JP6704564B2 - Tractor - Google Patents

Description

The present invention relates to a tractor including steering angle detection means for detecting a steering angle of front wheels.

A tractor including a steering angle detecting means for detecting a steering angle of front wheels is known. For example, the tractors described in Patent Documents 1 and 2 determine whether or not the steering angle of the front wheels exceeds a predetermined turning angle (turning determination angle) when performing front wheel speed-up control for speeding up the front wheels during turning of the airframe. The steering angle detection means (turn detection switch) for detecting is provided. Further, in recent years, in order to perform various controls according to the steering angle of the front wheels, a tractor that widely detects the steering angle of the front wheels using a rotation angle sensor such as a potentiometer is also known.

Japanese Patent No. 4602108 JP, 2008-56071, A

In recent years, an automatic steering control function has been proposed which automatically steers the front wheels based on various sensor information. For example, a straight-ahead assist control function has been proposed in which a camera for photographing the front of the aircraft is provided and the front wheels are automatically steered so that the target object in the image captured by the camera is maintained at a predetermined position so that the aircraft travels straight. .. However, since the conventional steering angle sensor detects the steering angle of the front wheels over a wide range, it is difficult to detect the steering angle near straight ahead with high accuracy, and as a result, the steering angle near straight ahead is controlled by the straight ahead assist control function. There is a problem in that the change cannot be fed back with high accuracy, and the control accuracy of the straight-ahead assist control function deteriorates.

The present invention has been made in view of the above circumstances in order to solve these problems, and the invention of claim 1 provides a front wheel steering mechanism that steers the front wheels according to the operation of the steering wheel. A tractor comprising: a steering angle detecting member that is connected to the front wheel steering mechanism via a connecting member and that rotates according to a steering angle of the front wheel; and a steering angle detecting member that rotates based on a turning position of the steering angle detecting member. Based on the first steering angle sensor that detects the steering angle of the front wheels and the turning position of the steering angle detection member, the steering angle near the straight ahead of the front wheels can be locally detected with higher accuracy than the first steering angle sensor. And a second steering angle sensor for detecting.
The invention according to claim 2 is the tractor according to claim 1, wherein the first steering angle sensor detects a rotation angle of the steering angle detection member, and the second steering angle sensor detects the steering angle. It is characterized in that the displacement of the driven member that comes into contact with the cam portion of the detection member is detected.
A third aspect of the present invention is the tractor according to the second aspect, wherein the cam portion displaces the driven member according to the rotation of the steering angle detection member when the steering angle of the front wheel is in the vicinity of straight travel. And a dead zone area in which the driven member is not displaced even if the steering angle detection member rotates when the steering angle of the front wheel deviates from the vicinity of a straight line.
An invention according to claim 4 is the tractor according to claim 3, wherein the cam portion is provided with a mark indicating an intermediate position of the detection region.
A fifth aspect of the present invention is the tractor according to any one of the second to fourth aspects, further comprising a sensor bracket that displaceably supports the driven member and is attached to a body, and the sensor bracket is the A long-hole guide hole for guiding the displacement of the driven member according to a change in the steering angle of the front wheels in a straight line, and an outer end of the guide hole are opened to respond to a change in the steering angle of the front wheel other than in the straight line. A notch that allows the driven member to be displaced.
The invention according to claim 6 is the tractor according to any one of claims 1 to 5, wherein the steering angle detection member includes a plurality of connection points with the connection member, and is based on selection of the connection points. It can be used for multiple models.
A seventh aspect of the present invention is the tractor according to any one of the first to sixth aspects, wherein the front wheel steering mechanism includes a turning detection switch unit when the steering angle of the front wheels exceeds a predetermined turning angle. A switch pressing portion that presses the switch pressing portion is provided, and the connecting member is connected to the front wheel steering mechanism via a connecting bracket that can be fixed to the switch pressing portion in a sandwiched manner.
The invention of claim 8 is the tractor according to claim 7, wherein the connecting bracket includes a notch for avoiding interference with the turning detection switch portion.

