JP2010179978A - Lifting magnet control system and lifting magnet control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lifting magnet control system capable of reducing energy consumption during an excitation period of a lifting magnet. <P>SOLUTION: The lifting magnet control system 1 includes a generator 4, a power conversion unit 5 which converts power generated by the generator 4 and supplies it to a lifting magnet 2, and a control unit 7 for controlling the number of revolutions of the generator 4 so that the output power of the power conversion unit 5 is gradually reduced during the excitation period of the lifting magnet 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lifting magnet control system and a lifting magnet control method.

  Generally, a lifting magnet for lifting an iron piece in cargo handling work or construction work is known. As a lifting magnet, in addition to what is installed in a factory or the like, there are some that are mounted on a vehicle. When using a lifting magnet, the lifting magnet is energized and lifted by attracting iron pieces. Then, when releasing the iron piece, the lifting magnet is demagnetized.

  Patent Document 1 describes a working machine including a lifting magnet. In this work machine, as a lifting magnet control system for controlling excitation and demagnetization of the lifting magnet, a generator (17), and a magnet controller (20) for supplying the generated power of the generator (17) to the lifting magnet, Power generation stopping means (25). This power generation stop means stops the power generation operation of the generator (17) via the hydraulic motor (16) when the adsorption action of the lifting magnet is stopped, that is, when the lifting magnet is stopped, thereby preventing unnecessary operation. is doing.

JP 2002-348087 PR

  By the way, in the conventional lifting magnet control system, in order to supply a constant voltage to the lifting magnet during the excitation period of the lifting magnet, the rotational speed of the generator is kept constant. Further, in the conventional lifting magnet control system, a power conversion unit is provided between the lifting magnet and the generator, and the voltage supplied to the lifting magnet is controlled by performing PWM control in the power conversion unit. For this purpose, the rotational speed of the generator is set to be large in consideration of PWM control in the power converter. As a result, the energy consumption during the excitation period of the lifting magnet was large.

  Therefore, an object of the present invention is to provide a lifting magnet control system and a lifting magnet control method capable of reducing energy consumption during the excitation period of the lifting magnet.

  The lifting magnet control system of the present invention is configured to gradually reduce the output power of the generator, the power converter that converts the power generated by the generator and supplies the power to the lifting magnet, and the excitation period of the lifting magnet. And a control unit for controlling the rotational speed of the generator.

  A lifting magnet control method according to the present invention includes a generator, a power converter that converts the power generated by the generator and supplies the converted power to the lifting magnet, and a controller that controls the output power of the power converter. In the lifting magnet control method, the rotational speed of the generator is controlled so that the output power of the power converter is gradually decreased during the excitation period of the lifting magnet.

  Here, gradually decreasing the output power of the power conversion unit is a concept including that the output power of the power conversion unit increases due to unintended factors such as external environmental fluctuations in the process. The output power of the power converter is a concept including output power, output voltage, and output current, and is controlled by a lifting magnet control method, that is, by power control, voltage control, or current control. Any one of the output currents shall be indicated.

  The excitation period of the lifting magnet includes, for example, an overshoot period in which the excitation current to the lifting magnet is raised in a short time, an overexcitation period in which the magnetic force of the lifting magnet 2 is temporarily increased so that the suspended load can be easily captured, and It can be divided into a rated excitation period in which the excitation state is maintained while supplying power in the vicinity of the rated power of the lifting magnet 2, and the required power decreases in this order. The exciting period of the lifting magnet may not have an overexciting period.

  According to the present invention, since the rotational speed of the generator is controlled so as to gradually decrease the output power of the power conversion unit during the excitation period of the lifting magnet, the rotational speed of the generator gradually decreases. Therefore, energy consumption during the excitation period of the lifting magnet can be reduced as compared with the conventional case where the rotational speed of the generator is controlled to be constant.

  The control unit described above has a target power pattern that gradually decreases in the order of the overshoot period, the overexcitation period, and the rated excitation period in the excitation period of the lifting magnet so that the output power of the power conversion unit becomes the target power pattern. Furthermore, it is preferable to control the rotation speed of the generator. Here, the target power pattern is a concept including a target power pattern, a target voltage pattern, and a target current pattern, and is controlled by a lifting magnet control method, that is, by power control, voltage control, or current control. Any one of a pattern and a target current pattern shall be shown.

