WO2024120695A1

WO2024120695A1 - Method for operating an electromechanical braking device, and electromechanical braking device for a motor vehicle

Info

Publication number: WO2024120695A1
Application number: PCT/EP2023/079666
Authority: WO
Inventors: Zoltan Szabolcs ERDELYI; Barna Szimandl; Mark Muller
Original assignee: Thyssenkrupp Presta Ag; Thyssenkrupp Ag
Priority date: 2022-12-08
Filing date: 2023-10-24
Publication date: 2024-06-13

Abstract

The present invention relates to a method for operating an electromechanical braking device (1) comprising a brake part (32), a counter brake part (2), and an electromotive actuating device (5), in which method, in order to generate a braking action, the brake part (32) is moved into braking contact (K) with the counter brake part (2), being moved from a release position, in which an air gap (L) is located between the brake part (32) and the counter brake part (2), by means of the actuating device (5) in an adjusting direction, overcoming the air gap (L). In order to enable improved operation, according to the invention, before a braking action is generated, the brake part (32) is positioned by the actuating device (5) in an initial position (IN) in which a defined air gap width (B) of the air gap (L) between the brake part (32) and the counter brake part (2) is predefined.

Description

Method for operating an electromechanical braking device and electromechanical braking device for a motor vehicle

State of the art

The invention relates to a method for operating an electromechanical braking device, comprising a braking part, a counter-braking part and an electromotive actuating device, in which, in order to generate a braking intervention, the braking part is moved from a release position in which an air gap is arranged between the braking part and the counter-braking part by means of the actuating device in an adjustment direction while overcoming the air gap into braking contact with the counter-braking part. An electromechanical braking device is also the subject of the invention.

Such a braking device of a motor vehicle is designed as a friction brake, in which a braking part supported on the chassis and fixed relative to the rotation of the wheel to be braked can be brought into braking engagement by means of an adjusting device with a counter-braking part which rotates with the wheel. During braking engagement, a frictional contact is generated between the braking part and the counter-braking part, the so-called braking contact, whereby the braking torque generated by friction is greater the higher the adjusting force exerted by the adjusting device in the adjustment direction.

A common design is the known disk brake, in which the counter-braking part is formed by a brake disk that rotates with the wheel and is axially gripped by a brake caliper on both sides. By means of at least one, preferably linear, actuator axially supported on the brake caliper, a brake part, usually a brake pad, can be adjusted in an axial adjustment direction and thereby brought into frictional contact with an axial side of the brake disk, whereby the brake disk is frictionally clamped in the braking engagement between the adjusted brake part and another brake part that is axially opposite and supported on the brake caliper.

The prerequisite for a perfect function and a precise response of the brake is that in the non-actuated state a distance, the so-called air gap, is provided between the braking part and the counter-braking part in the adjustment direction. When the When braking, the braking part is moved by the adjusting device perpendicular to the air gap towards the counter-braking part until the air gap is overcome and the frictional braking contact is reached, so that the braking intervention is generated.

For a reproducible response of the brake in ferry operation, it is crucial that the air gap has as constant a gap width as possible when measured in the axial adjustment direction when not actuated. This air gap width can increase during operation, for example due to wear of the brake pad and/or the brake disc, and must be readjusted accordingly. It is known from DE 10 2017 123 266 A1 that the actuating device comprises at least one actuating drive that can be driven by an electric actuator, for example a spindle drive or the like. This can be used to advance the brake part in the adjustment direction towards the counter-brake part in order to reduce the air gap width and generate a brake intervention, or conversely to move it back away from the counter-brake part in order to increase the air gap width and release the brake. The air gap width can be changed by the actuating device, but this does not show how a better reproducible response behavior could actually be achieved in ferry operation. This can also lead to noise levels during ferry operations that are perceived as disturbing.

In view of the problems explained above, it is an object of the present invention to enable improved operation in an electromotive braking device.

Description of the invention

This object is achieved according to the invention by the method having the features of claim 1 and the braking device according to claim 11. Advantageous further developments emerge from the subclaims.

In a method for operating an electromechanical braking device, comprising a braking part, a counter-braking part and an electromotive actuating device, in which, in order to generate a braking intervention, the braking part is moved from a release position in which an air gap is arranged between the braking part and the counter-braking part by means of the actuating device in an adjustment direction while overcoming the air gap into braking contact with the counter-braking part, it is provided according to the invention that before generating a braking intervention, the The braking part is positioned by the adjusting device in an initial position in which a defined air gap width of the air gap between the braking part and the counter-braking part is specified.

According to the method according to the invention, the braking device is initialized by means of the adjusting device, whereby the braking part is positioned in a defined manner relative to the counter-braking part. This is achieved by adjusting the braking part to the initial position. The defined air gap width, preset to a predetermined value, corresponds to the distance in the adjustment direction between the corresponding friction surfaces of the braking part and the counter-braking part, which are directed against each other in the axial direction. As a result, the adjustment path required for a braking process between the initial position and the brake contact, which must be overcome by actuating the adjusting device, can be kept constant during operation. Changes in the air gap width that occur during operation, for example due to wear, tear, temperature fluctuations and the like, can be compensated for by the method according to the invention during operation of the vehicle, so that a consistent, reproducible response behavior of the brake can advantageously be achieved.

In the prior art, the air gap is usually adjusted when the brake device is installed or maintained, whereby, despite the relatively high level of effort involved, changes in the air gap width that occur due to continuous wear during ferry operation cannot be satisfactorily compensated. In contrast, the invention has the advantage that, by means of the electromotive actuating device, optimal functional reliability can be achieved during vehicle operation without external maintenance or adjustment effort, and a consistently high level of operating comfort can be achieved simply by means of the actuating device integrated in the brake.

