JPS6239112B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a print position control method during reciprocating movement of a print head in an impact printer, a non-impact printer, or the like.

Known impact printers include wire dot printers, and non-impact printers include thermal printers and inkjet printers. Printing in these printers involves moving a carriage equipped with a print head back and forth in the horizontal direction while facing the print paper, and using a print timing signal generated by some method as a trigger to drive a wire or emit ink droplets, resulting in a dot. A collection of characters or figures is formed on printer paper. Therefore, the image quality of printed characters or figures is determined by whether or not the dot printing positions of wires and ink droplets can be accurately spaced at regular intervals during reciprocating movement.

In the past, various proposals have been made regarding the generation method of the print timing signal to obtain good print image quality.The first is a method in which it is generated in synchronization with the rotation of the motor, which is the drive source for the horizontal movement of the carriage. In this method, a rotary encoder is attached to the motor rotation shaft or a part of the transmission system, and the pulse signals generated by the rotation of the rotary encoder are basically used. The second method is to make the printing correspond to the printing density as shown in FIG. 1, or to print by using a film (printing indicator plate) 1 with markings 1a at every integer fraction of the printing density, facing the direction of carriage movement. There is a method based on which the markings 1a of the print index plate 1 are read over the entire width by optical or magnetic means as the carriage moves, and a print timing signal is generated.

However, these methods have the following problems. The biggest problem with the first method, that is, the method of using a rotary encoder as a printed index, is that since the position of the carriage is not directly detected, there is a transmission between the rotary encoder mounting shaft and the horizontal movement of the carriage. The problem is that the dot misalignment and position errors caused by vibrations and slippage occurring in the system are large. This causes the image quality to deteriorate significantly over time. Furthermore, since the encoder disk cannot be made very large, it is necessary to make several or even tens of revolutions for one scan of the carriage, resulting in problems such as complicated control.

On the other hand, in the second method, that is, the method using a printed indicator board installed along the carriage path, the dot spacing is usually 1/120 inch in pica letters, so the width of indicators 1a and 1b is 1/60 inch or 1/2 inch. /12
0 inches. The width of indicators 1a and 1b is 1/6
If the printing timing signal is created using a 0 inch one, the signal actually used as the printing timing signal needs to be electrically processed to have a repetition frequency twice as high as the repetition frequency of the signal read from the index plate 1. Therefore, when there is a sudden change in the moving speed of the carriage or when the carriage moves while hunting, the dot spacing becomes uneven. Therefore, it is better to set an index with a width of 1/120 inch and print all dots using the original timing signal read from the index, since it is possible to obtain a print timing signal that corresponds to changes in carriage movement. Good quality characters or figures can be obtained. On the other hand, in order to increase the overall printing speed of the printer, it is possible to print during both forward and return scanning of the carriage, and to use the shortest distance printing method, which means that the carriage stops immediately after printing all the print data in the line. Based on that point, the carriage approaches the next line's print start position or print end position, whichever is closer, depending on the number of print data on the next line, and then moves the carriage forward or backward from that position. A method has been proposed in which the overall printing speed is increased by minimizing wasted movement time in the margin area by printing while moving the paper. When employing such a printing method, it is essential to accurately detect the stop position of the carriage. However, when using an index plate like the one shown in Figure 1, the photo sensor becomes index 1 due to hunting of the carriage that occurs when the carriage stops and starts.
The carriage moves back and forth between a and 1b many times, and the sensor generates a large number of signals during this period, making it impossible to accurately detect the position of the carriage. Therefore, in order to avoid this problem, conventionally, the index plate shown in FIG. 2 has been used. In other words, in addition to indicators 2a and 2b corresponding to the printing density of dots, which are printing constituent units, position indicators 3 are arranged at the same width as indicator 2b and at intervals of pica character units, that is, at intervals of 1/10 inch. The control is performed so that the position indicator 3 always stops at the center between the position indicator 3 and the adjacent position indicator 3. Therefore, if the distance from when a stop command is input until the carriage actually stops, that is, the run-up distance, is longer by one character or more due to a difference in the drive system, determining the interval of the position index 3 will be approximately the same depending on the drive system, etc. This is approximately twice the run-up distance that can be kept constant. In other words, the position index interval is always set wider than the run-up distance, and the movement control is such that when a stop command is input, the carriage stops at the center of position index 3, and then is accelerated by driving in the opposite direction, with the first position index detected as a reference. control the printing position on the return path to that position on the outward path. As a result, the problems that occurred when using the index plate shown in FIG. 1 could be avoided. However, a new problem arises here. In other words, when the moving speed of the carriage is increased in order to further improve the overall printing time, if the conditions related to inertial force, such as the weight of the print head and cartridge, and the sliding resistance between the carriage and the moving support rod, are kept constant. The length of the run-up distance increases in proportion to the acceleration. In the method shown in Fig. 2, the position indicators 3 are installed at intervals twice the run-up distance, so as the run-up distance becomes longer, the position indicators 3
The interval between them will inevitably become wider. As a result, the third
As shown in the figure, if the printing 4a ends immediately after passing the position indicator 3a, in the conventional method, that is, the method of always setting the interval between the position indicators 3a at an interval twice the run-up distance, the carriage starts decelerating before printing. Since it starts from the time when the first position index 3a' is detected after the end of the run, the part corresponding to _l2 in FIG. 3 becomes the run-up distance. Therefore, _l1 is the part where printing is not performed, and the longer this run-up distance becomes, the more this negative factor increases, and even if the carriage movement speed is increased, the overall printing time cannot be effectively shortened The effect is reduced. On the other hand, in order to keep this run-up distance constant even as the speed increases, it is necessary to use a drive source, that is, a motor with a high output power, and to strengthen the braking force. However, as a result, the motor drive circuit and its power supply need to have a very large capacity, which inevitably lowers cost performance. An even bigger drawback is that a sudden braking force is constantly applied to the carriage, which increases the shock and vibration applied to the head. For example, in the case of an inkjet head, especially a stem type inkjet head, this shock and vibration manifests itself in the phenomenon of air bubbles being mixed into the head or unnecessary ink droplets being ejected, resulting in a loss of printer functionality. becomes. The present invention has been made to solve the above problems, and uses a printing index equal to the dot density, which is a printing pixel unit, and a position index provided at an interval that is an integral multiple of this, to move a printing head that moves horizontally back and forth. The object of the present invention is to obtain an economical printer with excellent image quality, which can print at high speed without being affected by position detection errors caused by hunting or the like in position detection. The present invention will be explained in detail below using the drawings.

