EP2635470A1

EP2635470A1 - Brake booster and method for operating a brake booster

Info

Publication number: EP2635470A1
Application number: EP11752223.5A
Authority: EP
Inventors: Dirk Mahnkopf
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2010-11-02
Filing date: 2011-09-05
Publication date: 2013-09-11
Also published as: CN103180181B; WO2012059260A1; DE102010043203B4; JP2013541460A; CN103180181A; DE102010043203A1; US20130269337A1; US9845086B2; JP5676001B2

Abstract

The invention relates to a brake booster (1), comprising an input element (2), which can be operated by a driver, an actuator for generating a support force (F_sup), an output element (6), to which an input force (F_in) or the support force (F_sup) can be applied by the input element (2) and/or by the actuator and by means of which an actuating force can be applied to a piston of a main brake cylinder. The brake booster further comprises a force transmission unit (5) having elastic properties, which is arranged between the input element (2) and the actuator on the one side and the output element (6) on the other and which transmits the input force ((F_in) and/or the support force (F_sup) to the output element (6). An air gap (21) is provided between the input element (2) and the force transmission unit (5), wherein said air gap in an idle mode is smaller or larger than a desired air gap at the beginning of the braking process. According to a method for operating the brake booster, a support force (F_sup) is generated by the actuator prior to a braking command to be anticipated, or directly after detecting a braking command in a time span prior to or directly after detecting an actuation of the input element (2).

Description

description

title

Brake booster and method for operating a brake booster

The invention relates to a brake booster and a method for operating a brake booster.

State of the art

Brake booster with so-called "Springer function" have long been known. In this case, an air gap is provided between an input element and a power transmission unit of the brake booster. This air gap causes the driver initially does not have to press against the power transmission unit when operating the input member, but can move it with little force. The control or regulation of the Aktuatorkraft takes place in this area path-dependent as a function of the path of the input element with almost constant input force. The actuating force is applied in this area mainly by an actuator of the brake booster.

In vehicles with conventional disc brakes occur during a

unbraked operating state, so with unoperated brake pedal, often

Energy losses in the form of a residual braking torque, as the brake pads grind on the brake disc. This grinding can e.g. due to disc impact and / or in many cases improper pad resetting and clearance compliance

be caused. To save energy therefore disc brakes have been developed in which the brake is in the unbraked state in a so-called "zero-drag" position, so that in this case no friction between the brake pads and the brake disc occurs. A correspondingly designed caliper is often referred to as a "zero drag caliper". A disadvantage of such brake systems, however, is that often the

After releasing the brake pedal, retract the brake pads very far from the brake disc, so that when the brake actuation element is actuated, an

Compared to conventional braking systems increased Leer- or Todweg results. Such an additional empty or dead path is undesirable and should therefore be avoided or compensated. It should be noted that such increased empty or death paths system-related and independent of "zero-drag-calipers" may result. So far, the compensation of such unwanted additional empty or dead paths could only be realized by the use of so-called pure power-brake systems in which the energy required to generate the braking force of one or more energy supply facilities, but not of the physical force of

Driver, is generated.

Disclosure of the invention

A brake booster according to the invention comprises an input element actuatable by a driver, an actuator for generating an assisting force

Output element, which is acted upon by the input member and / or the actuator with an input force or the supporting force and by which a piston of a master cylinder is acted upon by an actuating force, and a power transmission unit with elastic properties, which between the

Input element and the actuator on the one hand and the output element on the other hand is arranged and the input force and / or the supporting force on the

Output element transmits. According to the invention, an air gap is provided between the input element and the force transmission element which, in the idle state, is smaller or larger than a desired air gap at the beginning of a braking process. A further brake booster according to the invention comprises an input element which can be actuated by a driver, an actuator for generating an assisting force, an output element which can be acted upon by the input element and / or the actuator with an input force or the assisting force and by which a piston of a master brake cylinder with an actuating force can be acted upon, and a power transmission unit with elastic properties, which between the

Input element and the actuator on the one hand and the output element on the other is arranged and the input force and / or the supporting force on the

Output element transmits. According to the invention, the input element has a first subelement actuated by the driver for generating the input force and a second subelement separated therefrom for transmitting the input force to the force transmission unit. In this case, an air gap is provided between the first sub-element and the second sub-element of the input element, which in

Hibernation is less than or greater than a desired air gap at the beginning of a braking process. Finally, the present invention provides a method for operating a

brake booster according to the invention, wherein in advance of an expected braking request or immediately after detecting a braking request in a

Time range before or immediately after detecting an actuation of the input element, an assisting force is generated by the actuator.

