JP2008191213A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which forms a good-quality image by accurately controlling toner concentration without being influenced by the change of bulk density of two-component developer containing toner and carrier. <P>SOLUTION: The image forming apparatus has a first sensor which outputs an output value related to the density of a toner image formed on the surface of a photoreceptor, and a second sensor which outputs an output value corresponding to magnetic permeability of the developer remaining on the surface of a developer carrier after development, so as to control the operation of a toner replenishing means based on the output value from the first sensor and the output value from the second sensor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to toner density management in an image forming apparatus using a two-component developer.

  Among electrophotographic image forming apparatuses, there is a developing type using a developer including a carrier that is a magnetic material and a toner that is a non-magnetic material, a so-called two-component developer. The developing method using a two-component developer is a surface of a developing roller comprising a relatively rotating non-magnetic roller and a magnet body having a plurality of magnetic poles arranged in the circumferential direction inside the non-magnetic roller. Then, the developer is adhered and carried and conveyed, and the toner in the developer is transferred and adhered to the surface of the photoconductor disposed facing the developing roller to form a toner image. The process of transferring toner to the photoreceptor and forming a latent image into a toner image is called development.

  The toner image formed on the photoconductor by development is transferred to a transfer material such as recording paper and provided to the user.

  The developer remains on the developing roller after development, and the developer remaining on the developing roller after development is reused.

  Usually, the developer supplied to the developing roller is stored in a stirring chamber. When the developer is stirred in the stirring chamber, the developer is frictionally charged and adheres to the surface of the developing roller. The developer remaining on the developing roller after development is peeled off from the developing roller and then conveyed to the agitation chamber, mixed with the developer contained in the agitation chamber, stirred, and used for development.

  Since the developer remaining on the developing roller after development has a reduced toner component, when such development, recovery and reuse are repeated, the toner concentration of the developer stored in the stirring chamber decreases.

  The toner concentration is a ratio of the toner mass (Wt) to the carrier mass (Wc) in the developer, and is expressed by toner concentration = (Wt / (Wt + Wc)) × 100 (%).

  The toner density affects the toner image formed by the development to be formed. When the toner density is low, the density of the toner image formed by the development to be formed is insufficient, and when the toner density is high, the density of the toner image is excessive and fogging is caused.

  Therefore, normally, the toner concentration of the developer stored in the stirring chamber is measured, and when the toner concentration becomes low, the toner separately stored in the developer in the stirring chamber is supplied, and the developer in the stirring chamber is supplied. The toner density is managed in an appropriate range.

  The development method using a two-component developer requires such toner density control, but the toner triboelectric charge control is relatively easy, toner particles do not easily aggregate, and a high-quality image can be formed. There are so many.

  As a toner concentration detecting means for detecting the toner concentration of a two-component developer (hereinafter simply referred to as a developer), for example, the developer is irradiated with light, and the amount of reflected light from the developer is received to detect the toner concentration. There are a toner concentration detection sensor using a reflected light amount detection method, a toner concentration detection sensor using a magnetic permeability detection method using a phenomenon in which the magnetic permeability of a developer changes depending on the toner concentration, and the like.

  In the toner concentration detection by the magnetic permeability detection method, when the toner concentration is low, the magnetic carrier is relatively large, so that the magnetic permeability is high. When the toner concentration is high, the magnetic carrier is relatively small, and thus the permeability is relatively small. This is preferably used because it uses the phenomenon that the magnetic susceptibility is lowered and is not affected by the color tone of the carrier.

  The toner concentration detection sensor based on the magnetic permeability detection method outputs a characteristic based on the magnetic permeability of the developer as the object to be measured, for example, as a voltage value. Normally, the output value is low when the toner concentration is high, and the output value is high when the toner concentration is low. As described above, in the toner concentration detection sensor based on the magnetic permeability detection method, the toner concentration can be known from the output value.

  In an image forming apparatus incorporating a toner concentration detection sensor based on a magnetic permeability detection method, toner is replenished when the toner concentration decreases and the output value of the toner concentration detection sensor exceeds a predetermined value (judgment reference value). The toner density is controlled to be kept within a preferable range.

  However, it is known that the magnetic permeability of the developer changes depending on factors other than the toner concentration. For example, if the charge amount of the developer changes, the electrostatic repulsion force between carriers in the developer changes even if the toner concentration is the same, so the bulk density of the developer changes. If the charge amount is increased, the repulsive force between carriers having the same polarity is increased, so that the bulk density of the developer is decreased.

  When the bulk density is lowered, the magnetic permeability of the developer is lowered, and the output value of the toner concentration detection sensor based on the magnetic permeability detection method is lowered. That is, when the bulk density decreases, an output value indicating that the toner concentration is high is obtained in the magnetic permeability detection method.

  In general, the bulk density of the developer changes with a certain tendency depending on the developer durability, usage environment, stirring stop time, etc., so the output value of the toner concentration detection sensor is the developer durability, usage environment, stirring stop. It changes with time.

  As described above, it is difficult to accurately detect the toner density only by the output value of the toner density detection sensor based on the magnetic permeability detection method. In the conventional image forming apparatus, the magnetic permeability due to such factors other than the toner density is difficult. Consideration is made so as not to cause erroneous detection of the toner density due to the change. For example, by controlling the control voltage that controls the output value of the toner concentration detection sensor, the output value of the toner concentration detection sensor is corrected according to the developer durability, use environment, stirring stop time, etc., and the corrected output value A method for supplying toner is used. When controlling the control voltage applied to the toner concentration detection sensor, the control voltage applied to the toner concentration detection sensor for developer durability, usage environment, stirring stop time, etc. is stored in the form of a correction table, and the detected developer durability and It is carried out with reference to the correction table according to conditions such as the use environment and the stirring stop time.

  However, in practice, there are many cases where the developer bulk density does not change according to the tendency assumed in advance in the correction table, and it is difficult to accurately detect the toner concentration only by the output value of the magnetic permeability sensor. The resulting image may be affected.

  Further, a magnetic permeability sensor is arranged in the stirring chamber, and it is determined whether or not the developer in the stirring chamber is in a state of replenishing toner based on the result of comparing the output value of the magnetic permeability sensor with the determination reference value. In addition to density control, a reflective optical sensor is arranged downstream of the development area of the photoconductor to detect the image density of the toner image for detection formed on the photoconductor, and from the detection result of the image density A technique is disclosed in which toner density control is performed based on the result of comparison with a judgment reference value obtained by correcting a judgment reference value and correcting an output value of a magnetic permeability sensor (Patent Document 1).

  If the development characteristics change due to changes in the developer over time, the image density of the formed image is less than the desired image density or the desired image density, even if the output value of the magnetic permeability sensor is within the predetermined range. Although the following may occur, according to this toner density control method, even when the development characteristics change, the reference value corrected based on the detection result of the toner image for detection is compared with the output value of the magnetic permeability sensor. Since the toner is replenished depending on the result, the toner density in the developing device can be increased to obtain a desired image density.

However, since the toner concentration control method disclosed in Patent Document 1 measures the toner concentration of a developer in which the toner and the carrier are not separated by a magnetic permeability sensor, the measured value is influenced by the bulk density of the developer. . In addition, the toner image for detection on the photosensitive member detected by the optical sensor is not formed by separating all the toner in the developer carried on the surface of the developing roller, but one in the developer. It is merely formed by transferring part of the toner to the photoreceptor. Therefore, it cannot be said that the toner concentration can be accurately measured under various environments and conditions from the output of the magnetic permeability sensor and the optical sensor obtained in this manner, and accurate toner concentration control cannot be performed.
JP-A-5-158348

  It is an object of the present invention to provide an image forming apparatus capable of managing toner density with high accuracy and forming an image with good image quality without being affected by a change in the bulk density of the developer.

