EP3530891B1 - Hydraulic valve for a pivoting engine adjuster of a camshaft - Google Patents

Description

Technical area

The invention relates to a hydraulic valve, in particular for a swivel motor adjuster of a camshaft of an internal combustion engine of a motor vehicle. The invention also relates to a valve for a swivel motor adjuster of a camshaft and a method for operating a valve for a swivel motor adjuster of a camshaft.

State of the art

The one from the DE 10 2006 012 775 A1 known swivel motor adjustment system, the pressure chambers of the rotor are provided with check valves, so that pressure peaks, such as those that occur with a rapid adjustment, are used. From the EP 2 375 014 A1 as well as the EP 2 905 434 A1 It is known to integrate check valves for utilizing camshaft alternating torques in the central valve by attaching band check valves to the inside of the bushing. At the two working connections and at the supply connection of the socket, a band check valve presses from the inside against the inside of the socket. If there is a sufficiently high pressure at the corresponding connection, the band check valve opens so that hydraulic fluid flowing into the central valve at one working connection can be fed together with hydraulic fluid from the supply connection to the other working connection.

Starting from a middle position of the central valve, a switching position can first be proportionally controlled, in which the pressure peaks of the working connection to be relieved are blocked with respect to the working connection to be loaded. A further switching position for using the camshaft alternation torques can be controlled in each connection.

The DE 10 2008 055 175 A1 discloses a hydraulic valve for a swivel motor adjuster, which has check valves arranged in the piston in the form of ball seat valves for utilizing camshaft alternating torques.

From the DE 10 2010 005604 A1 It is known to integrate a double check valve into a hydraulic valve and to arrange control edges of a piston in such a way that in the end positions of the piston a flow of pressure medium from the pressure medium pump to a first working chamber and a flow through the double check valve from a second working chamber into the first working chamber is possible is.

From the DE 19 10 392 U a fully hydraulic braking device with no control edges can also be found.

Furthermore, from the EP 2 796 673 A1 a central valve for a swivel motor adjuster can be found, the piston of which has one or more check valves on its outside for utilizing camshaft alternating torques.

Disclosure of the invention

One object of the invention is to create a valve for a swivel motor adjuster which, in a simple and compact design, enables better system behavior of a swivel motor adjuster, and to provide an efficient concept of a valve and a method for operating a valve of a camshaft adjuster that has improved cold behavior , ie enables an improved function in the lower temperature range.

The aforementioned objects are achieved in accordance with the independent claims.

Favorable configurations and advantages of the invention emerge from the further claims, the description and the drawing.

A valve for a swivel motor adjuster of a camshaft is proposed, with a bushing with a piston arranged displaceably in a bore along a longitudinal direction between a first end position and a second end position, a supply connection for supplying a hydraulic fluid, at least one first working connection and a second working connection, and at least one tank drain port for discharging the hydraulic fluid, the first working port and the second working port being designed to be fluidly connectable to one another by suitable positioning of the piston, and the piston having outer annular webs arranged at its axially outer ends in order to surround the tank drain port in the first and the second to completely close the second end position, wherein in the first end position the connection between the first working connection and the tank drain connection and in the second end position the connection between d The second working connection and the tank drain connection are throttled without a control edge. The throttling of the respective connection between the working connection can be switched or controlled.

In this way, for example, the technical advantage can be achieved that on the one hand the so-called fast phaser function and also an improved function in the lower temperature range can be ensured in a valve. As stated by way of example, in a camshaft adjuster of the vane cell type, hydraulic communication paths are provided from one chamber via a valve into an opposite chamber. Depending on the control behavior of the valve, the connecting paths can be used for alternating flow, whereby hydraulic fluid flows out of the first chamber as well as flows into the second chamber of the vane adjuster. Accordingly, the fluid can also flow out of the second chamber and flow into the first chamber. In order to accelerate the system behavior of the camshaft adjuster, the fast phaser function provides a bypass, which enables the fluid to be quickly diverted directly from the first chamber into the second chamber or vice versa. Check valves can also be used to ensure that the bypass function is only possible above a certain threshold value. The improved function in the lower temperature range results from the arrangement according to the invention of the outer ring webs, which in the end positions of the piston completely close the respectively assigned tank outflow, but throttled the opposite tank outflow without control edges. The control edge-free throttling of the opposite tank outlet has the advantage, for example, that the oil exchange works well even with viscous cold oil. Overall, the valve according to the invention results in a slightly reduced adjustment speed in the lower speed range compared to a pure fast phaser valve. In addition, there is a significant increase in the adjustment speed in the upper speed range, as well as the improved function already carried out in the lower temperature range.

