DE102012206698A1 - Hydrostatic positive-displacement engine, has housing comprising housing portions extending in plane separating surface abutting each other, and plane separating surface incorporating rotational axes of gear wheels - Google Patents

Abstract

The engine (10) has two gear wheels (20, 23) comprising two parallel rotational axes (21, 24) that mesh with one another such that a housing (30) is surrounded by two fluid connectors (11, 12), so that rotating movement of a fluid stream is accommodated between the fluid connectors. The housing comprises two housing portions (50, 52) extending in a plane separating surface (32) abutting each other. The plane separating surface incorporates the rotational axes of two gear wheels. One of the gear wheels comprises a drive shaft that stands out from the housing. An independent claim is also included for a method for manufacturing housing portions of a hydrostatic positive-displacement engine.

Description

The invention relates to a hydrostatic displacement machine according to the preamble of claim 1 and a method for their preparation.

From the DE 41 24 466 C2 is a hydrostatic displacement machine known. The hydrostatic displacement machine comprises a first and a second external gear whose axes of rotation are parallel and which mesh with each other. The two gears are surrounded by a housing. The housing is almost gap-free at the tip diameter of the external gears. The housing comprises two separate, planar intermediate plates, which are aligned perpendicular to the gears and arranged between the side surfaces of the gears and the housing. The free spaces between the teeth of the gears are thus substantially sealed by the housing, so that a rotational movement of the gears is accompanied by a fluid flow between a first and a second fluid port. When the hydrostatic positive displacement machine is operated as a pump, the drive shaft of the first gear is driven by a drive device, such as an electric motor, wherein the fluid, preferably hydraulic oil, flows from the fluid port at the lower pressure to the fluid port at the higher pressure. When the positive displacement machine is operated as a motor, the fluid flows from the fluid port at the higher pressure to the fluid port at the lower pressure, with the drive shaft of the first gear being rotated.

The present housing is composed of a plurality of housing parts, which have a plurality of planar separation surfaces, which are all aligned perpendicular to the axes of rotation of the gears. This design of the housing is common practice, since the corresponding housing parts are easy to produce with the required high accuracy in order to achieve the smallest possible gaps between the gears and the housing. As a result, the leakage is small and therefore the efficiency of the hydrostatic positive displacement machine high.

The disadvantage of the known hydrostatic displacement machine is that the distance and the parallelism of the axes of rotation of the two gears is determined by many components. Each of these components has a manufacturing tolerance, which add up in the worst case, so that said center distance or said parallelism has a high dimensional tolerance. As a result, the leaks increase and the efficiency of the hydrostatic displacement machine decreases.

The object of the invention is to increase the efficiency of the hydrostatic displacement machine. At the same time, the number of components and therefore the production cost should be minimized.

According to the independent claim, this object is achieved in that the flat parting surface contains the axes of rotation of the first and the second gear. Accordingly, the first and the second housing part respectively enclose the first and the second gear like a trough. In each of the housing parts mentioned one half of all rotary bearings for the gears is arranged. The axial distance of the gears thus results solely from the distance of said halves of the pivot bearing. Since these are arranged on a single component, only the dimensional tolerance of this one component for the dimensional tolerance of the axial spacing and the angular error of the axes is decisive. Long tolerance chains do not occur. As a result, small leaks occur and the efficiency of the hydrostatic positive displacement machine is high. As far as it is mentioned that the separation surface contains the axis of rotation, so should also be included cases in which the axes of rotation are minimally adjacent to the interface, as far as the functionality of the hydrostatic displacement machine is not affected.

It should be noted that the first and second housing parts do not necessarily abut each other directly. Rather, it may be thought that between the first and the second housing part, a seal is arranged, which, however, does not affect the parallel alignment of said housing parts. In this case, for example, be thought of brushing the housing parts with a liquid sealant, which cures after assembly to a thin sealing layer.

In the dependent claims advantageous refinements and improvements of the invention are given.

The first gear may have a drive shaft which protrudes from the housing, wherein a third housing part is provided, which surrounds the drive shaft, wherein the third housing part is attached from the outside to the first and the second housing part, wherein the third housing part fastening means for a drive device having. The drive device may be, for example, an electric motor, which is optionally equipped with a gear transmission. Such drive devices are offered in a conspicuous variety on the market, they differ in particular with regard to the fasteners for the driven assembly. In the proposed hydrostatic displacement machine, it is sufficient to the third housing part to adapt the planned drive device. The first and the second housing part, however, can be made the same regardless of the drive device and thus produced inexpensively in large quantities.

