JP3089968B2 - Method of forming latent image in magnetic printing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a latent image in a magnetic printing apparatus.

[0002]

2. Description of the Related Art It has been known that high-resolution printing can be obtained with a magnetic printing apparatus. In a magnetic printing apparatus, as shown in Japanese Patent Publication No. 2-6065, a magnetization pattern is recorded on a magnetic recording medium such that at least two magnetization transition regions are formed for one dot of a pixel. In a magnetic latent image recording circuit for recording such a magnetization pattern, a recording clock completely synchronized with the image signal is employed so that one recording pulse is supplied in correspondence with one dot of the image signal. In addition, the circuit configuration is simplified.

In such magnetic printing apparatuses, further improvement in print quality has been demanded in recent years, and therefore, the recording density tends to increase for the purpose of high-definition printing.

[0004]

However, a new problem has arisen that the print density is reduced with the increase in the recording density. That is, as shown in FIG. 13, in a magnetic printing apparatus, a constant (flat) print density is generally obtained up to a certain recording density, but when the recording density is exceeded, the print density decreases. . The reason is as follows. That is, an increase in the recording density means that the period of the image signal is shortened,
As a result, the period of the recording clock synchronized with the image signal is also shortened (that is, the frequency is increased). As described above, when the pulse width of the recording clock decreases as the recording density increases, the magnetization pattern recorded on the recording medium becomes shorter, and as a result, the interval between the magnetization transition regions becomes too short, and therefore, the magnetic toner is attracted. Because the force is reduced, the print density is reduced.

In view of such circumstances, an object of the present invention is to provide a method of forming a latent image in a magnetic printing apparatus which does not cause a decrease in print density even when the recording density increases.

[0006]

According to the present invention, a recording clock that does not correspond to a pixel, that is, a recording clock that is asynchronous with an image signal is employed to secure a constant pulse width of a recording signal for forming a magnetization pattern. In addition, based on the basic idea of providing a new circuit for correcting the inconvenience associated with the adoption of such an asynchronous recording clock,
The above object is achieved by adopting a technical configuration as described below.

In other words, the method for forming a latent image in a magnetic printing apparatus according to the first invention of the present application is such that the black image area of one dot on the recording medium has at least two magnetization transition areas. Forming a magnetization pattern in the second direction in the black image area of two dots or more, in addition to the magnetization pattern in the first direction, forming at least one magnetization pattern in the second direction on the recording medium. In a magnetic printing apparatus in which a magnetization pattern in the second direction longer than the magnetization pattern of the black image area is formed in the area and the direction of the developing magnetic field is the same as that in the second direction, the period of the recording clock is changed. The image signal is corrected to be longer than the period of the image signal and to extend a black portion of the image signal by a predetermined length for a continuous black image region having a predetermined number of dots or less. To.

According to a second aspect of the present invention, as one mode of the latent image forming method according to the first aspect, a white portion of the image signal is applied to a continuous white image area having a predetermined number of dots or less. The image signal is corrected so as to be extended by a predetermined length.

[0009]

According to the latent image forming method according to the first aspect of the present invention, since the synchronization between the recording clock and the image signal is not required, the pulse width, that is, the period of the recording clock causes the above-described decrease in print density. It can be set freely so that there is no problem. However, since the recording clock and the image signal are asynchronous, some of the magnetization pattern recording signals, which are the logical product signals thereof, cannot secure a sufficient pulse width depending on the timing. The problem is that if the black image area continues more than a predetermined number of dots (for example, 3 dots), the above-mentioned logical product can be completely obtained in portions other than both sides of the area, and no countermeasure is required. However, in a black image area shorter than that, there is a case where the pulse width of the logical product signal becomes small and the printing becomes thin. Therefore, according to the first aspect, in such a case, the image signal is corrected so that the logical product of the image signal and the recording clock can be easily obtained, and a recording signal having a sufficient pulse width can be obtained. .

A predetermined number of dots (for example, three dots)
On the other hand, in the following white image area, an insufficient logical product can be obtained depending on the timing, so that sufficient white may not be ensured in some cases. According to the second aspect, in such a case, the problem is solved by expanding the white portion of the image signal by a predetermined length and making it difficult to obtain the logical product of the image signal and the recording clock. Has been resolved.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a magnetic printing apparatus according to an embodiment of the present invention. Hereinafter, the operation will be described. Recording drum 1
Moves in the direction of arrow 11, and the recording head 2 records a magnetic latent image on the recording drum 1. The magnetic latent image is developed by the developing device 3, and the magnetic toner 31 is attracted to the recording drum 1. On the other hand, the recording paper 4 is fed out by the paper feed roller 41 and is fed in the direction of the arrow 44 along the path indicated by the broken line 43. Then, the toner on the recording drum 1 is transferred to the recording paper 4 by the transfer roller 5. Next, the recording paper 4
Is fed in the direction of arrow 45, passes between the fixing rollers 61 and 62 to fix the toner image, and is discharged in the direction of arrow 46. The remaining toner is transferred to the cleaner blade 71.
And is removed from the recording drum 1 by the suction cleaner 72. Then, prior to the recording of the next latent image, the erasing head 8 operates to erase the previous latent image.

