JP2000006479A - Thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal printer that can prevent characters from being broken or a print position from being displaced. SOLUTION: When printing is finished, a pulse motor is temporarily stopped to wait until the vibration of a driving force transmission mechanism for transmitting a driving force of the pulse motor to a platen is turned still. Thereafter, a rotation direction of the pulse motor is reversed thereby freeing a warp of the driving force transmission mechanism to prevent the platen from reversing and characters from being broken. After an excitation current for the pulse motor is made minute to surely prevent the rotation of the platen, the excitation is turned off. When printing is to be started, the platen is rotated forward to offset the reverse, so that a print start position is prevented from being displaced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer, and more particularly to a thermal printer in which characters are not easily collapsed or a printing position is not shifted.

[0002]

2. Description of the Related Art In recent years, information processing equipment has been used in various industrial fields. However, in order to output the result of information processing, a thermal printer is often used because of its quietness. FIG. 1 is a perspective view of a thermal printer 1 currently used. A platen 12 on which thermal paper is wound is driven to rotate by a pulse motor 11.

FIG. 2 is a perspective view of a driving force transmitting mechanism of the pulse motor 11. The driving force of a driving gear 21 attached to a rotating shaft of the pulse motor 11 is controlled by three intermediate gears 22.
The power is transmitted to the driven gear 25 attached to the rotation shaft of the platen 12 via 23 and 24. FIGS. 3A and 3B are explanatory diagrams of the operation of the driving force transmission mechanism. FIG. 3A shows the case where the thermal paper is normally conveyed, and FIG. The behavior at the time is shown.

That is, when printing is being performed and the thermal paper is being conveyed normally, the pulse motor 11 rotates clockwise, and the platen 12 also rotates clockwise. That is, during printing, the driving gear 21, the intermediate gears 22, 23 and 24, and the driven gear 25 are fitted to each other without play.

[0005]

However, in order to reduce the weight and size of the thermal printer, each gear is often formed of a thin synthetic resin. It is in a deformed state. Therefore,
When the excitation current of the pulse motor 11 is cut off when printing is completed, each gear rotates in the opposite direction to that during printing due to restoration of deformation of each gear. For this reason, the platen 12 rotates counterclockwise and pulls back the printed thermal paper, so that the next time printing is started, character collapse occurs.

Further, since the pulse motor 11 also rotates in the counterclockwise direction, the relative position between the rotor and the stator of the pulse motor 11 is shifted, and when the next printing is started, the printing start position is easily shifted. In order to prevent character crushing or displacement of the printing position, measures such as continuing excitation of the pulse motor 11 even after printing, increasing the thickness of the gear, or forming the gear with a material having little elastic deformation are taken. Required.

However, continuation of the excitation causes an increase in power consumption, an increase in the thickness of the gear increases the mass, and a change in the material of the gear deteriorates the economy, so that it is difficult to adopt any of them. SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a thermal printer capable of preventing character crushing or printing position shift without increasing power consumption, mass, and price.

[0008]

According to a first aspect of the present invention, a thermal printer includes a platen, a pulse motor for driving the platen, a driving force transmitting mechanism for transmitting a driving force of the pulse motor to the platen, and printing. A reverse rotation driving means for driving the pulse motor in a rotation direction opposite to the rotation direction during printing after the printing is completed, and a pulse motor for driving the pulse motor in a rotation direction during printing before the start of printing. And a normal rotation drive unit before printing is started.

In the thermal printer according to the first aspect of the invention, after the printing is completed, the pulse motor is reversely rotated to release the distortion of the gear for driving the platen, and before the printing is started, the pulse motor is normally rotated to start printing. Return the position to the original position. A thermal printer according to a second aspect of the present invention comprises: a post-printing stop means for stopping the pulse motor for a predetermined time before the pulse motor is reversely rotated by the reverse rotation driving means after the printing is completed after the printing is completed; A print start stop means for stopping the pulse motor for a predetermined time after the pulse motor is rotated forward by the forward forward drive means.

In the thermal printer according to the second aspect of the invention, the rotation of the driving force transmitting mechanism for transmitting the driving force of the pulse motor to the platen is stopped by stopping the rotation of the pulse motor for a predetermined time before the reverse rotation or the forward rotation of the pulse motor. Let it be determined.

[0011]

FIG. 4 is a drive circuit diagram of a pulse motor applied to a thermal printer according to the present invention.
The pulse motor 11 has four exciting coils 111, 112,
It has 113 and 114 and corresponding drive circuits. Since each drive circuit has the same configuration, the excitation circuit 21 of the excitation coil 111 and the reference voltage generation circuit 22 will be described.

