FR2510710A1 - END OF RACE DEVICE FOR ASSISTED HYDRAULIC DIRECTIONS - Google Patents

Abstract

THE INVENTION CONCERNS A LIMIT SWITCH DEVICE FOR ASSISTED HYDRAULIC STEERING COMPRISING A CYLINDER 1 IN WHICH SLIDES A PISTON 2 EQUIPPED WITH A RACK 3 ENGAGING WITH A TOOTH SECTOR 4 SHIM ON A TURNING SHAFT. THE PROBLEM SOLVED CONSISTS OF ALLOWING THE ADJUSTMENT OF THE DEVICE WITHOUT WAITING FOR THE ASSEMBLY OF THE HYDRAULIC COMPONENTS OF THE VEHICLE INSTALLATION. THE DEVICE IS CHARACTERIZED IN THAT IT INCLUDES TWO VALVE ORGANS 35, 36 NORMALLY CLOSED AND ACTIVATED BY THE TOOTH SECTOR 4 IN THE MAXIMUM TURNING POSITIONS TO STOP THE MOVEMENT OF THE PISTON 2. THE INVENTION IS APPLICABLE TO VEHICLES WITH HYDRAULIC STEERING ASSISTED.

Description

End-of-stroke device for assisted hydraulic steering.

  The subject of the present invention is a

  positive end-of-travel device for hydraulic power steering, comprising a cylinder in which a piston defining two opposed working chambers is mounted for sealingly sliding a distributor for sending hydraulic fluid under pressure into one or the other of the chambers opposite and connect at the same time to the discharge chamber not fed with fluid under

  pressure, a shaft to control the steering of the wheels

  of a vehicle, a sloping sector wedged on that shaft and

  grantee with a rack made on the body of the piston to transmit the rectilinear displacements of this piston to the steering shaft and convert them into corresponding angular displacements, and a screw arranged axially in a cavity of the piston and meshing, by reversible connection , with a threaded member mounted on one end of the piston with limited rotation possibility for the control of the distributor, the free end of this screw coming out axially and so

  sealed cylinder to ensure the connection with a body of

  noeuvre. Assisted hydraulic steering of the type generally indicated above is well known in the art of this sector.

  their construction and operation, reference may be made to

  For example, see British Patents Nos. 576,051 and 1,576,052.

  In order to have a correct functioning of the assisted hydraulic steering systems in general and, in particular, of those of the type indicated above, it is necessary to have an end-of-stroke device to limit in both directions the angular travel of the shaft. steering wheel steering and primarily to prevent damage to the steering

  the vehicle in the maximum steering position of the wheels

  as well as to stop the hydraulic fluid supply pump under pressure and to avoid an excessive heating -2- of the fluid contained in the tank with the consequences

  harmful effects that may result to the pump.

  For this purpose, various types of end-of-stroke devices having two valves mounted on, for example, the piston and two corresponding adjustable stops have already been proposed.

  located on the end walls of the cylinder

with the valves.

  These are thus alternately open at the moment of impact on the corresponding abutment element with the consequence that the pressure in the working chamber of the cylinder is removed by discharge and that the piston

finished his race.

  An example of a limit device of this type is shown in the German patent application.

No. 1,455,939.

  Alternatively, according to the known technique,

  both valves are mounted stationary on the body of the cy-

  lindre or on elements attached to it and the adjustable stops

  are actuated by the piston or the shaft controlling the

wheels.

  Constructive examples of these technical solutions of end-of-stroke devices are shown in

  German Patent Nos. 1,291,644, 1,159,286 and 1,160,318.

  One of the essential limitations encountered

  in end-of-travel devices known to function-

  the fact that it is impossible to carry out the adjustment without delay during their assembly on vehicles when

  there are only the purely mechanical parts of the con-

  In fact, it is necessary to carry out their adjustment to wait for the assembly of the vehicle to be completed, including that of the pump, which implies the presence of the corresponding lines, the hydraulic fluid reservoir, this fluid.

  hydraulic and motor running.