According to the invention of claim 1, in addition to the first steering angle sensor for detecting the steering angle of the front wheels, the second steering angle sensor for locally detecting the steering angle near the straight ahead of the front wheels with higher accuracy than the first steering angle sensor. Since the steering angle sensor is provided, it is possible to highly accurately feed back the steering angle change in the vicinity of straight traveling by the straight traveling assist control function, and improve the control accuracy of the straight traveling assist control function. Moreover, since the first steering angle sensor and the second steering angle sensor detect the steering angle of the front wheels based on the same rotational position of the steering angle detecting member, compared to the case where the steering angle detecting member is provided for each steering angle sensor. It is possible to reduce the number of parts and simplify the setting.
According to the invention of claim 2, since the first steering angle sensor detects the turning angle of the steering angle detecting member, the steering angle of the front wheels can be detected in a wide range. Further, since the second steering angle sensor detects the displacement of the driven member that comes into contact with the cam portion of the steering angle detection member, the steering angle near the straight ahead of the front wheels is determined based on the shape setting of the cam portion. It can be detected locally with higher accuracy.
According to the invention of claim 3, when the steering angle of the front wheels is in the vicinity of straight ahead, the cam portion detects the displacement of the driven member in accordance with the rotation of the steering angle detection member, and the steering angle of the front wheels is in the vicinity of straight ahead. When the steering angle of the front wheel deviates from the vicinity of the straight line, the driven member is unnecessarily moved to an incorrect steering angle. It is possible to prevent detection. Further, the second steering angle sensor always outputs, and when it is out of the measurement range, the output is fixed by hardware and no software restriction is required, so that the control can be simplified.
According to the invention of claim 4, since the cam portion is provided with the mark indicating the intermediate position of the detection area, the position adjustment of the cam portion and the driven member can be easily performed.
According to the invention of claim 5, the sensor bracket for displaceably supporting the driven member includes an elongated hole-shaped guide hole for guiding the displacement of the driven member according to a change in the steering angle of the front wheels near the straight movement, and a guide hole. Since the outer end is provided with a notch that allows the driven member to be displaced in accordance with a change in steering angle other than near the straight running of the front wheels, while guiding the displacement of the driven member near the straight running, the It is possible to prevent damage to the driven member.
According to the invention of claim 6, the steering angle detecting member is provided with a plurality of connecting portions with the connecting member and can be used for a plurality of models based on the selection of the connecting portions. Compared with the case of preparing, the cost can be reduced significantly.
According to the invention of claim 7, the front wheel steering mechanism includes a switch pressing portion that presses the turning detection switch portion when the steering angle of the front wheels exceeds a predetermined turning angle, and the connecting member is sandwiched between the switch pressing portions. Since it is connected to the front wheel steering mechanism via a connecting bracket that can be fixed in a fixed shape, the steering angle of the front wheel can be changed by retrofitting the steering angle detecting member and the steering angle sensor even on existing models that do not have connecting points for connecting members. It becomes possible to detect.
According to the invention of claim 8, since the connecting bracket is provided with the notch for avoiding the interference with the turning detection switch portion, there is no inconvenience of degrading the detection accuracy of the turning detection switch portion.

It is a side view of the tractor concerning one embodiment of the present invention. It is the perspective view which looked at the front wheel steering mechanism and steering angle detection mechanism of the tractor concerning one embodiment of the present invention from the lower part. It is a perspective view showing a steering angle detection mechanism of a tractor concerning one embodiment of the present invention. FIG. 3 is an exploded perspective view showing a steering angle detection unit of the steering angle detection mechanism according to the embodiment of the present invention. It is a perspective view showing a steering angle detection unit of a steering angle detection part concerning one embodiment of the present invention. It is a figure which shows the steering angle detection unit which concerns on one Embodiment of this invention, (a) is a bottom view of a steering angle detection unit, (b) is a side view of a steering angle detection unit, (c) is a steering angle detection unit. FIG. It is an exploded perspective view showing a steering angle detection unit concerning one embodiment of the present invention. It is an exploded perspective view showing a connecting bracket of a steering angle detecting mechanism concerning one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 is a tractor, and the tractor 1 includes an engine mounting portion 2 in which an engine (not shown) is mounted, a mission case 3 for shifting engine power, and front wheel power output from the mission case 3. 4, a front axle case 5 (see FIG. 2) for driving the vehicle 4, a rear axle case (not shown) for driving the rear wheels 6 with rear wheel power output from the mission case 3, and various work machines (not shown). Is provided with a work implement connecting portion 7 and an operating portion 9 provided with an operating tool such as a steering wheel 8.

