JP3539346B2 - Reach forklift - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reach type forklift, and more particularly to a brake device thereof.
[0002]
[Prior art]
FIG. 11 shows a side view of a conventional reach-type forklift. FIG. 12 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. A mast device 4 that supports a pair of left and right forks 3 is provided between the pair of reach legs 2 so as to be slidable along the reach leg 2. A front wheel 5 is provided at the front end of each reach leg 2. On the other hand, a machine base 7 having a driver's seat 6 is provided at the rear of the vehicle. Further, a first rear wheel 8 functioning as a driving wheel and a steering wheel and a second rear wheel 9 merely supporting the traveling of the vehicle are provided as support wheels for supporting the machine base 7 on the machine base 7. ing. The reach type forklift is provided with a brake device (not shown) that brakes only the first rear wheel 8.
[0003]
[Problems to be solved by the invention]
However, in the above-described conventional reach-type forklift, as shown in FIG. 11, when the load 10 is placed on the pair of forks 3, the weight W of the load 10 causes the front wheel 5 to move counterclockwise in the drawing. , The vertical downward load (hereinafter referred to as “rear wheel load”) N acting on the rear wheel 8 may decrease. Therefore, 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 increases by the weight of the load 10. In addition, there is a problem that the braking distance becomes long.
[0004]
Further, as shown in FIG. 12, the first rear wheel 8 on which the braking force is applied is displaced to one side from the center C in the vehicle width direction. Sometimes turned.
[0005]
The present invention has been made to solve such a conventional problem, and provides a reach type forklift capable of shortening a braking distance and reducing a turning amount of a vehicle during braking. The purpose is to do.
[0006]
[Means for Solving the Problems]
In order to achieve the above-described object, a reach-type forklift of the present invention is located at a rear portion of a vehicle, a machine provided with rear wheels, a driver seat formed in the machine, and a vehicle located at a front portion of the vehicle. 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, a pair of left and right forks supported by the mast device, and a slip for detecting slip of the rear wheel. Detecting means, functioning as a deadman brake, and a rear wheel brake device for applying a brake to the rear wheel when a brake operation command is issued; and a rear wheel brake by the rear wheel brake device. a hydraulic front wheel brake device for braking the front wheel when it detects a predetermined condition or more slippage of wheels, the operation of the hydraulic front wheel brake device Braking force change means for changing the front wheel brake force by acting on the hydraulic front wheel brake system oil which is stored in the accumulator at a desired selection pressure by the oil pump for handling in accordance with the pitching moment may act on the forklift And characterized in that:
[0007]
Further, preferably, the braking force changing means may change the front wheel braking force based on the lift of the fork, and furthermore, the front wheel braking device in consideration of the weight of a load mounted on the fork. The braking force may be changed.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0009]
Embodiment 1 FIG.
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 parallel to each other and separated 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 so as to be slidable along the reach legs 22. A pair of left and right forks 25 are attached to the mast device 24 via lift brackets 26.
[0010]
On the other hand, a machine base 29 having a driver's seat 27 and a functional product room 28 is provided at the rear of the vehicle. A first rear wheel 30 that functions as a drive wheel and a steering wheel is provided below the functional product room 28. Further, below the driver's seat 27, a second rear wheel 31 is provided as a support wheel for supporting the machine base 29, the second rear wheel 31 only following the traveling of the vehicle. On the floor 32 of the driver's seat 27, a so-called deadman type brake pedal 33 is provided. That is, the brake pedal 33 functions as a safety brake such that the brake is released when the driver steps on the brake pedal 33 and the vehicle does not run when the driver does not step on the brake pedal. The driver's seat 27 is provided with an accelerator lever 34 as accelerator means for moving the vehicle forward and backward and accelerating and decelerating.
