JP2003309904A - Driving control device for working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a working vehicle provided with a working device and a traveling device and capable of switching a traveling driving system between motor driving and engine driving as necessary, thus efficiently utilizing engine power even if a traveling condition changes. <P>SOLUTION: When a traveling instruction switching device 30 is placed into a backward position, or the traveling instruction switching device 30 is placed into a forward position and an operation mode setting device 50 is placed into a working position; a clutch 20 is turned off, and a clutch 21 is turned on to drive the working vehicle forward by the power of an electric motor 5. When the traveling instruction switching device 30 is placed into the forward position, and the operation mode setting device 50 is placed into the traveling position; the clutch 20 is turned off, and the clutch 21 is turned on to drive the working vehicle forward by the power of the electric motor 5. When a speed detected by a rotation sensor 60 is high, the clutch 20 is turned ON, the clutch 21 is turned OFF, and the working vehicle is driven forward by the power of the engine 1. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for a work vehicle such as a wheel loader, and more particularly to a drive control device for a work vehicle provided with a hydraulically driven work device and an electrically driven traveling device.

[0002]

2. Description of the Related Art A hydraulic drive system is generally adopted as a traveling device for a work vehicle such as a wheel loader.
However, in recent years, an electric drive system has been studied as described in, for example, Japanese Patent Laid-Open No. 11-158937. This traveling device is a system in which a generator and a hydraulic pump are driven by driving an engine, an electric motor is driven by electric power generated by the generator, and the vehicle body is driven to travel by driving the electric motor.

Further, since the electric motor used in such a drive system is usually an AC electric motor,
Requires an inverter. In addition, a battery is required to store the surplus electric power when the vehicle is lightly loaded, such as when the vehicle is not traveling, and to store the electric power when the vehicle is heavily loaded, such as when the vehicle is traveling.

FIG. 7 schematically shows such an electric drive system.

In FIG. 7, a generator 202 is driven by driving an engine 201 to generate electric power. Generator 2
The electric power generated by 02 is the inverter / converter 2
The control stored in the battery 204 by 03 and the control for driving the electric motor 205 by the electric power of the battery 204 are performed, and the electric motor 205 is driven. The drive of this electric motor 205 drives the mission 206,
The wheels 207, 207 are driven, and the vehicle body moves forward and backward.

In the drive system using the electric motor configured as described above, when the vehicle is decelerated, the electric motor 205 is operated as a generator, the kinetic energy during vehicle deceleration is recovered as electric power, and the inverter / converter 203 stores it in the battery 204. store. The recovered electric power is used to cause the electric motor 205 to make a noise during traveling driving.

[0007]

However, the above-mentioned prior art has the following problems.

The working mode of a working vehicle equipped with a working device, for example, a wheel loader, is used to drive the vehicle while excavating and loading earth and sand at the work site, and to move the road to the work site. It may be driven to run.

[0009] Here, when the vehicle is driven for traveling while excavating and loading earth and sand, the traveling purpose is to move to the object to be excavated and to move the loaded earth and sand. Will be used mainly for work equipment that is under heavy load. Therefore, in the electric drive system as shown in FIG. 7, when the load condition applied to the work device is light, a large amount of electric power can be generated by the generator, and excess electric power can be stored in the battery and used for traveling. The power of the engine can be used efficiently.

However, when the vehicle is driven to travel to move to a work site on a road, the working device is not driven and the engine power is used only for traveling.
Therefore, in the electric drive system as shown in FIG. 7, the generator is driven by the power of the engine and the electric motor is driven by the generated electric power to drive the vehicle, even though the power of the engine is used only for traveling. Loss occurs due to power conversion by each device, and engine power cannot be used efficiently.

Further, a working vehicle such as a wheel loader is
Generally, a transmission capable of switching between the second speed and the third speed is provided, and when traveling forward, the operator switches the missions by switching the shift lever according to the traveling state. In this way, when the traveling mode is changed by switching the mission with the shift lever, the same problem as described above occurs.

In other words, the traveling performed by switching the shift lever to the low speed side is carried out when the vehicle is started or stopped, or when the front working device is driven as described above to excavate the earth and sand,
The traveling is a short time traveling while carrying out the loading work, and the traveling performed by switching the shift lever to the high speed side is often a long time traveling to the work site on the road as described above.

When the shift lever is switched to the low speed side to drive the vehicle at a low speed while excavating and loading the earth and sand, the driving power is small. Therefore, in the electric drive system shown in FIG. When the load condition is light, the electric power generated by the generator and stored in the battery can be used for traveling, so that the power of the engine can be efficiently used.

However, when the shift lever is switched to the high speed side and the vehicle is driven at a high speed for moving to a work site on the road, the power of the engine is used only for traveling, but the generator of the power of the engine is used. Since the electric motor is driven and the electric motor is driven by the generated electric power to travel, loss occurs due to power conversion by each device, and the power of the engine cannot be used efficiently.

A first object of the present invention is to provide a working vehicle equipped with a working device and a traveling device so that the traveling drive system can be appropriately switched between electric drive and engine drive so that the engine power can be changed even when the traveling conditions change. It is to provide a drive control device for a working vehicle that can efficiently use the above.

A second object of the present invention is to provide a working vehicle equipped with a working device and a traveling device for driving the vehicle while excavating and loading earth and sand, and for moving a road to a work site. It is an object of the present invention to provide a drive control device for a working vehicle, which can adopt an optimum drive system in any case of traveling drive and can efficiently use the power of the engine.

A third object of the present invention is to provide a working vehicle equipped with a working device and a traveling device, which can be an optimum drive system for both low speed running and high speed running, and the engine. It is an object of the present invention to provide a drive control device for a work vehicle that can efficiently use the power of the above.

[0018]

(1) In order to achieve the above-mentioned first object, the present invention provides an engine, a hydraulic pump and a generator driven by the engine, and a discharge from the hydraulic pump. In a drive control device for a working vehicle comprising a working device driven by pressure oil, an electric motor rotationally driven by electric power generated by the generator, and a traveling device driven by the electric motor, the generator is A power storage device that stores the generated electric power, a first power transmission mechanism that transmits the power of the electric motor to the traveling device, a second power transmission mechanism that transmits the power of the engine to the traveling device, and the first power When the transmission mechanism and the second power transmission mechanism are selectively operated, and when the first power transmission mechanism is operated, the electric motor is driven by the electric power of the power storage device, When operating the power transmission mechanism is assumed and a control means for stopping the electric motor.

