JPH11174753A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device equipped with toner-concentration detection/ control means which accurately detect amounts of attached toner in a part where the toner is thinly attached and a part where the toner is densely attached. SOLUTION: The image forming device is equipped with the toner-concentration detection/ control means 17, 21, and 22 for emitting light from a light emitting element to toner pattern images, except black one, formed on an image carrier 11, and for controlling image forming conditions based on the result of the detection of an amount of reflected light from them by a light receiving element. In the image forming device, the toner-concentration detection/ control means 17, 21, and 22 have a first light receiving element 1 which photodetects the amount of regular reflected light from the surface of the image carrier, and a second light receiving element 2 which photodetects the amount of diffused reflected-light. When the number of toner layers on the image carrier 11 is not more than one, the amount of regular reflected light is detected by the first light receiving element 1 and, based on the result, toner concentration (an amount of attached toner) is calculated. When the number of toner layers on the image carrier 11 is not less than one, the amount of defused reflected-light is detected by the second light receiving element 2 and, based on the result, toner concentration (an amount of attached toner) is calculated.

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 printer, a facsimile, etc., provided with a developing device using a two-component developer and a toner replenishing device. The present invention relates to an image forming apparatus capable of detecting the density of a non-black toner pattern image formed on an image carrier and controlling toner supply.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, an electrostatic latent image is formed on an image carrier such as a photoreceptor by exposing a document image or writing light with a laser beam. After the electrostatic latent image is visualized with toner of a developing device, the toner image is transferred to a transfer material directly or via an intermediate transfer member, and fixed by a fixing device to obtain an image. In such an image forming apparatus using a color toner, a pattern image of a color toner is formed on an image carrier such as a photoconductor, and light from a light emitting element of a toner adhesion amount detection sensor is formed on the color toner pattern image. Is provided with a toner density detection / control means for estimating the amount of adhered toner based on the amount of reflected light (sensor output) detected by receiving the reflected light by a light receiving element of a sensor.

In such a toner concentration detecting / controlling means, as shown in FIG. 6 (b), when the degree of toner adhesion is up to one layer on the image carrier, as the toner adhesion increases, the image carrier When the regular reflection light on the surface decreases and one layer of toner adheres to the pattern portion, the sensor output of the light receiving element becomes minimum as shown in FIG. Further, when the toner adhesion increases and the toner becomes one layer or more as shown in FIG. 6C, the amount of reflected light on the toner surface increases, so that the amount of reflected light received by the light receiving element increases, and the sensor output becomes lower. Reverse. However, the increment is very small, and high accuracy is required to predict the amount of toner adhesion based on the increment.

In order to detect the amount of toner adhering to one or more layers, there is known a sensor which receives only diffused light so as not to receive specularly reflected light, and is capable of generally detecting from two layers to about two layers from the absence of toner. . However, since the diffused light on the image carrier is generally much smaller than the specularly reflected light, the sensor that detects only diffused light as described above has a poor SN ratio and cannot be accurately detected.

[0005]

In an image forming apparatus of the type in which the density of a non-black toner pattern image formed on an image carrier is detected by a toner adhering amount detection sensor to control toner replenishment, the above-described reasons are given. Therefore, there is a problem that the detection accuracy of the low adhesion portion is deteriorated when trying to detect the high adhesion portion of the toner, and the detection accuracy of the high adhesion portion is deteriorated when trying to detect the low adhesion portion. In addition, if the amount of toner pattern attached is increased, the toner pattern is usually formed outside the paper (non-image area of the image carrier), which places a burden on the cleaning device and increases the consumption of toner used by the user. was there.

The present invention has been made in view of the above circumstances, and an object of the present invention is to accurately determine the amount of toner attached to each of a low-adhesion portion (highlight portion) and a high-adhesion portion (shadow portion). An object of the present invention is to provide an image forming apparatus provided with a toner density detecting / controlling means capable of detecting. A second object of the present invention is to reduce the load on the cleaning device by minimizing the number of times of forming the shadow portion pattern, in addition to the first object. Claim 3 aims at claim 1
In addition to the object of (1), by detecting a shadow portion pattern and a highlight portion pattern, it is possible to perform replenishment that maintains the toner density so that the image density is optimal for all gradations without excessive toner.

