WO2011063955A2

WO2011063955A2 - Brake system having a multifunction memory device

Info

Publication number: WO2011063955A2
Application number: PCT/EP2010/007146
Authority: WO
Inventors: Heinz Leiber; Valentin Unterfrauner; Christian KÖGLSPERGER
Original assignee: Ipgate Ag
Priority date: 2009-11-26
Filing date: 2010-11-25
Publication date: 2011-06-03
Also published as: WO2011063955A3; CN102639370A; DE102009055721A1; CN102639370B

Abstract

The invention relates to a brake system for a motor vehicle, having a master brake cylinder (4, 5), which is driven by an electric drive, wherein a piston plunger (25) and a spindle (2a) are in operative connection with a piston (3) of the master brake cylinder (4, 5), having wheel brake valves (7) for selectively opening and closing the pressure lines (BL) connecting the wheel brakes (RB) to the master brake cylinder (4, 5), having an actuation device (1), in particular in the form of a brake pedal, that acts on a travel simulator (15, 16), wherein in the event of a malfunction, in particular in the event of failure of the drive (2), the actuation device (1) acts mechanically, in particular by means of the pedal shaft (1a), on the piston plunger (25) to build up pressure in at least one wheel brake, and in normal operation there is a particularly small free travel between the piston plunger (25) and the actuation device, in particular between the piston plunger (25) and the pedal shaft (1a), having a control device including a brake-by-wire function, which actuates the drive (2) with the piston (3) as well as the wheel brake valves (7), in particular for either simultaneous or consecutive pressure build-up and pressure reduction in the wheel brakes (RB) for the ABS, ESP and/or recuperation functions, wherein the storage tank (6) of the brake system or a fluid reservoir (20, 20') is used to adjust the magnitude of the free travel (a).

Description

Brake system with memory device with multiple function

The present invention relates to a brake system according to the preamble of claim 1.

Known in the art are conventional brake booster (BKV), as a so-called. Follower amplifier in which the pedal travel is proportional to the Kol ^¬ benweg of the master cylinder. In addition, there are increasingly systems for brake-by-wire operation with path simulator, in which the above assignment no longer applies. Such a system is described as "Electrohydraulic Brake (EHB)" in Brake Manual 2nd edition, Vieweg Verlag, pp. 251 and 252, and is not yet optimized in all its functions.

For different functions of the brake system Wegsimulationssysteme need a free path between pedal plunger and BKV plunger or HZ pistons to z. B. in ABS pressure modulation to produce little or no pedal feedback or recuperative braking, in spite of the generator braking effect the same assignment of pedal travel and power to the braking effect (driving zeugver delay)

CONFIRMATION COPY consists. In some systems, this free travel acts in case of failure of the brake booster or its drive as a significant pedal travel displacement, which the driver perceives as failure of the brake. This is described in WO2004 / 005095 AI. The main task here is in brake-by-wire operation to decouple the pedal from the brake booster. Here, an additional means is proposed, which reduces the free travel in case of failure of the brake booster. This means does not work if the BKV failure already occurs during partial braking, since the agent can not be introduced into the smaller Leerwegspalt here. Extremely critical is the case with full modulation of the path simulator and simultaneous BKV failure, since the free travel is even greater here. Here, the normal driver can not produce sufficient braking effect due to excessive pedal travel or insufficient brake pressure, since the ergonomic limit is approximately 60% pedal stroke.

In DE 10 2005 018 649.1 a more advanced Wegsimulatorsystem is described, which has no means for Leerwegreduzierung, so that in this case the ABS function acts on the pedal. In DE 10 2005 059 609.6 a system with electromagnetic decoupling is described which is only effective in the ABS function or recuperation. For this, a comparison of the Wegsimulatorweges must be carried out with the piston position. At a small distance, the coupling of pedal plunger for piston actuation is released with a free travel. If the brake booster BKV fails during a normal braking, this activation does not have a negative effect. In extreme cases, so in case of failure of the brake booster on ice, are anyway only small blocking impressions, d. H. Pedal ways, required, so that in this case an additional free travel does not adversely affect. This system has only one detent position.

In DE 10 06059840.7 a system with adaptive multi-stage Leerwegverschaltung is described, which only uses the free travel and turns on mainly recuperative braking and ABS function in the low coefficient of friction range, z. By S. The effect of the extreme case is as above In addition, the actuating magnet is no longer movable, but arranged fixed to the housing.

