JP2002002966A - Image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device and an image forming method capable of effectively solving a problem of the misdetection caused by the disturbance light of a fluorescent lamp or the like without using an optical filter in detecting a size of a recording material on a paper feeding part exposed to the external of an image forming device body. SOLUTION: A light emitting part and a light receiving part of a reflection- type photosensor for detecting a length in a conveying direction, of the recording material placed on a manual paper feeding part, can be independently driven, whereby the misdetection caused by the disturbance light can be reduced by executing the judgment in different ways between a case when only the light receiving part is driven, and a case when the light emitting part and the light receiving part are simultaneously driven.

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 and an image forming method, and more particularly, to an image forming apparatus and an image forming method capable of reducing erroneous detection of a size of a recording material placed on a sheet feeding unit.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a facsimile, a printer, or the like, in addition to a paper feeding unit capable of storing only a recording material of a predetermined size, recording materials of various sizes according to the needs of a user are used. There is a printer having a so-called “manual paper feeder” that can be placed.

For the sake of convenience, FIG.
3 will be described with reference to FIG. 3. The manual paper feed unit indicated by reference numeral 60 in FIGS. 1 to 3 is disposed so as to be exposed outside the image forming apparatus main body 1. I have. In the manual paper feeder 60, reference numeral 60
Reference numeral 1 denotes a sheet feeding plate, 602 denotes a width detecting unit, 603 denotes a length detecting unit which is a reflection type photosensor, and 604 denotes a placement detecting unit of a recording material such as a photo interrupter.

The paper supply plate 601 is a plate-like member for mounting a recording material, and the mounting detection means 604 is a photo interrupter for detecting whether the recording material is mounted on the paper supply plate 601.

The width detecting means 602 is a means for detecting the length in the width direction orthogonal to the conveying direction of the recording material.
02 obtains, for example, A4 (or A
3), B5 (or B4), A4R, B5R, and B6.

The length detecting means 603 is a reflection type photo sensor, but the conventional length detecting means is a mode in which the light emitting portion and the light receiving portion are driven integrally (as described later, the length detecting means 603 of the present invention). Indicates that the light emitting unit and the light receiving unit are driven independently.) Therefore, in the conventional type, the length detecting means 603
When a recording material exists on the upper side, light emitted from a light emitting unit using an LED or the like is reflected on the recording material and detected by the light receiving unit, but no recording material exists on the length detecting unit 603. In such a case, the light emitted from the light emitting unit is emitted as it is, so the light receiving unit does not detect the light. This detection information,
Together with the above information obtained from the width detecting means 602,
It is determined whether the size is 4 or A3, or B5 or B4.

However, since the manual sheet feeding section 60 is exposed outside the image forming apparatus main body 1, the length detecting means 603 detects disturbance light (except for light emitted from the light emitting section of the reflection type photo sensor). External light).
That is, even though the recording material does not exist on the length detecting unit 603, the light receiving unit of the reflection type photo sensor detects the disturbance light, so that an erroneous detection is made as if the recording material exists. A4 is determined to be A3 and B5 is determined to be B4). For example, the sensitivity wavelength of a reflection type photosensor that is widely used is about 850 nm, and the peak of the emission wavelength of a fluorescent lamp is usually about 720 nm, so this does not cause much problem. A phenomenon occurs in which the emission wavelength shifts to the longer wavelength side, and the tail of the emission wavelength is detected by the reflective photosensor.

In order to solve such a problem, an optical filter which blocks the wavelength of disturbance light is provided with a length detecting means 6.
03, but the optical filter itself is expensive, and the optical filter cuts off some of the light wavelengths required for sensing, which lowers the sensitivity of the sensor. There is a problem that it cannot cope with disturbance light having a wavelength equal to the wavelength used for sensing.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to detect the size of a recording material in a paper feeding unit exposed outside the main body of an image forming apparatus, which is erroneously detected by disturbance light such as a fluorescent lamp. Another object of the present invention is to provide an image forming apparatus and an image forming method that can solve the problem efficiently without using an optical filter.

[0010]

The above object of the present invention has been attained by the following constitutions.

