[0001] The present invention relates to a brake system, having an actuating device, in particular a brake pedal, and a control and regulating device, the control and regulating device controlling an electromotive drive device on the basis of the movement and/or position of the actuating device, the drive device having a piston of a piston Cylinder system adjusted via a non-hydraulic transmission device, so that a pressure is established in the working chamber of the cylinder, the working chamber being connected to a wheel brake via a pressure line.
State of the art:
[0002] Modern braking systems consist of brake boosters, i. H. Conversion of the pedal force into a correspondingly increased braking torque on the wheel brakes and braking force control via open or closed control circuits. With a few exceptions, the hydraulic line is used as a means of transmission for generating the brake pressure from the pedal force.
[0003] A division into structural units between brake booster (BKV) or brake force control and brake force regulation in a hydraulic unit (HE) is widespread. This configuration is primarily used in systems such as the anti-lock braking system (ABS), anti-slip system (ASR), electronic stability program (ESP) or electro-hydraulic brakes (EHB).
[0004] The hydraulic unit (HE) consists of solenoid valves, multi-piston pumps for 2-circuit brake systems, an electric motor to drive the pump, a hydraulic accumulator and several pressure transmitters. The pressure is regulated in such a way that, to reduce the braking torque, pressure medium is released from the wheel brakes into a reservoir via solenoid valves and is pumped back by the pump into the master brake cylinder, which causes a pedal movement. Both pressure rise and fall are controlled via solenoid valves, some of which use pressure transducers for solenoid valve control. Except for the EHB, the brake booster takes place with the vacuum BKV, which partly contains switching means and sensors for the so-called brake assistant function and also for detecting the so-called control point. The internal combustion engine is used as the energy source for the vacuum in petrol engines, but as a direct injection engine, it only supplies a weak vacuum, especially at higher altitudes. A mechanically or electrically driven vacuum pump is used in diesel engines. The latest ESP systems are able to achieve an additional brake booster or, if the BKV fails, a brake booster with a longer time constant by switching the solenoid valves and pump. These systems and functions are described in detail in the brake manual Vieweg Verlag, 2003 edition.
[0005] In the mid-1980s, Teves used the so-called Mark II and Bosch used the ABS3, which as integrated units included all components for brake boosting and control with hydraulic BKV, see Bosch technical manual 1986, 20th edition. For cost reasons, these systems have not prevailed, except for use in special protection vehicles. The same applies to fully electric brake systems, so-called EMB, with electric motors on the wheel brakes, which were intensively developed in connection with the 42-V vehicle electrical system. In addition to the additional costs, a new redundant on-board network for the energy supply is required here in order 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 an electric motor drive. A redundant vehicle electrical system is also necessary for this despite the lower energy requirement. The constructive realization of the wedge brake, which requires additional rollers for hysteresis reasons, which require integration into the brake caliper, has not been solved at the moment. The wedge brake with its electromotive drives with sensors has to 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 to ESP. For example, the pressure-controlled control of the solenoid valves enables very fine metering of the brake pressure, which also enables variable brake force adjustment EBV. The pressure reduction rate is not yet optimal because it is highly non-linear. In addition, in the case of a µ jump or a small coefficient of friction, the pressure reduction rate is determined by the relatively low pump capacity, which leads to large control deviations and thus to a loss of braking distance.
[0008] A braking system is known from DE 3342552. In this brake system, the master brake cylinder is used to generate a pedal-dependent pressure, which 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 drive control of the motor vehicle 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, the working chamber of which is connected to the brake circuit and the piston of which can be adjusted axially by means of 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 brake 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 that the maximum piston speed when the spindle is retracted and thus the maximum pressure reduction speed 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 using a pressure sensor, with the pressure being the controlled variable for the brake pressure control.
[0010] DE 3723916 A1 shows a brake system with a hydraulic brake booster which, in addition to the pure brake booster, also implements the ABS function. In the pressure line, which connects the piston-cylinder system and the respective wheel brake, only one valve is arranged in each case, which is opened to change the pressure in the wheel brake and closed to hold the wheel brake pressure. The pressure is also the controlled variable with this brake pressure control.
[0011] DE 195 00544 A1 discloses an electronically controllable brake actuation system for anti-lock motor vehicle brake systems, in which a master brake cylinder can be actuated by means of a brake pedal. The actuation travel of the brake pedal is determined by means of a sensor, which represents an input variable for a control unit which controls a plurality of brake pressure transmitters to which the vehicle brakes are connected directly or via solenoid valves by means of hydraulic lines. The connection of the hydraulic lines to the master brake cylinder can be shut off by a valve device. In order to achieve an increase in functional reliability, especially in the event of an electrical defect or failure of the vehicle electronics, the piston of the master brake cylinder in the fallback level can be adjusted 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, which adjusts a piston in a cylinder, so that a pressure is set in the brake circuit, which is determined by a pressure sensor and is fed to the control unit as an input variable. The pressure is also the controlled variable with this brake pressure control. A brake system that works in a similar way is already known from DE 4239386 A1.
