JPH0373791A - Controller for quantity of suspended steel plate on lifting magnet type crane - Google Patents

Abstract

PURPOSE:To correctly suspended a prescribed number of steel plates by installing a processing means which cuts off the supply of the exciting current after suspended objective articles are suspended and restarts the supply of the exciting current when detection value of an electric current detecting means lowers to the second electric current value which is smaller than the first electric current value. CONSTITUTION:After n+1 pieces of steel plates are suspended by the flow of the excitation current having the first electric current value, the excitation current is cut off, and after the electric current which flows in an exciting coil 52 reduces to the second electric current value, the flow of the exciting current is restarted by a processing means RCU. The min. value of the magnetic attractive force which acts between the exciting coil 52 and a steel plate 71 is determined according to the second electric current value. In other words, if the magnetic attractive force which acts between the n-th steel plate corresponding to the second electric current value and the n+1-th steel plate is set less than the downward force w(n+1) which acts onto the n+1-th steel plate, the n+1-th steel plate can be dropped, and a prescribed number (n) of steel plates can be suspended correctly.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lifting magnet crane device that uses electromagnets to lift magnetic objects such as steel plates, and in particular, the present invention relates to a lifting magnet crane device that uses electromagnets to lift magnetic objects such as steel plates. The present invention relates to control of the number of sheets lifted by an apparatus that simultaneously lifts a desired number of sheets in a stacked state.

[Prior Art] A lifting magnet crane is a crane that uses magnetic force to hold steel plates, and is equipped with an electromagnet called a lifting magnet for adsorbing steel plates. Furthermore, since a relatively wide surface of the steel plate is attracted by the excitation of the lifting magnet, it is suitable for lifting steel plates that are thinner than their length.

When lifting a steel plate that is much larger than the magnets, multiple lifting magnets distributed in one place can be used.
In preparation for one crane, multiple lifting magnets simultaneously attract different parts of the steel plate to prevent the steel plate from bending during lifting.

[Problems to be Solved by the Invention] By the way, it is extremely difficult to simultaneously lift only a desired number of steel plates located above from among a large number of stacked steel plates.

Basically, in order to lift only an arbitrary number of steel plates above from a large number of steel plates loaded on the ground, magnetism is used by a lifting magnet.

The adsorption force F(n) acting between the (n - 1)th steel plate and the nth steel plate from the top is made larger than the downward force w(n) acting on the nth steel plate, and the nth steel plate and ( The magnetic attraction force F(n+1) that acts between the n+1)th steel plate and the (n+1)th steel plate is expressed as (n+
1) The force should be smaller than the downward force w(n+1) acting on the th steel plate.

However, the magnetic attraction force that acts between each steel plate varies depending on the magnitude of the excitation current of the lifting magnet, the total thickness of all steel plates on the side to be attracted, and the thickness of the steel plate on the side to be attracted. .

Furthermore, the magnitude of the downward force acting on the steel plate changes depending on the acceleration of lifting and vibration.

In reality, the minimum necessary excitation current that can reliably lift up to the nth steel plate can be predicted within a certain range if various conditions at that time are given. However, since the range has a certain width, the maximum value of the excitation current range that can reliably lift up to the nth steel plate is greater than the excitation current range that can reliably lift up to the (n+1)th steel plate. In some cases, the minimum value of is large. In such a case, even if you expect to lift up to the nth steel plate,
Steel plates up to +1 may be lifted.

Accurate number control is not possible.

Therefore, the inventors of the present invention have proposed an invention that has already been applied for (Patent Application No. 1-1-1)
No. 18231), when it is difficult to control the number of sheets by adjusting the excitation current, when lifting up to the nth steel plate, lift up to the n+1th steel plate in one stretch, and then lift the lowest n+1th steel plate. We have developed a new control method that allows only the nth steel plate to be lifted by dropping only the nth steel plate.

In this control method, after lifting n+1 steel plates, the excitation current is interrupted for - time, and from the nth steel plate to the n+1
When the second steel plate is separated, the excitation current is restarted. By appropriately selecting the time to cut off the excitation current, only the n+1th steel plate can be reliably separated, and even under special conditions where it was difficult to control the number of sheets in the past, the desired number of steel plates can be lifted accurately. It becomes possible to do it.

However, in this control method, there is a problem to be solved in that it is difficult to set the time for cutting off the excitation current. Therefore, the present invention aims to solve this problem.

[Means for Solving the Problems] In order to solve the above 11 problems, a first aspect of the present invention includes a magnetic core and an excitation coil for exciting the core, and magnetically attracts a magnetic object. at least one electromagnet that generates an excitation current to be supplied to the excitation coil; current supply means that generates an excitation current to be supplied to the excitation coil;
Current control means for detecting the current flowing through the excitation coil; Vertical movement means for moving the electromagnet up and down; and current supply means and current control means to control the number of sheets to be attracted to the excitation coil. After passing an excitation current having a corresponding first current value and lifting the attracted object to be lifted, the supply of the excitation current is cut off, and the current value detected by the current detection means is set to the first current value. A processing means is provided for restarting supply of the excitation current when the current decreases to a second value smaller than the current value.

Further, in the second aspect of the present invention, the processing means determines in advance the cutoff time required for the current flowing through the exciting coil to decrease to the second current value, and continues cutting off the exciting current until the time elapses. do.

