JP2002020093A - Load lifter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load lifter capable of performing a proper operation control for various characteristic variations according to the size of loads by detecting the weight of a lifted load. SOLUTION: This load lifter comprises speed detection means 15 and 21 for detecting the lifting speed of the load, a storage means 20 having the data showing the relation between the weight of the load and the lifting speed under the load stored therein beforehand, and a load judgment means 21 for judging the weight of the load based on the lifting speed of the load detected by the speed detection means 15 and 21 and the data stored in the storage means 20. The weight of the load is detected by a difference in lifting speed of the load, and the operation control according to the magnitude of the load is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load lifting device such as a forklift for lifting and lowering and transporting various loads, and a stacker crane for loading and unloading loads stored in a rack. The present invention relates to a technology for detecting and performing appropriate operation control according to the load.

[0002]

2. Description of the Related Art In general, in a load lifting device, for example, a forklift, when a load is not loaded on a fork and when a load is loaded on a fork, various factors such as a steering ability and a braking ability during traveling are used. Changes.

Therefore, in the prior art, a presence sensor such as a limit switch is provided at a place where a load is placed on a fork to detect the presence or absence of the load, and thereby the operation according to the change in the characteristics between no load and load. Control is performed.

[0004]

However, various changes in characteristics such as the steering ability and the braking ability during traveling have a great influence not only on the presence or absence of a load but also on the weight of the load. Therefore, as in the past, merely providing a presence sensor for detecting the presence / absence of a load cannot be detected at a large load, and operation control sufficiently responds to changes in various characteristics. Difficult to do.

As a countermeasure, for example, it is conceivable to directly detect the magnitude of the load by providing a pressure sensor at the place where the load is placed on the fork. However, the provision of the pressure sensor is not advisable because it leads to an increase in cost since extra parts and devices are added.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and detects the weight of a baggage which is lifted and lowered by using existing equipment as it is, and performs an appropriate operation according to the magnitude of the load. An object of the present invention is to provide a luggage elevating device capable of performing control.

[0007]

The present invention has the following features to attain the object mentioned above.

That is, in the load lifting device according to the first aspect, speed detecting means for detecting the lifting speed of the load, and data indicating the relationship between the weight of the load and the lifting speed under the load are stored in advance. It is characterized by comprising storage means, and load determining means for determining the weight of the load based on the lifting / lowering speed of the load detected by the speed detecting means and data stored in the storage means.

Thus, when lifting or lowering the load placed on the fork, the speed at the time of ascending becomes slower when the load is large, and conversely, the speed becomes faster at the time of descending. The magnitude of the load can be determined, and based on the result of the determination, it becomes possible to perform operation control suitable for various characteristic changes depending on the magnitude of the load.

Normally, the luggage lifting device is provided with a lifting encoder for generating a pulse train of a number corresponding to the lifting distance of the fork in order to detect the lifting height of the fork on which the load is placed. As described in Item 2, it is convenient to use the existing lifting encoder as a part of the speed detecting means, because the magnitude of the load can be detected without providing a pressure sensor or the like.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described by taking an unmanned forklift as an example of a load lifting device.

FIG. 1 is a side view showing an entire configuration of an unmanned forklift according to an embodiment of the present invention. In the figure, reference numeral 1 denotes an entire unmanned forklift, 2 denotes a vehicle body,
Reference numeral 3 denotes a two-stage mast which is vertically provided on the front side of the vehicle body 2, 4 denotes a lift bracket attached to the mast 3, 5 denotes a fork fixed to the lift bracket 4, 6
Is a load placed on the fork 5.

Reference numeral 7 denotes a traveling wheel provided on the left and right of the front side of the vehicle body 2, 8 denotes a single driving steering wheel provided behind the vehicle body 2, and 9 denotes a traveling driving device for driving the driving steering wheel 8. , 1
Reference numeral 0 denotes a steering device for steering the drive steered wheels 8. Reference numeral 11 denotes a magnetic sensor provided on the vehicle body 2 for automatically traveling the unmanned forklift 1, and reference numeral 12 denotes a metal magnetic rod embedded in a road surface for automatically traveling the unmanned forklift 1.

Further, the vehicle body 2 is provided with a lifting motor 14 for driving the fork 5 up and down, and a lifting encoder 15 for detecting the lifting height of the fork 5.
The lifting encoder 15 and the fork 5 are connected by a wire 16 and a wire 1
6 is guided by a guide roller 17. The vehicle body 2 includes the above components 9, 10, 1
A controller 13 for controlling the control units 4,... Is provided.

