EP2547564A1

EP2547564A1 - Brake booster having flexible actuation

Info

Publication number: EP2547564A1
Application number: EP11703681A
Authority: EP
Inventors: Lin Feuerrohr; Jochen Moench; Christian Meyer; Hans-Peter Dommsch; Stefan Demont; Martin-Peter Bolz
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2010-03-16
Filing date: 2011-02-15
Publication date: 2013-01-23
Also published as: WO2011113658A1; CN102791548A; CN102791548B; DE102010002924A1

Abstract

A brake booster for a brake system that can be actuated by moving an actuating element comprises an electric motor having a rotatable shaft for outputting a torque and a converter for converting the torque into a moving force that acts on the actuating element. The converter comprises a rolling body which is connected to the shaft and has a radial outer surface and a lateral flexible transfer element, wherein a section of the transfer element is seated against the outer surface of the rolling body and the transfer element is designed to carry out the conversion by transferring forces directed along the transfer element.

Description

description

title

Brake booster with flexible control An actuation of a brake system, for example in a motor vehicle, is usually facilitated by means of a brake booster, which increases a force applied by a driver of the motor vehicle braking force by a certain amount or a certain factor. The resulting braking force is imparted to a brake system of the motor vehicle, which then brakes one or more wheels of the motor vehicle. One common type of brake boosters operates on the basis of a vacuum accumulator evacuated from a suction port of an internal combustion engine of the motor vehicle so that the vacuum reservoir provides energy to boost the braking force. Not every motor vehicle has an internal combustion engine that can be used to evacuate the pressure accumulator. For example, in diesel or electric vehicles, one occasionally manages to use instead an electrically operated vacuum pump. Vacuum accumulator and brake booster based thereon, however, are bulky and an arrangement of the brake booster with respect to the brake system is not very flexible.

It is an object of the invention to provide a brake booster, which overcomes one or more of the disadvantages mentioned. The invention solves this problem with a brake booster with the features of claim 1. Subclaims indicate preferred embodiments.

According to the invention, a brake booster for an actuatable by displacement of an actuator braking means comprises an electric motor having a rotatable shaft for delivering a torque and a converter for converting the torque in a force acting on the actuating element displacement force. For this purpose, the converter comprises a shaft connected to the shaft. which rolling body with a radial outer surface and a laterally flexible transmission element, wherein a portion of the transmission element bears against the outer surface of the rolling body and the transmission element is adapted to carry out the implementation by means of transmission of forces along the transmission element directed.

Due to the laterally flexible but preferably longitudinally rigid transmission element, it is possible to select an installation position of the brake booster relatively independent of an installation position of the braking device. In addition, the conversion by means of the transmission element can be designed in such a way that an over or reduction ratio between the movement of the rolling body and the movement of the actuating element is realized. A costly and possibly vulnerable gear of the electric motor can be dimensioned weaker in this way or omitted altogether. The conversion of the torque into the displacement force by means of the laterally flexible

Transmission element can achieve a very high efficiency in the range of 95 to 99%. As a result, wear of the brake booster can be minimized and a power demand on the electric motor can be reduced, so that the electric motor can be dimensioned smaller economically.

The forces running along the transmission element can essentially be tensile forces. As a result, the displacement force can be introduced in a simple manner in the actuating element, at the same time a driver-controlled operation of the actuating element independent of the function of the brake booster ("punch-through") remains possible. Thus, legal requirements for a reliability of the brake booster can be met.

The transmission element may be one of a rope, a chain, a flat band, a Bowden cable or a belt. These each laterally flexible

Transmission elements are available in a variety of designs in standard sizes, which can be accordingly cost. The properties of such standard components are well known, so that the brake booster can be optimized in terms of manufacturing costs and reliability. The length of an effective lever arm between a rotational axis of the rolling body and the voltage applied to the outer surface transmission element may be dependent on an angular position of the shaft. The rolling body may comprise, for example, a cable drum mounted eccentrically on the shaft. The displacement force on the actuating element is thus dependent on an angular position of the electric motor. For example, a defined progression of the braking force can be realized over an adjustment range of the electric motor.

The converter may comprise a further laterally flexible transmission element, of which a portion bears against the outer surface of the rolling body, wherein the displacement forces exerted on the actuating element by means of the transmission elements are anti-parallel to each other. Thus, the force applied by the brake booster displacement force counteract an operating force of the driver, for example, to give the driver a force feedback or a request for reduced braking. An amplification factor of the brake booster can therefore be less than one.

The transmission element can run in the manner of a pulley over a loose role, which is connected to the actuating element. As a result, when reducing an actuating travel, the displacement force acting on the actuating element can be increased. As a result, the electric motor can be dimensioned correspondingly smaller, resulting in reliability and cost advantages.

