WO2015022264A1

WO2015022264A1 - Braking system for motor vehicles and related operating method

Info

Publication number: WO2015022264A1
Application number: PCT/EP2014/067055
Authority: WO
Inventors: Holger Kollmann; Christian Courth
Original assignee: Continental Teves Ag & Co. Ohg
Priority date: 2013-08-16
Filing date: 2014-08-08
Publication date: 2015-02-19
Also published as: DE102013216314A1

Abstract

The invention relates to a braking system (50) for motor vehicles, which can be actuated in a "brake-by-wire" operating mode both by the vehicle driver and independently of the vehicle driver, and has a hydraulic fallback mode in which it can only be actuated by the driver, said braking system (50) having: two braking circuits (94, 96), wherein two wheel brakes (98, 100, 102, 104) are allocated to each braking circuit (94, 96); a brake pedal (56) for actuating a pedal decoupling unit (62); a path detection device (220), which detects the actuating path of the brake pedal (56) or of a piston connected to the brake pedal; a simulator (68) having a simulator release valve (222) which, in the "brake-by-wire" operating mode, imparts a brake pedal feel to the driver and which, in the fallback mode, is hydraulically separated; an electrohydraulic pressure supply device (86) which can be actuated by a control and regulating unit (80) to build up braking pressure; a pressure modulation device (92), which has an inlet valve (110, 112, 114, 116) and an outlet valve (120, 122, 124, 126) for adjusting wheel-individual braking pressures for each wheel brake (98, 100, 102, 104), wherein two normally closed actuator circuit separating valves (120, 212) are provided, via which the pressure supply device (86) can be hydraulically connected to the two braking circuits (94, 96) and wherein precise pressure modulations are made possible, particularly during a recuperative braking process. An outlet valve (124) of a rear wheel brake (102) is designed as a normally closed analog outlet valve and an actuator circuit separating valve (212) is designed as a normally closed analog actuator circuit separating valve.

Description

Brake system for motor vehicles and related operations

The invention relates to a brake system for motor vehicles, which is actuated in a "brake-by-wire" mode both by the driver and independently controllable by the driver and has a hydraulic fallback level in which it can only be operated by the driver, with two brake circuits, wherein each brake circuit are each associated with two wheel brakes, with a brake pedal for actuating a pedal decoupling unit, with a position detecting device which detects the actuation of the brake pedal or a piston connected to the brake pedal, with a simulator with a Simulatorsfreigebeventil, in the mode "Brake-by "The driver gives a brake ^¬ pedal feeling and is hydraulically separated in the fallback level, with an electro-hydraulic Druckbe ^¬ provisioning device, which can be controlled by a control and regulating unit to build up brake pressure, with a pressure modulation device for setting wheel-individual brake pressures for each wheel brake each having an inlet valve and an exhaust valve, wherein isolation valves are provided, through which the pressure chambers of the pedal decoupling unit can be hydraulically separated from the wheel brakes, and wherein two normally closed Aktuatorkreis separation valves are pre ^¬ see, by the pressure supply device hydraulically can be connected to the two brake circuits. It further relates to an operating method for such a brake system.

The "brake-by-wire" mode of braking system, especially electrohydraulic braking systems, results in a mechanical-hydraulic decoupling of the driver's brake pedal operation, whereby the driver operates a simulator or brake pedal feel simulator to give him a comfortable and familiar pedal feel However, this operation does not directly displace brake fluid into the brake circuits, as in conventional hydraulic brake systems Simulators of the driver's braking request determined, which then enters into the determination of a desired braking torque or target brake pressure. The actual braking is then carried out by active pressure build-up in the brake circuits by means of a Druckbe ^¬ riding position means which is actuated by a control and regulating unit. Due to 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 realized in such brake systems in a comfortable way.

In such brake systems, there is usually provided a hydraulic fallback mode 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 ^¬ decoupling unit is carried out the above-described hydraulic Ent ^¬ coupling between brake pedal and brake pressure build-up, in the fallback level, this decoupling is canceled, so that the driver can move directly braking means in the braking circuits.

From DE 10 2010 040 097 AI a brake system is known, which is operated in normal mode in the "brake-by-wire" mode.

