JP2002188603A - Switching valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching valve which is simple in structure of a spool and furthermore is cheap in cost without requiring to restrain a turn of the spool. SOLUTION: The switching valve is so configured that if the spool 101 is moved from neutral position, the communication between a drain port 118 and a tank oil passage 119 is shut off and simultaneously a load pressure detection port 105 and a pressure inlet port 115 are communicated with each other via sub annular groove 125 and in addition, the load pressure detection port 105 and an actuator oil passage 103 are communicated with each other via an metering notch 123 and thereafter the actuator oil passage 103 and a supplied oil passage 102 are communicated with each other via the metering notch 123.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching valve of a hydraulic control device used for a forklift or the like.

[0002]

2. Description of the Related Art A circuit diagram shown in FIG. 3 shows a lift switching valve 2 for controlling a lift cylinder and a tilt switching valve 3 for controlling a tilt cylinder in a supply passage 1 connected to a pump P.
And an attachment switching valve 4 for controlling an attachment cylinder are connected in parallel. These switching valves 2 to 4 maintain the closed position when in the illustrated neutral position, and shut off the supply flow path 1. The pilot chambers 5 to 10 of the switching valves 2 to 4 have proportional electromagnetic pressure reducing valves 1 respectively.
1 to 16 and these proportional electromagnetic pressure reducing valves 11 to 16
The pilot pressure controlled by each pilot chamber 5
To 10.

[0003] A first branch flow path 17 is connected to the supply flow path 1, and a compensator valve 18 is connected to the first branch flow path 17. This compensator valve 18
Is guiding the supply pressure of the pump P to one of the pilot chambers 18a via the damper throttle 19. A first shuttle valve 21 is connected to the other pilot chamber 18 b of the compensator valve 18 via a damper throttle 20. The second shuttle valve 22 is connected to the upstream side of the first shuttle valve 21, and the first load pressure line 24 and the connecting load pressure line 27 are connected to the upstream side of the second shuttle valve 22. A third shuttle valve 23 is connected to the communication load pressure line 27, and a second load pressure line 25 and a third load pressure line 26 are connected upstream of the third shuttle valve 23. The first to third load pressure lines 24 to
Each of 26 is provided with a fixed restrictor f to control the flow rate passing therethrough.

A second branch flow path 28 is connected to the supply flow path 1, and a flow control valve 29 is connected to the second branch flow path 28.
Are connected. A fixed throttle 30 is provided downstream of the flow control valve 29, and pressure upstream of the fixed throttle 30 is guided to one pilot chamber 29 a of the flow control valve 29 via a damper throttle 31 to provide a fixed throttle. 30 to the other pilot chamber 29b of the flow control valve 29.
To lead to. The flow control valve 29 thus configured
The spring 32 changes the differential pressure generated before and after the fixed throttle 30.
It exerts a control function that keeps the amount of spring force equivalent to and maintains a constant flow rate through it. The flow control valve 29 always supplies a constant flow rate to the second branch flow path 28 side.

[0005] A relief valve 33 for setting a primary pressure is connected to the downstream side of the second branch flow path 28 to which a constant flow rate is supplied as described above, and the pressure on the upstream side is controlled by the relief valve 33 to a predetermined value. To maintain the set pressure. Then, the primary pressure set by the relief valve 33 is guided to the proportional electromagnetic pressure reducing valves 11 to 16 and the first shuttle valve 21 via the pilot line 34 connected between the flow control valve 29 and the fixed throttle 30. ing.

The first to third load pressure lines 24 to 26 are:
When the switching valves 2 to 4 are switched, the load pressure generated in the cylinder connected to the switching valves is guided. The third shuttle valve 23 is configured to select one of the load pressure of the tilt cylinder led through the second load pressure line 25 and the load pressure of the attachment cylinder led through the third load pressure line 26. The higher load pressure is selected and guided to the second shuttle valve 22. The second shuttle valve 22 selects the higher one of the load pressure selected by the third shuttle valve 23 and the load pressure of the lift cylinder led through the first load pressure line 24. 1st shuttle valve 2
Lead to 1. That is, among the load pressures of the respective cylinders, the highest load pressure is selected by the second and third shuttle valves 22 and 23 and guided to the first shuttle valve 21.