As described above, the power storage device, the first and second power transmission mechanisms, and the control means are provided, and the first power transmission mechanism and the second power transmission mechanism are provided.
By selectively operating the power transmission mechanism, driving the electric motor with the electric power of the power storage device when operating the first power transmission mechanism, and stopping the electric motor when operating the second power transmission mechanism, The traveling drive system can be appropriately switched between electric drive and engine drive, and the power of the engine can be efficiently used even when traveling conditions change.

(2) In order to achieve the first and second objects, the present invention provides an engine, a hydraulic pump and a generator driven by the engine, and a pressure discharged from the hydraulic pump. In a drive control device for a working vehicle, which includes a working device driven by oil, an electric motor rotationally driven by electric power generated by the generator, and a traveling device driven by the electric motor, the generator is generated. A power storage device that stores the generated electric power, a first power transmission mechanism that transmits the power of the electric motor to the traveling device, a second power transmission mechanism that transmits the power of the engine to the traveling device, and the working device. A mode setting device capable of selecting one of a first mode mainly for carrying out the driving and a second mode mainly driving the traveling device, and the mode setting means for setting the first mode. The first power transmission mechanism is operated when the mode is selected, and the second power transmission mechanism is operated when the mode setting means selects the second mode. The electric motor drives the electric motor when operating the mechanism, and controls the electric motor to stop when operating the second power transmission mechanism.

Thus, the power storage device, the first and second power transmission mechanisms, the mode setting device, and the control means are provided, and the first power transmission mechanism is operated when the mode setting means selects the first mode. When the mode setting means selects the second mode, the second power transmission mechanism is operated, and when the first power transmission mechanism is operated, the electric motor is driven by the electric power of the power storage device. 2 When operating the power transmission mechanism, stop the electric motor to drive the vehicle while excavating and loading earth and sand. When the first mode is selected by the mode setting means, the electric motor is driven to work on roads. When the vehicle is driven to move to the site, the engine is driven when the second mode is selected by the mode selection means. It can be the power used efficiently.

(3) Further, in order to achieve the above first to third objects, the present invention provides an engine, a hydraulic pump and a generator driven by the engine, and a pressure discharged from the hydraulic pump. A working device driven by oil, and an electric motor rotationally driven by the electric power generated by the generator,
In a drive control device for a work vehicle including a traveling device driven by the electric motor, a power storage device for storing electric power generated by the generator, and a first power transmitting the power of the electric motor to the traveling device. A transmission mechanism, a second power transmission mechanism that transmits the power of the engine to the traveling device, a speed detection unit that detects the speed of the work vehicle, and a speed of the work vehicle that is detected by the speed detection unit is low. The first power transmission mechanism is operated, the second power transmission mechanism is operated when the speed of the work vehicle is high, and when the first power transmission mechanism is operated, the power of the power storage device is used. Driving the electric motor to drive the second
A control means for stopping the electric motor when operating the power transmission mechanism is provided.

As described above, the power storage device, the first and second power transmission mechanisms, the speed detection means, and the control means are provided, and the first power transmission is performed when the speed of the work vehicle detected by the speed detection means is low. The mechanism is operated, and when the speed of the work vehicle is high, the second power transmission mechanism is operated and the first power transmission mechanism is operated.
When the power transmission mechanism is operated, the electric motor is driven by the electric power of the power storage device, and when the second power transmission mechanism is operated, the electric motor is stopped. Since the engine is driven, the drive system is optimal in any case, and the power of the engine can be used efficiently.

Further, when traveling is performed while excavating and loading earth and sand, the vehicle is driven by an electric motor when traveling at low speed, and when traveling traveling to travel to a work site at high speed, the engine is traveling at high speed. Since it is driven, the drive system is optimal in any case, and the power of the engine can be used efficiently.

(4) In order to achieve the above first to third objects, the present invention provides an engine, a hydraulic pump and a generator driven by the engine, and a pressure discharged from the hydraulic pump. A working device driven by oil, and an electric motor rotationally driven by the electric power generated by the generator,
In a drive control device for a work vehicle including a traveling device driven by the electric motor, a power storage device for storing electric power generated by the generator, and a first power transmitting the power of the electric motor to the traveling device. A transmission mechanism, a second power transmission mechanism that transmits the power of the engine to the traveling device, and a first instruction to indicate whether to perform low speed traveling or high speed traveling.
The first power transmission mechanism is operated when the traveling instruction means and the first traveling instruction means instruct low speed traveling, and the second power transmission mechanism is operated when the first traveling instruction means instructs high speed traveling. Control for operating the power transmission mechanism, driving the electric motor with the electric power of the power storage device when operating the first power transmission mechanism, and stopping the electric motor when operating the second power transmission mechanism And means.

As described above, the power storage device, the first and second power transmission mechanisms, the first traveling instruction means and the control means are provided, and when the first traveling instruction means instructs the low speed traveling, the first power is transmitted. The transmission mechanism is operated, the second power transmission mechanism is operated when the first traveling instruction means instructs high speed traveling, and the electric motor is driven by the electric power of the power storage device when the first power transmission mechanism is operated. However, when the second power transmission mechanism is operated, the electric motor is stopped so that when the low speed traveling is instructed to the low speed traveling by the first traveling instruction means, the electric motor is driven, and when the high speed traveling is performed by the first traveling instruction means. When the high-speed running is instructed, the engine is driven. Therefore, in any case, the optimum drive system is used, and the power of the engine can be efficiently used.

When traveling at a low speed when traveling is performed while excavating and loading earth and sand, when the low speed traveling is instructed by the first traveling instructing means, the electric motor is driven.
When traveling at high speed when traveling to drive to a work site on a road or the like, the engine is driven when the first traveling instructing means instructs the traveling at high speed. Therefore, in any case, the drive system is optimal and the engine power is Can be used efficiently.

(5) In the above item (2), preferably
Further comprising speed detection means for detecting the speed of the work vehicle,
The control means operates the first power transmission mechanism regardless of the speed of the working vehicle when the mode setting means selects the first mode, and the mode setting means sets the second mode. When selected, the first power transmission mechanism is operated when the speed of the work vehicle detected by the speed detection means is low, and when the speed of the work vehicle is high, the second power transmission mechanism is selected. Shall be operated.

