FR2462325A1 - HYDRAULIC STEERING ASSISTED - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS ASSISTED HYDRAULIC STEERING. IT INCLUDES THREE MAIN ELEMENTS, WHICH ARE A POWER SUPPLY 1, A CONTROL UNIT 2 AND A STEERING MOTOR 3. THE POWER SUPPLY UNIT 1 HAS TWO STEERING VALVES 5, 5 AND A PISTON PUMP 7. THE TWO STEERING VALVES HAVE RESPECTIVELY A VALVE PISTON 9 AND 9 AND A SPRING 11, 11. PUMP 7 SUPPLIES A HIGH PRESSURE DUCT 12 CONNECTED TO THE VALVES. PASSAGES 15, 29 AND 35, DEFINED BY COUPLES OF FLANGES, ARE ARRANGED SO THAT PASSAGE 29 CLOSES FIRST, PASSAGE 15 SECOND, WHILE PASSAGE 35 OPENS. THE DEVICE IS DESIGNED TO BE FITTED ON UTILITY VEHICLES.

Description

1. The present invention relates to an assisted hydraulic steering,

  which can preferably be used on commercial vehicles and

  particular, to be coupled to the steering wheel or the wheel (on the boats). Characteristics

  The preamble of claim 1 is known from the pre-examination German Patent Application No. 27 29 766, concerning an assisted steering system, ie an installation by means of which the steering can be controlled by the intermediate flywheel or via a cam in contact with a command line. The pre-control valves, mentioned in the preamble of claim 1, are in this case controlled by this cam, while they are controlled by the steering wheel in the frame.

of the present invention.

  Hydraulic power steering systems shall be

  wear a device to obtain the cut-off effect. When there is a proportionality relation, the pressure in one of the chambers of the steering motor cylinder increases in proportion to the force exerted on the control unit. Beyond a certain value of pressure and force, a small increase in force must result in an increase

  very important pressure. In this case, significant pressure is

  for a relatively small force on the steering wheel, which is

  particularly useful for parking maneuvers. However, when

  cut, there are still forces acting on the management bodies (eg

  the wheels), which are no longer reflected on the control

which is particularly harmful.

  The present invention proposes to provide a hydraulic direction

  with high hydraulic efficiency, and in which the

  steering valves do not act on the totality of the hydraulic fluid

  to the steering motor, and may therefore have a less sophisticated structure. By this means, the cut-off effect must be achievable,

  as usual, on power steering systems.

  This goal is achieved by the assisted steering according to the invention, such

  as defined in the feature of claim 1.

  By the use of an adjustable piston pump on the suction side

  tion and by controlling the direction by passing the fluid sucked by a third passage defined by a corresponding third pair of rim, we obtain a use without loss of hydraulic energy generated by the slave pump. This is achieved, despite a very limited complexity of the system

  direction, thanks to the low transmission of energy to the

  When the direction is connected to the steering control unit, the annoying noise due to the circulation of the hydraulic fluid is not transmitted via the steering column to the inside of the cab of the steering wheel.

  driver of a commercial vehicle.

  Thanks to the cut-off facility, as defined in the

  tion 1, the necessary cut-off effect is also achieved with the

  energy-saving power steering system according to the invention.

  The breaking effect, characterizing the installation, is obtained from dif--

different ways.

  Claims 2 and 3 relate to a hydraulic solution of this

  problem, resolved in this case with minimal structural investment.

  Claims 4 and 5 relate to a mechanical solution of this

  problem, which guarantees a very high security of use.

  The present invention will be better understood with reference to the

  DESCRIPTION OF PREFERRED EMBODIMENTS AND DETAILED DRAWING, IN WHICH: FIG. 1 schematically illustrates the principle of the invention, but without the installation making it possible to obtain the cut-off effect; FIGS. 2 and 3 schematically represent two different uses of the invention adapted to rack-and-pinion directions,

  Figure 4 is a representation of the principle of a direction

  equipped with hydrostatic means to obtain the cutting effect, Figures 5 and 6 show an axial section, respectively

  cross-sections of a mechanical installation to obtain the effect of

  pure, and Figure 7 shows the functional diagram of a steering mechanism. With reference to FIG. 1, a hydraulic power steering according to

  the invention comprises three main elements, which are a food unit.

  energy supply 1 (shown inside a circle), a communication unit

  Mande 2 and a steering motor 3.