Advantages of the invention

To realize a "jumper function", many brake boosters have an air gap between the input element and the power transmission unit or between two subelements of the input element. The size of the air gap defines the size of the so-called jump-in, that is, the force or

the pressure at which the brake system transitions from an external power mode to an auxiliary power mode. The invention is based on the basic idea, a

Brake booster, which has such an air gap for realizing a "Springer function" to design such that unwanted empty or

Deadlocks of the braking system without appreciable influence on the pedal characteristics, e.g. in the form of a displacement of the brake actuator, be compensated. This is achieved according to the invention in that the air gap, e.g. is set in the context of manufacturing or assembly so that it is at rest or less than a desired air gap at the beginning of a braking operation. Is now in the run-up to an expected braking request or immediately after detecting a braking request in a time range before or immediately after detecting an operation of the

Input element generates an assisting force by the actuator, it can be overcome by suitably dimensioning the generated supporting force a predefined path at the output of the brake booster and thus on the piston of the master cylinder. Since in this time range but still no connection between the input element and the power transmission unit, this has no

Effects on the actuator. The empty or dead path can thus be compensated without the driver, e.g. through an appropriate

Shifting of the input element, noticed. However, the bridged path at the output of the brake booster and caused by the support force deformation of the force transmission element directly affect the size or width of the air gap. Depending on the ratio of the deformation properties

(Stiffness) of the power transmission unit and the master cylinder in conjunction with the brake system, on the piston, the output element of

Brake booster acts causes the generation of the supporting force to increase or decrease of the originally set in the rest position

Air gap. Now, if the air gap in the rest position set too small or too large, then there is an air gap after the generation of the supporting force and thus after the compensation of the unwanted empty or dead paths, which is exactly as large as he to realize the desired "Springer function" is required. The air gap is thus replaced by the support force at the beginning of a

Braking brought desired level.

Compared to the complex and costly realization of a pure

Fremdkraftbremssystems represents the inventive design of a

Brake booster is a particularly simple and therefore cost-effective variant for the compensation of idle or dead paths in brake systems. The brake booster according to the invention and the operating method according to the invention are also characterized by the fact that both death paths in the caliper and death paths in the region of the master cylinder can be compensated , In addition, the compensation for the driver is imperceptible, so that a high level of comfort is ensured.

A further advantageous application of the brake booster according to the invention or the operating method according to the invention results when used in a hybrid or electric vehicle. Here, the Fremkraftmodus the brake booster when blending a generator torque can be used. In the case of braking, the pressure is first built up as part of the dead-end compensation. If a regenerative torque is added, the hydraulic braking torque can

be reduced accordingly, so that the total braking torque remains constant. In this case, brake fluid flows from the brake system in the Hauptbrenmszylinder back, whereby the power transmission unit in the direction of

Brake actuator moves. In a conventional brake system, the air gap is designed to be correspondingly large, so that in this case no contact between the power transmission unit and the input element is formed. With a

The inventive brake booster or when using the operating method according to the invention, the air gap, however, does not need to be increased, which inter alia in the case of an amplifier failure, there is no increased free travel. Since during the blinding no direct connection between the brake system and the

Brake actuator is made, there is no reaction from the

Brake actuator, that is the pedal characteristic remains constant.

The invention can be used independently of the type of brake booster, that is, the actuator of the brake booster as pneumatic or hydraulic or electro-hydraulic or electro-mechanical or

be designed electrothermal actuator.

