Work vehicle

Abstract

To enable travel to be more efficient compared to a configuration in which torque is fixed in a continuously variable transmission.SOLUTION: A work vehicle stores travel loads detected by load detection members (SN4, SN5, and SN6) when the work vehicle travels on a field and positions measured by a positioning device (SN7) in association with each other. By increasing capacity of a hydraulic motor (49) when the travel load is higher than a reference value to a level larger than when the travel load is lower than the reference value based on the stored travel loads and positions during past travel, the work vehicle enables travel to be more efficient compared to a configuration in which torque is fixed in a continuously variable transmission.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to work vehicles such as tractors, rice transplanters, and seedling transplanting machines.

Background Art

[0002] In work vehicles such as tractors, a configuration is known in which power from the engine of the vehicle body is transmitted through a continuously variable transmission (HST: Hydraulic Static Transmission) equipped with a variable displacement hydraulic pump and a fixed displacement hydraulic motor to operate a work implement. In a work vehicle equipped with an HST, the rotational speed of the hydraulic motor is changed by changing the inclination angle of the swash plate of the hydraulic pump, and the vehicle speed is controlled (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional technology described in Patent Document 1, since the swash plate of the hydraulic motor had a fixed inclination angle, the vehicle traveled at a constant torque even when high torque was not required, which could be inefficient.

[0005] The technical problem of the present invention is to enable efficient running compared to a configuration in which the torque in the continuously variable transmission is fixed.

Means for Solving the Problems

[0006] The above problems of the present invention are solved by the following means. The invention according to claim 1 includes a vehicle body (1a) having an engine (E), a variable displacement hydraulic pump (47) connected to an input shaft (32a) from the engine (E), and a variable displacement hydraulic motor (49) connected to an output shaft (32b) to drive wheels (2, 3) of the vehicle body (1a). It has a continuously variable transmission (31) capable of continuously varying the rotation from the input shaft (32a) to the output shaft (32b), a load detection member (SN4, SN5, SN6) for detecting the running load of the vehicle body (1a), and a positioning device (SN7) for measuring the current position of the vehicle body (1a). When running in a field, the running load detected by the load detection member (SN4, SN5, SN6) and the position measured by the positioning device (SN7) are stored in association with each other. Based on the stored past running load and position, when the running load is higher than a reference value at a certain position, the capacity of the hydraulic motor (49) is made larger than that at a position where the running load is lower than the reference value. This is a working vehicle characterized by this.

[0007] The invention according to claim 2 is the working vehicle according to claim 1, characterized in that it includes the load detection member (SN4) constituted by a torque sensor (SN4) for detecting the load torque of the drive wheels (2, 3) as the running load.

[0008] The invention according to claim 3 is the working vehicle according to claim 1, characterized in that it includes the load detection member (SN5) constituted by a pressure sensor (SN5) for detecting the internal pressure of the continuously variable transmission (31) as the running load.

[0009] The invention according to claim 4 includes the load detection member (SN6) constituted by a rotational speed sensor (SN6) for detecting the rotational speed of the engine (E) as the running load. Based on the rotational speed of the engine and the position during past running, when the amount of decrease in the engine rotational speed is higher than the reference value at a certain position, the capacity of the hydraulic motor (49) is made larger than that at a position where the amount of decrease in the engine rotational speed is lower than the reference value. This is a working vehicle according to claim 1, characterized by this.

Effect of the Invention

[0010] According to the invention described in claim 1, when traveling in the field, the traveling load detected by the load detection members (SN4, SN5, SN6) is associated with the position measured by the positioning device (SN7) and stored. Based on the stored traveling load and position during past travel, at positions where the traveling load is higher than the reference value, by increasing the capacity of the hydraulic motor (49) compared to positions where the traveling load is lower than the reference value, efficient travel can be enabled compared to a configuration where the torque in the continuously variable transmission is fixed.

[0011] According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, by controlling the capacity of the hydraulic motor (49) based on the load torque of the drive wheels (2, 3), efficient travel can be enabled compared to a configuration where the torque in the continuously variable transmission is fixed.

[0012] According to the invention described in claim 3, in addition to the effect of the invention described in claim 1, by controlling the capacity of the hydraulic motor (49) based on the internal pressure of the continuously variable transmission (31), efficient travel can be enabled compared to a configuration where the torque in the continuously variable transmission is fixed.

