JPS63121538A - Travel control device for hydraulically driven vehicle - Google Patents

Abstract

PURPOSE:To prevent a creep start due to pump idling by changing over a pipe line from a pilot pump on stepping down an accelerator pedal and operating a pipe line changeover valve on a main pump via changeover valve for moving forward and backward. CONSTITUTION:In a hydraulically driven vehicle such as a wheel type hydraulic power shovel, a prime mover 1 is operated to drive a pilot pump 4 and a main pump 8 and generated hydraulic pressure is introduced to a running motor 9, thereby effectuating the travel of a vehicle. A pipe line from the pilot pump 4 is connected to an electromagnetic changeover valve 21 operating for changeover on the foot switch 23 of an accelerator pedal 2. After a pilot valve 5 for changeover between forward and backward running has been set, the accelerator pedal 2 is stepped down. Then, the hydraulic pressure of the pilot pump 4 is introduced to the predetermined port 6a or 6b of a control valve 6 and the hydraulic pressure of a main pump 8 is led to the running motor 9, thereby starting the travel of the vehicle. According to the aforesaid constitution, a creep start due to pump idling can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a travel control device for a hydraulically driven vehicle, typified by a wheeled hydraulic excavator.

B. Conventional technology The conventional technology will be explained with reference to FIG. 11, taking the running circuit of a wheeled hydraulic excavator as an example.

In the figure, a prime mover 1 is driven by operation of an accelerator pedal 2 in conjunction with a governor lever 3. A pilot pump 4 driven by the prime mover 1 is connected to a pilot boat of a control valve 6 via a pilot valve 5, and when the pilot valve 5 is in the neutral position (N position), the oil discharged from the pilot pump 4 is transferred to a tank 7. be returned. A main pump 8 driven by the prime mover 1 is connected to a travel motor 9 via a control valve 6, and when the control valve 6 is in neutral (N position).

The oil discharged from the main pump 8 is returned to the tank 7. At this time, the travel motor 9 is not driven.

When the operating lever 5a of the pilot valve 5 is operated to switch the pilot valve 5 to the F position, the oil discharged from the pilot pump 4 is transmitted to the pilot port of the control valve 6 via the pilot valve 5, and the control valve 6 is switched to the F position. Switch to position. As a result, the oil discharged from the main pump 8 drives the travel motor 9 in the forward direction via the control valve 6, and the vehicle moves forward.

When the pilot valve 5 is switched to the R position by operating the operating lever 5a, the vehicle similarly moves backward. The traveling speed of the vehicle is controlled by controlling the rotational speed of the prime mover 1 by operating the accelerator pedal 2.

C0 Problems to be Solved by the Invention However, in the prior art represented by FIG. 11, while the prime mover 1 is in operation, the pilot pump 4 and the main pump 8 discharge oil equivalent to the number of idle revolutions. When the pilot valve 5 is switched to the F position or the R position,
The vehicle starts without operating the accelerator pedal 2. Therefore, in order to switch the pilot valve 5 to the F position or the R position without starting the vehicle, the operator must depress the brake pedal (not shown) in advance. For this reason, it is not only bad in workability but also unfavorable in terms of safety.

An object of the present invention is to provide a travel control device for a hydraulically driven vehicle that solves the above-mentioned problems by preventing the vehicle from starting unless a speed control member such as an accelerator pedal is operated.

Means for Solving the D0 Problem In the claim correspondence diagram of the first invention shown in FIG.
00, a hydraulic pump 101 driven by this prime mover 100, a command means 102 such as an operating lever that takes an operating position corresponding to at least forward or backward movement of the vehicle, and a command means 102 that switches from the hydraulic pump 101 according to the operating position. a directional control valve 103 that controls the direction of oil discharged from the directional control valve 1;
The vehicle is driven at a predetermined speed by controlling the rotation speed of the prime mover 100 according to the amount of operation of a speed control means 105 such as an accelerator pedal.