The switchable or controllable throttling of the respective connection between the working connection and the tank drain connection can in particular ensure the hydraulic clamping of the swivel motor adjuster in the middle position and the control quality of the hydraulic valve. For example, the tank outflow can be throttled less in the end positions than in the remaining positions. The respective pressure chamber can thus be emptied more quickly in the end position.

In order to precisely control the closing and opening of the tank outflow connections, the socket has two groove-shaped recesses in the region of the bore, which are each assigned to the outer ring webs. The fluid flow can be switched or controlled through an annular gap which can be formed between an outer annular web and an associated groove-shaped recess. For example, the groove-shaped recesses are made wider than the wall thickness of the outer ring webs. As a result, the flow rate of the fluid can be precisely controlled as long as there is an outer ring web in the area of the groove-shaped recess. As soon as an outer ring web is positioned in front of or behind the groove-shaped recess, the respective tank drain is closed.

According to a preferred embodiment, the groove-shaped recesses are each arranged in the longitudinal direction between the working connection and the tank drain connection. In this way, for example, a particularly compact design of the valve is realized.

In order to additionally ensure the desired fast phaser function of the valve, the piston has two inner ring webs between the outer ring webs, which are each assigned to the first working connection and the second working connection. The inner ring webs are arranged spaced inwardly from the outer ring webs in the longitudinal direction of the piston. They are made wider in relation to the outer ring webs, since they have to completely close the working connections, depending on their position. Arranged directly on the inner ring webs are check valves which determine the threshold value for releasing the bypass.

According to an advantageous embodiment, in the first end position or the second end position, a distance between an outer diameter of the respective outer ring web and a groove base of the respective groove-shaped recess is smaller than a distance between the groove side surfaces of the groove-shaped recess and the end faces of the ring land. As a result, a control edge-free throttling of the tank outflow connection can be made possible such that the pressure chamber of the swivel motor adjuster connected to the tank outflow connection can be emptied more quickly in the end positions.
Control edge-free means that the throttling of the tank outflow is achieved almost solely by an annular surface between the annular web and the groove-shaped recess. The throttling is accordingly produced by the annular gap described, not by the control edges formed on the bushing and annular webs.

In order to achieve a particularly stable or constant volume flow in the direction of the tank drain connection in the end positions, a ratio A2 to A1 greater than 1.4 to 1 is preferably provided. This can significantly increase process reliability in production.

According to a preferred embodiment, the piston can be moved into a first position, the tank outflow connection of both working connections being designed to be closed by the outer annular webs. The second working port is designed to be fluidly connectable to the supply port and the first working port to the second working port. This first position is part of the classic control range of a fast phaser valve. The tank drain connections are closed. So that the working connection can be connected to the second working connection (fast phaser function), only a certain threshold value has to be exceeded so that the associated check valve is opened and a fluid flow takes place directly from the first working connection to the second working connection.

In order to suppress any fluid flow and to enable a stable operating state of an internal combustion engine at constant speed, the piston can be moved into a second position, the tank drain connection of both working connections being closed by the outer ring webs and the first working connection and the second working connection each being closed by the inner one Ring webs are formed closed.

According to an additional embodiment, the piston can be moved into a third position, the tank outflow connection of both working connections being designed to be closed by the outer annular webs. The first working port is designed to be fluidly connectable to the supply port and the first working port to the second working port.

