FR2559435A1 - STOP HOLDING DEVICE FOR MOTOR VEHICLE WITH AUTOMATIC TRANSMISSION - Google Patents

Abstract

THE INVENTION CONCERNS DEVICES FOR HOLDING AT STOP OF MOTOR VEHICLES. IT RELATES TO A DEVICE IN WHICH A SENSOR 101 OF THE ENGINE SPEED AND A BRAKE SENSOR 100 FORM SIGNALS THAT ARE USED FOR THE CONTROL OF A VALVE 70 WHICH CONTROLS A SELECTOR DISTRIBUTOR 75 SO THAT IT TAKES A FIRST OR A SECOND POSITION DEPENDING ON WHETHER A C1 CLUTCH MUST BE MAINTAINED IN TOTALLY DISENGAGED OR NOT. APPLICATION TO AUTOMOTIVE VEHICLES EQUIPPED WITH AN AUTOMATIC TRANSMISSION.

Description

The present invention relates to a stationary hold device for

to a motor vehicle

  equipped with an automatic transmission, and more precisely-

  a device of this type which can be put into the operating state or in the inoperative state without causing an impact on a clutch frictional engagement element, with the necessary sensitivity according to the depression of the clutch. the accelerator pedal. In

  a motor vehicle equipped with an automatic transmission

  With a fluid coupling, for example a torque converter, it can happen that, due to a friction torque of the torque converter, the vehicle moves forward or progresses despite the driver's will when the vehicle is in position. stop, the gear shift lever being in the forward position, so that a load is applied to the engine. This load applied to the engine, when it is idling, causes a drop in the speed of rotation of the engine, which can sometimes cause its

  rigging. The driver who wants to remedy this incon-

  veénient must press the accelerator pedal by an amount corresponding to the friction torque so that it prevents the decline in engine idling speed. However, this is not desirable at

  point of view of fuel consumption. As a result

  therefore, when the engine is idling, the transmission should be automatically

  in the neutral state so that the energy is no longer trans-

  between the engine and the driving wheels,

  that the driver does not have to depress the accelerator pedal.

  a significant amount and can save fuel. It is known that a stationary hold device, manufactured for this purpose, can also have

  as a benefit a reduction of the vibrations of the body-

  when the engine is idling, this being particularly effective when the device is

  applied to vehicles with front wheel drive.

  Although the progression of the vehicle

  be prevented by reducing the capacity for trans-

  couple mission of a co-operation element

  used for the start-up of the vehicle, ie

  say a first gear clutch, so that this torque is virtually zero when stopping the vehicle, the torque transmission capacity must be quickly restored when a load is applied to the engine,

  that is to say when depressing the accelerator pedal

  rator, so that the vehicle starts. When the driver

  the driver must move his vehicle in a narrow space, for example to park his vehicle in a space between other vehicles parked in line in the street in particular, it is desirable that the clutch remains in a state that allows a certain slip so that a low power transmission capacity can be obtained through the clutch, this capacity depending on the depression of the accelerator pedal with high accuracy. On the other hand, when the vehicle is started when no other vehicle is ahead, the period in which slippage is permitted should be as short as possible so that clutch engagement is quickly established. . Otherwise, the clutch is only engaged after the motor has reached a high speed, with an unpleasant shock and wear

premature clutch.

  In a vehicle equipped with a conventional device

  when the accelerator pedal is

  The idler is depressed and immediately released in the idle position, the hold-down device operates rapidly, so that the entire system formed by the engine and the transmission is suddenly released from the torque that rotated the rubber members. assuring the mounting and supporting all, in a significant manner, this torsional energy being abruptly removed from the mounting members, etc. and creating an unpleasant shock. The stopping function of the stopping device, so that it avoids this disadvantage, must appear with a relatively short delay, that is to say when the speed of the motor has sufficiently

  even after the accelerator pedal has been released.

  tor. In addition, it is known that increasing the internal pressure of the clutch of the first gear, in a manner that corresponds to the depression of the accelerator pedal, requires that the pressure in the clutch is not not reduced to a null value

  even when the hold-down device

  this pressure must be set beforehand to a value as close as possible, but less, to a pressure beyond which the clutch is engaged despite the force of a return spring placed

  in the clutch, that is to say the clutch pressure Pe.

  However, when the pressure in the clutch is thus increased to such a value close to the clutch pressure, previously, this increased pressure can play the role of a residual pressure during a subsequent displacement of the shift lever. speed towards the neutral position or the reverse position, so that the sensitivity of the

  response of the clutch to a speed change

  sent by the driver, especially in cold weather, is degraded. The subject of the invention is a device for

  stopping a motor vehicle of con-

  simple truction and which allows the adjustment of the energy transmission capacity of a friction cooperation element used for starting the vehicle, according to an exact function of a parameter representative of the load of the engine, for example the accelerator pedal depression, so that an unpleasant shock given by the friction co-operation element

  avoided during the sudden release of the accelerator pedal.

  the user, and so that a state allowing progress

  quickly obtained when the accelerator pedal is

rateur is brutally depressed.

  The invention also relates to a stopping device for a motor vehicle having an automatic transmission, which can have a high sensitivity to the movement of the shift lever by the driver, to a neutral position or a position reverse even

in cold weather.

  The invention relates to a device for stopping a motor vehicle having a motor, a fluid coupling, a transmission mechanism coupled in series with the coupling and having a frictional friction element, and a power source. an operating fluid for transmitting a fluid

  operation to the friction cooperation element.

  The stationary holding device comprises a motor load sensor for forming a signal with a fluid whose pressure is representative of the load applied to the motor, a control device placed between the friction cooperation element and

  the source of operating fluid, and a channelization

  of fluid for transmitting the fluid

  signal from the engine load sensor to the controller, the latter being

  to adjust the energy transmission capacity of the

  friction friction in a range between about zero and a predetermined value, depending on the pressure of the fluid representative of the signal, so that the progression of the vehicle when the engine is at

  a no-load state is prevented. A selective distributor

  The actuator is located in the fluid line and is intended to assume a first position in which it transmits fluid representative of the signal in both directions, from the load sensor of the motor to the control device and vice versa when the pressure of the fluid representative of the signal is less than a predetermined value, and to take

  a second position when it allows the fluid to be

  sensing of the signal to flow in one direction from the sensor of the load of the engine to the control device, when the pressure of the fluid representative of the signal

  exceeds the predetermined value.

  Preferably, the selector valve comprises a delay device for reducing the speed of a displacement from the second to the first position, when the pressure of the fluid representative of the signal

  falls below the speed of travel

  from the second position to the first when

  the repesentative fluid pressure of the signal increases.

  The control device, in a preferred embodiment, comprises a fluid inlet duct connected to the operating fluid source, a fluid outlet duct connected to the friction co-operating element, a distributor body placed in position. selectively ensuring the connection and disconnection of the inlet pipe and the outlet pipe and having a first and a second end face a first pressure chamber delimited in part by the first end face of the distributor body and intended to receive the pressure of the operating fluid of the outlet pipe, a second chamber under

  pressure delimited in part by the second end face.

  the third fluid channel having a constriction and arranged to always transmit the pressure of the operating fluid in the outlet line to the second pressure chamber , an elastic device pushing the body of the distributor in the direction which ensures the connection of the inlet and outlet pipes, and an evacuation pipe intended to allow the evacuation of the fluid at the operating pressure of the outlet pipe to a zone at a lower pressure when the distributor body is pushed in the direction of the disconnection of the inlet and outlet pipelines, due to a difference between the pressures existing in the first and second chambers under pressure, of a quantity corresponding to that for which

  the body of the dispenser is resiliently biased.

