EP2118485A1

EP2118485A1 - Hydraulic piston engine

Info

Publication number: EP2118485A1
Application number: EP07819432A
Authority: EP
Inventors: Thomas Seufert; Brian Kane
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2007-01-05
Filing date: 2007-10-30
Publication date: 2009-11-18
Also published as: DE102007001794A1; WO2008080444A1; CN101573532A

Abstract

The invention relates to a hydraulic piston engine comprising at least one swash plate or wobble plate on which a plurality of pistons are supported, said pistons each being pre-stressed against the swash or wobble plate over a sliding block. According to the invention, the pistons are pre-stressed against the swash or wobble plate by the force of at least one tension spring guided in sections inside the piston. An end section of the tension spring is supported on at least one abutment shoulder of a piston insert arranged in the piston, and surrounds said insert at least in sections.

Description

description

Hydraulic piston machine

The invention relates to a hydraulic piston engine according to the preamble of patent claim 1.

From DE 10 2004 060 954 A1, for example, a double swashplate machine is known, in which a plurality of pistons are received in a stationary drum, which are each guided in pairs in opposite directions in the drum and define a common working space. The axial displacement of the counter-rotating piston via two arranged on both sides of the drum swash plates, which are rotatably connected to a drive shaft. Each piston is supported via a sliding bore provided with a sliding block on its associated swash plate, wherein the pistons are penetrated by a capillary, is guided over the pressure medium to the sliding surface of the sliding shoe, so that it is hydrostatically supported. In this known solution, the pistons are each biased against the helical or swash plate via spring biased return plates engaging the sliding shoes, so that the sliding shoes do not lift off the associated swash plate during the suction stroke. The supply of pressure medium to the working chambers takes place in each case by a suction chamber which is accommodated in working space-side end sections of the pistons and which delimits in each case a pressure chamber which is connected to suction connections of the axial piston machine via oblique bores introduced into the piston base. For pressure medium removal, pressure valves are provided between the working space and a pressure connection arranged radially or axially in the piston drum. A disadvantage of such reciprocating engines is that the pistons have a relatively large dead volume, which can lead to a deteriorated volumetric efficiency and considerable noise level of the axial piston engine. Another disadvantage is that such piston machines due to the spring-biased retraction plates ferti- technically extremely expensive. The spring-biased retraction plates are required to bias the shoes against the swash plates and prevent them from lifting off the swash plates during a suction stroke of the pistons.

To reduce the dead volume, it is known from WO 96/01946 A1, to arrange piston inserts in the piston, which are provided on its outer circumference with a helically shaped pressure medium channel for supplying pressure medium of the sliding shoes. In this known solution, the pressure medium supply and pressure fluid discharge takes place via designed as a slide suction and pressure valves, the pusher sleeves are guided on the outer circumference of the piston in the cylinder or in the piston drum. Such piston engines are also expensive to manufacture due to the spring-biased retraction plates.

In contrast, the invention has for its object to provide a hydraulic piston engine in which the hydraulic losses are minimized with minimal device complexity.

This object is achieved by a hydraulic piston machine having the features of ^■ claim 1.

The piston engine according to the invention has at least one inclined or swash plate, on which a plurality of pistons are supported, which are each biased via a sliding shoe against the oblique or swash plate. According to the invention, the pistons are biased against the oblique or swash plate by the force of at least one tensioning spring guided in sections within the pistons, wherein one end portion of the tension spring is supported on at least one contact shoulder of a piston insert arranged in the piston and surrounds the latter at least in sections. In this solution, due to the tension spring guided inside the pistons, spring-tensioned return plates can be used to pre-stress the sliding shoes. conditions the oblique or swash plate are omitted. The piston inserts reduce each of the piston interior of the piston and fill the interior of the tension spring at least in sections, so that the dead volume is minimized.

The piston engine has in an embodiment according to the invention in opposite directions movable, a common working space limiting piston, which are biased via at least one common tension spring each with a shoe against a helical or swash plate, wherein the end portions of the tension spring are each supported on a contact shoulder of a piston insert of the piston , For example, the piston engine is designed as a double swashplate machine or double-inclined piston machine, which can advantageously be operated in both directions of rotation.

