DE102018002286B4 - Pilot-operated switching and control valve and method for operating the same - Google Patents

Abstract

Pilot-operated switching and control valve (1), comprising at least
• an actuator (2) for external actuation of the switching and control valve (1),
• a valve sleeve (3) with a connection P for incoming fluid and one or two connections (T, T') for outgoing fluid,
• a first valve body (5) movably mounted in the valve sleeve (3) which, by means of a sealing surface (6) in cooperation with a sealing seat (4) on the valve sleeve (3), blocks or opens a first fluid connection (15) between the connection P and the connection T and increases or reduces the cross-section of the fluid connection (15) depending on its stroke,
• a pilot valve (10) which compares the force of the actuator (2) with the force of a pressure in the chamber P1, which results from the pressure at the port P reduced by a pressure difference at a supply bore (9) for the pilot valve (10),
characterized in that
the first valve body (5) has three effective surfaces (31, 32, 33), a first effective surface (31) for the pressure in the space P1, a second effective surface (32) for the pressure at the radial connection P and a third effective surface (33) for the pressure at the axial connection T, the first effective surface (31) being as large as the other two effective surfaces (32, 33) together,
and wherein the pressure force from the pressure P1 and the first effective surface (31) presses the valve body (5) into a position closing the valve (1), and wherein the pressure forces from the pressure at the connection P and the second effective surface (32) and from the pressure at the connection T and the third effective surface (33) press the valve body (5) into a position opening the valve (1),
and wherein the first valve body (5) is pressed into a position opening the valve (1) by a spring means consisting of a first spring (7) and/or a second spring (8), wherein the spring means, when the first valve body (5) is in a position closing the valve (1), End position counteracts the differential pressure force of P1 and P and wherein, at a pressure of P1 which is less than a predetermined proportion of a limit pressure required to completely close the valve (1), the valve body (5) assumes a stable position which partially or completely opens the valve (1), wherein the stroke of the valve body (5) is determined by a force equilibrium of the pressure forces of the pressures of P, P1 and T and the position-dependent force of the springs (7, 8), and wherein an opening cross-section of the fluid connection (15) from the connection P to the connection T which is dependent on the said stroke is released.

Description

The invention relates to a pilot-operated switching and control valve according to the preamble of the first patent claim, as well as a method for operating the valve.

State of the art:

Well-known and widely used are pilot-operated pressure relief valves in which a pilot valve, also called a pilot valve, controls a considerably larger main valve in order to regulate or limit the pressure in large fluid flows. The pilot valve and main valve are usually designed as seat valves.

Also well-known and widespread are pilot-operated directional valves that are pilot-operated by pressure control valves and whose main slide moves against a strong spring in proportion to the pressure difference generated by the pressure control valve, which in turn releases a cross-section for a fluid flow. Here, the main valve is usually designed as a slide valve.

Finally, pilot-operated check valves are also known, which can be opened by a hydraulic actuator. These check valves are also usually designed as seat valves.

The pilot-operated pressure relief valves preferably limit or regulate a pressure; they are not very suitable for controlling a fluid flow; in particular, they do not allow for fine control of a fluid flow because the opening of the main valve depends only on the applied pressures.

The pilot-operated directional valves mentioned allow fine control of a fluid flow, but they are not suitable for limiting pressure, especially since they are usually designed as slide valves and therefore cannot be completely tight.

The pilot-operated check valves are suitable for switching a fluid flow and they can also seal well as seat valves, but they are not suitable for fine control of a fluid flow.

Tasks:

A valve is intended to switch a fluid flow under external control, regulate and limit a pressure in a proportional manner and additionally control a fluid flow in a proportional manner.

Fluid flows of up to 12 l/min and pressures of up to 25 bar must be controlled.

When switching the fluid flow, only a small pressure difference of less than 0.8 bar should fall across the valve, so a large opening cross-section and consequently a pilot-controlled design is required. When limiting and regulating the pressure, the opening cross-section should be very well sealed so that the leakage rate is very low; for this purpose, a self-reinforcing pressure-dependent seal in the form of a seat valve should be provided.