[Effect] When the current is turned off to the excitation coil, the current flowing through the excitation coil will immediately stop, since a certain amount of magnetic energy has been accumulated in the excitation coil due to the current supplied up to that point. does not become zero. For example, if the terminals of the excitation coil are short-circuited, the current value will normally gradually decrease according to a unique time constant depending on the inductance L and resistance value R of the excitation coil. Therefore, by monitoring the current value in that case, it is possible to know changes in the magnitude of the magnetic attraction force acting between the excitation coil and the steel plate.

In the present invention, an excitation current having a first current value is applied to n
After lifting the +1 steel plate, the excitation current is cut off and the excitation current is restarted after waiting for the current flowing through the excitation coil to drop to the second current value. The minimum value of the magnetic attraction force acting during this period is determined according to the second current value. In other words, the magnetic attraction force acting between the nth and n+1th steel plates corresponding to the second current value is
By making the downward force w(n+1) acting on the n+1th steel plate smaller, the n+1th steel plate can be dropped.

The change in the current flowing through the excitation coil when the supply of excitation current is stopped is usually determined according to the function of the current value before interruption and the unique time constant of the excitation coil, so the time at which the current should be interrupted is , which can also be obtained by calculation. In the first aspect of the present invention, it is checked whether the current value has decreased to the second current value by monitoring the actual current of the excitation coil. In the second aspect, the cut-off time, which is substantially the same as the cut-off time, is calculated in advance, and the timing for restarting the supply of the excitation current is determined by managing the time.

In a preferred embodiment of the present invention, which will be described later, the second current value is set to the minimum value in the range of current values necessary to lift n steel plates. This makes it possible to reliably lift only n steel plates.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[Example] FIG. 1 schematically shows a lifting magnet crane implementing the present invention as an example. This crane has travelers 2. Arm 3-1.3-2. which is engaged with the traveler 2 so as to be able to rise and fall freely. Beam 4-1.4-2. fixed to the tip of each arm. Lifting magnets (hereinafter abbreviated as rifmags) 5-1 to 5-J suspended from each beam, landing sensors, and load cells 6-1, 6-2 for detecting suspended loads. and,
It consists of a moving device that moves the traveler 2, a lifting device that raises and lowers each arm, a spacing adjustment device that adjusts the spacing between the lift mags, a control device, etc. (However, in FIG. 1, the landing sensor is shown).

The illustration of the moving device, the interval adjustment device of the elevating device 9, and the control device is omitted. ).

Each riffmag is an electromagnet and is individually energized. Figure 2a shows the appearance of one riff mag as seen from below, and Figure 2b shows its cross section on the nB-IIB line.In this way, each riff mag has a modified E-shape as shown in Figure 2b. A core 51 having a cross section (when discussing individual riff mags, branch numbers are given in the same way as above, the same applies to others), an excitation coil 52 for exciting the core 51, and a magnetic flux at the center of the core 51 (hereinafter referred to as central magnetic flux). , ) is comprised of a search coil 53 for detecting.

The control device, as shown in FIG.
It is mainly composed of a CPU and a riffmag control unit RCU. The host computer MCPU is responsible for controlling the operation of the embodiment apparatus as a system, and the rifmag control unit RCU is responsible for controlling the lifting of steel plates. input/output devices, communication devices with other control devices, and movement devices of the traveler 2 are connected, and the RIF MAG control unit RCU includes various sensors including search coils, load cells, and landing sensors of each RIF MAG, and an arm lifting device. A drive device including a refmag interval adjustment device, etc., and a current supply unit REG are connected.

In addition, in FIG. 3, only one riff mag MG and the circuit that controls it are shown and the others are omitted, but in reality, each of the riff mags 5-1 to 5-J shown in FIG. It is connected to the unit RCU, and other circuit elements associated therewith, such as a current supply unit REG, are also provided in a number corresponding to each riffmag. However, since substantially the same control is normally performed on all riff mags, only one riff mag (represented by MG) will be explained regarding common matters.

The Refmac control unit RCU includes a microcomputer and various interface circuits (eg, an A/D converter, a waveform shaping circuit, an amplifier, and a driver).

The current supply unit REG is the refmag control unit RC.
It is a type of constant current source that supplies an excitation current set by the RiffMag control unit RC1J to the excitation coil of the RiffMag selected by U. Specifically, AC power supply (AC400V)
The power supplied from the thyristor is supplied to the excitation coil through the thyristor. The firing angle of the thyristor is adjusted by the excitation current control circuit.

That is, the current flowing through the excitation coil 52 is maintained at a constant (IA) by increasing or decreasing the energization phase angle in the direction in which the target current IA given from the riffmag control unit RCU matches the actually measured average current detected by the current detection circuit. do.

Between the current supply unit REG and the exciting coil 52,
Relay RLY is inserted. When the riffmag control unit RCU turns on the relay RLY, the electrical contacts C1,
Since C4 is closed and the other electrical contacts C2 and C3 are opened, the current (IA) output from the current supply unit REG is supplied to the exciting coil 52. Also, when the riffmag control unit RcU turns off the relay RLY, the electric contact CI
.

Since C4 is opened and the other electrical contacts C2 and C3 are closed, both ends of the excitation coil 52 are short-circuited via the current detector DET. The detection output Id of the current detector DET is read by the refmag control unit RCU.

Here, the following control is roughly performed.

The host computer MCPU determines, through dialogue with the operator, the position of the source "mountain" of the steel plate to be moved, and the specifications (thickness t9 width WD, length L), the number of steel plates to be moved from the “mountain” n
, and the position of the destination "mountain", etc., it gives the necessary information to the rifmag control unit RCU to instruct execution of control to lift the steel plate, and also moves the traveler 2 to the destination "mountain". Move directly above.

