DE102023108135A1 - Electro-hydraulic brake unit - Google Patents

Abstract

The invention relates to an electro-hydraulic brake unit (10) for a motor vehicle, comprising a pressure source (36) designed as an actuator (30), at least one brake piston (70, 80), and a brake circuit (38) which contains the pressure source (36) and connects the at least one brake piston (70, 80) to one another, the pressure source (36), the at least one brake piston (70, 80) and the brake circuit (38) being arranged in a wheel brake. The invention also relates to a vehicle with such an electro-hydraulic brake unit (10) and a method for controlling the electro-hydraulic brake unit (10).

Description

The invention relates to an electro-hydraulic brake unit, a vehicle with such an electro-hydraulic brake unit and a method for controlling the electro-hydraulic brake unit.

In conventional electro-hydraulic brake systems of motor vehicles, it is known to use a central actuator to detect the braking request and provide hydraulic pressure. The hydraulic pressure is distributed to the individual wheel brakes of the motor vehicle using pipes.

Electromechanical braking systems (EMB) are already in widespread use. The actuators are assigned to each wheel and are mounted directly on the brake disc. The wheel brake unit is usually installed directly on the single wheel axle, in the inner rim space.

It is also known to combine conventional electro-hydraulic brake systems and EMB. For example, the EP 0774 391 A1 the control and energy supply of the brake force generator is electrical. However, hydraulic access from the centrally located master brake cylinder to the wheel brakes is provided for the fallback level in the event of partial failure.

The disadvantage here is that the hydraulic expansion tank and piping in the motor vehicle are sometimes difficult to reach. The maintenance of such centrally arranged brake systems is therefore extensive and complex. A disadvantage of the known EMB is an uneven force transmission to the brake piston, which results in uneven wear of the brake lining and the friction partner, in particular the brake disc or drum. In addition, in EMB, sometimes maintenance and cost-intensive gears, such as a planetary gear, have to be used to change a movement variable and to transmit power from the actuator to the brake piston. Another disadvantage of the known EMB is that the design used there does not allow the use of a single actuator in a fixed caliper brake.

It is therefore the object of the present invention to provide an alternative brake for a motor vehicle. A further object is to provide a brake for a motor vehicle in which the disadvantages listed above are at least partially overcome.

This object is achieved according to the invention by the electro-hydraulic brake unit. Advantageous refinements and further developments of the invention emerge from the dependent patent claims.

The invention relates to an electro-hydraulic brake unit for a motor vehicle. The electro-hydraulic brake unit comprises a pressure source designed as an actuator, at least one brake piston, and a brake circuit that connects the pressure source and the at least one brake piston to one another. The pressure source, the at least one brake piston and the brake circuit are arranged in a wheel brake.

The invention also relates to a method for controlling an electro-hydraulic brake unit for a motor vehicle. The electro-hydraulic brake unit here comprises a pressure source designed as an actuator, at least one brake piston, and a brake circuit which connects the pressure source and the at least one brake piston to one another. The pressure source, the at least one brake piston and the brake circuit are arranged in a wheel brake. The actuator has a piston and the brake circuit has a working space and a connecting line, the piston being movably arranged in the working space. In addition, the connecting line connects the working space with the at least one brake piston. The brake circuit also has a reservoir designed as a low-pressure accumulator and a first switchable check valve. The connecting line has a second switchable check valve through which the working space can be decoupled from the at least one brake piston. The reservoir can be decoupled from the connecting line by the first switchable check valve at a position between the second switchable check valve and the working space. The electro-hydraulic brake unit also includes a circuit board on which a pressure sensor, the first switchable check valve and the second switchable check valve are arranged. The connecting line has the pressure sensor for determining a pressure in the connecting line. The method includes: (i) performing a normal operation in which the first check valve is closed and the second check valve is open, the normal operation being adapted to achieve a braking effect; (ii) performing an alternative operation in response to exceeding a first pressure threshold in which the first check valve is open and the second check valve is closed, the alternative operation being adapted for a resetting of the piston in which the piston contacts the actuator; and (iii) performing normal operations in response falling below a second pressure threshold value, wherein the second pressure threshold value is lower than the first pressure threshold value.

The electro-hydraulic brake unit is in particular and preferably a single wheel brake of a motor vehicle. In particular and preferably, the brake circuit is only present in the electro-hydraulic brake unit. This means that there is no connection, in particular a fluid connection, of the brake circuit with other components of a motor vehicle located outside the electro-hydraulic brake unit, including another electro-hydraulic brake unit.

Furthermore, the brake is preferably designed as an electromechanical brake system (EMB). The actuator or plunger arrangement, for example an electric motor, preferably a brushless direct current electric motor, is connected to a piston or plunger, for example via a spindle. The actuation of the actuator results in a displacement of the piston, which is transmitted via the brake fluid contained in the brake system to the brake piston with a brake pad arranged thereon. Due to the brake lining arranged on the brake piston, the brake lining is brought into contact with the friction lining of a brake disc or drum and the motor vehicle is subsequently braked.

Depending on the design of the electro-hydraulic brake unit as a floating caliper brake or as a fixed caliper brake, a distinction can be made between a first brake pad and a second brake pad. With floating caliper brakes, the brake piston is only on one side of the brake disc. Here, in the case of a single brake piston with a first brake pad arranged thereon, the first brake pad is pressed onto the brake disc when the motor vehicle brakes and this is brought into contact with a second brake pad, the second brake pad being on a side of the brake disc facing away from the brake piston, is attached to the housing of the floating caliper brake. With the fixed caliper brake, at least two brake pistons are arranged on opposite sides of the brake disc and connected to the pressure source via the brake circuit.

