JPH0516963B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an electric motor that drives an awl built into an electric drill (hereinafter referred to as an awl motor), and a feed motor that moves the electric drill up and down along a drill stand. The present invention relates to a drilling machine having a circuit for controlling the same.

[Background of the invention]

Conventionally, when an electric drill mounted on a drill stand is lowered by a feed motor to automatically drill a hole in a workpiece, the drill motor may break during drilling or the drill motor control circuit may malfunction. If the power supply is interrupted, the drill bit may be damaged, the mechanism for lowering the electric drill, or the drilling machine itself may be destroyed.

[Purpose of the invention]

The aim of the invention is to eliminate the drawbacks of the prior art mentioned above.

[Summary of the invention]

The present invention constantly detects the current flowing through the drill bit motor while the electric drill is descending, and stops feeding the electric drill when the current becomes zero. This was done to eliminate the influence.

[Embodiments of the invention]

FIG. 1 is an overview diagram showing one embodiment of the present invention, and FIG.
The figure is a circuit diagram showing one embodiment of the present invention. In the figure, 1 is a drill stand, 2 is a drill motor that rotates a drill bit 9, 3 is an electric drill with built-in drill motor 2, and 4 is an electric feed motor consisting of a field winding 4' and an armature winding 4''. The drill 3 is raised and lowered along the drill stand 1. 5 is a control box containing a circuit for controlling the drill motor 2 and the feed motor 4, and 6 is an electromagnetic base containing a built-in electromagnetic coil 13. When the electromagnetic coil 13 is excited, It sticks to the object to be drilled. 7 is a switching knob that turns on the power switch 10 in one step operation and turns on the automatic switch 11 in two step operation;
8 is a rotation speed setting knob for setting the rotation speed of the drill motor 2 and the feed motor 4, and a single-shaft dual variable resistor 1.
62 and 172 are attached, and the rotational speed of the drill motor 2 and feed motor 4 (lowering speed of the electric drill 3) corresponding to the drill diameter is set. 12
1 is a rectifier bridge, 14 and 15 are semiconductor control elements that control the voltage supplied to the cone motor 2 and the feed motor 4, 16 is a speed control circuit that controls the rotation speed of the cone motor 2, a time delay resistor 161, and a time delay resistor 161; This is a phase control circuit consisting of a delay variable resistor 162, a delay capacitor 163, and a diagonal 164. Reference numeral 17 denotes a speed control circuit for controlling the rotational speed of the feed motor 4, which is a phase control circuit consisting of a time delay resistor 171, a time delay variable resistor 172, a time delay capacitor 173, and a diagonal 174. Speed control circuit 16, 17
A constant speed control circuit that performs constant speed control by feeding back rotation signals from the motors 2 and 4 has a similar function. The variable resistor 162 sets the rotation speed of the cone motor 2, and the variable resistor 172 sets the rotation speed of the feed motor 4.
Set the rotation speed.

Reference numerals 18 and 19 are operation control circuits that control the operations of the speed control circuits 16 and 17, and 20 is a current detector that detects the current flowing through the conical motor 2, which is comprised of a current transformer and the like. 21 is a signal conversion circuit that converts the current flowing through the conical motor 2 into a DC signal according to the magnitude of the resistor 2.
11, 214, 215, capacitor 212, 21
6. Consists of a rectifying bridge 213. 22 is an A/D converter that converts an analog signal into a digital signal; 23 is an A/D converter that converts an analog signal into a digital signal; When the current becomes zero, the electric drill 3 stops descending and then rises to the position before drilling, and when the automatic switch 11 is turned on, the electric drill 3 is turned off from the signal conversion circuit 21 to avoid the starting current of the drill motor 2. A motor operation control system that stores the no-load current value of the CPU, determines whether drilling is in progress or completed based on the no-load current value, and outputs a signal to control the operation of the drill motor 2 and the feed motor 4. It consists of a single-chip microcomputer unit with built-in ROM, RAM, and external input/output I/O ports. 24 is a driver IC that receives a signal from the motor operation control system 23 and drives an external element; 25 is a switch for switching relay contacts 25' and 25'' that rotates the feed motor 4 in forward and reverse directions (lowers and raises the electric drill 3); 26 is a relay coil that switches relay contacts 26' and 26'' for rotating and braking the feed motor 4; 27 is an upper limit switch that determines the lifting stop position of the electric drill 3 mounted on the drill stand 1; 28 is a semiconductor; This circuit is a motor full speed control circuit that maximizes the conduction angle of the control element 15, applies the maximum voltage to the feed motor 4, and rotates the feed motor 4 at full speed, and includes resistors 281, 283 and a photorelay 282. 29 is a brake resistor for the feed motor 4, 30 is a motor operation control system 23, A/D
This power supply circuit serves as a power source for the converter 22 and the like, and includes a transformer 301, a rectifier bridge 302, a smoothing capacitor 303, and a three-terminal constant voltage IC 304. 31
is an abnormality warning device that warns of an abnormality when the current of the drill motor becomes zero, and consists of a buzzer, LED, etc.

