JP5530727B2 - Working machine and control method of working machine - Google Patents

Description

  The present invention relates to a battery-powered work machine and a work machine control method in which safety measures are taken when a semiconductor switching element that controls a motor fails.

  As a battery-powered working machine powered by a motor, an electric tool for processing a piece of wood or a metal piece, or a lawn mower used to cut grass such as turf or weed (eg, Patent Document 1), a mower (eg, patent Document 2) or a brush cutter is known. FIG. 4 shows a control circuit of the electric lawn mower disclosed in Patent Document 1, and the supply current from the battery 100 to the DC motor 400 is pulse-controlled by a FET (Field Effect Transistor) 800 which is a semiconductor switching element. The rotational speed of the DC motor 400 is controlled to be substantially constant. When starting the lawn mowing work, the main switch 200 is turned on, and when the work is finished, the operation is turned off.

Japanese Patent Laid-Open No. 9-201126 Japanese Utility Model Publication No. 7-5321

  By the way, the main switch 200 of the above control circuit cuts off the current supplied to the DC motor 400, so it must be able to withstand a relatively large current, and a large switch must be adopted. There wasn't. The large switch requires a certain amount of force for operation, requires a certain place for mounting on the work machine, and has the disadvantage of being costly.

  In order to eliminate this drawback, the main switch 200 is abolished, a start switch is provided in the control unit 500 in the control circuit, the control unit 500 is started by turning on the start switch, and the control of the FET 800 is started. Can be considered. In such a control circuit, since the supply current to the DC motor 400 is turned on and off only by the FET 800, a start switch for small current that can turn on and off the control unit 500 can be adopted. However, in the above configuration, when the FET 800 is short-circuited, there is a problem that the rotation of the motor does not stop even when the start switch is turned off, and the battery 100 must be pulled out. In addition, when the battery 100 that has been charged is mounted on the work machine, there is a problem that the DC motor 400 rotates regardless of the operation of the start switch.

  The present invention solves the above problem, and even when the semiconductor switching element has a short circuit failure, the current supplied to the DC motor can be turned on and off by operating the start switch, and the semiconductor switching element is short-circuited. A battery-driven work machine having a function of detecting a failure and a method for controlling the work machine are provided.

In order to achieve the above object, in a working machine including a battery, a rotating unit that rotates a blade, a motor that drives the rotating unit, and a control circuit that controls the motor, the control circuit includes the battery and the motor. A built-in main circuit and a control unit having a start switch are built in. A relay contact controlled by the control unit and a semiconductor switching element are provided in series in the main circuit and a current detection unit is provided. The relay contact and the semiconductor switching element are turned on to supply current from the battery to the motor, and the semiconductor switching element is turned off when the start switch is turned off. And controlling the semiconductor switching by a signal from the current detection unit at the predetermined time. It was to determine the short-circuit fault of the child.

According to the onset bright, even when the semiconductor switching element is caused a short-circuit failure, it stops the rotation of the motor if off the start switch, also turn on the start switch when fitted with a battery charging is completed on the work vehicle Otherwise, since the motor does not rotate, the work machine can be used safely. Further, it is possible to know the short-circuit failure of the semi-conductor switching elements appropriately.

It is an external view for demonstrating the whole structure of the brush cutter concerning this invention. It is a control circuit diagram concerning the present invention. 3 is a timing chart for explaining the operation of the control circuit according to the present invention. It is a conventional control circuit diagram.

  Hereinafter, a preferred embodiment for carrying out the present invention will be described by taking a brush cutter as an example of a working machine.

  In the following description, for convenience of explanation, a direction corresponding to the usage state of the brush cutter 1 is defined. That is, in FIG. 1, the side on which the rotating unit 7 on which the cutting blade rotates is installed is called “front”, and the drive unit 3 side is called “rear”.

  The brush cutter 1 according to the present embodiment includes an operating rod 2 formed in a shaft shape extending in the longitudinal direction, a rotating portion 7 installed on the front side that is one end side of the operating rod 2, and the operating rod 2 A drive unit 3 provided on the rear side which is the end side and including the motor 20 and the battery 10 shown in FIG. 2 inside the housing, and a handle 4 installed in an intermediate portion in the longitudinal direction of the operation rod 2 are provided. ing.

  The operation rod 2 is constituted by a hollow rod-like pipe member, and a driven shaft (not shown) is incorporated in the inside thereof so as to be rotatable. A rotating portion 7 is attached to the front end of the operation rod 2, and a holder 7a of the rotating portion 7 has a disk-like metal shape in which a plurality of saw blade-shaped blade portions are formed on the outer peripheral surface. The cutting blade is rotatably attached. The holder 7a rotates according to the rotational movement of the driven shaft, and can cut grass and the like. In addition, a protective cover 7b is provided in the immediate vicinity of the rear of the cutting blade so as to cover a part of the cutting blade. Is secured. As for the cutting blades, it is possible to adopt all types of cutting blades, such as ceramic ones and cords extending radially from the center of rotation, instead of disk-shaped metal ones. It has become.

