JP7738530B2 - Work vehicle - Google Patents

Description

The present invention relates to a work vehicle suitable for moving over uneven, rough terrain.

In the past, the above-mentioned work vehicle has been configured so that four running wheels driven by a hydraulic motor are supported on the vehicle body via an articulating link mechanism that can be extended or retracted by operating a hydraulic cylinder. By changing the height of the running wheels, the vehicle body can be driven while maintaining its posture even on uneven terrain (see, for example, Patent Document 1). This work vehicle is equipped with a hydraulic pump driven by the engine as a hydraulic supply source that supplies hydraulic oil to the hydraulic cylinders and hydraulic motor, and the engine output is always set to a high output close to maximum.

JP 2020-1440 A

The above-mentioned work vehicle is used in a work style in which cargo is loaded on top of the vehicle body and travels while maintaining the vehicle body in a horizontal position. Conventionally, engine output has always been set to a high output close to maximum, so it can handle situations where cargo is loaded even when the vehicle is located on uneven ground.

However, with the above-mentioned conventional configuration, there is not always cargo loaded on top of the vehicle body, and there are times when there is no cargo. Even when there is no cargo, the engine operates at high power, which unnecessarily increases the amount of fuel consumed per unit time, potentially shortening the amount of work that can be done before the stored fuel is consumed, and also has other disadvantages such as increased noise.

Therefore, there was a demand for a system that could maintain the vehicle's proper posture regardless of the load condition, while also reducing unnecessary fuel consumption by the engine.

The work vehicle according to the present invention comprises a vehicle body having a loading section capable of loading cargo, a plurality of traveling devices that are driven to travel by a traveling hydraulic device and are located at the front and rear of both the left and right sides of the vehicle body, a plurality of support mechanisms that are supported by the vehicle body and driven by a position-changing hydraulic device to support the traveling devices so that their positions can be changed relative to the vehicle body, a hydraulic pump that supplies hydraulic oil to the traveling hydraulic device and the position-changing hydraulic device, an engine that drives the hydraulic pump, loading status detection means that measures the loading status of the cargo loaded on the loading section, and a loading status detection device that detects the loading status. and a change adjustment means for changing and adjusting the driving state of the engine in accordance with differences in the loading status of the luggage detected by a load condition detection means, wherein the loading status detection means measures the variation in the loading location of the luggage relative to the loading section as the loading status, and the change adjustment means determines the magnitude of the load caused by the luggage based on the detection result of the loading status detection means, and adjusts the engine output as the driving status of the engine so that if the load is large, the engine output is increased, and as the load is smaller, the engine output is decreased.

According to the present invention, the load condition detecting means detects the load condition of the luggage loaded on the loading section, i.e. , the load condition caused by the luggage, and the changing and adjusting means adjusts the driving state of the engine according to the luggage load condition.
If the load is unevenly distributed relative to the loading section, an uneven load is applied to the vehicle body, increasing the load load when maintaining the vehicle body's position and increasing the driving load on the engine. Therefore, in this configuration, the uneven distribution of the load is measured as the loading condition. As a result, if the load is balanced and centered relative to the loading section, it is possible to reduce unnecessary fuel consumption by the engine compared to when the load is unevenly distributed.

According to this configuration, when the luggage load is heavy, the engine output is increased, thereby enabling the vehicle body to maintain its posture properly. On the other hand, when the luggage load is light , the engine output is reduced, thereby reducing the driving load on the engine and thereby reducing unnecessary fuel consumption by the engine. Note that, since the luggage load is light at this time, it is possible to maintain the vehicle body's posture even if the engine output is reduced. By changing the engine output in this way, it is possible to appropriately reduce engine fuel consumption when the load is light.

As a result, it is possible to maintain good vehicle posture regardless of the load condition, while also reducing unnecessary fuel consumption by the engine.

