Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/17—Using electrical or electronic regulation means to control braking
  • B60T8/172—Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/17—Using electrical or electronic regulation means to control braking
  • B60T8/176—Brake regulation specially adapted to prevent excessive wheel slip during vehicle deceleration, e.g. ABS
  • B60T8/1763—Brake regulation specially adapted to prevent excessive wheel slip during vehicle deceleration, e.g. ABS responsive to the coefficient of friction between the wheels and the ground surface
  • B60T8/17636—Microprocessor-based systems
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
  • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
  • B60T8/42—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition having expanding chambers for controlling pressure, i.e. closed systems
  • B60T8/4208—Debooster systems
  • B60T8/4225—Debooster systems having a fluid actuated expansion unit
  • B60T8/4233—Debooster systems having a fluid actuated expansion unit with brake pressure relief by introducing fluid pressure into the expansion unit
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
  • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
  • B60T8/42—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition having expanding chambers for controlling pressure, i.e. closed systems
  • B60T8/4208—Debooster systems
  • B60T8/4266—Debooster systems having an electro-mechanically actuated expansion unit, e.g. solenoid, electric motor, piezo stack
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
  • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
  • B60T8/44—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition co-operating with a power-assist booster means associated with a master cylinder for controlling the release and reapplication of brake pressure through an interaction with the power assist device, i.e. open systems
  • B60T8/447—Reducing the boost of the power-assist booster means to reduce brake pressure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
  • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
  • B60T8/48—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition connecting the brake actuator to an alternative or additional source of fluid pressure, e.g. traction control systems
  • B60T8/4809—Traction control, stability control, using both the wheel brakes and other automatic braking systems
  • B60T8/4827—Traction control, stability control, using both the wheel brakes and other automatic braking systems in hydraulic brake systems
  • B60T8/4863—Traction control, stability control, using both the wheel brakes and other automatic braking systems in hydraulic brake systems closed systems

