JPH11301886A - Electronic photograph printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printer for printing two sheets at a time in one process, capable of preventing the dissipation of exposed printing information without using a backup memory. SOLUTION: An electronic photograph printer includes a sheet storage part 11 for separately feeding stacked sheets one by one, a feeding passage 15 for guiding the sheets from the sheet storage part 11 before image transfer and stopping the sheets once in front of a transfer part, a first sheet sensor 16 for detecting the sheets in the feeding passage, a second sheet sensor 17 having the same property as the first sheet sensor for detecting the stacked sheets in the sheet storage part 11 and a comparison part for comparing a detection level between the first sheet sensor 16 and the second sheet sensor 17 and judging the number of the remaining sheets in the sheet storage part 11, the comparison part comparing the detection level between the first sheet sensor 16 and the second sheet sensor 17 in a first process and stopping exposure in the next process if judgement that the number of the remaining sheets in the sheet storage part 11 runs short of the number of sheets for printing in the next process is made.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic printing apparatus using an electrophotographic recording process,
In particular, the present invention relates to an apparatus capable of executing a plurality of prints having a print length of 1/2 or less of a normal print length in one process in order to improve a printing speed.

[0002]

2. Description of the Related Art FIG. 5 is a view showing a printing mechanism of a color electrophotographic printing apparatus using a conventional electrophotographic recording process disclosed in, for example, Japanese Patent Application Laid-Open No. 4-3107979.
In the figure, reference numeral 1 denotes a photoreceptor, 2 denotes an exposure unit using a laser, and 3 denotes a charger, which applies a uniform charge to the surface of the photoreceptor 1 and charges the same. The charge is removed according to the image information to form a latent image. Reference numeral 4 denotes a developing device, which is generally composed of a developing device of three colors of a yellow developing device 4a, a cyan developing device 4b, and a magenta developing device 4c, or a four-color developing device including a black developing device 4d. A toner image is formed by adhering to the image information latent image on the surface of the body 1. Reference numeral 5 denotes a cleaner for removing toner remaining on the surface of the photoconductor 1 after development. Reference numeral 6 denotes an intermediate transfer member, which forms a color toner image on the surface by superimposing toner images formed for each color in a first transfer unit 7. Reference numeral 8 denotes a second transfer unit that transfers a color toner image onto a sheet. Reference numeral 9 denotes a fixing device that fixes a color toner image on a sheet by heating or the like, and 10 denotes a sheet conveying unit that transfers the sheet from the second transfer unit 8 to the fixing unit 9. The peripheral speed of the photoconductor 1, the peripheral speed of the intermediate transfer body 6, and the transport speed of the sheet to the second transfer unit 8 are controlled to the same speed.

[0003] Reference numeral 11 denotes a sheet storage unit which stores a plurality of sheets stacked thereon, and separates the sheets one by one by a sheet feeding mechanism 12 and supplies the separated sheets to a second transfer unit 8. The sheet fed from the sheet feeding mechanism 12 is temporarily stopped by the registration roller 14 by the transport roller 13 to align the leading position of the sheet, and the second transfer unit is adjusted in timing with the transfer of the toner image on the intermediate transfer body 6. 8 is supplied. Normally, the registration roller 14 is composed of a pair of rollers, reads a timing mark provided on the intermediate transfer body 6, and uses the electrical signal from the registration roller 14 to convey the sheet so that the sheet and the toner image are aligned. I do.

In the above-described conventional electrophotographic printing apparatus, since a process of exposure or development is performed three or four times for one color image output, it takes a long time for image output. In order to improve the time efficiency, a plurality of images having a length equal to or less than 1/2 of the entire length of the intermediate transfer body 6 are exposed or developed at a time to form a plurality of images on the intermediate transfer body 6, and There is a type in which short sheets are continuously supplied to the second transfer unit 8 and a plurality of images are output in one process.
For example, this corresponds to a case where two or more A4 size paper size images are exposed or developed at a time by a device capable of printing A3 size.

