JPH0889014A - Automatic shift structure of work vehicle - Google Patents

Abstract

(57) [Abstract] [Purpose] There are two modes: an automatic speed change state in which a continuously variable transmission for traveling is automatically operated according to a work load, and a manual speed change state in which a continuously variable transmission is operated by a speed change lever. In a work vehicle configured to be selectively switchable, a handle operation (steering operation of a machine body) during reverse travel is facilitated. Constitution: A selection means 12 capable of artificially selecting an automatic shift state and a manual shift state is provided, and when the shift lever 11 is operated to the reverse side R, the selection means 12 is given priority and the manual shift state is set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic transmission structure for a traveling system in a work vehicle such as an agricultural tractor.

[0002]

2. Description of the Related Art An example of an automatic transmission structure for a work vehicle as described above is disclosed in Japanese Utility Model Laid-Open No. 58-21237. This structure is equipped with a work load sensor that detects the work load on the machine body, so that the work load is maintained at the set value. Equipped with means.

In this case, a gear shift lever (corresponding to a gear shift operation tool) that is artificially operated is provided, and a continuously variable transmission is performed by a gear shift actuator so that the continuously variable transmission is at the gear shift position corresponding to the operation position of the gear shift lever. There is a structure in which a manual transmission means for shifting the device is provided so that the operating state of the automatic transmission means and the operating state of the manual transmission means can be artificially selected.

[0004]

As described above, in a work vehicle constructed so that the operating state of the automatic transmission means and the operating state of the manual transmission means can be selected, for example, the operating state of the automatic transmission means is selected to move forward. In this state, it is assumed that the worker starts the backward movement of the machine by switching the traveling continuously variable transmission itself or another forward-reverse switching device to the reverse side.

Since the worker is generally seated forward in the driver's seat, when the machine body is moved backward as described above, the worker twists his body and turns to the rear to operate the steering wheel (steering machine operation). Will be done. In this case, if the operating state of the automatic shifting means remains selected, the traveling speed of the machine automatically changes to the high speed side and the low speed side (the continuously variable transmission automatically shifts according to the work load). In this state), the operator has to turn the steering wheel backward and operate the steering wheel when moving backward. INDUSTRIAL APPLICABILITY The present invention makes it easy to perform a steering wheel operation during reverse travel in an automatic speed change structure for a work vehicle that includes an automatic speed change means and a manual speed change means for automatically changing the speed of a continuously variable transmission for traveling according to a work load. The purpose is to obtain such a configuration.

[0006]

A feature of the present invention resides in the following structure in the automatic speed change structure for a work vehicle as described above. That is, [1] a gearshift actuator for gearshifting a continuously variable transmission for traveling, a gearshift operation tool for manually shifting gears, and a work load sensor for detecting a work load on the machine body are provided. , So that the detection value of the work load sensor is maintained at the set value, the automatic shifting means for automatically shifting the continuously variable transmission by the shifting actuator and the shift position corresponding to the operating position of the shift operating tool are set. And a manual shifting means for shifting the continuously variable transmission by means of a shifting actuator, a selecting means for artificially selecting and operating one of the automatic shifting means and the manual shifting means, and switching to the reverse side. Setting means for setting the operating state of the manual transmission means prior to the selection means based on the operation.

[2] In the construction of the above item [1], based on the detection by the ascending detection means for detecting that the ground work device connected to the machine body so as to be capable of ascending / descending operation is greatly ascended from the ground, and the detection by the ascending detection means. And a deceleration means for automatically decelerating the continuously variable transmission to the low speed side.

[3] In the configuration of [1] above, the vertical position detecting means for detecting the vertical position of the ground working apparatus connected to the machine body so as to be able to move up and down, and the ground working apparatus based on the detection of the vertical position detecting means. And a deceleration means for automatically decelerating the continuously variable transmission to the low speed side while the vehicle is being lowered from near the ground to a predetermined working depth.

