JPS614488A - Controller of motor-driven driver - Google Patents

Abstract

PURPOSE:To reduce a reaction applied to a hand when additionally clamping after clamping a screw by freely varying the peak value of a current flowed when a motor-driven motor is started. CONSTITUTION:When a power source switch 9 is closed, the first delay circuit 14 outputs a H signal for the prescribed time T. When the output of a current detector 10 becomes set value ic or higher during this period, the first voltage comparator 11 outputs a H signal, and a gate circuit 15 outputs the H signal. On the other hand, the second delay circuit 15 outputs a H signal after the prescribed time is elapsed. At this time, when the output of the detector 10 arrives at the set value i8, the second voltage comparator 1 outputs a H signal, and a holding circuit 13 outputs a H signal. A gate circuit 18 turns OFF the switch 9 OFF when the holding circuit 13 or the gate circuit 15 outputs the H signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control device for an electric screwdriver that is driven by electric power supplied from a DC power supply and is used for tightening screws.

Configuration and Problems of Conventional Example The configuration and operation of a conventional control device for an electric screwdriver will be explained with reference to FIGS. 1 and 2. Figure 1 shows an example of the configuration of a control device for an electric screwdriver, and 1 is a power switch;
A detector that converts the current i flowing through the 2-piece electric motor 8 into voltage, and when the voltage of the 3-piece detector 2 exceeds a preset value, it goes from H to low level (hereinafter abbreviated as "low").
It is a hold circuit that changes to , and thereafter maintains that state, and is a cutoff circuit that cuts off the current i flowing to the electric motor 8 when the output of the six-digit hold circuit 4 is L.

FIG. 2 shows how the current i flowing through the electric motor 8 changes after the power switch 1 is turned on.

When the power switch 1 is turned on at time to, the current flowing through the electric motor 8 increases according to an increasing curve determined by the power supply voltage and the coil resistance and coil inductance of the electric motor 8, and reaches a peak value ip. Thereafter, it decreases as the rotational speed of the electric motor 8 increases, and reaches a minimum value of 13 at time t3. If the final current value for screw tightening is set to 14, it will generally be lp') 14, so the voltage comparator 3 is activated when the electric motor 8 is started, and the cutoff circuit 5 is activated at time t. Therefore, even if the voltage comparator becomes H, it is necessary not to input this to the hold circuit 4 during a certain time T (>t2-0) when the electric motor 8 is started. Therefore, a delay circuit 7 is provided whose output becomes L for a certain period of time when the power switch 1 is turned on, and the voltage comparator -3□1□. i? g7. stomach. 8. , the current l flowing through the electric motor 8 is cut off for the first time in the hold circuit.

However, in the above configuration, even if the screw tightening is slightly changed, the current i flowing at the time of starting the electric motor reaches the peak value ip, and after that, the current i reaches the set current value 14 and the electric motor stops.

As a result, a large reaction occurs to the worker () who is working with an electric screwdriver, regardless of the set current value i40, causing him to swing his wrist around, causing him to have to continuously retighten the screws. Needless to say, the one-off screw tightening work has the disadvantage that it is undesirable from the standpoint of industrial hygiene.Purpose of the InventionThe present invention solves the above-mentioned conventional disadvantages, and it The force applied to your hand when retightening screws
- To provide a control device for an electric screwdriver with reduced motion.

Structure of the Invention The control device for an electric motor and a driver of the present invention includes a detector that converts the current flowing from a DC power source into a voltage, and a signal that outputs a signal when the output voltage from the detector is larger than a predetermined set value. a first voltage comparator that outputs a signal, a first delay circuit that holds the signal of the electric motor start switch for a certain period of time, and a logical product of the output signals of the first electric sign comparator and the first delay circuit. a first gate circuit that outputs an output; a second voltage comparator that outputs a signal when the output voltage from the detector is greater than a predetermined setting value; a second delay circuit that outputs an output; a second gate circuit that outputs an output when an AND of the output signals of the second voltage comparator and the second delay circuit is obtained;
a hold circuit that holds the output signal of the gate circuit; a third gate circuit that outputs an output when the output signals of the first gate circuit and the hold circuit are obtained; and an output of the third gate circuit; This circuit consists of a cutoff circuit that cuts off the current flowing to the electric motor when the electric motor is started, and allows the peak value of the current flowing when the electric motor is started to be freely changed, and the current that flows when the screw is tightened after screw tightening is completed. It has the unique effect of reducing recoil.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will now be described with reference to the drawings.

FIG. 3 shows the configuration of a control device for an electric screwdriver according to an embodiment of the present invention. In Fig. 3, there are 9 power switches, 10 detectors that convert the current i flowing through the electric motor 20 into voltage, and 11 a switch that changes the output to H when the current i flows to the electric motor 20 exceeds a preset value. 1 voltage comparator. 12 is also a second voltage comparator which sets the output to H when the voltage exceeds a preset value. When the output of the 13 second voltage comparators becomes H, the hold circuit changes from L to H and maintains that state thereafter. It is a 14-digit first delay circuit, which receives the 7N signal from the power switch 9 and
H is maintained between 0 and 100 qec. 15
This is a first gate circuit that outputs an H output when the logical product of the output signals of the first voltage comparator 11 and the first delay circuit is obtained. A second delay circuit 16 outputs an H signal when the output signal of the first delay circuit changes from H to L. 17
This is a second gate circuit that outputs an H output when the logical product of the output signals of the second voltage comparator 12 and the second delay circuit is obtained, and its output is input to the hold circuit 13. 1
8 is a third gate circuit that outputs an H output when the logical sum of the output signals of the first gate circuit 16 and the hold circuit 13 is obtained, and when the output signal is H, the current 1 flowing to the electric motor 20 is It is cut off by the cutoff circuit 19.

