JP2008249106A - Working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify change-over operation between on-road travel and working travel. <P>SOLUTION: This working vehicle comprises a transmission case having a main transmission device A of a plurality of stages or no stage, and a sub transmission device for changing over the main transmission device between two high and low stages. Herein, there are provided a shift position storage means S1 for storing the shift position of the main transmission device, which is set before low-to-high speed shift of the sub transmission device B, and an automatic shift means S2 for changing the shift portion of the main transmission device. When the sub transmission device is changed over from a low speed into a high speed, the main transmission device shifts a speed into a low speed region or a first speed with the automatic shift means. When the sub transmission device is changed over form a high speed into a low speed, the main transmission device is automatically restored into the shift position of the main transmission device, which is stored in the shift position storage means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a work vehicle such as a tractor. In particular, the present invention relates to a work vehicle provided with a transmission transmission for transmission having a multi-stage or continuously variable main transmission and a sub-transmission for switching the main transmission to two stages of high and low.

  The work vehicle travels at an extremely low speed during work such as rotary work, and travels at a high speed when traveling on the road. Therefore, a multi-stage or continuously variable main transmission and a gear shift are provided in a transmission case that transmits power from the engine to the traveling device. The sub-transmission device is incorporated, and the vehicle is allowed to travel at a desired traveling speed by a shift operation in which the main transmission device and the sub-transmission device are appropriately combined with the main transmission lever and the sub transmission lever provided in the vicinity of the steering operation seat.

For example, Japanese Patent Laid-Open No. 2000-320644 discloses a main transmission comprising a hydraulic continuously variable transmission and a sub-transmission comprising four gears, and Japanese Patent Laid-Open No. 2002-250437 discloses a hydraulic transmission. There is described a configuration in which a main transmission composed of a continuously variable transmission and a sub-transmission composed of three gears are incorporated in a transmission case.
JP 2000-320644 A JP 2002-250437 A

  In the work vehicle described above, the speed change operation for adjusting the travel speed to a desired speed requires the operation of both the main speed change lever and the sub speed change lever, for example, from a normal speed to a very low speed. When switching, it is necessary to perform a troublesome shifting operation in which the main transmission is set to the lowest speed and the auxiliary transmission is set to the low speed side.

  Accordingly, it is an object of the present invention to simplify the speed change operation by automatically selecting the optimum speed change position of the main speed change device according to the speed change operation of the auxiliary speed change device, and to reduce the operator's operation load. .

The problems of the present invention are solved by the following technical means.
That is, an operation equipped with a transmission case (12) provided with a multi-stage or continuously variable main transmission (A) and a sub-transmission (B) that switches between the main transmission (A) and two stages of high and low. In the vehicle, a shift position storage means (S1) for storing a shift position (H) of the main transmission (A) set before shifting from the low speed to the high speed of the auxiliary transmission (B), and the main transmission An automatic transmission means (S2) for changing the shift position of (A) is provided, and when the auxiliary transmission (B) is switched from a low speed to a high speed, the main transmission (A) is automatically changed to a low speed range or a first speed. When the sub-transmission device (B) is switched from a high speed to a low speed, the main transmission (A) is stored in the shift position storage means (S1). The main transmission (A) is configured to automatically return to the position (H). It was a work vehicle, wherein the door.

  With this configuration, the main transmission A can be automatically operated at a low speed or first speed suitable for starting on the road without operating the main transmission A by operating the auxiliary transmission B from low speed to high speed. The speed is changed by the speed change means S2, and a sudden increase in travel speed is eliminated so that no speed change shock is felt.

  Further, by simply operating the auxiliary transmission B from high speed to low speed, the automatic transmission is automatically shifted to an optimum low speed work speed such as rotary work before moving on the road without operating the main transmission A.

  According to the present invention, when the work such as the rotary work is interrupted and the vehicle is moved on the road, only the auxiliary transmission B is changed from the low speed to the high speed, and the main transmission becomes the low speed range or the first speed. Is simple. Further, since the main transmission is in the low speed range or the first speed when traveling on the road, it is possible to perform a safe traveling while suppressing a rapid increase in speed. When resuming the rotary work from the road traveling, Since only the transmission B needs to be changed from high speed to low speed, the operation is simplified. Then, the speed change operation can be simplified, and the operation operation of the work vehicle, which is frequently operated such as the lifting and lowering operation of the rotary in addition to the steering operation, can be reduced, thereby reducing the operator's steering operation load.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an overall view of a crawler tractor T to which a transmission case of the present invention is applied.

