JP3812171B2 - Paper discriminating method in image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a paper discrimination method in an image forming apparatus that forms an image (including characters) on paper, such as a printer, a copier, and a facsimile machine. In particular, the present invention relates to a paper discriminating method capable of discriminating whether or not a paper supplied to an image forming apparatus is a specific paper.
[0002]
[Prior art]
In general, OHP (overhead projector) sheets are known in addition to plain paper as paper used in the image forming apparatus.
[0003]
An OHP sheet (also simply referred to as an OHP sheet) is a transparent sheet, and a transparent image-receiving layer for obtaining a good image is usually formed on one side thereof. Since the physical properties required for the image receiving layer vary depending on the image forming apparatus (or apparatus manufacturer), it is desirable to use an OHP sheet dedicated to the image forming apparatus in order to obtain a high quality image.
[0004]
Japanese Patent Application Laid-Open No. 7-175369 discloses an image forming apparatus in which when an OHP sheet other than a genuine product is used, it is determined and a warning operation such as warning display or machine stop is performed.
[0005]
FIG. 7 is an explanatory view of the apparatus, (a) is a plan view of a genuine OHP sheet, and (b) is a schematic functional process diagram showing an example of the apparatus.
[0006]
As shown in FIG. 1A, the genuine OHP sheet 1 is provided with a detection mark 1a. The mark 1a becomes transparent when heated.
[0007]
In FIG. 2B, 2 is a paper feed unit, 6a is an optical characteristic measurement unit, 3 is an image forming unit, 4 is a heating unit, 6b is an optical characteristic measurement unit, 5 is a paper discharge unit, and 7 is a discrimination unit.
[0008]
The paper (including the genuine OHP sheet 1) is conveyed from the paper supply unit 2 toward the paper discharge unit 5.
[0009]
According to this prior art, it is possible to determine whether the paper is an OHP sheet or paper, and if it is an OHP sheet, whether it is genuine or non-genuine, for example, as follows. .
[0010]
After the leading edge of the sheet is detected by the optical characteristic measuring unit 6a, the transparency / opacity of the sheet is detected again by the measuring unit 6a after a predetermined time has elapsed. At this time, if it is transparent, it is determined to be an OHP sheet, and if it is opaque, it is determined to be paper.
[0011]
In the case of an OHP sheet, after passing through the heating unit 4, the optical property measuring unit 6a detects the leading edge of the paper. At this time, if it is transparent, it is determined that it is a genuine OHP sheet 1, and if it is opaque, it is determined that it is non-genuine.
[0012]
According to the publication, the heating unit 4 can also be used as a toner fixing unit when the image forming apparatus is of an electrophotographic type, and can also be used as a thermal head when the image forming apparatus is of a thermal transfer type. However, it is desirable to provide a dedicated heating means for stably transparentizing the detection mark having a large heat capacity necessary for transparency, and if the dedicated heating means is provided, the paper is imaged. There is a description that non-genuine discrimination is possible before being sent to the forming unit 4.
[0013]
[Problems to be solved by the invention]
The conventional technology described above has the following problems.
[0014]
When the heating unit 4 is also used as, for example, a toner fixing unit, an image is already formed on the paper when the paper is determined, which is not desirable.
[0015]
In the case where a dedicated heating means is provided, it is necessary to make the detection mark 1a having a large heat capacity necessary for transparency transparent enough to stably make the detection mark 1a transparent. There is a problem that the power consumption of the apparatus is significantly increased.
[0016]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and a sheet supplied to an image forming apparatus is a specific sheet before an image is formed on the sheet and without causing a significant increase in power consumption. It is an object of the present invention to provide a paper discrimination method that can discriminate whether or not.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, the paper discrimination method in the image forming apparatus according to claim 1 detects the part when the detection target part is opaque or has a high reflectance, and the detection target part is transparent or has a low reflectance. In some cases, at least two sensors that do not detect the part are arranged in the width direction of the sheet at a position facing the sheet conveyance path in a specific image forming apparatus,
The dedicated paper for the specific image forming apparatus is provided with a portion that is detected by the sensor and a portion that is not detected at a position facing the at least two sensors in the conveyance process,
Based on the presence or absence of detection signals from the at least two sensors, if both detection signals from the sensors are in the detection state, it is determined that the paper to be conveyed is plain paper, and the detection signal from the sensor is If both are in the non-detection state, it is determined that the conveyed paper is a normal transparent sheet, and the detection signal from at least one of the at least two sensors is in the detection state and the other at least one other When the detection signal from the sensor is in the non-detection state, it is determined that the sheet to be conveyed is the dedicated sheet.