[4] In the configuration of [1] above, the posture change detection means for detecting the magnitude or frequency of the posture change of the ground work device connected to the machine body, and the ground work based on the detection by the posture change detection means If there is a large or frequent change in the posture of the device, there is provided deceleration means for automatically decelerating the continuously variable transmission to the low speed side.

[0010]

[Action]

[I] According to the constitution described in [1] above, when the operating state of the automatic transmission means is selected, the manual transmission means is automatically operated when the vehicle is started to move backward by switching to the reverse side. The operating state of is set. In the operating state of this manual transmission,
Since the continuously variable transmission is in a state of being gear-shifted so as to correspond to the operation position of the gear-shift operation tool operated by the operator, the continuously-variable transmission is not gear-shifted unless the gear shift operation tool is operated.
As a result, the vehicle body moves backward at a constant traveling speed unless the gear shift operation tool is operated during backward movement, so that the steering wheel operation facing backward can be performed relatively easily.

[II] When configured as in the above item [2],
As in the case of the configuration of the above [1], the "action" described in the above [I] is provided, and in addition to this, the following "action" is provided. When turning at the end of the work ground, the ground work device located near the ground is lifted from the ground largely before turning, and it is better that the traveling speed of the airframe during turning is low. Therefore, with the configuration of the above [2], when the ground work device is operated to move up while the automatic transmission means is running, the continuously variable transmission is automatically decelerated to the low speed side. It is not necessary for the operator to perform a switching operation to the operating state of the manual speed changer and to perform a speed change operation of the continuously variable transmission to a low speed side by the speed change operation tool.

[III] The constitution as in the preceding paragraph [3] has the "action" described in the preceding paragraph [I] as in the case of the constitution in the preceding paragraph [1]. It has "action". As described in the previous section [II],
When turning the ground working device while raising it and lowering the ground working device to the ground again, it takes a little time for the ground working device to reach the predetermined working depth after it touches the ground. At this time, if the machine body travels at high speed, the ground work by the ground work device becomes shallow in a long portion.

Therefore, if the configuration as described in [3] above is adopted,
When lowering the ground work device to the ground, the continuously variable transmission is automatically decelerated to the low speed side.Therefore, the aircraft should run at low speed until the ground work device reaches a predetermined working depth. Therefore, the portion where the ground work by the ground work device becomes shallow can be shortened. Further, it is not necessary for the operator to switch to the operating state of the manual transmission means when the ground work device is being lowered, and to perform a troublesome operation such as shifting the continuously variable transmission to the low speed side by the gear shift operation tool.

[IV] When constructed as in the above item [4],
As in the case of the configuration of the above [1], the "action" described in the above [I] is provided, and in addition to this, the following "action" is provided. When the machine body is run at a relatively high speed in the working state of the ground work device, if there are many irregularities on the ground, the ground work device swings along the irregularities of the ground, and the ground work cannot be performed sufficiently. Therefore, with the configuration of the above [4], the continuously variable transmission is automatically decelerated when the ground has a large amount of unevenness, so that the ground work device is prevented from swinging due to the unevenness of the ground and ground work is prevented. The number of situations in which it cannot be fully performed is reduced. Further, it is not necessary for the operator to switch to the operating state of the manual transmission means when there is a lot of unevenness on the ground, and to perform a troublesome operation such as operating the continuously variable transmission to the low speed side with the gear shift operation tool.

[0015]

According to the first aspect of the present invention, there is provided an automatic speed change structure for a work vehicle, comprising automatic speed change means and manual speed change means for automatically changing the speed of a continuously variable transmission for traveling according to a work load. , When the vehicle is moving backward, the aircraft will move backward at a constant traveling speed unless the gear change operation tool is operated, which makes it easier to operate the steering wheel facing backward and improves operability when moving backward. did it.

According to the second aspect of the invention, as in the case of the first aspect, the "effect of the invention" of the first aspect is provided. According to the present invention, the continuously variable transmission is automatically decelerated when the ground work device is lifted, so that the operator switches to the operating state of the manual shift means, and the gear shift operation tool is operated. As a result, there is no need to perform a troublesome operation such as shifting the continuously variable transmission to the low speed side, and operability can be improved.

