DE102010029851A1 - A braking system for a vehicle and method for operating a braking system of a vehicle - Google Patents

Abstract

The invention relates to a brake system for a vehicle with a master brake cylinder (10), a brake medium reservoir (12), a first brake circuit with a first wheel brake cylinder (20a), which is hydraulically connected to the brake medium reservoir (12), and a second brake circuit with a second Wheel brake cylinder (20b) which is hydraulically connected to the master brake cylinder (10) at least in a first operating mode of the brake system, the second brake circuit to the first brake circuit via a first isolating valve (18) and to the master brake cylinder (24) via a second isolating valve (24). 10) is connected in such a way that the brake system can be switched into a second operating mode by opening the first isolating valve (18) and closing the second isolating valve (24), in which the second wheel brake cylinder (20b) is hydraulically connected to the brake medium reservoir (12) and the hydraulic connection between the master brake cylinder (10) and the second wheel brake cylinder (20b) un has broken. The invention also relates to a method for operating a brake system of a vehicle.

Description

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

State of the art

Electric and hybrid vehicles have a braking system designed for recuperative braking with an electric motor regeneratively operated in the regenerative braking. The electrical energy obtained in recuperative braking is preferably accelerated after caching. used of the vehicle. In this way, a power loss and energy consumption and a pollutant emission of the electric or hybrid vehicle occurring during frequent braking during a journey can be reduced.

However, the generator operation of the electric motor, for example of the electric drive motor, generally requires a certain minimum speed of the vehicle. A recuperative braking system is thus often not able to exert a regenerative braking torque on the wheels of the vehicle until the previously moving vehicle is at a standstill. Therefore, in addition to the recuperatively operated electric motor, a hybrid vehicle often also has a hydraulic brake system by means of which the declining braking effect of the recuperative brake can be compensated, at least in a low speed range. In this case, even with a full electrical energy storage, when the recuperative brake usually exerts no braking torque on the wheels, the entire braking torque can be applied via the hydraulic brake system.

On the other hand, it is desirable in some situations to exert the lowest possible hydraulic braking force on the wheels to a high. Recuperation achieved. For example, after switching operations, the decoupled generator is often activated as a recuperative brake in order to ensure reliable charging of the buffer and high energy savings.

In general, a driver prefers a total braking torque of his vehicle, which corresponds to its actuation of a brake input element, such as its brake pedal actuation, independently of an activation or deactivation of the recuperative brake. Some electric and hybrid vehicles therefore point. an automatic, which take over the task of the deceleration controller and the braking torque of the hydraulic brake system to the current braking torque of the recuperative brake to adjust so that a desired total braking torque is maintained. Examples of such an automatic are brake-by-wire brake systems, in particular EHB systems. However, due to their complex electronics, mechanics and hydraulics, brake-by-wire brake systems are relatively expensive.

As an alternative to the brake-by-wire braking systems describes the DE 10 2008 002 345 A1 a brake system comprising a decoupled from a master cylinder and connected to a brake fluid reservoir first brake circuit. This first brake circuit is assigned a wheel axle, on which a recuperative braking torque of a generator-operated electric motor can be exercised. Two additional brake circuits are coupled to the master cylinder so that the driver can brake directly into them and thus exert an immediate hydraulic brake torque on the wheels associated with the two other brake circuits.

Disclosure of the invention

The invention provides a braking system for a vehicle having the features of claim 1 and a method for operating a braking system of a vehicle having the features of claim 13.

In the brake system according to the invention, in the first operating mode, the driver has the option of actively slowing at least into the second wheel brake cylinder by means of an operation of a brake input element to increase an internal pressure of the master brake cylinder. In addition, in the second operating mode, a desired brake pressure in the second wheel brake cylinder can be decoupled / independently of an actuation of the brake input element by means of a brake medium transfer between the brake medium reservoir and the second wheel brake cylinder. Thus, the (second) hydraulic braking torque exerted by the second wheel brake cylinder can be set in the second operating mode such that there is a preferred overall hydraulic brake torque of all the wheel brake cylinders of the brake system.

In particular, the present invention makes it possible to blind a generator braking torque without the driver having to carry out any additional work. At least the second hydraulic braking torque of the second wheel brake cylinder can be set (decoupled) after decoupling from the master brake cylinder such that a time-varying generator braking torque is masked, or that an advantageous / preferred overall deceleration of the vehicle, for example, is maintained in accordance with the operation of the brake input member by the driver and / or a default of a speed control automatic, despite the time varying generator braking torque. In this case, a veneering process is ensured, which has no effect on the braking distance.

The present invention thus offers a cost-effective alternative to a conventional brake-by-wire brake system, which is very advantageous in particular for rear-wheel or all-wheel drive vehicles. However, the invention can also be used for front-wheel drive with a by-wire front axle.

However, the present invention is not limited to use in an electric or hybrid vehicle. For example, it is also possible to realize a lateral acceleration-dependent braking force distribution by means of the present invention. In a lateral acceleration-dependent braking force distribution, the braking force is divided at some wheels of the vehicle, preferably at the two rear axle wheels, according to a tamping force which occurs when driving around a curve. In this way, the coefficient of friction of the wheels, especially the coefficient of friction of the two rear wheels, can be adjusted to the lateral acceleration. The vehicle thus brakes more stable in turns. Preferably, a transverse acceleration determined by a sensor device is used to determine the at least one hydraulic braking torque to be actively set.

In addition, use of the present invention for dynamic corner braking is possible. In dynamic cornering braking, the braking force on a curve-inward wheel is increased relative to the braking force on a curve-outward wheel. This achieves a more dynamic driving behavior.

Furthermore, the invention may also be used for more advantageous braking during reverse travel. In particular, a better braking force distribution is achieved by increasing the braking force on the rear axle for a reverse drive. This is also called a backward braking force distribution. Especially with a slow reverse downhill this allows a much more stable braking performance.

