FR2555277A1 - DISPENSER COMPRISING BRAKE PISTONS - Google Patents

Abstract

THE INVENTION RELATING TO A VEHICLE ACCESSORY. THE INVENTION RELATES TO A DISTRIBUTOR FOR APPLYING A FLUID UNDER PRESSURE TO A HYDRAULIC MOTOR 40 OF A VEHICLE. THE DISTRIBUTOR IS PROVIDED WITH BRAKING PISTONS 15, 16 WHICH ACT IN BOTH DIRECTIONS OF OPERATION AND WHICH ARE CONTROLLED BY THE SUPPLY PRESSURE OF A PUMP 26. THE CONTROL IS SET AS, WHEN THE PRESSURE IS BUILT UP THE PUMP SUPPLY, THE BRAKING PISTON CONCERNED IS GRADUALLY OPENED, IN ORDER TO DRAIN THE WORKING FLUID REFLUTING FROM THE MOTOR TO THE RESERVOIR, WHILE IN THE EVENT OF A PRESSURE DROP THE BRAKE PISTON IS QUICKLY CLOSED THE REFLUX TO THE RESERVOIR IS RESTRICTED. THEREFORE THE VEHICLE IS EFFECTIVELY BRAKED DURING A DOWNHILL TRIP. APPLICATION IN PARTICULAR TO AN EXCAVATOR.

Description

The present invention, relating to a

  vehicle, and more particularly the hy-

  hydraulic system of a suitable vehicle engine, is

  only relative to a distributor, that is to say a multi-way valve, comprising brake pistons, this distributor serving to control the paths of a fluid under pressure between a receiver, in particular the propulsion engine of a vehicle, and a pump or between this receiver and a tank, by a piston of

  command that has holes on its fronts

  rate, in each of which a brake piston is

  guided, the latter being brought towards the opening

  re, in the working position of the control piston,

  contrary to the strength of a spring that builds

  be the control piston, by the pressure of

  of the pump acting between the brake piston and

  the control piston, a cross section of

  mande being cleared for the flow of the fluid under

  pressure from the receiver to the reservoir, and said pis-

  braking tone being displaced by the spring in the di-

  closing when the feed pressure

  drop, the control cross-section being

then strangled.

  The role of such valves provided with brake pistons or "distributors" is to avoid in a downhill run that the vehicle accelerates, in

  particular in the case of an excavator, and

  to be a safe descent. Such distributors can

  may also be provided with other receivers, eg with a hydraulic crane motor for "spinning"

a charge.

  With the distribute.r according to the invention, it

  is a double-acting valve comprising two

  brake, so that the receiver can be braked in both directions of rotation, in case it is working as a pump driven by

a charge.

  The invention starts from a known valve, in the-

  a brake piston is disposed in each of the front bores of the control piston of the multi-way valve. The braking piston is requested by the

  pump supply pressure and controls the

  flow of working fluid from the receiver to the reservoir.

  As long as the supply pressure of the pump, ie the pressure in the receiver, is sufficiently large, the flow cross-section for the

  circulating fluid is released by the brake piston.

  swimming from the receiver to the tank. When the feed pressure drops, the brake piston is pushed by a spring in the closing direction and causes the receiver to brake-because of the smaller cross-sectional area. But

  the braking pistons known until now have

  during unsatisfactory switching behavior

  and unstable operation that tends to cause

storage.

  The problem underlying the invention therefore consists in the fact that it is desired to perfect a valve comprising braking pistons of the type exhibited so as to stabilize its operation, even in the event of fluctuating pressure, and to obtain a control mode. job

  reliable both in the running position of the vehicle

  it is also in the braking position of the pis-

braking tones.

  According to the invention, this problem is

  solved by the fact that the order volume of each

  brake piston communicates via an annular gap between the brake piston and the control piston bore and via a channel in the brake piston and a brake valve.

  retainer closing the control chamber, with a groove

  ring, which opens into an annular channel

  linked to the pump. The invention will be further characterized in other aspects as will result from the following.