In vehicles with electric motor - pure electric vehicles or hybrid vehicles with additional combustion engine - is advantageously the battery that supplies the electric motor with power during driving, charged by recuperative braking. In this case, the electric motor acts as a generator and generates on the corresponding axis a recuperative braking ^¬ moment. Especially with such recuperative braking operations, it is important to distribute the desired braking torque precisely to a recuperative component and a hydraulic component. That is, the admixture of the hydraulic portion is just the difference between the desired braking torque and the recuperative share correspond. The invention is therefore based on the object of specifying a brake system in which precise pressure modulations, in particular during a recuperative braking process, are possible. Furthermore, a method for operating such a brake system is to be specified.

With respect to the brake system, this object is achieved in that an exhaust valve of a rear brake as normally closed analog outlet valve and a

Aktuatorkreis-separating valve is designed as normally closed analog Aktuatorkreis-separating valve.

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

The invention is based on the consideration that a very precise pressure modulation is required for the necessary during recuperative braking admixtures of hydraulic braking torque. The pressure reduction is preferably carried out via the control of the exhaust valves.

As has now been recognized, can be particularly accurate

Pressure modulations resp. Achieve pressure settings by a combination of two analogously designed valves, namely an exhaust valve and an Aktuatorkreis-separating valve is set ^¬ . All other valves can be digital. Due to the analogous functionality, pressure profiles which correspond to an admixture of a hydraulically generated braking torque can be reproduced or realized essentially with a smooth progression and continuously. This eliminates the pressure stages associated with the frequent and rapid opening and closing of digital valves. Advantageously, exactly one analogue outlet valve and exactly one analogue actuator circuit isolation valve are provided. In other words, in the case of four wheel brakes, each with one exhaust valve, through which the respective wheel brakes can be drained liquid, three of the four exhaust valves are digitally designed, and only one of them as an analog valve. This is based on the consideration that in vehicles with recuperative energy recovery recuperative braking usually takes place on an axis, in particular the rear axle, so that an analogue exhaust valve for the

Pressure reduction can be used for both rear brakes.

Accordingly, in a preferred embodiment, a first brake circuit, the two front brakes and a second brake circuit, the two rear brakes, the analog exhaust valve is assigned to a rear brake and wherein the analog Aktuatorkreis-separating valve to the second brake circuit to ^¬ ordered. If a braking torque is built up recuperatively on the rear axle, a hydraulic braking torque can be mixed very precisely and without undesired jumps by the targeted control of the analog exhaust valve on one of the wheel brakes on the rear axle and the analog Aktuatorkreis-separating valve, so that the target braking torque is achieved.

The pedal decoupling unit preferably comprises two

Pressure chambers, in each of which a piston is arranged movable, wherein isolation valves are provided, through which the pressure chambers of the pedal decoupling unit can be hydraulically separated from the wheel brakes. As a result, hydraulic decoupling from the pedal decoupling unit and the wheel brakes is achieved in "by-wire" mode In the fallback stage, the isolating valves are opened, so that the driver can hydraulically actuate the wheel brakes by virtue of muscular force.

The simulator advantageously has a pressure chamber into which brake fluid is displaced from at least one of the pressure chambers of the pedal decoupling unit in the "brake-by-wire" mode, ie the driver shifts brake means into the simulator and is decoupled from the direct actuation of the brakes. This is important, for example, in recuperative braking, where the currently available maximum recuperative braking torque is to be used, and the hyd ^¬ raulische additional braking torque is just large enough that overall the desired braking torque is present. In a preferred embodiment, in the simulator for

Generation of a pedal feel a piston pressed against an elastic spring element. The piston is preferably actuated by the pressure medium flowing in the pressure medium. The simulator ^release valve is preferably a check ^¬ valve connected in parallel, which ensures an unthrottled in ^¬ flow of pressure medium in the pressure chamber.

With respect to the method for operating such a brake system, the above object is achieved according to the invention by the analog exhaust valve is controlled during the pressure reduction in the rear brakes and the intake valves of the rear wheel brakes are opened. This results in a hydraulic pressure equalization between the two rear wheel brakes and the analogue exhaust valve can be used for analog controlled and even pressure equalization of both rear brakes.