According to an advantageous embodiment, the first working port and the second working port are each assigned a check valve and the first working port and the second working port can be alternately connected to one another and / or to the supply port and / or the tank drain port by moving the piston via at least one of the check valves. The check valve (s) can be arranged, for example, on an outside of the piston.

According to a further aspect, the object is achieved with a method for operating a valve according to one of the preceding embodiments. Here, in the first end position, the tank drain connection of the second working connection is completely closed by an outer ring web. The tank outflow connection of the first working connection is throttled through an annular gap between an outer annular web and a groove-shaped recess without control edges, and the first working connection is fluidly connected to the second working connection. In addition, the second working connection is fluidly connected to the supply connection. The advantages resulting from the method for operating a valve are comparable with the advantages from the valve or from the hydraulic valve. On the one hand, they concern an improvement in the so-called fast phaser function and an improved function in the lower temperature range within the valve. In order to accelerate the system behavior of the camshaft adjuster, the method provides a fast phaser function via a bypass, which enables the fluid to be quickly diverted directly from the first chamber to the second chamber or vice versa. An improved function in the lower temperature range results from the operation of the valve according to the invention with the outer ring webs, which in the end positions of the piston completely close the respectively assigned tank drain connection, but throttled the opposite tank drain connection free of control edges. The control edge-free throttling of the opposite tank drain connection has the advantage, for example, that the oil exchange works well even with viscous cold oil. Overall, the method according to the invention results in a slightly reduced adjustment speed in the lower speed range compared to operating a pure fast phaser valve. In addition, there is a significant increase in the adjustment speed in the upper speed range, as well as the improved function already carried out in the lower temperature range.

A preferred embodiment relates to the method for operating the valve, the tank outflow connection of both working connections being completely closed by the outer annular webs in a first position. Furthermore, the first working connection fluidly connected to the second working connection, and the second working connection is fluidically connected to the supply connection. This results in the technical advantage, for example, that the valve is located exclusively in the control range of a fast phaser function, with leakage in the direction of the tank drain connection being suppressed.

In a further embodiment, in a second position, the tank outflow connection of both working connections is completely closed by the outer annular webs, and the first working connection and the second working connection are each fluidly closed by the inner annular webs. As a result, for example, the technical advantage is achieved that the fluid flow is suppressed and a stable operating state is made possible.

In the third position, the tank outflow connection of both working connections is completely closed by the outer ring webs, the first working connection is fluidly connected to the second working connection, and the first working connection A is fluidically connected to the supply connection P.

According to a further embodiment, the tank drain port of the first working port is completely closed by an outer annular web in the second end position and the tank drain port of the second working port is throttled free of control edges by an annular gap between an outer annular web and a groove-shaped recess.
In order to make the functionality of the valve particularly efficient, the piston is moved continuously between the first end position and a second end position.

Brief description of the drawings

Further advantages emerge from the following description of the drawings. In the drawings, an embodiment of the invention is shown. The drawings, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

It shows by way of example:

Fig. 1

a hydraulic valve for adjusting a swivel motor adjuster according to an embodiment of the invention in a first switching position, shown in a longitudinal section;

Fig. 2

the hydraulic valve according to Figure 1 in perspective view;

Fig. 3

a circuit diagram of the hydraulic valve according to Figure 1 ;

Fig. 4

a piston assembly of the hydraulic valve according to Figure 1 in perspective view;

Fig. 5

the piston assembly according to Figure 4 in longitudinal section;

Fig. 6

a socket of the hydraulic valve according to Figure 1 in longitudinal section;

Fig. 7

a characteristic of the hydraulic valve according to Figure 1 and

Fig. 8

an enlarged section of the hydraulic valve according to Figure 1 in the first switching position, shown in a longitudinal section.

The following description applies to both valves and hydraulic valves. Each valve can be designed as a hydraulic valve and each hydraulic valve can be designed as a valve.

Embodiments of the invention

In the figures, the same or similar components are numbered with the same reference symbols. The figures show only examples and are not to be understood as restrictive.

