DE102009043484B4

DE102009043484B4 - Braking system for a hybrid vehicle and method of its operation

Info

Publication number: DE102009043484B4
Application number: DE102009043484.4A
Authority: DE
Inventors: Heinz Leiber; Dr. Leiber Thomas; Christian Köglsperger; Valentin Unterfrauner
Original assignee: Ipgate AG
Current assignee: Ipgate AG
Priority date: 2009-09-30
Filing date: 2009-09-30
Publication date: 2018-05-03
Anticipated expiration: 2029-10-01
Also published as: DE102009043484A1

Abstract

Braking system for a hybrid vehicle with a control device and a brake pedal (1), which acts to brake pressure generation mechanically on a piston (3) of a piston-cylinder system, wherein the power assisting the brake pedal (1) actuated person additionally an electric drive to the piston (3) of the piston-cylinder system acts, and the pressure build-up in wheel brakes (RB) by adjusting the piston (3), and each wheel brake (RB) or each brake circuit is assigned at least one switching valve (7) which is to hold pressure in the associated wheel brake (s) (RB) closed and the change in pressure in the or the associated wheel brake (s) (RB) is open, wherein the control device, the drive (2) in dependence of the person or by a Brake controller predetermined master cylinder pressure or wheel brake pressure for controlling a piston position and a driving force controls, wherein at least one wheel brake (RB) or at least one m brake circuit, a fluid reservoir (20, 20 ') is assigned, the storage chamber via a switchable accumulator valve (8) with a pressure line (BL) of the wheel brake (RB) or the brake circuit is selectively connectable, wherein in the ABS function of the fluid reservoir ( 20, 20 ') during the pressure reduction in a wheel brake (RB) optionally for receiving fluid from this wheel brake or the associated brake circuit, characterized in that the brake pedal (1) for brake pressure generation mechanically via an elastic member (15) on the piston (3 ) of the piston-cylinder system, and wherein a force feedback to the brake pedal (1) upon action of a generator braking torque of an electric drive of the hybrid vehicle by adjusting the piston (3) by means of the drive while simultaneously filling the fluid reservoir (20, 20 ') is adjusted ,

