CS215136B2 - Appliance for limiting the stroke of hydraulic servofacility - Google Patents

Abstract

A hydraulic servo steering system comprising a cylinder 1 in which a piston 4 is slidingly mounted in sealing-tight manner so as to define, within the cylinder, two working chambers 6, 7 alternately connectable, via a distributor 8, to a source of fluid under pressure and to an exhaust duct connected with a fluid reservoir at low pressure, in order to effect reciprocating movement of the piston 4 and consequent pivotal movement of a steering shaft carrying a toothed sector 14 engaging a rack formed in the piston, incorporates a stroke limiting device which effectively removes the hydraulic bias applied to the piston at each of two limiting positions of the piston. The stroke limiting device comprises a pair of cavities 15, 16 extending in the radial direction into piston 4 from its periphery, one cavity 15 being disposed between a duct 25 permanently communicating with the source of fluid under pressure and one working chamber 6 of cylinder 1 and the other cavity 16 is disposed between the two working chambers 6, 7 of the cylinder. The device also comprises a respective valve member 21, 24 in each cavity cooperating with a respective valve seat formed in an apertured cap partly closing the respective cavity, each valve member 21, 24 being held in a closed position against its valve seat, by a respective spring 23, 24 and cam means 57, 58, 60, 61 adjustable from outside the cylinder 1 and arranged to act mechanically on the respective valve member 21, 22 when the piston 4 reaches its predetermined end of travel in one or the other direction. <IMAGE>

Description

(54) Hydraulic power steering stroke limiting device

To limit the stroke of the hydraulic iseirvorilenie consisting of - a cylinder in which a piston separates slidingly and tightly - two opposing working chambers alternately connected with - a pressure fluid source - and - with a drain, from a pair of radial cavities of the valve - formed on ( - one seat is located between the duct permanently connected to the pressure fluid source and - with a single cylinder working chamber, - from the closing balls abutting the seat of each valve held in a closed position by springs and - from the cams - adjustable from - outside the cylinder and acting mechanically on the respective shut-off ball at the moment the piston reaches the end of the set stroke in one direction or the other.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stroke limiting device. The device consists of a cylinder in which it is slidably and tightly disposed between two opposing working chambers, a distributor for supplying a pressurized fluid to one of the other opposing chambers and simultaneously connecting the working chamber to which a waste pressure fluid is not supplied from the drive shaft of the vehicle, the toothed section keyed on the shaft and engaging in the toothed section formed on the piston body to transmit the linear movement of the piston and the control shaft by converting the linear movement into. movement corresponding to angular movement, and from a bolt mounted axially in the mold cavity for engagement and reciprocation with a nut disposed at one end of the piston and (rotatable to a limited extent to actuate the distributor, the free sealed end of the bolt protruding axially And is connected to the actuating means.

Hydraulic systems and systems of this type are known.

However, if they are to function properly, they must be equipped with means for restricting the rectilinear movement of the piston between completely locked positions of the drive wheels of the vehicle in order to avoid an extreme stroke which could damage the steering mechanism.

To this end, a variety of limiting devices have been proposed, some of which are provided with a longitudinal passage extending through the piston, the valve being loaded by a spring located at both ends of the passage connected via a waste distributor and a pair of stops at the end of the cylinder wall. working with these valves. The valves then open alternately when the respective stop is seated, which results in the pressure in the active cylinder chamber being reduced and the piston stops.

One embodiment of this type of stroke limiting device is known, for example, from German Patent Specification No. 1,455,939.

One of the main drawbacks of this embodiment of the stroke limiting device is that it requires adjusting the right stop to a different position from the left stop. This is not always possible, especially when the steering control is mounted on the vehicle.

Another embodiment of the stroke limiting device is shown, for example, in German patent 487 176. In this latter device, the stops are adjustable only on one side of the control cylinder and a very complicated mechanism is required for adjustment if a sufficiently wide range is to be achieved The positioning is carried out in a direction perpendicular to the direction of movement of the piston.

The invention solves the problem of designing a hydraulic power steering stroke limitation device which can be adjusted from one location to both the right and left stops and which can be adjusted within a reasonably wide range without interfering with the operation of the nut in the piston.

According to the invention, the principle of the hydraulic power steering stroke limiting device consists in that it consists of a pair of radial valve cavities formed at the opposite end of the piston to that of the nut, of closing balls held in the closed position in each valve seat by a spring mounted in a radial one of the two radial valve cavities is located between the duct permanently connected to the pressurized fluid source and one working chamber of the cylinder, while ^one other radial valve cavity is located between the two working chambers of the cylinder, of cams adjustable from the outside of the cylinder parallel to the longitudinal rotation of the cylinder and adapted to be mechanically applied by means of levers on one or the other sealing ball in the radial cavities of the valve at the end of the set piston stroke in one or the other direction.

