JPS587007B2 - 3 way valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a three-way valve, and more particularly to a three-way valve suitable for a fluid pressure drive device for a circuit breaker, etc., which is equipped with a reciprocating spool within a valve body.

Conventionally, as a three-way valve used for switching between high pressure and low pressure, a valve body having a high pressure port, a control port, and a kunk port has a valve body that alternately communicates and disconnects between the high pressure port and the control port, and between the control port and the kunk port. A structure in which a spool with two poppets is arranged is known.

This type of 3-way valve is a so-called 2-position 3-port valve,
The reciprocating drive mechanism causes the spool to reciprocate. For example, when the spool is positioned at one position, the high pressure port and control port communicate with each other, and the low pressure side poppet disconnects the control port and the kunk port, causing the control port to open to high pressure. Then,
Conversely, if you position the spool in the other position,
The high pressure port and the control port are shut off by the high pressure side poppet, the control port and the tank port are communicated, and the control port becomes low pressure.

In such three-way valves, a certain amount of time is required to move the spool from one position to the other.

For this reason, a time delay occurs from when a high voltage/low pressure switching command is input until the switching operation is completed.

In fluid pressure equipment that requires high-speed operation, such as circuit breaker drive devices, it is necessary to minimize the time required for this switching.

The switching time can be shortened by increasing the moving speed of the spool, but there is a limit to this.

Assuming that the moving speed of the spool is constant, in order to shorten the switching time, it is conceivable that the switching is performed while the spool is moving from one position to the other.

To do this, for example, in the three-way valve mentioned above, the high pressure side poppet is a spool land type, and this spool land is slidably fitted from the high pressure port side to the control port side, and the control port is connected to the control port. When switching from high pressure to low pressure, the spool land fits into the fluid chamber on the control port side while the spool is moving from one position to another, thereby shutting off the high pressure port and the control port. Just do it like this.

In this way, it is possible to significantly shorten the time required to switch the control port from high pressure to low pressure.

Note that with this configuration, it is not possible to shorten the time it takes to switch the control port from low pressure to high pressure, but if the switching time can be shortened even by operation in one direction, for example, in a circuit breaker, the time required to switch the control port from low pressure to high pressure can be reduced. In particular, since the former can be done quickly, its utility value is extremely high.

However, with the above configuration, the high pressure port and the control port are shut off by the fitting between the spool land and the control port side fluid chamber, so high pressure fluid is likely to leak from this fitting surface. In order to eliminate this leakage, it is necessary to process the outer circumferential surface of the spool land and the inner circumferential surface of the control port side fluid chamber with extremely high precision, which has the disadvantage of high manufacturing costs.

The object of the present invention is to eliminate the above-mentioned drawbacks and to provide a three-way system that does not require high-pressure fluid leakage and that does not require high processing accuracy, although it can significantly shorten the time it takes to switch the control port from high pressure to low pressure. There is a valve to provide.

In order to achieve this object, the present invention forms a cavity in which a high-pressure side poppet is slidably fitted between a high-pressure port-side fluid chamber and a control port-side fluid chamber of a valve body; a first valve seat on which the high pressure side poppet is seated, and a second valve seat on which the low pressure side poppet is directly seated between a control port side fluid chamber and a tank port side fluid chamber of the valve body. When a valve seat is formed and the low-pressure side poppet is seated on the second valve seat, the high-pressure side poppet is in a non-fitted state with the cavity, and there is a gap between the high-pressure port and the control port. is in a communicating state, and the control port and the Kunku port are in a disconnected state. From this state, the spool moves toward the tank port, and after the low-pressure side poppet is separated from the second valve seat, the high-pressure side poppet is closed. At the initial stage of the spool stroke until reaching the entrance of the cave, the high pressure port, control port and tank port are in communication at the same time, and the high pressure side poppet reaches the entrance of the cave and is connected to the cave. 1st after mating
At the stage of the spool stroke until the spool is seated on the valve seat, the high pressure port and the control port are in a disconnected state;
It is characterized in that the control port and the tank port are configured to be in communication with each other.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In these figures, 1 is a valve body and 2 is a spool.

The valve body 1 has three ports: a high pressure port 3, a control port 4, and a tank port 5.
4 and 5 communicate with a high pressure port side fluid chamber 6, a control port side fluid chamber 7, and a tank port side fluid chamber 8, respectively.

