JP2003341495A - Industrial vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrial vehicle equipped with a wheel loader capable of reducing the number of times the brake is pedaled in running down a slope, etc., and making its resistance device for braking small. <P>SOLUTION: The industrial vehicle equipped with the wheel loader includes a brake valve 31 to be changed over from the neutral position N to the working position F in compliance with working of the brake pedal 13 and emitting an oil pressure to a brake device 10 and a solenoid valve 32 to emit a pilot pressure for changing over the brake valve 31 to the working position F, in which the vehicle running speed command value is set proportional to the working amount of an accelerator pedal, and in case the actual running speed value of the vehicle is greater than the running speed command value corresponding to the working amount of the accelerator pedal, a control means changes over the solenoid valve 32 and emits the pilot pressure to the brake valve 31, and in case the actual running speed value is equal to or less than the running speed command value, changes over the solenoid valve 32 and releases the pilot pressure to the brake valve 31. <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 an industrial vehicle such as a wheel loader, and more particularly to a braking system (brake system).

[0002]

2. Description of the Related Art Conventionally, as this type of industrial vehicle, there is a wheel loader 1 as shown in FIGS. 7 and 8, for example.
That is, the vehicle body 2 includes a plurality of traveling wheels 3, an electric motor 4 (induction motor or the like) for rotating and driving each traveling wheel 3, and an inverter device 5 for driving each of the motors 4. Each motor 4 and inverter device 5
A generator 6 that supplies electric power to the engine, an engine 7 that drives the generator 6, an operator cab 8, and a control unit 9 are provided.

The output shaft of each motor 4 is connected to a traveling wheel 3, and a hydraulic wet multi-plate brake device 10 for braking the rotation of the output shaft of the motor 4 with respect to each motor 4.
Is attached.

A steering wheel 11 is provided in the cab 8.
An accelerator pedal 12 and a brake pedal 13 are provided. The control means 9 turns the wheel loader 1 to the left or right according to the rotation angle of the handle 11, and controls the rotation speed of each motor 4 according to the depression amount of the accelerator pedal 12. Also, brake pedal 1
By depressing 3, the brake device 10 operates,
The braking force is configured to be obtained according to the depression amount of the brake pedal 13.

According to this, when the operator depresses the accelerator pedal 12, each motor 4 is rotationally driven at a rotational speed corresponding to the amount of depression, and the wheel loader 1 runs. Further, when the brake pedal 13 is depressed, a braking force corresponding to the amount of depression acts on each traveling wheel 3, and the wheel loader 1 is decelerated.

[0006] When the wheel loader 1 having the above-described structure descends a slope (downhill), a force in the downhill direction acts in proportion to the own weight of the wheel loader 1, and the rotational speed of each traveling wheel 3 changes. Since the wheel loader 1 travels at a speed higher than the speed corresponding to the amount of depression of the accelerator pedal 12, the operator frequently depresses the brake pedal 13 to activate the brake device 10, and the wheel loader 1 operates. Had to slow down, and the brake operation was troublesome.

As measures against this, for example, as shown in FIG. 8, between the inverter devices 5 of the left and right traveling wheels 3,
In addition, the inverter device 5 for the rear left and right traveling wheels 3
A braking resistance device 15 that consumes the regenerative braking energy of each motor 4 is connected therebetween. The front and rear braking resistance devices 15 each include a regenerative resistor and a regenerative braking unit that regulates the value of the current flowing through the regenerative resistor.

According to this, since the regenerative braking energy generated from each motor 4 is converted into heat by the braking resistance device 15 and consumed when descending a slope, a braking force acts on each motor 4 and each motor 4 The rotation speed of 4 is reduced. Therefore, it is possible to reduce the number of times of the brake operation in which the operator depresses the brake pedal 13 to operate the brake device 10.

[0009]

However, in the above-mentioned conventional type, as the wheel loader 1 becomes larger, a larger braking force is required when descending the hill, so that the braking resistance device 15 becomes very large and expensive. There is a problem such as.

The present invention provides an industrial vehicle that can reduce the number of times the operator depresses the brake pedal (the number of times the brake is operated) at the time of descending a hill and the size of the braking resistance device can be reduced. To aim.