As shown in FIG. 1, the developing device 3 includes a toner 31 and a sleeve 32 which rotates in the direction of an arrow 34.
And a developing magnet 33 fixed in the sleeve.
, A toner height regulating plate 35, and a housing 36. N ₁ , S ₁ , N ₂ and S _{2 in the} developing magnet 33
Represents a magnet.

FIG. 2 schematically shows the relationship among the drum 1, the erasing head 8, the recording head 2, and the developing machine 3 in FIG. The recording drum 1 moves in the direction of arrow 11. First, the recording medium 12 of the recording drum 1 is magnetized in one direction by the erasing head 8. The erasing head 8 is, for example, one in which a permanent magnet 81 is sandwiched between soft magnetic material holders 82 and 83 and a butt gap portion 84 is provided at a position closest to the recording medium 12. In the state shown in FIG. 2, the butting gap 84 causes the N pole of the permanent magnet 81
A leftward magnetic field indicated by a dashed arrow 85 is generated toward the pole, and when the recording medium 12 passes nearby, a leftward
1, the recording medium 12 is magnetized. When the erasing head 8 is not operated, the butting gap portion 84 is moved away from the recording medium 12. Of course, a winding type erasing head may be used instead of the permanent magnet type.

Next, a magnetic latent image corresponding to the image signal is recorded on the recording medium 12 by the recording head 2. Head 2
Core 21, coil 22, and butt gap 23
Depending on the polarity of the pulse current 24 flowing through the coil 22, the direction of the recording magnetic field generated outside from the butt gap 23 is 25, which is the same direction as the magnetic field 85 generated by the erase head 8, or the opposite direction. 26. Here, when the reverse recording magnetic field 26 is generated, the recording medium 12 is magnetized rightward 102. At the boundary between the leftward magnetization pattern 101 and the rightward magnetization pattern 102, a magnetization transition region 103 is formed.

Next, as shown in Japanese Patent Publication No. 2-6065, it is possible to obtain a high-resolution print by setting the developing magnetic field 37 of the developing machine 3 in the same direction as the erasing magnetic field 85 and thus the magnetization pattern 101. It is.

At this time, the print density of the print is determined by whether the amount of the magnetic toner 31 adsorbed on the recording medium 12 is large or small.

FIG. 3 is a diagram showing the correlation among image signals, magnetization patterns, developing magnetic fields, and the like. The magnetization pattern recorded for the image signal of FIG. 3A is as shown in FIG. Since a magnetic field is generated in the air from the magnetization transition region 103, the magnetic toner 31 is attracted. For example, FIG.
As shown in (B), the magnetization transition regions 103a and 103b
From this, a magnetic field in the direction shown by 110a is generated. Then, when development is performed in the presence of the developing magnetic field 37 as shown in FIG. 3C, as shown in FIG.
The toner 31 slightly protrudes from between 3a and 103b.
a is adsorbed. On the other hand, the magnetization transition regions 103d and 103d
From 3e, a magnetic field in the direction shown by 110d is generated,
This is opposite to the developing magnetic field 37. Therefore, when vectorwise addition is performed, the magnetization transition regions 103d and 103e
Is much smaller than the toner 31a.

FIG. 4 shows an example of a latent image recording circuit for recording a magnetization pattern as shown in FIG. 3B with respect to the image signal of FIG. 3A, and FIG. 5 shows a time chart thereof. .
The details of the operation are as shown in Japanese Patent Publication No. 2-6065. In brief, when AND of the image signal and the recording clock is established, the transistors Q1 and Q
4 is turned on, Q2 and Q3 are turned off, and the power supply + E → Q1
→ A resistance R1 → a coil L → Q4 → ground, a recording current flows, and a rightward magnetization pattern (102a or the like) is recorded. On the other hand, when the AND between the image signal and the recording clock is not established, the transistors Q2 and Q3 are turned on,
1, Q4 is turned off, power supply + E → Q3 → resistor R2 →
A recording current flowing through the coil L → Q2 → ground is generated,
A leftward magnetization pattern (101a etc.) is recorded.