The riffmag control unit RCU is a host computer MC.
The riff mag to be used is selected based on the information given from the PU, the interval between them is adjusted, and the excitation current of the selected riff mag is set.

After that, when the traveler 2 moves directly above the "mountain" from which it is moving, each arm is driven downward to lower each riffmag onto the peak, and the selected rifmag is set via the current supply unit RIEG. The arm is excited by the excitation current, and each arm is driven upward.

The host computer MCPU is the Riffmag control unit R.
When a desired steel plate is lifted under the control of the CU, the traveler 2 is moved to the destination "mountain" and the rifmag control unit RCU is instructed to execute control for placing the steel plate. As a result, the rifmag control unit RCU drives each arm downward, places the lifted steel plate on the "mountain", de-energizes each riffmag, and drives each arm upward again.

Next, among the controls related to lifting of steel plates performed by the rifmag control unit RCU, steel plate suction control for controlling suction of a specified number of steel plates according to the gist of the present invention will be described in detail.

In order to excite the rifmag placed on the "mountain" of steel plates and lift n steel plates, the magnetic attraction force that acts between the (n-1)th steel plate and the nth steel plate from the top is required. F (n) is n
The riff mag is set so that the magnetic attraction force acting between the n-th steel plate and the (n+1)-th steel plate is smaller than the downward force acting on the (n+1)-th steel plate. All you have to do is excite it.

On the other hand, the attraction force between each steel plate is determined by the excitation current, the total thickness of all the steel plates on the side to be attracted (hereinafter, the total thickness of multiple steel plates of this type is referred to as layer thickness), and the attraction force. Thickness of the side steel plate (hereinafter, the thickness of each steel plate is referred to as plate thickness)
For example, the thickness t (n
) is constant (tc), and the layer thicknesses T(n-1) of the l to (n-1)th steel plates are set in three ways (Tc1, Tc2
, Tc3), and the excitation current IA of the riffmag and (
When examining the relationship between the magnetic attraction force F (n) that acts between the n-1)th steel plate and the nth steel plate, three graphs are obtained as shown in Figure 4, and the plate thickness t ( If n) is changed, it becomes even more diverse. However, the magnetic attraction force that acts between the excitation current of the LifMag and the steel plate on the adsorbing side (in this case, the (n-1)th steel plate) and the steel plate on the adsorbed side (in this case, the nth steel plate) The relationship can be specified by the combination of the thickness of all the steel plates on the side to be attracted and the thickness of the steel plate on the side to be attracted, so it is necessary to clarify the relationship between the excitation current and the magnetic attraction force for each combination in advance. By doing so, it is possible to know the excitation current of the rifmag required to lift the desired number of steel plates.

For example, FIG. 5 shows data 1 to (n
-1) A combination of the layer thickness T (n-1) of the steel plate up to the th steel plate and the plate thickness t (n) of the n th steel plate, and.

1 = Layer thickness T(n) and (n+1) of steel plate up to nth
This is a graph that organizes the combinations of plate thickness t(n+1) of the th steel plate, and from this graph, when the riff mag is excited with the current IA, the difference between the (n-1)th steel plate and the nth steel plate. The magnetic attraction force acting between them and the magnetic attraction force acting between the nth steel plate and the (n+1)th steel plate can be read.

By the way, in stationary systems (including equi-connected systems).

The downward force acting on the steel plate to be attracted is equal to the weight of the steel plate, that is, the mass of the steel plate x the acceleration of gravity.

That is, (n-)) read from the graph shown in Figure 5.
The magnetic attraction force acting between the th steel plate and the nth steel plate is n
The excitation current that makes the weight of the steel plate equal to the weight w (n) is I
Let A'(n) be the exciting current that makes the magnetic attraction force acting between the nth steel plate and the (n+1)th steel plate equal to the weight w(n+1) of the (n+1)th steel plate, IA''(n+1). )
Then, if the riffmag is stationary, IA'(
By exciting the riff mag with an excitation current of n) or more and less than IA'(n+1), the first to nth steel plates can be attracted to the riff mag.

Similarly, the excitation current required to lift n steel plates from a "mountain" can be found, but in actual lifting, accelerations such as lifting and vibration are applied, so the nth steel plate The downward force acting on the steel plate does not match the weight of the steel plate.In other words, in order to find the excitation current required for actual lifting, this downward force must be found first.

Therefore, as a result of conducting various experiments using the device of this embodiment, we found that depending on the layer thickness of all the steel plates to be lifted (for example, the 1st to nth steel plates), the effect on the lowest steel plate (for example, the nth steel plate) It turned out that the downward force can be identified within a certain range. Figure 6 shows the layer thickness of all the steel plates to be lifted on the horizontal axis.
This is a graph that shows the relationship between "downward force" and "weight" (the former divided by the latter, the value less than or equal to 2 correction ratio) on the vertical axis.In other words, in this graph, The maximum value of the correction ratio when the layer thickness of all the steel plates to be raised is T(n) is !Iaxs F(T(n)) - the minimum value at that time is m1nSF(T(n)), and T(n+1) is The maximum value of the correction ratio when +waxS F (T(n+1)),
The minimum value at that time is +*inS F (T(n+1))
Then, when n steel plates are lifted, the downward force acting on the nth steel plate is in the range w(n)XminSF(T(n)) to w(n) When (n+1) steel plates are lifted, (n
+1) What is the downward force acting on the @-th steel plate?

w(n+1)XminS F(T(n+1))~w(n
+1) X+++axS F(T(n+1)).

