JP2012245976A - Work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a work vehicle that improves agricultural workability.SOLUTION: The work vehicle includes a control device that achieves a variable ratio mode which changes a steering ratio that is a ratio of an operation amount of an input shaft of a steering device corresponding to an operation amount of a steering handle by controlling rotation of an electric motor, and a straight steering mode that controls the rotation of the electric motor to automatically steering the moving body along a preset position or direction.

Description

  The present invention relates to a work vehicle configured such that a steering operation can be performed by operating an input shaft of a steering device by operating a steering handle.

  As a conventional technique, for example, as disclosed in Patent Document 1, a metering pump (Patent Document 1) linked to a steering device (16 in FIG. 2 of Patent Document 1) by operating a steering handle. 2 of FIG. 2 can be operated to steer the front wheel, and the steering shaft (23 of FIG. 2 of Patent Document 1) is driven to drive the steering shaft (FIG. 2 of Patent Document 1). Agricultural work vehicles configured to be able to steer front wheels by operating 4a) are known.

Japanese Patent Laying-Open No. 2005-80578 (see FIGS. 2 and 3)

However, in the steering control device of Patent Document 1, the steering shaft of the steering handle is directly connected to a metering pump linked to the steering device, and the steering device is steered in response to the steering handle operation. Was configured to operate. For this reason, even when the steering wheel needs to be operated a lot, such as when turning the work vehicle on the coast, the steering device is steered in response to the steering handle, and the steering ratio ( The ratio of the steering device operation amount corresponding to the steering handle operation amount) cannot be changed, and the driver needs to operate the steering handle a lot when turning the work vehicle at the shore, etc. When the operation of the steering wheel was delayed, it was necessary to turn the work vehicle at a slower speed. As a result, there is room for improvement from the viewpoint of improving the workability of the turning operation of the work vehicle at the shore.
An object of the present invention is to realize a work vehicle that can change the steering ratio without difficulty and can improve workability such as farm work.

[I]
(Constitution)
A first feature of the present invention is that the work vehicle is configured as follows.
A steering differential mechanism is provided between the input shaft of the steering device and the handle operating shaft of the steering handle,
The steering differential mechanism includes a first gear fixed to the input shaft, a second gear fixed to the handle operation shaft having a different number of teeth from the first gear, and the input shaft or the handle operation shaft. A carrier supported rotatably, a turning member supported rotatably on a rotation shaft of the carrier, and fixed to the turning member and engaged with each of the first gear and the second gear. A first planetary gear and a second planetary gear, and an electric motor capable of rotating the carrier are configured.

(Function)
According to the first feature of the present invention, when the electric motor is rotated forward and backward, the rotation member rotatably supported by the rotation axis of the carrier rotates, and the first and second planetary gears rotate. When the first and second planetary gears rotate, the first gear rotates due to the transmission ratio difference between the first and second gears set to different numbers of teeth, and the input shaft of the steering device according to the number of rotations of the electric motor. Thus, the steering ratio (ratio of the operation amount of the input shaft of the steering device corresponding to the operation amount of the steering wheel) can be changed. As a result, when a large amount of steering wheel operation is required, for example, when the work vehicle is turned on the coast, the work vehicle can be operated with relatively few steering handles by rotating the electric motor forward and backward. Can be turned with a small turning radius.

  Specifically, for example, the electric motor (for example, 30 in FIG. 2) is rotated so that the carrier (for example, 23 in FIG. 2) rotates in the direction opposite to the direction in which the driver operates the steering handle (for example, 6 in FIG. 2). Then, the rotating member rotatably supported on the rotation shaft (for example, 23a in FIG. 2) of the carrier rotates, and the first and second planetary gears (for example, 24 and 25 in FIG. 2) rotate. When the first and second planetary gears rotate, the first gear rotates due to the transmission ratio difference between the first and second gears (for example, 21 and 22 in FIG. 2) set to different numbers of teeth, and the electric motor rotates. Depending on the number, the rotation of the input shaft of the steering device (for example, 18a in FIG. 2) is accelerated, and the steering ratio (ratio of the operation amount of the input shaft of the steering device corresponding to the operation amount of the steering wheel) is greatly changed. be able to. As a result, when the work vehicle is turned, for example, when leaning, the input shaft of the steering device is increased by rotating the electric motor so that the carrier rotates in the direction opposite to the direction in which the driver operates the steering handle. As a result, the input shaft of the steering device can be operated more quickly, and the work vehicle can be turned with a small turning radius by operating the steering handle relatively little.

  According to the first aspect of the present invention, when the carrier is rotated by the electric motor, the rotating member rotatably supported by the rotation shaft of the carrier rotates and the first planetary gear rotates, and the first planetary gear rotates. The first gear engaged with the steering wheel rotates to rotate the input shaft of the steering device, and the power of the electric motor is transmitted to the steering device via the carrier, the rotating member, the first planetary gear, and the first gear. Can be transmitted to the input shaft. As a result, the power of the electric motor can be smoothly transmitted to the input shaft of the steering device, and the steering ratio can be smoothly changed steplessly.

(Effect of the invention)
According to the first feature of the present invention, it is possible to improve the workability of the turning operation of the work vehicle, for example, at the shore, and it is possible to improve the workability of the farm work and the like.

  According to the first feature of the present invention, the steering ratio can be changed smoothly in a stepless manner, and the operability of the steering wheel can be improved in a work vehicle.

[II]
(Constitution)
The second feature of the present invention is that the work vehicle of the first feature of the present invention is configured as follows.
The steering differential mechanism is configured to be detachable integrally with the input shaft and the handle operation shaft.

(Function)
According to the second feature of the present invention, the “action” described in the preceding item [I] is provided in the same manner as the first feature of the present invention, and in addition to this, the following “action” is provided.
According to the second feature of the present invention, for example, in a state where the input shaft and the handle operating shaft are assembled to the work vehicle, the steering differential mechanism can be integrally assembled to the input shaft and the handle operating shaft. Can be assembled to work vehicles. Further, for example, the steering differential mechanism can be integrally removed from the input shaft and the handle operating shaft without removing the input shaft and the handle operating shaft from the work vehicle, and the steering differential mechanism can be easily detached from the work vehicle. it can. As a result, assembly work and maintenance work of the steering differential mechanism can be easily performed.

(Effect of the invention)
According to the second feature of the present invention, the “effect of the invention” described in the preceding item [I] is provided in the same manner as the first feature of the present invention. In addition, the following “effect of the invention” is provided. ing.
According to the second feature of the present invention, the workability of the assembly and maintenance work of the steering differential mechanism can be improved, and the manufacturing cost and maintenance cost of the work vehicle can be reduced.

Overall left side view of the tractor Schematic showing structure of steering device and steering differential mechanism Block diagram of control device Schematic explaining how to set the field area Flow chart of main routine of control device Flow chart of variable ratio mode Flow chart for straight mode Graph explaining the rotation speed of the steering motor Schematic plan view of the field showing the working status of the tractor Schematic which shows the structure of the steering differential mechanism in 1st another form of implementation of invention. Schematic which shows the structure of the steering differential mechanism in 1st another form of implementation of invention. The graph explaining the rotation speed of the steering motor in the second alternative embodiment of the invention The graph explaining the rotation speed of the steering motor in the second alternative embodiment of the invention Flowchart of the main routine of the control device according to the second embodiment of the invention Flowchart of variable ratio mode in the second alternative embodiment of the invention

[Overall structure of tractor]
FIG. 1 is an overall left side view of a tractor as an example of a work vehicle. As shown in FIG. 1, an engine 2 is disposed at the front of the traveling vehicle body 1, and a pair of left and right steerable front wheels 3 and a pair of left and right rear wheels 4 are driven by power from the engine 2. Thus, the tractor travels and turns according to the operation of the steering wheel 6 of the driver seated on the driver seat 5.

  A pair of left and right lift arms 8 are linked to the rear part of the transmission case 7 disposed at the rear part of the traveling vehicle body 1, and the swing arm 10 is swung up and down by operating the lift cylinder 9. A work device (not shown) such as a vertical device or a tilling device connected to the rear end of the swing arm 10 can be moved up and down.

  A rearward PTO shaft 11 for extracting power from the engine 2 is provided at the rear portion of the transmission case 7, and the working device can be driven by interlockingly connecting the working device to the PTO shaft 11. The PTO shaft 11 is linked to a PTO lever (not shown) provided in the vicinity of the steering handle 6, and the operation device linked to the PTO shaft 11 is driven and stopped by operating this PTO lever. can do.

  As shown in FIG. 2, the steering device 12 includes a power cylinder 13, an operation valve 14, a main pump 16, and a metering pump 18. A different configuration may be adopted as the steering device 12, not the hydraulic steering device 12 using the main pump 16, the power cylinder 13, or the like, but the steering device 12 that does not include the power cylinder 13, or other than the power cylinder 13. You may employ | adopt the steering device 12 provided with the actuator.

  The power cylinder 13 is linked to the knuckle arms 3a of the left and right front wheels 3, and a main pump 16 linked to the engine 2 is connected to an operation valve 14 of the power cylinder 13 via a hydraulic circuit 15. Yes. A metering pump 18 is connected to the operation valve 14 via a hydraulic circuit 17, and an input shaft 18 a of the metering pump 18 is linked to the steering handle 6 via a steering differential mechanism 20 described later. .

[Steering differential mechanism]
As shown in FIG. 2, the steering differential mechanism 20 is constituted by a planetary gear mechanism, and includes a first gear 21 as a sun gear fixed to the input shaft 18 a of the metering pump 18, and a handle of the steering handle 6. The second gear 22 fixed to the operating shaft 6a, the carrier 23 supported on the steering wheel operating shaft 6a of the steering handle 6 so as to be relatively rotatable, and the carrier 23 and the first and second gears 21, 22 A plurality of first and second planetary gears 24 and 25 are provided.

  The input shaft 18a of the metering pump 18 constituting the steering device 12 and the handle operation shaft 6a of the steering handle 6 are disposed concentrically, and a steering differential is provided between the input shaft 18a and the handle operation shaft 6a. A mechanism 20 is provided.

  The carrier 23 is fixed to a first tube shaft 26 that is rotatably supported by the handle operating shaft 6 a of the steering handle 6, and support shafts 23 a (autorotated) disposed at a plurality of locations on the outer periphery of the carrier 23. The second cylinder shaft 27 (corresponding to a rotating member) is supported so as to be relatively rotatable. A first planetary gear 24 is fixed to the second cylindrical shaft 27, and the first planetary gear 24 is engaged with a first gear 21 fixed to the input shaft 18 a of the metering pump 18.