Description

State of the art
In cars, so-called auxiliary power systems with closed brake circuits are used almost exclusively. The exception is the electrohydraulic brake system EHB, in which the brake circuit is opened to reduce the pressure for the ABS / ESP function. If the pressure supply fails, the brake circuit is also closed in the EHB system. For the usual systems with brake vacuum booster, with tandem master cylinder THZ and separate hydraulic unit, a storage chamber SPK is used for ABS / ESP in the low-pressure circuit.
In Reimpell suspension technology, wheel slip systems, Vogel Business Media Verlag, 1993, p 285, an ABS system with a low-pressure accumulator, the so-called storage chamber SPK, between exhaust valve and pump is described. The storage chamber is thus switched on in the suction line of the pump. In this system, a check valve is additionally provided. The storage chamber is advantageous for a rapid pressure reduction from the wheel brake cylinder, especially when the pressure drop is high. At a small pressure gradient, z. B. on ice with a blocking pressure of about 10 bar and a storage chamber pressure of 5 bar, this is no longer the case. The volume drained into the storage chamber is pumped back into the master cylinder by the pump.
The 2003 brake manual shows on p. 78 the entire hydraulic ESP system. Again, the storage chamber is installed in the pump circuit between exhaust valve and pump, and thus also in the low pressure circuit in the suction line. Between the pump and the master cylinder HZ a pilot valve is arranged, which is necessary when for ASR or ESP function, the pump from the master cylinder volume to brake pressure build-up in the wheel cylinder sucks without the brake pedal is actuated. The function of the storage chamber is equivalent to the ABS. It is used for each brake circuit, a storage chamber.
An additional storage chamber is used in braking systems for hybrid vehicles. Here, this storage chamber is arranged in the primary circuit between HZ and ABS control valves and takes up the volume of the master cylinder in the phase in which the braking torque of the generator during recuperation is large and no or only low brake pressure is allowed. Since the pedal characteristic (distance and force) for normal braking without generator should be the same or similar, this storage chamber acts together with a so-called fluidic pedal force simulation, as shown in the DE 10 2008 005 145 A1 is known. This pedal force simulation and storage chamber are fixed to a value of path and counterforce course. Further solutions with storage chambers are from the WO2009 / 083217 A2 and WO2009 / 083216 A2 known. In the from the WO2009 / 083217 A2 known brake system is stored in the storage chamber a certain volume of about 5 bar, which is fed to the brake circuit at a certain path of the HZ-piston or pressure or fed back. 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 is smaller. This storage chamber is in the brake system according to WO2009 / 083216 A2 used for setting the brake clearance, to eliminate the residual friction of the brake lining, which is about 300 W. This is also in a Wegsimulatorsystem after WO2006 / 111392 A1 , The generic state of the art, the HZ piston controlled and stored a small volume in the storage chamber. During the subsequent retraction of the piston creates a negative pressure, which is measured via the pressure transducer. When negative pressure is reached, the subsequent piston movement is in relation to the movement of the brake piston. Preferably, the individual brake pistons are set in succession to clearance.
The described applications of low-pressure storage chambers are either for conventional brake systems with separate brake booster with tandem master cylinder and pressure modulation with the described return pump or a braking system with displacement simulator, in the pedal movement and HZ piston movement are unequal and are equal only in case of failure of the brake booster.
Out DE 10 2006 055 766 A1 is a vacuum brake booster known.
Starting from the WO 2006/111 392 A1 It is an object of the present invention to provide an improved braking system for use in a hybrid vehicle.
The object is achieved by the braking system of the independent claim 1 and by the method according to claims 14 to 17.
Further advantageous embodiments will be apparent from the dependent claims.
The invention is advantageously characterized in that a storage chamber in the form of a fluid reservoir is provided, wherein the Storage chamber via a switchable accumulator valve with the brake circuit or the pressure line to the wheel brake is connectable and the fluid from the brake circuit or the pressure line can flow into the storage chamber. If the pressure reduction, especially with rapid pressure changes, would take place solely via the HZ or THZ pistons of the piston-cylinder system, this would possibly lead to rapid and large and thus disturbing pedal movements due to the reaction of the piston to the brake pedal. The brake system according to the invention advantageously has a highly dynamic electric motor, which moves via a transmission or directly the push rod piston of the THZ and thus does the function of the BKV and allows the pressure modulation for ABS / ESP together with the switching valves in the MUX process. With the brake system according to the invention very rapid pressure change are possible, which is necessary for the MUX method, since usually the wheel brakes are operated one behind the other.
In the ABS and / or ESP function, the pressure reduction in a wheel brake can take place either solely by means of the respective wheel brake associated and open storage valve, wherein the fluid from the brake circuit flows only in the fluid reservoir. However, the control device can make the pressure reduction by adjusting the piston of the piston-cylinder system and the fluid reservoir under appropriate conditions. In this case, e.g. first the pressure reduction via the fluid reservoir and subsequently or the remaining pressure reduction via the piston adjustment done. Depending on the type of braking process, however, the pressure reduction in ABS / ESP can also be achieved solely by adjusting the piston of the piston-cylinder system via the drive.
The high dynamics result in a correspondingly fast pedal return effect during pressure reduction, which is disturbing if larger pressure changes occur during rapid braking or in the event of a μ-jump, which necessitate a large pedal travel change. The solution according to the invention is the use of one fluid reservoir per brake circuit, but preferably only one fluid reservoir for both brake circuits in the primary circuit together with a pressure transducer between the DK piston and the two 2/2-way switching valves, which are used in the connecting line to the wheel brake , The fluid reservoir is advantageously combined with a 2/2-way solenoid valve, i. H. Filling and emptying are controlled. If, in special cases, a higher pressure change is necessary, part of the brake fluid volume of the wheel cylinder or cylinders is introduced into the fluid reservoir when the valve is open. The rest of the pressure reduction can be done by appropriate piston movement with appropriate pedal reaction. This pedal reaction can hereby be controlled within certain limits by the storage chamber of the fluid reservoir is proportionally turned on for the pressure reduction. Find z. B. now during the scheme small Reibwertsprünge z. B. water puddles or winter typically between snow and ice instead, so the pedal reaction is not so violent. Also, the piston speed for depressurization, i. Pedal reaction speed, can be varied by the engine. In particular, this method is particularly clear in a negative μ-jump, in which even in today's system a strong pedal reaction is felt, since the return pump must empty the full storage chamber quickly for further pressure reduction cycles. Here, the pedal feedback can be made much smaller than at o. G. conventional systems according to the prior art.
When adjusting the piston of the piston-cylinder system for changing the pressure and / or the rate of pressure change in one or more wheel brakes, the pressure-volume characteristics of the individual wheel brakes are advantageously taken into account.
During continuous control, the volume stored in the fluid reservoir is gradually returned to the master cylinder in small amounts as the master cylinder pressure under the MUX pressure modulation comes under the accumulator pressure. In this case, the 2/2-way solenoid valve is briefly opened to feed a small volume into the master cylinder circuit. In borderline cases, such as negative and then positive μ-jump, the stored volume can be returned by appropriate piston control back into the master cylinder circuit, so that the brake pedal can come back into the pressure-proportional pedal position.
In addition, the fluid reservoir can be emptied in phases of large wheel slip and closed switching valves on the piston movement by means of the drive.
In the described prior art, the storage chamber or the fluid storage is arranged in the low-pressure absorption circuit of the pump, the emptying is also determined by the pump and can not be variably controlled.

