JPS6333462B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a dot printer in which a print head placed on a carriage reciprocates along a platen via the carriage to print on print paper.

Prior Art In conventional dot printers, a carriage is moved back and forth at a constant speed using a DC motor, and a print head placed on the carriage is brought in at a predetermined timing to print on printing paper. Ta.

Therefore, if the moving speed of the carriage and the timing of the printing operation of the print head operate as preset, a well-proportioned and high-quality character M will be printed as shown in FIG. 1A. However, if the DC motor used to move the carriage forward changes its driving characteristics due to long-term use, that is, if the rotational speed becomes faster than originally, and the moving speed of the carriage becomes faster, Since the timing of the printing operation of the print head does not change from the beginning, the character M shown in FIG. 1A as shown in FIG.
A character M1 that is long horizontally is printed compared to , and conversely, when the rotation speed becomes slower than the initial speed and the moving speed of the carriage becomes slower, a character M2 that is shorter horizontally is printed as shown in Figure 1C. Therefore, it was not possible to obtain a certain high print quality.

Further, even when the moving speed of the carriage changes during printing operation due to changes in the load while the DC motor is being driven, it is not possible to print the letter M with a constant high print quality in the same manner as described above. Ta.
Furthermore, since the drive characteristics of each DC motor vary, it is necessary to adjust the timing of the printing operation of the print head for each dot printer.
In order to obtain a certain level of high printing quality, advanced technology and precision were required.

Purpose An object of the present invention is to eliminate the above-mentioned defects, and to maintain printing even when the moving speed of the carriage changes based on fluctuations in the driving characteristics of the motor, fluctuations in load, and variations in the driving characteristics of individual motors. prevent disturbance,
To provide a dot printer that can obtain constant high print quality.

Embodiment An embodiment of a dot printer embodying the present invention will be described below with reference to the drawings.

In FIG. 2, a platen 1 is arranged on a printer frame (not shown), and a pair of guide rods 2 are arranged on the machine frame at a predetermined interval so as to be parallel to the platen 1. ing. A carriage 3 is supported on the guide rod 2 so as to be able to reciprocate, and a printing head 4 is placed on the upper surface of the carriage 3. This printing head 4 is equipped with a plurality of plunger-type electromagnetic solenoids (not shown) and printing needles 5 corresponding to them, and as the electromagnetic solenoids are selectively energized, appropriate printing needles 5 are driven.
onto the printing paper 7 on the platen 1 via the ribbon 6,
Numbers or symbols are printed in a dot matrix pattern. The driving timing of the printing needle 5 in accordance with the selective energization of the electromagnetic solenoid, that is, the timing of the printing operation is determined based on a control circuit to be described later.

A direct current motor 8 capable of forward and reverse rotation is fixed on the right machine frame, and a pulley 9 is attached to its drive shaft so as to face the center position on the right side of the carriage 3. Similarly, a freely rotatable driven pulley (not shown) is provided on the left machine frame at a position opposite to the pulley 9. The transfer belt 10 stretched between the pulley 9 and the driven pulley has one end located at the center position on the right side of the carriage 3.
The other ends are fixed to the center position of the left side of the carriage 3, respectively. Therefore, the DC motor 8
When the carriage 3 is driven in the forward and reverse directions, the carriage 3 is reciprocated in the left-right direction along the guide rod 2.

A detector 12 for detecting the moving speed of the carriage 3 is provided on the lower right side of a detector base 11 attached to the rear lower surface of the carriage 3. The detector 12 is composed of a light emitting part 12a made of a light emitting element such as a light emitting diode, and a light receiving part 12b made of a light receiving element such as a phototransistor. They are arranged to face each other at intervals. Further, a large number of cords 13 are attached to the upper surface of the detector base 11, and signals for driving the electromagnetic solenoid, detection signals from the detector 12, etc. are inputted and outputted via these cords 13.

The light emitting part 12a and the light receiving part 12b of the detector 12
A plate-shaped object to be detected 14 is disposed between the two, and both ends thereof are fixed to the machine frame. And the third
As shown in the figure, rectangular detection holes 15 are transparently provided at both left and right ends of the detection object 14.
In this embodiment, in order to use the inner opening edges 15a of the platen 1 as indicators for stopping the carriage, the inner opening edges 15a of the platen 1 are formed to be located relatively inward from both ends of the platen 1, respectively.

A measurement slit 16 is transparently provided on the right side of the left detection hole 15, and the measurement slit 16 is located to the left of the printing operation start position of the print head 4 relative to the platen 1, and is located at the inner opening of the left detection hole 15. The relative distance l to the hole edge 15a is defined as the measurement distance.

