JP2010216642A - Switching position detecting device of forward-backward advance switching valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid an enlargement of a forward-backward advance switching valve, and to improve reliability of a detection switch, when highly accurately detecting the engaging-disengaging timing of a forward advance hydraulic clutch and a backward advance hydraulic clutch, regardless of looseness and play existing in a passage reaching the forward-backward advance switching valve from a forward-backward advance switching lever. <P>SOLUTION: This switching position detecting device 101 of the forward-backward advance switching valve 100 has a neutral position detecting switch 34 for detecting respective operation positions of a spool 102 by directly or indirectly contacting with a recess-projection part 103 of the spool 102, a forward advance position detecting switch 35 and a backward advance position detecting switch 36. These position detecting switches 34-36 are intensively arranged in a parallel state, and are also contacted from above with the recess-projection part 103 of the spool 102. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is provided in a work vehicle including a forward hydraulic clutch interposed in a forward power transmission path and a reverse hydraulic clutch interposed in a reverse power transmission path, and selectively turns on and off each hydraulic clutch. The present invention relates to a switching position detecting device for a forward / reverse switching valve.

  2. Description of the Related Art A work vehicle is known in which a main transmission device and a forward / reverse switching device are configured using a plurality of hydraulic clutches, and main transmission and forward / backward switching are performed based on selective switching of the hydraulic clutch. For example, the forward / reverse switching device disclosed in Patent Document 1 includes a forward hydraulic clutch interposed in the forward power transmission path and a reverse hydraulic clutch interposed in the reverse power transmission path. By selectively turning on and off the clutch with a forward / reverse switching valve, the airframe is moved forward and backward.

  By the way, in this type of work vehicle, there is a case where not only the hydraulic valve of the corresponding transmission device is switched according to a predetermined shift operation, but also the hydraulic valve of another transmission device is controlled to be interlocked. For example, when the forward / reverse switching lever is operated to the neutral position, not only the hydraulic clutch of the forward / reverse switching device is disconnected, but also the hydraulic clutch of the main transmission is disconnected, and the forward / reverse switching lever moves forward from the neutral position. When operated to the position or reverse position, the hydraulic clutch of the forward / reverse switching device is engaged, and then the hydraulic clutch of the main transmission is engaged by boost control, thereby enabling smooth start. In a work vehicle that performs such control, in order to shorten the time lag from the forward / reverse switching operation to the vehicle start, the main shift valve is as soon as possible after the hydraulic clutch of the forward / reverse switching device is engaged. It is required to start boosting control of the (proportional control valve).

Japanese Patent No. 4217417

  However, in the conventional work vehicle, the operation position of the forward / reverse switching lever is detected by the position detection switch, and the control timing of the main transmission valve is determined based on the detection signal of the position detection switch. Due to backlash and play existing in the path from the lever to the forward / reverse switching valve, there is a possibility that a large deviation occurs in the sequence control of the forward / reverse switching valve and the main transmission valve.

The present invention has been created in order to solve these problems in view of the above circumstances, and is provided with a forward hydraulic clutch interposed in a forward power transmission path and a reverse power transmission path. And a forward / reverse switching valve switching position detecting device for selectively turning on and off each hydraulic clutch, wherein the forward / reverse switching valve includes a forward hydraulic clutch and a reverse traveling clutch. Comprising a spool that is slidably operated in a neutral position where the hydraulic clutch is disengaged, a forward position where only the forward hydraulic clutch is engaged, and a reverse position where only the reverse hydraulic clutch is engaged, The switching position detecting device includes a neutral position detecting switch, a forward position detecting switch, and a reverse position for detecting each operation position of the spool by directly or indirectly contacting the uneven portion of the spool. Provided with a detection switch, these position detecting switch concentrate arranged in parallel form, and, characterized in that it is constituted by contacting from above uneven portion of the spool.
The forward / reverse switching valve has a valve body that slidably supports a spool, a pump port to which a hydraulic pump is connected, a tank port to which an oil tank is connected, and a forward hydraulic clutch to which A is connected. Port and a B port to which the reverse hydraulic clutch is connected, and the switching position detecting device includes a switch case that is provided in the valve body and surrounds the concave and convex portions of the spool, and the inside of the switch case is The tank port is communicated with a breather hole formed in the switch case and / or the valve body.