The initialization of the braking device according to the invention can be carried out by controlling the actuating device, for example automatically by the electronic control systems present in the vehicle. It is possible, for example, to routinely set the braking part to the initial position each time the vehicle is started, so that not only wear but also potential influences from changing environmental conditions, such as extreme temperature changes or the like, can be compensated for. Alternatively or additionally, the initial position can be set after one or every braking process, so that optimal operating conditions can be guaranteed for a subsequent braking process.

The defined air gap width, which can also be referred to as the initial width, is greater than zero. In the brake contact, which can also be referred to as the engagement position or brake intervention, there is no air gap, ie the air gap width is zero. The defined air gap width is preferably smaller than a maximum air gap width that can be specified by the adjusting device between the braking part and the counter-braking part.

The initial position set by the adjusting device according to the invention forms a starting position or initial position of the braking or working stroke, which is also generated by the adjusting device and by means of which the braking part is adjusted in the adjustment direction until it comes into frictional braking contact with the counter-braking part during a braking process. Accordingly, the braking part is preferably held at rest or releasably fixed in the initial position, at least temporarily, before a subsequent braking process is initiated. It is then moved by the braking stroke from the initial position into the braking contact. Accordingly, the advantage is realized that the braking stroke must correspond consistently to the defined air gap width during each braking process. This results in the essential advantage that the response behavior remains constant regardless of wear.

A further advantage is that the adjustment characteristics of the actuating device can be optimally adapted to the adjustment path, which is constant for each braking process according to the invention. It is possible, for example, to specify an optimized force-path characteristic adapted to the air gap width. For example, the braking part can be moved quickly with little force starting in the initial position, and when or shortly before the braking contact is reached, a higher force can be applied, optionally with a lower adjustment speed. This can be done, for example, by appropriate electrical control of a servomotor. Alternatively or additionally, non-linear mechanical adjustment kinematics of the actuating device can be provided, for example by means of known wedge disk, ball ramp or tilt pin arrangements or the like. This can optimize the response behavior and avoid unwanted noise.

A further advantage is that by specifying the defined air gap width, the braking characteristics and the response of the brake can be adjusted without additional assembly or adjustment effort. For example, by specifically reducing the defined air gap width, a faster and more sensitive response of the brake can be achieved, for example for a sporty driving style. An advantageous embodiment of the method can provide that a calibration routine is carried out to set the defined air gap width, comprising the steps:

- Adjusting the brake part to a reference position,

- Adjusting the brake part from the reference position to the initial position.

It is preferred that the reference position is formed by the brake contact.

The calibration routine forms a calibration procedure for determining the defined air gap width using the adjustment drive. The reference position is a position that is clearly correlated with the brake contact, for example the position of the brake contact in the adjustment direction itself. A possible reference position has a fixed distance from the brake contact and is therefore referred to as the brake contact in the following.

In the first step, the braking part is adjusted by the adjusting device towards the counter-braking part, by definition forwards, until it contacts the counter-braking part in the braking contact. This adjustment can also be referred to as advancing in accordance with the forward adjustment direction. The reference position in the braking contact can preferably be set as the zero position. From the braking contact, the braking part is adjusted away from the counter-braking part in the opposite adjustment direction by an adjustment path corresponding to the defined air gap width back to the initial position. This adjustment can also be referred to as resetting in accordance with the rearward adjustment direction. This makes it possible to achieve exact positioning of the braking part in the initial position with little effort by simply specifying the adjustment path, regardless of any possible shift in the absolute position of the braking contact due to wear or the like.

A calibration routine can be carried out when the vehicle is started before the journey begins, preferably automatically. Alternatively or additionally, it is conceivable and possible to carry out the calibration after one or every braking process, based on the brake contact that inevitably occurs.

To implement the above-mentioned procedure, it is possible with little effort to record a reference position in the brake contact and then control the actuating device in order to adjust the brake part from the reference position to the initial position by a predetermined adjustment path. For example, a current zero position can be stored in the brake contact recorded and stored electronically. Based on this, the adjusting device can be controlled to adjust the air gap width by the amount defined in order to set the initial position.

It is advantageous that the current position of the braking part is detected, preferably by a sensor device. The braking contact can preferably be detected by an electrical sensor device, set as the zero position and stored in an electrical control device. The sensor device can preferably be arranged on the actuating device or designed together with it. For example, a force sensor that registers the stop of the braking part on the counter braking part in the braking contact. With particularly little effort, the stop in the braking contact can be detected by a current increase in the electrical actuator motor that is generated in the process. Alternatively or additionally, measuring devices can also be provided that are designed to measure absolute position values or relative position values of the braking part relative to the counter braking part, for example by means of known distance or position measuring methods.

In an advantageous embodiment, the sensor device can be designed as a rotor position sensor of the servomotor. Servomotors, for example in the form of a synchronous machine, are often already equipped with a rotor position sensor. Due to the previously known mechanical transmission between the angle of rotation of the rotor shaft and the stroke of the pressure piece, the absolute position value can be determined by determining the angle of rotation of the rotor shaft.

Preferably, the rotor position sensor can be designed as an inductive, magnetic or optical sensor.

It is possible for the actuating device to be position-controlled. For example, a position sensor can be provided that indicates absolute position values or a relative position value of the braking part relative to the counter-braking part. From the detected zero position in the braking contact, a value for the initial position can be determined with the defined air gap width, which is used to control the actuating device.