  Preferably, the stationary holding device further comprises a first valve mounted in the aforementioned first fluid channel between the control device and the selector valve, and arranged so that it allows the fluid to circulate in the

  only one direction, from the selector distributor to the

  control device, and a second valve placed in the aforementioned first fluid channel, parallel to the first valve and arranged to allow the fluid to flow in one direction, from the control device to the selector valve, the second valve being intended to open when the fluid pressure upstream of itself exceeds the pressure of the fluid

  downstream of a quantity which exceeds a predetermined value

undermined.

  The vehicle preferably also has a braking device, and the second valve is an electromagnetically controlled valve. The holding device

  at the stop includes in addition a brake sensor de-

  detecting whether the braking device is in operation or not, and a control circuit for opening the electromagnetic control valve when the braking device is detected in the operating position by the braking sensor, so that the braking capability is transmission of the frictional friction element is set to different values depending on whether the braking device is in

functioning or not.

  In a second preferred embodiment, the controller has a fluid inlet pipe connected to the operating fluid source, a fluid outlet pipe connected to the frictional engagement member, a distributor body for selectively connecting and disconnecting the inlet and outlet pipes and having a first and a second end face, a first pressure chamber delimited in part by the first end face of the distributor body and for receiving fluid at the operating pressure, in the outlet pipe, a second pressure chamber delimited in part by the second end face of the distributor body and intended to receive the pressure of the fluid representative of the signal,

  a third fluid channel having a constriction

  able and willing to always connect the canali-

  entrance to the outlet pipe, a

  resilient device pushing the body of the dispenser in the direction in which it provides the connection of the inlet and outlet pipes, and an evacuation pipe for discharging the fluid at the operating pressure of the outlet pipe to a zone to a reduced pressure when the body of the distributor is pushed in the direction corresponding to the disconnection of the inlet and outlet pipes, by a pressure difference existing between the first and the second chamber under pressure, by a quantity

  corresponding to the magnitude of the recall of the body of the dis-

  tributor. The stopping device also preferably includes a stopping valve for

  block the drainage pipe when the

  braking device is detected in the operating position

by the brake sensor.

  The control device, in the first and in the second preferred embodiment, further comprises a device for adjusting the amplitude of the

  the operating fluid pressure in the channeling

  output, preferably of the force of the elastic device, so that the power transmission capacity of the frictional friction element is substantially zero.

  Preferably, the control device com-

  also takes a fluid bypass line

  placed in derivation compared to the device of com-

  mating and connecting the frictional engagement member to the operating fluid source, and a check valve disposed in the bypass fluid conduit and for allowing fluid flow in a single direction, from the cooperation by

  friction at the source of operating fluid.

  Other features and advantages of the invention will be better understood when reading the

  description which will follow of examples of realization and

  with reference to the accompanying drawings, in which: FIG. 1 is a diagram of an automatic transmission of a motor vehicle to which the stopping device according to the invention applies; FIG. 2 is a diagram of the hydraulic control circuit used in the automatic transmission of FIG. 1, comprising the holding device

  when stationary according to a first embodiment of the invention.

  vention; FIG. 3 is a graph showing the variation of the operating fluid pressure, plotted on the ordinate, as a function of the opening of the throttle valve, plotted on the abscissa, in the case of the stopping device represented on FIG. Figure 2; FIG. 4 is a diagram of a similar circuit

  to that of FIG. 2, representing a hydraulic circuit

  control unit comprising the holding device

  when stationary according to a second embodiment of the invention.

  tion; Figure 5 is a diagram of a part of the control circuit of Figure 4, partly in section, showing a stationary holding distributor in a position in which it ensures the holding at the stop of the vehicle; and

  FIG. 6 is a diagram of the hydraulic circuit

  4 of the control circuit, in part, represents

  a selector valve having a speed change retarding function, in a second position taken when a throttling pressure

  Pt increases beyond a predetermined value.

  Figure 1 schematically shows an automatic transmission of a motor vehicle having four reduction ratios forward and reverse, the invention being applied to this transmission. The power of the motor E is transmitted

  the driving wheels W and W 'so that they are

  generated by means of a crankshaft 1 of the engine, a torque converter T constituting a coupling by a fluid, an auxiliary transmission M, and

  of a differential Df, in the order indicated.

  The torque converter T comprises a pump 2 connected to the crankshaft 1, a turbine 3 coupled to an input shaft 5 of the auxiliary transmission M, and a stator 4 which is coupled by a freewheel clutch 7 to a shaft 4a of stator which is itself supported on the input shaft 5 so that it rotates relative thereto. A torque is transmitted from the crankshaft 1 to

  the pump 2 and then to the turbine 3, in hydrodynamic mode.

  When an amplification of the torque is performed while the torque is transmitted from the pump 2 to the turbine 3, the resulting reaction force is collected by the

i sZtator 4, in a known manner.

  A drive gear 8 of the pump is

  mounted at the right end of pump 2 as

  1 in order to drive a hydraulic pump P shown in FIG. 2. A stator arm 4b is attached to the right end of the shaft 4a so that it controls a regulating valve Vr shown in FIG. FIG. 2. The auxiliary transmission M has an output shaft 6 which is parallel to the input shaft 5, and it comprises a gear train G1 of a first speed, a gear train G2 of a second speed, a gear train G3 of a third gear, a gear train G4 of a fourth gear and a gear gear Gr of reverse, placed in juxtaposed form between the input and output shafts, 6. The gear train G1 of the first gear has a drive gear 17 to be connected to the input shaft 5 by a clutch C1 of the first gear, and a driven gear 18 to be connected to the gear. tree

  output 6 by a CO freewheel clutch and cooperating with

  The gear train G2 of the second speed comprises a driving pinion 19 intended to be connected to the input shaft 5 by a clutch C2 of the second speed, and a driven pinion 20 fixed to the second gear. the output shaft 6, and cooperating with the driving pinion 19, while the gear train G3 of the third gear has a driving pinion 21 fixed to the input shaft and a driven pinion 22 intended to be connected to the output shaft 6 through a clutch C3 of the third gear and cooperating with the driving gear 21. The gear train G4 of the fourth gear has a driving gear 23 to be connected to the gear shaft. input 5 by a clutch C4 of the fourth gear, and a driven gear 24 to be connected to the output shaft 6 by a clutch selector Cs and cooperating

  23. On the other hand, the gear train

  Gr of reverse gear has a drive gear 25 solid-

  23 of the gear gear G4 of the fourth gear, a driven gear 27 to be connected to the output shaft 6 via

  of the selector clutch Cs, and an idle gear 26 cooperated with

  The selector clutch Cs is mounted between the driven gears 24 and 27 and has a selector sleeve S which can be moved between a left or forward position and a straight or reverse position such as shown in FIG. 1 so that it selectively connects the driven gear 24 or 27 to the output shaft 6. The freewheel clutch CO allows the transmission of the driving torque of the motor E only to the drive wheels W, W ', while preventing the transmission of the torque of the drive wheels W, W 'to the engine E. When the clutch C1 of the first gear is only engaged while the selector sleeve S is

  maintained in the forward position as

  1, the driving gear 17 is connected to the input shaft 5 and sets the gear train G1 of the first gear, allowing the transmission

  the torque of the input shaft 5 to the output shaft 6.

