Coupling device for connecting a brake input element to a master brake cylinder and method for operating such a coupling device

Abstract

Coupling device for connecting a brake input element (16) to a master brake cylinder (10) of a vehicle, comprising: an input piston (14) which can be arranged on the brake input element (16) in such a way that the input piston (14) can be adjusted by a braking distance (s) from an initial position (s0) upon actuation of the brake input element (16); and an output piston (12) to which a driver braking force (Ff) exerted on the brake input element (16) can be transmitted via the input piston (14) which is adjusted from its initial position (s0) by a braking distance (s) of at least a predetermined first minimum braking distance, and which can be arranged on the master brake cylinder (10) in such a way that an internal pressure in the master brake cylinder (10) can be increased by means of the driver braking force (Ff) transmitted to the output piston (12) via the input piston (14); wherein, at least in a first operating mode of the coupling device, the input piston (14) adjusted from its initial position (s0) by a braking distance (s) smaller than the first minimum braking distance is spaced from the output piston (12) in such a way that a force transmission from the input piston (14) to the output piston (12) is prevented; wherein the coupling device can additionally be converted into at least one second operating mode with a second minimum braking distance less than the first minimum braking distance, wherein in the second operating mode of the coupling device the input piston (14), which is adjusted from its initial position (s0) by a braking distance (s) less than the second minimum braking distance, is spaced from the output piston (12) in such a way that force transmission from the input piston (14) to the output piston (12) is prevented, and the driver braking force (Ff) can be transmitted to the output piston (12) via the input piston (14), which is adjusted from its initial position (s0) by a braking distance (s) between the second minimum braking distance and the first minimum braking distance; and wherein the coupling device comprises a control device (50) by means of which the coupling device can be transferred from at least the first operating mode with the first minimum braking distance into at least the second operating mode with the second minimum braking distance smaller than the first minimum braking distance; characterized in that the coupling device comprises an adjustable force transmission component (52) attached to either the output piston (12) or the input piston (14), and the control device (50) is additionally designed to control an actuator of the power transmission component (52) by means of a control signal (54) such that the power transmission component (52) is transferred from a retracted position of the first operating mode into at least one extended position of at least the second operating mode.

Description

The present invention relates to a coupling device for connecting a brake input member to a master cylinder of a vehicle. Furthermore, the invention relates to a method for operating such a coupling device.Prior ArtElectric and hybrid vehicles have a braking system designed for regenerative braking, having an electric motor operated in a generator mode in the case of regenerative braking. The electrical energy obtained during the regenerative braking is preferably used after intermediate storage for accelerating the vehicle. In this way, a power loss which a conventional vehicle exhibits during frequent braking during a trip, an energy consumption and a pollutant emission of the electric or hybrid vehicle can be reduced.However, the generator operation of the electric motor, for example of the electric drive motor, generally presupposes a specific minimum speed of the vehicle. A regenerative braking system is thus often not capable of applying a generator braking torque to the wheels of the vehicle until the vehicle running beforehand is at a standstill. A hybrid vehicle therefore often also has, in addition to the regeneratively operated electric motor, a hydraulic brake system by means of which the braking action of the regenerative brake that is omitted can be compensated for at least in a low speed range. In this case, even in the case of a full electrical energy store, if the regenerative brake usually exerts no braking torque on the wheels, the entire braking torque can be applied via the hydraulic brake system.On the other hand, in some situations, it is desirable to apply as low a hydraulic braking force as possible to the wheels in order to achieve a high degree of recuperation. For example, after switching operations, the decoupled generator is frequently activated as a regenerative brake in order to ensure reliable charging of the buffer store and a high energy saving.Generally, a driver prefers a total braking torque of his vehicle corresponding to its operation of a brake input member, such as its brake pedal operation, independently of an activation or deactivation of the regenerative brake. Some electric and hybrid vehicles therefore have an automatic system which is intended to adapt the braking torque of the hydraulic brake system to the current braking torque of the regenerative brake in such a way that a desired total braking torque is maintained. The driver therefore does not have to take over the task of the deceleration regulator by himself adapting the actuation of the brake input element to the current braking torque of the regenerative brake. Examples of such an automatic system are brake-by-wire brake systems, in particular EHB systems, as described, for example, at http: / / en.wikipedia.org / wiki / Brake-by-wire.DE 10 2009 033 499 A1 describes a brake system for motor vehicles. The brake system comprised a master brake cylinder and a pedal decoupling unit with a retaining piston which together with a rod piston of the master brake cylinder delimits a chamber to which a hydraulic pressure can be applied. An electrically controllable pressure supply device is used for supplying the hydraulic pressure.Similarly, DE 10 2006 059 840 A1 describes a brake system in which a transmission of a driver braking force from a pedal tappet via a coupling element to a brake booster tappet is influenced by means of a latching element engaging in the coupling element.The object of the present invention is to provide a coupling device which can be used in the first operating mode as a decoupling device for decoupling the brake input element from the master brake cylinder and in the second operating mode as a coupling device for coupling the brake input element to the master brake cylinder.Disclosure of the InventionThe invention provides a coupling device for connecting a brake input element to a master brake cylinder of a vehicle having the features of claim 1.Advantages of the InventionThe present invention provides a coupling device