The operation will be explained based on the cone motor current characteristic diagram for drilling shown in FIG. 3 and the operation flowchart of the motor operation control system shown in FIG. 4. After fixing the drill bit 9 to be used on the electric drill 3 and turning the rotation speed setting knob 8 to a position corresponding to the drill diameter, turn the switching knob 7.
When the power switch 10 is turned on, the electromagnetic coil 13 is excited and the electromagnetic base 6 is attracted to the object to be drilled.
Furthermore, turn the switching base 7 to switch the automatic switch 11.
When input, the motor operation control system 23 outputs an operation signal to the operation control circuit 18 through the driver IC 24, operates the speed control circuit 16, and rotates the drill bit motor 2 at a rotation speed corresponding to the diameter of the drill bit used.
At the same time, the motor operation control system 23 monitors the current flowing through the cone motor 2 from the current detector 20 through the signal conversion circuit 21 and the A/D converter 22,
When it is detected that the current is not a starting current (there is no change in current), the current value from the A/D converter 22 (no-load current value) is stored. In the above method, as a method of not inputting the starting current value, there is also a method of not detecting the current while the starting current is flowing.
Next, the motor operation control system 23 energizes the relay coil 26 through the driver IC 24,
The relay contacts 26' and 26'' are switched to the normal contact side, an operation signal is output to the operation control circuit 19, the speed control circuit 17 is operated, and the electric drill 3 is lowered at a lowering speed corresponding to the drill diameter used. The feed motor 4 is rotated. When the electric drill 3 descends and drills the object to be drilled, the drill motor current increases. When the drilling is finished, the drill motor current returns to the original no-load current. Motor operation control system 23 determines the drilling state based on the memorized no-load current value, and when it detects the completion of drilling, stops outputting the operation signal to the operation control circuit 18 through the driver IC 24, and at the same time de-energizes the relay coil 26. Then, the relay contacts 26' and 26'' are switched to the normally closed contact side, the feed motor 4 is braked and stopped, and the operation of the speed control circuit 16 is stopped. Next, the relay coil 25 is energized, the relay contacts 25', 25'' are switched to the normally open contact side, the feed motor 4 is set to the reverse mode, and the relay coil 26 is energized again, so that the contacts 26', 26'' are turned on. is switched to the normally open contact side, the motor full speed control circuit 28 is operated, and the electric drill 3 is raised to full speed. When the electric drill 3 rises and the upper limit switch 27 operates, the relay coil 26 is deenergized, the relay contacts 26' and 26'' are switched to the normally closed contact side, the feed motor 4 is braked, and the electric drill 3 is stopped. stops rising and the drilling operation is completed.The above is the case of normal operation.

On the other hand, in the case of an abnormality, that is, while the electric drill 3 is being lowered by the feed motor 4, the current of the drill bit motor 2 becomes zero due to a disconnection of the drill bit motor 2 or a failure of the drill motor control unit. If the control system 23 detects, the abnormality warning device 31
issues an abnormality warning, stops outputting the operation signal to the operation control circuit 18 through the driver IC 24, simultaneously deenergizes the relay coil 26, and closes the relay contacts 26',
26'' to the normally closed contact side, brakes the feed motor 4 to stop it, and stops the operation of the speed control circuit 16. Next, the relay coil 25 is energized and the relay contacts 25' and 25'' are normally open. Switching to the contact side, the feed motor 4 is placed in reverse mode, the motor full speed control circuit 28 is operated, and the electric drill 3 is raised to full speed. When the electric drill 3 rises and the upper limit switch 27 operates, the relay coil 2
6 is deenergized, the relay contacts 26' and 26'' are switched to the normally closed contact side, the feed motor 4 is braked and stopped, and the electric drill 3 is stopped from rising.

〔Effect of the invention〕

According to the present invention, during automatic drilling, when the current becomes zero due to an abnormality in the drill motor or the drill motor control circuit, drilling is stopped, thereby preventing damage to the drill, the mechanism for lowering the electric drill, or the drilling machine itself. can be prevented from occurring.

[Brief explanation of drawings]

FIG. 1 is an overview diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a circuit diagram showing an embodiment of the present invention, FIG. 3 is a current characteristic diagram of a conical motor during drilling, and FIG. 4 is an operation flowchart of the motor operation control system of the present invention. In the figure, 1 is a drill stand, 2 is a drill motor, 3 is an electric drill, 4 is a feed motor, 20 is a current detector, 21 is a signal conversion circuit, 23 is a motor operation control system, and 31 is an abnormality warning device.

Claims (1)

[Scope of Claims] 1. A drill motor that rotates a drill bit, an electric drill incorporating the drill motor, a feed motor that lowers the electric drill along a drill stand to drill a hole in a workpiece, and the drill motor. and a current detector that detects the current flowing through the drill, and stores the no-load current value detected by the current detector at the start of operation when only the drill motor is rotated, and rotates the feed motor to lower the electric drill. When the detected current value of the drill motor detected by the current detector during drilling operation becomes equal to the memorized no-load current value, drilling is completed and the feed motor is reversed to raise the electric drill. 1. A drilling machine, characterized in that when the detected current value becomes zero during the drilling operation, a feed motor is stopped to stop the electric drill from descending.