JP2012103567A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of detecting toner concentration, while achieving reduction in cost.SOLUTION: An image forming apparatus includes: an image carrier for carrying a toner image on the surface thereof; a toner image forming means for forming a toner image on the surface of the image carrier; an optical detection means having a light-emitting means for irradiating the surface of the image carrier or the toner image carried on the surface of the image carrier with light and a light-receiving means for receiving the light emitted from the light-emitting means and reflected by the surface of the image carrier and the toner image; a toner concentration calculating means for separating detected values of the optical detection means into a regular reflected light component from the image carrier and a diffuse reflected light component from the toner image and calculating toner concentration of the toner image by using at least one of the regular reflected light component and the diffuse reflected light component; and a control means for performing a control of the toner image forming means to adjust a toner image forming condition so that a desired toner concentration is obtained based on the toner concentration calculation value calculated by the toner concentration calculation means.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer.

  Conventionally, a regular reflection light receiving element and diffuse reflection that can detect both specular reflection light and diffuse reflection light at the same time immediately after the power is turned on or when the cumulative number of printouts reaches a predetermined number. An image forming apparatus that performs image forming condition adjustment control such as process control using an optical sensor that is an optical detection unit having a light receiving element is known (for example, see Patent Document 1).

  The image forming condition adjustment control is performed as follows, for example. First, the light emitted from the light emitting element of the optical sensor is reflected by the background portion (the portion where the toner is not attached) on the surface of the intermediate transfer belt as an image carrier, and the reflected regular reflected light is reflected by the optical sensor. Light is received by the light receiving element and an output value corresponding to the specularly reflected light is output. Next, a reference toner image having a predetermined shape is formed on the surface of the photoconductor, the reference toner image is transferred onto the intermediate transfer belt, and the light emitted from the light emitting element is reflected by the reference toner image. The diffuse reflected light is received by the diffuse reflected light receiving element, and an output value corresponding to the diffuse reflected light is output. Then, using the output value at the background portion of the surface of the intermediate transfer belt as a reference value, the reference value and the output value of the reference toner image are compared, and the toner density (toner adhesion amount per unit area) of the reference toner image is determined. To grasp. Based on the toner density thus grasped, control of the uniform charging potential of the photosensitive member, the developing bias, the optical writing intensity to the photosensitive member, and the toner concentration of the developer so that the toner density becomes a desired density. Adjust imaging conditions such as target values. Such image forming condition adjustment control makes it possible to perform a printout with a stable image density over a long period of time.

  However, if the optical sensor is provided with a specular reflection light receiving element that receives specular reflection light from the intermediate transfer belt and a diffuse reflection light receiving element that receives diffuse reflection light from the toner image as separate light receiving elements, the cost is reduced. There arises a problem that increases.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of detecting the toner density while reducing the cost.

In order to achieve the above object, an invention according to claim 1 is an image forming apparatus comprising: an image carrier that carries a toner image on a surface; and a toner image forming unit that forms a toner image on the surface of the image carrier; Optical detection having light emitting means for irradiating light on the surface of the image carrier or a toner image carried on the surface, and light receiving means for receiving reflected light irradiated from the light emitting means and reflected by the surface or the toner image And the detection value of the optical detection means are separated into a specular reflection light component from the image carrier and a diffuse reflection light component from the toner image, and the specular reflection light component and the diffuse reflection light component are used. Toner density calculating means for calculating the toner density of the toner image, and control for adjusting the toner image forming conditions so as to obtain a desired toner density based on the toner density calculated value calculated by the toner density calculating means. For forming means It is characterized in further comprising a Cormorant control means.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a straight line that intersects a light emission center of the light emitting means and a straight line that connects a point at which the straight line intersects the image carrier among the perpendicular lines of the image carrier. M1, the distance between the straight line that intersects the light receiving center of the light receiving means and the straight line that intersects the point where the straight line intersects the image bearing body, m2, the light receiving area of the light receiving means d, The light receiving area d maintains a specular reflection angle at which the specular reflection light from the image carrier can be received, and the irradiation light opening angle from the light emission center is θ1, and a straight line that intersects the light emission center among the perpendicular lines of the image carrier. And the irradiation light opening angle θ1 is the narrowest angle θ2, the irradiation light opening angle from the light emission center is θ3, and the straight line intersecting the light emission center among the perpendiculars of the image carrier and the Formation with irradiation light from the emission center When the narrowest angle among the angles is θ4, the relationship d = (m1 + m2) × {tan (θ1 + θ2) −tanθ2} is satisfied, and θ4 <θ2 and (θ3 + θ4)> (θ1 + θ2) It is characterized by satisfying at least one of the relationships.
According to a third aspect of the present invention, in the image forming apparatus of the second aspect, any one of the optical detection means and the image carrier is movable in a direction parallel to the opposing surfaces, The detection direction of the image carrier by the optical detection means is parallel to the moving direction of one of the optical detection means and the image carrier.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect, the toner density calculating means calculates at least the image carrier by the optical detection means when calculating the density of a black toner image. Using the detection value of specularly reflected light from the body, when calculating the density of a toner image of a color different from black, the toner density is calculated using at least the detection value of diffused light from the toner image by the optical detection means It is characterized by doing.
According to a fifth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect, the toner density calculating means calculates at least the image carrier by the optical detecting means when calculating the density of a black toner image. When the density of a toner image having a color different from black is calculated using the output value of specularly reflected light from the toner, the toner density is calculated using the maximum value of the detected value by the optical detection detecting means. Is.
According to a sixth aspect of the present invention, in the image forming apparatus of the first, second, or third aspect, the toner density calculating means calculates at least the image carrier by the optical detecting means when calculating the density of a black toner image. When calculating the density of the toner image having a color different from black using the output value of the regular reflection light from the image, the image holding is performed for each of a plurality of detection timings set in advance by the optical detection unit. Calculating a difference value obtained by subtracting a detection value when receiving regular reflection light from the image carrier from a detection value when receiving regular reflection light from the body and diffuse reflection light from the toner image; A cumulative value obtained by accumulating the difference values is used.

