WO2010079011A1

WO2010079011A1 - Pump unit for producing brake pressure in a brake system

Info

Publication number: WO2010079011A1
Application number: PCT/EP2009/066022
Authority: WO
Inventors: Reiner Fellmeth; Erwin Sinnl
Original assignee: Robert Bosch Gmbh
Priority date: 2009-01-08
Filing date: 2009-11-30
Publication date: 2010-07-15
Also published as: DE102009000069A1

Abstract

A pump unit (15) for producing brake pressure in a brake system has two hydraulic brake circuits (2, 3), with which in each case at least one wheel brake device (8, 9; 10, 11) is associated. For each brake circuit (2, 3), the pump unit (15) has at least one delivery piston (16, 17, 18; 19, 20, 21), wherein the delivery pistons can be driven by eccentric cams (28, 29), which are arranged on a common shaft (23). The eccentric cams (28, 29) have differing eccentricity (e1, e2).

Description

description

title

PUMP UNIT FOR GENERATING BRAKE PRESSURE. IN A BRAKING SYSTEM

The invention relates to a pump unit for generating brake pressure in a brake system according to the preamble of claim 1.

State of the art

In DE 10 2007 020 503 A1, a hydraulic vehicle brake system is described, which is designed as a dual-circuit brake system with two connected to a common master cylinder brake circuits, each brake circuit acts on two wheel brake on the wheels. The vehicle brake system is equipped with a hydraulic pump unit, consisting of a respective one brake circuit associated hydraulic pump and a common, both hydraulic pumps actuated electric motor. By controlling the pump unit driving assistance systems can be realized or supported, for example, a traction control or vehicle dynamics control.

When designing the pumps, it is important to consider brake circuit-related dimensioning. In diagonal brake circuits pumps of the same power can be used, whereas in the case of axle-related brake circuits in the case of equally sized pumps hydraulic reactive currents arise for the electrical motor drive power must be delivered. However, differently sized pumps require additional design effort and are associated with increased costs.

Disclosure of the invention The invention is based on the object, with simple constructive measures, to adapt a pump unit for generating brake pressure in a brake system with at least two hydraulic brake circuits to the pump delivery flows required per brake circuit.

This object is achieved with the features of claim 1. The dependent claims indicate expedient developments.

The pump unit according to the invention is used in brake systems of vehicles, which are provided with at least two hydraulic brake circuits, each of which is assigned at least one wheel brake device. The pump unit generates the required hydraulic pressure per brake circuit. For this purpose, the pump unit has at least one delivery piston per brake circuit, wherein each delivery piston is to be driven via an eccentric cam assigned to it and the eccentric cams are arranged on a common shaft. When the shaft rotates, the delivery pistons resting against the contour of the eccentric cam are driven. Since only one shaft is provided for all eccentric cams, a single drive unit which drives the shaft, for example an electric motor, is sufficient for both brake circuits.

According to the invention, it is provided that the eccentric cams have different eccentricity for realizing different high delivery flows per brake circuit. Due to the different eccentricity, the delivery pistons are deflected to different degrees, and a correspondingly different hydraulic fluid delivery flow is established. Thus, the different high demands on the flow rates in the brake circuits are taken into account, especially in the case of a Bremskreisaufteilung on a Vorderachskreis and a Hinterachskreis, since in this case, the brake circuits have a very different elasticity due to different levels of braking requirements. For example, the Vorderachskreis has an elasticity in the order of 30 mm ³ / bar and the Hinterachskreis an elasticity of about 15 mm ³ / bar. These different levels of elasticity require different pump flow rates, which are realized via the different eccentricities of the eccentric cam. In contrast to prior art embodiments in which the same pump delivery flows are conveyed in the front axle and in the rear axle circle, since reactive currents must circulate in the rear axle due to the different degrees of brake circuit elasticity, the pump delivery flow in the case of the elasticity-related design according to the invention can be adjusted to the respective one

Bremskreiselastizität be aligned. The advantage is a power reduction in the overall system, since no hydraulic reactive currents are generated.

The adaptation to the different brake circuit elasticities is achieved with simple design measures. To change the eccentricity or to adapt to the respective hydraulic flow rate per brake circuit is to be realized with relatively little design effort. Here are various measures for implementation into consideration. On the one hand, it is possible to realize the different high flow rates alone over a non-circular outer contour of the eccentric cam, wherein the outer contours, relative to the axis of the shaft on which the eccentric cams are arranged, differ from each other. In this case, if necessary, the eccentric cams may also be arranged centrically to the shaft, so that the eccentricity is set solely by way of adaptation of the outer contour of the eccentric cams. Basically possible is a combination with an eccentric arrangement of the cams on the

Wave despite the non-round outer contour of each cam.

On the other hand disc-shaped, round eccentric cam can be provided which are arranged eccentrically on the shaft. The different eccentricity is here set either via a different Exzentermaß with which the cam axis relative to the shaft axis is radially displaced, and / or over a different outer radius of the eccentric cam. If necessary, it is sufficient to arrange eccentric cam with different outer diameter with the same eccentric on the shaft, since in this embodiment, the respective associated delivery pistons are subjected to different large radial deflection.

