DE102009053612A1 - Pilot operated pressure control valve i.e. pressure-feeding valve, for use as working valve in e.g. traction drive, has valve device including throttle element, where element and/or bushing is formed with respect to cross sectional plane - Google Patents

Abstract

The pressure control valve (1) has a throttle valve device (58) including a movable throttle element that is arranged between a main piston bore (60) and a seat bushing that is provided in a main piston (34) for throttling pressure fluid flow direction-dependent between a high-pressure port (38) and a spring space (44). The throttle element and/or the seat bushing is symmetrically formed with respect to a cross sectional plane. The throttle element is movably guided in a valve chamber in a longitudinal direction of the pressure control valve.

Description

The invention relates to a pilot operated pressure relief valve, in particular a pressure feed valve, according to the preamble of patent claim 1.

Such pressure feed valves are used, for example, as a working valve in hydrostatic drives, such as drive and slewing drives and to protect linear loads, such as cylinders, in the open or closed hydraulic circuit. For drive / slewing drives, these valves are used, for example, to open a connection from the high pressure side to the low pressure side when a given system pressure is exceeded. In this case, pressure fluid is then passed to a hydraulic motor of the rotary / chassis drive from the high-pressure branch in the low-pressure branch, so that pressure peaks in the high-pressure branch can be avoided. In the Nachsaugfunktion can - for example, in a downhill - pressure medium from the low-pressure branch (which then leads the higher pressure) are sucked into the high-pressure branch, so that cavitation can be prevented.

From the DE 103 45 712 A1 Such a pressure feed valve is known. This has a main and a preliminary stage, wherein a piston of the main stage controls a pressure medium connection between a high pressure port and a low pressure port. The piston is biased by a valve spring in a closing direction. A spring chamber bounded by the piston can be connected to the high-pressure connection via a piston bore and to the low-pressure connection via the preliminary stage. In the piston, a throttle check valve is arranged with a nozzle plate. This has a nozzle bore with a smaller diameter than the piston bore and can be brought with an end face in contact with a screwed into the piston seat sleeve. The nozzle plate has an approximately triangular base formed by flats, at the corner regions of supporting legs are formed which can be brought into abutment against an annular end face of the piston bore and which abut with curved outer peripheral surfaces on an inner peripheral wall of an enlarged portion of the piston bore slidably. By the support legs, the base of the nozzle plate is generally spaced from the annular end face of the piston bore, whereby the nozzle bore of the nozzle plate in the lifted from the seat sleeve state by the flow around the flats is bypassed. As a result, a nozzle is created in the piston whose opening cross-section in the flow direction from the spring chamber to the high pressure port is greater than in the reverse flow direction.

A disadvantage of this solution is the complex installation of the throttle check valve, since the nozzle plate can be used only with the support legs in the direction of the piston bore in the extended part of the piston bore, which for example a fitter must pay attention to the orientation of the nozzle plate, and a wrong insertion to malfunction of the Pressure feed valve would result.

In contrast, the present invention seeks to provide a pilot operated pressure relief valve that is easy, inexpensive and with low error rate mountable.

This object is achieved by a pilot operated pressure relief valve having the features of patent claim 1.

According to the invention, a pilot-operated pressure relief valve, in particular a pressure feed valve, with a Nachsaugfunktion, a biased via a main piston spring to a valve seat main piston of a main stage. With this a pressure medium connection between a high and a low pressure connection aufsteuerbar. A spring chamber delimited by the main piston is connectable, on the one hand, via a main piston arranged throttle valve device and a piston bore to the high pressure port and on the other hand via a preliminary stage with the low pressure port. The throttle valve device has a movable throttle element which is arranged between a main piston bore and a seat sleeve inserted into the main piston. The throttle element is used for different throttling a pressure fluid flow between the high-pressure port and the spring chamber. The throttle element and / or the seat sleeve are each symmetrically shaped with respect to a central cross-sectional plane.

This solution has the advantage that an extremely simple mounting of the pressure limiting valve and in particular of the throttle valve device is made possible because the symmetrical design of the throttle element and / or the seat sleeve these are independent of their orientation mountable.