Therefore, the magnetic attraction force acting between the (n-1)th steel plate and the nth steel plate is the maximum downward force expected to act on the nth steel plate due to lifting, that is, w (n ) X wax S F (T (n)) or more, and it is expected that the magnetic attraction force acting between the nth steel plate and the (n+1)th steel plate will act on the (n+1)th steel plate by lifting it. The minimum value of the downward force, i.e. w(n+1) Xm1nS F (T(n+1))
If the excitation current IA is set so that it is less than When n steel plates are lifted, n
The exciting current IA(n
) between the nth steel plate and the (n+1)th steel plate,
The excitation current IA(n+
1), the excitation current IA may be set to a value greater than or equal to IA(n) and less than IA(n+1).

By the way, when a riffmag is excited to generate enough magnetic attraction force to attract the nth steel plate to the (n-1)th steel plate, the (n+1)th steel plate will be magnetically attracted to the nth steel plate. In some cases, a magnetic attraction force sufficient or capable of causing the magnetic attraction force to occur may be generated. In other words,
Even if the riffmag is excited to the extent that it generates a magnetic attraction force sufficient to attract the (n+1)th steel plate to the nth steel plate, or a magnetic attraction force that is likely to attract the (n+1)th steel plate, the (n−1)th steel plate Sufficient magnetic attraction force may not be generated to attract the n-th steel plate. For example, in the graph shown in FIG. 5, this corresponds to the case where the magnetic attraction force required between the (n-1)th steel plate and the nth steel plate is F''(n). In this case, (n+
1) Even if the riffmag is excited with an excitation current IA (n+1) that can generate a magnetic attraction force F (n+1) that may magnetically attract the (n-1)th steel plate and the nth steel plate There is a magnetic attraction force F' smaller than F#(n) between
(n) In order to prevent L from occurring, (n+
1) It is not possible to excite the riffmag to cause the (n-1)th steel plate to attract the nth steel plate without magnetically attracting the steel plate. Such a phenomenon may occur when the nth steel plate is wide or long and therefore has a large weight compared to its thickness.

For this reason, it is determined whether or not it is possible to make the (n-1)th steel plate adsorb the nth steel plate without magnetically adsorbing the (n+1)th steel plate to the nth steel plate (hereinafter referred to as "nth steel plate"). It is necessary to determine whether lifting is possible or not.Here, it is necessary to generate a magnetic attraction force F(n+1) that may cause the (n+1)th steel plate to be magnetically attracted to the nth steel plate. When the riffmag is excited with n + 1), the magnetic attraction force F' (n
) and the magnetic attraction force F (n) that can reliably magnetically attract the nth steel plate to the (n-1)th steel plate F'
(n) / F (n) is calculated, and the value of the ratio is (I+
If it exceeds α), it is determined that “lifting is possible”, and it is determined that it is possible to lift (
1+α) or less, it is determined that “lifting is not possible”.

If it is determined that it is not possible to lift the n-th steel plate, the lifting including the (n+1)ti-th steel plate is performed.

In other words, in the same way as above, the magnetic attraction force F (n
), and an exciting current I that generates a magnetic attraction force F(n+2) that may cause the (n+1)th steel plate and the (n+2)th steel plate to magnetically attract each other.
Find A (n + 2), I , A (n) or more I
Set the excitation current IA to be less than A (n + 2). When the rifmag is excited with this excitation current IA, ``mountain'' etc. (n
+1) Since the steel plates are lifted, they are definitely “mountain”.
The excitation current IA is momentarily cut off when it is separated from the current IA. If the excitation current continues to be cut off, the magnetism that attracts the riffmag and the (n+1) steel plates will disappear, causing each steel plate to fall, but in this example, the lowest steel plate is the nth steel plate. The supply of excitation current is restarted when the device separates from the object and falls.

In other words, at the moment when the supply of excitation current is stopped.

Since magnetic energy is stored in the excitation coil,
Magnetism does not disappear until the energy is consumed, and magnetism gradually decreases over time. Therefore, by appropriately selecting the instantaneous interruption time of the excitation current and/or the rifmag that instantaneously interrupts the excitation current, the lowest one of the steel plates being lifted using the residual magnetism at the time of interruption, that is, the unnecessary Only the (n+1)th steel plate can be dropped.

In this embodiment, instantaneous interruption processing is carried out as follows. That is, when relay RLY is switched from on to off while excitation current Io is flowing through excitation coil 52, excitation coil 52 is turned off by relay RLY. Because it is short-circuited,
As shown in FIG. 10, the current {circle around (2)} flowing through the excitation coil 52 gradually decreases from Io along an exponential function curve determined by the time constant specific to the excitation coil. Since the size of this current corresponds to the size of the residual magnetism of the excitation coil 52, the current I is monitored and it is set to a predetermined current Ic.
When the current is reached, relay RLY is turned on and supply of excitation current is started again.

The magnitude of the current Ic is set to the lower limit of the range of current required to lift n steel plates. In other words, the current required to lift n + 1 steel plates is lower than the maximum value of the range of current required to lift n steel plates (the current value when the correction value is maxsF (T (n))). Even if the minimum value of the range (current value when the correction value is m1nsF (T (n + 1)) is smaller, the range of current required to lift n steel plates is smaller than the latter. minimum value (current value when correction value force is 1 m1 nsF (T(n)))
is smaller, so when a current of that value flows through the excitation coil, the downward force acting on the n+1 steel plate will be greater than its magnetic attraction force, so the n+1 steel plate must be reliably separated. I can do it. Further, by restarting the excitation current when the current value has decreased to Ic, it is possible to prevent the n-th steel plate from falling.

