JP3239222B2 - Paper winding detection device for image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper wrap detecting device for detecting paper wrap around a photoreceptor in an image forming apparatus such as an electrophotographic copying machine, and more particularly to a paper wrap detecting device for preventing erroneous detection of paper wrap. About technology.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, the peripheral surface of a photosensitive drum as a photosensitive member is uniformly charged by a charger, and then the peripheral surface of the photosensitive drum is exposed to an image. An electric latent image is formed. This latent image is developed and visualized by a developing device to become a toner image. The toner image formed on the peripheral surface of the photoconductor drum is transferred by physical means onto recording paper fed in time, and the recording paper on which the toner image has been transferred is separated from the photoconductor drum and fixed. The toner image is conveyed to the apparatus, and the toner image is discharged onto the recording paper after being fixed on the recording paper.

In the transfer of the toner image adhered to the peripheral surface of the photosensitive drum onto the recording paper, the toner is charged from the back of the recording paper with a polarity opposite to that of the toner by a transfer device which discharges the toner image. Transfer onto the recording paper is performed, and after the transfer, a high AC voltage is applied to eliminate the charge, and the recording paper is separated from the photosensitive drum. However, it is difficult to reliably maintain transferability and separability, especially when the drum diameter of the photosensitive drum is large, it is difficult to separate the photosensitive drum from the recording paper, and the recording paper after the transfer of the toner image is completed. Is easily separated, adheres to the photosensitive drum without separation, and causes paper jams and the like.

For this reason, a paper winding detecting device for detecting whether or not the photosensitive drum and the recording paper have been separated has conventionally been provided. FIG. 6 shows a conventional example of such a paper wrap detecting device.
And will be described. In FIG. 6, a reflection type photosensor 2 for detecting paper winding is provided around the photosensitive drum 1 downstream of the transfer device with respect to the rotation direction of the photosensitive drum 1. As shown in the figure, the photo sensor 2 includes a light emitting diode 3 as a light emitting element installed so as to irradiate a light beam at a right angle to the surface of the photosensitive drum 1, and a surface of the photosensitive drum 1 by a light beam from the light emitting diode 3. And a phototransistor 4 as a light receiving element installed so as to receive the reflected light from the light at a certain angle θ, and is controlled by a control unit 5 containing a microcomputer. That is, the light emitting diode 3 emits light in response to a light emission signal output from the control unit 5 at a predetermined timing, and the light beam is irradiated at right angles to the surface of the photosensitive drum 1. The reflected light of the irradiation light is received by the phototransistor 4. Here, the amount of received light increases in an object having a large amount of irregular reflection such as paper, and the amount of received light decreases in an object having a large amount of regular reflection and a small amount of irregular reflection such as the photosensitive drum 1. The developed toner may remain on the surface of the photosensitive drum 1, and the reflected light from the toner may be received by the phototransistor 4.
The light receiving level is substantially the same as that of the photosensitive drum 1.

Accordingly, as shown in FIG. 7, based on the difference between the light receiving level of the photosensitive drum and toner (shown by a dashed line in the figure) and the light receiving level of the recording paper (shown by a solid line), a certain value between the two is obtained. A threshold value S is set in advance, and the threshold value S is compared with the light receiving output from the phototransistor 4 by the control unit 5. If the light receiving level is smaller than the threshold value S, it is determined that the light is reflected from the photosensitive drum 1 or the toner, and the paper is wound. When the light receiving level is equal to or higher than the threshold value S, it is determined that the sheet is paper, and it is determined that the paper is wound, and the apparatus is automatically stopped. Incidentally, the light receiving levels of the photosensitive drum 1 and the toner vary from device to device as shown by the solid line in FIG.

[0006]

However, in the conventional paper winding detecting apparatus, the threshold value S is fixed. For this reason, the light receiving level varies due to a change in the environmental temperature of the photosensor 2 and the photosensitive drum 1, and
If the light receiving level is reduced due to dirt on the photo sensor 2, the actual light receiving level of each detection object fluctuates. On the other hand, the threshold value S is fixed and does not fluctuate. There was a problem that it easily occurred.