Figure 1 shows a hydraulic valve 1 for adjusting a swivel motor adjuster, not shown, according to an exemplary embodiment of the invention in a first switching position 10, shown in a longitudinal section. The hydraulic valve 1 comprises a bushing 2 with a piston 4 arranged displaceably in a bore 3 along a longitudinal direction L. The piston 4 is supported by a helical compression spring 5 on the bushing 2 or on a washer 6 arranged by a ring 7 in the bushing 2 .

The socket 2 has a supply connection P for supplying a hydraulic fluid and a first working connection A and a second working connection B, which are each provided as a radial recess or a plurality of radial recesses in the socket in the sequence A - P - B. The supply connection P is protected from contamination by a sieve 8 arranged on the outside of the socket 2. Furthermore, a band check valve 9 is arranged on the inside of the socket in the area of the supply termination in order to prevent a backflow of hydraulic fluid in the direction of the pump.

The hydraulic valve 1 comprises a first and a second tank outflow connection T1, T2 for discharging the hydraulic fluid, which are each formed axially. The tank outflow connections T1 and T2 can alternatively be connected to one another, for example, via a central bore in the piston 4, so that the entire tank outflow connection can take place via a single tank outflow connection T. The described Tank outflow connections T1 and T2 are understood in this case as a tank outflow assigned to the respective working connection A or B, both being led out of the valve by means of the single tank outflow connection T.

The first working port A and the second working port B are each assigned a check valve 15, 16, the first working port A and the second working port B by moving the piston 4 via at least one of the check valves 15, 16 alternately with one another and / or with the supply port P and / or can be connected to one of the tank outflow connections T1, T2.

According to the invention, the hydraulic valve 1 has five switching positions 10-14, wherein in a first, in Figure 1 switching position 10 of the piston 4, the second working connection B via the bore 3 and an annular space 17 formed therein around the piston 4 with the supply connection P and the first working connection A via the bore 3 and a fluid path between a first piston attachment 18, which will be explained in more detail below and the inside of the socket is connected to the first tank drain port T1.

On the opposite side of the piston 4, an outer annular web 27 completely closes the second tank outflow connection T2. The first switching position can also be understood as the first end position of the piston 4.

If a pressure applied to the first working port A exceeds a certain threshold value, a fluid path can also be opened from the first working port A to the second working port B via the check valve 15 assigned to the first working port A, and the hydraulic fluid becomes in a fast-phaser characteristic second working connection B passed through.

In a second switching position 11 of the piston 4, the second working connection B is connected to the supply connection P and a connection between the first working connection A and the first tank outflow connection T1 is interrupted by the piston attachment 18, in particular by the outer annular web 25, whereby In this position, too, the fluid path from the first working connection A to the second working connection B can be opened via the check valve 15 assigned to the first working connection A. The tank outflow connection T2 is also closed by the annular web 27, which is arranged on the piston attachment 19. In this position, the hydraulic valve 1 has a pure fast phaser characteristic. This second switching position can also be understood as the first position of the piston 4 within the control range of the fast phaser characteristic.

In a third switching position 12 of the piston 4, the latter is positioned in a central position in which a connection between the working connections A, B and the supply connection P and the tank outflow connections T1, T2 is completely interrupted. This third switching position can also be understood as the second position of the piston 4 within the control range of the fast phaser characteristic.

In a fourth switching position 13 of the piston 4, the first working connection A is connected to the supply connection P and a connection between the second working connection B and the second tank outflow connection T2 is interrupted by a second piston attachment 19, in particular by the outer annular web 27. A fluid path from the second working connection B to the first working connection A can be opened via the check valve 16 assigned to the second working connection B by a pressure exceeding a threshold value. The tank outflow connection T1 is also closed by the annular web 25, which is arranged on the piston attachment 18. This third switching position can also be understood as the third position of the piston 4 within the control range of the fast phaser characteristic.

