Brake system with electric motor-driven piston-cylinder system

Abstract

braking system, comprising 1.1 an actuating device (30), namely a brake pedal, 1.2 a pedal travel sensor (38) for detecting the pedal travel of the brake pedal and 1.3 a control and regulating device (22); 2. wherein the control and regulating device (22) controls a drive device (5c, 6, 7, 7a) with an electric motor (8) taking into account the detected pedal travel; 2.1 wherein the electromotive drive device is a brushless motor controlled by output stages (21) via three strands by a microcontroller (22), 3. wherein the drive device (5c, 6, 7, 7a) adjusts a piston (1, 1a) of a piston-cylinder system via a non-hydraulic transmission device, so that a pressure is established in the working chamber (4', 4a', 4b') of the cylinder; 4. wherein the working chamber (4', 4a', 4b') is connected to a wheel brake via a pressure line (13); 5. In the event of failure of the drive device (5c, 6, 7, 7a), the actuating device adjusts the piston (1). 6. The braking system comprises a current sensor (23) for measuring a current of the electric motor; 7. the control and regulating device (22) is designed to carry out a current-proportional pressure control according to an amplifier characteristic curve, 8. using the current sensor (23) to move the piston to a position corresponding to a specific pressure; 9. wherein the piston-cylinder system is designed to generate a brake pressure build-up and brake pressure reduction in order to implement ABS control.

Description

[0001] The present invention relates to a brake system, an actuating device, in particular a brake pedal, and a control and regulating device, wherein the control and regulating device controls an electromotive drive device based on the movement and / or position of the actuating device, wherein the drive device adjusts a piston of a piston-cylinder system via a non-hydraulic transmission device so that a pressure is established in the working chamber of the cylinder, wherein the working chamber is connected to a wheel brake via a pressure line. State of the art:

[0002] Modern braking systems consist of brake boosting, i.e., converting pedal force into a correspondingly increased braking torque at the wheel brakes, and brake force control via open or closed control circuits. With few exceptions, hydraulic lines are used as the transmission medium for generating brake pressure from pedal force in passenger cars.

[0003] A common approach is to divide the brake booster (BKV) or brake force control and brake force regulation into components within a single hydraulic unit (HE). This configuration is primarily used in systems such as anti-lock braking systems (ABS), anti-skid systems (ASR), electronic stability programs (ESP), and electro-hydraulic brakes (EHB).

[0004] The hydraulic unit (HE) consists of solenoid valves, multi-piston pumps for dual-circuit brake systems, an electric motor to drive the pump, a hydraulic accumulator, and several pressure sensors. Pressure is regulated by releasing pressure fluid from the wheel brakes into a reservoir via solenoid valves to reduce braking torque. The fluid is then pumped back into the master cylinder by the pump, causing pedal movement. Both the pressure increase and decrease are controlled by solenoid valves, some of which use pressure sensors to control the solenoid valves. Except for the EHB, brake boosting is achieved with the vacuum brake booster, which sometimes includes switching devices and sensors for the so-called brake assist function and also for detecting the so-called activation point. In gasoline engines, the combustion engine is used as the energy source for the vacuum. However, as a direct injection engine, it only delivers a weak vacuum, especially at higher altitudes.Diesel engines use a mechanically or electrically driven vacuum pump. The latest ESP systems are capable of providing additional brake boost by switching the solenoid valves and pump, or, in the event of brake booster failure, brake booster with a longer time constant. These systems and functions are described in detail in the 2003 edition of the Vieweg Verlag Brake Manual.

[0005] In the mid-1980s, Teves introduced the so-called Mark II and Bosch introduced the ABS3. These integrated units included all components for brake boosting and control with a hydraulic brake servo (see Bosch Automotive Handbook 1986, 20th edition). For cost reasons, these systems did not gain widespread acceptance, except for use in special-armored vehicles. The same applies to fully electric braking systems, so-called EMB, with electric motors on the wheel brakes, which were intensively developed in conjunction with the 42-V electrical system. In addition to the additional costs, a new redundant electrical system for the power supply is required to ensure the braking capability of a brake circuit in the event of a failure.

[0006] The wedge brake with electric motor drive also belongs to the EMB system category. This also requires a redundant on-board power supply despite its lower energy consumption. The design of the wedge brake, which requires additional rollers for hysteresis reasons, necessitating integration into the brake caliper, has not yet been resolved. The wedge brake, with its electric motor drives and sensors, must withstand harsh environmental conditions (dust, water, high temperatures).

[0007] The systems for brake and clutch control (BKV) and brake and clutch control (HE) are highly advanced, particularly the control and regulation functions for ABS and ESP. For example, the pressure-controlled control of the solenoid valves enables very fine dosage of the brake pressure, which also enables variable brake force adjustment (EBV). The pressure reduction rate is not yet optimal because it is highly nonlinear. Furthermore, in the case of a µ-step or a small friction coefficient, the pressure reduction rate is determined by the relatively low pump power, which leads to large control deviations and thus a loss of braking distance.

[0008] A generic braking system is known from DE 33 42 552 A1. In this braking system, the master brake cylinder generates a pedal-dependent pressure that serves as a reference variable for an electronic control and regulating device, which regulates the output pressure of an electrohydraulic servo device directly connected to the brake circuit to a value determined by the reference variable. If the control device or the servo device itself fails, the pressure in the brake circuit is generated by the master cylinder. Instead of the reference variable generated by the master brake cylinder during normal operation, it is possible to have a reference variable generated as part of an anti-lock braking system or as part of a slip control of the motor vehicle's drive system act on the electronic control and regulating device and thus on the electrohydraulic servo device.The servo system features an electrically operated hydraulic piston-cylinder unit whose working chamber is connected to the brake circuit and whose piston is axially adjustable by an electric motor. The rotary movement of the electric motor is converted into a longitudinal movement of the piston via a spindle connected to the piston.

[0009] A braking system is previously known from WO2004 / 005095 A1 in which an electric motor drives the pistons of a piston-cylinder system via a spindle drive. The pistons are not rigidly coupled to the spindle, so the maximum piston speed when the spindle retracts, and thus the maximum pressure reduction rate, is determined by the strength of the compression springs in the piston-cylinder system. The brake pressure to be set in the wheel brakes is determined by a pressure sensor, with the pressure being the controlled variable for the brake pressure control.

[0010] DE 3723916 A1 shows a braking system with a hydraulic brake booster that, in addition to pure brake boosting, also performs the ABS function. In the pressure line connecting the piston-cylinder system and the respective wheel brake, only one valve is located at a time. This valve is open to change the pressure in the wheel brake and closed to maintain the wheel brake pressure. In this brake pressure control system, the pressure is also the controlled variable.