According to the third aspect, similar to the case of the first aspect, the above-mentioned "effect of the invention" is provided. According to the third aspect of the invention, when the ground work device is lowered to the ground, the continuously variable transmission is automatically decelerated to the low speed side, and the ground work by the ground work device becomes shallow. Since it can be shortened, the workability of ground work can be improved. Further, at this time, it is not necessary for the operator to perform a switching operation to the operating state of the manual speed changing means and to perform a speed changing operation of the continuously variable transmission to a low speed side by the speed change operation tool, so that the operability is also improved. Can be made.

According to the fourth aspect, similar to the case of the first aspect, the above-mentioned "effect of the invention" is provided. According to the present invention, the continuously variable transmission is automatically decelerated when there are many irregularities on the ground, and the number of situations in which the ground work cannot be sufficiently performed is reduced. Therefore, the workability of the ground work is reduced. Can be improved. Further, at this time, it is not necessary for the operator to perform a switching operation to the operating state of the manual speed changing means and to perform a speed changing operation of the continuously variable transmission to a low speed side by the speed change operation tool, so that the operability is also improved. Can be made.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. (1) As shown in FIG. 1, an agricultural vehicle, which is an example of a work vehicle, is provided with an engine 3 at the front of the machine supported by front wheels 1 and rear wheels 2 and a control section 4 and a mission case 5 at the rear of the machine. It constitutes a tractor. As shown in FIGS. 2 and 1,
A pair of left and right lower links 15 and one top link 16
The rotary tiller 10 (corresponding to the ground work device)
Is connected so that it can move up and down. A single-acting lift cylinder 17 is arranged above the mission case 5, and a pair of left and right lift arms 18 and a lower link 15, which are vertically driven to swing by the lift cylinder 17, constitute a lift rod 1.
9 and a double-acting rolling cylinder 20.

As a result, as shown in FIG. 3, the three-position switching type lift control valve 21 for the lift cylinder 17 is operated to lift and lower the entire rotary tiller 10 by the lift cylinder 17 and the lift arm 18. And
The rolling control valve 22 of the three-position switching type with respect to the rolling cylinder 20 is operated to roll the rotary tiller 10 around the connection point with the lift rod 19 by the rolling cylinder 20.

In this agricultural tractor, automatic tilling depth control means for maintaining the rotary tiller 10 at a set height from the field scene G (corresponding to the ground) and keeping the tilling depth (corresponding to the working depth) constant, The control device 14 is provided with position control means for maintaining the height of the rotary tiller 10 at a set position with respect to the machine body and rolling control means for maintaining the left and right inclinations of the rotary tiller 10 in a set posture. As shown in FIGS. 3 and 2, the rotary tilling device 10 is provided with a tilling depth sensor 23 that detects the vertical angle of the rear cover 10a that is vertically swingably provided. As a result, by the automatic tilling depth control means of the control device 14, the detection value (tilting depth) of the tilling depth sensor 23 becomes the set tilling depth set by the tiller depth setting device 24 of the potentiometer type provided on the airframe. Then, the lift control valve 21 is operated, and the lift cylinder 17 and the lift arm 18 automatically move the rotary tiller 10 up and down.

At the base of the lift arm 18, an angle sensor 25 for detecting the vertical angle of the lift arm 18 with respect to the machine body.
Is provided. As a result, the position control means of the controller 14 operates the lift control valve 21 so that the lift cylinder 17 controls the lift control valve 21 so that the detected value of the angle sensor 25 becomes the target value set by the position setter 26 provided on the machine body. The lift arm 18 is vertically rocked. Therefore, when the rotary tiller 10 is located above the field scene G, the operator operates the position setter 26 to change the position of the rotary tiller 10 with respect to the machine body by the position control means. It can be operated. And the position setter 2
When the rotary tilling device 10 is operated to descend to a position in contact with the field scene G by 6, the automatic tilling depth control means is automatically switched to the operating state, and the detection value (tilting depth) of the tilling depth sensor 23 becomes the tilling depth. The rotary tiller 10 is automatically moved up and down to reach the set tilling depth of the setter 24.