Due to the design as a pilot-operated valve with control function, the stability of the control must be ensured in the expected temperature and pressure range.

Ultimately, the valve should take up as little space as possible and it should be able to be produced cost-effectively in large quantities.

Solution:

The objects directed to the device are solved by the features of the first claim, in conjunction with subclaims 2 to 9. The last claim describes a method for operating the valve according to the invention.

The pilot-operated switching and control valve according to the invention contains at least one actuator for external actuation of the switching and control valve, a valve sleeve with a connection P for incoming fluid and one or two connections T for outgoing fluid, a first valve body movably mounted in the valve sleeve and a pilot valve which compares the force of the actuator with the force of a pressure in the space P1.

The pressure in chamber P1 results from the pressure at port P reduced by a pressure difference at a throttling supply bore for the pilot valve and from the force of the actuator.

The pilot valve is preferably designed as a seat valve, with a second sealing seat in a disk, which also guides the second valve body, which is preferably designed as a ball. The actuator acts with its force on the second valve body.

The first valve body can, by means of a first sealing surface in cooperation with a first sealing seat on the valve sleeve, block or open a first fluid connection between the port P and the port T, and, depending on its stroke, can control the effective cross-section of the Increase or decrease the fluid connection. The valve stroke is large enough to release a large opening cross-section appropriate to the task.

The first valve body has three effective surfaces for pressures, a first effective surface for the pressure in the chamber P1, a second effective surface for the pressure at the radial connection P and a third effective surface for the pressure at the axial connection T, whereby the first effective surface is as large as the other two effective surfaces together.

The pressure force from the pressure P1 and the first effective area pushes the valve body into a position that closes the valve.

The pressure forces from the pressure at port P and the second effective area and from the pressure at port T and the third effective area press the valve body into a position that opens the valve.

When the valve is closed, the first valve body seals flatly or linearly against the first sealing seat of the valve sleeve with an at least partially axially acting sealing force, which also increases with a larger pressure difference between the P port and the T port because the associated effective surfaces are not pressure-balanced. This results in a self-reinforcing pressure-dependent sealing force, as required in the task.

The first valve body is pressed into a position that opens the valve by a spring means consisting of a first spring and/or a second spring. The spring means counteracts the force of the pressure in space P1. If the actuator on the pilot valve determines a reduced pressure in space P1 that is less than a predetermined proportion of the limit pressure required to completely close the valve, the valve body assumes a stable position that partially or completely opens the valve. The stroke of the valve body is determined by a force balance of the pressure forces of the pressures of P, P1 and T and the position-dependent force of the springs, and an opening cross-section of the fluid connection from port P to port T that depends on this stroke of the first valve body is released.

The specified proportion of the limit pressure is preferably designed to be less than 85% of the limit pressure, more preferably less than 75% of the limit pressure. The design is carried out by selecting the effective areas of the first valve body and the spring forces of the spring means.

Advantageously, the first valve body has a fine control geometry adjacent to its sealing surface, which opens up an opening cross-section dependent on the stroke of the valve body for the fluid connection between the port P and the port T. This fine control geometry is intended to reduce the increase in the opening cross-section as a function of the stroke and preferably consists of notches in the surface of the valve body. Grooves or transverse bores are also suitable.

In order to reduce the risk of vibrations when controlling the pilot-operated valve, the valve-closing movement of the first valve body is advantageously braked by a first damper pot, the damping effect being adjusted by the radial gap between the damper pot and an extension of the first valve body.

In addition to the first damper pot, a second damper pot can advantageously dampen the valve-opening movement of the first valve body, wherein the damping effect is adjusted here by the radial gap between an inner diameter of the valve body and an outer diameter of a shoulder of the disc.

The supply bore of the pilot valve also has a damping effect on the movement of the first valve body, with the damping effect being set by the diameter of the supply bore. The radial connection T', which drains the fluid from the pilot valve, can also contribute to the damping if its cross-section is suitably designed.

Furthermore, the movement of the first valve body can be braked by a change in the force of the actuator depending on the stroke of the actuator, whereby the damping effect is adjusted by the slope of the force function.

