JPH03268970A - Color printer - Google Patents

Abstract

PURPOSE:To prevent degradation of an image quality by compressing a misaligned amount of a printing start position for each color to a minimum controllable transport distance range. CONSTITUTION:A microprocessor 2 holds count value C1, C2, at which an output from a passage detection sensor 23 starts from LOW to HIGH. Then if the held count value C1 is given as 'n' and the held count value C2 is 'p1' when the first color is used for printing, time equal to the N pieces of the count value C1 (N times the minimum transport time T:NdeltaT) is set as a remaining time required for transport up to a printing start position PP1. In addition, if the count value C1 held when the second color is used for printing is 'n' and the count value C2 is 'p2', a microprocessor 21 calculates the value as ¦p2-p1¦. If this value is not more than half the variable range of the count value C2, that is, ¦p2-p1¦<5, NdeltaT is set as a remaining transport time for printing in the second color. Further, the microprocessor 21 sets (N+1)deltaT, if p1-p2>=5 and (N-1)deltaT is p2-p1>=5 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color printer used as office equipment.

(Prior Art) Some color printers used as office equipment create a color image including a plurality of hues by overlapping printing of images of each color. For example, by thermal transfer from an ink film, a cyan hue image is first printed on one page, and then a magenta hue image is printed superimposed on the cyan hue image.
Finally, an image of a yellow hue is printed superimposed on these.

In this overlapping printing method, a major technical challenge is how to perform highly accurate positioning when printing each hue in order to prevent image quality deterioration such as blurring due to misalignment of images of each hue.

This positioning is performed as part of conveyance control in which the printing paper is conveyed and positioned to a printing start position determined by the relationship with the printing gutter. A pulse motor, a combination of a DC motor and a rotary encoder, etc. are used for this conveyance control. In this conveyance control, the minimum controllable distance is determined by the rotation angle of one pulse of the pulse motor, the resolution of the rotary encoder, and the like.

(Intelligence M to be solved by the invention) In the above-mentioned conventional color printer, the printing start position (D
The positioning accuracy is determined by the rotation angle of one pulse of the pulse motor, the resolution of the rotary encoder, etc. Therefore, high-resolution actuators and sensors are required to improve positioning accuracy! FrlF
There is a problem that it becomes an RL machine control mechanism.

(Means for Solving the Problems) According to the color printer of the present invention, the conveyance control section detects passing of a reference point set at a predetermined point of the printing paper being conveyed. a sensor; a speed control means for controlling the passing speed of the reference point to a predetermined value ■ before and after the passing detection sensor; and a controllable minimum transport distance δD determined by the minimum unit δP of the transport control parameter P to the predetermined value The first clock pulse whose period is the minimum transport time δT divided by the passing speed V of
The first . a second counter; a holding means for holding a first count value q of the first counter, a second count value p of the second counter, and a conveyance control parameter Po at the time when the passage detection sensor detects passage of the reference point; and this retained first . and a print start position setting means for setting a conveyance control parameter Ps for conveying the printing paper to the print start position based on the second count values q, p and the conveyance control parameter Po.

This printing start position setting means is configured such that the first count value when printing the first color and the second color is the same, and the second count value is pl.

In the case of p2, if p2-pH<n/2, the same value as the transport control parameter Ps set when printing the first color is set when printing the second color, and p2-pH≧n/2. If,
Conveyance control parameter Ps set when printing the first color
When printing the second color, a conveyance control parameter that is different by one value is set, and the first control parameter L f that is retained when printing the third color and thereafter is retained when printing the first and second colors. This first
If the second count value p3 is the same as the count value of p1 and p2, then these p1,
Select the side of p2 that is close to p3, and select this selected p
The same value as the transport control parameter Ps set during printing where l or p2 was retained is set as the transport control parameter during printing of the third and subsequent colors, and the above p3 does not exist between pl and p2. In this case, one of these p1 and p2 is selected which is closer to p3 or the count value p3' which is advanced or delayed by the minimum transport time δT, and when printing is performed in which this selected pl or p2 is held. The same value as the set transport control parameter Ps is set as the transport control parameter when printing the third and subsequent colors, and the one selected from pl or p2 as the adjacent side is set as the adjacent p3 or lower. ,
The operation of the present invention will be explained in detail together with examples.