Despite the possibility of actively setting at least the (second) hydraulic braking torque exerted by the second wheel brake cylinder, the driver can brake directly into the second wheel brake cylinder after switching the brake system into the first operating mode. Thus, the driver can easily perform sudden braking operations.

A hydraulic connection of a wheel brake cylinder to the master brake cylinder can be understood to mean that the respective wheel brake cylinder is connected to the master brake cylinder via at least one brake fluid-permeable brake medium-conducting component in an open state such that a brake fluid transfer between the master brake cylinder and the respective wheel brake cylinder can be realized is. For example, upon actuation of a brake input element for increasing a pressure in the master brake cylinder due to the hydraulic connection between the master brake cylinder and the at least one wheel brake cylinder, a brake pressure in the respective wheel brake cylinder can be established / increased. One can also designate this so that due to the hydraulic connection via the first supply line, the driver has the opportunity to slow down by pressing the brake input element directly into the respective wheel brake cylinder. Accordingly, when the pressure in the master brake cylinder decreases, the brake pressure in the respective wheel brake cylinder can be established / increased due to the hydraulic connection between the master brake cylinder and the at least one wheel brake cylinder.

Likewise, a hydraulic connectedness of a wheel brake cylinder / a hydraulic connection of a wheel brake cylinder to the brake fluid reservoir can also be interpreted such that a brake medium transfer between the brake fluid reservoir and the respective wheel brake cylinder can be realized via at least one brake fluid-permeable brake medium line component that can be shifted in an open state , Thus, via the hydraulic connection of a wheel brake cylinder with the brake medium reservoir, a brake pressure in the interior of the respective wheel brake cylinder can be reduced / reduced or increased / built up.

A particular advantage of the coupling ability of the second brake circuit to the first brake circuit instead of direct coupling of the second brake circuit to the brake medium reservoir is that the first brake circuit and the second brake circuit can form a common brake circuit after opening the first isolation valve. Thus, at least one component of the first brake circuit and / or the second brake circuit can be used for both brake circuits. By this multi-functionality of at least one component costs can be saved and / or the space requirement of the brake system can be reduced.

Advantageously, the brake system is by closing the first isolation valve and opening the second isolation valve in the first Operating mode switchable, in which the second wheel brake cylinder is hydraulically connected to the master cylinder and the hydraulic connection between the brake fluid reservoir and the second wheel brake cylinder is interrupted. This ensures easy switching of the brake system in the at least two operating modes.

In addition, the first brake circuit may be connected to the master brake cylinder via a third disconnect valve such that the first wheel brake cylinder is hydraulically connectable to the master brake cylinder via the opened third disconnect valve and the hydraulic connection between the master brake cylinder and the first wheel brake cylinder can be interrupted by closing the third disconnect valve , In this case, the first brake circuit can also be hydraulically connected to the master brake cylinder so that the driver can brake into the first wheel brake cylinder. The advantageous multi-functionality of the second brake circuits as brake circuit hydraulically connected to the master cylinder in the first operating mode and as hydraulically connected to the brake fluid reservoir brake circuit in the second operating mode is thus cost-expandable to the second brake circuit.

Preferably, the brake system comprises a control device, by means of which the brake system is switchable at least in the first operating mode and in the second operating mode, wherein in the first operating mode, the first separating valve is closed, the second separating valve and the third separating valve are opened, and in addition to second wheel brake cylinder of the first wheel brake cylinder is hydraulically connected to the master cylinder, and wherein in the second operating mode, the first isolation valve is opened, the second isolation valve and the third isolation valve are closed, and the hydraulic connection between the master cylinder and the first wheel brake cylinder in addition to the hydraulic connection between the master cylinder and the second wheel brake cylinder is interrupted. The advantages of such a braking system will be described in detail below.

In particular, the first isolation valve may be designed as a normally closed valve and the second isolation valve and the third isolation valve as normally open valves. This ensures an easy and fast switchability of the brake system at least between the first operating mode and the second operating mode.

In an advantageous embodiment, the brake system comprises a third brake circuit with a third wheel brake cylinder, which is hydraulically connected to the master brake cylinder, wherein the second brake circuit is connected via the second isolation valve to the third brake circuit. Thus, at least one component of the third brake circuit can be used to form a hydraulic connection of the second brake circuit to the master cylinder.

Furthermore, the brake system may comprise a fourth brake circuit with a fourth wheel brake cylinder, which is hydraulically connected to the master brake cylinder, wherein the first brake circuit is connected to the fourth brake circuit via the third isolation valve. This ensures increased usability of the first wheel brake cylinder.

In a further advantageous embodiment, the first brake circuit comprises a pump, by means of which a first brake medium volume from the brake medium reservoir in the first wheel brake cylinder is pumped and with which the second brake circuit is connected via the first isolation valve, that by means of the pump, a second brake fluid volume from the brake fluid reservoir is pumpable through the open first isolation valve in the second wheel brake cylinder. Thus, the pump can be used for at least two brake circuits.

As an alternative or in addition thereto, the first brake circuit may comprise a continuously adjustable valve, by means of which a first brake medium displacement from the first wheel brake cylinder is controllable in the brake medium reservoir and with which the second brake circuit is connected via the first isolation valve that by means of the continuously adjustable valve a second brake medium displacement from the second wheel brake cylinder through the opened first isolation valve is controllable in the brake fluid reservoir. The increased usability of the continuously adjustable valve also contributes to reducing the costs, in particular since a continuously adjustable valve is generally more expensive than a separating valve.

Advantageously, the brake system can have exactly twelve controllable valves, which can be controlled by means of an electrical signal provided by a control device of the brake system at least into an open state and into a closed state. The limitation of the required by the brake system valves, which are electrically switchable at least in the open state and in the closed state, to the number of twelve, reduces the requirements and / or the cost of an electronics suitable as a control device.

