JP4847366B2 - Working vehicle - Google Patents

Description

  The present invention relates to a working vehicle such as a tractor, and in particular, a constant speed power transmission path and a speed increasing power transmission path are configured in parallel to a front wheel power transmission path, and a hydraulic clutch provided in each transmission path is selected. The present invention relates to a working vehicle that makes a two-wheel drive state, a four-wheel drive state, and a front-wheel acceleration drive state appear by turning on and off.

A constant speed power transmission path and a speed increasing power transmission path are configured in parallel with the front wheel power transmission path, and a two-wheel drive state and a four-wheel drive are performed by selectively turning on / off a hydraulic clutch interposed in each transmission path. 2. Description of the Related Art A working vehicle that reveals a state and a front wheel acceleration drive state is known (see, for example, Patent Document 1). In this type of working vehicle, as shown in FIG. 7, the hydraulic clutch 101 of the constant speed power transmission path is normally a spring-actuated hydraulic clutch (negative hydraulic clutch), while the hydraulic clutch of the speed increasing power transmission path is used. 102 is a hydraulically actuated hydraulic clutch (positive hydraulic clutch), and these hydraulic clutches 101 and 102 are selectively turned on and off by a three-position switching valve 103, whereby a two-wheel drive state in which the front wheels are not driven, A four-wheel drive state in which the rear wheel is driven at a substantially constant speed and a front wheel acceleration drive state in which the front wheel is driven at a higher speed than the rear wheel are made to appear.
JP 2000-52799 A

  By the way, in the conventional working vehicle, when switching from the four-wheel drive state (hydraulic clutch 101 = engaged, hydraulic clutch 102 = disengaged) to the front wheel acceleration drive state (hydraulic clutch 101 = disengaged, hydraulic clutch 102 = engaged). In addition, the three-position switching valve 103 is switched to the front wheel acceleration position, and the pressure oil from the hydraulic pump 104 is supplied to the two hydraulic clutches 101 and 102 simultaneously. In actuality, it is difficult to operate the two hydraulic clutches 101 and 102 at the same time because the leak amount differs depending on the accuracy variation. In the worst case, the two hydraulic clutches 101 and 102 are simultaneously engaged, and friction is caused. There was a risk of burning of the plate.

The present invention has been created in view of the above circumstances and has been created for the purpose of solving these problems, and the invention of claim 1 is directed to a front wheel power transmission path with a rear wheel power and a substantially constant power. The constant speed power transmission path for transmitting the power to the front wheels and the increased speed power transmission path for transmitting the power increased from the rear wheel power to the front wheels are configured in parallel. A spring-actuated hydraulic clutch that is turned on by the urging force and turned off when the hydraulic pressure is supplied is interposed. On the speed increasing power transmission path, the hydraulic pressure that is turned on by the urging force of the spring and turned on when the hydraulic pressure is supplied. A two-wheel drive state in which an actuated hydraulic clutch is interposed, and the front wheels are not driven by selective on / off of these hydraulic clutches, a four-wheel drive state in which the front wheels are driven at substantially the same speed as the rear wheels, and the front wheels Than the rear wheel In working vehicle for revealing the front-wheel acceleration drive state to speed drive, a first 2-position switching valve for On / Off spring-actuated hydraulic clutches of the constant velocity power transmission path, the speed increasing power transmission When separately providing a second two-position switching valve for turning on / off the hydraulically operated hydraulic clutch of the path, the first and second two-position switching valves are supplied from the hydraulic pump to the hydraulically operated hydraulic clutch. For working, characterized in that it is interposed in series in the oil passage so that the operation of engaging the hydraulically operated hydraulic clutch is prohibited when the first and second two-position switching valves are individually switched to the inlet side. It is a traveling car. In this way, the timing for turning on / off the spring-actuated hydraulic clutch on the constant-speed power transmission path and the timing for turning on / off the hydraulic-actuated hydraulic clutch on the speed increasing power transmission path can be individually controlled. The two hydraulic clutches can be turned on and off at appropriate timings, and the driving state can be switched smoothly.
According to a second aspect of the present invention, when the four-wheel drive state is switched from the four-wheel drive state to the front wheel acceleration drive state, the hydraulic operation of the speed increasing power transmission path is performed with respect to the timing at which the spring operated hydraulic clutch of the constant speed power transmission path is disengaged. The working vehicle according to claim 1, wherein a timing for engaging the mold hydraulic clutch is delayed. In this way, when switching from the four-wheel drive state to the front wheel acceleration drive state, the spring-actuated hydraulic clutch of the constant-speed power transmission path and the hydraulic-actuation type hydraulic clutch of the acceleration power transmission path are simultaneously engaged. Can be reliably avoided and seizure of the friction plate can be prevented.