which can be used in the first operating mode as a decoupling device for decoupling the brake input element from the master brake cylinder and in the second operating mode as a coupling device for coupling the brake input element to the master brake cylinder. Thus, in the first operating mode, an internal pressure of the master brake cylinder is not increased despite an actuation of the brake input element, by means of which the input piston is adjusted from its initial position by a braking distance smaller than the predefined first minimum braking distance. In contrast, in the second operating mode, the driver can brake directly into the master brake cylinder already upon actuation of the brake input element, by means of which the input piston is adjusted from its initial position by the adjustment path between the predefined second minimum braking path and the first minimum braking path.At the same time, the coupling device according to the invention ensures the advantages of a brake-by-wire system. Both in the first operating mode and in the second operating mode, it is possible to set the internal pressure in the master brake cylinder independently of the actuation of the brake input element. The decoupling can likewise be used to block a regenerative braking torque of a braking system capable of recuperation.A further advantage of the technology according to the invention is that both in the first operating mode and in the second operating mode, the input piston makes contact with the output piston during a (longer) actuation of the brake input element, i.e. after overcoming the first minimum braking path or the second minimum braking path, and the driver braking force exerted on the brake input element is thus transmitted to the output piston via the input piston. Thus, in such an actuation of the brake input element, the force exerted by the driver on the brake input element can be used to increase the brake pressure in the master brake cylinder. By means of the technology according to the invention, a brake device can therefore be used whose power and its energy consumption must meet lower requirements than an external force brake device of a brake-by-wire system. At the same time, the usable brake device, which is used as an external force brake or as an auxiliary force brake depending on an operating mode, ensures reliable braking of a vehicle. Thus, the comparatively high cost of a brake-by-wire system is eliminated in the present invention. In addition, the direct transmission of force from the brake input element to the output piston via the input piston in the case of a braking path of at least the second minimum braking path increases the safety standard of the vehicle equipped therewith.The present invention can be used for a recuperation-capable and / or brake-force-boosted brake system. It offers in particular the possibility of determining, by means of a sensor or by means of an estimate, which total braking torque is desired by the driver and / or a control system of the vehicle and which current regenerative braking torque is exerted by the regenerative brake. A difference between the desired total braking torque and the regenerative braking torque can then be determined, which is actively defined after decoupling the brake input element by means of setting a corresponding internal pressure in the master brake cylinder. This enables the (time-variable) regenerative braking torque to be matched without the driver having to perform additional work. For carrying out the method steps described in this paragraph, no expensive electronics are necessary. Thus, sufficient recuperation efficiency is ensured at reasonable costs when using the present invention.In an advantageous embodiment, the coupling device comprises an external force brake device, by means of which an external force can additionally be transmitted to the output piston in such a way that the internal pressure in the master brake cylinder can be increased by means of the external force transmitted to the output piston. By means of such an external force brake device, which can also be referred to as a brake booster, a desired internal pressure can be actively set in the master brake cylinder in a simple manner. A controllable brake booster, such as in particular an electromechanical brake booster, can be used as a suitable external force brake device, for example. Thus, in particular when decoupling the brake pedal, a generator braking torque of an electric generator can be recuperated by means of the power brake device. In addition, the power brake device can also be used to reduce the force to be applied by a driver for braking the vehicle to a standstill.Preferably, the coupling device can be transferred by means of the control device, at least into the first state or into the second operating mode, taking into account at least one variable with respect to an operating speed of the operation of the brake input element, a temporal change of the operating speed, the driver braking force, a temporal change of the driver braking force, a state of at least one vehicle component of the vehicle, a temporal change of the state, at least one driving style of the vehicle and / or a temporal change of the driving style. In this way, for example, at least one characteristic variable of the brake actuation can be taken into account during the selective transfer of the coupling device at least into the first operating mode or into the second operating mode. On the basis of the characteristic variables of the brake actuation listed here, it is possible to reliably identify whether the driver prefers abrupt braking of the vehicle or slow braking of the vehicle. For example, a rapid actuation of the brake input member, a sudden acceleration of the brake input member actuation, a comparatively large driver braking force, and a rapid increase in the driver braking force indicate that the driver desires an abrupt braking of the vehicle. In this case, the technology according to the invention can be used to transmit the driver braking force to the output piston even in the case of a small brake application path and thus to use it to increase the internal pressure in the master brake cylinder.Likewise, the coupling device can be convertible by means of the control device, taking into account at least one variable with respect to a state and / or a change over time in the state of a component of a regenerative braking system, at least into the first state or into the second operating mode. This also ensures an advantageous determination of the updated operating mode. Such a state variable of a component of the regenerative braking system may be, for example, a state of charge of the battery and / or an operating mode of a generator.Furthermore, the coupling device can be transferred by means of the control device at least into the first state or into the second operating mode taking into account a vehicle speed, a vehicle direction, a vehicle direction change