Preferably, the brake system comprises a generator, by means of which a first generator braking torque to a first Wheel brake cylinder assignable first wheel and / or a second generator braking torque on a second wheel brake cylinder assignable second wheel are exercisable. Since the hydraulic braking torques of the first wheel brake cylinder and the second wheel brake cylinder are actively adjustable, the first generator braking torque and / or the second generator braking torque can be blended in a simple manner.

The invention enables a brake system which can be used in a vehicle with X-brake circuit distribution. Thus, in contrast to conventional brake systems with a decoupled / decoupled from the master cylinder, the brake system according to the invention is not limited to use in vehicles with axle brake circuit distribution.

The brake system according to the invention enables adequate recuperation efficiency with optimal veneering processes at a reasonable cost. At the same time, the brake system according to the invention is compatible with hydraulic brake systems.

The advantages described in the above paragraphs are also ensured in a corresponding vehicle with such a brake system. Preferably, the first wheel brake cylinder and the second wheel brake cylinder are assigned to two arranged on a common axis wheels of the vehicle. In particular, the first wheel brake cylinder and the second wheel brake cylinder can be assigned to the wheels of the rear axle. This ensures a particularly safe and quickly executable deceleration of the vehicle.

The advantages described in the upper paragraphs can also be realized by means of a corresponding method.

Brief description of the drawings

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

1 a circuit diagram of an embodiment of the braking system; and

2 a flowchart for illustrating an embodiment of the method.

Embodiments of the invention

1 shows a circuit diagram of an embodiment of the braking system.

This in 1 schematically illustrated brake system is not only used in an electric or hybrid vehicle. Instead, the brake system can also be used in a vehicle, for example, to ensure a preferred distribution of braking force at the wheels of the vehicle when braking during cornering and / or a reverse drive. The notes on the applicability of the brake system in an electric or hybrid vehicle described below are merely exemplary.

The brake system includes a master cylinder 10 and an additional brake fluid reservoir 12 , Under the brake fluid reservoir 12 is not the master cylinder 10 to understand. Instead, under the brake fluid reservoir 12 a brake fluid volume or a brake fluid tank are understood, the internal pressure of which is independent of an internal pressure of the master cylinder 10 is adjustable or a fixed predetermined pressure, such as the atmospheric pressure corresponds. Between the master cylinder 10 and the brake fluid reservoir 12 For example, a brake fluid replacement bore, such as a sniffer bore, may be formed. The master cylinder 10 and the brake fluid reservoir 12 However, can also be formed without a hydraulic connection.

On the master cylinder 10 may be a brake input element 14 , such as a brake pedal, be coupled. As an alternative or as a supplement to a brake pedal and a differently designed brake input element 14 with the master cylinder 10 interact. By means of an actuation of the brake input element 14 For example, a driver of a vehicle equipped with the brake system can increase the pressure in an inner volume of the master cylinder 10 cause. A preferred embodiment is also a brake booster 16 on the master cylinder 10 coupled so that an increase in pressure in the inner volume of the master cylinder 10 also by means of the brake booster 16 is feasible. The brake booster 16 For example, it may be a hydraulic brake booster, in particular an active vacuum booster, and / or an electromechanical brake booster. It should be noted that the executability of the brake booster 16 is not limited to the examples listed here. For the brake booster 16 For example, any amplifier device that is capable of being used without an operation of the brake input element can be used 14 by the driver a brake pressure in the inner volume of the master cylinder 10 build. Preferably, the brake booster 16 a controllable / controllable brake booster 16 (active brake booster).

Optionally, at the brake input element 14 Also, a (not sketched) sensor be arranged so that an actuation of the brake input element 14 can be detected by the driver by means of the sensor. Preferably, the sensor is adapted to one of the actuation of the brake input member 14 to provide corresponding Bremskraft- and / or braking distance signal to a (not shown) evaluation / control electronics. An application for the information provided by the sensor will be discussed in more detail below. Cost-effective manner, the sensor can be a subunit of the brake booster 16 be. Likewise, the sensor may be a pedal travel sensor, a booster membrane path sensor, and / or a rod path sensor. The feasibility of the sensor is not limited to the examples listed here.

The brake system has a first brake circuit with a first wheel brake cylinder 20a on which hydraulically with the brake fluid reservoir 12 connected is. In addition, the brake system comprises a second brake circuit with a second wheel brake cylinder 20b , which via a first separating valve 18 with the first brake circuit and a second isolation valve 24 with the master cylinder 10 connected is. In a first operating mode of the brake system is the second wheel brake cylinder 20b over the opened second isolation valve 24 hydraulically with the master cylinder 10 connected, wherein at the same time the hydraulic connection between the brake fluid reservoir 12 and the second wheel brake cylinder 20b through the closed first isolation valve 18 is interrupted. In a second operating mode of the brake system is the second wheel brake cylinder 20b over the opened first separating valve 18 hydraulically with the brake fluid reservoir 12 is connected and the hydraulic connection between the master cylinder 10 and the second wheel brake cylinder 18b is through the closed second isolation valve 24 interrupted.

The first wheel brake cylinder 20a is a first bike 22a assigned. Accordingly, a second wheel 22b the second wheel brake cylinder 20b assigned. Via a brake medium transfer between the brake fluid reservoir 12 and the first wheel brake cylinder 20a may be a brake pressure in the first wheel brake cylinder 20a be actively set. In this way, one is on the first wheel 22a applied first hydraulic braking torque (to a preferred value) actively adjustable. If the first isolation valve 18 opened and the second isolation valve 24 are closed, can also be a brake pressure in the second wheel brake cylinder 20b be actively set, causing one on the second wheel 22b exerted second hydraulic braking torque can be determined. In addition, the driver has after closing the first isolation valve 18 and after opening (at least) the second isolation valve 24 the possibility of at least the second wheel brake cylinder 20b to slow yourself down.

