DE102005063658B3

Description

[0001] The present invention relates to a brake system, an actuating device, in particular a brake pedal, and having a control and regulating device, wherein the control and regulating device based on the movement and / or position of the actuating device controls an electric motor drive device, wherein the drive device comprises a piston of a piston Adjusted cylinder system via a non-hydraulic transmission device, so that sets in the working space of the cylinder, a pressure, wherein the working space via a pressure line with a wheel brake is in communication. State of the art:

[0002] Modern brake systems consist of brake booster, d. H. Implementation of the pedal force in a corresponding increased braking torque at the wheel brakes and braking force control over open or closed control and control circuits. As a transfer means for generating the brake pressure from the pedal force, the hydraulic line is used with a few exceptions in the car area.

[0003] Widely used is a division into units between brake booster (BKV) or brake force control and braking force control in a hydraulic unit (HE). This configuration is mainly used in systems such as Anti-lock Braking System (ABS), Anti-Slip System (ASR), Electronic Stability Program (ESP) or Electro-Hydraulic Brake (EHB).

[0004] The hydraulic unit (HE) consists of solenoid valves, multi-piston pumps for 2-circuit brake systems, electric motor for pump drive, hydraulic accumulator and several pressure transmitters. The pressure control is carried out in such a way that for braking torque reduction pressure medium is discharged via solenoid valves from the wheel brakes in a memory and is pumped back from the pump in the master cylinder, causing a pedal movement. Both pressure increase and decrease is controlled by solenoid valves, where partial pressure transmitters are used for the solenoid valve control. Except for the EHB, the brake boosting takes place with the vacuum BKV, which partly includes switching means and sensors for the so-called brake assist function and also for the detection of the so-called control point. As an energy source for the vacuum gasoline engines of the internal combustion engine is used, but as a direct injection, especially at higher altitude, only a weak vacuum. In diesel engines, a mechanical or electrically driven vacuum pump is used. Latest ESP systems are able to achieve an additional brake boost by switching the solenoid valves and the pump or, if the BKV fails, to achieve a brake boost with a larger time constant. The description of these systems and functions is described in detail in the Brake Manual Vieweg Verlag, Edition 2003.

[0005] In the mid-1980s Teves used the so-called Mark II and Bosch the ABS3, which as integrated units included all components for brake booster and control with hydraulic BKV, s. Automotive Manual Bosch 1986, 20th edition. For cost reasons, these systems have not enforced, except for the use of special protection vehicles. The same applies to fully electric braking systems, so-called EMB, with electric motors on the wheel brakes, which were developed intensively in conjunction with the 42 V vehicle electrical system. In addition to the additional costs, a new redundant on-board network for the energy supply is necessary to ensure the braking capability of a brake circuit in the event of a fault.

[0006] The type of EMB systems also includes the wedge brake with electric motor drive. For this purpose, a redundant electrical system is also necessary despite the lower energy consumption. The constructive realization of the wedge brake, which requires additional roles for hysteresis reasons, which require integration into the caliper, is not solved at the moment. The wedge brake with its electromotive drives with sensors must withstand the harsh environmental conditions (dust, water, high temperatures).

[0007] The systems for BKV and HE are very well developed, especially the control and regulation functions for ABS up to ESP. For example, by the pressure-controlled control of the solenoid valves, a very fine dosing of the brake pressure is possible, with the variable braking force EBV is also possible. The pressure decay rate is not yet optimal because it is highly nonlinear. In addition, with a μ-jump or with a small coefficient of friction, the pressure drop sensitivity is determined by the relatively low pump power, which leads to large control deviations and thus results in a braking distance loss.

[0008] A genattungemäßes brake system is from the DE 33 42 552 A1 known. In this brake system, the master cylinder is used to generate a pedal-dependent pressure, which is used as a reference variable for an electronic control and regulating device is used, which regulates the output pressure of an electrohydraulic servo device connected directly to the brake circuit to a value determined by the reference variable. In case of failure of the control device or the servo device itself, the pressure in the brake circuit is generated by the master cylinder. Instead of the reference variable generated in the normal mode by means of the master brake cylinder, it is possible for a reference variable generated as part of an anti-lock braking system or as part of a slip control of the drive control of the motor vehicle to act on the electronic control and regulating device and thus on the electrohydraulic servo device. The servo device has an electrically actuated hydraulic piston-cylinder unit whose working space communicates with the brake circuit and whose piston is axially adjustable by means of an electric motor. The rotational movement of the electric motor is thereby converted via a spindle connected to the piston in a longitudinal movement of the piston.

[0009] From the DE 44 45 975 A1 is a brake system for motor vehicles with a drivable by an electric motor hydraulic brake pressure generator known. From the DE 44 10 299 A1 is a control scheme or control program known by the driving conditions with low coefficient of friction, when at the same time the form is low and a wheel instability occurs, the receipt of cornering forces is given priority over the achievement of a short braking distance.

[0010] From the DE 35 00 745 C2 a circuit arrangement for adjusting the control of an anti-lock brake system for road vehicles is known by the brake pressure control valves are controlled, which are inserted in the pressure medium paths. Object of the invention

[0011] The present invention has the object to provide a novel brake system that is small and compact in size.

[0012] This object is advantageously achieved by a brake system with the features of claim 1. Further advantageous embodiments of the brake system according to claim 1 result from the features of the subclaims.

[0013] The brake system according to the invention is advantageously characterized in that it realizes the brake booster and the servo device in the smallest space per brake circuit by means of only one piston-cylinder unit. The piston-cylinder unit serves as it were for the brake pressure build-up and brake pressure reduction, to realize the ABS and traction control and in case of failure of the power supply or malfunction of the drive device. Thus, advantageously results in a small integrated and cost-effective assembly for the brake booster (BKV) and control, which is associated with a saving of space, installation costs and additional hydraulic and vacuum connecting lines. In addition, due to the short length, advantageously acts e.g. the spring dome in a frontal crash not on the master cylinder and the pedal unit.

