Patent Description:
Patent Document <NUM> discloses a work vehicle in which a flat panel display unit is disposed on a steering post and a steering wheel is attached to a steering shaft that extends upward from the steering post. The steering wheel is constituted by a ring and a plurality of spokes that extend in the radial direction of the ring, and an opening is formed by the ring and adjacent spokes. The size of the opening and the position of the flat panel display unit are determined such that a driver seated on the driver seat can see the flat panel display unit through the opening. Therefore, the driver can have a clear view of the screen of the flat panel display unit through the opening of the steering wheel. <CIT> describes a vehicle which is able to be set to operate in a factory mode (as opposed to a normal mode) in which certain features are disabled, such as an alarm system, a power liftgate, etc. The following features of claim <NUM> are disclosed: a driver seat; a steerable wheel; a display unit configured to display various types of information; a steering wheel disposed on the rear side with respect to the display unit, in front of the driver seat; a wheel angle detector configured to detect a wheel angle that is a rotation angle of the steering wheel about a wheel rotation shaft; a steering mechanism configured to change a steering angle of the steerable wheel based on the wheel angle; an adjusting unit configured to adjust a relationship between the wheel angle and the steering angle; and a manual operation tool, wherein the steering wheel includes a plurality of spokes and a ring-shaped member that is connected to the spokes, and an opening is formed between the spokes and the ring-shaped member. <CIT> describes a motor vehicle steering system with a vehicle steering wheel and a steering drive for adjusting the alignment of a left and a right wheel hub carrier of a corresponding wheel suspension system according to a steering wheel position specified by the driver via the vehicle steering wheel. <CIT> describes a steering apparatus for a vehicle provided with an angular ratio varying device which can vary a ratio of a steering angle of a steerable vehicle wheel with respect to an operational angle of a steering member. <CIT> describes a steering gear for a vehicle capable of easily diagnosing displacement of a middle point when abnormality occurs due to displacement of the middle point which shows that a steering angle or steering torque of a steering angle signal or a steering torque signal is zero.

Work vehicles mainly travel in a straight line, and therefore, in the work vehicle disclosed in Patent Document <NUM>, the attachment position of the steering wheel is determined such that the driver can have a clear view of the screen of the flat panel display unit through the opening of the steering wheel when the rotation position of the steering wheel is that of straight travel. However, an original correct relationship between a wheel angle, which is the rotation angle of the steering wheel, and a steering angle of a steerable wheel cannot be maintained in a steering mechanism for converting the wheel angle to the steering angle, due to change over time or the like. As a result, the wheel angle of straight travel shifts in the clockwise or counterclockwise direction from an original angle, the field of view is interrupted by a spoke, and the driver cannot see the entire screen of the flat panel display unit through the opening of the steering wheel.

Under the above circumstances, there is demand for a work vehicle that allows the driver to have a clear view of the screen of the flat panel display unit through the opening of the steering wheel regardless of change over time in the steering mechanism. The present invention is defined by the independent claim. A preferred example is defined in the dependent claim.

A work vehicle according to the present invention includes: a driver seat; a steerable wheel; a display unit configured to display various types of information; a steering wheel disposed on the rear side with respect to the display unit, in front of the driver seat; a wheel angle detector configured to detect a wheel angle that is a rotation angle of the steering wheel about a wheel rotation shaft; a steering mechanism configured to change a steering angle of the steerable wheel based on the wheel angle; and an adjusting unit configured to adjust a relationship between the wheel angle and the steering angle. The steering wheel includes a plurality of spokes and a ring-shaped member that is connected to the spokes, and an opening is formed between the spokes and the ring-shaped member.

The steering mechanism sets a wheel angle (relationship between the wheel angle and the steering angle) of an initial state in which the display unit can be seen from the driver seat side through the opening of the steering wheel, as the wheel angle of the steering wheel that generates a steering angle (straight travel steering angle) that makes the steerable wheel travel straight. When the initial state changes, a view of the display unit from the driver seat side is interrupted by a spoke when the steering wheel is at the rotation position at which the straight travel steering angle (commonly called a neutral steering angle) is generated. In such a case, according to the configuration of the present invention, it is possible to restore the original initial state by adjusting the relationship between the wheel angle and the steering angle through the adjusting unit.

