US20120156080A1

US20120156080A1 - Hydraulic Toothed Wheel Machine

Info

Publication number: US20120156080A1
Application number: US13/256,072
Authority: US
Inventors: Marc Laetzel; Michael Wilhelm; Dietmar Schwuchow; Guido Bredenfeld; Stefan Cerny; Sebastian Tetzlaff; Klaus Griese
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2009-03-12
Filing date: 2010-02-25
Publication date: 2012-06-21
Also published as: WO2010102723A3; DE102009012916A1; WO2010102723A2; BRPI1011690A2; JP2012519799A; JP5502909B2; EP2406496A2; CN102362073A

Abstract

A toothed wheel machine including a housing for receiving two meshing toothed wheels. The toothed wheels are axially mounted in a sliding manner by axial surfaces between bearing bodies received in the housing, and radially by a bearing shaft received in the bearing bodies. Hydraulic mechanical forces are generated during the operation of the toothed wheel machine, an axial force component of the forces acting on each toothed wheel in the same axial direction. In order to counteract said axial force component, a pressure field is provided between at least one axial surface of one of the toothed wheels in the direction of the action of the axial force component, and the bearing body adjacent to the at least one axial surface.

Description

The invention relates to a hydraulic toothed wheel machine in accordance with the preamble of patent claim 1.
EP 1 291 526 A2 shows a toothed wheel machine having a housing in which two intermeshing toothed wheels supported in bearing bushes or bearing bodies are arranged, the housing being closed at the ends by a first and a second housing cover respectively. The toothed wheels are each supported in a sliding manner axially by two axial surfaces between the bearing bodies and radially by respective bearing shafts accommodated in the bearing bodies. During the operation of the toothed wheel machine, hydraulic and mechanical forces act on the toothed wheels along the same toothed wheel longitudinal axis in each case. To ensure that the first bearing body, which lies in the direction of action of the forces, is not pushed beyond the axial surfaces of the toothed wheels, between the toothed wheels and the first housing cover, and that only a small sliding gap occurs between the toothed wheels and the second bearing body, a counter-force is applied to the toothed wheels and to the first bearing body. This counter-force is larger than the hydraulic and mechanical forces, with the result that the first bearing body is pressed against the toothed wheels, the toothed wheels are pressed against the second bearing body, and the second bearing body is pressed against the second housing cover. All the resultant forces on the bearing bodies and the toothed wheels thus act in the direction of the second housing cover.
The counter-force on the toothed wheels is applied via pistons acting on the bearing shafts. The pistons are accommodated in a sliding manner, approximately coaxially with respect to the toothed wheel longitudinal axis, in an intermediate cover arranged between the first housing cover and the housing and rest by means of a first piston end face against a shaft end face of the bearing shafts which faces in the direction of the first housing cover and are each subjected to pressure by way of a second piston end face. The counter-force is applied to the first bearing body by way of a pressure field formed between the bearing body and the intermediate cover.
The disadvantage with this solution is that the entire assembly of bearing bodies and toothed wheels is pressed onto the second housing cover of the toothed wheel machine, with the result that the second housing cover and the housing are subjected to very high and uneven loads. The pressing together of the toothed wheels and the bearing bodies results in very high wear between the axial surfaces of the toothed wheels and the bearing bodies. Moreover, the application of the counter-force to the bearing shafts and the bearing bodies requires a high outlay in terms of apparatus, involving a large number of components.
It is the object of the present invention to provide a hydraulic toothed wheel machine which is simple in terms of the apparatus involved and is constructed using a small number of components and exhibits low wear.
This object is achieved by a hydraulic toothed wheel machine in accordance with the features of patent claim 1.
According to the invention, a toothed wheel machine has a housing for accommodating two intermeshing toothed wheels. These are supported in a sliding manner axially by axial surfaces between bearing bodies accommodated in the housing and radially by respective bearing shafts accommodated in the bearing bodies. During the operation of the toothed wheel machine, an axial force component of a force resulting from hydraulic and mechanical forces arising during operation acts on each toothed wheel in the same axial direction. At least one pressure field is provided between at least one axial surface of a toothed wheel, said axial surface lying in the direction of action of the axial force component, and the bearing bodies adjoining the at least one axial surface.
This solution has the advantage that a counter-force acting against the axial force component can be applied to the toothed wheels by means of the pressure field, without additional components. Moreover, the pressure field reduces the axial force component acting as a contact pressure force on the toothed wheels, thereby reducing the sliding friction between the toothed wheels and the bearing bodies lying in the direction of action of the axial force component and minimizing wear.
The toothed wheels are preferably helically toothed.
In a preferred embodiment, a pressure field is provided between each of those axial surfaces of the toothed wheels which lie in the direction of action of the axial force component and those sliding surfaces of the bearing body which lie opposite the axial surfaces. This has the advantage that the pressure fields can be of different sizes, making it possible to apply different pressure forces to each toothed wheel.
The pressure fields can simply be designed as pressure pockets.
It is advantageous if the pressure pockets are introduced as cheap-to-produce pressure grooves into the sliding surfaces of the bearing body lying in the direction of action of the axial force component.
The sliding surface of the bearing body lying in the direction of action of the axial force component preferably has introduced into it a first pressure groove, running concentrically around a first bearing eye, and a second pressure groove, spanning a partial circle around a second bearing eye, and different effective areas of the pressure grooves are thereby obtained.
It is advantageous if the pressure grooves are in pressure-medium communication with the high pressure of the toothed wheel machine via connection grooves. This enables the pressure force acting in the pressure grooves to be linked to the operating conditions of the toothed wheel machine.
In another preferred embodiment, the pressure pockets are introduced into those axial surfaces of the toothed wheels which lie in the direction of action of the axial force component.
To enable them to be produced in a simple manner, the pressure pockets are formed around and along a portion of the circumference of the respective bearing shafts of the toothed wheels and, as a result, the leakage gap that forms is small too.
To enable the toothed wheels to be supplied with a uniform pressure, it is advantageous if the pressure pockets are formed so as to run around the respective bearing shafts of the toothed wheels.
To increase the effective area of the pressure pockets, at least one pressure pocket is preferably enlarged by tooth pocket sections introduced into the tooth end faces of the teeth of the toothed wheel.
The pressure pockets can be supplied with pressure oil via the adjoining bearing body, the pressure pockets being in pressure-medium communication with the high pressure of the toothed wheel machine, for example.
Other advantageous developments of the invention form the subject matter of further subclaims.