[0011]

In order to achieve the above object, the first aspect of the present invention is directed to a motor for rotationally driving a traveling wheel, an accelerator pedal for adjusting the rotational speed of the motor, and an operating fluid pressure. An industrial vehicle equipped with a brake device for braking the rotation of the motor, and a brake pedal for operating the brake device, wherein the vehicle body has an operating position from a neutral position in response to depression of the brake pedal. A brake valve that outputs the working fluid pressure to the brake device by switching to a brake valve, and a control valve that outputs the pilot pressure to the brake valve to switch the brake valve to the operating position are provided. The vehicle traveling speed command value is set in proportion to the actual traveling speed value of the vehicle detected by the speed detecting means. When the traveling speed command value corresponding to the stepping amount is larger, the control valve is switched to output the pilot pressure to the brake valve, and when the actual traveling speed value is less than or equal to the traveling speed command value, the control valve is Is provided to release the pilot pressure to the brake valve.

According to this, when the operator depresses the accelerator pedal, the traveling speed command value corresponding to the depression amount of the accelerator pedal is set. When an industrial vehicle is downhill, etc., a force in the downhill direction acts in proportion to the weight of the industrial vehicle, the rotational speed of each traveling wheel gradually increases, and the accelerator pedal depression amount is increased. Industrial vehicles run faster than they can. Then, when the actual traveling speed value of the vehicle detected by the speed detecting means becomes larger than the traveling speed command value corresponding to the depression amount of the accelerator pedal, the control means switches the control valve to apply the pilot pressure to the brake valve. Output. As a result, the brake valve is switched from the neutral position to the operating position, the operating fluid pressure is output to the braking device, the braking device operates, and the rotation of the motor is braked. Therefore, even if the operator does not step on the brake pedal, if the actual traveling speed value of the vehicle detected by the speed detecting means becomes larger than the traveling speed command value corresponding to the depression amount of the accelerator pedal, the braking device automatically operates. Since the industrial vehicle is decelerated by decelerating, the number of times the operator depresses the brake pedal (the number of brake operations) can be reduced when going down a slope or the like.

Further, when the braking resistance device is provided, both of the automatic operation of the braking device as described above and the consumption of the regenerative braking energy by the braking resistance device at the time of descending the slope. Therefore, the industrial vehicle is decelerated, so that the braking resistance device can be made smaller than the conventional one.

Further, when the industrial vehicle is decelerated as described above and the actual traveling speed value of the vehicle detected by the speed detecting means becomes equal to or less than the traveling speed command value corresponding to the depression amount of the accelerator pedal, The control means switches the control valve to release (eliminate) the pilot pressure to the brake valve. As a result, the brake valve returns from the operating position to the neutral position, so that the working fluid pressure is not output to the braking device,
The industrial vehicle travels in a normal traveling state in which the brake device does not operate and the rotation of the motor is not braked (the braking force does not act).

According to the second aspect of the present invention, a proportional solenoid valve is used as the control valve, and the subtraction value obtained by subtracting the traveling speed command value from the actual traveling speed value of the vehicle is proportional to the excitation signal output to the control valve. The control valve outputs a pilot pressure proportional to the input excitation signal to the brake valve, and the brake valve outputs a working fluid pressure proportional to the input pilot pressure to the brake device. It is a thing.

According to this, since the value of the excitation signal output to the control valve increases as the subtracted value increases, the pilot pressure output from the control valve to the brake valve increases. As a result, the brake valve is switched from the neutral position to the operating position, and the brake valve outputs the working fluid pressure proportional to the input pilot pressure to the braking device, so that the braking device operates and the rotation of the motor is braked. It Since the braking force at this time is proportional to the working fluid pressure, the larger the subtracted value, the larger the braking force can be obtained.

In the third aspect of the present invention, the relationship between the depression amount of the accelerator pedal and the traveling speed command value of the vehicle is set by a plurality of speed proportional straight lines, and the relationship between the subtracted value and the excitation signal is set by a plurality of braking force proportional straight lines. A speed stage changeover switch which is set and selects a specific speed proportionality straight line from the plurality of speed proportionality straight lines is provided, and the control means specifies a specific speed proportional straight line corresponding to the specific speed proportional straight line selected by the speed stage changeover switch. The excitation signal is output to the control valve based on the braking force proportional straight line.

According to this, by selecting a specific speed proportional straight line from a plurality of speed proportional straight lines by the speed stage changeover switch, a specific braking force proportional straight line corresponding to the selected specific speed proportional straight line is obtained. Based on this, since the excitation signal is output to the control valve, the control valve is switched and the pilot pressure is output to the brake valve. By switching the speed stage changeover switch, the selected speed proportional straight line and braking force proportional straight line are changed, so that the excitation signal can be made to correspond to a wide range of subtraction values. Can correspond to a value.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. In addition, about the member of the same structure as the above-mentioned conventional member, the same code | symbol is attached and description is abbreviate | omitted.

