JPH0655777A - Dot printer - Google Patents

Abstract

PURPOSE:To prevent a deterioration of printing quality even in a high-density printing by a method wherein when a printing duty increases to be more than a predetermined value, dot pattern data to be printed per dot pin is divided every two dots in a column direction, and two-pass printing is conducted under control in accordance with the divided data. CONSTITUTION:In a high-density printing, i.e., when a printing duty is more than a predetermined value, in the first pass, for example, odd-numbered dots d11, d13,... are printed using a dot pin al and odd-numbered dots d21, d23,... are similarly printed using a dot pin a2 regardless of a column number. In the second pass, even-numbered dots d12, d14,... are printed using the dot pin al and even-numbered dots d22, d24,... are printed using the dot pin a2 regardless of a column number. Therefore, in a high-density printing action, dot pins are not driven at the same time for preventing a drop of a printing head drive voltage, eliminating the need for a special design of a drive circuit, and obtaining a low-cost printer. In addition, since a printing omission phenomenon caused by a voltage drop is also eliminated, a deterioration of printing quality never occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of a printing operation by a dot printer which executes a printing operation on a paper by a print head having a plurality of dot pins in a direction orthogonal to a printing column, that is, a paper feeding direction in two passes. It is a thing.

[0002]

2. Description of the Related Art In general, a serial dot printer has 9 to 24 dot pins arranged in a line or in a staggered pattern in the vertical direction (printing line direction) of a recording paper, and is directed to a platen by a piezoelectric element or an electromagnetic solenoid. And a carriage for moving the recording head in a vertical direction, a carriage for moving the carriage equipped with the print head in a horizontal direction (print digit direction or column direction) at a predetermined speed. And a feeding means. Then, as the print operation control of this printer, the input print data is temporarily stored in the storage buffer, the print data in the print line extracted from this is expanded into a dot pattern (image data) and stored in the line buffer. It is well known to control the dot pins of the print head to drive in correspondence with the dot pattern.

By the way, in such a printer,
During high-density printing (high-duty printing), where most of the printing area is occupied by the printed dots (the density of the dot pattern is high), if all the dot pins are operated at once, the power supply voltage drops sharply. However, a plurality of dot pins do not completely project and a so-called dot omission phenomenon occurs, resulting in an incomplete dot pattern.

In order to eliminate such inconvenience, when a predetermined print duty value is exceeded, for example, two-pass printing is performed in which the printing operation for one line is divided into two and executed. Therefore, a method has been devised in which the odd-numbered pins are driven in the first pass and the even-numbered pins are driven in the second pass. In recent years, however, in this method, the dot position is changed due to the looseness of the paper. It is pointed out that it is easy to shift.

Therefore, for example, as disclosed in Japanese Patent Application Laid-Open No. 61-58748, continuous dot printing by the dot pins in each column is prohibited, and all the dot pins in the row direction are, for example, in the first pass. At the time of printing, a method of driving so as to dot the first, second, fifth and sixth, and ninth and tenth dots in the print column direction is adopted.
Then, in the second pass, the dot pins of all rows are changed to the third and fourth positions in the print column direction, the seventh and eighth positions, and the first and second positions.
It is driven so that the 1st and 12th dots are made. In other words, the dot pins of each row are driven every other column in the first pass, and the dot pins are driven for every two columns skipped (not printed) in the first pass in the second pass. It is proposed to print.

[0006]

However, in this prior art, for example, a dot pattern in a straight line in the vertical direction (paper feed direction), for example, a dot in two adjacent columns such as a character of "1". In some cases, the dot pins in all columns may be driven at the same time, so the power supply voltage drops drastically as in the past, and during high-density printing (high duty printing), all dot pins are Since the so-called dot omission phenomenon does not occur due to the complete protrusion operation, the defect that the dot pattern becomes incomplete cannot be eliminated.

An object of the present invention is to solve this problem and to provide a printer in which the printing quality is not deteriorated even in high density printing.