  As shown in FIG. 1, the tractor T has an engine mounting frame 10 at the front of the vehicle body, an engine 11 attached to the frame 10, and an engine output shaft (not shown) protruding from the rear of the engine 11. In this configuration, the coaxial rotation is transmitted to the transmission in the casting trans-transmission case 12 arranged in the longitudinal direction of the vehicle body. In addition, the rotational power appropriately decelerated by the transmission is transmitted to the left and right crawler type traveling devices 13 via bevel gears 56 and 85 described later, a sprocket shaft 86 in the left and right axle case, and the like.

  Above the trans-transmission case 12, a floor 14 is supported, and on this floor 14, a steering handle 15 serving as a steering operation section and a forward / reverse switching lever 24 for switching the traveling to the left and right of the steering handle 15 to forward and backward. And a finger lever 23 (see FIG. 2) for raising and lowering a ground work machine such as a rotary R or a front dozer (not shown) mounted on the front side of the machine body, and a cockpit 18 on the rear side of the steering handle 15 are provided. Sits down and performs maneuvering.

  Provided on the left side of the cockpit 18 are a main transmission lever 9 for shifting the traveling speed in four steps, a position lever 16 for adjusting the height of the work implement, and an auxiliary transmission lever 17 for shifting the traveling speed in two steps of high and low, A backup switch 19, a tilt adjustment dial 20, a manual adjustment lever 21, and a horizontal control changeover switch 22 for adjusting the tilt of the rotary R are provided on the right side of the cockpit 18. A brake pedal 25, a clutch pedal 26, and the like are provided on the floor 14 at the foot. It has a configuration.

  The front dozer may be moved up and down by the position lever 16 instead of the finger lever 23. At this time, the position lever 16 is preferably urged so as to return to the neutral position.

  Fenders 27 that cover the top of the crawler 13 are provided on the left and right sides of the floor 14. The left and right fenders 27 are configured to be attached with a detachable fuel tank 28. The upper shape of the fuel tank 28 is formed along the fender 27, and a handle 29 extending in the front-rear direction is provided on the upper surface. It has become. This handle 29 becomes a hand catcher for getting on and off as it is.

  On the upper surface of the transmission case 12, a lifting hydraulic cylinder 30 serving as a working machine lifting actuator is provided, and a lift arm 31 connected to a piston of the cylinder 30 is turned up and down to thereby operate the working machine via a link mechanism. It is the structure which raises / lowers.

  Also, a part of the link mechanism at the rear of the vehicle body is provided with a left and right horizontal cylinder 32 as a left and right rolling actuator of a work machine, and the operation amount is detected by a stroke sensor (not shown) provided in the cylinder 32. It has become.

  As shown in FIGS. 3 and 4, the front panel 33 provided at the lower front side of the steering handle 15 includes a fuel gauge 34, a battery charge warning light 35, an engine oil pressure warning light 36, a water temperature warning light 37, and a system abnormality warning light 38. , A spin turn indicator lamp 39, a mild turn indicator lamp 40, an hour meter 41 for indicating work time, a main shift position indicator lamp 42, and a horn switch 44, a blinker lever on the lower left side of the front panel 33. 43, a light switching lever 45, and a turning mode switching switch 46 are provided.

Next, the power transmission structure in the transmission case 12 of the tractor T will be described mainly with reference to FIGS.
As shown in FIG. 9, the transmission case 12 has a configuration in which five hollow cases of a front case 99, a first intermediate case 100, a second intermediate case 101, a third intermediate case 102, and a rear case 103 are connected.

  The rotational power input from the output shaft of the engine 11 to the input shaft 50 in the front case 99 is first pivoted to the first intermediate case 100 of the transmission case 12 by the reduction gear set 51 provided on the input shaft 50. The main clutch 52 is driven by being transmitted to the clutch input shaft 54. The power that is turned on and off by the main clutch 52 is appropriately decelerated by the main transmission A and the sub-transmission B provided in the third intermediate case 102 of the transmission case 12 and pivotally supported by the rear case 103. It is transmitted to an output shaft 55 having a bevel gear 56. A hydraulic pump 57 is mounted on the outer side of the front case 99 of the main clutch input shaft 54 and driven.

