JP5995281B2 - Drive control mechanism for work vehicle - Google Patents

Description

  The present invention relates to a technique for a drive control mechanism for a work vehicle, and more particularly to a technique for a drive control mechanism for a work vehicle that automatically switches the work vehicle from a two-wheel drive state to a four-wheel drive state according to the situation.

  2. Description of the Related Art Conventionally, a technique for a drive control mechanism for a work vehicle that automatically switches the work vehicle from a two-wheel drive state to a four-wheel drive state according to the situation has been known. For example, as described in Patent Document 1.

  In the technique described in Patent Document 1, when the slip ratio calculated from the rotational speeds of the left and right rear wheels becomes a predetermined value or more, the work vehicle can be automatically switched from the two-wheel drive state to the four-wheel drive state. Is possible. By comprising in this way, the slip of a work vehicle can be eliminated (slip rate is improved) and the driving force (traction) with respect to the grounding surface of the work vehicle can be improved.

  However, since the technique described in Patent Document 1 switches the work vehicle from the two-wheel drive state to the four-wheel drive state for the first time when a certain degree of slip occurs, it is difficult to quickly improve the driving force with respect to the ground plane. It was disadvantageous in that.

Japanese Patent Laid-Open No. 10-114229

  The present invention has been made in view of the above situation, and the problem to be solved is to improve the driving force quickly when it is desirable to improve the driving force against the ground contact surface of the work vehicle. It is to provide a drive control mechanism for a possible work vehicle.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

That is, in claim 1, drive switching means for switching between a four-wheel drive state in which driving force is transmitted to the front wheels and rear wheels of a work vehicle and a two-wheel drive state in which driving force is transmitted only to the rear wheels, A state detecting means for detecting a state in which it is desirable to improve the driving force with respect to the ground contact surface of the work vehicle; and a first detecting device for automatically switching the work vehicle to a four-wheel drive state when it is desired to improve the driving force. Control means for performing four-wheel drive switching control, and further comprising actual travel speed detection means for detecting the actual travel speed of the work vehicle, wherein the control means has a predetermined actual travel speed of the work vehicle. If equal to or greater than the value, the first in preference to the four-wheel drive switching control, the working vehicle have rows automatically switching two-wheel drive switching control to two-wheel drive state, the status detection module, the work vehicle En Target rotational speed detection means for detecting the target rotational speed of the engine, and actual rotational speed detection means for detecting the actual rotational speed of the engine, wherein the control means is configured so that the actual rotational speed of the engine is the target rotational speed. A second four-wheel drive switching control for automatically switching the work vehicle to a four-wheel drive state is performed in preference to the two-wheel drive switching control when the rotational speed becomes greater than a predetermined value. .

According to a second aspect of the present invention, the state detection means includes start detection means for detecting start of the work vehicle, and the control means performs the first four-wheel drive switching control immediately after the work vehicle starts. Is what you do .

According to a third aspect of the present invention, the state detecting unit includes a shift operation detecting unit that detects that the shift mechanism of the work vehicle has been shifted, and the control unit is configured to perform a shift operation of the shift mechanism. The first four-wheel drive switching control is performed .

According to a fourth aspect of the present invention, the state detection means includes engine operation detection means for detecting that the target rotation speed of the engine of the work vehicle has been changed, and the control means has the target rotation speed changed. In this case, the first four-wheel drive switching control is performed .

According to a fifth aspect of the present invention, the state detection means includes a slip ratio detection means for detecting a slip ratio of a wheel with respect to the ground contact surface , and an inclination angle detection means for detecting an inclination angle of the work vehicle in a forward upward direction with respect to a horizontal direction. When the slip ratio exceeds a threshold value, the control means stores the tilt angle when the slip ratio exceeds the threshold value as a stored value, and the first four-wheel drive switching control. When the work vehicle is automatically switched to the four-wheel drive state, the slip ratio decreases below the threshold value, and the tilt angle decreases below a predetermined angle less than the stored value. The two-wheel drive switching control is performed .

  As effects of the present invention, the following effects can be obtained.

According to the first aspect of the present invention, it is possible to suppress the occurrence of slipping of the work vehicle when it is desired to improve the drive force with respect to the ground plane of the work vehicle, and to quickly improve the drive force of the work vehicle. Further, when the work vehicle is traveling at a high speed, the steering operation can be easily performed as compared with the four-wheel drive state by automatically switching the work vehicle to the two-wheel drive state. In addition, it is possible to improve the driving force of the work vehicle when the actual rotational speed of the engine is larger than the target rotational speed by a predetermined value or more (so-called engine follow-up occurs).

  According to the second aspect of the present invention, it is possible to suppress the occurrence of slipping of the work vehicle immediately after the work vehicle is started, and to improve the driving force of the work vehicle.

  According to the third aspect of the present invention, it is possible to suppress the occurrence of slipping of the work vehicle when the speed change mechanism of the work vehicle is operated to improve the driving force of the work vehicle.

  According to the fourth aspect of the present invention, it is possible to suppress the occurrence of slip of the work vehicle when the target rotational speed of the engine of the work vehicle is changed, and to improve the driving force of the work vehicle.

In claim 5, even if the work vehicle is inclined, the slip can be appropriately eliminated .

FIG. 2 is a schematic plan view showing a configuration of a tractor and a drive control mechanism. The block diagram which showed the structure of the drive control mechanism. The flowchart which showed the 1st control aspect. The time chart which showed the specific example of the 1st control aspect. The side surface schematic diagram which showed the mode of the tractor in a 1st control aspect. The flowchart which showed the modification of the 1st control aspect. The flowchart which showed the 2nd control aspect. The flowchart which showed the modification of the 2nd control aspect.

  Below, the whole structure of the tractor 1 which comprises the drive control mechanism 10 which concerns on one Embodiment of the drive control mechanism of the working vehicle which concerns on this invention using FIG. 1 is demonstrated.

  In the present embodiment, the tractor 1 is illustrated as a work vehicle including the drive control mechanism 10, but the present invention is not limited to this. In other words, the work vehicle including the drive control mechanism 10 may be other agricultural vehicles, construction vehicles, industrial vehicles, or the like.

  The tractor 1 mainly includes front wheels 2 and 2, rear wheels 3 and 3, an engine 4, a transmission mechanism 5, a driving operation unit 6, a cabin 7, and a drive control mechanism 10.

  The front part of the vehicle body of the tractor 1 is supported by a pair of left and right wheels (front wheels 2 and 2) via a front axle. The rear portion of the vehicle body is supported by a pair of left and right wheels (rear wheels 3 and 3) via a rear axle. An engine 4 is provided at the front of the vehicle body. A transmission mechanism 5 (transmission) is provided at the rear of the vehicle body.

  The power of the engine 4 can be transmitted to the front wheels 2 and 2 through the front axle after being shifted by the transmission mechanism 5 and can be transmitted to the rear wheels 3 and 3 through the rear axle. The front wheels 2 and 2 and the rear wheels 3 and 3 are rotationally driven by the power of the engine 4 so that the tractor 1 travels.

  A driving operation unit 6 for an operator to ride and operate the tractor 1 is provided from the middle part of the vehicle body of the tractor 1 to the rear part. The driving operation unit 6 is provided with a steering wheel 6a, a seat (not shown) and the like for an operator to perform a steering operation of the tractor 1. The driving operation unit 6 is covered with a cabin 7.

  Each part of the tractor 1 is provided with each member constituting the drive control mechanism 10.

  Below, the structure of the drive control mechanism 10 is demonstrated using FIG.1 and FIG.2.

  The drive control mechanism 10 appropriately switches the tractor 1 to a two-wheel drive state (a state in which only the rear wheels 3 and 3 are rotationally driven) or a four-wheel drive state (a state in which the front wheels 2 and 2 and the rear wheels 3 and 3 are rotationally driven). Is.

  The drive control mechanism 10 mainly includes an accelerator sensor 12, a shift position detection sensor 14, a brake switch 16, a front wheel turning angle switch 18, a drive change switch 20, a double speed change switch 21, a mode change switch 22, a threshold setting dial 24, an axle rotation sensor. 26, inclination sensor 28, GPS receiver 30, variable speed electromagnetic valve 32, four-wheel drive electromagnetic valve 34, double speed electromagnetic valve 35, slip notification buzzer 36, GPS non-reception notification lamp 38, crank position sensor 40, engine ECU 42, and this machine An ECU 44 is provided.