  The power conversion unit includes a DC conversion unit that converts the generated power of the generator into DC power, and an H bridge circuit unit that receives the DC power of the DC conversion unit and controls excitation and demagnetization of the lifting magnet. The switching element in the H-bridge circuit section is preferably a contact switch.

  Thus, instead of power control by PWM control in the H bridge circuit unit of the conventional power conversion unit, by performing power control by rotation speed control of the generator, as a switching element in the H bridge circuit unit of the power conversion unit Instead of a contactless switch such as a relatively high speed transistor or IGBT, a contact switch such as a relatively low speed mechanical switch can be used. As a result, the price can be reduced. Also, maintainability can be improved.

  According to the present invention, energy consumption during the excitation period of the lifting magnet can be reduced.

It is a figure which shows the electrical structure of the lifting magnet control system which concerns on embodiment of this invention. The electric structure of the power converter shown in FIG. 1 is shown. It is a figure which shows the target voltage pattern of the target value supply part shown in FIG. It is a figure which shows the time waveform of the voltage applied to the both ends of a lifting magnet, and the electric current supplied to a lifting magnet.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a diagram showing an electrical configuration of a lifting magnet control system according to an embodiment of the present invention. FIG. 1 illustrates a lifting magnet control system mounted on a lifting magnet vehicle (work machine). The lifting magnet control system 1 receives a driving force from a generator driving unit 3 that receives energy from an engine in a lifting magnet vehicle, and controls excitation and demagnetization of the lifting magnet 2. The lifting magnet control system 1 includes a generator 4, a power conversion unit (control panel) 5, a target value supply unit 6, and a control unit 7.

  The generator 4 receives the rotational driving force from the generator driving unit 3 and generates power. In the present embodiment, the generator 4 supplies three-phase AC power to the power conversion unit 5 as generated power. Here, the generator drive unit 3 is exemplified by a hydraulic motor. In the generator driving unit 3 of the present embodiment, the rotational driving force is controlled in accordance with a control signal from the control unit 7.

  The power converter 5 converts the power generated by the generator 4 and supplies it to the lifting magnet 2. FIG. 2 shows an electrical configuration of the power converter 5. The power conversion unit 5 is a circuit that performs excitation and demagnetization of the lifting magnet 2, and includes a DC conversion unit 30, an H bridge circuit unit 40, and a demagnetization energy absorption unit 50.

The DC converter 30 converts the AC voltages V _{AC1 to} V _AC3 supplied from the generator 4 into a DC voltage V _DC . The DC converter 30 has a positive output terminal 30a and a negative output terminal 30b, and provides the generated DC voltage _VDC between the positive output terminal 30a and the negative output terminal 30b. In the present embodiment, the positive output terminal 30a functions as a high potential power source, and the negative output terminal 30b functions as a low potential power source. The DC converter 30 may be configured to convert an AC voltage from a single-phase AC power source into a DC voltage. Further, when the generator 4 is a DC generator, the DC converter 30 is not necessarily provided.

  The DC conversion unit 30 of the present embodiment is configured by a bridge circuit including six diodes 31a to 31f, and performs three-phase full-wave rectification. Specifically, among the diodes 31a to 31f, the diodes 31a and 31b are connected in series, the diodes 31c and 31d are connected in series, and the diodes 31e and 31f are connected in series. In addition, the group consisting of the diodes 31a and 31b, the group consisting of the diodes 31c and 31d, and the group consisting of the diodes 31e and 31f are connected in parallel to each other. One end on the cathode side of the set of these diodes is electrically connected to the positive output end 30a, and the other end on the anode side is electrically connected to the negative output end 30b.

  An AC power supply line 4a extending from a one-phase power supply terminal in the generator 4 is electrically connected between the diode 31a and the diode 31b. An AC power supply line 4b extending from another one-phase power supply terminal of the generator 4 is electrically connected between the diode 31c and the diode 31d. Between the diode 31e and the diode 31f, an AC power supply line 4c extending from another one-phase power supply terminal of the generator 4 is electrically connected. In addition, the DC conversion unit may be configured by, for example, a pure bridge circuit using a thyristor or a mixed bridge circuit using a diode and a thyristor. In the case where the DC conversion unit is configured by a pure bridge circuit or a mixed bridge circuit, the thyristor is phase-controlled at a predetermined control angle by a phase control circuit (not shown).

