FR2594769A1 - ANTI-LOCKING DEVICE OF MOTOR VEHICLE WHEELS HAVING A CONTROL UNIT PILOTED BY A PRESSURE SENSOR - Google Patents

Abstract

Anti-lock device for motor vehicle wheels comprising a control unit controlled by a pressure sensor. It comprises actuating valves 22, 32 for interrupting the braking action by connecting the brakes 18, F to a discharge line 26, an electronic control unit 28 and associated detection means 30 of the speed of rotation. wheels, the unit 28 being designed, if the wheels lock, so as to cause successive cycles of brake release and braking by means of the actuating valves 22, 32, at least one region 36 in the valves of 'actuation 22, 32, in which the pressure is directly linked to the pressure applied to the brakes 18, F, electrical pressure detection means 70 associated with the actuating valves 32 for supplying the control unit 28 with electrical signals representative of the pressure in said region 36. The control unit 28 controls the pressure applied to the brakes 18, F during the brake release and braking cycles as a function of the signals supplied by the pressure detection means. on 70. (CF DRAWING IN BOPI)

Description

I

  ANTI-LOCKING DEVICE FOR MOTOR VEHICLE WHEELS

  COMPRISING A CONTROL UNIT PILOTED BY A DETEC-

TEUR OF PRESSURE

  The present invention relates to an anti-lock device for the wheels of a motor vehicle comprising a braking system incLuding

  a master cylinder connected to the brakes.

  The technical field of the invention is an anti-lock device comprising: pneumatic actuation valves,

  hydraulically or hydropneumatically controlled electric

  these valves being designed to interrupt the braking action by connecting the brakes to an evacuation pipe; an electronic control unit connected to the operating valves and comprising associated detecting means for detecting the rotation speed of the wheels, the unit being designed, if the wheels are locked, so as to cause successive cycles of release of braking and braking by means of actuating valves; and - at least one region being defined in the actuating valves, in which the pressure is

  directly related to the pressure applied to the brakes.

  In the Italian patent application 67710-A / 85, a hydraulic braking system is described comprising

  a pneumatic servo driven by Vacuum.

  This servo control comprises an anti-lock wheel device of the type described above. This device comprises a solenoid valve interposed between the master cylinder and the brakes and designed to interrupt braking by connecting the brakes to a brake.

  drainage pipe, and a hydro-electric actuator

  pneumatic connected to the evacuation pipe and having a pneumatic control circuit connected to the pneumatic servo-control. If the wheels are

  block, the electronic unit of this device pro-

  by the solenoid valve, a first inter-

  rupturing of the braking then successive cycles of braking and releasing of the braking action by the closing and the pressurization, as well as the opening, respectively, of the pipe

  evacuation using the hydropneumatic actuator.

  The anti-lock device described above can be manufactured at a cost that is comparable to that of fully pneumatic devices in comparison with which, however, it has

  much shorter response times.

  The hydropneumatic device described above

  on it actually shows response times

  to those of fully hydrau-

  which are more complex and expensive.

  Among these, anti-lock devices are particularly known in which, during the braking phases controlled by the control unit, the hydraulic pressure applied to the brakes is

  reduced by being controlled by a hydrau-

  It decreases linearly with a constant predetermined negative gradient. Therefore, in such devices, the duration of each phase of the braking release is directly related to the decrease of the hydraulic pressure

  applied to the brakes. The control unit of such discs

  This way, positive people can very accurately assess the reduction

  induced pressure and therefore develop the optimal way of increasing pressure in

  the braking phase commanded immediately thereafter.

  In such devices of the prior art of the type

  fully hydraulic, these features

  taggers are obtained by very complex devices

  and expensive that limit their use to vehicles-

high-end exclusively.

  In the anti-lock device hydropneuma-

  As described in copending application No. 67710-A / 85, the decrease in hydraulic pressure applied to brakes during brake release cycles occurs in a non-linear manner, in a manner

  which varies in large salt tone an exponential curve

  tial. Consequently, in this device, the duration of the braking release controlled does not constitute an accurate and reliable indication of the reduction of

  the brake pressure caused by the com-

  request in each brake release cycle.

