FR2604406A1 - CIRCUIT ARRANGEMENT FOR A BRAKE SYSTEM WITH ANTI-LOCK CONTROL - Google Patents

Abstract

AN ARRANGEMENT OF CIRCUITS INTENDED FOR THE BRAKING SYSTEM OF A MOTOR VEHICLE WITH ANTI-LOCK REGULATION, WHICH CAN BE CONTROLLED ACCORDING TO THE TEMPORAL MULTIPLEXING PROCESS AND WHICH INCLUDES A MASTER CYLINDER EQUIPPED WITH A RETURN DEVICE FOR A PRESSURE GENERATOR, THE WHEEL BRAKES BEING CONNECTED WITH THE MASTER CYLINDER AUDIT THROUGH ELECTROMAGNETIC CONTROLLED MULTIDIRECTIONAL VALVES, IS DESIGNED TO ENSURE THAT, DURING ANTI-LOCK REGULATION, THE SEQUENCE OF PRESSURE REGULATION IN THE WHEEL BRAKES AND OR INTERVALS THEREFORE. WHEEL BRAKES ARE CONNECTED TO THE MASTER CYLINDER DEPENDING ON THE ROTATIONAL BEHAVIOR OF THE WHEELS. ACCORDING TO AN EMBODIMENT OF THE PRESENT INVENTION, BRAKE PRESSURE REDUCTION IS A PRIORITY DURING ANTI-LOCK REGULATION AS LONG AS THE PRESSURE REDUCTION TIMES NECESSARY TO RETURN TO WHEEL ROTATIONAL STABILITY ARE LESS THAN A MAXIMUM TMAX. WHEN THE SAID MAXIMUM VALUE TMAX IS REACHED, THE PRIORITY GIVEN TO PRESSURE REDUCTION IS TEMPORARILY SUSPENDED FOR THE BENEFIT OF A PRESSURE ESTABLISHMENT IN THE BRAKES OF ONE OR MORE STABLE-LOOK VR WHEELS. THE CIRCUIT ARRANGEMENT INCLUDES A MEASURING CIRCUIT 47 TO DETERMINE THE PRESSURE REDUCTION TIMES AND A PRESSURE ALLOCATION CIRCUIT 49 WHICH KEEP THE PRESSURE CONSTANT IN THE BRAKE OF THE UNSTABLE WHEEL VL AND WHICH ALLOWS TO ESTABLISH A PRESSURE IN THE BRAKES OF OTHER WHEELS WHEN A PREDETERMINED MAXIMUM PRESSURE REDUCTION TIME T, TMAX IS EXCEEDED.

Description

- 1 - 2604406

  The present invention relates to a circuit arrangement

  intended for an anti-lock braking system, in particular

  motor vehicle, which allows the regulation of

  braking voltage according to a time division multiplexing method

  the rotational behavior of the vehicle wheels, which comprises a master cylinder for a brake pressure generator and equipped with a controllable return device, the wheel brakes being connected to the master cylinder through multidirectional valves with electromagnetic control that can

  to be switched to close the pressure agent passage, the varia-

  pressure in the brakes of the individual wheels and / or

  groups of wheels that can be modified after the start of

  braking slip, by regulating the pressure in the

  working chambers of the master cylinder by means of the

  pel and opening, that is to say by switching in the on state, the pressure agent paths leading from the brake cylinder to the brake of

  affected wheel and closing the pressure agent paths leading to

other wheels.