It can be advantageous for the actuating device to be controlled in a path. This makes it possible to adjust the actuating device to the initial position by an adjustment path specified by the control system with little effort. Such a path control can be implemented with little effort, for example, by an electric motor control, which Actuator is controlled with a signal sequence that produces an adjustment over a defined adjustment path.

An advantageous implementation is made possible by the fact that the actuating device has an actuator and a spindle drive that can be driven in rotation by an actuator motor. The spindle drive forms a continuously operating linear drive for the braking part, which in a manner known per se has a threaded spindle that engages in a spindle nut and can be driven in rotation by the actuator motor relative to the threaded spindle. The adjustment path is directly correlated with the amount of rotation of the rotor shaft of the actuator motor and the pitch of the threaded spindle. Accordingly, by controlling the actuator motor with a control signal, a defined angle of rotation of the rotor shaft can be specified, which causes a linear adjustment of the braking part by a defined adjustment path. For example, the actuator motor in the brake contact can be controlled with a defined electrical control signal in order to move the braking part in a path-controlled manner into the initial position. One advantage of this is that the method according to the invention can be implemented solely by electrically controlling the actuator motor, including the detection of the braking contact by evaluating the motor current and the precise setting of the initial position.

If required, additional position, displacement, force or other sensors can be provided, for example to detect the brake contact or to redundantly monitor the defined air gap width.

It can preferably be provided that the actuating device has a first actuator and a second actuator coupled in series with it. Each actuator forms a lifting or adjusting device that is axially effective in the adjustment direction. For example, an actuator can have a spindle drive. Other types of actuator can also be used, which can include, for example, ramp bearings, cam or cam disks, tilting pin arrangements or the like, and also convert a rotation of the drive element into a linear adjustment of the output element. Because the two actuators are arranged serially in the adjustment direction, i.e. one behind the other, the braking element can be adjusted linearly together with the second actuator by actuating the first actuator in order to produce the braking intervention. The air gap defined according to the invention can be adjusted by adjusting the second actuator independently of the actuation of the first actuator. The first actuator can thus be operated continuously in the optimal working range. In the aforementioned embodiment, it is advantageous that the braking intervention is generated by a first actuator, which can be referred to as the braking drive or working drive, and the initial position is set by the second actuator, which can be referred to as the adjusting drive. During operation, when the brake is applied, the braking drive preferably carries out a constant braking stroke with each braking process, which moves the braking part forwards into the braking intervention. The adjusting drive, which preferably has a spindle drive, can be used to adjust the braking part to the initial position. Because the defined air gap width is adapted to the specified, constant braking stroke of the braking drive, it can be operated continuously at the optimal working point.

In an adjustment device with two actuators arranged in series, in which the first actuator, the braking drive, carries out a constant braking stroke and the second actuator, the adjusting drive, is adjustable to adjust the air gap, the method according to the invention can comprise the following steps:

Resetting the adjustment drive,

Introducing the braking drive,

Advance the adjusting drive into the brake contact, reset the brake drive.

By advancing the brake drives, we mean an adjustment in the adjustment direction towards the counter-brake part, by definition forwards. Similarly, resetting means an adjustment in the opposite adjustment direction away from the counter-brake part, by definition back, i.e. backwards.

After carrying out the above steps, the brake part is positioned in the initial position. This has the advantage that during a subsequent braking process, the brake part is adjusted with a constant braking stroke forwards, towards the counter brake part, until the optimal braking intervention is achieved.

In an electromechanical braking device for a motor vehicle, comprising an adjusting device and a brake part connected thereto, which can be adjusted by the adjusting device in an adjustment direction and can be brought into braking engagement with a counter-brake part, and comprising a control device for controlling the adjusting device, the invention provides that the adjusting device can be controlled by the control device to set an initial position in which a defined air gap width of the air gap between the braking part and the counter-braking part is specified.

The features mentioned above in connection with the method according to the invention can be implemented individually and in combinations in the braking device according to the invention.

The adjustment direction preferably extends along an axis, for example the axis of a spindle drive of an actuator.

It is advantageous that the control device is connected to at least one sensor device that is designed to detect the position of the actuating device and/or to detect the adjustment path of the actuating device. An advantageous embodiment is that the control device is connected to at least one sensor device that is designed to detect a brake contact between the brake part and the counter-brake part. As explained above in connection with the method according to the invention, it is advantageous, for example, to detect the brake contact as a zero position, for example by monitoring the motor current of a servomotor, or by another measuring method. The measured values recorded in this way can be stored and processed in the control unit in order to control the servomotor(s) of the adjustment device on this basis.

It is preferred that the control device is designed to set the actuating device to a predetermined position and/or to adjust the actuating device by a predetermined adjustment path. This allows the initial position to be set, for example, starting from the brake contact.

It can preferably be provided that the control device has a control input for entering an initial value, and the control device is designed to set the actuating device to an initial position corresponding to the entered initial value. The initial position can thus be adapted to achieve a desired braking characteristic. For example, the defined air gap width can be reduced for a faster response of the brake and/or a higher braking effect.

Preferably, the adjustment drive for setting the air gap width, which can also be referred to as the adjustment drive, can have a spindle drive. The other adjustment drive, which can also be referred to as What can be referred to as a braking drive or working drive can have, for example, ramp bearings, cam or cam disks, tilting pin arrangements or the like. These are preferably designed in such a way that they carry out a constant braking stroke each time the brake is applied, ie a constant adjustment path in the adjustment direction.

