JP2000132016A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device making a service life of a sensor possible to be prolonged, being free from the abnormality such as wrong detection or the malfunction of the sensor, and making an excellent image possible to be recorded, with simple measuring system. SOLUTION: This image forming device, equipped with a photoreceptor 1 on which a preliminarily stipulated reference reflection surface is formed, a developing device 4 forming the toner image thereon, a sensor 11 capable of performing measurement of density on the toner image and the measurement of a range between the reference reflection surface and the sensor, and a controlling part 43 capable of performing control based on the measured value, is constituted so that the controlling part 43 is provided with an abnormality judgment part 47 capable of judging the abnormality of the measured value, in comparing the preliminarily determined set value of the range between the reference reflection surface and the sensor by the sensor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine and a printer.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, there is known an image forming apparatus which performs image density control for adjusting the density of an image formed on a sheet to a predetermined level before forming an image on the sheet.

[0003] In the image density control, for example, as shown in FIG. 12, a toner image 5 is formed on a photoreceptor 1, the density of the formed toner image is detected by an optical sensor 6, and the detected value of the optical sensor 6 is calculated. Based on the control, the values of parameters relating to the potential of the photoconductor 1, the exposure amount, and the toner adhesion amount such as the developing bias power supply 9 are controlled.

An optical sensor for detecting the reflectance of the toner image 5 is used as the optical sensor 6, and the image density is determined from the reflectance.

[0005] Japanese Patent Application Laid-Open Nos. 9-244391 and 9-244313 disclose an image forming apparatus that performs such image density control.
And JP-A-63-131152.

[0006]

However, in the conventional image forming apparatus, since the optical sensor is used as the density sensor, the surface of the optical sensor is contaminated by the toner floating in the apparatus, which tends to cause erroneous detection and erroneous operation. was there.
In particular, in a high-speed machine having a large print amount, the toner contamination tends to increase.

A first object of the present invention is to provide an image forming apparatus capable of recording a high-quality image with a simple measurement system, without any abnormality such as erroneous detection or malfunction of the sensor, and extending the life of the sensor. provide.

A second object of the present invention is to provide an image forming apparatus which does not cause density unevenness due to the eccentricity of the photoreceptor and can stabilize the image density more uniformly.

[0009]

To achieve the above object, the present invention provides a photoconductor having a predetermined reference reflection surface formed thereon, a developing machine for forming a toner image on the photoconductor, At least one sensor that enables measurement of the image density of the toner image and measurement of the distance between the reference reflection surface and the sensor, and a control unit that performs control based on a measurement value measured by the sensor An abnormality determining unit configured to compare a predetermined set value of a distance between the reference reflection surface and the sensor with a measured value measured by the sensor, and determine abnormality of the measured value. It has composition which has.

As described above, by providing the abnormality judging unit, it is possible to know the abnormality before the deterioration of the image due to the abnormality of the sensor, the photosensitive member, or the measuring system, and to detect the erroneous detection or malfunction of the sensor. It is possible to provide an image forming apparatus capable of recording a high-quality image with no abnormality, a long sensor life, and a simple measurement system.

Further, by using an optical fiber sensor as the above sensor, the image density measurement and the distance measurement are measured in accordance with the characteristics of the optical fiber sensor. An image forming apparatus capable of recording an image can be provided.

A control unit for controlling based on the measured value measured by the optical fiber sensor, and correcting the measured value of the image density in consideration of the eccentricity information of each part of the photosensitive member forming the toner image. Configure.

With such a configuration, it is possible to provide an image forming apparatus capable of achieving uniform and stable image density without density unevenness due to eccentricity of the photosensitive member.

[0014]

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

FIG. 1 shows a first embodiment of the present invention.
1 is a schematic configuration diagram of an image forming apparatus according to an embodiment.
The image forming apparatus 23 has a photoreceptor take-up port 16, a charger 2 disposed around a take-up type photoreceptor 1 provided with a feed roller 18 and a take-up roller 19, and an exposure device 3.
, Developing machine 4, current copying machine 7, cleaner 41, fixing device 42
And the like, a developing bias power supply 9, an optical sensor 6, a stain removing unit 12, a stain removing control unit 43 for controlling the stain removing unit 12, a pump 44, an image density controlling unit 8, and the like. You.