[0018]
[Function and effect]
According to the sheet discrimination method in the image forming apparatus according to claim 1, when the detection target part is opaque or high reflectance, the part is detected, and when the detection target part is transparent or low reflectance, the part is detected. At least two sensors that do not detect the sheet are arranged in the width direction of the sheet at a position facing the sheet conveyance path, and a specific sheet has a position facing the at least two sensors in the conveyance process. Since the part detected by the sensor and the part not detected are provided, whether or not the sheet to be conveyed is the specific sheet depending on the presence / absence of a detection signal from the at least two sensors is, for example, It is determined as follows.
[0019]
When the paper is plain paper, since the plain paper is opaque, all the detection signals from the sensors are in the detection state (ON).
[0020]
Further, when the paper is a normal transparent sheet (without a mark), all the detection signals from the sensors are in a non-detection state (OFF).
[0021]
On the other hand, a specific sheet is provided with a portion that is detected by the sensor and a portion that is not detected at a position facing the at least two sensors in the conveyance process. At least one of the sensors is OFF.
[0022]
Therefore, according to the sheet discrimination method in the image forming apparatus according to claim 1, for example, whether the sheet to be conveyed is the specific sheet depending on the presence / absence of detection signals from at least two sensors as described above. It can be determined whether or not.
[0023]
Since at least two sensors need only be arranged in the width direction of the sheet at a position facing the sheet conveyance path, it is easy to arrange these sensors in front of the image forming unit in the apparatus. In addition, the sensor only needs to detect the part when the detection target part is opaque or has a high reflectance, and does not detect the part when the detection target part is transparent or has a low reflectance. This heating means is unnecessary, and therefore, the power consumption is not significantly increased.
[0024]
That is, according to the paper discrimination method in the image forming apparatus according to claim 1, the paper supplied to the image forming apparatus is specified before the image is formed on the paper and without causing a significant increase in power consumption. It is possible to discriminate whether or not the paper is the first paper.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0026]
FIG. 1 is a schematic view showing an example of an image forming apparatus used for carrying out an embodiment of a paper discrimination method in an image forming apparatus according to the present invention.
[0027]
First, an outline of the image forming apparatus will be described.
[0028]
This image forming apparatus forms a single-color image and a full-color image using a developing cartridge of toner (developer) of four colors of yellow (Y), cyan (C), magenta (M), and black (K). It is a device that can.
[0029]
In FIG. 1, reference numeral 50 denotes a photoconductor unit, and a photoconductor 51 as a latent image carrier is rotationally driven in a direction indicated by an arrow by an appropriate drive means (not shown).
[0030]
The photoreceptor 51 has a thin cylindrical conductive substrate and a photosensitive layer formed on the surface thereof.
[0031]
Around the photosensitive member 51, along the rotation direction thereof, together with the photosensitive member 51, a charging roller 52 serving as a charging unit, an exposure unit 60 serving as an exposure unit, and a developing cartridge 70 serving as a developing unit ( Y, C, M, K) and an intermediate transfer unit 80 are arranged. A cleaning means 53 is also arranged. The photoreceptor unit 50 includes a photoreceptor 51, a charging roller 52, and a cleaning unit 53.
[0032]
The charging roller 52 contacts the outer peripheral surface of the photoconductor 51 to uniformly charge the outer peripheral surface. On the outer peripheral surface of the uniformly charged photoconductor 51, the exposure unit 60 performs selective exposure L1 according to desired image information, and an electrostatic latent image is formed on the photoconductor 51 by this exposure L1. .
[0033]
The electrostatic latent image is developed with toner applied by the developing cartridge 70.
[0034]
As the developing cartridge, a yellow developing cartridge 70Y, a cyan developing cartridge 70C, a magenta developing cartridge 70M, and a black developing cartridge 70K are provided.
[0035]
Each of the developer cartridges is attached to a case 72 containing toner, and the case 72 so as to be rotatable around the shaft 73 by a conductive shaft 73. A developing roller 71 as a developer carrying member to be applied to the body 51 and a supply roller 74 for supplying toner in the case 72 to the developing roller 71 are provided.
[0036]
These developing cartridges 70Y, 70C, 70M, and 70K are configured to be swingable, so that only the developing roller 71 of one developing cartridge can selectively contact the photosensitive member 51. Accordingly, these developing cartridges 70 apply toner of any one of yellow, cyan, magenta, and black to the surface of the photoconductor 51 to develop the electrostatic latent image on the photoconductor 51.