Thus, when the first mode is selected by the mode setting means, the electric motor drive is maintained even when the work vehicle changes at high speed, and the drive is performed during the traveling drive while excavating and loading the earth and sand. It is possible to prevent the system from being switched and to obtain good running performance. Further, when the second mode is selected by the mode setting means, even when the vehicle is driven to travel to move to a work site on a road or the like, the driving mode is switched to the electric motor driving at low speed to obtain good traveling performance. To be

(6) Further, in the above (2) to (4), preferably, further provided is a second traveling instruction means for instructing whether to perform forward traveling or backward traveling, and the control means comprises the first traveling means. When the second traveling instruction means instructs forward traveling, the first power transmission mechanism and the second power transmission mechanism are selectively operated, and when the second traveling instruction means instructs backward traveling, It is assumed that the first power transmission mechanism is operated.

As a result, the above (2)-
The action described in (4) is obtained, and the electric motor drive is always used during the backward traveling, and good traveling performance is obtained.

(7) Further, in the above (1) to (4), preferably, the first power transmission mechanism is connected to the electric motor through a gear mechanism having a gear ratio set to a low speed, and the second The power transmission means is connected to the engine through a gear mechanism having a gear ratio set at a high speed.

As a result, the electric motor drive is optimized for low speeds, the engine drive is optimized for high speeds, and good running performance is obtained.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing a drive control device for a working vehicle according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a prime mover, for example, a diesel engine (hereinafter simply referred to as an engine), which is provided with a fuel injection amount control device 1a, and the engine speed is controlled by controlling the fuel injection amount. The shaft 10 rotated by the drive of the engine 1 has three gears 11, 13, 15
Is fixed, the gear 11 meshes with the gear 12, transmits the power of the shaft 10 to the generator 2, and the generator 2 generates electric power by the rotation of the engine 1.

Further, the gear 13 meshes with the gear 14 to transmit the power of the shaft 10 to the hydraulic pump 8, and the hydraulic pump 8 is rotated by the rotation of the engine 1 to discharge the pressure oil, and a working device (not shown) is installed. To drive.

The gear 15 meshes with the gear 16, and the gear 16 transmits the power of the shaft 10 to the output shaft 22 via the clutch 20. The gear ratio (power transmission ratio) between the gear 15 and the gear 16 is set for high speed.

The generator 2 is connected to the battery 4 and the electric motor 5 via the inverter / converter 3, and the inverter / converter 3 controls the storage of the electric power generated by the generator 2 in the battery 4 and the generator 2 The control for driving the electric motor 5 is performed by the electric power generated by the above or the electric power stored in the battery 4.

A shaft 17 rotated by driving the electric motor 5
A gear 18 is fixed to the gear, and the gear 18 is meshed with the gear 19. The gear 19 transmits the power of the shaft 17 to the output shaft 22 via the clutch 21. Gear 18 and gear 1
The gear ratio (power transmission ratio) of 9 is set for low speed.

The output shaft 22 is an axle 23a in front of the vehicle body.
The vehicle front wheels 7a, 7a are rotated via the vehicle body, and the vehicle body rear wheels 7b, 7b are rotated via the axle 23b at the rear side of the vehicle body to move the working vehicle forward and backward. Output shaft 22,
Axles 23a, 23b and front wheels 7a, 7a and rear wheels 7
b and 7b constitute a traveling device.

A traveling instruction changeover device 30 having a shift lever 31 is provided as means for instructing switching between forward and backward movements of the work vehicle, and an accelerator pedal 70 is provided as means for instructing the number of revolutions of the engine 1 and the electric motor 5. An operation mode setting device 50 including a traveling mode button 51 and a work mode button 52 is provided as means for instructing the operation mode of the work vehicle. The position signal of the traveling instruction switching device 30, the operation amount signal of the accelerator pedal 70, and the instruction signal of the operation mode setting device 50 are the controller 4
Input to 0.

When moving the work vehicle backward, the operator switches the position of the shift lever 31 of the traveling instruction switching device 30 from the initial position "N" to the "R" position,
When traveling forward, switch to the "F" position.

Further, when increasing the traveling speed or the working speed of the work device, the operator increases the depression amount of the accelerator pedal 70 and adjusts the depression amount by adjusting the depression amount.

Further, when the operator drives the work vehicle to travel to move to a work site on the road, the operator turns on the travel mode button 51 of the operation mode setting device 50 to drive the work device. When excavating and loading earth and sand, the work mode button 52 of the operation mode setting device 50 is turned on.

A rotation speed sensor 6 for detecting the rotation speed of the output shaft 22 as a means for detecting the traveling speed of the work vehicle.
0 is provided. The detection signal of the rotation speed sensor 60 is also input to the controller 40.

The working vehicle to which the present invention is applied is, for example, a wheel type crane, a wheel type shovel, a wheel loader, a telehandler, etc., and the embodiment shown in the drawing is a wheel type shovel to which the present invention is applied. is there.

The controller 40 operates the clutch 2 according to the position of the shift lever 31, the instruction of the operation mode setting device 50 (mode selection status), and the detection value of the rotation speed sensor 60.
Controls ON / OFF of 0 and 21. The controller 40 controls the rotation direction of the electric motor 5 by switching the position of the shift lever 31, and controls the engine 1 and the electric motor 5 according to the amount of depression of the accelerator pedal 70.
Control the rotation speed of. For these controls, the controller 40 inputs the position signal of the traveling instruction switching device 30, the instruction signal of the operation mode setting device, the operation amount signal of the accelerator pedal 70, and the detection signal of the rotation speed sensor 60, and performs predetermined arithmetic processing. Then, the control signal is output to the clutches 20 and 21, the inverter / converter 3, and the fuel injection amount control device 1a.

FIG. 2 is a flowchart showing the processing contents of the switching control of the clutches 20 and 21, the rotational direction control of the electric motor 5, and the speed control of the engine and the electric motor 5, which are performed by the controller 40.