[0005]

As described above, when two images (first and second images) are printed at one time by one exposure or development process, the two images are printed. The print data is output from the exposure device 2 and the process elapsed time until it is transferred to the paper by the second transfer unit 8, and the paper is fed and transported from the paper feed mechanism 12 to the second transfer unit 8. In comparison with the interval time until the paper is fed, the former is generally longer. Therefore, in order to improve the time efficiency of printing, the exposure of the next process (third and fourth sheets) is naturally started at the timing when the second sheet is fed to the second transfer unit 8. Like that.

At this time, in a sheet remaining amount detecting mechanism provided in the sheet storing section 11 for detecting when the last sheet has run out, sheets of the next process are stored in the sheet storing section 11. The detection of the presence of the image data is later than the start of the exposure to the image data in the next process, and the already exposed image data is deleted without being printed on the sheet. In order to avoid this, a measure has been taken in which data for a plurality of sheets is stored in a memory to back up the data, and after the sheets are replenished, the third and fourth sheets of data are printed. However, recently, when the image data becomes large like an image image or a color image, a large-capacity memory is required to cover the image data having a large data amount, and there is a problem that the memory becomes too expensive. .

The present invention has been made to solve such a problem. In a color electrophotographic printing apparatus capable of printing two sheets at a time in one process, for example, The remaining amount of the last two or three sheets is accurately detected, and in the case of a paper shortage, the start of the next exposure, which is started prior to the paper supply, is stopped, so that the backup memory is not required in the next time. The present invention provides an electrophotographic printing apparatus for preventing data from being erased in the above process.

[0008]

An electrophotographic printing apparatus according to the present invention is an electrophotographic printing apparatus having means for printing on a plurality of sheets in one process of exposure and development. A paper storage unit for separating and supplying sheets one by one, a paper feed path for guiding paper from the paper storage unit before image transfer, and temporarily stopping short of the transfer unit; a first paper sensor for detecting paper in the paper feed path; A second paper sensor having the same characteristics as the first paper sensor and detecting the laminated paper in the paper storage unit;
And a comparator for comparing the detection levels of the paper sensors and determining the remaining amount of paper in the paper storage unit.

In the above configuration, the comparison unit compares the detection levels of the first paper sensor and the second paper sensor in the first process, and determines whether the remaining amount of paper in the paper storage unit is printed in the next process. If it is determined that the number is not enough, the exposure in the next process is stopped.

Further, when the first sensor detects a sheet in the sheet feeding path, the second sheet sensor is set at a position deviated from the rear end of the sheet.

Further, as the first paper sensor and the second paper sensor, light transmission type sensors each including a light emitting section and a light receiving section are employed.

When printing on two sheets in one process, when the first sheet sensor detects the first sheet in the first process, the detection level of the second sheet sensor is set. When the comparison unit determines that the value exceeds 1/3 of the detection level of the first sheet sensor, the exposure in the next process is stopped.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a configuration diagram showing a color electrophotographic printing apparatus according to Embodiment 1 of the present invention, and FIG. 2 is an enlarged view of a main part thereof. Hereinafter, an example in which two prints are performed at once by one process will be described.
1 and 2, reference numerals 1 to 14 are the same as those described in the conventional example. Reference numeral 15 denotes a paper feed path from the paper feed mechanism 12 of the paper storage unit 11 to the registration rollers 14.
Reference numeral 16 denotes a first paper sensor provided in the paper feed path 15 and includes a light emitting unit 16a and a light receiving unit 16b. When a paper is present in the paper feed path 15, the paper blocks light and detects "paper present". I do. Reference numeral 17 denotes a second paper sensor, in which a light emitting unit 17a and a light receiving unit 17b are installed to face each other with the paper stacked in the paper storage unit 11 interposed therebetween. Here, the first paper sensor 16 and the second paper sensor 17 have the same characteristics. An opening is provided in the bottom plate 1la so that when there is no sheet in the sheet storage unit 11, the light of the light emitting unit 17a reaches the light receiving unit 17b as it is. Bottom plate 1la
Is pivoted with one end serving as a fulcrum, and the other end is urged upward by a spring 11b so that the position of the uppermost surface of the sheet becomes constant due to the decrease in the stacking thickness due to the use of the sheet.