[0037]
The developed toner image is transferred onto an intermediate transfer belt 86 that forms an intermediate transfer member of the intermediate transfer unit 80.
[0038]
The cleaning unit 53 includes a cleaner blade 53a that scrapes off the toner remaining on the outer peripheral surface of the photosensitive member 51 after the transfer, and a receiving portion 53b that receives the toner scraped off by the cleaner blade 53a. Yes.
[0039]
The intermediate transfer unit 80 includes a driving roller 81, four driven rollers 82, 83, 84, and 85, and an endless intermediate transfer belt 86 as an intermediate transfer member stretched around these rollers. is doing.
[0040]
The drive roller 81 has a gear (not shown) fixed to the end thereof meshed with a drive gear (not shown) provided at the end of the photoconductor 51, so that the drive roller 81 has substantially the same circumference as the photoconductor 51. Accordingly, the intermediate transfer belt 86 is driven to circulate in the direction indicated by the arrow at substantially the same peripheral speed as that of the photoreceptor 51.
[0041]
The driven roller 85 is disposed at a position where the intermediate transfer belt 86 is pressed against the photosensitive member 51 by its own tension between the driven roller 81 and the primary roller at the pressure contact portion between the photosensitive member 51 and the intermediate transfer belt 86. A transfer portion T1 is formed. The driven roller 85 is disposed near the primary transfer portion T1 on the upstream side of the intermediate transfer belt 86 in the circulation direction.
[0042]
An electrode roller (not shown) is disposed on the driving roller 81 via an intermediate transfer belt 86, and a primary transfer voltage is applied to the intermediate transfer belt 86 via this electrode roller.
[0043]
The driven roller 82 is a tension roller, and biases the intermediate transfer belt 86 in the tension direction by a biasing means (not shown).
[0044]
The driven roller 83 is a backup roller that forms the secondary transfer portion T2. A secondary transfer roller 88 as a secondary transfer unit is disposed opposite to the backup roller 83 via an intermediate transfer belt 86. The secondary transfer roller 88 can be brought into contact with and separated from the intermediate transfer belt 86 by a contact and separation mechanism (not shown). A secondary transfer voltage is applied to the secondary transfer roller 88.
[0045]
The driven roller 84 is a backup roller for the belt cleaner 89. The belt cleaner 89 includes a cleaner blade 89a that contacts the intermediate transfer belt 86 and scrapes off toner remaining on the outer peripheral surface thereof, and a receiving portion 89b that receives the toner scraped off by the cleaner blade 89a. ing. The belt cleaner 89 can be brought into and out of contact with the intermediate transfer belt 86 by a contact and separation mechanism (not shown).
[0046]
The intermediate transfer belt 86 is formed of a multilayer belt having a conductive layer and a resistance layer formed on the conductive layer and pressed against the photoreceptor 51. The conductive layer is formed on an insulating substrate made of synthetic resin, and a primary transfer voltage is applied to the conductive layer via the electrode roller described above.
[0047]
In the process in which the intermediate transfer belt 86 is circulated, the toner image on the photoconductor 51 is transferred onto the intermediate transfer belt 86 at the primary transfer portion T1, and the toner image transferred onto the intermediate transfer belt 86 is transferred to the secondary transfer belt 86. In the transfer portion T2, the image is transferred to a sheet (a recording material such as plain paper, an OHP sheet, glossy paper, etc.) S supplied between the secondary transfer roller 88.
[0048]
The intermediate transfer unit 80 also incorporates the electrode roller, the urging means for the tension roller 82, the secondary transfer roller 88, and the belt cleaner 89.
[0049]
The sheet S is fed from a sheet feeding device 90 serving as a sheet feeding unit, and is supplied to the secondary transfer unit T2 by a gate roller pair G at a predetermined timing. 91 is a paper feed tray for stacking and holding the paper S, and 92 is a pickup roller.
[0050]
The sheet S on which the toner image has been transferred at the secondary transfer portion T2 passes through the fixing unit 100 serving as a fixing unit, whereby the toner image is heated and melted and fixed.
[0051]
The fixing unit 100 includes a heating roller 101 having a heat source and a pressure roller 102 pressed against the heating roller 101, and the rollers 101, 102 are heated while pinching the paper S passing therethrough to The image is melted and fixed on the paper S.
