JP2000056643A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which always securely prevents the sensor face of a light sensor for detecting the image density of a toner image formed on a recording medium such as a drum-like photoreceptor from being soiled with toner particles, etc. SOLUTION: This image forming device is provided with the movable drum- like photoreceptor 1 on which the toner image is formed, the light sensor 6 which is disposed near the photoreceptor 1 and detects the image density of the toner image formed on the surface of the photoreceptor 1, and an image- density control part which compares the image density, detected by the light sensor 6, and a reference image-density and adjusts the image density of the toner image according to the result of the comparison. In the image forming device, an air-flow generation means 11 is provided. The air-flow generation means 11 is disposed between the light sensor 6 and the surface of the photoreceptor 1 with a sensor face 6S between them and is composed of a jet nozzle 12 for jetting an air flow F onto the sensor face 6S and a suction nozzle 13 for sucking the air flow F on the sensor face 6S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus, and more particularly, to contamination of a sensor surface of an optical sensor for detecting an image density of a toner image formed on a movable recording medium with various particles. The present invention relates to an electrophotographic image forming apparatus used in a copying machine, a printer, or the like, provided with a contamination prevention unit for preventing contamination.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus used in a copying machine, a printer, or the like, is a typical one.
At least, a rotatable photoreceptor, a charging device, an exposing device, a developing device, and a transfer device that are sequentially arranged around the photoreceptor, and a recording paper transport device that transports recording paper between the photoreceptor and the transfer device. In addition, an optical sensor disposed in proximity to the photoconductor between the developing device and the transfer device, and an image density control device responsive to a detection output of the optical sensor are provided.

In this case, when the image sensor detects the image density of the toner image formed on the photoreceptor surface, the image density controller compares the detected image density with the reference image density stored in advance. Then, based on the comparison result, one or more of the charging voltage of the charging device, the exposure amount of the exposure device, and the developing bias voltage of the developing device are adjusted, and the amount of toner adhering to the photoconductor is adjusted. By controlling, the image density of the toner image formed on the surface of the photoreceptor is made constant.

FIG. 10 is a main part configuration diagram showing an example of the configuration of an image forming apparatus provided with a known image density control device. For example, Japanese Patent Application Laid-Open Nos. 9-244391 and 9-244313. And JP-A-63-131152.

In FIG. 10, reference numeral 51 denotes a drum-shaped photosensitive member,
52 is a charging device, 53 is an exposure device, 54 is a developing device, 5
4 ₁ developing roll, 54 ₂ developer, 55 toner, 5
6 is an optical sensor, 56S is a sensor surface, 57 is a transfer device, 5
8 is an image density control unit, 59 is a developing bias power supply, and L is exposure light.

When the drum-shaped photoreceptor 51 rotates in the direction of the arrow, the charging device 52 charges the surface to a predetermined potential, and then the exposure device irradiates exposure light L to form an electrostatic latent image on the surface. and, then, the potential difference formed between the developing roller 54 ₁ and the electrostatic latent image forming portion in the developing device 54, an electrostatic latent image developer 54 ₂ is adhered to the electrostatic latent image forming part of the surface Is formed, the optical sensor 56 detects the image density of the toner image, and then the transfer device 57 transfers the toner image formed on the surface to recording paper (not shown).

The image density controller 58 compares the image density data detected by the optical sensor 56 with reference image density data stored in advance, and if there is a difference between them, controls the developing bias power supply 59. a developing bias voltage to be supplied to the developing roller 54 ₁ to control adjustment Te, detected image density data is controlled to be equal to the reference image density data.

[0008]

An image forming apparatus provided with the above image density control device, when the image density of a toner image formed on the surface of the drum-shaped photoreceptor 51 is detected by the optical sensor 56, the image formation is performed. Particles such as toner floating in the apparatus adhere to the sensor surface 56S of the optical sensor 56, and the sensor surface 56S is contaminated by the adhered particles such as toner.
As a result, the detection output of the optical sensor 56 may become inaccurate and erroneous image density data may be detected.
There is a problem that the image density control unit 58 may perform an incorrect image density control operation.

Particularly, in an image forming apparatus provided with a known image density control device for performing a high-speed recording operation, since the recording amount of a toner image increases, the scattering of fine particles such as toner increases, Sensor surface 5 of optical sensor 56
There is a problem in that contamination of 6S is increased, erroneous image density data is detected with a high probability, and an erroneous image density control operation is performed.

[0010] In order to solve such problems, it is not a technical means relating to an image forming apparatus provided with an image density control device, but an image forming apparatus provided with a rotary developing device, that is, a toner of a plurality of colors is individually provided. An optical sensor for detecting the home position of the rotary developing device and the presence or absence of the toner cartridge is arranged around the rotary developing device in which a plurality of stored toner cartridges are mounted, and is attached to the rotary developing device. The sensor surface of the optical sensor is periodically cleaned by an operation of the cleaning member that has been operated, or by a driving operation of a cleaning member disposed around the rotary developing device by a cleaning auxiliary member attached to the rotary developing device. Patent application title: Image forming apparatus provided with a rotary developing device provided with cleaning means for preventing particles such as toner and dust from adhering to the sensor surface of an optical sensor and contaminating the sensor surface of the optical sensor , Proposed by JP-A-9-146367.

As a specific example of the cleaning means in the image forming apparatus having the rotary developing device according to the above proposal, a cleaning brush attached to the rotary developing device is used as a cleaning member, and the cleaning brush is an optical sensor. A first one that periodically cleans the sensor surface of the optical sensor when moved over the sensor surface, a projection member attached to the rotary developing device as a cleaning auxiliary member, and a peripheral member of the rotary developing device as a cleaning member When the cleaning brush is turned on the sensor surface of the optical sensor, the sensor surface of the optical sensor is periodically cleaned when the protrusion member is engaged with the cleaning brush. The second one uses an actuator attached to the rotary developing device as a cleaning auxiliary member, and a flexible container with an air outlet disposed around the rotary developing device as a cleaning member, and the actuator is When pressing the shaking of the container, only blowing exhaust air from the air outlet to the sensor surface of the optical sensor, a third one to clean periodically the sensor surface of the optical sensor are shown.

An image forming apparatus provided with a rotary developing device according to the above-mentioned proposal uses a cleaning brush or a flexible container for cleaning means for cleaning a sensor surface of an optical sensor. If a cleaning brush or a flexible container is repeatedly used many times to clean the sensor surface of the optical sensor, the shape of the brush material at the wiping portion of the sensor surface of the optical sensor gradually changes, and As the material gradually wears, it may not be possible to sufficiently remove fine particles such as toner and dust attached to the sensor surface of the optical sensor.In a flexible container, repeated pressing by the actuator may cause a problem. The flexible characteristics are fatigued, and when the pressing is released, it does not return to the original shape, as a result, the amount of air discharged from the outlet decreases,
Another problem is that it is not possible to sufficiently remove fine particles such as toner and dust attached to the sensor surface of the optical sensor. It cannot be used as a means for cleaning the sensor surface of the optical sensor in the forming apparatus.