Here, in FIG. 2, the clutches 20 and 21 are
Means that the output shaft 22 and the gears 16 and 19 corresponding to the respective clutches are connected when "ON" to transmit power, and the output shaft 22 and the gears 16 and 19 corresponding to the respective clutches are connected to each other when "OFF". It is assumed that they are not connected and power is not transmitted. Also, the clutch 21 is "ON"
When the power of the gear 19 is transmitted to the output shaft 22, the working vehicle is driven forward when the rotation direction of the electric motor 5 is forward rotation, and the working vehicle is driven backward when the rotation direction of the electric motor 5 is reverse rotation. .

In FIG. 2, the controller 40 reads the position of the shift lever 31, the mode setting state of the operation mode setting device 50, the detection value of the rotation speed sensor 60, and the depression amount of the accelerator pedal 70 (step S100). Next, it is determined whether or not the position of the shift lever 31 is "N" (step S102), and if it is "N", both the clutches 20 and 21 are turned "OFF" (step S1).
04), the electric motor 5 is stopped (step S10).
6). Further, the rotation speed of the engine 1 is controlled according to the depression amount of the accelerator pedal 70 (step S108).
In this way, when the position of the shift lever 31 is "N", the gear 1 corresponding to the output shaft 22 and the clutches 20 and 21.
The connection with 6, 19 is disconnected, the output shaft 22 does not rotate, and the work vehicle does not run. Further, the number of revolutions of the engine 1 increases or decreases according to the amount of depression of the accelerator pedal 70,
The working speed of a working device (not shown) driven by the oil discharged from the hydraulic pump 8 can be arbitrarily adjusted.

If it is determined in step S102 that the position of the shift lever 31 is not "N", then it is determined whether the position of the shift lever 31 is "R" (step S110), and the shift lever 31 When the position is "R", the clutch 20 is "OFF" and the clutch 21 is "
It is switched to the "ON" position (step S112). Further, the electric motor 5 is rotated in the reverse direction in accordance with this switching operation (step S114).
The number of revolutions of the engine 1 and the number of revolutions of the electric motor 5 are controlled according to the depression amount of 0 (step S116). In this way, when the position of the shift lever 31 is "R", the connection between the output shaft 22 and the gear 16 corresponding to the clutch 20 is disconnected, and the gear 1 corresponding to the output shaft 22 and the clutch 21.
9 is connected to the electric motor 5 regardless of the mode setting state of the operation mode setting device 50 and the detection value of the rotation speed sensor 60.
Is used to rotate the output shaft 22 via the gears 18, 19 set at a low speed, move the vehicles 7a, 7b, and drive the work vehicle in reverse. Further, the rotation speed of the electric motor 5 is increased / decreased according to the depression amount of the accelerator pedal 70, and the traveling speed can be arbitrarily adjusted. On the other hand, the number of revolutions of the engine 1 also increases or decreases according to the depression amount of the accelerator pedal 70,
The working speed of a working device (not shown) driven by the oil discharged from the hydraulic pump 8 can be arbitrarily adjusted.

When it is determined in step S110 that the position of the shift lever 31 is not "R", it is determined that the position of the shift lever 31 is in the "F" position. At this time, the mode of the operation mode setting device 50 is set. It is determined whether or not the setting state is selected as "work" (step S120), and "
When it is selected to "work", the clutch 20 is set to "O".
The FF "and the clutch 21 are switched to the" ON "position (step S122), and the electric motor 5 is rotated forward in accordance with this switching operation (step S124).
Further, the rotation speed of the engine 1 and the rotation speed of the electric motor 5 are controlled according to the depression amount of the accelerator pedal 70 (step S126). In this way, the shift lever 31
Even in the position of "F" and the mode setting state of the operation mode setting device 50 is selected to "work", the connection between the output shaft 22 and the gear 16 corresponding to the clutch 20 is disconnected, and the output shaft 22 And the gear 19 corresponding to the clutch 21 are connected, and the output shaft 22 is rotated by the power of the electric motor 5 via the gears 18 and 19 set to a low speed regardless of the detection value (actual traveling speed) of the rotation speed sensor 60. , Wheel 7
By moving a and 7b, the work vehicle is driven forward. Further, the rotation speed of the electric motor 5 is increased / decreased according to the depression amount of the accelerator pedal 70, and the traveling speed can be arbitrarily adjusted. On the other hand, the number of revolutions of the engine 1 also increases or decreases according to the depression amount of the accelerator pedal 70, and the working speed of a working device (not shown) driven by the oil discharged from the hydraulic pump 8 can be arbitrarily adjusted.

As a result, the work mode button 52 of the operation mode setting device 50 is used in the forward traveling at low speed when the work device is driven to excavate and load the earth and sand.
By turning on the power of the engine 1, the power of the engine 1 is mainly used for a working device under load, and when the load on the working device is light, the power generated by the generator 2 is supplied to the battery 4
Since it can be stored in the vehicle and used for traveling, the engine 1
The power of can be used efficiently.

By turning on the work mode button 52 of the operation mode setting device 50, the work vehicle can be driven forward by the power of the electric motor 5 regardless of the actual traveling speed. The discomfort caused by switching the drive system of the traveling device is eliminated, and good traveling performance is obtained.

In step S120, the operation mode setting device 5
When it is determined that the mode setting state of 0 is not selected as "work", the shift lever 31 is in the "F" position and the mode setting state of the operation mode setting device 50 is "running".
It is determined that the rotation speed sensor 60 has a low rotation speed of 1000 rpm or lower (step S130), and the rotation speed sensor 60 has a low rotation speed. If number, clutch 2
The 0 is switched to the "OFF" position and the clutch 21 is switched to the "ON" position (step S132). Further, the electric motor 5 is rotated in the forward direction in accordance with this switching operation (step S13).
4). Further, the rotation speed of the engine 1 and the rotation speed of the electric motor 5 are controlled according to the depression amount of the accelerator pedal 70 (step S116). In this way, the lever 31
Is in the “F” position, the mode setting state of the operation mode setting device 50 is selected to “running”, and low speed running,
The output shaft 22 and the gear 16 corresponding to the clutch 20 are disconnected from each other, the output shaft 22 and the gear 19 corresponding to the clutch 21 are connected, and output by the power of the electric motor 5 via the gears 18 and 19 set at a low speed. Rotate the shaft 22 to rotate the wheels 7
By moving a and 7b, the work vehicle is driven forward. Further, the rotation speed of the electric motor 5 is increased / decreased according to the depression amount of the accelerator pedal 70, and the traveling speed can be arbitrarily adjusted. On the other hand, the number of revolutions of the engine 1 also increases or decreases according to the depression amount of the accelerator pedal 70, and the working speed of a working device (not shown) driven by the oil discharged from the hydraulic pump 8 can be arbitrarily adjusted.

