DE102010038548A1 - Brake system i.e. recuperative brake system, for e.g. electrical car, has piston-cylinder-unit arranged at brake actuating element, where braking force is partially transmitted to piston such that inner pressure is increased in unit - Google Patents

Abstract

The system has a piston-cylinder-unit (34) i.e. tandem main brake cylinder, arranged at a brake actuating element (10) i.e. brake pedal, via a mechanical connection device (26). A driver braking force exerted on the brake actuating element is partially transmitted to a piston (36) such that inner pressure is increased in the piston-cylinder-unit. A wheel brake cylinder (46) is hydraulically connected with the piston-cylinder unit and another piston-cylinder unit (12) e.g. single-chamber-main brake cylinder, and the brake actuating element is adjusted around a minimum-adjusting path. An independent claim is also included for a method for operating a brake system.

Description

The invention relates to a braking system for a vehicle. Furthermore, the invention relates to a method for operating a brake system for a vehicle.

State of the art

In the DE 103 16 750 A1 is a hydraulic vehicle brake system with a arranged on a pedal travel simulator brake pedal and a hydraulic brake pressure generator from a master cylinder and an upstream hydraulic booster described. By means of a designed as an external pressure source high pressure source, such as a hydraulic high-pressure accumulator, a piston of the master cylinder can be adjusted by pressurizing the hydraulic booster, that an internal pressure of the master cylinder is increased. In normal operation, the pedal travel simulator is decoupled from the brake pressure generator. Only in case of failure or malfunction of the electrically controllable external pressure source of the pedal travel simulator is so hydraulically coupled to the brake pressure generator that the internal pressure in the master cylinder can be increased upon actuation of the brake pedal.

Disclosure of the invention

The invention provides a braking system for a vehicle having the features of claim 1 and a method for operating a braking system for a vehicle having the features of claim 12.

Advantages of the invention

The equipment of the brake system according to the invention with two piston-cylinder units is associated with the advantage that a brake pressure of at least one hydraulically connected to the two piston-cylinder units wheel brake cylinder is independently adjustable independently of an actuation of the brake actuator of the driver. For example, the two pistons of the two piston-cylinder units can be adjusted in a common adjustment direction with respect to their associated piston-cylinder units or opposite. As explained in greater detail below, this can be used to reinforce a brake pressure applied by the driver via a driver braking force or to blind an additional braking torque, for example a generator braking torque. At the same time, it is ensured in the braking system and the corresponding method described here that the driver braking force applied by the driver to the brake actuating element can be used, in particular, when setting a greater brake pressure. Thus eliminating the need for a trained as a high pressure source source of external pressure, and a cooperating motor-pump unit. The brake system according to the invention and the corresponding method are therefore inexpensive to implement.

After an adjustment of the brake actuation element by at least the second minimum adjustment path, the driver can actively brake into the second piston-cylinder unit. Likewise, after the brake actuating element has been adjusted by at least the first minimum displacement, the driver has the option of actively braking into the first piston-cylinder unit. Thus, the driver braking force applied by the driver to the brake actuator can be used to set high brake pressures. The brake system described here does not need to be equipped with an expensive actuator for applying a comparatively high braking force. In this way, the space requirement of the brake system can be reduced.

The first piston-cylinder unit may for example be a master cylinder. In particular, a 1-chamber master cylinder can be used as the first piston-cylinder unit. For the second piston-cylinder unit, a plunger, such as a master cylinder can be used. In particular, a tandem master cylinder is usable for the second piston-cylinder unit.

It is pointed out here that in the brake system described here and the corresponding method, even in the event of a failure of the electronics of the brake system or in the event of an interruption of the energy supply of the brake system, the driver has the opportunity to brake into both piston-cylinder units. Advantageously, the direct braking in the two piston-cylinder units is possible without a comparatively large displacement (pedal travel) of the brake actuator must be overcome.

Preferably, the brake system comprises at least one wheel brake cylinder which is hydraulically connected to the first piston-cylinder unit and the second piston-cylinder unit such that by means of the increased first internal pressure in the first piston-cylinder unit and / or by means of the increased second internal pressure in the second piston-cylinder unit, a brake pressure of the at least one wheel brake cylinder is steigerbar. Thus, the brake pressure of the at least one wheel brake cylinder via a relative to the associated piston-cylinder units rectified adjustment of the two pistons and / or via an opposite adjustment of the two pistons active be set. Likewise, the hydraulic connection between the two piston-cylinder units and the at least one wheel brake cylinder can be formed so that the at least one brake pressure is selectively adjustable by means of the second internal pressure and by means of this and the first internal pressure. The brake system described here thus ensures advantageous possibilities for actively setting a preferred brake pressure in the at least one wheel brake cylinder.