The piston of the actuator preferably has a small diameter with a comparatively long piston travel in the working space. For example, a ratio of the piston diameter to the piston travel is at least 1:5, preferably at least 1:8 or 1:12. This allows the pressure of the brake fluid to be adjusted more precisely.

The proposed electro-hydraulic brake unit is suitable for both single-piston and multiple-piston brake calipers. The advantages of the electric drive are combined with the simple and efficient transmission of hydraulics. The hydraulic part of the brake system is only contained in the respective wheel brake and is not distributed over the entire motor vehicle. The hydraulic part can be encapsulated so that it is neither visible when installed in the vehicle nor during operation and maintenance. This means that hydraulic expansion tanks and hydraulic piping are not required in the motor vehicle. In particular, purely electrically powered vehicles can be operated with significantly longer maintenance intervals because there is no need to change the brake fluid. Furthermore, a gear ratio that is favorable for engine efficiency can be selected, with losses in the gear ratio being low compared to a mechanical transmission. The electro-hydraulic brake unit can be made from existing and proven elements. These are robust and can also be produced inexpensively. Another advantage is that the inner space of the actuator is filled with a liquid medium and is therefore less exposed to water entry and corrosion. The driver's braking request can be recorded using a dry pedal force simulator. Furthermore, the content of brake fluid in the system, especially in the brake piston that transmits the braking force, serves to compensate for short-term heat impressions on the actuator.

The first and second pressure threshold values represent pressures in the brake circuit that can be detected by a pressure sensor. The first and second pressure threshold values are freely definable. Since the pressure in the brake circuit that can be detected by the pressure sensor correlates with the piston distance and/or the extent of the actuator actuation or is proportional to these variables, the first and second pressure threshold values can also be based on a piston distance traveled and/or on the basis of the actuator actuation. For example and preferably, the method includes before (ii) detecting whether a signal provided by the pressure sensor exceeds the first pressure threshold and after (ii) detecting whether a signal provided by the pressure sensor falls below the second pressure threshold.

According to one embodiment, the actuator has a piston which is non-positively connected to the actuator, and wherein the piston and the actuator are aligned parallel to one another are, preferably wherein the piston and the actuator are arranged adjacent to one another, more preferably wherein the piston is at least partially integrated into one of the brake pistons. The arrangement of the piston and the actuator, in particular an electric motor, parallel to one another, preferably adjacent to one another, enables the space-saving arrangement of the brake circuit in the electro-hydraulic brake unit. The drive side of the actuator and the spindle, for example and in particular a ball screw, which drives the piston, can be present on the same side of the electro-hydraulic brake unit. This also simplifies the connection of the actuator, in particular via an actuator control, to a circuit board, and thus possibly also to the vehicle electronics. The pressure source can be designed as a single-acting piston pump (SAP, Single Acting Plunger) or as a double-acting piston pump (DAP, Dual Acting Plunger). The piston can be at least partially integrated into the brake piston. A brake piston area is preferably larger than a piston area. An exemplary ratio may be 12:1 to 5:1. Preferably, the pressure is transmitted from the piston to the brake piston via a brake fluid. As a result, further space can be saved and the dimensions of the electro-hydraulic brake unit can be reduced or it can be provided in an optimized installation space. An integrated brake control (IBC, integrated brake control) can thus be further improved.

According to one embodiment, the electro-hydraulic brake unit comprises a parking brake designed as an electromagnet, the electromagnet comprising a solenoid coil and a coil core movably arranged therein, the coil core being designed to prevent the piston from resetting, preferably the coil core being aligned parallel to the piston, and/or wherein the actuator has a gear arranged between the actuator and the piston, preferably wherein the actuator is designed as an electric motor which is provided with a torque sensor, and/or wherein the brake circuit has a working space, a connecting line and a reservoir , wherein the piston is movably arranged in the working space, wherein the connecting line connects the working space with the at least one brake piston and the reservoir, the reservoir and the brake piston being aligned parallel to one another, preferably wherein the reservoir has a vent, the vent being adjacent the piston is arranged. The parking brake, designed as an electromagnet, provides a reliable parking lock, requires little installation space and can also be integrated into the electro-hydraulic brake unit in a space-optimized manner. The parking brake, designed as an electromagnet, is also easy to manufacture and can be easily integrated into braking systems. Preferably, the parking brake designed as an electromagnet can also be connected to a circuit board and, if necessary, to the vehicle electronics. For this purpose, the electromagnet is preferably located on the spindle side of the piston. The electromagnet includes a solenoid coil and a core movably arranged therein. The coil core can be selectively moved axially and locked in axial positions by controlling the solenoid coil, which is done, for example, by the vehicle electronics. By appropriately arranging the coil core in relation to the piston, its reset, especially in the direction of bottom dead center, can be prevented. This allows the self-locking effect of the parking brake to be provided. The actuator can have a gear or intermediate gear arranged between the actuator and the piston. As a result, the transmission can be arranged adjacent to a printed circuit board and, if necessary, connected via a transmission control and, if necessary, to the vehicle electronics. By choosing a suitable transmission ratio, for example 2:1 to 5:1, such as 3:1, the actuator, for example an actuator designed as an electric motor, can be dimensioned smaller and therefore cost-effective, space-saving and space-optimized in the electro-hydraulic brake unit to be provided. The torque provided by the actuator can thus be smaller. The dimensions of the spindle and/or piston can also be influenced via the gearbox. Preferably, the spindle and the gear are present as a single component, for example and preferably as a ball screw or ball screw arrangement (BNA). The actuator can be designed as an electric motor, which is provided with a torque sensor. The torque sensor can, if necessary, be connected to the vehicle electronics via the circuit board. The torque sensor can bring about improved control of the actuator, in particular the electric motor. The brake circuit has a working space, a connecting line and a reservoir, the piston being movably arranged in the working space, the connecting line connecting the working space with the at least one brake piston and the reservoir, the reservoir and the brake piston being aligned parallel to one another. A vent of the reservoir is preferably arranged adjacent to the piston or the circuit board, if present. The alignment of the reservoir and the brake piston parallel to each other enables them to be incorporated into the electro-hydraulic brake unit in a space-saving and space-optimized manner. The reservoir can be provided with a filling valve to ensure easy filling and/or at least partial filling to enable this replacement at least as part of maintenance. The filling valve can preferably provide the only access to an otherwise encapsulated electro-hydraulic brake unit.