Also, the ratio of the light receiving level between the recording paper and the photosensitive drum is measured and stored in advance, and this is used as a reference ratio. There is one that detects paper winding by comparing the ratio with a ratio (for example, Japanese Patent Application Laid-Open No. 58-46366).
Reference). However, in the case of such a conventional device,
If the light receiving level of each photosensitive drum varies, the photosensitive drum is damaged, etc., and the light receiving level of the used photosensitive drum fluctuates, the ratio between the photosensitive drum and the recording paper is stored. There is a possibility that an erroneous detection will occur because the reference ratio will differ. Also, for color printing, etc.
In addition to black toner having a large light receiving level difference from recording paper as in the case of monochrome printing, a plurality of color toners such as yellow toner are used in addition to black toner. In this case, depending on the type of toner, such as yellow toner, the light receiving level approaches the recording paper, so that when the toner is adhered to the photosensitive drum, there is a problem that erroneous detection may occur. ing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a paper winding of an image forming apparatus capable of reliably detecting paper winding without being influenced by a change in a light receiving level due to a temperature change or contamination of a light detecting means. It is an object to provide a detection device.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention is directed to FIG.
As shown in, after transferring the toner image formed on the photoreceptor onto the recording paper while rotating the photoreceptor, the image forming apparatus is provided with an image forming apparatus that separates the recording paper from the photoreceptor and conveys the recording paper to fixing means, In a paper wrap detecting device for detecting wrapping of a recording paper around a photoconductor after transfer, a light emitting element that irradiates light to the surface of the photoconductor and light reflected from the surface based on irradiation light of the light emitting element is received. A light detecting means comprising a light receiving element and generating an output value corresponding to the light receiving amount of the light receiving element; and a toner having a light receiving output value from the light detecting means based on the light receiving amount and having a substantially constant proportional relationship with the recording paper. Based on the toner light receiving output value measured by the light detecting means in a state where the photoreceptor surface is solid-coated and the light receiving output value of the photoreceptor surface itself measured by the light detecting means in a state where the photoreceptor surface has no toner. Record Proportional constant calculating means for calculating a proportional constant of a light receiving output value between the light receiving surface and the photoreceptor surface; rewritable proportional constant storing means for storing the proportional constant calculated by the proportional constant calculating means; A threshold calculating means for calculating a threshold by multiplying a light receiving output value of the photoreceptor surface measured by the light detecting means immediately before the start by a proportional constant stored in the proportional constant storing means; Comparing the output value from the light detecting means based on the light beam irradiated on the photoreceptor surface from the light detecting means with the threshold value calculated by the threshold value calculating means, and judging the presence or absence of paper winding based on the comparison result. And determination means for performing the determination.

Further, the proportional constant calculation means is configured to execute a calculation of a proportional constant every time the photosensitive member is replaced, and to update a value stored in the proportional constant storage means. Previously, it is configured to also execute a calculation of updating the proportional constant based on the usage frequency of the photoconductor. Further, at the start of the paper-winding detection operation, when the previous paper-winding failure release is in an unconfirmed state at the start of the paper-winding detection operation, the threshold calculation means multiplies the output value of the light-detecting means at the previous paper-winding determination by a predetermined correction coefficient, and Is calculated.

In addition, the surface of the photoreceptor is measured once or a plurality of times during the paper winding detection operation, and when all the values are out of a predetermined range, an abnormality is determined, and the threshold value is fixed to a predetermined fixed value. Configuration. Further, when the proportional constant calculation value calculated by the proportional constant calculation means is out of a predetermined range, an abnormality is determined and the apparatus is stopped.

When the output value of the light detecting means is out of the predetermined range when the light emitting element emits light or when the light emitting element does not emit light, an abnormality is determined and the detecting operation of the paper winding is stopped. And

[0013]

In this configuration, a light emitting element for irradiating light to the surface of the photoreceptor and a light receiving element for receiving light reflected from the surface of the photoreceptor based on the light emitted from the light emitting element are provided according to the amount of light received by the light receiving element. Using a light detecting means for generating an output value, the proportionality constant calculating means outputs the light from the light detecting means in a state where the toner having the output value of the light detecting means and the recording paper in a substantially constant proportional relationship is solid-coated on the surface of the photoreceptor. And the toner on the photoreceptor is cleaned to make the surface of the photoreceptor free of toner, and the output from the light detecting means in this state is measured. Calculate the proportionality constant of the received light output value with the body surface. This calculated value is stored in the proportional constant storage means. Each time printing is performed, the threshold value calculation means multiplies the measured value of the light output of the light detection means on the photoreceptor surface immediately before the start of the operation by the proportionality constant stored in the proportionality constant storage means. The threshold value is set in the above, and in the paper-winding detection timing in which it is estimated that the recording paper reaches the light detection means, the judgment means outputs the output from the light detection means based on the light beam irradiated on the photosensitive member surface from the light detection means. The value is compared with the threshold value calculated by the threshold value calculating means. Based on the comparison result, for example, when the output value is equal to or larger than the threshold value, it is determined that the paper is wound.

