DE1238789B - Pressure medium control device in assisted steering systems, especially for motor vehicles - Google Patents

Description

GERMAN WWW PATENT OFFICE

EDITORIAL

German class: 63 c - 47

Number: 1238 789

File number: Z1163411 / 63 c

1 238 789 filing date: July 6, 1965

Opened on: April 13, 1967

The invention relates to a pressure medium control device in power assisted steering systems, especially for motor vehicles, with two in a rotatable by the steering spindle control part transversely to Steering spindle axis mounted and displaceable in opposite directions and as a valve piston trained control and feedback piston with unequal size, of the one surrounding the piston Annular groove prevailing pressure medium acted upon end faces and with one of the smaller ones End face switchable annular face, with one of the control and feedback pistons each at steering angle in both directions one dependent on the working pressure and opposite to its movement Reaction force experiences, while the other piston remains pressure-neutral.

The power steering of the type described is designed so that in the entire steering range on Steering wheel is to overcome a reaction force proportional to the pressure of the working medium. this has with the result that even with a large steering angle, which is usually the case at low driving speeds, or when parking while stationary, undesirably high reaction forces occur.

So-called cutting off the manual steering force component is known per se, but it was previously possible not yet provided for steering systems with control valves rotating together with the steering spindle especially those in which the control valves are arranged in the inlet groove.

The invention is therefore based on the object of providing a device of the type mentioned at the beginning create, in which the reaction force is reduced with a larger steering angle and high pressure medium pressure is.

The solution to this problem is according to the invention that the reaction force through an additional device is switched off in a manner known per se from a certain steering force value increases or increases only slightly.

In a preferred embodiment according to the invention, a part of the larger end face is in each case each of the two channeled valve pistons through one in the valve piston below the Effect of the working medium against the force of a spring is limitedly displaceable and with further the said channel cooperating control channels provided control sleeve against the from Pressurized medium is applied to the annular groove when the corresponding counterforce of the spring predominates Working medium pressure lockable.

Another embodiment contains only one intermediate pressure medium control device in power assisted steering systems, in particular for
Motor vehicles

Applicant:

Gear factory in Friedrichshafen
Corporation,
Friedrichshafen, Löwentalerstr. 100

Named as inventor:

Erich Jablonsky, Schwäbisch-Gmünd

^x 5 see the two control and feedback pistons in the housing to the annular groove serving as pressure medium inlet, the pressure medium inlet is connected via two channel systems that can be closed when the specified pressure is exceeded, each with an annular partial surface of the control piston, the partial surfaces with the annular groove also being connected via each a channel in the housing and in the bushes are connected, one of which can be closed by the control slide adjusted in the direction of a larger end surface, so that the annular partial surface is separated from the pressure medium inlet when the pressure relief valve responds at the same time.

The control device according to the invention has a pressure proportional to this up to a certain working pressure Reaction on the steering wheel and at higher pressures, such as those that occur when parking, a constant reaction, the amount of which is arbitrarily determined by the choice of the dimensions of the control parts can be.

In the drawing, two exemplary embodiments according to the invention are shown in a longitudinal section. It shows
1 shows a control device in the neutral position,

F i g. 2 the control device when cornering to the right,

F i g. 3 the control device in a position when the vehicle is parked, in which the steering wheel after is hit on the right,

F i g. 4 diagrams for the course of the reaction force with different dimensions of the disconnectable Piston area and

F i g. 5 shows an embodiment with only one pressure relief valve.

The control housing 1 of a control part of a hydraulic steering system is contained in a pressurized oil

709 549/245

Annular groove 2 rotatably mounted about the axis O of the steering spindle. Of the other control part of the steering, which can also be rotated about the axis O , the two pins 5 and 5 'are shown in section, which form the parts of a fork shaft (not shown). The pins 5 and 5 'engage in elongated holes 6 and 6' of two control pistons 8 and 8 '. Both control pistons 8 and 8 'each move in the bore 10 and 10' of sleeves 11 and 11 '. The bushings are pressed into the control housing 1. The control housing 1 and the fork shaft are connected to the steering worm or steering spindle, not shown, via a torsion bar 3. If there is no torque acting on the steering spindle, the control housing 1 and the control pistons 8 and 8 'take the steps shown in FIG. 1 drawn neutral position to each other.

If the steering wheel with the steering spindle is turned to the right while driving, the control housing 1 and the fork shaft (not shown) with the pins 5 and 5 'rotate resiliently against each other, causing the valve pistons 8 and 8' in the direction of the arrows (F i g. 2) can be adjusted. When the steering wheel is turned to the left, the control pistons 8 and 8 'are adjusted against the arrows shown. It should be noted that the control housing 1 rotates with the steering spindle about the axis O and generally assumes an inclined position. For the sake of simplicity, however, the control housing 1 is always drawn in the same position.

