JPH10109277A - Method and device for fastening screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a shock caused when the screw is fastened as much as possible and to finely adjust a fastening force by forcibly rotating an inertia body directly connected to the output shaft of a motor and having predetermined mass and by stopping a current to the motor when its rotational speed reaches a predetermined value to fasten a screw by means of the moment of inertia of the inertia body. SOLUTION: At the same time when an output shaft 100A of a motor 100 starts to rotate, a flywheel 1 fixed to the output shaft 100A rotates and, when a control 6 judges that an angular acceleration reaches the predetermined maximum set value ω1, a current supplied to the motor 100 is stopped to light a display 7. Next, when a bit 8 is fitted and pressed in the head of a screw, the controller 6 makes an electromagnetic clutch 2 in a connected state to transmit the moment of inertial of the flywheel 1 to the bit 8 and to fasten the screw and, when it judges that the screw fastening is finished, it makes the electromagnetic clutch 2 in a disconnected state, which can reduce a shock to a hand and realize a calm safe screw fastening operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw tightening method and a screw tightening device in which a bit is rotated by a driving force of a motor and a screw is tightened by the rotating force of the bit.

[0002]

2. Description of the Related Art Various screw tightening devices such as an electric screwdriver, an impact wrench, and an oil pulse driver have been developed.

For example, as shown in FIG. 6, in an electric screwdriver, after a screw is attached to a bit 103 to be described later, a switch is turned on by pushing the main body toward a screw to be tightened, and the motor 100 rotates. The rotational force of the motor 100 is
It is known to transmit to bit 103 via bit 02. Thus, the screw provided at the tip of the bit 103 is tightened.

[0004] When the seated screw is completely tightened, a reaction force acts on the bit 103 side, so that the clutch 102 is disengaged by the action of the reaction force, and the motor 100
Is prevented from being transmitted to the bit 103. Further, when the pushing operation of the main body is stopped in accordance with the completion of the screw tightening operation, a predetermined detection signal is output from the screw tightening detecting unit 104 which has detected that the screw tightening operation has been completed, and the control unit 105 Control automatically stops the operation of motor 100

[0005]

However, in such a screw tightening device, a reaction force acting from the screw side at the time of screw tightening exerts a constant impact force on a hand or arm gripped by an operator. Therefore, especially when many screws are tightened, the load on the arm or the like may be increased.

Further, in such a screw tightening device, when the material for tightening the screw is different, the tightening force is also slightly changed. However, usually, a fine adjustment of the tightening force (torque) according to this is required. Very little is done.

In view of the above circumstances, the present invention can minimize the shock at the time of tightening, and can finely adjust the tightening force (torque), and furthermore, a relatively large tightening. It is an object of the present invention to provide a screw tightening method and a screw tightening device capable of generating a torque.

[0008]

That is, according to the first aspect of the present invention, a bit is rotated by a driving force of a motor,
In a screw tightening device for tightening a screw by the rotation force of the bit, an inertia body having a predetermined mass directly connected to an output shaft of the motor is provided, and the inertia body is forcibly rotated by the rotation force of the motor, and After the power supply to the motor is stopped when the body reaches a predetermined number of revolutions, the screw is tightened by the inertia moment of the inertia body.

According to a second aspect of the present invention, when a stop signal is input, display means for externally displaying that the inertial body has reached an effective rotational speed is provided, and after confirming the display by the display means, a bit is displayed. The screw is set on the screw and the screw is tightened.

According to a third aspect of the present invention, there is provided an inertial body having a specific mass and diameter, which is rotated by a rotational force of a motor, and an electromagnetic clutch for transmitting the rotational inertial force of the inertial body to a bit side. Rotation speed detecting means for detecting that the inertial body has reached a predetermined effective rotation speed and having decreased to a certain re-driving rotation speed and outputting a stop signal and a restart signal, respectively; and inputting the stop signal. By stopping the operation of the motor and connecting the electromagnetic clutch to transmit the rotational inertia force of the inertial body to the bit, and after the screw tightening is completed, the electromagnetic clutch is shut off and the rotational inertia force from the inertial body to the bit is transmitted. And a control section for restarting the motor by inputting the restart signal.

