DE2361893A1 - Pressure control system for servo steering - has locking system for control valve regulating spring so that power failure is compensated - Google Patents

Abstract

The main patent describes a complete system with two servo valves that alternate connection of a servo motor to either a pressure source of a pressure outlet and a mechanical feedback system for the movement of the servomotor. The servo valves are pressure regulated with the applied pressure being counteracted by a regulating spring. In this addition there is at least one locking position where the spring is held. This is set for a specified value of operating force. If this force is not exceeded, a percentage of the force is supplied by the servo system itself, reaching a maximum where the power connection between operating member and regulating spring is broken. The operating member has position screws for adjustment.

Description

Additional registration

S3 SS =: = 1SSSSSSSS rs SS S = S ===! S3 S = «Β S = CZ = SSSBZ

for patent application P 22 42 022 “Ο

Subject: Pressure fluid sequence control for power steering or the like

Applicant: Fa. Langen a Co, 4000 Düsseldorf, Klosterstrasse 49

The invention relates to a pressure medium sequence control for power steering systems or the like with two of one common Actuator operated control valves for weehselwelsen connecting the working spaces of a hydraulic servo motor with a pressure source or a drain as well as with a mechanical feedback of the movement of the servo motor and a Feedback of the pressures existing in the working spaces to the actuating member via reaction surfaces acted upon by these pressures on the control members of the control valves or reaction surfaces on operatively connected to the control members Reaction members, the control valves each from the pressure of a working space with the help of reaction surfaces against the force of a regulating spring controlled pressure regulating valves of the type which establish a connection below a certain pressure share from the pressure source to the work room, this If the pressure is exceeded, increasingly throttle the connection and finally block it, and if the pressure continues to increase, a Open the connection from the work area to the drain, whereby the Support control springs on the common actuator, according to patent application P 22 42 Ο22.Ο. .

S09826 / 0378

Pressure fluid sequence controls of this type are used in the working areas of the servomotor without significant consumption Pressure medium to maintain a minimum pressure. That means, that the control springs are pretensioned at least in the middle position. When actuated, one will become gradually increasing reaction force as a result of a further tension in a control spring and a pressure proportional to this tension result in the associated work space. In this way, a certain pre-pressure is achieved in the work rooms and Jerks in the steering and the generation of noise are avoided.

However, it is not possible to use certain modern servol

to meet the demands made. One of the most important requirements calls for a power transmission from the vehicle driver to the steered wheels without power assistance up to a limit actuation force. It is based on the consideration that in certain operating conditions of a vehicle z. B. when driving fast on the motorway or on black ice the already not large actuation forces would be even lower with a directly starting servo assistance and thus the driving experience considered necessary would be lost. On the other hand, the marginal actuation force should use the power assistance as soft as possible to overcome and the operating force above a second .fi ^ enzkraft_JLm ^ SJ ^ nne a steering force limiting knnat-anj- ^ hJ ^ j ^ flXL-Pdjar ... ANNM ηΛ »η * · βι? Χ increase insignificantly.

In conventional power steering, one has to achieve these goals in the power flow between the actuator and the Control valves containing valve housings built in prestressed mechanical transmission members. To operate the control valves The necessary relative movements between the actuator and the valve housing could only be made after the preload had been overcome

OBlQl ^ L. INSPECTED

509826 / Ό 378

the transmission links, which are in the form of some springs take effect. Until then, however, a purely mechanical power transmission from the vehicle driver took place to the steered wheels. Disadvantage of this "version was that the transmission means require additional installation space and also caused undesirable costs. aside from that So far it has not yet succeeded with reasonable effort, after overcoming the preload for a soft one Address to worry.