[0012]DE 4445975 A1 discloses a brake system for motor vehicles in which the brake pressure in a wheel brake is regulated by means of a piston of a piston-cylinder system driven by an electric motor, a pressure sensor for measuring the controlled variable also being provided in this brake system. A 2/2-way valve, by means of which the hydraulic line between the piston-cylinder system and the wheel brake can be shut off, is used to hold the brake pressure in 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 is transmitted to a control unit. Depending on the driving condition and the position of the brake pedal, the control unit controls an electric motor drive of a piston-cylinder system, which is used 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 no pressure can be built up in the wheel brakes by means of the brake pedal in the fallback level. The pressure in the wheel brakes is regulated by means of the inlet and outlet valves assigned to the respective wheel brakes.
[0014] DE 19936433 A1 and DE 10057557 A1 disclose brake systems in which a supporting force can be applied to the piston of the master brake cylinder, which can be adjusted by the brake pedal, by means of electromagnetic drives. In these brake systems, too, the pressure in the main brake cylinder is the controlled variable for the brake pressure control process.
[0015] DE 695 15 272 T2 discloses a brake system in which a piston position is set as a function of a pedal position. The piston position is adjusted by specifying a current, with errors in the piston position being detected by appropriate sensors.
[0016] Based on DE 195 00 544 A1, the task is to provide an improved brake system.
[0017] This object is advantageously achieved by a brake system having the features of claim 1. Further advantageous configurations of the brake system according to claim 1 result from the features of the dependent claims.
[0018] The brake system according to the invention is advantageously characterized in that it implements the brake booster and the servo device in a very small space per brake circuit using only one piston-cylinder unit. The piston-cylinder unit is used to build up and reduce brake pressure, to implement ABS and anti-slip control and in the event of a power failure or malfunction of the drive device. This advantageously results in a small, integrated and cost-effective structural unit for the brake booster (BKV) and control, which is associated with savings in installation space, assembly costs and additional hydraulic and vacuum connecting lines. In addition, due to the short overall length, the spring dome, for example, does not affect the main cylinder and the pedals in the event of a front crash.
[0019] Thanks to the advantageous provision of a sensor system and a travel simulator, a variable pedal characteristic such as the brake-by-wire function, i.e. brake pressure increase independently of pedal actuation, can be adjusted in a freely variable manner, also taking into account the braking effect of the generator with recuperable brakes.
[0020] Furthermore, in the corresponding embodiment, there is no disadvantageous dropping of the brake pedal if the drive fails, since the pedal acts directly on the piston of the system. This also advantageously results in lower pedal forces in the event of a power supply failure, since the pistons have a smaller effective area than conventional master brake cylinders. This is possible by separating the piston travel with intact and failed reinforcement. This is referred to as a gear ratio jump that reduces the pedal force by up to 40% for the same braking effect. The reduction in the overall expense, including the electrical connections, also advantageously results in a reduction in the failure rate.
[0021]The electric motor drive can also improve the ABS/ESP control through finely metered pressure control with variable pressure increase and, in particular, pressure decrease speeds. A pressure drop below 1 bar in the vacuum area is also required for function with the smallest coefficients of friction, e.g. B. wet ice, possible. Likewise, a rapid increase in pressure at the start of braking, e.g. 0 – 100 bar, can be achieved in less than 50 ms, which results in a considerable reduction in braking distance.
[0022] 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.
[0023] It is also possible to provide a separate piston-cylinder system with a respective associated drive for each brake circuit or each wheel brake. It is also possible to use a piston-cylinder system in which two pistons are arranged in a cylinder in an axially displaceable manner, the cylinders being hydraulically coupled and only one piston being driven mechanically by the drive device by an electric motor.
[0024] Various configurations of the brake system according to the invention are explained in more detail below with reference to drawings.