  Next, embodiments of the present invention will be described with reference to the drawings. 1 and 2, reference numeral 1 denotes a transmission case mounted on an agricultural tractor T. The transmission case 1 inputs the power of the engine E through the main clutch mechanism 2 and travels the input power. The power transmission path 3 and the PTO power transmission path 4 are branched. The traveling power transmission path 3 includes a plurality of transmission shafts S1 to S11, a first main transmission mechanism 5 including four-stage hydraulic clutch transmission mechanisms C1 and C2, and a forward / rearward movement including a hydraulic clutch transmission mechanism C3. A switching mechanism 6, a sub-transmission mechanism 7 comprising a three-speed meshing transmission mechanism K, a second main transmission mechanism 8 comprising a two-speed hydraulic clutch transmission mechanism C 4, and a two-speed hydraulic clutch type A front wheel transmission mechanism 9 including a transmission mechanism C5 is provided. The present invention is characterized by the front wheel speed change mechanism 9 and its hydraulic operation circuit. Hereinafter, specific configurations thereof will be described with reference to FIGS.

  As shown in FIGS. 3 and 4, the front wheel speed change mechanism 9 transmits the power of the rear wheel R and the power of substantially the same speed to the front wheel F on the front wheel power transmission path between the transmission shaft S10 and the transmission shaft S11. A constant speed power transmission path 10 and a speed increasing power transmission path 11 for transmitting the power increased from the power of the rear wheel R to the front wheels F are configured in parallel, and the constant speed power transmission path 10 includes a spring. A spring-actuated hydraulic clutch (negative hydraulic clutch) 13 that is turned on by an urging force of 12 and turned off by the supply of hydraulic pressure is interposed, while the motive force of the spring 14 is turned off in the speed increasing power transmission path 11. Thus, a hydraulically actuated hydraulic clutch (positive hydraulic clutch) 15 that is turned on when hydraulic pressure is supplied is interposed, and the front wheel F is not driven by selectively turning on / off these hydraulic clutches 13 and 15. Driving state (hydraulic clutch 13 = disengaged, hydraulic clutch 15 = disengaged), four-wheel driving state in which front wheel F is driven at substantially constant speed with rear wheel R (hydraulic clutch 13 = on, hydraulic clutch 15 = disengaged), front wheel The front-wheel accelerated drive state (hydraulic clutch 13 = disengaged, hydraulic clutch 15 = engaged) in which F is driven at a higher speed than the rear wheel R can be made to appear.

  As shown in FIG. 4, the hydraulic operation circuit for operating the front wheel transmission mechanism 9 includes a hydraulic pump 16 and a first two-position switching valve that engages / disengages the spring-actuated hydraulic clutch 13 of the constant speed power transmission path 10. 17 and a second two-position switching valve 18 for turning on and off the hydraulically operated hydraulic clutch 15 of the speed increasing power transmission path 11. In this way, the timing for turning on / off the spring-actuated hydraulic clutch 13 of the constant-speed power transmission path 10 and the timing for turning on / off the hydraulic-actuated hydraulic clutch 15 of the speed increasing power transmission path 11 are individually controlled. Therefore, the two hydraulic clutches 13 and 15 can be turned on and off at appropriate timing, and the driving state can be switched smoothly.

