JP2016185870A - Lifting magnet device and work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lifting magnet device enabling an easy measurement of insulation resistance of a power cable and capable of suppressing a generation frequency of a trouble such as a breakage of a control component, in view of a fact that when measuring insulation resistance of a power cable for supplying electric power to a lifting magnet, it is necessary to measure by using an insulation resistance meter after removing an end part of the power cable to be measured, therefore there lies a problem that the work takes time.SOLUTION: There is provided a lifting magnet device, including: a power supply part for outputting electric power; a magnet drive circuit for controlling the electric power from the power supply part; a lifting magnet to which the electric power is supplied from the magnet drive circuit via a cable; current measuring means for measuring the current of the electric power supplied to the lifting magnet; and insulation resistance measuring means for measuring insulation resistance of the cable.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lifting magnet device and a work vehicle. More specifically, the present invention relates to a lifting magnet device capable of measuring an insulation resistance of a power cable and a work vehicle.

  In general, a lifting magnet device for lifting an object such as an iron piece in a cargo handling work or a construction work is known. This lifting magnet device attracts and releases iron pieces only by magnet excitation and demagnetization. For this reason, the control device constituting the lifting magnet device protects the control component using a caution warning unit as shown in Patent Document 1 in addition to the protection unit that protects the control component from overcurrent, and at the same time, the operator's intention This prevents the iron pieces from being released without doing anything.

  Here, many troubles such as parts in the control device of the lifting magnet device are caused by breaking the insulation of the power cable in the mechanically operating portion. If the insulation resistance of the power cable becomes low due to the operation by changing the position of the lifting magnet or the contact with the attracted conveyance object, and an overcurrent flows, problems occur in the components in the control device. Therefore, in order to prevent such an overcurrent situation in advance, the operator of the lifting magnet device periodically measures the insulation resistance of the power cable, and the insulation resistance of the power cable is lowered Replace the power cable in advance. However, the measurement of the insulation resistance needs to be performed using an insulation resistance meter after removing the end of the power cable to be measured, and there is a problem that it takes time.

  Further, when the operator neglects the inspection, an overcurrent flows, and there is a problem that it is necessary to replace the protection means of the control parts or to replace the damaged control parts themselves.

JP 2008-222368 A

  In view of the above circumstances, the present invention can easily measure the insulation resistance of a power cable, thereby suppressing the occurrence frequency of problems such as breakage of control components, and a work vehicle using the same. The purpose is to provide.

A lifting magnet device according to a first aspect of the present invention includes a power supply unit that outputs electric power, a magnet drive circuit that controls electric power from the power supply unit, a lifting magnet to which electric power is supplied from the magnet drive circuit via a cable, It is characterized by comprising current measuring means for measuring the current of power supplied to the lifting magnet and insulation resistance measuring means for measuring the insulation resistance of the cable.
The lifting magnet device according to a second aspect of the present invention is the lifting magnet device according to the first aspect, wherein the cable has a main line for connecting the magnet driving circuit and the lifting magnet, and a sub-line provided in parallel in the middle of the main line, The measuring means is provided in the main line, the insulation resistance measuring means is provided in the subline so as to be in parallel with the current measuring means, and the subline is provided with a subline switch capable of switching between energization and non-energization of power. It is characterized by being.
The lifting magnet device according to a third aspect of the present invention further includes a main line switch provided in the cable and capable of switching power supply / cut-off to the lifting magnet in the second invention. The main line switch is provided in the main line. It is characterized by being.
According to a fourth aspect of the present invention, in the third aspect, the magnet drive circuit includes a positive line connected to the positive output end of the power supply unit, and a negative line connected to the negative output end of the power supply unit. , And a negative line is provided with a ground line switch connected to the ground potential.
The lifting magnet device according to a fifth aspect of the present invention is the control device according to the second aspect, further comprising a control unit, wherein the control unit opens the subline switch when power is supplied to the lifting magnet and the object is attracted and transported. Thus, the current is not supplied to the insulation resistance measuring means.
A lifting magnet device according to a sixth aspect of the present invention is the display device according to any one of the first to fifth aspects, wherein a display unit for displaying the state of the lifting magnet device is provided, and the display unit is a result measured by an insulation resistance measuring means. Is displayed. The working vehicle of the seventh invention is characterized in that the lifting magnet device of any one of the first to sixth inventions is mounted.