According to one embodiment, the electro-hydraulic brake unit comprises a circuit board, wherein the piston and the actuator are arranged adjacent to the circuit board, preferably wherein the pressure source has an actuator control which is adapted to control the actuator, and wherein the circuit board is connected to one or more of the Electromagnet of the actuator control, a control unit of the transmission, the torque sensor, a pressure sensor that is designed to determine a brake fluid pressure in the reservoir is connected. This means that the components mentioned can be easily connected to a common circuit board and, if necessary, to the vehicle electronics. The spatial arrangement of the components of the electro-hydraulic brake unit can thereby be further optimized with regard to the installation space and their number can be reduced if necessary by connecting the components to a common circuit board. This also enables improved encapsulation of the electronics and the resulting improved protection against environmental influences. The pressure sensor can also be manufactured more cost-effectively than a force sensor.

According to one embodiment, the actuator has a piston and the brake circuit has a working space or plunger space and a connecting line, the piston being movably arranged in the working space, the connecting line connecting the working space with the at least one brake piston. As a result, the brake fluid present in the working space and in the connecting line can be transmitted to one or more brake pistons through the piston movement and these can be moved accordingly. Brake pads arranged on the brake pistons are subsequently moved in the direction of the corresponding friction partner, for example the brake disc, contact them, or are retracted from them. The advantage of this is that a uniform distribution of force can be achieved on the brake piston or pistons. This can prevent uneven wear of the brake pads.

According to one embodiment, the brake circuit has a reservoir and a first switchable check valve, the connecting line having a second switchable check valve through which the working space can be decoupled from the at least one brake piston, the reservoir being separated from the connecting line at one position by the first switchable check valve can be decoupled between the second switchable check valve and the working space. This design of the brake system enables two different operating modes of the electro-hydraulic brake unit. In normal operation, the first switchable check valve is in a closed position, it is an NC (normally closed) valve, and the second switchable check valve is in an open position, it is a NO (normally open) valve. This creates the connection necessary for generating a braking force between the working space and the at least one brake piston via the connecting line. In a further alternative operating mode, the first switchable check valve is in an open position and the second switchable check valve is in a closed position. On the one hand, this interrupts a fluid connection between the working space and the at least one brake piston. On the other hand, a fluid connection is established between the reservoir and the work space. By moving the actuator and therefore the piston, any excess brake fluid that may be present can be released into the reservoir or any deficit of brake fluid that may be present can be removed from the reservoir. The two check valves are then switched back to normal operation. Switching between normal operation and alternative operation can be carried out using the vehicle electronics, for example at regular time intervals or depending on the situation, for example every time the motor vehicle stops. This ensures that an optimal braking effect of the electro-hydraulic brake unit can be achieved at any time during normal operation. Highly dynamic reductions in clamping force, as required in ABS, are easily achieved by opening the NC valve, as is known from proven hydraulic systems.

According to one embodiment, the reservoir is designed as a low-pressure reservoir. The term low pressure is to be understood to mean that the brake fluid present in the reservoir is under ambient pressure, such as atmospheric pressure. The reservoir therefore includes a fluid connection to the surroundings of the motor vehicle. The reservoir preferably has means for equalizing pressure with the environment. For example, the reservoir is provided via a diaphragm arranged in the housing of the electro-hydraulic brake unit and a membrane, if present in the reservoir, which is arranged between the brake fluid and the diaphragm. Alternatively or additionally, a vent screw or a vent nipple can be provided in the reservoir. This allows pressure equalization with the Environment, whereby on the one hand any high pressure that may be present in the brake circuit can be reduced and / or the piston can be easily moved. This ensures that an optimal braking effect of the electro-hydraulic brake unit can be achieved at any time during normal operation. Furthermore, any heating of the elements of the electro-hydraulic brake unit caused by braking can be dissipated more easily via the brake fluid.

According to one embodiment, the electro-hydraulic brake unit comprises a circuit board on which a pressure sensor, the first switchable check valve and the second switchable check valve are arranged, wherein the connecting line has the pressure sensor for determining a pressure in the connecting line. For this purpose, the circuit board is preferably arranged within the electro-hydraulic brake unit. By means of coils arranged on the circuit board, the check valves can be easily controlled by the vehicle electronics and the pressure within the brake circuit can be recorded and, if necessary, regulated via the check valves and/or actuation of the actuator. This makes it possible to provide an electro-hydraulic brake unit that can be installed as such in the motor vehicle, whereby in addition to the attachment to the chassis of the motor vehicle, only electrical connections have to be made between the circuit board and the vehicle electronics, in particular a control unit. Hydraulic expansion tanks and hydraulic piping in the motor vehicle are therefore not necessary. One or more further sensors can be mounted in the electro-hydraulic brake unit and, for example, connected to the circuit board in order, for example, to provide information regarding the operating state, preferably regarding the functionality of individual elements of the electro-hydraulic brake unit, to the vehicle electronics. The vehicle electronics preferably provide appropriate driving and braking assistance functions. These driving and braking assistance functions are used, among other things, for autonomous or semi-autonomous driving as well as during heavy braking.