Hereinafter, an example of the steel plate suction control will be specifically explained with reference to the flowcharts shown in FIGS. 7a to 7d. The momentary interruption of the excitation current is shown in FIG. 7d.

This control is activated by instructions from the host computer MCPU. At this time, the configuration of the source "mountain", that is, the thickness t1 width WD and length L of each steel plate stacked there, the stacking order, and the number n of steel plates to be sucked are given from the host computer MCPU. Therefore, in step 1, the riff mags 5-i to 5-j to be used are selected based on the length of the steel plate to be attracted, and the interval between the selected riff mags is adjusted.

In step 2, from the table (previously stored in non-volatile memory, the same is true for the others) corresponding to the graph shown in FIG. 6, the maximum value of the correction ratio x S F (T (n)) = and
Minimum value tmins of correction ratio corresponding to layer thickness T(n+1)
Read F (T(n+1)). As mentioned above, these correction ratios ensure the desired lifting of the steel plate against fluctuations in the downward force acting on the steel plate during lifting, so in step 3, the correction ratio waxs F(T(n
)) multiplied by the seal w(n) of the nth steel plate (n-1)
Find the magnetic attraction force F (n) that can reliably magnetically attract the n-th steel plate to the n-th steel plate, and.

The correction ratio wins F (T(n+1)) is multiplied by the weight w(n+1) of the (n+1)th steel plate, and the weight of the nth steel plate is (
The magnetic adsorption force F(n+1) that is likely to magnetically adsorb the n+1)th steel plate is determined.

Next, in step 4, an exciting current IA( n), and (n)th steel plate and (n+1)
When the exciting current IA(n+1) that can generate the magnetic attraction force F(n+1) between the steel plate and the steel plate is read, in step 5, the exciting current IA(n+
The magnetic attraction force F' (
n) is read, and in step 6 it is determined whether or not the n-th steel plate can be lifted.

Here, as mentioned above, F' (n) / F (
If the value of n) exceeds (1+α), it is determined that lifting is possible, and if the value is less than (1+α), it is determined that lifting is not possible.

If it is determined that "lifting the n-th steel plate" is possible in this determination, in step 7, the lift mags 5-i to 5-j selected based on the excitation currents IA(n) and IA(n+1) obtained previously are IA(n) or more to excite IA
An excitation current IA of less than (n+1) is set (K in the flow chart is a value of O or more and less than l).

After this, from the upper computer MCPU to the source "mountain"
When it is notified that the movement of the traveler 2 has been completed, in step 9, the arms 4-1 and 4-2 are driven downward (
(lowering). During this lowering, the landing sensor detects landing before each selected Riff Mag descends to the top of its "mountain." When this is detected, the lowering scale is reset after landing in step 11, and step Riff mags 5-i to 5- selected according to excitation current IA in 12
Start excitation of j.

When lowering further, the riff mags 5-i to 5-j become “
Since it descends onto the topmost steel plate of the mountain and is magnetically attracted to it, a sudden increase in the central magnetic flux is detected via the search coils 53-1 to 53-j.However, the amount of lowering after landing is lower than the set value D
When there is no detection even after o.

There is a possibility that an abnormality may be occurring such as an error in the positional relationship between the riff mags 5-i to 5-j and the "mountain" or an abnormality such as the presence of foreign matter on the topmost steel plate of the "mountain". In step 14, the lowering is stopped and the error is reported to the host computer MCPU.

When a sudden increase in the central magnetic flux is detected without any abnormality.

Arms 4-1 and 4-2 in steps 16-18
The descending drive (lowering) of these is stopped, and then the ascending drive (winding) thereof is started to reset the hoisting amount U.

By this hoisting, the riffmags 5-i to 5-j separate and lift a plurality of steel plates (n sheets are planned) from the "mountain". At this time, if the total thickness of the lifted steel plates does not reach the thickness that saturates the central magnetic flux, a decrease in the central magnetic flux is detected as shown in Figure 8a, but the thickness saturates the central magnetic flux. When the thickness is at or near the thickness, the central magnetic flux does not change much as shown in FIG. 8b. Therefore, if a decrease in the central magnetic flux is detected in step 19, or if the winding amount U is detected in step 20,
is the set value U. If it exceeds the limit, separation is detected and step 2
At step 1, hoisting is stopped for a moment and a judgment is made as to whether the hoisting is appropriate or not.

``The suitability of lifting depends on the layer thickness of the steel plate to be lifted,
That is, it is determined based on the central magnetic flux or the hanging load according to the layer thickness T(n) of the first to nth steel plates.

As an example is shown in FIG. 9, the central magnetic flux changes in proportion to the layer thickness T below the saturation layer thickness To if the excitation current is constant. Since this relationship is determined only by electromagnetic conditions, it is not affected by mechanical vibrations or the like. Therefore, the layer thickness T (n) of the steel plate scheduled to be lifted is the saturated layer thickness To
If it is below, the central magnetic flux φ is read in step 23, and in step 24, the value corresponding to the central magnetic flux φ is determined from the table for reading the layer thickness of the excitation current IA at that time (a table corresponding to the graph shown in FIG. 9). Read the layer thickness T of the steel plate being lifted. In step 25, the layer thickness T read at this time and the layer thickness T of the steel plate scheduled to be lifted are
(n), and if they are equal within the error range, it is determined to be ``suitable for lifting.'' If they differ beyond the error range, it is determined to be ``unsuitable for lifting.''

