Abstract
Brake actuating device, with an actuating device, a travel simulator (21), a first piston-cylinder device (3) with a first piston (2) and a further piston (4), the first piston (2) and the further piston (4) each forming a working space, first hydraulic connections (11, 12) leading from the working spaces of the first piston-cylinder device (3) to wheel brakes, first valve devices being provided in the first hydraulic connections (11, 12), and with a booster device (25) driven by an electric motor, which has a second piston-cylinder device (26) with precisely one working space, 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, the booster device (25) driven by an electric motor actuating a plunger piston (29), characterized the first valve devices for each wheel brake have an inlet/outlet switching valve (15, 16, 17, 18), with safety valves (33, 34) being arranged in the hydraulic lines from the second piston-cylinder device (26) to the wheel brakes, wherein a pressure sensor (38) is arranged between the working chamber (30) of the second piston-cylinder device (26) and the safety valves (33, 34), wherein the first piston (2) actuated by the actuating device is used to control the travel simulator (21).
Claims
[1] Brake actuating device, with an actuating device, a travel simulator (21), a first piston-cylinder device (3) with a first piston (2) and a further piston (4), the first piston (2) and the further piston (4) each forming a working space, first hydraulic connections (11, 12) leading from the working spaces of the first piston-cylinder device (3) to wheel brakes, first valve devices being provided in the first hydraulic connections (11, 12), and with a booster device (25) driven by an electric motor, which has a second piston-cylinder device (26) with precisely one working space, 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, the booster device (25) driven by an electric motor actuating a plunger piston (29), characterized in that the first valve devices for each wheel brake have an inlet/outlet switching valve (15, 16, 17, 18), with safety valves (33, 34) being arranged in the hydraulic lines from the second piston-cylinder device (26) to the wheel brakes, wherein a pressure sensor (38) is arranged between the working chamber (30) of the second piston-cylinder device (26) and the safety valves (33, 34), wherein the first piston (2) actuated by the actuating device is used to control the travel simulator (21).
[2] Brake actuating device according to one of the preceding claims, characterized in that the device has a hydraulic path simulator (21) which can be actuated by means of the first piston (2) of the first piston-cylinder device (3) and which is arranged in the same housing as the latter.
[3] Brake actuating device according to one of the preceding claims, characterized in that, to detect a brake circuit failure, the displacement of the piston of the second piston-cylinder device (26) is compared with the pressure or motor current by means of the pressure-volume characteristic of the brake circuits or of the individual wheel cylinders.
[4] Brake actuating device according to one of the preceding claims, characterized in that, 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 disconnected by closing the corresponding valve (15, 16, 17, 18) of the first valve device.
[5] Brake actuating device according to one of the preceding claims, characterized in that a valve means (36) is provided for replenishing hydraulic fluid when the volume requirement is greater than the delivery volume of the second piston-cylinder means.
[6] Brake actuating device according to one of the preceding claims, characterized in that the booster device (25) has a gear mechanism (28) with a spindle drive, the spindle pitch being designed with self-locking or approximate self-locking or having a latching device.
[7] Brake actuating device according to one of the preceding claims, characterized in that a resilient device or member (1b) is provided between the brake pedal (1) and the piston (DK) (2) of the first piston/cylinder device (3) member (1b) is provided in order to carry out a force measurement by means of the relative movement between the pedal (1) and the piston (2) and corresponding sensor signals.
[8] Brake actuating device according to one of the preceding claims, characterized in that a pressure generator (DG) and valve devices are provided in the hydraulic connections (11, 12) from the working spaces of the first piston-cylinder device (3) to the wheel brakes.
[9] Brake actuating device according to one of the preceding claims, characterized in that an elastic device or an elastic element is provided between the brake pedal (1) and the first piston (2).
[10] Brake actuating device according to one of the preceding claims, characterized in that an evaluation of the motor current strength is carried out to determine the pressure-volume characteristic and a failure of the brake force booster.