In one embodiment of the invention, the abutment shoulder is in each case formed on a radial collar of the piston insert which has a support shoulder opposite the abutment shoulder on which an end section of a respective second tension spring is supported with respect to the first tension spring reduced spring constant. The centrally located tension spring with the larger spring constant is effective for a first partial stroke of the pistons, preferably in the range of about 30 to 50% of the total stroke length, and then substantially relaxed. The two outer springs with reduced spring constant center each of the piston inserts and bias the piston in the area of the outer dead center with relatively little force against the inclined or swash plate. The lower force of the outer tension springs compared to the middle tension spring is sufficient since no further acceleration of the pistons is required when reaching the outer dead center (v = 0 when the outer dead center is reached). The weaker spring is preferably effective only from a stroke length of 30 to 50% of the total stroke. An advantage of this variant is that lifting the piston from the oblique or swash plates by the stronger tension spring is prevented, wherein the spring diameter is reduced due to the limited effective length of the tension spring with a large spring constant over a piston biasing the piston over the entire stroke length strong spring.

The radial collar of the piston insert can be brought in an embodiment of the invention by the force of the middle tension spring with a larger spring constant with a stop of the piston in abutment. The stop of the piston is preferably formed by a radially enlarged portion of the inner wall of the piston as a stop shoulder.

The weight of the piston engine can be reduced if at least the piston inserts, the pistons and / or the sliding shoes made of wear-resistant plastic, such as carbon fiber reinforced plastic, are made. Due to the mass inertia reduced by the weight optimization, the efficiency of the piston engine is improved. In a partially hollow-bored metallic piston, the plastic inserts reduce the dead volume without the weight being as large as a solid piston or less deeply drilled piston.

As a manufacturing technology, it has proven to be particularly advantageous if the plastic components of the piston engine are produced by injection molding. As a result, the mechanical reworking of the components is reduced to a minimum or can be omitted, so that a cost-effective production of the piston machine is made possible.

According to a particularly preferred embodiment, the piston inserts arranged in the oppositely displaceable pistons overlap at least in sections and are axially displaceable one inside the other. It has proved particularly advantageous in this case if the piston inserts have slidably guided support projections (support legs), which form a substantially cylindrical, tension spring. complementing common support section. That is, the piston inserts lead in a double pump, the tension springs along their entire length, the tension spring is guided by the Axialverschiebbarkeit the piston inserts over the entire stroke length of the piston.

The piston inserts extend in sections in the working space, so that the tension spring is supported in this area by the piston inserts and prevent buckling of the tension spring.

The support projections preferably each have a substantially circular section-shaped (circular sector-shaped) cross section. In a preferred embodiment of the piston engine, the piston inserts are each provided with three support projections offset by approximately 120 ° from one another. The abutment shoulders are preferably formed in the region of the support projections.

The piston inserts preferably have at least one recess, in particular a through hole, which opens on the one hand in the working space and on the other hand in a sliding surface of the sliding block and forms a pressure medium connection. About the recess pressure medium is guided to the sliding surface of the shoe, so that it is hydrostatically supported on the oblique or swash plate.

Other advantageous developments of the invention are the subject of further subclaims.

In the following preferred embodiments of the invention will be explained in more detail with reference to schematic drawings. Show it:

FIG. 1 shows a partial view of a piston machine designed as a double swash-plate pump according to a first embodiment of the invention; Figure 2 is a detail view of a piston insert of Figure 1;

Figure 3 is a plan view of the piston insert of Figure 2;

Figure 4 is a longitudinal section of the piston insert of Figure 2 and

FIG. 5 shows a partial view of a piston machine designed as a double swash-plate pump according to a further exemplary embodiment of the invention.

