JP2000337505A - Travel speed control system for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a travel speed control system that can drive vehicles at a high speed. SOLUTION: The travel speed control system 40 has a speed change switch 31 operable in a selected one of three, low, middle and high, speed positions, a throttle position control circuit 45 arranged in a controller 41 to set the throttle position of an engine E in two, high and low, stages depending upon the operation of the speed change switch 31, a variable-displacement travel motor 15 with a swash plate, a displacement varying cylinder 53 for varying the tilt angle of the swash plate to vary the displacement of the travel motor 15, and a valve operation control circuit 49 disposed in the controller 41 to drive the displacement varying cylinder 53 telescopically and thus switch the speed ratio of the travel motor 15 over in two, high and low, stages depending upon the operation of the speed change switch 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling speed control device for a vehicle, and more particularly, to a traveling hydraulic motor for driving a crawler type traveling body provided on a vehicle body and a hydraulic pump for driving the traveling hydraulic motor. The present invention relates to a vehicle traveling speed control device that controls a traveling speed of a vehicle having the same.

[0002]

2. Description of the Related Art An aerial work vehicle that performs an aerial work is provided with a pair of crawler traveling bodies in the width direction of the vehicle body, and a telescopic vehicle mounted on the vehicle body.
It comprises a boom capable of raising and lowering and turning, a work table provided at the end of the boom, on which a worker can ride, and a traveling speed operation device provided on the work table to operate the traveling speed of the vehicle. There is something. Each of the pair of crawler traveling bodies is provided with a traveling motor that is operated by hydraulic pressure to rotationally drive the crawler traveling body. The traveling motor is driven to rotate by the supply of hydraulic oil discharged from a hydraulic pump driven by the engine, and the engine is controlled so that the number of rotations can be changed in two stages of height. In addition, as the traveling motor, a positive displacement pump having a fixed displacement is used, and when the traveling speed operating device is operated to select and operate the engine rotational speed to either high or low, the vehicle is moved at either high or low traveling speed. be able to.

[0003]

However, the traveling speed of the vehicle obtained by operating the traveling speed operating device to the high speed side is extremely low as a speed for moving the vehicle to another work site far away. It takes a lot of time to move the vehicle to another work place, reducing the work efficiency of the whole work.

If the engine speed is increased, the running speed of the vehicle can be further increased. However, in order to obtain a desired moving speed of the vehicle, the engine speed must be extremely increased. In addition, the noise generated from the engine is increased to deteriorate the environment around the vehicle. Further, there is a problem that a desired vehicle moving speed cannot be obtained due to the limitation of the allowable rotation speed of the hydraulic pump.

The present invention has been made in view of such a problem, and has a vehicle running speed that allows a vehicle to move in a short time even when the vehicle travels a long distance in a state where noise generated from the engine is small. It is an object of the present invention to provide a traveling speed control device for a vehicle that can obtain the following.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a traveling speed control apparatus for a vehicle according to the present invention comprises a traveling speed of a vehicle (for example, an aerial work vehicle 1 in the embodiment) having a free-running body. A control device that is rotatably provided on the vehicle body and travels the vehicle body (for example, the crawler belt 9 in the embodiment); A traveling hydraulic motor capable of switching the speed ratio (for example, the traveling motor 15 in the embodiment), and traveling motor speed ratio control means (for example, the second switching valve 47 in the embodiment, 1 switching valve 61), a hydraulic pump that supplies hydraulic oil to the traveling hydraulic motor, an engine that drives the hydraulic pump to rotate,
Speed setting operation means capable of selecting and operating three speeds of medium speed and high speed (for example, the speed changeover switch 3 in the embodiment)
1) When the speed setting operation means is operated at a low speed, the throttle opening of the engine is set to a low opening, and the traveling hydraulic motor is set to a low speed ratio by the traveling motor speed ratio control means. When the operating means is operated at medium speed, the throttle opening of the engine is set to a high opening, and the traveling hydraulic motor is set to a low speed ratio by the traveling motor speed ratio control means. When operated, the throttle opening of the engine is set to a high opening and the traveling motor speed ratio control means sets the traveling hydraulic motor to a high speed ratio. It is preferable to have a degree control circuit 45 and a valve operation control circuit 49).

