Patent Application
20210309201
The present invention claims priority from 102020109449.3, filed 3 Apr. 2020, the entirety of which is incorporated herein by reference.
The present disclosure generally concerns an assembly for an electromechanical brake booster of a vehicle braking system. In concrete terms, aspects are described which are connected with the reduction of an undesirable angular deflection of an output element of the assembly during operation of the brake booster.
Known electromechanical brake boosters of a vehicle braking system are provided for example to amplify an actuating force generated by a driver via the brake pedal, so as to reduce the force application by the driver for a braking process. This is frequently achieved using an electrically operable actuator which, on operation, causes an adjustment movement of one or more components, which increase or generate a brake pressure in a brake cylinder. Known electromechanical brake boosters may also build up a brake pressure by operation of the actuator alone and independently of actuation of the brake pedal, for example in an autonomous driving mode.
Such electromechanical brake boosters comprise a housing which can be loaded with an actuating force by the actuator and is mounted movably. Both the actuating force generated by the actuator and the actuating force generated by the driver are received by an elastically deformable transmission element (e.g. a reaction disc) arranged in or on the housing, and transmitted to an output element which in turn transmits the actuating forces to the vehicle braking system in order to initiate a braking process. The transmission element is typically arranged between an actuating member (which is loaded with an actuating force by the driver) and the housing on one side, and the output element on the other.
It has been observed that during operation of the brake booster, for example due to unevenness of the road surface or by jerky actuation of the brake pedal in emergency braking, an angular deviation can occur between the longitudinal axes of the components executing the adjustment movement, in particular between the longitudinal axis of the housing and that of the output element.
This angular deviation may lead to a unilateral loading and hence to an uneven deformation of the transmission element. In the worst case, the transmission element may be permanently damaged. Other damage, for example to bearing components may be attributed to these angular deviations.
The present disclosure is based on the object of indicating an assembly for an electromechanical brake booster of the vehicle braking system, which counters a damage of the elastically deformable transmission element and generally an angular deflection of the output element.
According to a first aspect, an assembly is provided for an electromechanical brake booster of a vehicle braking system. The assembly comprises an actuating member which can be loaded with a first actuating force generated by means of a brake pedal, and a housing in which the actuating member is received, wherein the housing can be loaded with a second actuating force generated electromechanically. Furthermore, the assembly comprises an output element extending away from the housing and configured for transmitting the first and second actuating forces to a brake cylinder of the vehicle braking system, and an elastically deformable transmission element which is arranged to transmit force in a brake application direction between the actuating member and the housing on one side and the output element on the other, and is configured to receive the first actuating force from the actuating member and the second actuating force from the housing and transmit these to the output element. According to the present disclosure, the assembly also comprises a support that is rigidly arranged on the housing for a portion of the output element, wherein the supported or supportable portion of the output element is arranged between the support on one side and the transmission element on the other.
The actuating member may be displaceable relative to the housing, namely in the brake application direction and in a direction opposite the brake application direction. The actuating member may be connected at its one end directly or indirectly (e.g. via an input rod) to the brake pedal, via which the driver can apply the first actuating force. The actuating member may in particular be displaced in the brake application direction by actuation of the brake pedal, and be returned to a rest position by means of the return force from a return spring and/or a brake cylinder. The actuating member may at its other end be configured to transmit the first actuating force to the transmission element. The actuating member may be configured as an actuation rod or actuation piston with substantially circular cross-section. The actuating member may furthermore be coupled to the housing, for example by means of correspondingly formed coupling elements. A displacement of the actuating member may also lead to a displacement of the housing.
The housing may be part of an actuator of the electromechanical brake booster. On electrical actuation of the actuator, the housing may be displaced in the brake application direction in order to actuate the vehicle braking system. The housing may also be coupled directly or indirectly to a pressure piston of the brake cylinder, so that a displacement of the housing leads to a displacement of the pressure cylinder and hence to a build-up of brake pressure. Furthermore, the housing may be coupled to the actuating member so that a displacement of the housing may also lead to a displacement of the actuating member.
The output element may be partially received inside the housing. For example, a first portion of the output element may protrude from the housing and into the brake cylinder of the vehicle braking system. A second portion of the output element (for example the supported or supportable portion) may be received in the housing at least in regions and be configured to receive the first and/or second actuating force. The supported or supportable portion of the output element may be configured to be or come into contact with the transmission element.
The transmission element may be formed as a disc (e.g. as a so-called reaction disc). The transmission element may have a radially outer face which can make contact with the housing in order to receive the second actuating force. The transmission element may furthermore have a radially inner face which may be configured to receive the first actuating force. In the supported state of the output element, such as on performance of the braking process, the transmission element may be or become elastically deformed for transmitting the first and/or second actuating force to the output element.