FIG. 2 shows a hydraulic circuit of the multi-plate wet brake device 10 of the wheel loader 1. In the vehicle body 2, the hydraulic pressure (operation) is switched from the neutral position N to the operating position F according to the depression of the brake pedal 13. A brake valve 31 that outputs an example of fluid pressure) to each of the brake devices 10, and a solenoid valve 32 (control valve) that outputs a pilot pressure (hydraulic pressure) for switching the brake valve 31 to the operating position F to the brake valve 31. An example), a plurality of accumulators 33 that store hydraulic pressure and output it to the brake valve 31, and a hydraulic pump 34 that supplies hydraulic oil to the accumulator 33 and the solenoid valve 32.

The solenoid valve 32 is a proportional solenoid valve which is switched by the solenoid 32a, and outputs to the brake valve 31 a pilot pressure proportional to the voltage (or current) of the excitation signal (electric signal) input to the solenoid 32a. It is a thing. That is, when the excitation signal is input to the solenoid 32a, the solenoid valve 3
The spool No. 2 is switched from the neutral position B to the switching position B, and the pilot pressure is output to the brake valve 31.
If the excitation signal is not input to the solenoid 32a, the spool of the solenoid valve 32 returns to the neutral position B due to the biasing force of the spring, and the pilot pressure is not output to the brake valve 31.

The brake valve 31 applies hydraulic pressure proportional to the input pilot pressure to each brake device 10.
Is a proportional control valve that outputs to the brake pedal 13 and is urged by a spring 35 to return to the neutral position N.

A pipe line 36 is provided between the inlet port of the brake valve 31 and the accumulator 33, and a pipe line 37 is provided between the outlet port and each brake device 10. A pipe 38 is provided between the inlet port of the solenoid valve 32 and the hydraulic pump 34, and a pilot pressure supply pipe 39 is provided between the solenoid valve 32 and the brake valve 31.

Further, as shown in FIG. 4, the wheel loader 1 is provided with speed detecting means 41 for detecting the actual traveling speed of the wheel loader 1 based on the rotational speed of the traveling wheels 3. In addition, the actual traveling speed is determined by each traveling wheel 3
It can be obtained from the average value of the rotation speed of. Further, in the driver's cab 8, a depression amount detection means 42 for detecting the depression amount of the accelerator pedal 12 and, as shown in FIGS.
There is provided a speed stage changeover switch 43 which can be switched between the first to fourth changeover positions corresponding to the speed.

The depression amount of the accelerator pedal 12 and the traveling speed command value of the wheel loader 1 detected by the depression amount detecting means 42 are represented by a plurality of speed proportional straight lines A1 to A4 in the speed command value calculation table of FIG. As shown, they are set in a proportional relationship. That is, when the speed stage changeover switch 43 is switched to the first switching position, it is set to the speed proportional straight line A1, and when it is switched to the second switching position, it is set to the speed proportional straight line A2 and the third switching position. When it is switched to the position, it is set to the speed proportional straight line A3, and when it is switched to the fourth switching position, it is set to the speed proportional straight line A4. In the speed command value calculation table, 100% of the depression amount means that the accelerator pedal 12 is fully depressed, and 0% means that the accelerator pedal 12 is depressed.
It is in the state where it has not stepped on at all.

The subtraction value obtained by subtracting the traveling speed command value in the speed command value calculation table from the actual traveling speed of the wheel loader 1 detected by the speed detecting means 41 and the solenoid of the solenoid valve 32 from the control means 45. The voltage (or current) of the excitation signal output to 32a (see FIG. 2) is, as shown by a plurality of braking force proportional lines B1 to B4 in the braking force calculation table of FIG.
It is set in proportion. That is, when the speed stage changeover switch 43 is changed over to the first changeover position,
When the braking force proportional straight line B1 is set and the second switching position is set, the braking force proportional straight line B2 is set and the third
When switched to the switching position, the braking force proportional straight line B3
And the braking force is switched to the fourth switching position, the braking force proportional line B4 is set.