  In the present invention, the detected value of the reflected light received by the light receiving means included in the optical detecting means is separated into the regular reflected light component and the diffuse reflected light component by the toner density calculating means to obtain the toner density of the toner image. Can be calculated. Accordingly, it is not necessary to separately provide the regular reflection light receiving unit that receives the regular reflection light from the image carrier and the diffuse reflection light reception unit that receives the diffuse reflection light from the toner image. Therefore, the cost can be reduced by reducing the number of light receiving means.

  As described above, according to the present invention, there is an excellent effect that the toner density can be detected while reducing the cost.

FIG. 3 is an enlarged schematic configuration diagram in the vicinity of an intermediate transfer belt showing a pattern formation position and an optical sensor arrangement position. 1 is a schematic configuration diagram of a printer according to an embodiment. FIG. 3 is a schematic configuration diagram of an image forming unit. FIG. 3 is an enlarged schematic configuration diagram in the vicinity of an intermediate transfer belt showing a pattern formation position and an optical sensor arrangement position. FIG. 3 is a block diagram related to image forming condition adjustment control. Detailed view of the optical sensor. 6 is a graph showing a relationship between an output signal of an optical sensor, a regular reflection light component from an intermediate transfer belt, and a diffuse reflection light component from toner. Optical sensor control flowchart. The figure which shows the time change of the output value of an optical sensor. 6 is a flowchart according to toner density calculation control.

Hereinafter, an embodiment in which the present invention is applied to a full-color printer (hereinafter referred to as a printer) 100 as an image forming apparatus will be described.
FIG. 2 is a configuration diagram showing a schematic configuration of the printer 100. As shown in FIG. 2, the printer 100 includes an apparatus main body that is fixed in position for storing each component as an image forming unit, and a drawable sheet cassette 21 that stores a transfer material S. An image forming unit 1Y, 1C, 1M, 1Bk for forming toner images of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) is provided at the center of the apparatus main body. Yes. Hereinafter, the subscripts Y, C, M, and Bk of the respective symbols indicate members for yellow, cyan, magenta, and black, respectively.

  FIG. 3 is a configuration diagram showing a schematic configuration of the image forming means. As shown in FIGS. 2 and 3, in the present embodiment, drum-shaped photoreceptors 2Y, 2C, 2M, and 2Bk as image carriers, charging rollers 3Y, 3C, 3M, and 3Bk as charging means, and image writing As a unit having at least a laser exposure device 20 as means (exposure means), developing devices 4Y, 4C, 4M, and 4Bk as developing means, and cleaning devices 6Y, 6C, 6M, and 6Bk that remove transfer residual toner on the surface of the photoreceptor. The image forming units 1Y, 1C, 1M, and 1Bk for each color are configured in a plurality of groups (four in this embodiment), and the above-described colors for yellow (Y), magenta (M), cyan (C), and black (Bk) are described above. The image forming units 1Y, 1C, 1M, and 1Bk face the horizontal stretching surface of the intermediate transfer belt 7 as an image carrier that runs in a loop shape, and the left side of the image forming unit 1Y, 1C, 1M, and 1Bk Y, are arranged C, M, in the order of Bk. The four image forming units 1Y, 1C, 1M, and 1Bk for each color have the same configuration.

  The charging rollers 3Y, 3C, 3M, and 3Bk charge the photoreceptors 2Y, 2C, 2M, and 2Bk by charging with the same polarity as the toner held at a predetermined potential (negative charging in this embodiment). The uniform potential is applied to the photoreceptors 2Y, 2C, 2M, and 2Bk. The charging means is not limited to the charging roller, and various devices such as a charging brush and a charging charger can be used as appropriate.

  The laser exposure device 20 exposes the upstream sides of the developing devices 4Y, 4C, 4M, and 4Bk to the charging rollers 3Y, 3C, 3M, and 3Bk on the downstream side in the rotation direction of the photoreceptors 2Y, 2C, 2M, and 2Bk. Further, the laser exposure device 20 is arranged to perform exposure scanning in the main scanning direction in parallel with the rotation axes of the photoreceptors 2Y, 2C, 2M, and 2Bk.

  The laser exposure apparatus 20 includes, for example, a light source composed of a semiconductor laser (LD), a coupling optical system (or beam shaping optical system) composed of a collimating lens, a cylindrical lens, and the like, an optical deflector composed of a rotating polygon mirror, and the like. The image data of each color (or the image data (or the image data) read by an image reading device (not shown) provided in another configuration and recorded in the memory (or the like) is formed by an imaging optical system that condenses the laser light deflected by the optical deflector onto the photosensitive member 2. Image exposure of the photosensitive layers 2Y, 2C, 2M, and 2Bk for the respective colors with laser beams LY, LC, LM, and LBk intensity-modulated in accordance with image data of each color input from an external device such as a personal computer, An electrostatic latent image for each color is formed. As the image writing means (exposure means), in addition to the laser exposure apparatus 20 described above, an LED writing apparatus combining a light emitting diode array (LED array) and a lens array can be used.

  The photoreceptors 2Y, 2C, 2M, and 2Bk are formed on the undercoat layer formed on the surface of the conductive cylindrical support, in the order of the charge generation layer (lower layer) and the charge transport layer (upper layer) as the photosensitive layer, or These photosensitive layers are laminated in the reverse order. Further, a known surface protective layer such as an overcoat layer mainly composed of a thermoplastic or thermosetting polymer may be formed on the surface of the charge transport layer or the charge generation layer. In the present embodiment, the conductive cylindrical supports of the photoreceptors 2Y, 2C, 2M, and 2Bk are grounded.

