FI84291C - STYRFOERFARANDE I HYDRAULISKT MANOEVERORGAN. - Google Patents

Description

1 84291

Hydraulic actuator control method

The present invention relates to a hydraulic actuator control system in which the switching position of a three-position on-off hydraulic valve controlling the movement of the hydraulic actuator in opposite directions and the stopping of the movement is changed by direct current control voltages which activate two separate electromagnets via a common pair of conductors, one of which receives voltage when the other is de-energized or both are de-energized at the same time and to which conductors the electromagnets are connected in parallel with the opposite rectifier elements 15 (D1, D2), where only one of the electromagnets is activated according to the direction of movement, the polarity of the conductors determining the direction of movement of the hydraulic actuator and both conductors being 20 the de-energized movement stops.

In currently used cylinder controls, where the hydraulic valve is controlled by two DC magnets, a three-wire control cable is required for each magnet to control the valve 25 to three different switching positions. A total of six conductors are then required between the valve and the control center, making the control cable relatively thick. The control electronics must also be placed separately from the actuator in a separate unit, which must be taken into account in the design of the equipment. Hardware installation and maintenance can also be costly.

It is known from GB C 1 206 877 and DE A 2 131 517 that the direction of movement of the hydraulic valve is changed by changing the polarity of the conductors, by means of rectifier-35 elements and reference logic.

It is an object of the present invention to provide a method and control system for controlling a hydraulic actuator which is simpler and less expensive than those currently in use, both in terms of equipment design and installation and maintenance. This object is achieved by a control system according to the invention, the characteristic features of which are set out in claim 1.

An advantage of the invention over current control systems is that only one two-conductor control cable 10 is required between the control center and the hydraulic valve to be controlled, whereby the cable size and the terminal block housing and terminal blocks are reduced. The invention can be utilized in limit-Kim controlled cylinder controls in numerous use in industry.

By further replacing the limit switches with a cylinder position-15 measurement, whereby the cylinder position is given to the control electronics in voltage form, the control logic can be placed in connection with the valve. The DC control signal then also acts as a power supply for the control electronics. The valve, the control electronics and the position measuring 20 can thus be formed together with the cylinder into an actuator unit, which can be treated as a separate component by the device designer and the service / maintenance.

The invention will now be described in detail with reference to the accompanying drawing, in which Figure 1 shows diagrammatically the control of a hydraulic valve at two-wire control cable voltages, Figure 2 shows diagrammatically an embodiment including a Fig. 4 shows graphically a possible series of reciprocating movements of a cylinder controlled by the control system according to Fig. 3, and Fig. 84291 when cross-sectioned.

Figure 1 shows in schematic form the main principle of the present invention. The DC voltages of the two-wire control cable are applied to terminals 1 and 2, for example +24 V and 0 V, whereby in the example of hydraulic valve 3 the electrically controlled four-way three-position valve-10 switching position and thus also the direction of movement of hydraulic actuator, e.g. hydraulic cylinder (not shown) with the polarity of the input voltages. When the voltage at terminal 1 is +24 V and the voltage at terminal 2 is 0 V, 15 solenoid 5 is activated and valve 3 controls the movement of the cylinder forward. When the polarity changes, when the voltage at terminal 2 is +24 V and the voltage at terminal 1 is 0 V, the solenoid 4 is activated and the valve 3 controls the cylinder to move backwards. When both connectors are de-energized, the valve 3 is in the middle position and the cylinder stops moving. The diodes D1, D2 activate only one of the electromagnets 4, 5 at a time. Diodes D3, D4 prevent the generation of harmful voltage spikes that could damage the control equipment. These latter diodes D3, D4 are known and do not form part of the invention.

In the embodiment of Fig. 2 from the resistors in series with the diodes D1, D2, the control voltages of the conductors 1, 2 are connected via reference logic 6 to transistors TR1, TR2, which act as terminals for reference logic 6. The operation of the reference logic is based on cylinder 7 position measurement 8. , e.g. 0 to 10 V. The voltage is compared with the potentiometers 9, 10 to the preselected voltage values 35 in the comparators 11, 12. The comparators are connected via the AND gates 13, 14 to the transistors TRI, TR2. For example, when both inputs of the AND gate 13 have a voltage corresponding to logic 84291 4 l, a voltage is applied to the base of the transistor TRI, whereby the transistor TRI becomes conductive and the electromagnet 4 is activated. As in the embodiment of Figure 1, the cylinder moves in opposite directions with one of the electromagnets activated. When both transistors TRI, TR2 are in a non-conducting state, no current flows over the electromagnets and the valve 3 settles to the middle position and the movement stops. The stopping points can be determined with potentiometers 9, 10 10. The polarity of the conductors 1, 2 determines the direction of movement of the cylinder 7.

The comparison logic 6, the electromagnets 4, 5 and the position measurement 8 obtain their operating voltage from the voltages 1,2 of the two-wire control cable via the diode bridge 15, whereby the effect of the changing polarity of the conductors 1, 2 on the voltage supply is eliminated. When the valve 3, the reference electronics 6 and the position measuring 8 are placed in connection with the cylinder 7, an actuator unit is formed, which contains the functions of the limit-controlled cylinder in one size-20.

