JPH03124468A - Thermal printer control method - Google Patents

Abstract

PURPOSE:To prevent the shift of dot pitch in printing by a method wherein the angle of reverse rotation of a motor caused by the restoring force from deflection of a rubber part of a platen is previously identified, and at the restart of the stepping motor, the motor is returned by that angle before excitation. CONSTITUTION:A two-phase stepping motor is used as a motor 1. A platen 2 having an outer diameter of 14.2mmphi is covered with a rubber part 22 having a wall thickness of 2.6mm. The platen 2 is driven by the motor 1 through a three-stage reducing gear 5. A thermal head 4 of a line dot system is brought into elastic contact with the platen 2 through a recording medium 3 made of heat sensitive paper. When the excitation of a stator 12 is interrupted, a magnetic tooth (a) of a rotor 11 which has been stopped at a position of a pole tooth phi1' of the stator 12 is rotated reversely by an angle theta=4 degrees to face a pole tooth phi1. Therefore, at the restart of the motor 1, the stator 12 is not excited at phi1'-phi2' but at phi1, whereby idle rotation of the platen corresponding to the return angle of the rotor of the motor 1 in the reverse direction is offset. As a result, the head of a character printed on the recording medium cannot be contracted.

Description

[Detailed Description of the Invention] [Summary] Regarding the control method of a thermal printer, in a line dot type printer, the problem occurs when the motor is returned to the opposite direction due to the bending of the rubber of the platen, and then printing is started. A method for controlling a thermal printer including a platen rotationally driven by a stepping motor and a line-dot type thermal head in elastic contact with the platen via a recording medium, the method of controlling the thermal printer includes: When restarting the stepping motor, control is performed by returning the excitation phase by a return angle θ at which the stepping motor rotates in reverse due to the restoring force of the bending of the rubber portion of the platen.

[Industrial application field]

The present invention relates to thermal printers, and particularly to line-dot type thermal printers in which the platen is driven by a stepping motor, to prevent dot pitch deviation in printing due to reverse rotation of the motor due to the restoring force of the deflection of the rubber part of the platen. The present invention relates to a method for controlling a motor.

In recent years, with the progress of information technology, the demand for printers, which are information output devices, has been increasing more and more.

Printers can be classified into various types depending on their purpose, and are broadly divided into impact type and non-impact type.

In the impact method, wire dot printers are currently being used in most fields, replacing the method of directly printing type, due to their print quality, speed, and price.

On the other hand, in the area of non-impact printers, laser printers have recently surpassed wire dot printers. However, for personal use, whether it is a personal computer or a word processor, there is a need for smaller, lighter, and faster printing speeds. Thermal printers are attracting attention because they have many features such as being reasonably fast, noiseless, and maintenance-free.

This trend is also spreading to areas such as document creation for office use and receipt printing for cash registers for store use.

[Prior Art] Thermal printing methods can be divided into two methods depending on the form of the thermal head and how the thermal head scans the recording medium to print.

The thermal head has several to several tens of heat-generating dots lined up parallel to the direction in which the recording medium travels.For example, while the recording medium is being intermittently fed line by line, the thermal head is placed at right angles to the direction in which the recording medium is traveling. The method of printing by mechanically moving and scanning is called the serial dot method. This method is mainly used by low-end printers.

On the other hand, hundreds to dozens of heat-generating dots are lined up in the width direction perpendicular to the direction in which the recording medium travels, and the heat-generating dots are electrically fed while the recording medium is continuously fed or fed intermittently in dot pitch units. The method of scanning and printing is called the line dot method. For facsimiles, etc.
This method is often used.

FIG. 3 is a configuration diagram of a drive system in a line dot thermal printer.

In the figure, ■ is a stepping motor (hereinafter abbreviated as motor)
, 2 is a platen, 3 is a recording medium such as thermal paper, and 4 is a thermal head. Reference numeral 5 denotes a reduction gear that reduces the rotational speed of the motor 1 in order to rotate the platen 2 at a low speed, and the motor 1 may have a configuration of a so-called geared motor in which a reduction gear is incorporated.

Here, the motor 1 is composed of a metal core 21 and a rubber portion 22 wrapped with rubber.

The recording medium 3 is connected to this platen 2 and the platen 2.
The thermal head 4 is sandwiched between the rubber part 22 of the thermal head 4 and the thermal head 4 which is in elastic contact with the rubber part 22 by a spring or the like. Generally, the friction coefficient between the recording medium 3 and the rubber portion 22 is overwhelmingly larger than that between the thermal head 4 and the recording medium 3, so when the platen 2 rotates, the recording medium 3 is fed. .

Printing is performed by rotating the motor 1 to rotate the platen 2 and feeding the recording medium 3 while energizing the thermal head 4 . Then, when printing is completed, the excitation is cut off to prevent abnormal heat generation of the motor l.