  Further, a right grip 5R and a left grip 5L are attached to the handle 4, and an activation switch 51 for activating the motor 20 is provided on the right grip 5R. Reference numeral 6 denotes a hook to which a shoulder belt (not shown) can be attached.

  FIG. 2 shows a control circuit according to the present invention, the main part of which is built in the drive unit 3, and a main circuit for supplying the supply current from the battery 10 to the motor 20 is formed by the wirings 11 and 13. . In addition to the battery 10 and the motor 20, the main circuit is provided with a relay contact 40, an FET 30, and a current detection unit 12 in series. Reference numeral 50 denotes a control unit which controls ON / OFF of the relay contact 40 and the FET 30 by an internal microcomputer program (not shown). Further, it is possible to detect whether or not current is flowing through the main circuit based on a signal from the current detection unit 12. The current detection unit 12 is configured by a resistor, and it can be determined whether or not a current flows in the main circuit based on the presence or absence of a voltage generated at both ends of the resistor due to the current flowing. When the start switch 51 is turned on, the control unit 50 is started by a power source (not shown), and the program of the internal microcomputer starts control. You may comprise so that the power supply of the control unit 50 may be taken from the battery 10. FIG.

  When the mowing operation is performed with the brush cutter 1 configured as described above, the operator hangs a shoulder belt (not shown) attached to the hook 6 around the shoulder, and the left and right grips 5R and 5L provided in the handle 4 Can be manipulated freely by gripping with both hands.

  Next, the motor is activated to rotate the cutting blade. For this purpose, the operator turns on the activation switch 51 to the ON side. FIG. 3 is a timing chart of the control circuit. When the control unit 50 is activated by turning on the start switch 51 (Ton timing), electricity flows to a relay (not shown) in the control unit, and the relay contact 40 is opened. Is closed and connected (conducted), and an ON signal is output to the gate 31 of the FET 30 so that the FET 30 is turned on and conductive, current is supplied to the motor 20 and the cutting blade starts rotating. When the work is finished, the worker tries to stop the motor 20 by turning the start switch 51 to the off side. However, when the start switch 51 is turned off (Toff timing), the control unit 50 immediately turns off the FET gate 31. Is output to turn off the FET 30, and then control is performed so that the relay is turned off (the relay contact 40 is opened) with a delay of time t. The time t is appropriately about 1 second. During this time, the control unit 50 detects the signal from the current detection unit 12 by the wiring 14 and checks whether or not current is flowing through the motor 20. If the FET 30 is normal, no current flows in the main circuit during the time t. However, if the FET 30 is short-circuited, a current flows during the time t, and the current detection unit 12 detects this. When a short circuit failure of the FET 30 is detected, the control unit 50 is configured to turn on an error lamp (not shown) to notify the operator of the failure.

  When the battery 10 needs to be charged, the worker removes the battery 10 from the work machine 1 and charges it with a charging device (not shown). When charging is completed, the operator attaches the battery 10 to the work machine 1, but since the start switch 51 is not operated, the control unit 50 is not activated and the relay contact 40 remains open. Even if the FET 30 causes a short-circuit failure, current does not flow through the main circuit and the motor 20 does not start rotating carelessly, which is safe.

  The brush cutter 1 according to the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made within the scope described in the claims. For example, in the present embodiment, the brush cutter 1 using the motor 20 driven by the battery 10 has been described, but a motor driven by an AC power source may be used. Further, the semiconductor switching element may be a semiconductor element such as a power transistor or a thyristor as well as an FET.

  The present invention is useful for a working machine such as a brush cutter.

  1 brush cutter, 2 operation rod, 3 drive unit, 4 handle, 7 rotating unit, 10 battery, 12 current detection unit, 20 motor, 30 FET, 40 relay contact, 50 control unit, 51 start switch

Claims (2)

In a working machine including a battery, a rotating unit that rotates a blade, a motor that drives the rotating unit, and a control circuit that controls the motor, the control circuit is formed by connecting the battery and the motor. A main circuit and a control unit having a start switch; a relay contact controlled by the control unit and a semiconductor switching element are provided in series in the main circuit; a current detection unit is provided; and the relay is turned on when the start switch is turned on. The contact and the semiconductor switching element are turned on to supply current from the battery to the motor, and the semiconductor switching element is turned off when the start switch is turned off, and then the relay contact is turned off after a certain period of time. Control and short circuit failure of the semiconductor switching element by a signal from the current detection unit at the predetermined time Working machine, characterized in that the determination.   A battery, a rotating unit that rotates a blade, a motor that drives the rotating unit, and a control circuit that controls the motor, the control circuit starting with a main circuit that connects the battery and the motor A control unit having a switch, a relay contact controlled by the control unit and a semiconductor switching element are provided in series in the main circuit, and the main circuit is provided with a current detection unit. When the start switch is turned on, the relay contact and the semiconductor switching element are turned on to supply current to the motor from the battery, and when the start switch is turned off, the semiconductor switching element is turned off, and then a certain time has elapsed. The relay contact is controlled to be non-conductive later, and the semiconductor switching is performed by a signal from the current detection unit at the predetermined time. The method of the working machine, characterized in that to determine the short-circuit failure of the child.

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