  Braking systems are already known in which, in order to carry out the anti-lock regulation or, respectively, to regulate the sliding, the braking pressure can be regulated according to a time division multiplexing method. For this purpose, in a system of

  known braking (German Patent Application No. 33 17 629), it is pre-

  pressure lines, multi-directional valves

  electromagnetic actuators through which the brakes

  wheels are connected individually and / or in pairs to a general

  braking pressure and that open or close the pressure medium passage. The brake pressure generator

  consists of a master cylinder and an im-

  planted upstream. By means of this recall device and the valves of

  command, it is possible to produce an auxiliary force

  This is in contrast to the force exerted on the pedal which makes it possible, for the purposes of the regulation of the sliding, to reduce the force acting on the pistons of the master cylinder and therefore the brake pressure produced in the master cylinder. If all the wheels are

- 2 - 2604406

  all wheel valves, that is to say, the valves

  between the master cylinder and the wheel brakes, are switched to the open position. If a tendency to blockage occurs at any of the wheels, the wheel valves which lead to the other wheels are briefly switched to the closed position, so that only

  the wheel pressure agent circuit which is the subject of the

  anti-lock is connected to the wheel cylinder. By introducing

  the pressure in a controlled manner in the return device, it is

  an auxiliary force which partially or completely compensates for the pressure exerted on the brake pedal, which has the effect of reducing the brake pressure in the brake of the single wheel connected during this phase. The pressure of the other wheels remains constant during this phase. When it returned to the desired level, the reduced pressure is kept constant, by switching the valve, at the wheel which, first, had lost its stability. As soon as

  the antagonistic force is reduced again and a pressure is re-

  established in the brake master cylinder, it is possible to

  continue to establish a brake pressure in the other brakes

  wheels. It is thus possible, consecutively or by temporary division

  rel, to adjust the brake pressure at any level

  wheel to the desired value calculated by the corresponding electronic unit

  dante. In systems of this type which are ordered according to a

  temporal multiplexing process and which involve the master-cyclist

  lindre in the pressure modulation, it is impossible to regulate

  pressure simultaneously and independently in the various cir-

  cooked by regulation. During a pressure reduction phase, it is possible, at most, to keep the brake pressure constant in the other circuits, but not to increase it. In

  unfavorable situations, such as when cornering or when

  their friction are different to the right and left of the vehicle, there is a braking of reduced efficiency in the wheels whose behavior is stable. Conversely, if pressure build-up continues and the pressure reduction is delayed, a wheel may lock up, which can compromise the stability of the pump.

- 3 - 2604406

driving and maneuverability.

  The present invention therefore aims to remedy these problems.

  and provide a circuit arrangement for a system

  braking system operating according to the time-division multiplexing method.

  rel, ensuring, even in adverse situations, a deceleration associated with a short braking distance as well as the

  maintaining driving stability and maneuverability.

  It has been found that this object can be reached in a simple and technically advanced manner by means of a circuit arrangement of the type indicated above, the improvement of which is that, during an anti-lock regulation, the control sequence of

  pressure in the brakes of different wheels and / or in

  valles o the wheel brakes are connected to the maltre-cylinder depends

  the behavior in rotation of the wheels.

  According to an advantageous embodiment of the present invention,

  vention, the braking pressure may be modulated during the

  anti-blocking, according to predetermined criteria which can be modified or switched according to the rotational behavior of the

  wheels. Another embodiment lies in that, in the case of

  In an anti-lock system, in a braking system, the reduction of the braking pressure takes precedence as long as the pressure reduction times necessary to regain the rolling stability of a wheel or, respectively, to suppress the blocking tendency are less than a predetermined maximum value, and in that the priority given to the reduction of pressure can be suspended, at least temporarily, in favor of establishing pressure in the brake or brakes of one or more wheels with a stable speed, when

this maximum value is reached.

  According to another embodiment, the circuit arrangement according to the invention comprises a measuring circuit for

  determine the pressure reduction times and a circuit for

  priority reduction which first gives priority to the pressure reduction and which, when a predetermined maximum pressure reduction time is exceeded, maintains the constant pressure in the brake of the unstable-rate wheel and makes it possible to establish a pressure

-4- 2604406

  in the brakes of the remaining wheels.

