JPH03128887A - Control method for steel plate lifting number selection - Google Patents

Abstract

PURPOSE:To certainly lift a designated number of steel plates even if the ground or a lifting magnet has a difference in level or flatness of lifted material is bad by increasing exciting current just after separation in the process of attracting and lifting a steel plate. CONSTITUTION:The exciting current of a lifting magnet 11 is preliminarily set according to lifting number, and a designated number of steel plates are adsorbed and lifted from piled steel plates by the lifting magnet 11. In this process of attracting and lifting the steel plates, the separation between lifted material and non-lifted material is detected by a sensor 12, and just after this detection, the exciting current is increased. Consequently, the lifted material is more strongly and certainly adsorbed by the lifting magnet 11. As the exciting current is increased just after separation, the non-lifted material is never lifted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for controlling the number of suspended steel plates, and particularly to a method for controlling the number of suspended steel plates when lifting a specified number of steel plates by an overhead crane equipped with a lifting magnet.

[Prior Art] Overhead cranes equipped with lifting magnets are widely used to transport steel plates. Lifting magnet refers to a lifting device for a crane that is equipped with one or more electromagnets. In an overhead crane for conveying steel plates, one or more lifting magnets are suspended via chains from a lifting beam wound around a trolley.

When transporting steel plates, it may be necessary to suspend a specified number of steel plates from a stack of steel plates. In such a case, adjust the excitation current of the Lifting Macnet so that the magnetic attraction force acting between the lower surface of the lifted material and the upper surface of the non-lifted material is smaller than the weight of the non-lifted material. The material and the non-hanging material are separated. For example, in order to separate only the lifted material from the non-lifted material, first the lifting magnet to be used is selected according to the length of the lifted material. Next, the lifting magnet pitch is calculated from the size of the lifting material, etc., and the lifting weight to be applied to each lifting magnet is determined. Then, in consideration of the shared weight and the deflection of the steel plate during lifting, the excitation current of each selected lifting magnet is set in accordance with the total thickness of the lifting material and the steel type.

Another method for selecting the number of hanging steel plates is JP-A-154-154.
There is a method disclosed in No. 767. This method consists of arranging the Wt poles in the lifting magnet alternately as N and S poles or in a staggered manner, and then
This makes it possible to select the pole and south pole from a wide range. Further, as another method, there is a method disclosed in Japanese Utility Model Application Publication No. 53-105279. In this method, a suction attachment with a concave portion formed on the suction surface is attached to the steel plate of each magnetic pole in the lifting magnet, thereby making it possible to widely control the penetration density and depth of magnetic flux into the steel plate.

[Problem to be solved by the invention] However, if there is a difference in height between the ground or the level of the lifting magnet, the lifting material will fall off immediately after the lifted material and non-lifted material are separated during the initial stage of lifting the steel plate. Sometimes. For example, suppose that among a plurality of arrayed lifting magnets, the level of the center lifting magnet is higher than the other lifting magnets. When lifting starts, the lifted material is separated from the non-lifted material faster by the central lifting magnet than by the other edge ink magnets. Since the steel plate is a continuous body, it will bear the share of the center glue and edge ink magnet or other lifting magnets. As a result, the lifting magnet at the center is momentarily subjected to an excessive load, and the lifting material cannot be lifted with the preset excitation current, and the lifting material detaches from the lifting magnet and falls.

In addition, even if the level difference between the ground and the lifting magnet is even to some extent, if the hoisting material is not flat,
A phenomenon similar to the above occurs, and the specified number of steel plates cannot be lifted.

In order to solve the above-mentioned problems, methods of changing a large number of WtFi arrangements, changing the way the excitation current flows, or modifying the attachment of the suction surface have been proposed, and the hanging selectivity has been improved to a certain extent. However, as mentioned above, if there is a large difference in the level of the lifting magnet or the height of the ground, this cannot always be said to be a perfect solution.

In addition, the difference in the level of the lifting magnet is caused by wear of the lifting magnet chain and hook, the mechanical condition of the machine body, or deformation due to the hanging load, so it is difficult to quantitatively manage and maintain the difference in the level of the lifting magnet. Have difficulty. Even on the ground, unevenness occurs due to the weight of the stacked steel plates, making it difficult to maintain a uniform level inside the warehouse.