Advantageously, to build up the pressure

Actuator circuit-separating valve controlled, in particular fully ^¬ constantly closed to prevent an influx of brake fluid from the pressure supply device or a return to it. Are preferred in a fallback the

Actuator circuit isolation valves closed and that

Simulatorfreigebeventil closed so that brake fluid from the pressure chambers of the pedal decoupling in the

Brake circuits can be moved.

The advantages of the invention are, in particular, that precise analogue pressure modulations are possible without the use of two analogue valves at the points described above that all valves must be designed analog. For example, using only one rear wheel exhaust analog exhaust valve (the other rear wheel brake has a digital exhaust valve associated with it) is more precise

Pressure reduction possible in both brakes. The use of an analog exhaust valve to build up pressure in the rear brakes, closing the two intake valves, prevents the formation of yawing moments due to pressure variations in the two brakes, thus increasing driving stability.

By using an analog Aktuatorkreis-separating valve, a pressure difference between the two brake circuits can be set proportionally to a current specification according to a pressure ^¬ minderventil function. This is also infinitely possible, so that a continuously decreasing braking torque from the electric recuperation can be fully compensated by correspondingly increasing hydraulic braking torque on the rear axle. In conjunction with the analog outlet on a rear-circle as rising and falling off brake force distribution can be continuously re ^¬ ALISE in any form.

If only two analogue valves are used at the above-described positions, costs can be saved compared to configurations with other analogue valves. Compared to a configuration with two fully analog Raddruckreglern (an analog inlet and an analog From ^¬ inlet valve per rear wheel) two current-controlled amplifiers for analog inlet valves can be replaced by digital, when the intake valve converts the digital ABS control and performs no brake torque distribution. Also, the intake valve itself can be deferred due to the omission of the fully-analogous function. An embodiment of the invention will be described with reference to a

Drawing explained in more detail. In it show in a highly schematic representation: FIG. 1 the exemplary time course of braking torques during a recuperative braking process,

FIG. 2 to FIG. 1 associated course of brake pressures,

FIG. FIG. 3 shows the flow of flows in the analog exhaust valve and the analog actuator circuit intake valve, and a brake system in a preferred embodiment. FIG

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

On an x-axis 2 in FIG. 1 is the time and on a y-axis 8, the braking torque plotted. The total braking torque 14 during a braking operation of a motor vehicle (to ^¬ particular passenger cars) with an electric motor, which is used for recuperative braking, is composed of a recuperative braking torque 20 on the rear axle, a hyd ^¬ raulischen braking torque 26 on the front axle and a hyd ^¬ Raulischen braking torque 32 at the rear axle. The braking torques 20, 26, 32 add up the total braking torque 14 (the drawing is not to scale). Between times ti and t ₂ , the total braking torque 14 increases linearly in order to then be substantially constant between the time t ₂ and a time t ₃ . Between the time te and a time t ₇ , it then decreases linearly again. The hydraulic braking torque 26 on the front axle runs between t ₂ and te also constant.

The regenerative braking torque 20, however, initially runs between t ₂ and t ₃ constant, then rises linearly between t ₃ and t ₄ in order then to extend constant between t ₄ and t s and fall between ts and te linear. Such a chronological course of the recuperative braking torque corresponds, for example, to a braking from high speed to a standstill, in which, as a result of the characteristic of the electric machine, the recuperatively usable torque is first with decreasing speed. ₀

O

increases, but then drops sharply to a standstill. The course of the hydraulic braking torque 32 results from the difference between the total braking torque 14, and recuperative braking moment20 and hydraulic braking torque at the front axle, there is a certain extent admixed such that the total braking ^¬ moment is realized.

In FIG. 2, the time is shown again on the x-axis 2, while the brake pressure is now plotted on the y-axis 8. A braking pressure 40 on the front axle runs linearly after a linear increase between the times ti and t ₂ , in order then to become linearly smaller again between te and t ₇ . A brake pressure 46, however, at the front axle runs between the times t ₂ and te not constant, since the brake pressure on the rear axle in each case depends on the instantaneous recuperative braking torque 20.

