FR2657059A1 - HYDRAULIC BRAKING SYSTEM. - Google Patents

Abstract

This hydraulic braking system comprises a device for regulating the braking slip and / or the traction slip, this system comprising a master cylinder (1), actuated by a pedal, at least one wheel brake (3), communicating with this master cylinder (1) via a brake line (2), the pressure medium being sent from the brake master cylinder into the wheel brake cylinder via the brake line brake when the pedal is actuated, and a hydraulic pump (4). According to the invention, it is characterized in that the pump (4) is interposed in the brake line (2) in such a way that the suction side (S) of the pump (4) communicates with the master cylinder brake (1), while its discharge side (D) communicates with the wheel brake cylinder.

Description

The invention relates to a hydraulic braking system comprising a

  device for regulating the brake slip and / or the traction slip, this system comprising a master cylinder, actuated by a pedal, at least one wheel brake, communicating with this master cylinder via a brake, pressure agent being sent from the brake master cylinder to the wheel brake cylinder via the brake line when actuated

  pedal, and a hydraulic pump.

  A braking system of the type indicated above is for example

described in DE-A-3 831 426.

  The function of the pump is to return the pressure agent discharged from the wheel brakes to the brake line during regulation. For this purpose, the suction side of the pump communicates with a pressure agent accumulator which can be connected to the brakes. wheels, while the

  discharge side of the pump communicates with the brake master cylinder.

  The pump is therefore mounted as a bypass with respect to the brake line, so that it is not crossed by the pressure agent during a

braking without regulation.

  A connection on the suction side with the brake master cylinder is only established during a traction slip regulation In this case, the pump sucks in the pressure agent from the associated reservoir

  to the brake master cylinder so that it is sent to the All-wheel brake

  times, this only happens when the brake master cylinder is not

  actuated, i.e. is without pressure.

  A circuit of the type described above has two essential drawbacks In regulating the braking slip, the pump delivers from the pressure agent accumulator, which is without pressure, against the pressure prevailing in the master -cylinder, which has the consequence that, especially in the case of a cold and viscous brake fluid, the pump does not reach its full flow until after a phase

  extended start-up This in turn reduces the quality of the regulation.

  Another disadvantage is that the auto pump

  priming creates a depression if there is not enough pressure agent available on its suction side Air can get into this depression if the corresponding seals are damaged It is difficult to extract this air of the braking system since the pump is bypassed on the brake line Air inclusions in the braking system may cause

failure of the latter.

  This is why the invention aims to provide a hydraulic braking system which, whatever the ambient temperature, permanently ensures a high quality of the regulation and presents a low risk of failure, that is to say to say whose air can be

  evacuated in a particularly easy way.

  To this end, the invention relates to a hydraulic braking system, of the aforementioned type, characterized in that the pump is interposed in the brake line in such a way that the suction side of the pump communicates with the master- brake cylinder, while its side

  discharge communicates with the wheel brake cylinder.

  Since the pump is provided in the brake line, there is, when starting the pump, a pressure balance between its suction and discharge sides, which ensures, in particular at low

  temperatures, a significant improvement in pumping.

  swimming, inevitable air pockets are forced out of the pump Capacity

  of operation of this pump is thus maintained.

  The device for modulating the braking pressure comprises, in the usual manner, inlet and outlet valves which control the sending of a pressure agent to the wheel brake. These valves are electromagnetically controlled; the control signals are supplied by an electronic operating device which processes the sensor signals

  which record the rotational behavior of the wheels.

  A separation valve located between the master cylinder and the

  suction side of the pump causes, during a sliding regulation

  braking, uncoupling the master cylinder from the braking circuit, so that pressure fluctuations in the

  system have no impact on this master cylinder.

  A high pressure accumulator placed on the discharge side of the pump receives the pressure agent delivered by the latter and serves as a pressure generator in place of the master cylinder To prevent this accumulator from already receiving pressure agent during normal braking, its spring has a sufficiently high preload so that the accumulator does not receive a pressure agent for a pressure which does not

  not yet lead to a wheel lock.