The first shuttle valve 21 selects the higher one of the maximum load pressure of the cylinder and the primary pressure derived from the pilot line 34 and sends the selected pressure to the pilot chamber 18 b of the compensator valve 18. Supply.
When the maximum load pressure of the cylinder is guided to the pilot chamber 18b, the compensator valve 18
The opening of the switching valve is adjusted so that the differential pressure before and after the throttle passage formed according to the opening of the switching valve is kept high by an amount corresponding to the spring force of the spring 18c. That is, the opening of the compensator valve 18 is controlled so that the operating speed of the cylinder at which the maximum load pressure is generated is kept constant.

On the other hand, when none of the cylinders is operated, or when the maximum load pressure of the cylinder is lower than the primary pressure, the pilot chamber 18 of the compensator valve 18
The primary pressure set by the relief valve 33 is led to b. In this case, the compensator valve 18 controls the supply pressure to be higher than the primary pressure by an amount corresponding to the spring force of the spring 18c. That is, in a state in which none of the cylinders is operated, that is, in a so-called standby state, the supply pressure of the pump P is suppressed only to maintain the primary pressure, thereby preventing energy loss. Note that reference numeral R in the figure is a main relief valve that controls the maximum pressure of this circuit.

FIG. 4 shows a specific structure of the switching valve 2. A spool hole 51 is formed in the valve body 50, and a spool 52 is slidably incorporated in the spool hole 51. The spool 52 has axial holes 53 and 54 opened at both ends thereof.
Small diameter portions 55 and 56 are provided at the bottoms of 3 and 54. Further, caps 57 and 58 are fixed to the valve body 50. These caps 57 and 58 have bolts 5
9 and 60 are fixed, and these bolts 59 and 60 are inserted into the axial holes 53 and 54 of the spool 52. The pilot chambers 5 and 6 are formed by closing the spool hole 51 with the caps 57 and 58.

Centering springs 63 and 64 are incorporated in the pilot chambers 5 and 6, and these centering springs 63 and 64 are inserted into axial holes 53 and 54.
Has been inserted. The spring force of the centering springs 63, 64 is applied to the heads of the bolts 59, 60 via spring receiving members 65, 66. The neutral position of the spool 52 is maintained while the two spring receiving members 65 and 66 are pressed against the steps 67 and 68 of the spool 52. Notches 69 and 70 are formed at both ends of the spool 52. The rotation of the spool 52 is regulated by inserting the rotation regulating parts 71 and 72 provided on the caps 57 and 58 into these notched grooves 69 and 70.

In the valve body 50 incorporating the spool 52, pilot passages 73, 74 are formed, and these pilot passages 73, 74 communicate with the pilot chambers 5, 6. Further, pressure reducing valves (not shown) are incorporated in the valve body 50, and proportional solenoids 75 and 76 for controlling these pressure reducing valves are fixed to the upper surface of the valve body 50. The pilot pressure controlled by the pressure reducing valve is guided to the pilot chambers 5 and 6 via the pilot passages 73 and 74.

The valve body 50 has a supply oil passage 7
7. Actuator oil passages 78, 79 and tank oil passages 80, 81 are formed, and these oil passages 77 to 81 communicate with the spool holes 51, respectively. In the land between the supply oil passage 77 and the actuator oil passages 78 and 79, load pressure detection ports 82 and 83 are formed, and these load pressure detection ports 82 and 83 are connected to the first load pressure line 24. Connected. Further, the load pressure detection ports 82, 83
When the spool 52 is at the neutral position, the spool 52 blocks communication with other oil passages.

On the other hand, the annular grooves 84, 8 are formed in the spool 52.
5 are formed. These annular grooves 84 and 85 form metering notches 90 and 91 at both upper ends thereof, and sub notches 86 and 87 are continuously formed. If the spool 52 moves rightward from the neutral position,
When the load pressure detection port 82 communicates with the actuator oil passage 78 via the sub notch 86 and the spool 52 moves to the left, the load pressure detection port 83 communicates with the actuator oil passage 79 via the sub notch 87.