  The circuit arrangement according to the invention therefore rests

  on the principle that, for reasons of stability of con-

  In terms of ease and maneuverability, priority must first be given to the reduction of pressure. However, if, for example, in a bend

  - because of the relief of the wheels inside the vir-

  ge - or if the friction coefficients are different on the right and left sides of the vehicle, the pressure reduction takes too long, indicating that the wheel contributes little to deceleration and driving stability, pressure regulation achieved at the brake of this wheel will be temporarily suspended and priority will be given to the establishment of pressure at the wheel or wheels at steady pace. Thus, even in situations of this type that are difficult to master, a short stopping distance is obtained, without impairing driving stability or handling. It is assumed that the relieved wheel or, respectively, the wheel which evolves with a low coefficient of friction and whose braking pressure is kept temporarily constant at a low value which is not yet an optimal value with respect to the sliding, continues to

  turn with a relatively high slip for a short time

  or - as in very unfavorable and rare cases - hangs.

  However, this can be tolerated because of the poor contact of this

  you wheel with the pavement. However, this relatively simple measure

  dramatically improves the general behavior

swimming.

  The different objects and features of the invention are

  will now be detailed in the description which follows, made in

  By way of nonlimiting example, with reference to the appended figures which represent: FIG. 1, in schematic and simplified form, the main hydraulic and electronic components of a braking system that can be controlled by the circuit arrangement according to FIG. the invention, - Figure 2, the time variation diagram of the

  wheel speed and wheel brake pressure when

-5- 2604406

  In FIG. 3, a block diagram of the units, essential for the present invention, of a circuit arrangement according to the invention. FIG. 1 represents a hydraulic braking system

  antilock control system controlled by a time division multiplexing method

  porel. This system comprises a brake pressure generator 2 that can be controlled by means of a brake pedal 1 and consists of

  essentially a tandem 3 cylinder, connected to an ampli

  hydraulic braking indicator 4 installed upstream, and a

  It is necessary to modulate the braking pressure.

  An auxiliary pressure source 6 is provided for feeding

  the braking amplifier 4 and the return device 5. The auxiliary pressure source 6 consists, for the most part, of

  a hydraulic pump with electromotive drive 7 and a battery

  hydraulic pressure transmitter 8. The auxiliary pressure source 6 is directly connected to the brake booster 4. Through

  a valve arrangement 9, it is connected to the return device 5.

  A common pressure compensation and pressure medium storage tank provides pressure medium at a time.

  master cylinder 2, the return device 5 and the source of pres-

auxiliary session 6.

  Of course, it is necessary to provide separate pressure agent tanks if different pressure agents or hydraulic agents are used to operate the device.

  recall 5 and for the master cylinder 2 and, respectively, the cir-

  Braking Cookies I, II. Instead of using the training device

  electromotor M of the pump 7, it is also possible to

  dragging this pump through the engine of the motor vehicle. To the two braking circuits I, II of the tandem master cylinder 3 are connected the brakes 11 to 14 of the vehicle wheels VR, HL,

  VL, HR through each of a multidirectional control valve

  open in the initial position. Multi-control valves

6- 2604406

  directional are two-way valves / two positions 15 to 18

  which can be electromagnetically switched to the closed position.

  In the embodiment shown, we have opted for a distribution

  Diagonal braking circuit. The front right wheel is designated by VR, the front left wheel by VL, the right rear wheel

  by HR and the left rear wheel by HL.

  In the embodiment shown, the rotational behavior of the wheels is detected by means of wheel sensors 19 to 22

  which, for example, send to an electronic unit 27, through

  signal lines 23 to 26, a signal having a frequency of

  proportional to the rotation of the wheel. The signals of

  are processed in the control unit 27 as part of a

  logical combination realized with the aid of electronic circuits

  program control signals are generated from the sensor signals and provided via the

  signal lines 30, to the wheel valves 15 to 18, namely to the val-

  two-way / two-position positions on the pressure agent paths leading from the brake cylinder 2 to the wheel brakes 11 to 14.

  Via signal lines 31, they are supplied to the

  9 of valves installed at the inlet of the

pel 5.