One end of the exciting coil 111 is connected to a DC bus V
_C and the other end is connected to the drain of the conduction control FET 211. The source of the conduction control FET 211 is grounded via the current detection resistor 212. Energization control FET 21
One gate is connected to the output of the first comparator 213. The negative input terminal of the first comparator 213 is connected via an input resistor 214 to the microprocessor 23 functioning as a control unit. An excitation command pulse for the coil of the pulse motor is output from the microprocessor 23. The rotation direction is controlled by changing the excitation order of the four excitation coils.

Further, the negative input terminal of the first comparator 213 is connected to the second comparator 216 via a diode.
Connected to the output of Note that the first comparator 213
The first reference voltage generated by the reference voltage generation circuit 22 is applied to the positive input terminal of the first reference voltage. Second comparator 216
The voltage at both ends of the current detection resistor 212 is applied to the negative input terminal, and the second reference voltage generated by the reference voltage generation circuit 22 is applied to the positive input terminal.

The reference voltage generating circuit 22 generates a first reference voltage by using a Zener diode 221.
A second reference voltage is generated by a voltage dividing circuit. That is, the first reference voltage is generated by dividing the first reference voltage by the first resistor 222 and the second resistor 223, and the third reference voltage is generated in parallel with the second resistor 223. The resistor 224 and the reference voltage control FET 225 are installed,
By changing the switching frequency of the reference voltage control FET 225, the second reference voltage can be changed.

In the above drive circuit, if the drive command output from the microprocessor 23 is lower than the first reference voltage, the conduction control FET 211 is turned on and a current flows through the excitation coil 111. If the voltage proportional to the exciting current detected by the current detecting resistor 212 becomes larger than the second reference voltage, the output of the second comparator 216 is inverted and the drive command output from the microprocessor 23 is blocked. Thus, an increase in the exciting current is suppressed.

FIG. 5 is a flowchart of a pulse motor stop routine executed by the microprocessor 23. The execution is started as an interrupt process upon completion of printing of data stored in a print accumulator (not shown). At step 51, a settling time stand-by process at stop is executed, at step 52 a reverse process is executed, and at step 53 a small current process at stop is executed.

In step 54, the excitation of the excitation coil of the pulse motor is turned off. Finally, in step 55, the flag F indicating the timing of generating a new print request is set to "0", and this routine ends. FIG. 6 is a flowchart of the settling time waiting time at stop executed in step 51. In step 511, the settling time is set. The settling time is a time from the end of printing until the pulse motor 11 starts to reversely rotate, and is a time for waiting for the vibration of the gears for driving the platen to settle.

At step 512, it is determined whether there is a new print request. When there is no print request, it is determined at step 513 whether the settling time set at step 511 has elapsed. If the settling time has not elapsed, the process returns to step 512, and steps 512 and 513 are repeated. vice versa,
If the settling time has elapsed and the determination in step 513 is affirmative, this process is completed.

If there is a new print request, an affirmative determination is made in step 512 and a flag F is set in step 514.
Set to "1" and end this routine. FIG. 7 is a flowchart of the reverse rotation process executed in step 52. In step 521, the amount of reverse rotation is set. This reverse rotation amount is set in advance as a rotation angle for eliminating the deformation of the gear during normal rotation and releasing the distortion force. In step 522, the output order of the excitation command pulse is set to reverse, and in step 523
To start reverse rotation.

In step 524, the process waits until the reverse rotation of the amount set in step 521 is completed, and the process ends. FIG. 8 is a flowchart of the stop minute current processing executed in step 53. The minute current time is set in step 531. This is because the pulse motor 11 and the platen 12 are further rotated by the vibration of the gears or the like. This is a process for generating a holding torque to prevent this.

In step 532, the microprocessor 23
, The frequency of the switching pulse of the reference voltage control FET 225 output from the controller is made high, and the second reference voltage is made low. In step 533, it is determined whether there is a new print request.
It is determined whether the minute current time set in 31 has elapsed.

If the minute current time has not elapsed, a negative determination is made in step 534 and the process returns to step 533. If the minute current time has elapsed, the process ends if an affirmative determination is made in step 534. If there is a new print request, a positive determination is made in step 533, and
At step 5, the flag F is set to "2" and this routine is terminated.

FIG. 9 is a flowchart of a pulse motor start routine executed as an interrupt process when a print command is generated. In step 91, the value of a flag F indicating a new print request generation timing is checked. Flag F
Is "0", that is, when the pulse motor stop routine ends normally, the routine proceeds to step 92, where the startup minute current processing is executed.

Next, in step 93, normal rotation processing is executed. When it is determined in step 91 that the flag F is "2", that is, when a print request is issued during execution of the stop minute current processing. The process proceeds to step 93 in order to immediately execute the normal rotation process without executing the startup minute current process. After that, at step 94, a start-up settling time standby process is executed. The details of the startup minute current process, the normal rotation process, and the startup settling time standby process will be described later.

