brake actuation device

Abstract

Brake operating device, with - an actuating device, in particular a brake pedal (1); - a path simulator (21); - a first and a second brake circuit, each with two wheel brakes; - a first piston-cylinder device (3) with a first piston (2) and a second piston (4), each defining a first working chamber and a second working chamber, wherein the working chambers are detachably connected to one of the brake circuits via hydraulic connections (11, 12); and - an electric motor-driven booster device (25) which has a second piston-cylinder device (26) for building up and / or reducing a pressure in a common hydraulic connecting line, wherein the common hydraulic connecting line is connected to the first brake circuit via a first safety valve (33) and to the second brake circuit via a second safety valve (34), characterized in that the brake actuating device is designed to implement ABS and traction control and / or assistance functions using the second piston-cylinder device (26), wherein the brake circuits pressurized by the second piston-cylinder device (26) can be separated by means of the safety valves (33, 34), wherein a pressure sensor (38) is arranged between a working chamber (30) of the second piston-cylinder device (26) and the safety valves (33, 34).

Description

[0001] The invention relates to a brake actuating device according to claim 1. State of the art

[0002] DE 10 2010 040 097 A1 discloses a brake actuation device that offers various advantages, such as compact structural and functional integration, the elimination of a pump and the associated noise, weight savings, and high dynamics. In this device, each wheel brake is assigned an inlet valve and an outlet valve, which makes the actuation device structurally relatively complex. DE 10 2009 033 499 A1 describes a brake system for motor vehicles. DE 10 2010 002 406 A1 discloses a hydraulic brake system and a method for its operation. DE 10 2010 003 082 A1 describes a brake system for motor vehicles. DE 10 2010 022 493 A1 proposes a safety circuit for a blocking drive of a brake booster.

[0003] Further braking systems can be found in the documents CN 1 232 430 A, WO 2010 / 143 660 A1, CN 1 02 099 231 A, WO 2011 / 105 406 A1, DE 10 2011 082 492 A1, WO 2011 / 105 405 A1, DE 10 2011 081 463 A1, DE 10 2011 081 601 A1, US 5 609 399 A, and DE 197 53 786 A1.

[0004] A brake booster for a brake system can be found in the publication CN 1 872 599 A. Object of the invention

[0005] The object of the invention is therefore to provide an improved brake actuation device. In particular, the system's fail-safety is to be improved. Solution to the task

[0006] The object of the invention is achieved with the brake actuating device according to claim 1.

[0007] Advantageous embodiments of the invention are contained in the subclaims.

[0008] The solution according to the invention and its embodiments create a brake actuation system for motor vehicles in a surprisingly simple manner. This system has the advantages of the actuation device described above, while also being structurally even simpler and, in particular, requiring fewer valves. Pressure modulation is advantageously achieved in multiplex mode, particularly by means of plungers in the closed brake circuit.

[0009] Improved dynamics and control-related advantages are also achieved through larger valve cross-sections or through precise pressure control by means of volume metering via the piston travel and evaluation of the pressure-volume characteristic curve.

[0010] The piston actuated by the actuating device (DK) is expediently used to control a travel simulator. This can advantageously be provided in the same housing as the first piston-cylinder device or first piston-cylinder unit or integrated into it.

[0011] Furthermore, the solution according to the invention and its embodiments improve the system's fault tolerance. Diagnosis of the switching function and the tightness of all solenoid valves can be performed. A brake circuit failure can also be detected by pressure modulation in the closed brake circuit. In the event of a failure, the valve to the wheel cylinder or the safety valve of the failed brake circuit closes to the plunger. This maintains greater braking efficiency. For the extreme case of an internal leak, a second 2 / 2-way solenoid valve is optionally provided in one brake circuit. This ensures that braking efficiency is maintained in the second brake circuit if the brake booster (plunger) fails, even if one of the safety valves fails. The braking efficiency remains fully intact for the first brake circuit. Without these valves, the failure of the brake booster would result inof the plunger and leaking safety valve, the brake circuit would be emptied into the plunger, since the spindle would be moved by the pressure force without self-locking and the piston would return to its starting position.