The adjusting unit is configured to set, as an appropriate angle, a wheel angle that allows the display unit to be in a field of view from the driver seat side through the opening, and adjust the relationship such that the steering angle becomes the neutral steering angle when the wheel angle is the appropriate angle. In this configuration, the wheel angle that allows the display unit to be seen from the driver seat side through the opening of the steering wheel is set as the appropriate angle, and the steering mechanism is adjusted through the adjusting unit such that the appropriate angle corresponds to the neutral steering angle. As a result, the driver seated on the driver seat can always have a clear view of the screen of the flat panel display unit through the opening of the steering wheel.

In a preferable embodiment of the present invention, the appropriate angle is stored in advance, the adjusting unit reads out the stored appropriate angle, and adjusts the steering mechanism based on the read appropriate angle such that the steering angle becomes the neutral steering angle. With this configuration, the adjusting unit can automatically adjust the steering mechanism at a predetermined timing or based on a request from the driver such that the display unit is in the field of view of the driver from the driver seat side through the opening when the work vehicle is traveling in a straight line.

The adjusting unit sets, as the appropriate angle, a rotation angle of the steering wheel at a point in time at which a manual operation tool for setting the appropriate angle is operated, and adjusts the steering mechanism such that the steering angle becomes the neutral steering angle when the wheel angle is the appropriate angle. With this configuration, the steering angle that makes the steerable wheel travel straight is generated from the wheel angle of the steering wheel at the time when the driver feels that it is easy to see the display unit.

Next, an embodiment of a work vehicle according to the present invention will be described using the drawings. <FIG> is a side view of a tractor that is an example of the work vehicle, and <FIG> is a plan view of the tractor. As shown in <FIG>, in the tractor, a hood <NUM> that covers an engine compartment is disposed in a front region of a vehicle body <NUM> that is supported by front wheels <NUM> and rear wheels <NUM>, and a driver seat <NUM> and a ROPS <NUM> are disposed in a rear region of the vehicle body <NUM>. The front wheels <NUM> are configured as steerable wheels, and the rear wheels <NUM> are configured as driving wheels. In a four-wheel drive mode, the front wheels <NUM> also function as driving wheels. A panel assembly <NUM> is disposed at the rear end of the hood <NUM>, and a steering wheel <NUM> is disposed between the panel assembly <NUM> and the driver seat <NUM>. The steering wheel <NUM> is supported by a steering post <NUM> that is connected to the panel assembly <NUM>. Various operation tools and various meters are attached to the panel assembly <NUM>. As shown in <FIG>, a display unit <NUM> for displaying various types of information is disposed on the lower front side of the steering wheel <NUM>. The display unit <NUM> is attached to the panel assembly <NUM>.

<FIG> schematically shows a steering mechanism <NUM> for changing the steering angle of the front wheels <NUM>, which are steerable wheels, based on a wheel angle that is a rotation angle of the steering wheel <NUM> about a wheel rotation shaft <NUM>. The steering mechanism <NUM> includes a power steering unit <NUM> that is coupled to the left and right front wheels <NUM>. A wheel angle detector <NUM> that detects the wheel angle is provided in the surrounding region of the wheel rotation shaft <NUM>, and a steering angle detector <NUM> that detects the steering angle of the front wheels <NUM> is provided in the surrounding region of the power steering unit <NUM>. In the steering mechanism <NUM>, a steering ratio that is a ratio between the wheel angle and the steering angle is not fixed and can be adjusted by an adjusting unit <NUM>. The adjusting unit <NUM> can be constituted by a mechanical transmission unit that performs variable magnification of a change in the rotation angle to generate the steering angle. If the steering mechanism <NUM> is constituted by steering-by-wire, the adjusting unit <NUM> is incorporated into an electronic steering control unit that outputs a steering signal for generating the steering angle corresponding to the wheel angle, to the power steering unit <NUM>.

The tractor is configured to be capable of automatic traveling. Therefore, a steering actuator <NUM> for automatic steering is provided. The steering actuator <NUM> operates based on a steering control signal that is transmitted in automatic traveling, and steers the front wheels <NUM> by rotating the wheel rotation shaft <NUM> in place of the steering wheel <NUM>.

As shown in <FIG> and <FIG>, the steering wheel <NUM> is constituted by three spokes <NUM> that extend in the radial direction of the wheel rotation shaft <NUM>, and a ring-shaped member <NUM> that is connected to end portions of the spokes <NUM>. The three spokes <NUM> are arranged at central angle intervals of <NUM>°, and therefore, substantially fan-shaped openings <NUM> each having a central angle of <NUM>° are formed between the spokes <NUM> and the ring-shaped member <NUM>. Note that the ring-shaped member <NUM> does not need to have a complete ring shape, and a portion of the ring-shaped member <NUM> may be cut out. Also, the number of spokes <NUM> may be two or four or more, and intervals between the spokes <NUM> may be nonuniform.