[11] Brake actuating device according to one of the preceding claims, characterized in that a brake circuit failure is detected by comparing the plunger travel with the pressure or motor current using the pressure-volume characteristic of the brake circuits or individual wheel cylinders.
[12] Brake actuating device according to one of the preceding claims, characterized in that the piston-cylinder unit (26) is used, as it were, for building up and reducing the brake pressure, for realizing the ABS and traction control system and for assistance functions.
[13] Brake actuating device according to one of the preceding claims, characterized in that pressure control is carried out by means of volume measurement over the piston travel and evaluation of a pressure-volume characteristic.
[14] Brake actuating device according to one of the preceding claims, characterized in that a diagnostic test is carried out on a switching function and on the sealing of all solenoid valves.
[15] Brake actuating device according to one of the preceding claims, characterized in that, if a failure of the brake circuit is detected by pressure modulation in a closed brake circuit, the valve (15, 16, 17, 18) to the wheel cylinder or the safety valve (13, 14) of the failed brake circuit to the plunger is closed.
[16] Brake actuating device according to one of the preceding claims, characterized in that the valves and the hydraulic lines with low flow resistances are designed in such a way that a rapid pressure build-up and pressure reduction by means of the second piston-cylinder device (26) is ensured, and in that the second piston-cylinder device (26) or the piston speed alone determines the rate of pressure build-up and pressure reduction.
[17] Brake actuating device according to one of the preceding claims, characterized in that a pressure transducer (DG) is arranged in a hydraulic connection (11, 12) of a working chamber of the first piston-cylinder device (3).
Description
[0001] The invention relates to a brake actuating device for motor vehicles according to the generic term of patent claim 1.
Prior art
[0002] A brake actuating device of the type mentioned at the beginning is already known from DE 10 2010 040 097 A1. This actuating device already offers various advantages, such as compact structural and functional integration, elimination of a pump and the associated noise, weight savings and high dynamics. In this device, an inlet valve and an outlet valve are assigned to each wheel brake, which makes the actuating device even more complex in terms of design. 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.
Aim of the invention
[0003] The invention’s task is therefore to create a brake actuating device of the type mentioned at the beginning, which, while maintaining the advantages in terms of the structural effort, is less elaborate.
Solution to the task
[0004] The invention’s task is solved by an object with the features of patent claim 1.
[0005] Advantageous embodiments of the invention are contained in the sub-claims.
[0006] The solution according to the invention and its embodiments provide a surprisingly simple way of creating a brake actuation system for motor vehicles that has the advantages of the actuation device described at the beginning, but is even further simplified in construction and, in particular, manages with fewer valves. In this case, the pressure modulation advantageously occurs in multiplex operation, in particular by means of plungers in a closed brake circuit.
[0007] Improved dynamics and control advantages also arise due to enlarged valve cross sections and/or precise pressure control by means of volume metering over the piston path and evaluation of the pressure-volume characteristic.
[0008] It is useful to use the piston (DK) actuated by the actuating device to control a travel simulator. This can advantageously be provided in the same housing as the first piston-cylinder device or integrated into it.
[0009] Furthermore, the solution according to the invention and its embodiments improve the system’s reliability. It is possible to diagnose the switching function and the tightness of all solenoid valves. It is also possible to detect a failure of the brake circuit by means of 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 a higher braking effect. In the extreme case of an internal leak, a second 2/2-way solenoid valve is optionally provided in a brake circuit. This means that if the brake booster (plunger) fails in the second brake circuit, there is still a braking effect even if one of the safety valves fails. The braking effect remains fully intact for the first brake circuit. Without these valves, if the brake booster, i.e. the plunger, fails and the safety valve is leaking, the brake circuit would empty into the plunger, since the spindle would be moved by the pressure force without self-locking and the piston would return to its initial position.
