DE102012203779A1 - Method for operating brake system of vehicle e.g. hybrid car, involves controlling pressure equalization valve of brake circuit, where brake circuit is connected with brake fluid container of brake system in opened state - Google Patents

Abstract

The method involves closing a separation valve (54). Braking pressure is reduced in another brake circuit (10), and valves (40a, 42a) of the latter brake circuit is controlled, where the latter brake circuit is controlled during limiting pressure increase in the first latter circuit in an opened state. The separation valve is controlled in the opened state. A pressure equalization valve (56) of the former brake circuit (12) is controlled, where the former brake circuit is connected with a brake fluid container (20) of a brake system in the opened state. The latter brake circuit is designed as a by-wire-brake circuit. An independent claim is also included for a control device for a brake system of a vehicle.

Description

The invention relates to a method for operating a brake system of a vehicle. Furthermore, the invention relates to a control device for 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. In a deceleration of the vehicle using the electric drive for simultaneous charging of a battery, the force exerted by the at least one wheel brake cylinder of the hydraulic brake system on at least one wheel hydraulic braking torque despite an operation of the brake pedal is reduced / disabled. For this purpose, the displaced by the actuation of the brake pedal from the master cylinder to the wheel pressure means is to be counteracted by the opening of the Radauslassventile the hydraulic brake system, the displaced from the master cylinder pressure medium is transferred via the at least one wheel brake cylinder in at least one storage chamber. In this way, should be executed by the electric drive regenerative deceleration be blinded.

Disclosure of the invention

The invention provides a method for operating a brake system of a vehicle having the features of claim 1 and a control device for a brake system of a vehicle having the features of claim 11.

Advantages of the invention

The present invention makes it possible to set a brake pressure below a set pressure of the storage volume of the first brake circuit despite the operation of the arranged on the master cylinder / connected brake actuator. Thus, despite the driver's direct braking into the master cylinder, a brake pressure build-up can be reliably prevented / prevented both in the first brake circuit and in the second brake circuit. In particular, despite the successful operation of the brake operating member, such as a brake pedal, a brake pressure of almost zero can be maintained in the two brake circuits.

The method according to the invention and the corresponding control device are particularly advantageous for a recuperative braking system. It should be understood, however, that the utility of the present invention is not limited to recuperative braking systems.

In one embodiment of the present invention, there are no residual grinding torques which conventionally occur when blending according to the response force / spring force of a storage volume. Instead, the brake pressures on both axles can be reduced to 0 bar.

In an advantageous embodiment, during the limitation of the pressure buildup in the first brake circuit and / or during the additional reduction of the brake pressure in the first brake circuit, a non-zero generator braking torque is applied to the vehicle by means of a generator. The reduced compared to the prior art brake pressure in the two brake circuits can thus be used to exercise a comparatively large generator braking torque to the vehicle without a specified by the driver target total braking torque is exceeded. The advantageous method thus allows, for example, a faster charging of a vehicle battery.

For example, at least one wheel outlet valve may be controlled as the at least one valve during the limiting of the pressure build-up in the first brake circuit to the open state. Thus, to perform the method usually used in the first brake circuit valve can be used. Thus, performing the method does not require an additional component on the brake system.

In an advantageous development, after the additional reduction of the brake pressure in the first brake circuit, a brake pressure build-up in the first brake circuit is carried out to the set pressure of the storage volume of the first brake circuit by the steps: controlling the pressure compensation valve in a closed state, controlling the isolation valve in the open state, and operating a pump of the second brake circuit. By means of the method steps described here, brake fluid can be returned to the first brake circuit, or a pressure chamber of the master brake cylinder connected to the first brake circuit, in accordance with the quantity previously discharged via the pressure compensation valve into the brake fluid reservoir.

Preferably, at least one wheel inlet valve of the second brake circuit is additionally controlled into a closed state during the brake pressure build-up in the first brake circuit. Thus, an undesirable brake pressure build-up in at least one wheel brake cylinder of the second Brake circuit in a simple manner reliably preventable.

In a further advantageous embodiment, an additional pressure build-up in the first brake circuit is performed by the steps of: controlling the isolation valve in the closed state, and additionally operating the pump of the first brake circuit. By means of the method steps described here, a relatively high brake pressure can be built up comparatively quickly in the first brake circuit. For example, by means of the method steps described here, the reduction of the maximum executable generator braking torque by reacting a hydraulic braking torque of the wheel brake cylinder of the first brake circuit can be reacted quickly.

In an advantageous embodiment, the limiting of the brake pressure build-up in the first brake circuit and / or the additional reduction of the brake pressure in the first brake circuit are carried out exclusively if a brake actuation strength of the actuation of the brake actuation element is below a predetermined threshold value. In this case, the brake system due to the targeted by the method described here switching the valves, or its hydraulic circuit diagram, an additional / increased "hydraulic" free travel. A formation of an additional mechanical free travel on the brake system is therefore no longer necessary. The driver of the vehicle equipped with the brake system thus has a standard brake feel / pedal feel due to the jump-in effect. Due to the hydraulic design of the idle path ensures that changes in the idle travel to changes in a mechanical void are easier and less expensive to carry out and present as needed depending on the current situation.