The object is achieved by the following means.
(1) An image forming apparatus using a developer containing toner and carrier,
Toner storage means for storing the toner;
A developer storage section for storing the developer;
A toner replenishing means for supplying toner stored in the toner storage means to the developer storage section; and a developing device having a developer carrier for carrying the developer;
A photoreceptor carrying an electrostatic latent image;
And an image forming apparatus that develops a latent image carried on the photoconductor at a position facing the photoconductor and the developer carrying body into a toner image with the developer carried on the developer carrying body. In
A first sensor that outputs an output value corresponding to the density of a toner image formed on the surface of the photoreceptor;
A second sensor that outputs an output value corresponding to the magnetic permeability of the developer remaining on the surface of the developer carrying member after development;
Control means for controlling the operation of the toner replenishing means based on the output value of the first sensor and the output value of the second sensor;
An image forming apparatus comprising:
(2) The control unit calculates a calculated value from the output value of the first sensor and the output value of the second sensor, and controls the operation of the image forming apparatus based on the calculated value. The image forming apparatus according to (1).
(3) The calculated value is calculated by a calculation formula of C = A / B, where C is the calculated value, A is the output value of the first sensor, and B is the output value of the second sensor. (2) The image forming apparatus according to (2).
(4) The control means controls the operation of the toner replenishing means based on a comparison result between the calculated value and a preset reference value. (2) or (3) Image forming apparatus.
(5) Measurement by the first sensor and the second sensor and output of the output value, calculation of the calculated value by the control means, comparison of the calculated value with the reference value, and results of the comparison The control of the operation of the toner replenishing unit based on the above is performed after a developing operation performed under a condition different from that in normal image formation, according to any one of (1) to (4) The image forming apparatus described.
(6) The image forming apparatus according to any one of (1) to (5) includes a toner density sensor having a variable output level for measuring a toner density of the developer accommodated in the developer accommodating portion. And
The image forming apparatus, wherein the control unit controls an output level of the toner density sensor based on an output value of the first sensor and an output value of the second sensor.

  According to the present invention, it is possible to provide an image forming apparatus that performs toner density management with high accuracy and forms an image with good image quality without being affected by a change in the bulk density of the developer.

  The present invention relates to an image forming apparatus having means for acquiring an information value corresponding to a toner density of a developer and suitably managing the toner density based on the acquired information value. Prior to describing the embodiment, an information value corresponding to the toner density, which is the basis of the present invention, will be described.

  FIG. 1 is a schematic diagram for explaining a process for obtaining an information value corresponding to a toner density in the present invention. In FIG. 1, reference numeral 1 denotes a photosensitive drum that rotates in the direction indicated by an arrow. A magnet roll having a plurality of magnets therein and a developing sleeve that rotates in the direction indicated by an arrow on the outer periphery of the magnet roll. A developing roller 41 that functions as a developer carrying member is disposed.

  Reference numeral 44 denotes an agitation chamber for storing the developer. The agitation chamber 44 corresponds to a developer storage portion described in claims.

  Reference numerals 441 and 442 denote screws which are stirring members disposed in the stirring chamber 44, and the developer stored in the stirring chamber 44 is stirred by rotating. The developer composed of the toner and the magnetic carrier is frictionally charged by stirring, and the toner is attached to the outer periphery of the carrier. The developer is attached to the peripheral surface of the developing sleeve by a magnetic force, and is carried and conveyed by the developing roller 41.

  The developer adhering to the developing roller 41 is limited to a predetermined amount by the layer thickness regulating member 43, and is conveyed to the developing region facing the photosensitive drum 1 as the developing roller 41 rotates.

  A developing bias in which a DC voltage and an AC voltage are superimposed is applied to the developing roller 41, and the developer toner carried and conveyed by the developing roller 41 is applied to the electrostatic latent image portion on the photosensitive drum 1 in the developing region. Adhering development is performed. A toner image is formed on the photosensitive drum 1 that has passed through the development area. On the developing roller 41 that has passed through the developing region, a developer carrier that has lost toner due to the development remains.

  In such a development process, the optical sensor S4 is disposed at a downstream position in the rotation direction in the development region of the photosensitive drum 1, and a magnetic permeability sensor S5 is disposed at a downstream position in the rotation direction of the development region in the developing roller 41. .

  The optical sensor S4 detects the density of the toner image formed on the photosensitive drum 1, and the magnetic permeability sensor S5 remains on the developing roller 41 that has passed through the developing area, and the magnetic permeability of the developer that has lost toner due to the development. Is detected.

  The optical sensor S4 emits a light beam from the light emitting element to irradiate the object to be measured, detects the amount of light reflected from the object to be measured by the light receiving element, and reflects the amount of light emitted from the light emitting element and the object to be measured. The logarithm of the ratio with the amount of light coming in is used as an output value, and functions as a first sensor that measures and outputs the characteristics relating to the toner image described in the claims. The optical sensor S4 has an output value A = when the density of the characteristic relating to the toner image formed on the photosensitive drum 1 is Vs, the light amount of the light emitting element is Vs, and the light amount reflected from the object to be measured is Vt. The output value A is output as −log (Vt / Vs).

  The magnetic permeability sensor S5 has the same configuration as the toner density detection sensor based on the magnetic permeability detection method, and outputs an output value B based on the magnetic permeability of the characteristics relating to the developer remaining on the developing roller 41 as a voltage value. Yes, it functions as the second sensor described in the claims.

  Incidentally, the development efficiency in the development process, that is, the toner application rate to the photosensitive drum 1, can be changed by changing the ratio of the linear velocities of the outer peripheral surfaces of the photosensitive drum 1 and the developing roller 41. it can.

  For example, after development, development in which the development toner carried by the development roller 41 is applied to the photoreceptor drum 1, that is, development with a development efficiency of 100%, is the linear velocity of the outer peripheral surface of the development roller 41 during development. Is set smaller than the linear velocity of the outer peripheral surface of the photosensitive drum 1, for example, by setting the ratio of the linear velocity of the outer peripheral surface of the developing roller 41 to the linear velocity of the outer peripheral surface of the photosensitive drum 1 to 1:10. .

  When the developing efficiency is 100%, the toner contained in the developer carried on the developing roller 41 moves to the 100% photosensitive drum 1, so that the developer on the photosensitive drum 1 that has passed through the developing region A toner image is formed with 100% of the toner, and only the carrier of the developer that has lost 100% of the toner due to the development remains on the peripheral surface of the developing roller 41 that has passed through the development region.

  Therefore, when the development is performed under the condition that the development efficiency is 100%, the output value A of the optical sensor S4 is a numerical value that reflects the amount of toner in the developer subjected to the development, and the magnetic permeability sensor S5. The output value B is a numerical value reflecting the amount of carrier in the developer used for development.

  The inventor of the present application provides an output value A that reflects the amount of toner in the developer before development and the amount of carrier in the developer before development when development is performed under conditions such that the development efficiency is 100%. As a result of studying to obtain an index value corresponding to the toner density in the developer before development from the output value B reflecting the above, the calculated value C calculated by the formula C = A / B is given to the developing roller 41. It has been found that the index value corresponds to the toner concentration of the supplied developer.

  FIG. 2 is data and a diagram for explaining the correspondence between the toner density of the developer and the calculated value.

  FIG. 2A shows an output value A of the optical sensor S4 when a latent image of a measurement pattern formed on the photosensitive drum is developed at a development efficiency of 100% using a developer having a known toner density. The calculated value C (= A / B) calculated from the output value B of the magnetic permeability sensor and the output value A of the optical sensor S4 and the output value B of the magnetic permeability sensor are listed in the table.

