable capacity swash plate compressor using CO₂ includes a thrust flange 140 rigidly fitted on the shaft 105, the swash plate 110 tiltably fitted on the shaft 105 and connected to the thrust flange 140 via a linkage 141, for rotating in unison with the thrust flange 140 as the thrust flange 140 rotates, and pistons 107 each connected to the swash plate 110 via a pair of shoes 160, 161 for relatively sliding on respective sliding surfaces 110a, 110b of the swash plate 110. Each of the pistons 107 reciprocates within a cylinder bore 106 as the swash plate 110 rotates.
The inclination angle of the swash plate 110 varies with pressure within a crankcase 108 in which the swash plate 110 is received, whereby the stroke length of each piston is changed.
The linkage 141 is comprised of a link pin 111 and a guide slot 144.
The link pin 111 is fixed to a front surface of the swash plate 110 via a pair of brackets 116.
The guide slot 144 is formed linearly through a projection 146 projecting from a rear surface of the thrust flange 140. The link pin 111 is guided linearly along the guide slot 144. The guide slot 144 has a center line 144a thereof inclined at a predetermined angle with respect to a sliding surface 140a of the thrust flange 140.
When the torque of an engine, not shown, installed on an automotive vehicle, not shown, is transmitted to the shaft 105 to rotate the same, the torque of the shaft 105 is transmitted to the swash plate 110 via the thrust flange 140 and the linkage 141 to cause rotation of the swash plate 110 about the shaft 105. The rotation of the swash plate 110 causes relative rotation of the shoes 160, 161 on the respective sliding surfaces 110a, 110b of the swash plate 110 with respect to the circumference of the swash plate 110, whereby the torque transmitted from the swash plate 110 is converted into reciprocating motion of each of the pistons 107.
The linkage 141 has a characteristic concerning the Y coordinate value of the center O of the moment acting on the swash plate 110 in a tilting direction that the Y coordinate value continuously increases as the swash plate angle increases (see the curve C in FIG. 7). The center O of the moment is defined as an intersection of a line extending through the center of rotation of the swash plate 110 on the axis of the shaft 105 and perpendicular to the axis, and a line extending from the center of the link pin 111 through a contact point between the link pin 111 and an inner wall of the guide slot 144 (a normal to the inner wall of the guide slot 144, which extends through the center of the link pin 111) toward the piston 107, and hereinafter referred to as the instantaneous rotational center O of the swash plate 110.
In general, a variable capacity swash plate compressor can be stably controlled if the compressor has a tilting rotation characteristic of the swash plate in relation to pressure within a crankcase that the pressure within the crankcase decreases as the inclination angle of the swash plate increases (which characteristic is hereinafter referred to as "the pressure-decrease tilting rotation characteristic").
A curve "a" in FIG. 8 represents a tilting rotation characteristic of the swash plate of the conventional variable capacity swash plate compressor using CO₂.
The tilting rotation characteristic shows at which inclination angle position the swash plate 110 comes into a stable angular standstill position according to a change in the pressure within the crankcase. In other words, the tilting rotation characteristic represents a dynamic balance between the swash plate angle and the pressure within the crankcase, under predetermined conditions of suction pressure, discharge pressure, and rotational speed.
There is a correlation between the changes in the pressure within the crankcase and the changes in the Y coordinate value of the instantaneous rotational center O of the swash plate 110.
More specifically, if the linkage 141 provides the characteristic concerning the Y coordinate value of the instantaneous rotational center O that the Y coordinate value decreases with an increase in the swash plate angle, as shown in FIG. 7, the compressor has a characteristic concerning pressure within the crankcase that the pressure increases as the swash plate angle increases (which characteristic is hereinafter referred to as "the pressure-increase tilting rotation characteristic", see the curve "a" in FIG. 8). This makes the control of tilting of the swash plate 110 unstable.
In the case of a variable capacity swash plate compressor using chlorofluorocarbon as refrigerant, a moment acting in the direction of stroke of each piston is decreased by reducing the mass of each piston, or a moment acting in the direction of de-stroke of each piston is increased by increasing the mass of a swash plate, so as to obtain the pressure-decrease tilting rotation characteristic that the pressure within the crankcase decreases as the swash plate angle increases.
However, the variable capacity swash plate compressor using CO₂ suffers from the following problem:
The piston of the variable capacity swash plate compressor using CO₂ is smaller in diameter than that of the variable capacity swash plate compressor using chlorofluorocarbon, and the PCD (pitch circle diameter) of the pistons of the former compressor is also smaller. For instance, the PCD of the pistons of a variable capacity swash plate compressor using chlorofluorocarbon is 70 to 90 mm, whereas the PCD of pistons of a variable capacity swash plate compressor using CO₂ is 50 to 70 mm.