The above-mentioned problem is solved by the detection means 106 that outputs a detection signal when the speed control means 105 is operated, and the detection signal that supplies the direction control valve 103 with a switching signal according to the operating position of the command means 102. The directional control valve 103
This problem can be solved by providing a drive control means 107 that switches between the two.

In the claim correspondence diagram of the second invention shown in FIG.
and a hydraulic pump 1o1. driven by the prime mover 100.
, a command means 102 such as an operating lever that assumes an operating position corresponding to at least forward or backward movement of the vehicle, and a direction control valve 103 that switches according to this operating position to control the direction of oil discharged from the hydraulic pump 101. , a travel motor 104 driven by oil discharged from a direction control valve 103, and controls the rotational speed of the prime mover 100 according to the amount of operation of a speed control means 105 such as an accelerator pedal to move the vehicle at a predetermined speed. While running, the vehicle is decelerated and stopped by a braking means 108 such as a brake pedal. The above-mentioned problem occurs when the speed control means 105 is operated.
a first detection means 106 that outputs a detection signal; a second detection means 109 that outputs a second detection signal when the braking means 108 is operated; and a second detection means 109 that outputs a second detection signal when the braking means 108 is operated; A switching signal according to the position is sent to the directional control valve 10.
3 to switch the directional control valve 103, and at the same time, a second detection signal sends a switching signal to switch the directional control valve 103 to a switching position where discharged oil is not supplied to the travel motor 104 regardless of the operating position of the command means 102. The present invention is solved by including a drive control means 107 that supplies the direction control valve 103.

81 Effect In the first invention, if the command means 102 is operated to the operation position for moving the vehicle forward or backward, the speed control means 10
5 is operated, a switching signal corresponding to the operating position of the command means 102 is supplied from the drive control means 107 to the directional control valve 103.

As a result, the direction control valve 103 switches and the travel motor 1
04 is driven and the vehicle runs.

Further, in the second invention, in addition to such an effect, when the travel motor 104 is driven, the second detection means 10
When the second detection signal is output from 9, the command means 102
A switching signal is supplied from the drive control means 107 to the directional control valve 103 to switch the directional control valve 103 to a switching position in which discharged oil is not supplied to the travel motor 104 regardless of the operating position of the directional control valve 103 .

As a result, the direction control valve 103 is switched to the neutral position, the driving of the travel motor 104 is stopped, and the vehicle is decelerated to a stop.

F. Embodiments First, three embodiments of the first invention will be described with reference to FIGS. 2 to 6.

First Embodiment The first embodiment will be explained with reference to FIG. In FIG. 2, the same parts as in FIG. 11 are given the same reference numerals and will be explained.

The traveling hydraulic circuit is the same as the conventional example shown in FIG. 11, except that an electromagnetic switching valve 21 is provided between the pilot pump 4 and the pilot valve 5. A 1 selection switch 22 and an accelerator switch 23, which closes when the accelerator pedal 2 is depressed and opens when the accelerator pedal 2 is released, are connected in parallel to the solenoid portion 21a of the electromagnetic switching valve 21, and are connected to a power source 30 through each switch. ing. When either switch closes, the solenoid section 21a is energized, and the electromagnetic switching valve 2
1 turns on and switches to the "A" position.

When the operating lever 5a is operated and the pilot valve 5 is in the F or R position, oil discharged from the pilot pump 4 is supplied to the pilot port 6a or 6b of the control valve 6 via the pilot valve 5. When the solenoid section 21a is de-energized, the solenoid section 21a is switched to the "1 port" position, and all of the oil discharged from the pilot pump 4 is returned to the tank 7.

In the configuration of the first embodiment described above, the operating lever 5a controls the command means 102, the control valve 6 controls the direction control valve 103, the accelerator pedal 2 controls the speed control means 104,
Accelerator switch 23 and control unit 24
constitutes the detection means 106, the pilot valve 5 and the electromagnetic switching valve 21 constitute the drive control means 107, and the pressure oil from the pilot valve 5 constitutes the switching signal.

The operation of this first embodiment will be explained next.