When the speed setting operation means is operated at a low speed, the opening speed ratio setting means sets the throttle opening of the engine to a low opening, and the traveling motor speed ratio control means sets the traveling hydraulic motor to a low speed ratio. Set. Then, the engine set to a low opening operates to rotate the hydraulic pump at a low speed, and the hydraulic pump supplies low-speed hydraulic oil to the traveling hydraulic motor. Since the traveling hydraulic motor is set at a low speed ratio, the low-speed hydraulic oil flowing into the traveling hydraulic motor is further decelerated and discharged from the traveling hydraulic motor, and the traveling hydraulic motor is driven to rotate at a low speed. Then, the traveling unit is rotationally driven at a low speed by the traveling hydraulic motor that is rotationally driven at a low speed, and the vehicle moves at a low speed.

When the speed setting operation means is operated at the medium speed, the opening speed ratio setting means sets the throttle opening of the engine to a high opening, and the traveling motor speed ratio control means switches the traveling hydraulic motor to the low speed ratio. Set to. Then, the engine set to a high opening degree operates to rotate the hydraulic pump at a high speed, and the hydraulic pump supplies high-speed hydraulic oil to the traveling hydraulic motor. Since the traveling hydraulic motor is set at a low speed ratio, the high-speed hydraulic oil flowing into the traveling hydraulic motor is decelerated and discharged from the traveling hydraulic motor, and the traveling hydraulic motor is driven to rotate at a medium speed. Then, the traveling means is rotationally driven at the medium speed by the traveling hydraulic motor that is rotationally driven at the medium speed, and the vehicle moves at the medium speed.

When the speed setting operation means is operated at high speed, the opening speed ratio setting means sets the throttle opening of the engine to a high opening, and the traveling motor speed ratio control means sets the traveling hydraulic motor to a high speed ratio. Set. Then, the engine set to a high opening degree operates to rotate the hydraulic pump at a high speed, and the hydraulic pump supplies high-speed hydraulic oil to the traveling hydraulic motor. Since the traveling hydraulic motor is set at a high speed ratio, the high-speed hydraulic oil flowing into the traveling hydraulic motor is further accelerated and discharged from the traveling hydraulic motor, and the traveling hydraulic motor is driven to rotate at high speed. Then, the traveling means is rotationally driven at high speed by the traveling hydraulic motor which is rotationally driven at high speed, and the vehicle moves at high speed.

The traveling hydraulic motor can switch between high and low speed ratios, and the throttle opening of the engine is controlled in two high and low stages. By setting the throttle opening of the traveling motor speed ratio control means to the speed ratio of the traveling hydraulic motor, the traveling means can be rotationally driven at three different speeds. Also, by increasing the speed ratio of the traveling hydraulic motor and setting the throttle of the engine to a high degree of opening, the traveling speed of the vehicle can be moved at a higher speed as compared with the conventional technology in which the traveling hydraulic motor has a constant speed ratio. Can be done.

The traveling hydraulic motor is a variable displacement motor whose capacity can be switched between high and low by changing the inclination angle of the swash plate, and the traveling motor speed ratio control means controls the traveling hydraulic motor to have two high and low displacements. It is preferable to use a capacity adjusting cylinder (for example, the capacity changing cylinder 53 in the embodiment) operable to change the inclination angle of the swash plate.

When the speed setting operating means is operated, the opening speed ratio setting means sets the throttle opening of the engine based on the contents of the operation, and the traveling motor speed ratio controlling means operates the swash plate of the variable displacement motor. A tilt angle is set, and the capacity adjusting cylinder is operated to expand and contract based on the set tilt angle to move the swash plate to the set tilt angle.