1. In an image forming apparatus having an image forming unit, a sheet feeding unit for placing a recording material, and a conveying unit for conveying the recording material from the sheet feeding unit to the image forming unit, the sheet feeding unit includes a recording material. Placement detection means for detecting whether or not is placed, width detection means for detecting the width of the recording material,
Length detecting means for detecting the length of the recording material in the conveying direction, the length detecting means is a reflective photo sensor, the light emitting unit and the light receiving unit can be driven independently, Control means for switching between a first detection state in which only the light receiving section is driven and a second detection state in which the light emitting section and the light receiving section are simultaneously driven to detect the length of the recording material. Image forming apparatus.

2. A size detection step of detecting the size of the recording material placed on the paper feeding unit, a conveyance step of conveying the size-detected recording material to an image forming unit, and an image formation on the recording material conveyed in the conveyance step The size detection step includes performing width detection for detecting a width of the recording material and length detection for detecting a length of the recording material in the conveyance direction, and performing the length detection. The detection is performed by switching between a first detection state in which only the light receiving portion of the reflection type photosensor is driven and a second detection state in which the light emitting portion and the light receiving portion of the reflection type photosensor are simultaneously driven. An image forming method comprising:

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of a digital electrophotographic copying machine (hereinafter, simply referred to as an image forming apparatus). FIG. FIG. 3 is an enlarged view of a part of FIG.

Here, a copying machine will be described. However, the image forming apparatus of the present invention is not limited to this, and may be a facsimile or a printer as long as it has a paper feeding unit, a conveying unit, and an image forming unit. Alternatively, the image forming apparatus may be of another type such as an inkjet type.

Referring to FIG. 1, the image forming apparatus main body 1 includes:
An automatic document feeder (ADF) A, a document image reading unit B for reading an image of a document conveyed by the automatic document feeder, an image control board C for processing the read document image, A writing unit D including a writing unit 12 for writing on an image carrier 10 made of a photosensitive drum in accordance with the data of the above; a charging electrode 14 around the image carrier 10 and a developing means 16 comprising a magnetic brush type developing device; Image forming unit E including image forming means such as transfer electrode 18, separation electrode 20, and cleaning means 21
And a plurality of paper supply units (hereinafter, also referred to as a paper supply tray or simply a tray) 22, 24, 60, etc., for storing recording materials (hereinafter, referred to as sheets) P. In particular, the paper feed unit 60 protruding outside the image forming apparatus main body 1 is referred to as a manual paper feed unit in the present invention.

The automatic document feeder A includes a document table 2
6, and a document transport processing unit 28 including a roller group including the roller R1 and a switching means (without reference symbols) for appropriately switching a document moving path, etc., as main components.

The original image reading section B is located under the top glass G and can move back and forth while maintaining the optical path length, a fixed imaging lens (hereinafter simply referred to as a lens) 33, and a line. Image sensor (hereinafter referred to as CCD
The writing unit D includes a laser light source 40, a polygon mirror (polarizer) 42, and the like.

Although the automatic document feeder A has a difference in configuration from a conventional automatic document feeder, the principle itself is well known, and the original image reading section B, writing section D, image processing means, An image forming apparatus and an image forming process provided with forming means (means for forming a toner image on the image carrier 10 and transferring the toner image onto a sheet) are well known. Is simply performed.

It should be noted that R shown on the front side of the transfer electrode 18
Reference numeral 10 denotes a registration roller, and H shown on the downstream side of the separation electrode is a fixing unit.

In the embodiment, the fixing means H comprises a roller having a built-in heating source and a pressure roller which rotates while pressing the roller.

In the above configuration, a process of forming a toner image on the image carrier 10, transferring the toner image onto a sheet, and then discharging the toner image to a paper discharge tray is as follows.

In the present specification, including this section, the transfer area where the transfer electrode is located may be referred to as an image recording section.

One of the originals (not shown) placed on the original placing table 26 is transported in the original transport processing unit 28, and the slit exposure by the exposure means L is performed while passing under the roller R1. Done.

The reflected light from the original is imaged on the CCD via the mirror units 30 and 31 and the lens 33 at fixed positions, and is read.

The image information read by the document image reading section B is processed by image processing means, encoded, and stored in a memory provided on the image control board C.