  The accelerator sensor 12 detects an operation position of an accelerator operating tool (an accelerator pedal, an accelerator lever, or the like) for changing the target value (target rotational speed) of the rotational speed of the engine 4. The accelerator operating tool is provided at a position where the operator of the driving operation unit 6 can operate. The accelerator sensor 12 is provided at a position where the operation position of the accelerator operation tool can be detected (for example, a rotation base end portion of the accelerator operation tool).

  When a plurality of accelerator operation tools are provided, a plurality of accelerator sensors 12 are provided corresponding to the plurality of accelerator operation tools, respectively.

  In this embodiment, the accelerator sensor 12 is used as a state detection means, an engine operation detection means, and a target rotation speed detection means.

  The shift position detection sensor 14 detects an operation position of a shift operation tool (a main shift lever, a sub shift lever, etc.) for shifting the speed change mechanism 5. The shift operation tool is provided at a position where the operator of the driving operation unit 6 can operate. The shift position detection sensor 14 is provided at a position where the operation position of the shift operation tool can be detected (for example, the rotation base end portion of the shift operation tool).

  When a plurality of shift operation tools are provided, a plurality of shift position detection sensors 14 are provided corresponding to the plurality of shift operation tools, respectively.

  In the present embodiment, the shift position detection sensor 14 is used as the state detection unit and the shift operation detection unit.

  The brake switch 16 detects whether or not a brake operation tool (brake pedal, parking brake lever, etc.) for braking the tractor 1 has been operated. The braking operation tool is provided at a position where the operator of the driving operation unit 6 can operate. The brake switch 16 is provided at a position where it is possible to detect whether or not the brake operation tool has been operated (for example, the rotation base end portion of the brake operation tool).

  When a plurality of braking operation tools are provided, a plurality of brake switches 16 are provided corresponding to the plurality of braking operation tools, respectively.

  The front wheel turning angle switch 18 detects whether or not the turning angle of the front wheels 2 and 2 has exceeded a predetermined value. The front wheel turning angle switch 18 is provided in the vicinity of the front wheel 2 of the front axle (in the present embodiment, the left front wheel 2).

  In the present embodiment, the front wheel turn angle switch 18 is used as the front wheel turn angle detection means.

  The drive changeover switch 20 is an operating tool for manually switching the tractor 1 to a four-wheel drive state or a two-wheel drive state. The drive changeover switch 20 is provided at a position where the operator of the driving operation unit 6 can operate.

  The double speed changeover switch 21 is an operating tool for permitting or prohibiting automatic switching of the tractor 1 to the double speed state in a predetermined case. The double speed changeover switch 21 is provided at a position where the operator of the driving operation unit 6 can operate.

  Here, the “double speed state” refers to a state in which the front wheels 2 and 2 of the tractor 1 are rotationally driven at a ground speed faster than the rear wheels 3 and 3. By switching the tractor 1 to the double speed state, it is possible to easily turn and to make it difficult to roughen the ground contact surface (farm field).

  The mode switch 22 is an operating tool for manually switching a control mode by the machine ECU 44 described later. The mode switch 22 is provided at a position where the operator of the driving operation unit 6 can operate.

  The threshold setting dial 24 is an operating tool for manually setting a threshold St of a slip ratio S described later. The threshold setting dial 24 is provided at a position where the operator of the driving operation unit 6 can operate.

  In the present embodiment, a threshold setting dial 24 is used as the threshold changing means.

  The axle rotation sensor 26 detects the driving speed in the power transmission path from the engine 4 to the driving wheels (in the present embodiment, the rear wheels 3 and 3 that are always driven to rotate). The axle rotation sensor 26 is provided on the axle that transmits power to the differential mechanism (diff) on the rear wheels 3 and 3 side of the tractor 1 and can detect the driving speed of the axle.

  In the present embodiment, the axle rotation sensor 26 detects the driving speed of the axle, but the present invention is not limited to this. In other words, the detection position of the axle rotation sensor 26 is not limited as long as it can detect the drive speed in the power transmission path to the drive wheels (rear wheels 3 and 3).

  In the present embodiment, the axle rotation sensor 26 is used as a slip ratio detection unit, a drive speed detection unit, a state detection unit, and a start detection unit.

  The inclination sensor 28 detects an inclination angle θ in the front-rear direction of the tractor 1 with respect to a horizontal plane. The inclination sensor 28 is provided at an appropriate position of the tractor 1.

  In the present embodiment, the tilt sensor 28 is used as the tilt angle detecting means.

  The GPS receiver 30 receives a signal from a GPS satellite and detects the current position of the tractor 1. The GPS receiver 30 is provided in the upper part of the cabin 7.

  In the present embodiment, the GPS receiver 30 is used as the slip ratio detecting means and the GPS receiving means.

  The speed change electromagnetic valve 32 controls the operation of a speed change hydraulic clutch provided in the speed change mechanism 5 and, as a result, shifts the speed change mechanism 5. The transmission electromagnetic valve 32 is provided in the vicinity of the transmission mechanism 5.

  Although one transmission electromagnetic valve 32 is shown in the drawing, a plurality of transmission electromagnetic valves 32 are actually provided corresponding to a plurality of hydraulic clutches provided in the transmission mechanism 5.

  The four-wheel drive electromagnetic valve 34 controls the operation of a front-wheel drive hydraulic clutch provided in the speed change mechanism 5 and, by extension, switches between a four-wheel drive state and a two-wheel drive state. The four-wheel drive electromagnetic valve 34 is provided in the vicinity of the speed change mechanism 5.

  In the present embodiment, a four-wheel drive electromagnetic valve 34 is used as the drive switching means.

  The double speed electromagnetic valve 35 controls the operation of a hydraulic clutch for double speed provided in the transmission mechanism 5 and, by extension, switches between a double speed state and other states (two-wheel drive state and four-wheel drive state). The double speed electromagnetic valve 35 is provided in the vicinity of the speed change mechanism 5.

  In the present embodiment, a double speed electromagnetic valve 35 is used as the double speed switching means.

  The slip notification buzzer 36 is a buzzer for notifying the operator when a slip rate S described later increases to a value close to the threshold value St. The slip notification buzzer 36 can emit a predetermined sound (warning sound). The slip notification buzzer 36 is provided in the driving operation unit 6.

  Instead of the slip notification buzzer 36, a notification lamp or a liquid crystal screen may be used to notify the operator.

  The GPS non-reception notification lamp 38 is a lamp (light emitting device) for notifying the operator of the fact when the GPS receiver 30 has not received a signal from a GPS satellite. The GPS non-reception notification buzzer can emit predetermined light. The GPS non-reception notification lamp 38 is provided in the driving operation unit 6.

  Instead of the GPS non-reception notification lamp 38, a notification buzzer or a liquid crystal screen may be used to notify the operator.

  The crank position sensor 40 detects the rotational position of the flywheel of the engine 4 and thus detects the actual rotational speed (actual rotational speed) of the engine 4. The crank position sensor 40 is provided in the vicinity of the engine 4 (more specifically, the flywheel of the engine 4).

  In the present embodiment, the crank position sensor 40 is used as the state detection means and the actual rotation speed detection means.

  The engine ECU 42 manages information on the common rail system of the engine 4 and controls the operation of each connected device. The engine ECU 42 is provided at the front portion of the vehicle body of the tractor 1. The engine ECU 42 includes a storage unit, an arithmetic processing unit, and the like. The engine ECU 42 stores a program for controlling the common rail system of the engine 4 and various data.

The engine ECU 42 is connected to the crank position sensor 40 and can receive information on the actual rotational speed of the engine 4.
The engine ECU 42 is connected to each part of the engine 4 (more specifically, a supply pump, rails, injectors, various sensors, etc. (not shown)), and can control the operation (rotation speed, etc.) of the engine 4.

  In addition, although the engine 4 which concerns on this embodiment shall be provided with a common rail system, this invention is applicable also to the work vehicle which has an engine which is not provided with the common rail system.

  This machine ECU44 manages the information of the drive control mechanism 10, and controls operation | movement of each connected apparatus. The machine ECU 44 is provided in the driving operation unit 6. The machine ECU 44 includes a storage unit, an arithmetic processing unit, and the like. The machine ECU 44 stores a program for controlling the drive control mechanism 10 and various data.