The traveling hydraulic motor uses a variable displacement motor capable of switching the capacity in two stages of height and operates a displacement adjusting cylinder to expand and contract to change the inclination angle of the swash plate of the variable displacement motor. Can be switched between high and low levels, and the rotational drive speed ratio of the traveling hydraulic motor can be set to two levels when the flow rate of the hydraulic oil supplied to the traveling hydraulic motor is the same.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS. This embodiment shows an embodiment of a self-propelled aerial work vehicle having a pair of crawler-type lower traveling bodies at both ends in the width direction of a vehicle body. Before describing the vehicle traveling speed control device of the present invention at first, an aerial work vehicle equipped with the traveling speed control device will be described. As shown in FIG. 1, the aerial work vehicle 1 has a crawler-type lower left traveling body 5 and a right lower traveling body 7 at both ends in the width direction of the vehicle body 3. The left lower traveling body 5 is a crawler belt 9
A starting wheel 11 provided inside the front side of the crawler belt 9 to drive the crawler belt 9; an idle wheel 13 provided inside the crawler belt 9 behind the vehicle body to guide the crawler belt 9; And a traveling motor 15 that is provided inside and drives the starting wheel 11 to rotate. Since the lower right traveling body 7 has the same configuration as the lower left traveling body 5, the same reference numerals are given to the same aspects, and the description thereof will be omitted.

On the upper part of the vehicle body 3, a swivel table 17 which can be swiveled is provided.
Is provided in the vehicle body 3 below the turntable 17, and a turn motor (not shown) is provided, and the turntable 17 is turned by the operation of the turn motor. Swivel 1
7 has a concave groove 19 formed in the front-rear direction of the vehicle body 3.
Is provided. The retractable boom 21 is configured to be retractable in the concave groove 19. The telescopic boom 21 is configured to be telescopically movable, and the base of the telescopic boom 21 is provided on a pair of pivot plates 2 erected above the concave groove 19 at the rear of the vehicle body.
3, an up-and-down cylinder 25 is pivotally connected between the lower part of the side wall of the telescopic boom 21 and the bottom of the concave groove 19. The telescopic boom 21 is raised and lowered by operating the raising and lowering cylinder 25.

At the end of the telescopic boom 21, there is provided a worktable 27 on which a worker can ride. The workbench 27 is connected to a leveling device (not shown),
The work table 27 is always kept horizontal by the operation of the leveling device irrespective of the undulation angle of 1. Workbench 27
Has a boom operating device 29 for raising / lowering, expanding / contracting / turning the telescopic boom 27, a speed changeover switch 31 for selecting and operating the traveling speed of the vehicle, and a direction operating device 33 for operating the traveling direction of the vehicle. .

Next, a description will be given of a vehicle speed control device. The traveling speed control device controls the traveling speed of the vehicle at low speed, medium speed,
This is a device that drives the vehicle at any one of three high speeds. The traveling speed control device 40 includes a speed changeover switch 31, a controller 41, and a hydraulic circuit 43, as shown in FIG. Speed switch 4
Reference numeral 1 denotes a switch which is selectively operated when an operator who is on the work table 27 shown in FIG. 1 manually operates the vehicle to move the vehicle at one of three speeds: low speed, medium speed, and high speed. The speed changeover switch 31 includes an operation lever L1 which can be tilted in the front-rear direction of the vehicle body 3 shown in FIG. 1, and when the operation lever L1 is tilted forward, the vehicle moves at a low speed.
When 1 is in a neutral state (state in which the operation lever L is directed upward), the vehicle moves at a medium speed, and when the operation lever L1 is tilted backward, the vehicle moves at a high speed. The speed changeover switch 31 and the direction operation device 33 can be combined into a single operation device so that the traveling speed can be controlled simultaneously with the traveling direction of the vehicle in accordance with the tilt angle of the lever. In this case, the traveling speed of the vehicle is configured to be three stages of low, middle, and high according to the tilt angle of the lever.