According to one embodiment, the connecting line has a pressure sensor. The pressure sensor can be designed, for example, as an absolute pressure sensor or differential pressure sensor, or relative sensor. The pressure sensor is preferably arranged on the connecting line in such a way that the pressure present in the brake circuit and its change caused by movement of the piston, possibly with regard to atmospheric pressure, can be determined at any time. Further pressure sensors can be provided in the brake circuit, for example for more precise pressure determination and/or as redundancy sensors. This means that the brake pressure for each individual wheel brake can be determined at any time during normal operation and these can be optimally controlled. The electro-hydraulic brake units are preferably controlled by vehicle electronics, in particular a control unit, in the motor vehicle in such a way that all wheel brakes provide an identical brake pressure. This achieves a uniform braking effect and makes it easier for the driver to maintain control of the motor vehicle, even during emergency braking.

According to one embodiment, the electro-hydraulic brake unit is designed as a floating caliper brake or fixed caliper brake. The electro-hydraulic brake unit is preferably designed as a fixed caliper brake, with at least two, for example four, six or eight, brake pistons being arranged in pairs symmetrically on the brake disc, more preferably with each of the brake pistons being connected via the connecting line to the working space for actuation by the actuator . This means that a distributed and optimal braking effect can be achieved at several points and on both sides of the brake disc.

According to one embodiment, the electro-hydraulic brake unit is designed as a closed system. The closed or encapsulated system preferably only has fastening means for fastening the electro-hydraulic brake unit to the motor vehicle and electrical contacts for electrical connection to, for example, the circuit board of the electro-hydraulic brake unit. The circuit board can provide an electrical connection of one or more components, preferably the actuator, the check valves, and the pressure sensor, to vehicle electronics, in particular a control unit.

Hydraulic lines and/or containers are present in the closed system in such a way that no brake fluid escapes into the environment or the brake fluid does not absorb any water, for example in the form of atmospheric moisture. As a result, the electro-hydraulic brake unit as such can be removed or installed and/or its maintenance can be simplified.

According to one embodiment, each wheel of the vehicle is provided with the electro-hydraulic brake unit. The electro-hydraulic brake units are preferably controlled by vehicle electronics, in particular a control unit, of the vehicle in such a way that in the event of a braking process, all wheels of the vehicle experience essentially the same brake pressure. This achieves a uniform braking effect and makes it easier for the driver to maintain control of the motor vehicle.

The braking system is in particular an integrated braking system. An integrated braking system is a structural unit that combines a variety of functions in a compact structure. It is clear that further brake systems can be integrated into the motor vehicle, for example and preferably, the electro-hydraulic brake unit can comprise a second pressure source designed as an actuator, at least one second brake piston, and a second brake circuit which has the second pressure source and the at least one second brake piston connects to each other, wherein the second pressure source, the at least one second brake piston and the second brake circuit are arranged in the wheel brake. A second, for example auxiliary or redundancy, braking system can therefore be present.

The vehicle electronics, in particular the control unit, preferably provides corresponding driving and braking assistance functions. These driving and braking assistance functions are used, among other things, for autonomous or semi-autonomous driving as well as during heavy braking.

The invention further relates to a vehicle comprising an electro-hydraulic brake unit according to the invention. The vehicle is preferably a motor vehicle. Examples of motor vehicles are passenger cars, trucks, buses, agricultural machinery or motorcycles. More preferably, the vehicle is a passenger car.

• 1 eine schematische Darstellung eines elektrohydraulischen Bremsaggregats für ein Kraftfahrzeug gemäß einer ersten Ausführungsform;
• 2 eine schematische Ansicht eines elektrohydraulisches Bremsaggregats für ein Kraftfahrzeug gemäß einer zweiten Ausführungsform;
• 3a und b beispielhafte Betriebszustände des als Schwimmsattelbremse ausgebildeten elektrohydraulischen Bremsaggregats 10 der ersten Ausführungsform; und
• 4 eine schematische Schnittansicht eines elektrohydraulischen Bremsaggregats 10 für ein Kraftfahrzeug gemäß einer dritten Ausführungsform.

The invention is explained below by way of example and in detail using several figures. Show it:

• 1 a schematic representation of an electro-hydraulic brake unit for a motor vehicle according to a first embodiment;
• 2 a schematic view of an electro-hydraulic brake unit for a motor vehicle according to a second embodiment;
• 3a and b exemplary operating states of the electro-hydraulic brake unit 10 of the first embodiment designed as a floating caliper brake; and
• 4 a schematic sectional view of an electro-hydraulic brake unit 10 for a motor vehicle according to a third embodiment.

The same objects, functional units and comparable components are designated with the same reference numerals across the figures. These objects, functional units and comparable components are identical in terms of their technical features, unless the description explicitly or implicitly states otherwise.

In the braking systems known from the prior art and based on the use of EMB, actuators act on the brake pistons directly or via other mechanical components, in particular gears. The uniform transmission of the force exerted by the actuator to the brake piston has proven to be problematic. A hydraulic connection between the actuator and brake piston is proposed below, which eliminates the construction-related disadvantages of the EMB proposed from the prior art.

1 shows a schematic representation of an electro-hydraulic brake unit 10 for a motor vehicle according to a first embodiment. The electro-hydraulic brake unit 10, which in the present case is designed purely as an example as a floating caliper brake, is a component of a brake system, not shown, of a motor vehicle, also not shown. The braking system is preferably an integrated braking system in which a large number of functions are combined in a compact structure.

