WO1993009349A1

WO1993009349A1 - Vane cell pump

Info

Publication number: WO1993009349A1
Application number: PCT/EP1992/002506
Authority: WO
Inventors: Armin Lang
Original assignee: Zf Friedrichshafen Ag
Priority date: 1991-11-02
Filing date: 1992-11-02
Publication date: 1993-05-13
Also published as: DE4136150A1

Abstract

In a pump casing of a vane cell pump is held a curve ring (1) in which a rotor (2) is arranged to rotate. Vanes (4) can be moved in slots (3) of the rotor (2). Between the curve ring (1), the rotor (2), the vanes (4) and the fronts of casing sections adjacent these components are formed working chambers having two intake and pressure regions each. In each of the two intake regions there is an intake chamber (6, 7) and in each of the two pressure regions there is a discharge chamber (8, 10). The two partial flows of pressure agent from the two discharge chambers (8, 10) are connected in parallel at low and in series at high pump revolution speeds by means of a flow control valve (14) fitted with three pairs of control edges (26, 27, 30).

Description

Vane pump

The invention relates to a vane pump according to the preamble of claim 1. A cam ring and a rotor rotatably mounted therein are arranged in a pump housing. The rotor has slots in which blades can be moved. Working chambers are formed between the cam ring, the rotor and the vanes, which are laterally delimited by end faces of the adjacent housing parts. Two suction and pressure zones are formed by the formation of the cam ring. An inlet chamber is arranged in each of the two suction zones and an outlet chamber is arranged in each of the two pressure zones. In a pressure line leading to a consumer, there is one

Throttle point arranged. A flow control valve contains, in a valve bore, an axially displaceable valve piston, one end surface of which is loaded by a compression spring is acted upon by the pressure prevailing downstream of the throttle point and the other end face is acted upon by the pressure prevailing upstream of the throttle point.

Such a vane pump is known from DE-AS 12 51 156. Such a pump is used, for example, for power steering of a motor vehicle. In order to adapt the very different speeds of the drive motor to the pressure medium requirement of the power steering system, vane pumps of this type are equipped with a flow control valve. The aim of this is to ensure that, at a high drive speed of the pump, the same liquid flow reaches the power steering system as when the pump is operated at a low speed. Since the idle speeds of a vehicle engine are very low, the displacement volume of the vane pump must be chosen to be large enough to ensure the minimum power required for power steering. The consequence of this is that a correspondingly high flow rate is uselessly circulated at high engine speeds, which worsens the overall efficiency of the system.

The invention has for its object to provide a vane pump whose efficiency is significantly improved at higher speeds.

This object is achieved by the vane pump characterized in claim 1. The solution is in particular that in a generic

Vane pump the two outlet chambers are separately connected to the flow control valve, and that the two pressure medium tubes from the two outlet chambers via the flow control valve are connected in parallel at low pump speeds and in series at higher pump speeds.

Advantageous and expedient refinements of the invention are specified in the subclaims. However, the invention is not limited to the combinations of features of the claims. For the specialist, there are further useful combinations of claims and individual claim characteristics from the task.

According to claim 2, the flow control valve contains two piston ring grooves on its valve piston and two ring grooves in its valve bore, which together form a total of three control edge pairs. These control edge pairs are opened or closed one after the other by the displacement of the valve piston as the pump speed increases. This results in the following flow conditions: First, the means at low pump speeds, both partial pressurized medium flows from the two outlet chambers together into the pressure line leading to the consumer. Both pressure medium partial flows are connected in parallel. With increasing pump speed and thus increasing flow and increasing pressure difference across the throttle point, the valve piston of the flow control valve is moved against the force of its compression spring until the first pair of control edges opens. As a result, the first pressure medium partial flow from the one outlet chamber is divided into two parts, one of which continues to flow towards the consumer, while the other is supplied via the opened control edge pair to charge the second pump branch of the other inlet chamber. As a result, this inlet chamber has to suck up less pressure medium from the container. If the pump speed continues to rise and the valve piston is shifted further, the ratio of the division of the first pressure medium partial flow shifts more and more in the direction of the charging of the second pump branch. This continues until the first pump branch only pumps into the second inlet chamber. At the same time, a check valve arranged in the suction line of the other inlet chamber is closed, so that no more pressure medium is drawn from the pressure medium container for this branch. The two pressure medium partial flows are thus connected in series. When the valve piston is displaced further against the force of the compression spring, a point is reached at which the third pair of control edges opens and a part of the residual pressure medium flow is sprayed into the pressure medium container.