[0011] DE 195 00544 A1 discloses an electronically controlled brake actuation system for anti-lock motor vehicle brake systems, in which a master brake cylinder is actuated by means of a brake pedal. A sensor determines the actuation travel of the brake pedal, which represents an input variable for a control unit that controls several brake pressure sensors, to which the vehicle brakes are connected directly or via solenoid valves using hydraulic lines. The connection of the hydraulic lines to the master brake cylinder can be shut off by a valve device. To increase functional reliability, particularly in the event of an electrical defect or failure of the vehicle electronics, the piston of the master brake cylinder can be adjusted in the fallback level directly by means of the brake pedal to build up pressure in the wheel brakes, with the valve device being open for this purpose.The brake pressure sensors each have an electric drive that adjusts a piston in a cylinder, creating a pressure in the brake circuit. This pressure is measured by a pressure sensor and fed to the control unit as an input variable. The pressure is also the controlled variable in this brake pressure control system. A similarly operating brake system is already known from DE 4239386 A1.

[0012] DE 4445975 A1 discloses a braking system for motor vehicles in which the brake pressure in a wheel brake is regulated by means of an electric motor-driven piston of a piston-cylinder system. This braking system also includes a pressure sensor for measuring the controlled variable. A 2 / 2-way valve is used to maintain the brake pressure in the wheel brake, which can be used to shut off the hydraulic line between the piston-cylinder system and the wheel brake.

[0013] DE 10318401 A1 discloses a motor-driven vehicle braking device in which the position of the brake pedal is determined by means of a displacement sensor and transmitted to a control unit. Depending on the driving condition and the brake pedal position, the control unit controls an electric motor drive of a piston-cylinder system, which serves to build up pressure in the brake circuits. A mechanical connection between the piston of the piston-cylinder system and the brake pedal is not provided, so that in the fallback mode, no pressure can be built up in the wheel brakes using the brake pedal. The pressure in the wheel brakes is regulated by means of inlet and outlet valves assigned to the respective wheel brakes.

[0014] DE 19936433 A1 and DE 10057557 A1 disclose braking systems in which an assisting force can be applied to the piston of the master brake cylinder, which is adjustable by the brake pedal, by means of electromagnetic drives. In these braking systems, too, the pressure in the master brake cylinder is the control variable for the brake pressure control process. Object of the invention

[0015] The present invention has the object of providing a novel braking system which is small and compact in its dimensions.

[0016] This object is advantageously achieved by a braking system having the features of claim 1. Further advantageous embodiments of the braking system according to claim 1 result from the features of the subclaims.

[0017] The braking system according to the invention is advantageously characterized by the fact that it implements the brake booster and the servo device in the smallest possible space per brake circuit using only a single piston-cylinder unit. The piston-cylinder unit serves simultaneously for brake pressure build-up and brake pressure reduction, for implementing ABS and anti-skid control, and in the event of a power failure or drive system malfunction. This advantageously results in a small, integrated and cost-effective unit for the brake booster (BKV) and control, which saves installation space, assembly costs, and additional hydraulic and vacuum connecting lines. Furthermore, due to the short overall length, the spring dome, for example, does not affect the master cylinder and pedal assembly in the event of a frontal crash.

[0018] By advantageously providing a sensor system and a travel simulator, a variable pedal characteristic such as a brake-by-wire function, i.e. brake pressure increase can be freely variable independently of pedal actuation, also taking into account the braking effect of the generator in the case of recuperable brakes.

[0019] Furthermore, with this design, the brake pedal does not detrimentally collapse in the event of a power failure, as the pedal acts directly on the system's piston. This also advantageously results in lower pedal forces in the event of a power failure, as the pistons have a smaller effective area than conventional master brake cylinders. This is made possible by separating the piston travel when the booster is working and the booster fails. This is referred to as a step change, which reduces the pedal force for the same braking effect by up to 40%. The reduction in overall complexity, including the electrical connections, also advantageously results in a reduced failure rate.

[0020] The electric motor drive further improves ABS / ESP control through finely dosed pressure control with variable pressure increase and, in particular, pressure decrease rates. A pressure reduction of less than 1 bar in the vacuum range is also possible for operation with the smallest friction coefficients, such as wet ice. Likewise, a rapid pressure increase at the start of braking, for example, from 0 to 100 bar in less than 50 ms, is achievable, resulting in a significant reduction in braking distance.

[0021] Due to the advantageous provision of a 2 / 2-way valve for the brake booster and the control function, the brake system according to the invention requires considerably less energy.

[0022] It is also possible to provide a separate piston-cylinder system with its own drive for each brake circuit or wheel brake. It is also possible to use a piston-cylinder system in which two pistons are arranged axially displaceably within a cylinder, with the cylinders hydraulically coupled and only one piston being mechanically driven by the electric motor of the drive device.

[0023] Various embodiments of the braking system according to the invention are explained in more detail below with reference to drawings.

[0024] They show: Fig. 1 : A first embodiment of a braking system with a braking circuit for two wheel brakes; Fig. 2: a second embodiment of the brake system with two piston-cylinder systems for two brake circuits for two wheel brakes each; Fig. 3: a travel simulator for the braking system according to the invention; Fig.4: a piston-cylinder system with one cylinder and two pistons; Fig. 5 and Fig. 5a: Connection between actuating device and piston-cylinder systems; Fig. 6: a side view of the integrated unit with housing; Fig. 7: Characteristic curves of the braking system; Fig. 8 and Fig. 8a: Piston drive via a crank arm Fig. 9: Piston drive via a spindle Fig. 10: Piston actuation with superimposed pedal force

[0025] The Fig.Figure 1 shows a section of the integrated unit responsible for pressure generation and brake boosting. Piston 1, with the usual seals 2 and 3, is moved parallel to the piston in the cylinder housing 4 via a specially designed rack 5a. Seal 2 is designed to seal even in the event of negative pressure in the piston chamber 4'. This rack 5a transmits the force to the front, spherical end of piston 1. At this point, the piston has a collar bolt 1a, via which rack 5a, with return spring 9, returns the piston to its initial position. Here, the rack rests against the cylinder housing 4a. This external spring has the advantage of keeping the cylinder short and having little dead space, which is beneficial for venting. Due to the transverse forces, the rack is supported by rollers 10 and 11 with a sliding piece 12. Fig.Figure 1 clearly shows that the parallel arrangement of the rack to the piston results in a short overall length. The assembly must be very short in order to be outside the crash zone. The rack is secured by a Fig.The H-profile shown in Figure 5a is very rigid. The arrangement of the rollers is selected such that the rack in the end position 5b (shown in dashed lines) with the greatest bending force has a relatively short bending length due to the offset compressive force. The rack is driven by the pinion of motor 8 via tooth profile 5a' and gear 6 via gear wheel 7. This motor with a short time constant is preferably a brushless motor as a bell-shaped rotor with ironless winding or preferably a motor according to PCT patent applications PCT / EP2005 / 002440 and PCT / EP2005 / 002441. This is controlled by the output stages 21, preferably via three phases, from a microcontroller (MC) 22. For this purpose, a shunt 23 measures the current and a sensor signal 24 and indicates the position of the rotor and, via corresponding counters, the position of the piston.In addition to engine control, current and position measurement are used for indirect pressure measurement, as engine torque is proportional to pressure force. For this purpose, a map must be created in the vehicle during commissioning and during operation, in which the piston position is assigned to the various current intensities. During operation, the piston is then moved to a position corresponding to a specific pressure according to the map, according to the amplifier characteristic curve described later. If position and engine torque do not entirely match, e.g. due to temperature influences, the map is adapted during operation. This means that the map is continuously adapted. The initial map is formed from, preferably, the pressure-volume characteristic curve of the wheel brake, engine characteristic value, transmission efficiency, and vehicle deceleration.The latter allows vehicle deceleration proportional to pedal force to be achieved so that the driver does not have to adjust to different braking effects.

