JPH11139750A - Hoist electromagnet for attachment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a rise up time of an excitation current in an excitation coil of a hoist electromagnet, and to suppress increasing of power consumption. SOLUTION: A control circuit 20 for coil excitation is provided, which has a first/second excitation coil C1, C2 constituted by dividing into two parts an excitation coil of a hoist electromagnet 10 and a DC constant voltage power source E exciting the first/second excitation coil C1, C2, in the beginning of excitation, relating to the DC constant voltage power source E, to make an excitation current flow in the first/second excitation coil C1, C2 connected in parallel, after a prescribed time, to switch so as to connect the first/second excitation coil C1, C2 in series to the DC constant voltage power source E so as to allow the excitation current to flow. Here, when the first/second excitation coil C1, C2 is formed so as to be almost equally divided, the excitation current uniformly flows, its rise up time can be further shortened. In the circuit 20 for excitation, when a short-circuit preventing series protection resistor Rs is provided, a short-circuit, when a switch M1, M2 is switched, can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a lifting electromagnet for an attachment, which is mounted on a tip of an arm of a hydraulic shovel or the like to lift scrap steel or the like.

[0002]

2. Description of the Related Art Heretofore, lifting electromagnets for attachments which are attached to the tip of an arm of a hydraulic shovel or the like and which lift scrap steel or the like have been put to practical use. For example,
FIG. 3 (A) shows a process of exciting an attachment lifting electromagnet having a power consumption of 10 kW or more.
This will be described with reference to FIG. FIG. 3A is a diagram showing a coil excitation control circuit used for the excitation coil of the conventional lifting electromagnet for attachment, and FIG. 3B is a characteristic diagram showing a change over time of the excitation current of the lifting electromagnet. .

In FIG. 3A, En is an engine for driving a hydraulic excavator or the like (not shown) equipped with the above-mentioned conventional lifting electromagnet for attachment, G is a DC generator driven by the engine En, and Ex is an engine. Is an exciter. C is an exciting coil of the lifting electromagnet LM, MC1 and M
C2 is a switch such as a contact, R is a resistor for short-circuit protection, C
g is a field coil of the generator G. The excitation coil C of the lifting electromagnet LM having a power of 10 kW or more includes the excitation coil C shown in FIG.
A DC generator G dedicated to the exciting coil as shown in FIG. 3 is used, or a voltage that changes over time as shown in FIG. 3B is applied to the exciting coil C by a combination of an AC generator and a rectifier (not shown). To excite.

[0004] In this case, during the initial 3 to 10 seconds of the excitation,
The switches M1 and MC2 are closed, and the magnetic field coil Cg is overexcited by the exciter Ex to increase the voltage of the DC generator G. For example, as shown in FIG. The magnetic poles of the lifting electromagnet are over-excited to shorten the time required for the current to rise, thereby improving the work efficiency of the lifting operation. On the other hand, at the time of transporting scrap steel or the like (not shown) in which the attracting force of the lifting electromagnet is stable, the switch MC2 is opened to switch to a DC voltage of 200 V, thereby increasing the power consumption of the lifting electromagnet as a desired attraction force. Has been prevented.

[0005]

By the way, for a lifting electromagnet for an attachment, such as a lifting electromagnet for a hydraulic shovel, which consumes less power than the above-described lifting electromagnet, a small DC generator or a storage battery is used as a power source. May be used. In this case, for example, by opening and closing the switch with a DC constant voltage of 24 V,
Excitation of the lifting electromagnet will be adjusted.However, since the excitation coil of the lifting electromagnet has self-inductance, the current rise at the initial stage of the excitation of the lifting electromagnet is slow, especially when transferring scrap steel. Need to be turned on and off, which causes a problem that work efficiency is reduced.

FIG. 4 shows a case where a conventional lifting electromagnet for an attachment is excited by a 24 V DC power supply.
This will be described using (A) and (B). FIG. 4A is a diagram showing an exciting control circuit used for an exciting coil of a conventional small attachment lifting electromagnet, and FIG. 4B is a characteristic diagram showing a change over time of an excitation current of the lifting electromagnet. . In FIG. 4A, BT is a storage battery, and MC is a switch such as a contact. In addition, C is an excitation coil of the lifting electromagnet LM, En is a driving engine, and Ex is an exciter.

