DE3301948A1 - METHOD AND DEVICE FOR CONTROLLING THE BRAKING DISTRIBUTION - Google Patents

Description

ALFRED TEVES GMBH · _":;: ** * _·;.. 'R' 5 ^ 95

Method and device for controlling the braking force distribution

The invention relates to a method for controlling the braking force distribution to the front axle and the rear axle of a motor vehicle as a function of the static and dynamic axle load distribution as well as from other measured variables derived from the braking behavior, in which the measured variables used for the control determined with transducers or sensors, electronically linked and processed and at by controlling the braking pressure on the rear wheels in relation to the braking pressure on the front wheels. The invention also relates to a brake force distributor for carrying out the method, which is carried out with sensors to determine for the regulation of the braking force distribution usable measurands, with electronic circuits for linking, processing and evaluation the sensor signals as well as for generating the control signals is equipped for one or more brake pressure modulators.

A brake force distributor of this type is already known, where the sensors determine the static axle load

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Distribution is measured when the vehicle is stationary and fed into a microcomputer, which takes into account generation of these measured values according to a stored mathematical relationship with additional consideration of the measured pressure in the front axle and rear axle circuit controls the braking force distribution (European patent application EP-A1 062246). The disadvantage here is that the actual adhesive value between the road and the wheel on the rear axle and the front axle on the braking force distribution cannot exert any influence, which is why, in order to avoid dangerous overbraking of the rear axle, in most cases the contribution of the rear axle to braking will be small.

The brake force distributors commonly used today are limited to a fixed, pressure-dependent control. Load-dependent or delay-dependent brake force regulator are also known in numerous variants. Even with a lot of assembly and adjustment work, a satisfactory adjustment achieved at most in one of the two borderline cases "empty / loaded", so that in many Operating conditions, the theoretically possible utilization of the adhesion value on the front and rear axles is not achieved will.

The invention was therefore based on the object of the braking force distribution to be further developed in motor vehicles in such a way that in both borderline cases empty / loaded and at the braking force distribution in good approximation with each deceleration is adapted to the actual static and dynamic axle load distribution. To the realization

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of the requirements / i.e. the production of a corresponding brake force distributor, with comparatively low Effort was also valued.

It has now been found that this object can be achieved in a surprisingly simple manner with that described in claim 1 Procedure can be resolved. Advantageous embodiments of the invention and particularly expedient Devices for carrying out the method are explained in the subclaims.

The invention is based on the knowledge that the brake slip on the front and on the rear axle of one Motor vehicle to control the braking force distribution or particularly suitable for the construction of an effective, relatively easy-to-implement brake force distributor is. The required measured variables can be obtained with conventional speed sensors from their signals the deceleration and a reference speed can also be derived, and possibly with an additional one Determine the sensor for measuring the translational speed of the vehicle. With electronic circuits are processed and logically linked from these sensor signals after they have been processed in a conventional manner are generated, control signals for solenoid valves that directly act on the rear axle portion of the Control brake pressure. This achieves on the one hand that the front and rear wheels are approximately uniform to the Contribute to braking the vehicle; on the other hand it ensures that the rear wheels only after the front wheels can block, which is of great importance for the driving stability of the vehicle.

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Further advantages and possible uses of the invention will emerge from the following description of details and exemplary embodiments of the invention.

Show it

Fig. 1 is a schematically simplified block diagram of an embodiment of the brake force distributor according to the invention,

Fig. 2 in the diagram, the frictional connection effort over the brake slip and over the braking at a braking force distribution of the known type (Fig. 2a) and when controlled according to the invention Method (Fig. 2 b),

Fig. 3 in the diagram, the brake pressure curve over time at the front and rear wheels when using the Embodiment according to Fig. 1,

FIG. 4 shows the brake pressure curve in the same representation as in FIG. 3 according to a further embodiment of the invention.

