DE102021209615A1 - braking system - Google Patents

Abstract

The invention relates to a brake system for a motor vehicle, the brake system having two electrohydraulic actuators and two brake circuits and an electrically activatable circuit connection device, the electrically activatable circuit connection device separating the connection between the two brake circuits in its inactive state.

Description

The invention relates to a braking system for a motor vehicle.

Braking systems are typically used in motor vehicles to decelerate them in a controlled manner. In particular, brake systems can be embodied as hydraulic brake systems, with hydraulic actuators typically being used to pressurize brake fluid and thus actuate wheel brakes.

It is an object of the invention to provide a braking system for a motor vehicle which is designed as an alternative or better than known designs.

According to the invention, this is achieved by a braking system according to claim 1 . Advantageous configurations can be found in the dependent claims, for example. The content of the claims is made part of the content of the description by express reference.

The invention relates to a braking system for a motor vehicle. The brake system has an electrohydraulic actuator for displacing and pressurizing pressure medium. The braking system includes a second electro-hydraulic actuator for displacing and pressurizing fluid. The brake system has a first brake circuit and a second brake circuit. In addition, the braking system has an electrically activatable circuit connection device. The first brake circuit is connected to the first actuator and the second actuator. The second brake circuit is connected to the first actuator and the second actuator. The circuit connection device is set up to connect the first brake circuit to the second brake circuit when it is activated, the circuit connection device being connected on the one hand to the first brake circuit between the first actuator and the second actuator and on the other hand to the second brake circuit between the first actuator and the second actuator is connected. In its inactive state, the circuit connection device separates the connection between the two brake circuits. It can thus connect the two brake circuits, in particular in a switchable manner.

By means of such a brake system, pressure can first be built up in the pressure medium with the electrohydraulic actuators, which pressure actuates hydraulic wheel brakes and can thus bring about a deceleration of a motor vehicle that can be controlled via actuator pressures. A displacement of a pressure medium is understood in particular to mean that the pressure medium is displaced into the respective wheel brakes, since due to the unavoidable mechanical resilience of a wheel brake, a pressure increase only takes place in combination with a pressure medium volume increase in the respective wheel brake cylinder. In the event of a leak in a brake circuit, a separation between the two brake circuits can be brought about by simply switching off an energization of the circuit connection device, so that braking with the brake circuit in which no leak occurs is still possible.

The electrohydraulic actuators can pressurize the pressure medium and move it into the wheel brakes, in particular in response to a braking force request from a driver or an electronic unit such as a driver assistance system or a unit for autonomous driving. By activating the circuit connection device, which typically means energizing the circuit connection device, the two brake circuits can be connected to one another, as a result of which pressure equalization between the brake circuits is made possible. By connecting the two actuators to both brake circuits, they can basically both be used for both brake circuits.

The connections mentioned are typically to be understood as fluidic, i.e. a connection between the first actuator and the second actuator typically means that a connection is made to a connecting line between the two actuators, in particular in the respective brake circuit.

A total of components that belong to a coherent hydraulic pressure medium path or are connected to it can in particular be understood as a brake circuit. For example, instead of saying that something is connected to a brake circuit, it can also be said that something is part of the brake circuit.

An actuator can in particular be understood to mean a device for “providing” (providing) a movement variable (displacement, angle, volume displacement, . . . ) and/or a force variable (force, torque, pressure, . . . ). For this purpose, the actuator typically has a control input and an energy supply input. Typically, the actuator takes the energy required for the positioning process from the energy supply input. An electromechanical actuator typically includes an electromechanical converter and an electrical converter control. The converter control includes, for example, control electronics and power electronics (= electronics for control of energy flows). The control input is typically connected to the control electronics inside the actuator.

The circuit connection device can be activated in particular by charging the circuit connection device with an electric current. This allows easy activation, but also ensures automatic deactivation in the event of a power failure.