[0052]
The paper S that has passed through the fixing unit 100 is finally discharged through the paper discharge path 110 onto the sheet receiving portion 41 formed on the case 40 of the apparatus main body. A reverse return path 110 ′ is provided that can reverse the front and back of the paper S that has passed through the fixing unit 100 and return the paper S to the secondary transfer portion T 2 again.
[0053]
The reverse return path 110 ′ is a switchback path 113 having two paper discharge paths 111 and 112 that can carry the paper S that has passed through the fixing unit 100 and can reversely feed the paper S once carried. And a return path 114 for returning the sheet S fed back from the switchback path 113 to the secondary transfer portion T2 again. Therefore, the sheet S returned to the secondary transfer portion T2 by the reverse return path 110 ′ is reversed and turned back to the secondary transfer portion T2.
[0054]
Such an image forming apparatus can form an image only on the front surface (first surface) of the paper S, and can also form an image on both surfaces (first and second surfaces which are front and back surfaces).
[0055]
Reference numeral 120 denotes a control unit, which constitutes a control unit that controls the entire apparatus and a determination unit that will be described later. Reference numeral 123 denotes an operation panel of the apparatus, which has a display unit.
[0056]
The outline of the operation of the entire image forming apparatus as described above is as follows.
[0057]
(I) When a print command signal (image formation signal) from a host computer (not shown) or the like (personal computer or the like) is input to the control unit 120 of the image forming apparatus, the photosensitive member 51, each roller 71 of the developing cartridge 70, and The intermediate transfer belt 86 is driven to rotate.
[0058]
(Ii) The outer peripheral surface of the photoconductor 51 is uniformly charged by the charging roller 52.
[0059]
(Iii) The exposure unit 60 selectively exposes L1 according to the image information of the first color (for example, yellow) on the outer peripheral surface of the uniformly charged photoconductor 51 to form an electrostatic latent image for yellow. Is done.
[0060]
(Iv) Only the developing roller of the developing cartridge 70Y for the first color (for example, yellow) is brought into contact with the photoreceptor 51, whereby the electrostatic latent image is developed, and the toner image for the first color (for example, yellow) is developed. Is formed on the photoreceptor 51.
[0061]
(V) A primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied to the intermediate transfer belt 86, and the toner image formed on the photoreceptor 51 is transferred onto the intermediate transfer belt 86 at the primary transfer portion T1. The At this time, the secondary transfer roller 88 and the belt cleaner 89 are separated from the intermediate transfer belt 86.
[0062]
(Vi) After the toner remaining on the photosensitive member 51 is removed by the cleaning unit 53, the photosensitive member 51 is neutralized by the neutralizing light L2 from the neutralizing unit 61.
[0063]
(Vii) The operations (ii) to (vi) are repeated as necessary. That is, the second color, the third color, and the fourth color are repeated according to the content of the print command signal, and the toner images according to the content of the print command signal are superimposed on the intermediate transfer belt 86 to be intermediate. It is formed on the transfer belt 86.
[0064]
(Viii) The sheet S is supplied from the sheet feeding device 90 at a predetermined timing, and immediately before or after the leading end of the sheet S reaches the secondary transfer portion T2 (in short, the intermediate transfer belt at a desired position on the sheet S). The secondary transfer roller 88 is pressed against the intermediate transfer belt 86 and a secondary transfer voltage is applied to the toner image on the intermediate transfer belt 86 (basically four colors). A full color image on which the toner images are superimposed) is transferred onto the paper S. Further, the belt cleaner 89 contacts the intermediate transfer belt 86, and the toner remaining on the intermediate transfer belt 86 after the secondary transfer is removed.
[0065]
(Ix) When the sheet S passes through the fixing unit 100, the toner image is fixed on the sheet S, and then the sheet S is directed to a predetermined position (if the sheet S is not double-sided printing, the sheet receiving unit 41 is directed to double-sided printing. In this case, the sheet is conveyed to the return path 114 via the switchback path 113.
[0066]
In other words, when an image is formed only on the front surface (first surface), the toner image is transferred to the first surface of the paper S fed from the paper feeding device 90 by the secondary transfer unit T2, and the fixing unit. After being fixed at 100, the sheet is discharged onto the sheet receiving portion 41 through the paper discharge path 111 or 112. Note that a path switching unit (not shown) is provided at the entrance portion 110A of the paper discharge paths 111 and 112, and this determines which paper discharge path (111 and 112) the paper S is carried into. .