According to the first invention, it is possible to easily measure the insulation resistance of the power cable by including the current measurement means for measuring the current supplied to the lifting magnet and the insulation resistance measurement means for the cable. It is possible to quickly know the insulation breakdown of the power cable that causes the control parts to be damaged. Therefore, it is possible to suppress the occurrence frequency of defects such as control parts.
According to the second invention, the cable has a main line and a subline provided in parallel to the main line, the current measuring means is in the main line, and the insulation resistance measuring means is in parallel with the current measuring means. As a result, a large current flows through the insulation resistance measuring means during normal operation by providing a subline switch that can switch between energization and deenergization of power in the subline. Therefore, the insulation resistance measuring means can be made inexpensive.
According to the third invention, the cable is provided with a main line switch capable of switching supply / cut-off of power to the lifting magnet, and the main line switch is provided in the main line so that the lifting magnet is excluded. It becomes possible to measure the insulation resistance of only the cable.
According to the fourth invention, the magnet drive circuit has a positive line connected to the positive output end of the power supply unit and a negative line connected to the negative output end of the power supply unit. Since the side line is provided with a ground line switch connected to the ground potential, the insulation resistance of the cable can be measured using the total potential difference of the power supply unit. Thereby, the potential difference for measurement can be increased and the insulation resistance can be measured with high accuracy.
According to the fifth aspect of the present invention, when the power is supplied to the lifting magnet and the half-collection is attracted or transported, the control unit opens the subline switch so that no current is supplied to the insulation resistance measuring means. This eliminates the need for the operator to operate the subline switch and prevents a large current from flowing through the insulation resistance measuring means by mistake. As a result, the insulation resistance measuring means can be prevented from failing.
According to the sixth aspect of the invention, since the result measured by the insulation resistance measuring means is displayed on the display unit, it is not necessary to provide a separate indicator of insulation resistance.
According to the seventh invention, since the lifting magnet device is mounted on the work vehicle, the power cable is easily insulated in the work vehicle in which there are many cases in which the iron pieces of various shapes are lifted and the power cable is damaged by the iron pieces. Resistance can be measured.

It is a circuit block diagram of the magnet drive circuit which comprises the lifting magnet apparatus which concerns on 1st Embodiment of this invention. It is a block block diagram of the lifting magnet apparatus which concerns on 1st Embodiment of this invention. (A) It is a graph which shows the time waveform of the voltage applied to the both ends of a lifting magnet. (B) It is a graph which shows the time waveform of the electric current supplied to a lifting magnet. It is a circuit block diagram of the magnet drive circuit which comprises the lifting magnet apparatus which concerns on 3rd Embodiment of this invention. It is a general view of the work vehicle carrying the lifting magnet apparatus of FIG.

  Next, the lifting magnet device 2 according to the first embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In the following description, a transistor includes both a bipolar transistor and a field effect transistor (FET). When the transistor is an FET, the base is read as the gate, the collector as the drain, and the emitter as the source.

  In FIG. 2, the block block diagram of the lifting magnet apparatus 2 which concerns on 1st Embodiment is shown. The lifting magnet 10 is mounted as an attachment at the tip of a hydraulic excavator that is moved by a crawler, or is used at the tip of a suspended portion of an overhead crane installed in a building. The structure of the lifting magnet device 2 includes a lifting magnet 10 that attracts and releases iron pieces, a magnet control unit 3 that supplies electric power to the lifting magnet 10, an input / output for displaying the operation and information of the magnet control unit 3. The display unit 4 and an AC generator (synchronous generator) 18 that supplies three-phase AC power to the magnet control unit 3 are provided. In this embodiment, the AC generator 18 is a so-called permanent magnet (PM) synchronous generator having a permanent magnet as a field. The AC generator 18 is a power supply unit that supplies (outputs) electric power.