As shown in FIG. 4, the control means 45 has a storage section 46, a subtractor 47, and a speed command value calculation section 4 as shown in FIG.
8, the braking force calculation unit 49, the first and second amplifiers 5
0 and 51 are provided. The speed command value calculation table shown in FIG. 5 and the braking force calculation table shown in FIG. 6 are stored in the storage unit 46. Further, the speed command value calculation unit 48 inputs the stepping amount of the accelerator pedal 12 detected by the stepping amount detection means 42 and the switching position of the speed stage changeover switch 43, and the stored speed command value calculation table. The travel speed command value is calculated based on (see FIG. 5). In addition, the first amplifier 5
0 amplifies the traveling speed command value (electrical signal) output from the speed command value calculation unit 48 and outputs it to the subtractor 47 and the inverter device 5.

The subtractor 47 subtracts the traveling speed command value from the actual traveling speed value of the wheel loader 1 detected by the speed detecting means 41 to obtain a subtraction value (speed difference value).
Is calculated and the subtracted value is output to the braking force calculation unit 49. The braking force calculation unit 49 inputs the subtracted value and the switching position of the speed stage changeover switch 43, and calculates the voltage of the excitation signal based on the stored braking force calculation table (see FIG. 6). It is a thing. The second amplifier 5
1 is for amplifying the voltage of the excitation signal output from the braking force calculation unit 49 and outputting it to the solenoid 32a of the solenoid valve 32 (see FIG. 2).

As shown in FIG. 1, the wheel loader 1
Is provided with a braking resistance device 15. The operation of the above configuration will be described below.

When the wheel loader 1 is run, the operator switches the speed stage changeover switch 43 to select one of the first speed to the fourth speed. That is, when it is desired to make the traveling speed faster than the traveling torque, the speed stage changeover switch 43
Is switched to the fourth switching position to set the fourth speed, and when it is desired to increase the running torque more than the running speed, the first switching position is set to the first speed.

For example, when the speed stage changeover switch 43 is switched to the first changeover position as shown by the solid line in FIG. 3, the speed proportional straight line A1 in the speed command value calculation table in FIG. 5 and the braking force calculation table in FIG. And the braking force proportional straight line B1 are selected. Then, by depressing the accelerator pedal 12,
As shown in FIG. 4, the pedaling amount P of the accelerator pedal 12 detected by the pedaling amount detecting means 42 and the switching position of the speed stage changeover switch 43 are input to the speed command value calculating section 48, and the speed command value of FIG. Speed proportional line A1 in the calculation table
Based on the travel speed command value Q corresponding to the depression amount P
Is calculated, and this traveling speed command value Q is amplified by the first amplifier 50 as an electric signal and output to each inverter device 5 and the subtractor 47.

Since each inverter device 5 drives each motor 4 to rotate based on the input traveling speed command value Q, each traveling wheel 3 rotates and the wheel loader 1 travels.

The actual traveling speed value of the wheel loader 1 detected by the speed detecting means 41 and the traveling speed command value Q are input to the subtractor 47, and the traveling speed is calculated from the actual traveling speed value. Subtracted value obtained by subtracting the command value Q (=
The actual traveling speed value-traveling speed command value) is obtained, and the subtracted value and the switching position of the speed stage changeover switch 43 are input to the braking force calculation unit 49.

For example, when the wheel loader 1 is downhill, a force in the downhill direction acts in proportion to the weight of the wheel loader 1, and the rotational speed of each traveling wheel 3 gradually increases to accelerate the accelerator. The wheel loader 1 travels at a speed higher than the speed corresponding to the depression amount P of the pedal 12. As a result, the subtracted value becomes a positive value (that is, the actual traveling speed value> the traveling speed command value Q), and the braking force calculation unit 49 calculates the braking force proportional line B1 in the braking force calculation table of FIG. When the subtraction value R becomes larger than the constant value T, the voltage S of the excitation signal corresponding to the subtraction value R is calculated, the voltage S is amplified by the second amplifier 51, and the solenoid 32a of the solenoid valve 32 is calculated. Is output to. As a result, as shown in FIG. 2, the spool of the solenoid valve 32 is switched to the switching position B, and the solenoid valve 3
2 outputs a pilot pressure proportional to the voltage S of the excitation signal input to the solenoid 32a to the brake valve 31, the brake valve 31 is switched from the neutral position N to the operating position F, and the brake valve 31 is input. The hydraulic pressure proportional to the pilot pressure is output to each brake device 10. As a result, each brake device 10 is activated, and the rotation of each motor 4 is braked. Since the braking force at this time is proportional to the hydraulic pressure output to each brake device 10, the larger the subtraction value is, the larger the braking force is obtained.