The machine ECU 44 is connected to the accelerator sensor 12 and can receive information about the operation position of the accelerator operating tool.
The machine ECU 44 is connected to the shift position detection sensor 14 and can receive information about the operation position of the shift operation tool.
The machine ECU 44 is connected to the brake switch 16 and can receive information on whether or not the braking operation tool has been operated.
This machine ECU 44 is connected to the front wheel turning angle switch 18 and can receive information about whether or not the turning angles of the front wheels 2 and 2 have reached a predetermined value or more.
This machine ECU 44 is connected to the drive changeover switch 20 and can receive information about the operation position of the drive changeover switch 20.
The machine ECU 44 is connected to the double speed changeover switch 21 and can receive information about the operation position of the double speed changeover switch 21.
The machine ECU 44 is connected to the mode change switch 22 and can receive information about the operation position of the mode change switch 22.
The machine ECU 44 is connected to the threshold setting dial 24 and can receive information about the operation position of the threshold setting dial 24.
This machine ECU 44 is connected to the axle rotation sensor 26 and can receive information on the driving speed in the power transmission path from the engine 4 to the driving wheels.
This machine ECU 44 is connected to the tilt sensor 28 and can receive information about the tilt angle θ of the tractor 1 in the front-rear direction.
This unit ECU 44 is connected to the GPS receiver 30 and can receive information about the current position of the tractor 1.

This machine ECU 44 is connected to the transmission electromagnetic valve 32 and can control the operation of the transmission electromagnetic valve 32.
This machine ECU 44 is connected to the four-wheel drive electromagnetic valve 34 and can control the operation of the four-wheel drive electromagnetic valve 34.
The machine ECU 44 is connected to the double speed electromagnetic valve 35 and can control the operation of the double speed electromagnetic valve 35.
The machine ECU 44 is connected to the slip notification buzzer 36 and can control the operation of the slip notification buzzer 36 (switching ON / OFF of warning sound).
This machine ECU 44 is connected to the GPS non-reception notification lamp 38 and can control the operation of the GPS non-reception notification lamp 38 (switching ON / OFF of light emission).

This machine ECU 44 is connected to the engine ECU 42 and can receive information about the actual rotational speed of the engine 4 via the engine ECU 42.
This machine ECU 44 is connected to the engine ECU 42, and can receive various information related to the engine 4 via the engine ECU 42.

In addition, this machine ECU44 can also be comprised not only by 1 body but by multiple bodies (main ECU, sub ECU, etc.).
Further, the main unit ECU 44 and the engine ECU 42 can be configured by a single ECU.

  In this embodiment, this machine ECU44 is used as a control means.

  Below, the control aspect of the drive control mechanism 10 comprised as mentioned above is demonstrated.

  The drive control mechanism 10 has a “fixed mode” and an “auto mode” as control modes for appropriately switching the tractor 1 to a two-wheel drive state or a four-wheel drive state. When the mode switch 22 is switched by the operator, the machine ECU 44 switches the control mode to either the fixed mode or the auto mode.

  Hereinafter, the fixed mode will be described first.

  The fixed mode is a mode in which the operator can arbitrarily switch the tractor 1 to the two-wheel drive state or the four-wheel drive state. In the fixed mode, the machine ECU 44 switches the tractor 1 to the two-wheel drive state or the four-wheel drive state based on the operation of the drive changeover switch 20.

  That is, when the operator operates the drive changeover switch 20 to select the two-wheel drive state, the machine ECU 44 controls the operation of the four-wheel drive electromagnetic valve 34 and releases the connection of the front-wheel drive hydraulic clutch. As a result, transmission of power to the front wheels 2 and 2 is cut off, and a two-wheel drive state in which only the rear wheels 3 and 3 are rotationally driven can be achieved.

  When the operator operates the drive changeover switch 20 to select the four-wheel drive state, the machine ECU 44 controls the operation of the four-wheel drive electromagnetic valve 34 and connects the front-wheel drive hydraulic clutch. As a result, power can be transmitted to the front wheels 2 and 2, and the front wheels 2 and 2 and the rear wheels 3 and 3 can be driven in a four-wheel drive state.

  Next, the auto mode will be described.

  The auto mode is a mode in which the machine ECU 44 automatically switches the tractor 1 to the two-wheel drive state or the four-wheel drive state regardless of the operation of the drive switch 20 by the operator.

  Hereinafter, one of the control modes (first control mode) by the machine ECU 44 in the auto mode will be described with reference to FIGS. 1 to 6.

  The first control mode is control for appropriately eliminating the slip (improving the slip ratio S) when the slip occurs during the traveling of the tractor 1.

  First, the flow of processing by the machine ECU 44 in the first control mode will be described mainly with reference to FIG.

  In step S101, the machine ECU 44 determines whether or not the slip rate S of the tractor 1 exceeds the threshold value St. Hereinafter, the process of step S101 will be described in detail.

  The slip ratio S is a value indicating how much the driving wheel of the tractor 1 slips with respect to a ground contact surface such as a farm field. The slip ratio S (%) is calculated based on the equation S = (Vi−Vp) / Vi × 100. Here, Vp is an actual traveling speed (actual traveling speed) of the tractor 1, and Vi is a theoretical traveling speed of the tractor 1.

  The actual traveling speed Vp is an actual traveling speed with respect to the ground contact surface of the tractor 1. The actual traveling speed Vp is calculated by the main unit ECU 44 based on a change in the position of the tractor 1. Specifically, this unit ECU 44 continuously receives information about the current position of the tractor 1 from the GPS receiver 30. This machine ECU44 calculates the speed (actual traveling speed Vp) of the said tractor 1 from the variation | change_quantity per unit time of the position of the said tractor 1. FIG.

  The theoretical travel speed Vi is the travel speed of the tractor 1 when the driving wheel does not slip with respect to the ground contact surface (theoretical). The theoretical travel speed Vi is calculated by the main unit ECU 44 based on the drive speed of the drive wheels of the tractor 1. Specifically, this machine ECU 44 receives information about the driving speed in the power transmission path from the axle rotation sensor 26 to the driving wheel. This machine ECU 44 calculates the drive speed of the drive wheels based on the drive speed and the reduction ratio of the power transmission path stored in advance. The machine ECU 44 calculates the theoretical travel speed Vi of the tractor 1 based on the drive speed of the drive wheel and the diameter of the drive wheel.

For example, when the tractor 1 is traveling without slipping with respect to the ground contact surface, the actual traveling speed Vp and the theoretical traveling speed Vi coincide (Vp = Vi), and the slip ratio S = 0 (%).
Further, when the driving wheel of the tractor 1 is completely idle with respect to the ground contact surface, the actual traveling speed Vp = 0, so that the slip ratio S = 100 (%).

  The threshold value St is a value of the slip ratio S that serves as a reference when the ECU 44 automatically switches the tractor 1 to the two-wheel drive state or the four-wheel drive state. The machine ECU 44 receives information about the operation position of the threshold setting dial 24. The machine ECU 44 sets the threshold value St based on information about the operation position of the threshold value setting dial 24. That is, the operator can arbitrarily set the threshold value St by operating the threshold value setting dial 24.

When the machine ECU 44 determines that the slip ratio S of the tractor 1 exceeds the threshold value St, the process proceeds to step S102.
When the machine ECU 44 determines that the slip rate S of the tractor 1 does not exceed the threshold value St, the process proceeds to step S107.

In step S102, the main unit ECU 44 stores the tilt angle θ in the front-rear direction of the tractor 1 when it is determined that the slip ratio S of the tractor 1 exceeds the threshold value St (step S101).
This machine ECU44 transfers to step S103, after performing the said process.

  In step S103, the machine ECU 44 automatically switches the tractor 1 to the four-wheel drive state. That is, in this case, the machine ECU 44 controls the operation of the four-wheel drive electromagnetic valve 34 and connects the front-wheel drive hydraulic clutch. As a result, power can be transmitted to the front wheels 2 and 2, and the front wheels 2 and 2 and the rear wheels 3 and 3 can be driven in a four-wheel drive state.

  If the tractor 1 is already in the four-wheel drive state at the time of the processing (step S103), the main unit ECU 44 maintains that state.

  This machine ECU44 transfers to step S104, after performing the said process (step S103).

In step S104, the machine ECU 44 determines whether or not the slip rate S of the tractor 1 is equal to or less than the threshold value St.
When the machine ECU 44 determines that the slip ratio S of the tractor 1 is equal to or less than the threshold value St, the process proceeds to step S105.
When the machine ECU 44 determines that the slip ratio S of the tractor 1 exceeds the threshold value St, the process of step S104 is performed again.

In step S105, this unit ECU 44 determines whether or not the tractor 1 is substantially horizontal in the front-rear direction. Specifically, this unit ECU 44 determines whether or not the inclination angle θ in the front-rear direction of the tractor 1 is a value close to 0 (°) (for example, −1 (°) ≦ θ ≦ 1 (°)). to decide.
When the tractor 1 determines that the tractor 1 is not substantially horizontal in the front-rear direction, the present ECU 44 proceeds to step S106.
When the tractor 1 determines that the tractor 1 is substantially horizontal in the front-rear direction, the present ECU 44 proceeds to step S107.

