DE102013220975A1 - Control device and brake system for a vehicle and method for operating a brake system of a vehicle - Google Patents

Abstract

The invention relates to a control device (10) for a brake system of a vehicle, by means of which at least one Radauslassventil control signal (22) to at least one Radauslassventil (18) can be output, whereby the at least one Radauslassventil (18) is controllable in an at least partially open state, and by means of which at least one valve control signal (26) can be output to at least one valve (28) in at least one line (30) to a brake fluid reservoir (32), whereby the at least one valve (28) is controllable in an at least partially open state, and a brake fluid forced out of the master brake cylinder (24) during actuation of the brake actuation element (16) is displaceable at least partially via the at least one wheel outlet valve (18) and the at least one valve (28) into the brake fluid reservoir (32) and a brake pressure buildup in at least one wheel brake cylinder (36a, 36b) can be prevented or reduced. Likewise, the invention relates to a braking system for a vehicle for interacting with the control device (10). Furthermore, the invention relates to a method for operating a brake system of a vehicle.

Description

The invention relates to a control device for a brake system of a vehicle and a brake system for a vehicle for interacting with the control device. Furthermore, the invention relates to a method for operating a brake system of a vehicle.

State of the art

In the DE 196 04 134 A1 a method and a device for controlling a brake system of a motor vehicle with an electric drive are described. During an application of the method or the device, a deceleration of the motor vehicle should preferably take place by means of a regenerative operation of the electric drive. A pressure build-up in at least one wheel brake cylinder of the brake system equipped with a hydraulic friction brake should be preventable during the regenerative operation of the electric drive by moving by opening a Radauslassventilen a pressed out by a pedal actuation of a master cylinder pressure medium in at least one brake circuit internal storage chamber.

Disclosure of the invention

The invention provides a control system for a braking system of a vehicle having the features of patent claim 1, a braking system for a vehicle for interacting with such a control device with the features of patent claim 4 and a method for operating a braking system of a vehicle with the features of patent claim 8.

Advantages of the invention

By means of the present invention, a brake pressure buildup in at least one wheel brake cylinder of a memory chamberless brake circuit can be prevented or reduced. Thus eliminating the need for equipment of the respective brake circuit with a storage chamber, such as a low-pressure storage chamber to ensure a temporary caching of brake fluid in this. Instead, by means of the present invention, the brake fluid reservoir, which is usually already connected to the master brake cylinder of the brake system, for example via at least one sniffer bore, can be used for temporarily storing brake fluid. The increased by means of the present invention multifunctionality of the brake fluid reservoir eliminates the cost and space requirements of at least one conventionally required storage chamber. The present invention thus contributes to reducing the cost and space requirements of a brake system.

It should be noted that the method according to the invention can be controlled by means of simple and inexpensive electronics. Accordingly, the electronic device can be formed inexpensively and with a comparatively small volume.

The invention can be advantageously used in particular for all hybrid and electric vehicles.

In a preferred embodiment of the control device, at least one generator control signal can additionally be output to the at least one generator by means of the electronic device, taking into account at least the desired brake torque signal and provided information relating to a maximum generator-can-generator braking torque that can be carried out by means of at least one generator. The control device can thus also be used for a recuperative braking system. Due to the multifunctional applicability of the control device, a control designed especially for the at least one generator can be saved. If the predetermined setpoint braking torque is smaller than the maximum executable optional generator braking torque, the electronic device is preferably designed such that a generator braking torque equal to the predetermined setpoint braking torque can be exerted by means of the at least one generator controlled by the at least one generator control signal. At the same time, the pressure buildup in the at least one wheel brake cylinder of the respective brake circuit can be prevented at least partially via the at least one wheel outlet valve of the respective brake circuit and via the at least one valve into the brake fluid reservoir by means of the displacement of the brake actuation element pressed out of the master brake cylinder during actuation of the brake actuation element. It should be noted that in the case of the blending of the generator braking torque described here (almost) no residual pressure remains in the at least one wheel brake cylinder. Thus, it must also not be accepted that the at least one wheel brake cylinder carries out an undesired friction braking due to the residual pressure present therein. Instead, the predetermined desired generator braking torque can be used completely for inserting the at least one generator, and thus for charging at least one vehicle battery. The embodiment of the control device described here thus contributes to the additional reduction of the energy requirement of a vehicle. If the embodiment of the control device described here is used on a hybrid vehicle, therefore a fuel consumption and a pollutant emission of the hybrid vehicle can be reduced.

In an advantageous refinement, by means of the electronic device, at least one pump control signal can additionally be output to at least one pump connected to the at least one printed conductor, taking at least the nominal braking torque signal and the information provided with reference to the maximum executable optional generator braking torque. For example, if a time-decreasing maximum executable optional generator braking torque is less than the predetermined desired braking torque, by means of at least one pump controlled by the at least one pump control signal brake fluid from the brake fluid reservoir via the at least one open-controlled valve in the at least one wheel brake cylinder be pumped the respective brake circuit. The control device can thus react comparatively quickly to an omitted applicability of the at least one generator for braking the vehicle.

