DE102017211955A1 - Brake system with an additional module - Google Patents

Abstract

Brake system (1) for motor vehicles, in particular for highly automated driving, with a brake pedal (5a) with an associated driver braking request detection device (341), with, in particular at least four, hydraulically actuable wheel brakes (8, 9, 10, 11) and with a primary brake control unit ( 1d) comprising at least one electrically operable wheel valve (6a-6d, 7a-7d) per wheel brake (8, 9, 10, 11) for setting wheel-specific brake pressures; a pressure medium reservoir (4) under atmospheric pressure; and an electrically controllable pressure supply device (5) for actuating the wheel brakes (8, 9, 10, 11) with a hydraulic pressure chamber (37), wherein each wheel brake (8, 9, 10, 11) is hydraulically connected to the pressure chamber (37) ; wherein the brake system (1) comprises an additional module (70) comprising a hydraulic unit (80) with a pressure supply device for active pressure build-up in at least two wheel brakes (8, 10); and wherein there is no hydraulic and / or mechanical operative connection between the brake pedal (5a) and the wheel brakes (8, 9, 10, 11).

Description

The invention relates to a braking system for motor vehicles, in particular for highly automated driving, according to the preamble of claim 1.

In automotive engineering, brake-by-wire brake systems are becoming increasingly widespread. Such brake systems often comprise, in addition to an actuatable by the driver master cylinder an electrically ("by-wire") controllable pressure supply device by means of which in the operating mode "brake-by-wire" takes place an actuation of the wheel brakes.

In these brake systems, in particular electro-hydraulic brake systems with the "brake-by-wire" mode, the driver is decoupled from the direct access to the brakes. Upon actuation of the pedal usually a pedal decoupling unit and a simulator are operated, which is detected by a sensor, the braking request of the driver. The pedal simulator, which is usually designed as a master brake cylinder, serves to give the driver as familiar and comfortable a brake pedal feel as possible. The detected braking request leads to the determination of a desired braking torque, from which then the target brake pressure for the brakes is determined. The brake pressure is then actively built up by a pressure-providing device in the brakes.

The actual braking thus takes place by active pressure build-up in the brake circuits with the aid of a pressure supply device, which is controlled by a control and regulation unit. As a result of the hydraulic decoupling of the brake pedal actuation from the pressure build-up, many functionalities such as ABS, ESC, TCS, hill-start assist etc. can be comfortably realized for the driver in such brake systems.

In such brake systems, there is usually provided a hydraulic fallback level by which the driver can decelerate or stop the vehicle by muscular force upon actuation of the brake pedal when the "by-wire" mode fails or is disturbed. While in normal operation by a pedal decoupling unit, the above-described hydraulic decoupling between brake pedal operation and brake pressure build-up, this decoupling is canceled in the fallback so that the driver can move brake means directly into the brake circuits. In the fallback level is switched when with the help of the pressure supply device no pressure build-up is possible. This is i.a. then the case when the check valve, which connects the pressure supply device with the reservoir, no longer reliably locks, so that a pressure build-up is no longer possible reliably.

The pressure-providing device in brake systems described above is also referred to as an actuator or hydraulic actuator. In particular, actuators are designed as linear actuators or linear units in which a piston is axially displaced into a hydraulic pressure chamber for pressure build-up, which is built in series with a rotational-translation gear. The motor shaft of an electric motor is converted by the rotation-translation gear in an axial displacement of the piston.

From the DE 10 2013 204 778 A1 is a "brake-by-wire" -Bremsanlage for motor vehicles is known which a brake pedal operable tandem master cylinder, the pressure chambers are connected via an electrically actuated release valve separable with a brake circuit with two wheel brakes, a hydraulically connected to the master cylinder, switched on and off simulation device , And an electrically controllable pressure-supplying device, which is formed by a cylinder-piston arrangement with a hydraulic pressure chamber whose piston is displaceable by an electromechanical actuator includes, wherein the pressure-supplying device is connected via two electrically actuated Zuschaltventile with the intake valves of the wheel brakes.

