DE3313318A1 - Arrangement for adjusting the control edges of a follow-up piston system - Google Patents

Abstract

The arrangement relates to an arrangement for adjusting the control edges of a follow-up piston system, with a pilot piston rotatable in the main control piston and having sloping control edges, the main control piston being axially displaceable but not freely rotatable, while the pilot piston is axially fixed and can be rotated, for example, via a stepping motor. Both the pilot piston and the main control piston are centred in a spring-loaded manner. To adjust the position of the control edges with regard to the two centring arrangements, a lever with a radial slot, elongated hole or fork, with which a pin eccentrically rotatable in the housing interacts, is fastened to the follow-up or main control piston.

Description

The invention relates to a control edge adjustment of a Follower piston system with the features of the preamble of the claim

It is known that follower piston systems have a tendency in the event of a pressure failure easy to get into an undefined position, unless special control oil circuits and / or centering of the follower piston are used will. If the drive of the pilot piston, e.g. = a stepper motor, which is given a predetermined zero position by centering, is used to facilitate assembly and to reduce the Manufacturing costs are desirable if a comparison between the Zero position of the drive and the zero position of the control edges of the pilot piston can be brought about, provided that the follower piston itself is centered.

It is the object of the invention to provide such a comparison with simple To enable funds. The operation should also be able to be carried out in a simple manner by inexperienced persons.

This object is achieved according to the invention by the in the characterizing Part of claim 1 mentioned features.

In an advantageous manner, there is then the possibility of choosing one comparatively large eccentricity even rough manufacturing tolerances to compensate, although the sensitivity is reduced. It is even better, however, as early as possible during assembly to fix exactly the zero position and then just fine-tune it with the help of a small eccentricity. In particular the spring centering of the stepper motor, i.e. the pilot piston, should be mounted on a test bench.

Claim 2 is directed to a screw drive for the pin. Claim 3 is directed to the starting position of the pin.

Claim 4 is based on the ratio of eccentricity and lever length to the number of steps of the stepper motor.

Using an exemplary embodiment shown in the figures the invention is explained in more detail.

Figure 1 shows a section through a two-stage electro-hydraulic Proportional directional control valve.

Figure 2 shows a schematic representation of the interaction of Pilot piston and main control piston.

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The invention relates to an electro-hydraulic two-stage ■ Proportional directional control valve with the features of the generic term des Claim 1.

It is well known that proportional directional control valves take with regard to their technical Values and their price a middle position between directional control valves and servo valves. Special servo valve pilot stages that work e.g. with nozzle-flapper systems' come practically nonexistent with proportional directional control valves. However, pilot controls with two proportional pressure regulating valves are common or two proportional pressure relief valves are working. The control pressures are varied proportionally to the electrical input signals and adjust the main control piston Centering springs. An inevitable coupling between the pre-control stage and main tax level is not given here. Depending on the effects of friction and changes in the springs, deviations can occur arise that only allow exact reproducibility and a small hysteresis to a limited extent.

It is the object of the invention to provide electro-hydraulic two-stage Proportional directional control valves mentioned in the preamble of claim 1 Kind of designed so that a coupling between the pilot stage and main control stage is such that the influences of. Frictions or spring forces are eliminated. The dependence the main control spool position from the input signals should be optional either be strictly proportional or follow a desired mathematical law. The design should be simple and be functionally reliable and work as wear-free as possible.

This object is achieved according to the invention with the features of the characterizing part of claim 1.

The advantage of this design is that it is a follow-up system in which the position of the rotatable pilot piston is exactly determined by a predetermined number of steps of the stepper motor. The main control piston then works as a follower piston,

its position no longer depends on friction or springs, but only on the accuracy of the control edges.

Claim 2 relates to the design of the main control piston as a stepped piston.

Claim 3 relates to a drainage duct which represents the system at lower pressure.

Claim 4 is directed to pressed sleeves in the main control piston to simplify the wiring.

Claim 5 is directed to the sealing and support of the pilot piston.

Claim 6 relates to balls between which the plunger is clamped is.

Claim 7 is directed to a sealing bulb.

Claim 8 is directed to a pressure reducing device for reducing the inlet pressure into a constant control pressure.

Claim 9 relates to a spring centering for the main control piston.

Claim 10 is based on positive or zero coverage of the main control piston.

Claim 11 is directed to a spring centering of the step " motors with the help of two counter-rotating spiral springs.

On the basis of an exemplary embodiment shown in the figures the invention is explained in more detail. FIG. 1 shows a section through a proportional directional control valve 1 according to the invention.

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Figure 2 shows schematically the interaction of pilot pistons and main control piston.