As described above, the threshold value for judging the paper winding is variably set every time the printing operation is performed, so that even if the environmental temperature of the photosensitive member or the light detecting means changes, the light receiving level changes at that time. The threshold value can also be varied, so that erroneous detection of paper winding can be prevented. When the photoconductor is replaced or the photoconductor usage frequency increases to a certain extent, the proportional constant calculation is executed again to update the stored value of the storage unit, thereby obtaining the light receiving level accompanying the aging of the photoconductor. There is no risk of erroneous detection even if there is a variation or a difference in the reflection characteristics of each photoconductor.

At the start of the paper winding detection operation, if the previous paper winding failure has not been cleared yet, it is determined whether the output of the light detecting means at the time of detecting the paper winding is from the recording paper or from the photosensitive member surface. Since it is impossible to make a determination, the threshold value is calculated by multiplying the output value of the light detection means at the time of the previous paper-wrap determination by a predetermined correction coefficient, and thus the threshold value is calculated.

Further, the surface of the photoreceptor is measured once or plural times at the time of detecting the paper-winding operation, and when all the values are out of a predetermined range or when the proportional constant calculated by the proportional constant calculating means is calculated. Is outside the predetermined range, or
When the output value of the light detection means is out of the predetermined range when the light emitting element emits light or when the light emitting element does not emit light, abnormality determination is performed, and the threshold value is fixed to a predetermined fixed value or the device is stopped. By taking measures such as stopping the paper winding detection operation or the like, the malfunction of the paper winding detection device when an abnormality occurs in the device is prevented as much as possible.

[0017]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a configuration of a color image forming apparatus which is an image forming apparatus to which an embodiment of the paper winding detection apparatus of the present invention is applied. In FIG. 2, reference numeral 10 denotes a photosensitive drum as a photosensitive member, in which an OPC photosensitive layer is applied on the drum.
Grounded and rotated clockwise. Reference numeral 11 denotes a scorotron charger, which applies V _H (−600) to the peripheral surface of the photosensitive drum 10.
A uniform charge of _{~-800 V) V G (} -550 ~-850 V)
Is provided by a corona discharge by a grid and a corona discharge wire which is held at a potential. This scorotron charger
Prior to the charging by 11, the photosensitive member is exposed to light by a PCL 12 using a light emitting diode or the like in order to eliminate the history of the photosensitive member until the previous printing.

After uniform charging of the photosensitive drum 10, image exposure
The device 13 performs image exposure based on the image signal. image
The exposure device 13 uses a laser diode (not shown) as a light source.
Through the rotating polygon mirror 13A and fθ lens 13B
The optical path is bent by the reflecting mirror 13C and scanning is performed.
Therefore, the latent image is formed by the rotation (sub-scan) of the photosensitive drum 10.
It is formed. In this embodiment, the character portion is exposed,
Character part has lower potential V _L(−100 to 0)
A latent image is formed.

On the periphery of the photosensitive drum 10, yellow (Y),
Developing devices each containing a built-in developer composed of a toner such as magenta (M), cyan (C), black (K) and a carrier.
First, development of the first color is performed by a developing sleeve 14A which rotates while holding a developer with a built-in magnet. The developer consists of a carrier with ferrite as the core and an insulating resin coated around it, and a toner with polyester as the main material and a pigment according to the color, a charge control agent, silica, titanium oxide, etc. The agent is applied on the developing sleeve 14A by a layer forming rod.
It is conveyed to the developing zone after being regulated to a layer thickness of 300 to 600 μm.