In normal operation, the driver is disconnected from the wheel brakes by switching driver isolation valves and the linear actuator is hydraulically connected to the wheel brakes by switching actuator control valves. A method of the linear actuator from its rest position forward causes a pressure build-up and in the opposite case a pressure reduction in the wheel brakes.

Such a brake-by-wire brake system is not suitable for use in automated driving in which the vehicle control is partially or substantially fully automated so that the driver can engage in other activities. In case of failure of the normal level of the brake system, it may take a relatively long time for the driver to notice this failure and he himself pressed the brake pedal by muscle power.

For automated driving, in particular highly automated driving (HAF), therefore, a backup module is needed, which can ensure a basic brake functionality until it is taken over by the driver in case of failure of the main brake system. In this way, exactly the time span is bridged, which is between the failure and the operational readiness of the driver.

There are already various solutions for this. In some of these technical solutions it is envisaged to install on the additional module its own brake fluid reservoir, which is connected via a hose to the container of the primary brake system.

For vehicles used in autonomous driving, it is necessary to ensure that in the event of failure of the primary brake control device accidental braking of the driver can continue to be prevented. In known brake systems, however, the driver usually receives direct access to the rear brakes in case of failure of the primary brake control device.

The invention is therefore based on the object to improve an above-mentioned brake system to prevent direct access of the driver to the brakes in case of failure of the primary brake control unit reliably while allowing braking.

This object is achieved by a braking system according to claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the consideration that in particular in the autonomous or highly automated driving operation of a motor vehicle (HAF) in the event of failure of the primary control unit, the driver's access to wheel brakes, in particular a braking of the driver, should be prevented. Such driver intervention may run counter to the automatic control of an add-on module that actively applies pressure to two wheel brakes, which may cause the vehicle to enter dangerous and uncontrollable situations.

As has now been recognized, this problem can be avoided by not providing a master cylinder operable by the driver in a fallback mode and not providing hydraulic or mechanical engagement of the brake pedal with the wheel brakes. This reliably prevents the driver from decelerating the vehicle by actuating the brake pedal or from engaging in the braking operations performed by the control and regulation unit of the brake system and / or additional module. The brake pedal is thus used essentially exclusively for detecting the driver's braking request.

Advantageously, two wheel brakes are hydraulically connected via a common, in particular normally open, separating valve with the pressure medium reservoir. In this way, a brake system module or a primary brake control unit with isolation valves can also be advantageously used for the brake system according to the invention.

Two wheel brakes are preferably connected via a common Zuschaltventil with the pressure supply device.

Preferably, the primary brake control unit is designed with two circuits, wherein each brake circuit, a center port is provided, to which the wheel brakes of the brake circuit are connected, which is connected via a Zuschaltventil to the pressure chamber, and which is connected via a separating valve with the pressure medium reservoir. In this way, a primary brake control unit with separating valves and connecting valves can also be advantageously used for the brake system according to the invention.

Preferably, the driver braking request detection is not hydraulically coupled to the wheel brakes or run dry from the outset.

Advantageously, the driver's braking request detection device comprises a, in particular redundant, travel sensor.

In a first preferred embodiment, the driver braking request detection device is made dry.

Preferably, the driver braking request detection device is designed as a dry simulator having a simulator space in which an elastic element is arranged against which an actuating piston presses when the brake pedal is actuated.

In a second preferred embodiment, the driver's brake request detection device has a hydraulic pressure chamber, which is hydraulically connected to a simulator chamber.

Preferably, a pressure sensor is provided for measuring the pressure in the simulator chamber. The signal of the pressure sensor is advantageously used to control the desired setpoint brake pressure.

The driver's braking request detection device is preferably designed as a separate or independent module. This allows it to be mounted on the bulkhead of the motor vehicle, while the primary brake control unit and / or the additional module can be installed at other locations. The driver brake request detection can also be designed together with the brake pedal as a common module.

In an alternative embodiment, the driver's braking request detection device is integrated in the primary brake control unit.

In the additional module, at least one reservoir for brake fluid is advantageously integrated into the hydraulic unit.

The respective reservoir is preferably connected to a hydraulic equalization line to form an atmosphere port.

