JP2000098813A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent trouble from being caused by discriminating whether or not supplied paper is a specified paper without causing the increase of power consumption before an image is formed on the paper. SOLUTION: Sensors A and B which detect a detection object part when it is opaque or has high reflectance and do not detect it when it is transparent or has low reflectance, are arranged in the width direction of a paper at a position facing the carrying path of the paper. A specified paper S1 is provided with a part Sa1 which is detected by the sensor and a part Sa2 which is not detected by the sensor at positions opposed to the sensors A and B to discriminate whether or not the paper is a specified paper according as detection signals from the sensors A and B. Then, image forming operation is stopped in the case of setting that the paper is the specified paper by a paper kind setting means set by a user whether or not the paper is the specified paper and discriminating that the actual paper is not the specified paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image (including characters) on paper, such as a printer, a copying machine, a facsimile, and the like. In particular, the present invention relates to a discriminating technique for discriminating whether a sheet supplied to an image forming apparatus is a specific sheet, and a control technique of the apparatus based on the discriminating technique.

[0002]

2. Description of the Related Art In general, OHP (overhead projector) sheets as well as plain paper are known as paper used in an image forming apparatus.

An OHP sheet (also simply referred to as an OHP sheet) is a transparent sheet, and usually has a transparent image-receiving layer for obtaining a good image on one side thereof. Since the physical properties required for the image receiving layer differ 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.

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 a warning display or a machine stop is performed. ing.

FIGS. 7A and 7B are explanatory views of the apparatus. FIG. 7A is a plan view of a genuine OHP sheet, and FIG. 7B is a schematic functional process diagram showing an example of the apparatus.

As shown in FIG. 1A, a genuine OHP sheet 1 is provided with a detection mark 1a. The mark 1a becomes transparent when heated.

In FIG. 1B, reference numeral 2 denotes a paper feeding unit, 6a denotes an optical characteristic measuring unit, 3 denotes an image forming unit, 4 denotes a heating unit, 6b denotes an optical characteristic measuring unit, 5 denotes a paper discharging unit, and 7 denotes a discriminating unit. It is.

[0008] The paper (including the genuine OHP sheet 1) is conveyed from the paper supply unit 2 to the paper discharge unit 5.

According to this conventional technique, it is determined whether the sheet is an OHP sheet or a paper, and if the sheet is an OHP sheet, whether it is genuine or non-genuine is determined as follows, for example. be able to.

After the leading end of the sheet is detected by the optical property measuring section 6a, the transparency / opacity of the sheet is detected again by the measuring section 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.

In the case of an OHP sheet, after passing through the heating unit 4, the leading end of the sheet is detected by the optical characteristic measuring unit 6a. At this time, if it is transparent, it is determined that it is the genuine OHP sheet 1, and if it is opaque, it is determined that it is non-genuine.

According to the publication, the heating section 4 can also be used as a toner fixing means when the image forming apparatus is of an electrophotographic type, and a thermal head when the image forming apparatus is of a thermal transfer type. It is also possible to use
It is desirable to provide a dedicated heating means for stably making the detection mark having a large heat capacity necessary for transparency transparent, and if the dedicated heating means is provided, the sheet is sent before being sent to the image forming unit 4. Describes that non-genuine discrimination is possible.

[0013]

The above-mentioned prior art has the following problems.

If the heating section 4 is also used as, for example, a toner fixing means, it is not desirable because an image has already been formed on the sheet when the sheet is determined. In particular, when the non-genuine OHP sheet is determined to be a non-genuine OHP sheet, the non-genuine OHP sheet has already reached the toner fixing unit, and there is a possibility that a trouble such as the sheet wrapping around the toner fixing unit may occur.

On the other hand, when a dedicated heating means is provided,
Since it is necessary to use only enough heating means to stably make the detection mark 1a having a large heat capacity necessary for making it transparent, the power consumption of the apparatus is remarkably increased. There's a problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to prevent a sheet supplied to an image forming apparatus from being specified before an image is formed on the sheet and without causing a significant increase in power consumption. An object of the present invention is to provide an image forming apparatus capable of determining whether or not a sheet is a sheet and preventing the occurrence of the above-mentioned trouble.

[0017]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: a conveying path for conveying a sheet to an image forming unit; At least two sensors are arranged in the width direction, and 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 sensor is not detected. According to the state of the presence or absence of the detection signals from at least two sensors, the sheet to be conveyed is specified such that a part detected by the sensor and a part not detected are provided at a position facing the at least two sensors in the conveyance process. Discriminating means for discriminating whether or not the sheet is a sheet of paper, and sheet type setting means for setting whether or not the sheet to be fed is the specific sheet by a user A control unit for stopping the image forming operation when the setting by the paper type setting unit is set by the user to be the specific paper and the determination by the determination unit is determined to be not the specific paper; It is characterized by having.