According to the first aspect of the present invention, since the spool position of the forward / reverse switching valve is detected by the neutral position detection switch, the forward position detection switch, and the reverse position detection switch, the path from the forward / reverse switching lever to the forward / reverse switching valve is detected. Regardless of the play and play that exist, it is possible to detect the on / off timing of the forward hydraulic clutch and the reverse hydraulic clutch with high accuracy. Further, since the neutral position detection switch, the forward position detection switch and the reverse position detection switch are concentratedly arranged in parallel, it is possible not only to avoid the enlargement of the forward / reverse switching valve but also to simplify the switch wiring. . In addition, the neutral position detection switch, the forward position detection switch, and the reverse position detection switch come into contact with the concave and convex portions of the spool from above, so that it is difficult for metal wear powder to enter the switch, resulting in metal wear powder, etc. It is possible to prevent the occurrence of contact failure due to, and improve the reliability.
According to the invention of claim 2, since the inside of the switch case communicates with the tank port via the breather hole, pressure fluctuations in the switch case due to the pushing and pulling of the spool are eliminated, and the operation load of the spool is reduced. Can be reduced.

It is a side view of a tractor. It is a whole sectional view of a transmission case. It is a hydraulic circuit diagram which shows the hydraulic structure of a tractor. It is a top view of an operation part. It is a front view of a meter panel. It is a block diagram which shows the input / output of a control apparatus. It is explanatory drawing of a transmission pattern. It is a timing chart which shows the example of control when a forward / reverse switching device is switched. It is a flowchart which shows the example of control in case a forward / reverse switching device is switched. It is a front view of the forward / reverse switching valve showing the mounting state. It is sectional drawing of a forward / reverse switching valve. It is a hydraulic circuit diagram which shows the structure of the forward / reverse switching valve.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, T is an agricultural tractor (work vehicle), and a transmission case 1 is mounted on the tractor T. As shown in FIG. 2, the transmission case 1 inputs the power of the engine E via the main clutch mechanism 2 and branches the input power into the travel power transmission path 3 and the PTO power transmission path 4.

  The travel power transmission path 3 is configured using friction multi-plate hydraulic clutches C1 to C4, and includes a first main transmission 5 that performs four-speed shifting, and friction multi-plate hydraulic clutches CF and CR. A forward / reverse switching device 6 that performs forward / reverse shifting of the traveling power, a sub-transmission device 7 that performs a three-speed shifting, a friction multi-plate hydraulic clutch CL, A second main transmission 8 that is configured by using CH and performs two-step shift between high and low is provided.

  Of the hydraulic clutches CF and CR that constitute the forward / reverse switching device 6, the forward hydraulic clutch CF is interposed in the forward power transmission path, while the reverse hydraulic clutch CR is interposed in the reverse power transmission path. The hydraulic clutches CF and CR are selectively turned on and off by a forward / reverse switching valve 100, which will be described later, to switch between forward and reverse. Further, the forward power and the reverse power can be changed in eight steps by combining the first main transmission device 5 and the second main transmission device 8, and 24 by combining the transmission by the auxiliary transmission device 7. Gear shifts are possible.

  The traveling power changed by the first main transmission 5, the sub transmission 7, and the second main transmission 8 is transmitted to the front axle and the rear axle. The power transmission path to the front axle is provided with a double speed transmission device 9 that shifts or cuts the power transmitted to the front axle at a high or low level, and the front wheel at the time of turning is changed by shifting or cutting the power by the double speed transmission device 9. Switching between double speed drive, 4WD and 2WD is performed. The double speed transmission device 9 is configured using a frictional multi-plate hydraulic clutch, thereby enabling smooth shifting and disconnection.

