Work vehicles

Abstract

To provide a work vehicle capable of achieving easy working operation.SOLUTION: A work vehicle according an embodiment includes: a running vehicle body; a steering wheel; a steering sensor; a steering device; a control unit; a work machine; a lifting device; and a lifting sensor. The running vehicle body has a steering wheel. The steering wheel operates a driver. The steering sensor detects the operation amount of the steering wheel. The steering device steers the steering wheel. The control section controls the steering device according to a detection value of the steering sensor. The work machine is fitted on the running vehicle body. The lifting device lifts the work machine. The lifting sensor detects a lifting position of the lifting device. The control section, when the lifting position of the lifting device detected by the lifting sensor reaches at least a prescribed position, increases the steering ratio of the steering wheel by the steering device against the detection value of the steering sensor more than when the lifting position of the lifting device is less than the prescribed position.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a work vehicle. [Background technology]

[0002] Conventionally, there is known a work vehicle equipped with a steering device that sets multiple steering ratios of the steered wheels relative to the amount of steering wheel operation (for example, if the steered wheels are front wheels, the ratio of the amount of change in the turning angle of the front wheels) and allows the driver to switch between the set ratios using a selector switch, thereby reducing the steering ratio of the steered wheels relative to the amount of steering wheel operation when traveling at high speeds and increasing it when traveling at low speeds, thereby reducing fatigue during work driving (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-45014 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional work vehicles such as those described above, the driver must operate a changeover switch to switch (change) the steering ratio of the steered wheels relative to the amount of steering wheel operation. Since situations arise frequently in work vehicles where it is desired to change the steering ratio of the steered wheels relative to the amount of steering wheel operation, operating the changeover switch can be cumbersome, which can make work driving cumbersome.

[0005] The present invention has been made in view of the above, and has an object to provide a work vehicle that can be easily driven for work. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a work vehicle (1) according to an embodiment includes a traveling body (2) having steering wheels (21), a steering wheel (26) operated by a driver, a steering sensor (54) that detects an operation amount (D1) of the steering wheel (26), a steering device (62) that steers the steering wheels (21), a control unit (100) that controls the steering device (62) in accordance with a detection value of the steering sensor (54), a work implement (3) attached to the traveling body (2), a lifting device (63) that lifts and lowers the work implement (3), and a lifting sensor (57) that detects a lifting position of the lifting device (63), and the control unit (100) detects whether the lifting position of the lifting device (63) detected by the lifting sensor (57) is a predetermined position (P O ), the lifting position of the lifting device (63) reaches the predetermined position (P O The steering ratio of the steered wheels (21) by the steering device (62) relative to the detection value of the steering sensor (54) is made larger than when the steering ratio is less than 0.5. [Effects of the Invention]

[0007] According to the work vehicle of this embodiment, work driving can be easily performed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic explanatory diagram (part 1) of a work vehicle according to an embodiment. [Figure 2] FIG. 2 is a schematic explanatory diagram (part 2) of the work vehicle according to the embodiment. [Figure 3] FIG. 3 is a block diagram showing an example of a control system centered around a control unit in a work vehicle according to this embodiment. [Figure 4] FIG. 4 is an explanatory diagram of a steering control system in the work vehicle according to the embodiment. [Figure 5] FIG. 5 is an explanatory diagram (part 1) of the steering control in the work vehicle according to the embodiment. [Figure 6]FIG. 6 is an explanatory diagram (part 2) of the steering control in the work vehicle according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the work vehicle disclosed in the present application will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below.

[0010] <Overview of the work vehicle> First, an overview of a work vehicle 1 according to an embodiment will be described with reference to Figures 1 and 2. Figures 1 and 2 are schematic explanatory diagrams of a work vehicle 1 according to an embodiment. Figures 1 and 2 also show schematic left side views of the work vehicle 1. Figure 1 shows the work vehicle 1 with the work implement 3 raised, and Figure 2 shows the work vehicle 1 with the work implement 3 lowered.

