EP1672215A2 - Hydraulic piston pump - Google Patents

Abstract

Hydraulic piston engine has multiple pistons (8,10) arranged in the cylinder (4) limiting the working space (36) whereby suction valves (42,44) are arranged in pressurizing chamber with pressure control valve (38) to maintain the pressure in the chamber. The pressurizing medium flow path (62) is bounded by capillary tube.

Description

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

Such hydraulic piston machines are designed for example as a radial or axial piston machine. In EP 0 742 870 B1, a double swashplate machine is shown, in which a plurality of pistons are accommodated in a fixed drum, which are each guided in pairs in opposite directions in the drum. 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 block on its associated swash plate, said piston and the piston are penetrated by a pressure equalization bore, is guided over the pressure medium to the sliding surface of the shoe, so that it is hydrostatically supported. In the known solution, the pressure medium supply and pressure fluid discharge takes place via suction and pressure valves, which are designed as a slide whose slide sleeves are guided on the outer circumference of the piston and in the cylinder.

Such a valve construction is extremely expensive, in particular, the reversal between low pressure and high pressure in each working space requires a precise tuning of the slide.

In US 3,514,223 an axial piston pump is shown in which the piston receiving cylinder is driven by a drive shaft. The pistons are over Sliding shoes supported on a fixed swash plate. In this known solution, the pressure medium supply to the working spaces is carried out in each case by a suction valve received in the piston. A pressure equalization as in the above solution is not provided.

US Pat. No. 3,183,848 discloses a swash-plate pump in which the supply and removal of pressure medium is carried out by means of a slot control which has a comparatively complex structure.

DE 27 16 888 C3 discloses a radial piston pump in which the pistons are arranged in the radial direction about an eccentric shaft. In this solution, the suction valves are integrated into the piston, but there is no hydrostatic bearing of the shoes.

In US-5, 354, 181 a generic piston machine is disclosed, which is designed as an axial piston pump with swash plate. In this known construction, the suction valves are arranged on the working chambers facing the end portions of the pistons. The pressure equalization takes place via a throttle bore, which passes through the piston and which produces a pressure fluid connection from the working space to the voltage applied to the swash plate sliding surface of the respective sliding shoe. A disadvantage of this solution is that the production of the piston is very expensive, since they are designed with a plurality of inner holes and further must be formed to guide the closing body of the suction valve, a radially recessed piston projection. Another disadvantage of this known solution is that this axial projection always dips axially into the working space with the closing body guided thereon and correspondingly increases the overall length of the pump.

In contrast, the invention has for its object to provide a hydraulic piston machine that is compact and easy to manufacture.

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

According to the invention, the hydraulic piston engine has a multiplicity of pistons displaceably guided in a cylinder, each defining a working space. The pressure medium supply during the suction stroke via a suction valve integrated in the piston, wherein a pressure equalization or a hydrostatic support of the piston takes place via a pressure compensation pressure medium flow path. This is inventively formed by a capillary tube which is inserted into the piston. By using such a capillary tube with constant capillary diameter eliminates the need to form a nozzle bore as in the aforementioned prior art. This capillary tube is less susceptible to dirt because it has no radial shoulders and, moreover, the diameter of the capillary tube is larger than that part of the prior art stepped bore over which the nozzle of the pressure compensating pressure fluid flow path is formed. The production of this piston is particularly simple, since only the receiving bore for the capillary tube must be made as a through hole and this is then inserted into the receiving bore.

According to the invention it is particularly preferred if the suction valve is inserted into a space on the working space side end portion, so that the axial length is minimal. In this case, the closing body of the suction valve is preferably designed as a cone, which against a on Inner circumference of the piston formed valve seat is biased.

In a particularly preferred embodiment, the closing body of the suction valve is displaceably guided in the piston and along the capillary tube.

The weight of the piston engine can be minimized if the pistons and also the suction valve closing bodies integrated in them are made of a wear-resistant plastic, for example PEEK.

The capillary tube is preferably designed as a metal tube and is extended at its working-side end portion in the radial direction to a support portion on which a closing spring of the suction valve is supported. The radially expanded region can be formed, for example, by crimping.

It is preferred to support the piston foot via a sliding shoe on a helical or swash plate. In a particularly preferred embodiment, the piston engine is designed as a double swashplate machine or Doppelschrägkolben-machine, so that the axial forces are balanced.

The weight of the piston engine can be further reduced even if the closing body of the pressure valves are made of plastic.