The control piston 8 is provided with control edges 12 and 13, which have corresponding control edges 15 and 16 cooperate in the rifle rope. In the sleeve 11, annular grooves 18 and 19 are incorporated, which open into the space 23 or into the annular groove 24 via bores 20 and 21, respectively. The room 23 and the Annular groove 24 are via the bores 25 and 26 in the housing 1 with the pressure chamber 7 'and 7, respectively Servo cylinder in connection. Correspondingly, the bore 25 'or 26' is connected to the pressure chamber 7 or 7 ' connected.

On the valve piston 8, a piston surface 28 and another piston surface are formed, which are made up of the Surfaces 29 and 30 composed.

In a bore of the valve piston 8, a sleeve 31 is used, which with the valve piston through a pin 32 is firmly connected. In one end of the sleeve 31, a valve sleeve 34 is inserted, which is supported by a collar on a spring 36, which in turn is attached to the valve piston 8 on the surface 37 supports. A fixed in a cover 38 and provided with a collar bolt 39 is through the Bushing 34 passed through and limits its stroke.

The pressure prevailing in the annular groove 2 is also effective via an inlet groove 40 in an annular space 42. Likewise, a pressure chamber 43 formed by the cover 38 is via a channel 45, an annular groove 46, a bore 48 and an inlet groove 50 are connected to the annular groove 2. The spring chamber 51 is on the other hand in connection with the oil return via a channel 52.

Since the two control valves have the same structure, the same reference numbers are used for both parts, but are used to differentiate the reference numbers of one control valve are provided with dashes.

The pressure medium control device works as follows: If the steering wheel is turned to the right, for example, so the pins 5 and 5 'move in the same direction

the axis O. The housing 1 follows the pins 5 and 5 ', with a certain angular displacement as a result of the torsion bar 3 acting between the two control parts. The control piston 8' is moved to the right and the control piston 8 to the left. The control edges 12 'and 13' on the now pressure-neutral control piston 8 'move further away from each other, while the control edges 12 and 13 close on the control piston 8, ίο the pressure medium now flows from the annular groove 2 through the open control edge 12' and the bore 25 'into the pressure chamber 7, while the pressure medium return from the control edge 13 is closed. The pressure medium present in the other cylinder pressure chamber 7 'can flow off via the open control edge 13' to the oil return.

Since the force of the springs 36 and 36 'is initially even greater than that on the control sleeve 34 or 34' acting hydraulic force, the control sleeves 34 and 34 'against the sleeves 31 and 31' pressed. The control channels 45, 46 and 48 or 45 ', 46', 48 'overlap so that in the spaces 43 and 43 'the full working pressure of the pressure medium prevails.

Since the piston surface 28 is smaller than the opposite piston surface 29, 30, acts as a result of the In the annular groove 2 prevailing working pressure on the piston 8 opposed to a differential force the in F i g. 2 indicated arrow direction. This differential force, which is proportional to the working pressure, can be felt as a reaction force on the steering wheel.

The second valve piston 8 'is pressure-neutral because it acts on the piston surface 28' and on the space 23 'lying annular surface 17' together the same force acts as on the opposite piston surface 29 ', 30'.

If the steering wheel is turned to the right when the vehicle is stationary, the two valve pistons are turned 8 and 8 'again adjusted in the direction of the arrow (F i g. 3) and the flow of the pressure medium through the The valve is set up as already explained above. The working pressure prevailing in the annular groove 2 builds up first appears again in both rooms 43 and 43 '. Since the steering forces are considerable when the vehicle is stationary are higher than when the vehicle is moving, the increased working pressure on the increases Control sleeve 34 or 34 'acting force via the force of the pretensioned springs 36 and 36', see above that the control sleeves are moved to the right. The sleeve 34 'lies on the collar of the bolt 39 'at. The space 43 'remains over the annular space 42', the bore 45 ', the annular groove 46' and the Inlet groove 50 'with the annular groove 2 in connection. On the other hand, on the valve piston 8 adjusted to the left the mutual displacement of the sleeves 31 and 34 so large that the connection between the Bore 45 and the annular groove 46 is interrupted and no higher pressure can develop in the space 43 can.

If the pressure in the space 43 rises further due to leakage oil, the sleeve 34 pushes itself further to the right until the annular groove 46 is in communication with the spring chamber 51. Since the spring chamber 51 over the channel 52 is connected to the oil return, the overpressure can be reduced. So that's just the force of the spring 36 on the steering wheel is still effective.

In Fig. 4 shows the influence of the various valve piston areas on the steering force.