[0011] 1 and 2, a three-dimensional Cartesian coordinate system is shown that includes a Z-axis with the positive direction pointing vertically upward (upward). Therefore, in the following, the positive direction of the X-axis is defined as the left, the negative direction of the X-axis as the right, the positive direction of the Y-axis as the forward direction, and the negative direction of the Y-axis as the backward direction, and the X-axis direction may be referred to as the left-right direction, the Y-axis as the front-back direction, and the Z-axis as the up-down direction.

[0012] Furthermore, the work vehicle 1 according to the embodiment travels within a field while performing work in the field. In the following, an agricultural tractor will be used as an example of the work vehicle 1. A driver (also referred to as a worker) rides in the agricultural tractor (hereinafter referred to as the tractor) 1, which is a work vehicle, and the driver drives the vehicle to perform predetermined work while traveling within the field. In the following, the tractor 1 and the traveling vehicle body 2, which will be described later, may be referred to as the "machine body."

[0013] As shown in Figures 1 and 2, the tractor 1 includes a traveling body 2, a work implement 3, a positioning device 40, and a control unit 100 (see Figure 3). The traveling body 2 is capable of traveling within a field and includes front wheels 21 and rear wheels 22. The front wheels 21 are a pair of left and right wheels for steering (steering wheels). The rear wheels 22 are a pair of left and right wheels for driving (driving wheels).

[0014] The front wheels 21, which are steered wheels, are steered by the driver operating a steering wheel 26, which will be described later. In this case, the front wheels 21 are steered by a steering device 62, which will be described later, in accordance with an operation amount D1 of the steering wheel 26 (see FIG. 4).

[0015] Rotational power generated by an engine E, which is a drive source housed in a hood 23, is transmitted to rear wheels 22, which are drive wheels, after being appropriately reduced in speed by a speed change device (transmission) 61 (see FIG. 2) provided in a power transmission device (mission case) 24. The rear wheels 22 are driven by the rotational power transmitted from the engine E. The speed change device 61 switches the rotational power transmitted from the engine E to one of a plurality of gear stages.

[0016] The traveling vehicle body 2 is configured to be able to transmit power generated by the engine E and reduced in speed by the transmission 61 to the front wheels 21 via the 4WD clutch. In this case, when the 4WD clutch transmits power, the four wheels, the front wheels 21 and the rear wheels 22, are driven by the power transmitted from the engine E. Also, when the 4WD clutch cuts off the transmission of power, only the two wheels, the rear wheels 22, are driven by the power transmitted from the engine E. In this way, the traveling vehicle body 2 is configured to be able to switch between two-wheel drive (2WD) and four-wheel drive (4WD).

[0017] A PTO (Power Take-Off) device (not shown) equipped with a PTO shaft (not shown) that transmits power to drive the work implement 3 (described later) is provided at the rear of the traveling body 2. A driver's seat 25 in which the driver sits when operating the tractor 1 is provided at the center of the traveling body 2.

[0018] A steering wheel 26 that is operated by the driver to steer the front wheels 21 is provided in front of the driver's seat 25. The steering wheel 26 is provided at the upper end of a steering post 27. In addition, various operation pedals 28 (accelerator pedal, brake pedal, clutch pedal, etc.) are provided below the steering post 27 near the feet of the driver seated in the driver's seat 25.

[0019] Further, a lifting device 63 (see FIG. 2) is provided at the rear of the traveling body 2 to raise and lower the working implement 30 attached to the traveling body 2. The lifting device 63 includes a hydraulic lifting cylinder 63a and a lifting arm 63b. The lifting device 63 raises the working implement 30, thereby moving the working implement 3 to a non-working position P U (see FIG. 1) and then lower the work implement 3, thereby moving the work implement 3 to the ground work position. When the work implement 3 is in the ground work position, the work implement 3 is in contact with the soil surface F of the field. S It is grounded to.