  The conditions for obtaining the output value A and the output value B are as follows.

  Developer: A two-component developer in which a styrene acrylic polymerized toner having a volume average particle diameter of 4.5 μm and an acrylic resin-coated Mn ferrite carrier having a volume average particle diameter of 25 μm are formed so that the toner concentration is 2 to 10%.

Measurement pattern: Fully exposed pattern for solid image Development condition: Development roller rotation peripheral speed 40 mm / s
Photosensitive member rotation speed peripheral speed 400 mm / s
Optical sensor: a sensor having a light-emitting element and a light-receiving element, which irradiates the surface to be measured with a light flux Vs emitted from the light-emitting element, detects the amount of reflected light Vt from the surface to be measured by the light-receiving element, and a calculation formula The reflectance of the surface to be measured represented by A = −log (Vt / Vs) is output as an output value A. (A: 0-3 range)
Magnetic permeability sensor: The magnetic permeability of the object to be measured is output as an output value B. The output value B is output as the magnetic permeability (= carrier mass per unit area) of the developer on the sleeve to be measured. (B: 0 to 5 (V) range)
FIG. 2B is a graph showing the relationship between the toner density of the developer and the calculated value C, in which the data of FIG. 2 is represented on a coordinate plane. The horizontal axis represents the developer toner concentration, and the vertical axis represents the calculated value C. 2A and 2B that the toner density of the developer and the calculated value C have a strong correspondence.

  The obtained calculated value C depends on the output value of the sensor obtained from the toner image formed on the photosensitive drum 1 with 100% toner in the developer and the magnetic permeability of 100% carrier on the developing roller 41. Therefore, the index value represents the toner density of the developer with high accuracy without being affected by the bulk density.

According to the present invention, by determining and controlling the necessity of toner replenishment based on the calculated value C that expresses the toner density of the developer with high accuracy, the toner density can be properly managed and a high-quality image can be formed. The present invention provides an image forming apparatus capable of achieving the above.
<First Embodiment of the Invention>
FIG. 3 is a diagram showing an example of an image forming apparatus to which the present invention is applied. The image forming apparatus 100 shown in FIG. 3 is called a tandem type color image forming apparatus, and includes an image reading apparatus 200.

  The image forming apparatus 100 includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer member 6, a paper feeding / conveying unit 20, and a fixing device 70.

  The image forming apparatus 100 operates in two modes: an image forming mode and a toner density management mode. The image forming mode is a mode for performing normal image formation, and the toner density management mode is a mode for managing the toner density of the developer. Details of these two modes will be described later.

  An image reading device 200 including an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the image forming apparatus 100.

  The document d placed on the document table of the automatic document feeder 201 is transported by a transport unit, and an image on one or both sides of the document is scanned and exposed by the optical system of the document image scanning exposure device 202, and the line image sensor CCD is scanned. Is read.

  The analog signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in the image processing unit 50, and once stored, exposure means (image writing means) Input to 3Y, 3M, 3C, 3K.

  The image forming unit 10Y that forms a yellow (Y) image includes a charging unit 2Y, an exposure unit 3Y, a developing device 4Y, and a cleaning unit 5Y disposed around a photosensitive drum 1Y as an image carrier.

  The image forming unit 10M that forms a magenta (M) color image includes a photosensitive drum 1M as an image carrier, a charging unit 2M, an exposure unit 3M, a developing device 4M, and a cleaning unit 5M.

  An image forming unit 10C for forming a cyan (C) color image includes a photosensitive drum 1C as an image carrier, a charging unit 2C, an exposure unit 3C, a developing device 4C, and a cleaning unit 5C.

  The image forming unit 10K that forms a black (K) image includes a photosensitive drum 1K as an image carrier, a charging unit 2K, an exposure unit 3K, a developing device 4K, and a cleaning unit 5K.

  The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K constitute latent image forming units, respectively, and the photosensitive drums 1Y, 1M, and 1C. An electrostatic latent image is formed on 1K.

  4Y, 4M, 4C, and 4K are developing devices that contain a two-component developer composed of a small particle size toner of yellow (Y), magenta (M), cyan (C), and black (K) and a carrier, respectively. Yes, the photosensitive drums 1Y, 1M, 1C, and 1K carrying the electrostatic latent images are developed to form toner images of the respective colors on the photosensitive drums.

  The intermediate transfer body 6 is wound around a plurality of rollers and is rotatably supported.

  The toner images of the respective colors formed on the photosensitive drums 1Y, 1M, 1C, and 1K are sequentially transferred (primary transfer) by the primary transfer means 7Y, 7M, 7C, and 7K onto the rotating intermediate transfer body 6 to be combined. A colored image is formed.

  The transfer material 90 accommodated in the paper feeding cassette 21 of the paper feeding / conveying means 20 is fed by the paper feeding means 22 and passed through the paper feeding rollers 23, 24, 25, 26, the registration rollers 27, etc., and the secondary transfer. A color image is transferred onto the transfer material 90 (secondary transfer) by being conveyed to the means (transfer roller) 9.

  The transfer material 90 onto which the color image has been transferred is fixed on the transfer material 90 after the color toner image (or toner image) is fixed by the fixing device 70, and is sandwiched between the discharge rollers 28 to be discharged outside the apparatus. 29.

  In the description of the image forming apparatus 100, the color image formation has been described. However, the present invention includes a case of forming a monochrome image.

  FIG. 4 is a schematic diagram illustrating a process for performing toner density management in the embodiment of the invention.

  In FIG. 4, 1 is a photosensitive drum, 4 is a developing device, 60 is a toner storage unit, 61 is a toner supply unit, S4 is an optical sensor, S5 is a magnetic permeability sensor, and 11 is a control unit.

  The developing device 4 includes a magnet roll having a plurality of magnets therein, and a developing roll 41 that functions as a developer carrier by rotating the outer periphery of the magnet roll in the direction of the arrow, and faces the photosensitive drum 1. Be placed.

  The developing chamber 4 is a stirring chamber 44 for storing the developer supplied to the developing roller 41 and stirring the developer stored by the rotation of the screws 441 and 442 disposed therein.

  In step S4, the optical sensor measures the density of the toner image formed on the photosensitive drum 1 after development, and outputs the measurement result as an output value A.

  The permeability sensor S5 measures the permeability of the developer remaining and carried on the developing roller 41 after development, and outputs the measurement result as an output value B.

  A control unit 11 controls the rotation of the photosensitive drum 1, the developing roller 41, and the screws 441 and 442, and the developing roller 41 carries the developing in the developing region where the developing roller 41 and the photosensitive drum 1 face each other. Control of development for forming a toner image on the photosensitive drum 1 by the agent, and control of toner concentration management of the developer stored in the stirring chamber 44 based on output values from the optical sensor S4 and the magnetic permeability sensor S5. Do.

  The operation process in the embodiment will be described with reference to the configuration diagram shown in FIG.

  The developer composed of the toner and the magnetic carrier housed in the stirring chamber 44 is stirred and frictionally charged, so that the toner adheres to the outer periphery of the carrier, and is attached and carried on the peripheral surface of the rotating developing roller 41.

  The developer carried and transported by the developing roller 41 is restricted by the layer thickness regulating member 43 so as to have a predetermined layer thickness.

  The developer attached and carried on the peripheral surface of the developing roller 41 moves to a developing region where the photosensitive drum 1 and the developing roller 41 face each other as the developing roller 41 rotates.

