DE3306611A1 - METHOD AND DEVICE FOR CONTROLLING THE BRAKING DISTRIBUTION - Google Patents

Description

ALFRED TEVES GMBH 'I:. :: ■: p '532 * 5

Method and device for controlling the braking

force distribution according to

DBP ... (patent application P 33 01 948.7)

The invention relates to a method and a
Device 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 and / or other measured variables derived from the braking behavior. The wheel behavior on the front and rear axles as well as the longitudinal deceleration of the vehicle are determined accordingly
electrical signals generated, electronically linked and processed. The signals obtained therefrom become
Then the brake slip on the front and rear wheels or the brake slip is determined measured values proportional to the brake slip, and it becomes the brake slip of the rear wheels
limited with the help of a control to the value of the brake slip on the front wheels or to a slightly smaller value. The invention includes an addition to the DBP ... (patent application P 33 01 948.7).

To measure the wheel rotation behavior and the longitudinal deceleration of the vehicle, sensors are used, their
Output signals in hardwired or programmed

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controlled electronic circuits, for example with a microprocessor, linked and processed. The brake pressure is controlled with the help of modulators, e.g. solenoid operated switching valves.

It is already known a brake force distributor in which the static axle load distribution is measured with sensors when the vehicle is stationary and fed into a microcomputer is stored, taking into account these measured values and the measured pressure after a mathematical relationship the braking force distribution in Controls the front and rear axles (European patent application EP-Al 062246). Such a braking force distributor has the disadvantage that the number of parameters actually given at the time of braking Dependent adhesion value between the road and the wheel on the rear axle and the front axle on the braking force distribution cannot exert any influence. Therefore, the brake must be used to avoid the dangerous overbraking of the rear axle To avoid safety, be designed in such a way that in most cases the contribution of the rear axle to the braking becomes quite low. Furthermore, it has proven to be disadvantageous that the actual values in practice differ from the arithmetically specified target values deviate significantly. The design of the braking force distribution and the In practice, the stored mathematical relationship is assumed to be constant significant changes, 2, .B. as a result of manufacturing tolerances in the coefficient of friction, aging, contamination, changes the spring constant during operation, inadequate adjustment, strong temperature changes, etc. This has to

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Consequence that the actual characteristic of the braking force distribution can deviate significantly from the forecast.

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. For the reasons mentioned above, even with a high assembly and adjustment effort with these known devices at most in one of the two borderline cases "empty / loaded" achieve a satisfactory adjustment, so that in many operating states the theoretically possible utilization of the adhesion value is not reached on the front and rear axles.

The invention is therefore based on the object of overcoming the aforementioned disadvantages of known arrangements and the braking force distribution in motor vehicles to develop further that both in the two borderline cases "empty / loaded" as well as with each braking of the vehicle the braking force distribution as a good approximation of the actual static and dynamic axle load distribution is adapted, so that an optimal braking function, i.e. driving stability, short braking v / eg and smooth Load of the two axes is achieved. Furthermore, a fulfillment of the requirements with the lowest possible Effort in the manufacture and assembly of the brake system is important.

It has now been shown that this task is progressive Way with that described in claim 1

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Can solve the procedure. Advantageous types of execution of the Invention and preferred devices for performing of the method are described in the subclaims.

The invention is based on the consideration that by the Measurement of the wheel and vehicle speeds or the changes in these measured variables over time, through processing these measured values to a control signal in an electronic circuit, e.g. in a microprocessor, and a brake force distributor can be implemented by using simple switching valves as pressure modulators which, taking into account the conditions actually prevailing at the time of brake actuation, including road conditions, condition of the braking system, static and dynamic axle load distribution etc., the braking force on the front and rear wheels in distributed almost ideally. This means, above all, a short braking distance, a low risk of blocking and thus high driving stability as well as an even load on the braking system is achieved. Only in exceptional cases necessary reduction of the pressure on the rear axle is also the relatively rare driving conditions that E.g. when the road conditions change rapidly are taken into account. In such situations could namely on the rear axle, after reaching an initially correct wheel cylinder pressure, held constant Brake pressure subsequently cause the wheels to lock. Unlike in brake slip control systems takes place in the brake force distributor according to the invention no renewed build-up of brake pressure within a braking process, In contrast to brake slip control systems, there is no external energy supply - for reconstruction

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of the brake pressure as a rule - required. This is in With regard to the manufacturing effort required for the brake system and the operational safety of great Meaning.