There may be provided an elongated seal having a constant cross-sectional shape disposed in the interface between the first and second housing parts, the elongated seal surrounding the first and second gears. The seal prevents hydraulic fluid from escaping from the housing in the area of the interface. In this case, the elongated seal can optionally be formed endless or composed of several pieces. An interruption of the seal comes into consideration at the points at which the housing has openings to the outside, so for example on the drive shaft of the first gear or on the closure means in the second gear.

The second gear may have an outer toothing and two circular cylindrical bearing journals, wherein in the housing a first and a second bearing bore for the two said bearing pins is provided, wherein the first bearing bore is in the form of a blind hole, wherein the second bearing bore to the outer surface of the housing is open, wherein a separate closure means is provided, which closes the second bearing bore to the outside. As will be shown below, the housing parts should preferably be produced with the aid of a form milling cutter. For this form cutter can be driven in a suitable manner, the housing must have corresponding openings. In the area of the first gear, the opening for the drive shaft is sufficient. In the area of the second gear, however, as proposed, a separate opening must be provided. This must later be tightly closed with the aid of the closing means, so that the hydrostatic displacement machine can fulfill its function. As closure means, for example, a screw plug into consideration.

The first and / or the second gear may comprise at least one circular cylindrical bearing journal, which is received in an associated, separate annular bearing bush, wherein the bearing bush consists of at least two halves, which abut against each other at the flat parting surface, while firmly held in the associated housing part are. As will be shown below, in one embodiment of the invention, the first and the second gear itself are used for producing the associated recess in the first and in the second housing part. To ensure that they are accurately guided during the machining process, it is necessary that the first and the second housing part are fixedly provided with corresponding pivot bearings for said gears. This can be achieved by the proposed bushings, which are divided in half. Instead of the separate multi-piece bushings, it is also conceivable to store the bearing pins directly to the housing halves or in a one-piece bearing bushing.

At least one separate, flat intermediate plate may be provided, which is aligned perpendicular to the axes of rotation of the first and the second gear, wherein it is arranged between the first and the second gear and the housing. By the intermediate plate a good seal on the side surfaces of the gears should be achieved in a known manner. This is particularly necessary if the hydrostatic displacement machine is operated at pressures greater than 35 bar.

• – Herstellung eines Rohteils für das erste und das zweite Gehäuseteil, welches die ebene Trennfläche aufweist,
• – Gleichzeitige Relativverschiebung der genannten Rohteile quer zur ebenen Trennfläche, bis diese an der Trennfläche aneinander anliegen, wobei zwischen den Rohteilen wenigstens ein rotierender Formfräser angeordnet ist, der zur Herstellung der Ausnehmungen für das erste bzw. das zweite Zahnrad ausgebildet ist.

The first and the second housing part of the hydrostatic displacement machine according to the invention can be produced by a method which comprises the following steps:

• - Production of a blank for the first and the second housing part, which has the flat separation surface,
• - Simultaneous relative displacement of the said blanks transversely to the flat parting surface until they abut against each other at the parting surface, wherein between the blanks at least one rotary forming cutter is arranged, which is designed for producing the recesses for the first and the second gear.

Thus, the recesses for the first and the second gear on the first and on the second housing part are produced simultaneously in a single operation and thus cost. In this case, the form cutter is loaded symmetrically, so that a high manufacturing accuracy can be achieved.

The first and / or the second gear may be formed sharp-edged at the transition between the tip circle diameter and the tooth flank, wherein the form cutter is formed by the first and the second gear. The recesses for the first and the second gear are thus produced in the anyway required mounting of the hydrostatic displacement machine. A separate form cutter is not required. The gears are preferably made of steel, which is hardened at least on the surface. They are thus readily suitable to process the first and the second housing part, which are preferably made of aluminum. By the mentioned sharp edge, the desired chip is lifting off Material removal causes. This production process is particularly cost-effective. At the same time, the recesses are particularly well adapted to the gears installed therein, so that only small leaks occur, which in turn has a high efficiency of the hydrostatic displacement machine result.