[0008]

In order to achieve the above object, the present invention provides a print head moving means for moving a print head having a plurality of dot pins in a direction intersecting with the print column in the print column direction, and a unit column. The print duty detecting means detects the print duty by detecting the number of print dots of the print duty, and the print control means executes two-pass printing along the print column direction based on the detection of the print duty detecting means. When the value exceeds a predetermined value, the dot pattern data to be printed is divided every other dot pin in the column direction, and two-pass printing is executed according to this division.

[0009]

As a result, in a normal printing operation in which the number of print dots per unit column is smaller than a predetermined value, one-pass printing is executed, while the number of print dots per unit column is higher than the predetermined value. When printing,
Performs 2-pass printing without continuously operating the dot pins.

In this two-pass printing operation, the dot pattern data to be printed is divided every other dot pin in the column direction, and two-pass printing is executed in accordance with this division. Therefore, when the print head moves in the column direction (print digit direction) at a predetermined speed, the dot pins of all rows do not operate simultaneously. In other words, even with high-density printing (high-duty printing), which is a continuous dot pattern in the column direction, only about half the dot pins in the row direction are activated (driven) at the same column location, so dot dropout is prevented. It is possible to avoid the occurrence, and there is an effect that the printing quality in the high-density printing operation is not deteriorated.

[0011]

Next, an embodiment in which the present invention is applied to a serial type dot printer as an impact printer will be described. 1 and 2, reference numeral 1 denotes a platen rotatably supported on left and right side plates 3a and 3b of a frame of a printing device, and a print head 2 facing the platen 1.
Is mounted on a carriage 4, and the carriage 4 is mounted on a guide shaft 5 arranged along the surface of the platen 1 so as to be slidable in the axial direction thereof, and an auxiliary guide arranged parallel to the guide shaft 5. A rearward U-shaped guide groove of the rear portion of the carriage 4 is fitted on the shaft 6 so as to be slidable along the axis and capable of moving closer to and away from the surface of the platen 1.

An eccentric shaft 5a protruding from the left and right ends of the guide shaft 5 is rotatably supported by the left and right side plates 3a and 3b, and a speed change gear 9, which meshes with a fan-shaped gear 7 mounted on one of the eccentric shafts 5a, The driving force from the step motor 8 is transmitted via the motor 10, and the nose portion 2 of the print head 2 mounted on the carriage 4 is moved according to the rotation angle of the guide shaft 5.
The gap (printing gap) between a and the platen 1 is configured to be wide or narrow. It should be noted that a slit provided in the transmission gear 9 or the like is associated with a light transmission type sensor (photointerrupter or the like) (neither is shown) to calculate the number of forward / reverse rotation steps of the step motor 8 to calculate the print gap. Is set to a predetermined value.

A pulley 11 mounted on the one side plate 3a or the like.
a and a timing belt 13 wound around a pulley 11b mounted on the output shaft of a carriage driving motor 12 such as a step motor or the like which is arranged on the side plate 3b of the other side and which can rotate forward and backward.
Is fixed to the lower surface of the carriage 4, and the carriage 4 is fixed in the longitudinal direction of the platen 1 (width direction of recording paper, digit direction of printing,
It is configured to reciprocate along the print column direction).

The platen 1 is rotated by the power of the paper feed drive motor 14 via the gear group 15, and is continuously conveyed by the tractor unit 16 which is a pin tractor driven by the drive motor 14. The recording paper P, which is a multi-part paper, is sent to a roller pair (not shown) through the guide passage 17, passes through one platen, and is discharged to the outside of the machine on the downstream side.

An ink ribbon supplied by a ribbon cassette (not shown) is interposed between the recording paper P and the print head 2 so as to move appropriately in a direction substantially parallel to the moving direction of the carriage 4. FIG. 3 shows a functional block diagram of a microcomputer as a control device of the present invention.
A central processing unit (CPU) 0 has an input / output interface (not shown). Reference numeral 31 is a reception buffer for receiving print data and the like from a host computer 32 which is a higher-level device, and 33 is a character pattern of commonly used Kanji such as first level Kanji and second level Kanji and a character designating the same. A read-only character generator (character generator) in which codes are stored in advance, 34 is a read-only non-Kanji character generator in which characters other than Kanji such as alphabetic characters, numbers, Hiragana characters, Katakana characters are stored in advance, and 35 is It is a work memory in which a control signal for controlling the operation of the mechanical portion of the printing device can be read and written.