Fig. 4 shows the method of installing position indicators according to the present invention, and shows an indicator (second position indicator) corresponding to each printed dot.
2a and 2b in the figure) are omitted in the drawing. In other words, the relationship between the interval l between the position indicators 3b and the run-up distance l ₂ ′ (l ₂ ′=l ₂ ) is the interval l between the position indicators 3b.
The distance between the position marks is set and the drive is controlled so that the carriage is always narrower than the run-up distance l ₂ ', and the carriage stops or turns around near the center of any position mark and its adjacent position mark. Therefore, since the number of position indicators 3b included in the run-up distance l ₂ ' section is plural, the printing position control method in this system is also different from that in the system shown in FIG. The minimum interval between the position indicators 3b in the present invention is determined by taking into account the amount of hunting at the stopping or turning point, the accuracy of the run-up distance l ₂ ' caused by structural and mechanical factors, and the like, plus a margin.

Next, the print position control operation according to the present invention will be explained based on FIG. The carriage, which moves horizontally at high speed, is equipped with two optical sensors.
That is, a sensor 11 for reading a print index for each print dot unit (not shown in FIG. 4, but corresponds to FIGS. 2a and 2b), a sensor 11 corresponding to an integral multiple thereof, and the method described above. A sensor 12 for reading the position index 3b determined in is provided. In response to a print start command, the print indicators 2a and 2b are read by the sensor 11, and the print timing signal (hereinafter referred to as a dot clock) obtained by waveform shaping by the waveform shaping circuit 13 controls the print control circuit 14 to generate characters corresponding to the print signal. , print out figures, etc. At this time,
A position timing signal (hereinafter referred to as a marker clock) generated by reading the position index 3b by the sensor 12 and shaping the waveform by the waveform shaping circuit 15 is ignored.
When the forward printing is completed and a printing end command is issued, the printing operation is stopped, the counter 16 is set, and the dot clock starts counting from the next dot clock, and continues counting until the marker clock is input from the waveform shaping circuit 15. Continue. That is, the number of printed indicators included in _l1 shown in FIG. 4 is counted. When the marker clock is input, the counter 16 stops counting and holds its contents.