Preferably, the throttle element is displaceably guided in a valve space in the longitudinal direction of the pressure limiting valve. The valve space is limited by an inner end face of the main piston and an annular end face of the seat sleeve. About the seat sleeve of the valve chamber is then connected to the spring chamber and the main piston bore to the high-pressure port, wherein the seat sleeve secures the throttle element.

Advantageously, the throttle element is a very inexpensive producible nozzle plate, the is simply penetrated by a nozzle bore with a smaller diameter than the main piston bore and wherein the nozzle bore is in bypassed by the seat sleeve throttle element by its flow around bypasses.

In a further embodiment of the invention, the inner end face of the main piston recesses. These are designed in such a way that the throttle element can be flowed around in a state abutting the inner end face by the pressure medium flow.

The recesses of the inner end face of the main piston can be easily formed inexpensively as offset from the longitudinal axis in parallel spacing bores.

Preferably, three bores are provided, which are arranged at the same radial distance and uniform to each other in the circumferential direction with respect to the longitudinal axis.

For simple flow around the throttle element on the circumference at least one flattening, which limits the Umströmungsquerschnitt.

For fixed fixation of the seat sleeve, this has an external thread through which the seat sleeve is screwed into an internal thread of the hollow main piston.

For easy installation of the seat sleeve, this has an inner circumferential surface with a hexagonal cross-section. As a result, for example, a hexagonal wrench for screwing the seat sleeve on the inner circumferential surface attack.

Preferably, the throttle element, the seat sleeve and the main piston bore are arranged approximately coaxially with each other.

Other advantageous developments of the invention are the subject of further subclaims.

In the following, a preferred embodiment of the invention is explained in more detail with reference to schematic drawings. Show it:

1 in a longitudinal section, a pilot-controlled pressure relief valve according to an embodiment;

2 an enlarged section A of the pressure relief valve 1 ;

3 a plan view of a throttle element; and

4 a plan view of an inner end surface of a main piston.

In the 1 is a pilot-operated pressure relief valve in a longitudinal sectional view 1 disclosed according to an embodiment. This is used as a pressure feed valve with a Nachsaugfunktion. The pressure relief valve 1 has a main level 2 a preliminary stage 4 and a pilot control 6 the preliminary stage 4 on, which are arranged in a multi-part cartridge-shaped housing.

The pressure relief valve 1 is essentially rotationally symmetrical or concentric about a valve longitudinal axis 8th educated. The main and preliminary stage 2 . 4 are in a housing 10 recorded and the feedforward control 6 is in a reducer 12 , a socket 14 and a bushing 16 arranged.

The housing 10 is over a thread 18 screwed into a hydraulic device, not shown, while a sealing ring 20 sealed. The reducer 12 Again, there is a thread around 22 in the case 10 screwed in and over a sealing ring 24 sealed. The socket 14 is over a thread 26 in the reducer 12 screwed in and over a sealing ring 28 sealed. The adjusting bush 16 is over a thread 30 in the socket 14 screwed in and over a sealing ring 32 sealed.

The main stage 2 in the case 10 has one along the longitudinal axis 8th sliding main piston 34 , This is from his in the 1 lower end face 36 from a high pressure of a high pressure connection 38 the hydraulic device, not shown, while it is from its front side 36 repellent piston side 40 forth with a force of a main piston spring 42 and a pressure in a spring chamber 44 is charged. The high pressure of the hydraulic device acts in the opening direction of the main piston 34 while the force of the main piston spring 42 and the pressure in the spring chamber 44 in the closing direction of the main piston 34 Act.

The main piston spring 42 relies on an intermediate piece 46 in the case 10 picked up and between a paragraph of the case 10 and the reducer 12 is firmly clamped. The main piston 34 is hollow and has three stages, wherein in the first stage 52 in sections, the main piston spring 42 is used and at an inner annular end face 54 of the main piston 34 is applied. In a second stage 56 of the main piston 34 is a throttle valve device 58 or throttle check valve arranged. A third stage of the main piston 34 is a main piston bore 60 ,

The spring chamber 44 is via the throttle valve device 58 and the main piston bore 60 with the high pressure connection 38 in pressure medium connection.