[0067]
In the case of forming images on both sides (first side and second side), the toner image is transferred to the first side of the paper S fed from the paper feeding device 90 by the secondary transfer portion T2 and fixed. After being fixed by the unit 100, it temporarily enters the paper discharge path 111 or 112 (switchback path 74), is reversely fed, passes through the return path 73, and again returns to the secondary transfer portion T2 at a predetermined timing by the gate roller pair G. The toner image is transferred to the second surface. Thereafter, the image (toner image) is also fixed on the second surface by the fixing unit 100, and is discharged onto the sheet receiving portion 41 via the paper discharge path 111 or 112.
[0068]
Although the outline of the image forming apparatus has been described above, the image forming apparatus can form an image on the dedicated OHP sheet and the dedicated glossy paper as the paper S in addition to the plain paper.
[0069]
The dedicated OHP sheet is a dedicated OHP sheet for the image forming apparatus, and is a sheet in which a transparent resin coating layer dedicated to the apparatus is formed as an image receiving layer on one side of the transparent sheet. By using this dedicated OHP sheet, it is possible to obtain a high-quality image (particularly a full-color image) with high transparency.
[0070]
The dedicated glossy paper is one in which a resin coating layer dedicated to this apparatus is formed as an image receiving layer on the surface (one side or both sides) of the paper. By using this dedicated glossy paper, a high-quality image (particularly a full-color image) can be obtained.
[0071]
By the way, as described above, when there are a plurality of types of paper (in this case, plain paper, dedicated OHP sheet, and dedicated glossy paper), which paper is actually supplied to the image forming apparatus. It is necessary to correctly determine whether the type of paper is used.
[0072]
If this determination is not made correctly, for example, the following problem occurs.
[0073]
When the image forming apparatus is activated when it is determined that the sheet actually supplied is plain paper but is a dedicated OHO sheet or glossy paper, the sheet (plain paper) is heated by the heating roller 101 of the fixing unit 100. There is a risk that troubles such as winding will occur.
[0074]
In addition, even if the paper actually supplied is a dedicated OHO sheet or a dedicated glossy paper, when it is determined that the paper is plain paper and the image forming apparatus is activated, a high-quality image that should be originally obtained can be obtained. It will disappear.
[0075]
Therefore, the paper discrimination method of this embodiment detects the relevant part when the detection target part is opaque or has a high reflectance, and does not detect the relevant part when the detection target part is transparent or has a low reflectance. Are disposed in the width direction of the sheet at a position facing the sheet conveyance path, and a specific sheet is detected by a sensor at a position facing the at least two sensors in the conveyance process. And a portion that is not detected, and whether or not the sheet to be conveyed is the specific sheet is determined based on the presence or absence of detection signals from the at least two sensors.
[0076]
This will be specifically described below.
[0077]
2 is an enlarged view of the sheet feeding device 90, and FIG. 3A is a partially omitted plan view thereof.
[0078]
In these drawings, A and B are sensors, which are arranged in the width direction of the sheet (the direction perpendicular to the sheet conveyance direction and the vertical direction in FIG. 3) at the position facing the conveyance path P of the sheet S. . These sensors A and B are connected to the control unit 120 (see FIG. 1). These sensors are sensors that detect the part when the detection target part is opaque or has a high reflectance, and do not detect the part when the detection target part is transparent or has a low reflectance. Specifically, for example, it can be constituted by a limited reflection type photosensor.
[0079]
FIG. 4 is a diagram for explaining the configuration and operation of the limited reflection photosensor, in which 121 is a light emitting element, and 122 is a light receiving element.
[0080]
As shown in FIG. 5A, this sensor is emitted from the light emitting element 121 when, for example, the detection target portion Sa in the paper S is opaque or has a high reflectance (that is, for example, when the paper S is plain paper). Light is scattered on the surface of the detection target part Sa, and a part of the scattered light reaches the light receiving element 122. At this time, the part Sa can be detected by a signal (ON signal (H signal)) generated by the light receiving element 122.
[0081]
On the other hand, as shown in FIG. 5B, for example, when the detection target part Sa on the paper S is transparent or has a low reflectance (for example, black), most of the light emitted from the light emitting element 121 is the detection target part Sa. Or is absorbed by the detection target site Sa, and the scattered light hardly reaches the light receiving element 122. Therefore, the light receiving element 122 does not emit a signal (it remains OFF (L)), and the part Sa is not detected.