  The H bridge circuit unit 40 controls excitation and demagnetization of the lifting magnet 2. The H-bridge circuit unit 40 includes first to fourth switching elements 41a to 41d and first to fourth diodes electrically connected between both ends of the first to fourth switching elements 41a to 41d. It is comprised by the H bridge circuit containing 42a-42d.

  Specifically, one end of the first switching element 41a is connected to the positive output end 30a of the DC converter 30, and the other end of the first switching element 41a is connected to one end of the second switching element 41b. Has been. The other end of the second switching element 41 b is connected to the negative side output end 30 b of the DC converter 30. On the other hand, one end of the third switching element 41c is connected to the positive output end 30a of the DC converter 30, and the other end of the third switching element 41c is connected to one end of the fourth switching element 41d. Yes. The other end of the fourth switching element 41 d is connected to the negative output end 30 b of the DC conversion unit 30. The anodes of the first to fourth diodes 42a to 42d are connected to the other ends of the first to fourth switching elements 41a to 41d, respectively, and the cathodes of the first to fourth diodes 42a to 42d are Are connected to one ends of the first to fourth switching elements 41a to 41d, respectively. The other end of the first switching element 41a and one end of the second switching element 41b are connected to one end of the lifting magnet 2, and the other end of the third switching element 41c and one end of the fourth switching element 41d. Is connected to the other end of the lifting magnet 2.

  The control terminals of the first to fourth switching elements 41a to 41d are connected to a control circuit (not shown), and the conduction state between one end and the other end of each of the first to fourth switching elements 41a to 41d is It is controlled by a control voltage (or control current) provided from the control circuit. In the present embodiment, the adjustment of the output voltage of the H-bridge circuit unit 40 is performed according to the number of rotations of the generator 4, as will be described later. Therefore, the duty of PWM control in the control circuit is fixed.

  The first to fourth switching elements 41a to 41d are contact switches. As a contact switch, it is a switch which has a contact which contacts mechanically, Comprising: Mechanical switches, such as an electromagnetic contactor (MC switch), are applicable.

  The demagnetizing energy absorbing unit 50 is a circuit part for absorbing energy accumulated in the lifting magnet 2 when the lifting magnet 2 is demagnetized. The demagnetizing energy absorbing unit 50 is connected between the positive output end 30 a and the negative output end 30 b of the DC converter 30. In the present embodiment, the demagnetization energy absorbing unit 50 includes a capacitive element 51. Various circuit configurations can be applied to the demagnetizing energy absorbing unit 50.

  Returning to FIG. 1, the target value supply unit 6 has a target voltage pattern for adsorption by the lifting magnet 2, that is, excitation of the lifting magnet 2, and supplies the target voltage pattern to the control unit 7. FIG. 3 shows a target voltage pattern. This target voltage pattern is set so that the excitation period of the lifting magnet 2 is divided into three periods and the voltage is gradually lowered.

First, the overshoot period (OS period) T _OS is a period for raising the exciting current I ₁ (see FIG. 2) to the lifting magnet 2 in a short time, and the largest target voltage V _OS is set. Then, over Excite period (OE _{period) T OE} is a period during which temporarily increase the force of the lifting magnet 2 to be easily capture the suspended load, the target voltage _{V OE (V OE <V OS} ) is set Is done. Next, the rated excitation period (RA period) T _RA is a period in which the excitation state is maintained while supplying power in the vicinity of the rated power of the lifting magnet 2, and a target voltage V _RA (V _RA <V _OE ) is set. The

  The target value supply unit 6 may have a plurality of target voltage patterns corresponding to the various lifting magnets, and may selectively output one target voltage pattern corresponding to the lifting magnet to be used. Further, the target value supply unit 6 is not necessarily provided. In this case, the target voltage pattern is supplied to the control unit 7 from the outside.