(Embodiment) FIG. 1 is a sectional view showing a portion related to a conveyance mechanism and a conveyance control section of a color printer according to an embodiment of the present invention together with printing paper P to be conveyed. DC motors 13a and 13b are gears, 14 is a capstan, 15 is a pinch roller, 22 is a rotary encoder, and 23 is a passage detection sensor.

FIG. 2 is a block diagram showing the configuration of a conveyance control section that controls the conveyance mechanism of FIG. 1 together with the relationship with the conveyance mechanism;
1 is a microprocessor, 22 is a rotary encoder, 23 is a normal detection sensor, 24 is a clock generation circuit, 2
5.26 is a counter, 27 is a decoder, 12 is a motor driver, and 11 is a DC motor.

When the DC motor 11 constituting the printing paper conveyance mechanism rotates, the paper passes through a gear 13a that is attached to the rotation shaft of the DC motor 11 and a gear 13b that is attached to the rotation shaft of the capstan 14. The capstan 14 rotates,
The stamp P, which is held between the capstan 14 and the pinch roller 15, is conveyed from side to side in FIG.

& The microprocessor 21 that constitutes the side of the sending side ill is
The motor driver 12 monitors the output of the rotary encoder 22 that detects the rotation angle of the DC motor 11.
The conveyance of the printing paper P is controlled by controlling the rotation of the DC motor 11 via the DC motor 11 .

Passage detection sensor 2 installed in the conveyance path of printing paper P
Reference numeral 3 is composed of a light emitting element and a light receiving element disposed opposite to the light emitting element, and detects passage of the edge of the printing paper P. That is, as shown in FIG. 3, before the edge of the printing paper P passes, the light emitted from the light emitting element of the passage detection sensor 23 is blocked by the printing paper P, and therefore does not reach the light receiving element. The output S of keeps low level (L). When the end of the printing paper P passes the position of the passage detection sensor 23, the light that has been blocked by the printing paper P reaches the light receiving element, and the output S of this light receiving element rises to a high level (H). .

Before starting printing each hue, the microprocessor 21 of the conveyance control unit aligns the right end of the printing paper P (FIG. 1) with the conveyance start position located on the right side of the passage detection sensor 23, and then transports it to the left side. Start. The conveyance speed to the left is controlled to a predetermined value V before and after the passage detection sensor 23.

In the transport control system of this embodiment that combines the DC motor 11 and the rotary encoder 22, the minimum controllable transport distance δD is determined by the resolution δP of the rotation angle P that can be measured by the rotary encoder. The clock generation circuit 24 in FIG. 2 generates a clock pulse having a period equal to the value obtained by dividing the controllable minimum transport distance δD determined by the resolution δP by the predetermined passing speed V. Hereinafter, the above-mentioned division value δD/V will be referred to as the minimum transport time δT. Clock pulses having a period equal to this minimum transport time δT are counted by a counter 25, and the count value C2 is supplied to the microprocessor 2 and the decoder 27. Every time the count value C2 of the counter 25 reaches "9", a pulse is output from the decoder 27.
At the same time, the counter 25 is reset and its count value becomes "O". counter 2
The count value CI of 6 is supplied to the microprocessor 21.

The microprocessor 21 calculates the count values C1 and C2 at the time when the output of the passage detection sensor 23 rises from low to high.
and hold. In the example shown in FIG. 3, "nj" is held as the count value C1, and "4" is held as the count value C2. Based on the read count values C1 and 02, the microprocessor 21 activates the ill excess detection sensor 23.
(PPo in Figure 1) to the printing start position (PPo in Figure 1)
A transport control parameter Ps for controlling transport to PI) is set. This conveyance control parameter Ps is the rotation angle of the DC motor 11 detected by the rotary encoder 22 in this embodiment. That is, the printing start position is set depending on how much rotation angle is added to the rotation angle of the DC motor 11 at the time of detection of passage by the passage detection sensor 231. However, in the following, for convenience of explanation, it is assumed that the conveyance is performed at a constant passing speed &V until the moment of rest at the printing start position, and the conveyance time normalized by the minimum conveyance time δT is selected as the conveyance parameter Ps.

