JPH029348B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a laser beam printer (hereinafter referred to as LBP).
In particular, the present invention relates to a recording apparatus that controls to prevent missing pages and disorder of page order when double feeding of sheets (hereinafter referred to as paper) occurs.

Recording devices such as LBP can continuously write images on the photoreceptor, so if you keep the minimum distance between sheets when feeding paper, you can maximize the print output with the minimum time loss. You can get the number.
With such a device, even if problems occur during paper transport, such as jams, double feeds where two or more sheets of paper are transported without being separated, or skewed feeding, the throughput (unit time It is desirable to avoid reducing the number of output prints as much as possible. Normally, when a jam occurs, it is necessary to quickly stop the printer and remove the jammed paper, but double feeding does not necessarily result in a jam. Therefore, in the case of double feeding, for example, if you set up a storage section separate from the storage section that stores normal output paper and control the double feeding paper to be ejected there, the printing operation can be continued without stopping the printer. be able to. However, if the double-fed sheets are simply discharged to another storage section, the information printed out on the double-fed sheets will be missing, and it is necessary to compensate for this.

It is an object of the present invention to eliminate the above-mentioned drawbacks, to minimize the decline in printer throughput when double feeding occurs, and to automatically remove information missing due to double feeding without disrupting the order in which it is printed out. The objective is to provide a recording device that can be supplemented. That is, the present invention provides a storage means for storing sheets, a conveyance means for conveying the sheets stored in the storage means to an image forming position along a conveyance path, and a sheet conveyed to the image forming position. an image forming means for forming an image according to the image information, a detection means for detecting double feeding of sheets at a predetermined position on the conveyance path, image information for the sheet in which double feeding has occurred,
control means for controlling the image forming means to record on sheets fed from the storage means after double feeding is detected; and further, even if double feeding is detected by the detection means, double feeding does not occur. The present invention provides a recording device characterized in that the conveying operation of sheets of paper is not stopped.

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

FIG. 1 schematically shows the basic configuration of LBP. A laser beam emitted from a laser oscillator 1 enters an optical modulation system composed of a lens 2, an A/O modulation element 3 that utilizes the known acousto-optic effect, and a lens 4. Here, lens 2 is A/
Lens 4 functions to focus and project the laser beam onto the black reflection surface generated within the O modulation element.
serves to convert the laser beam diffracted and diverging from the black reflection surface into a parallel beam.

When using an E/O modulation element that utilizes a known electro-optic effect, lenses 2 and 4 are unnecessary, and when the laser oscillator is a gas laser or the like capable of current modulation, the above-mentioned optical modulation system can be omitted. Needless to say.

The laser beam emitted from the lens 4 becomes a parallel light flux, enters the beam expander 7, and the beam diameter is expanded while maintaining the parallel light velocity.

Furthermore, the laser beam whose beam diameter has been expanded is incident on a polyhedral rotating mirror 8 having one or more mirror surfaces. The polyhedral rotating mirror 8 is mounted on a shaft supported by a high-precision bearing (for example, an air bearing), and is driven by a motor 9 that rotates at a constant speed (for example, a hysteresis synchronous motor, a DC servo motor). The laser beam horizontally swept by the polyhedral rotating mirror 8 is imaged as a spot on the photosensitive drum 14 by an imaging lens 13 having f-θ characteristics. In a general imaging lens, when the incident angle of the light ray is θ, the image forming position r on the image plane is
r=f・tanθ−(1) (f: focal length of imaging lens)
When the polyhedral rotating mirror 8 is rotated at a constant speed as in this embodiment, the reflected laser beam (52 in the second diagram) is reflected by the imaging lens 13.
The angle of incidence changes linearly with time. Therefore, the moving speed of the imaged spot position on the photosensitive drum 14, which is the image plane, changes non-linearly and is not constant. That is, the moving speed increases at the point where the angle of incidence increases. Therefore, when a row of spots is drawn on the photosensitive drum 14 by turning on the laser beam at regular time intervals, the spacing between the spots will be wider at both ends than at the center.

In order to avoid this phenomenon, the imaging lens 13 is r=f・θ…(2) It is designed to have certain characteristics.

