Koki Holdings Co., Ltd.

Yuuki Takeda

Hironori Sakai

Kyouichi Nakayama

An electric tool includes a housing; a brushless motor, housed in the housing; an output shaft configured to hold a tip tool; a switching circuit controlling the brushless motor; a circuit board; a case, accommodating the circuit board, the case is filled with a resin, wherein the resin covers at least a part of the circuit board; the housing includes a motor housing element and a cover element covering at least a part of the case. The motor housing element includes a motor housing part accommodating the brushless motor, and a fixing part, configured to fix the case to the motor housing by the fixing part abutting the case.

Electric tool

The electric tool including a motor having a stator and a rotor, a rotation shaft integrally rotating with the rotor, a casing accommodating the motor, a ventilating window disposed in the casing, a cooling fan sucking an air through the ventilating window to cool off the motor, a magnetic body disposed to the rotation shaft, a magnetic detection unit detecting a rotational position of the magnetic body, and a circuit substrate on which the magnetic detection unit is mounted. The circuit substrate and the magnetic body are disposed to be isolated from a wind path of a cooling wind generated by rotation of the cooling fan.

Provided is an electric tool in which the risk of short-circuiting between conductive members of multiple installed switching elements has been reduced by providing partitioning plates between the switching elements. An electric tool, which has a motor, an inverter circuit with multiple switching elements for performing switching operations and controlling the driving of the motor, a control unit for controlling switching element on-off operations, and a circuit board on which the switching elements are loaded, is configured so that the circuit board is housed inside a container-shaped case () and the circuit board is secured with a partitioning member () that is interposed between the multiple switching elements and has partitioning plates () obtained from an insulating material.

A rectifier circuit for rectifying an AC voltage supplied from a commercial power supply into a DC voltage, a smoothing capacitor for smoothing the output of the rectifier circuit, and an electrically powered tool for supplying the smoothed pulsating DC voltage to a motor by an inverter circuit, wherein when the motor is driven while no load is being applied to a tip tool, the smoothed DC voltage repeatedly generates a maximal value and a minimum value so as to synchronize with the fluctuation in the AC voltage. During no-load rotation, control is performed so that driving is performed at a value that is less than a threshold value Dfor the duty ratio at which the generation of a gear sound starts in any of the speed dial setting values 1-6. It is thereby possible to suppress a gear sound generated by a power transmission mechanism during no-load rotation.

Electrically powered tool

Provided is an easy-to-use electric tool with which braking force can be changed according to work conditions. When an operation switchis turned off, a control unitdetects a rotation rate Rof an electric motor. The control unitstands by for a prescribed period, detects a rotation rate Rof the electric motor, and calculates the difference between the rotation rates R, R(R=R&#x2212;R). Since the rotation rate difference R corresponds to the rate of change in rotation rate with time during deceleration of the electric motorand is smaller the larger the moment of inertia of the attached rotary tool, the control unitcan determine the moment of inertia of the rotary tool on the basis of the rotation rate difference R. The control unitsets the braking force according to the moment of inertia and performs braking.

An electric tool is provided. The electric tool prevents anomalies in motor rotation due to dust and moisture sucked in together with a cooling wind, and is configured such that rotational position detection operations and switch operations are not affected. In the electric tool which drives a brushless DC motor using a controller, a magnetic body for rotational position detection is provided on a rotation shaft which can rotate integrally with a rotor, Hall ICs are provided to detect the rotational position of the magnetic body and output a position signal to the controller, and the magnetic body and the Hall ICs mounted on a substrate are arranged in a region isolated from the wind path of the cooling wind generated by rotation of a cooling fan. The Hall ICs are accommodated in a housing filled with resin.

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Ibaraki, Japan

Yuuki Takeda