In a housing 1 there is a stepped bore 2 in which a main control piston 4 designed as a stepped piston is axially displaceable but not freely rotatable, forming an annular space 3. The main control piston 4 has a spring centering 5 which centers it in a central position in such a way that a pressure connection P is separated from consumer connections A and B and these in turn from tank connections T. Depending on the shift, the connections PA and BT or PB and AT result. The pressure connection P is connected, not shown, to the inlet connection P] of a pressure control valve 6, the reduced pressure of which serves as control pressure and is guided via a line 7 to the annular space 3 and there permanently acts on an active surface 8 of the main control piston 4. The main control piston 4 has an axially continuous bore 9 in which, starting from the end face serving as the second active surface 10, a pilot piston 11 is guided, which penetrates the control chamber 12 adjoining the active surface 10 and seals the housing 1 to the outside and there via a coupling 13 is connected to a stepper motor 14. The clutch 13 and thus of course the pilot piston 11 is connected to a spiral spring 15 which, on the other hand, has its detachable abutment 16 on the housing 1. Another spiral spring 17, not fully visible in the sectional view, is also attached, but has the opposite effect. A driver 18 is connected via a lever 19 to a hub 20 which can be fastened by means of a locking screw 21 relative to the drive shaft 22 of the stepping motor 14 in the sense of a zero adjustment. The driver 18 releases one end of the spiral springs 15 depending on the direction of movement.

. and 17 from the abutment 16. The driver 18 is free of play between the coil springs 15 and 17 when they are in contact with the abutment 16. The pilot piston 11 is in contact with a sealing piston in the bore 9 23, which in turn via a ball 24 on a plunger 25 and via a further ball 26 in the sense of a support on the Housing 1 acts. The main control piston 4 is in a cavity

connected within the housing 1, a radially directed lever 28, the has a slot 29 at its outer end, into which a pin 30 engages tangentially without play and is fastened in an eccentric 31 is. The eccentric 31 is supported by a shaft 32 in the housing 1 and can be secured by a lock nut 33 on the outside of the shaft located thread is screwed. The pilot piston 11 is, insofar as it interacts with the main control piston 4, with a trapezoidal thread 34 is provided, the edges of which serve as inclined control edges. From the annular space 3 is a connection 35 in the form of a Cross hole to hole 9 and is there just from a thread of the trapezoidal thread 34 closed, the edge 36 serving as a control edge which either:. the connection 35 closes or for The thread groove 37 opens, which leads to the control space 12. The opposite Edge 38 also serves as a control edge which connects the threaded groove 37 with either another connection opening into the bore 9 39 connects or the connection 39 closes. The connection 39 leads to a system of lower pressure, i.e. in practice to the Drain connection T. In the embodiment according to FIG. 1 the connection 39 consists of a transverse bore with an inner part 40 and an outer part 41, which parts through a into a the Transverse bore cutting longitudinal bore inserted sleeve 42 are separated. The sleeve has a blind hole 43, which has a transverse hole 44 is connected to the inner part 40. The outer part 41 is closed by the outer jacket of the sleeve 42.

It is readily apparent to those skilled in the art that each rotation of the stepping motor 14 causes a rotation of the pilot piston 11, see above that the edges 36 and 38 alternately open or close the connections 35 and 39. Provided that the active surfaces 10 and 8 behave like about 2: 1, the result is a two-edge control, with the main control piston facing the deflected edges follows until at least a zero overlap is reached. By assigning the steps of the stepper motor .14 you can therefore position the main control piston very precisely. The rough comparison of the the zero positions are carried out via the spring centering of the pilot piston 11, i.e. via the positioning of the driver 18. The fine-tuning

then takes place via the rotation of the eccentric 31, whereby the main control piston 4 can be rotated in two directions until there is a balance between the pilot piston 11 and the main control piston 4. This setting is fixed by the lock nut 33.

Claims (4)

PATENT APPLICATION Description: arrangement for control edge adjustment a follower piston system Applicant: INTEGRAL HYDRAULIK & CO.
At the blast furnace 108
4000 Düsseldorf 11 Patent claims: M) / arrangement for the control edge adjustment of a Follower piston system with a) a follower piston hydraulically controlled by a pilot piston, b) which receives the pilot piston in an inner bore and which opens into the inner bore and is provided with control edges Has control openings, c) rotatable during the pilot piston, but axially immovable is arranged and interacting with the control openings, control surfaces provided with control edges running obliquely to the axis of the pilot piston, in particular a trapezoidal thread, owns, d) the follower piston being installed so that it can be moved axially but cannot be rotated due to an anti-rotation device, characterized, e) that on the follower piston (4) a lever {28) with a radially extending Slot (29), elongated hole or the like is arranged, f) wherein a pin (30) or the like is radially movable, but essentially free of play in the tangential direction intervenes, g) which pin (30) or the like is connected to an eccentric (31) rotatable relative to the housing (1). 2) Arrangement according to claim 1, characterized in that the eccentric (31) on its opposite the pin (30) or the like Side is provided with a screw drive received in a threaded hole in the housing. 3) Arrangement according to claim 1 or 2, characterized in that the Pin (30) or the like is initially mounted in a position corresponding to the greatest distance from the follower piston (4). 4) Arrangement according to at least one of the preceding claims, characterized in that the eccentricity of the pin (30) in connection with the length of the lever (28) is dimensioned so that there is an adjustment range of about 2 to 5 steps of the Stepper motor corresponds.