OBJECT OF THE INVENTION It is the object of the present invention to provide a simple, stepless, controllable and fail-safe decoupling between pedal plunger and piston of the master cylinder or HZ piston actuation for realizing the brake-by-wire functions. This object is achieved with a braking system with the features of claim 1 advantageous. It is advantageous z. B a recuperative braking with unchanged pedal characteristics and reduction of the pedal reaction in pressure modulation of ABS possible. The braking systems known from the prior art are relatively complex, especially in assembly, and require high investment at high production volume. In addition, it should be noted that a Wegsimulator braking system, which acts on a tandem master cylinder THZ in BKV failure, still requires additionally a lock of the WS housing. For this purpose, electromechanical and hydraulic solutions are known. Here the task is to integrate this lock in the overall construction with minimal manufacturing and investment costs. A possible solution provides, in a multiplex brake system with travel simulator, in which simultaneously or successively the setting of a pressure in the individual wheel brakes, provided in the primary brake circuit between HZ and switching valves at least one fluid reservoir with an upstream solenoid valve. If this happens, especially in the case of small coefficients of friction, the pedal tappet strikes or threatens to hit the HZ piston or a connecting link during ABS pressure modulation. so pressure medium is introduced from the brake circuit or the brake circuits in the memory, so that the piston stroke lengthens, and a coincidence with the pedal plunger and thus the pedal reaction in ABS is prevented. Optionally, especially in the first control cycle, a small pedal reaction can act. Good ABS pressure modulation requires large pressure gradients, especially in the multiplex system. For this purpose, it is proposed to use a switching valve with a large cross-section in front of the fluid reservoir and to achieve the further pressure reduction by rapid return movement of the piston at a low pressure level. This creates a small pedal reaction.

Subsequently, when the wheel brake valves are closed, additional pressure medium is conveyed into the storage chamber (SPK) or the fluid reservoir by corresponding piston movement, in order to ensure the necessary distance from the piston to the pedal tappet.

Another possibility is to continue to fill the fluid reservoir immediately after the pressure reduction in the fluid reservoir then by closing all Radbremsventile by the piston of the HZ. Again, the distance from piston to pedal ram is increased accordingly and can be variably controlled.

If the distance from the piston plunger to the pedal plunger is too large, follows by appropriate piston control emptying of the fluid reservoir in the brake circuits, so that in case of failure of the brake booster or the drive of the master cylinder only a small free travel. This is advantageously a fully adaptive and stepless Leerwegeinstellung the pedal plunger possible.

In the case of recuperative braking, a specific pressure is regulated as a function of the generator braking effect by introduction of pressure medium into the fluid reservoir, so that no contact takes place between the HZ piston or connecting link to the pedal tappet. The realization of the functions by the fluid reservoir SPK and the associated solenoid valve are similar to known valve blocks for known ABS systems and is made by minor modification of standard components such as solenoid valve and storage chamber. This results in only small investment costs and the assembly takes place on existing facilities of the ABS / ESP line. A further solution of the problem arises when the already existing reservoir takes over the function of the above-described fluid reservoir. An additional fluid reservoir is not needed in this case, at least for the function according to the invention. The fluid can also be discharged via a switchable valve from the pressure line out into the reservoir or the return line or the pressure line is fed again.

Similarly, the locking of the Wegsimulatorgehäuses via a small piston with cylinder with hydraulic line to the valve block with connection to a standard solenoid valve. At the start of braking, the solenoid valve is turned on, so that the hydraulic line to the valve block / reservoir is interrupted and the piston acting on the Wegsimulatorgehäuse prevents further movement of the Wegsimulatorgehäuses upon actuation of the pedal plunger. In case of failure of the brake booster BKV or its drive, the lock is switched off or the solenoid valve is not energized, so that the hydraulic line is released to the reservoir, and the piston of the locking device can retreat due to the force acting on him from Wegsimulatorgehäuse force. With regard to costs the same applies as for the above-mentioned Leerwegschaltung. All components, such as. B. THZ, motor with drive, WS with housing, WS-lock, valve block ECU and sensors are advantageously combined in an integrated unit. However, the fluid reservoir SPK used for the path adjustment can also be used for the functions known from WO2009 / 083216. In the braking system known from WO2009 / 083217, a specific volume of about 5 bar is stored in the storage chamber, which is the brake circuit at a certain way the HZ piston or pressure is fed or returned. The advantage lies in particular in a brake system with displacement simulator in that a master cylinder can be used with a smaller diameter, whereby the required spindle forces and the required engine torque are smaller. Furthermore, this storage chamber can be used in the brake system according to WO2009 / 083216 for setting the brake clearance to eliminate the residual friction of the brake lining, which makes up about 300 W. For this purpose, the HZ piston is also controlled in a Wegsimulatorsystem according to WO2006 / 111392 and stored a small volume in the Speieherkämmer. Subsequent retraction of the pistons creates a negative pressure, which is measured via the pressure transducer. When negative pressure is reached, the subsequent piston movement is related to the movement of the brake piston. Preferably, the individual brake pistons are set in succession to clearance. For all the functions described above, the fluid reservoir SPK used for setting the idle travel can advantageously also be used.