[0025] Show it:
figure 1: A first embodiment of a brake system with a brake circuit for two wheel brakes;
figure 2: a second embodiment of the brake system with two piston-cylinder systems for two brake circuits for two wheel brakes each;
figure 3: a path simulator for the braking system according to the invention;
figure 4: a piston-cylinder system with one cylinder and two pistons;
figure 5 and figure 5a: Connection between actuating device and piston-cylinder systems;
figure 6: a side view of the integrated assembly with housing;
figure 7: Braking system characteristics;
figure 8 and figure 8a: Piston drive via a rocker arm
figure 9: Piston drive via a spindle
figure 10: Piston actuation with superimposed pedal force
[0026] the figure 1 shows a section of the integrated unit that is responsible for generating pressure or boosting the brake force. Here, 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 even with negative pressure in the piston chamber 4′ seals. This rack 5a transfers the force to the front convex end of the piston 1 . This has a collar bolt at this point 1a , over which the rack 5a with return spring 9 brings the piston to the starting position. Here the rack rests on the cylinder housing 4a. This external spring has the advantage that the cylinder is short and has little dead space, which is advantageous for venting. Because of the transverse forces, the toothed rack has a bearing in the rollers 10 and 11 with slide 12 . the figure 1 clearly shows that the parallel arrangement of the toothed rack to the piston results in a short overall length. The assembly must build very short to be outside of the crash zone. The rack is connected by an in figure 5a shown H-profile very rigid. The arrangement of the rollers is chosen so that the rack is in the end position 5b (shown in dashed lines) with the greatest bending force due to the compressive force acting in an offset manner has a relatively small bending length. The rack is about tooth profile 5a’ and gear 6 over the gear wheel 7 from the engine pinion 8 driven. This motor with a small time constant is preferably a brushless motor as a bell-shaped rotor with an ironless winding or preferably a motor according to the PCT patent applications PCT/EP2005/002440 and PCT/EP2005/002441. This is from the power amplifiers 21 preferably via three strands from a microcontroller (MC) 22 controlled. A shunt measures for this 23 the current and a sensor signal 24and 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 motor control for indirect pressure measurement, since the motor torque is proportional to the pressure force. For this purpose, a map must be created in the vehicle when it is started up and during operation, in which the position of the piston is assigned to the different current intensities. During operation, a position of the piston is then approached according to the booster characteristic described later, which corresponds to a specific pressure according to the characteristic map. If position and motor torque do not match, e.g. B. by temperature influence, the map is adapted during operation. As a result, the map is continuously adapted. The output map is formed from the pressure-volume characteristic of the wheel brake, engine parameter, transmission efficiency and vehicle deceleration. With the latter, a vehicle deceleration proportional to the pedal force can be achieved so that the driver does not have to adjust to different braking effects.
[0027] The piston 1 generated in the line 13 a corresponding pressure, which is generated via the 2/2 solenoid valve (MV) 14 to the wheel brake 15 or via solenoid valve MV 16 to the wheel brake 17 reached. This arrangement as described above has several advantages. Instead of the two inexpensive small solenoid valves, another piston motor unit could be used as shown in figure 4 is shown. However, this means considerably more costs, weight and installation space.
[0028] It is sufficient to use one piston motor unit for each brake circuit.
[0029] The second advantage is the very low energy requirement and the fact that the motor is only designed for pulsed operation. This is achieved by closing the solenoid valves when the pressure or engine torque setpoint is reached and the engine is then only operated with a low current until a new setpoint is specified by the brake pedal. This means that the energy requirement or the average power is extremely small. For example, with a conventional design, when braking hard from 100 km/h the engine 3 draw a high current. According to the invention, the motor only needs about 0.05 s of electricity for the piston travel, which accounts for 1.7%. If the values are related to the power, then in the conventional case the vehicle electrical system would be loaded with >1000 W for at least 3 s and with the proposed impulse operation only approx. 50 W average power. An even greater energy saving results from emergency braking from 250 km/h with braking times of up to 10 s on a dry road. A storage capacitor can be used here to relieve the impulse load on the vehicle electrical system 27 used in the power supply, which can also be used for the other electric motors according to the line with the arrow.
[0030] In the pressure line 13 can be used before or after the solenoid valve pressure sensors, which are not shown because they correspond to the prior art.
[0031] The piston 1 is filled with liquid from the reservoir via the snifter hole 18 provided. There is a solenoid valve in this line 19 turned on. If the piston moves quickly to reduce the pressure, the seal could 3 sniff liquid from the reservoir, especially at low pressures, which is known to be disadvantageous. The low-pressure solenoid valve is used for this 19 switched on and the connection to the reservoir interrupted. This circuit can also create a vacuum in the wheel circuits 15 / 17 be achieved, what the wheel control at very low coefficients of friction z. B. benefits on wet ice, since no braking torque is generated in the wheel brake. On the other hand, sniffing can be used consciously when vapor bubbles form when the piston is already at the stop without the corresponding pressure being reached. The pistons are controlled accordingly with the solenoid valves so that the oscillating piston builds up pressure. If you omit this function, instead of the solenoid valve 19 a sniff-proof seal 3 be used.
[0032] The solenoid valves14 , 16 , 19 are via power amplifiers 28 from the microcontroller 22 controlled.
[0033] If the power supply or the electric motor fails, the piston is activated by a lever 26 the actuating device moves. There is built-in clearance between this and the piston, which prevents the lever from hitting the piston before the motor moves the piston when the pedal is pressed quickly.