In one particularly preferred embodiment, one cam is formed at the free end of one rod parallel to the cylinder, the other cam is formed at the free end of the other rod parallel to the cylinder, both cams being in dynamic relationship with the corresponding convex parts of the levers which are The plungers are connected by plungers and each of which is mounted above the closing balls of the radial cavities of the valve, the free end of each corresponding lever being provided with a spring for holding this end opposite the closing balls of the corresponding radial cavities of the valve.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal cross-sectional view of a hydraulic power steering apparatus equipped with a stroke limiting device according to the invention; FIG. 1, FIG. 3 is a longitudinal cross-sectional view of the apparatus of FIGS. 1, 2 in the plane III - III of FIG. 2.

The power steering cylinder consists of a bolt 2 connected to a steering wheel (not shown) and a bearing nut 3 for a bolt 2, which is partially mounted at one end of the axial cavity 5 in the piston 4. The cylinder 2 is mounted in the piston. The piston 4 divides the cylinder 1 into two opposing working chambers 6, 7, into which pressure fluid is supplied in a known manner via the hydraulic distributor 8 (FIG. 2J). In the embodiment shown, the hydraulic distributor 8 is located on the piston 4 in the cavity 9. the piston 4 is provided with a toothed section 12 engaging a toothed counter-gate 13 which is lubricated on a control shaft 14 controlling the drive wheels of the vehicle (not shown). činnolst and control mechanisms such ^as, described above, are given in the published patent při21513В

With NSR notifications 26 30 615 and -. No. 26 30 617 to which reference is made.

According to the invention, two radial cavities 15, 16 forming the valve seats are formed on the piston 4, at the end facing away from the bearing nut 3.

In each radial cavity 15, 16 a tube 17, 18 is provided with corresponding necks 19, 20 cooperating in a known manner with the sealing balls 21, 22.

The sealing balls 21, 22 are pressed against the respective necks 19, 20 by springs. 23,

24. In the bottom of the radial cavity 15 is an aperture 25 which communicates with the distributor chamber 8 in a known manner permanently connected to a pressurized fluid source (not shown).

The bottom of the second radial cavity 16 is provided with an opening 26 opening into the axial cavity 5 of the piston 4, which in turn is in permanent communication with the opposing working chamber 7 of the cylinder 1.

The throats 19, 20 lead to corresponding channels 27, 28 formed on the circumference of the piston 4 and permanently connected to the adjacent working chamber 6 of the cylinder 1.

For reasons which will be described in more detail below, the spring 23 exerts a pressure which is sized to hold the ball 21 against the neck 19 in the closed position, while the spring 24 is sized to exert a pressure on the ball 22 which holds it this ball in the closed position even at the maximum achievable pressure in the working chamber 6 during operation of the steering.

The levers 29, 30 are located above the respective radial cavities 15, 16 of the rivets and are rotatably supported on pins 31, 32 mounted in brackets 33, 34 attached to the blocks 35, 36. The blocks 35, 36 are inserted into respective radial seats 37, 38 formed on the piston body 4 parallel to the radial cavities 15, 16. Screws 39, 40 are fastened in the seats 37, 38.

Commonly used springs 41, 42 hold the respective levers 29, 30 in positions in which their free ends, provided with respective pins 43, 44, abut the corresponding locking balls 21, 22, preventing them from moving during the movement of the piston 4.

According to another feature of the invention shown in Fig. 1, two parallel rods 45, 46 are disposed in the cylinder 1, mounted as a bracket in the end wall 47 of the cylinder 1, their threaded ends 48, 49 projecting from the cylinder 1 and engage to - the respective lock nuts 50, 51.

The parallel rods 45, 46 extend through their central portions 52, 53 with threaded holes 54 and 55 formed in the wall 47 of cylinder 1. As a result, the rods 45, 46 can be axially adjusted to the right or left stop of the control mechanism as explained in more detail below.

The free end 56 of the parallel rod 45 in the cylinder 1 and the working chamber 6 is provided with a cam 57 adapted to engage the convex portion 58 of the lever 29, thereby exerting a pressure which is transmitted to the lever on the closing ball.

21, clearing the throat 19. The rod 46 is longer than the rod 45. Its free end 59 within the cylinder 1 and the working chamber 6 is also provided with a cam 60 adapted to engage the convex portion 61 of the lever 30, thereby pressing the lever onto the shut-off ball 22. and opens bind-lo 20.

For constructional reasons, the rod 46 in the cylinder 1 extends through a groove 62 which is formed axially on the piston 4 and is open in the direction away from the surface of the piston 4.

If the device is to be put into operation, the cams 57, 60 at the ends of the corresponding rods 45, 46 occupy a position in which they can engage the corresponding ends 48, 49 outside the cylinder 1 depending on the maximum stroke of the piston 4 in one. or second direction, thereby forming stops -fly piston 4.

