JPH1150868A - Engine speed adjustment structure of traveling vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the engine speed setting operation of a traveling vehicle for working which is mounted with a diesel engine with electronic governor mechanism and shifted by an HST type continuously variable transmission. SOLUTION: An input power to a hydraulic motor of an HST type continuously variable transmission is detected, the speed of an engine E is controlled so that the input power does not exceed the maximum allowable power of the HST type continuously variable transmission, and an engine speed can be set by an accelerator lever HL and a foot pedal 80. When a shift operating device 62 is switched over to high speed side, the engine speed is set by the foot pedal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agricultural traveling vehicle such as a tractor provided with an engine equipped with an electronic governor mechanism, the transmission of which is shifted by an HST type continuously variable transmission, and the shifted power is transmitted to a traveling side and a working machine side. Regarding what to communicate.

[0002]

2. Description of the Related Art Conventionally, as a technology relating to a control device accompanying a change in load of a work vehicle, a device for providing an engine with an electronic governor mechanism to control the engine speed and an HST type continuously variable transmission for shifting the output of the engine. Equipment and the like were provided. The electronic governor mechanism is disposed on a side of a fuel injection pump that supplies fuel to the engine. The electronic governor mechanism was controlled by a controller to adjust the amount of fuel injected by the fuel injection pump. For example, isochronous control has been performed in which the amount of fuel supplied is adjusted in accordance with engine load fluctuations and the engine speed is maintained at the set speed of the accelerator lever. In addition, reverse droop control has been performed in which the output of the engine is imparted in low and medium speed ranges of the engine speed.
Further, the controller is provided with a switch for storing a constant number of rotations required for the operation and performing isochronous control for maintaining the stored number of rotations. Further, the controller stores a map exhibiting the optimum engine performance (output and torque) for high-speed work, and can switch from normal engine performance to engine performance for high-speed work by operating a mode switching button. Such a configuration is also known.

The HST type continuously variable transmission is composed of a variable displacement hydraulic pump and a constant displacement hydraulic motor, and the constant displacement hydraulic motor is driven by pressure oil discharged from the variable displacement hydraulic pump. Was. The discharge amount of pressure oil by the variable displacement hydraulic pump is determined by a pump stroke volume (discharge amount per rotation) due to tilting of a swash plate of the pump,
The rotation speed of the hydraulic motor has been increased by adjusting the rotation amount of the engine input to the pump and increasing the discharge amount.

[0004]

However, in the conventional configuration in which the output of the engine is shifted by using the HST type continuously variable transmission, the efficiency is maintained high at the time of low-speed traveling such as work, but the high speed is maintained. When traveling, the efficiency of shifting by the HST-type continuously variable transmission is poor, and the discharge amount of pressure oil by the hydraulic pump of the HST-type continuously variable transmission is limited even if the engine speed is increased. There was something. Driving the engine at high speed beyond the limit of the HST-type continuously variable transmission is wasteful in terms of efficiency.
This also caused the ST type continuously variable transmission to fail.

[0005] The movable swash plate of the HST-type continuously variable transmission is interlocked with a main transmission lever, and in order to regulate the speed of the work vehicle, an engine speed is first set by operating an accelerator lever. After increasing the engine speed, the running speed of the aircraft was adjusted by operating the main shift lever. In order to run at high speed in this operation method, it is necessary to adjust the vehicle speed by operating the main transmission lever after rotating the engine speed at high speed. Operating the main shift lever in the high-speed range of the engine causes a sudden change in speed, and every time the main shift lever is switched, a strong impact is caused on the operator, resulting in poor ride comfort. there were.

[0006]

The present invention uses the following means in order to solve such a problem. First, in a working vehicle equipped with a diesel engine with an electronic governor mechanism and shifting the power of the engine by an HST-type continuously variable transmission, the input horsepower to a hydraulic motor of the HST-type continuously variable transmission is detected. The engine speed is controlled so that the horsepower does not exceed the maximum allowable horsepower of the HST type continuously variable transmission. Further, in a working traveling vehicle equipped with a diesel engine with an electronic governor mechanism, the power of the engine is traveled by a transmission, the engine speed is set, and the traveling speed is set by a shift operation tool that shifts the transmission. The engine speed can be set by an accelerator lever and a foot pedal, and when the speed change operation tool is switched to a high speed side, the engine speed is set by the foot pedal.