a) Die Pedalsteuerung und Kraftrückwirkung bei Hybridfahrzeugen und rekuperativer Bremsung kann mit dem elektromotorischen Antrieb des Kolbens des Kolben-Zylinder-Systems zusammen mit dem Fluidspeicher erfolgen. Hierzu ist eine fluidische Pedalkraftgegensimulation nicht notwendig. Der elektromotorische Bremskraftverstärker kann dabei vorteilhaft beliebig in der Bremskraftverstärkung auch mit umgekehrter Wirkung gegen die Pedalkraft wirken. Der Pedalweg ohne hydraulische Bremswirkung ist durch Einspeisung des Hauptzylinder-Volumens in den Fluidspeicher in weiten Grenzen möglich. Die elektrische Verstärkung ist voll variabel und richtet sich nach der gewollten Abbremsung und dem verfügbaren Generatorbremsmoment sowie den Reibungs- und Rückstellkräften der Kolben und des Antriebs.
b) Für die Bremslüftspielsteuerung wird entsprechend der WO2009/083216 A2 ein kleines Volumen im Fluidspeicher gespeichert, bei dem zunächst das 2/2-Wege-Magnetventil des Fluidspeichers öffnet und später schließt. Bei der anschließenden Rückstellung des Hauptzylinder-Kolbens kann dann über Unterdruck in den Kolbenkammern nacheinander das Lüftspiel der Bremskolben eingestellt werden, da auch hier der Unterdruck zur Verstellung der Bremskolben wirkt. Hierzu sind zusätzlich je ein Absperrventil zwischen Vorratsbehälter und Hauptzylinder bzw. Tandem-Hauptzylinder THZ notwendig, damit nicht über die Kolbendichtung Bremsflüssigkeit angesaugt wird.
c) Es kann eine Vorfüllung des Fluidspeichers bei Bremsbetätigung erfolgen. Da die Lüftspieleinstellung ein kleines Zusatzvolumen an Fluid erfordert, kann sich dies unter Umständen negativ bei der anschließenden Bremsbetätigung im Pedalweg bemerkbar macht. Um dies zu vermeiden, kann nach der Lüftspieleinstellung ein entsprechendes kleines Volumen in der Speicherkammer durch entsprechende Kolben und Schaltventil-Steuerung abgespeichert werden. Dieses wird nach Bremsbeginn bei einer entsprechenden Kolbenstellung nach Schließen des Schnüffellochs in den Hauptzylinder-Kreis eingespeist.

In the brake system according to the invention, the fluid reservoir can be used with its associated 2/2-way solenoid valve for all the additional functions described above. These are listed below:

a) The pedal control and force feedback in hybrid vehicles and recuperative braking can be done with the electromotive drive of the piston of the piston-cylinder system together with the fluid reservoir. For this purpose, a fluidic pedal force simulation is not necessary. The electromotive brake booster can advantageously act arbitrarily in the brake booster with the reverse effect against the pedal force. The pedal travel without hydraulic braking effect is possible by feeding the master cylinder volume into the fluid reservoir within wide limits. The electrical gain is fully variable and depends on the desired deceleration and the available generator braking torque and the friction and restoring forces of the piston and the drive.
b) For the brake clearance control is according to the WO2009 / 083216 A2 a small volume stored in the fluid reservoir, in which initially opens the 2/2-way solenoid valve of the fluid reservoir and closes later. In the subsequent return of the master cylinder piston can then be adjusted by vacuum in the piston chambers successively the clearance of the brake piston, since the negative pressure for adjusting the brake piston acts also here. 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.
c) 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 negatively noticeable in the subsequent braking operation in the pedal travel noticeable. To avoid this, a corresponding small volume in the storage chamber can be stored 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.

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 drive or at least one spring acts on the piston for its adjustment, wherein the spring pressurizes the piston of the fluid reservoir, in particular biases. 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 above-described functions, it is advantageous for the piston movement to use a switch which switches with a 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 the storage chamber of the fluid reservoir can advantageously be adapted to the volume of fluid required for a μ jump.