In this configuration, when the switch MC of the control circuit for exciting the coil shown in FIG. 4A is turned on, as shown in the change over time of the exciting current in FIG. The time required to reach 2% (hereinafter referred to as time constant τ) is large. By the way, in the transfer operation of the scrap steel material by the above-mentioned lifting electromagnet for the attachment for the hydraulic excavator, since the lifting operation is performed once every 15 to 30 seconds, if the time constant τ is a large value, the lifting is performed as described above. This will hinder work. The present invention
Solving the above-mentioned problems (problems), shortening the rise time of the exciting current of the exciting coil of the lifting electromagnet,
An object of the present invention is to provide a lifting electromagnet for an attachment that suppresses an increase in power consumption.

[0008]

In order to solve the above-mentioned problems, a lifting electromagnet for an attachment according to the present invention is configured such that the excitation coil of the lifting electromagnet is divided into two parts. And a second excitation coil, and a DC constant voltage power supply for exciting the first and second excitation coils, and the first and second excitation coils are supplied to the DC constant voltage power supply at an initial stage of the excitation. And a coil excitation control for passing an exciting current by connecting the first and second exciting coils to the DC constant voltage power supply after a predetermined time and connecting the first and second exciting coils in series. It was configured to provide a circuit. Thereby, the rise time of the exciting current of the exciting coil of the lifting electromagnet can be shortened, and the work efficiency of the lifting operation of the scrap steel material can be improved. In addition, after the lifting electromagnet has obtained the desired attraction force, the excitation current was supplied in parallel to the excitation coil, but this time, when the excitation current is switched in series, the power consumption of the lifting electromagnet can be reduced. Can be.

In the lifting electromagnet for an attachment according to the second aspect, the first and second excitation coils are divided substantially equally. In this way, the winding resistance and the self-inductance of the coil are almost equally divided into two, so that the exciting current also flows evenly, so that the rise time of the exciting current can be further reduced, and the work efficiency of the lifting work of the scrap steel material Can be further improved.

In the lifting electromagnet for an attachment according to the third aspect, the coil exciting control circuit is provided with a series protection resistor for preventing short circuit. This can prevent a short circuit at the time of switch switching.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a lifting electromagnet for an attachment according to the present invention is shown in FIGS.
This will be described with reference to FIG. FIG. 1 is a diagram showing a control circuit for exciting a coil used for a lifting electromagnet for an attachment;
FIG. 2A is a vertical cross-sectional side view showing a state in which the exciting coil of the lifting electromagnet is divided into upper and lower parts, and FIG. 2B is a case where a current is applied to the coil by the coil exciting control circuit. FIG. 4 is a characteristic diagram showing a change over time of an exciting current of the conventional device compared with a conventional device.

In FIG. 1, C1 and C2 are excitation coils of the lifting electromagnet 10 for an attachment of the present invention.
As shown in FIG. 2 (A), the upper and lower layers are equally divided into two layers.
The first and second excitation coils M1 configured by dividing and arranging them are used for initial excitation switches formed of switches such as electromagnetic switches, and M2 is also used for transporting steel materials formed of switches such as electromagnetic switches. This is a transport excitation switch to be activated. Rs is a short-circuit prevention series protection resistor inserted when each of the switches M1 and M2 is switched, and E is a DC constant voltage power supply such as a storage battery. In FIG. 2A, 1
1A and 11B are outer poles, 12 is an inner pole, and in FIG. 1B, I ₁ is the current value of the conventional lifting electromagnet, I ₂ is the current value of the lifting electromagnet of the present invention, and I ₀ is the height of the scrap steel material. This is a standard current value for obtaining the necessary attraction force. Note that the current value I ₁ of the conventional lifting electromagnet is
As shown in FIG. 2 (B), is a standard current value I ₀ after sufficient time has passed.

With the above configuration, the outer poles 11a and 11b and the inner pole 12 of the lifting electromagnet 10 for an attachment according to the present invention are provided.
Is excited by, for example, a 24 V DC constant-voltage power supply E, first, the initial excitation switch M1 is turned on at the beginning of the excitation, and an excitation current flows through the first excitation coil C1. Then, after turning on the initial excitation switch M1, exciting current value I ₂ flowing through the first excitation coil C1 is a standard current value I ₀
That is, at a timing approaching the value of I ₀ = 24 / (2 × Rh) = 12 / Rh (for example, after 2 to 3 seconds), the initial excitation switch M1 is turned off, and the transport excitation switch M2 is turned off. Turn on. Here, Rh is the value of the electric resistance of the first and second excitation coils C1 and C2.