  The PTO power transmission path 4 is provided with a PTO clutch 10 configured using a frictional multi-plate hydraulic clutch and a PTO transmission 11 configured using a constantly meshing gear transmission. An independent PTO power transmission system that is not influenced by the state, that is, a PTO power transmission path 4 of an independent PTO specification is configured.

  The tractor T of the present embodiment is configured with a hydraulic circuit as shown in FIG. This hydraulic circuit includes two hydraulic pumps P1 and P2, operates the double speed transmission device 9, the lift cylinder 12 and the lift rod cylinder 13 with the hydraulic pressure supplied from one hydraulic pump P1, and from the other hydraulic pump P2. The steering unit 14, the first main transmission device 5, the forward / reverse switching device 6, the second main transmission device 8, the PTO clutch 10, and the automatic brake turning device 15 are operated by the supplied hydraulic pressure.

  At least the hydraulic clutches C1 to C4, CL, and CH of the first main transmission 5 and the second main transmission 8 are operated based on the control of the electromagnetic valve. According to the hydraulic clutch operation control based on the pressure increase control of the electromagnetic proportional valve, a smooth traveling shift with less shift shock is possible. However, the hydraulic clutches C1 to C1 of the first main transmission 5 and the second main transmission 8 are provided. When all of C4, CL, and CH are controlled by an electromagnetic proportional valve, there is a problem that the required number of electromagnetic proportional valves increases, resulting in an expensive travel transmission. Further, when the hydraulic clutches CL and CH of the second main transmission 8 are controlled by electromagnetic proportional valves and the hydraulic clutches C1 to C4 of the first main transmission 5 are controlled by electromagnetic direction switching valves, the cost is low. However, in order to perform a smooth running shift based on the pressure increase control of the electromagnetic proportional valve, the hydraulic clutches CL and CH of the second main transmission 8 are intermittently connected at every shift. Therefore, the durability of the hydraulic clutches CL and CH provided in the second main transmission 8 must be improved.

  Therefore, in the tractor T of the present embodiment, as shown in FIG. 3, the hydraulic clutches C1 to C4 of the first main transmission 5 are alternatively operated based on the boost control of the electromagnetic proportional valves 16a to 16d, respectively. The hydraulic clutches CL and CH of the second main transmission 8 are controlled to operate based on the switching control of the electromagnetic direction switching valve 17. In this case, the traveling transmission device is configured at a lower cost than that in which the hydraulic clutches C1 to C4, CL, and CH of the first main transmission device 5 and the second main transmission device 8 are all controlled by electromagnetic proportional valves. Can do. Further, since it is not necessary to connect / disconnect the hydraulic clutches CL, CH of the second main transmission 8 at every shift, the cost for improving the durability of the hydraulic clutches CL, CH provided in the second main transmission 8 is increased. Is avoided. A pressure switch 18 for detecting the connection state of the hydraulic clutches CL and CH is provided in an oil passage for operating the hydraulic clutches CL and CH of the second main transmission 8 and is also provided at an appropriate position of the hydraulic circuit. An oil temperature sensor 19 for detecting the temperature of the hydraulic oil is provided.

  As shown in FIGS. 1 and 4, an operation unit 20 on which an operator gets on the tractor T body is configured. The operation unit 20 is provided with a driver's seat on which an operator is seated, and various operation tools for performing a traveling operation and an operation of the work machine W. For example, in front of the driver's seat 21, there is a steering handle H for steering the airframe, and a forward / reverse switching lever 22 for switching the forward / reverse switching device 6 (forward / reverse switching valve 100) via a wire or a rod. Provided on the left side of the driver's seat 21 is an auxiliary transmission lever 23 for switching the auxiliary transmission 7. The grip portion 23a of the auxiliary transmission lever 23 is provided with a transmission switch (speed increase switch 24, speed reduction switch 25) for changing the speed of the first main transmission 5 and the second main transmission 8. A high speed start switch 26 that is selectively operated when the shift lever 23 is switched to the high speed side is provided.