  A direct line, comprising a non-return valve and located between the wheel brake and the master cylinder, prevents the pressure prevailing in the wheel brake from being higher than the pressure prevailing in the

  brake master cylinder, allowing the driver of the motor vehicle

  bile to interrupt braking in regulation by reducing the pressure it exerts on the pedal The reduction in pressure during braking

  without regulation is also carried out by this direct line.

  So that pressure can develop in the wheel brake when the pedal is not actuated, as is necessary in the case of traction traction regulation, there is provided in the direct line a control valve electromagnetic which blocks this

  direct driving during traction slip regulation.

  A pressure relief valve located between the suction and discharge sides of the pump prevents the pressure from rising in a way

  excessive on the discharge side of the pump.

  Preferably, the separation valve located in the brake line can also be actuated mechanically; in this case it would

  advantageous to mechanically couple the separation valve and the accumulator

  lator, which would cause this separation valve to close during a

  displacement of the accumulator piston.

  The function of the pressure relief valve can also be fulfilled in the accumulator For this purpose, the accumulator piston is provided

  a valve which, after a determined stroke of this piston of the accumulator

  lator, is pushed back by a pusher so as to open against the force of the spring The pressure agent located in the

  the accumulator can flow into the back-pressure chamber which

  connects to the suction side of the pump via a connecting line The energy required to fill the accumulator is therefore reduced. However, it is also possible to bring a quantity of high pressure additional pressure agent (corresponding to the volume of the back-pressure chamber), so that, even if the pump fails during regulation, this

the latter can be continued.

  An adjustable throttle located in the connection provided between the suction side and the discharge side of the pump can also have a

  positive influence on the operating capacity of the pump.

  Another advantage offered by the system lies in the fact that an amplification effect can be obtained. For this purpose, the pump must be controlled in a manner proportional to the force exerted by the

pedal.

  Other characteristics and advantages of the invention stand out

  derive from the description which will follow as nonlimiting examples and

next to the accompanying drawings.

  We must first describe Figure 1 which illustrates the basic principle of the invention The braking system comprises a master cylinder of

  brake 1 to which one or more wheel brakes 3 are connected by means of

  diary of a brake line 2 Pump 4, which must be described below

  after in more detail, is provided in this brake line, its suction side S communicating with the brake master cylinder 1 via a first portion of brake line 5 and its discharge side D communicating with the wheel brake via a second portion of brake line 6 In this second portion of brake line 6, an inlet valve 7 is provided which is actuated electromagnetically In its basic position, it keeps the pipe open, while it blocks it in its switched position A wheel brake 3 communicates with a pressure agent accumulator 10 via a return pipe 9, an outlet valve 8 being provided in this return line 9; this outlet valve 8 is also actuated electromagnetically, but, in its basic position, it blocks the return line, while it opens it in its switched position The pressure agent accumulator 10 is an accumulator low pressure with limited accumulation capacity It communicates with the first portion of brake line 5 (outlet point E) via

  a non-return valve 11 Between the outlet point E and the master-

  brake cylinder 1, an isolation valve 12 is provided which, in the present embodiment, is actuated electromagnetically and which, in its basic position, keeps the brake line open,

  while, in its switched position, it blocks this brake line.

  The wheel brake 3 communicates directly with the master cylinder.

  dre brake 1 via a direct line 13 This direct line 13 comprises a non-return valve 14 opening in the direction of the brake master cylinder Furthermore, in this direct line 13, a blocking valve is provided 15 which, in view of its function, will be called hereinafter ASR valve (in German: traction slip regulation) In its basic position, it keeps the direct line open, while, in its switched position, it takes during a traction slip regulation, it blocks this direct line The discharge side of the pump is connected to a high pressure accumulator 16 which, in the present embodiment, is a piston type accumulator The piston 17 of the accumulator is charged by a powerful spring 18 so that the accumulator chamber has its smallest volume The spring accumulator 1 i is subjected to a prestress such as a minimum pressure d must be available on the discharge side D of the pump so that the volume of this accumulator increases. The pump 4 according to this embodiment is in the form of a piston pump, the piston 19 of which is moved by means of an eccentric 20 driven by a motor. The chamber 21 of the pump which is located in front of this piston 19 communicates with the suction side S and with the discharge side D of the pump 4 respectively via a non-return valve 22 and a non-return valve 23 The non-return valve 22 opens in the direction of the the pump, while the valve

  non-return 23 blocks in the direction of this chamber An over-pressure valve

  sion 24 connects the discharge side of the pump to its suction side, thereby preventing an overload from occurring on the pressure accumulator 16. The braking system shown operates according to the following principle:

1 Braking without regulation.

  By actuating the pedal (shown diagrammatically),

  the pressure agent is sent to the wheel brake 3 from the master

  brake cylinder 1 The path of the pressure agent passes through the isolation valve 12, which is opened, by the first non-return valve 22, by the chamber 21 of the pump, by the second non-return valve 23 and by the valve input 7 which is open Pressure builds up in the wheel brake 3, which brakes the wheel and therefore slows down the motor vehicle If the pedal is released, the pressure agent

  returns from wheel brake 3 to the brake master cylinder in step-

  sant by the non-return valve 14, which is open, by the direct line 13 and by the ASR valve 15 which is open It is important that the pressure development path passes through the chamber 21 of the pump to the

during normal braking.

  2 Braking slip regulation.

  The braking behavior of the wheel to be braked is monitored

  permanently using sensors (not shown) An electro-

  The operating unit can immediately detect when the wheel has a tendency to lock up. When this happens, the operating unit requests the following actions: the inlet valve 7 is first switched, so as to block the brake line The outlet valve 8 is open, so that the pressure agent can flow from the wheel brake into the low-pressure accumulator 10 The valve 12 is closed, which disconnects the master -brake cylinder in relation to the braking circuit The pump motor M is started, which allows the pump to send the pressure agent from the low pressure accumulator 10 to the high pressure accumulator 16 The piston 17 moves against the force of the spring 18, so that there prevails, at the outlet of the pump D, a pressure corresponding to this force of the spring By means of a successive switching of the inlet valve 7 and outlet valve 8, age pressure can be sent to the brake

  wheel and be removed from it This is done according to a specific algorithm.

  mined, so that an optimal slip value can be set on the wheel Via the direct line 13, the pressure prevailing in the wheel brake is limited to the pressure prevailing in the brake master cylinder Si so the driver releases the force he exerts on the pedal, the pressure prevailing in the wheel brake also decreases, so that the braking operation or the regulation operation

stops.

  3 Traction slip regulation.

  If the wheel is a drive wheel, the torques transmitted by the engine of the motor vehicle may exceed the torques which can be transmitted between the tire and the roadway, which causes the wheel to slip. This situation can be prevented by an action applied to the brakes, the engine torque being compensated by a braking torque to such an extent that the remaining torque is adapted to the forces that can be transmitted between the tire and the

  pavement The sensors mentioned above are also capable of detecting

  ter a tendency to slip The electronic operating unit controls the following actions: the pump motor is started, which causes the reservoir pressure agent associated with the brake master cylinder to be sent to the pump '' to the wheel brake via the brake master cylinder and the isolation valve which is open The ASR 15 valve is closed, so that the pressure agent sent to the wheel brakes cannot return to the brake master cylinder passing through the direct line As in the case of brake slip regulation, an optimal brake pressure can now be set in the wheel brake by switching valves 7 and 8 If a system braking system must comply with such an eventuality, the pump must be of the self-priming type, since, in the case of traction traction control, there is no static pressure on the suction side of the pump L pressure relief valve 24 prevents pressure

  excessive to develop on the discharge side of the pump.

  We will now describe the embodiment in accordance with the

figure 2.

  This embodiment according to FIG. 2 corresponds essentially to that of FIG. 1 Unlike FIG. 1, the isolation valve is not actuated electromagnetically, but on the contrary mechanically, by depending on the filling level of

the high pressure accumulator 6.