A number of illustrative embodiments of the invention are explained in greater detail below with reference to schematic drawings. In the drawings:

FIG. 1 shows a simplified illustration of a toothed wheel machine in a longitudinal section;

FIG. 2 shows a simplified illustration of an assembly of bearing bodies and toothed wheels of the toothed wheel machine from FIG. 1, in a side view;

FIG. 3 shows a simplified illustration of bearing bodies and toothed wheels of the toothed wheel machine according to a first illustrative embodiment in a longitudinal section;

FIG. 4 shows a plan view of the bearing body from FIG. 3; and

FIG. 5 shows a plan view of the toothed wheels of the toothed wheel machine according to a second illustrative embodiment.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

FIG. 1 shows a hydraulic machine, embodied as a toothed wheel machine 1, according to one illustrative embodiment in a longitudinal section. This machine has a machine housing 2, which is closed by means of two housing covers 4 and 6. Housing cover 6 of the toothed wheel machine 1, which is on the right in FIG. 1, is penetrated by a first bearing shaft 8, on which a first toothed wheel 10 is arranged within the machine housing 2. The first toothed wheel 10 is in engagement with a second toothed wheel 12 by way of helical toothing 14, toothed wheel 12 being arranged on a second bearing shaft 16 for conjoint rotation therewith. The first and second bearing shafts 8 and 16 are each guided in two plain bearings 18, 20 and 22, 24 respectively. The plain bearings 20, 24 on the right in FIG. 1 are accommodated in a bearing body 26, and the plain bearings 18, 22 on the left in FIG. 1 are accommodated in a bearing body 28. The toothed wheels 10 and 12 are each supported in a sliding manner in the axial direction by respective first axial surfaces 30 and 32 on the second bearing body 26 (on the right in FIG. 1) and by respective second axial surfaces 34 and 36 on the bearing body 28 on the left. To reduce friction, sliding surfaces between the toothed wheels 10, 12 and the bearing bodies 26, 28 can be provided with an antifriction coating, such as MoS₂, graphite or PTFE. Respective end faces 38 and 40 of the bearing bodies 26 and 28 face the housing covers 6 and 4.
The housing covers 4, 6 are aligned on the machine housing 2 by means of centering pins 42. A housing seal 44 is arranged between the housing covers 4 and 6 and the machine housing 2. Respective axial field seals 46 are furthermore inserted into the end faces 38 and 40 of the bearing bodies 26 and 28 to separate a high-pressure zone from a low-pressure zone of the toothed wheel machine 1. A shaft seal ring 48 seals off the first bearing shaft 8 where it passes through the housing cover 6 on the right in FIG. 1.
Hydraulic and mechanical forces arise during the operation of the toothed wheel machine 1, this being illustrated schematically in detail in FIG. 2 below.
FIG. 2 shows a simplified illustration, in side view, of the assembly of toothed wheels 10 and 12 and bearing bodies 26 and 28 in order to illustrate the hydraulic forces that arise during operation and the mechanical forces that essentially act due to the helical toothing in the toothed wheel machine 1 from FIG. 1. A force component of a hydraulic force acts in the same axial direction on both toothed wheels 10, 12, toward the left in FIG. 2. In addition, a driving toothed wheel, which is the upper toothed wheel 10 in FIG. 2, is acted upon by a mechanical force component of a mechanical force in the direction of action of the hydraulic force component, and a driven toothed wheel, which is the lower toothed wheel 12 in FIG. 2, is acted upon by a mechanical force component counter to the direction of action of the hydraulic force component. The hydraulic and mechanical force components each produce a resultant axial force component 47, 49 in the same direction (to the left in FIG. 2) on both toothed wheels 10, 12, although there is a difference in magnitude.
The toothed wheels 10 and 12 subjected to axial force components 47, 49 are each supported by axial surfaces 34 and 36, respectively, on the bearing body 28 on the left in FIG. 2. The right-hand bearing body 26 is not subject to the axial force components acting on the toothed wheels 10, 12. To reduce wear between the toothed wheels 10, 12 and the bearing body 28 on the left in FIG. 2, a counter-force is applied to the toothed wheels, this being indicated by dashed arrows in FIG. 2.
FIG. 3 shows a simplified illustration of the bearing bodies 26, 28 and the toothed wheels 10, 12 according to a first illustrative embodiment of the toothed wheel machine 1 from FIG. 1 in a longitudinal section. To apply the counter-force to the toothed wheels 10, 12, a pressure field is provided between those axial surfaces 34, 36 of the toothed wheels 10, 12 which lie in the direction of action of the axial force components 47, and those sliding surfaces 50, 52 of the bearing body 28 which lie opposite the axial surfaces 34, 36. The bearing bodies 26, 28 can be of two-part construction, as illustrated in FIG. 3. The pressure field is delimited by pressure grooves 54 and 56, respectively, introduced into the sliding surfaces 50 and 52 and by the respective axial surfaces 34 and 36. Pressure forces 58, 60 acting on bearing body 28 and the toothed wheels 10, 12 by virtue of the pressure field are illustrated in simplified form by double arrows in FIG. 3, with bearing body 28 having been moved to the left to enable the pressure forces 58, 60 to be illustrated more clearly. The design of the pressure grooves 54, 56 can be seen in the following figure, FIG. 4.
