JP2002023433A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device where a good image can be obtained by stabilizing the image density by carrying out an accurate detection of attached quantity of the toner with a simple constitution. SOLUTION: In the image forming device provided with an optical sensor 70 measuring the attached quantity of the toner by having a reference toner image that is formed on a transfer belt 49a irradiated with light and then detecting the light quantity of specular reflection and adjusting the image density based on a measured value of the optical sensor 70, a surface of the transfer belt 49a is provided with glossiness that is >= than specified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a laser beam printer, and a facsimile, and more particularly to an image density control method.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using this type of electrophotography, as a means for obtaining an appropriate image density, a reference toner image (hereinafter referred to as a toner patch) is formed on a toner carrier such as a photoconductor. Description) is formed, the amount of toner patch attached is measured by optical means, and based on the measured values, the charging potential, exposure intensity, developing bias potential, transfer voltage, toner supply amount (in the case of a two-component developer) There is a method of appropriately controlling the image density by giving feedback to parameters that affect the image density, such as.

As an optical means for measuring the amount of adhered toner, light is emitted from a light emitting element such as an LED to a toner patch formed on a toner carrier, and depends on the amount of adhered toner on the toner patch. Means using a sensor that detects the amount of reflected light with a light receiving element such as a photodiode is used.

As a sensor for detecting the amount of reflected light, an optical system as shown in FIG. 2 is used to detect the amount of specular reflection from the surface of the toner carrier which decreases with an increase in the amount of adhered toner. There is a type of optical system that detects the amount of irregularly reflected light from the toner itself, which decreases in the case of black toner and increases in the case of color toner as the amount of toner adhered increases.

Recently, stations for forming images of a plurality of colors such as yellow, magenta, cyan, and black have been arranged in a row for the purpose of high-speed output of color images.
A so-called tandem type image forming apparatus has been proposed and implemented in which a transfer medium such as paper is conveyed by a transfer belt and toner images of respective colors are successively transferred.

In the case of such a system, Japanese Patent Application Laid-Open No. 63-14 / 1988
As proposed in 7177, it is better to transfer the toner patches formed at each station onto a transfer belt and measure the toner adhesion density of the toner patches of multiple colors with one sensor facing the transfer belt. This is advantageous in terms of cost because only one sensor is required.

Also, in the case of an image forming apparatus of a system in which a plurality of color toner images are transferred to an intermediate transfer member and the toner images are collectively transferred onto a transfer medium, a toner patch is formed on the intermediate transfer member.
A method of detecting the toner adhesion amount by one sensor has been proposed and implemented.

[0008]

However, in the case where a configuration is adopted in which toner patches of a plurality of colors are formed on a transfer belt or an intermediate transfer member as described above and the amount of adhesion is detected by a single sensor. However, the following problems have occurred.

As the material of the transfer belt or the intermediate transfer member, a material such as polyimide, polycarbonate, or PET is used. Adjustments within the range may be used. To adjust the resistance value, for example, carbon, which is a conductive substance, is used.

As described above, when a black toner patch containing carbon is formed on a transfer belt to which carbon as a resistance value adjusting substance is added or a medium such as an intermediate transfer member, both patches have the same light absorption band. Therefore, LED light (near infrared light), which is a light emitting element of the sensor, is absorbed together, and it is difficult to accurately detect the amount of toner adhesion.

[0011] Such a problem is caused by the use of a sensor that detects the amount of irregularly reflected light as the sensor, or the use of a sensor that detects the amount of specularly reflected light as the sensor, such as a transfer belt or an intermediate transfer member. The use of a medium having a low glossiness on the medium surface becomes remarkable. Because black toner hardly generates diffuse reflection because it absorbs LED light,
In addition, a medium having a low glossiness on the surface hardly causes regular reflection, and in both cases, the amount of light incident on the light receiving element is extremely small, so that the detection value is reduced as a whole.

In order to solve such a problem, conventionally, the color of the surface of a transfer belt or a part of an intermediate transfer member is changed for measuring a black toner patch, or when a black toner patch is measured. Methods for measuring a patch, such as using two different types of sensors, have been proposed, but each of these methods is disadvantageous in cost due to the complicated configuration.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to enable accurate detection of the amount of applied toner with a simple configuration.
An object of the present invention is to provide an image forming apparatus capable of stabilizing an image density and obtaining a good image.