The developing sleeve 14 and the photosensitive drum in the developing area
The gap with the ram 10 is larger than the layer thickness (developer).
0 mm, and V_AC(1.5 to 3.0 KV_PP)of
AC bias and V_DC(-500 to -700 V) DC via
Are superimposed and applied. V _DCAnd V_H, The toner is charged
Since they have the same polarity, V_ACLeave the carrier by
The triggered toner is V_DCV with higher potential_H
Does not adhere to the part_DCV of lower potential_LAttached to part
Then, visualization (reversal development) is performed.

After the visualization of the first color is completed, the image forming process of the second color is started, and the uniform charging is again performed by the scorotron charger 11, and the latent image based on the image data of the second color is formed by the image exposure device 13. It is formed. At this time, the charge removal by the PCL 12 performed in the image forming process of the first color is not performed because the toner attached to the image portion of the first color scatters due to a sharp drop in the surrounding potential.

V is again applied to the entire surface of the photosensitive drum 10
_HOf the photoreceptor that has the potential of
For each minute, a latent image similar to the first color is created and developed.
But develop again for the part where the first color image is
In the part, light shielding and toner
V is determined by the charge_M'Is formed, and V _DC
And V_M'Is performed in accordance with the potential difference of'. This first color
In the part where the image of the second color overlaps, the development of the first color is_L
When the latent image is created, the balance between the first color and the second color
Is reduced, the exposure amount of the first color is reduced and V_H> V_M′
(−100 to −300 V)> V_LIntermediate potential
There is also.

The same image forming process as that of the second color is performed for the third color and the fourth color, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 10. On the other hand, the recording paper P fed from the paper feeding cassette 15 by the paper feeding mechanism 16 is fed to the transfer area by the transfer device 17, and the multicolor image on the peripheral surface of the photosensitive drum 10 is collectively recorded on the recording paper. Moved onto P. That is, the fed recording paper P enters between the conductive brush 17A and the transfer belt 17B, charges are injected into the recording paper P from the conductive brush 17A, and the transfer of the recording paper P and the transfer belt 17B takes place. A suction force is generated in between. Thereafter, the recording paper P is transferred to the photosensitive drum 10 and the transfer belt 17.
B enters a nip (transfer area) 17C formed by the transfer belt 17B, and a transfer electric field is applied from the back surface of the transfer belt 17B by a corona discharger 17D or a bias roller instead of the corona discharger 17D, and a multicolor image is transferred onto the recording paper P. I do.

Thereafter, the recording paper P separated from the photosensitive drum 10 is held by holding rollers 17E, 17 which stretch a transfer belt 17B.
F, after receiving the charge by AC corona discharge using the shaft of the downstream holding roller 17F as a counter electrode, or
The sheet is separated from the transfer belt 17B while receiving corona discharge.
17G is a transfer belt 17B rotated by a cleaning blade
The toner adhering to is removed. The transfer belt 17B of the transfer unit 17 is separated from the photosensitive drum 10 about the axis of the downstream holding roller 17F as the rotation center during the formation of the multicolor image.

The recording paper P holding the multicolor image by the transfer operation by the transfer unit 17 is conveyed to a fixing device 18 comprising two pressure rollers having a heater inside at least one of the rollers, and heat is applied between the pressure rollers. When the pressure is applied, the adhered toner melts, is fixed on the recording paper P, and is discharged out of the apparatus. The residual toner remaining on the peripheral surface of the photoreceptor drum 10 after the transfer is subjected to static elimination by a static eliminator 19 using an AC corona discharger, and then enters a cleaning device 20 or a cleaning blade made of a rubber material in contact with the photoreceptor. The toner is scraped into the cleaning device 20 by 20A, discharged by a screw or the like, and stored in a collection box. It should be noted that the above-described neutralizer 19 can also serve to neutralize the recording paper as shown in FIG. 2, depending on its arrangement. The photosensitive drum 10 from which the residual toner has been removed by the cleaning device 20 is subjected to exposure by the PCL 12 and then exposed to the scorotron charger 11.
, And enters the next image forming cycle. During the formation of the multicolor image, the cleaning blade 20a is separated from the surface of the photoreceptor, and the AC neutralization by the neutralizer 18 is performed in the OF mode.
It is kept in the F state.

Here, immediately after the charge eliminator 18, the photo sensor 30 as a light detecting means for detecting the paper winding of the present embodiment is provided.
As in the prior art, as shown in FIG. 6, a light beam from a light emitting diode is irradiated on the toner forming surface of the photosensitive drum 10 at a right angle, and the reflected light is received by a phototransistor at a predetermined angle θ. The presence or absence of paper winding is detected by the light receiving level.