As a result, even when the vehicle travels forward only when traveling alone and only when traveling, the vehicle speed is reduced when the vehicle starts or when the vehicle is stopped, or when traveling on an ascending slope and the vehicle speed decreases. Since the driving is performed by the power of the electric motor 5 that can be controlled from low rotation, good traveling performance can be obtained.

If it is determined in step S130 that the value detected by the rotation speed sensor 60 is not lower than 1000 rpm (higher than 1000 rpm), the clutch 20 is "ON" and the clutch 21 is "OF".
It is switched to the position of F ″ (step S140).
The electric motor 5 is stopped in accordance with this switching operation (step S142). Further, the rotation speed of the engine 1 is controlled according to the depression amount of the accelerator pedal 70 (step S108). In this way, the shift lever 31 is "F"
In the case of high speed traveling in the position of 1, the output shaft 22 is rotated by the power of the engine 1 via the gears 15 and 16 set to high speed, the wheels 7a and 7b are moved, and the working vehicle is driven forward. Further, the rotation speed of the engine 1 is 70
The traveling speed can be arbitrarily adjusted by increasing or decreasing according to the amount of depression.

As a result, when the vehicle body is traveling at a certain vehicle speed in forward traveling during traveling alone operation in which only traveling is performed, the output shaft of the engine 1 is directly output by the power of the engine 1 in the efficient rotational speed range of the engine 1. Since 22 is rotated to drive the work vehicle forward, it is possible to perform efficient traveling drive without causing a loss due to power conversion by each device that occurs when the electric motor 5 is driven.

When the traveling speed changes from a low speed to a high speed in the forward traveling in the traveling only operation for traveling only, the traveling speed is detected by the rotation sensor 60 and the clutches 20 and 21 are switched. It is possible to automatically switch from driving by the power of 5 to driving by the power of the engine 1.

According to the present embodiment configured as described above, the following effects can be obtained.

(1) When traveling is performed while excavating and loading earth and sand, by turning on the work mode button 52 of the operation mode setting device 50, the electric motor 5
When the vehicle is driven at a high speed to move to a work site on a road or the like, the engine 1 is driven by turning on the traveling mode button 51 of the operation mode setting device 50. Also becomes an optimal drive system, and the power of the engine can be used efficiently.

(2) The work device is driven to excavate the earth and sand,
When traveling at low speed when carrying out loading work,
Turn on the work mode button 52 of the operation mode setting device 50
By doing so, there is no sense of discomfort when the drive system of the traveling device is switched during work, and good traveling performance can be obtained.

(3) Even when the vehicle is traveling forward only when traveling alone, the vehicle speed is reduced when starting the vehicle or stopping the vehicle, or when traveling on an ascending slope and the vehicle speed decreases. Since the driving is performed by the power of the electric motor 5 that can be controlled from low rotation, good traveling performance can be obtained.

(4) When the traveling speed changes from a low speed to a high speed in the forward traveling in the traveling only operation in which only the traveling is performed, the driving by the power of the electric motor 5 is automatically switched to the driving by the power of the engine 1. You can

A second embodiment of the present invention will be described with reference to FIGS.
Will be described. In the present embodiment, the drive system of the traveling device is switched without using the operation mode setting device in the first embodiment shown in FIGS. 1 and 2. In the figure, the same members or portions as those shown in FIGS. 1 and 2 are designated by the same reference numerals.

FIG. 3 is a diagram showing a drive control device for a working vehicle according to a second embodiment of the present invention. The drive control device for a working vehicle according to the present embodiment is the same as that of the first embodiment except that the operation mode setting device 50 shown in FIG. 1 is not provided. In the figure, the controller is indicated by reference numeral 40A.

FIG. 4 is a flow chart showing the processing contents of the switching control of the clutches 20 and 21, the rotational direction control of the electric motor 5, and the speed control of the engine and the electric motor 5 which are carried out by the controller 40A.

In FIG. 4, the controller 40A reads the position of the shift lever 31, the detection value of the rotation speed sensor 60, and the depression amount of the accelerator pedal 70 (step S).
100A). Subsequent steps S102 to S1
The processing content of 16 is the same as that of the first embodiment.

When it is determined in step S110 that the position of the shift lever 31 is not "R", it is determined that the position of the shift lever 31 is "F". At this time, the detected value of the rotation speed sensor 60 is, for example, It is determined whether the rotation speed is 1000 rpm or lower (step S130). The subsequent processing contents of steps S132 to S44 are the same as those of the first embodiment.

Even when the shift lever 31 is in the "F" position in this way, when the vehicle is traveling at a low speed, the output shaft 22
And the gear 16 corresponding to the clutch 20 are disconnected, the output shaft 22 and the gear 19 corresponding to the clutch 21 are connected, and the low speed setting gear 1 is driven by the power of the electric motor 5.
The output shaft 22 is rotated through the wheels 8 and 19 and the wheels 7a and 7b are rotated.
To drive the work vehicle forward. Further, the rotation speed of the electric motor 5 is increased / decreased according to the depression amount of the accelerator pedal 70, and the traveling speed can be arbitrarily adjusted.
On the other hand, the number of revolutions of the engine 1 also increases or decreases according to the depression amount of the accelerator pedal 70, and the working speed of a working device (not shown) driven by the oil discharged from the hydraulic pump 8 can be arbitrarily adjusted.

As a result, in the forward traveling at low speed when the work device is driven to excavate and load the earth and sand, the power of the engine 1 is mainly used for the work device to which a load is applied, and the load to the work device is applied. When the situation is light, the electric power generated by the generator 2 can be stored in the battery 4 and used for traveling, so that the power of the engine 1 can be efficiently used.

Even when the vehicle is traveling forward alone and only traveling, it is low when the vehicle starts or when the vehicle speed is reduced to stop the vehicle or when the vehicle travels on an ascending slope and the vehicle speed decreases. Since the driving is performed by the power of the electric motor 5 that can be controlled from the rotation, good traveling performance can be obtained.