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

1: Aufbau des erfindungsgemäßen Bremssystems;
2: typischer Verlauf der ABS-Regelung mit den wichtigsten Daten der Regelung;
3: zeitlicher Verlauf des Druckabbaus im Fluidspeicher;
3a: zeitlicher Verlauf der Entleerung des Fluidspeichers;
4: Grenzfälle der ABS-Regelung;
5: Funktion des Bremskraftverstärkers M_B = f(Sp)
5a: Funktion des Bremskraftverstärkers mit Einwirkung der Generatorbremswirkung.

Show it:

1 : Structure of the brake system according to the invention;
2 : typical course of the ABS control with the main data of the control;
3 : time course of the pressure reduction in the fluid reservoir;
3a : time course of the emptying of the fluid reservoir;
4 : Borderline cases of ABS regulation;
5 : Function of the brake booster M _B = f (Sp)
5a : Function of the brake booster with the effect of the generator braking effect.

The 1 shows the basic structure of the system with electric brake booster, which may have a highly dynamic electric motor. Are also conceivable not drawn piezoelectric actuators, which z. B. move a piston per brake circuit with two switching valves in the MUX process, and control the pressure change for the brake booster and the ABS / ESP function. To the electric motor with preferably spindle drive 2a is the push rod piston 3 firmly coupled, which in the tandem master cylinder 5 in a known manner hydraulically on the piston 4 acts. In the brake lines 22 are 2/2-way switching valves. 7 arranged, which together with the brake booster the in WO2006 / 111393 A1 allow described multiplex operation. The brake pedal 1 acts on the pedal ram 1a on an elastic member 15 , The pedal travel is from the sensor 13 and the motor rotation across the sensor 14 detected. The sensor 14 can be designed as an angle sensor, which also detects the piston stroke. The motor drive 2 acts in a known manner on the spindle 2a on the piston 3 , Instead of the spindle, other drives are conceivable, as exemplified in WO2006 / 111392 A1 are described. The elastic member 15 can serve both the damping in the pressure modulation and the damping of the pedal reaction in ABS, as well as in the Differenzwegauswertung between pedal travel sensor 13 and piston stroke sensor 14 used for BKV amplification, as in the WO 2010/017 998 A1 is described. The functions brake booster and pressure modulation are also detailed in the WO2006 / 111393 A1 and WO2006 / 111392 A1 described. What is new in the brake system according to the invention is that the fluid reservoir 20 with pistons 9 , Return spring 10 and piston path switch or sensor 24 directly in the master cylinder with the switching valves 7 connecting pressure line BL is arranged together with a central pressure sensor.

Dashed is a second optional fluid reservoir 20 ' shown, with the emptying of both brake circuits in the fluid storage is possible.

The feather 10 tenses the piston 9 to a value between 2 to 4 bar, in particular 3 bar, before. If now the described greater pressure reduction, so opens the storage valve 8th and at the same time one or more switching valves 7 and the volume flows into the storage chamber of the fluid reservoir 20 , In detail, the temporal process is based on the 2 - 5a explained. The emptying can be defined - as explained later - via the storage valve 8th take place, alternatively also via the check valve 16 with throttle when the master cylinder pressure is lower than the fluid storage pressure. For the pressure modulation and also fluid storage control is a central pressure transmitter 12 built-in. Instead of a central fluid reservoir 20 It is also possible to install a second SPK in the SPK circuit.

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

The 2 shows a typical course of the ABS control with the most important data of the control for the control cycles ① to ⑤. When braking begins, the pressure builds up quickly, which already triggers a regulator signal to reduce pressure at P1. The controller determines z. B. the amount of pressure reduction, which corresponds directly via the elastic member with the pedal reaction. If this determined value is above a limit value, then the storage _valve will become active over the time .DELTA.t _MV8 8th for partial filling of the fluid reservoir 20 turned on, what in detail based on 3 is described. The master cylinder pressure drops even further, so that at P2 the pressure reduction is completed. The curve Sp (t) shows the pedal travel over time. Without fluid storage 20 would be the pedal travel Δs _P , with fluid storage 20 the result is Δs _P-red . The proportion of pedal travel can be limited by appropriate control of the storage valve 8th be varied. Subsequently, in the cycle ①, the known pressure build-up begins, which leads to a renewed pressure reduction in the cycle ②. Here, the pressure reduction is small, so that the storage chamber is turned on only when the pressure in the master cylinder HZ under the pressure of the fluid reservoir 20 lies. Over a short time a small volume is let into the master cylinder. In this case, the storage chamber is emptied by Δss with corresponding effect in the pedal reaction by Δs _P. In the subsequent control cycle ③ this emptying repeats itself. In cycle ④, a greater pressure reduction is necessary again, which again activates the storage valve 8th conditioned over the time .DELTA.t _MV8 . The cycle ⑤ is normal again as with ② and ③, since only a small pressure reduction takes place without the filling of the fluid reservoir 20 , ie solely by the piston adjustment takes place. Through the small fluid storage emptying can in the course of the scheme, the entire fluid reservoir 20 be emptied, the emptying process essentially of the degree of filling of the fluid reservoir 20 and the duration of the entire ABS control is dependent.