The circuit connection device can in particular have a first valve and a second valve. The first valve and the second valve can in particular be connected in series. The first valve can in particular be connected to the first brake circuit and be designed as a seat valve, with an electromagnetically forceable valve body which is additionally acted upon by the pressure of the first brake circuit in the direction of the valve seat. The second valve can in particular be connected to the second brake circuit and be designed as a seat valve, with an electromagnetically forceable valve body which is additionally acted upon by the pressure of the second brake circuit in the direction of the valve seat.

Such an embodiment can in particular ensure that the circuit connection device is closed from both brake circuits by the pressure present in the brake circuit, which improves the closing process and can ensure a particularly high level of tightness. The use of two valves can also fundamentally increase safety.

In an alternative embodiment, the circuit connection device can have only one valve. This corresponds to a simple implementation.

In particular, when it is actuated in the first brake circuit and the second brake circuit, the first actuator can emit a pressure medium volume output that is proportional to or identical to one another. Likewise, when the second actuator is actuated in the first brake circuit and the second brake circuit, it can deliver a pressure medium volume output that is proportional to or identical to one another. A uniform loading of the brake circuits is achieved by such designs.

The first actuator can in particular be designed as an electromechanically actuated piston-cylinder arrangement, in whose cylinder or cylinders the pressure medium to be delivered is stored in the unactuated state. The second actuator can be designed in particular as a motor-pump module that draws in pressure medium from a first brake circuit section in order to release pressure medium into a second brake circuit section. As a result, pressure can be built up, for example, by means of the first actuator in normal operation and/or in other operating modes, for example operating modes with ABS, TCS or ESC interventions or special operating modes to ensure maximum residual functionality when errors are detected, the pressure from the second actuator be reinforced or the second actuator can work as the sole pressure generating entity.

The second actuator can in particular have one cylinder or several or a large number of cylinders with pistons, the cylinder or each piston-cylinder unit being connected to the first brake circuit and/or the second brake circuit or the first brake circuit and/or is assigned to the second brake circuit. In particular, a cylinder together with a piston can form a cylinder-piston unit. This allows easy build up of pressure and shifting of volume in both brake circuits while maintaining circuit separation with the second actuator.

The first actuator can in particular have a first cylinder with a first piston and a second cylinder with a second piston. The first cylinder can in particular be connected to the first brake circuit and the second cylinder can be connected in particular to the second brake circuit. This enables the two brake circuits to be acted upon in a simple manner and a ratio of the delivery volumes to one another to be set in a simple manner.

According to one embodiment, the first cylinder and the second cylinder can be arranged parallel to one another. The first piston and the second piston can, for example, be rigidly connected to one another. Alternatively, the first piston and the second piston can be actuated together by a swivel arm. In particular, the swivel arm can move the first piston and the second piston in different directions and/or in opposite directions to one another. Such designs allow a reliable mechanical actuation with a high degree of variability in the design.

In particular, the brake system can have an electronic stability module, which partially forms the first brake circuit and the second brake circuit and/or which has a motor-pump module, which forms the second actuator. Provision can also be made for an electronic stability module to have hydraulic sections which are exclusively associated with the first brake circuit and hydraulic sections which are disjunctive thereto and which are exclusively associated with the second brake circuit. As a result, separate components can be used are, which can be positioned freely in particular relative to other units of the braking system. This allows, for example, better utilization of the installation space available in an engine compartment.

The first actuator can be, for example, an electrohydraulic pressure generator and/or a linear actuator or a combination of an electromotive linear actuator with a hydraulic master cylinder. This has proven itself for typical designs.

The brake system can have a pedal-actuated brake cylinder, which is connected to at least one of the two brake circuits. This allows an immediate pedal-controlled pressure build-up. This can be used in particular in addition to the pressure build-up already mentioned with the aid of the actuators. In particular, a hydraulic fallback level can be implemented in a simple manner by means of a pedal-actuated brake cylinder, since in this case a direct pedal-controlled pressure build-up is possible even in the event of a complete power failure in the vehicle electrical systems. In particular, the pedal-operated brake cylinder can be connected to both brake circuits.

According to one embodiment, the brake system has a simulator and at least one isolating valve, the brake cylinder being connected exclusively to the simulator when the isolating valve is closed and the brake cylinder being connected to one or both brake circuits when the isolating valve is open. This allows brake-by-wire operation, i.e. a driver steps into the simulator during a pedal-controlled braking process and the pressure is generated independently by means of the actuators already mentioned.

