JP2010058706A - Front wheel steering device for working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a front wheel steering device for a working vehicle capable of being made to a simple constitution while capable of detecting a plurality of steering angles, a steering direction and a steering speed. <P>SOLUTION: The front wheel steering device 20 is constituted so as to be provided with: a shaft-like cam member 45 having large diameter parts 45a, 45c, 45f and small diameter parts 45b, 45d, 45e, 45g; a position detection cylinder 43 penetrated/arranged with the shaft-like cam member 45; and a steering position detection device 40 having a left detection switch 41 and a right detection switch 42 fixed to the position detection cylinder 43. During when the shaft-like cam member 45 is moved based on the steering operation and becomes in the maximum steering angle from the neutral state, the steering angles of a plurality of stages are detected by outputting a plurality of numbers of state variations according to the steering angles to the left detection switch 41 and the right detection switch 42. Further, the steering speed is detected from the displacement time between the plurality of steering angles. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a front-wheel steering device for a working vehicle such as a tractor, and more particularly to a front-wheel steering device for a working vehicle that includes a steering angle detection unit that detects a steering angle of a front wheel of the vehicle.

  2. Description of the Related Art Conventionally, for example, a working vehicle such as a tractor includes a front wheel steering device having a steering angle detection unit that detects a steering angle of a front wheel based on an operation of a steering wheel or the like. In addition, some of such work vehicles are provided with a function of automatically raising a work machine mounted on the rear part of the vehicle as an automatic control function for assisting the operation when making a U-turn at the end of the field. (For example, refer to Patent Document 1).

  The working vehicle disclosed in Patent Document 1 detects a predetermined steering angle range using a potentiometer as a steering angle detection means, and lifts the work implement related to the automatic control function based on the steering speed in the predetermined steering angle range. The timing to be changed has been changed.

Japanese Patent Laid-Open No. 11-308903

  However, the use of a potentiometer as the steering angle detection means can detect a plurality of steering angles with a single detection device, but the potentiometer itself is expensive and hinders cost reduction. was there. Further, since the potentiometer is a precision instrument, a detector having a simple structure has been desired from the viewpoint of reliability and durability as a detection instrument of the steering angle detection means in the working vehicle exposed to dust and vibration.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a front wheel steering device for a working vehicle that can detect a plurality of steering angles, steering directions, and steering speeds but can be simply configured. is there.

The present invention according to claim 1 (see, for example, FIGS. 1 to 14) is a front wheel of a working vehicle (1) having steering angle detection means (40, 140, 240, 340) for detecting the steering angle of the front wheel (5). In the steering device (20),
The steering angle detecting means (40, 140, 240, 340)
Two switches (41, 42, 141, 142);
At least one of the two switches (41, 42, 141, 142) is displaced while the steering angle of the front wheel (5) reaches the maximum steering angle from the neutral state while being displaced based on the steering angle. A cam (45, 145, 245, 345) having a shape that changes output on and off multiple times;
A calculation unit (determining a steering direction and a plurality of steering angles based on output signals of the two switches (41, 42, 141, 142)) and calculating a steering speed from a displacement time between the plurality of steering angles ( 60), and
This is in the front wheel steering device (20) of the working vehicle.

  In addition, although the code | symbol in the said parenthesis is for contrast with drawing, this is for convenience for making an understanding of invention easy, and has no influence on the structure of a claim. It is not a thing.

  According to the first aspect of the present invention, the two switches and the displacement of the front wheel according to the steering angle, and before the steering angle of the front wheel reaches the maximum steering angle from the neutral state, A cam having a shape in which at least one of the plurality of on / off output changes is performed, and a steering direction and a plurality of steering angles are determined based on respective output signals of the two switches, and the displacement between the plurality of steering angles. Since it has a steering angle detection means having a calculation unit for calculating the steering speed from time, it can detect a plurality of steering angles, steering directions, and steering speeds, but it can detect only two switches. It can be set as the simple structure.

  Further, since the steering speed can be detected, for example, the start timing of the automatic control function and the operation speed of the automatic control function can be matched with the operation state of the vehicle, and the work accuracy can be improved.

<First Embodiment>
A first embodiment of the present invention will be described below with reference to FIGS.

