JPH089772Y2 - Pressure reducing control valve for traveling hydraulic clutch - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure reducing control valve for causing a vehicle to run at a low speed by selectively reducing the hydraulic pressure applied to a traveling hydraulic clutch of a vehicle to obtain a half-clutch state of the hydraulic clutch. It is a thing.

[0002]

2. Description of the Related Art There are two types of pressure reducing control valves conventionally proposed, one of which is a pump port and a clutch port as disclosed in, for example, Japanese Utility Model Publication No. 54-11331. The control valve spool formed with a small diameter portion for communicating between the two is provided with a land which is adjacent to the small diameter portion and which normally blocks communication between the inside of the valve hole on the outer peripheral side of the small diameter portion and the drain port. A cutout groove or a throttle oil passage for communicating the inside of the valve hole on the outer circumference of the small diameter portion with the drain port is formed on the outer peripheral surface of the spool, and the spool is always held at a position where the pump port and the clutch port communicate with each other. The spool is displaced against the valve spring for operating to obtain the oil drain state to the drain port via the throttle oil passage, and thus the oil in the clutch port connected to the hydraulic clutch. Those such obtain reduced pressure.

Other types include, for example, Japanese Patent Laid-Open No. 48-3524.
As disclosed in Japanese Patent Publication No. 9, a valve spring moves and urges a spool of a pressure reducing valve in a valve hole in a direction in which a pump port and a clutch port are communicated with each other, and a hydraulic pressure of the clutch port is opposite to the spool. The hydraulic pressure of the clutch port is determined by the balance between the hydraulic pressure and the valve spring force, and the spring receiving member that receives the base end of the valve spring is displaced by pedaling to reduce the valve spring load. It is supposed to obtain the pressure reduction of the clutch port oil pressure. In the case of JP-A-48-85243, the drain port is opened in the valve hole on the side opposite to the pump port across the clutch port when viewed in the axial direction of the valve hole, and the rod integrated with the spring receiving member is spooled. Is provided to project outside the spool, and an engaging member capable of engaging with the spool is provided on the projecting end portion, and when the pedal is depressed greatly, the engaging member causes the spool to communicate between the clutch port and the drain port. It is supposed that it will be displaced to the position and oil will be drained from the clutch port to disengage the traveling hydraulic clutch.

[0004]

Among the two types of pressure reducing control valves described above, the former type is such that the hydraulic pressure of the clutch port in the non-pressure reducing state is such that the hydraulic pressure of the clutch port is applied to the spool at both ends of the small diameter portion. The valve spring has a load that returns the spool to the decompression non-acting position by releasing the operating force on the spool and holds it in the same position because the spool is not urged to move evenly in the opposite direction by the same hydraulic pressure. It suffices, and therefore gives little resistance to depressurization. However, on the contrary, it is difficult to control the position of the throttle oil passage on the outer peripheral surface of the land of the spool properly with a pedal or the like so that the desired half-clutch state can be obtained. It was easy to get a situation where the pressure was reduced to a low oil pressure. On the other hand, in the latter type of pressure reducing control valve described above, the pressure reducing degree is determined by the balance between the valve spring force and the hydraulic pressure, so that the half-clutch region is large and the pressure reducing control operation is easy. Since the valve spring load is a large value corresponding to the normal acting hydraulic pressure for the hydraulic clutch, there was a problem that the depressurizing operation by the pedal biased by the return spring against the valve spring load was heavy. .

Therefore, the present invention follows the former type of structure described above to facilitate decompression operation, while expanding the half-clutch region to obtain the half-clutch state accurately and easily. The present invention is intended to provide a new pressure reducing control valve for a vehicle. Another object of the present invention is to provide the pressure reducing control valve with a proper clutch disengagement function with a simple structure.

[0006]

For this purpose, the present invention is directed to the pump port 2, the clutch port 3, and the drain port 4, which are opened in the valve hole 1, as shown in the accompanying drawings, when viewed in the axial direction of the valve hole. Is provided in the center, and a small diameter portion 5a for communicating between the pump port 2 and the clutch port 3 and a throttle oil passage 6 for communicating the inside of the valve hole 1 on the outer peripheral side of the small diameter portion 5a with the drain port 4 are provided. A spool 5 having a land 5b having an outer peripheral surface in the valve hole 1,
The valve spring 7 is slidably provided so as to be slidable by a valve spring 7 in a direction in which communication between the drain hole 4 on the outer peripheral side of the small diameter portion 5a and the drain port 4 is blocked by the land 5b. In the pressure reducing control valve for the traveling hydraulic clutch, which is configured to obtain the pressure reduction of the oil pressure of the clutch port 3 by the oil drain to the drain port 4 through the throttle oil passage 6 against the above sliding displacement, I took various technical measures. That is, the present invention provides the spool 5 with oil passage holes 8 which respectively open to the outer peripheral surface of the small diameter portion 5a and the outer peripheral surface of the land 5b within the width of the throttle oil passage 6 when viewed in the spool axial direction. The small diameter portion 5a is provided in the oil passage hole 8.
A low pressure relief valve 9 capable of relieving oil is inserted and installed from the inside of the valve hole 1 on the outer peripheral side to the drain port 4.