It has now been found that the desired steering characteristics in an amazingly simple way with negligible additional costs and practically the same installation space can be achieved by appropriate design of the pressure medium sequence control according to the main application “The Design is that the control springs of the pressure control valves at least in that the connections block Position are biased and deal with their free Enolfb. support directly or via spring plates or the like above% of the limit actuating force acting on them solely on the actuating element or on a part that is rigidly connected to it, so that the entire spring force is absorbed by the actuator alone is, while below the limit actuation force at least a portion of the spring force also on the control valve housing or a part firmly connected therewith is supported in such a way that this part is based on the limit actuation force increases when the actuating force decreases and reaches a maximum when the flow of force between the actuating member and control spring is interrupted.

5 0 9826/0378

2361833

As already mentioned above, the control springs also had a preload according to the main application. The control springs are generally supported on the actuating member, so that in the central position of the control members this was to be regarded as a torque or force comparator in equilibrium. A deflection from the central position was possible with a force starting from zero. The tension of one rule spring corresponded to a relaxation of the other and vice versa. According to the invention, the control springs are now tied up in the control valve housing; a control element can only be deflected via the actuating member when the preload of the associated control spring has been overcome. The other control spring then loses all contact with the actuator and no longer influences the first control spring. Until the preload has been overcome, the system of regulating spring and control element, which is under pressure, is a fluid column in the reaction chamber that can be regarded as a mechanical-hydraulic linkage, which enables a direct power transmission from the actuating element to the control valve housing. It is therefore possible to move the servomotor together with the steered wheels without servo assistance. The pressure medium quantities to be supplied or discharged due to the change in the working spaces can flow via the control valves, since the pressure differences that arise in the working spaces are sufficient to move the control elements into the correct position via the reaction spaces. More _v advantages and features of the invention will become apparent from the description and the dependent claims.

The description is based on the ones shown in the figures Embodiments.

509826/0378

- 5 - ,, Figure 1 shows the schematic structure of a Servole.nkeinrichtung.

Figure 2 shows the characteristic curve of the force to be applied on the steering wheel. above the force required to operate the steered wheels.

FIG. 3 shows a section along the axis of the steering valve from FIG.

FIG. 4 shows a section according to the section line · C-D of FIG

Figure 5 shows schematically two coaxially arranged translationally moved control members.

FIG. 6 shows a variant for the support in a partial section the rule spring.

FIG. 7 shows a further possibility for supporting the control spring.

A pump 1 sucks pressure medium from a storage container 2 and conveys it into a pressure line 3. The pressure line 3 leads to a connection P of a steering valve 4, which has further connections A, B and T. The connection T is connected to a drain line 5, while the connections A, B are connected to lines 6 and 7 which lead to connections A ₁ and B _{1 of} a servo motor 8. The servomotor 8 has a cylinder 9 in which a piston 12 connected to bilateral piston rods 10 and 11 slides. The piston rods 10 and 11 are surrounded by working spaces 13 and 14 within the cylinder 9. The piston rod 11 is connected to a transmission part 15 which acts on the steered wheels 16 in a manner not shown in detail. The gear part 15 engages in a further gear part 17, which is connected to the valve body 18 which is arranged inside the steering valve 4 and from there tightly to the outside. A steering wheel 19 wirktMüber a steering shaft 20 to a detail illustrated in Figure 3 'e $ tätigungsglied 21. The steering valve 4 has a check i