Further, according to the present invention, the operation of the motor is stopped by the operation of pushing the casing of the apparatus body toward the front end, and the electromagnetic clutch is actuated to connect the inertial body and the bit, thereby pushing the casing. A bit switch is provided to perform the control operation of the control unit for stopping the operation of the electromagnetic clutch by releasing the operation and disconnecting the connection between the inertial body and the bit.

Further, the invention according to claim 5 is provided with a display means for externally displaying that the inertial body has reached the effective rotation speed when a stop signal is inputted.

[0013]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a screw tightening device according to the present invention. This electric driver comprises a motor 100, a flywheel 1, which is an inertial body, a clutch 2, a gear train 3, a rotational speed detecting unit. 4, a screw tightening detection unit 5, a control unit 6, and a display unit 7. In FIG. 1, reference numeral 8 indicates a bit.
A start switch (not shown) is provided to start the motor.

The flywheel 1 is adapted to be rotated by a driving force of a motor 100 via an output shaft 100A. In this embodiment, the flywheel 1 has an appropriate mass w, for example, a diameter D, a thickness L, and a density L. Is used, and when rotating at a predetermined angular velocity ω, the inertia energy E E = (1/2) I · ω ² (where I is the moment of inertia) It has occurred.

In this case, the screw tightening torque T is determined by the following equation: T = I · (dω / dt) (where dω / dt is the angular acceleration), so that the angular velocity ω is appropriately changed. As a result, the screw tightening torque as well as the inertia energy can be freely changed and adjusted.

Furthermore, since the moment of inertia I of the flywheel 1 is proportional to the fourth power of the diameter D (effective), a large moment of inertia I can be obtained even if the diameter is not so large.

The electromagnetic clutch 2 connects the drive shaft 1A fixed to the flywheel 1 rotating integrally with the motor 100 to the rotation shaft 3A provided on the gear train 3, and reduces the rotational inertia force of the flywheel 1 to the bit 8 To the side,
The connection and disconnection are performed by the control unit 6. That is, in the electromagnetic clutch 2 of this embodiment, when the motor 100 reaches a predetermined maximum set angular acceleration (effective rotation speed) ω1, the power supply to the motor 100 is stopped, and then the control unit 6 (or an appropriate micro The electromagnetic clutch 2 is brought into a connected state (by an ON operation of a switch, etc.), and a stop signal from a screw tightening detecting unit 5 that detects a reaction force from the screw side when the screw tightening operation is completed is controlled by the control unit 6 so that the electromagnetic The clutch 2 is configured to be in a disconnected state. Therefore, the electromagnetic clutch 2 is connected to the output of the control unit 6.

The rotation speed detector 4 detects that the flywheel 1 has reached a predetermined maximum set angular acceleration ω1 and has decreased to a predetermined minimum set angular speed (redrive rotation speed) ω2, and outputs a stop signal and a stop signal, respectively. It outputs a restart signal, and detects the rotation speed of the output shaft 100A of the motor 100. The output is connected to the input of the control unit 6.

The screw tightening detector 5 detects a reaction force transmitted from the tightened member side to the bit 103 side via the screw when the screw is finally tightened to a predetermined state. An appropriate sensor (for example, a torque sensor) is used, and an output is connected to an input of the control unit 6 so that a detection signal (stop signal) output at this time is input to the control unit 6.

The control unit 6 stops the operation of the motor by inputting a stop signal and connects the electromagnetic clutch 2 to transmit the rotational inertia of the flywheel 1 to the bit 8. Between the relay switch 100B and the electromagnetic clutch 2 between the first and second relay switches.
Is output. In addition, the control unit 6 outputs the third control signal to the electromagnetic clutch 2 in order to cut off the electromagnetic clutch 2 after the screw tightening is completed and cut off the transmission of the rotational inertia force from the flywheel 1 to the bit 8. It has become. Furthermore, this control unit 6
In order to restart the motor by inputting a restart signal from the rotation speed detection unit 4, a fourth control signal is output to the relay switch 100B.