Therefore, when the DC motor 8 moves the detector 12 along with the carriage 3 along the platen 1 from the left end to the right end, the detector 12 outputs a detection signal SG1 as shown in FIG. .
That is, when the detector 12 passes the inner opening edge 15a of the left detection hole 15, the output signal SG1 falls from a positive potential (hereinafter referred to as H level) to zero potential (hereinafter referred to as L level), and then the output signal SG1 falls to zero potential (hereinafter referred to as L level).
passes through the measurement slit 16, the output signal
SG1 goes from L level to H level and immediately goes to H
When the level changes from the level to the L level, the detector 12 outputs a pulse with a short pulse width. When the detector 12 passes through the inner opening edge 15a of the right detection hole 15, the output signal SG1 rises from the L level to the H level.

Next, an electric circuit for controlling the timing of the printing operation of the print head 4 in the dot printer constructed as described above will be explained based on the electric block circuit shown in FIG.

This electric circuit is broadly divided into a timing generation circuit 21 that generates a dot timing signal SG2 for driving the printing needle 5 and performing a desired printing operation, a measurement circuit 22 that measures the moving speed of the carriage 3, A dot timing signal SG2 output from the timing generation circuit 21 based on the moving speed measured by the measurement circuit 22.
and a control circuit 23 that controls the cycle of. Therefore, first, the timing generation circuit 21 will be explained.

Timing generation circuit The timing generation circuit 21 is a clock oscillator 24
and a timing signal generation circuit 25. The clock oscillator 24 generates a clock signal SG3 having a very high clock frequency as shown in FIG.
is output to the timing signal generation circuit 25. The timing signal generation circuit 25 includes a frequency dividing circuit, and receives a control signal SG4 from the control circuit 23, which will be described later.
The frequency division ratio of the frequency divider circuit is changed based on the clock signal.
SG3 is frequency-divided and output as a dot timing signal SG2 as shown in FIG.

Measuring Circuit The measuring circuit 22 includes the detector 12 and the counter 26.
It is made up of The counter 26 receives the clock signal SG3 from the clock oscillator 24 and the detection signal SG1 from the detector 12, and as the carriage 3 moves, the detector 12 detects the inner opening edge 15a of the left detection hole 15. passing through
From the time when the detection signal SG1 falls from the H level to the L level until the time when the detector 12 passes through the measurement slit 16 and the detection signal SG1 rises from the L level to the H level (required to move the measurement distance l). It is designed to count how many times the clock signal SG3 is inputted during a period of time).
Then, the number of clock signals SG3 counted by the counter 26 is measured as the actual moving time (that is, the actual moving speed) of the carriage 3, and the counted number of clock signals SG3 is sent to the next stage control circuit 23. Output.

Control Circuit The control circuit 23 consists of a timing signal control circuit 27 and a reference time setting circuit 28. The reference time setting circuit 28 stores the time required to move the measured distance l when the DC motor 8 is normally driven and the carriage 3 is reciprocated at a predetermined moving speed (the actual speed) is the reference time (i.e. the reference moving speed of carriage 3)
The reference moving speed is set as a BCD code signal and output to the timing signal control circuit 27. Then, the timing signal control circuit 27 compares the reference moving speed from the reference time setting circuit 28 with the actual moving time of the carriage 3 from the counter 26, and
Quantitatively calculate how fast or slow the actual moving speed is relative to the reference speed, and calculate the quantitative value.
The signal is converted into BCD code and outputted to the timing signal generation circuit 25 as a control signal SG4.

Therefore, in the frequency dividing circuit of the timing signal generating circuit 25, when the actual moving speed of the gear carriage 3 is faster than the reference speed, the control signal SG4 is
Based on this, the frequency division ratio is increased, and the period T of the dot timing signal SG2 output from the timing signal generating circuit 25 becomes shorter than the actual moving speed of the carriage 3. Conversely, if the actual moving speed is slower than the reference speed, the control signal SG4
The frequency division ratio is lowered based on , and the period T of the dot timing signal SG2 becomes longer relative to the actual moving speed.