In a fifth switching position of the piston 4, the latter is in a second end position. Here the first working connection A is via the bore 3 and an annular space 17 formed therein around the piston 4 with the supply connection P and the second working connection B is via the bore 3 and a fluid path between the second piston attachment 19 and the inside of the bushing, which will be explained in more detail below connected to the second tank drain port T2. On the opposite side of the piston 4, an outer ring web 25 closes the second tank outflow connection T1 complete. The fifth switching position can also be understood as the second end position of the piston 4.

If a pressure applied to the second working connection B exceeds a certain threshold value, a fluid path can also be opened from the second working connection B to the first working connection A via the check valve 16 assigned to the second working connection B.

How in particular Figure 5 As can be seen, the first working port A and the second working port B are each assigned a check valve 15, 16 on the outside of the piston 4. These are each arranged on the piston attachments 18, 19, which surrounds the piston 4 and is rigidly connected to the piston 4, for example by pressing or welding. This enables a construction of the hydraulic valve that is as compact as possible, and the piston assembly 20 that is produced in this way can be designed simply and inexpensively.

The check valves 15, 16 are each provided as disc-shaped closing bodies which are pretensioned against the piston attachments 18, 19 by a common compression spring 21 and thus close openings 22, 23 through which hydraulic fluid can be passed through the check valves 15, 16 from the pressure threshold described above . In this way, a preassembled piston assembly 20 can advantageously be provided, which can be easily installed in the socket 2.

Axial projections 46, 47 of the check valves 15, 16 allow secure axial displacement on the piston 4.

The piston attachments 18, 19 each have two inner ring webs 24, 25 and two outer ring webs 26, 27, which each have two control edges 28, 29, 30, 31, 32, 33, 34, 35 that interact with recesses in the bushing 2. By means of these control edges 28 to 35, the volume flow of the hydraulic fluid can be controlled in an improved manner in such a way that a significant increase in the adjustment speed, in particular in the upper speed range, as well as a better force behavior is achieved becomes.

The control edges 28 to 35 of the inner and outer annular webs 24 to 27 interact with the working connections A, B as radial recesses 38, 39 in the socket 2 and two groove-shaped recesses 36, 37 in the area of the bore 3, the groove-shaped recesses 36 , 37 are arranged in the axial direction between the working port A or B and the associated tank drain port T1 or T2. The groove-shaped recesses 36, 37, in conjunction with the control edges 28 to 30 and 33 to 35, allow the tank drain connections T1, T2 to be opened and closed depending on the position 19 and the inside of the socket, a fluid path is opened between the first and the second working connection A or with the first and the second tank outflow connection T1 and T2, respectively. The in Figure 1 The first switching position 10 shown, the outer annular web 25 of the first piston attachment 18 in the area of the groove-shaped recess 36 and a fluid flow between the annular web 25 and the inside of the socket in the direction of the tank drain connection T1 is possible.
How out Figure 8 As can be seen, which shows an enlarged section of the hydraulic valve 1 in the first switching position 10 or the first end position, in this first end position a distance A1 between an outer diameter 50 of the annular web 25 and a groove base 51 of the groove-shaped recess 36 is smaller than a Distance A2 between groove side surfaces 52, 53 of groove-shaped recess 36 and end faces 54, 55 of annular web 25. For the defined control of the tank outflow in direction T1, it is provided that distance A1 is smaller than distance A2, so that a ratio of A2 to A1 is greater than 1.4 to 1. This creates a control edge-free throttle point or orifice with a fluid flow in the direction of the tank outflow connection T1, which is only constant in the end positions. Control edge-free means that the throttling of the tank outflow is achieved almost solely by an annular surface between the annular web 25 (or 27 in the fifth switching position or second end position) and the groove-shaped recess 36 (or 37 in the fifth switching position). The throttling is therefore produced by the annular gap described, not by the on Bushing 2 and annular webs 25, 27 formed control edges.

