DE102005034571A1 - Electrohydraulic unit - Google Patents

Abstract

The invention relates to an electro-hydraulic unit - in particular device for controlling the brake and traction slip and the vehicle dynamics control. DOLLAR A The invention is based on the object to provide an electro-hydraulic unit, which easily enables different power generation modes. DOLLAR A The object is achieved by the electro-hydraulic unit is provided with a piston pump 2 and with a device to between different hydraulic active surfaces or active surface combinations A1; Switch A1 + A2.

Description

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

in the Passenger vehicle construction is a trend towards variable passenger cars such as 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 theirs increased mass, what reinforced Brakes required. Also in the rest There is a trend to strengthen the brake system to reduce the braking distance. Large volume Brakes have one increased brake fluid volume intake - also as a result of elasticities. The recording volume is to fulfillment the above functionalities provided by the electro-hydraulic unit.

Besides is an essential one Task of a brake system therein, unwanted changes in position of a parked Vehicle to prevent, in short, the so-called parking brake function to enable. traditionally, is the active energy to press or release the parking brake muscular from a driver or generated mechatronically by a motor-gear unit. Such variants are associated with the disadvantage that they are either not very comfortable or extra Require units for energy conversion, namely an electromotive Actuator with electronic control unit, which is the cost of a brake system inappropriately increased.

A concerns further development of electrohydraulic aggregates a so-called hydraulic parking brake (HPB). Such parking brake devices differ significantly of conventional parking brake actuation comprising a brake cable that is susceptible to wear, by an already existing engine-pump unit, the hydraulic energy which applies the pistons in wheel brakes, so that these be locked in the tensioned state by means of a separate device, thereby maintaining the park braking effect. The electromechanical generated hydraulic pressure is effectively chambered in the wheel brakes, what the desired Achieved braking effect. This makes it possible to have a muscular activity Parking brake or on an additional to dispense with electromechanical transducer. A mere actuation of a electric actuator or switch is completely sufficient.

The described tasks confront a modern vehicle brake system with the problem that very different funding conditions for the Piston pump present, and that a simple enlargement of the Conveying capacity in terms of to a theoretically conceivable extreme case to a complete oversizing of the conveyor in view of the vast majority practical applications to lead would.

From the DE 102 49 909 A1 goes out a piston pump for a vehicle brake system. 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 each have brake circuit, shows the unpublished WO 2005/050015 A1 an aggregate with 3 conveyors each brake circuit. Thereby can high volume flows overcome become. Unfortunately, this proposal is not space neutral.

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

Finally is also been proposed elsewhere, an electric motor specifically temporary to overload, 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. A further object is to avoid the disadvantages mentioned, and to provide an electrohydraulic aggregate which, in a simple, robust and preferably purely mechanical way, enables grading of the hydraulic power light.

According to the invention, it is proposed that the electro-hydraulic unit is provided with a device is to easily between different sized hydraulic surfaces or Effective surface combinations (A1, A1 + A2) to switch a piston pump.

With the device according to the invention is the advantage linked for example, a first power generation mode on a first hydraulic active surface (A1 + A2) is based, and that a second power generation mode on a second hydraulic active surface (A2) is based, wherein the first effective area (A1 + A2) greater than the second effective area (A2) is formed. This makes it possible, high flow rates, for example only in the low pressure range with a relatively large piston effective area A1 + A2 to promote and, for example, from entry into the high pressure area either to switch suddenly or successively on the relatively small piston effective area A1.

The Invention allows in a sense a targeted, either by certain physical process variables automatically initiated or electronically controlled introduced hydraulic gearshift, on the basis of which the advantage is achieved that one - in comparison with conventional Aggregates - undersized Motor can handle even peak loads without complaint, without being permanently overloaded to become. It need not be further stressed that this measure with a power reduction of the required electric motor, as well can be associated with a cost reduction, in addition to the Height of consumed electricity is reduced. So the invention leads to a reduction the on-board network load.