The image data is called in accordance with the image formation, and the laser light source 40 in the writing section D is driven according to the image data, so that the image carrier 10 is exposed.

Prior to the exposure, the image carrier 10 rotating in the direction of the arrow (counterclockwise) is charged with the charging electrode 14.
A predetermined surface potential is applied by the corona discharge action of the above, but the exposure reduces the potential of the exposed portion in accordance with the amount of exposure, and as a result, an electrostatic latent image corresponding to the image data is formed on the image carrier 10. Formed on top.

The electrostatic latent image is reversely developed by the developing means 16 to be a visible image (toner image).

On the other hand, before the leading end of the toner image on the image carrier 10 reaches the transfer area, for example, one sheet P in the paper feed tray 22 is fed and conveyed to the registration roller R10. Reached and regulated at the tip.

The sheet P is conveyed toward the transfer area by the registration roller R10, which starts rotating in synchronization with the toner image, that is, the image area on the image carrier 10, so as to overlap.

In the transfer area, the toner image on the image carrier 10 is transferred onto the sheet P by the urging of the transfer electrode, and the sheet P is then urged by the separation electrode 20. Separated from

Thereafter, the toner powder for forming the toner image is applied to the sheet P by pressurizing and heating the fixing means H.
The sheet P is melted and fixed thereon, and is discharged onto a discharge tray T via a discharge path 78 and a discharge roller 79.

Returning to FIG. 1, the sheet P is
Only shown in FIG. The reference symbol S in the paper feed tray 24 is a movable plate whose free end is always urged upward by an urging means such as a coil spring (not shown). It comes into contact.

The paper feed tray 22 also has the same configuration as that described above. In the embodiment, the paper feed trays 22 and 24 are arranged in two stages in the vertical direction, but may be provided with more paper feed trays.

[0036] Of the sheet feeding trays, the lower stage (in the embodiment, the sheet feeding tray is a two-stage stack, so the lower stage is used.
A space 25 having a predetermined gap is formed between the bottom of the sheet feed tray 24 (same as the bottom wall) and the bottom wall of the apparatus main body.

The space 25 is used in a mode (mode) for forming an image on both sides of the sheet P, and cooperates with a second transport path 80 (described later) for reversing the sheet front and back. Helps achieve reversal.

Reference numerals 50 and 53 above the respective leading end portions of the sheet feed trays 22 and 24 (corresponding to the leading ends of the stored sheets P when viewed in the sheet feeding direction) denote sheet feeding means (hereinafter referred to as feed-out means) comprising rollers. Roller), 51 and 5
4 is a feed roller, and 52 and 55 are double feed prevention rollers.

Hereinafter, in the present specification, a configuration including the feed roller, the feed roller, and the double feed prevention roller may be referred to as a sheet feeder.

Numeral 60 denotes a manual paper feed unit, which can be opened and closed with the lower end as a fulcrum with respect to the side wall of the image forming apparatus main body 1.

Numeral 61 denotes a paper feeding means (hereinafter, referred to as a feeding roller) comprising rollers for feeding out the sheet P placed on the manual paper feeding unit 60 along with image formation, 63
Is a feed roller provided downstream of the feed roller 61; 65 is a double feed prevention roller for pressing against the feed roller 63 to prevent a plurality of sheets P from being fed;
In order to fulfill the same function as the sheet feeding device provided corresponding to the above-mentioned sheet feeding trays 22 and 24, it has substantially the same configuration.

Reference numeral 70 denotes a first transport path for performing image formation (image recording) on the sheet P by transfer, and extends upward from below when viewed in the sheet moving direction.

Reference numeral 72 denotes a sheet feeding path for sheets stored in the upper sheet tray 22; 74, a sheet feeding path for sheets stored in the lower sheet tray 24; This is a merging section (a part of the first conveyance path 70) where the sheets P sent from the sheet 24 merge.

Reference numeral 78 denotes a discharge path for discharging a sheet on which a predetermined image has been formed onto the discharge tray T.

Numeral 80 denotes a second conveyance path for reversing the front and back of a sheet used for forming an image on both sides of the sheet.
The upper part of the figure communicates with the first transport path.

The second transport path 80 extends downward from above when viewed from the sheet moving direction.