The PCD of pistons is correlated with the tilting rotation characteristic of the compressor, and if the PCD is reduced, the moment acting in the de-stroke direction is reduced due to an increase in the inertial force of the pistons resulting from an increased length of stroke of the pistons, or due to a decrease in the inertial force of the swash plate resulting from a decrease in the diameter of the swash plate. As a result, the compressor tends to have the pressure-increase tilting rotation characteristic that the pressure within the crankcase increases as the swash plate angle increases. Therefore, the conventional variable capacity swash plate compressor using CO₂ as refrigerant is apt to suffer from unstable control of tilting of the swash plate 110. A similar compressor as the above described compressor is also known by document JP 03130584.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a variable capacity compressor which is capable of maintaining excellent control stability even when carbon dioxide is used as refrigerant.
To attain the above object, there is provided a variable capacity compressor including a rotary member rigidly fitted on a shaft, for rotating in unison with the shaft as the shaft rotates, and an tilting rotary plate fitted on the shaft in a manner tiltable with respect to a plane perpendicular to the shaft and connected to the rotary member via a linkage, for rotating in unison with the rotary member as the rotary member rotates, the tilting rotary plate having an inclination angle with respect to the plane perpendicular to the shaft, the inclination angle being changed according to a change in pressure within a crankcase in which the tilting rotary plate is received, to change a stroke length of each piston connected to the tilting rotary plate.
The variable capacity compressor according to the invention is characterized in that:

the linkage comprises a pin fixed to one of the tilting rotary plate and the rotary member, and guide means formed in another of the tilting rotary plate and the rotary member and extending in a form of an arc, for engagement with the pin, and that
an arc drawn by a center line of the guide means has a radius of curvature which progressively decreases from one end of the arc toward the shaft to an opposite end of the arc remote from the shaft.

According to this variable capacity compressor, the arc drawn by the center line of the guide means has the radius of curvature which progressively decreases from one end of the arc toward the shaft to the opposite end of the arc remote from the shaft. Therefore, the Y coordinate value of the center of a moment acting on the tilting rotary plate in a tilting direction decreases more sharply as the inclination angle of the tilting rotary plate increases, i.e. forms a more sharply decreasing curve with respect to the inclination angle, than in the compressor according to the first aspect of the invention.
Preferably, the guide means is a slot formed through the another of the tilting rotary plate and the rotary member.
Preferably, the radius of curvature of the center line of the guide means is within a range of 5 to 25 mm.
According to this preferred embodiment, so long as the radius of curvature of the center line of the guide means is within a range of 5 to 25 mm, the pin as part of the linkage can maintain a high strength, and further, the compressor can have a tilting rotation characteristic that the pressure within the crankcase required for a dynamic balance decreases as the inclination angle of the tilting rotary plate increases.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a variable capacity swash plate compressor with a swash plate thereof at a minimum inclination angle with respect to a plane perpendicular to a shaft on which the swash plate is fitted;
FIG. 2 is a longitudinal cross-sectional view of the FIG. 1 variable capacity swash plate compressor with the swash plate thereof at a maximum inclination angle with respect to the plane perpendicular to the shaft;
FIG. 3 is a longitudinal cross-sectional view of a variable capacity swash plate compressor according to an embodiment of the invention, with a swash plate thereof at a minimum inclination angle with respect to a plane perpendicular to a shaft on which the swash plate is fitted;
FIG. 4A is a longitudinal cross-sectional view of the FIG. 3 variable capacity swash plate compressor with the swash plate thereof at a maximum inclination angle with respect to the plane perpendicular to the shaft;
FIG. 4B is an enlarged view of a guide slot;
FIG. 5 is a longitudinal cross-sectional view of a conventional variable capacity swash plate compressor with a swash plate thereof at a minimum inclination angle with respect to a plane perpendicular to a shaft on which the swash plate is fitted;
FIG. 6 is a longitudinal cross-sectional view of the FIG. 5 variable capacity swash plate compressor with the swash plate thereof at a maximum inclination angle with respect to the plane perpendicular to the shaft;
FIG. 7 is a graph useful in explaining changes in the Y coordinate value of the center O of a moment acting on the swash plate in a tilting direction with respect to a swash plate angle;
FIG. 8 is a graph showing a tilting rotation characteristic of the FIG. 1 variable capacity swash plate compressor and a tilting rotation characteristic of the FIG. 5 variable capacity swash plate compressor; and
FIG. 9 is a graph showing changes in the radius of curvature of a center line of a guide slot of each of the FIG. 1 and FIG. 3 variable capacity swash plate compressors and the FIG. 5 variable capacity swash plate compressor, with respect to the swash plate angle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will now be described in detail with reference to drawings showing a preferred embodiment thereof.