As shown in FIGS. 3 and 2, a stroke sensor 27 for detecting the expansion / contraction amount of the rolling cylinder 20,
Weight-type tilt sensor 28 that detects left and right tilt of the aircraft
Is provided. As a result, the rolling control means of the control device 14 sets the inclination setter 29 provided on the vehicle body based on the inclination of the vehicle body by the inclination sensor 28 and the inclination of the rotary tiller 10 with respect to the vehicle body by the stroke sensor 27. The rolling control valve 22 is operated to be in the posture, and the rolling cylinder 20 automatically performs the rolling operation of the rotary tiller 10.

As shown in FIG. 3, this agricultural tractor is equipped with a hydrostatic continuously variable transmission 6 for traveling,
The continuously variable transmission 6 is configured to be capable of continuously shifting gears between the forward drive side F and the reverse drive side R across the neutral stop position N.
A double-acting type shift cylinder 7 (corresponding to a shift actuator) that shifts the continuously variable transmission 6 by changing the angle of a swash plate (not shown) of the continuously variable transmission 6 and hydraulic oil to the shift cylinder 7. An electromagnetically-operated control valve 8 for supplying / discharging and expanding / contracting the same is provided, and a potentiometer 9 for detecting the expansion / contraction position of the transmission cylinder 7. A gearshift lever 11 (corresponding to a gearshift operation tool) for a continuously variable transmission 6 that can be freely operated on a forward drive side F and a reverse drive side R with a neutral stop position N sandwiched in a control section 4 of the machine body, an automatic gearshift state described later, and a manual operation. Momentary type changeover switch 12 (corresponding to selecting means) for selecting a gear shift state
Is equipped with a gearshift lever 11 and a changeover switch 1.
The operation position 2 and the detection value of the potentiometer 9 are input to the control device 14.

(2) Next, the control of the agricultural tractor during traveling will be described. As shown in FIGS. 4 and 5, when the changeover switch 12 is operated in the manual shift state (the operating state of the manual shift means) (step S1), the lamp 31
Disappears (step S2), and the manual shift state is set. As a result, the control device 14 operates the control valve 8 and the transmission cylinder 7 in accordance with the operation of the transmission lever 11.
The continuously variable transmission 6 is operated to shift so as to correspond to the operation position of the shift lever 11 (step S3) (the above corresponds to the manual shifting means).

Next, when the changeover switch 12 is operated to the automatic shift state (step S1), the lamp 31 is turned on (step S5), and the automatic shift state is set. The automatic shift state is set in this way only when the shift lever 11
Is operated to the forward drive side F (step S4), and the shift lever 11 is operated to the reverse drive side R even if the changeover switch 12 is operated to the automatic shift state (step S4). With the switch 12 left in the automatic shift state, the process proceeds to step S2 and the manual shift state is set (corresponding to the setting means).

As a result, when the speed change lever 11 is operated to the reverse side R, the manual speed change state is set irrespective of the operation position of the changeover switch 12, and the continuously variable transmission 6 is operated depending on the operation position of the speed change lever 11. Is in a state in which a gear shift operation is performed. Then, even if the shift lever 11 is operated to the reverse side R while the changeover switch 12 is operated to the automatic shift state and the manual shift state is set, as long as the changeover switch 12 is not operated to the manual shift state (the automatic shift state (As long as it is left), the automatic shift state is set again by operating the shift lever 11 to the forward drive side F.

As shown in FIG. 3, a rotary tiller 10 is provided.
Is provided with a work switch 30 for selecting the work state, and the operator operates the work switch 30 to the deep plowing position, the standard position, the shallow plowing position and the scraping position according to the work state. As a result, when the automatic shift state is set by the changeover switch 12, a turning speed position V1, which will be described later, and swallowing are performed in accordance with the operating position (deep tilling position, standard position, shallow tilling position and scraping position) of the work switch 30. Speed position V
2, wasteland upper limit position V3, standby speed position V4, speed increasing operation ratio A1 and deceleration operation ratio A2 are set for the continuously variable transmission 6 (step S6).

