EP0221062A1

EP0221062A1 - Regulation device for a positive displacement pump, particularly a vane-type pump.

Info

Publication number: EP0221062A1
Application number: EP85903278A
Authority: EP
Inventors: Gunther Seidl
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1984-07-12
Filing date: 1985-07-06
Publication date: 1987-05-13
Also published as: EP0221062B1; WO1986000671A1; DE3524413A1

Abstract

Un dispositif de régulation pour une pompe volumétrique, en particulier une pompe à cellules semi-rotative, est doté d'un piston de régulation de l'écoulement (7) dont la surface de piston avant est en liaison avec un espace de pression (24) avant un dispositif d'étranglement (2) présentant au moins un trou d'étranglement (4) de section transversale d'ouverture modifiable grâce à un coulisseau de commande (15) fixé au piston de régulation de l'écoulement (7) et dont la surface de piston arrière est en liaison avec une chambre de pression (11) derrière le dispositif d'étranglement (2); il est également doté d'une canalisation de retour d'écoulement de transport (14) dont l'ouverture d'admission (13) est libérée en fonction de la position du piston de régulation de l'écoulement (7). L'ouverture d'entrée du trou d'étranglement (4) est au moins approximativement perpendiculaire à l'axe longitudinal du piston de régulation de l'écoulement (7). Le coulisseau de commande (15) comporte une plaque d'étranglement (16) déplaçable parallèlement à l'axe longitudinal du piston de régulation de l'écoulement (7) sur l'ouverture d'entrée du trou d'étranglement (4).A regulating device for a positive displacement pump, in particular a semi-rotary cell pump, is provided with a flow regulating piston (7) whose front piston surface is in connection with a pressure space (24 ) before a throttle device (2) having at least one throttle hole (4) of cross section of opening which can be modified by means of a control slide (15) fixed to the flow control piston (7) and the rear piston surface of which is connected to a pressure chamber (11) behind the throttle device (2); it also has a transport return flow line (14), the inlet opening (13) of which is released as a function of the position of the flow control piston (7). The inlet opening of the throttle hole (4) is at least approximately perpendicular to the longitudinal axis of the flow control piston (7). The control slide (15) has a throttle plate (16) movable parallel to the longitudinal axis of the flow control piston (7) over the inlet opening of the throttle hole (4).

Description

Control device for a positive displacement pump, in particular vane cell pump

The invention relates to a control device according to the kind described in the preamble of claim 1.

In particular, vane pumps are used very frequently for supplying auxiliary pressure steering systems. To regulate the flow rate for power steering, it is known to narrow the pressure channel in the area of the tapping point. This measure results in a higher flow velocity and thus a reduction in the static pressure on the rear side of the flow control piston. In this way, the differential pressure between the two piston areas becomes larger and the flow control piston experiences a speed-dependent opening tendency, with which the inlet opening into the delivery flow return line is released to a corresponding extent. This way the pump More hydraulic fluids circulated and the flow to the consumer decreases. A "falling" characteristic of the vane pump is thus achieved; ie the volume throughput is not increased further from a certain control point in accordance with the output of the vane pump, but may even be reduced.

Different characteristic curve variants are desired for various reasons. For example, a falling characteristic curve with an auxiliary power steering at high speeds better steering behavior. In addition, the throughput pressure in the steering system decreases when the flow rate characteristic falls as the rotational speed increases. The result is a lower power consumption of the pump, which leads to lower temperatures.

For reasons of energy saving and to avoid high temperatures, one would particularly like at high speeds and a low pressure in the system, i.e. e.g. when driving straight on the freeway, only a low volume throughput. On the other hand, with a steering movement, i.e. with a high operating pressure, a high flow rate is available.

A control device for a positive displacement pump is therefore already known from DE-OS 32 11 948, in which the control slide is designed as a bow spring which is attached to the front of the flow control piston. During the displacement of the flow control piston, the free end of the bow spring correspondingly covers the throttle bore (s). In this way, after the cut-off point, a falling flow rate characteristic is achieved over the entire speed range, and a preselected characteristic curve can be set according to the design. The object of the present invention is to create even more possible variations in comparison to this previously known solution with regard to the characteristic curves.

According to the invention, this object is achieved by the features mentioned in the characterizing part of claim 1.

Due to the inventive arrangement of the throttle bore or throttle bores in cooperation with the throttle plate, numerous characteristic curve variants can be set without problems. For this purpose, it is only necessary that corresponding control slides are provided. It is also advantageous that this configuration is very simple and safe. Since there is a parallel displacement of the throttle plate to the displacement of the flow control piston and no bow spring is necessary, there is no risk of permanent failure. Furthermore, the control slide with the throttle plate can be produced simply and inexpensively.

In an advantageous embodiment of the invention it is provided that the throttle device and the flow control piston are parallel to one another and that the throttle bore is arranged in a peripheral wall of the throttle device.