When the control unit 6 receives a stop signal, the display unit 7 illuminates to the outside that the flywheel 1 has reached the maximum set angular acceleration ω1 by the fifth control signal output from the control unit 6. Yes, an appropriate lamp (a buzzer or the like may be used) or the like is used. Thus, the screw tightening operation can be performed after confirming that the optimum torque has been generated.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG.

First, for example, the power switch is turned on to start up the motor 100 of the electric tool (first step S
1).

Thus, the output shaft 10 of the motor 100
0A starts rotating, and the flywheel 1 to which the output shaft 100A is fixed starts rotating (second step S2).

Next, the control unit 6 determines whether or not the flywheel 1 has reached a predetermined maximum set angular acceleration ω1 based on a signal from the rotation speed detection unit 4 (third step S).
3). Here, if the maximum set angular acceleration ω1 has not been reached, the process returns to the second step S2.

When the control unit 6 determines that the flywheel 1 has reached the maximum set angular acceleration ω1, the motor 1
00 and the lamp of the display unit 7 is turned on (fourth step S4).

Next, when the bit is fitted on the head of the screw and pushed in, the electromagnetic clutch 2 is connected by the control unit 6, and the moment of inertia of the flywheel 1 is transmitted to the bit 8. Thus, torque can be transmitted from the bit 8 to the screw to tighten the screw (fifth step S5).

It is determined whether or not the screw tightening operation has been completed.
The control unit 6 determines based on a signal from the screw tightening detection unit 5 (sixth step S6).

When it is determined that the screw tightening operation has been completed, the control unit 6 controls the electromagnetic clutch 2.
Is turned off (seventh step S7).

Next, the control unit 6 determines whether or not all the screw tightening operations have been finally completed (eighth step S8). Then, when it is determined that the screw tightening operation is finally completed (for example, the screw tightening operation is not started for a certain time or longer), the motor 100 is not restarted (ninth step S9). If it is determined that the screw tightening operation has not been finally completed, the motor 100 is restarted and the process returns to the third step S3.

Next, another screw fastening device according to the present invention will be described with reference to FIGS. Note that the same members as those in the previous embodiment are denoted by the same reference numerals, and redundant description will be avoided.

In the screw tightening device of this embodiment shown in FIGS. 3 and 4, a microswitch 60 for performing a part of the control of the control unit 6 of the first embodiment is used.

When the housing 80 of the device body is pushed into the tip end of the bit 8,
It is configured to operate in contact with an operation plate 8B provided on a part of the rotation shaft 8A against the elastic force of the spring 8C, and is fixed to the back surface of the housing 80.

The micro switch 60 is the same as that shown in FIG.
As shown in FIG. 5, the power supply 9 is normally closed so as to supply power to the motor 100, and the circuit between the power supply 9 and the motor 100 is closed. During the contact operation with the operation plate 8B, the electromagnetic clutch 2 and the power supply 9 are closed. Is closed, the power supply to the motor 100 is stopped, and the electromagnetic clutch 2 is brought into the connected state.
The moment of inertia of the flywheel 1 is transmitted to the bit 8 to rotate.

The control section 6 'of this embodiment is configured to only output a control signal for closing the relay switch 100B for supplying power to the restart signal motor 100 from the rotation speed detecting section 4. . In this embodiment, the screw tightening detecting section and the display section provided in the previous embodiment are additionally provided, but are omitted in FIG. 5 for convenience of explanation.

According to this embodiment, the flywheel 1 can effectively absorb the recoil at the time of completion of the tightening in the housing 80 of the apparatus main body held by hand, so that the shock applied to the hand can be minimized. Can be suppressed.