FIG. 1 shows a partial representation of a piston machine designed as a double swash-plate pump 1. Such a pump 1 consists essentially of a arranged in a housing, not shown, piston drum 2, which is penetrated by a plurality of lying on a common pitch axis parallel cylinder bores 4, each in the end faces 6, 8 of the piston drum 2 open and two opposite directions accommodate movable pistons 10, 12 record. These protrude with a piston foot 14, 16 out of the respective end face 6, 8 of the piston drum 2. The piston feet 14, 16 are spherical and each carry a shoe 18, 20. About the sliding blocks 18 are in Figure 1 from the left end face 6 of the piston drum 2 protruding piston 10 on a first swash plate 22 and the sliding shoes 20 from the right end face 8 protruding piston 12 supported on a second swash plate 24. The swash plates 22, 24 are rotatably connected to a drive shaft of the pump 1, not shown, which is mounted via axial / radial bearings in the housing. In such a construction with symmetrically arranged swash plates 22, 24, the axial forces are symmetrically introduced into the drive shaft and supported by this, so that the housing and the bearing of the moving parts are relieved and thus can be made smaller than it with a simple swash plate pump only a swash plate is the case. From the assigning final cut the respectively received in a cylinder bore 4 piston, which are shown in the region of its inner dead center, is limited by the opposing piston movement during the intake stroke and zooming during the Druckhübs working space 28 limited in the axial direction, in the pressure medium via a suction port can be fed and discharged from the pressure medium via a pressure connection (not shown). Each piston 10, 12 has an approximately cylindrical piston skirt 26, 30, which merges via a constriction 32, 34 in the spherical piston 14, 16. This is in ball-joint-like engagement with the associated slide shoe 18, 20, which in turn rests with its sliding surface 36, 38 on an end face 40, 42 of the swash plate 22, 24.

The pistons 10, 12 are biased against the swash plates 22, 24 by the force of a tension spring 44 in sections within the pistons 10, 12 so that the shoes 18, 20 do not lift off the associated swash plate 22, 24 during the suction stroke, with end portions 46, 48 of the tension spring 44 are supported on abutment shoulders 50, 52 of a piston insert 54, 56 respectively arranged in the pistons 10, 12 and engage around sections thereof. The piston inserts 54, 56 reduce the piston interior of the pistons 10, 12 and fill the interior of the tension spring 44, so that the dead volume is minimized and a significant improvement in efficiency and noise reduction is achieved. Due to the tension spring 44 can be dispensed with spring-biased return plates for biasing the shoes 18, 20 against the swash plates 22, 24. This simplifies the structure of the pump 1, wherein the sliding blocks 18, 20 can be designed freely. The piston inserts 54, 56 are provided with a pressure medium connection forming through hole 58, on the one hand in the working space 28 and on the other hand via a connecting hole 60, a funnel-shaped extension 62 of the piston 10, 12 and a capillary 63 of the slide shoe 18, 20 in the sliding surface 36, 38 of the slide shoe 18, 20 opens. The funnel-shaped enlargement 62 is required in order to ensure the pressure medium connection to the sliding surface 36, 38 even during a relative movement. Pivoting between shoe 18, 20 and piston 10, 12 maintain. Pressure medium is guided via the pressure medium connection to the sliding surface 36, 38 of the sliding shoe 18, 20, so that it is supported hydrostatically on the swash plate 22, 24.

A special feature of the solution described is that at least the piston inserts 54, 56, the pistons 10, 12 and also the sliding shoes 18, 20 are made of wear-resistant plastic, for example carbon fiber reinforced PEEK or POM, so that the double tumbler disc pump 1 with minimal Weight and minimum moving masses is executed. Due to the mass inertia reduced by the weight optimization, the efficiency of the piston engine 1 is improved. In a piston machine with metallic piston can also be achieved due to the piston inserts made of plastic, a significant weight reduction. As a manufacturing technology, it has proven particularly advantageous if the plastic components of the piston engine 1 are produced by injection molding. As a result, the mechanical reworking of the components is reduced to a minimum or can be omitted, so that a cost-effective production of the piston engine 1 is made possible. The piston inserts 54, 56 arranged in the oppositely displaceable pistons 10, 12 can be axially displaced into one another in sections, so that the tension springs 44 are guided over the entire stroke length of the pistons 10, 12. It has proved to be particularly advantageous in this case if the piston inserts 54, 56 have slidably guided support projections 64, 66, 68 (see FIG. 2), which complement each other to form a substantially cylindrical support section 70 passing through the tension spring 44. The tension spring 44 is guided along an inner wall 72 of the piston skirt 26, 30 of the pistons 10, 12 and the support section 70 of the piston liners 54, 56. These extend into the working space 28, so that the tension spring 44 is also supported in this area by the piston inserts 54, 56 and buckling of the tension spring 44 is prevented. According to FIG. 2, which shows an individual view of the piston insert 54 from FIG. 1, these have a sectionally cylindrical foot part 74, which has a conical end section 76 adapted to the piston inner wall 72 (see FIG. 1). The piston insert 54 is provided in the illustrated embodiment working space side with three support projections 64, 66, 68, which complement according to Figure 1 with the support projections 64, 66, 68 of the opposite piston insert 56 to the substantially cylindrical support portion 70. The support projections 64, 66, 68 are each provided with an abutment shoulder 50 on which the tension spring 44 (see FIG. 1) is supported (the piston inserts 56 of the other side are constructed identically so that a separate description is omitted). That is, the piston inserts 54, 56 cover each other in sections, so that the tension spring 44 is supported over its entire length by the piston inserts 54, 56 and prevent buckling of the tension spring 44.

