JP2001151494A - Reach type forklift - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reach type forklift capable of shortening a braking distance and reducing revolving amount of a vehicle when braking the vehicle. SOLUTION: When a difference of rotational speed of front wheels 23 and rear wheels 30 becomes a prescribed value or more, the rear wheels 30 are slipped or locked, braking for also the front wheels 23 is decided to be required and the braking is applied to also the front wheels 23. Therefore, sufficient braking force can be obtained even in a loaded state of a fork 25, a braking distance is reduced and the braking can be safely applied. Between loading time of load and unloading time, a difference of the braking distance can be reduced and braking feeling which is not changed in particular can be imparted to a driver.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reach type forklift, and more particularly to a brake device thereof.

[0002]

2. Description of the Related Art FIG. 16 shows a side view of a conventional reach type forklift. FIG. 17 conceptually shows a plane of such a reach type forklift. A pair of left and right reach legs 2 is provided at the front of the vehicle of the reach type forklift 1. Between a pair of reach legs 2,
A mast device 4 that supports a pair of left and right forks 3 is slidably provided. At the front end of each reach leg 2,
A front wheel 5 is provided. On the other hand, a machine base 7 having a driver's seat 6 is provided at the rear of the vehicle. The machine base 7 is provided with a first rear wheel 8 functioning as a drive wheel and a steering wheel, and a second rear wheel 9 serving as a support wheel for supporting the machine base 7 merely following the traveling of the vehicle. . The reach type forklift is provided with a brake device (not shown) for braking only the first rear wheel 8.

[0003]

However, in the conventional reach-type forklift as described above, when a load 10 is placed on a pair of forks 3 as shown in FIG. As a result, a moment M1 in the counterclockwise direction in FIG.
, A vertical downward load (hereinafter, referred to as “rear wheel load”) N acting on the tire may decrease. For this reason, when the brake is applied with the load 10 loaded, the rear wheel 8 is likely to slip due to a decrease in the rear wheel load, and the weight of the entire vehicle may increase by the weight of the load 10. Together,
There was a problem that the braking distance was long.

[0004] The first rear wheel 8 to which the braking force acts is
As shown in FIG. 17, since the vehicle is deviated to one side from the center C in the vehicle width direction, a moment is generated in the vehicle, and the vehicle may turn slightly during braking.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and a reach type in which a braking distance can be shortened and a turning amount of a vehicle during braking can be reduced. The purpose is to provide a forklift.

[0006]

In order to achieve the above-mentioned object, a reach-type forklift according to the present invention is provided at a rear portion of a vehicle, provided with a machine provided with rear wheels, and a driving machine formed inside the machine. A seat, located at the front of the vehicle, including a pair of left and right reach legs having a pair of left and right front wheels, a mast device slidable along the reach leg, and a pair of left and right forks supported by the mast device, Further, a rear wheel brake device for applying a brake to the rear wheel in conjunction with a brake operation command, slip detection means for detecting slip of the rear wheel, and the slip detection when the brake operation command is issued. A front wheel brake device that brakes the front wheel when the occurrence of slip of the rear wheel is detected by the means.

[0007] The brake operation command is issued when the safety brake means is operated, or when the accelerator means is moved in a direction opposite to the vehicle traveling direction while the safety brake means is not operated. It may be. Further, the safety brake means is a brake pedal provided in the driver's seat, and when the brake pedal is depressed, the safety brake means is deactivated, and when the brake pedal is released, the safety brake means is released. The operating state of the safety brake means may be set.

Further, the occurrence of the slip of the rear wheel may be determined based on a slip speed, or may be determined based on a slip ratio. Further, the front wheel brake device is used when the front wheels are stopped, or when the vehicle speed is close to stopping, when the accelerator means is returned to the neutral position or when the vehicle is moved in the same direction as the vehicle travel direction, Can be configured to release the brakes on the front wheels when is inactive.

Further, the above-described reach type forklift may include an oil pump for hydraulically driving the fork, and an accumulator for storing oil from the oil pump and supplying the oil to the front wheel brake device.

