JPH0744877B2 - Pulse motor drive circuit - Google Patents

Description

The present invention provides a pulse motor drive circuit that does not require a dedicated circuit or signal for supplying a lock drive current when locking a pulse motor.

[Industrial application field]

The present invention relates to a pulse motor drive circuit that does not require a dedicated circuit for generating a drive current for locking or a signal when locking a pulse motor.

The pulse motor has the same number of applied pulses and the same rotation angle,
Since a cumulative error does not occur, it is possible to configure a positioning mechanism without a feedback circuit, that is, capable of open loop control.

By the way, it is good if the positioning mechanism driven by the pulse motor is mechanically stable and can be stopped sufficiently by the holding torque of the pulse motor. A driving current for locking is supplied to maintain the positioning mechanism stopped at a predetermined position.

When supplying the lock drive current to the pulse motor in this way, it is desirable that no dedicated circuit or signal is required.

[Conventional technology]

A thermal head retracting mechanism of a thermal transfer printer will be described as an example of a positioning mechanism using a pulse motor.

The thermal transfer printer heats a heating element of a thermal head, melts ink on a ribbon, and transfers the melted ink onto a sheet to perform printing.

Therefore, the ribbon is brought into close contact with the paper by the thermal head, so that the ribbon is wound at the same speed as the moving speed of the thermal head so as not to contaminate the paper by rubbing the paper.

When printing is not performed to save the ribbon, the thermal head is retracted from the printing position, the ribbon is separated from the paper, and the ribbon winding is stopped.

A pulse motor is used as a power source for moving the thermal head between the printing position and the retracted position. This is because the pulse motor can accurately position the thermal head by the open loop control as described above.

By the way, since the ribbon of the thermal transfer printer cannot be used again after being used once, it is important to save the ribbon.
Therefore, the retreat control of the thermal head is performed by selecting the retreat position where the retreat position of the thermal head is the minimum retreat distance and the normal retreat position is the retreat position. There is.

That is, if there is a part where printing is not performed in one line and ribbon saving can be performed when the thermal head is retracted to the small retracted position, the thermal head is retracted to the small retracted position and line feed or ribbon replacement is performed. Sometimes the thermal head is retracted to the large retracted position.

FIG. 4 is a diagram for explaining the approach / escape state.

In order to realize the approach state in which the thermal head is in close contact with the sheet and the escape state in which the thermal head is retracted, a cam 21 provided with, for example, a groove 22 is attached to the shaft of the pulse motor, and the cam 21 rotates in the direction of arrow E. Then, the groove 22 becomes the dotted line 2
The lever 23 which moves as shown by 2'and slides along the groove 22 is displaced as shown by a dotted line 23 ', and the tip of the lever 23 is also displaced by the fulcrum G as shown by a dotted line.

Therefore, the escaped thermal head 13 (retracted to the large retracted position) attached to the lever 23 enters the approach state and moves to the position of the thermal head 13 'shown by the dotted line. Therefore, in order to bring the thermal head 13 'into the escaped state, the cam 21 is rotated in the arrow F direction.

By the way, in order to save the ribbon, when the thermal head is retracted, the smaller the moving distance of the thermal head is, the less time it takes to move the thermal head. Therefore, when the thermal head is retracted in order to save the ribbon, the rotation amount of the cam 21 is reduced and the lever 23 is moved to the position 23 ″ shown by the alternate long and short dash line to move the thermal head 13 ′ to 1
It is moved to the small retracted position as shown in 3 ".

In this case, the lever 23 ″ is stopped at the inclined position shown by the groove 22, which is mechanically unstable and cannot be stopped only by the holding torque of the pulse motor.

Therefore, by supplying the lock drive current to the pulse motor,
Although the lever 23 ″ is stopped at this small retracted position, this lock drive current must generate a predetermined holding force without burning the pulse motor.

FIG. 5 is a diagram showing an example of a conventional pulse motor drive circuit, and FIG. 6 is a time chart showing waveforms at various parts in FIG.

Signals for driving the pulse motor 20 are input from terminals A, B, C, and D to A, B, C, and D of FIG. 6 (a), respectively. That is, the pulse motor 20 has four phases, and each excitation phase A, B, C, D has CD, DA, A
Excitation current is sequentially supplied to B and BC, and a drive signal is supplied so that the lock drive current is supplied to the C phase when the C phase is stopped.