  When the clutch C2 of the second speed is then engaged, the clutch C1 of the first speed remaining engaged, the driving gear 19 is connected to the input shaft 5 and sets the gear train G2 of the second gear by which the torque can be transmitted from the input shaft 5 to the output shaft 6. Thus, even when the clutch C1 of the first gear is engaged, the gear train G2 of the second gear, the Third gear G3 gear train or the fourth gear gear G4 can be established using the CO freewheel clutch, rendering the gear train G1 of the first gear inoperative. When the clutch C2 of the second speed is disengaged and the clutch C3 of the third gear is engaged instead, the driven gear 22 is connected to the output shaft 6 and establishes the gear train G3 of the third gear. while, when the clutch C3 of the third gear is disengaged and the clutch C4 of the fourth gear is engaged instead, the driving gear 23 is connected to the input shaft 5 so that it establishes the G4 gear train of the fourth gear. On the other hand, when the clutch C4 of the fourth gear is

  only engaged while the selector sleeve S of the em-

  selector clutch Cs is moved to the right or the reverse position, the driving gear 25 and the driven gear 27 are respectively connected

  at the input shaft 5 and at the output shaft 6 and

  the gear train Gr of reverse gear,

  both the transmission of torque from the input shaft to the output shaft 6 via the train

gearing Gr of reverse gear.

  The torque transmitted to the output shaft 6 is then transmitted via an output pinion 28 mounted at a first end of the output shaft.

  6 to an enlarged pinion Dg differential Df.

  Referring now to Figure 2 which shows a holding device at a standstill according to a first embodiment of the invention; the hydraulic pump P draws working or operating hydraulic fluid into a reservoir R so that it transmits it under pressure to the pipes 29 and 94. The pressure of the fluid coming from the pump P is regulated to a predetermined value (called "pressure of channel Pi "in the rest of this paper)

  by the regulating valve Vr, and it is then trans-

  put to a distributor Vm gearshift, to a valve Vt controlled by the opening of the butterfly

  gases, and a distributor Vg maneuvering.

  After regulation to a predetermined value by the regulating valve Vr, the pressurized fluid is transmitted in part inside the torque converter T via an inlet pipe 34 which has a constriction 33 so that the internal pressure of the

  torque converter T is increased and that cavitation

avoidance.

  When the stopping device according to the invention is to be used with a gasoline engine, the valve Vt controlled by the opening of the throttle valve forms a representative parameter

  of the power of the engine E which is the pressure of foreign

  Pt or pressure corresponding to the depression of the accelerator pedal which is not shown, the engine E, that is to say that this parameter depends on the opening of the throttle valve (not shown) placed in the intake circuit E, the value being transmitted to a pipe 48 of pilot fluid. On the other hand, the maneuvering distributor Vg is rotated by the output shaft 6 of the auxiliary transmission M or by the enlarged pinion Dg differential Df and creates a maneuvering pressure Pg which varies with the speed of the vehicle and that is transmitted to a line 49

of pilot fluid.

  The speed change valve Vm is mounted between the fluid line 39 from the line 94 and a fluid line 40 and can be moved between a neutral position, forward positions such as D3 and D4 and a reverse position. When the shift valve Vm which has a manual control has one of the forward positions, the pipes

  38, 40 communicate with each other whereas, when

  that the distributor Vm is in the neutral position or in the reverse position, the pipe

  fluid communicates with a pipe 39 'of

  cuation of the pressurized fluid from the pipe to the reservoir R. A pipe 41 of fluid from the pipe 40 and contains a stationary maintenance distributor 50, described below in this mimicry, and it is connected to a part hydraulically operating first clutch clutch C1 constituting the frictional engagement element for starting the vehicle. The pressurized fluid of the pipe 40 is transmitted not only to the clutch C1 of the first speed via the distributor 50 for stopping, but also to the hydraulically operated parts of the clutches C2, C3 and C4 of the second, third and fourth gear, selectively, according to the switching provided by the change distibuteurs 1-2, 2-3 and 3-4 identified by the reference Vl, V2 and V3 respectively as described in the following of this memoir. The V1-V3 gearshift valves each have a drawer including a first end face

  is subject to the combined force of foreign pressure

  Pt and a not shown spring, and the other end is subjected to the operating pressure Pg, the distributors being intended to move from a first position or left position to a second position or right position when the operating pressure Pg exceeds the combined force due to Pt and spring pressure when increasing

  maneuver pressure Pg, that is to say an increase of

  speed of the vehicle. The forces of the springs

  V1-V3 distributors are set to different values

  respective parties. More precisely, the distributor

  V1 which is mounted between the pipe 40 and the pipe

  42 which is provided with a constriction 43, is intended to take the first position as shown when the speed of the vehicle is low so that it disconnects the pipes 42 and 40 from one another.

  When the distributor Vl is held in this position, the clutch Cl of the first speed can only be engaged so that it establishes the ratio of

  reduction of the first gear, as long as the

  stationary stopper 50 is open.

  As the vehicle speed increases, the distributor V1 is moved to the second or upright position to connect the lines 40 and 42 with each other. At this

  opportunity, the V2 distributor is in its first posi-

  As shown, it communicates line 42 with line 44 which is connected to the hydraulically operated portion of clutch C2 of the second speed. Although the two clutches C1 and C2 are engaged on this occasion, only the gear train G2 of the second gear is established and gives the reduction ratio of the second gear, because the gear train of the first gear GI is rendered practically inoperative when the clutch C1 of the first gear is maintained in the engaged state, due to the action of the freewheel clutch CO of FIG. 1. Similarly, when the clutch C3 or C4 of the third or fourth gear is engaged, the gear train G3 or G4 alone from the third gear

  or fourth gear is established, the gear train

  swims of the first speed G1 being rendered patiently

  inoperative although it remains in the engaged state.

  When the vehicle speed increases further, the change distributor V2 2-3 is moved to the right or to the second position so that it communicates the lines 42 and 45. In this respect, the distributor V3 still retains its first position or left position as shown so that it communicates the pipe 45 with a pipe 46 which is connected to the hydraulically operating part of the clutch C3 of the third gear, so that this clutch C3 is engaged and establishes the

  reduction ratio of the third gear.

  The change V3 distributor 3-4 is moved to the right or to the second position for a further increase in the speed of the vehicle, and the line 45 communicates with a pipe 47 connected to the hydraulically operated part of the clutch C4 of the fourth gear so that this clutch C4 is engaged and establishes the gear ratio of the fourth gear. The realization of this automatic transmission previously described

is known in the art.

  The stationary holding distributor 50, mounted in the pipe 41, has an inlet channel 51 connected by the pipe 41 to the pipe 40, and an outlet channel 52 connected to the operating part.

  hydraulically from Cl clutch of the first gear.