The spool 2 also includes a high-pressure poppet 9 that communicates and disconnects the high-pressure port-side fluid chamber 6 and the control port-side fluid chamber 7, and a high-pressure side poppet 9 that communicates between the control port-side fluid chamber 7 and the tank port-side fluid chamber 8. It has a low pressure side poppet 10 that shuts off.

A valve seat 11 is formed between the control port side fluid chamber 7 and the tank port side fluid chamber 8 of the valve body 1, on which the tapered surface 10a of the low pressure side poppet 10 is seated.

The taper angles of the tapered surface 10a and the valve seat 11 are both α (see FIG. 2), and the control port side fluid chamber 7 and the crank port side fluid chamber 8 are reliably isolated by this tapered surface engagement.

Further, a cavity 12 is formed between the high pressure port side fluid chamber 6 and the control port side fluid chamber 7 of the valve body 1, into which the high pressure side poppet 9 is slidably fitted. At the back is a valve seat 13 on which the tapered surface 9a of the high pressure side poppet 9 is seated.
is formed.

Although the inner diameter d1 of the cavity 12 is 2δ larger than the outer diameter d2 of the high-pressure poppet 9 (see FIG. 2), this gap δ prevents the high-pressure poppet 9 from sliding within the cavity 12. It is desirable to make it as small as possible.

Further, the depth X of the cavity 12 is smaller than the reciprocating stroke 2 of the spool 2, and the difference y is set so that y>δ.

The taper angle between the tapered surface 9a of the high pressure side poppet 9 and the valve seat 13 is β, and the high pressure port side fluid chamber 6 and the control port side fluid chamber 7 are reliably isolated by this tapered surface engagement.

Note that α and β are selected as appropriate, but may be the same value.

In order to reciprocate the spool 2 from side to side, both poppets 9,
Spool shafts 14 and 15 are integrally formed on the outside of 10, respectively.

One spool shaft 14 is slidably fitted into the fluid chamber 16, and its end surface serves as a pressure receiving end surface 14a.

The other spool shaft 15 passes through the fluid chamber 17 and is slidably fitted to the end of the valve body 1.

The outer end of the low-pressure poppet 10 is slidably fitted into the fluid chamber 17, and its outer end surface serves as a pressure receiving end surface 10b.

The pressure receiving area of the pressure receiving end surface 14a of the spool shaft 14 is larger than that of the pressure receiving end surface 10b of the low pressure side poppet 10.

When operating this three-way valve, the high pressure port 3 is connected to the high pressure fluid source 18, the tank port 5 is connected to the tank 19, and the control port 4 is connected to the opposite side of the cylinder tube 21 of the fluid pressure cylinder 20 to be controlled. connected to the side.

22 and 23 are a piston and a piston rod of the fluid pressure cylinder 20, respectively.

The rond side of the cylinder tube 21 is connected to the high pressure fluid source 18 .

Further, the fluid chamber 16 is connected to a high pressure fluid source 18 via a pilot valve 24, and the fluid chamber 17 is directly connected to the high pressure fluid source 18.

Next, the operation of this three-way valve will be explained.

FIG. 2a shows the spool 2 located on the right side.

This is the same state as in FIG. That is, the low pressure side poppet 10 is seated on the valve seat 11, the control port side fluid chamber 7 and the tank port side fluid chamber 8 are cut off, and the high pressure port side fluid chamber 6 and the control port side fluid chamber 7 are disconnected. It's communicating.

Therefore, the control port 4 is under high pressure, and the piston 22 of the fluid pressure cylinder 20 is pushed toward the rond side.

In this case, the pilot valve 24 is off (not shown, but the fluid chamber 16 and the tank 19 are in communication with each other),
The spool 2 is pushed to the right by the pressure applied to the pressure-receiving end surface 10b of the low-pressure side poppet 10 in the fluid chamber 17.

When a switching command is input to the pilot valve 24 in this state, the pilot valve 24 is instantly turned on (a state that communicates the fluid chamber 16 with the high-pressure fluid source 18), and high-pressure fluid flows into the fluid chamber 16.

As a result, the spool 2 begins to move to the left due to the difference in pressure receiving area between the spool shaft 14 and the low-pressure poppet 10.