In an advantageous embodiment, the first piston-cylinder unit is additionally arranged on the brake actuating element via the mechanical connecting device such that a force transmission from the adjusted from its initial position by an adjustment at a predetermined first minimum displacement unequal to zero brake actuator on the first piston first piston-cylinder unit is prevented. For example, by means of the mechanical connecting device, a gap between a contact part of the first piston and a contact part of the mechanical connecting device may be formed, which is closed only at an adjustment of the brake actuating element by at least the first minimum displacement not equal to zero. Thus, in the brake system described here, a jump-in behavior of the characteristic of the brake operating member can be ensured.

In an advantageous embodiment, the second minimum displacement is greater than the first minimum displacement. In particular, the second minimum adjustment path can be greater than the first minimum adjustment path by a factor of at least 1.5, in particular 2, preferably 3. As can be explained in more detail below, an advantageous ABS (pumpless ABS) and / or recuperative braking with feedback compensation can thus be carried out.

In a further advantageous embodiment, the brake system comprises a brake booster, by means of which an adjusting force on the second piston of the second piston-cylinder unit is exercisable. The brake booster, for example, an electric drive to understand, by means of which the second piston of the piston-cylinder unit is adjustable in at least one adjustment. Thus, an active adjustment of the brake pressure of the at least one wheel brake cylinder by means of a simple operable and inexpensive arranged on the second piston-cylinder unit component can be realized.

Preferably, by means of the exercisable by the brake booster adjusting force of the second piston of the second piston-cylinder unit is adjustable so that a partial volume of a brake fluid of the brake system in the second piston-cylinder unit is sucked. In this case, the brake booster can also be used for reducing the brake pressure present in the at least one wheel brake cylinder. Thus, the brake booster can be used to ensure that a predetermined / predefinable maximum vehicle deceleration is not exceeded.

In an advantageous development, the brake system comprises an evaluation and control device which is designed, taking into account at least one information provided by an onboard sensor with respect to an actuation of the brake actuation element at least one desired size with respect to a second piston of the second piston-cylinder Set unit to be applied adjustment force of the brake booster, and to control the brake booster, taking into account the at least one specified target size. Thus, despite a decoupling of the first piston of the first piston-cylinder unit from the adjusted by an adjustment under the first minimum displacement non-zero brake actuator, a desired brake pressure, preferably in accordance with the operation of the brake actuator, by means of the second piston-cylinder unit the at least one wheel brake cylinder set / actively established.

Furthermore, the evaluation and control device may additionally be designed to be able to exert the at least one desired variable with respect to the adjusting force with additional consideration of at least one additional braking torque which can be exerted on at least one wheel of the vehicle in addition to the at least one hydraulic braking torque of the at least one wheel brake cylinder is to set. The braking system described here is thus designed at least for a partial compensation of the at least one additional braking torque. In particular, the at least one additional braking torque can be so masked that a preferred total braking torque is exerted on the at least one wheel of the vehicle.

Preferably, the at least one additional braking torque comprises at least one generator braking torque of a generator of the brake system. Such a brake system can be used advantageously as a recuperative brake system in a hybrid vehicle and in an electric vehicle.

In a particularly advantageous embodiment, by means of the evaluation and control device, the at least one desired variable with respect to the adjustment so fixed and the first brake booster so controlled that by means of the displaced second piston, a time increase of at least one additional braking torque corresponding brake medium volume in the second piston-cylinder unit is sucked. Correspondingly, by adjusting the second piston by means of the adjustment force provided by the brake booster, a braking medium volume corresponding to a time decrease of the at least one additional brake torque can be transferred again into the at least one wheel brake cylinder. Thus, a temporally rapidly varying additional braking torque by means of the brake system described here is veneer.

As an alternative or in addition to this, the first piston-cylinder unit may be connected to the at least one wheel brake cylinder via a valve which is designed such that a pressure difference not equal to zero between the brake pressure present in the at least one wheel brake cylinder and the first Internal pressure in the first piston-cylinder unit is adjustable. The valve can be designed in particular as a continuous valve. Thus, when changing the brake pressure present in the at least one wheel brake cylinder by means of the second piston-cylinder unit, the driver does not feel any changed brake feel (pedal feel). The actuation of the brake actuation element is thus connected to a good ease of operation for the driver, in particular when the at least one additional brake torque is blended. Preferably, the at least one valve is designed such that it is automatically switched on interruption of its power supply in a mode in which the driver can brake fully into the at least one wheel brake cylinder via the first piston-cylinder unit.