  A slide 55 of the dispenser 50 has a first end face 55a with a diameter greater than that of the other end face 55b, and the pressure application section of the first face is larger than that of the second face. . The face 55a of the slide 55 has a central portion which has a hole 56 of large size and a hole 57 of smaller size than the hole 56 and adjacent thereto, while the other end face 55b has a hole 58 at its end face. An annular groove 59 is formed at the outer peripheral surface of the spool 55 and is arranged to communicate the inlet channel 51 with the outlet channel 52 when the spool 55 is in the first position shown. The annular groove 59 communicates with the holes 57 and 58 through small holes (hereinafter referred to as "narrowing") and 61. A check valve 62 is placed in the hole 57 to allow the fluid to be pressurized. to flow in one direction, from hole 57- to

hole 56.

  A pressurized chamber 65 is delimited between the end face 55a of the spool 55 and an opposite end face of an end block 63, and a through hole (referred to as "the channel" in the remainder of this specification). 63a is in the block 63 and opens into the chamber 65 under pressure. A spring 64 is placed in the hole 56 of the slide 55 and pushes, at its first end, the face of the hole 56 and, at its other end, the opposite face of the block 63. The channels 51, 52 are arranged so that they communicate with each other by a line 67 of fluid connected in parallel with the dispenser 50 holding stationary and provided with a check valve 68 which allows the pressurized fluid to flow in one direction, the channel 52 output to the input channel 51. Line 67

  and the valve 68 ensure the return of the fluid under pres-

  in the clutch C1 from the first speed to a lower pressure zone when the manual shift valve Vm is moved from the forward position to the neutral position or the reverse position, so that the pressure internal clutch C1 is reduced rapidly and allows

  a rapid interruption of its maintenance in the engaged state.

  This arrangement is particularly advantageous when the viscosity of the operating fluid is high,

for example in cold weather.

  A valve 70 with electromagnetic control

  or the solenoid valve is mounted at one end of the

  The shut-off body 50 of the valve is intended to be displaced by the return force of a spring 72 so that it closes the channel 63a when electromagnet 73 is not powered, and that it is attracted. despite the force of the spring 72 and opens the channel 63a when the electromagnet 73 is energized, with communication of the chamber 65 under pressure with a channel 53. The valve 70 is of the needle type in which the body 71 or The needle 72 is urged out of the spring 72 to close the channel 63a, and the spring force 72 and the channel diameter 63a are set to suitable values so that when the solenoid 73 is not energized. , the pressure 3i prevailing in the chamber 65 is maintained at a predetermined value, as indicated hereinafter. The adjustment of the force of the spring and the diameter of the channel allows the opening of the valve 70 even when the electromagnet 73 is not powered, when the

  pressure in chamber 65 exceeds the predetermined value

  minus, to a degree corresponding to the difference between the predetermined pressure and the pressure prevailing in the chamber 65, so that this chamber 65 is placed in communication with the channel 53 via

  of channel 63a. The pressure chamber 65 can communicate with

  along with the channel 53 also by a bypass line 54 in which is mounted a check valve 66 so that the pressurized fluid can flow in one direction, from the channel 53 to the chamber

under pressure.

  A pilot fluid line 90 starts from the pilot fluid line 48 and is connected to a channel 75a of a selector distributor 75.

  described later in this

  a stop valve 74 associated with the distribution

  Vm manual change of speed and intended to open when the distributor Vm is in one of the forward positions. The selector valve has a channel 75b connected to the channel 53 of the device 50

  stopping, through a channel

  Another pilot fluid line 92 starts from the line 48 and connects to the pilot fluid line 91 disposed.

  between the channel 53 and the selector valve 75.

  A check valve 82 is mounted in the pipe 92 so that it allows the flow of the fluid under pressure in one direction, from the pipe 48 to the valve 82. The selector valve 75 has a slide 76, a chamber 78 under pressure delimited in part by a left end face of the slide 76, in Figure 2, and a spring 77 which pushes the slide 76 to the chamber 78 under pressure. This is placed so that it communicates with the pipe via a check valve 79 which allows the pressurized fluid to flow only from the pipe 90 of pilot fluid to the chamber 78, and it also communicates with line 92

  of pilot fluid by shrinkage 80.

  An annular groove 76a is formed on the surface

  external device of the drawer 76 of the selective distributor

  75, and is intended to communicate the channels 75a and 75b with each other when the drawer 76 is in the first position shown. The drawer 76 is pushed by the force of the spring 77, to the first position. When the pressure in the chamber 78 exceeds a reference pressure Ps determined by the force of the spring 77, the slide 76 moves to the right in FIG. 2, to a second position in which the channels 75a, 75b are disconnected. on the other hand, so that the selector valve is closed and prevents communication between

  conduits 90 and 91 of pilot fluid.

  The selector valve 75 has a shift delay function which is presented

  when it moves from a closed position to a posi-

  opening pressure imposed by the check valve 79 and the constriction 80. More specifically, when

  the throttling pressure Pt increases, it is trans-

  put in the chamber 78 under pressure both by the

  valve 79 and the constriction 80, so that the distribution

  scorer 75 closes quickly without delay and disconnects the pipe 90 of the pipe 91] On the other hand, when the throttling pressure Pt decreases, the fluid

  under pressure in chamber 78 is uni-

  only by shrinkage 80, with a lower flow rate. As a result, when the throttling pressure Pt has fallen below the reference pressure Ps due to the sudden closure of the throttle valve 33, the distributor 75 remains temporarily in the closed state and thus provides the delay function. . As previously indicated, the check valve 79, the narrowing

  and the selector distributor 75 cooperate in the training

  a retarder 81, and the flapper

  79 and the constriction 80 are made with the distribution

  selector scorer 75 in a one-piece package.

  In this arrangement, the stationary holding distributor 50 and the selector distributor 75 are connected to each other by a single line 91 of pilot fluid. Accordingly, the dispensers and 50, the latter having an electromagnet and an adjusting mechanism, can be placed individually at different locations, for example within the transmission and at the outer peripheral surface thereof, so that the construction of the whole

  of the hold device is simplified.

  A braking sensor 100 is intended to determine

  if the brake pedal, not shown, of the vehicle is depressed or not, and it creates a high level signal when the brake pedal is depressed. For example, a switch to turn on and off the brake warning lights can be used as

100 brake sensor.

  A sensor 101 of rotation speed of the engine

  detects the speed Ne of the engine by counting the inter-

  time range between adjacent pulses of an ignition signal for example, and it creates a high level signal when the detected speed Ne of the engine is lower than a predetermined speed Ns which is slightly greater than a reference speed, by

example an idle speed.

  The brake sensor 100 and the engine speed sensor 101 are connected to respective input terminals of an AND circuit 103 of an electromagnet control circuit 102. The AND circuit 103 has its output terminal connected to the base of a transistor Tr whose emitter is grounded and whose collector is connected to one end of the coil 73 of the electromagnet.

  , by a line 104. The other end of the electro-

  magnet 73 is connected by a line 105 to a power supply

  predetermined, not shown.