[0034] The control function with regard to wheel speed and wheel pressure with ABS / ASR or yaw rate and wheel pressure with ESP has been presented in various publications, so that it is not described again. The essential functions of the new system are to be shown in a table:
| functions | electric motor | Wheel brake 15 | Solenoid valve 14 | Wheel brake 17 | Solenoid valve 15 |
| 1 | 1 | ||||
| On | Construction | 0 | Construction | 0 | |
| BKV | partially powered | P = constant | 1 | P = constant | 1 |
| partially powered | degradation | 0 | degradation | 0 | |
| On | Construction | 0 | Construction | 0 | |
| partially powered | P = constant | 1 | P = constant | 0 | |
| brake control | On | Construction | 0 | P = constant | 1 |
| partially powered | degradation | 0 | P = constant | 1 | |
| partially powered | degradation | 0 | degradation | 0 |
[0035] The level of the partial flow depends on the pressure increase or reduction speed desired by the BKV or the brake control. An extremely small time constant of the electric motor is decisive for this, i. H. a faster torque increase and torque reduction over small moving masses of the entire drive, since the piston speed determines the speed of pressure change. In addition, fast and precise position control of the pistons is necessary for brake control. In the case of rapid torque reduction, the compressive force originating from the brake caliper also has a supporting effect, but this is small at low pressures. But it is precisely here that the pressure drop rate should also be high, in order to avoid large control deviations from the wheel speed, e.g. B. to avoid ice.
[0036] This concept has a decisive advantage over conventional pressure control via solenoid valves, since the piston speed determines the rate of pressure change. For example, with a small differential pressure at the outlet valve that determines the pressure reduction, the flow and thus the pressure reduction speed is low. As already mentioned, the piston unit can be used separately for each wheel, with and without a solenoid valve. In order to take advantage of the low energy consumption, the electric motor would have to be expanded with a fast electromagnetic brake, which is more complex. The design shown with a piston unit and two solenoid valves is preferable in terms of installation space and costs. In terms of control technology, however, the restriction applies here that if there is a pressure reduction on one wheel, the other wheel cannot build up any pressure. However, since the pressure reduction time is approx. < 10% of the pressure build-up time in the control cycle, this limitation has no significant disadvantage. The control algorithms must be adjusted accordingly, e.g. after a phase of constant pressure from the opening of the solenoid valve, the electric motor must be energized with a current that is assigned the appropriate pressure in the wheel brake according to the BKV characteristic or is e.g. 20% higher than the previous blocking pressure in the control cycle. Alternatively, an adaptive pressure level that is 20% higher than the highest locking pressure of the axle or the vehicle can also be set during the control, for example. The locking pressure is the pressure at which the wheel runs unstably with greater slip.
[0037]The concept also offers new options for pressure reduction in terms of control technology. In terms of control technology, the pressure reduction and braking torque reduction are essentially proportional to the rotational acceleration of the wheel, the hysteresis of the seal and inversely proportional to the moment of inertia of the wheel. The amount of the required pressure reduction can be calculated from these values and the piston can already provide the corresponding volume when the MV is closed, taking into account the characteristic map described. When the MV then opens, the pressure drops very quickly, practically into a vacuum. This is based on the fact that, in contrast to today’s solutions, the MV has a smaller throttling effect due to the corresponding opening cross-sections. Here, the pressure can be reduced faster than with conventional solutions via a specially provided chamber volume according to the pressure volume characteristic. Alternatively, the pressure can be lowered into a chamber volume that is slightly larger than the necessary pressure reduction, e.g. by adjusting the piston accordingly. A very short switching time for closing the solenoid valve is necessary here for precise regulation of the pressure reduction, which can preferably be solved by pre-excitation and/or over-excitation. In addition, it is advantageous for special control cases to bring the magnet armature of the 2/2-way magnet valve into an intermediate position using known PWM methods in order to generate a throttling effect.
[0038] The very rapid reduction in pressure can possibly generate pressure oscillations that have an effect on the wheel. In order to avoid this harmful effect, the piston travel can be controlled as a further alternative, e.g. 80% of the required pressure reduction (rapid pressure reduction). The remaining 20% of the pressure reduction required can then take place slowly by means of a subsequently controlled, slow piston movement or, in the alternative, with the pressure reduction control via solenoid valves, by pulsing the solenoid valve and gradual reduction. This prevents harmful wheel vibrations. The slow reduction in pressure can be continued until the wheel accelerates again during ABS control.
[0039] This means that very small control deviations in wheel speed are possible. The method described above can also be applied to the pressure build-up. The speeds of the pressure increase can be optimized according to technical control criteria. In this way, the goal can be achieved that the wheel is braked in the immediate vicinity of the maximum friction force and thus optimal braking effect is achieved with optimal driving stability.