On the other hand, when the marker clock is generated, the carriage deceleration device 17 starts decelerating the carriage, and the run-up distance (corresponding to l ₂ ' in FIG. 4) starts. In this embodiment, the stop position of the carriage is determined by a tachometer generator. That is, the counter 18 adds up the number of position indicators included in the run-up distance until the stoppage of the carriage is detected, and calculates the stopped state of the carriage that has stopped between the last counted position indicator and the adjacent position indicator. Detected by tachogenerator. Next, the carriage accelerator 20 moves the carriage from deceleration to acceleration, and the counter 21 adds up the position index in the acceleration run-up section, and this is the number of position indexes added in the deceleration run-up section, that is, the counter 18
The counter 23 counts the printed index, ie, the dot clock, from the point where the content matches the content of the dotted line.

22 is a matching circuit. Note that the count of the marker clock in the carriage acceleration run-up section is added to the counter 18 without using the counter 21, and the contents of the counter 18 are subtracted.
The counter 23 may be set when the content of the counter 21 becomes 0.
The matching circuit 22 can be omitted.

When the dot clock counted by the counter 23 matches the value counted and held by the counter 16 on the outward pass, the coincidence circuit 24 controls the print control circuit 14 and starts printing on the return pass from the next dot clock. The point where printing ends and the point where printing starts on the return trip can be matched dot by dot.

In this embodiment, a tachometer generator is used to detect the stopped state of the carriage, but this can be omitted if the number of position indicators included in the run-up section is determined to be a constant number at the beginning of the design. It is possible.

According to the printing position control method according to the present invention, the third
As is clear from a comparison between this figure and FIG. 4, the overall printing time can be shortened by high-speed movement and scanning of the carriage. In other words, in the conventional method shown in FIG. 3, in which the position index interval is twice the run-up distance, as the carriage moves at higher speeds, the interval between the position indexes becomes wider, and the distance _l1 that is wasted moves becomes larger. If installed according to the method of the present invention, as shown in FIG. 4, the distance l ₁ ' of unnecessary movement can be reduced to the minimum limit.

As described above, the present invention eliminates the problem of shortening printing time due to wasteful travel that has arisen as a result of high-speed carriage movement. Compared to the conventional printing method, the effective printing time can be shortened by setting the unnecessary travel distance of the carriage to a minimum. In addition, when the position index intervals are the same, in the conventional method the run-up distance becomes extremely short and the shock to the carriage increases, but according to the present invention, the shock to the carriage is alleviated. Furthermore, since sudden braking is not involved, it is possible to provide an inexpensive drive system.

[Brief explanation of the drawing]

1 and 2 are respectively plan views of the position indicator board in the conventional print position control method, FIG. 3 is an explanatory diagram of the operation of the position indicator part in the conventional position indicator board, and FIG. 4 is the print position according to the present invention. FIG. 5, which is an explanatory diagram of the operation of the position indicator section used in the control method, is a block diagram of the print position control method in one embodiment of the present invention. 1...Position indicator board, 1a, 1b, 2a, 2b...
...Print index section, 3a, 3b...Position index section, 4
a, 4b...Printed dot, l ₂ , l ₂ '... Run-up distance,
11, 12...sensor, 14...printing control circuit,
16, 18, 21, 23...Counter, 22, 2
4... Matching circuit.

Claims (1)

[Claims] 1. Providing an index plate having a print index formed in relation to the print density opposite to the direction of movement of the print head that moves back and forth, and generating a print timing signal by reading this print index along with the movement of the print head; The printing head is configured to be driven by this printing timing signal, and position indicators are provided on the indicator plate in parallel with the printing indicators at an interval that is an integral multiple of the interval between the printing indicators and narrower than the run-up distance when the printing head is stopped. The print head is controlled so as to stop midway between one of the position indicators and the adjacent position indicator, and the print head is moved in one direction until the first position indicator is read. The printed index read in the section and the position index in the run-up section are counted, and when the count number of the position index after reversing the moving direction of the print head matches the count number of the position index in the run-up section, the print index is counted. A printing position control method comprising: starting counting, and starting printing when the next printing indicator is read when the counted number matches the counting number of the printing indicator in the first section.