[0007]

In order to achieve the above object, the present invention is directed to an image carrier, a latent image forming means for forming a latent image on the image carrier, and a latent image forming means for forming a latent image on the image carrier. Developing means for developing the developed latent image with toner to visualize the toner image, irradiating the light of a light emitting element to a non-black toner pattern image formed on an image carrier, and detecting the amount of reflected light with a light receiving element In an image forming apparatus having a toner density detecting / controlling means for controlling an image forming condition based on a detected result, the toner density detecting / controlling means includes a first light receiving element for receiving a regular reflection light amount from the surface of the image carrier. And a second light receiving element for receiving the diffuse reflected light amount. When the toner on the image carrier has one layer or less, the first light receiving element detects the regular reflected light amount, and based on the result, the toner density (toner adhesion amount) ) Is calculated, and if the toner on the image carrier has one or more layers, Detects a diffuse reflection light intensity in the second light receiving element, and configured to calculate the toner density (toner amount) by the result.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, there is provided a pattern image forming means capable of forming a pattern of one layer or less of toner and a pattern of one or more layers of toner. The number of times of image formation of the pattern of one or more layers was smaller than the number of times of image formation of the pattern of one or less layers of toner.

According to a third aspect of the present invention, in the image forming apparatus of the first aspect, the toner density detecting / controlling means adjusts the toner supply amount based on the output values (detection results) of the two light receiving elements.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction and operation of the present invention will be described below in detail with reference to the illustrated embodiment.

FIG. 1 is a view for explaining the arrangement of an image forming apparatus according to an embodiment of the present invention, and FIG. 1 (a) is a view showing a schematic arrangement of the image forming apparatus. In FIG. 1A, reference numeral 11 denotes a drum-shaped photoconductor serving as an image carrier, 12 denotes a charger (a charging charger or a charging roller) for charging the photoconductor 11, and 13 denotes a charged photoconductor 11 An optical writing device (comprising a laser diode (LD), an optical deflector, an imaging lens system, etc.) for scanning a laser beam modulated according to an image signal to perform optical writing to form an electrostatic latent image;
Is a developing device that develops the electrostatic latent image formed on the photosensitive member with the toner of the two-component developer carried on the developing roller 15 to make the image visible, and 16 is a toner supply unit (not shown) that supplies the toner into the developing device. A toner replenishing motor for replenishing the toner, a toner adhering amount detecting sensor 17 for detecting an amount of toner adhering (toner density) on the surface of the photoreceptor, and a transfer material 18 such as transfer paper for transferring the toner image formed on the photoreceptor Transfer device (transfer roller or transfer charger, etc.) for transferring to the intermediate transfer member, 1
Reference numeral 9 denotes a cleaning device (a cleaning blade, a cleaning brush, a cleaning roller, or the like) for cleaning the surface of the photoreceptor after the transfer of the toner image, and reference numeral 20 denotes a discharge lamp (QL) for removing charges remaining on the surface of the photoreceptor.

Reference numeral 21 denotes an I / O board including an A / D conversion circuit and a toner supply motor control circuit, and 22 denotes a central processing unit (CP) including a microcomputer or the like.
U) and a printer main board that includes a memory (ROM, RAM), a counter, a clock, various control circuits, and controls each unit of the image forming apparatus to control an image forming operation and a toner supply. The detection output of the I / O board 21 is binarized by an A / D conversion circuit of the I / O board 21 and input to the CPU of the printer main board 22. The printer main board 22 outputs the toner of the I / O board 21 according to the sensor output. The supply motor control circuit is controlled to control toner supply by the toner supply motor 16 of the developing device 14.

Next, FIGS. 1B and 1C show examples of the structure and arrangement of the toner adhesion amount detection sensor. The toner adhering amount detection sensor 17 includes one light emitting element 3 and two light receiving elements 1 and 2, and the first light receiving element 1 is light that is emitted from the light emitting element 3 and is specularly reflected (specularly reflected) on the surface of the photoconductor. And a plane s1 that includes the optical axis of light emitted from the light emitting element 3 and the optical axis of light that is specularly reflected on the surface of the photoreceptor and reaches the light receiving element 1 is arranged at a position perpendicular to the reflection surface. The second light receiving element 2 is arranged at a position not including the plane s1. That is, the first light receiving element 1 is a light receiving element for detecting the amount of specular reflection from the surface of the photoreceptor, and the second light receiving element 2 is a light receiving element for detecting the amount of diffuse reflection from the surface of the photoreceptor.
In general, the diffuse reflection light on the photoreceptor surface is smaller than the regular reflection light, so the amplification factor of the second light receiving element 2 is increased to about 10 to 100 times that of the light receiving element 1. This amplification rate is set by experiments or the like so that the sensitivity is maximized in the entire range from 0 to 1.0 mg / cm ² of the toner adhesion amount. The first
The light receiving element 1 shown in FIG.
2B, and the second light receiving element 2 has an output characteristic as shown in FIG.