Since the power transmission unit and in particular their rigidity in comparison to conventional brake booster is not or only slightly changed, resulting in the case of failure of the brake booster no changed behavior. In particular, no appreciable increase in the driver's necessary operating force to achieve a desired deceleration occurs.

According to one embodiment of the invention, the force transmission unit, which may be formed as an elastically deformable reaction disc or an elastic spring construction, is configured such that a deviation of the ratio of the assisting force to the input force of a predetermined ratio leads to a deflection of the power transmission unit.

An additional compensation of unwanted empty or dead paths of the

Brake system can be realized that the brake booster a

Biasing unit which acts on the power transmission unit such that it acts on the power transmission unit in the idle state of the brake booster with a pair of forces. Is now in the run-up to an expected braking request or immediately after detecting a braking request in a time range before or immediately after detecting an actuation of the input element a

Supporting force generated by the actuator, so can by appropriate interpretation of the A pre-defined path at the output of the brake booster and thus on the piston of the master cylinder can be overcome without a corresponding path at the input of the brake booster and thus to the biasing unit and thus of the pair of forces as well as in advance of an expected braking request or immediately after detection of a desired braking force the

Input element must be present. An empty or dead path can thus be compensated without the driver, e.g. by a corresponding displacement of the input element, noticed. The Leerwegkompensation caused in this way is then taken into account when designing the "too large" or "too small" air gap accordingly.

A structurally particularly simple and thus cost-saving embodiment of the invention results when the bias unit on the one hand a force generating unit which actively acts on the power transmission unit at rest with a first force of the force pair, and on the other hand, a reaction unit which generates a reaction force to the first force, which together with the first force forms the pair of forces.

According to one embodiment of the invention, the force-generating unit is designed as a pretensioned in the idle state of the brake booster spring element, which is supported on one side of the power transmission unit. It can as

Spring element, for example, serve a return spring of the brake booster or a spring of the master cylinder, which contributes to a further reduction of the design and cost.

In a particularly simple manner, the reaction force can be generated in that the reaction unit comprises a stop on which the

Power transmission unit directly or indirectly supported. Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings.

Brief description of the drawings In the drawings: a replacement model of a brake booster according to the invention,

Fig. 2 is a schematic representation of a first embodiment of a

brake booster according to the invention and

Fig. 3 is a schematic representation of a second embodiment of a

brake booster according to the invention.

Embodiments of the invention

FIG. 1 shows a substitute model of a brake booster 1 according to the invention, by means of which the mode of operation will also be explained below. One

Input element 2 is mechanically coupled to an actuating element, not shown, which may be embodied as a brake pedal or brake lever, for example, and in this way actuated by a driver. Acts an input force F _in , which is greater than a force threshold, on the input element 2, which, for example in the form of a

Input piston can be configured, so this shifts by a path s _in . The input force F _in corresponds to an actuating force of the driver as a rule. The Kraftschwell value is shown in Figure 1 in the form of a spring element 3 with a stiffness c _t and a spring preload F _t . An unillustrated actuator can apply an assist force F _sup to an amplifier body 4, resulting in a

Adjustment s _{sup of} the amplifier body 4 leads. The actuator can be designed in any form, for example as a pneumatic or hydraulic or electro-hydraulic or electromechanical or electrothermal actuator. Of the

Amplifier body 4 may be configured, for example, as a support piston. Via a power transmission unit 5, which has elastic properties, the input force F _in and the assisting force F _{sup are combined} to form an output force F _out and transmitted to an output element 6. The output element 6 shifts by a distance s _out . The output member 6 is mechanically coupled to a non-illustrated piston of a master cylinder, which is acted upon by the power transmission unit with a (brake) actuating force. The power transmission unit 5 is designed such that a deviation of the

Ratio of the assist force F _sup to the input force F _in of a predetermined ratio leads to a deflection or deformation of the power transmission unit 5. The power transmission unit 5 is thus designed as a force balance, which by an elastically deformable reaction disc or an elastic spring construction can be realized. From the side of the output element 6 acts on the