The 3 shows the time course of the pressure reduction P in the wheel brake RB by means of the fluid reservoir 20 and the piston adjustment of the piston 3 , In addition, the path s _s (t) of the piston of the fluid reservoir 20 shown. At time ①, the pressure reduction command is issued by the controller and the storage valve simultaneously becomes 8th and the switching valve 7 activated, ie switched to the open position. After the delay time t _{vMV / M} is now via the storage _valve 8th the pressure reduction over the time .DELTA.t _MV8 . At time ②, the accumulator valve closes 8th , This can be followed by a brief pressure maintenance phase, which serves to evaluate the pressure level. The controller compares the pressure difference ΔP _MV with the setpoint Δp. After a small time difference of Δt to ② again the engine and thus the piston adjustment by means of Drive done so that after Δp _K, the setpoint at ④ is reached. In the phase Δt _{MV8 the fluid reservoir} fills 20 , In some cases, the entire pressure reduction can be done by Δt _MV8 , especially in the higher pressure range. In the small pressure range limits the filling pressure of the fluid reservoir 20 From approx. 2 - 5 bar the pressure reduction, so that here the piston adjustment by means of drive is unavoidable. As is known, a pressure control over the timing of the solenoid valves is inaccurate. The system has z. B. applied at startup a map of the pressure volume or determined, ie Druckvolumenwegkennlinien the entire brake and each wheel were recorded, after which the pressure control via the piston adjustment, ie a quotient .DELTA.V / bar is 100 to 1 bar for the entire control range , On this basis, another map for the wheel brakes .DELTA.p = f (.DELTA.T, p _o ) can then be applied, so that the pressure control of either one wheel up to four wheels is simultaneously possible and accurate.

The 3a shows the temporal process of the fluid storage emptying. After ① preferably simultaneous control of solenoid valve occurs 7 and the drive motor and time-offset of the storage valve 8th , The pressure reduction via piston adjustment without fluid storage filling S _k is initiated when smaller Δp are required by the controller. The dot-dash line of the master cylinder pressure in the primary circuit of the piston 3 falls below the pressure level of the storage chamber in particular at low blocking pressure level of p ₀ . At ② the value falls below P _HZ the filling pressure P _{S of} the fluid reservoir 20 , Here opens the switching valve 7 and a selectable small volume is taken over by the fluid storage drain Δs _s in the primary circuit. As based on the 2 already described, this is repeated at small Δp values until the fluid reservoir 20 is empty. Also for this timing of the storage valve 8th a map ΔS = f (ΔT, p _S ) can be applied.

The 4 shows borderline cases of the ABS control: the so-called μ-jump from high to low and back to high. Shown is similar 2 the course of v _R , v _F , p _R , s _P and ss. At time ①, the control starts as in the 2 and 3 described. At time ③, the μ jump occurs with a large pressure change Δp. As in 3 described, the pressure reduction takes place in stages.

The storage chamber stroke of the fluid reservoir .DELTA.ss is correspondingly large, yet there is only a relatively small pedal movement of .DELTA.s _P- red. This is considerably smaller compared to the dashed curve of p. To reduce the pedal backlash, the rate of change of pressure and thus also the rate of pedal change can be reduced at ③a. This can also be applied in the entire control range, in particular if the pressure change predetermined by the regulator is small. After the pressure has been reduced, the wheel speed accelerates again into the smaller slip range, so that at ④ the next control cycle already starts at low μ. At ⑤ the positive μ-jump now takes place, which can be detected by correspondingly high wheel acceleration. Immediately follows a larger pressure build-up + Δp. So that subsequently a further necessary pressure build-up does not lead to large pedal paths, the fluid reservoir is emptied between ⑤ and ⑥ by appropriate piston control until the pressure level is reached again at ⑥ in order to start the control cycles at high μ.

As an alternative or in addition to this emptying, the fluid reservoir emptying can also take place earlier, for example according to .about.a, as indicated by dashed lines, at .mu., In particular if the switching valves are replaced by higher slip 7 are closed. The emptying can also be realized stepped to optimize the pedal reaction in any time function. The emptying takes place in cooperation of the piston control, control of the switching valves and the storage valve.

