Brake system with pedal feedback

Abstract

A braking system (10) for a motor vehicle comprising a brake pedal (20) configured to receive a braking request from a driver operating the motor vehicle and to transmit it to a braking device (30), wherein the braking device (30) is configured to translate the braking request into a corresponding brake pressure and to transmit this to brake actuators (32), wherein the brake pedal (20) is mechanically and / or hydraulically decoupled from the braking device (30), and wherein the braking system (10) comprises at least one mechanical actuator (40), characterized in that the at least one mechanical actuator (40) is designed in the form of an unbalanced motor and / or a magnetic plunger and is connected to the brake pedal (20) and is configured to vibrate the brake pedal (20) in the event of anti-lock braking.

Description

The invention relates to a brake system for a motor vehicle, in particular a brake-by-wire brake system, which gives the driver haptic feedback via the brake pedal in the event of antilock braking. The invention further relates to a motor vehicle having a brake system according to the invention and to a method for operating a brake system according to the invention.A brake-by-wire brake system is referred to as a brake system of a motor vehicle in which the brake pedal is mechanically and hydraulically decoupled from a brake device which generates the actual brake pressure. In this case, the braking request of the driver, which he expresses by the actuation of a brake pedal, is usually recorded by a hydraulic brake simulator and converted into an electrical signal. Based on the signal, the brake pressure is then generated by a separate hydraulic system.These brake systems generally have only the communication direction from the brake pedal to the brake device. Thus, information cannot be transmitted from the brake device to the brake pedal and thus to the driver. In conventional systems, i.e. brake systems which operate with a classic brake booster (thus not brake-by-wire systems), feedback to the brake pedal in the form of a vibration / pulsation of the pedal is provided to the driver for technical reasons when the antilock brake system is engaged in the braking (antilock braking). Based on this information, the driver can adapt his driving style to the road conditions.In order to counteract this problem, various possibilities have developed in the prior art. Patent document DE 10 2018 220 544 B4 discloses a brake system of a motor vehicle, wherein the brake system has a wheel brake cylinder, a brake pedal, a master brake cylinder, a master brake cylinder circuit, a primary brake unit and a secondary brake unit having a further pressure product unit, wherein, in the event of a loss of traction during an antilock braking operation, a pulsation is generated in the master brake cylinder circuit via the further pressure product unit in order to provide a feedback at the brake pedal.The publications DE 10 2018 220 578 A1 and U.S. Pat. No. 10479335 B2 disclose a brake system for a motor vehicle, wherein the brake system has a pedal feel simulation device which is connected to a master brake cylinder in such a way that feedback is provided to a brake pedal and to the driver during antilock braking.DE 10 2017 214 828 A1 discloses a brake system of a motor vehicle, having an anti-lock brake system and a simulator valve, wherein an ABS pedal feel is generated by alternating opening and closing operations of the simulator valve.The document DE 10 2017 213 620 A1 discloses a brake system for a motor vehicle, wherein the brake system has a brake pedal and a brake device which is mechanically and / or hydraulically decoupled from the brake pedal, wherein the brake pedal is coupled to a pressure unit, and wherein feedback is provided to the brake pedal via the pressure unit in the case of an activated anti-lock brake system.US 2018 / 257613 A1 discloses a brake system having a brake feedback control unit for tactile, acoustic and / or visual feedback to the brake pedal.US 2017 / 225664 A1 discloses a brake-by-wire brake system, wherein an antilock brake operation is fed back by a pulsation at the pedal.The document DE 10 2013 222 281 A1 discloses a method for the haptic information of a driver of a motor vehicle equipped with a brake-by-wire brake system, wherein a brake pedal reaction is carried out by means of a release valve at the beginning of an anti-lock control or an electronic brake force distribution function.The document DE 10 2013 204 778 A1 discloses a method for haptic information of the driver of a motor vehicle equipped with a brake-by-wire brake system about the operating state of the brake system, in which the brake pedal characteristic is generated by a simulator in the form of a functional relationship between brake pedal counterforce and brake pedal travel and is modified as a function of the operating state, wherein a basic brake pedal characteristic is generated by means of a passive simulator spring.The publications DE 10 2012 025 247 A1 and EP 1 864 875 B1 disclose further embodiments of a brake system having a device for haptically feedback a braking process on the brake pedal.JP 2022-45171 A discloses a brake control of a brake-by-wire brake system having a brake pedal to which a force or vibration can be applied by an actuator to provide information on the specific brake control disclosed in this publication to the driver.Against the aforementioned background, it is the object of the invention to provide a further possibility for pedal feedback for brake-by-wire systems.This object is achieved by the brake system, the method and the motor vehicle according to the independent claims. Advantageous refinements of the invention are disclosed in the dependent claims.The brake system according to the invention for a motor vehicle has a brake pedal configured to receive a braking request from a driver guiding the motor vehicle and to forward it to a brake device, wherein the brake device is configured to translate the braking request into a corresponding brake pressure and to transmit it to brake actuators, wherein the brake pedal is furthermore mechanically and / or hydraulically decoupled from the brake device. The brake system further comprises at least one mechanical actuator in the form of an imbalance motor and / or a magnetic plunger, which is connected to the brake pedal and is configured to set the brake pedal in vibration in the event of an antilock braking.By means of the mechanical actuator in the form of an imbalance motor or a magnetic plunger, which are preferably fastened directly to the brake pedal, a comparatively structurally simple possibility can be provided for ensuring haptic feedback on the pedal.The term magnetic plunger is understood to mean an electromagnet which can move a plunger, in the simplest case an iron rod, back and forth in one direction between two different positions similar to the functional