<FIG> shows the steering wheel <NUM> viewed from a driver seated on the driver seat <NUM>. The rotation position of the steering wheel <NUM> is such that one of the openings <NUM> is located above the display unit <NUM>. When the steering wheel <NUM> is at this rotation position, the opening <NUM> is within the field of view of the driver seated on the driver seat <NUM>, and the driver can see almost the entire screen of the display unit <NUM> through the opening <NUM>. Here, the wheel angle of the steering wheel <NUM> at such a rotation position is defined as an appropriate angle.

<FIG> shows an example of the display unit <NUM>. The display unit <NUM> in the present embodiment includes a group of meters <NUM>, a group of LED lamps <NUM>, and a liquid crystal panel <NUM>. The group of meters <NUM> includes a tachometer that is arranged in a left end region and a liquid temperature meter and a fuel meter that are arranged in a right region. The group of LED lamps <NUM> includes a plurality of LED lamps that are arranged in an upper region and a lower region at the center. These LED lamps serve as various warning lamps and confirmation lamps. Note that the entirety or most of the display screen of the display unit <NUM> may be constituted by the liquid crystal panel.

At the time of shipment from a factory or maintenance, the steering mechanism <NUM> (see <FIG>) is adjusted by the adjusting unit <NUM> (see <FIG>) such that, in a state where the wheel angle of the steering wheel <NUM> is the appropriate angle, the steering angle of the front wheels <NUM> is a neutral steering angle (which is a steering angle for making the vehicle body <NUM> travel straight and is <NUM>°). As a result, when the tractor is traveling straight, the driver can have a clear view of information that is displayed in the display unit <NUM> and is important for traveling of the tractor.

Next, main functional units of a control system of the tractor will be described using <FIG>. The tractor includes a function of automatically traveling along a target travel route, and accordingly, needs to calculate a vehicle position. Therefore, a satellite positioning module 8a and an inertial measurement module 8b are provided as a positioning unit <NUM>. The satellite positioning module 8a is provided in an upper portion of the ROPS <NUM> as shown in <FIG>, and adopts the principle of a satellite positioning system (GNSS) for detecting the position of the vehicle body <NUM> by receiving radio waves from satellites. The inertial measurement module 8b includes a gyroscope sensor and an acceleration sensor, and can determine an angular change in the orientation of the vehicle body. The inertial measurement module 8b may be disposed at a position different from the satellite positioning module 8a, rather than the same position as the satellite positioning module 8a. Of course, the inertial measurement module 8b may be disposed at a different position, for example, the same position as the satellite positioning module 8a.

A control device <NUM> includes an input output processing unit <NUM> as an input output interface. The input output processing unit <NUM> is connected to the wheel angle detector <NUM>, the steering angle detector <NUM>, the adjusting unit <NUM>, and the steering actuator <NUM> described above. Furthermore, the input output processing unit <NUM> is connected to a group of state detectors <NUM>, a group of manual operation tools <NUM>, and the like. The positioning unit <NUM> described above is connected to the control device <NUM> via an in-vehicle LAN. The display unit <NUM> displays various types of information based on notification signals from a notification control unit <NUM>.

The group of state detectors <NUM> is constituted by various sensors and switches, and includes a travel device state detector <NUM> and a work device state detector <NUM>. The travel device state detector <NUM> includes sensors that detect the state of travel, such as a vehicle speed sensor, an engine speed sensor, a brake pedal detection sensor, and a parking brake detection sensor (not shown). The work device state detector <NUM> includes a sensor that detects the state of a work device that the tractor is provided with.

The group of manual operation tools <NUM> collectively refers to levers, switches, buttons, volume knobs, and the like that are operated by the driver (of which only some are shown in <FIG>), and control instructions are given to the control device <NUM> as a result of these tools being operated.

The control device <NUM> includes a travel control unit <NUM>, a work control unit <NUM>, a route setting unit <NUM>, a steering management unit <NUM>, a vehicle position calculation unit <NUM>, and a travel divergence calculation unit <NUM>, for example.

