SE443959B - HYDRAULIC SERVICE CONTROL DEVICE - Google Patents

Description

15 20 25 30 35 40 * Ef 8005527-5 2 is transferred to the passenger compartment of a vehicle via the steering column.

By means of the limiting device in accordance with the invention, the energy-saving control device is also achieved with the unnecessarily necessary limiting effect.

The invention will now be described in connection with the embodiments shown in the accompanying drawings, in which Fig. 1 schematically shows the principle of the invention, but without a device for achieving the limiting effect; Figures 2 and 3 schematically show two different uses of the invention on rack control devices; Fig. 4 is a schematic diagram of a control device with hydrostatic means for achieving the limiting effect; Figures 5 and 6 show in axial section and cross section, respectively, a mechanical device for achieving the limiting effect; and where Fig. 7 shows a control curve.

As can be seen from Fig. 1, a hydraulically reinforced control device according to the invention has three main parts, namely an energy supply unit 1 shown inside a circle, an actuating unit 2 and a control motor 3.

The energy supply unit 1 includes two control valves 5 and 5 'and a piston pump 7 (hereinafter referred to as "pump") arranged on the suction side. The two control valves each have their own valve pistons 9 and 9 'and their respective working springs 11 and 11' and function as a pressure wave. The associated valve housing is only shown schematically.

The pump 7 opens into a high-pressure line 12, the branch lines of which are connected to the two valve housings. In the following, only the left half of the device will be described. The right-hand booklet is designed in the same way. The high pressure line 12 communicates with the control valve 5 with a ring groove 17 via a control edge pair 15. These are connected through the wall bushing 19 of the valve piston to its inner pressure space 21. This is connected to one working space of the control motor 3 via a working line 23.

From a tank 25 for the working fluid leads a tank line 28 with branches to the two control valves. The tank line serves as both suction and return lines. In the control valve 5, the connection of the tank line 28 is connected to an annular groove 31 of the valve housing via a control edge pair 29. A suction line 34 for the pump 7 connects to the annular groove 31.

Through a further pair of working edge 35 a connection is obtained from the pressure chamber 21 of the control valve to the tank line 28. The valve piston 9 has a throttle opening 37 at its side located against the working spring 11. The connecting spring chamber 39 communicates with a control valve or pre-regulating valve 43 in the form of a pressure holding valve via a control line 41. The spring spaces of the two pre-regulating valves 43 and 43 'are connected to a tank line 28a.

The actuating unit 2 has an actuating device 45 (eg a steering wheel), which, in the event of a steering deflection in both directions, affects the two springs 47, 47 'of the interlock valve. In addition, the actuator mechanically acts on a control means, which is schematically shown here by broken lines 49. The pre-control valves 43, 43 'are open in the neutral position if the actuator 45 is not subjected to forces. In the event of a steering deflection, one or the other spring 47, 47 'will be proportionally loaded by the force acting on the actuating device.

The function of the control device will now be described: The flow course of the working fluid will be described in the following for the left part in Fig. 1 and the neutral position shown thereby. From the tank line 28 working fluid flows to the suction side of the pump 7 via the control edge pair 29 and the suction line 34. The pressure fluid fed by the pump flows through the high pressure line l2 and the control edge pair l5 into the pressure chamber 21, through the throttle opening 37, control line 41 and the open pre-control valve 43 to the tank. 25. In this case, the control edge pair 29 and the working spring 11 ensure that the pre-control valve 43 is provided with a constant control current. The pump 7 is regulated on the suction side.

If, in the event of a control stroke, for example, the force is increased, which exerts an influence on the spring 47 of the control valve 43, its flow cross-section will decrease. Thereby the pressure in the spring chamber 39 is increased and the valve piston 9 moves downwards (seen in Fig. 1), whereby the control edge pair is opened so much that the pump 7 obtains the required suction current. The increased pressure in the pressure chamber 21 of the control valve 5 affects the left working space 4 of the control motor and the pump feeds the amount of liquid required for adjustment. The amount of liquid expelled from the working space 4 enters the pressure chamber 21 'of the right control valve 5'. Due to the increasing pressure, the valve piston 9 '(Fig. 1) will be moved upwards, until the control edge pair 35' opens, so that the working fluid can flow away in the tank line 28.