Next, detection of the toner adhesion amount (toner density)
The control operation will be described. FIG. 3 is a flowchart illustrating an example of the toner adhesion amount detection operation, and FIG. 4 is a timing chart illustrating an example of the toner pattern image forming timing and the toner adhesion amount detection timing. When the toner adhesion amount detection operation is started, first, zero adjustment of the light receiving elements 1 and 2 of the toner adhesion amount detection sensor 17 is performed (S
1). Next, the laser diode (L
D) The light emitting pattern LD1 or LD2 is selected (S
2) The optical writing device 1 according to the selected pattern
3 is performed on the photoreceptor 11 to form an electrostatic latent image. Then, the pattern latent image is developed with the color toner of the developing device 14 to form a toner pattern (S3).

Here, the toner pattern is formed in a non-image area (between sheets) of the photoconductor 11. Also, the optical writing device 13
The write signal (LD_PWM signal) for controlling the light emission of the LD has a correlation (FIG. 5) with the amount of toner adhered in advance through experiments or the like. LD_ for light pattern
The PWM signal (LD1 = 30 value / 255 value) and the shadow pattern LD_P in which the toner is a pattern of one or more layers
The WM signal (LD2 = 180 value / 255 value) is stored. Further, the printer main board 22 holds a counter capable of detecting the number of uses of the LD1 signal for the highlight pattern and the number of uses of the LD2 signal for the shadow pattern.
Using the D2 signal, it has means for resetting the counter. That is, a shadow pattern is created once every 30 times in the creation of a toner pattern.

When a toner pattern is formed, the toner pattern is detected by a toner adhesion amount detection sensor 17. Specifically, the light emitting element 3 (for example, a light emitting diode (LED)) of the sensor 17 is turned on (S4), and the light receiving elements 1 and 2 are turned on.
2 is selected (S5), and the light receiving element output is read into the CPU of the printer main board 22 via the I / O board 21 (S6). At this time, the selected light receiving element is different depending on whether the toner pattern is a highlight pattern or a shadow pattern. When the toner forms a highlight pattern of one layer or less, the first light receiving element that detects the amount of specular reflection is used. 1 is selected, and when the toner forms a shadow pattern of one or more layers, the second light receiving element 2 for detecting the amount of diffusely reflected light is selected.

When the CPU of the printer main board 22 detects the toner pattern by the sensor (the light receiving element 1 or the light receiving element 2), the toner adhesion is calculated based on the adhesion amount calculation formula (or the adhesion amount conversion table) obtained in advance by experiment. The amount is calculated (S7). Here, the adhesion amount calculation formula is determined by calculating an approximate expression from the relationship between the toner adhesion amount and the sensor output as shown in FIGS. 2A and 2B. However, if the calculation expression is complicated, An adhesion amount conversion table which is set in advance and stored in the ROM may be used.

If the toner pattern is a highlight pattern and the first light receiving element 1 is selected, the first
, The amount of specular reflection of the highlight pattern is detected by the light receiving element 1 to calculate the toner adhesion amount. When the toner adhesion amount is calculated, the data is stored in the RAM and used as a calculation parameter of the toner supply amount. That is, the toner supply amount is determined by referring to a preset table based on a difference between the detected toner adhesion amount and a preset target adhesion amount (S9). Table 1 below shows an example of a data table for determining the toner supply amount. In this case, the toner supply amount is controlled by the supply time (the operation time of the toner supply motor).

[0019]

[Table 1]

Next, when the second light receiving element 2 is selected with the toner pattern being a shadow pattern, the amount of diffuse reflection of the shadow pattern is detected by the second light receiving element 2 to calculate the toner adhesion amount. When the toner adhesion amount is calculated, the data is stored in the RAM, referring to a preset table, and calculating the difference between the detected toner adhesion amount and the preset target adhesion amount by using the LD for highlight pattern.
The LD_PWM of 1 is corrected (S10). Table 2 shows LD
1 shows an example of a data table for performing one LD_PWM correction.

[0021]

[Table 2]

As described above, in the present invention, the normal toner replenishment amount control is performed by detecting the highlight portion pattern by the light receiving element 1 and periodically detecting the shadow portion pattern by the light receiving element 2 to perform the LD 1 for highlight pattern. LD_PWM is corrected to adjust the toner supply amount.
It is possible to perform replenishment that maintains the toner density (toner adhesion amount) so that the image density is optimal for all gradations without excessive toner.