  A second planetary gear 25 having a smaller number of teeth than the first planetary gear 24 is fixed to the second cylindrical shaft 27, and the second planetary gear 25 is connected to the handle operating shaft 6 a having a larger number of teeth than the first gear 21. It meshes with the fixed second gear 22. An input gear 28 is fixed to the first cylindrical shaft 26, and this input gear 28 is fixed to a drive shaft 30a of a steering motor 30 (corresponding to an electric motor) and has an output with a smaller number of teeth than the input gear 28. It is engaged with the gear 29.

As described above, by configuring the steering device 12 and the steering differential mechanism 20, when the steering motor 30 is stopped and the drive shaft 30a is not rotating, the output gear 29 connected to the drive shaft 30a, the first Since the one cylinder shaft 26 and the carrier 23 do not rotate, when the handle operating shaft 6a is rotated by the operator's operation of the steering handle 6, the second gear 22, the second planetary gear 25, the second cylinder shaft 27, the first The input shaft 18 a of the metering pump 18 is configured to rotate according to the operation amount of the steering handle 6 via the planetary gear 24 and the first gear 21.

  Since the first gear 21, the second gear 22, and the first and second planetary gears 24 and 25 are set to have different numbers of teeth, the rotation of the handle operating shaft 6a of the steering handle 6 is accelerated and metered. It is configured to be transmitted to the input shaft 18 a of the ring pump 18.

  On the other hand, when the driver holds the steering handle 6 and the steering operation shaft 6a is not substantially rotated, when the steering motor 30 is rotated forward and backward, the output gear 29 and the input gear connected to the drive shaft 30a of the steering motor 30 are provided. The first cylinder shaft 26 is rotated via 28, the carrier 23 fixed to the first cylinder shaft 26 rotates relative to the handle operating shaft 6 a, and the second cylinder relative to the support shaft 23 a of the carrier 23. The shaft 27 relatively rotates, and the first and second planetary gears 24 and 25 fixed to the second cylindrical shaft 27 rotate. Since the second planetary gear 25 is engaged with the non-rotating second gear 22, when the first and second planetary gears 24, 25 rotate, the first and second gears 21, 22, The input shaft 18a of the metering pump 18 rotates according to the transmission ratio of the second planetary gears 24 and 25.

  The output gear 29 and the input gear 28 are set to have different numbers of teeth, and the input gear 28 is connected to the input shaft 18a of the metering pump 18 via the steering differential mechanism 20, so that the steering motor 30 The rotation of the drive shaft 30a is decelerated by the output gear 29, the input gear 28, and the steering differential mechanism 20, and is transmitted to the input shaft 18a of the metering pump 18.

  The rotational speed of the steering motor 30 can be arbitrarily changed and adjusted. By changing the rotational speed of the steering motor 30 via the motor drive circuit 39 from the control device 31 described later, the rotational speed of the steering motor 30 is adjusted. Accordingly, the rotational speed of the input shaft 18a of the metering pump 18 can be arbitrarily changed and adjusted.

  Therefore, the input shaft 18a of the metering pump 18 can be rotated by rotating the steering motor 30 forward and backward while holding the steering handle 6 and the handle operating shaft 6a is not rotating, and the left and right front wheels 3 can be operated. Can be operated in the opposite direction.

  When the steering motor 30 is rotated forward so that the first cylinder shaft 26 rotates in the direction opposite to the direction in which the driver rotates the steering handle 6, the input shaft of the metering pump 18 according to the number of rotations of the steering motor 30. As the rotation of 18a is increased, the steering ratio (ratio of the operation amount of the input shaft 18a of the steering device 12 corresponding to the operation amount of the steering handle 6) can be greatly changed.

  On the contrary, when the steering motor 30 is reversed so that the first cylinder shaft 26 rotates in the same direction as the direction in which the driver rotates the steering handle 6, the metering pump 18 of the metering pump 18 is changed according to the rotation speed of the steering motor 30. The rotation of the input shaft 18a is decelerated, and the steering ratio (ratio of the operation amount of the input shaft 18a of the steering device 12 corresponding to the operation amount of the steering handle 6) can be changed small.

  When the steering handle 6 is operated or the steering motor 30 is rotated to rotate the input shaft 18a of the metering pump 18, the operation valve 14 is operated in accordance with the operation amount of the input shaft 18a. 13 is supplied with pressure oil, and the operation of the power cylinder 13 causes the left and right front wheels 3 to operate in the steering direction corresponding to the rotational direction of the steering handle 6 or the steering motor 30 and to operate the input shaft 18a of the metering pump 18. The knuckle arm 3a is swung with a cutting angle corresponding to the amount. Then, the traveling vehicle body 1 is steered so as to travel in the traveling direction corresponding to the operation direction of the steering handle 6 or the steering motor 30 according to the operation amount of the steering handle 6 or the steering motor 30.

[Block diagram of control device]
FIG. 3 shows a block diagram of the control device 31 for the tractor. As shown in FIG. 3, the tractor includes a steering angle sensor 32, a drive shaft rotation sensor 33, an input shaft rotation sensor 34, a lever position detection sensor 36, an operation position detection sensor 45, an orientation sensor 37, a yaw rate sensor 38, and an area setting. Detection devices such as a button 46, a front wheel turning angle sensor 47, and a vehicle speed sensor 48 are mounted.

  The steering angle sensor 32 is provided on the handle operating shaft 6a of the steering handle 6 (see FIG. 2), and calculates the steering angle of the left and right front wheels 3 by measuring the rotation angle of the handle operating shaft 6a from the reference position. Thus, the operation amount (steering operation amount) of the steering handle 6 and the operation speed (steering operation speed) of the steering handle 6 of the driver can be detected.

  The drive shaft rotation sensor 33 and the input shaft rotation sensor 34 are respectively provided on the drive shaft 30a of the steering motor 30 and the input shaft 18a of the metering pump 18 (see FIG. 2). The rotational speed of the input shaft 18a of the ring pump 18 can be detected.

  The detection results from the steering angle sensor 32, the drive shaft rotation sensor 33, and the input shaft rotation sensor 34 are fed back and output from the motor drive circuit 39 to the steering motor 30, whereby the input shaft 18a of the metering pump 18 is output. , It can be accurately rotated to a predetermined rotational speed. In this tractor, the three sensors of the steering angle sensor 32, the drive shaft rotation sensor 33, and the input shaft rotation sensor 34 are provided and output from the motor drive circuit 39 to the steering motor 30. Any two of the sensors are mounted on the tractor, and the control device 31 performs arithmetic processing based on the detection results from the two sensors so as to output from the motor drive circuit 39 to the steering motor 30. May be.

  The lever position detection sensor 36 is mounted on a mode switching lever 35 provided on the side of the steering handle 6 so as to be swingable. The lever position detection sensor 36 operates the operation position (variable ratio) of the mode switching lever 35. Mode and straight mode). The forward / reverse switching lever 44 is provided on the side of the driver's seat 5 and can switch between forward and backward travel of the traveling vehicle body 1, and the operation position (forward position F, reverse position) of the forward / backward switching lever 44. R and the neutral position N) can be detected by the operation position detection sensor 45.

  The azimuth sensor 37 is disposed at the left and right center of the traveling vehicle body 1 and detects the traveling direction of the traveling vehicle body 1. The yaw rate sensor 38 is disposed near the center of gravity of the traveling vehicle body 1 and detects the yaw rate acting on the tractor. The area setting button 46 is provided on the side of the driver's seat 5 and is used for setting the field area X described later.

  The front wheel break angle sensor 47 is mounted on the rotating part of the knuckle arm 3a linked to the front wheel 3, and can detect the cut angle of the front wheel 3 operated by the steering device 12 (see FIG. 2). The vehicle speed sensor 48 is mounted on the traveling vehicle body 1 and can detect the vehicle speed at which the tractor travels.

  Based on the detection result of the front wheel cutting angle sensor 47, the cutting angle of the front wheel 3 is monitored by the control device 31, and for example, when the cutting angle of the front wheel 3 changes due to leakage of hydraulic oil in the power cylinder 13, etc. The control device 31 corrects the cutting angle of the front wheel 3 based on the detection result of the front wheel cutting angle sensor 47, and the accurate cutting angle of the front wheel 3 is grasped by the control device 31, and this corrected cutting angle of the front wheel 3 will be described later. The variable ratio mode and the straight traveling mode are configured to be implemented.

  A motor drive circuit 39, a GPS receiver 40, a navigation system 41, a monitor 42 and an electromagnetic valve 43 are connected to the control device 31. The motor drive circuit 39 is connected to the steering motor 30, and is output from the control device 31 to the motor drive circuit 39, so that the steering motor 30 is driven and stopped based on the output from the control device 31, and the rotation direction. Can be changed.

  The GPS receiver 40 is configured as an SBAS receiver corresponding to SBAS (stationary satellite type satellite navigation augmentation system), and in addition to position information from a GPS satellite (not shown), a reference station (not shown) It is configured to receive correction information for aviation.

  The GPS receiver 40 is connected to a GPS antenna 19 provided in the center of the front portion of the steering handle 6 (see FIG. 1). The GPS receiver 40 receives position information from GPS satellites and GPS reception. The correction information from the reference station received by the machine 40 is input to the control device 31, and the current position of the tractor is detected with an error of, for example, several centimeters.

  The navigation system 41 provides map information. The position of the tractor detected by the GPS receiver 40, the operation position of the forward / reverse switching lever 44 detected by the operation position detection sensor 45 (the traveling direction of the traveling vehicle body 1). ), A field area X, which will be described later, and a setting position L in a straight traveling mode, which will be described later, are displayed together with the map information of the navigation system 41 on a monitor 42 mounted on the side of the steering handle 6.

  The monitor 42 is configured as a touch panel, and is configured to be able to select and display a field area setting screen for setting a field area X, which will be described later, and a tractor position display screen for displaying the current position of the tractor. ing. An operation button (not shown) may be provided on the side of the monitor 42 so that a display screen displayed on the monitor 42 can be selected by the operation button.

  The electromagnetic valve 43 is linked to the lift cylinder 9, and the lifting / lowering operation of the working device by the lift cylinder 9 can be performed by outputting the electromagnetic valve 43 from the control device 31.