• ◯ Kennlinie des Stellorgans
• ◯ Wirkdurchmesser des zweiten Ventilkörpers (im Vorsteuerventil)
• ◯ Durchmesser der Versorgungsbohrung für das Vorsteuerventil
• ◯ Querschnitt des Anschlusses T'
• ◯ Federsteifigkeit des Federmittels zur Abstützung des ersten Ventilkörpers
• ◯ Dämpfungstopf für den Maximalhub des ersten Ventilkörpers
• ◯ Dämpfungstopf für den Minimalhub des ersten Ventilkörpers
• ◯ Abstimmung der Wirkflächen am ersten Ventilkörper
• ◯ Auslegung der Feinsteuergeometrie an dem ersten Ventilkörper

The pilot-operated valve has a high control gain, so it may be necessary to use the above and other damping measures in combination. Experience has shown that at least the following features affect the dynamics and damping of the pilot-operated valve:

• ◯ Characteristic curve of the actuator
• ◯ Effective diameter of the second valve body (in the pilot valve)
• ◯ Diameter of the supply hole for the pilot valve
• ◯ Cross section of connection T'
• ◯ Spring stiffness of the spring means supporting the first valve body
• ◯ Damping pot for the maximum stroke of the first valve body
• ◯ Damping pot for the minimum stroke of the first valve body
• ◯ Adjustment of the effective surfaces on the first valve body
• ◯ Design of the fine control geometry on the first valve body

The valve sleeve and the first valve body are advantageously made of plastic, although it may also be advantageous to manufacture only one of these components from plastic.

The actuator is preferably a proportional electromagnet which generates a force that is proportional to its coil current and only slightly dependent on the stroke of the actuator. The aforementioned dependence on the stroke can advantageously be used to dampen the control behavior of the pilot-operated valve.

1. 1. Bei einer Kraft des Stellorgans in einem ersten vorgegebenen kleinen Kraftbereich I kann sich nur ein so geringer Druck in P1 aufbauen, dass das Ventil durch die Kraft der Feder und/oder der Feder vollständig geöffnet wird, weil die Federkraft überwiegt. Hier ist es auch zulässig, dass das Stellorgan gar keine Kraft aufbringt, wenn das Stellorgan ein Elektromagnet ist, kann er in diesem Betriebszustand stromlos sein.
2. 2. Bei einer Kraft des Stellorgans in einem zweiten vorgegebenen mittleren Kraftbereich II bringen die Druckkräfte an P, P1 und T den ersten Ventilkörper in eine durch die genannten Druckkräfte und die hubabhängige Kraft der Federmittel bestimmte Lage, in der das Ventil teilweise geöffnet ist und- soweit vorhanden- eine Feinsteuergeometrie den Öffnungsquerschnitt für eine Fluidverbindung von dem Anschluss P zum Anschluss T bestimmt. Weil der erste Ventilkörper für den Druck am Anschluss P nicht druckausgeglichen aufgebaut ist, beeinflusst dieser Druck auch die Lage des ersten Ventilkörpers.
3. 3. Bei einer Kraft des Stellorgans in einem dritten vorgegebenen hohen Kraftbereich III und gleichzeitig vorhandenem ausreichend hohem Druck am Anschluss P wird der Öffnungsquerschnitt der Fluidverbindung von P nach T im Sinne einer Druckregelung vorrangig von dem Druck am Anschluss P bestimmt, wobei die genannte Druckregelung in dem Vorsteuerventil durch einen Vergleich der Druckkraft des Drucks im Raum P1 mit der Kraft des Stellorgans bewirkt wird, und die Wirkung dieser Druckregelung durch ein Zusammenwirken des von dem Druck im Raum P1 beaufschlagten ersten Ventilkörpers mit der Ventilhülse verstärkt wird.
4. 4. Bei einer hohen Kraft des Stellorgans im Vergleich zur Druckkraft am Anschluss P in einem vorgegebenen Kraftbereich IV ist das Ventil geschlossen und es kann kein Fluid vom Anschluss P zum Anschluss T abfließen.

During operation of the pilot-operated switching and control valve according to the invention, it can assume at least four different operating states depending on the force of the actuator. A schematic representation of the valve body stroke as a function of the force of the actuator shows 7 This representation also gives a rough indication of what is to be understood as a small or large force.