  A developing bias in which a DC voltage and an AC voltage are superimposed is applied to the developing roller 41, and toner in the developer carried by the developing roller 41 is exposed to light in a developing region where the developing roller 41 and the photosensitive drum 1 face each other. Development is performed to move to and adhere to the electrostatic latent image portion on the photosensitive drum 1 to form a toner image on the photosensitive drum 1.

  In the image forming mode in which normal image formation is performed, the rotational speeds of the photosensitive drum 1 and the developing roller 41 are the linear velocity of the outer peripheral surface of the photosensitive drum 1 and the linear velocity of the outer peripheral surface of the developing roller 41. The ratio is set to 1: 2.

  In the image forming mode, the toner image formed on the photosensitive drum 1 is transferred to the transfer material 90 via the intermediate transfer body 6 under such process conditions, and is discharged outside the apparatus after fixing.

  In the toner density management mode, the linear velocity of the outer circumferential surface of the developing roller 41 and the photosensitive drum 1 are adjusted so that the linear velocity of the outer circumferential surface of the developing roller 41 is smaller than the linear velocity of the outer circumferential surface of the photosensitive drum 1. The ratio of the linear velocity of the outer peripheral surface is set to 1:10, predetermined measurement pattern image data is written to the photosensitive drum 1, and the latent image of the measurement pattern on the photosensitive drum 1 is developed and measured. A toner image of a pattern is formed.

  When the development is performed under the condition that the ratio of the linear velocity of the outer peripheral surface of the developing roller 41 to the linear velocity of the outer peripheral surface of the photosensitive drum 1 is 1:10, the developer carried on the developing roller 41 All the toner inside can be moved to the electrostatic latent image on the photosensitive drum 1 to form a toner image.

  Therefore, a measurement pattern toner image is formed on the photosensitive drum 1 that has passed through the development area with 100% toner of the developer used for development, and the toner on the development roller 41 that has passed through the development area is subjected to development. Only the carrier of the developer lost 100% remains.

  The output value A as a result of measuring the density of the measurement pattern toner image on the photosensitive drum 1 by the optical sensor S4, and the result of measuring the magnetic permeability of the carrier remaining on the developing roller 41 by the magnetic permeability sensor S5. A calculated value divided by the output value B is obtained, the obtained calculated value is compared with a reference value stored in advance, and control is performed so that toner supply is performed when the calculated value is smaller than the reference value.

  The output value A of the optical sensor S4 is obtained by measuring the total toner amount of the developer subjected to development and separated as an image density and outputting it as a voltage value. The output value B of the magnetic permeability sensor S5 is the development value. Since the total carrier amount in the separated developer is measured as the magnetic permeability and output as a voltage value, it is equal to the total toner mass and the total carrier mass in the developer unit mass. The toner density is directly measured. Since the toner and the carrier in the developer are completely separated and each of them is measured, even if the bulk density of the developer changes, it is not affected.

  In the toner density management mode, the ratio of the linear velocities of the photosensitive drum 1 and the outer peripheral surface of the developing roller 41 is different from that in the image forming mode. Therefore, the toner density management mode is simultaneously performed in parallel with the image forming mode. I can't. The operation in the toner density management mode is performed when image formation is not performed, for example, when the fixing device is warmed up, when one image formation is completed, when one job unit is completed, or predetermined When the number of image formations is made, etc. From the aspect of image formation productivity, when one job unit in the image formation mode is completed, or when a predetermined number of image formations are performed, the mode is automatically switched to the toner density management mode. Is preferred. In the present embodiment, when one job unit in the image forming mode is completed, the mode automatically switches to the toner density management mode, and when the toner density management operation in the toner density management mode is completed, the image forming mode is automatically restored. Is configured to do.

  FIG. 5 is a block diagram showing an outline of a toner density management control system in the image forming apparatus of the present embodiment.

  In FIG. 5, reference numeral 100 denotes a control unit, and a CPU 111 that performs arithmetic and control processing uses an image forming unit driving unit, a toner supply unit 61, and a toner density sensor S <b> 2 of the image forming apparatus 100 according to a program stored in the storage unit 121. The operations of the optical sensor S4 and the magnetic permeability sensor S5 are controlled via the interface 150.

  The image forming unit driving unit drives the photosensitive drum 1M, the charging unit 2M, the exposure unit 3M, the developing unit 4M, and the cleaning unit 5M in the image forming apparatus 100.

  The toner supply unit 61 supplies the toner stored in the toner storage unit 60 to the stirring chamber 44.

  The CPU 111 is connected with storage means 121 to 124, a calculation means 131, and a comparison means 141.

  The storage unit 121 includes an image formation mode program that is a program for executing the image formation mode, a toner density management mode program that is a program for executing the toner density management mode, and a calculation formula for calculating a calculation value to be described later. Stored.

  The storage unit 122 stores measurement pattern image data. The measurement pattern (image data) will be described later.

The storage unit 123, the reference value C _K is accommodated. The storage means 124 stores the output value A of the optical sensor S4, the output value B of the magnetic permeability sensor S5, and the calculated value C. The storage means 124 can store a plurality of information, and the stored information can be replaced.

  The computing unit 131 functions to calculate the calculated value C based on the calculation formula stored in the storage unit 121 according to an instruction from the CPU 111.

The comparison unit 141 functions to compare and determine whether or not the calculated value C is smaller than the reference value C _K according to an instruction from the CPU 111.

  At the time of image formation, the CPU 111 operates the respective units of the image forming apparatus 100 via the interface 150 according to the image formation mode program to perform image formation.

  Further, during execution of the toner density management mode, the toner density is managed by operating the respective units of the image forming apparatus 100 via the interface 150 by the toner density management mode program.

  The switching from the image forming mode to the toner density management mode in the image forming apparatus according to the first embodiment is performed when one job executed in the image forming mode is completed by the program stored in the storage unit 121. Made automatically.

  Next, operations in the image forming mode and the toner density management mode will be described with reference to FIGS.

  In the image forming mode in which normal image formation is performed, the CPU 111 controls the developing roller 41 and the photosensitive drum 1 to rotate at a predetermined speed, respectively. In the image forming mode, the respective rotational speeds are controlled so that the ratio of the linear speeds of the developing roller 41 and the outer peripheral surface of the photosensitive drum 1 is 2: 1. The developing roller 41 agitates in the agitating chamber 44 and carries and conveys the frictionally charged developer.

  The developing roller 41 is applied with a bias voltage, and the toner in the developer adhered and transported to the peripheral surface of the developing roller 41 moves to the photosensitive drum 1 in the developing region, and is electrostatically carried by the photosensitive drum 1. The latent image is developed into a toner image.

  On the other hand, in the toner density management mode, the CPU 111 sets the rotational speed of the photosensitive drum 1 and the developing roller 41 to be different from the image forming mode, and the linear velocity of the outer peripheral surface of the developing roller 41 is the same as that of the outer peripheral surface of the photosensitive drum 1. Control is performed so that the ratio of the linear velocity of the outer peripheral surface of the developing roller 41 to the linear velocity of the outer peripheral surface of the photosensitive drum 1 is 1:10 so as to be smaller than the linear velocity.

  Next, the CPU 111 controls to read the measurement pattern image data stored in the storage unit 122 and write the measurement pattern image data called to the writing unit to the photosensitive drum 1.

  The measurement pattern is a solid image exposed on the entire surface. The electrostatic latent image of the measurement pattern written and formed on the photosensitive drum 1 is developed in the development area to become a measurement pattern toner image.

  In the toner density management mode, the ratio of the linear velocity of the outer peripheral surface of the developing roller 41 to the linear velocity of the outer peripheral surface of the photosensitive drum 1 is 1:10, so that all the developer in the developer carried on the developing roller 41 The toner can be moved to the electrostatic latent image on the photosensitive drum 1 to obtain a measurement pattern toner image.