Definitions

• the present invention relates to a method for optimizing the use of the grip available when a torque - braking or acceleration - is applied to the wheels of a vehicle, motorcycle, automobile, or trailer.
• the grip of the wheel on the road surface depends on several parameters: the state of the tire, the state of the road surface, the slip of the wheel. .
• the coefficient of adhesion can be represented as a function of the slip by a curve represented in FIG. 1.
• This representation shows that the coefficient of adhesion increases with the slip until reaching a maximum value, for a slip value called ⁇ critical. Beyond this maximum value of the coefficient of adhesion, the wheel enters an unstable zone which quickly leads to blocking of the wheel, and which corresponds to a reduction in the coefficient of adhesion (increase in the braking distance), and in a decrease in the maneuverability and the directional stability of the vehicle, in the case of a torque resulting from braking - or either at total slip, or to a loss of traction and maneuverability in the case of a torque resulting from the engine.
• the regulation of the torque applied to the wheels of a vehicle in order to optimize both acceleration traction and braking safety, should therefore ensure that the slip which results from the application of the torque is close to the critical value ⁇ , without this slip value is exceeded.
• French patent FR9113119 describes a method and device for braking vehicles by controlling the braking torque applied to a wheel.
• the grip of a wheel on a braking track is defined by a variable operating point (P) on a grip curve as a function of the slip (g) of the wheel.
• the braking torque control parameter is the sign of the variation in the slope of the grip curve at the abovementioned operating point (P).
• the braking torque is controlled so that this operating point (P) coincides with the maximum grip point (M) of the grip curve.
• the maximum grip corresponds exactly to the start of the unstable (and decreasing) part of the curve shown in Figure 1, part for which the natural balance corresponds to the complete locking of the wheel (in the case of braking - and to total slippage in the case of an engine torque): it would therefore be necessary, to optimize grip, to detect in advance when this maximum will be reached: now, for all previous systems, it is the detection of the effective crossing of this maximum that is performed, hence the need to immediately reduce the brake pressure and regulate it around this optimal value.
• the invention relates more particularly to the early detection of the maximum adhesion.
• ⁇ denotes the true rotation speed of the front wheel
• ⁇ 3.2T denotes the true rotational speed of the rear wheel
• ⁇ 'de notes the first derivative of the true rotational speed of the rear wheel.
• this term ⁇ substantially constant over the normal grip range, increases suddenly when one of the two wheels comes close to its maximum grip. Near-maximum detection is obtained when ⁇ crosses a predetermined threshold, which can be self-generated from previous values (for example 150% or 200% of this substantially constant previous level).
• the rear wheel used in the calculation of ⁇ can be fixed a priori (eg same side), or the faster of the two rear wheels.
• a priori eg same side
• the faster of the two rear wheels e.g., one can advantageously use two wheels on the same side.
• a variant advantageously making it possible to eliminate certain artefacts from the data coming from the pressure and / or speed sensors consists in applying to the function ⁇ determining the activation threshold for closing the valve a filtering function.
• This filtering function can be a function proportional to time, a function proportional to the braking pressure applied to the wheel, a function inversely proportional to the braking pressure gradient dP / dt, or a combination of these functions or the association a thresholding of the pressure signal eliminating the data corresponding to pressures lower than a threshold value and corresponding to measurement noise.
• the signal taken into account for the detection of the valve closing threshold will be a signal of type: d ⁇ / dt.l / (dp / dt) .f (p, t, dt / dp).
• Vs designates a predetermined threshold value f (p, t, dt / dp) designates the filtering function. are applied when braking,
• the valve In a first mode, the valve will be closed when it detects: - the maximum braking power C. ⁇ , U
• This mode of combination by an "OR" logic gives anti-lock priority, and is particularly suitable for emergency braking.
• the second combination mode consists in closing the valve when it is detected:
• This second combination mode is more particularly suited to moderate braking situations and avoids untimely closing of the valve.
• This detection controls the reopening of the isolation valve, and an increase (if any) of the pressure, depending on the braking pressure exerted by the pilot: the cycle then begins again.
• this detection will command a reduction in the torque reduction (progressive suppression of the braking of the wheel concerned for example)
• Minimum passive system (or: "intelligent” limiter): An optical / acoustic signal warns the pilot, who must "pump” (release, then brake again);
• ABS + new optimal pressure function In this case, the pressure drop applied to return to the interior of the available grip (stable area before the maximum) - and the pressure rise which follows (the cycle starts again) are obtained by the usual means of ABS.
• the pressure in the downstream circuits must never be higher than the pressure in the upstream circuits. - an upstream pressure greater than or equal to the downstream pressure controls the opening of the valve d 'insulation.
• the braking optimization system In the event of a malfunction of one of the detection systems, the braking optimization system remains fully operational.
• the isolation valve being in the open position at rest, the braking system remains fully functional (safety), the optimization / anti-blocking function no longer being ensured.