Reference numeral 36 is a memory for external character registration for writing and storing a character pattern of an external character sent from the host computer in response to an external character registration command and a character code corresponding thereto. Non-volatile memory (EEPRO)
M), or a memory that can retain the stored contents even when the main power supply is turned off by the backup power supply.

Reference numeral 37 is a character generator 33, 34 or a memory 36 for external character according to a command from the central processing unit 30.
IC for printing data to call a specified character from the text or convert the character to vertical writing or horizontal writing
(Gate array), 38 is a non-volatile memory (EEPROM) in which data for fine adjustment according to the mechanism of the printing unit can be written, and reference numeral 39 is for switching the mode of the interface or font of characters. This is a switch for switching between.

Reference numeral 40 is an image for constructing a duty counter or the like for controlling the printing timing and for developing the print data received by the reception buffer 31 into print dot images for each line. An IC (gate array) that controls the buffer 44. When the number of print dots per unit column in the gate array 40 exceeds a predetermined value (for example, 50%) set in advance, two-pass printing is executed as described later, and when it is below the predetermined value, one-pass printing is performed. The gate array 45 described later is controlled so as to execute.

The image buffer 44 is provided with a line buffer area for developing continuous print data for at least two lines into a print dot pattern image for each line and temporarily storing the data. In this embodiment, line buffer areas 41, 42, 43 for three consecutive rows are provided. Each line buffer area has dot pattern data for each line and line start position and line end position data for the print line.

An IC (gate array) 45 for controlling the drive circuit 46 of the print head 2 commands the print head drive circuit 46 to output data of dot pins to the print head 2. Reference numeral 47 is a panel switch as an operation unit of the printing device, and the panel switch 47 switches between an online state in which data can be exchanged between the host computer 32 and the printing device and an offline state in which data cannot be exchanged. , "Line break" and "Page break" when offline
A switch for instructing is provided.

Reference numeral 48 is a limit switch for stopping printing operation and paper feeding by sensing that the paper is exhausted, 49 is an alarm drive circuit for giving a warning with a buzzer or the like when the paper is fed and no paper is detected, and 50 is inside the printing apparatus. A fan driving circuit for driving a fan for cooling the fan is associated with on / off of a power switch (not shown).
Reference numeral 51 is a carriage motor drive circuit for driving the carriage drive motor 12, 52 is an encoder for counting the number of rotations of the carriage drive motor 12 and for detecting the direction, and 53 is the carriage motor drive circuit. An IC (gate array) for driving, a paper feed motor drive circuit for driving the paper feed drive motor 14 (step motor) for feeding the recording paper P in a line, and an IC 55 for controlling the paper feed motor drive circuit. (Gate array), 56 is the paper feed drive motor 14
It is an encoder that counts the number of rotations of.

Reference numeral 57 is an auto-cut sheet feeder for automatically feeding cut sheets, reference numeral 58 is a speed change switch for switching the printing speed to at least two types, and reference numeral 59 is the step motor 8 positive. It is a gap adjustment drive circuit for adjusting the print gap by performing reverse rotation drive. A portion surrounded by a dotted line in FIG. 4 shows an IC (gate array) 45 for controlling the drive circuit 46 for each dot pin in the print head 2. Each IC
The (gate array) 45 includes 20 AND circuits 61 and 62.
And the D flip-flop circuits 60 and 63, and the print timing signal T is input to the print timing input terminal T. The print data input terminals D1, D2, ... Dn are
It is a terminal for inputting print data d1, d2, ... dn for each dot pin a1, a2 ,. Terminal RE
The initialization signal R is input to SET.