Power transmission unit a force F _T MC, which results from the bias of the springs in the master cylinder and possibly by a form. The replacement model of the brake booster 1 further includes variables that characterize the power transmission unit 5. Thus, the power transmission unit 5 has a rigidity c ₂ . In addition, in FIG. 1, an attachment point 7 of the output element 6 can be seen on the power transmission unit 5. A quotient X gives the ratio of the distance x between the contact point 7 and a point of application of the amplifier body 4 and the distance between the contact point 7 and a point of application of the

Input element 2 (marked here with the length one). The lever lengths, ie the lengths "x" and "1" correspond to e.g. Contact surfaces between the

Eingangslement 2 or the amplifier body 4 and a reaction disc. If an assist force F _sup and / or an input force F _{in is} present, this can lead to a deformation of the power transmission unit 5, which is shown in FIG. 1 as a dashed-dotted line 5 '. This deformation of the power transmission unit 5 leads to a differential path ds between the new position of the point of application of the input element 2 and its old position. In addition, a return spring 8 is provided with a stiffness c _R for the power transmission unit 5.

A first embodiment of a brake booster 1 according to the invention in accordance with the equivalent circuit diagram of FIG. 1 is shown in FIG.

In the upper part of Figure 2, the brake booster 1 is shown in the rest position of the brake system. Between the power transmission unit 5, which in the illustrated

Embodiment is designed as a reaction disk 20, and the input member 2, an air gap 21 can be seen. Such an air gap 21 serves to realize a so-called "jumper function" and must first be overcome before the

Input member 2, the reaction disc 20 with the input force F _in acted upon.

In particular, when using so-called "zero drag calipers" or

Depending on the system, unwanted empty or dead paths can occur in the area of the brake system. To compensate for this is in advance of an expected braking request or immediately after detecting a braking request in a

Time range before or immediately after detecting an actuation of the input element 2 generates an assisting force F _sup by the actuator, not shown. This will on the one hand, the output element 6 is displaced in the direction of the master cylinder, wherein an output s _ou ti is overcome. On the other hand, the

Reaction disk 20, as shown in the lower part of Figure 2, deformed. Since there is no connection between input element 2 and reaction disk 20, this displacement and deformation but neglecting the spring element 3 have no influence on the actuator and therefore remain unnoticed by the driver.

However, the bridged output path s _ou ti and the deformation of the reaction disk 20 have a direct effect on the dimensions of the air gap 21. In the illustrated

Embodiment, the bridged output s _ou ti is greater than the

Therefore, the air gap 21 after applying the support force F _sup in the run-up to an expected braking request or immediately after detecting a braking request (Figure 2 below) is greater than the air gap 21 at rest (Figure 2 above).

The situation shown in the lower part of Figure 2 represents the initial situation at the beginning of the actual braking process. It should then also act the desired "jumper function", that is, the air gap 21 should have exactly the desired level in this operating situation. To realize this, the air gap 21 is to be set smaller in the idle state than the desired air gap at the beginning of a

Braking. The assisting force F _sup serving for the compensation of undesired empty or dead paths in the run-up to an expected braking request or immediately after detecting a braking request is thus used to bring the air gap 21 to the desired level.

In another design of the individual components of the brake system, the

Support force F _sup in advance of an expected braking request or immediately after detecting a braking request in contrast to the variant shown also lead to a reduction of the air gap 21. In such a case, the air gap 21 in the idle state is set correspondingly larger than the desired air gap at the beginning of a braking operation.