  The power supply unit 1 has two control valves

  5 and 5 'and a piston pump 7 adjustable on the suction side, which will be

  subsequently peeled pump. The two steering valves, acting as balancing

  this pressure, respectively comprise a valve piston 9, 9 'and a

  spell 11, ll '. The seats of the valves are schematically represented.

  The pump 7 supplies a high-pressure pipe 12, whose openings

  are connected to the two valve seats. Subsequently, we will not describe

  than the left side of the installation. The right part is entirely similar

  lar. The high pressure conduit 12 is connected to an annular groove 17, which is

  in the direction valve 5, through a passage 15 defined by a pair of flange adjustable in position. The groove 17 is connected to the inside of the valve piston, ie the pressure chamber 21, thanks to

  19. The pressure chamber 21 is connected by a conduit 23 to the chamber

3.

  work of the steering motor 3.

  A tank duct 28, with taps, brings the working fluid from the tank 25 to the two steering valves. The tank duct serves both as a supply duct and as a return duct. In the steering valve 5, the connection with the steering ducts 28 is made by

  through a passage 29 defined by a pair of flanges adjustable in po-

  sition, with an annular groove 31 formed in the seat of the valve. This

  groove 31 is in communication with a suction duct 34 of the pump 7.

  A connection between the pressure chamber 21 of the control valve

  tion-and the tank duct 28, is obtained through another passage 35, also

  defined by a pair of flanges adjustable in position.

  The valve piston 9 has a constricted opening 37, which is

  located adjacent to the spring 11. The adjacent chamber 39, containing the res-

  is connected with a pre-control valve 43 via a control line 41, the pre-control valve being under the

  form of a stop valve or pressure reducing valve. The rooms

  holding the springs of the two pre-control valves 43 and 43 'are connected

to a tank duct 28a.

  The control unit 2 comprises a control installation 45 (a steering wheel) which acts respectively on the two springs 47 and 47 'of the

  pre-control valves, when the steering wheel is turned in one direction or in the

  be. Furthermore, the control device acts mechanically on a control member, which is shown diagrammatically, in broken lines, by the

  line 49. The pre-control valves 43, 43 'are in a neutral position, that is,

  , say open, when the control installation 45 is not subjected to any force.

  During a change of direction, one or the other of the springs 47, 47 'is

  in proportion to the force exerted on the

  mande. The fluid circulation of the hydraulic installation will be described

  with reference to the left part of FIG. 1, representing the neutral position.

  The fluid, coming from the tank 28, is brought to the inlet of the pump 7 through

  to the passage 29 and the suction duct 34. The amount of fluid under

  pressure, sucked by the pump, passes through the high pressure conduit 12 and the

  15 to enter the pressure chamber 21, through the opening e-

  37, the control conduit 41 and finally the pre-control valve 43 towards the reservoir 25. In this case, the passage 29 and the spring 11 cooperate so that the pre-control valve 43 is supplied with a current

  constant. The pump 7 is set on the suction side.

  If, at the time of a change of direction, the force acting on the

  spring 47 of the pre-control valve 43 is increased, the section of the

  4. fluid wise is decreased accordingly. This results in an increase of the pressure in the chamber 39 of this spring, and the valve piston 9 moves downwards (in Fig. 1), so that the passage 29 opens sufficiently

  so that the pump 7 is fed by the fluid flow requested. The pressure

  increased pressure in the pressure chamber 21 of the direction valve 5 acts on

  the compression chamber 4 (left) of the engine, and the pump supplies the quantity

  the fluid required to execute the change of direction. The amount of fluid expelled from the compression chamber 4 'enters the pressure chamber 21' of the right steering valve 5 '. As a result of the resulting increase in pressure, the valve piston 9 '(FIG 1) moves upwardly until the passage 35' opens to allow the fluid to pass through.

the tank duct 28.

