JP2006267809A - Developing device, image forming apparatus, and measuring method of mixing ratio - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that measures the mixing ratio of a mixed developer with high precision. <P>SOLUTION: The image forming apparatus 2 of the present invention is equipped with storage container 14 for a mixed developer, which contains a developer obtained by mixing at least two kinds of toners having nearly the same hues, and different reflection densities and different spectral characteristics outside the visible light range, an irradiation means 64 of irradiating the mixed developer with light, a detecting means 66 of detecting the quantity of reflected light or transmitted light from the mixed developer, and a mixing ratio measuring means 84 of measuring the mixing ratio of the at least two kinds of toners in the storage container on the basis of the quantity of reflected light or transmitted light detected by the detecting means 66. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine thereof, and a developing device used in the image forming apparatus. The present invention particularly relates to an image forming apparatus and a developing apparatus using a mixed developer having a plurality of types of toners having substantially the same hue and different reflection densities. The present invention also relates to a method for measuring the mixing ratio of the mixed developer.

  An image forming apparatus using a mixed developer composed of two kinds of toners having the same hue and different reflection densities in order to suppress the consumption of the developer while enhancing the image quality of the image including the highlight portion is disclosed in, for example, Patent Document 1 is disclosed.

  In this apparatus, the charge amount of the low reflection density toner is made smaller than the charge amount of the high reflection density toner, so that the low reflection density toner can be supplied from the developing roller to the photosensitive drum more easily than the high reflection density toner. It is. Therefore, when developing a low density latent image area on the photosensitive drum (low exposure amount and therefore low potential attenuation level), low reflection density toner is mainly used. As a result, it is possible to suppress density unevenness that can occur when only toner having a high reflection density is used, and to obtain a fine image without graininess.

  Further, the amount of high reflection density toner in the developing device is set larger than that of low reflection density toner. Therefore, when developing a high density latent image region (a large amount of exposure and therefore a large potential attenuation level) on the photosensitive drum, a high reflection density toner is mainly used. As a result, the consumption of the developer can be suppressed as compared with the case where the high density latent image area on the photosensitive drum is developed using only the toner having a low reflection density.

  In the image forming apparatus, in order to stably obtain a good image quality even when the number of printed sheets is increased, it is necessary to control the mixing ratio of the two types of toner in the developer within a predetermined range.

Patent Document 2 discloses an image forming apparatus that forms a test patch image on a photosensitive drum, detects the reflection density of the image, and supplies low-reflection density toner from a toner hopper when the detected reflection density of the test patch image decreases. Are listed.
JP 2000-98712 A JP 2000-293003 A

  However, it is difficult to obtain the developer mixing ratio (toner mixing ratio) with high accuracy based on the test patch image. In addition, a dead time (waiting time) is increased by a series of steps of forming a test patch image and detecting its reflection density.

  Accordingly, the present invention provides a mixed developer mixing ratio measuring method that can be easily performed with high accuracy, and a developing device and an image forming apparatus that can measure the mixed developer mixing ratio using the mixed ratio measuring method. The purpose is to do.

In order to achieve the above object, one aspect of an image forming apparatus according to the present invention is:
A mixed developer container containing a developer formed by mixing at least two types of toners having substantially the same hue, reflection density and spectral characteristics outside the visible light region; and
An irradiation means for irradiating the mixed developer with light;
Detection means for detecting the reflected light amount or transmitted light amount from the mixed developer;
And a mixing ratio measuring unit that measures a mixing ratio of at least two types of toner in the mixed developer container based on the reflected light amount or the transmitted light amount detected by the detecting unit.

Another aspect of the image forming apparatus is:
The mixed developer is composed of two types of toners having substantially the same hue and different reflection densities,
One of the toners contains an infrared light absorber.

Another aspect of the image forming apparatus is:
The mixed developer is composed of at least two kinds of toners having substantially the same hue and different reflection densities,
Each toner contains an infrared ray absorbent having a different absorption wavelength.

In order to achieve the above object, a developing device according to the present invention includes:
A mixed developer container containing a developer formed by mixing at least two types of toners having substantially the same hue, reflection density and spectral characteristics outside the visible light region; and
An irradiation means for irradiating the mixed developer with light;
Detection means for detecting the reflected light amount or transmitted light amount from the mixed developer;
And a mixing ratio measuring unit that measures a mixing ratio of at least two types of toner in the mixed developer container based on the reflected light amount or the transmitted light amount detected by the detecting unit.

Furthermore, in order to achieve the above object, the mixing developer measuring method of the mixed developer according to the present invention includes:
A mixing ratio measurement method for measuring a mixing ratio of a developer obtained by mixing at least two kinds of toners having substantially the same hue, reflection density and spectral characteristics outside the visible light region,
Irradiating the mixed developer with light;
Detecting the amount of reflected light or transmitted light from the mixed developer;
And a step of measuring a mixing ratio of at least two kinds of toners based on the detected reflected light amount or transmitted light amount.

  According to the image forming apparatus of the present invention, since at least two kinds of toners having substantially the same hue and different reflection densities have different spectral characteristics outside the visible light region, at least two toners in the mixed developer container are used. The toner mixing ratio in the container can be measured with high accuracy simply by irradiating the mixed developer mixed with different types of toners with light and detecting the amount of light reflected or transmitted from the mixed developer.

  Further, according to the developing device of the present invention, since at least two types of toners having substantially the same hue and different reflection densities have different spectral characteristics outside the visible light region, at least in the mixed developer container. The toner mixing ratio in the container can be measured with high accuracy simply by irradiating light to the mixed developer in which two kinds of toners are mixed and detecting the amount of light reflected or transmitted from the mixed developer.

  Furthermore, according to the mixed developer mixing ratio measuring method of the present invention, at least two types of toners having substantially the same hue and different reflection densities have different spectral characteristics outside the visible light region. By irradiating the mixed developer mixed with the toner with light and detecting the reflected light amount or transmitted light amount from the mixed developer, the toner mixing ratio can be measured with high accuracy and easily.