For example, a rotary encoder is applied as the lifting encoder 15, and a wire 16 is pulled out from the lifting encoder 15 as the fork 5 moves up.
Further, as the wire 16 is wound around the elevating encoder 15 as the fork 5 moves down, the elevating encoder 15 rotates according to each operation, and accordingly, the elevating encoder 15 moves from the elevating encoder 15 to the elevating distance of the fork 5. A corresponding number of pulse trains are generated.

FIG. 2 is a block diagram schematically showing a control system for controlling the operation of the unmanned forklift 1.

In FIG. 1, reference numeral 9 denotes a traveling drive device, 10 denotes a steering device, 14 denotes an elevating motor, and 15 denotes an elevating encoder. These components are the same as those in FIG.

The controller 13 includes a memory 20 and an operation control unit 21. The memory 20 is storage means composed of a ROM, a RAM, or an external storage device. As shown in FIG. 3, the memory 20 stores the weight of the load 6 and the lifting and lowering of the fork 5 under the load. Data indicating the relationship with the speed is stored in advance. That is, when lifting or lowering the load 6 placed on the fork 5, when a large load is applied to the fork 5, the speed at the time of lifting becomes slow, and conversely,
The descent speed is faster. Accordingly, the memory 20 has a characteristic curve indicating the relationship between the load moving downward and the ascending / descending speed indicated by the solid line in FIG. Correspondingly, characteristic curves indicating the relationship between the upward-sloping load and the ascending / descending speed as shown by the broken lines in FIG.

The arithmetic and control unit 21 determines the weight of the load 6 based on the detection output from the elevation encoder 15 and the data stored in the memory 20 and controls the traveling drive unit 9 and the steering unit 10. To do
The arithmetic control unit 21 constitutes a part of the speed detecting means in the claims and also functions as a load determining means.

Next, in the unmanned forklift 1 having the above-described configuration, the detection of the weight of the load 6 and the associated operation control operation will be described with reference to the flowchart shown in FIG. The symbol S means a step.

When the fork 5 is moved up and down by driving the elevating motor 14, the arithmetic and control unit 21
Of the fork 5 on which the load 6 is placed is detected from the detection output of the fork 5 and the driving time of the lifting motor 14.

On the other hand, when detecting the weight of the load 6 placed on the fork 5, the arithmetic control unit 21
The fork 5 on which the load 6 is placed is moved up or down by the drive control of 4 (S1). Then, the elevation encoder 15 rotates in accordance with this, and accordingly, the number of pulse trains corresponding to the elevation distance of the fork 5 is generated from the elevation encoder 15 as shown in FIG. In this case, for example, as shown in FIG. 4A, the more the number of pulses per unit time T, the faster the fork 5 moves up and down,
(B) When the number of pulses is small, the lifting speed of the fork 5 is slow.

Then, since this pulse train is taken into the arithmetic control unit 21 (S2), the arithmetic control unit 21 counts the number of pulses N per unit time T output from the elevation encoder 15 and calculates the number of pulses based on the following equation. Then, the vertical speed V of the load 6 is calculated (S3). V = kN / T (where k is the moving distance of the fork corresponding to one pulse)

Subsequently, the arithmetic and control unit 21 determines the weight of the baggage 6 based on the value of the lifting / lowering speed V obtained based on the above equation and the data of FIG. 3 stored in the memory 20. (S4, 5). That is, the arithmetic control unit 21
When the load 6 is lifted by the lift motor 14, the load value corresponding to the lift speed V obtained by the equation is determined using the characteristic curve indicating the relationship between the load and the speed indicated by the solid line in FIG. Conversely, when the load 6 is lowered by the lifting motor 14, the value of the load corresponding to the lifting speed V obtained by the equation using the characteristic curve indicating the relationship between the load and the speed indicated by the broken line in FIG. To determine.

The arithmetic and control unit 21 sets the luggage 6
When the weight of the vehicle is determined, the traveling drive device 9 and the steering device 1 are driven so as to be adapted to the magnitude of the load.
Control 0. For example, it is determined whether or not the load calculated as described above is within a predetermined ratio (for example, 70%) of the maximum load that can be raised and lowered by the fork 5 (S6). It is determined that the danger is low, and traveling at the normal maximum speed is allowed (S7). On the other hand, if the predetermined ratio is exceeded in S6, it is determined that the danger is high, and the limit value of the maximum traveling speed is set (for example, set to 80% of the maximum speed of normal traveling).
(S8), it is restricted so that the vehicle cannot run at a higher speed.