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

By the invention will be advantageously enabled, for example a hydraulic parking brake by using a delivery piston with big ones hydraulic effective surface fast with big ones Flows are filled can, without a change the delivery hub to have to make. For the Supply with low flow rates in one High pressure area, however, a reduced hydraulic effective area is provided. Because the active surfaces So are formed selectively reducible, this allows a reduction the load of a pump drive motor and consequently a reduced electrical current consumption. The electrical load of the vehicle electrical system is therefore reduced.

The The invention is not tied to parking brake applications but can in principle always be used, if an intelligent energy management is required. this makes possible Further fields of application, also beyond the brake and suspension control technology new uses to open up.

According to one sibling solution said problem, the piston pump comprises a device with the at least one piston is formed telescopically. This causes a change possibility for the Displacement stroke.

In Another embodiment of the invention, the device is a switching device provided 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 to enable or to stop. This makes it possible, the hydraulically effective cross-sections bundled in different combinations or act individually to let. The switching device is at least operative, but preferably also locally, placed between the piston segments.

The Piston segments have identically sized or different sized hydraulic Active surfaces on.

In Another embodiment of the invention is the piston pump as a radial piston pump trained, and has one first centric piston segment, which is of a radially outer, concentric Piston segment is surrounded. The centric piston segment has a comparatively small hydraulic effective area (A1), while the large effective area is additive from the hydraulic active surfaces (A1 + A2) is composed of two piston segments together.

Of the Cross section of the piston segments - and thus also the active surfaces - is circular or circular.

According to the first embodiment of the invention, the switching takes place in the composition of the active surfaces A1, A1 + A2 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 directly from the drive (eccentric) driven. 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 frictional Switching device, it is conceivable and advantageous if a positive coupling is provided. After such an embodiment of the invention are hydraulically operated, form-locking coupling means provided that cause that the hydraulic active surfaces coupled or decoupled.

In Variation of this thought is a mechanical interlock, like in particular spring-loaded locking means, conceivable which one frictional Coupling or decoupling cause.

According to the invention the device at least one Elastoelement, which under the effect of a predetermined hydraulic pressure in a displacement space gives way to a switch in the composition of the hydraulic active surfaces to enable.

advantageously, the switching device has a first elastomeric element which is suitable, the two piston segments in a rear dead center to urge while a second elastomeric element is intended for one of the two piston segments to elastically bias against the action of the hydraulic pressure.

at another embodiment of the invention, the switching device at least one electromagnetically switchable element, which in order Activation or deactivation of the clutch with an electronic Controller communicates to the activation or deactivation using the electronic controller.

Further Features, advantages and applications of the invention go in the following from the description of exemplary embodiments with reference to FIG Drawing forth.

In the drawing shows:

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

2 an embodiment of the invention using a coupling device with an elastomeric element, and

3 a schematic diagram for clarifying Wirwirächenverhältnissen on piston segments.

First, be in short, the principle hydraulic connection of a hydraulic Vehicle brake system explained.

A Brake system usually includes a pneumatic brake booster, and a, a pressure fluid reservoir having, master cylinder or simulator, its pressure chambers via brake lines with wheel brakes can be connected. The pressure chambers and wheel brakes are in pairs in so-called brake circuits I, II summarized. In the brake circuits I, II, the so-called Diagonal distribution under summary of diagonally opposite Enforced wheel brakes of the front axle and rear axle of a vehicle, in principle, other divisions such as the so-called black and white division pairwise combination of the wheel brakes of an axle is possible.

to Detection of driver-side pressure in a connection between the pressure chamber and wheel brakes is usually a pressure sensor in the brake line, which is a pressure chamber with wheel brakes from Brake circuit I connects.