[0026] Piston 1 generates a corresponding pressure in line 13, which is then passed via the 2 / 2-way solenoid valve (MV) 14 to the wheel brake 15 or via the solenoid valve MV 16 to the wheel brake 17. This arrangement has several advantages. Instead of the two inexpensive small solenoid valves, another piston-motor unit could be used, as in Fig. 4. However, this means considerably more cost, weight, and installation space.

[0027] It is sufficient to use one piston motor unit for each brake circuit.

[0028] The second advantage is the very low energy consumption and the fact that the motor is designed for pulsed operation only. This is achieved by closing the solenoid valves when the setpoint pressure or engine torque is reached and then running the motor at a low current until a new setpoint is entered from the brake pedal. This means that the energy consumption or average power is extremely low. For example, with a conventional design, motor 3 would draw a high current during an emergency stop from 100 km / h. According to the invention, the motor only requires around 0.05 s of current for the piston travel, which represents 1.7%. If the values ​​are related to the power, in the conventional case the vehicle electrical system would be loaded with > 1000 W for at least 3 s, whereas with the proposed pulsed operation the average power would be only around 50 W.Even greater energy savings are achieved during emergency braking from 250 km / h, with braking times of up to 10 seconds on dry roads. To reduce the impulse load on the vehicle's electrical system, a storage capacitor 27 can be used in the power supply. This capacitor can also be used for the other electric motors, as shown by the line with the arrow.

[0029] In the pressure line 13, pressure sensors can be used before or after the solenoid valve, which are not shown because they correspond to the state of the art.

[0030] Piston 1 is supplied with fluid from the reservoir 18 via the sniffer hole. A solenoid valve 19 is connected in this line. If the piston moves quickly to reduce the pressure, the seal 3 could sniff out fluid from the reservoir, particularly at low pressures, which is known to be disadvantageous. To do this, the low-pressure solenoid valve 19 is switched on and the connection to the reservoir is interrupted. With this circuit, negative pressure can also be achieved in wheel circuits 15 / 17, which benefits wheel control at very low friction coefficients, e.g., on wet ice, since no braking torque is generated in the wheel brake. On the other hand, sniffing can be deliberately used in the event of vapor lock, where the piston is already at its stop without the corresponding pressure being reached. In this case, the pistons are controlled accordingly using the solenoid valves so that the oscillating piston builds up pressure.If this function is omitted, a sniff-proof seal 3 can be used instead of the solenoid valve 19.

[0031] The solenoid valves 14, 16, 19 are controlled by the microcontroller 22 via output stages 28.

[0032] If the power supply or the electric motor fails, the piston is moved by a lever 26 of the actuating device. A clearance is built in between the lever and the piston, preventing the lever from striking the piston before the motor moves the piston during rapid pedal operation.

[0033] The control function regarding wheel speed and wheel pressure in ABS / ASR or yaw rate and wheel pressure in ESP has been described in various publications, so a further description will be omitted. The table below illustrates the key functions of the new system: Pressure Pressure Functions electric motor Wheel brake 15 Solenoid valve 141 Wheel brake 17 Solenoid valve 151 BKV A Construction 0 Construction 0 partially powered P = constant 1 P = constant 1 partially powered dismantling 0 dismantling 0 Brake control A Construction 0 Construction 0 partially powered P = constant 1 P = constant 0 A Construction 0 P = constant 1 partially powered dismantling 0 P = constant 1 partially powered dismantling 0 dismantling 0

[0034] The level of partial current supply depends on the rate of pressure increase or decrease desired by the brake control system or the brake control. An extremely short time constant of the electric motor is crucial for this, i.e., a rapid torque increase and torque reduction via small moving masses of the entire drive, since the piston speed determines the rate of pressure change. In addition, fast and precise position control of the pistons is necessary for brake control. During the rapid torque reduction, the pressure force originating from the brake caliper also has a supporting effect; however, this force is low at low pressures. However, it is precisely here that the pressure drop rate should also be high to avoid large control deviations from the wheel speed, for example on ice.

[0035] This concept has a decisive advantage over conventional pressure control using solenoid valves, as the piston speed determines the rate of pressure change. For example, with a small differential pressure at the outlet valve that determines pressure reduction, the flow rate and therefore the rate of pressure reduction is low. As already mentioned, the piston unit can be used separately for each wheel, with or without a solenoid valve. In order to utilize the advantages of low energy consumption, the electric motor would have to be supplemented with a fast electromagnetic brake, which is, however, more complex. The design shown with a piston unit and two solenoid valves is preferable in terms of installation space and cost. In terms of control technology, however, the restriction applies here that if the pressure is reduced at one wheel, the other wheel cannot build up pressure. However, since the pressure reduction time is approx.< 10% of the pressure build-up time in the control cycle, this restriction does not pose any significant disadvantage. The control algorithms must be adapted accordingly. For example, after a phase of constant pressure from the opening of the solenoid valve, the electric motor must be excited with a current that is assigned to the appropriate pressure in the wheel brake according to the BKV characteristic curve or, for example, is 20% higher than the previous blocking pressure in the control cycle. Alternatively, an adaptive pressure level can be controlled during control, which is 20% higher than the highest blocking pressure of the axle or vehicle. The blocking pressure is defined as the pressure at which the wheel runs unstably with greater slip.

[0036] The concept also offers new control engineering options for pressure reduction. In terms of control engineering, the pressure reduction and braking torque reduction are essentially proportional to the wheel's rotational acceleration, the seal hysteresis, and inversely proportional to the wheel's moment of inertia. From these values, the amount of pressure reduction required can be calculated, and the piston can already provide the corresponding volume when the MV is closed, taking into account the described characteristic map. When the MV then opens, the pressure is reduced very quickly, practically into a vacuum. This is based on the fact that the MV has a smaller throttling effect than current solutions due to its corresponding opening cross-sections. In this case, the pressure reduction can occur more quickly than with conventional solutions via a specially provided chamber volume corresponding to the pressure-volume characteristic curve.Alternatively, a pressure reduction into a chamber volume slightly larger than the required pressure reduction is possible, e.g., by adjusting the piston speed accordingly. To precisely control the pressure reduction, a very short switching time is required to close the solenoid valve, which can preferably be achieved by pre-excitation and / or over-excitation. Furthermore, for special control cases, it is advantageous to move the armature of the 2 / 2-way solenoid valve to an intermediate position using known PWM methods to create a throttling effect.

[0037] The very rapid pressure reduction can potentially generate pressure oscillations that affect the wheel. To avoid this harmful effect, the piston travel can be controlled accordingly, e.g., 80% of the required pressure reduction (rapid pressure reduction). The remaining required 20% of the pressure reduction can then occur slowly through a subsequently controlled slow piston movement or, in the alternative with pressure reduction control via solenoid valves, by pulsing the solenoid valve and gradual reduction. This prevents harmful wheel vibrations. The slow pressure reduction can continue until the wheel accelerates again under ABS control.