Next, the operation will be described. The sheet separated from the sheet storage unit 11 into one sheet is stopped in the sheet feeding path 15 with its leading end abutting on the nip portion of the registration roller 14. As a result, the light receiving portion 16b of the first paper sensor 16
The transmitted light for the number of sheets is detected. Since the light receiving portion 17b of the second paper sensor 17 detects light transmitted through the paper stacked in the paper storage portion 11, the number of papers is reduced, and the transmitted light is detected at a level inversely proportional to the number of remaining papers. Will be. The detection signal of the first paper sensor 16 and the detection signal of the second paper sensor 17 are sent to a comparison unit (not shown) so that the levels of both signals are compared.
Since the first paper sensor 16 and the second paper sensor 17 have the same characteristics, the transmission of the second paper sensor 17 is based on the detection level of the transmitted light of the first paper sensor 16. If the light detection level is the same as the detection level of the first paper sensor 16, it can be recognized that the number of remaining papers in the paper storage unit 11 is one, and if the detection level is １ ／, the number of remaining papers is two. Light receiving section 1 of second paper sensor 17
When the transmitted light is hardly detected in 7b, the number of remaining sheets in the sheet storage unit 11 is large. This relationship is maintained even if the type of paper is different, as long as the same paper is loaded.

The positional relationship of the paper sensor in the paper supply path will be described in more detail with reference to FIG. When the length of paper L2 for executing two printings in one process with respect to the length of paper L1 for normal printing of the electrophotographic printing apparatus using the color laser, there is generally a relationship of L2 ≦ L1 / 2.
The distance from the second paper sensor 17 including the paper feed path 15 to the nip of the registration roller 14 is L0. Then, the relationship between these lengths is set to L2 <L0 <L1. As a result, during normal printing, the sheet having the sheet length L1 separated from the sheet feeding mechanism 12 and conveyed to the sheet feeding path 15 receives the first sheet sensor 16 and the second sheet sensor 1.
7 are in both detection ranges. On the other hand, the sheet length L2
When the sheet is conveyed to the sheet feed path 15, the sheet is detected by the first sheet sensor 16, but falls outside the detection range of the second sheet sensor 17. Therefore, the paper length L can be obtained by one process.
The second sheet sensor 17 for printing two sheets of the second sheet detects the number of sheets excluding the sheet conveyed to the sheet feeding path 15.

The position of the second paper sensor 17 changes according to the amount of paper loaded since the light receiving portion 17b is attached to the bottom plate 11a. It is desirable that the light emitting portion 17a is also attached to the bottom plate 11a and that the interval between the light receiving and light emitting portions is always kept constant. Therefore, the light emitting unit 1
7a is attached to a frame or the like of an electrophotographic printing apparatus,
The interval between the light receiving unit 17b and the light emitting unit 17a in a state where the last one or two sheets remain on the bottom plate 11a may be the same as that of the first sheet sensor 16. The reason will be described later.

FIG. 3 is a time chart of the color electrophotographic printing process, and FIG. 4 is a diagram for explaining the determination based on the paper sensor detection result. Hereinafter, the operation of the first embodiment will be described with reference to FIGS. The explanation is an operation when two short images are printed in one process. For the sake of explanation, the first and second sheets are used in the first process. The third sheet of paper used in
Take the sheet.