It can be provided that the braking device comprises an adjusting device and a braking part connected thereto, which can be adjusted by the adjusting device along an axis, i.e. in an adjustment direction, and can be brought into braking engagement with a counter-braking part, wherein the adjusting device has a first adjusting drive and a second adjusting drive coupled in series therewith, wherein the first adjusting drive has a first drive wheel that can be driven in rotation, and the second adjusting drive has a second drive wheel that can be driven in rotation and is coaxial with the first drive wheel, wherein a coupling device is arranged between the first drive wheel and the second drive wheel. It can be provided that the coupling device is designed as a friction clutch with a friction element that can be frictionally connected to a counter-friction element in the coupling engagement.

In the following, the first and second drive wheels are referred to together as the two drive wheels or simply as the drive wheels.

The drive wheels can be designed as a gear wheel, for example as a spur gear, or as a belt or toothed belt wheel or worm wheel, so that generally a gear wheel is provided via which a drive torque from an electric actuator can be coupled into the actuator.

A friction clutch can be implemented between the drive wheels. This comprises a friction element which is connected to one of the drive wheels in a torque-locking manner and a corresponding counter-friction element which is connected to the other drive wheel in a torque-locking manner. The friction element can be brought into frictional coupling engagement with the counter-friction element in any relative angular position. In this case, a purely force-locking coupling is implemented, in contrast to the positive locking connection in the prior art. This means that the relative position of the drive wheels to one another can be continuously specified, in contrast to the discrete locking steps in the prior art. Accordingly, a uniform, continuous adjustment of the second actuating drive relative to the first actuating drive is possible, and a continuous adjustment of the air gap can take place. This is particularly advantageous with regard to a uniform tracking of the optimal operating point of the braking device to the continuous wear. of the braking part during operation, ie the continuous wear of the brake pad. Compared to the only gradual adjustment option in the prior art, a continuously improved response of the braking device can be achieved, and thus increased operational safety and greater ease of use.

An advantage over a locking coupling described in the prior art is that essentially no axial relative movement is required between the coupling elements in engagement to actuate and release the coupling device, for example between the drive wheels or the locking elements, which must necessarily be movable relative to one another to create and release the lockable positive connection. In contrast, the pure frictional connection between the friction and counter-friction elements according to the invention can simply be specified by the applied axial actuating force, whereby the friction and counter-friction elements do not have to be moved axially relative to one another. This enables a simpler and more reliable structural design of the coupling device.

It is preferably provided that the friction clutch has a defined, predeterminable clutch torque. The clutch torque indicates the maximum differential torque that can be transmitted force-lockingly between the friction element and the counter-friction element through the frictional engagement in the clutch engagement. If the clutch torque is exceeded, the clutch device slips, so that the two drive wheels are rotated relative to each other. One advantage of this is that the friction clutch according to the invention slips continuously in a sliding manner, so that an improved, uniform readjustment of the air gap is possible. In addition, no axial evasive movements of locking elements, as with the known locking clutch, have to be taken into account and absorbed in the design.

It is advantageous that the friction element and the counter friction element are arranged coaxially. The coaxial arrangement corresponds to the coaxial arrangement of the drive wheels. The friction element and the counter friction element can be arranged in a simple and compact design in the area of the axially opposing front sides of the drive wheels. Due to the above-described generation of the pure frictional connection of the clutch, no moving parts are required, as is the case with the locking clutch in the prior art.

In an advantageous embodiment, it can be provided that the friction element and the counter friction element are conical. The friction element can have a conical section, which converges at least in sections in the axial adjustment direction, with a conical Have a friction surface that can be designed as an outer cone or inner cone, and which has a corresponding conical section on the counter friction element, which is designed in the opposite direction as an inner cone or outer cone and has a conical counter friction surface. To generate the clutch engagement, the outer cone dips into the inner cone, with the conical friction and counter friction surfaces being frictionally loaded against one another by an axial actuating force of the clutch. One advantage of this is that the cone can convert the axially acting actuating force of the clutch into the normal force acting between the conical friction surfaces in the frictional contact. A flatter gradient can therefore convert a relatively small axial actuating force into a larger normal force in the frictional contact, meaning that a high clutch torque can be achieved even with a relatively small axial actuating force of the clutch.

Alternatively or in addition to the above-mentioned embodiment, it can be provided that the friction element and the counter friction element are designed to be planar. The friction surfaces corresponding to one another are designed at least in sections as flat axial surfaces, similar to a disk clutch. This enables a space-saving arrangement, in particular if only a relatively small clutch torque is to be achieved.

It can preferably be provided that the friction element and the counter friction element are prestressed against each other. The friction element and the counter friction element are preferably prestressed against each other elastically or resiliently. The friction and counter friction surfaces are pressed against each other with a predetermined axial prestressing force in frictional engagement. An elastic prestressing element, for example a spring element or the like, can preferably be provided to generate the prestressing force. The clutch torque of the friction clutch is determined by the actuating force acting perpendicular to the friction contact, i.e. the force applied axially between the friction and counter friction elements, whereby the clutch torque is greater the greater the prestressing force. This opens up the advantageous possibility of simply specifying the clutch torque by the prestressing force exerted by the prestressing element. For example, in the case of a spring element that is elastic in the axial direction, such as a compression spring, the prestressing force exerted can simply be specified and adjusted by the spring constant and the compression of the spring.