On an inner peripheral portion of the housing 10 in the closed state of the main stage 2 from the main piston 34 is covered, is a circumferential groove 62 brought in. Furthermore, to an inner peripheral portion of the housing 10 , the intermediate piece 46 is covered, a circumferential groove 64 intended. In the installed state of the pilot-operated pressure relief valve according to the invention 1 in the hydraulic arrangement are these two grooves 62 . 64 connected via tank channels with a tank, not shown, or a low pressure connection, wherein in the 1 only one tank channel 66 the groove 64 is shown.

The main stage 2 has a Nachsaugfunktion over which can be sucked from the low pressure port into the hydraulic device, for example, in advance of a consumer connected to the hydraulic device pressure medium. It takes a main piston 34 encompassing suction ring 68 the main piston 34 over one on the main piston 34 cantilevered radial projection 70 (in 1 ) with and opens a connection from the low-pressure connection via the groove 62 to the hydraulic device via the high pressure port 38 , A more detailed functional description of the vacuuming function will be given later in this description.

In the intermediate piece 46 and in the reducer 12 is designed as a seat valve precursor 4 provided, which consists essentially of a longitudinal channel 72 , a valve seat 74 , an adjoining and on a pilot piston 76 attached ball 78 , a pilot spring 80 and one in the groove 64 opening bore star 82 consists. The longitudinal channel 72 connects the spring chamber 44 with the valve seat 74 , The ball 78 is over the pilot piston 76 and about the pilot spring 80 against the valve seat 74 curious; excited. The hole star 82 connects the valve seat 74 over the groove 64 and the tank channel 66 with the low pressure connection.

The pilot spring 80 is in the reducer 12 taken and relies on a spool 84 from. This is part of the feedforward control 6 and serves for precontrol of the preliminary stage 4 , The spool 84 has one of the pilot control spring 80 embraced spring section 86 , one with clearance fit in the reducer 12 accommodated Reduzierstückabschnitt 88 , and one in the socket 14 slidably mounted bushing section 90 that about a piston seal 92 in the socket 14 is sealed. Furthermore, the spool has 84 a radially extended Stellbuchsenabschnitt 94 and an opposite in diameter reduced Stellbuchsenabschnitt 96 each in the adjusting bush 16 are slidably mounted.

Between the two Stellbuchsenabschnitten 94 and 96 is an override spring 98 taken up, which is at the Stellbuchse 16 supports and the spool 84 over its radially extended Stellbuchsenabschnitt 94 against an inner ring end face 100 the socket 14 biases. A spring chamber in which the override spring 98 is arranged, is about piston seals 104 and 106 the Stellbuchsenabschnitte 94 respectively. 96 sealed and via a relief well 108 relieved to the atmosphere.

Between an annular end face 110 of the actuating sleeve section 94 of the spool 84 and the ring end face 100 the socket 14 is an annulus 112 educated. This is about at least one eccentric and through the adjusting bushing 16 extending control pressure channel 114 with one at a free end portion 116 the adjusting bush 16 arranged control pressure connection 118 the pressure relief valve according to the invention 1 connected. The control pressure connection 118 has a hollow cylindrical shape and an internal thread, which serves to connect a control pressure line, not shown.

In one area of the adjusting bush 16 that is between the control pressure port 118 and a receptacle for the Stellbuchsenabschnitt 96 is arranged is a stop screw 120 screwed. It has a radially extended section 122 whose diameter is approximately that of the Stellbuchsenabschnitt 96 of the spool 84 equivalent. The extended section 122 serves as a stop for an end stop surface 124 of the spool 84 , where in the in the 1 shown clamping position of the spool 84 a room 126 between the stop surface 124 and the extended section 122 remains. The space 126 is over a sealing ring 128 of the extended section 122 opposite the control pressure connection 118 sealed and over a longitudinal channel 130 the spool, 84 with a pilot control chamber 132 the pilot spring 80 connected to pressure equalization.