On the other hand, when the shift lever 31 is in the "F" position for high speed running, the output shaft 22 is rotated by the power of the engine 1 via the gears 15 and 16 set at high speed to move the wheels 7a and 7b. , Drive the work vehicle forward. Further, the rotation speed of the engine 1 is increased / decreased according to the depression amount of the accelerator pedal 70, and the traveling speed can be arbitrarily adjusted.

As a result, when the vehicle body is traveling at a certain vehicle speed in forward traveling during traveling alone operation in which only traveling is performed, the output shaft of the engine 1 is directly output by the power of the engine 1 in the efficient rotational speed region of the engine 1. Since 22 is rotated to drive the work vehicle forward, it is possible to perform efficient traveling drive without causing a loss due to power conversion by each device that occurs when the electric motor 5 is driven.

When the traveling speed changes from a low speed to a high speed in the forward traveling during the traveling only operation in which only the traveling is performed, the traveling speed is detected by the rotation sensor 60 and the clutches 20 and 21 are switched. It is possible to automatically switch from driving by the power of 5 to driving by the power of the engine 1.

According to this embodiment, the following effects can be obtained.

(1) When traveling at a low speed while excavating and loading earth and sand, driving is performed by the power of the electric motor 5, and when traveling at a high speed to move to a work site on the road, the engine is used. Since it is driven by 1, the drive system is optimal in any case, and the power of the engine can be used efficiently.

(2) Even when traveling and driving while excavating and loading earth and sand, switching to driving by the engine 1 when driving at high speed, even when traveling forward only by traveling alone that only travels, low speed When the vehicle is driven by, the drive is switched to the drive of the electric motor 5, so that the optimal drive system is suitable for both low speed traveling and high speed traveling, and the power of the engine 1 can be used efficiently.

(3) Even when the vehicle is traveling forward only in the traveling alone operation, when the vehicle is started or when the vehicle speed is reduced toward stopping the vehicle, or when traveling on an ascending slope and the vehicle speed decreases, Since the driving is performed by the power of the electric motor 5 that can be controlled from low rotation, good traveling performance can be obtained.

(4) When the traveling speed changes from a low speed to a high speed in the forward traveling in the traveling alone operation in which only the traveling is performed, the driving by the power of the electric motor 5 is automatically switched to the driving by the power of the engine 1. You can

FIG. 5 and FIG. 6 show the third embodiment of the present invention.
Will be described. In this embodiment, instead of providing the rotation speed sensor in the second embodiment shown in FIGS. 3 and 4, the shift lever of the traveling instruction switching device is changed to “F (L
o) ”and“ F (Hi) ”can be switched to the second speed. In the drawings, the same members or parts as those shown in FIGS. 1 and 2 are designated by the same reference numerals.

Referring to FIG. 5, a drive control device for a working vehicle according to a third embodiment of the present invention is provided with a shift lever 31 as a means for instructing switching of the working vehicle between forward and reverse. The apparatus 30A is provided, and the accelerator pedal 70 is provided as a means for instructing the number of rotations of the engine 1 and the electric motor 5. The position signal of the traveling instruction switching device 30A and the operation amount signal of the accelerator pedal 70 are input to the controller 40B.

When moving the work vehicle backward, the operator switches the position of the shift lever 31 of the traveling instruction switching device 30 from the initial position "N" to the "R" position.
The position is switched to the "F (Lo)" position for low speed forward travel, and to the "F (Hi)" position for high speed forward travel.

Further, when increasing the traveling speed or the working speed of the work device, the operator increases the depression amount of the accelerator pedal 70 and adjusts the depression amount by adjusting the depression amount.

The controller 40B uses the shift lever 31
ON / OFF of the clutches 20 and 21 is controlled according to the position. Further, the controller 40B controls switching of the rotation direction of the electric motor 5 depending on the position of the shift lever 31. Further, the controller 40B controls the rotation speeds of the engine 1 and the electric motor 5 according to the depression amount of the accelerator pedal 70. For these controls, the controller 40B inputs the position signal of the traveling instruction switching device 30 and the operation amount signal of the accelerator pedal 70, performs a predetermined arithmetic processing, and clutches 20, 21, the inverter / converter 3, and the fuel injection amount. The control signal is output to the control device 1a.

FIG. 6 is a flowchart showing the processing contents of the switching control of the clutches 20 and 21, the rotational direction control of the electric motor 5, and the speed control of the engine and the electric motor 5 performed by the controller 40B.

In FIG. 6, the controller 40B reads the position of the shift lever 31 and the depression amount of the accelerator pedal 70 (step S200). Next, it is determined whether or not the position of the shift lever 31 is "R" (step S202), and if it is "R", the clutch 20
Is switched to the "OFF" position and the clutch 21 is switched to the "ON" position (step S202). Further, the electric motor 5 is reversely rotated in accordance with this switching operation (step S20).
6). Further, the rotation speed of the engine 1 and the rotation speed of the electric motor 5 are controlled according to the depression amount of the accelerator pedal 70 (step S208). In this way, the shift lever 31
Is in the "R" position, the output shaft 22 and the gear 16 corresponding to the clutch 20 are disconnected, and the output shaft 22 and the gear 19 corresponding to the clutch 21 are connected,
The output shaft 22 is rotated by the power of the electric motor 5 via the gears 18 and 19 set at a low speed to move the vehicles 7a and 7b,
Drive the work vehicle in reverse. Further, the rotation speed of the electric motor 5 is increased / decreased according to the depression amount of the accelerator pedal 70, and the traveling speed can be arbitrarily adjusted. On the other hand, the rotation speed of the engine 1 is increased or decreased according to the depression amount of the accelerator pedal 70, and the working speed of a working device (not shown) driven by the oil discharged from the hydraulic pump 8 can be arbitrarily adjusted.

If it is determined in step S110 that the position of the shift lever 31 is not "R", then it is determined whether the position of the shift lever 31 is "F (Lo)" (step S210). In the case of F (Lo) ", the clutch 20 is switched to the" OFF "position and the clutch 21 is switched to the" ON "position (step S212). Further, the electric motor 5 is rotated in the forward direction in accordance with this switching operation (step S214). Further, the rotation speed of the engine 1 and the rotation speed of the electric motor 5 are controlled according to the depression amount of the accelerator pedal 70 (step S216). In this way, even when the lever 31 is in the "F (Lo)" position,
The output shaft 22 and the gear 16 corresponding to the clutch 20 are disconnected from each other, the output shaft 22 and the gear 19 corresponding to the clutch 21 are connected, and the power of the electric motor 5 causes the low speed gears 18 and 19 to be connected. The output shaft 22 is rotated, the wheels 7a and 7b are moved, and the working vehicle is driven forward. Further, the rotation speed of the electric motor 5 is increased / decreased according to the depression amount of the accelerator pedal 70, and the traveling speed can be arbitrarily adjusted. On the other hand, the rotation speed of the engine 1 is increased or decreased according to the depression amount of the accelerator pedal 70, and the working speed of a working device (not shown) driven by the oil discharged from the hydraulic pump 8 can be arbitrarily adjusted.