  As shown in FIG. 5, a meter panel 27 is provided in front of the driver seat 21. In the meter panel 27, not only a tachometer and various monitor lamps are provided, but also a display unit 28 for performing various status displays and setting displays. The display unit 28 of the present embodiment is configured by a liquid crystal panel, and a screen switching operation and various setting operations are performed by a plurality of operation switches SW1 to SW6 provided below the display unit 28. ing.

  As shown in FIG. 6, the tractor T is provided with a control device 29 configured using a microcomputer or the like. The control device 29 of the present embodiment is configured by using three microcomputers 29a to 29c, and on the input side thereof, the pressure switch 18, the oil temperature sensor 19, the speed increasing switch 24, the speed reducing switch 25, and the high speed described above are provided. In addition to the start switch 26 and the operation switches SW1 to SW6, four auxiliary transmission switches 30 to 33 for detecting the operation position (high speed, medium speed, low speed, neutral) of the auxiliary transmission lever 23, and forward / reverse switching operation (neutral, forward) , Reverse position), a forward position detection switch 35 and a reverse position detection switch 36, a vehicle speed sensor 37 for detecting vehicle speed, and an engine rotation sensor 38 for detecting engine rotation are connected. Further, the electromagnetic proportional valves 16a to 16d, the electromagnetic direction switching valve 17, the display unit 28, and the like described above are connected to the output side of the control device 29.

  The control device 29 mainly controls the electromagnetic proportional valves 16a to 16d and the electromagnetic direction switching valve 17 in accordance with a program written in the ROM in advance, and causes a shift pattern as shown in FIG. 7 to appear. Specifically, the upshift control for shifting the first main transmission 5 and the second main transmission 8 according to the operation of the speed increasing switch 24, and the first main transmission 5 and the second according to the operation of the deceleration switch 25. Shift-down control for shifting the two main transmissions 8, sub-shift operation interlocking control for shifting the first main transmission 5 and the second main transmission 8 according to the operation of the sub-transmission lever 23, the first main at the time of engine start Interlocking with forward / reverse operation for turning on and off the first main transmission device 5 and the second main transmission device 8 in accordance with the initial gear setting control for setting the initial gear position of the transmission 5 and the second main transmission 8 and the forward / reverse switching operation. Control is performed.

  As shown in FIGS. 8 and 9, the forward / reverse operation interlocking control is a control for turning on and off the first main transmission device 5 and the second main transmission device 8 according to the forward / reverse switching operation. When switching from neutral to forward or reverse, the hydraulic clutches C1 to C4 at predetermined gear stages of the first and second main transmissions (5, 8) set by the transmission switches (24, 25). , CL, CH are turned on, and when the forward / reverse switching device 6 is switched from forward or reverse to neutral, the hydraulic clutches C1 to C4 to which the first and second main transmissions (5, 8) are connected. , CL and CH are turned off. Then, when the hydraulic clutches C1 to C4, CL and CH are engaged by the pressure increase control of the electromagnetic proportional valves 16a to 16d, a smooth start is possible.

  When such interlocking control is performed, in order to shorten the time lag from the forward / reverse switching operation to the vehicle start, after the hydraulic clutches CF and CR of the forward / reverse switching device 6 are engaged, the electromagnetic proportionality is as soon as possible. Although it is required to start the pressure increase control of the valves 16a to 16d, conventionally, the operation position of the forward / reverse switching lever 22 is detected by the position detection switch, and the control timing is determined based on the detection signal of the position detection switch. Therefore, due to backlash and play existing in the path from the forward / reverse switching lever 22 to the forward / reverse switching valve 100, there is a risk that a large shift occurs in the sequence control of the forward / reverse switching valve 100 and the electromagnetic proportional valves 16a to 16d. There was this.