  As shown in FIG. 1, a tractor (working vehicle) 1 according to the first embodiment includes a traveling machine body 2 composed of an engine 3, a transmission case 4, and the like, and a working machine (not shown). The traveling machine body 2 is supported by front wheels 5 and rear wheels 6 which are steered wheels. The engine 3 is covered with a hood 11 and has a driver's seat 12 behind the hood 11. Further, between the left and right front wheels 5, there is a front wheel steering device 20 that transmits power from the engine 3 to the front wheels 5 via the transmission case 4 and steers the front wheels 5 based on the operation of the steering wheel 13. Is provided. The front wheel steering device 20 includes a front axle case 21, a hydraulic cylinder device 35 provided along the front axle case 21, and the like.

  On the other hand, a working machine having a rotary blade (not shown) or the like is connected to the rear part of the traveling machine body 2 via a lifting link mechanism (not shown). The elevating link mechanism is a three-point type including one top link and a pair of left and right lower links, and various working machines other than the working machine having such a rotary blade can be selected and mounted. Further, the elevating link mechanism is rotated up and down by an extension / contraction operation of a lift cylinder 83 (see FIG. 6) arranged on the traveling machine body 2 side. That is, the lift cylinder 83 can be hydraulically driven to move the working machine up / down.

  The driver's seat 12 is provided with a seat 14, left and right brake pedals (not shown), a steering wheel 13 that is a travel operation device, and the like. Further, an operation panel (not shown) which is a work machine operating device is disposed in front of the steering wheel 13 and on the side of the seat 14, and below the operation panel disposed on the side of the seat 14. The microcomputer unit 50 to be described later is arranged.

  Further, the transmission case 4 is provided with a front wheel speed increasing device 78 (see FIG. 6) capable of transmitting the power transmitted from the engine 3 to the front wheels 5 at a higher speed than usual at a desired timing. It has been.

  As shown in FIG. 2, the front axle case 21 includes a center case 25 formed to extend in the left-right direction of the traveling machine body 2 and a kingpin case 26 fixed to both left and right ends of the center case 25. As shown in FIG. 3, a protrusion 25 a is fixed to the front side of the center portion of the center case 25. The front axle case 21 has a front bracket 32 that rotatably supports the protruding portion 25a, and a rear bracket 33 that rotatably supports the rear portion, with respect to the main frame 31 that is integral with the traveling machine body 2. Thus, it is supported so as to be swingable up and down around an axis in the longitudinal direction of the machine body.

  As shown in FIG. 2, the center case 25 includes a front differential 22 having a differential ring gear 22 a and a differential pinion 22 b, and a differential shaft 23 that is drivingly connected in the left-right direction of the front differential 22. The kingpin case 26 includes a kingpin 28, and the kingpin 28 is drivingly connected to the differential shaft 23 on the upper side thereof.

  Further, the king pin 28 is drivably coupled to a front wheel axle 29 on the lower side thereof, and the front wheel axle 29 is provided in an axle case 27 provided so as to be rotatable around the king pin 28. A knuckle arm 30 is integrally fixed to the axle case 27, and the knuckle arm 30 is rotatably connected to a portion on the central axis of the kingpin 28 on the upper surface side of the kingpin case 26. 27 is configured to be rotatable around a king pin 28.

  As shown in FIG. 4, the hydraulic cylinder device 35 includes a cylinder portion 36 that is fixed to the center case 25, and a piston rod 37 that passes through the cylinder portion 36. The cylinder portion 36 is provided with hydraulic ports 39 and 39 for communicating an oil chamber formed therein and a hydraulic control device 70 described later. The piston rod 37 is connected to the knuckle arm 30 via rod ends 38 at both left and right ends.

  The hydraulic cylinder device 35 is provided with a steering position detection device (steering angle detection means) 40 which will be described in detail later.

  As shown in FIG. 5, the microcomputer unit 50 includes a CPU 51, a RAM 52, a microcomputer (hereinafter referred to as a microcomputer) (arithmetic unit) 60 having a flash memory 53, a power supply 61, and an EEPROM (Electrically Erasable Programmable Read-). Only memory) 54, a communication circuit 62, a driver (driving circuit) 55, and the like. On the input side of the microcomputer unit 50, in addition to the power supply 61, a left detection switch 41 and a right detection switch 42 of the steering position detection device 40 are connected. In addition, various switches such as a turning-up control changeover switch 65, a front wheel acceleration / autobrake control changeover switch 66, and various sensors such as a lift rod cylinder sensor 67 and a position lever sensor 68 are connected.