About a thread 134 is the stop screw 120 along the longitudinal axis 8th positionable. At one in the control pressure connection 118 extending end portion of the stop screw 120 a hexagon socket is provided for turning the stop screw 120 serves. Such a selected position of the stop screw 120 is about a lock nut 136 that on the thread 134 is screwed on, opposite the actuating sleeve 16 secured.

A set position of the adjusting bush 16 in the socket 14 is about a lock nut 138 secured while a selected position of the socket 14 in the reducer 12 about a locknut 140 is secured.

Against a complete unscrewing of the reducer 12 out of the case 10 is a snap ring 142 provided during circlips 144 . 146 unscrew the socket 14 from the reducer 12 or unscrewing the actuating sleeve 16 from the socket 14 prevent.

The 1 shows the pilot operated pressure relief valve according to the invention 1 in a state where the main piston 34 on a valve seat 150 is present, and the main stage 2 thus closed.

The pilot spring 80 is maximally biased, since the spool 84 along the longitudinal axis 8th over his Stellbuchsenabschnitt 94 at the socket 14 is applied. Thus, the spring in the room 44 necessary pressure to open the preliminary stage 4 maximum. By twisting the socket 14 in the reducer 12 can this maximum pressure change, from the in the 1 shown position of the socket 14 only a reduction of the maximum pressure is possible.

The in the spring room 44 for the opening of the preliminary stage 4 necessary pressure can be during operation of the pressure relief valve 1 reduce, in which a control pressure at the control pressure port 118 is increased, this via the control pressure channel 114 in the annulus 112 acts and the spool 84 in the 1 moved upwards. This is done against the force of the override spring 98 , which are attached to the adjusting bush 16 supports and the spool 84 pretensioned in the basic position shown.

The relief for the preliminary stage 4 necessary control pressure can be reduced, in which the bias of the override spring 98 is reduced. This is done by unscrewing the adjusting bushing 16 from the socket 14 , where in the 1 the maximum preload of the override spring 98 is shown.

At a predetermined control pressure of the spool device 84 with its stop surface 124 in attachment with the extended section 122 the stop screw 120 , Then, even with further increase in the control pressure no further relief of the pilot spring 80 and thus no further reduction of the opening pressure of the precursor 4 possible. This limitation of the pressure reduction is by turning the stop screw 120 in the adjusting bush 16 possible via the hexagon socket. This adjustment - as well as the adjustment of the bias of the override spring 98 and the pilot spring 80 - By loosening the respective locknut 136 . 138 respectively. 140 followed by turning the corresponding adjustment part 14 . 16 respectively. 120 with final countering by the locknut 136 . 138 respectively. 140 ,

When the on the ball 78 by the pressure medium in the spring chamber 44 acting opening force that of the adjustable pilot spring 80 exceeds, the precursor opens 4 , and pressure medium from the spring chamber 44 escapes through the tank channel 66 to the low-pressure connection or tank. After this relief of the spring chamber 44 the opening force prevails on the main piston 34 , and this moves along the longitudinal axis 8th in the 1 up. As a result, pressure fluid from the hydraulic device, not shown, via the groove 62 and non-shown tank channels to the low pressure port or tank flow out.

In 2 is a section A of the pressure relief valve 1 out 1 with the throttle valve device 58 shown enlarged. The in the 2 left end face 36 of the main piston 34 has a concentric projection 152 on, in which the main piston bore 60 empties. This is in the 2 to the right with the second step 56 extended, with following the main piston bore 60 a valve room 154 is formed, in which a throttle element in the form of a movable nozzle plate 156 is arranged. The valve room 154 is from a seated sleeve 158 limited, over a thread 160 in the second stage 56 of the main piston 34 is screwed. The front face (left in 2 ) of the seat sleeve 158 is as a seat 162 for the nozzle plate 156 educated. The nozzle plate 156 serves as a valve member of the throttle valve device 58 , wherein the nozzle plate 156 from a centrally introduced nozzle bore 163 is interspersed. This has a much smaller diameter than that in the region of the projection 152 in the high pressure connection 38 opening main piston bore 60 ,

