WO2001012988A1

WO2001012988A1 - Axial piston drive mechanism with a continuously adjustable piston stroke

Info

Publication number: WO2001012988A1
Application number: PCT/EP2000/008085
Authority: WO
Inventors: Otfried Schwarzkopf
Original assignee: Zexel Valeo Compressor Europe Gmbh
Priority date: 1999-08-18
Filing date: 2000-08-18
Publication date: 2001-02-22
Also published as: DE19939130B4; DE19939130A1; AU6997400A; JP2003507626A

Abstract

The invention relates to an axial piston drive mechanism with a continuously adjustable piston stroke comprising an input shaft (10, 12, 170) and a bearing seat (14) for a swash-plate (16, 18) having a first tilting angle (22) in relation to the longitudinal direction (20), wherein the swash-plate (16, 18) is mounted in a crank chamber (24) with a bearing bore (30) which is tilted at a second tilting angle (28) relative to the perpendicular (26) of the swash-plate (16, 18, 174) and can be rotated around a tilting area with the aid of a regulating device to regulate the piston stroke. Said mechanism also comprises at least one piston (44, 46, 48, 50) that is drivingly connected to the swash-plate (16, 18, 174) and movable in a cylinder (36, 38, 40, 42). According to the invention, the rotational movement is shifted from a resulting maximum tilting angle (52) to a resulting minimum tilting angle (54) by an axial stroke (56) of the swash-plate (16, 18, 174) in the direction of the piston (44, 46, 48, 50) and from the resulting minimum tilting angle (54) to the maximum resulting tilting angle (52) by an axial stroke (116) in the direction opposite to the piston (44, 46, 48, 50).

Description

Axial piston engine with an infinitely adjustable piston stroke

State of the art

The invention is based on an axial piston engine with an infinitely adjustable piston stroke according to the preamble of claim 1.

It is known to use axial piston engines with an infinitely adjustable piston stroke, in particular for motor vehicle air conditioning systems, specifically as a refrigerant compressor.

An air conditioning system of a motor vehicle essentially has a refrigerant compressor, a first heat exchanger, a so-called evaporator, a second heat exchanger, a so-called condenser or gas cooler in supercritical processes, an expansion device and pipes which connect the components to one another. The task of the refrigerant compressor is to draw in a refrigerant from the evaporator, in which the refrigerant evaporates at a low pressure level while absorbing heat, and to compress it to a higher pressure. In the second heat exchanger, the refrigerant can then heat at a higher pressure and temperature O 01/12988-2 - PCT / EPOO / 08085

release level and is again throttled to a pressure level of the evaporator in the expansion element. A closed circular process is created.

The performance of the refrigerant compressor can be made infinitely variable via the piston stroke via a drive speed and particularly energetically favorable in axial piston engines. Known axial piston engines or axial piston compressors for motor vehicle air conditioning systems have a drive shaft driven by a pulley. In a crank chamber, a swash plate is rotatably and tiltably mounted on the drive shaft via a joint. The swash plate drives at least one piston that is movable in a cylinder. In order to absorb tensile and compressive loads, each piston is connected to the swash plate by means of two articulated blocks, in each case with an articulated block on the swash plate of the swash plate facing the piston and away from the piston. The articulated blocks run with their flat surfaces on the running surfaces of the swash plate at full circumferential speed with superimposed radial movement, which results in an elliptical raceway. The articulated stones lie with their curved surfaces in molded spherical bearings of the pistons, in which there is a comparatively small relative movement during operation.

Furthermore, the swash plate can also be connected to the pistons by means of a swash plate instead of simply by means of articulated stones. The swash plate is secured against rotation to the drive shaft either on a housing or via piston rods. A bearing between the swash plate and the swash plate takes up the entire relative movement. Because of the rotating swashplate, the swashplate only performs a wobble movement. O 01/12988-3 - PCT / EPOO / 08085

The piston stroke and thus the performance of the axial piston compressor is set via the degree of tilt angle of the swash plate. With a large tilt angle there is a large piston stroke and a high output, with a small tilt angle there is a small piston stroke and a low output. The tilt angle of the swashplate is usually limited to a minimum and a maximum value by two stops. Usually one or two guide pins are required to guide the tilting movement in a defined manner and to avoid jamming. The tilt limits or the stops can be integrated in the guide pins.