The brake device may include a foot brake lever acting on the actuator, and the transmission element may be configured to actuate the foot brake lever. A Hebelüber- or -Üntersetzung the Fußbremshebels can thus be advantageously used for the brake booster. A relationship between an actuation force of the footbrake lever and an actuation travel of the footbrake lever caused by the arrangement of the footbrake lever with respect to the actuation element can thus also apply to a relationship between the displacement force and a displacement path of the brake booster. The function of the brake booster is thus adjusted to the function caused by the driver of the motor vehicle. The electric motor may include a reduction gear. The deliverable by the electric motor torque can be increased, so that the electric motor can be dimensioned correspondingly smaller.

The actuating element may comprise a pressure piston of a brake cylinder. A known hydraulically actuated brake system can thus be used without or with only a few changes in connection with the brake booster according to the invention.

The invention will now be described in more detail with reference to the attached figures, in which:

FIG. 1 shows a brake booster on a brake system; FIG.

FIG. 2 shows the brake booster from FIG. 1 with actuation of the brake system via a foot brake lever; FIG.

FIG. 3 shows the brake booster from FIG. 1 with two transmission elements running antiparallel to each other; FIG.

FIG. 4 shows the brake booster from FIG. 1 in a further embodiment; FIG. and

FIG. 5 shows the brake booster from FIG. 1 with an angle-controlled transmission characteristic.

Detailed description of embodiments

Fig. 1 shows a brake booster 1 10 in a brake system 100. The brake system 100 is shown only in part; typically it is a brake system of a motor vehicle 105, in particular a passenger car. The brake system 100 is actuated by means of an actuating element 120 ("plunger"), which can be inserted into a brake cylinder 130. The illustrated embodiment with the brake cylinder 130 uses a hydraulic brake. Raulische actuation of brakes. In alternative embodiments, a different brake operation can be performed, for example by means of a push rod, so that the brake cylinder 130 is omitted. The brake booster 1 10 includes an electric drive 140 with a

Worm gear 150, which drives a drum 160. The electric drive 140 includes an electric motor that may include a reduction gear, such as a spur gear or planetary gear. A cable pull 170 is partially laid around the drum 160 and fastened to it in such a way that, during rotation of the drum 160, the cable pull 170 is wound up or unwound depending on the direction of rotation of the electric drive 140. The cable 170 runs via a deflecting element 180 to a loose roller 190, which is arranged on the actuating element 120, and from there to a closing element 185. The deflecting element 180 and the closing element 185 are attached to a common fastening structure, for example a chassis of the motor vehicle 105. In further embodiments, more or less than the one deflecting element 180 drawn in can also be used. The brake cylinder 130 and the electric drive 140, as well as optionally further elements of the brake system 100, are connected to the same fastening structure.

If the electric drive 140 rotates so that the drum 160 winds up the cable pull 170, the loose roller 190 drives the actuating element 120 to the right and the brake system 100 is actuated. In this case, the loose roller 190 causes a tensile force, which the cable pull 170 transmits in its longitudinal direction, to be only half as large as a shift force exerted by the loose roller 190 on the actuating element 120, to the right. At the same time a length of the cable 170, which is wound on the drum 160 during actuation of the brake system 100, twice as large as a actuation of the actuator 120. By providing more loose rollers 190 on the actuator 120 and optionally further deflecting elements 180 in the manner of a pulley For example, the ratio between tensile force in the cable 170 and displacement force of the loose roller 190 can be controlled as needed. In another embodiment, the loose roller 190 can also be dispensed with and the cable pull 170 can be connected directly to the actuating element 120 instead of the closing element 185. A foot brake lever 195 also acts on the actuator 120. When a driver of the motor vehicle 105 operates the foot brake lever 195, the foot brake lever 195 effects a rightward force on the actuator 120, which moves the actuator 120 to the right, thereby actuating the brake system 100.

As indicated by the dashed lines elements of the electric drive 140, the worm gear 150 and an additional deflecting element 180, a position of those elements that generate a tensile force in the cable 170 can be varied. According to further requirements, such as an available installation space, a preferred mounting position or other influencing factors, the brake booster 1 10 may be relatively independent of the other elements of the brake system 100 in the motor vehicle 105.

The illustrated worm gear 150 is self-locking, so that a pulling force caused in the cable pull 170 can be maintained even when the electric drive 140 is not activated. In other embodiments, another or an additional gear may also be used on the electric drive 140 and optionally be covered by it, for example a

Helical or planetary gear.