The aforementioned embodiment can be realized in an advantageous manner in that the friction element and/or the counter friction element is axially displaceable and is supported against the first drive wheel or the second drive wheel via an axially effective spring element. The friction element or the counter friction element are torque-locking and axially displaceable. connected to one drive wheel, for example via radially projecting drivers that produce a positive connection effective in the circumferential direction. The spring element axially clamped between the friction element or the counter-friction element and one drive wheel, which is preferably designed as an axially effective compression spring, ensures that the friction or counter-friction element is axially pre-tensioned against the corresponding counter-friction or friction element axially supported on the other drive wheel, i.e. is pressed axially against it in frictional contact. The corresponding counter-friction or friction element is connected in a rotationally locked manner to the other drive wheel. It is also possible that alternatively or additionally the counter-friction element is supported on one of the drive wheels via a spring element. An advantage of this arrangement is that the friction clutch according to the invention can be integrated between the drive wheels in a structurally simple and space-saving manner.

In an advantageous development, it is possible for the friction element and/or the counter-friction element to be arranged in the first drive wheel or the second drive wheel. For example, it is possible to design one drive wheel essentially in the shape of a drum, so that the friction or counter-friction element can be arranged in an interior space enclosed by the rotating gear or gear ring. This enables a compact design that is protected against external influences. For example, the drive wheel of the first actuator can have a conical friction element that axially engages in a counter-friction element designed as an inner cone, which is arranged at least partially within the second drive wheel.

A particularly compact design can be achieved - especially in the last-mentioned embodiment - by arranging the drive wheels within the axial extension of the actuators, i.e. by not being mounted axially protruding on one side.

It is preferred that the friction element and/or the counter friction element have a friction lining. The friction and counter friction elements preferably have a metallic base body, for example made of steel. To avoid metal-metal contact, a coating or lining can preferably be applied to create a friction pairing with a defined friction force, for example made of sintered, metal and/or ceramic friction materials, composite materials or the like. This can ensure a defined, reproducible clutch torque.

It can be provided that an actuator has a spindle drive. In this case, a threaded spindle engages in a spindle nut in a known manner and a relative rotating Drive via a drive wheel connected to the threaded spindle or spindle nut. It is possible for the spindle nut to form the drive element of the actuator on the drive side and the threaded spindle to form the output-side output element that is linearly adjustable relative to it, or vice versa.

It is possible for an actuator to have a ball ramp arrangement, wedge disk arrangement, or tilt pin arrangement. In a ball ramp arrangement, also known as a ramp bearing, the drive and driven elements preferably have cam disks with raceways or ramps inclined against the axis, between which balls that can roll in the circumferential direction are arranged. A relative rotation leads to the output element being axially displaced relative to the drive element due to the ball rolling on the ramps. In a tilt pin arrangement known per se, tilt pins are arranged between the drive and driven elements and each supported in the circumferential direction in such a way that during a relative rotation they are inclined more or less towards the axis depending on the direction of rotation, whereby the distance between the drive and driven elements can also be adjusted.

In the actuating device, two similarly acting actuators can be combined as first and second actuators, for example two spindle drives. It is also possible to combine two different designs, for example a ball ramp arrangement as the first actuator and a spindle drive as the second actuator for adjusting the air gap. The respective characteristic properties of each design can be optimally utilized. For example, a ball ramp arrangement can be used to achieve a non-linear adjustment characteristic with little effort, and/or at least partially self-locking properties, and/or a defined dead center or extended position that enables a defined adjustment path. The realization of the positive properties mentioned can at least partially require a precise specification of the air gap, which is not possible with the locking clutch in the prior art, but can be easily achieved using the friction clutch according to the invention.

In a method for operating an electromechanical braking device which has an actuating device comprising a first actuating drive and an actuating drive coupled in series therewith, and which acts on a braking part which can be brought into braking engagement with a counter-braking part in the direction of an axis, wherein the first actuating drive has a first drive wheel which can be driven in rotation and to which a first drive torque can be applied for actuation, and the second actuating drive has a second drive wheel which can be driven in rotation and is coaxial with the first drive wheel and to which a second drive torque can be applied for actuation can, wherein a clutch device is arranged between the first drive wheel and the second drive wheel, it can be provided that the clutch device is designed as a friction clutch and has a predeterminable clutch torque, when exceeded which the first drive wheel slips relative to the second drive wheel, wherein to actuate the first actuator the first drive wheel and the second drive wheel are driven synchronously so that the second actuator remains unactuated, and to actuate the second actuator the second drive wheel is driven and the first drive wheel is brought to a standstill relative to it so that the friction clutch slips and the first actuator remains unactuated.

The features mentioned above in connection with the braking device can be used individually and in combinations to implement the method.

To adjust the first actuator, an actuating torque can be coupled into the first drive wheel by means of a first electric actuator motor, and correspondingly the second actuator can be driven by a second electric actuator motor.

In normal braking operation, the first and second drive wheels rotate synchronously. This can be achieved by driving the first and second drive wheels with synchronized drive torques by the first and second actuators. The second drive wheel can also be driven synchronously by the clutch device when the first drive wheel is driven, as long as the transmitted drive torque remains below the clutch torque. In this operating mode, the second actuator remains unactuated and rotates freely as a whole together with the braking element.

In contrast to the prior art, the clutch device can slip continuously and smoothly when the clutch torque is exceeded to adjust the air gap. This can be achieved, for example, by fixing the drive wheel of the first actuator, for example by a brake or a corresponding control of the first drive motor, while the second drive motor applies a second drive torque to the second drive wheel that is greater than the clutch torque. This causes the second drive wheel to rotate relative to the first drive wheel, and by operating the second actuator, the air gap can be adjusted continuously and sensitively, so that continuously advancing wear of the brake element or brake pad can be optimally compensated. It is possible for the first drive wheel and the second drive wheel to be torque-locked by the friction clutch to generate a synchronous drive.