As shown in FIG. 2, the front axle case 5 is provided in the center case 10 extending to the left and right, the final case 11 connected to both left and right ends of the center case 10 so as to be rotatable back and forth, and the final case 11. The front wheel 4 is attached to a front wheel axle (not shown) that is rotatably supported by the final case 11 and includes a knuckle arm 12.

As shown in FIG. 2, the tractor 1 includes a front wheel steering mechanism 13 that steers the front wheels 4 according to an operation of the steering wheel 8, a turning detection mechanism 14 that detects a turning operation of the front wheel steering mechanism 13, and a front wheel steering mechanism 13. The steering angle detection mechanism 15 detects the steering angle of the front wheels 4 according to the above.

The front wheel steering mechanism 13 is composed of a double-acting double rod hydraulic cylinder, and both ends of the rod are connected to the left and right knuckle arms 12 via rod ends 16 and a power steering cylinder 17, and a steering wheel 8 is operated in response to the operation. A steering unit (not shown) for operating the power steering cylinder 17 is provided.

The turning detection mechanism 14 is provided at both ends of a rod of the power steering cylinder 17 and a turning detection switch portion 18 arranged in parallel in the vicinity of the power steering cylinder 17, and the steering angle of the front wheels 4 is a predetermined turning angle (turning determination angle). ) Is exceeded, a switch pressing portion 19 for pressing the turning detection switch portion 18 is provided.

The turning detection switch portion 18 is a tubular sensor case 20 extending in the left-right direction, and left and right sensors supported by the sensor case 20 so as to be slidable left and right and biased in a direction projecting outward from the sensor case 20 in the left and right directions. A rod 21, a disk-shaped sensor plate 22 provided at the tip of the sensor rod 21, and a turning detection switch (not shown) provided at the center of the sensor case 20 for detecting the pushing operation of the sensor rod 21. Prepare

The switch pressing portion 19 of the present embodiment is a disk-shaped plate provided at both ends of the rod of the power steering cylinder 17, and when the steering angle of the front wheels 4 exceeds a predetermined turning angle, the sensor plate 22 is pressed in the pushing direction. Then, the turning detection switch is turned on via the sensor rod 21. As a result, the tractor 1 can detect the turning operation of the front wheel steering mechanism 13 and execute the front wheel speed-up control for speeding up the front wheels 4 when the vehicle body turns.

As shown in FIG. 2 and FIG. 3, the steering angle detection mechanism 15 has a connecting portion 23 whose one end is connected to the front wheel steering mechanism 13, and a steering angle of the front wheel 4 which is connected to the other end of the connecting portion 23. The steering angle detection unit 24 for detecting the steering angle. As shown in FIGS. 2 to 4, the steering angle detection unit 24 includes a steering angle detection unit 25, which is a main part of the present invention, and a mounting bracket 26 for mounting the steering angle detection unit 25 to the vehicle body. The angle detection unit 25 is attached to the mounting bracket 26 and then fixed to the tractor 1 via the mounting bracket 26. Hereinafter, a specific configuration of the steering angle detection unit 25 will be described with reference to FIGS. 2 to 7.