In the brake system according to the invention, the fluid reservoir with its associated 2/2-way solenoid valve can thus be used for the following additional functions. These are listed below: a) Nachförderung of volume from the fluid reservoir SPK in the brake circuit in vehicles with large volume intake according to DE 10 2007062839.2 with the advantage of using a small HZ piston diameter with small operating forces. For this purpose, the SPK is pre-filled with a small volume before braking and is then further filled for the Leerwegf action. b) For the brake clearance control, a small volume is stored in the fluid reservoir according to WO2009 / 083216, in which initially the 2/2-way solenoid valve of the fluid reservoir opens and closes later. In the subsequent reset of the master cylinder piston can then be adjusted by means of negative pressure in the piston chambers successively the clearance of the brake piston, since also here the negative pressure acts to adjust the brake piston. For this purpose, in addition ever a shut-off valve between reservoir and master cylinder or tandem master cylinder THZ necessary so that is not sucked on the piston seal brake fluid.

There may be a pre-filling of the fluid reservoir during brake application. Since the Lüftspieleinstellung requires a small additional volume of fluid, this may be negative in the subsequent brake operation in the pedal travel may be noticeable. To avoid this, a corresponding small volume can be stored in the storage chamber by appropriate piston and switching valve control after the Lüftspieleinstellung. This is fed after the start of braking at a corresponding piston position after closing the Schnüffellochs in the master cylinder circuit.

With recuperative braking, the storage chamber is also used. Thus, in comparison to the normal braking the same pedal characteristic is given, a dependent of the generator braking torque brake pressure, which is determined by the brake management according to the braking effect predetermined by the driver. Here, a pressure control in the brake circuit with the involvement of the storage chambers, so that no contact of pedal plunger to HZ piston or connecting means takes place - preferably with a small free travel.

The storage chamber thus has a multiple function for the aforementioned functions. It is sufficient in principle a fluid reservoir in the primary circuit of the push rod piston. However, it is also possible to arrange a fluid reservoir with associated storage valve in the secondary circuit of the floating piston. The fluid reservoir used advantageously has a piston-cylinder system, wherein in particular a fluid storage actuator or at least one spring acts on the piston for its adjustment, wherein the spring pressurizes, in particular biases, the piston of the fluid reservoir. Thus, in one possible embodiment, the fluid in the brake line can only adjust the piston at a pressure which is greater than a preset or adjustable pressure and thus flow into the storage chamber of the fluid reservoir. At zero pressure in the brake circuit, the fluid reservoir can also be fully emptied via the storage valve.

The fluid reservoir can be completely or partially filled or emptied by means of adjusting the piston of the piston-cylinder system for the various aforementioned functions in cooperation with the pressure sensor and the valves and the piston drive with fluid.

For the prescribed functions, it is advantageous for the piston movement to use a switch which switches with the corresponding piston travel, or a displacement sensor for determining the piston position of the fluid reservoir. Also, a pressure sensor may be provided for determining the pressure in the fluid reservoir.

The size of the volume of Speieherkämmer the fluid reservoir can be advantageously adapted to the required for a μ-jump fluid volume.

The term brake booster used in connection with the brake system according to the invention is understood to mean that the control device of the brake system generates a required or required pressure change in the brake circuit or the wheel brakes by means of the drive of the master brake cylinder in cooperation with the wheel brake valves. An amplification of the foot force acting on the brake pedal does not take place, since, except in the normal case, a free travel between actuator and piston plunger is set / adjusted. Of course, in all possible embodiments, the control device of the brake system can also control the other brake assistance functions in addition to the ABS, ESP and recuperation functions.

Hereinafter, some possible embodiments of the brake system according to the invention will be explained in more detail with reference to drawings.

Show it:

Fig. 1: Structure of a first possible embodiment of the brake system according to the invention;

Fig. La: Structure of a second possible embodiment of the brake system according to the invention;

Fig. 2: Structure with extended functions;

Fig. 3: time course of the various functions for the

Control of the fluid reservoir SPK;

3a shows an alternative course of the various functions for the control of the fluid reservoir SPK;

Fig. 4: time course for adaptive Leerwegsteuerung.

1 shows the basic structure of the highly dynamic motor drive 2, which moves the piston 3 to the pressure change in the wheel brakes RB, each wheel brake RB is assigned a respective wheel brake valve 7, so that the brake pressure in the wheel brakes sequentially, ie in multiplex mode, can be adjusted , The drive 2 also adjusts the piston 3 for ABS / ESP function. To the electric motor 2 preferably with spindle drive 2a of the push rod piston 3 is preferably fixedly coupled, which acts in a tandem master cylinder 5 in a known manner hydraulically to the floating piston 4. In the brake lines BL 2/2-way wheel brake valves 7 are arranged, which together with the Brake booster enable the multiplex operation described in WO2006 / 111393. The brake pedal 1 acts on the pedal plunger la on a Wegsimulatorfeder 16, which is mounted in the WS housing 15. This is preferably mounted in the center of the housing 33 in the middle of the axle.

Of course, the electric motor drive can also be replaced by a piezo element drive.

