JPH06199404A - Stacker crane - Google Patents

Abstract

PURPOSE:To offer a stacker crane capable of making a minute control of crane traveling speed and acceleration and deceleration in accordance with the weight of a load carried on an elevating base and making efficient transport according to the weight or the load. CONSTITUTION:This stacker crane 1 is equipped with a detecting means, which detects the weight of a load carried on an elevating base 4 of the crane 1, and a speed control means which makes the crane 1 travel fast when the weight of the load detected by the detecting means is light and makes the crane 1 travel slow when the weight of the load detected by the detecting means is heavy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stacker crane. In particular, the present invention relates to a stacker crane capable of finely controlling the speed of the crane according to the weight of the load mounted on the lifting platform of the crane.

[0002]

2. Description of the Related Art In factories, warehouses, etc., a shelf station having a plurality of shelves arranged in a matrix in order to temporarily store products and workpieces, and a station by running and elevating the front of the shelf station. An automated warehouse consisting of a stacker crane that conveys loads to and from shelves is used. The stacker crane includes a traveling machine body and an elevating platform that moves up and down along a mast that is erected on the traveling machine body, and is equipped with various sensors and a control device connected to the sensors.
It controls the lifting of the lift.

Generally, a stacker crane determines the presence or absence of a load by means of a load sensor provided on a lift table. The traveling speed and acceleration / deceleration of the crane are controlled according to the presence or absence of a load.

[0004]

The above-mentioned conventional stacker crane has the following problems.

The traveling speed and acceleration / deceleration of the crane are controlled according to the presence or absence of luggage, and not the weight of luggage. Therefore, there is a problem that it is not possible to carry out the transportation efficiently according to the weight of the package.

The object of the present invention is to solve the above problems and to control the traveling speed and acceleration / deceleration of a crane in accordance with the weight of the load to be mounted on the lifting platform. An object of the present invention is to provide a stacker crane that can perform efficient transportation according to weight.

[0007]

In order to achieve the above object, the present invention provides a detecting means for detecting the weight of a load mounted on a lifting platform of a crane, and a light weight of the load detected by the detecting means. Sometimes, the crane is made to travel fast, and when the weight of the load detected by the detection means is heavy, a speed control means for causing the crane to travel slowly is provided.

[0008]

Since the present invention has the above-described structure, the following operational effects are obtained.

That is, the detection means detects the weight of the load mounted on the lifting platform of the crane, and the speed control means causes the crane to travel fast when the weight of the load detected by the detection means is low, and the detection means. Since the crane is made to travel late when the weight of the load detected by is heavy, the speed of the crane is finely controlled according to the weight of the load mounted on the lifting platform.

As described above, according to the stacker crane of the present invention, it is possible to finely control the traveling speed and acceleration / deceleration of the crane according to the weight of the load to be mounted on the lift, and to adjust the load according to the weight of the load. There is an effect that efficient transport can be performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments shown in the drawings will be described below.

<First Embodiment> FIG. 1 is a front view showing a first embodiment of a stacker crane according to the present invention, and FIG. 2 is a block diagram for explaining the detection means and speed control means.

In these drawings, 1 is a traveling rail R
It is a traveling body of a crane traveling along. Reference numerals 2 and 2 denote masts provided upright on the traveling machine body 3, reference numeral 3 denotes an upper frame provided on the upper portions of the masts 2 and 4, and reference numerals 4 and 5 denote lifts that move up and down along the masts 2 and 2.

The stacker crane of this embodiment is provided with a detecting means for detecting the weight of the load mounted on the lifting platform of the crane.

The detecting means comprises a lifting drive motor 5, an inverter section 6 connected to the lifting drive motor 5, and a control section 7.

The tip of the lifting drive motor 5 is the lifting table 4
Winding mechanism 7 for two chains 6a and 6b connected to
Is connected to the chain 6 by the winding mechanism 7.
The elevating table 4 is moved up and down by winding up or sending out a and 6b.

The inverter section 6 has a sampling function for detecting the current value of the lifting drive motor 5. The inverter unit 6 also has a function of outputting the current value detected by the sampling function to the control unit 7. It should be noted that an inverter unit that can output in the form of torque instead of the current value may be used.

The control unit 7 has a function of ascertaining the weight of the load by comparing the increase in the current value of the lifting drive motor 5 due to the load when the load is loaded with the current value when the load is empty.