principle of a solenoid valve. If the latter strikes the brake pedal in one of the two positions, for example, the latter can be set in vibration when the tappet moves sufficiently rapidly between the two positions. An embodiment with a magnetic plunger is also conceivable, in which the plunger is fastened to the brake pedal and the vibration is generated solely by the inertia of the mass of the plunger without the plunger striking the pedal. This presupposes that the plunger has a sufficiently high mass.An imbalance motor (also referred to as a vibration motor or a vibration motor) is understood to mean a motor, usually an electric motor, on the output shaft of which an eccentric mass is arranged. By operating the motor, centrifugal forces are generated on the shaft by the eccentric mass, which set the motor or objects in contact with the eccentric mass into vibration. Imbalance motors are known, for example, from vibration conveying technology and exist in various strengths and designs. This is thus a shelf part which is comparatively simple to integrate.In an advantageous embodiment of the invention with an imbalance motor, the latter has an adjustable imbalance. The intensity of the vibration can be adjusted by means of the adjustable imbalance. Alternatively or additionally, two or more imbalance motors can be provided, which have different imbalance levels. Thus, in embodiments with multiple motors, the intensity of vibration can be adjusted by operating the imbalance motors with different imbalance. By simultaneously operating imbalance motors with different imbalance (at possibly different rotational speeds), it is possible to generate a superposition of the vibration and thus a further form of the vibration.Embodiments of the invention with an imbalance motor are thus conceivable in which an imbalance motor with non-adjustable imbalance, two or more imbalance motors with non-adjustable imbalance, an imbalance motor with adjustable imbalance and a plurality of imbalance motors, at least one of which has an adjustable imbalance, are provided in the brake system.The imbalance is composed of two variables. On the one hand, the size of the eccentric mass and, on the other hand, the eccentricity of the mass. Eccentricity is to be understood as the distance of the mass from the output shaft of the electric motor. This distance can be adjustable, for example, as a result of which the imbalance can be changed. If the distance from the mass to the shaft is increased, the eccentricity increases. In the opposite case, it decreases.An advantage of embodiments with adjustable imbalance is that the intensity, i.e. the intensity, of the vibration transmitted to the brake pedal can be adjusted. Thus, the driver can be given the feedback as to how much antilock braking is performed. On the basis of a plurality of imbalance motors with imbalance that differ from one another, it is likewise possible to transmit different intensities to the brake pedal and thus to transmit the feedback to the driver in a differentiated manner.In a further advantageous embodiment of the invention, the at least one mechanical actuator is designed to apply different frequency and / or intensity to the brake pedal as a function of the strength of the antilock braking. Alternatively or additionally, the actuator is likewise designed to apply vibrations to the brake pedal in packs (vibration packs). By means of different operating possibilities with regard to frequency, intensity and vibration packets, the driver can be given differentiated feedback via the brake pedal about the strength of the intervention of the anti-lock brake system (ABS).As already described above, different intensities can be achieved in the case of imbalance motors via different imbalance. In embodiments with magnetic plungers, vibrations of different intensity can be achieved by the speed of the plunger when changing from one position to the other.The frequency of the vibration is understood to mean how many oscillations per second are transmitted to the brake pedal. The frequency can thus be set by the rotational speed of the imbalance motor or by the frequency of the movements of the plunger between the two positions per second in the case of the magnetic plunger.By the term "to vibrate in packages" is meant that for a period of time the brake pedal is vibrated, followed by a period of time during which no vibration is transmitted, but anti-lock braking is still in progress. By changing between the periods of vibration and not vibration, information can also be transmitted to the driver. The set of vibrations which are separated by the pauses are understood within the scope of this application as vibration sets. For example, in the case of severe ABS interventions in the braking, only small pauses can be provided between the vibration packets, while in the case of a low ABS intervention, the pauses are significantly longer.In a further advantageous embodiment of the invention, the brake system has a brake force simulator, wherein the at least one mechanical actuator is arranged integrated in the brake force simulator. Brake force simulators in vehicle brake systems are frequently designed as hydraulic cylinders, wherein a piston guided in the hydraulic cylinder displaces fluid located in the hydraulic cylinder by a coupling to the brake pedal. An exemplary embodiment for a brake force simulator in which the mechanical actuator is integrated would be, for example, if it acts directly on the piston. The connection between the brake pedal and the piston transmits the vibration to the brake pedal.In an alternative embodiment of the invention to the embodiment described in the paragraph above, the at least one mechanical actuator is arranged directly on the brake pedal. This is to be understood as meaning that the at least one mechanical actuator is fastened to the brake pedal or the eccentric mass, or the tappet, directly contact the brake pedal. A comparatively simple implementation of the feedback and a direct action of the actuator on the brake pedal can thus be ensured.The brake system according to the invention preferably has a brake control unit for controlling the brake device, wherein the at least one mechanical actuator is likewise actuated by the brake control unit. The brake control unit is also responsible for the ABS control of the brake control unit. Thus, no further control device is required for controlling the at least one mechanical actuator and a compact and effective system is ensured.A further advantageous embodiment of the invention provides that, in the case of anti-lock braking, an acoustic signal is output via an audio system of the motor vehicle and / or an optical signal is output, in particular via a combination instrument of the motor vehicle and / or via a head-up display of the motor vehicle, in addition to the vibration in the pedal. This presupposes that the brake system can access the output instruments and system mentioned