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

• Figur 1 einen Längsschnitt durch eine ventilgesteuerte Doppeltaumelmaschine;
• Figur 2 eine Schemadarstellung der Doppeltaumelmaschine aus Figur 1 zur Erläuterung des Funktionsprinzips;
• Figur 3 eine Detaildarstellung einer Ventilsteuerung aus Fig. 2;
• Figur 4 eine Variante einer Doppeltaumelscheibenmaschine und
• Figur 5 ein Ausführungsbeispiel einer Einfachtaumelscheibenmaschine.

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 longitudinal section through a valve-controlled double tumbling machine;
• FIG. 2 shows a schematic representation of the double wobble machine of FIG. 1 for explaining the functional principle;
• Figure 3 is a detail view of a valve control of Fig. 2;
• FIG. 4 shows a variant of a double swashplate machine and
• Figure 5 shows an embodiment of a single swashplate machine.

In Figure 1, a double swashplate pump 1 is shown in longitudinal section. Such a pump 1 has a rotatably received in a housing 2 cylinder 4, which is traversed axially parallel with a plurality of lying on a common pitch cylinder bores 6. These open in each case in the end faces of the cylinder 4 and each receive two oppositely movable pistons 8, 10. These protrude with a piston foot 12, 14 out of the respective end face of the cylinder 4. The piston 12, 14 is spherical and carries a shoe 16, 18. About these shoes 16 are in Figure 1 from the right end face of the cylinder 4 protruding piston 10 on a first swash plate 20 and the sliding shoes 18 from the left end face (perpendicular to the plane in Figure 1) protruding piston 8 supported on a second swash plate 22. These swash plates 20, 22 are rotatably connected to a drive shaft 24 of the swash plate pump 1, which is mounted via an axial / radial bearing 26 in the housing 2. In such a construction with symmetrically arranged swash plates 20, 22, the axial forces are introduced symmetrically into the shaft and carried by this, so that the housing and the bearing of the moving parts are relieved and thus can be made smaller than in a simple swash plate pump with only one swash plate Case is.

The two swash plates 20, 22 are each arranged in a suction chamber 28, 30, which each open into a suction port 32, 34, which is connected to a tank or the like.

Of the mutually facing end portions of each received in a cylinder bore 6 piston 8, 10, a working space 36 is limited in the axial direction, which increases by the opposite piston movement during the suction stroke and reduced during the compression stroke. The pressurized pressure medium is conveyed in the illustrated embodiment via a respectively a working space 36 associated, arranged radially in the housing 4 pressure valve 38 and a pressure port 40 to the connected consumer. The pressure fluid connection between the working chamber 36 and the suction chamber 28, 30 is controlled via a respective suction valve 42, 44, the closing body - as explained in more detail below - in the associated piston 8, 10, is mounted. D. h., In this embodiment, each working space two suction valves 42, 44 and a pressure valve 38 are assigned. As further shown in FIG. 1, the sliding shoes 12 bearing against each swashplate 20, 22 are positioned relative to one another via a retraction plate 46, 48. These retraction plates 46, 48 are supported on a counter bearing 50, 52, which is biased by a central clamping device 54 in the direction of the respective adjacent swash plate 20, 22, so that the sliding blocks 16, 18 do not lift off the associated swash plate 20, 22 during the suction stroke.

Figure 2 shows a schematic partial representation of the swash plate pump 1 of Figure 1 with the two recorded in a cylinder bore 6 piston 8, 10 the common pressure valve 38 and the two suction valves 42, 44, which are shown in its inner dead center, while Figure 1 shows a position just before the inner dead center shows. Each piston 8, 10 has an approximately cylindrical piston skirt 56, which merges via a constriction 58 in the spherical piston 14 (the pistons of the other side are identically constructed, so that a separate description is omitted). This is in ball-joint-like engagement with the associated shoe 18, which in turn rests with its sliding surface 60 on the end face of the swash plate 22. In order to reduce the friction and for the hydrostatic support of the sliding shoes 18, the piston 10 and the sliding block 18 are penetrated by a pressure medium flow path 22, which opens on the one hand in the working space 36 and on the other hand in the sliding surface 60. This pressure compensating pressure medium flow path is usually provided with a nozzle to dampen the pressure fluctuations during the working cycle. In the illustrated embodiment, this nozzle, which is usually formed by an inner shoulder of the piston, is omitted and instead a continuous capillary tube 64 is used, which will be explained in more detail with reference to FIG. As can also be seen from FIG. 2, the pressure chamber 30 is connected via oblique bores 66 of the constriction area 58 to a space 68 surrounded by the cylindrical portion 56 of the piston 10.