FIG. 1 shows a prior art variable capacity swash plate compressor with a swash plate thereof at a minimum inclination angle with respect to a plane perpendicular to a shaft on which the swash plate is fitted, while FIG. 2 shows the FIG. 1 variable capacity swash plate compressor with the swash plate thereof at a maximum inclination angle with respect to the plane perpendicular to the shaft
This variable capacity swash plate compressor is used as a component of a refrigerator using CO₂ as refrigerant.
The variable capacity swash plate compressor has a cylinder block 1 having one end thereof secured to a rear head 3 via a valve plate 2 and the other end thereof secured to a front head 4. The front head 4, the cylinder block 1, the valve plate 2, and the rear head 3 are tightened in a longitudinal direction by through bolts 31 and associated nuts 32 to form a one-piece assembly.
The cylinder block 1 has a plurality of cylinder bores 6 axially extending therethrough at predetermined circumferential intervals about the shaft 5. Each cylinder bore 6 has a piston 7 slidably received therein.
The piston 7 has one end portion thereof formed with concave portions 51a, 51b for slidably supporting a pair of shoes 60, 61, respectively.
The front head 4 defines therein a crankcase 8 in which the swash plate (tilting rotary plate) 10 and a thrust flange (rotary member) 40 are received.
Within the rear head 3, there are formed a suction chamber 13 and a discharge chamber 12 in a manner such that the suction chamber 13 surrounds the discharge chamber 12. The suction chamber 13 receives a low-pressure refrigerant gas which is supplied to each compression chamber 22, while the discharge chamber 12 receives a high-pressure refrigerant gas delivered from each compression chamber 22.
The shaft 5 has one end thereof rotatably supported via a radial bearing 26 by the front head 4 and the other end thereof rotatably supported via a radial bearing 25 and a thrust bearing 24 by the cylinder block 1.
The thrust flange 40 is rigidly fitted on the shaft 5, for rotating in unison with the same. The swash plate 10 is tiltably and slidably fitted on the shaft 5 via a hinge ball 9. Further, the swash plate 10 is connected to the thrust flange 40 via a linkage 41, for rotating in unison with the thrust flange 40 as the thrust flange 40 rotates.
A peripheral portion of the swash plate 10 and one end of each piston 7 are connected to each other via a pair of shoes 60, 61 each of which has a semispherical surface 60a (61 a) and a flat surface 60b (61b). The semispherical surface 60a (61a) is held in contact with the concave portions 51a (51b) of the piston 7, while the flat surface 60b (61b) is held in contact with a sliding surface 10a (10b) of the swash plate 10.
The shoes 60, 61 perform relative rotation on respective sliding surfaces 10a, 10b of the swash plate 10 as the shaft 5 rotates. The rotation of the swash plate 10 causes the piston 7 to reciprocate in the cylinder bore 6.
The valve plate 2 is formed with refrigerant outlet ports 16 each for communicating between a compression chamber 22 and the discharge chamber 12, and refrigerant inlet ports 15 each for communicating between a compression chamber 22 and the suction chamber 13. The refrigerant outlet ports 16 and the refrigerant inlet ports 15 are arranged at predetermined circumferential intervals.
The refrigerant outlet ports 16 are opened and closed by respective discharge valves 17. The discharge valves 17 are fixed to a rear head-side end face of the valve plate 2 by a bolt 19 together with a valve stopper 18.
On the other hand, the refrigerant inlet ports 15 are opened and closed by respective suction valves 21 arranged between the valve plate 2 and the cylinder block 1.
The thrust flange 40 rigidly fitted on a front end of the shaft 5 is rotatably supported on an inner wall of the front head 4 via a thrust bearing 33. The thrust flange 40 and the swash plate 10 are connected with each other via the linkage 41, as described above, and the swash plate 10 can tilt with respect to a plane perpendicular to the shaft 5.
The linkage 41 is comprised of a link pin (pin) 11 and a guide slot 44. The link pin 11 is fixed to a pair of brackets 47 formed on a front surface of the swash plate 10.