In addition to the above construction, the present invention also provides another drain port 10 which opens in the valve hole 1 on the opposite side of the pump port 2 across the clutch port 3 when viewed in the valve hole axial direction. The clutch port 3 and the other drain port 1 are located on the opposite side of the land 5b across the portion 5a.
The other land 5c that cuts off the communication between 0s to the spool 5,
Inside the valve hole 1 on the outer peripheral side of the small diameter portion 5a and the drain port 4
When the land 5b is displaced to the position where the disconnection between the clutch port 3 and the drain port 10 is released, the other land 5c is displaced to the position where the disconnection between the clutch port 3 and the drain port 10 is released. It is also proposed to provide it.

[0008]

When the spool 5 is not displaced, as shown in FIG. 2, the pump port 2 and the clutch port 3 are in communication with each other through the valve hole 1 on the outer peripheral side of the small diameter portion 5a, and the small diameter portion is formed by the land 5b. Since the inside of the valve hole 1 on the outer peripheral side of 5a is cut off from the drain port 4, the clutch port 3
A normal high hydraulic pressure is applied to the hydraulic clutch. In this state, the same high oil pressure acts on the low pressure relief valve 9 to bring the low pressure relief valve 9 to a position where the oil passage hole 8 is completely brought into a conductive state as illustrated in FIG. 2 as well. Since the open end of the outer peripheral surface of the land 5b of 8 is blocked by the inner peripheral surface of the valve hole and does not communicate with the drain port 4, oil relief to the drain port 4 is not performed.

When the spool 5 is displaced against the valve spring 7 and the end of the throttle oil passage 6 slightly overlaps the drain port 4 as shown in FIG. 3, the valve hole 1 on the outer peripheral side of the small diameter portion 5a comes out. Since oil is drained to the drain port 4 via the throttle oil passage 6, the oil pressure in the clutch port 3 is correspondingly reduced. The degree of pressure reduction corresponds to the displacement operation amount of the spool 5, and the hydraulic pressure is relatively greatly reduced with a relatively small spool displacement amount, and enters the half clutch region of the hydraulic clutch.

When the spool 5 is displaced a little further and the opening end of the oil passage hole 8 to the outer peripheral surface of the land 5b is relatively large and overlaps with the drain port 4, a throttle oil passage is obtained as shown in FIG. A state in which the oil drain is prioritized by the relief operation of the low-pressure relief valve 9 that takes a relief position than the oil drain through 6 is obtained, and the oil pressure of the clutch port 3 is reduced to the relief pressure of the low-pressure relief valve 9 and is constant. To do. As shown in FIG. 5, this state continues until the throttle oil passage 6 almost completely overlaps the drain port 4. Therefore, during that time, the low clutch hydraulic pressure set by the low pressure relief valve 9 can ensure the half-clutch state.

When the spool 5 is operated to be largely displaced against the valve spring 7 and the land 5b is moved to a position where the inside of the valve hole 1 on the outer peripheral side of the small diameter portion 5a is opened to the drain port 4, as shown in FIG. The other land 5c is moved to a position where the clutch port 3 is opened to the other drain port 10, the hydraulic pressure of the clutch port 3 is drained, and the hydraulic clutch is disengaged. The low-pressure relief valve 9 takes the non-relief position because the hydraulic pressure on its primary side is drained to the drain port 4.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numerals 12F and 12R denote forward and reverse hydraulic clutches provided in a traveling power transmission path of a work vehicle, and a pressure reducing control valve provided with a spool 5 supplies hydraulic pressure to the hydraulic clutches 12F and 12R. It is inserted and installed in the circuit on the front side of the switching valve 13 for selectively operating each of the hydraulic clutches 12F and 12R. An oil passage opening / closing valve 14 having a common valve case with the control valve is provided on the primary side of the pressure reducing control valve.