A drain port 88 is formed in a land between the actuator oil passage 78 and the tank oil passage 80. The drain port 88 communicates with the first load pressure line 24, and in a state shown in the drawing, a tank oil passage 80 is formed through a drain groove 89 formed in the spool 52.
Is in communication with Therefore, when the spool 52 is at the neutral position, the first load pressure line 24 becomes the tank pressure. However, when the spool 52 is moved in any direction, communication between the drain port 88 and the tank oil passage 80 is cut off. Then, the communication between the drain port 88 and the tank oil passage 80 is cut off, and at the same time, the load pressure detection ports 82 and 83 communicate with the sub notches 86 and 87. That is, the actuator oil passages 78 and 79 are
It does not communicate with the tank oil passages 80, 81 via the load pressure detection ports 82, 83 and the drain port 88.

On the other hand, the metering notches 90 and 91 formed on the spool 52 communicate only with the actuator oil passages 78 and 79 when the spool 52 is at the neutral position shown in the figure. , The metering notch 90 communicates with the supply oil passage 77,
The metering notch 91 communicates with the tank oil passage 81.
Therefore, the supply oil passage 77 and the actuator oil passage 78 communicate with each other, and the actuator oil passage 79 and the tank oil passage 81 communicate with each other. When the spool 52 is moved to the left, the metering notch 91 communicates with the supply oil passage 77,
The metering notch 90 communicates with the tank oil passage 80.
Therefore, the supply oil passage 77 and the actuator oil passage 79 communicate with each other, and the actuator oil passage 78 and the tank oil passage 80 communicate with each other. However, as described above, the metering notch 9
Before 0, 91 communicates with the supply oil passage 77, the sub notch 8
6, 87 are set to communicate with the load pressure detection ports 82, 83.

A flow path 92 is connected to the supply oil path 77, and communicates with the high-pressure oil path 93 via the flow path 92. Then, the pressure oil from the high pressure oil passage 93 is supplied to the supply oil passage 7.
7 Further, a load check valve 94 is provided in the flow path 92, and the load check valve 94 is provided.
Thus, the flow from the supply oil passage 77 to the high-pressure oil passage 93 is regulated.

Next, the operation of the switching valve 2 will be described. When the spool 52 is moved rightward by introducing pilot pressure to the pilot chamber 5 from the illustrated neutral state, the communication between the tank oil passage 80 and the drain groove 89 is cut off, and at the same time, the load is applied via the sub notch 86. The pressure detection port 82 and the actuator oil passage 78 communicate with each other. Further spool 52
Moves rightward, the actuator oil passage 78 communicates with the supply oil passage 77 via the metering notch 90,
Actuator oil passage 7 via metering notch 91
9 communicates with the tank oil passage 81. Therefore, the pump P
Of the high-pressure oil passage 93 → check valve 94 → supply oil passage 77 → metering notch 90 → actuator oil passage 7
8, the return oil of the actuator is discharged to the tank via the actuator oil passage 79 → the metering notch 91 → the tank oil passage 81.

When the above-described flow occurs, a pressure difference occurs before and after the metering notch 90. At this time, since the actuator oil passage 78 communicates with the first load pressure line 24 via the load pressure detection port 82, the pressure on the downstream side of the metering notch 90, that is, the load pressure of the actuator is changed to the load pressure detection port. From 82, it is led to the second shuttle valve 22 (see FIG. 3) via the first load pressure line 24. The pressure on the upstream side of the metering notch 90 is
The compensator valve 18 shown in FIG.
To the pilot room 18a. When the load pressure of the actuator is guided to the pilot chamber 18b of the compensator valve 18, the compensator valve 18 exhibits a load sensing function with respect to the actuator.