[0014] By advantageously providing a sensor and a path simulator, a variable pedal characteristic such as brake-by-wire function, i. Brake pressure increase independent of pedal operation freely variable, also taking into account the braking effect of the generator with recuperable brakes, be adjusted.

[0015] Furthermore, in the corresponding embodiment, no adverse falling through of the brake pedal in case of failure of the drive, since the pedal acts directly on the piston of the system. Advantageously, this also results in lower pedal forces in case of failure of the power supply, since the pistons have a smaller effective area than conventional master cylinder. This is possible by separating the piston travel with intact and failed gain. This is referred to as a translation jump that reduces the pedal force by up to 40% for the same braking effect. By reducing the total effort including the electrical connections, also results in a favorable reduction of the failure rate.

[0016] By the electric motor drive an improvement of the ABS / ESP control by finely metered pressure control with variable pressure increase and in particular pressure drop rates is further feasible. Also, a pressure reduction below 1 bar in the range of the vacuum for function at the smallest Reibkraftbeiwerten, z. As wet ice, possible. Likewise, a rapid increase in pressure at the onset of braking, e.g. 0 - 100 bar achievable in less than 50 ms, which has a significant Bremswegverkürzung result.

[0017] Due to the advantageous provision of a 2/2-way valve for the brake booster, holding the adjusted brake pressure and the control function, the brake system according to the invention requires considerably less energy.

[0018] The valves are connected to the hydraulic lines with the smallest possible flow resistance, i. large flow cross-sections, form, so advantageously as fast as possible and variable pressure build-up or pressure reduction by means of (the) piston-cylinder system (s) can be realized, since then in particular the valves and the connecting channels and pipe no longer have throttle effect. This ensures that the piston-cylinder system alone determines the pressure build-up or pressure reduction speed.

[0019] It is also possible to provide for each brake circuit or each wheel brake its own piston-cylinder system with each associated drive. It is also possible to use a piston-cylinder system in which two pistons are arranged axially displaceably in a cylinder, wherein the cylinders are hydraulically coupled and only one piston is mechanically driven by the drive device by an electric motor.

[0020] These explanations show that the concept with the fast and variably controlled electromotive piston drive and the solenoid valve with the evaluation of the pressure and characteristic map represents a high potential for the controller, which enables additional braking distance shortening and driving stability. Pressure-balanced poppet valves or slide valves with a low temperature dependence and a short switching time are advantageous, so that smaller dead times can be achieved and thus short cycle times can be achieved.

[0021] The brake system is also to be controlled by a control technique such that the shortest possible switching times arise, i. as quickly as possible to another control channel or another wheel can be switched to control this. It has been found to be advantageous if already during the Einregelns a pressure for a wheel brake already the signals for the next wheel brake to be adjusted are evaluated, so that can be switched immediately after completion of the control process for the first wheel directly to the other wheel.

[0022] The invention shows a special method for controlling constant and variable gradients by evaluating the pressure volume characteristic of the corresponding brake via the piston stroke, current or pressure.

[0023] Furthermore, it has been found to be advantageous to provide larger brake tube diameter and heated brake tubes.

[0024] Various embodiments of the brake system according to the invention will be explained in more detail with reference to drawings.

[0025] Show it

[0026] The 1 shows a section of the integrated unit, which is responsible for the pressure generation or brake booster. This is the piston 1 with the usual seals 2 and 3 in the cylinder housing 4 parallel to the piston via a specially designed rack 5a emotional. The seal 2 is designed to work well under negative pressure in the piston chamber 4 ' seals. This rack 5a transfers the force to the front crowned end of the piston 1 ,

[0027] This has a collar bolt at this point 1a over which the rack 5a with return spring 9 puts the piston in the starting position. Here is the rack on the cylinder housing 4a on. This external spring has the advantage that the cylinder builds short and has little dead space, which is advantageous for the vent. The rack has a storage in the rollers because of the lateral forces 10 and 11 with slider 12 , The 1 clearly shows that the parallel arrangement of the rack to the piston causes a short length. The unit must build very short to be outside the crash zone. The rack is to train in particular by means of a very rigid H-profile. The arrangement of the rollers is chosen so that the rack in the end position 5b (shown in dashed lines) with the greatest bending force by the offset attacking compressive force has a relatively small bending length. The rack is about tooth profile 5a ' and gear 6 over the gear wheel 7 from the pinion of the engine 8th driven. This small time constant motor is preferably a brushless motor as a bell tower with an ironless winding or preferably a motor according to the PCT patent applications PCT / EP2005 / 002440 and PCT / EP2005 / 002441 , This one is from the power amplifiers 21 preferably over three strands of a microcontroller (MC) 22 controlled. For this a shunt measures 23 the current and a sensor signal 24 and indicates the position of the rotor and, via corresponding counters, the position of the piston. The current and position measurement is used in addition to the engine control for indirect pressure measurement, since the engine torque is proportional to the pressure force. For this purpose, a map must be created in the vehicle during commissioning and also during operation, in which the position of the piston is assigned to the different flow rates. In operation, a position of the piston is then approached in accordance with the amplifier characteristic curve described later, which corresponds to a specific pressure according to the map. The position and engine torque are not exactly the same. B. by temperature influence, the map is adapted during operation. As a result, the map is constantly adapted. The output map is formed from preferably pressure-volume curve of the wheel brake, engine characteristic, transmission efficiency and vehicle deceleration. With the latter, a pedalkraftproportionale vehicle deceleration can be achieved so that the driver does not have to adjust to different braking effects.