Further, the paper feed mechanism 16 is provided with a paper feed sensor 21 on its transport path so as to detect whether or not the recording paper P has been fed. Further, a paper discharge sensor 22 is provided downstream of the fixing device 18 so as to detect whether or not the recording paper P has been discharged after fixing. Next, the paper winding detection device of the present embodiment will be described in detail.

FIG. 3 is a circuit diagram of the paper-winding detecting device of this embodiment. In FIG. 3, the photo sensor 30 is of a reflection type similar to the conventional one, and its circuit configuration is the same as that of the photosensitive drum 10.
A light emitting diode 31 as a light emitting element that irradiates a light beam at right angles to the surface, and a phototransistor 32 as a light receiving element that receives light reflected by irregular reflection from the surface of the photosensitive drum 10 based on the light beam from the light emitting diode 31 Two fixed resistors R _{1 and} R ₂ , a noise absorbing capacitor C,
Is composed of a increasing width 33 and the variable resistor VR _1, VR ₂ for variation adjustment of the circuit elements in the photosensor 30 by the operational amplifier.

The control unit 40 incorporates a microcomputer and has a predetermined timing, that is, at the time of replacement of the photosensitive drum 10 or at the frequency of use of the photosensitive drum 10, for example, at a predetermined rotation number (for example, 10,000 times) of the photosensitive drum 10. When calculating the JAM constant to be performed when
When the threshold value to be calculated immediately before the paper winding detection timing is calculated using the AM constant, and when the paper winding is detected by the tamping that is assumed that the recording paper P reaches the photosensor 30, the photo sensor 30 has an L signal. A (low) level operation signal is output, the light emitting diode 31 emits light, the photosensor 30 is operated, and the output signal from the photosensor 30 is input to use the photoconductor drum 10 for calculating a threshold value for detecting paper winding. A JAM constant A is set and stored as a proportional constant between the sheet and the recording paper P, a threshold value calculation using the JAM constant A is performed, and a paper winding detection operation is performed.

The output end of the photo sensor 30 and the control unit 40 are connected by using a plurality of connectors 34 since the positions are separated from each other. Next, a schematic operation of the paper-winding detecting device according to the present embodiment will be described with reference to a flowchart of FIG. First, step 1 (in the figure, described as S1,
In the following, the JAM constant A used for the threshold calculation is calculated.

As shown in the flow chart of FIG. 5, the calculation of the JAM constant A determines whether or not the photosensitive drum 10 has been replaced (S11).
Is calculated (S12). Also, even if the photosensitive drum 10 is not replaced, the number of print operations overlaps and the photosensitive drum 10
When the number of rotations of the motor reaches a predetermined value (for example, 10,000 times) (S1
The calculation of the JAM constant A is also performed in 3).

The reason that the JAM constant A is updated based on the number of rotations of the photosensitive drum 10 without replacing the photosensitive drum 10 is that the surface of the photosensitive drum 10 becomes rougher as the number of prints increases, so that the photosensitive drum 10 is not renewed. This is because the diffused reflection of the recording paper P increases and the light receiving level rises, so that there is a risk that the threshold value becomes higher than the light receiving level from the recording paper P, and the paper winding may not be detected. The update of the JAM constant is not limited to the number of rotations of the photoconductor drum 10 and may be performed based on the usage time of the photoconductor drum 10, such as the total print time and the number of prints.

The calculation of the JAM constant is performed as follows. First, with the photoconductor drum 10 solidly coated with toner (for example, yellow toner), the photosensor 30 measures the light receiving level of the reflected light from the surface of the photoconductor drum 10 (solid toner coating level). Next, the solid toner is cleaned to make the surface of the photoconductor drum 10 completely free of toner, and the photosensor 30 receives a light receiving level of light reflected from the surface of the photoconductor drum 10 (photoconductor drum surface level).
Is measured. Then, when the measured two level values are T _{L and} D _L , a JAM constant A is calculated by the following equation.