In particular, in an emergency operating mode, the hydraulic function of the pedal brake cylinder can be used to feed a pressure medium volume corresponding to the pedal actuation into the connected brake circuit or circuits. This can be relevant in particular when neither of the two actuators that are regularly used is operational. To ensure that the volume displaced from the master brake cylinder when the pedal is actuated does not disturb the actuator volume balance, the volume of pressure medium displaced by the pedal cylinder can be routed to a hydraulic simulator during regular operation, which simulates the volume absorption of wheel brakes and thus allows the brake pedal to exhibit the necessary flexibility for a comfortable brake pedal feel .

In other words, a braking system with two separate electrohydraulic modules that are hydraulically connected in series is proposed. The first module can provide two brake circuit pressures, for example. The second module can be a conventional ESC unit that has two brake circuit connections and four wheel circuit connections. The first module can have an electrohydraulic actuator with two hydraulic connections assigned to the brake circuits, it being possible for the actuator to be designed in such a way that the pressure medium volume output of the two connections is mechanically rigidly coupled to one another. In particular, the pressure medium volumes released at the two connections can be proportional to one another. Furthermore, the first module can include a normally closed circuit connecting valve, with which the two brake circuits can be hydraulically connected to one another. There are different ways of realizing such a first module. Variants are shown for example in the figures.

A switchable device that is already known in brake technology for representing a switchable connection of the brake circuits with the feature of an active energization of the circuit connection device for separating the brake circuits has the particular disadvantage that this energization must be maintained to maintain the braking function even after the vehicle is parked and at the latest then fails when the vehicle battery can no longer generate the current. In contrast to this, in the embodiment described here, the circuit connection device is automatically closed in the de-energized state. In the event of a wheel circuit leak, a hydraulic brake function is maintained in the brake circuit not affected by the leak, regardless of the availability of the electrical energy supply.

• 1: ein Bremssystem,
• 2: einen elektrohydraulischen Aktuator, und
• 3: einen weiteren elektrohydraulischen Aktuator.

The person skilled in the art will derive further features and advantages from the exemplary embodiment described below with reference to the attached drawing. show:

• 1 : a braking system,
• 2 : an electrohydraulic actuator, and
• 3 : another electro-hydraulic actuator.

1 shows purely schematically a brake system BS according to an embodiment of the invention. The braking system BS is divided into a first module M1 and a second module M2. Furthermore, there are electronic control modules assigned to the modules M1, M2, namely a first control module SM1 and a second control module SM2 as well as a pedal-actuated brake cylinder BZ. Both control modules SM1, SM2 are signal connections with a Vehicle control module FSM connected. A vehicle control module FSM provided for automated driving can, for example, use these signal connections to brake the vehicle and monitor it. The braking system BS is connected to a total of four wheel brakes B1, B2, B3, B4, which are typically associated with the respective wheels of a motor vehicle. The wheel brakes B1, B2, B3, B4 can also be regarded as part of the brake system from at least one perspective.

A reservoir R is used to supply and store pressure medium, typically brake fluid. A first brake circuit BK1 and a second brake circuit BK2 originate from this reservoir. In the present case, a first electrohydraulic actuator A1 is designed as a combination of an electrohydraulic linear actuator with a piston-cylinder arrangement, which has a motor M, a transmission and a piston K. Furthermore, in the second module M2 there is a second electro-hydraulic actuator A2, which in the present case is designed in the form of a combination of an electric motor with at least two piston pumps. In the second module M2 there are also several valves, which are designated collectively with V and are used to control a fluid flow to and from the respective wheel brakes B1, B2, B3, B4. Their functionality is not discussed in detail here. The second module M2 can also be referred to as an electronic stability module because a program typically works in the control module SM2, which ensures the stability of the wheel rotation movements and the vehicle body movement with the aid of suitable activation of the valves V and the actuator A2.