Advantageously, for cooperation with such a control device, a brake system for a vehicle with a master cylinder, to which a brake actuator is attachable or connected, a brake fluid reservoir, and at least one brake circuit with at least one wheel brake cylinder, at least one of the wheel brake cylinder hydraulically connected Radauslassventil, and a line , via which the at least one wheel outlet valve is connected to the brake fluid reservoir of the brake system, with a valve arranged therein. Such a brake system is inexpensive and requires comparatively little space. It is again pointed out that the equipment of the at least one brake circuit of the brake system with a storage chamber, such as a low-pressure storage chamber, is optional.

In a low cost embodiment, the brake system includes a vacuum brake booster. By guaranteed by means of the present invention possibility for temporary storage of brake fluid in the brake fluid reservoir, a brake pressure build-up in the at least one wheel brake cylinder of the brake system can be prevented restdruckfrei without the use of an electronic electromechanical brake booster. This eliminates the conventional need to equip the brake system with an electromechanical brake booster to ensure a residual pressure-free veneering. The brake system can thus be equipped with a less expensive vacuum brake booster.

In a further advantageous embodiment, the brake system has an X-brake circuit distribution. This is possible because the present invention extends the possibility of veneering also to brake systems with X-brake circuit split.

The above-mentioned advantages of the various embodiments of the control device are also ensured in a brake system with such a control device.

The advantages can also be realized by carrying out a corresponding method for operating a brake system of a vehicle. The method can be further developed in accordance with the devices described above.

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 schematic representations of embodiments of the control device and the cooperating brake system;

2 a schematic representation of another embodiment of the cooperating with the control device brake system;

3 a schematic representation of another embodiment of the cooperating with the control device brake system;

4a to 4c Coordinate systems for explaining a first embodiment of the method for operating a brake system of a vehicle;

5a to 5c Coordinate systems for explaining a second embodiment of the method for operating a brake system of a vehicle; and

6a to 6c Coordinate systems for explaining a third embodiment of the method for operating a brake system of a vehicle.

Embodiments of the invention

1 shows schematic representations of embodiments of the control device and the cooperating brake system.

In the 1 schematically illustrated control device 10 has an electronic device 12 on. The electronic device 12 is at least designed to take into account at least one provided desired brake torque signal 14 with respect to one by means of an actuation of a brake actuation element 16 the braking system predetermined braking torque at least one Radauslassventil 18 at least one brake circuit 20 to control the braking system. This is done by means of the electronic device 12 at least one wheel outlet valve control signal 22 to the respective Radauslassventil 18 dispensable. The at least one means of the at least one Radauslassventil control signal 22 controlled wheel outlet valve 18 of the respective brake circuit 20 is controllable in an at least partially open state. In this way it can be ensured that one during actuation of the brake actuator 16 from one to the brake actuator 16 Tailored master cylinder 24 The brake system pushed out brake fluid at least partially via the at least one Radauslassventil 18 of the respective brake circuit 20 is displaceable.

The electronic device 12 is additionally designed (taking into account at least the desired braking torque signal 14 ), at least one valve control signal 26 to at least one valve 28 in at least one track 30 output, wherein the at least one Radauslassventil 18 over the at least one conductor track 30 with a brake fluid reservoir 32 the braking system is connected. Under the brake fluid reservoir 32 is preferably to be understood as a liquid container in which (almost) the atmospheric pressure is present. The brake fluid reservoir 32 can eg via at least one sniffer hole 34 with the master cylinder 24 be connected. The at least one by means of the at least one valve control signal 26 controlled valve 28 is controllable in an at least partially opened state. In particular, by (almost) simultaneously outputting the control signals 22 and 26 the valves 18 and 28 be simultaneously / jointly convertible into an open state. This ensures that during actuation of the brake actuator 16 from the master cylinder 24 pushed out brake fluid at least partially via the at least one Radauslassventil 18 of the respective brake circuit 20 and the at least one valve 28 into the brake fluid reservoir 30 is displaced so that a brake pressure build-up in at least one wheel brake cylinder 36a and 36b of the respective brake circuit 20 during operation of the brake operating member 16 can be prevented or reduced.

In the case of the control device 10 cooperating brake system can therefore be dispensed with the use of a storage chamber, in particular a low-pressure storage chamber. Because of in the brake fluid reservoir 32 (usually) constant atmospheric pressure is the displacement of brake fluid in the brake fluid reservoir 32 without overcoming a back pressure possible. In contrast, for a displacement of brake fluid in a storage chamber, even in a low-pressure storage chamber, a presence of a due to a spring constant of at least one return spring of the storage chamber / low-pressure storage chamber justified residual pressure must be taken into account. Since the choice of the at least one return spring of the storage chamber / low-pressure storage chamber, the high viscosity of the brake fluid at low temperatures is taken into account, the residual pressure is not / hardly reduced below a certain threshold. At a buffering of the master cylinder 24 pushed out brake fluid in the storage chamber / low pressure storage chamber, which via the at least one Radauslassventil 18 with the at least one associated wheel brake cylinder 36a and 36b is connected, thus still a residual pressure in the respective wheel brake cylinder would be present, which is not / hardly minimized.

In contrast, by temporarily storing the brake fluid in the brake fluid reservoir 32 despite an actuation of the brake actuator 16 a brake pressure of nearly zero / the atmospheric pressure in the wheel brake cylinders 36a and 36b be ensured. By means of simultaneous / joint opening of valves 18 and 28 is the presence of the undesirable residual pressure in the at least one wheel brake cylinder 36a and 36b thus preventable. By means of the control device 10 feasible caching of the brake fluid in the brake fluid reservoir 32 What a rest pressure-free state of the at least one wheel brake cylinder 36a and 36b ensures, for example, a wear of the brake pads of the at least one wheel brake cylinder 36a and 36b be reduced. Further advantages will be outlined below.