The work vehicle according to the present invention comprises a vehicle body having a loading section capable of loading cargo, a plurality of traveling devices which are driven to travel by a traveling hydraulic device and which are located at the front and rear of both the left and right sides of the vehicle body, a plurality of support mechanisms which are supported by the vehicle body and driven by a position-changing hydraulic device to support the traveling devices so that their positions can be changed relative to the vehicle body, a hydraulic pump which supplies hydraulic oil to the traveling hydraulic device and the position-changing hydraulic device, a loading status detection means which measures the loading status of the cargo loaded on the loading section, and a load status detection means for detecting the loading status of the cargo loaded on the loading section. and a change/adjustment means for changing/adjusting the amount of hydraulic oil supplied in accordance with differences in the loading status of the luggage detected by the loading means, wherein the loading status detection means measures the variation in the loading location of the luggage relative to the loading section as the loading status, and the change/adjustment means determines the magnitude of the load caused by the luggage based on the detection result of the loading status detection means, and adjusts the amount of hydraulic oil supplied to be large if the load is large, and adjusts the amount of hydraulic oil supplied to be small as the load load becomes smaller.

According to the present invention, the load condition detection means detects the load condition of the cargo loaded on the loading section, i.e., the load condition caused by the cargo being loaded, and the varying/adjusting means adjusts the supply amount of hydraulic oil according to the load condition of the cargo.
If the load is unevenly distributed relative to the loading section, an uneven load is applied to the vehicle body, increasing the load load when maintaining the vehicle body's position and increasing the driving load on the engine. Therefore, in this configuration, the uneven distribution of the load is measured as the loading condition. As a result, if the load is balanced and centered relative to the loading section, it is possible to reduce unnecessary fuel consumption by the engine compared to when the load is unevenly distributed.
According to this configuration, when the luggage load is heavy, the amount of hydraulic oil supplied from the hydraulic pump is increased, thereby enabling the posture of the vehicle body to be maintained well. On the other hand, when the luggage load is light, the driving load can be reduced by reducing the amount of hydraulic oil supplied from the hydraulic pump. By changing the amount of hydraulic oil supplied by the engine-driven hydraulic pump in this way, the driving load of the engine that drives the hydraulic pump is reduced, and engine fuel consumption under light loads can be suppressed. Furthermore, since the luggage load is light at this time, it is possible to maintain the posture of the vehicle body even if the amount of hydraulic oil supplied is reduced.
Therefore, it is possible to maintain the vehicle body in a good position regardless of the load condition of the luggage, and also to suppress unnecessary fuel consumption by the engine.

The work vehicle according to the present invention comprises a vehicle body having a loading section capable of carrying luggage, a plurality of travelling devices driven by a hydraulic motor and positioned at the front and rear of both the left and right sides of the vehicle body, a plurality of support mechanisms supported by the vehicle body and driven by hydraulic cylinders to support the travelling devices so that their positions can be changed relative to the vehicle body, a hydraulic pump that supplies hydraulic oil to the hydraulic motors and the hydraulic cylinders, a pressure oil supply line that supplies the hydraulic oil from the hydraulic pump to the plurality of hydraulic motors and the plurality of hydraulic cylinders, and an unloader switchable between an open state in which the pressure oil supply line is shut off and the hydraulic oil from the hydraulic pump is returned to a reservoir, and a closed state in which the hydraulic oil is supplied to the plurality of hydraulic motors and the plurality of hydraulic cylinders through the pressure oil supply line. and a change /adjustment means for changing/adjusting the amount of hydraulic oil supplied in accordance with the difference in the loading status of the luggage detected by the loading status detection means, wherein the change/adjustment means is capable of interval operation for alternately switching the unload valve between the closed state and the open state at a set period, and is characterized in that the change/adjustment means determines the magnitude of the load caused by the luggage based on the detection result of the loading status detection means, and adjusts the amount of hydraulic oil supplied to be large by lengthening the interval for the closed state if the load is large, and adjusts the amount of hydraulic oil supplied to be large by lengthening the interval for the open state as the load load becomes smaller.

According to the present invention, the loading condition detection means detects the loading condition of the cargo on the loading section, such as the weight of the cargo or the unevenness of the cargo loading location on the loading section, and the load burden caused by the cargo being loaded. Then, the changing and adjusting means adjusts the supply amount of hydraulic oil according to the difference in the cargo loading condition.
According to this configuration, the varying/adjusting means performs interval operation to alternately switch the unloading valve between the closed state and the open state at set intervals.

If the interval between shutoff states within the set cycle becomes longer, the interval between open states will become shorter. In this case, the amount of hydraulic oil supplied to the multiple hydraulic motors and multiple hydraulic cylinders through the pressure oil supply line will increase, resulting in a greater driving load on the engine.