  In step S106, the main unit ECU 44 determines whether or not the inclination angle θ in the front-rear direction of the tractor 1 is equal to or smaller than a predetermined angle θt.

  Here, the predetermined angle θt is set to be an angle smaller than the inclination angle θ stored in step S102. Further, the predetermined angle θt is set to be a predetermined ratio with respect to the inclination angle θ stored in step S102. In the present embodiment, the predetermined angle θt is set to be a value of 50 (%) of the tilt angle θ stored in step S102. The predetermined ratio is set (stored) in the ECU ECU 44 in advance.

In addition, the predetermined ratio with respect to the above-described inclination angle θ is not limited to 50 (%). In addition, the predetermined ratio can be configured so that an operator can arbitrarily change it with an operation tool (such as a dial) provided in the tractor 1.
In addition, the predetermined angle θt is not a predetermined ratio with respect to the inclination angle θ, and can be set to a constant value.

When the machine ECU 44 determines that the front-rear inclination angle θ of the tractor 1 is equal to or smaller than the predetermined angle θt, the process proceeds to step S107.
When this machine ECU 44 determines that the front-rear inclination angle θ of the tractor 1 exceeds the predetermined angle θt, the process proceeds to step S104 again.

  In step S107, this unit ECU 44 automatically switches the tractor 1 to the two-wheel drive state. That is, in this case, the machine ECU 44 controls the operation of the four-wheel drive electromagnetic valve 34 and releases the connection of the hydraulic clutch for driving the front wheels. As a result, transmission of power to the front wheels 2 and 2 is cut off, and a two-wheel drive state in which only the rear wheels 3 and 3 are rotationally driven can be achieved.

  If the tractor 1 is already in the two-wheel drive state at the time of the processing (step S107), the main unit ECU 44 maintains that state.

  Next, a specific example of the first control mode will be described with reference to FIGS.

  FIG. 4 is a time chart showing how the driving state (two-wheel driving state or four-wheel driving state), slip ratio S, and inclination angle θ of the traveling tractor 1 change with time t.

  When the slip rate S exceeds the threshold value St at time t1 during travel of the tractor 1 (see step S101 in FIG. 3 and FIG. 5A), the ECU ECU 44 determines the inclination angle θ at that time (time t1). (In this embodiment, θ1 is stored) (see step S102 in FIG. 3). Moreover, this machine ECU44 switches the tractor 1 to a four-wheel drive state automatically (refer step S103 of FIG. 3, and FIG.5 (b)). Thereby, the slip rate of the tractor 1 can be improved (reduced), and the driving force with respect to the ground contact surface of the tractor 1 can be improved.

  The slip rate S of the tractor 1 decreases to the threshold value St or less immediately after switching to the four-wheel drive state (immediately after time t1) (see step S104 in FIG. 3). However, the tractor 1 is not substantially horizontal (see step S105 in FIG. 3), and the inclination angle θ is also a predetermined angle θt (in this embodiment, θ2 (= θ1 × 50 (%) / 100)) or less. It has not decreased (see step S106 in FIG. 3). For this reason, this machine ECU44 maintains the tractor 1 in a four-wheel drive state.

  When the inclination angle θ decreases to a predetermined angle θt (θ2) or less at time t2 (see step S106 in FIG. 3 and FIG. 5C), the ECU 44 automatically puts the tractor 1 into the two-wheel drive state. Switching (see step S107 in FIG. 3).

  In addition, when the slip ratio S again exceeds the threshold value St at time t3 (see step S101 in FIG. 3 and FIG. 5D), the machine ECU 44 determines the inclination angle θ at this time (time t3) (this implementation). In the embodiment, the inclination angle θ = 0) is stored (see step S102 in FIG. 3). Moreover, this machine ECU44 switches the tractor 1 to a four-wheel drive state automatically (refer step S103 of FIG. 3, and FIG.5 (e)). Thereby, the slip ratio of the tractor 1 can be improved and the driving force with respect to the ground contact surface of the tractor 1 can be improved.

  The slip rate S of the tractor 1 decreases to a threshold value St or less at time t4 after switching to the four-wheel drive state (see step S104 in FIG. 3). At that time (time t4), the tractor 1 is substantially horizontal (inclination angle θ = 0) (see step S105 in FIG. 3). Therefore, this machine ECU44 automatically switches the tractor 1 to a two-wheel drive state (refer step S107 of FIG. 3, and FIG.5 (f)).

  As described above, in the first control mode, the machine ECU 44 switches the tractor 1 to the four-wheel drive state only when the slip ratio S of the tractor 1 exceeds the threshold value St (step S101 in FIG. 3) (FIG. 3 step S103). That is, this unit ECU 44 puts the tractor 1 into a two-wheel drive state except when the slip rate S of the tractor 1 becomes high (step S101 and step S107 in FIG. 3).

As a result, the tractor 1 can be driven as much as possible in a two-wheel drive state, and fuel efficiency can be improved.
In general, the front wheels 2 and 2 rotate faster than the rear wheels 3 and 3 in the four-wheel drive state. For this reason, when the tractor 1 travels through the farm field in a four-wheel drive state, the surface of the farm field is roughened. Therefore, it is possible to suppress the surface of the field from being roughened by causing the tractor 1 to travel as much as possible in a two-wheel drive state.
Further, when the tractor 1 travels on a paved road or the like in a four-wheel drive state, the front wheels 2 and 2 and the rear wheels 3 and 3 are easily worn due to a rotational difference between the front wheels 2 and 2 and the rear wheels 3 and 3. . Therefore, by causing the tractor 1 to travel as much as possible in the two-wheel drive state, wear of the front wheels 2 and 2 and the rear wheels 3 and 3 can be suppressed.

  In addition, the ECU 44 not only reduces the slip ratio S of the tractor 1 to a threshold St or less (step S104 in FIG. 3), but further decreases the inclination angle θ to a predetermined angle θt or less (step S106 in FIG. 3). Or when the tractor 1 is substantially horizontal (step S105 in FIG. 3), the tractor 1 is returned to the two-wheel drive state for the first time (step S107 in FIG. 3).

  Thus, this machine ECU44 returns the said tractor 1 to the two-wheel drive state in the state which inclination-angle (theta) of the tractor 1 became loose. As a result, it is possible to prevent the slip ratio S from exceeding the threshold St again at the moment when the tractor 1 returns to the two-wheel drive state, and to immediately switch to the four-wheel drive state. It is possible to prevent a state in which the state is switched alternately and endlessly.

  Further, when the slip rate S exceeds the threshold St when the tractor 1 is substantially horizontal (step S101 in FIG. 3), a predetermined ratio is obtained with respect to the inclination angle θ (a value close to 0 (°)). It is difficult for the tilt sensor 28 to detect a predetermined angle θt (in this embodiment, an additional 50 (%) close to 0 (°) in this embodiment). That is, it is difficult to detect that the inclination angle θ is reduced to a predetermined angle θt or less (step S106 in FIG. 3), which is a condition for returning the tractor 1 to the two-wheel drive state. However, even when the tractor 1 is substantially horizontal (step S105 in FIG. 3), the tractor 1 is appropriately brought into the two-wheel drive state by adopting a configuration in which the tractor 1 is returned to the two-wheel drive state (step S107 in FIG. 3). Can be returned.

As described above, the drive control mechanism 10 of the tractor 1 (work vehicle) according to the present embodiment is
A four-wheel drive electromagnetic valve 34 for switching between a four-wheel drive state in which drive force is transmitted to the front wheels 2 and 2 and the rear wheels 3 and 3 of the tractor 1 and a two-wheel drive state in which drive force is transmitted only to the rear wheels 3 and 3. (Drive switching means);
Slip ratio detecting means for detecting a slip ratio S of the wheel with respect to the ground contact surface;
An inclination sensor 28 (inclination angle detection means) for detecting the inclination angle θ of the tractor 1 in the front-rear direction;
When the slip rate S exceeds the threshold value St while detecting the inclination angle θ, the tractor 1 is automatically switched to the four-wheel drive state,
In a state where the tractor 1 is automatically switched to the four-wheel drive state, the slip ratio S decreases (below the threshold St) and the inclination angle θ (when the tractor 1 is automatically switched to the four-wheel drive state) The main unit ECU 44 (control means) that automatically switches the tractor 1 to the two-wheel drive state,
It comprises.

By comprising in this way, even if the tractor 1 inclines, a slip can be eliminated appropriately.
That is, it is possible to prevent the slip ratio S from exceeding the threshold value St again by returning the tractor 1 to the two-wheel drive state for the first time when not only the slip ratio S decreases but also the inclination angle θ decreases. . As a result, it is possible to prevent the tractor 1 from being switched between the two-wheel drive state and the four-wheel drive state in an alternating manner.