The vehicle position calculation unit <NUM> calculates map coordinates (vehicle position) of the vehicle body <NUM> based on satellite positioning data that is successively transmitted from the positioning unit <NUM>. At this time, the vehicle position calculation unit <NUM> converts a position that is directly calculated from the satellite positioning data to a reference point of the vehicle body <NUM> (e.g., the center of the vehicle body or the center of work). The vehicle position calculation unit <NUM> also includes a function of calculating a traveling direction that is the orientation of the vehicle body <NUM> in the front-rear direction by chronologically processing the calculated vehicle position.

Based on the vehicle position and the traveling direction calculated by the vehicle position calculation unit <NUM>, the travel divergence calculation unit <NUM> calculates travel divergence from the target travel route set for automatic traveling. The travel divergence includes a lateral deviation that is a divergence in a lateral direction from the target travel route and a directional deviation that is expressed using an angle formed between the target travel route and the traveling direction.

The travel control unit <NUM> transmits a steering control signal to the steering actuator <NUM> and transmits a transmission control signal and a brake control signal to travel devices such as the transmission and the brake. The tractor is capable of automatic traveling and manual traveling, and therefore, the travel control unit <NUM> includes an automatic travel control unit <NUM>, a manual travel control unit <NUM>, and a travel mode management unit <NUM>.

An automatic travel mode is set to perform automatic driving and a manual travel mode is set to perform manual driving. These travel modes are managed by the travel mode management unit <NUM>. If the automatic travel mode is set, the automatic travel control unit <NUM> gives a steering control signal to the steering actuator <NUM> such that the lateral deviation and the directional deviation calculated by the travel divergence calculation unit <NUM> are reduced.

The work control unit <NUM> controls operations of the work device (not shown) installed in the vehicle body <NUM>.

The route setting unit <NUM> calculates a travel route that covers the entire work target area using a program, and sets the travel route as the target travel route according to a determined travel pattern. Note that the travel route may be calculated by another computer or the like, rather than the route setting unit <NUM> installed in the tractor, and may be transmitted to the route setting unit <NUM>.

The steering management unit <NUM> gives, to the adjusting unit <NUM>, an adjustment control signal for making the steering angle detected by the steering angle detector <NUM> be the neutral steering angle in the state where the wheel angle detected by the wheel angle detector <NUM> is the appropriate angle. The adjusting unit <NUM> adjusts a relationship between the wheel angle and the steering angle in the steering mechanism <NUM> (see <FIG>) based on the adjustment control signal. As a result, when the rotation position of the steering wheel <NUM> (see <FIG>) is that of straight travel, almost the entire display unit <NUM> or at least an important display region of the display unit <NUM> is inside the opening <NUM> (see <FIG>) when viewed from the driver seat side.

Two states of the steering mechanism <NUM> before adjustment are schematically shown in the middle portion of <FIG>. In these states, when the steering wheel <NUM> is operated by the driver to make the steering angle β be the neutral steering angle so that the vehicle body <NUM> travels in a straight line, the wheel angle α is not the appropriate angle (=<NUM>°) and the steering wheel <NUM> deviates from the appropriate angle in the counterclockwise direction. Therefore, a spoke <NUM> of the steering wheel <NUM> overlaps the display unit <NUM>, and the driver seated on the driver seat <NUM> (see <FIG>) cannot see a portion of the important display region of the display unit <NUM> through the opening <NUM>.

In other words, if the wheel angle α is set to the appropriate angle so that the important display region of the display unit <NUM> can be clearly seen through the opening <NUM>, the steering angle deviates from the neutral steering angle and the vehicle body cannot travel in a straight line (see the left diagram in <FIG>). In order to solve this problem, steering adjustment is performed by the steering management unit <NUM> (see <FIG>) and the adjusting unit <NUM>.

The right diagram in <FIG> schematically shows a state of the steering mechanism <NUM> that is adjusted by the adjusting unit <NUM>. Processing for this adjustment is described below. First, when the wheel angle is represented by α, the steering angle is represented by β, and a steering function for determining the steering ratio in the steering mechanism <NUM> is represented by G() (corresponding to a function or a table), a steering angle that is generated from a wheel angle can be found as follows: β=G(α). At the time of shipment from a factory or maintenance, basically, <NUM>°=G(<NUM>°). If the steering function in the steering mechanism <NUM> changes from the original steering function G( ) to a changed steering function G <NUM> () due to damage or the like of the steering wheel <NUM> or the steering mechanism <NUM> over time, the steering ratio changes and <NUM>°=G1(<NUM>°) does not hold true. That is, when the wheel angle is the appropriate angle (α=<NUM>°), the steering angle is not the neutral steering angle (β=<NUM>°) but <NUM>°, for example. In other words, when the steering angle is the neutral steering angle (β=<NUM>°), the wheel angle is not the appropriate angle (α=<NUM>°) but <NUM>°, for example.

