JP2586757B2 - Control circuit for clutch-type electric driver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for a clutch-type electric driver, and more particularly, to a clutch-type electric driver which releases a clutch by receiving a tightening reaction force of a screw and automatically stops a motor. The present invention relates to a driver control circuit.

[0002]

2. Description of the Related Art As is well known, electric drivers in recent years
When the screw tightening is completed, the clutch is disengaged, not only to shut off the rotational force of the motor, but also to cut off the power to the motor,
At the same time, the machine is suddenly stopped by applying dynamic braking.

[0003]

However, in this type of conventional driver as described above, if the operation switch is turned off for a short time immediately after the screw tightening is completed,
The motor does not stop and performs unnecessary continuous tightening.
There was a disadvantage that the screw head and the female screw were damaged.

FIG. 4 (ie, a timing chart showing the state of each element from the time the operation switch is turned on until the screw tightening is completed) is shown in the timing chart of FIG. As shown in FIG. 4), this phenomenon is relatively easy to occur when the operation switch causes chattering due to the reaction at the completion of screw tightening, or when the operation switch is turned off due to erroneous operation of the operation switch unconsciously.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved clutch-type electric screwdriver which eliminates the above-mentioned disadvantages of the prior art, eliminates unnecessary continuous tightening immediately after completion of screw tightening, and does not damage a screw head or a female screw. To provide.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a clutch mechanism for automatically releasing a clutch engagement under a predetermined load when tightening a screw, and to release the clutch engagement when a driver operation switch is turned on. A clutch disengagement detection switch for detecting, a thyristor that receives a signal from the clutch disengagement detection switch, ignites and self-holds the state until the driver operation switch is turned off, and a motor that is energized by the thyristor And a switching circuit for interrupting power supply to the motor and for short-circuiting the motor to apply power generation braking, comprising a backup circuit for supplying a holding current to the thyristor after the driver operation switch is turned off. Achieved by:

[0007]

According to the present invention having the above structure,
The thyristor is extinguished by the discharge current of the capacitor in the backup circuit, even if the operation switch causes chattering due to the reaction at the completion of screw tightening, or even if the operation switch is turned off unintentionally by mistake. Without turning on the power, maintaining the holding current to keep the
The stop of the screw can be reliably stopped, and unnecessary continuous tightening immediately after the completion of the screw tightening can be eliminated.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on one embodiment of FIG. 1 with reference to an explanatory diagram of an internal structure of an electric screwdriver shown in FIG. 2 and an effect explanatory diagram of FIG.

In FIG. 2 showing the internal structure of the electric screwdriver, reference numeral 1 denotes a motor for driving the driver, and 2 denotes a reduction gear using a planetary gear 2a.

The sun gear 2b of the reduction gear 2 is mounted on the output shaft of the motor 1, and the planetary gear 2a is rotatably supported by the fixed clutch 3. The fixed clutch 3 has two rollers 4 projecting therefrom to form a fixed cam.

Reference numeral 5 denotes a driver output shaft. At one end of the driver output shaft 5, a socket 7 holding a driver bit 6 is connected and supported via a pin 8 and a set screw 9. At the other end, a movable clutch 12 comprising a rotating plate 10 and a steel ball 11
Are mounted so as to rotate integrally with the driver output shaft 5 via a key 13.

The steel balls 11 are housed at both ends of the rotating plate 10 so as to be freely protruded and retracted. The pressing force of the screw tightening force adjusting spring 14 causes the sleeves 15 and 17 and the push pin 1 to move.
6, a part of the steel ball 11 protrudes to the opposite surface side of the fixed clutch 3, and this protruding portion is engaged with the outer peripheral surface of the roller 4.

Reference numeral 18 denotes a gear cover.
Accommodates the aforementioned reduction gear 2, fixed clutch 3, movable clutch 12, sleeve 15, push pin 16, and the like.

Reference numeral 20 denotes a clutch disengagement detection switch for detecting that the movable clutch 12 has disengaged from the fixed clutch 3. The clutch disengagement detection switch 20 has a gear cover-1.
8 is held on a part of the outer surface via a pin 19, and is normally pressed via a sleeve 17 by a pressing force of a screw tightening force adjusting spring 14, and a switch contact of a clutch disengagement detection switch 20 is provided. Is open.

Reference numeral 21 denotes an adjuster for adjusting the pressing force of the screw tightening force adjusting spring 14, and reference numeral 22 denotes a top cover for holding the screw tightening force adjusting spring 14.

In FIG. 1, which shows the control circuit of the present invention, 2
Reference numeral 3 denotes a DC power supply, 24 denotes a driver operation switch for starting the motor 1, and 25 denotes a forward / reverse switch for switching the forward / reverse rotation of the motor 1.