  The turning-up control changeover switch 65 detects that the steering wheel 13 has given a steering angle greater than a certain angle to the upper limit position where the work implement is set based on a control signal from the microcomputer 60. It is a switch that switches on and off the control that automatically raises. Thereby, for example, when making a U-turn at the end of the field or the like, the work implement can be raised to the set upper limit position only by operating the steering wheel 13, and the operation can be facilitated. In such a case, when it is detected that the steering speed of the steering wheel 13 is operated at a constant speed or less, the timing for raising the work machine is delayed, or the steering speed of the steering wheel 13 is constant. When it is detected that the operation has been performed as described above, it is possible to increase the ascent speed of the work implement, and further facilitate the operation.

  Further, the front wheel acceleration / autobrake control changeover switch 66 is provided with a steering angle greater than a certain angle by the steering wheel 13, and based on a control signal from the microcomputer 60 based on the steering amount, This is a switch for switching on and off the control in which the brake device (not shown) is braked. That is, by operating the steering wheel 13, the brake acts on the rear wheel 6 on the inside of the turn. Thereby, for example, a small turn is possible even at the end of the field. Further, for example, when it is detected that the steering speed of the steering wheel 13 is less than a constant speed and a steering angle greater than a certain angle is given, a brake is not applied to the rear wheel 6 inside the turn. It is also possible to operate in accordance with one operation situation.

  In addition to these, the microcomputer 60 is also connected to switches and sensors such as a tilling depth adjusting volume switch for adjusting the tilling depth, not shown.

  On the output side of the microcomputer unit 50, in addition to a display unit 56 constituted by an LCD, a lamp (including LEDs) 57, a buzzer 58, a solenoid (for example, a lift cylinder raising solenoid) 59, and the like are provided via a driver 55. Connected.

  As shown in FIG. 6, the hydraulic control device 70 includes a power steering pump 72, a hydraulic lift pump 73, a power steering unit 74, a relief valve 75, a flow divider valve 77, a hydraulic lift device 82, an oil tank 71, and a filter 87. , 88 and the like. Note that the hydraulic control device 70 of the tractor 1 according to the first embodiment actually has many other valves and oil passages, but is omitted for convenience of explanation. Yes.

  The power steering unit 74 supplies the hydraulic oil from the power steering pump 72 to the left and right hydraulic ports 39 based on the operation of the steering wheel 13 via the power steering valve 74 a that is switched based on the operation of the steering wheel 13. The front wheel 5 is steered by hydraulically operating the piston rod 37 of the cylinder portion 36.

  Hydraulic fluid from the hydraulic lift pump 73 is supplied to the flow divider valve 77 via a relief valve 75 and a filter 88, and the flow divider valve 77 is used to increase the front wheel speed of the front wheel speed increasing device 78. An electromagnetic switching valve 78a and an automatic brake turning electromagnetic switching valve 80c for hydraulically operating the brake cylinder 80 are supplied. The front-wheel speed-increasing electromagnetic switching valve 78a is switched based on the control signal from the microcomputer 60, thereby supplying hydraulic oil to operate the front-wheel speed increasing device 78. The electromagnetic switching valve 80c for automatic brake turning supplies hydraulic oil to one of the left and right brake cylinders 80a, 80b based on a control signal from the microcomputer 60 based on detection signals of the left detection switch 41 and the right detection switch 42, Activate the brake device inside the turn.

  Further, the hydraulic oil from the flow divider valve 77 is supplied to the hydraulic lift device 82 to operate the lift rod cylinder 81 and the lift cylinder 83. In the lift rod cylinder 81, the hydraulic oil from the flow divider valve 77 is supplied to the lift rod cylinder electromagnetic switching valve 81a via the hydraulic lift device 82, and the tilt setting volume switch is supplied from the lift rod cylinder electromagnetic switching valve 81a. The hydraulic oil is supplied based on the control signal of the microcomputer 60 based on the setting (not shown), thereby changing the left / right inclination angle of the work implement. Further, the lift cylinder 83 is supplied with hydraulic oil from the flow divider valve 77 to the lift cylinder control valve 84, and the lift cylinder control valve 84 controls the control signal of the microcomputer 60 and the driver's seat based on the operation of various automatic control switches. When the hydraulic oil is supplied based on the operation of the lever arranged at 12, the working machine is moved up / down.

  Next, the steering position detection device 40 will be described.

