JP2003182548A - Brake device for reach forklift - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake device for a reach forklift capable of braking stably. <P>SOLUTION: The pressure of pressure oil from a hydraulic source 1 is adjusted to set pressure set in advance by a pressure adjusting means 2 to supply it to left and right front wheel brakes 4 by a brake valve 3 as brake pressure. The brake valve 3 is operated halfway in a return stroke of a brake pedal which releases a rear wheel brake at an utmost step-in position and brakes in accordance with the return stroke from the utmost step-in position. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake device for a reach truck.

[0002]

2. Description of the Related Art Generally, a brake device for a reach forklift is equipped with a deadman type brake that brakes the rear wheels, which are driving wheels, when the brake pedal is stepped on, and brakes as the brake pedal is released. . Since this brake device is a deadman brake for only the rear wheels, there is a limit to the maximum braking force set by a spring or the like.

Japanese Patent Application Laid-Open No. 2000-151494 proposes an additional front wheel brake device for applying a braking force to the left and right front wheels as well, in order to make up for the conventional lack of braking force.

According to this proposal, the rear wheel brake device is operated during braking, and when slip or lock is detected on the rear wheel being braked by the slip detecting means,
It is configured to operate the braking device for the left and right front wheels.

[0005]

However, in this proposal, since the front wheels are also braked from the time when the slip of the rear wheels or the occurrence of the lock is detected, the slip is irrelevant regardless of the intention of the operator. The braking force may change depending on the occurrence or non-occurrence.

Moreover, the braking force of the front wheels is added to the braking force of only the rear wheels until slipping or locking occurs, and the overall braking force increases stepwise, which may cause an uncomfortable feeling in the vehicle behavior.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a brake device for a reach forklift that can obtain a stable vehicle behavior.

[0008]

According to a first aspect of the present invention, a front wheel brake that brakes left and right front wheels disposed on the front end side of a straddle arm respectively according to a supplied brake pressure, and a rear wheel brake that brakes a rear wheel, A hydraulic pressure source that generates pressure oil, a pressure adjusting means that adjusts the pressure oil from the hydraulic pressure source to a preset pressure setting, a brake valve that supplies the pressure oil from the pressure adjusting means to the front wheel brakes, and the most stepping A brake pedal for releasing the braking of the rear wheel brake at the position and increasing the braking force according to the return stroke from the most depressed position, and a control means for operating the brake valve from the middle of the return stroke of the brake pedal. Is characterized by.

Even if the brake pedal is in the middle of the return stroke, even if it is near the most depressed position of the brake pedal,
It may be near the center of the pedal stroke or at another position.

In a second aspect based on the first aspect, the control means starts the operation of the brake valve at any point in the return stroke excluding the return start and the return end of the brake pedal. And

In a third aspect based on the first aspect, the brake valve is composed of a pressure control valve capable of regulating the brake pressure by controlling the pressure oil of the pressure regulating means to reduce the pressure, and the front wheel has:
Front wheel slip detection means for detecting the slip is arranged, and when the slip signal from the front wheel slip detection means is input, the control means reduces the pressure oil of the pressure adjusting means by the brake valve so as to cancel the slip. It is characterized by outputting a controlled brake pressure.

In a fourth aspect based on the first aspect, the brake valve is constituted by a pressure control valve capable of regulating the brake pressure by controlling the pressure oil of the pressure regulating means to reduce the pressure, and the control means comprises: The feature is that the brake pressure output from the brake valve is increased or decreased according to the return stroke of the brake pedal.

The stroke range in which the brake pressure is increased / decreased in accordance with the return stroke of the brake pedal may be increased / decreased in the entire stroke area as necessary or may be an appropriately set section. The brake pressure is raised from a slightly returned position and linearly increased so that the pressure of the pressure adjusting means is reached at a position about half the pedal stroke. The present invention is not limited to this, and may be set freely as vehicle tuning.

In a fifth aspect based on the first aspect, the brake valve is a pressure control valve capable of regulating the brake pressure by controlling the pressure oil of the pressure regulating means to reduce the pressure, and the front wheel has: Slip detection means for detecting the slip is arranged, and the control means increases or decreases the brake pressure output from the brake valve according to the return stroke of the brake pedal when the slip signal is not input from the slip detection means, When a slip signal is input from the slip detecting means, the brake pressure output from the brake valve is further reduced so that the slip is eliminated, and the brake pressure is increased or decreased according to the return stroke of the brake pedal.

In a sixth aspect based on the first aspect, the pressure adjusting means stores an accumulator for accumulating pressure oil having a pressure within a preset range, and a pressure of the pressure oil accumulated in the accumulator is preset. It is characterized by comprising selector means for opening the valve to introduce pressure oil from a hydraulic pressure source when the pressure drops below the pressure.

The pressure adjusting means may be provided with a regulator valve which opens when the pressure of the pressure oil accumulated in the accumulator exceeds a preset pressure so as to keep the pressure of the pressure oil below the preset pressure. .

In a seventh aspect based on the sixth aspect, the selector means includes pressure detecting means for detecting that the pressure of the pressure oil accumulated in the accumulator has dropped below a preset introduction pressure, and the pressure detecting means. And a solenoid valve that is switched from the shut-off position to the open position according to the output signal from the detection means.

In an eighth aspect based on the first to seventh aspects, the hydraulic power source includes a pump driven by a motor independently of a cargo handling pump for supplying pressure oil to the cargo handling device, and selector means. Is characterized in that the motor is driven by a signal from a pressure detecting means for detecting that the pressure of the pressure oil accumulated in the accumulator has dropped below a preset introduction pressure.

A ninth invention is characterized in that, in the first to seventh inventions, the hydraulic pressure source is a bottom pressure generated in a bottom chamber of a lift cylinder of the cargo handling apparatus.

In a tenth aspect based on the first to seventh aspects, a flow rate limiting means for limiting the flow rate supplied to the accumulator is arranged in the pressure adjusting means or between the hydraulic pressure source and the pressure adjusting means. It is characterized by being.

The flow rate limiting means can be constituted by an orifice or the like, and the size thereof may be the minimum required amount because the required oil amount of the brake device is very small.

An eleventh invention is characterized in that, in the first to seventh inventions, the pressure adjusting means has a backflow preventing means arranged in a passage to a hydraulic pressure source.

The backflow preventing means can be constituted by a check valve which allows the flow in one direction.

[0024]

Therefore, according to the first aspect of the invention, the control means operates the brake valve from the middle of the return stroke of the brake pedal to supply the pressure oil adjusted to the set pressure as the brake pressure to the front wheel brakes. The front wheels can be braked over the entire return stroke of the brake pedal, the vehicle can be efficiently braked, and the stop distance can be shortened. Moreover, the returning operation of the brake pedal is based on the operator's intention of braking, so that there is no sense of discomfort when the front wheel brake is braked.