The two control valves thus function as limiting valves for the suction flow to the pump, whereby the desired energy saving is achieved. The differential pressure obtained through the working spring 11, 11 'and the cross section of the control valve holds the wave through the current passing through the throttle openings 37, 37'. The current in the control lines 41, 41 'is small in relation to the working current. In the control unit, therefore, only a small energy density occurs, so that no disturbing flow noises are transmitted, eg via the steering column to the passenger compartment of the vehicle.

The two mutually independent control valves provide a trouble-free operation, as the following description will show.

Assume that in the neutral position, or at a control stroke, for example, through the throttle opening 97, a current that is too small for the control stroke flows. It follows that too small a pressure difference occurs between the pressure chamber 21 and the spring chamber 39. The working spring 11 consequently pushes the valve piston 9 (Fig. 1) downwards. Thereby, the control edge pair 29 is further opened and the supply amount of the pump 7 is increased until the current through the choke opening 37 reaches its setpoint.

If, in contrast, too much current flows through the throttle opening 37, e.g. when the control edge pair 29 of the control valve 5 'is too open, it may happen that a closure of the control edge pair 29 due to the passage past the control edge pair 29' proposes to establish a balance of the control valve 5 acting as a pressure wave. In this case, the control edge pair 35 limits the flow from the high-pressure line 12 to the pressure chamber 21.

Should this also not be sufficient to limit the current flowing through the choke opening 37, since eg by displacing the piston of the control motor 3 to the left when additional working fluid is fed into the pressure chamber 21 via the working line 23, 40, the valve piston 9 will be displaced further towards its shaft - 10 15 20 25 30 35 40 8005327-5, 5 pick spring 11, whereby the excess working fluid can flow away to the tank 25 via the then opened control edge pair 35.

This has ensured that, regardless of the position of the valve pistons 9, 9 'in relation to each other, the control current going to the actuating device 2 will be constant at each operating condition. The pressure wave reflects in a known manner the pressure set at the pre-control valves 43, 43 'in the two working spaces of the control motor 3.

Hereinafter, the case where a pressure prevails in one working space of the control motor 3, for example in the working space 4, is assumed without the spring 47 being tensioned by the operating device 45. This increases the pressure difference between the pressure space 21 and the operating space 39, fig 1).

Should this force not be sufficient, control builds up a pressure in the working space 4 ', which pressure affects the pistons of the control motor and thereby increases the pressure in the working space 4. Through the control, the pre-control valve 43 has been opened and the spring space 39 has become depressurized. Thus, the full force acts on the valve piston 9 by the pressure in the working space 4 of the control engine. The valve piston will be pushed against its working spring 11 until the control edge pair 35 opens and working fluid flows to the tank, so that the working space 4 is pressure relieved.

If now the opposite case is assumed. ie it is desired to build up a pressure in the working space 4 but that this does not succeed, eg due to the valve body of the interlock valve 43 not sealing due to penetrated contaminants, or that the interlock throttle 37 is clogged. Then the valve piston 9 will be pushed upwards, as a result of the pressure prevailing in the pressure chamber 21, so that the pressure chamber 21 and the working space 4 will be depressurized. However, this position is not critical, as it corresponds to a failure of the pump 7, and in this position the control will take place via the mechanical connection 49.

The guide device according to the invention will now be described when used together with a rack and pinion guide device.

Fig. 2 shows a control device with a mechanical rack arrangement 52 with the control head 54 and a motor-powered power supply unit 1, which comprises the pump 7 and the control valves 5, 5 '(Fig. 1), the tank 25 and the control motor 3. in this connection, special consideration must be given to the fact that lines with a relatively small cross-section need to be led to the control head, namely the two control lines 41, 41 'and the tank line 28a. On the other hand, the work lines 23, 23 'which transfer the actual control energy only go between the energy supply unit 1 and the control motor 3, respectively from the unit 1 (line 28) to the tank 25.