Such an imaging lens 13 is called an f-θ lens. Furthermore, when collimated light is imaged into a spot by an imaging lens, the minimum diameter of the spot dmin is dmin=fλ/A...(3) where f: focal length of the imaging lens λ: wavelength of the light used A : Given by the entrance aperture of the imaging lens; if f and λ are constant, a smaller spot diameter dmin can be obtained by increasing A. The beam expander 7 mentioned above is used to provide this effect. Therefore, if the required dmin can be obtained by the beam diameter of the laser oscillator, the beam expander 7 is omitted.

As described above, the deflected and modulated laser beam (second illustration 52) is irradiated onto the photosensitive drum 14,
After being visualized using an electrophotographic processing process, it is transferred and fixed onto plain paper and output as a hard copy. As an example of the electrophotographic process applied to this embodiment, a photosensitive plate whose basic constituents are a conductive support, a photoconductive layer, and an insulating layer, as described in Japanese Patent Publication No. 1973-23910 by the present applicant. The surface of the insulating layer 14 is uniformly charged positively or negatively in advance by the first corona charger 16, and the surface of the insulating layer 14 is charged at the interface between the photoconductive layer and the insulating layer or inside the photoconductive layer with a polarity opposite to the charged polarity. Then, the surface of the insulating layer to be charged is irradiated with the laser beam, and at the same time, an AC corona discharge is applied by the AC corona discharger 17, and a difference in surface potential occurs according to the light and dark pattern of the laser beam. A pattern is formed on the surface of the insulating layer, and the entire surface of the insulating layer is uniformly exposed with a full-surface exposure lamp 18 to form a high-contrast electrostatic latent image on the surface of the insulating layer. After the latent image is developed and visualized by a developing device 19 using a developer mainly composed of charged colored particles, the visible image is transferred to a paper that is pressed onto a photosensitive drum 14 by means described later using a charger 22. After the transfer, the transferred image is then fixed by a fixing means as described later to obtain an electrophotographic print image. After the transfer is performed, the surface of the insulating layer is cleaned by a cleaning device 23 to remove remaining charged particles, and the photosensitive plate 14 is used repeatedly.

As still another example, the present applicant's Japanese Patent Publication No. 42
An electrophotographic electrostatic image forming process such as that described in Japanese Patent No. 19748 is applied. That is, a photosensitive plate is used whose basic components are a conductive support, a photoconductive layer, and an insulating layer, and the surface of the insulating layer is uniformly charged positively or negatively by a first corona discharge, and the surface of the insulating layer or the inside of the photoconductive layer is captured by a charge having a polarity opposite to the charged polarity,
Furthermore, an alternating current corona discharge is applied to the charged surface to attenuate the charge on the surface of the insulating layer, and then the laser beam as an information signal is irradiated to form an electrostatic latent image on the surface of the insulating layer according to the brightness of the laser beam. The process of forming the electrostatic image on top and then developing the electrostatic image is the same as that of the first embodiment.

Note that 15 is a charger for pre-static elimination, and 16 is a pre-exposure lamp.The pre-neutralization charger 15 makes the surface potential of the photosensitive drum 14 constant and uniform, and the pre-exposure lamp 16 makes the characteristics of the photosensitive layer constant and uniform. These work together to clean the photosensitive drum 14 after passing through the cleaning device 23.
It functions to erase the previous history, such as residual potential, that remains in the image, and is useful for always obtaining stable images.

The applicant has proposed an electrostatic latent image stabilization method as a means of always obtaining stable and good images in the electrophotographic process applied to this embodiment. 21
1 is an electrostatic electrometer for realizing such a means, and it measures the electrostatic potential of a bright part of the photosensitive drum 14, that is, a part scanned and exposed by a laser beam, and a dark part.

A carrier removing device 20 prevents the carrier immersed in the developer in the developing device 19 from adhering to the photosensitive drum 14, adhering to the paper, or being mixed into the cleaning device 23.

FIG. 2 shows the arrangement of the optical system in FIG. 1 three-dimensionally, and in the explanation of FIG. 1, parts having the same functions are given the same numbers (the same applies hereinafter).

In FIG. 2, 51 detects the scanning start position of the swept laser beam 52 with a beam detector consisting of a small entrance slit and a photoelectric conversion element with a fast response time (for example, a PIN diode), and uses this detection signal to detect the scanning start position of the laser beam 52. , determines the start timing of a modulation control signal for providing desired optical information on the photosensitive drum 14, as will be described later.

