KR20160038577A - Agriculture vehicle with Front Wheel speed turn prevention apparatus when high-stage shift and control method for Front Wheel speed turn prevention - Google Patents

Abstract

Disclosed are an agricultural vehicle with a front wheel speed turn prevention apparatus in a high-stage shift and a control method for front wheel speed turn prevention. According to an embodiment of the present invention, the agricultural vehicle with a front wheel speed turn prevention apparatus in a high-stage shift has a high-stage shift detection unit to detect a high-stage fork rod of two fork rods to change a speed of a sub-shift unit to be moved to a high-stage shift position, and is configured to release a front wheel speed turn function which is being carried out by means of a front wheel speed increase transfer unit when detecting a high-stage shift of the high-stage fork rod by the high-stage shift detection unit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a control method for an agricultural work vehicle and a double speed turn prevention system,

More specifically, the present invention relates to an agricultural work vehicle. More particularly, the present invention relates to an agricultural work vehicle, and more particularly, to a work vehicle for agricultural use wherein a double speed turn function is automatically released during a high speed speed change operation, Speed turn-by-turn preventing function for high-speed speed change, and a control method for double speed turn prevention.

Farmers such as tractors, which are mainly used for cultivation, work very often to rotate the gas to the left or right side due to the nature of the work. Particularly, in turning the gas to the left or right side during operation, the smaller the radius, the higher the work efficiency can be, and the turning speed of the front wheel is made faster than that of the rear wheel at the time of turning.

In order to improve the work efficiency, it is a double turn function that enables the front wheel to rotate faster than the rear wheel when turning the vehicle so that the turning radius is small. The double speed turn function for the conventional agricultural work vehicle is realized through the front wheel speed increasing switching clutch which is automatically switched by the hydraulic control based on the information obtained through the sensor when turning the steering wheel to the left or right.

The double speed turn function applied to the conventional agricultural work vehicle is such that when the double speed turn mode is executed by the driver's selective operation and when the vehicle is turned to the left or right in the state in which the double speed turn mode is being executed, A double turn function is performed to make the rotational speed of the front wheel faster than that of the rear wheel, and the double turn function is temporarily released when the vehicle runs straight again.

FIG. 1 is a schematic cross-sectional view schematically showing a constitution of a front wheel accelerating switching clutch for a double speed turn of an agricultural work vehicle according to the prior art, and a conventional front wheel accelerating switching clutch will be briefly described with reference to FIG.

1, the front wheel speed increasing / reducing switching clutch includes an all-wheel drive container 100a provided in a traveling system driving shaft 100 that is directly connected to a transmission shaft, A shaft 300 and a double speed turn shaft 400 connected to the idle shaft 300 and the hydraulic clutch 110 so as to transmit power.

The idle shaft 300 is provided with two speed increasing gears 600 and a non-speed increasing gear 700 for determining the speed of the speed turning shaft 400. The non-speed increasing gear 700 includes a speed- And is always maintained in the engaged state with the non-proof type synchronous gear 800 provided in the shaft 400. A clutch 110 is installed in front of the non-proof type synchronous gear 800.

The clutch 110 is provided with a speed-driven driven gear 100 that meshes with the speed increasing gear 600. The clutch 110 is reciprocated between a clutch 110 and a non- And a piston 130 partitioning the hydraulic chamber 150 together with the shift 120 so that the shift 120 can reciprocate by pressure fluid.

The hydraulic oil is supplied to the hydraulic chamber 150 between the shift 120 and the piston 130 through the hydraulic oil passage 160 formed in the speed-change turn shaft 400, When the clutch is engaged with the clutch 110 in the direction of the arrow 110 and then engaged with the clutch 110 and the clutch is engaged with the non-clutch type dog gear 800 by the hydraulic pressure release and the restoring force of the return spring 17, do.

That is, the shift 120 is shifted to the hydraulic operation when the vehicle is turned to the left or right in the double speed turn mode, and the clutch 110 is connected to perform the double speed turn for the front wheel acceleration. The speed increasing and non-accelerating speed of the double speed turn shaft 400 can be selectively implemented.

As described briefly above, the double speed turn-on function through the front wheel speed increasing / reducing device having the above-described configuration is executed when there is a switch or a lever operation for executing the double speed turn function through the driver. The switch or lever is operated again to continue the double speed turn mode before releasing the double speed turn mode.

However, if a double speed turn occurs at high speed without releasing the double speed turn mode while the double speed turn mode is being executed, there is a danger that the vehicle may be seriously shaken or overturned. Therefore, the double speed turn function is automatically canceled at the time of high speed speed change without releasing the double speed turn mode, and an additional function is required to prevent safety accidents such as rolling or overturning of the vehicle.

Korean Patent No. 10-0988155 (registered on Oct. 10, 2010) Japanese Patent Laid-Open No. 2005-239008 (published on September 09, 2005)

A problem to be solved by the present invention is to provide an automatic transmission capable of automatically shutting off the double speed turn mode in the case of performing the high speed single speed in the state that the double speed turn mode is being executed, And to provide a control method for prevention of turning-over of agricultural work vehicle and double speed.

According to an aspect of the present invention, there is provided a vehicular drive system including: a peripheral speed portion that primarily shifts power output from an engine; a sub speed change portion that performs a secondary speed change by receiving a primary speed- And a front-wheel accelerating / decelerating section provided on the front wheel drive line for transmitting the secondary-shifted power to the front wheel side by the auxiliary speed-change section, for increasing or decreasing the secondary speed- A low-speed and high-speed two fork rods for shifting the auxiliary transmission; And a high speed S / C sensing unit for sensing that the high speed fork load is moved to the high speed S / C position during the two fork loads. If the high speed S / Speed turn-by-turn anti-turn-stop function during the high speed change-speed operation.

In one aspect of the present invention, there is further provided a double speed turn execution input means for executing a double speed turn mode by the front speed increase switching section, and in the state where the double speed turn mode is being executed through the operation of the double speed turn execution input means, If the speed change sensing unit detects a high speed speed change, the control unit may output a double speed turn stop command to release the double speed turn mode.

At this time, the front wheel speed increasing / reducing portion may be a hydraulic clutch type in which a speed increasing or non-speed increasing clutch is selectively operated according to the selective supply of pressure oil to implement a speed increasing or non-speed increasing switching. When the operation for steering is detected, the speed increasing clutch is actuated to be power-connected with the side of the auxiliary speed change portion to realize the double speed turn. In the state of operation in the double speed turn mode, If it is sensed, the non-accelerated clutch of the front wheel acceleration / deceleration switching section is fixed to the connection side through the hydraulic pressure valve control by the control section so that the double speed turn is not generated.

When the high speed fork rod is slid in the axial direction to the high speed short speed changing position, the high speed speed change sensing portion is provided corresponding to the groove portion or the projection portion position. .

Here, the high speed speed-change sensing unit may be a non-contact type sensor for noncontact sensing of the groove or the protrusion when the high-speed fork rod is axially slid to the high speed, short-speed position.

Alternatively, the high-speed speed-change sensing portion may be a contact switch that is switched on by contact with the protruding portion when the high-speed short fork rod is axially slid to the high-speed, short-speed shift position.

In addition, when the high-speed-speed-speed sensing portion is a contact switch, the operation rod may further include an operating rod for turning on / off the contact switch between the projection and the contact switch.

According to another aspect of the present invention as a solution to the problem, there is provided a computer readable recording medium storing a computer program for causing a computer to execute the steps of: Sensing a high speed step-variable operation of the auxiliary speed change section during the execution of the double speed turn function; And performing control for releasing the double speed turn mode when a high speed speed change operation of the auxiliary speed change unit is detected during the execution of the double speed turn function.

At this time, in the step of performing the control for releasing the double speed turn-on function, the non-speed increasing clutch of the front wheel speed increasing / reducing portion is fixed to the connection side through the hydraulic pressure valve control by the control portion.

According to the agricultural working vehicle according to the embodiment of the present invention, when the high speed fork rod is moved from the high speed fork load position to the high speed short speed position for fast speed change during operation in the double speed turn mode, It is possible to prevent a safety accident such as rolling or rollover due to double speed turn at high speed driving in the double speed turn mode.

Brief Description of the Drawings Fig. 1 is a cross-sectional view showing a clutch for an increase in front speed of an agricultural work vehicle according to the prior art. Fig.
FIG. 2 is a side view of an agricultural work vehicle having a double-speed turn preventing function during a high-speed shift according to an embodiment of the present invention. FIG.
3 is a plan view of an agricultural work vehicle having a double speed turn preventing function in a high speed single speed according to an embodiment of the present invention.
FIG. 4 is a development view showing a mission combination applied to the agricultural work vehicle of FIGS. 2 to 3. FIG.
5 is an enlarged view of the auxiliary speed change portion shown in Fig.
Fig. 6 is a schematic side view of the shift operating portion for the transmission of the negative speed change portion of Fig. 4; Fig.
FIG. 7 is a schematic view showing a preferred embodiment of a high-speed-speed-change sensing portion for sensing a high-speed short-speed operation of a high-speed end fork rod during a downshift operation via the shift operating portion of FIG.
8 is a schematic view showing another preferred embodiment of a high-speed-speed-change sensing portion that senses a high-speed short-speed operation of a high-speed end fork rod in a negative shift operation;
9 is a control logic for preventing the double speed turn-over in the high-speed shift.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.

Hereinafter, a non-cabin type tractor will be described as an agricultural work vehicle having a double speed turn prevent function in high speed change according to an embodiment of the present invention. First, a general configuration of a non-cabin type tractor having a double speed turn preventing function at high speed speed change will be schematically described with reference to FIG. 2 to FIG.

2 to 3, the non-cabin type tractor comprises a base 1 having a traveling wheel composed of a front wheel FW and a rear wheel RW, a driver protection structure Over Protective Structure, 2). The base 1 includes a central driver's seat 4 and a forward driving portion 3 thereof and has a mission case 6 extending from the driving portion 3 to the rear of the base 1.

The driving unit 3 includes an engine room 32 on which an engine 34 and major components involved in driving the vehicle are mounted and a bonnet 30 covering the engine room 32. The driving unit 3 includes an engine room 32, A lifting type traction device (not shown) in which a working machine such as a rake, a rotator, a plow, and a harrow is vertically attached to the rear of the base 1 Omitted).

The engine 34 is a mechanical engine or a foot operated accelerator pedal or an accelerator lever operated by a manual accelerator lever. The displacement of the cable is controlled by an engine And is mounted and fixed on the vehicle body frame 5 at the bottom of the engine room 32 protected by the bonnet 30.

A front axle case 8F having a front wheel transmission shaft mounted thereon is disposed in the vehicle body width direction at the bottom of the vehicle body frame 5. A clutch housing 7 is connected to a rear portion of the engine 34 mounted on the vehicle body frame 5. [ The rear case 8R and 8L are connected to the rear of the clutch housing 7 so that the transmission case 6 is directly connected to the rear of the vehicle body and the transmission case is mounted on both left and right sides of the rear case of the transmission case 6.

The driver's seat 4 is provided with various levers related to the operation of the vehicle such as a steering wheel 40, a foot accelerator pedal 44 and a hand accelerator lever 48 for controlling the engine output, and an auxiliary speed- And a rear wheel fender 9R and 9L on the curved surface of an arcuate cross section covering the upper portions of the left and right rear wheels RW are installed on both sides of the driver's seat 4.

FIG. 4 is a development view showing a mission combination applied to the agricultural work vehicle of FIGS. 2 to 3. FIG.

Referring to FIG. 4, the mission combination is largely composed of a mission unit 10 and a rear-drive unit 16. The mission section 10 is constituted by a forward / backward transmission portion 12 relating to forward and backward shifts, a peripheral speed portion 13 and a negative speed change portion 14 for implementing a wide speed change step, and a front wheel speed increasing portion 15 , And the rear differential section (16) appropriately distributes the power shifted by the mission section (10) to the left and right rear wheels.

The forward / backward transmission portion 12 constituting the mission portion 10 is constituted by a hydraulic multi-plate clutch system which implements selective power connection by the pressure allowed to flow by the operation of a driver lever or a hydraulic multi-plate clutch system of Synchromesh type) manual transmission structure, and the peripheral speed section 13 may be constituted by a synchronizer type (synchromesh type) four-stage gear.

The auxiliary speed change section 14 performs the secondary shift in four stages (ultra-low speed, low speed, medium speed, high speed) as the selection method in accordance with the shift movement, and the front wheel speed increasing / An accelerator clutch 152 and an non-accelerated clutch 154 are provided, and the power transmitted from the auxiliary speed change portion is increased or transmitted to the front wheel side without further shifting.

Various components (a power transmission shaft, a transmission, a hydraulic clutch, a transmission shaft, etc.) constituting the mission part 10 and the rear differential part 16 are accommodated in the transmission case 6, At this time, the interior of the transmission case 6 is filled with oil as a lubricant which smoothly drives the parts and reduces friction and wear between the parts when the apparatus is driven.

The primary shift power in which the speed and the rotation direction are determined while passing through the peripheral speed portion 13 and the forward / backward transmission portion 12 is finally shifted via the auxiliary speed change portion 14, and the final speed change Some of the power is provided to the front wheel accelerating / switching portion 15 for front wheel drive when the four-wheel drive is selected and a part of the power is transmitted to the rear wheel axle portion 16 to be appropriately distributed to the left and right rear wheels.

In the drawing, reference numeral 17 denotes a PTO driving unit for drawing engine power out of the gas to utilize the power output from the engine as a power for driving a working machine.

FIG. 5 is an enlarged view of the auxiliary speed change portion. The auxiliary speed change portion 14 can be configured in a selective manner in accordance with the shift motion, and the secondary shift over four stages (ultra low speed, low speed, medium speed, .

As shown in FIG. 5, the negative speed change portion specifically includes a negative speed change gear shaft 143 connected to the output side shaft of the forward / reverse speed change portion 12 and having a plurality of gears g having different diameters, And a pinion shaft 144 having gears (g) that mesh with gears one by one.

The pinion shaft 144 is shifted by the peripheral speed section 13 and the auxiliary speed change section 14 and the final transmission power in which the rotational direction is determined by the forward and backward transmission unit 12 is output to the rear axle side, Shift shifts 146 and 147 are disposed between the gears of the pinion shaft 144. [ At this time, the downshift shift 146 (147) is linked with the auxiliary shift lever 49 (see FIG.

Thus, when one of the negative speed shifts 146 (147) is shifted to the selection of one of the gear pairs engaged by the operation of the negative speed change lever, the negative speed change gear shaft 143, And the pinion shaft 144 are connected so as to be able to transmit power, and a secondary shift is performed in which the rotational speed is increased or decreased at a ratio corresponding to the gear ratio of the gear pair.

6 is a view schematically showing a shift operating portion for implementing the shifting of the auxiliary speed portion in Fig.

6, the auxiliary speed-change section 14 is provided with two low-speed and high-speed forklifts for the four-stage (ultra-low speed, low speed, medium speed, high speed) (140) (142). The low speed short fork rod 140 is involved in a shift that decelerates the primary shifted power to the ultra low speed and the low speed and the high speed short fork rod 142 is involved in the shift which increases the primary shifted power at medium speed and high speed do.

The low speed short fork rod 140 and the high speed short fork rod 142 are axially slidably supported by the front and rear partition walls 65 and 67 in the transmission case 6 and the fork rod 140 The ball bearings 68 and 69 are provided on the front side partition wall 65 of the portion through which the fork rod 142 penetrates. The ball bearings 68 and 69 are rocked in a direction perpendicular to the axial direction of the fork rod. Grooves 140a to 140c (142a to 142c) are formed at regular intervals along the axial direction on the outer surface of the base plate 140 (142).

One of the recesses formed in the low speed short fork rod 140 or the high speed short fork rod 142 when the fork rod is axially slidably operated for an ultra low speed or low speed or a medium speed or a high speed, The ball bearings 68 and 69 are selectively engaged with the grooves of the fork rollers 68 and 69 so that the fork rod is positioned at an axial position where the shift operation can be accurately performed.

The low speed short fork rod 140 involved in the ultra low speed and the low speed transmission is provided with three grooves 140a to 140c corresponding to the ultra low speed-neutral low speed single speed change, Speed short fork rod 142 that engages in middle and high speed shifts to provide a shifting operation feeling in response to a medium speed-neutral-high speed shift, (142a to 142c) are formed.

A high speed speed change sensing portion 19 is provided in the vicinity of the high speed fork rod 142. The high speed speed change sensing unit 19 detects the high speed short speed change of the high speed fork rod 142 and transmits the signal to the control unit. The control unit controls the high speed speed change sensing unit 19 Speed speed-change detection signal is input through the input terminal, the control for releasing the double speed turn mode which is being executed is performed.

That is, in the state in which the vehicle is operating in the double speed turn mode by the operation of the double speed turn execution input means (not shown) provided around the driver's seat, the high speed speed change sensing portion 19 controls the high speed The speed change mode is canceled to prevent the occurrence of the double speed turn at the high speed traveling and thus the safety accident due to the double speed turn at the high speed traveling is prevented.

When the steering operation is detected while the vehicle is in the double speed turn mode, the double speed turn is connected to the side of the auxiliary speed change portion 14 so as to be able to transmit power by connecting the increased speed clutch 152 of the front wheel speed increase switching portion 15 . The disengagement of the double speed turn mode during operation in the double speed turn mode allows the non-accelerated clutch 154 of the front wheel speed increase switching section 15 to be operated through a hydraulic valve (not shown) control by a control section (not shown) (See FIG. 4).

Of course, while the double speed turn mode is in operation, the double speed turn inputting means, for example, the double speed turn switch is operated once again or the double speed turn mode is normally released through the separate double speed turn releasing switch. However, If the high-speed single-speed operation is carried out for high-speed travel without releasing, the double-speed turn mode is automatically released to secure safety at high speed.

Reference numerals 148 and 149 in FIG. 6 are coupled to the low speed short fork rod 143 and the high speed short fork rod 144 to transmit the axial shift operation force according to the fork rod axial slide movement to the auxiliary speed change portion 14, Speed speed fork and a high-speed speed-change fork that transmit to the low-speed shift 146 (see Fig. 5) and the high-speedshift shift 147 (see Fig.

Hereinafter, a preferred embodiment of a configuration for detecting a high-speed end operation of the auxiliary speed change portion during the execution of the double speed turn function will be described with reference to FIG. 7 to FIG.

7 is a diagram showing a preferred embodiment of an arrangement for detecting a high-speed short-speed operation of a high-speed fork rod.

7, the groove portion 145a or the projection portion 145b is formed on one side of the outer surface portion of the high speed fork fork 142 and the high speed fork rod 142 is axially slid to the high speed, The high speed speed change sensing portion 19 is provided corresponding to the position of the groove portion 145a or the projection portion 145b so that the groove portion 145a or the projecting portion 145b can be moved to the high speed speed sensing portion 19 So that the high speed end fork rod 142 can be detected as being operated at the high speed end side.

At this time, the high-speed speed-change sensing unit 19 detects the high-speed short-speed-change sensing unit 19 after the high-speed short-fork rod 142 fires light, electromagnetic waves, ultrasonic waves, etc., For example, an ultrasonic sensor or an infrared sensor that senses that the groove portion 145a or the protrusion 145b reaches the sensing position through a reflected wave and outputs a corresponding signal.

8 is a view showing another preferred embodiment of a configuration for sensing a high speed single-speed operation of a high-speed fork load rod, in which a protrusion 145b is formed on one side of the outer surface of the high- (ON) by contact with the protruding portion 145b when the high-speed short fork rod 142 is slid in the axial direction to the high-speed short-speed changing position.

8, an operating rod 18 is provided between the protruding portion 145b and the contact switch in a direction perpendicular to the axial direction of the high-speed short fork rod 142, The contact switch 19 is operated by being pushed down upon contact with the protruding portion 145b or the protruding portion 145b or the switch input side is formed somewhat longer so that the connection switch is operated by direct contact with the protruding portion 145b without the operating rod You may.

A brief description will be made of a control process in which the double speed turn mode is automatically released when the agricultural work vehicle is in the double speed turn mode and the high speed speed change mode is operated.

FIG. 9 shows control logic for preventing double speed turning at high speed.

Referring to FIG. 9 and FIG. 6 attached heretofore, the double speed turn mode can be executed by directly operating the double speed turn execution input means, for example, the double speed turn switch, as described briefly above. If the double speed turn execution command is input through the double speed turn execution input means by the driver-selective operation, the control unit recognizes the double speed turn execution instruction and switches the operation mode of the vehicle to the double speed turn mode.

When the operation of the steering wheel is detected during operation in the state of being switched to the double speed turn mode, the control unit controls the front wheel acceleration / reduction switching unit through the hydraulic pressure valve based on the detection signal, thereby realizing the double speed turn. More specifically, the hydraulic pressure valve is controlled so that the speed increasing clutch of the front wheel speed increasing / reducing portion is connected to the output side of the auxiliary speed changing portion so as to transmit power, so that the double speed turn is generated.

When the secondary shift lever is moved to the high speed short-speed position for high-speed-speed shifting, the high-speed end fork rod 142, which is linked to the secondary shift lever in a linkable manner, Speed shifting position of the high-speed end fork rod 142 is sensed by the high-speed speed-change sensing portion 19 and the sensed signal is output in an electrical form.