As the charger 2, a scorotron charger having a discharge wire for performing corona discharge and a control electrode was used to control the surface potential of the photoreceptor 1. The surface potential can be controlled by changing the grid voltage applied to the control electrode.

The exposure device 3 comprises a laser and its scanning optical system. Further, an optical system such as an LED array and a rod lens may be combined.

The developing device 4 holds a developer 39 containing a toner 60 and a magnetic carrier by the magnetic force of a magnet body built in the developing roll 10, and transfers the developer 39 to an electrostatic latent image on the photoreceptor 1. The toner image 5 is formed by the contact. Further, in addition to the developing device 4 and the developing roll 10, a regulating plate for regulating the transport amount of the developer 39, a toner hopper for supplementing the consumed toner, a replenishing roll, the replenished toner 60 and the developer 39 And a magnetic sensor for detecting the mixing ratio between the toner and the magnetic carrier. The magnetic carrier and the toner 60 are charged to have opposite polarities by frictional charging. When the magnetic brush-shaped developer 39 is brought into contact with the photoconductor 1 by rotating, a bias voltage is applied to the developing roll 10 from the developing bias power supply 9. Apply and develop roll 1
By applying an electric field between the photoconductor 1 and the photoconductor 1, a toner image 5 was formed on the photoconductor 1.

The developer 39 has a particle size of 40 to 100 μm.
Resin-coated magnetic carrier and particle size of 6 to 11 μm
The toner 60 used was a developer having an average toner concentration (≡100 × toner weight / developer) of 1.5 to 5 (Wt%), more preferably 2 to 4 (Wt%).

The toner mixing ratio is controlled by detecting the magnetic substance content by a magnetic sensor, and when the toner mixing ratio falls below a predetermined value, generating a replenishment signal and replenishing the toner to make the toner mixing ratio substantially constant. To control.

The optical sensor detects the reflectance of a toner image. Since the reflectance and the image density have a one-to-one relationship, the image density (optical density of a solid image or a halftone image) is measured. can do.

The optical sensor includes an irradiation fiber bundle 28 for guiding irradiation light and a light receiving fiber bundle 2 for guiding reflected light.
9 can be used. The optical fiber sensor 11 can be stabilized against a temperature change by using a glass fiber. Further, since the optical fiber sensor 11 has a rod shape, the installation space can be reduced. There is an advantage that noise, which is a measurement error, does not occur even if a charging unit that involves discharge is arranged nearby.

Optical fiber sensor 11 for detecting reflectance
In this case, the sensor output is affected by the reflectance of the reflecting surface and the gap between the reflecting surface.

FIG. 4 shows the relationship between the sensor output and the gap between the optical fiber sensor 11 and the object to be detected when the reflection surface is substantially a mirror surface. The output characteristic is mountain-shaped, and has an area L1 and an area L2 whose output is substantially proportional to the gap and an almost flat area Z (the gap value is near Gr) where the output is near the peak. Therefore, it can be seen that the following (1) and (2) are possible.

(1) If the optical fiber sensor 11 is arranged in the region L1 or L2 with respect to a reflecting surface having a substantially constant reflectance (hereinafter referred to as a reference reflecting surface), the output is substantially proportional to the gap. Can be measured.

(2) If the optical fiber sensor 11 is arranged in the area Z with respect to the reflecting surface where the gap is kept substantially constant, the sensor output is not affected by the gap, and the reflectivity of the reflecting surface is measured. It is possible.

According to the present invention, based on these findings (1) and (2), as shown in FIG. 3, the optical fiber sensor 11 is placed in the region Z (ie, the gap) with respect to the surface of the photosensitive member 1 on which the toner image 5 is formed. Is arranged so as to be Gr), and the photosensitive member winding opening 16 is provided as a reference reflecting surface (having a thickness of Gr-G1).
Protrusions 17 are provided and the gap between the protrusions 17 and the optical fiber sensor 11 is configured to be G1 (the gap is a region L1 in FIG. 4), and a plurality of image densities detected by the optical fiber sensor 11, as shown in FIG. A density calculating unit 45 for calculating an average value of data, a gap calculating unit 46 for calculating an average value of a plurality of gap data detected by the optical fiber sensor 11, a gap measurement value by the optical sensor, and a known gap setting value. Judging unit 47 which judges that there is an abnormality when the values are not consistent
Removing means 12 for removing toner stain on the optical sensor
And an image density control unit 8 and a process control unit 48.