[0007]

Embodiments of the present invention will be described with reference to the accompanying drawings. 1 is a side view of a tractor to which a working machine is mounted, FIG. 2 is a plan view of the same, FIG. 3 is a block diagram showing a control structure of an electronic governor mechanism of the present invention, FIG. 4 is a perspective view of a main shift lever, and FIG. FIG. 6 is a diagram showing the relationship between the rotational speed of the HST-type continuously variable transmission and the discharge amount of the pressure oil, FIG. 6 is a diagram showing the relationship between the engine rotational speed and the output, and FIG. FIG. 8 is a diagram showing a relationship with an allowable rotational speed, FIG. 8 is a diagram showing isochronous control and reverse droop control of a tractor, FIG. 9 is a diagram showing allowable output control of an engine, and FIG. 10 is a side sectional view of an electronic governor mechanism.

First, a schematic configuration of a tractor provided with an engine speed adjusting mechanism of the present invention will be described with reference to FIGS. The clutch housing CH and the transmission case M are supported by the front wheel FW and the rear wheel RW.
A bonnet B is mounted on the upper part of the clutch housing CH. An engine E with an electronic governor mechanism is built in the bonnet B. A steering handle S is disposed behind the bonnet B. Has a seat SE.

An HST type continuously variable transmission H formed integrally with the transmission case M is housed in the clutch housing CH together with the clutch. Further, a step 1 projects from the left and right sides of the clutch housing CH, and a brake pedal 2 projects upward from the step 1. At the rear end of the machine body, a work mechanism is mounted, and a link mechanism 5 configured to be able to move up and down is provided.

Next, the power transmission configuration in the clutch housing CH will be described. A front end of the clutch housing CH is connected to a rear end of the engine E, and a clutch 9 is housed in a front portion inside the clutch housing CH. By operating the clutch 9, transmission of power from the engine E to the drive shaft can be interrupted.

An HST-type continuously variable transmission H for transmitting the rotation of the drive shaft to the transmission case M by shifting the rotation of the drive shaft is accommodated in a rear portion of the clutch housing CH. An output shaft (not shown) projecting rearward from the rear end of the HST-type continuously variable transmission H is connected to an input shaft in the transmission case case M, and transmits the power continuously variable by the HST-type continuously variable transmission H. It is transmitted to the mission case M.

A rear axle case 8 is disposed at the rear of the transmission case M, and power is transmitted through a power transmission shaft. The rear wheels RW, RW are driven through a differential gear device inside the rear axle case 8 to
A PTO shaft (not shown) is protruded from the rear surface to transmit power via a universal joint to an input shaft of a working machine such as the rotary cultivator.

A hydraulic cylinder for adjusting the tillage depth is arranged in the link mechanism 5 on which the rotary tiller is mounted, and the solenoid valve is operated and set according to the setting of the tillage setting lever 21. The rotary tiller is driven down to the tillable depth position. Further, a hand accelerator lever HL and an accelerator lever sensor 25 are arranged beside the seat SE, and an accelerator setting device 2 is provided behind the hand accelerator lever HL.
2, and a changeover switch 23 is further provided rearward. On the opposite side of the seat SE, a main shift lever 60, an auxiliary shift lever, and the like are arranged.

As shown in FIG. 4, the main shift lever 60 is guided so as to be operable in the front-rear direction. The tilting operation of the main transmission lever 60 is performed by the HST-type continuously variable transmission H.
Is linked to the movable swash plate. On the front surface of the knob 61 of the main shift lever 60, an auxiliary shift switch 6 as a shift operation tool is provided.
2 are provided. The auxiliary transmission switch 62 is a push button type switch. The auxiliary transmission switch 62 is set to the low-speed position with the auxiliary transmission switch 62 protruding outward, and is switched to the high-speed position by pressing the auxiliary transmission switch 62. The auxiliary transmission switch 62 is connected to the controller C as shown in FIG. When the sub-transmission switch 62 is operated, the transmission gear mechanism in the transmission case M is shifted. Further, a speed increasing switch 63 is disposed on a side surface of the knob 61 of the main speed change lever 60.

As shown in FIG. 3, the engine E with an electronic governor mechanism is connected to a controller C, and a signal from the controller C sends an operation signal to the electronic governor mechanism G. I have.