[0011]
As shown conceptually in FIG. 2, the machine base 29 has a controller 40, a cargo handling motor 41, an oil pump 42, an oil tank 43, an oil control valve 44, a brake valve assembly 45, an accumulator 46, and a pressure switch 47. Is provided. A drum type front wheel brake device 48 and a front wheel speed sensor 49 are provided near each of the pair of front wheels 23. In the vicinity of the rear wheel 30, a rear wheel brake device and a rear wheel speed sensor 50 (not shown) are provided. The brake valve assembly 45 includes a pressure reducing valve 60, a shut-off valve 61, and a linear solenoid valve 62, as shown in FIG.
[0012]
Also, as shown in FIGS. 4A and 4B, the mast device 24 includes an inner mast 70 that supports the fork 25 so as to be able to move up and down, an outer mast 71 that supports the inner mast 70 so that it can be moved up and down, and a fork 25. A switch 72 and a switch operating unit 73 are provided as a lift detecting means for detecting the height of the switch. The switch 72 is attached to the outer mast 71, and the switch operating section 73 is attached to the inner mast 70. The fork 25 is configured to move up along the inner mast 70 with the operation of moving the inner mast 70 up along the outer mast 71. Therefore, when the fork 25 rises to the set height, the switch operating section 73 activates the switch 72 due to the rise of the inner mast 70. Accordingly, it is determined whether the height of the fork 25 is higher than the set height specified for the switch 72. Is detected.
[0013]
Next, the operation of the reach type forklift having such a configuration 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 in an up state, and this state is an operation state of the safety brake, and The rear wheel 30 is braked by a typical link. At this time, the information that the safety brake is in operation and the information that the front wheel 23 is stopped, that is, the information that the rotation speed of the front wheel 23 is zero are also sent to the controller 40, whereby the front wheel brake device 48 Remains released.
[0014]
Next, when the reach type forklift 21 is driven, first, when the driver steps on the brake pedal 33, the rear wheel brake device acting on the rear wheel 30 is released. Then, when the driver swings the accelerator lever 34 forward of the vehicle, the operation is sent to the controller 40 as an accelerator lever forward signal, and the forward movement of the vehicle starts. Next, when decelerating or stopping the vehicle, when the accelerator lever 34 is swung to the rear of the vehicle, the operation is sent to the controller 40 as an accelerator lever reverse signal. Thereby, the controller 40 recognizes that the accelerator lever 34 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 30.
[0015]
Here, when the load is mounted on the fork 25, the wheel load of the drive wheel (first rear wheel) may decrease depending on the position of the mast in the sliding direction. For this reason, when the brake is applied to the rear wheel 30, the braking capability of the brake is larger than the transmission force of the tire, and the rear wheel 30 may lock or slip, and the braking force may be insufficient. If the rear wheel 30 is not locked or the like, the rotation speeds of the front wheel 23 and the rear wheel 30 are almost 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. Should be. On the other hand, when the rear wheel 30 is locked or the like, the rotation speed calculated from the rotation speed of the rear wheel 30 becomes substantially zero. During that time, the front wheel 23 which is a driven wheel rotates because the vehicle is moving forward. Subsequently, the rotation speed obtained from the rotation speed of the front wheel 23 detected by the front wheel rotation speed sensor 49 is not zero. Therefore, when the rear wheel 30 is locked or the like, a difference occurs in the rotation speed between the front wheel 23 and the rear wheel 30, that is, a slip speed occurs.
[0016]
Therefore, when the slip speed, which is the difference between the rotational speeds of the front wheel 23 and the rear wheel 30, becomes equal to or more than a predetermined value, the rear wheel 30 is locked or slipped, and the front wheel 23 needs to be braked. It is determined that there is, and the front wheel 23 is also braked by the front wheel brake device 48. 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.
[0017]
In addition, when the load is loaded, when the fork 25 is raised, the position of the center of gravity of the fork 25 and the load is also raised accordingly, and as a result, the position of the center of gravity of the entire forklift is also raised. Therefore, even if the same braking force is applied, a large pitching moment (moment of forward fall) is applied by an amount corresponding to an increase in the center of gravity of the entire forklift, which may cause anxiety to the driver. Therefore, in the present invention, as described above, the braking force applied to the front wheel 23 by the front wheel brake device 48 is changed as follows in consideration of the magnitude of the pitching moment that is assumed to act on the forklift during braking. ing.