With this solution, a significant improvement in pedal performance compared to today's ABS / ESP is possible. The disturbing pedal bumps in rain puddles, ice sheets are significantly reduced.

Below is now another second function "pad clearance adjustment with negative pressure" by means of the fluid reservoir, as it is known from WO2009 / 083216 A2 is known described. As is known, a friction power of 300 W ≈ 8 g CO _{2 is} connected by the slightly applied brake linings. With the braking system according to the invention, this can be improved in a simple manner. When the braking operation is completed, the sequence of the clearance adjustment follows when the driver preferably depresses the accelerator pedal and is at a speed higher than 10 km / h.

At the beginning of the pad clearance adjustment, the piston becomes 3 over the motor drive 2 drove up to a small path or volume. This is dimensioned so that when subsequently moving back the piston 3 and 4 the negative pressure for Lüftspieleinstellung all brake pistons is possible. With the valve open 8th then become the fluid storage 20 . 20 ' filled accordingly. Subsequently, the storage valves 8th closed. After closing the storage valves 8th becomes one of the switching valves 7 open. The piston 3 , which is still in the extended position, is withdrawn by the motor spindle drive a bit towards the starting position. This creates negative pressure, which is over the brake lines 22 on the wheel brake RB with the brake piston transmits, the switching valve 7 is open. Now the remaining three wheel brakes RB retracted by sequentially opening the respective control valves. The travel of the piston 3 is proportional to the travel of the brake piston via the area ratio with the brake piston. In this phase, the negative pressure on the pressure transducer 12 evaluated, so that only under a pressure level or temporal pressure curve, the piston movement is evaluated. By temporal pressure curve is meant that when the negative pressure on the piston friction is constant, this is equivalent to a movement of the brake piston. Finally, the storage valves 8th opened again. Thus, the negative pressure in the tandem master cylinder THZ is canceled. Task of the shut-off valves 18 it is to prevent that during the negative pressure phase in the THZ brake fluid from the reservoir via the THZ seals in the working spaces A ₁ and A _{2 of} the THZ passes. It is also possible to use all brake pistons of the wheel brakes RB retract at the same time by all switching valves in the negative pressure phase 7 be opened.

Another third function "pre-filling or subsequent delivery" can also be realized by means of the fluid reservoir. The clearance adjustment described above causes a small stroke of the brake piston, which means a small pedal travel extension. This can be eliminated by prefilling the fluid reservoir after completion of the second function. For this purpose, if the driver does not brake, the piston 3 over the motor drive 2 similar to the second function briefly moved over a small way or up to a certain pressure, but with closed switching valves 7 , After the appropriate volume in the fluid reservoir 20 is fed, there is a closing of the storage valve 8th and a retraction of the piston 3 in the starting position. During the following braking, this volume is removed from the fluid reservoir 20 into the brake circuits by switching the storage valve 8th fed when the pistons 3 and 4 have run over the sniffer hole. This method can, for. B. be extended to use smaller HZ diameter and to reduce the burden of the entire drive. For this purpose, a larger volume in the fluid reservoir 20 stored and preferably promoted at a larger pedal stroke by appropriate piston control in the brake circuits. This is preferably done with a larger pedal travel, possibly also in stages. For the second and third functions, it is advantageous to have a piston travel switch or sensor 24 which is also useful for diagnosis, e.g. B. Kennfeldeinstellung.

The fourth possible function "Pedal Characteristics in Hybrid Vehicle" will be described below. As is known, the same pedal characteristic with respect to pedal travel and pedal force both during normal braking and with additional braking action of the generator, z. B. in recuperation, desired. In the DE 102008005145 A1 is a solution with storage chamber in conjunction with a fluidic pedal force Gegensimulationseinrichtung with fixed adjustment of force and way described. This solution is complex and not variable for strongly fluctuating generator braking torque, in each case to achieve the same pedal characteristics as the normal brake. For example, a pedal travel or piston travel sensor is also missing here. A pressure transducer is arranged, for example, in the floating piston circuit without detailed description of the function and not in the primary circuit of the push rod piston, where a storage chamber with solenoid valve and a storage chamber without sensor is provided to achieve a pedal travel and a pedal force without recuperative braking effect of the hydraulic brake. Parallel pressure medium is controlled in the pedal force Gegensimulationseinrichtung and storage chamber, so that a similar Pedalwegcharakteristik is achieved as without generator braking effect.

In the inventive solution, the counterforce counter-simulation via the electric drive is fully variable in cooperation with the controllable fluid reservoir 20 together with the measurement of the pressure in the primary circuit as well as the pedal travel.