[0013] According to the invention described in claim 4, in addition to the effect of the invention described in claim 1, by controlling the capacity of the hydraulic motor (49) based on the amount of decrease in the engine speed, efficient travel can be enabled compared to a configuration where the torque in the continuously variable transmission is fixed.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0015] Embodiments of this invention will be described below. FIG. 1 is an explanatory diagram of a tractor as an example of the work vehicle of the embodiment. In FIG. 1, a tractor 1, which is an example of an agricultural machine as the work vehicle of the present invention, includes front wheels 2, 2 and rear wheels 3, 3 as examples of drive wheels at the front and rear of the vehicle body 1a, and the rotational power of an engine E mounted in an engine room 4 at the front of the vehicle body is appropriately decelerated by a transmission in a transmission case 5 and transmitted to these front wheels 2, 2 and rear wheels 3, 3. The engine room 4 is configured to be covered by a bonnet 6. Also, a work implement such as a rotary tiller 18 is attached to the rear of the machine body, and the work implement is driven by a PTO shaft. In this specification, the left and right sides are referred to as the left side and the right side respectively toward the forward direction of the tractor 1, the forward direction is referred to as the front side, and the reverse direction is referred to as the rear side.

[0016] A cabin 7 is supported on the upper part of the vehicle body 1a. Inside the cabin 7, a driver's seat 8 is arranged at the upper position of the transmission case 5, and in front of this driver's seat 8, a steering wheel 10, a forward and reverse lever 11, a parking brake (not shown), etc. are arranged. Also, in front of the driver's seat 8, a speedometer (not shown), various operation switches (not shown), etc. are arranged. At the lower front of the driver's seat 8, traveling operation tools such as a clutch pedal 12, an accelerator pedal 13, and left and right brake pedals (not shown) are arranged.

[0017] In FIG. 1, a hydraulic cylinder case 14 is provided above the rear part of a transmission case 5, and lift arms 15, 15 are pivotally attached to both the left and right sides of the hydraulic cylinder case 14 so as to be rotatable. Lift rods 17, 17 are interposed and connected between the lift arms 15, 15 and lower links 16, 16, and a rotary tilling device 18, which is an example of a working machine and also an example of a cultivator, is connected to the rear parts of the lower links 16, 16.

[0018] When hydraulic oil is supplied to a hydraulic cylinder 14a housed in the hydraulic cylinder case 14, the lift arms 15, 15 are rotated upward, and the working machine (rotary tilling device) 18 rises via the lift rods 17, lower links 16, etc. Conversely, when the hydraulic oil in the hydraulic cylinder 14a is discharged into the transmission case 5 that also serves as a hydraulic tank, the lift arms 15, 15 descend. A rotary tilling device 18 is connected to the rear of the body of the tractor 1, and the rotary tilling device 18 includes a tilling part 18a, a main cover 18b that covers the upper part of the tilling part 18a, a rear cover 18c pivotally attached to the rear part of the main cover 18b, and the like.

[0019] A position sensor SN1 for detecting the tilt angle of the lift arm 15, that is, the elevation of the rotary tilling device 18, is arranged at the base end of the lift arm 15. Also, a draft sensor (traction load sensor) SN2 for detecting the load during operation, particularly the traction load, is provided at the base end of the lower link 16. In the rotary tilling device 18 of the embodiment, a tillage depth sensor SN3 for detecting the tillage depth by detecting the rotation angle of the rear cover 18c is arranged.

[0020] FIG. 2 is an explanatory view of the state in which a plow is attached as a working machine to the tractor of the embodiment. FIG. 3 is an explanatory view of the state in which a trailer is attached as a working machine to the tractor of the embodiment. Furthermore, a work implement connector 20 (not shown in FIG. 1) extends from the vehicle body of the tractor 1 and is connected to a cable 23 extending from a mounted work implement such as a rotary tiller 18, a plow 21, or a trailer 22. By performing communication, the tractor 1 is configured to be able to recognize the types of the work implements 18, 21, 22.