[0014]

In order to achieve the above object, according to the present invention, a reference toner image formed on a toner carrier is irradiated with light and the amount of specular reflection is detected. In an image forming apparatus including a measuring unit for measuring an amount of adhesion, and adjusting an image density based on a measurement value of the measuring unit, the toner carrier includes at least one kind of toner used in the image forming apparatus. The toner carrier contains a substance having the same light absorption band as that of the toner, and the surface of the toner carrier has a glossiness of a predetermined level or more.

Therefore, even when both the toner carrier and the toner contain a substance having the same light absorption band, a sufficient regular reflection can be generated on the surface of the toner carrier, so that a simple configuration and high accuracy can be obtained. The toner adhesion amount of the reference toner image can be measured.

The glossiness of the surface of the toner carrier is 50 or more,
When it is 98 or less, more regular reflection can be generated on the surface of the toner carrying member, and the amount of attached toner can be measured more accurately.

The present invention is characterized in that the amount of toner adhered to a plurality of reference toner images of toner is measured by one measuring means provided opposite to the toner carrier.

Since the amount of toner adhesion of a plurality of toners is measured by one measuring means, the configuration is simplified. Further, even when any of the toners has the same light absorption band as the toner carrier, sufficient regular reflection can be generated on the surface of the toner carrier, and the toner adhesion amount of a plurality of toners can be reduced with a simple configuration. Measurement can be performed with high accuracy.

The toner carrier is preferably a transfer belt for conveying a transfer medium.

The toner carrier is preferably an intermediate transfer belt.

The toner carrier is preferably an intermediate transfer drum.

[0022]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The materials, shapes, relative arrangements, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
1 is a schematic configuration diagram of an image forming apparatus according to an embodiment.
In the image forming apparatus according to the present embodiment, the first, second, third, and fourth image forming units 4Y, 4M, 4C, and 4K are arranged in a line so that a full-color image can be formed at high speed. ing. The signs Y, M, C, and K indicate that yellow, magenta, cyan, and black images are formed, respectively.

An outline of the configuration and processing of the image forming unit will be described below.

The photosensitive drum 41Y is rotatably supported in the direction of the arrow shown in FIG. 1. After the photosensitive drum 41Y is uniformly charged by the primary charger 46Y, for example, a laser beam exposure device or the like is used. A light image corresponding to the yellow portion, which has been color-separated by the exposing unit 47Y, is irradiated to form an electrostatic latent image on the peripheral surface of the photosensitive drum 41Y.

Thereafter, the electrostatic latent image is developed by the developing device 9Y to become a visualized toner image. In this embodiment, a two-component developer composed of a non-magnetic toner and a magnetic carrier is used.

The yellow toner image formed by the image forming section 4Y is transferred by the transfer device 49Y onto a recording medium such as paper conveyed by the transfer belt 49a. Further, the toner remaining on the photosensitive drum 41Y without being completely transferred is removed and collected by the cleaning device 48Y.

Similarly, the image forming units 4M, 4C, 4K
, Toner images of respective colors are formed, and are successively superimposed and transferred onto a recording medium.

The transfer belt 49a is made of polycarbonate. Carbon is added to the transfer belt 49a, and the volume resistivity is adjusted to about 10 ¹³ Ω · m, whereby good transfer is obtained. The recording medium on which the toner image has been transferred is further conveyed by the transfer belt 49a, and is pressed and heated by the fixing device 51, whereby a full-color permanent image is obtained.

In the image forming apparatus using the multicolor toner as in the present embodiment, in order to obtain a high-quality full-color image, it is required that the image density of each color is appropriate and stable. Therefore, in addition to the normal image forming mode as described above, a mode for appropriately setting the image density of each color (hereinafter, referred to as a patch detection mode) is executed.

In the patch detection mode, the photosensitive drum 41C,
An electrostatic latent image of a patch pattern having a certain area is formed on 41M, 41Y, and 41K, developed by a predetermined developing contrast voltage, and then transferred to a transfer belt 49a serving as a toner carrier for each color. A toner patch as a toner image is formed.

The amount of toner adhered to the toner patch after the transfer is determined by one optical sensor 7 facing the transfer belt 49a.
Measure at 0. As shown in FIG. 2, the optical sensor 70 includes an LED 11 (center wavelength = 970
nm) and a photodiode 12 serving as a light receiving element, and irradiates the toner patch 20 with light from the LED,
The optical system is such that the photodiode 12 detects the amount of regular reflection light corresponding to the amount of toner attached to the toner patch 20.

That is, as the amount of toner adhered to the toner patch increases, the amount of specular reflection decreases, and the amount of light incident on the photodiode 12 decreases. Here, if a sensor of the type that detects the amount of diffusely reflected light as shown in FIG. 3 is used, accurate detection of the amount of adhered toner cannot be performed as described above.