An image forming apparatus according to a second aspect is the first aspect.
The image forming apparatus according to any one of claims 1 to 3, further comprising a notifying unit that notifies the user that the setting is made by the user or that the sheet is upside down at the time of the suspension.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the first aspect.
Or the image forming apparatus according to 2, wherein the sensor comprises:
In the sheet transport direction, the sheet is disposed in front of the gate roller that regulates the timing of supplying the sheet to the image forming unit, and also serves as a detection unit for detecting whether the sheet has reached the gate roller. It is characterized by fulfilling.

[0020]

According to the image forming apparatus of the first aspect, when the detection target portion is opaque or has high reflectance, the detection portion is detected, and when the detection target portion is transparent or has low reflectance, the relevant portion 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 conveyance path for conveying the sheet to the image forming unit, and the specific sheet has the at least two sensors in the conveyance process. In the position opposite to the above, a part detected by the sensor and a part not detected are provided, and the sheet to be conveyed is the specific sheet depending on the presence or absence of the detection signals from the at least two sensors. Is determined by the determining means as follows, for example.

When the paper is plain paper, since the plain paper is opaque, all of the detection signals from the sensors are in the detection state (ON).

Also, if the paper is normal (has no mark)
In the case of a transparent sheet, the detection signals from the sensors are all in a non-detection state (OFF).

On the other hand, a specific sheet is provided with a part detected by the sensor and a part not detected at a position facing the at least two sensors during the transport process, so that at least one sensor is ON. And at least one other sensor is turned off.

Therefore, for example, based on the presence or absence of the detection signals from at least two sensors as described above, the determination unit determines whether or not the transported paper is the specific paper.

On the other hand, the user sets in the paper type setting means whether or not the paper to be fed is the specific paper.

If the setting by the paper type setting means is set by the user to be the specific paper, and if the determination by the determination means determines that the paper is not the specific paper, the control means sets the image to the specified paper. Since the forming operation is stopped, even though the user intends to form an image on the specific sheet, an image is formed on a sheet of a type other than the specific sheet contrary to the intention. Is prevented beforehand. Therefore, the above-mentioned trouble is also prevented.

In addition, at least two of the sensors need only be arranged in the width direction of the sheet at a position facing the sheet conveyance path, so that it is easy to arrange them in front of the image forming section in the apparatus. is there.

Further, the sensor only needs to detect the portion to be detected when the portion to be detected is opaque or high reflectance, and not to detect the portion when the portion to be detected is transparent or low reflectance. Therefore, no special heating means is required, and therefore, the power consumption is not significantly increased.

That is, according to the image forming apparatus of the present invention, the sheet supplied to the image forming apparatus is specified 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 the sheet is a sheet, thereby preventing the trouble from occurring.

According to the image forming apparatus of the second aspect, in the image forming apparatus of the first aspect, at the time of the stop, the user is notified that the setting by the user or that the sheet is upside down is reversed. Since there is a notification means,
The user can be notified of the reason for stopping the image forming operation.

According to the image forming apparatus of the third aspect, in the image forming apparatus of the first or second aspect, the sensor is configured to control a timing of supplying a sheet to the image forming section in a sheet conveying direction. Since it is arranged in front of the roller and also serves as a detecting means for detecting whether or not the sheet has reached the gate roller, it is not necessary to separately provide a detecting means, and the cost of the apparatus is reduced. be able to.

[0032]

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

FIG. 1 is a schematic view showing an embodiment of the image forming apparatus according to the present invention.

First, an outline of the image forming apparatus will be described.

This image forming apparatus forms a single-color image and a full-color image using a developing cartridge of four color toners (developer) of yellow (Y), cyan (C), magenta (M), and black (K). It is a device that can do it.

In FIG. 1, reference numeral 50 denotes a photoreceptor unit, and a photoreceptor 51 as a latent image carrier is rotationally driven in a direction indicated by an arrow by an appropriate driving means (not shown).

The photoreceptor 51 has a thin cylindrical conductive base material and a photosensitive layer formed on the surface thereof.

Around 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 unit serving as a developing unit constitute an image forming unit together with the photosensitive member 51 along the rotation direction. Cartridge 70
(Y, C, M, K), and the intermediate transfer unit 80. Further, a cleaning unit 53 is provided.
The photoconductor unit 50 incorporates a photoconductor 51, a charging roller 52, and a cleaning unit 53.

The charging roller 52 contacts the outer peripheral surface of the photoreceptor 51 to uniformly charge the outer peripheral surface. The outer peripheral surface of the uniformly charged photoconductor 51 is selectively exposed L1 according to desired image information by the exposure unit 60, and an electrostatic latent image is formed on the photoconductor 51 by the exposure L1. .

This electrostatic latent image is developed with toner applied by a developing cartridge 70.

As the developing cartridges, a developing cartridge 70Y for yellow and a developing cartridge 7 for cyan
0C, a magenta developing cartridge 70M, and a black developing cartridge 70K are provided.

Each of the developer cartridges is rotatably mounted on a case 72 containing toner and a rotatable shaft 73 with a conductive shaft 73. Toner 5
A developing roller 71 as a developer carrier to be applied to 1;
A supply roller 74 for supplying the toner in the case 72 to the developing roller 71 is provided.