The magnet control unit 3 includes a magnet drive circuit 31, a bridge driver 32, a control unit 33, and a communication circuit 34. Three-phase AC voltages V _{AC1 to} V _AC3 are supplied from the AC generator 18 to the magnet drive circuit 31. The magnet drive circuit 31 is a circuit that supplies power to the lifting magnet 10 and includes an H-bridge circuit that controls the direction of the current flowing through the lifting magnet 10. The bridge driver 32 is a circuit that drives the H bridge circuit. The control unit 33 controls the current and voltage supplied to the magnet 10 via the bridge driver 32.

  The control unit 33 includes, for example, a digital arithmetic processing circuit including a memory storing a predetermined program and a CPU that reads and executes the predetermined program, and performs input / output / display of control signals through the communication circuit 34. . The communication circuit 34 is connected to the communication circuit 43 in the input / output / display unit 4 operated by the operator of the lifting magnet device 2 via the wiring 16, and communicates with the communication circuit 43. The magnet drive circuit 31, the bridge driver 32, the control unit 33, and the communication circuit 34 are accommodated in one housing 35. The input / output / display unit 4 is referred to as a display unit in the claims.

  The input / output / display unit 4 includes an input / output / display device 40 for inputting / outputting an operation command of an operator, a signal processing unit 42, and a communication circuit 43. The input / output / display device 40 has a function of receiving a setting input related to a current and a voltage supplied to the lifting magnet 10 from an operator. The signal processing unit 42 makes the operator aware of the state of the control unit 33 or the like based on the signal received via the communication circuit 43, or the magnet via the communication circuit 43 based on the input signal of the operator. A command is given to the control unit 33 of the control unit 3. Note that the input / output / display device 40, the signal processing unit 42, and the communication circuit 43 are accommodated in one housing 45.

  The magnet operation unit 5 is a device for an operator to operate the excitation operation and the release operation of the lifting magnet 10, and is arranged together with the input / output / display unit 4. The magnet operation unit 5 has two switches 51 and 52. One terminal of each of the switches 51 and 52 is connected to each other, is connected to the magnet drive circuit 31 via the wiring 53, and is connected to a constant potential line inside the magnet drive circuit 31. The other terminals of the switches 51 and 52 are connected to the control unit 33 of the magnet drive circuit 31 via wirings 54 and 55, respectively.

  For example, when the operator presses the switch 51, a predetermined potential is transmitted to the control unit 33 via the wiring 54, and the control unit 33 controls the bridge driver 32 so that a positive direction current (excitation current) is supplied to the lifting magnet 10. Control. When the operator presses the switch 52, a predetermined potential is transmitted to the control unit 33 via the wiring 55, and the control unit 33 controls the bridge driver 32 so that a reverse current (release current) is supplied to the lifting magnet 10. Control. Alternatively, the control unit 33 recognizes only the potential of the wiring 54, and when the switch 51 is pressed once, the exciting current is supplied to the lifting magnet 10, and when the switch 51 is pressed again, the release current is supplied to the lifting magnet 10. May be.

  The earth leakage operating unit 6 is an apparatus for performing an operation when detecting an earth leakage of the lifting magnet device 2 and includes three switches 61, 62, and 63. The switch 61 is a switch for performing normal operation. The switch 62 is a switch that detects leakage while flowing current through the lifting magnet 10. The switch 63 is a switch for detecting leakage while preventing current from flowing through the lifting magnet 10. The terminals 61, 62, and 63 are connected to the control unit 33 of the magnet drive circuit 31 through the wiring 64, respectively.

  In FIG. 1, the circuit block diagram of the magnet control part 3 which comprises the lifting magnet apparatus 2 which concerns on 1st Embodiment of this invention is shown. As shown in FIG. 1, the magnet control unit 3 includes a DC power supply unit 36, an H bridge circuit unit 37, and a capacitor 38. FIG. 1 shows the state of a circuit during normal operation in which the lifting magnet device 2 passes an exciting current and a demagnetizing current, and the state of the circuit when measuring the insulation resistance will be described later.