In addition, this ECU 44
When the inclination angle θ decreases to a predetermined ratio (50 (%) in the present embodiment) or less with respect to the inclination angle θ when the tractor 1 is automatically switched to the four-wheel drive state, the tractor 1 Is automatically switched to the two-wheel drive state.

With this configuration, the predetermined angle θt is determined according to the state of the ground contact surface when the slip rate S exceeds the threshold value St, so that the slip can be more appropriately eliminated.
That is, as compared with the case where the predetermined angle θt is set to a constant value, it is possible to expect the appropriate elimination of slip (improvement of the slip ratio S) according to the state of the contact surface.

In addition, this ECU 44
In the state where the tractor 1 is automatically switched to the four-wheel drive state, when the slip ratio S decreases below the threshold value St and the tractor 1 becomes substantially horizontal, the tractor 1 is automatically switched to the two-wheel drive state. Is.

  Thus, when the tractor 1 becomes substantially horizontal, the tilt angle θ of the tractor 1 has almost no influence on the slip. Therefore, in this case, by switching to the two-wheel drive state based only on the slip rate S regardless of the inclination angle θ (more specifically, whether the inclination angle θ has decreased to a predetermined angle θt or less), Slip can be properly eliminated.

The drive control mechanism 10
A threshold setting dial 24 (threshold changing means) capable of arbitrarily changing the threshold St is further provided.

  With this configuration, the threshold value St can be arbitrarily set based on the state of the ground contact surface, the work content, and the like.

Further, the slip ratio detecting means includes
A GPS receiver 30 (GPS receiver) for detecting the position of the tractor 1;
An axle rotation sensor 26 (driving speed detecting means) for detecting the driving speed in the driving force transmission path to the rear wheels 3 and 3 (wheels);
Comprising
This machine ECU44 is
The actual traveling speed Vp of the tractor 1 calculated based on the change in the position of the tractor 1,
The theoretical traveling speed Vi of the tractor 1 calculated based on the driving speed,
The slip ratio S is calculated based on the above.

With this configuration, the slip ratio S can be calculated using GPS. In particular, when the present invention is applied to the tractor 1 on which the GPS receiver 30 is originally mounted, it is not necessary to separately provide a sensor for calculating the slip ratio S, and thus the cost can be reduced.
In addition, as the tractor 1 on which the GPS receiver 30 is mounted, there is a precision agricultural tractor (a tractor including a working machine or the like that performs work using a GPS function).

  Below, the modification of the 1st control mode in the auto mode mentioned above (control for canceling the said slip appropriately when a slip generate | occur | produces during the driving | running | working of the tractor 1) is demonstrated.

  As a first modification of the first control mode, it is possible to adopt a configuration in which hysteresis is provided to the threshold value St of the slip ratio S.

  That is, the threshold value St (step S101 in FIG. 3) serving as a reference for the slip ratio S when the tractor 1 is switched from the two-wheel drive state to the four-wheel drive state (hereinafter simply referred to as “threshold S4”), A difference is provided in the value of the threshold value St (step S104 in FIG. 3) (hereinafter simply referred to as “threshold value S2”), which serves as a reference for the slip ratio S when returning from the driving state to the two-wheel driving state. Specifically, the threshold value S2 is set so as to be appropriately smaller than the threshold value S4. For example, when the threshold value S4 is 10 (%), the threshold value S2 is set to 6 (%).

  Thus, by setting the value of the threshold value S2 slightly smaller than the value of the threshold value S4, the slip recurs immediately after the tractor 1 is returned to the two-wheel drive state (the slip rate S again exceeds the threshold value St (S4)). ) Can be prevented.

  Further, when the tractor 1 is returned from the four-wheel drive state to the two-wheel drive state (step S104 in FIG. 3), it is a condition that a predetermined time elapses with the slip ratio S being equal to or less than the threshold value St (threshold value S2). It is also possible to do.

  Thus, by returning to the two-wheel drive state after a predetermined time has elapsed with the slip ratio S being low, the slip reoccurs immediately after the tractor 1 is returned to the two-wheel drive state (the slip ratio S is again the threshold value St (S4 ) Can be prevented.

  As a second modification of the first control mode, when the slip rate S increases to a value Sr close to the threshold St, it is possible to notify the operator of that fact.

  That is, this machine ECU 44 generates a warning sound from the slip notification buzzer 36 when the slip rate S of the tractor 1 increases to a value Sr (<St) close to the threshold value St. The operator can know that the tractor 1 is slipping (slip rate S is increased to some extent) by listening to a warning sound from the slip notification buzzer 36.

  As a third modification of the first control mode, when the GPS receiver 30 does not receive a signal from a GPS satellite, the operator is notified of this and the tractor 1 is switched to the four-wheel drive state. It is also possible to do.

  That is, this unit ECU 44 causes the GPS non-reception notification lamp 38 to emit light when the GPS receiver 30 has not received a signal from a GPS satellite. The operator can know that the GPS function cannot be used, that is, the slip rate S cannot be calculated by visually recognizing the light emission of the GPS non-reception notification lamp 38.

  Further, in this case, the machine ECU 44 switches the tractor 1 to the four-wheel drive state. As a result, when the slip ratio S cannot be calculated, the tractor 1 can always be maintained in the four-wheel drive state, and the occurrence of slip (increase in the slip ratio S) can be prevented in advance.

  A fourth modification of the first control mode is shown in FIG. In the flowchart shown in FIG. 6, the same processes as those in the flowchart shown in FIG.

  As a fourth modification of the first control mode, if the slip ratio S is not reduced below the threshold St even when the tractor 1 is switched to the four-wheel drive state (step S104), the speed change mechanism 5 is operated to change the speed. It is also possible to reduce the speed. Details will be described below.

In step S104 in FIG. 5, the present ECU 44 determines whether or not the slip rate S of the tractor 1 is equal to or less than the threshold value St.
When the machine ECU 44 determines that the slip ratio S of the tractor 1 is equal to or less than the threshold value St, the process proceeds to step S105.
When the machine ECU 44 determines that the slip ratio S of the tractor 1 exceeds the threshold value St, the process proceeds to step S111.

In step S111, the machine ECU 44 decelerates the tractor 1. That is, in this case, the present ECU 44 controls the operation of the shift electromagnetic valve 32 to switch the shift hydraulic clutch. As a result, the speed ratio (reduction ratio) in the speed change mechanism 5 is switched so that the tractor 1 decelerates.
This machine ECU44 transfers to step S104 again after performing the said process.

  As described above, even if the tractor 1 is switched to the four-wheel drive state (step S103), if the slip ratio S does not decrease below the threshold value St (step S104), the transmission mechanism 5 is shifted to decelerate the tractor 1 ( Step S111). As a result, slip can be more reliably eliminated.

  If the slip rate S does not decrease below the threshold value St even when the tractor 1 is decelerated, it is possible to further activate the differential lock (lock the differential mechanism). As a result, slip can be more reliably eliminated.

  FIG. 6 shows a fifth modification of the first control mode. As a fifth modification of the first control mode, when the tractor 1 is switched to the four-wheel drive state (step S103) and the slip ratio S is decreased to the threshold value St or less (step S104), the inclination angle θ is a predetermined angle. If it does not decrease below θt (step S106), the tractor 1 can be switched to the two-wheel drive state regardless of the inclination angle θ if a predetermined time has passed in that state. Details will be described below.

In step S106 in FIG. 6, the main unit ECU 44 determines whether or not the inclination angle θ in the front-rear direction of the tractor 1 is equal to or smaller than a predetermined angle θt.
When the machine ECU 44 determines that the front-rear inclination angle θ of the tractor 1 is equal to or smaller than the predetermined angle θt, the process proceeds to step S107.
When the machine ECU 44 determines that the front-rear inclination angle θ of the tractor 1 exceeds the predetermined angle θt, the process proceeds to step S112.

In step S112, this unit ECU 44 determines whether or not a predetermined time has passed in a state where the slip ratio S is equal to or less than the threshold value St (step S104).
If the ECU 44 determines that the predetermined time has elapsed with the slip ratio S being equal to or less than the threshold value St, the process proceeds to step S107.
If the ECU 44 determines that the predetermined time has not elapsed with the slip rate S being equal to or less than the threshold value St, the process proceeds to step S104 again.