  The CPU 111 causes the optical sensor S 4 to measure the reflected light amount of the measurement pattern toner image formed on the peripheral surface of the photosensitive drum 1, outputs the measurement result as an output value A, and stores the output value A in the storage unit 124. .

  Further, the magnetic permeability sensor S5 measures the magnetic permeability of the developer remaining on the surface of the developing roller 41 after the development, that is, the carrier remaining on the surface of the developing roller 41, and outputs the measurement result as an output value B. The output value B is stored in the storage unit 124.

  The CPU 111 causes the computing unit 131 to calculate the calculated value C based on the calculation formula stored in the storage unit 121 from the output value A and the output value B stored in the storage unit 124, and the calculated value C is stored in the storage unit 124. Store in. The storage unit 121 stores a calculation formula C = A / B.

Next, the CPU 111 causes the comparison unit 141 to compare the calculated value C stored in the storage unit 124 with the reference value C _K stored in the storage unit 123.

The reference value _CK is derived using a developer having a toner density at a limit value that is determined to require toner replenishment in advance, and corresponds to the limit toner density value for whether or not toner replenishment is performed. It is a numerical value. Is a numerical value serving as a reference is determined that it is necessary to supply toner when the calculated value C is smaller than the reference value C _K.

When the comparison result is C <C _K is CPU 111 instructs to perform toner supply to the toner replenishing unit 61. If C <C _K is not satisfied, no toner replenishment instruction is given.

The toner replenishing unit 61 that is instructed to replenish toner operates to supply the toner stored in the toner storage unit 60 to the stirring chamber 44. The toner supply operation by the toner replenishing means 61 stops when a predetermined time according to the program elapses after the toner supply is started. Thus, when the calculated value C is an index value of the toner concentration of the test have been developer to the developing is smaller than the reference value C _K, i.e., by performing the replenishment of toner when the toner density is less than the reference value The toner concentration of the developer accommodated in the stirring chamber 44 as the developer accommodating portion increases, and the toner concentration of the developer accommodated in the developer accommodating portion can always be kept at a preferable level.

After the comparison result is C <C _K , or when C <C _K is not satisfied, the toner density management mode is terminated and the image forming mode is restored.

Note that the image forming apparatus according to the above-described embodiment supplies toner for a predetermined time when it is determined that the calculated value C is smaller than the reference value C _K based on the magnitude determination result between the calculated value C and the reference value C _K. The difference D = C _K −C between the calculated value C and the reference value C _K is obtained, and after the toner supply is started according to the magnitude of the difference D, the toner supply is stopped. It is also possible to make the time variable. With this configuration, the toner density can be controlled more finely.

  FIG. 6 is a flowchart for explaining the flow of operations in which the image forming apparatus of the present embodiment performs toner density management in the toner density management mode. Hereinafter, description will be given with reference to the flowchart shown in FIG.

First, when a job to be executed is input by the user, the CPU 111 performs image formation in an image forming mode. (Step S1)
In the subsequent step S2, the CPU 111 checks whether or not the execution job has been completed each time image formation is performed. When the execution job has not ended (No in step S2), the CPU 111 returns to step S1 and step S1. Steps S2 to S2 are repeated until the execution job is completed.

  When the execution job is finished (Yes in step S2), the process proceeds to step S3.

  In step S <b> 3, the CPU 111 switches the operation mode from the image forming mode to the toner density management mode according to the program stored in the storage unit 121.

  In step S4, the CPU 111 instructs to change the respective rotational speeds so that the ratio of the linear speed of the outer peripheral surface of the developing roller 41 to the linear speed of the outer peripheral surface of the photosensitive drum 1 is 1:10. Control.

  In step S5, the CPU 111 calls the photometric pattern image data stored in the storage unit 122, instructs the writing unit to write the photometric pattern image data that has been called to the photoconductive drum 1, and causes the photoconductive drum 1 to perform photometric measurement. An electrostatic latent image of the pattern is formed.

  In step S6, the CPU 111 performs development with the developer carried on the developing roller 41, and forms an electrostatic latent image of a photometric pattern on the photosensitive drum 1 into a toner image. By developing the ratio of the linear velocity of the outer peripheral surface of the developing roller 41 and the linear velocity of the outer peripheral surface of the photosensitive drum 1 to 1:10, all the toner in the developer carried on the developing roller 41 is obtained. Transfer to the photosensitive drum 1 to form a toner image.

  Next, in step S7, the CPU 111 causes the optical sensor S4 to measure the density of the toner image formed on the photosensitive drum 1, stores the output value A of the measurement result in the storage unit 124, and develops it in the magnetic permeability sensor S5. The magnetic permeability of the developer after development carried on the roller 41 is measured, and the output value B of the measurement result is stored in the storage unit 124.

  In step S8, the CPU 111 calls the output value A and the output value B stored in the storage unit 124, and calculates the calculated value C by the calculation formula (C = A / B) stored in the storage unit 121 in the calculation unit 131. The calculated value C is stored in the storage unit 124.

In step S9, the CPU 111 calls the reference value C _K stored in the storage unit 123 and the calculated value C stored in the storage unit 124, and checks whether or not the calculated value C is smaller than the reference value C _{K in} the comparison unit 141. When the calculated value C is smaller than the reference value C _K (step S9 Yes), the process proceeds to step S10. When the calculated value C is not smaller than the reference value C _K (step S9 No), the process proceeds to step S11. Control to do.

  In step S <b> 10, the CPU 111 instructs the toner supply unit 61 to supply toner. The toner replenishing unit 61 supplies the toner stored in the toner storage unit to the stirring chamber 44 in accordance with an instruction from the CPU 111. When the toner supply in step S10 is completed, the process proceeds to step S11.

  In step S11, the CPU 111 switches the operation mode from the toner density management mode to the image formation mode in accordance with the program stored in the storage unit 121, and ends the operation.

  By determining and controlling the necessity of toner replenishment based on the calculated value C in the toner density management mode as described above, the toner density of the developer carried on the developing roller 41 can be properly managed, and high quality can be achieved. Images can be formed.

  Three image forming apparatuses (No. 1, No. 2, No. 3) to which the toner density management method described in the first embodiment of the invention is applied are used as examples, and a toner density management method according to the prior art The three image forming apparatuses (No. 4, No. 5, and No. 6) to which No. 4 was applied were used as comparative examples, and a real print test was performed for each, and toner density transitions were compared.