The guide motor 3 can, in a manner known per se, be integrated with the rack guide arrangement 52. However, the arrangement with different parts offers advantages, especially in a later installation, since in mechanical rack guides a guide damper is mostly arranged, in in which place the engine then becomes replaceable.

In the embodiment shown in Fig. 3, the control valve is instead of the pump 7 integrated with the tank of a unit 56, which provides advantages if the pump 7 can only be connected via lines 12, 34 in the form of hose lines for installation reasons.

The hydraulically obtained limiting effect must be explained below.

Fig. 4 shows an embodiment in which the limiting effect is achieved by means of hydraulic means. The parts which function in the same way as those shown in Fig. 1 have been given the same reference numerals and will not be described in more detail.

Thus, in this embodiment, the two control valves 60 and 60 'are not integrated with the pump 7, but with the tank 25.

The control edge pairs here have a different position than that shown in Fig. 1, but have the same function, which is also apparent from their reference numerals. The valve pistons 62 and 62 'have throttle openings 64 and 64' at the sides facing away from the working spring, the throttle openings acting as recoil throttles. The associated recoil spaces 66, 66 'of the control valve are connected to a common pressure relief valve 70 via their respective non-return valve 68 , 68 '. The spring space of this valve is arranged at the tank line 28.

The feedback throttles 64, 64 'together with the non-return valves 68, 68' and the pressure relief valve 70 limit the pressure in the feedback spaces 66, 66 'of the pressure wave and thus the control pressure. If, in the event of a control stroke, for example, the pre-control valve 43 is set to a higher pressure than the pressure limiting valve 70, then there is no longer any flow through the pre-control throttle 37. As a result, the control effect of the pressure wave will be disturbed. The working fluid flows through the feedback throttle 64, the non-return valve 68 and through the pressure relief valve 10 15 20 25 30 35 40 8005327-5 70 to the tank. The valve piston 62 will, independently of even greater forces acting on the pre-control valve 43, be displaced downwards (Fig. 4). As a result, the pressure in the working space 4 of the control motor will increase. In this case, the control motor 3 will be switched without repercussion.

A mechanically obtained limiting effect is also possible.

Figs. 5 and 6 show an exemplary embodiment of the operating unit 2 (compare Fig. 1), which here comprises mechanical means for obtaining the limiting effect.

A control spindle 72 rotatable by the actuating device is rotatably mounted in a driven part 76 by means of needle bearings 74.

The driven member may be integral with a rack and pinion gear 78 within the framework of a rack and pinion guide arrangement. The two pre-control valves 43 and 43 'are located in a housing 80, the inner space of which is connected to the tank line 28a. The two control lines 41 and 41 'lead to the valve seats, via separate ring grooves and channels 82, 82'.

The guide spindle 72 is formed integrally with a cross arm 88. In a cross recess 84 of the guide spindle 72 flush with this cross arm 88. a leaf spring 86 is secured by a screw 90 to the cross arm. At the drive part 76 fixed stops 92 are arranged for the ends of the transverse arm 88, whereby the free turning area of the control spindle is limited in relation to the drive part, whereby a control in case of failure of the hydraulic reinforcement is still possible.

The leaf spring 86 forms the two working springs of the pre-control valves 43 and 43 'and provides the valve operation within the proportionality range.

The transverse arm 88 has two transverse bores at its ends, in which bores two cups 94 are loosely placed. They each abut with their flange 96 against the transverse arm and each receive their center spring 98. Two adjusting screws 100 serve for central centering, which are placed in projections 102 fixedly connected to the drive part 76.

The center springs have a significantly greater (eg 100 times greater) spring stiffness than the leaf spring's 86 arms. The center springs are also used for pressure limitation, ie limitation of a maximum working pressure permitted for the control device.