  In the present embodiment, only the first two-position switching valve 17 is interposed in the supply oil path from the hydraulic pump 16 to the spring-operated hydraulic clutch 13, and the spring-operated hydraulic clutch 13 is independently engaged and operated by the switching. However, the first two-position switching valve 17 and the second two-position switching valve 18 are interposed in series in the supply oil path from the hydraulic pump 16 to the hydraulically operated hydraulic clutch 15, thereby providing hydraulic pressure. The actuating hydraulic clutch 15 is prohibited from being independently operated. That is, in order to engage and operate the hydraulically operated hydraulic clutch 15, it is required to switch the first two-position switching valve 17 and the second two-position switching valve 18 to the ingress side. Thereby, the simultaneous engagement state of both hydraulic clutches 13 and 15 due to the single engagement operation of the hydraulically operated hydraulic clutch 15 can be avoided, and seizure of the friction plate can be prevented.

  As shown in FIG. 4, the two-position switching valves 17 and 18 are switched and controlled by a control device 19 mounted on the tractor T. For example, the control device 19 switches and controls the two-position switching valves 17 and 18 according to the switching operation of the front wheel drive switching dial 20 and selectively selects the two-wheel drive state, the four-wheel drive state, and the front wheel acceleration drive state. To appear. The control device 19 according to the present embodiment switches from the four-wheel drive state (hydraulic clutch 13 = engaged, hydraulic clutch 15 = disengaged) to the front wheel acceleration drive state (hydraulic clutch 13 = disengaged, hydraulic clutch 15 = entered). The timing for turning on the hydraulically actuated hydraulic clutch 15 in the speed increasing power transmission path 11 is delayed with respect to the timing for disengaging the spring actuated hydraulic clutch 13 in the constant speed power transmission path 10. In this way, when switching from the four-wheel drive state to the front wheel acceleration drive state, the spring-actuated hydraulic clutch 13 of the constant-speed power transmission path 10 and the hydraulic-actuated hydraulic clutch 15 of the acceleration power transmission path 11 are simultaneously performed. It is possible to reliably avoid entering and prevent seizure of the friction plate.

  Next, the control procedure of the control device 19 will be specifically described with reference to FIG. However, when the front wheel drive switching dial 20 is at the 2W position, the two-wheel drive state is always displayed, and when the front wheel drive switching dial 20 is at the 4W position, the four-wheel drive state is always displayed. When 20 is in the double speed position and in the non-aircraft turning state, the four-wheel drive state is displayed, and when the front wheel drive switching dial 20 is in the double speed position and in the airframe turning state, the front wheel acceleration drive is performed. Let the state appear.

  As shown in FIG. 6, in the front wheel drive control performed by the control device 19, first, the switching position of the front wheel drive switching dial 20 is determined (S11, S12). Here, when the front wheel drive switching dial 20 is in the 2W position, the first two-position switching valve 17 is turned on and the second two-position switching valve 18 is turned off, so that the four-wheel drive hydraulic clutch 13 and The front wheel acceleration hydraulic clutch 15 is disengaged (S13, S14), and the two-wheel drive state is always displayed. When the front wheel drive switching dial 20 is in the 4W position, the two-position switching valves 17 and 18 are turned off to engage the hydraulic clutch 13 for driving the four wheels (S16), and the front wheel speed increasing hydraulic clutch. 15 is turned off (S15), and the four-wheel drive state is always displayed. When the front wheel drive switching dial 20 is in the double speed position, it is determined whether or not the vehicle is turning (S17). If the determination result is NO, the two-position switching valves 17 and 18 are turned off. Thus, the four-wheel drive hydraulic clutch 13 is engaged (S16), the front wheel acceleration hydraulic clutch 15 is disengaged (S15), and the four-wheel drive state is revealed. After turning on the first two-position switching valve 17 and disengaging the hydraulic clutch 13 for driving the four wheels (S18), after waiting for a predetermined waiting time (S19), the second two-one switching valve 18 is turned on. Is turned on, the front wheel acceleration hydraulic clutch 15 is engaged (S20), and the front wheel acceleration drive state is revealed.