  FIG. 1 shows a color printer according to an embodiment of the present invention. The printer 2 includes a photosensitive drum 4 that can be driven to rotate in the clockwise direction of the drawing as an image carrier. Around the photosensitive drum 4, a charging device 6, an exposure device 8, four developing devices 10C, 10M, 10Y, and 10K, and a primary transfer device 12 are sequentially arranged along the rotation direction of the drum.

The charging device 6 is for uniformly charging the surface of the photosensitive drum 4 (surface potential V ₀ ). The exposure device 8 selectively irradiates the photosensitive drum 4 with laser light 8a in accordance with image data, thereby forming a latent image on the photosensitive drum.

Each of the developing devices 10 </ b> C to 10 </ b> K supplies toner corresponding to the photosensitive drum 4 to visualize the latent image. Specifically, the developing devices 10C, 10M, 10Y, and 10K respectively include developer containers 14C, 14M, and 14Y that respectively store cyan (C), magenta (M), yellow (Y), and black (Y) developers. , 14K, and developing rollers 16C, 16M, 16Y, 16K that are connected to a motor (not shown) so as to be rotatable counterclockwise in the drawing. As the developing rollers 16C to 16K rotate, the developer adhering to the surface of the developing roller is conveyed to a region where the developing roller and the photosensitive drum 4 are opposed to each other, where the developer is supplied to the latent image region of the photosensitive drum. Will be. Each developing roller 16C～16K, bias voltage _{V B} is applied.

  The cyan developer in the developer container (mixed developer container) 14C is composed of two types of toners having a low reflection density and a high reflection density having substantially the same hue (in the sense of not including a carrier). The mixed developer. Similarly, the magenta developer in the developer container (mixed developer container) 14M is a one-component mixed developer composed of two types of toners having a low reflection density and a high reflection density having substantially the same hue. The yellow developer in the developer container 14Y is made of one type of yellow toner. Similarly, the black developer in the developer container 14K is made of one type of black toner. The cyan developer and magenta developer, which are mixed developers, will be described in more detail later.

The primary transfer device 12 includes an intermediate transfer belt 18. The intermediate transfer belt 18 is made of a resin sheet such as polycarbonate, and carbon black is dispersed in the resin sheet so that the surface electrical resistance value of the intermediate transfer belt is about 10 ⁵ to 10 ¹² Ω / cm ² . The intermediate transfer belt 18 is supported on the outer periphery of five rollers 20, 22, 24, 26 and 28. The roller 22 is a tension roller that applies tension to the intermediate transfer belt 18. The roller 20 is drivingly connected to a motor (not shown). As the roller 20 rotates, the rollers 22, 24, 26, and 28 rotate, and the intermediate transfer belt 18 rotates counterclockwise in the drawing. The intermediate transfer belt 18 between the rollers 26 and 28 is in contact with the outer periphery of the photosensitive drum 4 so that a toner image (cyan toner image, magenta toner image, yellow toner image, or black toner image) on the photosensitive drum is formed. A primary transfer region 30 to be transferred to the intermediate transfer belt is formed.

A secondary transfer roller 32 that rotates in the clockwise direction of the drawing is provided facing the belt portion 34 immediately upstream of the roller 24 with respect to the rotation direction of the intermediate transfer belt 18. The secondary transfer roller 32 is made of a foam rubber material such as silicone or urethane, and carbon black is dispersed in the foam rubber material so that the surface transfer resistance of the secondary transfer roller is about 10 ⁵ to 10 ¹² Ω / cm ^2. Has been. The belt portion 34 and the secondary transfer roller 32 pass through the sheet (recording medium) S along the direction of the arrow, and thereby the secondary toner image (described later) on the intermediate transfer belt 18 is transferred onto the sheet. Region 36 is formed.

  In the printer 2 having such a configuration, a controller (described later) drives the charging device 6 to uniformly charge the surface of the photosensitive drum 4. The controller generates a control signal based on the color image data stored in the image memory (not shown) and sends it to the exposure device 8. The exposure device 8 selectively irradiates the photosensitive drum 4 with laser light 8a. As a result, the potential of the surface portion irradiated with the laser beam 8a is attenuated, and a cyan latent image is formed on the photosensitive drum 4. The cyan latent image on the photosensitive drum 4 is visualized by supplying a mixed cyan developer to the latent image by the developing device 10C, and a cyan toner image is formed. The cyan toner image is conveyed to the primary transfer region 30 by the rotation of the photosensitive drum 4 and transferred onto the intermediate transfer belt 18.

  Next, the magenta toner image formed on the photosensitive drum 4 in the same manner using the mixed magenta developer is transferred onto the intermediate transfer belt 18 so as to overlap the cyan toner image. Subsequently, the yellow toner image formed on the photosensitive drum 4 in the same manner using a single yellow developer is transferred onto the intermediate transfer belt 18 so as to be superimposed on the cyan and magenta toner images. Thereafter, the black toner image formed on the photosensitive drum 4 in the same manner using a single black developer is transferred onto the intermediate transfer belt 18 so as to be superimposed on the cyan, magenta, and yellow toner images.

  The superimposed image is conveyed to the secondary transfer region 36 by the movement of the intermediate transfer belt 18. On the other hand, the sheet S is supplied from a sheet supply cassette (not shown) to the secondary transfer region 36. The superimposed image is transferred to the sheet S that passes through the secondary transfer region 36 by the action of the secondary transfer roller 32.

  The sheet S on which the color toner image is formed is supplied to a fixing device (not shown), and the color toner image is fixed on the sheet S.