As an alternative to the illustrated embodiment, the input element 2 may also be designed in two parts and a driver-operable first sub-element for generating the input force and a second sub-element separated therefrom

Have transmission of the input force to the power transmission unit. In this case For example, the air gap 21 may also be provided between the first subelement and the second subelement of the input element without affecting the usability of the invention. FIG. 3 shows a further embodiment of the invention. In this case, the input element 2 is made in two parts and has a driver operable first sub-element 30 for generating the input force F _in and a separate second sub-element 31 for transmitting the input force F _in the configured as a reaction disc 20

Power transmission unit 5 on. In a resting phase of the brake system, which is shown in the upper part of Figure 3, the return spring 8 of the brake booster 1, which serves as a force generating unit in this case, via the reaction disc 20 on the second sub-element 31 of the input member 2 from. This in turn is supported on its side facing away from the reaction disk 20 on a stop 32, which serves as part of a reaction unit in this embodiment. The

Reaction disk 20 is thus on the one hand actively acted upon by the prestressed return spring 8 with a first force. This first force leads via the second sub-element 31 and the stop 32 to a reaction force acting in the opposite direction, which also acts on the reaction disk 20. The reaction disc 20 is acted upon in this way in the rest position with a pair of forces, which for

shown deformation of the reaction disc 20 leads. The force generating unit thus forms together with the reaction unit a biasing unit, which acts on the power transmission unit 5 in such a way that it is at rest

Brake booster 1 is acted upon by a couple of forces. As an alternative to the illustrated embodiment, the first force of the force couple can also be achieved by another spring element, such as a spring element. a spring of the master cylinder can be generated. The first force may also be otherwise, e.g. be generated by means of an electric motor. Likewise, it is conceivable that the second force of the force pair not as a reaction force, but also as an active force, e.g. with the help of an electric motor is generated. Between the first sub-element 30 and the second sub-element 31 of the

Input element 2, an air gap 21 'is provided, which analogous to the

Embodiment according to Figure 2 of the realization of a "jumper" - function is used.

Is in the run-up to an expected braking request or immediately after detecting a braking request in a time range before or immediately after detecting an actuation of the input element 2, an assisting force F _sup by not generates actuator shown, the output element 6 is moved in the direction of the master cylinder. On the other hand, the reaction disk 20, as shown in the middle part of Figure 3, deformed. This leads to that though one

Output path s _ou t the output element 6 is overcome, the two sub-elements 30 and 31 of the input element 2 but exactly in their position remain until a

Contact force between the input element 2 and the reaction disc 20 (with loose coupling of the second sub-element 31 to the reaction disc 20) or

Input element 2 and the stop 32 (with fixed coupling of the second

Part element 31 to the reaction disc 20) is equal to "0". If the assisting force F _{sup is} further increased, the air gap 21 'between the first subelement 30 and the second subelement 31 of the input element 2 increases as the second subelement 31 is firmly coupled to the reaction disc 20 (see FIG. In a not shown loose coupling of the second sub-element 31 of the input member 2 to the reaction disc 20 results in further increase the supporting force F _sup an additional air gap between the reaction disc 20 and the second sub-element 31 of the input member 2 and / or an enlargement of the air gap 2T. Both the enlargement of the air gap 21 'and the formation of an additional air gap between the reaction disc 20 and the second sub-element 31 of the

Input elements 2 would, however, lead without further measures to the fact that the total air gap would become too large for the realization of the desired "jumper function." This effect is analogous to the embodiment according to FIG

compensates that the air gap 21 'in the idle state, which z. B. is set within the production of the brake booster 1, is smaller than a desired air gap at the beginning of a braking operation. Also in this embodiment, depending on the ratio of the deformation properties (rigidity) of the

Power transmission unit 5 and the master cylinder, on the piston of the

Output element 6 acts, in conjunction with the braking system with a further increase in the supporting force F _sup also come to a reduction of the originally set air gap 21 'come. In this case, in order to compensate for this effect, the air gap 21 'in the idle state is analogous to the embodiment according to FIG. 2

set correspondingly larger than a desired air gap at the beginning of a

braking action

The brake booster 1 is thus able to anticipate an expected

Braking request or immediately after detecting a braking request one

Ausgangsweg s _ou t without any reaction to the first sub-element 30 of the Input element 2 and thus unnoticed for a driver to overcome. This can be exploited to compensate for unwanted dead or free travel in the brake system. The resulting change in the extent of the air gap 2T is compensated by corresponding reduction or enlargement of the air gap 2T in the rest position.