An output signal from an AND circuit 61 having the print data input terminal and the print timing input terminal T as input signals is input to the T bar terminal (L (low) active input terminal) of the D flip-flop circuit 60. To do. The external reset signal R is input to the R bar terminal (L active input terminal) of the D flip-flop circuit 60. Then, the signal (inverted output) from the Q bar terminal (L active output terminal) in the D flip-flop circuit 60 is branched and input to the S terminal, that is, so-called input feedback is performed.

An output signal (driving signal, DAT) from the Q bar terminal (L active output terminal) of the D flip-flop circuit 60 is supplied to the AND circuit 62 via the OR circuit 64.
AENABL) and the data signal from the print data input terminal are input, and the output signal (latch signal, LATCH DATA) from the AND circuit 62 is input to the D terminal in the D flip-flop circuit 63.

The other input terminal 64a of the OR circuit 64
A signal SW that determines whether to perform 2-pass printing is input to the. The print timing signal T is applied to the T terminal (H active input terminal) of the D flip-flop circuit 63.
, The external reset signal R is input to the R bar terminal (L active input terminal), and print data for processing is output from the output terminals (Q terminal, H active output terminal) of the D flip-flop circuit 63. It is what is output.

Next, with reference to the timing chart of FIG. 5, dot driving during high-density printing operation will be described. First, when 2-pass printing is not performed, the OR gate signal S
Make W high. Then, the AND gate always outputs D1. Further, during the 2-pass printing, the signal SW of the OR gate is set to low. And the carriage 4
While moving to the right, the print dot information (high when the dot is displayed) is sequentially output from the left column.

Further, both D flip-flop circuits 6 are provided.
A reset signal is output to the R bar terminal (L active input terminal) at 0 and 63 as the initialization signal R before the start of the first pass of the second pass printing, and the first pass in the printing operation of one line is performed. The initial states of both D flip-flop circuits 60 and 63 in the second pass are made constant. For example, for the dot pin a1, the data signal of the print data is D1
It is assumed that pulses are given as 1, D12, .... The pulse of the print timing signal T is extremely shorter than the pulse of each of the data signals. The pulse cycle of the print timing signal T will be described below as being the same as the cycle when the print head moves in the print column direction and prints dots at each column number position.

When the data signal and the print timing signal T are input to the input terminal of the AND circuit 61 shown in FIG. 4, the output of the AND circuit 61 is H (high) for both the data signal and the timing signal T. Only when, the H (high) signal is output. Since the T bar terminal of the D flip-flop circuit 60 is an L active input terminal, it becomes a so-called negative edge trigger type and operates at the falling edge of the timing signal T. Then, the high state of the print data signal when the timing signal is input, which immediately follows the next low state, is held until the next timing signal is input, and the drive signal (DATAENABL) is ANDed. 62 to one input terminal. In other words, among the print data, the drive signal that is in the low state is formed only for the section that cuts the preceding and following sections with printing across the non-printing section with the timing signal.

Since the high or low data signal of the print data is input to the other input terminal of the AND circuit 62, the output of the AND circuit 62 is high or low in synchronization with the drive signal (DATAENABL). It becomes a latching signal that outputs a low signal. Therefore, the timing signal is input to the T terminal (which operates at the rise of the timing signal to the H active input terminal) of the D flip-flop circuit 63, and the latching signal is input to the D terminal of the D flip-flop circuit 63. As a result, the high or low state of the latch signal is held until the next timing signal comes in, and the signal in that state is sent from the Q terminal to the drive circuit 46.

When the first pass is completed, the carriage 4 is moved to the left and the print dot information is sequentially output from the right column. Then, when the last (rightmost) dot to be printed is printed in the first pass, the Q bar terminal of the D flip-flop 60 outputs low, so this time (that is, 2 passes). Eyes) are not printed. If the last dot to be printed is not printed, printing is done this time. Then, after that, the same processing as the first pass is performed in order, so in the first pass,
The dot positions that were not printed will be printed.

