Braking system without path simulator

Abstract

A braking system comprising an electromechanical brake booster, in which the master brake cylinder or tandem master brake cylinder (5) with a piston (24) is driven by an electric motor (11, 12) via a spindle drive with a spindle (13), wherein the working chamber(s) of the brake booster are connected to the wheel cylinders of wheel brakes (9a-9d) via hydraulic lines (6, 7) and a controllable valve (8a-8d) is assigned to each wheel brake (9a-9d), and in that pressure build-up and pressure reduction in the wheel brakes (9a-9d) is carried out simultaneously or sequentially by means of a control device by means of the brake booster and the controlled valves (8a-8d), characterized in that a brake actuation device (16, 16a, 14) acts in a force-assisting manner on a piston (24) of the brake booster in normal braking operation, wherein in ABS operation the spindle (13) or the piston (24) Brake actuation device (16, 16a,14) is acted upon and / or adjusted and the piston (24) of the brake booster is moved back and forth via the electric motor (11, 12) to regulate the wheel brake pressures, , wherein the brake actuation device (16, 16a, 14) acts on the piston (24) of the brake booster via at least one spring element (20), wherein the brake system has sensors (4, 22) for determining a position of the piston (24) and a position of the brake actuation device (16, 16a, 14), wherein the sensors (4, 22) are arranged to detect a possible travel difference between the piston (24) and the brake actuation device (16, 16a, 14) due to the spring element (20, 20b); wherein in normal braking operation the control unit of the brake system actuates the drive of the brake booster depending on the travel difference, wherein in ABS operation the current proportional to the pressure is measured by means of a shunt (26) and the pressure control for the wheel brakes (9a-9d) is based on the current without the use of a pressure sensor.

Description

[0001] The 10th Civil Senate of the Federal Court of Justice, in its oral hearing of August 21, 2025, recognized as rightful: Upon the defendant's appeal, the judgment of the 6th Senate (Nullity Senate) of June 21, 2023 is amended, and the further appeal is dismissed. German patent 11 2009 005 541 is declared invalid insofar as it goes beyond the following version. Description

[0002] The invention relates to methods for controlling an electromechanical brake force amplification with the features of the preamble of claim 1. State of the art

[0003] The effectiveness of the active safety functions of ABS and especially ESP is so high that it will soon be legally mandated in the USA and the EU. Significant efforts are being made to reduce the complexity of these systems. Various solutions are currently available that can reduce complexity.

[0004] One initial solution involves integrating pressure control and brake force amplification, as described in DE 10 2005 018 649 A1. This system is based on a displacement simulator with additional functions and actuators to handle faults in the event of drive failure. This requires a corresponding level of effort.

[0005] A second solution involves reducing the number of valves through multiplex operation. DE 34 40 972 A1 describes a hydraulic brake booster (BKV) in which pressure regulation is achieved using the THZ with corresponding valves in multiplex operation. This system does not meet the high dynamic requirements, resulting in excessively long switching times. Furthermore, the noise generated during valve switching is too high. The same dynamic limitations apply to a pneumatic system as previously disclosed in DE 38 43 159 A1 or DE 39 08 062 A1.

[0006] German patent DE 10 2005 018 649 A1 describes a high-dynamic, electromechanical multiplex system as a so-called twin and tandem solution with a travel simulator. To prevent pedal feedback during ABS operation, a free stroke is provided between the pedal and the drive unit. A disadvantage of this design is that an additional pedal travel is required if the drive fails.

[0007] From FR 2860474 A1, an electromechanical brake booster is also known, in which an electric motor regulates a brake booster force via a spindle. The brake pedal acts on the piston of the brake booster via a pedal plunger. Based on the force applied to the piston by the brake pedal, the force booster is regulated by the electric motor via the spindle drive. However, measuring the force to determine the necessary brake booster force has proven impractical.

[0008] Various brake boosters are known from DE 10 2006 050 277 A1, DE 195 00 544 A1, DE 422 90 42 A1, US 5 758 930 A, EP 0 284 718 A2 and DE 4 327 206 A1.

[0009] German patent DE 10 2004 050 103 A1 describes a brake booster in which a pedal mechanically acts on the pistons of a tandem master brake cylinder via a linkage and a spring element. At least the master cylinder is adjusted by a motor via a drive mechanism. The motor enables force to be applied exclusively to the piston.

[0010] Based on DE 10 2004 050 103 A1, the object of the present invention is to provide an improved braking system.

[0011] This problem is advantageously solved with a braking system according to claim 1.

[0012] Further advantageous features are evident from the dependent claims.