  Therefore, in every braking cycle controlled

  The control unit makes it impossible to

  apply the pressure applied to the brakes, and in fact the hydraulic pressure applied to the brakes during these

  cycles is very often higher than the optimal value

less than or equal to this value.

  The object of the present invention is to create an anti-lock device of the type mentioned above, in which it is possible to precisely control the reduction of the pressure applied to the brakes during the phases of release of the pressure controlled by the control unit and, consequently, in which it is possible to control the increase of the pressure during the braking phases in an optimal manner, avoiding the disadvantages described above, which allows to achieve performances which are thus comparable to those of fully known devices

  hydraulic, which are very expensive.

  This object is achieved according to the present invention by means of an anti-lock device

  hydropneumatic type of the type described above, the character

  essential feature of this resident device

  in that it furthermore comprises electrical means

  pressure detectors associated with the actuating valves for supplying the control unit with

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  electrical signals representative of the pressure in said region defined in the operating ranges,

  and that the control unit is designed to com-

  the pressure applied to the brakes during the braking and braking release cycles

  function of the signals provided by the means of detection

pressure.

  Other features and advantages of the device according to the invention will appear

  still reading the detailed description which

  follows, with reference to the attached single figure,

  provided for information purposes only and in no way

  tative. This figure represents a diagram of a system

  hydraulic braking system with a servo

  pneumatic control actuated by the vacuum and including a hydropneumatic anti-lock device according to the

The present invention.

  Referring to the figure, a master cylinder of a hydraulic braking circuit for the brakes F of the wheels of a motor vehicle is designated by the reference 10. The master cylinder 10 is actuated by means of a pedal of control 12 by a vacuum servo-brake of known type comprising a pneumatic cylinder 14. The master cylinder 10 is connected to a reservoir

  16 and, through a channel

  20, to hydraulic actuators 18 for the brakes F. In the embodiment described, the pipe 20 is connected to a pipe 24 via a solenoid valve 22, the pipe 24 being connected to an actuator hydraulic brake 18 of known type. The vaLve 22

  is a three-way valve connected at 22a to the

  20, 22b to 24 and 22c

  to an evacuation pipe 26 connected to the reservoir

see 16.

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  The solenoid valve 22 is controlled by an electronic unit 28 connected to electrical detection means 30 for detecting the speed of rotation.

wheel rotation.

  The solenoid valve 22 is normally

  maintained in a non-powered state in the confi-

  illustrated in Figure, in which it closes the way 22c. The evacuation pipe 26

  is connected to a hydropneumatic actuator 32 comprising

  a pneumatic cylinder 34 comprising a first chamber 36 and a second chamber 38 separated by a

  elastic membrane connected to a rod 42.

  The pneumatic cylinder 14 of the servo-brake comprises a first chamber 43 connected to a vacuum source D (for example the intake manifold of the internal combustion chamber of the vehicle) and

  a second chamber 44 which, in a known manner,

  nique with the chamber 43 when the brake pedal 12 is not actuated and which is placed in communication with the atmosphere when the brake pedal 12 is actuated. The first chamber 43 of the pneumatic cylinder 14 of the servo brake communicates with the second chamber 38

  of the hydropneumatic actuator 32 by a channel

46.

  The duct 46 is also connected to the first chamber 36 of the hydropneumatic actuator 32 by a first duct portion 48 and a second duct portion 50. Between the portions 48 and 50 is disposed a three-way solenoid valve.

  52. A first lane 52a is connected to

  48, a second channel 52b communicates with the pipe 50 and a third channel 52c is connected to a pipe 54 which communicates with the second channel 52b.

  chamber 44 of the pneumatic cylinder 14 of the brake servo.

  The hydropneumatic actuator 32 has a hydraulic part. This portion comprises a piston 56 having a central opening 58 which

  faces the piston 42 and is aligned with it.

  The piston 56 slides in a cylinder 60 which

  munic with evacuation pipe 26.