• the goal main of the invention being to obtain an optimal adhesion, the use of only one of these two detection systems, sufficient to obtain this optimal adhesion, remains of the field of the invention.
• Hydraulic system preferably, when the detection threshold is reached, the brake pressure applied to the wheel is kept constant by closing a valve located upstream of the brake cylinder on the main brake circuit which transmits the hydraulic pressure applied by the pilot, this valve being re-opened as soon as the pressure upstream of the main circuit becomes lower than the pressure downstream of the brake cylinder, and in that the braking device also comprises, in bypass on this main circuit, a regulation circuit intended to adjust this pressure in the event of variation in adhesion during this phase when the valve is closed, by means of a floating piston, permanently upstream subjected to the hydraulic pressure, applied by the pilot, of the main circuit, and hydraulically connected to the brake cylinder either via an open valve, separate or coincident with the valve, or, during limitation-regulated phases lation where the valve is closed, via a non-return valve allowing the depressurization of the brake cylinder; this floating piston can also be subjected during the pressure limitation-regulation phases to an external opposing force opposing the upstream pressure, and thus making it possible to reduce the downstream
• the floating piston has a chamber normally connected to the low reservoir pressure, and which can be, in the event of a sudden variation in the deceleration ⁇ '- therefore of the adhesion - while the valve is closed, temporarily put into communication, by a valve or solenoid valve, with the hydraulic braking pressure applied by the pilot, which makes it possible to reduce the downstream pressure, as well as that of the braking cylinder up to a predetermined threshold which controls the re-opening of the valve and initiates a new braking and detection cycle for optimal grip, possible restrictions or making it possible to ensure in this cycle a compatible pressure rise gradient with the system response time.
• the floating piston comprises a chamber normally under low pressure, and which can be, in the event of sudden variation in the deceleration ⁇ '- therefore of the adhesion - while the valve is closed, temporarily put into communication , by a valve or solenoid valve, with a high hydraulic pressure of external origin, and supplied by a device comprising a jack consisting of a plunger and a chamber, which may be integral with one of the chassis, and the other of the wheel, the force transmitted by the piston during braking generating in the cylinder an internal pressure balancing this force, therefore increasing with the load transfer and having an anti-diving effect, a high pressure accumulator, and a low accumulator pressure, both in communication with this room at rest (except braking), a valve or solenoid valve activated by the braking pressure and isolating the two accumulators during the braking phases swimming, the maximum pressure induced by the force of the piston during this phase being transmitted via a non-return valve to the high pressure accumulator which
• the floating piston includes a chamber normally under negligible pressure, and which can be in the event of a sudden variation in the deceleration ⁇ '- therefore of the adhesion - while the valve is closed, put under high pressure by the means of a jack, electric or other, compressing by a plunger the hydraulic oil of a chamber communicating with the chamber, in order to reduce the braking pressure and initiate a new cycle of search for optimal grip, the gradient of pressure build-up in this cycle being controlled by the cylinder return speed.
• FIG. 3 shows a schematic view of an alternative embodiment of the braking circuit
• - Figure 4 shows the algorithm of a first embodiment of the detection
• - Figure 5 shows the algorithm of a second embodiment of the detection.
• FIG. 8 represents the diagram of a device for adapting the pressure in the event of a fall in the available grip.
• FIG. 9 shows an embodiment of this pressure adaptation device.
• FIG. 10 shows another embodiment of this pressure adaptation device.
• FIG. 11 shows another embodiment of r this pressure adaptation device.
• - Figure 12 shows another embodiment of this pressure adaptation device.
• FIG. 13 shows an external pressure supply device.
• FIG. 14 shows another embodiment of this pressure adaptation device, in a closed circuit.
• FIG. 2 shows the block diagram of the braking circuit and the detection system. It comprises in known manner a brake cylinder (1) supplied by a conduit (2) connected to a brake distributor (3) receiving the brake fluid under pressure from the master cylinder (4) associated with the brake pedal According to the invention, a solenoid valve (6) is interposed between the brake pedal and the brake cylinder (1). The solenoid valve (6) occupies at rest a position in which it allows the passage of the brake fluid between the brake distributor (3) and the brake cylinder (1). The operation of the hydraulic braking circuit is therefore not disturbed.
• the hydraulic system (5) also includes a regulation circuit for adjusting the braking pressure in the event of variation in grip.
• the electronic box controls the hydraulic system based on data received from speed and pressure sensors.
• the invention relates more precisely to the control of the solenoid valve (6).
• the object of the invention is to control the activation of the solenoid valve (6) just before the braking force reaches its maximum value, which corresponds to the maximum grip.
• the invention described below proposes two modes for determining the approach of the maximum value of the braking force.
• the first method consists in cyclically calculating the braking power by applying the product between the braking torque which can be measured from the braking pressure in the braking cylinder (1) (or from the reaction of the caliper ) on the one hand and the speed of rotation of the wheel associated with this brake cylinder on the other hand.