[0013] In ABS control, the piston of the brake booster is moved back and forth by an electric motor to regulate the wheel brake pressures. Due to the mechanical connection between the piston or spindle on the one hand and the brake actuation device, particularly the brake pedal, on the other, the driver feels the piston movement through the feedback in the form of vibrations and shocks. To dampen these shocks and vibrations, the invention, in a further advantageous embodiment, proposes a spring element arranged between the actuation device on the one hand and the piston system or spindle on the other. Forces can also be transmitted from the brake actuation device to the spindle by means of this spring element.

[0014] The spring element advantageously exhibits a linear or degressive spring characteristic for the upper force range.

[0015] The feedback effect on the brake actuation mechanism can be advantageously reduced by appropriate control of the electromechanical pressure modulation. It is beneficial if only smaller pressure amplitudes are regulated or controlled as a result of more precise pressure control. By providing smooth pressure transitions, an unpleasant sensation and the harshness of the feedback can be reduced. By using a strongly linear or degressive spring between the drive and the brake pedal transmission mechanism, the feedback effect on the brake pedal during rapid piston movement is more elastic.

[0016] Furthermore, it is possible to selectively block the movement of the brake actuation device completely or partially by means of a locking device. The locking device can be designed such that blocking can occur in any position or within a specific range of motion of the brake actuation device. By blocking the transmission device by electrohydraulic or electromechanical means, this feedback can be eliminated, significantly reduced, or precisely controlled during normal operation with small to medium pressure amplitudes, which is particularly advantageous.

[0017] In a high-dynamic electric motor drive, it is particularly important in the lower pressure range to couple the pushrod piston to the drive. This can be achieved either with a spring or, alternatively, with a rigid coupling, e.g., using a plunger.

[0018] To prevent pressure generation from being impossible in the event of a failure of the electric motor drive or a blockage of the spindle drive, appropriate fallback mechanisms must be provided. In the braking system according to the invention, the pedal continues to act directly on the piston in the event of a drive failure.

[0019] In an advantageous further development, the braking system according to the invention can include a clutch by which the piston, particularly for piston return, can be separated from the spindle. In this embodiment, when the electric motor is not active, the brake actuation device does not act on the spindle but on the pushrod piston or a piston tappet. By opening the clutch, the spindle return springs no longer act on the piston, so that, advantageously, only smaller actuation forces need to be applied by the driver to brake. The piston is advantageously coupled to the spindle by means of a locking bolt that engages through the cylindrical wall of the spindle. The drive for the clutch can be attached either to the housing of the brake booster or to the spindle.If the drive is located on the housing, the locking bolt must be mounted to be axially displaceable from the drive so that it can move with the spindle. Advantageously, a force transmission element, particularly in the form of a flexible plunger, is arranged in the spindle, connecting the piston to the brake actuation device. A driver mounted on the spindle ensures that the force transmission element is moved along with the spindle by its movement to build up pressure. The force transmission element is designed to interact with the driver and advantageously features a collar-shaped thickening for this purpose. This collar-shaped thickening also interacts with the locking bolt and, when the clutch is closed, forms a positive connection between the spindle and the force transmission element. This allows the brake to be engaged against the pedal force.Spring force moves the pistons to reduce pressure, and the piston is coupled to the drive, which enables high pressure reduction gradients across the entire pressure range.

[0020] The coupling between piston and spindle can be achieved either by positive locking or by frictional locking.

[0021] The electromechanical brake booster according to DE 10 2004 050 103 A1 requires a force sensor to control the electromechanical brake force amplification. This sensor is complex due to drift compensation and the lines that move across the full pedal travel. When using the described, particularly strong, spring between the drive and the brake actuation device, the stroke of the brake actuation device, or the pedal travel, is greater than the piston travel, which is detected by the motor with its rotary encoder. This travel difference can be used for brake force control or amplification, resulting in a significantly simpler control system. Advantageously, sensor tolerances, e.g., different offset voltages, are normalized by incorporating a small free stroke between the actuation device and the drive, and this position serves as a baseline when, for example, the voltage of the pedal travel encoder changes.Another possibility is that, during commissioning or servicing of the system, the brake pedal is depressed until it moves the spindle and thus the rotor. The movement is measured using the rotary angle sensor. At this position, the sensor voltages or corresponding digital values ​​are then compared.