In the conventional lifting electromagnet for attachment, if the value of the self-inductance of the exciting coil is L and the value of the electric resistance is R, the time constant τ0 is τ0 = L / R. On the other hand, in the lifting electromagnet of the present invention, since the exciting coil is equally divided into two, the electric resistance value Rh of each of the first and second exciting coils C1 and C2 is half of the resistance value R, similarly. The value Lh of the self-inductance is also half of the value L of the self-inductance. By the way, assuming that a resistor having a resistance value of 1/3 of the resistance value Rh of the first and second excitation coils C1 and C2 is used as the series protection resistor Rs provided for short-circuit protection, the time constant in this case is as follows. τ
Is τ = Lh / (Rh + Rh / 3) = Lh / (1.33 · Rh) = (L / R) / 1.
33 = τ0 / 1.33. Also, the exciting current value I ₂ flowing through each of the exciting coils C1 and C2 is also I ₂ = 24 / 1.33 · Rh = 18 / Rh = 1.5 · I ₀ . Therefore, the time constant τ can be reduced to 75% as compared with the conventional time constant τ0, and the exciting current value I ₂
After a sufficient time elapses, the current rises to a value that is about 1.5 times the standard current value I ₀ , so that a current rise curve as shown in FIG.
Can be greatly reduced.

Further, if an exciting current is passed in parallel to the exciting coils C1 and C2, the power consumption of the lifting electromagnet 10 increases, so that the lifting electromagnet 10 reaches a desired excitation current value I ₀ and the scrap steel material After obtaining the attraction force sufficient to lift the lifting electromagnet 10, the lifting electromagnet 10 is adjusted to an appropriate attraction force by operating the switch promptly as described above and connecting the exciting coils C1 and C2 in series to supply an exciting current. Power consumption can be suppressed. As shown in FIG. 2 (A), when the excitation coils C1 and C2 are divided into two upper and lower layers, the coils can be stored compactly in a well-balanced manner.

[0016]

The lifting electromagnet for an attachment according to the present invention has the following excellent effects because it is configured as described above. (1) With the configuration as described in claim 1, the rise time of the exciting current of the exciting coil of the lifting electromagnet can be shortened, and the work efficiency of the lifting operation of the scrap steel material can be improved. (2) In addition, after the lifting electromagnet has obtained the desired attraction force, the excitation current is passed in parallel to the excitation coil, but now the excitation current is passed in series, so that the power consumption of the lifting electromagnet is reduced. Can be held down.

(3) If the first and second exciting coils are divided almost equally as described in claim 2, the current resistance and the inductance of the coils are divided almost equally into two, so that the exciting The current also flows evenly, the rise time of the excitation current can be further reduced, and the work efficiency of the scrap steel lifting operation can be further improved.

(4) If the exciting circuit is provided with a series protection resistor for short circuit prevention as described in claim 3, a short circuit at the time of switch switching can be properly prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a control circuit for exciting a coil used in a lifting electromagnet for an attachment according to the present invention.

FIG. 2A is a vertical sectional side view showing a state in which an excitation coil of a lifting electromagnet for an attachment of the present invention is divided into upper and lower parts, and FIG. 2B is an excitation coil of a lifting electromagnet for an attachment of the present invention. FIG. 7 is a characteristic diagram showing a change with time of an exciting current flowing through the magnet in comparison with that of a conventional lifting electromagnet for attachment.

FIG. 3A is a diagram showing an exciting control circuit used for an exciting coil of a conventional lifting electromagnet having a power consumption of 10 kW or more, and FIG. 3B is a diagram showing the exciting current of the lifting electromagnet. It is a characteristic view which shows a time-dependent change.

FIG. 4A is a diagram showing an exciting control circuit used for an exciting coil of a conventional small lifting electromagnet for an attachment, and FIG. 4B shows a temporal change of an exciting current of the lifting electromagnet. It is a characteristic diagram.

[Explanation of symbols]

 10: Lifting electromagnet for attachment of the present invention 20: Coil excitation control circuit C1, C2: First and second excitation coils M1: Initial excitation switch M2: Carrier excitation switch Rs: Series protection resistor E: DC constant Voltage power supply

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideaki Iwami 150 Motoyashiki, Miya-cho, Toyohashi-shi, Aichi Prefecture Inside the Shinko Electric Co., Ltd. Toyohashi Office

Claims (3)

[Claims] A first excitation coil formed by dividing an excitation coil of a lifting electromagnet into two parts; and a DC constant voltage power supply for exciting the first and second excitation coils. Initially, the DC constant voltage power supply is connected in parallel to the first and second excitation coils to flow an excitation current,
A coil excitation control circuit for switching the first and second excitation coils to be connected in series to the DC constant voltage power supply after a predetermined time so as to allow an excitation current to flow is provided. Lifting electromagnet. 2. A lifting electromagnet for an attachment according to claim 1, wherein said first and second excitation coils are divided substantially equally. 3. The lifting electromagnet according to claim 1, wherein the coil excitation control circuit includes a series protection resistor for preventing short circuit.