[0040] Special cases of regulation were mentioned above, in which a throttling effect is advantageous. This is the case, for example, if both wheels need to be depressurized at the same time. The throttling effect is advantageous here until the actuating piston has provided such a large chamber volume that the pressure can then be rapidly reduced into the vacuum from a different pressure level. 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 be built up in both wheel circuits at the same time. However, the individual alternating pressure build-up is to be preferred because of the metered pressure build-up with evaluation of the characteristic map and controlled adjustment speed of the piston. The same alternating method can be used as an alternative to the above with the throttling effect for the pressure reduction. As a further possibility, the piston can already be moved back with a control signal with a lower response threshold than the control signal for the pressure reduction. According to the state of the art, this is the signal at which the controller detects a tendency to lock and switches the MV to hold pressure (see brake manual, p. 52-53). This signal is issued 5-10 ms before the pressure reduction signal. The proposed fast drive is able to provide a chamber volume for a pressure reduction of 10 bar within approx. 5 ms.
[0041] Based on the piston position for the pressure reduction, the controller can decide whether there is enough chamber volume available for the simultaneous pressure reduction for both wheel brakes.
[0042]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 map represents a high potential for the controller, which enables additional braking distance reductions and driving stability.
[0043] the figure 2 shows the entire integrated unit for BKV and control functions. The unit consists of two piston units with associated electric motors and gears acc. figure 1 for two brake circuits and four wheel brakes. The piston units are in the housing 4 accommodated. This housing is on the bulkhead 29 fastened.
[0044] The brake pedal 30 transmits the pedal force and movement via the bearing pin 31 on a fork 32 , which is connected to the actuating device via a ball joint 33 works. This has a cylindrical extension 34 with a pole 35 .
[0045] cylinder 34 and rod 35 are in a box 37 stored. This one takes the travel simulator springs 36 and 36a on, whereby one spring acts weakly and the other spring acts strongly, progressively increasing the force. The path simulator can also be made up of even more springs or rubber elements. This specifies the pedal force characteristics. The pedal travel is determined by a sensor 38 detected, which is constructed in the example shown according to the eddy current principle, in which the rod 35 with a target.
[0046] The pedal movement is based on the elements 32 and 33 transferred, the piston 34 moves with the pole 35 in the socket 37 . There is a lever on the actuator 26 rotatably mounted, which hits the piston if the power supply fails. The pedal travel sensor delivers the travel signal to the electronic control unit, which, according to the BKV characteristic curve, as shown in figure 7, a movement of the pistons is effected via the electric motor. The parameters of this characteristic are in figure 7 described in more detail. Between the lever 26 and the two pistons 1 is a game s o provided as in figure 1 shown. The actuating device has over the bolt 39 , which is shown offset, an anti-rotation device and a return spring 40 , which supports the undrawn pedal return spring. According to the state of the art, many travel simulator solutions are known, some of which are actuated hydraulically via pistons and are shut off via solenoid valves when the power supply fails. This solution is complex and subject to hysteresis. Solutions are also known in which the travel simulator travel is lost if the energy supply fails when the pistons are actuated to generate brake pressure.
[0047] The aim of the invention is a simple solution in which the path simulator is switched off if the power supply fails. For this purpose, on the jack 37 with an intact energy supply via the anchor lever 41 with a large transmission ratio and the holding magnets 42 exerted a counterforce that is lost when the electrical power supply fails. Two-stage levers can also be used to reduce the magnet. In detail, this will be figure 3 described. In this case, the lever comes into contact with the two pistons via the brake pedal after running through the play and can thus transfer the pedal force to the pistons. The pistons are dimensioned in such a way that they generate a pressure at full pedal stroke that still results in a good braking effect, e.g. B. 80%. However, the piston stroke is considerably greater than the pedal stroke and can generate much higher braking pressures if the energy supply and electric drive are intact. However, the driver cannot apply the corresponding pedal force. With this design, one speaks of a translation jump, which is possible by decoupling the actuating unit with displacement simulator from the piston. With a conventional design, in which the BKV and master brake cylinder with pistons are connected in series, the required pedal force increases by up to a factor in the event of a power supply failure 5for the same wheel brake pressure. In the new design z. B. the factor can be reduced to 3. This case is z. B. relevant when towing a vehicle with a failed battery.
[0048] The lever 26 is rotatably mounted so that it can take into account tolerances in the movement of the pistons, e.g. B. due to different ventilation. This compensation can also be limited so that the lever hits a stop 33a the actuating device comes into contact.
[0049] However, other error cases must also be considered.
Failure of an electric motor.
[0050] In this case, amplification and control are fully effective in the neighboring, intact piston drive. About the lever 26 brake pressure is generated in the failed circuit after it hits the stop 33a applied. The amplifier characteristic of the second circuit can also be increased here, which reduces the required pedal force. However, this can also be done without a stop.
Failure of a brake circuit.
[0051] Here the piston moves to the stop in the housing 4 . The intact second circuit is fully effective. Unlike today’s conventional systems, there is no pedal that falls through, which is known to be very irritating to the driver. The irritation can also lead to a total loss of braking effect if he does not depress the pedal.
