WO2006051066A1 - Electrohydraulic unit - Google Patents

Abstract

The invention relates to an electrohydraulic unit, especially a device for controlling brake and traction slip and for regulating driving dynamics. The aim of the invention is to provide an electrohydraulic unit which allows various power generation modes in a simple manner. For this purpose, the electrohydraulic unit is provided with a reciprocating pump (2) and with a device for switching between various hydraulic effective areas or effective area combinations (A1; A1+A2).

Description

Electrohydraulic unit

The invention relates to an electro-hydraulic unit for motor vehicles. For example, it may be an aggregate for the conversion of electrical energy into mechanical energy, which is used in a brake system with a device for controlling the brake and traction slip and optionally for driving dynamics control in a motor vehicle, so that functions such as ABS, ASR or ESP be enabled.

In passenger cars, there is a trend towards variable passenger cars, in particular so-called SUVs (sports utility vehicles), to MPVs, to 7-seaters or, for example, preferably in the USA to so-called light trucks. A feature of all these vehicles is their increased mass, which requires increased brakes. Moreover, there is a trend to strengthen the brake system to reduce the braking distance. Large-volume brakes have an increased volume of brake fluid - also due to elasticity. The intake volume must be provided by the electrohydraulic unit to meet the above functionalities.

In addition, an essential task of a brake system is to prevent unwanted changes in position of a parked vehicle, in short to allow the so-called parking brake function. Conventionally, the active energy for actuating or releasing the parking brake is muscular by a vehicle driver or mechatronic a motor-gear unit generates. Such variants are associated with the disadvantage that they are either not very comfortable, or require additional units for energy conversion, namely an electromotive actuator with electronic control unit, which increases the cost of a brake system inappropriate.

Another development in electrohydraulic units relates to a so-called hydraulic parking brake (HPB). Such parking brake devices differ significantly from conventional Parkbremsaktuatorik comprising a wear-prone brake cable by an already existing engine-pump assembly builds up the hydraulic energy which acts on the pistons in the wheel brakes so that they are locked by means of a separate device in the tensioned state, thereby to maintain the park braking effect. The electromechanically generated hydraulic pressure is effectively chambered in the wheel brakes, which achieves the desired braking effect. This makes it possible to dispense with a muscular operation of a parking brake or on an additional electromechanical transducer. A mere actuation of an electric actuator or switch is completely sufficient.

A completely new trend is towards so-called hybrid vehicles, which have an electric drive motor. In this case, a strong networking between a flexible, adaptable electro-hydraulic brake system and a drive train is required so that the energy recovery - for example, by recuperative braking - is possible. The described problems confront a modern vehicle brake system with the problem that there are very different delivery conditions for the piston pump, and that a simple increase in the delivery capacity with respect to a theoretically conceivable extreme case would lead to a complete oversizing of the conveyor device in view of the predominant practical applications ,

From DE 102 49 909 Al a piston pump for a vehicle brake system is apparent. The piston is designed in several parts and comprises at least two synchronously movable part pistons, wherein the first part piston is associated with a first hydraulically effective Duchmesser, and wherein the second part piston is associated with the second hydraulically effective diameter.

While conventional brake systems each have a conveyor device per brake circuit, shows the unpublished WO 2005/050015 Al an aggregate, each with 3 conveyors per brake circuit. As a result, high volume flows can be handled. Unfortunately, this proposal is not space neutral.

Furthermore, quite generally stroke-adjustable pumps with swash plates are known, wherein an angular displacement of the swash plate causes a Hubveränderung of pump piston and thereby a flow control. However, an articulation of the swash plate is provided, and swash plate solution are useful only in conjunction with axial piston pumps.

Finally, it has already been suggested elsewhere been specifically targeted to overload an electric motor temporarily to handle stress peaks of a pump.

The invention is based on the task of electrohydraulic units with respect to their capacity to better adapt to the varying requirements of modern passenger cars, but without unduly increasing the construction costs and in particular the size. Another object is to avoid the disadvantages mentioned, and to provide an electro-hydraulic unit, which allows a simple, robust and preferably purely mechanical way, a gradation of hydraulic power.

According to the invention, it is proposed that the electrohydraulic unit be provided with a device in order to switch easily between hydraulic surfaces of differing dimensions or effective surface combinations (Al, Al + A2) of a piston pump.

The advantage of the device according to the invention is that, for example, a first energy generation mode is based on a first active hydraulic surface (Al + A2) and a second energy generation mode is based on a second active hydraulic surface (A2), the first active surface (A1 + A2) greater than the second effective area (A2) is formed. This makes it possible to promote high flow rates, for example, only in the low pressure range with a relatively large piston effective area Al + A2, and, for example, to switch suddenly or successively on the relatively small piston effective area Al from entry into the high pressure area. As a result, the invention makes it possible to provide a targeted hydraulic gearshift, which is automatically initiated either by specific physical process variables or electronically controlled, on the basis of which the advantage that a motor, undersized compared to conventional power units, can even cope with peak loads without lasting damage to be overloaded. Needless to say, this measure may be associated with a reduction in the power of the required electric motor, as well as a reduction in cost, with the added benefit of reducing the amount of power consumed. So the invention leads to a reduction of the on-board network stress.

