JP2003238091A - Fork lift truck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fork lift truck ensuring the safety of an operator while effectively preventing the damage of a rack or the like due to the fork being caught on it. <P>SOLUTION: This fork lift truck is provided with a lifted height detecting means 26 for detecting the lifted height of a fork 5 for placing a load; a speed computing means 21 for computing the actual lifting speed V of the fork 5 on the basis of the variation of the lifted height; a speed determining means 22 for determining whether the actual lifting speed V is less than the allowable lower limit value Co of a predetermined lifting reference speed C; and an operation stop instructing means 23 for instructing the lifting operation stop of the fork 5 when the actual lifting speed V is determined to be less than the allowable lower limit value Co of the lifting reference speed C. <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 forklift truck, and more particularly to a technique for controlling a lift operation of a fork.

[0002]

2. Description of the Related Art Conventionally, a picking truck, which is a kind of forklift, has been used in the work of dispensing a wide variety of loads stored on rack shelves installed in a warehouse. Generally has a configuration as shown in FIG. That is,
This picking truck includes a vehicle body 1 in which a traveling and steering device, a hydraulic device (both not shown) for performing a lift (elevation) operation, and the like are incorporated.

A mast device 2 is erected on one end side of the vehicle body 1, and an operator rides on a lift bracket 3 which lifts along the mast device 2 to drive a picking truck. A driver's cab 4 and a fork 5 for cargo handling work are provided. Meanwhile, cab 4
An operating portion 6 is installed on the mast device 2 side, and the operating portion 6 includes a lift-up switch 7 and a lift-down switch 8 for instructing an operator to perform a lift operation.
An accelerator 9 for adjusting the traveling speed, a steering handle 10 for changing the traveling direction, and the like are provided.

The vehicle body 1 also has a built-in controller 11 for controlling the traveling and steering devices and the hydraulic device in accordance with the operation of the operating portion 6 by the operator. And
For example, when the lift-up switch 7 is operated, the controller 11 controls the hydraulic device to perform the lift-up operation, and when the lift-down switch 8 is operated, the lift-down operation is performed.

[0005]

However, when carrying out a load operation or a load operation using a forklift, the fork 5 during the lift operation may be caught on a rack shelf or the like due to an erroneous operation of the operator. As a result, there is a risk that the rack shelves may be damaged. Particularly, in a picking truck in which the driver's cab 4 lifts together with the forks 5, since the lift operation is continued despite the forks 5 being caught on the rack shelves, as soon as the forks 5 come off the racks and the like, Until then, the lift chain (not shown), which had been loosened by being caught on a rack shelf or the like, suddenly extended, and the driver's cab 4 could fall, which was a problem in ensuring the safety of the operator.

In order to solve such a problem, a sensor detects that an upward external force of a predetermined value or more is applied to the fork 5 during the lift down operation, and the lift down of the fork 5 is performed based on the detection signal from this sensor. A forklift configured to prohibit operation has been proposed. In addition,
In this forklift truck, a structure is adopted in which the fork 5 is supported by the lift bracket 3 so as to be capable of swinging upward in order to allow the fork 5 to move freely.

According to the forklift having such a structure, even if the fork 5 is caught on the rack shelf during the lift-down operation, it is possible to minimize the damage to the rack shelf and the like. It is possible to ensure the safety of the operator.

However, in this forklift, it is inevitable that the supporting structure of the fork 5 becomes complicated because the fork 5 needs to be swingable. Further, the fork 5 is for loading a load, and since a downward external force is applied to the fork 5 in a loaded state, the above configuration is applied to the fork 5 to a rack shelf or the like during lift-up operation. We couldn't solve the catching problem.

The present invention was devised in view of these inconveniences, and it is possible to effectively prevent a rack shelf or the like from being damaged due to a fork being caught, and it is possible to easily ensure the safety of an operator. The purpose is to provide.

