Method of controlling stopping operation of a sewing machine and system thereof

In a sewing machine which includes a motor, a main shaft driven to be rotated by the motor, a needle operatively coupled to the main shaft, a decelerating unit for decelerating the motor so as to decrease a rotational speed of the main shaft at a fixed rate, a speed detecting unit for detecting a rotational speed of the main shaft which represents a shifting speed of phase of the rotating main shaft, a position detecting unit for detecting a position of the needle which represents a shifting amount of phase of the rotating main shaft, and a control unit for receiving a stop command and controlling the decelerating unit to perform a stopping operation of the motor in response to the stop command, a method of stopping the motor of the sewing machine comprising the steps of:

• controlling the speed detecting unit to detect an initial rotational speed of the main shaft at a time when the control unit receives the stop command and judging whether or not the initial rotational speed of the main shaft is higher than a predetermined middle rotational speed;
• controlling the decelerating unit to decelerate the motor so that the rotational speed of the main shaft may be decreased from the initial rotational speed toward the middle rotational speed, in the case where the initial rotational speed is judged to be higher than the middle rotational speed;
• interrupting the deceleration operation of the decelerating unit at a first interruption time when the rotational speed of the main shaft reaches the middle rotational speed so as to allow the motor to continue rotating the main shaft at the middle rotational speed until a first deceleration time when a needle operatively coupled to the main shaft first reaches a predetermined first position after the first interruption time;
• controlling the decelerating unit to resume the deceleration operation, at the first deceleration time when the needle first reaches the predetermined first position while the main shaft is rotating at a rotational speed equal to the middle rotational speed, so that the rotational speed of the main shaft may be decreased from the middle rotational speed via a stop permission rotational speed which is lower than the middle rotational speed toward a low rotational speed whig is lower than the stop permission rotational speed, the middle rotational speed and the first position of the needle being determined dependently on the fixed rate of the decelerating unit to allow a phase amount of the rotating main shaft to be attained between the first deceleration time when the main shaft is rotating at the middle rotational speed and the needle is in the first position and a second deceleration time when the needle first reaches a predetermined second position after when the rotational speed of the main shaft reaches the stop permission rotational speed to have such a value as prevents the needle from reaching the second position while the rotational speed decreases from the stop permission rotational speed toward the low rotational speed;
• judging whether or not the rotational speed of the main shaft reaches the stop permission rotational speed;
• interrupting the deceleration operation of the decelerating unit at the second interruption time when the rotational speed of the main shaft reaches the low rotational speed so as to allow the motor to continue rotating the main shaft at the low rotational speed;
• and
• controlling the decelerating unit to resume the deceleration of the motor at the second deceleration time when the needle first reaches the second position after the rotational speed is judged to reach the stop permission rotational speed, to thereby completely stop the motor at the second deceleration time when the needle is in the second position and the main shaft is rotating at the low rotational speed.

A system for controlling the stopping operation of a sewing machine, comprising:

• a speed detecting unit for detecting a rotational speed of a main shaft of the sewing machine which is driven to be rotated by a motor of the sewing machine;
• a position detecting unit for detecting a position of a needle of the sewing machine which is operatively coupled to the main shaft;
• a command producing unit for producing a decelerating command for decelerating the motor;
• a decelerating unit for receiving the decelerating command and decelerating the motor in response thereto;
• first deceleration disabling means for disabling the deceleration operation of said decelerating unit irrespective of the decelerating command, at a first disable time when the rotational speed becomes equal to a predetermined middle rotational speed, after said decelerating unit receives the decelerating command, to thereby allow the motor to continue rotating the main shaft at the middle rotational speed from the first disable time until a first deceleration time when the position detecting unit detects that the needle first reaches a predetermined first position after the first disable time;
• first deceleration resuming means for resuming the deceleration operation of said decelerating unit in accordance with the decelerating command, at the first deceleration time, to thereby decrease the main shaft rotational speed from the middle rotational speed via a stop permission rotational speed which is lower than the middle rotational speed toward a low rotational speed which is lower than the stop permission rotational speed, the middle rotational speed and the first position of the needle being determined to allow said decelerating unit to decelerate the motor in such a manner as to prevent the needle from reaching a predetermined second position while the rotational speed decreases from the stop permission rotational speed toward the low rotational speed;
• second deceleration disabling means for disabling the deceleration operation of said decelerating unit irrespective of the decelerating command, at a second disable time when the rotational speed reaches the low rotational speed, to thereby allow the motor to continue rotating the main shaft at the low rotational speed from the second disable time until a second deceleration time when the position detecting unit detects that the needle first reaches a predetermined second position after the speed detecting unit detects that the rotational speed reaches the stop permission rotational speed;
• and
• second deceleration resuming means for resuming the deceleration operation of said decelerating unit in accordance with the decelerating command, at the second deceleration time, to thereby completely stop the motor, at the second deceleration time when said position detecting unit detects that the needle first reaches the second needle position while the main shaft is rotating at the low rotational speed.

In a sewing machine which includes a motor, a main shaft driven to be rotated by the motor, a needle operatively coupled to the main shaft, a decelerating unit for decelerating the motor so as to decrease a rotational speed of the main shaft at a fixed rate, a speed detecting unit for detecting a rotational speed of the main shaft which represents a shifting speed of phase of the rotational main shaft, and a position detecting unit for detecting a position of the needle which represents a shifting amount of phase of the rotating main shaft, a method of stopping the motor of the sewing machine which is rotating the main shaft at an initial rotational speed comprising the steps of:

• decelerating the motor so that the rotational speed of the main shaft may be decreased from the initial rotational speed toward a predetermined middle rotational speed, in the case where the initial rotational speed is higher than the middle rotational speed;
• interrupting the deceleration operation of the decelerating unit at a first interruption time when the rotational speed of the main shaft reaches the middle rotational speed so as to allow the motor to continue rotating the main shaft at the middle rotational speed until a first deceleration time when the needle first reaches a predetermined first position after the first interruption time;
• resuming the deceleration operation at the first deceleration time so that the rotational speed of the main shaft may be decreased from the middle rotational speed toward a low rotational speed which is lower than the middle rotational speed, the middle rotational speed and the first position of the needle being determined dependently on the fixed rate of the decelerating unit, with which the decelerating unit decreases the rotational speed, to allow a phase amount of the rotating main shaft to be attained between the first deceleration time and a second deceleration time when the needle first reaches a predetermined second position after the first deceleration time to have such a value as prevents the needle from reaching the second position until the rotational speed reaches the low rotational speed;
• interrupting the deceleration operation of the decelerating unit at the second interruption time when the rotational speed of the main shaft reaches the low rotational speed so as to allow the motor to continue rotating the main shaft at the low rotational speed;
• and
• resuming the deceleration operation at the second deceleration time, to thereby completely stop the motor at the second deceleration time when the needle is in the second position and the main shaft is rotating at the low rotational speed.