A = T _L × K ₁ ÷ D _L ÷ K _M where K ₁ is a proportional constant of the light receiving level between the recording paper P and the yellow toner, and T _L × K ₁ is the lowest expected value of the recording paper P. Indicates the light receiving level value. Also, K _M is the margin, in order to prevent erroneous detection by setting the threshold value than expected minimum level value of the recording paper P to be lower.

As the values of K ₁ and K _M , for example, a green OPC drum for a semiconductor laser, a yellow toner, and a yellow light emitting diode as a light emitting element are used. When light is received at an angle of K ₁ , K ₁ = 1.39 and K _M = 1.20. Note that when using different light-emitting element and the toner of different types of drums and colors may be changed to K _1, K _M according to these.

J calculated in step 1 in this way
In step 2, the AM constant A is stored and held in the memory. In this way, in the state where the JAM constant A is calculated and stored, the paper winding detection operation is executed as in step 3 and subsequent steps. In step 3, it is determined whether or not it is the timing of detecting the paper-winding. In the present embodiment, the timing for performing the paper winding detection operation is as follows: during normal printing, when the machine is stopped due to a failure that cannot be repaired by the user (serviceman call) or a failure in which the paper remains in the machine. Immediately thereafter, further, at the start of warming-up (including when the power is turned on), and when the detection of the paper winding is not confirmed after the detection of the paper winding, the paper winding detection operation is executed at such a time. In any of these states, the determination in step 3 becomes YES and the process proceeds to step 4.

In step 4, a threshold value is calculated as described below. During normal printing, or immediately after the machine stops due to a serviceman call failure, a paper jam failure, or the like, the surface level value of the photosensitive drum 10 immediately before the start of printing is measured, and the J value stored in the measured value is stored.
The threshold value S is calculated by multiplying the AM constant A. Further, in the case of the start of warming-up in which the unwrapping of the paper has not been confirmed after the paper has been wound, the surface of the photosensitive drum 10 is irradiated with a light beam from the photo sensor 30 to measure the light reception level in the same manner as described above. However, since it has not been confirmed that the paper has been unwound, it cannot be determined whether the measured value at this time is the reflected light from the recording paper P or the reflected light from the surface of the photosensitive drum 10, and in this case, The threshold value S is set based on the stored light receiving level at the time of the previous detection of the paper winding. In other words, the threshold value S is obtained by correcting the stored previous light receiving level value with a temperature compensation coefficient previously determined experimentally in advance (previous light receiving level value ÷ temperature compensation coefficient). This is because when starting warm-up after the previous paper winding, the photo sensor
Since it is considered that the temperature of the surface 30 or the surface of the photosensitive drum 10 has decreased, a certain reference temperature corresponding to a state where the machine is not operating at all is set, and the previous light receiving level value at the time of the reference temperature is set. By converting the value into a value, erroneous detection due to a temperature drop is prevented. When the calculation of the threshold value S is completed as described above, the process proceeds to step S5.

In step 5, a light beam is emitted from the photo sensor 30 at the expected timing at which the recording paper P reaches the position of the photo sensor 30 in order to detect paper wrapping, and the light receiving level L ₁ at that time is measured. In step 6, and compared with the threshold value S computed by the light receiving level L ₁ and step 4 measured in step 5, when the L ₁ ≧ S generates the decision output of there with cigarette proceeds to step 7, L ₁ <S In the case of, the process proceeds to step S8, and a judgment output indicating that no paper is wound is generated.

The above-described calculation of the threshold value S is performed for each print because the temperature increases as printing is performed during continuous printing during printing. As described above, there is a proportional relationship between the light reflection levels of the recording paper P, the photosensitive drum 10, and the toner, and it is noted that this proportional relationship is substantially constant for each apparatus and is not affected by a temperature change or the like. The proportional relationship between the recording paper and the photosensitive drum used is set as the JAM constant A based on the proportional relationship with the recording paper, and the threshold is variably set using the JAM constant A. Even if the light receiving level value on the surface of the photoconductor drum 10 or the recording paper fluctuates due to the contamination of the photo sensor 30, the threshold value can be appropriately changed and set by anticipating these level fluctuations. Therefore, erroneous detection of paper winding can be prevented,
The reliability of the paper winding detection device can be improved.