and / or a yaw rate. Thus, in traffic and driving situations in which a rapid brake pressure increase is advantageous, it is possible, by transferring the coupling device into the second operating mode, to transmit the driver braking force exerted by the driver on the actuating element to the output piston even in the case of a smaller brake application path.The control device is preferably designed to control the force transmission component from the retracted position into the at least one extended position such that, in the first operating mode, a force transmission from the input piston adjusted from its initial position by a braking path between the second minimum braking path and the first minimum braking path to the output piston is prevented via the force transmission component controlled into the retracted position, and, in the second operating mode, the driver braking force can be transmitted from the input piston adjusted from its initial position by a braking path between the second minimum braking path and the first minimum braking path to the output piston via the force transmission component controlled into the at least one extended position. By means of an extension of the force transmission component, a force transmission connection can be created between the input piston and the output piston even in the second minimum braking path. Accordingly, retraction of the force transmitting component may cancel the force transmitting connection between the output piston and the input piston at a stopping distance less than the first minimum stopping distance. The transfer of the coupling device into the first operating mode and into at least the second operating mode can be easily carried out in this way.For example, the force transmission component can comprise a multistage pawl. In this case, the coupling device can also be transferred in at least one further operating mode in addition to the first operating mode and the second operating mode.The advantages listed in the above paragraphs are also ensured in a brake system having such a coupling device and a vehicle having a corresponding coupling device, or having such a brake system.Brief Description of the DrawingsFurther features and advantages of the invention are explained below with reference to the figures. The following are shown: FIG. 1 is a schematic illustration of a coupling device which does not fall under the present invention; FIG. 2 shows a schematic illustration of an embodiment of the coupling device according to the invention; and FIG. 3 is a flow chart of a method which does not fall under the present invention.Embodiments of the InventionFig. 1 shows a schematic representation of a coupling device which does not fall under the present invention.The coupling device schematically shown in FIG. 1 has an output piston 12 which is / can be arranged on a master brake cylinder 10. By pushing at least a part of the output piston 12 into the master brake cylinder 10, a pressure in at least one internal volume of the master brake cylinder 10 can be increased. The technology described below is not limited to a specific type of the master cylinder 10 or the output piston 12.The coupling device also comprises an input piston 14, which can be / is arranged on a brake input element 16 (only partially shown) in such a way that the input piston 14 can be adjusted by a braking path s from an initial position s 0 when the brake input element 16 is actuated. A sensor (not shown), for example a pedal travel sensor or a force sensor, can be attached to the brake input element 16, by means of which sensor an actuation of the brake input element 16 can be determined. The brake input element 16 can be designed, for example, as a brake pedal. However, it should be noted that the feasibility of the coupling device described herein does not require a particular configuration of the brake input member 16 or the input piston 14.Advantageously, the output position s0of the input piston 14 is defined such that a gap 18 is located between the (non-actuated) output piston 12 and the input piston 14 present in its output position s0when the brake input element 16 is not actuated. This can also be described in such a way that the two pistons 12 and 14 do not contact one another in their starting positions upon non-actuation of the brake input element 16. A transmission of force between the pistons 12 and 14 present in their initial positions is thus prevented because of the gap 18. A decoupling of brake input element 16 from master brake cylinder 10 is thus able to be realized via gap 18 between pistons 12 and 14.In contrast, an adjustment of the input piston 14 from its initial position s 0 by a braking path s of at least one predefined first minimum braking path causes the two pistons 12 and 14 to contact one another. In this way, a driver braking force Ff exerted on the brake input element 16 can be transmitted to the output piston 12 via the input piston 14 adjusted from its initial position s0 by the braking path s of at least the first minimum braking path. The transmittable driver braking force Ff can be understood to mean a partial force exerted by the driver on the brake input element 16. In addition to the driver braking force Ff, the driver can also apply a further partial force to the brake input element 16 in order to overcome the frictional forces counteracting the adjustment of the brake input element 16 and / or of the input piston 14.By means of the driver braking force Ff transmitted to the output piston 12 via the input piston 14, the output piston 12 can be adjusted in such a way that the at least one internal volume of the master brake cylinder 10 is reduced, and the internal pressure present therein is thus increased. By means of the increased internal pressure, a brake pressure of at least one wheel brake cylinder (not shown) of at least one brake circuit (not shown) which can be coupled to the master brake cylinder 10 can be increased. In this way, at least one (hydraulic) braking torque of the at least one wheel brake cylinder that can be exerted on at least one wheel of the vehicle can be built up. It is pointed out that the usability of the coupling device described here does not require a special configuration of the at least one brake circuit or a specific type of wheel brake cylinder arranged therein.The coupling device optionally comprises an external force brake device, by means of which an external force (not shown) can be transmitted to the output piston 12 in such a way that the internal pressure in the master brake cylinder 10 can be increased by means of the external force transmitted to the output piston 12. The external force brake device can be designed, for example, as a brake booster, in particular as an electromechanical brake booster and / or as a hydraulic brake booster (i-booster). The external force brake device is preferably a continuously adjustable / controllable brake booster (active brake booster). However, it is pointed