Conventionally, as shown in FIGS. 5A and 5B, the image signal and the recording clock are completely synchronized, and in the NAND gate G1 in FIG.
An AND signal with a constant pulse width has been obtained. However, when the recording density is increased (for example, 480
Even in the case where the density is increased from DPI to 600 DPI), if such synchronization is to be maintained, the problem of a decrease in print density occurs as described above. Therefore,
In the present invention, for example, a recording clock equivalent to 480 DPI is adopted for an image signal of 600 DPI. And
The problems that occur at that time are eliminated by correction. Hereinafter, such a correction method will be described in detail.

FIG. 6 is a time chart for explaining a method of correcting an image signal representing a one-dot black image area. In the case where the recording signal shown in (C) is obtained by using the conventional synchronized clock signal shown in (B) for the image signal shown in (A) in FIG. As described above, when the recording density is high, the pulse width of the recording signal is too narrow, the magnetization pattern recorded on the recording medium becomes short, and as a result, the interval between the magnetization transition regions becomes too short. The printing force is reduced, and the printing density is reduced.

Therefore, in the present invention, a clock (D) having a larger period is employed asynchronously with the image signal in order to secure a constant pulse width of the recording signal for forming the magnetization pattern. In this case, when a recording signal is created as a logical product signal of a one-dot black image signal (A) and a clock (D) as in the related art, the result is as shown in FIG. That is, since both signals are asynchronous, the pulse width of the recording signal (E) can be completely ANDed and the clock (D)
In some cases, a pulse (of the same figure) having the same pulse width is formed, and in some cases, the logical product becomes incomplete and a pulse (of the same figure) having an insufficient pulse width is formed, resulting in a thin print. is there.

In consideration of such circumstances, in the present invention,
When the number of continuous dots of the black image signal is equal to or less than a predetermined value, the black portion of the image signal (A) is extended and corrected, and then ANDed with the clock (D). That is, the extension correction (1.5 in this figure) is performed so that the pulse width of one dot portion of black of the image signal (A) is equivalent to one cycle of the clock (D).
2) to obtain a corrected image signal as shown in (F). The recording signal obtained from the corrected image signal (F) and the clock (D) has a sufficient pulse width as shown in FIG. 2G, and an asynchronous clock is employed according to the present invention. The inconvenience caused by is eliminated.

FIG. 7 shows an example of the configuration of a circuit for performing the above-described correction on an image signal representing a one-dot black image area. This circuit includes a 3-bit shift register 210 that latches input data (image signal) by a predetermined clock, and the content of the shift register 210 is “01”.
A determination circuit 220 for determining whether or not the value is "0"; a 3-bit shift register 230 for creating a delay signal of an input signal when the determination circuit 220 detects a state of "010"; Register 21
8 includes a data processing unit 240 for generating final output data (corrected image signal) from 0 and 230.
The input / output operation as shown in the time chart of FIG.

FIG. 9 is a time chart for explaining a method of correcting an image signal representing a 2-dot black image area for the same purpose. The signals shown in FIGS. 6A to 6G are the same as the signals shown in FIGS. 6A to 6G. That is, for the two black dots, the pulse width is extended and corrected to obtain a corrected image signal (F).
By generating a recording signal (G) based on the clock and the clock (D), two pulses are secured. At this time, as shown in FIG. 9G, since the corrected image signal (F) and the clock (D) are asynchronous,
A complete pulse and an incomplete pulse may be formed.However, the narrower pulse width does not cause a problem that the print density is considerably reduced, and the larger pulse width does not cause a problem. This will contribute to printing. Thus, it has been experimentally confirmed that there is no problem that the corrected image signal (F) and the clock (D) are asynchronous. It should be noted that it is appropriate to apply the above-described correction to the black image area when the number of dots is three or less. That is, the image signal black partial expansion correction for the black image area of 4 dots or more is unnecessary since the logical product described above can be completely obtained in a part other than both sides of the area.

FIG. 10 is a time chart for explaining a method of correcting an image signal representing a 2-dot white image area. When a recording signal shown in (C) is obtained by using a conventional synchronized clock signal shown in (B) with respect to an image signal shown in (A) in FIG. The image portion is at the low level by the length of the figure. However, in the present invention, since a clock (D) having a larger cycle is employed asynchronously with the image signal, the recording signal is generated as a logical product signal of the image signal (A) and the clock (D). (E).
That is, since both signals are asynchronous, the low level as the white image portion is the length of the recording signal (E), which may be shorter than in the conventional case, and sufficient whiteness may not be secured.

Therefore, for a white image area having a predetermined number of dots (for example, 3 dots) or less, it is difficult to obtain the logical product of the image signal and the clock, that is, the length of the white portion of the image signal is reduced. The problem is solved by extension. Specifically, the image signal (A) is corrected as shown in (F) to obtain a recording signal as shown in (G).
At this time, an imperfect pulse as shown in the figure may be generated, but since the width is narrow, the print density is considerably low (close to white), which is not a problem.