Since the pressure oil adjusted to a preset pressure is supplied to the front wheel brake as the brake pressure, it is necessary for the front wheel brake as compared with the case where the pressure generated by pedal depression is supplied as the brake pressure. The above hydraulic pressure does not act, and the optimum strength design of the front wheel brake system can be easily performed without increasing the cost.

Since the front and rear wheels are braked, the braking force distribution to the rear wheels can be reduced, the spring force for setting the braking force can be reduced, and the pedal effort of the brake pedal can be lightened to improve the pedal operability. . The operability of the pedal can be improved by changing the link ratio between the pedal and the rear wheel brake to reduce the stroke of the pedal.

When the brake distribution to the rear wheels is reduced, there is also an effect that the rear wheels are less likely to slip. In that case, since the brake distribution to the front wheel brakes is increased, the braking force of the entire vehicle can be increased rather than the braking force of the entire vehicle.

According to the second invention, in addition to the effect of the first invention, the operation of the brake valve is started at any point in the return stroke excluding the return start and the return end of the pedal return stroke. Therefore, there is no sudden rise of the braking force that occurs when the operation start point is set at the beginning of the brake pedal return, and the braking force of the front wheels rises with the brake pedal being returned to some extent and the braking force acting on the rear wheels. It is possible to prevent the entire braking force from changing significantly.

In addition to the effects of the first aspect of the invention, the third aspect of the invention supplies the pressure oil regulated by the pressure regulating means to the front wheel brakes as brake pressure, and when the slip state of the front wheels is detected. Since the brake pressure is controlled by the brake valve so as to eliminate the slip and the supplied brake pressure is reduced, the slip of the front wheels that occurs when the friction coefficient of the road surface is small can be effectively prevented, and the behavior of the vehicle can be stabilized.

Since the maximum braking force is limited by the frictional force on the road surface, even if the hydraulic pressure of the front wheel brake is reduced regardless of the operator's will, the braking force obtained on the vehicle is reduced. The operator does not feel uncomfortable.

In the fourth invention, in addition to the effect of the first invention, the brake pressure output from the brake valve is increased / decreased according to the return stroke of the brake pedal. Therefore, the braking force is interlocked with the return operation of the brake pedal. Therefore, the adjustment of the vehicle braking force by the return operation of the brake pedal is easy because it matches the operation feeling of the operator.

In addition to the effect of the first invention, the fifth invention increases or decreases the brake pressure output from the brake valve according to the return stroke of the brake pedal when no slip signal is input from the slip detecting means. When a slip signal is input from the slip detection means, the brake pressure output from the brake valve is controlled so as to cancel the slip and the brake pressure is increased or decreased according to the return stroke of the brake pedal. The adjustment of the braking force can be made to match the operation feeling of the operator, and further, the slip of the front wheels can be effectively suppressed by the brake pressure that is controlled to be reduced, and the vehicle behavior can be stabilized.

In the sixth invention, in addition to the effect of the first invention, an accumulator for accumulating the pressure oil having a pressure within a preset range and a pressure of the pressure oil accumulated in the accumulator are preset. Since it is configured with selector means for opening the valve to introduce pressure oil from the hydraulic source when the pressure drops below the introduced pressure, each component is composed of a simple spring and spool or piston, and has a simple structure. An inexpensive and highly reliable pressure adjusting means can be provided. Further, since there is no electric control part and a pressure sensor is not necessary, a highly reliable pressure adjusting means can be obtained in this respect as well.

Further, if a regulator valve is added to open the valve when the pressure of the pressure oil accumulated in the accumulator exceeds a preset pressure and keep the pressure of the pressure oil below the preset pressure, the selector means is opened. Even when a failure occurs in which the valve does not close as it is, the upper limit of the pressure of the accumulator can be regulated, high pressure oil can be prevented from being accumulated and supplied to the front wheel brakes, and an effect of protecting them can be obtained.

In the seventh invention, the selector means is a pressure detecting means for detecting that the pressure of the pressure oil accumulated in the accumulator has dropped below a preset introduction pressure,
Since the electromagnetic valve is configured to be switched from the shut-off position to the open position in accordance with the output signal from the pressure detecting means, it is possible to obtain the highly reliable pressure adjusting means similar to the sixth invention.

In the eighth invention, in addition to the effects of the first to seventh inventions, the hydraulic power source is a pump driven by a motor independently of a cargo handling pump for supplying pressure oil to the cargo handling device. Since the selector means drives the motor when the pressure of the pressure oil accumulated in the accumulator falls below a preset introduction pressure, a dedicated pump is driven when the pressure of the accumulator falls regardless of the presence or absence of cargo handling work. It is possible to accumulate pressure. That is, when the pressure oil is supplied from the cargo handling pump, it is limited to the cargo handling work in which the pump is driven, and when the pressure is accumulated in the accumulator when the pump is not working, the cargo handling pump is driven. There was an effect on the system.

In the ninth invention, in addition to the effects of the first to seventh inventions, since the hydraulic pressure source is the bottom pressure generated in the bottom chamber of the lift cylinder of the cargo handling device, a dedicated hydraulic pressure for braking is used. It does not require a source and can be constructed inexpensively.

As for the bottom pressure, the hydraulic pressure surely exists in the loaded state, and the pressure corresponding to the own weight of the carriage, the fork and the like is generated even in the empty state without loading, and a certain level of pressure can be secured. Moreover, as compared with the case of taking in from the cargo-handling pump, the probability of obtaining the necessary hydraulic pressure is high even when the cargo-handling work is not in progress, and the energy efficiency is good.

In the tenth invention, in addition to the effects of the first to seventh inventions, a flow rate for limiting the flow rate supplied to the accumulator in the pressure adjusting means or between the hydraulic pressure source and the pressure adjusting means. Since the restricting means is provided, even if the selector valve or the like fails in the open state, the sudden outflow of the pressure oil can be restricted and the adverse effect on the cargo handling system can be minimized or eliminated.

Further, since the rapid inflow of the pressure oil into the accumulator is restricted, it is possible to prevent the pressure adjusting means from being damaged. Note that the amount of oil required for the brake is very small, and even if a means such as an orifice is interposed, it will not cause any effect.

In the eleventh invention, in addition to the effects of the first to seventh inventions, in the pressure adjusting means, the backflow preventing means is arranged in the passage to the hydraulic pressure source, so that the accumulated pressure of the accumulator is increased. When the pressure drops and the selector opens, the backflow that occurs when the pressure of the hydraulic source is also low can be prevented.