The valve 28 can be a cost-effective isolation valve. Alternatively, as a valve 28 also a steadily adjustable / controllable valve can be used.

The desired braking torque signal 14 is by means of a brake actuator element sensor 38 , such as a brake actuation travel sensor, a rod travel sensor, a differential travel sensor, a driver brake force sensor, and / or a driver brake pressure sensor. A detection of the driver's braking request is also possible via a different type of sensor. That by means of the actuation of the brake actuator 16 predetermined desired braking torque, for example, as determined adjustment of the brake actuator 16 , as Stangenweg, as difference way, as Driver brake pressure and / or as driver braking force to the electronics device 12 be issued. In the embodiment of the 1 is the brake actuator 16 a brake pedal 16 , It is noted, however, that this is with the control device 10 interacting brake system does not affect a specific brake actuator 16 or to a particular type of brake actuator element sensor 38 is limited.

In the embodiment described here, this is with the control device 10 interacting brake system two identical brake circuits 20 on, each with two wheel brake cylinders 36a and 36b are equipped. Both brake circuits 20 are each via a supply line 40 to the master cylinder 24 and one suction line each 42 (as part of each line 30 ) to the brake fluid reservoir 32 tethered. The usability of the control device 10 is not limited to a certain number of brake circuits 20 limited the cooperating brake system. By way of example, the brake system of 1 an X-brake circuit split. A first wheel brake cylinder 36a each brake circuit 20 is thus associated with a first vehicle axle, while a second wheel brake cylinder 36b each brake circuit 20 is assigned to another vehicle axle. The electronic device 12 therefore controls only one Radauslassventil 18 per brake circuit 20 with the at least one wheel outlet valve control signal 22 at. It is noted, however, that the control device 10 Also suitable for a brake system with a parallel brake circuit distribution. Likewise, also several Radauslassventile 18 per brake circuit 20 with the at least one wheel outlet valve control signal 22 be controllable.

In the embodiment of the 1 is by means of the electronic device 12 additionally at least one (not sketched) generator controllable. The at least one generator can be understood to be a generator that can be used as a generator, such as an electric drive motor. The electronic device 12 is designed to take into account at least the desired braking torque signal 14 and information provided 44 with respect to a maximum executable by means of the at least one generator Kann generator braking torque at least one generator control signal 46 to output to the at least one generator. The information provided 44 For example, the maximum executable can-generator braking torque, a state of charge of a rechargeable by means of the at least one generator vehicle battery and / or a vehicle speed include. The information 44 can eg from a sensor and / or a central vehicle control to the control device 10 be provided.

Preferably, the electronic device 12 designed for, provided that the predetermined target braking torque is smaller than the maximum executable can-generator braking torque, the at least one generator by means of the at least one generator control signal 46 to be controlled so that by means of the at least one controlled generator, a generator braking torque equal to the predetermined desired braking torque is exercisable. This is possible because by means of the displacement during actuation of the brake actuator 16 from the master cylinder 24 pushed out brake fluid at least partially (via the at least one Radauslassventil 18 of the respective brake circuit 20 and about the at least one valve 28 ) in the brake fluid reservoir 32 the pressure build-up in the at least one wheel brake cylinder 36a and 36b of the respective brake circuit 20 is completely preventable.

The drive device 12 Thus, when driving the at least one generator, the residual pressure-free presence of the at least one wheel brake cylinder 36a and 36b use. Due to the residual pressure-free presence of the at least one wheel brake cylinder 36a and 36b For example, the at least one generator for purely generative braking can be actuated without the predetermined setpoint braking torque being exceeded. Compared to the conventional blending a generator braking torque by means of a storage chamber / low pressure storage chamber is therefore by means of the control device 10 an increased regenerative efficiency feasible. Thus, a greater proportion of the kinetic energy of the vehicle can be used to charge the vehicle battery.

In addition, the electronic device 12 in the embodiment of the 1 additionally designed, taking into account at least the desired braking torque signal 14 and the information provided 44 (with respect to the maximum executable on-generator braking torque) at least one pump control signal 48 at least one of the at least one conductor track 30 connected pump 50a , or at least one motor 50b the respective pump 50a to spend. The at least one pump 50a For example, a return pump 50a be. Thus, it is possible to add extra volume from the brake fluid reservoir 32 in both brake circuits 20 (targeted and individual brake circuit) to bring. Exemplary is the brake system of 1 designed as a two-piston ESP system. However, differently designed modulation systems, such as multi-piston pumps, asymmetric pumps and / or gear pumps, are also applicable to the brake system. If a time-decreasing maximum executable optional generator braking torque becomes smaller than the predetermined setpoint braking torque is preferably by means of the at least one with the at least one pump control signal 48 controlled pump 50a Brake fluid from the brake fluid reservoir 32 via the at least one open-controlled valve 28 in the at least one wheel brake cylinder 36a and or 36b of the respective brake circuit 20 pumpable. Thus, even with a purely regenerative braking can be responded quickly to an attributable applicability of the at least one generator.