It should be noted that, in addition to the traveling control described above, heavy luggage 6
When the load is loaded, the timing of the start of braking by the traveling drive device 9 may be earlier than in the case of the light luggage 6, or the timing of starting the turning of the drive steered wheels 8 by the steering device 10 may be shortened. Operation control suitable for accompanying various characteristic changes is performed.

Further, operation control as shown in FIG. 6 may be performed. That is, when the load is calculated by the arithmetic control unit 21 in the same procedure as in FIG.
Next, it is determined whether the load is within a preset allowable load (S1).
0) If it is within the allowable load, it is determined that there is relatively little risk, and the continuation of the work is permitted (S11). On the other hand, if the load exceeds the allowable load in step 6, it is determined that there is a high risk in the overloaded state, and an emergency stop is performed (S12).

With respect to the above embodiment, the following modifications and applications can be considered. In the above-described embodiment, an unmanned forklift 1 has been described as an example of a load lifting device, but the present invention is not limited to this, and the present invention can be applied to a manned forklift. In this case, for example, as shown in FIG. 7, when the load is calculated by the arithmetic control unit 21 in the same procedure as in FIGS. 5 and 6 for S1 to S5, the calculated load value is stored in the driver's seat. It may be displayed on a display such as an LCD provided (S21) so that the worker can recognize the current load. Further, the present invention can be applied to a device such as a stacker crane or a picking lift for loading and unloading luggage stored in a rack.

In the above embodiment, the lifting speed V is detected by detecting the number of pulses in the unit time T by the lifting encoder 15.
It is also possible to detect the ascending and descending speed V by measuring the time during which the robot moves a certain distance L. In such a case, instead of using the elevation encoder 15 as described above, a pair of upper and lower limit switches, a photocoupler, and the like are attached to the mast 3 at a fixed distance L to constitute the speed detecting means. be able to.

[0030]

According to the present invention, the following effects can be obtained. (1) In a luggage elevating device, the weight of the luggage can be determined based on the difference in the lifting speed depending on the weight of the luggage when the luggage placed on the fork is raised and lowered, and the load is determined based on the determination result. It is possible to perform appropriate operation control suitable for various characteristic changes due to differences in the above.

(2) In particular, if an existing elevation encoder provided for detecting the elevation of a fork carrying a load is used as part of the speed detection means, the load can be directly detected. It is not necessary to provide a pressure sensor or the like, which can avoid an unnecessary increase in cost.

(3) Further, by detecting the load, it is determined whether or not the load is dropped, and further, the load is raised or lowered, such as whether or not the load placed on the fork is proper. It is also possible to determine whether there is an abnormality in the luggage to be performed.

[Brief description of the drawings]

FIG. 1 is a side view showing an entire configuration of an unmanned forklift according to an embodiment of the present invention.

FIG. 2 is a block diagram schematically showing a control system for performing operation control in the unmanned forklift according to the embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between the weight of a load placed on a fork and a fork elevating speed at that time in the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an example of a pulse train output from a lifting encoder in the embodiment of the present invention.

FIG. 5 is a flowchart for explaining an operation when the operation control of the luggage elevating device according to the embodiment of the present invention is performed.

FIG. 6 is a flowchart for explaining an operation when another operation control is performed in the luggage elevating device of the present invention.

FIG. 7 is a flowchart illustrating still another operation of the luggage elevating device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Unmanned forklift 2 Body 5 Fork 6 Luggage 9 Travel drive 10 Steering device 14 Elevation motor 15 Elevation encoder 20 Memory (storage means) 21 Operation control part (load judgment means)

Claims (2)

[Claims] 1. A speed detecting means for detecting a lifting / lowering speed of a load, a storage means in which data indicating a relationship between a weight of the load and a lifting / lowering speed under the load is stored in advance, and the speed detecting means detects the speed. A load judging device for judging the weight of the baggage based on the determined lifting speed of the baggage and the data stored in the storage device. 2. The luggage elevating device according to claim 1, wherein said speed detecting means includes an elevating encoder for generating a pulse train of a number corresponding to an elevating distance of the luggage.