[0020] The work machine 3 performs work in the field. The work machine 3 is, for example, a rotary tiller. The rotary tiller rotates the tiller tines 31 by power transmitted from the PTO shaft of the PTO device, thereby cultivating the soil surface F of the field. S The height of the work implement 3 can be detected by a lift sensor 57 (see FIG. 2) that detects the rotation angle of the lift arm 63b of the lift device 63 as the lift position of the work implement 3.

[0021] The positioning device 40 is provided, for example, on the upper part of the traveling vehicle body 2, and acquires position information (current position) of the traveling vehicle body 2 (tractor 1). The positioning device 40 is, for example, a GPS (Global Positioning System) device or a GNSS (Global Navigation Satellite System) device, and is capable of receiving radio waves from a navigation satellite S (see FIG. 4) orbiting in the sky to determine position and measure time.

[0022] The control unit 100 (see FIG. 3) controls the engine E. The control unit 100 also controls the traveling of the traveling vehicle body 2 (tractor 1). The control unit 100 also controls the work equipment 3.

[0023] The control unit 100 also has a non-working mode in which the tractor 1 travels on the road and does not work in the field, and a working mode in which work is performed in the field, and causes the tractor 1 to execute these modes. In the non-working mode, for example, as shown in FIG. 1, the working implement 3 is moved to a non-working position P U In the work mode, as shown in FIG. 2, the work implement 3 is raised to a ground work position (above the soil surface F of the field). S The control unit 100 may have a remote control mode that enables remote control of the tractor 1 from a terminal device (for example, a tablet terminal).

[0024] <Work vehicle control system> Next, a control system for the work vehicle 1 according to the embodiment will be described with reference to Fig. 3. Fig. 3 is a block diagram showing an example of a control system centered around a control unit 100 in the work vehicle (tractor) 1 according to the embodiment.

[0025] As shown in Fig. 3, in the tractor 1, the control unit 100 includes an engine ECU (Electronic Control Unit) 101, a travel system ECU 102, and a work machine system ECU 103. The engine ECU 101 controls the rotation speed of the engine E. The travel system ECU 102 controls the transmission 61 to control the travel speed of the tractor 1. The travel system ECU 102 also controls the steering device 62 to control the direction of the tractor 1. The work machine system ECU 103 controls the lifting device 63 to control the lifting and lowering of the work machine 30.

[0026] In addition, the control unit 100 (engine ECU 101, driving system ECU 102, and work machine system ECU 103) is capable of controlling each part through electronic control, and is equipped with a processing unit (not shown) having a CPU (Central Processing Unit) and the like, as well as a memory unit (not shown) consisting of, for example, a hard disk, ROM (Read Only Memory), RAM (Random Access Memory), etc., in which various programs and necessary data are stored.

[0027] Sensors such as an engine rotation speed sensor 51, a vehicle speed sensor 52, a gear change sensor 53, a steering sensor 54, an inclination sensor 55, a PTO rotation speed sensor 56, and an elevation sensor 57 are connected to the control unit 100. Switches such as a change-over switch 58 are also connected to the control unit 100. Also connected to the control unit 100 are an engine E, a transmission 61, a steering device 62, an elevation device 63, a communication device 64, and the like.

[0028] The engine rotation speed sensor 51 detects the rotation speed of the engine E. The vehicle speed sensor 52 detects the traveling speed (vehicle speed) of the tractor 1. The gear change sensor 53 detects which of a plurality of gear changes in the transmission 61 is in.

[0029] The steering sensor 54 detects the amount of operation D1 (see Figure 4) of the steering wheel 26. The tilt sensor 55 detects the rolling angle of the traveling body 2 (see Figures 1 and 2) of the tractor 1. That is, the tilt sensor 55 detects the left-right tilt of the traveling body 2. The PTO rotation speed sensor 56 detects the rotation speed of the PTO shaft. The lift sensor 57 detects the lift position of the lifting device 63. That is, the lift sensor 57 detects the height of the work implement 3 (the vertical position of the work implement 3).