The brake system according to the invention has only an electric drive compared to a standard brake system with a vacuum brake booster with ABS / ESP unit. Due to this nature, active braking interventions, such as for automatic distance keeping (ACC) or increased braking on an inclined plane (Hill-Hold) are conveniently carried out. In contrast to a brake system with a reaction disc having brake booster, the feedback for the driver is instead determined by the area ratio of the first piston-cylinder unit (eg a master cylinder) and the second piston-cylinder unit (e.g. a plunger) realized. This process can also be referred to as a hydraulic reaction.

The advantages described in the above paragraphs also apply accordingly to a corresponding procedure.

Brief description of the drawings

Further features and advantages of the present invention will be explained below with reference to the figures. Show it:

1 a schematic representation of a first embodiment of the brake system; and

2 a schematic representation of a second embodiment of the brake system.

Embodiments of the invention

1 shows a schematic representation of a first embodiment of the brake system.

This in 1 schematically reproduced braking system for a vehicle has a brake actuator 10 on, which is designed for example as a brake pedal. The feasibility of the brake system described here, however, is not based on a trained as a brake pedal brake actuator 10 limited. Preferably, the brake actuator is located 10 in a non-operation by a driver of the vehicle in its initial position.

The brake system has a first piston-cylinder unit 12 which may be preferably designed as a master cylinder, in particular as a 1-chamber master cylinder. Such a design of the first piston-cylinder unit 12 and their equipment with the components described below is to be understood merely as an example. In one embodiment, a first piston 14 the first piston-cylinder unit 12 an adjustable component 16 Contact, which has an internal volume of the first piston-cylinder unit 12 in a piston chamber 19 with a jump-in spring 18 and an inner chamber 21 with a return spring 20 (hermetically) divided. An adjustment of the first piston 14 in the first piston-cylinder unit 12 along a first adjustment direction 22 causes in this case a rectified adjustment of the adjustable component 16 leading to a decrease in the volume of the inner chamber 21 upon compression of the return spring 20 leads. Accordingly, an adjustment of the first piston leads 14 in one of the first adjustment direction 22 opposite second adjustment 24 to a compression of the jump-in spring 18 , and thus to a decrease in the volume of the piston chamber 19 and an increase in the volume of the inner chamber 21 , This is a first internal pressure in the inner chamber 21 the first piston-cylinder unit 12 by means of an adjustment of the piston 14 variable.

The first piston-cylinder unit 12 is via a mechanical connection device 26 such with the brake actuator 10 connected / on the brake actuator 10 arranged that on the adjusted from its initial position by at least a predetermined first minimum displacement brake actuation element 10 applied driver braking force at least partially on the first piston 14 is transferable so that the first internal pressure is steigerbar. The first minimum adjustment can also go to zero. In this case, already causes a slight adjustment of the brake actuator 10 from the initial position, an adjustment of the first piston 14 ,

In an alternative embodiment, the first piston-cylinder unit 12 via the mechanical connection device 26 such with the brake actuator 10 be connected, that a power transmission between the adjusted from its initial position by an adjustment under a predetermined first minimum displacement unequal to zero brake actuator 10 and the first piston 14 is prevented. This can be realized, for example, by between a first contact part 28 the mechanical connection device 26 and one with the first piston 14 with adjustable trained second contact part 30 an air gap with a maximum width d1 (non-zero) in the presence of the brake actuator 10 is formed in its initial position. The maximum width d1 corresponds to the first minimum adjustment path. Thus, the braking system can be designed for a jump-in (non-zero idle travel). In order to ensure an advantageous jump-in, in particular an initial spring 32 between the first piston-cylinder unit 12 and the first contact part 28 the mechanical connection device 26 be arranged.

The brake system shown here also has a second piston-cylinder unit 34 with a second piston 36 on. The second piston-cylinder unit 34 For example, it can be a plunger. In particular, a master cylinder, as advantageously a tandem master cylinder, as a second piston-cylinder unit 34 usable. However, the design of the second piston-cylinder unit is not limited to the examples listed here.