A controller 41 shown in FIG. 2 controls a throttle opening degree control circuit 45 for switching the throttle opening degree of the engine E between high and low levels in accordance with the operation contents of the speed changeover switch 31, and a traction motor for two levels. A valve operation control circuit 49 for controlling the operation of the second switching valve 47 for switching to the speed ratio. The hydraulic circuit 43 includes a hydraulic pump 51 that is rotationally driven by the engine E, the traveling motor 15, a second switching valve 47, and a displacement cylinder 53. Note that the traveling motor 15 and the capacity changing cylinder 53 can be integrally configured.

The hydraulic circuit 43 will be described in more detail with reference to FIG. The hydraulic circuit 43 is a left oil passage 5 that rotationally drives the left lower traveling body 5 and the right lower traveling body 7 shown in FIG.
5 and a right oil passage 57. Since the left oil passage 55 and the right oil passage 57 have substantially the same configuration, only the right oil passage 57 will be described, and the left oil passage 55 will be replaced with the right oil passage 57.
The same reference numerals are given to the same aspects as those described above, and the description thereof will be omitted. The right oil passage 57 is connected to the hydraulic pump 5 from the downstream side.
1, the main operation valve 59 and the traveling motor 15. The hydraulic pump 51 obtains the driving force of the engine E and is driven to rotate to discharge hydraulic oil. The main operation valve 59 is a three-position switching valve that switches the flow direction of the hydraulic oil based on the operation content of the direction operation device 33 shown in FIG. 1, and shuts off the supply of the hydraulic oil from the hydraulic pump 51 at the neutral position. When the solenoid 59a of the operation valve 59 is excited, the direction in which the hydraulic oil flows is switched.

The traveling motor 15 is a swash plate type variable displacement motor.
The swash plate 15a is movable within a range of positions (hereinafter, referred to as "capacity setting positions") at which the swash plate 15a moves beyond the capacity setting positions. The swash plate 15a is pivotally connected to the rod-side tip of a capacity changing cylinder 53 that changes the inclination angle of the swash plate 15a. When the capacity changing cylinder 53 extends, the displacement angle of the swash plate 15a is changed to reduce the capacity of the traveling motor 15, and when the capacity changing cylinder 53 is contracted, the displacement angle of the swash plate 15a is changed to increase the capacity of the traveling motor 15. Become.

A first switching valve 61 is connected to a bottom chamber 53 a of the capacity changing cylinder 53 via a cylinder flow path 60. The first switching valve 61 is a two-position switching valve. Normally, the bottom chamber 53a of the capacity changing cylinder 53 communicates with the drain D to be in a low pressure state so that the capacity changing cylinder 5
3, the second switching valve 47 and the first switching valve 6
When the hydraulic oil in the switching flow path 67 connecting the two is operated as pilot oil pressure, the main flow path 63 and the bottom chamber 53a
The capacity change cylinder 53 is extended by making the spaces communicate with each other.

The second switching valve 47 is a two-position switching valve. When the solenoid 47a is excited, the branch flow path 65 and the switching flow path 67 communicate with each other, and the solenoid 47a
Is not excited, the branch flow path 65 is shut off, and the switching flow path 67 is opened to the drain D to be in a low pressure state. Second
ON / OF of excitation of solenoid 47a of switching valve 47
The F operation is controlled by the valve operation control circuit 49 of the controller 41 according to the operation of the speed changeover switch 31 shown in FIG. More specifically, as shown in FIG. 4, when the operation lever L1 of the speed changeover switch 41 is tilted forward or set to the neutral state and the vehicle travel speed is set to low or medium speed, the valve is turned on. The operation control circuit 49 controls the solenoid 4
7a is turned off. Also, the speed changeover switch 41
When the operation lever L1 is tilted backward and the vehicle travel speed is increased, the valve operation control circuit 49 is operated.
Puts the solenoid 47a in an excited state.

When the operating lever L1 of the speed changeover switch 31 is tilted forward, the throttle opening control circuit 45 shown in FIG. 2 sets the throttle opening of the engine E to a low opening.
Further, when the operation lever L1 is operated in the neutral state or tilted backward, the throttle opening control circuit 45 sets the throttle opening of the engine E to a high opening. The high and low throttle openings can be set within a range that does not exceed the allowable rotation speed of the hydraulic pump 51.