As an example, when the optical fiber sensor 11 is composed of fiber bundles 26 and 27 having two semicircular cross sections (similar to FIG. 7) and a diameter of 2.5 mm, Gr ≒
Since 4.3 mm, Z ≒ 1 mm and 1.0 ≦ G1 ≦ 3.0 mm, 1.3 ≦ Gr−G1 ≦ 3.3 mm, that is, the gap Gr
Is set to 4.3 mm, and 1.3 to 3 mm from the surface of the photoreceptor 1.
What is necessary is just to provide the convex part 17 protruded by mm.

As the dirt removing means 12, for example, as shown in FIG. 1 and FIG. 2, a device in which a pair of ejection nozzles 21 and a suction nozzle 22 for forming an air flow 20 on the surface of the optical fiber sensor 11 are used. Can be. The details of the stain removing means 12 will be described below with reference to FIG. 2 which is a sectional view taken along the line ZZ in FIG.

The dirt removing means 12 is an optical fiber sensor 1
As shown in FIG. 2, a guide member 55 for guiding the air flow is interposed as necessary, and a pair of ejection nozzles 21 and suction nozzles 22 are arranged as shown in FIG. , And communicates with an inlet duct 14 that guides an inlet airflow 24 and an outlet duct 15 that guides an outlet airflow 25.

Further, in addition to the pair of ejection nozzles 21 and suction nozzles 22, it is desirable to arrange a blocking plate 13 in the vicinity of the optical fiber sensor 11 and upstream of the photoconductor 1 in the rotation direction.

Further, it is more desirable that the blocking plate 13 protrudes toward the photosensitive member 1 than the pair of the ejection nozzle 21 and the suction nozzle 22. This is to prevent the airflow 20 on the surface of the optical fiber sensor 11 from being disturbed by the influence of the rotating airflow accompanying the rotation of the photoconductor 1. Developing machine 4
Even when the toner 60 or the developer 39 is scattered around, the toner 60 or the developer 39 selected below by the rotating airflow.
However, this is to prevent direct attachment to the surface of the optical fiber sensor 11.

In general, the working distance of the optical fiber sensor 11 (the distance between the optical fiber sensor 11 and the photosensitive member 1) is
The working distance is 1.5 mm or more, and the working distance is more preferably 3 mm or more, in order to arrange the pair of the ejection nozzle 21 and the suction nozzle 22. If the width of the ejection nozzle 21 is small, not only a sufficient flow rate cannot be obtained, but also a pressure loss increases and the internal pressure of the inlet side duct 14 that guides the inlet side air flow 24 increases, so that a robust duct and a larger blower are required. Because it becomes.

The dirt removing means 12 forms an air flow 20 on the surface of the optical sensor when the dirt on the optical sensor is detected, and removes toner and paper dust adhering thereto. Soil removal means 12
In this case, the air flow 20 is always formed and the toner is prevented from adhering to the optical sensor by the air curtain effect.
And it is desirable to remove dirt.

The optical fiber sensor 11 has an optical fiber portion as long as several meters or an integrated photosensor in which a light emitting element, a light receiving element, a lens and the like are integrally formed. It is also possible to use one incorporating an optical fiber.

In such a configuration, the measured value of the gap of the convex portion by the optical fiber sensor 11 is sent to the abnormality judging unit, and when the known gap set value does not match the abnormality judging unit, it is judged as abnormal (contaminated state). Then, a command to activate the stain removing means 12 is issued in the stain removing control section, and the stain removing means 12 receiving this command forms an airflow 20 on the surface of the optical fiber sensor 11 to remove the adhered toner and paper dust. This can prevent erroneous detection of the toner image density due to toner contamination of the optical fiber sensor 11. The abnormality detection step is set in advance so as to be performed at the time of warm-up, at the time of paper exchange, or at regular intervals, and is controlled by the process control unit 48.

Accordingly, even in long-term printing, there is an effect that it is possible to prevent erroneous operation or erroneous detection of the image density control system due to toner contamination of the optical sensor.

When the measured value of the interval of the convex portion by the optical fiber sensor 11 matches the known interval set value,
The abnormality determination unit 47 determines that the image is normal (no contamination), performs a process of forming a toner image and detecting the image density, and sends the detected value of the image density to the image density control unit 8 via the abnormality determination unit 47. Image density control is performed.