The second piston-cylinder unit 34 is via the mechanical connection device 26 such with the brake actuator 10 connected / on the brake actuator 10 arranged that a power transmission from the adjusted from its initial position by an adjustment under a predetermined second minimum displacement not equal to zero brake actuator 10 on the second piston 36 prevented (prevented). At the same time, it is ensured that a brake actuating element adjusted from its initial position by at least the second minimum adjustment path 10 applied driver braking force at least partially on the second piston 36 is transferable. By means of the at least partially transmitted driver braking force of the second piston 36 in a first adjustment direction 38 at least partially in the second piston-cylinder unit 34 adjusted in. In this way, a second internal pressure of the second piston-cylinder unit 34 be increased. You can also rewrite that between the second piston 36 and the mechanical connection device 26 a Gap is present, which only in a markable as a backup adjustment of the brake actuator 10 is closed by at least the second minimum adjustment. Such a gap can be realized, for example, by placing it between a third contact part 40 the mechanical connection device 26 and one with the second piston 36 with adjustable fourth contact part 42 a gap with a maximum width d2 (non-zero) in the presence of the brake actuator 10 is formed in its initial position, which only after an adjustment of the brake actuator 10 at least the second minimum adjustment path is closed. The maximum width d2 corresponds to the second minimum adjustment path.

Preferably, the mechanical connection device 26 formed so that in the presence of the brake operating member 10 in its initial position, the contact parts 28 and 40 around the maximum widths d1 and d2 of the contact parts assigned to them 30 and 42 are spaced. About a suitable design of the mechanical connection device 26 it is possible to ensure that the contact parts 28 and 40 at an increasing force on the brake actuator 10 in the direction of their associated contact parts 30 and 42 to be moved. The mechanical connection device 26 may be formed, for example, as a linkage. Accordingly, the mechanical connection device 26 comprise an input piston and / or at least one output piston. As for the mechanical connection device 26 suitable linkage through the 1 are sufficiently disclosed, will not be discussed in more detail here. On a particularly advantageous embodiment of the second minimum displacement, or the gap, is discussed in more detail below.

The brake system preferably comprises a brake booster 44 , by means of which an adjusting force on the second piston 36 exercisable. Under the brake booster 44 For example, an electrical actuator can be understood. As will be apparent from the following explanations, the brake booster 44 not limited to a specific type of motorized actuator. On particularly advantageous Embodiments of the brake booster 44 will be discussed in more detail below.

Advantageously, the brake system comprises at least one wheel brake cylinder 46 , which with the first piston-cylinder unit 12 hydraulically connected such that by means of the increased first internal pressure in the first piston-cylinder unit 12 a brake pressure of the at least one wheel brake cylinder 46 can be increased. Furthermore, the at least one wheel brake cylinder 46 with the second piston-cylinder unit 34 be hydraulically connected such that by means of the increased second internal pressure in the second piston-cylinder unit 34 the brake pressure of the at least one wheel brake cylinder 46 can be increased. Preferably, the hydraulic connection can be designed such that the brake pressure of the at least one wheel brake cylinder 46 can be increased simultaneously by means of an increase of the first internal pressure and the second internal pressure.

In the illustrated embodiment, the brake system comprises two brake circuits with a total of four wheel brake cylinders 46 , which each have a wheel, each with a brake disc 48 assigned. Advantageously, each of the four wheel brake cylinders 46 designed to (with an increase in its brake pressure) a corresponding hydraulic braking torque on the adjacent brake disc 48 or on the assigned wheel, exercise. Two of the wheel brake cylinders 46 are assigned to a common brake circuit. The two wheel brake cylinders 46 A brake circuit may be arranged on the wheels of a common axle, on the wheels arranged on one side of the vehicle or on the wheels diagonally mounted on the vehicle. In particular, the two brake circuits of the brake system can be designed the same. It should be noted, however, that the brake system described herein is not limited to a particular number of wheel brake cylinders 46 or to a specific hydraulic connection of the wheel brake cylinder 46 with the piston-cylinder units 12 and 34 is limited. The following statements on the illustrated embodiment are to be understood as examples only:
Each of the two brake circuits is via a supply line 50 with the second piston-cylinder unit 34 connected. Each supply line 50 connects the second piston-cylinder unit 34 with a wheel inlet valve 52 , which via a line 54 with a wheel brake cylinder 46 connected is. About one in each supply line 50 trained branch point 56 and a branching line 58 is another wheel inlet valve 60 with the second piston-cylinder unit 34 connected, which via a line 62 additionally with a wheel brake cylinder 46 connected is. In each of the lines 54 and 62 is a branch point 64 or 66 formed, which via a line 68 or 70 with a wheel outlet valve 72 or 74 connected is. The two Radauslassventile associated with a brake circuit 72 and 74 lead over the lines 76 and 78 into a common branch point 80 , The branch point 80 is over a line 82 with a non-return valve inserted therein 84 via another in the supply line 50 trained branch point 86 connected. The check valve 84 is oriented so that a brake fluid displacement of the second piston-cylinder unit 34 over the branch point 86 to the branch point 80 is prevented.

