JPH0671909A - Serial wire dot printer - Google Patents

Abstract

PURPOSE:To satisfy both the printing quality and the reduction of printing noises by shifting printing timing signals for every wire in a serial wire dot printer using a conventional printing head wherein a plurality of rows of wires are arranged in zigzag. CONSTITUTION:A print head is mounted to a carriage so that wire rows L, R at the end of the print head are inclined an angle theta to the vertical direction to satisfy an equation 100.b(1-costheta)/e<=4 wherein (b) is the distance of the wire rows and (e) is the pitch of the printing dots. When an output of a counter counting in accordance with an output of a printing starting timer is decoded, each wire is sequentially actuated, and stopped similarly. Accordingly, a printing controlling means shifts the printing timing as above. Both the printing quality and the reduction of printing noises can be fulfilled with the use of a conventional print head having two rows of wires arranged in zigzag.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial wire dot printer.

[0002]

2. Description of the Related Art One of the problems with serial wire dot printers is the magnitude of printing noise.
There is one such as No. 04534 which reduces the printing noise by shifting the printing timing for each wire. At this time, since the print head is mounted on the carriage and prints while moving to the left and right, the wire rows of the print head are rearranged obliquely from the vertical as much as the printing timing is shifted.

[0003]

However, the above-mentioned method cannot utilize the conventional print head, and it is difficult to manufacture a print head having a diagonally arranged wire array in terms of accuracy.

Therefore, the present invention solves such a problem, and its purpose is to achieve both print quality and print noise reduction by using a conventional print head in which two wire rows are arranged in a staggered manner. To provide a serial wire dot printer.

[0005]

According to the present invention, a plurality of wires are arranged in two rows (L, R) parallel to each other at a position separated by a vertical distance b.
And the distance between adjacent wires in the same row is 2 ・ a
And the center of each wire of the other wire row (R) is on a straight line that passes through the midpoint between the wires of one wire row (L) and is perpendicular to this wire row (L). In a serial wire dot printer having a print head in which wires are arranged so as to be positioned and a carriage configured to mount the print head and move in the horizontal direction, a pitch between print dots is set to e,
The print head is mounted on the carriage in a state in which the wire row (L, R) is inclined by an angle θ with respect to a vertical direction that satisfies 100 · b (1-cos θ) / e ≦ 4. Provides a serial wire dot printer.

Further, according to the present invention, in the above serial wire dot printer, the print data latch means for latching print data and the output of the latch means are connected,
Print data output means for turning on / off the print data for each wire, and td when the carriage speed is Vcr.
/ 2 = a · sin θ / Vcr, a print start timer that generates a pulse at a constant cycle td / 2, and print data for each wire sequentially each time an output pulse of the print start timer is generated. Print start control means for controlling the print data output means to turn on,
A print stop timer for generating a pulse at the constant period td / 2, and the print data output means for sequentially turning off the print data for each wire each time an output pulse of the print stop timer is generated. And a print stop control means for controlling the serial wire dot printer.

[0007]

The conventional print head having a staggered arrangement of wires is mounted on the carriage while being inclined by a predetermined angle .theta., And the print timing is shifted for each wire. Therefore, the timing at which the wire vibrates the platen differs for each wire, and the phase of the vibration of the platen also differs for each wire, so the combined platen vibration is smaller than when the wires are simultaneously vibrated. This reduces printing noise. On the other hand, since the conventional print head is tilted and used, there is a problem that the print quality deteriorates.
If the following expression 1 is satisfied, the deterioration of the printing quality does not hinder the practical use.

[0008]

FIG. 2 is a sectional view showing an embodiment of the present invention. The print head 1 is mounted on the carriage 2, and is arranged at a position facing the platen 5 so that a diameter line of the platen 5 passes through a wire row center O of the print head 1 which will be described later. Further, the carriage 2 to which the belt 4 is attached is passed through a shaft 3, and a motor (not shown) scans the shaft 3 in a direction parallel to the central axis of the platen 5 (referred to as horizontal direction in this specification). Print head 1 tip 11
A plurality of wires are arranged on the print head 1. While scanning the print head 1, the selected wire is ejected and the ink ribbon 6 is hit on the print paper 7 to form a character.

FIG. 1 is a front view of the print head 1 mounted on the carriage 2 as seen from the platen 5 side. Two rows of wires are provided in the tip portion 11 of the print head 1 to satisfy Expression 1 in a direction perpendicular to a plane including the central axis of the platen 5 and the wire row center O described later (which is referred to as a vertical direction in this specification). It is arranged at a predetermined angle θ. The tilting method is such that the wire is rotated by θ around the center O of the wire row described later.