  To this end, the accumulator 17 and the valve 12 are arranged in a common housing. On its face facing the accumulator chamber, the piston 17 has an extension 30 of a smaller diameter than this accumulator piston 17 Ce extension 30 is guided in a sealed manner inside a bore and, at its end opposite to the accumulator piston 17, it comprises a pusher 31 which can pass through a bore 32 This bore communicates an inlet chamber 36 with an outlet chamber 37, the inlet chamber 36 communicating with the brake master cylinder and the outlet chamber 37 communicating with the discharge side of the pump The outlet chamber 37 is delimited by the front face of the extension 30 The valve isolation includes a valve ball 34 located in the inlet chamber 36 and a valve seat 33 located on the bore 32 A valve spring 35 pushes the valve ball towards the valve seat 33 When the valve piston e 17 is in its basic position, i.e. in a position in which the accumulator chamber

  offers the minimum volume, the plunger 31 passes through the bore 32,

  thus providing the valve ball 34 at a distance from the valve seat 33 There is a free passage of pressure agent from the brake master cylinder 1 to the pump During regulation of the brake slip or of the slip

  of traction, the accumulator is filled, as has been explained above.

  demment, which causes the accumulator piston to move to the right as shown in the figure, as soon as there is sufficient pressure on the discharge side of the pump The plunger 31 is removed from the bore 32, which brings the valve ball 36 into contact with the

  valve seat 33: the brake line is blocked The rest of the function-

  braking system corresponds to that of the braking system

according to figure 1.

  FIG. 3 represents another embodiment of the braking system in accordance with FIG. 1, the essential residing in the fact that

  the pressure valve is now shown inside the accumulator

  For this purpose, the accumulator piston contains a valve 43 The accumulator piston separates the chamber 40 from the counterpressure chamber 41 The valve 43 includes a communication bore formed in the piston 17 between the two chambers 40 and 41 A valve element is disposed inside the accumulator chamber 40 and can be applied to the communication bore When the accumulator piston is moved to the right in the figure, a pusher 44 moves in the bore , by lifting from this bore the ball of the valve 43, so that a communication allowing the passage of fluids is established between the accumulator chamber 40 and the back-pressure chamber 41 The latter communicates with the suction side of the pump via a connecting pipe 42 If, as a result, a determined level of

  filling of the accumulator, and therefore a pressure determined inside

  of the accumulator chamber, pressure which corresponds to the compression

  the spring 18 is reached, the valve 43 opens, so that the pressure agent admitted additionally into the accumulator chamber returns to the suction side of the pump via the counter chamber. pressure 41 The rest of the arrangement and operation of the braking system correspond to that of the braking system of the

figure 1.

  FIG. 4 represents a complete braking system for a four-wheeled motor vehicle comprising wheels 64, 65, 66 and 67, the designations HR, HL, VL and VR having the following meanings HR = rear right, HL = rear left, VL = front left,

VR = front right.

  The master cylinder 1 comprises two chambers 60 and 61, each of which forms a braking circuit. The brakes of the wheels HR and HL are connected to the chamber 60 by means of brake lines 2 '. The braking pressure prevailing in the two brakes of wheels is subject to current regulation using a regulation system of the type shown in Figure 2 The VL and VR wheel brakes communicate with

  chamber 61 of the brake master cylinder respectively via

  diary of line branches 62 and 63 of brake line 2 '.

  Each of these branch lines 62 and 63 comprises a system of

  regulation of the type represented in figure 2.

  The braking system therefore has three control circuits.

  tion each of which includes a 4 ', 4 "or 4" pump. It should be noted in this regard that the regulation system can naturally also correspond

in Figures 1 and 3.

  Special mention should be made of the fact that the 4 ', 4 "and 4"' 'pumps are driven by means of a common drive, namely the EM electric motor. Another particular characteristic resides in the fact that the valves respectively inlet and outlet are in the form of a 3-way valve / 2 positions 58, 69 or 70 This results in a simplified system, but this implies the drawback that a maintenance phase cannot be carried out pressure in which both the

  brake line and return line are blocked.

  Each of the regulation systems operates on the principle previously described, while it is of course possible that the pressure prevailing in the wheel brakes of each regulation circuit is

  set independently.