For example, the predetermined threshold may correspond to a jump-in threshold. In particular, the predetermined threshold value of a vehicle deceleration may correspond to between 0.15 g and 0.2 g. The method described here can thus be carried out without this being perceptible to the driver with a changed brake actuation feeling / pedal feeling. In particular, the threshold value can be selected arbitrarily high if the brake booster / amplifier device can reduce the amplifier power in accordance with the pressure reduction.

The advantages described in the upper paragraphs are also ensured in a corresponding control device for a recuperative braking system of a vehicle.

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 an embodiment of the control device;

2a to 2e five coordinate systems for illustrating a first embodiment of the method for operating a recuperative braking system; and

3a to 3e Five coordinate systems for illustrating a second embodiment of the method for operating a brake system.

Embodiments of the invention

1 shows a schematic representation of an embodiment of the control device.

In the 1 schematically reproduced control device 100 and the cooperating brake system can be advantageously used for example in a hybrid or in an electric vehicle. However, the applicability of the braking system described below is not limited to use in a hybrid or in an electric vehicle.

The brake system has a first brake circuit 10 and a second brake circuit 12 each with at least one wheel brake cylinder 14a . 14b . 16a and 16b , Optionally, each of the two brake circuits 10 and 12 two wheel brake cylinders 14a . 14b . 16a and 16b on. In this case, the first wheel brake cylinder is preferably the first 14a of the first brake circuit 10 and the second wheel brake cylinder 16a of the first brake circuit 10 assigned to a first vehicle axle, while the third wheel brake cylinder 14b of the second brake circuit 12 and the fourth wheel brake cylinder 16b of the second brake circuit 12 assigned to another vehicle axle. For example, the first wheel brake cylinder 14a and the second wheel brake cylinder 16a be assigned to the front axle, while the third wheel brake cylinder 14b and the fourth wheel brake cylinder 16b associated with the rear axle. However, the brake system described below is not limited to such a brake circuit distribution. The one brake circuit 10 and 12 associated wheels can for example also be arranged diagonally on the vehicle or on one side of the vehicle.

The brake system has a master cylinder 18 on, which is executable, for example, as a tandem master cylinder. Of the Master Cylinder 18 may have at least one adjustable piston, which at least partially in at least one pressure chamber 18a or 18b of the master cylinder 18 is adjustable. Preferably, the master cylinder comprises 18 a first adjustable piston, which can be labeled as a rod piston, which at least partially into a first brake circuit 10 associated first pressure chamber 18a of the master cylinder 18 protrudes, and as a floating piston markable second adjustable piston, at least partially into a second brake circuit 12 associated second pressure chamber 18b of the master cylinder 18 protrudes. In a preferred embodiment, the floating piston is adjustable so that when adjusting the floating piston in a first direction, the first inner volume of the first pressure chamber 18a decreases while the inner volume of the second pressure chamber 18b increases. Accordingly, via an adjustment of the floating piston in a second direction, the inner volume of the first pressure chamber 18a at a decrease in the internal volume of the second pressure chamber 18b increase. The applicability of the control device 100 However, it is not on the use of a tandem master cylinder or on a particular design of the master cylinder 18 limited. The master cylinder 18 can have at least one brake fluid exchange port, such as a sniffer bore, with a brake fluid reservoir 20 be connected.

The brake system preferably has one on the master cylinder 18 arranged brake actuator 22 , such as a brake pedal on. Advantageously, the brake actuating element 22 such on the master cylinder 18 arranged that upon actuation of the brake actuator 22 with at least a minimum brake actuation strength on the brake actuator 22 applied driver braking force on the at least one adjustable piston, such as on the rod piston and the floating piston, is transferable, that the piston is adjustable by means of the driver brake force. Preferably, by means of this adjustment of the piston, an internal pressure in at least one pressure chamber 18a and 18b of the master cylinder 18 increased.

The brake system preferably also comprises at least one brake actuation element sensor 24 , By means of which the operating strength of the actuation of the brake actuating element 22 can be determined by the driver. The brake actuator sensor 24 For example, it may include a pedal travel sensor, a differential travel sensor, and / or a rod travel sensor. To detect the operating force, which corresponds to the driver's brake request, however, a different type of sensor is used instead of or in addition to the sensor types listed here.

The illustrated brake system also includes a brake booster 26 , preferably an electromechanical brake booster 26 , on. The brake booster 26 In particular, it may be a continuously variable / continuously controllable brake booster. An electromechanical brake booster 26 is characterized by a variable gain. So it is by means of an electromechanical brake booster 26 possible to easily influence the driver's perceivable brake operating force during braking. Instead of an electromechanical brake booster 26 can do that with the control device 100 cooperative brake system also has a brake booster 26 of a different type.