[0030] The control unit 100 receives inputs of position information (current own position) of the tractor 1 in the field from the positioning device 40, the rotation speed of the engine E from the engine rotation speed sensor 51, the running speed of the tractor 1 from the vehicle speed sensor 52, the current gear position from the gear change sensor 53, the operation amount of the steering wheel 26 from the steering sensor 54, the rolling angle of the traveling body 2 from the inclination sensor 55, the rotation speed of the PTO shaft from the PTO rotation speed sensor 56, and the lifting position of the lifting device 63 from the lifting sensor 57.

[0031] In addition, a direction sensor (not shown) that detects the direction of the tractor 1 is connected to the control unit 100. The direction sensor detects, for example, the absolute direction angle of the traveling direction of the tractor 1 (for example, "north" is 0° (360°), "east" is 90°, "south" is 180°, and "west" is 270°). The direction sensor detects the absolute direction angle at regular intervals and outputs the detected absolute direction angle to the control unit 100.

[0032] The selector switch 58 is a switch for selectively switching the tractor 1 between a non-working mode for traveling on roads and a working mode for working in a field. The control unit 100 switches the tractor 1 between the non-working mode and the working mode in response to the operation of the selector switch 58.

[0033] In the control unit 100, the engine ECU 101 is connected to the engine E, the travel system ECU 102 is connected to the transmission 61 and the steering system 62, and the work machine system ECU 103 is connected to the lifting device 63. The work machine system ECU 103 raises and lowers the work machine 3 via the lifting device 63.

[0034] Here, the control unit 100 controls the steering device 62 in accordance with the detection value of the steering sensor 54 (the amount of operation of the steering wheel 26) so that the driver can easily drive the tractor 1, for example, when turning the tractor 1. That is, the control unit 10 controls the direction and steering of the front wheels 21 (see FIGS. 1 and 2), which are the steered wheels, via the steering device 62 in accordance with the detection value of the steering sensor 54.

[0035] <Steering control for work vehicles> Next, the steering control in the work vehicle 1 according to the embodiment is explained with reference to Figures 4 to 6. Figure 4 is an explanatory diagram of a steering control system in the work vehicle (tractor) 1 according to the embodiment. Figures 5 and 6 are explanatory diagrams of the steering control in the work vehicle (tractor) 1 according to the embodiment.

[0036] As shown in Figure 4, the steering control system of the tractor 1 (see Figures 1 and 2) is a control system centered around the travel system ECU 102. The steering configuration of the tractor 1 is a so-called steer-by-wire configuration that enables highly accurate control by electrically connecting the steering wheel 26 and the front wheels 21, which are the steered wheels. In the steer-by-wire configuration, the front wheels 21, which are the steered wheels, are electronically controlled by the travel system ECU 102.

[0037] In the steering configuration of the tractor 1, the steering sensor 54, the steering solenoid 62a, and the front wheel steering sensor 59 are connected to the traveling system ECU 102. As described above, the steering sensor 54 detects the operation amount D1 of the steering wheel 26. The steering sensor 54 is, for example, a potentiometer. The steering sensor 54 outputs, as a detected value, a voltage value proportional to the operation amount D1 of the steering wheel 26 to the traveling system ECU 102.

[0038] The steering solenoid 62a is an electromagnetic proportional flow control valve, and controls the steering device 62 (the operation amount D2 of the actuator 621) under the control of the traveling system ECU 102. The front wheel steering sensor 59 detects the steering amount D3 (see FIG. 6) of the front wheels 21, which are steered wheels.

[0039] Also connected to the traveling system ECU 102 is an elevation sensor 57 that detects the elevation position of the elevation device 63 (see FIG. 3) to detect the height of the work implement 3 (see FIGS. 1 and 2). Also connected to the traveling system ECU 102 is a positioning device 40 that receives radio waves from a navigation satellite S to acquire position information of the tractor 1 (its current position).