The in FIG. 3 current profiles of an outlet ^¬ valve on the rear axle and an actuator circuit-separating valve, which are provided in a brake system according to the invention, will be described below in connection with a in FIG. 4 illustrated embodiment of a brake system 50 discussed.

An in FIG. 4 illustrated braking system 50 of the invention in a preferred embodiment comprises an operable by a brake pedal 56 hydraulic cylinder-piston-An ^¬ proper 62, a hydraulically cooperating with the cylinder-piston assembly 62, simulator 68, a cylinder-piston arrangement associated with their hydraulically connectable pressure fluid reservoir 74, an electronically controllable by an electronic control and regulation unit 80 pressure supply device 86 and a hydraulic pressure modulation device 92. This comprises each of a wheel brake 98, 100, 102, 104 associated intake valves 110, 112, 114, 116 and exhaust valves 120, 122, 124, 126. The brakes 98, 100 are designed as front brakes and connected to a first brake circuit 94, the brakes 102, 104 are formed as rear brakes and a second brake circuit 96th connected. The brake circuit distribution is thus "black and white".

For brake pressure build-up, the brake brakes 98, 100, 102, 104 are supplied with brake means via supply lines 132, 134, 136, 138, into which the inlet valves 110, 112, 114, 116 are connected. The pressure reduction in the wheel brakes 98, 100, 102, 104 takes place through discharge lines 140, 142, 144, 146 into which the outlet valves 120, 122, 124, 126 are connected.

The hydraulic cylinder-piston assembly 62, which effectively acts as a pedal decoupling unit for the brake system 50, has two successively arranged pressure piston 150, 152, the hydraulic chambers or pressure chambers 154, 156 limit, which together with the pressure piston 150, 152 a two-circuit Tandem master cylinder 160 form. The two pressure chambers 154, 156 are in the pressure piston 150, 152 formed radial bores 162, 164 with the pressure medium ^¬ reservoir 74 in conjunction. The bores 162, 164 can be shut off by relative movements of the respective pressure piston 150, 152. Via hydraulic lines 168, 170, brake fluid can be conveyed from the pressure chambers 156, 156 into the supply lines 130, 132, 134, 136. In the supply lines 130, 136, normally closed isolation valves 172, 174 are connected.

The simulator 68 is hydraulically designed with a simulator chamber 176 and a pressure chamber, a piston 178, which is movable in a Simulatorfederkammer 180, and arranged in the simulator chamber 180 spring element 182. Die

Simulator chamber 172 is hydraulically connected via a hydraulic line 186 to the pressure chamber 154 of the tandem master cylinder 160. In the normal mode of the brake system, the "brake-by-wire" mode, upon actuation of the brake pedal 56 by the driver from the pressure chamber 154 braking means via the line 186 pushed into simulator chamber 176, whereby the piston 178 against the spring element 182 in the simulator spring chamber 180 is pressed, thereby giving the driver as familiar and comfortable a brake pedal feel as possible. The pressure supply device 86 is designed as a single-cylinder hydraulic cylinder-piston arrangement with a hydraulic pressure chamber 190, in which, if necessary, for active pressure build-up in the "brake-by-wire" mode when controlling an electric motor 192 by the control and regulating unit 80, a piston 196, whereby pressure medium can be passed through a line 200 in the brakes 98, 100, 102, 104. Via a line 204, the pressure chamber 190 is connected to the pressure medium reservoir 74 with the interposition of a check valve 206 which opens when the pressure in the brake fluid reservoir 74 is higher than in the pressure chamber 190, ie negative pressure in the pressure chamber 190 prevails.

Two normally closed actuator circuit isolation valves 210, 212 are connected in two lines 216, 218 outgoing from a common node 214 in line 200.

In the normal operating mode "brake-by-wire", the two actuator circuit isolation valves 210, 212 are energized or opened and the two isolation valves 172, 174 are closed A simulator release valve 222, to which a check valve 230 is connected in parallel, is opened.