or can pass on corresponding information.The additional warnings via acoustic and optical signals can further improve the feedback and information transmission from the brake system to the driver in addition to the haptic feedback via the brake pedal, and thus further increase driving safety.The method according to the invention for operating a brake system according to the invention includes the method step that, in the event of anti-lock braking, the at least one mechanical actuator is actuated in order to set the brake pedal in vibration.In the case of anti-lock braking, an optical signal is preferably output to the driver in addition to the vibration in the pedal, in particular via a display in a head-up display and / or in a combination instrument, and / or an acoustic signal, in particular via an audio system of the motor vehicle. As already described, the additional warnings via acoustic and optical signals can further improve the feedback and information transmission from the brake system to the driver in addition to the haptic feedback via the brake pedal, and thus further increase driving safety.In a further advantageous embodiment of the method according to the invention, the at least one mechanical actuator is operated at a variable frequency and / or intensity and / or in vibration packs in accordance with the strength of the antilock braking. Thus, as explained in detail above, the strength of the ABS intervention can also be fed back to the driver.The motor vehicle according to the invention has a brake system according to the invention.Various aspects and embodiments of the invention are explained in more detail below with reference to the attached drawings. They show in detail: FIG. 1 shows a schematic illustration of the brake system according to the invention FIG. 2 illustrates an embodiment of the operating strategy of the mechanical actuatorFIG. 1 shows a schematic illustration of the brake system 10 according to the invention, which has a brake pedal 20 which, in the embodiment shown, is connected to a brake force simulator 31 via a mechanical connection 21. The brake force simulator 31 converts the braking request expressed by a driver of a motor vehicle using the corresponding brake system 10 via the actuation of the brake pedal 20 into a corresponding electrical signal. The electrical signal is in turn converted by the brake device 30 into a brake pressure which is provided on the basis of a hydraulic pressure line to brake actuators 32 on wheels of the motor vehicle. In the context of this application, the brake simulator 31 is already to be understood as part of the brake device 30. The brake actuators are designed to reduce the speed of the motor vehicle.Furthermore, the brake system 10 has a mechanical actuator 40, which is designed to set the brake pedal 20 into vibration during an ABS intervention in the braking operation. The mechanical actuator 40 is either an imbalance motor or a magnetic plunger in the sense described above. In one embodiment of the invention, the mechanical actuator 40 is directly attached to, for example, screwed to, the brake pedal 20 such that vibration of the mechanical actuator 40 itself is transmitted to the brake pedal 20. Such an embodiment is conceivable both for embodiments with a magnetic plunger and also with an imbalance motor.In embodiments with an imbalance motor, the imbalance motor is set in vibration by the centrifugal forces and inertia of the eccentric mass of the imbalance motor, wherein the imbalance motor and brake pedal 20 are likewise set in vibration by the rigid connection between the imbalance motor and the brake pedal 20. The greater the eccentricity, mass and / or speed of the motor, the greater the intensity of the vibration.In embodiments of the invention with a magnetic plunger, the vibration can be generated as described above by moving the plunger from one position to the other and by the movement of the mass of the plunger connected therewith, or by the plunger striking the brake pedal 20.As an alternative to being fastened directly to the brake pedal 20, the mechanical actuator 40 can, in an alternative embodiment, for example likewise be connected to the connection 21 and integrated in the brake simulator 31. Any arrangement of the mechanical actuator 40 in which a transmission of vibration to the brake pedal 20 is possible is conceivable.FIG. 2 shows an exemplary operating strategy of the brake system 10 with imbalance motor as mechanical actuator 40. The imbalance motor is activated in the event of an ABS intervention in the braking operation.If the imbalance motor is activated (state 1 in the upper diagram), a movement x of the brake pedal 20 is induced by the centrifugal force of the imbalance. The movement x fluctuates about a zero point, which is to be defined as the position of the brake pedal 20 when the imbalance motor is inactive. With a correspondingly fast movement x between maximum and minimum, i.e. with a correspondingly high rotational speed of the imbalance motor, the movement of the brake pedal 20 is perceived as vibration by the driver.It is clear from FIG. 2 that the active phases and the inactive phases, indicated by the dashed lines, are of equal length. The movement x of the brake pedal 20 during an active phase of the imbalance motor is understood here as a vibration package. By different timing of the vibration packets with pauses of different lengths between them, information about the intensity of the ABS intervention can be transmitted to the driver. In the case of strong antilock braking, a plurality of vibration packs can be suspended one behind the other and only a few pauses can be provided therebetween. In the case of easier interventions, therefore, only a few vibration packs occur one after the other, which are separated from long pauses (a plurality of inactive phases of the imbalance motor).In the exemplary embodiment shown, therefore, as mentioned, the intensity, i.e. the intensity of the vibration, and the frequency of the movement x and thus of the vibration at the brake pedal 20 are not adjusted, but instead the information about the intensity of the ABS intervention is passed on via the sequence of vibration packets.Of course, other embodiments are possible in which the rotational speed of the imbalance motor and thus the frequency of the vibration and / or the eccentricity of the imbalance mass and thus the intensity of the vibration can be varied.In embodiments with a magnetic plunger as well, an adaptation of the frequency over the number of position changes of the plunger per second is possible, as is an adaptation of the intensity of the vibration over the speed of the position change of the plunger. Information transmission via the above-described vibration packets is also possible with the magnetic plunger.List of reference characters10 Brake system 20 Brake pedal 21 Connection 30 Brake device 31 Brake force simulator 32 Brake actuator 40 Mechanical actuator