Although an example of bidirectional printing has been shown above,
In the case of one-sided printing, in the first pass, a signal is input to the reset terminal R of the D flip-flop 60 and then the first pass is printed, and in the second pass, the signal is sent to the transition terminal S of the D flip-flop 60. After inserting, the second pass is printed. Further, when the print duty is lower than a predetermined value (50% in the embodiment) (when the print density is low), a constant period pulse (long pulse period) is applied to the R bar terminals of both the D flip-flop circuits 60 and 63. By inputting, the continuous drive of each dot pin is allowed.

With the above configuration, in the case of high-density printing operation (when the print duty is larger than a predetermined value), for example, in the dot pin a1, as shown in FIG. 6, in the first pass, regardless of the column number, Dot printing of odd-numbered dots in the dot order, d11, d13, d15. In addition, in the dot pin a2, odd-numbered dots in the same dot order, d21, d2
Dot print 3, d25. On the dot pin a3, odd-numbered dots d31, d33, d35, d37, ... Are dot-printed (see black circles in FIG. 6).

In the second pass, regardless of the column number, the dot pin a1 is dot-printed with even-numbered dots d12, d14 ,.
About the even number of dots, d22, d24, d26
Is printed on the dot pin a3, and even-numbered dots in the dot order, d32, d34, d36 ,.

Therefore, in the high-density printing operation, it is possible to prevent all the dot pins arranged in the vertical direction from being driven all at once, and as a result, the drive voltage of the print head does not drop. In other words, there is no need to specially design a drive circuit for preventing the drive voltage from decreasing even when all dot pins are continuously driven all at once, and an inexpensive printer can be provided. . Further, since the print missing phenomenon due to the decrease of the driving voltage is eliminated, the print quality is not deteriorated.

In the embodiment shown in FIG. 7, when the print duty exceeds a predetermined value, the dot pattern division for 2-pass printing is performed by software, and the three line buffers in the image buffer 44 are used. Area 41, 4
Use 2,43. That is, as shown in the subroutine flowchart of FIG. 7, after the data to be printed is read (step S1), it is once developed into a dot pattern for one line in the first line buffer area 41 (step S).
2). When it is determined that the print duty exceeds the predetermined value (step S3), the print dot pattern of one line developed and accumulated in the line buffer area 41 is set to 1
The dot pattern of the first pass and the dot pattern of the second pass are divided, and the dot pattern of the first pass is accumulated in the line buffer area 41, and the dot pattern of the second pass is accumulated in the line buffer area 42 (step S4). ). In this case, the dot pattern is divided so that the odd-numbered dot printing order can be printed in the first pass and the even-numbered printing can be printed in the second pass, regardless of the column position. Is. Then, in step S5, the printing operations of the first pass and the second pass are executed one by one according to the divided dot pattern.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a printer.

FIG. 2 is a schematic perspective view of a printer.

FIG. 3 is a functional block diagram of a control device.

FIG. 4 is a drive circuit diagram of a dot pin.

5 is a timing chart of a printing operation by the drive circuit of FIG.

FIG. 6 is an example of dot printing.

FIG. 7 is a flowchart of another embodiment.

[Explanation of symbols]

 1 Platen 2 Print Head 4 Carriage 12 Carriage Drive Motor 14 Paper Feed Drive Motor 30 Central Processing Unit 31 Receive Buffer 32 Host Computer 41, 42, 43 Buffer Area 44 Image Buffer 40, 45, 53, 55 Gate Array

Claims (1)

[Claims] 1. A print duty is detected by detecting a print head moving means for moving a print head having a plurality of dot pins in a direction intersecting with the print column in the print column direction and the number of print dots per unit column. It is composed of a print duty detecting means and a print controlling means for executing two-pass printing along the print column direction based on the detection of the print duty detecting means. When the print duty exceeds a predetermined value, each dot pin should be printed. A dot printer characterized in that dot pattern data is divided every other column direction, and two-pass printing is controlled in accordance with this division.