1. 1. When the actuator exerts a force in a first, predefined small force range I, only such a small pressure can build up in P1 that the valve is fully opened by the force of the spring and/or the spring, because the spring force predominates. Here, it is also permissible for the actuator to exert no force at all; if the actuator is an electromagnet, it can be de-energized in this operating state.
2. 2. When the actuator force is in a second predetermined medium force range II, the pressure forces at P, P1 and T bring the first valve body into a position determined by the pressure forces mentioned and the stroke-dependent force of the spring means, in which the valve is partially opened and - if present - a fine control geometry determines the opening cross-section for a fluid connection from the connection P to the connection T. Because the first valve body is not pressure-balanced for the pressure at the connection P, this pressure also influences the position of the first valve body.
3. 3. When the force of the actuator is in a third predetermined high force range III and at the same time there is a sufficiently high pressure at the connection P, the opening cross-section of the fluid connection from P to T is determined primarily by the pressure at the connection P in the sense of pressure control, wherein the said pressure control in the pilot valve is brought about by a comparison of the pressure force of the pressure in the chamber P1 with the force of the actuator, and the effect of this pressure control is reinforced by an interaction of the first valve body acted upon by the pressure in the chamber P1 with the valve sleeve.
4. 4. If the actuator force is high compared to the pressure force at port P in a given force range IV, the valve is closed and no fluid can flow from port P to port T.

Application:

The valve according to the invention is used to supply a transmission or an internal combustion engine with fluid for cooling and/or for actuating clutches.

• 1 zeigt einen Schnitt durch das erfindungsgemäße Schalt- und Regelventil in der ersten Ausführung ohne Feinsteuergeometrie.
• 2 zeigt eine Ansicht des ersten Ventilkörpers zur Darstellung der Wirkflächen
• 3 zeigt einen Schnitt durch das Schalt- und Regelventil in der zweiten Ausführung mit Feinsteuergeometrie
• 4 zeigt einen Schnitt durch eine Ausführung des Schalt- und Regelventils mit einer Feder im Ringraum um den ersten Ventilkörper
• 5 zeigt einen Schnitt durch eine Ausführung des Schalt- und Regelventils mit zwei Dämpfertöpfen
• 6 zeigt eine Detailansicht des ersten Ventilkörpers mit einer Feinsteuergeometrie
• 7 zeigt eine grafische Darstellung des Ventilkörperhubs als Funktion der Kraft des Stellorgans

Pictures

• 1 shows a section through the switching and control valve according to the invention in the first embodiment without fine control geometry.
• 2 shows a view of the first valve body to show the effective surfaces
• 3 shows a section through the switching and control valve in the second version with fine control geometry
• 4 shows a section through a design of the switching and control valve with a spring in the annular space around the first valve body
• 5 shows a section through a version of the switching and control valve with two damper pots
• 6 shows a detailed view of the first valve body with a fine control geometry
• 7 shows a graphical representation of the valve body stroke as a function of the force of the actuator

Example execution:

The pilot-operated switching and control valve (1) according to 1 contains an actuator (2) for external actuation of the switching and control valve (1), a valve sleeve (3) with a connection P for incoming fluid and two connections (T, T') for outgoing fluid, one in the valve sleeve (3) movably mounted first valve body (5) which can block or open a first fluid connection (15) between the connection P and the connection T by means of a sealing surface (6) in cooperation with a sealing seat (4) on the valve sleeve (3), a pilot valve (10) which compares the force of the actuator (2) with the force of a pressure P1 which results from the pressure at the connection P, reduced by a pressure difference at a supply bore (9) for the pilot valve (10).

The first valve body (5) has three effective surfaces (31, 32, 33), a first effective surface (31) for the pressure P1, a second effective surface (32) for the pressure at the connection P and a third effective surface (33) for the pressure at the connection T, wherein the first effective surface (31) is as large as the other two effective surfaces (32, 33) together.

The pilot valve (10) has a sealing seat (12) in a disk (11) and a second valve body (13), which is preferably designed as a ball. The disk (11) also guides the second valve body (13), and the actuator (2) acts on the second valve body.