This pedal ram la acts in case of failure of the drive or brake booster BKV directly to the piston plunger 25 for actuating the HZ pistons 3, 4. Between spindle 2a and piston plunger 25 is a coupling 26 which connects the spindle 2a with the piston 3 with an intact motor to allow rapid pressure build-up at low pressure. The Wegsimulatorfeder 16 is mounted in the Wegsimulatorgehäuse 15. The spindle reset via the spring 31. In Pedalstö ^¬ ßelkolben la, a damping element may be positioned 32 to a shock upon striking is reduced to the plunger 25th By appropriate speed control of the piston 3 when approaching the pedal plunger la, this can also be reduced, since both positions on the pedal travel sensor 11 and the rotation angle sensor 14 of the motor 2 are known.

The pedal travel is detected by the sensor 11 and the motor rotation via the sensor 14. The sensor 14 can be designed as an angle sensor, which also detects the piston travel. The motor drive 2 acts in a known manner via the spindle 2a on the piston 3. Instead of the spindle and other drives are conceivable, as described by way of example in WO2006 / 111392.

The pedal travel sensor 11 is used for BKV amplification or for pressure build-up and pressure reduction and is preferably redundant. The functions brake force boosting and pressure modulation are also described in detail in WO2006 / 111393 and WO2006 / 111392. What is new about the brake system according to the invention is that the fluid reservoir 20, comprising the piston 9 and the return spring 10, can be connected via the upstream solenoid valve 8 to the pressure line BL connecting the master cylinder 5 and the wheel brake valves 7. By means of the piston travel switch or sensor 24 and the central pressure sensor 12, the fluid reservoir 20 performs various functions. Not shown is a second optional fluid reservoir, which is designated in Fig. 2 with 20 ', so that an emptying of both brake circuits in the fluid reservoir 20, 20 ^{Λ is} possible.

The spring 10 biases the piston 9 to a value between 2 to 4 bar, in particular 3 bar before. Now takes the described greater pressure reduction in the fluid reservoir 20, 20 ^λ for the required free travel a, the storage valve opens 8 and at the same time one or more Radbremsventile 7, and the volume flows into the storage chamber of the fluid reservoir 20, 20 ^Λ . The chronological process will be explained in detail with reference to FIGS. 3 to 4. The emptying can be defined - as explained later - done via the storage valve 8. For the pressure modulation and fluid storage control a central pressure transducer 12 is a ^¬ built.

At the Wegsimulatorgehäuse 15 of the plunger 27a of the piston 27 is supported by a return spring 29. The piston 27 is guided in the cylinder 28 and connected via a feed line 30 with a 2/2 solenoid valve 13. This is switched on at the beginning of braking and thus locks the Wegsimulatorgehäuse. In case of failure of the motor 2, this is turned off, and the housing moves with the pedal ram la, which acts on the piston 3 to generate pressure. The output line of the solenoid valve 13 is connected to the reservoir 6 via the master cylinder 5. The cylinder 28 is small and simple and, together with the Wegsimulatorgehäuse with spring and pedal plunger with storage the structure simple, inexpensive, easy and cheap for assembly. The valve block contains the remaining components. The brake system according to the invention advantageously has only six Solenoid valve 7, 8, 13 and a fluid reservoir 20. In comparison, a conventional ESP system requires twelve solenoid valves, two fluid reservoirs and a pump.

In the starting position, the system already has a small free travel a ₀ between pedal plunger 1 a and piston plunger 25 or spindle 2 a. This is also shown in the temporal sequences of FIGS. 3, 3a and 4. This small Leerweg a ₀ is favorable for a small initial force in the pedal characteristic. In addition, when the pedal is pressed quickly, the pedal plunger does not strike the spindle directly.

FIG. 2 shows the structure with two fluid reservoirs 20, 20 'and an additional valve 8 ^X for the additional functions.

For the function of Nachförderung, as described in DE 10 2007062839.2, preferably two fluid reservoir 20, 20 ^λ low. According to the Nachfördervolumen of z. B. 2 cm ³ , the fluid reservoir 20, 20 ^Λ pre-filled before braking. The piston 9 is therefore in an intermediate position. For the empty ^¬ wegsteuerung a further volume uptake of about 3 - 4 cm ^{3 is} necessary. Accordingly, the fluid reservoir 20, 20 ^λ dimensioned or dimensioned from its volume. The return spring 10 is designed in this function to a pressure of 6 to 8 bar. For fast filling and emptying here solenoid valves 8, 8 are used ^Λ with a large valve cross-section. Preferably, a position switch or sensor 24 is used. For the function of the brake release control additional shut-off valves 18 and 19 may still be necessary.

