DE1252989B - Control slide with damping chambers - Google Patents

Description

GERMAN WTTWl PATENT OFFICE

EDITORIAL

German class: 47 g-29

Number: 1 252 989

File number: C 29474 XII / 47 g

1 252 989 filing date: March 26, 1963

Opening day: October 26, 1967

The invention relates to a control slide with a longitudinally displaceable in a longitudinal bore of a housing Reduced slide piston with controlling collars and sections in between Diameter, by means of their connections opening into annular grooves of the longitudinal bore from one another separated or connected to each other, as well as with frontal damping chambers, in the parts penetrate the slide piston when it is moved.

In the case of hydraulic control spools, it can be of great importance, especially at higher working pressures, to limit the speed of movement of the spool. Under certain circumstances, the slide piston can otherwise hit its end positions with great force. If the passages are opened too suddenly, pressure surges can also occur, which propagate through the entire hydraulic system. Finally, the piston may arise in which he commutes to a control position contributes to free movement of the piston and unfavorable ao flow and pressure oscillations.

Such control slides can be found, for example, in servo systems for steering assistance in vehicles with as steerable wheels use. In some vehicles, the power steering system does not work smoothly or bump-free and uniform. In these cases, the one to overcome the breakaway torque is the steerable one Wheels and at the beginning of the steering process when the vehicle is stationary or moving very slowly necessary force much greater than that to continue the steering movement of the steerable wheels necessary force when the vehicles are in motion. Here it happens that when the Steering wheel to initiate the displacement of the slide piston relative to the valve housing high pressure is built up in the power steering cylinder without substantial movement of the actuator the power control, the steering linkage or the steerable wheels takes place. There will be energy in the Deformation of the tires, in the mechanical bending of the steering linkage, the ball joints, the Steering pivot bearings, the bending of the operating linkage, the expansion of the hoses, etc. saved. When the wheels finally begin to steer, it accelerates whole system very quickly and soon assumes a relatively high speed as a result. That Valve housing or the valve piston - depending on the type of control valve and used in the system its arrangement in this - then passes over the control slide with damping chambers

Applicant:

Clark Equipment Company,
Buchanan, Me. (V. St. A.)

Representative:

Dipl.-Ing. W. Kuborn, patent attorney,
Düsseldorf, Brehmstr. 23

Named as inventor:

Richard Oscar Gordon,

New Buffalo, Me. (V. St. A.)

Claimed priority:

V. St. v. America March 27, 1962 (182 887)

neutral position and opens the slide in the opposite direction, so that pressure fluid to the other Cylinder end is directed. The same overshoot then takes place in the opposite direction. If the The swing energy is sufficiently large, the steered wheels overcome the breakaway resistance and accelerate the system, as mentioned above, works at a relatively high speed in the opposite direction, whereby the valve housing or the slide piston again pass the neutral position. This process can continue automatically and has the consequence that the steered wheels and the steering linkage is subject to violent forces and movements. Every now and then this can Oscillating movement caused by a slight movement of the steering wheel when the steering wheel is stationary or when the Vehicle are initiated.

This example shows the urgency of damping the movement of the spool will.

In a known embodiment of a control slide with damping spaces, these are located inside the hollow-drilled slide piston itself. A piston rod protrudes axially into its bore a damping piston resting against the inner wall of the bore, the other end of the Piston rod is attached to the valve body. When the spool moves, it shifts the damping piston in this and forms with the other loading provided on the spool itself

709 679/285.

delimitation of the bore of the spool a variable, pressure fluid-filled damping space, which only through narrow channels with the outside area of the spool is in communication, which occurs during a movement of the spool and the This inevitably associated enlargement or reduction of the damping space the passage make it difficult for the hydraulic fluid and thus limit the speed of movement.

In another known control slide, the slide piston points to the ends outside of the Control zone, collar with a smaller diameter than the valve body, which acts as a damping piston on. This is limited axially by frontal closure and sealing covers, which have a cylinder-like, have inwardly protruding approach, in which the acting as a damping piston Immerse the collar of the spool. Their outside diameter is only slightly smaller than that Inner diameter of the cylinder-like cover approaches, so that the escape or inflow of the hydraulic fluid a flow resistance when the collar acting as a damping piston moves is opposed, which has a damping of the movement speed result.