Hereinafter, with reference to 1 further components of the embodiment of the brake system described. It is expressly pointed out that the components of the brake system described below represent only one example of a possible embodiment of the advantageous brake system. An advantage of the control device described in more detail below 100 lies in the fact that the cooperating brake circuits 10 and 12 are not fixed to a specific training or to the insertion of certain components. Instead, the brake circuits can 10 and 12 be modified with a high freedom of choice without the usability and advantages of the control device 100 be affected:
Each of the brake circuits 10 and 12 is designed so that the driver, if desired, via the master cylinder 18 directly into the wheel brake cylinders 14a . 14b . 16a and 16b can brake in. The first brake circuit 10 has a high pressure switching valve 28 and a changeover valve 30 on while the second brake circuit 12 is preferably formed without a corresponding valve. In the first brake circuit 10 are the first wheel brake cylinder 14a a first wheel inlet valve 32a and the second wheel brake cylinder 16a a second wheel inlet valve 34a , each with a parallel thereto bypass line 36a and one in each bypass line 36a arranged check valve 38a assigned. In addition, a first Radauslassventil 40a the first wheel brake cylinder 14a and a second wheel outlet valve 42a the second wheel brake cylinder 16a assigned. Accordingly, in the second brake circuit 12 a third wheel inlet valve 32b the third wheel brake cylinder 14b and a fourth wheel inlet valve 34b the fourth wheel brake cylinder 16b be assigned. Parallel to each of the two wheel inlet valves 32b and 34b of the second brake circuit 12 can each have a bypass line 36b with a non-return valve disposed therein 38b run. Furthermore, also in the second brake circuit 12 a third wheel outlet valve 40b the third wheel brake cylinder 14b and a fourth wheel outlet valve 42b the fourth wheel brake cylinder 16b be assigned.

In addition, each includes the brake circuits 10 and 12 a pump 44a and 44b , the suction side with the Radauslassventilen 40a and 42a or 40b and 42b is connected and their delivery side to the Radeinlassventilen 32a and 34a or 32b and 34b is directed. The first brake circuit 10 additionally has one between the wheel outlet valves 40a and 42a and the pump 44a arranged storage chamber 46 (eg a low-pressure accumulator) and one between the pump 44a and the storage chamber 46 horizontal overpressure valve 48 on. It should be noted that the storage chamber 46 as ESP storage chambers of the first brake circuit 10 is usable.

The pumps 44a and 44b can on a common shaft 50 an engine 52 be arranged. Each of the pumps 44a and 44b can be designed as a three-piston pump. However, instead of a three-piston pump, another type of pump may be used for at least one of the pumps 44a and 44b be used. Differently executed modulation systems, such. As pumps with several or fewer pistons, asymmetric pumps or gear pumps are also used. That with the control device 100 cooperative braking system is thus as a modified standard modulation system, in particular as a six-piston ESP system, executable.

The second brake circuit 12 still includes a separating valve 54 , via which the previously described components of the second brake circuit 12 are connected to the master cylinder. Preferably, the isolation valve 54 between the master cylinder and the Radeinlassventilen 32b and 34b of the second brake circuit 12 arranged. In addition, the second brake circuit 12 via a pressure compensation valve 56 to the brake fluid reservoir 20 tethered. Preferably, the pressure compensation valve 56 the brake fluid reservoir 20 and a delivery side of the pump (disposed from the intake valves) 44b of the second brake circuit 12 interposed. About a parallel to the pressure compensation valve 56 guided tour 58 is the suction side of the pump 44b of the second brake circuit 12 with the brake fluid reservoir 20 connected. Preferably, the pressure compensation valve 56 a continuously adjustable / continuously controllable valve. However, the feasibility of the pressure compensation valve 56 not limited to a specific type of valve. In addition, each of the two brake circuits 10 and 12 at least one pressure sensor 60 in particular for determining a pre-pressure and / or a circular pressure.

The braking system described above is by means of the subsequently executed control device 100 controllable. However, it is again pointed out that the applicability of the control device described below 100 is not limited to the interaction with such a trained braking system. Instead, the control device 100 also for a variety of differently designed brake systems with one on the master cylinder 18 firmly coupled / unsolvable connected first brake circuit 10 , which at least one storage volume (storage chamber 46 ), and one of the master cylinder decoupled / separable / abbindbaren second brake circuit 12 (By-wire brake circuit), which with a separating valve 54 is equipped to be used:
The control device 100 includes a valve and / or pump driver 102 by means of which the brake system can be controlled in a limited brake pressure build-up mode by at least one valve 40a and 42a of the first brake circuit 10 by means of a first control signal 104 is controllable in an open state. During actuation of the master cylinder 18 arranged brake actuator 22 by a driver of the vehicle is thus brake fluid on the at least one open valve 40a and 42a from the master cylinder 18 and / or the first brake circuit 10 in the storage chamber 46 as storage volume of the first brake circuit 10 displaceable. Thus, after controlling the brake system in the limited brake pressure build-up mode, despite the operation of the brake operating member 22 a brake pressure build-up in the first brake circuit 10 to a response pressure of the storage volume of the first brake circuit 10 used storage chamber 46 be limited.

In addition, by means of the valve and / or Pumpenansteuereinrichtung 102 the isolation valve 54 over which the second brake circuit 12 with the master cylinder 18 is hydraulically connected by means of a second control signal 106 controllable in a closed state. Thus, a brake pressure buildup despite the operation of the brake operating member 22 also in the second brake circuit 12 be prevented.

Furthermore, the brake system by means of the valve and / or Pumpenansteuereinrichtung 102 additionally controllable in a pressure-reducing mode by the at least one previously by means of the first control signal 104 controlled valve 40a and 42a of the first brake circuit 10 by means of a third control signal 108 in the closed state, the isolation valve 54 by means of a fourth control signal 110 in an open state, and the pressure compensation valve 56 of the second brake circuit 12 over which the second brake circuit 12 with the brake fluid reservoir 20 is connected (by means of a fifth control signal 112 ) are controllable in an open state. This causes a brake fluid shift (from the first brake circuit 10 in the first pressure chamber 18a connected and from the second pressure chamber 18b over the second brake circuit 12 in the brake fluid reservoir), whereby in the first brake circuit 10 present pressure additionally below the set pressure of the storage volume of the first brake circuit 10 used storage chamber 46 is reducible. This brake pressure reduction can be used to increase an executed by means of a generator (not shown) generator braking torque. Thus, a battery of the vehicle equipped with the brake system can be charged more quickly without being caused by a driver by means of an operation of the brake operating member 22 predetermined vehicle deceleration is exceeded.