[0010]

In order to achieve such an object, a forklift according to the invention of claim 1 is a lift detecting means for detecting a lift of a fork on which a load is placed,
Speed calculation means for calculating the actual lift speed of the fork based on the amount of change in lift, and speed judgment for judging whether or not the actual lift speed is below a preset lower limit of the lift reference speed And means for stopping operation of the lift of the fork when it is determined that the actual lift speed is lower than the lower limit of the lift reference speed.

With this configuration, when the actual forklift speed of the fork drops to less than the preset lower limit of the lift reference speed due to the fork being lifted during being caught on the rack shelf or the like. In addition, the lift operation of the fork is stopped when it is determined that the actual lift speed is less than the allowable lower limit value of the lift reference speed. Therefore, the lifting operation of the fork will not continue under the condition that the forks are caught on the rack shelves, resulting in damage to the rack shelves or threatening the safety of the operator. Will not happen.

A forklift according to a second aspect of the present invention is the forklift according to the first aspect, wherein the actual lift-up speed during the lift-up operation of the fork is less than the allowable lower limit value of the preset lift-up reference speed. If the following lift-down operation is permitted, and the actual lift-down speed during the lift-down operation of the fork is less than the preset lower limit of the lift-down reference speed, the subsequent lift-down operation is performed. It is characterized by comprising an operation permitting means for permitting a lift-up operation.

With the above arrangement, the lift-down operation is permitted after the lift-up operation of the fork is stopped, and the lift-up operation of the fork is permitted after the lift-down operation is stopped. Therefore, the state where the fork is caught on the rack shelf or the like can be promptly resolved, and the work of picking up and loading by the forklift can be restarted.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an external perspective view showing a simplified overall structure of a picking truck which is a type of forklift according to the present embodiment, and FIG. 2 is a functional block showing a simplified control system of a controller included in the picking truck. It is a figure. 3 is an explanatory diagram showing changes in the lift-up speed during the lift-up operation of the fork according to the present embodiment, and FIG. 4 is an explanatory view showing changes in the lift-down speed during the lift-down operation, FIG. 5 is a flowchart showing a control procedure executed by the controller according to the present embodiment.

As shown in FIG. 1, the picking truck according to the present embodiment includes a traveling and steering device including a traveling motor and a steering motor, and a drive circuit for these, a hydraulic motor for driving a hydraulic pump, and a flow path switching and Proportional valve for flow rate adjustment,
A vehicle body 1 including a hydraulic device (not shown) configured by these drive circuits and the like for performing a lift operation is provided, and a drive for traveling and steering is provided at the bottom of the vehicle body 1. A ring (not shown) is provided. A pair of left and right straddle arms 13 extend from one end of the vehicle body 1, and a road wheel 14 is pivotally supported at the tip of each straddle arm 13.

A pair of left and right mast devices 2 facing each other along the width direction of the vehicle body 1 are provided upright on one end side of the vehicle body 1. The mast device 2 includes an outer mast 15
And an inner mast 16 which is arranged inside each outer mast 15 and lifts along the outer mast 15.
It consists of and. A lift cylinder (not shown) is provided upright along the inner mast 16, and the inner mast 16 is expanded and contracted as the lift cylinder expands and contracts.
Works to lift.

Further, the picking truck is provided with a driver's cab 4 for an operator to board and drive the picking truck, and a fork 5 for cargo handling work.
These cab 4 and fork 5 are supported by a lift bracket 3 that lifts along the mast device 2. That is, with respect to a predetermined position of the lift bracket 3, one end is fixed to a lower position of the outer mast 15 and is lifted over a chain sprocket arranged on an upper end of the inner mast 16 (both are The other end (not shown) is fixed.

Therefore, the inner mast 16 is lifted according to the expansion and contraction of the lift cylinder. With the lift operation of the inner mast 16, the lift bracket 3 supporting the driver's cab 4 and the forks 5 is mounted on the inner mast 16. The lift operation is performed at double speed. In addition,
A pressure sensor (not shown) for detecting the supply pressure is branched and attached to a hydraulic pipe for supplying pressure oil to a lift cylinder that realizes these lift operations, and the pressure sensor is mounted on the fork 5. It is also supposed to function as a load sensor that detects the weight of the placed load.