[0010] The rear wheel may function as a drive wheel and may be provided at a position deviated from the center in the width direction of the vehicle, and the brake device may simultaneously apply a braking action to the pair of left and right front wheels.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIG. 1 shows a reach type forklift according to Embodiment 1 of the present invention. A pair of left and right reach legs 22 extending in the vehicle front-rear direction and separated from each other in the vehicle width direction are provided at a front portion of the reach forklift 21 in the vehicle. A front wheel 23 is attached to the front end of each reach leg. A mast device 24 is provided between the pair of reach legs 22.
Is provided so as to be slidable along. Mast device 2
4 is a pair of left and right forks 25
6 is attached.

On the other hand, a machine base 29 having a driver's seat 27 and a functional product room 28 arranged in the vehicle width direction is provided at the rear of the vehicle. A first rear wheel 30 that functions as a driving wheel and a steering wheel is provided below the functional product room 28. The rear wheel 30 is provided at a position shifted leftward from the center in the vehicle width direction. In addition, below the driver's seat 27, a second support wheel for supporting the machine base 29 only follows the traveling of the vehicle.
Rear wheel 31 is disposed. A so-called deadman type brake pedal 33 is provided on the floor 32 of the driver's seat 27. That is, the brake pedal 33
When the driver depresses the brake pedal 33, the brake is released, and functions as a safety brake means such that the vehicle does not run when the driver does not depress the brake pedal.

As shown in FIG. 2, an instrument panel 41 is formed at the front of the driver's seat 27.
There, an accelerator lever 42 is provided as accelerator means. Furthermore, the instrument panel 41
An oil tank 43 for storing hydraulic oil and an oil control valve 44 for controlling the flow of hydraulic oil are installed near the internal accelerator lever 42.

A functional product room 28 formed on the left side of the machine base 29
As shown in FIG. 3, functional goods such as a cargo handling motor 51, an oil pump 52, a drive motor 53, and a rear wheel brake device 54 are accommodated therein. The rear wheel 30 is connected below the drive motor 53, and the vehicle travels by the driving force of the drive motor 53. The drive motor 53 includes a drive motor 53
A rotation speed sensor 55a for detecting the rotation speed of the drive motor 53, that is, a rotation direction of the rear wheel 30, that is, a rotation speed sensor 55a for detecting the rotation speed of the rear wheel 30 connected thereto. Is attached. The rear wheel brake device 54 is provided with a drive motor 5.
3 comprises a disc brake which brakes the rotation and thereby brakes the rear wheel 30.

As shown in FIG. 4, the brake pedal 33 provided on the floor 32 of the driver's seat 27 is
1 is connected to the rear wheel brake device 54. When the driver releases his / her foot from the brake pedal 33 and the brake pedal 33 is raised, the operation is performed via the link mechanism 61. The rear wheel brake device 54 stops the rotation of the drive motor 53 and the rear wheel 30 thereunder. Conversely, when the driver depresses the brake pedal 33, the rear wheel brake device 54 is released. A brake switch 62 is provided below the brake pedal 33. When the brake pedal 33 is depressed and moves downward, the operation piece of the brake switch 62 is pressed.
The brake switch 62 can output a deadman brake release signal.

As shown in FIG. 5, a first fitting 71 for branching an oil passage is provided at an oil inlet from the cargo handling motor 51 in front of the oil control valve 44, and a front wheel brake hydraulic circuit is provided. The supply of oil to the country is now possible.

In FIG. 6 and FIG. 7, a first supply pipe 81 branched from a first fitting 71 is connected to an accumulator 82. The first supply pipe 81 includes a check valve 83 and an accumulator pressure switching valve 84. The accumulator pressure switching valve 84 is an electromagnetic valve,
Controller 101 provided in front of loading motor 51
The opening and closing are controlled by. Accumulator 8
A pressure sensor 85 is attached to 2, and pressure data for controlling opening and closing of the accumulator pressure switching valve 84 is output to the controller 101. Also,
The accumulator 82 is connected to a pair of left and right front wheel brake devices 111 via a second supply pipe 86 and a brake pipe 87.
It is connected to the. A brake pressure increasing valve 89 is provided in the middle of the second supply pipe 86. Also, the second supply pipe 86
A return pipe 91 is connected to the brake pipe 87 via a fitting 90. The downstream end of the return pipe 91 is connected to the oil tank 43. In the middle of the return pipe 91, a brake pressure reducing valve 92 is provided. The brake pressure increasing valve 89 and the brake pressure reducing valve 92
Are solenoid valves, the opening and closing of which are controlled by the controller 101. The pressure data in the fitting 90 is measured by the pressure sensor 93 and is input to the controller 101.