  We now consider the operation

  of the distributor 50 for holding down and distributing

  81 delay. When the vehicle is traveling, the output signals of the brake sensor 100 and the engine speed sensor 101 have a low level so that the transistor Tr is in the non-conductive state and prevents the supply of the coil 73 of the valve. 70. A

  this occasion, the pressure of the fluid or the pressure of

  Pt regulation corresponding to the depression of the accelerator pedal, not shown, is transmitted to the pipes 90 and 92 of pilot pressure. When the

  throttling pressure Pt exceeds the reference pressure

  Ps, the delay valve 81 is closed, its spool 76 being moved to the right in FIG. 2, so that the pilot fluid line 91 is disconnected from the pipe 90. Consequently,

  the pressure Pt throttling can be transmitted li-

  the pressurized chamber 65 of the standstill dispenser through line 92, valve 82 and pilot fluid line 91, but the pressurized fluid in chamber 65 can not not leave it. On this occasion, the pressure Pi of the pipe 41 has been transmitted in part by the constrictions 60, 61 of the distributor 50 to the opposite end faces a, 55b of the slide 55. As a result, the slide 55 moves downwards, to the first position as shown due to the difference of the pressure application sections between the end faces a and 55b and also because of the force of the spring 64, so that the channel 51 communicates with the channel 52

* via the annular groove 59. As a result,

  quence, the pipe pressure P1 is transmitted

  by the distributor 50 to the hydrau-

  liquefy C1 clutch of the first gear

which is thus engaged.

  When the accelerator pedal is released from its depressed state and at the same time the brake pedal is depressed so that the vehicle stops,

  the pressure Pt of throttling decreases when the

  throttle pedal decrease. However, the delay dispenser 81 remains temporarily in the closed state because of its shift delay function, thus avoiding the shocks due

  by the sudden release of the accelerator pedal.

  When the engine speed does not decrease below the reference speed Ns, the output signal of the engine speed sensor Ne is reversed and goes to a high level. On this occasion, the output signal of the braking sensor 100 has already been reversed to a

  high level since depressing the brake pedal

  swimming. As a result, the AND circuit 103 creates a high level signal which keeps the transistor Tr in the conductive state, the electromagnetically controlled valve

  then being excited and opening the channel 63a.

  At this time, the delay dispenser 81 has moved to the first position shown so that it communicates the pilot fluid lines 91 and 90, so that the pressurized fluid in the chamber 65 of the dispenser 50 escapes to the zone at lower pressure through the channel 63 which is thus open, and through the conduits 91, 92 of pilot fluid so that the pressure in the chamber 65 is reduced. Consequently, the slide 55 moves in the direction of the disconnection of the channels 51, 52 from each other, that is to say upwards in FIG. 2, under the action of the fluid under pressure acting on the end face 55b of the slide 55, with communication of the channel 52 with an evacuation channel 69 connected to the reservoir R, the pressure of the fluid in the pipe 51, at the channel 52, thus decreasing, c that is, the hydraulic fluid pressure (clutch pressure) transmitted to the operating part

  hydraulically clutch C1 of the first gear.

  The force acting on the slide 55 and lifting it in FIG. 2, that is to say the clutch pressure then applied to the clutch C1 of the first speed, is set to a value Po determined by the spring force 64. The pressure Po is set to a value almost equal to but slightly less than a clutch pressure Pe above which the clutch C1 of

  the first gear is engaged and causes a progress

  vehicle pressure, this pressure being determined by the force of a return spring, not shown, disposed

  in the clutch C1 of the first gear. As a result

  quence, this clutch C1 remains in the fully disengaged state, and the progression of the vehicle when it

is stopped is avoided.

  When the brake pedal is then brought back

  in its initial position, with a view to starting the vehicle

  cule, the signal of the braking sensor 100 is reversed and takes a low level. As a result, the output signal of the AND circuit 103 takes a low level and the transistor Tr goes to the non-conductive state,

  the electromagnetically controlled valve 70 being de-energized

  so that its body 71 moves under the action of the force of the spring 72 and closes the channel 63a. If the accelerator pedal is not depressed at this time, the body 71 begins to rise under the action of the pressure of the fluid present in the chamber 65 when this pressure becomes greater than the adjustment pressure Po of a value predetermined AP, so that the pressure in the chamber 65 under pressure escapes to the zone at lower pressure through the channel 63a, the pipe 91 of pilot fluid, the valve 81 of delay which is then open, and the pilot fluid line 90, the pressure of the fluid in the chamber 65 thus being set to a predetermined value Po + AP. This means that the force of the spring 64 of the stopping dispenser 50 is significantly increased by a value corresponding to a predetermined pressure AP, so that the internal pressure of the clutch C1 of the first gear, acting on its hydraulically operating part, increases from the adjustment pressure Po to the predetermined pressure Po + AP. Given this increase in the pressure of the value AP, the hydraulically operated part of the clutch C1 of the first gear can not

  perform ineffective running. This predetermined pressure

  completed AP may be weak. With this deletion

  the ineffective race, clutch C1 can now be

  positively maintained in a state in which progress is

  vehicle can take place. In addition, a shock caused during the return of the brake pedal can be reduced to a minimum value given the small pressure difference AP. The clutch pressure Pe then present in the clutch C1 of the first speed is indicated by the mixed line I of FIG. 3. In this same figure, the broken line represents the clutch pressure Pe at which the spring force

  of the piston of the hydraulic operating part

  liquefy C1 clutch of the first gear

  is balanced by the internal pressure of the C1 clutch.

  As mentioned before, when the internal pressure

  clutch C1 is greater than the operating pressure

  clutch Pe, the vehicle can progress, while when the first is less than the second, the

vehicle can not progress.

  When the accelerator pedal is then depressed, a throttling pressure Pt corresponding to the depressing of the accelerator pedal is transmitted

  to Line 91 through the channeling

  90 and the retarder 81 as well as through the line 92 and the valve 82, and it reaches the chamber 65 under pressure of the distributor 50 through the valve 66 so that the drawer 55 is pushed back downwardly in FIG. 2. When the throttling pressure Pt is lower than the reference pressure Ps and thus when the delay distributor 81 is in the open state, the slide 55 is moved downwards for an increase of the throttling pressure Pt, so that the outlet channel 52 is disconnected from the exhaust channel 69 and communicates with the single inlet channel 51. Thus, the clutch clutch pressure P Cl of the first speed is gradually increasing as

  indicates the curve in solid line II of Figure 3.

  The stationary hold dispenser 50 is usually

  The throttle opening of the throttle valve is increased to a position which allows progression for such an increase in the throttle pressure Pt. When the opening of the throttle valve increases beyond a predetermined opening Oo so that the throttling pressure Pt exceeds the pressure of

  Ps as shown in Figure 3, the distribution

  scorer 81 of delay closes and separates the canalisa-

  91 and 90 from each other. As a result, the pressures acting on the opposite faces 55a, 55b of the drawer 55 of the dispenser 50 become equal, and the drawer 55 is moved downward to the first position, given the difference between the sections.

  application of the pressure of the faces 55a and 55b of

  mity and the restoring force of the spring 64, the channels 52 and 51 then being put in communciation. Thus, the pressure Pi of the pipe 41 is transmitted to the hydraulically operating part of the clutch C1 of the first speed so that the clutch pressure P is increased to a value equal to the pipe pressure Pi, as indicated by the solid curve IIi of FIG. 3, the torque transmission capacity of the clutch C1 of the first speed thus being brought to a maximum value ensuring

  engaging clutch C1.