A receiving body (HCU) 1 includes the electromagnetic valves and essentially the hydraulic bore. 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 on, 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 (towards the master cylinder) and parking brake control operation by means of the piston pump 2 to allow each opens brake circuit I, II downstream between the low-pressure accumulator and a schematically illustrated input E of the piston pump 2 each a suction line in a suction channel. In each suction line, an electromagnetically actuated changeover valve is used, for example, with active vehicle dynamics control a pressure medium connection between the master cylinder, a brake fluid reservoir and the input E of the piston pump 2 manufactures.

Because the 1 and 2 match in large part, matching features are provided with matching reference numerals. After explaining the common features and contexts will be followed by peculiarities of 2 received.

From the 1 goes the described piston pump 2 on a greatly enlarged scale. A drive shaft 3 passes with one end into a crank chamber 4 in the receiving body 1 , and turns an eccentric 5 , of an eccentric camp 6 is surrounded. A largely cylindrical pump cartridge 7 comprises at least one bushing section 8th and is in a stepped bore 9 of the recording body 1 attached by a lid 10 is closed. Input E and output A open into the stepped bore 9 , The pump cartridge 7 includes a segmented, partially hollow piston 11 , which is sealed and oscillatory movable in the pump cartridge 7 is arranged. For this purpose, the piston is located 11 with one end on a bearing outer ring 12 of the eccentric bearing 6 and another end juts into a repressive room 13 and has a seat in this area 14 for a check valve body 15 , A return spring 16 is between receiving body 1 and pistons 11 clamped, and serves the elastic bias of the piston 11 to return to bottom dead center. Inside the pump cartridge 7 is a - already described in parts - pressure valve 17 and a suction valve 18 provided, which together the ventilation of the displacement chamber 13 serve.

A special feature of the invention is that the piston 11 a first, directly from the bearing outer ring 12 driven, central piston segment 19 has, which is necessarily taken along with each eccentric rotation. As a result, an effective hydraulic active surface A1 is provided, which generally contributes to fluid delivery.

The central piston segment 19 has substantially circular or circular cross-section and is of a second, annular piston segment 20 surrounded, which has a circular ring cross-section, and has the hydraulic effective area A2. The active surfaces A1 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 is a sealing element 21 at the central piston segment 19 intended. For sealing between liner section 8th and radially outer, annular piston segment 20 is this with a sealing element 22 Mistake.

A switching device may be a relative movement between the piston segments 19 . 20 enable or disable. The switching device in particular allows kinematics, in which either all piston segments 19 . 20 together with additive combined hydraulic effective area A1 + A2, or only the central, forcibly driven piston segment 19 Participate with its effective area A1 on the conveying movement. To the switching device according to 1 therefore belongs to a contact surface between the central piston segment 19 and radially outer piston segment 20 , which is so tolerated that a frictional entrainment of the indirectly entrained radially outer piston segment 20 takes place only in the low and medium pressure range. The switching device is characterized between the piston segments 19 . 20 effective. After exceeding a certain limit pressure in the displacement chamber 13 solves the switching device to a certain extent automatically automatically the force or friction between the piston segments 19 . 20 , This leaves the radially outer piston segment 20 In a sense, stand, and only the forced-driven, central, radially inner piston segment 19 participates in the repression.

The 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 Elastoelement - in the form of a known ansich known return spring 16 - acts on the two piston segments 19 . 20 directly or indirectly in the direction of the eccentric 5 , This will cause the radially inner piston segment 19 always put back in a bottom dead center and in contact with the eccentric 5 held (lower half of the figure). At the same time is for the radially outer piston segment 20 an attack 23 Are defined.