As already mentioned, according to the invention, an assisting force F _sup in advance of an expected braking request or immediately after detection of a braking request in a time range before or immediately after detecting an actuation of the

Input element 2 generated. The exact time can be set in many ways. For example, a release of an accelerator pedal or a response of a brake light switch or a detection of a drag torque can be interpreted as indicia of a soon to be expected operation of the input element 2 of the brake booster and thus as a trigger for successive

Increase the support force F _sup serve.

As an alternative to the embodiment illustrated in FIG. 3, the input element 2 can also be movably arranged in a tube, which in the rest position of the

Brake booster 1 rests against the power transmission unit 5 and is supported with its side facing away from the power transmission unit 5 on the stop 32. In this case, the reaction force is generated via the pipe in cooperation with the stopper 32. Of course, the power transmission unit 5, that is, e.g. the reaction disc 20, by appropriate design interpretation of

Brake booster 1 without affecting the applicability of the invention also directly on the stop 32 support.

Claims

Claims 1. Brake booster (1) with

a driver-operable input element (2),

an actuator for generating an assisting force (F _sup ),

- An output element (6), which by the input element (2) and / or the actuator with an input force (F _in ) or the supporting force (F _sup )

can be acted upon and by which a piston of a master cylinder with an actuating force can be acted upon, and

- A power transmission unit (5) having elastic properties, which between the input member (2) and the actuator on the one hand and the output member (6) on the other hand is arranged and the input force (F _in ) and / or

Transmitting support (F _sup ) to the output element (6),

wherein between the input element (2) and the force transmission element (5) an air gap (21) is provided, which is at rest or less than a desired air gap at the beginning of a braking operation.

2nd brake booster (1) with

a driver-operable input element (2),

an actuator for generating an assisting force (F _sup ),

- An output element (6), which by the input element (2) and / or the actuator with an input force (F _in ) or the supporting force (F _su )

Transmitting power (F _su ) to the output element (6),

wherein the input member (2) comprises a driver-operable first sub-element (30) for generating the input force (F _in ) and a second sub-element (31) separate therefrom for transmitting the input force (F _in ) to the power transmission unit (5), and wherein between the first sub-element (30) and the second sub-element (31) of the input element (2) an air gap (2T) is provided, which is at rest or smaller than a desired air gap at the beginning of a braking operation.

3. Brake booster according to one of claims 1 or 2, wherein the actuator is designed as a pneumatic or hydraulic or electro-hydraulic or electromechanical or electrothermal actuator.

4. Brake booster according to one of claims 1 to 3, wherein the

Power transmission unit (5) is designed such that a deviation of the

Ratio of assisting force (F _sup ) to input force (F _in ) of one

predetermined ratio leads to a deflection of the power transmission unit (5).

5. Brake booster according to one of claims 1 to 4, wherein the

Power transmission unit (5) is designed as an elastically deformable reaction disc (20) or an elastic spring construction.

6. Brake booster according to one of the preceding claims, wherein the

Brake booster (1) comprises a biasing unit, which in such a way

Power transmission unit (5) acts, that they the power transmission unit (5) in

Idle state of the brake booster (1) acted upon by a pair of forces.

7. The brake booster according to claim 6, wherein the biasing unit comprises:

- A force generating unit, which actively acts on the force transmission unit (5) with a first force of the force pair, and

- A reaction unit which generates a reaction force to the first force, which forms the pair of forces together with the first force.

8. The brake booster according to claim 7, wherein the force generating unit is formed as a biased in the rest state of the brake booster spring element (8) which is supported on one side on the force transmission element (5).

9. Brake booster according to one of claims 7 or 8, wherein the reaction unit comprises a stop (32) on which the power transmission unit (5) is supported directly or indirectly.

10. A method for operating a brake booster (1) according to one of claims 1 to 9, wherein in advance of an expected braking request or immediately after detecting a braking request in a time range before or immediately after Recognizing an actuation of the input element (2) an assist force (F _sup ) is generated by the actuator.

1 1. The method of claim 10, wherein the air gap (21, 21 ') through the

Supporting force (F _sup ) is brought to the desired at the beginning of a braking action.