The adjusting unit <NUM> and the steering management unit <NUM> have a function of adjusting the steering mechanism <NUM> such that <NUM>°=G1(<NUM>°) holds true even in the changed steering function G1( ). That is, the steering management unit <NUM> finds θ with which <NUM>°=G1(<NUM>°)+θ holds true, and gives adjustment data that corresponds to θ to the adjusting unit <NUM>. The adjusting unit <NUM> adjusts the steering mechanism <NUM> based on the adjustment data. As a result, even in the changed steering function G1( ), the steering angle becomes the neutral steering angle (β=<NUM>°) when the wheel angle is the appropriate angle (α=<NUM>°).

In a state before the steering mechanism <NUM> is adjusted, the driver operates an operation tool of the group of manual operation tools <NUM> that is designated in advance as a trigger switch for adjusting steering. As a result, the processing for adjusting the steering mechanism <NUM> is executed. In this adjustment processing, the steering mechanism <NUM> is adjusted by the adjusting unit <NUM> and the steering management unit <NUM> (see <FIG>) to change the steering ratio of the steering mechanism <NUM> such that the steering angle becomes the neutral steering angle when the wheel angle of the steering wheel <NUM> is the appropriate angle.

Note that, if the appropriate angle is stored in a memory, the adjusting unit <NUM> reads out the stored appropriate angle from the memory, and the steering mechanism <NUM> is adjusted such that the steering angle becomes the neutral steering angle when the wheel angle is the read appropriate angle. This configuration makes it possible to automatically adjust the steering mechanism <NUM> at a predetermined timing or based on a request from the driver such that the driver can have a clear view of the display unit <NUM> through the opening <NUM> when the tractor is traveling in a straight line.

The appropriate angle of the steering wheel <NUM> may vary depending on the driver. In order to solve this problem, it is possible to adopt a configuration in which the appropriate angle is determined by each driver. In this configuration, an operation tool that is a trigger switch for determining the appropriate angle is designated in advance as an operation tool for setting the appropriate angle, from the group of manual operation tools <NUM>. The wheel angle at a point in time at which this operation tool is operated is set as the appropriate angle, and the steering mechanism <NUM> is adjusted such that the steering angle becomes the neutral steering angle when the steering wheel has this wheel angle. Thus, the steering angle that makes the steerable wheels travel in a straight line is generated from the wheel angle of the steering wheel <NUM> at the time when the driver feels that it is easy to see the display unit <NUM>.

Claim 1:
A work vehicle comprising:
a driver seat (<NUM>);
a steerable wheel (<NUM>);
a display unit (<NUM>) configured to display various types of information;
a steering wheel (<NUM>) disposed on the rear side with respect to the display unit (<NUM>), in front of the driver seat (<NUM>);
a wheel angle detector (<NUM>) configured to detect a wheel angle that is a rotation angle of the steering wheel (<NUM>) about a wheel rotation shaft;
a steering mechanism (<NUM>) configured to change a steering angle of the steerable wheel (<NUM>) based on the wheel angle;
an adjusting unit (<NUM>) configured to adjust a relationship between the wheel angle and the steering angle; and
a manual operation tool (<NUM>),
wherein
the steering wheel (<NUM>) includes a plurality of spokes (<NUM>) and a ring-shaped member (<NUM>) that is connected to the spokes (<NUM>), and an opening (<NUM>) is formed between the spokes (<NUM>) and the ring-shaped member (<NUM>),
the adjusting unit (<NUM>) sets, as an appropriate angle, a wheel angle that allows the display unit (<NUM>) to be in a field of view from the driver seat side through the opening (<NUM>), and adjusts the relationship such that the steering angle becomes a neutral steering angle when the wheel angle is the appropriate angle, and
the adjusting unit (<NUM>) sets, as the appropriate angle, a rotation angle of the steering wheel (<NUM>) at a point in time at which the manual operation tool (<NUM>) for setting the appropriate angle is operated, and adjusts the steering mechanism (<NUM>) such that the steering angle becomes a neutral steering angle when the wheel angle is the appropriate angle.