[0028] The piston 1 generated in the pipe 13 a corresponding pressure, which via the 2/2 solenoid valve (MV) 14 to the wheel brake 15 or via solenoid valve MV 16 to the wheel brake 17 arrives. This above-described arrangement has several advantages. Instead of the two inexpensive small solenoid valves, another piston engine unit could be used as in 4 is shown. However, this means considerably more cost, weight and space.

[0029] It is sufficient to use a piston motor unit for each brake circuit.

[0030] The second advantage is the very low energy requirement and the design of the motor only for pulsed operation. This is achieved by the solenoid valves are closed when the set value of the pressure or engine torque and the engine is then operated only with low amperage until the brake pedal is given a new setpoint. Thus, the energy requirement or the average power is extremely small. For example, in a conventional design with a full braking from 100 km / h of the engine 3 to absorb a high current. According to the invention, the motor requires only about 0.05 s of current for the piston travel, which is 1.7%. If the values are related to the power, then in the conventional case, the electrical system with> 1000 W would be charged for at least 3s and in the proposed pulse mode only about 50 W average power. An even greater energy saving results from a full braking of 250 km / h with braking times up to 10 s on a dry road. To relieve the pulse load of the electrical system can here a storage capacitor 27 be used in the power supply, which can also be used according to the line with arrow for the other electric motors.

[0031] In the pressure line 13 can be used before or after the solenoid pressure transducer, which are not shown, since these correspond to the prior art.

[0032] The piston 1 gets over the breather hole with liquid from the reservoir 18 provided. In this line is a solenoid valve 19 switched on. If a quick piston movement to reduce pressure, so could the seal 3 sniff out liquid from the reservoir, especially at low pressures, which is known to be detrimental. For this purpose, the low-pressure solenoid valve 19 switched on and the connection to the reservoir interrupted. With this circuit can also be negative pressure in the Radkreisen 15 / 17 be achieved what the wheel control at very low friction coefficients z. B. benefits on wet ice, since in the wheel brake no braking torque is generated. On the other hand, the Nachschnüffeln be used consciously in vapor bubble formation, in which the piston is already at the stop without the appropriate pressure is reached. Here, the pistons are controlled in accordance with the solenoid valves, so that the oscillating piston builds pressure. When dispensing with this feature may be in place of the solenoid valve 19 a sniff-proof seal 3 be used.

[0033] The solenoid valves 14 . 16 . 19 are about power amplifiers 28 from the microcontroller 22 controlled.

[0034] In case of failure of the power supply or the electric motor, the piston of a lever 26 the actuator moves. Between this and the piston, a clearance is built in, which prevents the lever from striking the piston during rapid pedaling, before the engine moves the piston.

[0035] The control function with respect to wheel speed and wheel pressure in ABS / ASR or yaw rate and wheel pressure in ESP has been presented in various publications, so that a renewed description is omitted.

[0036] In a table the essential functions of the new system are shown:

[0037] The amount of partial energization depends on the desired pressure increase or decrease speed of the BKV or the brake control. Decisive for this is an extremely small time constant of the electric motor, d. H. a temporally rapid increase in torque and torque reduction over small moving masses of the entire drive, since the piston speed determines the pressure change rate. In addition, brake control requires fast and accurate position control of the pistons. In the case of rapid torque reduction, the compressive force resulting from the caliper also has a supporting effect, which is low at low pressures. But just here, the pressure drop speed should be large to large deviations from the wheel speed to z. As to avoid ice.

[0038] With this concept, there is a decisive advantage over the conventional pressure control via solenoid valves, since the piston speed determines the pressure change rate. For example, the flow and thus the pressure reduction rate is low at low differential pressure at the pressure-reducing outlet valve. As already mentioned, the piston unit can be used separately for each wheel with and without a solenoid valve. To take advantage of the low energy consumption, the electric motor would have to be extended with a fast electromagnetic brake, which is more complex. The embodiment shown with a piston unit and two solenoid valves is preferable from the installation space and the cost. Regulatory, however, the restriction applies here that at a Pressure reduction on a wheel the other wheel can not build up pressure. However, since the pressure reduction time is approximately <10% of the pressure build-up time in the control cycle, this limitation is without significant disadvantage. The control algorithms must be adjusted accordingly, for example, after a phase of constant pressure opening of the solenoid valve, the electric motor must be energized with a current to which the appropriate pressure in the wheel brake according to the BKV characteristic is assigned or eg 20% higher than the previous blocking pressure in control cycle. Alternatively, it is also possible to control an adaptive pressure level, for example, which is 20% higher than the highest blocking pressure of the axle or of the vehicle during regulation. As blocking pressure is the pressure at which the wheel runs unstable in greater slippage.

[0039] The concept also offers new control possibilities for pressure reduction. Control technology is that the pressure reduction and braking torque reduction are substantially proportional to the rotational acceleration of the wheel, the hysteresis of the seal and inversely proportional to the moment of inertia of the wheel. From these values, in each case the amount of the required pressure reduction can be calculated and the piston can already provide the corresponding volume in the case of closed MV taking into account the characteristic map described. Then, when the MV opens, there is a very rapid pressure drop practically in the vacuum. This is based on the assumption that the MV has a smaller throttling effect by means of corresponding opening cross-sections, in contrast to today's solutions. In this case, the pressure reduction can be faster than conventional solutions via a specially provided chamber volume corresponding to the pressure volume curve. Alternatively, it is possible to lower the pressure in a chamber volume which is slightly larger than the necessary pressure reduction, e.g. by appropriate adjustment speed of the piston. For precise control of the pressure reduction is here a very small switching time for closing the solenoid valve necessary, which can be preferably achieved by pre-energizing and / or overexcitation. In addition, it is advantageous for special cases of the control to bring the armature of the 2/2 solenoid valve via known PWM method in an intermediate position to produce a throttle effect.