In the braking system, such an electro-hydraulic brake unit 10 is attached to each wheel of the motor vehicle, the brake unit 10 being electrically connected via connections 66 to a control unit (not shown here). The control device is preferably a control device designed as a driving assistance system, which, in conjunction with the drive unit of the motor vehicle, provides control of the electro-hydraulic brake units 10. The control can take place by means of a pressure sensor 56 and possibly other sensors not shown here. The control unit preferably also provides corresponding driving and braking assistance functions, which are used, among other things, for autonomous or semi-autonomous driving as well as for braking processes.

The electro-hydraulic brake unit 10 comprises a housing 20, in which a pressure source 36 designed as an actuator 30, a brake piston 70 and a brake circuit 38 are encapsulated in such a way that the brake circuit 38 is in a non-fluid connection with the environment of the electro-hydraulic brake unit 10, in particular the other components of the motor vehicle, including the further electro-hydraulic brake units 10.

All components of the electro-hydraulic unit 10 are therefore present in a single wheel brake, so that they can be controlled via a control signal line between the electro-hydraulic brake unit 10 and the control unit of the motor vehicle. This enables simplified control of the electro-hydraulic brake unit 10 or its various components while at the same time reducing installation space for additional control signal lines. Hydraulic connections are not distributed over the entire motor vehicle, but are rather limited to the electro-hydraulic brake unit 10, which means that the brake unit 10 is equally suitable for single-piston and multiple-piston brake calipers and also results in less wear on the above components and longer maintenance intervals for the brake system as a whole . The electro-hydraulic brake unit 10 can be made from existing, low-maintenance and cost-effective components. The driver's braking request can be recorded, for example, using a dry pedal force simulator.

The in 1 Actuator 30 shown and designed as an example of a plunger arrangement drives a spindle 32 with a piston 34 designed as a plunger for movement in a working space 40. Extending the piston 34 causes compression of the brake fluid present in the working space 40. The brake fluid compressed in this way flows through a connecting line 42, 44 of the brake circuit 38, which connects the working space 40 with the brake piston 70 movably arranged in the housing 20 and thereby the brake piston 70, which is contained in an annular seal 76 and sealed via a fold seal 78, with a brake piston 70 arranged thereon first brake pad 72 presses onto a brake disc 90. The brake disc 90 is in turn pressed against a second brake pad 74 which is firmly attached to the housing 20. The resulting frictional forces counteract the rotational movement of the brake disc 90 and thereby brake the motor vehicle.

Likewise, a reset of the piston 34 not only causes the brake fluid present in the working space 40 and in the connecting line 42, 44 to relax but also returns it to the enlarging working space 40, whereby the brake piston 70 is also retracted from the brake disc 90.

Out of 1 It can also be seen that the brake circuit 38 has a reservoir 46 with brake fluid held therein and a first switchable check valve 52. Furthermore, a second switchable check valve 54 is arranged on the connecting line 42, 44, through which the working space 40 can be decoupled from the at least one brake piston 70. In addition, the reservoir 46 can be decoupled from the connecting line 42, 44 by the first switchable check valve 52 at a position between the second switchable check valve 54 and the working space 40. As a result, depending on the switching state of the two check valves 52, 54, the working space 40 of the piston can be selectively connected via the connecting line 42, 44 either to the reservoir 46 or the brake piston 70 or decoupled from both. A pressure sensor 56 is also attached to the connecting line 42, 44 and between the first switchable check valve 52 and the second switchable check valve 54. The pressure sensor 56 detects the pressure acting on the brake disc 90 based on a change in pressure of the brake fluid and transmits corresponding signals to the control unit of the motor vehicle, which uses the control unit to control the electro-hydraulic brake unit 10.

The use of the reservoir 46, the first and second check valves 52, 54 and the pressure sensor 56 enables, depending on the switching state of the first and second check valves 52, 54, essentially three operating states of the electro-hydraulic brake unit 10. These three operating states - a so-called normal operation, an alternative operation and a pressure compensation operation - are explained in more detail below.

During normal operation, the electro-hydraulic brake unit 10 can be used for normal braking of the motor vehicle. Here, the first switchable check valve 52 is closed as an NC check valve and the second switchable check valve 54 is open as a NO check valve. As a result, the reservoir 46 is separated from the connecting line 42, 44 in such a way that the brake fluid, as mentioned above, can only be moved between the working space 40 and the brake piston 70 in accordance with the direction of movement of the actuator 30. As a result, the brake piston 70 with the first brake pad 72 mounted thereon will be moved either toward the brake disk 90 or away from it. If the first brake pad 72 is pressed against the brake disc 90, the brake disc 90 is in turn pressed against the second brake pad 74 attached to the housing 20, whereby the rotational movement of the brake disc 90 is forcefully counteracted and the motor vehicle is thus braked.

As soon as a braking effect has been used several times as part of the normal operation of the electro-hydraulic brake unit 10, a partial redistribution of the brake fluid between the working space 40 and the brake piston 70 can be achieved such that the brake fluid is only partially returned to the starting position when the piston 34 is retracted is returned. A certain amount of brake fluid remains on the brake piston 70.

Therefore, in the case of several consecutive braking processes, the piston 34 must cover a shorter extension distance in a later braking process than in one of the previous braking processes. As a result, during several consecutive braking operations, a smaller amount of brake fluid is moved through the piston 34, which reduces the braking effect. In addition, the pressure determination by the pressure sensor 56 and, as a result, the control of the electro-hydraulic brake unit 10 by the control unit become less precise.

In alternative operation, the first switchable check valve 52, 54 is open and the second switchable check valve 52, 54 is closed. This creates a connection between the working space 40 and the reservoir 46, with the connection between the working space 40 and the brake piston 70 being interrupted at the same time.