In an advantageous embodiment, between the branch point 80 and the check valve 84 a branch point 88 be formed, of which a line 90 branches. The two lines 90 the two brake circuits can be in a common branch point 92 from which a reservoir line 94 to a brake fluid reservoir 96 leads. The brake fluid reservoir 96 can hydraulically with the second piston-cylinder unit via at least one brake fluid exchange bore, for example via a sniffer bore 34 be connected.

Also the first piston-cylinder unit 12 is hydraulic with at least one wheel brake cylinder 46 connected. In particular, the first piston-cylinder unit 12 only with the two wheel brake cylinders 46 be hydraulically connected to a brake circuit. On the advantages of such a hydraulic connection between the wheel brake cylinders 46 and the piston-cylinder units 12 and 34 for actively setting a preferred overall brake torque is discussed in more detail below.

Preferably, the first piston-cylinder unit 12 with at least one wheel brake cylinder 46 via a valve 98 , such as a continuous valve and / or a differential pressure valve connected. This can be realized, for example, by a line 100 from (the inner chamber 21 ) of the first piston-cylinder unit 12 to the valve 98 which leads over another line 102 with one in the line 58 trained branch point 104 connected is.

The valve 98 is preferably designed such that by means of the valve 98 a pressure difference not equal to zero between in the at least one wheel brake cylinder 46 present brake pressure and the first internal pressure in (the inner chamber 21 ) of the first piston-cylinder unit 12 is adjustable. As explained in more detail below, by means of such a valve 98 an advantageous brake feel (pedal feel) for the driver upon actuation of the brake actuator 10 realizable.

In the following, a particularly advantageous embodiment of the brake system will be discussed in more detail:
Preferably, the second minimum displacement is greater than the first minimum displacement. In this case, it is ensured that upon the occurrence of a force transmission contact between the brake actuator 10 and the first piston 14 via the mechanical connection device 26 a power transmission from the brake actuator 10 on the second piston 36 is prevented. This can be achieved, for example, by a first maximum width d1 smaller than the second maximum width d2. The decoupling of the second piston-cylinder unit realized in this way 34 from the brake actuator 10 while ensuring the power transmission from the brake actuator 10 on the second piston 36 may be to reduce the brake pressure of the at least one wheel brake cylinder at a braking of the driver in the first piston-cylinder unit 12 be used.

The second minimum adjustment can be by a factor of 1.5, preferably by a factor of 2, in particular by a factor of 3 greater than the first minimum adjustment. Accordingly, the second maximum width d2 may be greater than the first maximum width d1 by a factor of 1.5, preferably by a factor of 2, in particular by a factor of 3. In a particularly advantageous embodiment, the second maximum width d2 can correspond to an additional (non-hydraulic) additional braking torque that can be additionally exerted on the at least one wheel, such as a maximum generator braking torque.

Preferably, the second piston-cylinder unit 34 so formed and so on the mechanical connection device 26 arranged that the second piston 36 in the absence of a force transfer contact between the mechanical connection means 26 and the second piston 36 for at least partially transmitting the driver braking force, z. B. at a distance not equal to zero between the contact parts 40 and 42 , is present in a starting position, in which the piston-cylinder unit 34 Stock volume has. You can also rewrite this so that the second piston 36 from its initial position in a second adjustment 39 at least partially from the second piston-cylinder unit 34 is also adjustable.

The brake booster 44 can be designed in particular to the second piston 36 from the initial position in the (the first adjustment 38 opposite) second adjustment 39 to adjust. Thus, the second piston 36 by means of the brake booster 44 so adjustable that a partial volume. the brake medium of the brake system in the second piston-cylinder unit 34 is sucked. By means of such a reduction of the brake pressure of the at least one wheel brake cylinder 46 For example, it is preventable that a maximum deceleration of the vehicle is exceeded.