The DC power supply unit 36 is a circuit part for converting the three-phase AC voltages V _{AC1 to} V _AC3 supplied from the AC generator 18 into a DC power supply voltage V _DC . The DC power supply unit 36 of the present embodiment is configured by a bridge circuit including six diodes 36a to 36f, and performs three-phase full-wave rectification. In addition, the DC power supply unit 36 may be constituted by, for example, a pure bridge circuit using a thyristor or a mixed bridge circuit using a diode and a thyristor. When the DC power supply unit 36 is constituted 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 37 is a circuit part for controlling the direction of the current supplied to the lifting magnet 10. The H-bridge circuit unit 37 includes four npn transistors 37a to 37d and four diodes electrically connected between current terminals (collector-emitter or source-drain) of the four transistors 37a to 37d. (Flywheel) It is comprised by the H bridge circuit containing 37e-37h and the terminals 37i and 37j to which the power cable for supplying an electric current to the lifting magnet 10 is connected.

  Specifically, one current terminal of the transistor 37a is electrically connected to the positive output terminal 36g of the DC power supply 36, and the other current terminal of the transistor 37a is electrically connected to the terminal 37i. . The cable connected to the positive output terminal of the DC power source 36 is referred to as a positive line 39a. One current terminal of the transistor 37 b is electrically connected to the terminal 37 i, and the other current terminal of the transistor 37 b is electrically connected to the negative output terminal 36 h of the DC power supply unit 36. The cable connected to the negative output terminal of the DC power supply 36 is referred to as a negative line 39b. One current terminal of the transistor 37c is electrically connected to the positive output terminal 36g of the DC power supply unit 36, and the other current terminal of the transistor 37c is electrically connected to the terminal 37j. One current terminal of the transistor 37d is electrically connected to the terminal 37j, and the other current terminal of the transistor 37d is electrically connected to the negative output terminal 36h of the DC power supply unit 36. The anodes of the diodes 37e to 37h are electrically connected to the other current terminals of the transistors 37a to 37d, respectively. The cathodes of the diodes 37e to 37h are electrically connected to the one current terminals of the transistors 37a to 37d, respectively. It is connected to the.

  The control terminals (bases or gates) of the transistors 37a to 37d are electrically connected to the bridge driver 32, and the conduction state between the current terminals of the transistors 37a to 37d is a control current (from the bridge driver 32). Or control voltage). For example, when a control current is provided to the control terminals of the transistors 37a and 37d, an exciting current in one direction flows in the order of the transistor 37a, the terminal 37i, the magnet 10, the terminal 37j, and the transistor 37d. When a control current is provided to the control terminals of the transistors 37b and 37c, a demagnetizing current in a direction opposite to a certain direction flows in the order of the transistor 37c, the terminal 37j, the magnet 10, the terminal 37i, and the transistor 37b.

  The bridge driver 32 makes any of the transistors 37 a to 37 d conductive according to the output signal of the control unit 33. The control unit 33 determines which of the transistors 37a to 37d is to be conducted based on the signal provided from the magnet operation unit 5 illustrated in FIG. Further, the bridge driver 32 intermittently turns on the transistors 37a to 37d as necessary, and adjusts the voltage supplied to the magnet 10 by pulse width modulation (PWM). The PWM pulse width is controlled by the control unit 33.

  The capacitor 38 is provided to reduce the ripple of the excitation current to the lifting magnet 10. The capacitor 38 is electrically connected between the positive output terminal 36g and the negative output terminal 36h of the DC power supply unit 36.

  As shown in FIG. 1, the lifting magnet device 2 according to the first embodiment of the present invention includes a current measuring unit 21 and an insulation resistance measurement between an H bridge circuit in the H bridge circuit unit 37 and the lifting magnet 10. Means 22 are provided. The current measuring means 21 is a measuring instrument that measures the magnitude of the current supplied to the lifting magnet 10, and includes, for example, a shunt resistor and an A / D converter that converts the voltage across the shunt resistor into a digital signal. It is composed of In the present embodiment, the configuration of the insulation resistance measuring unit 22 is the same as that of the current measuring unit 21, but is configured to detect a minute current because it is for detecting a leakage. . The insulation resistance measuring means 22 is composed of an ammeter composed of a shunt resistor or the like, but is not particularly limited as long as it can measure a minute current. For example, a semiconductor that generates heat when a current flows can be used.