As can be seen from FIG. 3, which shows a plan view of the piston insert 54 from FIG. 2, the support projections 64, 66, 68 in the exemplary embodiment shown are offset by approximately 120 ° with respect to one another and have an approximately circular cut-out (circular sector-shaped) cross section , The opening angle α of the support projections 64, 66, 68 is in this case chosen slightly smaller than the opening angle ß adjacent recesses 78, 80, 82, so that the piston inserts 54, 56 are slidably axially slidably into each other axially.

According to Figure 4, which is a longitudinal section of the piston insert 54 of FIG

2, the abutment shoulders 50 for the tension spring 44 are formed in the region of the support projections 64, 66, 68. In order to facilitate the assembly of the tension spring 44, the support projections 64, 66, 68 are each provided with an outer insertion bevel 84.

FIG. 5 shows a partial view of a piston machine 1 designed as a double swash-plate pump according to a further inventive device Embodiment shown. This exemplary embodiment differs from the above-described exemplary embodiment essentially in that the abutment shoulders 50, 52 of the tension spring 44 are each formed on a radial collar 86 of the piston insert 88, 90, each having a support shoulder 92, 94 opposite the abutment shoulders 50, 52 in which one end section 96, 98 of a second tension spring 100 is supported with respect to the first tension spring 44 substantially reduced spring constant. The two tension springs 100 are arranged coaxially with the central tension spring 44 and engage in each case at the bottom of the pistons 10, 12. The radial collar 86 of the piston insert 88, 90 is in the illustrated region of the inner dead center of the pistons 10, 12 brought by the force of the tension spring 44 with a larger spring constant with a stop 102 of the piston 10, 12 in abutment. The stop 102 of the piston 10, 12 is formed by a radially enlarged portion of the inner wall 72 of the piston 10, 12 as a stop shoulder. The support portion 70 of the piston insert 88, 90 has a correspondingly larger outside diameter in the region of the stronger tension spring 44. However, the stop 102 is not absolutely necessary for the function of the piston engine 1 according to the invention. The centrally located tension spring 44 with a larger spring constant is effective for a first partial stroke of the pistons 10, 12 in the range of about 30 to 50% of the total stroke length and then relaxed. The tension springs 100 with reduced spring constant center each of the piston inserts 88, 90 and bias the pistons 10, 12 in the region of the outer dead center with relatively little force against the swash plates 22, 24. The opposite of the tension spring 44 with a large spring constant lower force of the tension springs 100 is sufficient, since upon reaching the outer dead center no further acceleration of the piston 10, 12 is required (v = 0 when reaching the outer dead center). The weaker tension springs 100 are effective only from a stroke length of 30 to 50% of the total stroke with a relaxed tension spring 44. An advantage of this variant is that lifting of the pistons 10, 12 is prevented by the swash plates 22, 24 by the stronger tension spring 44, wherein the spring diameter due to the limited effective length of the tension spring 44 with large spring constant against a piston 10, 12 is biased over the entire stroke length strong spring is reduced.

In this embodiment of the invention, it is also possible to form the piston inserts 88, 90 such that they overlap each other in sections, so that the tension spring 44 is supported over its entire length by the piston inserts 88, 90 and prevent buckling of the tension spring 44.

The piston engine 1 according to the invention is not limited to the described embodiment, but the working machine 1 can be designed as a single disc or swash plate pump, wherein in the piston drum 2, only the piston 10 are guided axially displaceable and on the sliding blocks 18 on the single swash or swash plate 22nd issue. In such a solution, the housing is subjected to compressive forces on one side, but the advantage is that the pump builds shorter in the axial direction.