[0040] The travel system ECU 102 determines whether the lift position of the lift device 63 detected by the lift sensor 57 is at a predetermined position P O (see FIG. 1), the lifting position of the lifting device 63 reaches the predetermined position P O The steering ratio of the front wheels 21 by the steering device 62 to the detection value of the steering sensor 54 (in other words, the ratio of the amount of change in the steering angle (also called the turning angle) of the front wheels 21 to the amount of operation D1 of the steering wheel 26) is controlled to be larger than when the lifting position of the lifting device 63 is less than the predetermined position P O If it is less than the predetermined reference value.

[0041] That is, when the work implement 3 is raised to turn the tractor 1, the traveling system ECU 102 increases the steering ratio of the front wheels 21 by the steering device 62. In this case, the steering ratio of the front wheels 21 is set within a range in which the driver does not need to change hands when operating (steering) the steering wheel 26. This allows the driver to turn the tractor 1 with a small operation amount D1 of the steering wheel 26.

[0042] In addition, the soil surface F S Since the surface of the vehicle (see FIGS. 1 and 2) has unevenness, the traveling body 2 (see FIGS. 1 and 2) of the tractor 1 is prone to rolling. In other words, the traveling body 2 is prone to tilting in the left and right directions. For this reason, an inclination sensor 55 that detects the rolling angle (left and right tilt) of the traveling body 2 is connected to the traveling system ECU 102.

[0043] The running system ECU 102 performs control to increase the steering ratio of the front wheels 21 as described above according to the detection value of the inclination sensor 55. Specifically, when the running vehicle body 2 is inclined downward to the left, the running system ECU 102 increases the steering ratio in the right direction of the front wheels 21 with respect to the steering ratio in the left direction. When the running vehicle body 2 is inclined in a posture of being inclined downward to the left (upward to the right), the higher right-side steering is less effective, and the lower left-side steering is more effective. Therefore, by increasing the steering ratio of the higher right-side front wheels 21, the left and right steering sensations can be made closer.

[0044] Also, when the running vehicle body 2 is inclined downward to the right, the running system ECU 102 increases the steering ratio in the left direction of the front wheels 21 with respect to the steering ratio in the right direction. When the running vehicle body 2 is inclined in a posture of being inclined downward to the right (upward to the left), the higher left-side steering is less effective, and the lower right-side steering is more effective. Therefore, by increasing the steering ratio of the higher left-side front wheels 21, the left and right steering sensations can be made closer.

[0045] Also, when the running system ECU 102 increases the steering ratio of the front wheels 21, as shown in FIG. 5, for example, when the running vehicle body 2 is inclined downward to the left and the steering wheel 26 is operated to turn to the right, control is performed such that the steering angle r1 of the steering wheel 26 is smaller than the steering angle r2 of the front wheels 21. That is, control is performed so that "r1 < r2". Thereby, the straight-ahead performance is improved. In this case, the "r1 < r2" control is adjusted according to the inclination of the running vehicle body 2 in the left-right direction.

[0046] Normally, in a tractor, when the steering wheel 26 makes a maximum rotation (for example, two rotations), the front wheels 21, which are the steering wheels, reach the maximum steering angle. That is, the steering angle of the front wheels 21 is evenly divided with respect to the steering angle of the steering wheel 26. For this reason, in the above relationship between the steering angle r1 of the steering wheel 26 and the steering angle r2 of the front wheels 21, for the sake of convenience of explanation, the magnitude relationship between the steering angle of the steering wheel 26 and the steering angle of the front wheels 21 evenly divided with respect to the steering angle of the steering wheel 26 is shown as "r1 < r2".

[0047] Also, during straight-ahead operation, in order to reduce unintentional turning due to an incorrect operation of the steering wheel 26, "r1 < r2" control is performed. As a result, the straight-ahead performance is improved.