[0021] (Explanation of the continuously variable transmission) FIG. 4 is an explanatory view of the continuously variable transmission according to the embodiment. FIG. 5 is a hydraulic circuit diagram of the continuously variable transmission according to the embodiment. In FIGS. 4 and 5, a continuously variable transmission (HST) 31 as an example of the continuously variable transmission according to the embodiment includes a variable displacement hydraulic pump 47 and a variable displacement hydraulic motor 49. In FIG. 5, a plurality of relief valves 61 and 62 are provided in the HST 31 to release pressure oil to protect the HST 31 when the hydraulic pressure in the circuit increases. The first movable swash plate 48 of the hydraulic pump 47 is configured such that the inclination with respect to the pump output shaft 51 can be changed. Further, in the embodiment, the second movable swash plate 50 of the hydraulic motor 49 is configured such that the inclination with respect to the motor output shaft 32b can be changed. In FIG. 4, the inclination of the first movable swash plate 48 in the hydraulic pump 47 is changed by an electric motor (trunion motor) that detects the movement of an HST lever (not shown) as an example of the main transmission operation member and operates. Then, by changing the inclination of the first movable swash plate 48, the capacity of the hydraulic pump 47 changes, and the rotational speed of the hydraulic motor 49 changes.

[0022] In the HST 31, the first movable swash plate 48 rotates together with the input shaft 32a of the HST 31, so that each piston 470 moves by sliding on the surface of the first movable swash plate 48, and the hydraulic oil flows through an oil passage formed in the metal 40a and is supplied to the hydraulic motor 49. Further, the hydraulic motor 49 rotates the motor output shaft 32b by the pistons 490 moved by the supplied hydraulic oil sliding on the second movable swash plate 50 in a manner opposite to that of the hydraulic pump 47.

[0023] Thus, when the second movable swash plate 50 is held at a predetermined tilt angle, by changing the tilt angle of the first movable swash plate 48, the rotational speed and torque of the motor output shaft 32b of the hydraulic motor 49 change. Note that the rotation of the pump output shaft 51 directly connected to the hydraulic pump 47 is the same as the rotational speed of the input shaft 32a. The pump output shaft 51 is connected to a PTO shaft that transmits drive to the work implement. Therefore, when controlling the rotational speed and torque of the work implement, the output of the work implement can be controlled by controlling the output of the engine E to which the input shaft 32a is connected.

[0024] Also, in the hydraulic pump 47, when the tilt angle of the first movable swash plate 48 becomes perpendicular to the input shaft 32a of the HST 31, the capacity of the hydraulic pump 47 becomes "0", and the hydraulic motor 49 stops rotating. In this way, the position where the tilt angle of the first movable swash plate 48 becomes perpendicular to the input shaft 32a of the HST 31 is called the "neutral position", and the state of the HST 31 at that time is called the "neutral state". That is, when the tilt angle of the first movable swash plate 48 reaches the neutral position, power transmission in the HST 31 stops.

[0025] In the HST 31, when the first movable swash plate 48 is tilted to the side shown in FIG. 4 with respect to the neutral position, the power of the engine E is output as a force to move the vehicle body 1a forward. On the other hand, when the first movable swash plate 48 is tilted to the side opposite to the side shown in FIG. 4 with respect to the neutral position, the rotation of the hydraulic motor 49 becomes reverse rotation with respect to the hydraulic pump 47 side, and the power of the engine E is output as a force to move the vehicle body 1a backward. Also, the second movable swash plate 50 is configured such that its tilt angle can be changed with respect to the motor output shaft 32b, similar to the first movable swash plate 48. Therefore, by changing the tilt angle of the second movable swash plate 50, the capacity of the hydraulic motor 49 changes, and the rotational speed and torque of the motor output shaft 32b change. The motor output shaft 32b transmits power to the drive wheels of the front wheels 2 and the rear wheels 3. The drive wheels are configured to be switchable by a four-wheel drive clutch (not shown) in the transmission case 5. In the four-wheel drive state, the front wheels 2 and the rear wheels 3 become drive wheels, and in the two-wheel drive state, the rear wheels 3 become drive wheels.

[0026] In the case of the HST31, a first trunnion shaft that rotates in conjunction with the inclination of the first movable swash plate 48 and a second trunnion shaft that rotates in conjunction with the inclination of the second movable swash plate 50 are supported. Each trunnion shaft is configured such that its rotation angle can be adjusted by trunnion motors M1 and M2. By rotating the trunnion motors M1 and M2 forward and backward, each trunnion shaft is rotated, and the inclination angles of the respective movable swash plates 48 and 50 can be configured to be continuously variable. Note that the trunnion shafts, trunnion motors, etc. can be configured in the same manner as those provided in a conventionally known HST having a fixed-capacity type (fixed inclination angle of the swash plate), and thus the illustration and detailed description thereof are omitted.