Contrary to the above, if the spool 52 is moved to the left, the communication between the drain port 88 and the drain groove 89 is cut off, and at the same time, the load pressure detecting port 83 and the actuator oil passage are connected via the sub notch 87. 79 communicates. The actuator oil passage 78 and the supply oil passage 77 communicate with each other via the metering notch 91, and the actuator oil passage 79 and the tank oil passage 80 communicate with each other via the metering notch 90. Therefore, the discharge oil of the pump P is supplied to the actuator via the high-pressure oil passage 93 → the check valve 94 → the supply oil passage 77 → the metering notch 91 → the actuator oil passage 79, and the return oil of this actuator is supplied to the actuator. The oil is discharged to the tank via the oil passage 78 → the metering notch 90 → the tank oil passage 80. Then, at this time, the pressure on the downstream side of the metering notch 91 is guided to the second shuttle valve 22 via the load pressure detection port 83, so that the compensator valve 18 exerts a load sensing function on the actuator. become.

The switching valve 2 as described above is provided before the actuator oil passages 78 and 79 and the supply oil passage 77 communicate with each other.
The actuator oil passages 78 and 79 are connected to the load pressure detection port 8
It communicates with 2,83. By doing so, the load pressure of the actuator is quickly introduced into the pilot chamber 18b of the compensator valve 18, and the switching response of the compensator valve 18 is improved. However, when the spool 52 is slightly moved and stopped, the actuator oil passages 78 and 79 are in communication with the load pressure detection ports 82 and 83 only. In such a state, the load pressure of the actuator is changed to the actuator oil passage 78, 79 → the load pressure detection port 82, 83 →
It flows into the first load pressure line 24. 1st load pressure line 2
Although the flow rate flowing into the valve 4 is very small, the actuator operates in the direction opposite to the direction in which the switching valve is operated, which causes a problem of giving an uncomfortable feeling to the operator. Therefore, as a switching valve that has solved the uncomfortable feeling, there is a switching valve that has already been proposed by the present applicant as Japanese Patent Application No. 2000-087533.

As shown in FIG. 5, this conventional switching valve has:
First passages 35 and 36 are formed in the spool 52, and these first passages 35 and 36 are opened in annular grooves 84 and 85. In addition, the shaft holes 37, 38 communicate with the first passages 35, 36, and the shaft holes 37, 38 and the first passage 35,
Check valves 39 and 40 are incorporated in portions communicating with the check valve 36, respectively. And these check valves 39, 40
This restricts the reverse flow from the first oil passages 35, 36 to the shaft holes 37, 38. Further, in the spool 52, drill holes 41 and 42 and drill holes 43 and 44 are formed.
These drill holes 41 to 44 communicate with the shaft holes 37 and 38, respectively. When the spool 52 is in the illustrated neutral position, the drill holes 41 and 42 communicate with the actuator oil passages 78 and 79, respectively, while the drill holes 43 and 44
Is blocked.

In this conventional example, when the spool 52 is moved rightward from the illustrated neutral position, the drain groove 89
At the same time as the communication between the oil passage and the tank oil passage 80 is interrupted, the drill hole 43 communicates with the supply oil passage 77, and the drill hole 41 communicates with the load pressure detection port 82. For this reason, the pressure in the supply oil passage 77 is changed from the drill hole 43 → the shaft hole 37 → the drill hole 41 → the load pressure detection port 82 → the first load pressure line 24 → the second shuttle valve 2.
2 (see FIG. 3). And this pressure is the second
When being guided from the shuttle valve 22 → the first shuttle valve 21 → the pilot chamber 18b of the compensator valve 18, both pilot chambers 18a and 18b of the compensator valve 18 have the same pressure. Therefore, the compensator valve 18
The position is switched to the closed position shown in FIG. 3 by the spring force of the spring 18c, and the pressure in the supply flow path 1 increases.

When the pressure in the supply passage 1 increases, the pressure in the supply oil passage 77 communicating therewith also increases, and the check valve 39 incorporated in the spool 52 opens to open the shaft hole 37 and the first passage 3.
5 communicates. For this reason, the pressure oil in the supply oil passage 77 is supplied to the actuator oil passage 78 via the drill hole 43 → the shaft hole 37 → the check valve 39 → the first passage 35. Backflow from 78 to the load pressure detection port 82 is regulated. Therefore, the load pressure of the actuator does not cause the pressure oil to flow into the first load pressure line 24 from the actuator oil passages 78 and 79, and does not give an uncomfortable feeling to the operator.

