Printing apparatus

1. A printing apparatus provided with a printing section to print text or an image on a printing target medium from a film-shaped medium, comprising:

a supply spool that feeds out a film-shaped medium to the printing section side in printing processing;

a wind-up spool that winds up the film-shaped medium from the printing section in the printing processing;

a DC motor that rotates at least one of the supply spool and the wind-up spool;

a motor driver that supplies a drive current to the DC motor;

a rotation amount detector that detects a rotation amount of the DC motor; and

a controller that controls the motor driver,

wherein the controller calculates a drive current to be supplied to the DC motor for providing the DC motor with a same rotation velocity as a rotation velocity of a reference DC motor based on a difference between a rotation velocity of the DC motor in driving the DC motor at a predetermined supply current in a state in which the film-shaped medium is broken, or the film-shaped medium is separated from the supply spool, and a rotation velocity of the reference DC motor in driving the reference DC motor at the predetermined supply current, and controls the motor driver to supply the calculated drive current.

2. The printing apparatus according to claim 1 , wherein in driving the DC motor in a state in which the film-shaped medium is broken, or the film-shaped medium is separated from the supply spool, the controller drives the DC motor in the same direction as the rotation direction of the DC motor for transporting the film-shaped medium from the supply spool side to the wind-up spool side.

3. The printing apparatus according to claim 1 , further comprising:

a mark detector that detects an empty mark indicative of a use limit of the film-shaped medium attached to an end portion of the film-shaped medium,

wherein after the mark detector detects the empty mark, the controller drives the DC motor to break the film-shaped medium or separate the film-shaped medium from the supply spool, and then drives the DC motor to calculate a supply current of the DC motor.

4. The printing apparatus according to claim 1 , further comprising:

a nonvolatile memory,

wherein the controller stores the calculated value of supply current in the nonvolatile memory, reads the value of supply current stored in the nonvolatile memory after replacing the film-shaped medium with a new film-shaped medium, and controls the motor driver to supply the supply current with the read value of supply current.

5. The printing apparatus according to claim 1 , further comprising:

a temperature detector that detects an ambient temperature of the DC motor,

wherein the controller applies the calculated rotation velocity to a beforehand determined relationship between the rotation velocity and the temperature to make a temperature correction to the rotation velocity at a predetermined temperature.

6. The printing apparatus according to claim 1 , wherein in a state in which the film-shaped medium is broken, or the film-shaped medium is separated from the supply spool, the controller drives the DC motor, calculates a rotation velocity of the DC motor based on the rotation amount of the DC motor detected in the rotation amount detector, refers to a relationship between the rotation velocity and the supply current in the reference motor, calculates a supply current of the DC motor for providing the same rotation velocity as a rotation velocity of the time the reference motor is driven with the supply current of the DC motor at the calculated rotation velocity, and controls the motor driver to supply the calculated supply current.

7. The printing apparatus according to claim 1 , further comprising:

a mark detector that detects an empty mark indicative of a use limit of the film-shaped medium attached to an end portion of the film-shaped medium,

wherein in the film-shaped medium is formed a weak portion on the end side closer to the end than a position in which the empty mark is attached,

the DC motor is comprised of a first DC motor that rotates the supply spool, and a second DC motor that rotates the wind-up spool, and

after the mark detector detects the empty mark, the controller drives the first DC motor and the second DC motor so as to apply tension to the film-shaped medium, breaks the film-shaped medium in the weak portion, and subsequently, calculates a supply current of the second DC motor by driving at least the second DC motor to rotate in the same direction as a rotation direction for transporting the film-shaped medium.

8. The printing apparatus according to claim 1 , further comprising:

a mark detector that detects an empty mark indicative of a use limit of the film-shaped medium attached to an end portion of the film-shaped medium,

wherein the DC motor is comprised of a first DC motor that rotates the supply spool, and a second DC motor that rotates the wind-up spool,

and after the mark detector detects the empty mark, the controller drives the second DC motor, winds up the film-shaped medium with the wind-up spool, thereby separates the film-shaped medium from the supply spool, and subsequently, calculates a supply current of the second DC motor by driving at least the second DC motor to rotate in the same direction as a rotation direction for transporting the film-shaped medium.