The lower end of the second conveying path 80 is a conveying path extending substantially vertically, and the lower end extends below the lower sheet feeding tray 24 and is connected to the first conveying path 70. Connected (communication).

The first transport path 70 and the second transport path 80
Is provided with a transport unit R20 (hereinafter, referred to as a switchback roller R20 for convenience of description) including a pair of reversible rollers.

Reference numeral 90 denotes an (upper) branch guide, which is controlled so as to direct the sheet P, on which an image has been formed on the first surface, to the paper discharge path 78 or to the second transport path 80. You.

Reference numeral 93 denotes a (lower) branch guide for switching the sheet conveying path.
In one embodiment, the sheet P is used so that the sheet P moving on the second conveyance path 80 is directed to the space 25 when the sheet P is turned upside down.

In the image forming process, when the sheet P moving on the second conveying path 80 is sent out toward the space 25, the rear end of the sheet P is gripped by the switchback roller R20. Therefore, a part of the sheet is stored in the space 25.

In the figure, reference numeral 94 denotes an opening provided on the bottom wall of the apparatus main body 1. The opening 94 is formed on an extension of a substantially vertical conveyance path portion of the second conveyance path 80 so as to allow passage of the sheet P conveyed by the switchback roller R20.

Between the switchback roller R20 and the opening 94, a guide surface 101 formed on an inner surface of an opening / closing door 100 described later and the branch guide 93 restrict the movement of the sheet. It is.

The branch guide 93 is provided with the branch guide 9.
Similarly to 0, control is performed via the control unit according to the image forming mode set by the user.

The image forming process for the second side of the sheet in the image forming apparatus having the above configuration is as follows.

As described above, when the sheet P on which the image is formed on the first surface moves up the first transport path 70 and the leading end reaches the branch guide 90, the branch guide 90
Since the sheet P is maintained at the position indicated by the broken line in the figure, the sheet P enters the second conveyance path 80 and continues to move.

When the sheet P descends on the second conveying path 80 and reaches the lower end thereof, the sheet P is nipped by the switchback roller R20 and is sent out in the direction of the branch guide 93 deviating from the second conveying path. .

At this time, since the branch guide 93 is located at the position indicated by the solid line in the drawing, the sheet P to be fed out is stored in the space 25 formed below the lower sheet feed tray 24.
It is led to. At this time, the first image formed on the sheet P
The face is on the lower side.

Eventually, the switchback roller R2
0 stops the rotation while holding the rear end of the sheet P, and then starts to rotate in the opposite direction, the sheet P is turned upside down, that is, the sheet P on which no image is formed. The sheet is fed into the first conveyance path 70 with the two surfaces facing the image carrier 10, and the leading end is regulated by the registration roller R <b> 10.

On the other hand, a second toner image is formed on the image carrier 10 by the above-described process, and the registration roller R is synchronized with the rotation of the image carrier 10.
When the rotation of the sheet P starts, the sheet P enters the transfer area while overlapping the second toner image area.

Thereafter, when the leading end of the sheet P subjected to the transfer process, the separation process, and the fixing process reaches a certain portion of the branch guide 90, the branch guide 90 is maintained at the solid line position in FIG. Since the first conveyance path 70 and the paper discharge path 78 are in communication with each other, and the communication with the second conveyance path 80 is cut off, the sheet P enters the paper discharge path 78 and passes through the paper discharge roller 79. And is discharged onto the discharge tray T.

The first transport path 70 and the second transport path 8
As shown in FIG. 2, the connecting portion at the lower end with 0
Allowing the sheet to move down the second conveyance path 80,
A regulating plate 77 is provided to prevent the sheet having been turned upside down from being erroneously entered into the second conveyance path 80 when the sheet is fed into the first conveyance path 70.

By the way, as for the manual sheet feeding section 60, in the embodiment, as shown in FIG. 2, the outer surface thereof is provided on the opening / closing door 100 serving as a side wall of the apparatus main body.

Further, the sheet feeding device including the manual sheet feeding portion 60 for handling the sheets placed thereon is placed at the same height position as the sheet feeding device for the sheet feeding tray 22, and is attached to the opening / closing door. It is attached.