[0023]

As described above, according to the first aspect of the present invention, the toner density detecting / controlling means of the image forming apparatus comprises:
A first light-receiving element for receiving the amount of specular reflection from the surface of the image carrier and a second light-receiving element for receiving the amount of diffusely reflected light; when the toner on the image carrier has one layer or less (highlight portion), The first light receiving element detects the amount of regular reflection light, and calculates the toner density (toner adhesion amount) based on the result. When the toner on the image carrier is one layer or more (shadow portion), the second light receiving element detects the toner density. Since the configuration is such that the amount of diffuse reflection is detected and the toner density (toner adhesion amount) is calculated based on the result, the toner adhesion amount in each of the highlight portion and the shadow portion can be accurately detected.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, further comprising a pattern image forming means capable of forming a pattern of one layer or less of toner and a pattern of one or more layers of toner. However, since the number of times of forming the pattern of one or more layers is smaller than the number of times of forming of the pattern of one layer or less, the burden on the cleaning device can be reduced by minimizing the number of times of forming the shadow portion pattern. As a result, wasteful toner consumption can be suppressed.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the toner density detecting / controlling means includes:
Since the toner replenishment amount is adjusted based on the output values (detection results) of the two light receiving elements, the image density is optimal for all gradations by detecting the shadow portion pattern and the highlight portion pattern, without excessive or insufficient toner. It is possible to perform replenishment that maintains the toner concentration such that

[Brief description of the drawings]

FIGS. 1A and 1B are explanatory diagrams of a configuration of an image forming apparatus according to an embodiment of the present invention, in which FIG. 1A is a diagram illustrating a schematic configuration example of the image forming apparatus, and FIGS. FIG. 3 is a diagram showing the configuration of the photodetector and the arrangement position of the light receiving elements.

FIGS. 2A and 2B are diagrams illustrating output characteristics of a toner adhesion amount detection sensor, wherein FIG. 2A is a diagram illustrating output characteristics of a first light receiving element with respect to a color toner adhesion amount, and FIG. FIG. 7 is a diagram illustrating output characteristics of a light receiving element No. 2;

FIG. 3 is a flowchart illustrating an example of a toner adhesion amount detection operation.

FIG. 4 is a timing chart showing an example of an image forming timing of a toner pattern image and a detection timing of a toner adhesion amount.

FIG. 5 is a diagram illustrating a relationship between a writing signal (LD_PWM signal) and a toner adhesion amount.

6A and 6B are explanatory diagrams of output characteristics of a conventional toner adhesion amount detection sensor with respect to a toner adhesion amount, wherein FIG. 6A is a diagram illustrating a relationship between a toner adhesion amount and a sensor output, and FIGS. FIG. 3 is a diagram illustrating a state of toner adhesion on a body surface and a detection state of a sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st light receiving element 2 2nd light receiving element 3 light emitting element 11 photoreceptor 12 charger 13 optical writing device 14 developing device 15 developing roller 16 toner supply motor 17 toner adhesion amount detection sensor (toner density detection means) 18 transfer device 19 Cleaning Device 20 Static Elimination Lamp (QL) 21 I / O Board 22 Printer Main Board (Toner Density Control Means)

Claims (3)

[Claims] An image carrier, a latent image forming means for forming a latent image on the image carrier, and a developing means for developing the latent image formed on the image carrier with toner to visualize the latent image. The image forming apparatus further includes a toner density detecting / controlling unit that irradiates light of a light emitting element to a toner pattern image other than black formed on the image carrier and controls an image forming condition based on a result of detecting a reflected light amount by a light receiving element. In the image forming apparatus, the toner density detecting / controlling means includes a first light receiving element for receiving the amount of specular reflection from the surface of the image carrier and a second light receiving element for receiving the amount of diffusely reflected light from the image carrier. When the upper toner has one layer or less, the first light receiving element detects the regular reflection light amount, and calculates the toner density (toner adhesion amount) based on the result. When the toner on the image carrier has one layer or more, The diffused reflected light amount is detected by the second light receiving element, and according to the result, An image forming apparatus for calculating a toner density (toner adhesion amount). 2. The image forming apparatus according to claim 1, further comprising a pattern image forming unit capable of forming a pattern of one layer or less of toner and a pattern of one or more layers of toner, wherein the pattern of toner is one or more layers. Wherein the number of times of image formation is less than the number of times of image formation of a pattern having less than one layer of toner. 3. An image forming apparatus according to claim 1, wherein said toner density detecting / controlling means adjusts a toner supply amount based on output values (detection results) of said two light receiving elements.