  As described above, when the tractor 1 is switched to the four-wheel drive state (step S103) and the slip rate S is decreased to the threshold St or less (step S104), the inclination angle θ is not decreased to the predetermined angle θt or less (step S104). S106) If a predetermined time has passed in this state (step S112), the tractor 1 is switched to the two-wheel drive state regardless of the inclination angle θ (step S107). Thereby, the time for which the four-wheel drive state is continued is limited to a certain time (predetermined time after the slip ratio S is reduced below the threshold value St), and then switched to the two-wheel drive state. Can be improved.

  As a sixth modification of the first control mode, it is possible to adopt a configuration in which a plurality of threshold values St of the slip ratio S are set.

  That is, this machine ECU44 memorize | stores several threshold value St according to conditions, such as the state of an agricultural field, an inclination angle, and work content. And this machine ECU44 uses threshold value St according to the conditions when tractor 1 actually travels as a value of slip rate S used as a standard at the time of switching between the two-wheel drive state and four-wheel drive state of tractor 1 To do.

  In this case, the tractor 1 may be provided with a plurality of threshold setting dials 24 for setting the plurality of thresholds St. Moreover, it is also possible to employ a configuration in which an operator can arbitrarily select which threshold value St is used to control the tractor 1 among a plurality of set threshold values St using a switch or the like.

  Hereinafter, one of the control modes (second control mode) by the machine ECU 44 in the auto mode will be described with reference to FIGS. 1, 2, and 7.

  The second control mode is control for improving the driving force when it is desirable to improve the driving force with respect to the ground contact surface of the tractor 1.

  In the following, the flow of processing by the machine ECU 44 in the second control mode will be described mainly using FIG.

In step S201, this unit ECU 44 determines whether or not the tractor 1 is braked (the brake is applied). Specifically, this unit ECU 44 determines that the tractor 1 is braked when the braking operation tool is operated.
When determining that the tractor 1 is not braked, the ECU ECU 44 proceeds to step S202.
When the machine ECU 44 determines that the tractor 1 is braked, the process proceeds to step S209.

  In step S202, the present ECU 44 determines whether or not the engine 4 is being driven. Hereinafter, the process of step S202 will be described in detail.

  The state where the engine 4 is being driven means a state where the tractor 1 is accelerated by gravity when traveling downhill or the like, and the actual rotational speed of the engine 4 is greater than a target rotational speed by a predetermined value or more. . The “predetermined value” can be arbitrarily set, and is stored in the ECU 44 in advance.

When the actual rotational speed of the engine 4 is not greater than the target rotational speed of the engine 4 set based on the operation position of the accelerator operating tool by a predetermined value or more, the ECU 4 is following the engine 4 If not, the process proceeds to step S203.
If the actual rotational speed of the engine 4 is greater than the target rotational speed by a predetermined value or more, the main unit ECU 44 determines that the engine 4 is being driven and proceeds to step S209.

  In step S203, this unit ECU 44 determines whether or not the tractor 1 has just started. Hereinafter, the process of step S203 will be described in detail.

  This machine ECU 44 receives information about the driving speed in the power transmission path from the axle rotation sensor 26 to the driving wheels. This unit ECU 44 determines that the tractor 1 has started when the drive speed has changed from zero.

  Moreover, this machine ECU44 judges that it is immediately after starting until predetermined time passes after the tractor 1 starts. The “predetermined time” can be arbitrarily set, and is stored in the ECU 44 in advance. The “predetermined time” is preferably set based on experiments and numerical calculations so as to be a value larger than the time required for the speed to stabilize after the tractor 1 starts.

When the tractor 1 determines that the tractor 1 is not immediately after starting, the process proceeds to step S204.
If it is determined that the tractor 1 has just started, the ECU ECU 44 proceeds to step S207.

  In step S204, this unit ECU 44 determines whether or not the tractor 1 is accelerating or decelerating (acceleration or deceleration). Hereinafter, the process of step S204 will be described in detail.

  This machine ECU 44 determines that the tractor 1 has accelerated or decelerated when (1) the speed change mechanism 5 is operated for speed change or (2) when the target rotational speed of the engine 4 is changed.

  The machine ECU 44 determines that the speed change mechanism 5 has been changed when the operation position of the speed change operation tool is changed.

  The machine ECU 44 determines that the target rotational speed of the engine 4 has been changed when the operating position of the accelerator operating tool is changed.

  Moreover, this machine ECU44 judges that acceleration / deceleration is in progress until predetermined time passes after the tractor 1 accelerates / decelerates. The “predetermined time” can be arbitrarily set, and is stored in the ECU 44 in advance. The “predetermined time” is preferably set based on experiments and numerical calculations so as to be a value larger than the time required for the speed to stabilize after the tractor 1 is accelerated or decelerated.

If the present ECU 44 determines that the tractor 1 is not accelerating or decelerating, the process proceeds to step S205.
When determining that the tractor 1 is accelerating or decelerating, the ECU 44 proceeds to step S207.

In step S205, this unit ECU 44 determines whether or not slip has occurred in the tractor 1. Specifically, this machine ECU 44 determines that slip has occurred in the tractor 1 when the slip rate S of the tractor 1 exceeds the threshold value St.
When determining that no slip has occurred in the tractor 1, the ECU 44 proceeds to step S <b> 206.
When this machine ECU 44 determines that slip has occurred in the tractor 1, the process proceeds to step S <b> 207.

  In step S206, the machine ECU 44 automatically switches the tractor 1 to the two-wheel drive state. That is, in this case, the machine ECU 44 controls the operation of the four-wheel drive electromagnetic valve 34 and releases the connection of the hydraulic clutch for driving the front wheels. As a result, transmission of power to the front wheels 2 and 2 is cut off, and a two-wheel drive state in which only the rear wheels 3 and 3 are rotationally driven can be achieved.

  If the tractor 1 is already in the two-wheel drive state at the time of the processing (step S206), the main unit ECU 44 maintains that state.

  In step S207, this unit ECU 44 determines whether or not the tractor 1 is traveling at a high speed. Specifically, this unit ECU 44 determines that the tractor 1 is traveling at a high speed when the actual traveling speed Vp of the tractor 1 exceeds the threshold value Vt.

  The threshold value Vt is a value of the actual traveling speed Vp that serves as a reference when determining that the tractor 1 is traveling at a high speed. The threshold value Vt can be arbitrarily set (for example, 20 (km / h), etc.), and is stored in the ECU 44 in advance.

When determining that the tractor 1 is not traveling at a high speed, the present ECU 44 proceeds to step S208.
If the tractor 1 determines that the tractor 1 is traveling at a high speed, the present ECU 44 proceeds to step S206.

In step S208, this unit ECU 44 determines whether or not the tractor 1 is turning. Specifically, this unit ECU 44 determines that the tractor 1 is turning when the turning angle of the front wheels 2 and 2 is equal to or greater than a predetermined value. The “predetermined value” can be arbitrarily set (for example, 30 (°) or the like), and can be adjusted by changing the mounting position of the front wheel turning angle switch 18.
When the tractor 1 determines that the tractor 1 is not turning, the present ECU 44 proceeds to step S209.
If the tractor 1 determines that the tractor 1 is turning, the process proceeds to step S206.

  In step S209, the machine ECU 44 automatically switches the tractor 1 to the four-wheel drive state. That is, in this case, the machine ECU 44 controls the operation of the four-wheel drive electromagnetic valve 34 and connects the front-wheel drive hydraulic clutch. As a result, power can be transmitted to the front wheels 2 and 2, and the front wheels 2 and 2 and the rear wheels 3 and 3 can be driven in a four-wheel drive state.

  If the tractor 1 is already in the four-wheel drive state at the time of the process (step S209), the main unit ECU 44 maintains that state.

  As described above, in the second control mode, when the tractor 1 is being braked (step S201), the ECU 44 determines that it is desirable to improve the driving force with respect to the ground contact surface of the tractor 1, and the tractor 1 is The mode is automatically switched to the four-wheel drive state (step S209). Thereby, the driving force of the tractor 1 can be improved, the posture of the tractor 1 can be stabilized, and the braking distance of the tractor 1 can be shortened.

  Further, when the engine 4 is being driven (step S202), the present ECU 44 determines that it is desirable to improve the driving force with respect to the ground contact surface of the tractor 1, and automatically sets the tractor 1 to the four-wheel drive state. Switching (step S209). Thereby, the driving force of the tractor 1 can be improved and the posture of the tractor 1 can be stabilized.

  Further, when the tractor 1 is immediately after starting (step S203), the ECU 44 determines that it is desirable to improve the driving force with respect to the ground contact surface of the tractor 1, and automatically sets the tractor 1 to the four-wheel drive state. Switching (step S209). Thereby, the driving force of the tractor 1 can be improved and the tractor 1 can be started quickly.