In the illustrated state, both the selection switch 22 and the accelerator switch 23 are open, and the electromagnetic switching valve 21 is in the "open" position.
It is located at Therefore, the entire amount of oil discharged from the pilot pump 4 is returned to the tank 7.

Therefore, the pilot valve 5 is operated by the operating lever 5a.
Even if the control valve 6 is switched to the F or R position, the pressure oil does not reach the pilot ports 6a, 6b of the control valve 6, the control valve 6 remains at the neutral position (N position), and the travel motor 9 is not driven.

After switching the pilot valve 5 to the F or R position, when the accelerator pedal 2 is depressed and the solenoid part 21a is energized via the accelerator switch 23, the electromagnetic switching valve 21
is switched to the "A" position, pressure oil is supplied to the pilot port 6a or 6b of the control valve 6 via the pilot valve 5, and the control valve 6 is switched to the F or R position. Therefore, main pump 8
Discharged oil is supplied to the travel motor 9 via the control valve 6, and the travel motor 9 is driven.

When the accelerator pedal 2 is released, the accelerator switch 23 is opened, power to the solenoid part 21a is cut off, the pilot valve 21 is switched to the "open" position, and the entire pressure oil from the pilot pump 4 is returned to the tank 7. Even if the pilot valve 5 is in the F or R position, the pressure oil does not reach the pilot ports 6a, 6b of the control valve 6, and the control valve 6 returns to the N position.

The same operation as described above can be obtained by opening and closing the selection switch 22 without operating the accelerator pedal 2.

Further, in this case, since the travel motor 9 can be rotated while the rotational speed of the prime mover 1 is maintained at idling, inching travel is possible by slight operation of the operating lever 5a.

1. Second Embodiment - In this embodiment, as shown in FIG. 3, a selection switch 22 and an accelerator switch 23, each of which is grounded at one end, are connected to a control unit 24 consisting of a microcomputer or the like. A switching signal is appropriately generated using the program shown in Embodiment 1, and this switching signal is used to switch the electromagnetic switching valve 21.The rest is the same as the first embodiment, and similar parts are given the same reference numerals. The explanation will be omitted.

The operation of this embodiment will be explained with reference to FIG.

In step S1, the state of the accelerator switch 23° selection switch 22 is read, and as described later, the elapsed time after the foot is removed from the accelerator pedal 2, that is, the time after the accelerator switch 23 switches from closed to open. Reads the value of the timer (built-in microcomputer) that measures the elapsed time. In step S2, the state of the selection switch 22 is determined. If it is off, the process proceeds to step S3; if it is on, the process proceeds to step S7. In step S7, the solenoid portion 21a of the electromagnetic switching valve 21 is energized,
1 to the "A" position. As a result, if the pilot valve 5 is switched to the F or R position, the oil discharged from the pilot pump 4 is transferred to the control valve 6.
The control valve 6 is switched to the F or R position, and the travel motor 9 is driven.

Further, when the process advances to step S3, the state of the accelerator switch 23 is determined. If it is on, the flag is set to “1” in step S8.
'' is set, the process advances to step S7, and each part operates in the same manner as described above. If it is off, the process proceeds to step S4, and it is determined whether the flag is "1". If the flag is not equal to 1, step S5 is skipped and the process proceeds to step S6, where the flag is 1.
Then, in step S5, the elapsed time after the accelerator switch 23 is switched is determined based on the value of the timer, and if the predetermined time has not elapsed, the process proceeds to step S7, and if the predetermined time has elapsed, the process proceeds to step S6. In S6, the energization to the solenoid portion 21a of the electromagnetic switching valve 21 is cut off, and the electromagnetic switching valve 21 is switched to the "open" position. Also resets the flag.

That is, when the electromagnetic switching valve 21 is switched to "A" by depressing the accelerator pedal 2, even if the accelerator switch 23 is released by releasing the accelerator pedal 2, the electromagnetic switching valve 21 does not immediately switch to "Open", and the accelerator is turned off. switch 2
If the pilot valve 5 remains in the F or R position until a predetermined period of time elapses after switching from closed to open in step 3, pressure oil is supplied to the travel motor 9 at a flow rate corresponding to the idling rotation speed, and the travel motor 9 is activated. Driven. The flag was set by
This is to prevent step S5 from being denied and the electromagnetic switching valve 21 being turned on when the vehicle is stopped.