(A) Conditions for live-action print test (a) Common condition image forming device; A4 horizontal 80 sheets / minute machine (digital full-color machine)
Linear velocity of the outer peripheral surface of the photosensitive drum: 400 mm / sec
Photoconductor drum diameter: 80 mm
Developing roller potential Vdc: -500 V (variable: standard value on the left)
Photoconductor solid exposure potential Vi: -50V
Development bias AC component Vac: 1 kVp-p rectangular wave 5 kHz
Latent image exposure means: semiconductor laser (wavelength 780 nm)
Developing roller diameter: 30 mm
Development roller-photoreceptor distance Ds: about 0.30 mm
Developer transport amount D on developing roller: about 25 mg / cm ²
Linear velocity of developing roller outer peripheral surface / linear velocity of outer peripheral surface of photosensitive drum 1: 2.0
Developer: Two-component developer Toner: Styrene acrylic polymer toner Volume average particle diameter 4.5 μm
Carrier: Acrylic resin-coated Mn ferrite carrier Volume average particle size 25 μm
Set toner density: 6%
(B) Example toner density management method: the output value A of the optical sensor S4 of the image density of the measurement pattern toner image formed on the photoconductor under predetermined conditions, and the remaining on the developing roller after developing the measurement pattern toner image The calculated value C (= A / B) is calculated from the output value B of the permeability sensor of the developer (carrier) to be supplied, and toner is replenished based on the comparison result between the calculated value C and the reference value C _K. Before the actual print test, the output value levels and judgment criteria of each sensor so that a good image density can be obtained when an image is formed under NN environmental conditions (temperature 20 ° C., humidity 50%). Toner density management conditions such as values were set.
Measurement pattern: linear velocity of the outer peripheral surface of the pattern developing roller exposed on the whole surface for a solid image / linear velocity of the outer peripheral surface of the photosensitive drum 1: 0.1
Optical sensor: light emitting element = infrared LED (central wavelength 880 nm)
Photodetector = Phototransistor
Incident angle 45 ° / light receiving angle 45 °
Magnetic permeability sensor: According to the magnetic permeability of the developer on the sleeve (= carrier mass per unit area)
To output an output value B. (B: 0 to 5 (V) range)
Toner density management: 1 formed on a photoreceptor on a predetermined condition each time a print job is completed
The output value A of the optical sensor S4 of the image density of the measurement pattern toner image, and the measurement
The developer remaining on the developing roller after forming the constant pattern toner image (carrier
Calculate the calculated value C (= A / B) from the output value B of the magnetic permeability sensor in a).
The toner is replenished based on the comparison result between the output value C and the reference value C _K.
(C) Comparative Example Toner Concentration Management Method: A magnetic density toner concentration sensor is disposed in the stirring chamber, and toner concentration control is performed based on a comparison result between the output value of the magnetic permeability sensor and a determination reference value. Further, a reflective optical sensor is arranged on the downstream side of the development area of the photoconductor to detect the image density of the toner image for detection formed on the photoconductor, and to correct the determination reference value from the detection result of the image density, The toner density control is performed based on the comparison result between the output value B of the magnetic permeability sensor and the corrected determination reference value. Before performing the actual print test, the output value level and judgment reference value of each sensor so that a good image density can be obtained when an image is formed under NN environmental conditions (temperature 20 ° C., humidity 50%). The toner density management conditions such as were set.
Measurement pattern: linear velocity of the outer peripheral surface of the pattern developing roller exposed on the whole surface for a solid image / linear velocity of the outer peripheral surface of the photosensitive drum 1: 2.0
Optical sensor: light emitting element = infrared LED (central wavelength 880 nm)
Photodetector = Phototransistor
Incident angle 45 ° / light receiving angle 45 °
Magnetic permeability sensor: Outputs an output value B according to the magnetic permeability of the developer in the stirring chamber.

(B: 0 to 5 (V) range)
Toner concentration management: Output value and criterion value of magnetic permeability sensor placed in stirring chamber during image forming operation
Based on the comparison result, toner density control is implemented.

Each time a print job is completed, it is formed on the photoconductor under predetermined conditions.
Based on the output value A of the optical sensor S4 of the image density of the measurement pattern toner image.
Then, the judgment reference value is corrected.

(B) Confirmation / Evaluation For each of the three examples and comparative examples, a full-color image printing pattern with an average color printing rate of 6% for each of the three units was made into a continuous print of A4 size (horizontal feed) single-sided 5 sheets, totaling 60000 prints. (1) LL environmental conditions (temperature 10 ° C., humidity 20%). 1, Comparative Example No. 4
(2) NN environmental conditions (temperature 20 ° C., humidity 50%) 2, Comparative Example No. 5
(3) HH environmental conditions (temperature 30 ° C., humidity 80%) 3, Comparative Example No. 6
For all print images formed under the environmental conditions (1), (2), and (3), the presence / absence of over-density / fogging and occurrence of fogging were visually confirmed. A case where all good images were obtained was marked with ◯, and a case where image defects such as excessive / insufficient image density or fogging occurred were marked with ×.

(C) Results Evaluation results are shown in Table 1.

As shown in Table 1, in the embodiment, a good image without excessive / deficient image density or fogging through all prints formed under the environmental conditions (1), (2), and (3). was gotten. On the other hand, in the comparative example, although the toner density control is performed, the print formed under the LL environmental conditions (temperature 10 ° C., humidity 20%) has insufficient image density and HH environmental conditions (temperature 30 ° C.). The print formed at a humidity of 80%) has excessive image density or fog. This is presumably because the bulk density of the developer changed under the LL environmental condition or the HH environmental condition, which had an influence on the measurement of the toner density.

  From the above test results, it can be seen that the image forming apparatus that performs toner density management according to the embodiment of the present invention can perform toner density management without being affected by the bulk density of the developer, and obtain a good image.

That is, an optical sensor is arranged as a first sensor that outputs an output value corresponding to the density of the toner image formed on the surface of the photosensitive member, and the magnetic permeability of the developer remaining on the surface of the developer carrying member after development is set. A control unit that arranges a magnetic permeability sensor as a second sensor that outputs a corresponding output value and controls the operation of the toner replenishing unit 61 based on the output value of the first sensor and the output value of the second sensor. By providing the toner density management, it is possible to provide an image forming apparatus capable of managing the toner density and obtaining a good image without being affected by the bulk density of the developer.
<Second Embodiment of the Invention>
In the first embodiment of the invention described above, the toner density management is provided by providing the control means for controlling the operation of the toner replenishing means 61 based on the output value of the first sensor and the output value of the second sensor. In addition, a magnetic permeability detection type toner density sensor is arranged in the stirring chamber, and during normal image formation, toner density management is performed by the output of the toner density sensor. In addition, it is possible to perform toner density management by correcting the output level of the toner density sensor based on the output value of the first sensor and the output value of the second sensor.

  In the toner density management method for controlling the operation of the toner replenishing means 61 based on the output value of the first sensor and the output value of the second sensor, the ratio of the linear velocities of the outer peripheral surfaces of the photosensitive drum 1 and the developing roller 41 is Since it is different from the image forming mode, the toner density management mode cannot be performed simultaneously with the image forming mode. Therefore, the first embodiment of the present invention is configured to automatically switch to the toner density management mode when one job in the image forming mode is completed, for example, a condition for shifting to the toner density management mode. It was. In the second embodiment of the invention described below, even when the image forming mode is being executed, the toner density is measured by the toner density sensor disposed in the stirring chamber, and the toner density management is executed. When the image formation is executed a predetermined number of times, or when the image forming mode is less than the predetermined number of image formations and the warm-up of the fixing device is not completed, the output value of the first sensor and the first output The control voltage of the toner density sensor is corrected based on the output value of the sensor No. 2, and the toner density management by the toner density sensor is performed without being affected by the change in the bulk density of the developer at high temperature and high humidity or low temperature and low humidity. It is what you want to do.

  FIG. 7 is a schematic diagram illustrating a process for correcting the output level of the toner density sensor in the second embodiment.

  In FIG. 7, 1 is a photosensitive drum, 4 is a developing device, 60 is a toner storage unit, 61 is a toner supply unit, S2 is a toner concentration sensor, S4 is an optical sensor, S5 is a magnetic permeability sensor, and 11 is a control unit. .

  The developing device 4 includes a magnet roll having a plurality of magnets therein, and a developing roller 41 that rotates the outer periphery of the magnet roll in the direction of the arrow and functions as a developer carrier, and faces the photosensitive drum 1. Be placed.

  Reference numeral 44 in the developing device 4 denotes a stirring chamber that stores the developer supplied to the developing roller 41 and stirs the stored developer by the rotation of screws 441 and 442 disposed inside.