The 5 describes the function of the normal brake M _B = f (s _P ) with pedal force and piston force, which is applied by the electric drive in addition to the pedal force. The ratio F _K / F _P gives the reinforcement.

The 5a shows in a simple representation of the function with the effect of the generator braking effect M _G , The driver operates the brake, in which a generator braking effect M _G is retrieved according to the desired deceleration. With increasing braking torque M _B (Deceleration) increases the driver controlled by the pedal force and the pedal travel M _B at. The braking torque M _B of the hydraulic brake is effective only after ①. Here, the desired deceleration is greater than the generator braking torque M _G , so that now by closing the accumulator valve, the pressure in the brake circuit is built up and a hydraulic braking torque M _P caused by the brake pressure. In this phase, up to ①, the usual pedal travel and the usual pedal force are created by means of the fluid reservoir 20 and the variable gain of the electric drive. Because this force of the electric drive is not on the piston 3 may act with corresponding counterforce, the volume displacement s _s takes place in the fluid reservoir 20 , The motor force F _M is generated here by the electric drive, which in the first phase up to ① partly has a correspondingly weaker boosting effect on the pedal force than without a generator braking effect M _G , Only from ① does F _{M have a} strong boosting effect with higher deceleration. Here, from ①, this also works in accordance with the higher deceleration M _P from the pressure in the wheel brakes. In special cases, the power from the electric drive can also act against the pedal force. The dotted lines show the force of the electric drive via the pedal travel with and without generator braking effect M _G ,

In the present example is M _G constant, but may in practice increase over the period of In this case, not shown, pressure has to be reduced from the wheel brakes by feeding corresponding volume into the fluid reservoir. For this purpose, in addition to the correspondingly controlled piston movement of the piston 3 . 4 a pressure measurement via the pressure sensor 11 necessary. The different conditions for the hybrid vehicle with a good brake dosage require a variable pedal force simulation, which is possible with a highly dynamic electric drive.

These possible functions of high complexity can be achieved with a highly dynamic electric drive with little effort by means of a storage valve 8th and the fluid reservoir 20 will be realized.

LIST OF REFERENCE NUMBERS

11: Bremspedalbrake pedal
1a1a: Pedalstößelpedal tappet
22: Motorantriebmotor drive
2a2a: Spindelspindle
33: Kolbenpiston
44: Kolbenpiston
55: TandemhauptzylinderTandem master cylinder
66: Vorratsbehälterreservoir
77: Schaltventileswitching valves
88th: Speicherventilmemory valve
99: Kolbenpiston
1010: RückstellfederReturn spring
1111: Drucksensorpressure sensor
1212: Druckgeberthruster
1313: Sensorsensor
1414: Kolbensensorplunger sensor
1515: elastisches Gliedelastic member
1616: Rückschlagventilcheck valve
1818: Absperrventilshut-off valve
1919: Absperrventilshut-off valve
20,20'20.20 ': Fluidspeicherfluid reservoir
2222: Bremsleitungbrake line
2424: KolbenwegschalterKolbenwegschalter
ZLZL: Zufuhrleitungsupply line
RBRB: Radbremsewheel brake
V_R V _R: Radgeschwindigkeitwheel speed
V_F V _F: Fahrzeuggeschwindigkeitvehicle speed
P_R P _R: Raddruckwheel pressure
P_HZ P _HZ: HZ-DruckHZ-pressure
Δ T_MV8 _{ΔT MV8}: Ansteuerzeit MV 8Control time MV 8
Δ ssΔ ss: Kolbenweg SPKPiston stroke SPK
S_P S _P: Pedalwegpedal travel
Δ S_P ΔS _P: Pedalhubpedal stroke
Δ S_P-red ΔS _P-red: reduzierter Pedalhub mit SPKreduced pedal stroke with SPK
Tvtv: Verzögerungszeit MV / MotorDelay time MV / motor
M_B M _B: Bremsmomentbraking torque
M_P M _P: hydraulischer Bremsmomenthydraulic braking torque
M_G M _G: GeneratorbremsmomentGenerator braking torque
F_P F _P: Pedalkraftpedal power