FIG. 5 shows, in the same representation as FIG. 4, a further type of embodiment with pressure limitation at the start of blocking and

Fig. 6 is a schematically simplified block diagram of an embodiment of the brake force distributor according to the invention with diagonal brake circuit division.

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According to the embodiment of the invention shown in FIG there is the brake force distributor according to the invention essentially from a controller 1 / several sensors 2,3,4 and from a brake pressure modulator 5, which is in the embodiment shown from a fast-switching, electromagnetically operated 2/2-way valve 6 and a check valve 7 for rapid pressure reduction when the brake is released.

With the sensors 2,3 the wheel rotation behavior on the front axle ( Co " _n ) and on the rear axle ( co _un )

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determined. For example, an inductive speed sensor can be used in each case in a known manner, whereby one sensor per axis should be sufficient in most cases. To measure the deceleration of the vehicle, the Sensor 4 can be designed, for example, in the form of a known electromechanical translation sensor. A corresponding Reference speed can, however, also with the help of wheel speed sensors and suitable linkage of the sensor signals or by averaging the measurements of several speed sensors will.

The electronic circuits for processing and linking the sensor signals and for generating the control signals for the switching valve 6 are located in the circuit block 1. To form the control cycle for the Switching valve 6, a microcomputer can also be used in block 1.

The switching valve 6 according to FIG. 1 connects as long as it

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is de-energized, the hydraulic front wheel circuit VR with the rear wheel circle HR of the braking system. To reduce the proportion of braking force applied to the rear axle the valve 6 is closed in pulses, which is shown below with reference to FIGS. 3 and 4 will be explained in more detail.

The brake parameters previously assumed to be constant when designing the braking force distribution are subject to considerable changes in practice, e.g. as a result of manufacturing tolerances in the coefficient of friction, due to aging, contamination, temperature changes, etc. can vary significantly. In the inventive process, these are changes, however, taken into account because the proportional value of the real detention effort tire slip% ~ or Me'ßgroßen derived from the tire slip is evaluated for controlling the braking force distribution. Figg. 2 a and 2 b illustrate this mode of operation and the progress made.

For conventional brake force distributors with a fixed The diagram according to FIG. 2a applies to the distribution of braking force between the front axle and rear axle. When braking of e.g. ζ = 0.3, as shown, results in a frictional connection effort of for the front axle VR f "= 0.46, but only one for the rear axle HR

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Frictional connection effort of f _DT , = 0.19. The corresponding

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the working points on the adhesion / slip curve - that is the right part of Fig. 2a - are therefore significantly apart. The contribution of the rear axle to braking is therefore relatively low.

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With a braking force distribution according to the invention Teaching or when using a brake force distributor of the type according to the invention, as shown with reference to FIG has been described, both axles contribute almost equally to the braking, because the brake pressure component is on the rear wheels is regulated in such a way that the frictional connection effort on the rear axle only by the specified value of a few percent, preferably 3 to 15%, is under the frictional effort on the front axle. For a given master cylinder pressure, therefore the braking distance is considerably shorter because the rear wheels are stronger, especially with smaller braking can be used.

As already indicated in the description of the embodiment according to FIG. 1, the variation of the braking pressure component on the rear axle can be achieved in a particularly simple manner and nevertheless very precisely and finely by clocked control of the switching valve 6. As shown in FIGS. 3 to 5, this results in a pulsed increase in pressure p " _D at the wheels of the

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Rear axle. By varying the pulse pause ratio of the circuit block 1 supplied to the switching valve 6 Switching signals and thus the switching position "continuity / interruption" can be achieved that sets the desired distribution of the brake pressure on the front and rear axles.

The time course of the brake pressure p " _n at the front

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the axle to the brake pressure p _UT1 on the rear axle

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dimensional representation in Fig. 3 applies preferably to vehicle

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ge; those on the front axle with disc brakes, on the The rear axle are equipped with drum brakes. It is recommended for such braking systems / as a shortcut of the application process of the drum brake at the start of braking for a short time t .. without delay also one to allow limited pressure build-up on the rear axle and only then to provide a pressure holding phase t "before the further pulsating pressure build-up takes place on the rear axle.