In the present case, the reservoir 46 is designed as a low-pressure reservoir for the brake fluid. The brake fluid present in the reservoir 46 is separated from the housing 20 by a membrane 48. In addition, a bleeder screw 50 is provided on the reservoir 46 in such a way that extending the piston 34 causes the brake fluid to be compressed and transports it into the reservoir 46 via the connecting line 42, 44. Diaphragms 22 are also provided on the housing 20 for pressure equalization with the environment. The membrane 48, a diaphragm 22 provided in the reservoir 46 and the bleeder screw 50 enable the brake fluid to be absorbed while at the same time preventing brake fluid from escaping from the housing 20 into the reservoir 46. Retracting the piston 34, on the other hand, causes the brake fluid to be removed the reservoir 46.

In the case of several consecutive braking operations, for example after five braking operations of the motor vehicle and when it comes to a stop, or when a predefined maximum or first pressure threshold value is exceeded, the check valves 52, 54 are moved into the alternative position and the working space 40 is preferably completely retracted by retracting the piston 34 , filled. Subsequently, for example after falling below a predefined minimum or second pressure threshold, the two check valves 52, 54 are returned to the normal position, so that a full braking effect can be provided by the electro-hydraulic brake unit 10.

During the pressure equalization operation, both check valves 52, 54 are opened at the same time. Both the brake piston 70 and the piston 34 are therefore in fluid communication with the reservoir 46 via the connecting line 43, 44 and the brake fluid contained therein. Any temperature increase that occurs locally on the brake piston 70 and/or the piston 34, for example due to strong and/or frequent braking, can thereby be passed on via the brake fluid into the brake fluid present in the reservoir 46 and effectively released into the environment. This makes it possible to avoid, if necessary local, overheating of the electro-hydraulic brake unit 10.

Regarding the structure of the electro-hydraulic brake unit 10 1 It can also be seen that the two check valves 52, 54 and the pressure sensor 56 are attached directly to a circuit board 60 with connections 66 for vehicle electronics, not shown. Through the circuit board 60 and coils 62, 64 also provided thereon, the two check valves 52, 54 can be switched to the open or closed position independently of one another. In addition, the sensor data received from the pressure sensor 56 is recorded and forwarded to the vehicle electronics. Likewise, the actuator 30 can also be actuated by the vehicle electronics via the circuit board 60. The circuit board 60 is completely accommodated in the housing 20 of the electro-hydraulic brake unit 10 or is completely integrated there and can be tempered via a cooler 24 provided on the housing 20. The circuit board 60, with the exception of the connections 66, is also included in the encapsulation, whereby it is better protected against environmental influences.

The 2 shows a schematic representation of an electro-hydraulic brake unit 10 for a motor vehicle according to a second embodiment. In the present case, the electro-hydraulic brake unit 10 is designed purely as an example as a fixed caliper brake.

The electro-hydraulic brake unit 10 is the in 1 The embodiment shown is basically similar, but has a further brake piston 80 with the second brake pad 74 arranged thereon. Furthermore, the ver In the present case, the connecting line 42, 44 provides brake fluid to both brake pistons 70, 80. The brake pistons 70, 80 and the brake pads 72, 74 are arranged symmetrically to the brake disc 90 in such a way that when the brake 10 is actuated, both brake pads 72, 74 are moved with the same force in the direction of the brake disc 90. As a result, the brake disc 90 is simultaneously subjected to force by both brake pads 72, 74, whereby a uniform braking effect and uniform wear of the two brake pads 72, 74 can be achieved.

3a and 3b show exemplary operating states of the electro-hydraulic brake unit 10 of the first embodiment designed as a floating caliper brake in a schematic flow diagram 1 . The ordinate 100 shows the increasing piston travel 112 of the piston 34, with the piston 34 contacting the actuator 30 at the value zero, as well as the increasing brake pressure 110. The abscissa 102 shows the elapsed time. Also shown are the switching states 104, 106 of the, usually closed, first check valve 52 (NC valve) and the second, usually open, check valve 54 (NO valve). Deviations from the closed position of the first check valve 52 or from the open position of the second check valve 54 are described below with reference to the reference numbers 114a-g and 124.

Out of 3a It can also be seen that in the normal operation described above, a distinction can be made between a passive operation 114a, a pressure build-up operation 114b and an analog pressure reduction operation 114c.

The passive operation 114a characterizes the rest position of the electro-hydraulic brake unit 10, in which both the brake and the actuator 30 are not actuated. As a result, the brake pressure 110, the piston travel 112 and the piston pressure are each zero.

The pressure build-up operation 114b and the analog pressure reduction operation 114c characterize the actual braking process. During pressure build-up operation 114b, the actuator 30 is controlled by actuating the brake in such a way that the piston 34 is extended. As a result, the brake pressure 110 and the piston pressure each increase, with the piston travel 112 either remaining the same or also increasing. In the analog pressure reduction operation 114, the actuator 30 is operated after the brake has been actuated in such a way that the piston 34 is retracted. As a result, the brake pressure 110 and the piston pressure each drop, with the piston travel 112 either remaining the same or also decreasing.

How out 3a taken further, in the alternative operation described above, a distinction can be made between a reloading operation after the pressure has been reduced 114e and a reloading operation with an increased volume requirement 114f.

The reloading operation after the pressure has been reduced 114e and the reloading operation with an increased volume requirement 114f each take place while the piston 34 is being retracted. As a result, brake fluid is removed from the reservoir 46, the piston pressure being constant, the piston travel 112 converging towards zero and the brake pressure 110 being smaller or is equal to zero.