In the neutral position shown in Fig. 6, the arms of the leaf spring 86 do not exert a force on the balls of the locking valves 43, 43 '. "F" 10 15 20 25 30 35 40 8005327-5 As a result, there is no pressure in the spring chamber 39 (compare Fig. 1) and the hydraulics. If a torque is introduced from the control spindle 72, this is absorbed by the gear 78 and the two parts turn in relation to each other. If the transverse arm 88 rotates relative to the drive part 76, for example in the direction of the arrow 104, the center spring 98 'is tensioned and the spring 98 is relieved. Fig. 7 shows graphically the relationship between the pressure p acting in the steering motor and the force F exerted on the actuator. To begin with, during a steering stroke, only the force F increases from the point Oi, without the hydraulics being effective. Until the point G (limit force) is reached, the left arm of the leaf spring 86 does not exert any force on the control valve 43. Nevertheless, the force exerted on the actuator increases due to the action of the two center springs 98 and 98 '. After reaching the limit force G, the leaf spring exerts a force on the valve 43 and the pressure p in the working space of the steering motor increases along the straight line 106. The device is now in a range of proportionality. The force noticeable in the actuating device is obtained almost exclusively by the action of the center springs 98, 98 'and only a vanishingly small part by the action of the leaf spring.

However, only the leaf spring is decisive for influencing the pre-regulating valve 43.

At the end of the proportionality range, when the limit point A is reached, the pressure p in the control motor must rise sharply, while the force F at the actuating device must only increase to a small degree. The device should thus operate in accordance with the steep branch 108. This is achieved in such a way that the cup 94 touches the left arm of the leaf spring 86. At a minimal further angle of rotation, the valve 43 will, under the influence of the center spring 98, close completely and the pressure in the control motor rises according to the curve branch 108 to its maximum permissible pressure.

From the moment corresponding to the point of limitation by the contact between the cup 94 and the leaf spring arm, the effect of the center spring 98 on the cross arm and on the actuating device decreases and only the effect of the already strongly tensioned center spring 98 'remains. Nevertheless, with the actuating device, any sudden increase in force is not noticeable when passing the limit point. The increasing pressure in the control motor from the limitation point takes care of the fact that it is more inactive via it. 800 15 32 25 30 35 40 8005327-5 9 the canary connection 49 at the piston rod of the steering motor via the guide member 110, the rack 112 and the gear 78 (compare Fig. 2) for a rotation of the gear and the drive part 76 (Fig. S) from the steering spindle 72 The hydraulics thus become effective before the above-mentioned jump-like force increase can take effect, ie no force increase in point A becomes noticeable.

When point H (Fig. 7) is reached, the pressure in the steering motor must not be increased further. This is achieved in that one center spring (in the case described - the left center spring 98) yields so much that pressure fluid can pass out of the pre-control valve 43. As a result, the valve piston 9 in Fig. 1 moves so much upwards that the pressure in the working space 4 of the control motor is limited to the maximum maximum pressure H.

When passing at point H, the cup 94 will be lifted by the cross arm 88. The action of the center spring 98 'on the cross arm then remains, whereby a jump-like force increase becomes noticeable on the actuating device - along the curve 114 (Fig. 7). This increase in force cannot be rendered ineffective by the hydraulics, since its pressure Ju is limited to the maximum pressure H. However, the increase in force is also desired here, since the driver must notice that a greater hydraulic gain is not available.

With a further increase in force along the branch 114, a point is finally reached, where the transverse arm 88 comes into abutment against the stop 92 and where the drive part 76 is mechanically carried by the guide spindle 72. This also takes place in the event of the hydraulics failing.

By means of the screws 100 a center correction of the center springs 98 and 98 'is permitted, i.e. in such a way that no force is exerted on the actuating device at the neutral position. By tightening the two adjusting screws 100 equally, an increase in the steepness of the straight line 106 within the area of proportionality is allowed. If center springs with different spring stiffness are used, the control device can be set with respect to different maximum pressures for the right and left working spaces of the control motor.