  Next, the latent image formed on the photosensitive drum 4 and the mixed developer will be described in detail. The printer 2 performs pulse width modulation control of the laser beam 8a in order to express gradation. Therefore, the latent image includes a “low density” region having a small potential decay level and a “high density” region having a large potential decay level. If the laser irradiation time is relatively short, the potential attenuation on the surface of the photosensitive drum is small (the potential does not saturate), and thus a low density region is formed. On the other hand, if the laser irradiation time is sufficiently long, the potential attenuation on the surface of the photosensitive drum is large (the potential is saturated), and thus a high density region is formed. In the present application, a “low density” latent image area and a “high density” latent image area represent areas where a developer is supplied to form a highlight portion and a shadow portion, respectively.

As described above, the cyan developer is a mixed developer composed of two kinds of toners having substantially the same hue and different reflection densities. The mixing ratio of the developer in the developer container 14C is adjusted to be _RL or more. In the present embodiment, the mixing ratio is defined as the weight ratio of the low reflection density toner to the high reflection density toner, but another definition may be used. According to the above definition, R _L is a value greater than 0 and less than 1. That is, the developer container 14C contains a higher amount of high reflection density cyan toner than the low reflection density cyan toner.

  FIGS. 2A and 2B show examples of a low reflection density cyan toner and a high reflection density cyan toner. In the example of FIG. 2A, the high reflection density toner 40H is obtained by dispersing a colorant 44H and a charge control agent 46 in a resin 42. An external additive 48 may be added. The low reflection density toner 40L is substantially the same as the high reflection density toner 40H except that the colorant 44L has a lower reflection density than the colorant 44H. In the example of FIG. 2B, the colorants 44H and 44L have the same reflection density, and the weight ratio of the colorant 44H to the resin 42 is larger than that of the colorant 44L. In the latter example, as an example, an appropriate range of the mixing ratio is 0.45 or more, and the weight ratio is 4% for the low reflection density cyan toner and 10% for the high reflection density cyan toner.

  In order to make the adhesion of the low reflection density cyan toner to the developing roller 16C of the developing device 10C smaller than that of the high reflection density toner so that the low reflection density cyan toner can be easily attached to the photosensitive drum 4. The charge amount of the low reflection density cyan toner is smaller than that of the high reflection density cyan toner. To achieve this, the average particle size may be different between the low reflection density cyan toner and the high reflection density cyan toner, and the amount of post-treatment agent such as a charge control agent added to each cyan toner may be different. May be.

  Instead, the low reflection density cyan toner has a larger sphericity than the high reflection density cyan toner, thereby reducing the adhesion of the low reflection density cyan toner to the developing roller 16C compared to the high reflection density toner. Good.

With reference to FIGS. 3 and 4, the characteristics of the mixed cyan developer composed of low reflection density and high reflection density cyan toner will be described. FIG. 3 shows low reflection density cyan toner and high reflection density cyan toner adhering to the photosensitive drum as a function of the potential difference between the developing roller to which the bias voltage V _B is applied and the latent image area on the photosensitive drum. Each amount is shown.

  As shown in FIG. 3, if the potential difference between the developing roller and the latent image area on the photosensitive drum is relatively small, the adhesion force between the low reflection density cyan toner and the development roller is the high reflection density cyan toner. As a result, the low reflection density cyan toner is mainly supplied to the latent image area. When the potential difference between the developing roller and the latent image area on the photosensitive drum is smaller than a certain value ΔV1, the amount of the low reflection density cyan toner supplied to the latent image area of the photosensitive drum increases as the potential difference increases. . When the potential difference is larger than ΔV1, the amount of low reflection density cyan toner supplied to the photosensitive drum is substantially constant (ie, the supply amount of low reflection density toner is saturated). This means that if the potential difference is large to some extent, most of the low reflection density cyan toner in the mixed cyan developer facing the latent image area is supplied to the latent image area.

  On the other hand, if the potential difference between the developing roller and the latent image area on the photosensitive drum is relatively small, the amount of high reflection density cyan toner supplied to the latent image area is small. However, the larger the potential difference between the developing roller and the latent image area on the photosensitive drum, the greater the amount of high reflection density cyan toner supplied to the latent image area of the photosensitive drum as long as the potential difference is smaller than a certain value ΔV2. There are many. When the potential difference is larger than ΔV2, the amount of high reflection density cyan toner supplied to the photosensitive drum is substantially constant (ie, the supply amount of high reflection density toner is saturated). This is because, if the potential difference is sufficiently large, most of the high reflection density cyan toner in the mixed cyan developer facing the latent image area (and thus the majority of the mixed cyan developer facing the latent image area) will enter the latent image area. It means that it is supplied. The weight ratio of the two types of cyan toner supplied to the photosensitive drum when the potential difference is larger than ΔV2 is substantially the same as the mixing ratio of the two types of cyan toner in the developer container. In FIG. 3, the potential difference ΔV3 indicates a value at which the potential of the latent image area of the photosensitive drum is saturated.

  FIG. 4 schematically shows the relationship between the potential difference between the latent image areas (two) on the photosensitive drum and the developing roller and the ratio of the two types of cyan toner supplied to the latent image area. Shown in The latent image area 50 is a low density area (corresponding to a highlight portion) corresponding to the potential difference ΔV4 in FIG. The latent image area 52 is a high density area (corresponding to the shadow portion) corresponding to the potential difference ΔV2 in FIG. As shown in the drawing, the low-density region 50 is supplied with more low-reflection density cyan toner 54 than the high-reflection density cyan toner 56. On the other hand, more high reflection density cyan toner 56 is supplied to the high density area 52 than the low reflection density cyan toner 54.

  As is clear from the above description, it is inevitable that the low reflection density cyan toner is supplied even when developing a high density latent image area (corresponding to a shadow portion). Therefore, when developing a high-density latent image region, in order to obtain the same image density with the same adhesion amount as that of a conventional image forming apparatus that uses only one type of cyan toner, the printer according to this embodiment is used. The high reflection density cyan toner used in No. 2 needs to have a higher reflection density than the cyan toner used in the conventional image forming apparatus. As an example, when the weight ratio of the colorant to the resin of the conventional single cyan toner is 8%, the weight ratio of the high reflection density cyan toner is set to 10%.