[0018]
As shown in FIG. 5, when the brake operation command by the accelerator lever 34 is input to the controller 40 in step S1, the controller 40 determines whether the slip speed of the front and rear wheels is equal to or more than a predetermined value in step S2. Here, if the slip speed is less than the predetermined value, it is determined that the rear wheel is not locked or the like so that the front wheel brake is required, and the normal braking action is performed only by the rear wheel brake. On the other hand, when the slip speed is equal to or higher than the predetermined value, the target hydraulic pressure is acquired from the brake hydraulic pressure map shown in FIG. That is, the controller 40 receives information on whether or not the fork 25 detected by the switch 72 has risen above the set height, and if the fork 25 has not risen above the set height, The controller 40 selects the normal hydraulic pressure, and if the pressure is higher than the set height, the correction hydraulic pressure lower than the normal hydraulic pressure is low enough that the pitching operation in the front-rear direction during braking does not deteriorate the driver's feeling. select. When the selection of the brake fluid pressure is completed, the controller 40 activates the front wheel brake in step S4.
[0019]
2 and 3, the controller 40 energizes the shut-off valve 61 and the linear solenoid valve 62 to open the shut-off valve 61 and open the linear solenoid valve 62 so as to generate a selected hydraulic pressure. Adjust the volume. Thus, the oil stored in the accumulator 46 acts on the front wheel brake device 48 at a desired selected hydraulic pressure, and the pair of front wheels 23 is braked. At this time, if the fork 25 is higher than the set height, the front wheel braking force is set low and the excessive front wheel braking force is prevented from acting, so that the pitching operation of the vehicle is promoted. Therefore, the braking distance can be reduced without deteriorating the driver's feeling even when the fork is elevated. Further, the release of the hydraulic pressure of the front wheel brake device 48 is performed only by operating the linear solenoid valve 62 to communicate the front wheel brake device 48 with the oil tank 43. Therefore, the supply and release of the hydraulic pressure to the front wheel brake device 48 are not performed. Substantially, only the linear solenoid valve 62 can be used.
[0020]
Also, the accumulator of the oil to the accumulator 46, is performed as follows. When carrying out the cargo handling work, the cargo handling motor 41 is activated and the oil pump 42 is driven. Thus, the oil in the oil tank 43 is supplied to the oil control valve 44 for generating a hydraulic pressure for the cargo handling operation, and is also supplied to the accumulator 46 via the pressure reducing valve 60. When the pilot pressure of the pressure reducing valve 60 becomes equal to or higher than a predetermined value, the pressure reducing valve 60 closes, and the fluid pressure in the accumulator 46 is kept constant by the action of the shut-off valve 61 and the check valve 60a during the closing. . When the cargo handling operation is not performed, when the hydraulic pressure in the accumulator 46 monitored by the pressure switch 47 drops below a certain value, the oil pump 42 is driven by the controller 40 to accumulate the pressure in the accumulator 46. It has become so.
[0021]
When the front wheel brake is applied as described above, the controller 40 determines whether or not the vehicle has stopped at step S5 in FIG. If the vehicle is not stopped, it is further determined in step S6 whether or not the braking signal may be released. That is, if the sliding speed of the front and rear wheels is less than the predetermined value, it is determined that the rear wheels are not locked or the like so that the front wheel brake is required. If the controller 40 determines in step S5 that the vehicle is stopped, or determines in step S6 that the brake signal may be released, the controller 40 releases the front wheel brake in step S7.
[0022]
Further, the above-described front wheel braking operation is performed not only by a braking operation command by the accelerator lever 34 but also by inputting information on a safe brake operating state by the brake pedal 33. That is, for example, when the driver loses his / her foot from the brake pedal 33 due to a driving posture collapse or falling from the driver's seat 27 for some reason during traveling, the brake pedal 33 is raised and the safety brake is activated. The controller 40 recognizes the information and, even if there is no “brake action command” by the accelerator lever 34, the rear wheel 30 is braked by the action of the rear wheel brake device that is mechanically applied. If so, the front wheel brake is applied, and the front wheel braking force is changed and adjusted according to the lift of the fork 25.