In the configuration of the second embodiment described above, the operating lever 5a controls the command means 102, the control valve 6 controls the direction control valve 103, the accelerator pedal 2 controls the speed control means 104,
Accelerator switch 23 and control unit 24
constitutes the detection means 106, the pilot valve 5 and the electromagnetic switching valve 21 constitute the drive control means 107, and the pressure oil from the pilot valve 5 constitutes the switching signal.

-Third Embodiment- In this embodiment, an electromagnetic switching type control valve 61 is provided in place of the hydraulic pilot type control valve.
In the electromagnetic switching valve 21 shown in FIG. 3, the pilot valve 5 is omitted, and a changeover switch 31 for switching the control valve 61 to the F position or the R position is connected to the control unit 24.

That is, in FIG. 5, only the main pump 8 is connected to the prime mover 1, and this main pump 8 and the travel motor 9
An electromagnetic switching type control valve 61 is provided between the two. Then, a switching signal is sent to the control unit 24 from the forward/reverse selector switch 31 that selects forward/reverse movement of the vehicle.
has been entered. This changeover switch 31 has N, F,
It has R terminals, the N terminal is grounded, and the F and R terminals are each connected to a terminal of the control unit 24. The control unit 24 operates the solenoid section 6 of the control valve 61 according to the processing procedure shown in FIG.
A switching signal is output to 1a or 61b.

The processing procedure of the control unit 24 in this embodiment will be explained according to the flowchart shown in FIG.

When this program is started, in step Sll, the states of the accelerator switch 231, selection switch 22, and changeover switch 31 are read, and the value of the timer is read for the same purpose as in the second embodiment. Then step S1
2, the state of the selection switch 22 is determined. If it is off, go to step S13; if it is on, go to step S13. S
14 and proceed to step S15, step S
In step S13, the state of the accelerator switch 23 is determined, and if it is on, the flag is set to "1" in step S14, and then the process proceeds to step S15. In step S15, the state of the changeover switch 31 is determined, and if it is in the F position, step S1
6, a switching signal is supplied to the solenoid part 61a of the control valve 61 to switch it to the F position, and if it is in the R position,
In step S17, a switching signal is supplied to the solenoid part 61b of the control valve 61 to switch it to the R position, and if it is in the N position, in step S318, the control valve 61
is switched to the N position and the flag is reset.

As a result, if the control valve 61 is in the F or R position, pressure oil is supplied from the main pump 8 to the travel motor 9, and the vehicle runs.

When it is determined in step S13 that the accelerator switch 23 is off, it is determined in step S19 whether or not the flag is "1". If the flag is not equal to 1, the process skips step S20 and proceeds to step 818, and if the flag is 1, the process proceeds to step 818. In S20, the elapsed time after the accelerator switch 23 is switched from closed to open is determined, and if the predetermined time has not elapsed, the process proceeds to step S15, and the solenoid section 61a or 61b of the control valve 61 is subsequently switched to the solenoid section 61a or 61b according to the state of the changeover switch 31. Provide a switching signal to hold in F or R position. After a predetermined period of time has elapsed, the process proceeds to step S18 and the control valve 61 is switched to the N position.

The operation of this embodiment is completely similar to that of the second embodiment.

In the configuration of the third embodiment described above, the changeover switch 31
is the command means 102, the control valve 61 is the direction control valve 103, and the accelerator pedal 2 is the speed control means 104.
The accelerator switch 23 and the control unit 24 constitute the detection means 106, the control unit 24 constitutes the drive control means 107, and the signal from the control unit 24 to the solenoid part 61a constitutes the switching signal.

Next, two embodiments of the second invention will be described with reference to FIGS. 7 to 10.

First Embodiment The first embodiment will be explained with reference to FIGS. 7 and 8. In FIG. 7, the same parts as in FIG. 3 are given the same reference numerals and explained.