[0027] (Description of the control unit) FIG. 6 is a functional block diagram of the control unit of the embodiment. In the block diagram of FIG. 6, illustration and description are omitted for elements not related to the description of the embodiment of the present invention.

[0028] (Description of the control unit of the tractor) The tractor 1 of the present embodiment has a control unit 210 that controls each function. The control unit 210 has an input / output interface I / O that performs input / output of signals to and from the outside. Further, the control unit 210 has a ROM (read-only memory) in which programs, information, etc. for performing necessary processes are stored. Further, the control unit 210 has a RAM (random access memory) for temporarily storing necessary data. Further, the control unit 210 has a CPU (central processing unit) that performs processes according to programs stored in the ROM and the like. Therefore, the control unit 210 of the present embodiment is configured by a small information processing device, so-called a microcomputer. Thus, the control unit 210 can realize various functions by executing programs stored in the ROM and the like.

[0029] Signals from signal input elements such as the position sensor SN1, traction load sensor SN2, tillage depth sensor SN3, implement connector 20, drive torque sensor SN4, pressure sensor SN5, engine speed sensor SN6, positioning device SN7, and various other sensors (not shown) are input to the control unit 210. The position sensor SN1 detects the height (rise or fall) of the implement. The traction load sensor SN2 detects the traction load during operation. The tillage depth sensor SN3 detects the tillage depth when the rotary tillage device 18 is attached.

[0030] The implement connector 20 detects the connection of the implement. The drive torque sensor SN4 detects the load torque of the drive wheels. In the embodiment, the drive torque sensor SN4 detects the load torque during the drive of the rear wheels 3 that serve as drive wheels both during four-wheel drive and two-wheel drive. Note that the drive torque sensor SN4 can be, for example, a load cell installed on the axle. The pressure sensor SN5 detects the internal pressure (hydraulic pressure) of the HST 31. The engine speed sensor SN6 detects the rotational speed of the engine E.

[0031] The positioning device SN7 includes a GNSS (Global Navigation Satellite System) receiver SN7a and an IMU (Inertial Measurement Unit) SN7b. The GNSS receiver SN7a can receive positioning signals from GNSS satellites and measure the current position of the tractor 1. The IMU SN7b can measure acceleration and angular velocity and measure the attitude of the tractor 1 (left and right tilts and front and rear tilts). Therefore, the positioning device SN7 in the embodiment can measure the current position with higher accuracy by correcting the measurement result of the GNSS receiver SN7a with the measurement result of the IMU SN7b compared to the case of measuring the current position only by the GNSS method.

[0032] Further, the control unit 210 transmits control signals to the engine E, the first transion motor M1, the second transion motor M2, the hydraulic cylinder 14a, etc., which are examples of controlled elements, to control the traveling, stopping, acceleration and deceleration of the tractor 1, the driving of the work implement, and the raising and lowering thereof.

[0033] In FIG. 6, the control unit 210 of the present embodiment has the following functional means (program modules). The field information storage means 211 of the control unit 210 stores information related to the field (field information). In the embodiment, as the field information, information on the position of the field (latitude, longitude, altitude, slope of the field, etc.) and information on the map such as the entrances and exits of the field are stored in association with information related to the work in the field (work information). As an example, in the work information of the embodiment, the type of the work implement, the traveling load when traveling while working with the work implement, and the position information are stored in association with each other. Note that it is also possible to divide one field into a plurality of sections and store the traveling load for each section corresponding to the position information for the work information and the field information. Note that it is preferable that the field information can be confirmed by the operator by being displayed on a display panel (not shown) in the cabin 7.

[0034] The positioning means 212 measures the current position of the tractor 1 based on the measurement result of the positioning device SN7. The load detection means 213 includes a load torque detection means 213a, an internal pressure detection means 213b, and an engine speed detection means 213c, and detects the traveling load when the tractor 1 travels while working in the field (during working travel).

[0035] The load torque detection means 213a detects a load torque as an example of the traveling load. The load torque detection means 213a detects the load torque of the drive wheels 2 and 3 during working travel. When the soil in the field is soft or there is a local convex and an upward slope, the traveling load and the traveling resistance during the traveling of the tractor 1 increase, and a large value of the load torque is also detected. Therefore, the load torque detection means 213a of the embodiment can indirectly detect the traveling load by detecting the load torque of the drive wheels 2 and 3.