In accordance with the operation position of the accelerator pedal 32 shown in FIG. 3, a target value M1 of the engine speed of the engine 3 (the set value is subtracted from the engine speed without load of the engine 3 corresponding to the operation position of the accelerator pedal 32). (Corresponding to the set value) is set (step S9), the rotational speed M of the engine 3 (corresponding to the detected value) is set to the rotational speed sensor 13 of FIG.
The target value M1 and the detected rotation speed M are detected by (corresponding to a work load sensor) (step S10), and the detected rotation speed M and the target value M1 are input to the control device 14.
And are compared (step S11).

In this case, the detected rotational speed M is the target value M.
If it is lower than 1, it is determined that the work load on the machine body is large. As a result, the deceleration operation ratio A2, the detected rotational speed M and the target value M which are preset in step S6 are set.
1 based on the difference from 1 and the rate of change of the rotational speed M.
The continuously variable transmission 6 is operated to shift to the low speed side by the 4 and the shift cylinder 7 (step S12). When the detected rotation speed M matches the target value M1, the continuously variable transmission 6 is left at the current gear position.

On the contrary, if the detected rotation speed M is higher than the target value M1, it is determined that the work load on the machine body is small. Thus, based on the speed increasing operation ratio A1, the difference between the detected rotational speed M and the target value M1 and the rate of change of the rotational speed M, which are set in advance in step S6, the control device 14 and the shift cylinder 7 are controlled. The continuously variable transmission 6 is operated to shift to the high speed side (step S13). In this case, the operation position of the speed change lever 11 is the upper limit position V of the speed change range of the continuously variable transmission 6, and the continuously variable transmission 6 goes beyond the upper limit position V (the operation position of the speed change lever 11) to the high speed side. When a gear shift operation is performed (step S14), the continuously variable transmission 6 is held at the upper limit position V (the operation position of the gear shift lever 11) (step S15) (the above corresponds to the automatic gear shift means).

(3) Next, a description will be given of control in the case where the field scene G has irregularities when the machine body is traveling in the automatic shift state described above. When the tilling work is performed by the rotary tilling device 10 while the machine is traveling with the automatic shifting state set as described above, when the rotary tilling device 10 is automatically operated by the automatic tilling depth control means described in (1) above. The vertical tilling operation and the automatic rolling operation of the rotary tiller 10 by the rolling control means are performed. In this way, when the rotary tiller 10 is automatically moved up and down by the automatic tilling depth control means, the frequency N of the up and down operations (the number of up and down operations within the set time) is controlled by the controller 1.
4 is detected (step S16) (corresponding to attitude change detection means), and the detected frequency N is compared with the set value N1 (step S17).

In this case, the detected frequency N is the set value N
If it is smaller than 1 (step S17), it is determined that the rotary field 10 is not moved up and down frequently because the unevenness of the field scene G is small, and the upper limit position V for the continuously variable transmission 6 in steps S14 and S15 is , Shift lever 1
The operation position 1 remains set (step S1).
8). On the contrary, when the detected frequency N is equal to or higher than the set value N1 (step S17), it is determined that the rotary tiller 10 is frequently moved up and down due to the unevenness of the field scene G, and the steps S14 and S15 are performed. The upper limit position V for the continuously variable transmission 6 is set to the wasteland upper limit position V3 preset in step S6 (step S19).
(Corresponding to deceleration means). Then, when the frequency N detected next time returns to a state where it is smaller than the set value N1, step S
The upper limit position V is again set to the operation position of the shift lever 11 by 18.

This wasteland upper limit position V3 is set to a lower speed side than the normal traveling speed when the aircraft is traveling in the automatic speed change state while performing the plowing work by the rotary tilling device 10, so that the upper limit is set as described above. When the position V is replaced with the wasteland upper limit position V3 from the operation position of the speed change lever 11, the speed change range in the automatic speed change state is suppressed to the low speed side as a whole. Wasteland upper limit position V3 at the deep plowing position of the work switch 30, wasteland upper limit position V3 at the standard position,
The wasteland upper limit position V3 at the shallow plowing position and the wasteland upper limit position V3 at the scraping position are gradually higher in this order.