  The present invention essentially

  purpose of producing a limit device for directing

  This device can be adjusted immediately when the only mechanical components are mounted.

  of the vehicle, without waiting for the assembly and the aptitude of the

hydraulic components.

  The invention relates to a device of the above type characterized in that it comprises two

  valve members inserted in respective conduits of

  pressurized fluid charge, housed in the wall of the cylinder body and arranged on the sides of the toothed sector, these valve members being normally held in the closed position by a predetermined load spring greater than the maximum operating pressure in the chambers; of the cylinder, as well as respective operating rods connected by one end

  to the corresponding valve member and penetrating through the other end

  in the cylinder body in meshing connection with the sidewalls of the toothed sector when the latter is moved in one direction or in the opposite direction when the maximum steering positions are reached, these maneuvering rods being movable in axial direction of a predetermined distance in opposition

to the spring.

  According to another characteristic of the in-

  vention, the valve members are housed in respective tubular sleeves provided with a thread on at least a portion of their outer wall, the thread meshing with a threaded conjugate threading in corresponding holes made in

the wall of the cylinder body.

  According to another preferred characteristic

  of the invention, the free end of each operating rod penetrating inside the body of the cylinder is provided with an oscillating spherical cap and the flanks of the toothed sector are provided with corresponding housings having a surface

conjugated to that of the cap.

  The invention will be better understood with regard to

  of the following description and the accompanying drawings

  an embodiment of the invention, drawings in which FIG. 1 is a vertical longitudinal section, with

  partially represented in lateral view, of a di-

  assisted rection provided with the end-of-stroke device according to the invention; Figure 2 is a section taken along the line II-II of Figure 1;

  Figure 3 shows on a larger scale the details of the dis-

  limit switch according to Figure 1 in a position

maximum steering.

  In the drawings, the body of the power assisted steering cylinder has been designated by 1

  cylinder is arranged the piston 2 with a rack 3 A sec-

  4 toothed on the steering shaft 5 meshes with the crank

  Maillère. The piston 2 divides the cylinder so

  classic in two working chambers 6 and 7 connected, by the in-

  of a dispenser designated as a whole by 8, alternately to a source of pressurized fluid and to the discharge, according to modes of operation wholly

  known and classical and therefore not represented.

  The piston 2 internally has an axial cavity 9 in which moves a screw 10 meshing with a threaded member Il which is in turn connected, by means

  from an oscillating lever 12 to the rod-and-control 13 of the

8.

  For the other details of construction and operation, conventional in themselves, we refer for example

  British Patent Specifications Nos. 576,051 and 1,576,052.

  The end 14 of the screw 10 comes out of the cylinder.

  by passing through the end wall 15 in the form of a removable cover. This end is intended to be

  connected to a conventional steering wheel and therefore not shown.

  Referring particularly to Figure 2,

  it can be seen that the piston 2 comprises a passage 16 intended to maintain

  establish a permanent hydraulic communication between the chamber 6 and the volume 17 of the cylinder in which the sector is located

toothed 4.

  The wall 18 of the cylinder 1 is crossed

  by two holes 19 and 20 with a tapped inner wall, these

  the holes being symmetrical with respect to the axis of the toothed sector 4 and perpendicular to the axis of the cylinder 1 The holes 19 and 20 respectively have cylindrical enlargements 21 and

  22 put in communication with each other by a conduit 23

  in the thickness of the wall 18 of the cylinder 1.

  The duct 23 is also in communication with pipe sections 24, 25 made in the thickness of the walls 26, 27 of the cylinder 1 and opening through the orifice 28.

  in room 7 opposite room 6.

  In the threaded bore 19 is disposed a first valve member of the end-of-stroke device according to the invention. The second valve member, entirely similar to the first, is disposed in the threaded bore 20 Z. As seen in FIG. 1 and FIG. 2, a tubular sleeve 31 is disposed in the bore 19 engaged by the conjugate threads 29 and 30 The sheath

  tubular 31 comprises a first hollow axial section 32, one

  x hollow axial section 33 communicating with the previous and

a third hollow section 34.

