JP6578753B2 - Magnet work machine - Google Patents

Description

  The present invention relates to a magnet working machine in which a magnet (electromagnet, referred to as “lifting magnet” or abbreviated as “lift magnet”) is attached to the tip of a work attachment, and a load such as metal scrap is adsorbed to the magnet and transported.

  A magnet working machine that adsorbs metal scrap etc. with a magnet is a self-propelled base machine consisting of a lower traveling body and an upper swing body, and a hydraulic excavator equipped with a work attachment having a boom and an arm as the base body. A magnet is attached to the tip of an arm or a bucket (not shown).

  As this magnet working machine, for example, an engine, a generator motor driven by the engine, and a hybrid machine including a power storage device (battery) are used as a base and a magnet is operated using a battery as a power source (patent) Reference 1).

  On the other hand, as a technique for detecting electric leakage of a hybrid machine, as shown in Patent Document 2, a test voltage such as a sine wave or a pulse wave is applied between a DC bus and the machine body (earth), and the wave Techniques for measuring high values are known.

  This earth leakage detection technology can also be applied to magnet work machines other than hybrid machines, that is, magnet work machines that have a configuration in which a capacitor is provided in the magnet drive circuit instead of a battery as a power storage device, and a magnet is driven using a generator motor as the main power source. it is conceivable that.

Japanese Patent Laid-Open No. 2005-1775 International Publication No. 2007/007749

However, in a magnet working machine, as a unique problem, when driving a magnet,
(i) During magnet adsorption (excitation) operation,
(ii) When the magnet is released (demagnetized),
(iii) After a release operation, the current change is large within a certain period of time, and a large current may flow temporarily, resulting in a decrease in insulation resistance value. This phenomenon may be erroneously detected as a leakage.

  Therefore, the present invention provides a magnet working machine capable of accurately detecting leakage of a magnet drive circuit without erroneous detection.

As means for solving the above-described problems, in the present invention, a magnet that performs the load adsorption / release operation, a generator motor that is driven by the engine to perform a generator action and that performs an electric motor action using electric power from the magnet, Apparatus, a magnet drive circuit that drives the magnet using at least one of the generator motor and the power storage device as a power source, and a leakage detection device that detects a leakage of the magnet drive circuit. The leakage detection device releases the magnet. After the operation, the leakage current is detected only after a certain time has passed as a time when a large current flows and there is a possibility of erroneous detection of leakage , and until the next adsorption operation starts. It is a thing.

  According to this configuration, leakage detection is performed only after a certain time has elapsed after the release operation until the next adsorption operation is started, during adsorption, during release, and before a certain time has elapsed since the release operation. Since leakage detection is not performed while a large current flows and there is a possibility of erroneous detection, leakage in the magnet drive circuit can be accurately detected without erroneous detection.

In the present invention, provided with a capacitor as the electrical storage device to the DC main circuit of the magnet drive circuit, it is possible to adopt a configuration connecting said leakage detecting device to the DC main circuit of the magnet drive circuit (claim 2) .

  According to this configuration, in the magnet working machine in which the capacitor as the power storage device is provided in the magnet drive circuit, the leakage can be detected directly and accurately from the DC main circuit close to the power storage device (capacitor).

  According to the present invention, the leakage of the magnet drive circuit can be accurately detected without erroneous detection.

It is a block diagram which shows the apparatus structure of embodiment of this invention. 2 is a system configuration diagram of a magnet drive circuit and a leakage detection device in the same embodiment. FIG. It is a time chart which shows the change state of ON / OFF of an adsorption switch and magnet voltage in the embodiment. It is a flowchart for demonstrating the effect | action of the embodiment.

  An embodiment of the present invention will be described with reference to the drawings.

  The embodiment is applied to a magnet working machine that drives a magnet using a generator motor as a main power source.

  As shown in FIG. 1, when a generator motor 2 is driven by an engine 1 to perform a generator action and the adsorption switch 3 is operated to the adsorption side, the electric power generated in the generator motor 2 is converted into an inverter for the generator motor. Is supplied to the magnet 5 through the magnet drive circuit 4 which also serves as As a result, the magnet 5 is excited and a load (scrap, etc.) adsorption operation is performed.

  On the other hand, when the adsorption switch 3 is operated to the release side, the power supply to the magnet 5 is interrupted. That is, the magnet 5 is demagnetized and the load releasing operation is performed.

  In this case, the power of the magnet 5 is sent to the generator motor 2 through the magnet drive circuit 4 as regenerative power and consumed, contrary to the time of adsorption. That is, the generator motor 2 assists the engine 1 by performing a motor action.

  In addition, a leakage detection device 6 is connected to the magnet drive circuit 4, and a test voltage such as a sine wave or a pulse wave is applied between the DC main circuit and the machine body (earth) as shown in Patent Document 2, for example. In addition, leakage detection is performed by measuring the peak value.

  An alarm device 7 is connected to the leakage detection device 6, and when the leakage is detected, the alarm device 7 is activated to display the fact to the operator.

  FIG. 2 shows the internal configuration of the magnet drive circuit 4 and the leakage detection device 6.

  The magnet drive circuit 4 includes a switching circuit 8, an excitation / demagnetization switching circuit 9 composed of, for example, an H bridge circuit, a control unit 10 that controls both the circuits 8 and 9, and a DC main circuit 11 that connects both the circuits 8 and 9. And a capacitor (a large-capacity capacitor that performs smoothing) 12 as a power storage device provided in the DC main circuit 11.

