FR2604674A1 - DEVICE FOR MONITORING A PRESSURE LIQUID PUMP OF A BRAKING SYSTEM FOR A MOTOR VEHICLE - Google Patents

Abstract

TO MONITOR A PRESSURE LIQUID PUMP 30 FOR THE LIQUID SUPPLY OF A HYDRAULIC BRAKING SYSTEM FOR A MOTOR VEHICLE, A UNIT OF PISTONS IS PROVIDED, AN EFFECTIVE SURFACE OF WHICH CAN BE SUSPICED BY THE PRESSURE AT THE EXIT OF THE PUMP 28 AND THE EFFECTIVE OPPOSITE SURFACE MAY BE SOLICITED BY THE PRESSURE IN A BRAKING LINE 13, 14. IN THE PRESENCE OF SUFFICIENT PUMP PRESSURE, THE PISTON UNIT 37, 38 MOVES IN THE DIRECTION OPPOSITE TO THE PRESSURE IN THE BRAKE LINE 13, 14 AND OF THE CONTROL PISTON 49 IS ACTIVATED BY MEANS OF A CONICAL SURFACE 48, THIS PISTON ACTING ON A MONITORING SWITCH 52. THE CONTROL PISTON 49 IS ACTED BY THE PRESSURE OF THE PUMP IN THE OPPOSITE DIRECTION TO THE FORCE OF A COMPRESSION SPRING 51, THE FORCE OF WHICH IS PROVIDED SO THAT, IN THE PRESENCE OF THE MAXIMUM PUMP PRESSURE, THE CONTROL PISTON 49 CAN BE ACTUATED INDEPENDENT OF THE PISTON UNIT 37 , 3 8. THEREFORE, THE MONITORING SWITCH 52 IS AVOIDED FROM RETURNING TO ITS INITIAL POSITION IF THE PRESSURE IN THE BRAKE LINE 13, 14.

Description

The present invention relates to a device for monitoring

  the operation of a pressure liquid pump for feeding

  specification of a hydraulic braking system for a motor vehicle

  bile. Hydraulic braking systems for motor vehicles are frequently supplied with pressure fluid by a pressure fluid pump to allow the amplification of the braking force and the operation of a brake slip regulating device. For this purpose, the pressure liquid pump can for example charge a pressure accumulator in which the

  pressure liquid is withdrawn when necessary by means of the

  valve, or it can bring the liquid directly into the

  braking system, the pump drive being actuated only-

  ment when necessary, for example from the start of regulation

tion of the brake slip.

  Patent application P 36 01 914.3 describes a system

  hydraulic braking system for motor vehicles in which the pump brings the liquid directly into the brake lines without the intermediary of a pressure accumulator. A braking system of this type requires special monitoring of the working condition of the pump, in order to allow the disconnection of the brake slip regulating device in the event of an anomaly in the flow of this pump and in order to '' in this way avoid reducing the

  brake pressure established by the brake pressure generator

  swim. To monitor the pump pressure, the brake system

  described in this old patent application is equipped with a commuta-

  electric monitoring device which can be actuated by a piston urged by the pressure prevailing at the outlet of the pump in one direction and urged in the other direction by the pressure prevailing in the two braking circuits of the braking system, and which will actuate the

  monitoring switch as soon as a predefined pressure difference

  completed is exceeded. However, this arrangement has proved insufficient

  making it practical, because the flow rate of the pump

  that pressure is not enough, in the event of vigorous application of the brakes, to cause sufficient back pressure to oppose

  at the high brake pressure established in the brake circuits

  swimming by this braking action. For this reason it can happen,

  although the pressure liquid pump operates satisfactorily

  doing, that the monitoring switch takes the wrong position and that a malfunction of the pump control

is indicated in error.

  The object of the present invention is therefore to provide a provision

  sitive for monitoring the operation of a pressure liquid pump for supplying liquid to a hydraulic system

  braking for motor vehicle, device which will not be brought.

  by the excess pressure prevailing in the brake system, take a position indicating a malfunction when the pump

  pressure fluid works satisfactorily.