The brake system can in particular be an evaluation and control device 106 which is designed to take into account at least one of an onboard sensor 108 provided information regarding an actuation of the brake actuator 10 at least one desired size with respect to one on the second piston 36 applied adjusting force of the brake booster 44 set. The sensor 108 for providing a sensor signal 110 The information may be, for example, a pedal travel sensor and / or a force sensor. However, the brake system is not limited to the examples of the sensor described here 108 limited. Also a signal from a pressure sensor 109 can be taken into account when determining the at least one target size.

The of the evaluation and control device 106 fixed at least one desired value, for example, a desired adjustment, a target speed of a motor of the brake booster 44 and / or a desired operating mode of the brake booster 44 include. The of the evaluation and control device 106 definable at least one target size is not limited to the examples listed here. The evaluation and control device 106 can then be a control signal 112 for driving an electronics 114 of the brake booster 44 spend according to the specified target size.

Preferably, the evaluation and control device 106 additionally designed, the at least one desired size with respect to the adjusting force with additional consideration of at least one additional braking torque, which in addition to the at least one hydraulic braking torque of the at least wheel brake cylinder 46 on the at least one wheel is exercisable, set. The at least one additional braking torque may include at least one generator braking torque. In particular, by means of the evaluation and control device, the at least one desired variable with respect to the adjusting force so fixed and the brake booster 44 be controlled so that despite a time varying additional braking torque a preferred total braking torque from at least the at least one hydraulic braking torque of the at least wheel brake cylinder 46 and the additional braking torque is maintainable. For example, by means of the in the second adjustment 39 adjusted second piston 36 one Brake medium volume in the second piston-cylinder unit 34 be sucked, which corresponds to a time increase of at least one additional braking torque. Likewise, by means of the in the first adjustment 38 adjusted second piston 36 a braking medium volume corresponding to a time decrease of the at least one additional braking torque in the at least one wheel brake cylinder 46 be transferred.

Several operating modes can be executed by means of the advantageous braking system described in the upper paragraphs:
In an executable first operating mode (partial braking mode), the driver operates the brake operating member 10 light, so that it is adjusted by an adjustment below the first minimum adjustment. The driver thus still feels no reaction from the brake actuator 10 still decoupled present first piston-cylinder unit 12 , By means of the brake booster 44 can the second piston 36 so in the first adjustment 38 be adjusted, that due to the increase of the second internal pressure in the second piston-cylinder unit 34 a brake pressure in the at least one wheel brake cylinder 46 is constructed, which by means of the sensor 108 detectable driver brake request corresponds.

Preferably, while the valve 98 be controlled so that the generated pressure build-up to a reduction of the distance between the contact parts 28 and 30 leads. After this jump-in, the driver feels a force feedback from the brake system according to the area ratios of the piston-cylinder units 12 and 34 and the opening state of the valve 98 ,

In particular, the two pistons 14 and 36 travel in the first mode (partial braking mode) analog adjustment paths.

As an alternative to a driver-controlled deceleration, in an executable second mode (active pressure build-up mode), too, the active pressure build-up for ASR, ESP, ACC is from the brake booster 44 and the second piston-cylinder unit executable. The brake actuation element can meanwhile be in its starting position. The valve 98 can be (automatically) closed during some interventions, so that the volume of brake fluid required to close the jump-in is saved (increase in dynamics).

In a third mode (recuperation mode), a generator braking torque of a generator (not shown) is exerted on at least one of the wheels. A time increase or decrease of the generator braking torque can in the manner described above by means of an adjustment of the second piston 36 through the brake booster 44 be compensated. In addition, the valve can 98 be controlled during the veneering so that the thus adjustable first internal pressure corresponds to a standard brake feel (pedal feel). The veneering process thus runs without any effect on the driver.

For correcting / filtering out the reaction, it is also possible to use the inlet valves 52 and 60 during recuperation (automatically) short-circuiting the first internal pressure in the first piston-cylinder unit 12 by means of the valve 98 and the second piston-cylinder unit 34 to set to a preferred (standard) value.

Furthermore, the brake pressure in the at least one wheel brake cylinder 46 also about the exhaust valves 72 and 74 be reduced. For example, this can be a brake medium volume via the exhaust valves 72 and 74 in the brake fluid reservoir 96 be drained.

In an executable fourth mode (ABS braking mode), the conventional ABS functions such as maintaining pressure, depressurizing and pressure build-up across the intake and exhaust valves 52 . 60 . 72 and 74 executed. Thus, the braking system described here is compatible with these ABS functions.