In the embodiment of the 1 includes each conductor track 30 a branching line section 52 , at the junction of which the two Radauslassventile 18 and at its opposite end a suction side of the pump 50a of the respective brake circuit 20 are connected. In the line section 52 opens a line section 54 on which the valve 28 of the respective brake circuit 20 is connected, which in addition via the associated suction line 42 with the brake fluid reservoir 32 connected is. It is noted, however, that the in 1 illustrated embodiment of the conduit 30 merely to be interpreted as an example.

With the control device 10 Any braking system that uses the components can be used 18 . 24 . 28 . 30 . 32 . 36a and 36b in at least simple design. It should be noted that when choosing the components 18 . 24 . 28 . 30 . 32 . 36a and 36b a great design freedom is given. The following descriptions for the formation of brake circuits 20 of the brake system are also to be understood as examples only:
Each of the brake circuits 20 the braking system of 1 includes a switching valve 56 , which via the associated supply line 40 to the master cylinder 24 is connected. From the switching valve 56 each brake circuit 20 ever leads a branching line section 58 to two wheel inlet valves 60 , Each wheel inlet valve 60 is over a line section 61 with the associated wheel brake cylinder 36a or 36b hydraulically connected. In each line section 61 each opens a line section 62 with the associated associated Radauslassventil 18 , In addition, a line section leads 64 from a delivery side of each pump 50a to the pipe section 58 , Optionally, a smoothing filter 66 in the line section 64 be used. In addition, at least one pressure sensor, such as a pre-pressure sensor 68 or a brake pressure sensor on at least one brake circuit 20 be connected. When using at least two pumps 60 for the brake system, these can be via a shaft 70 through a common engine 50b be operable.

Preferably, this is with the control device 10 interacting brake system a vacuum brake booster 72 on. As the control device 10 already the desired brake pressure-free presence of the wheel brake cylinder 36a and 36b can be guaranteed to use an electromechanical brake booster to reduce the in the wheel brake cylinders 336a and 36b present brake pressure below a response pressure of a storage chamber, such as in particular a low-pressure storage chamber are dispensed with. (Such a technique is known to the applicant as an internal prior art.) Thus, the use of the possible in an electromechanical brake booster control strategies can be dispensed without the presence of a residual pressure in the Radbremszylindern 36a and 36b would be acceptable. The braking system can thus with a comparatively cheap vacuum brake booster 72 be equipped. It is noted, however, that this is with the control device 10 cooperative brake system can also be used with another type of brake booster or without a brake booster.

2 shows a schematic representation of another embodiment of the cooperating with the control device brake system.

This in 2 schematically illustrated brake system, as a development of the embodiment described above, each have a storage chamber 80 (eg a low-pressure storage chamber) per brake circuit 20 on which at the line section 52 is connected. In the brake system of 2 During an ABS control / ESP control, only the storage chambers can be used 80 be used. Opening / holding open / inserting the valves 28 during the ABS control / ESP control is therefore not necessary. Thus, conventional process steps for ABS control / ESP control can continue to be performed. The ABS control / ESP control is thus in the braking system of 2 easier to carry out.

Separately, in a regenerative braking, the valves 28 and the suction lines 42 be used. By the realized separability between a use of the storage chambers 80 and use of the valves 28 is a driving the braking system with simpler algorithms guaranteed.

3 shows a schematic representation of another embodiment of the cooperating with the control device brake system.

This in 3 schematically illustrated brake system has only one on the suction line 42 to the brake fluid reservoir 32 connected brake circuit 20 on. Another brake circuit 90 of the brake system has (instead of the suction line 42 and the valve 28 ) a high pressure switching valve 92 , which hydraulically to the supply line 40 is connected. In addition, in the line section 52 a storage chamber 80 and a pressure relief valve 94 integrated.

It should be noted that also in the wheel brake cylinders 36a and 36b the suction line-free brake circuit 90 a residual pressure-free brake pressure reduction is possible, provided the master cylinder 24 equipped with a floating piston. In this case, opening the Radauslassventile causes 18 the suction line-free brake circuit 90 a shift of brake fluid into the storage chamber 80 , wherein at the same time by an adjustment of the floating piston in the master cylinder 24 in the wheel brake cylinders 36a and 36b the suction line-free brake circuit 90 present brake pressure below a set pressure of the storage chamber 80 is reducible. Thus, also in the brake system of 3 the advantageous purely regenerative braking possible. In addition, due to the advantageous features of the suction line brake circuit 90 with the storage chamber 80 an ABS control / ESP control easier executable.

In all of the braking systems described above, active pressure builds (ie, pressure assemblies without actuation of the brake operating member 16 ) via the at least one pump 50a , the open valves 28 and the closed wheel outlet valves 18 performable. Even with a failure of the modulation system, all the brake systems described above still have an enhanced braking function on all wheel brake cylinders 36a and 36b on.

4a to 4c show coordinate systems for explaining a first embodiment of the method for operating a brake system of a vehicle. In the coordinate systems of 4a and 4b the abscissas are the time axis t. The ordinate of the coordinate system of 4a gives braking moments M, while the ordinate of the coordinate system of 4b indicates a current I of control signals. In the coordinate system of 4c the abscissa represents a front axle braking torque MF exerted on a front axle, and the abscissa represents a rear axle braking torque MB exerted on a rear axle.