Therefore, even if the operator does not step on the brake pedal 13, when the subtracted value obtained by subtracting the traveling speed command value from the actual traveling speed value becomes larger than a certain value, each braking device 10 is automatically operated. Wheel loader 1
Is reduced, it is possible to reduce the number of times the operator depresses the brake pedal 13 (the number of brake operations) when going down a slope or the like. Further, as described above, the brake device 10 automatically operates and the braking resistance device 15 (see FIG. 1).
Since the wheel loader 1 is decelerated due to the fact that the regenerative braking energy is consumed by the above (see), the braking resistance device 15 can be made smaller than the conventional one.

Further, when the wheel loader 1 is decelerated as described above and the subtracted value becomes equal to or less than the constant value T, the braking force calculation unit 49 causes the braking force proportional line B1 in the braking force calculation table of FIG. Based on the above, the voltage of the excitation signal = 0 is calculated in response to the subtraction value ≦ constant value T.
As a result, the excitation signal is not output to the solenoid 32a of the solenoid valve 32. Therefore, as shown in FIG. 2, the spool of the solenoid valve 32 returns to the neutral position B due to the biasing force of the spring, so that the pilot pressure is applied to the brake valve 31. Is not output to the brake valve 31 and the spring 3
The urging force of 5 returns to the neutral position N. As a result, the hydraulic pressure is not output from the brake valve 31 to each brake device 10, each brake device 10 does not operate, and the rotation of each motor 4 is not braked (the braking force does not act) in the normal load state. Runs.

In the above embodiment, the case where the speed stage changeover switch 43 is switched to the first changeover position as shown by the solid line in FIG. 3 has been described, but it is changed to the second changeover position as shown by the phantom line in FIG. When switched, the speed proportional straight line A2 of the speed command value calculation table of FIG. 5 and the braking force proportional straight line B2 of the braking force calculation table of FIG. 6 are selected, and when switched to the third switching position, the speed command value calculation table Speed proportional straight line A3
And the braking force proportional straight line B3 of the braking force calculation table are selected and switched to the fourth switching position, the speed proportional straight line A4 of the speed command value calculation table and the braking force proportional straight line B4 of the braking force calculation table are selected. , And similar control is performed.

Further, as described above, by switching the speed stage changeover switch 43, the speed proportional straight line and the braking force proportional straight line to be selected are changed, so that as shown in the braking force calculation table of FIG. The voltage of the excitation signal can be made to correspond to the subtracted value, so that the braking force can be made to correspond to a wide range of subtracted values.

When the operator depresses the brake pedal 13, the brake valve 31 is switched from the neutral position N to the operating position F in association with the brake pedal 13, and the brake valve 31 is braked, as shown in FIG. The hydraulic pressure proportional to the depression amount of the pedal 13 is output to each brake device 10. As a result, each brake device 10 is activated, and the rotation of each motor 4 is braked. Since the braking force at this time is proportional to the hydraulic pressure output to each brake device 10, the larger the depression amount of the brake pedal 13, the larger the braking force is obtained.

In the above-described embodiment, as shown in FIG. 3, the speed stage changeover switch 43 can switch to four speed stages of 1st to 4th speeds, and in response to this, the speed command value calculation of FIG. 5 is performed. Although four speed proportional straight lines A1 to A4 are set in the table and four braking force proportional straight lines B1 to B4 are set in the braking force calculation table of FIG. 6, a plurality of speeds other than the first speed to the fourth speed are set. A single speed stage may be provided without providing the speed stage changeover switch 43.
In this case, the speed proportional straight line and the braking force proportional straight line are set in correspondence with the number of speed stages.

In the above embodiment, in the braking force calculation table of FIG. 6, each of the braking force proportional lines B1 to B4 has a constant subtraction value greater than 0 as a starting point, but the subtraction value = 0. It may be the starting point.

In the above-described embodiment, the wheel loader 1 is mentioned as an example of the industrial vehicle, but the invention is not limited to the wheel loader 1, and a forklift or the like may be used.

In the above-described embodiment, the four vehicle wheels 3 are provided on the vehicle body 2, but a plurality of wheels other than the four wheels may be provided.

[0044]

As described above, according to the first aspect of the present invention, the actual traveling speed value of the vehicle detected by the speed detecting means corresponds to the depression amount of the accelerator pedal even if the operator does not step on the brake pedal. When the traveling speed becomes larger than the command value, the braking device automatically operates to decelerate the industrial vehicle. Therefore, it is possible to reduce the number of times the operator depresses the brake pedal (the number of braking operations) when going downhill. it can.

