CN115107721A

CN115107721A - Electro-hydraulic brake system, pressure supply device for a brake system and method for controlling a brake system

Info

Publication number: CN115107721A
Application number: CN202210278563.1A
Authority: CN
Inventors: J·洛加查里; M·瓦尔海斯; S·伯格
Original assignee: Continental Teves AG and Co OHG
Current assignee: Continental Automotive Technologies GmbH
Priority date: 2021-03-19
Filing date: 2022-03-17
Publication date: 2022-09-27
Also published as: DE102021202710A1

Abstract

The invention relates to an electrohydraulic brake system (100) having at least one hydraulically driven wheel brake (104) and a hydraulic pressure supply device (102) having a pressure cylinder (122) which is hydraulically connected to the wheel brake and a pressure piston (126) which is displaceable in the pressure cylinder (122) in an actuation direction (124) and which is designed for applying a pressure to a fluid located in the pressure cylinder (122), and a pivotably mounted manual brake lever (136) is arranged on the pressure supply device (102) in such a way that a force acting on the manual brake lever is at least partially converted into a force acting on the pressure piston in the actuation direction. In accordance with the invention, it is proposed that the pressure supply device has a motor drive which is designed to apply a force to the pressure piston in the actuating direction. The invention also relates to a pressure supply device and a method for controlling a brake system.

Description

Electro-hydraulic brake system, pressure supply device for a brake system and method for controlling a brake system

Technical Field

The present invention relates to an electrohydraulic brake system according to the preamble of claim 1, as well as to a pressure supply device for such a brake system and to a method for controlling such a brake system.

Background

A brake system of this type is described, for example, in DE 102005024979 a 1. The brake system described here has hydraulically actuated wheel brakes and a hydraulic pressure supply device, wherein the pressure supply device has a pressure cylinder which is hydraulically connected to the wheel brakes and a pressure piston which is displaceable in the pressure cylinder in the actuating direction. The pressure piston is designed for applying pressure to a fluid located in the pressure cylinder, wherein a pivotably mounted manual brake lever is arranged on the pressure providing device such that a force acting on the manual brake lever is at least partially converted into a force acting on the pressure piston in the actuating direction.

In brake systems of this type, the modulation of the brake pressure acting on the wheel brakes is usually effected by means of an assembly of an electric pump and a number of valves. For example, in the case of anti-lock brake control (ABS), these elements are controlled in a targeted manner such that locking of the wheel decelerated by the wheel brake is avoided by a corresponding adaptation of the brake pressure. This type of control is accompanied by a certain complexity in the control of the pumps and valves and in the arrangement of these elements in the same hydraulic unit.

Disclosure of Invention

Against this background, it is the basic object of the present invention to provide a brake system, a pressure supply device for the brake system and a method for controlling the brake system, which brake system simplifies the modulation of the pressure acting on the wheel brakes.

This object is achieved by a brake system according to claim 1, a pressure providing device according to claim 17 and a method according to claim 18, respectively. Preferred embodiments are the subject matter of the dependent claims.

In a first aspect, the invention relates to an electrohydraulic brake system having at least one hydraulically driven wheel brake and a hydraulic pressure supply device, wherein the pressure supply device has a pressure cylinder which is hydraulically connected to the wheel brake and a pressure piston which is displaceable in the pressure cylinder in an actuating direction, wherein the pressure piston is designed for applying a pressure to a fluid which is located in the pressure cylinder, and wherein a pivotably mounted handbrake lever is arranged on the pressure supply device such that a force acting on the handbrake lever is at least partially converted into a force acting on the pressure piston in the actuating direction. In accordance with the invention, it is proposed that the pressure supply device has a motor drive which is designed to apply a force to the pressure piston in the actuating direction.

The invention is based on the following considerations: the additional force which is superimposed on the force exerted by the driver by means of the handle lever is controllably applied to the element provided in the pressure providing device for providing the pressure in any case. In this way, it is possible to realize a plurality of driving functions in a simple manner. Thus, for example, the force exerted by the vehicle driver on the manual brake lever can be increased by correspondingly actuating the electric motor drive, so that the described assembly can be used as a brake force booster. It is also possible to modulate the brake pressure generated by the pressure piston by means of a corresponding force applied to the pressure piston by the motor drive in order to prevent locking of the wheel, for example, as a result of excessively high brake pressure.