100 · b (1-cos θ) / e ≦ 4 [Equation 1] where e is a pitch between print dots (for example, when the print density is 360 dpi, e = 25.4 / 360 mm)
Is.

FIG. 3 is an array view of the two rows of wires of the print head 1 as seen from the printing paper surface side, and the number of each wire is #.
Is attached. A wire row L in which twelve odd-numbered wires are arranged at intervals of 2 · a and a wire row R in which twelve even-numbered wires are arranged at intervals of 2 · a are parallel to a position separated by a vertical distance b. , And zigzag so that the center of each wire of the other wire row R is located on a straight line perpendicular to this wire row L, passing through the midpoint between the adjacent wires of the one wire row L. Has been done. The values of a and b are as shown in Table 1, for example. Here, the midpoint of a straight line connecting the center of the outermost end wire # 1 of one wire row L and the center of the outermost end wire # 24 of the other wire row R located on the opposite side is the wire row center. Define as O.

[0012] Since the print head 1 is originally designed to have a correct character height when used in a state where each wire row is vertical, the character height l when tilted by an angle θ in the arrow direction shown in FIG. It changes like Formula 2.

L = 2 [(23 · a / 2) ² + (b / 2) ² ] ^1/2 · sin (ψ + θ) [Equation 2] Here, when (ψ + θ) exceeds 90 degrees, the wire row L The positional relationship between the left and right wires (for example, # 1 and # 24) at the ends of R and R is reversed, and # 1 may be located to the right of # 24. Since that is meaningless, (ψ + θ) does not exceed 90 degrees, and the character height l in that range is higher than that when the print head 1 is not tilted.

The character height error ε1 at this time is calculated from the character height l when tilted by an angle θ from the vertical to the original character height 23 · a.
Equation 3 is expressed as a percentage of the value obtained by subtracting the value of the original character height 23.a.

Ε1 = 100 (1-23a) / (23a) [Formula 3] Also, by tilting the print head 1 from the vertical direction in the direction of the arrow in FIG. The center of each wire of the wire row R, which should be located on the horizontal line passing through the midpoint between adjacent wires, is shifted downward by p2 shown in FIG. 3, which affects the print quality as dot pitch unevenness. The value of p2 is given by Equation 4 below.

P2 = b · sin θ [Equation 4] If the dot pitch error ε2 at this time is expressed in percentage as the ratio of p2 to the pitch p1 in FIG.
become that way.

Ε2 = 100P2 / (acos θ) = 100btan θ / a [Equation 5] Using the values of Table 1 in FIGS. FIG. 4 shows the character height error ε1 and the dot pitch error ε2 with respect to. From this figure, it is understood that the character height error ε1 hardly increases even if the angle θ increases, and the dot pitch error ε2 is the dominant factor for the print quality rather than the character height error ε1.

On the other hand, the angle θ obtained by inclining the wire rows L and R from the vertical is plotted on the horizontal axis together with the time td for shifting the printing timing between the wires, and the vertical axis is the noise (dB) during printing. Show. The print timing shift time td on the horizontal axis is the time for shifting the print timing between the adjacent wires in each wire row, and its value is given by the following equation 6 when the carriage scanning speed is Vcr.
Can be found at.

Td = 2 · a · sin θ / Vcr [Equation 6] Here, td shown in FIG. 5 is capable of printing 300 characters in a standard size of 10 characters arranged in 10 inches per second. For intermediate printers (denoted as 300 cps), t for 100 and 200 cps
d is not shown here. From this figure, it can be seen that the noise reduction effect almost converges to a constant value when θ is about 4.5 degrees, regardless of the printing speed. This value is 30
When td is 0 cps, td = 28 (μsec)
Equivalent to.

Furthermore, generally, the interval between two wire rows of the print heads 1 arranged in a staggered manner (b in FIG. 3) is designed to be an integral multiple of the dot pitch, and the wire rows L and R are arranged.
Are driven at the same timing. In the case of the print head 1 having the values shown in Table 1, the wire row interval is 1/30.
Inches, which corresponds to 12 dots in high quality printing. However, since the print head 1 of the present invention is mounted on the carriage 2 in an inclined state of the angle θ, the horizontal distance between the wire rows L and R is c in FIG. 3, which is shorter than the original distance b. The length of the shortened portion is given by the following Expression 7.

(B−c) = b− (a ² + b ² ) ^½ cos (φ + θ) = b [1-cos (φ + θ) / cosφ] [Equation 7] Here, φ = tan ⁻¹ (a / B). Therefore, the print control signal of the wire row L when the carriage 2 is scanned in the direction of the arrow in FIG. ) Is divided by the carriage velocity Vcr to be output earlier by the wire row correction time tr defined as time.