That with the control device 100 equipped braking system thus combines the advantages of high recuperation efficiency with the feasibility of Vorderachsverblendung. In addition, it is by means of the insertion of the control device 100 possible to perform a veneering on at least one axis, such as the front axle, without any repercussions thereof on the brake actuator 22 are noticeable.

For example, at least one Radauslassventil 40a and 42a of the first brake circuit 10 or at least one high pressure switching valve 28 of the first brake circuit 10 than the at least one valve 40a and 42a by means of the first control signal 104 and the third control signal 108 be controllable. Instead of the valves mentioned here 40a and 42a However, other valve types can also be controlled by means of the control signals 104 and 108 be controllable.

In an advantageous development, the brake system by means of the valve and / or Pumpenansteuereinrichtung 102 additionally be controllable in a first pressure build-up mode by the pressure compensation valve 56 in a closed state and the isolation valve 54 in the open state are controllable and the pump 44b of the second brake circuit 12 is controllable in an active mode. After the pressure-reducing mode is thus a brake pressure build-up in the first brake circuit 10 at least to the set pressure of the storage volume of the first brake circuit 10 used storage chamber 46 (by means of operating the pump 44b of the second brake circuit 12 ) executable. In this case, advantageously, the intake valves 32b and 34b of the second brake circuit 12 closed by a pressure build-up in the wheel brake cylinders 14b and 16b to prevent. In addition, the brake system by means of the valve and / or Pumpenansteuereinrichtung 102 additionally be controllable in a second pressure build-up mode by the isolation valve 54 in the closed state is controllable and the pump 44a of the first brake circuit 10 in an active mode is controlled so that after the limited-brake pressure build-up mode and / or the first pressure build-up mode, a (further) pressure build-up in the first brake circuit 10 is executable. For example, by means of the pressure build-up in the first brake circuit 10 a reduction of the generator braking torque can be compensated.

In a further advantageous development, the control device can additionally have a comparison device 114 include, by means of which a (eg from the sensor 24 ) provided brake actuation strength 116 with respect to the actuation of the brake actuator with a predetermined threshold 118 is comparable. (The threshold 118 can from a storage unit 117 be provided.) If the brake actuation strength 116 below the threshold 118 is, can by means of the comparator 114 a corresponding comparison signal 120 to the valve and / or Pumpenansteuereinrichtung 102 be dispensable. In this case, the valve and / or Pumpenansteuereinrichtung 102 is preferably designed to control the brake system exclusively in the limited-brake pressure build-up mode and / or the pressure-reducing mode, if the brake actuation strength 116 below the threshold 118 lies. As will be explained in more detail below, in this embodiment, by means of the pressure variation in the first brake circuit 10 taking into account the brake actuation strength 116 Also, a brake actuation feeling can be effected, which corresponds to the response of a braking system formed with an idle travel. When using the development of the control device 100 is therefore also in a low delay range, a "hydraulic" free travel feasible, which ensures a high recuperative efficiency. The constructive implementation of the "hydraulic" Leerwegs is associated with no mechanical effort. In particular, no actuation components or their specifications need to be adapted to a mechanical free travel.

It should be noted that when using the development of the control device 100 In the realizable "hydraulic" jump-in area, the driver braking force / pedal force to be applied by the driver is almost constant. In the realizable "hydraulic" jump-in range, the driver can thus set the deceleration purely via the brake actuation path / pedal travel. The translation between one on the brake actuator 22 applied driver braking force and the booster power of the brake booster 26 is theoretically infinite in this area. At the same time, pressure variations in the brake system can be performed largely imperceptibly for the driver in the jump-in area.

For a standard system (standard ESP system) and a hybrid variant, the same actuation can be used using the technology described here. Thus, no duplication of effort is required for a second actuation with increased free travel.

In addition, the control device 100 additionally be designed to carry out the method steps described below. For a more detailed description of further realizable operations of the control device 100 is therefore omitted here.

2a to 2e show five coordinate systems for illustrating a first embodiment of the method for operating a recuperative braking system.

For better clarity, the method is described using the recuperative braking system described above, wherein the first wheel brake cylinder and the second wheel brake cylinder of a front axle formed as a first axis and the third wheel brake cylinder and the fourth wheel brake cylinder are assigned to a second axis formed as a rear axle. However, the feasibility of the method is not limited to the use of the braking system described above or to this assignment of the wheel brake cylinder.

In the coordinate systems of 2a to 2d the abscissa is the time axis t. The ordinate of the coordinate system of 2a is a braking torque b again, while the ordinates of 2 B to 2d indicates a (normalized) current I. The abscissa of the coordinate system of 2e is a first axle braking torque ba1 exerted on the first axle, while the ordinate of the co - ordinate system is 2e represents an exerted on the second axis axle brake ba2.

Until a time t0, the brake operating element of the braking system operated by means of the method is in its starting position / non-actuating position. Thus, the driver does not exert any force on the brake actuating element until time t0.