The advantages of the invention are, in particular, that actuation of the wheel brakes by the driver can be reliably prevented by the described prevention of an operative connection of the brake pedal with the wheel brakes. The brake system requires fewer components than known brake systems, which can be dispensed with the tandem master cylinder. As a result, the brake system in their construction is more compact and cheaper. When forming the driver's braking request recognition device as an independent module primary brake control unit and / or additional module can be installed at other locations and not necessarily on the bulkhead, which in particular NVH interference can be avoided.

• 1 ein Bremssystem mit einem Zusatzmodul in einer ersten bevorzugten Ausführungsform;
• 2 ein Bremssystem mit einem Zusatzmodul in einer zweiten Ausführungsform;
• 3 eine Fahrerbremswunscherfassung des Bremssystems gemäß 2 und 4; und
• 4 ein Bremssystem mit einem Zusatzmodul in einer dritten Ausführungsform.

An embodiment of the invention will be explained in more detail with reference to a drawing. In it show in a highly schematic representation:

• 1 a braking system with an additional module in a first preferred embodiment;
• 2 a braking system with an additional module in a second embodiment;
• 3 a driver brake request detection of the brake system according to 2 and 4 ; and
• 4 a braking system with an additional module in a third embodiment.

Identical parts are provided with the same reference numerals in all figures.

In the 1 is a preferred embodiment of a brake system according to the invention or a brake system according to the invention 1 with a primary brake control unit 1d shown. The primary brake control unit 1d includes under atmospheric pressure pressure medium reservoir 4 , an electrically controllable pressure supply device 5 , which by a cylinder-piston arrangement with a hydraulic pressure space 37 is formed, whose pistons 36 by an electromechanical actuator comprising an electric motor 36a and a rotational-translation gear 36b , Is displaceable, an electrically controllable pressure modulation device for setting wheel-individual brake pressures and an electronic control unit 12 ,

The unspecified pressure modulation device comprises according to the example per hydraulically actuated wheel brakes 8th . 9 . 10 . 11 and each operable wheel brake 8th . 9 . 10 . 11 an inlet valve 6a - 6d and an exhaust valve 7a - 7d in pairs via center connections 12a . 12b hydraulically interconnected and to the wheel brakes 8th . 9 . 10 . 11 are connected. The inlet connections of the inlet valves 6a - 6d be by means of brake circuit supply lines 13a . 13b . 13c . 13d supplied with pressures that are derived in a "brake-by-wire" mode from a system pressure in one to the pressure chamber 37 the pressure supply device 5 connected system pressure line 38 is present. The inlet valves 6a - 6d is one to each of the brake circuit supply lines 13a - 13d opening check valve 50a - 50d connected in parallel. The outlet connections of the outlet valves 7a - 7d are via a return line 14b with the pressure medium reservoir 4 connected.

The electrically controllable pressure supply device 5 is designed as a hydraulic cylinder-piston arrangement or a single-circuit electrohydraulic actuator whose / whose pressure piston 36 which the pressure room 37 limited, of the schematically indicated electric motor 36a with the interposition of a rotation-translation gear also shown schematically 36b is operable. One of the detection of the rotor position of the electric motor 36a serving, only schematically indicated rotor position sensor is denoted by the reference numeral 44a designated. In addition, a temperature sensor can also be used 44b be used to sense the temperature of the motor winding.

The by the force effect of the piston 36 on the in the pressure room 37 enclosed pressure fluid generated actuator pressure is in the system pressure line 38 fed and with a preferably redundant pressure sensor 19 detected.