  The hollow section 33 has a smaller diameter than that of the section 32 thus defining a seat

  valve 35 against which applies the shutter 36 of the or-

  This shutter 36 is constantly maintained

  applied against the seat 35 and thus maintained in a position of

  by a helical spring 37 disposed in the hollow section 32 which is threaded on the part 38 of the inner wall. In the thread of the threaded portion 38, the cap 39 which serves as a support for the spring 37 is screwed, which makes it possible to adjust load

of this spring.

  A diametrical passage 40 is provided opposite the valve seat 35, this passage being intended to bring the hollow axial section 32 into communication with the enlargement 21.

piercing 19.

  In the hollow axial section 33 is disposed an operating rod 41 freely from one end to the shutter 36 and the other end-to the barrel 42 of a body 43 housed with a radial clearance in the axial cavity 34 and shaped, at

  the outside of the sleeve 31, in the shape of a spherical cap 44.

  The hollow axial section 33 is in turn provided with a diametrical passage 45 which maintains the interior of this

  section in constant communication with volume 17 of the

Biorance of the cylinder 1.

  The barrel of the body 43 is provided with a glue

  47 The flange 47 is provided for abutment against the pins 46 to maintain the body 43 in position, while an annular shoulder 49 of the hollow axial portion 34 constitutes the plan of abutment of the body 43 according to modalities of

  described in the following.

  An O-ring 50 provides the hydraulic seal between the sleeve 31 and the wall 18 of the cylinder 1,

  while a threaded cap 51 guarantees the tightening and the pro-

  tection of the outer end of the sleeve 31.

  Since the valve member introduces

  -25 duit in piercing 20 is entirely similar to the one that

  is introduced into the bore 19, it will not be described.

  In the drawings, the identical elements are designated by the

same numerical references.

  On the flanks 52 and 53 of the toothed sector 4 are finally formed respective housings 54, 55 with a curved surface having the same radius as the spherical caps 44 of the valve members which, for brevity, will be designated by

  right organ and left organ with reference to the drawings.

  The end-of-travel device described above

  It functions as follows: It is assumed that the piston 2 is moving to the right (referring to FIG. 1 and FIG. 2 of the drawings) and thus that the toothed sector 4 is moving

  angular in the direction of clockwise.

  The chamber 6 and the volume 17 of the cylinder 1

are then under pressure.

  However, room 7 is connected to the

  discharge, in a conventional manner, through the

8.

  During this journey and as long as the posi-

  limit switch is not reached, the valve elements

  right and left are both closed.

  In fact, each shutter 36 closes the valve seat 35 and, consequently, the pressurized fluid can not go from the volume 17 to the hollow axial section 32 and from this, through the diametrical passage 40, the enlargements 21 and, in the ducts 23, 24, 25 and the chamber 7 which is

thus connected to the discharge.

  The spherical cap 44 of the two valve elements is in the position of maximum penetration in the volume 17, the flange 47 of the barrel 42 coming against the pins 46 and thus being raised by a predetermined dimension "S" by

  relative to the plane defined by the annular shoulder 49.

  When reaching the end position corresponding to the maximum steering position of the wheels in the clockwise direction considered, the curved surface housing 55 of the sidewall 53 of the sector 4 meshes mechanically with the oscillating spherical cap 44 of the organ

valve right.

  When the angular displacement of the sector

  4 continues, the cap 44 is pushed down together.

  with the operating rod 41 which brings the shutter 36 into the open position away from the seat 35 against the force exerted by the spring 37 which normally exceeds the force due

  at the pressure of the fluid in the cylinder.

  When opening the valve seat, the pressurized volume 17 of the cylinder 1 is immediately

  placed in communication with the chamber 7 and thus with the discharge.

  The movement of the piston 2 is therefore automatically

  have been stopped as a result of the particular hydraulic conditions

of the circuit.