  Thanks to the above characteristics,

  the switching behavior of the brake piston

  swimming is stabilized. In this way, during the acceleration

  the vehicle's engine, the opening movement of the

  braking piston is slowed down and damped, because the

  in the control chamber of the brake piston increases gradually. It is avoided that on arrival of the control piston in the working position, the pressure increases in the control chamber of execute, so sudden, that the brake piston!

  contrary to the strength of the spring, movements

  sudden and sudden, which would lead to a mode of operation

  unstable. Moreover, when

  braking position, the displacement of the brake piston

  swimming runs very fast, so the engine

  the vehicle can not take, for reasons of safety

  speed, and the braking effect is achieved quickly and safely. The stroke of the control piston over time has the shape of a sawtooth pattern, with which the cross section

  gradually increases, but decreases

  pidement. Thanks to the nozzle provided in the channel in addition to the check valve, the movement of the piston of

  braking is slightly damped in the braking position

  stroke, so that oscillations of the brake piston are avoided in the event of pressure fluctuation. A clean hole in the control chamber ensures a safe and reliable start even with a

cold working fluid.

  In addition, the operation of the brake piston

  is improved thanks to the fact that each control piston has first, second and third

  bores and each of the brake pistons, a second

  the annular groove which communicates in the working position of the control piston via the first holes with the annular channel connected to the pump and, via the second holes, with an annular channel connected to the corresponding feed.

  of the receiver and communicates through the

  of the first holes, with an annular channel connected to the corresponding output of the receiver and with

  an annular channel connected to the reservoir via the intermediary

  re third holes controlled by a board edge

  brake piston. While doing it

  supply of the pressurized fluid to the receiver

  through the first and second

  in the control piston, connected to corresponding annular channels, the second holes are

  blocked for the return of the circulating fluid of the re-

  the receiver to the tank and this return is made

  early by third holes in a piston of com-

  the cross section is controlled by the brake piston. With this flow path, the hydraulic resistance in the feed of the pressurized fluid is decreased. Food and return

  each is carried out through the intermediary of the second

my and third holes.

  Advantageously, it is expected in each

  braking piston a bypass duct con-

  turning the control edge towards the third

  which is always open, so that the

  back to the tank is not completely inter-

  broken, which would cause too much pressure buildup. In addition this diversion channel, during the

  deflection of the control piston out of the cen-

  trale, allows immediate response from the receiver, because there is communication with the tank by the bypass duct, even before the brake piston is released to come into the running position. As a result the distributor according to the invention, comprising brake pistons, is distinguished by improved operation; it has a relatively large damping, when switching the position

  braking force in the running position, and a damping

  relatively small, when switching the

  operating position in the braking position. In-

  to avoid flutter and oscillations

  braking pistons and, in the event of

  pressure, the vehicle does not swing. An exemplary embodiment of the invention is exposed more

  detail in the following with reference to the drawing. Celui-

  shows: - in FIG. 1, the schematic representation of a

  distributor for a vehicle engine, comprising a piston

  control tone and brake piston shown cut off; - In Figure 2, on an enlarged scale, a section of the left half of the control piston shown in FIG.

figure 1.

  The distributor 10, shown in the drawing, comprises a control piston 11, which can move in the bore 12 of a housing not otherwise shown and which has, in each frontal face, a recess or bore 13, 14, in which is placed a brake piston 15, 16. Each brake piston 15, 16 is biased by a spring 17, 18, which bears against a

  respective cover 19, 20 of the corresponding control piston.

laying.

  The control piston 11 has in the center

  an annular groove 22 including compression grooves

  23, 24. In FIG.

  mande ll is shown in central neutral position, in which the pressurized fluid, supplied by a

  pump 26, passes through an annul-

  28 in the housing, the annular groove 22 and an annular channel 29 in the housing into a conduit 30 which is connected to each of the annular channels

  31 and 32 and the tank T. In the central position

  trale shown in Figure 2, the fluid or liquid

  hydraulic system flows without pressure until the

  see. If the control piston 11 is brought to the right

  or to the left in a working position, the pressurized fluid supplied by the pump 26 is more or less throttled by the fine control grooves 23 and

  24 and thereby undergoes an increase in pressure.

  In Figure 1, the control spool is in its working position completely to the right,

  position in which the annular channel 28 is complete

  and the entire discharge current of the pump 26 flows through a channel

  ring 34, a first bore 35, an annular groove

  nular 36 in the brake piston 15, a second

  piercing 37 and an annular channel 38 and through

  39 of a duct 39 to the hydraulic motor 40 of a vehicle, for example an excavator. As the constriction of the fluid under pressure is carried out for

  execution of the order through the reas-

  annular ring 22 or fine control grooves 23,

  24, the passage of the pressurized fluid from the annular channel

  re 34 to the annular channel 38 is carried out essentially

without obstacle.