Further, as shown by L in FIG. 6A, a lock signal is supplied from the terminal L, and is sent to the AND circuits 27 to 30 via the OR circuit 26. The chopper clock generator 25 is shown in Fig. 6 (a).
As shown in the chopper clock of 1), a pulse having a period of 1/10 to 1 / several tens of the period of the drive signal input from the terminals A to D is sent to the OR circuit 2.

Therefore, the driver 31 controls the excitation phases A to D of the pulse motor 20.
In addition, it is possible to supply current from the power supply V as shown in A to D of FIG. 6 (b). And the pulse motor 20
In the C phase, as shown by C in FIG. 6 (b), after the DC lock drive current flows for a certain period of time, the lock drive current due to the high frequency pulse flows. In this way, by flowing the lock current of the high frequency pulse, the average current flowing in the C phase is reduced to prevent burnout of the pulse motor.

[Problems to be solved by the invention]

As described above, in the related art, since the lock drive current is supplied, the dedicated chopper clock generator 25, the OR circuit 26 and the lock signal are required, and there is a problem that the circuit is complicated and expensive.

In view of such a problem, the present invention, when driving the pulse motor, gradually increases the rotation of the pulse motor at the start, so that a pulse having a long pulse width, a pulse having a long cycle, and a pulse having a short pulse width and a short pulse are sequentially arranged. Since it is supplied and gradually delayed when stopped, it is controlled to supply pulses with a long pulse width and a long pulse cycle from a pulse with a short pulse width and a short cycle, but the pulse width during rotation is also locked when the pulse motor is locked. By utilizing the fact that a short holding period pulse is supplied, a predetermined holding force can be obtained without reducing the average current and burning the pulse motor.

[Means for solving problems]

 FIG. 1 is a block diagram of the principle of the present invention.

Reference numeral 1 is a host device such as a word processor or personal computer, 2 is a display unit of the host device 1, 3 is a body of the host device, and 4 is a keyboard for inputting commands and data to the body 3.

Reference numeral 5 denotes a thermal transfer printer that prints characters and the like under the control of the higher-level device 1, and 6 controls the entire thermal transfer printer 5 based on the print data sent by the higher-level device 1 to perform a printing operation and to rotate the pulse motor forward or forward. Excitation phase switching sequence data required for reverse rotation or stop, and storage means for storing pulse width data required for generating drive currents having different pulse widths, moving direction and stop of the controlled object Based on the excitation phase switching sequence data read from the storage means depending on the rotation direction and the stop position of the pulse motor determined from the position, the excitation current is sequentially switched to determine the excitation phase to be supplied, and when accelerating the pulse motor, the storage means is used. When the pulse width data for which the pulse width is gradually shortened is read and the pulse motor is decelerated, the pulse width data for which the pulse width is sequentially increased is stored in the storage means. It reads the data, if stopping the pulse motor reads the pulse width data necessary to stop from the storage means, a control means comprised of a processor for supplying to the drive means for driving the pulse motor.

The control means 6 of the thermal transfer printer 5 reads out pulse width data having a short pulse width and a short cycle used when driving the pulse motor stored in the storage means, and locks the pulse motor based on the pulse width data. The drive current is created and supplied.

[Action]

With the above-described configuration, the control unit 6 can supply a lock drive current to the pulse motor that can obtain a predetermined holding force without burning the pulse motor.

〔Example〕

FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention.

The processor 7 operates by reading the program from the ROM 8. In the ROM 8, in addition to the program for controlling the entire thermal transfer printer 5 to perform the printing operation as described above, the excitation phase switching sequence data necessary for performing the forward rotation, the reverse rotation, or the stop of the pulse motor 20 is stored. , Pulse width data required to generate drive currents having different pulse widths are stored.

Therefore, when the processor 7 receives print data from the host device 1 such as the word processor shown in FIG. 1 through the interface circuit 10, the print data is stored in the RAM 11 and the length of the portion of the print data for one line that is not printed is increased. It is calculated and stored in the RAM 11.

Then, the processor 7 sends a signal for driving the pulse motor 20 to the driver 19 via the approach / escape control port 18.

That is, when starting the pulse motor, the processor 7 reads the excitation phase switching sequence data and the pulse width data in the direction in which the pulse motor 20 is desired to rotate from the ROM 8, and sets the excitation phase switching sequence data in the approach / escape control port 18. , Driver based on this excitation phase switching sequence data
When driving 19 to perform two-phase excitation of the pulse motor 20,
For example, a drive current is supplied to the excitation phases A and B, pulse width data is set in the soft timer at the same time, and counting of the time of this pulse width data is started.