The reloading operation after the pressure has been reduced 114e indicates the return of the piston 34 to its initial position for the special case of slip control, in which the spinning of one or more wheels of the motor vehicle with reduced or no grip on the road surface is counteracted by targeted braking initiated by the control unit becomes.

The recharging operation with increased volume requirement 114f, on the other hand, is only used if there is a loss of brake fluid from the brake circuit, for example and in particular due to a leak. The loss can be detected, for example, by a falling pressure in the brake circuit while the brake is in the rest position.

Furthermore, in the pressure compensation operation, a distinction can be made between a rapid pressure reduction operation 114d and a pressure compensation operation in the passive state 116.

The rapid pressure reduction operation 114d occurs during slip control, takes place without actuation of the actuator 30 and only requires a brief opening of the second check valve 54, whereby the brake pressure 110 and the piston pressure each drop quickly and the piston travel 112 remains the same or also decreases quickly.

The pressure equalization operation in the passive state 116 also takes place without actuation of the actuator 30 and requires both check valves 52, 54 to be opened simultaneously over a period of time that is usually longer than, for example, in passive operation 114a or one of the operations 114b-f. As a result, the brake pressure 110, the piston travel 112 and the piston pressure each drop to zero. Depending on the duration of the opening of both check valves 52, 54, in addition to pressure equalization, there is also a temperature equalization between the Connecting line 42, 44, the work space 40 and the reservoir 46, as well as the environment. In this way, frictional heat generated during braking, for example, can be effectively dissipated into the environment.

In 3b a regular reloading operation after pressure reduction 124 is shown purely schematically and by way of example. In contrast to the case mentioned above, the return of the piston 34 to its initial position occurs in response to the exceeding of a maximum pressure threshold value, which describes a maximum pressure, or in response to a certain number of braking operations. In contrast to the above-mentioned recharging operation after the pressure has been reduced 114e, in the present case the first check valve 52 is opened for a period of time that is usually longer than in the pressure equalization operation in the passive state 116 and one of the operations 114b-f. Once the pressure falls below a minimum threshold, the check valves 52, 54 are switched back to normal operation. As a result, the full braking effect of the electro-hydraulic brake unit 10 can be provided again in a simple manner.

The 4 shows a schematic sectional view of an electro-hydraulic brake unit 10 for a motor vehicle according to a third embodiment. In the present case, the electro-hydraulic brake unit 10 is designed purely as an example as a floating caliper brake.

The electro-hydraulic brake unit 10 has in the 4 Embodiment shown has an actuator 30 designed as a single-acting piston pump with an electric motor and a piston 34, which are arranged parallel to one another and adjacent to one another. The actuator 30 is non-positively connected to the piston 34 via a gear 202 designed as a ball screw. 4 It can also be seen that the piston 34 is partially arranged in the brake piston 70 of the electro-hydraulic brake unit 10 designed as a floating caliper brake, which is operated directly by the actuator 30.

A reservoir 46 with a filling valve 224 and a vent 222 is also arranged adjacent to and parallel to the piston 34. The reservoir 46 is in fluid communication with the working space 40 and the brake piston 70 via connecting lines 42, 444. The reservoir 46 also has a pressure sensor 56 which determines the pressure in the reservoir 46.

The electro-hydraulic brake unit 10 also has a parking brake or parking lock designed as an electromagnet 210. The electromagnet 210 has a solenoid coil 212 and a coil core 214 movably arranged therein. The electromagnet 210 is arranged on the spindle side, i.e. gear 202 formed adjacent to the ball screw, on the piston 34 in such a way that, by energizing the solenoid coil 212, the coil core 214 moves with respect to the solenoid coil 212 in a direction parallel to the direction of movement of the piston 34 and in can be locked in certain positions other than a bottom dead center. This prevents the piston from returning to its starting position, i.e. to bottom dead center. As a result, a brake pressure of the brake fluid present in the working space 40 is maintained and the brake piston 70 is also locked in a certain position. In this way, the self-locking effect of a parking brake or parking lock can be provided easily and inexpensively.

4 It can further be seen that the actuator 30 designed as an electric motor has an actuator control 206 and a torque sensor 204. Actuator control 206 and torque sensor 204 enable better control of the actuator 30, which is designed as an electric motor, and thus an optimized braking effect.

The actuator control 206, the torque sensor 204, a transmission control connected to the transmission 202, the electromagnet 210 and the pressure sensor 56 are as shown 4 can be seen, in particular due to the parallel and adjacent arrangement of the components mentioned, via circuit board connections 600 and a circuit board 60 connected to the vehicle electronics, not shown. The piston 34 and thus the brake piston 70 which is non-positively connected to it can thereby be selectively controlled by the vehicle electronics. The number of electrical components present in the electro-hydraulic brake unit 10 can thereby be reduced and these can be combined in such a way that encapsulation and the associated protection of the electrical components are simplified and improved. An integrated brake control is further simplified and optimized.

Due to the parallel and adjacent arrangement of the actuator 30 or reservoir 46 with respect to the piston 34, by a suitable choice of the gear ratio (purely by way of example 3:1) of the gear 202, and/or a ratio of the brake piston surface 700 to the piston surface 341 (purely example haft 8:1) the size of the actuator 30 can ultimately be reduced. As a result, the electro-hydraulic brake unit 10 can be provided in a cost- and space-optimized manner.