ORIGINAL INSPECTED

236 7

Closing body 22 in which the connections P, A, B and T in the form of Screw connections are arranged. In a central bore 23 of the connection body 22 a sleeve 2.4 is arranged, which has ring channels connected by transverse bores on its outer and inner jacket, which are connected to said connections are connected by further channels. In the inner bore 25 of the sleeve 24 is a wave-shaped part 26 of the valve body 18 led. The wave-shaped part 26 projects beyond the connection body 22 on both sides. On one side there is one Connection possibility for the transmission part 17 is provided, while on the other side of the wave-shaped part 26 in a valve housing 27 passes. In the valve housing 27, control pistons 28 and 29 are perpendicular in a manner that can be seen in more detail in FIG to the axis of the valve body and arranged off-center. The supply of pressure medium to the control piston or the discharge line of the control piston takes place via outside the plane of the drawing Longitudinal and transverse bores in the valve body 18. These bores open into the outer surface of the part 26 in such a way that they are connected to the ports P, A, B and T via the aforementioned annular grooves and transverse bores in the sleeve 24. Of simplicity For the sake of this, the designations of the connections are repeated once again on the associated bores or annular grooves in FIG. That Valve housing 27 is surrounded by a cup-shaped cover 30, which is tightly attached to the connector body 22. ' In its bottom side 31, the cover 3O has a bore 32 through which sealed the actuator 21 protrudes through. The actuator 21 is within the valve body with the aid of two bearings 33 and 34 18 stored. The otherwise wave-shaped actuator 21 is in the area of the control piston 28 and 29 with a vertical to its axial direction extending lever 35 is provided. The control pistons 28 and 29 slide in bores 36 and 37 within

509826/0378

of the valve housing 27. On the end face facing the lever 35 A control spring 38 acts on the control piston 28 and is supported on a spring plate 39. The spring plate 39 takes place its abutment on a shoulder 40 between the bore 36 and a bore 41 of smaller diameter. The spring retainer 39 has a pin-like extension 42 which penetrates the bore 41 and comes into contact with a set screw 43 in the lever 35. One with. the plunger 44 connected to the spring plate 39 protrudes into a countersink 45 within the control piston 28 with a certain amount axial play into it. In an analogous manner, a control 'acts on the end face of the control piston 29 facing the lever 35 spring 46 which is supported on a spring plate 47. The spring plate 47 finds its abutment on a shoulder 48 between the Hole 37 and one hole, 49 of smaller diameter. The spring plate 47 has a pin-like extension 50, which with a Adjusting screw 51 in lever 35 comes into contact. A plunger 52 connected to the spring plate 47 protrudes into a with axial play Countersink 53 inside the control piston 29. Through a channel 54 within the control piston 29, the connection A is permanent connected to a reaction space 55 adjoining the other end face of the control piston 29. An analog connection exists between the connection B and a reaction space 56 adjoining the control piston 28 on the end face. In the middle position of the lever 35 and provided that the connection P is pressurized, the control piston 28 takes a position one, in which a shoulder 57 has an annular groove 58 corresponding to the connection B in the bore 36 of two on both sides of the shoulder 57 arranged annular grooves 59 and 60 separates. The annular groove 59 is permanently connected to the connection P, while the annular groove 60 is permanently connected to the terminal T. In a corresponding manner, the control piston 29 has a shoulder 61 with which Help in the middle position of the lever 35 or the control piston 29 an annular groove 6 2 in the bore 37 of two to the school

50 98267 0378

ter 61 subsequent annular grooves 63 and 64 is separated. the Annular groove 63 is continuously connected to the terminal P. The annular groove 64 is permanently connected to the connection T.

To explain the function, it is assumed that the lever 35 is initially in the middle position and that no external forces intervene on the steering wheel 19 or on the steered wheels 16. Before the pump 1 delivers pressure medium, the control springs 38 and 46 will then press the control pistons 28 and 29 into a position in which the connections A and B are connected to the connection P. As soon as the pump 1 begins to deliver the pressure medium, there will be a pressure increase which will propagate from the connection P via the connections A and B _{, the lines 6 and and the connections A 1 and B 1} to the working spaces 13 and 14. Since the effective areas of the working spaces 13 and 14 are equal, the piston 12 will not move. The pressure increase continues to propagate from the connections A and B through the channels running inside the control pistons 28 and 29 into the reaction spaces 55 and 56 As soon as the pressure here becomes so great that the compressive force exerted by it on the control pistons 28 and 29 overcomes the bias of the control springs 38 and 46, the control pistons 28 and 29 are displaced, shortening the control springs 38 and 46, until finally the Shoulders 57 and 61 interrupt or throttle the connection from port P to ports A and B so much that leakage losses can just be fed in. Pressure is thus created in working spaces 13 and 14 and in reaction spaces 55 and 56 a, which is dependent on the bias of the control springs 38 and 46. For further explanation, it is now assumed that a movement of the Le nkrades 19 clockwise may correspond to a movement of the gear part 15 to the right. In addition, the on the steered wheels 16 at