  As described above, the low reflection density cyan toner 54 is mainly used to develop the low density latent image area (corresponding to the highlight portion). This is also true for magenta developers. Therefore, the printer 2 enables a fine image without graininess by developing a low density latent image area mainly with a low reflection density toner.

When cyan and magenta developers are used to continuously print an image including a relatively large number of highlights such as a photographic image using the printer 2, a large amount of low reflection density toner is consumed. As a result, the amount of low reflection density toner per unit volume in the developer decreases. For this reason, the amount of high reflection density toner supplied from the developing roller to the low density latent image region increases, and the graininess of the image increases. As the amount of low reflection density toner decreases, the mixing ratio of the developer decreases. Therefore, the printer 2 is configured to control each mixing ratio of cyan and magenta developer so as to be equal to or more than a predetermined appropriate value _RL .

On the other hand, when images including many shadow parts such as character images are continuously printed, high reflection density toner is consumed at a ratio (weight ratio) almost the same as the mixing ratio in the developer container, although the consumption amount of the high reflection density toner is large. The low reflection density toner will continue to be consumed, so the mixing ratio will not increase. However, if too much low reflection density toner is replenished from the replenishing device to the developing device as will be described later, a large amount of low reflection density toner is consumed when an image including many shadow portions is printed thereafter. In order to suppress the consumption amount of the low reflection density toner, it is necessary to set the upper limit _RH of the mixing ratio and to control the amount of toner supplied from the replenishing device so that the mixing ratio does not exceed the upper limit when the toner is supplied. is there.

  For the purpose of measuring the toner mixture ratio, the high reflection density toner and the low reflection density toner in cyan and magenta developers are different in spectral reflectance (characteristic) outside the visible light region (invisible light region). . Therefore, the spectral reflectance outside the visible light region of the mixed developer varies depending on the mixing ratio. Therefore, the mixing ratio can be calculated from the detection value obtained by detecting the amount of reflected light outside the visible light region of the mixed developer.

In the cyan and magenta developers, for example, the spectral reflectance in the infrared light region is set to satisfy the relationship of Equation 1, that is, the low reflection density toner is larger than the high reflection density toner.

  In order to realize this, one toner contains an infrared light absorber, or each toner contains an infrared light absorber having a different absorption wavelength. In order to increase detection accuracy, it is preferable to increase the difference in spectral reflectance between the low reflection density toner and the high reflection density toner in the infrared light region.

  Examples of the infrared light absorber include a cyanine compound, a diimonium compound, an aminium compound, a nickel complex compound, a phthalocyanine compound, an anthraquinone compound, and a naphthalocyanine compound having a maximum absorption wavelength at a wavelength of 750 to 1100 nm.

  The reason for using the spectral reflectance outside the visible light region for the calculation of the mixing ratio is that the spectral reflectance of the low light density toner and the high reflectance toner in the visible light region are different, which affects the image quality and toner adhesion amount. Because there is. Therefore, it is preferable that the spectral reflectance outside the visible light region having a small influence is different between the low reflection density toner and the high reflection density toner.

  When the toner is a polymerized toner, the infrared light absorber used is preferably in a proportion of 0.01 to 5% by weight with respect to the polymerizable monomer. This is because if the amount of the added infrared light absorber exceeds 5% by weight, the color tone of the toner may be affected.

  Note that the spectral reflectance to be differentiated between the low reflection density toner and the high reflection density toner is not limited to the infrared light region as long as it is outside the visible light region, and may be, for example, the ultraviolet light region. In this case, an ultraviolet light absorber is used. Alternatively, the spectral reflectance may be higher for the high reflection density toner than for the low reflection density toner.

  Returning to FIG. 1, the developing devices 10C and 10M respectively detect the reflected light amount detecting unit 60C for detecting the reflected light amount in order to calculate the mixing ratio of cyan and magenta developer in the developer containers 14C and 14M. , 60M on the bottom wall of the container. Since the structures of the both reflected light amount detection units are the same, only the reflected light amount detection unit 60C will be described with reference to FIG.

  The reflected light amount detection unit 60C includes a transparent window 62C provided on the bottom wall of the developer container 14C of the developing device 10C, an infrared LED 64C (irradiation means) that irradiates infrared light, and reflection from the cyan developer. It has a phototransistor 66C (detection means) that detects light, and is configured as a part of the developing device 10C. The infrared LED 64C irradiates the cyan developer in the developer container 14C with infrared light through the transparent window 62. The phototransistor 66C receives the reflected light from the cyan developer via the transparent window 62C, and outputs a voltage signal corresponding to the amount of received light to a controller described later. Note that it is preferable that the phototransistor 66C can detect diffused light because the reflected light from the cyan developer has many irregular reflection components.

  The relationship between the output voltage of the phototransistor 66C and the mixing ratio of the cyan developer will be described. Here, the measurement of the mixing ratio of the developer in which the low reflection density cyan toner has a higher reflection efficiency in the infrared region than the high reflection density cyan toner will be described.

FIG. 6 shows the relationship between the output voltage of the phototransistor 66C and the mixing ratio of the cyan developer. As shown in the figure, the amount of reflected light received by the phototransistor 66C increases as the mixing ratio increases, that is, as the amount of low reflection density cyan toner having a large spectral reflectance in the cyan developer increases. The voltage to be increased. In the figure, the output voltage V _L corresponds to the mixing ratio R _L described above, and V _H corresponds to R _H. The relationship between the output voltage and the mixing ratio is examined in advance, and the printer 2 adjusts the mixing ratio of the cyan developer based on this relationship and the output voltage from the phototransistor 66C.