Explaining the circuit structure shown in FIG. 1, a hydraulic pump 17 which is driven by the engine 16 and guides hydraulic oil from the oil tank to the hydraulic clutches 12F, 12R is provided. The circuit 18 is connected to the inlet port 19 of the oil passage opening / closing valve 14. The hydraulic pressure of the discharge circuit 18 is set by the relief valve 20. The switching valve 13 having a pump port connected to the clutch port 3 has a forward drive position F for operating the forward drive hydraulic clutch 12F and a reverse drive position R for operating the reverse drive hydraulic clutch 12R. Each hydraulic clutch 12F, 12
The acting hydraulic pressure on R is set by well-known modulated relief valves 21F and 21R. Each of the modulation type relief valves 21F and 21R receives the control piston 2 which receives the end of the valve spring 21a for hydraulic pressure setting as usual.
1b and an orifice 21c for gradually applying a clutch working oil pressure to the control piston 21b.
The valve spring 21a is gradually compressed by b to gradually increase the clutch working oil pressure to the normal high oil pressure. Relief circuit 22 of relief valve 20 and modulated relief valves 21F, 2
The relief circuits 23F and 23R of the 1R are joined as shown in the drawing, and are connected to a lubricating oil supply circuit 25 that guides the lubricating oil to a lubrication necessary portion 24 such as a friction emerent portion of the hydraulic clutches 12F and 12R. In the illustrated example, the drain port 4 of the pressure reducing control valve is also connected to the lubricating oil supply circuit 25. The oil pressure of the lubricating oil is set by a relief valve 26 that operates in a very low oil pressure such as 0.3 kg / cm ² .

Next, the oil passage opening / closing valve 14 will be described. The main opening / closing valve 14 is commonly used by arranging the oil passage hole forming the pump port 2 of the pressure reducing control valve as an outlet port in parallel with the pressure reducing control valve. It is inserted and installed in the valve hole 27 of the valve case. Further, there is an oil passage hole 28 which is opened to the end surface on the inlet port side and the outer peripheral surface and which communicates between the ports 19 and 2, and the oil passage hole 28 is positioned so as to be blocked with respect to the inlet port 19. It is slidingly biased by the valve spring 14a. The oil passage opening / closing valve 14 is moved in conjunction with the displacement operation of the pressure reducing control valve to an oil passage opening position as shown in FIG. 2-6, that is, a position where the ports 19 and 20 communicate with each other via the oil passage hole 28. After that, even after the operation force is released, it is configured to be held in the same open position.

That is, the illustrated pressure reducing control valve or its spool 5 is supposed to be displaced by a pedal 30, but a push pin 31 for displacing the oil passage opening / closing valve 14 against its valve spring 14a is provided. Push pin 3
1 is connected to the spool 5 by the interlocking plate 32, and the pedal 30
The pressing rod 33 interlocked with the is contacted with the interlocking plate 32. The valve spring 7 for urging the spool 5 to move is the interlocking plate 3
It acts on the spool 5 via 2. Oil passage open / close valve 14
An oil passage hole 34 for draining oil from the port 2 through the installation space of the valve spring 14a is also formed in the port 2. The opening end of the oil passage hole 34 on the port 2 side is provided with a push pin 31 for opening / closing the valve 14. When it is pushed in by a certain amount, it is supposed to be blocked by the inner peripheral surface of the valve hole 27. Therefore, when the pedal 30 is depressed to obtain the displacement of the spool 5 against the valve spring 7 and at the same time the oil passage opening / closing valve 14 is pushed by the push pin 31, the oil pressure of the inlet port 19 acting from the opposite side of the valve spring 14a causes The oil passage opening / closing valve 14 is shown in FIG.
It is moved to the position illustrated in 6 and held at the same position. The reason for providing the oil passage opening / closing valve 14 will be described later.

A more specific structure of the illustrated pressure reducing control valve will be described. A common valve case for the control valve and the oil passage opening / closing valve 14 is arranged in a vehicle mission case (not shown) which also serves as an oil tank. The other drain port 10 is provided by the open end of the valve hole 1 into the mission case. The displacement of the spool 5 in the biasing direction by the valve spring 7 is obtained by forming an annular shoulder portion 37 at the end of the spool 5 that abuts the valve case or its end cover 36.