out that the design of the power brake device is not limited to the examples of brake boosters listed here.The power brake device can comprise a motorized transmission 22 (electric motor) that can be controlled by means of a control device 20, by means of which a support piston 24 arranged / arrangeable on the output piston 12 can be adjusted such that the output piston 12 can be adjusted together with the support piston 24 for varying the internal pressure in the master brake cylinder 10. In particular, despite the prevented transmission of force from the input piston 14 to the output piston 12 spaced apart from the input piston 14, the output piston 12 can be adjustable by means of the power brake device. Further advantageous design possibilities of the power brake device will be discussed in more detail below.The coupling device of FIG. 1 has a first operating mode in which, during an adjustment of the input piston 14 from its initial position s 0 by a braking distance s smaller than the first minimum braking distance, the input piston 14 is spaced apart from the output piston 12 such that a transmission of force from the input piston 14 adjusted from its initial position s 0 by the braking distance s smaller than the first minimum braking distance to the output piston 12 is prevented. Actuating the brake input element 16 with a comparatively low driver braking force Ff thus brings about an adjustment of the input piston 14 from its initial position s 0 by a (small) braking distance s smaller than the first minimum braking distance, which is not sufficient to overcome the gap 18. Thus, in the first operating mode, it is ensured that the driver only brakes directly into the master brake cylinder 10, or into the at least one wheel brake cylinder, starting from a minimum actuation defined by the first minimum braking path.Furthermore, the coupling device can be transferred into at least one second operating mode with a second minimum braking distance smaller than the first minimum braking distance. In the second operating mode of the coupling device, the input piston 14, which is adjusted from its initial position s 0 by a braking distance s smaller than the second minimum braking distance, is spaced apart from the output piston 12 such that a transmission of force from the input piston 14 to the output piston 12 is prevented. This can also be described in such a way that, during an adjustment of the input piston 14 from its initial position s0 by the braking path s smaller than the second minimum braking path, the force transmission from the input piston 14 to the output piston 12 is prevented on the basis of its spacing. In contrast, the driver braking force Ff can be transmitted to the output piston 12 via the input piston 14 which is adjusted from its initial position s0 by a braking distance s between the second minimum braking distance and the first minimum braking distance.The second operating mode of the coupling device thus ensures the driver the possibility of braking directly into the master brake cylinder 10, or into the at least one wheel brake cylinder, already after overcoming a shorter idle travel (the second minimum braking travel). Thus, the brake system with the coupling device transferred into the second operating mode can react more quickly to the actuation of the brake input element 16 by the driver even without the use of electronics inherent in the brake system.In contrast, the first operating mode ensures advantageous decoupling between the brake input element 16 and the master brake cylinder 10 with a greater idle travel (the first minimum braking travel). The (slight) restrictions on the brake feel / pedal feel that possibly occur on account of the decoupling are not / hardly perceptible to the driver on account of their low magnitude and are therefore tolerable. The decoupling of the brake input element 16 from the master brake cylinder 10 can be configured by advantageously defining the first minimum braking path such that it is present in particular in regions of the brake actuation in which a generator for regenerative braking is often used. For example, the first minimum braking path can be defined over an advantageous maximum width b of the gap 18 in such a way that a higher generator braking torque can also be exerted on at least one wheel of the vehicle during decoupling, without a setpoint deceleration of the vehicle predefined by the driver being exceeded. In particular, the maximum width b of the gap 18 can correspond at least to the braking path s necessary for maximum regenerative deceleration. Further possibilities for advantageously configuring the first minimum braking path are also mentioned below.A particularly advantageous embodiment of the power brake device for cost-effective realization of the coupling device is discussed in more detail below:The control device 20 is preferably designed to adjust the output piston 12 at the predefined brake adjustment speed v0in a direction away from the input piston 14 starting from an adjustment of the input piston 14 from its output position s0. Upon actuation of the brake input element 16, the gap 18 present between the pistons 12 and 14 decreases by a difference which can be defined / fixed at least via the brake displacement speed v0and the displacement speed v of the input piston 14. The difference can also be increased if the motor (electric motor) of the transmission 22 is not set in motion until a time delay (caused by signal latency times and computing times) occurs.The dynamics of the output rod 12 (brake adjustment speed v0) are dependent on the transmission and motor dimensions of the transmission 22 and can be designed such that a closing of the gap 18 and thus a frictional connection between the pistons 12 and 14 only takes place after an adjustment of the input piston 14 by a definable (advantageous) idle travel. Thus, by advantageously defining the at least one brake adjustment speed v 0 or by advantageously controlling the transmission 22 by the control signal 26 output by the control device 20, it is possible to realize preferred values for at least the first minimum stopping distance and the second minimum stopping distance.In a preferred embodiment, the output piston 12 is adjustable by means of the power brake device at a first maximum adjustment speed for the brake adjustment speed v0, which is less than a second maximum adjustment speed for the adjustment speed v of the input piston 14 adjusted from its output position s0. It is thus ensured that by means of actuating the brake input element 16 at a maximum actuating speed at which the input piston 14 can be adjusted at the second maximum adjusting speed, the coupling device can be automatically transferred from the first operating mode into the second operating mode.This can be described in such a way that an adjustment of the input piston 14 with an adjustment speed v less than a limit adjustment speed predetermined by the first maximum adjustment speed of the