  The developing devices 4Y, 4C, 4M, and 4Bk are formed of a cylindrical non-magnetic stainless steel or aluminum material that maintains a predetermined gap with respect to the peripheral surface of the photoconductor 2 and rotates in the forward direction and the rotation direction of the photoconductor 2. Development sleeves 41Y, 41C, 41M, and 41Bk, and one or two components of yellow (Y), magenta (M), cyan (C), and black (Bk) in the developing device 4 according to the development color of each color. Contains component developer. In the present embodiment, as an example, a two-component developer composed of toner and a magnetic carrier (in this embodiment, the toner is negatively charged) is accommodated in the developing device 4. In this case, the developing sleeve 41 includes A plurality of fixed magnets or magnet rolls magnetized with a plurality of magnetic poles are arranged. Further, each color developing device 4Y, 4C, 4M, 4Bk is provided with an agitating / conveying member 42 for conveying the developer in the container while stirring, and a replenishing portion 43 for supplying toner from each color toner bottle 37. It has been. Further, the developing devices 4Y, 4C, 4M and 4Bk for the respective colors are provided with toner concentration sensors 44Y, 44C, 44M and 44Bk for detecting the toner concentration of the developer in the container as required.

  The developing sleeves 41Y, 41C, 41M, and 41Bk of the developing devices 4Y, 4C, 4M, and 4Bk for the respective colors are placed on the drum surface of the photoreceptors 2Y, 2C, 2M, and 2Bk and a predetermined gap, for example, 100 [ [mu] m] to 500 [[mu] m] is maintained in a non-contact state, and a developing bias in which a DC voltage and an AC voltage are superimposed is applied to the developing sleeves 41Y, 41C, 41M, and 41Bk. Contact or non-contact reversal development is performed to form toner images on the surfaces of the photoreceptors 2Y, 2C, 2M, and 2Bk.

  The cleaning devices 6Y, 6C, 6M, and 6Bk include, for example, a cleaning blade 61 and a cleaning roller (or cleaning brush) 62, and the cleaning blade 61 is provided in contact with the counter direction of the photosensitive member surface.

  The intermediate transfer belt 7 that is an intermediate transfer member and an image carrier is stretched in contact with the driving roller 8 that also serves as a secondary transfer backup roller, the support roller 9, the tension rollers 10a and 10b, and the backup roller 11 to be intermediate transfer. The belt 7 is provided so that the rotation direction thereof is counterclockwise as indicated by an arrow in the drawing.

  Further, a secondary transfer roller 14 is provided through the intermediate transfer belt 7 so as to face the driving roller 8. A cleaning blade 12 a of the belt cleaning device 12 is provided in contact with the intermediate transfer belt 7 at the position of the support roller 9 in the counter direction. Similarly, primary transfer rollers 5Y, 5C, 5M, and 5Bk for each color are provided to face the photoreceptors 2Y, 2C, 2M, and 2Bk with the intermediate transfer belt 7 interposed therebetween.

This intermediate transfer belt 7 is an endless belt having a volume resistance of 10 ⁶ [Ω · cm] to 10 ¹² [Ω · cm]. For example, polycarbonate (PC), polyimide (PI), polyamideimide (PAI), polyvinylidene Conductive fillers such as carbon are dispersed in resin materials such as fluoride (PVDF), tetrafluoroethylene-ethylene copolymer (ETFE), and rubber materials such as EPDM, NBR, CR, polyurethane, etc. A material containing a material is used, and the thickness is set to about 50 [μm] to 200 [μm] in the case of a resin material and about 300 [μm] to 700 [μm] in the case of a rubber material. preferable. A rubber layer may be provided on the resin belt, and a coating layer may be provided on the surface layer. Further, in order to prevent the toner from adhering to the surface of the intermediate transfer belt 7 or to improve the cleaning property, a means for applying a release agent such as a fluorine-based resin or a lubricant may be provided on the belt surface. .

  The intermediate transfer belt 7 is driven by rotation of the drive roller 8 by a drive motor (not shown). The drive roller 8 is a conductive or semi-conductive material in which a conductive filler such as carbon is dispersed in a circumferential surface of a conductive metal bar (not shown) such as stainless steel, or a rubber or resin material such as polyurethane, EPDM, or silicon. A material coated with a conductive material is used.

  The primary transfer rollers 5Y, 5C, 5M, and 5Bk are provided to face the photoreceptors 2Y, 2C, 2M, and 2Bk with the intermediate transfer belt 7 interposed therebetween, and the intermediate transfer belt 7 and the photoreceptors 2Y, 2C, 2M, and 2Bk are provided. A transfer zone is formed between the two. A DC voltage having a polarity opposite to that of the toner (plus polarity in the present embodiment) is applied to the primary transfer rollers 5Y, 5C, 5M, and 5Bk by a DC power source (not shown) to form a transfer electric field in the transfer area. Each color toner image formed on the photoreceptors 2Y, 2C, 2M, and 2Bk is transferred onto the intermediate transfer belt 7.

The primary transfer rollers 5Y, 5C, 5M, and 5Bk, which are the first transfer means for each color, are made of polyurethane on the peripheral surface of a conductive metal core (not shown) such as stainless steel having an outer diameter of 8 [mm], for example. , EPDM, silicon, or other rubber material is dispersed with a conductive filler such as carbon or an ionic conductive material, so that the volume resistance is from 10 ⁵ [Ω · cm] to 10 ⁹ [Ω · cm. A semi-conductive elastic rubber (not shown) having a thickness of 5 [mm] and a rubber hardness of 20 [°] to 70 [°] (Asker-C) in a solid or foamed sponge state. Formed.

  The secondary transfer roller 14 that performs transfer onto the surface of the transfer material S is provided to face the driving roller 8 that is grounded with the intermediate transfer belt 7 interposed therebetween, and has a polarity opposite to the toner charging polarity (in this embodiment, plus). (Polarity) DC voltage is applied by a DC power source, and the superimposed toner image carried on the intermediate transfer belt 7 is transferred to the surface of the transfer material S via the secondary transfer roller 14.