  The toner concentration sensor S2 detects the magnetic permeability of the developer stored in the stirring chamber 44 and stirred, and outputs an output value P corresponding to the toner concentration of the developer. The output value P is low when the toner density is high, and is high when the toner density is low. The toner concentration sensor S2 is provided with toner concentration sensor driving means S21, and the level of the output value P with respect to the magnetic permeability can be changed by changing the control voltage.

  In step S4, the optical sensor measures the density of the toner image formed on the photosensitive drum 1 after development, and outputs the measurement result as an output value A.

  The permeability sensor S5 measures the permeability of the developer remaining and carried on the developing roller 41 after development, and outputs the measurement result as an output value B.

  A control unit 11 controls the rotation of the photosensitive drum 1, the developing roller 41, and the screws 441 and 442, and the developing roller 41 carries the developing in the developing region where the developing roller 41 and the photosensitive drum 1 face each other. Control of development for forming a toner image on the photosensitive drum 1 by the agent, and the toner concentration of the developer stored in the stirring chamber 44 based on the output values from the density sensor S2, the optical sensor S4, and the magnetic permeability sensor S5 Control management.

  The operation process in the second embodiment will be described with reference to the block diagram shown in FIG.

  The developer composed of the toner and the magnetic carrier housed in the stirring chamber 44 is stirred and frictionally charged, so that the toner adheres to the outer periphery of the carrier, and is attached and carried on the peripheral surface of the rotating developing roller 41.

The control means 11 acquires the output value P of the toner density sensor S2, compares it with a predetermined reference value P _K, and controls the toner replenishing means 61 to be stored in the toner storage means 60 when P <P _K. The toner is supplied to the stirring chamber 44.

  The developer in the agitating chamber 44 is carried and conveyed by the developing roller 41 and is restricted by the layer thickness regulating member 43 so as to have a predetermined layer thickness.

  The developer attached and carried on the peripheral surface of the developing roller 41 moves to a developing region where the photosensitive drum 1 and the developing roller 41 face each other as the developing roller 41 rotates.

  A developing bias in which a DC voltage and an AC voltage are superimposed is applied to the developing roller 41, and toner in the developer carried by the developing roller 41 is exposed to light in a developing region where the developing roller 41 and the photosensitive drum 1 face each other. Development is performed to move to and adhere to the electrostatic latent image portion on the photosensitive drum 1 to form a toner image on the photosensitive drum 1.

  In the image forming mode in which normal image formation is performed, the rotational speeds of the developing roller 41 and the photosensitive drum 1 are the linear velocity of the outer peripheral surface of the photosensitive drum 1 and the linear velocity of the outer peripheral surface of the developing roller 41. Is set to be 2: 1.

  In the image forming mode, the toner image formed on the photosensitive drum 1 is transferred to the transfer material 90 via the intermediate transfer body 6 under such process conditions, and is discharged outside the apparatus after fixing.

  FIG. 8 is a block diagram illustrating an outline of a toner density sensor correction control system in the image forming apparatus according to the second embodiment. In FIG. 8, reference numeral 100 denotes a control unit, and a CPU 111 that performs arithmetic and control processing uses an image forming unit driving unit, toner replenishing unit 61, and toner density sensor S <b> 2 of the image forming apparatus 100 according to a program stored in the storage unit 121. The operations of the optical sensor S4 and the magnetic permeability sensor S5 are controlled via the interface 150.

  The image forming unit driving unit drives the photosensitive drum 1, the charging unit 2, the exposing unit 3, the developing unit 4, and the cleaning unit 5 in the image forming apparatus 100.

  The toner supply unit 61 supplies the toner stored in the toner storage unit 60 to the stirring chamber 44.

  The toner concentration sensor S2 measures the magnetic permeability of the developer stored in the stirring chamber 44 and outputs the result as an output value P. The toner density sensor S2 is provided with toner density sensor driving means S21. The toner concentration sensor driving means S21 drives the toner concentration sensor S2 with a predetermined control voltage and outputs an output value P corresponding to the measured magnetic permeability, but when the CPU 111 instructs, changes the control voltage based on the instruction. The level of the output value P corresponding to the measured magnetic permeability can be changed.

  Storage means 121 to 129, calculation means 131, and comparison means 141 are connected to the CPU 111.

  The storage unit 121 includes an image forming mode program that is a program that executes an image forming mode, a toner density sensor correction mode program that is a program that executes a toner density sensor correction mode, and a calculation formula for calculating a calculation value that will be described later. And is housed. The calculation formulas to be stored are calculated values C = A / B and D = PQ.

  The storage unit 122 stores measurement pattern image data. The measurement pattern (image data) will be described later.

The storage means 123 stores a reference value P _K and a reference value n _K. The reference value P _K is a reference value that is a threshold value for determining whether or not an output value P of a toner density sensor S2, which will be described later, is at a level that requires toner replenishment. Further, as will be described later, when the operation of the image forming apparatus is switched to the toner density sensor correction mode based on the image formation integrated value, the reference value n _K is switched from the counter value n that is the image formation integrated value to the toner density sensor correction mode. This is a reference value that is a threshold for determining whether or not a level has been reached.

  The storage means 124 stores the output value A of the optical sensor S4, the output value B of the magnetic permeability sensor S5, and the calculated value C. The storage means 124 can store a plurality of information, and the stored information can be replaced.

  The storage unit 125 stores a toner density evaluation value conversion table. The toner density evaluation value conversion table divides the calculation value C into a predetermined range and tabulates the toner density evaluation values Q corresponding to the divided calculation values C, and is separately prepared and stored.

  In the storage means 126, the toner density evaluation value Q extracted from the output value P and calculated value D of the toner density sensor S 2 with reference to the toner density evaluation value conversion table stored in the storage means 125, by the calculation means 131. The calculated value D is stored.

  The storage means 126 can store a plurality of information, and the stored information can be replaced.

  The storage means 127 stores a control voltage table. The control voltage table table divides the calculated value D into a predetermined range and tabulates the control voltage V corresponding to each of the divided calculated values D, and is prepared and stored separately.

  The storage means 128 is a counter and stores the print number integrated value n. The print number integrated value n stored in the storage unit 128 is incremented (incremented) so that n = n + 1 every time an image is formed according to an instruction from the CPU 111. Further, n = 0 is reset by an instruction from the CPU 111.

  The storage unit 129 stores a control voltage value information value for controlling the output level of the toner density sensor S2. The CPU 111 transmits the control voltage value information value V stored in the storage means 129 to the toner density sensor driving means S21, and drives the toner density sensor S2 with the control voltage value information value V, thereby outputting the output value of the toner density sensor S2. P can be varied.

  The calculation means 131 functions to calculate the calculated value C = A / B or D = PQ based on the calculation formula stored in the storage means 121 according to an instruction from the CPU 111.

The comparison unit 141 functions to compare and determine whether the output value P of the toner density sensor S2 is larger than the reference value P _K or the calculated value D is smaller than the reference value n _K according to an instruction from the CPU 111. .

In the image forming apparatus having such a configuration, when operating in the image forming mode,
At the time of image formation, the CPU 111 operates the respective units of the image forming apparatus 100 via the interface 150 according to the image formation mode program to perform image formation.

  In the image forming mode, the CPU 111 controls the developing roller 41 and the photosensitive drum 1 to rotate at predetermined speeds.

  In the image forming mode, the respective rotational speeds are controlled so that the ratio of the linear speeds of the developing roller 41 and the outer peripheral surface of the photosensitive drum 1 is 2: 1. The developer stirred and frictionally charged in the stirring chamber 44 adheres to and is carried on the peripheral surface of the developing roller 41.