Then, the dot timing signal SG2 from the timing signal generation circuit 25 is sent to the print control circuit 2.
9 is output. This printing control circuit 29 excites an appropriate number of electromagnetic solenoids selected based on a control signal from another control device (not shown) in synchronization with the dot timing signal SG2, and selects the electromagnetic solenoid. A printing signal SG5 is outputted so as to drive an appropriate printing needle 5 in accordance with the target bias. In the printing control circuit 29 of this embodiment, a detection signal SG1 is output when the detector 12 passes through the measurement slit 16, as shown in FIG.
Based on this signal, the print head 4 starts printing after a certain period of time from that signal, and from then on, among the dot timing signals SG2 that are sequentially input to the print control circuit 29, the 6×nth (n is integer)
The dot timing signal SG2 with the signal SG2 erased is output as the print signal SG5.
With these five print signals SG5, one character M is formed as shown in FIG. 1A. Further, when the print control circuit 29 completes a predetermined number of prints, it becomes inactive and is controlled not to output the print signal SG5.

Next, the operation of the electric circuit configured as described above will be explained.

Now, if the carriage 3 is positioned relative to the left end of the platen 1 and the DC motor 8 is driven,
The carriage 3 starts moving to the right. Simultaneously with the start of driving of the DC motor 8, the clock oscillator 24 generates a clock signal SG3.

When the DC motor 8 rotates at a constant speed, the moving speed of the carriage 3 also becomes constant. When the carriage 3 moving to the right at a constant speed passes the inner opening edge 15a of the left detection hole 15, the detection signal SG1 from the detector 12 changes from the H level to the L level.
When the level falls, the counter 26 starts counting the clock signal SG3, and continues counting until the carriage 3 passes through the measuring slit 16. Immediately after the carriage 3 passes through the measurement slit 16, the counter 26 outputs the counted value to the timing signal control circuit 27. As a result, the timing signal control circuit 27 compares and calculates the actual moving speed of the carriage 3 with the reference speed, and outputs the variation in the actual moving speed with respect to the reference speed to the timing signal generating circuit 25 as a control signal SG4.

The timing signal generating circuit 25, which receives the control signal SG4, outputs a dot timing signal _SG2 corrected to a pulse period T corresponding to the actual moving speed of the carriage 3. Then, after a predetermined period of time, the next-stage print control circuit 29 operates, and the print signal SG5
Based on this, the print head 4 starts printing operation.

Therefore, the dot timing signal SG2 is corrected to a period T relative to the actual moving speed, and the dot timing signal SG2 is corrected to a period T relative to the actual moving speed of the carriage 3. Even if the moving speed of the printer changes, the disturbance of printing as shown in FIGS. 1B and 1C does not occur.

Eventually, when a predetermined number of prints are completed, an operation stop control signal is input to the print control circuit 29 from another control device (not shown), and the print head 4 stops its print operation. Then, when the carriage 3 further moves to the right with the printing operation stopped and passes the inner opening edge 15a of the detection hole 15 on the right side, the detection signal SG1 of the detector 12 changes from the L level to the H level. The DC motor 8 is stopped based on the rising signal, and immediately after the stop, the carriage 3 is driven in the reverse direction to return it to its original position on the left side. While the carriage 3 is moved to the left, the print head 4 is not operated for printing.

Then, when the carriage 3 is moved to the left and passes through the inner opening edge 15a of the detection hole 15 on the left side, the detection signal SG1 of the detector 12 rises from the L level to the H level, and based on the rising signal, The DC motor 8 is stopped, and after the carriage 3 is stopped at its original position, it is immediately driven in normal rotation to start the next printing operation.

In this way, in the unidirectional printing method, the actual moving speed of the carriage 3 is measured before the printing operation of the print head 4 for each printing line starts, and the period T of the dot timing signal SG2 is adjusted relative to this actual moving speed. As a result, even if the drive characteristics of the DC motor 8 change due to long-term use, there is no disturbance in the printing, and characters, etc. of constant high quality are printed on each printing line of the printing paper 7 at all times. can be done.

Note that the present invention is not limited to the above-mentioned embodiment, and in the case of a bidirectional printing type in which the printing operation is performed even when the carriage 3 moves back to the left as shown in FIG. As shown in FIG. 7, a slit 16a similar to the measurement slit 16 is provided on the left side of the right side detection hole 15 of the object 14 to be detected, and this slit 16a and the right side detection hole 1 are transparently provided.
detecting the actual transfer speed when the carriage 3 moves backward in the left direction between the carriage 3 and the inner opening edge 15a of the carriage 3;
The period T of the dot timing signal SG2 may be controlled. Therefore, this embodiment is effective when the drive characteristics of the DC motor 8 are different when the DC motor 8 is driven in normal rotation and when it is driven in reverse.