In an advantageous embodiment, the first brake circuit via a third separating valve 32 so with the master cylinder 10 connected to that of the first wheel brake cylinder 20a over the opened third separating valve 32 hydraulically with the master cylinder 10 is connectable and the hydraulic connection between the master cylinder 10 and the first wheel brake cylinder 20a about closing the third isolation valve 32 is interruptible. This is also the first wheel brake cylinder 20a about opening the third isolation valve 32 so to the master cylinder 10 coupled, that by means of a pressure change in the inner volume of the master cylinder 10 a corresponding pressure change in the first wheel brake cylinder 20a is feasible. The driver has in this case after opening the third isolation valve 32 the additional possibility of the first hydraulic braking torque on the first wheel 22a via an actuation of the brake input element 14 directly to control. You can also rewrite this so that the driver after opening the third Tennventils 32 even / directly in the first wheel brake cylinder 20a can brake in.

Preferably, the brake system comprises a (not outlined) control device, by means of which the brake system is switchable at least in the first operating mode and in the second operating mode, wherein in the first operating mode, the first separating valve 18 is closed, the second isolation valve 24 and the third isolation valve 32 are open, and in addition to the second wheel brake cylinder 20b the first wheel brake cylinder 20a hydraulically with the master cylinder 10 connected is. Accordingly, in the second operating mode, the first isolation valve 18 opened and the second isolation valve 24 and the third isolation valve 32 closed. Thus, in the second mode of operation, the hydraulic connection between the master cylinder 10 and the first wheel brake cylinder 20a in addition to the hydraulic connection between the master cylinder 10 and the second wheel brake cylinder 20b interrupted. Such a control device can quickly switch the braking system back and forth between the first operating mode and the second operating mode, whose advantageous insertion options are discussed in more detail below.

In the illustrated embodiment, the brake system comprises a third brake circuit with a third wheel brake cylinder 26a and a fourth brake circuit with a fourth wheel brake cylinder 26b , which hydraulically with the master cylinder 10 are connected. This corresponds to the structure of the third brake circuit the structure of the fourth brake circuit. However, such an identical design of the third brake circuit and the fourth brake circuit is not necessary for the realization of the brake system.

On the master cylinder 10 For example, they are a first supply line 30a and a second supply line 30b arranged so that over the supply lines 30a and 30b a transfer of a brake medium, such as a brake gas and / or a brake fluid, between the interior of the master cylinder 10 , the third wheel brake cylinder 26a and / or the fourth wheel brake cylinder 26b is executable. Thus, via the first supply line 30a a first volume of the brake fluid from the master cylinder 10 in the third wheel brake cylinder 26a be transferred. Likewise, via the second supply line 30b a second volume of the brake fluid from the master cylinder 10 in the fourth wheel brake cylinder 26b be moved. The driver thus has the option of actuating the brake input element 14 directly into the third wheel brake cylinder 26a and in the fourth wheel brake cylinder 26b hineinzubremsen. About the direct braking by the driver, a third hydraulic braking torque of the third wheel brake cylinder 26a on a third wheel 28a and a fourth hydraulic braking torque of the fourth wheel brake cylinder 26b on a fourth wheel 28b activated / increased. Accordingly, the brake fluid from the third wheel brake cylinder 26a and the fourth wheel brake cylinder 26b back in the master cylinder 10 be fed back, whereby the third hydraulic braking torque and the fourth hydraulic braking torque are reduced / reduced.

Preferably, the second brake circuit via the second isolation valve 24 with the third brake circuit, in particular with the first supply line 30a , connected. Thus, with an opened second isolation valve 24 also the second wheel brake cylinder 20b via the first supply line 30a hydraulically with the master cylinder 10 connected. Preferably, the first brake circuit via the third isolation valve 32 connected to the fourth brake circuit.

The first bike 22a and the second wheel 22b , or the third wheel 28a and the fourth wheel 28b , Can be arranged on a common axis of a vehicle.

As will be explained in more detail below, the brake system described here offers particular advantages when using the wheels 22a and 22b as rear wheels. However, the applicability of the brake system described here is not on an axle-wise arrangement of the wheels 22a and 22b , or an axle-wise arrangement of the wheels 28a and 28 , limited. As an alternative to an axle arrangement, the wheels 22a and 22b for example, be arranged on one side of the associated vehicle or diagonally on the vehicle. It should be noted that the braking system shown is not limited to the fixed number of four wheels 22a . 22b . 28a and 28b is limited. Instead, the braking system can be extended so that a larger number of wheels can be braked.

At the in 1 shown brake system, the first brake circuit, a first pump 34 on, by means of which a first brake medium volume from the brake medium reservoir 12 in the first wheel brake cylinder 22a is pumpable. In addition, the second brake circuit is so via the first isolation valve 18 with the first pump 34 Connected that by means of the pump 34 also a second brake medium volume from the brake medium reservoir 12 through the opened first separating valve 18 in the second wheel brake cylinder 20b is pumpable. Thus, the first pump 34 be used both for an active building / increasing the first hydraulic braking torque and for an active building / increasing the second hydraulic braking torque. Due to the increased applicability of the pump 34 The cost of the braking system can be reduced.

Likewise, the first brake circuit comprises a continuously adjustable valve 36 , by means of which a first brake medium displacement from the first wheel brake cylinder 20a in the brake fluid reservoir 12 is controllable. At the same time, the second brake circuit is via the first separating valve 18 so with the continuously adjustable valve 36 Connected that by means of the continuously adjustable valve 36 also a second brake medium displacement from the second wheel brake cylinder 20b through the opened first separating valve 18 in the brake fluid reservoir 12 is controllable. Such a design of the first brake circuits and the second brake circuit thus allows the saving of a further continuously adjustable valve, which would be necessary for the second brake circuit conventionally. The first isolation valve 18 , by means of which a further continuously adjustable valve can be saved, is easier to switch, less expensive and requires less production effort than a continuously adjustable valve.

By connecting the second brake circuit to the first brake circuit via the first isolation valve 18 ensures that the two brake circuits after closing the first isolation valve 18 act as two separate brake circuits. At the same time, it can be opened by opening the first isolation valve 18 be sure that the first pump 34 and the continuously adjustable valve 36 for both brake circuits, especially for the first wheel brake cylinder 20a and for the second wheel brake cylinder 20b , are usable.