  Each of the detection devices described above is connected to the control device 31, and based on the detection result from each detection device, the control device 31 sends a motor drive circuit 39, a GPS receiver 40, a navigation system 41, a monitor 42, a solenoid valve. By performing output to 43, a variable ratio mode and a straight traveling mode, which will be described later, can be realized.

[Setting method of field area]
Based on FIG. 4, the setting method of the agricultural field area | region X used for the rectilinear advance mode mentioned later is demonstrated. The position of the GPS antenna 19 in a plan view (the position of the front central portion of the steering handle 6 of the tractor) is input to the control device 31 by the GPS receiver 40 as the current position, and the current position received by the GPS receiver 40 Based on the position and the vehicle body conditions (the width of the working device, the total length of the traveling vehicle body 1, etc.) previously input to the control device 31, the control device 31 determines the position of the right rear end portion of the working device equipped at the rear of the tractor. Arithmetic processing is performed.

  As shown in FIG. 4, the field area setting screen is displayed on the monitor 42, and the position of the right rear end of the work device is moved to the four corners (P1 to P4) of the field to be set as the field area X. By pressing the area setting button 46 at the position, the field area X (area surrounded by P1 to P4) for automatically performing the tilling work by the tractor is set on the map information provided by the navigation system 41, This field area X is configured to be displayed together with the map information of the navigation system 41 on the tractor position display screen of the monitor 42. In addition, you may comprise so that the agricultural field area | region X may be set by inputting the positional information on P1-P4 of the agricultural field area | region X to the control apparatus 31. FIG.

  The setting operation of the field area X is stored in the control device 31 by setting it once for the first time in the field where the first tilling work or the like is performed, and the tractor is moved closer to the field area X in the second and subsequent tilling work, etc. By displaying the tractor position display screen on the monitor 42, the field area X is automatically displayed on the monitor 42.

[Variable ratio mode and straight mode]
A variable ratio mode in which the steering ratio can be changed and a straight-ahead mode in which a straight-ahead traveling can be performed will be described with reference to FIGS. FIG. 5 shows a main routine of the control device 31, and FIGS. 6 and 7 show subroutines when the variable ratio mode and the straight-ahead mode are selected, respectively. FIG. 8 is a graph for explaining the rotational speed N of the steering motor 30, and FIG. 9 is a schematic plan view of the field showing the work situation by the tractor using the variable ratio mode and the straight traveling mode (the tractor position of the monitor 42). Display screen display).

  As shown in FIG. 5, the data detected by the detection devices shown in FIG. 3 and input to the control device 31 are constantly monitored (step # 11). If it is determined that the mode switching lever 35 has been operated in the variable ratio mode based on the detection result of the lever position detection sensor 36 (step # 12 • YES, step # 13), the control device 31 switches to the solenoid valve 43. As a result, the lift cylinder 9 is operated, and the working device connected to the rear portion of the traveling vehicle body 1 is raised (step # 14).

  On the other hand, when it is determined that the mode switching lever 35 is operated in the straight traveling mode based on the detection result of the lever position detection sensor 36 (step # 12 / NO, step # 15), the control device 31 sends the electromagnetic valve 43 to the solenoid valve 43. , The lift cylinder 9 is operated, and the working device connected to the rear portion of the traveling vehicle body 1 is lowered (step # 16).

  As shown in FIG. 6, when the mode switching lever 35 is operated to the variable ratio mode (step # 13), whether or not the vehicle speed of the tractor is slower than a preset set speed based on the detection result of the vehicle speed sensor 48. (Step # 21), and when it is determined that the vehicle speed of the tractor is slower than the set speed (step # 21, YES), the driver pushes the steering handle 6 based on the detection result of the steering angle sensor 32. It is determined whether or not an operation is being performed (step # 22).

  When it is determined that the driver is operating the steering handle 6 (step # 22, YES), an output is output from the control device 31 to the motor drive circuit 39, and the direction in which the driver rotates the steering handle 6 and The steering motor 30 is rotated so that the first cylinder shaft 26 rotates in the reverse direction, the rotation of the input shaft 18a of the metering pump 18 is increased, and the steering ratio (the steering corresponding to the operation amount of the steering handle 6) is increased. The ratio of the operation amount of the input shaft 18a of the device 12 is greatly changed (step # 23).

  As shown in FIG. 8, from the motor drive circuit 39, the rotation speed of the drive shaft 30a detected by the drive shaft rotation sensor 33 is fed back so that the steering motor 30 rotates at a predetermined rotation speed N1. It is configured to be output to the steering motor 30.

  Next, based on the detection result of the vehicle speed sensor 48, it is determined whether or not the vehicle speed of the tractor is faster than a preset set speed (step # 23), and the vehicle speed is set while the steering handle 6 is being operated. During the later time, the rotation of the steering motor 30 is continued (step # 24 · YES, step # 25 · NO). Conversely, when it is determined that the driver is not operating the steering wheel 6 (step # 24, NO), or when it is determined that the vehicle speed is higher than the set speed (step # 25, YES), The output from the control device 31 to the motor drive circuit 39 is turned off, and the steering motor 30 is stopped (step # 26).

  In this way, by switching to the variable ratio mode and configuring the steering ratio to change greatly when the driver operates the steering handle 6, for example, when the tractor enters a state of turning at a slower vehicle speed, The operation of the steering handle 6 by the driver can be automatically assisted, and the workability of the turning operation of the tractor can be improved.

  As shown in FIG. 7, when the mode switching lever 35 is operated in the straight traveling mode (step # 15), it is determined whether or not the driver is operating the steering handle 6 based on the detection result of the steering angle sensor 32. If it is determined that the driver holds the steering handle 6 and does not steer in either the right or left direction (step # 31, NO), the self-propelled vehicle body The steering device 12 is automatically operated so that 1 travels along the preset setting position L (steps # 32 to # 35).

  As shown in FIG. 9, the field area X (P1 to P4) set in advance on the map information of the navigation system 41 is displayed on the monitor 42, and further received by the GPS receiver 40 on this map information. The current position of the tractor and the traveling direction of the traveling vehicle body 1 detected by the operation position detection sensor 45 are always displayed on the monitor 42.

  For example, when the tractor is moved to the point A in FIG. 9 and the mode switching lever 35 is operated in the straight mode, the field area X (P1 to P4), the current position of the tractor received by the GPS receiver 40, and the operation position detection Based on the traveling direction of the traveling vehicle body 1 detected by the sensor 45, a set position L1 (solid line connecting A and B in FIG. 9) parallel to the straight line connecting P1 and P2 where the tractor goes straight is set.

  As shown in FIG. 7, it is determined that the driver holds the steering handle 6 and does not steer the steering handle 6 in either the right or left direction (step # 31, NO). If it is determined that the current position received by the GPS receiver 40 from the point A in FIG. 9 deviates from the set position L1 set at the point A in FIG. 9 (step # 32 YES) ), Output from the control device 31 to the motor drive circuit 39 so that the front wheel 3 is steered in the direction opposite to the direction deviated from the set position L1 (right or left direction (downward or upward in FIG. 9)). And the steering motor 30 is driven to automatically steer the tractor so as to move along the set position L1 (step # 33).

  As shown in FIG. 8, the motor drive circuit 39 feeds back the rotation speed of the drive shaft 30a detected by the drive shaft rotation sensor 33 so that the steering motor 30 rotates at a predetermined rotation speed N2. It is configured to be output to the steering motor 30. The rotational speed N2 is set to a rotational speed smaller than the rotational speed N1.

  As shown in FIG. 7, when the current position received by the GPS receiver 40 after running the tractor is corrected to the set position L1 (step # 34, YES), the motor drive circuit from the control device 31 The output to 39 is turned off, and the steering motor 30 is stopped (step # 35). When the state in which it is determined that the driver holds the steering handle 6 and does not steer the steering handle 6 in either the right or left direction is continued, the above-described forward / reverse rotation and stop of the steering motor 30 are performed. Is repeated (steps # 32 to # 35), the position of the tractor is corrected, and the tractor is driven along the set position L1 set at the point A in FIG.

  When it is determined that the driver steers the steering handle 6 to the right or left in the straight traveling mode, the driver's intention to operate the steering handle 6 is prioritized, and the steering motor 30 is not rotated forward or backward. Further, the front wheel 3 is steered in accordance with the driver's operation of the steering handle 6 (step # 31, YES).

  As described above, the steering motor 12 is automatically operated by rotating the steering motor 30 constituting the steering differential mechanism 20 in the forward and reverse directions so that the traveling vehicle body 1 is automatically operated along the preset position L. It is comprised so that it may face.

  As shown in FIG. 9, for example, when performing a tillage work in a range surrounded by Q1 to Q4, the mode switching lever 35 is operated to the variable ratio mode and the working device is raised, and the tractor is moved to the point A. After moving and driving the working device with the PTO lever, when the mode switching lever 35 is operated to the straight traveling mode at point A, the working device is lowered. When the steering wheel 6 is held and the tractor is driven, the steering motor 30 of the steering differential mechanism 20 automatically repeats forward and reverse rotations and stops, and the steering device 12 is operated to be set at point A in FIG. The tractor can travel along the set position L1.

  When the tractor travels and reaches point B, the mode switching lever 35 is operated to the variable ratio mode and the working device is raised, and the tractor is turned to point C as shown by the two-dot chain line in FIG. The position of the traveling vehicle body 1 and the working device is positioned in accordance with the position of the farm field that has already been plowed. When turning the tractor from point B, if the driver slows down the vehicle speed of the tractor, the steering motor 30 is assisted by the rotation of the steering motor 30, and the steering handle 6 is turned and operated. Even without this, the tractor can be easily turned.

  When the mode switching lever 35 is operated again at the point C and the steering handle 6 is held and the tractor is driven, the steering motor 30 of the steering differential mechanism 20 automatically repeats forward and reverse rotations and stops. The device 12 is operated, and the vehicle can travel along the set position L2 (solid line in FIG. 9) set at the point C. Thereafter, the range surrounded by Q1 to Q4 of the field area X shown in FIG. 9 can be cultivated by repeating traveling and turning while operating the mode switching lever 35 described above.

[First Alternative Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention], the example in which the steering differential mechanism 20 is configured as shown in FIG. 2 is shown. For example, the steering differential mechanism 20 is shown in FIGS. 10 and 11. You may comprise. Other configurations other than those described later are the same as those described in [Best Mode for Carrying Out the Invention].