On the other hand, if the interval between open states within the set cycle becomes longer, the interval between closed states will become shorter. In this case, the amount of hydraulic oil supplied to the multiple hydraulic motors and multiple hydraulic cylinders through the pressure oil supply line will decrease, thereby reducing the driving load on the engine.

The control device performs interval operation so that the interval between the blocked state is longer when the load is heavy and the interval between the open state is longer as the load becomes lighter.As a result, the engine driving load is reduced as the load becomes lighter, and engine fuel consumption at light loads can be suppressed.
In the present invention, it is preferable that the loading status detection means measures the weight of the luggage as the loading status.
If the weight of the luggage loaded on the loading section is heavy, the load caused by the luggage will be heavy, and if the weight is light, the load will be light. Therefore, in this configuration, the weight of the luggage to be loaded is measured and the amount of hydraulic oil supplied is changed and adjusted according to the measured luggage weight. As a result, if the luggage weight is light, it is possible to reduce unnecessary fuel consumption by the engine.
In the present invention, it is preferable that the loading status detection means measures, as the loading status, variations in the loading positions of the luggage relative to the loading section.
If the load is unevenly distributed relative to the loading section, an uneven load is applied to the vehicle body, increasing the load load when maintaining the vehicle body's position and increasing the driving load on the engine. Therefore, in this configuration, the uneven distribution of the load is measured as the loading condition. As a result, if the load is balanced and centered relative to the loading section, it is possible to reduce unnecessary fuel consumption by the engine compared to when the load is unevenly distributed.

FIG. FIG. FIG. FIG. FIG. FIG. 10 is a flowchart of a control operation. 10 is a flowchart of a control operation. 10 is a flowchart of a control operation. FIG. 10 is a hydraulic circuit diagram of a hydraulic oil supply unit according to another embodiment. 10 is a flowchart of a control operation according to another embodiment.

Embodiments of the present invention will be described with reference to the drawings. In the following description, the direction of the arrow FW shown in the drawings will be referred to as "front," the direction of the arrow BK as "rear," the direction of the arrow RH as "right," the direction of the arrow LH as "left," the direction of the arrow UP as "up," and the direction of the arrow DW as "down."

As shown in Figures 1 to 3, the work vehicle is equipped with a vehicle body 1 that is generally rectangular in plan view and supports the entire vehicle, multiple running wheels 2 that serve as running devices and support the vehicle body 1, multiple auxiliary wheels 3 that correspond to each of the multiple running wheels 2, a support mechanism A that supports the multiple running wheels 2 so that their positions can be changed relative to the vehicle body 1, and multiple hydraulic motors 4 that serve as running hydraulic devices that individually drive the multiple running wheels 2.

Traveling wheels 2 are located at the front and rear of both the left and right sides of the vehicle body 1. In this embodiment, the work vehicle has four traveling wheels 2: the left front, right front, left rear, and right rear. It also has four support mechanisms A: the left front, right front, left rear, and right rear. The support mechanisms A include a bending link mechanism 5 and multiple hydraulic cylinders 6, 7 as position-changing hydraulic devices that can individually change the position of the bending link mechanisms 5.

The vehicle body 1 is generally rectangular in plan view, and is provided with a flat loading section 8 on the top surface of the vehicle body 1 that can carry cargo. The loading section 8 is a generally rectangular section in plan view, and extends from the right end to the left end of the vehicle body 1. The loading section 8 is configured so that cargo can be placed on it. Examples of cargo that can be placed on the loading section 8 include agricultural machinery, agricultural supplies such as fertilizer and chemicals, harvested crops and harvest baskets, and pallets on which these are placed.

The vehicle body 1 is equipped with a hydraulic supply source 9 located below the loading section 8, which sends hydraulic oil to the hydraulic cylinders 6, 7 and hydraulic motor 4; multiple hydraulic control valves 10 that adjust the supply of hydraulic oil from the hydraulic supply source 9; an ECU (Electronic Control Unit) 11 that controls the operation of the hydraulic control valves 10; and a battery 12 for power supply. The hydraulic supply source 9 includes a hydraulic pump 9b driven by the engine 9a. The hydraulic supply source 9 also includes a hydraulic oil tank 9c, a radiator 9d, and other components. The hydraulic supply source 9 is supported by the underframe 24. A fuel tank 9e is provided at a high position on the rear side of the vehicle body 1. A speed governor 9f for the engine 9a is also provided, and the ECU 11 is configured to control the operation of the speed governor 9f to change or adjust the engine output.