[0082]
In FIG. 2, reference numerals 93 and 94 denote a pair of separation rollers. When two or more sheets S fed by the pickup roller 92 are about to be fed simultaneously, this is prevented. This is for feeding only the sheet to the transport path P. Reference numerals 95 and 96 denote paper guides for guiding the paper S to be fed.
[0083]
3A and 3B, S1 is a dedicated OHP sheet, which is an example of “specific paper”. FIG. 3B is a cross-sectional view taken along line bb in FIG.
[0084]
The dedicated OHP sheet S1 is provided with a part Sa1 that is detected by the sensor and a part Sa2 that is not detected at a position facing the two sensors A and B in the conveyance process.
[0085]
The detected portion Sa1 is formed by an opaque white portion Sa1 ′ printed in a frame shape on the edge of one side of the sheet (the surface on which the image receiving layer is formed). The part Sa2 that is not detected is formed by not performing the printing partly. Therefore, the part Sa2 that is not detected is a transparent part.
[0086]
These portions Sa1 and Sa2 are provided at four points symmetrically with respect to the center O1 of the sheet. Therefore, when the dedicated OHP sheet S1 is sent in a horizontally placed state as shown in FIG. 1A, when it is sent in a vertically placed state rotated 90 degrees around the center O1 from the state shown in FIG. In any case when the paper is sent in a horizontally placed state rotated by a predetermined degree, the parts Sa1 and Sa2 face the two sensors A and B in the process of transporting the dedicated OHP sheet S1.
[0087]
FIG. 5A is a partially omitted plan view of FIG. 2 and shows a case where the dedicated glossy paper S2 is set as the paper S. FIG. FIG. 2B is a cross-sectional view taken along line bb in FIG.
[0088]
The special glossy paper S2 is also an example of “specific paper”, and the special glossy paper S2 is not detected as a part Sa3 detected by the sensor at a position facing the two sensors A and B in the conveyance process. A site Sa4 is provided.
[0089]
The dedicated glossy paper S2 has an image receiving layer formed only on one side, and the undetected portion Sa4 is a black partly printed on the edge of one side of the sheet (the side on which the image receiving layer is formed). It is formed by the part. The detected portion Sa3 is formed by the white surface of the dedicated glossy paper S2 itself that has not been printed.
[0090]
These parts Sa3 and Sa4 are provided at four points symmetrically with respect to the center O2 of the sheet. Therefore, when the dedicated glossy paper S2 is sent in the horizontal state as shown in FIG. 1A, when it is sent in the vertical state rotated 90 degrees around the center O2 from the state shown in FIG. In any case where the paper is sent in a horizontally placed state rotated by two degrees, the parts Sa3 and Sa4 face the two sensors A and B in the process of transporting the dedicated glossy paper S2.
[0091]
Whether or not the sheet S supplied to the image forming apparatus is a specific sheet (dedicated OHP sheet S1 or dedicated glossy sheet S2) is determined as follows.
[0092]
6A and 6B are diagrams illustrating states of output signals from the sensors A and B. FIG. 6A illustrates a case where plain paper is supplied as the paper S, and FIG. 6B illustrates a normal transparent sheet (without a mark) as the paper S. When (for example, a normal OHP sheet) is supplied, (c) shows a case where the dedicated OHP sheet S1 is supplied as the paper S, and (d) shows a case where the dedicated glossy paper S2 is supplied as the paper S. .
[0093]
As shown in FIG. 5A, when plain paper is supplied as the paper S, the plain paper is opaque. Therefore, when the leading edge (tip in the transport direction) reaches the sensors A and B, the sensors A and B The output signals from both are in the detection state (ON), and this state continues until the trailing edge of the paper passes the position of sensors A and B. Accordingly, the length L in the figure corresponds to the length in the sheet conveyance direction.
[0094]
As shown in FIG. 2B, when a normal transparent sheet (not having a mark) (for example, a normal OHP sheet) is supplied as the paper S, the entire sheet is transparent. , B, the output signals from the sensors A, B remain in the non-detected state (OFF), and this state does not change even if the sheet is further conveyed.
[0095]
As shown in FIG. 3C, when the dedicated OHP sheet S1 is supplied as the sheet S, the dedicated OHP sheet S1 includes the two sensors A in the conveyance process as shown in FIG. , B are provided with a part Sa1 detected by the sensor and a part Sa2 not detected by the sensor. When these parts reach the sensors A, B, the output signal from one sensor A is Although it is in the detection state (ON), the output signal from the other sensor B remains in the non-detection state (OFF). After that, when the sheet is further conveyed and the detected part Sa1 passes the sensor A, the output signal from the sensor A is turned off, so that the output signals from both the sensors A and B are turned off. When the rear end (rear end in the transport direction) reaches the position of sensors A and B, the detected part Sa1 is opposed to both of these sensors, so that the output signals from both sensors A and B Are both ON.