These developing cartridges 70Y, 70C,
70M and 70K are configured to be swingable, respectively, and are selectively provided with the developing roller 71 of one developing cartridge.
Only the photosensitive member 51 can come into contact with the photosensitive member 51. Therefore, these developing cartridges 70 are yellow,
The electrostatic latent image on the photoconductor 51 is developed by applying any one of cyan, magenta, and black toners to the surface of the photoconductor 51.

The developed toner image is transferred onto an intermediate transfer belt 86 forming an intermediate transfer body of the intermediate transfer unit 80.

After the transfer, the cleaning means 53
A cleaner blade 53a for scraping off the toner remaining on and adhering to the outer peripheral surface of the photoconductor 51, and a receiving portion 53b for receiving the toner scraped off by the cleaner blade 53a are provided.

The intermediate transfer unit 80 includes a driving roller 81
And four driven rollers 82, 83, 84, 85, and an endless intermediate transfer belt 86 as an intermediate transfer member stretched around these rollers.

The drive roller 81 is substantially connected to the photosensitive member 51 by a gear (not shown) fixed to the end of the drive roller 81 meshing with a drive gear (not shown) provided at the end of the photosensitive member 51. The intermediate transfer belt 86 is driven to rotate at the same peripheral speed, so that the intermediate transfer belt 86 is driven to circulate at substantially the same peripheral speed as the photosensitive member 51 in the direction of the arrow in the figure.

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 85 and the driven roller 85. In the primary transfer section T1
Are formed. The driven roller 85 is disposed near the primary transfer portion T1 on the upstream side in the circulation direction of the intermediate transfer belt 86.

The driving roller 81 has an intermediate transfer belt 86
A primary transfer voltage is applied to the intermediate transfer belt 86 via the electrode roller (not shown).

The driven roller 82 is a tension roller, and urges the intermediate transfer belt 86 in the direction of its tension by urging means (not shown).

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 opposed to the backup roller 83 via an intermediate transfer belt 86. The secondary transfer roller 88 can be moved toward and away from the intermediate transfer belt 86 by a contact / separation mechanism (not shown). A secondary transfer voltage is applied to the secondary transfer roller 88.

The driven roller 84 is a backup roller for the belt cleaner 89. Belt cleaner 89
Is a cleaner blade 89 which comes into contact with the intermediate transfer belt 86 and scrapes off the toner remaining and adhering to the outer peripheral surface thereof.
a, and a receiving portion 89b for receiving the toner scraped off by the cleaner blade 89a. The belt cleaner 89 can be moved toward and away from the intermediate transfer belt 86 by a contact / separation mechanism (not shown).

The intermediate transfer belt 86 is composed of a multilayer belt having a conductive layer and a resistive layer formed on the conductive layer and pressed against the photosensitive member 51. The conductive layer is formed on an insulating substrate made of a synthetic resin, and a primary transfer voltage is applied to the conductive layer via the above-described electrode roller.

In the course of circulating the intermediate transfer belt 86, the toner image on the photosensitive member 51 is transferred onto the intermediate transfer belt 86 in the primary transfer portion T1, and the intermediate transfer belt 8
The toner image transferred on the sheet 6 is transferred to a sheet (recording material such as plain paper, OHP sheet, glossy paper, etc.) S supplied between the secondary transfer roller 88 and the secondary transfer roller 88 in the secondary transfer section T2. You.

The intermediate transfer unit 80 also incorporates the electrode roller, biasing means for the tension roller 82, a secondary transfer roller 88, and a belt cleaner 89.

The sheet S is fed from a sheet feeding device 90 serving as a sheet feeding means, and is supplied to the secondary transfer portion T2 at a predetermined timing by a gate roller pair G. Reference numeral 91 denotes a paper feed tray for holding the sheets S stacked, and 92 denotes a pickup roller.

The sheet S to which the toner image has been transferred in the secondary transfer section T2 passes through a fixing unit 100 serving as a fixing unit, and the toner image is heated and melted and fixed.

The fixing unit 100 includes a heating roller 101 having a heat source and a pressing roller 10 pressed against the heating roller 101.
The rollers 101 and 102 heat the passing paper S while pinching it, thereby fusing and fixing the toner image on the paper S.

The sheet S that has passed through the fixing unit 100 is finally discharged through a sheet discharge path 110 to a sheet receiving portion 41 formed on a case 40 of the apparatus main body. The apparatus is provided with a reversing return path 110 ′ that can reverse the sheet S that has passed through the fixing unit 100 and return the sheet S to the secondary transfer unit T2 again.

The reverse return path 110 ′ is connected to the fixing unit 1
The switchback path 113 has two independent paper discharge paths 111 and 112 that can carry in the paper S that has passed through 00 and return the paper S once carried in.
And a return path 1 for returning the sheet S, which has been reversely fed from the switchback path 113, to the secondary transfer portion T2 again.
14. Therefore, this reverse return path 1
Sheet S returned to secondary transfer portion T2 again by 10 '
Is returned to the secondary transfer portion T2 with its front and back reversed.

Such an image forming apparatus can form an image only on the front side (first side) of the sheet S, or can form an image on both sides (first and second sides, front and back). Can also.