  Both steering valves act as limit valves

  pressure for the current sucked by the pump, which leads to

  quence the desired energy saving. The differential pressure reached, thanks to the springs 11, 11 'and the cross section of the steering valves,

  maintains in balance the current flowing through the constricted openings 37, 37 '.

  The currents of the steering ducts 41, 41 'are small compared to the

  active assets. In the control installation, the density of the energy used is low, so that annoying noises, due to the circulation of the fluids, are non-existent and can not be transmitted, for example by the column of

  towards the driver's cab of the truck.

  The two independent steering valves result in a function

  irreproachable behavior which gives rise to the following remarks.

  Suppose that in the neutral position or when ordering

  change of direction, the constricted opening 37 is too small to allow

  be the passage of the fluid needed to make this change of direction.

  The consequence is a too small pressure difference between the pressure chamber 21 and the spring chamber 39. The spring 11 therefore pushes the valve piston 9 downwards (FIG 1). This results in an increase in the opening of the passage 29, which increases the supply current of the pump 7, until the current, passing through the constricted opening 37, has reached its

theoretical value.

  Conversely, the current flowing through the constricted opening 37 is too low, for example because the passage 29 'of the steering valve 5'

  is largely open, this may result in closure of passage 29,

  towards the derivation of passage 29 ', is not sufficient to restore equi-

  free at the direction valve 5 (acting as pressure balance).

  In this case, the passage 15 limits the current coming from the high pressure conduit

  12 and directed to the pressure chamber 21.

5.

  In the event that this measure is not sufficient to limit the

  pouring the constricted opening 37, for example because the displacement of the piston in the steering motor 3 to the left has provided additional fluid to

  the pressure chamber 21 via the conduit 23, the piston of

  Pope 9 is pushed further against the spring 11, so that the excess fluid can flow towards the reservoir 25 through the open passage 35 at this time.

  As a result, it is certain that whatever the position of the

  9 to 9 'relative to each other, the control currents of the control system 2 remain constant in all cases. The pressure balances represent, in known manner, the pressures set at the pre-control valves 43, 43 ', in the compression chambers of the engine of the engine.

direction 3.

  Now, suppose that in the compression chamber of the engine 3, for example in the chamber 4, there is a pressure without the spring 47 being compressed by means of the control device 45. Therefore , the pressure difference between the pressure chamber 21 and the

  control chamber 39 is increased, so that the valve piston 9 is

  put a force directed upwards (Fig. 1). If this force is not enough

  counter-ignition generates in the compression chamber 4 'a pressure

  acting on the piston of the steering motor which increases the pressure in the compression chamber 4. By counter-braking, the pre-control valve

  43 opened, which released the pressure inside Chamber 39.

  The entire pressure therefore acts on the valve piston 9 due to the pressure prevailing inside the compression chamber 4 of the steering motor. The valve piston is pushed against the spring 11, until the passage 35 opens and the fluid flows towards the reservoir, which has the effect of releasing the overpressure in the chamber

compression 4.

  Suppose now that we are in the opposite case, that is

  that is, it is desired to generate an overpressure in the compression chamber.

  4, but this is not achieved for example because a foreign object prevents the closing of the pre-control valve 43 or because the constricted opening 37 is blocked. In this case, the valve piston 9 is pushed upwards, due to the overpressure prevailing in the pressure chamber 21,

  whereby the pressure chamber 21 and the compression chamber 4 are released.

  overpressure. This case is not critical, however, because it

  responds to a defect of the pump 7, which is corrected by the link

mechanical 49.

  Fig. 2 illustrates a steering installation comprising a di-

  The mechanical rack arrangement 52 with a steering head 54 and a power supply unit i driven by the motor, this unit comprising the pump 7, the steering valves 5, 5 '(FIG. tank 25 and the steering motor 3. It will be noted in particular that the ducts connected to the steering head have relatively small diameters; these include the steering ducts 41, 41 'and the tank duct 28a. However,

  ducts transmitting the operational energy of the steering system,

  The ducts 23, 23 'are arranged only between the supply unit 1

  and the motor 3, respectively the unit 1 and the tank 25.