In the case of vehicles with brakes of the same type on the front and rear axles, on the other hand, control of the pressure increase according to FIG. 4 is preferable. The front wheel _{pressure p VR} in turn increases linearly in proportion to the pedal force. The pressure p " _R on the rear wheels, which is also built up in a pulsating manner here, on the other hand, follows the front wheel pressure with a time offset and only reaches its steady-state value, which is determined by the electronics according to the selected criteria, at time t".

Further, the Figure can be according to a further embodiment of the invention, Figure 5 illustrates, interpret the electronics to the effect that upon detection of a risk of locking of the front wheels at the time t. _A - d ^v ies is the time of the blocking start - a further increase in pressure p _UT . on the rear axle beyond ρ _οηο

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is prevented. A blocking tendency or blocking danger can be determined e.g. electronically with the sensors 2.3 derive measured speed change or the wheel deceleration; exceed these measured values an upper threshold value, this can be the start of blocking be interpreted.

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When the rise in rear wheel pressure, as shown in Figs. 4 and 5, is restrained behind the front wheel pressure can be achieved by limiting the pressure increase on the rear axle when the tendency to lock is detected in many cases prevent the rear wheels from locking on the front wheels. The logic decides namely, consequently, to prevent further pressure build-up on the rear axle. As the pressure builds up the rear axle, as already described, follows the pressure on the front axle offset in time, is to this Point in time the rear wheel is still away from the maximum of the slip curve, so it will definitely not come to block. With regard to the directional stability of the vehicle, this variant is the one according to the invention Brake slip controller of great importance.

In the vehicle equipped with the brake force regulator according to the invention, shown symbolically in FIG. 6, two hydraulic brake circuits are provided which are diagonally divided between the wheels. On a tandem master cylinder 9 actuated by the foot pedal 8, the hydraulic connection 10 leads directly to the wheel brake cylinder of the right front wheel ^v _recnts ^and via a ball isolating valve 12 to the left rear wheel H 1. . . In the same way, the second brake circuit leads directly to the left front wheel V, via connection 11. . as well as an electromagnetic isolation valve 13 to the right

Rear wheel H,. . The solenoid valve 13 is a back right

check valve 14 for faster pressure reduction when loosening connected in parallel to the brake.

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The mode of operation of the arrangement according to Pig. 6 corresponds to that of FIG. 1. A central electronic Logic circuit 15, here a microprocessor contains signals corresponding to the rotational behavior of the rear wheels, which are received by the sensors 16, 17 as well as a signal from a sensor 18 and corresponding to the average front wheel speed finally a delay signal generated with the aid of a sensor 19 is supplied. The sensor 18 sits in in this case on a differential gear 20 via which the front wheels are driven.

When the brake is actuated via the pedal 8, the pressure on the two front wheels is immediately increased. As soon as the solenoid valve 13 is activated or excited and switched, the pressure build-up in the rear wheel ^{H can} begin on the right. At the same time the control piston of this valve is displaced via the hydraulic connection leading from the solenoid valve 13 to the ball valve 12, and thereby the rear wheel H,. . connected to the second brake circuit.

Instead of the ball valve 12, a second solenoid valve can be used, which is then also from the circuit block 15 is controlled and expediently operated in parallel with the solenoid valve 13.

Furthermore, it should be beneficial in many cases, both to form the solenoid valve 13 and the ball valve 12 as integral components of the tandem master cylinder 9.