Reference numeral 120 denotes a control unit, which constitutes control means for controlling the entire apparatus and discrimination means described later. Reference numeral 123 denotes an operation panel of the apparatus, which has a display unit. The operation panel 123 and the control unit 120 constitute a paper type setting unit and a notification unit.

The outline of the operation of the entire image forming apparatus as described above is as follows.

(I) When a print command signal (image forming signal) from a host computer or the like (personal computer or the like) not shown is input to the control unit 120 of the image forming apparatus, each roller of the photosensitive member 51 and the developing cartridge 70 7
1, and the intermediate transfer belt 86 is driven to rotate.

(Ii) The outer peripheral surface of the photosensitive member 51 is uniformly charged by the charging roller 52.

(Iii) The exposure unit 60 selectively exposes the outer peripheral surface of the uniformly charged photoreceptor 51 in accordance with the image information of the first color (for example, yellow). An image is formed.

(Iv) Only the developing roller of the developing cartridge 70Y for the first color (for example, yellow) comes into contact with the photosensitive member 51, whereby the electrostatic latent image is developed.
A first color (for example, yellow) toner image is formed on the photoconductor 51.

(V) A primary transfer voltage having a polarity opposite to that of the toner is applied to the intermediate transfer belt 86, and the toner image formed on the photosensitive member 51 is transferred to the intermediate transfer belt 86 at the primary transfer portion T1. Is transferred to At this time, the secondary transfer roller 88 and the belt cleaner 89 are separated from the intermediate transfer belt 86.

(Vi) After the toner remaining on the photoreceptor 51 is removed by the cleaning means 53, the photoreceptor 51 is discharged by the discharging light L2 from the discharging means 61.

(Vii) The above operations (ii) to (vi) are repeated as necessary. That is, the second color, the third color, the fourth color,
Is repeated on the intermediate transfer belt 86 to form a toner image corresponding to the content of the print command signal.

(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, at a desired position on the sheet S, The secondary transfer roller 88 is pressed against the intermediate transfer belt 86 (at the timing when the toner image on the intermediate transfer belt 86 is transferred), and a secondary transfer voltage is applied. Is a full-color image in which four color toner images are superimposed) on the sheet S. Further, the belt cleaner 89 comes into contact with the intermediate transfer belt 86, and the toner remaining on the intermediate transfer belt 86 after the secondary transfer is removed.

(Ix) The toner image is fixed on the sheet S by passing the sheet S through the fixing unit 100, and thereafter, the sheet S is directed to a predetermined position (or to the sheet receiving portion 41 in the case of not performing double-sided printing). In the case of double-sided printing, the sheet is conveyed via the switchback path 113 to the return path 114).

That is, when an image is to be formed only on the front surface (first surface), the sheet S
After the toner image is transferred to the first surface by the secondary transfer portion T2 and fixed by the fixing unit 100,
The sheet is discharged onto the sheet receiving section 41 through 1 or 112. In addition, the entrance portion 110 of the paper discharge paths 111 and 112
A is provided with a path switching unit (not shown), which determines which sheet discharge path (111, 112) the sheet S is carried in.

When images are formed on both sides (first and second sides), the sheet S fed from the sheet feeding device 90 is
After the toner image is transferred to the first surface by the secondary transfer portion T2 and is fixed by the fixing unit 100, the sheet
Or 112 (the switchback path 74), the sheet is fed backward, passes through the return path 73, and is returned to the secondary transfer portion T2 again at a predetermined timing by the gate roller pair G.
The toner image is also transferred to the surface. Then, the fixing unit 1
At 00, the image (toner image) is also fixed on the second surface, and is discharged onto the sheet receiving unit 41 via the discharge path 111 or 112.

Although the outline of the image forming apparatus has been described above, this image forming apparatus can form an image on a special OHP sheet or a special glossy paper as the paper S in addition to the plain paper. .

The image forming apparatus has two operation modes (also referred to simply as modes) according to the type of paper on which an image is to be formed. The first operation mode is a mode for plain paper, in which the paper S fed from the paper feeding device 90 is transported by a transport means (secondary transfer roller 88, roller 101 of the fixing unit 100, etc.) after the gate roller G. ) Is a mode for transporting at a relatively high speed. The second operation mode is a mode for exclusive OHP sheets and exclusive glossy paper, and the sheet S fed from the sheet feeding device 90 is transported by the conveying means after the gate roller G at a relatively low speed (first mode). (1/10 to 1/7 of the speed of the above). Therefore, a relatively small amount of heat is applied by the fixing unit 100 to the sheet conveyed in the first operation mode, and a relatively small amount of heat is applied by the fixing unit 100 to the sheet conveyed in the second operation mode. A large amount of heat will be applied.

When the user operates the operation panel 123,
If the paper to be fed (to form an image) is set to be plain paper, the control unit 120 operates the apparatus in the first mode, and the paper to be fed is a specific paper. If it is set to (exclusive OHP sheet or exclusive glossy paper), the control unit 120 operates the apparatus in the second mode. However, as described later, even when the user sets the paper to be fed to be a specific paper, when the determination by the paper determination unit determines that the paper is not the specific paper, the control unit 120 determines The image forming operation is stopped.