The disadvantage of the known measures for achieving damping is that they are not insignificant require additional construction elements that must be of high precision if they should be effective. This means an increase in the cost of manufacture, a more difficult assembly and an increased susceptibility to failure of the control spool.

The object of the invention is to create a simplified control slide with damping spaces, in which the attenuation is achieved by slightly redesigning what is already required for the control Construction elements without additional components and without significant additional processing steps is achieved.

For this purpose, according to the invention, the damping chambers have the same diameter as the longitudinal bore of the valve body and sealed to the outside of the valve body and is the penetrating into it part of the spool of the same outer collar, the one has such an outer shape that a connection between the respective outer annular groove and the associated Damping chamber is produced or increasingly throttled.

According to the invention is essentially only the removal of a small amount of material to the both outer control collars are necessary to reduce the throttle points that dampen the movement of the spool to obtain.

Further features of the invention emerge from the subclaims. In the description below An exemplary embodiment of the invention is described in connection with the drawing.

F i g. 1 is a longitudinal section through a steering control valve;

FIG. 2 shows an enlarged section from FIG. 1; FIG.

F i g. 3, 4 and 5 show the part of the control slide according to FIG. 1 located above the center line. 2, wherein the slide from the neutral position in a partially open position, in a more open position and is slid to a fully open position;

F i g. 6 shows the slide when overshooting,

after originally being moved to the right.

F i g. 7 is a cross section taken along line 7-7 in FIG.

In Fig. 1, the power control device (steering aid) is generally designated by 10 , which is equipped with a control slide 12 , on which an actuating device 14 for the steering in the form of a double-acting one at opposite ends

ίο Pistons and a cylinder and a drive 16 for the control slide are connected.

The actuator 14 operated with liquid consists of a cylinder 18 and a piston 20 which is displaceable therein. The cylinder 18 is double-walled and has an outer sleeve 22 and an inner sleeve 24. The sleeves form an annular liquid passage 26 in the longitudinal direction. The outer sleeve 22 is attached to a cylindrical head part 28 . At the other end of the outside

ao sleeve 22 is a piston rod guide 30 mounted on a piston rod 32nd The piston rod has a thread 34 and can be connected to the vehicle frame in an articulated manner. The annular fluid passage is connected to the interior of the cylinder through an opening 36 in the inner sleeve 24 at the end of the piston rod guide 30 . At the other end, the liquid passage 26 is connected to the liquid passage 38 in the head part 28. The passage 38 can be made to cover with a liquid passage in the control slide 12. The head part 28 also has a liquid passage 40 which opens into the cylinder 18 and can be made to cover on the other side with another liquid passage.

A bore 42 is provided in the right-hand end of the head end. The bore 42 is in communication with the atmosphere via a passage 44 and serves for the outflow of leakage fluid located in the bore 42.

The control slide 12 has a housing 48 . A longitudinal bore 50 is then provided, in which a slide piston 52 is arranged.

The drive 16 consists of a housing 54 with a longitudinal bore 56, a countersink 58, a recess 59 and an internal thread 60. The part provided with the thread 60 forms part of an articulated connection between the force control device 10 and the steering linkage (not shown). A cup-shaped sleeve 62 is slidably disposed in the bore 56 and is connected to a part of the slide piston 52 that is offset to a smaller diameter by a screw 66 . In the housing 54 and in the sleeve 62 , openings 68 and 70 on the same axis are provided for a ball stud 72. The ball stud 72 is located in a bearing which is formed by a pair of sockets 74 in the sleeve 62 . Each socket has a bearing surface in the form of a hollow spherical surface 76 which cooperates with the spherical head 78 of the pin 72 . This results in a connection that is movable on all sides to a limited extent. The sockets 74 are held in contact with the ball head 78 by a member 80 which is screwed into the sleeve 62. To prevent the ball joint from rattling, a spring 82 is inserted between a spacer ring and one of the sockets 74. A resilient protective cap 86 surrounds the pin 72 and rests against the housing 54 . Load on the pin 72

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there is a steering push rod 88, which is fixed via a castle nut 90. The handlebar 88 is connected as usual to a steering lever, not shown, which is connected via a corresponding worm gear so that the rotation of the steering wheel results in an axial movement of the slide piston 52 .