[0022] For pressure control, a pressure sensor is integrated into the pushrod circuit, which, together with the piston stroke, determines the pressure-volume characteristic curve. This characteristic curve forms the basis for precise pressure control. To further simplify the system, particularly for ABS applications, the motor current can also be measured via a shunt, which is proportional to the motor torque and thus the pressure. This measurement, or the pressure itself, can also be used for plausibility monitoring of the sensor signals, eliminating the need for redundant sensors.

[0023] The following section provides an exemplary explanation of various possible embodiments of the braking system according to the invention, illustrated with drawings.

[0024] They show: Fig. 1: Two possible embodiments of a braking system according to the invention; Fig. 2: third possible embodiment of a braking system according to the invention; Fig. 3: fourth possible embodiment of a braking system according to the invention; Fig. 3a: Cross-sectional view through section xx in Fig. 3; Fig. 4: fifth possible embodiment of a brake system according to the invention with a clutch for decoupling the HZ piston and the brake actuation device for the unamplified brake pressure build-up in the event of a malfunction; Fig. 4a: Detailed representation of the coupling acc. Fig. 4; Fig. 5: Brake pressure P, sensor voltage U, piston travel s K and pedal stroke S Pwith suspension; Fig. 5a: Pedal force and piston force versus pedal stroke s; Fig. 5b: Brake pressure P, sensor voltage U, piston travel s K and pedal stroke S P with suspension in case of a brake circuit failure;

[0025] The Fig. Figure 1 shows the basic structure of the brake system according to the invention, consisting of HZ or THZ 5, EC motor with stator 11 and rotor 12, spindle 13 for driving the pushrod piston 24 via the plunger 21 and a rotary angle encoder 4 for determining the position of the pushrod piston 24 and detecting the rotor position or the piston travel.

[0026] When piston 24 receives the command to build up a specific pressure, the corresponding piston movement is carried out via the rotary encoder 4, resulting in the corresponding pressure in the brake circuits. This movement is based on the pressure-volume characteristic curve previously recorded via piston travel and pressure measurement and stored in a characteristic map. In simplified systems, such as ABS, a shunt 26, which is necessary for engine control anyway, can also be used to measure the current of the control circuit 25. Following a brief period of constant pressure, which usually occurs during braking, a correlation comparison is performed based on the new measurement data with the stored characteristic map data. If a deviation is found, the pressure-volume characteristic curve for each wheel brake is recorded again individually when the vehicle is stationary, and the characteristic map is corrected. If the deviation is significant, for example, at a wheel cylinder, a message is displayed indicating that the vehicle should be taken to a workshop.

[0027] The pressure generated in the HZ or THZ is transmitted via lines 6 and 7 from the pushrod piston and floating piston, through the 2 / 2 solenoid valves 8a to 8d, to the wheel cylinders 9a to 9d. The dimensioning of the flow resistances for the multiplexing process in the lines and valves is of great importance. Furthermore, the coordination of the switching and changeover times is crucial. This is described in detail in other applications of the applicant and is not the subject of this invention.

[0028] When the brake pedal 16 is pressed, it acts via the pedal plunger 16a on the actuating device 14, which in turn acts on the spindle 13. A free stroke Δs is shown in the lower half of the diagram. When the brake pedal 16 is not pressed, the spring 17 lifts the transmission device 14 away from the spindle 13 by the free stroke Δs. This free stroke Δs must be overcome during each braking action until the collar of the transmission device 14 contacts the spindle 13. In this design, the drive (spindle) acts directly on the brake pedal 16 via the transmission device 14, which can be disruptive during pressure reduction in ABS and the corresponding rapid piston movement caused by the impact. Brake force amplification is achieved here via a force sensor (not shown) as described in DE 10 2004 050 103 A1. The return spring 17 between spindle 13 and transmission device 14 presses the latter against a stop in the housing 15.

[0029] A significant reduction in shock is achieved by a solution as shown in the upper half of the image. Here, a strong compression spring 20 acts on the spindle 13 via a disc 18. For assembly reasons, this disc 18 is fixed by a retaining ring 19. The spring 20 is linear or degressive, designed for a pedal force or rod force in the case of brake booster operation, for a maximum pressure of, for example, 200 bar, and has a spring stroke of 4–6 mm. The spring 20 is designed proportionally to the rod force and transmits this force to the spindle 13, on which the adjusting force of the motor 11, 12 also acts, depending on the selected brake booster amplification. Both forces together constitute the force acting on the piston. If a rapid piston return occurs during pressure reduction for ABS control, this is dampened by the spring 20 and affects the pedal. A 10 bar pressure reduction during the control cycle corresponds to approximately 0.5 mm 10% of the suspension travel in a mid-range vehicle.