Further features, advantages and possible uses of the invention will emerge from the following description Details based on exemplary embodiments of the invention.

It show in a schematically simplified principle representation

1 shows a brake force distributor according to one embodiment the invention for a two-circuit braking system with diagonal braking force distribution,

2 in a diagram the pressure curve over time when the brake force distributor according to the invention is used, and

FIG. 3 shows an embodiment for a two-circuit brake system in the same manner of representation as in FIG. 1 One brake circuit each for the front and rear axles.

In the two-circuit brake system according to FIG. 1, the brake circuits are divided diagonally. To one symbolically illustrated tandem master cylinder 1 of conventional design / on the, as is symbolized by the arrow, the braking force F is exerted via a pedal, are on a brake

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circle 2 the left front wheel VR and the right rear wheel HR are connected. The second brake circuit 3 acts on the other two wheels, VR and HR.

Fast-switching 2/2-way valves 4.5 _Λ 6 are used as pressure modulators in the embodiment of the invention shown. While the two front wheels are directly connected to the associated brake circuit 2 or 3 of the tandem master cylinder 1, pressure build-up on the rear wheels is only possible after the two switching valves 4/5 have been energized. These valves are controlled via an electronic controller 1, to which the measured variables generated with the aid of sensors 8, 9 and 10 are supplied via the signal lines 8 ', 9' / 10 ¹ in the form of electrical signals and to which the required values are logically linked Calculates control signals and controls the internal pressure inodulators. The controller 7 can contain, for example, a microprocessor for processing the sensor signals and generating the control signals. In the exemplary embodiment described here, a mean value £>"" the wheel speed is measured with the sensor 8

VR

speed on the front axle, with the sensor 10 a mean value CO ₁ T _{n of} the wheel speeds on the rear axle ti κ

and with the sensor 9, the translational deceleration -b of the vehicle during the braking process or the wheel speeds or the deceleration determined measured values proportional to. If the vehicle is already equipped with an electronic sensor for the speedometer, this can also be used to generate the measured variable CO .

VK

With the help of the modulators or switching valves 4.5

2 shows the pressure curve p _HA on the rear axle and the brake pressure curve p " _A on the front axle, on which p" _{A is dependent.} 5, whereby by pulsing or by clocked switching of the valves 4, 5 from the (shown) closed position into the flow position, the pressure increase ρ required for an ideal pressure distribution

rl A

is adjusted on the rear wheels.

According to the invention is also to reduce the rear wheel pressure another 2/2-way valve 6 is provided. By the hydraulic connection of the two rear wheel circuits via a line with two in series, oppositely directed Check valves 11,12 was achieved that a single 2/2-Wegeventi1 6 to reduce pressure in the both rear wheel circles is sufficient. From the illustration in Fig. 1 it can be seen that via the electrical connection of the electronic which leads to the actuating magnet of the valve 6 Regulator 7, the normally closed 2/2-way valve 6 to reduce the pressure in the flow position can be switched, after which both rear wheel circuits via the check valves 11, 12 with the for Brake system belonging to the pressure equalization container 13 are connected.

As shown in Fig. 2, when the rear wheels have a tendency to lock, the pressure becomes stepped reduced to a lower value at which the brake slip on the rear axle equals the brake slip on the Front axle corresponds to or lags behind. The pressure-

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degradation begins at time t ,, after controller 7 by comparing the wheel deceleration on the rear axle with the vehicle deceleration at time t a Has determined that the rear wheels have a tendency to lock.

The check valves 14.15 provided in parallel to the pressure build-up valves 4.5 accelerate the reduction of the Brake pressure when releasing the brake.