It is also possible to implement a driving function that assists the driver of the vehicle when starting on a slope. Thus, after the driver has correspondingly applied a hand lever for actuating the brake when the vehicle is on a slope of a certain inclination, it can be proposed that the pressure piston continues to be applied in the direction of movement by correspondingly operating the motor drive even if the driver of the vehicle has released the hand brake lever. In this way, the brake pressure is maintained, thereby preventing the vehicle from slipping backward. If a start request is detected, the brake pressure can be reduced in a targeted manner by corresponding actuation of the electric motor drive, so that a reliable start can be achieved.

All these functions can be performed without intermediate connection valves between the pressure supply device and the wheel brakes, since the required brake pressure is set directly by the pressure supply device actuated by the vehicle driver. The design of the brake system according to the invention thus makes it possible to set the brake pressure in the wheel brake in a targeted manner in a very compact and simple manner.

In this case, it can be provided in particular that the force acting on the manual brake lever is transmitted to the pressure piston in only one direction. For example, it can be provided that a force acting on the hand brake lever is transmitted to the pressure piston, which force brings the hand brake lever from an unactuated resting position into an actuated position, while a force returning the hand brake lever to the resting position is not transmitted to the pressure piston.

In order to achieve a transmission of the force caused by the motor drive to the pressure piston, it is proposed according to a preferred embodiment that at least one transmission is arranged between the motor drive and the pressure piston, wherein the transmission is designed to convert a rotation of a drive shaft of the motor drive into a translation of the pressure piston in the actuation direction.

In principle, various types of transmission devices can be used here, which are suitable for converting a rotational movement into a translational movement. In this case, in particular, the drive shaft of the motor drive can also be oriented arbitrarily with respect to the pressure piston or the actuating direction of the pressure piston. However, according to a further embodiment, the drive shaft of the motor drive is arranged perpendicular to the actuating direction, and the transmission can be designed particularly simply here. In this case, the rotational movement can be converted into a translational movement in a very simple manner without additional transmission elements for further deflecting the force flow between the drive shaft and the pressure piston.

A further advantageous orientation between the drive shaft and the pressure piston consists in the parallel arrangement of the drive shaft relative to the actuation direction of the pressure piston. In this arrangement too, only a few operating elements are required in order to guide the force acting on the drive shaft onto the pressure piston.

In this case, according to a particularly preferred embodiment, it is provided that the gear mechanism has a toothed rack arranged on the pressure piston and a toothed wheel engaging into the toothed rack, wherein the teeth of the toothed rack extend perpendicularly to the actuating direction, and wherein the motor drive is designed for applying a torque to the toothed wheel. In this simple case, the conversion of the rotary movement of the drive shaft into a translation of the pressure piston is accordingly effected only by means of two transmission elements (i.e. by means of the drive gear and the toothed rack engaged into the gear). In this case, by means of a particularly simple design of the transmission, only very small frictional losses occur when the drive torque is transmitted from the motor drive to the pressure piston.

In order to ensure the greatest possible stability and durability of the elements involved in the force transmission, it is proposed according to a further embodiment that the toothed rack is designed in one piece with the pressure piston. In particular, the toothed rack can be milled into the pressure piston. In this case, it can also be provided for the durability of the lifting element that the region of the pressure piston which is designed with the toothed rack is hardened or coated. Wear of the teeth of the rack due to friction can thus be reduced.

Furthermore, according to another embodiment, it is provided that the transmission has a reduction transmission, wherein the reduction transmission reduces the rotational speed of the gear wheel relative to the rotational speed of the drive shaft of the motor drive. In this way, a motor that is weak in performance but rotates quickly can be used as the motor drive device. Such machines are typically smaller than electric motors capable of producing high torque. Thus, a compact design of the pressure supply device can be achieved by such a design. The reduction gear can also be designed in particular in a multistage manner.