[0042]

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

FIG. 1 shows an example of a reach forklift braking device to which the present invention is applied. A hydraulic pressure source 1, a pressure regulating means 2 for regulating pressure oil from the hydraulic pressure source 1 to a prescribed pressure, and a pressure regulating means 2 are shown. Brake valve 3 that outputs the pressure oil of
A front wheel brake 4 which is operated by the brake pressure from the brake valve 3, a rear wheel brake 6 whose braking is released by stepping on the brake pedal 5, and a brake switch 7 which outputs a brake signal depending on the stepped position of the brake pedal 5. Equipped with.

The hydraulic power source 1 includes a reservoir tank 10 and
Pump 12 for cargo handling driven by electric motor 11
And a cargo handling control valve 13 to which the working hydraulic pressure discharged by the pump 12 is supplied, and a passage 15 for supplying the hydraulic pressure between the cargo handling control valve 13 and the cargo handling device 14 to the pressure adjusting means 2. . In the illustrated hydraulic power source 1, the cargo handling device 14
As a result, the bottom pressure of the bottom chamber 14B of the lift cylinder 14A is guided to the pressure adjusting means 2 via the supply passage 15.

The brake pedal 5 is arranged on the floor of the driver's seat and is connected to the rear wheel brake 6 via a master cylinder 16, a brake pipe 17, and a brake cylinder 18. The rear wheel brake 6 includes a brake disc 6A provided on a drive motor for a drive wheel (not shown) and a brake pad 6
Braking is performed by pressing B. The brake cylinder 18 is constantly urged toward the brake operating side by the spring 19, and the hydraulic pressure generated from the master cylinder 16 when the brake pedal 5 is stepped on the floor urges the brake cylinder 18 in the direction opposite to the brake operating direction. . Therefore, when the depression of the brake pedal 5 is released, the rear wheel brake 6 is activated, and by depressing the brake pedal 5, the operation state of the rear wheel brake 6 is released. The brake switch 7 is closed at a position where the brake pedal 5 starts to return from the most depressed position where the brake pedal 5 comes into contact with the floor, and a control circuit 8 as a control means for the brake valve 3 outputs a brake signal.
Output to.

The front wheel brakes 4 are respectively arranged on a pair of front wheels provided on the front end side of a pair of reach legs at a front portion (not shown) of the reach forklift. The pair of front wheel brakes 4 actuate the brake cylinders 4A in accordance with the brake pressure supplied from the brake valve 3 to brake the front wheels respectively.

As shown in FIG. 2, the pressure adjusting means 2 includes an accumulator 20, a regulator valve 21 for setting an upper limit value of the pressure of the accumulator 20, and pressure oil from the hydraulic pressure source 1 when the pressure of the accumulator 20 decreases. And a selector valve 22 as a selector means to be introduced.

The brake valve 3 is an electromagnetic valve which is operated by the control circuit 8 and receives the supply of pressure oil from the accumulator 20 of the pressure adjusting means 2 to control the brake oil pressure to the front wheel brake 4.

The pressure of the accumulator 20 of the pressure regulating means 2 is regulated between the maximum pressure PT (max) at the most contracted position of the accumulator 20 and the minimum pressure PT (min) at the most extended position of the accumulator 20. .
The minimum pressure PT (min) is the maximum pressure PT (m
It is set close to ax) and suppresses the pressure fluctuation of the accumulator 20. The accumulator 20 appropriately accumulates pressure oil from the hydraulic pressure source 1 introduced from the selector valve 22 by the accumulator 20. The amount of hydraulic oil stored is sufficient to fill the front wheel brake 4 in several operations.

The regulator valve 21 is a valve that opens when the preset relief pressure is slightly higher than the maximum pressure PT (max) of the accumulator 20. The regulator valve 21 is closed when the pressure of the accumulator 20 does not reach the relief pressure, and is opened when the pressure of the accumulator 20 exceeds the relief pressure to transfer the pressure oil of the accumulator 20 to the reservoir tank 10 via the drain passage 23. Relief limits the rise in pressure in the accumulator 20.

The selector valve 22 is a valve which opens slightly below the maximum pressure PT (max) of the accumulator 20 and below a preset selector pressure. The selector valve 22 is closed when the pressure of the accumulator 20 exceeds the selector pressure, and opened when the pressure of the accumulator 20 drops below the selector pressure to introduce the pressure oil of the hydraulic source 1 into the accumulator 20. Accumulator 2
The pressure of 0 is increased to exceed the selector pressure.

A check valve 24 is arranged downstream of the selector valve 22 to prevent the pressure of the accumulator 20 from flowing back to the hydraulic pressure source 1. When the hydraulic pressure of the hydraulic pressure source 1 is lower than the pressure of the accumulator 20 when the selector valve 22 is opened, the check valve 24 prevents the pressure oil of the accumulator 20 from flowing back to the hydraulic pressure source 1 side and lowering the pressure of the accumulator 20. To prevent.

An orifice 25 for restricting the flow rate of passage is arranged upstream of the selector valve 22. The orifice 25 limits the flow rate of the hydraulic oil introduced from the hydraulic pressure source 1 to the accumulator 20, and limits the outflow rate of the pressure oil supplied to the cargo handling apparatus 14 to ensure the operation of the cargo handling apparatus 14. The flow rate of pressure oil consumed by the front wheel brake 4 is a small flow rate consumed by the expansion and contraction of the wheel cylinder 4A of the front wheel brake 4, and even if the orifice 25 is inserted, the pressure adjusting means 2, the brake valve 3, and the front wheel brake. It does not affect the operation of No. 4.

The brake valve 3 includes a brake port 26 communicating with the front wheel brake 4, a pressure oil port 27 communicating with the accumulator 20, and a drain port 28 communicating with the reservoir tank 10. The spool 29 is located at a shut-off position 29B that shuts off the pressure oil port 27 and allows the brake port 26 and the drain port 28 to communicate with each other when the solenoid 30 is not operating and is not operating. This blocking position 29
In B, no brake pressure is generated in the front wheel brake 4.
When the solenoid 30 operates, the spool 2
9 is located at a brake position 29A that blocks the drain port 28 and connects the pressure oil port 27 and the brake port 26. At the brake position 29A, the pressure oil of the accumulator 30 is introduced into the front wheel brake 4 to operate the brake cylinder 4A of the front wheel brake 4 to generate a braking force on the front wheel. The solenoid 30 is operated by the control circuit 8 in conjunction with the brake signal from the pedal switch 7.

The operation of the brake device for the reach forklift having the above structure will be described.