Therefore, this invention provides a method for controlling the number of suspended steel plates that can reliably lift a specified number of steel plates even if there is a difference in height between the ground or the level of the lifting magnet, or even if the hoisting material has poor flatness. This is what we are trying to provide.

[Means for Solving the Problems] The first invention is a method in which the excitation current of a lifting magnet is set in advance according to the number of sheets to be lifted, and a specified number of steel sheets from a stack of steel sheets is attracted by the lifting magnet and lifted. In the process of attracting and lifting, the excitation current is increased immediately after the lifted material and the non-lifted material are separated.Hereinafter, the separation of the lifted material and the non-lifted material is referred to as ground cutting.

The rate of increase of the excitation current with respect to the initial setting value varies depending on the number of lifting magnets used, the pitch between lifting magnets, the size, weight, material, number of materials to be lifted, and other lifting conditions, but for example, 1.1 to 2.
It is about 0 times. Further, the time from when the lift is cut off to when the excitation current is increased varies depending on the lifting conditions, but is, for example, about 0.1 to 0.5 seconds. This delay time is a time for confirming the ground cutting. The increase rate and delay time of these excitation currents are determined in advance for the actual machine, and
It is stored as a calculation table in a control computer, etc. The increased excitation current is maintained until the steel plate is completely lifted.

The second invention is a method in which a plurality of edge ink magnets are arranged or the excitation current of the edge ink magnet is set in advance for each lifting magnet according to the number of sheets to be lifted, and a specified number of steel plates are attracted and lifted by the lifting magnet from the stacked steel plates, During the process of attracting and lifting the steel plate, ground breaking is detected for each lifting magnet, and the excitation current is increased for each lifting magnet immediately after separation.

To detect ground breaking, for example, a change in the load acting on the chain that suspends the lifting magnet is detected.

To detect this load change, a combination of a spring and a switch or a load cell placed between the lifting beam and the lifting magnet is used. The increase rate and delay time of the excitation current are the same as in the first invention. in general,
The lifting magnets are arranged in a line along the lifting beam, and the excitation current is sequentially increased starting from the lifting magnet. In addition, in all lifting magnets, if the lifted material and non-lifted material are separated at the same time,
Increase the excitation current at the same time.

The third invention is a method in which the excitation current of three or more lifting magnets arranged in an array is set in advance for each lifting magnet according to the number of lifting magnets, and a specified number of steel plates from the stacked steel plates are attracted and lifted by the lifting magnets. In the process of suctioning and lifting the steel plate,
A ground break is detected for each lifting magnet, and the excitation current is increased for each lifting magnet immediately after the ground break, and the excitation current of the lifting magnet placed in the center is increased more than the exciting current of the lifting magnets placed at both ends. increase the rate.

The ratio of the excitation current of the lifting magnets placed at both ends to the excitation current of the center or edge ink magnets may vary depending on the lifting conditions, for example 1.
．． It is about 5 times as large. The number of lifting magnets in the center and both ends does not need to be one each. In other words, multiple lifting magnets are distributed to the center and both ends, and the increase rate of excitation current for the group of lifting magnets belonging to the center is made larger than for the group of edge ink magnets belonging to both ends. Good too. The ground breaking detection, excitation current increase rate and delay time are the same as in the above invention.

According to a fourth aspect of the present invention, in the second or third aspect, the rate of increase of the excitation current is increased for a lifting magnet that breaks ground earlier.

The ratio of the increase rate corresponding to the order of the speed of ground cutting varies depending on the lifting conditions, but for example, the ratio of the increase rate of the first ground cutting to the last ground cutting is about three times.

0 [Function] In the process of attracting and lifting the steel plate, the excitation current is increased immediately after breaking the ground, so the material to be lifted is more strongly and reliably attracted by the lifting magnet. Since the excitation current is increased immediately after the ground is cut, non-lifted materials are not lifted.

When multiple lifting magnets are arranged and there is a difference in height between these levels, the lifting magnet with the highest level will break ground earlier than the other lifting magnets. As a result, the highest lifting magnet bears the weight of the other lifting magnets and receives an excessive load, but the increased excitation current prevents the lifting member from detaching or falling.