Then, the processor 7 reads the next excitation phase switching order data and the pulse width data from the ROM 8 upon completion of the time counting of the pulse width data, and sets the excitation phase switching order data in the approach / escape control port 18. ,
Based on this excitation phase switching sequence data, the driver 19 is driven to supply the drive current to the excitation phases B and C of the pulse motor 20, and at the same time, the pulse width data is set in the soft timer, and the time of this pulse width data is set. Start counting.

Then, the processor 7 reads the next excitation phase switching order data and the pulse width data from the ROM 8 upon completion of the time counting of the pulse width data, and sets the excitation phase switching order data in the approach / escape control port 18. ,
Based on this excitation phase switching sequence data, the driver 19 is driven to supply the drive current to the excitation phases C and D of the pulse motor 20, and at the same time, the pulse width data is set in the soft timer, and the time of this pulse width data is set. Start counting.

Then, the processor 7 reads the next excitation phase switching sequence data and the pulse width data from the ROM 8 upon completion of the time counting of the pulse width data, excites the next two phases of the pulse motor 20 in the same manner as described above, and at the same time, outputs the pulse width data. Then, the operation of reading the next data from the ROM 8 is repeated.

When accelerating the pulse motor 20 when reading the pulse width data from the ROM 8, the processor 7 reads the pulse widths in the order of decreasing pulse widths, so that the counting time of the soft timer decreases corresponding to the pulse widths. Therefore, a driving current whose pulse width is sequentially shortened at a cycle that is shortened is supplied to each excitation phase of the pulse motor 20, so that the rotation speed of the pulse motor 20 is sequentially increased.

When the processor 7 reads the shortest pulse width data from the ROM 8, only the excitation phase switching order data is read from the ROM 8 from then onward, and the pulse width data is not read. The read excitation phase switching order data is used for approach / escape control. port
Set to 18 and continue the operation to make the soft timer count the time of the shortest pulse width data.

Therefore, the pulse motor 20 maintains the constant speed rotation at the maximum speed.

When decelerating the pulse motor 20, the processor 7 performs the same process as that at the time of acceleration by using the pulse width data in which the pulse width becomes longer in sequence contrary to the case of the acceleration.

That is, the processor 7 reads out from the ROM 8 the pulse width data in which the pulse width is sequentially lengthened every time the counting of the soft timer is completed, by the address opposite to that in the case of acceleration.

Then, set this pulse width data in the soft timer to count the time.
The excitation phase switching sequence data to be read from is set in the approach / escape control port 18, and the driver 19 is driven to pulse for the time for counting the set pulse width by the soft timer based on the excitation phase switching sequence data. motor
Drive current is supplied to 20 excitation phases.

Therefore, since a drive current whose pulse width is sequentially increased with a cycle that is sequentially increased is supplied to each excitation phase of the pulse motor 20, the rotation speed of the pulse motor 20 is gradually decreased.

At the stop position of the pulse motor 20, the processor 7 reads from the ROM 8 the excitation phase switching order data and the pulse width data necessary for stopping, and approaches this excitation phase switching order data /
Set it to the escape control port 18 and set the pulse width data to the soft timer.

FIG. 3 is a time chart showing pulse motor drive waveforms.

FIG. 3 is a time chart of pulse motor drive waveforms from deceleration to stop. In the present embodiment, it is an example of two-phase excitation and one-phase stop. BC phase → CD phase → DA phase → AB phase → BC phase. After being excited, it is in stop lock at phase C.

The C phase, which is the stop phase, is, for example, BC indicated by the excitation phase switching sequence data last read from the ROM 8 by the processor 7.
The intermediate C phase is calculated from the phase and the CD phase of the excitation phase switching sequence data stored in the ROM 8 next.

The processor 7 stops the exciting current supplied to the stop phase C by the completion of the time counting by the soft timer for counting the timing when the stop lock shown in FIG. 3 is completed, and therefore the off data is output to the approach / escape control port 18. At the same time as setting, the pulse width data of the shortest pulse width stored in ROM8 is read and set in the soft timer.

When the soft timer completes the time counting of the set pulse width data, the stop phase C is approached again /
While setting to the escape control port 18, the pulse width data of the shortest pulse width is set in the soft timer, and the driving current of the short pulse width is set in the stop phase C as shown in the intermittent lock in FIG. Is performed, and a driving current having a short pulse width is intermittently supplied to the C phase by repeating this processing.

