JPH1165185A - Copying machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent transfer paper from being wasted unwittingly by correctly detecting a blank original. SOLUTION: This copying machine is constituted to form an electrostatic latent image by an exposing process irradiating a photoreceptor drum 12 with reflected light from an original image, after uniformly electrifying the photoreceptor drum 12, to make a toner stick on the electrostatic latent image with a developing section 18 and to transfer it on transfer paper 20 with a transferring section 22. A controlling section, when detecting the potential of the electrostatic latent image formed by the exposing process by the potential sensor 16, comparing the potential with a threshold value of a reference potential generating section and judging it as a blank original in the case that the potential is below the threshold value, makes a transporting roller rotate reversely to return the transfer paper 20 to a paper feeding tray 32 passing through a reversely transporting path 40 and the feeding paper tray reversely transporting path 44 and so as to be used again for a copying process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, and more particularly, to reading an original image to form an electrostatic latent image on a photoreceptor, attaching toner to the electrostatic latent image, and conveying the electrostatic latent image from a tray. The present invention relates to a copying machine for transferring to a transfer paper.

[0002]

2. Description of the Related Art Heretofore, when a document image to be copied is a blank sheet, the copying process itself has been stopped in order to suppress waste of transfer paper. For example,
In the copying machine described in Japanese Patent Application Laid-Open No. 7-23156,
An image scanner (CCD) that reads the image density of a document on both sides and detects the presence or absence of a blank page is located in the middle of the document transport path of an automatic document feeder (ADF) as a means to detect blank pages in the document. In some cases, the copying process on the side determined to be blank is stopped. In digital copiers,
If the amount of black pixels in the original image is below a certain threshold,
In some cases, it was determined that the paper was blank and copying was stopped. As this type of apparatus, for example, Japanese Patent Application Laid-Open No. 4-6875
No. 7, JP-A-62-31866, and the like.

[0003]

However, in such a conventional copying machine, the original is blank by detecting the density of the original when the original is conveyed by using the automatic document feeder (ADF) described above. For example, in the case of a device that determines that a document has only one small character, the document may be erroneously detected and determined to be a blank sheet, which is inconvenient in terms of detection accuracy. Also, in the above-mentioned digital copiers and the like, an original image is captured in pixel units,
Since a blank page of a document is detected based on whether or not the amount of black pixels exceeds a certain threshold value, it is difficult to distinguish between a blank page but a slightly dirty corner and a document in which only one line is described. However, there is an inconvenience that it is difficult to distinguish a blank manuscript. SUMMARY OF THE INVENTION The present invention has been made in view of the inconveniences of the related art, and an object of the present invention is to provide an analog copying machine which has high detection accuracy for a blank document and does not use an automatic document feeder (ADF). However, an object of the present invention is to provide a copying machine capable of accurately detecting a blank document and preventing waste of transfer paper. An object of the present invention is to provide a copying machine capable of accurately detecting a blank document and preventing waste of the transfer sheet even in a double-sided copy machine capable of transferring an image to both sides of a transfer sheet. Is to provide. A third object of the present invention is to provide a copying machine capable of always properly detecting a blank document by enabling a detection standard of a blank document to be appropriately changed according to a situation.

[0004]

According to the first aspect of the present invention, an original image is read to form an electrostatic latent image on a photoreceptor, toner is attached to the electrostatic latent image, In a copying machine for transferring to a conveyed transfer sheet, a potential sensor for detecting the potential of the photoreceptor surface and a potential of a portion for transferring to the transfer sheet detected by the potential sensor are lower than a predetermined threshold potential Potential determining means for determining whether or not
When the potential discriminating means determines that the original image is blank when the potential of the photoreceptor surface is lower than a predetermined threshold potential, the transfer paper conveyed from the paper feed tray is returned to the paper feed tray. And reverse transport means. According to the present invention, the potential of the surface of the photosensitive member is detected by the potential sensor, and the potential of the portion of the photosensitive member, which is detected by the potential sensor and transferred to the transfer paper, is lower than the predetermined threshold potential. It is determined whether the potential of the photoreceptor surface is lower than a predetermined threshold potential as a blank document, and the transfer paper transported from the paper feed tray by the reverse transport means is returned to the paper feed tray. I will put it back. For this reason, for example, if a potential at a critical level for determining whether or not toner adheres to the photoconductor is set as the threshold, if the potential on the photoconductor surface is equal to or higher than the threshold level, the toner is applied to the photoconductor. Is attached and the image is transferred to the transfer paper, so it is treated as a normal original.If the potential of the photoconductor surface is below the threshold level,
Since the toner is not attached to the photoreceptor and is not transferred to the transfer paper, it is determined that the original is a blank document, and the transfer paper is returned to the paper feed tray by the reverse conveyance means, so that the transfer paper can be prevented from being wasted. .