The travel hydraulic circuit is the same as the conventional example shown in FIG. 11, except that an electromagnetic switching valve 21 is disposed between the pilot pump 4 and the pilot valve 5. This electromagnetic switching valve 21 is switched to the "A" or "Open" position by a signal from the control unit 24. Basically, when the accelerator pedal 2 is depressed, the switch is switched to "A", and when the brake pedal 10 is depressed, the switch is switched to "1".

The control unit 24 is composed of, for example, a microcomputer, and includes an accelerator switch 23 that detects depression of the accelerator pedal 2, a brake switch 25 that detects depression of the brake pedal 10, and a selection switch 22 installed in the driver's seat or the like. Each signal is input, and the electromagnetic switching valve 21 is operated according to the processing procedure shown in FIG.
Outputs a switching signal to switch to the "1" or "1" position.

The operation of the first embodiment will be explained with reference to the flowchart in FIG.

When this program starts, in step S21, the accelerator switch 23. The states of the brake switch 252 selection switch 22 and flag are read (0).Then, the process advances to step S22, where the state of the selection switch 22 is determined. If it is on, the process advances to step S27, and the electromagnetic switching valve 21
Turn on to switch to the "A" position and reset the flag. And then go back to the beginning.

If the 1 selection switch 22 is turned on, the pilot pump 4 and the pilot valve 5 will communicate via the electromagnetic switching valve 21, so the pilot valve 5 will be set to F or R.
By switching to this position, the vehicle runs as before. Furthermore, inching travel is possible using the selection switch 22.

Furthermore, if it is determined in step S22 that the selection switch 22 is off, the state of the accelerator switch 23 is determined in step S23. If the accelerator switch 23 is on, the process proceeds to step S27, where the electromagnetic switching valve 21 is turned on, the flag is reset, and the process returns to the beginning.

That is, when the accelerator pedal 2 is depressed, the pilot pump 4 and the pilot valve 5 communicate with each other via the electromagnetic switching valve 21, so if the pilot valve 5 is switched first, the vehicle will run by operating the accelerator pedal 2.

Therefore, the vehicle will not run if the pilot valve 5 is simply switched without operating the accelerator pedal 2.

Further, when it is determined in step S23 that the accelerator switch 23 is off, it is determined in step S24 whether the flag is "1" or not. If the flag = 1, skip step S25 and proceed to step S26, turn off the electromagnetic switching valve 21 and switch it to the "1 port" position, and set the flag to "1".
Set.

If it is determined in step S24 that the flag≠1, the process proceeds to step S25, and the state of the brake switch 25 is determined. If the brake switch 25 is on, the process proceeds to step 826, and if it is off, the process proceeds to step S27 and returns to the beginning.

That is, when the brake pedal 10 is depressed while the electromagnetic switching valve 21 is on, the electromagnetic switching valve 21 is turned off.
The communication between the pilot pump 4 and the pilot valve 5 is cut off, and the oil supply to the travel motor 9 is stopped. When the accelerator pedal 2 is depressed, the electromagnetic switching valve 21 is turned on again, and the pilot pump 4 and the pilot valve 5 are connected to the electromagnetic switching valve 2.
1, and communicates with the operating lever 5 of the pilot valve 5.
Pressure oil is supplied to the travel motor 9 according to the operating position a. Further, if the accelerator pedal 2 is simply released while driving, step S24. Since S25 and S27 are executed sequentially, the electromagnetic switching valve 21 maintains the 1-port position, and if the pilot valve 5 is at F or Rlfl, the control valve 6 maintains the F or R position, so the idling speed is maintained. A corresponding discharge amount of pressure oil is supplied to the travel motor 9, and cavitation is prevented.