9 -

509826/0378

2361833

forces K occurring during a steering process be relatively small, as they do, for example, when driving fast on the motorway or occur in black ice. If the steering wheel is turned clockwise under these conditions, the lever will also turn 35 clockwise and acts with a certain force via the adjusting screw 43 on the pin-like projection 42 of the Spring plate 39 a. However, this force is initially not sufficient to overcome the bias of the regulating spring 38, so that a Power transmission via the control spring 38, the control piston 28 '; and the pressure medium cushion, which is under pressure in the reaction chamber 56, is applied to the valve housing 27. The valve housing 27 ' therefore also rotates clockwise synchronously with the lever 35 and transmits this movement to the gear member 17, which in turn moves the gear member 15 to the right. The gear member 15 on the one hand causes a corresponding Impact of the steered wheels 16 and, on the other hand, a movement of the piston 12. This reduces the working space 13 with displacement of pressure medium. This repression takes place such that the movement of the piston 12 in the working space 13 caused a small pressure increase that propagates into the reaction space 55 and there a correspondingly increased Force on the control piston 29 causes. This increase in strength is sufficient to move the control piston 29 with a very slight further shortening of the control spring 46 so that a Connection from port A to port T is established so that the pressure medium can flow out. Enlarged in reverse the working space 14, generating a pressure drop in the working space 14 and the associated reaction space 56. The decreasing force on the control piston 28 as a result of this pressure drop allows the control spring 38, the control piston 28 to move into a position in which pressure medium can flow from port P to port B in the required amount. From this process it can be seen that although pressure medium from the

- 10 OWGJNAt-INSPECTED

509826/0378

Circuit P flows to port B, but no servo assistance takes place. Rather, the turning of the steered wheels and the movement of the piston 12 take place solely through the manual force K “applied to the steering wheel. This process is shown in Figure 2 in the curve 0-1. We now assume that what is necessary to turn the steered wheels Force is greater than in the example described above, as well as when driving slowly in tight corners or when driving softly Underground could be the case. The pressure in the reaction space 56 is then no longer sufficient to transmit the required force, d. H. the pressure medium cushion in the reaction space 56 is no longer to be regarded as rigid. When the lever 35 is moved in Therefore, in a clockwise direction above a limit force, which corresponds to point I in FIG. 2, the spring plate 39 is removed 14 lifted. The control spring 38 is tensioned a little higher and has the tendency to move the control piston 28 so that that the shoulder 57 establishes a connection between the connections P and B. In this process it must be noted that although a relative movement has taken place between the lever 35 and the valve housing 27, but no relative movement between the valve housing 27 and the connection body 22. Only when that from connection P into connection B and from there into the working space 14 flowing pressure medium causes a pressure increase there, which for the movement of the piston 12 and thus the transmission member to the right is sufficient, the steered wheels 16 are turned. At the same time, the gear member 17 and the Valve body 18 a mechanical return of this movement, i.e. the valve body 18 and thus the valve housing 27 follow the Movement of the lever 35 in each case so that the shoulder 57 after the movement of the lever 35 is complete again the connection between interrupts the connections P-B. The force acting on the steered wheels 16 is made up of two components in this operating state together. One part corresponds to that caused by the servo