In this way, a space-saving arrangement is achieved. The control slide no longer has to be fixedly attached to the end face, but can be arranged, for example, in a transverse bore in the flow regulating piston. This means, no rigid attachment to the piston is necessary and the spool can be easily assembled or disassembled. In this way, changes to the characteristic are still possible without problems or the control device can be manufactured in series and then adapted to the respective requirements by means of a corresponding control slide.

In a simple manner, the throttle device can have a cylindrical shape at least in the region of the throttle bore. In this case, the throttle plate will advantageously be at least approximately designed as a segment of a hollow cylindrical shape, the inner diameter of which is at least approximately matched to the outer diameter of the pressing device.

In this way, in addition to simple manufacture, good and, above all, precise throttling is also possible.

So that the throttle plate of the control slide is always free from play on the throttle device and the distance between the throttle device and the flow regulating piston can also be designed with large tolerances, the throttle plate can be pressed against the peripheral wall of the throttle device by a spring. For this purpose, it can lie in a transverse bore designed as a blind bore behind a pin of the control slide or it is clamped between the underside of the throttle plate and the peripheral wall of the flow control piston.

This spring also serves to make assembly easier. For this purpose, the throttle device can also have a collar at the front end facing the pressure chamber. This The collar serves to facilitate assembly and at the same time also ensures that the throttle plate is held on the throttle device. In this way, additional security measures are unnecessary.

If the throttle bore is offset in the circumferential direction from the throttle plate, further characteristics can be set. In this way e.g. one side of the throttle bore becomes a control edge.

Likewise, the throttle bore or the throttle bores can be given any shape. In the same way, the throttle plate, in coordination with the throttle bore, can have any shape in plan view, so that there are corresponding possibilities of variation.

A very advantageous development of the invention is achieved if the throttle device has, in addition to the throttle bore, a bore with an invariable cross section for the passage of the pressure medium.

Such a bore can e.g. Kaitstartverehteteπ be improved in a vehicle steering.

For easier assembly, the control slide can be provided with a notch, a cam or the like in the area of its web between the throttle plate and the flow control piston. be missed. This provides a point of attack for installation or removal. Advantageous refinements and developments of the invention also result from the other subclaims and from the exemplary embodiment described below with reference to the drawing.

Show it:

F.ig. 1 a section of a longitudinal section through a vane cell pump with the control device according to the invention, the flow control piston of which is in the closed state;

2 shows a longitudinal section, corresponding to that according to FIG. 1 with the flow control piston in the open position;

Fig. 3 is a section along the line III - III in Fig. 2;

Fig. 4 Prinzipdarstellungeπ of different Drosselpla th to 8 in plan view;

9 shows the front part of the flow control piston on a smaller scale (corresponding to the representation according to FIG. 2) with a control slide which is connected to the flow control piston via a thread.

The vane pump is essentially of a known construction, which is why only the parts essential for the invention are shown and described here.

The pump has a rotor with vanes in the usual manner, the rotor being arranged between a front end plate (not shown) and a rear pressure plate 1. Behind the pressure plate 1 there is a pressure chamber 24, which has pressure bores is in connection with pressure kidneys, not shown.

After passing through a throttle device 2, the pressurized pressure medium reaches an outlet opening 3, from which a line leads to a consumer, e.g. to an auxiliary power steering.

The throttle device 2 has a throttle insert in the form of a cylinder. A throttle bore 4 and a fixed bore 5 are arranged in the peripheral wall. The connection from the pressure chamber 2 to the outlet opening 3 takes place via the bores 4 and 5, the throttle insert 2 being provided with a longitudinal bore 6 for this purpose.

A flow regulating piston 7 projects into the pressure chamber 24 with its front face, the back of the pressure plate 1 also simultaneously forming an end stop. The flow control piston 7 is slidably arranged in a bore in the housing or the cover of the vane pump. The rear piston surface of the flow control piston 7 lies in a spring chamber 8 of the bore, in which a spring 9 is arranged, which exerts a closing force on the flow control piston 7 in the direction of the pressure plate 1. The spring chamber 8 is connected via a transverse bore 10 to a pressure chamber 11, which is located behind the throttle device 2.

The flow control piston 7 is provided with a control edge 12, behind which there is an inlet opening 13 with an adjoining flow return line 14. The throttle device 2 and the flow control piston 7 are parallel to each other. The inlet opening of the throttle bore 4 is perpendicular to the longitudinal axis of the flow control piston 7. A control slide 15 consists of a throttle plate 16 and a web 17. The web 17 is mounted in a transverse bore 18 of the flow control piston 7. The transverse bore 18 is designed as a blind bore and a spring 19 is stretched between the bottom of the blind bore 10 and the rear end of the web 17. In this way, the throttle plate is always pressed against the peripheral wall of the throttle device 2.