  As shown in FIG. 10A, the first cylinder shaft 26 to which the carrier 23 is fixed is rotatably supported on the input shaft 18a of the metering pump 18, and the first cylinder disposed on the metering pump 18 side. The steering differential mechanism 20 may be configured such that the input gear 28 is fixed to the shaft 26 and the output gear 29 fixed to the drive shaft 30 a of the steering motor 30 is engaged with the input gear 28.

  Further, a different structure may be adopted as a structure for rotating the carrier 23 by the steering motor 30. For example, as shown in FIG. 10B, an input gear 28 is extended from the carrier 23, and the input gear 28 is steered. The steering differential mechanism 20 may be configured to engage the output gear 29 fixed to the drive shaft 30a of the motor 30.

  As shown in FIG. 11A, a first operation shaft 51 concentric with the input shaft 18 a of the metering pump 18 is provided, and the first gear 21 is fixed to the first operation shaft 51. On the other hand, a second operation shaft 52 concentric with the handle operation shaft 6 a is provided, the second gear 22 is fixed to the second operation shaft 52, and the first cylinder shaft 26 is rotated relative to the second operation shaft 52. It is supported freely. Devices constituting the steering differential mechanism 20 other than the steering motor 30 are accommodated in a transmission case 55, and the steering motor 30 is fixed to the transmission case 55. First and second operation shafts 51 and 52 are extended from the transmission case 55, and the first and second operation shafts 51 and 52 are respectively connected to the input shaft 18a and the handle operation shaft 6a of the metering pump 18 and to the first operation shaft 6a. The second connection members 53 and 54 are detachably connected.

  By configuring the steering differential mechanism 20 in this way, the steering differential mechanism 20 can be easily attached and detached integrally at the positions of the first and second connecting members 53 and 54. The workability of the assembly work and the maintenance work can be improved.

  Further, as shown in FIG. 11B, the first connecting members 53 and 53 are fixed to the input shaft 18a and the first operating shaft 51 of the metering pump 18, and the first connecting members 53 and 53 are fastened and fixed. In addition, by adopting a configuration in which the second connecting members 54 and 54 are fixed to the handle operating shaft 6a and the second operating shaft 52, respectively, and the second connecting members 54 and 54 are fastened and fixed, the first and second. You may comprise so that the steering differential mechanism 20 can be attached or detached integrally in the position of the connection members 53 and 54. FIG.

  In the above-mentioned [Best Mode for Carrying Out the Invention], the number of teeth of the first planetary gear 24 is set to be larger than the number of teeth of the second planetary gear 25, and the number of teeth of the first gear 21 is set to the second gear 22. Although an example in which the steering differential mechanism 20 is configured with a smaller number is shown, the number of teeth of the first planetary gear 24 is set to be smaller than the number of teeth of the second planetary gear 25, and the number of teeth of the first gear 21 is set. The steering differential mechanism 20 may be configured by setting more than the second gear 22.

  When the steering differential mechanism 20 is configured in this way, the rotation of the steering operation shaft 6a of the steering handle 6 is decelerated and transmitted to the input shaft 18a of the metering pump 18, and the direction in which the driver rotates the steering handle 6 is achieved. When the steering motor 30 is rotated forward so that the first cylinder shaft 26 rotates in the same direction as the rotation of the input shaft 18a, the rotation of the input shaft 18a of the metering pump 18 is accelerated and transmitted according to the rotational speed of the steering motor 30. When the steering motor 30 is rotated forward so that the first cylinder shaft 26 rotates in the direction opposite to the direction in which the driver rotates the steering handle 6, the input of the metering pump 18 according to the rotation speed of the steering motor 30. The rotation of the shaft 18a is decelerated and transmitted.

[Second Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Different Embodiment of the Invention], it is determined that the vehicle speed of the tractor detected by the vehicle speed sensor 48 is slower than a preset set speed. The rotation of the input shaft 18a of the metering pump 18 is accelerated by rotating the steering motor 30, and the steering ratio (the amount of operation of the input shaft 18a of the steering device 12 corresponding to the amount of operation of the steering handle 6) is increased. In the example, the ratio is greatly changed. As a condition for changing the steering ratio (ratio of the operation amount of the input shaft 18a of the steering device 12 corresponding to the operation amount of the steering handle 6), The condition may be different, and the steering ratio (the steering device corresponding to the operation amount of the steering wheel 6) It may be configured to change reduced the ratio) of the operation amount of the second input shaft 18a.

  In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Different Embodiment of the Invention], the steering motor 30 is rotated on the assumption that the tractor is turning. Although the example in which the ratio of the operation amount of the input shaft 18a of the steering device 12 corresponding to the operation amount of the steering device 12 is greatly changed has been shown, the steering ratio (the steering handle 6) The ratio of the operation amount of the input shaft 18a of the steering device 12 corresponding to the operation amount) may be changed to be larger or smaller.

  In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Alternative Embodiment], the current position of the tractor received by the GPS receiver 40 and the traveling vehicle body detected by the operation position detection sensor 45 are described. An example in which the steering device 12 is automatically operated via the steering differential mechanism 20 based on the traveling direction of 1 to automatically steer the traveling vehicle body 1 along a preset position L. However, based on the traveling direction of the traveling vehicle body 1 detected by the direction sensor 37 and the yaw rate acting on the tractor detected by the yaw rate sensor 38, the traveling vehicle body 1 is automatically steered in a preset setting direction. You may comprise.

  Specifically, the traveling direction of the traveling vehicle body 1 detected by the azimuth sensor 37 is set as the set direction, and when the yaw rate detected by the yaw rate sensor 38 changes with respect to the set direction, the direction in which the yaw rate changes Alternatively, the steering device 12 may be automatically operated in the reverse direction via the steering differential mechanism 20 so that the traveling vehicle body 1 is automatically steered in a preset setting direction.

  Further, different configurations may be adopted as the position or direction detection means, for example, traveling by adopting a combination of any two of the GPS receiver 40, the yaw rate sensor 38, the direction sensor 37, or all three. The vehicle body 1 may be configured to automatically steer, or the traveling vehicle body 1 may be configured to be automatically steered by a sensor (not shown) different from these sensors. Specifically, for example, by automatically steering the traveling vehicle body 1 based on the current position of the tractor received by the GPS receiver 40 and the yaw rate detected by the yaw rate sensor 38, the traveling vehicle body 1 in the set position or the setting direction. Can be made to follow quickly, and the response of straight running can be improved.

  In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Alternative Embodiment], the rotation speed of the steering motor 30 is set to the preset rotation speed N1 or N2 shown in FIG. Although the example output from the motor drive circuit 39 is shown as shown in FIG. 12, the motor drive circuit 39 may be configured to gradually increase from the motor drive circuit 39 toward the preset rotation speed N1 or N2. Good.

  Further, the rotational speeds N1 and N2 for rotating the steering motor 30 may be set to different rotational speeds. For example, as shown in FIG. 13 (a), the rotational speed of the steering motor 30 is proportional to the vehicle speed V of the tractor. N1 (or N2) may be configured to increase, and as shown in FIG. 13B, the steering motor 30 rotation speed N1 (or N2) gradually increases with respect to the vehicle speed V of the tractor. It may be configured.

  In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Different Embodiment of the Invention], the mode switching lever 35 is used to switch the variable ratio mode or the straight traveling mode to raise or lower the working device. Although the example configured as described above is shown, it is determined whether or not the working device is lowered to the lowered position based on the raising and lowering operation by the artificial operating means for raising and lowering the working device artificially, and the variable ratio mode or the straight traveling mode You may comprise so that it may switch.

  Specifically, as shown in FIG. 14, data input to the control device 31 is constantly monitored (step # 41), and a work switch (not shown) provided in the driver's seat 5 is turned on. If yes (step # 42, YES), whether or not the working device has been lowered based on the lifting and lowering operation of the working device by a manipulating means (for example, a position lever or a pump lever (not shown)). Judgment is made (step # 43). If the work device is lowered to the lowered position (step # 43, YES), the process proceeds to the straight-ahead mode (step # 44). On the other hand, when the working device is raised (step # 43, NO), the mode is shifted to the variable ratio mode (step # 45).

  As described above, by providing the work switch, it is possible to switch between a state in which it is possible to shift to the variable ratio mode or the straight traveling mode and a state in which it is not possible to transition to the variable ratio mode and the straight traveling mode. Also, when the work device is lowered to the lowered position with the work switch turned on and operated, it automatically shifts to the straight-ahead mode, and when the work device is raised while the work device is turned on and operated, it automatically shifts to the variable ratio mode. Therefore, when the work switch is turned on and operated, the straight traveling mode and the variable ratio mode are operated in conjunction with the lifting operation of the working device.

  Note that step # 45 in FIG. 14 may be omitted and the variable ratio mode may be operated at all times, and although not shown, by an operation switch (not shown) or an operation button (not shown). A straight traveling mode or a variable ratio mode may be activated by an artificial entry operation.

  In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Different Embodiment of the Invention], it is determined that the vehicle speed of the tractor detected by the vehicle speed sensor 48 is slower than a preset set speed. In this example, the steering motor 30 is rotated. However, the steering motor 30 is rotated based on the steering speed (steering operation speed) or the operation amount (steering operation amount) detected by the steering angle sensor 32, for example. You may comprise.

  Specifically, for example, as shown in FIG. 15, based on the detection result of the steering angle sensor 32, the operation speed (steering operation speed) of the steering handle 6 is faster than a preset setting operation speed, and the driver When it is determined that the steering handle 6 has been operated quickly (specifically, for example, when the steering handle 6 is operated when shifting from straight running to turning work) (step # 51, YES), control is performed. An output from the device 31 to the motor drive circuit 39 is made to rotate the steering motor 30 to accelerate the rotation of the input shaft 18a of the metering pump 18, and the steering ratio (the steering device 12 corresponding to the operation amount of the steering handle 6) is increased. Of the input shaft 18a) is greatly changed (step # 52). When the operation speed (steering operation speed) of the steering handle 6 becomes slower than a preset setting operation speed (step # 53, YES), the output from the control device 31 to the motor drive circuit 39 is cut off and the steering motor is operated. 30 is stopped (step # 54).

  In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Alternative Embodiment], whether or not the driver is operating the steering handle 6 based on the detection result of the steering angle sensor 32. However, instead of the steering angle sensor 32, a torque sensor (not shown) is provided on the handle operating shaft 6a, and the rotational torque of the handle operating shaft 6a detected by the torque sensor is used. Based on this, it may be configured to determine whether or not the driver is operating the steering handle 6. By adopting the torque sensor, the driver's delicate operation of the steering handle 6 can be detected, and automatic steering can be performed with high accuracy.