The steering angle detection unit 25 is connected to the front wheel steering mechanism 13 via a connecting portion 23 and is based on a steering angle detection member 27 that rotates according to the steering angle of the front wheels 4 and a rotation position of the steering angle detection member 27. Based on the first steering angle sensor 28 that detects the steering angle of the front wheels 4 and the rotational position of the steering angle detection member 27, the steering angle of the front wheels 4 near the straight ahead is more accurate than the first steering angle sensor 28. A second steering angle sensor 29 that locally detects the temperature and a sensor bracket 30 that supports these members.

The sensor bracket 30 is a U-shaped member in a side view including a pair of upper and lower bracket portions 30a and 30b facing each other in the vertical direction. The steering angle detection member 27 is provided on the first bracket portion 30a via a support shaft 27a. It is rotatably attached, and the first steering angle sensor 28 and the second steering angle sensor 29 are attached to the second bracket portion 30b.

The first steering angle sensor 28 of the present embodiment is a potentiometer that detects the rotation angle of the sensor shaft 28a, and the sensor shaft 28a is arranged on the same axis as the support shaft 27a of the steering angle detection member 27. A detection lever 31 is integrally rotatably provided on the sensor shaft 28a of the first steering angle sensor 28, and an engagement groove 31a is formed at the tip of the detection lever 31.

A cam member 34 (cam portion) is attached to the steering angle detection member 27 via a pair of fixtures 32 and 33. The fixtures 32 and 33 include bolts 32a and 33a penetrating the steering angle detection member 27 and the cam member 34, and nuts 32b and 33b screwed to the bolts 32a and 33a. The bolt 32 a that constitutes 32 is formed in an elongated shape, and the tip end thereof is engaged with the engagement groove 31 a of the detection lever 31. As a result, the first steering angle sensor 28 can input the rotation angle of the steering angle detection member 27 via the bolt 32a, the detection lever 31, and the sensor shaft 28a, and can detect the steering angle of the front wheels 4 in a wide range. become.

Like the first steering angle sensor 28, the second steering angle sensor 29 of the present embodiment is a potentiometer that detects the rotation angle of the sensor shaft 29a, but it does not detect the rotation angle of the steering angle detection member 27. Instead, the displacement of the driven member 35 that comes into contact with the cam member 34 provided on the steering angle detecting member 27 is input, and the steering angle of the front wheels 4 in the vicinity of straight running is more accurate than the first steering angle sensor 28 based on the displacement. To detect locally.

More specifically, the driven member 35 includes an arm 35b that is rotatably provided on the first bracket portion 30a of the sensor bracket 30 via a support shaft 35a, and a roller that is rotatably provided on a tip portion of the arm 35b. A shaft 35c, a roller 35d provided on one end side of the roller shaft 35c and abutting on the cam member 34, and a torsion spring 35e for biasing the roller shaft 35c in a direction in which the roller 35d abuts on the cam member 34, The sensor shaft 29a of the second steering angle sensor 29 is provided with a detection lever 36, which has a contact piece 36a that abuts from the outside on the other end side of the roller shaft 35c at the tip end thereof so as to be integrally rotatable. .. Then, the second steering angle sensor 29 detects the displacement of the driven member 35 by bringing the contact piece 36a of the detection lever 36 into contact with the roller shaft 35c by the urging force of a spring (not shown) incorporated therein. It will be possible.

As shown in FIGS. 6A and 7, the cam member 34 has a detection area 34a for displacing the driven member 35 in accordance with the rotation of the steering angle detection member 27 when the steering angle of the front wheels 4 is in the vicinity of a straight line. And dead zone regions 34b and 34c that do not displace the driven member 35 even if the steering angle detecting member 27 rotates when the steering angle of the front wheels 4 deviates from the vicinity of straight ahead. More specifically, the detection region 34a has a shape in which the distance from the support shaft 27a changes greatly so as to largely displace the driven member 35 in accordance with the rotation of the steering angle detection member 27, and The shape is set so that the output of the second steering angle sensor 29 changes linearly. Further, one dead zone region 34b is connected to one end side of the detection region 34a, so that the driven member 35 is not displaced even if the steering angle detection member 27 rotates (the output of the second steering angle sensor 29 changes. (Not so), it has an arc shape centered on the support shaft 27a. The other dead zone region 34c is connected to the other end side of the detection region 34a and has an arc shape centered on the support shaft 27a so as not to displace the driven member 35 even if the steering angle detection member 27 rotates. Have. With such a configuration, when the steering angle of the front wheels 4 is in the vicinity of the straight ahead, the detection area 34a is largely displaced by the driven member 35 in accordance with the rotation of the steering angle detecting member 27, so that the front wheels 4 are in the vicinity of the straight ahead. It is possible to detect the steering angle of the vehicle with higher accuracy than the first steering angle sensor 28.

