DE102012206699B4 - Gear machine with a trough-like recess on the outer surface of the housing - Google Patents

Abstract

The invention relates to a gear machine (10), in particular an external gear pump or external gear motor, with a housing (30), in the interior of which a first and a second gear (12) are arranged, which mesh with one another in external engagement, the first gear (12) with a shaft (14) is connected, which protrudes with a drive pin (15) from the housing (30), wherein the second gear (12) is connected to an axis (16), the axis (16) and the shaft (14 ) are rotatably mounted in two oppositely arranged bearing brackets (50) in associated bearing bores (51), a low-pressure and a high-pressure connection (32; 33) being provided on the housing (30). According to the invention, the housing (30) is on the outer surface provided with a trough-like recess (60).

Description

The invention relates to a gear machine according to the preamble of claim 1.

From the DE 10 2005 056 909 A1 a gear machine is known which can be operated either as a pump or as a motor. The gear machine comprises a housing, in the interior of which a first and a second gear are arranged, which mesh with one another in external engagement. The first gear is connected to a shaft which protrudes with a drive pin from the housing, the second gear being connected to an axle. The first or second gear can be connected in one piece to the shaft or the axle, but it is also possible for the parts mentioned to be designed separately from one another. The axis and the shaft are rotatably mounted in two oppositely arranged position brackets, which seal the two gears at the same time on the end faces against the escape of fluid. A low-pressure and a high-pressure connection are also provided on the housing, the pressure of the hydraulic fluid being higher at the high-pressure connection than at the low-pressure connection when the gear machine is in operation. When the gear machine is operated as a pump, the hydraulic fluid, in particular hydraulic oil, flows from the low-pressure connection to the high-pressure connection. When the gear machine is operated as a motor, the hydraulic fluid flows from the high pressure port to the low pressure port, causing the drive pin to rotate.

It is known that the two gears are displaced by the pressure forces acting in the gear machine, specifically away from the high pressure connection in the direction of the low pressure connection. This leads, especially if the two gears are provided with a sharp edge at the tip diameter, to a running-in effect, which results in an optimally small sealing gap between the tip diameter of the gears and the housing in the area of the low pressure connection. This almost completely prevents hydraulic fluid from flowing past the tooth tips from the high pressure side to the low pressure side of the pump, so that the volumetric efficiency of the gear machine is high. However, the optimum state is only achieved at the maximum operating pressure of the gear machine. As soon as the operating pressure, in particular the pressure at the high-pressure connection, is reduced, the gears shift back in the direction of their unloaded position, so that the sealing gap at the tip diameter increases again, so that the volumetric efficiency decreases compared to that at maximum operating pressure. This behavior is particularly pronounced at low speeds of the gear wheels and at low fluid viscosities.

From the DE 20 2005 010 467 U1 a gear machine is known in which the high-pressure and the low-pressure connection are designed overall like a trough. There is no trough-like depression that is different from the low-pressure connection.

From the DE 20 2009 012 158 U1 a gear machine is known which, analogous to the gear machine according to FIG DE 20 2005 010 467 U1 is executed.

The object of the invention is to increase the volumetric efficiency of the gear machine, in particular at medium operating pressures. The duration of the running-in process should also be shortened.

According to the independent claim, this object is achieved in that the housing is provided with a trough-like depression on the outer surface. Surprisingly, it has been shown that the housing of the gear machine is not only deformed radially outward under the pressure of the hydraulic fluid acting from the inside. Rather, it is precisely in the area of the low-pressure connection that deformation takes place radially inward, towards the gears. This further intensifies the run-in effect described above and at the same time improves the volumetric efficiency in the medium operating pressure range. The proposed trough-like recess changes the deformation behavior of the housing under the action of the fluid pressure acting from the inside so that it no longer deforms radially inward in the area of the low-pressure connection. Ideally, the trough-like recess is designed in such a way that almost no deformation of the housing at all occurs in the area of the low-pressure connection when the operating pressure changes.

The low-pressure connection is arranged at the lowest point of the trough-like depression. It has been shown that the deformations in the area of the low-pressure connection are then very small and in particular not directed inwards when the low-pressure connection is arranged as proposed.

In the dependent claims, advantageous developments and improvements of the invention are specified.