- 11 -

509826/0 378

2361 & 93

motor 8 applied auxiliary force, while the other part again from Lever 35 via the control spring 38, the control piston 28 and the Druckmittelpolster.'im reaction chamber 56 on the valve housing 27 is transmitted and thus corresponds to the respective tension of the spring 38. This operating behavior corresponds to the curve I-II of Figure 2. It can be seen that this Kurvenzug.I-II flatter runs as the curve O-I. This flatter course corresponds to the saving in manual strength through the gradually starting power assistance. The outflow of pressure medium from the working space 13, which is becoming smaller, also takes place here in the manner already described above described way. Since when the lever 35 is rotated relative to the valve housing 27, the contact between the adjusting screw and the extension 50 of the spring plate 47 is canceled, a slight movement of the control piston 29 does not affect in any way the control piston 28. Since, on the other hand, the control spring 46 remains tensioned, a certain one is definitely established in the working space 13 Maintain the form. After a certain shortening of the control spring 38, there is finally a mechanical contact take place between the tappet 44 and the control piston 28, point II in Figure 2 may correspond to this contact. from At this point, of course, no further shortening of the control spring 38 can take place. On condition that after a further specific increase in force, a steering force limitation, which is not described in more detail here, is used may, after running through the curve il-III becomes the curve take a course essentially parallel to the abscissa. Steering force limits are already in the most varied of designs have become known and are generally based on that the pressure in the reaction chambers to a certain

- 12 -

509826/0378

Value is limited, even if the pressure in the work rooms continues to rise. It is therefore necessary in this context will not be discussed in more detail. The slope of curve II-III is the same as that of the curve I-II / so that a continuous curve I-III results. Apart from the levers occurring in the steering kinematics, the gradient of the curve I-III is primarily Line dependent on the ratio of the effective areas in the reaction space 56 or in the working space 14. The smaller the effective The area of the reaction space 56 is the larger the hydraulic transmission and the flatter the curve I-III. The return of the pressure medium from the working chamber 13 takes place here again in the manner already described Way. The same return effect occurs when the button is released Steering wheel the steered wheels have a tendency to return to the straight-ahead position. Here too is a automatic resetting possible with a corresponding displacement or suction of pressure medium. When turning of the steering wheel counterclockwise, all the processes are carried out in reverse with respect to the control piston 29. With the aid of the adjusting screws 43 and 51 it is possible to adjust the lever 35 symmetrically to the valve housing 27. It it is also possible, compared to approaches 42 and 50, to have a specific game, freedom from play or even a specific one Adjust preload.

In Figure 5, a valve housing 27 'is indicated by way of illustration, in which two coaxial bores 36 'and 37' are arranged, between which there is a bore of smaller diameter 65

- 13 -

509826/0378

2361833

finds. ^{An actuating member 35 f} slides in the bore 65 and is in operative connection with a steering wheel 19 'in a manner not shown in detail. In a central position, the actuating member 35 'acts on both sides of the spring plates 39' and 47 ', which ^{abut the shoulders 40 1} and 48' between the bore 65 and the .bores 36 "and 37 '. A regulating spring is supported on the spring plate 39' 38 *, which acts on an end face of a control piston 28 '. The control piston 28' has three shoulders 66 ·, 67 and 68, which are separated from one another by waists 69 and 70. In a central position, the shoulder 67 closes an annular groove 71 in which a terminal B ¹ opens. In the area of the waists 69 and 70 surrounding the annular spaces 72 and 73 open a terminal ^T! and a port P ", which is connected via a line 74 to a pressure source 1 '. A drain line 75 is connected to the connection T ^1. A line 76 leads from connection B ¹ to a connection B 'of a servo motor 8' which contains a cylinder 9 ', a piston 12' with piston rods 10 'and 11' on both sides, and working spaces 13 'and 14'. A regulating spring 46 'acts on the spring plate 47' and acts on a control piston 29 '. The control piston 29 'has shoulders 77 _s 78 and 79. In a central position, the shoulder 78 blocks an annular groove 80 in which a connection A ¹ opens which is connected via a line 81 to a connection A' which opens in the working chamber 13 ' . The shoulders 77, 78 and 79 are separated from one another by waists 82 and 83. In an annular space 84 surrounding the waist 82 opens a connection P 'which is also connected to the pressure source 1' via a pressure line 85. A connection T 'leads from an annular space 86 surrounding the waist 83 to a drain line 87. From the line 76 A control line 88 branches off to a reaction space 89 adjoining the shoulder 66. In a similar way, the line 81 is connected via a control line 90 to a reaction space 91 adjoining the shoulder 79 on the front side. The valve housing 27 'protrudes over