Between the center connection 12a and the pressure room 37 is a connection valve 26a connected. center connection 12a is via a separating valve 27a with the pressure medium reservoir 4 separably connected. Between the center connection 12b and the pressure room 37 is a connection valve 26b connected. center connection 12b is via a separating valve 27b with the pressure medium reservoir 4 separably connected. With open connection valves 26a . 26b the pressure medium enters the wheel brakes 8th . 9 . 10 . 11 for their operation. By pushing back and forth the piston 36 takes place with open connection valves 26a . 26b during a normal braking in the "brake-by-wire" mode Wheel brake pressure buildup and removal for all wheel brakes 8th . 9 . 10 . 11 , During pressure reduction, this flows from the pressure chamber before 37 in the wheel brakes 8th . 9 . 10 . 11 shifted pressure medium with closed separating valves 27a . 27b back to the pressure room the same way 37 back. The valves 27a . 27b are needed to implement the atmospheric connection. Without these valves, the brake fluid could not relax when the vehicle is parked. You can also be used here additionally to reduce the pressure in each case in a circle, since the driver is hydraulically decoupled from the whole system in this invention.

On the other hand, when braking with different individual wheel flows, with the help of the intake and exhaust valves 6a - 6d . 7a - 7d regulated wheel brake pressures (eg in the case of anti-lock control (ABS control)) via the exhaust valves 7a - 7d drained pressure medium content in the pressure fluid reservoir 4 and thus initially stands the pressure supply device 5 for actuating the wheel brakes 8th . 9 . 10 . 11 no longer available. A suction of pressure medium in the pressure chamber 37 is by a return of the piston 36 with closed connection valves 26a . 26b through a suction line 58 , in which a check valve is connected, possible.

The brake system 1 includes an additional module 70 , which in case of failure of the pressure build-up possibility of the brake system 1 with the help of the primary brake control unit 1d in two wheel brakes, namely the front brakes 8th . 10 , Can perform braking interventions.

The additional module 70 has one in a housing or hydraulic housing 76 arranged hydraulic unit 80 on. A pressure delivery device 86 includes an electric motor 92 , by the demand, two pumps 96 . 98 operate. The pump 96 is on the pressure side via a hydraulic line or Radbremszuleitung 102 with the wheel brake 8th connected. The pump 98 is on the pressure side via a line or Radbremszuleitung 108 with the wheel brake 10 connected.

The additional module 70 is designed to be able to reliably assume a braking function if required and brake pressure in the wheel brakes 8th . 10 to build up. There are two reservoirs for this purpose 120 . 130 intended for brake fluid contained in the hydraulic unit 80 are integrated and in the hydraulic housing 76 are arranged. The brake fluid reservoir 120 is with the suction side of the pump 96 via a hydraulic line 136 hydraulically connected, into which a normally closed reservoir valve 142 is switched. The reservoir 130 is on the suction side via a hydraulic line 148 into which a normally closed reservoir valve 152 is switched, with the pump 98 hydraulically connected. A preferably redundantly designed pressure sensor 160 measures the pressure in the pipe 102 ; a preferably redundantly designed pressure sensor 162 measures the pressure in the pipe 108 , A control unit 182 is signal input side with the pressure sensors 160 . 162 connected.

From the line 102 branches a hydraulic return line 170 off, the wire 102 with the reservoir 120 connects hydraulically, wherein in the return line, a normally closed return valve 176 is switched. From the line 108 Branches a hydraulic return line 180 into which a normally closed return valve 186 is switched.

The following is the hydraulic connection of the additional module 70 with the brake system 1 described. A common hydraulic equalization line 190 connects both reservoirs 120 . 130 with the brake fluid reservoir 4 at a brake fluid reservoir connection 196 ,

The wheel brake 10 , which in this case corresponds to the right front brake, is with the pressure delivery device 5 via a brake line 202 connected. The wheel brake 8th , which corresponds to the left front brake, is through a brake line 200 with the pressure delivery device 5 connected. wheel brakes 9 . 11 are each with a brake line 204 . 206 with the pressure-providing device 5 connected.

The additional module 70 is hydraulic in the brake lines 200 . 202 switched such that a portion of these brake lines in the additional model 70 runs. In this way, the additional module in the brakes 8th . 9 if necessary build up brake pressure. The brake line 200 runs in a line section 210 within the add-on module 70 , In the line section 210 is a normally open isolation valve 220 connected. A pressure sensor 194 measures the pressure in the brake line 200 , The signal of the pressure sensor 194 is preferably the driver brake request detection in a fallback level, in the brake pressure position of the additional module 70 is taken over.