An inner jacket surface 164 the seat sleeve 158 is hexagonal shaped to a screwing the seat sleeve 158 in the main piston 34 to allow with a hexagon wrench. The cross-sectional area of the of the inner circumferential surface 164 limited volume of the seat sleeve 158 is slightly larger than the diameter of the main piston bore 60 ,

The seat sleeve 158 and the nozzle plate 156 are approximately perpendicular to the longitudinal axis 8th extending median cross-sectional plane symmetrically shaped. As a result, these components are extremely simple and inexpensive to produce and on the other hand, in contrast to the above-described prior art, regardless of their orientation in the main piston 34 mountable.

3 discloses a top view from the left onto the nozzle plate 156 in 2 , Accordingly, this has an approximately quadrangular base 166 with rounded corners 168 . 170 . 172 . 174 the radius of curvature about the radius of the valve chamber 154 corresponds, so that these corner regions abut slidably on the inner peripheral wall. The nozzle bore 163 is at the center of this base 166 educated.

As will be described in more detail below, gets an end face 175 the nozzle plate 156 when the throttle valve device is open 58 in contact with an inner ring end face 176 of the main piston 34 in 2 , So that the nozzle plate 156 at a pressure medium flow from the spring chamber 44 to the main piston bore 60 along the flattening forming the quadrangular structure 178 in 3 are flowed around, are in the ring end face 176 several depressions in the form of holes 180 brought in.

4 shows in a plan view of the annular end face 176 of the main piston 34 with the holes 180 out 2 , These are each about at a distance parallel to the main piston bore 60 formed, wherein a respective diameter slightly larger than the diameter of the main piston bore 60 is. The center of the holes 180 is located approximately in the middle between the diameter of the main piston bore 60 and the diameter of the second stage 56 , Thus, a respective bore extends 180 in the radial direction substantially over the entire annular end face 176 , However, the holes are 180 in the radial direction, slightly from the inner wall of the second stage 56 spaced to allow a drill tool access to the bore in the second stage 56 Has. In the circumferential direction of the annular end face 176 are the holes 180 evenly distributed and thus evenly spaced from each other.

Is the nozzle plate 156 approximately at the ring end face 176 of the main piston 34 on, so can pressure medium from the spring chamber 44 over the flats 178 and the holes 180 to the main piston bore 60 stream. An entire coverage of the holes 180 through the, nozzle plate 156 can not. A complete concern of the nozzle plate 176 to the ring end face 176 of the main piston 34 is however by a radius 181 between the ring end face 176 and an inner circumferential surface of the second stage 56 of the main piston 34 in 2 avoided.

The minimum flow cross-section for the pressure medium is when the throttle valve device is closed 58 through the diameter of the nozzle bore 163 and with the throttle valve device open 58 through the diameter of the much larger main piston bore 60 certainly.

In the in 1 illustrated basic position of the pressure relief valve 1 is the main piston 34 biased into its closed position, the preliminary stage 4 is closed and the nozzle plate 156 the throttle valve device 58 lies sealed on the seat 162 the seat sleeve 158 on, so that pressure medium comparatively strongly throttled from the front-side high pressure port 38 through the nozzle bore 163 through into the spring chamber 44 can occur.

With a pressure increase at the high-pressure connection 38 Accordingly, the pressure in the spring chamber increases accordingly 44 so that about this pressure also at the valve seat 74 the preliminary stage 4 acts. When the preset system pressure is exceeded, the ball will become 78 the preliminary stage 4 against the force of the pilot spring 80 from the valve seat 74 lifted, so that pressure fluid from the spring chamber 44 over the opened preliminary stage 4 to the low pressure connection via the tank channel 66 can flow out. Due to the resulting discharge, the back of the main piston 34 lifts this from the valve seat 150 off, leaving the connection of the high pressure port 38 and the groove 62 , which is connected to the low pressure port, is turned on. The main piston 34 Adjusts to a control position in which the system pressure at the high pressure port 38 is limited to the set maximum value. Thereby the nozzle plate becomes 156 against the seat 162 printed, so that the pressure fluid flow through the diameter of the comparatively small nozzle bore 163 is determined.