A rightward displacement force on the actuating element 120 can therefore be exercised independently both by means of the footbrake lever 195 and by means of the brake booster 10. The electric drive 140 is controlled in normal operation such that a driver-controlled actuation of the foot brake lever 195 is supported or amplified. An applied by the brake booster 120 operating force can be up to 2 kN in a large passenger car. Even if there is a defect in the area of the brake booster 110, so that the cable pull 170 is not tensioned, the foot brake lever 195 can be used to actuate the brake system 100.

Ends of the cable 170 in the region of the end element 185 and in the region of the drum 160 may be provided with terminating nipples in order to anchor the ends of the cable 170 to the respective element. Such a terminating nipple can for example consist of die-cast aluminum and Spliced end of the cable 170 to be splashed around. The diameter of the deflecting element 180 and the diameter of the loose roller 190 are chosen to be large enough to minimize wear of the traction cable 170 by bending stress. Preferably, the loose roller 190 and / or the deflecting element 180 has a circumferential groove in the respective roller body, so that a

Contact surface between the roller and the pull cable 170 is maximized.

FIG. 2 shows the brake booster 10 of FIG. 1 with actuation of the brake system 100 via the foot brake lever 195 as a variant of the embodiment shown in FIG. 1. In contrast to the embodiment shown in FIG. 1, the loose roller 190 is not connected to the actuating element 120, but to the foot brake lever 195. By means of a suitable choice of a distance between the loose roller 190 and a pivot point of the foot brake lever 195, an over or under reduction of the movement of the cable pull 170 relative to the movement of the actuating element 120 can be used. In particular, the ratio between the tensile force in the cable pull 170 and the displacement force exerted on the actuating element 120 can also be influenced.

In another embodiment, shown with dashed elements, the loose roller 190 is eliminated, and the cable 170 terminates at the foot brake lever 195.

As indicated by a dashed circle, a drive unit 210 of the brake booster 1 10, which comprises the drum 160, the worm gear 150, the electric drive 140 (not shown) and a deflecting element 180, relatively independent of the remaining elements of

Brake system 100 may be arranged. The drive unit 210 can be rotated, for example, in the illustrated circle, without jeopardizing a functional safety of the brake booster 1 10 or the brake system 100. When the drive unit 210 is rotated, it may be necessary to carry out a length compensation of the cable pull 170, for example by opening or closing.

Unwinding on or from the drum 160.

In further embodiments, as a transmission element between the drum 160 and the actuating element 120 instead of the cable 170 also a chain, a flat band, a Bowden cable, a belt or a similar component can be used, which is suitable, at least partially winding the drum 160 and transmitting forces acting along the transfer member.

FIG. 3 shows the brake booster 10 of FIG. 1 with two cable pulls 170 running parallel to one another. The cable pulls 170 are in different directions

Each direction of rotation partially wound on the drum 160. Remaining portions of the cables 170 extend in opposite directions via two deflecting elements 180 and from there to an introduction element 310, which is rigidly connected to the actuating element 120. Depending on the direction of rotation of the drum 160, the introduction element 310, and thus the actuating element 120, is moved to the right or to the left. Due to the rigid connection of the introduction element 310 with the actuating element 120, the brake booster 1 10 can also counteract a force caused by the foot brake pedal 195 on the actuating element 120. As a result, a driver-controlled brake actuation can be alleviated and / or the driver can be given a haptic feedback via the footbrake lever 195, for example when using an antilock braking system (ABS). However, in the illustrated embodiment, in particular when using the non-illustrated, self-locking worm gear 150 of Figure 1, an operation of the brake system 100 may not be possible even if the electric drive 140 is not functioning. Failure of the electric drive 140 causes the brake boost to fail. The vehicle remains braked by actuation by means of the foot lever 195. If the electric drive 140 fails in the actuated state, the brake operation that has already taken place must be solved in another way, for example by means of ABS valves of a downstream hydraulic transmission of the braking force. Thereafter, a limited brake function is available over a remaining travel of the actuator 120. Fig. 4 shows the brake booster 1 10 in another embodiment.

Here, a ribbon 410 is used instead of the pull cable 170, which can transmit at least limited forces in the thrust direction. A portion of the flat belt 410 is wound on the drum 160. From there, the flat strip 410 is guided to the deflecting element 180 and further parallel to the actuating element 120 to an introduction element 310 on the actuating element 120. To- At least a portion of the portion of the flat belt 410 wound on the drum 160 is held by a guide member 420 on the drum 160.

If the drum 160 rotates in the counterclockwise direction, as indicated by the dotted arrow, a tensile force is exerted on the flat strip 410, which converts the flat strip 410 into a displacement force on the introduction element 310, so that the actuating element 120 is pushed to the right and the brake system 1 10 is operated. On the other hand, if the drum 160 rotates in a clockwise direction, the flat belt 410 transmits a pushing force to the introduction element 310, which counteracts a driver-controlled actuation force introduced by means of the footbrake lever 195.