[0036] The internal pressure detection means 213b detects the internal pressure of the HST 31 as an example of the running load. When the running load increases, it becomes difficult to rotate even if oil is sent from the hydraulic pump 47 of the HST 31, and the internal pressure (hydraulic pressure) rises. Therefore, the internal pressure detection means 213b of the embodiment can indirectly detect the running load by detecting the internal pressure of the HST 31.

[0037] The engine speed detection means 213c detects the rotational speed of the engine E (engine speed) as an example of the running load. When the running load increases, the torque of the engine E becomes insufficient and the rotational speed decreases. And the greater the running load, the greater the decrease in the engine speed. Therefore, the engine speed detection means 213c of the embodiment can indirectly detect the running load by detecting the rotational speed of the engine E.

[0038] The work implement type discrimination means 214 discriminates the type of the work implement (rotary tiller 18, plow 21, trailer 22, etc.) connected via the work implement connector 20.

[0039] The field information registration means 215 registers the running load (load torque, internal pressure, engine speed) detected by the load detection means 213 in the field information of the field information storage means 211 in association with the position information (measured by the positioning means 212) where the running load is detected. When registering the field information, the field information registration means 215 also registers the type of the work implement used during the work discriminated by the work implement type discrimination means 214 in addition to the running load and the position information. In the embodiment, for the sake of simplicity, when registering the running load as the field information, information classified into two levels of "high load" and "low load" is registered based on the detected value and a predetermined reference value. It is also possible to register the detected value itself. In addition, it is also possible to provide a plurality of reference values (first reference value, second reference value) and register information classified into three or more levels such as "high load", "medium load", and "low load".

[0040] The travel control means 216 controls the travel of the tractor 1 by controlling the engine E. During manual travel, the travel control means 216 controls the travel speed and steering according to the manual operations of the accelerator pedal 13, brake pedal, and steering wheel 10. During automatic travel (autonomous travel), based on the current position of the tractor 1 measured by the positioning means 212, the engine E and the steering angle of the steering wheel 10 are controlled so as to travel along the work path for each of the working machines 18, 21, 22 registered in the field information storage means 211.

[0041] The HST control means 217 has a pump capacity control means 217a and a motor capacity control means 217b, and controls the HST 31. The pump capacity control means 217a changes the capacity of the hydraulic pump 47 by controlling the inclination angle of the first movable swash plate 48. Accordingly, the transmission of drive from the hydraulic pump 47 to the hydraulic motor 49 is controlled.

[0042] The motor capacity control means 217b changes the capacity of the hydraulic motor 49 by controlling the inclination angle of the second movable swash plate 50. Accordingly, the transmission of drive from the hydraulic motor 49 to the motor output shaft 32b is controlled. In the motor capacity control means 217b of the embodiment, during manual travel, as an example, the inclination angle of the second movable swash plate 50 is controlled to a predetermined reference angle, and the capacity of the hydraulic motor 49 is controlled to the reference capacity. Accordingly, in a state where the hydraulic motor 49 is controlled to the reference capacity, the drive of the rotational speed and torque corresponding to the rotational speed of the engine E and the speed change in the hydraulic pump 47 is transmitted to the drive wheels 2, 3.

[0043] Further, the motor capacity control means 217b of the embodiment, during automatic travel, based on the past travel load and position information stored in the field information storage means 211, in a position where the travel load is higher than the reference value (high load area), the second movable swash plate 50 is controlled so that the capacity of the hydraulic motor 49 is larger than that in the low load area. Therefore, at a position where the load torque was large during past running, the capacity of the hydraulic motor 49 is controlled to be larger than that at a position where the load torque was small. Also, at a position where the internal pressure of the HST 31 was large during past running, the capacity of the hydraulic motor 49 is controlled to be larger than that at a position where the internal pressure was small. Further, at a position where the amount of decrease in the engine speed was high during past running, the capacity is controlled to be larger than that at a position where the amount of decrease in the engine speed was low. In the embodiment, during automatic running, the capacity of the hydraulic motor 49 is controlled according to the running load, but it is also possible to perform the control during manual running.

[0044] In the embodiment, as the running load, three parameters, namely, the load torque, the internal pressure, and the amount of decrease in the engine speed, are detected. Then, in the determination of high load and low load of the running load, the motor capacity control means 217b in the embodiment controls such that the larger the number of the three parameters indicating high load, the larger the capacity of the hydraulic motor 49, and the larger the number of the three parameters indicating low load, the smaller the capacity of the hydraulic motor 49. For example, the motor capacity is controlled to decrease in the order of the running loads of all high load > two high loads > one high load > all low loads.

