JPS5993368A - Thermal printer - Google Patents

Abstract

PURPOSE:To simplify the constitution of a thermal printer by providing a drive pulse control means by which the width of drive pulse supplied to the thermal head is directly proportioned to that of pulse signal sent out of an encoder, and the voltage value is inversely proportioned to the interval of the pulse signals. CONSTITUTION:By an applied voltage control circuit 7 for a thermal head, the width of drive pulse sent out from a thermal head drive circuit 8 is controlled to be proportioned to the width of pulse signal sent out from an encoder 4, and also the voltage value of the drive pulse is controlled to be inversely proportioned to the intervals of pulse signals on the basis of the output characteristics of moving speed-applied voltage. An optical slit 6 has large numbers of slits 6a of an interval dimension Ld which is equal to the dot interval in the sideward direction of the 24X24 dot matrix, and the width dimension Lt is set up such that the passage time of light becomes equal to electrification time to thermal bead 3, requiring in the printing of one dot row, in case where the thermal head 3 is operated for printing at a rating speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates (1) to a thermal printer that sequentially performs printing by feeding drive pulses to the thermal head while moving the thermal head along print lines on a recording medium.

[Prior art]

This type of conventional thermal printer generates a pulse signal as the thermal head moves from an encoder based on an optical signal from an optical slit having slits with the same spacing as the printing dot spacing, and drives the thermal head in response to this pulse signal. A driving pulse of constant width and constant voltage is generated from the circuit, and this driving pulse is supplied to the thermal head to execute the printing operation. However, if the moving speed of the thermal head changes, the printing dots The size and shading of the image also change, resulting in a problem of deterioration of print quality.

For this reason, conventionally, a motor that processes the pulse signal from the encoder to generate a control signal, and supplies this control signal to a motor drive circuit of a motor that drives the thermal head to control the thermal head at a constant speed. Although a control circuit is provided, a motor control circuit using such feedback control has a problem that the configuration is complicated and expensive.

(2) [Purpose] The present invention has been made in view of the above circumstances, and its purpose is to achieve high printing quality even if the motor that drives the thermal head is controlled in an oven loop. To provide a thermal printer that does not require feedback control, has a simple configuration, and can be made at low cost.

〔Example〕

A first embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

First, the overall configuration will be described with reference to FIGS. 1 to 3. 1 is a motor driven by open loop control by a motor drive circuit 2, which is connected to a thermal head 3.
is moved along a printing line of a thermal printing paper (not shown) which is a recording medium. In this case, the thermal head 3 is of a 24-dot type in which, for example, 24 light-emitting elements are arranged in one vertical line, and is moved, for example, 24 times in the horizontal direction, which is the moving direction, so that the thermal head 3 has an i-direction of 24×24. Dora(
3) It prints a single character such as a kanji character using tomatrix. Reference numeral 4 denotes an encoder which together with the motor 1 and the thermal head 5 constitutes the printing section 5, and is adapted to be moved together with the thermal head 3. The encoder 4 outputs a pulse signal by receiving an optical signal from the optical slit 6 as the thermal head 3 moves. In addition, as shown in FIG. 2, there are six optical slits, and a large number of slits 6a whose spacing dimension Ldl is equal to the horizontal dot spacing of a 24×24 dot matrix, whose width dimension Lt is rated for the thermal head 5. Thermal head 3 requires light passing time to print one dot row when printing at high speed.
The time is set to be equal to the energization time. Reference numeral 7 denotes a thermal head applied voltage control circuit serving as a drive pulse control means, which generates a fil+ signal in response to a pulse signal from the encoder 4, and applies a drive pulse to the thermal head 3 based on this control signal. It controls the thermal head drive circuit 8 that supplies power. This is detailed (
4) In other words, the thermal head applied voltage control circuit 7 controls the width of the drive pulse output from the thermal head drive circuit 8 so that it is proportional to, for example, equal to, the width of the pulse signal output from the encoder 4. The voltage value of the drive pulse is controlled so as to be inversely proportional to the interval of the pulse signal based on the output characteristic of moving speed versus applied voltage as shown in FIG.

Next, the operation of this embodiment will be explained with reference to FIG. 4.

First, when the thermal head 3 is moved at a large speed V, & as shown in FIG.
), pulse signals Pa& of 827 widths Tta and intervals Tda corresponding to the speed va are output.

The thermal head applied voltage control circuit 7 to which this pulse signal P4a is applied operates at an interval T of the pulse signal P4a.
Calculate the speed va from ta, set the applied voltage value Va based on the output characteristics shown in FIG. 3 from this speed V&, and set the applied voltage value Va based on the output characteristics shown in FIG.
G) (5) Pulse signal 9 to the thermal head drive circuit 8 P4'
The drive pulse P1. has an energization (on) time equal to the pulse width Tta of P1. The drive pulse Psa is now controlled so that the pulse a appears at
When power is supplied to the thermal head 3, the thermal head 3 becomes a printer 9 that performs printing operations on thermal printing paper one after another.

