JP2003149952A - Transfer carrier and image forming device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size and cost of an image forming device by providing a reference patch in the image formation area of a transfer carrier without providing a dedicated mechanism for the correction of the sensitivity of the photo-sensor, thereby minimizing the width of the transfer carrier. SOLUTION: The transfer carrier is used in the image forming device that forms a toner image on a photoreceptor according to image data, transfers the toner image to a recording material and controls the process of toner image formation and the process of transfer by detecting the density of a toner image by a photo-sensor. The transfer carrier operates in such a manner that a toner image formed on the photoreceptor is directly or indirectly transferred to a recording material. In the transfer carrier, a reference patch for correcting the sensitivity of the photo-sensor is provided in an area where a transfer material or a toner image is held.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer carrier and an image forming apparatus including the transfer carrier, and more specifically, it is used for an image forming apparatus such as a laser printer, a digital copying machine, a facsimile, and is formed on a photoconductor. The present invention relates to a transfer carrier that directly or indirectly transfers the formed toner image to a recording material, and an image forming apparatus including the transfer carrier.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus used as a laser printer, a digital copying machine, a facsimile, etc., an electrostatic latent image corresponding to image data is formed on a drum-shaped photosensitive member, and the electrostatic latent image is formed. Develop to obtain a toner image. Then, the toner image formed on the photoconductor is transferred to a recording material (mainly paper is used, but it may be other than paper, so called a recording material) held on a belt-shaped transfer carrier. ing.

In such an image forming apparatus, since an image is formed by using electrostatic force, the characteristics of the image change depending on the usage of each process section and the surrounding environmental conditions, and the density of the formed image tends to change. .

Therefore, there is provided an adjusting step for adjusting the control conditions (charge output, developing bias, transfer bias, etc.) of each part of the image forming section, and the adjusting step is executed in accordance with certain conditions to always obtain an appropriate image density. I am allowed to do so.

Specifically, in this adjusting step, various patch images for density test are formed on the transfer carrier at a predetermined timing, and the density of the patch image is detected by an optical sensor and detected. The control condition of each part of the image forming unit is adjusted based on the density to control the image forming process.

However, the performance of the optical sensor for detecting the density of the patch image is deteriorated due to stains and aging, and the sensitivity characteristic is changed depending on temperature. Therefore, it is necessary to correct the sensitivity (may be referred to as compensation or calibration).

As a method of correcting the sensitivity of this optical sensor,
A method is known in which another optical sensor is made to read and store a reference patch (usually a white or gray patch) and the sensitivity is corrected by the difference between the stored reference patch and the patch image for density test. ing.

Further, as described in JP-A-5-322760, a movable plate on which a reference patch is printed is provided, and a density test patch image and the reference patch are switched and read by an optical sensor. There are known methods of correcting the sensitivity based on the difference between the two, and by applying these methods, the sensitivity of the optical sensor is corrected and an appropriate image density is maintained.

[0009]

By the way, such sensitivity correction of the optical sensor is performed when adjusting the image density, that is, the weather or environment changes, or the deterioration of the photoconductor or the consumables such as the developer. Alternatively, it is carried out based on the period of neglect, etc., and the number of times of execution is at most several times a day.

As described above, for the sensitivity correction operation which is performed a small number of times, providing the optical sensor dedicated to the sensitivity correction or providing the movable plate on which the reference patch is printed leads to an increase in the number of parts, which leads to the increase of the number of parts of the image forming apparatus. It is a factor that raises the manufacturing cost.

Further, when the reference patch is provided on the transfer carrier, if the reference patch is provided outside the image forming area, the width of the transfer carrier becomes large and the apparatus becomes large.

The present invention has been made in consideration of such circumstances, and a reference patch is provided in the image forming area of the transfer carrier without providing a dedicated mechanism for correcting the sensitivity of the optical sensor. The object of the present invention is to reduce the size and cost of the image forming apparatus by making the transfer carrier the minimum necessary width.

[0013]

According to the present invention, a toner image corresponding to image data is formed on a photoconductor, the toner image is transferred to a recording material, and the density of the toner image is detected by an optical sensor. A transfer carrier used in an image forming apparatus configured to control a process of forming and transferring a toner image, which operates to directly or indirectly transfer a toner image formed on a photoconductor to a recording material. At the same time, the transfer carrier is provided with a reference patch for correcting the sensitivity of the optical sensor in the area for carrying the recording material or the toner image.