As shown in FIG. 8, each front wheel 23 has
A front wheel brake device 111 including a drum brake is attached. The front wheel brake device 111 is bolted to a shaft portion 112 welded to the reach leg 22. Further, a wheel 115 of the front wheel 23 is press-fitted into the shaft portion 112 via bearings 113 and 114, and the wheel 115 is fastened by a cap 117 via a nut 116. Wheel 11
5 is machined so that the inner surface of the cylinder functions as a brake drum.
The contact of the 11 linings causes the friction brake to work. The baseband portion 119 on the side surface of the tire 118 has irregularities formed thereon, and the front wheel rotational speed sensor 120 fixed to the lower portion of the reach leg 22 by bolts detects the irregularities, so that the rotational speed of the front wheels is measured. You.

Next, the operation of the above-described reach type forklift will be described. First, when the reach type forklift 21 is parked, that is, when the driver is not in the driver's seat 27, the brake pedal 33 is raised, and this state is the operating state of the safety brake means. The information on the brake pedal 33 is sent to the controller 101 via the brake switch 62, and the controller 101 recognizes the information as a "brake operation command" and activates the rear wheel brake device 54 to operate the rear wheel 30.
Brake on At this time, the controller 1
01 indicates that the front wheel 23 is stopped, that is, the front wheel 23
The information that the rotation speed of the vehicle is zero is also sent, so that the front wheel brake device 111 remains released. Thus, the brake pedal 33 also functions as a parking brake.

Next, a description will be given of the braking operation when no load is loaded on the fork 25. When the reach type forklift 21 is driven, first, when the driver depresses the brake pedal 33, that is, when the safety brake device is deactivated, the "brake operation command" is released and the rear wheel brake acting on the rear wheel 30 is released. The device 54 is released. When the driver swings the accelerator lever 42 forward of the vehicle, the operation is sent to the controller 101 as an accelerator lever forward / backward travel signal, and the drive motor 5
3 starts driving and the vehicle starts moving forward. Next, when decelerating or stopping the vehicle, when the accelerator lever 42 is swung to the rear of the vehicle, the operation is sent to the controller 101 as an accelerator lever forward / reverse signal. At this time, information indicating that the vehicle is moving forward is also sent to the controller 101 by the rotation direction sensor 55b for detecting the rotation direction of the rear wheel 30. As a result, the controller 101 recognizes that the accelerator lever 42 is swung in the direction (reverse direction) opposite to the vehicle traveling direction (forward direction), recognizes the state as a “brake operation command”, and By applying regenerative braking or plugging braking force to the wheels,
Brakes on zero.

When the driver loses his / her driving posture or falls off the driver's seat 27 for some reason during running, and his foot is released from the brake pedal 33, the brake pedal 33 is raised and the safety brake means is activated. .
The controller 101 recognizes the information as a “brake action command” by the safety brake means, and operates the rear wheel brake device 54 to apply a brake to the rear wheel 30 even without a “brake action command” by the accelerator lever 42. . That is, the brake pedal 33 functions as a safety brake unit.

Next, a description will be given of a case where the cargo handling work is performed mainly with reference to FIG. When the driver operates the cargo handling lever, the cargo handling motor 51 starts in response thereto, the oil pump 52 directly connected to the cargo handling motor 51 rotates, and the hydraulic oil in the oil tank 43 is sent to the oil control valve 44. At this time, if the controller 101 determines from the signal of the pressure sensor 85 that the pressure of the oil stored in the accumulator 82 is lower than the predetermined value, the controller 101 determines that the accumulator storage pressure switching valve 8
4 is opened, and the oil pressure in the accumulator 82 is increased. When the oil pressure in the accumulator 82 becomes equal to or more than a predetermined value, the accumulator pressure switching valve 84 is closed, and the oil pressure in the accumulator 82 is held by the action of the check valve 83. On the other hand, the accumulator storage pressure switching valve 84
Is closed, the hydraulic oil in the oil tank 43 flows into the oil control valve 44, and is further sent to the lift cylinder of the mast device 24, where the fork 2
5 is operated to carry out cargo handling.