The drive 16, the control slide 12 and the piston 14 are combined with the aid of screws 92 .

In the countersink 58 a pair of disks 94 are provided, which are penetrated by the part 64 of the circular slide 52 , which is offset to a smaller diameter, and which are supported by a helical spring 96 with the sleeve 62 and the shoulder formed by the offset part 64, which is arranged between the disks 94 be kept in the plant. When the spool 52 is in the central position, then there is one of the discs 94 against a ring 97 that the joint housing 54 is disposed in a recess 59 between the housing 48 and slider ao. The washers 94 and the coil spring 96 cooperate with the sleeve 62, the shoulder of the circular slide 52 and the ring 97 to hold the slide piston in the central or neutral position or to return it to this, as shown in FIG. 1 is shown.

Between the disks 94 and the helical spring 96 there is a spacer sleeve 98 which serves to limit the stroke of the slide piston 52 in both directions to the size of the gap between the spacer sleeve 98 and the disks 94.

According to FIG. 2 to 6, three annular grooves 100, 102 and 104 spaced apart from one another in the longitudinal direction are provided on the bore 50 . An inlet opening communicates with the annular groove 104 and through connecting passages 108 and 110 with the annular groove 100 in communication. An outlet opening 112 is in communication with the annular groove 102. Between the annular grooves 100 and 102 there is an opening 114 leading to the piston 14 which is open after the bore 50. One end of the opening 114 is connected to the longitudinal passage 116 , which is aligned with the passage 38. Another motor opening 118 is disposed between the annular grooves 102 and 104 . It is connected on the one hand to the longitudinal bore 50 and on the other hand to a second longitudinal passage 120 which is aligned with the passage 40.

In Fig. 2 shows the slide piston 52 in the neutral position. The slide piston 52 has three collars 122, 124 and 126 spaced apart from one another in the longitudinal direction. These collars form a pair of annular grooves 128 and 130 between them. The opening 114 is always connected to the annular groove 128 . In the same way, the opening 118 is in constant communication with the annular groove 130.

Each end of the spool 52 is sealed by an O-ring 132. A retaining ring 134 prevents the O-ring from being pushed out of the bore 50 .

The collar 122 and the sealing ring 132 form, with the longitudinal bore 50, a damping chamber 136 which, in the neutral position, is connected to the annular groove 100 via a flat area 138 on part of the surface of the collar 122 . In the same way, the collar 126, the seal 132 and the bore 150 at the other end form a damping

989

Fung chamber 140. In the neutral position, it is connected to the annular groove 104 via a flattened area 142 on the collar 126 (see FIG. 7).

In the neutral position according to FIG. 1 and 2, the liquid flow passes through the inlet opening 106 and divides one half into the annular groove 100 and the other half into the annular groove 104. From the annular groove 100 , the liquid flow goes into the annular groove 128 and then into the annular groove 102. The same liquid flow goes from the annular groove 104 into the annular groove 130 and then into the annular groove 102. The liquid flow passes from the annular groove 102 to the outlet opening 112 and then to the collecting container. The flow of liquid is essentially uninhibited in the neutral position, so that only a very low pressure can build up in the control slide. The damping chambers 136 and 140 are also connected to the annular grooves 100 and 104. The openings 114 and 118 are connected to the annular grooves 128 and 130 .

In Fig. 3 , the slide piston 52 is shown shifted somewhat to the right, so that the annular groove 100 is no longer connected to the annular groove 128 and the annular groove 130 is no longer connected to the annular groove 102 . The flow of fluid to and from the cylinder 18 is such that the actuator 14 extends with the result that the steering angle of the steering wheels is changed in one direction. In this state, the liquid flow passes from the inlet opening 106 into the annular groove 104 and then into the annular groove 130. From there it passes through the opening 118, the passages 120 and 40 to the head end of the cylinder 18. At the same time, liquid is removed from the piston rod into the cylinder 18 and through the opening 114 (FIG. 2) into the annular groove 128 . The liquid flow passes from the annular groove 128 to the annular groove 102 and then via the outlet opening 112 into the sump. In this position, both damping chambers 136 and 140 are still in connection with the annular grooves 100 and 104. However, the liquid is only pressed out of the damping chamber 140 via the flattened area 142 to a limited extent.