Reference numeral 27 denotes a relay constituting the switching circuit 26. The normally closed contacts NC of the relay 27 form a circuit for supplying electricity to the motor 1, and the normally open contacts NO of the relay 27 represent the motor. The short circuit of the data 1 is formed.

Reference numeral 28 denotes a three-terminal thyristor that receives a signal from the clutch disengagement detection switch 20 and energizes the relay 27. A backup circuit 29 composed of a resistor 30, a diode 33, and a capacitor 31 is connected between the anode and the cathode of the thyristor 28.

Next, the operation of this embodiment will be described.

When the driver operation switch 24 is turned on,
Via a resistor 30 and a relay coil 27a of the relay 27,
The capacitor 31 of the backup circuit 29 is charged and the motor 1 is started.

The rotational force of the motor 1 is transmitted to the fixed clutch 3 and the movable clutch 12 via the reduction gear 2,
Further keys 13, driver output shaft 5, socket 7
And transmitted to the driver bit 6 to perform screw tightening.

When the screw tightening progresses and reaches a predetermined tightening force, the roller 4 of the fixed clutch 3 operates by a cam and the steel ball 11
To the sleeve 17 side, the engagement between the fixed clutch 3 and the movable clutch 12 is released, and the transmission of the rotational force of the motor 1 is interrupted.

Further, the steel ball 11 pushes out the sleeve 15 in the axial direction via the sleeve 17 and the push pin 16, and turns on the clutch disengagement detection switch 20.

Further, when the clutch disengagement detection switch 20 is turned on, the gate of the thyristor 28 is urged via the resistor 32, and the relay 27 is driven to cut off the power supply to the motor 1. The motor 1 is short-circuited to apply the power generation braking, and the motor 1 is suddenly stopped.

As shown in the timing chart of FIG. 4, even if the operation switch causes chattering due to the reaction at the completion of the screw tightening, or is erroneously operated to turn off the operation switch. By the discharge current of the capacitor 31 in the backup circuit 29, the thyristor 28 maintains the holding current without extinguishing,
Keep on.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the clutch disengagement detection switch 20 is connected to the capacitor 31 of the backup circuit 29. Even if the clutch 3 and the movable clutch 12 are stopped in the disengaged state, when the driver operation switch 24 is turned on next time, the voltage of the capacitor 31 is low (the voltage is reduced by the relay coil 27a, the resistor 30 and the capacitor). Since the gate of the thyristor 28 is not energized until the capacitor 31 is charged, the motor 1 starts rotating immediately to connect the fixed clutch 3 and the movable clutch 12 with each other. The motor 1 is quickly returned to the engaged state, and the startability of the motor 1 can be improved.

[0027]

As described above, according to the present invention, even if the operation switch causes chattering due to the recoil at the time of completion of screw tightening, or the operation switch is unintentionally erroneously turned off, the backup circuit is provided. The thyristor does not extinguish due to the discharge current of the capacitor in the part, maintains the holding current and keeps the ON state, without stopping the motor, and eliminates unnecessary continuous tightening immediately after completion of screw tightening. In addition, it is possible to eliminate the problem that the screw head and the female screw are damaged.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing one embodiment of a control circuit of the present invention.

FIG. 2 is a longitudinal sectional view showing an internal structure of the electric screwdriver.

FIG. 3 is a connection diagram showing another embodiment of the control circuit of the present invention.

FIG. 4 is a timing chart showing the state of each element until the screw tightening is completed after the operation switch of the electric screwdriver employing the present invention is turned on.

FIG. 5 is a timing chart showing the state of each element until the screw tightening is completed after the operation switch of the conventional electric screwdriver is turned on.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Driver motor, 20 ... Clutch disengagement detection switch, 23 ... DC power supply, 24 ... Driver operation switch, 25 ... Motor forward / reverse changeover switch, 26 ... Switching circuit, 27 ... Relay, 27a ... Relay -Coils, 28 ...
3 terminal thyristor, 29 backup circuit, 30 resistor, 31 capacitor, 32 resistor, 33 diode
, NC: Relay normally closed contact, NO: Relay normally open contact.

Claims (2)

(57) [Claims] A clutch mechanism for automatically releasing a clutch engagement by receiving a predetermined load during screw tightening; a clutch disengagement detection switch for detecting release of the clutch engagement when a driver operation switch is on; A thyristor that fires upon receiving a signal from the clutch disengagement detection switch and self-holds its state until the driver operation switch is turned off, and energized by the thyristor to cut off power to the motor; and A clutch-type electric driver having a switching circuit for short-circuiting a motor to apply dynamic braking, comprising a backup circuit for supplying a holding current to a thyristor after the driver operation switch is turned off. Driver control circuit. 2. A control circuit for a clutch-type electric driver according to claim 1, further comprising a circuit system for supplying electric power from a backup circuit to a clutch disengagement detection switch.