• the calculation of the braking power in the case of a vehicle with several braked wheels, is carried out independently for each of the wheels.
• a first example of controlling the solenoid valve (6) consists in determining the moment when the product of the pressure pi in the braking system and the angular speed ⁇ i decreases.
• An algorithm of this first control method is shown in FIG. 4.
• This process consists in carrying out the periodic acquisition, at times ti, of the following two parameters:
• the start t0 of the acquisition phase of these two parameters corresponds to the start of braking.
• This start t0 may correspond to the signal from a detector on the brake control, for example at the brake pedal, or more simply to a certain (minimum) brake pressure threshold. This detection of a braking action initializes the values ⁇ i and pi and triggers the iteration of the index i.
• the values of the three parameters ⁇ i, pi and ⁇ ixpi and ⁇ i + i, pi + 1 and ⁇ i + i pi + i are stored in registers in random access memory.
• a shift register replaces the values corresponding to the index i-1 with the values corresponding to the index i, and stores the new value i + 1.
• a comparator checks if Pi + i is less than Pi. If the response is negative, it iterates i, and the acquisition phase continues. If the response is positive, the solenoid valve (6) is closed.
• the reopening can occur at different times, for example by a timed command, or by a signal delivered by a comparator comparing the pressure upstream of the solenoid valve (6) and the pressure downstream of this solenoid valve, and controlling the opening when the downstream pressure is greater than the upstream pressure.
• FIG. 5 represents the algorithm of another mode for detecting the adhesion limit, and for controlling the solenoid valve (6).
• the solenoid valve is activated when the difference between ⁇ '/ ⁇ of the front wheel and ⁇ ' / ⁇ of the rear wheel is greater, in absolute value, than a threshold value, for example a value equal to 150 or 200% of the value before braking.
• a threshold value for example a value equal to 150 or 200% of the value before braking.
• 1 • solenoid valve is activated when the difference between ⁇ '/ ⁇ of the front wheel and ⁇ ' / ⁇ of the rear wheel is greater, in absolute value, than a threshold value, for example a value equal to 150 or 200% of the average value of the previous values (from tl to ti-k). This is done, from the start of braking, to the periodic acquisition of the value ⁇ of the rotation of the front wheel on the one hand and of the rear wheel on the other hand.
• a threshold value for example a value equal to 150 or 200% of the average value of the previous values (from tl to ti-k).
• the re-opening can take place at different times, for example by a timed command, or by a signal delivered by a comparator comparing the pressure upstream of the solenoid valve (6) and the pressure downstream of this solenoid valve, and controlling the opening when the downstream pressure is higher than the upstream pressure.
• This threshold S can be predetermined, or depend on the parameters measured.
• This threshold S can be predetermined, or depend on the measured parameters, or on the adhesion conditions, which can be determined from the measured parameters:
• the solenoid valve is activated when the value of the term
• FIG. 6 shows the algorithm for checking instantaneous grip and adapting the braking pressure while the solenoid valve (6) is closed.
• the reopening of the solenoid valve (6) is ordered: the cycle begins again.
• a reduction in the braking pressure upstream of the solenoid valve (6) is commanded, sufficient to return to the stability domain (domain before the maximum adhesion ): for example, at around 50% of the braking pressure value corresponding to the maximum grip on dry ground.
• This pressure lower than the pressure downstream of the solenoid valve (6), causes the solenoid valve to reopen, and the cycle begins again.
• this pressure reduction is obtained by means of a regulating solenoid valve (7).
• This solenoid valve (7) comprises a core (8) making it possible to vary the value of the downstream pressure independently of the pressure imposed by the brake distributor.
• the displacements of the core (8) cause a variation in the downstream pressure by a value F / S where F denotes the force opposite to the upstream pressure exerted on the core by the winding and S the section of the core.
• the upstream pressure variation control can also be carried out in a known manner by an ABS type system.
• the force F applied to the pressure transmitter piston (8) in order to reduce the downstream braking pressure in the event of a decrease in grip, is obtained by the application of a repelling hydraulic pressure the piston, here in the annular chamber (15).
• This hydraulic pressure is supplied by a vacuum cylinder (9), analogous to those of the brake assist devices known as vacuum booster, or by an electric cylinder, which compresses the fluid by means of a piston (10). of the high pressure chamber (11) - this hydraulic pressure could also be supplied by a pump -.
• This vacuum cylinder will for example be activated under each brake.
• the annular chamber (15) remains in communication, via
• 1 solenoid valve (14) is briefly switched, this mistletoe puts the chamber (15) in communication with the high pressure (11), and drops the brake pressure downstream of (8), depending on the dimensioning - for example to 50% or less of the pressure corresponding to optimal braking on dry ground.
• This drop in downstream pressure - which has thus become lower than the pressure in the brake cylinder - leads to the reopening of the solenoid valve (6), and a very brief reduction in the braking applied to the wheel, which returns to the conditions of adhesion: 1 solenoid valve (14) immediately returning to its initial position, the pressure begins to increase again and the cycle begins again.