The structure of the electronic governor mechanism G is configured as shown in FIG. 10, and is attached to a side surface of the fuel injection pump NP. A rack actuator 91 composed of a linear solenoid slides the fuel injection amount adjusting rack 90 of the fuel injection pump NP left and right. Below the rack actuator 91, a rack position sensor 92 is arranged, and the movement of the rack actuator 91 is detected. Further, a rotation speed sensor 93 of the engine E and a lubricating oil temperature sensor 94 of the engine E are also disposed in the electronic governor mechanism G.

As shown in FIG. 3, a signal from the rack position sensor 92, a signal from the rotation speed sensor 93, and a signal from the hand accelerator lever HL are sent from the electronic governor mechanism G.
Of the accelerator lever sensor 25, the key switch, the brake switch 2a disposed on the brake pedal 2, the auxiliary speed change switch 62, and the like are transmitted to the controller C. Also,
The direction in which the signal from the controller C is output is determined by the rack actuator 91 of the electronic governor mechanism G.
Is operated, and a signal for adjusting the fuel injection amount adjustment rack 90 to the left and right is transmitted. And the controller C
In the above, a command signal is transmitted to each unit by collating with a predetermined map, and the engine E with an electronic governor mechanism is controlled.

Next, the engine E with the electronic governor mechanism
Will be described. FIG. 8 shows the isochronous control and the reverse droop control of the tilling work by the tractor. The control mechanism operates the fuel injection amount adjusting rack 90 and the fuel injection pump NP by the microcomputer of the electronic governor mechanism G so that the output of the engine E can be maximized in all operations of the tractor, and the fuel injection amount is controlled. It is for optimal control. As the method, isochronous control for keeping the rotation of the engine E constant irrespective of the magnitude of the load, and reverse droop control for exhibiting stickiness in a low-speed region of the engine E are performed. The load on the engine E is calculated by the controller C based on the set value of the number of revolutions by the accelerator lever sensor 25 and the values detected by the rack position sensor 92 and the number of revolutions sensor 93. Alternatively, a sensor for detecting a load may be provided in the electronic governor mechanism G or the engine E.

In the isochronous control, when the engine speed is set by rotating the hand accelerator lever HL, work is started by the tractor, and the engine speed is kept constant even if the load fluctuates. is there.
Therefore, the work can always be performed at a constant speed. However, when the brake is operated by the brake pedal 2, this function is automatically released, and the operation shifts to the normal droop control. The droop control is the same when a mechanical governor is provided instead of the electronic governor mechanism G. When the load increases, the engine speed decreases, and when the load decreases, the engine speed increases.

In the reverse droop control, when the rotation speed of the engine E is equal to or lower than the rotation speed at which the engine torque reaches the maximum torque and the work load approaches the limit of the engine output, the rotation speed is automatically increased to reduce the output limit of the engine E. It greatly increases the stability during low-speed work.

Next, the allowable output control of FIG. 9 will be described. This control operates in all modes after the engine is started. In this control, the controller C limits the fuel injection amount so that the permissible output torque is regulated by the map for each engine speed.

Further, the map stored in the controller C can be changed between the traveling mode and the work mode in accordance with the work characteristics by switching the changeover switch 23. In the traveling mode, the rotational speed of the engine E is controlled in accordance with the rotational speed set by the hand accelerator lever HL as shown in FIG. In the work mode, even when the hand accelerator lever HL is tilted to the high speed side, the engine E does not increase in rotation speed to the set rotation speed or more as shown by the two-dot chain line b, and is controlled at the set rotation speed or less. Is what you do. The rotation speed at which the maximum output in this work mode is exhibited is higher than that in the running mode, and an output suitable for high-speed work is exhibited. Further, the switching operation of the changeover switch 23 may be configured to control the engine E to maintain a constant rotation speed or to maintain a constant torque regardless of the tilting operation of the hand accelerator lever HL.

In this embodiment, the switching between the work mode and the traveling mode is performed by the knob 6 of the main shift lever 60.
1 may be switched by the sub-transmission switch 62 disposed at the position indicated by reference numeral 1. As described above, the sub speed switch 6
Reference numeral 2 is connected to the controller C, and the switching of the sub speed change switch 62 between the low speed position and the high speed position is input. When the sub speed switch 62 is switched to the low speed position, the output characteristics of the engine E are matched with the map in the work mode state. Further, when the sub-shift switch 62 is switched to the high-speed position, the output characteristic of the engine E is set to be switched to the driving mode map.

