JPH03131479A - Power tool - Google Patents

Abstract

PURPOSE:To automatically align screw heads and save a work trouble by providing a control means for controlling the output shaft of a motor for the rotation thereof in a stepping mode via the operation of a selector switch during motor rotation. CONSTITUTION:A power tool tightens screws as a normal tool, and the rotation of a motor 2 is selected to a stepping mode via a selector switch 12 at the time of the final positioning of the screws, thereby aligning screw head. As a result, manual work conventionally required for screw head alignment can be eliminated and the power tool can be used instead for continuous alignment work, thereby saving a work trouble.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a power tool such as a rechargeable drill/driver having a motor.

[Prior Art] Fig. 7 shows a conventional power tool such as a rechargeable drill/driver, in which a main body 1 includes a motor 2 and a gearbox connected to the output shaft of the motor 2 to reduce the rotation speed of the motor 2. 3 is arranged, and a chuck 4 is provided at the tip. A rechargeable battery 6 is housed in a handle 5 that hangs down from the approximate center of the main body 1, and a switch 7 for turning the motor 2 on and off is provided at the top of the handle 5. The function is that the shaft rotates to make a hole,
It tightens screws and can control the speed to any desired speed by feeding back a speed signal.

Figure 8 shows the circuit configuration of a DC motor when performing conventional speed control.Normally, the motor (DC motor) 2 is rotated by turning the current on and off using mechanical contacts, but when performing speed control In this case, a sensor that detects the rotation speed of motor 2 (
The speed is detected by the FG sensor (FG sensor) 8, and the speed signal obtained by the sensor 8 is input to the control circuit 9. Then, the control circuit 9 compares the voltage with a voltage preset by the speed setting volume 10 and converts it into a PWM signal for controlling the current of the motor 2, and the semiconductor switch 11 performs pulse width control. In the case of FIG. 8, when the PWM signal output from the control circuit 9 is at H level, the semiconductor switch 11
is driven on.

[Problems to be Solved by the Invention] In such conventional examples, for example, when it is desired to fix the fixed position of the screw threads of several or more screws at a fixed angle, such as in the case of decorative screws, although the rotation speed can be varied, I couldn't decide where the screw thread would stop, so I ended up having to align it by hand.

The present invention has been provided in view of the above-mentioned points, and the output shaft of the motor is controlled to rotate in steps by operating a changeover switch during the rotation of the motor, for example, to change the position of the thread of a screw. The purpose of this invention is to provide a power tool that can be stopped at any position.

[Means for Solving the Problems] The present invention is provided with a control means for controlling the rotation of the output shaft in steps by operating a changeover switch during rotation of the motor.

Further, in claim 2, a DC motor, a sensor that detects the rotational speed of the DC motor, and a speed signal from the sensor is compared with a preset value to control the current of the DC motor so that the set speed is achieved. a control circuit that outputs a PWM signal, a semiconductor switch that is turned on and off by the control circuit output to rotate the DC motor, and a timer circuit that outputs an on/off signal to the semiconductor switch to drive the rotation of the DC motor in steps. and a changeover switch for switching between the control circuit output and the timer circuit output.

Further, in claim 3, there is provided a brushless motor, a semiconductor switch that excites a coil of the brushless motor, a position detector that detects the position of the brushless motor, and an excitation that turns on and off the semiconductor switch based on a signal from the position detector. It includes a distribution circuit that outputs a signal, and a timer circuit that outputs an on/off signal via a changeover switch that drives the distribution circuit and drives the rotation of the brushless motor in steps.

[Function] According to the above configuration, the rotation of the output shaft is controlled stepwise by operating the selector switch during rotation of the motor. The rotation of the DC motor is driven in steps by the timer circuit output.

Furthermore, in claim 3, the motor is a brushless motor,
By operating the changeover switch, the distribution circuit is controlled by the timer circuit output, and the rotation of the brushless motor is driven in steps.