The location of the above mentioned effective areas is shown in 2 shown.

The pressure force from the pressure P1 and the first effective area (31) presses the first valve body (5) into a position that closes the valve (1). The pressure forces from the pressure at the connection P and the second effective area (32) and from the pressure at the connection T and the third effective area (33) press the first valve body (5) into a position that opens the valve (1).

The first valve body (5) is pressed into a position that opens the valve (1) by a spring means consisting of a first spring (7) and/or a second spring (8). When the first valve body (5) is in the end position that closes the valve (1), the spring means counteracts at least half of the differential pressure force of P1 and P.
wherein the remaining differential pressure force of P1 and P presses the valve body (5) by means of its sealing surface (6) against the valve seat (4).

In 1 and 3 the spring 7 is shown, which is arranged in the connection T, and in 4 The spring 8 is shown, which encloses part of the valve body (5). Both springs can also be used in combination.

In the execution according to 3 the first valve body of the pilot-operated switching and control valve (1) has, adjacent to the sealing surface (6), a fine control geometry (14) which releases an opening cross-section for the fluid connection (15) between the connection P and the connection T, which opening cross-section is dependent on the stroke of the valve body (5).

In an advantageous embodiment according to 5 the movement of the first valve body (5) is braked by a first damper pot (21), wherein the damping effect is adjusted by the radial gap between the damper pot and an extension (23) of the first valve body.

Also in 5 the advantageous embodiment is shown in which the movement of the first valve body (5) is braked by a second damper pot (22), wherein the damping effect is set by the radial gap between an inner diameter of the valve body (24) and an outer diameter of a shoulder (25) of the disc (11).

The movement of the first valve body (5) is advantageously also braked by the supply bore (11), wherein the damping effect is adjusted by the diameter of the supply bore (11).

Also advantageously, the movement of the first valve body (5) is braked by a change in the force of the actuator (2) which depends on the stroke of the actuator (2), the damping effect being adjusted by the slope of the force function.

Advantageously, when the first valve body (5) is in the valve-closing position, the sealing force with which the sealing surface (6) of the first valve body (5) is pressed into the sealing seat (4) of the valve sleeve (2) is increased when the force difference acting on the first valve body (5) from the pressures of the connections P, P1 and T increases.

The first valve body (5) has in an advantageous embodiment according to 6 a fine control geometry (14) which is adjacent to the sealing surface (6). In the embodiment shown, the fine control geometry consists of notches, but grooves, transverse bores or other shaped elements can also be used which influence the opening cross-section for the fluid connection (14) of the valve (1) depending on the stroke of the first valve body (5).

• • Wenn das Stellorgan (2) keine oder eine sehr kleine Kraft aufbringt, kann sich in diesem Kraftbereich I nur ein sehr geringer Druck in P1 aufbauen und das Ventil (1) wird durch die Kraft der Feder (7) und/oder der Feder (8) vollständig geöffnet,
• • bei einer Kraft des Stellorgans (2) in einem zweiten vorgegebenen mittleren Kraftbereich II bringen die Druckkräfte an P, P1 und T den ersten Ventilköper (5) in eine durch die genannten Kräfte und die hubabhängige Kraft der Feder (7) und/oder der Feder (8) bestimmte Lage, in der das Ventil (1) teilweise geöffnet ist und vorzugsweise eine Feinsteuergeometrie (14) den Öffnungsquerschnitt für eine Fluidverbindung (15) von dem Anschluss P zum Anschluss T bestimmt, wobei auch die Höhe des Drucks am Anschluss P die Lage des ersten Ventilkörpers (5) beeinflusst, weil der Ventilkörper (5) für diesen Druck nicht druckausgeglichen aufgebaut ist,
• • bei einer großen Kraft des Stellorgans (2) in einem dritten vorgegebenen hohen Kraftbereich III und gleichzeitig vorhandenem ausreichend hohem Druck am Anschluss P wird der Öffnungsquerschnitt der Fluidverbindung (15) im Sinne einer Druckregelung vorrangig von dem Druck am Anschluss P bestimmt, wobei die genannte Druckregelung in dem Vorsteuerventil (10) durch einen Vergleich der Druckkraft des Drucks in P1 mit der Kraft des Stellorgans (2) bewirkt wird, und die Wirkung dieser Druckregelung wird durch ein Zusammenwirken des von dem Druck in P1 beaufschlagten ersten Ventilkörpers (5) mit der Ventilhülse (3) verstärkt,
• • bei einer sehr großen Kraft des Stellorgans (2) im Vergleich zur Druckkraft am Anschluss P in einem vorgegebenen Kraftbereich IV ist das Ventil (1) geschlossen und es kann kein Fluid vom Anschluss P zum Anschluss T abfließen.