  The insulation resistance measuring means 22 is expressed as being “between” the H-bridge circuit and the lifting magnet 10, which means that the insulation resistance means 22 is electrically arranged between these elements in series. And the case where the elements are arranged in parallel with the cable connecting these elements. In this embodiment, the insulation resistance measuring means 22 is provided between the H bridge circuit and the lifting magnet 10, but the place where the insulation resistance measuring means 22 is provided is provided between the DC power supply unit 36 and the H bridge circuit. There is no problem.

  The H bridge circuit constituting the magnet drive circuit 31 and the lifting magnet 10 are electrically connected via a cable. This cable has a main line for connecting the magnet drive circuit 31 and the lifting magnet, and a sub-line provided in the middle of the main line. The insulation resistance measuring means 22 is provided so as to be positioned in parallel with the current measuring means 21. That is, the current measuring means 21 is provided on the main line, and the insulation resistance measuring means 22 is provided on the subline. A first switch 25 for operating whether or not the current measuring means 21 is energized and a second switch 26 for operating whether or not the insulation resistance measuring means 22 is energized, that is, a subline switch, are provided. The first switch 25 and the second switch 26 are exclusively controlled. That is, when the first switch 25 is closed and the current measuring means 21 is energized, the second switch 26 is opened and the insulation resistance measuring means 22 is not energized, and conversely, the insulation resistance measuring means 22 is energized. Sometimes the current measuring means 21 is not energized.

  The H bridge circuit unit 37 and the lifting magnet 10 are connected by a power cable having a diameter of several mm to several tens of mm. Of the power cable, the first cable 23 and the second cable 24 are movable when the lifting magnet 10 is used for cargo handling. The lengths of the first cable 23 and the second cable 24 vary depending on the movable distance of the lifting magnet 10 and the length of the movable part, but when the lifting magnet 10 is mounted on a hydraulic excavator, the length is a few tens of meters. become. The first cable 23 is a power cable that is on the positive potential side when exciting the lifting magnet 10, and the second cable 24 is a power cable that is on the positive potential side when demagnetizing the lifting magnet 10.

  During normal operation of exciting and demagnetizing the lifting magnet 10, the first cable 23 and the second cable 24 are connected to the lifting magnet 10. In the vicinity of the lifting magnet 10, the first cable 23 and the second cable 24 are provided with main line switches that are third switches 27-1 and 27-2 that electrically disconnect the connection. If the third switches 27-1 and 27-2 are opened at the time of leakage detection, no current flows through the lifting magnet 10.

  Between the DC power supply unit 36 and the H-bridge circuit unit 37 side (side on which the drive current returns to the AC generator 18 side), a ground line as a fourth switch 28 is provided between the power supply lines on the transistors 37b and 37d side and the frame ground. A switch is provided. When the fourth switch 28 is closed, the power line is connected to the frame ground.

  Here, the operation of the magnet drive circuit 31 during normal operation will be described. 3A is a graph showing a time waveform of the voltage applied to both ends of the lifting magnet 10, and FIG. 3B is a graph showing a time waveform of the current supplied to the lifting magnet 10. FIG. 3B shows the result measured by the current measuring means 21. As described above, the voltage applied to the lifting magnet 10 is adjusted by PWM. In FIG. 3A, the effective voltage value obtained by temporally averaging the voltage change in PWM is shown. . 3A and 3B, the direction of the excitation current in FIG. 2 (the direction in which current flows from the terminal 37i to the lifting magnet 10) is positive.

First, at a certain time t0, the AC generator 18 is driven, so that the three-phase AC voltages V _{AC1 to} V _AC3 are provided to the DC power supply unit 36. The three-phase AC voltages V _{AC1 to} V _AC3 are converted into the DC power supply voltage V _DC by the DC power supply unit 36. Subsequently, when the operator presses the switch 51 (or 52) of the magnet operation unit 5 (time t1), the control unit 33 starts exciting the lifting magnet 10. In other words, the bridge driver 32 that has received an instruction from the control unit 33 causes the transistors 37 a and 37 d of the H bridge circuit unit 37 to conduct. As a result, an exciting current flows through the lifting magnet 10.