[0023]
Embodiment 2 FIG.
Next, a reach type forklift according to Embodiment 2 of the present invention will be described. In the present embodiment, the outer mast 71 is provided with two switches, and uses a brake hydraulic pressure map having two corrected hydraulic pressure values as shown in FIG. 7 accordingly. As a result, a more appropriate brake fluid pressure can be obtained than in the case where there is one correction fluid pressure value. Further, the correction hydraulic pressure value is not limited to two, and may be implemented with three or more.
[0024]
Embodiment 3 FIG.
Next, a reach type forklift according to Embodiment 3 of the present invention will be described. In the present embodiment, a brake hydraulic pressure map as shown in FIG. 8 in which the correction hydraulic pressure changes steplessly according to the lift of the fork is used. That is, for example, a wire or a chain is connected to the inner mast, and the amount of sliding of the wire or the like due to the raising and lowering of the inner mast is detected by a reel with a built-in encoder or potentiometer, thereby detecting the lift of the fork 25. Then, as shown in the map of FIG. 8, when the lift is equal to or less than a predetermined value, the normal hydraulic pressure is used. Thereby, the brake fluid pressure can be continuously changed according to the lift of the fork 25, and the front wheel braking force that satisfies a more optimal balance from the viewpoint of shortening the braking distance and preventing the feeling from being deteriorated due to the pitching operation. Can be obtained.
[0025]
Embodiment 4 FIG.
Next, a reach type forklift according to Embodiment 4 of the present invention will be described. In the present embodiment, a brake hydraulic pressure map as shown in FIG. 9 is used in which the hydraulic pressure for the front wheel brake is changed in consideration of not only the lift of the fork 25 but also the weight of the load mounted on the fork 25. Specifically, a loading pressure sensor is provided in the oil passage connected to the loading cylinder of the fork, and the weight of the load detected thereby is recognized in three classes of "light", "medium" and "heavy" and recognized. In addition, the lift of the fork is recognized in three classes of "low", "medium" and "high". When the lift is in the "low" class, the front wheel brake is applied by the normal hydraulic pressure regardless of the load, and when the lift is in the "medium" class, the load is in the "heavy" class. Only apply the front wheel brake with the corrected hydraulic pressure lower than the normal hydraulic pressure, and apply the front wheel brake with the corrected hydraulic pressure when the load is in the "medium" and "heavy" class when the lift is in the "high" class To do. In other words, in other words, the larger the weight of the load, the lower the fork lift, which is the boundary between the normal hydraulic pressure and the correction hydraulic pressure, is set lower. This reduces the front wheel braking force to reduce pitching motion when the load is heavy even in the middle lift class, and brakes without reducing the front wheel brake force when the load is light even in the high lift class. It is possible to obtain a sufficient front wheel brake to shorten the distance, and it is possible to change the front wheel braking force according to a practical requirement. The classes of the weight and the height of the load are not limited to three classes, but two classes or four or more classes can be adopted.
[0026]
Embodiment 5 FIG.
Next, a reach type forklift according to a fifth embodiment of the present invention will be described. In the present embodiment, a brake hydraulic pressure map as shown in FIG. 10 in which the correction hydraulic pressure is continuously changed in consideration of the lift of the fork 25 and the weight of the load is used. A loading pressure sensor is provided in the oil passage connected to the loading cylinder of the fork in the same manner as in the fourth embodiment, and a value obtained by multiplying the weight of the load detected by the sensor by one-half of the fork lift is used as an evaluation target value. When the value to be evaluated is less than a predetermined value, a constant normal hydraulic pressure is used. When the value is more than the predetermined value, a corrected hydraulic pressure that decreases in inverse proportion to the increase in the value to be evaluated is used. This makes it possible to change the front wheel braking force more realistically, taking into account the weight of the load, and to achieve a more optimal balance of the front wheel braking force in terms of shortening the braking distance and preventing deterioration in feeling due to pitching operation. Can be obtained.