Claims (13)

  1 hydraulic braking system comprising a device for regulating the braking slip and / or the traction slip, this system comprising a master cylinder (1), actuated by a pedal, at least one wheel brake (3), communicating with this master cylinder (1) via a brake line (2), the pressure agent being sent from the brake master cylinder into the wheel brake cylinder via the brake when the pedal is actuated, and a hydraulic pump (4), characterized in that the pump (4) is interposed in the brake line (2) in such a way that the suction side (S) of the pump (4) communicates with the brake master cylinder (1), while its discharge side (D) communicates with the cylinder of the wheel brake.   2 brake system according to claim 1, characterized in that, in the brake line portion (6) located between the pump (4) and the wheel brake cylinder (3), there is provided an inlet valve (7) which, in its basic position, is open and, in its switching position, blocks the brake line and in that the wheel brake (3)   communicates with a pressure agent accumulator (10) via   diary of a return line (9), an outlet valve (8) being inter-   laid in this return line (9) so as to block, in its   basic position, the return line and, in its commu- to open this line.   3 braking system according to claim 2, characterized   in that the pressure agent accumulator (10) communicates via the   medial of a non-return valve (11) and at a point (E), with the portion of   brake line (5) which is located between the pump (4) and the master   brake cylinder (1) and in that it is provided, interposed between the outlet point (E) and the brake master cylinder, an isolation valve (12)   which in its basic position is open and in its communal position   tation, blocks the brake line.   4 Braking system according to claim 2, characterized in that a high pressure accumulator (16) is connected to the discharge side (D) of the pump (4).   5 braking system according to claim 4, characterized in that the accumulator (16) is charged only at a minimum pressure on   the discharge side (D) of the pump.   6 braking system according to claim 2, characterized   in that the wheel brake (3) communicates directly with the master   i 1 brake cylinder (1) via a direct line (13), a non-return valve (14), opening in the direction of the brake master cylinder   (1), being interposed in the direct pipe (13).   7 braking system according to claim 6, characterized in that a blocking valve (valve ASR 15) is interposed in the direct line (13), this valve maintaining, in its basic position, the pipe   open and, in its switching position, blocking this line.   8 braking system according to claim 1, characterized in that the pump is a pump (4) of the reciprocating piston type whose pump chamber (21) communicates respectively with the suction side (S) and the discharge side (D) via a non-return valve (22, 23). 9 Braking system according to claim 1, characterized in that the suction side (S) of the pump and its discharge side (D)   communicate with each other via a pressure relief valve (24).   Braking system according to claims 3 and 4,   characterized in that the isolation valve (12) is mechanically actuated   by the piston (17) of the high pressure accumulator (16).   11 Braking system according to claim 10, characterized in that the isolation valve (12) is in the form of a seat valve whose valve element (34) is actuated by a push-button (31) provided on the piston (17) in such a way that the valve (12) closes during the charging the accumulator (16).   12 Braking system according to claim 5, characterized in that the isolation piston (17) of the high pressure accumulator (16) separates an accumulator chamber (40) from a back pressure chamber (41) , a valve (43) being arranged in the isolation piston (17), this valve (43) being actuated by means of a pusher in such a way that, for a determined level of loading of the chamber d accumulator (40), communication is established between the accumulator chamber (40) and the back pressure chamber (41).   13 braking system according to claim 12, characterized   in that the back-pressure chamber (41) communicates with the vacuum side   ration (S) of the pump (4) via a connecting line (42).   14 Braking system according to claim 1, characterized in that between the suction side (S) and the discharge side (D) of the   pump (4), an adjustable throttle is connected, the cross section of which   side is determined by the pressure difference between the vacuum side   ration (S) and the discharge side (D) of the pump.   Braking system according to any of the claims   previous cations, characterized in that a triple circuit system is provided for a four-wheeled motor vehicle, the wheel brakes of the rear axle and the wheel brakes of each of the front wheels respectively forming a control circuit, while that the pumps (4 ', 4 ", 4'" ') provided for the different control circuits have a joint training.   16 Braking system according to any one of the claims   previous actions, characterized in that the inlet valve (7) and the valve   outlet (8) are in the form of a 3-way / 2-way valve tions.