[0052] the figure 3 describes the function of the travel simulator lock. In borderline cases, the driver can apply high pedal forces, which prevents locking via the anchor lever 41 have to raise. To avoid the magnet 42 with excitation coil 43 has to apply these forces to the full, the upper convex end takes hold 41a of the lever asymmetrically on the socket 37 on. Will now pedal until it hits the rod 35 on the ground 37b deflected, this leverage causes the bushing to rotate slightly 37 , which creates friction in the guide, in addition to the nose 37a itself on the housing 4 can support. Thus, the magnetic force can be kept relatively small. The magnet is also used as a holding magnet 42 designed so that due to the small air gap, a small holding power is required. If the power supply fails, the anchor lever 41 is released from the socket 37 to the dotted line position 41′ deflected. If the actuating device 33 returns to the starting position brings the return spring 44 the anchor lever back to its original position.
[0053] the sensor 38 was at the end of the bushing bore in the housing 4 offset, which has advantages for contacting the electronic control unit, as shown in figure 6 is shown. The same applies to the brake light switch 46 . In this embodiment, the target 45 drawn for the eddy current sensor.
[0054] The path simulator is locked via the socket 37 can be changed to the in figure 7 described pedal reaction to avoid ABS. The lever can do this 41 with its storage and magnet 42 with recording 42a via an electric motor 60 be moved by a spindle 60a via a gearbox 60b drives. The lever is mounted on the extension of the spindle and the magnet housing is attached.
[0055] the figure 4 shows a basic representation of a solution with only one electric motor 7a . This description builds up figure 1 and figure 2 on. The drive pinion of the motor moves the rack 5c , which similar figure 1 can also be moved in parallel. This one is with a plunger 1a connected, what pressure in the brake circuit 13a builds up and at the same time the piston via the pressure 1a shifts that in the brake circuit 13 pressure builds up. This piston arrangement corresponds to a conventional brake master cylinder for which there are many variants of piston and seal designs. As in the previous figures, the 2/2-way solenoid valves are in the brake circuits 14 , 14a , 15′ , 15aarranged. The ABS pressure modulation takes place in the manner previously described. The BKV function takes place via a path simulation arranged in parallel 36 and displacement sensor 38 . Again, between pistons 1a and brake pedal play or idle stroke s 0 intended. 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 motors, since the electric motor has to generate twice the torque. The redundancy function of the 2nd motor as shown in figure 7, including a pedal failure event of brake circuit failure.
[0056] the figure 5 shows the view from the end wall of the integrated unit, its flange 4b by means of screws 47 is bolted to the bulkhead. The operating unit can be seen here 33 , lever 26 and a non-offset drawn bolt 39 as an anti-twist device. The outline of a 10″ vacuum BKV is drawn here for size comparison. Here, an important advantage in the overall height with the cover can be seen 48 of the reservoir. According to the distance A, the bulkhead could be lowered, which is what the designers want. On the left side of the flange is pointing to figure 5a, broken line drive of the rack 5 drawn. This detail is enlarged as figure 5a shown on the right half of the image. The pinion of the gear 6 engages in the H-shaped design of the rack on both sides 5 . The lateral forces described are from the role 10 or. 11 accordingly figure 1 with storage 10a supported. For cost reasons, the rack can be made of plastic. Since its surface pressure is not sufficient, hard sheet metal strips are used here 49 inserted, which adapt to the roles with a slightly crowned design of the support. Into the pinion 6 is the gear wheel 7 pressed in, which meshes with the motor pinion. Preferably the pinion is in the motor housing 8a stored.
[0057] the figure Figure 6 shows the side view of the integrated package with housing 4 , fork piece 32 for brake pedal 30 , actuation unit 33 , flange 45 , mounting screws 47 , Lid 48 . This view shows the short overall length with the electronic control unit on the front 50 is attached. This is according to the state of the art with the coils or part of the magnetic circuit of the solenoid valves 14 and 16 connected in order to save additional contacting and electrical connection lines. This feature can be enhanced by adding any electrical components such as electric motor 8 , magnetic coil 43 , displacement sensor 38 , brake light switch 46 , brake fluid level sensor 53 be contacted directly with the control unit without electrical connection lines. In this case, the control unit would have to be directed from above 50a to be built in. However, it is also towards 50b possible, which results in a different arrangement of the magnetic coil.
[0058] The solenoid valves are preferably mounted on a support plate 51 fastened, as these are pressed into aluminum with a high elongation at break for reasons of cost. The locking screws are placed in this carrier plate 52 screwed in for the brake lines. The contact is shown in the middle part of the control unit, which is in the area 54 a redundant power supply, in the area 55 the bus line, at 56 contains the sensors for ABS and ESP.