[Example 1] Hereinafter, an example of the present invention will be described with reference to the drawings. A block diagram is shown in FIG. 1.The overall configuration is the same as that shown in FIG. Semiconductor switch 1
1 and a changeover switch 12 for inputting the input signal to the input signal. The changeover switch 12 is composed of an analog switch, a digital switch, etc., and the timer circuit 1 constitutes a control means.
The semiconductor switch 11 is operated intermittently with three outputs.

FIG. 2 shows a specific circuit diagram of the timer circuit 13, 555
Using a timer IC, the on period and off period can be set using external resistors Ra and Rb and a capacitor C8. Note that, assuming that the on period is Ton and the off period is T o f , Ton and T o f are determined by the following equation.

Ton=0.693・(Ra+Rb)・CToff=
0.693 ・Rb-C+ FIG. 3 shows a cutaway side view, and a changeover switch 12 is provided at the upper part of the back surface of the handle 5.

In the latter half of the screw tightening process, after switching by operating the changeover switch 12, the semiconductor switch 11 and the timer circuit 13 turn on and off the power to the motor 2 intermittently for a predetermined period of time, thereby controlling the rotation of the motor 2. By repeating this and stopping in a short period of time, the tip of the drill shaft repeatedly rotates and stops intermittently and little by little in a step-like manner. Then, tighten it little by little until it reaches the final position, allowing you to align the threads at any desired position. Note that the semiconductor switch 11 is turned on and conducts current when the input signal is at H level. Furthermore, by using the semiconductor switch 11, a conventional semiconductor switch can be used if the power tool is of a type that has a speed control circuit.

By the way, the signal from the timer circuit 13 is -PWM
Although it seems to be the same signal, the PWM signal has a frequency of several kHz, and one pulse has a large inertia of the motor 2, so it does not affect the rotation of the motor 2.

In comparison, the signal from the timer circuit 13 is
It is long enough to be turned on only for the rotor to rotate several times. Even if the motor 2 rotates several times, in this type of tool, the speed is usually reduced by a gear, so the rotation of the tool shaft is a fraction of one rotation.

In this way, screws are tightened as a normal power tool, and at the time of final positioning, the changeover switch 12 is used to switch the motor 2.
Learn how to rotate by turning it into a step motion.

Align the heads of the screws. Therefore, what used to be done manually to align the screw heads can now be done continuously using an electric tool, which saves time and effort.

[Embodiment 2] FIGS. 4 to 6 show another embodiment, in which a brushless motor is used as the motor. FIG. 4 shows an example of the configuration of a drive circuit for a brushless motor, and shows an example of a full-wave drive system. Semiconductor switch Q1 consisting of power MO8FET
~Q6 drives the coil of the brushless motor ~L, and the semiconductor switches Q1, . . . are driven by an excitation signal from the distribution circuit 15. In this embodiment, a signal generated from a timer circuit 13 consisting of a multivibrator is input to a brake terminal of a distribution circuit 15. The brushless motor distribution circuit 15 will be described later, but in the case of a three-phase bipolar type, all the semiconductor switches Q, ~Q of the upper power MO8FET are turned on, and the lower power MO3FET is turned on.
By turning off all semiconductor switches Q, ~Q, the brushless motor coils 1 ~ can be short-circuited and stopped rapidly.
The brushless motor is operated intermittently by applying a signal to the brake terminal. It should be noted that whether the operation signal is L active or H active differs depending on the IC, and can be handled by simply inverting the timer signal, so any signal is acceptable. In this example,
It is assumed that the brushless motor rotates at H.

Also in this embodiment, the signal from the timer circuit 13 seems to be the same as the PWM signal, but the PWM signal has a frequency of several kHz, and a single pulse of the PWM signal is Since the inertia of the motor is large, it does not affect the rotation of the brushless motor.In contrast, the signal from the timer circuit 13 is long enough to turn on the brushless motor rotor for several rotations. Even if the brushless motor rotates several times, this type of tool usually uses gears to reduce the speed, so the rotation of the tool shaft is a fraction of one rotation.