  The arrangement of valves 9 consists of a two-way / two-position valve 32, which is open in the rest position, which can be electromagnetically switched in the closed position and which

  connects a pressure chamber or, respectively, a chamber of

  pel 34 of the return device 5 to the reservoir 10, and a two-way / two-position valve 33 which is normally closed, which can be electromagnetically switched to the open position and which serves to supply pressure from the auxiliary pressure source 6 at the

  pressure chamber 34 of the return device 5.

  The operating mode of the braking system represented in FIG. 1 is as follows: In the rest position and in normal braking, that is to say no

  regulated, all the valves 15 to 18 and 32, 33 are in the position

  represented rest. Wheel brakes 11 to 14 communicate

- 7 - 2604406

  therefore hydraulically with working chambers 35 and 36 arranged

  inside the tandem master cylinder 2. If a brake force

  ge is applied to the brake pedal 1 in the direction of the arrow F, an amplified force in the brake amplifier 4 is transmitted to a piston 38 of the return device 5 via a rod 37. Piston 38, it is transmitted to the maltre-cylinder 2 by means of a second rod 39. No restoring force is

  produced because, under normal braking, the pressure chamber 34 communicates

  that directly with the pressure compensation tank 10 through the valve 32. Through the two pistons 40 and 41 of the tandem master cylinder 2, a brake pressure proportional to the force F exerted on the pedal is produced in circuits of

braking I, II.

  If a blocking tendency is detected at one or

  of several wheels of the vehicle, the anti-lock

  che. By closing the wheel valves which lead to the brakes of the wheels at steady speed, the pressure agent is enclosed, so that the

  Brake pressure is kept constant in these wheels. In com

  mutant the two valves 32, 33 of the valve arrangement 9, a pressure

  sion is transmitted from the auxiliary pressure source 6 to the pressure chamber 34 of the return device 5. The piston 38 of the return device 5 is then brought back against the direction of actuation of the pedal and the master cylinder 2 is finally relieved. The pressure prevailing in the braking circuits I, II is reduced. Through a wheel valve - any of the valves 15 to 18 - which remained

  open or returned to the open position of the

  The pressure then flows back from the corresponding wheel brake to the working chamber 35 or 36 of the master cylinder 2. The braking pressure of this wheel is thus lowered by means of the master cylinder 2.

  by actuation of the return device 5.

  By returning one of the wheel valves 15 to 18 to the open position for certain periods determined by means of the electronic circuits of the regulating unit 27, simultaneously closing the pressure agent paths leading to the brakes of the other wheels of the

  vehicle and by establishing the desired pressure in the maltre-cy-

- 8 - 2604406

  lindre 2 - namely by putting pressure and relieving the piston 38 of the return device 5 -, it is possible to vary, that is to say, to lower, to maintain constant and to increase, the brake pressure in the brakes of the different wheels and thus to individually regulate the braking slip for each wheel. This type of anti-lock regulation is called the time division multiplexing method. Of course, by means of several wheel valves 15 to 18 simultaneously opened or brought back in open position, it is also possible and judicious to lower and to increase

  braking pressure in several wheels at a time.

  The characteristics and mode of operation in conformity

  to the invention of a circuit arrangement for controlling a system

  This type of braking system is illustrated by the diagrams of FIG. 2 which refer to braking performed on a roadway having different friction values on the right and left sides. The same scale was adopted for the three diagrams of

  Figure 2. The curves shown show the brake pressure

  PVL, PVR, PHRHL which prevails simultaneously in the brakes of the different

  the wheels of the vehicle, the speed of the vVL wheels,

  vVR, VHR, VHL and finally the vF speed of the vehicle.

  The diagram at the top corresponds to the left front wheel VL which has the least good contact with the road surface during braking

  considered here. In the situation considered, the coefficient of

  is much lower on the left side than on the side-

  right of the vehicle. Conditions of this type may appear in

  turning to the left because we know that the wheel placed inside the

  Rabies is relieved because of the centrifugal force.

  During braking according to FIG.

  blocking is triggered substantially at the moment to. At first, as shown in the diagram above, the left front wheel VL becomes unstable. Pressure reduction starts at the end

  a very short phase during which the pressure remains

  aunt. During the period t1 - t2, the wheel valve 17 - see figure

- 9 - 2604406

  1 - was switched to the open position, while the other valves

  wheels 15, 16, 18 interrupted the pressure medium path.