Next, the vehicle traveling speed control device 4 of the present invention will be described.
The operation of 0 will be described for the case where the traveling speed of the vehicle is set to high speed, medium speed and low speed. In the description of the operation, the lower right traveling body 7 will be described, and the operation of the left lower traveling body 5 will be the same as that of the right lower traveling body 7, so that the detailed description thereof will be omitted. First, a case where the vehicle is moved at a high speed will be described. In a state where the telescopic boom 21 shown in FIG. 1 is stored in the swivel table 17, an operator (not shown) who has boarded the work table 27 tilts the operation lever L <b> 1 of the speed switch 31 backward. Also,
The operator operates the direction operation device 33 to move the vehicle forward. When the operating lever L1 is tilted backward, a high-speed signal for causing the vehicle to travel at a high speed is sent to the valve operation control circuit 49 and the throttle opening control circuit 45 of the controller 41 shown in FIG. Thus, the solenoid 47a of the second switching valve 47 shown in FIG. 3 is excited so that the branch channel 65 and the switching channel 67 communicate with each other.

At the same time, the throttle opening control circuit 45 shown in FIG. 2 drives the engine E by setting the throttle opening of the engine E to a high opening based on the high speed signal, and the hydraulic pump 51 shown in FIG. And the operating oil flows in the main flow path 65
Discharge at high speed. Also, the direction operation device 33 shown in FIG.
By the operation described above, the solenoid 59a of the main operation valve 59 (one of the left and right solenoids 59a in FIG. 3) is excited, and the main operation valve 59 is operated in a direction for moving the vehicle forward. The high-speed hydraulic oil discharged into the main flow path 63 further flows through the main flow path 63 via the main operation valve 59, and the traveling motor 1
5 to drive the traveling motor 15 to rotate. Also,
Part of the hydraulic oil discharged into the main flow channel 63 flows into the branch flow channel 65 and raises the pilot oil pressure in the switching flow channel 67 via the second switching valve 47. The first switching valve 61 is switched by the pilot oil pressure to communicate between the main passage 63 and the bottom chamber 53 a of the capacity changing cylinder 53, and the main passage 63
Flows into the bottom chamber 53a to extend the capacity changing cylinder 53.

When the displacement cylinder 53 is extended,
The inclination angle of the swash plate 15a changes, and the swash plate 15a moves to a low-capacity capacity setting position and stops, thereby reducing the capacity of the traveling motor 15. Then, the high-speed hydraulic oil flowing through the main flow path 63 flows into the traveling motor 15 having a reduced capacity, further accelerates the speed of the hydraulic oil, discharges the traveling oil from the traveling motor 15, and drives the traveling motor 15 to rotate at a high speed. As a result, the starting wheel 11 shown in FIG.
Rotate at high speed, and the crawler belt 9 rotates at high speed.
Similarly, the starting wheel 11 shown in FIG. 1 connected to the traveling motor 15 of the lower left traveling body 5 is driven to rotate at high speed to rotate the crawler belt 9 at high speed, so that the vehicle moves at high speed.

Next, a case where the vehicle is moved at a medium speed will be described. The operator operates the speed switch 31 shown in FIG.
To set the operation lever L1 in the neutral state. Further, the operator operates the direction operation device 33 to perform an operation of moving the vehicle forward. When the operation lever L1 is operated to the neutral state, a middle speed signal of the speed changeover switch 31 is sent to the valve operation control circuit 49 and the throttle opening control circuit 45 shown in FIG. On the basis of this, the solenoid 47a of the second switching valve 47 shown in FIG. 3 is de-energized to shut off the branch channel 65 and open the switching channel 67 to the drain D.