  The detection timing of the reflected light is preferably immediately after the developer is sufficiently stirred by the agitator of the stirring means described later. Further, the mixing ratio of the developer may be adjusted based on the average of the voltages output by detecting the reflected light a plurality of times. Further, the above-described reflected light amount unit is provided at a position facing the photosensitive drum 4 or the intermediate transfer belt 18, and the reflected light amount from the test patch of the solid image by the developer formed on the photosensitive drum 4 or the intermediate transfer belt 18. May be detected to calculate the mixing ratio. Furthermore, the mixing ratio may be calculated from the amount of transmitted light instead of the amount of reflected light. In this case, the irradiation unit and the detection unit may be positioned facing each other with the developer interposed therebetween.

  Returning to FIG. 1, each of the developing devices 10C, 10M, 10Y, and 10K determines whether or not a certain amount of developer that guarantees the image quality remains in the containers 14C, 14M, 14Y, and 14K (in other words, the developing device). Empty sensors 68C, 68M, 68Y and 68K for detecting (whether or not the developer container is near empty) are provided on the container side wall. The empty sensor is, for example, an optical sensor including a light emitting element and a light receiving element. When the light emitted from the light emitting element is blocked by the developer and does not enter the light receiving element, the empty sensor does not output a signal. In this case, a sufficient amount of developer remains in the container. When light emitted from the light emitting element enters the light receiving element, the empty sensor outputs a signal. In this case, only a small amount of developer remains in the container, and image quality cannot be guaranteed.

The developing devices 10C, 10M, 10Y, and 10K are connected to replenishing devices 70C, 70M, 70Y, and 70K for replenishing the developing devices with the respective developers. More specifically, as shown in FIG. 7, the replenishing device 70 </ b> C includes two containers 72 </ b> L and 72 </ b> H and conveying screws 74 </ b> L and 74 </ b> _H that respectively store the low reflection density cyan toner _TL and the high reflection density cyan toner TH. Prepare. Conveying screws 74L, 74H are low reflection density cyan toner _{T L} and conveying path 76L highly reflective density cyan toner _{T H,} replenishing port 78L through 76H, for dropping the developer container 14C and conveyed to 78H Is. The developer container 14C includes an agitator (not shown) for stirring and mixing the low reflection density and high reflection density cyan toner. The screws 74L and 74H are drivably coupled to motors 82L and 82H electrically connected to the drive circuit 80, respectively. The drive circuit 80 drives the motors 82L and 82H according to a signal from the controller 84 that controls the printing operation of the printer 2.

The replenishing device 70C also determines whether the low and high reflection density cyan toners T _L and T _H are substantially present in the toner containers 72L and 72H, in other words, the toner containers 72L and 72H are full. Empty sensors 86L and 86H are provided for detecting whether or not the toner is empty (the toner is substantially not present in the toner container (a state in which the developer container 14C can be replenished)).

  The replenishing device 70M has the same configuration as the replenishing device 70C except that the low reflection density magenta toner and the high reflection density magenta toner are accommodated in the two toner containers, respectively.

  Each of the replenishing devices 70Y and 70K is a conventional one that contains one type of toner in one toner container and an empty sensor that detects whether or not toner is substantially present in the toner container. Therefore, the description is omitted in this specification.

  Signals from the reflected light amount detection unit 60C (phototransistor 66C) and the empty sensors 68C, 86L, 86H are output to the controller 84. Although not shown in the drawing, detection signals of other color sensors, for example, sensors 60M, 68M, 68Y, and 68K, are also output to the controller 84. As will be described below, the controller 84 replenishes a controlled amount of toner from the toner container to the developer container by controlling a corresponding replenishing device in response to a detection signal relating to one of the developing devices.

  As a printing mode, the printer 2 outputs a first mode (also referred to as a character image in this application) that includes only binary images such as characters and drawings (also referred to as a character mode in this application), and a photograph. And a second mode (also referred to as a photographic mode in the present application) for outputting a multi-value image (also referred to as a photographic image in the present application) having a halftone density. In the present embodiment, as will be described below, the controller 84 does not prohibit the printing operation depending on the printing mode even if one of the two toner containers becomes full in the mixed developer supply device 70C or 70M. It has become. The print mode may be selected by the user himself (that is, the selected print mode is included in the print command output to the printer 2) or automatically according to the image data output to the printer 2. You may make it set to.

Next, the cyan developer replenishment sequence will be described with reference to the flowcharts shown in FIGS. This sequence is performed, for example, when the printer 2 is activated or whenever the developing device 10C is used for a predetermined period. First, in step S1, the controller 84 determines whether or not a detection signal is output from the empty sensor 68C. When the detection signal is not output, that is, when a sufficient amount of cyan developer remains in the container 14C, the process proceeds to step S2, and the controller 84 is sent from the reflected light amount detection unit 60C (phototransistor 66C). Based on the signal, it is determined whether or not the output voltage is equal to or higher than _VL (the mixing ratio is equal to or higher than _RL ) (in this way, the controller 84 determines whether or not the inside of the container 14C detected by the reflected light amount detection unit 60C). It functions as a means for measuring the mixing ratio of the two types of toner based on the reflectance of the mixed developer). When the output voltage is equal to or higher than V _L , replenishment is not performed, and the developing device 10C, if the printer 2 accepts image data (to be stored in the image memory) together with a print command, is in photo mode even in character mode. Even if it exists, it will be in the state which can supply a cyan developer to the photosensitive drum 4 (step S3). Whether or not printing is actually performed depends on the states of the other developing devices 10M, 10Y, and 10K. For example, if all the developing devices 10C to 10K can supply the corresponding developer in the character mode or the photographic mode, the printer 2 performs the printing operation.