At a pressure reduction, the brake fluid volume over the exhaust valves 72 and 74 directly into the brake fluid reservoir 96 transferred. Thereafter, the brake pressure in the at least one wheel brake cylinder 46 over the intake valves 52 and 60 be rebuilt.

At the same time, by means of the valve 98 the volume balance of the first piston-cylinder unit 12 so regulated / controlled that one between the second piston 36 and the mechanical connection device 26 present gap, z. B. the distance between the contact parts 40 and 42 , is enlarged. If a certain threshold is reached, the intake valves 52 and 60 (automatically) closed for a short time. The second piston-cylinder unit 34 then promotes a braking medium volume of the brake medium reservoir by reducing the gap 96 over the check valves 84 back to the brake circuits. After this return promotion, the gap can be increased again.

In a fifth mode (back-up mode, failure mode), which in particular in case of failure of the electronics of the brake system and / or in an interruption of the power supply of the Brake system is executable, the gap between the mechanical connection device 26 and the second piston 36 closed. The driver experiences an extension of the pedal travel corresponding to a product of gap measurement and pedal ratio, which, however, is usually negligible. Thus, even if one of the above-mentioned fault situations occurs, the driver can still bring the vehicle safely to a standstill. The addition to the brake actuator 10 applied driver braking force does not exceed the force which is applied in such a situation for braking a vehicle with a vacuum brake booster system. This in 1 Brake system shown thus ensures an advantageous safety standard.

The present invention also ensures elimination of isolation valves between the two piston-cylinder units 12 and 34 through the mechanical coupling in the event of a power failure.

2 shows a schematic representation of a second embodiment of the brake system.

The schematically reproduced brake system comprises the components already described 10 to 88 and 96 to 108 , A renewed description of these components can therefore be dispensed with. In contrast to the embodiment described above, in the brake system shown here are each a storage chamber 120 to the branch points 88 connected.

By means of the brake system reproduced here, all the functions described above can be performed. However, in the executable third mode (recuperation mode), when the brake pressure in the at least one wheel brake cylinder is reduced 46 the brake fluid volume via the Radauslassventile 72 and 74 in the storage chambers 120 transferred. In the executable fourth mode (ABS braking mode), the pressure reduction also takes place via a discharge of the brake fluid or the brake gas into the associated storage chamber 120 ,

As in the embodiment described above, the volume balance in the first piston-cylinder unit 12 through the valve 98 so controlled that the gap between the second piston 36 and the mechanical connection device 26 increases. For return promotion, as in the embodiment described above, the intake valves 52 and 60 closed. In this way it is ensured that the gap is reduced and the brake fluid (brake fluid or brake gas) via the check valves 72 and 74 from the storage chambers 120 is conveyed back into the brake circuits.

As described in the paragraphs above, the braking systems described are designed to carry out the methods according to the invention. A description of these methods is therefore omitted here.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10316750 A1 [0002]

Claims (14)