Exposure of Y (yellow) to the surface of the photoreceptor 1
Development is performed, and the Y-color development is transferred to the intermediate transfer body 6.
Exposure and development of M color (magenta) are started during transfer of Y color in accordance with the rotation timing of the intermediate transfer body 6, and similarly, development of C color (cyan) and BK color (black) is performed on the intermediate transfer body 6. It is transcribed again. The two images on which the four colors are superimposed on the intermediate transfer body 6 are second-transferred sequentially to the first and second sheets by the transfer unit 8. The sheet on which the image has been transferred by the second transfer is discharged from the printing apparatus through a fixing process. When the development of the BK color is completed to improve the printing processing speed, the exposure and development of the Y color in the second process are started. At this time, the first sheet sensor 16 and the second sheet sensor 17 indicate that two or more third and fourth sheets used in the second process remain in the sheet storage unit 11.
The determination unit determines from the detected output signal level of the above (2) whether or not to start the second process.

Before the start of exposure in the second process, the detection levels of the first paper sensor 16 and the second paper sensor 17 are determined. The sheet sensor 16 detects the first sheet in the sheet feed path 15. The paper sensor 16 always detects one sheet, and determines the detection result of the paper sensor 17 based on the detection level. Paper sensor 17
Detects the second and subsequent sheets remaining in the sheet storage unit 11, and the sheet sensor 16 and the sheet sensor 17 are light transmission sensors having the same characteristics.
If the detection level of No. 6 is the same as the detection level of the sheet sensor 17, the presence of the first sheet (second sheet) in the sheet storage unit 11 is detected. The detection level of the paper sensor 17 is the paper sensor 1
6 is 1/2 of the detection level, two sheets (2
The presence of the third and third sheets is detected. Paper sensor 17
If the detection level is 1/3 or less of the paper sensor 16, it means that three or more (fourth or more) papers remain.

Therefore, when the paper sensor 16 detects the presence of the first sheet, if the detection level of the paper sensor 17 is の of that of the paper sensor 16, the second process exposes no paper. The exposed image data is deleted. However, when the detection level of the paper sensor 17 is 1/3, the fourth or more sheets remain, so that printing in the second process is not hindered. By setting the threshold value of the detection level of the paper sensor 17 between 1/2 and 1/3 of the paper sensor 16, it is possible to determine whether or not the second process can be started. In this manner, the next printing process (third and fourth sheets) that starts accurately before the sheet supply by accurately detecting the remaining amount of the last two or three sheets in the sheet storage unit 11.
The start of exposure is stopped, paper is replenished, and then restarted.
The erasure (deletion) of the data of the first and fourth sheets can be prevented.

When a large number of sheets are stacked in the sheet storage section 11, the light emitting section 17a and the light receiving section 17 of the sheet sensor 17 are used.
The light receiving sensitivity is lowered while the interval b is low, but when the light receiving sensitivity is low, the direction of the remaining number of sheets does not hinder the continuation of the process. The interval between the light receiving unit 17b and the light emitting unit 17a may be the same as the interval between the first paper sensors 16.

Embodiment 2 FIG. In the first embodiment, the position of the second paper sensor 17 is
4, the length from the second paper sensor 17 including the paper feed path 15 to the nip of the registration roller 14 is set to a position larger than の of the normally used paper length. The position may be shorter than 1/2. That is, assuming that the paper length L2 when two prints are executed in one process and the distance length L0 from the nip portion of the registration roller 14 to the paper sensor 17, L0 <L2.