As can be seen from FIG. 3, the throttle plate 16 forms a segment of a hollow cylindrical shape, the inner diameter of which is at least approximately matched to the outer diameter of the throttle device. A good seal or throttling is provided in this way. Furthermore, the control slide 15 also forms an anti-rotation lock for the flow control piston 7. The control slide can be simple and inexpensive, e.g. be made from diecast or injection molding. Also different materials, e.g. Plastic, possible.

Instead of the illustrated throttle bore 4, a plurality of throttle bores can optionally also be arranged one behind the other in the longitudinal direction or in the circumferential direction in the throttle device 2. Throttle bores can also be offset on the circumference of the throttle plate 16. In this way, partial coverage may be possible and thus also a certain independence from the piston travel.

A pressure kidney 20, via which the pressure chamber 24 is supplied with pressure oil, is indicated by dashed lines in FIG. 3. - 9 -

As can be seen from FIGS. 1 and 2, the cylindrical throttle device 2 has a collar 21 at the front end projecting into the pressure chamber 24, which collar forms a stop for the pressure plate 16. Furthermore, the web 17 of the control slide 15 can be provided in its free area with a notch 22 (shown in dashed lines in FIG. 1). In this way, a point of attack for easier assembly and disassembly is formed.

4-8 different configurations of the throttle plate 16 are shown in plan view. In addition to a simple rectangular shape, as described in FIGS. 1-3, shapes can be selected, the front edge 23 in particular deviating from a straight line. In this way, the possibilities of variation with regard to the characteristic curves become even more variable. In addition, subsequent changes in operation are easily possible by a corresponding exchange of the control slide with a modified throttle plate 16.

With the designs according to FIGS. 4-6, at the beginning of the coverage area, the characteristic curves decrease less. In particular with a configuration according to FIG. 6, in which there is a semicircular cutout at the front edge 23, a partial linearization of the characteristic curve is achieved, because when the throttle bore 4 is passed over it is closed more strongly at the beginning. An opposite effect is achieved with an embodiment according to FIG. 7. In this case, the characteristic curve can even increase slightly after the cut-off point.

8 shows a front edge 23 with an oblique edge.

The examples shown in FIGS. 4-8 can only be seen as part of a multitude of possibilities. Depending on the application and the desired curve, there are numerous possible variations.

The control device according to the invention now works in the following way:

When the vane pump starts and up to a cut-off point, the flow control piston 7 is in the closed position shown in FIG. 1, ie the pressure chamber 24 is not connected to the inlet opening 13 to the delivery flow return line due to the position of the control edge 12 of the flow control piston 7 14 connected. The pressure medium coming from the pressure kidneys, in general oil, flows through the fixed bore 5 and the throttle bore 4 into the 'throttle device 2 and from there via the central longitudinal bore 6 to the outlet opening 3 Spring chamber 8 before a corresponding pressure difference. Up to the cut-off point, the volume throughput increases correspondingly with increasing speed. After the control point has been exceeded, its size and arrangement come about, which is influenced, for example, by the bores 4 and 5, the piston 7 experiences an opening movement. This creates a connection created between the pressure chamber 2 and the return line 14 and the excess pressure medium can flow out of the two pressure kidneys to an appropriate extent and be returned to the suction side of the pump.

Through the opening movement of the flow control piston 7, however, the control slide 15 with the throttle plate 16 approaches the throttle bore 4. If the flow control piston 7 is now opened further, the throttle plate 16 is increasingly pushed laterally over the throttle bore 4. In this way, a gradual throttling is achieved.

As soon as the hydraulic steering is actuated, the flow control piston 7 experiences a relative closing movement due to the back pressure from the line that is moved thereby, namely because of the higher pressure in the spring chamber 8. This in turn leads to a complete or partial opening of the throttle bore 4. In this way, especially when steering in the upper speed range, a larger amount of oil is available, which ensures a sufficient steering speed. At high speeds, for example when driving on a motorway, there is only a low volume throughput. If it is now to be steered at this high speed, for which the operating pressure rises accordingly, the volume throughput also increases correspondingly with increasing pressure. Sufficient volume throughput is therefore always available for steering. The bore 5 serves to improve the cold start behavior. In this case it acts alone in the open position and the risk of cavitation is reduced due to the low flow rate.

Instead of a blind bore 18, a continuous transverse bore can optionally also be used. In this way there is symmetry and no assembly errors can occur. In this embodiment, the spring 19 is then arranged between the underside of the throttle plate 16 and the peripheral wall of the flow control piston 7 above the web 17.

The longitudinal bore 6 in the throttle device can be dimensioned such that it determines the cut-off point. All that is required is that the flow cross-sections of the throttle bore 4 and the bore 5 together are larger than the flow cross-section of the longitudinal bore 6.