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 operating the image forming apparatus in the second operation mode using the dedicated OHP sheet, it is possible to increase the melting state of the toner and obtain a high-quality image with high transparency (particularly, a full-color image).

The exclusive glossy paper is a paper in which a resin coat layer dedicated to this device is formed as an image receiving layer on the surface (one side or both sides) of the paper. By operating the image forming apparatus in the second operation mode using the special glossy paper, it is possible to obtain a high-quality image (particularly, a full-color image) by increasing the melting state of the toner.

As described above, when there are a plurality of types of paper (in this case, plain paper, dedicated OHP sheet, and dedicated glossy paper) as the used paper, the paper type setting and the actual The type of paper supplied to the image forming apparatus may be different. In this case, if no measures are taken, for example, the following problem occurs.

(1) Actually supplied paper (paper feeder 9
If the paper type setting is plain paper due to a user error even though the paper set to 0) is a dedicated OHO sheet or a dedicated glossy paper, the image forming apparatus operates in the first mode. , The melting of the toner becomes insufficient and a high quality image which should be originally obtained cannot be obtained.

(2) If the paper type setting is determined to be the specific paper due to a user's error, even though the paper actually supplied is plain paper, the image forming apparatus operates in the second mode. In this mode, the toner may be melted more than necessary and the paper (plain paper) may be wound around the heating roller 101 of the fixing unit 100.

In particular, in the case of the above (2), there is a possibility that the image forming apparatus is seriously damaged.

Therefore, in this embodiment, in order to prevent at least the fatal damage to the image forming apparatus, if the detection target is opaque or has a high reflectance, the target is detected. If the detection target part is transparent or has low reflectance, a sensor that does not detect the part is
At a position facing the paper transport path, at least two are arranged in the width direction of the paper, and a specific paper is located at a position facing the at least two sensors in the transport process.
A part that is detected by a sensor and a part that is not detected are provided, and a determination unit that determines whether a sheet to be conveyed is the specific sheet based on the presence or absence of detection signals from the at least two sensors is provided. If the setting by the paper type setting unit is set by the user to be the specific paper and the determination by the determining unit determines that the paper is not the specific paper, the control unit 120 stops the image forming operation. I decided to make it.

Hereinafter, a specific description will be given.

FIG. 2 is an enlarged view of the sheet feeding device 90, and FIG.
Is a partially omitted plan view thereof.

In these figures, reference numerals A and B denote sensors, which are arranged in the width direction of the paper (in the direction perpendicular to the paper transport direction and in the vertical direction in FIG. 3) at the position facing the transport path P of the paper S. Have been. These sensors A and B
Are connected to the control unit 120 (see FIG. 1). These sensors are sensors that detect the detection target portion when the detection target portion is opaque or high reflectance, and do not detect the detection target portion when the detection target portion is transparent or low reflectance.
Specifically, for example, it can be constituted by a limited reflection type photosensor.

FIG. 4 is a diagram for explaining the configuration and operation of the limited reflection type photosensor. In FIG.
122 is a light receiving element.

As shown in FIG. 9A, this sensor is used, for example, when the detection target portion Sa on the paper S is opaque or has high reflectance (ie, when the paper S is plain paper, for example).
The light emitted from the light emitting element 121 is scattered on the surface of the detection target portion Sa, and a part of the scattered light is
Reach 2. At this time, the signal (O
The portion Sa can be detected by the N signal (H signal).

On the other hand, as shown in FIG. 9B, when the detection target portion 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 detected. The light passes through the target portion Sa or is absorbed by the detection target portion Sa, and the scattered light hardly reaches the light receiving element 122. Therefore, the light receiving element 122 does not emit a signal (remains OFF (L)), and the portion Sa is not detected.

In FIG. 2, reference numerals 93 and 94 denote a pair of separation rollers, which prevent two or more sheets S fed by the pickup roller 92 from being fed at the same time. This is to ensure that only one sheet is fed to the transport path P. 95 and 96 are paper guides for guiding the paper S to be fed.

In FIGS. 3A and 3B, S1 is a dedicated O
An HP sheet, which is an example of “specific paper”. FIG. 3B is a cross-sectional view taken along line bb in FIG.

The dedicated OHP sheet S1 is provided with a portion Sa1 detected by the sensors and a portion Sa2 not detected by the sensors at positions opposed to the two sensors A and B in the transport process.

The detected portion Sa1 is formed by an opaque white portion Sa1 'printed in a frame shape on one edge of the sheet (the surface on which the image receiving layer is formed).
The undetected portion Sa2 is formed by partially not performing the printing. Therefore, the undetected portion Sa2 is a transparent portion.

These portions Sa1 and Sa2 are provided at four points symmetrically with respect to the center O1 of the sheet. Accordingly, when the dedicated OHP sheet S1 is sent in a horizontal state as shown in FIG. 10A, when the dedicated OHP sheet S1 is sent in a vertical state rotated by 90 degrees around the center O1 from the state shown in FIG. In any case where the sheet is sent in a horizontal state rotated by degrees, the parts Sa1 and Sa
2 is the aforementioned 2 in the process of transporting the dedicated OHP sheet S1.
And two sensors A and B.