The main clutch 52 engages / disengages power to the main clutch output shaft 53 and is turned on / off by a clutch petal 26 on the floor 14.
The main transmission A includes a main drive shaft 58 provided on an extension line of the main clutch output shaft 53, and a first driven shaft 59 and a second driven shaft 60 that are vertically arranged around the main drive shaft 58. Has been.

  The rotational power of the main clutch output shaft 53 is transmitted to a reduction shaft 63 having a large diameter gear 62 that meshes with a gear 61 provided at the rear end of the main clutch output shaft 53, and meshes with the small diameter gear 64 of the reduction shaft 63. Is transmitted from the gear 65 to the main drive shaft 58.

  A gear 66 that is spline-engaged with the main drive shaft 58 and a gear 67 that is bearing on the second driven shaft 60 via a needle bearing are always meshed with each other, and is spline-engaged with the main drive shaft 58. A small-diameter gear 68 and a gear 69 that is supported by the first driven shaft 59 via a needle bearing are always meshed with each other. The gear 65 and the gear 66 are an integral gear.

  Further, a gear 70 that is spline-engaged with the main drive shaft 58 and a gear 71 that is supported by a first driven shaft 59 via a needle bearing are in constant mesh. Further, the gear 72 that is spline-engaged with the main drive shaft 58 and the gear 73 that is supported by the second driven shaft 60 via a needle bearing are always meshed with each other.

The first driven shaft 59 is provided with a cylinder case 74 in which a first-speed clutch C1 and a third-speed clutch C3 are housed so as not to be relatively rotatable.
The first intermediate shaft 101 side of the first driven shaft 59, the second driven shaft 60, and the main drive shaft 58 is pivotally supported by bearings 104, 105, 106, and the third intermediate case 102 side is connected to the first driven shaft 59. The second driven shaft 60 is spline-fitted to gears 75 and 81 pivotally supported by bearings 97 and 95, and the main drive shaft 58 is pivotally supported by a bearing 96. (See Figure 10)
In assembling these shafts 58, 59, 60 to the third intermediate case 102, first, the gear 75 and the gear 81 are pivotally supported by the bearings 97, 95 on the third intermediate case 102, and the cylinder cases 74, 80 are sub-assembled. The first driven shaft 59 and the second driven shaft 60 are spline-fitted to the gear 75 and the gear 81, and the gears 70 and 72 are spline-fitted to the drive shaft 58 and then fitted to the bearing 96.

  Thereafter, gears 68, 65, 61 are spline-fitted to the drive shaft 58, and the shaft ends of the first driven shaft 59 and the second driven shaft 60 are fitted to bearings 104, 105 attached to the second intermediate case 101, The gear 61 is fitted to the bearing 106, and the third intermediate case 102 and the second intermediate case 101 are assembled together.

  In this assembling operation, since the protrusion amount L from which the gear 75 protrudes from the bearing 97 and the protrusion amount M from which the gear 81 protrudes from the bearing 95 are different (see FIG. 10), the first driven shaft 59 and the second driven shaft are different. If 60 is mistaken, the second intermediate case 101 cannot be attached and the mistake is noticed, so that it is not mistakenly assembled.

  Further, the first driven shaft is connected to the gear 76 provided on the axis of the drive shaft 58 by making the distance D1 between the drive shaft 58 and the first driven shaft 59 equal to the distance D2 between the drive shaft 58 and the second driven shaft 60. 59 and the second driven shaft 60 are meshed with the gears 75 and 81 having the same number of teeth that are spline-fitted.

  The first driven shaft 59 is sub-assembled with a cylinder case 74 incorporating the clutches C1 and C3 together with the gears 69 and 71, but is provided with retaining rings 107 and 109 for pressing the gear end face so as not to come off. Similarly, the second driven shaft 60 is sub-assembled with the gears 67 and 73 and the cylinder case 80 in which the clutches C2 and C4 are incorporated, but is provided with retaining rings 110 and 108 for pressing the gear end face so that the cylinder case 80 is not detached. Retaining rings 107, 108, 109, and 110 fitted at the end of the sub set have different end faces of the gears 67, 73, 69, and 71 from the cylinder cases 74 and 80. Also become.