FIG. 4 discloses the sliding surfaces 50, 52 of the spectacle-shaped bearing body 28 from FIG. 3 in a plan view. The first pressure groove 54 is introduced into the sliding surface so as to run around a bearing eye 62 at the top in FIG. 4. The second pressure groove 56 is formed substantially in the high pressure zone of the toothed wheel machine 1 from FIG. 1, spanning a partial circle around a lower bearing eye 64. The pressure grooves 54, 56 are in pressure-medium communication with the high pressure of the toothed wheel machine 1 via radial grooves 66.
The pressure forces 58, 60 are applied to the toothed wheels 10, 12 and bearing body 28 by means of the respective pressure grooves 54 and 56 introduced into the sliding surfaces 50 and 52 in FIGS. 3 and 4. The pressure forces 58, 60 counteract the axial force components 47, 49, thereby reducing the sliding friction and wear between the toothed wheels 10, 12 and bearing body 28. The size of the pressure grooves 54, 56 is designed in such a way that the axial force components 47, 49 applied to the toothed wheels 10, 12 are thus substantially compensated for by the pressure forces 58, 60, and the toothed wheels 10, 12 are thus supported approximately hydrostatically. The axial force component 47 at the top in FIG. 3 is larger than the lower axial force component 49, for which reason the upper pressure groove 54 from FIG. 4 is designed with a larger area than the lower pressure groove 56.
FIG. 5 shows a plan view of the axial surfaces 34, 36 of the toothed wheels 10, 12 in accordance with a second illustrative embodiment of the toothed wheel machine 1 from FIG. 1. Here, the pressure field is not delimited by pressure grooves 54, 56 introduced into bearing body 28 as in FIG. 3 but by respective pressure pockets 68 and 70 introduced into the axial surfaces 34 and 36 of the toothed wheels 10 and 12. The pressure pocket 70 in toothed wheel 12, said pocket being at the bottom in FIG. 5, is designed as an annular groove which is introduced around the axial surface 36 between tooth end faces 72 of teeth 74 of toothed wheel 12 and an outer circumferential surface of bearing shaft 16. In addition to an annular groove corresponding to pressure pocket 70, the pressure pocket 68 in toothed wheel 10, said pocket being at the top in FIG. 5, has tooth pocket sections 76 introduced into the tooth end faces 72, pressure pocket 68 thus being introduced into the axial surface 34 over a large area. Pressure pocket 68 is then delimited radially by a wall 78 running around the periphery of toothed wheel 10. The pressure pockets 68, 70 are in pressure-medium communication with the high pressure of the toothed wheel machine 1 from FIG. 1 via connection grooves in the adjoining bearing body 28 (see FIG. 1), for example.
By virtue of the pressure pockets 68, 70 in the toothed wheels 10, 12, the pressure forces 58, 60 from FIG. 3 are introduced in the area of action on bearing body 28 of the toothed wheels 10, 12 subjected to axial force components 47, 49. Since the pressure pocket 68 at the top in FIG. 4 has a larger axial pressure application area than the lower pressure pocket 70, the pressure force acting on the upper toothed wheel 10 is greater.
As an alternative, it is conceivable for the pressure pockets 68, 70 from FIG. 4 to be introduced into the toothed wheels 10, 12 in such a way that they do not run around but merely span a partial circle and have a larger radial width. This would be a way, for example, of simplifying manufacture and reducing the size of a leakage gap, which would result in smaller hydraulic losses.
The operation of the axial-gap and axial-force compensation explained above is independent of the construction of the bearing elements used and can therefore be employed for all components suitable for axial sealing of toothed wheel machines. The same applies also to the type of toothing and the parameters thereof. Such axial-gap and axial-force compensation can be employed both in external and internal toothed wheel machines.
The toothed wheel machine can be used as a gear pump or motor.
The disclosure is of a toothed wheel machine having a housing for accommodating two intermeshing toothed wheels. These are supported in a sliding manner axially by axial surfaces between bearing bodies accommodated in the housing and radially by respective bearing shafts accommodated in the bearing bodies. Hydraulic and mechanical forces arise during the operation of the toothed wheel machine, and an axial force component of these forces acts in the same axial direction on each toothed wheel. To counteract this axial force component, a pressure field is provided between at least one axial surface of a toothed wheel, said axial surface lying in the direction of action of the axial force component, and the bearing body adjoining the at least one axial surface.