[0096]
As shown in FIG. 5D, when the dedicated glossy paper S2 is supplied as the paper S, the dedicated glossy paper S2 includes the two sensors A in the conveyance process as shown in FIG. , B are provided with a part Sa3 detected by the sensor and a part Sa4 not detected by the sensor. When these parts reach the sensors A, B, the output signal from one sensor A is Although it is in the detection state (ON), the output signal from the other sensor B remains in the non-detection state (OFF). Therefore, the signal state at this time is the same as that when the dedicated OHP sheet S1 is supplied (see FIG. (C)), but after that, the sheet is further conveyed, and the undetected part Sa4 passes the sensor B. Then, since the output signal from the sensor B is turned on, the output signals from both the sensors A and B are both turned on. In this state, the rear end of the dedicated glossy paper S2 passes the position of the sensors A and B. Continue until
[0097]
Since the states of the output signals from the sensors A and B change as described above depending on the type of paper to be supplied, the control unit 120 as the discrimination unit first reaches the position of the sensors A and B at the leading edge of the paper. At the time t1, the state of the output signal from the sensors A and B is detected. The detection timing t1 is, for example, the number of rotations of the pickup roller 92 (the number of rotations at which the leading edge of the sheet should reach the sensor A or B position in the paper feeding operation or the number of driving steps of the step motor that is the driving means of the pickup roller 92) Can be determined.
[0098]
Then, the control unit 120 determines whether or not the sheet S to be conveyed is the specific sheet depending on the presence / absence of detection signals from the sensors A and B as follows. In response to this, the image forming apparatus is controlled as follows.
[0099]
(A) When the output signals from the sensors A and B at the detection timing t1 are both in the detection state (ON) (see FIG. 6A), it is determined that the supplied paper S is plain paper. To do. In this case, the image forming apparatus is operated as usual.
[0100]
(B) When the output signals from the sensors A and B at the detection timing t1 are both in the non-detection state (OFF) (see FIG. 6B), the supplied paper S is the normal (mark mark). It is not determined that the sheet is a transparent sheet, and it is determined that the feeding is defective. As can be seen from this, the sensors A and B are also used as sensors for detecting a feeding failure.
[0101]
In this case, the operation of the image forming apparatus is stopped, and a display indicating that there is a feeding failure is displayed on the display unit of the operation panel 123.
[0102]
(C) The output signal from the sensor A at the detection timing t1 is in the detection state (ON), the output signal from the other sensor B is in the non-detection state (OFF), and thereafter (the part that is not detected in the dedicated glossy paper S2) The time required for Sa4 to pass through the sensor B (or the corresponding number of rotations of the pickup roller 92 (or after the number of driving steps of the stepping motor as its driving means) elapses) is also the output signal from the sensor B. When the non-detection state (OFF) remains (see FIG. 6C), it is determined that the supplied sheet S is the dedicated OHP sheet S1. The sheet conveying speed by the conveying means (secondary transfer roller 88, heating roller 101 of the fixing unit 100, etc.) is about 1/10 to 1/7 as compared with the case of plain paper. Transporting the exclusive OHP sheet S1 in the. Thus, only the toner transferred onto the OHP sheet S1 is being sufficiently melted with a dedicated image-receiving layer of the a high quality image can be obtained.
[0103]
(D) The output signal from the sensor A at the detection timing t1 is in the detection state (ON), the output signal from the other sensor B is in the non-detection state (OFF), and thereafter (the part that is not detected in the dedicated glossy paper S2) The time required for Sa4 to pass through the sensor B (or after the corresponding number of rotations of the pickup roller 92 (or the number of drive steps of the stepping motor as its driving means) has elapsed), the output signal from the sensor B is When it is turned on (see FIG. 6D), it is determined that the supplied paper S is the dedicated glossy paper S2. In this case, the conveying means (secondary transfer) after the gate roller G is used. The dedicated glossy paper S2 is transported by setting the paper transport speed by the roller 88, the roller 101 of the fixing unit 100, etc. to about 1/10 to 1/7 of that of plain paper. As a result, the toner transferred onto the dedicated glossy paper S2 is sufficiently melted together with the dedicated image receiving layer to obtain a high quality image. When an image is also formed on the surface that does not have (), the output signals from the sensors A and B are both in the detection state (ON) (see the right end in FIG. 6D). In order to obtain a high-quality image similar to the front surface on the back surface, an image receiving layer is formed on the back surface and the same part Sa3 as the front surface is formed. , Sa4, it is possible to obtain a high-quality image similar to the surface.