[0030] Thus, the pedal stroke is greater than the piston travel, corresponding to this stroke. The spring 20 can also be slightly pre-tensioned for a specific pedal characteristic. Different strokes can be used for brake force amplification, with the pressure being proportional to the differential travel. This travel is derived from the signals of the pedal stroke sensor 22 and the piston travel. The piston travel can be determined via the rotary angle sensor 4. Brake pressure control is achieved via the piston travel based on the pressure-volume characteristic curve. The brake actuation device 16, 16a, 14 is in constant contact with the drive via the spring 20 during braking. Depending on the desired amplification, the motor transmits the corresponding force to the piston 24 via the spindle 13, so that the pedal force and the amplification force result in the piston force proportional to the pressure. The spindle force is transmitted to the pushrod piston 24 via a movable plunger 21.The plunger 21 is coupled to both the pushrod piston 24 and the spindle 13 to enable high pressure gradients even at low pressures. The plunger's function is to prevent any potential offset of the spindle 13 and any runout of the ball screw drive from being transmitted to the pushrod piston 24. The spindle torque support 27 runs in a groove in the housing, preferably with good sliding properties, corresponding to the piston stroke. The torque support also serves as a stop, since the THZ return springs act on the spindle 13 and, in addition to piston return, also serve to return the motor to its resting position.

[0031] The piston or drive return is effected by the motor. To reduce additional stress on the ball screw drive in the event of an incorrect return or a hard stop, a disc spring 23 is provided between the torque support 27 and the ball screw drive 28. The actuating device is typically protected against the ingress of dirt by an elastic bellows 29.

[0032] The Fig. Figure 2 shows a third and fourth possible embodiment of the brake system according to the invention. A rigid coupling exists between the piston 24 and the spindle 13, in that the plunger 21 is designed as a ball joint on both sides. A corresponding insert 30 is screwed into the right side of the spindle.

[0033] On the side of the brake actuation device 16, 16a, 14, the spring 20 is mounted in a corresponding component of the pedal transmission device 14, whose guide web 14a actuates the pedal position sensor 22. The spring 20 acts on a collar 31a of a bearing part 31 with an internal return spring 17. This bearing part is additionally guided in a bore.

[0034] The transmission device 14 is additionally designed as a piston, which is mounted and sealed in the housing 15. The piston chamber is connected to the reservoir via solenoid valves 33 and 33a. The valve serves to block the pedal travel by means of the transmission device 14. If the piston retracts to relieve pressure, this action acts on the spring 20 and not on the pedal 16, since with solenoid valves 33 and 33a closed, movement can only occur within the fluid compression. The return flow from the piston chamber is closed for this purpose via solenoid valve 33. If the piston travel is greater than the spring travel, e.g., due to a change in the coefficient of friction, solenoid valves 33 and 33a are opened by evaluating the difference between the piston travel and the pedal travel. In the lower half of the image, the pedal's forward movement is blocked for the same purpose by preventing the pedal travel from increasing further.

[0035] The Fig. Figure 3 shows a fourth possible embodiment of the braking system according to the invention. Fig. Figure 3a shows a cross-sectional view corresponding to section xx according to. Fig. 3. In this embodiment, an electromechanical pedal lock is implemented. The transmission device 14 is connected via webs 14a in the housing 15a (see figure). Fig. 3a) mounted. A magnetic yoke 34 with return 36 is vertically floating in the housing 15a. The magnetic flux, generated by coil 35, flows through yoke 34, return 36, and webs 14a, generating a frictional force to lock the pedal in both directions. Magnetically conductive lamellae can be used to increase the frictional force using known techniques. The pedal locking force can be varied by varying the current. It is also possible to generate a small amount of pedal feedback by activating the electromagnetic pedal lock only after a certain piston travel. This locking is deactivated when the piston returns to its initial position before the pressure reduction. The upper half of the image shows how a progressive spring characteristic can be created using several springs (20, 20b) and a spring washer 20a.

[0036] The Fig. Figure 4 shows a further embodiment of the braking system according to the Fig. 2 and Fig. 3 without pedal locking, with the aim of being able to generate pressure even when the drive is blocked. This is made possible by the transmission device 14 transferring the pedal force to the plunger 21, and, when the brake force amplification is active, the spindle forces also act on the HZ piston 24 via the drive element 41. If the brake force amplification fails, only the pedal force is effective.

[0037] If a piston retraction occurs for pressure reduction in the ABS system, the solenoid 39 becomes active and moves the clutch element 40 in front of the plunger collar 21a. This transmits the spindle force to the plunger 21, which acts against the transmission device 14, thus enabling pressure reduction in the corresponding brake circuit. In this configuration, the solenoid 39 is movably mounted to the spindle 13 and requires a flexible connection 39a.