Brake system for a vehicle with a brake actuator ( 10 ); a first piston-cylinder unit ( 12 ), which via a mechanical connection device ( 26 ) on the brake actuation element ( 10 ) is arranged such that a to the from its initial position by at least a predetermined first minimum displacement adjusted brake actuating element ( 10 ) applied driver braking force at least partially on a first piston ( 14 ) of the first piston-cylinder unit ( 12 ) is transferable so that a first internal pressure in the first piston-cylinder unit ( 12 ) can be increased; and a second piston-cylinder unit ( 34 ); characterized in that the second piston-cylinder unit ( 34 ) via the mechanical connection device ( 26 ) on the brake actuation element ( 10 ) is arranged such that a power transmission from the adjusted from its initial position by an adjustment under a predetermined second minimum displacement non-zero brake actuator ( 10 ) to a second piston ( 36 ) of the second piston-cylinder unit ( 34 ) is prevented and the at least partially applied to the second brake from its initial position by at least the second minimum displacement adjustment brake actuator applied to the second piston ( 36 ) of the second piston-cylinder unit ( 34 ) is transferable so that a second internal pressure in the second piston-cylinder unit ( 34 ) is risigerbar. Brake system according to claim 1, wherein the brake system at least one wheel brake cylinder ( 46 ) associated with the first piston-cylinder unit ( 12 ) and the second piston-cylinder unit ( 34 ) is hydraulically connected such that by means of the increased first internal pressure in the first piston-cylinder unit ( 12 ) and / or by means of the increased second internal pressure in the second piston-cylinder unit ( 34 ) a brake pressure of the at least one wheel brake cylinder ( 46 ) is risigerbar. Brake system according to claim 1 or 2, wherein the first piston-cylinder unit ( 12 ) via the mechanical connection device ( 26 ) additionally on the brake actuating element ( 10 ) is arranged such that a force transmission from the adjusted from its initial position by an adjustment under a predetermined first minimum displacement non-zero brake actuator ( 10 ) on the first piston ( 14 ) of the first piston-cylinder unit ( 12 ) is prevented. Brake system according to claim 3, wherein the second minimum displacement is greater than the first minimum displacement. Brake system according to one of the preceding claims, wherein the brake system comprises a brake booster ( 44 ) by means of which an adjusting force on the second piston ( 36 ) of the second piston-cylinder unit ( 34 ) is exercisable. Brake system according to claim 5, wherein by means of the brake booster ( 44 ) exercisable adjusting force of the second piston ( 36 ) of the second piston-cylinder unit ( 34 ) is adjustable so that a partial volume of a brake medium of the brake system in the second piston-cylinder unit ( 34 ) is sucked. Brake system according to claim 5 or 6, wherein the brake system comprises an evaluation and control device ( 106 ), which is designed taking into account at least one of an on-board sensor ( 108 ) ( 110 ) with respect to an actuation of the brake actuation element ( 10 ) at least one desired variable with respect to the adjusting force of the brake booster ( 44 ), and the brake booster ( 44 ), taking into account the at least one specified target value. Braking system according to claim 7, wherein the evaluation and control device ( 106 ) is additionally designed, the at least one desired size with respect to the adjusting force with additional consideration of at least one additional braking torque, which in addition to the at least one hydraulic braking torque of the at least one wheel brake cylinder ( 46 ) is exercisable on at least one wheel of the vehicle. Braking system according to claim 8, wherein the at least one additional braking torque comprises at least one generator braking torque of a generator of the brake system. Braking system according to one of claims 2 to 9, wherein the first piston-cylinder unit ( 12 ) with the at least one wheel brake cylinder ( 46 ) via a valve ( 98 ), which is designed such that by means of the valve ( 98 ) a pressure difference not equal to zero between in the at least one wheel brake cylinder ( 46 ) and the first internal pressure in the first piston-cylinder unit ( 12 ) is adjustable. Brake system according to claim 10, wherein the valve ( 98 ) is a continuous valve. Method for operating a braking system for a vehicle having a brake actuating element ( 10 ), a first piston-cylinder unit ( 12 ) with a first piston ( 14 ), on which one of them has been moved from its initial position by at least one predetermined first minimum value. Adjustment adjusted brake actuator ( 10 ) is at least partially transmitted so that a first internal pressure in the first piston-cylinder unit ( 12 ), a second piston-cylinder unit ( 34 ) with a second piston ( 36 ), on which the driver braking force exerted on the brake actuating element that is displaced from its starting position by at least a second minimum displacement path not equal to zero is at least partially transmitted such that a second internal pressure in the second piston-cylinder unit ( 34 ), wherein a power transmission from the adjusted from its initial position by an adjustment under the predetermined second minimum displacement brake actuation element ( 10 ) on the second piston ( 36 ) is prevented, and at least one wheel brake cylinder ( 46 ), whose brake pressure by means of the increased first internal pressure in the first piston-cylinder unit ( 12 ) and by means of the increased second internal pressure in the second piston-cylinder unit ( 34 ), with the step: increasing the brake pressure of the at least one wheel brake cylinder ( 46 ) by adjusting the second piston ( 36 ) of the second piston-cylinder unit ( 34 ) by means of a brake booster ( 44 ). Method according to Claim 12, with the additional steps of determining information relating to at least one additional braking torque, which in addition to the at least one hydraulic braking torque of the at least one wheel brake cylinder ( 46 ) is exerted on at least one wheel of the vehicle; Determining at least one target size with respect to one on the second piston ( 36 ) of the second piston-cylinder unit ( 36 ) to be applied adjusting force taking into account the information obtained; and driving the brake booster ( 44 ) taking into account the at least one specified target size. The method of claim 13, wherein the at least one target size is set and the first brake booster ( 44 ) is controlled, taking into account the at least one specified target variable, such that by adjusting the second piston ( 36 ) a time increase of the at least one additional brake torque corresponding brake medium volume in the second piston-cylinder unit ( 34 ) is sucked.

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