  The control unit 7 receives the target voltage pattern from the target value supply unit 6 and also receives the driving voltage of the lifting magnet 2, that is, the output voltage of the power conversion unit 5. The control unit 7 controls the rotational speed of the generator 4 via the generator driving unit 3 so as to gradually decrease the output voltage of the power conversion unit 5 during the excitation period of the lifting magnet 2. In the present embodiment, the control unit 7 includes an error amplifier, controls the number of revolutions of the generator 4 according to the difference between the target voltage pattern and the output voltage of the power conversion unit 5, and Control is performed so that the output voltage matches the target voltage pattern.

For example, the control unit 7 sets the rotation speed of the generator 4 to 1800 rpm and 1600 rpm in order to set the output voltage of the power conversion unit 5 to the target voltages V _OS = DC 290 V, V _OE = DC 240 V, and V _RA = DC 200 V, respectively. Control to 1400 rpm (FIG. 3).

Next, the operation of the lifting magnet control system 1 will be described, and the lifting magnet control method according to the embodiment of the present invention will be described. FIGS. 4A and 4B are diagrams showing the voltage applied to both ends of the lifting magnet 2 and the time waveform of the current supplied to the lifting magnet 2, respectively. FIG. 4A shows the value of the effective voltage obtained by averaging the pulse voltage over time. Further, FIG. 4 (a), the the sign of the voltage and current in (b) is in the direction of the excitation current I ₁ shown in FIG. 1 as positive.

First, at a certain time t ₀ , when the generator 4 is driven, three-phase AC power supply voltages V _{AC1 to} V _AC3 are provided to the DC conversion unit 30 of the power conversion unit 5. The AC power supply voltages V _{AC1 to} V _AC3 are converted into the DC power supply voltage V _DC by the DC conversion unit 30. Thereafter, in order to start excitation of the lifting magnet 2 (time t ₁ ), the switching elements 41 a and 41 d of the H bridge circuit unit 40 are turned on. As a result, the exciting current I ₁ flows through the lifting magnet 2.

The control unit 7, in the first OS period T _1, the excitation voltage (effective value), that is set large rotational speed of the generator 4 so that the output voltage of the power converter 5 becomes the target voltage V _OS, the lifting magnet launch the excitation current I ₁ to 2 in a short time. Next, the control unit 7, the OE period _{T 2,} the excitation voltage (effective value) and the lower the rotational speed of the generator 4 so that the _V OE _{(<V OS),} so that the suspended load can be easily caught The magnetic force of the lifting magnet 2 is temporarily increased. Next, the controller 7 further reduces the rotational speed of the generator 4 so that the excitation voltage (effective value) becomes V _RA (<V _OE ) in the RA period T ₃ , and near the rated power of the lifting magnet 2. The excitation state is maintained while supplying electric power. The rated excitation period T ₃ is continued until the process proceeds to the next release operation.

  By supplying such excitation power to the lifting magnet 2, the lifting magnet 2 is excited, and it becomes possible to attract and lift a suspended load such as an iron piece.

Next, in order to release the iron pieces from lifting magnet 2 (release) (time t ₂₎ in order to initiate the demagnetization of the lifting magnet 2, the switching elements 41a and 41d of the H-bridge circuit portion 40 is non-conductive, Switching elements 41b and 41c are conducted. As a result, the direction of the current of the lifting magnet 2 is reversed, and the release current I ₂ flows (period T ₄ ). The release current I ₂ approaches a predetermined value with a certain time constant due to the influence of the inductance of the lifting magnet 2. Thereby, the lifting magnet 2 and the suspended load are demagnetized, and the suspended load is released.

Thereafter, the switching elements 41b and 41c of the H-bridge circuit portion 40 is non-conductive, after the switching element 41a and 41d for electric power regeneration is conductive for a certain time (time _T 5), all the switching elements 41a~41d The power supply is stopped due to non-conduction.

  By the way, in the conventional lifting magnet control system, in order to supply a constant voltage to the lifting magnet during the excitation period of the lifting magnet, the rotational speed of the generator is kept constant. Further, in the conventional lifting magnet control system, the rotational speed of the generator is set to be large in consideration of PWM control in the power converter. For example, the rotational speed of the generator was set to a larger 2000 rpm (see FIG. 3).