A conveyance path for the sheet P fed into the apparatus from above the manual sheet feeding section 60 (hereinafter, referred to as a third conveyance path).
66 extends across the second transport path 80, and
It is configured to communicate with the transport path 70.

More specifically, it is configured such that the merging portion 76, which is on the front side of the image forming portion where the transfer electrode 18 is located, more specifically, on the front side of the registration roller R10, is terminated. is there.

Further, since the distance between the feed roller 63 and the double feed prevention roller 65 constituting the paper feeder and a pair of transport rollers (without reference symbols) provided across the second transport path 80 can be reduced, the sheet can be shortened. P can be transported reliably.

It is desirable that the inclination and the like of the third conveying path 66 have a straightness as much as possible so as to avoid applying an extra load to the sheet.

In the image formation using the sheet placed on the manual sheet feeding section 60, only the conveyance route until the leading end is regulated by the registration roller R10 is different. Is the same as the process described above, and the description is omitted.

As described above, the first to third transport paths are each
A transport unit that transports the recording material from 2, 24, and 60 to the image forming unit E.

Next, sheet size detection in the manual sheet feeding section 60 will be described with reference to FIGS.

In the manual paper feed unit 60, reference numeral 6
Reference numeral 01 denotes a sheet feeding plate, 602 denotes a width detecting unit, 603 denotes a length detecting unit which is a reflection type photo sensor, and 604 denotes a recording material placement detecting unit such as a photo interrupter.

The sheet supply plate 601 is a plate-like member for placing sheets, and is integrally formed with the side wall surface of the image forming apparatus main body 1 when not in use, with the connecting portion to the image forming apparatus main body 1 as a rotation axis. It is configured to be.

When the recording material is placed on the sheet supply plate 601, the placement detection means 604 protrudes from the sheet supply plate 601 to a connection portion with the image forming apparatus main body 1 so as to be able to be pushed. The protruding member is tilted (not shown) by the leading end of the recording material, and the tilted protruding portion is positioned by the placement detecting means 60.
4 is a photo-interrupter for detecting the presence or absence of a recording material by obstructing an optical path between a light emitting unit and a light receiving unit.

In the width detecting means 602, holding members 602h for holding both ends of the recording material are fitted in the grooves 602m, and can be moved in the direction of the arrow in the figure. When the holding member 602h is moved according to the width of the recording material, the voltage value of a variable resistor (not shown) connected thereto changes, and the width of the recording material can be detected. Information obtained by the width detecting means 602 is, for example, A4 (or A3), B
5 (or B4), A4R, B5R, B6.

In the present invention, the length detecting means 603 is a reflection type photo sensor in which the light emitting section and the light receiving section can be driven independently. Conventionally, in a reflection type photo sensor, the circuit of the light emitting unit and the light receiving unit are generally the same, and the light emitting unit is turned on.
The light-receiving section is driven in conjunction with the light-emitting section (usually, there is no point in driving the light-emitting section and the light-receiving section separately). Circuits are provided separately so that they can be driven independently. In order to avoid erroneous detection of the length of the sheet P in the conveying direction (= size erroneous detection), there are two modes: a first detection state in which only the light receiving unit is driven, and a second detection state in which the light emitting unit and the light receiving unit are simultaneously driven. That's why.

In the first detection state, the length detection means 603
In this state, the light emitting unit is turned off and the light receiving unit is turned on. In this state, if it is indicated that the light is received (when the voltage value LOW is output), when the function of the length detecting means 603 itself is normal, the disturbance light is received and the sheet length is not detected. It can be determined that there is a possibility of erroneous detection. That is,
When the mode of the length detecting means 603 is switched to a second detection state (light emitting section ON / light receiving section ON) described below, even though the sheet does not cover the length detecting means 603 (from the light emitting section). By indicating that light has been received (even though light is not reflected by the sheet), it can be determined that there is a possibility that the sheet may be erroneously recognized as existing on the length detecting means 603. In addition, the fact that light is received in the first detection state indicates that the sheet is not covered on the length detecting means 603, and therefore, the sheet is not placed or the sheet is placed. Even if the length is detected, it can be determined that the length does not cover the length detecting means 603 (A4, B5, etc.).