When the driver swings the accelerator lever 42 forward while the load is loaded on the fork 25, the operation is performed as an accelerator lever forward / reverse signal.
1 and the drive motor 53 is driven to start the forward movement of the vehicle. Next, when the driver swings the accelerator lever 42 backward during forward movement for deceleration or stop of the vehicle, as in the case of the braking action without the load on the fork 25, The operation is recognized by the controller 101 as a “brake action command”, and the brake is applied to the rear wheel 30.

Further, when the load is mounted on the fork 25, the weight of the vehicle increases and the inertia force increases accordingly, so that a larger braking force is required than when no load is mounted. For this reason, when the brake is applied to the rear wheel 30, the braking force is insufficient due to the large inertial force of the vehicle, and the rear wheel 3
0 may lock up. If the lock of the rear wheel 30 occurs, the state can be determined by the rear wheel speed sensor 55a that the rotation speed of the rear wheel 30 is substantially zero, that is, the rotation speed is substantially zero. on the other hand,
Even if the rear wheel 30 is locked, the vehicle is moving forward during that time, so that the front wheel 23 as a driven wheel continues to rotate, and the rotational speed is detected from the rotational speed of the front wheel 23 detected by the front wheel rotational speed sensor 120. You. Here, when the rear wheel 30 is not locked, the rotation speeds of the front wheel 23 and the rear wheel 30 are substantially the same, and the difference between the rotation speeds of the front wheel 23 and the rear wheel 30, that is, the slip speed is zero. When the rear wheel 30 is locked, there is a difference between the rotational speeds of the front wheel 23 and the rear wheel 30, and a slip speed is generated.

Therefore, the controller 101 controls the front wheel 23
When the slip speed, which is the difference between the rotation speeds of the rear wheel 30 and the rear wheel 30, becomes equal to or greater than a predetermined value, it is determined that the rear wheel 30 is slipping or locked, and that the front wheel 23 also needs to be braked. When the pressure valve 89 is opened, the operating oil stored in the accumulator 82 is sent to the wheel cylinder of the drum brake, the brake shoe expands, the lining comes into contact with the drum, and the brake acts on the front wheel 23. In this way, by applying a brake to the front wheels 23 as well, a sufficient braking force can be applied to the vehicle. As a result, even when a load is loaded on the fork 25, a sufficient braking force can be obtained, and the braking distance can be reduced and the brake can be applied safely. Further, it is possible to reduce the difference in the braking distance between when the load is loaded and when the load is not loaded, and to provide the driver with a braking feeling that does not change much.

In this embodiment, even if the load on the front wheels increases and the load on the rear wheels decreases with the braking, a sufficient braking force can be obtained by the brake applied to the front wheels 23 in the present embodiment. The distance does not increase. Further, in the related art, when the rear wheel is displaced to the left from the center in the vehicle width direction, the vehicle may turn to the left and stop at the time of abrupt braking. The brakes are simultaneously applied to the front wheels 23 to reduce the influence of the moment caused by the rear wheels being displaced from the center in the vehicle width direction. Can be stopped.

The pressure value in the wheel cylinder is measured by a pressure sensor 93. When the pressure value reaches a specified value, the controller 101 sets a brake pressure increasing valve 89.
And maintain the pressure in the wheel cylinder to maintain the front wheel braking action.

Next, when the vehicle is stopped by the brake, that is, when the rotation speed of the front wheel 23 becomes zero and the front wheel 23 stops, or when the front wheel 23 becomes low speed close to the stop, or when the accelerator lever 42 becomes neutral. When the controller 101 is swung in the same direction as the position or the traveling direction of the vehicle, the controller 101 determines that the request for the front wheel brake has been cancelled, and releases the front wheel brake device 111. That is, the controller 101 opens the brake pressure reducing valve 92 and maintains the brake pressure increasing valve 89 closed, and returns the hydraulic oil in the wheel cylinder to the oil tank 43. Thereby, when the front wheel brake is not necessary, the front wheel 23
Can be rotated as driven wheels, and the front wheels 23
Alternatively, even when a so-called regeneration mechanism is connected to the rear wheel 30, it is possible to efficiently recover energy.

Further, in the present embodiment, when the slip speed exceeds a predetermined value, it is possible to apply a brake to the front wheels 23 irrespective of whether a load is loaded or not. . Therefore, even during braking on a slippery road surface, for example, a wet road surface or a frozen road surface, during normal traveling without a load loaded on the fork 25, the braking distance can be reduced and the brake can be safely applied.

The means for measuring the rotation speed of the front wheels is not limited to the front wheel rotation speed sensor 120 shown in the above embodiment, and the measurement mode and the installation position can be appropriately modified. is there. The same applies to the means for measuring the rotation speed of the rear wheel. In the above embodiment, the rotation speed is attached to the drive motor 53, but may be attached to the rear wheel 30. Further, the rotation direction sensor 55b for detecting the traveling direction of the vehicle is different from the mode for detecting the rotation direction of the drive motor 53 as in the first embodiment, and directly detects the rotation direction of the rear wheel 30 itself, Or the direction of travel of the vehicle may be detected by other methods.

Embodiment 2 FIG. Next, Embodiment 2 of the present invention
Will be described with reference to FIG. In this reach type forklift, a front wheel brake device 131 including an electromagnetic brake is provided instead of the drum brake in the first embodiment.
A brake disk 136 of the electromagnetic brake is bolted to a wheel 135 attached to the shaft portion 132 via bearings 133 and 134 via a spline process so as to be slidable in the shaft axis direction. The attraction portion 137 of the electromagnetic brake is fixed to the reach leg 22 by bolts, and the brake disk 136 is attracted to the attraction portion 137 by a magnetic force generated in the attraction portion 137 by a brake operation signal from the controller 101 to obtain a braking force. According to such an electromagnetic brake, a dedicated hydraulic pressure source is not required, and a braking action can be obtained without using hydraulic oil for cargo handling.

Embodiment 3 The reach type forklift according to Embodiment 3 of the present invention will be described with reference to FIG. In this reach type forklift, a front wheel brake device 141 including a cam type drum brake operated by a solenoid is provided instead of the wheel cylinder type drum brake in the first embodiment. In response to a brake operation signal from the controller 101, the solenoid 142 operates to pull the rod 143, the brake cam 144 rotates with the operation of the rod 143, and the brake shoe 145 expands as the contact surface of the brake cam 144 changes. , And comes into contact with the drum to provide a braking force. According to the cam-type drum brake operated by such a solenoid, a dedicated hydraulic pressure source is not required, and a braking action can be obtained without using hydraulic fluid for cargo handling.

Embodiment 4 A reach forklift according to Embodiment 4 of the present invention will be described. FIG.
FIG. 12 is a view conceptually showing a configuration of a reach type forklift, and FIG. 12 is a detailed view of the brake valve assembly. As shown conceptually in FIG. 11, a machine of a reach-type forklift according to the present embodiment includes a controller 240, a cargo-handling motor 241, and an oil pump 24.
2, oil tank 243, oil control valve 2
44, a brake valve assembly 245, an accumulator 246, and a pressure switch 247 are provided. A drum type front wheel brake device 248 and a front wheel speed sensor 249 are provided near each of the pair of front wheels 223. Further, a rear wheel brake device and a rear wheel speed sensor 250 (not shown) are provided near the rear wheel 230. The brake valve assembly 245 is shown in FIG.
, The pressure reducing valve 260 and the shut-off valve 26
1 and a linear solenoid valve 262.

Next, the operation of the reach type forklift according to the present embodiment will be described. First, when the reach-type forklift is parked, that is, when the driver is not in the driver's seat, the brake pedal 233 is in an up state, and this state is an operating state of the safety brake. 233 is sent to the controller 240 via the brake switch 233a.
The controller 240 uses the information as a “brake action command”
And the rear wheel brake device is actuated to
Brakes on zero. At this time, information that the front wheel 223 is stopped, that is, information that the rotation speed of the front wheel 223 is zero is also sent to the controller 240, whereby the front wheel brake device 248 remains released.

Next, when running the reach type forklift, first, when the driver steps on the brake pedal 233, the "brake operation command" is released and the rear wheel brake device acting on the rear wheel 230 is released. When the driver swings the accelerator lever 234 forward of the vehicle, the operation is transmitted as an accelerator lever forward signal to the controller 2.
It is sent to 40 and the forward movement of the vehicle starts. Next, when the vehicle is decelerated or stopped, when the accelerator lever 234 is swung to the rear of the vehicle, the operation is sent to the controller 240 as an accelerator lever reverse signal. Thereby, the controller 240 recognizes that the accelerator lever 234 is swung in the direction (reverse direction) opposite to the vehicle traveling direction (forward direction), recognizes the state as a “brake operation command”, and Apply brake to wheel 230.

Further, when the rear wheel 230 locks or slips, the front wheel brake device 24
Also apply the front wheel brake by 8. As shown in FIG. 13, when a brake operation command by the accelerator lever 234 is input to the controller 240 as step S1,
The controller 240 energizes the shut-off valve 261 and the linear solenoid valve 262 in order to shorten the rise time of the hydraulic pressure of the brake oil as step S2.
Further, as step S3, the controller 240 obtains respective rotational speeds from the rotational speeds of the front and rear wheels detected by the front wheel rotational speed sensor 249 and the rear wheel rotational speed sensor 250, and calculates a slip ratio from the values. . The slip ratio is calculated from [front wheel rotation speed−rear wheel rotation speed] / [front wheel rotation speed (that is, ground speed of the vehicle)].

Here, the relationship between the slip ratio and the transmission force of the tire will be described. In FIG. 14, the state indicated by A is a state in which both the front and rear wheels are rotating at high speed, and the state indicated by B is a state in which both the front and rear wheels are rotating at low speed. However, the states indicated by A and B are states in which the difference between the front wheel rotation speed and the rear wheel rotation speed has the same value. That is, in the state of B where the front and rear wheels are rotating at a low speed, it can be said that the state is close to the slip region where assistance by the front wheel brake is required, but in the state of A where the front and rear wheels are rotating at a high speed, the slip still occurs. It can be said that this is a state where the user is not approaching the area. That is, in the state A, the braking force by the rear wheels is still obtained even if the rotational speed difference between the front and rear wheels is further increased, and the timing for operating the front wheel brake is slightly earlier. Therefore, in the present embodiment, the timing at which the front wheel brake is applied is determined based on the slip ratio, so that the front wheel brake is not applied until a slip region where the transmission force of the tire is actually reduced is achieved. To prevent the feeling from being deteriorated due to the excessive braking force by the front wheel brake while rotating.

Returning to FIG. 13, in step S4, the controller 240 determines whether the calculated slip ratio is equal to or greater than a set value. If the slip ratio is equal to or greater than the set value, a target set hydraulic pressure value is acquired from the brake hydraulic pressure map shown in FIG.
In step 6, the front wheel brake is operated.

In FIGS. 11 and 12, the controller 240 energizes the shut-off valve 261 and the linear solenoid valve 262 to open the shut-off valve 261 and to generate the selected hydraulic pressure. Adjust the valve opening. Thus, the oil stored in the accumulator 246 acts on the front wheel brake device 248 with a desired selected hydraulic pressure, and the pair of front wheels 223 is braked. Further, release of the hydraulic pressure of the front wheel brake device 248 is performed only by operating the linear solenoid valve 262 to communicate the front wheel brake device 248 with the oil tank 243. Therefore, supply and release of the hydraulic pressure to the front wheel brake device 248 are not performed. Substantially linear solenoid valve 2
Only 62 can be used.

The pressure of the oil stored in the accumulator 246 is determined as follows. When the cargo handling work is performed, the cargo handling motor 241 is activated and the oil pump 242 is driven. Thereby, the oil tank 243
The oil in the tank is supplied to an oil control valve 244 that generates a hydraulic pressure for cargo handling, and is also supplied to an accumulator 246 through a pressure reducing valve 260. When the pilot pressure of the pressure reducing valve 260 becomes equal to or more than a predetermined value, the pressure reducing valve 260 closes, and the shutoff valve 261 is closed.
The accumulator 246 is operated by the action of the check valve 260a.
The internal fluid pressure is kept constant. Further, when the cargo handling operation is not being performed, when the fluid pressure in the accumulator 246 monitored by the pressure switch 247 drops below a certain value, the oil pump 242 is driven by the controller 240 and the accumulated pressure in the accumulator 246 is implemented. It is supposed to be.

When the front wheel brake is applied as described above, the controller 40 determines whether or not the vehicle has stopped at step S7 in FIG. If the vehicle has not stopped, it is further determined in step S8 whether or not the braking signal may be released. That is, if the slip ratio is less than the predetermined value, it is determined that the rear wheel is not locked such that the front wheel brake is necessary. Controller 24
If 0 is determined in step S7, the vehicle is stopped, or if it is determined in step S8 that the braking signal may be released, the front wheel brake is released in step S9.

Other Embodiments Further, the present invention is not limited to the above-described embodiment, and various modifications can be made as follows.

That is, in the above-described embodiment, the front wheel braking action is performed by the accelerator levers 42, 234.
Not only brake operation command by but also brake pedal 3
3, 233. That is, for example, during driving, the driver loses his / her driving posture or falls off the driver's seat 27 due to some factor, causing the brake pedals 33 and 233 to travel.
When the foot is released, the brake pedals 33 and 233 are raised and the safety brake is activated. Controller 4
0, 240 recognizes the information as a "brake operation command" by the brake pedals 33, 233 as safety brakes, and activates the rear wheel brake device without the "brake operation command" by the accelerator levers 42, 234. To brake the rear wheels 30, 230.

Further, as the front wheel brake device of the present invention, a cam type drum brake, a disc brake, or another type of brake which is operated by hydraulic pressure can be appropriately used in addition to the above-mentioned ones.

The swinging accelerator levers 42, 23
The accelerator means of the present invention shown as 4 is not limited to this, and may be, for example, a rotary or sliding means.

The safety brake means of the present invention shown as the brake pedals 33, 233 is not limited to this, and may be, for example, a button type.

Further, the existing oil pump or the like for cargo handling is also used for the operation of the front wheel brake. However, the present invention is not limited to this, and a hydraulic component dedicated to the front wheel brake may be provided.

[0049]

As described above, according to the reach type forklift of the present invention described in the first and second aspects, the brake is also applied to the front wheels, so that even if the rear wheels are locked, the vehicle can be sufficiently driven. It can give a great braking force. As a result, even when the fork is loaded with a load, sufficient braking force can be obtained, the braking distance can be reduced and the brake can be safely applied, and the difference in the braking distance between when the load is loaded and when the load is not loaded is reduced. In addition, it is possible to provide the driver with a braking feeling that does not change much. In addition, the ratio of the braking force of the front wheel relative to the rear wheel is increased as compared with the conventional case, and accordingly, the moment generated due to the rear wheel being displaced from the center in the vehicle width direction is reduced, and the braking time is reduced. Of the vehicle can be suppressed.

Further, according to the reach type forklift according to the third aspect, when the driver loses his / her driving posture or falls out of the driver's seat due to some factor during running and his foot is released from the brake pedal, the accelerator means is used. Even if there is no brake operation command, the front and rear wheels are braked, so that safety is further improved.

Further, according to the reach type forklift according to the fourth aspect, slip detection can be easily performed only by the rotation speed sensor, and the timing for applying a brake to the front wheels can be determined.

Further, according to the reach type forklift according to the fifth aspect, it is possible to prevent the feeling from being deteriorated due to the excessive braking force by the front wheel brake even when the front and rear wheels are rotating at high speed.

According to the reach-type forklift according to the sixth aspect, the front wheel brake works only when necessary, so that energy loss due to unnecessary braking is prevented, and a so-called regenerative mechanism is provided for the front wheel or the rear wheel. When connected, energy can be efficiently recovered.

Further, according to the reach type forklift according to the seventh aspect, the number of parts can be reduced and the cost can be reduced by using the existing oil pump for loading and unloading for operating the front wheel brake device. It has become.

According to the reach type forklift according to the present invention, the brake is applied to the pair of front wheels at the same time, so that the vehicle is stopped substantially in a straight line even if the rear wheels are displaced from the center in the vehicle width direction. be able to.

[Brief description of the drawings]

FIG. 1 is a perspective view of a reach type forklift according to Embodiment 1 of the present invention.

FIG. 2 is a perspective view when the instrument panel is viewed from the front.

FIG. 3 is a perspective view of the interior of the functional product when viewed from behind.

FIG. 4 is a side view showing a connection structure between a drive motor and a brake pedal.

FIG. 5 is a diagram showing a connection state between a control valve and a loading motor.

FIG. 6 is a diagram showing a hydraulic circuit of a front wheel brake.

FIG. 7 is a plan view of the reach type forklift according to the first embodiment of the present invention.

FIG. 8 is a front view showing a structure of a front wheel and a front wheel brake device of the reach type forklift according to the first embodiment of the present invention.

FIG. 9 is a front view showing a structure of a front wheel and a front wheel brake device of a reach type forklift according to a second embodiment of the present invention.

FIG. 10 is a side view showing a structure of a front wheel and a front wheel brake device of a reach type forklift according to Embodiment 3 of the present invention.

FIG. 11 is a diagram conceptually showing a configuration of a reach-type forklift according to a fourth embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a brake valve assembly in a reach type forklift according to Embodiment 4 of the present invention.

FIG. 13 is a flowchart illustrating an operation of a front wheel brake of a reach type forklift according to a fourth embodiment of the present invention.

FIG. 14 is a diagram showing a relationship between a slip ratio and a tire transmission force.

FIG. 15 is a diagram showing a front wheel brake hydraulic pressure map used for a reach type forklift according to Embodiment 4 of the present invention.

FIG. 16 is a side view of a conventional reach-type forklift.

FIG. 17 is a diagram conceptually showing a plane of a conventional reach-type forklift.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Reach type forklift 22 Reach leg 23, 223 Front wheel 24 Mast device 25, 225 Fork 27 Driver's seat 29 Machine stand 30, 230 Rear wheel 33, 233 Brake pedal 42, 234 Accel lever 43, 243 Oil pump 54 Rear wheel brake device 55a, 250 Rear wheel speed sensor 82, 246 Accumulator 111, 248 Front wheel brake device 120, 249 Front wheel speed sensor

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Claims (8)

[Claims] 1. A machine base located at a rear part of a vehicle and provided with rear wheels, a driver seat formed in the machine body, and a pair of left and right front wheels located at a front part of the vehicle and having a pair of left and right front wheels. A rear wheel brake device, comprising: a reach leg; a mast device slidable along the reach leg; and a pair of left and right forks supported by the mast device; And a slip detecting means for detecting slip of the rear wheel; and applying a brake to the front wheel when the slip detecting means detects occurrence of slip of the rear wheel when the brake operation command is issued. A reach type forklift comprising a front wheel brake device. 2. The brake operation command is issued when the safety brake means is operated, or when the accelerator means is moved in a direction opposite to the vehicle traveling direction while the safety brake means is not operated. The reach-type forklift according to claim 1, wherein: 3. The safety brake means is a brake pedal provided in the driver's seat. When the brake pedal is depressed, the safety brake means is in an inactive state, and the brake pedal is released. The reach-type forklift according to claim 2, wherein when the operation is performed, the safety brake means is in an operating state. 4. The reach type forklift according to claim 1, wherein the occurrence of the slip of the rear wheel is determined based on a slip speed. 5. The reach type forklift according to claim 1, wherein the occurrence of slip of the rear wheel is determined based on a slip ratio. 6. The front wheel brake device according to claim 1, wherein the front wheel is stopped, or when the speed of the vehicle approaches a stop, the accelerator is returned to a neutral position, or when the accelerator is moved in the same direction as the vehicle traveling direction. The reach-type forklift according to any one of claims 1 to 5, wherein the brake of the front wheel is released when the safety brake unit is in an inoperative state. 7. An oil pump for hydraulically driving the fork, and an accumulator for storing oil from the oil pump and supplying the oil to the front wheel brake device. Reach-type forklift described in. 8. The vehicle according to claim 1, wherein the rear wheel functions as a driving wheel and is provided at a position deviated from a center in a width direction of the vehicle, and the brake device simultaneously performs a braking action on the pair of left and right front wheels. The reach type forklift according to any one of claims 1 to 7.