  However, according to the lifting magnet control system 1 and the lifting magnet control method of the present embodiment, during the excitation period of the lifting magnet 2, the rotational speed of the generator 4 is controlled so as to gradually decrease the output voltage of the power converter 5. Therefore, the rotation speed of the generator 4 will fall gradually. Therefore, the energy consumption during the excitation period of the lifting magnet 2 can be reduced as compared with the conventional case where the rotational speed of the generator 4 is controlled to be constant. For example, in FIG. 3, the energy consumption corresponding to the shaded area A can be reduced.

  Thus, instead of the voltage control by the PWM control in the H bridge circuit unit of the conventional power conversion unit, the voltage control by the rotation speed control of the generator is performed, so that the switching in the H bridge circuit unit 40 of the power conversion unit 5 is performed. The duty of the elements 41a to 41d can be fixed. In other words, the switching elements 41 a to 41 d are not required to have high-speed response to voltage changes for exciting and demagnetizing the lifting magnet 2. Accordingly, as the switching elements 41a to 41d in the H bridge circuit unit 40 of the power conversion unit 5, a contact switch such as a relatively low speed mechanical switch is used instead of a contactless switch such as a relatively high speed transistor or IGBT. be able to. As a result, the price can be reduced. Also, maintainability can be improved.

  Further, the contact switch has an advantage that heat generation is small because the internal resistance is relatively small compared to the contactless switch IGBT. Further, the contact switch does not require a drive circuit or a complicated control circuit like the IGBT, and can improve reliability. In addition, since the contact switch does not generate noise, it is easy or unnecessary to take EMC countermeasures. In addition, the contact switch has high availability of parts and is very easy to replace. Thus, by using a contact switch, high performance, high reliability, and low price can be realized. Further, in a contact switch, contact wear can be drastically reduced by using an arcless circuit (with a minute arc), and maintenance can be greatly improved.

The present invention is not limited to the above-described embodiment, and various modifications can be made. In the present embodiment, the control unit 7 controls the number of revolutions of the generator 4 during the excitation periods T _{1 to} T ₃ of the lifting magnet 2, but the power generation is performed outside the excitation periods T _{1 to} T _{3 of} the lifting magnet 2. It is preferable to stop the operation of the machine 4. Thereby, the energy consumption in periods other than the excitation periods T _{1 to} T _{3 of} the lifting magnet 2 can also be reduced.

  Moreover, in this embodiment, although the contact switch was used as switching element 41a-41d in the H bridge circuit part 40 of the power converter 5, a non-contact switch may be used. As the non-contact switch, a switch that does not have a mechanical contact point, a semiconductor switch such as a transistor, an IGBT, or the like is applicable. The non-contact switch has a feature that heat generation is large because of its relatively large internal resistance, but switching speed is relatively fast.

DESCRIPTION OF SYMBOLS 1 ... Lifting magnet control system, 2 ... Lifting magnet, 3 ... Generator drive part, 4 ... Generator, 5 ... Power conversion part, 6 ... Target value supply part, 7 ... Control part, 30 ... DC conversion part, 31a- 31f ... Diode, 40 ... H bridge circuit part, 41a-41d ... Switching element, 42a-42d ... Diode, 50 ... Energy absorption part for demagnetization, 51 ... Capacitance element.

Claims (4)

A generator,
A power converter that converts the power generated by the generator and supplies it to the lifting magnet;
A control unit that controls the number of revolutions of the generator so as to gradually reduce the output power of the power conversion unit during the excitation period of the lifting magnet;
Comprising
Lifting magnet control system. The controller is
Having a target power pattern that gradually decreases in the order of an overshoot period, an overexcitation period, and a rated excitation period in the excitation period of the lifting magnet;
Controlling the number of revolutions of the generator so that the output power of the power converter becomes the target power pattern,
The lifting magnet control system according to claim 1. The power converter is
A direct current converter that converts the generated power of the generator into direct current power;
An H bridge circuit unit that receives direct current power of the direct current converter and controls excitation and demagnetization of the lifting magnet;
Have
The switching element in the H bridge circuit unit is a contact switch.
The control circuit according to claim 1. Lifting magnet control method using a lifting magnet control system comprising: a generator; a power converter that converts the power generated by the generator and supplies the power to the lifting magnet; and a controller that controls the output power of the power converter. Because
In the excitation period of the lifting magnet, the rotational speed of the generator is controlled so as to gradually reduce the output power of the power converter.
Lifting magnet control method.

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