Control unit 33, in the first period _{T 1,} the excitation voltage the duty ratio of the PWM to 100% of the maximum rms and maximum value _{V OS.} The period T ₁ called overshoot period (OS period) is a period for starting up the exciting current I ₁ to the lifting magnet 10 in a short time. In addition, in the period T ₂ following the period T ₁ , the control unit 33 reduces the PWM duty ratio from the maximum (for example, 90%) and sets the excitation voltage (effective value) to V _OE (<V _OS ). . The period T ₂ designated as over-excited period (OE period) is a period during which temporarily increase the force of the lifting magnet 10 so that the suspended load can be easily captured. The control unit 33, in the next period _{T 3} period _{T 2,} and further reduce the duty ratio of the PWM, and the excitation voltage (effective value) _V RA _{(<V OE).} It referred to the period T ₃ the rated exciting period, a period for maintaining the excited state while supplying power near rated power of the lifting magnet 10. Incidentally, the rated exciting period T ₃ is continued until the process proceeds to the next release operation.

  By supplying such excitation power to the lifting magnet 10, the lifting magnet 10 is excited, and it becomes possible to attract and lift a suspended load such as an iron piece.

Then, it moves to the operation | movement for releasing an iron piece etc. from the lifting magnet 10. FIG. When the operator presses the other switch 52 (or 51) of the magnet operation unit 5 (time t2), the control unit 33 starts demagnetization of the lifting magnet 10. That is, the bridge driver 32 that has received an instruction from the control unit 33 turns off the transistors 37a and 37d of the H bridge circuit unit 37 and turns on the transistors 37b and 37c. As a result, the direction of the current flowing through the lifting magnet 10 is reversed, and a release current flows (period T ₄ ). This release current approaches a predetermined value with a certain time constant due to the influence of the inductance of the lifting magnet 10. Thereby, the magnet 10 and the suspended load are demagnetized, and the suspended load is released. When the magnitude of the release current reaches the set value I _LM , the control unit 33 makes the transistors 37b and 37c of the H-bridge circuit unit 37 non-conductive and makes the transistors 37a and 37d conductive for a certain time for power regeneration. (period _T 5), and stops power supply to all of the transistors 37a~37d made nonconductive.

Next, the operation of the magnet drive circuit 31 at the time of detecting electric leakage, that is, at the time of measuring the power cable insulation resistance will be described. The operator of the lifting magnet device 2 detects leakage during a pre-start inspection. When the operator performs the first leakage detection mode by pressing the switch 62 of the leakage operating unit 6, the control unit 33 drives the AC generator 18, and the three-phase AC voltages V _{AC1 to} V _AC3 are supplied to the DC power supply unit 36. Supplied. The control unit 33 causes the second switch 26 and the third switches 27-1 and 27-2 to conduct, and also causes the fourth switch 28 to conduct. When the second switch 26 is turned on, the first switch 25 is turned off. In this state, the control unit 33 turns on the transistor 37a of the H-bridge circuit unit 37, turns off the transistors 37b, 37c, and 37d, and adds a DC voltage to the first cable 23 and the second cable 24. At this time, if insulation is deteriorated at any of the lifting magnet 10, the first cable 23, and the second cable 24, the lifting magnet 10 and the first cable 23 are connected from the transistor 37 a via the first cable 23. And the current leaked from either the second cable 24 flows to the switch 28 side via the frame ground and returns to the DC power supply 36 side. Then, the insulation resistance measuring means 22 detects a weak current of several milliamperes to several tens of amperes, and the control unit 33 displays the resistance value calculated from this value on the input / output / display unit 40. When the displayed value is smaller than a predetermined threshold value, there is no electric leakage, and the operator performs normal work. If it is equal to or greater than the threshold value, the operator exchanges the first cable 23 and the second cable 24 that are power cables.

  By providing the current measuring means 21 for measuring the current supplied to the lifting magnet 10 and the insulation resistance measuring means 22 for the power cable to which the H bridge circuit and the lifting magnet 10 are connected, the power cable is provided. The insulation resistance of the power cable can be easily measured, and the insulation breakdown of the power cable that causes damage to the control component can be known at an early stage. Therefore, it is possible to suppress the occurrence frequency of defects such as control parts.

  The insulation resistance measuring means 22 adds a DC voltage from the DC power supply unit 36 and measures the insulation resistance of the power cable, thereby obtaining a high voltage necessary for measuring the insulation resistance from the existing equipment. it can. Therefore, it is possible to easily measure the insulation resistance of the power cable while reducing the cost.