In the second detection state, the length detection means 603
This is a state where the light emitting unit is ON and the light receiving unit is ON. This corresponds to the same mode as a reflection type photosensor generally used conventionally. When a sheet is present on the length detecting unit 603, light emitted from a light emitting unit using an LED or the like is reflected by the sheet and detected by the light receiving unit (voltage value LO).
W is output), and when the recording material does not exist on the length detecting unit 603, the light emitted from the light emitting unit is emitted as it is, and the light receiving unit does not detect the light (voltage value HIG).
H). When there is no influence of disturbance light and the function of the length detection means 603 is also operating normally, the A4 size is combined with the detection information in the second detection state and the information obtained from the width detection means 602. It is determined whether the size is A3 or A3, or B5 or B4.

It is the control board C (control means) that switches between the first detection state and the second detection state and determines the sheet size.

By judging the first detection state and the second detection state in combination, whether the influence of disturbance light is present or not, whether the length detecting means 603 itself is abnormal or normal, A4 A3 or B5 or B4
It is possible to avoid the risk of erroneously detecting a certain sheet size.

FIG. 4 is a diagram showing a state in which erroneous detection is performed by switching between a first detection state in which only the light receiving section of the length detecting means is driven and a second detection state in which the light emitting section and the light receiving section are simultaneously driven. 9 is a flowchart illustrating an example of determining an accurate recording material size. Here, a case is shown in which the width detecting means detects the width of A4 or A3 as the sheet width, and the length detecting means determines whether the sheet is A4 or A3.

First, the power of the image forming apparatus is turned on at the beginning of the morning and the like, and as a check at the time of starting, whether or not the recording material is placed on the manual paper feed unit is detected by the placement detecting means (S1). This check at start-up is to check whether the length detecting means functions normally in the environment after the start of the image forming apparatus or whether the external environment is normal (whether there is no influence of disturbance light). Here, only when the power is turned on, this step is to be introduced as appropriate when there is a change in the installation place of the image forming apparatus or the external environment.

In the start-up confirmation, if the recording material is not placed on the manual sheet feeding unit (NO), the length sensor as the length detecting means is set to the first detection state (light emitting unit OFF / light receiving unit O).
N) (S2). In this state, it is determined whether or not the light receiving unit is receiving light (S3).
In O), it is determined that the length sensor is normal and there is no influence of disturbance light (S4). Thereafter, when the recording material is placed on the manual paper feed unit (S5 → YES), the length sensor is switched to the second detection state (light emitting unit ON / light receiving unit ON) (S6). In this state, it is determined whether or not the light receiving portion of the length sensor has received light (S7). If no light is received (NO), it is determined that the size of the recording material placed on the manual sheet feeding portion is A3 ( S8) If light is received (YE)
S) Judge as A4 size (S9). Step S
Steps S5 to S9 are normal operations.

On the other hand, at the time of the start-up confirmation, if the recording material is not placed on the manual sheet feeding portion and it is detected that the light receiving portion is receiving light in the first detection state of the length detecting sensor (S3). (→ YES), the length sensor determines that the sensor itself has malfunctioned or has been erroneously detected due to the influence of disturbance light (S10). Thereafter, when the recording material is placed on the manual paper feed unit (S11 → YES), the length sensor is set to the second position.
Switch to the detection state (light emitting unit ON / light receiving unit ON) (S
12). In this state, it is determined whether or not the light receiving section of the length sensor has received light (S13), and if no light has been received (NO),
This output is inconsistent with the detection result of the start-up confirmation, and it is determined that the length sensor itself has failed (S14), and "Length sensor failure" or the like is displayed on an arbitrary display section of the image forming apparatus (S14). S15). On the other hand, in step S13, if light is received (YES), it is erroneous detection due to disturbance light (A4), or is light received from the light emitting section reflected by the recording material (A3)? Is not certain (S16), the length sensor is again switched to the first detection state (light emitting unit OFF / light receiving unit ON) (S17), and it is determined whether the light receiving unit has received light (S18). If it is not received (NO), it is judged that the size is A3 because the disturbance light is blocked by the recording material (S19), and if it is not received (YES), it is A because it is the reception of disturbance light.
It is determined that the size is four (S20).