[0038] It is advisable that the clutch only engages if the engine is functioning properly beforehand to build up pressure. This prevents an ABS signal from being generated during pressure buildup if the drive is blocked, and subsequently the clutch being engaged despite the blocked drive, which would then lead to a blockage of the actuating mechanism.

[0039] Due to tolerances, the spindle 13 and the transmission device 14 have a radial misalignment and spindle runout. To prevent any load on the spindle 13 when the force of the transmission device 14 acts on the plunger 21, the plunger 31b connected to the transmission device 14 should either be designed to be flexible, as shown in the upper half of the image, or be connected to the transmission device 14 by means of a pivot 31c, in particular by means of a ball joint (lower half of the image).

[0040] The Fig. Figure 4a shows an alternative embodiment in which the solenoid with coil 44 is attached to the housing 15. The armature 45 is mounted with the coupling element 40 in a sliding bearing 47 and is held in its initial position by a return spring 46. The armature 45 with bearing pin 45a is connected to a guide rail 43 in which the coupling element 40 with its collar slides axially with the piston movement. When the solenoid 44 is activated, the guide rail 43 pushes the coupling element 40 against a sleeve 42, which is in contact with the plunger 21. This has the advantage that the hemispherical shape is subjected to less stress, as the sleeve 42 reduces the tension. The sleeve 42 must be axially fixed by a retaining ring or spring 48, as it moves in the spindle bore in the event of a brake booster failure, corresponding to the pedal stroke. The sleeve 42 and the coupling element 40 can be conical in shape.This means that even in the extremely rare event of a drive failure during ABS control, the unlocking forces are smaller when magnet 44 is switched off.

[0041] The Fig. 5 shows the brake pressure p, sensor voltage U, piston travel s K and pedal stroke S P with suspension. Depending on the counterforce-dependent deflection, a differential path Δh is created, which at small pedal stroke results in a pressure p1 and at maximum deflection with Δh max This results in a pressure p2. This function can be designed to be linear or degressive with a suitable spring.

[0042] Electromotive brake boosters, in accordance with the aforementioned state of the art, have redundant sensors for the rotation angle of the motor or piston stroke. Kand pedal stroke s, since the sensors are particularly safety-critical in displacement simulator systems because, among other things, pedal stroke and piston stroke are unequal. In the system according to the invention, the effort required for the otherwise usual redundancy can be reduced or even eliminated by means of a plausibility comparison. For example, if the sensor for determining the pedal stroke s fails, no differential stroke Δh occurs, and therefore no brake booster action is activated. However, the pedal acts on the piston as if the brake booster had failed. From the piston stroke s K The -value is detected through a plausibility comparison of the errors. A similar principle applies to s. K If the Δh calculation fails, a comparison of the pedal stroke can help. P with the measured pressure or current.

[0043] Due to differing output voltages, the sensor voltages must be normalized or calibrated to a reference point. It is proposed to calibrate the voltages in their initial state, taking into account a correction value, which could be, for example, the free play Δs. This value is device-specific and can be determined during vehicle commissioning in production or service.

[0044] The Fig. 5a shows the pedal force F p and piston force F K above the pedal stroke s. At s1 the pedal force F p1 and the piston force F K1 The BKV gain K is given at s1 as follows: FkFP1=K. At s max F results Pmax and F Kmax . With a linear spring, the gain K can be linear if Δh is proportional to the pressure or the piston force.

[0045] The Fig. 5b shows a brake circuit failure. Here, up to S ANo brake pressure, as the noticed brake circuit causes pedal dizziness up to S A which results in the piston counterforce acting upon it. This again creates a Δh relative to the BKV function, as in Fig. 5 described. Here, for example, the amplification can be increased, since at the same pressure, the overall braking force is lower due to the failure of the brakes.

[0046] In hybrid vehicles, variable amplification, especially lower amplification, can also be used to compensate for the additional braking effect of the generator during recuperation.