[0012] Advantageously, an inlet / outlet valve (EA) is provided in a line to the expansion tank, through which hydraulic fluid can be selectively pumped from the reservoir if necessary. The system also has a hydraulic fallback level, which enables the vehicle to be braked safely even if the brake booster fails. Advantageously, the motor current is evaluated to determine the pressure-volume characteristic curve (instead of a pressure sensor) and in the event of a brake booster failure. The pitch of the spindle thread can also advantageously be provided with a self-locking or locking device on the rotor or spindle of the plunger. This means that if a safety valve and the plunger fail, no additional volume is displaced by the plunger. Furthermore, particularly as an alternative to the pressure sensor, an elastic device orAn elastic member can be provided between the brake pedal and the piston (DK piston), which can increase fault tolerance, as described in further detail in the applicant's German patent application DE 10 2010 050133.6, to which reference is also made for disclosure purposes. During rapid pressure modulation, a vacuum is created in the plunger, particularly at low pressures, which can lead to the suction valve opening. For this purpose, the pressure can be controlled accordingly using the pressure sensor signal. If the relatively expensive pressure sensor is replaced by a motor current sensor, an electromagnetic shut-off valve is provided in the return line to avoid the vacuum; this also replaces the suction valve. A further advantage is that this shut-off valve is diagnosable because it can be switched on for diagnostic purposes. Character description Embodiments or refinements of the invention or its components and further advantages emerge from the drawing and the following description of the figures.

[0013] The brake actuating device illustrated in the single figure comprises an actuating device, in particular a pivotably mounted brake pedal 1, which acts on a first piston 2 of a first piston-cylinder unit 3 via an elastic device or resilient member. The first piston-cylinder unit 3 has a further piston 4. Springs 5 ​​and 6 are arranged between the pistons 2, 4 and between the bottom of the first piston-cylinder unit 3 and the piston 4, respectively. A reservoir 7 is connected via hydraulic lines 8, 9 to the working chambers formed by the pistons 2, 4. The piston-cylinder unit illustrated here thus has features of a tandem master cylinder, which can advantageously be provided with so-called central valves. The arrangement of the pistons or cylinders in a so-called twin configuration, i.e., parallel to one another, can also be expedient if the overall length is crucial.The movement, preferably of the first piston 2, can be determined by means of, in particular, redundant, displacement sensors 10a, 10b. The sensors can be activated by two different actuating elements, piston 2 and pedal tappet 1a, which are connected to the sensors via corresponding, in particular mechanical, actuating devices or elements. By interposing an elastic device 1b, which can, for example, comprise at least one suitable spring, the actuating force can be measured via the differential displacement in addition to the additional pedal displacement measurement, which is very valuable for fault detection. This is described in further detail in the applicant's German patent application DE 10 2010 050 133.6, which is also incorporated herein by reference for disclosure purposes.

[0014] The electronic control unit (ECU) typically used to evaluate the sensor signals and control or regulate the functions in such systems is not shown here.

[0015] Hydraulic connections or lines 11, 12, in which a pressure transducer DG and valve devices are provided, lead from the working chambers of the first piston-cylinder device 3 to wheel brakes (not shown here). The valve devices have isolating valves 13, 14, in particular normally open, as well as an inlet / outlet solenoid valve 15, 16, 17, 18 for each wheel brake, in particular normally open, to which two brake circuits are assigned in this embodiment.

[0016] The isolation valves 13 and 14 are used for pressure modulation and brake boosting. This is essentially done in the same way as with the familiar electro-hydraulic brake, as described, for example, in the "Brake Manual," 2nd edition, published by Vieweg-Verlag.

[0017] A hydraulic connection 20 leads from the first working chamber of the piston-cylinder device 3 to a travel simulator 21. In the hydraulic connection 20, a throttle 22 with a parallel check valve and a switching valve 23, which is closed in particular when de-energized, are arranged.

[0018] A booster device 25 comprises a piston-cylinder device 26 or piston-cylinder unit 26 (plunger) and a highly dynamic electric motor drive 27 with a gear 28. The gear 28 is advantageously a recirculating ball-spindle gear. The spindle acts on a plunger 29. The motor acts linearly on the plunger, thus enabling the brake force boosting function during driver braking and the pressure modulation of a slip control system and driver assistance systems. The rotation of the motor or spindle can be sensed by a rotation angle sensor 24. At least for brake pressures > 40 bar, it is expedient to provide a self-locking or nearly self-locking spindle pitch or a locking device on the drive so that no brake circuit failure occurs in the event of a plunger failure and a leaking safety valve 33, 34.