The ECU 11 is equipped with a microcomputer and is capable of executing various controls according to a control program. The control device C is made up of multiple hydraulic control valves 10 and the ECU 11. The battery 12 is charged by a generator driven by the power of the engine 9a. Reference numeral 13 in the figure denotes an operating handle that can be gripped and operated by the operator.

[Support mechanism]
As described above, the support mechanism A includes the articulating link mechanism 5 and the plurality of hydraulic cylinders 6, 7. As shown in Fig. 1, the plurality of (specifically, four) running wheels 2 are supported via the articulating link mechanism 5 so as to be able to move up and down independently relative to the vehicle body 1.

As shown in Figures 4 and 5, the articulating link mechanism 5 includes a base end 14 supported by the vehicle body 1, a first link 15 whose upper end is supported below the base end 14 so as to be rotatable about the horizontal axis X1, and a second link 16 whose one end is supported by the lower end of the first link 15 so as to be rotatable about the horizontal axis X2 and whose other end supports the running wheel 2.

The support bracket 17 that supports the running wheel 2 is supported so as to be swingable around the vertical axis Y by a boss 18 provided at the swing end of the second link 16. A hydraulic cylinder 20 (hereinafter referred to as the swing cylinder) for swing operation is provided between a bracket 19 on one end of the second link 16 and an arm 17a provided on the support bracket 17.

A plurality of hydraulic cylinders 6, 7 are provided corresponding to each of the plurality of bending link mechanisms 5, capable of individually changing the position of each bending link mechanism 5. That is, a first hydraulic cylinder 6 is provided that can change the swing position of the first link 15 relative to the vehicle body 1, and a second hydraulic cylinder 7 is provided that can change the swing position of the second link 16 relative to the first link 15.

When the first hydraulic cylinder 6 is extended or retracted with the second hydraulic cylinder 7 deactivated, the first link 15, the second link 16, and the running wheel 2 each oscillate together around the horizontal axis X1 of the pivot connection point to the base end 14 while maintaining a constant relative posture. When the second hydraulic cylinder 7 is extended or retracted with the first hydraulic cylinder 6 deactivated, the second link 16 and the running wheel 2 oscillate together around the horizontal axis X2 of the connection point between the first link 15 and the second link 16 while maintaining a constant posture of the first link 15.

An auxiliary wheel 3 is rotatably supported at an intermediate bending portion of each of the plurality of bending link mechanisms 5 .
The auxiliary wheels 3 are configured as wheels with approximately the same outer diameter as the running wheels 2. The support shaft that pivotally connects the first link 15 and the second link 16 is formed to extend so as to protrude outward in the lateral width direction of the vehicle body, and the auxiliary wheels 3 are rotatably supported at the extended protruding portion of the support shaft.

By operating the turning cylinder 20, the running wheel 2 can be rotated around the vertical axis Y relative to the articulating link mechanism 5, thereby allowing the vehicle to be turned.

The hydraulic control valve 10 corresponding to the hydraulic motor 4 adjusts the flow rate of hydraulic oil, thereby changing the rotational speed of the hydraulic motor 4, and therefore the rotational speed of the traveling wheels 2.

[Sensor]
This work vehicle is equipped with various sensors.
6 , each of the four second hydraulic cylinders 7 is provided with a head-side pressure sensor S1 and a cap-side pressure sensor S2. The head-side pressure sensor S1 detects the internal pressure of the oil chamber in the head-side chamber of the second hydraulic cylinder 7. The cap-side pressure sensor S2 detects the internal pressure of the oil chamber in the cap-side chamber of the second hydraulic cylinder 7.

Each of the four first hydraulic cylinders 6 and four second hydraulic cylinders 7 is equipped with multiple stroke sensors S3 capable of detecting the amount of extension/retraction operation. The amount of extension/retraction operation of each hydraulic cylinder 6, 7 is a detected value corresponding to the swing position of the first link 15 and second link 16, which are the objects of operation.

The vehicle body 1 is provided with an inclination sensor S4 for detecting the inclination state of the vehicle body. The inclination sensor S4 is an inertial measurement unit (IMS) having a well-known configuration.
The IMU has a three-axis acceleration sensor and a gyro sensor, and can detect changes in the attitude of the vehicle body 1, specifically, tilt in the front-rear and left-right directions.