The image density control of a solid image is performed, for example, as shown in FIG.
As shown in FIG. 1, a solid toner image 5 is formed as a test patch on the photosensitive member 1 as a recording medium, and the image density of the formed toner image 5 is detected by an optical fiber sensor 11.
Based on a comparison between the detected value of the optical fiber sensor 11 and the reference value in the image density control unit 8, a developing bias power supply 9 is provided.
, And the solid image density is controlled to a predetermined value.

In this case, if the difference between the surface potential and the developing bias voltage exceeds a predetermined range, fog and carrier adhesion increase, and the reproduction of fine lines and halftone dots is affected. Modify the surface potential by changing the voltage.

In the dot image density control, a dot / toner image 5 is formed on the photoreceptor 1 as a test patch, and a dot / toner image is formed.
The image density of the toner image 5 is detected by the optical fiber sensor 11, and the image density
Based on the comparison between the detected value of No. 1 and the reference value, the exposure amount of the exposure device 3 or the dot exposure time (pulse width) is changed to control the dot image density to a predetermined value.

In the above example, the projection 17 is provided on the photoreceptor winding port 6 as a reference reflection surface, and the surface is used. However, the gap with the optical sensor is G2 (the gap is the area L2 in FIG. 4). Concave (the amount of depression from the surface of the photoreceptor is 1.3 to 3.0 mm)
The same effect can be obtained by providing a reference reflection surface.

In the above-described example, the optical fiber sensor 11 is disposed so as to face the photoreceptor 1. However, the gap between the optical sensor and the optical sensor is G2 (the gap is the area L in FIG. 4).
2) Become concave (1.3-3.0mm concave from paper surface)
The optical fiber sensor 11 may be disposed so as to face the paper 40, and the distance between the image density of the toner image on the paper and the concave portion of the paper path may be measured.

Furthermore, a single optical fiber sensor may be disposed and its set gap may be switched to Gr when measuring the image density and to G1 (or G2) when measuring the gap. In this case, a mechanism for switching the gap is required, but there is an advantage that unevenness does not need to be provided on the photoconductor since the reference reflection surface uses the photoconductor surface (cut skin portion).

The causes of the abnormality of the output of the optical sensor (out of the predetermined range) include, in addition to toner contamination on the surface of the optical sensor, a change in the amount of light of the generating element due to a temperature change or deterioration with time, and a sensitivity of the light receiving element. There is a change in the photoreceptor surface due to a change, poor cleaning of the photoreceptor, scratches or abrasion. Therefore, when an abnormal signal is issued, the process of cleaning the photoconductor 1 and the process of cleaning the photoconductor 1
A process of calibrating the optical sensor after the cleaning may be interposed, and thereafter, the process control may be performed so as to operate the dirt removing means 12 of the optical fiber sensor 11 only when an abnormal signal is issued again. .

The optical sensor is calibrated by turning off the output voltage and light emission measured on a predetermined reflection surface (background portion or calibration plate).
The light emission drive current of the light emitting element may be adjusted so that the difference between the output voltage and the output voltage becomes a predetermined value.

[Second Embodiment] The second embodiment differs from the first embodiment in the configuration of the optical sensor unit. As shown in FIG. In this configuration, two optical fiber sensors 30 and 33 are arranged.

First and second optical fiber sensors 30, 3
Reference numeral 3 denotes irradiation fiber bundles 28 and 31 for guiding irradiation light and reflection fiber bundle 2 for guiding reflected light as shown in FIG.
9 and 32 have the same semicircular shape, and the diameter of the fiber bundle of the second optical fiber sensor 33 is larger than the diameter of the fiber bundle of the first optical fiber sensor 30.

The first optical fiber sensor 30 is set equal to the gap value (Gr) given by the peak value, and the diameter of the fiber bundle of the second optical fiber sensor 33 is set to the gap value (Gr).
In (r), the diameter of the fiber bundle of the second optical fiber sensor 33 is configured to be larger than the diameter of the fiber bundle of the first optical fiber sensor 33 so that the relationship between the output and the gap becomes substantially linear.