The invention is associated with the further advantage that the hydraulic switching is completely independent of an influence of a mechanical transmission such as in particular an eccentricity between the pump drive and the radial piston pump. Because the eccentricity remains constant.

By the invention it is advantageously possible that, for example, a hydraulic parking brake can be quickly filled by using a delivery piston with a large hydraulic effective area with large flow rates, without having to make a change in the delivery stroke. For the supply of low flow rates in a high pressure area, however, a reduced hydraulic effective area is provided. Because the active surfaces are thus formed reducible targeted, this allows a reduction of the load of a pump drive motor and consequently a reduced electrical current consumption. The electrical stress on the vehicle electrical system is consequently reduced.

The invention is not bound to parking brake applications, but in principle can always be used when intelligent energy management is required. This allows further fields of application in order to open up new uses beyond braking and chassis control technology.

According to a sidelined solution of said problem, the piston pump comprises a device with which at least one piston is formed telescopic. This causes a change possibility for the displacement stroke.

In a further embodiment of the invention, the device is provided as a switching device to allow a relative movement between a first piston segment with a first hydraulically effective cross section and a second piston segment with a second hydraulically effective cross section, or to prevent. This makes it possible to bundle the hydraulically effective cross-sections in different combinations or to act individually. The switching device is at least operatively, but preferably also locally, placed between the piston segments.

The piston segments have identically sized or differently sized hydraulic active surfaces.

In a further embodiment of the invention, the piston pump is designed as a radial piston pump, and has a first centric piston segment, which of a radial outer, concentric piston segment is surrounded. The centric piston segment has a comparatively small hydraulic effective area (Al), while the large effective area is additively composed of the hydraulic effective areas (A1 + A2) of two piston segments.

The cross section of the piston segments - and thus also the effective surfaces - is circular or circular.

According to the first embodiment of the invention, the switching in the composition of the active surfaces Al, A1 + A2 is hydraulically controlled due to the prevailing hydraulic pressure in a working space of the piston pump. For example, a radially outer, annular piston segment can be arranged by means of a transition fit frictionally engaged on the circumference of a central piston segment. The centric piston segment is driven directly by the drive (eccentric). The frictional engagement between the outer and inner piston segments is now tuned such that the radially outer piston segment only participates in the displacement movement in the low or medium pressure region. After exceeding a limit pressure, the hydraulic pressure forces exceed the friction stresses between the two piston segments. As a result, only the positively driven, centric piston segment participates in the displacement stroke. The radially outer piston segment only participates again in the displacement movement when the limiting pressure has fallen below.

In further development of the frictional or non-positive switching device, it is conceivable and advantageous if provided a positive coupling is. After such an embodiment of the invention hydraulically actuated, positive-locking coupling means are provided, which cause the hydraulic active surfaces are coupled or decoupled.

In a modification of this idea is a mechanical locking, in particular spring-loaded locking means, conceivable which cause a frictional coupling or decoupling.

According to the invention, the device comprises at least one elastomeric element, which yields under the action of a predetermined hydraulic pressure in a displacement chamber to allow a switch in the composition of the hydraulic active surfaces.

Advantageously, the switching device has a first elastomeric element which is suitable for urging the two piston segments into a rearward dead center position, while a second elastomeric element is intended to elastically bias one of the two piston segments against the action of the hydraulic pressure.

In another embodiment of the invention, the switching device has at least one electromagnetically switchable element, which in order to activate or deactivate the clutch with an electronic controller is in communication to make the activation or deactivation using the electronic controller.

Further features, advantages and possible applications of the invention will become apparent from the description of FIG Exemplary embodiments with reference to the drawing.

In the drawing shows:

1 is an enlarged section through a piston pump for use in a hydraulic unit, comprising a coupling device with a friction element, and

Fig. 2 shows an embodiment of the invention using a coupling device with an elastomer element, and

Fig. 3 is a schematic diagram to illustrate Wirwirächenverhältnissen on piston segments.

First, let us briefly explain the basic hydraulic interconnection of a hydraulic vehicle brake system.

A brake system usually includes a pneumatic brake booster, and one, a

Pressure medium reservoir having, master cylinder or simulator whose pressure chambers can be connected via brake lines with wheel brakes. The pressure chambers and wheel brakes are combined in pairs in so-called brake circuits I, II. In the brake circuits I, II, the so-called diagonal distribution has been enforced by combining diagonally opposite wheel brakes of the front axle and rear axle of a vehicle, in principle, other divisions such as the so-called black / white division under pairwise combination of the wheel brakes of an axle is possible.