Further, in the above-described variable-threshold-type paper-wrap detecting device, when an abnormality other than the paper-wrap, for example, an abnormality of the photosensitive drum, a photosensor, or a paper jam occurs, the paper-wrap cannot be detected. There is a risk of erroneous detection. Therefore, the following functions are provided as countermeasures when such an abnormality occurs. First, in an abnormal state where the cleaning of the photosensitive drum 10 is defective or the drum 10 is damaged, the surface level of the photosensitive drum 10 cannot be measured normally, the threshold value S becomes abnormal, and the normal paper winding detection becomes impossible. .

Therefore, when measuring the surface level value of the photosensitive drum 10, a plurality of (for example, three) times, in other words, the drum surface level values at a plurality of different positions of the photosensitive drum 10 are measured. If the level value measured in the previous detection operation is out of the predetermined range, in other words, if all the measured values deviate from the level values measured in the previous detection operation by more than a specified value, the drum surface level value is abnormal. Is determined, and the threshold is set to a predetermined fixed threshold. Then, when the photoconductor drum is replaced or after the photoconductor drum is repaired by a serviceman, the operation is returned to the paper winding detection operation using the normal variable threshold.

Here, the prescribed value of the deviation from the previous level value is about ± 10% of the previous level value. However, when printing is started after a while after continuous printing, the temperature is set to about ± 40% of the previous level only at the time of the first printing in consideration of the temperature drop. Next, for example, when the power is accidentally turned off during printing, the recording paper P remains in the apparatus and is not affected by any sensor such as a paper feed sensor or a paper discharge sensor. Detects the above-described abnormality by storing in a non-volatile memory that the recording sheet P is in the apparatus from when the recording sheet P passes through the paper feed sensor to when the recording sheet P reaches the paper ejection sensor. Then, when such an abnormality occurs, a value obtained by correcting the previous threshold value by a predetermined correction value as a threshold value is used as a threshold to perform an in-machine residual recovery function executed when the abnormality occurs, that is, to perform a recording paper discharging operation. During the automatic rotation of the photosensitive drum 10, the paper winding detection operation is executed. As a result, even if the paper is wrapped during the in-machine residual recovery operation after the occurrence of the abnormality, it can be reliably detected.

Next, when the photo sensor output value becomes abnormal due to a contact failure or erroneous insertion of the connector connecting the control unit 40 and the photo sensor 30, the photo sensor output is constantly checked. Such an abnormality is detected. That is, when the sensor output value when the light emitting diode 31 emits light is equal to or less than a predetermined value, or when the sensor output value when the light emitting diode 31 stops emitting light is equal to or more than the predetermined value, it is determined to be abnormal. are doing.
The check of the sensor output value when the light emitting diode does not emit light is performed before or after each time the light emitting diode emits light. When such an abnormality occurs,
Stop the paper-winding detection operation.

Next, when the toner solid coating operation for the JAM constant calculation cannot be performed, or when the reflectance of the photosensitive drum becomes abnormal, the threshold becomes abnormal, which may cause erroneous detection. Become. For this reason, it is checked whether the calculated value of the JAM constant A is within a predetermined range, and when it is outside the predetermined range, it is determined that the JAM constant is abnormal. If such an abnormality is determined, the machine is stopped by an error display.

As described above, even if an abnormality occurs in the apparatus which may cause an erroneous detection of the paper winding detection operation, such an abnormality detection function is provided so as to appropriately cope with the abnormality.
Erroneous detection of the paper winding detection is reduced, and the reliability can be further improved. In this embodiment, an example in which the photosensitive drum is used as the photosensitive member has been described.
The present invention can be applied to any rotating photoconductor.

[0046]

As described above, according to the present invention, the ratio of the reflection level between the recording paper and the photoreceptor can be automatically recorded by the microcomputer by using the toner. Because the proportional constant of the reflection level of the photoconductor used is set, and the proportional constant and the measured value of the photoconductor surface immediately before the detection of the paper winding detection are used to set the threshold value for the detection of the paper winding detection. An optimum threshold value can be variably set for a temperature environment at the time of detection and a sensor dirt state, and the presence or absence of paper winding can be accurately determined without being affected by a temperature change or sensor dirt. Therefore, erroneous detection of a paper wrap can be prevented, and the reliability of the paper wrap detection device can be significantly improved.