Upon actuation of the brake pedal 56, the path of the brake pedal is measured by a redundant displacement sensor 220 (alternatively or in combination with this, for example, an angle sensor may also be provided). The displacement sensor 220 is connected on the input side to the control and regulation unit 80. From the signal of the travel sensor 220 of the driver's braking request is determined and thus a target braking torque. To realize this target brake torque, the brake pressure build ^¬ from the control unit 80, the Druckbe ^¬ riding provision means 86 is driven. By one each - each redundantly executed -

Pressure sensor 226, 228, the pressure in the line 170 and the line 200 is measured and regulated by the Druckbereitstel ^¬ treatment device 86. The hydraulic fallback mode is activated automatically, for example, in the event of a power supply or the vehicle electrical system failure, since then the closed-circuit actuator circuit isolation valves 210, 212 close, so that none

Brake fluid can flow back into the pressure chamber 190 and the normally open release valves 172, 174 open, so that the driver by muscle power brake fluid from the pressure chambers 154, 156 in the wheel brakes 98, 100, 102, 104 can pump.

The brake system 50 is capable of allowing a precise pressure reduction at the rear axle, in particular

Yaw moments due to pressure variations between the rear brakes left and right are avoided.

For this purpose, the outlet valve 124 and the Aktuatorkreis-separating valve 212 as normally closed analog valves out ^¬ forms. For digital valves, the discrete switching states "on" or "open" and "off" or "closed" are provided. In the "closed" state completely blocks the valve the hyd ^¬ raulischen flow while the valve is in "open" state sets the hydraulic flow at a predetermined level. In between there are no states of the valve. An analogous valve, on the other hand, allows the hydraulic flow to be controlled substantially continuously between full flow and no flow at all, this being preferably controlled by the magnitude of the current with which the analogue valve is operated.

In the time interval between ti and t ₂ (see FIG. 3), in which hydraulic pressure is built up at the rear axle (brake pressure 46), the exhaust valve 124 is de-energized (current 242 is zero), so that pressure builds up in the wheel brakes 102 and 104 can be. The actuator-isolation valve 212 is energized (current 240), whereby it is opened and from the pressure chamber 190 active brake fluid in the wheel brakes 102, 104 can be promoted. At time t ₂ , the brake pressure 46 is kept constant until time t ₃ . The two valves 124 and 212 are de-energized switched, so that the flow of brake fluid is prevented by ver ^¬ and the pressure can be maintained.

In the time interval between t3 and _t4 remains

Aktuatorkreis isolation valve 212 still energized, while the exhaust valve is energized 124 to the hydraulic pressure reduction on the rear axle, the current intensity rises 242 linearly between a first value at the time t3 and a second value at time t ₄ in this time ^¬ interval. By choosing the desired differential pressure at the outlet valve 124 proportional linear increase in the current 242, a pressure reducing function between the desired pressure in the discharge line 144 and the return to the pressure medium reservoir 74 is achieved. Between the times t ₄ and ts, the hydraulic brake pressure 46 is constant 0, so that both valves 124, 212 are switched to the de-energized state.

In the time interval between ts and te again hydraulic brake pressure 46 is built to the declining recuperative

To equalize braking torque 20. The exhaust valve 124 therefore remains closed. The Aktuatorkreis-isolation valve 212, however, is energized with a linearly increasing current 240, which increases linearly from a first value at ts to a second value te. In the time interval between te and t ₇ , the hydraulic brake pressure 46 is linearly reduced until it reaches zero at time t ₇ ; the braking process is at this time from ^¬ closed. The exhaust valve 124 is energized during this time ^¬ interval with a linearly increasing current 242, which increases linearly between a first value te and a second value at t ₇ . The Aktuatorkreis-isolation valve 212 is de-energized. ₁