[Third Another Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention], [First Alternative Embodiment] and [Second Alternative Embodiment], the tractor is automatically steered to set position or setting direction. However, for example, the tractor may be automatically steered and turned.

  Specifically, the steering differential mechanism 20 is configured based on the traveling direction of the traveling vehicle body 1 detected by the direction sensor 37, the yaw rate detected by the yaw rate sensor 38, or the current position of the tractor received by the GPS receiver 40. The steering device 12 may be automatically operated by rotating the steering motor 30 forward and backward so that the traveling vehicle body 1 is automatically steered in a turning position or turning direction set in advance.

  With this configuration, the traveling vehicle body 1 is automatically turned in a state where the driver holds the steering handle 6 and does not steer the steering handle 6 in either the right or left direction. Therefore, the steering operation of the steering handle 6 at the time of leaning or the like is not necessary, and the workability of the turning operation of the tractor at the time of leaning or the like can be improved.

[Fourth Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention], [First Alternative Embodiment], [Second Alternative Embodiment] and [Third Alternative Embodiment], a tractor is provided. Although the example provided with the steering differential mechanism 20 or the like is shown, it can be applied to different work vehicles in the same manner, and may be applied to other farm work vehicles such as rice transplanters, and is not limited to the farm work vehicles. The same applies to construction work vehicles.

6 Steering handle 6a Handle operating shaft 12 Steering device 18a Input shaft 20 Steering differential mechanism 21 First gear 22 Second gear 23 Carrier 23a Support shaft (spinning shaft)
24 1st planetary gear 25 2nd planetary gear 27 2nd cylinder axis (rotating member)
30 Steering motor (electric motor)

  The present invention relates to a work vehicle configured such that a steering operation can be performed by operating an input shaft of a steering device by operating a steering handle.

  As a conventional technique, for example, as disclosed in Patent Document 1, a metering pump (Patent Document 1) linked to a steering device (16 in FIG. 2 of Patent Document 1) by operating a steering handle. 2 of FIG. 2 can be operated to steer the front wheel, and the steering shaft (23 of FIG. 2 of Patent Document 1) is driven to drive the steering shaft (FIG. 2 of Patent Document 1). Agricultural work vehicles configured to be able to steer front wheels by operating 4a) are known.

Japanese Patent Laying-Open No. 2005-80578 (see FIGS. 2 and 3)

The first feature of the present invention includes a steering differential mechanism disposed between the input shaft of the steering device and the handle operating shaft of the steering handle,
The steering differential mechanism includes a first gear fixed to the input shaft, a second gear fixed to the handle operation shaft having a different number of teeth from the first gear, and the input shaft or the handle operation shaft. A carrier supported rotatably, a turning member supported rotatably on a rotation shaft of the carrier, and fixed to the turning member and engaged with each of the first gear and the second gear. A first planetary gear and a second planetary gear, and an electric motor capable of rotating the carrier,
A variable ratio mode capable of changing a steering ratio, which is a ratio of an operation amount of an input shaft of the steering device corresponding to an operation amount of the steering handle by controlling the rotation of the electric motor, and the rotation of the electric motor Thus, a control device capable of executing a straight traveling mode in which the traveling machine body is automatically steered along a preset setting position or setting direction is provided.

The second feature of the present invention is that it is provided with an artificially operated mode switching operation section for switching between the variable ratio mode and the straight traveling mode.

The third feature of the present invention includes a lift cylinder and a working device that can be moved up and down by operating the lift cylinder at the rear of the traveling vehicle body.
  The control device is configured to determine whether or not the working device is lowered to the lowered position, and to switch between the variable ratio mode and the straight traveling mode.

Overall left side view of the tractor Schematic showing structure of steering device and steering differential mechanism Block diagram of control device Schematic explaining how to set the field area Flow chart of main routine of control device Flow chart of variable ratio mode Flow chart for straight mode Graph explaining the rotation speed of the steering motor Schematic plan view of the field showing the working status of the tractor Schematic which shows the structure of the steering differential mechanism in 1st another form of implementation of invention. Schematic which shows the structure of the steering differential mechanism in 1st another form of implementation of invention. The graph explaining the rotation speed of the steering motor in the second alternative embodiment of the invention The graph explaining the rotation speed of the steering motor in the second alternative embodiment of the invention Flowchart of the main routine of the control device according to the second embodiment of the invention Flowchart of variable ratio mode in the second alternative embodiment of the invention

[Overall structure of tractor]
FIG. 1 is an overall left side view of a tractor as an example of a work vehicle. As shown in FIG. 1, an engine 2 is disposed at the front of the traveling vehicle body 1, and a pair of left and right steerable front wheels 3 and a pair of left and right rear wheels 4 are driven by power from the engine 2. Thus, the tractor travels and turns according to the operation of the steering wheel 6 of the driver seated on the driver seat 5.

  A pair of left and right lift arms 8 are linked to the rear part of the transmission case 7 disposed at the rear part of the traveling vehicle body 1, and the swing arm 10 is swung up and down by operating the lift cylinder 9. A work device (not shown) such as a vertical device or a tilling device connected to the rear end of the swing arm 10 can be moved up and down.

  A rearward PTO shaft 11 for extracting power from the engine 2 is provided at the rear portion of the transmission case 7, and the working device can be driven by interlockingly connecting the working device to the PTO shaft 11. The PTO shaft 11 is linked to a PTO lever (not shown) provided in the vicinity of the steering handle 6, and the operation device linked to the PTO shaft 11 is driven and stopped by operating this PTO lever. can do.

  As shown in FIG. 2, the steering device 12 includes a power cylinder 13, an operation valve 14, a main pump 16, and a metering pump 18. A different configuration may be adopted as the steering device 12, not the hydraulic steering device 12 using the main pump 16, the power cylinder 13, or the like, but the steering device 12 that does not include the power cylinder 13, or other than the power cylinder 13. You may employ | adopt the steering device 12 provided with the actuator.

  The power cylinder 13 is linked to the knuckle arms 3a of the left and right front wheels 3, and a main pump 16 linked to the engine 2 is connected to an operation valve 14 of the power cylinder 13 via a hydraulic circuit 15. Yes. A metering pump 18 is connected to the operation valve 14 via a hydraulic circuit 17, and an input shaft 18 a of the metering pump 18 is linked to the steering handle 6 via a steering differential mechanism 20 described later. .

[Steering differential mechanism]
As shown in FIG. 2, the steering differential mechanism 20 is constituted by a planetary gear mechanism, and includes a first gear 21 as a sun gear fixed to the input shaft 18 a of the metering pump 18, and a handle of the steering handle 6. The second gear 22 fixed to the operating shaft 6a, the carrier 23 supported on the steering wheel operating shaft 6a of the steering handle 6 so as to be relatively rotatable, and the carrier 23 and the first and second gears 21, 22 A plurality of first and second planetary gears 24 and 25 are provided.

  The input shaft 18a of the metering pump 18 constituting the steering device 12 and the handle operation shaft 6a of the steering handle 6 are disposed concentrically, and a steering differential is provided between the input shaft 18a and the handle operation shaft 6a. A mechanism 20 is provided.

  The carrier 23 is fixed to a first tube shaft 26 that is rotatably supported by the handle operating shaft 6 a of the steering handle 6, and support shafts 23 a (autorotated) disposed at a plurality of locations on the outer periphery of the carrier 23. The second cylinder shaft 27 (corresponding to a rotating member) is supported so as to be relatively rotatable. A first planetary gear 24 is fixed to the second cylindrical shaft 27, and the first planetary gear 24 is engaged with a first gear 21 fixed to the input shaft 18 a of the metering pump 18.

  A second planetary gear 25 having a smaller number of teeth than the first planetary gear 24 is fixed to the second cylindrical shaft 27, and the second planetary gear 25 is connected to the handle operating shaft 6 a having a larger number of teeth than the first gear 21. It meshes with the fixed second gear 22. An input gear 28 is fixed to the first cylindrical shaft 26, and this input gear 28 is fixed to a drive shaft 30a of a steering motor 30 (corresponding to an electric motor) and has an output with a smaller number of teeth than the input gear 28. It is engaged with the gear 29.

  As described above, by configuring the steering device 12 and the steering differential mechanism 20, when the steering motor 30 is stopped and the drive shaft 30a is not rotating, the output gear 29 connected to the drive shaft 30a, the first Since the one cylinder shaft 26 and the carrier 23 do not rotate, when the handle operating shaft 6a is rotated by the operator's operation of the steering handle 6, the second gear 22, the second planetary gear 25, the second cylinder shaft 27, the first The input shaft 18 a of the metering pump 18 is configured to rotate according to the operation amount of the steering handle 6 via the planetary gear 24 and the first gear 21.

  Since the first gear 21, the second gear 22, and the first and second planetary gears 24 and 25 are set to have different numbers of teeth, the rotation of the handle operating shaft 6a of the steering handle 6 is accelerated and metered. It is configured to be transmitted to the input shaft 18 a of the ring pump 18.

  On the other hand, when the driver holds the steering handle 6 and the steering operation shaft 6a is not substantially rotated, when the steering motor 30 is rotated forward and backward, the output gear 29 and the input gear connected to the drive shaft 30a of the steering motor 30 are provided. The first cylinder shaft 26 is rotated via 28, the carrier 23 fixed to the first cylinder shaft 26 rotates relative to the handle operating shaft 6 a, and the second cylinder relative to the support shaft 23 a of the carrier 23. The shaft 27 relatively rotates, and the first and second planetary gears 24 and 25 fixed to the second cylindrical shaft 27 rotate. Since the second planetary gear 25 is engaged with the non-rotating second gear 22, when the first and second planetary gears 24, 25 rotate, the first and second gears 21, 22, The input shaft 18a of the metering pump 18 rotates according to the transmission ratio of the second planetary gears 24 and 25.

  The output gear 29 and the input gear 28 are set to have different numbers of teeth, and the input gear 28 is connected to the input shaft 18a of the metering pump 18 via the steering differential mechanism 20, so that the steering motor 30 The rotation of the drive shaft 30a is decelerated by the output gear 29, the input gear 28, and the steering differential mechanism 20, and is transmitted to the input shaft 18a of the metering pump 18.

  The rotational speed of the steering motor 30 can be arbitrarily changed and adjusted. By changing the rotational speed of the steering motor 30 via the motor drive circuit 39 from the control device 31 described later, the rotational speed of the steering motor 30 is adjusted. Accordingly, the rotational speed of the input shaft 18a of the metering pump 18 can be arbitrarily changed and adjusted.