output piston 12 causes the gap 18 to close in the event of a greater adjustment travel s of the input piston 14. In contrast, an adjustment of the input piston 14 with an adjustment speed v greater than the predefined limit adjustment speed leads to a closing of the gap 18 with a smaller adjustment travel s of the input piston 14, and therefore the adjustment of the input piston 14 with an adjustment speed v less than the limit adjustment speed, or a corresponding actuation of the brake input element 10, already causes the coupling device to be automatically transferred into the first operating mode. When the brake input element 16 is actuated in accordance with an adjustment speed v greater than the predefined limit adjustment speed, the coupling device is automatically transferred into the second operating mode. Thus, in the coupling device described here, the decoupling between the pistons 12 and 14 depending on the actuation speed of the brake input element 10 can be (automatically) cancelled by the driver via rapid actuation of the brake input element 16, without an electronic / sensor system being necessary for ascertaining the actuation speed of the brake input element 16. The energy (driver braking force Ff) applied by the driver when the brake input element 16 is quickly actuated can be simultaneously used for braking. In the coupling device described here, the decoupling and the coupling of the brake input element 16 to the master brake cylinder 10 are purely passive, i.e. without an activation of an additional actuator system. This ensures that, by coupling the brake input element 16 to the master brake cylinder 10 in the actuation cases in which a high power of the brake system is required and the driver therefore intuitively carries out a rapid actuation of the brake input element 16, the driver braking force Ff is also used for (rapid) building up the advantageous brake pressure into the at least one wheel brake cylinder. In this way, the electrical power to be provided by the power brake system can additionally be clearly reduced.In the embodiment shown, the coupling device has a hydraulic housing 35 with at least one interior chamber 36 which is embodied in a watertight manner and into which at least a portion of the input piston 14 directed away from the brake input element 16 and a portion of the output piston 12 directed away from the master brake cylinder protrude. The inner chamber 36 is preferably at least partially filled with a liquid, preferably with the hydraulic liquid (brake liquid) of the at least one brake circuit hydraulically connected to the master brake cylinder 10. By means of a suitable configuration of the walls of the inner chamber 36, it can be ensured that no liquid escapes at the contact surfaces of the walls with the pistons 12 and 14. Forming a "variable void" in a liquid realizes the advantages described in more detail below over forming the void as an "air gap.". However, the coupling device described herein is not limited to an arrangement of the pistons 12 and 14 in the hydraulic housing 35 filled with a liquid.Advantageously, the coupling device also comprises a pedal simulator 30. The pedal simulator 30 may be configured as a piston-cylinder unit, such as a plunger. The pedal simulator 30 may be connected to the internal chamber 36 via a first pipe 31. The arrangement of the pistons 12 and 14 in the liquid-filled inner chamber 36 makes this economically realizable design of the pedal simulator 30 as a piston-cylinder unit possible. In this case, an adjustment of the input piston 14 into the inner chamber 36 causes a displacement of the liquid from the inner chamber 36 into the pedal simulator 30 counter to the restoring force acting on the piston of the piston-cylinder unit. The driver thus feels a restoring force counteracting the actuation even when the brake input element 16 is actuated, in which the output piston 12 still remains in its initial position, although the input piston is also adjusted. This ensures an advantageous brake feel for the driver when actuating the brake input element 16 even before the clear travel is overcome.The pedal simulator 30, which is designed as a piston-cylinder unit, preferably has a non-linear spring characteristic, which corresponds to a standard (advantageous) brake characteristic. In this case, the driver has the usual brake feeling when the brake input member 16 is operated despite the output piston 12 remaining in its initial position.In particular, the pedal simulator 30 and the inner chamber 36 may be hydraulically connected via at least one second line 34 to a brake medium reservoir 28 (brake fluid reservoir) connected to the master brake cylinder 10. The hydraulic fluid of master brake cylinder 10 and of the at least one brake circuit may thus be used to fill internal chamber 36.In an advantageous development, the pedal simulator 30 and the inner chamber 36 are also hydraulically connected to the brake medium reservoir 28 via a further valve 32. As an alternative to the brake medium reservoir 28, the pedal simulator 30 and the inner chamber 36 can also be hydraulically connected to another counterpressure-free hydraulic fluid storage volume via the valve 32 and the second line 34.In the cases described above, a differential pressure p between a pressure in the inner chamber 36 and a pressure in the brake medium reservoir 28, in the back-pressure-free hydraulic fluid storage volume and / or the atmospheric pressure can be adjusted by means of the pedal simulator 30 and / or the regulating valve 32. The differential pressure p can be set in particular such that the following equations (Gl 1) and (Gl 2) apply to the simulator counterforce Fs exerted on the brake actuating element 16: wherein A of a surface of the input piston 14 projecting into the inner chamber 36 and Fsys correspond to a system reaction force from spring forces of the springs and / or frictional forces arranged in the hydraulic housing 35 and Fk is the characteristic curve of the brake input element 16 (pedal characteristic curve).In this case, upon operation of the brake input member 16, the driver notes a counterforce from a sum of the system reaction force Fsys of the output rod 12 and a simulator reaction force Fs. Equations (GI 1) and (GI 2) apply both when the valve 32 is closed and when the pedal simulator 30 is not connected to the brake medium reservoir 28 by means of the second line 34 and the valve 32.If the valve 32 is open, the liquid volume displaced from the inner chamber 36 during an adjustment of the inlet piston 14 can be transferred without counterpressure into the brake medium reservoir 28 or into a corresponding hydraulic liquid storage volume. The opening of the valve 32 establishes a connection of the inner chamber 36 with the brake medium reservoir 28 or the hydraulic fluid storage volume and effectively brings about a bypass of the simulator 30.After opening the valve 32, the driver thus has the possibility of carrying out the brake