When the braking resistance device is provided, both when the braking device is automatically operated as described above and when the braking resistance device consumes the regenerative braking energy at the time of a downhill or the like. Therefore, the industrial vehicle is decelerated, so that the braking resistance device can be made smaller than the conventional one.

According to the second aspect of the present invention, the value of the excitation signal output to the control valve increases as the subtracted value increases, so the pilot pressure output from the control valve to the brake valve increases. As a result, the brake valve is switched from the neutral position to the operating position, and the brake valve outputs the working fluid pressure proportional to the input pilot pressure to the braking device, so that the braking device operates and the rotation of the motor is braked. It Since the braking force at this time is proportional to the working fluid pressure, the larger the subtracted value,
A large braking force can be obtained.

Further, according to the third aspect of the invention, since the speed proportional straight line and the braking force proportional straight line that are selected are changed by switching the speed stage changeover switch, the excitation signal is made to correspond to a wide range of subtracted values. Therefore, the braking force can correspond to a wide range of subtracted values.

[Brief description of drawings]

FIG. 1 is a block diagram of a control system of a wheel loader according to an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of the brake device of the wheel loader.

FIG. 3 is a diagram of a speed changeover switch of the wheel loader.

FIG. 4 is a block diagram of control means of the wheel loader.

FIG. 5 is a diagram of a speed command value calculation table stored in the control means of the wheel loader.

FIG. 6 is a diagram of a braking force calculation table stored in the control means of the wheel loader.

FIG. 7 is a side view of a conventional wheel loader.

FIG. 8 is a block diagram of a control system of the wheel loader.

[Explanation of symbols]

1 Wheel loader (industrial vehicle) 2 vehicle body 3 traveling wheels 4 motor 10 Brake device 12 accelerator pedal 13 Brake pedal 31 brake valve 32 Solenoid valve (control valve) 41 Speed detection means 43 Speed switch 45 Control means A1-A4 speed proportional straight line B1-B4 Braking force proportional line N neutral position F working position

Continued front page    (72) Inventor Masami Higaki             1-15-10 Kyomachibori, Nishi-ku, Osaka City, Osaka Prefecture             TCM Co., Ltd. F term (reference) 3D046 AA06 AA09 BB17 BB26 CC02                       EE01 HH05 HH23 HH36 JJ05                       LL01 LL23                 5H115 PA08 PA15 PG04 PI16 PU01                       PU21 PU26 PV09 QE06 QE10                       QI04 QI07 QI12 SE10 TB01                       TO23

Claims (3)

[Claims] 1. A motor for rotationally driving traveling wheels,
An industrial vehicle including an accelerator pedal that adjusts the rotation speed of the motor, a brake device that operates by working fluid pressure to brake the rotation of the motor, and a brake pedal that operates the brake device, In the vehicle body, a brake valve that switches from a neutral position to an operating position in response to the depression of the brake pedal to output the working fluid pressure to a brake device, and a pilot pressure for switching the brake valve to the operating position. A control valve for outputting to the vehicle is provided, the vehicle traveling speed command value is set in proportion to the depression amount of the accelerator pedal, and the actual traveling velocity value of the vehicle detected by the speed detecting means is the depression amount of the accelerator pedal. If the traveling speed command value corresponding to is larger than the above, the control valve is switched and the pilot pressure is output to the brake valve. And industrial vehicles in which the actual traveling speed value, characterized in that the case of less than the running speed command value, the control means for releasing the pilot pressure to the brake valve is switched to the control valve is provided. 2. A proportional solenoid valve is used as a control valve, and a subtraction value obtained by subtracting a traveling speed command value from an actual traveling speed value of a vehicle and an excitation signal output to the control valve are set in a proportional relationship. The control valve outputs a pilot pressure proportional to the input excitation signal to the brake valve, and the brake valve outputs a working fluid pressure proportional to the input pilot pressure to the brake device. The industrial vehicle according to claim 1. 3. The relationship between the depression amount of the accelerator pedal and the traveling speed command value of the vehicle is set by a plurality of speed proportional straight lines, and the relationship between the subtraction value and the excitation signal is set by a plurality of braking force proportional straight lines. A speed stage changeover switch for selecting a specific speed proportional line out of a plurality of speed proportional lines is provided, and the control means has a specific braking force proportional corresponding to the specific speed proportional line selected by the speed stage changeover switch. The industrial vehicle according to claim 2, wherein an excitation signal is output to the control valve based on the straight line.