[0059] the figure 7 shows the essential characteristics of the braking system. Pedal force F is shown P , brake force pressure p and pedal travel at the actuation unit. A translation of 4 to 5 is usually selected from here to the pedal foot. The pedal travel is at its maximum S P and the pistons, as already mentioned, at a higher value s K . with 57is the so-called. Pressure-displacement characteristic shown, which here z. B. corresponds to a brake circuit. The non-linear progression results from various elasticities such as those of the brake caliper, seals, lines, residual air pockets and the compressibility of the fluid. This line shows the mean of a scatter band that is also temperature dependent, especially for the brake caliper. Therefore, a map must be created for the flow-proportional pressure control.
[0060] The characteristics 59 show the failure of the electric drive, in which after the game s 0 the pistons are actuated. To achieve e.g. 100 bar, the significantly higher pedal forces F PA of approx. 600 N is necessary, which corresponds to a more than 40% lower pedal force compared to today’s solutions.
[0061] 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 have any retroactive effect on the pedal, since the pedal S s encounters the detent. At lower locking pressures, when the pressure is reduced and built up, there is a reaction on the pedal when the pedal is fully depressed, and is therefore comparable to today’s ESP and ABS systems. However, it is possible to reduce or avoid the repercussion by using an in figure 4 electric motor described 60 , which adjusts the locking of the path simulator via a drive. About the piston drive 6 the pedal is moved back to decrease the pressure. At this time, the motor adjusts the drive with a small force. This also allows a pedal movement to warn the driver, e.g. B. in traffic jams or the like. Even without this additional motor, a reaction is possible if the pedal movement is greater than the play S o and the pistons are retracted briefly as a warning.
[0062] The thicker lines are the amplifier lines 58 and 58a , which the assignment of pedal force F P points to the brake pressure. At approx. 50% of the maximum pedal travel, the travel simulator is fully activated at Ss. This has the advantage that emergency braking is possible with a short pedal travel. The pedal travel is determined by the sensor 38 detected. The assignment of the pressure to the pedal force is freely variable and can e.g. B. in the dotted line, the vehicle deceleration can also be taken into account by including this as a correction value in the gain, so that when the brake fades, a higher pressure is applied with the same pedal force. This correction is also necessary for 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 at high pedal speed. Here, a much higher pressure can be fed in disproportionately to the pedal force, which again follows the static characteristic curve shown (solid line) with a time delay.
[0063] At F P1 a foot force of 200 N for a brake pressure of 100 bar is generally specified. This pressure corresponds to the blocking limit on a dry road. In this area, the displacement simulator characteristic is almost linear, so that good dosing is guaranteed. As a rule, a maximum pressure of 160 bar is sufficient, according to which the fatigue strength of the elements is dimensioned. However, a reserve R can be kept available for infrequent stresses, which can become effective, for example, if the blocking limit has not yet been reached at 160 bar.
[0064] In the event of a power failure, the electric drive can be regarded as more fail-safe than the vacuum BKV, since at least two electric motor drives are used for the proposed invention, i.e. one acts redundantly and is known to be the overall failure rate λ g = λ 1 · λ 2 is applicable. A failure of the energy supply while driving can almost be ruled out, since the generator and battery practically never fail at the same time. A break in the electrical power supply is covered by the in figure 7 described redundant power supply prevented. The vacuum BKV is not redundant with amplifier elements, supply lines and, if necessary, pump.
[0065] the figure8 shows another solution for the piston drive. A rocker arm can be used instead of the rack 60 are used, which have a tension strut 61 over the bearing pin 62 connected to the piston. The return spring 9 acts on the rocker arm whose initial position is determined by the stop 65 given is. The rocker arm is operated via a multi-stage gear 63 from the engine 11 driven.
[0066] the figure 8a shows a two-armed rocker arm 60 and 60a with two tie rods 61 and 61a . This means that only small 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 driven. The advantage of this solution lies in the encapsulation of the gearbox, which allows oil or grease filling, allows helical gearing and is therefore more resilient and quieter.
[0067] the figure 9 shows a further alternative with a spindle drive, which is arranged inside the rotor of the electric motor. This arrangement is known from DE 195 11 287 B4, which relates to electromechanically actuated disk brakes. In the presented solution is the mother 67 as a separate component in the bore of the rotor 66 and leans on the flange 66a of the rotor. The pressure forces of the piston act on this 1 . The spindle drive also acts as a reduction gear, with the spindle 65 transmits the force to the piston. All the drives shown so far have a reduction gear firmly coupled to the piston, which is moved by the brake pedal if the energy supply fails and which has to be accelerated by the motor if the pedal is pressed quickly. These mass inertia forces prevent rapid pedal actuation and irritate the driver. To avoid this, the nut can be moved axially in the bore of the rotor, so that the ball screw drive is switched off when the pedal is engaged. For normal operation with an electric motor, the nut is fixed by a 70 mm lever, which is effective when the piston returns quickly, especially when there is a vacuum in the piston chamber. This lever is over the shaft 71 stored in the rotor and is activated by the spring when the motor is not rotating 72 moved to a position where the nut is free. Since the drive motor accelerates extremely quickly, the centrifugal force acts on the lever and the nut is enclosed by the lever for the movement of the piston.