However, in the platen 2, the core bar 21 is driven to rotate, and the thermal head 4 comes into elastic contact with the rubber part 22 coated around it, so that the core bar 21 rotates with a so-called brake applied. be bent. and,
When the rotation stops, the surface of the rubber part 22 is exposed to the thermal head 4.
Since it is firmly supported by the rubber portion 22, the restoring force of the bending of the rubber portion 22 acts to reversely rotate the core metal 21.

Therefore, when the excitation of the motor l is cut off, it often happens that the motor l is rotated in the reverse direction.

[Problem to be solved by the invention]

FIG. 4 is an explanatory diagram of displacement due to the restoring force of the rubber portion.

In the figure, a platen 2 and a core bar 21 of the platen 2 are shown.
Let's take a look at the force relationship between the rubber part 22, the recording medium 3, and the thermal pad 4.

Now, P is the pressing force of the thermal head 4, μ is the coefficient of friction between the thermal head 4 and the recording medium 3, R is the radius of the platen 20, Tr is the restoring force of the rubber part 22 of the platen 2, and Md is the date of the motor l. Tent torque, C is the reduction ratio of reduction gear 5,
Let η be the efficiency of the reduction gear 5, and F=μP be the force for feeding the recording medium 3.

(1) Force relationship during motor excitation: Tr＜FXR−・・・・■ The recording medium 3 stops.

(2) Force relationship when excitation and cutting of the motor after printing: Tr>M
dXCXη -----■ Motor 1 rotates in reverse.

From relational formula ■2 and formula 0, FXR>Tr>MdXCXy+ --------1 ■
Then, from equation 0, until FXR=MdXCXη,
In other words, the motor 1 is reversely rotated through the reduction gear 5 by an angle θ corresponding to the angle θ” at the core metal 21 of the platen 2.

FIG. 5 is a schematic sectional view of the motor, and FIG. 6 is a drive sequence of the motor.

In this diagram, motor 1 is a stepping motor and 1 phase/2
This is an example of phase excitation.

In the figure, Ll is a rotor, and 12 is a stator. Also, φ,
・φ2゛, φ2 ・φ2゛, etc. indicate the pole teeth of each phase of the stator 12, and (a), (g)), (C), etc. indicate the rotor 11.
Each magnetic tooth is shown.

Now, the magnetic teeth (a) of the rotor 11 are the pole teeth φ of the stator 12.

Stop at the position. However, when the excitation of the motor l is cut off, the magnetic tooth (a) of the rotor 11 moves to the position of the pole tooth φ of the stator 12 due to the restoring force of the rubber part of the platen (not shown), that is, the magnetic tooth It is returned to the position shown in (b). In the conventional control method for a 1-phase/2-phase excitation stepping motor, the next thing to be excited is φ, ゛-φ2゛ of the stator 12, so this is due to the magnetic teeth (C) of the rotor 11. Corresponds to the position.

In this way, a phase shift corresponding to the return angle θ occurs between the magnetic teeth (b) and (C).

That is, when printing stops and the excitation of the motor 1 is cut off, the motor 1 is rotated in the opposite direction by the force that attempts to restore the deflection of the rubber portion of the platen.

Therefore, when the motor is stopped, the positions of the pole teeth of the stator 12 of the motor and the magnetic teeth of the rotor 11 become out of phase.

That is, when printing is restarted next time, a so-called step-out occurs in the motor 1 due to the phase shift, and the motor 1 does not start normally, and therefore the recording medium cannot be normally fed.

Figure 7 shows the printing results using the conventional control method.
A) is a normal state, and (B) is a completely packed state.

According to the conventional stepping motor control method for line dot thermal printers, once printing is finished and the motor excitation is cut off, the motor rotor is rotated in the opposite direction by the force that restores the bending of the rubber part of the platen. be done. As a result, the phase between the pole teeth of the stator at the originally stopped position and the magnetic teeth of the rotor that opposes it is shifted.

When the motor is restarted in order to resume printing in such a step-out state, abnormalities often occur in the rotation of the platen and, by extension, in the feeding of the recording medium. As shown in FIG. 2B, there was a problem in that the beginning of the print was too small, and for example, the alphabet "2" turned into "Z".

[Means to solve the problem]

The problem described above is a method for controlling a thermal printer including: a platen rotationally driven by a stepping motor; and a line dot type thermal head in elastic contact with the platen via a recording medium. The problem is solved by a thermal printer control method that controls the excitation phase by returning the excitation phase by the return angle θ at which the stepping motor rotates in reverse due to the restoring force of the deflection of the rubber portion of the platen when restarting.