The center part of the steel plate attracted by the lifting magnet is restrained by the surroundings, so it is less likely to bend than both ends.

Therefore, if there is a difference in the level of the lifting magnet or unevenness of the steel plate, the lifting magnet placed in the center may not sufficiently attract the steel plate. However, this insufficient adsorption can be prevented by increasing the rate of increase in the excitation current of the lifting magnets placed in the center compared to the excitation current of the lifting magnets placed at both ends.

The lifting magnet that breaks the ground quickly bears part of the load shared by the lifting magnet that does not break the ground, and an excessive load is added. However, a lifting magnet that breaks the ground quickly increases the rate of increase in excitation current and increases the attraction force, thereby preventing the board from falling due to excessive load.

[Example] In the overhead crane for conveying steel plates used in this example, five lifting magnets are arranged along the lifting beam. Each lifting magnet is equipped with 3x6 electromagnets. Further, in this embodiment, an example will be described in which the excitation current is increased depending on the parts of the lifting magnet (the center and the ends) and the order of ground cutting.

FIG. 1 is a block diagram showing an example of a control device for carrying out the method for controlling the number of suspended steel plates of the present invention. 2 FIG. 2 is a time chart during lifting of steel plates.

First, in the upper control computer 1, the lifting magnet 1 is
The number of magnets used (only one is shown in Figure 1) and the beam pitch (the distance between adjacent lifting magnets) are determined, and the results are sent to the lifting magnet lifting part discriminating circuit 3 and the excitation current as the lifting magnet selection signal SLn. It is output to the arithmetic circuit 2.

In addition, the host computer 1 determines the standard excitation current for each lifting magnet Il based on the size of the steel plate, the number of suspended steel plates, the number of lifting magnets used, and the beam pitch. n, determine the deflection correction current setting value Iea and the lifting correction current setting value Lb. The determined reference excitation current I.

0 is the deflection correction current setting value I in the excitation current calculation circuit 2.
ca is the lifting correction current setting value I in the deflection correction current calculation circuit 4; h is output to the lifting magnet part-specific correction current calculation circuit 5 and the ground cutting layer-specific correction current calculation circuit 6, respectively.

3 In the excitation current calculation circuit 2, for example, for the #1 lifting magnet 11, the reference excitation current I from the host computer 1. , and lifting magnet selection signal S, initial setting excitation current ■. , , (indicated by I. (.) in Figure 2) is obtained. Furthermore, the host computer 1 sends to the lifting failure determination circuit 17 the expected lifting weight WPLMID, its maximum value WPLmax, and its minimum value Wr'L□. , and the planned lifting thickness T
P.L.M.I. , its maximum value TPLmax and minimum value T
PL□,. Output.

On the other hand, the lifting beam was lowered from the trolley of the overhead crane.
When the lifting magnet 11 lands on the highest stacked steel plate, the initial setting excitation current IO+. is supplied as the excitation current ILMI from the excitation current calculation circuit 2 to the electromagnetic coil of the lifting magnet 11 via the setting current selection circuit 8 and the excitation current control device 9. When all the lifting magnets 11 are energized, hoisting starts. The hoisting control device 10 controls the hoisting motor 30 using the signal PSL from the set current selection circuit 8 and the signal PSM from the hoisting position sensor 22.

During the hoisting process, the ground breaking sensor 12 detects the separation of the lifted material and the non-lifted material, that is, the ground breaking for each lifting magnet 11. Ground cutting sensor] Signal S from 2
I+ is manually inputted to the excitation current calculation circuit 2, the set current calculation timing circuit 7, and the ground cut order determination circuit I4. The ground breaking order determination circuit I4 discriminates the lifting magnet 11 that breaks the ground early, and the discrimination signal Sln is manually inputted to the ground breaking layer-specific correction current calculation circuit 6. The ground cutting layer-specific correction current calculation circuit 6 calculates the correction current of the excitation current according to the ground cutting order.