The secondary transfer roller 14 serving as a second transfer unit that re-transfers the color toner image on the intermediate transfer belt 7 onto the transfer material S has a circumference of a conductive metal core such as stainless steel having an outer diameter of 16 [mm]. On the surface, a volume resistance is 10 ⁵ [Ω · cm] to 10 ⁹ by dispersing a conductive filler such as carbon in a rubber material such as polyurethane, EPDM, silicon, or containing an ionic conductive material. Semiconductive elastic rubber (not shown) having a thickness of 7 [mm] and a rubber hardness of about 20 [°] to 70 [°] (Asker-C) in a solid state or foamed sponge state of about [Ω · cm] ). Unlike the primary transfer rollers 5Y, 5C, 5M, and 5Bk, the secondary transfer roller 14 may come in contact with toner and may cover the surface with a good releasability such as semiconductive fluorine resin or urethane resin. Further, as described above, the driving roller 8 has a conductive core such as stainless steel dispersed on a peripheral surface of a conductive core metal such as polyurethane, EPDM, or silicon, or a conductive filler such as carbon, or an ionic property. A semiconductive material containing a conductive material is coated to a thickness of about 0.05 [mm] to 0.5 [mm].

  The cleaning blades 61 and 12a in contact with the surfaces of the photoreceptors 2Y, 2C, 2M, and 2Bk and the intermediate transfer belt 7 have a thickness of 1 [mm] to 3 [mm] and a JIS-A hardness of 60 [°] on the sheet metal holder. To 80 [°] plate-like urethane rubber is bonded so that the free length becomes about 5 [mm] to about 12 [mm], and is sensitive to a load of about 5 [gf] to about 50 [gf]. It is in contact with the bodies 2Y, 2C, 2M, 2Bk and the intermediate transfer belt 7. In some cases, the blade tip is coated with fluorine to prevent the blade from rolling up or conductive urethane rubber is used so that the other side is not charged.

  The transfer material S such as transfer paper is conveyed one by one by a paper feed roller 27 from the paper feed cassette 21 or the like, and is superimposed on the intermediate transfer belt 7 sandwiched between the secondary transfer roller 14 and the drive roller 8 via the registration roller 13. The toner image is transferred from the intermediate transfer belt 7 at the secondary transfer portion and sent to the fixing device 15 as fixing means, and is fixed by heat welding between the fixing roller 15a and the pressure roller 15b of the fixing device 15. Is discharged to the paper discharge unit 18.

  In the present embodiment, charging rollers 3Y, 3C, 3M, and 3Bk are used as charging means for the photoreceptors 2Y, 2C, 2M, and 2Bk, and primary transfer rollers 5Y, 5C, 5M, and 5Bk are used as primary transfer members. However, it is preferable from the viewpoint of suppressing the generation of harmful ozone, but is not limited to this, and the corotron discharger can be used as a charging means or a primary transfer means in a non-contact state.

  Further, the intermediate transfer belt 7 is opposed to the portion where the intermediate transfer belt 7 is wound around the driving roller 17 from the front surface side through a predetermined gap on the downstream side in the rotation direction of the intermediate transfer belt 7 from the secondary transfer portion. An optical sensor unit 16 provided with a plurality of optical sensors 160 as optical detection means is disposed (see FIG. 4). The optical sensor unit 16 detects a gradation pattern composed of a plurality of toner images formed on the intermediate transfer belt 7 by changing the toner density (toner adhesion amount) for image formation condition adjustment control in gradation. be able to. Specifically, as shown in FIG. 4, the optical sensor unit 16 includes an optical sensor 160Bk that detects a Bk tone pattern Sk, an optical sensor 160M that detects an M tone pattern Sm, and a C color sensor. An optical sensor 160C for detecting the gradation pattern Sc and an optical sensor 160Y for detecting the Y gradation pattern Sy are provided. (In the following description, when the optical sensors of the respective colors are not distinguished, the description will be made with the color code deleted.)

  As shown in FIG. 1, the optical sensor 160 of the optical detection means that is a toner state detection device is a reflection type optical sensor, and faces each of the optical sensor 160 and the intermediate transfer belt 7 (the bottom surface 160a of the optical sensor 160). The optical sensor 160 is disposed to face the surface of the intermediate transfer belt 7 so that the surface of the intermediate transfer belt 7 and the surface of the intermediate transfer belt 7 are parallel to each other. Then, the light receiving unit 162 receives and detects the reflected light that is irradiated from the light emitting unit 161 of the optical sensor 160 and reflected by the toner image on the intermediate transfer belt 7 or the intermediate transfer belt 7. Here, the intermediate transfer belt 7 includes a member that can be regarded as a part of the intermediate transfer belt 7 (a case where a member having different reflection characteristics is processed on the intermediate transfer belt 7 or the like). The light emitting unit 161 can be a light source such as an LED.

FIG. 5 is a block diagram relating to image forming condition adjustment control.
The analog signal obtained from the optical sensor 160 is digitized by digital conversion processing in an ADC (AD converter) 151, and the information stored in the ROM 153, the RAM 154, and the like is stored in the ROM 153, the RAM 154, and the like by the CPU 152 functioning as a toner concentration calculation unit. And based on the estimated toner density, so that the toner density becomes a desired density, the uniform charging potential of the photosensitive member 2, the developing bias, the optical writing intensity with respect to the photosensitive member 2, and The control device 155 performs image forming condition adjustment control for adjusting image forming conditions such as a toner density control target value of the developer. This makes it possible to perform a printout with a stable image density over a long period of time.