As a result, the power of the engine 1 is changed by switching the shift lever 31 to the "F (Lo)" position during low-speed forward traveling when the work device is driven to excavate and load earth and sand. Is mainly used for a working device with a load, and when the load condition applied to the working device is light, the electric power generated by the generator 2 can be stored in the battery 4 and used for traveling. It can be used efficiently.

Further, the shift lever 31 is set to "F (Lo)".
By switching to the position of 1, the work vehicle can be driven forward by the power of the electric motor 5 regardless of the actual traveling speed, so that there is no sense of discomfort when the drive system of the traveling device is switched during work, which is excellent. Driving performance is obtained.

Further, even when traveling forward only when traveling alone, the shift is performed when the vehicle is started or when the vehicle speed is reduced to stop the vehicle or when traveling on an ascending slope and the vehicle speed decreases. By switching the lever 31 to the “F (Lo)” position, the driving is performed by the power of the electric motor 5 that can be controlled from a low rotation, so that good traveling performance can be obtained.

If it is determined in step S210 that the position of the shift lever 31 is not "F (Lo)", then it is determined whether the position of the shift lever 31 is "F (Hi)" (step S220). , "F (Hi)", the clutch 20 is "ON" and the clutch 21 is "OF".
The position is switched to the position of F ″ (step S222).
The electric motor 5 is stopped in accordance with this switching operation (step S224). Further, the rotation speed of the engine 1 is controlled according to the depression amount of the accelerator pedal 70 (step 226). In this way, the shift lever 31 moves to "F (H
i) ”position, the output shaft 22 is rotated by the power of the engine 1 via the gears 15 and 16 set at high speed,
The wheels 7a and 7b are moved to drive the work vehicle forward. Further, the rotation speed of the engine 1 is increased / decreased according to the depression amount of the accelerator pedal 70, and the traveling speed can be arbitrarily adjusted.

Thus, when traveling at a high speed in forward traveling during traveling alone operation in which only traveling is performed, the output shaft 22 is directly rotated by the power of the engine 1 in the efficient rotational speed range of the engine 1 to perform work. Since the driving vehicle is driven forward, it is possible to perform efficient traveling driving without causing a loss due to power conversion by each device that occurs when driving the electric motor 5.

If it is determined in step S220 that the position of the shift lever 31 is not "F (Hi)", the shift lever 31 is in the "N" position. At this time, the clutch 2
Both 0 and 21 are turned "OFF" (step S230),
The electric motor 5 is stopped (step S232). Further, the number of revolutions of the engine 1 is controlled according to the depression amount of the accelerator pedal 70 (step S234). Thus, when the position of the shift lever 31 is "N", the connection between the output shaft 22 and the gears 16 and 19 corresponding to the clutches 20 and 21 is disconnected, the output shaft 22 does not rotate, and the work vehicle Does not run. Further, the rotation speed of the engine 1 increases or decreases according to the depression amount of the accelerator pedal 70, and the hydraulic pump 8
It is possible to arbitrarily adjust the working speed of a working device (not shown) that is driven by the discharged oil.

According to this embodiment, the following effects can be obtained.

(1) When driving at low speed while excavating and loading earth and sand, shift gear 31
The drive lever is driven by the power of the electric motor 5 by setting the position to “F (Lo)”, and when the vehicle is driven at a high speed to move to a work site on the road or the like, the shift lever 31
Since the drive is performed by the engine 1 by setting the position of "F (Hi)", the drive system is optimal in any case, and the power of the engine can be efficiently used.

(2) Even when traveling and driving while excavating and loading earth and sand, when driving at high speed, switching to the drive by the engine 1 by switching the shift lever 31 to the "F (Hi)" position. Even when the vehicle travels forward only by traveling alone, the vehicle is driven at a low speed by switching the shift lever 31 to the “F (Lo)” position, and the driving mode of the electric motor 5 is switched. The drive system is optimal for traveling and traveling at high speed, and the power of the engine 1 can be used efficiently.

(3) Driving the work device to excavate earth and sand,
When traveling at low speed when carrying out loading work,
By switching the shift lever 31 to the “F (Lo)” position, the electric motor 5 can be driven regardless of the actual traveling speed.
Since it is driven by the power of, the discomfort of switching the drive system of the traveling device during work is eliminated, and good traveling performance is obtained.

(4) Even if the vehicle is traveling forward only in the traveling alone operation, when the vehicle is started or when the vehicle speed is reduced to stop the vehicle or when the vehicle travels on a climbing slope and the vehicle speed decreases, By switching the shift lever 31 to the “F (Hi)” position, the driving is performed by the power of the electric motor 5 that can be controlled from a low rotation, so that good traveling performance can be obtained.

[0102]

According to the present invention, in a working vehicle equipped with a working device and a traveling device, the traveling drive system can be appropriately switched between electric drive and engine drive, and the power of the engine can be maintained even when the traveling conditions change. It can be used efficiently.

Further, according to the present invention, in a working vehicle equipped with a working device and a traveling device, the vehicle is driven while traveling while excavating and loading earth and sand, and traveling to move to a work site on a road or the like. In either case of driving, traveling can be driven by an optimum driving method, and the power of the engine can be efficiently used.

Further, according to the present invention, in the working vehicle provided with the working device and the traveling device, the traveling can be driven by the optimum driving system in both the low speed traveling and the high speed traveling, The power of the engine can be used efficiently.

[Brief description of drawings]

FIG. 1 is a diagram showing a drive control device for a work vehicle according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing the processing contents of the controller shown in FIG.

FIG. 3 is a diagram showing a drive control device for a work vehicle according to a second embodiment of the present invention.

FIG. 4 is a flowchart showing the processing contents of the controller shown in FIG.