The blanks of the first and second housing parts may have preformed recesses for the first and the second gear. In particular, it is intended to produce the said blanks in the casting process, wherein said preformed recesses have only a small oversize compared to the final shape. By the gears so that only a small material removal must be made, thereby shortening the break-in period of the gear machine. Consequently, their manufacturing costs are low.

The movement of the blanks of the first and the second housing part transversely to the separating surface can be effected by bolts, which engage in both blanks. The housing parts mentioned are preferably held together in the finished mounted hydrostatic displacement machine by bolts. It is precisely these bolts can be used to carry out the above-proposed manufacturing movement for said housing parts. A complex manufacturing device is therefore not required.

The invention will be explained in more detail below with reference to the accompanying drawings. It shows:

1 a sectional view of a hydrostatic Verdrängermaschine invention, wherein the sectional plane transverse to the axes of rotation of the first and the second gear;

2 a sectional view of the hydrostatic displacement machine according to 1 wherein the sectional plane is the interface; and

3 a rough schematic representation of the inventive method for producing the first and the second housing part.

1 shows a sectional view of a hydrostatic Verdrängermaschine invention 10 , wherein the sectional plane transverse to the axes of rotation 21 ; 24 the first and the second gear 20 ; 23 runs. The two gears 20 ; 23 are provided with external teeth, with only a single tooth is shown for simplicity. The tooth flanks 26 the gears 20 ; 23 For example, they may have an involute profile. But it can also be selected other profile shapes, as long as it is ensured that between the circular cylindrical tip diameter 27 and the tooth flanks 26 a sharp edge 28 results. At least the tooth flanks 26 the first and the second gear 20 ; 23 made of steel are preferably surface hardened.

The axes of rotation 21 ; 24 of the first and the second gear are aligned parallel to each other, wherein they are in the flat parting surface 32 between the first and the second housing part 50 ; 52 are arranged. The recesses 58 ; 59 in the housing parts 50 ; 52 from an aluminum wrought alloy are with high accuracy at the tip diameter 27 the associated first and second gear 20 ; 23 adapted, so that there occur at most very small leaks.

The hydraulic fluid may, for example, at the first fluid port 11 be sucked in at low pressure, taking it from the gears 20 ; 23 to the second fluid port 12 is promoted, where there is a higher pressure. The aim is that the smallest possible amount of fluid back to the first fluid port 11 flows. For this it is important that the distance between the axes of rotation 21 ; 24 is manufactured with the highest possible accuracy. This is precisely the proposed arrangement of the flat parting surface 32 reached.

In the interface 32 between the first and the second housing part 50 ; 52 For example, an elongated rubber seal having a constant circular cross-sectional shape is disposed. In the first and the second housing part 50 ; 52 are for this purpose to the seal 33 provided adapted grooves, such that the seal is installed under bias.

Next are between the first and the second housing part two cylindrical pins 35 provided so that they are aligned exactly to each other.

2 shows a sectional view of the hydrostatic Verdrängermaschine after 1 , where the cutting plane is the interface 32 is. Accordingly, the first housing part 50 in 2 not hatched. On the first and the second housing part 50 is a third housing part 70 attached, which is the drive shaft 22 of the first gear 20 surrounds. On the third housing part 70 are several fasteners 71 for a (not shown) driving device, which may be formed for example as threaded holes or as through holes in a flange. In this case, a plurality of fastening means are preferably provided, which are arranged uniformly distributed on a common pitch circle. In addition, one with respect to the axis of rotation 21 of the first gear 20 circular cylindrical centering geometry be provided so that the drive device can be aligned exactly.

The already mentioned seal 33 in the form of an elongated rubber cord with a circular cross-section surrounds the first and the second gear 20 ; 23 Completely. In the area of the radial shaft seal 34 and the closure means 37 is the seal 33 interrupted, so that the seal consists of two parts in total. Here is the seal 33 installed so that they are preloaded on the radial shaft seal 34 and the closure means 37 is present, which is surrounded by an O-ring. The radial shaft seal 34 lies with its sealing lip on a particularly smooth sealing surface on the drive shaft 22 on, so that there is no hydraulic fluid can escape.