The two eccentric cams are seen in the axial direction of the shaft one behind the other, preferably immediately one behind the other or with only a small axial distance. The drive of the shaft on which sit the eccentric cams and the

Recirculating eccentric cam, preferably via an electric motor. Furthermore, it may be expedient to associate with each brake circuit a plurality of delivery pistons which are each acted upon by an eccentric cam. According to a preferred embodiment, three delivery pistons are assigned to each brake circuit, which are arranged in particular at a 120 ° angle distance from one another and are grouped radially around the shaft with the eccentric cams. When the shaft rotates, each eccentric cam acts on all its associated delivery pistons. Providing three delivery pistons per brake circuit has the advantage that lower pressure pulsations occur in the brake circuits. In addition, the brake pressure can be controlled variable and better to the respective

Adjust the driving situation.

The two brake circuits of the brake system are in particular in a front-axle brake circuit with two wheel brake devices on the two front wheels and a rear axle brake circuit with two wheel brake devices on the rear wheels. In this division, a higher pump delivery flow of the hydraulic fluid is required in the front-axle brake circuit than in the rear-axle brake circuit, which is achieved via the different eccentricities of the eccentric cams.

Further advantages and expedient embodiments can be taken from the further claims, the description of the figures and the drawings. Show it:

1 shows a hydraulic circuit diagram of a vehicle brake system with a front axle brake circuit and a rear axle brake circuit and with an ESP system, which has a pump unit with three delivery pistons per brake circuit,

2 shows the pump unit of the ESP system in a perspective view,

3 shows a section through the pump unit with a representation of two eccentric cams seated on a common shaft, which each drive the delivery pistons assigned to them, wherein the eccentric cams have a different eccentricity,

Fig. 4, the eccentric cam in an enlarged detail view. In the figures, the same components are provided with the same reference numerals.

As can be seen from the hydraulic circuit diagram according to FIG. 1, the brake system 1 in a motor vehicle has two brake circuits 2 and 3, in which it is located in the

Embodiment is a front-axle brake circuit and a rear-axle brake circuit. The two brake circuits 2, 3 are connected to a common master cylinder 4, which is assigned a brake fluid reservoir 5, wherein the master cylinder 4 is operated by the driver via the brake pedal 6. The brake pedal 6 is associated with a pedal travel sensor 7 for measuring the pedal travel.

About the front axle brake circuit 2 wheel brake devices 8 and 9 are operated on the two front wheels, on the rear axle brake circuit 3 Radbrems- devices 10 and 1 1 on the rear wheels. In each brake circuit 2, 3 is a changeover valve 12 which is connected to the master cylinder 4, wherein the changeover valves are opened in their de-energized normal position. Each switching valve 12 is associated with a flow-through from the master cylinder to the respective wheel brake check valve, which is connected in parallel to the changeover valve.

Between the switching valves 12 and the respective Radbremsvorrichtungen 8, 9, 10, 1 1 are inlet valves 13, which are also open in the de-energized state and which are associated with check valves, which are traversed by the wheel brakes in the direction of the master cylinder.

Each wheel brake device 8, 9, 10, 1 1 is associated with an exhaust valve 14, which is closed in the de-energized state. The outlet valves 14 are connected to the suction side of a pump unit 15, which has in each case three individual pumps 16, 17, and 18 or 19, 20 and 21 per brake circuit 2, 3. The pump unit 15 is also associated with an electric drive motor 22 which drives a shaft 23 which actuates the pumps 16 to 21. The pressure side of the pumps 16 to 21 is connected to a line section between the switching valve 12 and the two inlet valves 13 per brake circuit. The suction sides of the pumps 16 to 21 are also connected to a main switching valve 24, which are hydraulically connected to the master cylinder 4. As part of a dynamic control intervention, the main switching valves 24, which are closed in the de-energized state, can be opened so that the pumps 16 to 21 draw in hydraulic fluid directly from the master brake cylinder 4 for a rapid buildup of brake pressure. The brake pressure build-up here is independent of an actuation of the brake system by the driver. The pump unit 25 with the individual pumps 16 to 21, the electric drive motor 22 and the shaft 23 forms part of a driving dynamics assistance system, in particular an ESP system (electronic stability program).

Between the outlet valves 14 and the suction side of the pumps 16 to 21 is located in each brake circuit 2, 3, a hydraulic accumulator 25, which serves for the interim storage of brake fluid, which omitted during a dynamic driving engagement through the exhaust valves 14 from the wheel brake 8 to 1 1 has been. Associated with the hydraulic accumulator 25 is a check valve arranged in the connecting line between the outlet valves 14 and the suction side of the pumps 16 to 21, which can be flowed through in the direction of the suction side of the pumps.