[0038] This allows for very small control deviations in wheel speed. The method described above can also be applied to pressure buildup. The rates of pressure increase can be optimized according to control-engineering criteria. This allows the goal of braking the wheel in the immediate vicinity of the maximum friction force, thus achieving optimal braking effect with optimal driving stability.

[0039] Special control cases were mentioned above where a throttling effect is advantageous. This is the case, for example, when pressure needs to be reduced at both wheels at the same time. Here, the throttling effect is advantageous until the actuating piston has provided such a large chamber volume that the subsequent rapid pressure reduction into a vacuum can take place from different pressure levels. A similar procedure can be used, i.e. if the solenoid valves have a built-in throttle in the valve cross-section and pressure is to build up in both wheel circuits at the same time. However, individual alternating pressure build-up is preferable because of the metered pressure build-up with evaluation of the characteristic map and controlled adjustment speed of the piston. The same alternating process can be used as an alternative to the above with the throttling effect for pressure reduction.As a further option, the piston can be retracted using a control signal with a lower response threshold than the control signal for pressure reduction. According to the current state of the art, this is the signal at which the controller detects a tendency to lock and switches the MV to pressure hold (see brake manual, pages 52-53). This signal is output 5-10 ms before the pressure reduction signal. The proposed high-speed drive is capable of providing a chamber volume sufficient for a 10 bar pressure reduction within approximately 5 ms.

[0040] Based on the piston position for pressure reduction, the controller can decide whether there is sufficient chamber volume available for simultaneous pressure reduction for both wheel brakes.

[0041] These statements 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 reductions in braking distances and driving stability.

[0042] The Fig. Figure 2 shows the entire integrated unit for the BKV and control functions. The unit consists of two piston units with associated electric motors and gearboxes. Fig. 1 for two brake circuits and four wheel brakes. The piston units are housed in housing 4. This housing is attached to the front wall 29.

[0043] The brake pedal 30 transmits the pedal force and movement via the bearing pin 31 to a fork 32, which acts on the actuating device 33 via a ball joint. This has a cylindrical extension 34 with a rod 35.

[0044] Cylinder 34 and rod 35 are mounted in a bushing 37. This bushing accommodates the travel simulator springs 36 and 36a, with one spring acting weakly and the other strongly, progressively increasing the force. The travel simulator can also be constructed from even more springs or rubber elements. This determines the pedal force characteristics. The pedal travel is recorded by a sensor 38, which in the example shown is constructed according to the eddy current principle, into which the rod 35 with a target is immersed.

[0045] The pedal movement is transmitted to elements 32 and 33, the piston 34 moves with the rod 35 in the bushing 37. A lever 26 is pivotally mounted on the actuating device, which strikes the pistons in the event of a power failure. The pedal travel sensor delivers the travel signal to the electronic control unit, which, according to the BKV characteristic curve, as shown in Fig.7, causes the pistons to move via the electric motor. The parameters of this characteristic curve are shown in Fig. 7. Between the lever 26 and the two pistons 1 there is a clearance s o provided as in Fig. 1. The actuating device has an anti-rotation device via the bolt 39, which is shown offset, and a return spring 40, which supports the pedal return spring (not shown). Many travel simulator solutions are known in the state of the art, some of which are also hydraulically actuated via pistons and are shut off via solenoid valves if the power supply fails. This solution is complex and subject to hysteresis. Solutions are also known in which the travel simulator path becomes a lost path in the event of a power supply failure when the pistons are actuated to generate brake pressure.

[0046] The aim of the invention is a simple solution in which the travel simulator is deactivated in the event of a power failure. For this purpose, a counterforce is exerted on the bushing 37 via the armature lever 41 with a high transmission ratio and the holding magnet 42 when the power supply is intact. This counterforce is eliminated when the electrical power supply fails. Two-stage levers can also be used to reduce the magnet's force. This is described in detail in Fig.3. In this case, the lever comes into contact with the two pistons via the brake pedal after passing through the play and can thus transfer the pedal force to the pistons. The pistons are dimensioned such that at full pedal stroke they generate a pressure which still results in good braking effect, e.g. 80%. However, the piston stroke is considerably greater than the pedal stroke and, with an intact power supply and electric drive, can generate much higher brake pressures. However, the driver cannot apply the corresponding pedal force. This design is referred to as a gear ratio jump, which is possible by decoupling the actuation unit with travel simulator from the piston. With a conventional design, in which the brake servo and master cylinder with pistons are connected in series, the required pedal force increases by up to a factor of 5 for the same wheel brake pressure in the event of a power supply failure. With the new design, for example, the factor can be reduced to 3.This case is relevant, for example, when towing a vehicle with a failed battery.

[0047] The lever 26 is pivotally mounted so that it can accommodate tolerances in the movement of the pistons, e.g., due to different venting. This compensation can also be limited so that the lever rests against a stop 33a of the actuating device.

[0048] However, further error cases must be considered. Failure of an electric motor.

[0049] In this case, the amplification and control of the adjacent intact piston drive are fully effective. Brake pressure is generated in the failed circuit via lever 26 after it reaches the stop 33a. Here, the amplifier characteristic of the second circuit can also be increased, which reduces the required pedal force. However, this can also be done without a stop. Failure of a brake circuit.

[0050] Here, the piston moves to its stop in housing 4. The intact second circuit is fully effective. Unlike conventional systems today, there is no drop in the pedal, which is notoriously irritating to the driver. This irritation can even lead to a complete loss of braking effect if the pedal is not fully depressed.

[0051] The Fig.Figure 3 describes the function of the travel simulator locking mechanism. In extreme cases, the driver can exert high pedal forces, which the locking mechanism must apply via the armature lever 41. To prevent the magnet 42 with excitation coil 43 from having to fully apply these forces, the upper, spherical end 41a of the lever engages the bushing 37 asymmetrically. If the pedal is now deflected until the rod 35 hits the floor 37b, this leverage causes a slight twist of the bushing 37, which generates friction in the guide, whereby the nose 37a can also be supported on the housing 4. This allows the magnetic force to be kept relatively small. The magnet is also designed as a holding magnet 42, so that a small holding power is necessary due to the small air gap. In the event of a power failure, the armature lever 41 is deflected by the bushing 37 into the dash-dotted position 41'.When the actuating device 33 returns to its original position, the return spring 44 returns the armature lever to its original position.

[0052] The sensor 38 has been moved to the end of the bushing bore in the housing 4, which has advantages for the contact with the electrical control unit, as shown in Fig. 6. The same applies to the brake light switch 46. In this embodiment, the target 45 for the eddy current sensor is shown.

[0053] The locking of the travel simulator via the socket 37 can be changed to Fig. 7 to avoid the pedal reaction in ABS. For this purpose, the lever 41 with its bearing and magnet 42 with holder 42a can be moved by an electric motor 60, which drives a spindle 60a via a gear 60b. The lever is mounted on the spindle extension, and the magnet housing is attached.