  The rod or piston 42 has an end 42a which plays the role of a shutter which is immersed in a chamber 62 situated above the piston 56. The chamber 62 communicates with the hydraulic fluid reservoir 16 via a pipe 64 and the shutter

  42a is normally spaced from the piston 56. This closure

  as will be explained in more detail later.

  is designed to cooperate with an annular valve seat 58a formed by the end of the opening 58 which is located opposite the

room 62.

  An electrical pressure sensor 70 is interposed on the pipe 50 between the channel 52b of the solenoid valve 52 and the chamber 36 of the hydropneumatic unit 32. This pressure sensor is

  preferably of the type comprising transducers exten-

  sometric formed by thick film resistors that have piezoresistive characteristics

well known.

  The output of the detector 70 is connected to the unit

electronic control system 28.

  When the pedal 12 is released, the hydraulic circuit comprising the pipes 20, 24, 26 and 64 is at a zero relative pressure, while the pneumatic circuit comprising the pipes 46, 48, 50 and 54 is in depression, since is in communication with the source of depression D. When the brake pedal 12 is actuated, the master cylinder 10 pressurizes the pipes and 24 and actuates the hydraulic actuator 18 of the brakes F. If the wheels of the motor vehicle does not

  do not block during braking, the hydraulic circuit

  The tick located downstream of the channel 22c of the solenoid valve 22 remains at a relative pressure of zero, and hence it is closed. During braking, the second chamber 44 of the pneumatic cylinder

  14-of the servo-brake is put in communication with the

  mosphere, so that the line 54 is also at atmospheric pressure. Since the channel 52c of the three-way valve 52 is closed, this pressure does not act on the hydropneumatic actuator.

which remains inactive.

  In case the wheels lock during the

  braking, the detector 30 sends signals corresponding to

  to the control unit 28 which is designed to feed the three-way valve 22 so as to close the track 22a and to open the track 22c, which allows the hydraulic pressure applied to the hydraulic actuator 18 to to be evacuated

  the tank 16 by the pipes 24 and 26, the

  58 in the piston 56 and the channeling

64.

  As soon as the braked wheel or wheels have begun to turn again, the detection means 30 send corresponding signals to the control unit 28 which, in this situation, feeds the solenorde valve 52 so as to cause the opening of track 52c and the closure of track 52a. As a result, the chamber 36 of the hydropneumatic actuator 32 tends to

  return to atmospheric pressure by channeling

  50 and 54 and the second chamber 44 of the pneumatic cylinder

  of the servo-brake 14, while the chamber 33 continues to communicate through the pipeline 46 with the

  Chamber 43 of the servo-brake 14 which is in depression.

  The pressure difference between the chamber 36 and the chamber 38 of the hydropneumatic actuator causes a corresponding movement of the diaphragm 40 and the rod 42 connected to this diaphragm moves towards the piston 56 having an opening. The shutter 42a

  The stem 42 closes the valve seat 58 of the piston 56.

  The communication between the cylinder 60 and the chamber 62 is thus interrupted. When the rod 42 continues its downward movement, it exerts an effort on

  The piston 56 for pressurizing the hydraulic fluid

  the cylinder 60 contained in the cylinder 60 and simultaneously actuate the hydraulic actuator 18 of the brakes F by the pipes 26, 24, and the track 22c of

  Solenoid valve 22. Therefore, when the

  the pedal 12 continues, the braking is

  The hydropneumatic actuator 32 undermines it by virtue of its pneumatic control circuit. During this braking action due to the hydropneumatic actuator 32, the wheel or wheels controlled could lock again. The electronic unit 28 is designed to shut off the supply of the solenoid valve 52 in this case so as to close the channel 52c and to put the two chambers 36 and 38 of the hydropneumatic actuator 32 in communication with the Chamber 43 of the servo-brake 14 which is maintained in depression. The pressure in the chamber 36 thus tends to return to equilibrium with the pressure prevailing in the chamber

  38. In this case, the rod 42 returns to its initial position.

  tial, which restores the communication between the cylinder 60 and the chamber 62 through the opening 58 provided

  in the piston 56. The pressure in the hydraulic actuator

  liquid 18 and in the pipes 24, 26, can

  then be discharged into the tank 16 through the opening

58 and Line 64.