By means of the method described below, a regenerative braking is to be realized with the highest possible regenerative efficiency. Preferably (almost) always, if possible, a purely regenerative braking is performed. Regenerative braking can be understood to mean that a non-constant but known generator braking torque Mg is exerted on the vehicle by means of at least one generator. Under the at least one generator, an electric motor, such as an electric drive motor, which is designed for a regenerative operation with slowing down of the vehicle can be understood.

However, as a rule, the at least one generator for slowing down / decelerating the vehicle can only be used if the at least one vehicle battery is not completely charged and the vehicle still has a sufficiently high speed for inserting the at least one generator. A maximum generator-executable by the at least one generator Kann-generator braking torque Mg0 thus varies in time. It is described below how, in spite of the time-varying of the maximum executable can generator braking torque Mg0, the highest possible recuperative efficiency can still be ensured.

However, it is pointed out prior to the description of the method steps that the method steps are not only feasible for blending the generator braking torque Mg of the at least one generator. For other uses, by means of some of the method steps, a residual pressure-free state of at least one wheel brake cylinder of the operated brake system can be ensured.

By way of example, a brake system with an X-brake circuit distribution is operated by means of the method described below. For example, one of the above-executed braking systems can be operated by means of the method described below. However, a feasibility of the method is not limited to the use of such a brake system. Likewise, a brake system with a parallel brake circuit distribution can also be operated by means of the (and possibly adapted) method steps described below.

The brake system with X-brake circuit distribution comprises two brake circuits, for example, each with a front-wheel brake cylinder and a rear-wheel brake cylinder. By means of the front wheel brake cylinders of both brake circuits, a front axle wheel braking torque Mrf can be exerted on the front axle. With both rear wheel brake cylinders, a rear axle wheel braking torque Mrb can be exerted on the rear axle. The at least one generator acts on the front axle. The total front axle braking torque MF that can be exerted on the front axle can thus include the front axle wheel braking torque Mrf and the generator braking torque Mg. In contrast, that is on the rear axle exerted rear axle braking torque MB equal to the rear wheel brake torque Mrb.

From a time t0 a driver actuates a brake actuation element of the brake system. From the time t0, therefore, a predetermined braking torque M0, which is predetermined by means of the actuation of the brake actuating element, is determined not equal to zero. The desired braking torque M0 is preferred, as long as it is smaller than the maximum executable can-generator braking torque Mg0, designed purely regenerative. At time t0, the current vehicle speed and a state of charge of the at least one vehicle battery allow a comparatively high maximum executable can generator braking torque Mg0. By means of the following method steps, the vehicle can thus initially be braked purely as a generator.

For this purpose, a brake pressure build-up in the at least one wheel brake cylinder of the brake system, ie in the front axle wheel brake cylinders and in the rear wheel brake cylinders, is suppressed during the actuation of the brake actuating element connected to a master brake cylinder of the brake system. This is done by controlling at least one Radauslassventils the respective brake circuit in an at least partially open state (at least temporarily) during the actuation of the brake actuator. In the embodiment of the 4a to 4c For example, the rear axle wheel outlet valves associated with the rear axle wheel brake cylinders are controlled to open from time t0. In the present example, since the rear axle Radauslassventile designed as a normally closed valve, this is done by means of a rear wheel outlet valve control signal Iab nonzero. The front axle Radauslassventile designed as normally closed valves are left in their closed state by means of a non-sketched Vorderachs Radauslassventil control signal equal to zero. However, instead of the rear wheel outlet valves, the front axle Radauslassventile can be used for veneering, if preferred.

While outputting the control signal Iab to the rear axle wheel outlet valves, the rear axle wheel inlet valves associated with the rear axle wheel brake cylinders and the front axle wheel inlet valves associated with the front axle wheel brake cylinders are maintained in their open state. Since the rear axle wheel inlet valves and the front axle wheel inlet valves are formed as normally open valves in the example described herein, a rear axle wheel inlet valve control signal Ieb becomes zero to the rear axle wheel inlet valves and a front axle wheel inlet valve control signal Ief equals zero Front-axle Radeinlassventile issued.

From the time t0, at least one valve in at least one line path, which connects at least one wheel outlet valve (rear axle wheel outlet valve) of the respective brake circuit with a brake fluid reservoir of the brake system, in an at least partially open state (at least temporarily) controlled during the actuation of the brake actuator. If the at least one valve is a normally closed valve, an actuator signal Iv not equal to zero is output to the at least one valve.

By means of the control signals Iab and Iv described here, it is possible to ensure that a brake fluid pressed out of the master brake cylinder is at least partially displaced into the brake fluid reservoir via the at least one wheel outlet valve (rear axle wheel outlet valve) of the respective brake circuit and the at least one valve. Therefore, the front axle friction braking torque Mrf exerted by the front wheel brake cylinders and the rear axle friction braking torque Mrb exerted by the rear wheel brake cylinders remain equal to zero despite the operation of the brake operating member. Thus, the process steps carried out from time t0 also ensure the desired residual pressure-free presence of all wheel brake cylinders of the brake system.

Therefore, the at least one generator can be controlled from the time t0 so that by means of the at least one driven generator, a generator braking torque Mg is applied equal to the predetermined target braking torque M0. It is again pointed out that this is possible because by the executed displacement of the (during actuation of the brake operating element) pushed out of the master cylinder brake fluid (at least partially via the at least one Radauslassventil the respective brake circuit and the at least one valve) in the brake fluid reservoir the brake pressure build-up in the at least one wheel brake cylinder of the respective brake circuit is prevented.