Therefore, when the sub-transmission switch 62 is switched to the low speed position, the output of the engine E is compared with the work mode map b, and the engine E is driven. When the hand accelerator lever HL is tilted to the high speed side,
The rotation speed of the engine E is increased according to the map b. The power of the output of the engine E is transmitted to the traveling side and the work implement through an HST-type continuously variable transmission H. When the hand accelerator lever HL is tilted to the high speed side, the engine E is driven at a constant rotation speed suitable for the set operation, and the operation is performed at a constant speed.

When the sub-transmission switch 62 is switched to the high-speed position and the driving mode is set, the operation of the hand accelerator lever HL is compared with the map a to adjust the rotation speed of the engine E. The hand accelerator lever HL
Is tilted toward the high speed side, the rotation speed of the engine E is increased according to the map a. The output of the engine E is
Power is transmitted to the traveling side and the working machine side via the HST-type continuously variable transmission H.

The HST-type continuously variable transmission H receives power from the engine E. However, when the maximum rotational speed of the engine E is input to the HST-type continuously variable transmission H, the HST-type continuously variable transmission H may be driven in some cases. In some cases, the transmission was driven beyond the allowable capacity of the stepped transmission H. Therefore, in the present invention, in the traveling mode, the maximum number of revolutions of the engine E is automatically adjusted according to the allowable capacity of the HST-type continuously variable transmission H regardless of the operation of the hand accelerator lever HL. The configuration is restricted.

The HST-type continuously variable transmission H comprises a variable displacement hydraulic pump and a constant displacement hydraulic motor, and the constant displacement hydraulic motor is driven by pressure oil discharged from the variable displacement hydraulic pump. . The discharge amount of the pressure oil by the variable displacement hydraulic pump is determined according to the pump stroke volume (discharge amount per rotation) due to the tilt of the swash plate of the pump and the discharge amount P according to the number of revolutions of the engine input to the pump. The rotation speed V of the hydraulic motor is increased by increasing the discharge amount P, which is adjusted as shown in FIG.

FIG. 7 shows the torque (traction force) of the motor of the HST type continuously variable transmission H with respect to the rotation speed of the motor.
F is shown. Maximum allowable torque F _{MA X} of the hydraulic motor is determined by the maximum allowable pressure of the hydraulic motor. _VMAX in the figure is the maximum rotation speed of the hydraulic motor. Since the allowable maximum torque is constant without changing according to the rotation speed of the hydraulic motor, O and V _MAX at each point in the figure,
The area surrounded by CP and _FMAX is the allowable use range. Thus, since the product of the rotational speed V and the torque F of the hydraulic motor is transmitted horsepower, maximum horsepower of the HST type continuously variable transmission device H is the product of the maximum speed V _{MA X} and allowable maximum torque F _MAX CP This is called the corner hose power (maximum transmission horsepower). In the present invention, even when the high-speed rotation of the engine E is transmitted to the HST-type continuously variable transmission H in the traveling mode, the corner hose power CP of the HST-type continuously variable transmission H is not exceeded. Regulates engine speed.

In order not to exceed the corner hose power CP of the HST-type continuously variable transmission H, the input horsepower from the hydraulic pump to the hydraulic motor is limited. The maximum value of the input horsepower is set to a value lower than the corner hose power CP. The maximum value of this input horsepower is
It is point A in the figure. The curve AD in the figure is a constant horsepower curve. At the maximum input horsepower, by inclining the swash plate toward the acceleration side, the torque F is increased as the rotation speed V increases as shown by the curve AD. Reduced, corner hose power C
The HST type continuously variable transmission H is driven below P.

The input horsepower to the hydraulic motor is determined by the swash plate angle of the HST type continuously variable transmission H interlocked with the operation of the main transmission lever 60, the number of revolutions of the engine E, and the number of revolutions V of the hydraulic motor. . In order to detect the swash plate angle of the movable swash plate,
As shown in FIG. 1, an angle sensor 30 such as a potentiometer is disposed on a swash plate, and a rotation sensor 31 is disposed on an output shaft of a hydraulic motor. As shown in FIG. 3, the angle sensor 30 and the rotation sensor 31 are connected to the controller C.