The brake line 202 runs in a line section 234 within the add-on module 70 , In the line section 234 is a normally open isolation valve 240 connected. The additional module 70 is designed to be needed in the front brakes 8th . 10 actively build pressure. To the respective isolation valve 220 . 240 each one check valve is connected in parallel.

The brake system 1 has two electrical systems 300 . 310 on, from your first electrical system 300 the primary brake control unit 1d feeds and a second electrical system 310 the additional module 70 fed.

The brake system 1 is fully designed for brake-by-wire operation and has no master cylinder. It thus also has no mechanical or hydraulic fallback level, in the event of failure of the primary brake control unit 1d the driver by muscle power when pressing a brake pedal 5a Brake pressure in at least two wheel brakes 9 . 11 (especially rear brakes) can build. The fallback level is present with the help of the additional module 70 realized. In this way, the driver is prevented when the brake control unit fails 1d the vehicle brakes on the rear axle. In highly automated driving situations, this intervention by the driver in connection with the regulations implemented can lead to dangerous maneuvers.

In the preferred embodiment shown, a measure of the operation of the brake pedal 5a directly with the help of a, preferably redundantly designed, displacement sensor 314 measured, the a driver brake request detection device 341 forms. displacement sensor 314 is via a signal line 320 Signal input side with the control unit 12 the primary brake control unit 1d connected. Another signaling connection of the displacement sensor 314 is given with the control unit 182 of the additional module 70 , so even in case of failure of the primary brake control unit 1d the driver's brake request can be detected.

The brake pedal 5a and the displacement sensor 314 are preferably structurally separate from the primary brake control unit 1d , ie as a separate module. While you are attached to the bulkhead, the brake control unit 1d and additional module are not attached to the bulkhead, so that NVH interference can be avoided.

A second preferred embodiment of a brake system 1 is in 2 shown. In this variant, the driver brake request detection is a dry run simulator 340 as driver braking request detecting device 341 used the brake pedal 5a and a pedal bar 348 and an actuating piston 344 is coupled. brake pedal 5a is by means of the pedal coupling rod 348 to the actuating piston 344 coupled. When the brake pedal is pressed 5a the actuating piston moves 344 in a dry running simulator room 350 of the simulator 340 in which an elastic simulator element 354 is arranged. When the actuating piston 344 in the simulator room 350 is moved, he presses against the simulator element 354 , causing the driver resistance on the brake pedal 5a learns and gets a familiar brake pedal feeling. Unlike known brake systems is the simulator 340 directly behind the actuating piston 344 arranged. The driver brake request detection takes place again with the aid of a preferably redundantly designed displacement sensor 214 ,

In 3 is a driver's brake request detecting device 341 in a first preferred variant 370a (left) and a second preferred variant 370b (right). In the example on the left is the elastic element 354 designed as a spring. In both variants is a magnet 380 provided, the spatial position change using a sensor detection element 314a is detected (magnet 380 and sensor detection element 314a form a displacement sensor 314 ). The driver request detection or driver brake request detection device 370a is designed hydraulically and corresponds in particular to the in 1 illustrated brake system 1 , Instead of a tandem master cylinder, a master cylinder is used. Due to the pressure in the pressure chamber of the master cylinder, the subsequent simulator is pressurized. The driver brake request detection device 370b is dry and corresponds in particular to the in 1 illustrated brake system 1 , The driver presses directly into the simulator or onto an elastic element 354 which is preferably formed as an elastomeric piece.

A receptacle for the piston rod or a pressure piece 390 is provided to the foot force on the piston surface of the component 344 to be able to forward. The figure also shows the piston rod 392 , the plastic case 394 the ECU and a circuit board 396 within the ECU.