In FIG. 2, the scanning direction of the laser beam is indicated by an arrow 53.

Next, transportation will be described. When the paper 31 stacked on the paper feeding stage 30 is sent out to the conveyance path by the paper feeding roller 32, a pair of registration rollers 33 corrects the skew during paper feeding, and
Align the edges of the paper. The paper leaving the registration rollers 33 passes through a conveyance guide 34 forming a part of the conveyance path and comes into contact with the drum 14 . A double feed detection sensor 47 is disposed between these two, and the presence or absence of double feed during paper feeding is detected based on the output of this sensor. The image on drum 14 is transferred onto paper 31 by transfer charger 22 . After the transfer, the paper is separated from the drum 14 by a separating means (not shown) and is sent to the conveyor belt 39. A photo sensor 35 is disposed in the middle of the conveyor belt 39, and the presence or absence of a jam in the conveyance path from the paper feed roller 32 to the drum 14 is detected based on the output of the photo sensor 35. Furthermore, the paper 31 is sent to a conveyor belt 39 and enters a fixing device 40. Here, the toner on the paper 31 is fused under the heat and pressure of the fuser 40 to become a permanent image. The paper 31 after fixing is conveyed by a conveyor belt 41, and a jam between the photo sensors 35 and 36 is detected by the photo sensor 36 and the photo sensor 35 arranged in front of the paper ejection roller 42. The normally conveyed paper exits the paper ejection roller 42 and is stacked on the first output tray 43.

Further, as will be described later, when double feeding is detected, the photo sensor 36 detects the paper, and the paper ejection switching plate 44 is switched to the position shown by the broken line, so that the paper that is considered abnormal is transferred to the paper ejection rollers 42 and 45. After that, the second
It is loaded onto the output tray 46. Paper ejection roller 45
A photo sensor 37 is placed just in front of the
It is detected that the non-sheets are reliably conveyed to the second output tray 46.

FIG. 3 is a block diagram showing the control section of the LBP. 100 is a CPU that controls the operation of the LBP according to a program stored in a ROM (not shown);
01 is a double feed detection sensor and corresponds to 47 in FIG. The signal from this double feed detection sensor 101 is amplified by an amplifier circuit 102, and the A/D converter 1
03 and input to the CPU 100. Further, a drive signal from the CPU 100 is output via switching circuits 104 and 105 to a paper feed roller clutch 106 and a paper discharge switching solenoid 107, respectively, and the paper feed roller 32 and paper discharge switching plate 44 are driven. Also, image writing timing signal
VTS outputs page information circuit 10 from CPU 100
8 is output.

Video signal from page information output circuit 108
VS and a permission signal PS from the CPU 100 are input to an AND gate 109, and the output from the AND gate 109 is input to an A/O modulator 111 via an A/O driver 110 (corresponding to 5 in FIG. 1). As a result, the A/O modulator 111 (corresponding to 3 in FIG. 1) is turned on and off according to the video signal.

4 to 9 are diagrams schematically showing the conveyance path from the paper feed section to the photosensitive drum. In Figure 4,
The image writing device on the photosensitive drum 14 is O, the image transfer position is T, the leading edge of the paper 31 in contact with the paper feed roller 32 is P, the paper feeding order is N, N+1, N+2, etc., and the image is written on the photosensitive drum 14. The order of page information of images to be loaded is assumed to be n, n+1, n+2, . . . . Further, the distance along the photosensitive drum 14 from the image writing position O to the image transfer position T is L ₁ , and the transport distance from the leading edge P of the paper 31 to the image transfer position T is L ₂ .

In the case of L ₁ L ₂ as shown in Figure 4, in order for the leading edge of the image to match the leading edge of the paper at the image transfer position T, the paper feeding must come first and the image writing must come later in terms of timing. is clear.

Also, as shown in Figure 5, when L ₁ > L ₂ , in order for the leading edge of the image to match the leading edge of the paper at the image transfer position T, the image writing must be done first in terms of timing, and the paper feeding must be done first. It is clear that this will come later.