The present invention also provides a photoconductor on which a toner image corresponding to image data is formed, and a transfer carrier for directly or indirectly transferring the toner image formed on the photoconductor to a recording material. An image forming apparatus comprising: an optical sensor for detecting a density of a toner image on a transfer carrier; and a control unit for controlling a process of forming and transferring a toner image based on the detected density of the toner image, In the image forming apparatus, the transfer carrier has a reference patch for correcting the sensitivity of the optical sensor in a region that carries a recording material or a toner image.

According to the present invention, the transfer carrier has the reference patch for correcting the sensitivity of the optical sensor in the area for carrying the recording material or the toner image. When the is used in the image forming apparatus, a dedicated mechanism for correcting the sensitivity of the optical sensor is not required, and the cost of the image forming apparatus can be reduced. Further, the width of the transfer carrier can be made as narrow as necessary, and the image forming apparatus can be downsized.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the transfer carrier is
It may be composed of a belt base material that operates to directly or indirectly transfer the toner image formed on the photoconductor onto a recording material (paper), for example, a belt base material such as a transfer conveyance belt or an intermediate transfer belt. . The transfer carrier is provided with a reference patch for correcting the sensitivity of the optical sensor in the area where the recording material or the toner image is carried.

It is desirable that the belt substrate has a colorless and transparent coat layer formed on the entire surface including the reference patch. It is desirable that this coat layer is formed so as to cover the entire reference patch and be thicker than the thickness of the reference patch and thinner than the thickness of the belt base material so that a step is not generated in the portion of the reference patch. It is possible to prevent the reference patch from being rubbed by a cleaning member or the like and largely changing its state, and it is possible to eliminate the surface step of the transfer carrier due to the edge of the reference patch, which enables smooth image transfer. .

Further, it is desirable that the volume resistance value of the reference patch portion and the other portion of the belt base material are substantially the same, so that the transfer when the image is transferred to the transfer carrier or the recording material. The unevenness can be eliminated.

As the belt substrate, PC (polycarbonate), PVDF (polyvinylidene fluoride), PTFE
(Polytetrafluoroethylene polymer), polyimide,
Examples thereof include materials such as CR rubber (chloroprene rubber), EPDM (ethylene propylene diene copolymer rubber) and urethane rubber. The thickness of the belt base material may be about 80 to 500 μm which is usually used in the art, and in the case of a rubber type, it is desirable to use a thick one. The material of the belt base material has a volume resistance value of 10 ¹⁰
It is desirable to use a material having a range of -10 ¹³ Ωcm.
In addition, it is desirable to use a non-transparent material so that the irradiation light from the light emitting portion of the optical sensor is difficult to transmit.

As the material of the coat layer, fluororesin which is a fluoropolymer material, fluororubber, or transparent urethane can be used. Examples of the fluororesin include PTFE (polytetrafluoroethylene polymer). As the fluororubber, for example, FKM
(Vinylidene fluoride fluororubber). The coat layer is preferably formed with a thickness in the range of 5 to 30 μm.

The reference patch can be formed by applying a conventionally known ink used for printing on a belt base material. As the ink, white or gray ink can be used. The thickness of the reference patch is not particularly limited as long as it is thinner than the coat layer. However, the minimum thickness is required to stably and sufficiently reflect the irradiation light from the light emitting portion of the optical sensor to the light receiving portion. Therefore, it is desirable that the thickness of the reference patch is not less than this minimum thickness and is within a range in which the smoothness of the surface of the coat layer is not impaired. It is desirable to form it with a film thickness.

In the transfer carrier of the present invention and the image forming apparatus provided with the transfer carrier, the belt base material is a conveyor belt that carries a recording material and transfers the toner image on the photoconductor to the recording material.
An image of a so-called intermediate transfer type, which is composed of a so-called direct transfer type image forming apparatus and a transfer belt in which a belt base material primarily transfers a toner image on a photoconductor onto a surface and secondarily transfers the toner image onto a recording material. The present invention can be applied to any image forming apparatus including the forming apparatus.

The present invention will be described in detail below based on the embodiments shown in the drawings. The present invention is not limited to this, and various modifications can be made.

FIG. 1 is an explanatory diagram showing the configuration of an embodiment in which the image forming apparatus of the present invention is applied to a digital color copying machine. The digital color copying machine is provided with a document table 111 and an operation panel on the upper surface, and an image reading section 11 is provided inside.
0 and the image forming unit 210 are provided. The upper surface of the document table 111 is supported in an openable and closable manner with respect to the document table 111, and has a predetermined positional relationship with the surface of the document table 111 and a double-sided automatic document feeder (RADF: Reve
rsing Automatic Document Feeder) 112 is attached.