In the configuration of the first embodiment described above, the operating lever 5a controls the command means 102, the control valve 6 controls the direction control valve 103, the accelerator pedal 2 controls the speed control means 104,
The brake pedal 10 serves as the braking means 108, the accelerator switch 23 and the control unit 24 serve as the first detection means 106, the brake switch 25 and the control unit 24 serve as the second detection means 109, and the pilot valve 5 and the electromagnetic switching valve 21 serve as the second detection means 109. constitute the drive control means 107, and the pressure oil from the pilot valve 5 constitutes the switching signal.

- Second Embodiment - As shown in FIG. 9, this embodiment is based on the first embodiment of the second invention shown in FIG. A control valve 61 is provided, and the electromagnetic switching valve 21 shown in FIG. The pilot valve 5 is omitted, and a changeover switch 31 for switching the control valve 61 to the F position or the R position is connected to the control unit 24. The apparatus is the same as the apparatus shown in FIG. 5, except for the provision of a brake switch 25 that is linked to the brake pedal 1o, and the different processing procedures involved.

The processing procedure of the control unit 24 in this embodiment will be explained according to the flowchart shown in FIG.

When this program is started, in step S31, the states of the accelerator switch 239, the selection switch 22, and the changeover switch 31 are read, and the contents of the flag are read in.Next, the process proceeds to step S32, where the state of the selection switch 22 is determined. If it is off, go to step S33;
If it is on, skip steps 833 and 834 and proceed to step S35. In step S33, the state of the accelerator switch 23 is determined, and if it is on, proceed to step S34.
If it is off, the process proceeds to step S39. In step S34, the state of the brake switch 25 is determined. If it is on, the process proceeds to step 338, and if it is off, the process proceeds to step 535. In step 835.

The state of the changeover switch 31 is determined, and if it is in the N position, the process advances to step 838 and the control valve 61 is switched to the N position and the flag is set to "1"; if it is in the R position, the process advances to step S37 and the solenoid of the control valve 61 is switched to the N position. A switching signal is supplied to the solenoid section 61b of the control valve 61 to switch it to the R position and the flag is set to "0", and if it is at the F position, the process proceeds to step 836 and a switching signal is supplied to the solenoid section 61a of the control valve 61 to switch it to the F position. At the same time, the flag is set to "0".

Further, in step S39, it is determined whether the flag is "1" or not. If the flag=1, the process proceeds to step S38, and if the flag≠1, the process proceeds to step S34.

According to the above processing procedure, this embodiment operates as follows.

Simply switching the changeover switch 31 to the F or R position will not cause a changeover signal to be output from the control unit 24 and the control valve 61 will not change over.If you press the accelerator pedal 2 after operating the changeover switch 31 to the F or R position, If the accelerator switch 23 is turned on and the brake pedal 1o is not depressed, a switching signal is supplied from the control unit 24 to the solenoid section 61a or 431b of the control valve 61, and the control valve 61 is switched to the F position or the R position, The travel motor 9 rotates. Even if the accelerator pedal 2 is released in this state, the flag is reset to rOJ, so a negative determination is made in step S39, and the control valve 6
1 is not switched to the N position, and the traveling motor 9 is supplied with an amount of pressurized oil corresponding to the idling rotation speed, thereby preventing cavitation of the traveling motor 9. If you press the brake pedal at this point, the control unit 24 will
A switching signal to the position is supplied to the solenoid parts 61a, 61b of the control valve 61.

The control valve 61 is switched to the N position, the hydraulic brake is applied, and combined with the mechanical braking force from the brake pedal 1o, the vehicle decelerates and comes to a stop.

Further, if the selection switch 22 is turned on, inching travel is possible by slight operation of the changeover switch 31.

In the configuration of the second embodiment described above, the changeover switch 31
is the command means 102, the control valve 61 is the direction control valve 103, and the accelerator pedal 2 is the speed control means 104.
The brake pedal 10 serves as the braking means 108, the accelerator switch 23 and control unit 24 serve as the first detection means 106, the brake switch 25 and control unit 24 serve as the second detection means 109, and the control unit 24 serves as the drive control means. 107 respectively, and the control unit 24 to the solenoid section 61
The signal to a constitutes the switching signal.