On the other hand, at this time, the vehicle body 1 is provided with lift detecting means (not shown) such as a reel type potentiometer, a rotary encoder and a magnet sensor, and the lift bracket 3 may be provided depending on the lift detecting means. The lift of the fork 5 is detected via the. Further, the mast device 2 of the cab 4 supported by the lift bracket 3
An operation unit 6 is installed on the side, and a lift-up switch 7, a lift-down switch 8, an accelerator 9, a steering handle 10 and the like are arranged on the operation unit 6.

Reference numeral 17 in FIG. 1 is a head guard provided over the operator's cab 4 to cover the operator's head, 18 is a guard bar for preventing the operator from falling, and 19 is a traveling picking truck. It is a brake pedal for stopping the operation.

Furthermore, the vehicle main body 1 has a built-in controller 11 for integrally controlling independent and coordinated operations of the traveling and steering devices and the hydraulic device.

As shown in FIG. 2, the controller 11 here is a CP that functions as a speed calculation means 21, a speed determination means 22, an operation stop instruction means 23, and an operation permission means 24.
It is composed of U20, and is additionally provided with a memory 25 including a ROM and a RAM. Then, on the input side of the controller 11, a lift detecting means 26 for detecting the lift of the fork 5, a lift up switch 7, a lift down switch 8, and a load placed on the fork 5 are provided. Load sensor (pressure sensor) that detects weight
27 is connected.

A hydraulic motor drive circuit 28 and a proportional valve drive circuit 29, which constitute a hydraulic device, are connected to the output side of the controller 11, respectively. The controller 11 does not necessarily have the function as the operation permitting means 24, but it is preferable that the controller 11 has such a function.

Further, in the memory 25 of the controller 11, various kinds of necessary for realizing the lift-up operation and the lift-down operation of the fork 5 according to each of the lift reference speeds A to C shown in FIGS. The data is stored. That is, for example, data of the lift-up reference speed C during the lift-up operation, that is, the lift-up reference speed C selected according to the weight of the load detected by the load sensor 22 is stored in the memory 25 as shown in FIG. As shown in, the data is also stored including the data of the allowable width Δ of the speed change set in advance for each of the acceleration process, the constant speed process, and the deceleration process.

By the way, the memory 25 also stores the lift-up reference speeds A and B during the lift-up operation and the lift-down reference speeds A to C during the lift-down operation in the same manner as shown in FIG. Also, illustration is omitted in FIG. The speed calculating means 21 included in the controller 11 is the actual lift of the fork 5 by the CPU 20, which constitutes the controller 11, based on the amount of change in the lift of the fork 5 detected by the lift detecting means 25 per unit time. It is the process of calculating the speed.

The speed determining means 22 in the controller 11 means that the actual lift speed of the fork 5, for example, the lift-up speed V is less than the allowable lower limit value Co of the lift-up reference speed C which is a preset lift reference speed. Whether or not it becomes CPU2 which forms the controller 11
0 is a process of determination. Further, the operation stop instruction means 23 is a CPU that constitutes the controller 11 when it is determined that the actual lift speed, that is, the lift-up speed V is less than the allowable lower limit value Co of the lift-up reference speed C.
20 is a process of instructing the lift operation stop of the fork 5.

Further, the operation permitting means 24 of the controller 11 means a lift down operation after the actual lift-up speed V of the fork 5 becomes less than the allowable lower limit value Co of the preset lift-up reference speed C. This is a process of allowing the lift-up operation after the actual lift-down speed of the fork 5 becomes less than the allowable lower limit value of the preset lift-down reference speed, and this process is performed by the controller 11. It is performed by the configuring CPU 20.

That is, the memory 25 stores a program as shown in the flowchart of FIG. 5, and this program is executed by the CPU 20. for that reason,
In the picking truck according to the present embodiment, control according to the procedure of the flowchart is executed by the controller 11.