(4) Next, a description will be given of the control at the time of turning at the edge of the ridge in the case where the machine body is traveling in the automatic shift state described above. As described above, when the automatic shifting state is set and the tilling work is performed along one side of the field and the vehicle reaches the edge of the ridge, the rotary tiller 10 is largely lifted from the field scene G to perform the turning operation of the vehicle. And again rotary tiller 1
0 is moved down to the field scene G, and the next tilling work is started.

When the machine reaches the edge in the automatic shifting state, the operator operates the position setting device 26 shown in FIG. 3 to control the position of the rotary tiller 10 which is vertically moved by the automatic tilling depth control means. A large ascending operation is performed from the field scene G by means. When the rotary tiller 10 is operated to rise in this way (step S7) (corresponding to the rise detecting means), the continuously variable transmission 6 causes the control device 14 to operate regardless of the operation position of the shift lever 11 as shown in FIG. Further, the speed change cylinder 7 decelerates and holds the turning speed position V1 preset in step S6 (step S20) (corresponding to a speed reducing means). As a result, at a low speed corresponding to the turning speed position V1, the operator operates the handle to turn the machine body on the edge. In this case, the turning speed position V1 of the work switch 30 in the deep plowing position, the turning speed position V1 of the standard position, the turning speed position V1 of the shallow plowing position, and the turning speed position V1 of the scraping position are little by little in this order. It is on the high speed side.

When the operator operates the position setter 26 to move the rotary tiller 10 down to the field scene G when the turn at the edge is completed and the next tillage work is started,
The operating state of the position control means is switched to the operating state of the automatic plowing depth control means, and the detection value (plowing depth) of the plowing depth sensor 23 of the rotary tilling device 10 is set by the automatic plowing depth control means. The rotary tiller 10 is automatically lowered until the set tilling depth of the vessel 24 is reached.

When the rotary tiller 10 is lowered as described above, the rear cover 10a of the rotary tiller 10 is grounded to the field scene G.
Is detected by the gear shift lever 1 (step S21).
Regardless of the operating position of No. 1, the continuously variable transmission 6 is
4 and the shift cylinder 7 decelerate to the plucking speed position V2 preset in step S6 (step S22), and the detection value (plow depth) of the plowing depth sensor 23 is set to plowing depth. The plow speed position V2 is maintained until the set plowing depth of the vessel 24 is reached (corresponding to the vertical position detecting means and the speed reducing means) (step S23).

In this case, the plow speed position V2 at the deep plowing position of the work switch 30, the plow speed position V2 at the standard position, the plow speed position V2 at the shallow plowing position, and the pluck speed position V2 at the surrogate position. Are gradually increasing in this order, and the plow speed position V2 is lower than the turning speed position V1 at the deep plowing position, and the plow speed position V2 is lower than the turning speed position V1 at the standard position. In addition, the swallowing speed position V is lower than the turning speed position V1 at the shallow plowing position.
2 is set to a low speed, and the feeding speed position V2 is set to be lower than the turning speed position V1 at the substitute position.

As described above, with the continuously variable transmission 6 held at the plow speed position V2, the detection value (plow depth) of the tillage depth sensor 23 of the rotary tiller 10 is determined by the automatic tillage depth control means. When the rotary tiller 10 is automatically lowered to the set tilling depth of the tiller depth setting device 24, the process proceeds from step S23 to step S9 in FIG.
The continuously variable transmission 6 automatically starts shifting based on the rotation speed M of the engine 3, and the next tilling operation is started.

(5) Next, a case will be described in which the main clutch 33 (see FIG. 1) is disengaged to temporarily stop the machine while the machine is traveling in the automatic shift state described above. Auxiliary transmission (gear shift type) in the mission case 5 during cultivating work with the automatic shift state set.
When performing a gear shifting operation (not shown), the operator depresses the clutch pedal 34 of FIG. 3 to operate the main clutch 33 of FIG.
Turn off the switch to perform gear shifting operation of the auxiliary transmission while the machine is temporarily stopped.