The guide slot 44 is formed through a projection 46 projecting from a rear surface of the thrust flange 40. The link pin 11 is fitted in the guide slots 44 in a relatively slidable manner. In this linkage 41, the curvature (radius R of curvature) of an arc drawn by a center line 44a of the guide slot 44 is constant irrespective of the inclination angle of the swash plate (see line B in FIG. 9), and the Y coordinate of the center of a moment acting on the swash plate 10 in a tilting direction (moment in a stroke direction or de-stroke direction (direction for decreasing the inclination angle of the swash plate□10)) changes with respect to the swash plate angle in a curve indicated by reference numeral B in FIG. 7. The center O of the moment is defined as an intersection of a line extending through the center of rotation of the swash plate 10 on the center of the shaft 5 and perpendicular to the axis, and a line extending from the center of the link pin 11 through a contact point between the link pin 11 and an inner wall of the guide slot 44 (a normal to the inner wall of the guide slot 44, which extends through the center of the link pin 11) toward the piston 7, and hereinafter referred to as the instantaneous rotational center O of the swash plate 10.
Next, the operation of the variable capacity swash plate compressor constructed as above will be described.
Torque of an engine, not shown, installed on an automotive vehicle, not shown, is transmitted to the shaft 5 to rotate the same. The torque of the shaft 5 is transmitted to the swash plate 10 via the thrust flange 40 and the linkage 41 to cause rotation of the swash plate 10 about the shaft 5. When the swash plate 10 is rotated, the shoes 60, 61 perform relative rotation on the respective sliding surfaces 10a, 10b of the swash plate 10, whereby the rotation of the swash plate 10 is converted into the reciprocating motion of each piston 7.
As the piston 7 reciprocates in the cylinder bore 6 associated therewith, the volume of a compression chamber 22 within the cylinder bore 6 changes, which causes, suction, compression and delivery of refrigerant gas to be sequentially carried out, whereby high-pressure refrigerant gas is delivered from the compression chamber 22 in an amount corresponding to the angle of inclination of the swash plate 10 (swash plate angle).
During the suction stroke of the piston 7, the corresponding suction valve 21 opens to draw low-pressure refrigerant gas from the suction chamber 13 into the compression chamber 22 within the cylinder bore 6. During the discharge stroke of the piston 7, the corresponding discharge valve 17 opens to deliver high-pressure refrigerant gas from the compression chamber 22 to the discharge chamber 12.
As the pressure within the crankcase 8 increases, the swash plate moves in a de-stroke direction (direction for decreasing the inclination angle thereof). As a result, the length of stroke of the piston 7 is decreased to reduce the delivery quantity or capacity of the compressor. In the meantime, the link pin 11 of the linkage 41 relatively slides along the guide slot 44 to one end of the guide slot 44 toward the shaft 5 (see FIG. 1).
On the other hand, as the pressure within the crankcase 8 decreases, the swash plate 10 moves in a stroke direction (direction for increasing the inclination angle thereof). As a result, the length of stroke of the piston 7 is increased to increase the delivery quantity or capacity of the compressor. In the meantime, the link pin 11 of the linkage 41 relatively slides along the guide slot 44 to the other end of the guide slot 44 remote from the shaft 5 (see FIG. 2).
As the inclination angle of the swash plate 10 decreases, the instantaneous rotational center O of the swash plate 10 moves away from the shaft 5, and a moment acting on the swash plate 10 in the de-stroke direction is progressively reduced, until an inclination angle at which the moment in the de-stroke direction is reduced to 0, where the control of tilting of the swash plate 10 becomes stable.
On the other hand, as the inclination angle of the swash plate 10 increases, the instantaneous rotational center O of the swash plate 10 moves closer to the shaft 5, and a moment acting on the swash plate 10 in the stroke direction is progressively reduced, until an inclination angle at which the moment in the stroke direction is reduced to 0, where the control of tilting of the swash plate 10 becomes stable.
This variable capacity swash plate compressor has a characteristic concerning the instantaneous rotational center O of the swash plate 10 that the instantaneous rotational center O moves closer to the shaft 5 as the inclination angle of the swash plate 10 increases (see a curve B in FIG. 7). Therefore, even if the compressor uses CO₂ as refrigerant, and hence the PCD of pistons is small, it can secure the pressure-decrease tilting rotation characteristic of the swash plate 10 that the pressure within the crankcase required for a dynamic balance decreases as the swash plate angle increases, whereby the control stability of the compressor is enhanced.