In this case, according to a further embodiment, a particularly compact design of the transmission can be achieved in that the reduction transmission has at least one planetary gear. In particular, the transmission can also have a combination of a planetary gear and a further transmission.

Furthermore, it is proposed according to a preferred embodiment that the transmission has a clutch device, wherein the clutch device is designed for controllably establishing or interrupting the coupling of the rotation of the drive shaft of the motor drive with the translation of the pressure piston. Here, the coupling of the rotation of the drive shaft to the translation of the pressure piston likewise means that a force flow from the motor drive to the pressure piston is established. In principle, various types of devices can be used as the coupling device, which are suitable for the controlled establishment of a kinematic connection between the motor drive and the pressure piston. In the present context, the expression "controllable" means that the clutch device is not opened or closed at random, but can be caused to open or close by acting on it in a targeted manner. Such a control can be effected, for example, by an electronic actuator which, when a corresponding actuation is carried out, causes the clutch device to open or close.

The use of such a clutch device has the following advantages: in normal operation of the brake system, the motor drive can be decoupled from the pressure piston, so that the vehicle driver does not experience a resistance when actuating the brake lever, which resistance can be caused by friction in the motor drive and the transmission. Rather, a connection between the motor drive and the pressure piston can be established in a targeted manner when the applied brake pressure needs to be modulated. The clutch device is preferably designed such that, in the event of a failure of the electrical system of the brake system, the clutch automatically opens, so that the electric motor drive is decoupled from the pressure piston.

Furthermore, the clutch device is preferably coupled in one direction, so that a movement of the pressure piston does not necessarily have to force a movement of the motor drive, which however always causes a movement of the pressure piston. This can be achieved, for example, in that the clutch device automatically closes when the drive shaft of the motor drive rotates.

Due to the use of such a clutch device, further functions can be achieved by the brake system according to the invention. It is thus possible, for example, to lock the brake pressure applied to the wheel brakes into the wheel brakes when the vehicle is parked, by: the pressure piston is locked in the actuated position by closing the clutch device. This is achieved in particular in combination with a reduction gear between the motor drive and the pressure piston, since in a corresponding embodiment of the reduction gear a strong self-locking of the movement of the gear part can be produced by the movement of the pressure piston. Furthermore, it can be provided that the motor drive can be locked in a defined motor position in a targeted manner.

In order to ensure a reliable and precise actuation of the motor drive, according to a further embodiment it is proposed that the motor drive has a rotation angle sensor, wherein the rotation angle sensor is designed to detect a rotation angle of a rotor of the motor drive or a rotation angle of a drive shaft. The information obtained in this way about the rotor position or the angle of rotation of the drive shaft can be used, for example, to determine the position of the pressure piston in the pressure cylinder and thus the set brake pressure. In addition, such a detection of the rotation of the drive can be used to detect the actuation of the manual brake lever in the case of a permanent connection between the pressure piston and the electric motor for driving. Thus, each actuation of the manual brake which causes a displacement of the pressure piston also automatically causes a rotation of the drive shaft of the motor drive. This information can, for example, omit a brake light switch of the brake system, since the actuation of the hand brake lever can be detected in another way.

Furthermore, it is proposed according to a further embodiment that the pressure supply device has a position sensor, wherein the position sensor is designed to detect the position of the pressure piston in the actuation direction. Similarly to the above-described embodiments, the direct acquisition of the position of the pressure piston can also be used for determining the brake pressure and for recognizing an actuation of the hand brake lever.

In order to ensure a defined and reproducible initial position of the pressure piston, it is proposed according to a further embodiment that a resetting device is arranged in the pressure cylinder, wherein the resetting device is designed to apply a force to the pressure piston in the direction of the unactuated initial position. The restoring device can be in particular a helical spring which is supported on the one hand on the bottom side of the pressure cylinder and on the other hand on the front side of the pressure piston.