LIST OF REFERENCE NUMBERS

2 x axis

8 y-axis

14 total braking torque

20 recuperative braking torque

26 hydraulic braking torque

32 hydraulic braking torque

40 brake pressure

56 brake pressure

50 brake system

56 brake pedal

62 cylinder-piston arrangement

68 simulator

74 pressure medium reservoir

80 control unit

86 pressure supply device

92 pressure modulation device

94 first brake circuit

96 second brake circuit

98 wheel brake

100 wheel brake

102 wheel brake

104 wheel brake

110 inlet valve

112 inlet valve

114 inlet valve

116 inlet valve

120 outlet valve

122 exhaust valve

124 exhaust valve

126 exhaust valve

130 supply line

132 supply line

134 supply line

136 supply line

140 discharge line

142 discharge line 144 discharge line

146 discharge line

150 pressure piston

152 pressure piston

154 pressure chamber

156 pressure chamber

160 tandem master cylinder

162 bore

164 bore

168 line

170 line

172 separating valve

174 separating valve

176 simulator chamber

178 pistons

180 simulator feather combs

182 spring element

186 line

190 pressure chamber

192 electric motor

196 piston

200 line

204 line

206 check valve

210 Actuator isolation valve

212 Actuator isolation valve

216 line

218 line

220 displacement sensor

222 simulator release valve

226 pressure sensor

228 pressure sensor

230 check valve tl,

, 15 / t6 /

t ₇ time

Claims

claims

1. Brake system (50) for motor vehicles operating in a "brake-by-wire" mode by both the driver

operable and independent of the driver is controlled and has a hydraulic fallback level in which it can only be operated by the driver, with two

Brake circuits (94, 96), wherein each brake circuit (94, 96) are each associated with two wheel brakes (98, 100, 102, 104), with a brake pedal (56) for actuating a pedal decoupling unit ^¬ (62),

a position sensing device (220) detecting the travel of the brake pedal (56) or a piston connected to the brake pedal,

with a simulator (68) with a simulator release valve

(222) which, in the "brake-by-wire" mode, gives the driver a brake pedal feel, and which is hydraulically disconnected in the fallback mode,

with an electrohydraulic pressure supply device (86), which can be actuated by a control unit (80) for establishing brake pressure, with a pressure modulation device (92) which is used to set wheel-specific brake pressures for each wheel brake (98, 100, 102, 104) each comprise an inlet valve (110, 112, 114, 116) and an outlet valve (120, 122, 124, 126), and two normally closed

Actuator circuit separating valves (120, 212) are provided, by which the pressure supply device (86) is hydraulically connectable to the two brake circuits (94, 96), characterized in that

an exhaust valve (124) of a rear wheel brake (102) is designed as a normally closed analog outlet valve and an actuator circuit isolation valve (212) is designed as a normally closed analog actuator circuit isolation valve.

2. Brake system (50) according to claim 1, wherein exactly one analogue exhaust valve (124) and exactly one analogue Aktuator- circuit separating valve (212) are provided.

3. Brake system (50) according to claim 2, wherein a first brake circuit, the two front brakes (98, 100) and a second brake circuit, the two rear wheel brakes (102, 104), and wherein the analog exhaust valve (124) of a rear ^¬ wheel brake (102 ) and wherein the analog Aktuatorkreis-separating valve (212) is associated with the second brake circuit.

4. Brake system (50) according to one of claims 1 to 3, wherein the pedal decoupling unit (62) comprises two pressure chambers (154, 156), in each of which a piston (150, 152) is arranged movable, and wherein separating valves (172, 174 ) are provided, through which the pressure chambers of the pedal decoupling unit hydraulically from the wheel brakes (98, 100, 102, 104) can be separated.

5. Brake system (50) according to one of claims 1 to 4, wherein the simulator (68) has a pressure chamber (176), in which in the "brake-by-wire" mode of at least one of the pressure chambers (154, 1569 of pedal decoupling unit

Brake fluid is moved.

6. Brake system (50) according to claim 5, wherein in the simulator (68) for generating a pedal feel, a piston (178) is pressed against an elastic spring element (182).

7. brake system (50) according to claim 5 or 6, wherein the simulator ^¬ latorfreigebeventil (222) a check valve (230) is connected in parallel ^¬ pa¬. Method for operating a brake system (50) according to one of claims 3 to 7, characterized in that during the pressure reduction in the rear wheel brakes (102, 104) the analogue exhaust valve (124) is activated and the intake valves (114, 116) of the rear wheel brakes ( 102, 104) are opened.

A method according to claim 8, wherein the respective ^¬ actuator control circuit separating valve (212) is driven to build up pressure.

The method of claim 8 or 9, wherein in a fallback the Aktuatorkreis separating valves (210, 212) are ge ^¬ closed and the Simulatorfreigebeventil ge ^{¬ is} closed, so that brake fluid from the pressure chambers (154, 156) of the pedal decoupling unit are moved into the brake circuits can.