[0040] The very rapid pressure reduction may possibly produce pressure oscillations, which react on the wheel. To avoid this detrimental effect, the piston path may be further selected as a further alternative, e.g. 80% of the required pressure reduction are controlled (rapid pressure reduction). The remaining required 20% of the pressure reduction can then be done slowly by a subsequently controlled slow piston movement or in the alternative with the Druckabbausteuerung via solenoid valves by timing the solenoid valve and stepped degradation. This avoids harmful wheel vibrations. The slow pressure reduction can be continued until the wheel accelerates again in the ABS control.

[0041] This allows very small control deviations of the wheel speed. Analogously, the method described above can also be applied to the pressure build-up. The speeds of the pressure increase can be optimized according to control criteria. Thus, the goal can be achieved, that the wheel is braked in the immediate vicinity of the friction force maximum and so optimal braking effect is achieved with optimum driving stability.

[0042] In the above, special cases of the control were mentioned in which a throttling effect is advantageous. This is e.g. the case when both wheels at the same time a pressure reduction is necessary. Here, the throttling effect is advantageous until the actuating piston has provided such a large chamber volume, so that the pressure can then subsequently be reduced rapidly to a vacuum from a different pressure level. The same procedure can be followed, i. if the solenoid valves in the valve cross-section have a built-in throttle and pressure build-up is to take place simultaneously on both wheel circuits. However, the individual alternating pressure build-up is to be preferred because of the metered pressure build-up with evaluation of the characteristic diagram and controlled adjustment speed of the piston. The same alternating method may alternatively be described above. be applied with the throttle effect for the pressure reduction. As a further possibility, the piston can already be moved back with a control signal with a lower threshold than the control signal for the pressure reduction. In the prior art, this is the signal where the controller detects a tendency to lock and turns the MV on to hold pressure (see the Brake Manual, p. 52-53). This signal is output 5-10 ms before the pressure reduction signal. The proposed fast drive is able to provide a chamber volume for 10 bar pressure reduction within about 5 ms.

[0043] Based on the piston position for pressure reduction, the controller can decide whether enough chamber volume is available for the simultaneous pressure reduction for both wheel brakes.

[0044] The 2 shows the entire integrated unit for BKV and control functions. The unit consists of two piston units with associated electric motors and gearbox acc. 1 for two brake circuits and four wheel brakes. The piston units are in the housing 4 accommodated. This housing is on the front wall 29 attached.

[0045] The brake pedal 30 transfers the pedal force and movement over the bearing pin 31 on a fork 32 , which via a ball joint on the actuator 33 acts. This has a cylindrical extension 34 with a pole 35 ,

[0046] cylinder 34 and rod 35 are in a socket 37 stored. This takes the Wegsimulatorfedern 36 and 36a on, with one spring weak and the other spring strongly progressive in the increase in force acts. The path simulator can also be made up of even more springs or rubber elements. This specifies the pedal force characteristic. The pedal travel is from a sensor 38 detected, which is constructed in the illustrated example according to the eddy current principle, in which the rod 35 immersed with a target.

[0047] The pedal movement is on the elements 32 and 33 transferred, the piston 34 moves with the rod 35 in the socket 37 , On the actuator is a lever 26 rotatably mounted, which hits in case of failure of the power supply to the piston. The pedal travel sensor supplies the path signal to the electronic control unit which, in accordance with the BKV characteristic, causes the pistons to move via the electric motor. Between the lever 26 and the two pistons 1 is a game s o provided as in 1 shown. The actuator has over the bolt 39 , which is shown offset, a rotation and a return spring 40 which supports the unshown pedal return spring. Many Wegsimulatorlösungen known in the prior art, which are also partially hydraulically actuated by pistons and shut off via solenoid valves when the power supply fails. This solution is complex and hysteresis. Solutions are also known in which the Wegsimulatorweg received in case of failure of the power supply as a loss path upon actuation of the pistons for brake pressure generation.

[0048] The aim of the invention is a simple solution in which the path simulator is switched off in case of failure of the power supply. For this purpose is on the socket 37 with intact power supply via the anchor lever 41 with large gear ratio and the holding magnet 42 exerted a counterforce, which is eliminated when the electrical power supply fails. To reduce the magnet and two-stage lever can be used. In detail this will be in 3 described. In this case, the lever via the brake pedal with the two pistons after passing through the game in contact and thus can transmit the pedal force to the piston. The pistons are dimensioned so that they produce a pressure at full pedal stroke, which still gives a good braking effect, eg. 80%. However, the piston stroke is significantly greater than the pedal stroke and can produce much higher brake pressures with intact power supply and electric drive. However, the driver can not apply the corresponding pedaling force. One speaks in this interpretation of a jump in the ratio, which is possible with decoupling of the actuator with displacement simulator from the piston. In conventional construction, in which BKV and master cylinder with pistons are connected in series, the required pedal force increases in case of failure of the power supply to the factor 5 for the same wheel brake pressure. In the new interpretation z. B. the factor can be reduced to 3. This case is z. B. relevant when towing a vehicle with a failed battery.

[0049] The lever 26 is rotatably mounted so that it can take into account tolerances in the movement of the piston, for. B. due to different ventilation. This compensation can also be limited, leaving the lever on a stop 33a the actuator comes to rest.

[0050] However, further errors must be considered. Failure of an electric motor.

[0051] In this case, the gain and control in the adjacent intact piston drive is fully effective. About the lever 26 brake pressure is generated in the failed circuit after it stops 33a is applied. Here, in addition, the amplifier characteristic of the second circle can be increased, which reduces the required pedal force. However, this can also be done without a stop. Failure of a brake circuit.

[0052] Here, the piston moves to stop in the housing 4 , The intact second circle is fully effective. It does not arise as in conventional systems today a falling pedal, which is known to irritate the driver very much. The irritation can also lead to a full loss of braking effect if he does not pass the pedal.