When the input values from the sensors 30, 31, and 93 are input to the controller C, the controller C calculates the input horsepower from the hydraulic pump to the hydraulic motor. When the controller C determines that the calculated input horsepower has reached the maximum input horsepower A, regardless of the operation of the hand accelerator lever HL,
Isochronous control is performed so as to regulate the increase in the number of revolutions of the engine E and maintain the number of revolutions. Therefore, the rotation speed of the engine E becomes constant, and the main speed change lever 6
Even if 0 is operated, the HST type continuously variable transmission H is driven by the curve AD.

If the load on the rotary cultivator, which is a working machine, or the load on the traveling driving force is large and the load on the HST type continuously variable transmission H is large, the HST
The torque of the continuously variable transmission H is below the curve AD. In this case, the HST type continuously variable transmission H is driven in a state where the horsepower is smaller than the corner hose power CP. In this state, the rotation speed of the engine E is changed to the maximum rotation speed in accordance with the operation of the hand accelerator lever HL. Can be raised up.

As described above, in the traveling mode, the rotational speed of the engine E is increased in accordance with the map by setting the hand accelerator lever HL, but when the load on the HST type continuously variable transmission H is large, , The engine speed is regulated. Therefore, the HST-type continuously variable transmission H is not rotated at the maximum rotation speed V or higher, and a pressure equal to or more than the allowable maximum torque F is not applied, and an excessive load is applied to the HST-type continuously variable transmission H. Therefore, the life of the HST-type continuously variable transmission H is extended without deterioration of the hydraulic oil.

Next, as a configuration for adjusting the number of revolutions of the engine E, a configuration in which the rotation speed is adjusted by a foot accelerator lever 80 different from the hand accelerator lever HL will be described. The foot accelerator lever 80 has a lower portion pivotally supported on the step 1 as shown in FIGS. The foot accelerator lever 80 is elastically supported by a damper, and is configured to smoothly rotate downward in response to a stepping operation by an operator. Further, the upper portion of the foot accelerator lever 80 is urged upward by a spring 81 or the like, and is positioned at a low speed when there is no stepping operation. The foot accelerator lever 80 is linked to a sensing arm of an angle sensor 83 such as a potentiometer. The angle sensor 83 is connected to the controller C. When the detection of the angle sensor 83 is input to the controller C, the depression amount is detected, and the set rotation speed according to the depression amount is determined by the controller C.
Is calculated by

As shown in FIG. 3, the controller C includes a position sensor 64 for detecting the operation position of the side of the main transmission lever 60, and a speed increasing switch 63 provided on the side of the knob 61 of the main transmission lever 60. And a sub-transmission switch 62 as a transmission operation tool.

With this configuration, the controller C adjusts the rotation speed of the engine E by the following operation. First, the fact that the sub-transmission switch 62 has been switched to the high-speed position is input to the controller C. Subsequently, the value detected by the position sensor 64 is input to the controller C, and the position of the main shift lever 60 is determined by the controller C. When it is determined that the position of the main shift lever 60 is the neutral position, the rotational speed of the engine E is set to the idling rotational speed regardless of the positions of the hand accelerator lever HL and the foot accelerator lever 80. The neutralization of the main shift lever 60 is used as a stop operation of the machine body, and the engine E has an idling rotational speed, so that energy is not wasted and low noise is generated.

When the neutralization of the main transmission lever 60 is detected and the engine C is driven by the controller C at the idling speed, the speed of the engine E is turned on when the speed increasing switch 63 is switched to the ON side. The speed is increased at a fixed rate from the idling speed. Due to this speed increase, the charge pump is sufficiently driven, and the hydraulic oil for the hydraulic cylinder that moves the working machine up and down is sufficiently secured.

When it is input to the controller C that the sub shift switch 62 has been switched to the high speed position, the controller C operates the foot accelerator lever 80 regardless of the position of the hand accelerator lever HL.
By inputting the position, the rotation speed of the engine E is set. Then, to start the aircraft, lightly depress the foot accelerator lever 80 in the manner of starting a passenger car,
By operating the main transmission lever 60, the aircraft can be made to travel slowly. During traveling, the main transmission lever 60 is set at a fixed position, and the foot accelerator lever 80 is operated to set the rotation speed of the engine E,
The aircraft is shifted. This foot accelerator lever 80
Accordingly, the aircraft can be made to travel with an operational feeling like a passenger car. Further, even when the main shift lever 60 is set to the high speed side, the traveling speed of the body can be smoothly shifted by a delicate operation of the foot accelerator lever 80, and the configuration is excellent in operability.