The trough-like depression can be curved with respect to two mutually perpendicular directions. This is to be achieved in particular that the tub-like recess extends only over a comparatively small part of the housing. The rest of the housing should not be weakened by the trough-like depression, so that it is deformed as little as possible by the fluid pressure prevailing inside. Furthermore, the wall thickness of the housing should change as continuously as possible so that increased notch stresses do not occur at any point.

The housing can have a main body, a bearing cap and an end cap, the bearing brackets being slidably received in the main body, the low-pressure and high-pressure ports being arranged on the main body, the trough-like recess being arranged exclusively on the main body. A housing consisting of a main body, a bearing cover and an end cover is from the already addressed DE 10 2005 056 909 A1 known. There the bearing brackets are also slidably received in the main body, on which the low-pressure and high-pressure connections are provided. For the mode of operation of the present invention, the deformation of the housing in the area of the low-pressure connection is mainly important. It has been shown that the bearing cap and the end cap have almost no influence on the corresponding deformation behavior of the main body. It is therefore sufficient if the trough-like depression extends only in the area of the main body.

The tub-like depression can end on all sides at a distance from the edge of the main body. This is intended to ensure that the main body has the full, non-weakened wall thickness, in particular at its front ends on which the said covers are in contact, so that it does not become excessively deformed there by the action of the internal pressure. A deformation at the mentioned front ends could lead to the gear machine no longer being tightly closed at the contact point between the main body and the end or bearing cover, especially if the gear machine is operated at a high operating pressure.

The trough-like indentation can be curved exclusively in the direction of the axes of rotation of the gearwheels, being straight perpendicular thereto. A trough-like depression of this type is particularly easy to produce since it is curved in only one direction. This curvature can easily be produced, for example, by means of a cylindrical milling cutter. At the same time, it can be achieved that the main body is not weakened in the area of its front ends.

In an embodiment not belonging to the invention, the low-pressure and high-pressure connections can be arranged away from the trough-like recess. It has already been proposed above to provide the low-pressure connection at the lowest point of the trough-like recess. It has been shown that other locations of the tub-like depression also produce the desired effect. It is crucial, however, that the housing is not significantly weakened in the areas in which there are very high internal pressures so that it does not become excessively deformed. The trough-like depression must therefore hardly weaken the area of the high-pressure connection.

In an embodiment not belonging to the invention, several trough-like depressions can be provided. It is preferably thought that the tub-like depressions are mirror-symmetrically opposite one another. Insofar as the trough-like depression is arranged away from the low-pressure and high-pressure connections, the trough-like depression lies outside the plane of symmetry of the housing. In order to nevertheless achieve a symmetrical deformation of the housing in the area of the low-pressure connection, several trough-like depressions are required. As a result of the mirror-symmetrical arrangement of the trough-like depressions, an equally mirror-symmetrical deformation of the housing is achieved from the start. However, asymmetrical arrangements of the trough-like depressions are also conceivable.

The housing can be designed to be less rigid in the area of the low-pressure connection than in the area of the high-pressure connection. The trough-like depression according to the invention inevitably locally reduces the rigidity of the housing. Although it is conceivable to compensate for this effect by other constructive measures, it has been shown that precisely this local reduction in the rigidity of the housing in the area of the low-pressure connection has a favorable effect on the gear head gaps there at medium operating pressures.

The wall thickness of the housing is made thinner in the area of the low-pressure connection than in the area of the high-pressure connection. In principle, it is also conceivable to achieve the local reduction in rigidity by means of a housing made of different materials. However, a housing made of a single material with a locally reduced wall thickness can be produced much more easily.

• 1 eine Explosionsdarstellung einer Zahnradmaschine gemäß dem Stand der Technik, welche durch die vorliegende Erfindung verbessert werden soll;
• 2 eine perspektivische Ansicht der Zahnradmaschine gemäß einer ersten Ausführungsform der Erfindung;
• 3 einen Teilquerschnitt der Zahnradmaschine nach 2 entlang der Linie A-A in 2; und
• 4 eine perspektivische Ansicht einer Zahnradmaschine gemäß einer zweiten Ausführungsform der Erfindung, wobei diese entlang zweier senkrechter Symmetrieebenen aufgeschnitten ist.