Figure 3 shows an enlarged view of those area in which the valve control with the suction valves 42, 44 and the pressure valve 38 are received. Accordingly, a valve seat 70 is formed on the inner, the receiving space 36 facing annular end face of each piston 8, 10, against which a closing body 72 of the suction valve 42, 44 is biased with its closing cone. Along the adjoining the closing cone cylindrical portion 74 of the closing body 72 longitudinal grooves 76 are formed, via the pressure medium from the space 68 to the valve seat 70, can pass. The maximum outer circumference of the cylindrical part 74 of the closing body 72 corresponds to the diameter of the inner circumferential wall of the space 68, so that the closing body is slidably guided along the inner circumferential wall radially bounding the space 68. The closing cone of the closing body 72 extends somewhat into the working space 36, but the maximum outside diameter of the closing cone is chosen to be slightly smaller than the diameter of the cylinder bore 6, so that the closing body 72 can dip into the cylinder bore 6 during the suction stroke. The closing body 72 is biased with its closing cone by means of a closing spring 80 (see also FIG. 1), which is supported on a radially projecting abutment shoulder 82 of the capillary tube 64 and acts on an inner shoulder 84 of the closing body 72. In the illustrated embodiment, the capillary tube 64 is made of metal, wherein the abutment shoulder 82 can be formed for example by crimping. The outer diameter of this abutment shoulder 82 is selected so that it can dive into the axially limited by the inner shoulder 84 of the closing body 72 at the inner dead center (Figure 3). As can further be seen from FIG. 3, the capillary tube 64 passes through the closing body, so that it is slidingly guided on the capillary tube 68 and also protects it against lateral buckling. A special feature of the solution described is that the closing body 72 of the suction valves 42, 44, the piston 8, 10 and the sliding blocks 16, 18 are made of fiber-reinforced plastic, preferably carbon fiber reinforced PEEK. These components are preferably produced by injection molding, wherein the sliding blocks 16, 18 can be molded directly to the associated piston 8, 10. This is described in the parallel filed application of the applicant (title: piston arrangement). As will be explained in more detail below, the valve body 86 of the common pressure valve 38 is made of plastic, so that the double swashplate pump 1 is designed with minimal weight and minimal moving masses.

As explained above, the suction valves 42, 44 are respectively disposed at the inner end portion of the working piston 8, 10, so that the dead volume is reduced compared to solutions in which the suction valves are provided in the region of the piston foot. The inner diameter of the capillary tubes 64 used is chosen so that the hydrostatic support of the sliding shoes 18 is ensured during the suction and compression stroke. The constant capillary diameter and the smooth walls of the capillary tube 64 provide no attachment surfaces for contamination of the pressure medium, so that this pressure fluid flow path 62 is always open. In the conventional solutions, soiling can attach relatively easily to the necessary for the formation of the nozzle inner stages.

As shown on the left in FIG. 3, the capillary tube 64 terminates in a funnel-shaped extension 87 of the pressure medium flow path 92. This extension 87 is required to maintain the pressure medium connection to the sliding surface 60 during the relative pivoting between the slide shoe 18 and the piston 10 shown in FIG.

The capillary tube 64 has according to the above embodiments, a dual function, on the one hand it forms the pressure fluid flow path 62 and has a throttling effect to compensate for pressure fluctuations, on the other hand it acts as Ventilhubbegrenzung for the closing body 72, which then with its inner shoulder 84 on the abutment shoulder 82 on inner end of the capillary tube 68 runs and thus can not be moved axially.

The pressure valve 38 is arranged in a radially extending through the housing 2 and the cylinder 4 pressure channel 88. This has a radial shoulder, which forms a valve seat 90, against which the plate-shaped valve body 86 is biased by a closing spring assembly 92 so that a return flow from a common pressure port to the working space 36 is prevented. The construction of such plate-shaped valves is known, so that further explanations are unnecessary.

The advantage of the above-described valve control over the conventional constructions with a control plate is that the volumetric efficiency can be improved by eliminating the end control plates and the concomitant reduction of leakage losses. Furthermore, the friction forces are reduced by eliminating the control plate. The relatively soft switching valve elements allow noise reduction and minimizing the dead volume. The above double swashplate pump 1 can be operated without conversion in both directions of rotation, wherein the inventive design with pistons made of plastic 8, 10, valve body 86 and closing body 72 and sliding shoes 16, 18 Die Making the pump simplified, since these components virtually no reworking is required.

FIG. 4 shows a variant of the concept explained with reference to FIGS. 1 to 3. In contrast to the above-described embodiment, the working space is subdivided by a thrust washer 94 inserted into the cylinder into two sub-work spaces 36a, 36b, to each of which a pressure valve 38a, 38b is assigned. Each pressure valve 38a, 38b has a valve body 86a, 86b biased against valve seats 90a, 90b by a common closing spring assembly 92.