The ribbon 410 can only transmit much lower shear forces than tensile forces. If a thrust force introduced into the flat belt 410 exceeds a certain amount, the flat belt 410 bulges in the area between the

Deflection element 180 and the introduction element 310 upwards, so that no significant displacement force is more introduced into the actuator 120. In this way, the haptic feedback described above with reference to FIG. 3 can be realized for the driver of the motor vehicle 105, while still having an independent actuation of the brake booster 1 10

Brake system 100 is maintained by means of the foot brake lever 195.

Fig. 5 shows a brake booster 1 10 with a angular controlled transmission characteristic. In contrast to the embodiments described above, the drum 160 is replaced by a cam 510. The basic principle of the above-described embodiments is maintained by turning the cam 510 clockwise to exert a pulling force on the cable 170 and exert a rightward displacement force on the actuator 120 by means of the introducing member 310, so that the brake system 100 is operated.

Depending on the angular position of the cam 510, an effective radius, which results as a distance between the pivot point of the cam and the point of the cable 170 on which it leaves the cam 510, differs large. In the illustrated embodiment, this effective radius decreases with increasing angle of rotation in a clockwise direction, starting from the illustrated Position on. The output from the electric drive 140 (not shown) to the cam 510 torque corresponds to the product of the described effective radius and the tensile force in the cable 170. By changing the effective radius in dependence on the angular position of the cam plate 510 results in a predetermined relationship between the angular position of the electric drive 140 and the force exerted on the actuator 120 displacement force. In this way, a course of the force exerted on the actuating element 120 displacement force over the displacement path of the actuating element 120 can be selectively influenced, for example, to increase the brake booster with a strong driver-controlled actuation of the actuating element 120 accordingly.

In the illustrated embodiment, a fast movement of the actuating element 120 is possible with a relatively large effective radius of the cam 510 at unopposed brake (position A) and thus lower acting on the foot lever 195 counterforce. The associated relatively low actuation force is sufficient to exert a sufficient actuation force on the actuator 120 at a given output torque of the electric drive 140.

When partially activated brake (position B), the achievable actuation force at the same output torque of the electric drive 140 by the relatively small effective radius on the cam 510 is higher. Thus, the electric drive 140 can be dimensioned smaller overall, wherein the reduced operating speed is sufficient for the operation.

Claims

claims

1 . Brake booster (1 10) for a braking device (100) which can be actuated by displacement of an actuating element (120), wherein the brake booster (110) comprises:

- An electric drive (140) with a rotatable shaft (145) for delivering a torque;

a converter (160, 170) for converting the torque into a displacement force acting on the actuating element (120),

characterized in that

the transducer (160, 170) comprises a rolling body (160) connected to the shaft (145) and having a radially outer surface and a laterally flexible transmission element (170),

- Wherein a portion of the transmission element (170) on the outer surface of the rolling body (160) abuts and the transmission element (170) is adapted to carry out the implementation by means of transmission of along the transmission element (170) directed forces.

2. brake booster (1 10) according to claim 1, characterized in that along the transmission element (170) extending forces are essentially tensile forces.

3. brake booster (1 10) according to any one of the preceding claims, characterized in that the transmission element (170) is one of a rope, a chain, a flat belt, a Bowden cable or a belt.

4. brake booster (1 10) according to any one of the preceding claims, characterized in that the length of an effective lever arm between an axis of rotation of the rolling body (160) and the voltage applied to the outer surface of the transmission element (170) of an angular position of Abrollkörpers (160) is dependent.

Brake booster (1 10) according to one of the preceding claims, characterized in that the converter (160, 170) comprises a further laterally flexible transmission element (170), of which a portion on the outer surface of the rolling body (160) is applied and wherein the means of Transmission elements (170) on the actuating element (120) exercisable sliding forces are anti-parallel to each other.

Brake booster (1 10) according to any one of the preceding claims, characterized in that the transmission element (170) in the manner of a pulley on a loose roller (190) runs, which is connected to the actuating element (120).

Brake booster (1 10) according to any one of the preceding claims, characterized in that the braking device (100) comprises a foot brake lever (195) acting on the actuating element and the transmission element (170) is adapted to actuate the foot brake lever (195).

Brake booster (1 10) according to one of the preceding claims, characterized in that the electric drive (140) comprises a reduction gear (150).

Brake booster (1 10) according to one of the preceding claims, characterized in that the actuating element (120) comprises a pressure piston of a brake cylinder (130).

10. brake booster (1 10) according to any one of the preceding claims, characterized in that the rolling body (160) comprises a cam (510) which has a decreasing effective radius with increasing actuating travel of the actuating element (120).