FIG. 4 shows how the current i flowing through the electric motor 20 changes after the power switch 9 is turned on.

Time t. When the power supply switch 9 is turned on, the current i flowing through the electric motor 2o increases according to the rising curve determined by the power supply voltage, the coil resistance of the electric motor 8, and the coil inductance l, and the current i flows through the electric motor 2o.
When the voltage from o exceeds the predetermined setting value of the first voltage comparator 11, an H signal is output during the first voltage ratio, so the output of the first gate circuit is also H, and the output of the third gate circuit is The output of is also H. Therefore, the cutoff circuit 19 is activated and the current i is cut off. Its value is 1°. Then electric motor 2
As the rotational speed increases, the rotation speed decreases, and at time t7, the minimum value is 17 tonal, and the final current value for screw tightening is set to 18. If 1c) is, the second voltage comparator is set at the time of starting the electric motor 20. 12 is activated and the cutoff circuit 19 is activated at time t5, so the second tonicity comparator is at H for a certain period of time T (>t60) when the electric motor 20 is started.
Even if this is the case, it is necessary that the hold circuit 13 is not manually operated. Therefore, for a certain period of time T during which the first delay circuit 14 is activated at the same time as the power switch 9 is turned on,
A second delay circuit 16 that becomes L and becomes H after T time is set 6f.
-'(Yes/Second voltage comparator"7 Second delay circuit'6
The second gate circuit 1 performs the AND of the output with the second gate circuit 1, and inputs the output signal to the hold circuit 13, thereby stopping the electric motor 20 at time t8 in FIG.

As described above, according to this embodiment, by adding another electric comparator, a delay circuit, and a gate circuit to the conventional electric screwdriver control device, a huge amount of current flows when the electric motor is started. It becomes possible to reduce
When retightening the screw after the screw has been tightened, a large amount of current does not flow at once, so the reaction force applied to the hand can be greatly reduced.

[Effects of the Invention] As described in [2], the present invention includes a detector that converts the current flowing from a DC power supply to an electric motor into voltage, and a signal that outputs a signal when the output voltage from the detector is larger than a predetermined set value. A first voltage comparator that outputs an output signal, a first delay circuit that holds the signal of the electric motor start switch for a certain period of time, and an output signal when the logical product of the output signals of the first voltage comparator and the first delay circuit is obtained. a first gate circuit that outputs a signal; and a 211i that outputs a signal when the output voltage from the detector is greater than a predetermined set value; 11. The logical product of the output signals of the E comparator, the second delay circuit that outputs an output from the time when the first delay circuit finishes outputting the output, the second voltage comparator, and the second delay circuit is obtained. a second gate circuit that outputs an output;
a hold circuit that holds the output signal of the gate circuit; a third gate circuit that outputs the result when the logical sum of the output signals of the first gate circuit and the hold circuit is obtained; By installing a cutoff circuit that cuts off the current flowing to the electric motor, it is possible to reduce the huge amount of current that flows during the electric motor when starting the electric motor, and when retightening the screws after tightening the screws. Since a large amount of current does not flow all at once, the recoil exerted on the hand can be greatly reduced, and the practical effects of this are significant.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a conventional electric screwdriver control device, Fig. 2 is an explanatory diagram showing changes in the current flowing through an electric motor in the conventional example, and Fig. 3 is an illustration of an electric screwdriver according to an embodiment of the present invention. FIG. 4, which is a configuration diagram of the control device, is an explanatory diagram showing how the current flowing through the electric motor changes in one embodiment of the present invention. 1o...Detector, 11...First voltage comparator, 12...Second voltage comparator, 13...
...Hold circuit, 14...First delay circuit, 16
...Second delay circuit, 19...Block circuit,
20...Electric motor. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 5Figure 2

Claims (1)

[Claims] a detector that converts the current flowing through the electric motor from a DC power source into voltage; a first voltage comparator that outputs a signal when the output voltage from the detector is greater than a predetermined set value; and an electric motor start switch. a first delay circuit that holds a signal for a certain period of time; a first gate circuit that outputs an output when an AND of the output signals of the first voltage comparator and the first delay circuit is obtained; and an output from the detector. a second voltage comparator that outputs a signal when the voltage is greater than a predetermined set value;
a second delay circuit that outputs an output from the time when the delay circuit finishes outputting the output; and a second gate circuit that outputs an output when the AND of the output signals of the second voltage comparator and the second delay circuit is obtained. , a hold circuit that holds the output signal of the second gate circuit; a third gate circuit that outputs an output when a logical sum of the output signals of the first gate circuit and the hold circuit is obtained; and the third gate circuit. A control device for an electric screwdriver that is equipped with a cutoff circuit that obtains the output of the electric motor and cuts off the current flowing to the electric motor.