  The excitation / demagnetization switching circuit 9 switches the excitation / demagnetization of the magnet 5 based on the ON / OFF operation (both operation on the adsorption side and the release side) of the adsorption switch 3 and determines the voltage applied to the magnet 5 at the time of excitation. .

  FIG. 3 shows a change state of the magnet voltage with respect to the switch operation. The magnet 5 is excited / demagnetized in accordance with the switch operation in FIG. 3A, and the magnet voltage changes as shown in FIG.

  “Overexcitation” in FIG. 3 (b) is a method in which the magnet 5 is magnetized at a voltage higher than the steady voltage for a certain period of time so that an adsorption force necessary to adsorb a load such as metal scrap can be obtained after the adsorption starts. After this overexcitation, it shifts to steady excitation.

  In addition, `` reverse excitation '' refers to generating a reverse magnetic field by flowing a current in the reverse direction to release the load as a demagnetization operation. Magnet voltage (such as excitation, overexcitation, demagnetization, reverse excitation) The main circuit voltage of the magnet drive circuit 4 changes according to the change of the magnet power).

  The switching circuit 8 is formed by combining a plurality of switching elements such as transistors, and controls the transfer of power between the generator motor 2 and the magnet 5.

  That is, the generator motor power required for excitation is supplied to the magnet 5, and the magnet power is sent to the generator motor 2 as regenerative power for demagnetization.

  At the time of demagnetization, a command value of the motor torque for the generator motor 2 is output from the control unit 10, and the switching operation of the switching circuit 8 is performed according to this command torque.

  The capacitor 12 stores a part of the magnet power when the magnet is demagnetized (at the time of release), and supplies the stored power to the magnet 5 together with the generator motor power when the magnet is excited (at the time of adsorption operation).

  As a result, the voltage and magnet power of the magnet drive circuit 4 are smoothed and stabilized, and serve as an auxiliary power source for the magnet 5.

  The leakage detection device 6 includes a leakage detection unit 13 to which a signal from the DC main circuit 11 of the magnet drive circuit 4 is input, a leakage determination unit 14 that determines whether there is a leakage based on the input signal, and a process at the time of leakage The leakage time processing unit 15 is configured to perform an alarm command from the leakage time processing unit 15 to the alarm 7, an engine stop command to the engine 1, and a generator motor stop command to the generator motor 2. Is issued.

  Here, as a measure for preventing erroneous detection, the leakage detection device 6 performs leakage detection only after a certain period of time has elapsed after the release operation of the magnet 5 and until the next adsorption operation is started.

  In other words, during the adsorption operation, the release operation, and within a certain time from the release operation, the leakage detection is suspended while a large current flows and there is a possibility of erroneous detection.

  The operation of this point will be described in detail with reference to the flowchart of FIG.

  For example, after starting the control based on the engine switch-on, it is determined in step S1 whether or not the magnet is being attracted based on the operation of the attracting switch 3. If not (NO), the process proceeds to step S2 and whether or not the magnet is being released. Is judged.

  Here again, if NO (not released), the process proceeds to step S3, where it is determined whether or not a certain time has elapsed after the release.

  If YES (a certain period of time has elapsed after release), it is determined whether or not there is a leak in step S4 as leakage detection is possible, and if there is a leakage (YES), processing in case of leakage (alarm activation and engine operation) in step S5 The output of the generator motor stop command) is performed, and in the case of NO (no leakage), the control is finished as it is.

  On the other hand, if YES in any of steps S1 and S2 and NO in step S3, that is, during magnet adsorption, magnet release, and before a certain time has passed since magnet release, the process proceeds to step S6. Then, it returns to step S1 as leakage detection is impossible. Or you may make it wait for the opportunity of the next electric leak detection as control end here.

  As described above, the leakage current is detected only after a certain period of time has elapsed since the release operation until the next adsorption operation starts, and during the adsorption, release, and before a certain time has elapsed since the release operation, Since the leakage detection is not performed while there is a possibility of erroneous detection, the leakage of the magnet drive circuit 4 can be accurately detected without erroneous detection.

  Further, according to the embodiment, in the magnet working machine in which the capacitor 12 as the power storage device is provided in the magnet drive circuit 4, the leakage detection device 6 is connected to the DC main circuit 11 of the magnet drive circuit 4. Electric leakage can be detected directly and accurately from the nearby DC main circuit 11.

  By the way, the present invention is basically similar to the above in a magnet working machine based on a hybrid machine including a generator motor driven by an engine and a battery as a power storage device and operating a magnet with the battery as a main power source. Can be applied.

DESCRIPTION OF SYMBOLS 1 Engine 2 Generator motor 3 Adsorption switch 4 Magnet drive circuit 5 Magnet 6 Leakage detection device 7 Alarm device 11 DC main circuit of magnet drive circuit 12 Capacitor as power storage device 13 Leakage detection portion of leakage detection device 14 Leakage determination portion 15 Same as above, Earth leakage processing section

Claims (2)

A magnet that performs an adsorption / release operation of a load, a generator motor that is driven by an engine to perform a generator action and performs an electric motor action by electric power from the magnet, a power storage device, and at least one of the generator motor and the power storage device A magnet drive circuit that drives the magnet as a power source and a leakage detection device that detects a leakage of the magnet drive circuit. This leakage detection device detects a false detection of a leakage due to a large current flowing after the release operation of the magnet . A magnet working machine configured to detect an electric leakage only until a predetermined time set as a possible time elapses and a next suction operation is started. Provided with a capacitor as the electrical storage device to the DC main circuit of the magnet drive circuit, a magnet working machine according to claim 1, wherein the connecting the leakage detecting device to the DC main circuit of the magnet drive circuit.

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