Actuating drive having a hydraulic outflow booster

Abstract

An electro-hydrostatic actuating drive has a variable-volume and/or variable-speed hydraulic machine, which is driven by an electric motor, for the provision of a volumetric flow of a hydraulic fluid. Furthermore, the actuating drive comprises a cylinder with a piston, a piston rod and a first piston chamber, a valve with a first position and a second position, which valve can be moved by a first hydraulic actuator into the first position and by a second hydraulic actuator into the second position, wherein the second position controls a greater volumetric flow of the hydraulic fluid than the first position, a sink, a main line which connects a first piston chamber of the cylinder to the sink and in which the hydraulic machine is arranged, an auxiliary line which connects the first piston chamber to the sink and in which the valve is arranged, a first control line to the first hydraulic actuator, and a second control line to the second hydraulic actuator. A hydraulic resistor is arranged in the main line in series with the hydraulic machine, the first control line is connected to the main line, and the second control line is connected between the hydraulic resistor and the first piston chamber.

Claims

1. An electro-hydrostatic drive for an actuating drive, comprising: a variable-volume and/or variable-speed hydraulic machine which is driven by an electric motor for the provision of a volumetric flow rate of a hydraulic fluid, a cylinder having a piston, a piston rod and a first piston chamber; a valve having a first position and a second position, which can be moved by a first hydraulic actuator to the first position and by a second hydraulic actuator to the second position, wherein the second position controls a greater volumetric flow of the hydraulic fluid than the first position, a sink, a main line which connects a first piston chamber of the cylinder to the sink and in which the hydraulic machine is arranged, an auxiliary line which connects the first piston chamber to the sink and in which the valve is arranged, a first control line to the first hydraulic actuator, and a second control line to the second hydraulic actuator, wherein a hydraulic resistor is arranged in the main line in series with the hydraulic machine, wherein the first control line is connected to the main line, and the second control line is connected between the hydraulic resistor and the first piston chamber; and the sink is the second piston chamber of the cylinder, wherein the cylinder is a synchronous cylinder.

2. The electro-hydrostatic drive according to claim 1, wherein the first control line is connected between the hydraulic resistor and the hydraulic machine.

3. The electro-hydrostatic drive according to claim 1, wherein the first control line is connected between the hydraulic machine and the first piston chamber.

4. The electro-hydrostatic drive according to claim 1, wherein the hydraulic resistor is a diaphragm valve.

5. The electro-hydrostatic drive according to claim 1, wherein the sink is a reservoir.

6. The electro-hydrostatic drive according to claim 5, wherein the reservoir is pre-tensioned and in particular embodied as a pressure accumulator.

7. The electro-hydrostatic drive according to claim 1, wherein the valve is a directional control valve, wherein the first position is locked, and the second position is flow.

8. The electro-hydrostatic drive according to claim 1, wherein the valve has a plurality of positions, each having different cross-sections.

9. The electro-hydrostatic drive according to claim 1, wherein the valve can continuously switch between a plurality of positions, each having a different volumetric flow of the hydraulic fluid.

10. The electro-hydrostatic drive according to claim 1, wherein the valve has the first locked position as the rest position, in which it is held, in particular by a spring.

11. The electro-hydrostatic drive according to claim 1, wherein the cylinder further comprises an energy accumulator.

12. The electro-hydrostatic drive according to claim 11, wherein the energy accumulator is a spring arranged in the second piston chamber or in front of the first piston chamber.

13. The electro-hydrostatic drive according to claim 1, wherein a further diaphragm valve is arranged in the auxiliary line.

14. The electro-hydrostatic drive according to claim 1, wherein a check valve is arranged parallel to the hydraulic resistor.

15. The electro-hydrostatic drive according to claim 1, wherein a further check valve is arranged parallel to the pump.

16. The electro-hydrostatic drive according to claim 1, wherein the cylinder further comprises an end-position damping in the first piston chamber.

17. The electro-hydrostatic drive according to claim 1, wherein the cylinder controls a process valve.

Description

(1) Thereby, the following are shown:

(2) FIG. 1: A circuit diagram of an actuating drive according to the invention;

(3) FIG. 2: A further embodiment of an actuating drive according to the invention;

(4) FIG. 3: A further variant of an actuator according to the invention.