When the main clutch 33 is disengaged in this manner to temporarily stop the machine body, the continuously variable transmission 6 is operated by the control device 14 and the transmission cylinder 7 regardless of the operation position of the transmission lever 11, as shown in FIG. , Is decelerated to the standby speed position V4 preset in step S6 and held (step S24). Then, when the shift operation of the auxiliary transmission device is completed and the operator releases the clutch pedal 34 and operates the main clutch 33 (step S2).
5), immediately shift to step S9 in FIG.
The automatic speed change operation of the continuously variable transmission 6 based on the number of revolutions M of the vehicle is not restarted, but the continuously variable transmission 6 is held at the standby speed position V4 for a set time, and the aircraft is kept at the standby speed position. It begins to move forward at a low speed of V4 (step S2
6) After that, the process proceeds to step S9 in FIG. 5, and the automatic speed change operation of the continuously variable transmission 6 based on the rotation speed M of the engine 3 is restarted.

In this case, the standby speed position V4 at the deep plowing position of the work switch 30, the standby speed position V4 at the standard position,
The standby speed position V4 at the shallow plowing position and the standby speed position V4 at the skimming position are gradually on the high speed side in this order, and each standby speed position V4 is the above-mentioned each swallowing speed position V.
It is set sufficiently slower than 2.

[Another embodiment] Even if the forward / reverse switching function of the continuously variable transmission 6 is eliminated in the above-described embodiment and another forward / reverse switching device (not shown) is connected to the continuously variable transmission 6 in series. Good. In this case, in steps S1 to S4 of FIG. 4, if the switch lever of the forward / reverse switching device is operated to the forward side while the automatic shift state is set by the changeover switch 12, the automatic shift state is set as it is. The manual shift state may be set when the switching lever of the forward / reverse switching device is operated to the reverse side.

In steps S9 to S15 of FIG. 5, the work load applied to the machine body is detected by the number of revolutions M of the engine 3, but instead of this, the traveling system on the lower side of the continuously variable transmission 6 is used. The work load on the machine body is detected by the shaft torque generated on the transmission shaft of the machine and the traction load on the machine body from the ground work device connected to the rear portion of the machine body, and the continuously variable transmission 6 May be configured to be operated to shift gears. Instead of the hydrostatic continuously variable transmission 6, a belt type continuously variable transmission having a neutral stop position N,
A taper cone type continuously variable transmission having a neutral stop position N may be used.

In step S20 of FIG. 6, the continuously variable transmission 6 is set to a preset turning speed position V1 when turning at the edge of the ridge.
However, instead of this, the continuously variable transmission 6 is decelerated by a set amount or set from the gear shift position of the continuously variable transmission 6 immediately before the rotary tiller 10 is raised. You may comprise so that it may carry out deceleration operation by a ratio. Even during the turning on this edge, steps S9 to S1 in FIG.
As shown in FIG. 5, the continuously variable transmission 6 is automatically shifted based on the rotation speed M of the engine 3 (automatic shifting means), and the upper limit position V at this time is set to the above-mentioned turning speed position V1. You may comprise.

In steps S21 to S23 of FIG. 6, it is detected that the rear cover 10a of the rotary tiller 10 has landed on the field scene G, and the continuously variable transmission 6 is decelerated to the plow speed position V2. Instead of this, the vertical position of the rotary tiller 10 is detected by the angle sensor 25 of the lift arm 18 shown in FIGS. 3 and 2, and the rotary tiller 10 (rear cover 10a) is placed in the field scene G. The continuously variable transmission 6 may be decelerated to the recessed velocity position V2 shortly before the contact with the ground.

In steps S17 and S19 of FIG. 5, the upper limit position V of the continuously variable transmission 6 is set to a preset wasteland upper limit position V3 when the unevenness of the field scene G is large. Instead of this, from the operating position of the speed change lever 11 immediately before when it is determined that there are many unevennesses in the field scene G, the position on the low speed side is set to the upper limit position V by a set amount, or the speed change lever 11 described above is operated. The position on the low speed side may be set to the upper limit position V by the set ratio from the position.