FIG. 5A is a partially omitted plan view of FIG. 2 and shows a case where a special glossy paper S2 is set as the paper S. FIG. (B) is bb in FIG.
It is sectional drawing.

The special glossy paper S2 is also an example of the “specific paper”, and the special glossy paper S2 has a portion Sa3 detected by a sensor at a position opposed to the two sensors A and B during the conveyance process. And a part Sa4 not detected.

The exclusive glossy paper S2 has an image receiving layer formed only on one side, and the undetected portion Sa4 is partially printed on the edge of one side of the sheet (the surface on which the image receiving layer is formed). It is formed by the black portion. The part Sa3 to be detected is formed by the white surface of the exclusive glossy paper S2 itself on which no printing is performed.

These portions Sa3 and Sa4 are provided at four points symmetrically with respect to the center O2 of the sheet. Therefore, when the special glossy paper S2 is sent in a horizontal state as shown in FIG. 9A, when it is sent in a vertical state rotated by 90 degrees around the center O2 from the state shown in FIG. In any case where the sheet is sent in a horizontal position rotated by degrees, the portions Sa3 and Sa4 are
In the process of transporting the special glossy paper S2, it faces the two sensors A and B.

Sheet S actually supplied to the image forming apparatus
Is determined as a specific sheet (dedicated OHP sheet S1 or dedicated glossy paper S2) as follows.

FIGS. 6A and 6B are diagrams showing states of output signals from the sensors A and B. FIG. 6A shows a case where plain paper is supplied as the paper S, and FIG. (C) When a transparent sheet (for example, a normal OHP sheet) is supplied, FIG.
(D) shows the special glossy paper S as the paper S
2 is supplied.

As shown in FIG. 10A, when plain paper is supplied as the paper S, the plain paper is opaque, and when the leading end (the leading end in the transport direction) reaches the sensors A and B, the sensor is The output signals from A and B are both in the detection state (ON), and the state is that the trailing edge of the sheet is the sensor A,
Continue until the position B is passed. Therefore, the length L in the figure corresponds to the length of the sheet in the transport direction.

As shown in FIG. 13B, a normal (no mark) transparent sheet (for example, a normal OH sheet) is used as the paper S.
When the sheet (P sheet) is supplied, the sheet is entirely transparent, so that even if the leading end of the sheet reaches the sensors A and B, the output signals from the sensors A and B are both in the non-detection state (OFF). This state remains unchanged even if the sheet is further conveyed.

As shown in FIG. 3 (c), when a dedicated OHP sheet S1 is supplied as the paper S, the dedicated OHP sheet S1 is supplied to the dedicated OHP sheet S1 in the transport process as shown in FIG. 3 (a). At a position facing the two sensors A and B,
Since the part Sa1 detected by the sensor and the part Sa2 not detected are provided, when these parts reach the sensors A and B, the output signal from one of the sensors A is in the detection state (ON). The output signal from the other sensor B remains in the non-detection state (OFF). afterwards,
Further, when the sheet Sa is conveyed and the detected portion Sa1 passes through the sensor A, the output signal from the sensor A is turned off, so that the output signals from both sensors A and B are turned off, When the end (rear end in the transport direction) reaches the position of the sensors A and B, the detected portion Sa1 faces any of these sensors,
Output signals from both sensors A and B are both turned on.

As shown in FIG. 5D, when the special glossy paper S2 is supplied as the paper S, as shown in FIG. A portion Sa3 detected by the sensors and a portion Sa4 not detected by the two sensors A and B at positions facing each other.
Are provided, these parts are sensors A, B
, The output signal from one sensor A is in the detection state (ON), while the output signal from the other sensor B is in the non-detection state (OFF). Therefore, the state of the signal at this time is the same as that when the dedicated OHP sheet S1 is supplied (see FIG. 3C), but thereafter, the sheet is further conveyed, and the undetected portion Sa4 passes through 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 special glossy paper S2 passes through the positions of the sensors A and B. Continue until you do.

Since the states of the output signals from the sensors A and B change as described above depending on the type of paper supplied, the control unit 120 as the discriminating means first determines whether the leading edge of the paper is the sensor A or B. At time t1 when the sensor A reaches the position,
The state of the output signal from 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 position of the sensors A and B in the sheet feeding operation or the number of drive steps of the step motor serving as a driving unit of the pickup roller 92). Can be determined by

The control unit 120 determines whether or not the sheet S to be conveyed is the specific sheet based on the presence or absence of the detection signals from the sensors A and B as follows.

(A) Both output signals from the sensors A and B at the detection timing t1 are in the detection state (ON)
(See FIG. 6A), the supplied sheet S
Is determined to be plain paper.

(B) The output signals from the sensors A and B at the detection timing t1 are both in the non-detection state (OF
In the case of F) (see FIG. 6B), the supplied paper S is not determined to be a normal (not having a mark) transparent sheet, and is determined to be a feeding failure. As can be seen from this, the sensors A and B are also used as sensors for detecting a feeding failure.