As shown, both electrohydraulic actuators A1, A2 are designed as combinations of an electromechanical actuator with at least two hydraulic components assigned to the different brake circuits. In the first actuator A1, the hydraulic components are master pistons and in the second actuator A2, the hydraulic components are pumps. Thus, both actuators A1, A2 can each be used to generate pressure in the two brake circuits BK1, BK2.

A circuit connection device KVE is also present in the first module M1. In the present case, this has a first valve V1 and a second valve V2, both of which are designed to be normally closed. Furthermore, the two valves V1, V2 are connected in series and are also designed in such a way that they are additionally pressed into a closed position by the pressure of a brake circuit BK, to which they are each directly connected. This means that the circuit connection device KVE very reliably ensures hydraulic separation of the two brake circuits BK1, BK2 without active energization. The two brake circuits BK1, BK2 are only connected to one another if the two valves V1, V2 are actively energized.

A connection of the two brake circuits BK1, BK2 by the circuit connection device KVE can be provided in particular when normal operation takes place, i.e. when, for example, due to an existing brake pedal actuation or a corresponding signal from the vehicle control module FSM for braking during automated driving, the wheel brakes with one for all wheel brakes should be subjected to the same pressure. The advantage of such a circuit connection is that the pressure in both brake circuits is exactly the same, which means that, for example, the vehicle can be prevented from being pulled sideways due to different brake pressures on the left and right. However, if a leak is detected in one of the two brake circuits BK1, BK2, the circuit connection device KVE can be closed by switching off the current. As a result, that brake circuit BK in which no leak has occurred can still be used for braking. This functionality is retained even if, for example, due to a longer standstill time or a weak battery, there is no longer any current available to actuate the valves V1, V2.

The control modules SM1 and SM2 of the two modules M1 and M1 are preferably connected to different vehicle electrical systems, namely a first vehicle electrical system EV1 and a second vehicle electrical system EV2, for their energy supply. This has the advantage that in the event of a possible error that leads to a failure of an energy supply, the other module in each case remains ready for use and all wheel brakes continue to be supplied with brake pressure. For a corresponding error detection, the control modules SM1, SM2 communicate with one another, in particular via a direct communication link or indirectly via the communication links to the vehicle control module FSM, so that the control module SM1, SM2 that is still functional can evaluate the operating situation. Experience has shown that vehicle electrical system failures are far more likely to occur than mechanical or hydraulic faults. Therefore, the protection mentioned against this error is particularly important for brake-by-wire braking systems that do not have a purely hydraulic fallback level with direct hydraulic penetration from the brake pedal to the wheel brakes, as well as for vehicles that are intended for automated driving.

2 shows an alternatively designed actuator A, such a design can be used both for the first actuator A1 and for the second actuator A2. This has not only a piston K, but a first piston K1 and a second piston K2. These are both arranged side by side and parallel to each other so that they can both be operated by the motor M at the same time. With the same design of the pistons K1, K2, they release an identical volume of fluid into the respective brake circuits BK.

3 shows an alternative embodiment of an actuator A, such an embodiment can be used both for the first actuator A1 and for the second actuator A2. The two pistons K1, K2 are not arranged side by side, but offset from one another, with a swivel arm S being provided between the two. The swivel arm S is actuated by the electric motor M and then actuates the two pistons K1, K2. This allows the two pistons K1, K2 to be arranged more freely relative to one another, which can enable better utilization of installation space in certain geometric configurations.

It should be noted that in the claims and in the description features can be described in combination, for example to facilitate understanding, although they can also be used separately. The person skilled in the art recognizes that such features can also be combined independently of one another with other features or combinations of features.

Back-references in dependent claims can identify preferred combinations of the respective features, but do not exclude other combinations of features.