FIG. 3 is a diagram showing the relationship between the current value and the load. In the figure, the solid line (a) shows a high load (rated load) and the dotted line (b) shows a low load (empty load). .

From the figure, the current value changes in the range X from the dotted line (b) to the solid line (a) depending on the weight of the loaded article. The control unit 7 grasps the weight of the luggage by comparing the increase in the current value due to the load when the luggage is loaded with the current value when the luggage is empty (dotted line (b)).

The control unit 7 sends a signal for controlling the traveling speed of the crane to the inverter unit, which will be described later, based on the grasp of the weight of the cargo. For example,
When the current value is the value indicated by the dotted line (b), the control signal is sent so that the crane travels the fastest, and hereafter, when the current value is the value indicated by the solid line (a), the vehicle travels the slowest. The control signal is sent out as described above.

The current value when the load is empty and when the load is rated is pre-stored in the control unit 7 by performing a trial operation before the start of operation.

The inverter unit 8 controls the rotation speed of the traveling motor 9 in response to the control signal from the control unit 7. That is, the inverter unit 8 causes the crane to travel fast when the control unit 7 recognizes that the weight of the load is light, and causes the crane to travel slowly when it is determined that the load is heavy. In addition, the acceleration / deceleration of the crane is also suitably controlled according to the traveling speed of the crane.

According to the above-mentioned stacker crane, the control unit 7 compares the increase in the current value of the lifting drive motor 5 with the current value when there is no load, and grasps the weight of the baggage. Since the rotation speed of the traveling motor 9 is controlled by the inverter unit 8 based on the above, the traveling speed and the acceleration / deceleration of the crane are finely controlled according to the weight of the load mounted on the lifting platform. It is possible,
Efficient transportation can be performed according to the weight of luggage.

As a result, when a heavy load is loaded, the traveling speed and acceleration / deceleration of the crane are controlled to be slow, so that it is possible to prevent the load from collapsing during transportation.

Also, since the traveling speed and the acceleration / deceleration of the crane are controlled to be high when the load is empty or when a light load is loaded, the cycle time can be shortened.

<Second Embodiment> FIG. 4 is a front view showing a second embodiment of the stacker crane according to the present invention, FIG.
(C) is the top view, front view, and side view which show a level detection apparatus part.

The difference between this embodiment and the above embodiment is that
Focusing on the elongation of the chain that suspends the lift, detect the elongation of the chain when the luggage is loaded, and compare this detection value with the detection value at the time of rating to grasp the weight of the loaded luggage. In point.

In these drawings, the lifting table 10 includes
An upper photoelectric sensor 13 and a lower photoelectric sensor 14 are arranged side by side in the vertical direction. On the side surface of the mast 12, a plurality of shielding plates 15 as shown in the drawing are attached, the number of which is the same as the number of shelves. Upper photoelectric sensor 13, lower photoelectric sensor 1
4 emits the light flux L, respectively, and the shielding plate 15 can be detected. The upper photoelectric sensor 13 and the lower photoelectric sensor 14 are connected to the control device 18 shown in FIG.

When the elevating table 10 is moved up and down, the light flux L of the upper photoelectric sensor 13 and the lower photoelectric sensor 14 is blocked by the shielding plate 15, so that the upper photoelectric sensor 13 and the lower photoelectric sensor 14 repeat ON and OFF. However, since the upper photoelectric sensor 13 and the lower photoelectric sensor 14 are juxtaposed side by side in the vertical direction, they are turned on and off at different timings.
FF.

In FIG. 6, Lu is the fork raising upper level of the lift table, and Ld is the same fork lowering level.

The length of the shield plate 15 in the vertical direction is the same as the distance between the upper level Lu and the lower level Ld, that is, the distance in the section of the fork zone, and the shield plate 15 having such a length is used. , When the fork 17 is at the upper level Lu, the upper photoelectric sensor 13 and the lower photoelectric sensor 14 shown by the solid lines in FIG. 5C have the same positional relationship, and when the fork 17 is at the lower level Ld, the phantom line is used. They are arranged on the mast 12 so as to have the positional relationship as shown.