Fig. 2b shows that the spool 2 has moved by y out of the total stroke 2, and the inner end of the cylindrical outer circumferential surface of the high-pressure side poppet 9 is in the hollow part 1.
This shows a state that corresponds to the entrance of No. 2.

In the movement up to this point, the gap between the high-pressure side poppet 9 and the entrance of the cavity 12 is only gradually narrowed, and high-pressure fluid flows from the high-pressure port side fluid chamber 6 to the control port side fluid chamber 7.

However, when the spool 2 comes to the position shown in FIG.
The flow of high pressure fluid from the high pressure port side fluid chamber 6 to the control port side fluid chamber 7 is almost eliminated.

In the subsequent strokes, the gap between the control port side fluid chamber 7 and the tank port side fluid chamber 8 only increases, so the fluid on the opposite side of the cylinder tube 21 is released at the beginning of the stroke of the spool 2. Ejection starts from the stage , and therefore the piston 22 starts moving within a short time after the switching command is input.

FIG. 2C shows the spool 2 having traveled a full stroke 2.

In this state, the tapered surface 9a of the high-pressure side poppet 9 is seated on the valve seat 13 at the back of the cavity 12, and the high-pressure boat side fluid chamber 6 and the control port side fluid chamber 7 are completely cut off.

The above operation is shown in a graph as shown in FIG.

The broken line A shows the change in the amount of inflow from the high pressure port side fluid chamber 6 to the control port side fluid chamber 7, and the broken line B shows the change in the flow rate from the high pressure port side fluid chamber 6 to the control port side fluid chamber 7.
The solid line C shows the change in the actual inflow and outflow from the control port side fluid chamber 7, which is the sum of both A and B.

According to this graph, a reversal from inflow to outflow occurs in the control port side fluid chamber 7 until the displacement of spool 2 reaches y, and after y only outflow occurs, and the amount depends on the displacement of spool 2. It can be seen that it increases proportionately.

The inflow of high pressure fluid from the high pressure port side fluid chamber 6 to the control port side fluid chamber 7 stops at the initial stage of displacement of the spool 2, and after that, the high pressure fluid flows out from the control port side fluid chamber 7 to the tank port side fluid chamber 8. This means that the control target can be switched more quickly.

According to the above embodiment, not only can the control port switch from high pressure to low pressure quickly, but also the high pressure side poppet is located at the valve seat deep in the cavity at the cutoff position of the high pressure port side fluid chamber and the control port side fluid chamber. Since the fluid chamber on the high pressure port side and the fluid chamber on the control port side are completely cut off, no leakage of high pressure fluid occurs. Since a very precise fit is not required with the inner circumferential surface of The pressure drive device will be explained with reference to FIGS. 4 to 6.

In FIGS. 4 to 6, the same reference numerals as in FIGS. 1 and 2 indicate the same or equivalent parts.

The three-way valve 100 according to the present invention used in this device differs from the one shown in FIGS. 1 and 2 in that stepped spool shafts 30 and 31 are formed on the outer end surface of the high-pressure side poppet 9. , the spool shaft 30 is in the fluid chamber 32, and the spool shaft 30 is in the fluid chamber 32.
1 is slidably fitted to the end of the valve body 1, stepped spool shafts 33 and 34 are formed on the outer end surface of the low pressure side poppet 10, and the low pressure side poppet 10 is fitted into the fluid chamber 35. , the spool shaft 33 is slidably fitted into the fluid chamber 36, the spool shaft 34 is fitted slidably into the end of the valve body 1, and each spool shaft 30, 31, 33, 34
As shown in FIG. 5, packings 37, 38, 39, 40, and 41 are attached to the low-pressure side poppet 10, respectively.

The width of each pressure receiving end surface 9b, 30b, 10b, 33b is such that the hydraulic pressure acting thereon is F9, F30, F1o, respectively.
, F33 (indicated by the arrow in Figure 5a), then F1o<
It is determined that F9<F33<F9+F3o<F1o+F33.

The driving cylinder 20 for driving the circuit breaker includes a cylinder tube 21, a piston 22, and a piston rod 2.
3.

Small diameter auxiliary fluid chambers 42 are provided at both ends of the cylinder tube 21.
, 43, the auxiliary fluid chamber 42 on the rondo side communicates with the high pressure fluid source 18, and the auxiliary fluid chamber 43 on the anti-rondo side communicates with the
It communicates with the control port 4 of the direction valve 100.