Below is the in 1 illustrated particularly advantageous embodiment of the brake system described. However, the formation of an advantageous braking system is not limited to the features mentioned below.

The third brake circuit and the fourth brake circuit each have a pump 38a or 38b on. The first pump 34 , the second pump 38a of the third brake circuit and / or the third pump 38b of the fourth brake circuit can be on a common shaft 40 an engine 42 be arranged. This reduces the engine number of the brake system. The first pump 34 can be a three-piston pump. In this case, an embodiment of the second pump 38a and / or the third pump 38b advantageous as a single-piston pump. It is noted, however, that for the pumps 34 . 38a and 38b Other pump types with one or more pistons, asymmetric pumps and / or gear pumps can be used.

In the illustrated brake system, the third brake circuit and the fourth brake circuit each have their own Radeinlassventil 44a or 44b and its own wheel outlet valve 46a or 46b , The respective wheel inlet valve 44a or 44b is about one in a supply line 30a or 30b arranged branching point 48a or 48b and one of them continuing leadership 50a or 50b hydraulically with the master cylinder 10 connected. From every wheel inlet valve 44a and or 44b leads a line 54a or 54b to the associated wheel brake cylinder 26a or 26b , Parallel to each wheel inlet valve 44a and 44b can be a bypass line with a check valve 52a or 52b be educated. The respective check valve 52a or 52b is aligned so that a brake fluid transfer from the master cylinder 10 to the associated wheel brake cylinder 26a or 26b is prevented. In the line 54a or 54b is each a branch point 56a or 56b arranged, from which another line 58a or 58b to the associated Radauslassventil 46a or 46b leads. The wheel outlet valve 46a or 46b is over an additional line 60a or 60b with the suction side of the pump 38a or 38b connected to the respective brake circuit. The delivery side of the respective pump 38a and 38b is via the first supply line 30a or via the second supply line 30b with the master cylinder 10 connected. By means of another branching point 62 or 62b in the pipes 60a and 60b each is a storage chamber 64a or 64b connected to the third brake circuit and to the fourth brake circuit.

The second isolation valve 24 and the third isolation valve 32 are each about a branch point 66a or 66b with the associated supply line 30a or 30b connected. Such a coupling of the first brake circuit to the fourth brake circuit and the second brake circuit to the third brake circuit is for a uniform braking in the first brake circuit and the second brake circuit upon actuation of the brake input member 14 by the driver after closing the first isolation valve 18 and opening the second isolation valve 24 and the third isolation valve 32 advantageous. In particular, this ensures a good brake feel (pedal feel) for the driver. However, the present invention is not limited to such a coupling of the first brake circuit to the fourth brake circuit and the second brake circuit to the third brake circuit.

About the branch point 66a can also be a pressure sensor 67 be connected to the third brake circuit. In this way, a pressure in the third brake circuit can be determined and a corresponding pressure in the fourth brake circuit derived.

From the third isolation valve 32 leads a line 68 to a first wheel brake cylinder 20a associated Radeinlassventil 70a , Also a second wheel brake cylinder 20b associated wheel inlet valve 70b is over a line 72 connected to the second isolation valve. The wheel inlet valves 70a and 70b are each over a line 76a or 76b with the associated wheel brake cylinder 20a or 20b connected. Parallel to each of the wheel inlet valves 70a and 70b is a bypass line with a check valve 74a or 74b educated. The respective check valve 74a or 74b is aligned so that a brake fluid transfer from the brake fluid reservoir 12 , or from the second isolation valve 24 or the third isolation valve 32 to the associated wheel brake cylinder 20a or 20b is prevented.

About one in the line 76a or 76b arranged branching point 78a or 78b and one each lead away 80a or 80b is also each a wheel brake cylinder 20a or 20b associated wheel outlet valve 82a or 82b associated with this. One from the wheel outlet valve 82a the first brake circuit leading line 84a and one of the wheel outlet valve 82b the second brake circuit leading line 84b lead to a common branching point 86 , The common branch point 86 is over a line 88 with the suction side of the first pump 34 connected. From the delivery side of the first pump 34 leads a line 90 to the continuously adjustable valve 36 , which via a suction line 92 with the brake fluid reservoir 12 connected is. Parallel to the continuously adjustable valve 36 is a line running 94 , which have a branching point 96 in the suction line 92 and via a branch point 98 into the pipe 88 opens, so that the suction side of the first pump 34 even with a closed, continuously adjustable valve 36 is hydraulically connected to the brake fluid reservoir.

The delivery side of the first pump 34 is over a line 100 with a branching point 102 in the pipe 68 between the third isolation valve 32 and the wheel inlet valve 70a connected to the first brake circuit. Thus, there is a brake medium transfer between the wheel inlet valve 70a the first brake circuit, the delivery side of the first pump 34 and the continuously adjustable valve 36 continuously ensured.

In contrast, the line 72 that of the second isolation valve 24 and to the wheel inlet valve 70b of the second brake circuit, exclusively via the first isolation valve 18 with the delivery side of the first pump 34 and the continuously adjustable valve 36 connected. This is feasible by the first isolation valve 18 over a line 104 with one in the line 100 arranged branching point 106 is connected. From the first isolation valve 18 leads a line 108 to the wheel inlet valve 70b of the second brake circuit. The administration 72 from the second isolation valve 24 flows into a branching point 110 in the pipe 108 , About another branch point is a pressure sensor 112 connectable to the second brake circuit, by means of which a pressure in the second brake circuit can be determined and a corresponding pressure in the first brake circuit can be deduced.