In this program, whether the lift-up operation is performed or not is determined depending on whether the lift-up switch 7 is turned on (S1). When the lift-up switch 7 is turned on, the hydraulic motor is operated. As the drive circuit 28 and the proportional valve drive circuit 29 are turned on and the lift cylinder extends, the fork 5 starts the lift-up operation together with the cab 4 (S2).

When the fork 5 starts the lift-up operation, its lift is detected by the lift detecting means 26 over time, and the detected lift of the fork 5 is input to the speed calculating means 21 ( S3). This speed calculation means 21
Then, the actual lift-up speed V of the fork 5 is calculated based on the input amount of change in lift (S4).
Subsequently, in the speed determination means 22, the actual lift-up speed V is compared with the preset lift-up reference speed C in each of the acceleration process, the constant speed process, and the deceleration process, and the actual lift-up speed V is compared. It is determined whether the up speed V is less than the allowable lower limit value Co of the lift up reference speed C (S5).

Then, unless the actual lift-up speed V of the fork 5 is less than the allowable lower limit value Co of the lift-up reference speed C, the lift-up operation of the fork 5 is continued (S6). However, if the fork 5 during the lift-up operation is caught on a rack shelf or the like, the lift-up speed V rapidly decreases. Therefore, the speed determination means 22 determines that the actual lift-up speed V has become less than the allowable lower limit value Co of the lift-up reference speed C (S5).

Then, the operation stop supporting means 23 gives an instruction for stopping the lift-up operation of the fork 5 to the hydraulic motor drive circuit 28 and the proportional valve drive circuit 29, and the hydraulic motor drive circuit 28 and the proportional valve. As a result of the drive circuit 29 being turned off, the lift-up operation of the fork 5 is stopped (S7). Therefore, fork 5
It is unlikely that the lift-up operation will be continued even though the vehicle is still caught on the rack shelf or the like.

After that, it is judged whether or not the lift down switch 8 is turned on (S8), and when the lift down switch 8 is turned on, the hydraulic motor drive circuit 28 and the proportional valve drive circuit 29. Are turned on to lift down the forks 5, and the lift cylinder shortening operation is started. As a result, the fork 5 starts the lift-down operation together with the cab 4 (S9), and the state where the fork 5 is caught on the rack shelf or the like is promptly eliminated.

That is, in this program, the actual lift-up speed V of the fork 5 becomes less than the allowable lower limit value Co of the preset lift-up reference speed C, and after the lift-up operation of the fork 5 is stopped, the operation is performed. The permitting means 24 permits the lift-down operation of the fork 5. When the controller 11 does not have the function as the operation permitting means 24, the lift-up speed V of the fork 5 becomes less than the allowable lower limit value Co of the lift-up reference speed C, and the lift-up operation of the fork 5 is performed. Even after being stopped, the lift down operation of the fork 5 is not allowed.

By the way, the lift-up operation of the fork 5 is controlled by the above-described procedure, but in the lift-down operation of the fork 5, the controller 11 executes the following control. That is, if the lift-up switch 7 is not turned on in S1 of the program shown in the flowchart of FIG. 5, it is determined whether the lift-down operation is performed or not depending on whether the lift-down switch 8 is turned on (S10). . When the lift down switch 8 is turned on, the hydraulic motor drive circuit 28 and the proportional valve drive circuit 29 are turned on and the lift cylinder performs a shortening operation, so that the fork 5 starts the lift down operation together with the cab 4 ( S11).

When the fork 5 starts the lift-down operation, its lift is detected by the lift detecting means 26, and the detected lift of the fork 5 is input to the speed calculating means 21 (S12). Then, the speed calculation means 21 calculates the actual lift-down speed of the fork 5 based on the amount of change in lift (S13), and the speed determination means 2
In 2, it is determined whether or not the actual lift down speed is below the preset lower limit of the lift down reference speed (S14). At this time, unless the lift-down speed of the fork 5 is less than the allowable lower limit value of the lift-down reference speed, the lift-down operation of the fork 5 is continued (S15).