Claims (4)

Claims ^ Method for controlling the braking force distribution on the front axle and the rear axle of a motor vehicle as a function of the static and dynamic axle load distribution as well as other measured variables derived from the braking behavior, in which the measured variables used for the control are determined / electronically linked and processed with sensors
and with the help of modulators of the
Brake pressure on the rear wheels in relation to that
Brake pressure on the front wheels is controlled, characterized in that the wheel rotation behavior on the front axle and on the rear axle
as well as the longitudinal deceleration of the vehicle measured directly or indirectly and from this the brake slip (λ-) at the front and rear wheels or the
Brake slip proportional measured values are determined, and that with the help of the control and the associated brake pressure modulators, the brake slip of the
Rear wheels is limited to about 70 to 100% of the brake slip of the front wheels by the
Brake pressure modulation on the rear wheels, the power flow effort (f _Trr) ) on the rear wheels to 80 VK to 100%, preferably 85 to 97%, the frictional connection effort (f _uri) einge- to the Vorderädern tln will provide. ALFRRD TEVIiS GMBH - ¹ "-.:." ·. .: "P * SÄ95 2. The method according to claim 1, characterized in that that after the tendency of the front wheels to lock up, the brake pressure at the rear wheels is kept constant. 3. The method according to claim 1 or 2, characterized in that when the brake pressure increases, the brake pressure (p _or ) to the rear wheel HK which, delayed by a few milliseconds, _{follows the brake pressure (ρ, 7Ώ} ) on the front wheels. VK 4. Brake force distributor, in particular for motor vehicles, for carrying out the method according to one of claims 1 to 3, with sensors for determining measurable variables that can be used for controlling the braking force distribution, with electronic circuits for linking, processing and evaluating the sensor signals and for generating control signals as well with one or more modulators to control the brake pressure on the rear axle as a function of the brake pressure on the front axle and the sensor signals, thereby gekenzeichn et that the sensors (2,3,16,17,18) to measure the wheel rotation behavior {tv _ττπ / & wn) ^at the front VK nK axis (VR) and on the rear axle (HR) are formed and that with the help of the "modulator (5) the brake pressure (p _ui j on the rear wheels can be controlled so that the _{frictional effort (f ur)} ) ^{on the} rear wheels as long as the Do not lock the front wheels, 80 to 100%, preferably 85 to 97% of the adhesion _{effort (f T7t)} ) on the front wheels VK amounts to. ALFRED TEVES GMBH. ". * L. ··..:, -P» 5.3.95 Brake force distributor according to claim 4, characterized in that that in addition a sensor (4) for measuring the longitudinal deceleration (-b) of the vehicle is provided, its output signals with the signals from the front axle (VR) and the rear axle (HR) can be linked in the electronic circuit (1). Brake force distributor according to claim 4 or 5, characterized in that the modulator (5) consists essentially of a fast-switching, electromagnetically operated 2/2-way valve (6, 13), which connects the hydraulic front wheel circuit (VR) with the rear wheel circuit (HR) in the de-energized state and interrupts after excitement .. Brake force distributor according to claim 4 or 5, characterized in that the modulator (5) contains a fast-switching, electromagnetically operated 2/2-way valve (6), which in the energized state connects the hydraulic front wheel circuit (VR) with the rear wheel circuit (HR) and in the de-energized state the connection is interrupted. Brake force distributor according to one of Claims 4 to 7, characterized in that the electronic circuit (1,15) for processing the sensor signals and for generating the control signals, i.e. the control signals of the modulator (5) contains a microprocessor as an essential component. ALFRED TEVES GMBH. '"- -I _". - -P .5235 Brake force distributor according to one of claims 4 to 8, characterized in that it is used in a hydraulic two-circuit brake system with diagonal braking force distribution, the distribution of the brake pressure in a first brake circuit (V _{left £ J} , ^H _right ) with the aid of an electromagnetically actuated, depending on the brake slip controlled 2/2-way valve (13) and in the second brake circuit ( ^v _rec h _ts ' ^H iinks ^ ^{with the} help of a depending on the brake pressure in the rear wheel circuit of the first brake circuit (V,.., H .. ) hydraulically controlled ball separation valve (12) can be changed.