Claims

1. A toothed wheel machine having a housing for accommodating two intermeshing toothed wheels, which are supported in a sliding manner axially by axial surfaces between bearing bodies accommodated in the housing and radially by respective bearing shafts accommodated in the bearing bodies, in which an axial force component of a force resulting from hydraulic and mechanical forces arising during operation of the toothed wheel machine acts on each toothed wheel in the same axial direction, wherein at least one pressure field is provided between at least one axial surface of a toothed wheel, said axial surface lying in the direction of action of the axial force component, and the bearing body adjoining the at least one axial surface.

2. The toothed wheel machine as claimed in claim 1, wherein the toothed wheels are helically toothed.

3. The toothed wheel machine as claimed in claim 1 , wherein a pressure field is provided between those axial surfaces of the toothed wheels which lie in the direction of action of the axial force component and that sliding surface of the bearing body which lies opposite the axial surfaces.

4. The toothed wheel machine as claimed in claim 3, wherein the pressure fields have different effective areas in the axial direction of the toothed wheels.

5. The toothed wheel machine as claimed in claim 2, wherein the pressure fields are designed as pressure pockets.

6. The toothed wheel machine as claimed in claim 5, wherein the pressure pockets are introduced as pressure grooves into the sliding surfaces of the bearing body lying in the direction of action of the axial force component.

7. The toothed wheel machine as claimed in claim 6, wherein the sliding surface of the bearing body lying in the direction of action of the axial force component has introduced into it a first pressure groove, running concentrically around a first bearing eye, and a second pressure groove, spanning a partial circle around a second bearing eye.

8. The toothed wheel machine as claimed in claim 7, wherein the pressure grooves are in pressure-medium communication with the high pressure of the toothed wheel machine via connection grooves.

9. The toothed wheel machine as claimed in claim 5, wherein the pressure pockets are introduced into those axial surfaces of the toothed wheels which lie in the direction of action of the axial force component.

10. The toothed wheel machine as claimed in claim 9, wherein the pressure pockets are formed around and along a portion of the circumference of the respective bearing shafts of the toothed wheels.

11. The toothed wheel machine as claimed in claim 9, wherein the pressure pockets are formed so as to run around the respective bearing shafts of the toothed wheels.

12. The toothed wheel machine as claimed in claim 11, wherein at least one pressure pocket is enlarged by tooth pocket sections introduced into tooth end faces of the teeth of toothed wheel.

13. The toothed wheel machine as claimed in claim 10, wherein the pressure pockets are supplied with pressure oil via the adjoining bearing body.