- 14 -

509826/037 8-

2361833

only schematically, shown gear member 92 with the piston rod 11 * in operative connection. The mode of operation is very similar to that of FIGS. 3 and 4. An actuation of the steering wheel in the clockwise direction may correspond to a movement of the actuating member 35 'to the left. Until the bias of the control spring 38 'is overcome, there is a direct flow of force from the steering wheel 19' via the actuating member 35 ', the spring plate 39, the control spring 38 *, the control piston 28 "and the pressure medium cushion in the reaction chamber 89 to the valve housing 27' and from there take place via the gear member 92 and the piston rod 11 'etc. to the steered wheels 16'. Pressure medium is displaced from the decreasing working space 13 ', which causes a pressure increase in the reaction space 91 and thereby brings the control piston 29' into a position in which the connection A ^{1 is} connected to the connection T '. Conversely, the pressure drop in the expanding working space 14' also causes a pressure drop in the reaction space 89, whereby the control spring 38 'pushes the control piston into a position releasing ^{the connection P'-B 1} This process again corresponds to the curve 0-1 of FIG The spring plate 39 'is lifted off its abutment. Since, as already mentioned above, the control pistons change their position only insignificantly, a steering process takes place when the power requirement increases with increasing shortening and thus higher pretensioning of the control spring 38 '. The contact between the spring plate 47 'and the actuating member 35' is lost. The steering characteristics correspond to curves I-II. When a further limit force is exceeded, there is finally mechanical contact between the spring plate 39 'and the control piston 28'. From this point on, the characteristic curve again corresponds to curve II-III. The pressure medium passes from port P ^{1 to} port B ¹ and from there via the

509826 / Ό378

23818-93

Line 76 as well as the connection B ^ ₁ in the working space 14 'and acts there on the piston 12' in the sense of servo support. The process from .dem work space 13 'takes place in the manner already described. The same process also occurs when the steered wheels are automatically returned to the straight-ahead position. . ·

Sometimes the requirement is that, despite a relatively high pre-pressure in the working areas of the servomotor, the manual The amount of force to be transmitted should be low before the servo assistance starts. In other words, this means that the manual force required to overcome the bias of the control spring should be less than the bias of the Rule spring. A solution to this problem is shown in FIG. In a valve housing 27 '"there is a bore 37" arranged, which tapers via a sharp-edged shoulder 93 to a coaxial bore 94, to which a shoulder 95 adjoins an outwardly leading bore 96 of smaller diameter. A control piston slides in the bore 37 ″ 29 ″, which is loaded by a control spring 46 ″. The rule spring 46 'on the other hand is supported on a spring plate 47' ''. The spring plate 47 ″ lies on the shoulder 93 in the starting position on and is firmly connected to a projection 50 ', which with radial Game penetrates the holes 94 and 96 and on one. Adjusting screw 51 'acts, which is arranged within a lever 35' ' is. A plunger 52 'is connected to the spring plate 47 ″, after a certain relative movement between the spring plate 47 '' and the control piston 29 * 'in mechanical contact comes with this. Between the underside of the spring plate 47 " and the shoulder 95 an additional spring 97 is arranged, the preload in the position shown is less than the preload the rule spring 46 ''.