[0053] The 3 describes the function of the Wegsimulatorarretierung. In the limit case, the driver can apply high pedal forces, what the locking over the anchor lever 41 must apply. To avoid the magnet 42 with excitation coil 43 has to apply these forces fully engages the upper crowned end 41a the lever is asymmetrical on the socket 37 on. Now the pedal is up to the impact of the rod 35 on the ground 37b deflected, this lever effect causes a slight rotation of the socket 37 , which creates friction in the guide, in addition to the nose 37a on the case 4 can support. Thus, the magnetic force can be kept relatively small. The magnet also acts as a magnet 42 designed so that a small holding power is necessary due to the small air gap. In case of failure of the power supply, the anchor lever 41 from the socket 37 in the dot-dash position 41 ' deflected. When the actuator 33 returns to its original position, brings the return spring 44 the anchor lever back to initial position.

[0054] The sensor 38 was at the end of the bore of the socket in the housing 4 which has advantages for contacting with the el. control unit, as in 6 is shown. The same applies to the brake light switch 46 , In this embodiment, the target is 45 drawn for the eddy current sensor.

[0055] The locking of the path simulator via the socket 37 can be changed to the in 7 described pedal reaction in ABS to avoid. For this purpose, the lever 41 with its storage and magnet 42 with recording 42a via an electric motor 60 to be moved, a spindle 60a via a gearbox 60b drives. At the extension of the spindle, the lever is mounted and the magnet housing attached.

[0056] The 4 shows a schematic representation of a solution with only one electric motor 7a , This description builds up 1 and 2 on. The drive pinion of the motor moves the rack 5c which are similar 1 can also be offset in parallel. This is with a piston 1a connected, which pressure in the brake circuit 13a builds up and at the same time on the pressure of the piston 1a that shifts in the brake circuit 13 Build up pressure. This piston assembly corresponds to a conventional master cylinder for the piston and seal designs many variants exist. In the brake circuits as in the preceding figures, the 2/2-way solenoid valves 14, 14a . 16 . 16a arranged. The ABS pressure modulation takes place in the manner described above. The BKV function takes place via a parallel path simulation 36 and displacement sensor 38 , Again, between pistons 1a and brake pedal a game or Leerhub s 0 provided. The brake fluid comes from the reservoir 18 . 18a into the piston chambers. This arrangement is inexpensive. The dynamics of the BKV function in the pressure build-up is lower than in the variant with two engines, since the electric motor has to apply twice the torque. It also eliminates the redundancy function of the 2nd motor as in 7 including a failing pedal in the event of brake circuit failure.

[0057] 5 shows the in the 1 and 2 described pressure modulation device, which is an electric motor 8th that contains the shunt 23 for pressure-proportional current measurement via power amplifiers 21 is controlled. The latter are shown simplified. The piston travel is via a rotary encoder 72 or a piston stroke sensor 74 which is also used to control the engine of an EC motor. This motor actuates the piston via the 2/2 solenoid valves 14 . 14a moves the pressure fluid to the corresponding wheel brakes. The corresponding brake fluid reservoir 18 is connected to the piston housing. It can also be a cost-effective central actuator for four wheel brakes and zus. 2/2-solenoid valves 14 ' and 14a ' be used. To control the piston, a piston stroke sensor 74 or a displacement or rotation angle sensor together with pressure transmitters 73 and 73a be used in the wheel circles.

[0058] In ABS, EHB and ESP systems, the solenoid valves for pressure regulation and pressure build-up and dismantling are constructed as throttle valves (ATZ Automobiltechnische Zeitung 101 (1999) 4 p.224). Basically, you want to make the pressure build-up and pressure reduction as high as possible, so that the braking torque excess is compensated quickly in the scheme. However, the solenoid valves used in the prior art have dead times, which means that after the control command - eg closing - an additional pressure change occurs. Usually this is approximately 3 bar when the gradient 1500 bar / s and a switching time of 2 ms is present. Among other things, this closing action also causes pressure oscillations, which have an effect on the wheel behavior and, inter alia, disadvantageously cause noise. This means that the solenoid valves with their switching characteristics determine the maximum gradient for pressure reduction or pressure build-up. Due to the fixed throttle resistance of the valves used, the pressure increase and decrease gradient is highly nonlinear and approximately follows the function, Δ P the differential pressure is. However, a variable and constant pressure gradient is advantageous for optimal and simple control.

[0059] It is essential to the invention that the design and dimensioning of the 2/2 solenoid valves be such that they have almost no throttling effect, so that the actuating device is the Pressure gradient determined. Preferably, pressure-relieved poppet valves are used with low temperature dependence.

[0060] Important for the gradient control is the knowledge of the pressure volume characteristic of the wheel brake as in 5a is shown. The upper part shows the dependence of pressure (current) over volume consumption, which is proportional to the piston travel or rotation angle α. This is known not to be linear. For a constant pressure gradient control, the pressure volume characteristic curve must be evaluated for a corresponding piston speed control.

[0061] For the method in which a plurality of control channels are operated by a central actuator, it is of great importance to make the dwell on a control channel as small as possible, since in this time the other control channels are not operated. Here, a fast pressure gradient, in particular in the pressure reduction and a short switching time of the 2/2-way solenoid valves is of great importance. This will be described in detail in the following figures.

[0062] 6 describes the pressure reduction of one level P 0 , which corresponds to the blocking limit of dry roads, for example. In a μ-jump on ice or aquaplaning, the pressure level must be at the level of line 89 be reduced. In the systems mentioned at the beginning of the pressure reduction takes place according to the line 86 nonlinear with very small gradients at low pressure levels. In systems with storage chamber according to the prior art fills in this 88 , The dashed very slow pressure curve is determined by the performance of the return pump. On the other hand, according to the proposal of the invention, the system produces a nearly constant gradient line 87 , which can be chosen larger or higher by design than conventional systems (line 86 ). Only in the lower course at very low pressures 80 is a transition region, due to the speed of the piston, available. Decisive for this advantageous pressure reduction is the dimensioning of the solenoid valves and pipes, which should not form any significant flow resistance even at low temperatures for the corresponding pressure gradients, so that only the adjustment speed of the piston is dominant. For the brake pipe, a larger diameter may be used, or alternatively, the brake pipe could be electrically heated.