• the vacuum servo-cylinder becomes inactive, the force of the piston (10) disappears, the pressure drops in the chamber (11), authorizing the return of the BP fluid by the valve (13).
• the diagram in FIG. (9) represents a possible example of an embodiment of the pressure regulation device in the form of a compact circuit.
• the movable piston (8) can be used as a pressure booster, and include a safety limit switch (19) which communicates the upstream and downstream pressures when the piston (8) comes to a stop - due to abnormal leaks and drift : the active reduction of the braking pressure in the event of a decrease in grip after intervention of the pressure limiting solenoid valve (6) then becomes ineffective (the pressure being however reduced from P downstream to P upstream in the event of amplification) , but all the other braking functions are retained (safety).
• the loss of the valve shutter function results in the only loss of the active reduction of the brake pressure and safety remains assured.
• the low pressure accumulator can be obtained by simple use in the chamber (13) of a compressible foam (17), advantageously insulated by a membrane (18), and possibly swollen (low pressure), or conventionally by swollen membrane.
• FIG. 9 and 10 show the diagram without scale and for a single wheel, hence a single solenoid valve (14) + piston (8) sub-assembly shown, and the solenoid valve (6) braking, on the downstream pressure P at the outlet of (8), is not shown:
• the chambers (11) and (12) of this figure 9 will be placed in communication with several solenoid valves of the same type as (14) - one for each wheel - associated with pistons of the same type (8) - for example according to a circular symmetry, of order 4 for 4 wheels.
• the valves, solenoid valves (14), (6), and pressure adapter piston (8) can be very small.
• FIG. 12 represents a particularly simple variant of the invention. In this variation,
• the main circuit (11) is normally open, and in communication with upstream and downstream of the floating regulating piston (8), in equilibrium under these two identical pressures, the chamber 15 being unpressurized
• a non-return valve 23 functionally in parallel with
• solenoid valve 16 causes the simultaneous drop in hydraulic pressure in the brake cylinder.
• this downstream pressure has reached the reguis threshold, the solenoid valve 14 returns to its initial position, depressurizing the chamber 15, again in communication with the reservoir pressure, and the valve 16 is reopened, letting the downstream pressure rise; the pressure gradient can be adjusted by possible restrictions 24 and 25 to ensure its compatibility with the response time of the system.
• the solenoid valves 6 and 16 are replaced by a single solenoid valve.
• the two annular chambers of the floating stage piston are in communication, by means of a 4-way / 2-position solenoid valve, which may be produced by four piloted valves , with those of a second identical or similar stage piston, subjected at one end to the pilot's braking pressure: at rest, the valve communicates the two annular chambers of the regulating piston; When activated (regulation phase), it sends the pressure (pilot) to the downstream annular chamber, and reduces the braking pressure accordingly. Only one such auxiliary piston can be used for all four wheels.
• a non-return valve (30), piloted or not, and a non-return valve (31) are used to isolate the brake cylinder, a third, non-return valve, piloted, allowing the pressure to be sent temporarily to the annular chamber to reduce the braking pressure: an internal or external bypass (33), with restriction, allowing the pressure in the brake cylinder to then rise gradually, until the new optimum.
• the high and low pressures for supplying the annular chamber of the floating regulating piston 15 are of external origin and supplied by the device of FIG. 13, which comprises: a cylinder consisting of a plunger 11 and a chamber 11, which can be respectively secured to the chassis and the wheel, the force transmitted by the piston during braking then being proportional to the load transfer, hence in addition to an anti-diving effect, an HP accumulator 26, and a BP accumulator 27 both in communication with this chamber 11 at rest (apart from the braking actions), a valve 28 activated by the braking pressure, which isolates the two accumulators during the braking phases: the maximum pressure then induced in the chamber 11 by the force of the piston 10 during this phase is transmitted via the non-return valve 29 to the HP accumulator which stores this pressure energy, which may, in the event of a fall in grip during optimal braking, be transmitted by the solenoid valve 14 to the chamber 15 of the floating piston, in communication otherwise by this same solenoid valve 14 with the low pressure accumul
• valve 28 After braking, the valve 28 returning to its rest position puts the accumulators 26 and 27 back in communication with the chamber 11, depressurizing the HP accumulator 26.
• FIG. 7 represents the algorithm for detecting the adhesion limit and controlling the torque applied during the acceleration phases (traction control).
• the torque applied is reduced when the difference between ⁇ '/ ⁇ of the driving wheel and ⁇ ' / ⁇ of the driven wheel is greater, in absolute value, than a threshold value, which can be self-generated, for example a value equal to 150 or 200% of the average value observed during the initial phase, before skating (stability zone, before maximum grip).

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• Engineering & Computer Science (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Regulating Braking Force (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9475523

Family Applications (1)

Country Status (3)

Family Cites Families (7)

• 1995
  • 1995-01-26 FR FR9500895A patent/FR2729908B1/fr not_active Expired - Fee Related
• 1996
  • 1996-01-26 WO PCT/FR1996/000138 patent/WO1996022905A1/fr not_active Ceased
  • 1996-01-26 EP EP96901863A patent/EP0804357A1/de not_active Ceased

Non-Patent Citations (1)

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