Then, the spool 5 is further moved from the above state.
2 moves to the right, the supply oil passage 77 and the actuator oil passage 78 communicate with each other via the metering notch 90, and the actuator oil passage 79 and the tank oil passage 81 communicate with each other via the metering notch 91. . At this time, the load pressure detection port 82 and the actuator oil passage 78
And are communicated via a passage in the spool 52,
The load pressure of the actuator is quickly guided to the second shuttle valve 22. Therefore, the switching response of the compensator valve 18 can also be maintained. The spool 5
When the valve 2 is switched to the left, the check valve 40 regulates the backflow from the actuator oil passage 79 to the load pressure detection port 83, but the operation is substantially the same, and the description thereof will be omitted.

[0025]

In the above conventional example, the first passages 35 and 36, the shaft holes 37 and 38, the drill holes 41 to 44 are formed in the spool 52, and the check valves 39 and 40 are incorporated. The structure becomes very complicated,
There was a problem that the cost was high. If the metering notches 90, 91 are always in communication with the load pressure detection ports 82, 83 due to the rotation of the spool 52, accurate load pressure cannot be detected. Therefore, in this conventional example, the rotation of the spool 52 must be regulated, and there is a problem that the cost is increased even by the structure for restricting the rotation of the spool. An object of the present invention is to provide an inexpensive switching valve that simplifies the structure of a spool and does not need to regulate the rotation of the spool.

[0026]

According to the present invention, a spool is slidably incorporated into a spool hole formed in a valve body, and a supply oil passage is provided in the spool hole, and a pair of oil supply passages provided on both sides of the supply oil passage. Actuator oil path, a tank oil path provided on both sides of these actuator oil paths, a pair of load pressure detection ports provided between the actuator oil paths, and a drain port.
A main annular groove constantly communicating with the actuator oil passage, an annular metering notch continuous with the main annular groove, and a drain groove for communicating the drain port with the tank oil passage when the spool is at the neutral position. It is assumed that the switching valve is provided with.

Based on the above-mentioned switching valve, the present invention provides
The opening of the supply oil passage communicated with the spool hole is made smaller than the diameter of the spool, and the opening of the supply oil passage is shifted in the circumferential direction from the opening of the load pressure detection port. A pressure introduction port between the load pressure detection ports and communicating with the spool hole, a load pressure line communicating the pressure introduction port, the load pressure detection port and the drain port, and a load pressure detection port. A check valve for restricting inflow from the spool hole to the load pressure line. The spool is provided between the main annular groove and the load pressure detection port and the supply oil passage when the spool is at the neutral position. And a pair of sub-annular grooves communicating with each other, between these sub-annular grooves,
When the spool is at the neutral position, a land portion for closing the pressure introduction port is provided, and when the spool is moved from the neutral position, communication between the drain port and the tank oil passage is cut off, and at the same time, the sub annular groove is formed. , The load pressure detection port and the pressure introduction port communicate with each other, and the load pressure detection port communicates with the actuator oil passage through a metering notch, and then supply the actuator oil passage through the metering notch. It is characterized in that it is configured to communicate with the oil passage.

[0028]

1 and 2 show an embodiment of the present invention. A spool hole 100 is formed in the valve body B, and a spool 101 is formed in the spool hole 100.
Is slidably assembled. Further, a supply oil passage 102 is formed in the valve body B, and the supply oil passage 102 is formed in the spool hole 100.
Is communicated to. However, as shown in FIG. 2, the diameter of the opening of the supply oil passage communicated with the spool hole 100 is
The diameter is smaller than the diameter of the spool 101.

A pair of actuator oil passages 103 and 104 are provided on both sides of the supply oil passage 102, and these actuator oil passages 103 and 104 are
00. As shown in FIG. 2, a pair of load pressure detection ports 105 and 106 are formed between the actuator oil passages 103 and 104 and at positions shifted in the circumferential direction of the supply oil passage 102. ing. These load pressure detection ports 105 and 106 have one ends opened to the spool hole 100 and
It is offset from the opening of the supply oil passage 102 in the circumferential direction. Also, the other ends of the load pressure detection ports 105 and 106 are
An opening is formed in a concave portion 116 formed in the mating surface Ba of the valve body B, and the enlarged diameter portion 10 is
7, 108 are formed. And, this enlarged diameter portion 10
Non-return members 109 and 110 are slidably incorporated in 7, 108, respectively.