If the top dead center of the piston is shifted towards the swash plate in the cylinder when the tilt angle is adjusted from a maximum value to a smaller value, already compressed gas cannot be pushed out completely. The compression energy introduced into the gas cannot be used for the cooling process. A so-called damaged space is created between the piston and a valve plate on the cylinder, which leads to energy loss. In order to avoid the dead space and to maintain the top dead center of the pistons, the swash plate is additionally axially displaceable against a preloaded compression spring. The swashplate is usually limited in the axial direction by stops.

Advantages of the invention

The axial piston engine according to the invention has a drive shaft and a radial bearing seat for a swash plate, which has a first tilt angle to the longitudinal direction. There is a swash plate on the bearing seat in a O 01/12988 - 4 - PCT / EPOO / 08085

Belraum with a bearing bore tilted by a second tilt angle for vertical inclination of the swash plate. The swash plate is drivingly connected to at least one piston which is movable in a cylinder. In order to be able to adjust the tilt angle and thereby the piston stroke and the power, the swash plate can be rotated with a control device over an angular range on the bearing seat.

It is proposed that the twisting movement from an axial resulting tilt angle to a minimum resulting tilt angle with an axial stroke movement of the swash plate in the direction of the piston and from the minimum resulting tilt angle to the maximum resulting tilt angle from an axial stroke movement in the direction away from the piston is superimposed. Tipping moments acting on the swash plate can advantageously be supported on the drive shaft via large bearing surfaces. Pinching is avoided and a long service life of the axial piston engine can be achieved. Furthermore, the axial stroke movement makes it possible to avoid or minimize a harmful space caused by the tilting movement. The top dead center of the piston can be maintained in the cylinder barrel, losses can be avoided and the axial piston engine can be used particularly advantageously as a compressor in air conditioning systems. The compressor can be designed as a pure swash plate compressor or as a swash plate compressor. Furthermore, the solution according to the invention can be applied to gears, hydraulic pumps, etc.

The axial stroke movement can be achieved in various methods which appear suitable to the person skilled in the art, for example via an axially moving adjusting piston, etc. However, the swash plate is particularly advantageous via a WO 01/12988 - 5 - PCT / EPOO / 08085

Thread connected to the drive shaft, which generates the additional axial stroke movement from the twisting movement of the swash plate. A desired connection between the twisting movement and the axial lifting movement can be established with little effort using a certain thread pitch. The thread pitch is advantageously chosen so that the swash plate is axially displaced by half a maximum piston stroke at an angle of rotation of 180 °. The top dead center of the piston in the cylinder liner is retained and damage space and energy losses are avoided.

Furthermore, the swash plate can be made particularly insensitive to vibrations and shocks in the axial and radial directions and to torque fluctuations due to a thread inhibition. The thread is preferably introduced into radial surfaces, but can also be introduced into axial surfaces, for example in the form of a ring wedge and a mating ring wedge, etc. Furthermore, the thread can be made with one or more threads. With a multi-start thread, it can advantageously be ensured that, despite a large pitch of the thread, the swash plate is securely connected to the drive shaft at more than one point via the thread at a minimum and maximum tilt angle. The thread can be introduced in an additional component fastened to the drive shaft, for example in an oblique cylinder. In one embodiment it is proposed that the thread be molded onto the drive shaft. Additional components, assembly effort and costs can be saved. In order to enable particularly simple assembly and to be able to move the center of dimension of the adjusting parts along a desired axis during the adjustment process, in particular WO 01/12988 - 6 - PCT / EPOO / 08085

along the shaft axis, the swash plate is advantageously rotatably mounted on an axially displaceable sleeve.