Further, the cam member 34 is provided with a mark 34d (for example, a hole) that indicates an intermediate position (position corresponding to a straight line) of the detection area 34a. With such a mark 34d, it is easy to adjust the positions of the cam member 34 and the driven member 35. The position adjustment of the cam member 34 and the driven member 35 is necessary when the steering angle detection unit 25 is attached to the tractor 1 or when the components of the steering angle detection unit 25 are replaced. The adjustment allowance is ensured by making the penetrating hole of the cam member 34 a long hole. Although the steering angle detection member 27 and the cam member 34 are separate members in the present embodiment, both members may be integrally formed. Further, the cam member 34 of the present embodiment has a point-symmetrical shape centered on the support shaft 27a and can be attached to the steering angle detecting member 27 even if it is inverted by 180°, but is limited to the point-symmetrical shape. Not a thing. Further, as shown in FIG. 6A, the cam member 34 of the present embodiment is attached to the steering angle detecting member 27 while being offset in the rotational direction about the support shaft 27a as a center. This is because when the steering angle detection member 27 and the cam member 34 are made compatible with multiple models, the difference in movement between the models is absorbed based on the offset amount between the steering angle detection member 27 and the cam member 34. Further, the detection area 34a of the present embodiment has an asymmetric shape with the mark 34d as the center, because the rotation amount of the steering angle detection member 27 is not uniform over the entire front wheel steering angle, and the front wheel steering angle is This is because there is a difference between the inward facing and the outward facing, and the asymmetrical output linearly changes the output of the second steering angle sensor 29.

As shown in FIG. 7, the sensor bracket 30 of the present embodiment is provided with a long hole-shaped guide hole 30c that guides the displacement of the driven member 35 (roller shaft 35c) according to the change in the steering angle of the front wheel 4 in the vicinity of straight movement. However, a notch 30d is formed on the outer end side of the guide hole 30c by opening the outer end of the guide hole 30c to allow the driven member 35 to be displaced in accordance with a change in the steering angle of the front wheel 4 other than in the straight traveling direction. .. This makes it possible to prevent the driven member 35 from being damaged by the displacement of the front wheels 4 other than in the straight-ahead direction in accordance with the change in the steering angle.

As shown in FIGS. 2 and 3, the connecting portion 23 of the present embodiment is connected to the front wheel steering mechanism 13 via a connecting bracket 50 that can be fixed to the switch pressing portion 19 in a sandwiched manner, and one end side thereof. , And a connecting member 37 whose other end is connected to the steering angle detecting member 27. The connecting member 37 is a rod member whose length is adjustable, and is connected to the connecting bracket 50 and the steering angle detecting member 27 via ball joints 37a provided at both ends. It should be noted that it is sufficient to connect the connecting bracket 50 (switch pressing portion 19) and the steering angle detecting member 27 to only one of the left and right sides of the machine body. As shown in FIG. 8, the connecting bracket 50 includes a connecting plate 38 having a connecting piece 38 a with the connecting member 37, a holding plate 39 for holding the switch pressing portion 19 between the connecting plate 38, the connecting plate 38, and the holding plate 38. A pair of end plates 40 and 41 sandwiching the plate 39 from both sides, a connecting plate 38, a plurality of bolts 42 penetrating the sandwiching plate and end plates 40 and 41, and a connecting plate 38 and a sandwiching plate screwed into each bolt 42. 39 and end plates 40 and 41 are integrally fixed to each other by a nut 43.