In order to ensure the hydraulic clamping of the swivel motor adjuster in the middle position and the control quality of the hydraulic valve 1, a relatively high tank throttling is created by the described design of the piston 4 and the bushing 2 outside the end positions 10, 14. In the end positions, however, the respective pressure chambers can be quickly emptied.
The specified ratio between A2 and A1 thus enables a lower throttling of the fluid flow in the direction T1 in the first end position shown, this lower throttling being able to be used to more quickly empty the pressure chamber of the swivel motor adjuster assigned to the working connection A. The same applies in the second end position 14 to the annular web 27 and the groove-shaped recess 37.

The outer ring web 27 of the second piston attachment 19, on the other hand, is located outside the groove-shaped recess 37, so that no fluid flow in the direction of the tank outflow connection T2 is possible through the closed control edges 34, 35.

During the second and fourth switching positions 11 and 13 of the hydraulic valve 1, both outer annular webs 25 and 27 are located outside the groove-shaped recesses 36 and 37, so that through the closed control edges 34, 35, 28, 29 no fluid flow in the direction of the tank outflow connections T1 or .T2 is possible.

Figure 7 shows the volume flow / travel characteristic curve of hydraulic valve 1. The volume flow / travel characteristic curve shows the resulting volume flow, depending on the position (five switching positions 10 to 14) of piston 4.

Lines 40 and 40 'show the volume flow from A to B and lines 41 and 41' show the volume flow from P to B during the first and second switching positions 10 and 11.

After about half the total travel, the middle position 12 is reached, in which a connection between the working connections A, B and the supply connection P is reached as well as the tank drain connections T1, T2 is completely interrupted.

Lines 42 and 42 'show the volume flow from P to A and lines 43 and 43' show the volume flow from B to A during the fourth and fifth switching positions 13 and 14.

As can be seen from the lines 44 and 44 ', the connection A to T1 is only open in the first switching position 10. The connection B to T2 is, as shown by the lines 45 and 45 ', only open in the fifth switching position 14.

Claims (16)