[0054] The Fig.4 shows a schematic diagram of a solution with only one electric motor 7a. This description is based on Fig. 1 and Fig. 2. The drive pinion of the motor moves the rack 5c, which is similar Fig.1 can also be moved in parallel. This is connected to a piston 1a, which builds up pressure in the brake circuit 13a and at the same time uses the pressure to move the piston 1a, which builds up pressure in the brake circuit 13. This piston arrangement corresponds to a conventional master brake cylinder, for which many variants of piston and seal designs exist. The 2 / 2-way solenoid valves 14, 14a, 15, 15a are arranged in the brake circuits, as in the figures above. The ABS pressure modulation takes place in the manner described above. The BKV function is carried out via a parallel arranged travel simulation 36 and travel sensor 38. Here, too, a play or idle stroke s0 is provided between piston 1a and the brake pedal. The brake fluid flows from the reservoir 18, 18a into the piston chambers. This arrangement is cost-effective. The dynamics of the BKV function during pressure build-up are lower than in the variant with two motors, since the electric motor has to generate twice the torque.The redundancy function of the 2nd motor as in is also no longer required. Fig. 7, including a falling pedal in the event of a brake circuit failure.

[0055] The Fig. Figure 5 shows the view from the end wall onto the integrated assembly, whose flange 4b ​​is bolted to the end wall by means of screws 47. The actuating unit 33, lever 26 and a bolt 39 (not shown offset) as an anti-twist device are visible here. For size comparison, the outline of a 10" vacuum BKV is shown here. This shows an important advantage in the overall height with the cover 48 of the storage container. According to the distance A, the end wall could be lowered, which is what the designers wanted. On the left side of the flange, with reference to Fig. 5a, the drive of the rack 5 is shown in dashed lines. This detail is enlarged as Fig.5a on the right half of the figure. The pinion of the gear 6 engages on both sides with the H-shaped design of the rack 5. The described transverse forces are transferred by the roller 10 or 11 accordingly. Fig. 1 is supported by bearings 10a. For cost reasons, the rack can be made of plastic. Since its surface pressure is insufficient, hard sheet metal strips 49 are inserted here, which adapt to the rollers with a slightly crowned support. The gear wheel 7 is pressed into the pinion 6 and meshes with the motor pinion. The pinion is preferably mounted in the motor housing 8a.

[0056] The Fig.Figure 6 shows the side view of the integrated assembly with housing 4, fork 32 for brake pedal 30, actuation unit 33, flange 45, fastening screws 47, and cover 48. This view shows the short overall length, with the electronic control unit 50 mounted on the front. According to the state of the art, this is connected to the coils or part of the magnetic circuit of the solenoid valves 14 and 16 in order to further eliminate the need for contact and electrical connecting cables. This feature can be enhanced by connecting all electrical components such as the electric motor 8, solenoid coil 43, travel sensor 38, brake light switch 46, and brake fluid level sensor 53 directly to the control unit without electrical connecting cables. In this case, the control unit would have to be installed from above toward 50a. However, it is also possible toward 50b, which results in a modified arrangement of the solenoid coil.

[0057] The solenoid valves are preferably mounted on a carrier plate 51, which, for cost reasons, is pressed into aluminum with high elongation. The plug screws 52 for the brake lines are screwed into this carrier plate. The contacting is shown in the middle part of the control unit, which contains a redundant power supply in area 54, the bus line in area 55, and the sensors for ABS and ESP at 56.

[0058] The Fig. Figure 7 shows the main characteristics of the braking system. It shows pedal force F P , brake pressure p and pedal travel at the actuating unit. Typically, a ratio of 4 to 5 is selected from here to the pedal foot. The pedal travel has its maximum at S P and the pistons, as already mentioned, at a higher value s K57 represents the so-called pressure-displacement characteristic curve, which here corresponds, for example, to a brake circuit. The non-linear curve results from various elasticities, such as those of the brake caliper, seals, lines, residual air pockets, and fluid compressibility. This line shows the mean value of a scatter band, which is also temperature-dependent, especially for the brake caliper. Therefore, a characteristic map must be created for the flow-proportional pressure control.

[0059] The characteristic curves 59 show the failure of the electric drive, in which the pistons are actuated after the clearance S0. To achieve, for example, 100 bar, the described considerably higher pedal forces F PA of approximately 600 N is necessary, which corresponds to a pedal force that is more than 40% lower than current solutions.

[0060] From the pedal position and the brake pressure it can be seen that the pressure modulation of 10 bar at blocking pressures > 50 bar does not affect the pedal, since the pedal at S S When the locking pressure is lower, a reaction occurs on the pedal when the pressure is fully depressed, which is comparable to today's ESP and ABS systems. However, it is possible to reduce or avoid this reaction by using a Fig. 4, which adjusts the locking of the travel simulator via a drive. The pedal is moved back via the piston drive 6 to reduce the pressure. At this point, the motor adjusts the drive with a small force. This also allows a pedal movement to warn the driver, e.g., in the event of a traffic jam or similar. Even without this additional motor, a reaction is possible if the pedal movement is greater than the play S. oand the pistons are briefly retracted as a warning.

[0061] The thicker lines are the amplifier lines 58 and 58a, which represent the assignment of pedal force F P to the brake pressure. At approximately 50% of the maximum pedal travel, the travel simulator is at S Sfully controlled. This has the advantage that emergency braking with a short pedal travel is possible. The pedal travel is recorded by sensor 38. The assignment of pressure to pedal force is freely variable and can, for example, in the dashed line, take vehicle deceleration into account by incorporating this as a correction value into the gain, so that when the brake fades, a higher pressure is applied with the same pedal force. This correction is also necessary in systems with recuperation of braking energy via the generator, since the braking effect of the generator must be taken into account. The same applies to panic braking with high pedal speed. Here, a much higher pressure can be fed in disproportionately to the pedal force, which, with a time delay, follows the shown static characteristic curve (solid line).

[0062] At F P1A foot force of 200 N is generally specified for a brake pressure of 100 bar. This pressure corresponds to the locking limit on dry roads. In this range, the travel simulator characteristic curve is almost linear, ensuring good controllability. A maximum pressure of 160 bar is generally sufficient, based on which the fatigue strength of the elements is dimensioned. However, a reserve R can be maintained for rare loads, which can be effective, for example, if the locking limit is not yet reached at 160 bar.

[0063] The electric drive can be considered more fail-safe than the vacuum BKV in the event of a power failure, since at least two electric motor drives are used for the proposed invention, ie one acts redundantly and is known to be the total failure rate λ g= λ1 · λ2 applies. A power failure during the journey is almost impossible, since generator and battery practically never fail simultaneously. A power failure is prevented by the Fig. The redundant power supply described in section 7 is prevented. The vacuum BKV is not redundant with amplifier elements, supply lines, and possibly a pump.

[0064] The Fig. Figure 8 shows another solution for the piston drive. Instead of the rack, a crank arm 60 can be used, which is connected to the piston via a tension rod 61 and the bearing pin 62. The return spring 9 acts on the crank arm, whose initial position is determined by the stop 65. The crank arm is driven by the motor 11 via a multi-stage gear 63.