According to a second aspect of the present invention, an original image is read, an electrostatic latent image is formed on a photoreceptor, toner is adhered to the electrostatic latent image, and a transfer paper conveyed from a paper feed tray is formed. A potential sensor for detecting the potential on the surface of the photoreceptor in a double-sided copying machine in which the image is transferred to the front side and retracted to the intermediate tray, and the next original image is transferred to the back side of the transfer paper conveyed from the intermediate tray. A potential discriminating means for discriminating whether or not the potential of the portion to be transferred to the transfer paper detected by the potential sensor is lower than a predetermined threshold potential; If the transfer image is lower than the threshold potential, the document image is determined to be a blank sheet, and if the transfer sheet has been conveyed from the sheet feed tray, it is returned to the sheet feed tray, and the transfer sheet is conveyed from the intermediate tray. If it is done, put it on the intermediate tray Reverse conveying means for Suyo, those having a. According to the present invention, the potential of the surface of the photosensitive member is detected by the potential sensor, and the potential of the portion of the photosensitive member, which is detected by the potential sensor and transferred to the transfer paper, is lower than the predetermined threshold potential. It is determined whether the potential of the photoconductor surface is lower than a predetermined threshold potential as a blank document, and if the transfer paper has been conveyed from the paper feed tray by the reverse conveyance means, the feeding is performed. Return to the paper tray, and if the transfer paper has been transported from the intermediate tray, return to the intermediate tray. For this reason, even in a two-sided copying machine, it is possible to accurately detect that the original image is blank,
If the transfer paper has not been transferred to any side, return it to the paper feed tray, if it has already been transferred to one side, return it to the intermediate tray, so that the blank document is skipped and the next document image is printed. It can be transferred sequentially. According to a third aspect of the present invention, in the copying machine according to the first or second aspect, a threshold potential varying means for varying a threshold potential in the potential determining means is provided. According to the present invention, since the threshold potential of the potential discriminating means can be changed by the threshold potential varying means, the detection reference of the blank document is changed to an appropriate value according to the situation, thereby always accurately. A blank document can be detected.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a schematic configuration of a copying machine according to the present embodiment, and FIG.
Is shown in the control block diagram of FIG. The copier 10 according to the present embodiment, in a state where the photoconductor is charged,
An electrophotographic process that forms an electrostatic latent image by irradiating the photoreceptor with reflected light extracted by irradiating the original image with strong light, attaching toner to this, transferring it to transfer paper, and then performing a fixing process. Is a copying machine using a single-sided copy mode in which transfer is performed only on one side of a transfer sheet and a double-sided copy mode in which transfer is performed on both sides of a transfer sheet. Here, an example of an analog copying machine having no automatic document feeder (ADF) having a function of detecting a blank document will be described. In FIG. 1, the copying machine 10 includes a photosensitive drum 12 for forming an electrostatic latent image, a charging unit 14 for charging the surface of the photosensitive drum 12 at a uniform potential, and a width of the photosensitive drum 12 (see FIG.
And a potential sensor 16 which can detect the potential of the surface of the photosensitive drum 12, and adheres toner to the surface of the photosensitive drum 12 on which the electrostatic latent image is formed. The developing unit 18 performs the development by causing the toner on the photosensitive drum 12 to be transferred onto the transfer paper 20. The transfer unit 22 includes a transfer charger. The toner remaining on the surface of the photosensitive drum 12 after the transfer is removed. And a cleaning unit 24 that prepares for the next latent image by performing charge elimination, a fixing roller 26 that heats and fixes the toner transferred to the transfer paper 20, and a state in which the fixing roller 26 is pressurized at a constant pressure. Pressure roller 2 rotatably arranged at
8. The transfer paper 20 is supplied to the transfer unit 22 via the conveyance path, and the transfer paper 2 is fixed by the fixing roller 26 or the like.
Transport system 3 for transporting the “0” to a predetermined tray via the transport path
0 and so on.