[0045] In the embodiment, as an example, the capacity when "one is high load" is made to match the reference capacity, but it is not limited to this. For example, it is also possible to make the capacity when "two are high load" match the reference capacity, or to set an arbitrary capacity as the reference capacity according to design, use, etc., such as setting the capacity between "two are high load" and "one is high load" as the reference capacity. Also, it is possible to assign priorities among the three parameters and perform control such that if the parameter with a higher priority is a high load, the motor capacity is made larger than when the parameter with a lower priority is a high load.

[0046] Furthermore, in the embodiment, an aspect of using three parameters was exemplified, but the present invention is not limited thereto. It is also possible to use two or less parameters, and it is also possible to adopt an aspect of controlling with only one of the parameters. In addition, it is also possible to use other parameters related to the running load, for example, the oil temperature of the HST 31, the traction load detected by the traction load sensor SN2, the tillage depth, the hardness or softness of the soil, the slope of the field (uphill, downhill), etc., and it is also possible to adopt an aspect of using four or more parameters. Therefore, although an aspect of changing the capacity of the hydraulic motor 49 in four steps by using three parameters was exemplified, the present invention is not limited thereto. It is also possible to use four or more parameters to make it five steps or more, and in addition, it is also possible to change it steplessly by managing the load torque or the like with the measured value itself.

[0047] In addition, when the work implements 18, 21, and 22 are descending, it is estimated that they are in the working state and the running load is large, and the capacity of the hydraulic motor 49 is increased. When the work implements 18, 21, and 22 are ascending, it is estimated that they are in the non-working state such as on-road driving and the running load is small, and the capacity of the hydraulic motor 49 is decreased. Note that since the running load increases during turning, it is preferable to increase the capacity of the hydraulic motor 49 even when the work implements 18, 21, and 22 are ascending. It is possible to determine whether or not turning is in progress based on whether or not the steering angle (operation amount, steering amount) of the steering wheel 10 is a certain value or more.

[0048] In addition, the motor capacity control means 217b of the embodiment preferably controls the capacity of the hydraulic motor 49 not only according to the past running data but also according to the actual running load during running. That is, when the load torque, the internal pressure of the HST 31, and the decrease amount of the engine speed reach their respective threshold values (reference values) (when the load becomes high) during running in a state where the capacity of the hydraulic motor 49 is controlled according to the past running data, it is preferable to control the inclination angle of the second swash plate 50 so that the capacity of the hydraulic motor 49 becomes even larger.

[0049] Furthermore, although the control for increasing or decreasing the capacity of the hydraulic motor 49 in response to the increase or decrease of the running load has been exemplified, the present invention is not limited thereto. It is also possible to use, as a parameter, a parameter that increases when the running load decreases and decreases when the running load increases, for example, the drive torque. In this case, it is also possible to perform control such that the motor capacity is increased when the drive torque decreases and the motor capacity is decreased when the drive torque increases so that the drive torque becomes constant.

[0050] In addition, in the HST control means 217 of the embodiment, although the mode of controlling the capacity of the hydraulic motor 49 when the running load (load torque, internal pressure, amount of decrease in engine speed) increases has been exemplified, the present invention is not limited thereto. It is also possible to combine the capacity control of the hydraulic pump 47. When the running load increases, internal oil leakage may occur in the HST 31 using hydraulic oil, and a decrease in output rotation (slip) may occur, and the vehicle speed may decrease. Therefore, in order to return the vehicle speed, it is also possible to adjust the inclination angle of the first swash plate 48 to suppress the decrease in the vehicle speed.

[0051] The work implement control means 218 controls the rotation of the hydraulic cylinder 14a and the PTO shaft to control the raising and lowering and driving of the work implements 18, 21, and 22. When manually traveling, the work implement control means 218 controls the raising and lowering and driving of the work implements 18, 21, and 22 in response to the operation of various switches, buttons, and levers such as the raising and lowering switch in the cabin 7. Also, during automatic traveling, when the work start position is reached on the traveling route, the work implements 18, 21, and 22 are lowered to start driving, when the turning start position is reached, the work implements 18, 21, and 22 are raised, when the turning end position is reached, the work implements 18, 21, and 22 are lowered, and when the work end position is reached, the work implements 18, 21, and 22 are raised to stop driving.