  The hydraulic piping that operates the clutches C1 and C3 in the cylinder case 74 connects the oil passage 114 drilled in the third intermediate case 102 and the oil passage 111 drilled in the second intermediate case 101 together with the joining of the case. By providing the oil passage 111 on the intermediate case 101 side in the raised portion 112 and connecting to the oil passage 114 provided in the recessed portion 116 on the third intermediate case 102 side, the sealing material applied to the case end face prevents the oil passage. I am trying not to. Reference numeral 115 denotes an oil ring.

The oil path to the cylinder case 80 is the same.
A gear 75 spline-fitted to the lower end of the transmission of the first driven shaft 59 is engaged with a gear 76 fixed to a gear cylinder 77 loosely fitted to the main drive shaft 58 to rotate the first driven shaft 59 to the gear cylinder 77. It is transmitted.

  An output shaft 55 is provided on the axis of the first driven shaft 59, and a clutch gear 78 constituting the auxiliary transmission B is spline-fitted to the output shaft 55. The clutch gear 78 is a gear formed on the gear cylinder 77. When meshed with the gear 79, the rotation of the gear cylinder 77 is transmitted from the gear 79 to the output shaft 55 via the clutch gear 78, and when meshed with the gear 75 of the first driven shaft 59, the rotation of the first driven shaft 59 or the first described later. The rotation transmitted from the two driven shafts 60 to the gear 75 is transmitted to the output shaft 55.

  Accordingly, when the first-speed clutch C1 is turned on, the rotation of the main drive shaft 58 is decelerated from the gear 68 to the gear 69, and the rotation of the gear 69 becomes the rotation of the first driven shaft 59 via the cylinder case 74. The gear 75 is rotated. At this time, when the clutch gear 78 is engaged with the gear 75, the rotation of the first driven shaft 59 is directly transmitted to the output shaft 55, and when the clutch gear 78 is engaged with the gear 79 formed on the gear cylinder 77, the rotation of the gear 75 is performed. The gear 76 is decelerated and transmitted to the gear cylinder 77 via the gear 76, and is decelerated and transmitted from another gear 79 of the gear cylinder 77 to the output shaft 55.

  Further, when the third-speed clutch C3 is turned on, the rotation of the main drive shaft 58 is transmitted at an increased speed from the gear 70 to the gear 71, and the rotation of the gear 71 and the rotation of the first driven shaft 59 via the cylinder case 74 are transmitted. The gear 75 is rotated. At this time, when the clutch gear 78 is engaged with the gear 75, the rotation of the first driven shaft 59 is directly transmitted to the output shaft 55, and when the clutch gear 78 is engaged with the gear 79 formed on the gear cylinder 77, the rotation of the gear 75 is performed. The gear cylinder 77 is decelerated and transmitted to the gear cylinder 77 via the gear 76, and the rotation is further decelerated and transmitted from another gear 79 of the gear cylinder 77 to the output shaft 55.

  A configuration similar to the gear transmission mechanism provided between the main drive shaft 58 and the first driven shaft 59 arranged in parallel is also provided between the main drive shaft 58 and the second driven shaft 60. Thus, a second-speed clutch C2 and a fourth-speed clutch C4 are configured.

  First, a gear 66 that is spline-engaged with the main drive shaft 58 is always meshed with a gear 67 that is supported by the second driven shaft 60 via a needle bearing, and the second driven shaft 60 is made relatively non-rotatable. A case 80 is attached. The cylinder case 80 includes a second-speed clutch C2 and a fourth-speed clutch C4.

  A gear 81 fixed to the rear end of the second driven shaft 60 is meshed with a gear 76 spline-fitted to a gear cylinder 77 loosely fitted to the main drive shaft 58 to transmit the rotation of the second driven shaft 60 to the gear cylinder 77. is doing.

  Therefore, when the second speed clutch C2 is turned on, the rotation of the main drive shaft 58 is transmitted at high speed from the gear 66 to the gear 67, and the rotation of the gear 67 becomes the rotation of the second driven shaft 60 via the cylinder case 80. The gear 81 is rotated, and the gear 75 is further rotated from the gear 81 through the gear 76. At this time, when the clutch gear 78 meshes with the gear 75, the rotation of the second driven shaft 60 is transmitted to the output shaft 55, and when the clutch gear 78 meshes with the gear 79 formed on the gear cylinder 77, the rotation of the gear 81 causes the gear 81 to rotate. The power is transmitted to the gear cylinder 77 via 76 and is decelerated from the gear 79 to the output shaft 55.

  Further, when the fourth-speed clutch C4 is turned on, the rotation of the main drive shaft 58 is increased in speed from the gear 72 to the gear 73, and the rotation of the gear 73 is coupled with the rotation of the second driven shaft 60 via the cylinder case 80. The gear 81 is rotated, and the gear 75 is further rotated from the gear 81 through the gear 76. At this time, when the clutch gear 78 meshes with the gear 75, the rotation of the second driven shaft 60 is transmitted to the output shaft 55, and when the clutch gear 78 meshes with the gear 79 formed on the gear cylinder 77, the rotation of the gear 81 causes the gear 81 to rotate. The power is transmitted to the gear cylinder 77 via 76 and is decelerated from the gear 79 to the output shaft 55.

  A support shaft 94 is pivotally attached to the left and right side walls of the rear case 103 that supports the left and right crawler travel devices 13, and a bevel gear 85 that meshes with the bevel gear 56 fixed to the output shaft 55 is spline-engaged with the support shaft 94. A brake disc 82 is provided at a position symmetrical to the bevel gear 85.

  Then, the brake pedal 25 and the brake disc 82 are connected by a link mechanism (not shown), and the brake disc 82 is crimped by depressing the brake pedal 25, whereby the rotation of the support shaft 94, that is, the left and right crawler travel devices 13, It is comprised so that rotation of 13 may be braked.

  The brake pedal 25 incorporates two sensors, a sensor S1 that is depressed and turned on and a sensor S2 that is depressed and turned off. If either of the sensors S1 and S2 breaks down, the brake pedal 25 is turned on or off at the time of depression or depression. I understand that.

FIG. 12 is a flowchart of control for determining a sensor abnormality of the brake pedal 25 when the forward / reverse lever 24 is neutral.
In step S30, the signals of the sensors S1 and S2 are read into the controller. In step S31, it is first determined whether the sensor S1 is on. If NO, it is determined in step S32 whether the sensor S2 is on. For example, it is determined that there is a brake operation in step S33, and in step S39, the forward rotation clutch 89 of the forward / reverse switching clutch D is turned on to transmit the braking action of the brake disc 82 to the traveling device 13 and stop. If determination of step S32 is NO, it will be determination of continuation time of step S37.

  If the determination in step S31 is YES, it is determined in step S34 whether the sensor S2 is on. If NO, it is determined that there is no brake operation in step S35, and the forward / reverse switching clutch D remains neutral in step S40. To. If determination of step S34 is YES, it will be determination of continuation time of step S37.

  The determination of the duration in step S37 is to eliminate mistakes that erroneously determine that it is instantaneously turned on or off at the time of sensor on / off switching. If the determination in step S37 is YES, it is determined in step S38 that one of the brake sensors S1, S2 is abnormal, the system abnormality warning lamp 38 is lit, and the forward rotation clutch 89 of the forward / reverse switching clutch D is turned on in step S41. Then, the brake action of the brake disc 82 is transmitted to the traveling device 13 and stopped.

A reduction gear set 83 is provided at the end of the support shaft 94, and the rotation of the support shaft 94 is transmitted to the input shaft 84 in the axle case via the reduction gear set 83.
Inside the axle case, a turning device constituted by a forward / reverse switching clutch D and a two-stage planetary gear mechanism 87 is disposed. The swivel device is interposed between the input shaft 84, a sprocket shaft 86 that is coaxially attached to the input shaft 84 on the outer end side of the input shaft 84, and the input shaft 84 and the sprocket shaft 86. A two-stage planetary gear mechanism 87, and a wet multi-plate forward clutch 89 and a reverse clutch 90 (forward / reverse switching clutch D) provided on a carrier 88 of the two-stage planetary gear mechanism 87. The left and right sides of the axle case are provided.

  When the forward rotation clutch 89 is engaged, the vehicle travels forward, and when the reverse rotation clutch 90 is engaged, the vehicle travels backward, but the forward rotation clutch 89 is engaged by the spring pressure and the forward / reverse lever 24 is moved backward. Is operated, the hydraulic pressure acts on the clutch plate to switch the reverse clutch 90 to ON. For this reason, as long as the hydraulic pressure does not generate the pressure necessary for the operation of the clutch, a situation occurs in which the vehicle travels forward even if the forward / reverse lever 24 is operated to the reverse side.

  Such a situation is unpredictable by the operator and dangerous, so control is performed using a controller as shown in FIG. That is, the clutch hydraulic pressure or the like is detected in step S1, and it is determined in step S2 whether the detected hydraulic pressure has reached a pressure required for clutch operation. If the reverse side operation is determined and the reverse side operation is performed, the solenoid that moves the clutches C1, C2, C3, and C4 of the main transmission A is operated to set the power to the neutral switching position, that is, to the crawler travel device 13. Avoid transmission.

  If the oil pressure becomes insufficient and the pressure is less than the required pressure during reverse travel, the main transmission lever 9 is also set to the neutral position and travel is stopped. When the travel is stopped due to such a shortage of oil pressure, the travel is not started until the main speed change lever 9 is returned to the neutral position and the speed change operation is performed again even if the oil pressure is restored.

  The left and right forward / reverse switching clutch D adjusts the hydraulic pressure acting on the clutch plate during turning to change the rotational speed of the left and right crawler travel devices 13 so that the inside of the turning becomes a low speed. When the speed change lever 9 is operated and the speed change operation is performed, the oil pressure adjustment change is not performed in order to perform stable turning. Similarly, the hydraulic pressure adjustment is not changed during forward / reverse operation by the forward / reverse switching lever 24 during turning.

  The oil pressure acting on the forward / reverse switching clutch D is gradually changed in order to eliminate the shock of power connection. However, when the main clutch 52 is disengaged by depressing the clutch pedal 26, the forward / reverse switching is performed. The pressure is changed immediately when the lever 24 moves forward and backward.

  Reference numeral 120 denotes a gear for detecting the rotation state of the sprocket shaft 86, and the rotation state is detected by the two rotation sensors 121 and 122. Whether the airframe is traveling is determined not only by the signals from the rotation sensors 121 and 122 but also when the main transmission lever 9, the auxiliary transmission lever 17 and the forward / reverse switching lever 24 are neutral and the clutch pedal 26 is depressed. However, under the condition of YES, the rotation signals from the rotation sensors 121 and 122 are ignored and it is determined that the vehicle is not in a traveling state, and no turning control signal is output. This is because even if the rotation sensors 121 and 122 detect rotation due to engine vibration when the aircraft is stopped, the hydraulic equipment is not operated wastefully.

The rotation of the main drive shaft 58 is transmitted to the PTO input shaft 91 connected to the shaft end, and is transmitted to the PTO output shaft 93 via the PTO transmission mechanism 92.
The first-speed clutch C1 and the third-speed clutch C3 are housed in one cylinder case 74, and the second-speed clutch C2 and the fourth-speed clutch C4 are housed in one cylinder case 80. Since it operates with a common hydraulic spool, there is a slight time lag in switching the clutch, but since it is not a continuous shift stage, when shifting from 1st speed to 4th speed sequentially, cylinder case 74 → cylinder case Since the working cylinder case is alternately changed from 80 → cylinder case 74 → cylinder case 80, there is no feeling of slack due to time lag. The same applies to the case where the gears are sequentially shifted from the fourth speed to the first speed.

  However, when the temperature of the hydraulic cylinder operating oil is low, the transmission-side clutch may be connected while the transmission-side clutch is not fully engaged, so that the hydraulic oil for the cylinder case 74 and the cylinder case 80 is connected. The pressure sensor is monitored by a pressure sensor, and when no pressure increase or pressure decrease is detected in a predetermined time, the forward / reverse switching clutch D is neutral so that power is not transmitted to the traveling device. Yes. This abnormal state is notified to the operator by blinking the system abnormality warning lamp 38. The abnormality process continues until the main speed change lever 9 is returned to the neutral position or the speed change position is changed to prevent unexpected jumping. Along with the cancellation of the abnormal state, the pressure monitoring is reset and the occurrence of the abnormality is monitored again.

  When the wiring of the pressure sensor is disconnected or short-circuited, the failure indicator is displayed by blinking the system abnormality warning lamp 38 together with the second and fourth gears or the gears for displaying the current gear. Like to do. In the case of a failure due to the disconnection of the pressure sensor wiring, the pressure monitoring control is interrupted to stop traveling.

  The main speed change lever 9 and the sub speed change lever 17 are appropriately operated to travel at a desired travel speed. The low speed of the sub speed change lever 17 is mainly used during operations such as rotary work, and the high speed of the sub speed change lever 17 is Use when traveling on the road. In order to reduce the operation of the main transmission lever 9 and the auxiliary transmission lever 17, the control shown in FIGS. 14 and 15 is performed.

  In the control block diagram shown in FIG. 14, a shift position signal is input from the main shift sensor 127 to the controller 125, and high and low shift position signals are input from the sub shift sensor 126. In the controller 125, the shift position of the main transmission is stored in or read out from the shift position storage means S1 including a RAM or the like. Further, a shift command signal is output from the controller 125 to the automatic transmission means S2 of the main transmission A that is constituted by a solenoid or a hydraulic cylinder.

  In the control flowchart shown in FIG. 15, first, the auxiliary transmission lever 17 is operated at a low speed in step S10, the main transmission lever 9 is operated at a first speed in step S11, and traveling starts in step S12. In step S13, the main transmission lever 9 is set to the work transmission position H and the work transmission position H is stored in the transmission position storage means S1, and the operation is performed in step S14.

  If there is an operation for changing the auxiliary transmission lever 17 in step S15 from a low speed to a high speed in the middle of the work, the main transmission lever 9 is returned to the first speed by the automatic transmission means S2 in step S16 to avoid a sudden speed increase. Thereafter, the main speed change lever 9 is operated to an arbitrary speed change position in step S17, and traveling is performed in step S18.

  If there is an operation for changing the auxiliary transmission lever 17 from high speed to low speed in step S19, the main transmission lever 9 is stored in the transmission position storage means S1 in step S13 in step S20, that is, the auxiliary transmission lever 17 is operated. Is changed by the automatic transmission means S2 to the main shift position before changing from low speed to high speed. As a result, the work speed before moving to the traveling state is reached, and the work can be resumed immediately. When the sub-shift lever 17 is started at a high speed, the shift position storage means S1 does not have the work shift position H of the main shift lever 9, so the speed is set to the first speed.

  Thereafter, if there is a stop operation in step S21, the main clutch 52 is disengaged and stopped in step S22.

It is a side view of the tractor which shows the Example of this invention. It is a partial perspective view of a tractor. It is a partial enlarged plan view of a tractor. It is a partial enlarged plan view of a tractor. 1 is an overall perspective view of a tractor. It is a partial top view of a tractor. It is a partial perspective view of a tractor. It is a power transmission diagram of a tractor. It is a whole sectional side view of a mission case. It is a front sectional view of a mission case. It is a partially expanded side sectional view of a mission case. It is a flowchart figure of control. It is a flowchart figure of control. It is a block diagram of control. It is a flowchart figure of control.

Explanation of symbols

12 Transmission case A Main transmission B Sub transmission S1 Shift position storage means S2 Automatic transmission means

Claims (1)

  In a work vehicle equipped with a transmission case (12) provided with a multi-stage or continuously variable main transmission (A) and a sub-transmission (B) that switches between the main transmission (A) and high and low two stages. , Shift position storage means (S1) for storing the shift position (H) of the main transmission (A) set before shifting from the low speed to the high speed of the auxiliary transmission (B), and the main transmission (A ) To change the shift position, and when the auxiliary transmission (B) is switched from the low speed to the high speed, the main transmission (A) is automatically changed from the low speed range to the first speed (S2). ), And when the auxiliary transmission (B) is switched from high speed to low speed, the shift position (A) of the main transmission (A) stored in the shift position storage means (S1). H) that the main transmission (A) is configured to automatically return. The work vehicle and butterflies.

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