[0027]
Other embodiments.
Further, the present invention can be carried out in the following modes in addition to the embodiments described above.
That is, as the front wheel brake device of the present invention, other types of brakes such as a disc brake can be appropriately used in addition to the drum type brake.
[0028]
Further, the accelerator means of the present invention is shown as the swing type accelerator lever 34, but is not limited to this, and may be, for example, a rotary or slide type accelerator means.
[0029]
Further, the safety brake means of the present invention is shown as the brake pedal 33, but is not limited thereto, and may be, for example, a button type.
[0031]
【The invention's effect】
As described above, according to the reach-type forklift of the present invention, a sufficient braking force can be obtained even when a load is mounted on a fork, a braking distance can be reduced, and a brake can be safely applied. It is possible to reduce the difference in braking distance between when the vehicle is mounted and when the vehicle is not mounted, and to provide the driver with a braking feeling that does not change much. In addition, the front wheel braking force is changed based on the lift of the fork and also taking into account the weight of the load loaded on the fork. It is possible to prevent the feeling from being deteriorated due to the pitching operation during the loading and unloading of heavy objects.
[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 diagram conceptually showing a configuration of a reach-type forklift according to Embodiment 1 of the present invention.
FIG. 3 is a diagram showing a configuration of a brake valve assembly of the reach type forklift according to the first embodiment of the present invention.
FIG. 4 is a diagram illustrating an outline of a mast device of the reach-type forklift according to the first embodiment of the present invention.
FIG. 5 is a flowchart illustrating an operation of a front wheel brake of the reach type forklift according to the first embodiment of the present invention.
FIG. 6 is a diagram showing a front wheel brake hydraulic pressure map used in the reach type forklift according to the first embodiment of the present invention.
FIG. 7 is a diagram showing a front wheel brake hydraulic pressure map used for a reach type forklift according to Embodiment 2 of the present invention.
FIG. 8 is a diagram showing a front wheel brake hydraulic pressure map used for a reach type forklift according to Embodiment 3 of the present invention.
FIG. 9 is a diagram showing a front wheel brake hydraulic pressure map used in a reach type forklift according to Embodiment 4 of the present invention.
FIG. 10 is a diagram showing a front wheel brake hydraulic pressure map used for a reach type forklift according to Embodiment 5 of the present invention.
FIG. 11 is a side view of a conventional reach-type forklift.
FIG. 12 is a diagram conceptually showing a plane of a conventional reach-type forklift.
[Explanation of symbols]
21 Reach type forklift 22 Reach leg 23 Front wheel 24 Mast device 25 Fork 27 Driver's seat 29 Machine stand 30 Rear wheel 48 Front wheel brake device 49 Front wheel speed sensor 50 Rear wheel speed sensor

Claims (3)

A machine located at the rear of the vehicle and provided with rear wheels,
A driver seat formed in the machine stand;
A pair of left and right reach legs having a pair of left and right front wheels, located at the front of the vehicle,
A mast device slidable along the reach leg,
A pair of left and right forks supported by the mast device,
Slip detection means for detecting the rear wheel slip,
A rear wheel brake device that functions as a deadman brake and applies a brake to the rear wheel when a brake operation command is issued,
A hydraulic front wheel brake device that applies a brake to the front wheel when the slip detection unit detects the occurrence of slippage of a predetermined condition or more of the rear wheel by rear wheel braking by the rear wheel brake device;
By operating the oil stored in the accumulator by the oil pump for cargo handling at a desired selected hydraulic pressure on the hydraulic front wheel brake device according to the pitching moment that can act on the forklift when the hydraulic front wheel brake device is operated, the front wheel braking force is increased. And a brake force changing means for changing the force of the forklift. The reach-type forklift according to claim 1, wherein the brake force changing means changes the front wheel brake force based on a lift of the fork. The reach-type forklift according to claim 2, wherein the braking force changing means changes the front wheel braking force in consideration of a weight of a load mounted on the fork.

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