The control device has at least one actuating unit with which the swash plate can be tilted and axially displaced via an actuating force. The actuating unit can be partially formed by the pistons in that, by varying a gas pressure difference between the top of the piston and the underside of the piston in the crank chamber, an actuating force is generated which adjusts the swash plate against a counterforce device. The counterforce device can be formed by a compression spring or advantageously by a torsion spring which acts directly on the swash plate via a torque and can therefore be made lighter and possibly more cost-effectively than a compression spring.

It is also possible that the control device has an actuating unit which is separate from the piston and by means of which the swash plate can be adjusted. With a control unit separated from the piston, a control range that is independent of the operating points can be achieved. Flow losses between the top of the piston and the crankcase can be reduced. Furthermore, the axial piston engine can be operated with a low pressure in the crank chamber. A leakage flow of refrigerant from the crankcase through shaft seals to the outside is roughly proportional to the pressure in the crankcase. With a low pressure, complex sealing of the crankcase can be avoided and a low leakage flow can be achieved. This is particularly advantageous in the case of refrigerants with high absolute pressures, in which high pressures in the crankcase are generally required for regulation via a gas pressure difference on the piston. At a low pressure, the solubility of the refrigerant in an air conditioning system is also a low lubricant of the compressor, whereby a high viscosity can be maintained.

Furthermore, the viscosity has a positive effect that heating of the lubricant by a gas heated by the high-pressure side of the piston can be avoided with a separate actuating unit. With a high viscosity, low friction can be achieved between highly loaded sliding pairs on the swash plate and between the pistons and the cylinders, which contributes to a long service life and high reliability.

With an actuating unit separate from the piston, no specific pressure in the crank chamber is required for regulation, as a result of which refrigerant can be passed through the crank chamber by an evaporator. The crankcase can thereby be cooled, an additional suction chamber on the top of the piston can be avoided and installation space can be saved. Furthermore, a mostly large volume of the crankcase can be used to dampen gas pulsations.

The actuating unit can be driven electrically, pneumatically or advantageously hydraulically. With hydraulic fluid, advantageous vibration damping can be achieved and a particularly vibration-resistant axial piston engine can be created. The actuating unit can act directly on the swash plate with a torque and / or with an axial actuating force. An axially acting actuating unit can be sealed particularly easily and can be designed inexpensively. In the case of an actuating unit which acts on the swash plate with a torque, the actuating torque acts directly in the direction of the twisting movement of the swash plate, as a result of which it has a small actuating torque and a small and space-saving one WO 01/12988 - P-PCT / EP00 / 08085

Actuator, the swash plate can be tilted and moved axially.

The hydraulic actuating unit can be supplied with pressure oil from a hydraulic unit that is independent of the pumped medium of the piston, for example advantageously from a hydraulic unit that is already present in a motor vehicle. Additional components can be saved and a large control range independent of the operating points of the axial piston engine can be achieved. Furthermore, no pressure build-up when starting the axial piston engine is required for the control, for example due to a minimum tilt angle of 2 °. A load-free start-up of the axial piston engine is made possible and starting an internal combustion engine driving the axial piston engine, for example, is made easier.

With an oil separator downstream of the compressor on the high pressure side, good heat transfer in the heat exchangers can be ensured and a high efficiency of an air conditioning system can be achieved. Furthermore, the oil separator can be used particularly cheaply to supply the hydraulic actuating unit with pressure oil. The pressure oil from the oil separator is pressurized depending on the operating point. If a high adjustment torque is required, there is a high pressure in the oil separator, a low adjustment torque is required, a low pressure is present.

In one embodiment, it is proposed to connect the hydraulic actuating unit to the crank chamber via a drain, as a result of which the oil separator and the

Actuator can be used to deliver the lubricant back into the crankcase. Here, an inflow from the oil separator to the control unit and / or the outflow from the Actuator to the crankcase can be made adjustable. The unregulated part is advantageously formed by a throttle point.

drawing

Further advantages result from the following description of the drawing. Exemplary embodiments of the invention are shown in the drawing. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into useful further combinations.

Show it:

Fig. 1 shows an axial piston engine with maximum piston stroke in section, Fig. 2 shows a section along the line II-II in

Fig. 1

3 shows an axial piston engine according to FIG. 1 with a minimum piston stroke in section,

4 shows a section along the line IV-IV in FIG. 3,

5 shows an axial piston engine with a hydraulic actuating unit,

6 shows a section along the line VI-VI in FIG.

