WO2012016552A2

WO2012016552A2 - External gear pump

Info

Publication number: WO2012016552A2
Application number: PCT/DE2011/001099
Authority: WO
Inventors: Marco Grethel; Andrej Lutz
Original assignee: Schaeffler Technologies Gmbh & Co. Kg
Priority date: 2010-06-14
Filing date: 2011-05-23
Publication date: 2012-02-09
Also published as: CN103026068A; CN103026068B; DE112011102000A5; DE102011102259A1; WO2012016552A3

Abstract

The invention relates to an external gear pump comprising at least two gears that mesh within an engagement zone as well as a bypass piston that makes it possible to reduce the pressure in the driven external gear pump by allowing a surplus of conveyed fluid to flow from a pressure side to a suction side of the driven external gear pump via a bypass. The invention is characterized in that the bypass piston is arranged with a small clearance in relation to the gears meshing in the engagement zone when the bypass is closed.

Description

External gear wheel pump

The invention relates to an external gear pump with at least two meshing with each other in an engagement region gears and a bypass piston, the construction of a Drucka driven external gear pump to the effect erm allows an excess flow through a bypass from a pressure side to a suction side of the driven external gear pump passes.

From the German patent application DE 44 36 518 A1 discloses a gear pump with two meshing with each other in a housing gears is known, at the end face a piston rests, which is mounted axially displaceably in a hollow cylinder. When a certain flow rate or a predetermined operating pressure is exceeded, the piston is pushed against a spring force in the hollow cylinder, so that opens a gap between the piston head and the end of the gear, a pressure reduction takes place and the excess flow through this bypass directly to the suction side of the pump chamber the gear pump can flow.

The object of the invention is to extend the life of an external gear pump according to the preamble of claim 1.

The task is in an external gear pump with at least two meshing with each other in an engaging portion gears and a bypass piston, the pressure built up a Drucka the external Außenzahnradpum PE to the effect erm allows that an excess flow through a bypass from a pressure side to a suction side of the driven external gear pump passes dadu rch solved that the bypass piston is arranged with closed bypass with a small clearance to the meshing with each other in the meshing gears. The external gear pump is preferably mechanically driven. To drive the external gear pump, for example, a drive shaft is used, which is mechanically coupled to an internal combustion engine. High open back pressures and the associated losses can be avoided via the opened bypass, especially if the pumped medium of the external gear pump is cold and tough. This provides the advantage that the external gear pump does not have to be decoupled from the internal combustion engine when no promotion is needed and the internal combustion engine is running. By the low Play between the bypass piston and the rotating gears can be significantly reduced unwanted friction losses, wear and damage to the driven Außenenzhnpump- pe.

A preferred Ausführungsbei play the external gear pump is characterized in that the bypass piston has an outer diameter which is significantly smaller than the outer diameter of the meshing gears. This ensures that an axial contact surface for the gears, for example on a housing of the external gear pump, is not so much reduced by the bypass piston, as for example in the known from the German patent application DE 44 36 518 A1 Zahnradpum PE.

Another preferred embodiment of the Außenzahnradpum PE is characterized in that the bypass piston is supported with a closed bypass on a housing paragraph. The housing paragraph may be provided in a pot-like housing base or in a lid of the housing. By supporting the bypass piston on the housing shoulder is made possible in a simple manner that the bypass piston can be arranged with little play to the engagement region of the meshing gears.

Another preferred embodiment of the Außenzahnradpum PE is characterized in that the bypass piston is hydraulically biased against the Gehäusea bsatz. The hydraulic bias ensures that the bypass piston rests against the housing shoulder when the bypass is closed. The hydraulic bias can be generated by a hydraulic pressure acting on the bypass piston. When the hydraulic pressure is reduced, and / or when the discharge pressure of the external gear pump becomes larger than the hydraulic bias in the engaging portion of the meshing gears, the bypass piston moves away from the housing shoulder and releases the by-pass.

A further preferred embodiment of the external gear pump is characterized in that the bypass piston is biased by a spring against the housing shoulder. The spring is preferably a pressure spring, by means of which the bypass piston is held in contact with the housing shoulder when the bypass is closed. When the discharge pressure in the engagement region of the meshing gears becomes large as the biasing force of the spring, the bypass opens. The bypass piston may additionally be subjected to a hydraulic pressure in order to improve the activation of the hydraulic piston. fibers. The spring can be used to represent a pressure relief valve together with the bypass piston. If, for example, the delivery pressure of the external gear pump is then fed back to the bypass piston as a control force via a differential surface on the bypass piston, the function of a differential pressure valve can also be represented with the bypass piston. Moreover, it is possible to at least partially make the bypass piston out of a material having a shape or shape memory capability, that is, a so-called shape memory alloy. It can thereby be achieved that the bypass piston changes its shape, in particular its size, as a function of the temperature. This effect can be used to control the bypass. In connection with the bypass piston, other temperature-dependent components can be used which provide a control force and / or a control path. The control force on the bypass piston can also be applied mechanically, electrically or by another technical height.

A further preferred embodiment of the external gear pump is characterized in that the bypass piston has an axial guide portion, with which the bypass piston in a housing Ausne is guided reciprocally movable back and forth. The housing recess may be arranged in a pot-like housing base body or in a cover of the housing.

A further preferred embodiment of the external gear pump is characterized in that the bypass piston has an axial bypass section which has a smaller outer diameter than the guide section and at the free end of which a bypass closing surface is formed. The bypass closing surface is, for example, circular and with a closed bypass with little play to the meshing with each other in the engagement region gears arranged.

A further preferred embodiment of the external gear pump is characterized in that the guide section has a greater axial extent than the bypass section. As a result, the guidance of the bypass piston in the housing recess is improved.

A further preferred embodiment of the external gear pump is characterized in that the bypass piston between the guide section and the bypass section has a step, with which the bypass piston with closed bypass on the GE. housing paragraph strikes. Via the axial extent of the bypass section, the play between the bypass closing surface and the gears meshing with one another in the engagement region can be adjusted.

The invention furthermore relates to the use of a previously described external gear pump for supplying a hydraulic control, in particular an automatic transmission of a motor vehicle. On the one hand, the hydraulic controls in A utomatic gearboxes supply the gearbox actuators and, on the other hand, are often required for cooling and lubrication functions. By the external gear wheel pump according to the invention, an advantageous alternative to a mechanical decoupling of the Pum pe is provided by its mechanical drive. The outside gear wheel pump can be short-circuited as required depending on the bypass enabled by the bypass piston in order to minimize pressure losses of the driven pump. As a result, the promotion of the external gear pump is interrupted.

Further advantages, features and details of the invention will become apparent from the nachf olgenden description in which with reference to the drawing, various Ausfüungs- examples are described in detail. Show it:

Figure 1 shows an external gear pump according to the invention in longitudinal section with a closed bypass;

Figure 2 shows the external gear pump of Figure 1 with open bypass and

Figure 3 shows a similar embodiment as in Figures 1 and 2 m with a biased by a spring bypass piston in its closed position.

In Figures 1 and 2 ei ne external gear pump 1 with a pump housing 2 in longitudinal section with open and closed bypass dargestel lt. The pump housing 2 comprises a pot-like housing basic body, the bottom of a P latte 3 is amplified. The cup-shaped main body of Pum pengehäuses 2 is closed by a pump cover 4.

In the pump housing 2, two gears 11, 12 mesh with each other. The gear 1 1 is driven by a drive shaft 14 (not illustrated) of a driver 15. The gear 12 is rotatably mounted on a pillow block 18 in the Pümpengehäuse 2. In one Engagement region 20 meshes the two gears 11, 12 so that a conveying medium is conveyed by means of the two gears 11, 12 from a suction side to a pressure side of the external gear pump 1, as long as the gear 11 is driven via the drive shaft 14 ,

The pump housing 2 has in the engagement portion 20 of the two gear wheels 11, 12 a housing recess 24 in which a bypass piston 25 is guided reciprocally movable. The bypass piston 25 defines with its end face remote from the engagement region 20 a control pressure chamber 26, which can be acted upon by hydraulic pressure. The bypass piston 25 is biased via the control pressure chamber 26 hydraulically against a housing shoulder 30, which is formed in the casement securement 24.

The bypass piston 25 is in the axial direction in an axial guide portion 31 and an axial By passportion 32 divided. The axi al guide portion 31 has a larger outer diameter than the axial bypass portion 32. Between the guide portion 31 and the bypass portion 32, a step 33 is formed with which the bypass piston 25 abuts in its closed position shown in Figure 1 on the housing shoulder 30 or abuts. At its front side facing the engagement region 20, the bypass piston 25 has a bypass closing surface 35, which in the closed position of the bypass piston 25 is arranged with a small clearance, which is not visible in FIG. 1, to the toothed wheels 11 and 12 in the engagement region 20 in its in FIG 2 dargestel opened opening position of the bypass piston 25 with its bypass closing surface 35 far as far from the gears 11 and 12 in the engaging portion 20 that a sufficiently large bypass 40 is released, which shorts the pressure side with the suction side of the external gear pump 1. The opening of the bypass piston 25 is effected, for example, by reducing the hydraulic pressure in the control pressure space 26. By a corresponding Druc kerhöhung in the control pressure chamber 26, the bypass piston 25 can be closed again depending on demand.

In Figure 3, an external gear pump 41 is shown, which is similar to the external gear pump 1 of Figures 1 and 2 se hr. Identical parts are provided with the same reference numerals. To avoid repetition, only the differences between the two external gear pumps 1 and 41 will be discussed below. In the FIG. 3 dargestell th external gear pump 41, the bypass piston 45 is biased by a spring 46 in its closed position. The spring 46 is executed as a helical compression spring and partially received in a corresponding recess of the bypass piston 45. The bypass piston 45 can be additionally hydraulically actuated via the control pressure.

LIST OF REFERENCE NUMBERS

External gear pump

pump housing

plate

pump cover

gear

drive shaft

takeaway

Plummer

engagement area

Housing recess

bypass piston

Control pressure

housing shoulder

axial guide section

axial bypass section

step

Bypass closing surface

bypass

External gear pump

bypass piston

feather

Claims

claims

1. External gear pump with at least two in an engagement region (20) meshing gears (11, 12) and m with a bypass piston (25), which allows a pressure reduction of the driven A ußenzahnradpumpe (1, 41) to the effect that an excess flow rate over a bypass (40) passes from a pressure side to a suction side of the driven external gear pump (1; 41), characterized in that the bypass piston (25) with closed bypass (40) with a small clearance to the in the engagement region (20) arranged with each other meshing gears (11, 12).

2. Außenenzahnradpum PE according to claim 1, dadu rch in that the bypass piston (25) has an outer diameter which is significantly smaller than the outer diameter of the meshing gears (11, 12).

3. External gear pump according to one of the preceding A nsprüche, characterized in that the bypass piston (25) is supported with a closed bypass on a housing shoulder (30).

4. external gear pump according to claim 3, characterized in that the bypass piston (25) hydraulically against the Gehäusea offset (30) biased i st.

5. external gear pump according to claim 3 or 4, characterized in that the bypass piston (25) by a spring (46) is biased against the housing housing paragraph (30).

6. external gear pump according to one of claims 3 to 5, characterized in that the bypass piston (25) has an axial Führungsabs chnitt (31), with which the bypass piston (25) in a Gehäuseausnehm ung (24) back and forth bew isbar performed ,

7. external gear pump according to claim 6, characterized in that the bypass piston (25) has an axial bypass section (32) having a smaller outer diameter than the guide portion (31) and at its free end a bypass closing surface (35) is formed.

8. external gear pump according to claim 7, characterized in that the guide portion (31) has a greater axial extent than the bypass section (32).

9. external gear pump according to claim 7 or 8, characterized in that the bypass piston (25) between the guide portion (31) and the bypass section (32) has a step (33), with which the bypass piston (25) with closed bypass ( 40) abuts the housing shoulder (30).

10. Use of an external gear pump (1; 41) according to egg nem of the preceding claims for supplying a hydraulic control, in particular an automatic transmission of a motor vehicle.