[0007] The transport system 30 includes a paper feed tray 32 for storing new transfer paper 20, an intermediate tray 34 for temporarily storing the transfer paper 20 copied on one side in the double-sided copy mode, and a transfer end. A transfer path 38 for transporting the transfer paper 20 supplied from the paper feed tray 32 or the intermediate tray 34 to the transfer unit 22, and a transfer paper transported to the discharge position A in reverse. Reverse transfer path 40, an intermediate tray reverse transfer path 42 for returning the transfer paper 20 to the intermediate tray 34 via the reverse transfer path 40, and a reverse transfer path 40.
The paper feed tray reverse conveyance path 44 for returning the transfer paper 20 to the paper supply tray 32 through the intermediate paper feed path, and the intermediate tray conveyance path 4 for conveying the transfer paper 20 that has been copied on one side in the double-sided copy mode to the intermediate tray 34
6. A switching claw 48 for switching the transfer paper 20 having undergone the fixing process to the direction of the discharge position A or to send the transfer paper 20 to the intermediate tray conveyance path 46;
Claw 50, reverse conveyance path 40 for switching to send out to
The switching claw 52 for switching the transfer paper 20 that has come to the intermediate tray reverse transport path 42 or the paper feed tray reverse transport path 44, a feed roller 54 for feeding the transfer paper 20 from the paper feed tray 32, and a transfer paper from the intermediate tray 34 The paper feed roller 56 feeds out the paper 20 and the transport roller 58 near the outlet of the paper discharge tray for discharging the transfer paper 20 at the paper discharge position A to the paper discharge tray 36. A transport roller for transporting the transfer paper 20 at predetermined intervals is disposed in each of the above-described transport paths.

As shown in the control block diagram of FIG. 2, each of the above-described components (charging unit 14, potential sensor 16,
Developing unit 18, transfer unit 22, fixing units 26 and 28, transport system 3
0) is controlled by a control unit 68 including a CPU and the like. The control unit 68 controls the latent image forming unit 62 (not shown in FIG. 1) that irradiates the original image with light to extract reflected light and irradiates the photosensitive drum 12 to form an electrostatic latent image. At the same time, the potential of the surface of the photosensitive drum 12 detected by the potential sensor 16 is compared with a reference (threshold) potential generated by the reference potential generator 64 to determine whether the document is a blank document. In the present embodiment, there is provided a potential varying section 66 which can manually set and change the reference potential generated by the reference potential generating section 64 arbitrarily.

Next, the operation will be described. Control unit 6
Reference numeral 8 denotes the photosensitive drum 1 by the charging unit 14 shown in FIG.
2 is charged so as to be charged at a uniform potential, the latent image forming section 62 irradiates light onto a document image (not shown), and irradiates the photoconductive drum 12 with reflected light to thereby statically charge the image. Control is performed to form an electrostatic latent image. In other words, the reflected light of the original image becomes a strong reflected light at a low density and a weak reflected light at a high density according to the image density of the original, and is irradiated onto the surface of the photosensitive drum 12. The surface of the photosensitive drum 12 is uniformly charged by the charging unit 14 as described above, and a charge amount proportional to the intensity of the irradiated light is removed. For this reason, the portion where strong light is applied has a small charge and the amount of adhered toner is small, but the portion where weak light is applied has a large charge and the amount of attached toner is large. As described above, since the density of the original image is directly reflected on the amount of toner adhering to the surface of the photosensitive drum 12 and is transferred to the transfer paper 20, the original image can be copied onto the transfer paper.