7 shows the different working ranges of the valve (1) according to the invention depending on the force of the actuator (2):

• • If the actuator (2) applies no or only a very small force, only a very small pressure can build up in P1 in this force range I and the valve (1) is opened by the force of the Spring (7) and/or spring (8) fully opened,
• • when the actuator (2) is in a second predetermined medium force range II, the pressure forces at P, P1 and T bring the first valve body (5) into a position determined by the said forces and the stroke-dependent force of the spring (7) and/or the spring (8), in which the valve (1) is partially opened and preferably a fine control geometry (14) determines the opening cross-section for a fluid connection (15) from the connection P to the connection T, whereby the level of pressure at the connection P also influences the position of the first valve body (5) because the valve body (5) is not pressure-balanced for this pressure,
• • when the actuator (2) has a large force in a third predetermined high force range III and at the same time there is a sufficiently high pressure at the connection P, the opening cross-section of the fluid connection (15) is primarily determined by the pressure at the connection P in the sense of pressure control, wherein the said pressure control in the pilot valve (10) is brought about by a comparison of the pressure force of the pressure in P1 with the force of the actuator (2), and the effect of this pressure control is reinforced by an interaction of the first valve body (5) acted upon by the pressure in P1 with the valve sleeve (3),
• • If the force of the actuator (2) is very high compared to the pressure force at port P in a given force range IV, the valve (1) is closed and no fluid can flow from port P to port T.

List of reference symbols

1

Switching and control valve

2

Actuator

3

Valve sleeve

4

Sealing seat

5

First valve body (main valve)

6

Sealing surface

7

Feather

8th

Feather

9

Supply well

10

Pilot valve

11

disc

12

Sealing seat of the pilot valve

13

Second valve body (of the pilot valve)

14

Fine control geometry

15

Fluid connection

21

Damping pot

22

Damping pot

23

Extension

24

Inner diameter

25

Paragraph

31

First effective area on the valve body (pressure of P1)

32

Second effective area on the valve body (pressure of P)

33

Third effective area on the valve body (pressure of T)

P

Connection of supply pressure

P1

Space with intermediate pressure in front of the pilot valve

T, T'

Return pressure connections

Claims (10)