[0048] Also, during turning, the positioning device 40 may be used to detect the point A where the single brake is depressed for starting the turn and the point B where the single brake is released for ending the turn, and the "r1 < r2" control may be terminated. As a result, the turning can be performed by reducing the operation amount D1 of the steering wheel 26.

[0049] Note that sensors for detecting the single brake are provided on the left and right brakes. Also, when the single brake is depressed, the steering angle r2 of the front wheels 21 with respect to the operation amount D1 (steering angle r1) of the steering wheel 26 on the depressed side increases, and the steering angle r2 of the front wheels 21 with respect to the operation amount D1 (steering angle r1) of the steering wheel 26 on the side opposite to the depressed side does not change.

[0050] Also, when the single brake is depressed significantly, it may be controlled to perform a turn without operating the steering wheel 26. Also, when the working machine 3 is a plow, since straight-ahead performance is required, the steering angle r2 of the front wheels 21 may be reduced with respect to the operation of the steering wheel 26.

[0051] Also, during turning, the "r1 < r2" control may be started when the turn signal is turned on in the field, and the "r1 < r2" control may be terminated when the turn signal is turned off after the turn is completed. Also, during turning, the "r1 < r2" control may be started when the working machine 3 is lifted in the field. Also, by mapping the field using the positioning device 40, the ridges are detected and the turning points are calculated, and during turning, the "r1 < r2" control may be gradually started as the turning point is approached, and the "r1 < r2" control may be gradually terminated as the turning point is left.

[0052] As shown in FIG. 4, the travel system ECU 102 is connected to a changeover switch 58 for selectively switching the tractor 1 between a non-work mode and a work mode.

[0053] The traveling system ECU 102 detects that the work mode is selected by the selector switch 58 and the elevation position of the elevation device 63 (see FIG. 3) detected by the elevation sensor 57 is at a predetermined position P O (see FIG. 1), the steering ratio of the front wheels 21 by the steering device 62 is set to a larger value relative to the detection value of the steering sensor 54 than when the non-working mode is selected by the selector switch 58.

[0054] Further, the traveling system ECU 102 detects that the work mode is selected by the changeover switch 58 and the lifting position of the lifting device detected by the lifting sensor 57 is at the predetermined position P O When the vehicle is descending below this level, the steering ratio of the front wheels 21 by the steering device 62 relative to the detection value of the steering sensor 54 is set smaller than when the non-working mode is selected by the changeover switch 58.

[0055] That is, as shown in FIG. 6(a), when the tractor 1 turns during execution of the work mode, the traveling system ECU 102 increases the ratio of the steering amount D3 of the front wheels 21 (which is also the steering angle r2) to the operation amount D1 of the steering wheel 26.

[0056] In this way, when turning with the work implement 3 raised, the steering device 62 steers the front wheels 21 to a large degree with a small amount of operation D1 of the steering wheel 26, allowing the tractor 1 to turn appropriately.

[0057] On the other hand, when working with the work implement 3 lowered, if the steering device 62 steers the front wheels 21 too much, it could impair straight-line running during work or damage the work implement 3, so the steering ratio of the front wheels 21 is reduced to intentionally slow down the response of the front wheels 21 to the operation of the steering wheel 26. This improves straight-line running during work, allowing the tractor 1 to travel appropriately.

[0058] Furthermore, when the tractor 1 is traveling straight while the work mode is being executed, the travel-system ECU 102 reduces the ratio of the steering amount D3 of the front wheels 21 to the operation amount D1 of the steering wheel 26. In this case, when the tractor 1 is turning, the travel-system ECU 102 controls the steering amount (steering angle) D3 of the front wheels 21, but as shown in FIG. 6(b), when the work mode is being executed and straight-line assist (automatic straight-line control) is being executed while the tractor 1 is traveling straight, the travel-system ECU 102 controls the predetermined travel path R to be shifted to the left or right. In this way, when the work mode is being executed and straight-line assist (automatic straight-line control) is being executed while the tractor 1 is traveling straight, the travel path R is the control object. This allows the tractor 1 to be driven by intuitive operations while straight-line assist is being executed.