In the present embodiment, in order to determine whether or not a document is a blank sheet, as shown in FIG. A potential sensor 16 having substantially the same width as that of the photosensitive drum 12 is disposed at a portion of the stage shown in FIG.
The surface potential of a portion where an image is formed on the second transfer paper 20 is detected, and when the surface potential is equal to or less than a predetermined threshold value, it is determined that the document is a blank document. Here, the threshold potential is
Since the toner is set near the critical level of whether or not the toner adheres to the photosensitive drum 12, if only a potential lower than the threshold level can be detected, the toner does not adhere to the transfer paper. . If a potential equal to or higher than the threshold level is detected, there is a possibility that some image is displayed, and it is determined that there is a document image, and the image is processed. However, even for a blank document, the transfer paper 20
Potentials higher than the threshold level may be detected in areas other than the area where the image is formed, and if a blank document is judged to have a document image in response to minute dust or transfer paper stains, an erroneous detection is performed. Therefore, only the surface potential of the photosensitive drum 12 at the portion where the image is formed on the transfer paper 20 is detected, and the threshold level is adjusted (here, the threshold level is increased) to remove dust and dirt. Be careful not to mistake it for the original image.

As shown in FIG. 2, it is determined whether or not the potential detected by the potential sensor 16 is equal to or lower than a threshold value.
The control section 68 compares the threshold potential as a reference generated from the reference potential generating section 64 with the potential detected by the potential sensor 16.
Are compared. When the threshold potential is adjusted as described above, the setting of the threshold potential may be changed manually or the like using the potential variable unit 66. Transfer paper 2
In the case of a single-sided copy mode in which a single-sided copy is performed, the transfer paper 2 fed by the feed roller 54 from the paper feed tray 32 is used.
0 is conveyed to the transfer unit 22 through the conveyance path 38, the developed toner is transferred to the photosensitive drum 12, and is subjected to a fixing process by a fixing unit including a fixing roller 26 and a pressure roller 28. The sheet is conveyed to the discharge position A while being lowered, and is held by the conveying rollers 58 near the exit of the sheet discharge tray 36. In this state, when the control section 68 determines that the document is a blank sheet, the transport roller is rotated in the reverse direction with the switching claws 50 and 52 raised, and the transfer paper is passed through the reverse transport path 40 and the paper feed tray reverse transport path 44. 20 is returned to the paper feed tray 32.

The returned transfer paper 20 can be reused because the toner is not attached thereto, and when the copy start button (not shown) is pressed next time, the paper feed tray 32 is returned again.
And a copying process similar to that described above is performed.
The transfer paper 20 transported to the discharge position A after the fixing process is
When the control section 68 determines that the document is not a blank sheet, it rotates the transport roller 58 in the forward direction and discharges the document to the discharge tray 36. In the case of the duplex copy mode in which copying is performed on both sides of the transfer paper 20, the transfer paper 20 fed by the feed roller 54 from the paper feed tray 32 is transported to the transfer unit 22 through the transport path 38, and is developed on the photosensitive drum 12. The transferred toner is transferred to the front side of the transfer paper 20 and is subjected to a fixing process by the fixing roller 26 and the pressing roller 28. Then, the toner is conveyed with the switching claw 48 raised, and is passed through the intermediate tray conveyance path 46. Once stored in the tray 34. Here, when the control section 68 determines that the document is a blank sheet and presses the next copy start button, the transfer sheet 20 stored in the intermediate tray 34 is fed by the feed roller 56, passes through the transport path 38, and is again sent. A copying process is performed in the transfer unit 22.

If the controller 68 determines that the original is not blank, and then presses the next copy start button, the above-described copying process is a transfer on the back side of the transfer paper 20, and after the fixing process is performed, The sheet is conveyed to the discharge position A with the switching claw 48 lowered, and is held by the conveying rollers 58 near the exit of the sheet discharge tray 36. In this state, if the control unit 68 determines that the original is a blank sheet, the control unit 68 reversely rotates the transport roller in a state where the switching claw 50 is raised and the switching claw 52 is lowered, and the reverse transport path 40 and the intermediate tray reverse transport path. 42
, The transfer paper 20 is returned to the intermediate tray 34. Thus, the copying process on the back side of the transfer paper 20 is performed again. In this manner, the transfer paper 20 copied on both sides
After the fixing process, the sheet is conveyed to the discharge position A, and is held by the conveying rollers 58 near the exit of the sheet discharge tray 36. Here, when the control unit 68 determines that the document is a blank sheet again, the same processing as described above is repeated. However, when it is determined that the document is not a blank sheet, the transport roller 58 is sequentially rotated to discharge the document to the discharge tray 36.