According to a further embodiment, the transmission of the force acting on the hand brake lever to the pressure piston is ensured by an actuating cam arranged on the hand brake lever spaced apart from the pivot axis of the hand brake lever, wherein the actuating cam is placed on an end face of the pressure piston and transmits the movement of the hand brake lever to the pressure piston via the end face. In this case, it can be provided, in particular, that the end faces of the actuating cam and/or of the pressure piston which rest on the actuating cam are coated or hardened, so that the wear of these two elements is reduced. The pivot axis of the manual brake lever is preferably oriented perpendicular to the actuation direction of the pressure piston.

In accordance with a further embodiment, it is provided that the actuating cam is embodied in one piece with the handbrake lever. In particular, the actuating cam can be designed on a manual brake lever. The hand brake lever is preferably made of metal (in particular aluminum).

Furthermore, it is proposed according to a further embodiment that the brake system has at least one electrical control unit, wherein the control unit is designed as a motor drive for controlling the pressure supply. Here, there is no need for a unified/unitary device in the control unit. More precisely, the control unit may be assembled from a plurality of individual elements which may be fitted at different locations of the vehicle.

In this case, according to a further embodiment, it is provided that the brake system has at least one wheel speed sensor for determining a wheel speed of a wheel assigned to the wheel brake, wherein the control unit is designed for controlling the electric motor drive as a function of the wheel speed determined by the wheel speed sensor. In particular, an anti-lock braking control in the brake system can thus be implemented by the control unit, for example.

According to a further embodiment, a particularly compact embodiment of the components of the brake system is achieved in that a control unit is arranged on the pressure supply device control unit. For this purpose, the control unit is preferably designed as a uniform/single block which is arranged, for example, in a housing which is fitted directly on the pressure supply device.

In a further aspect, the invention relates to a pressure supply device for a brake system of the type described above, wherein the pressure supply device has a pressure cylinder which can be hydraulically connected to the wheel brake and a pressure piston which is displaceable in the pressure cylinder in an actuating direction, wherein the pressure piston is designed for exerting a pressure on a fluid located in the pressure cylinder, and wherein a pivotably supported handbrake lever is arranged on the pressure supply device in such a way that a force acting on the handbrake lever is at least partially converted into a force acting on the pressure piston in the actuating direction. In accordance with the invention, it is proposed that the pressure supply device has a motor drive which is designed to apply a force to the pressure piston in the actuating direction.

In another aspect, the invention relates to a method for controlling a brake system as described above, wherein the method comprises: obtaining wheel speeds of wheels assigned to the wheel brakes; acquiring a wheel slip of the wheel based on the acquired wheel speed; operating the motor drive when the measured wheel slip of the wheel is outside the tolerance value of the wheel slip, so that a force acting on the pressure piston counter to the actuating direction is caused by the motor drive; and, as soon as the determined wheel slip is within the tolerance value of the wheel slip, actuating the motor drive so as to reduce the force acting on the pressure piston by the motor drive.

The method is preferably carried out by an electrical control unit of the brake system.

Drawings

Preferred embodiments of the invention are explained in detail below with reference to the drawings. In the drawings:

figure 1 shows a schematic view of an exemplary braking system,

figure 2 illustrates a detailed view of an exemplary pressure providing device,

figure 3 shows a detailed view of an exemplary creeper gear arrangement,

FIG. 4 shows a perspective view of an exemplary pressure providing device, an

FIG. 5 illustrates a flow chart of an exemplary method for controlling a brake system.

Detailed Description

In the following, features similar or identical to each other are denoted by the same reference numerals.

Fig. 1 shows a schematic view of an exemplary brake system 100, wherein the brake system 100 comprises a pressure providing device 102, wheel brakes 104, a control unit 106 and a sensor device 108 for determining the rotational speed of a wheel of a vehicle, to which the brake system 100 is applied, at which a braking torque is applied by the wheel brakes 104.