A rotation sensor S5 is provided near the running wheels 2 to detect the rotational speed of the running wheels 2 driven by the hydraulic motor 4. Based on the rotational speed of the running wheels 2 detected by the rotation sensor S5, the supply of hydraulic oil to the hydraulic motor 4 is controlled so that the rotational speed of the running wheels 2 reaches a target value. A pressure sensor S6 is provided to detect the pressure of the hydraulic oil supplied to the hydraulic motor 4. Based on the pressure of the hydraulic oil detected by the pressure sensor S6, the supply (pressure) of hydraulic oil to the hydraulic motor 4 is controlled so that the drive torque of the running wheels 2 reaches a target value. Each of the four swing cylinders 20 is provided with a stroke sensor S7 that can detect the extension/retraction operation amount.

[ECU]
The ECU 11 (Electronic Control Unit) includes a non-volatile memory (not shown) that stores programs corresponding to the functional units described below, and a CPU (not shown) that executes the programs. The functions of the functional units are realized by the CPU executing the programs.

The ECU 11 has, as its functional units, an attitude control unit 100, a driving control unit 101, a weight calculation unit 102, and a drive load adjustment unit 103. When the vehicle is traveling with all four running wheels 2 in contact with the ground, the driving control unit 101 controls the operation of the hydraulic motor 4 for each of the four running wheels 2 so that the rotational speed of the running wheels 2 detected by the rotation sensor S5 reaches a target speed and the drive torque detected by the pressure sensor S6 reaches a target value. Specifically, it performs a switching operation on the hydraulic control valve that supplies and discharges hydraulic oil to and from the hydraulic motor.

When the vehicle body is moving, the posture control unit 100 performs horizontal control, controlling the operation of the support mechanism A so that the loading section 8 of the vehicle body 1 is in a horizontal position, based on the detection information from the inclination sensor S4. During horizontal control, the posture control unit 100 controls the operation of the four first hydraulic cylinders 6 and the four second hydraulic cylinders 7 based on the detection information from the inclination sensor S4 and the stroke sensor S3 so that the tilt angles in the front-to-back direction and the left-to-right direction of the vehicle body 1 from a horizontal position become values corresponding to the horizontal position.

To explain further, the target operating amounts of the four first hydraulic cylinders 6 and the four second hydraulic cylinders 7 required to bring the loading section 8 to a horizontal position are calculated from the inclined position of the loading section 8 detected by the inclination sensor S4, and the operation of the four first hydraulic cylinders 6 and the four second hydraulic cylinders 7 is controlled so that the actual operating amounts detected by the stroke sensor S3 become the target operating amounts.
Specifically, the control unit 10 switches the hydraulic control valve 10 that supplies and discharges hydraulic oil to the four first hydraulic cylinders 6 and the four second hydraulic cylinders 7 .

The actual operating amount of each hydraulic cylinder 6, 7 detected by the stroke sensor S3 indicates the relative change in posture of the link being operated relative to the vehicle body member. In other words, based on the detection value of the stroke sensor S3, it is possible to determine the swing posture of the first link 15 relative to the vehicle body 1, the swing posture of the second link 16 relative to the first link 15, etc. As a result, it is possible to determine the height from the ground contact area of the running wheel 2 to the vehicle body 1.

When the vehicle is stopped, the weight calculation unit 102 determines the load status of the luggage loaded on the loading unit 8 based on the detection results of the pressure sensors S1, S2 and the stroke sensors S3, and calculates the weight of the luggage and the variation in the location of the luggage relative to the loading unit 8. Therefore, the pressure sensors S1, S2, the stroke sensors S3, and the weight calculation unit 102 constitute a load status detection means SJ that measures the load status of the luggage loaded on the loading unit 8.

The weight calculation will be explained.
Based on the detection value of the stroke sensor S3, the swinging posture of the first link 15 relative to the vehicle body 1, the swinging posture of the second link 16 relative to the first link 15, etc. can be determined, so it is possible to determine the height from the contact point of the running wheel 2 in each support mechanism A to the vehicle body 1.