At the position shown by the solid line in FIG. 5 (c), that is, at the position where the fork 17 is at the upper level Lu, the upper photoelectric sensor 13 is above the shield plate 15, so the shield plate 15 is detected. No, lower photoelectric sensor 1
Since the light flux L of No. 4 is blocked by the shield plate 15, the shield plate 15 is detected. On the other hand, at the position indicated by the phantom line, that is, at the position where the fork 17 is at the lower level Ld, the upper photoelectric sensor 13 detects the shield plate 15,
The lower photoelectric sensor 14 does not detect the shield plate 15. Therefore, the state in which one of the upper photoelectric sensor 13 and the lower photoelectric sensor 14 detects the shield plate 15 is the fork extension level, and when only the lower photoelectric sensor 14 detects the upper level Lu, the upper photoelectric sensor. If only 13 is detected, it can be determined that it is at the lower level Ld.

FIG. 7 is a diagram showing the ON / OFF transitions of the upper photoelectric sensor 13 and the lower photoelectric sensor 14 as the elevator table 10 rises. The signal is shown inverted, so that when the light beam L is blocked by the shield plate 15, each sensor 1
If 3 and 14 are turned on and the light flux L is not blocked, OF
This will be described as F.

As the elevator table 10 rises, the light flux L of the upper photoelectric sensor 13 is blocked by the shield plate 15 at a and turned on. At this time, the lower photoelectric sensor 1 on the lower side
4 is still off. When it further proceeds to reach b, the light flux L of the lower photoelectric sensor 14 is also blocked by the shielding plate 15 and turned on. The middle level between a and b is the lower level Ld.

When the platform 10 further rises and reaches c, the upper photoelectric sensor 13 is turned off, and subsequently, the lower photoelectric sensor 14 is turned off at d. In the meantime, there is an upper level Lu. This procedure is the same for the delivery of the load to and from the loading / unloading station for loading / unloading with the shelf of the automated warehouse.

Upper photoelectric sensor 13 and lower photoelectric sensor 14
It is desirable that the vertical distance between the upper photoelectric sensor 1 and the upper photoelectric sensor 1 be as short as possible so that accurate positioning can be performed.
3. Due to the accuracy of the lower photoelectric sensor 14, there is a limit in reducing the distance between the two. Therefore, in reality, the lift 10
The position of the encoder 19 is further finely adjusted by the encoder 19 that detects the elevation of the.

FIG. 8 is a block diagram showing the main part of the control unit.

In the figure, the control device 18 is a lift 1
Lifting motor 20 that drives a chain 30 that lifts 0
Are in control. The rotation of the lift motor 20 is detected by the encoder 19. Further, the upper photoelectric sensor 13 and the lower photoelectric sensor 14 are connected.

The control device 18 controls the lifting / lowering of the lifting / lowering table 10 in the fork zone according to the procedure described above. As described above, the encoder 19 is used to finely adjust the positions of the lower level Ld and the upper level Lu between ab and cd. That is, the distances x and y shown in FIG. 7 are measured in advance and stored in the storage device 21, and while receiving the value from the encoder 19, the elevation motor 20 is feedback-controlled so as to match the stored value.

The control device 18 also controls the deceleration of the lifting platform 10 based on the data stored in the storage device 21. The storage device 21 stores the addresses of the lower level Ld and the upper level Lu for each shelf and station. The addresses of these fixed stop positions are stored as the values of the encoder 19. That is, for example, the lower level Ld and the upper level Lu are set with reference to the value of the encoder 19 when the lift 10 is lowered to the lowest position.
The value of the encoder 19 up to is stored. These values are stored as the values of the encoder 19 when the level detection device detects a certain position by performing the test operation before the operation starts.

When attempting to stop at a certain stop position, the controller 18 reads from the storage device 21 the address of the stop position to be stopped. Since the distance required for deceleration of the lift 10 is constant, the control device 18 controls the encoder 1
While receiving a value of 9, a certain distance from the stop position required for deceleration is in front (downward when ascending, upward when descending)
The deceleration is started at, and the stop position is reached immediately after the deceleration ends and the vehicle reaches a very low speed (slow speed at which the elevator can be stopped immediately).

By doing so, it takes only a short time for the lift 10 to move at a very low speed, so that the cycle time of stacker crane operation can be minimized. For that purpose, the address of the stop position must always be accurate. If it is incorrect, the time for traveling at a slow speed becomes long, the cycle time becomes long, and overrun may occur.