Here, if the length of the paper in the conveying direction is L _P , the feeding interval between papers is L _G , and the distance from the leading edge P of the paper to the double feed detection sensor is L _S , then continuous paper feeding The distance between the paper and the leading edge of the paper is L _P +L _G.

The arrangement position of the double feed detection sensor and the photoconductor 14 will be explained below with reference to the flowcharts in FIGS. 6 to 9 and 10 to 13, and the timing charts in FIGS. 14 to 17.
Control performed when double feeding is detected will be explained based on the relationship of page information written above.

As shown in FIG. 6, in the conveyance path where L ₁ L ₂ , L _P +L _G L _S , double feeding occurs in the Nth paper feed, the flowchart in FIG. 10 and the timing chart in FIG. 14 As shown in , the N+1th sheet feeding has already been performed. Also, to the photoconductor 14 is n+1.
Information on the page is being written. Therefore, if the Nth paper fed is ejected to the second output tray 46, and the N+1st paper fed is ejected to the first output tray 43 since double feeding has not occurred, the information on the nth page will be is missing. Furthermore, even if the information of the n-th page is outputted to the N+2-th paper fed, the order of the pages will be n-1, n+1, and n, and the order will be out of order.

Therefore, in order to prevent missing pages and to avoid disrupting the order of pages, if double feeding occurs on the Nth paper feed,
The +1st paper fed is also discharged to the second tray 46, and the nth page information is output for the N+2nd paper fed, thereby preventing missing pages and disrupting the page order. . In other words, double feed is detected by the double feed detection sensors 101 and 47,
When the output becomes "H", the permission signal PS from the CPU 100 becomes "L", and the video signal VS from the page information output circuit 108 is transmitted to the A/O modulator 1.
It is not output to 11 and 3. When the sensor 36 detects double feeding, the output signal from the CPU 100 turns on the paper ejection switching solenoid 107 via the switching circuit 105, and the paper ejection switching plate 44
is switched to the dashed line position in Figure 1, and the Nth and N+
The first fed paper is ejected to the second output tray 46. Further, when the paper feed roller clutch 106 is turned on and the N+2th paper is fed, the permission signal PS becomes "H" at a predetermined timing, and the information on the nth page is sent from the page information output circuit 108 to the AND gate 109. via A/O driver 110,5
The laser beam is modulated by the A/O modulators 111 and 3, and information for the n-th page is written onto the photosensitive drum 14. and image transfer position T
The transferred paper is discharged to the first output tray 43. At this time, the paper discharge switching solenoid 107 is turned off, and the paper discharge switching plate 44 has returned to the position shown by the solid line in FIG. Thereafter, the information of the (n+1)th page is transferred to the (N+3)th paper that is fed.

Next, as shown in Figure 7, L ₁ L ₂ and L _P +L _G > L _S
A case in which double feeding occurs in the Nth paper feed in the conveyance path having the following relationship will be described with reference to the flowchart of FIG. 11 and the timing chart of FIG. 15. At the time when double feeding is detected by the double feeding detection sensors 101 and 47, information on the n-th page is being written on the photosensitive drum 14. Therefore, instead of outputting the information on the (n+1)th page for the (N+1)th paper fed, it is possible to output the information on the nth page again. Therefore, when the outputs of the double feed detection sensors 101 and 47 rise to "H" level, the permission signal PS is set to "L" level so that the video signal VS is not output to the A/O modulators 111 and 3 in the same manner as described above. do. and paper feed clutch 106
is turned on and the N+1th paper is fed, the information on the nth page is transferred to the photosensitive drum 1 at a predetermined timing.
4 and is transferred to the N+1th paper fed. From then on, the N+ second paper fed is n+
The information on the first page is transferred to the (N+3)th fed paper, and the information on the (n+2)th page is transferred. Further, after the outputs of the double feed detection sensors 101 and 47 rise, when the photo sensor 36 detects double feed, the paper discharge solenoid 107 is turned on, and the Nth paper fed is transferred to the second paper feed.
It is discharged onto the output tray 46.