That is, in the case of this example, the sensor output characteristics of the first and second optical fiber sensors 30 and 33 are, as shown in FIGS. While the peak of the output is given by Gr, the peak of the second optical fiber sensor 33 having a larger diameter of the fiber bundle shifts to the side where the gap is larger, and the relationship between the output and the gap becomes substantially linear.

As an example, the first optical fiber sensor 3
When the diameter of the first optical fiber sensor 30 is 2.5 mm and the diameter of the second optical fiber sensor 30 is 4.3 mm, the gap Gr giving the output peak of the first optical fiber sensor 30 is 4.
The area where the output of the second optical fiber sensor 33 is linear is from 0.8 to 5.1 mm, and the gap is 4.3 mm.
Set to.

The first and second optical fiber sensors 3
The sensors 0 and 33 have the same set intervals, so that the arrangement of the dirt removing means is easy. However, from the viewpoint of prevention and removal of the toner dirt, the both are integrated and the front ends are covered with a window member. Is desirable.

In such a configuration, although the number of sensors is increased by one, the image density of the toner image on the photosensitive member 1 can be measured using the first optical fiber sensor 30, and the same gap as that of the first optical fiber is used. Gap measurement can be performed using the second optical fiber sensor 33 set to Gr. That is,
In this example, the surface of the photoconductor (background portion) can be used as a reference reflection surface for measuring the gap, so that a convex portion (or a concave portion) is provided on the photoconductor 1 as compared with the first embodiment. There are advantages that are not required.

Incidentally, two optical fibers having the same diameter may be used, and the interval may be set to Gr for image density measurement, and the interval may be set to G1 or G2 for interval measurement. In this case, since the surface of the photoconductor (background portion) can be used as the reference reflection surface, there is an advantage that it is not necessary to provide a convex portion (or a concave portion) on the photoconductor 1 as in the second embodiment.

[Third Embodiment] The present embodiment is a modification of the second embodiment, and the cross-sectional shape of the tip of the second optical fiber sensor 33 is different from that of the second embodiment. Things.

As shown in FIG. 8, the first optical fiber sensor 30 has an irradiation fiber bundle 28 for guiding irradiation light and a light receiving fiber bundle 29 for guiding reflected light in the same semicircular shape. , The second optical fiber sensor 33,
The irradiation fiber bundle 34 for guiding the irradiation light is circular, and the light receiving fiber bundle 35 for guiding the reflected light is the irradiation fiber bundle 3.
4, the first optical fiber sensor 30 is set to be equal to the gap value (Gr) given by the peak value, and the second optical fiber sensor 33 is set to the output value and the gap at the gap value (Gr). Is substantially linear.

That is, also in the case of this example, the sensor output characteristics of the first and second optical fiber sensors 30 and 33 are, as shown in FIGS. While the peak of the output is given by the gap Gr, the peak of the second optical fiber sensor 33 shifts to the side where the gap is larger, and the relationship between the output and the gap becomes substantially linear.

In such a configuration, as in the second embodiment, the number of sensors is increased by one, but the image density of the toner image on the photosensitive member 1 can be measured using the first optical fiber sensor 30. The gap can be measured using the second optical fiber sensor 33 set to the gap Gr. Therefore, also in the present embodiment, the surface of the photoconductor (background portion) can be used as a reference reflecting surface for measuring the gap, so that the convex portion (or the concave portion) is formed on the photoconductor 1 as compared with the first embodiment. ) Is not required.

[Fourth Embodiment] The fourth embodiment is an improvement of the third embodiment. Instead of the optical fiber sensor 11 in the first embodiment, one optical fiber is used as shown in FIG. It is configured by disposing a sensor 37. Hereinafter, description will be made with reference to FIGS. 10, 11, and 6. The optical fiber sensor 37 of this example has a three-part fiber bundle 28, 35, 3 as shown in FIG.
6, the fiber bundles 28, 36 have the same semicircular cross section, and the fiber bundle 35 is the fiber bundle 28, 3
6 has a concentric cross section.

As shown in FIGS. 11A and 11B,
The fiber sensor 3 is used for the image density measurement and the gap measurement.
The optical path switching unit 38 for switching the optical path in 7 is provided in front of the receiving / light emitting elements 51 and 52. Light emitting element 5
As the element 2, a GaAs infrared light emitting diode or a semiconductor laser can be used. As the light receiving element 51, an Si phototransistor or the like can be used.