  Further, when the tractor 1 is accelerating or decelerating (step S204), the ECU ECU 44 determines that it is desirable to improve the driving force with respect to the ground contact surface of the tractor 1, and automatically sets the tractor 1 to the four-wheel drive state. (Step S209). Thereby, the driving force of the tractor 1 can be improved, and the tractor 1 can be accelerated and decelerated quickly.

  In addition, when slip occurs in the tractor 1 (step S205), the present ECU 44 determines that it is desirable to improve the driving force with respect to the ground contact surface of the tractor 1, and automatically sets the tractor 1 to the four-wheel drive state. (Step S209). Thereby, the driving force of the tractor 1 can be improved and the slip of the tractor 1 can be eliminated.

  Further, even when the tractor 1 is just after starting (step S203), during acceleration / deceleration (step S204), or when a slip is generated (step S205), the present ECU 44 is in contact with the tractor 1 Is traveling at high speed (step S207), the tractor 1 is automatically switched to the two-wheel drive state (step S206). As a result, the steering operation can be performed more easily than in the four-wheel drive state.

  Further, even when the tractor 1 is just after starting (step S203), during acceleration / deceleration (step S204), or when a slip is generated (step S205), the present ECU 44 is in contact with the tractor 1 Is turning (step S208), the tractor 1 is automatically switched to the two-wheel drive state (step S206). As a result, the turning radius of the tractor 1 can be reduced as compared with the four-wheel drive state, and the ground contact surface (farm field) can be prevented from being rough.

As described above, the drive control mechanism 10 of the tractor 1 (work vehicle) according to the present embodiment is
A four-wheel drive electromagnetic valve 34 for switching between a four-wheel drive state in which drive force is transmitted to the front wheels 2 and 2 and the rear wheels 3 and 3 of the tractor 1 and a two-wheel drive state in which drive force is transmitted only to the rear wheels 3 and 3. (Drive switching means);
State detecting means for detecting a state in which it is desirable to improve the driving force with respect to the ground contact surface of the tractor 1;
When it is desirable to improve the driving force, this machine ECU 44 (control means) that automatically switches the tractor 1 to the four-wheel drive state;
It comprises.

  By configuring in this way, it is possible to suppress the occurrence of slip of the tractor 1 when it is desirable to improve the driving force with respect to the ground contact surface of the tractor 1, and thus to quickly improve the driving force of the tractor 1. .

The state detecting means includes
Including an axle rotation sensor 26 (start detection means) for detecting the start of the tractor 1,
This machine ECU44 is
Immediately after the tractor 1 starts, the tractor 1 is automatically switched to the four-wheel drive state.

By comprising in this way, generation | occurrence | production of the slip of the said tractor 1 immediately after the tractor 1 starts can be suppressed, and the driving force of the said tractor 1 can be improved by extension.
Thereby, the said tractor 1 can be started rapidly.

The state detecting means includes
Including a shift position detecting sensor 14 (shift operation detecting means) for detecting that the speed change mechanism 5 of the tractor 1 has been operated,
This machine ECU44 is
When the speed change mechanism 5 is changed, the tractor 1 is automatically switched to the four-wheel drive state.

By configuring in this way, it is possible to suppress the occurrence of slip of the tractor 1 when the speed change mechanism 5 of the tractor 1 is operated for shifting, and to improve the driving force of the tractor 1.
Thereby, the tractor 1 can be accelerated and decelerated quickly.

The state detecting means includes
An accelerator sensor 12 (engine operation detecting means) for detecting that the target rotational speed of the engine 4 of the tractor 1 has been changed;
This machine ECU44 is
When the target rotational speed is changed, the tractor 1 is automatically switched to the four-wheel drive state.

With this configuration, it is possible to suppress the occurrence of slip of the tractor 1 when the target rotational speed of the engine 4 of the tractor 1 is changed, and to improve the driving force of the tractor 1.
Thereby, the tractor 1 can be accelerated and decelerated quickly.

The state detecting means includes
An accelerator sensor 12 (target speed detecting means) for detecting the target speed of the engine 4 of the tractor 1;
A crank position sensor 40 (actual speed detecting means) for detecting the actual speed (actual speed) of the engine 4;
Including
This machine ECU44 is
When the actual rotational speed of the engine 4 becomes larger than the target rotational speed by a predetermined value or more, the tractor 1 is automatically switched to the four-wheel drive state.

By configuring in this way, the driving force of the tractor 1 is improved when the actual rotational speed of the engine 4 is larger than the target rotational speed by a predetermined value or more (so-called engine 4 is being driven). Can be made.
Thereby, the attitude | position of the said tractor 1 can be stabilized.

  Below, the modification of the 2nd control aspect in the auto mode mentioned above is demonstrated.

  A modification of the second control mode is shown in FIG. In the flowchart shown in FIG. 8, the same processes as those in the flowchart shown in FIG.

  As a modification of the second control mode, when the tractor 1 is turning, the tractor 1 can be switched to the double speed state in preference to other states. Details will be described below.

  When the operator switches the double speed changeover switch 21 and when it is permitted to automatically switch the tractor 1 to the double speed state in a predetermined case, the present ECU 44 performs the control shown in FIG. 8 instead of the control shown in FIG. I do.

In step S211 in FIG. 8, the present ECU 44 determines whether or not the tractor 1 is turning. Specifically, this unit ECU 44 determines that the tractor 1 is turning when the turning angle of the front wheels 2 and 2 is equal to or greater than a predetermined value. The “predetermined value” can be arbitrarily set (for example, 40 (°) or the like), and can be adjusted by changing the mounting position of the front wheel turning angle switch 18.
When the tractor 1 determines that the tractor 1 is not turning, the present ECU 44 proceeds to step S201.
When the tractor 1 determines that the tractor 1 is turning, the present ECU 44 proceeds to step S212.

  In step S212, this unit ECU 44 automatically switches the tractor 1 to the double speed state. That is, in this case, the machine ECU 44 controls the operation of the double speed electromagnetic valve 35 and connects the double speed hydraulic clutch. As a result, power at a driving speed faster than normal (four-wheel drive state) can be transmitted to the front wheels 2 and 2, and the front wheels 2 and 2 are set in a double speed state in which the front wheels 2 and 2 are rotationally driven at a higher ground speed than the rear wheels 3 and 3. be able to.

  If the tractor 1 is already in the double speed state at the time of the processing (step S212), the main unit ECU 44 maintains that state.

  Thus, when the tractor 1 is turning (step S211), the tractor 1 is switched to the double speed state in preference to other control (from step S201 to step S209) (step S212). Thus, during turning, the front wheels 2 and 2 can be rotationally driven at a ground speed faster than that of the rear wheels 3 and 3, and the vehicle can be easily turned and the ground contact surface can be made difficult to be roughened.

As described above, the drive control mechanism 10 of the tractor 1 according to this embodiment is
A front wheel turning angle switch 18 (front wheel turning angle detection means) for detecting that the turning angle of the front wheels 2 and 2 has become a predetermined value or more;
A double speed electromagnetic valve 35 (double speed switching means) for switching to a double speed state in which the front wheels 2 and 2 are rotated at a ground speed faster than the rear wheels 3 and 3;
Further comprising
This machine ECU44 is
When the turning angle of the front wheels 2 and 2 is equal to or greater than a predetermined value, the tractor 1 is set to double speed in preference to the control for automatically switching the tractor 1 to the four-wheel drive state (from step S201 to step S209 in FIG. 8). It automatically switches to the state.

  With this configuration, when the turning angle of the front wheels 2 and 2 exceeds a predetermined value, the tractor 1 can be easily turned by preferentially switching to the double speed state, and the ground contact surface Can be made difficult.

In the above embodiment, the control mode by the machine ECU 44 in the auto mode has been described separately for the first control mode and the second control mode. However, this machine ECU 44 can also perform two controls of the first control mode and the second control mode in parallel in the auto mode.
In this case, for example, the first control mode (FIG. 3) is applied instead of the control (step S205 and step S209 in FIG. 6) that switches to the four-wheel drive state when slip occurs in the tractor 1 in the second control mode. Is possible.

  Moreover, in the said embodiment, this machine ECU44 shall perform control which switches the tractor 1 to a double speed state automatically as a modification of the 2nd control mode in auto mode. However, this unit ECU 44 can also be configured to perform control to switch the tractor 1 to the double speed state even when the tractor 1 is turning in the fixed mode.