  According to the present invention this object is achieved by means of a piston unit, movable axially within limits, for the actuation of an electrical monitoring switch, an effective surface of the piston unit being able to be polluted by the

  pressure prevailing at the outlet of the pump and its surface effLcae op-

  posed being able to be applied by the pressure prevailing in the braking system, the dimensions of the effective surfaces being fixed in such a way that, in the presence of sufficient pressure from the pump, the piston unit moves in the opposite direction to the pressure of

  braking, as well as by means of a control piston, independently movable

  especially the piston unit, which can be stressed. by the pressure prevailing at the outlet of the pump in the opposite direction to the force of a pre-stressed spring and by which the monitoring switch is actuated in the presence of the maximum pressure of the pump. This device has the advantage of reacting to the pressure difference

  between the pressure prevailing at the pump outlet and the pressure

  in the braking system and at the absolute pressure

  constraining - the output of the pump, and that of bringing the switch of

  monitoring to take the malfunction position only-

  ment if the pump pressure does not reach -4a maximum value and if, simultaneously, the predetermined pressure difference between the pressure prevailing at the pump outlet and that prevailing in the

  braking system is exceeded.

  In a particularly advantageous embodiment of the device according to the invention, the control piston is arranged radially with respect to a piston of the piston unit and comes to bear, by its end urged by the pressure prevailing at the

  pump outlet, on a conical surface of the piston. Therefore

  quent, the control piston also forms an actuating push-piece which transmits the switching movement of the piston unit to the monitoring switch which can be actuated directly by the

  control piston. Therefore, the device is of simple design

  full and requires only an electrical monitoring switch.

  According to the present invention it is also possible to provide that the piston unit comprises two pistons arranged in series, that is to say a stepped piston actuating the monitoring switch, the surface of the end of plusgraRddiaTèdedecepistan being able to be stressed by the pressure of the pump and the surface of its smallest end which can be stressed by the pressure of a braking circuit of a two-circuit braking system,

  as well as a separation piston, the surfaces of the two ends of which

  tees have the same dimensions and can be requested respectively-

  by the pressure of one or the other braking circuit of the

  two-circuit braking system. In this conception the agency-

  The advantage is that even if the pressure in a brake circuit of the two-circuit brake system drops, it is still possible to reliably monitor the running condition of

the pressure liquid pump.

  In this embodiment, it may be practical, for

  to further refine the idea of the invention, that the separating piston

  tion has a central annular groove which communicates with a tank without pressure and thanks to which it is guaranteed that

  the two circuits of the two-circuit brake system are complete

isolated.

  The different objects and characteristics of the invention

  will now be detailed in the description which follows, made

  by way of nonlimiting example, with reference to the accompanying drawings which represent:

  - Figure 1, a Canmxicn diagram of a brake system

  two-circuit hydraulic stroke for an equipped motor vehicle

  of a device according to the invention for monitoring the operation

  ment of the pressure liquid pump, and - Figure 2, a longitudinal section taken in a mode

  of the monitoring device according to the invention.

  The two-circuit braking system shown in Figure

  gure 1 is composed of a tandem brake master cylinder 1 and an aplif ia er sicn 2 which can be actuated jointly by

  a brake pedal 3. The brake master cylinder in tandem 1 iilus-

  very sectional includes two isolated working chambers 4, 5 which can be reduced by a control stroke of the pistons 6, 7 of the

  master cylinder. Central valves 8, 9, open in their posi-

  initial tion, connect the working chambers 4, 5 to the chambers

  supply 10, 11 which communicate with a supply tank

  pressureless 12. The brake lines 13, 14 go from

  working chambers 4, 5 to solenoid valves 15, 16, open during

  that it is not excited, of a slip regulation device

  defreinap which are included in a valve block 17.