An angular deflection of the output element may be reduced or at least largely prevented by the support which is arranged rigidly on the housing, in that the supported or supportable portion of the output element may be locally fixed between the support on the one side and the transmission element on the other. This does not exclude that one or more further elements are arranged so as to transmit force between the supported or supportable portion of the output element and the support on one side and/or the transmission element on the other. The support is suitable for countering an angular deflection of the output element in that it is translationally displaceable substantially only parallel to the longitudinal axis of the housing. The force transmission in the assembly accordingly also takes place substantially evenly and along the longitudinal axis of the housing.
In a refinement, the support has an inner face arranged against the brake application direction and configured to be or come into contact with the supported or supportable portion of the output element. In particular while performing a braking process, the supported or supportable portion of the output element may be or come into contact with the inner face. The inner face may exert a force acting against the brake application direction on the supported or supportable portion of the output element, countering a forced leading to an angular deflection of the output element. At least a part portion of the inner face of the support may be arranged on the housing.
In any case, the support may be formed partially by a separate support component which is attached to the housing. The support component may be made of a rigid material such as steel or sheet metal. The support component may be attached to the housing by means of welding, in particular by means of ultrasound welding. The support component could also be attached to the housing by bolting or another fixing method.
In some embodiments, the support may at least partially form the limit of a receiver which receives (at least) the supported or supportable portion of the output element and the transmission element. In an exemplary embodiment, the receiver may be formed by a recess in the housing. The support may then extend at least partially beyond an end face of the housing in which the recess is molded. Alternatively, the transmission element and the supported or supportable portion of the output element may be arranged outside the housing. In this embodiment, the housing comprises for example an end face which faces the brake cylinder of the vehicle braking system and on which the support is arranged. In this embodiment, the supporting engages behind both the transmission element and the supported or supportable portion of the output element.
In a further refinement, the output element may comprise a shaft and a head which has a greater diameter than the shaft and is formed on an end of the shaft facing the housing. In this refinement, the supported or supportable portion may be formed on the head. The output element in this refinement may also comprise a transition portion arranged between the shaft and the head. The diameter of the transition portion may increase steplessly from the shaft to the head. The head and the shaft may be formed cylindrically along the longitudinal axis of the output element. At least portions of the head may be received in the receiver. In this refinement, the support may cooperate with a portion of the head of the output element facing away from the transmission element. In particular, this may be the end face of the head facing away from the transmission element. In this refinement, a force is exerted on the head of the output element by means of the rigid support, which force compensates for a force leading to an angular deflection of the output element (for example vibrations of the housing).
In one embodiment of the assembly, the support may be configured to support the output element such that in the supported state, a longitudinal axis of the output element and a longitudinal axis of the housing are oriented substantially parallel to each other. The supported state may for example be present during a braking process when the supported or supportable portion of the output element is brought into contact with the support. The support may then orient the output element so as to prevent a “kinking” of the output element relative to a longitudinal axis of the housing. In this embodiment, the support may furthermore be configured to support the output element such that, in the supported state, the elastically deformable transmission element is deformed substantially evenly over its extent perpendicular to the longitudinal axis of the housing.
According to a further embodiment of the assembly, the support may define a circular support face for the output element. The present disclosure is not however restricted to such a design of the support. Alternatively, the support may also take the form of support elements arranged spaced apart from each other along a circumferential direction of the shaft of the output element. Further suitable embodiments of the support are conceivable.
According to a second aspect, an electromechanical brake booster for a vehicle braking system is provided, which comprises an assembly according to the disclosure and an electric motor and gear mechanism for loading the housing with the second actuating force.
The electromechanical brake booster may be provided for amplifying the braking force provided by actuation of a brake pedal. The electromechanical brake booster may also be provided to provide a braking force independently of actuation of the brake pedal, for example in an autonomous or partially autonomous driving mode. The gear mechanism may be functionally provided between the electric motor and the housing of the assembly.
According to a third aspect, a vehicle braking system is provided which comprises an assembly according to the first aspect or a brake booster according to the second aspect. The vehicle braking system may be configured to be operated in an autonomous or partially autonomous driving mode.
Further aspects, details and advantages of the present disclosure arise from the following description of exemplary embodiments with reference to the figures. These show:
The vehicle braking system 1000 according to
An input element 110 which can be loaded with a first actuating force, generated by the driver by means of a brake pedal (not shown), protrudes into the assembly 100. An actuating member 120 is coupled force-transmissively to the input element 110. The actuating element 120 is received in a recess 162 of a housing 160 of the assembly 100. The actuating member 120 is held inside the recess 162 so as to be movable along a housing longitudinal axis L. The first actuating force may be transmitted by the actuating member 120 via a sensing disc 130 to an elastically deformable, disc-like transmission element 140 (a so-called reaction disc).
The elastically deformable transmission element 140 is configured to receive the first actuating force from the actuating member 120 (via the sensing disc 130) and a second actuating force which is generated electromechanically and transmitted via the housing 160. Furthermore, the elastically deformable transmission element 140 is configured to transmit the first and second actuating forces to an output element 150. For the purpose of this force transmission, the transmission element 140 is elastically deformable along its entire extent perpendicular to the longitudinal axis L.