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

• 1 an exploded view of a gear machine according to the prior art, which is to be improved by the present invention;
• 2 a perspective view of the gear machine according to a first embodiment of the invention;
• 3 a partial cross section of the gear machine 2 along the line AA in 2 ; and
• 4th a perspective view of a gear machine according to a second embodiment of the invention, this being cut open along two perpendicular planes of symmetry.

1 shows an exploded view of a gear machine 10 according to the prior art, which is intended to be improved by the present invention. The gear machine 10 includes a housing 31 ; 40 ; 41 which consists of a main body 31 exists, at the two opposite ends 34 a bearing cap 40 and an end cover 41 are arranged. The case 31 ; 40 ; 41 is held by four bolts 44 held together by those in 1 only one is shown.

In the main body 31 are mirror-symmetrical bearing glasses 50 and the first and second gears 12th ; 13th recorded. The interior 11 which from the main body 31 and the two camp glasses 50 is enclosed is substantially fluid-tight to the first and second gears 12th ; 13th customized. The camp glasses are in particular 50 on the opposite flat end faces of the first and second gears 12th ; 13th at, with the main body 31 on the tip diameter of the first and second gears 12th ; 13th is applied.

The first gear 12th is integral with a shaft 14th formed, which through the bearing cap 40 through with a drive pin 15th out of the case 31 ; 40 ; 41 protrudes. In the bearing cap 40 is a radial shaft seal 43 arranged, which with its sealing lip sealingly on the shaft 14th is applied so that no hydraulic fluid can escape there. Between the main body 31 and the bearing or end cover 40 ; 41 is a cover seal each 42 provided in the form of an O-ring made of rubber. The axis 16 and the wave 14th are in both bearing glasses 50 in an assigned bearing bore 51 rotatably mounted. In the bearing bore 51 a separate bearing bush is arranged so that when the gear machine 10 runs at low speed, there is no excessive wear on the corresponding plain bearings.

The axial seal should also be noted 53 and the associated support ring 54 on the back of the two bearing glasses 50 . The axial seal 53 is on the assigned bearing or end cover 40 ; 41 at. On the opposite side it lies on the support ring 54 which in turn depends on the pressure at the high pressure connection against the axial seal 53 is pressed. The axial seal 53 delimits two pressure fields from each other, in each of which the pressure at the high pressure connection 33 or the pressure at the low pressure connection 32 works. This gets the in the main body 31 displaceably received bearing glasses 50 against the flat side surface of the first and second gears 12th ; 13th pressed so that a pressure-tight seal is given.

The low and high pressure connection 32 ; 33 are on the main body 31 arranged. In the in 1 They are delivered with a separate plug each 35 closed, with the low pressure connection 32 the larger diameter and therefore the larger sealing plug 35 having.

2 Figure 13 is a perspective view of a gear machine 10 according to a first embodiment of the invention. This in 2 visible housing 30th the gear machine 10 replaces the housing of the gear machine 1 . Except for the differences described below, the housing of the gear machines are according to 1 and 2 designed identically, so that reference can be made to the above statements.

The case 30th consists of the main body 31 , at its forehead 34 the bearing cap 40 and the end cover 41 are attached so that the gears are tightly enclosed inside. On a side surface of the main body 31 is the low pressure connection 32 arranged at the deepest point of a trough-like recess according to the invention 60 . The tub-like recess 60 is with respect to two directions of curvature 61 ; 62 which are aligned perpendicular to one another, curved, in particular curved in the shape of a circular arc, formed. With regard to the second direction of curvature 62 the tub-like depression extends 60 not across the entire width of the main body 31 so that this one at his forehead 34 has the full wall thickness. There's a gap there 64 between the tub-like depression 60 and the edge of the main body 31 available. The low pressure connection 32 is provided with an internal thread which is surrounded by a countersink so that the corresponding fluid connection line can be screwed tightly.

3 shows a partial cross section of the gear machine 2 along the line AA in 2 . Only the main body is shown 31 . It can be seen that the tub-like depression 60 with respect to the first direction of curvature 61 is curved in a circular arc. This results in the area of the low pressure connection 32 a thinnest wall thickness 66 . At the edge of the tub-like depression 60 however, is the thickest, unweakened wall thickness 65 of the main body 31 available. This thickest wall 65 has the main body 31 also in the area of the high pressure connection.