A packing 44 is attached around the piston 22 to ensure sealing with the cylinder tube 21.
In addition, a truncated conical cushion member 45 is provided on both end surfaces.
46 are provided coaxially.

The cushion members 45 and 46 fit into the mouths of the auxiliary fluid chambers 42 and 43 near the stroke end of the piston 22,
This is to reduce the impact force of the piston 22.

Note that 47 and 48 are check valves, respectively, which are connected to the auxiliary fluid chamber 4.
2, 43 to the cylinder tube, and prevents fluid flow in the opposite direction.

The piston rod 23 passes through a packing 49 attached to the end of the cylinder tube 21 and is connected to the contacts of a circuit breaker (not shown).

A position valve 50 is provided on the opposite side of the cylinder tube 21 from the rod.

This position valve 50 is a 2-position, 3-way valve, and consists of a valve body 51 and a spool 52, as shown in FIG.

The valve body 51 includes a high pressure port 53, a control port 54, and a tank port 55, and these ports communicate with a high pressure port side fluid chamber 56, a control port side fluid chamber 57, and a tank port side fluid chamber 58, respectively.

The spool 52 also includes the high pressure port side fluid chamber 56,
It includes a high pressure side spool land 59 that communicates with and disconnects the control port side fluid chamber 57, and a low pressure side spool land 60 that communicates with and disconnects the control port side fluid chamber 57 and the tank port side fluid chamber 58.

A spring 61 is provided between the outer end surface of the high pressure side spool land 59 and the valve body 51 to always bias the spool 52 toward the drive cylinder 20 side.

A stepped spool shaft 62 is formed on the outer end surface of the low pressure side spool land 60, and this stepped spool shaft 62 is connected to the valve body 5.
1 and the cylinder tube 21 of the drive cylinder 20.
It is designed to be able to protrude inward.

The high pressure port 53 of this position valve 50 connects to the high pressure fluid source 18.
The control port 54 communicates with the fluid chamber 32 of the three-way valve 100, and the tank port 55 communicates with the tank 19 via the tank port side fluid chamber 8 of the three-way valve 100 (see FIG. 4).

A first pilot valve 63 operates the three-way valve 100 in response to a first command.

This first pilot valve 63 is also a type of three-way valve, and its high-pressure port 64 is connected to the high-pressure port side fluid chamber 6 of the three-way valve 100.
The control port 65 communicates with the high pressure fluid source 18 through the
It communicates with the fluid chamber 36 of the way valve 100, and the kunk port 66 communicates with the tank 19.

The first pilot valve 63 normally supplies high pressure fluid to the fluid chamber 36.
The high-pressure fluid is supplied to the fluid chamber 36, and this high-pressure fluid is discharged from the fluid chamber 36 when the first command is given.

The first pilot valve 63 in this case is required to be capable of high-speed operation because the three-way valve 100 operates at high speed in response to commands.

If high speed is strictly required, for example,
No. 1-65566 (Japanese Unexamined Patent Publication No. 148789/1989)
It is sufficient to use a force smoke drive type pilot valve as proposed by et al.

Reference numeral 67 denotes a time-limited operation type second pilot valve, which operates the three-way valve 100 in response to a second command.

This second pilot valve 67 is also a type of three-way valve, and its high-pressure port 68 communicates with the high-pressure fluid source 18 via the auxiliary fluid chamber 42 of the drive cylinder 20, and the control port 69 communicates with the fluid chamber of the three-way valve 100. 35 , and the tank port 70 communicates with the tank 19 .

The second pilot valve 67 normally makes the fluid chamber 35 of the three-way valve 100 a low pressure, and when a second command is given, the fluid chamber 35
quickly supplies high-pressure fluid to the drive cylinder 20.
The piston 22 is timed to drain the high pressure fluid in the fluid chamber 35 after switching the position valve 50 to bring the fluid chamber 32 to a low pressure.

The second pilot valve 67 does not supply high pressure fluid to the fluid chamber 35 unless the second command is given again after the second command is once turned off due to such a timed operation.

Note that an accumulator 71 for high-pressure fluid is provided in the middle of the path leading to the high-pressure fluid source 18 .

Next, the operation of this drive device will be explained.