You can also rewrite the brake system so that each of the wheel brake cylinders 20a . 20b . 26a and 26b is arranged in a separate brake circuit. In this case, the first brake circuit with the first wheel brake cylinder 20a and the second brake circuit with the second wheel brake cylinder 20b about opening the first isolation valve 18 be converted into a common brake circuit. The first wheel brake cylinder 20a and the second wheel brake cylinder 20b in this case have a common pressure supply / pressure increase component by means of the first pump 34 and a common pressure reducing component by means of the continuously adjustable valve 36 , In addition, the first wheel brake cylinder 20a and the second wheel brake cylinder 20b about closing the first isolation valve 18 and via a (simultaneous) opening of the second isolation valve 24 and the third isolation valve 32 be connected to the third brake circuit and the fourth brake circuit so that the driver via the master cylinder 10 can brake directly into it. The technology according to the invention thus enables a structure changeover between a brake system with X brake circuit split and a brake system with three brake circuits.

The valves 18 . 24 . 32 . 36 . 44a . 44b . 46a . 46b . 70a . 70b . 82a and 82b are controllable / switchable by means of an electrical signal provided by a control device of the brake system at least in an open state and in a closed state. The limitation of the required by the brake system controllable / switchable valves on the twelve valves 18 . 24 . 32 . 36 . 44a . 44b . 46a . 46b . 70a . 70b . 82a and 82b reduces the cost of the control device. Advantageously, the first separating valve 18 as a normally closed valve and the second isolation valve 24 and the third isolation valve 32 are formed as normally open valves. This facilitates the switching of the brake system from the first operating mode to the second operating mode by a (simultaneous / common) energizing the isolation valves 18 . 24 and 32 , In a particularly advantageous embodiment, the first separating valve 18 , the steadily adjustable valve 36 and the wheel outlet valves 46a . 46b . 82a and 82b designed as normally closed valves. In this case, it is advantageous, the second isolation valve 24 , the third isolation valve 32 and the wheel inlet valves 44a . 44b . 70a and 70b Form as normally open valves. Thus, the driver has even with a malfunction of all valves 18 . 24 . 32 . 36 . 44a . 44b . 46a . 46b . 70a . 70b . 82a and 82b the possibility, at least for a transitional phase in the wheel brake cylinder 20a . 20b . 26a and 26b to slow it down and bring the vehicle to a standstill.

In the first operating mode of the brake system (with a closed isolation valve 18 and open isolation valves 24 and 32 ), the driver via an operation of the brake input element 14 directly into all wheel brake cylinders 20a . 20b . 26a and 26b inside curb. In the second operating mode (with an open separating valve 18 and closed isolation valves 24 and 32 ) are the first wheel brake cylinder 20a and the second wheel brake cylinder 20b from the master cylinder 10 decoupled. Thus, in the second mode of operation, there is the possibility of being on the first wheel 22a exerted first hydraulic braking torque and that on the second wheel 22b exerted second hydraulic braking torque by means of the first pump 34 and the continuously adjustable valve 36 actively set. When the first hydraulic braking torque and the second hydraulic braking torque are actively set, for example, a braking request of the driver detected via an above-mentioned suitable sensor system and / or specification of a vehicle speed automatic control can be taken into account. Subsequently, the first pump 34 and the continuously adjustable valve 36 be controlled so that the braking request / the default corresponding sum of the first hydraulic braking torque and the second hydraulic braking torque is present. Setting the desired sum of the wheels 22a and 22b applied hydraulic braking torque can by means of a Δp control of the continuously adjustable valve 36 done with a high accuracy. As an alternative, a pressure control by means of at least one of the pressure sensors 67 and 112 respectively.

By means of operating the first pump 34 is the sum of the wheels 22a and 22b applied hydraulic braking torques steigerbar. Keeping the sum of the wheels constant 22a and 22b applied hydraulic braking torques consumed only for the permanent closing of the second isolation valve 24 and the third isolation valve 32 needed energy. For a reduction in the sum of the wheels 22a and 22b applied braking torque is the continuously adjustable valve 36 so controlled that a volume from the first wheel brake cylinder 20a and / or the second wheel brake cylinder 20b over the at least partially opened continuously adjustable valve 36 back to the brake fluid reservoir 12 flows.

At the in 1 brake system shown can be a brake pressure in at least one of the wheel brake cylinder 20a . 20b . 26a and 26b even without an operation of the brake input element 14 by means of the brake booster 16 being constructed. This can be carried out, for example, via a vacuum brake booster with controllable actuating device and / or by means of an electromechanical brake booster.

Furthermore, for a particularly fast braking of the vehicle additionally there is the possibility of all isolation valves 18 . 24 and 32 to open and by means of the first pump 34 in all four wheel brake cylinders 20a . 20b . 26a and 26b to promote a volume. This can be done with simultaneous operation of the brake booster 16 to increase the internal pressure in all four brake circuits 20a . 20b . 26a and 26b respectively.

This in 1 reproduced brake system has an advantageous safety standard. For example, in case of a leak in one of the four brake circuits, there are still three brake circuits available for braking the vehicle. Thus, after the failure of one of the four brake circuits, the driver still has the possibility of bringing the vehicle safely to a standstill.

Moreover, in the brake system described herein, a failure of the electronics, for example, due to an electrical fault in the controller and / or an interruption in the power supply, triggers an automatic closure of the first isolation valve 18 and an automatic opening of the isolation valves 24 and 32 , or an automatic switching of the brake system in the first operating mode, from. This forms two separate brake circuits in X-brake circuit distribution. The driver is thus still able, by means of the master cylinder 10 in all four brake circuits to slow down. Thus, the vehicle can still be brought to a safe standstill despite the failure of the electronics.

A particularly advantageous possibility of using the second operating mode is described below:
In an advantageous development, the brake system comprises a (not outlined) generator, by means of which a first generator braking torque to the first wheel 22a and / or a second generator braking torque on the second wheel 22b exercisable. Advantageously, the brake system is switched to an activation of the generator for blending the first generator limit torque and / or the second generator limit torque in the second operating mode.