The wheel brakes 104 are hydraulic wheel brakes having brake pistons 110 displaceably supported in a housing 112. Arranged on the brake piston 110 is a friction lining 114, which can be brought into contact with a brake disk 116 when the brake piston 110 is displaced. On the side of the brake disk 116 opposite the friction lining 114, a further friction lining 118 is arranged. For example, the wheel brakes 104 may be floating calipers. On the side of the brake piston 110 facing away from the friction linings 114, a fluid-filled pressure chamber 120 is provided, which is hydraulically connected to the pressure supply device 102. If a brake pressure is now applied to the pressure chamber 120 by the pressure supply device 102, this brake pressure causes a force acting on the brake piston 110 in the direction of the brake disk 116, so that the friction linings 114 and subsequently the friction linings 118 come into contact with the brake disk 116. By further inducing a force acting on the

friction linings

114 and 118 in the direction of the brake disk 116, a braking force acting on the brake disk 116 can then be induced, which generates a braking torque acting on the wheel connected to the brake disk 116 in a rotationally fixed manner.

In order to provide such a brake pressure, the pressure supply device 102 has a pressure cylinder 122 which is hydraulically connected to the wheel brake 120 and a pressure piston 126 which is displaceable in the pressure cylinder 122 in an actuating direction 124. The pressure cylinder 122 is designed here, for example, in a housing 128 of the pressure supply device 102. A fluid-filled cavity 132 is formed between the pressure piston 126 and the end face 130 of the pressure cylinder 122, wherein a fluid (preferably a hydraulic fluid, in particular a brake fluid) in the cavity 132 is pressurized in the actuating direction 124 when the pressure piston 126 moves. This pressure is transmitted to the wheel brake 104 due to the hydraulic connection 134 between the cavity 132 and the pressure chamber 120, so that a braking force corresponding to the pressure acts on the brake disc 116 and thus on the corresponding wheel of the vehicle.

In order to exert a force on the pressure piston 126 in the actuation direction 124, a manual brake lever 136 is arranged on the housing 128 of the pressure supply device 102. Here, the manual brake lever 136 is pivotably supported about an axis 138, wherein the axis 138 is oriented perpendicularly to the actuation direction 124. Furthermore, an actuating cam 140 is provided on the manual brake lever 136, which cam is placed on an end face 142 on the rear side of the pressure piston 126. The actuating cam 140 is designed here as an integral part of the hand brake lever 136, i.e. not fastened as a separate component to the hand brake lever 136.

When the vehicle operator actuates the manual brake lever 136, a downward force is induced on the manual brake lever 136 in the illustration of FIG. 1. This force is transmitted via the actuating cam 140 to the end face 142 of the pressure piston 126, so that a force acting in the actuating direction 124 on the pressure piston 126 is generated. Thereby, the pressure in the cavity 132 and thus the brake pressure in the wheel brake 104 is increased. Although the force 124 in the braking direction can be transmitted to the pressure piston 126 by means of the manual brake lever 136, it is not possible to apply a force acting counter to the actuating direction 124 to the pressure piston 126 by means of the manual brake lever 136, because of the manner in which the force is transmitted from the manual brake lever 136 to the pressure piston 126.

For this purpose, however, a motor drive 144 is provided in the pressure supply device 102, which motor drive is designed to apply a force to the pressure piston 126 counter to the actuating direction 124. For this purpose, the motor drive 144 has a drive shaft 146 with a gear wheel 148, wherein the gear wheel 148 engages in a section of the pressure piston 126 designed as a toothed rack 150. Here, the drive shaft 146 is arranged perpendicular to the actuation direction 124 and thus also to the direction of movement of the pressure piston 126. Thus, the gear 148 and the rack 150 act together as a transmission, so that a rotation of the drive shaft 146 is converted into a translation of the pressure piston 126. Thus, by means of the motor drive 144, not only the actuating direction 124 can be reversed, but also a force acting on the pressure piston 126 in the actuating direction 124 can be caused.

The control unit 106 of the brake system 100 is connected to the motor drive 144 in such a way that the motor drive 144 can be selectively actuated by the control unit 106 in such a way that a defined force acting in or against the actuation direction 124 on the pressure piston 126 can be generated. Thus, for example, a driving function (e.g., anti-lock brake control) can be implemented, or the motor drive 144 can be used as a brake booster, thus boosting the actuation of the manual brake lever 136 by the vehicle operator by correspondingly operating the motor drive 144.