[0010] An inlet/outlet valve (EA) is advantageously provided in a line to the expansion tank, via which hydraulic fluid can be supplied from the reservoir in a targeted manner if necessary. The system also has a hydraulic fall-back level, which makes it possible to brake the vehicle safely even if the brake booster fails. It is advantageous to evaluate the motor current strength to determine the pressure-volume characteristic curve (instead of a pressure transducer) and a failure of the brake booster. It is also advantageous if the thread of the spindle is provided with self-locking or a latching device on the rotor or spindle of the plunger. This ensures that no additional volume is displaced by the plunger if a safety valve and the plunger fail. Furthermore, in particular as an alternative to the pressure transducer, it is advantageous to provide an elastic device or an elastic link between the brake pedal and the piston (DK piston) can be advantageously provided, whereby the fail-safe performance can be increased, as described in further detail in the German patent application DE 10 2010 050133 A1 of the applicant, to which reference is also made for disclosure purposes in this regard.
[0011] With fast pressure modulation, a vacuum arises in the plunger, especially at low pressures, which can cause the suction valve to open. For this purpose, the pressure can be controlled accordingly by the pressure transducer signal. When replacing the relatively expensive pressure transducer with a motor current measurement, an electromagnetic shut-off valve is provided in the return line to avoid the vacuum, which also replaces the suction valve. A further advantage is that this shut-off valve can be diagnosed because it can be switched for diagnosis.
Description of figures
[0012] Examples, embodiments of the invention, their components and further advantages can be found in the drawing and the following
figure description
[0013] The brake actuating device shown in the only figure has an actuating device, in particular a pivotably mounted brake pedal (1), which acts on a first piston (2) of a first piston-cylinder device (3) via an elastic device (1b) or resilient member. The first piston-cylinder device 3 has a further piston 4. Springs 5 and 6 are arranged between the pistons 2, 4 and between the base of the first piston-cylinder device and the piston 4. A reservoir 7 is connected to the working chambers formed by the pistons 2, 4 via hydraulic lines 8, 9. The piston-cylinder unit shown here thus has the features of a tandem master cylinder, which can advantageously be equipped with so-called central valves. It may also be expedient to arrange the pistons and/or cylinders in a so-called twin configuration, i.e. parallel to one another, if the overall length is crucial. The movement of preferably the first piston 2 can be determined by means of, in particular redundant, displacement sensors 10a, 10b. In this case, 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 11, which may, for example, comprise at least one suitable spring, the actuating force can be measured via the differential travel in addition to the additional pedal travel measurement, which is very useful for fault detection. Further details are described in the German patent application DE 10 2010 050 133 A1 of the applicant, which is also referred to for disclosure purposes.
[0014] The electronic control and regulating unit (ECU) normally used for evaluating the sensor signals and controlling or regulating the functions in such systems is not shown here.
[0015] Hydraulic connections 11, 12, in which a pressure transducer DG and valve devices are provided, lead from the working chambers of the first piston-cylinder device to wheel brakes (not shown here). The valve devices have, in particular, normally open isolating valves 13, 14, as well as, for each wheel brake, a normally open inlet/outlet valve solenoid valve 15, 16, 17, 18, which in this embodiment are assigned to two brake circuits.
[0016] The separating valves 13, 14 are used for pressure modulation and brake boost. This is basically done in the same way as in the known electro-hydraulic brake, as described, for example, in the “Bremsenhandbuch” (Brake Manual), 2nd edition, Vieweg-Verlag.
[0017] A hydraulic connection 20 leads from the first working chamber of the piston-cylinder device 3 to a path simulator 21. A throttle 22 with a parallel non-return valve and a switching valve 23, which is in particular closed in the absence of current, are arranged in the hydraulic connection 20.
[0018] An amplifier device 25 has a piston-cylinder device 26 (plunger) and a highly dynamic electric motor drive 27 with a gearbox 28. The gearbox 28 is advantageously a ball-circulation spindle gearbox. The spindle acts on a plunger piston 29. The motor acts linearly on the plunger piston, thereby enabling the function of brake booster 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 means of a rotation angle sensor 24. At least for brake pressures > 40 bar, it is advisable to provide a spindle with self-locking or almost self-locking or a detent mechanism on the drive, so that no brake circuit failure occurs if the plunger fails and the safety valve 33, 34 leaks.