  When the wheel or wheels controlled by the control unit 28 begin to rotate again, the solenoid valve 52 is energized again so as to

  carry out a series of braking and releasing cycles

  braking equipment fully piloted by the

  hydropneumatic neur 32 and the solenoid valve 52 associated therewith. During these cycles, the solenoid valve 22 is continuously supplied with

to keep track 22a closed.

  When the motor vehicle reaches a sufficiently low speed, for example of the order

  10 kilometers per hour, the electronic unit 28

  breaks the supply of the solenoid valve 22 so as to cause the closure of the channel 22c again. Thus, the hydropneumatic actuator is disconnected from the brakes F.

  During braking and releasing cycles

  braking systems ordered by Unit 28 through

  In the middle of the hydropneumatic unit 32, the pressure sensor 70 supplies the control unit 28 with electrical signals which indicate the pressure of the air contained in the pneumatic chamber 36 of the actuator.

  32. This pressure is directly related to the pressure

  The electronic unit 28, on the basis of the signal supplied by the pressure sensor 70, can thus deduce information concerning the value of the hydraulic pressure applied to the actuators.

  brakes in real time. On the basis of this information,

  the control unit 28 can then control the brake pressure applied to the brakes during

  the braking phases controlled optimally.

Claims (4)

  1. Antilock braking device for the wheels of a motor vehicle having a braking system including a master cylinder (10) connected to the brakes (18, F), the anti-lock device comprising:   actuating valves (22, 32)   hydrauLic or hydropneumatic   electrically, these valves being designed for inter-   breaking the braking action by connecting the brakes (18, F) to an exhaust pipe (26); - an electronic control unit (28)   connected to the actuating valves (22, 32) and comprising   detection means (30) for detecting   The speed of rotation of the wheels, the unit (28) being designed, if the wheels are locked, so as to cause successive cycles of loosening of the wheels.   braking and braking by means of action valves   ment (22, 32); at least one region (36) being defined in the actuating valves (22, 32), wherein   the pressure is directly related to the pressure applied brakes (18, F);   characterized in that it further comprises electrical means   pressure sensing cues (70) associated with the valves   actuator (32) for delivering to the communication unit   Means (28) electrical signals representative of the pressure in said region (36), and in that the control unit (28) is designed to control the pressure applied to the brakes (18, F) during the release cycles. braking and braking according to the signals provided by the detection means of pressure (70).   2. Device according to claim 1, in particular for a hydropneumatic anti-lock device for a motor vehicle comprising   a hydraulic braking system with a servo   pneumatic control (14, 44) and in which the actuating valves comprise: - a solenoid valve (22) interposed between the master cylinder (10Y and the brakes (18) to interrupt the braking action by connecting the brakes (18 ) to an evacuation pipe (26), and - a hydropneumatic actuator (32) connected to the evacuation pipe (26) and comprising an electropneumatic control circuit (46-54) connected to the pneumatic servo-control (14). , 44), and wherein the control unit (28) is designed, if the wheels lock, to cause a first interruption of the braking action by means of the solenoid valve (22), and successive cycles braking and releasing braking system by closing, pressurizing and opening, respectively, the discharge line (26) via the hydropneumatic actuator (32), a pneumatic control chamber (36) being defined in the hydropneumatic actuator (32), in where the air pressure is directly related to the hydraulic pressure applied to the brakes (18) during braking and braking release cycles; characterized in that the detection means of   pressure (70) are associated with the hydraulic actuator   pneumatic (32) so as to detect the pressure   of air in the pneumatic control chamber (36).   Hydropneumatic anti-lock device according to claim 1 or 2, characterized in that the pressure sensing means comprise a pressure sensor (70) comprising at least one strain transducer consisting of by a thick film resistor.   4. Braking system for a motor vehicle having an anti-lock device for the wheels of this vehicle conforming to any one of the preceding claims.