The pressure channel 88 then extends as in the above-described embodiment in the radial direction through the cylinder 4 and the housing 2 through to the common pressure port.

In other words, the embodiment illustrated in FIG. 4 differs essentially in that each piston 8, 10 is assigned its own working space 36a, 36b and that the corresponding pressure valves 38a, 38b open not in the radial direction but in the axial direction.

The high-pressure valves of the above-described solutions can be switched out of phase by suitable design in order to achieve a minimization of the pressure pulsation.

Finally, FIG. 5 shows an exemplary embodiment in which the working machine is designed as a single-disc tumbling pump, wherein only the pistons 10 are guided axially displaceably in the cylinder 4 and rest against the single swash plate 22 via the sliding shoes 18. In such a solution, the housing 2 is one-sided with compressive forces acted, advantage is, however, that the pump 1 builds shorter in the axial direction.

The valve control is designed as in the illustrated in Figure 4 embodiment. Accordingly, the suction valves 44 are integrated into the respective pistons 10, the pressure chamber 38 connecting the working chamber 36 with the radial pressure channel 88 is arranged in the axial direction, the closing spring arrangement 92 being supported on the housing 2. With regard to further details regarding the exemplary embodiment according to FIG. 5, reference is made to the exemplary embodiments described above.

Disclosed is a hydraulic piston engine, in particular a Doppelaumelscheibenpumpe, with a plurality of pistons, which are guided displaceably in a cylinder, and each defining a working space in the pressure medium via a suction valve can be supplied and discharged from the pressure medium via a pressure valve. The piston is penetrated by a pressure-compensating pressure medium flow path, which is formed according to the invention by a capillary tube inserted into the piston.

LIST OF REFERENCE NUMBERS

1

Double swash plate pump

2

casing

4

cylinder

6

bore

8th

piston

10

piston

12

piston base

14

piston base

16

shoe

18

shoe

20

1. swash plate

22

2. swash plate

24

drive shaft

26

storage

28

suction

30

suction

32

suction

34

suction

36

working space

38

pressure connection

42

suction

44

suction

46

retraction plate

48

retraction plate

50

Against holding camp

54

jig

56

cylindrical section

58

constriction

60

sliding surface

62

Pressure fluid flow path

64

capillary

66

oblique bore

68

room

70

valve seat

72

closing body

74

cylindrical part

76

longitudinal groove

78

inner circumferential wall

80

closing spring

82

contact shoulder

84

inner shoulder

86

valve body

87

extension

88

pressure channel

90

valve seat

92

Closing spring arrangement

94

thrust washer

Claims (12)

Hydraulic piston machine having a multiplicity of pistons (8, 10) which are displaceably guided in a cylinder (4) and each delimiting a working space (36) into the pressure medium via a suction valve (42, 42) arranged on the piston (8, 10). 44) can be supplied and from the pressure medium via a pressure valve (38) can be discharged, wherein the piston (8, 10) of a pressure compensating pressure fluid flow path (62) is traversed, characterized in that the pressure medium flow path (62) at least partially by a in the Piston (8, 10) inserted capillary tube (64) is limited. Piston engine according to claim 1, wherein the suction valve (42, 44) in a space (68) of a working space side end portion of the piston (8, 10) is inserted. Piston engine according to claim 2, wherein a cone of a closing body (72) of the suction valve (42, 44) on a on the inner circumference of the piston (8, 10) formed valve seat (70) is supported. Piston engine according to claim 2 or 3, wherein the closing body (72) in the piston (8, 10) and / or on the capillary tube (64) is guided. Piston engine according to one of the preceding claims, wherein the closing body (72) and the piston (8, 10) are made of fiber-reinforced plastic. Piston machine according to one of the preceding claims, wherein the capillary tube (64) is made of metal. Piston engine according to one of the preceding claims, wherein a closing spring (80) of the suction valve (42, 44) on the capillary tube (64) is supported. Piston engine according to claim 7, wherein the closing spring (80) is supported on a radially enlarged portion (80) of the capillary tube (64). Piston engine according to claim 8, wherein the extended portion (80) is formed by crimping. Piston engine according to one of the preceding claims, wherein a piston foot (12, 14) via a slide shoe (16, 18) on a helical or swash plate (20, 22) is supported. Piston engine according to claim (10), wherein in the cylinder (4) oppositely arranged pistons (8, 10) are received, which two associated on both sides of the cylinder 4 oblique or swash plates (20, 22) are assigned. Piston engine according to one of the preceding claims, wherein the pressure valve (38) in the cylinder (4) or housing (2) of the machine is arranged, wherein the valve body (86) is also made of fiber-reinforced plastic.

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