  Therefore, the input shaft 18a of the metering pump 18 can be rotated by rotating the steering motor 30 forward and backward while holding the steering handle 6 and the handle operating shaft 6a is not rotating, and the left and right front wheels 3 can be operated. Can be operated in the opposite direction.

  When the steering motor 30 is rotated forward so that the first cylinder shaft 26 rotates in the direction opposite to the direction in which the driver rotates the steering handle 6, the input shaft of the metering pump 18 according to the number of rotations of the steering motor 30. As the rotation of 18a is increased, the steering ratio (ratio of the operation amount of the input shaft 18a of the steering device 12 corresponding to the operation amount of the steering handle 6) can be greatly changed.

  On the contrary, when the steering motor 30 is reversed so that the first cylinder shaft 26 rotates in the same direction as the direction in which the driver rotates the steering handle 6, the metering pump 18 of the metering pump 18 is changed according to the rotation speed of the steering motor 30. The rotation of the input shaft 18a is decelerated, and the steering ratio (ratio of the operation amount of the input shaft 18a of the steering device 12 corresponding to the operation amount of the steering handle 6) can be changed small.

  When the steering handle 6 is operated or the steering motor 30 is rotated to rotate the input shaft 18a of the metering pump 18, the operation valve 14 is operated in accordance with the operation amount of the input shaft 18a. 13 is supplied with pressure oil, and the operation of the power cylinder 13 causes the left and right front wheels 3 to operate in the steering direction corresponding to the rotational direction of the steering handle 6 or the steering motor 30 and to operate the input shaft 18a of the metering pump 18. The knuckle arm 3a is swung with a cutting angle corresponding to the amount. Then, the traveling vehicle body 1 is steered so as to travel in the traveling direction corresponding to the operation direction of the steering handle 6 or the steering motor 30 according to the operation amount of the steering handle 6 or the steering motor 30.

[Block diagram of control device]
FIG. 3 shows a block diagram of the control device 31 for the tractor. As shown in FIG. 3, the tractor includes a steering angle sensor 32, a drive shaft rotation sensor 33, an input shaft rotation sensor 34, a lever position detection sensor 36, an operation position detection sensor 45, an orientation sensor 37, a yaw rate sensor 38, and an area setting. Detection devices such as a button 46, a front wheel turning angle sensor 47, and a vehicle speed sensor 48 are mounted.

  The steering angle sensor 32 is provided on the handle operating shaft 6a of the steering handle 6 (see FIG. 2), and calculates the steering angle of the left and right front wheels 3 by measuring the rotation angle of the handle operating shaft 6a from the reference position. Thus, the operation amount (steering operation amount) of the steering handle 6 and the operation speed (steering operation speed) of the steering handle 6 of the driver can be detected.

  The drive shaft rotation sensor 33 and the input shaft rotation sensor 34 are respectively provided on the drive shaft 30a of the steering motor 30 and the input shaft 18a of the metering pump 18 (see FIG. 2). The rotational speed of the input shaft 18a of the ring pump 18 can be detected.

  The detection results from the steering angle sensor 32, the drive shaft rotation sensor 33, and the input shaft rotation sensor 34 are fed back and output from the motor drive circuit 39 to the steering motor 30, whereby the input shaft 18a of the metering pump 18 is output. , It can be accurately rotated to a predetermined rotational speed. In this tractor, the three sensors of the steering angle sensor 32, the drive shaft rotation sensor 33, and the input shaft rotation sensor 34 are provided and output from the motor drive circuit 39 to the steering motor 30. Any two of the sensors are mounted on the tractor, and the control device 31 performs arithmetic processing based on the detection results from the two sensors so as to output from the motor drive circuit 39 to the steering motor 30. May be.

  The lever position detection sensor 36 is mounted on a mode switching lever 35 provided on the side of the steering handle 6 so as to be swingable. The lever position detection sensor 36 operates the operation position (variable ratio) of the mode switching lever 35. Mode and straight mode). The forward / reverse switching lever 44 is provided on the side of the driver's seat 5 and can switch between forward and backward travel of the traveling vehicle body 1, and the operation position (forward position F, reverse position) of the forward / backward switching lever 44. R and the neutral position N) can be detected by the operation position detection sensor 45.

  The azimuth sensor 37 is disposed at the left and right center of the traveling vehicle body 1 and detects the traveling direction of the traveling vehicle body 1. The yaw rate sensor 38 is disposed near the center of gravity of the traveling vehicle body 1 and detects the yaw rate acting on the tractor. The area setting button 46 is provided on the side of the driver's seat 5 and is used for setting the field area X described later.

  The front wheel break angle sensor 47 is mounted on the rotating part of the knuckle arm 3a linked to the front wheel 3, and can detect the cut angle of the front wheel 3 operated by the steering device 12 (see FIG. 2). The vehicle speed sensor 48 is mounted on the traveling vehicle body 1 and can detect the vehicle speed at which the tractor travels.

  Based on the detection result of the front wheel cutting angle sensor 47, the cutting angle of the front wheel 3 is monitored by the control device 31, and for example, when the cutting angle of the front wheel 3 changes due to leakage of hydraulic oil in the power cylinder 13, etc. The control device 31 corrects the cutting angle of the front wheel 3 based on the detection result of the front wheel cutting angle sensor 47, and the accurate cutting angle of the front wheel 3 is grasped by the control device 31, and this corrected cutting angle of the front wheel 3 will be described later. The variable ratio mode and the straight traveling mode are configured to be implemented.

  A motor drive circuit 39, a GPS receiver 40, a navigation system 41, a monitor 42 and an electromagnetic valve 43 are connected to the control device 31. The motor drive circuit 39 is connected to the steering motor 30, and is output from the control device 31 to the motor drive circuit 39, so that the steering motor 30 is driven and stopped based on the output from the control device 31, and the rotation direction. Can be changed.

  The GPS receiver 40 is configured as an SBAS receiver corresponding to SBAS (stationary satellite type satellite navigation augmentation system), and in addition to position information from a GPS satellite (not shown), a reference station (not shown) It is configured to receive correction information for aviation.

  The GPS receiver 40 is connected to a GPS antenna 19 provided in the center of the front portion of the steering handle 6 (see FIG. 1). The GPS receiver 40 receives position information from GPS satellites and GPS reception. The correction information from the reference station received by the machine 40 is input to the control device 31, and the current position of the tractor is detected with an error of, for example, several centimeters.

  The navigation system 41 provides map information. The position of the tractor detected by the GPS receiver 40, the operation position of the forward / reverse switching lever 44 detected by the operation position detection sensor 45 (the traveling direction of the traveling vehicle body 1). ), A field area X, which will be described later, and a setting position L in a straight traveling mode, which will be described later, are displayed together with the map information of the navigation system 41 on a monitor 42 mounted on the side of the steering handle 6.

  The monitor 42 is configured as a touch panel, and is configured to be able to select and display a field area setting screen for setting a field area X, which will be described later, and a tractor position display screen for displaying the current position of the tractor. ing. An operation button (not shown) may be provided on the side of the monitor 42 so that a display screen displayed on the monitor 42 can be selected by the operation button.

  The electromagnetic valve 43 is linked to the lift cylinder 9, and the lifting / lowering operation of the working device by the lift cylinder 9 can be performed by outputting the electromagnetic valve 43 from the control device 31.

  Each of the detection devices described above is connected to the control device 31, and based on the detection result from each detection device, the control device 31 sends a motor drive circuit 39, a GPS receiver 40, a navigation system 41, a monitor 42, a solenoid valve. By performing output to 43, a variable ratio mode and a straight traveling mode, which will be described later, can be realized.

[Setting method of field area]
Based on FIG. 4, the setting method of the agricultural field area | region X used for the rectilinear advance mode mentioned later is demonstrated. The position of the GPS antenna 19 in a plan view (the position of the front central portion of the steering handle 6 of the tractor) is input to the control device 31 by the GPS receiver 40 as the current position, and the current position received by the GPS receiver 40 Based on the position and the vehicle body conditions (the width of the working device, the total length of the traveling vehicle body 1, etc.) previously input to the control device 31, the control device 31 determines the position of the right rear end portion of the working device equipped at the rear of the tractor. Arithmetic processing is performed.

  As shown in FIG. 4, the field area setting screen is displayed on the monitor 42, and the position of the right rear end of the work device is moved to the four corners (P1 to P4) of the field to be set as the field area X. By pressing the area setting button 46 at the position, the field area X (area surrounded by P1 to P4) for automatically performing the tilling work by the tractor is set on the map information provided by the navigation system 41, This field area X is configured to be displayed together with the map information of the navigation system 41 on the tractor position display screen of the monitor 42. In addition, you may comprise so that the agricultural field area | region X may be set by inputting the positional information on P1-P4 of the agricultural field area | region X to the control apparatus 31. FIG.

  The setting operation of the field area X is stored in the control device 31 by setting it once for the first time in the field where the first tilling work or the like is performed, and the tractor is moved closer to the field area X in the second and subsequent tilling work, etc. By displaying the tractor position display screen on the monitor 42, the field area X is automatically displayed on the monitor 42.

[Variable ratio mode and straight mode]
A variable ratio mode in which the steering ratio can be changed and a straight-ahead mode in which a straight-ahead traveling can be performed will be described with reference to FIGS. FIG. 5 shows a main routine of the control device 31, and FIGS. 6 and 7 show subroutines when the variable ratio mode and the straight-ahead mode are selected, respectively. FIG. 8 is a graph for explaining the rotational speed N of the steering motor 30, and FIG. 9 is a schematic plan view of the field showing the work situation by the tractor using the variable ratio mode and the straight traveling mode (the tractor position of the monitor 42). Display screen display).

  As shown in FIG. 5, the data detected by the detection devices shown in FIG. 3 and input to the control device 31 are constantly monitored (step # 11). If it is determined that the mode switching lever 35 has been operated in the variable ratio mode based on the detection result of the lever position detection sensor 36 (step # 12 • YES, step # 13), the control device 31 switches to the solenoid valve 43. As a result, the lift cylinder 9 is operated, and the working device connected to the rear portion of the traveling vehicle body 1 is raised (step # 14).

  On the other hand, when it is determined that the mode switching lever 35 is operated in the straight traveling mode based on the detection result of the lever position detection sensor 36 (step # 12 / NO, step # 15), the control device 31 sends the electromagnetic valve 43 to the solenoid valve 43. , The lift cylinder 9 is operated, and the working device connected to the rear portion of the traveling vehicle body 1 is lowered (step # 16).