If the output voltage is smaller than _{VL in} step S2 (that is, the amount of low reflection density cyan toner in the developer container 14C is insufficient), the process proceeds to step S4, and the controller 84 outputs a detection signal from the empty sensor 86L. It is judged whether it is done. When the detection signal is output, that is, when the low reflection density cyan toner _TL does not substantially remain in the container 72L, the low reflection density cyan toner cannot be supplied. Since the developer container 14C contains a higher amount of high reflection density cyan toner than the prescribed ratio, a photographic image with gradation cannot be reproduced, but a character image can be output. Therefore, in step S5, when the printer 2 receives the print command and image data in step S5, the developing device 10C does not supply the cyan developer to the photosensitive drum 4 in the photographic mode but can supply it in the character mode. Become. Whether or not printing is actually performed depends on the states of the other developing devices 10M, 10Y, and 10K. For example, the other developing devices 10M, 10Y, and 10K can supply developer corresponding to at least the character mode. If so, the printer 2 performs the printing operation in the character mode (in this way, the controller 84 detects whether each of the toner containers 72L and 72H is toner full empty or non-toner full empty. It also functions as a means for permitting or prohibiting the printing operation in accordance with the printing mode in accordance with the detection result of the detecting means. As described above, even when the low reflection density toner container 72L is fully empty, the character mode printing operation is permitted, so that the dead time can be reduced.

If the detection signal is not output in step S4, that is, if the low reflection density cyan toner _TL is substantially left in the container 72, the process proceeds to step S6, and the developer container from the toner container 72L. The low reflection density cyan toner _TL is supplied to 14C so that the output voltage is _VL or higher (mixing ratio is _RL or higher) unless the toner container is fully empty (steps S2 and S4).

If a detection signal is output from the empty sensor 68C in step S1, that is, if a sufficient amount of mixed cyan developer does not remain in the container 14C, the process proceeds to step S7, where the controller 84 detects the reflected light amount detection unit. Based on the signal sent from 60C, it is determined whether or not the output voltage is _VL or higher (mixing ratio is _RL or higher). When the output voltage is equal to or higher than _VL , the process proceeds to step S8, and it is determined whether or not the detection signal is output from the empty sensor 86L. When the detection signal is output (when the low reflection density cyan toner _TL does not substantially remain in the toner container 72L), the process proceeds to step S9, and whether or not the detection signal is output from the empty sensor 86H. Judging. If the detection signal is outputted (when the high reflection density cyan toner T _H in the toner containing vessel 72H do not remain essentially), the developing device 10C is not ready to provide a cyan developer to the photoreceptor drum 4 (Step S10). Therefore, even if the printer 2 receives a print command and image data, the print operation is not performed regardless of the type of print mode. In this case, the user needs to replace both toner containers 72L and 72H.

Step When the detection signal is not outputted in S9 (when the high reflection density cyan toner T _H in the toner containing vessel 72H remains essentially), the process proceeds to step S11, the high reflection from the toner container 72H predetermined amount replenishing the concentration cyan toner T _H in the developer accommodating vessel 14C. Alternatively, it may be supplemented with high reflection density cyan toner T _H until (even if not reached a predetermined amount) toner container 72H full empty. Although the mixing ratio of the mixed cyan developer in the developer container 14C may deviate from the specified value (below the lower limit _RL ), a photographic image with gradation cannot be reproduced, but a character image can be output. . Therefore, in step S12, when the printer 2 accepts the print command and image data in step S12, the developing device 10C is in a state where it can be supplied in the character mode without supplying the cyan developer to the photosensitive drum 4 in the photo mode. . As described above, even when the low reflection density toner container 72L is fully empty, the character mode printing operation can be performed without replacing the container, so that the dead time can be reduced.

When the detection signal is not output in step S8 (when the low reflection density cyan toner _TL is substantially left in the toner container 72L), the process proceeds to step S13, and the detection signal is output from the empty sensor 86H. Determine whether or not. Detecting when the signal is outputted (when the high reflection density cyan toner T _H in the toner containing vessel 72H do not remain essentially), the process proceeds to step S14, a predetermined amount from the toner container 72L low reflection density cyan toner _TL is supplied into the developer container 14C (at this time, the mixing ratio is maintained at _RL or higher). Alternatively, even when the predetermined amount is not reached, the low reflection density cyan toner _TL may be replenished until the toner container 72L becomes fully empty. The amount of high reflection density cyan toner T _H is small in the developer accommodating vessel 14C, but both photographic images and character images by using the low reflection density cyan toner T _L is reproducible. Accordingly, in step S15, when the printer 2 receives the print command and the image data in step S15, the developing device 10C can supply the cyan developer to the photosensitive drum 4 in the character mode or the photographic mode. .

In step S13, if the detection signal is not outputted (when the high reflection density cyan toner T _H in the toner containing vessel 72H remains essentially), the process proceeds to step S16, the mixing ratio is maintained higher R _L Yo toner container 72L, to replenish a predetermined amount of low reflection density and a high reflection density cyan toner _T L, a _{T H} in the developer accommodating vessel 14C from 72H. Thereafter, the flow proceeds to step S15.

If the output voltage is smaller than _VL in step S7 (that is, the ratio of the low reflection density cyan toner in the developer container 14C is small), the process proceeds to step S17, and whether or not the detection signal is output from the empty sensor 86L. Judging. When the detection signal is output (when the low reflection density cyan toner _TL does not substantially remain in the toner container 72L), the flow proceeds to step S18. Steps S18 to S21 are the same as steps S9 to S12. That is, when the high reflection density cyan toner T _H in the toner containing vessel 72H do not remain substantially (YES at step S18), and the developing device 10C is not ready to provide a cyan developer to the photoreceptor drum 4 (step S19). Therefore, even if the printer 2 receives a print command and image data, the print operation is not performed regardless of the type of print mode. If in container 72H high reflection density cyan toner T _H remains substantially (NO at step S18), and high reflection density cyan toner from the toner container 72H up to a predetermined amount or toner container 72H becomes full empty the T _H is replenished to the developer accommodating vessel 14C (step S20). At this time, when the printer 2 receives the print command and the image data, the developing device 10C is ready to supply the cyan developer in the character mode without supplying the cyan developer to the photosensitive drum 4 in the photo mode (step S21). . As described above, even when the low reflection density toner container 72L is fully empty, the character mode printing operation can be performed without replacing the container, so that the dead time can be reduced.