Until the time t1, the maximum executable on-generator braking torque Mg0 remains smaller than the setpoint braking torque M0. Between times t0 and t1, the maximum executable optional generator braking torque M0 is therefore sufficient to carry out the driver braking request completely as a generator. Thus, the generator braking torque Mg to be executed can be calculated and set via the known braking request of the driver.

From time t1, the desired braking torque M0 exceeds the maximum executable Generator braking torque Mg0. In order to continue to fully meet the driver's brake request, however, a hydraulic brake pressure can be built up in at least one wheel brake cylinder. However, the maximum executable on-generator braking torque Mg0 is still requested by the at least one generator. From the known braking request of the driver and the likewise known executed generator braking torque Mg of at least one generator, the required additional braking torque can be calculated.

In the embodiment of the 4a to 4c the required additional braking torque is exerted as a front axle friction braking torque Mrf by means of the front-wheel brake cylinders. By at least temporarily closing the rear axle Radeinlassventile (by means of a rear axle Radeinlassventil control signal Ieb not equal to zero) from the time t1 additionally shifted by the driver brake fluid volume can be (at least partially) moved into the Vorderachs wheel brake cylinder. Thus, starting from the time t1, a front axle friction braking torque Mrf not equal to zero builds up.

By means of the continuously adjustable rear axle Radeinlassventile also a pressure control in each brake circuit of the brake system is possible. Preferably, therefore, from the time t1, a rear axle wheel inlet valve control signal Ieb suitable for a delta-p control is output to the rear axle wheel inlet valves. The front axle friction braking torque Mrf can thus be adjusted for a precise compensation of the difference between the predetermined setpoint braking torque M0 and the maximum executable optional generator braking torque Mg0. Even after the time t1, the vehicle continues to decelerate according to the driver's brake request.

Even after a constant desired braking torque M0 is specified from the time t2, this advantage is maintained. From the time t3, the driver of the vehicle releases the brake actuating element and thus reduces the desired braking torque M0. As long as the desired braking torque M0 remains greater than the maximum executable optional generator braking torque Mg0, only the brake fluid volume displaced into the front axle wheel brake cylinders is fed back into the master brake cylinder. For this purpose, furthermore, a rear axle wheel inlet valve control signal Ieb suitable for the delta-p control can be output to the rear axle wheel inlet valves.

From the time t4, the target braking torque M0 falls below the maximum executable optional generator braking torque Mg0. Therefore, the rear-wheel inlet valves can be kept open again from the time t4 (by means of the rear wheel inlet control signal Ieb equal to zero). Again, a purely regenerative / regenerative braking with a generator braking torque Mg equal to the predetermined target braking torque M0 executable.

Between times t5 and t6, the driver specifies a constant desired braking torque M0 below the maximum executable optional generator braking torque Mg0. From the time t6, the setpoint braking torque M0 increases and, starting from the time t7, again exceeds the maximum executable optional generator braking torque Mg0, before it remains constant after the instant t8. The process steps executed between times t1 to t3 can thus be repeated.

The setting of the front axle friction braking torque Mrf not equal to zero between the times t1 to t4 and between the times t7 and t8 is possible without operation of a pump. The at least one pump of the brake system can therefore be driven between times t0 to t8 with a pump control signal Ip equal to zero.

As with the coordinate system of 4c can be seen, between the times t0 to t8 always a front axle braking torque MF not equal to zero exerted on the front axle. On the other hand, the rear axle braking torque MB exerted on the rear axle always remains zero between times t0 to t8.

5a to 5c show coordinate systems for explaining a second embodiment of the method for operating a brake system of a vehicle. Regarding the abscissa and ordinate of the coordinate systems of 5a to 5c will be on the 4a to 4c directed.

The procedure of 5a to 5c can be carried out with the same braking systems, which are also suitable for the method described above. For example only, the brake system with an X-brake circuit distribution is used again.

From the point in time t0, the driver prescribes an increasing setpoint braking torque M0, which reaches a value to be constantly maintained at the point in time t10, which is to be observed until after the point of time t11. Between times t0 to t11, the predetermined desired braking torque M0 is below the maximum executable optional generator braking torque Mg0. The method steps described above can thus be carried out again for purely regenerative braking.

From time t11, the maximum executable on-generator braking torque Mg0 decreases and becomes smaller than the predetermined setpoint braking torque M0 at time t12. The omitted Applicability of the at least one generator is compensated, however, by at least one pump connected to the at least one track is controlled so that pumped by the at least one controlled pump brake fluid from the brake fluid reservoir via the at least one open-controlled valve in the at least one wheel brake cylinder of the respective brake circuit becomes. For this purpose, the at least one pump is activated by means of a pump control signal Ip not equal to zero from the time t12. In addition, the rear axle Radauslassventile be closed by means of a rear axle Radauslassventil control signal Iab equal to zero. Thus, by means of the at least one pump brake fluid from the brake fluid reservoir can be moved back into the brake circuits. The rear axle wheel inlet valves and the front axle wheel inlet valves are kept open with control signals Ieb and Ief equal to zero so that brake pressure is built up in both the rear wheel brake cylinders and the front wheel brake cylinders.

Although from the time t12 the generator braking torque Mg is reduced in accordance with the decreasing maximum executable can generator braking torque Mg0, the predetermined target braking torque M0 may be further executed as the sum of the generator braking torque Mg, the front axle friction braking torque Mrf and the rear axle friction braking torque Mrb.