  Therefore, in the present invention, as shown in FIGS. 10 to 12, a switching position detecting device 101 is provided in the forward / reverse switching valve 100 so that the switching position of the forward / reverse switching valve 100 can be directly detected. More specifically, the forward / reverse switching valve 100 includes a neutral position where the forward hydraulic clutch CF and the reverse hydraulic clutch CR are disconnected, a forward position where only the forward hydraulic clutch CF is engaged, and a reverse hydraulic clutch. On the other hand, the switching position detecting device 101 is in direct or indirect contact with the concavo-convex portion 103 of the spool 102 while being configured to include the spool 102 that is slidably operated to the reverse position including only the CR. A neutral position detection switch 34 for detecting each operation position, a forward position detection switch 35 and a reverse position detection switch 36 are provided. In this way, it is possible to detect the on / off timing of the forward hydraulic clutch CF and the reverse hydraulic clutch CR with high accuracy regardless of the play and play existing in the path from the forward / reverse switching lever 22 to the forward / reverse switching valve 100. Is possible.

  Further, these position detection switches 34 to 36 are centrally arranged in parallel at one place and are brought into contact with the concavo-convex portion 103 of the spool 102 from above. In this way, based on the concentrated arrangement of the position detection switches 34 to 36, not only can the enlargement of the forward / reverse switching valve 100 be avoided, but also the switch wiring can be simplified. In addition, since the position detection switches 34 to 36 are in contact with the concave and convex portion 103 of the spool 102 from above, it is difficult for metal wear powder or the like to enter the switch, and as a result, it is possible to prevent contact failure due to metal wear powder or the like. In addition, reliability can be improved.

  The forward / reverse switching valve 100 includes a valve body 104 that slidably supports a spool 102, a pump port 105 to which a hydraulic pump P is connected, a tank port 106 to which an oil tank T is connected, and a forward hydraulic clutch CF. Is connected to the A port 107 and the reverse hydraulic clutch CR is connected to the B port 108. By changing the communication state of the ports 105 to 108 according to the sliding operation of the spool 102, The hydraulic clutches CF and CR are selectively turned on and off.

  On the other hand, the switching position detection device 101 includes a cylindrical switch case 109 that is provided on one side surface of the valve body 104 and surrounds the concavo-convex portion 103 formed at the tip of the spool 102. Three switch mounting holes 109a to 109c arranged in a row are formed in the upper part of the switch case 109, and the detection portions of the position detection switches 34 to 36 are inserted and mounted from above into these switch mounting holes 109a to 09c. Is done. As a result, the position detection switches 34 to 36 are concentrated and arranged in one place in parallel, and come into contact with the concave and convex portion 103 of the spool 102 from above.

  Inside the switch case 109, there is a possibility that pressure fluctuations occur as the spool 102 moves. Such pressure fluctuations may increase the operation load of the spool 102, so it is preferable to keep the pressure as constant as possible. Therefore, in the present embodiment, the inside of the switch case 109 is communicated with the tank port 106 via the breather hole 110 formed in the switch case 109 and / or the valve body 104. In this way, the pressure fluctuation in the switch case 109 due to the pushing and pulling of the spool 102 can be eliminated, and the operation load on the spool 102 can be reduced.