  When the brake pedal is held

  dark, the electromagnetically controlled distributor 70 remains in the open position as the engine speed Ne is less than the predetermined speed Ns. As a result, the clutch pressure P is then maintained at the value Po as indicated by the line curve.

  full IV of Figure 3. When the accelerator pedal is

  is then depressed, the clutch pressure P varies as indicated by the solid line curve II,

  so that the increased pressure Pt coming from the channeling

  91 of the pilot fluid is transmitted to the pressure chamber 65 via the channel 63a and

of the valve 66.

  The delay distributor 81 performs its function of delaying the change only when it is open, as indicated above. As a result, when the shift lever is moved to a forward position (D4), from the neutral position (N) in which the throttle

  gas is normally closed and thus the pressure of

  Pt is zero, the dispenser 81 is then in the open state so that the drawer 55 of the holding stationary dispenser is quickly pushed back so that it closes the pipe 41 placed between the clutch C1 of the first gear and the source of fluid at the operating pressure, preventing the clutch clutch from being clipped into the clutched state and thus preventing

  the application of a shock to the transmission.

  It should also be noted that when the stop valve 74 in the pipe 90 is made to open only when the shift lever is in a forward position (D4) and closes when the lever is in a position other than the forward (D4) position, vehicle progression can be avoided - only when the shift lever is in

the forward position (D4).

  FIG. 4 represents a holding device

  when stationary according to a second embodiment of the invention.

  tion, in which identical references designate corresponding elements, having substantially the same functions as those represented on the

  Figure 3 and whose explanation is deleted.

  A line 145 of fluid from the line 40 connected to the Vm distributor manual shift speed, the output side, and it is connected through a distributor 152 holding stationary whose construction is different

  from the distributor 50 of FIG. 2, to a channel

  tion 114 fluid connected to the clutch C1 of the first speed. A drawer body 153 of the dispenser 152 has an upper end face which has a pressure application section greater than that of its lower face. An axially central portion of the slide 153 has its outer peripheral surface which forms an annular groove 162 communicating through a small hole with a lower pressure chamber 161 delimited in part by the underside of the slide 153. The upper face of the slide 153 defines a part of an upper chamber 160 under pressure in which is mounted a spring 158 which constantly pushes the body 153 downwards in Figure 4. The spring 158 is abutted at its upper end against a set screw 165 so that that the axial displacement of the screw allows the adjustment of the force of the spring 158 to the desired value. Reference 165a denotes a locknut for securing adjusting screw 158 in the desired position, and 165b denotes a cover that can be removed from the dispenser 152.

  and which is intended to protect the adjusting screw 165.

  A bypass pipe 169 starts from the inlet fluid supply line 145 of the stop valve 152 and communicates permanently with the outlet pipe 114 of the same distributor.

  152 via a filter 164 and a retractable

  154. The upper chamber 160 under pressure of the distributor 152 communicates permanently with an outlet pipe 159 which is itself connected to a channel 180a of a selector valve 170 described hereinafter. A pipe 167 of reaction fluid leaves the pipeline of

  114 and is intended to communicate with a channel

  152 of Dispenser 152 through

  An electromagnetic control valve 156 and a conduit 166. The communication between the reaction line 167 and the evacuation line 163 is selectively established and stopped by

  the body 153 of the. dispenser drawer 152.

  The electromagnetically controlled valve 156 is electrically connected to a control circuit 102 '. The brake sensor 100, a vehicle speed sensor 182 and a temperature sensor 183 are

  The cooling water of the motor is connected to the respective input terminals of an AND circuit 103 'of the electromagnet control circuit 102'. These sensors

  , 182 and 183 determine predetermined conditions

  the sensor shown in FIG. 2. The vehicle speed sensor 182 is designed to form a signal having a high level. when the vehicle speed is below a reference value, and it includes a magnet that can be moved by a speedometer cable, and a switch to

  blade for example, while the temperature sensor 183

  engine cooling water is intended for

  to form a signal with a high level when the temperature

  the engine cooling water exceeds a reference value which can be set to a value of 0 C or less, and

  member formed of a ferrite-based material

  thermal flexibility, and a blade switch for example.

  When the speed of the vehicle is lower than the reference value and when simultaneously the temperature of the cooling water of the engine exceeds its reference value while the brake pedal is depressed, the output signal of the circuit AND 103 '

  to a high level and

  tor Tr in the conductive state, so that the valve 156

  is excited and moves its shutter 157 to the position

  higher or opening as shown. When any of the above conditions are not satisfied, the valve 156 is not energized so well.

  that its needle 157 takes a low or closed position.

  The selector valve 170 has its drawer body 171 which is always pushed to the left in FIG. 4 by a spring 172. A chamber 177 intended to house a spring is delimited in part by a right end face of the body 171 and it is connected to a drain pipe 178, while a pressure chamber 176 is delimited in part by a left end face of the body 171 and is connected by a parallel circuit formed by a valve

  174 of restraint and a narrowing 173, to a channeling

  tion 146 which transmits fluid to the foreign

  Pt. An axially central portion of the body 171 has its outer peripheral surface which has an annular groove 171a for communicating the channel 180a with a channel 180b when the body 171

  is in a first position as shown.

  Line 146 starting from line 48 of

  pilot fluid is connected to channel 180b, and a channelization

  tion 179 from the channel 146 is connected to a channel 180c which communicates in a permamence with the channel 180a. A check valve 175 is mounted in the pipe 179 so that it allows the fluid under

  pressure to flow in one direction, from the channeling

  146 to channel 180c. The distributor 170 also has a channel 180d which is connected to the pipe 145 and which is intended to be in communication, via the channel 180a, with the annular groove 171a when the body 171 takes a second position or right position shown on In this embodiment, the valve 174, the constriction 173 and the selector distributor 170 cooperate and act as a delay distributor 81 ', the like

  at the distributor 81 shown in FIG.

  The distributor 81 'of delay and the distribution

  stopping scorer 152 according to the second embodiment of the invention, operate in the following manner. When the vehicle speed is lower than its reference value and when the temperature of the engine cooling water exceeds its reference value while the brake pedal is depressed, ie when the vehicle is in conditions in which its progression must be inhibited, the valve 156 is in the excited state, its body 157 being pushed to the upper or open position. At this moment, if the throttling pressure Pt in the pipe 146 is practically zero, the body 171 of the selector distributor 170 remains in the left position under the action of the restoring force of the spring 172, putting into communication the pipe 146 and the pipe 159 via the annular groove 171a. Thus, the pressure in the upper chamber 160 of the distributor 152 is low. On the other hand, the pipe pressure P1 is introduced

  from Line 145 directly and / or through

  mediates the channel 169 provided with the constriction 154, in the lower pressure chamber and acts on the lower end face of the body 153 so that the latter moves upwards. When the body 153 moves upward during a certain stroke, the fluid conduit 166 which is connected to the conduit 114 communicates with the discharge conduit 163, and the fluid inlet conduit is closed. by the body 153 of the drawer. As the pipe pressure P1 acting on the underside of the body 153 is then transmitted only by the narrowing 154 of the pipe 169, to the annular groove 162 and the small hole 155,

  the body 153 of the drawer is held in the equilibrium position

  Figure 5 shows the pressure acting on the opposite end faces of the spool body. More precisely,

  when the body 153 of the drawer rises from the position

  5, the operating fluid in the annular groove 162 escapes through

  the pipes 167, 166 and the evacuation pipe

  163 so that the pressure in the annular groove 162 and in the lower chamber 161 decreases. So,

  the body 153 moves downwards and resumes its position.