This means that the two drive wheels do not need to be driven synchronously by the servomotors. Any torque differences can be compensated within specified tolerances.

It can advantageously be provided that a higher clutch torque is specified when the first actuator is actuated than when the second actuator is actuated. The first actuator is actuated by synchronous driving of the first and second drive wheels. The friction element and the counter-friction element are preloaded against each other by the spring force of the spring element, and in addition the adjusting force of the first actuator acts in the opposite direction to the spring force. This results in a relatively high clutch torque. If, however, only the second drive wheel is turned to adjust the air gap, the spring force alone acts, so that a lower clutch torque is set. This makes adjusting the air gap easier.

In the embodiments described above, the first actuator can preferably form a braking drive according to the function specified above, and the second actuator can accordingly form an adjusting drive.

Description of the drawings

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

Figure 1 shows a braking device according to the invention in a schematic perspective view,

Figure 2 is a side view of the braking device according to Figure 1,

Figure 3 shows the adjusting device according to the invention of the braking device according to Figure 1 in a schematic perspective view,

Figure 4 shows a section Q-Q through the braking device according to Figure 1,

Figure 5 shows the first actuator of the braking device according to Figure 1 in a schematic perspective view,

Figure 6 is an enlarged detailed view of the adjusting device from Figure 4,

Figures 7a-e show schematic representations of the steps in carrying out the method according to the invention.

Embodiments of the invention

In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

Figure 1 shows a braking device according to the invention as a whole, which is designed as a disc brake. This comprises a brake disc 2, which forms a counter-brake part in the sense of the invention and is connected to a vehicle wheel (not shown here) that can rotate about a wheel axis R. A brake calliper 3 surrounds the two axial end faces of the brake disc 2. The brake disc 2 is designed here as a non-ventilated brake disc made of solid material. Alternatively, it can also be designed as an internally ventilated brake disc.

An electric brake actuator 4 according to the invention is attached to the brake caliper 3, which is shown in Figure 3 in a separate, isolated schematic perspective view and is explained in detail in Figures 4 to 6.

The brake actuator 4 comprises an adjusting device 5 which extends axially in the direction of an axis A which is parallel to the wheel axis R and indicates the adjustment direction V of the adjusting device 5.

As can be seen in the sectional view of Figure 4 along the axis A, the brake disk 2 is arranged axially between two brake pads 31 and 32. One brake pad 31 is firmly supported on the brake calliper 3 on the side facing away from the brake actuator 4. The other brake pad 32, which forms a braking part in the sense of the invention, is attached to the adjusting device 5 and can be adjusted by it in the axial adjustment direction V given by the axis A to produce the braking intervention on the brake disk 2, as indicated by the arrow in Figure 4.

In the non-actuated state of the braking device 1, there is an axial air gap L between the brake disc 2 and the adjustable brake pad 32, which is shown schematically in exaggerated width in Figure 4.

The structure of the adjusting device 5 is shown in Figure 4 and in the enlarged section thereof in Figure 6.

The actuating device 5 comprises a first actuating drive 6, which has a ramp bearing, and a second actuating drive 7, which is coupled axially (with respect to the axis A) in series with the first actuating drive and has a spindle drive.

The first actuator 6, which in the example shown is designed as a ramp bearing, comprises a drive-side cam disk 61 supported axially and rotationally fixed on the brake actuator 4 and a driven-side cam disk 62. Balls 63 are arranged between the cam disks 61 and 62. As can be seen in the schematically isolated view of Figure 5, the cam disks 61 and 62 have ramp-like axially opposite, inclined to the Axis A has raceways 64 between which balls 63 can roll. A rotation of the output-side cam disk 62, in Figure 5 at the top, relative to the fixed drive-side cam disk 61 - as schematically indicated by the curved arrows - leads to a linear adjustment of the output-side cam disk 62 in the adjustment direction V parallel to axis A. As a result, the brake pad 32 can be brought into braking engagement by actuating the first actuator 6, as shown in Figure 4.

The cam disk 62 is connected to a coaxial gear 65, which is designed as a spur gear and forms a drive wheel in the sense of the invention.

The gear 65 is in gear engagement with a first electric actuator 41. This enables the rotating drive of the cam disk 62 and thus an actuation of the first actuator 6.

The second actuator 7, which in the example shown is designed as a spindle drive, has a threaded spindle 71 on the output side, which engages in the internal thread of a drive-side spindle nut 72. This internal thread is formed in the output-side cam disk 62 of the first actuator 6, so that the functions of the output-side cam disk 62 and the drive-side spindle nut 72 are combined in one component.

The threaded spindle 71 is connected via a hub part 74 to a coaxial gear 75, which is axially fixed and rotatably mounted in the brake actuator 4. The threaded spindle is coupled to the gear 75 in a torque-locking but axially displaceable manner via drivers 73, which can have, for example, radially projecting projections or teeth that engage axially displaceably in axial slots of the hub part 74.

The gear 75 can be designed as a spur gear like the gear 65 and is arranged coaxially adjacent to it. This gear 75 is in gear engagement with a second electric actuator 42. This enables the rotating drive of the threaded spindle 71 and thus an actuation of the second actuator 7.