  In the above embodiment, the accelerator sensor 12, the shift position detection sensor 14, the axle rotation sensor 26, and the crank position sensor 40 are used as the state detection means. However, the present invention is not limited to this. That is, the state detection means may be any device that can detect a state in which it is desirable to improve the driving force with respect to the ground contact surface of the tractor 1. For example, a sensor that detects the state of the ground contact surface (farm field) of the tractor 1 or a sensor that detects the content of work performed by the tractor 1 (the type of work implement that the tractor 1 wears) may be used.

  Moreover, in the said embodiment, although the accelerator sensor 12 shall be used as an engine operation detection means, this invention is not limited to this. That is, the engine operation detecting means may be any means that can detect that the target rotational speed of the engine 4 of the tractor 1 has been changed. For example, the sensor which detects that the link mechanism connected with the said accelerator operating tool moved, or engine ECU42 itself which controls operation | movement of the engine 4 may be sufficient.

  Moreover, in the said embodiment, although the accelerator sensor 12 shall be used as a target rotation speed detection means, this invention is not limited to this. That is, the target rotational speed detection means may be any means that can detect the target rotational speed of the engine 4 of the tractor 1. For example, it may be a sensor that detects an operation position of a link mechanism connected to the accelerator operation tool, or an engine ECU 42 that controls the operation of the engine 4 itself.

  In the above embodiment, the shift position detecting sensor 14 is used as the shift operation detecting means, but the present invention is not limited to this. That is, the speed change operation detecting means may be any means that can detect that the speed change mechanism 5 of the tractor 1 has been changed. For example, it may be a sensor that detects that the link mechanism connected to the speed change operation tool has moved, or the machine ECU 44 itself that controls the speed change electromagnetic valve 32 to change the speed of the speed change mechanism 5.

  In the above embodiment, the front wheel turn angle switch 18 is used as the front wheel turn angle detection means, but the present invention is not limited to this. That is, the front wheel turning angle detecting means may be any device that can detect that the turning angle of the front wheels 2 and 2 has reached a predetermined value or more. For example, a potentiometer or the like that can detect the turning angle of the front wheels 2 and 2 may be used. Further, the present invention is not limited to the one that directly detects the turning angle of the front wheels 2 and 2, but may be one that detects the turning angle of the steering wheel 6a and indirectly detects the turning angle of the front wheels 2 and 2.

  In the above embodiment, the threshold setting dial 24 is used as the threshold changing means, but the present invention is not limited to this. That is, the threshold value changing means may be any means that can arbitrarily change the threshold value St. For example, various other switches (slide switch, toggle switch, etc.) and a touch panel may be used.

  Moreover, in the said embodiment, although the axle shaft rotation sensor 26 and the GPS receiver 30 were used as a slip ratio detection means, this invention is not limited to this. That is, the slip ratio detecting means may be any means that can detect the slip ratio S of the wheel with respect to the ground contact surface. For example, the actual traveling speed Vp may be calculated using another sensor such as a ground sensor, and the slip ratio S may be detected from the actual traveling speed Vp. In addition, the slip ratio S is detected from the difference between the driving speeds of the front wheels 2 and 2 and the rear wheels 3 and 3 by using sensors for detecting the driving speeds (rotations) of the front wheels 2 and 2 and the rear wheels 3 and 3 It may be configured to do so.

  In the above embodiment, the axle rotation sensor 26 is used as the drive speed detecting means, but the present invention is not limited to this. That is, the drive speed detection means may be any means that can detect the drive speed in the drive force transmission path to the wheels. For example, the driving speed may be detected based on the actual rotational speed of the engine 4 and the reduction ratio of the power transmission path.

  Moreover, in the said embodiment, although the axle shaft rotation sensor 26 was used as a start detection means, this invention is not limited to this. That is, the start detection means may be any means that can detect the start of the tractor 1. For example, a sensor that detects the state of a clutch that switches whether or not power can be transmitted to the wheels of the tractor 1 (whether it is connected or disconnected), and the operating positions of the accelerator operating tool and the transmission operating tool May be sensors (accelerator sensor 12 and shift position detection sensor 14).

  Moreover, in the said embodiment, although the inclination sensor 28 shall be used as an inclination angle detection means, this invention is not limited to this. That is, the inclination angle detection means may be any means that can detect the inclination angle of the tractor 1 in the front-rear direction. For example, a configuration (image processing means) that detects an inclination angle of the tractor 1 in the front-rear direction from an image obtained by capturing the tractor 1 may be used.

  In the above embodiment, the four-wheel drive electromagnetic valve 34 is used as the drive switching means, but the present invention is not limited to this. That is, the drive switching means includes a four-wheel drive state in which driving force is transmitted to the front wheels 2 and 2 and the rear wheels 3 and 3 of the tractor 1, and a two-wheel drive state in which driving force is transmitted only to the rear wheels 3 and 3. Any device that can be switched may be used. For example, another actuator for controlling the operation of the front-wheel drive clutch provided in the speed change mechanism 5 may be used.

  Moreover, in the said embodiment, although the crank position sensor 40 shall be used as an actual rotational speed detection means, this invention is not limited to this. That is, the actual rotational speed detection means may be any means that can detect the actual rotational speed of the engine 4. For example, a sensor that detects the pulsation of the fuel injection pipe of the engine 4 or a sensor that detects the rotational speed of the alternator may be used.

  In the above embodiment, the present ECU 44 is used as the control means, but the present invention is not limited to this. That is, the control means may be any means that can control the entire drive control mechanism 10. For example, an ECU provided separately from the machine ECU 44 or an ECU provided outside the tractor 1 and capable of controlling the drive control mechanism 10 wirelessly (or by wire) may be used.

DESCRIPTION OF SYMBOLS 1 Tractor 10 Drive control mechanism 12 Accelerator sensor 14 Shift position detection sensor 18 Front wheel turning angle switch 24 Threshold setting dial 26 Axle rotation sensor 26
28 Inclination sensor 30 GPS receiver 34 Four-wheel drive solenoid valve 35 Double speed solenoid valve 40 Crank position sensor 44 This machine ECU

Claims (5)

Drive switching means for switching between a four-wheel drive state in which driving force is transmitted to the front wheels and rear wheels of the work vehicle and a two-wheel drive state in which driving force is transmitted only to the rear wheels;
State detecting means for detecting a state in which it is desirable to improve the driving force with respect to the ground plane of the work vehicle;
When it is desirable to improve the driving force, control means for performing first four-wheel drive switching control for automatically switching the work vehicle to a four-wheel drive state;
Comprising
An actual traveling speed detecting means for detecting an actual traveling speed of the work vehicle;
The control means includes
When the actual travel speed of the work vehicle is equal to or greater than a predetermined value, in preference to the first four-wheel drive switching control, the line physician to automatically switch the two-wheel drive switching control said working vehicle in two-wheel drive mode ,
The state detection means includes
Target rotational speed detection means for detecting a target rotational speed of the engine of the work vehicle;
An actual engine speed detecting means for detecting an actual engine speed;
Including
The control means includes
When the actual number of revolutions of the engine becomes greater than the target number of revolutions by a predetermined value or more, a second vehicle is automatically switched to the four-wheel drive state in preference to the two-wheel drive switching control. Perform four-wheel drive switching control,
Drive control mechanism for work vehicles. The state detection means includes
Including start detection means for detecting start of the work vehicle,
The control means includes
Immediately after the work vehicle starts, the first four-wheel drive switching control is performed.
The drive control mechanism for a work vehicle according to claim 1. The state detection means includes
A shift operation detecting means for detecting that the shift mechanism of the work vehicle has been shifted;
The control means includes
Performing the first four-wheel drive switching control when the speed change mechanism is operated to change speed;
A drive control mechanism for a work vehicle according to claim 1 or 2. The state detection means includes
Engine operation detecting means for detecting that the target rotational speed of the engine of the work vehicle has been changed,
The control means includes
When the target rotational speed is changed, the first four-wheel drive switching control is performed.
The drive control mechanism for a work vehicle according to any one of claims 1 to 3. The state detection means includes
Slip ratio detecting means for detecting the slip ratio of the wheel with respect to the ground contact surface;
An inclination angle detecting means for detecting an inclination angle in a forward ascending direction with respect to a horizontal direction of the work vehicle;
Including
The control means includes
When the slip ratio exceeds a threshold value, the tilt angle when the slip ratio exceeds the threshold value is stored as a memory value, and the first four-wheel drive switching control is performed.
In the state where the work vehicle is automatically switched to the four-wheel drive state, the two-wheeled vehicle, when the slip ratio decreases below the threshold and the tilt angle decreases below a predetermined angle less than the stored value. Drive switching control,
The drive control mechanism for a work vehicle according to any one of claims 1 to 4.

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