The throttle oil passage 6 is formed by a plurality of notch grooves formed on the outer peripheral surface of the land 5b of the spool 5 so as to be intermittently arranged in the circumferential direction over a constant width in the axial direction from the end on the small diameter portion 5a side. It is provided. The oil passage hole 8 is composed of a radial through hole that crosses the small diameter portion 5a of the spool 5, an axial hole that is continuous with the through hole, and a plurality of radial holes that cross the axial hole and open on the outer peripheral surface of the land 5b. .
In the illustrated example, the opening position of the outer peripheral surface of the land 5b of the oil passage hole 8 is within the throttle oil passage 6, but the opening position is the throttle oil passage 6
It may be located at any position on the outer peripheral surface of the land 5b as long as it is within the axial width. An annular step portion is formed on the inner peripheral surface of the oil passage hole 8 at a proper position of the axial hole, and the low pressure relief valve 9 is seated on the step portion from the side opposite to the small diameter portion 5a.
And is placed in the axial hole. The base end of the valve spring 9a is received by a radial pin 39 fitted to the end of the spool 5, and the pin that guides the valve spring 9a and regulates the rearmost retracted position of the low pressure relief valve 9 shown in FIG. 40 is also provided.

The other land 5c is, as shown in FIG.
The throttle oil passage 6 is arranged and provided so as to come into contact with the inner peripheral surface of the valve hole 1 between the pump port 2 and the clutch port 3 from the displacement operation position of the spool 5 at which the throttle oil passage 6 starts to overlap with the drain port 4. . And this other land 5c
On the outer peripheral surface of the land 5, another throttle oil passage 42 formed in the same manner as the throttle oil passage 6 on the outer peripheral surface of the land 5b is provided, and the spool 5 is moved from the position shown in FIG. 3 to the position shown in FIG. During the displacement operation up to, that is, while the reduced hydraulic pressure for obtaining the half-clutch state is obtained in the clutch port 3 as described above, the other throttle oil passage 42 allows the small diameter portion 5a.
It is provided so that the amount of oil flowing from the outer peripheral valve hole 1 to the clutch port 3 is appropriately reduced to obtain a stable pressure reducing action.

The illustrated pressure-reducing control valve operates as described above in the section of the function of the invention, and the pressure-reducing operation is further stabilized by the arrangement of the other land 5c and the throttle oil passage 42 on the outer peripheral surface thereof as described above. FIG. 7 is a graph showing the relationship between the displacement operation amount S of the spool 5 from the position shown in FIG. 2 and the oil pressure P of the clutch port 3, and C in the curve shown by the solid line.
1 corresponds to the state shown in FIG. 2, and the hydraulic pressure P is maintained at the normal high hydraulic pressure to be applied to the hydraulic clutches 12F and 12R. The curved portion C2 shows a sudden pressure reduction in the small displacement range of the spool 5 near the position shown in FIG. 3, and the portion C3 shows the spool 5 slightly beyond the position shown in FIG. FIG. 6 shows a low-pressure constant region of the hydraulic pressure P determined by the low-pressure relief valve 9 in a range in which the hydraulic pressure P is displaced from the position to the position shown in FIG. The portion C4 corresponds to the state in which the spool 5 is further displaced to the position shown in FIG. 6, and at this time, the hydraulic clutch 21F,
21R is maintained in a cut state. In FIG. 7, the curve shown by the broken line illustrates the relationship between the spool displacement amount and the clutch working oil pressure when the low pressure relief valve corresponding to the low pressure relief valve 9 is not provided. The displacement range is narrow.

In the vehicle equipped with the hydraulic clutches 12F and 12R shown in FIG. 1, even if the hydraulic pump 17 is driven by starting the engine from the stopped state of the engine 16, the oil passage opening / closing valve 14 causes the port 19 as shown in the figure. , 2 is cut off, hydraulic oil is not supplied in the direction of the hydraulic clutch and the vehicle does not start. Pedal 3 to start the vehicle
The oil passage opening / closing valve 14 is pushed in by pushing 0, and the oil passage opening / closing valve 14 is held in the position by the action of hydraulic pressure as described above.
It is necessary to take the oil passage open position illustrated in. When the pedal 30 is depressed, the spool 5 of the pressure reducing control valve is simultaneously brought to the pressure reducing position or the clutch disengagement position. Therefore, the spool 5 is moved to the maximum displacement operation position as illustrated in FIG. 6, for example. By gradually reducing the pedaling operation force of the pedal 30 above, the hydraulic pressure acting on the hydraulic clutch 12F or 12R is gradually increased to obtain the clutch engagement in the half-clutch state, and the vehicle is gradually shock-free. Can be started. That is, the oil passage opening / closing valve 14 is provided for the purpose of preventing a sudden start of the vehicle and ensuring safety. When the engine is turned off and the vehicle is stopped, the oil passage opening / closing valve 14 is moved to the oil passage closing position shown in FIG. 1 by the force of the valve spring 14a due to the release of the hydraulic action by stopping the driving of the hydraulic pump 17.