  As shown in FIGS. 4 and 7, the steering position detection device 40 includes a position detection cylinder 43 provided in parallel with the hydraulic cylinder device 35, and a left detection switch 41 and a right detection switch 42 fixed to the position detection cylinder 43. And a shaft-shaped cam member (cam) 45 disposed through the position detection cylinder 43, and springs 46, 46 disposed inside the position detection cylinder 43 and biasing the shaft-shaped cam member 45 toward the central portion. Has been.

  The shaft-like cam member 45 is fixed to the piston rod 37 of the hydraulic cylinder device 35 by connecting members 47 and 47 in the vicinity of both left and right end portions, and in accordance with the movement of the piston rod 37 based on the operation of the steering wheel 13. Is configured to move. The shaft-like cam member 45 is provided with a hook-shaped cam side plate that is not connected to the piston rod 37 in the vicinity of both left and right ends, and is not connected to the piston rod 37, and near the left and right ends of the piston rod 37. Alternatively, a rod-shaped rod side plate may be arranged so as to have a predetermined amount of gap with respect to the cam side plate. That is, when the piston rod 37 moves based on the operation of the steering wheel 13, the shaft-like cam member 45 moves by the predetermined amount of gap (for example, the turning angle of the front wheel 5 is 30 degrees), and the cam side plate And the rod side plate are moved in contact with each other. Thereby, the shaft-like cam member 45 can have a so-called “play” with respect to the movement of the piston rod 37 (steering wheel 13).

  Further, the shaft-like cam member 45 has large diameter portions 45a, 45c, 45f having substantially the same outer diameter as the inner diameter of the position detection cylinder 43 in the central portion disposed inside the position detection cylinder 43, and the large Small diameter portions 45b, 45d, 45e, and 45g having outer diameters smaller than the diameter portions 45a, 45c, and 45f are formed.

  The left detection switch 41 and the right detection switch 42 include detection units 41a and 42a that are urged from the proximal end side to the distal end side while being fixed to the position detection cylinder 43, respectively. The switch is configured to switch from OFF to ON when riding on the large diameter portions 45a, 45c, and 45f from the state in contact with the small diameter portions 45b, 45d, 45e, and 45g of the shaft-like cam member 45. The left detection switch 41, the right detection switch 42, and the shaft-like cam member 45 are arranged so as to be symmetrical with respect to the central portion A.

  Next, control of the tractor 1 according to the present invention will be described.

  For example, when the operator is in the driver's seat 12 and turns on the ignition which is the power on / off operation means, the power supply 61 is turned on, and the turning up control changeover switch 65 and the front wheel acceleration / autobrake control changeover switch 66 are turned on. Then, the steering position detection control shown in FIG. 8 is started (S1-1).

Next, the detection signals from the left detection switch 41 and the right detection switch 42 are converted into an operation detection value P (S1-2). The operation detection value P is a value when the microcomputer 60 is off when the signals from the left detection switch 41 and the right detection switch 42 are not detected, and when the value is 1 when the signals are detected. Formula P = 2 ¹ × value of left detection switch 41 + 2 ⁰ × value of right detection switch 42 (α)
Is a value calculated by.

That is, when the tractor 1 is in the straight traveling state, as shown in FIG. 10, the steering wheel 13 (see FIGS. 1 and 6) is not operated by the operator, and the piston rod 37 (see FIG. 4) does not operate. The shaft-like cam member 45 is not moved. For this reason, the left detection switch 41 is located in the small diameter portion 45b of the shaft-like cam member 45, and the right detection switch 42 is located in the small diameter portion 45e, and both the left detection switch 41 and the right detection switch 42 are turned off and no signal is detected. The value is 0. That is, by the above formula α
P = 2 ¹ x0 + 2 ⁰ x0 = 0
It becomes.

Further, when the steering wheel 13 is operated by the operator from the straight traveling state and the left steering (1) is performed, the piston rod 37 is operated to the left based on the operation of the steering wheel 13, Accordingly, the shaft-like cam member 45 is also moved leftward. For this reason, the left detection switch 41 is positioned at the large diameter portion 45a of the shaft-shaped cam member 45 and the right detection switch 42 is positioned at the large diameter portion 45f, and both the left detection switch 41 and the right detection switch 42 are turned on to detect the signal. Therefore, the value is 1. That is, by the above formula α
P = 2 ¹ × 1 + 2 ⁰ × 1 = 3
It becomes.