[0019] This is advantageous in the event of a drive motor failure during pressure modulation and, at the same time, due to, for example, dirt or a leaky safety valve 33, 34. Without self-locking, the pressure from the corresponding brake circuit would force the piston back, which would be equivalent to a brake circuit failure. As an alternative, an additional solenoid valve 33a can be used behind the safety valves; in this case, it is closed. This is important because when the safety valve is open, both brake circuits interact, thus losing the redundancy of the two brake circuits. In this case, it is advantageous to make the return spring force relatively large. This prevents pressure fluid from one brake circuit with a leaky valve from passing into the other brake circuit during ABS braking with different pressure levels in the brake circuits.

[0020] Brake circuit failure detection (BKA) can be conveniently performed by comparing the plunger travel with the pressure or motor current using the pressure-volume characteristic curve of the brake circuits or individual wheel cylinders. In the event of a brake circuit failure outside the valve block (HCU), the leaking wheel cylinder circuit is conveniently isolated using the corresponding inlet / outlet valve 15-18.

[0021] Hydraulic connections 31, 32 lead from the working chamber 30 of the piston-cylinder assembly 26 to the hydraulic connections 11, 12. Each connection 31, 32 contains a switching valve (safety valve) 33, 34, which can be used to isolate the brake circuits supplied with brake pressure by the plunger. In addition to the valves 31, 32, an additional valve can be provided in one of the brake circuits. This provides a redundant valve in the event of a brake circuit failure in this brake circuit, and the brake booster in the other circuit remains intact.

[0022] A hydraulic connection 35 also leads from the plunger's working chamber 30 to the reservoir 7. A switching valve 36 (inlet / outlet valve I / O), which is closed when de-energized, and a check valve 37 are arranged in this hydraulic connection. The I / O valve is used for refilling or drawing fluid from the reservoir when the volume requirement is increased, e.g., even in the event of a small leak.

[0023] The piston-cylinder unit 26 of the booster device has only one working chamber for both brake circuits, so that the single-circuit, electromotor-driven plunger with the inlet / outlet valves 15, 16, 17, 18 assigned to the wheel brakes achieves pressure modulation in multiplex operation. Under certain circumstances, it may also be advantageous to provide a piston-cylinder unit (plunger) with two working chambers in a tandem arrangement. In the solution according to the invention, the piston-cylinder unit 26 serves both to build up and reduce brake pressure, to implement ABS and traction control, as well as assistance functions. The electromotor drive further enables these functions to be improved through finely dosed pressure control with variable pressure increase and, in particular, pressure decrease rates.The valves and hydraulic lines should be designed with the lowest possible flow resistance to advantageously achieve the fastest possible pressure build-up and pressure reduction using the piston-cylinder system. This ensures that the piston-cylinder system, or rather the piston speed, alone determines the pressure build-up and pressure reduction rate. Pressure-balanced seat valves or slide valves with low temperature dependence and short switching times are advantageously used. Multiplex operation and the resulting advantages are described in detail in the applicant's German patent application DE 10 2005 055 751.1, which is also incorporated herein by reference for disclosure purposes.