The first and the second gear 20 ; 23 each have two circular cylindrical journals 25 on, on opposite sides of the relevant gear 20 ; 23 are arranged. The drive shaft 22 forms one of these journals 25 ,

Each journal 25 is an annular bearing bush 38 assigned, which is composed of two halves, located in the interface 32 touch. Accordingly, the bushings 38 in 2 not hatched. The aforementioned halves of the bearing bush 38 are permanently installed in the associated housing part, for example, glued. But it can also be thought of, one-piece bushings 38 in advance on the journals 25 to mount, with the bearing bushes together with the first and the second gear 20 ; 23 in the case 30 to be built in.

The second gear 23 is a first and a second bearing bore 56 ; 57 assigned, in which the relevant bearing bushes 38 are included. The first bearing bore 56 is designed in the form of a blind hole, so that the housing 30 There is tightly closed. The second bearing bore 57 is in contrast to the outer surface 31 of the housing 30 open towards, so in this area the drive of with respect to 3 can be done in more detail form mill. So that at this point in the subsequent operation of the hydrostatic displacement machine no hydraulic fluid leaks, is a closure means 37 provided, which may be formed for example in the form of a screw plug.

Between the opposite side surfaces of the first and the second gear 20 ; 23 and the housing 30 can each have a separate, flat intermediate plate 72 arranged so that the relevant areas of the gears 20 ; 23 are sealed well at high fluid pressure. Next is on the hole 55 to indicate in the first and in the second housing part. These holes 55 serve to receive bolts, which hold the first and the second housing part together. In this case, a counterbore is provided in the one housing part, wherein in the other housing part a threaded blind hole is provided.

3 shows a rough schematic representation of the inventive method for producing the first and the second housing part. The blanks 51 ; 53 of the first and the second housing part are preferably made by casting or forging of an aluminum alloy, wherein the separation surface 32 Span is processed lifting. The recesses (No. 58 ; 59 in 1 ) For the first and the second gear preferably as near net shape produced. The final contour is made by means of a form cutter 20 ; 23 manufactured, the shape of which is designed so that said recesses can be made in one operation. The form cutters may optionally be special tools. But it is also possible that the first and the second gear 20 ; 23 even be used as a form cutter. The sharp edge (No. 28 in 1 ) between the tip diameter and the tooth flanks is used as a cutting edge. Since the steel gears are preferably hardened in this area, said sharp edge is capable of machining the aluminum housing. As far as this option is used, the housing is preferably filled with fluid, which is below the planned operating pressure of the hydrostatic displacement machine. As a result, the housing is widened somewhat elastically, so that the gap between the tip circle diameter of the gears and the housing has the optimum width precisely at the said operating pressure. In order to avoid later disassembly, the hydraulic displacement machine is working through the gears 20 ; 23 preferably prefabricated.

In the above-described machining operation, the form cutters 20 ; 23 according to the in 3 Plotted arrows in a pure rotary motion. The individual form cutters can be used successively. In order to save time, the form cutters are preferably used simultaneously.

While the form cutters 20 ; 23 turn, the blanks become 51 ; 53 simultaneously moving towards each other in a rectilinear motion until they touch at the parting surface. In this case, the recesses for the first and the second gear Span are lifted off finishing.

The movement of the blanks can optionally by a special (not shown) Device to be executed. But it can also be thought of the already existing bolts 36 to use, which are provided for the fixed connection of the first and the second housing part. In particular, it is conceivable that the blanks are brought by the device in a position which is very close to the end position, wherein by the bolts 36 the residual path is brought about until the interfaces 32 abut each other. In this way it can be avoided that the housing parts deform unevenly due to the cutting forces, whereby the machining accuracy could suffer.

LIST OF REFERENCE NUMBERS

10

hydrostatic displacement machine

11

first fluid connection

12

second fluid connection

13

engagement area

20

first gear

21

Rotary axis of the first gear

22

drive shaft

23

second gear

24

Rotary axis of the second gear

25

pivot

26

tooth flank

27

Tip diameter

28

sharp edge

30

casing

31

outer surface

32

level interface

33

poetry

34

Radiwalwellendichtring

35

straight pin

36

bolts

37

closure means

38

bearing bush

50

first housing part

51

Raw part of the first housing part

52

second housing part

53

Blank of the second housing part

55

Bore for bolts

56

first bearing bore

57

second bearing bore

58

Recess for the first gear

59

Recess for the second gear

70

third housing part

71

fastener

72

intermediate plate

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4124466 C2 [0002]

