EP3728864B1 - Actuator with hydraulic drain amplifier - Google Patents

Description

The present invention relates to an actuator with a variable-speed pump, such as is used in steam turbines, gas turbines, die-casting machines, for example. Actuators are known in the prior art EP 0 604 805 A1 an actuating device for a hydraulic actuator with a pressure-proportional control signal, in which a piston-cylinder arrangement acting as a converter is interposed between the actuator and a hydraulic discharge booster.

This device has the following disadvantages, among others: The oil circuit is not closed and requires a fairly large volume of oil. An external pressure supply is also required for the function.

EP 2 711 560 A1 relates to a hydraulic drive and a hydraulically operated tool. Proceeding from this prior art, it is the object of the present invention to at least partially overcome or improve the disadvantages of the prior art.

The object is solved by a device according to claim 1. Preferred embodiments and modifications are the subject matter of the dependent claims.

For example, the cylinder can be used to control the hydraulics of a gas turbine or die casting machine. The hydraulic inflow or outflow is controlled by a closure that is arranged on the piston rod of the cylinder. In such machines, the situation arises that the hydraulic inflow or outflow must be blocked very quickly. For this very rapid outflow of hydraulic fluid from the cylinder, the actuator activates a hydraulic path that ensures a high flow of hydraulic fluid from the cylinder to a sink. The sink is part of a closed hydraulic system. For example, it can be implemented as a reservoir that is closed off from the environment. By realizing the actuator as a closed hydraulic system, the oil volume required can be significantly reduced compared to the prior art. This also reduces the risk to the environment - e.g. in the event of a system leak - because the lower quantity of oil reduces the risk of fire, for example, or the measures to prevent contamination are simplified because there is less space to enclose

The first piston chamber of the cylinder is filled by the hydraulic machine or pump via the main line. The hydraulic fluid is taken from the sink. In order to empty the first piston chamber quickly, the actuator has a secondary line, which has a higher cross section, in particular a significantly higher cross section, than the main line. This bypass line connects the first piston chamber to the sink.

A hydraulic valve is arranged in the secondary line. The valve can be implemented in quite different embodiments. In all embodiments, the valve has a first position and a second position, with the second position controlling a greater volume flow of hydraulic fluid than the first position. In one embodiment, the valve can have a first position “blocked” and a second position “flow”. The hydraulic valve is controlled by hydraulic actuators. It may be movable to the first position by a first hydraulic actuator and to the second position by a second hydraulic actuator. A first control line leads to the first hydraulic actuator and a second control line to the second hydraulic actuator.

A hydraulic resistance is arranged in the main line in series with the hydraulic machine. The order of arrangement plays a subordinate role; either the hydraulic machine or the hydraulic resistance can be arranged closer to the depression. The first control line is connected to the main line, for example between the hydraulic resistance and the sink, and the second control line is connected between the hydraulic resistance and the first piston chamber. If the first piston chamber is to be emptied quickly, the hydraulic machine first sucks the hydraulic fluid out of the first piston chamber via the main line. For clarification it is assumed that the volume flow in the main line is gradually increased. At a predefined volume flow, depending on the volume flow, an increased pressure arises in the second control line, which is connected between the hydraulic resistance and the first piston chamber. This increased pressure causes the second hydraulic actuator to move the valve into the second position. In one embodiment, this allows the valve to be moved from a first "blocked" position to a second "flow" position. In some embodiments, the first "locked" position may be the rest position of the valve, in which the valve is initially retained, e.g., by a valve spring. In this case, at least the counteracting force of the spring must be overcome by the pressure on the second hydraulic actuator.

The fact that the valve was moved into the second position—by means of the second hydraulic actuator—increases the volume flow in the secondary line. In one embodiment, in which the valve is moved from a first "blocked" position to a second "flow" position, the volumetric flow from the first piston chamber is increased in an almost abrupt manner. With this very rapid outflow of hydraulic fluid from the cylinder, the actuator activates a hydraulic path that very quickly blocks the inflow or outflow, for example of the hydraulics of a gas turbine or die-casting machine. In some embodiments, this effect can be intensified by arranging an energy store in or on the cylinder, e.g. in the form of a spring. This accelerates both the controlled inflow or outflow and the emptying of the first piston chamber.

It is within the meaning of the present invention if a correspondingly modified arrangement is not used for rapid emptying, but rather for rapid filling of the first piston chamber. It is also within the meaning of the present invention if a correspondingly modified arrangement is not used for rapid opening of the valve but rather for rapid closing of the valve.

In one embodiment, the first control line is connected between the hydraulic resistance and the hydraulic machine. In this case, hydraulic resistance is between the Hydraulic machine and the first piston chamber arranged. This embodiment is preferred for actuators where the hydraulic machine has only one pressure-resistant connection. The hydraulic resistance thus also functions as an instrument for pressure reduction.

In one embodiment, the first control line is connected between the hydraulic machine and the first piston chamber. This embodiment is preferred for actuators where the hydraulic machine has two pressure-resistant connections.

In one embodiment, the hydraulic resistance is an orifice valve. An orifice valve is a well-established, robust and easy-to-use component in hydraulics. It is available in various versions and can therefore be easily adapted to the requirements. In particular, the predefined flow rate that triggers the switching of the valve can be determined very precisely. In some embodiments, the orifice valve can also be designed to be variable.

In one embodiment, the hydraulic resistance is integrated into the hydraulic machine. This enables a particularly compact design of the actuator. In some embodiments, the hydraulic resistance can already be realized through the design of the hydraulic machine - e.g. if an internal resistance is realized - so that no additional component is required

In one embodiment, the sink has a reservoir in addition to the second piston chamber of the synchronous cylinder.

In one embodiment, the reservoir is preloaded and in particular designed as a pressure accumulator. This ensures a particularly compact design of the actuator and saves energy when filling the first piston chamber.

In one embodiment, the valve is a directional control valve, with the first position being "blocked" and the second position being "flow". For example, the valve can be implemented as a 2/2-way valve.

In one embodiment, the valve has a plurality of positions, each with different cross sections. This is advantageous when the actuator has a more complex controller is to realize, for example, a fast, but still soft control of the hydraulic inflow or outflow of the controlled device.

In one embodiment, the valve can switch steplessly between a number of positions, each with a different volume flow of the hydraulic fluid. "Infinitely variable" can also mean "very small steps". This is also an advantageous option for realizing more complex controls.

In one embodiment, the valve has the "blocked" position as the rest position, in which it is held, in particular by a spring. On the one hand, this largely prevents accidental activation, e.g. accidental opening of the valve. In addition, the selection of the spring - especially in combination with a defined orifice valve - allows the switching pressure of the valve to be set precisely.

In one embodiment, the cylinder also has an energy store and/or is connected to an energy store. The energy store can be a spring, for example. This can be arranged in the second piston chamber or in front of the first piston chamber. With such an energy store, the reaction speed of the actuator is significantly increased

In one embodiment, a further hydraulic resistance, in particular an orifice valve, is arranged in the secondary line. This ensures a defined maximum volume flow when the hydraulic fluid is quickly drained from the first piston chamber, i.e. in particular when the valve is - at least for some embodiments - in the second position "flow".

In one embodiment, a non-return valve is arranged parallel to the hydraulic resistance. As a result, the first piston chamber can be filled more quickly because the filling quantity is no longer limited exclusively by the hydraulic resistance.

An electro-hydrostatic drive according to the invention is used for steam turbines, gas turbines, die casting machines or plastic injection molding machines.

The invention is explained below using one of the various embodiments, it being pointed out that this example also includes modifications or additions as are immediately apparent to a person skilled in the art. Furthermore, this preferred embodiment does not impose any limitation on the invention, which is defined by the claims.

• Fig. 1: Ein Schaltbild eines nicht erfindungsgemäßen Stellantriebs;
• Fig. 2: Eine Ausführungsform eines erfindungsgemäßen Stellantriebs;
• Fig. 3: Eine Variante eines nicht erfindungsgemäßen Stellantriebs.

show:

• 1 : A circuit diagram of an actuator not according to the invention;
• 2 : An embodiment of an actuator according to the invention;
• 3 : A variant of an actuator not according to the invention.

1 shows a cylinder 200, the piston rod 230 of which has an actuator, namely 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 shutter 290 controls the opening of a line or passage 420 in one of said devices, which branches off from another line or passage 410 . In some operating modes, the opening to the passage 420 should be closed very quickly. In the embodiment shown, this is done by very quickly emptying the first piston chamber 220 and relaxing the spring 250 very quickly. The spring 250 is arranged within the second piston chamber 240 in this embodiment. The spring 250 acts as an energy store. The second piston chamber 240 may be open. If the first piston chamber 220 is to be emptied very quickly, then the hydraulic machine or pump 50 first pumps hydraulic fluid out of the first piston chamber 220 via the pressure lines 130 (which also uses part of the pressure line 110) and 160. The 2/2-way valve 100 is included initially in the "locked" position. This is the rest position of the valve 100 and is ensured by a valve spring 108 in this embodiment. The volume flow that results in the pressure line 130 causes a pressure difference between a first and a second side of the orifice valve 180, ie a higher pressure is created on the side of the orifice valve 180 that points in the direction of the first piston chamber 220. Consequently, there is also a higher pressure in the pressure line 140, which controls the actuator 102. The pressure is proportional to the volume flow that the Pump 50 generates When the pump 50 exceeds a predefined flow rate, 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 secondary lines 110 and 120, which have a significantly larger internal diameter than the pressure lines 130 and 160. As a result, the hydraulic fluid can flow out of the first piston chamber 220 very quickly. In this embodiment, the hydraulic fluid flows into the reservoir 190, which can be designed as a pressure chamber. The closed system advantageously enables a very compact design and requires a significantly smaller volume of hydraulic fluid than in the prior art.

The valve 100 is either closed by the valve spring 108 when the volume flow falls below a predefined level. 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 creates a higher pressure on the actuator 104, which moves the valve 100 into the position switched to "locked". The pump 50 is preferably implemented as a hydraulic machine 50 with variable volume and/or speed that is driven by an electric motor 60 .

2 shows an embodiment of an actuator according to the invention. The basic function is the same as for 1 explained. Also, the same reference numerals designate the same elements as in FIG 1 . 2 but has other elements that are advantageous for certain application scenarios. So shows 2 a pressure line 330 which connects the reservoir 190 and the second pump port 52 to the second piston chamber 240 . In some embodiments, the spring 250 can be omitted. This variant has the advantage that the reservoir 190 can be made smaller because the second piston chamber 240 can accommodate part of the hydraulic fluid flowing out of the first piston chamber 220 .

Furthermore shows 2 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 the orifice valve 180 . The orifice valve 180 is thus bypassed with the non-return valve 360, so that a more rapid filling of the first piston chamber 220 is possible.

2 FIG. 3 also shows a check valve 370 arranged in parallel with the hydraulic machine 50. The check valve 370 opens when the first piston chamber 220 is exhausted. Because most of the hydraulic fluid is flowing through lines 110 and 120, pump 50 may be undersupplied with hydraulic fluid. With some types of pumps, this can damage the pump. To avoid this hydraulic fluid is passed from line 120 into pump 50 via check valve 370

at 2 an orifice valve 170 is arranged in line 120. It is also possible to arrange orifice valve 170 in line 110, preferably hydraulically in the vicinity of valve 100. As a result, the maximum volume flow through lines 110 and 120 is not determined by the cross-section of these lines, but can be determined much more precisely by the dimensioning of the orifice valve 170.

In the cylinder 200 in the first piston chamber 220 - in the region of the end opposite the spring 250 - a cushioning 270 is arranged. If the energy store is designed as a spring 250, as in this embodiment, the piston of the cylinder can hit the inner wall of the cylinder very hard and thus cause damage to the cylinder, at least in the medium term. This is avoided with the end position cushioning 270 shown.