The check members 109 and 110 have convex portions 111 and 112 formed on the mating surface Ba side of the valve body B. In addition, the check members 109 and 110 include:
Through holes 113 and 114 are formed, and the through holes 113 and 1 are formed.
14 penetrates through the convex portions 111 and 112. Although not shown, another valve body or the like is overlapped on the mating surface Ba of the valve body B. Then, on the mating surface of the other valve body thus superimposed, the convex portions 111, 111 of the check members 109, 110 are provided.
In a state where 112 is pressed, the through holes 113 and 114
It is trying to block. As described above, the concave portion 116 becomes the load pressure line 117 in a state where another valve body is overlapped on the mating surface Ba of the valve body B. In addition, the above-described check members 109, 110, the enlarged diameter portions 107, 10
Check valves V1 and V2 are formed by the mating surfaces of the valve body 8 and other valve bodies.

A pressure introduction port 115 is formed between the load pressure detection ports 105 and 106. The pressure introduction port 115 has one end communicating with the spool hole 100 and the other end communicating with the load pressure line 117. The load pressure line 117 is connected to the pressure introduction port 115
And the load pressure detection ports 105 and 106 communicate with each other. A drain port 118 formed in the valve body B communicates with the load pressure line 117.
The other end of the drain port 118 also communicates with the spool hole 100. The load pressure line 117 communicating the drain port 118 and the load pressure detection ports 105 and 106 is connected to the first load pressure line 24 shown in FIG. The actuator oil passages 103, 1
The tank oil passages 119 and 120 are formed adjacent to the tank oil passage 04, and these tank oil passages 119 and 120 communicate with the spool hole 100.

The spool 101 has a main annular groove 12 constantly communicating with the actuator oil passages 103 and 104.
1, 122 are formed. These main annular grooves 12
An annular metering notch 1 is provided at one end of
23 and 124 are continuously formed. A pair of sub annular grooves 12 are provided between the main annular grooves 121 and 122.
5 and 126, and these sub annular grooves 12
A land 127 is formed between 5,126. And
When the spool 101 is in the illustrated neutral position, the load pressure detection port 105 communicates with the supply oil passage 102 via the sub annular groove 125, and the load pressure detection port 106 communicates with the supply oil passage 106 via the sub annular groove 126. And 102 communicate with each other. However, at this time, the pressure introduction port 115 is
Is closed by.

Further, an annular drain groove 128 is formed in the spool 101 as shown in FIG. The drain groove 128 allows the drain port 118 to communicate with the tank oil passage 119 when the spool 101 is at the neutral position. However, when the spool 101 moves left and right from the neutral position, communication between the drain port 118 and the tank oil passage 119 is cut off. Then, the communication between the drain port 118 and the tank oil passage 119 is interrupted, and at the same time, the pressure introduction port 115 is connected to the sub annular groove 125 or the sub annular groove 1.
It communicates with the supply oil passage 102 through 26. At this time, one of the actuator oil passages 103 and 104 is
It communicates with the load pressure detection port 105 or 106 via the metering notch 123 or 124. When the spool 101 moves further from the above state, the supply oil passage 102 and the actuator oil passage 103 or the actuator oil passage 104 communicate with each other via the metering notches 123 and 124. That is, the actuator oil passages 103 and 104 are connected to the load pressure detection port 1 first.
The communication with the supply oil passage 102 is made after the communication with the supply oil passages 05 and 106.

Plate-shaped closing members 130 and 131 are fixed to the valve body B with bolts b.
The spool holes 10 are formed by these closing members 130 and 131.
0 is closed to form pilot chambers 132 and 133. Pilot passages 134 and 135 are connected to the pilot chambers 132 and 133, respectively. Pilot pressure controlled by a pressure reducing valve (not shown) is applied through the pilot passages 134 and 135 to the pilot chamber 1.
32, 133. The pressure reducing valve is controlled by proportional solenoids 136 and 137.