  The steering motor 3 may, in a manner known per se, be integrated with the rack-and-pinion steering mechanism 52. However, the separate installation, in particular the subsequent installation, has advantages, since

  mechanical rack-and-pinion installations usually comprise

  a steering damper which can be replaced later by the

engine.

  In the exemplary embodiment illustrated in FIG. 3, the steering valves, instead of being integrated with the pump, are integrated in the tank in the form of a unit 56, which has advantages when the pump, for construction reasons, can be connected only through

  ducts 12, 34, in the form of flexible pipes.

  Fig. 4 represents an embodiment according to which the ef-

  Cutoff fet is obtained by hydraulic means. The elements, which are

  similar to corresponding elements of the. Fig. 1, bear the same references

  and will no longer be described in detail.

  In this case, the two steering valves 60 and 60 'are not

  integrated in the pump 7, but in the reservoir 25. The passages defined by

  In the example shown, the position-adjustable flanges have a positive position.

  different from that of fig. 1, but perform the same functions, this

  which emerges from their reference numbers. The valve pistons 62 and 62 '

  on the side of their compression springs, there are constricted openings 64

  and 64 '. The chambers 66, 66 'of the steering valves are respectively connected

  by means of a check valve 68, 68 'with a pressure limiting valve 70. The chamber, in which is housed the spring of

  this valve is connected. to the tank duct 28.

  The restraining restrictors 64, 64 'limit, in connection with the holding valves 68, 68' and with the pressure limiting valve 70, the pressure in the holding chambers 66, 66 'of the pressure balances, and by therefore the control pressure. If, for example, during a robbery of

  direction, the pre-control valve 43 is set to a higher pressure

  than the limit pressure of the valve 70, no current will flow through the

  7. Pre-control throttle 37. As a result, the regulating effect of the pressure balance is disturbed. The active fluid flows through the retaining constrictor 64, the check valve 68, and the pressure limiting valve toward the reservoir. The valve piston 62 is pushed down (in Fig. 4) independently of the higher force acting on the pre-control valve 43. As a result, the pressure in the compression chamber 4 of the

  steering motor is increasing. In this case, the steering motor 3 is dere-

with possibility of return.

  Figs. 5 and 6 illustrate an embodiment of the unit of

  control 2, comprising mechanical means to obtain the cut-off effect.

  A steering shaft 72, mounted on needle bearings housed in

  a branch piece 76, remained driven by the control installation.

  The branch piece can be integrated into a rack 78, in a direction

  racking. The two pre-control valves 43 and 43 'are housed

  in a housing 80, the interior volume of which is connected to the dream conduit.

  see 28a. The two control lines 41 and 41 'are connected to the seats of the

  valves via channels 82 and 82 '.

  The axis of the flywheel 72 is in one piece and comprises a transverse arm 88. A flat spring 86 is fixed by a screw 90 to the axis of the flywheel 72, in a lateral recess 84 of the latter, at the transverse arm 88 . The room

  branch 76 carries stops 92 cooperating with the ends of the trans-

  88, to limit the amplitude of rotation of the steering axis relative to the part 76, while allowing the control of the direction in case of

  defection of hydraulic assistance.

  The flat spring 86 constitutes the two return springs of the valves

  steering weights 43 and 43 ', which serve to control the valves in the field

of proportionality.

  The transverse arm 88 comprises, at its ends, two transverse bores, in which two free buckets 94 are arranged. It bears, by a flange 96, against the transverse arm and accommodates respectively one of two centering springs 98. For the adjustment of the midpoint, two adjustment screws 100 are used housed in two stops 102, integral with the piece of

diversion 76.

  The centering springs have a much greater rigidity (for example a hundred times) than that of the arms of the flat spring 86. The centering springs serve as a means of limiting the pressure, which limits the pressure

  maximum allowed in the management installation.

  In the neutral position, illustrated in fig. 6, the arms of the

  do not exert any force on the balls of the precompression valves.

  43 and 43 '. As a result, there is no pressure in the chamber 39, and the 8.

  hydraulic control is inoperative.

