A method for controlling reversal of a blade of a bush cutter. The method functions by detecting a parameter of a motor with a control circuit and, when a user presses a reversal button, by causing the control circuit to control the motor not to reverse when the detected parameter, e.g., speed of the motor, is greater than or equal to a preset threshold and to control the motor to reversely rotate and drive the blade to reversely rotate when the detected parameter is less than the preset threshold.

Method for controlling reversal of a blade of a bush cutter

PROBLEM TO BE SOLVED: To improve the efficiency of a motored fan and an electric vacuum cleaner, by smoothing an air flow from a blade (vane) to a return. SOLUTION: In this motored fan, a diffuser is composed of a diffuser vane body 121 which is integrally formed to an annular supporting body arranged on a fan casing side and has two or more vanes on the end bracket side of the annular supporting body, and a return guide 122 which has two or more return vanes 115d integrally formed with a partition board on the other side of the partition board with one side brought into contact with two or more vanes. The peripheral end diameter of the vane on the annular supporting body side is set larger than the peripheral end diameter of the vane on the partition board side. COPYRIGHT: (C)2007,JPO&INPIT

Motored fan, and electric vacuum cleaner equipped therewith

A Roots type pump comprising a pair of mating lobed rotors which are supported by rotor shafts, respectively. Each rotor is fixed to the corresponding rotor shaft by a pin forcibly inserted in a through hole provided through the rotor and rotor shaft. The outer surface of each rotor is surrounded by a coating layer of plastic material, at which the through hole has end openings having cross sectional dimensions greater than that of the substantial part of the through hole.

Roots type pump with pin connection for plastic coated rotor

PURPOSE: To provide the voltage of an optimum phase angle at start and during operation of a single-phase motor, by connecting an single-phase two-winding induction motor to a two-phase power supply circuit. CONSTITUTION: A main winding 152 and a start winding 154 of a single-phase two-winding induction motor 150 are connected to both ends of the a phase voltage VP1 and a second phase voltage VP2 of a two-phase power source. The windings 152 and 154 are connected by a common winding 156. The two- phase power source drives a motor 150 with a preferred phase angle.

Driving gear of ac electric motor

The center of gravity of a retaining pin which is struck into a retaining-pin receiving hole to join a rotor barrel with a rotor shaft is eccentrically positioned toward the leading end of the pin beyond the axis of the shaft so that upon rotation of the rotor, the pin is forced to thrust toward the bottom of the hole by the centrifugal force, thereby preventing the pin from pulling out of the hole.

Rotor with eccentrically positioned retainer pin

PURPOSE:To improve the response and resolution of an induction motor by driving the motor at a high speed by a commercial frequency in the range of large deviation voltage and at a low speed by a converter frequency in the range of small deviation voltage. CONSTITUTION:A reference voltage which is set by a speed setter is applied to an input terminal, and is applied to a subtractor 2. The output voltage from a rotation detector 4 which generates a voltage responsive to the rotating speed of an induction motor 3 is applied to the subtractor 2, and the difference between the values, i.e., the deviation a is outputted. This deviation a is applied through a variable gain amplifier 5 and an integrator 6 to a comparator 9, the output of which is applied to a pulse generator 10 and a drive circuit 11. When the deviation a is lower than the reference, the motor 3 is driven by the converter frequency which becomes lower proportional to the deviation a. And when the deviation a is higher than the reference voltage, the motor 3 is driven according to the commercial frequency.

Controller for induction motor

PURPOSE:To enable to drive an induction motor with variable frequency and with the frequency of a commercial power source by controlling a switching element with polyphase pulse altered in frequency in response to the signal for setting the rotating speed or fully conducting the switching element CONSTITUTION:The coils W1, W2 of a 2-phase induction motor M are connected at one ends through a neutral point to one terminal of a single phase commercial power source V and at the other ends through triacs TH1, TH2 to the other end of the power source V The gate circuits G1, G2 of the triacs TH1, TH2 are operated by a polyphase pulse altered in frequency in response to the signal for setting the rotating speed, or are perated by a gate pulse for conducting either oneof the thyristors TH1, TH2

Driving device for 2-phase induction motor

PURPOSE:To generate symmetrical 3-phase AC voltage with a simple configuration by generating a gate pulse by a normal logic gate, and triggering the thyristor of a thyristor bridge circuit. CONSTITUTION:A clock pulse from an oscillator 5 is applied to a ring counter 6 and a triangular wave generator 9, and the output of the counter 6 is applied to a pulse selector 8 and a ring counter 7. The output of the selector 8 is applied to a pulse width varying circuit 11. The output of the generator 9 is applied to the circuit 11 through a comparator 10. The outputs of the ring counter 7 and the circuit 11 are respectively applied to waveform synthesizers 12-14, thereby outputting gate pulses gs1-gs6 of the thyristors of a thyristor bridge circuit.

Control circuit for inverter

PURPOSE:To prevent an overcurrent at the switching time by detecting the decrease in the voltage when a normal/reverse rotation command is applied, while confirming that the value decreases to the degree not reaching the value which will give damage to a semiconductor element, thereby switching to normal or reverse CONSTITUTION:An induction motor 4 is drive by a converter 2 and an inverter 3, the converter 2 is controlled through a phase control circuit 6 with a signal from a speed setter 5 and the inverter 3 is controlled through an oscillator 11 The output of the converter 2 is detected by a voltage detector 14, compared by a comparator 15 with the reference voltage set to the value of the degree not flow an overcurrent to the thyristor or the like even if normal or reverse rotation is switched, and a normal/reverse rotation circuit 13 is switched through flip-flops 16, 20 Accordingly, safety conversion can be performed without applying an overcurrent to the semiconductor element at the normal/reverse switching step and without necessity of confirming the stop of the motor

Normal/reverse rotation controller for motor

PURPOSE:To decrease the turn-off time of a switch circuit of a power transistor, by providing a diode to discharge the excess charge produced when the power transistor is turned off via a transistor. CONSTITUTION:A diode D is connected between the base of a power transistor TRQ0 and the collector of a TRQ1 so that it is set forward to the collector. When the TRQ1 is turned on by an input signal, a TRQ2 is turned off to stop the flow of a base current IB1. Thus the power TRQ0 is turned off. In this case, the excess charge of the TRQ0 is discharged as a current IB2 via the diode D and the TRQ1. The current IB2 can be increased until it is limited as the collector current of the TRQ1.

Takemura Yutaka

Papers

Controller for induction motor

Driving device for 2-phase induction motor

Control circuit for inverter

Normal/reverse rotation controller for motor

Switch circuit of power transistor