In the depiction of
Further details of the force transmission within the brake booster 200 and the hydraulic pressure generation by means of the brake cylinder 300 are known to the person skilled in the art and do not require further explanation here.
As already stated, the housing 160 can be loaded with an electromechanically generated second actuating force. In the depiction of
To generate the second actuating force, the brake booster 200 comprises, as well as the assembly 100, an electrically actuatable electric motor 210 and a gear mechanism 220. The electric motor 210 and the gear mechanism 220 are configured to electromechanically generate the second actuating force which can be applied alternatively or additionally to the first actuating force on the brake cylinder 300 to execute or support a braking process.
The second actuating force may be determined using the actuation travel exerted by the driver on the brake pedal and/or the first actuating force generated by the driver, for example by means of a travel sensor coupled to the brake pedal or the actuating member 120, or by measurement of the brake pressure generated in the brake cylinder 300 by the driver, which is detected by sensors and in some cases plausibility-checked. Alternatively, the deceleration request and hence the actuating force to be applied by means of the brake booster 200 may also be initiated by a system for autonomous or partially autonomous driving, so no actuating force from the actual driver is required.
The vehicle braking system 1000 may be operated both in an autonomous and in a partially autonomous driving mode. In an autonomous or partially autonomous driving mode, the actuating force acting on the brake cylinder 300 is generated solely by the electric motor 210 and the gear mechanism 220, without the driver needing to actuate the brake pedal (there is therefore no force amplification in the true sense). In a conventional driving mode, the actuating force acting on the brake cylinder 300 corresponds to the sum of the first actuating force applied by the driver and the second (amplifying) actuating force applied by the brake booster 200.
Because of unevenness in the road surface or jerky actuation of the brake pedal during emergency braking for example, vibrations can arise in the assembly 100. In particular when the housing 160 is rigidly coupled to the actuating member 120, these vibrations can lead to an angular deflection (“kinking”) of the output element 150 relative to the housing 160. The longitudinal axis of the output element 150 and the longitudinal axis of the housing 160 in this case no longer align with each other. The “kinking” of the output element 150 may lead to an uneven, in particular unilateral distribution of the first and second actuating force on the transmission element 140 arranged between the output element 150 and the housing 160. This uneven distribution of the actuating force may in turn lead to an overload of and damage to the transmission element 140.
The angular deflection of the output element 150 according to the present disclosure may be prevented by means of a support 180 for a portion of the output element 150. The support 180 is here arranged, in the exemplary embodiment shown in
According to
The further configuration of the support 180 is described in more detail below with reference to
By deviation from
As evident from
In the depiction of
As already explained above in connection with
An end face 156b of the head 156 facing away from the actuating member 120 forms the supported or supportable portion of the output element 150 in the illustration of
Because of the support 180 and the resulting corresponding orientation of the output element 150, force is transmitted from the actuating member 120 and the housing 160 onto the output element 150 substantially only parallel to the longitudinal axis L. A force transmission or deflection of the components of the assembly 100 at an angle relative to the longitudinal axis L is prevented by the support 180. In particular, the force is transmitted by means of the transmission element 140 only parallel to the longitudinal axis L. In other words, when the supported or supportable portion of the output element 150 cooperates with the support 180, the transmission element 140 deforms substantially evenly over its entire extent perpendicular to the longitudinal axis L. An uneven loading, in particular an overloading, of the force transmission element 140 during operation of the brake booster 200 is prevented by the proposed support 180, since the output element 150 can no longer “kink” with respect to the transmission element 140 and thereby overly squeeze this. As a result, the wear and risk of damage on the transmission element 140 are reduced.
As
In the depiction of
In contrast to
According to the illustration in
The solutions disclosed herein reduce or prevent firstly the angular deflection (“kinking”) of the output element 150 relative to a longitudinal axis L of the housing 160, 160a. This guarantees that the first and/or second actuating force applied by the actuating member 120 and the housing 160, 160a are transmitted to the brake cylinder substantially completely parallel along a common longitudinal axis L of the housing 160, 160a and the brake cylinder 300. The occurrence of force components at a greater angle relative to the longitudinal axis L is avoided. Since these angular force components cannot be transmitted or not completely transmitted to the brake cylinder 300, a brake force loss resulting therefrom is also countered.
Also, according to the present disclosure, a unilateral load provoked by an uneven force transmission, in particular an overload (e.g. uneven squeezing) of the transmission element 140, is prevented by the support 180 which is rigidly arranged on the housing 160. The wear and hence the risk of damage to the transmission element 140 are accordingly reduced in the assembly 100 disclosed, in comparison with assemblies known from the prior art for electromechanical brake boosters. The service life of the assembly 100 and brake booster 200 is thereby extended.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102020109449.3 | Apr 2020 | DE | national |