In the double speed turn mode, the sensing signal output by the high speed step-change operation of the negative speed change section is transmitted to the control section, and the control section performs control for releasing the double speed turn mode. Specifically, when the detection signal is input, the control unit controls the non-accelerated clutch of the front wheel acceleration / deceleration switching unit via the hydraulic pressure valve control to the connection side so as to release the double speed turn mode so that the double speed turn does not occur.

According to the above configuration, when the high speed fork rod is moved from the high speed short fork position to the high speed short speed position for fast speed change during operation in the double speed turn mode, the double speed turn mode is automatically released based on the signal sensed by the high speed speed change sensor, It is possible to prevent safety accidents such as vehicle rolling or rollover due to double speed turn at high speed driving in double speed turn mode.

In the foregoing detailed description of the present invention, only specific embodiments thereof have been described. It is to be understood, however, that the invention is not to be limited to the specific forms thereof, which are to be considered as being limited to the specific embodiments, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. .

10: Mission combination 12: Shuttle transmission section
13: peripheral speed part 14:
15: front wheel speed increasing portion 16:
18: Operation rod 19: High speed speed change sensing part
140: Low speed short fork rod 142: High speed short fork rod
145a: groove portion 145b:
152: Incremental clutch 154: Non-incremental clutch

Claims (9)

A secondary speed-change portion for performing a secondary speed-change by receiving a first-speed-shifted power by the peripheral speed portion, and a secondary speed-change portion for shifting the secondary speed- And a front-wheel accelerating / switching section that is provided on the front wheel drive line for transmitting to the front wheel side and performs the non-speed-increasing or the speed-increasing switching of the secondary speed-
Two low-speed and high-speed fork rods for shifting the auxiliary speed change unit;
And a high-speed, speed-change sensing portion for sensing that the high-speed end fork rod is moved to the high-speed, short-shift position during the two fork loads,
Wherein the speed-change turn mode is automatically released when the high-speed short-speed-change sensing unit detects the high-speed short-speed shift of the high-speed fork-fork rod.
The method according to claim 1,
And a double speed turn execution input means for executing the double speed turn mode by the front wheel speed increasing switching portion,
When the high speed speed change sensing unit detects the high speed speed change state in the state where the double speed turn mode is being executed through the operation of the double speed turn execution input means, the control unit outputs the double speed turn mode execution stop command to release the double speed turn mode Features a high-speed, double-speed anti-turn-resistant agricultural work vehicle.
3. The method of claim 2,
Wherein the front wheel incremental switching unit is constituted by a hydraulic clutch system in which an accelerator or non-accelerator clutch is selectively operated according to selective supply of pressure oil to implement an accelerating or non-accelerating switching,
When an operation for steering is sensed while the vehicle is in the double speed turn mode by the double speed turn execution input means, the double speed turn is realized by power connection with the side of the auxiliary speed change portion by operating the speed increasing clutch,
When the high speed speed change sensing is detected by the high speed speed change sensing unit in the state where the double speed turn mode is being executed, the non-accelerated speed clutch of the front wheel speed increasing and switching unit is fixed to the connection side through the hydraulic pressure valve control by the control unit, Speed turning-speed preventing function in a high-speed speed change.
The method according to claim 1,
A groove or a projection is formed on one side of the outer surface of the high speed fork rod,
Wherein the high speed speed change sensing portion is provided corresponding to the groove portion or the projection portion when the high speed fork rod is axially slid to the high speed short speed changing position. .
5. The method of claim 4,
Wherein the high speed speed change sensing portion is a non-contact type sensor for noncontact sensing the groove portion or the protrusion portion when the high speed fork rod is axially slid to the high speed short speed changing position. .
5. The method of claim 4,
Wherein the high speed speed change sensing portion is a contact switch which is switched ON by contact with the protruding portion when the high speed fork rod is axially slid to the high speed short speed changing position. Agricultural work vehicle equipped with.
The method according to claim 6,
Further comprising an operating rod for turning on and off the contact switch between the projection and the contact switch.
Inputting an execution command for executing a double speed turn mode;
Sensing a high speed step-variable operation of the auxiliary speed change section during the execution of the double speed turn function; And
And performing control for releasing the double speed turn mode when the high speed speed change operation of the auxiliary speed change unit is detected during the execution of the double speed turn function.
9. The method of claim 8,
In performing the control for releasing the double speed turn-on function,
Speed control of the front wheel acceleration / deceleration switching section is fixed to the connection side through the hydraulic pressure valve control by the control section so that the double speed turn does not occur.

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