5, FIG. 7 shows a schematic diagram of a hydraulic control and FIG. 8 shows a section of a variant according to FIG. 2. Description of the embodiments

1 shows an axial piston engine for an air conditioning system of a motor vehicle, which works as a compressor. The axial piston engine has a drive shaft 10 with a bearing seat 14 for a swash plate 16, which has a first tilt angle 22 to the longitudinal direction 20 (FIG. 2). On the bearing seat 14, the swash plate 16 is mounted in a crank chamber 24 with a bearing bore 30 tilted by a second tilt angle 28 to the vertical 26 of the swash plate 16.

The swash plate 16 is connected in terms of drive via hemispherical jointed stones 78, 80, 82, 84, 86, 88, 90, 92 to four pistons 44, 46, 48, 50 guided in cylinders 36, 38, 40, 42 (Fig. 3 u. 4). To absorb tensile and compressive loads, each piston 44, 46, 48, 50 is connected to the swash plate 16 via two articulated blocks 78, 80, 82, 84, 86, 88, 90, 92, in each case via an articulated block 78 , 80, 82, 84, 86, 88, 90, 92 with a running surface 94, 96 of the swash plate 16 facing the pistons 44, 46, 48, 50 and facing away from the pistons 44, 46, 48, 50 Articulated stones 78, 80, 82, 84, 86, 88, 90, 92 run with their flat surfaces on the running surfaces 94, 96 of the swash plate 16 at full circumferential speed with superimposed radial movement, which results in an elliptical raceway. The articulated stones 78, 80, 82, 84, 86, 88, 90, 92 lie with their curved surfaces in shaped spherical bearings 98, 100, 102, 104, 106, 108, 110, 112 of the pistons 44, 46, 48 , 50, in which there is a comparatively small relative movement during operation.

In order to be able to continuously adjust the piston stroke and thus the power of the axial piston engine, the swash plate 16 has a control device 32 over an angular range O 01/12988-11 - PCT / EPOO / 08085

the bearing seat 14 rotatable. If the bearing seat 14 and the bearing bore 30 are inclined in the same direction, the tilt angles 22, 28 add up to a maximum resulting tilt angle 52 (FIG. 2), if the bearing seat 14 and the bearing bore 30 are inclined in the opposite direction, the tilt angles 22 subtract , 28 to a minimum resulting tilt angle 54 (FIG. 4). The minimum resulting tilt angle 54 is approximately 2 ° in order to ensure pressure build-up when the axial piston engine is started.

According to the invention, the rotational movement from the maximum resulting tilt angle 52 to the minimum resulting tilt angle 54 is from an axial stroke movement 56 of the swash plate 16 in the direction of the pistons 44, 46, 48, 50 and from the minimum resulting tilt angle 54 to the maximum resulting tilt angle 52 axial stroke movement 116 superimposed in the direction facing away from the piston 44, 46, 48, 50 (Fig. 1-4). The swash plate 16 is connected via a thread 58 to the drive shaft 10, which generates the additional stroke movement 56, 116 from the rotational movement of the swash plate 16. The thread 58 is integrally formed on the drive shaft 10 and has a pitch that the swash plate 16 is axially displaced by half a maximum piston stroke 60 at an angle of rotation of 180 ° and an upper dead center 114 of the pistons 44, 46, 48, 50 in the Cylinder race is retained (Fig. 2 and 4). The stroke movement 56, 116 and the twisting movement of the swash plate 16 is limited by stop plates 120, 122 fastened on the drive shaft 10, by means of which the drive shaft 10 is supported in the axial direction via axial bearings 160 and running disks 168 on a cover 162 and on a housing 164 of the axial piston engine is. The drive shaft 10 is supported radially via two radial bearings 166 in the cover 162 and in the housing 164. O 01/12988-12 - PCT / EPOO / 08085