The detection of the remaining number of sheets when printing two sheets at a time in one process will be described. Before the exposure of the second process is started, the paper sensor 16 and the paper sensor 17 are used.
Is determined by the comparing unit. The paper sensor 16 detects the first sheet in the paper supply path 15 and
7 detects the second and subsequent sheets remaining in the sheet storage unit 11 including the first sheet in the sheet feeding path 15. Paper sensor 16
Is equal to the detection level of the paper sensor 17, the remaining paper in the paper storage unit 11 is zero. If the detection level of the paper sensor 17 is の of the detection level of the paper sensor 16, the presence of the first (second) paper in the paper storage unit 11 is detected. Similarly, if the detection level of the paper sensor 17 is 1/4 or less of the paper sensor 16, it is detected that four or more sheets including the paper in the paper feed path 15 remain.
Therefore, by setting the threshold value of the detection level of the paper sensor 17 between 1/3 and 1/4 of the paper sensor 16, it is possible to determine whether or not the second process can be started. In this case, since the number of sheets detected by the sheet sensor 17 is one more than in the first embodiment, there is a problem in that the setting width of the threshold value of the sheet sensor 17 is reduced.

In the above description, the paper sensor 17 can also be used as a paper head position detection sensor for controlling the registration rollers 14 and the like.

[0025]

As described above, according to the present invention, in an electrophotographic printing apparatus capable of printing a plurality of sheets at a time in one process, the remaining amount of sheets in the sheet storage section is accurately detected, and
Since the start of exposure in the next printing process is stopped in advance, a backup memory is not required.

Further, when the first sensor detects the transmission of the paper in the paper feed path, the second paper sensor is set at a position deviated from the rear end of the paper, so that the more highly sensitive paper remaining amount can be obtained. Detection is possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a color electrophotographic printing apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG. 1 showing a paper feed path portion according to the first embodiment.

FIG. 3 is a time chart of the color printing process according to the first embodiment.

FIG. 4 is a diagram illustrating a determination based on a paper sensor detection result according to the first embodiment;

FIG. 5 is a configuration diagram illustrating a conventional color electrophotographic printing apparatus.

[Explanation of symbols]

Reference Signs List 1 photoreceptor, 2 exposure unit, 3 charger, 4 developing machine, 6
Intermediate transfer member, 7 first transfer section, 8 second transfer section,
9 fixing machine, 11 paper storage section, 12 paper feed mechanism, 13
Transport roller, 14 registration roller, 15 paper feed path,
16 First paper sensor, 16a Light emitting unit, 16b
Light receiving section, 17 second paper sensor, 17a light emitting section,
17b Light receiving unit.

Claims (5)

[Claims] 1. An electrophotographic printing apparatus having means for printing on a plurality of sheets in a single process of exposure or development, a sheet storage unit for separately feeding stacked sheets one by one, A paper feed path for guiding paper from the paper storage unit and temporarily stopping just before the transfer unit, a first paper sensor for detecting paper in the paper supply path, and a first paper sensor for detecting stacked paper in the paper storage unit; A second paper sensor having the same characteristics as the paper sensor, and a comparing unit for comparing the detection levels of the first paper sensor and the second paper sensor to determine the remaining amount of paper in the paper storage unit. An electrophotographic printing apparatus characterized by the above-mentioned. 2. The comparison section compares the detection levels of a first sheet sensor and a second sheet sensor in a first process, and determines that the remaining amount of sheets in the sheet storage section is smaller than the number of sheets that can be printed in the next process. 2. The electrophotographic printing apparatus according to claim 1, wherein when it is determined that there is no exposure, the exposure in the next process is stopped. 3. The apparatus according to claim 1, wherein when the first sensor detects a sheet in a sheet feeding path, the second sheet sensor is installed at a position deviated from a rear end of the sheet.
Or an electrophotographic printing apparatus according to claim 2. 4. The first sheet sensor and the second sheet sensor are light-transmitting sensors each including a light-emitting unit and a light-receiving unit.
An electrophotographic printing apparatus according to any one of the preceding claims. 5. When printing on two sheets in one process, when the first sheet sensor detects the first sheet of the first process, the detection level of the second sheet sensor is set. 5. The electrophotographic printing apparatus according to claim 4, wherein when the comparison section determines that the value exceeds 1/3 of the detection level of the first sheet sensor, the exposure in the next process is stopped.