(5) FIG. 1 shows a cylinder 200, whose piston rod 230 has an actuator, specifically a closure 290, at one end, as is used in particular for steam turbines, gas turbines, die-casting machines or plastic injection-molding machines. The closure 290 controls the opening of a line or passage 420 in one of the specified devices branching from another line or passage 410. In some operating modes, the opening to passage 420 should be closed very rapidly. In the embodiment shown, this takes place in that the first piston chamber 220 is emptied very rapidly and the spring 250 is relaxed very rapidly. The spring 250 is arranged within the second piston chamber 240 in this embodiment. The spring 250 functions as an energy accumulator. The second piston chamber 240 may be open. When the first piston chamber 220 is to be emptied very rapidly, the hydraulic machine or pump 50 first pumps hydraulic fluid from the first piston chamber 220 via the pressure lines 130 (which share a portion of the pressure line 110) and 160. The 2/2 directional control valve 100 is initially in the locked position. This is the rest position of the valve 100 and is ensured in this embodiment by a valve spring 108. The volumetric flow thereby produced in the pressure line 130 causes a pressure difference between a first and a second side of the diaphragm valve 180, that is, a higher pressure arises on the side of the diaphragm valve 180 which points in the direction of the first piston chamber 220. Consequently, a higher pressure also arises in the pressure line 140 which controls the actuator 102. The pressure is proportional to the volumetric flow generated by the pump 50. If the pump 50 exceeds a predefined volumetric flow, then the pressure in the line 140 is so high that the force of the valve spring 108 is overcome and the actuator 102 switches the valve 100 to the flow position. This opens the auxiliary lines 110 and 120, which have a much finer greater diameter than the pressure lines 130 and 160. As a result, the hydraulic fluid can very rapidly escape from the first piston chamber 220. In this embodiment, the hydraulic fluid enters the reservoir 190, which may be configured as a pressure chamber. The closed system advantageously allows a very compact design and requires a significantly lower volume of the hydraulic fluid than in the prior art.

(6) The valve 100 is closed either by the valve spring 108 if the volumetric flow falls below a predefined limit, or the valve 100 is closed by the hydraulic machine 50 when the hydraulic machine 50 pumps the hydraulic fluid from the reservoir 190, via the lines 160 and 130, into the first piston chamber 220. This results in a higher pressure at the actuator 104, which switches the valve 100 into the locked position. The pump 50 is preferably realized as a variable-volume and/or variable-speed hydraulic machine 50 driven by an electric motor 60.

(7) FIG. 2 shows another embodiment of an actuator according to the invention. The basic function is the same as explained for FIG. 1. The same reference signs also designate the same elements as in FIG. 1. FIG. 2, however, has further elements which are advantageous for specific use scenarios. FIG. 2 thus shows a pressure line 330 connecting the reservoir 190 and the second pump connection 52 to the second piston chamber 240. In some embodiments, the spring 250 may be omitted. This variant has the advantage that the reservoir 190 can be made smaller, because the second piston chamber 240 can receive part of the hydraulic fluid which is discharged from the first piston chamber 220.

(8) Furthermore, FIG. 2 shows a check valve 360 in the pressure line 310, which opens when the first piston chamber 220 is filled with the hydraulic fluid. The check valve 360 is arranged in parallel with diaphragm valve 180. The check valve 360 thus bypasses the diaphragm valve 180, such that a more rapid filling of the first piston chamber 220 becomes possible.

(9) FIG. 2 shows a check valve 370, which is arranged parallel to the hydraulic machine 50. The check valve 370 opens when the first piston chamber 220 is emptied. In this case, because the remainder of the hydraulic fluid will pass through the auxiliary lines 110 and 120, the pump 50 may have an undersupply of hydraulic fluid. With some types of pumps, this may result in damage to the pump. To avoid this, hydraulic fluid is directed from line 120 into pump 50 via the check valve 370.

(10) In FIG. 2, a diaphragm valve 170 is arranged in the line 120. It is also possible to arrange the diaphragm valve 170 in line 110, preferably hydraulically in the vicinity of the valve 100. As a result, the maximum volumetric flow through the lines 110 and 120 is not determined by the cross-section of such lines, but can be determined much more precisely by the dimensioning of the diaphragm valve 170.

(11) An end-position damping 270 is arranged in the cylinder 200 in the first piston chamber 220in the region of the end opposite the spring 250. If, as in this embodiment, the energy accumulator is embodied as a spring 250, the piston of the cylinder can impinge very hard on the inner wall of the cylinder and thus cause damage to the cylinder, at least in the medium-term. This is avoided with the end-position damping 270 shown.

(12) FIG. 3 shows another variant of an actuating drive according to the invention. As in FIG. 1, the valve 100 has the locked rest position. If the first piston chamber 220 is emptied, a pressure builds up upstream of the orifice valve 180 in the line 150, starting from a predefined volumetric flow, which pressure is so high that the force of the valve spring 108 is overcome and the actuator 104 switches the valve 100 into the flow position.

LIST OF REFERENCE SIGNS

(13) 10 Hydraulic system

(14) 50 Hydraulic machine, pump

(15) 51 First pump connection

(16) 52 Second pump connection

(17) 60 Motor

(18) 100 Valve, 2/2 directional control valve

(19) 102 First valve actuator

(20) 104 Second valve actuator

(21) 108 Valve spring

(22) 110, 120 Pressure line, auxiliary line

(23) 130, 160 Pressure line, main line

(24) 140, 150 Pressure line, control line

(25) 170 Further diaphragm valve

(26) 180 Diaphragm valve

(27) 190 Reservoir

(28) 200 Cylinder

(29) 210 Piston of the cylinder

(30) 220 First piston chamber

(31) 230 Piston rod

(32) 240 Second piston chamber

(33) 250 Spring

(34) 270 End-position damping

(35) 290 Closure

(36) 310 Pressure line

(37) 320 Pressure line

(38) 330 Pressure line

(39) 360 Check valve

(40) 370 Check valve

(41) 410, 420 Line, passage of controlled device