[0052] In the tractor 1 of the embodiment having the above configuration, at positions where the running load was high during past running, the capacity of the hydraulic motor 49 increases, and at positions where the running load was low, the capacity of the hydraulic motor 49 decreases. Therefore, at positions where the running load was high during past running and it is predicted that the running load will also be high during this running, the capacity of the hydraulic motor 49 is increased to increase the driving torque, suppressing the occurrence of running defects such as a decrease in running speed and working defects. Also, at positions where the running load was low during past running and it is predicted that the running load will also be low during this running, by reducing the capacity of the hydraulic motor 49, while maintaining running, waste of driving torque is suppressed and fuel efficiency is improved. Therefore, in the tractor 1 of the embodiment, more efficient running is possible compared to a configuration where the torque in the continuously variable transmission (HST) 31 is fixed.

[0053] Also, in the embodiment, the load torque that increases as the running load increases, the internal pressure of the HST 31 that increases as the running load increases, and the engine speed at which the amount of decrease in the engine speed increases as the running load increases are detected. Therefore, the running load can be detected via these parameters.

[0054] (Modified Example) The work vehicle of the present invention is not limited to a tractor and can also be applied to various work vehicles equipped with work implements such as a seedling transplanter and a chemical liquid spraying vehicle. Note that the work implement is not limited to a rotary tilling device 18, a plow 21, etc., and can be applied to any work implement such as a seedling transplanter, a land leveling machine, a seeding machine, and a fertilizer applicator. Also, as the work vehicle, a configuration in which an operator rides and operates has been exemplified, but it is not limited to this. It can also be applied to an autonomously drivable work vehicle that does not have an operator on board, so-called a work robot. Furthermore, in the embodiment, the mode in which the field information storage means 211 is provided in the tractor 1 is exemplified, but it is not limited thereto. For example, in a server (an example of an information processing device, an example of a computer device) that can communicate with the tractor 1 through a communication line, it is also possible to store field information and distribute the field information to the tractor 1. Also, each of the means 211 to 218 is not limited to the mode of centralized processing in the tractor 1, and it is also possible to adopt a mode of distributed processing by a plurality of information processing devices connected by a communication line.

Explanation of Signs

[0055] 1... Working vehicle, 1a... Vehicle body, 2, 3... Driving wheels, 18, 21, 22... Working machines, 31... Continuously variable transmission, 32a... Input shaft, 32b... Output shaft, 47... Hydraulic pump, 49... Hydraulic motor, E... Engine, SN4... Torque sensor, SN4, SN5, SN6... Load detection members, SN5... Pressure sensor, SN6... Rotational speed sensor, SN7... Positioning device.

Claims

1. A vehicle body (1a) having an engine (E), a variable displacement hydraulic pump (47) connected to an input shaft (32a) from the engine (E), and a variable displacement hydraulic motor (49) connected to an output shaft (32b) to drive wheels (2, 3) of the vehicle body (1a), and a continuously variable transmission (31) capable of continuously variable transmission of rotation from the input shaft (32a) to the output shaft (32b), a load detection member (SN4, SN5, SN6) for detecting a running load of the vehicle body (1a), a positioning device (SN7) for measuring a current position of the vehicle body (1a), and comprising: When running in a field, the running load detected by the load detection member (SN4, SN5, SN6) and the position measured by the positioning device (SN7) are associated and stored, and based on the stored running load and position during past running, at a position where the running load is higher than a reference value, the capacity of the hydraulic motor (49) is made larger than at a position where the running load is lower than the reference value A work vehicle characterized by the above.

2. The load detection member (SN4) constituted by a torque sensor (SN4) for detecting a load torque of the drive wheels (2, 3) as the running load, The work vehicle according to claim 1, characterized by comprising the above.

3. The load detection member (SN5) constituted by a pressure sensor (SN5) for detecting an internal pressure of the continuously variable transmission (31) as the running load, The work vehicle according to claim 1, characterized by comprising the above.

4. The load detection member (SN6) constituted by a rotational speed sensor (SN6) for detecting a rotational speed of the engine (E) as the running load, and comprising: Based on the engine rotational speed and position during past running, at a position where the decrease amount of the engine rotational speed is higher than the reference value, the capacity of the hydraulic motor (49) is made larger than at a position where the decrease amount of the engine rotational speed is lower than the reference value The work vehicle according to claim 1, characterized by the above.

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