FIG. 3 shows a variable capacity swash plate compressor according to an embodiment of the invention, with a swash plate thereof at a minimum inclination angle with respect to a plane perpendicular to a shaft on which the swash plate is fitted, while FIG. 4A shows the FIG. 3 variable capacity swash plate compressor with the swash plate thereof at a maximum inclination angle with respect to the plane perpendicular to the shaft. FIG. 4B is an enlarged view of a guide slot. Component parts and elements similar to those of the first embodiment are designated by identical reference numerals, and detailed description thereof is omitted.
A linkage 91 is comprised of a link pin 11 and the guide slot 94. The link pin 11 is fixed to a pair of brackets 47 formed on a front surface of the swash plate 10.
The guide slot 94 is formed through a projection 96 projecting from a rear surface of a thrust flange 40. The link pin 11 is fitted in the guide slot 94 in a relatively slidable manner. When respective radii of curvature at different portions of an arc drawn by a center line 94a of the guide slot 94 are represented by R1, R2 and R3, respectively, in the order of respective positions from one end of the arc toward the shaft 5 to the opposite end of the same remote from the shaft 5, they have the relationship which can be expressed as R1> R2 > R3 (see FIG. 4B). That is, the arc drawn by the center line 94a has a varying radius of curvature which progressively decreases from the one end toward the shaft 5 to the opposite end remote from the same.
Further, when the centers of curvature at different portions of the arc drawn by the center line 94a of the guide slot 94 corresponding to the radii R, R2, and R3 are represented by O1, O2 and O3, respectively, they shift in a direction away from the shaft 5 (see FIG. 4B).
In this linkage 91, the curvature of a portion of the arc drawn by the center line 94a of the guide slot 94 corresponding to an actual position of the link pin 11 determined by the swash plate angle increases as the swash plate angle increases (see line A in FIG. 9), and the Y coordinate value of the instantaneous rotational center O with respect to the swash plate angle changes in a curve A as shown in FIG. 7.
Further, since a manner of change in the Y coordinate value of the instantaneous rotational center O is correlated with the tilting rotation characteristic as described hereinbefore, if the Y coordinate value of the instantaneous rotational center O decreases as the swash plate angle increases, the pressure within the crankcase 8 required for a dynamic balance decreases as the swash plate angle increases (see curve b in FIG. 8).
The variable capacity swash plate compressor according to the present embodiment can provide the same effect as obtained by the first embodiment. Further, in the second embodiment, the Y coordinate value of the instantaneous rotational center with respect to the swash plate angle changes in a more sharply decreasing curve than in the first embodiment (see FIG. 7), and hence control stability is further improved.
It should be noted that when the radius of curvature of the center line 94a of the guide slot 94 is within a range of 5 to 25 mm, the curvature of a portion of the arc corresponding to the actual position of the link pin 11 determined by the swash plate angle is within a range of 0.04 to 0.20 (1/mm).
Although in the above embodiment, the linkage is comprised of the pin fixed to the swash plate 10 and the guide slot formed through the thrust flange 40, the linkage may be comprised of a pin fixed to the thrust flange 40 and the guide slot formed through the swash plate 10.
Further, although in the embodiment, the invention is applied to the variable capacity swash plate compressor, this is not limitative, but the invention is also applicable to a wobble plate compressor
It is further understood by those skilled in the art that the foregoing is the preferred embodiment and variations of the invention, and that various changes and modifications may be made without departing from the scope thereof.

Claims

A variable capacity compressor including a rotary member rigidly fitted on a shaft (5), for rotating in unison with the shaft (5) as the shaft (5) rotates, and an tilting rotary plate fitted on the shaft (5) in a manner tiltable with respect to a plane perpendicular to the shaft (5) and connected to the rotary member via a linkage, for rotating in unison with the rotary member as the rotary member rotates,
the tilting rotary plate having an inclination angle with respect to the plane perpendicular to the shaft (5), the inclination angle being changed according to a change in pressure within a crankcase in which the tilting rotary plate is received, to change a stroke length of each piston (7) connected to the tilting rotary plate,
wherein the linkage comprises a pin (11) fixed to one of the tilting rotary plate and the rotary member, and guide means formed in another of the tilting rotary plate and the rotary member and extending in a form of an arc, for engagement with the pin (11), and
wherein an arc drawn by a center line of the guide means has a radius of curvature which progressively decreases from one end of the arc adjacent to the shaft (5) to an opposite end of the arc remote from the shaft (5).
A variable capacity compressor according to claim 1, wherein the guide means is a slot formed through the another of the tilting rotary plate and the rotary member.
A variable capacity compressor according to claim 1, wherein the radius of curvature is within a range of 5 to 25 mm.