Further, as shown in FIG. 8, a large number of measuring slits 16 are provided at equal intervals, and the actual moving speed of the carriage 3 is measured for each printing position at any time during forward movement or during forward and backward movement, thereby determining the dot timing. signal sg
The period T of 2 may be modified as needed. Therefore, in this case, when the carriage 3 reciprocates along the guide rod 2, it is possible to compensate even when the moving speed changes based on a change over time in the frictional resistance between the carriage 3 and the guide rod 2. Similarly, the transfer speed may be measured only between predetermined printing positions.

In addition, in FIG. 4, except for the detector 12, a clock oscillator 24 and a timing signal generating circuit 25 are provided.
It is also possible to miniaturize the entire electrical circuit by using a microcomputer that incorporates each circuit such as the following.

Furthermore, as shown in FIG. 9, the drive shaft of the DC motor 8 is connected to one end of a cylindrical cam 32 provided with an endless cam groove 31, and the cam groove 31
In a dot printer of the type in which the carriage 3 is reciprocated only by the forward rotation of the DC motor 8 via the follower 33 that engages with the follower 33, there is a motor stopper on both the left and right ends of the detected object 15, as in the above embodiment. There is no need to provide a detection hole 15, and one reciprocation time of the carriage 3 can be measured using only the detector 34 that indicates the left end printing position. Furthermore, as shown in FIGS. 3, 7, and 8, the carriage 3 may be moved back and forth without any printing operation after the printer is powered on without providing the measuring slit 16 for measuring the moving speed. Accordingly, the actual moving speed may be measured based on the time required for the carriage 3 to move between the inner opening edges 15a of the left and right detection holes 15, without departing from the spirit of the present invention. It is also possible to arbitrarily change the range.

Effects As detailed above, the present invention includes a platen 1 on which a printing paper 7 having a large number of printing positions is mounted in a printing line, a printing head 4 having a plurality of printing needles 5, and a printing paper 7 on a printing line. A dot timing signal for driving the carriage 3 to move each printing position and the printing needle 5 to perform a desired printing operation.
The dot printer includes a timing signal generating circuit 25 that generates SG2, a measuring circuit 22 that measures the moving speed of the carriage 3, a clock oscillator 24, and a clock oscillator that measures the moving speed of the carriage 3 based on the moving speed measured by the measuring circuit 22. By changing the division ratio of the clock signal SG3 from the oscillator 24,
A control circuit 23 is provided for controlling the timing signal generation circuit 25 to output the dot timing signal SG2, and by preventing disturbances in printed dots due to changes in the moving speed of the carriage 3, fluctuations in the driving characteristics of the motor, Even if the moving speed of the carriage fluctuates due to changes in load or variations in the drive characteristics of individual motors, it has the excellent effect of preventing irregularities in printing and ensuring consistently high printing quality. be.

[Brief explanation of the drawing]

1A, B, and C are characters printed on printing paper to explain this invention, FIG. 2 is a perspective view of the main part of a dot printer showing an embodiment embodying this invention, and FIG. 3 is a Similarly, the front view of the detected object, the fourth
The figure also shows an electric block circuit diagram, FIG. 5 is an explanatory diagram showing the relative relationship between the signals output from each electric block circuit and the moving speed of the carriage, and FIG. 6 shows the moving speed of the carriage showing another example of this invention. 7 is a front view of the detected object, and FIG. 8 is a front view of the detected object showing another example of the present invention.
FIG. 9 is a front view of a cylindrical cam showing another example of the present invention. Platen...1, Carriage...3, Printing head...4, Printing needle...5, Printing paper...7, DC motor...8, Timing generation circuit...21, Measuring circuit...22, Control circuit... ...23, Print control circuit...29.

Claims (1)

[Claims] 1. Printing paper 7 having multiple printing positions in a printing line
a carriage 3 on which a printing head 4 having a plurality of printing needles 5 is mounted and moving to each printing position on the printing paper 7; and a carriage 3 that drives the printing needles 5 to perform a desired printing operation. A dot printer comprising a timing signal generation circuit 25 that generates a dot timing signal SG2 for performing a dot printing operation, a measurement circuit 22 that measures the moving speed of the carriage 3, a clock oscillator 24, and a movement measured by the measurement circuit 22. Based on the speed, the frequency division ratio of the clock signal SG3 from the clock oscillator 24 is changed to generate the dot timing signal SG from the timing signal generation circuit 25.
2. A dot printer comprising: a control circuit 23 for controlling the dots so as to output the dots 2, and preventing the printed dots from being disturbed due to changes in the moving speed of the carriage 3.