Further, when the steering wheel 13 is further operated from the above left turning state and the left steering (2) is performed near the maximum steering angle, the piston rod 37 is further operated in the left direction. The shaft-like cam member 45 is also moved leftward. For this reason, the left detection switch 41 remains positioned at the large diameter portion 45a of the shaft-like cam member 45, but the right detection switch 42 is positioned at the small diameter portion 45g, the left detection switch 41 is turned on, and the value is The right detection switch 42 is turned off again and the value becomes zero. That is, by the above formula α
P = 2 ¹ × 1 + 2 ⁰ × 0 = 2
It becomes.

On the other hand, when the steering wheel 13 is operated by the operator from the straight traveling state and the steering wheel 13 is turned to the right (1), the piston rod 37 is operated in the right direction based on the operation of the steering wheel 13. Accordingly, the shaft-like cam member 45 is also moved rightward. For this reason, the left detection switch 41 is positioned at the large diameter portion 45c of the shaft-shaped cam member 45, and the right detection switch 42 is positioned at the large diameter portion 45a. Both the left detection switch 41 and the right detection switch 42 are turned on to detect signals. Therefore, the value is 1. That is, by the above formula α
P = 2 ¹ × 1 + 2 ⁰ × 1 = 3
It becomes.

In addition, when the steering wheel 13 is further operated from the above-mentioned right turning state and the right steering (2) is performed in the vicinity of the maximum steering angle, the piston rod 37 further moves rightward. Accordingly, the shaft-like cam member 45 is further moved rightward. For this reason, the right detection switch 42 remains positioned at the large diameter portion 45a of the shaft-like cam member 45, but the left detection switch 41 is positioned at the small diameter portion 45d, and the left detection switch 41 is again turned off and becomes the value. Becomes 0, the right detection switch 42 is turned on, and the value becomes 1. That is, by the above formula α
P = 2 ¹ × 0 + 2 ⁰ × 1 = 1
It becomes.

  Thereafter, as shown in FIG. 8, the operation detection value P obtained by converting the detection signals from the left detection switch 41 and the right detection switch 42 is read (S1-3). When the motion detection value P is P = 0, the straight traveling state is determined as described above (S1-4). At this time, the microcomputer 60 does not output control signals relating to turning-up control, front wheel acceleration / autobrake control, and the like (see also FIG. 10).

  If the motion detection value P is P = 1, it is determined that the vehicle is in the right steering (2) state, which is a large turning motion in the right direction as described above (S1-5). That is, for example, it is determined that it is a clockwise U-turn at the end of the field, and the microcomputer 60 activates the front wheel speed increasing device 78 for front wheel speed increasing / auto brake control, and the automatic brake turning electromagnetic switching valve 80c. To output the control signal so as to operate the right brake cylinder 80b on the inside of the turn (see also FIGS. 6 and 10).

  Further, when the motion detection value P is P = 2, it is determined that the left steering (2) state, which is a large turning motion in the left direction as described above (S1-6). That is, for example, it is determined that the counterclockwise U-turn is at the end of the field, and the microcomputer 60 activates the front wheel speed increasing device 78 for front wheel speed increasing / auto brake control, and the automatic brake turning electromagnetic switching valve 80c. To output a control signal so as to operate the left brake cylinder 80a on the inside of the turn (see also FIGS. 6 and 10).

  When the motion detection value P is P = 3, it is determined that the left steering (1) or the right steering (1), which is a relatively small turning motion in the left direction or the right direction as described above. (S1-7). That is, for example, it is determined that it is the initial stage of the U-turn at the end of the field, and the microcomputer 60 operates the lift cylinder 83 by the lift cylinder control valve 84 with respect to the turning-up control, and sends a control signal to raise the work implement. Output (see also FIGS. 6 and 10). Then, after performing the processing based on the motion detection value P, the steering position detection control is finished (S1-8).

  Next, steering speed detection control will be described. As shown in FIG. 9, the steering speed detection control is started (S2-1), and when the displacement of the steering position is not detected by the steering position detection control (No in S2-2), the steering speed is 0. Is determined (S2-6), and the steering speed detection control ends (S2-7). Here, for example, when the steering wheel 13 is operated and the displacement of the steering position is detected by the steering position detection control (Yes in S2-2), first, the microcomputer 60 determines that the current steering direction is the same as the previous steering direction. It is determined whether or not it is a direction (S2-3).