The contour of the interior should also be noted 11 which is adapted to the circular first or second gear.

4th Figure 13 is a perspective view of a gear machine 10 according to an embodiment not belonging to the invention. A quarter of the gear machine is more accurate 10 shown, the remainder of the gear machine, not shown 10 is designed mirror-symmetrically with respect to the two perpendicular cutting planes. Except for the differences described below, the housing of the gear machines are according to 1 and 4th designed identically, so that reference can be made to the above statements.

The tub-like depression 60 is now away from the low pressure and high pressure connections 32 ; 33 arranged. Due to the mirror symmetry of the housing, there are two trough-like recesses 60 provided so that in the area of the low pressure connection 32 results in a symmetrical deformation of the housing. The trough-like depression is exclusively with respect to a first direction of curvature 61 that are parallel to the axes of rotation of the first and second gears 12th is aligned, curved, in particular curved in a circular arc. Perpendicular 63 to the first direction of curvature 61 is the tub-like depression 60 straight, being parallel to the central axis of the low and high pressure connections 32 ; 33 runs.

Reference should also be made to the in 4th marked sealing area 67 . The first gear is in this area 12th with its head clearance diameter sealing to the main body 31 the gear machine 10 at. In particular, it is caused by the area of the high pressure connection 33 high pressures prevailing against the sealing area 67 pressed because of the low pressure connection 32 only a slight counter pressure acts. Away from the sealing area mentioned 67 there are larger sealing gaps at the tip diameter due to the aforementioned shifting of the gears. Due to the mirror symmetry of the gear machine 10 there are similar sealing conditions on the second gear.

List of reference symbols

10

Gear machine

11

inner space

12

first gear

13th

second gear

14th

wave

15th

Drive journal

16

axis

30th

casing

31

Main body

32

Low pressure connection

33

High pressure connection

34

Front end

35

Sealing plug

40

Bearing cap

41

End cover

42

Cover seal

43

Radial shaft seal

44

Bolt

50

Bearing glasses

51

Bearing bore

53

Axial seal

54

Support ring

60

tub-like depression

61

first direction of curvature

62

second direction of curvature

63

Direction of the straight course

64

Distance to the edge of the main body

65

thickest wall thickness

66

thinnest wall thickness

67

Sealing area

Claims (6)

Gear machine (10), in particular external gear pump or external gear motor, with a housing (30), in the interior (11) of which a first and a second gear (12; 13) are arranged, which mesh with one another in external engagement, the first gear (12) is connected to a shaft (14) which protrudes from the housing (30) with a drive pin (15), the second gear wheel (13) being connected to an axis (16), the axis (16) and the shaft ( 14) are rotatably mounted in two oppositely arranged bearing brackets (50) in associated bearing bores (51), a low-pressure and a high-pressure connection (32; 33) being provided on the housing, characterized in that the housing (30) on the outer surface is provided with a trough-like recess (60), the Low-pressure connection (32) is arranged at the deepest point of the trough-like recess (60), so that the wall thickness (66) of the housing (30) in the area of the low-pressure connection (32) is thinner than in the area of the high-pressure connection (33). Gear machine after Claim 1 , characterized in that the trough-like recess (60) is curved with respect to two mutually perpendicular directions (61; 62). Gear machine according to one of the preceding claims, characterized in that the housing (30) has a main body (31), a bearing cover (40) and an end cover (41), the bearing brackets (50) being slidably received in the main body (31) , wherein the low-pressure and the high-pressure connection (32; 33) are arranged on the main body (31), the trough-like recess (60) being arranged exclusively on the main body (31). Gear machine after Claim 3 , related to Claim 2 , characterized in that the trough-like depression (60) ends on all sides at a distance (64) from the edge of the main body (31). Gear machine after Claim 3 , characterized in that the trough-like recess (60) is curved exclusively in the direction (61) of the axes of rotation of the gear wheels (12; 13), being perpendicular (63) straight to it. Gear machine according to one of the preceding claims, characterized in that the housing (30) is designed to be less rigid in the area of the low-pressure connection (32) than in the area of the high-pressure connection (33).

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