That is, as illustrated in FIG. 4(A), if the count value CI held during printing of the first color is "n" and the count value C2 is rpLJ, then r of the count value C1 is
A time equal to "N" times the minimum transport time δT divided by NJ times (N6T) is set as the remaining transport time required for transport to the printing start position PP1. Note that since it is assumed that conveyance is performed at a constant speed V to the printing start position, the distance on the time axis shown in FIG. 3 is directly proportional to the distance within the conveyance space.

As shown in FIG. 3(B), the count value CI held during printing of the second color is rnJ, and the count (IiIC2
Suppose that is "p2". The microprocessor 21 is
Calculate p2-pH, and if this is less than half of the range of count value C2, that is, p2-pi<5, the remaining conveyance time for printing this second color is the same as that for printing the first color. Set the value N6T.

As illustrated in FIG. 3(C), if pi-p2≧5, the microprocessor 21 determines that the remaining conveyance time when printing the second color is one unit longer than when printing the first color. Large value (N2l) δ
Set T.

As illustrated in FIG. 3(D), in the case of p2-pI≧5, the microprocessor 21 sets the first color as the remaining conveyance time when printing the second color.
Value (N-1) δ that is one unit smaller than when printing the color
Set T.

In this way, when ri2-all≧5, the remaining conveyance time when printing the second color is δT longer than when printing the first color.
By setting the value of the deviation, the amount of deviation during printing of the first color and the second color is compressed to a range that is half of the controllable minimum conveyance distance δD.

In the example of FIG. 3, the run HIC1 held during printing of the first color and the second color match. If the count values C1 do not match, the amount of deviation in the count value C1 is corrected when setting the remaining conveyance time.

Next, a method for printing the third and subsequent colors will be described.

It is assumed that the count value C1 held in the microprocessor 21 when printing the third color is "n", which is the same as the count values C1 for the first and second colors, and the count value C2 is p3. The microprocessor 21 first determines whether this count value p3 is between the count values p1 and p2 held when printing the first color and the second color.

If the above conditions are met, the microprocessor 21 selects the one closer to p3 between pl and p2, and sets the conveyance control parameter Ps set during printing in which the selected pl or p2 is held. The conveyance control parameter having the same value as is set as the remaining conveyance time during printing of the third color.

That is, if p3 exists between pi and p2 and pl is closer to p3 as illustrated in FIG. 5(B), the first color printing in which pl is retained The same value NδT as the remaining conveyance time set at the time of printing is set as the remaining conveyance time when printing the third color.

Well, as illustrated in Figure 5 (C), p3 is pl and p
2 and plO is closer to p3, the same value NδT as the remaining conveyance time set when printing the first color in which pl is held is the same value when printing the third color. The remaining transport time is set as the remaining transport time.

Furthermore, as illustrated in FIG. 5(D), p3 is pl and p
2 and p2 is closer to p3, the value (N-1) δT is the same as the remaining conveyance time set when printing the first color in which p2 was held. is set as the remaining conveyance time when printing the third color.

Even when printing the fourth color, fifth color, etc., the second count value p4. If p5... exists between pl and p2, pl
Alternatively, the same value as the remaining conveyance time set during printing in which the adjacent side of p2 was held is set as the remaining conveyance time during printing of the third color, fourth color, and so on.

On the other hand, if the second count value p3 read during printing of the third color does not exist between counts 4i1LpI and p2, different processing is performed.

That is, as illustrated in FIG. 6 (B), p3 becomes p
It is assumed that there is no value between l and p2.

In this case, it is determined which of pl and p2 approaches p3 or a value P3'' which is advanced or delayed by the minimum transport time δT. In the case of FIG. 6(B), pl and p2 Among them, pl is closer to p3.In this case, the same value N6T as that during printing of the first color in which pl is held is set as the remaining conveyance time during printing of the third color.

Furthermore, as shown in FIG. 6(C), after printing of the third color is completed, either pt or p3, which is closer to p3 among pl and p2,
This updated pl is kept together with the original p2 as a new criterion for the fourth and subsequent color side doors. When printing the fourth color, the updated p
The same control as for the third color is repeated using l and p2.