[0104]
When the plain paper is transported at the above slow transport speed, there is a possibility that the plain paper may be wound around the heating roller 101 of the fixing unit 100. However, in the case of the dedicated OHP sheet S1 or the dedicated glossy paper S2. However, since the peelability from the heating roller 101 is improved due to the physical properties of the dedicated image receiving layer, the above trouble does not occur.
[0105]
As described above, according to the sheet determination method in the image forming apparatus of this embodiment, whether the sheet to be conveyed is the specific sheet depending on the presence / absence of detection signals from the two sensors A and B. It can be determined whether or not.
[0106]
Since at least two sensors need only be arranged in the width direction of the sheet S at a position facing the conveyance path P of the sheet S, it is easy to arrange these sensors in front of the image forming unit in the apparatus. is there. In this embodiment, it is arranged in front of the gate roller G. Further, the sensor only needs to detect the part when the detection target part Sa is opaque or has a high reflectance, and does not detect the part when the detection target part Sa is transparent or has a low reflectance. No special heating means is required, and therefore there is no significant increase in power consumption.
[0107]
That is, according to the paper discrimination method in the image forming apparatus of this embodiment, the paper supplied to the image forming apparatus is identified before the image is formed on the paper S and without causing a significant increase in power consumption. It is possible to discriminate whether or not it is a sheet of paper.
[0108]
In addition, the sensor can be used as a sensor for detecting a feeding failure by arranging the sensor at an appropriate position (for example, near the gate roller pair G).
[0109]
Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the gist of the present invention.
[0110]
For example, although two sensors are provided in the above-described embodiment, three or more sensors are provided, and a specific sheet is detected as a part detected by the sensor at a position facing the three or more sensors in the conveyance process. It is also possible to provide a portion that is not provided, and to determine whether or not the sheet to be conveyed is a specific sheet according to the presence or absence of detection signals from the three or more sensors.
[0111]
【The invention's effect】
According to the sheet discrimination method in the image forming apparatus according to claim 1, the sheet supplied to the image forming apparatus is a specific sheet before the image is formed on the sheet and without causing a significant increase in power consumption. It is possible to determine whether or not there is.
[0112]
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an image forming apparatus used for carrying out an embodiment of a paper discrimination method in an image forming apparatus according to the present invention.
FIG. 2 is an enlarged view of a sheet feeding device 90 in the image forming apparatus.
3A is a partially omitted plan view of FIG. 2, and FIG. 3B is a cross-sectional view taken along line bb in FIG.
FIGS. 4A and 4B are diagrams for explaining the configuration and operation of a limited reflection photosensor. FIGS.
5A is a partially omitted plan view of FIG. 2, and FIG. 5B is a cross-sectional view taken along line bb in FIG.
6A to 6D are diagrams showing states of output signals from sensors A and B. FIG.
7A and 7B are explanatory diagrams of the prior art.
[Explanation of symbols]
A, B sensor
P Transport route
S paper
S1 OHP sheet (specific paper)
S2 Glossy paper (specific paper)
Sa detection target part
Sa1, Sa3 Detected part
Sa2, Sa4 Parts not detected

Claims (1)

When the detection target part is opaque or has a high reflectance, the part is detected. When the detection target part is transparent or has a low reflectance, a sensor that does not detect the part is transported in a specific image forming apparatus. At least two in the width direction of the paper at the position facing the path,
The dedicated paper for the specific image forming apparatus is provided with a portion that is detected by the sensor and a portion that is not detected at a position facing the at least two sensors in the conveyance process,
Based on the presence or absence of detection signals from the at least two sensors, if both detection signals from the sensors are in the detection state, it is determined that the paper to be conveyed is plain paper, and the detection signal from the sensor is When both are in the non-detection state, it is determined that the sheet to be conveyed is a normal transparent sheet, and the detection signal from at least one of the at least two sensors is in the detection state, and at least one other A paper discrimination method in an image forming apparatus, wherein when a detection signal from a sensor is in a non-detection state, a paper to be conveyed is judged to be the dedicated paper.

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