  According to the present embodiment configured as described, the front wheel power transmission path has a constant speed power transmission path 10 that transmits rear wheel power and substantially constant speed power to the front wheels, and the rear wheel power is accelerated. A speed-up power transmission path 11 that transmits power to the front wheels is configured in parallel, and the constant speed power transmission path 10 is turned on by the urging force of the spring 12 and is turned off by the hydraulic pressure supply. On the other hand, the speed increasing power transmission path 11 is provided with a hydraulically actuated hydraulic clutch 15 that is turned off by the urging force of the spring 14 and is turned on when the hydraulic pressure is supplied. , 15 by selectively turning on and off, the two-wheel drive state in which the front wheel F is not driven, the four-wheel drive state in which the front wheel F is driven at substantially the same speed as the rear wheel R, and the front wheel F increased from the rear wheel R. Front wheel to drive at high speed In the tractor T that reveals the high-speed drive state, a first two-position switching valve 17 that turns on and off the spring-actuated hydraulic clutch 13 of the constant-speed power transmission path 10 and a hydraulically-actuated type of the speed increasing power transmission path 11 Since the second two-position switching valve 18 for turning on and off the hydraulic clutch 15 is separately provided, the timing for turning on and off the spring-actuated hydraulic clutch 13 of the constant speed power transmission path 10 and the speed increasing power transmission path 11 are provided. The timing at which the hydraulic clutch 15 is engaged / disengaged can be individually controlled. As a result, the two hydraulic clutches 13 and 15 can be engaged / disengaged at an appropriate timing to smoothly switch the driving state. be able to.

  In addition, when switching from the four-wheel drive state to the front wheel acceleration drive state, the hydraulically operated hydraulic clutch 15 of the speed increasing power transmission path 11 with respect to the timing at which the spring operated hydraulic clutch 13 of the constant speed power transmission path 10 is turned off. Since the timing of turning on the vehicle is delayed, when switching from the four-wheel drive state to the front wheel acceleration drive state, the spring-actuated hydraulic clutch 13 of the constant speed power transmission path 10 and the hydraulic operation type of the acceleration power transmission path 11 are performed. It is possible to reliably avoid the simultaneous engagement of the hydraulic clutch 15 and prevent the friction plate from being seized.

It is a perspective view of a tractor. It is a transmission circuit diagram in a mission case. It is sectional drawing of a front-wheel transmission mechanism. It is a hydraulic circuit diagram which shows the operation circuit of a front-wheel transmission mechanism. It is a block diagram which shows the control structure of a front-wheel transmission mechanism. It is a flowchart which shows the control procedure of front-wheel drive control. It is a hydraulic circuit diagram which shows the operation circuit of the front-wheel transmission mechanism which concerns on a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission case 9 Front-wheel transmission mechanism 10 Constant speed power transmission path 11 Increase speed power transmission path 12 Spring 13 Spring actuated hydraulic clutch 14 Spring 15 Hydraulic actuated hydraulic clutch 17 First two-position switching valve 18 Second two-position switching Valve 19 Control device F Front wheel R Rear wheel T Tractor

Claims (2)

In parallel to the front wheel power transmission path, a constant speed power transmission path for transmitting rear wheel power and substantially constant speed power to the front wheels and a speed increasing power transmission path for transmitting power increased from the rear wheel power to the front wheels in parallel. The constant-speed power transmission path is provided with a spring-actuated hydraulic clutch that is turned on by the urging force of the spring and turned off when the hydraulic pressure is supplied. A hydraulically actuated hydraulic clutch that is turned off by the urging force and turned on when the hydraulic pressure is supplied is provided. A two-wheel drive state in which the front wheels are not driven by selective on / off of these hydraulic clutches, In a working vehicle for realizing a four-wheel drive state in which a wheel is driven at substantially constant speed and a front wheel acceleration drive state in which a front wheel is driven at a speed higher than that of a rear wheel, a spring-operated type of the constant-speed power transmission path Hydraulic A first 2-position switching valve for On / Off the pitch, per the separately and a second 2-position switching valve for On / Off the hydraulic hydraulic clutches of the speed increasing power transmission path, the first The second two-position switching valve is interposed in series in the supply oil path from the hydraulic pump to the hydraulically operated hydraulic clutch, and the first and second two-position switching valves are operated to engage the hydraulically operated hydraulic clutch. A traveling vehicle for work characterized in that it is forbidden to switch to the entrance side of the vehicle alone .   When switching from the four-wheel drive state to the front wheel acceleration drive state, the hydraulically operated hydraulic clutch of the speed increasing power transmission path is engaged with respect to the timing of disengaging the spring operated hydraulic clutch of the constant speed power transmission path. The working vehicle according to claim 1, wherein the timing is delayed.

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