[0059] In addition, the straight-line assist and manual driving can coexist. Furthermore, when the tractor 1 is driving autonomously, a dedicated operation unit for correcting the driving route R is not required, which prevents the operation unit from becoming complicated.

[0060] Furthermore, when ridge painting is performed by the tractor 1, the tractor 1 is controlled to continue moving closer to the ridge. In this ridge painting mode, even if the steering wheel 26 is operated to move straight ahead, the front wheels 21 are controlled so that the tractor 1 moves closer to the ridge. In this case, sensors capable of detecting the distance to the ridge are provided on the left and right sides of the traveling body 2 of the tractor 1, and the steering angle of the front wheels 21 is automatically controlled based on the detection results of the sensors.

[0061] Furthermore, as described above, since the tractor 1 has a steer-by-wire configuration and the steering wheel 26 and the front wheels 21 are not mechanically connected, there are no restrictions on the position where the steering wheel 26 can be installed. This means that the steering wheel 26 can also be installed so that the driver faces the rear of the tractor 1. By installing the steering wheel 26 so that the driver faces the rear of the tractor 1 in this way, the driver can drive the tractor 1 with the rear facing forward, and by using the lifting device 63 (see FIG. 3), for example, the tractor 1 can function as a forklift.

[0062] The above-described embodiment realizes the following work vehicle 1.

[0063] (1) A vehicle includes a traveling vehicle body 2 having steering wheels 21, a steering wheel 26 operated by a driver, a steering sensor 54 detecting an operation amount D1 of the steering wheel 26, a steering device 62 for steering the steering wheels 21, a control unit 100 (102) for controlling the steering device 62 in accordance with a detection value of the steering sensor 54, a working implement 3 attached to the traveling vehicle body 2, a lifting device 63 for raising and lowering the working implement 3, and a lifting sensor 57 for detecting a lifting position of the lifting device 63, and the control unit 100 (102) detects whether the lifting position of the lifting device 63 detected by the lifting sensor 57 is a predetermined position P O When the lifting position of the lifting device 63 reaches the predetermined position P O The steering ratio of the steered wheels 21 by the steering device 62 relative to the detection value of the steering sensor 54 is made larger than when the steering ratio is less than the case where ...

[0064] According to this type of work vehicle 1, because the work implement 3 is raised when the work vehicle 1 turns, the control unit 100 (102) determines that the work vehicle 1 will turn due to the raising of the work implement 3, and increases the steering ratio of the steered wheels 21 by the steering device 62 when the work vehicle 1 turns. This allows the driver to turn the work vehicle 1 with a small operation amount D1 of the steering wheel 26. In this way, when the work vehicle 1 turns, the steering ratio of the steered wheels 21 relative to the operation amount D1 of the steering wheel 26 is advantageous for turning, making work driving easier. Furthermore, when the work vehicle 1 turns, the steering ratio of the steered wheels 21 relative to the operation amount D1 of the steering wheel 26 is automatically changed to be advantageous for turning, eliminating the need for unnecessary manual operation such as changing the steering ratio of the steered wheels 21. This makes work driving easier.

[0065] (2) In the above (1), the work vehicle 1 is provided with an inclination sensor 55 that detects the rolling angle of the traveling body 2, and the control unit 100 (102) increases the steering ratio of the steering wheels 21 to the right relative to the steering ratio to the left when the traveling body 2 is tilted downward to the left, depending on the detection value of the inclination sensor 55, and increases the steering ratio of the steering wheels 21 to the left relative to the steering ratio to the right when the traveling body 2 is tilted downward to the right.