The connecting plate 38, the sandwiching plate 39, and the end plates 40, 41 are formed by inserting insertion holes 38b, 39a, 40a, 41a through which the rod 17a of the power steering cylinder 17 is inserted and a part of the insertion holes 38b, 39a, 40a, 41a. The power steering cylinder 17 is provided with notches 38c, 39b, 40b, 41b that allow the rod 17a to be retrofitted. The width dimension of the notches 38c, 39b, 40b, 41b is set to be larger than the diameter of the rod 17a, but in the present embodiment, further, the interference between the coupling bracket 50 and the turning detection switch portion 18 is avoided. The positions and width dimensions of the notches 38c, 39b, 40b, 41b are set.

The steering angle detection member 27 of the present embodiment includes a plurality of connecting portions 27b with the connecting member 37 at a position bent into a crank shape in a side view. That is, the steering angle detection member 27 of the present embodiment can change the connection position with the connection member 37 in the front-rear direction and the left-right direction based on the selection of the connection location, so that one steering angle detection member 27 in multiple models. It is possible to use both.

According to the present embodiment configured as described above, in addition to the first steering angle sensor 28 that detects the steering angle of the front wheels 4, the steering angle near the straight ahead of the front wheels 4 is more accurate than the first steering angle sensor 28. Since the second steering angle sensor 29 that locally detects the steering angle is provided, it is possible to highly accurately feed back the steering angle change in the vicinity of the straight traveling by the straight traveling assist control function and improve the control accuracy of the straight traveling assist control function.

Moreover, since the first steering angle sensor 28 and the second steering angle sensor 29 detect the steering angle of the front wheels 4 based on the same turning position of the steering angle detecting member 27, the steering angle detecting member is different for each steering angle sensor. The number of parts can be reduced and the setting can be simplified as compared with the case of providing.

Further, since the first steering angle sensor 28 detects the turning angle of the steering angle detecting member 27, the steering angle of the front wheels 4 can be detected in a wide range. Further, since the second steering angle sensor 29 detects the displacement of the driven member 35 that comes into contact with the cam member 34 provided on the steering angle detecting member 27, based on the shape setting of the cam member 34, the front wheel 4 is in the vicinity of straight traveling. The steering angle can be locally detected with higher accuracy than the first steering angle sensor 28.

Further, when the steering angle of the front wheels 4 is in the vicinity of the straight traveling, the cam member 34 displaces the driven area 35 in accordance with the rotation of the steering angle detecting member 27 and the steering angle of the front wheels 4 deviates from the vicinity of the straight traveling. When the steering angle detection member 27 rotates, the dead zone regions 34b and 34c that do not displace the driven member 35 are provided. Therefore, when the steering angle of the front wheels 4 deviates from the straight ahead, the driven member 35 moves unnecessarily. It is possible to prevent erroneous steering angle detection. In addition, the second steering angle sensor 28 always outputs, and when it is out of the measurement range, the output is fixed by hardware and no software regulation is required, so that the control can be simplified.

Further, since the cam member 34 is provided with the mark 34d indicating the intermediate position of the detection area 34a, the position adjustment of the cam member 34 and the driven member 35 can be easily performed.

Further, the sensor bracket 30 that supports the driven member 35 in a displaceable manner has a long hole-shaped guide hole 30c that guides the displacement of the driven member 35 in accordance with a change in the steering angle of the front wheels 4 in the vicinity of straight movement, and the outside of the guide hole 30c. Since the notch 30d is provided to open the end and allow the displacement of the driven member 35 according to the change in the steering angle other than the straight traveling of the front wheel 4, the displacement of the driven member 35 near the straight traveling is guided while the other portions are provided. It is possible to prevent the driven member 35 from being damaged by the displacement.

Further, the steering angle detecting member 27 is provided with a plurality of connecting portions 27b with the connecting member 37 and can be used for a plurality of models based on the selection of the connecting portions 27b. Therefore, a dedicated steering angle detecting member 27 is prepared for each model. Compared with the case of doing, a significant cost reduction can be achieved.