From the time t0, the driver exerts an increasing force on the brake operating member, whereby this is adjusted. Between times t0 and t1, however, the desired total braking torque bges requested by the driver is below a maximum executable can-generator braking torque b by means of a generator (for example on the first axis). Thus, between times t0 and t1, the (executed) generator braking torque bgen can be set in accordance with the desired total braking torque bges, and the complete driver brake request can be carried out purely regeneratively.

To carry out the purely regenerative braking between the times t0 and t1 a brake pressure build-up in the first brake circuit of the brake system (despite the operation of the arranged on the master cylinder of the brake system brake actuator by a driver of the vehicle) limited to a response pressure of the storage volume of the first brake circuit. This is done by controlling the at least one Radauslassventils the first brake circuit so in an open state that brake fluid is displaced via the at least one open Radauslassventil from the master cylinder and / or the first brake circuit in the storage volume of the first brake circuit. In an embodiment of the at least one wheel outlet valve of the first brake circuit as normally closed valve, a control signal Iav not equal to zero is output between the times t0 and t1 (as the first control signal) to the at least one wheel outlet valve of the first brake circuit. It should be noted that instead of the at least one Radauslassventils and another valve of the first brake circuit for transferring brake fluid in the storage volume of the first brake circuit is used.

Between times t0 and t1, the second brake circuit, which is designed as a by-wire brake circuit, is decoupled from the master brake cylinder. This is done by closing the isolation valve, via which the second brake circuit of the brake system is hydraulically connected to the master cylinder, during the limitation of the pressure build-up in the first brake circuit to the set pressure of the storage volume of the first brake circuit. In an embodiment of the isolation valve as normally open valve, a current signal It not equal to zero (as a second control signal) can be provided to the isolation valve. In addition, the pressure compensation valve of the second brake circuit, via which the second brake circuit is connected to the brake fluid reservoir of the brake system, between the times t0 and t1 remain in a closed state. In an embodiment of the pressure compensation valve as normally closed valve, therefore, no application of a current signal Id equal to zero to the pressure compensating valve is required.

Between the times t0 and t1, the driver thus shifts a volume of brake fluid from the master brake cylinder by means of its braking into the first brake circuit. However, this does not cause a buildup of brake pressure in the wheel brake cylinders over the set pressure of the preferably designed as a low-pressure accumulator storage volume. Between the times t0 and t1, a generator braking torque not equal to zero can thus be exerted on the vehicle by means of at least one generator (not shown) due to the limitation of the pressure build-up in the first brake circuit. Despite the exercise of the generator braking torque is not equal to zero is reliably ensured due to the method steps described above, that a predetermined by the driver by means of the brake application target total braking torque bges is not exceeded.

In addition, the brake pressure in the first brake circuit between times t1 and t2 can additionally be reduced (below the set pressure of the storage volume of the first brake circuit). This is possible by controlling the at least one Radauslassventils the first brake circuit, which is controlled during the limitation of the pressure build-up in the first brake circuit in the open state, in the closed state. This is preferably done by a current signal Iav equal to zero (as a third control signal). In addition, between the times t1 and t2, the isolation valve is controlled in an open state. This is reliably executable by a current signal It not equal to zero (as a fourth control signal). For the desired pressure reduction between the times t1 and t2 and the pressure compensation valve of the second brake circuit is controlled in an open state. This can be achieved by a current signal Id, which is applied to the pressure compensating valve between times t1 and t2, not equal to zero. In this way, the residual pressure in the first brake circuit, which the response pressure / the Ansprechkraft of the storage volume, z. B. corresponds to a low-pressure accumulator spring formed as a low-pressure storage chamber storage volume, are degraded. In this case, cause the wheel brake of the second brake circuit (the rear axle) even with open Radeinlassventilen the associated brake circuit no hydraulic braking torque, since the breakaway torque of the wheel brake cylinder is usually higher than the "Reservoir pressure" (atmospheric pressure) at an open pressure relief valve.

The additional reduction of the brake pressure in the first brake circuit below the response pressure of the storage volume can be used to increase the efficiency during recuperation. The requested by the driver target total braking torque bges can thus be applied between the times t1 and t2 ideally to 100% as a generator braking torque bgen.

In the embodiment of the method shown here, the limiting of the brake pressure build-up in the first brake circuit and / or the additional reduction of the brake pressure in the first brake circuit are carried out exclusively if a brake actuation strength of the actuation of the brake actuation element is below a predetermined threshold value. As a threshold, for example, a limit vehicle deceleration b0, in particular between 0.15 g and 0.2 g, are specified.

In carrying out the method described here, a "hydraulic" free travel for the driver can thus be effected by a targeted switching of the valves. This is feasible without pedal force fluctuations occurring during the jump-in range given by the limit vehicle deceleration b0. The driver thus has a standard brake feel / pedal feel.

In a further preferred embodiment, the limitation of the reduction / limitation of the brake pressure build-up to a predetermined threshold can be omitted if the brake booster 26 by a suitable control by means of a reduction in the gain compensated for the reduced pedal force.

From time t2, the increasing target total braking torque bges given by the driver approaches the limit vehicle deceleration b0. Therefore, in order to give the driver a standard brake operation feeling / pedal feeling, a brake pressure build-up in the first brake circuit is executed from time t2.