In addition to improving the cold start behavior through the bore 5, this bore can also be used to influence the characteristic curve itself. Depending on their size, they can influence the "falling" tendency of the characteristic curves.

9 shows the front region of a spring control piston 7 on a reduced scale, the web 17 of the control slide 15 not being inserted directly into a transverse bore 18 of the flow control piston 7. Instead, the control slide 15 has a base part 25 with a threaded bolt 26 in the lower region. The web 17 is likewise inserted into a transverse bore in the base part 25, or it is formed in one piece with it. In this case, the front end face of the flow control piston 7 has a threaded bore into which the threaded bolt 26 of the control slide 15 can be screwed. The advantage of this embodiment compared to the previously discussed exemplary embodiments is that the distance x can be adjusted or can also be changed subsequently if required. This means that changes in the characteristic curves are possible in this way, as a result of which the device according to the invention can be optimally adjusted to the existing conditions. It is only necessary that, after a final adjustment, the threaded bolt 26 is secured or locked in its position.

Claims

P a t e n t a n s r u c h e

1) Control device for a positive displacement pump, in particular a vane pump, with a flow control piston, the front piston surface of which has a pressure chamber in front of a throttle device which has at least one throttle bore which can be changed in the opening cross section by a control slide fastened to the flow control piston, and the rear piston surface of which is connected to a pressure chamber behind the throttle device, and to a delivery flow return line, the inlet opening of which is released as a function of the position of the flow control piston, the flow control piston being arranged in a bore next to the throttle device, characterized in that the inlet opening of the Throttle bore (4) at least approximately perpendicular to the longitudinal axis of the current control piston (7) and that the control slide (15) has a throttle plate (16) which can be pushed parallel to the longitudinal axis of the flow control piston (7) over the inlet opening of the throttle bore (4).

2) Control device according to claim 1 d a d u r c h g e k e n n z e i c h n e t that throttle device (2) and flow control piston (7) are parallel to each other and that the throttle bore (4) is arranged in a peripheral wall of the throttle device (2).

3) Control device according to claim 2 d a d u r c h g e k e n n z e i c h n e t that the throttle device (2) has a cylindrical shape at least in the region of the throttle bore.

4) Control device according to claim 3 d a d u r c h g e k e n n z e i c h n e that the throttle plate (16) has at least approximately a segment of a hollow cylindrical shape, the inner diameter of which is at least approximately matched to the outer diameter of the throttle device (2).

5) Control device according to one of claims 1-4, characterized in that the throttle plate (16) is provided with a web (17) which is mounted in a transverse bore (18) of the flow control piston (7). 6) Control device according to claim 5 characterized in that a spring (19) is supported on the flow control piston (7), which presses the throttle plate (16) against the peripheral wall of the throttle device (2).

7) Control device according to claim 6 d a d u r c h g e k e n n z e i c h n e t that the spring (19) in the transverse bore formed as a blind bore (18) lies behind the web (17).

8) Control device according to claim 6 d a d u r c h g e k e n n z e i c h n e t that the spring (19) between the underside of the throttle plate (16) and the peripheral wall of the flow control piston (7) is clamped.

9) Control device according to one of claims 1 - 8 d a d u r c h g e k e n n z e i c h n e t that the throttle device (2) at the front, the pressure chamber (24) facing end has a collar (21).

10) Control device according to one of claims 1 - 9 d a d u r c h g e k e n n z e i c h n e that the throttle bore (4) is offset in the circumferential direction to the throttle plate (16).

11) Control device according to one of claims 1-10, characterized in that the throttle bore (4) is designed as an elongated hole. 12) Control device according to one of claims 1-11, characterized in that the throttle plate (16) has a rectangular shape in plan view.

13) Control device according to one of claims 1 - 12 d a d u r c h g e k e n n z e i c h n e t that the front edge (23) of the throttle plate (16) - related to the closing direction - from the straight line in the form of recesses, incisions, recesses, roundings and the like. deviates.

14) Control device according to one of claims 1 - 13 d a d u r c h g e k e n n z e i c h n e t that the throttle device (2) in addition to the throttle bore (4) uf- 'has a bore (5) with an invariable cross section for the passage of the pressure medium.

15) Control device according to claim 5 d a d u r c h g e k e n n z e i c n e t that the web (17) in the free area between throttle

.platte (16) and flow control piston (7) has a notch, a cam or the like. (22).

16) Control device according to one of claims 1-15, characterized in that the throttle device (2) is provided with a longitudinal bore (6) into which the throttle bore (4) and possibly the bore (5) open and that the longitudinal bore (6) is dimensioned such that it determines the cut-off point. 17) Control device according to one of claims 1-16, characterized in that the control slide (15) in the lower region has a base part (25) with a threaded bolt (26), through which it can be adjusted and adjusted as a separate unit with the flow control piston (7) is connected.