On the other hand, when the layer thickness T(n) of the steel plate scheduled to be lifted exceeds the saturated layer thickness To, as can be seen from the graph shown in Figure 9, the central magnetic flux is saturated and the relationship with the layer thickness T is unstable, so the determination is made based on the hanging load W detected via the load cells 6-1 and 6-2. In this case, the detection of the hanging load W is strongly affected by mechanical vibrations, etc., so step 26 is performed. In step 27, wait until the difference between the continuously read local maximum value W+ and local minimum value W-'' becomes equal to or less than a predetermined value WO (mechanical vibration becomes small), and then in step 28, the local maximum value W+ and the local minimum value Find a probable value of the hanging load W from W-.In step 29, compare the hanging load W at this time with the total weight W(n) of the steel plate scheduled to be lifted, and check if they are equal within the error range. If it differs beyond the margin of error, it is determined to be unsuitable for lifting.

In the above, if it is determined that it is suitable for lifting the steel plate, the excitation current IA of the lift mags 5-i to 5-j is increased in steps 30 and 31 to ensure reliable magnetic attraction, and then the host computer MCPU is instructed to control the steel plate attraction. However, if it is determined that lifting is inappropriate, an error is notified to the host computer MCPU.

By the way, in step 6, it is determined whether or not the n-th steel plate can be lifted, and F' (n) / F (n)
If the value of is less than (1+α) and it is determined that "lifting is not possible", the process proceeds to step 35 and subsequent steps.

In step 35, the minimum value 1nSF(T(n+2)) of the correction ratio corresponding to the layer thickness T(n+2) is read from the table corresponding to the graph shown in FIG.

As mentioned above, this ratio compensates for the fluctuation of the downward force acting on the steel plate during lifting, and the magnetic attraction force F(
n+2) is its value and the weight of the (n+2)th steel plate w(
n+2), it is guaranteed that the (n+2)th steel plate will not be magnetically attracted. Therefore, in step 37, a magnetic attraction force F(n+2) can be generated between the (n+1)th steel plate and the (n+2)th steel plate from the table corresponding to the graph shown in FIG. 5. When (n + 2) is read, step 38
Then, using this excitation current I A (n + 2) and the excitation current I A (n) obtained previously, I
Set the excitation current IA to be less than A (n + 2) (in the flowchart, '' indicates a value of 0 or more and less than 1).

After this, from the upper computer MCPU to the source “mountain”
When it is notified that the movement of the trapella 2 has been completed, in steps 40 to 47, the riff mag 5-i is moved in the same manner as described above.
The arms 4-1 and 4-2 are lowered until ~5-j falls on the top steel plate of the "mountain" and is magnetically attracted to it, and then, in steps 48 to 52, a decrease in the central magnetic flux is detected. Alternatively, each arm is hoisted until the one hoisting amount U exceeds the set value Uo.

In this case, since (n+1) steel plates are expected to be lifted, the layer thickness T(
If n+1) is less than or equal to the saturated layer thickness To, "separation of unnecessary steel plates based on the central magnetic flux" is performed in steps 54 and below, and when one layer thickness T (n+1) exceeds the saturated layer thickness To, in steps 64 and below. ``Separation of unnecessary steel plates based on hanging load'' is performed.

When performing ``separation of unnecessary steel plates based on central magnetic flux'',
First, in step 54, the central magnetic flux φ of each riff mag is read, and in step 55, the excitation current I at that time is read.
The layer thickness T of the suspended steel plate corresponding to the central magnetic flux φ is read from the layer thickness reading table A. If the layer thickness T read at this time and the layer thickness T(n+1) of the steel plate scheduled to be lifted are equal within the range of error, in step 57 (
Among the riff mags that are adsorbing n+1) steel plates, riff mags 5-1# and 5 located at both ends in the arrangement direction
-j' (initially, they correspond to 5-i and 5-j, respectively), and in step 58, cut off the excitation current to the riff mags 5-1' and 5-j' selected at this time. Note that the processing in step 58 is the same as steps 68A, 68B, and 68C, which will be explained in detail later. As a result, when the (n+1)th steel plate peels off, the central magnetic flux of the riffmag that has attracted it decreases.

After this, in step 59, the central magnetic flux φ of each riffmag
is read, and the number of steel plates that each riffmag is attracted to is detected using a layer thickness reading table. At this time, if there are riff mags that are adsorbing (n+1) more steel plates, the process returns to step 57 and the riff mags located at both ends of the riff mags
-1' and 5-j' are selected and the above is repeated.

In this "separation", the (n+1)th steel plate separates from both ends of the riff mag arrangement, but each time there is separation, the magnetic attraction surface between the nth steel plate and the (n+1)th steel plate decreases. Therefore, the required adsorption force will apparently increase,
(2) The cutting of the (n+1)th steel plate is completed by repeating the process several times.

Therefore, when there are no more riffing mags holding the (n+1) steel plates, in step 61, the layer thickness T of the lifted steel plate corresponding to the central magnetic flux φ at this time is read from the table for reading the layer thickness of the exciting current IA. In step 62, it is compared with M thickness T(n) of the steel plate to be lifted. Here, as described above, if the two are equal within the error range, it is determined that the lifting is suitable, and if they differ beyond the error range, it is determined that the lifting is unsuitable. In addition, the layer thickness T of the lifted steel plate read before "separation" due to instantaneous interruption of the excitation current of the RIFF MAG and the layer thickness planned at that time, that is, the 1st to (n+1)th steel plate layers. If the thickness T(n+1) differs beyond the error range, the process proceeds directly from step 56 to step 62, so "separation" is not performed, but the layer thickness T of the steel plate to be lifted and the layer thickness of the steel plate to be lifted If the thickness T(n) is equal within the error range, it is determined that the material is suitable for lifting, and if it differs beyond the error range, it is determined that the material is "unsuitable for lifting."