[0063] 7 shows the pressure reduction and pressure build-up on the left side at high μ and at the right side at low μ. The dashed line should be the so-called.

[0064] form 91 correspond, which generates the driver in the master cylinder. The pressure reduction gradient p ab / dt depends, as already explained, on the pressure level and the build-up gradient p au / dt on the differential pressure to the admission pressure. Especially with control with low pressure level, high differential pressures and thus high p au / dt arise. The valves are clocked to a stepped pressure build-up. This generates pressure oscillations due to the fast closing process of the solenoid valve 92a and 93a which cause significant noise and even affect the wheel behavior.

[0065] 7a shows the pressure time behavior at high and low μ in the new system. The pressure gradients p ab / dt and p au / dt can be the same regardless of the pressure level. The pressure build-up gradient p au / dt can be different within the control cycle, eg during the first pressure build-up p au1 big and the second pressure build-up p au2 smaller.

[0066] Due to the variable pressure gradients, there can be a transitional area in the pressure reduction and pressure build-up 94 and 94a be created, which avoids pressure oscillations. Also, the form of the system by appropriate control of the actuator can be controlled so that the form is 20% higher than the maximum regulated pressure. This saves correspondingly electrical energy for driving the actuator.

[0067] 8th shows the time course of wheel speed and pressure. The courses are highly linearized. When braking, the wheel speed moves to the point 95 in which the blocking limit is exceeded, which is manifested by the fact that the wheel acceleration increases. Before the pressure reduction starts, a differential speed ΔV 0 is awaited. It makes sense to keep the pressure constant in this phase. At the time 96 the pressure reduction takes place according to the course 101 in the conventional system. This takes place after a dead time of t VA , Here the small gradient corresponding to small μ is drawn. At the time 102 is the torque surplus, which causes the blocking tendency, balanced by appropriate pressure reduction. The wheel speed V R1,2 increases again, so that the blocking tendency disappears. It is assumed for simplicity that both wheel speeds are at Contemplation of the conventional system synchronously run and be controlled at the same time. This sets the so-called. Control deviation .DELTA.V 3 in the conventional system.

[0068] When system according to the invention is also at the time 96 to t VA the advantageous rapid pressure reduction, which is terminated at 97 and a much smaller control deviation .DELTA.V 1 arises after the first wheel is no longer blocked (v r1 'increases again). Now it is switched to the second control channel, which after t VA leads to pressure reduction at the time 98 finished. This results in a control deviation .DELTA.V 2 , which despite the staggered control is still smaller than in the conventional system with .DELTA.V 3 .

[0069] In the first control cycle, pressure reduction can occur simultaneously with both wheels on the new system if both wheels become unstable and point 95 / 96 exceed, because the output pressure level is the same. This is of great importance, since when braking at high pressure rise speed, the torque surplus is greater than in the following control cycles, in which the average pressure increase is considerably smaller due to step-shaped pressure build-up.

[0070] As shown, in the conventional system in the first control cycle by the factor 2 to 3 larger deviations, which is known to mean braking distance and lateral force loss.

[0071] The above representations show that in the case of simultaneous instability and staggered pressure reduction, it is important to minimize this skew. It should be noted, however, that this case rarely occurs in practice.

[0072] The 9 and 10 show the main influence parameters on the time offset. Shown is the temporal pressure curve, shown linearized. The abbreviations mean: t VA : Warp or dead time of actuator or actuator t VM : Delay time 2/2 solenoid valve t C : Sample time or sample rate from the computer; this takes this time to calculate the speed when switching from one to the next wheel t from : Pressure-reduction time .DELTA.T: time offset

[0073] In 9 takes place at 103, marked with a triangle, from the controller the pressure reduction command, which follows t VA is done and after tab is completed. In this phase, the dashed second control passage is kept constant in the pressure by closing the 2/2-solenoid valves. After tab 104, tc simultaneously acts 2 × t VM . To t VA or parallel Opening of the 2/2 solenoid valves via t VM the next one takes place p from and after another t C the next pressure change, which can cause pressure build-up or -down. It should be noted that the pressure build-up is less critical as time is a factor 10 - 20 greater than tab in the control cycle, since many phases of constant pressure, s. 7a , be turned on. 9 has a quantitative offset of Δt = 17 ms as a time lag.

[0074] 9a shows a way to shorten Δt. at 103 the setting command is again carried out. This is during during t VA calculated the necessary pressure reduction, mainly from Radbeschleunigung and Radgtägheitsmoment, so that after t VA the computer is switched to the next control channel, so after tab and t VA or. t VM Δt is already reached for the next pressure reduction. Here, as shown on the left, Δt is reduced from 17 to 12 ms - 40%.

[0075] 10 and 10a correspond to the 9 or. 9a , with the difference, the tab by the factor 2 is chosen smaller, which has the consequence that with the method 9a Δt can be reduced from 17ms to 7ms. This is such a small value that the time offset is negligible in the control deviation and makes it possible to operate four control channels with one actuator. Further potential can be exploited in the reduction of the delay or dead times tVA and tVM.

[0076] As shown, determined t VA and the pressure reduction speed significantly the switching time .DELTA.t, ie t VA should be small and the pressure reduction rate as large as possible.