Preferably, the brake pressure in the rear axle wheel brake cylinders is equal to the brake pressure in the front axle wheel brake cylinders. However, due to the different coefficients of the wheel brake cylinders, the front axle friction braking torque Mrf can be significantly higher than the rear axle friction braking torque Mrb. Thus, a Vorderachslastige brake force distribution is still guaranteed.

Also on an increase of the desired braking torque M0 from the time t13 can be reacted by a rapid increase of the front-axle friction brake torque Mrf and the rear axle friction brake Mrb so that the driver's brake request is still met. Even after the maximum executable on-generator braking torque Mg0 becomes zero at time t14, the driver's braking request is still reliably maintainable. Thus, even after a purely generative braking to respond quickly to the attributable usability of the at least one generator.

6a to 6c show coordinate systems for explaining a third embodiment of the method for operating a brake system of a vehicle. Regarding the abscissa and ordinate of the coordinate systems of 6a to 6c will be back on the 4a to 4c directed.

The procedure of 6a to 6c is executable with the same braking systems as the previously described embodiments. Again, the brake system with an X-brake circuit distribution is used for the process steps explained below.

In the process of 6a to 6c Between the times t0 to t3, the method steps described above are carried out. In the embodiment of the 6a to 6c However, the driver increases from the time t3, the target braking torque M0. The case pressed out of the master cylinder brake fluid is, however, moved (automatically) in the front-wheel brake cylinder, whereby the front axle Reibbremsmoment Mrf is increased. The increased driver braking request is thus reliably satisfied by means of a sum of the generator braking torque Mg (equal to the maximum executable optional generator braking torque Mg0) and the mitgescheigerten front-axle friction brake Mrf.

From the time t20, the target braking torque M0 reaches a maximum value and is then kept constant. At time t21, the maximum executable on-chip braking torque Mg0 also increases, before it becomes equal to the predetermined setpoint braking torque M0 at time t22. This increase in the maximum executable on-generator braking torque Mg0 can be used for additional energy recovery by means of a delta-p control of the rear axle Radeinlassventile and on the still open rear axle Radauslassventile brake fluid in the brake fluid reservoir is displaced. Thus, the present in the brake circuits pressure can be additionally reduced, whereby further the executed generator braking torque Mg is equal to the maximum executable Kann-generator braking torque Mg0 adjustable. After a complete pressure reduction in the front-axle wheel brake cylinders via the rear axle wheel inlet valves and the rear wheel outlet valves, it is possible to brake purely regeneratively.

In addition to the volume veneering carried out in the method described above, it is optionally possible to perform a force veneering. In order to compensate for the reduced pressure (during operation of the at least one generator) in at least one brake circuit, a master brake cylinder pressure present in the master brake cylinder can be mitreduziert. This is possible by a brake booster of the brake system is driven so that a force exerted by the brake booster on at least one adjustable piston of the master cylinder force is also reduced. The driver thus feels during the operation of the Brake pedal not, whether and with what proportion of regenerative braking.

Correspondingly, the brake booster can be controlled so that the force exerted on the at least one adjustable piston by means of the brake booster is also increased in a pressure build-up in at least one brake circuit to compensate for an omitted / decreasing applicability of the at least one generator. Also in this case a tactile perception of the brake pressure increase by the driver is prevented.

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 19604134 A1 [0002]

Claims (11)