  Here, when the steering direction is different from the previous time (No in S2-3), it is determined that the steering speed is 0 (S2-6), the steering speed detection control is finished (S2-7), and the steering direction is changed. If the direction is the same as the previous time (Yes in S2-3), the speed at which the steering angle is displaced is calculated from the amount of displacement of the steering angle and the time required for the displacement (S2-4). In step S2-4, when the speed at which the steering angle is displaced is calculated, this is set as the steering speed (S2-5), and the microcomputer 60 reads this as a detection result, thereby ending the steering speed detection control. (S2-7).

  As described above, the tractor 1 according to the first embodiment of the present invention is displaced based on the left detection switch 41 and the right detection switch 42 and the steering angle, and the steering angle of the front wheels 5 is maximized from the neutral state. Until the steering angle is reached, at least one of the left detection switch 41 and the right detection switch 42 has an axial cam member 45 having a shape in which the output changes ON / OFF a plurality of times, the left detection switch 41, A steering position detection device 40 having a microcomputer 60 that determines a steering direction and a plurality of steering angles based on respective output signals of the right detection switch 42 and calculates a steering speed from a displacement time between the plurality of steering angles is provided. Therefore, while detecting a plurality of steering angles, steering directions, and steering speeds, the detection device is switched to two switches, a left detection switch 41 and a right detection switch 42. Can be a simple configuration in which only.

  Further, since the steering speed can be detected, for example, the start timing of the automatic control function and the operation speed of the automatic control function can be matched with the operation state of the vehicle, and the work accuracy can be improved.

  4 and 7, the steering position detection device 40 has been described as having a cam member as an axial shape. However, in addition to this, the cam member may have a cylindrical shape as another form. Can be applied. That is, the steering position detecting device 140 can be provided at the upper end portion of the kingpin case 26 fixed to the end portion of the center case 25 in the front axle case 21.

  As shown in FIGS. 11A and 11B, the steering position detection device 140 includes a cam case 143, a left detection switch 141 and a right detection switch 142 fixed to the cam case 143, and a cylindrical cam member 145. Has been. The cam case 143 is formed in a hollow cylindrical shape and is integrally fixed to the kingpin case 26. The cylindrical cam member 145 is disposed in the hollow portion of the cam case 143 and is fixed to the knuckle arm 130 by pin members 91 and 91. Further, the cylindrical cam member 145 is formed with concave portions 145b, 145d, 145e, and 145g each having a cutout outer peripheral surface, and convex portions 145a, 145c, and 145f formed by these concave portions.

  The left detection switch 141 and the right detection switch 142 include detection units 141a and 142a that are urged from the proximal end side to the distal end side while being fixed to the cam case 143, and the detection units 141a and 142a are cylindrical. The switch is configured to be switched from OFF to ON when the cam member 145 rides on the convex portions 145a, 145c, and 145f from the state in contact with the concave portions 145b, 145d, 145e, and 145g. The left detection switch 141, the right detection switch 142, and the cylindrical cam member 145 are arranged so as to be symmetric with respect to the central portion A ′.

  In the steering position detection device 140 configured as described above, the cylindrical cam member 145 fixed to the knuckle arm 130 rotates (moves) based on the operation of the steering wheel 13 with respect to the cam case 143. The operation and effect are the same as those of the position detection device 40.

<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, except for some changes, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The tractor 1 according to the second embodiment has a shaft in which the number of large-diameter portions and small-diameter portions is increased as compared with the shaft-like cam member 45 of the steering position detection device 40 according to the first embodiment. A steering position detecting device 240 having a cam member 245 is changed. As shown in FIG. 12, the shaft-like cam member 245 has large-diameter portions 245b and 245d having outer diameters that are substantially the same as the inner diameter of the position detection cylinder 43 in the central portion disposed inside the position detection cylinder 43. , 245f, 245h, 245j, 245l, 245m, 245o, 245q, 245s, 245u, 245w, and the large diameter portions 245b,. , 245k, 245n, 245p, 245r, 245t, and 245v.

  The steering position detection device 240 including the shaft-like cam member 245 configured as described above is, for example, a straight-ahead position (“N” in FIG. 12) that serves as a reference position when the steering wheel 13 performs steering position detection control. The left detection switch 41 is located at the small diameter portion 245g, the output state is off, and the right detection switch 42 is located at the small diameter portion 245r, and the output state is off, The value of the motion detection value P is 0. At this time, the microcomputer 60 stores this state in the RAM 52 (see FIG. 5) as the current steering position.