If the control unit 68 does not determine whether the original is blank or not, the operator of the copying machine 10 inputs a numerical value input to the variable potential unit 66 using a ten-key (not shown). And the reference potential generator 64
The error of the threshold potential set at the time of factory shipment or the type of the document to be handled can be corrected by changing the threshold potential at which the error occurs. As described above, according to the present embodiment, even if blank paper is mixed in a copy original, it is possible to accurately detect that the original is a blank original and return the original to the feed tray 32 or the intermediate tray 34. Therefore, there is an advantage that the transfer paper 20 can be used without waste. Further, according to the present embodiment, it is possible to accurately detect whether or not a document is a blank document in either the one-sided copy mode or the two-sided copy mode, and perform appropriate processing based on the detection result. Therefore, it is possible to prevent the transfer paper 20 from being wasted. Further, the setting of a reference (threshold) potential serving as a criterion for determining whether or not a document is a blank document can be arbitrarily changed, so that adjustment according to the situation is possible. In the above embodiment, the case of a copying machine has been described. However, the present invention can be applied to a facsimile apparatus using an electrophotographic process. Further, in the above-described embodiment, the copier having the configuration in which the one-sided copy mode or the two-sided copy mode can be selected has been described, but a copier dedicated to any one of the modes may be used.

[0015]

As described above, according to the first aspect of the present invention, the detection accuracy of a blank document is high, and even if the analog copy machine does not use the automatic document feeder (ADF), the blank document can be detected. Accurate detection can prevent waste of transfer paper. According to the invention described in claim 2,
Even in a double-sided copying machine capable of transferring an image to both sides of a transfer sheet, a blank document can be accurately detected so that the transfer sheet is not wasted. According to the third aspect of the present invention, the blank document detection criterion can be appropriately changed according to the situation, so that the blank document can always be properly detected.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a copying machine according to an embodiment.

FIG. 2 is a control block diagram of the copying machine shown in FIG.

[Explanation of symbols]

REFERENCE SIGNS LIST 10 copier 12 photoreceptor drum (photoreceptor) 16 potential sensor (part of potential discrimination means) 20 transfer paper 32 paper feed tray 34 intermediate tray 40 reverse transport path (part of reverse transport means) 42 intermediate tray reverse transport path (Part of the reverse transport unit) 44 paper feed tray reverse transport path (part of the reverse transport unit) 64 reference potential generation unit (part of the potential determination unit) 66 potential variable unit (threshold potential variable unit) 68 control Part (part of the potential determination means, part of the reverse transport means)

Claims (3)

[Claims] 1. A copying machine for reading a document image to form an electrostatic latent image on a photoreceptor, attaching toner to the electrostatic latent image, and transferring the latent image to transfer paper conveyed from a paper feed tray, A potential sensor for detecting a potential on the surface of the photoreceptor; a potential determination unit for determining whether a potential of a portion to be transferred to transfer paper detected by the potential sensor is lower than a predetermined threshold potential; When the determination unit determines that the potential of the photoconductor surface is lower than a predetermined threshold potential, the document image is determined to be a blank sheet, and the transfer sheet conveyed from the sheet feed tray is returned to the sheet feed tray. And a reverse conveying means. 2. An original image is read to form an electrostatic latent image on a photoreceptor, toner is adhered to the electrostatic latent image, and the toner is transferred to the front side of transfer paper conveyed from a paper feed tray to form an intermediate image. In a double-sided copying machine in which the next document image is transferred to the back side of the transfer paper conveyed from the intermediate tray by retracting to the tray, a potential sensor for detecting the potential of the photoreceptor surface; Potential determining means for determining whether or not the potential of the portion to be transferred to the transferred transfer paper is lower than a predetermined threshold potential; and wherein the potential determining means determines that the potential of the photoconductor surface is lower than a predetermined threshold potential. If it is determined to be low, the original image is determined to be blank, and if the transfer paper has been transported from the paper feed tray, it is returned to the paper feed tray, and the transfer paper has been transported from the intermediate tray. If there is, return it to the intermediate tray A copying machine, comprising: a reverse conveying means. 3. A copying machine according to claim 1, further comprising a threshold potential varying means for varying a threshold potential in said potential determining means.