The light incident on the photodiode 12 generates a current depending on the amount of the light, converts the current into a voltage, amplifies the voltage, and amplifies the output value Vsig. Is obtained. This output value V
sig. Is the reference value Vint. Compared with Vsig. > Vint. In the case of, it is determined that the image density is low, and feedback is applied to an arbitrary parameter in a direction to increase the image density. Conversely, Vsi
g. <Vint. In the case of, it is determined that the image density is high,
Feedback is applied to an arbitrary parameter in the direction of decreasing the image density.

The parameters affecting the image density include a charging potential, an exposure intensity, a developing bias potential, a transfer voltage, and a toner supply amount. For example, toner supply to the two-component developer used in the present embodiment is performed. The process of applying feedback to the quantity will be described with reference to FIG.

When the patch detection mode is started, first, a toner patch is formed on the transfer belt 49a (step S).
1). Next, the optical sensor 70 irradiates the toner patch with LED light, and outputs an output value Vsig. Is obtained (step S2). Step S
3, the output value Vsig. And the reference value Vint. Compare with Vsig. Is Vint.
If it is larger, it is determined that the image density is low, and Vs
ig. And Vint. The necessary toner supply amount is calculated from the difference (step S4), and toner supply is performed (step S5). The toner patch after the density measurement is removed by a transfer belt cleaner (not shown) (step S6), and the process returns to the normal image forming mode.

Further, Vsig. Is Vint. If it is smaller, it is determined that the image density is high, the toner patch is removed without replenishing the toner, and the process returns to the normal image forming mode.

The above processing is performed for each color toner, and the image density of each color is adjusted to an appropriate density.

The patch detection mode is executed as described above, but the transfer belt 49a used in this embodiment is used.
In order to obtain a sufficient amount of specular reflection, the surface must have a certain degree of glossiness.

When a transfer belt having a low glossiness on the surface is used, the specular reflection does not sufficiently occur on the surface, so that the detection value of the sensor as a whole decreases and the S / N (signal /
Noise).

However, when a transfer belt having a high glossiness on the surface is used, specular reflection is sufficiently generated on the surface, and by detecting the amount of specular reflection, it is possible to detect the amount of adhered toner of each color including black toner. Become.

Therefore, the glossiness of the transfer belt surface must be higher than a predetermined value. Here, the predetermined value is a gloss level that generates a sufficient amount of specular reflection light enough to perform good toner adhesion amount detection,
The value depends on the material and material of the surface of the transfer belt, or the configuration such as the amount of irradiation light and the resolution of the sensor.

In the configuration of the present embodiment, as a result of examination, it was necessary to set the glossiness of the surface of the transfer belt to be in a range of 50 or more and 98 or less in order to detect a good toner adhesion amount. The reason for setting the upper limit of the glossiness here is that in order to achieve a higher glossiness, the material of the transfer belt must be changed to a material that does not satisfy the performance as a transfer belt, and This is because it is not suitable. To measure glossiness, a gloss meter (Model, manufactured by Tokyo Denshoku Co., Ltd.)
(TC-108DP / A) at a measurement angle of 20 °. The value of the glossiness here is 1.56 for the refractive index.
The glossiness of the glass plate surface of No. 7 is set as 100 based on the glossiness,
It is expressed as a ratio to this.

An example of the study is described below. The graph shown by the solid line in FIG. 5 shows the output value Vsig. Of the sensor with respect to the toner adhesion amount of the black toner patch formed on the transfer belt having the glossiness of 90.2. Is shown. It can be seen that the output value of the sensor greatly changes with the change in the amount of the adhered black toner.

On the other hand, the output value Vsig. Of the sensor with respect to the toner adhesion amount of the black toner patch formed on the transfer belt having the glossiness of 20.3. Is the graph of FIG. In this case, the output value is small overall because specular reflection hardly occurs on the surface of the transfer belt, and the output value of the sensor hardly changes even if the amount of toner adhered on the transfer belt changes. It turns out that measurement has become difficult.

In addition, a belt having a gloss of 49.0 and a belt having a gloss of 44.7 were examined.
For the belt having a gloss of 49.0, the toner adhesion amount was successfully measured. On the other hand, for the belt having a gloss of 44.7, the S / N deteriorated rapidly and the belt having a gloss of 20.3 was obtained. Since it was difficult to accurately measure the amount of adhered toner, the lower limit of the appropriate gloss was set to 50 or more.