SUMMARY OF THE INVENTION The present invention has been made in view of such technical background, and an object of the present invention is to provide an optical sensor for detecting the image density of a toner image formed on a recording medium.
An object of the present invention is to provide an image forming apparatus capable of always reliably preventing contamination by fine particles such as toner.

[0014]

In order to achieve the above object, an image forming apparatus according to the present invention includes an optical sensor for detecting an image density of a toner image, which is provided near a movable recording medium on which a toner image is formed. The image density control unit coupled to the optical sensor compares the image density data detected by the optical sensor with reference image density data stored in advance, and determines the image density of the toner image in accordance with the comparison result. When controlling and adjusting to match the reference image density, between the sensor surface of the optical sensor and the recording medium, a jet nozzle that jets an air flow onto the sensor surface and a suction nozzle that sucks the air flow on the sensor surface Means provided with an air flow forming device.

According to the above means, particles such as toner adhered to the sensor surface of the optical sensor are scattered by the air flow ejected from the ejection nozzle onto the sensor surface of the optical sensor, and the particles containing the scattered toner and the like are included. Since an air flow forming device that works to suck the air flow by the suction nozzle is provided, all particles such as toner adhered to the sensor surface of the optical sensor are removed by the air flow forming device and formed on the surface of the recording medium. Thus, the image density of the toner image can be detected very accurately, and the control of the image density of the toner image by the image density control unit can be executed without error.

Further, according to the above-mentioned means, the removal of particles such as toner adhered to the sensor surface of the optical sensor is performed by the air flow forming apparatus utilizing the ejection of the air flow from the ejection nozzle and the suction of the air flow at the suction nozzle. The ejection nozzle and the suction nozzle are not deformed or worn due to aging, and furthermore, the ejection amount of the air flow from the ejection nozzle and the suction amount of the air flow at the suction nozzle do not change over time. Therefore, the function of removing fine particles such as toner can be constantly constant.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the present invention, an image forming apparatus includes a movable recording medium on which a toner image is formed on a surface thereof, and a toner image formed on the recording medium which is disposed close to the recording medium. An optical sensor for detecting the density, an image density control unit that compares the image density detected by the optical sensor with the reference image density, and adjusts the toner image density according to the comparison result; An air flow forming device which is disposed so as to sandwich a sensor surface between an optical sensor and a recording medium, and is provided with an ejection nozzle for ejecting air flow on the sensor surface and a suction nozzle for sucking air flow on the sensor surface. It is.

In one preferred embodiment of the present invention, the image forming apparatus includes an airflow forming device, which is disposed on the sensor surface, which is located close to the optical sensor and upstream in the moving direction of the recording medium. It has a particle shielding plate for preventing scattering of particles.

In another preferred embodiment of the present invention, in the image forming apparatus, the air flow forming device is arranged near the optical sensor and on the upstream side and the downstream side in the moving direction of the recording medium, respectively. It has a particle shielding plate for preventing scattering of various particles on the sensor surface.

In still another preferred embodiment of the present invention, in the image forming apparatus, the air flow forming device has a window member for covering a sensor surface of the optical sensor.

In one specific example of the embodiment of the present invention, in the image forming apparatus, the air flow forming device is configured such that the gap between the sensor surface and the recording medium is narrow on the ejection nozzle arrangement side and wide on the suction nozzle arrangement side. The optical sensor has an optical sensor that is arranged so as to be inclined.

In another specific example of the embodiment of the present invention, in the image forming apparatus, the air flow forming device has a filter device connected to one of ducts respectively connected to the ejection nozzle and the suction nozzle. Things.

In still another specific example of the embodiment of the present invention, in the image forming apparatus, the optical sensor comprises: an optical fiber bundle for guiding light emission of the light emitting element toward the surface of the recording medium;
An optical fiber bundle for guiding light reflected from the surface of the recording medium to the light receiving element.

In one control mode of the embodiment of the present invention, in the image forming apparatus, the image density control section detects a solid image detected by the optical sensor when the toner image formed on the recording medium is a solid image. Operates to control the bias voltage of the developing device in accordance with the density of the toner image. If the toner image formed on the recording medium is a halftone image, the toner image corresponds to the density of the halftone image detected by the optical sensor. It operates to control the exposure amount of the exposure device or the one-dot exposure time.

In one usage example of the embodiment of the present invention, in the image forming apparatus, the rotating drum photosensitive member is a movable recording medium on which an optical sensor is arranged in proximity.

In another use example of the embodiment of the present invention, in the image forming apparatus, the rotating drum-shaped intermediate transfer member is a movable recording medium on which an optical sensor is arranged in proximity.

In still another use example of the embodiment of the present invention, the image forming apparatus is configured such that a recording sheet on which a toner image is formed is a movable recording medium on which an optical sensor is disposed in proximity. is there.

According to these embodiments of the present invention, in order to remove particles such as toner adhering to the sensor surface of the optical sensor for detecting the image density of the toner image formed on the surface of the recording medium, An air flow forming device that is disposed between the sensor surface of the sensor and the surface of the recording medium so as to sandwich the sensor surface, and includes an ejection nozzle that ejects an air flow on the sensor surface and a suction nozzle that sucks the air flow on the sensor surface. The air flow ejected from the ejection nozzle onto the sensor surface of the optical sensor scatters particles such as toner attached to the sensor surface of the optical sensor, and the air flow containing the scattered toner particles. Is sucked by a suction nozzle to remove all particles such as toner adhered to the sensor surface of the optical sensor. It can be very accurately detect the image density of over image, resulting the control adjustment of the image density of the toner image in the image density control unit can be performed accurately without errors.

Further, according to these embodiments of the present invention, the ejection nozzle and the suction nozzle used for removing particles such as toner adhered to the sensor surface of the optical sensor are deformed with time. And the amount of air flow ejected and sucked does not change over time, so that the function of removing fine particles such as toner can be stabilized, and the toner image The image density can be kept constant.

[0030]

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

FIG. 1 shows a first embodiment of the image forming apparatus according to the present invention.
FIG. 2 is a partial development view illustrating a configuration of a portion taken along line AA in the image forming apparatus illustrated in FIG. 1.

1 and 2, reference numeral 1 denotes a drum-shaped photosensitive member (recording medium), 2 denotes a charging device, 3 denotes an exposure device, 4 denotes a developing device, 5 denotes a toner, 6 denotes an optical sensor, 6S denotes a sensor surface,
7 is a transfer device, 8 is an image density control unit, 9 is a developing bias power source, 10 is a developing roll, 11 is an air flow forming device, 12
Is a jet nozzle, 13 is a suction nozzle, 14 is a particle shielding plate,
15 is a light emitting element, 16 is a light receiving element, 17 is a window member, 18
Is a first duct, 19 is a second duct, 20 is toner, L is exposure light, and F is an air flow.