  The insulation resistance measuring means 22 is provided so as to be positioned in parallel with the current measuring means 21. When the current is measured by the current measuring means 21, no current is supplied to the insulation resistance measuring means 22. A current of several hundred amperes flowing during normal operation is not added to the insulation resistance measuring means 22. Therefore, an inexpensive insulation resistance measuring means 22 can be used.

  The control unit 33 of the lifting magnet device 2 causes the insulation resistance measurement means 22 to apply a voltage from the DC power supply unit 36 after grounding the H bridge circuit unit 37 in accordance with the measurement instruction signal, thereby The operator can detect a leakage by a simple operation such as pressing a button.

  The control unit 33 connects the lifting magnet 10 and the entire power cable by connecting the third switches 27-1 and 27-2 of the first cable 23 and the second cable 24 constituting the power cable according to the measurement instruction signal. Can be detected with a single operation.

Next, the operation of the magnet drive circuit 31 when leakage is detected in the lifting magnet device according to the second embodiment will be described. The operator of the lifting magnet device 2 detects leakage during a pre-start inspection. When the operator performs the second leakage detection mode by pressing the switch 63 of the leakage operating unit 6, the control unit 33 drives the AC generator 18, and the three-phase AC voltages V _{AC1 to} V _AC3 are applied to the DC power supply unit 36. Supplied. The control unit 33 opens the second switch 26 and the third switches 27-1 and 27-2 and opens the fourth switch 28. When the second switch 26 is turned on, the first switch 25 is turned off. In this state, the control unit 33 turns on the transistors 37a and 37d of the H bridge circuit unit 37, turns off the transistors 37b and 37c, and adds a DC voltage to the first cable 23 and the second cable 24. At this time, if the insulation between the first cable 23 and the second cable 24 is deteriorated, a leaked current flows from the transistor 37a through the first cable 23 to the second cable 24. And it returns to the direct-current power supply part 36 side via the transistor 37d from the 2nd cable 24. Then, the insulation resistance measuring means 22 detects a weak current of several milliamperes to several tens of amperes, and the control unit 33 displays the resistance value calculated from this value on the input / output / display device 40. When the displayed value is smaller than a predetermined threshold value, there is no electric leakage, and the operator performs normal work. If it is equal to or greater than the threshold value, the operator exchanges the first cable 23 and the second cable 24 that are power cables.

  In FIG. 4, the circuit block diagram of the magnet drive circuit 31 of the lifting magnet apparatus 2 which concerns on 3rd Embodiment of this invention is shown. Only the circuit between the H bridge circuit unit 37 and the lifting magnet 10 is different from the first embodiment.

  In the third embodiment, the insulation resistance measuring means 22 is provided on the lifting magnet 10 side of the current measuring means 21 of the first cable 23, and the first switch 25 is provided between the current measuring means 21 and the insulation resistance measuring means 22. Is provided. The first cable 23 is provided with a current measuring means 21 and an insulation resistance measuring means 22 in series. Further, in order to bypass the insulation resistance measuring means 22 and flow electricity to the lifting magnet device 2 side, a first connecting the lifting magnet device 2 side of the insulation resistance measuring means 22 from before the first switch 25 of the first cable 23 is connected. Three cables 29 are provided. The third cable 29 is provided with a second switch 26.

  During normal operation of the lifting magnet device 2, the first switch 25 is opened and the second switch 26 is closed, and the lifting magnet 10 and the H bridge circuit unit 37 are electrically connected by the third cable 29. When leakage is detected, the first switch 25 is closed and connected, and the second switch 26 is opened so that a current flows through the insulation resistance measuring means 22 from the power source side.

The difference of the operation of the magnet drive circuit 31 when leakage is detected in the lifting magnet device according to the third embodiment will be described. When the leakage detection mode is performed by pressing the switch 62 or 63 of the leakage operating unit 6, the control unit 33 drives the AC generator 18, and the three-phase AC voltages V _{AC1 to} V _AC3 are supplied to the DC power supply unit 36. The control unit 33 closes the first switch 25 so that the current flows from the power supply side to the insulation resistance measuring unit 22. As a result, the insulation resistance measuring means 22 can measure the leakage current. The subsequent operation of the control unit 33 is the same as in the first and second embodiments.