  On the opposite side of the control piston 11, the corresponding annular channels are marked 44 and 48, the first and second holes 47 and 47, and the annular groove 46. It is seen in Figure 1 that the second holes 47 are closed due to the situation of the spool valve 11 in the distributor housing, so that the pressurized fluid flowing from the vehicle engine 40

  through conduit 49, is brought back by the

  intermediate of third holes 51 in the piston of

  11 to the annular channel 32 and, through

  re duct 30, to the tank T. The passage through

  the third passages 51 from the annular groove

  46 is controlled by an existing control edge 52 on the brake piston 16. By means of a

  bypass channel 54 formed in the brake piston

  age 16 or 15, working fluid can still circulate

in the annular channel 32.

  In normal operation of the vehicle, either while driving on a level ground, or up

  coast, or during an acceleration, the brake piston

  Swim 16 shall be placed in the position shown in Figure 1, that is, the control edge

  52 must clear the entire section of the third

  51, so that the circulating fluid driven out by

  the motor 40 can flow without obstacle until the

  the engine can deploy any

his power.

  For this purpose, between the brake piston 16

  and the bottom of the bore 14 is provided a chamber of com

  55, who is in communication through the intermediary of

  of the annular slot 56 between the brake piston

  16 and the bore 14, an annular groove 57 in the brake piston and a channel 58 in the control piston 11, with the annular channel 44, in

  which the pressure of the receiver or the pres-

  supply voltage of the pump. As a result of this pressure, when the vehicle is running or when

  acceleration, the brake piston 16 moves

  the spring force 18 to the right in the open position, in which the edge of

  control 52 releases the third holes 51.

  In FIG. 1, the third holes cor-

  Respondents are marked on the other side of the control piston 11 by 61, the control edge of the brake piston 15 by 62 and the bypass channel 64.

  corresponding way a control chamber is provided.

  of 65, an annular slot 66, an annular groove 67 and a channel 68. In addition, each control chamber 55 or 65 is connected via a channel 59

  or 69 and a check valve 60 or 70, to the groove

ring annular 57 or 67.

  The right half of the control piston is shown in Figure 2 on a larger scale. At start-up or during acceleration, if the piston

  command ll comes in the representative working position

  As a result of this, the pressure of the circulated fluid circulating and supplied by the pump 26 is increased, the control chamber 55 is also immediately subjected to this pressure via a bore 62.

  practiced in the control piston 11, so that

  sit8t during startup, even with a cold circulating fluid, the pressure begins to settle in the room

  55, while communicating more slowly

  through the annular slot 56 and the annular groove 57. This means that by rapidly establishing the pressure in the chamber of

  control 55, the brake piston 16 begins to de

  place to the right, after which the bore 62 used at startup is closed, so that the pressure

  continues to assert itself in room 55 through

  diary of the annular slot 56 and thus obtains

  damping of the movement of the brake piston.

  This is why this depreciation is of

  This is because a sudden rise in pressure in the control chamber 55 would exert a stronger action on the brake piston 16 than the spring reaction.

  18. As a result of depreciation,

  that the pressure rises in the control chamber 55,

  a slow opening of the brake piston 16 and the stability

  the progress of his movement.

  Moreover, even before the release of the third

  my bores 51, the working fluid of the receiver can flow from the side of the control edge 52 through the branch channel 54 through the conduit 549 and holes 51 to the annular channel 32 connected to the reservoir, so that the vehicle engine responds

  immediately upon actuation of the control piston 11.

  If then the control edge 52 then releases the sec-

  In the transverse direction of the third bores 51, the flow fluid displaced by the motor 40 of the vehicle can flow unhindered from the annular channel 48 and

  passing through the first holes 45, the annular groove

  nular 46, the third holes 51 and the annular channel

32 to the tank.

  If the vehicle then arrives on a

  steep ash, so that the vehicle's engine is

  driven and works like a pump, the brake piston

  swim 16 should get going as quickly as possible,

  for safety reasons, in the braking position

  swimming. In a downhill trip we should be able to

  blow to the tank, without 40 engine brake piston working as pump, so much working fluid

  that it could not come sufficiently under the pressure

  filling and that the supply current of the

  working fluid to the machine 40 would be interrupted.