[0066] In addition to the effect (1) above, with this type of work vehicle 1, when the traveling body 2 is tilted to the left or right, steering on the higher side of the left or right becomes less effective, while steering on the lower side becomes more effective. Therefore, by increasing the steering ratio of the steering wheel 21 on the higher side, it is possible to make the left and right steering feel closer. This makes work driving easier.

[0067] (3) In the above (1) or (2), a changeover switch 58 is provided for selectively switching between a non-working mode in which the working implement 3 is in a raised state and a working mode in which the working implement 3 is raised and lowered, and the control unit 100 (102) detects that the work mode is selected by the changeover switch 58 and that the lifting position of the lifting device 63 detected by the lifting sensor 57 is at a predetermined position P OIf the lift position of the lift device 63 detected by the lift sensor 57 is higher than the predetermined position P, the steering ratio of the steering wheels 21 is set to be larger than when the non-work mode is selected by the changeover switch 58. O When the vehicle is descending below this level, the steering ratio of the steering wheels is set to a smaller value than when the non-work mode is selected by the selector switch.

[0068] In addition to the effects (1) or (2) above, such a work vehicle 1 has the advantage that, when turning with the work implement 3 raised during work, the steering device 62 steers the steered wheels 21 by a large amount with a small operation amount D1 of the steering wheel 26, allowing the work vehicle 1 to turn appropriately. On the other hand, when working with the work implement 3 lowered, if the steering device 62 steers the steered wheels 21 by a large amount, straight-line running ability during work may be impaired or the work implement 3 may be damaged, so the steering ratio of the steered wheels 21 is made small to intentionally slow the response of the steered wheels 21 to the operation of the steering wheel 26. This improves straight-line running ability during work, allowing the work vehicle 1 to travel appropriately.

[0069] Further advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. [Explanation of symbols]

[0070] 1. Work vehicle (tractor) 2 Running vehicle 3 Work equipment 21 Steering wheels (front wheels) 26 Steering wheel 54 Steering sensor 55 Inclination sensor 57 Lift sensor 58 Changeover switch 62 Steering device 63 Lifting device 100 control section P O predetermined position

Claims

1. a traveling vehicle body having steering wheels; A steering wheel operated by a driver; a steering sensor for detecting an operation amount of the steering wheel; a steering device that steers the steering wheels; a control unit that controls the steering device in accordance with a detection value of the steering sensor; a work machine attached to the traveling vehicle body; a lifting device that lifts and lowers the work machine; a lifting sensor for detecting the lifting position of the lifting device; Equipped with The control unit When the elevation position of the elevator device detected by the elevation sensor rises to a predetermined position or higher, the steering ratio of the steering wheel by the steering device relative to the detection value of the steering sensor is made larger than when the elevation position of the elevator device is less than the predetermined position. A work vehicle characterized by:

2. An inclination sensor for detecting the rolling angle of the traveling vehicle body Equipped with The control unit According to the detected value of the tilt sensor, if the traveling vehicle body is tilted downward to the left, the steering ratio in the right direction of the steering wheels is made larger than the steering ratio in the left direction, and if the traveling vehicle body is tilted downward to the right, the steering ratio in the left direction of the steering wheels is made larger than the steering ratio in the right direction.

2. The work vehicle according to claim 1.

3. A changeover switch for selectively switching between a non-working mode in which the working machine is raised and a working mode in which the working machine is raised and lowered. Equipped with The control unit When the work mode is selected by the selector switch and the elevation position of the lifting device detected by the elevation sensor is elevated to or above a predetermined position, the steering ratio of the steering wheels is set to be larger than when the non-work mode is selected by the selector switch, When the work mode is selected by the changeover switch and the lift position of the lifting device detected by the lift sensor is lowered below a predetermined position, the steering ratio of the steering wheels is set to be smaller than when the non-work mode is selected by the changeover switch.

3. The work vehicle according to claim 1 or 2.

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