In the supply lines ZL, which connect the reservoir 6 with the Tan ^¬ demhauptzylinder 5, a shut-off valve 18, 19 is arranged in each case. The shut-off occurs when the piston 3 for the brake clearance control generates a vacuum or a low pressure and thus a Nachschnüffeln from the reservoir is not possible. Alternatively, this can be done by appropriate piston be avoided seals and the tandem master cylinder THZ, so that the shut-off valves are not necessary.

Instead of the piston plunger 25, the power transmission can also take place on the shaft of the spindle 2a. Figures 3, 3a and 4 show the time course of vehicle speed v _F and wheel speed v _R , wheel pressure PR, piston s _K and pedal travel s _P with the various phases of brake pressure control and Leerwegsteuerung. At (0) is the beginning of braking and at (1) begins the first control cycle with pressure reduction in the fluid reservoir with corresponding movement of the piston s _K. When depressurization p _a i ⁿ the fluid reservoir 20, the piston movement of the piston 3 is zero, the Pedalweg s _P is delayed and later applies to the stationary piston 3. At time (3), when low pressure level is reached and the pressure reduction gradient by the fluid storage Filling is correspondingly small, the further pressure reduction via the piston movement s _{K of} the piston 3, 4 until the time (4). In this phase, a small pedal ^¬ repercussion, the fluid storage filling is interrupted. Subsequently, a fast piston movement of the piston 3,4 and a corresponding volume is conveyed into the fluid reservoir 20 with the wheel brake valves 7 closed. The piston stroke is chosen such that it is well above the locking position of the Pe ^¬ dalkolbens PA, at a distance a. Here, variable - also over time - piston speeds can be used. The pedal stroke follows here delayed to piston stroke s _K to Pe ^¬ dalstößelanschlag PA, ie when the pedal ram la impinges on the locked path simulator housing 15. At (5), the next pressure build-p _to be made. With a small delay t _v, the piston 3 to the stepped pressure build up P _on - In (6) of the next control cycle on the rapid piston movement starts without using the fluid reservoir 20. The pressure reduction times t _from or gradients are due to the large cross-sections of the solenoid valve 8, 8 "and the fast piston movement much faster than conventional systems, whereby the control deviation of Wheel speed is small, which is the goal of each scheme to achieve high stability and short braking distances.

3a shows an alternative _from the pressure reduction p. Here, the pressure reduction p _from i after the time (1) only by opening the switching valve 8 in the fluid reservoir 20 until the time (4a), as is the case with today's ABS / ESP systems, with the difference that the Fluid reservoir 20 is arranged in the primary circuit, and that 8 larger gradients are achieved in the higher pressure range due to the larger cross-sections of the fluid storage valve. Again, in (1) the piston 3 stops, and the pedal ram la is delayed on this or the Kol ^¬ plunger 25th Here, the phase of greater slippage ent ^¬ longer takes longer, so that at (5) again a pressure build-up with appropriate Piston and Pedalstößelbewegung follows, the latter now meets the catch PA. There is a renewed pressure reduction p _a b2 at (6) into the fluid reservoir 20. Only in the next control cycle at (9) of the piston 3 at a sufficient distance from the pedal plunger abutment PA, so that a rapid depressurization p _ab3 can be effected via the piston. 3 FIG. 4 shows a further alternative to depressurization control p _ab and idle travel control. Between the times (1) and (3) is again _from the pressure reduction p into the fluid reservoir 20. In the case (3) a pressure-holding phase by means of a closed wheel at the same time the fluid storage continues to fill, and will now be ^¬ brake valves 7, the flask well above the pedal plunger abutment PA is coming. Thereafter, at time (3a), a further pressure reduction p _{ab takes place} via the piston adjustment until the time (4). By this pressure reduction p _from the time duration of the larger wheel slip is greater, so that after the time (5) of the stepped pressure build-up _on p. Again, there is no pedal feedback. Previously, the piston 3 has a free travel of ai. In (6), the pressure reduction p _ab for the next control cycle via the quick piston adjustment to time (7). Here, the corresponding wheel brake valve 7 possibly closes with a short stop of the piston movement. The piston movement is continued with emptying of the fluid reservoir 20 until the time (8) with a free travel a ₂ . Here, the adaptive Leerwegsteuerung is shown, which allows both the distance to Pedalstößelanschlag PA and the pedal feedback controlled as desired. If the Leerwegabstand a too large, there is the disadvantage that in case of failure of the drive of the master cylinder, a large Pedalwegverlängerung arises. If, inter alia, during the ABS control, a small pedal effect desired, the free travel is a ge against zero ^¬ controls, so that the next pressure reduction, the piston 3 moves the pedal plunger la. The target distance a _will directed _off to the piston movement to reduce the pressure p. Upon reaching a Spei ^¬ cherkammerdrucks po of 8 - 10 bar, the further pressure reduction via the piston movement of the piston 3, in order to achieve a higher pressure gradient in the lower pressure range of about 0 - 1 bar. The corresponding volume, which must be promoted from the target pressure p ₀ down to 0 - 1 bar wheel cylinder pressure from the piston 3, corresponds to the maximum pedal reaction and applies to all cases where the piston position s is in front of the pedal stop PA. The pedal reaction can only be changed with a free travel a equal to zero by a piston movement or piston speed. Also, depending on the road surface, speed of the vehicle, outside temperature of the controller or the customer by appropriate programming, the described method for pressure control and pedal return according to the figures 3, 3a and 4 are selected. In conventional systems, the pressure reduction to p _min ~ 3 - 4 bar storage pressure is limited according to small pressure gradients, which is disadvantageous in particular ice and aqua-planing.