During the printing operation by the thermal head 3 as described above, in case the moving speed of the thermal head 3 changes to a small speed vb as shown in FIG. As shown in b), a pulse signal P4b with a pulse width Ttb corresponding to the speed vb and an interval Tdb is output. In this case, the pulse width Ttb of the pulse signals P, b is also large (pulse width TtaxJ) of the pulse signals P, a mentioned above (
Ttb > Tta) and the interval T'db is the interval Td
It is clear that a and shi are also large (Tdb) Tda). The thermal head applied voltage control circuit 7 to which the pulse signal P4b is applied receives the pulse signal P4b.
Calculate the speed vl from the interval Ttb of Pulse width T of pulse signal P4b is applied to circuit 8.
Control is now performed so as to output a driving pulse P8b having an energization time equal to tb and having an applied voltage value vb,
These driving pulses P and b are supplied to the thermal head 3, so that the thermal head 3 performs a printing operation on the thermal printing paper one by one.

As described above, according to the present embodiment, the radiation Tta of the drive pulses P, a, Pl, and b supplied to the thermal head 3.

Ttb is the pulse signal P, a output from the encoder 4
, P4b and the applied voltage value Va
, Vb to the pulse signal P4a+''4b(7) interval Tda.

Since it is inversely proportional to Tab, when the moving speed of the thermal head 3 is high, the energization time to the thermal head 3 is short and the applied voltage value is large, and conversely, when the moving speed of the thermal head 3 is small. When this happens, the thermal head 3 can be energized for a long time and the applied voltage can be controlled to be small. Therefore, regardless of the moving speed of the thermal head 3, the size and density of the printed dots can be controlled to be approximately the same. It is possible to achieve high printing quality at a constant rate (A), and as a result, it is possible to perform feedback control to always keep the speed of 1)-v-1 (speed of the thermal head 3) constant, which is different from the conventional method. There is no need to provide a motor control circuit for controlling the motor 1, and it is sufficient to simply control the motor 1 in an oven loop, which makes the configuration simple and inexpensive.

5 and 6 show a second embodiment of the present invention, and the same parts as in the previous embodiment are denoted by the same reference numerals, and only the different parts will be explained below.

That is, in this embodiment, the slit 6a in the optical slit 6 is divided vertically into odd-numbered slits 6al and even-numbered slits 6aI, and the optical signal detection circuit in the encoder 4 is installed in the slits 6al and 6a2, respectively. The corresponding optical signal detection circuits are divided into upper and lower parts 41+42,
Further, in place of the thermal head B, a first thermal head 31 for the vertical odd-numbered printing dot rows and a second thermal head 31 for the vertical even-numbered printing dot rows 3. The optical signal detection circuit 4 of the encoder 4 is configured to sequentially supply drive pulses (8) based on the light reception signals of the encoder 4 to the first and second thermal heads 31 and 3t, respectively. .

In FIG. 6, reference numeral 9 denotes a carriage that is inserted and supported by the guide rod 10 so as to be movable in the left and right direction, and the aforementioned encoder 4, thermal head 31+3□, etc. are mounted on this carriage.

This second embodiment can, of course, provide the same effects as the previous embodiment, and since driving pulses are alternately applied to the thermal heads 31 and 32, the carriage 9 can move at high speed. Even if the printer is moved at a certain angle, the printing operation can be sufficiently followed, and therefore, there is an advantage that a high printing speed can be achieved.

FIG. 7 shows a third embodiment of the present invention. The same parts as in the second embodiment are designated by the same reference numerals, and only the different parts will be described below.

That is, in this embodiment, the optical slit 6 has a large number of vertically long slits 6b with a width dimension Lt and an interval dimension 2n.
d, and the optical signal detection circuit 'le' of the encoder 4! (9) are arranged with a distance Ld in the direction of movement, and with this also the same effects as in the second embodiment can be obtained.

It should be noted that the present invention is not limited to the embodiment described above and shown in the drawings, but can of course be implemented with appropriate modifications within the scope of the invention.

〔effect〕

As explained above, the present invention provides drive pulse control in which the width of the drive pulse supplied to the thermal head is directly proportional to the width of the pulse signal output from the encoder, and the voltage value thereof is inversely proportional to the interval between the pulse signals. Since the structure is provided with a means, thermal/"-"/)"tIKi21
Even if the motor used for printing is subjected to open-loop control, the print dot size and shading can always be kept approximately constant regardless of the moving speed of the thermal head, resulting in high printing quality. It is possible to provide a thermal printer that does not require feedback control, has a simple configuration, and can be made at low cost.

[Brief explanation of the drawing]

(10) Figures 1 to 4 show a first embodiment of the present invention.
The figure is an overall block diagram, Figure 2 is a partial front view of the optical slit, Figure 3 is an output characteristic diagram of the thermal head applied voltage control circuit, and Figures 4 (a) to (0) are waveforms for explaining the operation. 5 and 6 show a second embodiment of the present invention, FIG. 5 is a partial front view of the optical slit along with the arrangement of the encoder, and FIG. 6 is a partial front view of the thermal head portion. 7 is a rear view, and FIG. 7 is a view corresponding to FIG. 5 showing a third embodiment of the present invention. In the drawings, 1 is a motor, 3 and 31+32 are thermal heads, 4 is an encoder, 6 is an optical slit, 7 is a thermal head applied voltage control circuit (drive bus control means), and 8 is a thermal head drive circuit. (11)

Claims (1)

[Claims] 1. In a thermal printer that moves a thermal head along the printing line of a recording body using an open-loop controlled motor and supplies power to the thermal head with driving pulses to print sequentially, as the thermal head moves, an encoder that outputs a pulse signal, and the width of the drive pulse supplied to the thermal head is made proportional to the width of the pulse signal output from the encoder, and the voltage value is inversely to the interval of the pulse signal output from the encoder. A thermal printer characterized in that it is provided with drive pulse control means for proportionality.