Further, FIGS. 8 and 9 show schematic diagrams of conveyance paths in the relationship L ₁ >L ₂ . In this case, as described above, the timing of writing an image onto the photosensitive drum is earlier than the paper feeding timing. Figure 8 In the case where L _P +L _G L _S ,
The control flowchart is shown in FIG. 12, and the timing chart when double feeding occurs in the Nth sheet feeding is shown in FIG. 16. In this case, at the time when it is detected that the Nth fed paper is double fed, information on the (n+2)th page has already been written on the photosensitive drum 14. Furthermore, since the N+1st sheet has already been fed, it is necessary to eject the Nth and N+1st fed sheets to the second output tray 46 in order to prevent missing pages and disrupting the page order. be. That is, when the outputs of the double feed detection sensors 101 and 47 rise, the video signal is
The permission signal PS is set to "L" level so that VS is not output to the A/O modulators 111 and 3. Also, n+2
Since it is not necessary to transfer the information on the page number, feeding of the N+2th paper is prohibited. When the photo sensor 36 detects double feeding after the outputs of the double feed detection sensors 101 and 47 rise, a drive signal is output from the CPU 100 to the switching circuit 104, turning on the paper ejection switching solenoid 107, and the paper ejection switching plate 44 is turned on. The N-th and N+1-th fed sheets are outputted to the second output tray 46.
Thereafter, control is performed to write information onto the photosensitive drum 14 from the n-th page onwards. In other words, during normal operation, n+3
Information on the n-th page is written on the photoreceptor 14 at the timing when the information on the page is output, and the N+2-th sheet is fed at a predetermined timing (the N+3-th sheet feeding timing during normal operation). After image transfer, the image is discharged onto the first output tray 43.

Fig. 9 shows the case where L _P + L _G + L _S , the control flowchart is shown in Fig. 13, and the timing chart when double feeding occurs in the Nth paper feed is shown in Fig. 17.
As shown in the figure. In this case, at the time when it is detected that the Nth fed paper is double fed, information on the n+1th page is being written, and the N+1th paper feeding has not yet been performed. Therefore, the feeding of the N+1th sheet is prohibited, and control is performed so that only the Nth sheet fed is discharged to the second output tray 46. That is, when the output signals of the double feed detection sensors 101 and 47 rise, the permission signal PS is set to "L" level so that the video signal VS is not output to the A/O modulators 111 and 3 as described above.
Also, feeding of the N+1th paper is prohibited. Then, the information on the nth page is written on the photosensitive drum 14 at the timing when the information on the n+2th page is written during normal operation, and the N+1th paper is fed at the timing when the N+2th paper is fed during normal operation. The image information of the page is transferred and discharged to the first output tray 43. Thereafter, the information after the (n+1)th page is output. Note that when the photo sensor 36 detects double feeding after double feeding is detected, the paper ejection switching solenoid 107 is turned on by a drive signal from the CPU 100, and the Nth fed paper is ejected to the second output tray 46. .

As described above, according to the present invention, wasted paper feeding can be minimized when double feeding is detected, and missing pages and page order disorder can be prevented.

Furthermore, since image formation is performed from the missing page without stopping the apparatus, a decrease in the throughput of the apparatus can be prevented as much as possible.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the LBP, Fig. 2 is a partially enlarged perspective view of the LBP shown in Fig. 1, Fig. 3 is a control block diagram, and Figs. 4 to 9 are from the photosensitive drum and paper feed section to the photosensitive drum. Schematic diagram showing the conveyance path of 10th to 1st
FIG. 3 is a flow chart, and FIGS. 14 to 17 are timing charts. In the figure, 1 is a laser oscillator, 3,111 is an A/O
A modulator, 5 and 110 are A/O drivers, 14 is a photosensitive drum, 44 is a paper ejection switching plate, 43 and 46 are output trays, 47 is a skew detection sensor, 100 is a CPU,
106 is a paper feed roller clutch, 107 is a paper discharge switching solenoid, and 108 is a page information output circuit.

Claims (1)

[Scope of Claims] (1) A storage means for storing sheets of paper; a conveyance means for conveying the sheets stored in the storage means to an image forming position along a conveyance path; and a sheet conveyed to the image forming position. an image forming means for forming an image on a sheet according to image information; a detection means for detecting double feeding of sheets at a predetermined position on the conveyance path; a control means for controlling the image forming means to record on a sheet fed from the storage means after the feeding is detected; A recording device characterized in that sheet conveyance operation is not stopped.