(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),
Thereafter (the undetected portion Sa on the special glossy paper S2)
The output signal from the sensor B also takes a time required for the sensor 4 to pass through the sensor B (or after the corresponding rotation speed of the pickup roller 92 (or the number of driving steps of the stepping motor as its driving means)). When the non-detection state (OFF) remains (see FIG. 6C),
It is determined that the supplied paper S is the dedicated OHP sheet S1.

(D) At the detection timing t1, the output signal from the sensor A is in the detection state (ON), the output signal from the other sensor B is in the non-detection state (OFF),
Thereafter (the undetected portion Sa on the special glossy paper S2)
After the time required for the sensor 4 to pass through the sensor B (or after the corresponding rotation speed of the pickup roller 92 (or the number of driving steps of the step motor serving as the driving means) has elapsed), the output signal from the sensor B When it is turned ON (see FIG. 6D), it is determined that the supplied paper S is the special glossy paper S2.

As described above, according to the determination means in the image forming apparatus of this embodiment, whether the sheet to be conveyed is the specific sheet depends on the presence or absence of the detection signals from the two sensors A and B. Can be determined.

Further, the control unit 120 controls the image forming apparatus in the following manner in accordance with the setting state by the above-described paper type setting means and the above determination result.

<When the setting by the paper type setting means is plain paper> (a) When it is determined that the actually supplied paper S is plain paper, the image forming apparatus is switched to the first paper. Operate in operating mode. Therefore, an image of normal quality can be obtained on plain paper.

(B) If the paper S actually supplied is a normal (no mark) transparent sheet and it is determined that the feeding is defective, the image forming operation is stopped, and the feeding is stopped. Is displayed on the display unit of the operation panel 123.

(C) The paper S actually supplied is a dedicated OH
Even if it is determined that the sheet is the P sheet S1, the image forming apparatus is operated in the first operation mode. Therefore, in this case, an image is formed on the dedicated OHP sheet S1, but a high-quality image that should be originally obtained cannot be obtained.

(D) Even if it is determined that the actually supplied paper S is the special glossy paper S2, the image forming apparatus is operated in the first operation mode. Therefore, also in this case, a high quality image that should be originally obtained cannot be obtained.

In the above cases (c) and (d), the image forming operation is stopped, and a notification that the paper type setting by the user is incorrect is displayed on the display unit of the operation panel 123. Can also. With this configuration,
Image formation contrary to the user's intention can be stopped or corrected.

<When the setting by the paper type setting unit is a specific paper> (a) When it is determined that the actually supplied paper S is plain paper, the image forming operation is stopped. A notification that the user has set the paper type or that the paper is upside down is displayed on the display unit of the operation panel 123.

As can be seen from FIGS. 3 and 6 (c),
When the dedicated OHP sheet S1 is supplied in an upside down state, the sensors A and B at the detection timing t1
The output signals from the printers are all in the detection state (ON) and are the same as in the case of plain paper (see FIG. 6A). At this point, the supplied paper is turned over.
It cannot be determined whether the sheet is the HP sheet S1 or the plain paper.

Therefore, in this embodiment, the user sets the paper type or sets the paper (in this case, the dedicated OHP sheet S
The notification that the front and back of 1) are reversed is displayed on the display unit of the operation panel 123.

However, when the supplied paper is the dedicated OHP sheet S1 set upside down, the output signals from the sensors A and B are both turned off thereafter, so that it is determined that the paper is not plain paper. can do.

Therefore, when the output signals from the sensors A and B at the detection timing t1 are both in the detection state (ON) and thereafter are both OFF, the front and back of the dedicated OHP sheet are reversed. It can also be made to notify that it is set.

(B) If the paper S actually supplied is a normal (no mark) transparent sheet and it is determined that the feeding is defective, the image forming operation is stopped, and the feeding is stopped. Is displayed on the display unit of the operation panel 123.

(C) The paper S actually supplied is a dedicated OH
If it is determined that the sheet is the P sheet S1, the image forming apparatus is operated in the second operation mode. Therefore, in this case, a high quality image that should be originally obtained is obtained on the dedicated OHP sheet S1.

(D) Even when it is determined that the actually supplied paper S is the special glossy paper S2, the image forming apparatus is operated in the second operation mode. Therefore, also in this case, a high-quality image that should be originally obtained is obtained. When a high-quality image similar to the front surface is to be obtained on the back surface of the special glossy paper S2, an image receiving layer is also formed on the back surface, and the same portion Sa3 as the front surface is formed.
By forming Sa4, a high-quality image similar to the surface can be obtained.

As described above, according to this image forming apparatus, the following functions and effects can be obtained.

(1) If the target site Sa is opaque or has high reflectance, the target site is detected and the target site Sa is detected.
In the case where is a transparent or low reflectance, at least two sensors that do not detect the relevant portion are arranged in the width direction of the paper at a position facing the transport path P that transports the paper to the image forming unit, Paper (Dedicated OHP sheet S1
Alternatively, the dedicated glossy paper S2) is provided with a part detected by the sensor and a part not detected by the sensor at a position facing the at least two sensors during the transport process, so that the detection from the at least two sensors is performed. Based on the presence or absence of the signal, the determination unit determines whether or not the sheet to be transported is the specific sheet.