Therefore, the average current flowing in the C phase can be suppressed to a low level, and the pulse motor 20 can maintain a predetermined holding force without causing burnout.

The processor 7 controls the pulse motor 20 as described above,
The cam 21 shown in FIG. 4 is rotated to displace the lever 23 to the position 23 'to bring the thermal head 13 into the approach state, and at the same time, the character code is extracted from the print data read from the RAM 11 to generate the character generation circuit. The corresponding character pattern is read from 9 and the thermal head 13 is passed through the head control circuit 12.
Then, the heating element is heated to transfer the ink on the ribbon onto the paper.

At the same time, the space motor 17 is driven through the space control circuit 16 to position the thermal head 13 at the printing position and the space operation is performed.

When the processor 7 has a portion which is not printed in one line and the thermal head 13 can be retracted, the pulse motor 20
Is controlled to rotate the cam 21 shown in FIG.
Displace the 3'to the 23 "position and set the thermal head 13 'to 1
Retract to the small retracted position as shown in 3 ".

At this time, the position of the lever 23 ″ is mechanically unstable,
Since the lock drive current is supplied to the pulse motor 20 as described above, the thermal head 13 ″ is placed in the small retracted position shown in FIG.
Can hold.

When the thermal head 13 reaches the printable position, the processor 7 controls the pulse motor 20 to bring the thermal head 13 into the approach state again.

When the processor 7 detects a line feed code from the print data, it drives the pulse motor 20 via the approach / escape control circuit 18, retracts the thermal head 13 to the large retracted position, and drives the line feed motor 15 via the line feed control circuit 14. , Feed the paper.

Further, even when there is no line feed code at the end, the thermal head 13 is retracted to the large retracted position at the end of printing for one line so that ribbon replacement and paper setting can be performed easily.

〔The invention's effect〕

As described above, the present invention can eliminate the need for a dedicated circuit or signal when supplying the lock drive current to the pulse motor.

[Brief description of drawings]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention, FIG. 3 is a time chart showing a pulse motor drive waveform, and FIG. 4 is an approach / escape state. FIG. 5 is an explanatory diagram, FIG. 5 is a diagram showing an example of a conventional pulse motor drive circuit, and FIG. 6 is a time chart showing waveforms of respective parts of FIG. In the figure, 1 is a host device, 2 is a display unit, 3 is a main body, 4 is a keyboard, 5 is a thermal transfer printer, 6 is control means, 7 is a processor, 8 is a ROM, 9 is a character generation circuit, 10 is an interface circuit, 11 is RAM, 12 is head control circuit, 13 is thermal head, 14 is line feed control circuit, 15 is line feed motor, 16 is space control circuit, 17 is space motor, 18 is approach / escape control port, 19, 31 is Driver, 20 is a pulse motor, 21 is a cam, 22 is a groove, 23 is a lever, 25 is a chopper clock generator, 26 is an OR circuit, 27 to 30 are AND circuits,

Claims (1)

[Claims] 1. A controlled object is controlled by sequentially supplying a driving current having a different pulse width to each excitation phase of a pulse motor through a driving means and controlling the rotation direction and speed of the pulse motor. In a device (5) for performing positioning control for supplying a high frequency pulse to lock the pulse motor after positioning at a predetermined position, the excitation required for causing the pulse motor to perform forward rotation, reverse rotation or stop. Storage means for storing phase switching sequence data and pulse width data necessary for generating drive currents having different pulse widths, and a rotation direction of the pulse motor determined from a moving direction and a stop position of the controlled object. Based on the excitation phase switching sequence data read from the storage means according to the stop position, the excitation current is sequentially switched to determine the excitation phase to be supplied. When accelerating the pulse motor, pulse width data whose pulse widths are sequentially shortened are read from the storage means, and when decelerating the pulse motor, pulse width data whose pulse widths are sequentially lengthened are read from the storage means. When the pulse motor is stopped, the pulse width data necessary for the stop is read from the storage means, and a processor for supplying the driving means with the processor is provided, and the pulse motor is stopped. A pulse width of the shortest pulse width stored in the storage means instead of the high frequency pulse for locking the pulse motor after the pulse width data necessary for stopping the pulse motor is supplied to the driving means. A pulse motor drive circuit for reading data and supplying the data to the drive means.