When the detection signal is not output in step S17 (when the low reflection density cyan toner _TL is substantially left in the toner container 72L), the process proceeds to step S22, and the detection signal is output from the empty sensor 86H. Determine whether or not. If the detection signal is outputted (when the high reflection density cyan toner T _H in the toner containing vessel 72H do not remain essentially), the flow proceeds to step S23. Steps S23 to S27 are similar to steps S2 to S6. That is, if the low reflection density cyan toner _TL remains in the toner container 72L, the mixing ratio becomes _RL or more from the toner container 72L to the developer container 14C unless the container becomes fully empty. Thus, the low reflection density cyan toner _TL is replenished (steps S23, S24, S26). If the mixing ratio is equal to or higher than _RL (YES in step S24), the developing device 10C has a certain amount of low reflection density cyan toner in the developer container 14C. Even so, the cyan developer can be supplied to the photosensitive drum 4 (step S25). However, if the toner container 72L before mixing ratio reaches _{R L} is accustomed to full empty (YES at step S26), the process proceeds to step S27, (as opposed to a step S5) a sufficient amount of the developer container in the 14C Since there is no high reflection density cyan toner and the mixing ratio is below the lower limit, the developing device 10C is not in a state in which the cyan developer can be supplied to the photosensitive drum 4. In this case, the user needs to replace both toner containers 72L and 72H.

When the detection signal in step S22 is not output (when a high reflection density cyan toner T _H in the toner containing vessel 72H remains essentially), the flow proceeds to step S28. In step S28, the toner container 72L or more mixing ratio _{R L} as the target, to replenish the low reflection density and a high reflection density cyan toner _T L, a _{T H} in the developer accommodating vessel 14C from 72H. If the mixing ratio is equal to or higher than _RL in step S29, the process proceeds to step S30, and the developing device 10C has a certain amount of mixed cyan developer in the container 14C. Even in such a case, the cyan developer can be supplied to the photosensitive drum 4. If the mixing ratio is smaller than _RL in step S29, the process proceeds to step S31. If neither of the toner containers 72L and 72H is full, the process returns to step S28 and toner replenishment is continued. If any of the toner containers 72L and 72H becomes full in step S31, the flow proceeds to step S32. Since there is no sufficient amount of high reflection density cyan toner in the developer container 14C and the mixing ratio is below the lower limit, the developing device 10C is not in a state where it can supply the cyan developer to the photosensitive drum 4. In this case, the user needs to replace the empty toner container.

  In this replenishment processing sequence, it is performed when the printer 2 is started up or whenever the developing device 10C is used for a predetermined period. In addition to this, the controller 84 changes the empty device 68C to the developing device 10C. It may be automatically started when a signal indicating empty is received. In this case, steps S7 to S32 are performed.

  The magenta developer supply operation is the same as that for the cyan developer.

  The replenishment operation of the yellow and black developers is the same as the conventional one. That is, when receiving a detection signal from the empty sensor 68Y or 68K, the controller 84 controls the replenishing device 70Y or 70K to replenish the corresponding toner from the toner container to the developer container 14Y or 14K. Further, when the toner container of the replenishing device 70Y or 70K becomes full, it is necessary to replace the container.

  The above description relates to an embodiment of the present invention, and the present invention is not limited to this and can be variously modified. For example, in the above-described embodiment, a mixed developer obtained by mixing two types of toners having substantially the same hue and different reflection densities is used. A mixture of toners may be used. In this case, a replenishing device provided with a plurality of containers for storing each toner may be used.

The mixing ratio of three or more types of toners is set so that the spectral reflectance in the infrared region satisfies the relationship of Formula 2 in the case of three types, for example, high reflection density toner, medium reflection density toner, and low reflection density toner. (The medium reflection density toner and the low reflection density toner are made the same, and the high reflection density toner is made smaller than these), and the spectral reflectance in the ultraviolet light region is satisfied (Equation 3). The medium reflection density toner is set the same, and the low reflection density toner is set larger than these).

  If the spectral reflectance of each toner is set in this way, the mixing ratio of the three types of toner can be calculated by detecting the amount of reflected light in the infrared light region and the ultraviolet light region. The mixing ratio of the three or more types of toners is expressed by, for example, the ratio of the weight of the remaining type of toner to the weight of one type of toner. In the above-described embodiment, a one-component developer not including a carrier is used. However, a two-component developer including a carrier and a plurality of types of toners having different reflection densities can be used.

  In the above-described embodiment, only the cyan and magenta developers are mixed developers obtained by mixing toners having different reflection densities. However, yellow developers and black developers may be mixed developers.

  Further, in the above-described embodiment, the mixing ratio of the mixed developer is the remaining amount of low reflection density toner / the remaining amount of high reflection density toner, but another definition may be used as the mixing ratio as described above. For example, if it is defined as the remaining amount of high reflection density toner / remaining amount of low reflection density toner, in the above embodiment, the mixing ratio takes into consideration the upper limit instead of the lower limit.

  In addition, in the above-described embodiment, it is detected whether or not the developer container is a mixed developer near empty. However, it is detected that the developer container is fully empty (substantially capable of supplying developer to the photosensitive drum. ), It may be detected whether or not the mixed developer is present. In this case (when the inside of the developer container becomes fully empty, the mixing ratio of the toner in the developer container cannot be measured), but if the toner is substantially present in each toner container, the appropriate amount of the toner is present. The mixed developer container is supplied. However, the configuration of the above-described embodiment in which it is detected whether or not the developer container is near empty in order to guarantee image quality is preferable.