The control device 32 has an actuating unit which is partially formed by the pistons 44, 46, 48, 50. By varying a gas pressure difference between the top 118 of the pistons 44, 46, 48, 50 and the bottom of the pistons 44, 46, 48, 50 in the crank chamber 24, an actuating force is generated with channels and control valves (not shown) (FIG. 1) that the swash plate 16 is adjusted against a counterforce device. The counterforce device is formed by four prestressed torsion springs 62, 64, 66, 68. The torsion springs 62, 64, 66, 68 are supported on the stop plates 120, 122 of the swash plate 16 and act on the swash plate 16 via stops not shown in more detail. If the swash plate 16 is adjusted from the maximum resulting tilt angle 52 to the minimum resulting tilt angle 54, the torsion springs 62, 64, 66, 68 are further pretensioned. If the swash plate 16 is adjusted from the minimum resulting tilt angle 54 to the maximum resulting tilt angle 52, the torsion springs 62, 64, 66, 68 are relaxed. Between the maximum and the minimum resulting tilt angle 52, 54, the swash plate 16 can be continuously adjusted to any tilt angle. The swash plate 16 is displaced on a tilted central axis, which results in a slight eccentricity of the swash plate in the extreme positions. An unbalance in the extreme positions can advantageously be avoided by using balancing weights.

FIG. 8 shows a section of a variant according to FIG. 1 with a drive shaft 170. A sleeve 178 is axially displaceable and rotatably mounted on the drive shaft 170. The sleeve 178 has a bearing seat 14 on which a swash plate 174 is rotatably mounted with a bearing bore 30. The swash plate 174 is axially and radially supported on the sleeve 178 via roller bearings 182, 184, 186 and is connected via a coupling lung 176 coupled to a nut 180 which is connected to the drive shaft 170 via a thread 172. With regard to the adjustment function, reference can essentially be made to the description of the exemplary embodiment in FIGS. 1 to 4. In contrast, the swash plate 174 can, however, be installed in a particularly simple manner and, furthermore, the center of mass of the adjusting parts can be guided along the shaft axis by means of a corresponding configuration of the sleeve 178.

5 shows an axial piston engine with a control device 34 which has a hydraulic actuating unit 70 which is separate from the pistons 44, 46, 48, 50. In the exemplary embodiments shown, essentially constant components are identified with the same reference numerals. The actuating unit 70 has a wheel 126 which is mounted in a housing 124 and has two vanes 128, 130 (FIG. 6) which, with two vanes 132, 134, form four chambers 136, 138, 140, 142 on the housing 124. In order to rotate a swash plate 18 on a drive shaft 12, the two chambers 142, 138 are subjected to high oil pressure via an axial and a radial bore

144, 146 in the drive shaft 12 and via a radial bore 148 in the wheel 126. The wheel 126 is fastened on the drive shaft 12, while the housing 124 is rotatably mounted relative to the wheel 126, exerts a torque on the swash plate 18 via a connecting element 150 and the

Swash plate 18 adjusted against the prestressed torsion springs 66, 68. The connecting element 150 engages in a recess 152 of the swash plate 18, can be displaced in the axial direction relative to the swash plate 18 and bears against the swash plate 18 over the entire adjustment range.

The actuating unit 70 is also carried by an oil separator 72 connected to the cylinders 36, 38, 40, 42 via an inflow 76 Pressurized oil is supplied and is connected to the crank chamber 24 via a drain 74 (FIG. 7). The coolant separated from the oil is conveyed by the oil separator 72 to a low-pressure side of the air conditioning system, as indicated by arrow 154. The inflow 76 from the oil separator 72 to the actuating unit 70 and the outflow 74 from the actuating unit 70 into the crank chamber 24 can each be regulated via a valve 156, 158. It would also be possible to replace a valve 156 or 158 with a fixed throttle point.