Claims

Braking system for a hybrid vehicle with a control device and a brake pedal (1), which acts to brake pressure generation mechanically on a piston (3) of a piston-cylinder system, wherein the force support of the brake pedal (1) actuating person additionally an electric drive to the piston (3) of the piston-cylinder system acts, and the pressure build-up in wheel brakes (RB) by adjusting the piston (3), and each wheel brake (RB) or each brake circuit is assigned at least one switching valve (7) which is to hold pressure in the associated wheel brake (s) (RB) closed and the pressure change in the or the associated wheel brake (s) (RB) is open, wherein the control device, the drive (2) in dependence of the person or by a Brake regulator predetermined master cylinder pressure or wheel brake pressure for controlling a piston position and a driving force controls, wherein at least one wheel brake (RB) or at least one m brake circuit is assigned a fluid reservoir (20, 20 '), the storage chamber via a switchable accumulator valve (8) with a pressure line (BL) of the wheel brake (RB) or the brake circuit is selectively connectable, wherein in the ABS function of the fluid reservoir ( 20, 20 ') during pressure reduction in a wheel brake (RB) optionally for receiving fluid from this wheel brake or the associated brake circuit, characterized in that the brake pedal (1) for brake pressure generation acts mechanically via an elastic member (15) on the piston (3) of the piston-cylinder system, and wherein a force acting on the brake pedal (1) by acting on a generator braking torque of an electric drive of the hybrid vehicle by adjusting of the piston (3) by means of the drive with simultaneous filling of the fluid reservoir (20, 20 ') is set.
Brake system after Claim 1 , characterized in that the fluid reservoir (20, 20 ') is arranged in a pressure piston circuit, and the filling and emptying of the fluid reservoir (20, 20') and a refilling of 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.
Brake system after Claim 1 or 2 , characterized in that a pressure sensor (11) determines the pressure in at least one brake circuit and the determined pressure for controlling the filling and emptying of the fluid reservoir (20, 20 ') is used.
Brake system according to one of the Claims 1 to 3 , characterized in that upon actuation of the brake pedal (1) via a pedal travel for braking the hybrid vehicle, a first portion of the pedal travel of a first phase and a second portion of the pedal travel of a second phase is assigned, wherein in the first phase via a corresponding control of the Storage valve (8) is a volume displacement in the fluid reservoir (20) and a hydraulic braking torque (Mp) is effected only in the second phase by closing the storage valve (8).
Brake system after Claim 1 , characterized in that at a low set pressure of the fluid reservoir (20, 20 '), namely less than 10 bar, the pressure reduction in a wheel brake (RB) exclusively by means of the respective wheel brake (RB) associated and opened storage valve (8).
Brake system after Claim 1 , characterized in that the fluid reservoir (20, 20 ') comprises a piston-cylinder system and at least one spring acts on the piston of the piston-cylinder system of the fluid reservoir (20, 20') for its adjustment, wherein the spring Piston of the fluid reservoir pressurized.
Brake system after Claim 5 or 6 , characterized in that the fluid reservoir (20, 20 ') comprises a fluid storage drive acting on the / a piston of the / a piston-cylinder system of the fluid reservoir (20, 20') for its adjustment and for its emptying.
Brake system after Claim 6 or 7 , characterized in that a pressure sensor determines the fluid pressure in the storage chamber of the fluid reservoir (20, 20 ') or a sensor, the piston displacement of the piston of the fluid reservoir (20, 20').
Brake system according to one of the preceding claims, characterized in that the fluid reservoir (20, 20 ') is associated with exactly one brake circuit with two wheel brakes.
Brake system according to one of the preceding claims, characterized in that the control device for the adjustment of the piston (3) of the piston-cylinder system takes into account the pressure-volume characteristics of the individual wheel brakes (RB).
Brake system according to one of the preceding claims, characterized in that the control device for the adjustment of the piston (3) of the piston-cylinder system (5) for generating a pressure difference dp = f (dT, p 0 ) uses an adaptive map.
Brake system according to one of the preceding claims, characterized in that the control device for emptying the fluid reservoir (20, 20 ') uses a determined and stored in a memory function ds = f (dT, P s ).
Brake system according to one of the preceding claims, characterized in that the control device controls or controls a variable pressure gradient in the master cylinder (5) by means of the piston drive (2).
Method for operating a brake system according to one of the preceding claims, characterized in that at a positive μ-jump, the fluid reservoir (20, 20 ') is emptied.
Method for operating a brake system according to one of the preceding claims, characterized in that the / an emptying of the fluid reservoir (20, 20 ') takes place during a continuous phase of closed switching valves (7).
Method for operating a brake system according to one of the preceding claims, characterized in that a brake pad clearance in the wheel brakes (RB) is adjusted by means of the brake system.
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 control of the switching valves (7) and the storage valve (8) and stored in the fluid reservoir (20, 20') fluid volume is fed into the brake circuit at the beginning of braking, wherein a Schnuffel hole of the tandem master cylinder (5) by the piston (3) is closed.