At the same time, the throttle opening control circuit 45 shown in FIG. 2 drives the engine E by setting the throttle opening of the engine E shown in FIG. High-speed rotation and hydraulic fluid flows into the main passage 63
Discharge at high speed. In addition, the operation of the direction operation device 33 excites the solenoid 59a of the main operation valve 59, so that the main operation valve 59 operates in a direction for moving the vehicle forward. The high-speed hydraulic oil discharged into the main flow path 63 flows into the travel motor 15 through the main operation valve 59 and drives the travel motor 15 to rotate. At this time, since the switching flow path 67 is opened to the drain D and the pilot oil pressure in the switching flow path 67 is in a reduced state, the first switching valve 61 is not switched and the bottom chamber 53a of the capacity changing cylinder 53 is connected to the drain D. The state is opened, the bottom chamber 53a is in a low pressure state, and the displacement cylinder 53 is contracted.

When the capacity changing cylinder 53 operates to contract,
The inclination angle of the swash plate 15a changes, the swash plate 15a moves to a high-capacity capacity setting position and stops, and the capacity of the traveling motor 15 increases. Then, the high-speed hydraulic oil flows into the high-capacity traveling motor 15 and its speed is reduced, and the traveling motor 1
5 and the traveling motor 15 is driven to rotate at a medium speed. Therefore, the crawler belt 9 rotates at a medium speed. Similarly, the traveling motor 15 of the lower left traveling body 5
Is also rotated at a medium speed, so that the vehicle moves at a medium speed.

Next, a case where the vehicle is moved at a low speed will be described. The operator operates the speed switch 31 shown in FIG.
To tilt the operation lever L1 forward. Further, the operator operates the direction operation device 33 to perform an operation of moving the vehicle forward. When the operating lever L1 is tilted forward, a low-speed signal of the speed changeover switch 31 is sent to the valve operation control circuit 49 and the throttle opening control circuit 45 shown in FIG. , The solenoid 47a of the second switching valve 47 is de-energized to shut off the branch channel 65 and open the switching channel 67 to the drain D.

At the same time, the throttle opening control circuit 45 shown in FIG. 2 lowers the throttle opening of the engine E based on the low speed signal to drive the engine E, and the hydraulic pump 51 rotates at a low speed. The hydraulic oil is discharged into the main flow channel 63 at a low speed. The solenoid 59a of the main operation valve 59 shown in FIG. 3 is excited by the operation of the direction operation device 33 shown in FIG. 1, and the main operation valve 59 is operated in a direction for moving the vehicle forward. The low-speed hydraulic oil discharged into the main flow path 63 flows into the traveling motor 15 through the main operation valve 59 and is driven to rotate. At this time, since the switching flow path 67 is open to the drain D and the pilot oil pressure in the switching flow path 67 is in a reduced state, the first switching valve 61 is not switched, and the bottom chamber 53 a of the capacity changing cylinder 53 is not switched. Is drain D
To a low pressure state, and as a result, the capacity changing cylinder 53 operates to contract.

When the capacity changing cylinder 53 operates to contract,
The inclination angle of the swash plate 15a changes, the swash plate 15a moves to a high-capacity capacity setting position and stops, and the capacity of the traveling motor 15 increases. Then, the low-speed hydraulic oil flowing through the main flow path 63 flows into the traveling motor 15 having a large capacity, the speed of the hydraulic oil is further reduced, and the hydraulic oil is discharged from the traveling motor 15 and the traveling motor 15 is rotated at a low speed. . Therefore, the crawler belt 9 shown in FIG. 1 rotates at a low speed. Similarly, the crawler belt 9 connected to the traveling motor 15 of the lower left traveling body 5 also rotates at a low speed, and as a result, the vehicle moves at a low speed.

In the above-described embodiment, the throttle opening of the engine E can be switched between two levels, and the speed ratio of the traveling motor 15 can be switched between two levels. Instead, it can be set and switched to two or more stages. In this case, the speed changeover switch 31 uses a switch capable of setting and operating a plurality of traveling speeds of four or more stages. In addition, the above-mentioned speed changeover switch sets the traveling speed of the vehicle at low speed, medium speed,
Although the switch can select and operate three high speeds,
It can be a switch for selecting and operating only two speeds of medium speed / high speed or low speed / high speed. In this case, the traveling speed control device 40 moves the vehicle at medium speed / high speed or low speed / high speed based on the medium speed signal / high speed signal or the low speed signal / high speed signal generated from the speed changeover switch.