reference numeral

10 drive shaft 58 thread

12 drive shaft 60 piston stroke

14 Bearing seat 62 torsion spring

16 swash plate 64 torsion spring

18 swash plate 66 torsion spring

20 longitudinal direction 68 torsion spring

22 Tilt angle 70 actuator

24 crankcase 72 oil separator

26 Vertical 74 drain

28 tilt angle 76 inflow

30 bearing bore 78 joint block

32 Control device 80 articulated stone

34 Control device 82 Articulated stone

36 cylinders 84 articulated stone

38 cylinder 86 articulated stone

40 cylinder 88 articulated stone

42 cylinder 90 articulated stone

44 pistons 92 articulated stone

46 pistons 94 tread

48 pistons 96 tread

50 pistons 98 bearings

52 tilt angle 100 bearings

54 tilt angle 102 bearings

56 stroke movement 104 bearings 106 bearing 162 cover

108 bearings 164 housing

110 bearings 166 bearings

112 bearings 168 running disks

114 Top dead center 170 drive shaft

116 stroke 172 thread

118 top 174 swash plate

120 stop plate 176 clutch

122 stop plate 178 sleeve

124 housing 180 nut

126 wheel 182 roller bearings

128 blades 184 bearings

130 wings 186 roller bearings

132 wings

134 wings

136 chamber

138 chamber

140 chamber

142 chamber

144 hole

146 hole

148 hole

150 connecting element

152 recess

154 arrow

156 valve

158 valve

160 thrust bearings

Claims

Expectations

1. Axial piston engine with a continuously adjustable

Piston stroke, which has a drive shaft (10, 12, 170) and a bearing seat (14) for a swash plate (16, 18, 174), which has a first tilt angle (22) to the longitudinal direction (20) on which the swash plate (16 , 18, 174) in a crank chamber (24) with a bearing bore (30) tilted to the vertical (26) of the swash plate (16, 18, 174) by a second tilt angle (28) and for adjusting the piston stroke with a control device (32, 34) can be rotated over an angular range and with at least one in a cylinder which is connected to the swash plate (16, 18, 174) by drive

(36, 38, 40, 42) movable piston (44, 46, 48, 50), characterized in that the rotational movement from a maximum resulting tilt angle (52) to a minimum resulting tilt angle (54) from an axial stroke movement (56) the swash plate (16, 18, 174) in the direction of the piston (44, 46, 48, 50) and from the minimum resulting tilt angle (54) to the maximum resulting tilt angle (52) from an axial stroke movement (116) into that of the piston (44, 46, 48, 50) opposite direction is superimposed.

2. Axial piston engine according to claim 1, characterized in that the swash plate (16, 18, 174) via a thread (58, 172) with the drive shaft (10, 12, 170) is operatively connected, which results from the rotational movement of the swash plate (16, 18, 174) generates the additional axial stroke movement (56).

3. Axial piston engine according to claim 2, characterized in that the thread (58, 172) on the drive shaft (10, 12, 170) is integrally formed.

4. Axial piston engine according to one of the preceding claims, characterized in that at an angle of rotation of 180 °, the swash plate (16, 18, 174) by half of a maximum piston stroke (60) is axially displaced.

5. Axial piston engine according to one of claims 2 to 4, characterized in that the swash plate (174) is rotatably mounted on an axially displaceable sleeve (178).

6. Axial piston engine according to one of the preceding claims, characterized in that the control device (32) has a counterforce device with at least one on the swash plate (16, 174) acting, prestressed torsion spring (62, 64, 66, 68).

7. Axial piston engine according to one of the preceding claims, characterized in that the control device (34) has a separate actuator (70) from the piston (44, 46, 48, 50).

8. Axial piston engine according to claim 7, characterized in that the actuating unit (70) is hydraulically driven.

9. Axial piston engine according to claim 8, characterized in that the hydraulic actuating unit (70) is supplied with pressure oil from an independent hydraulic unit from the pumped medium of the piston (44, 46, 48, 50).

10. Axial piston engine according to claim 8, characterized in that the hydraulic actuating unit (70) by a cylinder (36, 38, 40, 42) downstream oil separator (72) is supplied with pressure oil.

11. Axial piston engine according to claim 10, characterized in that the hydraulic actuating unit (70) is connected via an outlet (74) to the crank chamber (24) and an inflow (76) from the oil separator (72) to the actuating unit (70) and / or the outflow (74) from the actuating unit (70) to the crank chamber (24) can be regulated.