  FIG. 5 is a perspective view showing the configuration of the work vehicle 1 on which the lifting magnet device 2 according to the present invention is mounted. The work vehicle 1 is a hydraulic excavator in which a lifting magnet 10 is mounted on the tip of an arm 12 and operated by a crawler. As shown in FIG. 5, the work vehicle 1 is provided with a lifting magnet 10 that attracts and captures a suspended load 90 such as a steel material by a magnetic force at the tip of an arm 12. A cab 14 for accommodating an operator who operates the release operation is provided.

  The magnet control unit 3 is installed outside the cab 14, and the input / output / display unit 4 is installed inside the cab 14. The work vehicle 1 is equipped with a hydraulic pump driven by the engine and a hydraulic motor driven by the hydraulic pressure from the hydraulic pump, and an AC generator that supplies three-phase AC power to the magnet control unit 3 ( The synchronous generator 18 is driven by this hydraulic motor.

  Since the lifting magnet device 2 is mounted on the work vehicle 1, it is possible to easily measure the insulation resistance of the power cable in the work vehicle 1 in which there are many cases in which iron pieces of various shapes are lifted and the power cable is damaged by the iron pieces. .

  Although the configuration for supplying the three-phase AC power to the magnet control unit 3 has been described, the configuration is not limited thereto, and the AC generator 18 is configured by a power storage device such as a large-capacity lithium ion battery. It can also be used. In this case, the DC power supply unit 36 is unnecessary, and the power storage device is a power supply unit of the claims.

  In all of the three embodiments, the current measurement unit 21 and the insulation resistance measurement unit 22 are described as separate elements, but the present invention is not limited to this. For example, a single shunt resistor is installed in the power cable, and two means are combined with one ammeter as a substance by switching the display device corresponding to the voltage signal coming out of it during normal operation and leakage detection. It is also possible to do.

  Moreover, although all three embodiments demonstrated the example which converts the alternating current power supply from the alternating current generator 18 into direct current with the direct current power supply part 36, and supplies it to the lifting magnet 10 via the H bridge circuit 37, It is not limited. For example, it is possible to provide a thyristor type AC / DC converter that also serves as the DC power source 36 for converting AC to DC and the H-bridge circuit 37.

DESCRIPTION OF SYMBOLS 1 Working vehicle 2 Lifting magnet apparatus 10 Lifting magnet 21 Current measuring means 22 Insulation resistance measuring means 33 Control part 36 DC power supply part

Claims (7)

A lifting magnet device that attracts and conveys a conveyed object,
A power supply unit that outputs power;
A magnet drive circuit for controlling power from the power supply unit;
A lifting magnet to which power is supplied from the magnet drive circuit via a cable;
Current measuring means for measuring a current of electric power supplied to the lifting magnet;
Insulation resistance measuring means for measuring the insulation resistance of the cable. The cable includes a main line that connects the magnet drive circuit and the lifting magnet, and a subline provided in parallel in the middle of the main line,
The current measuring means is provided in the main line,
The insulation resistance measuring means is provided in the subline so as to be in parallel with the current measuring means,
The subline is provided with a subline switch capable of switching between energization / non-energization of power,
The lifting magnet device according to claim 1. The cable further includes a main line switch capable of switching between supply and interruption of power to the lifting magnet,
The main line switch is provided in the main line,
The lifting magnet device according to claim 2. The magnet drive circuit has a positive line connected to the positive output end of the power supply unit and a negative line connected to the negative output end of the power supply unit,
The negative line is provided with a ground line switch connected to the ground potential.
The lifting magnet device according to claim 3. The lifting magnet device includes a control unit,
The controller is configured to open the subline switch so that no current is supplied to the insulation resistance measuring means when power is supplied to the lifting magnet and the transported object is attracted or transported.
The lifting magnet device according to claim 2. A display unit for displaying the state of the lifting magnet device;
The display unit displays the result measured by the insulation resistance measuring means.
The lifting magnet device according to any one of claims 1 to 5, wherein the lifting magnet device is provided.   A work vehicle on which the lifting magnet device according to claim 1 is mounted.