In the Nachsaugfunktion, ie when the pressure at the high pressure port 38 drops below the pressure at the low-pressure connection, first the Nachsaugring 68 through the on his left end face 182 (please refer 2 ) acting higher pressure at the low pressure port in the 1 moved up. The left end face 182 in 2 is via a channel, not shown, with the low pressure port in pressure medium connection. The displacement of the Nachsaugrings 68 in 1 takes place up to the radial projection 70 of the main piston 34 , whereby the Nachsaugring 68 when attacking this radial projection 70 runs up and the main piston 34 continue up in 1 shifts until this on the adjacent end face of the intermediate piece 64 runs. The pressure medium connection from the low pressure connection to the high pressure connection 38 is fully open, so that pressure fluid can be sucked. Due to the low pressure at the high-pressure connection 38 becomes the nozzle plate 156 out 2 in the Nachsaugfunktion of the seat sleeve 158 lifted, leaving the spring chamber 44 very fast over the main piston bore 60 is relieved, with the lifted nozzle plate 156 is flowed around, so that the nozzle bore 163 is not effective. By switching the Throttle valve means 58 On a comparatively large throttle cross-section a quick switching to the Nachsaugfunktion is guaranteed, so that cavitations are reliably avoidable.

When the pressure conditions return, ie when the pressure at the high-pressure port increases 38 the pressure at the low-pressure connection becomes the main piston 34 moved back to its closed position, this closing movement by the action of the nozzle plate 156 with the smaller nozzle bore 163 is muted. This time-slow closing process of the main piston 34 For example, allows for a small pressure medium quantity compensation between the terminals of a hydraulic motor, so that it is not braced.

Disclosed is a pilot operated pressure medium limiting valve, in particular a pressure feed valve, with a Nachsaugfunktion. Here, a main piston is biased by a main piston spring on a valve seat, with the main piston, a pressure medium connection between a high and a low-pressure connection can be opened. A limited by the main piston spring chamber is connected via a throttle check valve and a piston bore, which are formed in the main piston, with the high-pressure port and a precursor with the low-pressure closing. The throttle check valve has a movable throttle element, which is arranged between a main piston bore and a seat sleeve inserted into the main piston for different throttling of a pressure medium flow between the high pressure port and the spring chamber. Advantageously, the throttle element and / or the seat sleeve each have a symmetrical shape relative to a central cross-sectional plane.

LIST OF REFERENCE NUMBERS

1

Pressure relief valve

2

main stage

4

preliminary stage

6

feedforward

8th

longitudinal axis

10

casing

12

reducer

14

Rifle

16

adjusting bush

18

thread

20

seal

22

thread

24

seal

26

thread

28

seal

30

thread

32

seal

34

main piston

36

front

38

High pressure port

40

piston side

42

Main piston spring

44

spring chamber

46

connecting piece

48

paragraph

52

first stage

54

Annular face

56

second step

58

Throttle valve means

60

Main piston bore

62

groove

64

groove

66

tank channel

68

anti-cavitation

70

radial projection

72

longitudinal channel

74

valve seat

76

pilot piston

78

Bullet

80

pilot spring

82

bore star

84

spool

86

Pilot spring section

88

reducing adapter

90

bushing section

92

piston seal

94

Adjusting bush section

96

Adjusting bush section

98

About control spring

100

Annular face

104

piston seal

106

piston seal

108

relief well

110

Annular face

112

annulus

114

Control pressure channel

116

end

118

Control pressure connection

120

stop screw

122

section

124

stop surface

126

room

128

seal

130

longitudinal channel

132

Pilot spring space

134

thread

136

locknut

138

locknut

140

locknut

142

snap ring

144

snap ring

146

snap ring

150

valve seat

152

head Start

154

valve chamber

156

nozzle plate

158

seat sleeve

160

thread

162

seat

163

nozzle bore

164

Inner surface area

166

Base

168

corner

170

corner

172

corner

173

face

174

corner

175

face

176

Annular face

178

flats

180

drilling

181

radius

182

face

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10345712 A1 [0003]