actuation quickly and with a relatively low exertion of force. In particular, in this case, the driver can overcome the lost travel quickly and with a small amount of force.The valve 32 is preferably a normally open valve, which can be electrically controlled at least in an open mode and in a closed mode. A cost-effective example of the valve 32 is a normally open switching valve / isolating valve. The normally open design of the valve 32 ensures the advantage that the valve 32 is automatically opened in the event of a functional impairment and / or in the event of a failure of the electronics of the brake system. Thus, in such a situation, the driver can easily overcome the clear travel and bring the vehicle to a standstill with a comparatively low braking force.In an advantageous development, the control device 20 or an additional control of the brake system can be designed such that, by means of the control device 20 or the control, the valve 32 is electrically controlled by means of a further control signal 38 while taking into account at least one variable / item of information regarding an actuation speed of the actuation of the brake input element, a temporal change of the actuation speed, the driver braking force, a temporal change of the driver braking force, an actuation of the accelerator pedal, a temporal change of the actuation of the accelerator pedal, a temporal change of the actuation speed of the accelerator pedal, a state of at least one vehicle component of the vehicle, a temporal change of the state, at least one driving mode of the vehicle, a temporal change of the driving mode, a traffic situation and / or an environmental situation. This can also be described in such a way that the valve 32 is actuated as a function of at least one braking system, vehicle and / or ambient condition. Examples of a quantity / information regarding an actuation speed of the actuation of the brake input element, a temporal change of the actuation speed, the driver braking force, a temporal change of the driver braking force are already mentioned above. A state variable of a component of the regenerative braking system taken into account can be, for example, a state of charge of the battery and / or an operating mode of a generator. Likewise, the at least one variable taken into account by the control device 20 / the controller can comprise a vehicle speed, a vehicle direction, a change in vehicle direction and / or a yaw rate. A variable relating to a traffic situation and / or an environmental situation can also be a warning signal provided by an in-vehicle environmental detection system, such as, for example, an ACC system, a radar system and / or an airbag deployment system. On the basis of the characteristic variables listed here, it can be reliably detected whether the driver prefers abrupt braking of the vehicle or slow braking of the vehicle. It can likewise be seen from these variables whether, on account of the current situation, high dynamics during braking of the vehicle are more important than the energy obtained during recuperation and / or than the comfort of the blending process.In such a development, it is possible, in particular in the case of a dynamic / rapid actuation of the brake, a sudden interruption of the accelerator pedal actuation, a relatively high speed of the vehicle and / or in the case of a hazardous situation being detected, to reduce the counterforce acting on the brake input element 16 and thus to release the driver with force during the braking operation and / or to enable a more rapid braking of the vehicle.In another refinement, the valve 32 can also be a continuously adjustable / controllable / switchable valve. The control device 20 / the controller can in this case be configured to control the valve 32 into a specific opening state taking into account at least one of the variables listed above. This ensures a more rapid variation of the counterforce acting on the brake input element 16. For example, the valve 32 can be briefly opened during an actuation of the brake input element 16 in order to ensure a particularly advantageous brake feel for the driver. However, the applicability of the coupling device is not limited to a fitting with the valve 32 and a control device 20 interacting therewith.FIG. 2 shows a schematic illustration of an embodiment of the coupling device according to the invention.The coupling device schematically illustrated in FIG. 2 has no / hardly any deviations from the above-described embodiment, except for the design of the power brake device. A new description of the components 10 to 16, 22, 24 and 28 to 36 is therefore omitted here.Alternatively or in addition to the above-described embodiment, the coupling device of FIG. 2 comprises a control device 50, by means of which the coupling device can be transferred from at least the first operating mode with the first minimum braking path into at least the second operating mode with the second minimum braking path smaller than the first minimum braking path.Likewise, the coupling device can be convertible from at least the second operating mode to at least the first operating mode by means of the control device 50. The control device 50 is designed to take into account, when controlling the coupling device between the at least two operating modes, at least one variable with respect to an actuating speed of the actuation of the brake input element, a temporal change of the actuating speed, the adjusting speed of the input piston 14, a temporal change of the adjusting speed, the driver braking force Ff, a temporal change of the driver braking force Ff, a state of at least one vehicle component of the vehicle, a temporal change of the state, at least one driving style of the vehicle and / or a temporal change of the driving style. As the at least one variable, at least one variable with respect to a state and / or a change over time in the state of a component of a regenerative braking system can be taken into account. Such a state variable of a component of the regenerative braking system may be, for example, a state of charge of the battery and / or an operating mode of a generator. Likewise, the at least one variable may include a vehicle speed, a vehicle direction, a change in vehicle direction and / or a yaw rate. Thus, variables independent of the actuation of the brake input element 16 can also be taken into account / evaluated for a determination of an advantageous operating mode of the coupling device. Since possibilities for providing the variables listed here to the control device 50 by means of a sensor and / or by means of an information output device are known, they will not be discussed in any further detail.In the embodiment shown, the control device 50 is additionally designed to actuate an actuator (not shown) of a force transmission component 52 by means of a control signal 54 in such a way that the force transmission component 52 is transferred from a retracted position of the first operating