The set current calculation timing circuit 7 receives the signal from the hoisting position sensor 22 and the ground cutting signal 5+1 manually.
After the delay time TLM shown in FIG. 2 has elapsed, a current correction start timing signal SGf is output to the excitation current calculation circuit 2. When the current correction start tie sharpening signal SGf is input, the excitation current calculation circuit 2 changes the initial setting excitation current I from the maximum excitation current. ,. > is subtracted to find the ground-off correction current 1ho. Here, the maximum excitation current is the excitation current required to lift the lifting material plus the top 15 non-lifting materials. Further, based on the site-specific correction current value Icbl-1 from the lifting magnet site-specific correction current calculation circuit 5 and the signal Icb'l-2 from the ground-cut layer-specific correction current calculation circuit 6, the ground-cutting correction current Iho is calculated using the formula ( 1) to obtain the transient correction current Ih.

Ih, = Ihoxk, xk2xkh - (1) Here, kI: 2 for the correction coefficient for each lifting magnet part
: Ground cutting order correction coefficient kh Niovershoot coefficient. In the lifting magnet 11, the excitation current rises quickly, but the magnetic flux density rises slowly.

The overshoot coefficient is used to compensate for the delay in magnetization of the electromagnet.

After holding the transient correction current Ih for a time Thd, the equation (2
) is switched to the steady-state correction current Ih2 given by

It+2=Ihox k, x k2・---・
- (2) The steady-state correction current Ih2 is maintained until the steel plate is completely lifted as shown in FIG. After complete lifting, the excitation current during transport is increased to more strongly attract the steel plate and transport it to a predetermined position. These transient correction currents 1h,
And the steady correction current 1h2 is the lifting magnet/hanging selection current ■. 7□ is supplied from the excitation current calculation circuit 2 to the set current selection circuit 8, and further supplied to the electromagnetic coil of the lifting magnet 11 via the excitation current control device 9. In addition, when compensating for a decrease in the attraction force of the lifting magnet 11 due to the deflection of the lifted steel plate, the excitation current is corrected at the same time as the above correction using the deflection correction current value Ical from the deflection correction current calculation circuit 4.

For each lifting magnet 11, the magnetic flux passing through the steel plate from the electromagnet is detected by the magnetic flux sensor 13, and the detected magnetic flux 521 is manually inputted to the suspension failure determination circuit 17 via the magnetic flux-plate thickness conversion circuit 15. If a thin plate occurs during lifting, or if there are too many plates to be lifted, this is detected by the lifting load sensor 16 and the lifting failure determination circuit 7. Based on this detection result, in the case of a thin plate, lifting is performed again by a signal from the beam try control circuit 19. Furthermore, when the number of suspended steel plates is large, the excess steel plates are cut off by a signal from the cutting control circuit 18 based on signals from the suspension failure determination circuit 17 and the thin plate detection circuit 20.

Here, an example will be described in which a specified number of steel plates are lifted by the above device.

The lifting conditions are as follows.

Steel plate dimensions: 10mm x 2m x 8m Lifting magnet part correction coefficient: 1 End lifting magnet = 0.5 Center lifting magnet = 1.0 Ground cutting order correction coefficient: 2 No. 1: 1.3 No. 2: 1.1 No. 3: 1.0 No. 4: 1.0 No. 5 = 1.0 (However, if all lifting magnets are lifted at the same time, the breaking coefficient is 1.
Set to 0. ) 8 Overshoot coefficient kl: 1.5 Delay time TLM: 0.1 sec Transient correction current holding time Thd: 1 sec The lifting results are shown in Table 1. In the table, the setting current is the excitation current ILMI
(see Figure 1), and the correction current is Ih in equation (1),
each represents.

Level differences of +5 mm and +10 mm were given to the center lifting magnet (#3) and the end lifting magnet (#5), and the method of the present invention and the conventional method were compared. As a result, it was confirmed that when the current is corrected using the method of the present invention, it is possible to correct the difference even if the level difference is large. In addition, in the conventional method, even if the level difference is O, if the steel plate is thin, the current setting range is small, so it is difficult to hang and separate, but with the method of the present invention, it was possible to hang and separate smoothly.

In the above embodiment, an example was explained in which the excitation current is increased depending on the location (center and end) of the lifting magnet and the order of ground cutting, but the present invention is not limited to this. For example, a control method for selecting the number of suspended steel plates may be used, which increases the excitation current depending on the location of the lifting magnet or the order of ground cutting, or lacks both.