[0047] The following are further embodiments of the invention: Example 1:

[0048] Braking system comprising an electromechanical brake booster, in which the master brake cylinder or tandem master brake cylinder 5 is driven by an electric motor 11, 12 via a spindle drive 13 and is connected to it for pressure reduction in ABS operation, wherein the working chamber(s) of the brake booster are connected to the wheel cylinders of wheel brakes 9a-9d via hydraulic lines 6, 7 and a controllable valve 8a, 8b, 8c, 8d is assigned to each wheel brake 9a-9d, and in which pressure build-up and pressure reduction in the wheel brakes 9a-9d is carried out simultaneously and / or sequentially by means of a control device by means of the brake booster and the controlled valves 8a-8d, wherein a brake actuation device 16, 16a, 14 acts force-assisted on the spindle 13 and / or the piston 24 of the brake booster in normal braking operation. Example 2:

[0049] Brake system according to embodiment 1, wherein in ABS operation the spindle 13 or the piston 24 applies force to and / or adjusts the brake actuation device 16, 16a, 14. Example 3:

[0050] Brake system according to embodiment 1 or 2, wherein the actuating device 16, 16a, 14 acts on the spindle 13 and / or the piston 24 of the brake booster via at least one spring element 20, 20b, in particular a compression spring. Example 4:

[0051] Braking system according to one of embodiments 1 to 3, wherein the spring element 20 is supported at one end on a transmission device 14 or the pedal plunger 16a and at the other end on the spindle 13, the piston 24 or the piston rod 21. Example 5:

[0052] Braking system according to embodiment 3 or 4, wherein the at least one spring element 20 has a linear or degressive force-displacement characteristic for the upper force range. Example 6:

[0053] Braking system according to one of embodiments 3 to 5, wherein the spring travel length for maximum braking pressure is at least 1 mm, preferably at least 4 mm. Example 7:

[0054] Braking system according to one of the preceding embodiments, wherein the brake actuation device has a brake pedal 16 which is connected to a pedal plunger 16a, wherein the pedal plunger 16a is connected to a transmission device 14 and the transmission device 14 acts on the spindle 13 and / or the piston 24 of the brake booster. Example 8:

[0055] Braking system according to embodiment 7, wherein the at least one spring element 20 is arranged in or on the transmission device 14. Example 9:

[0056] Braking system according to one of the preceding embodiments, wherein an additional return spring element 17 lifts the transmission device 14 or the pedal plunger 16a from the piston 24 or the spindle 13. Example 10:

[0057] Braking system according to one of the preceding embodiments, wherein the piston 24 and the spindle 13 are permanently or selectively connected, in particular by means of a switchable clutch 40-46, or can be selectively connected or uncoupled together. Example 11:

[0058] Brake system according to embodiment 10, wherein the piston 24 and the spindle 13 can be connected to each other either by means of positive or force locking. Example 12:

[0059] Brake system according to embodiment 10, wherein the piston 24 and the spindle 13 are connected or connectable to each other by means of a force transmission means, in particular in the form of a plunger 21, which may be designed as a bending rod. Example 13:

[0060] Braking system according to one of the embodiments 10 to 12, wherein the power transmission means 21 is in contact with the brake actuation device 16, 16a, 14 through the hollow spindle 13, wherein a drive element 41 is arranged on the spindle 13 by means of which the power transmission means 21 can be adjusted to build up pressure with the spindle 13, and in the direction of pressure reduction a positive locking or frictional locking between the power transmission means 21 and the spindle 13 can be established by means of the coupling 40-46. Example 14:

[0061] Braking system according to embodiment 13, wherein, when the clutch 40-46 is engaged, the positive locking for adjusting the power transmission means 21 for pressure reduction or for retracting the piston 24 is effected by a clutch element 40, which in particular serves as a stop for the power transmission plunger 21, wherein the clutch element 40 extends through the cylindrical wall of the spindle 13. Example 15:

[0062] Braking system according to one of the embodiments 10 to 14, wherein the coupling 40-46 has a housing-fixed drive 44, 46, 47 which adjusts the coupling element 40, wherein the coupling element 40 is mounted displaceably relative to the drive 44 parallel to the spindle axis. Example 16:

[0063] Braking system according to one of the embodiments 10 to 15, wherein the coupling 40-46 has a drive 44, 46, 47 for adjusting the coupling element 40, wherein the drive is attached to the spindle 13. Example 17:

[0064] Braking system according to one of embodiments 10 to 16, wherein the coupling element 40 extends through the cylindrical wall of the spindle 13. Example 18:

[0065] Braking system according to one of the embodiments 10 to 17, wherein the clutch element 40 is subjected to force by a spring element 46 in the direction of the disengaged position. Example 19:

[0066] Braking system according to one of the embodiments 10 to 18, wherein the control device closes the clutch 40-46 only if the motor function of the drive 11, 12 has previously been found to be OK. Example 20:

[0067] Braking system according to one of the preceding embodiments, wherein the braking system has a locking device by means of which the movement of the brake actuation device can be blocked. Example 21:

[0068] Braking system according to embodiment 20 wherein the locking device can block the brake actuation device in any position or in a specific range of movement. Example 22:

[0069] Braking system according to embodiment 20 or 21, wherein the locking device is hydraulically or electrically driven, in particular by means of an electric motor or electromagnet, and acts on the actuating device, in particular the transmission device 14. Example 23:

[0070] Braking system according to one of embodiments 18 to 20, wherein a control device controls the locking device depending on the signals from the ABS / ESP controller and the piston and actuating device positions. Example 24:

[0071] Brake system according to one of the preceding embodiments, wherein the brake system has sensors for determining the piston position and the position of the brake actuation device, and the control device of the brake system controls the drive of the brake booster depending on the two positions relative to each other. Example 25:

[0072] Brake system according to embodiment 24, wherein the control device determines the pedal force from the determined positions of piston 13 and brake actuation device 16, 16a, 14 and controls the drive 11, 12 of the brake booster on the basis of the differential stroke Δh which is proportional to the pedal force. Example 26:

[0073] Brake system according to one of the preceding embodiments, wherein the brake system has a pressure sensor 10 with which the pressure in the pressure piston circuit can be determined, wherein the pressure control for the wheel brakes 9a-9d is based on the pressure volume characteristics. Example 27:

[0074] Braking system according to one of the embodiments 1 to 25, wherein the current proportional to the pressure is measured by means of the current consumption of the electric drive of the brake booster, in particular by means of a shunt 26, and the pressure control for the wheel brakes 9a, 9b, 9c, 9d is carried out on the basis of the pressure volume characteristics and the current, in particular without the use of a pressure sensor. Example 28:

[0075] Braking system according to one of the preceding embodiments, wherein the control device for the state variables "brake actuation device, in particular pedal stroke s P , and piston position s K performs a plausibility check. Example 29:

[0076] Braking system according to one of the preceding embodiments, wherein the control device performs a normalization and adjustment of the sensor signals, in particular for the pressure, position and / or rotary angle encoders, wherein the adjustment is carried out in the initial position of brake pedal 16, spindle 13 and piston 24 taking into account the previously determined real distance Δs as a correction value. Example 30:

[0077] Braking system according to one of the preceding embodiments, wherein the control device uses the spring travel of spring 20 as a control variable for adjusting the brake force amplification. Example 31:

[0078] Braking system according to one of the preceding embodiments, wherein the return springs of the HZ or THZ adjust the piston 24 and the spindle 13 to their initial position. Example 32:

[0079] Braking system according to one of the preceding embodiments, wherein a spring 3 moves the spindle 13 in the direction of its initial position and the HZ or THZ springs act upon or adjust the piston 24 to its initial position. Example 33:

[0080] Brake system according to one of the preceding embodiments, wherein a bearing part 31 is mounted on the transmission device 14 or the piston system 24, 21, 30 so as to be displaceable parallel to the spindle axis, wherein the bearing part 31 has a flexible plunger 31b for force transmission to the piston system or the transmission device 14. Example 34:

[0081] Brake system according to embodiment 33, wherein the plunger 31c is articulated to the bearing part 31 by means of a ball joint. Example 35:

[0082] Braking system according to one of the preceding embodiments wherein the control device regulates the brake force amplification depending on the braking effect achieved by means of recuperation. Reference symbol list 1 EC motor 2 spindles 3 Spindle reset 4 Rotary angle encoders (position encoders) 5 Hz or THZ 6 Pressure line from the pushrod piston 7 Pressure line from the float piston 8a-8d 2 / 2 Solenoid valves as switching valves 9a-9d Wheel cylinders 10 pressure transmitters 11 Stator 12 Rotor 13 Spindle 14 Transmission device 14a Guide bridge 15 cases 15a Housing bearing for transmission device 16 Brake pedal 16a Pedal tappet 17 Return spring 18 disc 19 retaining ring 20 compression springs 20a Spring washer 20b second compression spring 21 pestles 21a Pestle bundle 22 Pedal stroke sensor 23 Belleville washers 24 pushrod pistons 25 Motor control 26 Shunt 27 Moment support 28 Ball screw drive 29 bellows 30 inserts 31 Bearing part 31a Bund of the storage section 31b flexible plunger 31c articulated plunger 32 bore 33 / 33a 2 / 2 Solenoid valve 34 Magnetic yoke 35 coil 36 Conclusion 37 Magnetic flux 38 slats 39 Lifting magnet 39a flexible electrical connection 40 coupling element 41 Drive element 42 Sleeve 43 Guide rail 44 Lifting magnet with coil 45 magnetic armatures 45a Bearing bolt 46 Return spring 47 Storage 48 Feder