In addition, when performing "separation of unnecessary steel plates based on the suspension load," the mechanical vibration is reduced in steps 63 and 64 (the continuous suspension load read through the load cells 6-1 and 6-2) Wait until the difference between the local maximum value W0 and the local minimum value W- becomes equal to or less than a predetermined value WO), and in step 65, the suspension load W is calculated from the local maximum value W+ and the local minimum value W-.
Find the probable value of. At this point, it is planned to lift (n+1) steel plates, so the lifting load W determined at this time is compared with the weight W(n+1) of the (n+1) steel plates.

If they are equal within the range of error, ``separation'' is performed by instantaneous interruption of the excitation current of the refmag in steps 67 and subsequent steps.

In this case, first, in step 67, the momentary interruption current determination value Ic is set to an initial value. As shown in Fig. 10, this value Ic is the current value that determines the conditions for restarting the current after the excitation current is cut off. It is set to the minimum value of the current range, that is, the required current value when the correction ratio is m1nsF(T (n)). Note that the initial value is similarly set to Tc between steps 56 and 57 described above.

In step 68A, the supply of the excitation current IA to the riff mags 5-i to 5-j (that is, all the riff mags selected in step 1) is stopped. That is, the excitation current IA is set to 0 in the current supply unit REG, and the relay RLY is turned off. In this case, the current supplied from the current supply unit REG to the excitation coil becomes zero, but magnetic energy is accumulated in the excitation coil at the time the current supply is stopped. Also, relay R
Since the excitation coil is short-circuited through the contacts C2 and C3 of LY and the current detector DET, a current I flows through the excitation coil due to the stored magnetic energy, and this current I is detected by the current detector DET.

In this case, if the inductance of the excitation coil is the inductance and the resistance value is R, then the magnitude of the current (2) can be determined by the following equation.

I = Io-e" However, α knee (R/L) t IO = current immediately before stopping the supply of excitation current t: time after stopping the supply of excitation current, that is, the current I is the 10th
It decreases with time t according to an exponential function, as shown in the range te in the figure.

Magnetic energy exists in the excitation coil according to the magnitude of the current I, and a corresponding attractive force acts between the nth and n+1th steel plates, and when I becomes less than a predetermined value, it acts on the steel plate. Since the suction force is smaller than the downward force, n+1
The th steel plate separates from the nth steel plate and falls.

Further, in step 68A, the current value Id detected by the current detector DET is input. Then, in the next step 68B, the detected value Id and the current determination value Ic are compared. Id is I
While the current is larger than c, the process returns from step 68B to 68A, and the excitation current continues to be stopped.

When Id becomes equal to or less than Ic, the process proceeds to step 68G and the current supply is restarted. That is, relay RLY is turned on and target current value IA given to current supply unit REG is returned to original value Io.

In reality, when relay RLY is switched from on to off, there will be some time delay until the correct detected value of current Id (Id>Ic) is obtained, so initially Id)I
c, and then execute step 68B.

Also, if there is a change in the condition of the steel plate being lifted, mechanical vibrations will occur, so wait until the detected value of the load cell 6-1, 6-2 becomes stable in steps 69 and 70, and then repeat the process in step 71 as described above. Find the hanging load W.

In step 72, the hanging load W obtained at this time and (
A comparison is made with the weight W(n+1) of n+1) steel plates. If the two are equal within the error range, the separation of the (n+1)th steel plate has failed, so proceed to step 73, reduce the current judgment value Ic by a minute value Δt, and return to step 68A to excite again. Perform a momentary interruption of the current.

In step 74, the hanging load W determined in step 65 (that is, before performing "separation" due to momentary interruption of the excitation current) and the weight W(n+1) of the (n+1) steel plates exceed the error range. If different, or step 71 (
In other words, if the hanging load W obtained after performing ``disconnection'' due to momentary interruption of the excitation current and the weight W(n+1) of the (n+1) steel plates differ beyond the error range, The hanging load W and the n pieces that were originally planned to be lifted (
The weight W(n) of the steel plate (the number specified by the host computer MCPU) is compared with the weight W(n) of the steel plate, and if the two are equal within the error range, it is determined that the weight is suitable for lifting, and the weight exceeds the error range. If they are different, it will be judged as unsuitable for lifting.

Similarly to the above, if it is determined that the lift is suitable in the above steps, the riff mag 5-i is
After increasing the excitation current IA of ~5-j to ensure reliable magnetic adsorption, the host computer MCPU is notified of the end of the steel plate adsorption control, but if it is determined that lifting is unsuitable, an error is sent to the host computer MCPU. inform.

In the above-mentioned embodiment, when the excitation current is instantaneously interrupted, the current ■ actually flowing through the excitation coil is detected, and its value I
The conditions for restarting the excitation current supply are determined by comparing d with the current determination value Ic. However, even without monitoring the current I, supply of the excitation current can be restarted at a preferable timing. That is, the magnitude of the current I is determined by the current value Io immediately before the excitation current supply is stopped as described above, the time t, and the time constant (
Since the time constant generally does not change, if Io is known, the value of the current I at each timing can be calculated.