  When the left steering operation is performed by the steering wheel 13 from this state and the shaft-like cam member 245 starts to move in the left direction, the left detection switch 41 has a large diameter from above the small diameter portion 245g, as indicated by L1-1. The output state is switched from OFF to ON. At this time, the right detection switch 42 remains on the small diameter portion 245r, and the output state is OFF. Further, as shown in FIG. 13, the value of the motion detection value P in this state is 2. At this time, the microcomputer 60 compares the value 2 of the motion detection value P with the previous value 0, recognizes that it is the steering position L1-1, determines that it is left steering, and stores this in the RAM 52. Remember.

  Thereby, the steering position detection device 240 recognizes that the value of the motion detection value P is different from the previous value every time the output state of at least one of the left detection switch 41 and the right detection switch 42 is switched. The steering position is determined by comparing with the value of the previous motion detection value P, whereby the steering positions L1-1, L1-2, L1-3, L2-1, L2-2, L2-3, L3- 1, L3-2, L3-3, R1-1, R1-2, R1-3, R2-1, R2-2, R2-3, R3-1, R3-2, R3-3, and a straight traveling position N Can be detected. That is, it is possible to detect the 19-stage steering angle including the straight traveling position N between the left and right maximum steering angles.

  When the steering position detection device 240 detects the steering direction and the steering angle, the microcomputer 60 stores the current position in the RAM 52 and uses the detection signals of the left detection switch 41 and the right detection switch 42 as well. There is a method in which the steering direction from the current position is determined based on the motion detection value P based on this, and the position on the steering direction side is newly stored.

  That is, as shown in FIG. 14, when the steering position detection control is started and the straight traveling state is recognized, the microcomputer 60 stores the straight traveling position in the RAM 52, and then, for example, detection signals from the left detection switch 41 and the right detection switch 42. When the motion detection value P = 1 based on the above is obtained, it is determined that the steering is rightward, and the position R1-1 is stored in the RAM 52. Next, when the motion detection value P = 3 is obtained, it is further determined that the steering is to the right, and the position R1-2 is stored in the RAM 52. Next, when the motion detection value P = 1 is obtained, it is determined that the left steering is performed, and the position R1-1 is stored. By performing the control as described above, the steering position detection device 240 can detect the 19-stage steering angle including the straight traveling state between the left and right maximum steering angles.

  When the steering position detection device 240 performs the above-described control, it is necessary for the microcomputer 60 to recognize the straight-ahead position where the motion detection value P = 0 after the steering position detection control is started.

<Third Embodiment>
Next, a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, except for some changes, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The tractor 1 according to the third embodiment has a shaft in which the number of large-diameter portions and small-diameter portions is increased as compared with the shaft-like cam member 45 of the steering position detecting device 40 according to the first embodiment. The steering position detecting device 340 having a cam member 345 is changed. As shown in FIG. 14, the shaft-like cam member 345 has large diameter portions 345 b and 345 d that have substantially the same outer diameter as the inner diameter of the position detection cylinder 43 in the central portion disposed inside the position detection cylinder 43. , 345f, 345h, 345j, 345k, 345m, 345o, 345q, 345s, 345u, and small diameter portions 345a, 345c, 345e, 345g, 345i, 345l having outer diameters smaller than the large diameter portions 345b,. , 345n, 345p, 345r, and 345t. Further, the large diameter portion 345f is formed to be longer than the other large diameter portions.

  The steering position detection device 340 including the shaft-like cam member 345 configured as described above indicates the output state of the right detection switch 42 when the output state of the left detection switch 41 changes when the steering wheel 13 is operated. By detecting, the steering direction is determined.

  That is, as shown in A4 to A7, in the steering position detection device 340, in the straight traveling state, the left detection switch 41 is positioned at the large diameter portion 345f, and the output state is on. When the left steering operation is performed by the steering wheel 13 from this state and the shaft-like cam member 345 starts to move leftward, as shown in A4, the left detection switch 41 moves from the large diameter portion 345f to the small diameter portion 345e. Move up and the output state switches from on to off. At this time, the right detection switch 42 is on the large diameter portion 345q, and the output state is ON.