Further, the front wheel steering mechanism 13 includes a switch pressing portion 19 that presses the turning detection switch portion 18 when the steering angle of the front wheels 4 exceeds a predetermined turning angle, and the connecting member 37 is sandwiched between the switch pressing portions 19. Since it is connected to the front wheel steering mechanism 13 via a connecting bracket 50 that can be fixed to the steering wheel, the steering angle detecting member 27 and the steering angle sensors 28 and 29 are retrofitted to an existing model that does not have a connecting portion of the connecting member 37. Thus, the steering angle of the front wheels 4 can be detected.

Further, since the connecting bracket 50 is provided with the notches 38c, 39b, 40b, 41b for avoiding the interference with the turning detection switch unit 18, there is no inconvenience of degrading the detection accuracy of the turning detection switch unit 18.

The present invention is not limited to the above-described embodiment, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. For example, the connecting member of the above embodiment is composed of a rod member and transmits the movement of the switch pressing portion to the steering angle detecting member, but the rotation angle of the final case may be transmitted to the steering angle detecting member. For example, the structure of the connecting member is arbitrary, and for example, the connecting member may be formed of a wire member.

DESCRIPTION OF SYMBOLS 1 tractor 4 front wheel 8 steering wheel 13 front wheel steering mechanism 14 turning detection mechanism 15 steering angle detection mechanism 17 power steering cylinder 18 turning detection switch unit 19 switch pressing unit 23 connection unit 24 steering angle detection unit 25 steering angle detection unit 27 steering angle detection member 27b Connection location 28 First steering angle sensor 29 Second steering angle sensor 30 Sensor bracket 30c Guide hole 30d Notch 34 Cam member 34a Detection area 34b Dead zone area 34d Mark 35 Follower member 37 Connecting member 38c, 39b, 40b, 41b Notch 50 connection bracket

Claims (8)

A tractor having a front wheel steering mechanism that steers the front wheels according to the operation of a steering wheel,
A steering angle detection member that is connected to the front wheel steering mechanism via a connecting member and that rotates according to the steering angle of the front wheels;
A first steering angle sensor for detecting a steering angle of the front wheels based on a turning position of the steering angle detecting member;
A second steering angle sensor for locally detecting a steering angle of the front wheel in the vicinity of straight ahead with higher accuracy than the first steering angle sensor, based on a turning position of the steering angle detection member. And a tractor. The first steering angle sensor detects a rotation angle of the steering angle detection member,
The tractor according to claim 1, wherein the second steering angle sensor detects a displacement of a driven member that comes into contact with a cam portion of the steering angle detection member. The cam portion is
A detection area for displacing the driven member according to the rotation of the steering angle detection member when the steering angle of the front wheel is in the vicinity of straight travel;
The dead zone region which does not displace the driven member even if the steering angle detection member rotates when the steering angle of the front wheel deviates from the vicinity of a straight line, and the tractor according to claim 2. The tractor according to claim 3, wherein the cam portion includes a mark indicating an intermediate position of the detection area. The driven member is movably supported, and includes a sensor bracket attached to the body,
The sensor bracket is
A long hole-shaped guide hole for guiding the displacement of the driven member according to a change in the steering angle of the front wheels near the straight line,
5. A notch formed by opening an outer end of the guide hole and allowing displacement of the driven member according to a change in steering angle other than near the straight traveling of the front wheel. The tractor according to one item. The steering angle detection member includes a plurality of connection points with the connection member, and can be used for a plurality of models based on selection of the connection points. The listed tractor. The front wheel steering mechanism includes a switch pressing portion that presses the turning detection switch portion when the steering angle of the front wheels exceeds a predetermined turning angle,
The tractor according to any one of claims 1 to 6, wherein the connecting member is connected to the front wheel steering mechanism via a connecting bracket that can be fixed to the switch pressing portion in a sandwiched manner. The tractor according to claim 7, wherein the connection bracket includes a notch that avoids interference with the turning detection switch unit.

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