The construction of a brake pressure perceptible for the driver in the first brake circuit can take place in two phases. Between times t2 and t3, a brake pressure equal to the set pressure of the storage volume of the first brake circuit in the first brake circuit is established. For this purpose, the pressure compensation valve are controlled in a closed state and the isolation valve in the open state. (The current signals It and Id provided to the valves therefore equal zero between times t2 and t3). In addition, between times t2 and t3, the at least one pump of the second brake circuit is controlled by means of a pump control signal Ip not equal to zero in an (active) mode. Preferably, between the times t2 and t3 and the at least one Radeinlassventil the second brake circuit is controlled in a closed state. In this way it can be prevented that the actuation of the pump of the first Brake circuit leads to a brake pressure build-up in at least one wheel brake cylinder of the second brake circuit. In order to control the at least one wheel inlet valve of the second brake circuit in the preferred closed state, a current signal Iev not equal to zero can be provided to this when the at least one wheel outlet valve of the second brake circuit is designed as a normally open valve.

As a result of the above-described method steps, a brake fluid volume equal to the amount previously discharged into the brake fluid reservoir can be conveyed back into the first brake circuit and / or a pressure chamber of the master brake cylinder assigned to the first brake circuit.

Between times t3 and t4, a second pressurization phase is listed. (The driver thus feels from time t4 a back pressure during braking in the master cylinder.) In this case, the separating valve is controlled in the closed state for an additional pressure build-up in the first brake circuit. At the in 1 reproduced training of the isolation valve as a normally open valve is for this purpose between the times t3 and t4 a current signal It not equal to zero applied to the isolation valve. In addition, between the times t3 and t4, the pump of the first brake circuit is operated so that by means of it the filled in the storage volume of the first brake circuit brake fluid is at least partially fed back into the first brake circuit. If desired, the storage volume of the first brake circuit can be completely emptied in this way. In addition, the pressure compensation valve of the second brake circuit can be opened during this process, for example by means of a current signal Id not equal to zero, in order to prevent that by means of operating the first pump of the first brake circuit, a pressure in the second brake circuit is established.

The operations described in the paragraph above can be carried out so that upon reaching a requested by the driver target total braking torque bges equal to the limit total delay b0 the previously shifted into the storage volume of the first brake circuit volume is completely conveyed back into the first brake circuit , And thus a standard brake pressure is built up in the first brake circuit, which causes the customary counterforce on the brake actuator. Parallel to this, the generator braking torque can be reduced in accordance with the braking torque build-up to the first brake torque bh1 of the wheel brake cylinders of the first brake circuit. This can be done so that the brake torque distribution on the vehicle level and the total delay remain constant.

At a predetermined by the driver target total braking torque bges equal to the limit total delay b0 at time t4, the pressure compensation valve is closed. The isolation valve remains closed. As a result, the brake system is in a brake-by-wire mode. The force exerted on the associated axle second hydraulic braking torque bh2 the wheel brake cylinder of the second brake circuit thus remains equal to zero.

The increase of the target total braking torque bges by the driver between the times t4 and t5 thus causes a direct braking of the driver in the first brake circuit. At the same time, the generator braking torque bgen between the times t4 and t5 can be increased in accordance with the theoretical proportion of the second brake circuit / theoretical Hinterachsbremsanteils. This can be done in a strategy according to the installed brake force distribution (see 2e ). Alternatively, a (theoretical) overbraking of the axle of the second brake circuit / rear axle to increase the recuperative efficiency can be performed. It should be noted that the complete (theoretical) portion of the second brake circuit / rear axle can be regeneratively used and blinded even with a target total braking torque bges over the limit total delay b0 / outside the jump-in area.

Between times t5 and t6, the target total braking torque bges is constant. Between times t6 and t7, the driver reduces the requested target total braking torque bges to a value equal to the total limit deceleration b0. One can also rewrite this so that the requested desired total braking torque bges from the time t7 again enters the jump-in area. With a setpoint total braking torque bges below the limit total delay b0, it is possible to switch back to the jump-in area without pedal reaction. For this purpose, between the times t7 and t8, the at least one valve of the first brake circuit, in this case the at least one wheel outlet valve of the first brake circuit, used to carry out limiting of the brake pressure buildup to the response pressure of the reservoir volume is controlled to an at least partially open state. (The term open state is to be understood as a state in which the respective valve is at least partially open.) This is done, for example, by means of a current signal Iav not equal to zero between times t7 and t8. In this way, brake fluid from the first brake circuit in the storage volume of the first brake circuit, for example, in a low-pressure storage chamber, are drained. This caused dropping first hydraulic Braking torque bh1 of the first brake circuit can be applied parallel thereto by the recuperative brake, ie an increasing generator braking torque. In order to further reduce the remaining pressure due to the response of the storage volume of the first brake circuit, the additional reduction of the brake pressure in the first brake circuit described above can additionally be carried out between times t8 and t9. For this purpose, the pressure compensation valve of the second brake circuit is controlled in an open state. For example, between the times t8 and t9, a current signal Id not equal to zero is applied to the pressure compensation valve of the second brake circuit. In addition, the isolation valve controlled to a closed state before time t8 is controlled to open state between times t8 and t9, for example by means of a current signal It equal to zero. From the time t9 is thus in both brake circuits before a brake pressure, which is at least smaller than the set pressure of the storage volume of the first brake circuit. In particular, the pressure in the two brake circuits can be equal to the atmospheric pressure. This can also be described in such a way that all wheel pressures of the wheel brake cylinders of the two brake circuits are reduced to (almost) 0 bar. From the time t9, the attributable braking effect of the wheel brake cylinders of the two brake circuits can thus be used for maximum operation of the generator. In this way, the efficiency of the recuperative brake can be maximized.