  5. On the other hand, when the body 153 takes a position which is lower than that of Figure 5, the pressure P1 of the pipe is directly transmitted from the pipe 145 to the annular groove 162 and rapidly increases the pressure in the groove 162 and in the lower chamber 161, so that the body 153 is returned to the equilibrium position shown in FIG. 5. The clutch pressure P prevailing in the pipe 114 is thus maintained. at the pressure Po by the distributor 152, this pressure not being high enough to cause the engagement of the clutch C1 of the first gear. In

  Consequently, the clutch C1 remains in the disengaged state,

  thus fishing the progression of the vehicle.

  The value Po of the set pressure is determined by the pressure application surface of the underside of the body 153 of the slide, by the section of the constriction 154, by the pressure of the pipe P1, by the force of the spring 158, etc. and it can be set to a larger value by axially inwardly moving the adjustment screw 165 so that the spring 158 is compressed a little more, and it can be reduced by moving the screw outwardly 165 so that

  the restoring force exerted by the spring 158 decreases.

  When the throttle is open so

  that the Pt strangulation pressure prevailing in the channel

  The pressure 146 exceeds the reference pressure Ps', the increased throttling pressure Pt thus enters the pressure chamber 176 of the selector valve via the valve 174 so that the body 171 is moved to the right towards the second valve. the position shown in FIG. 6, despite the force exerted by the spring 172. In this way, the pressure P1 in the pipe 145 is then transmitted to the pipe 159 via the annular groove 171a of the selector valve 170. The pressure P1 in the pipe, transmitted from the pipe, exceeds the throttling pressure Pt transmitted by the pipe 146 and thus the valve 175 is closed by the pipe pressure P1, and the throttling pressure Pt prevailing in the pipe 146 born

  can not reach Line 159 through

  valve 175 of the pipe 179. Thus, the pilot pressure P1 is transmitted to the pipe

  159 instead of the throttling pressure Pt, practicing

  without any loss of this throttling pressure Pt.

  Thus, the selector distributor 170, in function

  tion of the Pt-strangulation pressure which is transmitted to it

  set as a pilot signal by the pipe 146, transmits the pipe pressure P1 to the pipe 159 when the throttling pressure Pt exceeds the predetermined pressure Ps'. The pipe pressure P1 thus transmitted to the pipe 159 is then introduced into the upper pressure chamber 160 by the

  channel 168 so that the body 153 of the drawer is fast

  downwardly, given the difference between the pressure application sections of the upper and lower faces of the body 153 of the distributor, and given the force of the spring 158, the inlet pipe 145 then communicating in full with the outlet pipe 114 so that the clutch C1 of the first speed is in the state allowing

a progression.

  It is now assumed that electromagnetically operated valve 156 is not energized, its needle-shaped body 157 being moved to the

  lower or closing position.

  When the throttling pressure Pt of the

  channel 146 is practically zero and thus

  that the pressure in the pipe 159 is low, the pipe pressure P1 of the pipe 145

  input is transmitted directly and / or through

  of the diversion line 169, to the distribution

  152, and it then enters the lower chamber 161 through the annular groove 162 and the small hole 155, so that the pressure of

  P1 channel acts on the body 53, on its underside

  and pushes it upwards towards the second position or position of

  the body 153 is maintained in this position the cana-

  The inlet 145 is closed by the body 153 so that the pipe pressure P1 is transmitted to the lower pressure chamber 161 only.

  through the narrowing 154 of the channeling

  Bypass 169, the annular groove 162 and the small hole 155. However, since the pressurized fluid of the pipe 114 can not be discharged through the pipe 167 which is then closed by the body 157, the clutch Cl of the first gear receives fluid at the pressure of the pipe P1 which is greater than the clutch pressure Pe and is thus

  put in a state allowing progression.

  When the throttling pressure Pt in the pipe 146 increases beyond the reference pressure, the pipeline pressure P1 is then transmitted through the pipe 159 and the channel 168 to the pressurized upper chamber 160, as indicated above. Thus, the body 153 is quickly moved

  down because of the difference in application section

  pressure cation of the upper and lower faces

  of the body 153 and given the force of the spring 158.

  In this respect, the inlet pipe 145 still communicates with the outlet pipe 114 so that the clutch C1 of the first speed is constantly

  in the state allowing progression.

  When the brake pedal is released from its depressed position while the clutch C1 of the first speed is maintained in the state maintaining the stop, the state allowing the progression of the clutch C1 is restored in the following manner. While the clutch C1 is in the now off state, the body 153 of the stationary hold distributor 152 assumes the second position shown in FIG. 5. When the brake pedal is released from its depressed position and thus when the valve 156 is no longer supplied and prevents communication between the reaction pipe 167 and its body 157, the pipe pressure P1 is transmitted to the pipe 114 via

  of the narrowing 154 of the drain line 169

  tion, so that the clutch pressure P of the

  The transition 114 gradually increases beyond the clutch pressure Pe without causing a downward movement of the body 153 of the spool. In this way,

  the clutch C1 of the first gear regains progress

  the state allowing progression.

  However, when the accelerator pedal is then depressed, the pipe pressure P1 is rapidly introduced into the chamber 160 under pressure through the selector valve 170 and the channel 168b as previously indicated, so that the body 153 of the drawer descends rapidly due to the speed of depression of the accelerator pedal, and the pressure in the pipe 114 thus increases rapidly. On the other hand, it is now assumed that the accelerator pedal is depressed while the electromagnetically controlled valve 156 remains in the energized state, for example, and the throttling pressure Pt increases by an amount corresponding to depression of the

  accelerator pedal when starting the vehicle

  climb uphill. In this case, at the beginning, when the accelerator pedal is depressed, and because of the action of the connection distributor 81 ', the pressure in the upper chamber 160 of the holding distributor 152 stops increasing proportionally to the 'increase

  opening of the throttle valve and increases progressively

  the clutch pressure C1 of the first speed, and finally reaches a value equal to the pipe pressure P1, so that the vehicle starts gradually. On the other hand, when the throttle valve is suddenly opened so that the vehicle starts quickly, the pressure of the pipe P1 acts directly on the body 153 of the distributor 152 and moves it downwards, so that the clutch C1 of the first speed quickly returns to a state allowing the progression, thus giving a good sensitivity to the device of maintenance at the stop when the driver wishes a

quick start of the vehicle.

  On the other hand, when the accelerator pedal is suddenly released from its depressed position and accordingly when the throttling pressure Pt prevailing in the pipe 146 decreases abruptly, the pressure of the fluid in the chamber 176 under pressure of the selector valve 170 is reduced progressively through the shrinkage 173 alone, so that the body 171 of the dispenser can be moved progressively to the left, in the same manner as in the case of the dispenser 81 of FIG. 2, until, finally, the communication between the pipes 145 and 159 is blocked by the body 171. No sudden shock can then take place during the sudden closure of the throttle valve, thanks to

  to the action of the distributor 81 'of delay.