The threaded spindle 71 is connected axially to a pressure piece 44 via a thrust bearing 43, for example an axial roller bearing as shown, to which the displaceable brake pad 32 is attached, as can be seen in Figure 4. The pressure piece 44 can also be referred to as a piston. The clutch device according to the invention has a friction element 8, which is directed as a coaxial, conical extension from the cam disk 62 towards the second actuator 7. The conical extension has a conical friction surface 81 arranged on the outside on an outer cone. The friction element 81 can preferably be formed in one piece with the cam disk 62 / spindle nut 72.

In the clutch engagement, the friction element 8 is frictionally coupled to a counter friction element 9. The conical projection axially penetrates into a corresponding conical opening of the counter friction element 9, which has a conical friction surface 91 arranged in an inner cone. In the clutch engagement, the friction surface 81 and the counter friction surface 91 rest against each other in a frictionally engaged manner, as can be clearly seen in Figure 6.

The counter friction element 9 is coupled to the gear 75 in a torque-locking but axially displaceable manner via drivers 92 which engage in corresponding slots 76 in the hub part 74 or the gear 75 in an axially displaceable manner.

A spring element 93 is arranged between the gear wheel 75 or the hub part 74 connected thereto and the counter friction element 9. The axially effective spring force of this spring element elastically braces the counter friction element 9 against the friction element 8. This generates a defined coupling torque of the friction clutch according to the invention formed by the friction element 8 and the counter friction element 9.

The second embodiment shown in the same view as in Figure 6 differs in the design and arrangement of the friction surface 81 and the counter friction surface 91, which are both designed as flat axial surfaces, in contrast to the conical surfaces of the first embodiment according to the first embodiment shown in Figures 4 and 6. The functionality is essentially identical, and therefore the same reference numerals are used.

To actuate the braking device 1, the gears 65 and 75 are rotated synchronously so that the first actuator 6 executes a working stroke in the adjustment direction V so that the brake pad 32 passes through the air gap L and comes into braking engagement with the brake disk 2. The synchronous drive of the gears 65 and 75 can be achieved by synchronizing the drive speeds of the actuator motors 41 and 42, or by driving only one of the actuator motors 41 or 42, while the other actuator motor 42 or 41 runs idle. The frictional coupling engagement between the friction element 8 and the counter friction element 9 then ensures a synchronous rotation of the gears 65 and 75. To adjust the width of the air gap L, the gear 65 is fixed or blocked, for example by appropriately controlling the first servomotor 41. The second servomotor 42 rotates the gear 75 relative to the gear 65, whereby the friction clutch continuously slips. The second actuator 7 is adjusted uniformly accordingly, whereby the width of the air gap L can also be continuously adjusted and adapted, for example to compensate for wear on the brake pad 32.

Because the friction element 8 and the counter friction element 9 are arranged entirely or at least partially within the gear wheels 65 and 75, a particularly compact design can be realized.

The braking devices shown in Figures 1 to 7 are designed as floating caliper brakes, also referred to as floating caliper brakes. The brake pad 32 is pressed against the brake disc 2 by the pressure piece 44, and the brake pad 31 is pressed against the brake disc 2 by the brake caliper 3, which can be moved relative to the brake disc 2 in the direction of the axis A. Alternatively, the solution according to the invention can also be used with a fixed caliper brake.

In the embodiments according to Figures 1 to 6, the first actuator 6 forms a braking drive or working drive in the sense of the method according to the invention, and the second actuator 7 correspondingly forms an adjusting drive.

In Figures 7 a) to e), the individual steps of a possible embodiment of the method according to the invention for operating an electromechanical braking device are shown schematically, using a braking device 1.

The brake pad 32, which forms the braking part, and the brake pads 2, which form the counter-braking part, are shown in detail. In between there is the air gap L, the air gap width x of which, measured in the adjustment direction, can be adjusted by means of the actuators 6 and 7.

The second actuator 7, the brake drive, has a constant predetermined adjustment path when the brake is actuated. This corresponds to the air gap width B defined according to the invention. The initial position IN is spaced from the friction surface of the brake disk 2 by this defined air gap width B. Figure 7a shows an initial situation in the released position of the braking device 1 in a non-adjusted state, wherein the air gap width x is larger than the defined air gap width B, for example due to wear of the brake pad 32 and/or the brake disk 2. For clarity, the deviation from the initial position IN is shown exaggeratedly large.

From the situation shown in Figure 7a, the brake pad 32 is reset by means of the second actuator 7, the adjustment drive, by moving it away from the brake disk 2, as indicated by the arrow pointing to the right. The first actuator 6, the brake drive, is in the rest position in which it is reset to the maximum.

The resetting represents a path-controlled adjustment according to the fixed adjustment path of the first adjustment drive 6.

By resetting the brake pad 32 by means of the second actuator 7, the position shown in Figure 7b is achieved. Because both actuators 6 and 7 are reset to the maximum, a maximum air gap width xmax is set.

From the position shown in Figure 7b, the brake pad 32 is adjusted forwards, towards the brake disc 2, by actuating the first actuator 6 by a predetermined adjustment path B corresponding to the defined air gap width B, as indicated by the arrow pointing to the left.

This achieves the position shown in Figure 7c, in which the brake pad 32 is spaced from the brake disc 2 due to the above-mentioned wear.

Based on this, the second actuator 7 is activated to move the brake pad 32 further forward in the adjustment direction, as indicated by the arrow pointing to the left.

The adjustment by means of the second actuator 7 is continued until the brake pad 32 in the brake contact K strikes the brake disk 2, as shown in Figure 7d. This position in the brake contact K corresponds to the braking intervention.