3a to 3e show five coordinate systems for illustrating a second embodiment of the method for operating a brake system. Regarding the abscissa and ordinate of the coordinate systems of 3a to 3e Reference is made to the above statements.

This in 3a to 3e The reproduced method has the method steps already described above between times t0 to t6. A renewed description of these method steps is therefore omitted here.

From time t6, the maximum executable can generator braking torque bkann decreases, for example due to a charging state of a rechargeable by means of the generator vehicle battery and / or a reduction in the current speed of the vehicle near a generator insertion minimum speed. However, as will be described below, the method may also respond to such a situation.

At time t11, the maximum executable can-generator braking torque bkann equal to the executed generator braking torque bgen. However, a further reduction of the maximum executable can-generator braking torque bkann can be compensated by an additional pressure build-up in the first brake circuit and / or by a pressure build-up in the decoupled from the master cylinder second brake circuit (by-wire brake circuit). Thus, despite the decrease of the maximum executable can-generator braking torque bkann requested by the driver target total braking torque bges can be reliably maintained. In the embodiment of the 3a to 3e For this purpose, the at least one pump of the second brake circuit is activated by means of a pump drive signal Ip not equal to zero in order to build a brake pressure not equal to zero in the wheel brake cylinders of the second brake circuit by pumping brake fluid from the brake fluid reservoir into the second brake circuit. In this way, a second hydraulic braking torque bh2 of the second brake circuit not equal to zero can be built up from the time t11.

It should be noted that even during the "theoretical" jump-in range, a decreasing maximum executable can-generator braking torque bk can be reacted by a brake pressure in the first brake circuit and / or in the second brake circuit decoupled from the master brake cylinder is built. In this case, in order to build up a brake pressure in the first brake circuit, the wheel outlet valves of the first brake circuit are preferably closed after the hydraulic volume corresponding to the available generator braking torque has been shifted into the storage volume of the first brake circuit. Subsequently, the driver can again brake hydraulically in the first brake circuit and the brake pressure can be adjusted by means of at least one pump of the first brake circuit. Preferably, the axle / first brake circuit fixedly connected to the master brake cylinder is always first hydraulically filled again before pressure is actively built up in the second brake circuit / in the by-wire brake circuit.

Performing the methods described above ensures advantageous recovery of the braking energy through recuperative braking. In this case, the generator, which usually serves as the electric drive motor of the vehicle, are operated so that a braking torque is generated. The electrical energy generated thereby can be fed back into a memory. For later use, this energy can be used, for example, to accelerate the vehicle. The methods described above thus offer advantageous measures for reducing fuel consumption and pollutant emissions during a journey of a vehicle.

The processes carried out also offer the advantage that the volume to be veneered almost is stored / hidden completely in the associated brake circuit. Therefore, for carrying out the method, comparatively little brake fluid must be displaced between the reservoir / master cylinder and the brake circuits. This also ensures a fast feasibility and a low load on the pumps used.

It should be noted that the methods described above can also be applied to vehicles in which the generator is located on the rear axle. Likewise, the methods described above are applicable to vehicles in which the generator acts on all four wheels. In particular, in an arrangement of the generator on the rear axle and a strategy of overbraking the rear axle can be applied to increase the Rekuperationseffizienz. Even with such an embodiment of the method, it is possible to dispense with an additional free travel in the Aktuation.

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 (14)