For detecting a pressure applied by the driver in a connection between the pressure chamber and wheel brakes is usually a pressure sensor in the brake line, which connects a pressure chamber with wheel brakes from the brake circuit I.

A receiving body (HCU) 1 comprises the electromagnetic valves and essentially the hydraulic bore. Thus, the receiving body forms a core of an electro-hydraulic unit. Each brake circuit has an electromagnetic isolation valve and, for each wheel brake, one inlet valve and one outlet valve in each case. To the wheel brakes of each brake circuit I, II return lines are connected, which lead back to the respective master cylinder pressure chamber. The exhaust valves are intended for targeted pressure reduction in the wheel brake. Furthermore, at least one low-pressure accumulator is integrated in the return, which can absorb discharged fluid in a flash, if the pump delivery is delayed.

Each brake circuit has an electric motor driven piston pump 2, which sucks from the low pressure accumulator or from a brake fluid reservoir to - depending on the respective necessary function - to promote pressure chambers or in the wheel brakes.

To change between ABS return operation (in the direction of the master cylinder) and parking brake

To allow control operation by means of the piston pump 2, opens each brake circuit I, II downstream between the low pressure accumulator and a schematically illustrated input E of the piston pump 2 each have a suction line into a suction channel. In each suction line, an electromagnetically actuated changeover valve is used, For example, when active vehicle dynamics control establishes a pressure medium connection between the master brake cylinder, a brake fluid reservoir and the input E of the piston pump 2.

Because FIGS. 1 and 2 largely agree, matching features are provided with corresponding reference numerals. After explaining the common features and relationships will be discussed in connection with features of FIG.

From Fig. 1, the described piston pump 2 is shown in greatly enlarged scale. A drive shaft 3 extends with one end into a crank chamber 4 in the receiving body 1, and rotates an eccentric 5, which from an eccentric bearing

6 is surrounded. A largely cylindrical pump cartridge 7 comprises at least one bushing section 8 and is mounted in a stepped bore 9 of the receiving body 1, which is closed by a cover 10. Input E and output A open into the stepped bore 9. The pump cartridge

7 includes a segmented, partially hollow piston 11, which is arranged sealed and oscillatory movable in the pump cartridge 7. For this purpose, the piston 11 is at one end to a bearing outer ring 12 of the eccentric 6, and another end protrudes into a displacement chamber 13 and has in this area a seat 14 for a check valve body 15. A return spring 16 is between receiving body 1 and Clamp 11 is clamped, and serves the elastic bias of the piston 11 to return to the bottom dead center. Within the pump cartridge 7 a - already described in parts - pressure valve 17 and a suction valve 18 is provided, which together the ventilation of the Displacement space 13 serve.

A special feature of the invention is that the piston 11 has a first, directly from the bearing outer ring 12 driven, central piston segment 19, which is necessarily taken along with each eccentric rotation. As a result, an effective hydraulic active surface Al is provided, which generally contributes to fluid delivery.

The central piston segment 19 essentially has a circular or annular cross section and is surrounded by a second, annular piston segment 20, which has a circular ring cross section and has the hydraulic effective area A2. The active surfaces Al and A2 may have identical matching or different sized geometric surfaces. For sealing between the central piston segment 19 and radially outer piston segment 20, a sealing element 21 is provided on the central piston segment 19. For sealing between bushing section 8 and radially outer, annular piston segment 20, this is provided with a sealing element 22.

A switching device may allow or prevent a relative movement between the piston segments 19, 20. In particular, the switching device makes possible a kinematics in which either all the piston segments 19, 20 together with additive combined hydraulic active surface Al + A2, or only the central, positively driven piston segment 19 participate with its active surface Al on the conveying movement. To the switching device of FIG. 1, therefore, a contact surface between the central piston segment 19 and the radially outer piston segment 20, which is tolerated so that a frictional entrainment the indirectly entrained radially outer piston segment 20 takes place only in the low and medium pressure range. The switching device is thereby effective between the piston segments 19,20. After exceeding a certain limit pressure in the displacement chamber 13 solves the

Switching device in a sense automatically automatically the force or frictional engagement between the piston segments 19,20. As a result, the radially outer piston segment 20 remains as it were, and only the positively driven, central, radially inner piston segment 19 participates in the displacement.

Fig. 2 illustrates two different dead centers of another embodiment of the invention. In this embodiment, the switching device has Elastoelemente, which allow a switching operation. A first elastomeric element - in the form of a known prior art return spring 16 - acts on the two piston segments 19,20 directly or indirectly in the direction of the eccentric 5. Thus, the radially inner piston segment 19 is always placed back in a bottom dead center and held in contact with the eccentric 5 ( lower half of the figure). At the same time, a stop 23 is defined for the radially outer piston segment 20.