From the brake contact K according to Figure 7d, the brake pad 32 is reset by means of the first actuator 6 by an adjustment path directed away from the brake disc 2, which corresponds to the defined air gap width B, as indicated by the arrow pointing to the right. Due to the fixed adjustment path of the first actuator, this is again a path-controlled adjustment.

As a result, the brake pad 32 is positioned in the initial position IN, in which the air gap L has the optimum air gap width B.

During a subsequent braking operation, only the first actuator 6 is actuated, whereby an adjustment by the amount of the optimal air gap width B takes place and an optimized braking intervention is generated in the braking contact, which corresponds to the position according to Figure 7d.

To control the actuators 6 and 7, their actuator motors 41 and 42 are connected to an electrical control unit 45, which is shown schematically in Figures 1 and 3. This is designed to adjust the first actuator 6 during a braking process by the amount of the defined air gap width B. In addition, the control unit 45 can detect when the brake contact shown in Figure 7d is reached, for example by the increase in the motor current of the actuator motor 42 of the second actuator 7 when the brake pad 32 strikes the brake disk 2.

It is also conceivable and possible to carry out the method with a braking device that has only one actuator, which has a spindle drive similar to the second actuator 7. This then also takes over the advance according to Figure 7b and the resetting according to Figure 7d, and the generation of the brake contact in a subsequent braking process. The advance and resetting of the brake pad 32 can then be carried out by a path-controlled control of the actuator motor by the control unit 45.

List of reference symbols

1 braking device

2 brake disc

3 Brake caliper

31, 32 brake pad

4 Brake actuator

41 , 42 Actuator

43 Thrust bearing

44 Pressure piece

45 Control unit

5 Adjustment device

6 first actuator (brake drive)

61 Cam disc

62 Cam disc (integrated with spindle nut 72)

63 Ball

64 Career

65 gear

7 second actuator (adjustment drive)

71 Threaded spindle

72 Spindle nut (integrated with cam disc 62)

73 Carrier

74 Hub part

75 gear

76 Slot

8 Friction element

81 Friction surface

9 Counter friction element

91 Counter friction surface

92 carriers

93 Spring element

A axis

R wheel axle

V Adjustment direction

L air gap x air gap width

B defined air gap width IN initial position

K Brake contact

Claims

PATENT CLAIMS

1. Method for operating an electromechanical braking device (1), comprising a braking part (32), a counter-braking part (2) and an electromotive actuating device (5), in which, in order to generate a braking intervention, the braking part (32) is moved from a release position in which an air gap (L) is arranged between the braking part (32) and counter-braking part (2) by means of the actuating device (5) in an adjustment direction while overcoming the air gap (L) into braking contact (K) with the counter-braking part (2), characterized in that before generating a braking intervention, the braking part (32) is positioned by the actuating device (5) in an initial position (IN) in which a defined air gap width (B) of the air gap (L) between the braking part (32) and counter-braking part (2) is specified.

2. Method according to claim 1, characterized in that a calibration routine is carried out to set the defined air gap width (B), comprising the steps:

- Adjusting the brake part (32) to a reference position,

- Adjusting the braking part (32) from the reference position to the initial position (IN).

3. Method according to claim 2, characterized in that the reference position is formed by the brake contact (K).

4. Method according to one of the preceding claims, characterized in that a reference position is detected in the brake contact (K), and then the adjusting device (5) is controlled in order to adjust the brake part (32) from the reference position by a predetermined adjustment path into the initial position (IN).

5. Method according to one of the preceding claims, characterized in that the current position of the braking part (32) is detected.

6. Method according to one of the preceding claims, characterized in that the adjusting device (5) is position-controlled.

7. Method according to one of the preceding claims, characterized in that the adjusting device (5) is controlled away.

8. Method according to one of the preceding claims, characterized in that the adjusting device (5) has an actuator (7) and a spindle drive (71, 72) which can be driven in rotation by an actuator motor (42).

9. Method according to one of the preceding claims, characterized in that the actuating device (5) has a first actuating drive (6) and a second actuating drive (7) coupled in series therewith.

10. Method according to claim 8, characterized in that the initial position (IN) is set by one actuator (7) and the braking intervention is generated by the other actuator (6).

11. Electromechanical braking device (1) for a motor vehicle, comprising an adjusting device (5) and a braking part (32) connected thereto, which can be adjusted by the adjusting device (5) in an adjustment direction (along an axis (A)) and can be brought into braking engagement with a counter-braking part (2), and comprising a control device (45) for controlling the adjusting device (5), characterized in that the adjusting device (5) can be controlled by the control device (45) to set an initial position (IN) in which a defined air gap width (B) of the air gap (L) between the braking part (32) and the counter-braking part (2) is predetermined.

12. Braking device according to claim 11, characterized in that the control device (45) is connected to at least one sensor device which is designed to detect the position of the adjusting device (5) and/or to detect the adjustment path of the adjusting device (5).

13. Braking device according to one of claims 11 to 12, characterized in that the control device (45) is connected to at least one sensor device which is designed to detect a braking contact (K) between the braking part (32) and the counter-braking part (2).

14. Braking device according to one of claims 11 to 13, characterized in that the control device (45) is designed to set the adjusting device (5) to a predetermined position (K, IN) and/or to adjust the adjusting device (5) by a predetermined adjustment path. Braking device according to one of claims 11 to 14, characterized in that the control device (45) has a control input for entering an initial value, and the control device (45) is designed to set the actuating device (5) to an initial position (IN) corresponding to the entered initial value.