Further, according to this embodiment, since the moment of inertia I of the flywheel 1 is proportional (effective) to the fourth power of the diameter D, a large moment of inertia can be obtained without increasing the diameter of the flywheel 1. Can be demonstrated,
Accordingly, the outer diameter of the tool body can be minimized, and a small grip portion or the like can be easily gripped.

[0039]

As described above, according to the present invention, an inertia body having a predetermined mass directly connected to an output shaft of a motor is provided, and this inertia body is forcibly rotated by the rotation force of the motor.
After the power supply to the motor is stopped when the inertial body reaches a predetermined number of revolutions, the screw is tightened by the inertia moment of the inertial body, so the motor moves to the inertial body with the motor before tightening the screw. (Rotational) energy is stored, power supply to the motor is cut off before tightening the screw, and then the energy of the inertial body (which can also add inertial energy on the rotor side of the motor) is used. As a result of the screw tightening, not only the power saving effect is brought about but also a quiet and safe screw tightening operation with less shock to the hand can be realized.

Further, according to the present invention, the angular velocity of the inertial body can be freely controlled by adjusting the power supply time to the motor, and the torque at the time of screw tightening can be freely and accurately adjusted. The torque can be finely adjusted according to the type and size of the material and the material and hardness of the object to be tightened, so that a high-quality screw tightening operation can be realized.

Further, according to the present invention, since the moment of inertia of the inertial body is proportional to the fourth power of its diameter, a relatively large tightening torque can be realized even with a handy type whose outside diameter is not so large. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a screw fastening device according to the present invention.

FIG. 2 is a flowchart showing a screw tightening method according to the present invention.

FIG. 3 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 4 is an enlarged view of a main part of another screw fastening device shown in FIG. 3;

FIG. 5 is a schematic block diagram of another screw fastening device shown in FIG. 3;

FIG. 6 is a schematic block diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 1 flywheel 2 electromagnetic clutch 4 rotation speed detection unit 6, 6 'control unit 60 limit switch 7 display unit 8 bit

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yukio Sano 1-19-9 Tsutsumide, Sumida-ku, Tokyo Nippon Electric Seiki Co., Ltd.

Claims (5)

[Claims] 1. A screw tightening device for rotating a bit by a driving force of a motor and tightening a screw by the rotating force of the bit, comprising: an inertia body having a predetermined mass directly connected to an output shaft of the motor; Is forcibly rotated by the rotational force of the motor, after the power supply to the motor is stopped when the inertial body reaches a predetermined number of revolutions, the screw is tightened by the inertia moment of the inertial body. Screw tightening method. 2. When a stop signal is input, display means is provided for externally displaying that the inertial body has reached an effective rotational speed. After confirming the display by the display means, a screw is set on a bit and the screw is tightened. The method according to claim 1, wherein: 3. An inertial body having a specific mass and diameter and rotated by the rotational force of a motor, an electromagnetic clutch for transmitting the rotational inertial force of the inertial body to a bit side, and the inertial body having a predetermined effective rotation. A rotation speed detecting means for detecting that the speed has been reached and having decreased to a certain re-driving rotation speed and outputting a stop signal and a restart signal, respectively, and stopping the operation of the motor by inputting the stop signal The electromagnetic clutch is connected to transmit the rotational inertial force of the inertial body to the bit, and after the screw tightening is completed, the electromagnetic clutch is shut off to interrupt the transmission of the rotational inertial force from the inertial body to the bit, and the restart signal is input. And a control unit for restarting the motor by performing the operation. 4. The operation of the motor is stopped by the operation of pushing the casing of the apparatus body toward the distal end, and the electromagnetic clutch is operated to connect the inertial body and the bit, and the operation of the electromagnetic clutch is stopped by releasing the pushing operation of the casing. 4. The screw tightening device according to claim 3, further comprising a bit switch that performs a control operation of a control unit that disconnects the connection between the inertial body and the bit. 5. The screw tightening device according to claim 3, further comprising a display unit that externally displays that the inertial body has reached an effective rotation speed when a stop signal is input.