  According to the present embodiment configured as described above, the tractor T is provided with the forward hydraulic clutch CF provided in the forward drive power transmission path and the reverse hydraulic clutch CR provided in the reverse drive power transmission path. The forward / reverse switching valve 100 is a switching position detecting device 101 for selectively turning on and off the respective hydraulic clutches CF and CR, and the forward / reverse switching valve 100 switches between the forward hydraulic clutch CF and the reverse hydraulic clutch CR. And a spool 102 that is slidably operated to a forward position where only the forward hydraulic clutch CF is engaged, and a reverse position where only the backward hydraulic clutch CR is engaged, and a switching position detecting device. Reference numeral 101 denotes a neutral position detection switch 34 for detecting each operation position of the spool 102 by directly or indirectly contacting the concave and convex portion 103 of the spool 102. Since the position detection switch 35 and the reverse position detection switch 36 are provided, the position detection switches 34 to 36 are concentratedly arranged in parallel and contacted from above with the concave and convex portion 103 of the spool 102. Regardless of the play and play existing in the path from the forward / reverse switching lever 22 to the forward / reverse switching valve 100, it is possible to detect the on / off timing of the forward hydraulic clutch CF and the reverse hydraulic clutch CR with high accuracy. . Further, since the neutral position detection switch 34, the forward position detection switch 35, and the reverse position detection switch 36 are centrally arranged in parallel, the enlargement of the forward / reverse switching valve 100 can be avoided and the switch wiring is simplified. can do. Moreover, since the neutral position detection switch 34, the forward position detection switch 35, and the reverse position detection switch 36 are in contact with the concave and convex portion 103 of the spool 102 from above, it is difficult for metal wear powder or the like to enter the switch. It is possible to prevent the occurrence of contact failure due to metal wear powder and improve reliability.

  Further, the forward / reverse switching valve 100 includes a valve body 104 that slidably supports a spool 102, a pump port 105 to which a hydraulic pump P is connected, a tank port 106 to which an oil tank T is connected, and a forward hydraulic pressure. The switching position detecting device 101 is provided in the valve body 104 and surrounds the uneven portion 103 of the spool 102. The A port 107 is connected to the clutch CF and the B port 108 is connected to the reverse hydraulic clutch CR. Since the switch case 109 is provided and the inside of the switch case 109 communicates with the tank port T via the breather hole 110 formed in the switch case 109 and / or the valve body 104, the switch accompanying the pushing and pulling of the spool 102 The pressure fluctuation in the case 109 is eliminated, and the operation load on the spool 103 is reduced. It is possible.

DESCRIPTION OF SYMBOLS 1 Transmission case 6 Forward / reverse switching device 22 Forward / reverse switching lever 34 Neutral position detection switch 35 Forward position detection switch 36 Backward position detection switch 100 Forward / reverse switching valve 101 Switching position detection device 102 Spool 103 Uneven portion 104 Valve body 105 Pump port 106 Tank port 107 A port 108 B port 109 Switch case 110 Breather hole CF Forward hydraulic clutch CR Reverse hydraulic clutch

Claims (2)

A forward / reverse switching valve that is provided in a work vehicle having a forward hydraulic clutch interposed in the forward power transmission path and a reverse hydraulic clutch interposed in the reverse power transmission path, and selectively turns each hydraulic clutch on and off. Switching position detecting device,
The forward / reverse switching valve is
A spool that is slidably operated to a neutral position where the forward hydraulic clutch and the reverse hydraulic clutch are disconnected, a forward position where only the forward hydraulic clutch is engaged, and a reverse position where only the backward hydraulic clutch is engaged. Configured with
The switching position detecting device is
A neutral position detection switch, forward position detection switch, and reverse position detection switch that detect the respective operation positions of the spool by directly or indirectly contacting the concave and convex portions of the spool, and these position detection switches are centrally arranged in parallel. And a switching position detecting device for the forward / reverse switching valve, wherein the switching position detecting device is configured to be brought into contact with an uneven portion of the spool from above. The forward / reverse switching valve is
To the valve body that slidably supports the spool,
A pump port to which a hydraulic pump is connected;
A tank port to which the oil tank is connected;
A port to which the forward hydraulic clutch is connected;
A B port to which a reverse hydraulic clutch is connected,
The switching position detecting device is
A switch case that is provided in the valve body and encloses the concave and convex portions of the spool, and that the inside of the switch case is communicated with the tank port via a breather hole formed in the switch case and / or the valve body. 2. A switching position detecting device for a forward / reverse switching valve according to claim 1.

Images