FIG. 6(D) illustrates a case where p3 does not exist between pl and p2 and p2 is closer to p3 between pi and p2. In this case, the same value (N-1) δT is set as the remaining conveyance time when printing the third color, which is the same value as when printing the second color, in which pt is held. Furthermore, after this printing is completed, p2 is updated by p3 as shown in FIG. It is maintained as a criterion.

The case where the conveyance control parameter is the remaining conveyance time from the passage detection position to the printing start position has been described above. However, this conveyance control parameter may be the remaining rotation angle of the C motor that is necessary to convey the stamp P for ¥1 from the passage detection position to the printing start position. Furthermore, in a conveyance mechanism using a pulse motor, the conveyance control parameter is the total number of remaining pulses to be supplied to the pulse motor in order to convey the printing paper P from the passage detection position to the printing start position.

(Effects of the Invention) Since the color printer of the present invention has the above-described configuration, it is possible to compress the deviation of the printing start position for each hue to within the controllable minimum transport distance, and it is possible to perform multicolor overprinting. Image quality deterioration due to color shift can be effectively prevented.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a portion of a color printer according to an embodiment of the present invention related to a conveyance mechanism and a conveyance control unit together with printing paper P to be conveyed, and the second recess controls the conveyance mechanism shown in FIG. 1. A block diagram showing the configuration of the conveyance control unit along with the relationship with the conveyance mechanism, and FIG. 3 shows waveforms for explaining the operation of the passage detection sensor 33 that detects the passing point of a portion of the printing paper P being conveyed at a predetermined speed V. 4 to 6 are conceptual diagrams for explaining the control operation of the conveyance control section. 1...Print head, 11...DC motor-12...
・Motor driver, I4...Capstan, 15・
... Pinch roller, 21 ... Microprocessor, 2
2... Rotary encoder, 23... Passage detection sensor, 24... Clock generation circuit, 25.26...
Counter, 27...decoder, 12...motor driver.

Claims (1)

[Scope of Claims] A color printer that includes a transport mechanism that transports printing paper and a transport control unit that controls this transport mechanism, and prints images containing multiple hues on the printing paper by repeating and overlapping each color. In the printer, the conveyance control unit includes a passage detection sensor that detects passing of a reference point set at a predetermined position of the printing paper being conveyed, and a passage speed of the reference point set to a predetermined value before and after the passage detection sensor. a first speed controller whose period is a minimum transport time δT obtained by dividing the controllable minimum transport distance δD determined by the minimum unit δP of the transport control parameter P by the predetermined passing speed V; The clock pulse and this minimum transport time are divided into n equal parts (n is a natural number of 3 or more)
first and second counters each counting a second clock pulse having a period of time δT/n, and a first count of the first counter at the time when the passage detection sensor detects passage of the reference point; a holding means for holding a value q, a second count value p of a second counter, and the transport control parameter Po, and printing based on the held first and second count values q, p and the transport control parameter Po. a printing start position setting means for setting a conveyance control parameter Ps for conveying the paper to the print start position; When the count values are the same and the second count values are p1 and p2, respectively, if |p2-p1|<n/2, the same value as the transport control parameter Ps set when printing the first color is used for the first color printing. It is also set when printing the second color, and if |p2-p1|≧n/2, the conveyance control parameter Ps that is different by one from the conveyance control parameter Ps set when printing the first color is set for the second color. The first count value set at the time of printing and held when printing the third and subsequent colors is the first count value held when printing the first and second colors.
If the second count value p3 is the same as the count value of p1 and p2, then these p1, p2
Select the side closer to p3 among them, and use the same value as the transport control parameter Ps set during printing in which the selected p1 or p2 was held as the transport control parameter when printing the third color and thereafter. The first count value set and held when printing the third and subsequent colors is the first count value held when printing the first and second colors.
If the second count value p3 is the same as the count value of
2, p3 or the side closer to the count value p3' which is advanced or delayed by the minimum transport time δT is selected, and this selected p1 or p2 is held for the transport control set at the time of printing. The same value as the parameter Ps is set as the conveyance control parameter when printing the third and subsequent colors, and the one selected as the adjacent side of p1 or p2 is set as the adjacent side p3 or p3.
A color printer characterized in that the process of updating and saving with ' is repeated when printing the third and subsequent colors to reduce overlay errors.