  Similarly, in the left steering state in which the shaft-like cam member 345 moves to the left, when the output state of the left detection switch 41 is switched from on to off in the same manner in A2, A8, and A10, the right detection switch The output state 42 is turned on. That is, the steering position detection device 340 detects the output of the right detection switch 42 when the output state of the left detection switch 41 is switched from on to off, and if this output state is on, It can be determined that the vehicle is in a steering state.

  On the other hand, in the steering position detection device 340, the right steering operation is performed by the steering wheel 13 from the state where the left detection switch 41 in the straight traveling state is positioned at the large diameter portion 345f, and the shaft-like cam member 345 moves to the right. When starting, as shown in A7, the left detection switch 41 moves from the large diameter portion 345f to the small diameter portion 345g, and the output state is switched from ON to OFF. At this time, the right detection switch 42 is on the small diameter portion 345n, and the output state is OFF.

  Similarly, in the right steering state in which the shaft-like cam member 345 moves to the right, when the output state of the left detection switch 41 is switched from on to off in the same manner in A1, A3, and A9, the right detection switch The output state of 42 is off. That is, the steering position detection device 340 detects the output of the right detection switch 42 when the output state of the left detection switch 41 is switched from on to off, and when this output state is off, It can be determined that the vehicle is in a steering state.

  Then, the steering position detection device 340 can detect the steering direction by the two switches of the left detection switch 41 and the right detection switch 42 as described above, and the microcomputer 60 determines the left steering and the right steering. This is stored, and the steering angle can be detected by counting the number of times of left steering and right steering.

  In the third embodiment of the present invention, the steering direction is detected by detecting the output state of the right detection switch 42 when the output state of the left detection switch 41 is switched from on to off. Although described above, the present invention is not limited to this, and the present invention is also applicable to detecting the steering direction by detecting the output state of the right detection switch 42 when the output state of the left detection switch 41 is switched from OFF to ON. can do.

  Further, the steering direction may be detected by detecting the output state of the left detection switch 41 when the right detection switch 42 is switched from on to off. However, in this case, it is necessary to arrange the large-diameter portion and the small-diameter portion of the shaft-shaped cam member 345 so as to be reversed to the left and right.

  In the second and third embodiments according to the present invention, the steering position detecting devices 240 and 340 provided with the shaft-like cam members 245 and 345 have been described. However, the present invention is not limited to this. Needless to say, the steering position detecting device may include a cylindrical cam member as described in the embodiment.

  In the first, second, and third embodiments according to the present invention, the automatic control function that uses the steering direction and the steering angle detected by the steering position detection device has the front wheel acceleration / autobrake control and Although described as turning up control, the present invention is not limited to this, and the present invention can be applied to any other automatic control function operation timing.

The external appearance perspective view which shows the tractor which concerns on this invention. The fragmentary sectional view which shows a front axle case. Side surface sectional drawing which shows a front axle case. The upper view which shows a front axle case. The block diagram which shows a microcomputer unit. The circuit diagram which shows a hydraulic control apparatus. Sectional drawing which shows a steering position detection apparatus. The flowchart which shows steering position detection control. The flowchart which shows steering speed detection control. Explanatory drawing which shows steering position detection control. It is a figure which shows the steering position detection apparatus of another form, (a) is a longitudinal cross-sectional view, (b) is a cross-sectional view. Explanatory drawing which shows the steering position detection control which concerns on 2nd Embodiment. The figure which shows the detection state by the steering position detection control which concerns on 2nd Embodiment. The figure which shows the relationship between the detection state by the steering position detection control which concerns on 2nd Embodiment, and a steering position. Explanatory drawing which shows the steering position detection control which concerns on 3rd Embodiment.

Explanation of symbols

1 Tractor (work vehicle)
5 Front wheel 20 Front wheel steering device 40,140,240,340 Steering angle detection means (steering position detection device)
41,141 switch (left detection switch)
42,142 switch (right detection switch)
45, 245, 345 Cam (shaft cam member)
145 cam (cylindrical cam member)
60 Calculation unit (microcomputer)

Claims (1)

In a front wheel steering apparatus for a working vehicle having a steering angle detecting means for detecting a steering angle of a front wheel,
The steering angle detection means includes
Two switches,
A shape in which at least one of the two switches changes output on and off a plurality of times during the period from the neutral state to the maximum steering angle while being displaced based on the steering angle. And the cam
A calculation unit that determines a steering direction and a plurality of steering angles based on output signals of the two switches and calculates a steering speed from a displacement time between the plurality of steering angles;
A front-wheel steering device for a working vehicle.

Images