Method for operating a brake system of a vehicle, comprising the step of: limiting a brake pressure build-up in a first brake circuit ( 10 ) of the brake system to a response pressure of a storage volume ( 46 ) of the first brake circuit ( 10 ) during actuation of a master cylinder ( 18 ) of the brake system arranged brake actuator ( 22 ) by a driver of the vehicle by controlling at least one valve ( 40a . 42a ) of the first brake circuit ( 10 ) in an open state that brake fluid via the at least one open valve ( 40a . 42a ) from the master cylinder ( 18 ) and / or the first brake circuit ( 10 ) in the storage volume ( 46 ) of the first brake circuit ( 10 ) is moved; characterized by the steps of: closing a separating valve ( 54 ), via which a second brake circuit ( 12 ) of the brake system with the master cylinder ( 18 ) is hydraulically connected during the limiting of the pressure build-up in the first brake circuit ( 10 ) to the set pressure of the storage volume ( 46 ) of the first brake circuit ( 10 ); and additionally reducing a brake pressure in the first brake circuit ( 10 ) by the steps of: controlling the at least one valve ( 40a . 42a ) of the first brake circuit ( 10 ), which during the limitation of the pressure build-up in the first brake circuit ( 10 ) is controlled in the open state, in a closed state; Controlling the separating valve ( 54 ) in an open state; and controlling a pressure compensating valve ( 56 ) of the second brake circuit ( 12 ), via which the second brake circuit ( 12 ) with a brake fluid reservoir ( 20 ) of the brake system is in an open state. Method according to claim 1, wherein during the limitation of the pressure build-up in the first brake circuit ( 10 ) and / or during the additional reduction of the brake pressure in the first brake circuit ( 10 ) is applied a generator braking torque (bgen) not equal to zero by means of a generator on the vehicle. Method according to claim 1 or 2, wherein at least one wheel outlet valve ( 40a . 42a ) than the at least one valve ( 40a . 42a ) while limiting the pressure build-up in the first brake circuit ( 10 ) is controlled in the open state. Method according to one of the preceding claims, wherein after additionally reducing the brake pressure in the first brake circuit ( 10 ) a brake pressure build-up in the first brake circuit ( 10 ) to the set pressure of the storage volume ( 46 ) of the first brake circuit ( 10 ) is performed by the steps: controlling the pressure compensating valve ( 56 ) in a closed state; Controlling the separating valve ( 54 ) in the open state; and operating a pump ( 44b ) of the second brake circuit ( 12 ). Method according to claim 4, wherein during the brake pressure build-up in the first brake circuit ( 10 ) additionally at least one wheel inlet valve ( 32b . 34b ) of the second brake circuit ( 12 ) is controlled in a closed state. The method of claim 4 or 5, wherein an additional pressure build-up in the first brake circuit ( 10 ) is carried out by the steps: controlling the separating valve ( 54 ) in the closed state; and additional operation of the pump ( 44a ) of the first brake circuit. Method according to one of the preceding claims, wherein limiting the brake pressure build-up in the first brake circuit ( 10 ) and / or additionally reducing the brake pressure in the first brake circuit ( 10 ) are carried out exclusively provided that a brake actuation strength ( 116 ) the actuation of the brake actuator ( 22 ) below a predetermined threshold ( 118 , b0). Method according to claim 7, wherein the predetermined threshold value ( 118 , b0) corresponds to a jump-in limit. Method according to claim 7 or 8, wherein the predetermined threshold value ( 118 , b0) corresponds to a vehicle deceleration between 0.15g and 0.2g. Control device ( 100 ) for a brake system of a vehicle, comprising: a valve and / or pump driver ( 102 ), by means of which the brake system can be controlled in a limited-brake pressure build-up mode by at least one valve ( 40a . 42a ) of a first brake circuit ( 10 ) of the brake system by means of a first control signal ( 104 ) is controllable in an open state, that during actuation of a master cylinder ( 18 ) of the brake system arranged brake actuator ( 22 ) by a driver of the vehicle brake fluid via the at least one open valve ( 40a . 42a ) from the master cylinder ( 18 ) and / or the first brake circuit ( 10 ) into a storage volume ( 46 ) of the first brake circuit ( 10 ) is displaceable and a brake pressure build-up in the first brake circuit ( 10 ) to a response pressure of the storage volume ( 46 ) of the first brake circuit ( 10 ) is limited, and a separating valve ( 54 ) about which one second brake circuit ( 12 ) of the brake system with the master cylinder ( 18 ) is hydraulically connected by means of a second control signal ( 106 ) is controllable in a closed state; wherein the brake system by means of the valve and / or Pumpenansteuereinrichtung ( 102 ) is additionally controllable in a pressure-reducing mode by the at least one previously by means of the first control signal ( 104 ) controlled valve ( 40a . 42a ) of the first brake circuit ( 10 ) by means of a third control signal ( 108 ) in the closed state, the isolation valve ( 54 ) by means of a fourth control signal ( 110 ) in an open state, and a pressure compensation valve ( 56 ) of the second brake circuit ( 12 ), via which the second brake circuit ( 12 ) with a brake fluid reservoir ( 20 ) of the braking system is connected by means of a fifth control signal 112 can be controlled in an open state. Control device ( 100 ) according to claim 10, wherein at least one wheel outlet valve ( 40a . 42a ) or at least one high-pressure switching valve ( 28 ) than the at least one valve ( 40a . 42a ) by means of the first control signal ( 104 ) and the third control signal ( 108 ) are controllable. Control device ( 100 ) according to claim 10 or 11, wherein the brake system by means of the valve and / or Pumpenansteuereinrichtung ( 102 ) is additionally controllable in a first pressure build-up mode by the pressure compensation valve ( 56 ) in a closed state and the isolation valve ( 54 ) are controllable in the open state, and a pump ( 44b ) of the second brake circuit ( 12 ) in an active mode is controllable such that after the pressure-reducing mode in the first brake circuit ( 10 ) a brake pressure build-up on the response pressure of the storage volume ( 46 ) of the first brake circuit ( 10 ) is executable. Control device ( 100 ) according to claim 12, wherein the brake system by means of the valve and / or Pumpenansteuereinrichtung ( 102 ) is additionally controllable in a second pressure build-up mode by the isolation valve ( 54 ) is controllable in the closed state and the pump ( 44a ) of the first brake circuit ( 10 ) is controllable in an active mode so that after the limited-brake pressure build-up mode and / or the first pressure build-up mode, a pressure build-up in the first brake circuit ( 10 ) is executable. Control device ( 100 ) according to one of claims 10 to 13, wherein the control device ( 100 ) additionally a comparison device ( 114 ), by means of which a provided brake actuation strength ( 116 ) with regard to the actuation of the brake actuation element ( 22 ) with a predetermined threshold ( 118 , b0) is comparable and, if the brake actuation strength ( 116 ) below the threshold ( 118 , b0), a corresponding comparison signal ( 120 ) to the valve and / or pump driver ( 102 ), and wherein the valve and / or Pumpenansteuereinrichtung ( 120 ) is designed to control the brake system exclusively in the limited-brake pressure build-up mode and / or the pressure-reducing mode, provided that the brake actuation strength ( 116 ) below the threshold ( 118 , b0).

Images