  The delay distributor 81 used in the first embodiment shown in FIG. 2 can also be used directly in the second embodiment in place of the distributor 81 'of FIG. 4 or, conversely, the delay distributor 81'. of the second embodiment of Figure 4 can be used in the first embodiment instead of the distributor 81 of Figure 2. In the first case, the throttling pressure Pt alone is transmitted to the upper chamber 160 under pressure of the distributor 152 while, in the second case, the pipe pressure P1 is transmitted to the chamber 65 of the distributor 50 in place of the throttling pressure Pt when it exceeds

the reference pressure Ps.

  Although, in the previous embodiments

  teeth, the progression of the vehicle is prevented by stopping the communication between the clutch C1 of the first gear and the source of the operating fluid

  by the stop-hold dispenser, this distri-

  according to the invention can also be used in an arrangement in which the fluid under pressure

  which must be transmitted to the hydrau-

  liquefy clutch of the first gear C1 can be discharged to the tank, the vehicle progress

being prevented.

  Of course, various modifications can

37 -

  be made by those skilled in the art to the devices that have just been described as examples only

  non-limiting without departing from the scope of the invention.

Claims (11)

  A stationary holding device for a motor vehicle having a motor, a fluid coupling (T), a transmission mechanism (M) coupled in series with the fluid coupling and having an element (C1). ) of frictional cooperation, and an operating fluid source (P) for transmitting an operating fluid to the frictional engagement member, said device comprising a motor load sensor (101) for forming a signal in the form of a fluid having a pressure representative of the load applied to the engine, a control device placed between the friction cooperation element (C1) and the operating fluid source (P), and a circulation pipe   of fluid for transmitting the pressure   the signal from the load sensor of the motor (101) to the controller, the latter being adapted to adjust the power transmission capacity of the frictional friction element (C1) in a range. ranging from a substantially zero value to a predetermined value which depends on the pressure   of the fluid representative of a signal, so that the   the vehicle is prevented when the engine   is not subject to any load, said hand-held device   stationary being characterized in that it comprises   a selector valve (75) mounted in said channel   fluid circulation, and intended to take   a first position in which it allows the circulation   tion in both directions of the fluid at the pressure   the signal from the motor load sensor (101) to the controller and vice versa, when the pressure of the fluid at the pressure representative of the signal is less than a predetermined value, and   a second position in which it allows the circulation   pouring the fluid at the representative pressure of the one-way signal from the motor load sensor (101) to the controller when the pressure of the representative fluid of the signal is greater than said predetermined value.   2. Device according to claim 1, characterized   characterized in that the selector valve (75) comprises a delay device (81) for reducing the speed of displacement from the second to the first position, when the pressure of the fluid representative of the signal decreases, to a value below the speed moving from the second to the first position that takes place when the repesentative signal pressure increases.   3. Device according to claim 1, characterized   in that it comprises a second pipe for transmitting the operating fluid from the operating fluid source to the selector valve (75), and the selector valve (75) is for transmitting the operating fluid in place of the fluid at the signal representative of the signal to the controller through the aforementioned first fluid line when the selector valve is moved to the second position.   4. Device according to claim 1, characterized   in that the control device comprises a fluid inlet duct (51) connected to the operating fluid source (P), a fluid outlet duct (52) connected to the frictional engagement element ( C1), a distributor body (55) for selectively connecting and disconnecting the inlet pipe and the outlet pipe and having a first and a second end face, a first chamber under a portion delimited by the first face. end portion (55a) of the dispenser body and   intended to receive a fluid pressure of   in the fluid outlet duct, a second pressure chamber partially delimited   by the second end face (55b) of the body of the   scorer and for receiving the pressure of the fluid representative of the signal, a third fluid channel having a constriction and arranged so that it always transmits the pressure of the operating fluid in the outlet pipe   the second pressure chamber, an elastic device   pushing the body (55) of the distributor in the direction of the connection of the inlet and outlet pipes, and an evacuation pipe intended to allow the evacuation of the fluid at the operating pressure which is in the pipe of exit to a lower pressure zone when the distributor body is pushed in the direction of the disconnection of the inlet and outlet pipes under the action of a pressure difference between the first and the second pressure chamber, d an amount corresponding to the displacement of the body (55) of the dispenser.   5. Device according to claim 4, characterized   rised in that the third fluid channel   is formed in the body (55) of the dispenser.   6. Device according to claim 4, characterized   in that it further comprises a first check valve placed in the first fluid line between the control device and the selector valve (75), and intended to allow the flow of fluid in one direction, the selector valve to the controller, and a second valve disposed in the first fluid conduit in parallel   with the first flap and intended to allow the circulation   fluid in one direction, from the control device to the selector valve (75), and the second valve is intended to open when the pressure in   upstream exceeds the pressure downstream of a quantity exceeding a predetermined value.   7. Device according to claim 6, characterized   in that the vehicle has a braking device, and the second valve is an electromagnetically controlled valve (70), the stationary holding device further comprising a braking sensor (100) for detecting whether the braking operation or not, and a control circuit (102) for opening the electromagnetically operated valve (70) when the braking device is detected to be in the operating state by the brake sensor, if   although the energy transmission capacity of the   friction friction is set to different values depending on whether the braking or not.   Device according to claim 1, characterized   in that the control device comprises a fluid inlet pipe (51) connected to said operating fluid source (P), a pipe   fluid outlet (52) connected to the cooperative element   by friction (C1), a distributor body for   to selectively connect and disconnect channeling   inlet and outlet arrangements and having first and second end faces (55a, 55b), a first pressure chamber (65) delimited in part by   the first end face (55a) of the body of the   tor to receive fluid at an operating pressure in the outlet pipe, a second pressure chamber delimited in part by   the second end face (55b) of the body of the   tor and intended to receive the pressure of the fluid   signal, a third fluid channel having a constriction and intended to connect the inlet and outlet pipes, an elastic device pushing the body (55) of the distributor in the direction in which the inlet and outlet pipes are . connected, and an evacuation pipe   intended to evacuate the fluid at the operating pressure   which is in the outlet pipe to a lower pressure zone when the body of the   distributor (55) is pushed back in the direction of decon-   connection of the inlet and outlet pipes under the action of a difference between the pressures prevailing in the first and in the second chamber under pressure, an amount corresponding to the displacement of the body of the dispenser (55).   9. Device according to claim 8, characterized   characterized in that the vehicle comprises a braking device, the stationary holding device further comprising a braking sensor (100) for detecting the operation or otherwise of the braking device,   and a stop valve (74) for closing the channel   evacuation device when the braking device is detected as being in the operating state by the brake sensor.   10. Device according to claim 8, characterized   characterized in that the control device further comprises a device (165) for adjusting the pressure of the operating fluid in the outlet pipe so that the power transmission capacity by the frictional engagement element (C1) is substantially zero.   11. Device according to claim 10, characterized in that the adjusting device (165) is intended to adjust the elastic force of the organ elastic (168).   Device according to claim 1, characterized   characterized in that the control device further comprises a pipe which is shunt-mounted with respect to the control device and which connects the frictional engagement element (C1) to the operating fluid source (P), and a check valve mounted in this bypass pipe and intended to allow the flow of fluid in one direction only, from the friction element (C1) to the   the source of the operating fluid.