It should also be considered that, in the case of travel simulator systems, the piston travel s _{k is} greater than the pedal travel s _p , ie an idle travel a is predetermined. Thus, in a normal control in the high pressure range, a sufficient free travel exists, so that the control of the fluid reservoir is not necessary, except for a μ-jump, in which a large pressure change is necessary. The use of the fluid reservoir for pressure reduction or pressure build-up is mainly suitable for larger pressure changes in the ABS control and in particular at low friction coefficient, in which the distance from the piston to the pedal plunger is small. The solenoid valve should be designed with a large cross-section and with short switching times, in particular short closing time. At high flow rates, however, this leads to strong pressure oscillations. It is advantageous here, the solenoid valve 8 with a stroke control over z. B. PM, so here the closing operation is controlled by a corresponding change in cross section.

The fluid reservoir can be diagnosed on the volume displacement of the HZ-piston and the pressure transducer in both the opening pressure as well as on ^¬ acquisition volume or in the stored volume for the Nachförderung in the brake circuit. The same applies to the tightness and the valve cross-section of the switching valve 8. In this context, reference is made to the disclosure of DE 10 2007062839.

Figures 1 to 4 describe a hydraulic Leerwegf- reischaltung in which the free travel a, ie the distance from the piston to the pedal plunger is changed in dynamic operation by volume from one or both brake circuits via a 2/2 solenoid valve in a storage chamber 20, 20th 'is controlled. This is necessary with ABS function on low μ or recuperation, if the driver pushes the pedal plunger far and the piston 3 has to go back far enough for a low pressure level to be achieved. Changes z. B. the coefficient of friction from low to high, so this volume can advantageously be recycled back into the brake circuit. Must z. B. in a μ-jump, a large volume from the brake circuit in the Spei decorative chambers 20, 20 'are promoted, it takes place, as shown in Fig. 4 and described, the first P _from in the Spei more ebullient 20, 20'. This limits the filling pressure, z. B. 10 bar, the lowest pressure level. The further pressure reduction to near 0 bar, takes place in such a way that the DK piston 3 with closed switching valves 7 to the wheel further volume for Er- planning the desired free travel a in the Speiehe combs 20, 20 promotes'. This chronological course of the pressure reduction is, especially with respect to costs and volume of the storage chamber 20, 20 'not always meet all requirements It may therefore be useful in certain applications, the necessary volume for Leerwegsteuerung via a 2/3 solenoid valve directly in the fluid storage reservoir. 6 respectively. The missing volume can be sucked in and compensated for a positive μ-jump by appropriate piston and valve control, ie opening of the solenoid valve 8 in return movement of the DK piston and closed switching valves 7 to the wheel. The ability to aspirate additional volume can also be used to downsize the THZ.

For a faster pressure reduction is possible with even less effort.

The figure la is largely consistent with Figure 1 and describes the structure of such a further simplified embodiment.

The solenoid valve 8 is not connected here with the Spe icherkämmer, but with the return RL to the reservoir 6. The pedal stroke is measured via the pedal travel sensor 11 and the piston travel via the incremental encoder motor equals (=) the spindle stroke. Is now here in conjunction with a control signal ABS to P _from or recuperation determined by the braking effect of the generator that the free travel a is smaller or too small, so there is an opening of the solenoid valve 8 with simultaneous or staggered piston movement until the desired free travel reaches a is. Thereafter, the solenoid valve 8 is closed again, and the piston 3 follows the further control signals for pressure modulation for P _and _Pab. From the piston movement for Leerwegfreischaltung aware of a small pedal reaction can be generated to signal the driver in ABS the use of the scheme. In this case, for a short time during piston return movement of the free travel a = 0, by the piston force counteracts the pedal force. Subsequently, the Leerwegsteuerung described takes place. If a positive μ-jump occurs in the ABS control or if the generator braking torque is switched off, the solenoid valve 8 is opened for connection to the

Fluid storage with simultaneous closure of the switching valves 7 to the wheel brakes. Subsequently, the volume drawn out of the storage container is sucked in by short return movement of the DK piston. Thereafter follows, as described above, the normal piston control according to the control signals from the pedal travel sensor or ABS controller or brake management during recuperation.

A possible leakage of the solenoid valve 8 is at each braking by comparing pressure and piston position, d. H. Pressure volume curve, performed. The probability of failure of such a normally closed valve 8 is extremely rare.