  To avoid this, the pressure must be maintained on arrival. This is achieved by means of the brake piston, which is mounted as a resistor in the discharge outlet and which automatically ensures, being controlled by the filling pressure, that the pressure is maintained.

on admission.

  Thus, as soon as the motor 40 functions as a pump, the intake pressure falls in the chamber

  55, as well as the pressure of com-

  mande. The fluid under pressure in the chamber

  Mande 55 empties through the channel 59 and the check valve 60, which is then open, in the annular groove 57, as well as through the channel 58 in

  the annular channel 44. By releasing the pressure

  in the control chamber 55, the spring 18 de-

  places the brake piston 16 in the direction of closure, the discharge outlet being controlled by the control edge 52, in order to maintain the pressure of

  filling even with driving on a slope.

  If the filling pressure drops even further, the brake piston also reduces the discharge cross section until the pressure of

  filling is again constant. Thanks to the

  In the case of the discharge cross-section, the maximum operating pressure can be set on the return 49 of the machine 40, equal to the pressure of the brush, so that the machine 40 is braked and this allows a descent. without risk. Since the discharge cross-section is controlled by the filling pressure prevailing in the control chamber 55,

  we obtain that the filling pressure is now

  constant for any rotation speed of the machine.

  China. The diversion channel 54 leaves permanently

  a very small cross-section of open flow

  to the tank. The movement of the brake piston

  in the braking position can be influenced by

  a nozzle 71 placed in the channel 59. As a result, the pressure

  in the control room 55 can not abruptly

  fall. The corresponding nozzle in the brake piston

Swimming 15 is designated 81.

  The other brake piston 15 is also controlled by the intake pressure in the working position shown in FIG. 1, so that the

  communication between the annular groove 36 and the reservoir

  see is interrupted via channel 31.

he

Claims (6)

  1. Distributor to control the work   jets of a fluid under pressure between a receiver, in particular the hydraulic motor of a vehicle, and a pump or between this receiver and a reservoir, by a control piston which has holes on its front sides, in each of which a brake piston is   guided, the latter being brought towards the opening   re, in the working position of the control piston,   contrary to the strength of a spring that builds   be the control piston, by the pressure of   of the pump acting between the brake piston and   the control piston, a cross section of   mande being cleared for the flow of the fluid under   pressure from the receiver to the reservoir, and said pis-   braking tone being displaced by the spring in the di-   closing when the feed pressure   drop, the control cross-section being   strangled, characterized in that the volume of   (55,65) of each brake piston (15,16)   by means of an annular slot (56, 66) between the brake piston and the bore (13, 14) of the control piston and via a channel (59, 69) in the piston brake valve and a check valve (60,70) closing the control chamber, with a   ring groove (57,67) which opens into an annular channel nular (54,44) connected to the pump.   2. Dispenser according to claim 1,   characterized in that it comprises a nozzle (71,81) between the control chamber (55,65) and the check valve (60,70).   3. Dispenser according to claim 1 or 2,   characterized in that a bore (62,73) is provided   the control room (56,65) and the cancellation channel   re (34,44) connected to the pump, bore which opens into the annular channel (34,44) when the control piston (11) is in the central position and which is closed in the working position.   4. Dispenser according to one of the claims   1 to 3, characterized in that each control piston (11) comprises first, second and third bores (35, 37, 61, 45, 47, 51) and each of the braking pistons (15, 16), a second annular groove (36,   46) which communicates in the working position of the pis-   your order through the first   ges (35,45) with the annular channel (34,44) connected to the pump and, via the second holes   (37,47) with an annular channel (38,48) connected to the   corresponding reception and communication,   through the first holes, with a   annular valve (38, 48) connected to the corresponding output of the receiver and with an annular channel (31, 32) connected to the reservoir via the third bores (51, 61) controlled by a control edge (52, 62) of brake piston.   5. Dispenser according to claim 4,   characterized in that, starting from an annular groove (22) centrally provided in the control piston (11) for controlling the flow of the pressurized fluid of   the pump to the tank it is arranged in the   on both sides of the control piston and in the   succession, each time a cross section of communication (15,16) and the first, second and third holes -   6. Dispenser according to claim 5,   characterized in that in each braking piston (15, 16) there is provided a bypass channel (54, 64) by   intermediary of which communication is maintained   green, in the control piston, between the first   holes (35,45) and the third holes (51,61).