  If, via the steering axis, a

  of rotation, the spring bears on the axis 78 and the two parts turn

  in the opposite direction. If the transverse arm 88 is pivoted, for example in the direction of the arrow 104 relative to the part 76, the centering spring 98 'is brought into tension and the spring 98 is expanded. Fig. 7 represents, in the form

  of a graph, the relation between a pressure p and a form F acts

  on the steering installation. At the beginning of a robbery, only the force F

  increases from point 0, without the hydraulic installation being in-

  fluencée. Until point G is reached (force limit), the left arm

  The flat spring 86 exerts no force on the pre-control valve 43.

  At the same time, the force acting on the control system increases under the influence of the centering springs 98 and 98 '. From the limit point G, the

  the flat spring exerts a force on the valve 43 and the pressure p in the chamber

  of the steering motor, increasing to the right 106. The

  lation works proportionally. The sensible force at the level of the

  the control system, is almost exclusively generated by centrifugal springs

  trage 98 and 98 ', and only negligibly by the flat spring. Toute-

  only the leaf spring intervenes on the control of the pre-com-

43.

  At the end of the domain of proportionality, that is to say from

  from the point of cut-A, the pressure p in the steering motor must increase

  abruptly for a very moderate increase in the force F exerted on the control installation. This is illustrated by the steep branch 108 of the curve of FIG. 7. This is reached when the bucket 94 touches the left arm of the leaf spring 86. For a minimum rotation beyond this point, the valve 43 is fully closed by the centering spring 98, and the pressure

  in the steering motor increases to the point H corresponding to the

maximum permissible limit.

  From the moment corresponding to the cut, that is to say the

  tact between the bucket and the leaf spring arm) the reaction of the spring of cen-

  trage 98, on the transverse arm of the steering installation, ceases and only remains the reaction of the centering spring 98 strongly tensioned. At the moment of exceeding the cut-off point, no sudden increase in force is felt on the steering system. The rapid increase in pressure

  in the steering motor causes rotation of the axis and the

  rivet 76 (Fig. 5) relative to the steering axis 72, acting by means of

  the mechanical connection 49 on the piston rod of the engine of di-

  The hydraulic system therefore becomes effective before the jump of the force becomes sensitive, so that this increase is noticeable in the direction of the steering control member 110, the rack 112 and the axle 78. when passing through point A. When reaching point H (Fig. 7), the pressure in the engine

  direction can no longer increase. This is achieved by the fact that one of the

  Centering spells (e.g., left centering spring 98) yield sufficient so that the compressed fluid can exit the pre-control valve 43. Accordingly, the valve piston 9 of FIG. 1 moves sufficiently upwards so that the pressure in the compression chamber 4 of the steering motor remains limited to the value H.

  1D Beyond the point H, the bucket 94 is withdrawn from the transverse arm 88.

  Only then remains the action of the centering spring 98 'on the transverse arm

  sal, hence a sharp increase in the force along the arm 114 of the curve

  of fig. 7 becomes sensitive at the control installation. This ac-

  increase in force can not be compensated by the hydraulic installation

  that, because the pressure is limited to the maximum pressure H. However, it should be noted that the increase in the force is desirable at this time, for

  that the driver notices that his hydraulic installation is not opera-

in this area.

  During an increase in the force along the branch 114, a point is reached for which the transverse arm 88 bears against the stop 92, so that the part 76 is driven mechanically by the axis of

  72. This also occurs during a failure of the hy-

  draulic. The centering springs 98 and 98 'can be adjusted by means of the adjusting screws 100, so that no force acts on the control system at the neutral point. By simultaneous screwing and equivalent screw

  setting 100, it is possible to adjust the slope of line 106 in the field of

  proportionality. If stiffness centering springs are used

  different, it will be possible to differentially adjust the high pres-

  sions in the right and left compression chambers of the steering motor. This may be desired when the steering motor has a

  piston rod is guided unilaterally and thus presents

  differentiated tones. In this case, it would be desirable for the maximum pressure in the compression chamber 4 'to be greater than that of the chamber

  4, so that forces can be exerted to achieve the maximum pressures

the, are similar.