In the case of a two-circuit brake division, in which one circle acts on the front axle and the other acts on the rear axle, the brake force distributor according to the invention requires even fewer components; as shown in FIG. 17 to build up the brake pressure on the rear axle and to reduce the pressure, which is triggered as soon as the controller 7 ^{1 concludes} from the sensor signals fed to it via the signal lines 8 ', 9', 10 'that the rear wheels are likely to lock. The check valves 11, 12 located in the feed line to the pressure reducing valve 6 in the embodiment according to FIG. 1 are omitted in the embodiment according to FIG. 3.

In Fig. 1 there is also a differential pressure switch 18 indicated, the failure of a brake circuit bzvy. the resulting pressure difference between the signaled both brake circuits 2,3 via line 19 to the controller. This causes permanent excitation of the valves 4.5 and a permanent blocking of the valve 6 causes so that if a brake circuit fails, at least in second brake circuit, the full brake pressure can be built up on the front and rear axles. The driving resp.

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Directional stability of the vehicle is in this case even if the wheels of the intact diagonal circle are blocked by the non-braked wheels of the failed one Maintain the brake circuit.

Claims (4)

ALFRED TEVES GMBPi February 03, 1903 ZL / KDB / ro P 5323 0698P H.-Ch. Klein -71 claims 1./Method for controlling the braking force distribution - ^ the front axle and the rear axle of a motor vehicle depending on the static and dynamic axle load distribution and / or on other of the measured variables derived from the braking behavior, in which the wheel rotation behavior on the front axle and on the rear axle as well as the longitudinal deceleration of the vehicle corresponding electrical signals are generated, these signals are electronically linked and processed and thereby derived from the brake slip on the front and on the rear wheels prox ^ ortional control signals the brake slip on the rear wheels with the help of a control on the fourth of the Brake slip on the front wheels or to a slightly smaller value is limited, according to DBP ... (according to patent application P 33 01 948.7), characterized in that when one occurs a signal indicating the tendency of the rear wheels to lock (HR ,, HR), which is obtained by comparing the rear wheel deceleration with the vehicle deceleration or with a reference signal representing the vehicle deceleration is generated, the brake pressure on the rear axle is reduced. ALFREDTEVESGMBH :: ..:. ·: F.332.3 _oonrn,. 2. The method according to claim 1, characterized in that upon occurrence of the signal indicating the tendency to lock, the brake pressure (p _A ) on the rear axle (HA) to one of the. Brake pressure dependent on wheel and vehicle deceleration values is reduced and that the reduced pressure is then kept constant until the brake pressure on the front axle (VA) is reduced. 3. The method according to claim 1 or 2, characterized in that the brake pressure increase on the rear axle (HA) the brake pressure increase on the front axle is delayed and that both the Brake pressure increase on the rear axle as well as the gradual reduction when the tendency to lock occurs he follows. 4. Brake force distributor for motor vehicles, for implementation of the method according to one of claims 1 to 3, with sensors for generating the wheel rotation behavior electrical signals proportional to the front and rear axles of the vehicle, with electronic circuits for linking, processing and evaluating the sensor signals and for Generation of control signals and with one or more modulators to control the brake pressure on the rear axle depending on the brake slip on the front and rear axles, according to DBP (Patent application P 33 01 948.7), characterized in that one or more mo- ALFRED TEVES GMBH. ".:". · .. ·. β-5.32-3: dulators (6,16) to reduce the pressure on the rear axle (HA) are provided when the signals indicating a tendency to block occur. Braking force distributor according to Claim 4, characterized in that as modulators Fast-switching, electromagnetically operated 2/2-way valves (6,16) are provided which are energized in the condition of a rear wheel (HR- ,, HR) or a rear wheel brake cylinder with a pressure equalization tank (13) and block the flow in the de-energized state. Brake force distributor according to Claim 4 for a motor vehicle with a hydraulic brake system and with a diagonal brake circuit division, characterized in that the hydraulic brake circuits ( ₂ , 3) of the two rear wheels (HR 1, HR _r ) with a common electromagnetically actuated 2 / 2-way valve (6) are connected, which is blocked when de-energized and, when energized, establishes a connection to a pressure compensation tank (13) ) a check valve (11, 12) is interposed in each case.