Reference List

B.S

braking system

S

swivel arm

BZ

brake cylinder

M

engine

R

reservoir

K

Pistons

A

actuator

V

Valve

KVE

circuit connection device

M

module

SM

control module

FSM

vehicle control module

EV

vehicle electrical system

Claims (15)

Brake system (BS) for a motor vehicle, the brake system (BS) having the following: - a first brake circuit (BK1), - a second brake circuit (BK2), - a first electrohydraulic actuator (A1) for displacing and pressurizing pressure medium, - a second electro-hydraulic actuator (A2) for displacing and pressurizing pressure medium, and - an electrically activatable circuit connection device (KVE), - wherein the first brake circuit (BK1) is connected to the first actuator (A1) and the second actuator (A2), - wherein the second brake circuit (BK2) is connected to the first actuator (A1) and the second actuator (A2), - wherein the circuit connection device (KVE) is set up to connect the first brake circuit (BK1) to the second brake circuit (BK2) when it is activated, the circuit connection device (KVE) being connected on the one hand to the first brake circuit (BK1) between the first actuator (A1 ) and the second actuator (A2) and on the other hand is connected to the second brake circuit (BK2) between the first actuator (A1) and the second actuator (A2), and - Wherein the circuit connection device (KVE) separates the connection between the two brake circuits (BK) in its inactive state. Braking system (BS) after claim 1 , the circuit connection device (KVE) being activated by applying an electric current to the circuit connection device (KVE). Brake system (BS) according to one of the preceding claims, - wherein the circuit connection device (KVE) has a first valve (V1) and a second valve (V2), - wherein the first valve (V1) and the second valve (V2) are connected in series are, - wherein the first valve (V1) is connected to the first brake circuit (BK1) and is designed as a seat valve, with an electromagnetically forceable valve body which is additionally acted upon by the pressure of the first brake circuit (BK1) in the direction of the valve seat, and - wherein the second valve (V2) is connected to the second brake circuit (BK2) and is designed as a seat valve, with an electromagnetically force-loadable valve body, which is additionally from Pressure of the second brake circuit (BK2) is applied in the direction of the valve seat. Braking system (BS) according to one of Claims 1 or 2 - Wherein the circuit connection device (KVE) has only one valve. Braking system (BS) according to one of the preceding claims, - Wherein the first actuator (A1) when actuated in the first brake circuit (BK1) and the second brake circuit (BK2) emits a mutually proportional or identical pressure medium volume output. Braking system (BS) according to one of the preceding claims, - Wherein the second actuator (A2) when actuated in the first brake circuit (BK1) and the second brake circuit (BK2) emits a mutually proportional or identical pressure medium volume output. Braking system (BS) according to one of the preceding claims, - Wherein the first actuator (A1) is designed as an electromechanically actuated piston-cylinder arrangement, in whose cylinder or cylinders the pressure medium to be delivered is stored in the unactuated state, and - Wherein the second actuator (A2) is designed as a motor-pump module which sucks in pressure medium from a first brake circuit section in order to release pressure medium into a second brake circuit section. Braking system (BS) according to one of the preceding claims, - wherein the first actuator (A1) has a first cylinder with a first piston (K1) and a second cylinder with a second piston (K2), - Wherein the first cylinder is connected to the first brake circuit (BK1) and the second cylinder is connected to the second brake circuit (BK2). Braking system (BS) after claim 8 , - wherein the first cylinder and the second cylinder are arranged parallel to each other. Braking system (BS) according to one of Claims 8 or 9 , - wherein the first piston (K1) and the second piston (K2) are rigidly connected to each other. Braking system (BS) according to one of Claims 8 or 9 - Wherein the first piston (K1) and the second piston (K2) can be actuated jointly by a swivel arm (S). Braking system (BS) after claim 11 , - wherein the swivel arm (S) moves the first piston (K1) and the second piston (K2) in different directions. Braking system (BS) according to one of the preceding claims, - which has an electronic stability module (M2), which has hydraulic sections which have the first brake circuit (BK1) and disjunctive hydraulic sections which are assigned to the second brake circuit (BK2) and/or which has a motor-pump module, which forms the second actuator (A2). Braking system (BS) according to one of the preceding claims, - Which has a pedal-operated brake cylinder (BZ) which is connected to at least one of the two brake circuits (BK). Braking system (BS) after Claim 14 - Which has a simulator and at least one separating valve, with the separating valve being closed, the brake cylinder (BZ) being connected exclusively to the simulator and with the separating valve being open, the brake cylinder being connected to one or both brake circuits (BK).

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