Claims (1)

The diagram shows the steering force at P, while η indicates the steering wheel turns to one side, in this case from center to right. The size of the manual force component when steering (line I in Fig. 4), also called reaction force, is achieved by the size of the surfaces 17 and 17 '. When the areas 17 and 17 'are enlarged, the manual steering component increases (line II). When the same is reduced, the steering component becomes smaller (line III). While only up to 50% of the oil pressure is required when driving, the same increases by up to 100% when parking. However, since an increase in the force is undesirable when parking, the steering force is limited to a certain level by the device according to the invention (line IV). The steering force remains at a constant level. This is achieved by equal area between the areas 17 or 17 'and 30 or 30'. The line IV can still be influenced by changing the area 30 or 30 '. If the area 30 or 30 'is smaller than the area 17 or 17', the increase in force runs along the line V, i. H. after the switch-off point "A" the steering force increases slightly. If, on the other hand, the area 30 or 30 'is larger than the area 17 or 17', the steering force drops after the switch-off point and runs along the line VI. F i g. 5 shows a further embodiment in which, instead of the two pressure relief valves mounted in the valve slides, there is only a single pressure relief valve in the middle part 101 of the housing 1 between the control slides 108 and 108 '. A control sleeve 134 is mounted on a retaining bolt 139 so as to be limitedly displaceable in both directions against the pressure of a spring 151 in a spring chamber 136 connected to the return via a bore 152 and the chamber 153. The control sleeve is connected to the pressure medium inlet chamber 2 via an annular space 103 and a bore 104 in a cover 102. The two valve slides 108 and 108 'are offset and, with two covers 120 and 120' connected to fixed sockets 105 and 105 ', each form an annular space 129 and 129', which is connected to the space via a bore 110 or 110 ' 2 is connected. A further bore 111 or 111 'leads from the annular space through the fixed bushing 105 or 105' to the control bush 134. The upper valve slide 108 'is shown adjusted to the right and the lower slide 108 to the left. The control bushing has an annular groove 113 which is connected on the one hand to the annular space 103. The annular groove can come into contact with the bores 111 and III 'through transverse bores 112 and 112'. The annular space 129 or 129 'can be via the bores 117 or 117' and 118 or 118 'and annular grooves 115 or 115' and 116 or 116 'in the valve slide, and an annular groove 114 or 114' in the socket 105 or 105 'are connected to a central bore 119 or 119' in the control slide which opens into a return flow chamber 121 or 121 '. The other annular grooves 19 and 19 'in the sockets 105 and 105', the annular grooves 24 and 24 'in the valve slides, the bores 21 and 21', and the return openings 121 and 121 'have the same shape and function as the corresponding parts with the same reference numerals in the embodiment according to FIGS. 1 to 3 in the position according to FIG. 3. The grooves 19 and 24 are therefore under pressure, the grooves 19 'and 24' are depressurized. The control device is shown in a steering position which corresponds to that of FIGS. 3 corresponds to the first embodiment. The working pressure has exceeded a predetermined value, which in point A of the diagram according to FIG. 4 prevails. The control sleeve 134 is displaced to the right against the pressure of the spring 151 from its open position on the collar of the spring chamber 136, so that the bores 112 and 112 'are no longer connected to the bores 111 and 111'. The annular space 129 'is connected to the pressure space 2 via the bore 110'. The same pressure prevails in the cylinder chamber 143 'as in the chamber 2. The entire left end face of the valve slide 108' is therefore acted upon by the working pressure, since according to FIG. 3 the entire right end face of the valve slide 108 'is also under pressure, the hydraulic forces of the slide 108' are balanced. The valve slide 108 shown in its left deflection position covers the bore 110. Since the bore 111 is also cut off from the pressure chamber 2 by the valve bushing 134, no higher pressure can develop in the annular chamber 129 than the pressure mentioned above in point A of FIG. 4 corresponds to the prevailing pressure. The annular space 129 is connected to the vent hole 119 via the bores 117 and 118 and the annular grooves 114, 115 and 116. When the pressure in space 2 falls below the pressure that can be determined by the force of spring 151, control sleeve 134 moves back to the left to its stop and bore 112 connects annular space 113 with bore 111. Annular space 129 thus receives full pressure from the working chamber 2. A reaction force similar to that in the exemplary embodiment according to FIG. 1 acts on the valve piston 108. 2. If the annular space 129 is pressureless, as described above, and if the piston surface in the chamber 143 is the same as the piston surface 28 (FIG. 3), the valve slide 108 is also pressureless. The driver would not feel any manual force on the steering wheel when steering at slow speed or when parking. However, if the smaller piston area of the valve slide 108 or 108 'in the space 143 or 143' is somewhat larger than the area 28 or 28 ', a reaction force, which increases proportionally with the working pressure and its magnitude, acts at an increased working pressure the difference in area between the two smaller end faces of the valve spool can be determined. Patent claims: 1. Pressure medium control device in assisted steering systems, in particular for Motor vehicles, with two in a rotatable by the steering spindle Steuerteü transversely to the steering spindle axis mounted and displaceable in opposite directions and as a valve piston trained control and feedback piston with unequal size, one of which is the piston surrounding annular groove prevailing pressure medium acted upon end faces and with one of the smaller ones End face switchable ring face, with one of the control and feedback pistons