■ - 16 -

509826/0378

2361833

The function of this' arrangement is as follows:

The force applied by the control spring 46 ″ only acts still partly on the paragraph 93 or on the adjusting screw 51 *. Another in its height by suitable choice of Additional spring 97 determinable force component is determined by the additional spring 97 transferred to paragraph 95. The additional spring 97 thus acts in the same direction as the actuating force and accordingly reduces the force required to lift the spring plate 47 '' from paragraph 93 by the Degree of their preload. In certain applications, this mode of action has the advantage that after lifting off of the spring plate 47 '' the spring constants of the control spring 46 '' and the additional spring 97 add up, so that there is an overall higher spring constant for the system. With the help of this increased spring constant can be a relatively large increase of the pressure with comparatively small relative movements between the lever 35 ″ and the valve housing 27 ″. In this way, the feeling of a "hole" in the steering can be avoided under certain circumstances.

Another possibility for achieving this function is shown in FIG. In a valve housing 27 ^{'! L} a bore 37' is positioned * *, which propagates via a shoulder 95 'in a continuous outwardly bore 96'. A control piston 29 ″, on which a control spring 46 ″ ″ acts, which on the other hand is supported on a spring plate 47 ″ ″, slides in the bore 37 ′ ″. From its underside, the spring plate 47 '''is acted upon by an additional spring 98, which finds its abutment on the shoulder 95'. The spring plate 47 '"is firmly connected to a shoulder 50 *', which serves to guide the additional spring 98, penetrates the bore 96 'and on an adjusting

- 17th

50 9826 / 0-3 78

screw 51 'in lever 35 ·· acts. The spring plate 47 ″ is further connected to a plunger 52 ', which after a certain relative movement between spring plate 47' "and Control piston 29 'comes into mechanical contact with this.

To explain the function, it is assumed that the spring constant of the auxiliary spring 9 8 is dimensioned so that the auxiliary spring 98 in the central position of the control ^{piston 29 ri} is pressed against the block by the pre-tensioning of the regulating spring 46 '"and thus a fixed abutment Naturally, the additional spring 98 must be designed in such a way that there is no overstressing. The force applied in the central position by the control spring 46 '''is thus via the spring plate 47'"and the additional spring 98 against the shoulder 95 'and possibly via the shoulder 50 * also supported on the adjusting screw 51 '. The proportion of force by which the force acting on the shoulder 95 'exceeds the preload of the additional spring 9 8 pressed onto the block must be applied manually. After this manual force has been applied, the auxiliary spring 98 can expand, again adding up the spring constants. In this case too, the bias of the control spring 46 '''can have a relatively high value and generate a relatively large pre-pressure. Nevertheless, the manual force required to move the control piston 29 ″ can be kept small.

The invention is of course not limited to the exemplary embodiments shown limited, but in principle to be used with all types of pressure medium follow-up controls, provided that it is it is structurally possible to shackle the control springs in the valve housing without the possibility of influencing one another, via Ejifin-

C η ή ο «*> e / η »i * a '

thought is therefore not due to the mutual position of the Control members still to their embodiment or to the embodiment and points of application of the actuators tied. Nor does the way in which the relative movements necessary to actuate the control elements are generated. Furthermore, be on it pointed out that the proportion to be set in the middle position of the actuating element in the absence of external force the spring force can also be determined with just one adjusting screw. However, in this case it can be due to manufacturing inaccuracies a certain asymmetrical position of the actuator relative to the valve housing in the absence of external force.