[0034]

As described above, according to the running speed control apparatus for a vehicle of the present invention, the throttle opening of the engine E can be switched between high and low, and the speed ratio of the running hydraulic motor can be changed between high and low. The driving means can be driven to rotate at three different speeds. Also, by increasing the throttle opening of the engine E and increasing the speed ratio of the traveling hydraulic motor, the traveling speed of the vehicle can be reduced as compared with the prior art in which the speed ratio of the traveling hydraulic motor cannot be switched. Can be made faster, the vehicle can be moved in a short time when the vehicle is moved to a distant work site, and the work efficiency of the entire work can be improved.

A variable displacement motor capable of switching between two levels of height is used as the traveling hydraulic motor, and the displacement adjusting cylinder is extended and contracted to change the inclination angle of the swash plate of the variable displacement motor. The capacity of the hydraulic motor can be switched between high and low levels, and the rotational drive speed ratio of the traveling hydraulic motor can be set to high and low when the flow rate of the working oil supplied to the traveling hydraulic motor is the same.

[Brief description of the drawings]

FIG. 1 is a perspective view of an aerial work vehicle equipped with a vehicle traveling speed control device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a vehicle traveling speed control device according to one embodiment of the present invention.

FIG. 3 is a hydraulic circuit diagram of the vehicle traveling speed control device according to one embodiment of the present invention.

FIG. 4 is a diagram for explaining the operation of the work vehicle boom operation control device according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 aerial work vehicle (vehicle) 3 body 9 crawler belt (traveling means) 15 traveling motor (traveling hydraulic motor) 15a swash plate 27 worktable 31 speed changeover switch (speed setting operating means) 40 traveling speed control device 45 throttle opening Control circuit (opening speed ratio setting means) 47 Second switching valve (traveling motor drive speed controlling means) 49 Valve operation control circuit (opening speed ratio setting means) 51 Hydraulic pump 53 Capacity changing cylinder (capacity adjusting cylinder) 61 1 switching valve (traveling motor drive speed control means) E engine

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Claims (2)

[Claims] 1. A traveling speed control device for a vehicle having a vehicle body that is free to travel, comprising: traveling means rotatably provided on the vehicle body for traveling the vehicle body; A traveling hydraulic motor capable of driving a traveling means to switch between two high and low speed ratios; a traveling motor speed ratio control means for performing a speed ratio switching control of the traveling hydraulic motor; and supplying the hydraulic oil to the traveling hydraulic motor. A hydraulic pump, an engine that rotationally drives the hydraulic pump, speed setting operating means capable of selectively operating a traveling speed of the vehicle body at three speeds: low speed, medium speed, and high speed; When operated, the throttle opening of the engine is set to a low opening, and the traveling hydraulic motor is set to a low speed ratio by traveling motor speed ratio control means. When the gear is operated at the medium speed, the throttle opening of the engine is set to a high opening, and the traveling hydraulic motor is set to a low speed ratio by traveling motor speed ratio control means. When the high speed is operated, the opening degree speed ratio setting means for setting the throttle opening degree of the engine to a high opening degree and setting the traveling hydraulic motor to a high speed ratio by traveling motor speed ratio control means, A traveling speed control device for a vehicle, comprising: 2. The traveling hydraulic motor is a variable displacement motor capable of switching the displacement in two levels of height by changing the inclination angle of a swash plate, and the traveling motor speed ratio control means sets the displacement of the traveling hydraulic motor to 2. The traveling speed control device for a vehicle according to claim 1, wherein the displacement adjusting cylinder is a capacity adjusting cylinder operable to change an inclination angle of the swash plate so as to have two levels.