  At the same time, by activating the return device 5 -

  see by switching the valves 32, 33 and introducing pressure into the pressure chamber 34 - a force opposing force F

  the pedal was produced and, therefore, a reduction in

  pressure was caused in the working chambers 35, 36

  2. In the example of a mode of realization of the cir-

  boiling control shown here, the pressure modulation is pro-

  evoked by sequences of impulses. The first impetus for

  pressure loss was completed at time t2. The valve 17 moves to the closed position. The first pressure reduction pulse that regulates the pressure at the rear axle is also

  completed at time t3 - see bottom diagram in Figure 2.

  In the example shown, an embodiment of the

  the present invention, the braking pressure of the wheel brakes ar-

  12, 14 is jointly controlled by the known method of

  "low pressure" in which the braking pressure is determined by

  wheel having the least good contact with the roadway - in

  currence: by the left rear wheel. As the curve in

  discontinuous line of the lower part of Figure 2, the wheel ar-

  The right wing is therefore evolving with a slight

  a lot to driving stability. The speed vHR of the rear wheel

  right re coincides almost with the vehicle speed vF.

  The interval between impulses or, respectively, the inter-

  pressure reduction valle which starts at time t3 can be

  used to provide brake pressure to the right front wheel

  VR that rotates on the side having a friction value or, respectively, a high coefficient of friction. This appears on

  the PVR curve in the central diagram of Figure 2.

  At time t4, the priority pressure reduction in the circuit according to the invention continues in the brakes of the wheel

  front left VL and rear wheels HR, HL. The establishment of

  the right front wheel must therefore be interrupted

  than at the moment t5. It is not possible to keep the pressure constant

- 10 - 2604406

until the moment t5.

  The dashed line curve of the central diagram of FIG. 2 represents the ideal pressure variation Pi that can be obtained in

  case of full exploitation of the braking capacity during the

  individual regulation of the brake pressure, but not during operation with time division multiplexing, in the brake 11 of the right wheel VR whose friction coefficient is higher. If a wheel, such as the front wheel VL in the example described with reference to FIG. 2, remains unstable despite the continued reduction of the braking pressure, that is to say if it continues to rotate with

  excessive drift due to, for example, a very strong

  in the bend or a very slippery road on this side, one would obtain, without the improvement according to the invention, the pressure variation P'VR for the right wheel VR, this pressure variation P'VR being illustrated in dashed line in the diagram

  central. Because of the priority given to the reduction of

  sion, the pressure supplied to the VR wheel which evolves with a value of

  higher friction would therefore remain significantly lower than the

  ideal pressure pressure Pi shown in broken lines. accordance

  According to the present invention, the pressure reduction time which elapses until a wheel regains its stability is thus measured and the priority assignment is modified if the wheel retains a

  blocking tendency after a predetermined pressure reduction time

  mine. At time t6, the maximum pressure reduction time of the left front wheel VL is reached during the braking represented with the diagrams of FIG. 2. The wheel continues to turn from

  unstable way. As a result, this wheel contributes little to

  age and driving stability. The priority is therefore no longer given to the pressure reduction, but to the establishment of pressure in the brake of the front wheel VR which evolves with a friction value

  high. At time t6, as shown by the solid line curve

  corresponding to the variation of pressure PVR in the central diagram of FIG. 2, the establishment of pressure continues in the brake of the right front wheel until at the moment t7, the regulation of the

- 11 - 2604406

  slip is triggered for that wheel, as indicated by the

  pressure relief and the decrease in speed or, respectively, the short-term variation of the speed VVR of the right front wheel relative to the speed vF of the vehicle. The stability limit of the right front wheel VR is reached for the second time at time t8

  and for the third time at the moment tg.