For example, if the piston 4 moves in a known manner to the left in the direction of the arrow F in FIG. 1, the pressure chamber will be the working chamber 7. The working chamber 6, on the other hand, will be connected to the waste via the distributor 8. The working pressure will be applied below the shut-off ball 21, since, as explained above, the orifice 25 is permanently connected to the pressure fluid source via the distributor 8. Therefore, the neck 19 is also securely closed.

Similarly, under the same operating conditions, pressure is applied to the shut-off ball 22 in the working chamber 7, since the radial cavity 16 is connected to said working chamber 7 through an opening 26 and an axial cavity 5 in the piston body 4 which is opened into the working chamber 7a. closed into the working chamber 6. The neck 20 is therefore closed.

At one end of the stroke of the piston 4 to the left, the cam 57 of the rod 45 engages the convex portion 58 and pivots it about the pin 31, while the neck 20 remains closed. As a result, the shut-off ball 21 is lifted from the closed position in the seat by the pin 43, the neck 19 opens and the pressure fluid in the radial cavity 15 flows into the working chamber 6 and the distributor 8 into the drain. The piston - 4 - stops moving due to a short circuit in the pressure line.

Movement when the piston 4 is in the direction of arrow F1, and thus to the right of FIG. 1, the cam 60 of the bar 46 engages the convex portion 61 of the lever 30 that pivots about the pin 32 so that its pin 44 acts on the ball 22. The working chamber 6, which has been pressurized, communicates directly with the working chamber 7 through the bore 26 and the axial cavity 5 of the piston 4 and thus with the waste, since the working chamber 7 is also associated - with waste. As a result, the piston 4 stops.

When the piston 4 moves under the above circumstances before the cam 60a and the lever 30 engage, the neck 20 remains closed by a spring 24 which, as mentioned above, exerts a greater pressure on the shut-off ball 22 than the liquid pressure in working chamber 6.

Also, the closure of the throat 19 is ensured, 215136, since the closure ball 21 exerts a maximum working pressure of the device through the opening 25, apart from the pressure of the spring 23 to which it is connected.

The above-described device can therefore be used as an effective means for reducing the stroke of a hydraulic power steering piston 4, which is perfectly reliable in operation and simple to manufacture.

Another advantage of the device according to the invention is that the limiting positions can only be adjusted by acting on the bars 45, 46 only

Claims (2)

SUBJECT A device for limiting the stroke of a hydraulic seeding system comprising a cylinder in which it is. sliding and tightly mounted piston separating each other. two opposing working chambers, from a manifold for supplying pressure fluid to one or two. into the second opposite working. chambers and. for simultaneous connection of the working chamber, to. wherein no pressurized liquid with waste is supplied, from the drive shaft of the vehicle, from a toothed section nipped on the shaft and engaging in a toothed counter-section formed on the piston body a transmission of linear motion to a movement corresponding to angular motion; Piston cavity for engagement and reconnection - with nut mounted on one end of the piston and rotatable to a limited extent for. actuating the switchgear, wherein the free sealed end of the screw protrudes axially. and is connected to actuating means, characterized in that it consists of a pair of valve radial cavities (15, 16] formed at the opposite end of the piston (4) to which the nut (3) is formed by the sealing balls. (21, 22] retained in the closed position in the seat of each valve by a corresponding spring (23, 24] housed in the radial cavity (15, 16] of the valve, one (15) of both radial valve cavities (15, 16) being This is particularly important if the hydraulic power steering is mounted on the vehicle. An advantage of the device according to the invention is also that it is adjustable over a wide range without requiring a complicated mechanism, as is known in the art. equipment. of this type, as the setting range depends only on. the length of the bars 45, 46, corresponding to the length and power of the steering. BACKGROUND OF THE INVENTION a cylinder connected to a pressurized fluid source and to one working chamber (6) of the cylinder (1), while a second radial cavity (16) of the valve is located between the two working chambers (6, 7) of the cylinder (1). 60) adjustable from outside the cylinder. (1), parallel to the longitudinal axis of the cylinder (1) and adapted to be mechanically applied by means of levers (29, 30) to one or the other sealing ball (21, 22) in the radial cavities (15, 16) of the valve at the piston stroke ( 4) in one or the other. direction. 2. The stroke limiting device according to claim 1, characterized in that one cam (57) is formed on. the free end (56) of one rod (45) parallel to the cylinder (1), the second cam (60) being formed at the free end (59) of the second rod (46) parallel to the cylinder (1), both said cams (57) 60 are in dynamic coupling with corresponding convex parts (59, 61) of the levers (29, 30) which are connected by pins (31, 32) to the piston (4) and each of which is mounted above the closing balls (21). , 22) of corresponding radial cavities (15, 16) of the valve, the free end (43, 44) of each corresponding lever (29, 30) being provided with a spring (41, 42) for holding this end opposite the closing balls (21, 22) corresponding radial cavities (15, 16] of the valve.