To implement an anti-lock brake control, the control unit 106 is connected to a sensor device 108 for detecting the wheel speed of the wheel to which the braking torque is applied by the wheel brakes 104. Wheel locking can be detected early by detecting the wheel speed of the wheel, wherein upon detection of a locked wheel, the control unit 106 actuates the electric motor drive 144 in such a way that a force acting on the pressure piston 126 in the opposite actuation direction 124 is generated. Thereby, the force acting on the brake disc 116 is reduced, so that the slip of the wheel can be reduced.

Fig. 2 again shows a sectional or detailed view of the pressure supply device 102, wherein the dimensioning of the pressure piston 126 and the position of the motor drive 144 and thus of the gear wheel 148 differ from the illustration in fig. 1.

As can be seen well in fig. 2, the teeth of the rack 150 are designed to be integral with the pressure piston 126. In particular, the teeth of the toothed rack 150 can be milled into the pressure piston 126. In order to reduce wear at the connection between the toothed rack 150 and the gear wheel 148, preferably at least the region of the pressure piston 126 embodied as toothed rack 150 is hardened or coated with a friction-reducing coating. In similar terms, it can also be provided that the end face 142 of the actuating cam 140 and/or of the pressure piston 126 is coated or hardened.

As can also be seen well in fig. 2, a resetting device 152 is arranged in the pressure cylinder 122, which resetting device is designed for exerting a force on the pressure piston 126 counter to the actuating direction 124. The restoring device 152 is designed here as a helical spring which is supported on the one hand on the end face 130 of the pressure cylinder 122 and on the other hand on the front face of the pressure piston 126.

In principle, the motor drive 144 may be any form of electric motor. However, in order to design the pressure supply device 102 as compactly as possible, it is advantageous to use as small an electric motor as possible as the motor drive 144. The available torque of the electric motor generally scales with the structural dimensions of the electric machine. In order to be able to generate a sufficiently strong force acting on the pressure piston 126 despite the use of a smaller electric motor, the embodiment according to the invention provides that a reduction gear is arranged between the motor drive 144 and the gear wheel 148. Here, the rotation speed of the gear 148 is reduced relative to the rotation speed of the drive shaft 146 of the motor 144 by the reduction gear. Thus, to provide the force acting on the pressure piston 126, a smaller but rapidly rotating electric motor may be employed as the motor drive 144.

To this end, a perspective detail view of an exemplary reduction gear 154 is shown in fig. 3. Such a reduction gear 154 may be arranged, for example, between the electric motor 144 and the gear 148 serving as a driven gear. The reduction is effected in the reduction gear 154 by means of a planetary gear 156, wherein a sun gear 158 of the planetary gear 156 is arranged on the drive shaft 146 of the electric motor 144. Here, the sun gear 158 drives three planet gears 160, the movement of which is transmitted to a driven plate 164 via bolts 162. Here, the planet gears 160 roll on the fixed outer ring 166, so that the rotational speed of the drive plate 164 is reduced relative to the rotational speed of the sun gear 158 and thus relative to the rotational speed of the drive shaft 146.

The transmission 154 used in the pressure providing device 102 previously discussed herein is not limited to the type of transmission shown in FIG. 3. Rather, the transmission used can also be designed as a multi-stage planetary transmission or as a combination of one or more planetary transmissions with other transmission types. As already explained above, in the presently illustrated variant of the pressure provision device 102, the drive shaft 146 is oriented perpendicularly to the actuation direction 124. However, the drive shaft 146 may also be oriented, for example, parallel to the actuation direction 124. This may be necessary, for example, due to the particular mounting location of the pressure providing device 102. In this case, the deflection of the force direction can also be achieved by a transmission arranged between the drive shaft 146 of the motor drive 144 and the gear wheel 148, which can be achieved, for example, by a spur gear transmission.

Additionally, fig. 4 illustrates a perspective view of an exemplary pressure providing device 102. Here, the motor drive 144 is arranged on the front side of the housing 128 of the pressure supply device 102. On the top side of the housing 128, a further housing 166 is arranged, in which the control unit 106 of the brake system 100 is arranged. In this way, a very compact design of the components of the brake system 100 or of the pressure supply device 102 and of the control unit 106 is achieved.