Finally, in step 95, printing is executed in accordance with the printing request. When it is determined in step 91 that the flag F is "1", that is, when there is a printing request during the stop-time settling time standby process. Directly goes to step 95 to start printing immediately. FIG. 10 is a flowchart of the startup minute current process executed in step 92.
In step 921, a minute current time for generating the holding torque is set, and in step 922, the routine waits until a predetermined minute current time elapses, and ends this routine.

FIG. 11 is a flowchart of the normal rotation process executed in step 93. In step 931, the amount of normal rotation is set. This forward rotation amount is set as an amount for canceling the reverse rotation amount at the time of stoppage and returning the print start position to a correct position. In step 932, the output order of the excitation command pulses is set to normal rotation, and in step 933, reverse rotation is started. Step 93
In step 4, the process waits until the forward rotation of the amount set in step 931 is completed, and the process ends.

FIG. 12 is a flow chart of the start-up settling time standby process executed in step 94. In step 941, a settling time for calming the gear vibration is set, and in step 942, a predetermined settling time elapses. Then, the routine is terminated. FIG. 13 is a stop / start timing chart of the thermal printer according to the present invention. The upper part shows the rotation direction, and the lower part shows the reference voltage (solid line) and the excitation frequency (dashed line).

[0028] That is, when the stop command at time t ₁ is output, gradually decreases the driving frequency from the time t ₁ toward t ₂ stops the rotation of the pulse motor. The time t ₂ later also exciting current to prevent the pulse motor without reducing is reversed. After the time t ₂ has stopped rotating settling toward t _3, it reversed the pulse motor from the time t ₃ toward t ₄ to eliminate the distortion of the gears. Thereafter generating a holding torque by reducing the exciting current from time t ₄ toward t _5, to turn off the exciting current at time t _5.

Time t₆When a print request occurs at time t
₆To t₇The excitation current reduced during
Time t after the rotation of the₇To t₈Over
Rotate the pulse motor forward to cancel the reverse rotation when stopped. Times of Day
t₈To t₉Stopped rotation for a predetermined settling time
Later, time t₉To t _TenGradually increase the frequency to
The motor is rotated at a steady speed. And time t_TenLater on
Execute the printing process of.

[0030]

According to the thermal printer according to the first aspect of the present invention, the driving of the driving force transmission mechanism is released by reversing the pulse motor after the printing is completed, so that not only the printing collapse is eliminated but also the printing is started before the printing is started. It is possible to prevent the printing start position from being shifted by rotating the pulse motor forward in a direction to cancel the reverse rotation amount.

According to the thermal printer according to the second aspect of the invention, the pulse motor is stopped for a predetermined time before the pulse motor rotates in the reverse direction and the normal direction, and the vibration of the driving force transmission mechanism is calmed. It is possible to prevent the printing start position from being shifted.

[Brief description of the drawings]

FIG. 1 is a perspective view of a thermal printer.

FIG. 2 is a perspective view of a driving force transmission mechanism.

FIG. 3 is an operation explanatory view of a driving force transmission mechanism.

FIG. 4 is a driving circuit of a pulse motor.

FIG. 5 is a flowchart of a pulse motor stop routine.

FIG. 6 is a flowchart of a stop-time settling time standby process.

FIG. 7 is a flowchart of a reverse rotation process.

FIG. 8 is a flowchart of a minute current process at stop.

FIG. 9 is a flowchart of a pulse motor starting routine.

FIG. 10 is a flowchart of a startup minute current process.

FIG. 11 is a flowchart of a normal rotation process.

FIG. 12 is a flowchart of a start-up settling time standby process.

FIG. 13 is a stop / start timing chart of the thermal printer.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 pulse motors 111 to 114 excitation coil 21 excitation circuit 211 conduction control FET 212 current detection resistor 213 first comparator 215 diode 216 second comparator 22 reference voltage generation circuit 221 zener Diode 225: Reference voltage control FET 23: Microprocessor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C058 AB02 AB03 AB15 AB17 AC06 AF29 AF31 GE03 GE09 GE10 5H580 AA05 BB01 BB09 CA12 EE03 FA02 FA13 FA14 FA23 FA24 FB03 FD14 HH22

Claims (2)

[Claims] 1. A platen, a pulse motor for driving the platen, a driving force transmission mechanism for transmitting a driving force of the pulse motor to the platen, and a rotation direction during printing of the pulse motor after printing is completed. Is a reverse rotation driving means for driving a predetermined rotation angle in the reverse rotation direction after printing, and a forward rotation before printing for driving the pulse motor in the rotation direction during printing before starting printing. And a driving means. 2. A post-printing stop means for stopping the pulse motor for a predetermined time before the pulse motor is reversely rotated by the reverse rotation driving means after the printing is completed after the printing is completed; 2. The thermal printer according to claim 1, further comprising: a pre-printing stop means for stopping the pulse motor for a predetermined time after the pulse motor is normally rotated by the normal rotation drive means.