In addition, based on the detection results of pressure sensors S1 and S2, the pressure acting on hydraulic cylinders 6 and 7 via links 15 and 16 of support mechanism A when running wheel 2 touches the ground can be detected. A force acting in the vertical direction at the contact point where running wheel 2 touches the ground acts on first hydraulic cylinder 6 via first link 15, and on second hydraulic cylinder 7 via second link 16.

The weight of the entire vehicle acts vertically at the contact point of each running wheel 2. At this time, the vertical force acting on the running wheel 2 (hereinafter referred to as ground contact pressure) acts as internal pressure in the oil chambers of each of the hydraulic cylinders 6, 7 via the support mechanism A. Therefore, the ground contact pressure at each support mechanism A can be calculated using the detection information from pressure sensors S1, S2 and stroke sensor S3.

The drive load adjustment unit 103 changes and adjusts the drive state of the engine 9a depending on the load condition. In other words, it controls the operation of the speed governor so that the output rotational speed of the engine 9a becomes a rotational speed that corresponds to the load condition. Therefore, the drive load adjustment unit 103 constitutes the change adjustment means HT.

Next, the control operations of the weight calculation unit 102 and the drive load adjustment unit 103 by the ECU 11 will be explained based on the flowcharts in Figures 7 to 9.

As an initial setting, the ECU 11 controls the speed governor 9f to drive the engine 9a at rated speed (step #01). When the vehicle is traveling with a load, the engine 9a is driven at rated speed. Then, after the vehicle stops traveling (step #02), the load weight measurement process is executed (step #03).

As shown in Figure 9, the load weight measurement process uses the detection information from pressure sensors S1, S2 and stroke sensor S3 to calculate the ground pressure for each support mechanism A (step #31). At this time, it is assumed that the loading unit 8 has been placed in a horizontal position through horizontal control, but if the loading unit 8 is not placed in a horizontal position even after performing horizontal control, information from tilt sensor S4 may also be taken into account.

The weight of the entire vehicle is calculated by adding up the ground contact pressure of each of the multiple running wheels 2 (step #32). Next, the weight of the cargo loaded in the loading section 8 is calculated by subtracting the weight of the vehicle body, which has been measured and known in advance, from the weight of the entire vehicle (step #33).

Furthermore, the location of the cargo's center of gravity in the loading area is predicted based on the contact pressure determined at the contact points of the four running wheels 2, and the variation in the loading position is measured (step #34). To explain further, by comparing the variation in contact pressure of each of the four running wheels 2, the center of gravity position in a plan view of the entire vehicle can be determined, and the degree of variation in the loading position relative to the appropriate loading position in the center of the loading area can be determined.

For example, even if the loading section 8 is in a horizontal position, if the cargo is loaded unevenly on the loading section 8, the ground contact pressure of the running wheel 2 on the uneven side will be greater than the ground contact pressure of the running wheel 2 on the opposite side.

Next, the driving load adjustment process is executed (step #04).
As shown in Fig. 9, in the drive load adjustment process, the magnitude of the load caused by the luggage is determined based on the measurement results of the load weight measurement process (step #41). The load is determined according to the weight of the luggage and the variation in the loading position. The heavier the luggage, the greater the load, and the greater the variation in the loading position, the greater the load.

If the load is determined to be heavy, the engine will be kept running at rated speed (steps #41 and #42). Even when the vehicle is mainly loaded with cargo, the engine will continue to run at rated speed with high output, allowing for smooth travel and driving.

If it is determined that the load is light, the engine speed is reduced to an intermediate value (step #43). An intermediate value is a speed state that is halfway between rated speed and idling speed. When the load is light, reducing the engine output can minimize unnecessary fuel consumption.

If it is determined that there is no load, i.e., no luggage is loaded on the loading section 8, the engine speed is reduced to the lower limit (idling speed or close to it) (step #44). If no luggage is loaded, reducing the output of the engine 9a to a minimum or close to it can reduce fuel consumption and noise.

When the engine speed is reduced to an intermediate value or to the lower limit, once the vehicle starts moving (step #45), a driving load is applied due to the driving of the running wheels 2, so the engine 9a is returned to a state where it is driven at rated speed (step #46).

By changing and adjusting the driving state of the engine 9a in this way according to differences in load, it is possible to reduce unnecessary fuel consumption by the engine 9a, and it also contributes to an improved working environment by reducing engine 9a noise.