In Fig. 4 shows the slide piston 52 shifted even further to the right, so that the damping chamber 140 is no longer in direct connection with the annular groove 104 via the flattened area 142 . The liquid flow remains the same as in the position in FIG. 3 with the exception that liquid pressed into the damping chamber 140 must now be pressed out through the gap between the collar 126 and the bore 50 when the slide piston 52 moves further to the right.

When the spool 52 is pushed to the extreme right, as shown in FIG. 5 shows, the liquid flow is the same as in FIG. 4.

A safety valve 144 is provided in the slide housing 48. This consists of a ball 146 (FIG. 2) in a bore 148, which is held in tight contact with a seat 105 by the fluid pressure. The bore 148 communicates with the annular groove 104 through a passage 152 . In addition, the bore 148 is connected to the annular groove 102 through communication passages 154 and 156 . The end of the bore 148 opposite the seat 150 is closed with a solid plug 158 . If the fluid pressure fails, the vehicle can still be controlled by hand by pressing the slide.

1

About housing 48 is moved in one direction or the other, depending on the desired change in the steering angle of the steering wheels. That is, the slide piston 52 is moved on its entire way with respect to the slide housing 48 in one of the two directions and the slide housing and the remaining part of the power control set, which is connected to the steering housing, as a result of the interaction of the disks 94, the spacer sleeve 98 and the shoulders resting against the disks 94. The result is the same as if the handlebar and the steering lever were directly connected to the steering linkage. When the vehicle is being steered, fluid is displaced from one side of the piston 20 in the cylinder 18. It is assumed that the spool 52 is moved to the right and the slide housing 48 entrains, as liquid is displaced and the rod end of the cylinder 18 passes therefrom via the opening 114 in the annular groove 128. By enlarging volume in the cylinder 18 on the On the head side of the piston 20 , the ball 146 is lifted from the seat and the liquid in the annular groove 128 is sucked through the annular groove 102 into the connecting passages 156 and 154 and then into the bore 148 . From the bore 148 , the liquid is drawn through the passage 152 into the annular grooves 104 and 130 and the opening 118 and then into the head end of the cylinder 18 . The result is that liquid is transferred from one side of the piston to the other side of the piston. If such a fluid transfer through the safety check valve 144 were not provided, then a vacuum would arise in the cylinder 18 on one side of the piston, which would prevent the vehicle from being fully hand-steered.

In explaining the operation, it is assumed that movement of the ball stud 72 in FIG. 1 to the right changes the steering angle of the steering wheels so that the vehicle takes a right turn when driving forward. The slide piston is located in the position shown in FIG. 1 and 2, and the vehicle travels straight ahead. In addition, there is such a fluid pressure on both sides of the piston that when the steering wheels hit normal obstacles, the vehicle is not deflected from the straight ahead direction.

If the ball stud is moved to the right, so that the slide piston 52 moves out of the position shown in FIG. 1 and 2 in one of the positions shown in FIG. 3 to 5 positions shown, then the angle of the steered wheels is changed so that the vehicle goes into a right turn. When the slide piston is pushed to the right, liquid is pushed out of the damping chamber 140 via the flat portion 142 into the annular groove 104. When the spool 52 is shifted sufficiently far to the right (FIGS. 4 and 5), then the liquid remaining in the damping chamber 140 can no longer be expressed through the flat 142 , but must through the gap between the collar 126 and the bore 50 through. (The gap does not appear in the drawings because of its small size. In reality, it is only 5 to 8 μ in size.) The force necessary to push the liquid out of the damping chamber via the circumferential collar 126 is partly due to the pressure in applied to the damping chamber 136 ,