  Two wheel brakes 18 are connected to the solenoid valve 15, and two wheel brakes 19 are connected to the solenoid valve 16. In addition, the

  wheel brakes 18 can be connected by a solenoid valve 21, iron-

  mé when it is not excited, and the wheel brakes 19 can

  be connected by a solenoid valve 22, closed when not excited

  tee, to a return line 23 going to the supply tank 12. A pressure line 24, 25 starts from each brake line 13, 14. Each pressure line 24, 25 goes to a separate check valve 26, 27 which is closed in the initial position and which is also housed in the valve block 17. The anti-backflow valves 26, 27 are arranged so as to open only in the direction of the pressure lines 24, 25. A pressure line 28 go of

  the inlet of the anti-retcar valves 26, 27 at the outlet of a pump unit

  pe 29 which is composed of an electromotive drive pump 30 and a pressure relief valve 31 and the inlet of which communicates, via a line 32, with the supply tank 12. To monitor the operating state of the pump unit 29, a monitoring device 33 is provided which is connected to the braking lines 13, 14 and to the pressure line 28 and which is also included in the valve block 17. The operating mode of the system braking is

  described in detail in lac dmrE e evetallearcd 36 01 914.3.

  The details of the monitoring device 33 can be

  noted in the description of Figure 2. In a housing 35, a

  stepped bore 36 houses a stepped piston 37, while the smallest portion of stepped bore 36 houses a separating piston piston 38. The two stages of stepped piston 37 are guided by a cylindrical surface 39 on the wall of the stepped bore 36 and are sealed relative to the wall of the bore by means of a sealing ring disposed in each sliding surface 39. Similarly, the separation piston 38 comprises

  two cylindrical sliding surfaces 40 in which ba-

  sealing gues are arranged. Three compartments 41, 42, 43 and two annular chambers 44, 45 are cliTditês by the stepped piston 37 and

  in the pListoindc ration 38. Compartment 41 is located in the door

  tion of the end ceupzgardisrtre the stepped bore 36 and it is

  connected to the pressure line 28 of the pump unit 29. The comparison

  timent 42 is in communication with the brake line 13, and the compartment 43 is in communication with the brake line 14 of the brake system. The annular chambers 44, 45 communicate via the return line 23 with the supply tank 12. The annular chamber 44c1imited by the stepped piston 37 houses a compression spring 46 which rests on the stages of the stepped bore 36 and of the stepped piston 37 and which supports the stepped piston 37 oetreunbn vissédeferFeture47 by means of which the stepped bore

36 is closed.

  In the compartment 41, the stepped piston 37 comprises a conical surface 48 which decreases in the direction of the smallest stage of the piston. The conical surface 48 forms a ramp for actuating a control piston 49 which is slidably mounted in a radial bore inside the casing 35 and whose spherical end, which projects inside the compartment 41 , cooperates with the conical surface 48. The control piston 49 is sealed, at

  by means of a seal 50, relative to the casing 35 and it is supported

  dialing inwards against a hillock by a pre-stressed compression spring 51. By its end directed radially towards

  externally, the control piston 49 actuates a surge switch

electrical monitoring 52.

  The monitoring device 33 described operates in the following manner: When normal braking is carried out without the pump unit 29 being switched on and without the brakes being released, the stepped piston 27 assumes its position indicated on the drawing.

  mairteju by the compression spring 46. Likewise, the piston

  mande 49 is held by the compression spring 51 at the position

  indicated. As the pump unit 29 is not controlled, the compartment

  ment 41 remains without pressure. The same pressure prevails in the compartments 42 and 43 as in the braking lines 13 and 14. As the separation piston 38 is pressure balanced and the piston

  stepped 37 is applied on the bx mrde closing 47, no movement

  piston does not take place. Therefore, the monitoring device

  this receives no volume of pressure liquid.

  As soon as the pump unit 29 is switched on because 1diso-

  brake slip regulator detects a blocking state

  cage imminent during a braking operation, a pressure is established in compartment 41 which, in the presence of sufficient pump flow, moves the stepped piston 37 in the opposite direction to the force

  compression spring 46, resistance to displacement of the pis-

  control tone 49, and in the opposite direction to the brake pressure in compartments 42 and / or 43, while the control piston 49 is moved radially outward by the conical surface 48

  to the point that the monitoring switch 52 moves to take

  dre its other switching position. which is designed as if-

  general of the presence of a sufficient flow of the pump unit 29 given

  by the defreirge slip regulation device connected to the commu-

supervisor 52.