On the other hand, the user sets in the paper type setting means whether or not the paper to be fed is the specific paper.

If the setting by the paper type setting means is set by the user to be the specific paper, and if the determination by the determination means determines that the paper is not the specific paper, the control means sets the image to the specified paper. Since the forming operation is stopped, even though the user intends to form an image on the specific sheet, an image is formed on a sheet of a type other than the specific sheet contrary to the intention. Is prevented beforehand. Therefore, the trouble that the plain paper is wrapped around the fixing means is also prevented beforehand.

Further, it is sufficient that at least two of the sensors are arranged in the width direction of the sheet at a position facing the sheet conveying path, and it is easy to arrange them at the front of the image forming section in the apparatus. is there. In this embodiment, it is arranged in front of the gate roller G. In addition, the sensor
If the detection target portion Sa is opaque or has high reflectance, the target portion is detected. If the detection target portion Sa is transparent or has low reflectance, the detection portion is not required. Is unnecessary, and therefore, the power consumption is not significantly increased.

That is, according to the image forming apparatus of this embodiment, the sheet supplied to the image forming apparatus can be supplied to the specific sheet before the image is formed on the sheet and without causing a significant increase in power consumption. Is determined, it is possible to prevent the occurrence of the trouble beforehand.

(2) When the image forming operation is stopped, the user is provided with a notifying means for notifying the user that the paper type is set or that the sheet is upside down, so that the image forming operation is stopped for the user. You can tell the reason.

(3) The sensors A and B are arranged in front of the gate roller G that regulates the timing of supplying the sheet to the image forming section in the sheet transport direction, and whether the sheet reaches the gate roller G is determined. Since it also plays a role as a detecting means for detecting whether or not the apparatus is provided, it is not necessary to separately provide a detecting means, and the cost of the apparatus can be reduced.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the present invention.

For example, in the above-described embodiment, two sensors are used.
In the transporting process, a portion detected by the sensor and a portion not detected are provided at positions facing the three or more sensors, and the paper to be transported is determined based on the presence or absence of detection signals from the three or more sensors. Can be determined over a wider variety of papers as to whether or not is a specific paper.

[0137]

According to any one of the first to third aspects of the present invention, the sheet supplied to the image forming apparatus is formed before an image is formed on the sheet and without causing a significant increase in power consumption. It is possible to determine whether or not the sheet is a specific sheet, thereby preventing trouble from occurring.

Further, according to the image forming apparatus of the present invention, it is possible to inform the user of the reason for stopping the image forming operation.

According to the image forming apparatus of the third aspect, it is not necessary to separately provide a detecting means for detecting whether or not the sheet has reached the gate roller, and the cost of the apparatus can be reduced.

[0140]

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of 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.

3 (a) is a partially omitted plan view of FIG. 2, and FIG. 3 (b) is a sectional view taken along line bb in FIG. 3 (a).

FIGS. 4A and 4B are diagrams illustrating the configuration and operation of a limited reflection photosensor.

5 (a) is a partially omitted plan view of FIG. 2, and FIG. 5 (b) is a sectional view taken along line bb in FIG. 5 (a).

FIGS. 6A to 6D are diagrams showing states of output signals from sensors A and B. FIGS.

FIGS. 7A and 7B are explanatory diagrams of a conventional technique.

[Explanation of symbols]

A, B Sensor P Transport path S Paper S1 Dedicated OHP sheet (specific paper) S2 Dedicated glossy paper (specific paper) Sa Detected area Sa1, Sa3 Detected area Sa2, Sa4 Undetected area 120 Control unit (discriminating means , Paper type setting means, control means) 123 Operation panel (notification means) G Gate roller

Claims (3)

[Claims] A transport path for transporting a sheet to an image forming unit; and a position facing the transport path for the sheet, at least two of which are arranged in a width direction of the sheet, and a detection target portion is opaque or has a high reflectance. The sensor detects the part, and if the detection target part is transparent or has low reflectance, the sensor that does not detect the part, and the state of the presence or absence of the detection signals from at least two sensors, the paper to be conveyed, Determining means for determining whether or not the sheet is a specific sheet provided with a part detected by the sensor and a part not detected by the sensor at a position facing the at least two sensors in the conveying process; Paper type setting means for setting by the user whether or not the paper is the specific paper; and setting by the paper type setting means by the user if the paper is the specific paper. It is constant, and wherein when the discrimination by the discrimination means is not determined to be the said specific sheet, the image forming apparatus characterized by comprising a control means for stopping the image forming operation, a. 2. The image forming apparatus according to claim 1, further comprising: a notifying unit that notifies the user that the setting by the user or the front and back of the sheet is reversed at the time of the suspension. 3. The apparatus according to claim 2, wherein the sensor is configured to:
It is arranged at the front of a gate roller that regulates the timing of paper supply to the image forming unit, and also serves as a detection unit for detecting whether the paper has reached the gate roller. The image forming apparatus according to claim 1, wherein: