EP3175123B1 - Hydraulic actuator system - Google Patents

Description

The invention is based on a hydraulic axis.

Such hydraulic axes, such as in the document JP2001182716 are used, for example, in the power plant sector, in particular in gas and steam turbine plants. They can then be used, for example, when actuating a valve body which is used to regulate a pressure medium connection between a waste heat boiler and a steam turbine, with a quick closing being intended to be possible. The trend in this area is towards self-sufficient and compact valve or linear drives with such an axis, which in addition to a cylinder has in particular an electric control unit, an electric motor, a hydraulic pump and a hydraulic control block with valves. In a known and comparatively compact solution, the usually bulky components are arranged on the cylinder housing of the stroke-executing cylinder, the valve actuator then having a high weight overall and still requiring a comparatively large amount of installation space.

In contrast, the invention has for its object to provide a hydraulic axis that leads to a compact and small space requirement valve actuator.

The object is achieved with a hydraulic axis according to the features of claim 1.

Other advantageous developments of the invention are the subject of further dependent claims.

According to the invention, a compact hydraulic axis has a cylinder. This can be operated via a pump (hydraulic pump). The pump is advantageously installed in a cavity of the cylinder. The cylinder is designed as a synchronous cylinder, which is designed in a differential design. Thus, a synchronous cylinder in differential design with an integrated pump is provided.

This solution has the advantage that an autonomous valve drive with the hydraulic axis according to the invention is made possible for the regulation and for a quick closing of gas and steam turbines. By integrating the pump into the cavity of the cylinder, a housing of the pump, a control block together with valves and piping can be saved. A hydraulic energy generated in the pump can be used to control the cylinder with little or no deflection and with little or no flow loss. Since the synchronous cylinder is designed in a differential design, it is advantageously shorter in the axial direction than a conventional synchronous cylinder, since a piston rod extends from one piston only from one side and therefore no space must be provided or kept free for another piston rod of the synchronous cylinder. Thus, the synchronous cylinder in differential design provides space for the integration of the pump. It is also advantageous that the cylinder is volume-balanced, which means that, in contrast to a differential cylinder, no hydraulic accumulator is necessary for volume compensation. The hydraulic axis according to the invention thus makes it possible to reduce the components by combining cylinder and pump functions. As a result, the hydraulic axis is advantageously optimized in terms of weight and installation space and combines the advantages of the electrical with the advantages of the hydraulic linear drives if the pump is driven by an electric motor.

According to the invention, the cylinder has an outer cylinder tube which engages around an inner cylinder tube. The inner cylinder tube is preferably firmly connected to the outer cylinder tube. Furthermore, the cylinder tubes are preferably arranged coaxially with one another. In terms of device technology, the cavity with the pump can be formed in the inner cylinder tube.

The cylinder tubes, in particular the outer cylinder tube with its inner lateral surface and the inner cylinder tube with its outer lateral surface, delimit an annular space. A, in particular annular, piston is arranged axially displaceably in this. An approximately hollow cylindrical piston rod extends from this, whereby the piston is connected on one side to a piston rod. The piston rod asserts itself through a closing device of the cylinder and is closed on a side of the closing device facing away from the piston in order to delimit a first cylinder chamber. Furthermore, the piston delimits a second cylinder chamber on the piston rod side on a side of the closure device facing the piston.

A pressure in one or both cylinder chambers can be limited by a pressure relief valve. For example, a pressure limiting valve can be provided that opens a pressure medium connection between the second cylinder chamber and the first cylinder chamber from a certain pressure in the second cylinder chamber. Alternatively or additionally, it is conceivable that a further pressure relief valve or the same pressure relief valve opens a pressure medium connection between the first cylinder chamber and the second cylinder chamber from a certain pressure in the first cylinder chamber.

Diametrically to the locking device, the cylinder is additionally closed by a cylinder base. A piston cover can be provided to close the piston rod. The synchronous cylinder in differential design thus has an inner cylinder tube, an outer cylinder tube, a cylinder base and a locking device. The piston is arranged with a piston rod and a piston cover.

In a further embodiment of the invention, two chamber sections are separated in the second cylinder chamber by the hollow cylindrical piston rod. This preferably forms an outer annular chamber section and an inner annular chamber section. The chamber sections can be connected via a flow path. The chamber sections or the second can in the axial direction Cylinder chamber be limited by the piston and by the closure device.

In terms of device technology, the fluidic connection of the chamber sections takes place simply via at least one cutout made in the piston rod. This is, for example, a bore, an elongated hole or a groove. The recess is advantageously arranged adjacent to the piston, with which the fluidic connection of the chamber sections is not separated even when the piston rod is essentially fully extended.

So that the cylinder chambers are volume-balanced, an effective area of the piston delimiting the second cylinder chamber and an effective area of the piston rod delimiting the first cylinder chamber are approximately the same size.

To actuate the piston, pressure medium can simply be conveyed from the first cylinder chamber into the second cylinder chamber and vice versa via the pump. If pressure medium is conveyed from the first into the second cylinder chamber, the piston rod is retracted. The piston rod extends in the opposite direction.

The pump can also be driven in a simple manner via a drive shaft by a drive unit which, as already explained above, is preferably an electric motor. The drive unit is preferably arranged at least in sections within the inner cylinder tube and can alternatively be flanged to the cylinder from the outside. The hydraulic axis is thus essentially self-sufficient and only requires an energy supply, for example electrical energy, to drive the drive unit.

The drive shaft is coupled to the pump and guided to the drive unit and / or to the outside via the inner cylinder tube. The drive shaft is coupled to the pump, for example, via a clutch.

The pump is preferably a piston pump. Alternatively, it is conceivable to provide a gear pump. The piston pump is further preferably designed in a swashplate construction. A drive shaft of the piston pump in particular passes axially through a swash plate, a cylinder drum and a distributor plate of the piston pump and is rotatable in the inner cylinder tube via bearings, in particular Rolling bearings, stored. The drive shaft can be connected to the cylinder drum via a positive connection, for example via a feather key connection. The cylinder drum is preferably supported on its side facing away from the swash plate on the distributor plate.

The closure device, which is penetrated by the piston rod, can have an outer annular closure element, in particular an outer cylinder cover, which surrounds the piston rod, and an inner closure element, in particular an inner cylinder cover, arranged within the piston rod.

In a further embodiment of the invention, a first fluid channel can be formed in a space-saving manner in the inner closure element, which fluidically connects the first cylinder chamber to the pump. A second fluid channel is preferably formed, which fluidly connects the second cylinder chamber to the pump. For the fluidic connection of the fluid channels to the pump, for example, the distributor plate rests on the inner closure element. The inner closure element is preferably configured essentially in two stages, wherein it is inserted into the inner cylinder tube with a first smaller stage and is supported on the end face of the inner cylinder tube via a shoulder formed between the stages.

The pressure relief valve is preferably connected to the second fluid channel via a channel in the inner closure element. A pressure medium connection between the second fluid channel and the first cylinder chamber can then be opened via the pressure limiting valve. The pressure relief valve is, for example, firmly connected to the closure element.

The fluid channels are, for example, simply designed as bores in terms of device technology.

In a further embodiment of the invention, the distributor plate of the pump has control kidneys, which continue in the inner closure element as control kidneys on the closure element side, each of which is connected to one of the fluid channels. Here, the distributor plate is preferably connected to the inner closure element in a rotationally fixed manner.

To compensate for a change in volume of a pressure medium in the cylinder in the event of temperature changes, a, in particular small, hydraulic accumulator can be provided. This can also be designed in such a way that it can be used for prestressing the respective low-pressure region. In terms of device technology, the hydraulic accumulator can be integrated in the inner closure element. So that the hydraulic accumulator can be connected to the respective low-pressure region, the first fluid channel is connected to the hydraulic accumulator via a first check valve that closes toward the hydraulic accumulator and the second fluid channel is connected to the hydraulic accumulator via a second check valve that closes towards the hydraulic accumulator.

In a further embodiment of the invention, the hydraulic accumulator can be designed as a piston accumulator with a spring-preloaded accumulator piston. The pretensioning takes place, for example, in such a way that a respective low-pressure region is pretensioned. A preload can be about 5 bar, for example. The storage piston of the piston accumulator is guided axially, for example, in a blind hole in the inner closure element. To close the blind hole with respect to the first cylinder chamber, a cover element is provided which rests on the inner closure element. A storage spring can be supported on the cover element and act on the storage piston with a spring force. The hydraulic accumulator can also be connected to the pump for pump leakage via a leakage channel. The leakage channel extends, for example, starting from the blind hole, in particular coaxially to it, towards the drive shaft of the pump and can continue therein.

An optical rangefinder can advantageously be provided in the cylinder base of the cylinder, which can also be designed redundantly. A distance to the piston can preferably be measured via the range finder, since in the cylinder chamber, which is delimited by the piston and the cylinder base, no pressure medium, but instead, for example, a gas (air) can be provided. The optical range finder is, for example, a laser range finder, with which a distance measuring system can be integrated in a simple manner.

• Figur 1 in einer schematischen Darstellung die erfindungsgemäße hydraulische Achse gemäß einer ersten Ausführungsform,
• Figur 2 in einer perspektivischen Darstellung die hydraulische Achse in einem Längsschnitt gemäß einer zweiten Ausführungsform,
• Figur 3 in einem Längsschnitt einen Abschnitt der hydraulischen Achse aus Figur 2 im Bereich der Pumpe und des Kolbens und
• Figur 4 einen vergrößerten Ausschnitt aus Figur 3.

Preferred embodiments of the invention are explained in more detail below with reference to drawings. Show it:

• Figure 1 In a schematic representation, the hydraulic axis according to the invention according to a first embodiment,
• Figure 2 a perspective view of the hydraulic axis in a longitudinal section according to a second embodiment,
• Figure 3 in a longitudinal section a section of the hydraulic axis Figure 2 in the area of the pump and the piston and
• Figure 4 an enlarged section Figure 3 .

According to Figure 1 a hydraulic axis with a cylinder 1 is provided. This has an outer cylinder tube 2, which encompasses an inner cylinder tube 4. The cylinder 1 is fixed in position via a flange 6. An annular space 12 is delimited by an outer lateral surface 8 of the inner cylinder tube 4 and an inner lateral surface 10 of the outer cylinder tube 2. In this an annular piston 14 is axially displaceably guided. The annular space 12 is axially delimited on the one hand by the cylinder base 16 and on the other hand by the cylinder cover 18. Starting from the piston 14, a hollow cylindrical piston rod 20 extends on one side. It passes through the cylinder cover 18 and divides it into an annular outer cylinder cover 22 or an outer closure element and an inner annular cylinder cover 24 or an inner closure element. The piston rod 20 is closed on its side axially facing away from the piston 14 by a piston cover 26.

According to Figure 1 When viewed in the radial direction, the piston rod 20 extends approximately centrally starting from the piston 14. The piston rod 20, together with the piston cover 26 and the cylinder cover 18, delimits a first cylinder chamber 28 via an active surface 27. A second cylinder chamber 30 is provided by the piston 14 on the piston rod side via an active surface 29 limited. The piston rod 20 axially penetrates the cylinder chamber 30, whereby the piston rod 20 separates the second cylinder chamber into an inner chamber section 32 and an outer chamber section 34. For the fluidic connection of the chamber sections 32 and 34, a bore 36 is made in the piston rod 20 which is formed adjacent to the piston 14.

A pump 40 is inserted into a cavity 38 of the cylinder 1, which is delimited by the inner cylinder tube 4. A drive unit 42 (electric motor) is provided for driving the pump, which is also inserted into the inner cylinder tube 4. The pump 40 is thus seen in the axial direction between the drive unit 42 and the Cylinder cover 18 arranged. The pump 40 is fluidly connected to both cylinder chambers 28 and 30. It can thus convey pressure medium from the cylinder chamber 28 into the cylinder chamber 30 and vice versa from the cylinder chamber 30 into the cylinder chamber 28 in order to axially move the piston 14 together with the piston rod 20.

The in Figure 1 The cylinder shown is designed as a synchronous cylinder in a differential design, with which only a single piston rod 20 is required. The piston 14 can then, with its side 44 facing away from the piston rod 20, delimit a further cylinder chamber 46 which is connected, for example, to an atmosphere. Since no pressure medium has to be provided in the cylinder chamber 46, an optical distance meter for measuring the distance of the piston 14 can preferably be integrated in this area.

According to Figure 2 Another embodiment of the cylinder 1 is shown. Here, a drive unit 48 in the form of an electric motor is arranged outside the cylinder tubes 2 and 4. The drive unit 48 is flanged to the cylinder base 16 coaxially to the cylinder tubes 2 and 4. A drive shaft 50 of the drive unit 48 plunges from the outside into the inner cylinder tube 4 and extends up to a drive shaft 52 of the pump 40. The drive shaft 52 and the drive shaft 50 are coupled to one another via a coupling.

According to Figure 3 the piston 14 has a slide ring and a seal on the outside and inside. The piston rod 20 is different from Figure 1 seen in the radial direction not centrally located on the piston 14, but offset inwards in the radial direction.

The piston cover 26 is stepped back radially and is therefore of two stages. With its smaller step 54, it is inserted into the piston rod 20 and rests with its shoulder 56 formed at the step transition on an end face of the piston rod 20. The piston cover 26 is screwed to the piston rod 20 via a screw connection. A seal is introduced between the small step 54 and an inner lateral surface 58 of the piston rod 20.

The outer cylinder cover 22 is designed in a ring shape and is also stepped radially backwards, with which it is designed in a step-like manner. With its small step 60, it dips into the annular space 12 and delimits the outer chamber section 34 at the end. A sealant is provided between an inner lateral surface 8 of the outer cylinder tube 2 and an outer lateral surface of the step 60. The outer cylinder cover 22 also has a cylindrical inner jacket surface 62, which extends approximately coaxially to the cylinder 1 and serves to guide the piston rod 20. Seen in series in the axial direction, sealants are introduced into the inner lateral surface 62. Viewed in the axial direction, a slide ring is arranged between the sealing means. A diameter of the outer cylinder cover 22 is selected to be larger than a diameter of the outer cylinder tube 2, with which it projects beyond the outer cylinder tube 2 in the radial direction. The cylinder cover 22 is screwed to the outer cylinder tube 2 via a screw connection.

The inner cylinder cover 24 is cylindrical and radially stepped back, with which it has a first small step 64 and a second large step 66. The first stage 64 is inserted into the inner cylinder tube 4. The inner cylinder cover 24 bears against an end face of the inner cylinder tube 4 via a shoulder 68 formed between the steps 64 and 66.

According to Figure 4 inner cylinder cover 24 has a second fluid passage 70 that connects inner chamber portion 32 to pump 40. Furthermore, a first fluid channel 72 is formed in the inner cylinder cover 24, which also has the first cylinder chamber 28 Figure 3 , connects to the pump 40. The second fluid channel 70 is formed by a radial bore 74 which is introduced radially from the outside into the cylinder cover 24 and opens into an axial blind hole 76 which is introduced into the cylinder cover 24 from a side pointing away from the pump 40. The blind hole 76 is connected at the end to a control kidney 78 formed in the cylinder cover 24. The axial blind hole 76 is formed parallel to a longitudinal axis of the cylinder 1. For the first fluid channel 72, an axially extending blind bore 80 is introduced from the first cylinder chamber 28, which opens into a radial bore 82. The radial bore 82 is also introduced radially from the outside into the cylinder cover 24 and extends approximately coaxially with the other radial bore 74. The radial bore 82 is closed to the outside by a closure element. It also opens into an axially extending blind hole 84, which accordingly the blind hole 76 is configured and is arranged at a parallel distance from this and from the longitudinal axis of the cylinder 1. The blind hole 84 then opens into a further control kidney 86. In the region of the second stage 66 and in the region of the radial bores 82 and 74, the cylinder cover 24 is stepped back radially in order to connect the radial bore 74 to the inner chamber section 32. An outer circumferential surface 88 of the second stage 66 serves as a guide surface for the piston rod 20 and also has sealing means lying opposite the sealing means of the outer cylinder cover 22, a sliding ring being provided between the sealing means as seen in the axial direction.

A further large blind hole 90 is made coaxially with the cylinder cover 24, the bottom 92 of which is spaced axially from the radial bores 74 and 82. The blind hole 90 serves to form a hydraulic accumulator, which is designed as a piston accumulator 94. This has an axially displaceably guided in the blind bore 90 storage piston 96. The sleeve-shaped storage piston 96 can be acted upon by a spring force of a storage spring 98, which is supported on a cover element 100 screwed to the cylinder cover 24 and immersed in the storage piston 96. The cover element 100 closes the blind hole 90 here.

The blind holes 76 and 84 for the fluid channels 70 and 72, which intersect the radial holes 74 and 82, are made from the bottom 92 of the hole. A check valve 102 or 104 is inserted in each of the blind holes 76 and 84, seen in the axial direction, between the radial holes 74 and 82 and the bottom 92 of the hole. These each close in a flow direction towards the blind hole 90.

The blind hole 80 of the first fluid channel 72 is connected to a through hole through the cover element 100 for fluid communication with the first cylinder chamber 28.

A through hole 106 is made in the center of the cylinder cover 24 starting from the bottom 92 of the hole. This is widened radially at the end and serves to receive a first roller bearing 108 for a drive shaft 110 of the pump 40. A leakage channel 112 is introduced into the drive shaft 110, into which at least one transverse bore 113 opens, via which the leakage channel 112 with the leakage side of the pump 40 connected is. The leakage channel 112 opens into the through bore 106 and is connected to the piston accumulator 94 via this. According to Figure 3 the pump 40 is designed as a swash plate pump. It has a cylinder drum 114 which is connected in a rotationally fixed manner to the drive shaft 110. Pistons 116 are axially guided in cylinder bores in the cylinder drum 114. These are supported on a swash plate 118 firmly inserted into the inner cylinder tube 4. The rotatable cylinder drum 114, in turn, is supported with its end face facing the inner cylinder cover 24 on a distributor plate 120, which in turn abuts an end face of the inner cylinder cover 24. The distributor plate 120 is arranged in a rotationally fixed manner in the inner cylinder tube 4 and has control kidneys, which have a respective control kidney 78 or 86, see Figure 4 , are connected.

A radial shaft sealing ring 122 is provided in the swash plate 118, which surrounds the drive shaft 110. Furthermore, a second roller bearing 124 is arranged in the swash plate 118 for mounting the drive shaft 110.
In Figure 3 A bore 36 is shown which radially penetrates the piston rod 20 and thereby connects the two chamber sections 32, 34 of the second cylinder chamber 30 to one another.

The cylinder chambers 28, 30 can be connected via a pressure relief valve 126 that opens from a certain pressure in a respective cylinder chamber 28, 30. It would also be conceivable to limit the pressure in one of the cylinder chambers 28, 30 via a pressure relief valve or to provide a pressure relief valve for a respective cylinder chamber 28, 30. The pressure relief valve 126 is connected to the radial bore 74 of the second fluid channel 70 via an axial bore 128 extending parallel to the longitudinal axis of the cylinder 1. The axial bore 128 extends from the cover element 100 into the inner cylinder cover 24, completely penetrating the cover element 100 and opening into the radial bore 74 in the inner cylinder cover 24. The pressure limiting valve 126 is then connected to the axial bore 128 and is preferably fixed on the cover element 100 and is therefore preferably arranged in the first cylinder chamber 28.

If the pump 40 is driven by the drive unit 48 in a first direction of rotation, it pumps pressure medium from the first cylinder chamber 28, see Figure 3 , via the first fluid channel 72, see Figure 4 , in the second fluid channel 70. The second fluid channel 70 the pressure medium is further conveyed to the inner chamber section 32 and via the bore 36, see Figure 3 , into the outer chamber section 34. If the pump 40 is driven in the opposite direction of rotation, it conveys pressure medium from the chamber sections 32 and 34 via the second fluid channel 70 into the first fluid channel 72 and further into the first cylinder chamber 28.

What is disclosed is a compact hydraulic axle with a cylinder. In this a pump for controlling the cylinder is arranged. The pump is provided in a cavity of the cylinder. The cylinder is designed as a synchronous cylinder in a differential design.