The main switch (not shown) of the forklift is off and the brake pedal 5 is not depressed. Before starting, the pump 12 is stopped, the cargo handling control valve 13 is in the neutral state, and the cargo handling device 14 is operated by the pump 1
2 and the shut-off state in which the reservoir 10 is not communicated. In the bottom chamber 14B of the lift cylinder 14 of the cargo handling apparatus 14, the cargo handling apparatus 1 acting on the lift cylinder 14
Bottom pressure is generated to support the own weight of 4 and the load. The bottom pressure is the orifice 25 of the pressure adjusting means 2,
It is supplied to the accumulator 20 via the selector valve 22 and the check valve 24, and the accumulator 20 is kept in a pressure accumulation state. Brake valve 3 solenoid 3
Since 0 is the main switch off, the spool 29 is in the non-excitation state regardless of the depression state of the brake pedal 5, and the spool 29 is located at the cutoff position 29B. Therefore, the brake pressure of the brake cylinder 4A is discharged to the reservoir tank 10, and the front wheel brake 4 is held in the inoperative state. The rear wheel brake 6 is in the brake operating state by the spring 19 because the brake pedal 5 is not depressed. The pedal switch 7 is in the ON state,
No brake signal is output because the main switch is off.

Then, when the main switch is turned on, the brake signal is output because the pedal switch 7 of the brake pedal 5 is in the on state, and the solenoid 30 of the brake valve 3 is excited. The brake valve 3 has a brake position 29A.
Then, the pressure oil of the accumulator 20 is supplied to the brake cylinder 4A to operate the front wheel brake 4. The vehicle is in a state in which the front and rear wheel brakes 4, 6 are activated.
The brake pressure supplied to the front wheel brake 4 is the pressure accumulated in the accumulator 20. Since the pressure of the accumulator 20 is maintained at the pressure value between the relief pressure of the regulator valve 21 and the select pressure of the select valve 22, the brake pressure to the front wheel brake 4 is also the same pressure.

When the loading lever is operated, the motor 11
Is started, the pump 12 discharges pressure oil, and the cargo handling control valve 1
Supply to 3.

When the brake pedal 5 is depressed to the most stepped position where it comes into contact with the floor in order to drive the forklift, the master cylinder 16, the brake pipe 17, and the brake cylinder 18 are operated to oppose the spring 19 and the rear wheel brakes. Release 6. The brake switch 7 stops outputting the brake signal, and the solenoid 3 of the brake valve 3
0 becomes the non-excitation state, and the spool 29 is in the cutoff position 29B.
Move to. The pressure oil port 27 is closed, and the brake port 26 and the drain port 28 communicate with each other to drain the pressure oil of the brake cylinder 4A to the reservoir tank 10 to reduce the brake pressure and release the operation of the front wheel brake 4.
The vehicle can be driven by driving the rear wheels with a drive motor.

In order to reduce the traveling speed, the brake pedal 5 is slightly returned from the most depressed position. When the brake pedal 5 is returned from the most depressed position, the rear wheel brake 6
The brake cylinder 18 is returned from the extended position by the spring 19, and the rear wheel brake 6 brakes the rear wheel in proportion to the return amount of the brake pedal 5. Further, a brake signal is output from the brake switch 7, the solenoid 30 of the brake valve 3 is excited, and the spool 29 moves to the brake position 2.
9A, the brake port 26 and the pressure oil port 27
Communicate with. The pressure oil of the accumulator 20 of the pressure adjusting means 2 is supplied to the brake cylinder 4A as the brake pressure, and the front wheel brake 4 brakes the front wheels according to the brake pressure.

FIG. 3 shows the relationship between the pedal stroke of the brake pedal 5 and the brake pressure. As shown by the solid line, the brake signal is not output until the stroke S at which the brake pedal 5 starts to work, and the brake is not applied. No pressure is generated. When the stroke S at which the braking action starts exceeds the stroke S, as shown by the line A, the brake pressure is applied to the front wheel brake 4, and the front wheel brake 4 is braked. As shown by a dotted line B, the front wheel may be braked by issuing a brake signal when the brake signal generation stroke position is returned by more than half of the brake pedal 5. When the front wheel brake 4 is activated, the front wheel brake 4 and the rear wheel brake 6
Since the vehicle is braked by and, the traveling speed can be quickly reduced. When the desired traveling speed is reached, the front and rear brakes 4, 6 are released by depressing the brake pedal 5 to the most depressed position.

To stop the vehicle, if the brake pedal 5 is continuously depressed, the vehicle is braked by the braking force of the front wheel brake 4 and the increasing braking force of the rear wheel brake 6. The stopping distance of the vehicle can be greatly shortened compared to the conventional case in which the braking force is applied only to the rear wheels.

FIG. 4 shows the pedal return stroke and the front wheels when the brake pedal 5 is returned from the most depressed position.
5 is a graph showing the concept of changes in the braking force generated on the rear wheels and the total braking force generated on the vehicle. It should be noted that the braking force does not increase linearly in proportion to the pedal stroke, but since the essence does not change, a linear proportional relationship is shown in order to facilitate understanding of the concept of the change.

When the brake pedal 5 is returned from the most depressed position, no braking force is generated on the front wheels and the rear wheels during the strokes up to the stroke S at which the brake pedal 5 starts to work. When the stroke S at which the braking starts is passed and a braking signal is generated and the braking force of the front wheels rises to a constant value, the braking force of the rear wheels also rises. Line C shows the braking force of the rear wheels and increases in proportion to the pedal stroke. Line D represents the braking force of the front wheels, which is a constant braking force that does not change according to the pedal stroke. The line E shows the total braking force of the front and rear wheels, which increases in parallel with the line C according to the stroke. In this example, since the front wheel braking force is generated in the entire pedal stroke, the stopping distance of the vehicle can be shortened. The change in the braking force indicated by the dotted line indicates the braking force according to the conventional technique that applies the braking force to the front wheels in response to the rear wheel slip.

The pressure of the accumulator 20 that produces the brake pressure decreases due to leakage from the accumulator 20 and consumption of the brake pressure. This pressure drop is restored to the set pressure value by opening the select valve 22 and introducing the pressure oil from the hydraulic pressure source 1. In the case where pressure oil is not supplied from the hydraulic pressure source 1 even if the select valve 22 is opened,
The state where the select valve 22 is opened is maintained, and it waits until the pressure of the hydraulic oil of the hydraulic power source 1 exceeds the pressure of the accumulator 20. When the brake valve 3 is operated at the time when the pressure of the accumulator 20 is decreasing, the similarly decreased brake pressure is supplied to the front wheel brakes 4 and the braking force to the front wheels is also reduced. Since the hydraulic pressure source 1 of this example is the bottom pressure of the lift cylinder 14, it corresponds to the loading load. When the hydraulic pressure of the hydraulic pressure source 1 is low, it means that the loading load is small or not, and a high braking force is required. In this case, insufficient braking force does not cause a problem. When the load is loaded, the bottom pressure rises and is accumulated in the accumulator 20 of the pressure adjusting means 2 via the select valve 22. Accumulator 20
When the pressure rises, the selector valve 22 is closed. Since the pressure oil is supplied to the pressure adjusting means 2 in a short time, it does not affect the cargo handling operation.