[Function] As mentioned above, in a line dot type thermal printer in which the platen is driven by a stepping motor, the motor is rotated in the opposite direction by the restoring force of the flexure of the rubber part of the platen, and the motor is stopped. If the current phase of the stator's pole teeth and the rotor's magnetic teeth are out of sync, the next time the motor is restarted, it will not rotate normally using conventional control methods, but this method In the invention, such deviations are offset.

In other words, check in advance the angle at which the motor rotates in reverse due to the restoring force of the bending of the rubber part of the platen, and when restarting the stepping motor, move the phase of the pole teeth to be energized back by that angle. That's what I do.

Then, the rotational play of the platen corresponding to the angle of the stepping motor rotor returned in the opposite direction is canceled out, and the recording medium can be normally fed from the start.

As a result, it is possible to prevent the beginnings of characters printed on the recording medium from becoming too crowded.

〔Example〕

FIG. 1 is a detailed explanatory diagram of the present invention, and FIG. 2 is a partially enlarged view of FIG. 1.

In Figures 1 and 2, the motor 1 is a two-phase stepping motor, and the platen 2 has an outer diameter of 14.2 mmφ and a wall thickness of 2.6 mm.
A rubber portion 22 of mm is covered.

This platen 2 is connected to a motor 1 via a three-stage reduction gear 5.
A line dot type thermal head 4 is brought into elastic contact with a recording medium 3 made of thermal paper sandwiched therebetween.

The specifications of this thermal printer are as follows.

(1) To t-7/Lz,, F 4 (7) Press crab
P = 3,000g, (2) Coefficient of friction between thermal head 4 and recording medium 3: μ = 0.4, (3) Radius of platen 20: R = 7.1mm, (4)
Reduction ratio of reduction gear 5: C = 11.3, (5) efficiency of reduction gear 5: η = 1.37, (6) detent torque of motor l: Md = 35 gcm, then the rubber part of platen 2 The restored crab Tr of 22 is the formula μXPXR>Tr>M
dXCXη, 852gcm>Tr>542
gcm.

Then, the return angle θ at which the rotor 11 of motor l rotates in the opposite direction is
is θ=4 degrees.

That is, in the example shown in FIG. 1, when the excitation of the stator 12 is cut off, the magnetic teeth (a) of the rotor 11, which had stopped at the positions of the pole teeth φ,' of the stator 12, return at a return angle θ. = Reversely rotated by 4 degrees and located at pole tooth φ1.

Therefore, when starting the motor l again, normal driving can be achieved without step-out by performing φ excitation instead of the φ1°-φ2″ excitation that would normally continue.

In this case, a two-phase stepping motor was used to drive the platen recording medium, and one-phase/two-phase excitation was performed, but various modifications can be made to the number of phases of the motor, the excitation method, etc.

Further, various modifications can be made to the dimensions of the platen, the number of stages of the reduction gear, the reduction ratio, etc.

[Effects of the Invention] As described above, according to the conventional stepping motor control method in a line dot thermal printer, once the excitation is cut off, the motor rotor is is turned in the opposite direction, causing the stepping motor to go out of step.

In contrast, in the present invention, the return angle at which the magnet is turned in the opposite direction is confirmed in advance, and the excitation is controlled to be performed from the front by the return angle.

By doing this, step-out of the stepping motor is prevented, and as a result, the platen is driven normally, the paper feed of the recording medium is also normal, and printing jams can be prevented.

In this way, the present invention greatly contributes to improving the print quality of line-dot type thermal printers, and furthermore contributes to further expanding the applications of thermal printers.

[Brief explanation of the drawing]

Fig. 1 is a detailed explanatory diagram of the present invention, Fig. 2 is a partially enlarged view of Fig. 1, Fig. 3 is a configuration diagram of the drive system in a line dot thermal printer, and Fig. 4 is based on the restoring force of the rubber part. 5 is a schematic sectional view of the motor, FIG. 6 is a motor drive sequence, and FIG. 7 is a printing result using a conventional control method. In the figure, 2 is a stepping motor (motor), 2 is a platen, 3 is a recording medium, 4 is a thermal head, and 5 is a reduction gear. Line g-J Punishment-7) Rare link (Komukeu made moving thread j Nagisa (He figure 3 Figure rubber 1! 1 [2] Figure 1: 17) Department of Hirohito, Figure 2: Mork / 7th edition E-opening drawings, 5, Figure 1-2, Rhythm Sequences Figure 6 Conventional n-type Igi P Power Swimming Printing Chart Diagram

Claims (1)

[Scope of Claims] A platen (2) rotationally driven by a stepping motor (1), and a line dot type thermal head (4) that comes into elastic contact with the platen (2) via a recording medium (3). A method for controlling a thermal printer having a thermal printer, wherein when restarting the stepping motor (1), the platen (1) is
2) by the return angle θ at which the stepping motor (1) rotates in reverse due to the restoring force of the bending of the rubber portion (22);
A method of controlling a thermal printer characterized by controlling the excitation phase by returning it.