- 19 -

509826/0378

Claims (7)

2381893 Patent claims: Pressure fluid sequence control for power steering or the like with two control valves operated by a common actuator for alternating connection of the working spaces of a hydraulic servo motor with a pressure source or a process as well as with a mechanical feedback of the movement of the servo motor and a feedback of the pressures existing in the working spaces to the actuating member via These pressures acted upon reaction surfaces on the control members of the control valves or reaction surfaces on with the control members effective% control members, wherein the control valves are each controlled by the pressure of a working chamber with the help of reaction surfaces against the force of a control spring controlled pressure control valves of the type that below a certain pressure are a connection, Establish from the pressure source to the working space, increasingly throttle this connection when the pressure is exceeded and finally block and a 'conn opening from the working space to the drain, the control springs being supported on the common actuator, according to patent application P 22 42 022.0, characterized in that the control springs (38, 46, 38 ', 46', 46 »·, 46 ¹¹¹ ) of the pressure control valves are pretensioned at least in the position blocking the connections and with their ends facing the actuating member (35, 35 ', 35') directly or via spring plates (39, 47, 39 ', 47', 47 ', 47' ^lf ) or the like above a limit actuation force acting on them only on the actuating element or a part rigidly connected to it (adjusting screws 43, 51, 51 ') connected · ₂ o 50 9 826/037 8 support,> so that the entire spring force ^{is absorbed by the actuating member (35, 35 1} , 35 ¹¹ ) alone, while below the limit actuating force at least a portion of the spring force is also on the control valve housing (27, 27 ', 27 ", 27 ¹¹¹ ) or one with it firmly connected part is supported in such a way that this proportion, starting from the limit actuation force, increases when the actuation force decreases and reaches a maximum when the flow of force between actuation ^{element (35, 35 1} , 35 '') and control spring (38, 46, 38 ', 46 ', 46 ", 46 ¹ ") is interrupted. 2. - Pressure medium sequence control according to claim 1, characterized in that in the central position of the actuating member (35, 35 ', 35 ¹¹ ) in the absence of external force, the control springs (38, 46, 38 ¹ , 46', 46 ", 46 ¹ ' ¹ ) are supported solely against the control valve housing (27, 27 ', 27 ", 27"') or a part permanently connected to it. 3. - Druckini ttelsequsteuerung according to claim 1, characterized in that that adjusting means (adjusting screws 43, 51, 51 ') are provided on the actuating member (35, 35 "), which provides a backlash-free operative connection between the actuating element (35, 35 ") and control springs (38, 46, 46", 46 '") allow to adjust. 4. - Pressure medium sequence control according to claim 3, characterized in that that with the help of the adjusting means (adjusting screws 43, 51, 51 ·) already in the middle position of the Actuator (35, 35 ") in the absence of external force, a certain proportion of the force of the control springs (38, 46, 46 ", 46 '") of the actuator (35, 35 ") received will. - 21 - 509826/0378 5. - Pressure medium sequence control according to one or more of the t '- ■ previous claims, characterized / that after a predetermined shortening of a control spring (38, 46, 38 ', 46 ", 46", 46' ··) ■ between the actuating member (35, 35 ', 35 ") and the control member (control piston 28, 29, 28 ', 29', 29 ¹ ') directly or via rigid transmission means (43, 42, 44; 51, 50, 52; 39';47'j 51 ', 50', 47 ", 52 '; 51 ', 50', 47 ¹¹ ', 52') a mechanical contact that is rigid in the effective direction takes place. 6. - Pressure medium sequence control according to one or more of the Previous claims, characterized in that ^{an additional spring (97) acts on the spring plate (47 11} ) against the force of the regulating spring (46 ¹ '), which is supported on the valve housing (27 ¹¹ ) or a part firmly connected to it and in its strength is dimensioned so that in the central position of the control piston (29 ¹¹ ) in the absence of external forces, the spring plate (47 ″) is pressed against a stop (paragraph 93) fixed to the housing. 7. - Pressure medium sequence control according to one or more of claims 1 to 5, characterized in that ^{an additional spring (98) acts on the spring plate (47 * 11} J against the force of the control spring (46 ¹¹¹ ), which is located on the valve housing (27 * ^l! ) and is dimensioned in its strength so that it is pressed against the block in the middle position of the control piston (29 * ·) in the absence of external forces 509826/0 3 78