In the above-described operation, the braking force acting on the front wheels is a constant braking force set by the pressure value of the accumulator 20 whose brake pressure is adjusted by the pressure adjusting means 2. can do. Since a constant brake pressure acts, it is easier to design the optimum strength of the four front wheel brake systems as compared with a brake that generates brake pressure by the pedal effort. By the stable braking force of the front wheels, the braking force shared by the rear wheel brakes 6 can be reduced, and the spring force of the spring 19 that sets the braking force of the rear wheel brakes 6 can be changed to a smaller one. The operability of the brake pedal 5 can be improved by reducing the depression force or the depression stroke of the brake pedal 5.

Further, the braking force distribution of the front and rear wheels is set so as to reduce the sharing of the braking force of the rear wheels while increasing the total braking force generated in the vehicle as compared with the conventional vehicle having only the rear wheel brakes 6. It is also possible to prevent the rear wheels from slipping.

In the above description, the brake signal generation timing by the brake switch 7 is set near the rising point of the braking force of the rear wheel brake 6, but when the pedal 5 starts to be returned from the most depressed position. Then, the braking force of the front wheels will increase stepwise,
The operability is not very good. For example, when the friction coefficient of the road surface is extremely low and the ground load of the front wheels is small, the front wheels may be locked. Therefore, when the pedal 5 is returned to some extent, a brake signal is generated,
A braking force may be applied to the front wheels to prevent the front wheels from being locked. In this case, since the pedal 5 is returned to some extent, the braking force of the entire vehicle is controlled by the returning position of the pedal 5, so that the above-mentioned front wheel lock or the like can be avoided. For this purpose, the brake switch 7 is adjusted so that the brake signal is output at a stroke position of about 10% or more of the stroke, excluding the start of returning the pedal stroke. Desirably, the position of the brake switch 7 is adjusted and attached so that it is near the center of the stroke.

FIG. 5 shows a modification of the select valve of the pressure adjusting means 2. The select valve 22 shown in FIG. 2 directly introduces the pressure downstream of the check valve 24 as an operating element, but the select valve 31 shown in FIG. 5 has a normally closed shut-off position 32B and an opening that switches when the solenoid 33 is activated. Position 3
2A and the electromagnetic opening / closing valve 32. The pressure of the accumulator 20 downstream of the check valve 24 is detected by the pressure sensor 34. Pressure sensor 34
Energizes the solenoid 33 when the pressure of the accumulator 20 drops below the select pressure,
When the pressure of 0 is equal to or higher than the select pressure, the solenoid 33 is deenergized. The electromagnetic on-off valve 32 is in the shut-off position 32B when the solenoid 33 is not excited, and is switched to the open position 32A when the solenoid 33 is excited. Therefore, when the pressure of the accumulator 20 of the pressure regulating means 2 drops below the select pressure, the pressure oil of the hydraulic source 1 is introduced into the accumulator 20, and when the pressure exceeds the select pressure, the hydraulic source 1 and the accumulator 20 are shut off. To do.

In the present embodiment, the effects described below can be obtained. That is, the control circuit 8 as the control means actuates the brake valve 3 from the middle of the returning stroke of the brake pedal 5 to supply the pressure oil of the pressure adjusting means 2 adjusted to the set pressure to the front wheel brake 4 as the brake pressure. Therefore, the front wheels can be braked over the entire return stroke of the brake pedal 5, the vehicle can be efficiently braked, and the stop distance can be shortened. In addition, the returning operation of the brake pedal 5 is based on the operator's intention to brake, and there is no sense of discomfort when the front wheel brake 4 is braked.

Since the front wheel brake 4 is supplied with the pressure oil of the pressure adjusting means 2 adjusted to a preset set pressure as the brake pressure, compared with the case where the pressure generated by pedaling is supplied as the brake pressure. As a result, an excessive hydraulic pressure does not act on the front wheel brake 4, and the optimum strength design of the system of the front wheel brake 4 can be easily performed without increasing the cost.

Since the front and rear wheels are braked, the braking force distribution to the rear wheels can be reduced, the spring force that sets the braking force can be reduced, and the pedal effort of the brake pedal 5 can be lightened to improve pedal operability. it can. The operability of the pedal 5 can be improved by changing the link ratio between the pedal 5 and the rear wheel brake 6 to reduce the stroke of the pedal 5.

When the brake distribution to the rear wheels is reduced, the rear wheels are less likely to slip. In that case, since the brake distribution to the front wheel brakes 4 is increased, the braking force of the entire vehicle can be increased rather than the braking force of the entire vehicle.

Since the operation of the brake valve 3 is started at any point in the return stroke except the start and end of the return stroke of the pedal 5, the operation start point is set at the start of the return of the brake pedal 5. There is no sudden rise in the braking force that occurs when the braking force is applied to the front wheels, and the braking force is applied to the rear wheels to some extent to prevent the braking force from rising significantly, and the overall braking force does not fluctuate significantly. it can.

The pressure adjusting means 2 is opened when the accumulator 20 for accumulating the pressure oil having a pressure within a preset range and the pressure of the pressure oil accumulated in the accumulator 20 drops below a preset introduction pressure. Since it is composed of a selector valve 22 as a selector means for introducing the pressure oil of the hydraulic power source 1, each constituent element is composed of a simple spring and a spool or a piston, and has a simple structure and is inexpensive and highly reliable. It can be a pressure means. Further, since there is no electric control part and a pressure sensor is not necessary, the pressure adjusting means 2 having high reliability can be obtained in this respect as well.

Further, when the pressure of the pressure oil accumulated in the accumulator 20 exceeds a preset pressure, a regulator valve 21 is opened to keep the pressure of the pressure oil below the preset pressure.
By adding, even in the unlikely event that the selector valve 22 does not close in the open state, the upper limit of the pressure of the accumulator 20 can be regulated, and high pressure oil is prevented from being accumulated and supplied to the front wheel brake 4. It is possible to obtain the effect of protecting them.

Since the hydraulic pressure source 1 is the bottom pressure generated in the bottom chamber 14B of the lift cylinder 14 as a cargo handling device, a dedicated hydraulic pressure source for braking is unnecessary,
It can be constructed at low cost.

As for the bottom pressure, the hydraulic pressure surely exists in the loaded state, and the pressure corresponding to the own weight of the carriage, the fork, etc. is generated even in the empty state without loading, and a certain level of pressure can be secured.

Moreover, compared to the case where the pump 12 for cargo handling is used, the probability of obtaining the necessary hydraulic pressure is high even when cargo handling is not in progress, and energy efficiency is good.

In the unlikely event that an orifice 25 as a flow rate limiting means for limiting the flow rate supplied to the accumulator 20 is arranged in the pressure regulating means 2 or between the hydraulic pressure source 1 and the pressure regulating means 2. Even when the selector valve 22 or the like fails in the open state, the rapid outflow of the pressure oil is limited, and the adverse effect on the cargo handling system can be minimized or eliminated.

Further, since the rapid inflow of the pressure oil into the accumulator 20 is restricted, the pressure adjusting means 2 can be prevented from being damaged.

The amount of oil required for the front wheel brakes 4 is very small, and even if a flow rate limiting means such as the orifice 25 is interposed, it will not be affected.

Since the pressure regulating means 2 is provided with the check valve 24 as a backflow preventing means in the passage to the hydraulic pressure source 1, when the accumulated pressure of the accumulator 20 decreases and the selector valve 22 opens, Backflow that occurs when the pressure of the hydraulic source 1 is also low can be prevented.

In the example shown in FIG. 5, the selector valve 22
Is a pressure switch 34 as pressure detecting means for detecting that the pressure of the pressure oil accumulated in the accumulator 20 has dropped below a preset introduction pressure, and a shut-off position 32B according to an output signal from the pressure switch 34. Since it is constituted by the electromagnetic valve 32 that is switched from the open position to the open position 32A, it is possible to obtain the highly reliable pressure adjusting means 2.

FIG. 6 is a schematic view showing a brake device for a reach forklift according to a second embodiment of the present invention.
The brake valve 3 is replaced with a PWM valve 3A (Pulse Width).
Modulation valve) to adjust the brake pressure according to the return stroke of the brake pedal 5 from the most depressed position. The same parts as those in the previous embodiment are designated by the same reference numerals and the description thereof will be omitted.

The PWM valve 3A is a pressure control valve capable of pressure control by adjusting the duty ratio of the exciting pulse supplied to the solenoid 36. When the solenoid 36 is not excited, the control oil pressure is not generated, and the control oil pressure increases as the duty ratio increases. The control oil pressure of the PWM valve 3A is supplied to the wheel cylinder 4A of the front wheel brake 4.

The brake pedal 5 is provided with a potentiometer 7A that outputs a brake signal that increases with an increase in the return pedal stroke from the pedal fully depressed position. The brake signal from the potentiometer 7A is input to the PWM controller 8A as a control means.
The PWM controller 8A outputs a control pulse having a duty ratio corresponding to the brake signal to the PWM valve 3 that is a brake valve.
It outputs to the solenoid 36 of A and controls the solenoid 36 according to a duty ratio.

The PWM controller 8A can supply the duty ratio that linearly increases to the solenoid 36 in the entire stroke section where the brake signal is maximized from the initial stage of the brake signal input from the potentiometer 7A. It is also possible to set the duty ratio to increase linearly only in a stroke section that is appropriately set, not over the entire stroke. For example, the brake pedal 5
It is also possible to set the duty ratio to increase linearly from the point where it was slightly returned from the beginning of the return to the maximum duty ratio at the return position of about half of the stroke. Also,
It is also possible to set the increase ratio of the duty ratio to the stroke to be small (to decrease the increase ratio) when the friction coefficient of the road surface at the work site is low. That is, PWM
It is desirable that the controller 8A be capable of arbitrarily setting the duty ratio (which may be the obtained brake pressure) with respect to the return stroke of the pedal 5, the rising point, the ending point, the increase ratio, and the like. FIG. 7 shows an example of the relationship between the return stroke of the pedal 5 and the duty ratio (or brake pressure) set in the PWM controller 8A. The duty ratio (brake pressure) is shown at the time point S1 of the pedal return stroke. It is started up and linearly increased until time S2. It should be noted that time point S0 indicates the most depressed position of the pedal, and time point S3 indicates the time when the pedal is completely returned.

FIG. 8 shows the pedal return stroke and the front wheels when the brake pedal 5 is returned from the most depressed position.
5 is a graph showing the concept of changes in the braking force generated on the rear wheels and the total braking force generated on the vehicle. When the brake pedal 5 is returned from the time point S0 which is the most depressed position, the braking force of the rear wheel brake 6 increases in proportion to the pedal return stroke as shown by the line R, and the braking force of the front wheel changes at the time point S1. Stand up as shown in F. From time S1, both the braking force of the front and rear wheels are increased according to the return stroke. At time S2, the braking force on the front wheels stops increasing (see line F), and only the braking force on the rear wheels is increased toward time S3. The total braking force exerted on the vehicle is shown by the line FR. In this example, the braking force of the front and rear wheels increases in proportion to the increase of the pedal stroke, so that the braking force obtained by adjusting the return stroke of the pedal 5 can be adjusted, and the running control of the vehicle can be controlled. It will be easy.

In addition to the effects of the first embodiment, this embodiment can achieve the effects described below. That is, since the brake pressure output from the brake valve 3A is increased / decreased according to the return stroke of the brake pedal 5, the braking force is increased in association with the return operation of the brake pedal 5, and the vehicle braking force due to the return operation of the brake pedal 5 is increased. Adjustment is easy because it matches the operation feeling of the operator.

FIG. 9 is a schematic diagram showing a reach forklift braking device according to a third embodiment of the present invention.
The slip state of the front wheels during braking is detected, and the brake pressure applied to the front wheels is reduced to a non-slip pressure. The brake valve 3 is composed of a PWM valve 3A.

In FIG. 9, a PWM controller 8B serving as a control means receives a brake signal from a pedal switch 7 for notifying that the brake pedal 5 is in a braking state from a time when the brake pedal 5 is slightly returned from the most depressed position. To be done. The vehicle speed signal from the vehicle speed sensor 9A and the rotation signal from the front wheel rotation sensor 9B are also input to the PWM controller 8B.

Although not shown, the vehicle speed sensor 9A rotatably supports a wheel having the same diameter as the front wheel on the vehicle body and grounds its rolling surface on the road surface so that the vehicle can freely travel in proportion to the vehicle speed when the vehicle is running. It is formed to rotate and outputs the output of the wheel rotation sensor as a vehicle speed signal. Even wheels having the same diameter can be similarly used by multiplying the output signal by a coefficient. Instead of newly adding a wheel, the number of rotations of the caster wheel that constitutes one of the rear wheels may be detected.

The front wheel rotation sensor 9B outputs a front wheel rotation signal. The front wheels generate a braking force due to the frictional force with the road surface when the braking force is applied by the front wheel brakes 4. However, when the frictional force with the road surface is lower than the braking force of the front wheel brakes 4, the rotational speed of the front wheels is reduced. A slipping condition is created that decreases. When the braking force by the front wheel brakes 4 is reduced corresponding to the frictional force on the road surface, the rotation is restored, and the braking force corresponding to the frictional force on the road surface can be generated.

As shown in the block diagram of FIG. 10, the PWM controller 8B first outputs the PWM valve 3 via the PWM oscillation circuit 37 while the brake signal is being output.
When A is fully opened, the pressure of the accumulator 20 adjusted to a constant pressure by the pressure adjusting means 2 is output as the brake pressure. Further, the vehicle speed signal and the rotation signal are compared by the comparison circuit 38, and when the rotation signal is separated from the vehicle speed signal, it is determined that the front wheel is slipping. When there is no difference between the two, the output of the fully open duty ratio to the PWM valve 3A is continued. When it is determined that the front wheels are slipping, the duty ratio to the PWM valve 3A is reduced from the fully open state, and the brake pressure output by the PWM valve 3A is reduced. The duty ratio reduction amount is set in advance. The reduction of the duty ratio is repeated until the difference in rotation speed between the front wheel rotation sensor 9B and the vehicle speed sensor 9A disappears, and the duty ratio and the brake pressure are repeatedly reduced.

FIG. 11 shows a state in which the brake pressure is reduced when the front wheels slip, and when the slip does not occur, the pressure is adjusted by the pressure adjusting means 2 as indicated by the line G. When the brake pressure is supplied and a slip occurs, the brake pressure is reduced until the slip condition that occurs in the front wheels is eliminated as indicated by the line H. Since the maximum value of the braking force generated in the vehicle is limited by the friction coefficient of the road surface, the braking force of the vehicle does not decrease even if the brake pressure is reduced, and the operator does not feel uncomfortable.
Due to the decrease in the brake pressure, the maximum braking force obtained by the road surface is exerted when the rotation speed of the front wheels matches the vehicle speed signal. By preventing the front wheels from slipping in this way, the lateral stability of the vehicle is improved and the behavior of the vehicle is stabilized.

As the brake signal, the signal from the potentiometer 7A proportional to the return stroke of the brake pedal 5 from the most depressed position is the PWM controller 8
When input to B, the PWM controller 8B can control the PWM valve 3A with the characteristic shown in FIG. In this case, by comparing the rotation signal of the front wheels with the vehicle speed signal, the brake pressure having the characteristic shown in FIG. 12 can be obtained when the same control as in FIG. 9 is performed. That is, as indicated by the line J, it is possible to obtain the brake pressure proportional to the return stroke of the pedal 5. Moreover, when the front wheel slips, the brake pressure is reduced as indicated by the dotted line J1, and when the front wheel slip is not resolved at that time, the brake pressure is further reduced as indicated by the chain line J2 and the front wheel is reduced. You can eliminate the slip. In this case, the brake pressure is increased / decreased in proportion to the pedal stroke, so that the brake can be set according to the sensitivity of the operator, and the brake pressure is controlled so that the front wheels are not slipped. Also stabilizes.

In addition to the effects of the first embodiment, this embodiment can achieve the effects described below. That is, the pressure oil regulated by the pressure regulating means 2 is supplied to the front wheel brake 4 as a brake pressure, and when the slip state of the front wheel is detected, the brake valve 3A is pressure-reduced so as to eliminate the slip. Since the supplied brake pressure is reduced, the slip of the front wheels that occurs when the friction coefficient of the road surface is small can be effectively prevented, and the behavior of the vehicle can be stabilized.

Since the maximum braking force is limited by the frictional force of the road surface, even if the hydraulic pressure of the front wheel brake 4 is reduced without depending on the operator's will, the braking force obtained by the vehicle is There is no decrease, and the operator does not feel uncomfortable.

When the slip signal is not input from the comparison circuit 38 as the slip detecting means, it is possible to increase or decrease the brake pressure output from the brake valve 3A according to the return stroke of the brake pedal 5. When a slip signal is input from the comparison circuit 38 as a slip detecting means, the brake pressure output from the brake valve 3A is controlled so as to cancel the slip, and the brake pressure is controlled according to the return stroke of the brake pedal 5. Since the amount is increased or decreased, the braking force adjustment by the pedal operation can be matched with the operation feeling of the operator, and further, the slip of the front wheels can be effectively suppressed by the brake pressure controlled to be depressurized and the vehicle behavior can be stabilized.

13 and 14 show a modification of the hydraulic power source 1 of the reach forklift brake device according to the present invention.

In FIG. 13, the discharge pressure of the cargo handling pump 12 driven by the motor 11 is connected upstream of the selector valve 31 constituted by the electromagnetic opening / closing valve 32 of the pressure regulating means 2. In this hydraulic power source 1, the motor 11 also drives the cargo handling pump 12 during the operation of operating the cargo handling control valve 13, so that pressure can be accumulated in the pressure adjusting means 2. When the cargo handling work is not in progress, the motor 11
As a result, the cargo handling pump 12 is not driven, and thus pressure oil as the hydraulic pressure source 1 is not generated. In this case, even if the pressure of the accumulator 20 drops and the selector valve 31 opens, the check valve 24 prevents the pressure of the accumulator 20 of the pressure adjusting means 2 from flowing out. The cargo handling pump 12 may be driven by the motor 11 when the pressure of the accumulator 20 decreases.

In FIG. 14, a pressure sensor 34 detects a pressure drop in the accumulator 20 of the pressure adjusting means 2 and a motor 39 drives a pump 38 dedicated to accumulating pressure. The pump 38 is a pump dedicated to the brake, which is independent of the cargo handling system, and does not affect the cargo handling system. The pump 38 is driven by the motor 39 when the pressure of the accumulator 20 of the pressure adjusting means 2 drops, and the motor 39 is driven when the pressure of the accumulator 20 reaches a predetermined pressure.
To stop.

In this embodiment, in addition to the effect of the first embodiment, the hydraulic power source 1 is independent of the cargo handling pump 12 for supplying the pressure oil to the cargo handling device 14 and the motor 39.
And a pressure sensor 34 as a selector means and a motor 39 drive the motor 39 when the pressure of the pressure oil accumulated in the accumulator 20 drops below a preset introduction pressure. Therefore, the dedicated pump 38 can be driven to accumulate pressure when the pressure of the accumulator 20 drops regardless of whether cargo handling work is performed. That is, it is not necessary to drive a large-capacity cargo handling pump, which can save resources.

In each of the above-mentioned embodiments, the pressure adjusting means 2 having the accumulator 20 for accumulating the pressure oil has been described. However, although not shown, if the pressure can be adjusted to a predetermined pressure, the accumulator may not be provided. Good.

In the above embodiment, the brake valve 3 capable of adjusting the output pressure is provided with the PWM valve 3A. However, an electromagnetic proportional pressure control valve for adjusting the output pressure according to the current value supplied. May be

Further, in the above-mentioned embodiment, although the description is given of the one in which the brake pressure is continuously controlled corresponding to the pedal stroke of the brake pedal 5, although not shown, a plurality of control pressure values are different. The pressure control valve may be connected in parallel, and the pressure control valve may be switched from the low pressure output to the high pressure output to change the pressure stepwise.

When the pressure of the pressure adjusting means 2 has dropped below the specified pressure for a predetermined time or more,
The warning means may be activated.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a reach forklift brake device according to an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram that also includes pressure regulating means and a brake valve.

FIG. 3 is a graph showing the relationship between the brake stroke and the return stroke from the most depressed position of the brake pedal.

FIG. 4 is a graph showing the relationship between the return stroke of the brake pedal from the most depressed position and the braking force of the front and rear wheels.

FIG. 5 is a hydraulic circuit diagram showing a partially modified example of the pressure adjusting means.

FIG. 6 is a schematic configuration diagram of a reach forklift brake device according to a second embodiment of the present invention.

7 is a graph showing the relationship between the brake stroke and the return stroke from the most depressed position of the brake pedal in FIG.

8 is a graph showing the relationship between the return stroke from the most depressed position of the brake pedal in FIG. 6 and the braking force of the front and rear wheels.

FIG. 9 is a schematic configuration diagram of a reach forklift brake device showing a third embodiment of the present invention.

10 is a block diagram of the PWM controller in FIG.

11 is a graph showing the relationship between the brake stroke and the return stroke from the most depressed position of the brake pedal in FIG.

12 is a graph showing the relationship between the return stroke from the most depressed position of the brake pedal and the brake pressure in the modified example of FIG.

FIG. 13 is a circuit diagram showing another modification of the hydraulic power source.

FIG. 14 is a circuit diagram showing still another modified example of the hydraulic power source.

[Explanation of symbols]

1 hydraulic power source 2 Pressure regulation means 3 brake valve 3A PWM valve (brake valve) 4 front wheel brake 5 brake pedal 6 Rear wheel brake 7 Brake switch 8 Control circuit (control means) 8A, 8B PWM controller (control means) 9A vehicle speed sensor 9B rotation sensor 12 Pumps for cargo handling 13 cargo handling control valve 14 Cargo handling equipment (lift cylinder) 14A Bottom chamber 20 Accumulator 21 Regulator valve 22 Selector valve 24 Check valve (backflow prevention means) 25 Orifice (flow limiter) 30, 36 solenoid 31 Select Means 32 Solenoid valve 34 Pressure sensor (pressure switch) 38 Comparison circuit (slip determination means)

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3D045 AA06 BB37 CC02 EE21 FF42                       GG00 GG28                 3D046 AA06 AA09 BB28 BB31 CC01                       CC02 EE01 EE02 FF04 HH02                       HH36 JJ06 LL02 LL23 LL30                       LL39 LL41                 3F333 AA02 CA11 CA19 FA08 FA20                       FA34 FA38 FB06 FE03 FH08

Claims (11)

[Claims] 1. A front wheel brake for braking the left and right front wheels arranged on the front end side of the straddle arm respectively according to the supplied brake pressure, a rear wheel brake for braking the rear wheel, a hydraulic pressure source for generating pressure oil, and a hydraulic pressure. A pressure adjusting device for adjusting the pressure oil from the power source to a preset pressure, a brake valve for supplying the pressure oil of the pressure adjusting device to the front wheel brakes as a brake pressure, and a brake release for the rear wheel brake at the most depressed position. A brake device for a reach forklift, comprising: a brake pedal that increases a braking force according to a return stroke from the most depressed position, and a control unit that operates a brake valve from the middle of the return stroke of the brake pedal. 2. The reach forklift according to claim 1, wherein the control means starts the operation of the brake valve at any point in the return stroke except the return start and the return end of the brake pedal. Brake equipment. 3. The brake valve is composed of a pressure control valve capable of adjusting the brake pressure by controlling the pressure oil of the pressure adjusting means to reduce pressure, and the front wheel has front wheel slip detecting means for detecting the slip. When the slip signal from the front wheel slip detection means is input, the control means outputs the brake pressure obtained by controlling the pressure oil of the pressure adjusting means by the brake valve so that the slip is eliminated. The brake device for a reach forklift according to claim 1. 4. The brake valve comprises a pressure control valve capable of adjusting the brake pressure by controlling the pressure oil of the pressure adjusting means to reduce the pressure, and the control means outputs the brake pressure output from the brake valve to the brake pedal. The brake device for a reach forklift according to claim 1, wherein the brake device is increased / decreased according to the return stroke. 5. The brake valve is composed of a pressure control valve capable of adjusting the brake pressure by controlling the pressure oil of the pressure adjusting means to reduce pressure, and the front wheel is provided with a slip detecting means for detecting the slip. When the slip signal is not input from the slip detection unit, the control unit increases or decreases the brake pressure output from the brake valve according to the return stroke of the brake pedal, and the slip signal from the slip detection unit is input. The brake device for a reach forklift according to claim 1, wherein the brake pressure output from the brake valve is further reduced so as to eliminate the slip, and the brake pressure is increased or decreased according to the return stroke of the brake pedal. 6. The pressure adjusting means opens a valve when an accumulator for accumulating pressure oil having a pressure within a preset range and a pressure of the pressure oil accumulated in the accumulator drops below a preset introduction pressure. 2. The brake device for a reach forklift according to claim 1, further comprising selector means for introducing pressure oil from a hydraulic source. 7. The selector means detects pressure when the pressure of the pressure oil accumulated in the accumulator drops below a preset introduction pressure, and shuts off according to an output signal from the pressure detection means. The brake device for a reach forklift according to claim 6, wherein the brake device comprises a solenoid valve that is switched from a position to an open position. 8. The hydraulic source includes a pump driven by a motor independently of a cargo pump for supplying pressure oil to the cargo handling device, and the selector means preliminarily stores the pressure of the pressure oil accumulated in the accumulator. The brake device for a reach forklift according to any one of claims 1 to 7, wherein the motor is driven by a signal from a pressure detection means that detects that the pressure has dropped below a set introduction pressure. 9. The brake device for a reach forklift according to claim 1, wherein the hydraulic pressure source is a bottom pressure generated in a bottom chamber of a lift cylinder of the cargo handling device. . 10. A flow rate limiting means for limiting a flow rate supplied to the accumulator is arranged in the pressure adjusting means or between the hydraulic pressure source and the pressure adjusting means. Item 8. A brake device for a reach forklift according to any one of items 7. 11. The reach forklift brake according to claim 1, wherein the pressure adjusting means has a backflow preventing means arranged in a passage to a hydraulic pressure source. apparatus.