Next, the speed setting when the sub speed switch 62 is set to the low speed position will be described. When the controller C inputs that the sub shift switch 62 has been switched to the low speed position, the rotation speed of the engine E is set according to the amount of depression of the foot accelerator lever 80. Subsequently, by operating the main shift lever 60, H
The speed of the ST-type continuously variable transmission H is changed, and the vehicle is running. This operation is the same as the operation of the sub transmission switch 62 at the high speed position. When the sub speed switch 62 is switched to the low speed position, the foot accelerator lever 80
When the hand accelerator lever HL is operated during the operation by the operator, the traveling speed is reset, and the hand accelerator lever HL is set.
The aircraft is running according to the operation of. Traveling at a constant speed suitable for work is performed by the hand accelerator lever HL.

When the sub speed switch 62 is switched from the low speed position to the high speed position, the rotation speed of the engine E is changed regardless of the operation position of the hand accelerator lever HL or the foot accelerator lever 80. It is set to idling speed. Therefore, when the sub-transmission switch 62 is switched to the high-speed position due to an erroneous operation of the operator while the sub-transmission switch 62 is being driven at the low-speed position, the traveling speed of the aircraft is erroneously increased. Without this, the aircraft is decelerating in this case.

[0041]

The following effects can be obtained by the above configuration. First, as described in claim 1, even if the operator operates the normal accelerator lever to perform speed-up shifting, the input horsepower to the hydraulic motor of the HST-type continuously variable transmission is detected, and the input horsepower is detected. The engine speed is controlled so that the HST type continuously variable transmission does not exceed the maximum allowable horsepower of the HST type continuously variable transmission. The HST-type continuously variable transmission has a long service life, does not impose an excessive burden on the HST-type continuously variable transmission, does not accelerate the deterioration of hydraulic oil.

According to a second aspect of the present invention, the engine speed can be set by the accelerator lever and the foot pedal, and the setting operation by the foot pedal can be performed when the speed change operation tool is switched to the high speed side. Yes,
The running speed can be changed by depressing the foot pedal at the time of starting the aircraft or traveling at high speed, and the aircraft can be traveled with an operational feeling like a passenger car. Also,
Even when the transmission is set to the high-speed side, the running speed of the aircraft can be smoothly changed by a delicate operation of the foot accelerator lever, and the vehicle speed is stabilized, and the riding comfort is improved.

[Brief description of the drawings]

FIG. 1 is a side view of a tractor on which a work machine is mounted.

FIG. 2 is a plan view of the same.

FIG. 3 is a block diagram showing a control structure of the electronic governor mechanism of the present invention.

FIG. 4 is a perspective view of a main transmission lever.

FIG. 5 is a diagram showing the relationship between the rotation speed of the HST-type continuously variable transmission and the discharge amount of pressure oil.

FIG. 6 is a diagram illustrating a relationship between an engine speed and an output.

FIG. 7 is a diagram illustrating a relationship between an allowable torque and an allowable rotation speed of the HST-type continuously variable transmission.

FIG. 8 is a diagram illustrating isochronous control and reverse droop control of a tractor.

FIG. 9 is a diagram showing an allowable output control of the engine.

FIG. 10 is a side sectional view of the electronic governor mechanism.

[Explanation of symbols]

 Reference Signs List A Input horsepower G Electronic governor mechanism E Engine H HST-type continuously variable transmission HA Hand accelerator lever 62 Sub-transmission switch (transmission operation tool) 80 Foot pedal

Claims (2)

[Claims] 1. A work vehicle in which a diesel engine with an electronic governor mechanism is mounted and the power of the engine is shifted by an HST-type continuously variable transmission, the input horsepower to a hydraulic motor of the HST-type continuously variable transmission is detected. The engine speed is controlled so that the input horsepower does not exceed the maximum allowable horsepower of the HST type continuously variable transmission. 2. A work in which a diesel engine with an electronic governor mechanism is mounted, the power of the engine is travel-shifted by a transmission, the engine speed is set, and the traveling speed is set by a shift operation tool that shifts the transmission. In the traveling vehicle, the engine speed can be set by an accelerator lever and a foot pedal, and when the shift operation tool is switched to a high speed side, the engine speed is set by the foot pedal. .