The drum-shaped photosensitive member 1 is rotated in the direction indicated by the arrow in FIG.
The charging device 2 includes, for example, a scorotron charger.
The surface of the drum-shaped photoconductor 1 is charged so as to have a predetermined potential, and is arranged close to the surface of the drum-shaped photoconductor 1.
The exposure device 3 irradiates the drum-shaped photoconductor 1 with exposure light L made of a laser beam, and performs exposure of the surface of the drum-shaped photoconductor 1 with the exposure light L according to a formed image. It is located at a location slightly away from the surface. The developing device 4 has a developing roll 10 disposed therein, and is filled with a developer containing toner 5 and a magnetic carrier, and the exposed portion on the surface of the drum-shaped photoreceptor 1 is supplied with an amount of toner 5 according to the exposure intensity. The toner image is developed by attaching the toner image thereon, and is arranged close to the surface of the drum-shaped photoconductor 1. Optical sensor 6
Is for detecting the image density of a toner image formed on the surface of the drum-shaped photoreceptor 1 with the light-emitting element 15 and the light-receiving element 16 built-in and using the surface facing the drum-shaped photoreceptor 1 as a sensor surface 6S. The sensor surface 6S is arranged at a position close to the surface of the drum-shaped photoreceptor 1. The transfer device 7 transfers the toner image formed on the surface of the drum-shaped photoconductor 1 to another recording medium such as a recording sheet, and is arranged in contact with the surface of the drum-shaped photoconductor 1.

The image density control unit 8 is connected to the optical sensor 6 and the developing bias power supply 9, and responds to an image density detection output from the optical sensor 6 to form an image density of a toner image formed on the surface of the drum 1. To adjust the developing bias voltage output from the developing bias power supply 9. The developing bias power supply 9 supplies a developing bias voltage to the developing device 4 and is connected to the developing roll 10 of the developing device 4.

The air flow forming device 11 comprises an ejection nozzle 12 connected to a first duct 18 and a suction nozzle 13 connected to a second duct 19, and the surface of the drum-shaped photosensitive member 1 and an optical sensor 6 is disposed between the sensor surface 6S and the sensor surface 6S. An ejection port of the ejection nozzle 12 is disposed at one end of the sensor surface 6S, and a suction port of the suction nozzle 13 is disposed at the other end. The particle shielding plate 14 is disposed on the upstream side in the rotation direction of the drum-shaped photoreceptor 1 with respect to the optical sensor 6 so as to be substantially orthogonal to the airflow forming device 11, and the window member 17 flattens the sensor surface 6S. The sensor surface 6S of the optical sensor 6
Attached to.

The image forming apparatus of the first embodiment having the above configuration operates as follows.

When the drum-shaped photosensitive member 1 is driven to rotate, the drum-shaped photosensitive member 1 is first charged in the charging device 2 by a charging voltage so as to have a uniform surface potential.

Next, the surface of the drum-shaped photosensitive member 1 is irradiated with exposure light L from the exposure device 3 to form an electrostatic latent image on the irradiated portion.

Next, the drum-shaped photosensitive member 1 is
Contacting the developer with the electrostatic latent image formed on the surface in
A toner image corresponding to the electrostatic latent image is formed. The developing device 4 includes a developing roller 10, a regulating plate for regulating a transport amount of the developer, and a toner hopper for supplementing consumed toner.
A replenishing roll, a stirring member for mixing the replenished toner 5 and the developer to improve triboelectric charging, a magnetic sensor for detecting a mixing ratio between the toner 5 and the magnetic carrier, and the like. I have. The magnetic carrier and the toner 5 are charged to have opposite polarities by frictional charging. When the developer is brought into contact with the surface of the drum-shaped photoreceptor 1, the developing roller 10 and the developing roller 10 to which a developing bias voltage is applied are applied. The toner image is formed on the surface of the drum-shaped photoconductor 1 by an electric field generated between the drum-shaped photoconductor 1 and the photoconductor 1. As an example of the developer, a resin-coated magnetic carrier having a particle size of 40 to 100 μm and a toner 5 having a particle size of 6 to 11 μm are used, and the average toner concentration {(toner weight / developer) × 100} is obtained. It is 1.5 to 5.0% by weight, preferably 2 to 4% by weight. The mixing ratio (toner mixing ratio) of the toner 5 and the magnetic carrier in the developer is controlled by detecting the magnetic substance content by a magnetic sensor, and as a result of the detection, when the toner mixing ratio falls below a predetermined value. A replenishment signal is generated to replenish the toner, and control is performed so that the toner mixture ratio becomes substantially constant.

Subsequently, the drum-shaped photosensitive member 1 is
In, the image density of the toner image formed on the surface is detected. The light sensor 6 irradiates the light emission of the light emitting element 15 to the toner image, and detects the reflected light from the toner image by the light receiving element 16, that is, detects the so-called light reflectance of the toner image. In this case, since the light reflectance of the toner image and the toner image density have a one-to-one relationship, by detecting the reflectance of the toner image, the image density of the toner image (the optical density of a solid image or a halftone image) is detected. Concentration) can be measured. Optical sensor 6
As shown in FIG. 2, the photo sensor is composed of a photosensor in which a light emitting element 15, a light receiving element 16, a lens (not shown), and the like are integrally formed, and a sensor surface 6 </ b> S is covered with a window member 17.
As the light emitting element 15, for example, a GaAs (gallium arsenide) infrared light emitting diode is used.
For example, a Si (silicon) phototransistor is used.

Next, the drum-shaped photosensitive member 1 is transferred to the transfer device 7.
The toner image formed on the surface is transferred onto a recording sheet (not shown), and a toner image is formed on the surface of the recording sheet. Thereafter, the drum-shaped photoconductor 1 is cleaned and removed of the toner image remaining on the surface thereof by a cleaning device (not shown), and is used again to repeatedly execute the above-described operation.

When the image density of the toner image formed on the surface of the drum-shaped photosensitive member 1 is detected by the optical sensor 6, the image density control section 8 stores the image density data detected by the optical sensor 6 in advance. A comparison is made with reference image density data, and a control signal corresponding to the comparison result is supplied to a developing bias power supply 9.

In the first embodiment, as the optical sensor 6, light emitted from the light emitting element 15 is directly radiated to the surface of the drum-shaped photosensitive member 1, and reflected light from the surface of the drum-shaped photosensitive member 1 is emitted. Although a direct-type sensor that directly enters the light receiving element 16 is used, a first fiber bundle that guides light emitted from the light emitting element 15 to the surface of the drum-shaped photoconductor 1 and receives light reflected on the surface of the drum-shaped photoconductor 1 It may be modified to use a fiber optic sensor with a second fiber bundle leading to element 16. In this case, since the first and second fiber bundles are made of glass fiber bundles, the optical fiber type sensor operates stably with respect to temperature fluctuation,
Further, since the first and second fiber bundles are rod-shaped, the installation space can be reduced, and the circuit board on which the amplifier and the like are mounted can be mounted on the surface of the drum-shaped photosensitive member 1 (light reflecting portion). Since it can be arranged at a distance from the device, there is an advantage that even if the charging device 2 accompanied by corona discharge is installed in the vicinity, there is no generation of noise as a measurement error.