However, when the fork 5 during the lift-down operation is caught on the rack shelf or the like, the actual lift-down speed is reduced, so the speed determination means 2
In No. 2, it is determined that the actual lift-down speed has become less than the lower limit of the lift-down reference speed (S1).
4). As a result, the operation stop supporting means 23 turns off the hydraulic motor drive circuit 28 and the proportional valve drive circuit 29, and the lift down operation of the fork 5 is stopped (S16).

Therefore, the lift-down operation of the fork 5 will not be continuously executed even though the fork 5 is still hooked on the rack shelf or the like. After that, it is determined whether or not the lift-up switch 7 is turned on (S17), and when the lift-up switch 7 is turned on, the hydraulic motor drive circuit 28 and the proportional circuit are operated so as to lift-up the fork 5. As a result of the valve drive circuit 29 being turned on, the fork 5 moves to the cab 4
At the same time, the lift-up operation is started (S18).

In the present embodiment, the forklift is a picking truck, but the scope of application of the present invention is not limited to the picking truck, and a general forklift other than the picking truck is used. For example, the present invention can be applied to a counterbalance type forklift and a reach type forklift.

[0040]

In the forklift according to the first aspect of the present invention, the actual lift speed of the fork is the allowable lower limit value of the preset lift reference speed due to the fork during the lift operation being caught on the rack shelf or the like. If the actual lift speed is determined to be less than the allowable lower limit of the lift reference speed, the lift operation of the fork is stopped when the actual lift speed is determined to be less than the lower limit. Therefore, the lifting operation of the fork is not continued while the fork remains caught on the rack shelf, and as a result, the rack shelf is not damaged or the safety of the operator is not jeopardized. . Therefore, regardless of the lift-up operation or the lift-down operation, it is possible to effectively prevent the rack shelf or the like from being damaged and ensure the safety of the operator.

According to the forklift of the second aspect of the present invention, the lift-down operation after the lift-up operation of the fork is stopped is allowed, and the lift of the fork after the stop of the lift-down operation is allowed. Up motion is also allowed. Therefore, it is possible to quickly eliminate the state in which the fork is caught on the rack shelf or the like, and it is possible to easily resume the loading operation and the loading operation by the forklift.

[Brief description of drawings]

FIG. 1 is an external perspective view showing a simplified overall structure of a picking truck, which is a type of forklift according to the present invention.

FIG. 2 is a functional block diagram showing a simplified control system of a controller included in the picking truck according to the present embodiment.

FIG. 3 is an explanatory diagram showing changes in lift-up speed during lift-up operation of the fork according to the present embodiment.

FIG. 4 is an explanatory diagram showing changes in lift-down speed during lift-down operation of the fork according to the present embodiment.

FIG. 5 is a flowchart showing a control procedure executed by the controller according to the present embodiment.

[Explanation of symbols]

5 forks 11 Controller 20 CPU 21 Speed calculation means 22 Speed determination means 23 Operation stop instruction means 24 Action Allowance Means 25 memory 26 Lifting height detection means C Lift-up reference speed Co allowable lower limit V Actual lift-up speed

Claims (2)

[Claims] 1. A lift detecting means for detecting a lift of a fork on which a load is placed, a speed calculating means for calculating an actual lift speed of the fork based on a change amount of the lift, and an actual lift. A speed determining means for determining whether or not the speed is lower than a preset lower limit of the lift reference speed, and a lift of the fork when it is determined that the actual lift speed is lower than the lower limit of the lift reference speed. A forklift, comprising: an operation stop instruction means for instructing operation stop. 2. When the actual lift-up speed becomes less than the lower limit of the preset lift-up reference speed during the lift-up operation of the fork, the subsequent lift-down operation is allowed and the fork of the fork is allowed. When the actual lift-down speed becomes less than the allowable lower limit value of the preset lift-down reference speed during the lift-down operation, it is provided with operation permitting means for permitting the subsequent lift-up operation. The forklift according to claim 1.