G0 Effects of the Invention According to the first and second inventions, no matter what position the command means such as the operating lever for selecting forward or backward movement of the vehicle is operated, the vehicle will continue to run unless the speed control means such as the accelerator pedal is operated. Since the motor is not driven, there are the following effects.

■ Safety is improved by preventing the vehicle from starting against the operator's will.

■ When stopping with the command means in the starting position (forward or reverse), once the vehicle has stopped, the vehicle does not start without continuing to operate the brake etc., improving operability.

■ Operability is improved as there is no need to operate the command means to the neutral state every time the vehicle is stopped.

■ In addition, according to the second invention, the drive of the travel motor is stopped by operating the brake pedal, etc., so the travel motor can be stopped according to the operator's will.
The operability is improved compared to the invention of .

[Brief explanation of the drawing]

Figure 1(a) is a claim correspondence diagram of the first invention;
b) is a claim correspondence diagram of the second invention. 2 to 6 show three embodiments of the first invention. FIG. 2 is an overall configuration diagram of the first embodiment, FIG. 3 is an overall configuration diagram of the second embodiment, FIG. 4 is a flowchart of the second embodiment, and FIG. 5 is a diagram of the third embodiment. The overall configuration diagram, FIG. 6, is a flowchart of the third embodiment. Figures 7 to 10 show two embodiments of the second invention;
The figure is an overall configuration diagram of the first embodiment, FIG. 8 is a flowchart of the first embodiment, FIG. 9 is an overall configuration diagram of the second embodiment, and FIG. 10 is a flowchart of the second embodiment. be. FIG. 11 is a diagram showing a conventional hydraulic travel circuit. 1; Prime mover 2; Accelerator pedal 4: Pilot pump 5: Pilot valve 6.61: Control valve 8: Main pump 9: Travel motor 10 Brake pedal 21: Solenoid switching valve 22: Selection switch 23: Accelerator switch 24: Control unit

Claims (1)

[Scope of Claims] 1) A prime mover, a hydraulic pump driven by the prime mover, a command means that takes an operating position corresponding to at least forward or backward movement of the vehicle, and a command means that switches from the hydraulic pump in accordance with the operating position. a directional control valve that controls the direction of oil discharged from the directional control valve, and a travel motor driven by the oil discharged from the directional control valve, and controls the rotational speed of the prime mover according to the amount of operation of the speed control means to control the speed of the vehicle. A travel control device for a hydraulically driven vehicle that travels at a predetermined speed, comprising a detection means that outputs a detection signal when the speed control means is operated, and a switching signal according to the operation position of the command means based on the detection signal. A drive control device for a hydraulically driven vehicle, comprising: drive control means for supplying the directional control valve to the directional control valve to switch the directional control valve. 2) The directional control valve is switched to a neutral position by the drive control means after a predetermined time has elapsed after the operation of the speed control means is stopped and the detection signal disappears. A travel control device for a hydraulically driven vehicle according to scope 1. 3) A prime mover, a hydraulic pump driven by the prime mover, a command means that takes an operating position corresponding to at least forward or backward movement of the vehicle, and a command means that switches in accordance with the operating position to direct the direction of oil discharged from the hydraulic pump. The vehicle is equipped with a directional control valve to be controlled and a travel motor driven by oil discharged from the directional control valve, and the number of rotations of the prime mover is controlled according to the amount of operation of the speed control means to drive the vehicle at a predetermined speed. In the travel control device for a hydraulically driven vehicle, the vehicle is slowed down and stopped by a braking device, comprising: a first detection device that outputs a first detection signal when the speed control device is operated; and a first detection device that outputs a first detection signal when the speed control device is operated; a second detection means that outputs a second detection signal when the command means is operated; and a second detection means that outputs a second detection signal when the command means is operated; At the same time as switching the control valve, a switching signal is supplied to the directional control valve to switch the directional control valve to a switching position in which the discharged oil is not supplied to the travel motor regardless of the operating position of the command means based on the second detection signal. What is claimed is: 1. A travel control device for a hydraulically driven vehicle, comprising: drive control means for controlling a hydraulically driven vehicle.