A detailed view of the optical sensor 160 is shown in FIG.
The light emission center of the light emitting unit 161 and the light receiving unit 162 of the optical sensor 160 are opposed to the surface of the intermediate transfer belt 7. Of the perpendicular lines of the intermediate transfer belt 7, the straight line that intersects the light emission center and the straight line are the intermediate transfer belt 7. The distance of the straight line connecting the intersecting points is m1, the straight line intersecting the light receiving center of the light receiving unit 162 among the perpendicular lines of the intermediate transfer belt 7 and the distance of the straight line connecting the points where the straight line intersects the intermediate transfer belt 7 is m2, and the light receiving unit The light receiving area 162 is d, the light receiving area d holds the specular reflection angle at which the specular reflection light from the intermediate transfer belt 7 can be received, and the irradiation beam opening angle from the light emission center is θ1, and the light emission among the perpendicular lines of the intermediate transfer belt 7 is emitted. Of the angles formed by the straight line intersecting the center and the irradiation beam opening angle θ1, the narrowest angle is θ2, the irradiation beam opening angle from the light emission center is θ3, and light is emitted from the perpendicular of the intermediate transfer belt 7. And it intersects the straight line and the angle that is most narrow angle of an angle formed between the irradiation beam from the emission center when a .theta.4, satisfy formula 1 relationship.

  The values used in this example are m1 = 10 [mm], m2 = 5 [mm], θ1 = 7 [degree], θ2 = 14 [degree], and the light receiving area of the light receiving unit 162 is d = 2 [mm]. At this time, the light beam from the light emitting unit 161 is irradiated onto the intermediate transfer belt 7 or the toner image on the intermediate transfer belt 7 in an area where θ3 = 10.1 [degrees] and θ4 = 12 [degrees].

The toner image on the intermediate transfer belt 7 is detected by the optical sensor 160 described above.
When the detection direction by the optical sensor 160 is the arrow direction shown in FIG. 6, the optical sensor 160 on the detection side is moved in the arrow direction in the drawing, or the intermediate transfer belt 7 on the detection side is the arrow direction in the drawing. However, in this embodiment, the case where the intermediate transfer belt 7 moves in the direction of the arrow will be described.

  When the glossiness of the surface of the intermediate transfer belt is a gloss meter: JIS8741, 20 ° glossiness: Rs = 100 [%], and the brightness is a spectrophotometer: X-rite, Lab: L = 5, a magenta toner image is obtained. When the carried intermediate transfer belt 7 passed through the detection region of the toner state detection state, an output signal as shown in FIG. 7 (i) was obtained. This was considered to be mainly due to the combination of the regular reflection light component (ii) from the intermediate transfer belt 7 and the diffuse reflection light component (iii) from the toner.

  The specularly reflected light component (ii) from the intermediate transfer belt 7 outputs a predetermined output signal in the absence of a toner image, but the toner image enters a detection area where the optical sensor 160 detects specularly reflected light. Then, the regular reflection light from the intermediate transfer belt background portion decreases, and when the optical sensor 160 comes out of the detection area for detecting the regular reflection light, the regular reflection light from the intermediate transfer belt background portion increases again. To do.

  The diffuse reflection light component (iii) from the toner increases when the toner image enters the detection area where the optical sensor 160 detects the diffuse reflection light. When the light exits from the detection area for detecting the reflected light, the diffuse reflected light by the toner decreases.

  Here, the inventor of the present application paid attention to the difference in the timing of the output change points of the regular reflection light and the diffuse reflection light between B and D and D 'and B' in FIG. Since there is a difference between the output change points of the specular reflected light and the diffuse reflected light, the specular reflected light component and the diffuse reflected light component are separated from one output of the optical sensor 160 to extract the diffuse reflected light. Came to think that is possible. That is, it has been found that the regular reflection light component and the diffuse reflection light component can be completely separated from the same output value output from the optical sensor 160.

  By allowing the CPU 152 to separate the output value (detection value) of the reflected light received by the light receiving unit 162 of the optical sensor 160 into a regular reflected light component and a diffuse reflected light component, the toner density of the toner image can be calculated. Therefore, it is not necessary to separately provide a regular reflection light receiving unit that receives regular reflection light from the intermediate transfer belt 7 and a diffuse reflection light receiving unit that receives diffuse reflection light from the toner image. The cost can be reduced as much as possible.

  Here, as conditions under which the specular reflection light component and the diffuse reflection light component can be separated and the diffuse reflection light can be extracted, a detection region for detecting the specular reflection light of the optical sensor 160 and the optical sensor 160 are included. It is important that the detection area for detecting the diffuse reflection light does not completely match.

  When light is irradiated from the optical sensor 160 to the intermediate transfer belt 7 or the toner image, the specularly reflected light can be received only within the light receiving range that maintains the specular reflection angle. On the other hand, the diffuse reflected light diffuses into the space, so that it can enter the light receiving region regardless of the specular reflection angle. Therefore, by satisfying at least one of the relations of Formula 2 and Formula 3, the specular reflected light component and the diffuse reflected light component are separated from the same output value output from the optical sensor 160, and the diffuse reflected light is separated. Can be extracted.

  Here, either one of the optical sensor 160 and the intermediate transfer belt 7 can move in a direction parallel to the opposing surfaces, and the detection direction of the intermediate transfer belt 7 by the optical sensor 160 is intermediate between the optical sensor 160 and the intermediate transfer belt 7. By being parallel to one of the moving directions with respect to the transfer belt 7, it is possible to satisfy the relationship of Equation 1 and satisfy at least one of Equation 2 and Equation 3.

  In this embodiment, the output between the arrows in FIG. 7 means that the detection area of the optical sensor 160 is the belt background area. In the output between the ronies in FIG. 7, the toner image starts to enter the detection area of the optical sensor 160, the output from the intermediate transfer belt 7 in the non-toner image area, and the output from the toner image area (diffuse reflected light). Means that the toner image has not yet entered the regular reflection light receiving area. 7 indicates that the toner image area has entered the specularly reflected light receiving area of the optical sensor 160. In FIG.

  Therefore, the output change between the lonely and the output between the two '--ro' can be said to be the change in the output of only the diffuse reflected light component by the toner, and the toner density is estimated by using the information in this region. can do.

  Here, since the black toner absorbs most of the light, hardly any diffused light can be obtained. That is, since the black toner has almost no diffuse reflection light, the specular reflection light is dominant, and there is almost no output of the diffuse reflection light component in the region between the ronies and between the two '-ro' in FIG.