mode into at least one extended position of at least the second operating mode. The coupling device can thus be switched from the first operating mode into at least the second operating mode by extending the force transmission component 52. Accordingly, by retracting the force transmission component 52, the coupling device can be switched from at least the second operating mode into the first operating mode.In the first operating mode, a transmission of force from the input piston 14, which is adjusted from its initial position s 0 by a braking distance s between the second minimum braking distance and the first minimum braking distance, to the output piston 12 is prevented via the force transmission component 52 controlled into the retracted position. In contrast, in the second operating mode, the driver braking force Ff can be transmitted from the input piston 14, which is adjusted from its initial position s 0 by a braking distance s between the second minimum braking distance and the first minimum braking distance, to the output piston 12 via the force transmission component 52 controlled into the at least one extended position. The force transmitting component 52 may be adjustably attached to either the output piston 12 or the input piston.The driver braking force Ff can thus be transmitted to the output piston 12 via the (extended) force transmission component 52 in the second operating mode, even though the input piston 14 itself does not touch / contact the output piston 12. The actuator of the force transmission component 52 can likewise be controlled by means of the control signal 54 in such a way that, when the force transmission component 52 is retracted, the frictional connection between the output piston and the input piston adjusted from its initial position s0 by a braking distance s between the second minimum braking distance and the first minimum braking distance is canceled.The force transmission component 52 can also be referred to as an actively switchable lock. For example, the force transmission component 52 is designed as a pawl. The force transmission component 52 can also be designed such that it has a plurality of locking stages, for example as a multistage latch. Thus, in addition to the first operating mode and the second operating mode, the coupling device can also have at least one third operating mode with a third minimum braking distance smaller than the second minimum braking distance.A force transmission component 52 realized as a pawl is preferably present in the retracted position in the non-energized (de-energized) state. Preferably, such a force transmission component 52 can be unlocked by electromagnet, i.e. can be transferred into the at least one extended position. Thus, in the event of a failure of the power brake device or of its power supply, the coupling device can be automatically switched into a mode with a shorter braking distance.Optionally, the control device 50 can additionally be designed to output the control signal 38 already described above to the valve 32.Figure 3 shows a flow chart of a method which does not fall within the present invention.The method described here is suitable for reliable operation of a coupling device, by means of which a brake input element is connected to a master brake cylinder of a vehicle. The usable coupling device comprises at least one input piston (co-)adjusted by a braking path when the brake input element is actuated from an initial position, and an output piston, to which a driver braking force exerted on the brake input element is transmitted via the input piston adjusted from its initial position by a braking path of at least one predefined first minimum braking path in such a way that an internal pressure in the master brake cylinder is increased by means of the driver braking force transmitted via the input piston to the output piston. For example, one of the coupling devices described above can be used to carry out the method.In a method step S 1, the coupling device is operated in a first operating mode, in which the input piston, which is adjusted from its initial position by a brake application distance smaller than the first minimum brake application distance, is spaced apart from the output piston such that a transmission of force from the input piston to the output piston is prevented. Thus, during method step S 1, it is possible to use the "end coupling" of the brake input element from the master brake cylinder for activating a generator without a setpoint deceleration of the vehicle predefined by the driver being exceeded.In a method step S 2, the coupling device is transferred into at least one second operating mode with a second minimum engagement path smaller than the first minimum engagement path. In the second operating mode of the coupling device, the input piston, which is adjusted from its initial position by a brake application path smaller than the second minimum brake application path, is spaced apart from the output piston in such a way that a force transmission from the input piston to the output piston is prevented. However, the driver braking force is transmitted to the output piston via the input piston adjusted from its initial position by a braking distance between the second minimum braking distance and the first minimum braking distance. This ensures the advantages already described above.When carrying out method step S 2, at least one variable relating to an actuation speed of the actuation of the brake input element, a temporal change in the actuation speed, the driver braking force, a temporal change in the driver braking force, a state of at least one vehicle component of the vehicle, a temporal change in the state, at least one driving style of the vehicle and / or a temporal change in the driving style can be ascertained, and the at least one ascertained variable can be taken into account when transferring the coupling device into at least the second operating mode. For example, at least one variable with respect to a state and / or a temporal change of the state of a component of a regenerative braking system is taken into account. Likewise, a vehicle speed, a vehicle direction, a vehicle direction change and / or a yaw rate can be taken into account as the at least one variable.In a particularly advantageous embodiment, a force transmission component is adjusted from a retracted position into at least one extended position when the coupling device is transferred from the first operating mode into at least the second operating mode. In this way, it is possible to ensure that the driver braking force is transmitted from the input piston, which is adjusted from its initial position by a braking distance between the second minimum braking distance and the first minimum braking distance, to the output piston via the force transmission component adjusted into the at least one extended position.At a later point in time, the method step S 1 can be repeated by switching over the coupling device.