Control device ( 10 ) for a braking system of a vehicle comprising: an electronic device ( 12 ), which is designed, taking into account at least one provided desired brake torque signal ( 14 ) with respect to a by means of an actuation of a brake actuator ( 16 ) of the brake system predetermined braking torque (M0) at least one Radauslassventil control signal ( 22 ) to at least one wheel outlet valve ( 18 ) at least one brake circuit ( 20 ) of the brake system, wherein the at least one by means of the at least one Radauslassventil control signal ( 22 ) controlled wheel outlet valve ( 18 ) of the respective brake circuit ( 20 ) is controllable in an at least partially opened state such that during actuation of the brake actuating element ( 16 ) from one to the brake actuator ( 16 ) connected master cylinder ( 24 ) of the brake system at least partially via the at least one Radauslassventil ( 18 ) of the respective brake circuit ( 20 ) is displaceable; characterized in that the electronic device ( 12 ) is additionally designed to provide at least one valve control signal ( 26 ) to at least one valve ( 28 ) in at least one pathway ( 30 ), via which the at least one wheel outlet valve ( 18 ) with a brake fluid reservoir ( 32 ) of the brake system is connected, wherein the at least one by means of the at least one valve control signal ( 26 ) controlled valve ( 28 ) is controllable in such an at least partially open state that during actuation of the brake actuator ( 16 ) from the master cylinder ( 24 ) pushed out brake fluid at least partially via the at least one Radauslassventil ( 18 ) of the respective brake circuit ( 20 ) and the at least one valve ( 28 ) into the brake fluid reservoir ( 32 ) is displaceable so that a brake pressure build-up in at least one wheel brake cylinder ( 36a . 36b ) of the respective brake circuit ( 20 ) during actuation of the brake actuator ( 16 ) can be prevented or reduced. Control device ( 10 ) according to claim 1, wherein by means of the electronic device ( 12 ) additionally taking into account at least the desired braking torque signal ( 14 ) and provided information ( 44 ) with respect to a maximum executable by means of at least one generator Kann-generator braking torque (Mg0) at least one generator control signal ( 46 ) can be output to the at least one generator, and wherein, if the predetermined desired braking torque (M0) is smaller than the maximum executable optional generator braking torque (Mg0), by means of the at least one with the at least one generator control signal (M0). 46 ) generator driven a generator braking torque (Mg) equal to the predetermined target braking torque (M0) is exercised, and by means of the displacement of the during actuation of the brake actuator ( 16 ) from the master cylinder ( 24 ) pressed out brake fluid at least partially via the at least one Radauslassventil ( 18 ) of the respective brake circuit ( 20 ) and via the at least one valve ( 28 ) into the brake fluid reservoir ( 32 ) the brake pressure build-up in the at least one wheel brake cylinder ( 36a . 36b ) of the respective brake circuit can be prevented. Control device ( 10 ) according to claim 2, wherein by means of the electronic device ( 12 ) additionally taking into account at least the desired braking torque signal ( 14 ) and the information provided ( 44 ) with respect to the maximum executable on-generator braking torque (Mg0) at least one pump control signal ( 48 ) to at least one of the at least one conductor track ( 30 ) connected pump ( 50a ), and wherein, if a time-decreasing maximum executable on-generator braking torque (Mg0) is less than the predetermined setpoint braking torque (M0), by means of the at least one with the at least one pump control signal ( 48 ) controlled pump ( 50a ) Brake fluid from the brake fluid reservoir ( 32 ) via the at least one open-controlled valve ( 28 ) in the at least one wheel brake cylinder ( 36a . 36b ) of the respective brake circuit ( 20 ) is pumpable. Braking system for a vehicle for interacting with a control device ( 10 ) according to any one of the preceding claims, comprising: a master cylinder ( 24 ) on which a brake actuator ( 16 ) is connectable or connected; a brake fluid reservoir ( 32 ); and at least one brake circuit ( 20 ) with - at least one wheel brake cylinder ( 36a . 36b ), - at least one on the wheel brake cylinder ( 36a . 36b ) hydraulically connected wheel outlet valve ( 18 ), and - a conductor ( 30 ), via which the at least one wheel outlet valve ( 18 ) with the brake fluid reservoir ( 32 ) of the brake system is connected to a valve disposed therein ( 28 ). Braking system according to claim 4, wherein the brake system comprises a vacuum brake booster ( 72 ). A braking system according to claim 4 or 5, wherein the brake system comprises an X-brake circuit split. Brake system according to one of claims 4 to 6, wherein the brake system, a control device ( 10 ) according to one of claims 1 to 3. Method for operating a brake system of a vehicle, comprising the step of preventing or reducing a brake pressure build-up in at least one wheel brake cylinder ( 36a . 36b ) at least one brake circuit ( 20 ) of the brake system during actuation of a master cylinder ( 24 ) connected to the brake system brake actuator ( 16 ) by controlling at least one Radauslassventils ( 18 ) of the respective brake circuit ( 20 ) in an at least partially open state at least temporarily during the actuation of the brake actuation element ( 16 ) so that from the master cylinder ( 24 ) pushed out brake fluid at least partially via at least one Radauslassventil ( 18 ) of the respective brake circuit ( 20 ) is moved; characterized by the step of controlling at least one valve ( 28 ) in at least one at least one Radauslassventil ( 18 ) of the respective brake circuit ( 20 ) with a brake fluid reservoir ( 32 ) of the braking system connecting line ( 30 ) in an at least partially open state at least temporarily during the actuation of the brake actuation element ( 16 ) so that the from the master cylinder ( 24 ) pushed out brake fluid at least partially via at least one Radauslassventil ( 18 ) of the respective brake circuit ( 20 ) and the at least one valve ( 28 ) into the brake fluid reservoir ( 32 ) is moved. Method according to claim 8, with the additional steps of: determining by means of the actuation of the brake actuating element ( 16 ) of the braking system predetermined target braking torque (M0); Determining a maximum executable by means of at least one generator Kann-generator braking torque (Mg0); and, if the predetermined setpoint braking torque (M0) is less than the maximum executable on-generator braking torque (Mg0), activating the at least one generator so that by means of the at least one driven generator a generator braking torque (Mg) equal to the predetermined setpoint braking torque (M0 ) is applied, and inhibiting the brake pressure build-up in the at least one wheel brake cylinder ( 36a . 36b ) of the respective brake circuit ( 20 ) by the shifting during actuation of the brake actuator ( 16 ) from the master cylinder ( 24 ) pressed out brake fluid at least partially via the at least one Radauslassventil ( 18 ) of the respective brake circuit ( 20 ) and via the at least one valve ( 28 ) into the brake fluid reservoir ( 32 ). A method according to claim 9, wherein, if a temporally decreasing maximum executable optional generator braking torque (Mg0) becomes smaller than the predetermined setpoint braking torque (M0), at least one of the at least one conductor track (M0). 30 ) connected pump ( 50a ) is controlled so that by means of at least one controlled pump ( 50a ) Brake fluid from the brake fluid reservoir ( 32 ) via the at least one open-controlled valve ( 28 ) in the at least one wheel brake cylinder ( 36a . 36b ) of the respective brake circuit ( 20 ) is pumped. Method according to one of claims 8 to 10, wherein a brake system is operated with an X-brake circuit split.

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