  In the case where the sector 4 still continues its angular displacement in the direction of clockwise due to a manual steering action applied to the screw 10, when the cap 44 has moved the entire stroke allowed by the game "S", she can not move next because of

  the mechanical stop of the body 43 on the annular shoulder 49.

  The movement of the piston 2 is thus blocked as a result of mechanical conditions which guarantee the

  stop safety in end position.

  It can therefore be seen that the end-of-stroke device according to the invention has a stop action of the piston 2 both hydraulically and mechanically, which gives the maximum guarantee that no damage is caused to the organs In addition, this device eliminates the need for

  mechanical external limit switches.

  Similar operation occurs when

  the piston 2 moves to the left with reference to the drawings.

  When the end position is reached, the spherical housing 54 of the sector 4 engages with the spherical cap 44 of the left valve member, which gives operating conditions similar to those

  which have been described previously.

  Since under the conditions now considered, the chamber 7 is under pressure and the chamber 6 is connected to the discharge, the volume 17 is also

  connected to the landfill via passage 16.

  When opening the valve seat 35 of the left valve member, the pressurized fluid of the chamber 7 can go into the volume 17 and thus flow to the discharge through the conduits 25, 24 , 23, the enlargement 20, the diametrical passage 40, the axial section 33 and the other passage

diametrical 45.

  As a result of the structure and operation of the end-of-travel valve members shown, it is clear that these can be adjusted purely mechanically even before the hydraulic components of the circuit

  mounted on the vehicles and that the engine is running

tioning.

  In fact, the adjustment of these organs is achieved only by the correct axial position of the

  sleeve 31 in the holes 19 and 20 after having placed the

  4 in the respective positions of maximum permissible mechanical displacement and by contacting the cap 44 of the left valve member and the right valve member

  with dwellings 55 and 54 in sector 4.

-10

Claims (1)

  ) End-of-stroke device for direct   assisted hydraulic system, comprising a cylinder (1) in which a piston (2) defining two opposite working chambers (6, 7) is slidably mounted for sliding, a distributor (8) for delivering hydraulic fluid under pressure in one or the other of the opposite chambers and connect at the same time to the discharge the non-pressurized fluid chamber, a shaft (5) for controlling the steering of the steering wheels of a vehicle, a toothed sector (4 ) wedged on this shaft and meshing with a rack (3) made on the piston body to transmit the rectilinear displacements of the piston to the steering shaft and convert them into displacements   corresponding angles, and a screw (10) axially arranged   in a cavity (9) of the piston and meshing, by reversible connection, with a threaded member (11) mounted on one end of the piston with limited rotation possibility for the control of the distributor, the free end (14) of this screw protruding axially and sealingly from the cylinder for connection with an operating member characterized in that it comprises two valve members (35,36) inserted in respective pressurized fluid discharge conduits, (23, 24,25) housed   in the wall (26,27) of the barrel (1) of the cylinder   the sides of the toothed sector, (4) these valve members being normally   malently held in a closed position by a spring (37)   predetermined load greater than the operating pressure   in the chambers (6,7) of the cylinder, as well as respective operating rods (41) connected by one end   to the valve member corresponding and penetrating by the other ex-   tremity inside the cylinder body in connection with meshing   with the flanks of the toothed sector when the latter is moved in one direction or in the opposite direction when the maximum steering positions are reached, these maneuvering rods being movable axially by a predetermined distance in opposition of the spring.   -11-) Device according to claim 1, characterized in that the valve members are respectively arranged in tubular sleeves (31) provided with a thread   (30) on at least a portion of their outer wall, this file   stage meshing with a tapping (29) made in holes   respective (19,20) of the wall of the cylinder body.   ) Device according to any one of   Claims 1 and 2, characterized in that the free end   each operating rod (41) penetrating inside the body of the cylinder is provided with an oscillating spherical cap   (44), the flanks of the toothed sector being iminis of housing corres-   (54,55) with a surface conjugated to that of the cap.