Here, when controlling and adjusting the image density of the toner image formed on the surface of the drum-shaped photoreceptor 1, when the control adjustment toner image is formed as a solid image, the image density control unit 8 Compares the image density data information of the solid image detected by the optical sensor 6 with the reference image density data of the previously stored solid image, and supplies a control signal corresponding to the comparison result to the developing bias power supply 9; The developing bias voltage supplied to the developing device 4 is changed to control and adjust the image density of the solid image (solid toner adhesion amount) to a predetermined value. At this time, if the difference between the surface potential of the drum-shaped photoreceptor 1 and the developing bias voltage exceeds a predetermined range, toner fogging occurs, carrier adhesion increases, and thin lines and halftone dots are reproduced. Therefore, the developing bias voltage is changed, the grid voltage of the charging device 2 is changed, and the surface potential of the drum-shaped photoconductor 1 is adjusted and corrected.

On the other hand, when controlling and adjusting the image density of the toner image formed on the surface of the drum-shaped photoreceptor 1, when the control adjustment toner image is formed as a halftone image, the image density control unit 8 Compares image density data information of a halftone image detected by the optical sensor 6 with reference image density data of a halftone image stored in advance, and outputs a control signal corresponding to the comparison result to a dotted line in FIG. As shown, the exposure amount or dot exposure time (light pulse width) of the exposure light L supplied to the exposure device 3 and output from the exposure device 3 is changed to change the image density (dot / toner) of the halftone image. (Adhered amount) is controlled to a predetermined value.

Further, the image forming apparatus of the first embodiment is characterized in that an air flow forming device 11 is arranged between the sensor surface 6S of the optical sensor 6 and the surface of the drum-shaped photosensitive member 1. Hereinafter, the configuration and operation of the air flow forming device 11 will be described with reference to FIG.

The air flow forming device 11 causes the air flow F to flow on the sensor surface 6S of the optical sensor 6, and as shown in FIG. 2, the ejection nozzle 12 and the suction nozzle 13 sandwich the sensor surface 6S. It is what is arranged. The ejection nozzle 12 is connected to a first duct 18 for supplying the air flow for ejection, and the suction nozzle 13 is connected to a second duct 19 for discharging the air flow for suction. The first duct 18 and the second duct 19 are connected to an air pump (not shown) for forming an air flow, and form an air flow F on the sensor surface 6S by driving the air pump. In addition, the particle shielding plate 14
As shown in FIG. 1, is disposed near the optical sensor 6 and on the upstream side in the rotation direction of the drum-shaped photoconductor 1.
The particle shielding plate 14 slightly protrudes in the direction of the surface of the drum-shaped photoreceptor 1 beyond the sensor surface 6S of the optical sensor 6 and the position where the ejection nozzle 12 and the suction nozzle 13 are arranged, and in the direction in which the air flow F is formed. It has a plate-like structure that is long in the parallel direction, and rotates as the drum-shaped photoconductor 1 rotates.
The rotating airflow formed near the surface of the
At the same time that the air flow F formed on the surface S is not disturbed, and when fine particles such as the toner 5 scatter around the developing device 4, the fine particles are rotated downstream of the drum-shaped photoconductor 1 by the rotating air flow. Is not directly attached to the sensor surface 6S of the optical sensor 6.

The window member 17 covering the sensor surface 6S of the optical sensor 6 is provided for preventing the sensor surface 6S from being contaminated with toner due to the adhesion of fine particles such as toner to the light emitting element 15, the light receiving element 16 and the lens. It has a protection function and a function of preventing the accumulation of toner on the sensor surface 6S by causing the air flow F to flow along the window member 17 by smoothing the sensor surface 6S. Since F flows, fine particles such as toner do not adhere to the sensor surface 6S due to the air curtain effect.

It is desirable that the air flow F generated in the air flow forming device 11 be generated continuously, but may be generated intermittently in some cases. As a means for generating the air flow F intermittently, a shutter may be provided in the flow path of the air flow F, and the air flow F may be generated when the shutter is open.

As described above, according to the image forming apparatus of the first embodiment, the air flow forming device 1 is provided on the sensor surface 6S of the optical sensor 6.
1, the air flow F is caused to flow near the sensor surface 6S, so that erroneous detection of the toner image density of the optical sensor 6 based on toner contamination of the sensor surface 6S and erroneous control by the image density controller 8 The operation can be prevented from occurring, and the image density of the toner image formed on the surface of the drum-shaped photosensitive member 1 can be constantly controlled and adjusted at all times.

Further, according to the image forming apparatus of the first embodiment, since the particle shielding plate 14 is arranged near the optical sensor 6 and on the upstream side in the rotation direction of the drum-shaped photosensitive member 1, the drum-shaped photosensitive member is provided. The airflow F generated on the sensor surface 6S is not disturbed by the rotation airflow generated by the rotation of the first rotation unit 1. Further, even if fine particles such as the toner 5 scatter around the developing device 4, they are carried by the rotation airflow. Fine particles such as the toner 5 do not directly adhere to the sensor surface 6S.

Further, according to the image forming apparatus of the first embodiment, since the sensor surface 6S of the optical sensor 6 is covered with the window member 17, the light emitting element 15, the light receiving element 16, the lens and the like are protected from toner contamination. Not only can you protect
By forming the sensor surface 6S as a smooth surface and flowing the air flow F along the smooth surface, accumulation of fine particles such as the toner 5 on the sensor surface 6S can be suppressed.

In the image forming apparatus of the first embodiment, one optical sensor 6 is arranged close to the surface of the drum-shaped photoconductor 1, but a plurality of optical sensors 6 are connected to the drum-shaped photoconductor 1. May be arranged close to each other along the surface, and control adjustments to the image density of the toner image may be individually performed based on the detection outputs from these optical sensors 6. In this case, each of the plurality of optical sensors 6 has an airflow forming device 1 between the sensor surface 6S of the optical sensor 6 and the surface of the drum-shaped photoreceptor 1.
1 is arranged.

When the image forming apparatus of the first embodiment is applied to an electrophotographic printer and used for a long period of time, the sensor surface 6S of the optical sensor 6 does not become contaminated with toner over time. As a result, based on toner contamination of the optical sensor 6, there was no erroneous detection of the image density of the toner image formed on the surface of the drum-shaped photoreceptor 1 by the optical sensor 6, and no malfunction in the image density control unit 8. .

Next, FIG. 3 is a partially developed view showing a second example of the configuration along the line AA in the image forming apparatus shown in FIG.

In FIG. 3, the same components as those shown in FIG. 2 are denoted by the same reference numerals.

The configuration shown in FIG. 3 is such that the sensor surface 6S of the optical sensor 6 is disposed so as to be inclined with respect to the surface of the drum-shaped photoreceptor 1, and the sensor surface 6S is disposed obliquely. The shapes of the ejection nozzle 12 and the suction nozzle 13 are slightly changed so that the air flow F flows along the inclined sensor surface 6S.