  The residual pressure in the left front wheel VL is kept constant from t6. It is therefore admitted that the VL wheel continues to turn with excessive slippage or even crashes, as in very unfavorable cases. After the moment t7, the residual pressure of the left front wheel VL is reduced again in the context of the regulation represented here. During the brief phases of increasing PVR pressure occurring between times t7 and t9, the pressure reduction in the left front wheel VL must therefore be interrupted each time. However, this does not appear on the PVL curve because the residual pressure prevailing in the front wheel

  left is very weak during this period.

  With respect to the arrangement of circuits giving priority to

  Because of the better use of the braking effect of the rotating wheel with a higher friction value, the stopping distance is considerably reduced due to the permanent reduction in pressure. The braking system operating according to the method of

  time multiplexing makes it possible to obtain practically the same

  braking behavior that an individually controlled braking system

dual wheel slip.

  The circuit arrangement according to FIG.

  an embodiment of a circuit arrangement for obtaining

  describe the braking behavior described with reference to Figure 2.

  By means of the circuits 42 to 46, the instantaneous speed of all the wheels vVL, vVR, VHL, vHR is first compared to the vehicle speed vF or to the vehicle reference speed determined by the locomotive circuit 46 and the diffoe = crecs prdanIte. In addition to a travel circuit 47, which may also include a travel speed sensor, the pressure torque T is measured individually for each wheel. If the pressure reduction time exceeds a limit value

- 12- 2604406

  Tmax, a priority allocation circuit 49 is

  transferred via the signal lines 48. Whereas previously

  priority was given to reducing pressure, it was

  then given to the pressure increase, as described in

  Figure 3. The circuit according to Figure 3 may be realized by an additional circuit wired or by programming a circuit

  program-controlled and can be combined with a

  Antiblocking system 50 shown in schematic form.

- 13- 2604406

Claims (4)

  1. Circuit arrangement for a braking system   anti-lock control, in particular for vehicles. automobi-   the:, which regulates the brake pressure according to a time division multiplexing method according to the rotational behavior of the wheels of the vehicle, and which comprises a maler-cylinder intended for a   brake pressure generator and equipped with a   pel can be controlled, the wheel brakes being connected to the mal-   tre-cylinder through electromagnetically controlled multidirectional valves that can be switched to close the passage of pressure medium, the variation of pressure in the brakes of different wheels and / or groups of wheels can be changed,   after the start of the regulation of the braking slip, in   pressure in the working chambers of the master cylinder at   means of the return device and by opening, that is to say in   in the on-state, the pressure agent paths leading from the master   a cylinder to the respective wheel brake and closing the pressure medium paths leading to the other wheels, characterized in that, during brake slip control, the pressure control sequence in the brakes (11 to 14 ) of the different wheels (VR, VL, HR, HL) and / or in the intervals where the wheel brakes are connected to the master cylinder (3) depends on the behavior in wheel rotation.   2. Circuit arrangement according to claim 1,   characterized in that, during anti-lock control, the braking pressure can be modulated according to predetermined criteria which   can be modified or switched depending on the behavior in wheels (VR, VL, HR, HL).   Circuit arrangement according to claim 1 or   2, characterized in that, during anti-lock regulation, the   Braking pressure is given priority as long as the pressure reduction times necessary to regain the rolling stability of a wheel or, respectively, to eliminate the tendency - 14- 2604406   to the blocking are less than a predetermined maximum value (Tmax), and in that the priority given to the pressure reduction can be suspended, at least temporarily, in favor of a pressure establishment in the brake or brakes of one or several wheels with a stable speed, that is to say wheels with no tendency to   cage - when said maximum value (Tmax) is reached.   4. Circuit arrangement in accordance with any one of   1 or 3, characterized in that it comprises a circuit of   measuring (47) to determine the pressure reduction times and a priority assignment circuit (49) which first gives priority to the pressure reduction and which, when a reduction time of   predetermined maximum pressure (Tmax) is exceeded, maintains the pres-   constant tension in the brake of the unstable-looking wheel and allows   to establish a pressure in the brakes of the remaining wheels.