Reference symbols

10

Electro-hydraulic brake unit

20

Housing

22, 26

diaphragm

24

cooler

30

actuator

32

spindle

34

Pistons

36

Pressure source

38

Brake circuit

40

working space

42.44

connecting line

46

reservoir

48

membrane

50

bleeder screw

52

first switchable check valve

52

second switchable check valve

56

Pressure sensor

60

Circuit board

62, 64

Kitchen sink

66

connections

68

Housing

70.80

brake piston

72, 74

brake pad

76

Ring seal

78

Fold seal

90

Brake disc

100

ordinate

102

abscissa

110

Brake pressure

112

increasing piston travel

104, 106

Switching states of the first and second check valves

114a

Passive operation

114b

Pressure build-up operation

114c

analogue pressure reduction operation

114d

rapid depressurization operation

114e

Reloading operation after the pressure has been reduced

114f

Reloading operation with increased volume requirements

116

Pressure equalization operation in passive state

124

Regular recharging operation after the pressure has been reduced

202

transmission

204

Torque sensor

206

Actuator control

210

Electromagnet

212

Solenoid coil

214

Coil core

222

Venting

224

Fill valve

341

Piston area

600

PCB bindings

700

Brake piston area

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was 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

• EP 0774391 A1 [0004]

Claims (14)

Electro-hydraulic brake unit (10) for a motor vehicle, comprising a pressure source (36) designed as an actuator (30), at least one brake piston (70, 80), and a brake circuit (38) which connects the pressure source (36) and the at least one brake piston (70, 80), wherein the pressure source (36), the at least one brake piston (70, 80) and the brake circuit (38) are arranged in a wheel brake. Electro-hydraulic brake unit (10). Claim 1 , wherein the actuator (30) has a piston (34) which is non-positively connected to the actuator (30), and wherein the piston (34) and the actuator (30) are aligned parallel to one another, preferably wherein the piston (34) and the actuator (30) are arranged adjacent to one another, more preferably wherein the piston (34) is at least partially integrated into one of the brake pistons (70, 80). Electro-hydraulic brake unit (10) according to one of the preceding claims, comprising a parking brake designed as an electromagnet (210), the electromagnet (210) comprising a solenoid coil (212) and a coil core (214) movably arranged therein, the coil core (214) being designed to prevent the piston (34) from resetting , preferably wherein the coil core (214) is aligned parallel to the piston (34), and / or wherein the pressure source (36) has a gear (202) arranged between the actuator (30) and the piston, preferably wherein the actuator (30) is designed as an electric motor which is provided with a torque sensor (204), and / or wherein the brake circuit (38) has a working space (40), a connecting line (42, 44) and a reservoir (46), the piston (34) being movably arranged in the working space (40), the connecting line (42, 44 ) connects the working space (40) with the at least one brake piston (70, 80) and the reservoir (46), the reservoir (46) and the brake piston being aligned parallel to one another, preferably the reservoir (46) having a vent (222). has, wherein the vent (222) is arranged adjacent to the piston (34). Electro-hydraulic brake unit (10). Claim 3 , comprising a circuit board (60), wherein the piston (34) and the actuator (30) are arranged adjacent to the circuit board (60), preferably wherein the pressure source (36) is an actuator control (206) which is adapted to the actuator ( 30), and wherein the circuit board (60) is connected to one or more of the electromagnets (201) of the actuator control (206), a control unit of the transmission (202), the torque sensor (204), a pressure sensor (56), the is designed to determine a brake fluid pressure in the reservoir (46). Electro-hydraulic brake unit (10) according to one of the preceding claims, wherein the actuator (30) has a piston (34) and the brake circuit (38) has a working space (40) and a connecting line (42, 44), the piston (34) is movably arranged in the working space (40), the connecting line (42, 44) connecting the working space (40) to the at least one brake piston (70, 80). Electro-hydraulic brake unit (10). Claim 5 , wherein the brake circuit (38) has a reservoir (46) and a first switchable check valve (52), the connecting line (42, 44) having a second switchable check valve (54) through which the working space (40) of the at least one Brake piston (70, 80) can be decoupled, the reservoir (46) being decoupled from the connecting line (42, 44) by the first switchable check valve (52) at a position between the second switchable check valve (54) and the working space (40). . Electro-hydraulic brake unit (10). Claim 6 , wherein the reservoir (46) is designed as a low-pressure reservoir. Electro-hydraulic brake unit (10). Claim 7 , comprising a circuit board (60) on which a pressure sensor (56), the first switchable check valve (52, 54) and the second switchable check valve (54) are arranged, the connecting line (42, 44) connecting the pressure sensor (56) to Determining a pressure in the connecting line (42, 44). Electro-hydraulic brake unit (10) according to one of the preceding claims, wherein the connecting line (42, 44) has a pressure sensor (56) for determining a pressure in the connecting line (42, 44). Electro-hydraulic brake unit (10) according to one of the preceding claims, wherein the electro-hydraulic brake unit (10) is designed as a floating caliper brake or fixed caliper brake. Electro-hydraulic brake unit (10) according to one of the preceding claims, wherein the electro-hydraulic brake unit (10) is designed as a closed system. Vehicle comprising an electro-hydraulic brake unit (10) according to one of the preceding claims. Vehicle after Claim 12 , wherein each wheel of the vehicle is provided with the electro-hydraulic brake unit (10). Method for controlling the electro-hydraulic brake unit (10). Claim 5 , comprising: (i) performing a normal operation in which the first check valve (52) is closed and the second check valve (54) is open, the normal operation being adapted to achieve a braking effect, (ii) performing an alternative operation in response to exceeding a first pressure threshold value, at which the first check valve (52) is open and the second check valve (54) is closed, the alternative operation being adapted for a resetting of the piston (34), in which the piston (34) controls the actuator ( 30) contacted, and (iii) performing normal operation in response to falling below a second pressure threshold, wherein the second pressure threshold is less than the first pressure threshold.

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