The double-sided automatic document feeder 112 first conveys the document so that one side of the document faces the image reading section 110 at a predetermined position of the document table 111, and the image reading on this one side is completed. After that, the document is inverted so that the other surface faces the image reading unit 110 at a predetermined position of the document table 111,
It is designed to be transported toward. Then, the double-sided automatic document feeder 112 discharges this document after the double-sided image reading of one document is completed, and executes the double-sided conveyance operation for the next document. The above-described operation of conveying the document and inverting the front and back is controlled in relation to the operation of the entire copying machine.

The image reading unit 110 is arranged below the document table 111 in order to read the image of the document conveyed onto the document table 111 by the double-sided automatic document feeder 112. The image reading unit 110 is provided on the document table 11
A document scanning body 11 that reciprocates in parallel along the lower surface of the document 1.
3, 114, an optical lens 115, and a CCD line sensor 116 which is a photoelectric conversion element.

The document scanning bodies 113 and 114 are composed of a first scanning unit 113 and a second scanning unit 114. The first scanning unit 113 has an exposure lamp that exposes the image surface of the original document and a first mirror that deflects the reflected light image from the original document in a predetermined direction, and is fixed with respect to the lower surface of the original table 111. While reciprocating, the reciprocating movement is performed in parallel at a predetermined scanning speed. The second scanning unit 114 has second and third mirrors that further deflect the reflected light image from the document deflected by the first mirror of the first scanning unit 113 toward a predetermined direction. The first scanning unit 113 reciprocates in parallel while maintaining a constant speed relationship.

The optical lens 115 reduces the reflected light image from the document deflected by the third mirror of the second scanning unit 114, and the reduced light image is reflected by the CCD line sensor 11.
The image is formed at a predetermined position on 6.

The CCD line sensor 116 sequentially photoelectrically converts the formed light image and outputs it as an electric signal. The CCD line sensor 116 reads a monochrome image or a color image, and R (red), G (green), B (blue)
Is a three-line color CCD capable of outputting line data separated into respective color components. The document image information converted into an electric signal by the CCD line sensor 116 is further transferred to an image processing unit (not shown) and subjected to predetermined image data processing.

Next, the structure of the image forming unit 210 and the structure of each unit related to the image forming unit 210 will be described.
Below the image forming unit 210, a paper feeding mechanism 211 is provided, which separates the sheets (recording materials) P stacked and accommodated in the paper tray one by one and supplies them toward the image forming unit 210.

The sheets P separated and supplied one by one are paired with a pair of registration rollers 2 arranged in front of the image forming section 210.
12 controls the timing, and the image forming unit 210
Be transported to. When double-sided copying is performed, the sheet P having an image formed on one side is re-supplied and conveyed to the image forming unit 210 at the same timing as the image formation of the image forming unit 210.

A transfer / transport belt mechanism 213 is arranged below the image forming section 210. The transfer / transport belt mechanism 213 is configured such that the transfer / transport belt 2 is stretched between the drive roller 214 and the driven roller 215 so as to extend substantially in parallel.
The sheet P is electrostatically attracted to the sheet 16 and conveyed. Further, the patch image detection unit 300 is provided on the downstream side of the transfer / transport belt 216 and in the vicinity of the portion having the curvature of the transfer / transport belt 216. The patch image detection unit 300 is a unit that detects the densities of various patch images formed on the transfer / transport belt 216 for a density test. This patch image detection unit 30
Details of 0 will be described later.

An environment sensor 301 is provided on the downstream side of the transfer / transport belt 216. The environment sensor 301 detects the temperature and humidity inside the digital color copying machine, and is installed in the vicinity of the process unit where there is no sudden temperature change or humidity change.

Further, on the downstream side of the transfer / transport belt mechanism 213 in the paper transport path, a fixing device 217 for fixing the toner image transferred and formed on the paper P onto the paper P.
Are arranged. The paper P that has passed through the nip portion between the pair of fixing rollers of the fixing device 217 passes through the conveyance direction switching gate 218, and is discharged by the discharge roller 219 to the discharge tray 22 attached to the outer wall of the copying machine body.
Is discharged above zero.

The transport direction switching gate 218 is provided between the route for transporting the sheet P after fixing and the route for discharging the sheet P to the outside of the copying machine and the route for re-feeding the sheet P toward the image forming section 210. It selectively switches. The sheet P whose conveyance direction has been switched again toward the image forming unit 210 by the conveyance direction switching gate 218 is turned upside down through the switchback conveyance path 221, and then supplied again to the image forming unit 210.

Above the transfer / transport belt 216 in the image forming section 210, in the vicinity of the transfer / transport belt 216,
The first image forming station Pa, the second image forming station Pb, the third image forming station Pc, and the fourth image forming station Pd are arranged in parallel in order from the upstream side of the paper transport path.

The transfer / conveyance belt 216 is composed of the driving roller 21.
4, the paper P is frictionally driven in the direction indicated by the arrow Z, holds the paper P fed through the paper feeding mechanism 211 as described above, and sequentially conveys the paper P to the image forming stations Pa to Pd.

The image forming stations Pa to Pd have substantially the same structure. These image forming stations Pa, Pb, Pc, Pd are photoconductive drums 222a, 222b, 222 which are rotationally driven in the arrow F direction.
c and 222d, respectively.

Chargers 223a, 223b, 223c and 22 for uniformly charging the photoconductor drums 222a to 222d are provided around the photoconductor drums 222a to 222d.
3d and developing devices 224a, 22 for developing the electrostatic latent images formed on the photoconductor drums 222a to 222d, respectively.
4b, 224c, 224d and transfer dischargers 225a, 225b, 225c, 225d for transferring the developed toner images on the photosensitive drums 222a to 222d to the paper P.
And cleaning devices 226a, 226b, 2 for removing the toner remaining on the photosensitive drums 222a to 222d.
26c and 226d are the photosensitive drums 222a to 222.
They are sequentially arranged along the rotation direction of d.

Further, each of the photosensitive drums 222a to 222d
Above the above, laser beam scanner units 227a, 227b, 227c, 22 as optical writing units are provided.
7d are provided respectively. These laser beam scanner units 227a to 227d are a semiconductor laser element (not shown) that emits dot light modulated according to image data, and a polygon mirror for deflecting the laser beam from the semiconductor laser element in the main scanning direction. (Deflecting device) 240, an fθ lens 241 for forming an image of the laser beam deflected by the polygon mirror 240 on the surfaces of the photoconductor drums 222a to 222d, the mirror 242, and the like.
243 and the like.

Pixel signals corresponding to the black component image of the color original image are sent to the laser beam scanner unit 227a.
The laser beam scanner unit 227b has a pixel signal corresponding to the cyan color component image of the color original image, the laser beam scanner unit 227c has a pixel signal corresponding to the magenta color component image of the color original image, and the laser beam scanner unit 227d. Pixel signals corresponding to the yellow color component image of the color original image are input to each.

As a result, the electrostatic latent images corresponding to the color-converted original image information are converted into the respective photosensitive drums 222a to 222.
formed on d. The developing device 224a contains black toner, the developing device 224b contains cyan toner, the developing device 224c contains magenta toner, and the developing device 224d contains yellow toner. The electrostatic latent images on the photoconductor drums 222a to 222d are developed with the toners of the respective colors. As a result, the document image information color-converted by the image forming unit 210 is reproduced as a toner image of each color.

A paper suction (brush) charger 22 is provided between the first image forming station Pa and the paper feed mechanism 211.
8 is provided, and the paper suction charger 228 is
The surface of the transfer / transport belt 216 is charged, and
The sheet P supplied from the sheet feeding mechanism 211 is securely adsorbed onto the transfer / conveying belt 216, and the first image forming station Pa to the fourth image forming station Pd.
Transport without shifting.

The copying operation in this digital color copying machine is as follows. As the paper P, cut sheet-shaped paper is used. When the paper P is sent out from the paper feed cassette and fed into the guide of the paper feed transport path of the paper feed mechanism 211, the tip portion of the paper P is detected by a sensor (not shown). Based on the detection signal output from the pair of registration rollers 212, the registration rollers 212 temporarily stop.

Then, the paper P is sent onto the transfer / conveying belt 216 rotating in the direction of arrow Z at the timing of each of the image forming stations Pa to Pd. At this time, since the transfer / conveying belt 216 is charged to a predetermined level by the paper suction charging device 228 as described above, the paper P is stable while passing through the image forming stations Pa to Pd. Transported and supplied.

In each of the image forming stations Pa to Pd, a toner image of each color is formed on the paper P, and is superposed on the supporting surface of the paper P that is electrostatically attracted by the transfer and transport belt 216 and is transported. When the transfer of the image by the fourth image forming station Pd is completed, the paper P
Are sequentially peeled off from the transfer / transport belt 216 by the discharging discharging device from the leading end portion thereof and guided to the fixing device 217. Finally, the sheet P having the toner image fixed thereon is ejected onto the sheet ejection tray 220 from a sheet ejection port (not shown).

In the digital color copying machine having the above structure, the laser beam scanner unit 22 is used as the optical writing unit.
7a to 227d are used to scan and expose a laser beam to perform optical writing on the photosensitive drums 222a to 222d. However, as an optical writing unit,
Instead of the laser beam scanner unit, for example, an optical writing unit of an optical system (LED head) including a light emitting diode array and an imaging lens array may be used.

The LED head is smaller in size than the laser beam scanner unit and has no moving parts and is silent. Therefore, it can be preferably used in an image forming apparatus such as a tandem type digital color copying machine which requires a plurality of optical writing units.

FIG. 2 is a block diagram showing a control circuit for process control of the digital color copying machine. In the figure,
11 is a counter, 12 is a timer, 13 is an environment detection unit,
Reference numeral 14 is a toner density detecting portion arranged in the patch image detecting unit 300, 15 is a charging portion, 16 is a developing portion, 17 is a transfer portion, 18 is a writing portion, 19 is an image processing portion, 20 is a fixing portion, 21. Is a paper transport unit, and 22 is a control unit. Control unit 2
2 controls the entire digital copying machine.

In the present digital color copying machine, the control conditions (charging output, developing bias, transfer bias, etc.) of each part of the image forming unit are adjusted at regular intervals so that an appropriate image density can always be obtained. Perform process control.

The process control may be performed every time the power is turned on, or at the time when the power is turned on, and thereafter, for example, every two hours (predetermined time). Further, in the case of performing based on the number of formed images, it may be performed every time the number of formed images reaches 200, for example. This timing can be arbitrarily determined based on the design concept of the digital color copying machine.

The process control is performed based on the measured value of the density of the patch image formed on the transfer / conveyance belt 216, the information detected by the environment detection unit 13, and the like. The operation of each part when performing process control will be described below.

The counter 11 includes the photosensitive drums 222a to 222a.
The number of rotations of 222d and / or the number of image formations is counted. The timer 12 counts the time until the process control is executed, is started after the process control is executed after the power is turned on, and is reset each time the process control is executed thereafter. The environment detection unit 13 detects the temperature and humidity inside the digital color copying machine by the environment sensor 301 and sends the detected temperature and humidity to the control unit 22.

The density detecting section 14 includes a black (achromatic color) optical sensor (A sensor) and a chromatic color optical sensor (B sensor).
The toner density of the patch image is detected by the two sensors, and the detected toner density is sent to the control unit 22.

During process control, the charging section 15 controls the grid bias voltage of the charging means (charging charger) based on the instruction from the control section 22, and controls the surface potential of the photosensitive drum. When the charging means is a contact type charging roller or the like, the voltage applied to the charging means is directly controlled to control the surface potential of the photosensitive drum.

During the process control, the developing section 16 controls the developing bias voltage of the developing roller on the basis of the instruction from the control section 22 so that the developing process can be performed with an appropriate density. The transfer unit 17 controls the control unit 22 during process control.
Based on this instruction, the transfer bias voltage of the transfer means (transfer discharger) of the high voltage power supply for transfer (not shown) is controlled.

In the process control, the writing unit 18 controls the laser beam scanner units 227a to 227d as optical writing units based on an instruction from the control unit 22. Specifically, since the optical writing unit of this digital copying machine is of the laser beam scanner type, it controls the light beam power of the laser light emitting diode and the lighting time for each pixel. When the optical writing unit is a light emitting element array head type such as an LED, the light emitting intensity of the light emitting element and the light emitting time for each pixel are controlled.

During the process control, the image processing section 19 changes the halftone gradation table used when forming an image having a halftone based on an instruction from the control section 22, and controls the γ curve of the image. And maintain good halftone image reproduction.

The fixing unit 20 drives the fixing device 217 based on the instruction of the control unit 22 to fix the toner image transferred and formed on the sheet onto the sheet. The paper transport unit 21 is
Based on an instruction from the control unit 22, the transfer / transport belt mechanism 213
Is controlled to convey the paper.

FIG. 3 is an explanatory view showing the structure of the transfer / transport belt, and FIG. 4 is an explanatory view showing the sectional state of the transfer / transport belt. In these figures, 1 is a belt base material, 2 is a reference patch, 3 is a coat layer, 4 is a paper carrying area (shown by diagonal lines), and 5 is an area where a maximum width paper is carried. W2 indicates the width of the belt base material 1, and W1 indicates the width of the carrying region in the belt base material 1. W3 is a comparative example and shows the width of the belt base material 1 when the reference patch 2a is provided outside the carrying area of the paper. In the figure, the transfer dischargers 225a, 225b, 225c, and 225d are omitted, and only the transfer / transport belt 216 and rollers are shown.

The transfer / transport belt 216 is formed of the belt base material 1. The belt base material 1 is provided with the reference patch 2 in the carrying region of the paper, and the coat layer 3 is coated on the whole. The coat layer 3 covers the entire reference patch 2 so that no step is formed at the reference patch 2.

In this embodiment, a PC (polycarbonate) having a thickness of 100 μm is used as the belt base material 1. The belt base material 1 is made of a non-transparent material so that the irradiation light from the light emitting portion of the optical sensor arranged in the patch image detection unit 300 is difficult to pass through. The volume resistance value of this belt base material is 10 ¹⁰ to 10 ¹³ Ωcm.

The coat layer 3 is made of a transparent material and has a thickness of 5
It is coated with μm. As the material of the coat layer 3, fluororesin, fluororubber, or transparent urethane is used. As the fluororesin, for example, PTFE (polytetrafluoroethylene polymer) can be applied. As the fluororubber, for example, FKM (vinylidene fluoride fluororubber) can be applied. Coat layer 3
Need not be formed to a thickness of 5 μm, and may be formed to a thickness in the range of 5 to 30 μm. When using the above materials,
The volume resistance value of the coat layer 3 is 10 ¹⁰ to 10 ¹⁵ Ωcm.

The reference patch 2 is formed by applying a conventionally known white printing ink on the belt base material 1 to a thickness of 1 to 2 μm. This thickness is such that the irradiation light from the light emitting portion of the photosensor arranged in the patch image detection unit 300 can be reflected to the light receiving portion in a stable and sufficient manner, and the flatness of the flat surface of the coat layer 3 is not impaired. Is. The volume resistance value of the reference patch 2 is about 10 ¹⁵ Ωcm. Therefore, in the belt base material, since the volume resistance values of the reference patch portion and the other portions are substantially the same, there is no transfer unevenness when the image is transferred to the recording material.

FIG. 5 is an explanatory diagram showing patch images formed during process control. As described above, in the patch image detection unit 300, the optical sensor including the light emitting unit and the light receiving unit, and the toner concentration detecting unit 14 that receives the output from the optical sensor can be arranged. The optical sensor includes an optical sensor for black (achromatic color) and an optical sensor for chromatic color, and these two sensors are mounted substantially parallel to each other on one substrate.

The shape of the patch image detecting portion 1a of the transfer / conveying belt 216 is a portion supported by the driving roller 214 having an outer diameter of φ15 mm. Therefore, the radius of curvature of the patch image detecting portion 1a is approximately 7.5 mm. Has become.

During the process control, the transfer / conveyance belt 2
Various patch images for the density test are directly formed on the surface of 16 at a predetermined timing. In FIG. 5, the patch image 6 is formed on the upstream side of the reference patch 2 in high density, medium density, and low density, but it may be formed separately from the reference patch 2, or in three. However, the density may be divided into four or more levels.

Further, FIG. 5 shows only the patch image for one color, but in the case of a color copying machine, high density for each color image forming station Pa, Pb, Pc, Pd, that is, for each color, The patch images 6 having different middle and low densities are formed.

Then, the toner density of the patch image 6 is detected by the toner density detector 14. At the time of this detection, for example, one patch image is sampled at about 10 points, and the density of the patch image is detected from the averaged value by cutting the upper and lower parts. The density of the patch image 6 detected in this way and the environmental conditions (temperature and humidity) detected by the environment detection unit 13
The control value of each process unit of each image forming station is determined based on Then, the charging unit 1 described above
5, the developing unit 16, the transfer unit 17, the writing unit 18, and the image processing unit 19 are controlled to appropriately adjust the image density.

Prior to the execution of the above process control, the sensitivity of the optical sensor in the patch image detection unit 300 is corrected (may be referred to as compensation or calibration).
I do.

In this optical sensor sensitivity correction, the density of the reference patch is detected by each optical sensor, and the gain of each optical sensor is adjusted so that the output upon detection is a preset output. This is done by adjusting the amount of light emitted from the light emitting portion of the optical sensor.

FIG. 6 is an explanatory diagram showing the construction of the digital color copying machine of the intermediate transfer type. In the example of FIG. 1, the sheet P is attracted to the transfer / conveying belt 216, and the image formed on the photoconductor drums 222a to 222d is printed on the sheet P.
The digital color copying machine of the method of transferring the image onto the sheet (direct transfer method) has been described. However, the image is once transferred onto the transfer / transport belt 216, and the image is retransferred onto the paper P, that is, a so-called intermediate transfer method digital color copying. The present invention can be effectively applied to a machine. The intermediate transfer type digital color copying machine will be described below.

This digital color copying machine has the same image forming station as compared with the digital color copying machine shown in FIG. That is, the first image forming station Pa, the second image forming station Pb, and the third image forming station Pa.
The image forming station Pc and the fourth image forming station Pd are the same in that they are sequentially arranged in parallel from the upstream side of the paper transport path. The difference lies in the transfer / transport belt mechanism 213 and the paper feeding mechanism 211. The differences will be described below.

An intermediate transfer belt mechanism 213a is arranged below the image forming section 210. The intermediate transfer belt mechanism 213a includes a driving roller 214a and a driven roller 215.
a and the intermediate transfer belt 216a stretched around the backup roller 317 are driven. A cleaning member 251 and a cleaning unit 252 are provided in contact with the lower side of the intermediate transfer belt 216a to remove the toner remaining on the intermediate transfer belt 216a.

Below the intermediate transfer belt mechanism 213a,
A paper feeding mechanism 211a is provided for separating the papers P stacked and stored in the paper tray one by one and supplying them to the secondary transfer / conveying belt unit 253. The sheets P separated and supplied one by one are fed to the secondary transfer conveyance belt unit 253.
Be transported in. The sheet of paper P is fed and conveyed in time with the image formation with the intermediate transfer belt 216a on which the image is formed, and the image is transferred from the intermediate transfer belt 216a to the sheet of paper P by the secondary transfer discharger 254.

A fixing device 21 for fixing the toner image re-transferred and formed on the paper P on the paper P on the downstream side of the secondary transfer / transport belt unit 253 in the paper transport path.
7 are arranged. The paper P that has passed through the nip portion between the pair of fixing rollers of the fixing device 217 is discharged by the discharge roller 219 onto the paper discharge tray 220 attached to the outer wall of the copying machine main body. In this digital color copying machine, the switchback transport path 221 as shown in FIG. 1 is not shown.

The copying operation in this digital color copying machine is as follows. The intermediate transfer belt 216a is frictionally driven in the direction indicated by the arrow Z by the driving roller 214a, and sequentially moves to the image forming stations Pa to Pd.

In each of the image stations Pa to Pd, the toner image of each color is directly formed on the intermediate transfer belt 216a and is superimposed on a predetermined position of the intermediate transfer belt 216a. When the transfer of the image by the fourth image station Pd is completed, the intermediate transfer belt 216a
The image transferred onto the secondary transfer conveyor belt unit 2
On the belt 52, the high voltage applied to the secondary transfer discharger 254 causes retransfer to the sheet P. The sheet P on which the image is retransferred is guided to the fixing device 217 by the secondary transfer conveyance belt unit 252. Finally, the sheet P having the toner image fixed thereon is ejected onto the sheet ejection tray 220 from a sheet ejection port (not shown).

In this digital color copying machine, the reference patch is formed on the intermediate transfer belt 216a. The reference patch material and forming method may be the same as those of the direct transfer type digital color copying machine described above. The same applies to the coat layer.

Structure of the patch image detection unit 300, process control method, and patch image detection unit 30
The method of correcting the sensitivity of the optical sensor within 0 is also the same as in the direct transfer type digital color copying machine.

In this way, by providing the reference patch for correcting the sensitivity of the optical sensor in the image transfer area of the transfer carrier such as the transfer / transport belt 216 and the intermediate transfer belt 216a onto the paper, The transfer carrier can be made to have a necessary minimum width without providing a dedicated mechanism for correcting the sensitivity of the sensor, and the image forming apparatus can be downsized and the cost can be reduced.

Further, since the colorless and transparent coat layer is provided on the surface of the transfer carrier, even if the reference patch is rubbed by a cleaning member or the like, the state of the reference patch is not significantly changed.

Then, since the coat layer was formed on the transfer carrier so as to cover the whole of the reference patch and have a film thickness thicker than that of the reference patch and thinner than that of the belt base material, the edge of the reference patch was formed. It is possible to prevent a step from being formed on the surface of the transfer carrier at a portion, and it is possible to perform good image transfer.

Further, since the volume resistance values of the reference patch portion and the other portions of the transfer carrier are substantially the same, there is no transfer unevenness when transferring an image to the transfer carrier or recording material. Various images can be transferred, and good quality image formation can be performed.

Since the recording material or the image is carried on the transfer carrier regardless of the position of the reference patch, as compared with the method of detecting the reference patch and forming an image in synchronization with the reference patch, It is possible to perform speedy image formation without waiting for a detection signal and without waiting for recording.

[0086]

According to the present invention, since the reference patch for correcting the sensitivity of the optical sensor is provided in the image transfer area of the transfer carrier onto the sheet, it is dedicated for correcting the sensitivity of the optical sensor. The transfer carrier can be made to have a necessary minimum width without providing the mechanism of (1), and the size and cost of the image forming apparatus can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an embodiment in which an image forming apparatus of the present invention is applied to a digital color copying machine.