Conversely, the time tc required for the current ■ to reach Ic can also be calculated from the following equation.

tc = −Tz X Qn (Ic/Io) However,
Tz: time constant of excitation coil When momentary interruptions are controlled by this method, the process shown in FIG. 7d of the above-mentioned embodiment may be changed as shown in FIG. 11. That is, in step 68 of FIG. 11, after turning off relay RLY, the instantaneous interruption time S preset in step 67A is
After this period has elapsed, relay RLY is turned on again and the supply of excitation current is resumed.

The value set as the instantaneous interruption time S in step 67A corresponds to the time tc obtained by calculating the above formula. This instantaneous interruption time may be 0 under certain conditions.
．． The value is about 5 to 2.5 seconds.

Even if there is an instantaneous interruption for the calculated time tc, n
If the +1st steel plate cannot be separated, that is, if the separation fails, the instantaneous interruption time is increased in step 73A, and the instantaneous interruption process is performed again.

Further, in the embodiment shown in FIG. 11, if there are n + 1 riff mags to be picked up in step 60, the riff mags are reselected in the next step 60B.

If the number of riff mags to be sucked changes here, the process passes through step 60C and returns to step 58. However, if the number of riff mags does not change, the process proceeds to step 60D, where the instantaneous interruption time So is reduced to a minute time Δt. and returns to step 58. In other words, either change the number of riff mags to be adsorbed or change the instantaneous interruption time S.

After changing the value, cut the (n+1)th steel plate again.

〔Effect of the invention〕

As explained above, in the lifting magnet crane device of the present invention, the maximum value of the excitation current range required to lift n steel plates is the minimum value of the excitation current range required to lift n+1 steel plates. greater than the value
Even in cases where it is difficult to separate the n+1 steel plate from the n+1 steel plate, it is possible to separate the n+1 steel plate by lifting the n+1 steel plate in advance and then instantaneously interrupting the excitation current. It is possible to accurately lift only the desired number (n) of steel plates. Moreover, in the instantaneous interruption process, the current Ic or the time t required to separate the n+1th steel plate
The setting of c is easy, and as shown in the embodiment, it can also be set automatically.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of a lifting magnet crane that embodies the present invention as an example. FIG. 2a is a plan view of the lifting magnet 5 included in the lifting magnet crane shown in FIG. 1, viewed from below, and FIG. 2b is a sectional view taken along the line IIB-nB. FIG. 3 is a block diagram showing the configuration of a control device included in the lifting magnet crane shown in FIG. 1. Figures 4 and 5 show the layer thickness T of the steel plate on the magnetically adsorbed side.
, is a graph showing the relationship between the thickness t of the steel plate on the side to be magnetically attracted, the excitation current IA, and the magnetic attraction force F acting between each steel plate. FIG. 6 is a graph showing the relationship between the layer thickness of the steel plate to be lifted and the correction ratio. 7a to 7d are flowcharts showing an example of the operation of the microcomputer CPU shown in FIG. 3. FIG. FIGS. 8a and 8b are waveform diagrams showing changes in the detected magnetic flux due to the layer thickness and separation of the steel plate to be lifted. FIG. 9 is a graph showing the relationship between the layer thickness of the steel plate being lifted and the detected magnetic flux. FIG. 10 is a waveform diagram showing changes in the supply current IA and the current I flowing through the excitation coil during a momentary interruption. FIG. 11 is a flowchart showing part of the operation of the modified embodiment. 1: Rail 2: Traveler 3: Arm (vertical movement means) 4: Beam 5, MG: Lifting magnet (electromagnet) 51: Core (magnetic core) 52: Excitation coil (excitation coil) 53: Search coil (magnetic flux detection means) 〉 6: Load cell (hanging load detection means) Mcpu: Upper computer RCU: Riffmag control unit (processing means) REG
: Current supply unit (current supply means) RL''/ : Relay (current control means) DET : Current detector (current detection means) 71 to 73: Steel plate bundle 1 Figure 2a Figure 2b Figure East 4 Figure yK5 Figure East 6 Zuko Geimaru Questions

Claims (2)

[Claims] (1) At least one electromagnet that has a magnetic core and an excitation coil for exciting the core and magnetically attracts a magnetic object: Current supply means that generates an excitation current to be supplied to the excitation coil: The excitation coil current control means for controlling the current flowing through the excitation coil; current detection means for detecting the current flowing through the excitation coil; vertical movement means for moving the electromagnet up and down; and controlling the current supply means and the current control means to control the excitation coil. An excitation current having a first current value corresponding to the number of sheets to be attracted is applied to the object, and after lifting the attracted object, the supply of the excitation current is cut off, and the current value detected by the current detection means is set to the The second current value is smaller than the first current value.
A control device for controlling the number of steel plates hung on a LifMag crane, comprising: processing means for restarting the supply of excitation current when the current value has decreased to a current value of . (2) at least one electromagnet that has a magnetic core and an excitation coil for exciting the core and magnetically attracts a magnetic object; current supply means that generates an excitation current to be supplied to the excitation coil; the excitation coil current control means for controlling the current flowing through the electromagnet; vertical movement means for moving the electromagnet up and down; and controlling the current supply means and the current control means to excite the excitation coil at a first current value corresponding to the number of sheets attracted to the excitation coil. After applying current and lifting the attracted object to be lifted, the supply of excitation current is cut off, and the current flowing through the excitation coil is reduced to a second current value smaller than the first current value. A device for controlling the number of steel plates hung on a Lifmag crane, comprising: processing means for restarting the supply of excitation current when a predetermined cut-off time required for has elapsed.