[0024] Below are some embodiments of the invention which are part of the disclosure: 1. Brake actuation device, with an actuation device, in particular a brake pedal (1), a travel simulator (21), a first piston-cylinder device (3) which is connected to at least one wheel brake via a first hydraulic connection in which a first valve device is provided and which is connected to an electric motor-driven booster device (25) which has a second piston-cylinder device (26) which is connected to the wheel brake via a second hydraulic connection in which a second valve device is provided and is connected to a reservoir (7) via a third hydraulic connection in which a third valve device is provided, wherein the first valve device has an inlet-outlet switching valve (15, 16, 17, 18) assigned to a wheel brake in each case, which is operated in particular in multiplex mode. 2. Brake actuating device according to embodiment 1, wherein the third valve device comprises a switching valve (36, 33a). 3. Brake actuating device according to embodiment 1 or 2, wherein the electric motor-driven booster device (25) actuates a plunger piston (29). 4. Brake actuating device according to one of the preceding embodiments, wherein the device has a hydraulic travel simulator (21) which can be actuated in particular by means of a piston of the first piston-cylinder device (3) and which is arranged in particular in the same housing as the latter. 5. Brake actuating device according to one of the preceding embodiments, wherein, in order to detect a brake circuit failure, the travel of the piston of the second piston-cylinder device (26) is compared with the pressure or motor current, in particular by means of the pressure-volume characteristic curve of the brake circuits or the individual wheel cylinders. 6. Brake actuating device according to one of the preceding embodiments, wherein in the event of a brake circuit failure the cause of which lies outside the hydraulic unit (HCU) accommodating the first valve device, the corresponding circuit or wheel cylinder is separated by closing the corresponding valve of the first valve device. 7. Braking device according to one of the preceding embodiments, wherein a valve device (36) is provided for refilling hydraulic fluid when the volume requirement is greater than the delivery volume of the second piston-cylinder device. 8. Braking device according to one of the preceding embodiments, wherein safety valves (33, 34) are arranged in the hydraulic lines from the second piston-cylinder device to the wheel brakes, in particular safety valves assigned to the brake circuits. 9. Braking device according to embodiment 8, wherein an additional or redundant safety valve (33a) is provided. 10. Braking device according to embodiment 8 or 9, wherein the safety valves are equipped with a higher pressure-resistant closing spring, in particular for an overpressure > 80 bar on the inlet side of the valve seat. 11. Braking device according to one of the preceding embodiments, wherein the booster device comprises a gear (28) with a spindle drive, wherein in particular the spindle pitch is designed with self-locking or approximately self-locking or has a locking device. 12. Braking device according to one of the preceding embodiments, wherein an elastic device or member is provided between the brake pedal and the piston (DK) (2) of the first piston-cylinder device (3) in order to carry out a force measurement via the relative movement between pedal and piston or corresponding sensor signals. List of reference symbols 1 brake pedal 1a pedal tappet 1b elastic device or link 2 pistons (DK) 3 piston-cylinder device or unit 4 pistons (SK) 5 spring 6 spring 7 storage containers 8 hydraulic lines 9 hydraulic line 10a displacement sensor 10b displacement sensor 11 hydraulic line 12 hydraulic lines 13 Isolating valve 14 Isolating valve 15 2 / 2-way solenoid valve 16 2 / 2-way solenoid valve 17 2 / 2-way solenoid valve 18 2 / 2-way solenoid valve 20 hydraulic lines 21 Path simulator 22 Throttle 23 Switching valve 24 Position or angle sensor 25 Amplifier device 26 Piston-cylinder device or unit 27 electric motor drive 28 gearboxes 29 plunger pistons 30 workspace 31 hydraulic line 32 hydraulic line 33 Safety valve 33a additional safety valve 34 Safety valve 35 hydraulic line / hydraulic line 36 2 / 2-way solenoid valve 37 Check valve 38 pressure sensors

Claims

[1] Brake operating device, with - an actuating device, in particular a brake pedal (1); - a path simulator (21); - a first and a second brake circuit, each with two wheel brakes; - a first piston-cylinder device (3) with a first piston (2) and a second piston (4), each defining a first working chamber and a second working chamber, wherein the working chambers are detachably connected to one of the brake circuits via hydraulic connections (11, 12); and - an electric motor-driven booster device (25) having a second piston-cylinder device (26) for building up and / or reducing a pressure in a common hydraulic connecting line, wherein the common hydraulic connecting line is connected to the first brake circuit via a first safety valve (33) and to the second brake circuit via a second safety valve (34),characterized by in that the brake actuating device is designed to implement ABS and traction control and / or assistance functions using the second piston-cylinder device (26), wherein the brake circuits pressurized by the second piston-cylinder device (26) can be separated by means of the safety valves (33, 34), wherein a pressure sensor (38) is arranged between a working chamber (30) of the second piston-cylinder device (26) and the safety valves (33, 34). [2] Brake actuating device according to claim 1, characterized by that the brake actuating device, in particular the second piston-cylinder device (26), is designed to realize a pressure control with variable pressure increase and / or pressure decrease speeds. [3] Brake actuating device according to claim 1 or 2, characterized bythat the common hydraulic connecting line and the safety valves (33, 34) have such a small flow resistance that the second piston-cylinder device (26), in particular a piston speed of the second piston-cylinder device (26), alone determines the pressure build-up and pressure reduction speed. [4] Brake actuating device according to one of the preceding claims, characterized by that the second piston-cylinder device (26) comprises exactly one working chamber (30) which is connected to a storage container (7) via a hydraulic line (35). [5] Brake actuating device according to claim 4, characterized by that a check valve (37) is arranged in the hydraulic line (35). [6] Brake actuating device according to claim 4 or 5, characterized by that a switching valve (36) is arranged in the hydraulic line (35).

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