  In the area of proportionality, the use of centering springs of differential stiffness is of no interest. Indeed, on the right 106, it is the difference of the forces acting on the two centering springs that intervenes on the control system, so that whatever 10. is the steering direction, the increase in the force corresponds to two straight segments 2 of the same slope. _ 11.

Claims (7)

  1. Assisted hydraulic steering comprising a. A high pressure pump, b. At least one steering motor, c. Two valves with mechanically independent pistons, loaded by springs and acting as pressure balances, d. Each steering valve has a pressure chamber permanently connected to a working chamber of the steering motor, e. The pressure chamber is connected to a pressure line through a first passage defined by a first pair of adjustable edges in position, and to a conduit connected to the reservoir through a second passage defined by a second pair of adjustable edges in position,   f. Each piston having a constricted opening which makes   connect the first pressure chamber with a piston control chamber of   valve, arranged in such a way that the increase of the pressure in the chamber   control chamber, with respect to the pressure chamber, causes the opening of the said first pass,   g. The control chamber being connected to the conduit connected to the   by means of a pre-control valve constrained by a res-   go out, h. The springs of the two pre-control valves being in operative relation with the controller, characterized by the following properties i. The pump 7 is a piston pump, adjustable on the suction side, j. The reservoir duct 28 operates as a suction duct and return duct, and is connected with the suction duct 34 of the pump 7 via a third passage defined by a third pair of adjustable flanges in position 29 two steering valves, k. The pump supplies a pressure line 12, which is connected to the two directional valves independently of each other, respectively 1. The passages, defined by pairs of flanges in the steering valves, are arranged in such a way that way that when the steering valves are moved in the direction of their closure, the third pass   29 closes first, then the first passage 15, while the second wise 35 opens,   m. It includes a cut-off device (FIG 4, 5, 6), which de-   finished a domain adjacent to the proportionality domain, where the pressure in the   working chamber of the steering motor 3 increases proportionally with   the force exerted on the control device, in which the pressure   39 increases rapidly as we increase, to a small extent, the force 12. beyond the previous values.   2. Power steering according to claim 1, characterized by the following properties: a. Each valve piston 62, 62 'has another constricted opening 64, 64', which connects the pressure chamber of the control valve.   with a second control chamber 66, 66 'which is connected to a second   control face of the valve piston, active in the closing direction, and   b. This control chamber being connected to the control duct   see 28 through a pressure reducing valve 70.   3. Power steering according to claim 2, characterized in that the two steering valves is associated with a single pressure reducing valve 70, connected to two corresponding control chambers 66, 66 '   respectively by two holding valves 68, 68 '.   4. Power steering according to claim 1, characterized in that it has the following properties a. As part of a drive-transmitting link the moment   rotation of the control device to a steering member, the steering   carries two rotating elements in opposite directions and limited in their movements,   a drive member 72 and a delivery member 76.   b. One of these elements 72 comprises a transverse arm 88 and the   corresponding stops 92, c. Between the two parts is mounted a spring centering installation 98, 98 ',   d. One of the elements 76 includes the seats of the pre-com- mand valves   Mande 43, 43 ', and the other 72 a flexible spring 86 disposed transversely to the axis of rotation, the arms of this spring acting as a spring member for the pre-control valves, e. The transverse arm 88 carries, at its ends, stops 94 which cooperate with the arms of the flexible spring 86,   f. In such a way that the angle of rotation between the neutral position   and the position where the spring stops 94 are in contact with the arms of the flexible spring 86, corresponds to the proportionality range of the direction,   the adjacent angle corresponding to the cutoff range.   5. Power steering according to claim 4, characterized in that   that the springs, which hold the stops 94 at the ends of the transverse arm   sal 88 under tension, are also the centering springs 98 of the steering.   6. Power steering according to claim 5, characterized in that the tension of the centering springs 98, 98 'is adjustable, and in that the   pre-control valves 43, 43 'cooperate with the centering springs in action   as pressure limiting valves (limitation of high 13. pressure H, H ').   7. Power steering according to claim 6, characterized in that the centering springs 98 and 98 'have different elasticities, so as to allow to obtain different high pressures in the two working chambers 4, 4' of the engine. direction 3.