In the start-up confirmation, when the placement detecting means detects that the recording material is placed on the manual paper feed unit (S1 → YES), the length sensor is set to the first detection state (light emitting unit OFF). / Light receiving section ON) (S21), and determines whether the light receiving section has received light (S22). If light is received (YES), it is determined that the influence is due to disturbance light or erroneous detection due to sensor failure (S23), and then the length sensor is set to the second detection state (light emitting unit ON / light receiving unit ON). ) (S24). In this state, it is determined whether or not the light receiving unit has received light (S25). If light is received (YES),
It is known that there is an influence of the disturbance light (S26), and the fact that the disturbance light is received means that there is no recording material on the length sensor, so it is determined that the sheet is of A4 size (S27). on the other hand,
If it is determined in step S25 that no light is received (NO), it is determined that the length sensor is faulty because it conflicts with the detection result in step S22 (S28).
"Length sensor failure" or the like is displayed on an arbitrary display unit of the image forming apparatus (S29).

If it is determined in step S22 that no light is received (NO), it is determined that the length sensor has no influence of disturbance light or erroneous detection due to a failure (S3).
0) Then, the length sensor is set to the second detection state (light emitting unit ON /
(S31). It is determined whether or not the light receiving unit has received light (S32).
S) Since the recording material exists on the length sensor, it is determined that the size is A3 (S33), and if no light is received (N
O), since the light from the light emitting unit is emitted, it is determined that the size is A4 (S34).

As described above, the presence or absence of the influence of the disturbance light is determined based on the first detection state, and the size of the recording material is detected based on the determination based on the second detection state. Even in this case, the size of the recording material can be accurately determined.

[0088]

According to the present invention, in detecting the size of a recording material in a paper supply unit exposed outside the main body of an image forming apparatus, the problem of erroneous detection due to disturbance light such as a fluorescent lamp can be efficiently solved without using an optical filter. An image forming apparatus and an image forming method that can be solved can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a digital electrophotographic copying machine (hereinafter, simply referred to as an image forming apparatus).

FIG. 2 is a partially enlarged view of FIG. 1 including a side view of a manual sheet feeding unit and a portion from a conveyance unit to an image forming unit.

FIG. 3 is a plan view of a manual sheet feeding unit.

FIG. 4 is a flowchart illustrating an example of determining an accurate recording material size in the image forming method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus main body 10 Image carrier 12 Writing unit 14 Charging electrode 16 Developing means 18 Transfer electrode 20 Separation electrode 22, 24, 60 Paper feeder 66 Third transport path (transport section) 70 First transport path (transport section) 80 second conveyance path (conveyance unit) 601 paper supply plate 602 width detection means 603 length detection means 604 placement detection means C control board (control means) E image forming unit

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoshifumi Sasamoto 2970, Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (72) Inventor Yoshiteru Katayama 2970, Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 3F343 FA02 FB02 HB02 HE04 HE08 HE20 HE22

Claims (2)

[Claims] 1. An image forming apparatus comprising: an image forming unit; a paper feeding unit for placing a recording material; and a transporting unit for transporting the recording material from the paper feeding unit to the image forming unit. The unit includes a placement detection unit that detects whether a recording material is placed, a width detection unit that detects a width of the recording material, and a length detection unit that detects a length of the recording material in the conveyance direction. The length detecting means is a reflection type photo sensor, wherein a light emitting unit and a light receiving unit can be driven independently; a first detection state in which only the light receiving unit is driven; An image forming apparatus comprising: a control unit configured to switch between a second detection state for simultaneously driving the image forming unit and a second detection state and to detect a length of the recording material. 2. A size detecting step for detecting the size of a recording material placed on a sheet feeding unit, a conveying step for conveying the size-detected recording material to an image forming unit, and a conveying operation in the conveying step. An image forming method including an image forming step of forming an image on a recording material, wherein the size detecting step includes a width detection for detecting a width of the recording material, and a length detection for detecting a length of the recording material in a conveying direction. The length detection is performed by switching between a first detection state in which only the light receiving unit of the reflection type photo sensor is driven and a second detection state in which the light emitting unit and the light receiving unit of the reflection type photo sensor are simultaneously driven. An image forming method comprising detecting a length of a recording material.