Reference list

1

cylinder

2nd

outer cylinder tube

4th

inner cylinder tube

6

Flange mounting

8th

Outer surface

10th

Inner surface

12th

Annulus

14

piston

16

Cylinder bottom

18th

Cylinder cover

20

Piston rod

22

outer cylinder cover

24th

inner cylinder cover

26

Piston cover

27

Effective area

28

first cylinder chamber

29

Effective area

30th

second cylinder chamber

32

inner chamber section

34

outer chamber section

36

drilling

38

cavity

40

pump

42

Drive unit

44

Piston side

46

Cylinder chamber

48

Drive unit

50

drive shaft

52

Drive shaft

54

step

56

shoulder

58

Inner surface

60

step

62

Inner surface

64

first stage

66

second step

68

shoulder

70

second fluid channel

72

first fluid channel

74

Radial bore

76

Blind hole

78

Control kidneys

80

Blind hole

82

Radial bore

84

Blind hole

86

Control kidneys

88

Outer surface

90

Blind hole

92

Bottom of the hole

94

Hydraulic accumulator / piston accumulator

96

Accumulator piston

98

Spring

100

Cover element

102

check valve

104

check valve

106

Through hole

108

first rolling bearing

110

Drive shaft

112

Leakage channel

113

Cross hole

114

Cylinder drum

116

piston

118

Swashplate

120

Distribution plate

122

Radial shaft seal

124

second rolling bearing

126

Pressure relief valve

128

Axial bore

Claims (11)

1. Hydraulic spindle with a cylinder (1) which can be activated via a pump (40), wherein the pump (40) is installed in a cavity (38) of the cylinder (1), and the cylinder (1) is a differential-type double rod cylinder, with an outer cylinder tube (2) in which an inner cylinder tube (4) is arranged, wherein the cavity (38) with the pump (40) is formed in the inner cylinder tube (4), wherein the cylinder tubes (2, 4) bound an annular space (12) in which a piston (14) is arranged in an axially displaceable manner, from which piston a hollow-cylindrical piston rod (20) extends, the piston rod passing through a closure device (18) of the cylinder (1) and being closed on a side of the closure device (18) that faces away from the piston (14) in order to bound a first cylinder chamber (28), and wherein the piston (14) on the piston-rod side bounds a second cylinder chamber (30), wherein an operative surface (29) of the piston that bounds the second cylinder chamber (30) and an operative surface (27) of the piston rod that bounds the first cylinder chamber (28) are approximately identical in size, and therefore the volumes of the cylinder chambers (28, 30) are equalized.
2. Hydraulic spindle according to Claim 1, wherein the piston rod (20) separates the second cylinder chamber (30) in the radial direction into an outer chamber section (34) and an inner chamber section (32), wherein the chamber sections (32, 34) are connected fluidically via a flow path (36).
3. Hydraulic spindle according to either of the preceding claims, wherein the pump (40) can be driven via a drive unit (42, 48) which is arranged within the inner cylinder tube (4) or which is flange-mounted on the cylinder (1).
4. Hydraulic spindle according to one of the preceding claims, wherein the pump (40) is a piston pump of swash plate design.
5. Hydraulic spindle according to one of Claims 1 to 4, wherein the closure device (18) has an outer annular closure element (22) engaging around the piston rod (20) and an inner closure element (24) arranged within the piston rod (20).
6. Hydraulic spindle according to Claim 5, wherein the inner closure element (24) contains a first fluid channel (72) which fluidically connects the first cylinder chamber (28) to the pump (40), and contains a second fluid channel (70) which fluidically connects the second cylinder chamber (30) to the pump (40).
7. Hydraulic spindle according to one of the preceding claims, wherein a hydraulic accumulator (94) is provided for equalizing the temperature and/or for prestressing a respective low-pressure region.
8. Hydraulic spindle according to Claim 7, wherein the hydraulic accumulator (94) is formed in the inner closure element (24).
9. Hydraulic spindle according to Claim 7 or 8, wherein the first fluid channel (70) is connected to the hydraulic accumulator (94) via a first nonreturn valve (102) which closes towards the hydraulic accumulator (94), and wherein the second fluid channel (72) is connected to the hydraulic accumulator (94) via a second nonreturn valve (104) which closes towards the hydraulic accumulator (94).
10. Hydraulic spindle according to one of Claims 7 to 9, wherein the hydraulic accumulator (94) is connected to the pump (40) via a leakage channel (106, 112) .
11. Hydraulic spindle according to one of the preceding claims, wherein a distance measuring device is arranged on the bottom side of the cylinder (1).

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