  Therefore, in the case of a black toner image, information on the area between the knees, in other words, the minimum value of the optical sensor output is used. In the case of a black toner image, since there is almost no diffuse reflection light that becomes noise at the time of detection, a configuration in which diffuse reflection light may enter can be adopted. That is, there is no problem with the above-described optical sensor 160, and conversely, a complicated configuration of the optical sensor 160 that eliminates diffuse reflected light (throttle the optical path or devise the aperture shape) as in the prior art. This eliminates the problems that have arisen, and therefore has a great effect even when detecting a black toner image.

The following was devised as a method for estimating the toner density of a toner image having a color different from black.
The output of the optical sensor 160 in the image forming apparatus needs to be calibrated in advance. For example, when the optical sensor 160 detects a background portion where there is no toner or a reference body other than the toner or the intermediate transfer belt 7, a predetermined output is set. Here, the control flow of the optical sensor 160 is shown in FIG. When the detection by the optical sensor 160 is performed, the LED as the light source is turned on (S1), and after waiting for the LED stabilization time for the LED output to stabilize (S2), the sensor output is read (S3), and then the LED is turned off. Then, the detection ends (S4).

  In the image forming apparatus, when the CPU 152 executes a mode for estimating the toner density, the optical sensor 160 starts detecting the surface of the intermediate transfer belt and the toner image formed on the surface at a predetermined timing.

  The image forming apparatus creates one or more toner images of at least one color on the intermediate transfer belt 7. It is desirable that the created toner image is appropriately set according to the purpose, such as a solid pattern, a line pattern, or a dither pattern.

  The formed toner image on the intermediate transfer belt 7 sequentially passes through the detection area of the optical sensor 160. The output value acquisition trigger, the sampling time, the sampling interval, and the sampling number of the optical sensor 160 are defined in accordance with the toner image passage timing. Let the acquired output of the optical sensor 160 be Vp (n); n = 1, 2, 3... M, where m is a predetermined sampling number.

  Of Vp (n) detected by the optical sensor 160, a value at which the output becomes the maximum value is defined as Vmax (see FIG. 9). Then, the toner adhesion amount is estimated with reference to the output value Vmax of the optical sensor 160 or a calculated value using the output value Vmax and a toner density conversion table prepared in advance in the ROM 153. Note that when converting the output value Vmax of the optical sensor 160 or the calculated value using the output value Vmax into the toner density, a conversion formula may be used instead of the conversion table.

  Here, when a plurality of output values Vmax of the optical sensor 160 are obtained in one toner image (when the detection area of the toner image enters or exits by the optical sensor 160), for example, assuming that Vmax1 and Vmax2 respectively, toner adhesion When creating the amount conversion table, it is desirable to use a value having a good correlation with the toner adhesion amount among values calculated using Vmax1 or Vmax2 or Vmax1 and Vmax2 (such as an average value of Vmax1 and Vmax2). .

Another example of a toner density estimation method for a toner image having a color different from black will be described.
First, the output Vsg of the intermediate transfer belt background portion is detected, and an appropriate value is used among Vp (n); n = 1, 2, 3,. At this time, the intermediate transfer belt background portion is determined by an average value of a predetermined Vp (n) (n in a predetermined range of at least one position corresponding to the intermediate transfer belt background portion detected by the optical sensor 160). It is desirable to calculate the output Vsg.

  In the range of Vsg ≦ Vp (n), Vs is obtained by accumulating the difference between Vsg and Vp (n) as shown in Equation 4. Thereby, output information of only the diffuse reflection light component from the toner image can be obtained.

  In other words, in this configuration example, when the density of a toner image having a color different from black is calculated, the specularly reflected light and toner from the intermediate transfer belt are respectively detected for a plurality of preset detection timings by the optical sensor 160. A difference value obtained by subtracting the detection value when the regular reflection light from the intermediate transfer belt is received from the detection value when the diffuse reflection light from the image is received is calculated, and Vs is a cumulative value obtained by accumulating the difference values. Is used. As a result, output information of only the diffuse reflection light component from the toner image can be obtained, so that it is possible to calculate the toner density (toner adhesion amount) of the toner image of a color different from black from the information.

  The CPU 152 estimates the toner density with reference to Vs calculated from the output value of the optical sensor 160 and the toner density conversion table prepared in advance in the ROM 153. Note that a conversion formula may be used instead of a conversion table when converting Vs into toner density.

  Here, when a plurality of Vs are obtained in one toner image (when the detection area of the toner image enters or exits by the optical sensor 160), for example, assuming that Vs1 and Vs2 respectively, a toner density conversion table is created. At this time, it is desirable to employ a value having a good correlation with the toner density among the values calculated using Vs1, Vs2, or Vs1 and Vs2 (average value or total value of Vs1 and Vs2, etc.).

Furthermore, another example of a toner density estimation method for a toner image having a color different from black will be described.
First, the output Vsg of the intermediate transfer belt background portion is detected, but an appropriate value is used among Vp (n) acquired as described above. At this time, it is desirable to calculate Vsg based on an average value of Vp (n) (at least one predetermined range of n corresponding to the background portion).

  Then, assuming that the point where Vp (n)> Vsg is first reached is t1, and the point where Vp starts to decrease is t2, the CPU 152 calculates Δt1 from the difference between t2 and t1 using Equation 5. Accordingly, the CPU 152 can estimate a part of the time during which the optical sensor 160 receives diffusely reflected light from the toner image.

  Then, in the range of Δt1, which is a part of the time during which the optical sensor 160 receives diffusely reflected light from the toner image, Vs is obtained by accumulating the difference between Vsg and Vp (n) as shown in Equation 6. To do. Thereby, output information of only the diffuse reflection light component from the toner image can be obtained.

  Then, the CPU 152 calculates and estimates the toner density with reference to Vs calculated from the output value of the optical sensor 160 and the toner density conversion table prepared in advance in the ROM 153. Note that a conversion formula may be used instead of a conversion table when converting Vs into toner density.