[Another embodiment]
(1) The loading status detecting means may be configured as follows.
Instead of the pressure sensors S1 and S2, a torque sensor or a load cell that detects the drive torque applied to each link 15 and 16 of the support mechanism A may be used, or a sensor that directly detects the vertical ground contact pressure applied to the rotation axis of the traveling wheel 2 may be used. Also, instead of the stroke sensor S3, a potentiometer or a rotary encoder that detects the rotation angle of the joint portion of each link 15 and 16 of the support mechanism A may be used.

(2) The load magnitude determination is not limited to three stages, but may be two stages, four or more stages, or continuously. The driving load adjustment process may be configured to switch the output of the engine 9a in two stages, four stages, continuously, or the like, depending on how the load is determined.

(3) The driving load adjusting section (changing/adjusting means) may be configured as follows instead of changing/adjusting the output of the engine 9a.
10, an unloading valve 22 is provided in a pressure oil supply line 21 that supplies hydraulic oil from a hydraulic pump 9b to a plurality of hydraulic motors 4 and a plurality of hydraulic cylinders 6, 7, and 20. The unloading valve 22 can be switched between an open state in which the pressure oil supply line 21 is shut off and hydraulic oil from the hydraulic pump 9b is returned to a reservoir (hydraulic oil tank 9c), and a closed state in which hydraulic oil is supplied to a plurality of hydraulic devices through the pressure oil supply line 21. In the figure, reference numeral 23 denotes a relief valve, and 9g denotes an oil filter.

The drive load adjustment unit 103 may be capable of interval operation, which alternately switches the unload valve 22 between a closed state and an open state at a set cycle, and may adjust the amount of hydraulic oil supplied by performing interval operation such that the interval between the closed state is longer when the load is heavy and the interval between the open state is longer when the load is lighter.

That is, the following process is executed as the driving load adjustment process of step #04 in the above embodiment.
As shown in FIG. 11, in the driving load adjustment process, the magnitude of the load caused by the luggage is determined based on the measurement result of the loaded weight measurement process, as in the above embodiment (step #401).

If it is determined that the load is large and high, the unloading valve 22 is maintained in the closed state (step #402). In other words, in this case, during interval operation, the time spent in the closed state is 100%, and the time spent in the open state is 0%. Even when the vehicle is mainly carrying cargo, the unloading valve 22 is closed, so all of the pressurized oil from the hydraulic pump 9b is supplied to multiple hydraulic devices, allowing for good posture maintenance and travel.

If it is determined that the load is small and low, an interval operation is performed in which the unloading valve 22 is alternately switched between a closed state and an open state at regular intervals (step #403). When the load is light, a portion of the pressurized oil from the hydraulic pump is returned to the reservoir (hydraulic oil tank 9c), thereby minimizing unnecessary fuel consumption.

If it is determined that there is no load, i.e., no cargo is loaded on the loading section 8, the unload valve 22 is maintained in an open state (step #404). In other words, in this case, the time spent in the closed state during interval operation is 0% and the time spent in the open state is 100%. If no cargo is loaded, the supply of hydraulic oil to multiple hydraulic devices is stopped, thereby reducing the load on the engine 9a, suppressing fuel consumption, and reducing noise.

When the unloading valve 22 is operated at intervals, or when the unloading valve 22 is maintained in an open state, once the vehicle starts moving (step #405), a driving load is applied due to the driving of the running wheels 2, so the unloading valve 22 is returned to a state where it is maintained in a closed state (step #406).

Even in this configuration, the load magnitude is not limited to being divided into three stages when determining its magnitude, but may be divided into two stages, four or more stages, or even continuously. When dividing into stages continuously, the drive load adjustment process may be configured to change the ratio of the time spent in the blocked state to the time spent in the released state continuously during interval operation between a blocked state where the time spent in the blocked state is 100% and the time spent in the released state is 0%, and a released state where the time spent in the blocked state is 0% and the time spent in the released state is 100%.

(4) The weight calculation process may involve, for example, calculating the total weight by adding up the vertical ground contact pressure applied to the rotation axis of the running wheel 2, and the calculation method can be modified in various ways.

(5) As the tilt sensor S4, various sensors such as a weight-type tilt sensor or an optical fiber gyro may be used instead of an inertial measurement unit (IMU).

(6) The support mechanism A may be a mechanism having one link or three or more links, and may be equipped with an electric actuator instead of a hydraulic cylinder.