  Furthermore, in the above-described embodiment, one type of toner is stored in each of the two toner containers. However, a high reflection density toner is stored in one, and a high reflection density toner and a low reflection density toner are mixed and stored in the other. May be. In this case, the developer container is a mixed developer near empty (or full empty), and the toner container in which two types of toner are mixed and stored is a toner full empty and a toner having a high reflection density toner. When it is detected that the container is non-toner full empty, the controller controls the replenishing device to replenish the mixed developer container with the high reflection density toner and allow the character mode printing operation, but the photographic mode. The printing operation of is prohibited. On the other hand, the developer container is a mixed developer near-empty (or full-empty), and the toner container in which the high reflection density toner is stored is a toner full-empty toner container in which two types of toner are mixed and stored. When the controller is detected to be non-toner full empty, the controller controls the replenishing device to replenish the low and high reflection density toner mixed in the mixed developer container, Printing operation is permitted even in the photo mode.

  Further, a sensor (for example, an optical sensor) for preventing excessive toner from being supplied from the replenishing device may be provided in the mixed developer container.

  Furthermore, the present invention can be applied not only to a color image forming apparatus but also to a monochrome image forming apparatus (not limited to black). Needless to say, the present invention can be applied to an image forming apparatus other than a printer.

  In addition, when the number of printed sheets generally increases, for example, non-uniform film thickness due to deterioration of the photosensitive drum (surface scraping), non-uniform charging due to contamination of the charging device, or scratches on the intermediate transfer belt The image deteriorates due to the non-uniform transferability associated with the above. In order to cope with this, in the above embodiment, for example, as shown in FIG. 12, the lower limit of the mixture ratio is increased continuously [Figure (a)] or stepwise [Figure (b)] as the number of printed sheets increases. Set as follows. As a result, the toner is replenished so as to increase the ratio of the low reflection density toner in the mixed developer as the number of printed sheets increases, so that image deterioration can be reduced. For example, in addition to a counter for counting the number of printed sheets and a sensor for detecting the surface potential of the photosensitive drum, a storage unit for storing data corresponding to FIG. 12 is provided in the printer 2. The replenishing device may be controlled based on the above. In the above embodiment, the mixing ratio is defined so as to increase as the proportion of the low reflection density toner in the mixed developer in the mixed developer container increases. If the definition is such that the ratio of the low reflection density toner in the mixed developer in the container decreases as the ratio increases, the upper limit may be set to decrease as the number of printed sheets increases.

1 is a configuration diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 5A is a diagram illustrating an example of a low reflection density cyan toner and a high reflection density cyan toner using colorants having different reflection densities. FIG. 6B is a diagram illustrating an example of a low reflection density cyan toner and a high reflection density cyan toner using different amounts of colorant. 6 is a graph showing a relationship between a potential difference between a photosensitive drum and a developing roller and amounts of low reflection density cyan toner and high reflection density cyan toner supplied to the photosensitive drum. FIG. 6 is a diagram schematically illustrating a relationship between a potential difference between a photosensitive drum and a developing roller and a ratio of amounts of low reflection density cyan toner and high reflection density cyan toner supplied to the photosensitive drum. The figure which shows a reflected light amount detection unit. The graph which shows the relationship between a toner mixing ratio and the output voltage of both reflected light detection units. FIG. 2 is a configuration diagram illustrating the cyan developing device of FIG. 1 and a replenishing device that replenishes developer to the device. 7 is a flowchart showing a first part of a cyan developer supply process. 9 is a flowchart showing a second part of a cyan developer supply process. 10 is a flowchart showing a third portion of a cyan developer supply process. 10 is a flowchart showing a fourth portion of a cyan developer supply process. The graph which shows the example of the range of the desired mixing ratio made to change according to the number of printed sheets.

Explanation of symbols

2 Image forming apparatus 14C Developer container 60C Reflected light quantity detection unit 64C Infrared LED (irradiation means)
66C phototransistor (detection means)
84 Controller (Mixing ratio measuring means)

Claims (5)

A mixed developer container containing a developer formed by mixing at least two types of toners having substantially the same hue, reflection density and spectral characteristics outside the visible light region; and
An irradiation means for irradiating the mixed developer with light;
Detection means for detecting the reflected light amount or transmitted light amount from the mixed developer;
An image forming apparatus comprising: a mixing ratio measuring unit that measures a mixing ratio of at least two types of toner in the mixed developer container based on a reflected light amount or a transmitted light amount detected by the detecting unit. The mixed developer is composed of two types of toners having substantially the same hue and different reflection densities,
The image forming apparatus according to claim 1, wherein an infrared light absorber is contained in any one of the toners. The mixed developer is composed of at least two kinds of toners having substantially the same hue and different reflection densities,
The image forming apparatus according to claim 1, wherein each toner contains an infrared light absorber having a different absorption wavelength. A mixed developer container containing a developer formed by mixing at least two types of toners having substantially the same hue, reflection density and spectral characteristics outside the visible light region; and
An irradiation means for irradiating the mixed developer with light;
Detection means for detecting the reflected light amount or transmitted light amount from the mixed developer;
A developing apparatus comprising: a mixing ratio measuring unit that measures a mixing ratio of at least two kinds of toner in the mixed developer container based on the reflected light amount or the transmitted light amount detected by the detecting unit. A mixing ratio measurement method for measuring a mixing ratio of a developer obtained by mixing at least two kinds of toners having substantially the same hue, reflection density and spectral characteristics outside the visible light region,
Irradiating the mixed developer with light;
Detecting the amount of reflected light or transmitted light from the mixed developer;
And a step of measuring a mixing ratio of at least two kinds of toners based on the detected reflected light amount or transmitted light amount.

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