  Here, when a plurality of Vs are obtained in one toner image (when the detection area of the toner image enters or exits by the optical sensor 160), for example, assuming that each is Vs1 or Vs2, a toner density conversion table is created. At this time, it is desirable to employ a value having a good correlation with the toner density among calculated values (average value or total value of Vs1 and Vs2) calculated using Vs1, Vs2, or both Vs1 and Vs2.

  With these methods, the toner density of a toner image of a color different from black is calculated, and the toner density of a black toner image is calculated from Vsp_min, so that it is possible to detect toner density with high robustness with a single sensor. It becomes.

FIG. 10 shows an example of a flowchart relating to toner density calculation control.
First, the surface of the intermediate transfer belt and a toner image for image forming condition adjustment control previously formed on the surface are detected by the optical sensor 160 (S1). Next, the CPU 152 calculates the output of the intermediate transfer belt background from the optical sensor output (S2). If the toner image detected by the optical sensor 160 uses black toner (YES in S3), the minimum value of the optical sensor output with the calculated output value of the intermediate transfer belt background as a reference value. Is calculated by the CPU 152 (S4), the CPU 152 calculates and estimates the toner density of the black toner image by referring to the minimum value and the toner density conversion table of the ROM 153, and calculates the toner density. A series of control ends. On the other hand, if the toner image detected by the optical sensor 160 uses a toner different from black (NO in S3), the calculated output value of the intermediate transfer belt background is used as a reference value to output the optical sensor. Is calculated by the CPU 152 (S6), and the CPU 152 calculates and estimates the toner density of the toner image having a color different from black by referring to the maximum value and the toner density conversion table of the ROM 153. Then, a series of control for calculating the toner density is completed.

  Then, based on the toner density estimated in this way, the uniform charging potential of the photosensitive member 2, the developing bias, the optical writing intensity with respect to the photosensitive member 2, and the developer toner so that the toner concentration becomes a desired density. By performing the image forming condition adjustment control for adjusting the image forming condition such as the density control target value by the control device 155, it is possible to print out the image density stably for a long period of time.

As described above, according to the present embodiment, in the image forming apparatus, the intermediate transfer belt 7 that is an image carrier that carries a toner image on the surface, the image forming unit 1 that forms a toner image on the surface of the intermediate transfer belt 7, and the primary A toner image forming unit comprising a transfer roller 5 and the like, a light emitting unit 161 which is a light emitting unit for irradiating light on the surface of the intermediate transfer belt 7 and a toner image carried on the surface, and the surface and toner image irradiated from the light emitting unit 161. An optical sensor 160 that is an optical detection unit having a light receiving unit 162 that receives the reflected light reflected by the optical sensor 160, and a detection value of the optical sensor 160 is obtained from a regular reflection light component and a toner image from the intermediate transfer belt 7. A CPU 152 which is a toner concentration calculation unit that calculates a toner concentration of a toner image using the specular reflection light component and the diffuse reflection light component. CPU152 and a control device which is a control unit for performing the toner image forming means control for adjusting the toner image forming conditions so that the desired toner concentration based on the toner density calculation value calculated. As a result, the specular reflection light receiving element and the diffuse reflection light receiving element are not provided as separate light receiving elements in the optical sensor 160, so that the output of the specular reflection light component and the output of the diffuse reflection light component can be obtained. Cost reduction can be achieved.
Further, according to the present embodiment, the distance between the straight line that intersects the light emission center and the straight line that intersects the intermediate transfer belt 7 among the perpendicular lines of the intermediate transfer belt 7 is m1, and among the perpendicular lines of the intermediate transfer belt 7 The distance between the straight line that intersects the light receiving center and the straight line connecting the point where the straight line intersects the intermediate transfer belt 7 is m2, the light receiving area of the light receiving portion 162 is d, and the light receiving area d can receive the specularly reflected light from the intermediate transfer belt 7. The irradiation beam opening angle from the light emission center that maintains a specular reflection angle is θ1, and the angle that is the narrowest of the angles formed by the straight line intersecting the light emission center of the perpendicular line of the intermediate transfer belt 7 and the irradiation beam opening angle θ1. θ2 is an opening angle of the irradiation beam from the light emission center, θ3, and θ4 is an angle which is the narrowest angle among the angles formed by the straight line intersecting the light emission center of the perpendicular lines of the intermediate transfer belt 7 and the irradiation beam from the light emission center. In this case, the relationship of d = (m1 + m2) × {tan (θ1 + θ2) −tanθ2} is satisfied, and at least one of θ4 <θ2 and (θ3 + θ4)> (θ1 + θ2) is satisfied. It is possible to prevent the detection area for detecting the regular reflection light from completely matching the detection area for detecting the diffuse reflection light of the optical sensor 160. Therefore, the regular reflection light component and the diffuse reflection light component can be separated from the same output value output from the optical sensor 160.
Further, according to the present embodiment, one of the optical sensor 160 and the intermediate transfer belt 7 can move in a direction parallel to the opposing surfaces, and the detection direction of the intermediate transfer belt 7 by the optical sensor 160 is determined. Since the optical sensor 160 and the intermediate transfer belt 7 are parallel to one of the moving directions, the relationship d = (m1 + m2) × {tan (θ1 + θ2) −tanθ2} is satisfied, and θ4 <θ2 ( It is possible to maintain that at least one of the relations θ3 + θ4)> (θ1 + θ2) is satisfied.
Further, according to the present embodiment, the CPU 152 uses at least the detection value of the regular reflection light from the toner image by the optical detection unit when calculating the density of the black toner image, and the toner image having a color different from black. When calculating the density of the toner, the toner density is calculated using at least the detection value of the diffused light from the toner image by the optical detection means, so that the toner image of a color different from black does not include the regular reflection light output. Since information is used, it is possible to reduce information fluctuation caused by other than toner density fluctuation. Further, since the regular reflection light output is used only for the black toner image having almost no diffuse reflection light, diffuse reflection light may be entered, in other words, a robust regular reflection optical system can be used.
Further, according to the present embodiment, the CPU 152 uses at least the output value of the regular reflection light from the intermediate transfer belt 7 by the optical detection unit when calculating the density of the black toner image, and uses a toner having a color different from black. When calculating the density of the image, the toner density is calculated using the maximum value detected by the optical detection and detection means. The information that the amount of received light is maximized is different from black because the toner image has entered the specular reflection light detection area from the diffuse light detection area, and the output information of only the diffuse reflection detection area is used. The toner density of the color toner image can be calculated.
Further, according to the present embodiment, the CPU 152 uses at least the output value of the regular reflection light from the intermediate transfer belt 7 by the optical detection unit when calculating the density of the black toner image, and uses a toner having a color different from black. When calculating the density of the image, detection is performed when regular reflection light from the intermediate transfer belt 7 and diffuse reflection light from the toner image are received at each of a plurality of preset detection timings by the optical sensor 160. A difference value obtained by subtracting the detected value when the regular reflection light from the intermediate transfer belt 7 is received is calculated from the value, and the accumulated value obtained by accumulating the difference value is used. As a result, when calculating the density of a toner image of a color different from black, output information of only the diffuse reflected light component from the toner image can be obtained. From this information, the toner density of the toner image of a color different from black is obtained. Calculation is possible. Also, the density of the toner image having a color different from black is calculated using the estimation result of the CPU 152 which is also an estimation means for estimating the time during which the optical sensor 160 receives diffusely reflected light from the toner image. May be.

DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Photoconductor 3 Charging roller 4 Developing device 5 Primary transfer roller 6 Cleaning device 7 Intermediate transfer belt 8 Drive roller 9 Support roller 10a Tension roller 10b Tension roller 11 Backup roller 12 Belt cleaning device 12a Cleaning blade 13 Registration roller 14 Secondary transfer roller 15 Fixing device 15a Fixing roller 15b Pressure roller 16 Optical sensor unit 17 Drive roller 18 Paper discharge unit 20 Laser exposure device 21 Paper feed cassette 27 Paper feed roller 37 Toner bottle 41 Developing sleeve 42 Stirring / conveying member 43 Replenishment Unit 44 Toner concentration sensor 61 Cleaning blade 100 Printer 151 ADC
152 CPU
153 ROM
154 RAM
155 Control device 160 Optical sensor 160a Bottom surface 161 Light emitting unit 162 Light receiving unit

JP-A-3-209281

Claims (7)

An image carrier that carries a toner image on the surface;
Toner image forming means for forming a toner image on the surface of the image carrier;
Optical detection having light emitting means for irradiating light on the surface of the image carrier or a toner image carried on the surface, and light receiving means for receiving reflected light irradiated from the light emitting means and reflected by the surface or the toner image Means,
The detection value of the optical detection means is separated into a specularly reflected light component from the image carrier and a diffusely reflected light component from the toner image, and the toner image is obtained using the specularly reflected light component and the diffusely reflected light component. Toner concentration calculating means for calculating the toner concentration of
And a control unit that controls the toner image forming unit to adjust a toner image forming condition so as to obtain a desired toner density based on the toner density calculation value calculated by the toner density calculating unit. Forming equipment. The image forming apparatus according to claim 1.
The distance between the straight line that intersects the light emission center of the light emitting means and the straight line that intersects the point where the straight line intersects the image carrier is m1, and the light receiving center of the light receiving means is the vertical line of the image carrier. The distance between the straight line intersecting the line and the point where the straight line intersects the image carrier is m2, the light receiving area of the light receiving means is d, and the light receiving area d can receive the specularly reflected light from the image carrier. The irradiation light opening angle from the light emission center that holds the specular reflection angle is θ1, and is the narrowest angle among the angles formed by the irradiation light opening angle θ1 and the straight line that intersects the light emission center among the perpendicular lines of the image carrier. The angle is θ2, the irradiation light opening angle from the light emission center is θ3, and the angle that is the narrowest angle among the angles formed by the straight line intersecting the light emission center and the irradiation light from the light emission center among the perpendicular lines of the image carrier Where d = (m1 + M2) × {tan (θ1 + θ2) −tan θ2} and satisfy at least one of θ4 <θ2 and (θ3 + θ4)> (θ1 + θ2). The image forming apparatus according to claim 2.
Either one of the optical detection means and the image carrier is movable in a direction parallel to the opposing surfaces;
An image forming apparatus, wherein a detection direction of the image carrier by the optical detector is parallel to a moving direction of one of the optical detector and the image carrier. The image forming apparatus according to claim 1, 2 or 3.
When calculating the density of the black toner image, the toner density calculation means uses at least the detection value of the regular reflection light from the image carrier by the optical detection means, and the density of the toner image having a color different from black When calculating the toner density, the toner density is calculated using at least the detection value of the diffused light from the toner image by the optical detection means. The image forming apparatus according to claim 1, 2 or 3.
The toner density calculation means uses at least the output value of the regular reflection light from the image carrier by the optical detection means when calculating the density of the black toner image,
An image forming apparatus, wherein when calculating the density of a toner image having a color different from black, the toner density is calculated using a maximum value detected by the optical detection detection means. The image forming apparatus according to claim 1, 2 or 3.
The toner density calculation means uses at least the output value of the regular reflection light from the image carrier by the optical detection means when calculating the density of the black toner image,
When calculating the density of a toner image having a color different from that of black, for each of a plurality of detection timings set in advance by the optical detection means, the regular reflection light from the image carrier and the toner image Calculating a difference value obtained by subtracting a detection value when the regular reflection light from the image carrier is received from a detection value when the diffuse reflection light is received, and using a cumulative value obtained by accumulating the difference values. An image forming apparatus. The image forming apparatus according to claim 6.
The optical detection means has an estimation means for estimating the time during which diffuse reflected light from the toner image is received;
The image forming apparatus according to claim 1, wherein the toner density calculation unit uses the estimation result of the estimation unit when calculating the density of a toner image having a color different from black.

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