Pilot-controlled switching and control valve (1), at least containing • an actuator (2) for external actuation of the switching and control valve (1), • a valve sleeve (3) with a connection P for incoming fluid and one or two connections (T, T') for outgoing fluid, • a first valve body (5) which is movably mounted in the valve sleeve (3) and which, by means of a sealing surface (6) in cooperation with a sealing seat (4) on the valve sleeve (3), blocks or opens a first fluid connection (15) between the connection P and the connection T and increases or reduces the cross section of the fluid connection (15) depending on its stroke, • a pilot valve (10) which compares the force of the actuator (2) with the force of a pressure in the space P1 which results from the pressure at the connection P reduced by a pressure difference at a supply bore (9) for the pilot valve (10), characterized in that the first valve body (5) has three active surfaces (31, 32, 33), a first effective surface (31) for the pressure in the space P1, a second effective surface (32) for the pressure at the radial connection P and a third effective surface (33) for the pressure at the axial connection T, wherein the first effective surface (31) is as large as the other two effective surfaces (32, 33) together, and wherein the pressure force from the pressure P1 and the first effective surface (31) presses the valve body (5) into a position closing the valve (1), and wherein the pressure forces from the pressure at the connection P and the second effective surface (32) and from the pressure at the connection T and the third effective surface (33) press the valve body (5) into a position that opens the valve (1), and wherein the first valve body (5) is pressed into a position that opens the valve (1) by a spring means consisting of a first spring (7) and/or a second spring (8), wherein the spring means counteracts the differential pressure force of P1 and P when the first valve body (5) is in the end position that closes the valve (1), and wherein when the pressure of P1 is less than a predetermined proportion of a limit pressure that is required to completely close the valve (1), the valve body (5) assumes a stable position that partially or completely opens the valve (1), wherein the stroke of the valve body (5) is determined by a force balance of the pressure forces of the pressures of P, P1 and T and the position-dependent force of the springs (7, 8), and wherein an opening cross-section of the fluid connection (15) from the connection P to the connection T that is dependent on the said stroke is released. Pilot operated switching and control valve (1) according to Claim 1 , characterized in that the first valve body (5) has a fine control geometry (14) adjacent to the sealing surface (6), which opens an opening cross-section dependent on the stroke of the valve body (5) for the fluid connection (15) between the connection P and the connection T. Pilot-operated switching and control valve (1) according to one of the preceding claims, characterized in that the movement of the first valve body (5) closing the valve (1) can be dampened by a first damper pot (21), the damping effect being determined by the radial gap between the damper pot (21) and an extension (23) of the first valve body (5). Pilot-operated switching and control valve (1) according to one of the preceding claims, characterized in that the movement of the first valve body (5) opening the valve (1) can be dampened by a second damper pot (22), the damping effect being determined by the radial gap between an inner diameter of the valve body (24) and an outer diameter of a shoulder (25) of the disk (11). Pilot-operated switching and control valve (1) according to one of the preceding claims, characterized in that the movement of the first valve body (5) can be dampened by the supply bore (11) and/or the geometry of a radially designed connection T' for diverting a fluid flow from the pilot valve (10), wherein the damping effect is determined by the diameter of the supply bore (11) and/or the dimensions of the connection T'. Pilot-operated switching and control valve (1) according to one of the preceding claims, characterized in that the movement of the first valve body (5) can be dampened by a change in the force of the actuator (2) which is dependent on the stroke of the actuator (2), the damping effect being determined by the slope of the force function. Pilot-operated switching and control valve (1) according to one of the preceding claims, characterized in that when the first valve body (5) is in the valve-closing position, the force difference acting on the valve body (5) from the pressures of the connections P, P1 and T increases the sealing force with which the sealing surface (6) is pressed into the sealing seat (4). Pilot-operated switching and control valve (1) according to one of the preceding claims, characterized in that the valve sleeve (3) consists of plastic. Pilot-operated switching and control valve (1) according to one of the preceding claims, characterized in that the first valve body (5) consists of plastic. Method for operating a pilot-operated switching and control valve (1) according to Claim 1 characterized in that the switching and control valve (1) can assume at least four different operating states depending on a force of the actuator (2): • when the force of the actuator (2) is in a first predetermined small force range I, only such a low pressure can build up in P1 that the valve (1) is completely opened by the force of the spring (7) and/or the spring (8), • when the force of the actuator (2) is in a second predetermined medium force range II, the pressure forces at P, P1 and T bring the first valve body (5) into a position determined by the said forces and the stroke-dependent force of the spring (7) and/or the spring (8), in which the valve (1) is partially opened and a fine control geometry (14) determines the opening cross-section for a fluid connection (15) from the connection P to the connection T, • when the force of the actuator (2) is in a third predetermined high force range III and at the same time there is sufficiently high pressure at the connection P, the opening cross-section of the fluid connection (15) is in the sense of a Pressure control is primarily determined by the pressure at port P, said pressure control in the pilot valve (10) being carried out by comparing the pressure force of the pressure in P1 with the force of the actuator (2), and the effect of this pressure control is reinforced by an interaction of the first valve body (5) acted upon by the pressure in P1 with the valve sleeve (3), • when the force of the actuator (2) in comparison to the pressure force of P is in a high predetermined force range IV, the valve (1) is closed and no fluid can flow from the connection P to the connection T.

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