In Figure la, the Leerwegsteuerung is described only for the DK circuit. According to FIG. 2, the storage chamber circle can also be included. The advantage is that the relation of the piston positions remains the same and the pressure reduction can be done quickly and simultaneously in both circuits, as well as the suction.

Preferably, the solenoid valve 8 is designed with a large cross section, so that the sucked volume per unit time is as high as possible. This dimensioning is easily possible because the valve only has to switch at lower pressures, which are relevant for the Leerwegfreischaltung.

It is also possible to turn on a source of pressure in the line to the reservoir to reduce the intake time.

The aspiration of additional volume can also be used to dimension the THZ preferably stroke smaller. If this volume is required for high pressures, it can be sucked in for a short time. When reducing the pressure on the return of the brake pedal, this additional volume can be replaced by appropriate Control of the solenoid valve 8 are returned to the reservoir. By allocating pressure and piston travel, this return of the volume can be monitored and, if necessary, corrected.

LIST OF REFERENCE NUMBERS

1 brake pedal

la Pedalstößel

2 motor drive

2a spindle

3 push rod piston DK

4 floating pistons

5 brake cylinders HZ

6 reservoir

7 wheel brake valves

8 solenoid valve for fluid storage

9 pistons

10 return spring

11 pedal travel sensor

12 pressure sensor

13 solenoid valve for locking piston 27th

14 Incremental encoder motor / angle sensor

15 travel simulator housing

16 way simulator spring

17

18 shut-off valve

19 shut-off valve

20 fluid storage / storage chamber

21

22 brake circuit

23

24 piston sensor

25 piston plunger

26 clutch

27 locking piston

27a plunger of the piston 27th

28 cylinders

29 return spring

30 hydraulic line

31 spindle return spring

32 damping element

33 Housing flange

BL brake line / pressure line

ZL supply line

RB wheel brake

RL return

v _R wheel speed

v _F vehicle speed

p _R wheel pressure

s _P pedal way

s _K piston stroke DK

Asp-red reduced pedal stroke with SPK

t _v delay time for pressure build-up

a distance piston to pedal plunger

t _from pressure reduction time

PA pedal ram lock

Po storage chamber pressure when switching to piston control

Claims

P a n t a n s p r e c h e

Brake system for a motor vehicle,

- Having a master cylinder (4, 5), which is driven by an electric drive, wherein a piston plunger (25) and / or a spindle (2a) with a piston (3) of the master cylinder (4, 5) is in operative connection,

Radbremsenventile (7) for selectively opening and closing the wheel brakes (RB) with the master cylinder (4, 5) connecting pressure lines (BL) comprising

an actuating device (1) having, in particular in the form of a brake pedal, which acts on a travel simulator (W),

- In case of failure, in particular in case of failure of the drive (2), the actuating device (1) mechanically, in particular with the pedal plunger (la), on the piston plunger (25) for pressure build-up in at least one wheel brake acts, and in normal operation, in particular a small free travel (a ₀ ) between the piston plunger (25) and the actuating device, in particular between the piston plunger (25) and the pedal plunger (la), consists,

a control device with brake-by-wire function having the drive (2) with piston (3) and the wheel brake valves (7) in particular for either simultaneous or successive pressure build-up and pressure reduction in the wheel brakes (RB) for the ABS , ESP, and / or recuperation function,

characterized in that the reservoir (6) or a fluid reservoir (20, 20 ') for adjusting the size of the free travel (a) is used. Brake system according to claim 1, characterized in that at least one wheel brake (RB) or at least one brake circuit is associated with a fluid reservoir (20, 20 ') whose storage chamber can be selectively connected to the pressure line (BL) via a switchable accumulator valve (8), wherein the pressure line (BL) connects a working space (Ai, A ₂ ) of the piston-cylinder system (5) and at least one wheel brake valve (7).

Brake system according to claim 1, since you rchgekennzeichnet that via a switchable storage valve (8) a pressure line (BL) with either the reservoir (6) or a return line (RL) to the reservoir (6) is connectable, wherein the pressure line (BL) a Working space (Ai, A ₂ ) of the piston-cylinder system (5) and at least one wheel brake valve (7) connects.

Brake system according to claim 1, since you rchgekennzeichnet that the control device with active ABS function, ESP function and / or recuperation function, the storage chamber of the fluid reservoir (20, 20 ') for supply and delivery of fluid from or into the brake circuit utilizes, wherein the free travel (a) increases in the absorption of fluid into the storage chamber and in the discharge of fluid in the brake circuit, the free travel (a) decreases.