As described above, in order to detect the amount of toner adhering to the transfer belt containing a substance having the same light absorption band as that of the toner, the glossiness of the surface is high, preferably 5
Zero or more transfer belts must be used.

As described above, in the image forming apparatus which performs image density control in the patch detection mode, by adopting the configuration of the present embodiment, the transfer belt including the substance having the same light absorption band as the toner is formed on the transfer belt. Even if a toner patch is formed, the amount of toner adhered can be accurately detected with a simple configuration, so that high-precision image density control can be performed, and a high-quality image forming apparatus can be provided. .

(Second Embodiment) FIG. 7 shows a second embodiment of the present invention.
1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. In this embodiment, the toner images formed by the image forming units 4Y, 4M, 4C, and 4K are temporarily transferred to the intermediate transfer belt 49b, and then collectively transferred onto a recording medium such as paper by the secondary transfer roller 30. It is configured to be transferred.

The other configuration and operation are the same as those of the first embodiment. Therefore, the same components are denoted by the same reference numerals and description thereof will be omitted.

When the intermediate transfer belt 49b is used as described above, the fixing device 51 can be disposed below the image forming section, so that the width of the image forming apparatus main body can be reduced.
In addition, since each image forming unit does not come into contact with a recording medium such as paper, there is an advantage that there is no need to be affected by foreign matter such as paper dust.

The optical sensor 70 is disposed at a position facing the upper surface of the intermediate transfer belt 49b as shown in FIG. The contamination of the sensor is prevented, and a decrease in the sensor output due to the contamination can be suppressed.

The intermediate transfer belt 49b used here was prepared by adding carbon to polyimide and having a volume resistivity of about 10 ¹⁰ Ω ·
By adjusting to m, good transfer is obtained.

In this case, similarly to the first embodiment, a sufficient amount of regular reflection light can be obtained by using the intermediate transfer belt 49b having a surface glossiness of 50 or more. The amount of adhered toner could be accurately detected. Also in the present embodiment, the sensor output value Vsig. The image density is appropriately controlled by giving feedback to a parameter that affects the image density, for example, the toner replenishment amount, based on the image density.

As described above, also in the image forming apparatus in which the toner patch is formed on the intermediate transfer belt to control the image density, the intermediate transfer belt having a high surface gloss is used similarly to the first embodiment. As a result, the toner adhesion amount can be accurately detected with a simple configuration, so that high-precision image density control can be performed, and a high-quality image forming apparatus can be provided.

(Third Embodiment) FIG. 8 shows a third embodiment of the present invention.
1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. In the present embodiment, a black developing device 90K and yellow, magenta, and cyan developing devices 90Y, 90M, and 90C are rotatably provided around one photosensitive drum 41, and are developed on the photosensitive drum 41. After the toner images of each color are sequentially transferred onto the intermediate transfer drum 49c, they are collectively transferred onto a recording medium such as paper.

The outline of image formation in this embodiment will be described below.

The photosensitive drum 41 is rotatably supported in a direction indicated by an arrow shown in FIG. 8, and is uniformly charged by a primary charger (not shown). The exposure unit 47 first irradiates a light image corresponding to the yellow portion obtained by color separation, and forms an electrostatic latent image corresponding to the yellow portion on the peripheral surface of the photosensitive drum 41. At this time, a developing device 90Y is located at a position facing the photosensitive drum 41, whereby the latent image in the yellow portion is developed with yellow toner. Also in the present embodiment, a two-component developer composed of a non-magnetic toner and a magnetic carrier is used.

Next, the developed yellow toner image is transferred onto the intermediate transfer drum 49c. At the same time, the photosensitive drum 41 is uniformly charged again by the primary charger.
This time, a light image corresponding to the magenta portion is irradiated, and an electrostatic latent image corresponding to the magenta portion is formed on the peripheral surface of the photosensitive drum 41.
At the time of development, the rotating device rotates, so that the developing device 90M faces the photosensitive drum 41, and the magenta portion is developed. The magenta toner image is superimposed and transferred on the previously transferred yellow toner image on the intermediate transfer drum 49c.

After the cyan and black toner images are sequentially transferred onto the intermediate transfer drum 49c in this manner,
All colors are collectively transferred onto a transfer medium such as paper, and are further pressed and heated by the fixing device 51 to obtain a full-color permanent image.

An advantage of adopting the configuration of the present embodiment is that even in an image forming apparatus using only one photosensitive drum, the transfer path of a recording medium such as paper can be made linear, so that various transfer operations can be performed. Media can be used.