This requires an independent print timing shift control circuit for each of the wire rows L and R, resulting in a complicated and expensive circuit configuration. Therefore, if a half of the print timing shift time td is used instead of the wire row correction time tr,
The print timing shift control circuit can be shared by the wire rows L and R. That is, by configuring a print timing control circuit that sequentially drives the wires in the order of numbers at every print timing shift time td / 2, the wire trains L and R can be controlled by this one control circuit. However, in this case, due to an error between the correct wire-row correction time tr and the wire-row correction time td / 2 used by the control circuit, the print positions of the wire rows L and R are deviated from each other, so that the quality of Degradation occurs. In order to take this error, the following definition is made. That is, the length corrected by the print timing shift time td / 2 is subtracted from the length (b-c) of the shortened wire row interval given by Expression 7, and this is calculated as the pitch e between dots. The above error ε3 is represented by the ratio to. This ε3 is expressed by the following equation.

Ε = 100 · [b {1-cos (φ + θ) / cosφ} −Vcr · td / 2] / e = 100 · [b {1-cos (φ + θ) / cosφ} −a · sin θ] / e = 100b (1-cos θ) / e [Equation 8] When the above Equation 8 is applied to a printer (360 dpi) capable of striking 360 dots per inch, the result is as follows.

Ε3 = 100 · b (1-cos θ) · 360 / 25.4 [Formula 9] Here, it is used that 1 inch is 25.4 mm, and the wire row interval b is also expressed in mm. It has been done.

FIG. 6 shows the result obtained by plotting the angle θ of tilting the print head 1 on the abscissa axis and the ε3 on the ordinate axis according to the equation (9). As described above, since the dot pitch error ε2 is the dominant factor for the print quality rather than the character height error ε1, the dot pitch errors ε2 and ε3 will be compared. ε2 is an error in the vertical direction, which affects only the density of the vertical K lines, while ε3 is an error in the horizontal direction, which has a large effect on the linearity of the vertical K lines. Therefore, ε3 is considered to be a more dominant factor for print quality than ε2. The limit value allowed as ε3 is about 4%, and the angle θ corresponding to this error is about 4.5 degrees from FIG. This angle θ
Is a value at which the noise reduction effect is almost converged as seen in FIG. 5, so if the angle θ of tilting the print head is in a range smaller than this value, the wire rows L and R are controlled by one control means. The print quality is within the allowable range. This is represented by the general formula, and therefore, it can be seen that there is an optimum value within the range of the angle θ that satisfies the formula 1 for ensuring both print quality assurance and print noise reduction.

In this embodiment, since the print head 1 is tilted about the wire row center 0, the change in the distance d between the print head tip 11 and the platen 5 in FIG. It becomes symmetrical about the center, and the influence on the print quality can be minimized.

FIG. 7 is a block diagram showing the arrangement of an apparatus for determining the drive timing of the wires arranged in the print head 1. The output of the print data latch circuit 110 connected to the data bus 100 for latching print data is connected to the print data output circuit 120 for turning on / off the print data for each wire. Further, a print start timer 81 that generates a pulse with a cycle of the print timing shift time td / 2 is connected to the print start control circuit 91, and the output of the print start control circuit 91 corresponds to each wire of the print data output circuit 120. It is connected to the terminal. Similarly, a print stop timer 82 that generates a pulse with a cycle of td / 2 is connected to the print stop control circuit 92, and the output of the print stop control circuit 92 is output to the terminals corresponding to the respective wires of the print data output circuit 120. It is connected. A print control signal line 130 is connected to the print data latch circuit 110, the print start timer 81, and the print stop timer 82. As a more specific configuration of the apparatus in FIG. 7, a buffer can be used as the print data latch circuit 110 and a flip-flop can be used as the print data output circuit 120. Further, the print start control circuit 91 and the print stop control circuit 92 include an up / down counter 91.
A combination of 1,921 and decoders 912,922 can be used. At this time, the output of the buffer is connected to the data terminal of the flip-flop, the output of the decoder 912 is connected to the trigger terminal of the flip-flop, and the output of the decoder 922 is connected to the clear terminal of the flip-flop.

The operation of the apparatus shown in FIG. 7 when the carriage 2 moves in the direction of the arrow shown in FIG. 1 will be described with reference to the timing chart of FIG. Here, in the timing chart of FIG. 8, a high level represents ON and a low level represents OFF.