  The monitoring device 33 is designed such that the described switching action takes place before the pressure

  at the outlet of the pump unit exceeds that prevailing in the con-

  brake lines 13 and 14. In cases where the pressure in the

  brake lines 13 and 14 is comparatively low, the switching

  monitor 52 is activated as soon as the pump pressure

  is also weak. If due to a malfunction the

  the required pressure in the pressure line 28 of the pump unit 29 is not reached, the monitoring switch 52 will not be actuated and, therefore, the slip control device

  defreinage does not exercise its regulatory action.

  The prestressing force of the compression spring 51 is provided so as to be overcome by the pressure force exerted on the control piston 48 only if a maximum pressure is

  reached in the pressure line 28 and in the compartment 41.

  Below this maximum pressure, the prestressing force of the compression spring 51 can only be overcome by the stepped piston 37 by means of the conical surface 48. As the pressure prevailing at the outlet of the pump in the braking system described only slightly exceeds the respective braking pressure prevailing in the brake lines 13 and 14, the maximum pressure of the pump unit 29 will only be reached during the maximum application of the brakes

  for example when braking from u.rcoe In the case of this ftei-

  emergency stroke, the maximum pressure can still be exceeded in the brake lines 13 and 14 so that, as a result of this higher pressure prevailing in the compartments 42, 43, the stepped piston 37 can quickly return against the closing boazol 47 opposite the maximum pressure of the pump unit. Although the

  conical surface 48 d control piston 49 lifts up in this arrangement

  cement, - the control piston 49 remains in the position it has adopted

  due to the fact that the maximum pressure of the pump unit 29 is

  troduit in the compartment 41, and it thus allows the beginning of a regulation of the slip of braking-which assumes a particular importance especially in the cases of stop of urrioe. The monitoring switch 52 returns to its initial position only if the maximum pressure predetermined by the dimensioning of the spring

  compression 51 is not reached because it means a state of

  pressure fluid supply is required.

  -Seeing the mode of action described, the monitoring device

  33 even responds to extreme operating conditions and ac-

  faulty operation of the slip regulation device

freinge is avoided.

Claims (4)

  1. Device for monitoring the operation of a pressure liquid pump for supplying a hydraulic braking system for a motor vehicle, characterized by a piston unit (37, 38), movable in the axial direction, in limits, for the actuation of ixn cun / tbar of electrical monitoring (52), an effective surface of the piston unit which can be ground] here help the pressure prevailing at the outlet of the pump (28) and its effective surface   which may be soilJcite by the pressure prevailing in the system   braking system (13, 14), the dimensions of the effective surfaces   being fixed in such a way that, in the presence of sufficient pressure,   pump health, the piston unit (37, 38) moves in the opposite direction to the brake pressure, and by a control piston (49), movable independently of the piston unit (37, 38) ,   which can be stressed by the pressure prevailing at the outlet of the pump   pe (28) opposite to the force of a preloaded spring (51)   and by which the monitoring switch (52) can be   born in the presence of the maximum pump pressure.   2. Device according to claim 1, characterized in that the control piston (49) is arranged radially relative to a piston (37) of the piston unit (37, 38) and is supported by its end stressed by the pressure prevailing at the pump outlet   (28), on a conical surface (48) of the piston (37).   3. Device according to any one of claims 1   or 2, characterized in that the piston unit (37, 38) comprises two   pistons arranged in series, i.e. a stepped piston (37) action-   nant the monitoring switch (52), the surface of the end more grad diare dc oe pistn pviant being stressed by the pressure of the pump and the surface of its smallest end can be solicited by the pressure of a circuit of braking (13) of a two-circuit braking system, as well as a separation piston (38), the surfaces of the two ends of which have the same dimensions can be stressed respectively by the pressure of one (13) or of the other braking circuit (14) of the two-circuit braking system. 4. Device according to claim 3, characterized in that   that the separation piston (38) comprises an annular groove   which communicates with a non-pressurized tank (12).