In FIGS. 4 and 5a, the spool 2 of the three-way valve 100 is located on the right side, and the high pressure port side fluid chamber 6 and the control port side fluid chamber 7 communicate with each other, and the spool 2 of the three-way valve 100 is located on the opposite side of the drive cylinder 20. High pressure fluid is supplied from a high pressure fluid source 18 .

Therefore, the piston 22 is displaced toward the rod 23.

In this state, the control port 65 of the first pilot valve 63
is under high pressure, and the pressure receiving end surface 33b of the spool shaft 33
Hydraulic pressure F33 is acting on.

Further, the control port 69 of the second pilot valve 67 is under low pressure, and no pressure is applied to the pressure receiving end surface 10b of the low pressure side poppet 10.

Further, the control port 54 of the position valve 50 is also at low pressure, and no pressure is applied to the pressure receiving end surface 30b of the spool shaft 30.

A hydraulic pressure of F is applied to the pressure-receiving end surface 9b of the high-pressure poppet 9 (actually, hydraulic pressure is also applied to the right end surface of the low-pressure poppet 10 and the left end surface of the poppet 9, but these hydraulic pressures are almost equal). For the sake of explanation below, it is assumed that F9 pressure is applied), F9<F
33, so the spool 2 is pushed to the right.

In this state, when the first command is given to the first pilot valve 63, the control port 65 of the first pilot valve 63 communicates with the tank port 66 and discharges the fluid in the fluid chamber 36 of the three-way valve 100. , the force acting on spool 2 is only F9, and the spool moves to the left.

At this time, as explained in the above embodiment of the present invention, the high pressure port side fluid chamber 6 and the control port side fluid chamber 7 are rapidly shut off, so the fluid on the opposite side of the drive cylinder 20 is rapidly discharged. As a result, the piston 22 rapidly moves toward the opposite side.

When the piston 22 reaches near the stroke end on the anti-rond side, the piston 22 pushes the spool shaft 62 of the position valve 50 that protrudes into the cylinder tube 21, so that the position valve 50 changes from the state shown in FIG. 6a to the state shown in FIG. The state is switched to state b.

By this switching, the control port 54 of the position valve 50 communicates with the high pressure port 53, high pressure fluid is supplied into the fluid chamber 32 of the three-way valve 100, and the spool 2 is pushed to the left by the hydraulic pressure of F9+F3o. become.

Therefore, even if the first command is canceled after the piston 22 reaches the stroke end on the anti-rond side, the first pilot valve 63 returns, and high-pressure fluid is supplied to the fluid chamber 36 of the three-way valve 100, The hydraulic pressure acting on spool 2 is F
33<F9+F3o, and the spool 2 remains pushed to the left (Fig. 5b).

Note that in this state, the high-pressure side poppet 9 is seated on the valve seat 13 at the back of the cavity 12, so that no leakage of high-pressure fluid occurs, as described above.

Next, in this state, the second command is issued to the second pilot valve 67.
, the control port 6 of the second pilot valve 67
9 communicates with the high pressure port 68 and connects the fluid chamber 3 of the three-way valve 100.
5 is quickly supplied with high pressure fluid.

As a result, the hydraulic pressure acting on the spool is F9+F3o<
F33+F1o, and the spool 2 moves to the right and returns to the state shown in FIG. 5a.

As a result, the high pressure port side fluid chamber 6 and the control port side fluid chamber 7 of the three-way valve 100 are communicated with each other, so that high pressure fluid is supplied to the opposite side of the drive cylinder 20 to the piston 22.
moves to the Rondo side.

At this time, as soon as the piston 22 leaves the vicinity of the stroke end on the anti-rod side, the position valve 50 is switched from the state shown in FIG. 6b to the state shown in FIG. 6a.

As a result, the control port 54 of the position valve 50 communicates with the tank port 55, and the fluid in the fluid chamber 32 is discharged.

Therefore, the hydraulic pressure that pushes the spool 2 to the left is only F9.

Thereafter, when the second pilot valve returns to its original state due to the timed operation of the second pilot valve 67, the fluid in the fluid chamber 35 of the three-way valve 100 is discharged, and the hydraulic pressure pushing the spool 2 to the right is only from F33. becomes.

However, since F9<F33, the spool 2 remains pushed to the right.

Further, when the first command and the second command are given at the same time, the first command is always executed with priority no matter what state the piston 22 is in.