Each brake circuit 2, 3 is associated with a respective pressure sensor 26 in the area of the wheel brake devices 8, 9 or 10, 11. Another pressure sensor 27 is located in the brake circuit 2 adjacent to the master cylinder 4th

In Fig. 2, the pump unit 15 is shown in individual representation. Each brake circuit are assigned to three designed as a delivery piston individual pumps 16 to 18 and 19 to 21. The delivery pistons of a brake circuit are each grouped around a disc-shaped eccentric cam 28 or 29 at an angle of 120 ° and are acted upon by the eccentric cam 28 and 29, respectively. The eccentric cams 28 and 29 are arranged on the shaft 23 and rotate with the shaft 23, which is driven by the electric drive motor. Due to the eccentricity of the eccentric cam 28 and 29 results in the rotation of the shaft 23 at each delivery piston a radial actuation, so that each piston produces a delivery flow. The height of the flow per brake circuit can be adjusted via the eccentricity of the respective eccentric cam 28 and 29, which are placed on the shaft 23 directly axially behind one another.

As can be seen from the sectional illustration according to FIG. 3 and the enlarged illustration of FIG. 4, the eccentric cams 28 and 29 seated at a small axial distance from one another on the shaft 23 have a different degree with respect to the shaft 23 or the shaft axis 30 Eccentricity on. As a result, the delivery pistons of each brake circuit are deflected to different degrees and accordingly also convey a different high hydraulic fluid volume flow. Referring to FIG. 3, this means that the drawn delivery piston 16, which is assigned to the first brake circuit on the front axle, conveys a different volume flow than the second delivery piston 19, which is arranged axially offset and the second brake circuit is assigned to the rear axle. Since at the wheel brake devices of the front axle, a higher braking force than in the rear axle brake circuit is required, which has the first

Cam associated eccentric cam 28 a greater eccentricity than the second brake circuit associated eccentric cam 29th

The different sized eccentricities are, as shown in FIG. 4, referred to ei and e ₂ . In the embodiment shown, the two eccentric cams 28 and 29 are each disk-shaped and have the same outer diameter. The eccentricity is achieved by a radial offset ei or e ₂ between the respective cam center axis 31 or 32 and the shaft axis 30 of the shaft 23. Since a higher volume flow is to be conveyed in the first brake circuit, the eccentric dimension ei of the first eccentric cam 28 is greater than the eccentric dimension e _{2 of} the second eccentric cam 29. In addition, the eccentric cams 28 and 29 are arranged eccentrically offset by 180 ° relative to one another.

A typical eccentric dimension is for example for the front axle

Brake circuit ei = 0.8 mm and for the rear axle brake circuit e ₂ = 0.6 mm. This results in a circular elasticity in the front-axle brake circuit of approximately 30 mm ³ / bar and in the rear-axle brake circuit of approximately 15 mm ³ / bar.

Claims

claims

1 . Pump unit for generating brake pressure in a brake system in a vehicle, wherein the brake system (1) with at least two hydraulic brake circuits (2, 3) is provided, which at least one wheel brake device (8, 9, 10, 1 1) is assigned , characterized in that the pump unit (15) per brake circuit (2, 3) at least one delivery piston (16, 17, 18, 19, 20 21), wherein the delivery piston (16, 17, 18, 19, 20 21) via Eccentric cam (28, 29) are driven, which are arranged on a common shaft (23), and wherein the eccentric cam (28, 29) for the realization of different high flow rates per brake circuit

(2, 3) have a different eccentricity (βi, e ₂ ).

2. Pump unit according to claim 1, characterized in that each brake circuit (2, 3) three delivery pistons (16, 17, 18, 19, 20 21) are assigned.

3. Pump unit according to claim 2, characterized in that the three delivery pistons (16, 17, 18, 19, 20, 21) of a brake circuit (2, 3) can be driven by a common eccentric cam (28;

4. Pump unit according to claim 2 or 3, characterized in that the three delivery pistons (16, 17, 18, 19, 20 21) of a brake circuit (2, 3) are arranged to each other at a 120 ° -Winkelabstand.

5. Pump unit according to one of claims 1 to 4, characterized in that the eccentric cams (28, 29) are disc-shaped and arranged eccentrically to the shaft axis (30).

6. Pump unit according to one of claims 1 to 4, characterized in that the eccentric cam (28, 29) have a non-circular outer contour.

7. Pump unit according to one of claims 1 to 6, characterized in that the eccentric cam (28, 29) have the same diameter, but have a different sized eccentric distance to the shaft axis (30).

8. Pump unit according to one of claims 1 to 7, characterized in that the eccentric cam (28, 29) have different diameters.

9. Brake system in a vehicle with a pump unit (15) according to one of claims 1 to 8, with at least two hydraulic brake circuits (2,

3), which in each case at least one wheel brake device (8, 9, 10, 1 1) is associated

10. Brake system according to claim 9, characterized by a front axle brake circuit (2) and a rear axle brake circuit (3).

1 1. Brake system according to claim 10, characterized in that the front axle brake circuit (2) associated eccentric cam (28) has a greater eccentricity than the rear axle brake circuit (3) associated eccentric cam (29).