FIG. 5 shows a specific circuit diagram, in which the switching position of the coil current is detected by Hall elements A, B, and C, which are position detectors of the brushless motor. As shown in Figure 6, this signal shows the magnetic flux distribution of the sensing magnet as three sinusoidal signals.
Each has a phase difference of 120 degrees. As shown in FIG. 6, based on the signals from the Hall elements AB and C, the semiconductor switch Q,
...Create six timing pulse trains necessary for driving,
Furthermore, if there is a brake signal input, all the upper semiconductor switches Q+ are turned on, and the lower semiconductor switch Q
Generate a signal that turns off all 4....

In this embodiment, as in the previous embodiment, the changeover switch 12 is operated in the middle of the screw tightening process, and the timer circuit 13 is
The on/off signal is input to the brake terminal of the distribution circuit 12, the brushless motor is rotated in a stepwise manner, and the screws are aligned by repeating rotation and stopping.

[Effects of the Invention] As described above, the present invention is provided with a control means for controlling the rotation of the output shaft in steps by operating a changeover switch during rotation of the motor. By controlling the rotation of the output shaft in steps by operating a switch, screws can be tightened as a normal power tool, and at the time of final positioning, the motor rotation can be switched to step operation using a changeover switch, and the screw can be tightened in steps. It is possible to align the heads of screws, and therefore, what used to be done by hand to align the heads of screws can now be done continuously using power tools, which has the effect of saving time and effort. .

Further, in claim 2, a DC motor, a sensor that detects the rotational speed of the DC motor, and a speed signal from the sensor is compared with a preset value to control the current of the DC motor so that the set speed is achieved. a control circuit that outputs a PWM signal, a semiconductor switch that is turned on and off by the control circuit output to rotate the DC motor, and a timer circuit that outputs an on/off signal to the semiconductor switch to drive the rotation of the DC motor in steps. and a changeover switch that switches between the control circuit output and the timer circuit output, so even if the motor is a DC motor,
The rotation of the DC motor can be driven in steps by operating the changeover switch and the timer circuit output, and the positioning of the screw head can be easily performed. A semiconductor switch that excites the coil of the brushless motor, a position detector that detects the position of the brushless motor, a distribution circuit that outputs an excitation signal that turns on and off the semiconductor switch based on the signal from the position detector, and a distribution circuit. The motor is equipped with a timer circuit that outputs an on/off signal via a changeover switch to drive the rotation of the brushless motor in steps, so even if the motor is a brushless motor, the changeover switch can be operated. The distribution circuit is controlled by the timer circuit output, and the rotation of the brushless motor can be driven in steps, making it easy to align the screw head.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a specific circuit diagram of the timer circuit of the above, FIG. 3 is a cutaway side view of the same, and FIG. 4 is a block diagram of another embodiment of the same. Figure 5 is the specific circuit diagram as above, Figure 6 is the time chart as above, Figure 7 is the same as above.
The figure is a block diagram of a conventional example. FIG. 8 is a cutaway side view of the same. 2 is a motor, 8 is a sensor, 9 is a control circuit, 11 is a semiconductor switch, 12 is a selector switch, 13 is a timer circuit, and 15 is a distribution circuit.

Claims (3)

[Claims] (1) In an electric tool that rotates a motor to rotate a screw or the like at the tip of an output shaft, a control means is provided to control the rotation of the output shaft in steps by operating a changeover switch during rotation of the motor. A power tool featuring: (2) A DC motor, a sensor that detects the rotation speed of the DC motor, and a PWM signal that compares the speed signal from the sensor with a preset value and controls the current of the DC motor to reach the set speed. A control circuit that outputs an output, a semiconductor switch that is turned on and off by the control circuit output to rotate the DC motor, a timer circuit that outputs an on/off signal to the semiconductor switch to drive the rotation of the DC motor in steps, and the above control. The power tool according to claim 1, further comprising a changeover switch for switching between circuit output and timer circuit output. (3) A brushless motor, a semiconductor switch that excites the coil of the brushless motor, a position detector that detects the position of the brushless motor, and a distribution circuit that outputs an excitation signal that turns on and off the semiconductor switch based on the signal from the position detector. 2. The power tool according to claim 1, further comprising: a timer circuit that outputs an on/off signal via a changeover switch to drive the distribution circuit and drive the rotation of the brushless motor in steps.