Claims (11)

Pilot operated pressure relief valve, in particular a pressure feed valve, with a valve seat ( 150 ) associated main piston ( 34 ) of a main stage ( 2 ), with which a pressure medium connection between a high and a low pressure connection ( 38 . 62 ) is controllable, one of the main piston ( 34 ) limited spring space ( 44 ) via one in the main piston ( 34 ) arranged throttle valve device ( 58 ) and a main piston bore ( 60 ) with the high-pressure connection ( 38 ) and a preliminary stage ( 4 ) with the low pressure connection ( 66 ) is connectable, wherein the throttle valve device ( 58 ) a movable throttle element ( 156 ), that between the main piston bore ( 60 ) and one in the main piston ( 34 ) seat sleeve ( 158 ) for the direction-dependent throttling of a pressure medium flow between the high-pressure connection ( 38 ) and the spring chamber ( 44 ), characterized in that the throttle element ( 156 ) and / or the seat sleeve ( 158 ) are each symmetrically shaped with respect to a central cross-sectional plane. Pilot-controlled pressure relief valve according to claim 1, wherein the throttle element ( 156 ) in a valve chamber ( 154 ) in the longitudinal direction of the pressure limiting valve ( 1 ) is displaceably guided, wherein the valve space ( 154 ) from an annular end face ( 176 ) of the main piston ( 34 ) and a seat ( 162 ) of the seat sleeve ( 158 ) is limited, and over the seat sleeve ( 158 ) with the spring chamber ( 44 ) and via the main piston bore ( 60 ) with the high pressure connection ( 38 ) connected is. Pilot-operated pressure relief valve according to claim 1 or 2, wherein the throttle element ( 156 ) is a nozzle plate, which from a nozzle bore ( 163 ) with a smaller diameter than the main piston bore ( 60 ) is penetrated, wherein the nozzle bore ( 163 ) from the seat sleeve ( 158 ) lifted throttle element ( 156 ) Is bypassed by the flow around. Pilot-operated pressure relief valve according to claim 2 or 3, wherein the annular end face ( 176 ) of the main piston ( 34 ) Wells ( 180 ), through which the throttle element ( 156 ) in the ring end face ( 176 ) adjacent state is flowed around. Pilot-operated pressure relief valve according to claim 4, wherein the depressions ( 180 ) of the annular end face ( 176 ) of the main piston ( 34 ) as to a longitudinal axis ( 8th ) offset in parallel spacing holes ( 180 ) are formed. Pilot operated pressure relief valve according to claim 5, wherein three bores ( 180 ) are provided, which at the same radial distance with respect to the longitudinal axis ( 8th ) and uniformly in the circumferential direction of the annular end face ( 176 ) are arranged. Pilot-controlled pressure relief valve according to one of claims 1 to 6, wherein the throttle element ( 156 ) at least one flattening on the circumference ( 178 ), which limits a Umströmungsquerschnitt. Pilot operated pressure relief valve according to one of the preceding claims, wherein the seat sleeve ( 158 ) has an external thread and into a threaded receptacle of the hollow main piston ( 34 ) is screwed. Pilot operated pressure relief valve according to one of the preceding claims, wherein the seat sleeve ( 158 ) an inner circumferential surface ( 164 ), to which a conventional tool for mounting the seat sleeve ( 158 ) is vulnerable. Pilot-controlled pressure relief valve according to one of the preceding claims, wherein the throttle element ( 156 ) and the seat sleeve ( 158 ) are arranged approximately coaxially with each other. Pilot operated pressure relief valve according to one of the preceding claims, wherein this has a Nachsaugfunktion.

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