[0065] The Fig.Figure 8a shows a two-armed crankshaft 60 and 60a with two tension struts 61 and 61a. This ensures that only minimal transverse forces act on the piston. The gear 63 is encapsulated in an extended motor housing 64 and is driven by the drive pinion 11a of the motor 11. The advantage of this solution lies in the encapsulation of the gear, which allows for oil or grease filling, permits helical gearing, and thus provides higher load-bearing capacity and lower noise.

[0066] The Fig.Figure 9 shows a further alternative with a spindle drive arranged within the rotor of the electric motor. This arrangement is known from DE 195 11 287 B4, which relates to electromechanically actuated disc brakes. In the solution presented, the nut 67 is located as a separate component in the bore of the rotor 66 and rests on the flange 66a of the rotor. The compressive forces of the piston 1 act on this. The spindle drive also acts as a reduction gear, with the spindle 65 transmitting the force to the piston. All drives shown so far have a reduction gear permanently coupled to the piston, which must be moved by the brake pedal in the event of a power failure and accelerated by the motor in the event of rapid pedal actuation. These mass inertia forces prevent rapid pedal actuation and irritate the driver.To prevent this, the nut is axially movable in the bore of the rotor so that when the pedal is engaged, the ball screw drive is disengaged. For normal operation with an electric motor, the nut is held in place by a 70 mm lever, which is effective for rapid retraction of the piston, particularly when there is a vacuum in the piston chamber. This lever is mounted in the rotor via shaft 71 and, when the motor is not rotating, is moved by spring 72 into a position where the nut is free. Since the drive motor accelerates extremely quickly, centrifugal force acts on the lever, and the nut is enclosed by the lever to move the piston.

[0067] This movement can also be achieved by an electromagnet (shown in dashed lines), in which the lever represents a rotating armature. The torque generated by the nut on the spindle is absorbed by two bearing pins 69 and 69a. These pins also support the return spring 9. The rotor is preferably mounted in a ball bearing 74, which absorbs the axial forces of the piston, and in a plain bearing 75, which can also be a roller bearing. This solution requires a greater overall length, which is less advantageous compared to Fig. 9, since the insertion length of the spindle into the nut is equal to the piston stroke. To keep this extension small, the motor housing 74 is flanged directly to the piston housing 4. This also has the advantage of different materials for the motor and piston housing.

[0068] The nut 67 can also be connected directly to the rotor 66, e.g., by injection molding. A plastic nut with a low coefficient of friction can be used to provide the required forces.

[0069] In case of failure of a motor or the power supply, the pedal (not shown) acts on the fork piece accordingly Fig. 2 and, after the free travel, via lever 26 onto spindle 65 or piston 1. Since blocking of the drive is to be eliminated with this solution, stop 33 can be positioned closer to the lever. This has the advantage that the pedal force acts fully on the piston, for example, if an electric motor fails. As soon as the lever rests on the opposite end during rotation, only half the pedal force acts on the piston. In the design, the spindle and piston are decoupled, which was not implemented separately.

[0070] The return of the piston to its original position is important. If the motor fails in an intermediate position, the piston return spring can be additionally supported by a spiral spring 66a, which is arranged at and coupled to the end of the rotor 66 and the motor housing 74. This is intended to compensate for the cogging and friction torque of the motor. This is particularly advantageous for small return forces of the pistons, which act on the pedal in the event of a power failure, in conjunction with the Fig. 9 described clutch lever.

[0071] The Fig. Figure 10 shows a further simplified embodiment with an electric motor piston drive, in which the piston 1 again performs the brake force amplification and pressure modulation for ABS. The piston chambers 1' are arranged according to the Fig. 1 to Fig.9 is connected via lines 13 and 13a to the wheel brakes (not shown) and to the solenoid valves (also not shown). The structure corresponds Fig. 8 with spindle drive 65 and rotor 66, fixed nut 67, separation of motor and piston, housing 74 or 4, piston return springs 9 and bearing pin 69, spiral spring 66a for motor return. The pedal force is similar Fig.2 is transmitted from a forked piece 26 to an actuating device 34 with a rod 35. This is mounted in the motor housing 74 and carries a target 45 in its extension, for example for an eddy current sensor 38, which measures the pedal travel. The actuating device is reset via a spring 79. A lever 26 is in turn mounted on the actuating device 35, which at the end in connection to the piston preferably carries leaf springs 76, which are connected to a travel sensor 77 in the case of a strong leaf spring or to a force sensor 77a in the case of a softer spring. In both cases, the force transmitted by the lever or pedal is to be measured. The leaf spring 76 has the task of preventing a harsh reaction when the pedal is actuated before the motor starts.The function is such that, depending on the pedal force, the motors exert an amplifying force on the piston. This force can be determined from the current and piston travel or a pressure sensor. The pedal travel can be incorporated into this amplifier function or characteristic curve via the travel sensor 38. This sensor can also assume the amplifier function at the beginning of braking at low pressures in conjunction with the return spring 76. Here, the spring 79 assumes the function of the travel simulator spring.

[0072] The engine housing has a flange for attaching the unit via bolts 78 in the bulkhead. This simplified concept eliminates the complexity of the travel simulator and locking mechanism. Disadvantages include the limited pedal travel characteristic of the amplifier curve, the possibility of the pedal falling through in the event of a brake circuit failure, and higher pedal forces in the event of a booster failure, since the pedal travel and piston travel are identical. This design is primarily suitable for small vehicles.

[0073] In the embodiment according to Fig.Figure 10 shows safety valves 80 representative of all solutions. These valves are activated when, for example, a piston drive jams when the pedal returns to its original position. When the pedal is moved, a conical extension of the actuating device 35 actuates the two safety valves 80, which close the connection from brake circuit 13 or 13a to the return line. This ensures that no brake pressure builds up in the brake circuit when the pedal is in its original position. These valves can also be actuated electromagnetically.

[0074] Safety-critical systems usually have a separate shutdown option for faults in the output stages, e.g., full current flow due to alloying. For this case, a shutdown option, e.g., a conventional relay, is built in. The diagnostic part of the electrical circuit detects this fault and deactivates the relay that normally supplies the output stages with power. The concepts proposed here must also include a shutdown option, implemented using a relay or a central MOSFET.

[0075] Considering the pulse control of the electric motors, a fuse can also be used, since the pulse-off ratio is very high.