A second elastomeric element 24 acts against the return spring 16 and acts on the radially outer piston segment 20 against the effect of the hydraulic pressure in the displacement chamber 13 , This will make this piston segment 20 in principle with defined preload elastic in contact with the stop 23 held. The stop 23 is provided on a component, which at the same time as a spring plate for the rest of the return spring 16 on the centra len piston segment 19 serves. The second elastomer element 24 is provided to yield under a predetermined hydraulic pressure such that the frictional connection between the two piston segments 19 . 20 allowed or canceled. At the liner section 8th is a back stop 25 for the piston segment 20 provided, which prevents the elastomeric element 24 can be overly compressed. Like from the 2 continues to be readily apparent, is the second elastomeric element 24 formed as an elastically biased coil spring, which on the one hand on the radially outer piston segment 20 and on the other hand at a paragraph 26 the pump cartridge 7 is supported.

In Modification of the above-described embodiments of the invention are further designs possible, whose principle is based on a switching device according to the invention. This includes in particular Switching devices comprising a releasable coupling with mechanical activatable, positive locking Achieve means, or embodiments, which have electromagnetic switching means, in turn positive Can apply coupling agent. In this case, the electromagnetically switchable element for activation or deactivating the switching device, preferably from the same controlled electronic controller, which also for the control responsible for the electromagnetic valves.

1

receiving body

2

piston pump

3

drive shaft

4

crankcase

5

eccentric

6

eccentric

7

pump cartridge

8th

Liner section

9

stepped bore

10

cover

11

piston

12

Bearing outer ring

13

displacement space

14

Seat

15

Check valve body

16

Return spring

17

pressure valve

18

suction

19

piston segment

20

piston segment

21

sealing element

22

sealing element

23

attack

24

Elastoelement

25

attack

26

paragraph

e

entrance

A

output

A1

hydraulic effective area

A1 + A2

hydraulic effective area

Claims (13)

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 wheel brakes within brake circuits and separable by means of electromagnetically actuated valves of the wheel brakes, and at least one electromagnetically operable valve it a piston pump ( 2 ) allows to promote pressure medium either 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 (A1, A1 + A2) is provided. Electrohydraulic unit according to Claim 1, characterized in that the switching device is designed to permit relative movement between a first piston segment ( 19 ) with a defined hydraulic effective area (A1) and between a second piston segment ( 20 ) with a defined hydraulic effective area (A2) or to prevent. Electrohydraulic unit according to claim 2, characterized in that the piston segments ( 19 . 20 ) have a circular cross section or a circular ring cross section. Electrohydraulic unit according to claim 2 and 3, characterized in that the piston segments ( 19 . 20 ) have identical large or different sized hydraulic active surfaces (A1, A2). Electrohydraulic unit according to claim 2, characterized in that the switching device comprises at least one elastomeric element ( 24 ) to enable a switching operation. Electrohydraulic unit according to claim 5, characterized in that the elastomeric element ( 24 ) is adapted to yield under a predetermined hydraulic pressure such that the piston segments ( 19 . 20 ) coupled with each other or decoupled from each other. Electrohydraulic unit according to claim 2 and 5, characterized in that the switching device directly or indirectly at least one of the two piston segments ( 19 . 20 ). Electrohydraulic assembly according to claim 2 and 5, characterized in that the switching device each of the two piston segments ( 19 . 20 ). Electrohydraulic unit according to claim 2 and 5, characterized in that the switching device is an elastomeric element ( 16 ), which is suitable to both piston segments ( 19 . 20 ) to push in a dead center position. Electro-hydraulic unit according to claim 9, characterized in that one of the two piston segments ( 19 . 20 ) with the Elastoelement ( 24 ) is resiliently biased against the action of the hydraulic pressure. Electrohydraulic unit according to claim 2 and 5, characterized in that the switching device has a locking device, and that the locking device form-fitting, or non-positively, or frictionally connected to the piston segments ( 19 . 20 ) attacks. Electrohydraulic unit according to claim 2 and 5, characterized in that the switching device and / or the Locking device are mechanically formed. Electrohydraulic unit according to claim 2 and 5, characterized in that the switching device and / or the Locking device at least one electromagnetically switchable element having, which with an electronic controller of a vehicle brake system communicates to a coupling using the electronic controller to enable or disable.