As shown in FIG. 2, main springs 138 and 139 are incorporated in the pilot chambers 134 and 135, and one ends thereof are inserted into axial holes 140 and 141 formed in the spool 101. The main springs 138, 139 maintain a free length when the spool 101 is in the neutral position, and in this free length, one end abuts against the closing members 130, 131, and the other end has the axial holes 140, 139.
141 is in contact with the bottom. Therefore, the main spring 138, 1
No elastic force of 39 acts.

On the other hand, small diameter portions 142 and 143 are formed at both ends of the spool 101. In addition, enlarged diameter portions 144 and 145 are formed on the opening side of the spool hole 100. A centering spring S is provided between the small diameter portions 142 and 143 and the large diameter portions 144 and 145.
S is incorporated. These centering springs S, S have smaller spring constants than the main springs 138, 139, and are given a predetermined elastic force with the spool 101 in the neutral position. The spring force of the centering springs S, S causes the spring receiving members 14
6, 147 are pressed against a step 148 formed on the spool 101 and a stopper 149 formed on the valve body B. And this centering spring S,
The neutral position of the spool 101 is maintained only by the elastic force of S.

Next, the operation of this embodiment will be described. As shown in the drawing, when the spool 101 is in the neutral position, as shown in FIG.
The pressure is guided to the load pressure detection ports 105 and 106 via 126, and the high pressure acts on the lower pressure receiving surfaces of the check members 109 and 110 in the figure. Therefore, the check members 109 and 11
0 is pressed against the mating surface of another valve block (not shown), and the through holes 113, 112 are pressed.
Communication between 114 and the load pressure line 117 is interrupted. Therefore, the pressure in the load pressure line 117 is controlled by the drain port 118 through the drain groove 128.
9, the tank pressure is maintained.

When the pilot pressure is introduced into the pilot chamber 132 from the above state, a thrust is given to the spool 101 in the right direction in the drawing. When the rightward thrust of the spool 101 exceeds the elastic force of the centering spring S on the right side in the drawing, the spool 101 is bent while bending the centering spring S and the main spring 139.
Moves rightward in the drawing. When the spool 101 moves rightward, communication between the drain groove 128 and the drain port 118 is cut off, and at the same time, the pressure introduction port 115 communicates with the supply oil passage 102 via the sub annular groove 125. At this time, the load pressure detection port 105 is connected to the supply oil passage 1
The communication with the actuator oil passage 103 is communicated via the metering notch 123 while communication with the actuator oil passage 103 is interrupted.

Therefore, the pressure in the supply oil passage 102 is guided from the pressure introduction port 115 to the load pressure line 117.
This load pressure line 117 is connected to the second shuttle valve 22 shown in FIG. Therefore, the pressure is guided to the second shuttle valve 22, and the compensator valve 1 is transmitted from the second shuttle valve 22 through the first shuttle valve 21.
8, the pilot chambers 18a and 18b of the compensator valve 18 have the same pressure. When both pilot chambers 18a and 18b have the same pressure, the compensator valve 18 is switched to the left position by the spring force of the spring 18c, and the pressure in the supply flow path 1 increases accordingly.

The pressure in the supply passage 1 is guided to the supply oil passage 102 → the sub annular groove 125 → the pressure introduction port 115 → the load pressure line 117, and acts on the upper pressure receiving surface of the check member 109 in the drawing. Therefore, when the load pressure acting on the actuator oil passage 103 is exceeded, the check members 109 and 110 move downward in the figure, and the through-hole 113 and the load pressure line 11 move.
7 is communicated. Therefore, the high pressure of the supply oil passage 102 is guided to the pressure introduction port 115 → the load pressure line 117 → the metering notch 123 → the actuator oil passage 103. However, when pressure oil attempts to flow from the actuator oil passage 103 to the load pressure detection port 105, the check member 107 moves upward in the drawing and closes the through hole 113. Therefore, pressure oil can be prevented from flowing from the actuator oil passage 103 to the load pressure detection port 105, and the actuator does not move in the direction opposite to the operation direction of the operator.