Brake system according to claim 1, characterized in that the fluid reservoir (20, 20 ') is arranged in particular in the pressure piston circuit and the filling and emptying of the fluid reservoir (20, 20'), in particular also for adjusting a brake lining clearance in a wheel brake (RB) and for refilling the brake circuit with fluid, by means of the switching valves (7) and the storage valve (8) and by means of appropriate control of the piston drive (2). Brake system according to one of claims 1 to 5, since you rchgekennzeichnet that in the ABS, ESP and / or recuperation function of the pressure reduction in a wheel brake (RB) either

a) takes place solely by means of the respective wheel brake (RB) associated and opened storage valve (8) and the fluid from the brake circuit only in the fluid reservoir (20, 20 ') flows (Fig. 3a)

or

b) by in particular additional adjustment of the piston (3,

4) of the piston-cylinder system (5) in the lower pressure range, in particular at a pressure of less than 10 bar, while the storage valve (8) is closed at the same time (FIG. 3),

or

c) by sole adjustment of the piston (3, 4) of the piston-cylinder system (5) at the same time closed storage valve (8) takes place (Fig. 3, time (6), or

d) by filling the fluid reservoir (20, 20 ') in the first stage and then in a second stage by the piston movement of the master cylinder (4, 5) a further pressure reduction takes place, wherein between the first stage and the second stage an interruption of Pressure reduction P _ab takes place, during which the fluid reservoir (20, 20 ') is further filled, so that the free travel (a) is increased.

Braking system according to one of the preceding claims, characterized in that a

Pressure sensor, the fluid pressure in Speieherkämmer the fluid reservoir, in particular for pressure control and diagnosis, or in a brake circuit or a sensor (24) determines the piston displacement of the piston of the fluid reservoir (20, 20 '). Braking system according to one of the preceding claims, characterized in that the

Control device for the adjustment of the piston (3, 4) of the piston-cylinder system (5) takes into account the pressure-volume characteristics of the individual wheel brakes (RB), and in particular determines these.

Braking system according to one of the preceding claims, characterized in that the

Control means by means of the piston drive (2) einregelt or -steuert a variable pressure gradient in the brake circuit or the piston speed to Pedalrückwirkung.

Brake system according to one of the preceding claims, characterized in that the travel simulator housing (15) is supported on a piston (27) of a piston-cylinder system (27, 28, 29), and the working space of the piston-cylinder system (27, 28, 29) by means of a in particular arranged in or on the valve block, shut-off valve (13) for locking the Wegsimulatorgehäuses (15) can be shut off.

Master cylinder (4, 5), the drive (2), in particular coaxial with the master cylinder (4, 5) arranged displacement simulator (W), the Wegsimulatorgehäuse (15) arresting piston-cylinder system (27, 28, 29), together with all switching valves , Storage chamber are combined with sensors and pressure transducer in the valve block as a unit.

Method for operating a brake system according to one of the preceding claims, characterized in that the fluid reservoir (20, 20 ') is filled with appropriate activation of the switching valves (7) and the storage valve (8) and the fluid volume stored in the fluid reservoir (20, 20') at the beginning of braking in the Brake circuit is fed, in particular, the Schnüffelloch or the sniffer holes of the master cylinder (5) by the or the piston (3, 4) is closed or are.

Method for operating a brake system according to one of the preceding claims, characterized in that the brake system is arranged in a vehicle with full or partial electric drive, wherein the pedal characteristic of force and travel of the brake pedal while acting on a generator braking torque (recuperation) by filling the fluid reservoir (20, 20 ') or the reservoir (6) and the variable gain via the drive (2) is determined.

Method for operating a brake system according to one of the preceding claims, since you rchgekennzeichnet that in recuperative braking or similar brake-by-wire function to achieve an optimal pedal characteristic of the brake management certain pressure by filling the fluid reservoir (20, 20 ') or deflation of fluid in the reservoir (6) and pressure control in the brake circuit, so that a certain free travel (a) is formed.

Method for operating a brake system according to one of the preceding claims, characterized in that the Wegsimulatorgehäuse (15) at each braking by closing the shut-off valve (13) is locked and in case of failure, the shut-off valve (13) remains open.

Method for operating a brake system according to one of the preceding claims, characterized in that the adjustment of the free travel (a) is variable and adaptive, wherein a free travel a equal to zero causes a reaction of the piston plunger (25) on the actuating device (1). Method for operating a brake system according to one of the preceding claims, since you rchgekennzeichnet that the solenoid valve (8) has a large valve cross section, wherein by means of a stroke control of the valve (8), in particular by means of PWM method, the closing characteristic of the valve (8) It can be influenced that no excessive pressure oscillations occur in the brake circuit.

Method for operating a brake system, comprising an actuating device, a master brake cylinder with reservoir and at least one wheel brake and associated wheel brake valve, wherein in normal operation, a free travel between the actuator and a piston of the master cylinder is provided, in particular according to one of the preceding claims, since you rchgekennzeichnet, that provided for Leerwegsteuerung liquid volume via a solenoid valve from the at least one wheel brake directly or via the master cylinder to the reservoir or the fluid reservoir is supplied.