A second elastomer element 24 counteracts the restoring spring 16 and urges the radially outer piston segment 20 against the action of the hydraulic pressure in the displacement chamber 13. As a result, this piston segment 20 is held in elastic contact with the stop 23 in principle with a defined preloading force. The stopper 23 is provided on a component, which at the same time as a spring plate for the support of Return spring 16 on the central piston segment 19 is used. The second elastomeric element 24 is provided to yield under a predetermined hydraulic pressure such that the frictional connection between the two piston segments 19, 20 is made possible or canceled. To the

Bushing section 8, a rear stop 25 is provided for the piston segment 20, which prevents the elastomeric element 24 can be excessively compressed. As is further apparent from FIG. 2, the second elastomeric element 24 is designed as an elastically prestressed helical spring, which is supported on the radially outer piston segment 20 on the one hand and on the shoulder 26 of the pumping cartridge 7 on the other hand.

In a modification of the above-described embodiments of the invention, further designs are possible whose principle is based on a switching device according to the invention. These include, in particular, switching devices which achieve a detachable coupling with mechanically activatable, positive-locking means, or embodiments which have electromagnetic switching means which in turn can apply positive-locking coupling means. In this case, the electromagnetically switchable element for activating or deactivating the switching device is preferably controlled by the same electronic controller, which is also responsible for the control of the electromagnetic valves. LIST OF REFERENCE NUMBERS

1 Aufnähmekörper

2 piston pump

3 drive shaft

4 crank room

5 eccentrics

6 eccentric bearings

7 pump cartridge

8 bushing section

9 step drilling

10 lids

11 pistons

12 bearing outer ring

13 displacement space

14 seat

15 check valve body

16 return spring

17 pressure valve

18 suction valve

19 piston segment 20 piston segment

21 sealing element

22 sealing element

23 stop

24 Elasto element

25 stop 26 paragraph

E entrance

A output

Al hydraulic effective surface

A1 + A2 hydraulic effective area

Claims

claims 1. Electrohydraulic unit - in particular device for controlling the brake and traction and the vehicle dynamics control - which has a master cylinder whose pressure chambers are connected via brake lines with paired within brake circuits wheel brakes and separable by means of electromagnetically actuated valves of the wheel brakes, and wherein at least one electromagnetically operable valve allows a piston pump (2) to promote pressure medium selectively from the master cylinder in the direction of wheel brakes or from the wheel brakes in the direction of the master cylinder, characterized in that at least one piston (11) of the piston pump (2) is provided segmented, and that a Device for switching (switching device) between different hydraulic Active surfaces or active surface combinations (Al; A1 + A2) is provided. 2. Electrohydraulic unit according to claim 1, characterized in that the switching device is adapted to a relative movement between a first piston segment (19) having a defined hydraulic effective area (Al) and between a second piston segment (20) with a defined hydraulic effective area (A2) to allow or prevent. 3. Electro-hydraulic unit according to claim 2, characterized in that the piston segments (19,20) have a circular cross section or a circular ring cross section. 4. Electrohydraulic unit according to claim 2 and 3, characterized in that the piston segments (19,20) identically large or different sized hydraulic active surfaces (Al, A2). 5. Electrohydraulic unit according to claim 2, characterized in that the switching device comprises at least one elastomeric element (24) to enable a switching operation. 6. Electro-hydraulic unit according to claim 5, characterized in that the Elastoelement (24) is adapted to yield under a predetermined hydraulic pressure such that the Kolbenseqmente (19,20) are coupled together, or be decoupled from each other. 7. Electro-hydraulic unit according to claim 2 and 5, characterized in that the switching device indirectly or directly at least one of the two piston segments (19,20) acted upon. 8. Electrohydraulic unit according to claim 2 and 5, characterized in that the switching device acts on each of the two piston segments (19,20). 9. Electro-hydraulic unit according to claim 2 and 5, characterized in that the switching device comprises an elastomeric element (16) which is adapted to urge both piston segments (19,20) in a rear dead center. 10. Electrohydraulic unit according to claim 9, characterized in that one of the two piston segments (19,20) is resiliently biased against the effect of the hydraulic pressure with the Elastoelement (24). 11. Electrohydraulic unit according to claim 2 and 5, characterized in that the switching device has a locking device, and that the locking device positively, or non-positively, or frictionally engages the piston segments (19,20). 12. Electrohydraulic unit according to claim 2 and 5, characterized in that the switching device and / or the locking device are mechanically formed. 13. Electrohydraulic unit according to claim 2 and 5, characterized in that the switching device and / or the locking device comprise at least one electromagnetically switchable element, which is in communication with an electronic controller of a vehicle brake system to activate a coupling using the electronic controller or disable.