0 [Effects of the Invention] (1) Even if there is a slight difference in the level of the lifting magnet or the ground, it is possible to select the number of suspended steel plates even with poor flatness, and it can be used even under adverse environmental operating conditions.

(2) When correcting the excitation current according to the order of ground breaking, the first lifting magnet with a large load to break ground is multiplied by a large correction coefficient, and the closer to the end, the looser the coefficient is, thereby preventing the n+1th magnet from being attracted. This enables smooth hanging control.

(3) The part where the end lifting magnet is located is
Since it corresponds to the free end of the steel plate, it is relatively unaffected by level differences, but since the steel plate is a continuous body, the central part is easily affected by level differences. When correcting the excitation current for each part of the lifting magnet, prevent over- or under-lifting.
Smooth hanging control is now possible.

From the above, (4) Conventional maintenance can be done to prevent wear of lifting magnet chains, hooks, and differences in ground level.
+++ It has become possible to fully control the level difference management.

(5) For example, if the lowest steel plate of the steel plates to be lifted is a thin, narrow steel plate with a relatively small unit weight, it is extremely difficult to separate the steel plates from each other because the excitation current setting range is narrow. However, by instantaneously correcting the excitation current, it is possible to select the number of hanging sheets.
The hanging sheet sorting area has been expanded.

(6) The work time for separating steel plates has been shortened, improving crane work efficiency, and it has become possible to automate the selection of the number of steel plates to be hung.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a control device for implementing the method for controlling the number of suspended steel plates of the present invention, and FIG. 2 is an example of a time chart during lifting of steel plates. DESCRIPTION OF SYMBOLS 1... Upper level integrated control device, 2... Excitation current calculation circuit, 3... Lifting magnet lifting part determination circuit,
4... Deflection correction current calculation circuit, 5... Lifting magnet part-specific correction current calculation circuit, 6... 3. Footing magnet ground cutting layer-specific correction current calculation circuit, 7
... Set current calculation timing detection circuit, 8... Set current selection circuit, 9... Excitation current selection circuit, 10...
Hoisting control device, 11... lifting magnet,
12... Ground cutting sensor, 13... Magnetic flux sensor, 14
...Lifting magnet ground cutting order determination circuit, 15
... Magnetic flux - plate thickness conversion circuit, 16 ... Lifting load sensor, 17 ... Full suspension judgment circuit, 18 ... Separation control circuit, 19 ... Retry control circuit, 20 ... Thin plate detection circuit.

Claims (1)

[Claims] 1. In a method in which the excitation current of the lifting magnet is set in advance according to the number of sheets to be lifted, and a specified number of steel sheets from a stack of steel sheets are attracted and lifted by the lifting magnet, in the process of attracting and lifting the steel sheets. A method for controlling the number of suspended steel plates, characterized in that the excitation current is increased immediately after the suspended material and the non-suspended material are separated. 2. In this method, the excitation current of a plurality of lifting magnets arranged in a row is set in advance for each lifting magnet according to the number of sheets to be lifted, and a specified number of steel sheets from a stack of steel sheets is attracted and lifted by the lifting magnet. A method for controlling the number of suspended steel plates, characterized in that in the process, separation between lifted materials and non-lifted materials is detected for each lifting magnet, and immediately after separation, an excitation current is increased for each lifting magnet. 3. In a method in which the excitation current of three or more lifting magnets arranged in advance is set for each lifting magnet according to the number of sheets to be lifted, and a specified number of steel sheets from a stack of steel sheets are attracted and lifted by the lifting magnet, the steel sheets are attracted, During the lifting process, separation of the lifted material and non-lifted material is detected for each lifting magnet, and immediately after the lifted material and non-lifted material are separated, the excitation current is increased for each lifting magnet, and the lifting magnet placed at both ends A method for controlling the number of suspended steel plates, characterized in that the rate of increase in the excitation current of a lifting magnet disposed in the center is greater than the excitation current of the lifting magnet. 4. The method for controlling the number of suspended steel plates according to claim 2 or 3, characterized in that the rate of increase in the excitation current is increased for a lifting magnet that separates the lifted material from the non-lifted material more quickly.