At the time of image density measurement, the irradiation light 53 is guided by the fiber bundle 28, and the reflected light 5 is reflected by the fiber bundle 36.
The optical path 49 is set so as to guide No. 4, and the gap of the optical fiber sensor 37 is set equal to the gap value (Gr) at which the sensor output gives a peak value. Therefore, the sensor output characteristics at the time of measuring the image density are the same as those in FIG.

At the time of measuring the gap, the light path switching unit 38 switches the light path 50 to a light path 50 different from the light path 49 at the time of measuring the image density. The fiber bundle 28 and the fiber bundle 36 guide the irradiation light 53, and the fiber 35. The configuration is such that the reflected light 54 is guided, and the output of the optical fiber sensor 37 is configured such that the relationship between the output and the gap becomes substantially linear near the gap value (Gr). Accordingly, the sensor output characteristic at the time of measuring the gap is represented by B in FIG.
It becomes the characteristic equal to.

The optical path switching section 38 can be constituted by using an optical element such as a mirror, a beam splitter or a prism, or by using an optical fiber bundle or a waveguide.

In such a configuration, a mechanism for switching the optical path by the optical path switching unit 38 is added. However, the image density and the interval of the toner image can be measured using one optical fiber sensor 37, and the reference reflection surface can be measured. Therefore, there is an advantage that it is not necessary to provide a convex portion (or a concave portion) on the photoreceptor 1 because the surface (background portion) of the photoreceptor can be used.
In the above-described second to fourth embodiments, the optical fiber sensor 11 is arranged so as to face the photoconductor 1, but the optical fiber sensor 11 is arranged so as to face the intermediate transfer member and the paper transport path, and The image density of the toner image on the gap, the intermediate transfer member or the paper may be measured.

[Fifth Embodiment] Using any of the optical fiber sensors (30 and 33 or 37) described in the second to fourth embodiments, the gap at each position of the photosensitive member 1 is measured. The image density control is performed in consideration of the eccentricity information of the photoconductor 1.

That is, when the image density of the test patch is measured by the optical sensor and the developing bias is controlled based on the measured value, the eccentricity information (the gap Value) is taken into consideration to control the developing bias power supply 9.

Accordingly, in the present embodiment, the density unevenness due to the eccentricity of the photosensitive member 1 can be prevented, and the image density can be made more uniform and stable.

[0068]

According to the present invention, there is provided an image forming apparatus capable of prolonging the life of the sensor without any abnormality such as erroneous detection or malfunction of the sensor, and capable of recording a high quality image with a simple measuring system. can do.

Further, it is possible to provide an image forming apparatus which does not have density unevenness due to the eccentricity of the photoreceptor and is capable of stabilizing the image density more uniformly.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing one embodiment of an optical sensor dirt removing section of the present invention.

FIG. 3 is a diagram showing one embodiment of an optical fiber sensor measuring section of the present invention.

FIG. 4 is a diagram showing one embodiment of output characteristics of the optical fiber sensor of the present invention.

FIG. 5 is a diagram showing another embodiment of the optical fiber sensor measuring section of the present invention.

FIG. 6 is a diagram showing another embodiment of the output characteristics of the optical fiber sensor of the present invention.

FIG. 7 is a view showing one embodiment of a partial cross section of the optical fiber sensor of the present invention.

FIG. 8 is a diagram showing another embodiment of a partial cross section of the optical fiber sensor of the present invention.

FIG. 9 is a diagram showing another embodiment of the optical fiber sensor measuring section of the present invention.

FIG. 10 is a diagram showing another embodiment of a partial cross section of the optical fiber sensor of the present invention.

FIG. 11 is a diagram showing another embodiment of the optical fiber sensor measuring section of the present invention.