Preferably, during the veneering by means of a sensor, which is preferably a subunit of the brake booster 16 is, a braking request / braking force request of the driver detected and provided as appropriate information to an evaluation / control device. Taking into account the information provided, the at least one generator braking torque and optionally the third and / or fourth hydraulic braking torque, a preferred first and / or second hydraulic braking torque is subsequently determined by the evaluation device / control device. Thereafter, a corresponding to the preferred first and / or second hydraulic braking torque internal pressure by means of the first pump 34 and the continuously adjustable valve 36 in the first wheel brake cylinder 20a and / or in the second wheel brake cylinder 20b be actively set. Such activation of the first pump 34 and the continuously adjustable valve is easily executable by means of a low-cost electronics. A sufficient Rekuperationseffizienz is thus ensured in the present invention at an acceptable cost.

For blending at least one time-increasing first generator torque limit and / or second generator torque limit can at an open first isolation valve and closed isolation valves 24 and 32 by means of the continuously adjustable valve 36 the internal pressure (brake pressure) in the wheel brake cylinders 20a and 20b be reduced so that the time decrease of Sum of the first hydraulic braking torque and the second hydraulic braking torque corresponds to the increase in time of the at least one generator braking torque. A time decrease of the first generator braking torque and / or the second generator braking torque can be achieved by operating the first pump 34 for conveying a volume of brake fluid into at least one of the wheel brake cylinders 20a and 20b be compensated. Due to the present in the second operating mode closed isolation valves 24 and 32 These veneering processes are imperceptible to the driver. At the same time, the driver has also after the decoupling of the first wheel brake cylinder 20a and the second wheel brake cylinder 20b from the master cylinder 10 still the possibility to directly into the third wheel brake cylinder 26a and to brake into the fourth wheel brake cylinder.

Advantageously, the braking system with the generator also includes a controllable / controllable brake booster 16 , By means of such a brake booster 16 For example, an assisting force provided can be easily adapted to interrupting the hydraulic connection between the master cylinder and the first wheel brake cylinder and / or the hydraulic connection between the master cylinder and the second wheel brake cylinder. For example, the support force of the controllable / controllable brake booster 16 be reduced in a switching of the brake system in the second operating mode. The driver takes in this case, the interruption of the hydraulic connection between the master cylinder and the first wheel brake cylinder and / or the hydraulic connection between the master cylinder and the second wheel hardly / not true. This ensures additional ease of use of the brake input element 14 for the driver when using the braking system described here.

2 shows a flowchart for illustrating an embodiment of the method.

The method is executable for operating a brake system of a vehicle having a master brake cylinder, a brake fluid reservoir, a first brake circuit with a first wheel brake cylinder, which is hydraulically connected to the brake fluid reservoir, and a second brake circuit with a second wheel brake cylinder, which via a first isolation valve with the first Brake circuit and connected via a second isolation valve to the master cylinder. By means of the method described below, for example, the braking system described above can be operated. The feasibility of the method described here is not limited to this braking system.

In a method step S1, the first isolation valve is closed and the second isolation valve is opened. The brake system is thereby switched to a first operating mode, in which the second wheel brake cylinder is hydraulically connected to the master brake cylinder and the hydraulic connection between the brake fluid reservoir and the second wheel brake cylinder is interrupted. The driver thus has the opportunity to brake directly into the second wheel brake cylinder.

In a second method step S2, the brake system can be switched to a second operating mode in which the first separating valve is opened and the second separating valve is closed. In this second operating mode, the second wheel brake cylinder is hydraulically connected to the brake fluid reservoir. The hydraulic connection between the master cylinder and the second wheel brake cylinder is interrupted. In the second operating mode, therefore, at least the brake pressure (internal pressure) present in the second wheel brake cylinder can be actively built up.

The numbering of method steps S1 and S2 does not specify a time sequence for carrying out the method described here. Instead, the method step S2 can also be carried out before method step S1. Likewise, each of the method steps S1 and S2 can be repeated as often as desired.

In an advantageous development of method step S1, when the brake system is switched to the first operating mode, a third separating valve, via which the first brake circuit is connected to the master brake cylinder, is opened. In this way, the first wheel brake cylinder is hydraulically connected to the master cylinder in addition to the second wheel brake cylinder. Preferably, in the switching of the brake system from the first operating mode to the second operating mode, the first isolating valve designed as a normally closed valve, the second isolating valve designed as a normally open valve and the third isolating valve designed as a normally open valve are simultaneously energized. Accordingly, in the method step S2 when switching the brake system into the second operating mode, the third separating valve 32 getting closed. Thus, the hydraulic connection between the master cylinder and the first wheel brake cylinder is interrupted in addition to the hydraulic connection between the master cylinder and the second wheel brake cylinder. With regard to the advantages of the realization of the first operating mode and of the second described here Operating mode is referred to the above.

The basis of the 1 described method steps and functions are also transferable to the method presented here. However, one of the many possibilities for extending the procedure is not discussed here.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102008002345 A1 [0006]

Claims (15)