Further, since the proportionality constant is updated when the photosensitive member is replaced or under the condition where deterioration of the photosensitive drum is expected, there is no influence from the individual variation and deterioration of the photosensitive member. Further, even if an abnormality occurs in the apparatus that causes erroneous detection of the paper winding detection operation, such an abnormality detection function is provided so as to appropriately cope with the error.
The reliability can be further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a paper winding detection device according to the present invention.

FIG. 2 is a cross-sectional configuration diagram illustrating an image forming apparatus to which an embodiment of a paper winding detection device according to the present invention is applied;

FIG. 3 is a circuit configuration diagram showing an embodiment of a paper winding detection device of the present invention.

FIG. 4 is a flowchart for explaining the operation of the paper-winding detecting device of the embodiment.

FIG. 5 is a flowchart for calculating a JAM constant of the paper-winding detecting device of the embodiment.

FIG. 6 is a view for explaining the principle of measuring a photosensitive drum surface level value using a conventional photosensor.

FIG. 7 is a diagram showing a relationship between each light receiving level of paper, toner, and a photosensitive drum and a threshold value in a conventional paper winding detection.

[Explanation of symbols]

 10 Photoconductor drum 14 Developing device 17 Transfer device 20 Cleaning device 22 Fixing device 30 Photosensor 31 Light emitting diode 32 Phototransistor 40 Control unit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-59-220766 (JP, A) JP-A-58-23070 (JP, A) JP-A-58-46366 (JP, A) 229694 (JP, A) Jikai Sho 56-139162 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65H 7/06

Claims (7)

(57) [Claims] An image forming apparatus configured to transfer a toner image formed on a photoconductor onto recording paper while rotating the photoconductor, and then separate the recording paper from the photoconductor and transport the recording paper to a fixing unit; A paper wrap detecting device for detecting wrapping of the recording paper on the photoconductor after the transfer, wherein a light emitting element that irradiates light to the photoconductor surface and light reflected from the photoconductor surface based on irradiation light of the light emitting element A light detecting means comprising a light receiving element for receiving light and generating an output value corresponding to a light receiving amount of the light receiving element; and a light receiving output value from the light detecting means based on the light receiving amount is substantially constant proportional to the recording paper. Based on the light receiving output value of the toner measured by the light detecting means in a state where the toner is solid-coated on the photoreceptor surface and the light receiving output value of the photoreceptor surface itself measured by the light detecting means in a state where the photoreceptor surface has no toner. Before Proportional constant calculating means for calculating the proportional constant of the light receiving output value between the recording paper and the photoreceptor surface; rewritable proportional constant storing means for storing the proportional constant calculated by the proportional constant calculating means; At each start, a threshold calculating means for calculating a threshold by multiplying a light receiving output value of the photoreceptor surface measured by the light detecting means immediately before the start by a proportional constant stored in the proportional constant storing means; An output value from the light detecting means based on the light beam irradiated from the light detecting means to the photoreceptor surface in the detection timing is compared with a threshold value calculated by the threshold value calculating means. And a judging means for judging the condition of the paper winding of the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein said proportional constant calculating means executes a calculation of a proportional constant every time the photosensitive member is replaced, and updates a value stored in said proportional constant storing means. Paper wrapping detection device. 3. The apparatus according to claim 2, wherein said proportional constant calculating means executes a calculation for updating the proportional constant based on the frequency of use of the photoconductor before replacing the photoconductor. . 4. The apparatus according to claim 1, wherein the threshold calculating means multiplies the output value of the light detecting means at the time of the previous paper winding determination by a predetermined correction coefficient when the previous paper winding failure has not been cleared at the start of the paper winding detection operation. 2. The paper winding detection device for an image forming apparatus according to claim 1, wherein a threshold value is calculated. 5. A method for measuring the surface of a photoreceptor once or a plurality of times during a paper-winding detecting operation, and when all values are out of a predetermined range, performing an abnormality determination and fixing a threshold to a predetermined fixed value. The paper winding detection device for an image forming apparatus according to claim 1, wherein: 6. A cigarette for an image forming apparatus according to claim 1, wherein when the proportional constant calculation value calculated by said proportional constant calculation means is out of a predetermined range, an abnormality is determined and the apparatus is stopped. With detection device. 7. When the output value of said light detecting means is out of a predetermined range when a light emitting element emits light or when a light emitting element does not emit light, an abnormality is determined and a paper winding detection operation is stopped. The paper winding detection device of the image forming apparatus according to claim 1.