  As shown in FIG. 6, when the mode switching lever 35 is operated to the variable ratio mode (step # 13), whether or not the vehicle speed of the tractor is slower than a preset set speed based on the detection result of the vehicle speed sensor 48. (Step # 21), and when it is determined that the vehicle speed of the tractor is slower than the set speed (step # 21, YES), the driver pushes the steering handle 6 based on the detection result of the steering angle sensor 32. It is determined whether or not an operation is being performed (step # 22).

  When it is determined that the driver is operating the steering handle 6 (step # 22, YES), an output is output from the control device 31 to the motor drive circuit 39, and the direction in which the driver rotates the steering handle 6 and The steering motor 30 is rotated so that the first cylinder shaft 26 rotates in the reverse direction, the rotation of the input shaft 18a of the metering pump 18 is increased, and the steering ratio (the steering corresponding to the operation amount of the steering handle 6) is increased. The ratio of the operation amount of the input shaft 18a of the device 12 is greatly changed (step # 23).

  As shown in FIG. 8, from the motor drive circuit 39, the rotation speed of the drive shaft 30a detected by the drive shaft rotation sensor 33 is fed back so that the steering motor 30 rotates at a predetermined rotation speed N1. It is configured to be output to the steering motor 30.

  Next, based on the detection result of the vehicle speed sensor 48, it is determined whether or not the vehicle speed of the tractor is faster than a preset set speed (step # 23), and the vehicle speed is set while the steering handle 6 is being operated. During the later time, the rotation of the steering motor 30 is continued (step # 24 · YES, step # 25 · NO). Conversely, when it is determined that the driver is not operating the steering wheel 6 (step # 24, NO), or when it is determined that the vehicle speed is higher than the set speed (step # 25, YES), The output from the control device 31 to the motor drive circuit 39 is turned off, and the steering motor 30 is stopped (step # 26).

  In this way, by switching to the variable ratio mode and configuring the steering ratio to change greatly when the driver operates the steering handle 6, for example, when the tractor enters a state of turning at a slower vehicle speed, The operation of the steering handle 6 by the driver can be automatically assisted, and the workability of the turning operation of the tractor can be improved.

  As shown in FIG. 7, when the mode switching lever 35 is operated in the straight traveling mode (step # 15), it is determined whether or not the driver is operating the steering handle 6 based on the detection result of the steering angle sensor 32. If it is determined that the driver holds the steering handle 6 and does not steer in either the right or left direction (step # 31, NO), the self-propelled vehicle body The steering device 12 is automatically operated so that 1 travels along the preset setting position L (steps # 32 to # 35).

  As shown in FIG. 9, the field area X (P1 to P4) set in advance on the map information of the navigation system 41 is displayed on the monitor 42, and further received by the GPS receiver 40 on this map information. The current position of the tractor and the traveling direction of the traveling vehicle body 1 detected by the operation position detection sensor 45 are always displayed on the monitor 42.

  For example, when the tractor is moved to the point A in FIG. 9 and the mode switching lever 35 is operated in the straight mode, the field area X (P1 to P4), the current position of the tractor received by the GPS receiver 40, and the operation position detection Based on the traveling direction of the traveling vehicle body 1 detected by the sensor 45, a set position L1 (solid line connecting A and B in FIG. 9) parallel to the straight line connecting P1 and P2 where the tractor goes straight is set.

  As shown in FIG. 7, it is determined that the driver holds the steering handle 6 and does not steer the steering handle 6 in either the right or left direction (step # 31, NO). If it is determined that the current position received by the GPS receiver 40 from the point A in FIG. 9 deviates from the set position L1 set at the point A in FIG. 9 (step # 32 YES) ), Output from the control device 31 to the motor drive circuit 39 so that the front wheel 3 is steered in the direction opposite to the direction deviated from the set position L1 (right or left direction (downward or upward in FIG. 9)). And the steering motor 30 is driven to automatically steer the tractor so as to move along the set position L1 (step # 33).

  As shown in FIG. 8, the motor drive circuit 39 feeds back the rotation speed of the drive shaft 30a detected by the drive shaft rotation sensor 33 so that the steering motor 30 rotates at a predetermined rotation speed N2. It is configured to be output to the steering motor 30. The rotational speed N2 is set to a rotational speed smaller than the rotational speed N1.

  As shown in FIG. 7, when the current position received by the GPS receiver 40 after running the tractor is corrected to the set position L1 (step # 34, YES), the motor drive circuit from the control device 31 The output to 39 is turned off, and the steering motor 30 is stopped (step # 35). When the state in which it is determined that the driver holds the steering handle 6 and does not steer the steering handle 6 in either the right or left direction is continued, the above-described forward / reverse rotation and stop of the steering motor 30 are performed. Is repeated (steps # 32 to # 35), the position of the tractor is corrected, and the tractor is driven along the set position L1 set at the point A in FIG.

  When it is determined that the driver steers the steering handle 6 to the right or left in the straight traveling mode, the driver's intention to operate the steering handle 6 is prioritized, and the steering motor 30 is not rotated forward or backward. Further, the front wheel 3 is steered in accordance with the driver's operation of the steering handle 6 (step # 31, YES).

  As described above, the steering motor 12 is automatically operated by rotating the steering motor 30 constituting the steering differential mechanism 20 in the forward and reverse directions so that the traveling vehicle body 1 is automatically operated along the preset position L. It is comprised so that it may face.

  As shown in FIG. 9, for example, when performing a tillage work in a range surrounded by Q1 to Q4, the mode switching lever 35 is operated to the variable ratio mode and the working device is raised, and the tractor is moved to the point A. After moving and driving the working device with the PTO lever, when the mode switching lever 35 is operated to the straight traveling mode at point A, the working device is lowered. When the steering wheel 6 is held and the tractor is driven, the steering motor 30 of the steering differential mechanism 20 automatically repeats forward and reverse rotations and stops, and the steering device 12 is operated to be set at point A in FIG. The tractor can travel along the set position L1.

  When the tractor travels and reaches point B, the mode switching lever 35 is operated to the variable ratio mode and the working device is raised, and the tractor is turned to point C as shown by the two-dot chain line in FIG. The position of the traveling vehicle body 1 and the working device is positioned in accordance with the position of the farm field that has already been plowed. When turning the tractor from point B, if the driver slows down the vehicle speed of the tractor, the steering motor 30 is assisted by the rotation of the steering motor 30, and the steering handle 6 is turned and operated. Even without this, the tractor can be easily turned.

  When the mode switching lever 35 is operated again at the point C and the steering handle 6 is held and the tractor is driven, the steering motor 30 of the steering differential mechanism 20 automatically repeats forward and reverse rotations and stops. The device 12 is operated, and the vehicle can travel along the set position L2 (solid line in FIG. 9) set at the point C. Thereafter, the range surrounded by Q1 to Q4 of the field area X shown in FIG. 9 can be cultivated by repeating traveling and turning while operating the mode switching lever 35 described above.

[First Alternative Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention], the example in which the steering differential mechanism 20 is configured as shown in FIG. 2 is shown. For example, the steering differential mechanism 20 is shown in FIGS. 10 and 11. You may comprise. Other configurations other than those described later are the same as those described in [Best Mode for Carrying Out the Invention].

  As shown in FIG. 10A, the first cylinder shaft 26 to which the carrier 23 is fixed is rotatably supported on the input shaft 18a of the metering pump 18, and the first cylinder disposed on the metering pump 18 side. The steering differential mechanism 20 may be configured such that the input gear 28 is fixed to the shaft 26 and the output gear 29 fixed to the drive shaft 30 a of the steering motor 30 is engaged with the input gear 28.

  Further, a different structure may be adopted as a structure for rotating the carrier 23 by the steering motor 30. For example, as shown in FIG. 10B, an input gear 28 is extended from the carrier 23, and the input gear 28 is steered. The steering differential mechanism 20 may be configured to engage the output gear 29 fixed to the drive shaft 30a of the motor 30.

  As shown in FIG. 11A, a first operation shaft 51 concentric with the input shaft 18 a of the metering pump 18 is provided, and the first gear 21 is fixed to the first operation shaft 51. On the other hand, a second operation shaft 52 concentric with the handle operation shaft 6 a is provided, the second gear 22 is fixed to the second operation shaft 52, and the first cylinder shaft 26 is rotated relative to the second operation shaft 52. It is supported freely. Devices constituting the steering differential mechanism 20 other than the steering motor 30 are accommodated in a transmission case 55, and the steering motor 30 is fixed to the transmission case 55. First and second operation shafts 51 and 52 are extended from the transmission case 55, and the first and second operation shafts 51 and 52 are respectively connected to the input shaft 18a and the handle operation shaft 6a of the metering pump 18 and to the first operation shaft 6a. The second connection members 53 and 54 are detachably connected.

  By configuring the steering differential mechanism 20 in this way, the steering differential mechanism 20 can be easily attached and detached integrally at the positions of the first and second connecting members 53 and 54. The workability of the assembly work and the maintenance work can be improved.

  Further, as shown in FIG. 11B, the first connecting members 53 and 53 are fixed to the input shaft 18a and the first operating shaft 51 of the metering pump 18, and the first connecting members 53 and 53 are fastened and fixed. In addition, by adopting a configuration in which the second connecting members 54 and 54 are fixed to the handle operating shaft 6a and the second operating shaft 52, respectively, and the second connecting members 54 and 54 are fastened and fixed, the first and second. You may comprise so that the steering differential mechanism 20 can be attached or detached integrally in the position of the connection members 53 and 54. FIG.

  In the above-mentioned [Best Mode for Carrying Out the Invention], the number of teeth of the first planetary gear 24 is set to be larger than the number of teeth of the second planetary gear 25, and the number of teeth of the first gear 21 is set to the second gear 22. Although an example in which the steering differential mechanism 20 is configured with a smaller number is shown, the number of teeth of the first planetary gear 24 is set to be smaller than the number of teeth of the second planetary gear 25, and the number of teeth of the first gear 21 is set. The steering differential mechanism 20 may be configured by setting more than the second gear 22.