Claims

Coupling device for connecting a brake input element (16) to a master brake cylinder (10) of a vehicle, having: an input piston (14) which can be arranged on the brake input element (16) in such a way that the input piston (14) can be adjusted by a braking path (s) from an initial position (s0) when the brake input element (16) is actuated; an output piston (12), to which a driver braking force (Ff) exerted on the brake input element (16) can be transmitted via the input piston (14), which is adjusted from its initial position (s0) by a braking path (s) of at least one predefined first minimum braking path, and which can be arranged on the master brake cylinder (10) in such a way that an internal pressure in the master brake cylinder (10) can be increased by means of the driver braking force (Ff) transmitted via the input piston (14) to the output piston (12); wherein, at least in a first operating mode of the coupling device, the input piston (14), which is adjusted from its initial position (s0) by a brake application path (s) smaller than the first minimum brake application path, is spaced apart from the output piston (12) such that a force transmission from the input piston (14) to the output piston (12) is prevented; wherein the coupling device can additionally be transferred into at least one second operating mode with a second minimum stopping distance smaller than the first minimum stopping distance, wherein in the second operating mode of the coupling device the input piston (14), which is adjusted from its initial position (s0) by a stopping distance (s) smaller than the second minimum stopping distance, is spaced apart from the output piston (12) such that a transmission of force from the input piston (14) to the output piston (12) is prevented, and the driver braking force (Ff) can be transmitted to the output piston (12) via the input piston (14), which is adjusted from its initial position (s0) by a stopping distance (s) between the second minimum stopping distance and the first minimum stopping distance; and wherein the coupling device comprises a control device (50), by means of which the coupling device can be transferred from at least the first operating mode with the first minimum braking path into at least the second operating mode with the second minimum braking path smaller than the first minimum braking path; characterized in that the coupling device comprises an adjustable force transmission component (52) fastened either to the output piston (12) or to the input piston (14), and the control device (50) is additionally designed to actuate an actuator of the force transmission component (52) by means of a control signal (54) such that the force transmission component (52) is transferred from a retracted position of the first operating mode into at least one extended position of at least the second operating mode.Coupling device according to Claim 1, wherein the coupling device comprises an external force brake device (20, 22), by means of which an external force can additionally be transmitted to the output piston (12) in such a way that the internal pressure in the master brake cylinder (10) can be increased by means of the external force transmitted to the output piston (12).Coupling device according to Claim 1 or 2, wherein the coupling device can be transferred at least into the first state or into the second operating mode by means of the control device (50), taking into account at least one variable with respect to an actuating speed of the actuation of the brake input element (16), a temporal change of the actuating speed, the driver braking force (Ff), a temporal change of the driver braking force (Ff), a state of at least one vehicle component of the vehicle, a temporal change of the state, at least one driving mode of the vehicle and / or a temporal change of the driving mode.Coupling device according to one of the preceding claims, wherein the coupling device can be transferred by means of the control device (50) at least into the first state or into the second operating mode taking into account at least one variable with respect to a state and / or a temporal change of the state of a component of a regenerative braking system.Coupling device according to one of the preceding claims, wherein the coupling device can be transferred by means of the control device (50) at least into the first state or into the second operating mode taking into account a vehicle speed, a vehicle direction, a vehicle direction change and / or a yaw rate.Coupling device according to one of the preceding claims, wherein the control device (50) is designed to control the force transmission component (52) from the retracted position into the at least one extended position in such a way that, in the first operating mode, a force transmission from the input piston (14), which is adjusted from its initial position (s0) by a braking path (s) between the second minimum braking path and the first minimum braking path, to the output piston (12) is prevented via the force transmission component (52) controlled into the retracted position, and in the second operating mode, the driver braking force (Ff) can be transmitted from the input piston (14), which is adjusted from its initial position (s0) by a braking path (s) between the second minimum braking path and the first minimum braking path, to the output piston (12) via the force transmission component (52) controlled into the at least one extended position.The coupling device according to any of the preceding claims, wherein the force transmission component (52) has a plurality of locking steps.The coupling device of claim 7, wherein the force transmitting component (52) comprises a multi-stage pawl.Brake system having a coupling device according to one of the preceding claims.

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