In 4 is a braking system 1 represented in a further preferred embodiment. There is a hydraulic control room 400 provided, in which the actuating piston 344 upon actuation of the brake pedal 5a is moved. In the operating room 400 is an elastic element, in particular a spring element 404 arranged, of which the actuating piston 344 is charged. About a compensation line 408 and seals 412 in the operating room is the operating room 400 hydraulically with the pressure fluid reservoir 4 connected with unoperated brake pedal 5a , ie with unactuated actuating piston 344 , which is then shown in FIG. is at the right stop. Via a hydraulic line 420 is the operating room 400 with a hydraulic simulator chamber 426 connected. A preferably redundantly designed pressure sensor measures the pressure in the simulator chamber 426 or in the hydraulic line 420 , The simulator chamber 426 is from a simulator piston 430 limited by an elastic element 354 in a simulator room 350 is arranged. The driver brake request acquisition 341 is designed as a simulator and includes simulator chamber 426 , Simulator piston 439 , elastic element 354 , Simulator room 350 and a, preferably redundant, displacement sensor 314 and a, preferably redundant, pressure sensor 430 ,

In this embodiment, the driver's brake wash is done in a redundant manner with the aid of the displacement sensor 314 and with the help of the pressure sensor 430 certainly.

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 102013204778 A1 [0007]

Claims (13)

Brake system (1) for motor vehicles, in particular for highly automated driving, with a brake pedal (5a) with an associated driver braking request detection device (341), with, in particular at least four, hydraulically actuable wheel brakes (8, 9, 10, 11) and with a primary brake control unit ( 1d) comprising • at least one electrically operable wheel valve (6a-6d, 7a-7d) per wheel brake (8, 9, 10, 11) for setting wheel-specific brake pressures; • a pressure medium reservoir (4) under atmospheric pressure; and • an electrically controllable pressure supply device (5) for actuating the wheel brakes (8, 9, 10, 11) with a hydraulic pressure chamber (37), wherein each wheel brake (8, 9, 10, 11) is hydraulically connected to the pressure chamber (37) is; wherein the brake system (1) comprises an additional module (70) comprising a hydraulic unit (80) with a pressure supply device for active pressure build-up in at least two wheel brakes (8, 10); characterized in that there is no hydraulic and / or mechanical operative connection between the brake pedal (5a) and the wheel brakes (8, 9, 10, 11). Braking system (1) after Claim 1 , wherein the primary brake control unit (1d) is designed to be dual-circuited, wherein each brake circuit, a center port (12a, 12b) is provided, to which the wheel brakes (8, 9, 10, 11) of the brake circuit are connected, and which via a Zuschaltventil (26a , 26b) is connected to the pressure chamber (37), and which is connected via a separating valve (27a, 27b) with the pressure medium reservoir (4). Braking system (1) after Claim 1 or 2 , wherein in each case two wheel brakes (8, 9, 10, 11) are hydraulically connected via a common separating valve (27a, 27b) to the pressure medium reservoir (4). Braking system (1) according to one of Claims 1 to 3 , wherein in each case two wheel brakes (8, 9, 10, 11) via a common Zuschaltventil (26a, 26b) are connected to the pressure supply device (5). Braking system (1) according to one of Claims 1 to 4 wherein the driver braking request detection device (341) comprises a, in particular redundant, travel sensor (314). Braking system (1) according to one of Claims 1 to 5 wherein the driver braking request detecting device (341) is made dry. Braking system (1) after Claim 6 wherein the driver braking request detection device (341) is designed as a dry simulator with a simulator space (350) in which an elastic element (354) is arranged against which an actuating piston (344) presses when the brake pedal (5a) is actuated. Braking system (1) according to one of Claims 1 to 5 wherein the driver braking request detecting device (341) comprises a hydraulic pressure space (400) hydraulically connected to a simulator chamber (426). Braking system (1) after Claim 8 wherein a pressure sensor (430) is provided for measuring the pressure in the simulator chamber (426). Braking system (1) according to one of Claims 1 to 9 wherein the driver braking request detection device (341) is designed as a separate module. Braking system (1) according to one of Claims 1 to 9 wherein the driver braking request detecting device (341) is integrated with the primary brake control unit. Braking system (1) according to one of Claims 1 to 11 in which at least one reservoir (120, 130) for brake fluid is integrated in the hydraulic unit (80) in the additional module (70). Braking system (1) after Claim 12 wherein the respective reservoir (120, 130) is connected to a hydraulic compensating pipe (190) provided for forming an atmosphere port.

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