[0019] This is advantageous if the drive motor fails during pressure modulation and at the same time, e.g. due to dirt, the safety valve 33, 34 leaks. Without self-locking, the pressure from the corresponding brake circuit would push back the piston, which would be equivalent to a brake circuit failure. Alternatively, an additional solenoid valve 33a can be used behind the safety valves, which is closed in this case. This is important because when the safety valve is open, both brake circuits interact and thus the redundancy of the two brake circuits is lost. In this case, it is advantageous to make the return spring force relatively large. This prevents pressure medium from one brake circuit with a leaking valve from entering the other brake circuit during ABS braking with different pressure levels in the brake circuits.
[0020] A brake circuit failure detection (BKA) can be carried out by comparing the plunger travel with the pressure or motor current using the pressure-volume characteristic of the brake circuits or individual wheel cylinders. In the event of a brake circuit failure outside the valve block (HCU), it is useful to disconnect the leaking wheel cylinder circuit by means of the corresponding inlet/outlet valve 15-18.
[0021] Hydraulic connections lead from the working chamber 30 of the piston-cylinder device 26 to the hydraulic connections 11, 12, with a switching valve (safety valve) 33, 34 being arranged in each connection, by means of which the brake circuits to which the plunger applies braking pressure can be disconnected. In addition to valves 33, 34, a further valve can be provided in one of the brake circuits. This means that, in the event of a brake circuit failure in this brake circuit, a redundant valve is available and the brake booster function in the other circuit remains intact.
[0022] Furthermore, a hydraulic connection 35 leads from the working chamber 30 of the plunger to the reservoir 7. In this hydraulic connection, a switching valve 36 (inlet/outlet valve E/A), which is in particular closed when de-energized, and a non-return valve 37 are arranged. The E/A valve is used to refill or draw from the reservoir when the volume requirement is increased, e.g. even with a small leak.
[0023] The piston-cylinder device 26 of the booster device has only one working chamber for both brake circuits, so that the single-circuit electromotively driven plunger with the inlet/outlet valves 15, 16, 17, 18 assigned to the wheel brakes effects the pressure modulation in multiplex operation. Under certain circumstances, it may also be advantageous to provide a piston-cylinder device (plunger) with two working chambers in a tandem arrangement. In the solution according to the invention, the piston-cylinder unit 26 serves, as it were, for building up and reducing the brake pressure, for realizing the ABS and traction control system as well as assistance functions. Furthermore, the electromotive drive makes it possible to improve these functions by means of finely dosed pressure control with variable rates of pressure increase and, in particular, pressure decrease. The valves and the hydraulic lines are to be designed with the lowest possible flow resistances so that the fastest possible pressure build-up and pressure reduction can be realized by means of the piston-cylinder system. This ensures that the piston-cylinder system or the piston speed alone determines the speed of pressure build-up and pressure reduction. It is advantageous to use pressure-balanced seat valves or slide valves with low temperature dependence and short switching times. The operation in multiplex and the resulting advantages are described in detail in the German patent application DE 10 2005 055 751 A1 of the applicant, to which reference is also made for disclosure purposes.
List of reference signs
1 Brake pedal
1a Pedal tappet
1b Elastic device or element
2 Piston (DK)
3 Piston-cylinder device
4 Piston (SK)
5 Spring
6 Spring
7 Reservoir
8 Hydraulic line
9 Hydraulic line
10a Distance sensor
10b Distance sensor
11h Hydraulic line
12 Hydraulic line
13 Cut-off valve
14 Cut-off 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 line
21 displacement simulator
22 throttle
23 control valve
24 displacement or angle of rotation sensor
25 amplifier
26 Piston-cylinder unit
27 Electric motor drive
28 Gearbox
29 Plunger piston
30 Working area
33 Safety valve
33a Additional safety valve
34 Safety valve
35 Hydraulic line
36 2/2-way solenoid valve
37 Non-return valve
38 Pressure sensor