When the spool 101 further moves rightward from the above state, the actuator oil passage 103 and the supply oil passage 102 communicate with each other via the metering notch 123. The other actuator oil passage 104 and the tank oil passage 120 communicate with each other via the main annular groove 122.
Therefore, the actuator operates, but the load pressure detection port 105 and the actuator oil passage 103 have already been operated.
Communicate with each other through the metering notch 123, so that the load pressure of the actuator can be quickly changed to the load pressure line 11.
7 can be led. Therefore, the responsiveness of the compensator valve 18 controlled by the pressure oil guided through the load pressure line 117 can be maintained.

On the other hand, when the spool 101 is switched to the left in the drawing, the load pressure is led to the load pressure line 117 through the load pressure detection port 106, and the check valve V2
As a result, the backflow from the actuator oil passage 104 to the load pressure detection port 106 is regulated. However, the operation of the compensator valve 18 is substantially the same as in the above case, and a description thereof will be omitted.

According to this embodiment, since the check valves V1 and V2 are incorporated in the valve body B, the spool 101
The structure of the spool 101 can be simplified as compared with the conventional example in which a check valve is incorporated. Therefore,
As a result, the cost of parts can be reduced. Further, according to this embodiment, even if the spool 101 rotates, the load pressure can be accurately detected. Therefore, a mechanism for regulating the rotation of the spool can be omitted, and the cost can be reduced accordingly.

[0044]

According to the present invention, the structure of the spool can be simplified because the check valve or the like conventionally incorporated in the spool is incorporated in the valve body side. By simplifying the structure of the spool in this way,
Parts cost can be reduced. Further, even if the spool rotates, the load pressure can be accurately detected, so that a mechanism for regulating the rotation of the spool can be omitted. Thus, the cost can be further reduced by omitting the mechanism for regulating the rotation of the spool. Therefore, according to the present invention, the product cost of the entire switching valve can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a circuit diagram.

FIG. 4 is a sectional view showing a specific structure of the switching valve 2.

FIG. 5 is a sectional view showing a conventional example.

[Explanation of symbols]

 B Valve body 100 Spool hole 101 Spool 102 Supply oil passage 103, 104 Actuator oil passage 105, 106 Load pressure detection port 115 Pressure introduction port 117 Load pressure line 118 Drain port 119, 120 Tank oil passage 121, 122 Main annular groove 123, 124 Metering notch 125, 126 Sub annular groove 127 Land part 128 Drain groove

Claims (1)

[Claims] 1. A spool hole formed in a valve body,
The spool is slidably assembled, and the spool hole is provided with a supply oil passage, a pair of actuator oil passages provided on both sides of the supply oil passage, a tank oil passage provided on both sides of these actuator oil passages, and an actuator oil passage. While a pair of load pressure detection ports provided between the main oil passage and the drain port are communicated with each other, the spool has a main annular groove constantly communicating with the actuator oil passage, and an annular metering notch continuous with the main annular groove. When the spool is at the neutral position, in a switching valve having a drain groove for communicating the drain port with the tank oil passage, an opening portion of the supply oil passage communicated with the spool hole is formed by a diameter of the spool. While the opening of the supply oil passage is circumferentially shifted from the opening of the load pressure detection port, while the valve body is A pressure introduction port between the load pressure detection ports and communicated with the spool hole, a load pressure line communicating the pressure introduction port, the load pressure detection port and the drain port, and a load pressure detection port. A check valve for restricting inflow from the spool hole to the load pressure line, wherein the spool is between the main annular grooves, and the load pressure detection port and the supply oil passage are provided when the spool is at the neutral position. A pair of sub-annular grooves communicating with the first and second sub-grooves, and between these sub-circular grooves, when the spool is at the neutral position, a land portion closing the pressure introduction port is provided, and when the spool is moved from the neutral position, ,
At the same time as the communication between the drain port and the tank oil passage is interrupted, the load pressure detection port and the pressure introduction port communicate with each other through the sub annular groove, and the load pressure detection port and the actuator oil passage are connected with the metering notch. A switching valve, wherein the actuator oil passage and the supply oil passage communicate with each other via a metering notch.