That is, as described above, when the first command is given to the first pilot valve 63, the fluid in the fluid chamber 36 of the three-way valve 100 is discharged, and when the second command is given to the second pilot valve 67, the fluid is discharged. High pressure fluid is supplied to chamber 35 .

Since F1o<F9, the spool 2 will always be pushed to the left regardless of whether high-pressure fluid is acting on the fluid chamber 32 or not.

This is nothing but the operation of the spool 2 in response to the first command.

According to the fluid pressure drive device for a circuit breaker as described above, it operates reliably in response to two types of commands, the first and second, and when the first and second commands overlap, the first Operations in response to commands can be executed preferentially.

Furthermore, since the three-way valve used can discharge the high-pressure fluid from the drive cylinder while the stroke is small, the piston startup delay time in response to the first command is short, and high-speed shutoff is possible.

As is clear from the above description, according to the present invention, a cavity into which the high-pressure side poppet fits is formed between the high-pressure port side fluid chamber and the control port-side fluid chamber, and the high-pressure A first valve seat is formed on which a side poppet is seated, and a second valve seat is formed on which the low pressure side poppet is directly seated between a control port side fluid chamber and a tank port side fluid chamber of the valve body. , when the low-pressure poppet is seated on the second valve seat, the high-pressure poppet is not engaged with the cavity, and the high-pressure port and the control port are in communication; A state is cut off between the control port and the Kunku port, and from this state the spool moves toward the tank port, and after the low-pressure poppet moves away from the second valve seat, the high-pressure poppet moves to the entrance of the cave. At the initial stage of the spool stroke, the high pressure port, the control port and the tank port are in communication at the same time, and after the high pressure side poppet reaches the entrance of the cave and engages with the cave. At the stage of the spool stroke until it seats on the first valve seat, the configuration is such that the high pressure port and the control port are in a disconnected state, and the control port and the tank port are in a communicating state, so that the stroke The high pressure fluid in the control port side fluid chamber can be discharged from the initial stage of the process, which not only makes it possible to switch the control port from high pressure to low pressure at high speed.
This has the advantage of eliminating leakage of high-pressure fluid and reducing machining accuracy.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a three-way valve according to an embodiment of the present invention, and FIG.
Figures a and b1c are diagrams for explaining the operation of the three-way valve, Figure 3 is a graph for explaining the operation of the three-way valve, and Figure 4 is a fluid pressure 1 drive for a circuit breaker using the three-way valve according to the present invention. A sectional view of the device, Figures 5a and 5b are explanatory diagrams of the operation of the three-way valve used in the device,
FIG. 6 a1b is an explanatory diagram of the operation of the position valve used in the device. 1...Valve body, 2...Spool, 3
...High pressure port, 4...Control port,
5...tank port, 6...high pressure port side fluid chamber, 7...control port side fluid chamber, 8...
... Tank port side fluid chamber, 9 ... High pressure side poppet, 10 ... Low pressure side poppet, 11.
... Valve seat, 12 ... Cavity, 13 ...
··valve seat.

Claims (1)

[Claims] 1. A valve body having a high pressure port, a control port, and a crank port, and a spool having a high pressure side poppet and a low pressure side poppet that alternately communicate and cut off communication between the high pressure port and the control port and between the control port and the tank port. In the three-way valve, a cavity in which the high-pressure side poppet is slidably fitted is formed between a high-pressure port-side fluid chamber and a control port-side fluid chamber of the valve body, and the high-pressure forming a first valve seat on which a side poppet is seated, and a second valve seat on which the low pressure side poppet is directly seated between a control port side fluid chamber and a crank port side fluid chamber of the valve body; When the low-pressure poppet is seated on the second valve seat, the high-pressure poppet is not engaged with the cavity, and the high-pressure port and the control port are in communication, and the control A state is cut off between the port and the tank port, and from this state, the spool moves toward the crank port, and after the low-pressure poppet moves away from the second valve seat, the high-pressure poppet reaches the entrance of the cave. At the initial stage of the spool stroke, the high pressure port, control port and tank port are in communication at the same time, and after the high pressure side poppet reaches the entrance of the cavity and engages with this cavity, At the stage of the spool stroke until it seats on the valve seat 1,
A three-way valve, characterized in that the high pressure port and the control port are in a cutoff state, and the control port and the tank port are in a communication state.