[0077] The dead time of the 2/2-solenoid valves can vary within certain limits, as a small switching delay during pressure reduction is not noticeable, since the piston is already moved over the control signal. As soon as the solenoid valve opens, the liquid flows into the piston chamber virtually without throttling. The end of the pressure reduction is recognizable from the map and can be taken into account for the appropriate Vorhalt. When the pressure builds up, the control of the EC-motor takes place slightly earlier than the expected opening time of the solenoid valve. From the start of the engine can be seen how the opening time is because only when the valve open pressure fluid reaches the brakes and the piston can move. Possibly. the activation time must be corrected. Similarly, the closing time can be checked.

[0078] The time of the end of the pressure build-up is known from the drive algorithm and the map. If the intended pressure build-up is not reached, then the solenoid valve closes too early and its drive time undergoes a correction for later closing. The motor / piston remains after the pressure build-up a small time to be sure that the solenoid valve is closed.

[0079] The 11 describes the chronological sequence of several control cycles. Shown is the speed of two wheels V R1 and V R2 with associated pressure curve p 1 and p 2 , The pressure increase is shown. Here is known to form a differential speed of V R1 and V R2 to the vehicle speed V F , This is called slip. Signed is the so-called speed for optimal friction V opt , which usually has a slip of 10%, but also z. B. between 5% and 30% can vary. ie V opt is z. As a rule, 90% of V F , After the pressure increase becomes at 105 V opt exceeded, and after expiration of Δ v (s. 8th ) pressure is reduced on both wheels in the first control cycle, since both have the same pressure output level and V opt exceed. According to the procedure. the 9a or. 10a Here, preferably, proportional to the wheel acceleration and moment of inertia, a pressure reduction is initiated, which at V R1 and V R2 is different.

[0080] This calculation process runs independently of the calculation of the wheel speed or acceleration. The data for the pressure reduction can z. B. stored in a map so that no significant computing power / time is necessary. At the time 107 is at V R1 and 109 at V R2 the pressure reduction finished. This is determined in each case so that the friction torque on the wheel is greater than the braking torque, so that a Radwiederbeschleunigung arises. At the time 109 is at V R1 Vopt and at V R2 exceeded at 100. Here is a pressure build-up, the amount of which in turn follows proportionally to the wheel acceleration and Radgtägheitsmoment, compared to the pressure reduction somewhat reduced z. 90%.

[0081] After phases of pressure maintenance over e.g. For 30 ms, 101 produces a small pressure build-up of a few bars. However, this can be set higher when the wheel is at low slip values.

[0082] At the time 102 takes place at V R1 the next pressure reduction until 113 , at 114 is identical to 109 and 100 the pressure build-up, at 115 and 116 Pressure reduction at V R2 , At the time 119 fall the larger pressure build-up accordingly 100 and the smaller pressure build-up accordingly 111 together. Priority here is the large pressure build-up, the small one takes place to tv. At the time 117 shows up V R2 even with greater slip a large wheel acceleration. As a result, under the terms of 100 Pressure is built up. at 119 the same thing happens again.

[0083] In this presentation, the delay times were t VA and t VM and computing time t c not considered in favor of a clear presentation.

[0084] For the purposes of this invention, the term "control cycle" means the control process which, after falling below the speed for optimal friction or exceeding a corresponding slip value, see point 105 or. 106 the 11 , the pressure reduction is initiated. The end of the "control cycle" is given, see point 109 or. 110 the 11 if the speed for the optimum friction is exceeded or the slip value is fallen below again. A "control cycle" for a wheel brake thus always consists of a phase in which pressure is increased or decreased and an adjoining phase in which the pressure is kept constant.

[0085] There follow embodiments of the invention. Embodiment 1

[0086] Brake system, an actuating device, in particular a brake pedal, and having a control and regulating device, wherein the control and regulating device based on the movement and / or position of the actuating device controls at least one electromotive drive device, wherein the drive device via a piston of a piston-cylinder system adjusted a non-hydraulic transmission device, so that sets in the working space of the cylinder pressure, wherein the working space via a pressure line with a wheel brake in conjunction, characterized in that between the brake cylinder of the wheel and the working space of the piston-cylinder system Valve is arranged, wherein the control and regulating device opens the valve for Druckab- or pressure build-up in the brake cylinder and closes to hold the pressure in the brake cylinder. Embodiment 2:

[0087] Brake system according to the embodiment 1 , characterized in that the drive device has an electromotive or electromechanical drive for adjusting the piston of the piston-cylinder system. Embodiment 3

[0088] Brake system according to the embodiment 1 or 2 , characterized in that the drive device drives a piston which is arranged together with a hydraulically coupled further piston in a cylinder (tandem piston-cylinder system). Embodiment 4

[0089] Brake system according to one of the embodiments 1 to 3 , characterized in that the brake system comprises two mutually parallel piston-cylinder systems, and each piston is associated with a drive device which adjusts the respectively associated piston. Embodiment 5:

[0090] Brake system according to one of the preceding embodiments, characterized in that between each wheel brake and the working space of the piston-cylinder system, a valve, in particular a 2/2-way valve is arranged. Embodiment 6:

[0091] Brake system according to one of the preceding embodiments, characterized in that the working space of the piston-cylinder system with the brake cylinder connecting hydraulic lines have a negligible flow resistance. Embodiment 7:

[0092] Brake system according to embodiment 6, characterized in that the valve has a large flow cross-section, such that the valve has no throttle function, wherein the valve is in particular a 2/2-slide valve. Embodiment 8:

[0093] Brake system according to embodiment 6, characterized in that the valve is a pressure balanced 2/2-way seat valve. Embodiment 9:

[0094] Brake system according to one of the preceding embodiments, characterized in that the actuator displaced in case of failure, the at least one piston of the at least one piston-cylinder system directly or via a transmission. Embodiment 10:

[0095] Brake system according to one of the preceding embodiments, characterized in that the pressure is determined in the working space of the piston-cylinder system and / or the brake cylinders of the wheel brakes by means of sensors. Embodiment 11:

[0096] Brake system according to one of the preceding embodiments, characterized in that at least portions of the wheel brakes with the piston-cylinder system connecting hydraulic lines by means of heating devices, in particular electrical heating elements, are heated. Embodiment 12:

[0097] Brake system according to one of the preceding embodiments, characterized in that the control and regulating device has a knowledge database, in particular in the form of a characteristic field, which is designed in particular adaptive. Embodiment 13:

[0098] Method for adjusting a pressure in at least one brake cylinder of a brake system according to one of the preceding embodiments, characterized in that simultaneously or successively the pressure in one or more brake cylinders is adjusted by means of the at least one piston-cylinder system and the valves associated with the wheel brakes. Embodiment 14:

[0099] Method according to embodiment 13, characterized in that the rate of change of the pressure build-up and / or the pressure reduction in the wheel brakes is adjusted by means of the piston-cylinder system as a function of the driving condition or the brake control of the vehicle or the respective wheel to be braked. Embodiment 15:

[0100] Method according to embodiment 13 or 14, characterized in that the rate of change of the pressure build-up and / or the pressure reduction in a wheel brake changes during a control cycle. Embodiment 16:

[0101] A method according to embodiment 15, characterized in that the rate of change of the pressure reduction and / or pressure build-up during the time in which a valve of a wheel brake is opened, in particular initially high and is reduced toward the end of the pressure reduction or pressure build-up phase. Embodiment 17:

[0102] Method according to one of the embodiments, characterized in that the control and regulating device at least from the respective wheel speed, the vehicle acceleration and located in the respective brake cylinder of the wheel pressure the required pressure build-up, pressure reduction, the pressure holding phases and / or the optimum slip for each wheel or all braked vehicle wheels determined. Embodiment 18:

[0103] Method according to one of the embodiments, characterized in that the control and regulating device opens the valve associated with the wheel brake during pressure build-up or pressure reduction for a first wheel brake, and immediately after setting the pressure determined by the controller for the first brake that of the first wheel brake associated valve closes and regulates the necessary pressure for the second wheel brake by means of the piston-cylinder system by opening the valve for the second wheel brake. Embodiment 19:

[0104] A method according to embodiment 18, characterized in that the necessary pressure reduction or pressure build-up for the next einzugregelnordende wheel in particular based on the measured wheel acceleration and the Radträgheitsmoment, in particular from the map, is calculated. Embodiment 20:

[0105] Method according to embodiment 19, characterized in that the pressure reduction or pressure buildup to be newly regulated for the second wheel brake is calculated during the regulation of the pressure for the first wheel brake. Embodiment 21:

[0106] Method according to one of embodiments 13 to 20, characterized in that the pressure reduction takes place at two wheel brakes by opening the respectively associated valves at the same time, especially if in the brake cylinders of the two wheel brakes initially approximately the same pressure level prevails or in the first control cycle of a braking operation. Embodiment 22:

[0107] Method according to embodiment 21, characterized in that the valve for a first wheel is closed rather than the valve of the second wheel. Embodiment 23:

[0108] Method according to one of the embodiments 13 to 22, characterized in that the control and regulating device has a memory in which the adjusted at the time of closing the associated valve of a wheel brake pressure and / or the pressure signal, such as. Motor current or piston position is stored. Embodiment 24:

[0109] Method according to one of the embodiments 13 to 23, characterized in that during the control by means of the piston-cylinder system, a form is adjusted, which is about 10-30%, in particular 20% above the einzuregelnden pressure. Embodiment 25:

[0110] Method according to one of the embodiments 13 to 24, characterized in that the engine or piston is held in its position for a short time after reaching the pressure build-up to ensure that the last opened solenoid valve is fully closed. Embodiment 26:

[0111] Method according to one of the embodiments 13 to 25, characterized in that the response time tVA of the drive device is small for achieving a high pressure reduction speed (dp ab / dt) and / or pressure buildup speed (dp au / dt), in particular such that the pressure change speed is greater than 1500 bar per second. Embodiment 27:

[0112] Method according to one of the embodiments 13 to 26, characterized in that the pressure reduction speed (dp ab / dt) is very large or adjusted, if several wheels are simultaneously determined by the regulator for pressure reduction. Embodiment 28:

[0113] Method according to one of the embodiments 13 to 27, characterized in that the controller calculates the optimum pressure to achieve the optimum slip for the braked wheel and the pressure build-up for the associated wheel brake up to a pressure that is slightly smaller, in particular 1-20% , preferably 5-10% less than the calculated optimum pressure, so as to avoid exceeding the optimum slip again. Embodiment 29:

[0114] Method according to embodiment 28, characterized in that to achieve the best possible slip the pressure build-up in steps, wherein first a large pressure increase after the control cycle takes place, followed by pressure holding phases alternating with pressure buildup phases, each with small pressure changes. Embodiment 30:

[0115] Method according to embodiment 29, characterized in that during a pressure-maintaining phase for a first wheel, a pressure build-up phase for a second wheel is initiated or carried out by means of the same piston-cylinder system. Embodiment 31:

[0116] Method according to one of the embodiments 13 to 30, characterized in that the control device takes into account the control of the 2/2-way valves their response times or dead times, such that the 2/2-way valves to the response time of the valve earlier receive an open or close command so that the valve is actually open or closed at the calculated time. Embodiment 32:

[0117] Method according to one of the embodiments 13 to 31, characterized in that the 2/2-way valves controlling control device derived from the reaction of the activated drive means or the Kolbenverstellweg after appropriate activation, the response time of the valves and stores for subsequent control in a memory , Embodiment 33:

[0118] Method according to one of the embodiments 13 to 32, characterized in that for pressure build-up or pressure reduction in at least one wheel brake, the piston of the piston-cylinder system is already adjusted, and the associated valve (s) opens or opens later.