Claims

Brake system (10) for a motor vehicle, having a brake pedal (20), configured to receive a braking request from a driver guiding the motor vehicle and to transmit it to a brake device (30), wherein the brake device (30) is configured to translate the braking request into a corresponding brake pressure and to transmit it to brake actuators (32), wherein the brake pedal (20) is mechanically and / or hydraulically decoupled from the brake device (30), and wherein the brake system (10) has at least one mechanical actuator (40), characterized in that the at least one mechanical actuator (40) is designed in the form of an imbalance motor and / or a magnetic plunger and is connected to the brake pedal (20) and is configured to set the brake pedal (20) in vibration in the event of an antilock braking.Brake system (10) according to the preceding claim, wherein the imbalance motor has an adjustable imbalance and / or at least two imbalance motors are provided which have a different imbalance.Brake system (10) according to one of the preceding claims, wherein the at least one mechanical actuator (40) is designed to be acted upon by vibrations of different frequency and / or intensity and / or in vibration packs.Brake system (10) according to one of the preceding claims, wherein the brake system has a brake force simulator (31) and the at least one mechanical actuator (40) is arranged integrated in the brake force simulator (31).Brake system (10) according to one of the preceding claims 1 to 4, wherein the at least one mechanical actuator (40) is arranged directly on the brake pedal (20).Brake system (10) according to one of the preceding claims, wherein the brake system has a brake control unit for controlling the brake device (30), and the at least one mechanical actuator (40) is likewise actuated by the brake control unit.Brake system (10) according to one of the preceding claims, wherein the brake system is furthermore designed, in the event of anti-lock braking, to output an acoustic signal via an audio system of the motor vehicle and / or to output an optical signal in addition to the vibration in the brake pedal (20).Method for operating a brake system (10) according to one of the preceding claims, wherein, in the event of anti-lock braking, the at least one mechanical actuator (40) is actuated in order to set the brake pedal (20) in vibration.Method according to the preceding claim, wherein in the case of anti-lock braking, in addition to the vibration in the brake pedal (20), an optical signal is output to the driver, in particular via a display in a head-up display and / or in a combination instrument and / or an acoustic signal.Method according to one of the two preceding claims, wherein the at least one mechanical actuator (40) is operated at a different frequency and / or intensity and / or in vibration packs in accordance with the strength of the anti-lock braking.Motor vehicle comprising the brake system (10) according to one of the preceding claims 1 to 7.

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