In steps S17 and S19 of FIG. 5, the upper limit position V is set to the waste land upper limit position V3 based on the frequency N of the raising / lowering operations when the rotary tiller 10 is automatically raised / lowered by the automatic tilling depth control means. Although set, instead of this, the size of one lifting operation amount by the automatic tilling depth control means, the average deviation of the lifting operation within the set time, the frequency of the rolling operation of the rotary tiller 10 by the rolling control means, Based on the magnitude of one rolling operation amount, the average deviation of the rolling operation within the set time, etc., the upper limit position V
May be set to the wasteland upper limit position V3.

In steps S24 to S26 of FIG. 7, when the main clutch 33 is disengaged, the continuously variable transmission 6 is decelerated and held at the preset standby speed position V4. Instead of this, the gear shift position of the continuously variable transmission 6 immediately before the main clutch 33 is disengaged is maintained as it is, or set from the gear shift position of the continuously variable transmission 6 immediately before the main clutch 33 is disengaged. The continuously variable transmission 6 may be decelerated and held at the position on the low speed side by the amount or the position on the low speed side by the set ratio.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

1] Overall side view of an agricultural tractor

FIG. 2 is a perspective view of the rear part of the agricultural tractor showing the connected state of the rotary tiller.

FIG. 3 is a diagram showing a linked state of a continuously variable transmission, a shift lever, and the like.

FIG. 4 is a diagram showing the first half of the flow of control during traveling.

FIG. 5 is a diagram showing the latter half of the flow of control during traveling.

FIG. 6 is a diagram showing a flow of control during turning in control during traveling.

FIG. 7 is a diagram showing a flow of control when disengaging a main clutch in control during traveling.

[Explanation of symbols]

 6 Continuously Variable Transmission 7 Gear Change Actuator 10 Ground Work Device 11 Gear Change Operation Tool 12 Selection Means 13 Work Load Sensor M Detected Value M1 Target Value R Reverse Side G Ground

Claims (4)

[Claims] 1. A speed change actuator (7) for speed-changing a continuously variable transmission (6) for traveling, a speed-change operation tool (11) that is operated manually, and a work load applied to the machine body. And a work load sensor (13) for detecting the work load sensor (13) so that the detection value (M) of the work load sensor (13) is maintained at a set value (M1) by the shift actuator (7). The automatic transmission means for automatically shifting the device (6) and the continuously variable transmission device (6) by the shift actuator (7) so that the shift position corresponds to the operation position of the shift operation tool (11). ), And a selection means (12) for artificially selecting and operating one of the automatic transmission means and the manual transmission means, and a switching operation to the reverse side (R). Based on the above -Option means (12) to the automatic transmission structure of the working vehicle operating conditions are provided with a setting means for setting the manual speed change means in the priority. 2. An ascending detection means for detecting that the ground work device (10) operably connected to the machine body is greatly ascended from the ground (G), and based on the detection by the ascending detection means. 2. The automatic speed change structure for a work vehicle according to claim 1, further comprising a speed reduction means for automatically decelerating the continuously variable transmission (6) to a low speed side. 3. An up-and-down position detecting means for detecting an up-down position of a ground working device (10) connected to a machine body so as to be able to move up and down, and the ground working device (10) based on the detection of the up-down position detecting means. 2. The work vehicle according to claim 1, further comprising a speed reducing means for automatically decelerating the continuously variable transmission (6) to a low speed side during a downward operation from near the ground (G) to a predetermined working depth. Automatic shift structure. 4. A ground work device (10) connected to the airframe.
Posture change detection means for detecting the magnitude or frequency of posture change of the robot, and if the magnitude or frequency of posture change of the ground work device (10) based on the detection of the posture change detection means is large, the continuously variable transmission The automatic speed change structure for a work vehicle according to claim 1, further comprising a speed reduction means for automatically decelerating the device (6) to a low speed side.