Figure 3 shows an embodiment in which a proportional amplifier 16 is added to the comparison logic 17, 18, 19. This can be, for example, type VT 3000 S, manufactured by Rexroth. The valve is a proportional valve 3 '.

25 Potentiometers P5 - Pg are used to select the stopping points or positions where the speed of the cylinder 7 changes. The position data is fed from the comparators 17 via the AND gates 18 and the amplifier 19 to the proportional amplifier 16. The desired motion speeds corresponding to the position of the cylinder 7 30 are selected by means of potentiometers Ρχ to P4. As in the embodiment of Fig. 2, the operating voltage is supplied to the components of the control system from the two-wire control cable 1, 2 via the diode bridge 15. The polarity of the conductors 1, 2 determines the direction of movement of the cylinder 7.

Figure 4 shows graphically a series of movements of the cylinder 7 as the speed v changes at different positions s of the cylinder. Curve above the horizontal axis

II

5,84291 depicts the velocities as the cylinder moves forward and the curve below, respectively, as the cylinder moves backward.

Figure 5 shows the implementation of the embodiment of Figure 3 in practice. The reference electronics and the proportional amplifier are placed in a unit 20 on top of the valve 3 ', to which information about the position measurement 8 is also fed. The potentiometers -P4, Pg to P8 on the cover 21 select the stopping points and the speeds of movement. 10 The conductors 1, 2 of the cable attached to the cover 21 supply the operating voltage and determine the direction of movement of the cylinder 7 by means of the polarity of the conductors 1, 2. In this case, the cylinder 7, the valve 3 'and the control logic form an actuator unit with a wide range of applications. The invention offers a cheaper solution than cylinder control implemented with limit switches in terms of design, installation and maintenance.

In the embodiments described above, the connection between the control center and the actuator unit is realized by a two-conductor cable 1, 2, one of the conductors of which is connected to each other with a positive voltage while the other is at zero potential. In some cases, it could be circuit-friendly to add a third, separate neutral potential conductor to the cable, the positive voltage being connected to one of the conductors 1, 2 according to the desired direction of movement, said third conductor being continuously at zero potential.

Thus, it is not intended to limit the invention to the embodiments described above, but many modifications are possible within the scope of the inventive idea defined by the following claims.

Claims (4)

6 84291 A hydraulic actuator control system, wherein the switching position of a three-position 5-on-off hydraulic valve (3) controlling the movement of the hydraulic actuator in opposite directions and stopping is changed by direct current control voltages activating two separate solenoids of the hydraulic valve a common pair of conductors (1, 2), one of which is supplied with voltage when the other is de-energized or both are de-energized at the same time, and to which conductors (1, 2) the electromagnets (4, 5) are connected in parallel with them in series with opposite rectifiers. 15 via means (D1, D2), where when one conductor is energized only one of the electromagnets is activated according to the desired direction of movement, whereby the polarity of the conductors determines the direction of movement of the hydraulic actuator and both conductors are energized the inertial movement 20 stops, characterized in that it further comprises a reference logic (6) in which the voltage obtained from the hydraulic actuator position measuring element (8) is compared in the comparators (11, 12) with the potentiometers (9, 10) preselected voltage values with the comparators (11, 12) 25 connected from its outputs to the inputs of the AND gates (13, 14), the other inputs of the AND gates (13, 14) being connected to the direct current control voltage lines (1, 2) and the outputs of the AND gates (13, 14) being connected to semiconductor switch elements (TRI, TR2) to the control inputs, which semiconductor switches 30 each switch the operating voltage to one of the electromagnets (4, 5) according to the desired direction of movement, the potentiometers (9, 10) determining the stopping points of the hydraulic actuator (7) in the direction of polarity. Control system according to claim 1, wherein the hydraulic valve is a proportional valve (3 ·) controlled by a proportional amplifier (16) and a comparator 7 84291 logic (17, 18, 19), characterized in that the position (8) of the position of the hydraulic actuator (7) the obtained voltage is compared in comparators (17) with potentiometers (P5 - P8) to preselected voltage values-5, from which comparators the position data is fed to the first inputs of the JA gates (18) and further through amplifiers (19) to a proportional amplifier (16) with potentiometers (Ρχ - P4) selecting the desired speeds corresponding to the position of the actuator (7), the AND gates (18) 10 being further connected from their second inputs to the DC control voltage lines (1, 2), the potentiometers (P5 to Pfi) determining the stopping points of the actuators (7) in the direction of motion determined by the polarity. Control system according to Claims 1 and 2, characterized in that the operating voltage is supplied to the components (4, 5, 6, 8; 16, 17, 18, 19) of the control system via conductors (1, 2) via a diode bridge (15), the variable polarity the effect on the voltage supply, i.e.-20, is minimized. Control system according to one of Claims 1 to 3, characterized in that a third, separate neutral potential conductor is added to the direct current control voltage line (1, 2), the positive voltage 25 being connected to one of the two conductors (1, 2) according to the desired direction of movement. 8 84291