The surface of the intermediate transfer drum 49c is made of polyimide, and good transfer is obtained by adding carbon to the surface and adjusting the volume resistivity to about 10 ⁸ Ω · m.

In this case, similarly to the first or second embodiment, the intermediate transfer drum 49 having a surface glossiness of 50 or more is provided.
By using c, a sufficient amount of regular reflection light was obtained, and in the patch detection mode, the amount of toner adhered to the toner patch could be accurately detected.

Also in the present embodiment, the sensor output value Vsig. The image density is appropriately controlled by applying feedback to parameters that affect the image density based on the image density.

As described above, also in the image forming apparatus in which the toner density is controlled by forming the toner patch on the intermediate transfer drum, similarly to the first or second embodiment, the image forming apparatus having the high glossiness on the surface is also used. By using the transfer drum, the amount of applied toner can be accurately detected with a simple configuration, so that high-precision image density control can be performed, and a high-quality image forming apparatus can be provided.

(Other Embodiments) In the first to third embodiments described above, all are described as full-color image forming apparatuses. However, a monochrome image forming apparatus using only black toner is used. Needless to say, this can also be applied.

Although a two-component developer has been described as a developer used in the image forming apparatus of each embodiment, even when a one-component developer composed of only a magnetic toner or a non-magnetic toner is used. Of course, it can be applied.

[0068]

As described above, according to the present invention, since the surface of the toner carrier is constituted so as to have a glossiness of a predetermined level or more, the toner containing a substance having the same light absorption band as the toner used. Even when using the carrier, sufficient regular reflection can be generated on the surface of the toner carrier, and the amount of toner attached to the reference toner image formed on the toner carrier can be accurately measured. Highly accurate image density control is possible with a simple configuration, and a high quality image forming apparatus can be provided.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram of an optical sensor that detects the amount of specular reflection.

FIG. 3 is a schematic configuration diagram of an optical sensor that detects the amount of diffusely reflected light.

FIG. 4 is a diagram showing a flow of processing for increasing the toner supply amount and adjusting the image density.

FIG. 5 is a graph showing an output value of a sensor with respect to a toner adhesion amount of a black toner patch formed on a transfer belt having a glossiness of 90.2.

FIG. 6 is a graph showing a sensor output value with respect to a toner adhesion amount of a black toner patch formed on a transfer belt having a gloss level of 20.3.

FIG. 7 is a schematic configuration diagram of an image forming apparatus according to a second embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of an image forming apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 LED 12 Photodiode 20 Toner patch 30 Secondary transfer roller 4Y, 4M, 4C, 4K Image forming part 41, 41Y, 41M, 41C, 41K Photosensitive drum 46Y, 46M, 46C, 46K Primary charger 47, 47Y, 47M, 47C, 47K Exposure means 48Y, 48M, 48C, 48K Cleaning device 49Y, 49M, 49C, 49K Transfer device 49a Transfer belt 49b Intermediate transfer belt 49c Intermediate transfer drum 49c Transfer drum 51 Fixing device 70 Optical sensors 9Y, 9M, 9C, 9K developing device 90Y, 90M, 90C, 90K developing device

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G03G 15/16 G03G 15/16 F term (Reference) 2G059 AA01 BB09 CC20 EE02 GG02 HH01 KK01 2H027 DA09 DE02 DE07 EA01 EA02 EA03 EA05 EA05 EA06 EC03 EC07 2H030 AA02 BB36 BB42 2H032 BA08 BA09 BA18 BA23 CA02 CA15

Claims (6)

[Claims] 1. A measuring device for irradiating a reference toner image formed on a toner carrier with light and detecting the amount of specular reflection of the reference toner image to measure the amount of adhered toner, based on the measured value of the measuring device In the image forming apparatus for adjusting an image density, the toner carrier includes a substance having the same light absorption band as at least one kind of toner among toners used in the image forming apparatus, and the toner carrier An image forming apparatus, wherein a surface of a body has a glossiness of a predetermined level or more. 2. The image forming apparatus according to claim 1, wherein the glossiness of the surface of the toner carrier is 50 or more and 98 or less. 3. An image forming apparatus according to claim 1, further comprising:
3. The image forming apparatus according to claim 1, wherein the measuring unit measures a toner adhesion amount for a plurality of reference toner images. 4. The image forming apparatus according to claim 1, wherein the toner carrier is a transfer belt for conveying a transfer medium. 5. The image forming apparatus according to claim 1, wherein said toner carrier is an intermediate transfer belt. 6. An image forming apparatus according to claim 1, wherein said toner carrier is an intermediate transfer drum.