(7) The running wheels 2 may be driven by an electric motor, an engine, etc.

The present invention can be applied to work vehicles that are suitable for traveling on uneven, rough terrain.

REFERENCE SIGNS LIST 1 vehicle body 2 traveling device 4 traveling hydraulic device 5 hydraulic motor 6, 7 attitude change hydraulic device 9a engine 9b hydraulic pump 21 pressure oil supply line 22 unload valve HT change adjustment means SJ loading condition detection means

Claims (5)

a vehicle body having a loading section capable of loading luggage;
a plurality of traveling devices that are driven by a traveling hydraulic device and are located at the front and rear of both the left and right sides of the vehicle body;
a plurality of support mechanisms supported by the vehicle body and driven by an attitude changing hydraulic device to support the traveling device so as to change its position relative to the vehicle body;
a hydraulic pump that supplies hydraulic oil to the traveling hydraulic device and the attitude changing hydraulic device;
an engine that drives the hydraulic pump;
a loading status detection means for measuring the loading status of the cargo loaded on the loading section;
a change/adjustment means for changing/adjusting the driving state of the engine in accordance with the difference in the load state of the luggage detected by the load state detection means ,
The loading status detection means measures the variation in the loading positions of the luggage relative to the loading section as the loading status,
The change adjustment means determines the magnitude of the load caused by the luggage based on the detection results of the loading status detection means, and adjusts the engine output as the driving state of the engine so that if the load is large, the engine output is increased, and as the load becomes smaller, the engine output is decreased . a vehicle body having a loading section capable of loading luggage;
a plurality of traveling devices that are driven by a traveling hydraulic device and are located at the front and rear of both the left and right sides of the vehicle body;
a plurality of support mechanisms supported by the vehicle body and driven by an attitude changing hydraulic device to support the traveling device so as to change its position relative to the vehicle body;
a hydraulic pump that supplies hydraulic oil to the traveling hydraulic device and the attitude changing hydraulic device ;
a loading status detection means for measuring the loading status of the cargo loaded on the loading section;
and a change/adjustment means for changing and adjusting the supply amount of the hydraulic oil in accordance with the difference in the load status of the luggage detected by the load status detection means ,
The loading status detection means measures the variation in the loading positions of the luggage relative to the loading section as the loading status,
The change adjustment means determines the magnitude of the load caused by the luggage based on the detection results of the loading status detection means, and adjusts the amount of hydraulic oil supplied to be large if the load is large, and adjusts the amount of hydraulic oil supplied to be small as the load becomes smaller . a vehicle body having a loading section capable of loading luggage;
a plurality of travel devices that are driven to travel by hydraulic motors and are located at the front and rear of both the left and right sides of the vehicle body;
a plurality of support mechanisms supported on the vehicle body and driven by hydraulic cylinders to support the traveling device so as to change its position relative to the vehicle body;
a hydraulic pump that supplies hydraulic oil to the hydraulic motor and the hydraulic cylinder ;
a pressure oil supply passage for supplying the hydraulic oil from the hydraulic pump to the plurality of hydraulic motors and the plurality of hydraulic cylinders;
an unloading valve that is switchable between an open state in which the pressure oil supply path is blocked to return the hydraulic oil from the hydraulic pump to a reservoir, and a blocked state in which the hydraulic oil is supplied to the plurality of hydraulic motors and the plurality of hydraulic cylinders through the pressure oil supply path;
a loading status detection means for measuring the loading status of the cargo loaded on the loading section;
and a change/adjustment means for changing and adjusting the supply amount of the hydraulic oil in accordance with the difference in the load status of the luggage detected by the load status detection means ,
The change adjustment means is capable of interval operation to alternately switch the unload valve between the closed state and the open state at a set period, and determines the magnitude of the load caused by the luggage based on the detection results of the loading status detection means, and adjusts the amount of hydraulic oil supplied to a large amount by lengthening the interval for the closed state if the load is large, and adjusts the amount of hydraulic oil supplied to a large amount by lengthening the interval for the open state as the load becomes smaller, thereby adjusting the amount of hydraulic oil supplied to a small amount . 4. The work vehicle according to claim 3 , wherein said load condition detection means measures the weight of said luggage as said load condition. 4. The work vehicle according to claim 3 , wherein the loading condition detection means measures, as the loading condition, variations in the loading positions of the cargo relative to the loading section.