[0068] This movement can also be brought about by an electromagnet, shown in dashed lines, in which the lever represents a rotary armature. The twisting torque generated by the nut on the spindle is supported by two bearing pins 69 and 69a caught. These pins are also carriers of the return spring 9 . The rotor is preferably in a ball bearing 74 stored, which absorbs the axial forces of the piston and in a plain bearing 75 , which can also also be a roller bearing. This solution requires a greater overall length, which compared with figure 9 because the immersion length of the spindle in the nut is equal to the piston stroke. To keep this extension small is the motor housing 74 directly on the piston housing 4 flanged. This has the additional advantage of the different material selection for the motor and piston housing.
[0069] The mother 67 can also directly with the rotor 66 to be connected, e.g. B. by injection. A plastic nut with a low coefficient of friction can be used for the required forces.
[0070] If a motor or the power supply fails, the pedal (not shown) acts on the fork accordingly figure 2 and over the lever 26 after the free travel so on the spindle 65 or piston 1 . Since a blocking of the drive is to be switched off with this solution, the stop 33have a smaller distance to the lever. This has the advantage that the pedal force acts fully on the piston when z. B. an electric motor fails. As soon as the lever is supported on the opposite end when twisted, only half the pedal force acts on the piston. In terms of design, the spindle and piston are decoupled, which was not carried out separately.
[0071] Returning the piston to its initial position is important. If the engine fails in an intermediate position, the piston return spring can be additionally supported by a spiral spring 66a , which at the end of the rotor 66 and the motor housing 74 is arranged and coupled to this. This should compensate for the detent and friction torque of the motor. This is particularly advantageous for small restoring forces of the pistons, which act on the pedal in the event of a power failure in connection with the in figure 9 described clutch lever.
[0072] the figure 10 shows a further simplified embodiment with an electromotive piston drive, in which again the piston 1 which performs brake boosting and pressure modulation for ABS. The Piston Chambers 1′ are according to the figure 1 to figure 9 via lines 13 and 13a connected to the wheel brakes (not shown) and to the solenoid valves, also not shown. The structure corresponds figure 8 with spindle drive 65 and with rotor 66 , committed mother 67 , Separation of motor and piston, housing 74 or. 4 , piston return springs 9 and bearing pin 69 , spiral spring 66a to reset the engine. The pedal force will be similar figure 2 from a fork piece 26 on an actuating device 34 with rod 35 transfer. This is in the motor housing 74 stored and carries a target in the extension 45 e.g. for an eddy current sensor 38 which measures the pedal travel. The actuation device is via a spring 79 deferred. At the operating device 35 is again a lever 26 stored, which preferably leaf springs at the end in the connection to the piston 76 carries, which in a strong leaf spring with a travel sensor 77 or with a softer spring with a force transmitter 77a are connected. In both cases, the force transmitted by the lever or pedal should be measured here. The leaf spring 76 has the task of avoiding a hard reaction when the pedal is actuated before the engine starts. The function takes place in such a way that in a specific function of this pedal force, the motors exert an amplifying force on the piston, with this force in turn being able to be determined from current and piston travel or a pressure transmitter. Here, the pedal travel via the travel sensor 38 be processed in this amplifier function or characteristic. This sensor can also be used at the beginning of braking at low pressures in connection with the return spring 76 assume the role of amplifier. Here the pen takes over 79 the function of the displacement simulator spring.
[0073] The motor housing has a flange for attaching the unit via the screw bolts 78 in the front wall. This simplified concept does not have the hassle of the travel simulator and detent. Disadvantages are the limited pedal travel characteristics of the booster characteristic, the pedal falling through if the brake circuit fails and higher pedal forces if the booster fails, since the pedal travel and piston travel are identical. This version is mainly suitable for small vehicles.
[0074] In the embodiment gem. figure 10 are representative of all safety valve solutions 80 drawn in, which become effective if, for example, a piston drive jams when the pedal returns to the starting position. During pedal movement, a conical extension of the actuating device 35 the two safety valves 80 operated, which the connection from the brake circuit 13 or. 13aclose to return. This ensures that no brake pressure is built up in the brake circuit when the pedal is in the initial position. These valves can also be actuated electromagnetically.
[0075] Safety-relevant systems usually have a separate switch-off option for errors in the output stages, e.g. full current flow due to breakdown. In this case, a switch-off option is installed, e.g. using a conventional relay. The diagnostic part of the electrical circuit recognizes this error and switches off the relay, which normally supplies the output stages with power. The concepts proposed here must also include a switch-off option, which is implemented using a relay or a central MOSFET.
[0076] In view of the impulse control of the electric motors, a safety fuse can also be used, since the pulse-off ratio is very large.