FIG. 2 is a block diagram showing a control circuit for process control of the digital color copying machine of the embodiment.

FIG. 3 is an explanatory diagram showing a configuration of a transfer / transport belt of the digital color copying machine according to the embodiment.

FIG. 4 is an explanatory diagram showing a cross-sectional state of a transfer / conveying belt of the digital color copying machine according to the embodiment.

FIG. 5 is an explanatory diagram showing a patch image formed during process control of the digital color copying machine of the embodiment.

FIG. 6 is an explanatory diagram showing a configuration when the digital color copying machine is of an intermediate transfer type.

[Explanation of symbols]

1 Belt Base Material 1a Patch Image Detecting Point 2 Reference Patch 3 Coat Layer 4 Paper Carrying Area 5 Area with Maximum Paper Width 11 Counter 12 Timer 13 Environment Detection Section 14 Toner Density Detection Section 15 Charging Section 16 Development Part 17 Transfer part 18 Writing part 19 Image processing part 20 Fixing part 21 Paper transporting part 22 Control part 110 Image reading part 111 Document table 112 Double-sided automatic document feeder 113, 114 Document scanning body 115 Optical lens 116 CCD line sensor 210 image Forming Unit 211 Paper Feeding Mechanism 211a Paper Feeding Mechanism 213 Transfer Conveying Belt Mechanism 213a Intermediate Transfer Belt Mechanism 216 Transfer Conveying Belt 216a Intermediate Transfer Belt 217 Fixing Device 219 Discharging Roller 220 Discharging Tray 222a, 222b, 222c, 222d Photosensitive Drum 223a, 223b, 223c, 2 3d charger 224a, 224b, 224c, 224d developing device 225a, 225b, 225c, 225d transfer discharger 226a, 226b, 226c, 226d cleaning device 227a, 227b, 227c, 227d laser beam scanner unit 228 paper charger 251 Cleaning Member 252 Cleaning Unit 253 Secondary Transfer Conveying Belt Unit 254 Secondary Transfer Discharger 300 Patch Image Detection Unit 301 Environmental Sensor 317 Backup Roller P Paper Pa, Pb, Pc, Pd Image Forming Station W2 Belt Base Width W1 Belt Width W3 of the carrying area on the base material Width of the belt base material when the reference patch is provided outside the carrying area of the paper

Continued front page    (72) Inventor Koichi Yamauchi             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company (72) Inventor, Hiroshi Tachiki             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company (72) Inventor Toshio Yamanaka             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company F-term (reference) 2H027 DA09 DE02 DE07 DE09 EA03                       EB04 EC03                 2H200 FA17 FA19 GA12 GA23 GA34                       GA44 GA47 GB12 GB25 GB41                       HA02 HA12 HA28 HB03 HB12                       HB22 JA02 JA30 JB06 JB10                       JB43 JB46 JB50 JC03 JC07                       JC13 JC16 JC20 LA12 MB04                       PB17

Claims (7)

[Claims] 1. A toner image according to image data is formed on a photoconductor, and the toner image is transferred to a recording material.
A transfer carrier used in an image forming apparatus configured to control the process of forming and transferring a toner image by detecting the density of the toner image with an optical sensor, and directly transferring the toner image formed on the photoreceptor. Alternatively, a transfer carrier, which operates so as to indirectly transfer to a recording material, and which is provided with a reference patch for correcting the sensitivity of the optical sensor in the area for carrying the recording material or the toner image. 2. A photoconductor on which a toner image corresponding to image data is formed, a transfer carrier for directly or indirectly transferring the toner image formed on the photoconductor to a recording material, and a transfer carrier. An image forming apparatus comprising an optical sensor for detecting the density of an upper toner image and a control unit for controlling the process of forming and transferring the toner image based on the detected density of the toner image, wherein a transfer carrier is An image forming apparatus having a reference patch for correcting the sensitivity of the optical sensor in an area for carrying a recording material or a toner image. 3. The image forming apparatus according to claim 2, wherein the transfer carrier comprises a belt base material having a colorless and transparent coat layer formed on the surface thereof. 4. The image forming apparatus according to claim 3, wherein the belt base material has a coat layer thickness smaller than that of the belt base material and greater than that of the reference patch. 5. The image forming apparatus according to claim 3, wherein the belt base material has substantially the same volume resistance values in the reference patch portion and other portions. 6. The image forming apparatus according to claim 2, wherein the belt base material is a conveyance belt that carries a recording material and transfers the toner image on the photoconductor to the recording material. 7. The image forming apparatus according to claim 2, wherein the belt substrate is a transfer belt that primarily transfers the toner image on the photoconductor onto the surface and secondarily transfers the toner image onto a recording material.