FIG. 12 is a diagram illustrating a conventional image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor, 2 ... Charger, 3 ... Exposure apparatus, 4 ... Developing machine,
Reference Signs List 5: toner image, 6: optical sensor, 7: transfer unit, 8: image density control unit, 9: developing bias power supply, 10: developing roll, 11, 37: optical fiber sensor, 12: stain removing means, 13: blocking plate .., 14: inlet side duct, 15: outlet side duct, 16: photoreceptor winding port, 17: convex part, 18 ...
Roll-out roller, 19: take-up roller, 20: air flow, 2
DESCRIPTION OF SYMBOLS 1 ... Jet nozzle, 22 ... Suction nozzle, 23 ... Image forming apparatus, 24 ... Inlet side air flow, 25 ... Outlet side air flow, 26,
27, 28, 29, 31, 32, 34, 35, 36 ... fiber bundle, 30 ... first optical fiber sensor, 32 ...
Second optical fiber sensor, 38 ... optical path switching unit, 3
9: developer, 40: paper, 41: cleaner, 42: fixing device, 43: stain removal control unit, 44: pump, 45: density calculation unit, 46: gap calculation unit, 47: abnormality determination unit, 48 ...
Process control unit, 49, 50: optical path, 51: light receiving element,
52: light emitting element, 53: irradiation light, 54: reflected light, 55 ...
Guide member, 60: toner.

Continued on the front page (72) Inventor Akira Hosoya 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Research Laboratory, Hitachi Ltd. 2F065 AA06 AA21 BB06 BB08 BB16 CC00 DD16 FF44 GG06 GG07 JJ01 JJ15 LL03 LL46 NN19 NN20 PP22 QQ25 QQ42 RR08 TT04 2H027 DA10 DA50 DE02 EC20 ED01 ED30 EE07 EF09 HA02 HA12 2H035 CA03 CA07 CB03 9A001 BZ05 HZ28 JJ35 KK31 KK37 KK42 KZ16

Claims (8)

[Claims] A photoconductor on which a predetermined reference reflection surface is formed; a developing device for forming a toner image on the photoconductor; measurement of an image density of the toner image; And at least one sensor capable of measuring a distance of the sensor, and a control unit that controls based on a measurement value measured by the sensor, wherein the control unit determines a distance between the reference reflection surface and the sensor. An image forming apparatus comprising: an abnormality determining unit that compares a predetermined set value of the above with a measurement value measured by the sensor and determines abnormality of the measurement value. 2. The image forming apparatus according to claim 1, wherein said sensor is an optical fiber sensor. 3. An image forming apparatus according to claim 1, further comprising a cleaning unit for cleaning said sensor when said abnormality determining unit determines that said sensor is abnormal. 4. The image forming apparatus according to claim 2, wherein a distance between the photoconductor and the optical fiber sensor or a diameter of the optical fiber sensor is determined based on an output characteristic of the optical fiber sensor, and the optical fiber sensor is arranged. Image forming apparatus. 5. A photoreceptor having a predetermined reference reflection surface formed thereon, a developing device for forming a toner image on the photoreceptor, an image density measurement of the toner image, the reference reflection surface and a sensor. One optical fiber sensor capable of measuring the distance of, and a control unit that controls based on a measurement value measured by the optical fiber sensor, and when measuring the image density, and when measuring the distance An image forming apparatus having an optical path switching unit that switches an optical path of the optical fiber sensor. 6. A photoconductor, a developing device for forming a toner image on the photoconductor, and at least one optical fiber sensor capable of measuring an image density of the toner image and a distance between the photoconductor and a sensor. An image for correcting the measured value of the image density in consideration of the eccentricity information of each part of the photoreceptor forming the toner image, the control unit controlling based on a measured value measured by the optical fiber sensor. Forming equipment. 7. A photoreceptor, a developing device for forming a toner image on the photoreceptor, an intermediate transfer member having a predetermined reference reflection surface and formed by transferring the toner image, and the intermediate transfer At least one sensor capable of measuring the image density of the toner image formed on the body and measuring the distance between the reference reflection surface and the sensor; and controlling the control based on the measurement value measured by the sensor Having a unit, the control unit compares a predetermined set value of the distance between the reference reflection surface and the sensor with a measurement value measured by the sensor, and determines an abnormality of the measurement value. An image forming apparatus having an abnormality determining unit for determining. 8. A photoreceptor, a developing device for forming a toner image on the photoreceptor, a transfer unit for transferring the toner image to a sheet, and a predetermined reference reflection surface for forming the toner image Conveying means for conveying the formed paper, at least one sensor capable of measuring the image density of the toner image formed on the paper and measuring the distance between the reference reflection surface and the sensor; A control unit for controlling based on the measured value, wherein the control unit is a predetermined measurement value of a distance between the reference reflection surface and the sensor, and a measurement value measured by the sensor. And an image forming apparatus having an abnormality determining unit for determining an abnormality of the measured value.