The deviation between the actual stop position and the stored address is caused by the expansion and contraction of the elevating chain 30 which elevates the elevating table 10. That is, the tension applied to the chain changes depending on whether or not a load is placed on the lifting platform 10 and the weight of the load, so that the chain 30 expands and contracts. Since the encoder 19 detects the rotation of the lifting motor 20, it is affected by the expansion and contraction of the chain 30.

Expansion and contraction of the chain 30 occur in the fork zone. That is, the lifting platform 10 transfers loads to and from shelves or stations while moving up and down in the fork zone with the forks 17 left. If the fork 17 scoops a load, the lift 10 becomes heavy and the chain 30 extends, and if the fork 17 unloads, the lift 10 becomes light and the chain 30 contracts.

Therefore, the address is updated at the point b or c. Specifically, the procedure for updating at point c will be described first. As described above, when the lifting table 10 moves up with the fork 17 left, the chain 30 extends because it receives the load from the shelf or the station. Since the chain 30 extends, even if the value of the encoder 19 that detects the rotation of the lifting motor 20 matches the value stored in the storage device 21 and obtained by subtracting y from the upper level Lu,
The upper photoelectric sensor 13 is not turned off yet, and the upper photoelectric sensor 13 is turned off after the lifting motor 20 is further rotated.
Become FF.

Therefore, the distance from when the value of the encoder 19 coincides with the stored value until the upper photoelectric sensor 13 is turned off coincides with the extension amount of the chain 30. Therefore, the distance obtained by subtracting the stored value from the value when the upper photoelectric sensor is turned off is subtracted from the value of the constant stop position stored in the storage device 21 to obtain a new value. It is stored in the storage device 21, and control is performed based on this value.

The procedure for updating at point b is the opposite,
When the lift table 10 is lowered, the stored value of the point b and the value of the encoder 19 match after the lower sensor is turned off. Therefore, the difference between the two is added to the value of the constant stop position stored in the storage device 21, and the stored value is updated.

As described above, the address of the fixed stop position is updated every time the lifting platform 10 transfers the luggage.
At this time, it is possible to grasp the weight of the luggage loaded on the lifting table 10 based on the amount of extension of the chain 30 obtained as described above.

That is, as shown in FIG. 9, when the unloaded condition is 0, the elongation amount of the chain under high load W (rated load) is X, and the elongation amount of the chain when a certain load is loaded is Y. In that case, the load W1 (load) with respect to the elongation amount Y can be calculated by a proportional expression.

Based on the calculation result of the weight of the baggage as described above, the same speed control as that in the above-described embodiment is performed by the inverter unit 8 and the traveling motor 9, so that it is mounted on the lift as in the above-described embodiment. The traveling speed and acceleration / deceleration of the crane can be controlled in detail according to the weight of the load, and efficient transportation according to the weight of the load can be performed.

The embodiments of the present invention have been described above.
The present invention is not limited to the above-mentioned embodiments, and can be appropriately modified within the scope of the gist of the present invention.

[Brief description of drawings]

FIG. 1 is a front view showing a first embodiment of a stacker crane according to the present invention.

FIG. 2 is a block diagram for explaining a detection unit and a speed control unit.

FIG. 3 is a diagram showing a relationship between a current value and a load.

FIG. 4 is a front view showing a second embodiment of the stacker crane according to the present invention.

5A to 5C are a plan view, a front view and a side view showing a level detecting device portion.

FIG. 6 is a diagram showing a positional relationship between a fork and a rack in the same embodiment.

FIG. 7: ON and O of two photoelectric sensors in the same embodiment
The figure which shows the change of FF.

FIG. 8 is a block diagram showing a main part of a control structure of the same embodiment.

FIG. 9 is a diagram showing the relationship between the amount of elongation and the weight.

[Explanation of symbols]

 1 Crane 5 Lifting / driving motor 6 Inverter section 7 Control section 8 Inverter section 9 Traveling motor

Claims (1)

[Claims] 1. A detection means for detecting the weight of a load mounted on a lifting platform of a crane, and a load detected by the detection means for causing the crane to travel fast when the weight of the load detected by the detection means is light. A stacker crane having a speed control means for causing the crane to travel slowly when the weight of the stacker is heavy.