[0021]

In the pressure reducing control valve of the present invention, the valve spring 7 for urging the spool 5 is used only as a return spring from the displacement operation position of the spool 5 and is not involved in setting the hydraulic pressure. In the non-depressurized position, the oil pressure of the clutch port 3 is evenly applied in opposite directions to each other at both ends of the small diameter portion 5a so that a force for urging the spool 5 is not generated. Therefore, it is possible to easily operate with a small force. Then, in the depressurized state, over the constant displacement range of the spool 5, a low pressure relief valve 9 that drains oil to the drain port 4 is given priority over the throttle oil passage 6 on the outer peripheral surface of the land 5b, and a predetermined depressurized pressure obtained at the clutch port 3 is obtained. Since the hydraulic pressure is to be obtained over a wide displacement range of the spool 5, the low pressure relief valve 9
Even if the relief pressure is set appropriately, the half-clutch state of the hydraulic clutch can be accurately and easily obtained.

According to the structure of claim 2, the clutch port 3
Since the clutch port 3 is directly communicated with the other drain port 10 which is adjacent to the port 3, the hydraulic pressure of the port 3 is released, so that the pressure reducing control valve is provided with an appropriate clutch disengagement function, and Function is simply another drain port 1
It is achieved only by adding 0 and setting the width of the other lands 10 in the spool axial direction, and is provided with a very simple structure.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view and a circuit diagram showing an embodiment of the present invention together with other related valves and hydraulic circuits.

FIG. 2 is a vertical cross-sectional view showing another valve related to the embodiment.

FIG. 3 is a vertical sectional view similar to FIG. 2, showing a different state.

FIG. 4 is a vertical sectional view similar to FIG. 2, showing a different state.

5 is a vertical sectional view similar to FIG. 2, showing a different state.

6 is a vertical sectional view similar to FIG. 2, showing a different state.

FIG. 7 is a graph showing an operation of the example.

[Explanation of symbols]

 1 Valve hole 2 Pump port 3 Clutch port 4 Drain port 5 Spool 5a Small diameter part 5b Land 5c Other land 6 Throttle oil passage 7 Valve spring 8 Oil passage hole 9 Low pressure relief valve 10 Other land 12F Forward hydraulic clutch 12R For reverse Hydraulic clutch 13 Switching valve 14 Oil passage opening / closing valve 30 Pedal 32 Interlocking plate

 ─────────────────────────────────────────────────── ───Continued from the front page (56) References JP-A-1-131331 (JP, A) Actually opened 48-68224 (JP, U) Actually opened 1-100209 (JP, U) Actually opened 57- 140413 (JP, U)

Claims (2)

[Scope of utility model registration request] 1. A pump port 2, a clutch port 3, and a drain port 4, which are opened in the valve hole 1, are provided by arranging the pump port 2 in the center when viewed in the valve hole axial direction, and between the pump port 2 and the clutch port 3. Small diameter part 5 for communicating with
a and a land 5b having a throttle oil passage 6 on the outer peripheral surface for communicating the inside of the valve hole 1 on the outer peripheral side of the small diameter portion 5a with the drain port 4, a spool 5 in the valve hole 1 and a small diameter portion 5
a) The communication between the valve hole 1 on the outer peripheral side and the drain port 4 is slidably provided in the valve hole 1 by being biased by the valve spring 7 in a direction in which the communication between the drain port 4 is blocked by the land 5b. The clutch port 3 is slidably displaced against the spring 7 and oil is drained to the drain port 4 through the throttle oil passage 6.
In the pressure reducing control valve for the traveling hydraulic clutch configured to obtain the pressure reduction of the hydraulic pressure, the outer peripheral surface of the small diameter portion 5a and the outer peripheral surface of the land 5b within the width of the throttle oil passage 6 when viewed in the spool axial direction. The spool 5 is provided with oil passage holes 8 which open to the inside, respectively, and the small diameter portion 5a is provided in the oil passage holes 8.
A pressure reducing control valve, wherein a low pressure relief valve 9 capable of relieving oil is inserted and installed from the inside of the valve hole 1 on the outer peripheral side to the drain port 4. 2. Another drain port 10 opening to the valve hole 1.
Is provided on the opposite side of the pump port 2 across the clutch port 3 when viewed in the valve hole axial direction, and is located on the opposite side of the land 5b across the small diameter portion 5a, and the clutch port 3 and the other drain port. When the land 5b is displaced to a position where the other land 5c for blocking communication between the valve 10 and the drain port 4 is released from the valve hole 1 on the outer peripheral side of the small diameter portion 5a on the spool 5, the other land 5c is displaced. 2. The pressure reducing control valve according to claim 1, wherein the other land 5c is arranged so as to be displaced to a position where the disconnection between the clutch port 3 and the other drain port 10 is released.