Automatic screw tightening control method and device

An automatic screw tightening control device comprising:

• an electric driver comprising an electric motor, a drive switch configured to drive the electric motor, a driver bit coupled to a drive output shaft of the electric motor via a reduction gear mechanism and a clutch mechanism, a switch operating member for operating the drive switch, a clutch operation detection sensor configured to detect a clutch operation of the clutch mechanism, an electric motor control circuit configured to execute and stop control of the electric motor, and rotation amount detecting means for detecting a rotation amount of the electric motor;
• a control portion comprising:
• screw tightening time setting means for setting a screw-tightening start time for performing a first screw tightening operation responsive to an operation signal of an operation switch or of an encoder generated based on contact of the driver bit with a predetermined screw mounting target;
• clutch operation time setting means for setting a clutch operation time of the clutch mechanism detected by the clutch operation detection sensor as a clutch operation time of completion of screw tightening;
• target rotation amount setting means for, during performance of the first screw tightening operation, setting a detected and recorded rotation amount as a target rotation amount, wherein a rotation amount of the electric motor from the screw-tightening start time until the clutch operation time of completion of screw tightening is detected and recorded by the rotation amount detecting means, and wherein the target rotation amount includes a range of permissible rotation amounts;
• and
• determining means for, in a subsequent predetermined screw tightening operation, comparing a second rotation amount detected with the target rotation amount to determine acceptability of a screw tightened state,
• wherein in the subsequent predetermined screw tightening operation, the screw tightening time setting means sets a second screw-tightening start time for performing the subsequent predetermined screw tightening operation responsive to a second operation signal of the operation switch or of the encoder,
• wherein the second rotation amount corresponds to rotation of the electric motor from the second screw-tightening start time until a second clutch operation time of completion of screw tightening and is detected and recorded by the rotation amount detecting means, and
• wherein in further subsequent predetermined screw tightening operations, the determining means compares detected rotation amounts to the target rotation amount to determine acceptability of screw tightened states.

An automatic tightening control method comprising:

• at an electric driver comprising an electric motor, a driver bit coupled to a drive output shaft of the electric motor via a clutch mechanism, a clutch operation detection sensor for detecting operation of the clutch mechanism, an electric motor control circuit for executing driving and stop control of the electric motor, and rotation amount detecting means for detecting a rotation amount of the electric motor, performing:
• initiating a first tightening operation, the first tightening operation including:
• detecting a tightening start time for performing the first tightening operation based on an operation signal of an operation switch or an encoder;
• detecting, by the clutch operation detection sensor, a clutch operation end time of the clutch mechanism for completing the first tightening operation;
• and
• detecting, by the rotation amount detecting means, the rotation amount of the electric motor from the tightening start time until the clutch operation end time;
• setting the detected rotation amount, at the clutch operation end time, as a target rotation amount;
• and
• initiating a second tightening operation subsequent the first tightening operation, wherein the second tightening operation includes:
• detecting a second tightening start time for performing the second tightening operation based on a second operation signal of the operation switch or of the encoder,
• detecting, by the rotation amount detecting means, a second rotation amount of the electric motor, and
• comparing the second rotation amount with the target rotation amount to determine a tightened state.

An automatic tightening control device comprising:

• an electric driver comprising:
• an electric motor comprising a drive output shaft;
• a clutch mechanism;
• a driver bit coupled to the drive output shaft via the clutch mechanism;
• a clutch operation detection sensor configured to detect operation of the clutch mechanism;
• an electric motor control circuit configured to execute drive and stop control of the electric motor;
• and
• rotation amount detecting means for detecting and recording a rotation amount of the electric motor from a tightening start time until a clutch operation time;
• a controller configured to:
• detect a tightening start time for performing a first tightening operation based on an operation signal of an operation switch or of an encoder;
• detect a clutch operation time of completion of the first tightening operation based on a clutch operation of the clutch mechanism detected by the clutch operation detection sensor;
• set a first detected rotation amount, detected and recorded by the rotation amount detecting means during the first tightening operation, as a target rotation amount;
• detect a second tightening start time for performing a second tightening operation based on a second operation signal of the operation switch or of the encoder;
• and
• for the second tightening operation that is subsequent to the first tightening operation, compare a second rotation amount, determined by the rotation amount detecting means during the subsequent tightening operation, to the target rotation amount to determine a tightened state.