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who exerts a force against the covenant 122. The result of this is that the slide piston 52 moves from the position shown in FIG. 4 into the position shown in FIG. 5 position reproduced with normal steering speed with the expenditure of a force of 2 kg on the rim of the steering wheel in addition to a force of about 1 kg, which is necessary to overcome the resistance of the helical spring 96. Although the flat portions 138 and 142 preferably ίο designed so that on the steering wheel, an additional force of about 2 kg is required, it must be pointed out that the force required on the steering wheel of a negative force (ie, that the system is self-controlling, as soon as the Spool 52 is moved from the neutral position) can be changed to such a high force that the driver can no longer turn the steering wheel by hand because the flats extend more or less far over the circumferential collar and a more or less ao great depth to have. The steering speed depends on the magnitude of the displacement of the slide piston 52 relative to the slide housing 48 . The greatest steering speed is achieved when the slide piston is fully advanced, as shown in FIG. 5 shows. For minor longitudinal corrections, the retarding effect of the damping chambers is not very great, because none of the flattened areas 138 and 142 are blocked from the inlet opening next to them. In this way, the driver can steer the vehicle in a straight line and only needs a force which is slightly higher than the force necessary to overcome the helical spring 96 (e.g. 1.5 kg). Significant changes in direction of the vehicle require a greater force on the steering wheel (z. B. 3 kg), since one of the flats is blocked from the liquid inlet, which increases the damping effect significantly.

Above, the mode of operation of the invention is explained under operating operating conditions in which the force control system does not tend to generate vibrations. It is assumed that the vehicle is moving slowly or stopping, so that the initial movement of the slide piston to the right does not result in any movement of the steering wheels to the right, but rather causes an energy build-up in the steering system. In such a case, the steered wheels break loose and begin to steer when the spool 52 reaches a position between the positions shown in FIG. 3 and 5 assumes positions shown. When this occurs, the valve body is accelerated quickly to the right and passes the neutral position into a position as shown in FIG. 6 is reproduced. The liquid in the damping chamber 136 is expressed through the flat 138 into the annular groove 100 and then through the gap between the bore 50 and the slide piston 52 when the slide housing 48 has moved far enough to block the flat 138 . The result is that the chamber 136 acts as a shock absorber and the slide housing can not move faster than a predetermined speed 48, because a greater speed of movement would cause a greater displacement of liquid from the damping chamber 136, which increase the pressure of liquid in it to a point would, in which the force exerted on the valve body 48 to move it to the right is less than that of the fluid pressure in the

Claims (3)

Force exerted on chamber 136 would retard movement of valve body 48 to the right. Before the valve housing 48 can return to the neutral position or overrun it to any extent, depending on the amount of energy stored in the power control system, the stored energy has therefore had sufficient time to through the boom of the steering linkage, through the deformation of the tires etc. to be consumed. If the chamber 136 acts as a shock absorber in order to delay the overrun of the slide housing 48, then the slide piston 52 is subjected to a considerable force which tends to move it to the right. Due to the pitch of the worm and the segment toothing of the connection between the steering wheel and the slide piston 52, the effort required to rotate the worm gear in the opposite direction via the toothed segment is so great that most of the time no force is transmitted from the slide piston 52 to the steering wheel. Patent claims: 1. Control slide with a slide piston which is longitudinally displaceable in a longitudinal bore of a housing with controlling collars and intermediate sections of reduced diameter, separated from one another by means of their connections opening into annular grooves of the longitudinal bore or connected to each other, as well as with frontal damping chambers, in the parts of the Slide piston penetrates when it is moved gene, characterized in that the damping chambers (136, 140) are designed with the same diameter as the longitudinal bore (50) and are sealed to the outside of the housing (48) and that the part of the slide piston penetrating into them is the respective outer collar (122, 126) is the same, which has such an external shape that a connection between the respective outer annular groove (100, 104) and the associated damping chamber (136, 140) is established or increasingly throttled. 2. Control slide according to claim 1, characterized in that the circumference of the outer collars (122, 126) of the slide piston penetrating into the damping chamber (136, 140) is flattened on an outward part of its width. 3. Control slide according to claim 1 or 2, characterized in that the damping chambers (136, 140) on the collars (122, 126) facing away from, outwardly located sides are limited by ring seals (132) which are radially on the slide piston or on the Bore wall and axially outwards against support rings (134) . Considered publications:
German exposition no. 1027951,1107036; British Patent No. 837,856;
U.S. Patents Nos. 2,607,599, 2,916,019,
919 681, 2 924 239, 2 942 583, 2 952 275,
2971536. 1 sheet of drawings 709 679/288 10.67 © Bundesdruckerei Berlin