The counting directions of the up / down counters 911 and 921 are preset to up by a control unit (not shown). First, when the print control signal for the wire row L is turned on, the print data signal output to the data bus 100 is latched by the print data latch circuit 110, and at the same time, the print start timer 81 starts counting. The decoder 912 initially sets the print data output circuit 12
To turn on the trigger terminal of the flip-flop corresponding to the # 1 wire of 0,
The print data of the wire is output from the print data output circuit 120. When the print timing shift time td / 2 elapses, the print start timer 81 generates a pulse, which is input to the up / down counter 911, whereby the trigger terminal of the flip-flop corresponding to the # 2 wire of the print data output circuit 120. The output of the decoder 912 connected to is turned on, and the print data is output from the print data output circuit 120. Similarly, every time the print timing shift time td / 2 elapses, the print data is sequentially output with the # 24 wire as the last.
It is output from 20. The output data is input to a print head drive driver (not shown) to drive each wire.

The time tw required to drive the wire shown in FIG.
When the print control signal is turned off after a lapse of time, the print stop timer 82 starts counting. Decoder 922
First turns on the clear terminal of the flip-flop corresponding to the # 1 wire of the print data output circuit 120, so that the print data of the # 1 wire is stopped from being output from the print data output circuit 120 at the same time when the print control signal is turned off. . When the print timing shift time td / 2 elapses, the print stop timer 82 generates a pulse, and the pulse is input to the uptown counter 921, whereby the clear terminal of the flip-flop corresponding to the # 2 wire of the print data output circuit 120. The output of the decoder 922 connected to is turned on, and the print data is stopped from being output from the print data output circuit 120. Similarly, every time the print timing shift time td / 2 elapses, the # 24 wire is set as the last,
The print data is sequentially stopped from the print data output circuit 120. As a result, the print head drive driver (not shown) stops driving each wire.

When the carriage 2 is scanned in the direction opposite to the arrow in FIG. 1, it is necessary to reverse the order of the wires to be driven. Therefore, the counting directions of the up / down counters 911 and 921 are controlled by a control unit (not shown). Is set to.

In the embodiment of the present invention, the combination of the up / down counter and the decoder is used as the print start control circuit 91 and the print stop control circuit 92, but other combinations such as using a shift register are also possible.

[0033]

As described above, according to the present invention, by using the conventional print head in which the wires are arranged in a staggered manner, and arranging the print head in the carriage with a tilt smaller than a predetermined angle, the print quality and noise are reduced. A serial wire dot printer that achieves both effects can be realized.

[Brief description of drawings]

FIG. 1 is a front view showing a positional relationship between a carriage and a head in an embodiment of the present invention.

FIG. 2 is a sectional view showing a positional relationship between a carriage, a head and a platen in the embodiment.

FIG. 3 is a wire array diagram of the head used in the embodiment.

FIG. 4 is a graph showing a situation of deterioration of print quality in the example.

FIG. 5 is a graph showing a noise reduction situation in the example.

FIG. 6 is a graph showing a print quality deterioration situation in the embodiment.

FIG. 7 is a block diagram showing a print timing control circuit in the embodiment.

8 is a timing chart showing the operation of the circuit of FIG.

[Description of Codes] 1 print head 2 carriage 81 print start timer 82 print stop timer 91 print start control circuit 92 print stop control circuit 120 print data output circuit 911 print start up / down counter 912 print start decoder 921 print stop Up / Down counter 922 Decoder for printing stop

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuro Takahashi 3-5 Yamato 3-chome, Suwa City, Nagano Seiko Epson Corporation

Claims (2)

[Claims] 1. A plurality of wires are arranged in two rows (L, R) parallel to each other at a position separated by a vertical distance b, and adjacent wires in the row are arranged so that the distance between adjacent wires is 2 · a. And, the wires of the other wire row (R) are positioned so that the center of each wire of the other wire row (R) is located on a straight line passing through the midpoint between the adjacent wires of the one wire row (L) and perpendicular to this wire row (L). In a serial wire dot printer having a print head in which the print heads are arranged and a carriage configured to move the print heads in the horizontal direction, the wire row (L, L,
A serial wire dot printer, wherein the print head is mounted on the carriage in a state in which R) is inclined with respect to the vertical direction by an angle θ that satisfies 100 · b (1-cos θ) / e ≦ 4. 2. A serial wire dot printer according to claim 1, further comprising print data latch means for latching print data, and print data output means connected to the output of said latch means for turning on / off the print data for each wire. , Td / 2 = when the carriage speed is Vcr
a period td defined by a · sin θ / Vcr
A print start timer for generating a pulse every 1/2, and a print start control for controlling the print data output means so that the print data for each wire is sequentially turned on each time the output pulse of the print start timer is generated. Means, a print stop timer for generating a pulse at the constant period td / 2, and the print data output so that the print data for each wire is sequentially turned off each time an output pulse of the print stop timer is generated. A serial wire dot printer having a print stop control means for controlling the means.