1. Valve (1) for a pivoting motor adjuster of a camshaft, having
   a bushing (2) with a piston (4) which is arranged so as to be displaceable in a bore (3) along a longitudinal direction (L) between a first end position and a second end position,
   a supply connection (P) for the feed of a hydraulic fluid,
   at least one first working connection (A) and one second working connection (B), and
   at least one tank outflow connection (T1, T2) for the discharge of the hydraulic fluid,
   wherein the first working connection (A) and the second working connection (B) are configured to be fluidically connectable to one another through suitable positioning of the piston,
   and wherein
   the piston (4) has outer annular webs (25, 27) arranged in each case at the axially outer ends of said piston in order to completely close the tank outflow connection (T1, T2) in the first and in the second end position respectively, wherein, in the first end position, the connection between the first working connection (A) and the tank outflow connection (T1), and, in the second end position, the connection between the second working connection (B) and the tank outflow connection (T2), is throttled in a control-edge-free manner such that the throttling can be attained virtually exclusively by means of an annular area between the annular web (25, 27) and a groove-like recess (36, 37), which is assigned to the annular web (25, 27), of the bushing (2) in the region of the bore (3).
2. Valve (1) according to Claim 1, characterized in that the groove-like recesses (36, 37) are arranged in the longitudinal direction (L) in each case between the working connection (A, B) and the tank outflow connection (T1, T2).
3. Valve (1) according to either of Claims 1 and 2, characterized in that the piston (4) has, between the outer annular webs (25, 27), two inner annular webs (24, 26) which are respectively assigned to the first working connection (A) and to the second working connection (B).
4. Valve (1) according to either of Claims 2 and 3, characterized in that, in the first end position and/or the second end position, a spacing (A1) between an outer diameter (50, 60) of the respective outer annular web (25, 27) and a groove base (51, 61) of the respective groove-like recess (36, 37) is configured to be smaller than a spacing (A2) between groove side surfaces (52, 53, 62, 63) of the groove-like recess (36, 37) and face sides (54, 55, 64, 65) of the annular web (25, 27).
5. Valve (1) according to Claim 4, characterized in that a ratio A2:A1 of greater than 1.4:1 is provided.
6. Valve (1) according to any of Claims 1 to 5, characterized in that the piston (4) can be moved into a first position, wherein the tank outflow connection (T1, T2) of both working connections (A, B) is configured to be closed by the outer annular webs (25, 27) and the second working connection (B) is configured to be fluidically connectable to the supply connection (P) and the first working connection (A) is configured to be fluidically connectable to the second working connection (B).
7. Valve (1) according to any of Claims 1 to 6, characterized in that the piston (4) can be moved into a second position, wherein the tank outflow connection (T1, T2) of both working connections (A, B) is configured to be closed by the outer annular webs (25, 27) and the first working connection (A) and the second working connection (B) are each configured to be closed by the inner annular webs (24, 26).
8. Valve (1) according to any of Claims 1 to 7, characterized in that the piston (4) can be moved into a third position, wherein the tank outflow connection (T1, T2) is configured to be closed by the outer annular webs (25, 27) and the first working connection (A) is configured to be fluidically connectable to the supply connection (P) and the first working connection (A) is configured to be fluidically connectable to the second working connection (B).
9. Valve (1) according to any of Claims 1 to 8, characterized in that the first working connection (A) and the second working connection (B) are assigned a respective check valve (15, 16), and the first working connection (A) and the second working connection (B) are connectable alternately to one another, and/or to the supply connection (P) and/or to the tank outflow connection (T1, T2), via at least one of the check valves (15, 16) by means of a displacement of the piston (4).
10. Pivoting motor adjuster having a valve (1) according to any of the preceding claims, wherein the valve (1) is provided as a central valve.
11. Method for operating a valve (1) according to any of Claims 1 to 10, wherein, in the first end position,
    the tank outflow connection (T2) of the second working connection (B) is completely closed by an outer annular web (27),
    the tank outflow connection (T1) of the first working connection (A) is throttled in a control-edge-free manner by means of an annular gap between an outer annular web (25) and a groove-like recess (36) such that the throttling is attained virtually exclusively by means of an annular area between the annular web (25) and the groove-like recess (36), which is assigned to the annular web (25), of the bushing (2) in the region of the bore (3),
    the first working connection (A) is fluidically connected to the second working connection (B), and the second working connection (B) is fluidically connected to the supply connection (P).
12. Method for operating a valve (1) according to Claim 11, wherein, in the first position,
    the tank outflow connection (T1, T2) of both working connections (A, B) is completely closed by the outer annular webs (25, 27),
    the first working connection (A) is fluidically connected to the second working connection (B), and the second working connection (B) is fluidically connected to the supply connection (P).
13. Method for operating a valve (1) according to Claim 11 or 12, wherein, in the second position,
    the tank outflow connection (T1, T2) of both working connections (A, B) is completely closed by the outer annular webs (25, 27), and
    the first working connection (A) and the second working connection (B) are in each case fluidically closed off by the inner annular webs (24, 26).
14. Method for operating a valve (1) according to any of Claims 11 to 13, wherein, in the third position, the tank outflow connection (T1, T2) of both working connections (A, B) is completely closed by the outer annular webs (25, 27),
    the first working connection (A) is fluidically connected to the second working connection (B), and the first working connection (A) is fluidically connected to the supply connection (P).
15. Method for operating a valve (1) according to any of Claims 11 to 14, wherein, in the second end position,
    the tank outflow connection (T1) of the first working connection (A) is completely closed by an outer annular web (25),
    the tank outflow connection (T2) of the second working connection (B) is throttled in a control-edge-free manner by means of an annular gap between an outer annular web (27) and a groove-like recess (37) such that the throttling is attained virtually exclusively by means of an annular area between the annular web (27) and the groove-like recess (37), which is assigned to the annular web (27), of the bushing (2) in the region of the bore (3),
    the first working connection (A) is fluidically connected to the second working connection (B), and the first working connection (A) is fluidically connected to the supply connection (P).
16. Method for operating a valve (1) according to any of Claims 11 to 15, wherein the movement of the piston (4) between the first end position and a second end position takes place in continuously variable fashion.

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