In general, the distance between the sensor surface 6S of the optical sensor 6 and the surface of the drum-shaped photosensitive member 1 is selected to be 0.5 to 15 mm.
In addition, in order to dispose the suction nozzles 13, there is a restriction that the distance is 1.5 mm or more, preferably 3 mm or more. In this case, the ejection nozzle 12
If the width of the air flow outlet is small, a sufficient amount of air flow F
Not only is not obtained, but also the pressure loss of the air flow F increases, and the internal pressure of the first duct 18 for guiding the air flow increases,
The first duct 18 needs to be made robust and a large air pump is required.

In such a technical background, as shown in FIG. 3, the gap between the sensor surface 6S of the optical sensor 6 and the surface of the drum-shaped photoreceptor 1 goes from the ejection nozzle 12 side to the suction nozzle 13 side. Is inclined so as to be wider, the cross-sectional area of the flow passage of the airflow F tends to increase from the ejection nozzle 12 side to the suction nozzle 13 side. It is possible to make it sufficiently wide.

Next, FIG. 4 is a schematic diagram showing a main part of an image forming apparatus according to a second embodiment of the present invention, in which an air flow forming apparatus 11 is provided with two particle shielding plates. is there.

In FIG. 4, 14 ₁ is a first particle shielding plate,
14 ₂ is the second particle shielding plate, and other, are identified by the same reference numerals are given to the same configuration as the components shown in FIG.

In the image forming apparatus of the first embodiment, the particle shielding plate 14 is arranged only on the sensor surface 6S of the optical sensor 6 on the upstream side in the rotation direction of the drum-shaped photosensitive member 1. The image forming apparatus according to the second embodiment includes an optical sensor 6
Those of the first particle shielding plate 14 ₁ in the upstream side in the rotation direction of the drum-shaped photoreceptor 1 at the sensor surface 6S, and the second particle shielding plate 14 ₂ is arranged downstream in the rotation direction of the drum-shaped photoreceptor 1 It is.

[0063] Toner With such an arrangement, the toner carried by the whirling current caused by the rotation of the drum-shaped photosensitive member 1 is blocked by the first particle shielding plate 14 _1, falling from the upper left of the image forming apparatus since the possible blocked by the second particle shielding plate 14 _2, the adhesion ratio to the sensor surface 6S of the scattered fine particles, than the adhesion ratio of the image forming apparatus of the first embodiment can be reduced, to the sensor surface 6S Due to the adhesion of the fine particles, the optical sensor 6 does not perform erroneous detection, and the occurrence of a malfunction in the image density control unit 8 can be eliminated.

Next, FIG. 5 is a schematic diagram showing a main part of an image forming apparatus according to a third embodiment of the present invention, in which an intermediate transfer member is used to perform color printing on recording paper.

In FIG. 4, reference numeral 21 denotes a belt-shaped photosensitive member, 22 denotes a drum-shaped intermediate transfer member, 23 denotes a recording sheet, 24Y denotes a yellow developing device, 24M denotes a magenta developing device, and 24C denotes a magenta developing device.
Is a cyan developing device, 24B is a black developing device, 2
5Y is a yellow developing roll, 25M is a magenta developing roll, 25C is a cyan developing roll, 25B is a black developing roll, 26 is a first transfer device, 27 is a second transfer device, 28 is a first cleaning device, 29 Is a second cleaning device, 30 is a voltage switching unit,
The same reference numerals are given to the same components as those shown in FIG.

Then, the belt-shaped photoconductor 21 is
A charging device 2 for charging the surface of the photoconductor 1; an exposure device 3 for irradiating the surface of the belt-shaped photoconductor 21 with exposure light L;
A yellow developing device 24Y for attaching a yellow developer to the surface of the toner, a magenta developing device 24M for attaching a magenta developer to the surface, and cyan developing for attaching a cyan developer to the surface A device 24C, a black developing device 24B for adhering a black developer on the same surface, and a first cleaning device 28 for cleaning the surface of the belt-shaped photoreceptor 21 are respectively arranged in close proximity to each other. It is arranged in contact with the drum-shaped intermediate transfer body 22 at a position facing the device 26. The drum-shaped intermediate transfer member 22 includes an optical sensor 6 that detects an image density of a toner image formed on the surface of the drum-shaped intermediate transfer member 22, and a second cleaning device that cleans the surface of the drum-shaped intermediate transfer member 22. 29, and the second transfer device 2
The recording paper 23 is placed in contact with the recording paper 23 at a position facing the recording paper 23. The optical sensor 6 is provided with an airflow forming device 11 between the sensor surface 6S and the surface of the drum-shaped intermediate transfer body 22, and is located near the optical sensor 6 and upstream of the drum-shaped intermediate transfer body 22 in the rotation direction. A particle shielding plate 14 is disposed at the bottom of the screen. The image density control unit 8 is connected to the optical sensor 6 and also to the developing bias power source 9 and the voltage switching unit 30. The voltage switching unit 30 includes the developing bias power source 9, the yellow developing roll 25Y, and the magenta color developing unit. Roll 25M, cyan developing roll 25C, and black developing roll 25B.

The image forming apparatus of the third embodiment having the above-mentioned structure operates roughly as follows.

The belt-shaped photoreceptor 21 is moved in the direction of the arrow by the driving of a driving source (not shown). During the first cycle during the movement, the surface of the photoreceptor 2 is charged to a predetermined potential in the charger 2, and The electrostatic latent image is formed on the surface by exposure with the exposure light L, and the yellow developing device 24Y
Then, the developer containing the yellow toner adheres to the surface, a yellow toner image is formed, and unnecessary toner and the like are removed in the first cleaning device 28. In the next one cycle, the surface of the charging device 2 is charged to a predetermined potential, the exposure device 3 exposes the surface to exposure light L to form an electrostatic latent image on the surface, and the magenta color developing device 24M
Then, a developer containing magenta toner adheres to the surface, a magenta toner image is formed on the yellow toner image, and unnecessary toner and the like are removed in the first cleaning device 28. In the next one cycle, a cyan toner image is formed on each of the yellow and magenta toner images by the same operation as the above operation, and in the last one cycle, the same operation as the above operation A black toner image is formed on the yellow, magenta and cyan toner images, and a full color toner image is formed as a whole. Then, the full-color toner image formed on the surface of the belt-shaped photoconductor 21 is driven by the first transfer device 26,
The image is transferred from the surface of the belt-shaped photoconductor 31 to the surface of the drum-shaped intermediate transfer body 22.

The drum-shaped intermediate transfer member 22 is moved in the direction of the arrow by driving of a driving source (not shown), and at the time of the movement, the optical sensor 6 detects the image density of the full-color toner image formed on the surface. . At this time, the image density control unit 8 compares the image density data detected by the optical sensor 6 with the stored reference image density data, and controls and adjusts the developing bias voltage of the developing bias power supply 9 according to the comparison result. At the same time, by the control switching of the voltage switching unit 30, the developing devices 24Y, 24M, 2
4C and 24B are selected, and the control and adjustment are performed such that the image density of the full-color toner image formed on the surface of the drum-shaped intermediate transfer body 22 becomes the standard image density. Then, the full-color toner image formed on the surface of the drum-shaped intermediate transfer body 22 is transferred from the surface of the drum-shaped intermediate transfer body 22 to the surface of the recording paper 23 by driving the first transfer device 27,
Thereafter, in the second cleaning device 29, unnecessary toner and the like remaining on the surface of the drum-shaped intermediate transfer body 22 are removed.

The recording paper 23 is moved in the direction of the arrow by the driving of a drive source (not shown), and a full-color toner image formed on the surface is fixed by a fixing device (not shown). Is performed.

According to the image forming apparatus of the third embodiment, the optical sensors 6 are arranged at positions distant from the developing devices 24Y, 24M, 24C, 24B of the respective colors. Since the optical sensor 6 can be arranged in the state in which the optical sensor 6 is arranged, it is compared with the case where the optical sensor 6 is arranged between the developing device 4 and the transfer device 11 as in the first and second embodiments. And developing devices 24Y, 24M for each color,
The sensor surface 6S of the optical sensor 6 accompanying the scattering of the toner 5 of each color from 24C and 24B and the drop of the developer containing the toner 5 of each color.
The above toner contamination can be reduced.

According to the image forming apparatus of the third embodiment, the air flow forming device 11 is provided on the sensor surface 6S of the optical sensor 6.
And the particle shielding plate 14 is provided in the vicinity of the optical sensor 6 on the upstream side in the rotation direction of the drum-shaped intermediate transfer body 22, so that the sensor surface 6S based on the fine particles of the toner 5 floating in the image forming apparatus is provided. , And toner contamination due to toner scattering at the time of transferring the toner image in the first transfer device 26 can be effectively prevented.

FIG. 6 is a schematic diagram showing a main part of an image forming apparatus according to a fourth embodiment of the present invention. The transfer device is not operated when the image density of a toner image is detected by an optical sensor. Things.

[0074] In FIG. 6, 7 ₁ movable transfer device in the non-transfer position, 23 ₁ Non-transferable recording sheet, 31 is the static eliminator, 32 cleaning unit, 33 is moveable guide roll, 34 The position fixing guide roll, 35 is a feed roll, and the same components as those shown in FIG. 4 are denoted by the same reference numerals.

The image forming apparatus according to the second embodiment always uses the transfer device 7 capable of transfer, and connects the optical sensor 6 and the air flow forming device 11 between the developing device 4 and the transfer device 7. but in which are arranged, an image forming apparatus of the fourth embodiment, using a transfer device 7 ₁ movable in a non-transfer position,
And, in which they are arranged downstream in the rotation direction of looking at light sensor 6 and the air flow formation apparatus 11 from the transfer device 7 ₁ movable in the non-transfer position drum-like photoreceptor 1.

In the image forming apparatus of the fourth embodiment, when the image density of the toner image (solid image or halftone image) formed on the surface of the drum-shaped photosensitive member 1 is detected by the optical sensor 6, the image sensor is located at the non-transfer position. each movable transfer device ₇₁ and a movable guide roll 33 is moved to the non-transfer position, as indicated by the solid line in FIG. 6, the movable transfer device in the non-transfer position 7
_The recording paper 231 is conveyed at a position of ₁ while being separated from the surface of the drum-shaped photoconductor 1. At this time, the toner image formed on the surface of the drum-shaped photosensitive member 1, the recording sheet 23 ₁ by the non-transcribed movable transfer device to position 7 ₁
The image density remains without being transferred to the optical sensor 6. Thereafter, the remaining toner image is neutralized by the neutralization device 31 and then removed from the surface of the drum-shaped photoconductor 1 by the cleaning device 32. At this time, the image density control unit 8 compares the image density data detected by the optical sensor 6 with the stored reference image density data, and controls and adjusts the developing bias voltage of the developing bias power supply 9 according to the comparison result. .

[0077] In addition, the drum-shaped case where the toner image formed on the surface of the photosensitive member 1 is transferred onto the recording sheet 23 _1, respectively transfer positions a movable transfer device ₇₁ and a movable guide roll 33 to the non-transfer position is moved, as indicated by a dotted line in FIG. 6, is conveyed in contact with the recording paper 23 ₁ drum-shaped photosensitive member 1 surface at the position of the transfer device 7 ₁ movable in a non-transfer position. At this time, the toner image formed on the surface of the drum-shaped photosensitive member 1 is transferred onto the recording sheet 23 ₁ by the non-transcribed movable transfer to position device _71, a toner image is formed on the recording paper 23 ₁ .

At this point, most of the toner image formed on the surface of the drum-shaped photoreceptor ₁ is transferred to the recording paper 231, and the optical sensor 6 detects the image density of the toner image. Absent.

According to the image forming apparatus of the fourth embodiment, when the optical sensor 6 detects the image density of the toner image formed on the surface of the drum-shaped photosensitive member ₁ , the toner image is transferred to the recording paper 231. since it is not, it is possible to save the recording sheet 23 _1.

Further, according to the image forming apparatus of the fourth embodiment, since the optical sensor 6 is disposed at a position distant from the developing device 4, the developing device 4
The rate at which the fine particles such as the toner 5 scattered on the periphery of the optical sensor 6 adhere to the sensor surface 6S of the optical sensor 6 decreases, and accordingly, the flow rate of the air flow F of the air flow forming device 11 can be reduced. In the case where the air flow forming device 11 is operated intermittently, the operation pause time can be increased.

FIG. 7 is a schematic diagram showing a main part of an image forming apparatus according to a fifth embodiment of the present invention, in which an optical sensor is arranged to face a recording sheet, and the image density of a toner image transferred to the recording sheet. Is detected.

[0082] In FIG. 7, 33 ₁ is stationary guide roll, other, are identified by the same reference numerals for the same components as those shown in FIG.

In the image forming apparatus according to the fifth embodiment, the optical sensor 6 and the airflow forming device 11 are arranged close to the recording paper 23 instead of being arranged close to the surface of the drum-shaped photosensitive member 1. The image density of the toner image formed on the recording paper 23 is detected by the optical sensor 6. In this case, the optical sensor 6 and the airflow forming device 11 are arranged at positions facing the position fixing guide roll 34 that applies tension to the recording paper 23. If the arrangement position of the optical sensor 6 is selected as a position facing the position fixing guide roll 34, the distance between the sensor surface 6S of the optical sensor 6 and the surface of the recording paper 23 becomes substantially constant, and a constant measurement accuracy can be obtained. Will be possible.

According to the image forming apparatus of the fifth embodiment, even if the transfer efficiency of the toner image to the recording paper 23 changes depending on the environmental conditions and the type of the recording paper 23, it is necessary to correct the change in the transfer efficiency. There is no.

Further, according to the image forming apparatus of the fifth embodiment, since the optical sensor 6 is disposed at a position distant from the developing device 4, the developing device 4
The rate at which the fine particles such as the toner 5 scattered on the periphery of the optical sensor 6 adhere to the sensor surface 6S of the optical sensor 6 decreases, and accordingly, the flow rate of the air flow F of the air flow forming device 11 can be reduced. In the case where the air flow forming device 11 is operated intermittently, the operation pause time can be increased.

Further, according to the image forming apparatus of the fifth embodiment, when the optical sensor 6 is arranged to face the recording paper 23,
Although the paper dust adheres to the sensor surface 6S of the optical sensor 6 due to long-term use, the paper dust adhered to the sensor surface 6S can be easily removed by operating the air flow forming device 11. it can.

Next, FIG. 8 is a view showing the construction of a main part of an image forming apparatus according to a sixth embodiment of the present invention. The first and second air flow forming devices are arranged.

[0088] In FIG. 8, 6 ₁ first optical sensor, 6 ₂
Is a second optical sensor, 11 ₁ is a first air flow forming device, 11 ₂
The second air flow forming device, 36 a comparison determination unit 37 ₁ is first pump, 37 ₂ and the second pump, 38 ₁ the first air flow changing portion 38 ₂ and the second air flow changing portion, is 39 The same components as those shown in FIG. 4 are denoted by the same reference numerals as the stain removal control unit.

[0089] Then, the image forming apparatus of the sixth embodiment, the surface of the drum-shaped photosensitive member 1, a developing device 4 and the transfer device 7 first optical sensor 6 ₁ and the first air flow forming device during the 11
₁ is arranged, and a second optical sensor 6 ₂ and the second air flow forming device 11 ₂ is arranged downstream in the rotation direction of the drum-shaped photosensitive member 1 as viewed from the transfer device 7. First optical sensor ₆₁ and the second optical sensor 6 ₂ are connected to respective inputs of the comparison determination unit 36, one output of the comparison and determination section 36 is connected to the image density control unit 8. The first air flow forming device 11 ₁ is connected to the first pump 37 ₁ , and the second air flow forming device 11 ₂ is connected to the second pump 37 ₂
Connected to. The other output of the comparison / determination unit 36 is connected to the input of the dirt removal control unit 39, and one and the other outputs of the dirt removal control unit 39 are connected to the first air flow changing unit 38 ₁ , respectively.
Via the first pump 37 ₁ and the second air flow changing section 38 ₂
It is connected to the second pump 37 the control end of the ₂ through.

The image forming apparatus of the sixth embodiment having the above configuration operates as follows.

[0091] The first optical sensor ₆₁ detects the image density of a toner image formed on the surface of the drum-shaped photosensitive member 1, and supplies an output a first image density detection data to the comparison determination unit 36, similarly, the second optical sensor 6 ₂ detects the image density of a toner image formed on the surface of the drum-shaped photosensitive member 1, and supplies an output a second image density detection data to the comparison determination unit 36. The comparison / determination unit 36 compares the supplied first image density detection data with the second image density detection data.
The image density detection data is compared with the image density detection data, and if both data coincide with each other within a predetermined range, one of the data is supplied to the image density control unit 8, and the image density control unit 8 develops the developing bias in accordance with the supplied data. The output developing bias voltage of the power supply 9 is controlled to control and adjust the image density of the toner image formed on the surface of the drum-shaped photoconductor 1. On the other hand, the comparison determination unit 36
Compares the supplied first image density detection data with the supplied second image density detection data, and when both data do not match within a predetermined range or one of the data is missing,
The abnormal signal is supplied to the dirt removal control unit 39.

[0092] At this time, stain removal control unit 39, first each supplying a drive signal to the air flow changing portion 38 ₁ and the second air flow change unit 38 _2, an air flow changing portion 3 for receiving the driving signal
8 ₁ and the second air flow change unit 38 _2, the first pump 37 ₁
And second to the pump 37 ₂ is driven operation. As a result, the first air flow forming device 11 ₁ and the second air flow forming device 11 ₂
Are each an air stream is generated in the first optical sensor ₆₁ of the sensor surface and the second optical sensor 6 _second sensor plane, the first optical sensor ₆₁ of the sensor surface and the second optical sensor 6 ₂ sensor plane It works so as to remove fine particles such as the toner 5 adhered to the toner.

[0093] In this case, the driving operation of the air flow changing portion 38 ₁ and the second air flow changing portion 38 ₂ of the first pump 37 ₁ and a second pump 37 _2, as described above, the first pump 37
It may be one to shift to a normal operating state ₁ and the second pump 37 ₂ from the operation stop state, and also be such as enhance the first operating state of the pump 37 ₁ and a second pump 37 ₂ Good.

According to the image forming apparatus of the sixth embodiment, the first
The arrangement of the optical sensor ₆₁ and the second optical sensor 6 _2, it becomes possible to grasp the particulate contamination state of the toner 5 and the like of the sensors surface, the first optical sensor ₆₁ and the second optical sensor 6 only when either one in ₂ becomes contaminated, since it Hatarakasere the first air flow forming device 11 ₁ and the second air flow forming device 11 _2, the first air flow forming device 11 ₁ and the it is possible to reduce the power consumption in the second air flow forming device 11 _2.

[0095] According to the image forming apparatus of the sixth embodiment, only when the detection output of the first optical sensor ₆₁ and the second optical sensor 6 ₂ match within a predetermined range, the image density control unit 8 Performs the control adjustment of the image density of the toner image, so that the reliability in controlling the image density can be improved.

Next, FIG. 9 is a main part configuration diagram showing an example of an air flow forming device used in the image forming apparatus according to the present invention, in which a filter device is connected to a duct.

In FIG. 9, reference numeral 38 denotes an air pump, reference numeral 40 denotes a filter device, and other components which are the same as those shown in FIG. 3 are denoted by the same reference numerals.

The jet nozzle 12 is connected to the first duct 18
The suction nozzle 13 is connected to one end of the second duct 19. The other end of the first duct 18 is directly connected to the output end of the air pump 38, and the other end of the second duct 19 is connected to the input end of the air pump 38 via the filter device 40.

According to the air flow forming device 11 having the above-described structure, when the suction nozzle 13 sucks the fine particles including the toner 5 attached to the sensor surface 6S of the optical sensor 6, these fine particles are removed by the second flow. Only those particulate-free air removed by the filter device 40 connected to the duct 19 is input to the air pump 38. The air pump 38 jets the air not containing these fine particles through the first duct 18 and the jet nozzle 12 as the air flow F onto the sensor surface 6S. The flow can be clean.

In the airflow forming device 11, when the airflow passing through the first duct 18 is taken in from inside the image forming device other than around the optical sensor 6, the airflow passing through the first duct 18 is cleaned. It is desirable to couple the filter device 40 to the air intake of the first duct 18 or halfway of the first duct 18. On the other hand, when the air flow 25 of the second duct 19 is discharged to the outside of the image forming apparatus, a filter device 40 is connected to the air discharge port of the second duct 19 or the middle of the second duct 19 to clean the discharged air. It is desirable to do.

[0101]

As described above, according to the present invention, the ejection nozzle which is disposed between the sensor surface of the optical sensor and the surface of the recording medium so as to sandwich the sensor surface, and which jets an air flow onto the sensor surface. And an air flow forming device comprising a suction nozzle for sucking an air flow on the sensor surface.The air flow jetted from the jet nozzle onto the sensor surface of the optical sensor removes particles such as toner adhered to the sensor surface of the optical sensor. The air nozzle containing the scattered toner particles is sucked by the suction nozzle to remove all the toner particles adhered to the sensor surface of the optical sensor. The image density of the toner image formed on the medium surface can be detected extremely accurately, and as a result, the control of the image density of the toner image in the image density control unit can be performed accurately and without error. Ukoto there is an effect that it becomes possible.

Further, according to the present invention, the ejection nozzle and the suction nozzle used for removing particles such as toner adhered to the sensor surface of the optical sensor do not deform or wear over time. In addition, since the amount of air blown out and the amount of suction do not change with the passage of time, the function of removing fine particles such as toner can be made constant, and the image density of the toner image is always kept constant. There is an effect that can be.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of the image forming apparatus shown in FIG.
FIG. 3 is a partial development view illustrating a configuration of a line portion.

FIG. 3 is a diagram illustrating an AA in the image forming apparatus illustrated in FIG. 1;
FIG. 10 is a partial development view showing another configuration of the line portion.

FIG. 4 is a main part configuration diagram showing a second embodiment of the image forming apparatus according to the present invention.

FIG. 5 is a main part configuration diagram showing a third embodiment of the image forming apparatus according to the present invention.

FIG. 6 is a main part configuration diagram showing a fourth embodiment of the image forming apparatus according to the present invention.

FIG. 7 is a main part configuration diagram showing a fifth embodiment of the image forming apparatus according to the present invention.

FIG. 8 is a main part configuration diagram showing a sixth embodiment of the image forming apparatus according to the present invention.

FIG. 9 is a main part configuration diagram showing an example of an air flow forming device used in the image forming apparatus according to the present invention.

FIG. 10 is a main part configuration diagram illustrating an example of a configuration of an image forming apparatus including a known image density control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Drum-shaped photoreceptor (recording medium) 2 Charging device 3 Exposure device 4 Developing device 5 Toner 6 Optical sensor 6 ₁ First optical sensor 6 ₂ Second optical sensor 6S Sensor surface 7 Transfer device 7 ₁ Movable to non-transfer position Transfer device 8 Image density control unit 9 Developing bias power supply 10 Developing roll 11 Air flow forming device 11 ₁ First air flow forming device 11 ₂ Second air flow forming device 12 Jet nozzle 13 Suction nozzle 14 Particle shielding plate 15 Light emitting element 16 Light receiving Element 17 Window member 18 First duct 19 Second duct 20 Developer 21 Belt-shaped photoreceptor (recording medium) 22 Drum-shaped intermediate transfer body (recording medium) 23 Recording paper (recording medium) 23 ₁ Non-transferable recording paper 24Y Yellow Color developing device 24M Magenta developing device 24C Cyan developing device 24B Black developing device 25Y Yellow developing roll 25 M Magenta color developing roll 25C Cyan color developing roll 25B Black color developing roll 26 First transfer device 27 Second transfer device 28 First cleaning device 29 Second cleaning device 30 Voltage switching unit 31 Static elimination device 32 Cleaning device 33 Movable guide Rolls 33 ₁ , 34 Position fixed guide roll 35 Feed roll 36 Comparison / determination unit 37 ₁ First pump 37 ₂ Second pump 38 ₁ First air flow change unit 38 ₂ Second air flow change unit 39 Dirt removal control unit L Exposure light F Air flow

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akira Hosoya 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Research Laboratory, Hitachi Ltd. 2G059 AA05 BB10 CC20 DD05 DD12 EE02 EE13 GG01 GG02 GG03 HH02 JJ11 JJ17 KK02 KK03 LL04 MM05 2H027 DA09 DA10 DE02 EA02 EA05 EC06 ED06 HB20 JA01 JB01 JB12 JB14 JB15 JC18 JC20 2H077 DA03 DA47 DA49 DA63 DB08 GA04

Claims (11)

[Claims] 1. A movable recording medium on which a toner image is formed on a surface, an optical sensor disposed close to the recording medium and detecting the density of the toner image formed on the recording medium, and an optical sensor. An image density control unit that compares the detected image density with the reference image density and adjusts the toner image density in accordance with the comparison result; And an air flow forming device, which is provided so as to sandwich the sensor surface, and includes an ejection nozzle for ejecting an air flow on the sensor surface and a suction nozzle for sucking the air flow on the sensor surface. Image forming apparatus. 2. The air flow forming device further includes a particle shielding plate disposed near the optical sensor and disposed upstream of the recording medium in a moving direction to prevent scattering of various particles on the sensor surface. The image forming apparatus according to claim 1, wherein: 3. An air flow forming device, comprising: a particle shielding plate disposed near the optical sensor and disposed on an upstream side and a downstream side in a moving direction of the recording medium, respectively, for preventing scattering of various particles on the sensor surface. 2. The method according to claim 1, wherein
An image forming apparatus according to claim 1. 4. The image forming apparatus according to claim 1, wherein the air flow forming device has a window member that covers a sensor surface of the optical sensor. 5. The air flow forming device according to claim 1, further comprising an optical sensor arranged so that a gap between the sensor surface and the recording medium is narrow on the ejection nozzle arrangement side and wide on the suction nozzle arrangement side. The image forming apparatus according to claim 1, wherein: 6. The image forming apparatus according to claim 1, wherein the air flow forming device connects a filter device to one of ducts connected to the ejection nozzle and the suction nozzle, respectively. apparatus. 7. The optical sensor according to claim 1, further comprising: an optical fiber bundle that guides light emitted from a light emitting element toward a surface of the recording medium; and an optical fiber bundle that guides light reflected from the surface of the recording medium to a light receiving element. The image forming apparatus according to claim 1, wherein: 8. The image density control section, when the toner image formed on the recording medium is a solid image, adjusts a bias voltage of a developing device in accordance with the density of the solid image detected by the optical sensor. Operating to control, and when the toner image formed on the recording medium is a halftone image, the exposure amount of the exposure device or one-dot exposure corresponding to the density of the halftone image detected by the optical sensor. The image forming apparatus according to claim 1, wherein the image forming apparatus operates to control time. 9. The image forming apparatus according to claim 1, wherein the movable recording medium on which the optical sensor is disposed in proximity is a rotating photosensitive member. 10. The image forming apparatus according to claim 1, wherein the movable recording medium on which the optical sensor is disposed in proximity is a rotating intermediate transfer member. 11. The image forming apparatus according to claim 1, wherein the movable recording medium on which the optical sensor is disposed in proximity is a recording sheet on which the toner image is formed.