Provided that the two branches of the

Pump delivery flow have the same delivery volume - which is generally the case with double-flow vane pumps is -, the delivery pressure to be applied by each branch is halved, and with it the power loss of the pump.

In one embodiment of the invention, a control edge pair of the flow control valve can be replaced by a check valve.

In a further development, a precisely defined pressure distribution in the working cavities is achieved by an additional valve after the two pressure medium flows from the two outlet chambers are connected in series.

This allows the lateral forces on the rotor shaft of the

Reduce the vane pump.

The invention is explained in more detail below with reference to four exemplary embodiments shown in the drawing. Show it:

1 shows a schematic cross section through the vane pump according to the invention in a first exemplary embodiment, the valve piston of the flow control valve being in its neutral position,

2 shows a schematic cross section through the vane pump according to the invention in a second exemplary embodiment,

3, the vane pump according to FIG. 1, but with the valve piston of the flow control valve in an intermediate position, Fig. 4, the vane pump according to Fig. 1, the valve piston of the flow control valve almost in its second end position

-ϋ located,

5

1A, characteristic curves of the delivery flow Q as a function of 3A, 4A on the pump speed n for the respective operating states of FIGS. 1, 3, 4,

5 shows a schematic cross section through the vane pump according to the invention in a third exemplary embodiment,

Fig. 6 shows a schematic cross section through the ¹⁵ 'vane pump according to the invention in a fourth embodiment.

The structure of a vane pump is basically known. Therefore, only those for

20 invention describe essential parts in more detail.

The vane pump has a non-rotatably mounted cam ring 1 in a pump housing, not shown. In the interior of the cam ring 1, a ^ rotor 2 is arranged, which has a plurality of slots 3, which are directed essentially radially outwards. In the slots 3 vanes 4 are movably guided, the movement of which is controlled by the inner contour of the cam ring 1 when the rotor 2 rotates.

30

Working chambers 5 are formed between the cam ring 1, the rotor 2, the vanes 4 and the end faces of adjacent housing parts, not shown. The vane pump is designed as a double-flow pump, so that two suction zones with a first inlet chamber 6 and a second inlet chamber 7 and two pressure zones with a first outlet chamber 8 and a second outlet chamber 10 are formed according to the inner contour of the cam ring 1.

A throttle point 13 is arranged in a main pressure line 12 leading to a consumer 11. The consumer 11 is, for example, an auxiliary power steering system of a motor vehicle and - since known per se - is not shown or described in more detail.

The throttle point 13 belongs to a flow control valve 14 and is arranged in the exemplary embodiment according to FIG. 1 at the end of an axial bore 15 of a valve piston 16 which is guided axially displaceably in a valve bore 17. An end face 18 of the valve piston 16, in the vicinity of which the throttle point 13 is located, is loaded by a compression spring 20.

End surface 18 of valve piston 16, which is loaded by compression spring 20, is adjacent to a first piston ring groove 21, which is connected to axial bore 15 via transverse bores 22. The valve bore 17 has a first annular groove 23 and a second annular groove 24, between which a second piston annular groove 25 is arranged.

Between the first annular groove 23 and the first piston annular groove 21, a first pair of control edges 26 is formed, which is opened in the neutral position of the valve piston 16 set by the compression spring 20. A second pair of control edges 27 is formed between the first annular groove 23 and the second piston annular groove 25, which is closed in the neutral position of the valve piston 16. Between the second annular groove 24 and the another end surface 28 of the valve piston 16, a third pair of control edges 30 is formed, which is closed in the neutral position of the valve piston 16.

The first annular groove 23 is connected to the first outlet chamber 8 via a first pressure line 31. The second piston ring groove 25 is connected to the second inlet chamber 7 via a second suction line 32 and to a pressure medium container 33 via a check valve 34. The second annular groove 24 is connected to the pressure medium container 33. A space 35 adjoining the other end surface 28 of the valve piston 16 is connected to the second outlet chamber 10 via a second pressure line 36.

The first inlet chamber 6 is connected to the pressure medium container 33 via a first suction line 37.

The coverage of the second control edge pair 27 is less than the coverage of the first control edge pair 26. The coverage of the third control edge pair 30 is greater than the coverage of the first control edge pair 26. This means that when the valve piston 16 is displaced against the force of the compression spring 20 to the right first the second control edge pair 27 opens, then the first control edge pair 26 closes and finally the third control edge pair 30 opens.

According to the second exemplary embodiment shown in FIG. 2, the throttle 13 is not arranged in the valve piston 16, but outside the flow control valve 14 in the main pressure line 12, which leads to the consumer 11, not shown in FIG. 2. In this exemplary embodiment, the first piston ring groove 21 is connected to the main pressure line 12 via a first branch line 38 connected. The second pressure line 36 is also connected to the main pressure line 12 via a second branch line 40. The arrangement of the throttle point 13 outside the flow control piston makes it possible to provide an additional damping throttle 42 in a third branch line 41, which conducts the pressure prevailing downstream of the throttle point 13 in the pressure line 12 to the end face 18, with the aid of which, in a manner known per se How the dynamic properties of the flow control valve can be influenced.

The function of the first two exemplary embodiments of the vane pump according to the invention is described below: In the position shown in FIG. 1, the pump sucks a partial flow Q1 from the pressure medium container 33 via the first inlet chamber 6 and conveys it via the first outlet chamber 8, the first pressure line 31, the first annular groove 23, the opened first control edge pair 26, the first piston annular groove 21 and the transverse bores 22 into the axial bore 15 and from there via the throttle point 13 to the consumer 11 , the second piston ring groove 25 and the second suction line 32 are sucked into the second inlet chamber 7 and also conveyed as second partial flow Q2 via the second outlet chamber 10 and the second pressure line 36 into the axial bore 15 and from there via throttle point 13 to the consumer 11. In this position of the flow control valve 14, the function corresponds to the function of a known, customary, double-flow vane cell pump, with the two partial pressure flows being connected in parallel. The characteristic curve of the delivery flow versus the pump speed is shown in FIG. 1A. It is clear from this that the two

Add partial flows Ql and Q2 to the total flow. If the speed of the vane pump is increased, the flow rates Q1 and Q2 and thus the pressure difference at the throttle point 13 increase until the hydraulic force on the valve piston 16 exceeds the force of the compression spring 20. As a result, the valve piston 16 moves to the right and initially opens the second pair of control edges 27 (see FIG. 3). The first pair of control edges 26 is still open. This divides the partial flow Ql into two parts Q1A and QIB. The partial flow QIB is fed via the opened second control edge pair 27, the second piston ring groove 25 and the second suction line 32 to the second inlet chamber 7 and serves to charge the pump branch on the left in the drawing. This reduces the intake flow Q3 accordingly. The partial flow Q1A is combined with the partial flow Q2 in the axial bore 15 of the valve piston 16. Both reach the consumer 11 via the choke point 13. This results overall in a constant current Q1A + Q2, which is shown in FIG. 3A. As the speed increases further, the current Q2 rises steadily and the intake flow Q3 decreases to the same extent until it completely disappears. The intake flow Q3 is increasingly being replaced by the partial flow QIB. The pressure in the second inlet chamber 7 increases and the check valve 34 closes. At the same time, the valve piston 16 moves further

^• to the right and opens the third pair of control edges 30, via which the partial flow Q2B flows out to the pressure medium container 33. Thereafter, the constant results according to FIG. 4A

Flow rate Q2A (thick solid line).

The third exemplary embodiment, which is shown in FIG. 5, differs from the first two exemplary embodiments in that the first pair of control edges 26 is replaced by a check valve 43. The check valve 43 is in a fourth

Branch line 44 is arranged, which connects the first annular groove 23 to the main pressure line 12. This opens Check valve 43 towards the

Main pressure line 12. The remaining configuration of the third exemplary embodiment corresponds to that of the two first exemplary embodiments, wherein the throttle point 13 can either be arranged in the main pressure line 12 as shown or in the valve piston 16 as in FIG. 1.

Although a first piston ring groove 21 and a first pair of control edges 26 are not present in the exemplary embodiment according to FIG. 5, the previously chosen designations are retained for the remaining structural elements for reasons of uniformity, e.g. B. second piston ring groove 25, second pair of control edges 27.

The fourth exemplary embodiment according to FIG. 6 can be based on each of the first three exemplary embodiments of FIGS. 1, 2 or 5. In Fig. 6, the embodiment of Fig. 5 is chosen as the basis.

An additional valve 45 is connected to the flow control valve 14. The additional valve 45 is a

Differential piston valve and contains a stepped piston 46, which can be made in one piece or - as shown in Fig. 6 - divided. The smaller piston surface a of the stepped piston 46 borders on a smaller piston chamber 47, the larger piston surface A borders on a larger piston chamber 48. In the area of the smaller diameter of the stepped piston 46 there is a housing ring groove 50 which is connected via a line 51 to the first ring groove 23 Flow control valve 14 is connected. A housing ring groove 52, which lies in the region of the larger diameter of the stepped piston 46, is connected to the return to the pressure medium container 33. The smaller piston chamber 47 is connected to the second pressure line 36 via a line 53. The larger piston chamber 48 is over a

Line 54 connected to the second suction line 32. A control edge pair 55 is arranged between the smaller piston space 47 and the housing ring groove 50, and a control edge pair 56 exists between the larger piston space 48 and the housing ring groove 52.

The function of the auxiliary valve 55 in the fourth

Exemplary embodiment is as follows: If that

Flow control valve 14 is in the position shown in Fig. 6, then pumps the left side of the pump via the second

10 pressure line 36 and line 53 in the smaller

Piston chamber 47 and thereby acts on the smaller one

Piston area a. Because of the closed second

Control edge pair 27, the second intake line 32 is depressurized and thus - via line 54 - the larger

^■ * ^• Piston chamber 48 with the larger piston area A. The

Step piston 46 is thereby pushed to the right. The

Control edge pair 55 is open, the control edge pair 56 is closed. The additional valve 45 does not affect the function of the rest of the arrangement. 20th

However, the control piston 16 of the flow control valve 14 is moved so far to the right that the

Control edge pair 27 is open and in the second

Intake line 32 and thus also in line 54 and in the

² ^ larger piston chamber 48 builds up a pressure, the following balance of forces is established: pl x A = p2 xa where pl is the pressure in the first pressure line 31 and p2

Pressure in the second pressure line 36 is. 30

If pl x A> p2 xa, the control edge pair 56 opens to the pressure medium container 33 and restores the equilibrium. If, on the other hand, pl x A <p2 xa, the control edge pair 55 opens and thus increases the leak oil on the left ⁵ pump side until the desired balance is restored.

Claims

Expectations

1. Vane pump with a pump housing in which a cam ring (1) is held, with a rotor (2) rotatably mounted in the cam ring (1) with slots in which vanes (4) can be displaced, with end faces of the cam ring ( 1) and the

Rotor (2) adjacent housing parts together with the 0 cam ring (1), the rotor (2) and the vanes (4)

Working chambers (5) form, each of two suction and

Have pressure zones, one in each of the two suction zones

Inlet chamber (6, 7) and in each of the two pressure zones 5 an outlet chamber (8, 10) is arranged, with a throttle point (13) in one to one

Consumer (11) leading main pressure line (12) is arranged and with a flow control valve (14) which is axially displaceable in a "valve bore (17)

Valve piston (16), one end surface (18) of which is loaded by a compression spring (20) is acted upon by the pressure prevailing downstream of the throttle point (13), and the other end face (28) of which is the pressure prevailing upstream of the throttle point (13) is acted upon, characterized in that the two outlet chambers (8, 10) are separately connected to the flow control valve (14) and - that the two pressure medium partial flows from the two outlet chambers (8, 10) via the flow control valve (14) at low pump speeds can be connected in parallel and in series at higher pump speeds.

5

2. Vane pump according to claim 1, characterized in that the flow control valve has the following features:

- The end face (18) ^{5 of} the valve piston (16) loaded by the compression spring (20) is adjacent to a first piston ring groove (21), the valve bore (17) has a first ring groove (23) and a second ring groove (24) between which a second piston ring groove (25) is arranged, ¹⁰ - between the first ring groove (23) and the first

Piston ring groove (21) is formed a first pair of control edges (26) which is open in the neutral position of the valve piston (16) set by the compression spring, ^• "- between the first ring groove (23) and the second piston ring groove (25) is a second pair of control edges (27) which is closed in the neutral position of the valve piston (16),

- between the second annular groove (24) and the other ⁰ end surface (28) of the valve piston (16) is a third pair of control edges (30) formed, which is closed in the neutral position of the valve piston (16),

- The first piston ring groove (21) is connected to the upstream of the throttle point (13) part of the leading to the ^ consumer (11) pressure line (12), the first ring groove (23) via a first pressure line (31) with the first Outlet chamber (8) connected,

- the second piston ring groove (25) is connected to the second ⁰ inlet chamber (7) and via a check valve (34) with a pressure medium container (33), the second annular groove (24) is directly connected to the pressure fluid reservoir (33) and to the other end surface (28) of the valve piston (16) ⁵ adjoining space (35) is via a second

Pressure line (36) with the second Auslaßka mer (10) connected.

3. Vane pump according to claim 2, characterized in that the overlap of the second control edge pair (27) is smaller than the undercoverage of the first control edge pair (26), and that the overlap of the third control edge pair (30) is greater than the undercoverage of the first control edge pair ( 26).

4. Vane pump according to claim 2, characterized in that the throttle point (13) is arranged at the end of an axial bore (15) in the valve piston (16), and that the first piston ring groove (21) via transverse bores (22) with the axial bore (15 ) connected is. (Fig. 1)

5. Vane pump according to claim 2, characterized in that the throttle point (13) outside the valve piston (16) is arranged, and that in a downstream of the throttle point (13) from the leading to the consumer (11) main pressure line (12) branching third Branch line (41) has a damping throttle (42) is arranged. (Fig. 2)

6. Vane pump according to claim 1, characterized in that the flow control valve has the following features:

The valve bore (17) has a first annular groove (23) and a second annular groove (24), between which a second piston annular groove (25) is arranged, between the first annular groove (23) and the second piston annular groove (25) is a second one

Control edge pair (27) is formed, which is closed in the neutral position of the valve piston (16), between the second annular groove (24) and the other end face (28) of the valve piston (16) a third control edge pair (30) is formed, which in the

Neutral position of the valve piston (16) is closed, - The first annular groove (23) is over a first

Pressure line (31) connected to the first outlet chamber (8), the first annular groove (23) via a fourth ^J branch line (44), in which one in the direction of the

Main pressure line (12) opening check valve (43) is arranged, connected to the main pressure line (12), the second piston ring groove (25) is connected to the second inlet chamber (7) and via a check valve (34) to a pressure medium container (33), the second ring groove (24) is with the

Pressure medium container (33) connected and a space (35) adjoining the other end face (28) of the valve piston (16) is via a second one

Pressure line (36) connected to the second outlet chamber (10). (Fig. 5)

7. Vane pump according to one of claims 2 or 6, characterized in that to the first ring groove (23), the second piston ring groove (25) and the second pressure line (36), an additional valve (45) is connected for a defined pressure distribution in the inlet and outlet chambers (6, 7, 8, 10) of the vane pump. (Fig. 6)

8. Vane pump according to claim 7, characterized in that the additional valve (45) is designed as a differential piston valve with a one-piece or divided step piston (46), the smaller piston area (a) arranged smaller piston chamber (47) with the second pressure line (36 ) is connected and the larger piston space (48) arranged on the larger piston surface (A) is connected to the piston ring groove (25).

9. Vane pump according to claim 8, characterized in that the smaller piston chamber (47) via a control edge pair (55) with a to the first annular groove (23) leading line (51) is connectable and that the larger piston chamber (48) via a control edge pair (56) can be connected to the return to the pressure medium container (33).