This is desirable if the steering motor has a piston rod arranged on one side and thus different sized piston surfaces. Then it is desirable to have a greater maximum pressure in the working space 4 '(Fig. 1) compared to the pressure in the working space 4, so that both at one and the other piston the same maximum force is exerted.

In terms of proportionality, the use of center springs with different spring strengths is irrelevant. During the passage of the straight curve line 106, the power shield between the two center springs is applied to the actuator, and a straight force increase is obtained for the two control outlets along the curves 106, which have the same direction.

Claims (6)

H 8005327-5 PATENT CLAIM 1. Hydraulic power steering device with a pressure medium pump arranged to feed from an intake line to a pressure line, at least one control motor, two control valves acting as pressure waves with mutually mechanically independent, spring-loaded pistons, each having a pressure chamber, which is in permanent connection with a working chamber in the control motor and via a first guide edge pair is connectable to the pressure line and via a second guide edge pair is connectable to a return line, the first guide edge pair closing first at a control movement of the control valve the second guide edge pair then opens, and each piston has a guide opening leading from the pressure chamber to a control chamber for the valve piston, which is arranged so that the first guide edge pair opens at an increase in the pressure in the upper chamber relative to the pressure in the pressure chamber, the control chamber is connected via an associated, spring-loaded pre-control valve the return line and the working springs of the two control valves are in drive connection with an operating device for the control device, which has two rotatable parts which are limited in relation to each other, namely a driving part and a driven part, one of which is designed as a two-armed lever for a leaf spring which forms the working springs of the two pre-control valves, for actuating the closing body of the pre-control valves arranged at the second part, and acts as a centering spring device between the two parts, and the seats of the pre-control valves are formed in the second part is characterized in that - the pump (7) consists of an externally adjustable piston - PUWD »- that the intake line (28) in parallel connection via a third guide edge pair (29) of each of the two 1 10 15 20 25 30 35 2. ü 3. n I "| (V The control valves (5, 5 ') are connected to the pump (7), wherein, in the event of a closing movement of the control valve, the third control edge pair closes before the closing of the first control edge pair, that the pressure line (12) by parallel connection is connected to each of the two control valves, and that parallel to the leaf spring (86) is arranged a transverse arm (88) which at its ends cooperates with the arms of the leaf spring (86) via spring-loaded stops (94), so that the angle of oscillation between the neutral position of the control device and the contact of the spring-loaded stops (94) with the arms of the leaf spring (86) corresponds to the proportional range of the control device, at which the pressure in the control chamber (3) increases proportionally to that applied to the control device (45). the force and the associated angle of oscillation correspond to the limiting range, in which the pressure rises steeply at a, only slightly further increasing actuating force. Control device according to claim 1, characterized in that each valve piston (62, 62 ') on its side facing away from the pre-control valve (43, 43') has a baffling surface acting in the closing direction with an additional throttle opening (64, 64 '), which leads from the pressure chamber (21, 21') of the control valve (60, 60 ') to a further control chamber (66, 66'), and that the control chamber communicates with the container line (28) via an adjustable pressure relief valve (70). Control device according to Claim 1 or 2, characterized in that centering springs (98, 98 '), which hold the abutment pieces (94) at the ends of the cross arms 88) under prestress, simultaneously generate a proportional actuating force on the control device ( 45). Control device according to claim 3, characterized in that the pretension of the springs (98, 98 ') is unstable. Steering device according to Claim 3 or 4, characterized in that the center springs (98, 98 ') have different spring strength for the purpose of producing different maximum pressures in the two working chambers (4, 4') of the steering motor ( 3). Control device according to 2, in that a common pressure holding valve (70) is provided for the two control valves, which via each a non-return valve (68, 68 ') is in communication with the two operating operating rooms (6). 66, 66 ').