Claims (10)

Hydrostatic displacement machine ( 10 ) with a first and a second gear ( 20 ; 23 ), the parallel axes of rotation ( 21 ; 24 ) and meshing with each other, thereby being from a housing ( 30 ) with a first and a second fluid connection ( 11 ; 12 ) are surrounded, that their rotational movement with a fluid flow between the first and the second fluid port ( 11 ; 12 ), the housing ( 30 ) a first and a second housing part ( 50 ; 52 ) located on a plane separating surface ( 32 ) abut each other, characterized in that the plane separating surface ( 32 ) the axes of rotation ( 21 ; 24 ) of the first and the second gear ( 20 ; 23 ) contains. Hydrostatic displacement machine according to claim 1, characterized in that the first gear ( 20 ) a drive shaft ( 22 ), which from the housing ( 30 protrudes), wherein a third housing part ( 70 ) is provided, which the drive shaft ( 22 ), wherein the third housing part ( 70 ) from the outside to the first and the second housing part ( 50 ; 52 ), wherein the third housing part ( 70 ) Fastening means ( 71 ) for a drive device. Hydrostatic displacement machine according to one of the preceding claims, characterized in that an elongated seal ( 33 ) is provided with a constant cross-sectional shape, which in the separation surface ( 32 ) between the first and the second housing part ( 50 ; 52 ) is arranged, wherein the elongated seal ( 33 ) the first and the second gear ( 20 ; 23 ) surrounds. Hydrostatic displacement machine according to one of the preceding claims, characterized in that the second gear ( 23 ) an outer toothing and two circular cylindrical bearing journal ( 25 ), wherein in the housing ( 30 ) a first and a second bearing bore ( 56 ; 57 ) for the two bearing journals ( 25 ), wherein the first bearing bore ( 56 ) in the form of a blind hole, wherein the second bearing bore ( 57 ) is open to the outer surface of the housing, wherein a separate closure means ( 37 ) is provided, which the second bearing bore ( 57 ) closes to the outside. Hydrostatic displacement machine according to one of the preceding claims, characterized in that the first and / or the second gear ( 20 ; 23 ) at least one circular cylindrical journal ( 25 ), which in an associated, separate, annular bearing bush ( 38 ), the bearing bush ( 38 ) consists of at least two halves, which at the flat parting surface ( 32 ) abut each other while firmly in the associated housing part ( 50 ; 52 ) are held. Hydrostatic displacement machine according to one of the preceding claims, characterized in that at least one separate, flat intermediate plate ( 72 ) is provided, which perpendicular to the axes of rotation ( 21 ; 24 ) of the first and the second gear ( 20 ; 23 ), wherein between the first and the second gear ( 20 ; 23 ) and the housing ( 30 ) is arranged. Method for producing the first and the second housing part ( 50 ; 52 ) of a hydrostatic displacement machine ( 10 ) according to one of the preceding claims, comprising the steps - production of a blank ( 51 ; 53 ) for the first and the second housing part ( 50 ; 52 ), which the plane separation surface ( 32 ), - Simultaneous relative displacement of said blanks ( 51 ; 53 ) across the plane separating surface ( 32 ), until at the interface ( 32 ) abut each other, wherein between the blanks ( 51 ; 53 ) at least one rotary forming cutter is arranged, which is used for the production of the recesses ( 58 ; 59 ) for the first and the second gear ( 20 ; 23 ) is trained. A method according to claim 7, characterized in that the first and / or the second gear ( 20 ; 23 ) at the transition between the tip diameter ( 27 ) and the tooth flank ( 26 ) are sharp-edged, wherein the form cutter of the first and the second gear ( 20 ; 23 ) is formed. Method according to claim 7 or 8, characterized in that the blanks ( 51 ; 53 ) of the first and the second housing part ( 50 ; 52 ) preformed recesses ( 58 ; 59 ) for the first and the second gear ( 20 ; 23 ) exhibit. Method according to one of claims 7 to 9, characterized in that the movement of the blanks ( 51 ; 53 ) of the first and the second housing part ( 50 ; 52 ) across the interface ( 32 ) by bolts ( 36 ), which in both blanks ( 51 ; 53 ) intervene.

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