3 shows a variant of an actuator not according to the invention. As in 1 the valve 100 has the rest position "blocked". If the first piston chamber 220 is emptied, then, starting from a predefined volume flow, a pressure builds up in front of the orifice valve 180 in the line 150, which is so high that the force of the valve spring 108 is overcome and the actuator 104 pushes the valve 100 into the "Flow" position switches

List of References

10

hydraulic system

50

hydraulic machine, pump

51

first pump connection

52

second pump connection

60

engine

100

Valve, 2/2-way valve

102

first valve actuator

104

second valve actuator

108

valve spring

110, 120

Pressure line, secondary line

130, 160

Pressure line, main line

140, 150

Pressure line, control line

170

another orifice valve

180

orifice valve

190

reservoir

200

cylinder

210

piston of the cylinder

220

first piston chamber

230

piston rod

240

second piston chamber

250

feather

270

cushioning

290

closure

310

pressure line

320

pressure line

330

pressure line

360

check valve

370

check valve

410, 420

Conduction, passage of the controlled device

Claims (15)

1. Electro-hydrostatic drive (10) for an actuating drive, having

   a variable-volume and/or variable-speed hydraulic machine (50) which is driven by an electric motor (60), for providing a volumetric flow of a hydraulic fluid,

   a cylinder (200) with a piston (210), a piston rod (230) and a first piston chamber (220),

   a valve (100) with a first position and a second position, which valve (100) 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,

   main line (130, 160) which connects a first piston chamber (220) of the cylinder (200) to the sink and in which the hydraulic machine (50) is arranged,

   an auxiliary line (110, 120) which connects the first piston chamber (220) to the sink and in which the valve (100) is arranged,

   a first control line (140) to the first hydraulic actuator, and

   a second control line (150) to the second hydraulic actuator,

   wherein a hydraulic resistance (180) is arranged in the main line (130, 160) in series with the hydraulic machine (50),

   wherein the first control line (140) is connected to the main line (130, 160), and

   wherein the second control line (150) is connected between the hydraulic resistance (180) and the first piston chamber (220)

   characterized in that the sink is the second piston chamber (240) of the cylinder (200), wherein the cylinder (200) is a synchronizing cylinder.
2. Electro-hydrostatic drive (10) according to Claim 1,
   characterized in that the first control line (140) is connected between the hydraulic resistance (180) and the hydraulic machine (50).
3. Electro-hydrostatic drive (10) according to Claim 1, characterized in that the first control line (140) is connected between the hydraulic machine (50) and the first piston chamber (220).
4. Electro-hydrostatic drive (10) according to Claim 1 to 3, characterized in that the hydraulic resistance (180) is a diaphragm valve.
5. Electro-hydrostatic drive (10) according to Claim 1 to 4, characterized in that the sink is a reservoir (190).
6. Electro-hydrostatic drive (10) according to Claim 5, characterized in that the reservoir (190) is pre-tensioned and in particular, implemented as a pressure reservoir.
7. Electro-hydrostatic drive (10) according to any of the preceding claims, characterized in that
   the valve (100) is a multi-way valve, wherein the first position is "closed" and the second position is "flowing".
8. Electro-hydrostatic drive (10) according to Claim 1 to 6, characterized in that the valve (100) has multiple positions each with different cross-sections.
9. Electro-hydrostatic drive (10) according to Claim 1 to 6, characterized in that
   the valve (100) can switch smoothly between multiple positions, each with different volume flow rates of the hydraulic fluid.
10. Electro-hydrostatic drive (10) according to any of the preceding claims, characterized in that
    the valve (100) has the first position "closed" as a rest position in which it is held, in particular by a spring.
11. Electro-hydrostatic drive (10) according to any of the preceding claims, characterized in that
    the cylinder (200) additionally comprises an energy storage device (250).
12. Electro-hydrostatic drive (10) according to Claim 11, characterized in that
    the energy storage device (250) is a spring which is arranged in the second piston chamber (230) or in front of the first piston chamber (240).
13. Electro-hydrostatic drive (10) according to any of the preceding claims, characterized in that
    a further diaphragm valve (170) is arranged in the auxiliary line (110, 120).
14. Electro-hydrostatic drive (10) according to any of the preceding claims, characterized in that
    a non-return valve (360) is arranged in parallel with the hydraulic resistance (180).
15. Use of an electro-hydrostatic drive (10) according to any of the preceding claims, characterized in that
    a further non-return valve (370) is arranged in parallel with the pump (50).

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