FIG. 5 is a diagram showing a drive control device for a work vehicle according to a third embodiment of the present invention.

6 is a flowchart showing the processing contents of the controller shown in FIG.

FIG. 7 is an explanatory diagram of a drive control device for a working vehicle when an electric motor is used in the related art.

[Explanation of symbols]

1 Engine 2 Generator 3 Inverter / Converter 4 Battery 5 Electric Motors 7a, 7b Wheels 10, 17 Shafts 11, 12, 13, 14, 15, 16, 18, 19 Gears 20, 21 Clutch 22 Output Shafts 23a, 23b Axle 30 , 30A traveling instruction switching device 31 shift lever 40, 40A, 40B controller 50 operation mode setting device 51, 52 operation mode setting button 60 rotation speed sensor 70 accelerator pedal

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toru Kakunuma             Hitachi Construction Machinery Co., Ltd.             Ceremony Company Tsuchiura Factory (72) Inventor Seiji Yamashita             Hitachi Construction Machinery Co., Ltd.             Ceremony Company Tsuchiura Factory (72) Inventor Shuji Ohira             Hitachi Construction Machinery Co., Ltd.             Ceremony Company Tsuchiura Factory (72) Inventor Eiji Egawa             Hitachi Construction Machinery Co., Ltd.             Ceremony Company Tsuchiura Factory F-term (reference) 3D037 CA04 CB06 CB07 CB12                 5H115 PA12 PC06 PG04 PI22 PI29                       PO01 PO17 PU01 PU22 PU24                       PU25 PV09 PV22 QE09 QE18                       QN03 QN06 RE02 SE02 SE03                       SE05 SF01 SJ11 TB01 TE02                       TO21

Claims (7)

[Claims] 1. An engine, a hydraulic pump and a generator driven by the engine, a working device driven by pressure oil discharged from the hydraulic pump, and an electric motor rotationally driven by electric power generated by the generator. And a drive control device for a working vehicle including a traveling device driven by the electric motor, a power storage device storing electric power generated by the generator, and a power transmission device for transmitting power of the electric motor to the traveling device. A first power transmission mechanism, a second power transmission mechanism that transmits the power of the engine to the traveling device, a first power transmission mechanism and a second power transmission mechanism that are selectively operated, and the first power transmission mechanism Control for driving the electric motor with the electric power of the power storage device when operating the mechanism, and stopping the electric motor when operating the second power transmission mechanism And a drive control device for a work vehicle. 2. An engine, a hydraulic pump and a generator driven by the engine, a working device driven by pressure oil discharged from the hydraulic pump, and an electric motor rotationally driven by electric power generated by the generator. And a drive control device for a working vehicle including a traveling device driven by the electric motor, a power storage device storing electric power generated by the generator, and a power transmission device for transmitting power of the electric motor to the traveling device. 1 power transmission mechanism, a second power transmission mechanism that transmits the power of the engine to the traveling device, a first mode mainly for driving the work device,
A mode setting device capable of selecting any one of a second mode mainly for driving the traveling device, and operating the first power transmission mechanism when the mode setting means selects the first mode When the mode setting means selects the second mode, the second power transmission mechanism is operated, and when the first power transmission mechanism is operated, the electric motor is driven by the electric power of the power storage device. A drive control device for a working vehicle, comprising: a control unit that drives the second power transmission mechanism and stops the electric motor when operating the second power transmission mechanism. 3. An engine, a hydraulic pump and a generator driven by the engine, a working device driven by pressure oil discharged from the hydraulic pump, and an electric motor rotationally driven by electric power generated by the generator. And a drive control device for a working vehicle including a traveling device driven by the electric motor, a power storage device storing electric power generated by the generator, and a power transmission device for transmitting power of the electric motor to the traveling device. 1 power transmission mechanism, a second power transmission mechanism that transmits the power of the engine to the traveling device, speed detection means for detecting the speed of the work vehicle, and speed of the work vehicle detected by the speed detection means The first power transmission mechanism is operated at a low speed, the second power transmission mechanism is operated at a high speed of the work vehicle, and the first power transmission mechanism is operated. A control means for driving the electric motor with the electric power of the power storage device when operating the mechanism, and stopping the electric motor when operating the second power transmission mechanism. Drive controller. 4. An engine, a hydraulic pump and a generator driven by the engine, a working device driven by pressure oil discharged from the hydraulic pump, and an electric motor rotationally driven by electric power generated by the generator. And a drive control device for a working vehicle including a traveling device driven by the electric motor, a power storage device storing electric power generated by the generator, and a power transmission device for transmitting power of the electric motor to the traveling device. 1 power transmission mechanism, a second power transmission mechanism for transmitting the power of the engine to the traveling device, a first traveling instruction means for instructing whether to perform low speed traveling or high speed traveling, and the first traveling instruction means Is operating the low speed traveling, the first power transmission mechanism is operated, and when the first traveling instruction means is instructing the high speed traveling, the second power transmission mechanism is operated. And a control unit that drives the electric motor with the electric power of the power storage device when operating the first power transmission mechanism, and stops the electric motor when operating the second power transmission mechanism. A drive control device for a work vehicle, comprising: 5. The drive control device for a work vehicle according to claim 2, further comprising speed detection means for detecting the speed of the work vehicle, wherein said control means has said mode setting means select said first mode. The first power transmission mechanism is operated regardless of the speed of the work vehicle during the operation, and when the mode setting means selects the second mode, the work detected by the speed detecting means. A drive control device for a work vehicle, wherein the first power transmission mechanism is operated when the speed of the vehicle is low, and the second power transmission mechanism is operated when the speed of the work vehicle is high. 6. The drive control device for a working vehicle according to claim 2, further comprising a second traveling instruction means for instructing whether to perform forward traveling or backward traveling. The means selectively operates the first power transmission mechanism and the second power transmission mechanism when the second traveling instruction means instructs forward traveling, and the second traveling instruction means instructs backward traveling. During operation, the drive control device for the working vehicle is characterized in that the first power transmission mechanism is operated. 7. The drive control device for a working vehicle according to claim 1, wherein the first power transmission mechanism is connected to the electric motor via a gear mechanism having a gear ratio set to a low speed. The drive control device for a working vehicle is characterized in that the second power transmission means is connected to the engine via a gear mechanism having a gear ratio set to a high speed.