Claims

[1] Braking system comprising an electromechanical brake booster, in which the master brake cylinder or tandem master brake cylinder (5) with a piston (24) is driven by an electric motor (11, 12) via a spindle drive with a spindle (13), wherein the working chamber(s) of the brake booster are connected to the wheel cylinders of wheel brakes (9a-9d) via hydraulic lines (6, 7) and a controllable valve (8a-8d) is assigned to each wheel brake (9a-9d), and in which pressure build-up and pressure reduction in the wheel brakes (9a-9d) is carried out simultaneously or sequentially by means of a control device by means of the brake booster and the controlled valves (8a-8d), characterized by, that a brake actuation device (16, 16a, 14) acts to assist a piston (24) of the brake booster in normal braking operation, wherein in ABS operation the spindle (13) or the piston (24) applies force to and / or adjusts the brake actuation device (16, 16a, 14) and the piston (24) of the brake booster is moved back and forth via the electric motor (11, 12) to regulate the wheel brake pressures, wherein the brake actuation device (16, 16a, 14) acts on the piston (24) of the brake booster via at least one spring element (20), wherein the brake system has sensors (4, 22) for determining a position of the piston (24) and a position of the brake actuation device (16, 16a, 14), wherein the sensors (4, 22) are arranged to detect a possible travel difference between the piston (24) and the brake actuation device (16, 16a, 14) due to the spring element (20, 20b); wherein in normal braking operation the control unit of the brake system actuates the drive of the brake booster depending on the travel difference, wherein in ABS operation the current proportional to the pressure is measured by means of a shunt (26) and the pressure control for the wheel brakes (9a-9d) is based on the current without the use of a pressure sensor. [2] Braking system according to claim 1, characterized by, that the at least one spring element (20, 20b) is supported with one end on a transmission device (14) or a pedal plunger (16a) and with the other end on the spindle (13), the piston (24) or a plunger (21). [3] Braking system according to claim 1 or 2, characterized by , that the at least one spring element (20, 20b) has a linear or degressive force-displacement characteristic for the upper force range. [4] Braking system according to any one of claims 1 to 3, characterized by , that the spring travel length of the at least one spring element (20, 20b) for maximum brake pressure is at least 1 mm. [5] Braking system according to claim 1, characterized by , that the brake actuation device has a brake pedal (16) which is connected to a pedal plunger (16a), wherein the pedal plunger (16a) is connected to a transmission device (14) and the transmission device (14) acts on the piston (24) of the brake booster. [6] Braking system according to claim 5, characterized by , that the at least one spring element (20, 20b) is arranged in or on the transmission device (14). [7] Braking system according to any one of claims 2 to 6, characterized by , that an additional return spring element (17) lifts the transmission device (14) or the pedal plunger (16a) from the piston (24) or the spindle (13). [8] Brake system according to one of the preceding claims, characterized by , that the braking system has a locking device by means of which the movement of the brake actuation device (16, 16a, 14) can be blocked. [9] Braking system according to claim 8, characterized by , that the locking device can block the brake actuation device (16, 16a, 14) in any position or in a certain range of movement. [10] Brake system according to claim 8 or 9, characterized bythat the locking device is hydraulically or electrically driven and acts on the brake actuation device (16, 16a, 14). [11] Braking system according to any one of claims 8 to 10, characterized by , that a control device controls the locking device depending on the signals from an ABS / ESP controller and the piston (24) and actuating device positions. [12] Brake system according to any one of the preceding claims, characterized by , that the brake system has a pressure sensor (10) with which the pressure in the pressure piston circuit can be determined, wherein the pressure control for the wheel brakes (9a-9d) is based on pressure volume characteristics. [13] Brake system according to any one of the preceding claims, characterized by , that the control unit for measured variables relating to a pedal stroke sP and / or a piston position sK performs a plausibility check. [14] Brake system according to any one of the preceding claims, characterized by, that the return springs of the master brake cylinder or tandem master brake cylinder (5) adjust the piston (24) and the spindle (13) to their starting position. [15] Brake system according to any one of the preceding claims, characterized by , that a spindle return spring (3) moves the spindle (13) towards its initial position and return springs of the master brake cylinder or tandem master brake cylinder (5) actuate or adjust the piston (24) to its initial position. [16] Brake system according to any one of the preceding claims, characterized by that the control unit adjusts the brake force amplification depending on the braking effect achieved through recuperation.

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