In order to specifically control the motor drive 144 via the control unit 106, it can also be provided that: in the pressure supply device 102 in the actuating direction 124, on the one hand, a sensor device is arranged for determining the rotational position or the angle of rotation of the drive shaft 146 or for determining the rotational position of the motor drive 144, and on the other hand, a sensor device is arranged for determining the position of the pressure piston 126. Depending on the pressure piston 126, it can be determined, for example, how much brake fluid has been displaced out of the cavity 132 by the pressure piston 126, so that the brake pressure applied can be determined directly. Furthermore, a plausibility test of the position of the pressure piston 126 can be carried out on the basis of the position of the motor, or the angle of rotation of the drive shaft 146 and knowledge of the conversion of the rotation of the drive shaft 146 into a translation of the pressure piston 126.

In the case of a permanent connection of the pressure piston 126 to the motor drive 144, an actuation of the manual brake lever 136 can also be inferred by detecting a rotation of the drive shaft 146. Thus, for example, a brake light switch, which is typically used to identify actuation of a brake or a manual brake lever 136, may be omitted.

According to a preferred embodiment, it is also provided that the rotation of the drive shaft 146 of the motor drive 144 does not have to be transmitted all the way to the pressure piston 126. For this purpose, it can be provided, for example, that the transmission has a clutch device, by means of which the rotation of the drive shaft 146 can be decoupled in a targeted manner from the translation of the pressure piston 126. In particular, it can be provided that, during normal brake actuation, the pressure piston 126 can be moved independently of the rotation of the drive shaft 146, since the clutch device is disengaged in the normal state. Only when the motor drive 144 is actuated and the drive shaft 146 is rotated in conjunction therewith, the clutch device is automatically closed, so that a rotation of the drive shaft 146 effects a translation of the pressure piston 126 or a force acting on the pressure piston 126.

FIG. 5 illustrates an exemplary method for controlling the braking system 100 as previously described. In a first method step 200, wheel speeds of the wheels assigned to the wheel brakes 104 are detected by means of the sensor device 108 during the ongoing braking process. Next, in method step 202, a wheel slip of the wheel is determined from the detected wheel speed. This can be done, for example, by comparing the wheel speeds of the observed wheel with the wheel speeds of another wheel of the vehicle which is not decelerated by the braking force.

Then, in a method step 204, it is checked: whether the wheel slip acquired by the wheel is outside the tolerance value of the wheel slip. Here, if it is determined that the measured wheel slip is within the tolerance value, the method jumps back to method step 200. However, if it is determined that the measured wheel slip is outside the tolerance value, in method step 206 the motor drive 144 is actuated by the control unit 106 in such a way that a force acting in the opposite actuating direction 124 on the pressure piston 126 is caused by the motor drive 144. In this way, the brake pressure applied in the wheel brakes 104 is reduced, thereby reducing wheel slip and restoring lateral guiding forces that the wheels may lose. In this case, the force acting on the pressure piston 126 in the opposite actuating direction 124 is maintained until the wheel slip of the wheel is again within the tolerance value. The motor drive 144 can then be actuated again, so that the force acting on the pressure piston 126 is reduced.

Claims

1. An electro-hydraulic brake system (100) having at least one hydraulically actuated wheel brake (104) and a hydraulic pressure supply device (102),

the pressure supply device (102) has a pressure cylinder (122) which is hydraulically connected to the wheel brake (104) and a pressure piston (126) which is displaceable in the pressure cylinder (122) in an actuating direction (124),

the pressure piston (126) is designed to exert a pressure on a fluid located in the pressure cylinder (122), and a pivotably mounted manual brake lever (136) is arranged on the pressure supply device (102) in such a way that a force acting on the manual brake lever (136) is at least partially converted into a force acting on the pressure piston (126) in the actuating direction (124),

characterized in that the pressure supply device (102) has a motor drive (144) which is designed to apply a force in the actuation direction (124) to the pressure piston (126).