[0076] The following are exemplary embodiments according to the invention. Example 1:

[0077] Brake system, having an actuating device, in particular a brake pedal, and a control and regulating device, wherein the control and regulating device controls an electromotive drive device based on the movement and / or position of the actuating device, wherein the drive device adjusts a piston of a piston-cylinder system via a non-hydraulic transmission device so that a pressure is established in the working chamber of the cylinder, wherein the working chamber is connected to a wheel brake via a pressure line, characterized in that in the event of failure of the drive device, the actuating device adjusts the piston (1) or the drive device. Example 2:

[0078] Brake system according to embodiment 1, characterized in that a sensor device determines the position of the actuating device. Example 3:

[0079] Brake system according to embodiment 1 or 2, characterized in that a device, in particular a haptic device, for specifying or adjusting a force / displacement characteristic of the actuating device is in operative connection with the latter. Example 4:

[0080] Brake system according to one of the embodiments 1 to 3, characterized in that a valve (14, 16) controlled by the control and regulating device (22) is arranged in the pressure line (13) to the wheel brake (15, 17). Example 5:

[0081] Brake system according to embodiment 4, characterized in that the valve (14, 16) closes after the required brake pressure in the brake cylinder (15, 17) has been reached and is open to set a new brake pressure. Example 6:

[0082] Brake system according to one of the embodiments 1 to 5, characterized in that the piston (1) generates the required pressure change for the brake force booster (BKV) and the anti-lock braking system (ABS). Example 7:

[0083] Brake system according to one of the embodiments 1 to 6, characterized in that a spring (9) applies force to the piston (1) or the drive device, wherein the spring force acts in the direction that the working space is enlarged. Example 8:

[0084] Brake system according to one of the embodiments 1 to 7, characterized in that the drive device has at least one electric motor (8) with in particular a small time constant and / or a high acceleration capacity. Example 9:

[0085] Brake system according to embodiment 8, characterized in that the electric motor (8) is supplied with an excitation current when the valve (14, 16) is closed, which current is sufficient to hold the piston (1) in position against the spring force. Example 10:

[0086] Brake system according to one of the preceding embodiments, characterized in that each brake circuit has a piston-cylinder system. Example 11:

[0087] Brake system according to one of the preceding embodiments, characterized in that the working chamber (4) is connected to a plurality of brake cylinders (15, 17) via two or more pressure lines (13), wherein a valve (14, 16) is arranged in each pressure line (13). Example 12:

[0088] Brake system according to one of the embodiments 4 to 11, characterized in that the valve (14, 16) is a 2 / 2-way valve. Example 13:

[0089] Brake system according to one of the preceding embodiments, characterized in that the piston-cylinder system has a first and a second piston (1a, 1b) which are arranged to be axially displaceable in a cylinder, the first piston (1a) being mechanically coupled to the electromotive drive device (7a, 6, 5c) and the second piston (1b) being hydraulically coupled to the first piston (1a), the two pistons (1a, 1b) forming a working chamber (4a) between them which is connected to at least one brake cylinder via at least one pressure line (13a), and the second piston (1b) forming a second working chamber (4b) with the cylinder which is connected to at least one further brake cylinder via at least one further pressure line (13). Example 14:

[0090] Brake system according to embodiment 13, characterized in that valves 14, 15, 14a, 15a), in particular 2 / 2-way valves, controlled by the control and regulating device are arranged in the pressure lines (13, 13a). Example 15:

[0091] Brake system according to one of the preceding embodiments, characterized in that when generating the brake force boost, the actuating device is not or not in direct mechanical connection with the piston or the drive device, and only in the event of failure of the drive device or when the ABS is activated is the piston in mechanical connection with the actuating device. Example 16:

[0092] Brake system according to one of the preceding embodiments, characterized in that two piston-cylinder systems, each with an associated drive device, are arranged next to one another, in particular parallel to one another, wherein the actuating device (30) adjusts at least one of the two pistons directly or via intermediate means in the event of failure of at least one drive device. Example 17:

[0093] Brake system according to embodiment 16, characterized in that the actuating device adjusts a lever or the pivot point of a rocker (26) parallel to the adjustment path of the pistons (1) of the piston-cylinder systems, and each free end of an arm of the rocker (26) is assigned to a respective piston (1). Example 18:

[0094] Brake system according to embodiment 17, characterized in that a limiting element (33) limits the pivoting range of the rocker (26). Example 19:

[0095] Brake system according to one of the embodiments 16 to 18, characterized in that the rocker (26) is mounted on a piston (34) which is displaceably mounted in a cylinder parallel to the pistons (1) driven by the drives, wherein the piston (34) is pressurized in the direction of the brake pedal by means of at least one, in particular non-linear, spring (36, 36a), and the spring together with the piston forms a so-called travel simulator, and a sensor determines the position of the piston. Example 20:

[0096] Brake system according to embodiment 19, characterized in that the piston stroke of the piston (34) connected to the rocker (26) is limited by a stop, wherein the stop can be switched off via an actuating device, in particular an electromagnetic one. Example 21:

[0097] Brake system according to one of the preceding embodiments, characterized in that a channel connects the working chamber (4) of the piston-cylinder unit to a reservoir (18), wherein the piston (1) closes the channel (20) when retracting into the cylinder and the channel (20) is open in the initial position, ie only when the piston (1) is almost or completely retracted. Example 22:

[0098] Brake system according to embodiment 21, characterized in that a shut-off valve, in particular a 2 / 2-way valve (19) is arranged in the channel (20). Example 23

[0099] Brake system according to embodiment 22, characterized in that the seal of the piston does not sniff out any fluid due to vacuum in the working chamber when the piston is quickly returned from the reservoir. Example 24:

[0100] Brake system according to one of the preceding embodiments, characterized in that the drive drives a rack (5a) which is mounted displaceably and in particular with low friction parallel to the adjustment path of the piston (1), in particular next to the piston, wherein the rack is in particular firmly connected to the piston (1) via a coupling member (5). Example 25:

[0101] Brake system according to embodiment 16, characterized in that a spring (9) applies pressure to the coupling member or the rack. Example 26:

[0102] Brake system according to one of the preceding embodiments, characterized in that the control regulates a corresponding brake force boost depending on the movement and / or force applied to the brake pedal and / or the driving state and / or braking effect of an electric machine. Example 27:

[0103] Brake system according to one of the preceding embodiments, characterized in that the control determines the brake pressure in the working chamber of the cylinder from the drive current of the drive. Example 28:

[0104] Brake system according to one of the preceding embodiments 1 to 16, characterized in that a pressure sensor is provided for determining the brake pressure in the working chamber of the cylinder. Example 29:

[0105] Brake system according to one of the preceding embodiments, characterized in that the control and regulating device has a memory in which a characteristic map with various parameters for controlling the drive is stored. Example 30:

[0106] Brake system according to one of the preceding embodiments, characterized in that the control determines the piston position by means of at least one sensor, in particular an incremental encoder of the electric motor. Example 31:

[0107] Brake system according to one of the preceding embodiments, characterized in that the drive moves the piston out of the cylinder so that it comes into mechanical contact with the brake pedal and exerts a force on the brake pedal. Example 32:

[0108] Brake system according to one of the preceding embodiments, characterized in that the control, in order to generate a rapid pressure reduction in the wheel brake, generates a negative pressure by means of the associated piston by enlarging the working space before the respective valve is opened. Example 33:

[0109] Brake system according to one of the preceding embodiments, characterized in that the control and regulating device supplies the electric motor of the drive device with approximately 120% of the blocking pressure preceding the control cycle in order to build up an increased blocking pressure before the respective valve opens. Example 34:

[0110] Braking system according to one of the preceding embodiments, characterized in that fast energy storage devices for storing electrical energy, in particular capacitors with a large capacity, are provided for generating pulse currents. Example 35:

[0111] Brake system according to one of the preceding embodiments, characterized in that an additional drive adjusts the actuating device or the stop of the travel simulator in such a way that in normal operation the actuating device is not in mechanical connection with the piston. Example 36:

[0112] Brake system according to embodiment 35, characterized in that the additional drive acts on a travel simulator, wherein at a low blocking pressure the additional drive moves the travel simulator back to the starting position during the pressure reduction, such that the actuating device is not mechanically connected to the piston. Example 37:

[0113] Brake system according to one of the preceding embodiments, characterized in that the control and regulating device pre-excites the valve for rapid closing, so that the valve closes immediately due to a small excitation amplification. Example 38:

[0114] Brake system according to one of the preceding embodiments, characterized in that the drive device has at least one piston rocker (60, 61) by means of which the piston can be adjusted. Example 39:

[0115] Brake system according to embodiment 38, characterized in that the piston rocker is a double-armed crank rocker (60, 60a). Example 40:

[0116] Brake system according to embodiment 38 or 39, characterized in that the transmission is an encapsulated transmission and is in particular mounted in the engine housing. Example 41:

[0117] Brake system according to one of the embodiments 1 to 37, characterized in that the piston is driven by means of a spindle drive arranged within the rotor of an electric motor. Example 42:

[0118] Brake system according to embodiment 41, characterized in that the rotor drives the piston via a nut mounted axially displaceably in the rotor, wherein the nut is held in axial position by a lever actuated in particular by means of an electromagnet or centrifugal force during rotation of the rotor, and in the event of failure of the electric drive, the spindle together with the nut is axially displaceable in the rotor. Example 43:

[0119] Brake system according to embodiment 41 or 42, characterized in that the spindle is secured against rotation by two bearing pins outside the piston, which at the same time accommodate the piston return springs. Example 44:

[0120] Brake system according to one of the embodiments 41 to 43, characterized in that a torsion spring resets the motor. Example 45:

[0121] Brake system according to one of the preceding embodiments, characterized in that the brake system regulates a gain proportional to the pedal force, wherein the brake system determines the pedal force on the piston. Example 46:

[0122] Brake system according to one of the preceding embodiments, characterized in that a damping element, in particular in the form of a leaf spring, is arranged between the actuating device and the respective piston, wherein the leaf spring is arranged in particular on the rocker (26), and that a force and / or displacement sensor for measuring pedal force is arranged on the rocker or the damping element. Example 47:

[0123] Brake system according to one of the preceding embodiments, characterized in that a channel connects the working chamber (1') to the reservoir, in which a safety valve (80) is arranged, which opens in the event of a jammed piston and connects the working chamber (1') to the reservoir (18) for pressure reduction in the working chamber. Example 48:

[0124] Brake system according to embodiment 47, characterized in that the safety valve is a mechanical-hydraulic or an electromagnetic valve.

Claims

[1] Braking system, comprising 1.1 an actuating device (30), namely a brake pedal, 1.2 a pedal travel sensor (38) for detecting the pedal travel of the brake pedal and 1.3 a control and regulating device (22); 2. wherein the control and regulating device (22) controls a drive device (5c, 6, 7, 7a) with an electric motor (8) taking into account the detected pedal travel; 2.1 wherein the electromotive drive device is a brushless motor controlled by output stages (21) via three strands by a microcontroller (22), 3. wherein the drive device (5c, 6, 7, 7a) adjusts a piston (1, 1a) of a piston-cylinder system via a non-hydraulic transmission device, so that a pressure is established in the working chamber (4', 4a', 4b') of the cylinder; 4. wherein the working chamber (4', 4a', 4b') is connected to a wheel brake via a pressure line (13); 5. In the event of failure of the drive device (5c, 6, 7, 7a), the actuating device adjusts the piston (1).

6. The braking system comprises a current sensor (23) for measuring a current of the electric motor; 7. the control and regulating device (22) is designed to carry out a current-proportional pressure control according to an amplifier characteristic curve, 8. using the current sensor (23) to move the piston to a position corresponding to a specific pressure; 9. wherein the piston-cylinder system is designed to generate a brake pressure build-up and brake pressure reduction in order to implement ABS control. [2] Brake system according to claim 1, characterized by that the control and regulating device (22) is designed to use the current and position measurement in addition to the motor control for indirect pressure measurement. [3] Brake system according to claim 1 or 2, characterized bythat the characteristic map is created using an output characteristic map, wherein the output characteristic map is formed from a pressure-volume characteristic curve of the wheel brake, an engine characteristic value, transmission efficiency and vehicle deceleration. [4] Brake system according to one of claims 1 to 3, characterized by the control and regulating device (22) regulates the pressure change rate via the speed of the piston (1) taking into account the pressure-volume characteristic curve of the wheel brake. [5] Brake system according to claim 1, characterized by that a sensor device determines the position of the actuating device (30). [6] Brake system according to claim 1, characterized by that a device for specifying or adjusting a force / displacement characteristic of the actuating device (30) is in operative connection with the latter. [7] Brake system according to one of claims 1 to 5, characterized bythat at least one valve (14, 16) controlled by the control and regulating device (22) is arranged in the pressure line (13) to the wheel brake (15, 17). [8] Brake system according to claim 7, characterized by that the valve (14, 16) closes after the required brake pressure in the brake cylinder (15, 17) has been reached and is open to set a new brake pressure. [9] Brake system according to one of claims 7 or 8, in particular according to claim 10, characterized by that the valve (14, 16) has such a large opening cross-section that it has a small throttling effect. [10] Brake system according to one of claims 1 to 9, characterized by that the piston (1) generates the required pressure change for the brake booster (BKV) and the anti-lock braking system (ABS). [11] Brake system according to one of claims 1 to 10, characterized bythat a spring (9) applies force to the piston (1) or the drive device, wherein the spring force acts in the direction that the working space is enlarged. [12] Brake system according to one of claims 1 to 11, characterized by that the electric motor (8) has a small time constant and / or a high acceleration capacity. [13] Brake system according to claim 12, characterized by that the electric motor (8) is supplied with an excitation current when the valve (14, 16) is closed, which current is sufficient to hold the piston (1) in position against the spring force. [14] Brake system according to one of the preceding claims, characterized bythat when generating the brake force boost, the actuating device is not or not in direct mechanical connection with the piston or the drive device, and only in the event of failure of the drive device or when the ABS is activated is the piston in mechanical connection with the actuating device. [15] Brake system according to one of the preceding claims, characterized by that the control system regulates a corresponding brake force boost depending on the movement and / or force applied to the brake pedal and / or the driving condition and / or braking effect of an electric machine. [16] Brake system according to one of the preceding claims 1 to 15, characterized by that a pressure sensor is provided to determine the brake pressure in the working chamber of the cylinder. [17] Brake system according to one of the preceding claims, characterized bythat the control and regulating device (22) has a memory in which a / the characteristic map with various parameters for controlling the drive is stored. [18] Brake system according to one of the preceding claims, characterized by that the control and regulating device (22) determines the piston position using an incremental encoder of the electric motor. [19] Brake system according to one of claims 1 to 18, characterized by that the piston is driven by a spindle drive.

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