Disclosed is a hydraulic piston machine 1 with at least one inclined or swash plate 22, 24, on which a plurality of pistons 10, 12 are supported, which are each biased via a sliding block 18, 20 against the inclined or swash plate 22, 24. According to the invention, the pistons 10, 12 are prestressed against the helical or swash plate 22, 24 by the force of at least one tension spring 44, 100 guided in sections within the pistons 10, 12, wherein an end section 46, 48 of the tension spring 44 on at least one abutment shoulder 50, 52 of a piston 10, 12 arranged in the piston insert 54, 56, 88, 90 is supported and this at least partially surrounds.

Claims

claims

1. Hydraulic piston machine with at least one inclined or swash plate (22, 24) on which a plurality of pistons (10, 12) are supported, which define a working space (28), wherein the pistons (10, 12) each via a Sliding shoe (18, 20) are biased against the inclined or swash plate (22, 24), characterized in that the pistons (10, 12) by the force of at least one sectionally within the piston (10, 12) guided tension spring (44, 100) against the inclined or swash plate (22, 24) are biased, wherein an end portion (46, 48) of the tension spring (44) on at least one abutment shoulder (50, 52) of a in the piston (10, 12) arranged piston insert ( 54, 56, 88, 90) is supported and this at least partially surrounds.

2. Hydraulic piston engine according to claim 1, wherein at least the piston inserts (54, 56, 88, 90), the pistons (10, 12) and / or the

Sliding shoes (18, 20) made of plastic, in particular made of carbon fiber reinforced plastic.

3. Hydraulic piston engine according to claim 1 or 2, with oppositely movable, a common working space (28) limiting piston (10, 12), wherein the pistons (10, 12) via at least one common tension spring (44) each with a sliding shoe (18 , 20) are biased against an inclined or swash plate (22, 24).

4. Hydraulic piston machine according to claim 3, wherein in each case one end portion (46, 48) of the tension spring (44) on an abutment shoulder (50, 52) of the piston insert (54, 56, 88, 90) of the counter-movable piston (10, 12). is supported.

5. A hydraulic piston machine according to claim 4, wherein the abutment shoulder (50, 52) on a radial collar (86) of the piston insert (88, 90) is formed, one of the abutment shoulder (50, 52) opposite support shoulder (92, 94), on each of which an end portion (96, 98) of at least one second tension spring (100) is supported with respect to the first tension spring (44) reduced spring constant.

6. Hydraulic piston machine according to claim 5, wherein the radial collar (86) of the piston insert (88, 90) by the force of the tension spring (44) with a greater spring constant with a stop (102) of the piston (10, 12) is brought into abutment.

7. Hydraulic piston engine according to claim 5 or 6, wherein the tension spring (44) with the larger spring constant for a first partial stroke of the piston (10, 12), preferably in the range of about 30 to 50% of the total stroke length, is effective.

8. Hydraulic piston machine according to one of claims 3 to

7, wherein the piston inserts (54, 56) cover each other at least in sections.

9. Hydraulic piston machine according to one of claims 3 to

8, wherein support projections (64, 66, 68) of the piston inserts (54, 56) to a substantially cylindrical, the tension spring (44) passing through support section (70) supplement.

10. Hydraulic piston machine according to claim 9, wherein the support projections (64, 66, 68) each have a substantially circular segment-shaped cross-section.

11. Hydraulic piston machine according to one of claims 9 or

10, wherein the piston inserts (54, 56) in each case have three support projections (64, 66, 68) arranged offset by approximately 120 ° to one another.

12. Hydraulic piston machine according to one of claims 9 to

11, wherein the abutment shoulders (50, 52) in the region of the support projections (64, 66, 68) are formed.

13. Hydraulic piston engine according to one of the preceding claims, wherein the piston inserts (54, 56) at least one pressure medium connection forming a recess (58), in particular a passage bore have.

14. Hydraulic piston engine according to one of the preceding claims, wherein the piston inserts (54, 56) extend in sections into the working space (28).

15. Piston machine according to one of the preceding claims, wherein the components mentioned in claim 2 (54, 56, 10, 12, 18, 20) are made by injection molding.