Brake system for a vehicle with a master cylinder ( 10 ); a brake fluid reservoir ( 12 ); a first brake circuit with a first wheel brake cylinder ( 20a ), which hydraulically with the brake medium reservoir ( 12 ) connected is; and a second brake circuit with a second wheel brake cylinder ( 20b ), which at least in a first operating mode of the brake system hydraulically connected to the master cylinder ( 10 ) connected is; characterized in that the second brake circuit via a first separating valve ( 18 ) with the first brake circuit and via a second isolation valve ( 24 ) with the master cylinder ( 10 ) is connected so that the brake system by opening the first isolation valve ( 18 ) and closing the second isolation valve ( 24 ) is switchable in a second operating mode, in which the second wheel brake cylinder ( 20b ) hydraulically with the brake medium reservoir ( 12 ) and the hydraulic connection between the master cylinder ( 10 ) and the second wheel brake cylinder ( 20b ) is interrupted. A braking system according to claim 1, wherein the brake system is closed by closing the first isolation valve (10). 18 ) and opening the second isolation valve ( 24 ) is switchable in the first operating mode, in which the second wheel brake cylinder ( 20b ) hydraulically with the master cylinder ( 10 ) and the hydraulic connection between the brake medium reservoir ( 12 ) and the second wheel brake cylinder ( 20b ) is interrupted. Brake system according to claim 1 or 2, wherein the first brake circuit via a third separating valve ( 32 ) so with the master cylinder ( 10 ), that the first wheel brake cylinder ( 20a ) over the opened third separating valve ( 32 ) hydraulically with the master cylinder ( 10 ) is connectable and the hydraulic connection between the master cylinder ( 10 ) and the first wheel brake cylinder ( 20a ) via a closing of the third separating valve ( 32 ) is interruptible. A braking system according to claim 3, wherein the brake system is a. Control device, by means of which the brake system is switchable at least in the first operating mode and in the second operating mode, wherein in the first operating mode, the first separating valve ( 18 ) is closed, the second isolation valve ( 24 ) and the third separating valve ( 32 ) are open, and in addition to the second wheel brake cylinder ( 20b ) the first wheel brake cylinder ( 20a ) hydraulically with the master cylinder ( 10 ), and wherein in the second operating mode the first isolation valve ( 18 ), the second isolation valve ( 24 ) and the third separating valve ( 32 ) are closed, and the hydraulic connection between the master cylinder ( 10 ) and the first wheel brake cylinder ( 20a ) in addition to the hydraulic connection between the master cylinder ( 10 ) and the second wheel brake cylinder ( 20b ) is interrupted. Brake system according to claim 4, wherein the first separating valve ( 18 ) as a normally closed valve and the second isolation valve ( 24 ) and the third separating valve ( 32 ) are designed as normally open valves. Brake system according to one of the preceding claims, wherein the brake system comprises a third brake circuit with a third wheel brake cylinder ( 26a ), which hydraulically with the master cylinder ( 10 ), and wherein the second brake circuit via the second isolation valve ( 24 ) is connected to the third brake circuit. Brake system according to one of the preceding claims, wherein the brake system, a fourth brake circuit with a fourth wheel brake cylinder ( 26b ), which hydraulically with the master cylinder ( 10 ), and wherein the first brake circuit via the third isolation valve ( 32 ) is connected to the fourth brake circuit. Braking system according to one of the preceding claims, wherein the first brake circuit is a pump ( 34 ), by means of which a first brake medium volume from the brake medium reservoir ( 12 ) in the first wheel brake cylinder ( 20a ) is pumpable and with which the second brake circuit so via the first isolation valve ( 18 ), that by means of the pump ( 34 ) a second brake medium volume from the brake medium reservoir ( 12 ) through the opened first isolation valve ( 18 ) in the second wheel brake cylinder ( 20b ) is pumpable. Brake system according to one of the preceding claims, wherein the first brake circuit a continuously adjustable valve ( 36 ), by means of which a first brake medium displacement from the first wheel brake cylinder ( 20a ) into the brake medium reservoir ( 12 ) is controllable and with which the second brake circuit so via the first isolation valve ( 18 ) is connected by means of the continuously adjustable valve ( 36 ) a second brake medium displacement from the second wheel brake cylinder ( 20b ) through the opened first isolation valve ( 18 ) into the brake medium reservoir ( 12 ) is controllable. Brake system according to one of the preceding claims, wherein the brake system has exactly twelve controllable valves ( 18 . 24 . 32 . 36 . 44a . 44b . 46a . 46b . 70a . 70b . 82a . 82b ), which by means of a provided electrical signal at least in an open state and in a closed state are controllable. Brake system according to one of the preceding claims, wherein the brake system comprises a generator, by means of which a first generator braking torque to a first wheel brake cylinder ( 20a ) assignable first wheel ( 22a ) and / or a second generator braking torque to a second wheel brake cylinder ( 20b ) assignable second wheel ( 22b ) are exercisable. Vehicle with a braking system according to one of the preceding claims. Method for operating a brake system of a vehicle with a master brake cylinder ( 10 ), a brake fluid reservoir ( 12 ), a first brake circuit with a first wheel brake cylinder ( 20a ), which hydraulically with the brake medium reservoir ( 10 ), and a second brake circuit with a second wheel brake cylinder ( 20b ), which via a first separating valve ( 18 ) with the first brake circuit and via a second isolation valve ( 24 ) with the master cylinder ( 10 ), comprising the step of: closing the first isolation valve ( 18 ) and opening the second isolation valve ( 24 ) for switching the brake system in a first operating mode, in which the second wheel brake cylinder ( 20b ) hydraulically with the master cylinder ( 10 ) and the hydraulic connection between the brake medium reservoir ( 12 ) and the second wheel brake cylinder ( 20b ) is interrupted (S1); or opening the first isolation valve ( 18 ) and closing the second separating valve ( 24 ) for switching the brake system into a second operating mode, in which the second wheel brake cylinder ( 20b ) hydraulically with the brake medium reservoir ( 12 ) and the hydraulic connection between the master cylinder ( 10 ) and the second wheel brake cylinder ( 20b ) is interrupted (S2). The method of claim 13, wherein when switching the brake system in the first operating mode, a third isolation valve ( 32 ), via which the first brake circuit with the master cylinder ( 10 ) is opened, and in addition to the second wheel brake cylinder ( 20b ) the first wheel brake cylinder ( 20a ) hydraulically with the master cylinder ( 10 ), and wherein when the brake system is switched to the second operating mode, the third isolation valve ( 32 ) and the hydraulic connection between the master cylinder ( 10 ) and the first wheel brake cylinder ( 20a ) in addition to the hydraulic connection between the master cylinder ( 10 ) and the second wheel brake cylinder ( 20b ) is interrupted. A method according to claim 14, wherein, when the brake system is switched from the first operating mode to the second operating mode, the first separating valve formed as a normally closed valve 18 ), which is designed as a normally open open valve second isolation valve ( 24 ) and a valve designed as a normally open valve third separating valve ( 32 ) are energized simultaneously.

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