FIG. 11 shows a configuration example of a circuit for correcting an image signal portion representing a black or white image area of N dots or less in order to realize the correction of the image signal as shown in FIG. 9 or FIG. I have. This circuit is an extension of the circuit of FIG. 7, that is, an (N + 2) -bit shift register 310 that latches input data by a predetermined clock, and whether the contents of the shift register 310 are "01... 10". A (N + 2) -bit shift register group 330 for generating a delay signal of an input signal when the state of “01... 10” is detected by the determination circuit 320; The shift register 310 and the (N + 2) -bit shift register group 330 comprise a data processing unit 340 that creates final output data. For example, an input / output operation as shown in FIG. 12 is executed to realize the image signal white portion extension correction as shown in FIG.

Although the embodiments of the present invention have been described above, the present invention is of course not limited to these embodiments.
It will be easy for those skilled in the art to devise various embodiments.

[0030]

As described above, according to the present invention,
In a magnetic printing apparatus, there is provided a latent image forming method which does not cause a decrease in print density even when a recording density increases. That is, according to the latent image forming method according to the first aspect of the present invention, since the synchronization between the recording clock and the image signal is not required, the pulse width, that is, the cycle of the recording clock does not cause the decrease in the print density described above. Can be freely set as described above, in which case the black image area has a predetermined number of dots (for example, 3 dots).
In the shorter black image area, the inconvenience of thinning the print due to the correction of the image signal is prevented. According to the second aspect, in a white image area having a predetermined number of dots (for example, three dots) or less, a sufficient white is secured by correcting the image signal.

[Brief description of the drawings]

FIG. 1 is a diagram showing a magnetic printing apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a mutual relationship between a recording drum and its periphery in the magnetic printing apparatus of FIG. 1 by a linear model.

FIG. 3 is a diagram showing a mutual relationship between an image signal, a magnetization pattern, a developing magnetic field, and the like.

FIG. 4 is a connection diagram of a latent image recording circuit.

FIG. 5 is a time chart for explaining the operation of the latent image recording circuit of FIG. 4;

FIG. 6 is a time chart for explaining a correction method for an image signal representing a one-dot black image area.

FIG. 7 is a circuit diagram illustrating a configuration example of a correction circuit for an image signal representing a one-dot black image area.

8 is a time chart for explaining an input / output operation of the circuit shown in FIG. 7;

FIG. 9 is a time chart for explaining a correction method for an image signal representing a 2-dot black image area.

FIG. 10 is a time chart for explaining a correction method for an image signal representing a two-dot white image area.

FIG. 11 is a circuit diagram showing a configuration example of a correction circuit for correcting a black or white portion of N dots or less in an image signal.

FIG. 12 is a time chart for explaining the input / output operation of the circuit shown in FIG. 11;

FIG. 13 is a characteristic diagram showing a relationship between recording density and print density in a general magnetic printing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Recording drum 12 ... Recording medium 2 ... Recording head 21 ... Head core 22 ... Coil 23 ... Butt gap part 25, 26 ... Recording magnetic field 3 ... Developing machine 31 ... Magnetic toner 32 ... Sleeve 33 ... Developing magnet 35 ... Toner height regulation Plate 36 Housing 37 Developing magnetic field 4 Recording paper 41 Paper feed roller 5 Transfer rollers 61 and 62 Fixing roller 71 Cleaner blade 72 Suction cleaner 8 Erase head 81 Permanent magnets 82 and 83 Holder 84 Butt gap portion 85 ... Erasing magnetic field 101, 102 ... Magnetic pattern 103 ... Magnetic transition region

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masaharu Shishido 1-41 Kugayama, Suginami-ku, Tokyo Iwasaki Tsushinki Co., Ltd. (56) References JP 2-60665 (JP, B2) (58 ) Surveyed field (Int.Cl. ⁷ , DB name) G03G 19/00

Claims (2)

(57) [Claims] 1. A magnetic pattern in a first direction is formed so as to have at least two magnetic transition regions in a one-dot black image region on a recording medium, and the first image pattern is formed in a two-dot or more black image region. In addition to the magnetization pattern in one direction, at least one
And forming a magnetization pattern in the second direction longer than the magnetization pattern of the black image area in the white image area on the recording medium,
In the magnetic printing apparatus in which the direction of the developing magnetic field is the same as the second direction, the cycle of the recording clock is made longer than the cycle of the image signal, and the above-mentioned is applied to a continuous black image area having a predetermined number of dots or less. A method of forming a latent image in a magnetic printing apparatus, wherein the image signal is corrected so as to extend a black portion of the image signal by a predetermined length. 2. The image signal is corrected so that a white portion of the image signal is extended by a predetermined length even in a continuous white image area having a predetermined number of dots or less.
A method for forming a latent image in the magnetic printing apparatus according to claim 1.