  When the steering differential mechanism 20 is configured in this way, the rotation of the steering operation shaft 6a of the steering handle 6 is decelerated and transmitted to the input shaft 18a of the metering pump 18, and the direction in which the driver rotates the steering handle 6 is achieved. When the steering motor 30 is rotated forward so that the first cylinder shaft 26 rotates in the same direction as the rotation of the input shaft 18a, the rotation of the input shaft 18a of the metering pump 18 is accelerated and transmitted according to the rotational speed of the steering motor 30. When the steering motor 30 is rotated forward so that the first cylinder shaft 26 rotates in the direction opposite to the direction in which the driver rotates the steering handle 6, the input of the metering pump 18 according to the rotation speed of the steering motor 30. The rotation of the shaft 18a is decelerated and transmitted.

[Second Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Different Embodiment of the Invention], it is determined that the vehicle speed of the tractor detected by the vehicle speed sensor 48 is slower than a preset set speed. The rotation of the input shaft 18a of the metering pump 18 is accelerated by rotating the steering motor 30, and the steering ratio (the amount of operation of the input shaft 18a of the steering device 12 corresponding to the amount of operation of the steering handle 6) is increased. In the example, the ratio is greatly changed. As a condition for changing the steering ratio (ratio of the operation amount of the input shaft 18a of the steering device 12 corresponding to the operation amount of the steering handle 6), The condition may be different, and the steering ratio (the steering device corresponding to the operation amount of the steering wheel 6) It may be configured to change reduced the ratio) of the operation amount of the second input shaft 18a.

  In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Different Embodiment of the Invention], the steering motor 30 is rotated on the assumption that the tractor is turning. Although the example in which the ratio of the operation amount of the input shaft 18a of the steering device 12 corresponding to the operation amount of the steering device 12 is greatly changed has been shown, the steering ratio (the steering handle 6) The ratio of the operation amount of the input shaft 18a of the steering device 12 corresponding to the operation amount) may be changed to be larger or smaller.

  In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Alternative Embodiment], the current position of the tractor received by the GPS receiver 40 and the traveling vehicle body detected by the operation position detection sensor 45 are described. An example in which the steering device 12 is automatically operated via the steering differential mechanism 20 based on the traveling direction of 1 to automatically steer the traveling vehicle body 1 along a preset position L. However, based on the traveling direction of the traveling vehicle body 1 detected by the direction sensor 37 and the yaw rate acting on the tractor detected by the yaw rate sensor 38, the traveling vehicle body 1 is automatically steered in a preset setting direction. You may comprise.

  Specifically, the traveling direction of the traveling vehicle body 1 detected by the azimuth sensor 37 is set as the set direction, and when the yaw rate detected by the yaw rate sensor 38 changes with respect to the set direction, the direction in which the yaw rate changes Alternatively, the steering device 12 may be automatically operated in the reverse direction via the steering differential mechanism 20 so that the traveling vehicle body 1 is automatically steered in a preset setting direction.

  Further, different configurations may be adopted as the position or direction detection means, for example, traveling by adopting a combination of any two of the GPS receiver 40, the yaw rate sensor 38, the direction sensor 37, or all three. The vehicle body 1 may be configured to automatically steer, or the traveling vehicle body 1 may be configured to be automatically steered by a sensor (not shown) different from these sensors. Specifically, for example, by automatically steering the traveling vehicle body 1 based on the current position of the tractor received by the GPS receiver 40 and the yaw rate detected by the yaw rate sensor 38, the traveling vehicle body 1 in the set position or the setting direction. Can be made to follow quickly, and the response of straight running can be improved.

  In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Alternative Embodiment], the rotation speed of the steering motor 30 is set to the preset rotation speed N1 or N2 shown in FIG. Although the example output from the motor drive circuit 39 is shown as shown in FIG. 12, the motor drive circuit 39 may be configured to gradually increase from the motor drive circuit 39 toward the preset rotation speed N1 or N2. Good.

  Further, the rotational speeds N1 and N2 for rotating the steering motor 30 may be set to different rotational speeds. For example, as shown in FIG. 13 (a), the rotational speed of the steering motor 30 is proportional to the vehicle speed V of the tractor. N1 (or N2) may be configured to increase, and as shown in FIG. 13B, the steering motor 30 rotation speed N1 (or N2) gradually increases with respect to the vehicle speed V of the tractor. It may be configured.

  In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Different Embodiment of the Invention], the mode switching lever 35 is used to switch the variable ratio mode or the straight traveling mode to raise or lower the working device. Although the example configured as described above is shown, it is determined whether or not the working device is lowered to the lowered position based on the raising and lowering operation by the artificial operating means for raising and lowering the working device artificially, and the variable ratio mode or the straight traveling mode You may comprise so that it may switch.

  Specifically, as shown in FIG. 14, data input to the control device 31 is constantly monitored (step # 41), and a work switch (not shown) provided in the driver's seat 5 is turned on. If yes (step # 42, YES), whether or not the working device has been lowered based on the lifting and lowering operation of the working device by a manipulating means (for example, a position lever or a pump lever (not shown)). Judgment is made (step # 43). If the work device is lowered to the lowered position (step # 43, YES), the process proceeds to the straight-ahead mode (step # 44). On the other hand, when the working device is raised (step # 43, NO), the mode is shifted to the variable ratio mode (step # 45).

  As described above, by providing the work switch, it is possible to switch between a state in which it is possible to shift to the variable ratio mode or the straight traveling mode and a state in which it is not possible to transition to the variable ratio mode and the straight traveling mode. Also, when the work device is lowered to the lowered position with the work switch turned on and operated, it automatically shifts to the straight-ahead mode, and when the work device is raised while the work device is turned on and operated, it automatically shifts to the variable ratio mode. Therefore, when the work switch is turned on and operated, the straight traveling mode and the variable ratio mode are operated in conjunction with the lifting operation of the working device.

Also, although not shown, by artificial enters operation by the operation switch (not shown) and operation buttons (not shown), the straight mode or the variable ratio modes may be configured to operate.

  In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Different Embodiment of the Invention], it is determined that the vehicle speed of the tractor detected by the vehicle speed sensor 48 is slower than a preset set speed. In this example, the steering motor 30 is rotated. However, the steering motor 30 is rotated based on the steering speed (steering operation speed) or the operation amount (steering operation amount) detected by the steering angle sensor 32, for example. You may comprise.

  Specifically, for example, as shown in FIG. 15, based on the detection result of the steering angle sensor 32, the operation speed (steering operation speed) of the steering handle 6 is faster than a preset setting operation speed, and the driver When it is determined that the steering handle 6 has been operated quickly (specifically, for example, when the steering handle 6 is operated when shifting from straight running to turning work) (step # 51, YES), control is performed. An output from the device 31 to the motor drive circuit 39 is made to rotate the steering motor 30 to accelerate the rotation of the input shaft 18a of the metering pump 18, and the steering ratio (the steering device 12 corresponding to the operation amount of the steering handle 6) is increased. Of the input shaft 18a) is greatly changed (step # 52). When the operation speed (steering operation speed) of the steering handle 6 becomes slower than a preset setting operation speed (step # 53, YES), the output from the control device 31 to the motor drive circuit 39 is cut off and the steering motor is operated. 30 is stopped (step # 54).

In the above-mentioned [Best Mode for Carrying Out the Invention] and [First Alternative Embodiment], whether or not the driver is operating the steering handle 6 based on the detection result of the steering angle sensor 32. However, instead of the steering angle sensor 32, a torque sensor (not shown) is provided on the handle operating shaft 6a, and the rotational torque of the handle operating shaft 6a detected by the torque sensor is used. Based on this, it may be configured to determine whether or not the driver is operating the steering handle 6. By adopting the torque sensor, can detect a subtle operation of the steering wheel 6 of the driver, it is possible to auto-steering rather than by accuracy.

[Third Another Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention], [First Alternative Embodiment] and [Second Alternative Embodiment], the tractor is automatically steered to set position or setting direction. However, as a reference mode, for example, the tractor may be automatically steered and turned.

  Specifically, the steering differential mechanism 20 is configured based on the traveling direction of the traveling vehicle body 1 detected by the direction sensor 37, the yaw rate detected by the yaw rate sensor 38, or the current position of the tractor received by the GPS receiver 40. The steering device 12 may be automatically operated by rotating the steering motor 30 forward and backward so that the traveling vehicle body 1 is automatically steered in a turning position or turning direction set in advance.

  With this configuration, the traveling vehicle body 1 is automatically turned in a state where the driver holds the steering handle 6 and does not steer the steering handle 6 in either the right or left direction. Therefore, the steering operation of the steering handle 6 at the time of leaning or the like is not necessary, and the workability of the turning operation of the tractor at the time of leaning or the like can be improved.

[Fourth Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention], [First Alternative Embodiment], [Second Alternative Embodiment] and [Third Alternative Embodiment], a tractor is provided. Although the example provided with the steering differential mechanism 20 or the like is shown, it can be applied to different work vehicles in the same manner, and may be applied to other farm work vehicles such as rice transplanters, and is not limited to the farm work vehicles. The same applies to construction work vehicles.

6 Steering handle 6a Handle operating shaft 12 Steering device 18a Input shaft 20 Steering differential mechanism 21 First gear 22 Second gear 23 Carrier 23a Support shaft (spinning shaft)
24 1st planetary gear 25 2nd planetary gear 27 2nd cylinder axis (rotating member)
30 Steering motor (electric motor)
31 Control device

Claims (3)

A steering differential mechanism is provided between the input shaft of the steering device and the handle operating shaft of the steering handle,
The steering differential mechanism includes a first gear fixed to the input shaft, a second gear fixed to the handle operation shaft having a different number of teeth from the first gear, and the input shaft or the handle operation shaft. A carrier supported rotatably, a turning member supported rotatably on a rotation shaft of the carrier, and fixed to the turning member and engaged with each of the first gear and the second gear. A first planetary gear and a second planetary gear, and an electric motor capable of rotating the carrier,
A variable ratio mode capable of changing a steering ratio, which is a ratio of an operation amount of an input shaft of the steering device corresponding to an operation amount of the steering handle by controlling the rotation of the electric motor, and the rotation of the electric motor A work vehicle including a control device capable of executing a straight traveling mode in which the traveling machine body is automatically steered along a preset setting position or setting direction.   The work vehicle according to claim 1, further comprising an artificially operated mode switching operation unit that switches between the variable ratio mode and the straight traveling mode. At the rear of the traveling vehicle body, equipped with a lift cylinder and a working device that can be raised and lowered by operating the lift cylinder,
2. The work vehicle according to claim 1, wherein the control device is configured to determine whether the work device is lowered to a lowered position and to switch between the variable ratio mode and the straight-ahead mode.

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