2. Braking system (100) according to claim 1, characterized in that at least one transmission (154) is arranged between the motor drive (144) and the pressure piston (126), the transmission (154) being designed for converting a rotation of a drive shaft (146) of the motor drive (144) into a translation of the pressure piston (126) in the actuation direction (124).

3. Braking system (100) according to claim 2, characterized in that the drive shaft (126) of the motor drive (144) is arranged perpendicularly to the actuation direction (124).

4. A braking system (100) according to claim 2 or 3, characterized in that the transmission (154) has a rack (150) arranged on the pressure piston (126) and a gear wheel (148) engaged into the rack (150), the teeth of the rack (150) extending perpendicularly to the actuating direction (124), and the motor drive (144) is designed for applying a torque to the gear wheel (148).

5. A braking system (100) according to claim 4, characterized in that the rack (150) is designed to be integral with the pressure piston (126).

6. A braking system (100) according to claim 4 or 5, characterized in that the transmission (156) has a reduction transmission which reduces the rotational speed of the gear wheel (148) with respect to the rotational speed of the drive shaft (146) of the motor drive (144).

7. A braking system (100) according to claim 6, characterized in that said reduction gearing has at least one planetary gearing (156).

8. Braking system (100) according to any one of claims 2 to 7, characterized in that the transmission (156) has a clutch device designed for controllably establishing or interrupting the coupling of the rotation of the drive shaft (146) of the motor drive (144) with the translation of the pressure piston (126).

9. The brake system (100) according to one of claims 2 to 8, characterized in that the motor drive (144) has a rotation angle sensor which is designed for detecting a rotation angle of a rotor of the motor drive (144) or a rotation angle of the drive shaft (146).

10. Braking system (100) according to one of the preceding claims, characterized in that the pressure supply device (102) has a position sensor which is designed for acquiring the position of the pressure piston (126) in the actuation direction (124).

11. Braking system (100) according to one of the preceding claims, characterized in that a resetting device (152) is arranged in the pressure cylinder (122), which resetting device (152) is designed for applying a force to the pressure piston (126) towards an unactuated initial position.

12. Braking system (100) according to one of the preceding claims, characterized in that an actuating cam (140) is arranged on the manual brake lever (136) spaced apart from the pivot axis (138) of the manual brake lever (136), the actuating cam (140) being placed on an end face (142) of the pressure piston (126) and transmitting the movement of the manual brake lever (136) to the pressure piston (126) via the end face (142).

13. The brake system (100) according to claim 12, characterized in that the actuating cam (140) is embodied as integral with the manual brake lever (136).

14. Braking system (100) according to one of the preceding claims, characterized in that the braking system (100) has at least one electrical control unit (106), the control unit (106) being designed as a motor drive (144) for controlling the pressure supply device (102).

15. A braking system (100) according to claim 14, characterized in that the braking system (100) has at least one wheel speed sensor (108) for determining a wheel speed of a wheel assigned to the wheel brake (104), the control unit (106) being designed for controlling the motor drive (144) as a function of the wheel speed detected by the wheel speed sensor (108).

16. The brake system (100) according to claim 14 or 15, characterized in that the control unit (106) is arranged on the pressure providing device (102).

17. A pressure supply device (102) for a brake system (100) according to one of the preceding claims, the pressure supply device (102) having a pressure cylinder (122) which can be hydraulically connected to a wheel brake (104) and a pressure piston (126) which can be displaced in an actuation direction (124) in the pressure cylinder (122),

18. A method for controlling a brake system (100) according to one of claims 1 to 16, the method having the following steps:

● obtaining wheel speeds of wheels assigned to the wheel brakes;

● obtaining a wheel slip of the wheel based on the obtained wheel speed;

●, when the acquired wheel slip of the wheel is outside the tolerance value of the wheel slip, actuating the motor drive (144) in such a way that the motor drive (144) generates a force acting on the pressure piston (126) counter to the actuation direction (124); and is

●, the motor drive (144) is actuated to reduce the force acting on the pressure piston (126) by the motor drive (144) once the acquired wheel slip is within the tolerance value of the wheel slip.