  A bias voltage is applied to the developing roller 41, and the toner of the developer carried on the peripheral surface of the developing roller 41 and transported to the developing region moves to the photosensitive drum 1 in the developing region, and the photosensitive drum 1 The electrostatic latent image carried by is developed into a toner image.

  The toner concentration sensor S2 is housed in the stirring chamber 44, detects the toner concentration of the developer to be stirred by the change in the magnetic permeability, and outputs the result as an output value P.

The CPU 111 compares the output value P of the toner density sensor S2 with the reference value P _K stored in the storage unit 123 by using the comparison unit 141. When P> P _K , the toner supply unit 61 is supplied with toner. To instruct. When P> P _K is not _satisfied , no toner replenishment instruction is given.

The toner replenishing unit 61 that is instructed to replenish toner operates to supply the toner stored in the toner storage unit 60 to the stirring chamber 44. The toner supply operation by the toner replenishing means 61 stops when a predetermined time according to the program elapses after the toner supply is started. As described above, when the calculated value P, which is an index value of the toner density of the developer used for development, is smaller than the reference value P _K , that is, when the toner density is smaller than the reference value, toner is supplied. The toner concentration of the developer stored in the stirring chamber 44, which is the developer storage unit, increases, and image formation can be performed while maintaining the toner concentration of the developer stored in the developer storage unit at a preferable level. it can.

  On the other hand, in the toner density sensor correction mode, the operation is performed so as to correct the output level of the toner density sensor S2 without being affected by the bulk density.

In the toner density sensor correction mode, the CPU 111 operates the respective units of the image forming apparatus 100 via the interface 150 according to the toner density sensor correction mode program, and the photosensitive drum 1 under predetermined development conditions. A toner image is formed, and a toner density evaluation value Q is determined from the output value A of the first sensor based on the toner image density and the output value B of the second sensor based on the magnetic permeability of the developer after development. The difference D = | P−Q | between the output value P of the toner density sensor S2 and the measured toner density evaluation value Q is calculated. When D> n _K , that is, the output value P of the toner density sensor S2. And the measured toner density evaluation value Q exceed a separately determined reference value n _K , the output level of the toner density sensor S2 is changed, and the output value P of the toner density sensor S2 is changed to the first sensor. And the toner density evaluation value Q, which is the output value of the second sensor, is corrected. Correction of the output level of the toner density sensor S2 is performed by changing a control voltage for controlling the toner density sensor S2. The control voltage for controlling the toner density sensor is a control voltage table stored in the storage means 127 from the difference D = | PQ | between the output value P of the toner density sensor S2 and the measured toner density evaluation value Q. Refer to and be devised.

  Switching from the image forming mode to the toner density sensor correction mode in the present embodiment is performed when the integrated image forming value reaches a predetermined number or when the fixing warm-up is completed by a program stored in the storage unit 121. Automatically done when not.

  Next, operations in the image forming mode and the toner density sensor correction mode will be described with reference to FIGS.

  In the image forming mode in which normal image formation is performed, the CPU 111 controls the developing roller 41 and the photosensitive drum 1 to rotate at a predetermined speed, respectively. The developing roller 41 is agitated in the agitating chamber 44 and carries and carries the frictionally charged developer.

  In the image forming mode, the respective rotational speeds are controlled so that the ratio of the linear speeds of the developing roller 41 and the outer peripheral surface of the photosensitive drum 1 is 2: 1.

  A bias voltage is applied to the developing roller 41, and the toner in the developer adhered and transported to the peripheral surface of the developing roller 41 moves to the photosensitive drum 1 in the developing region, and is held by the photosensitive drum 1. The electrostatic latent image is developed into a toner image.

The toner density of the developer stored in the stirring chamber 44 is measured by the toner density sensor S2 disposed in the stirring chamber 44, and when the output value P of the toner density sensor S2 is larger than the reference value P _K , that is, the toner density sensor S2. The CPU 111 controls the toner supply means 61 to supply the toner to the stirring chamber 44 when the output value P is at a level that requires toner supply.

  On the other hand, in the toner density sensor correction mode, the CPU 111 sets the rotational speeds of the photosensitive drum 1 and the developing roller 41 different from the image forming mode, and the linear velocity of the outer peripheral surface of the developing roller 41 and the outer peripheral surface of the photosensitive drum 1. Is controlled so that the ratio to the linear velocity is 1:10.

  The CPU 111 controls the measurement pattern image data stored in the storage unit 122 to be written on the photosensitive drum 1 in the toner density sensor correction mode.

  The measurement pattern is a pattern exposed on the entire surface for a solid image.

  The electrostatic latent image of the measurement pattern written on the photosensitive drum 1 is developed in the development area to become a toner image.

  In the toner density sensor correction mode, the ratio of the linear velocity of the outer peripheral surface of the developing roller 41 to the linear velocity of the outer peripheral surface of the photosensitive drum 1 is 1:10, so that it is carried by the developing roller 41 in the developing region. All the toner in the developer can be moved to the electrostatic latent image on the photosensitive drum 1 to form a toner image.

  In the toner density sensor correction mode, the CPU 111 causes the optical sensor S4 to measure the reflected light amount of the toner image of the measurement pattern formed on the peripheral surface of the photosensitive drum 1, and outputs the measurement result as the output value A. The acquired output value A is stored in the storage unit 124.

  Further, the magnetic permeability sensor S5 measures the magnetic permeability of the developer remaining on the surface of the developing roller 41 after the development, that is, the carrier remaining on the surface of the developing roller 41, and outputs the measurement result as an output value B. The acquired output value B is stored in the storage unit 124.

  The CPU 111 causes the calculation unit 131 to calculate the calculated value C = A / B based on the calculation formula stored in the storage unit 121 from the output value A and the output value B stored in the storage unit 124, and the calculated value C is stored in the storage means 124.

  Next, the CPU 111 refers to the storage unit 125, calculates a toner density evaluation value Q corresponding to the calculation value C from the toner density evaluation value conversion table stored in the storage unit 125, and stores the toner density evaluation value Q. 126. Note that the storage unit 126 stores an output value P corresponding to the toner concentration of the developer in the stirring chamber 44 measured in advance by the toner concentration sensor S2.

  The CPU 111 causes the calculation unit 131 to calculate the calculated value D = P−Q based on the calculation formula stored in the storage unit 121 from the output value P stored in the storage unit 126 and the toner density evaluation value Q. The calculated value D is stored in the storage unit 126.

  Next, the CPU 111 refers to the storage unit 127, calculates the control voltage V corresponding to the calculated value D from the control voltage table stored in the storage unit 127, and passes the toner concentration sensor driving unit S21 of the toner concentration sensor S2. Thus, the toner density sensor S2 is operated at the control voltage V.

  By operating the toner density sensor S2 with the control voltage V corresponding to the calculated value D, the output value P of the toner density sensor S2 is changed to the output value A from the optical sensor S4 and the output value B from the magnetic permeability sensor S5. Thus, the toner density evaluation value Q calculated and devised can be approached, and toner density management can be performed with high accuracy.

  FIG. 9 is a flowchart for explaining an example of a flow of operations in which the image forming apparatus according to the second embodiment performs toner density correction in the toner density sensor correction mode. In the flowchart of FIG. 9, the toner density sensor correction mode is executed after image formation is performed a predetermined number of times or during the warm-up of the fixing device. This will be described below.

First, when job information to be executed is input by the user, the CPU 111 performs image formation in an image formation mode. (Step S1)
In subsequent step S <b> 2, the CPU 111 causes the toner concentration sensor S <b> 2 to detect the toner concentration of the developer in the stirring chamber 44 and acquires the output value P. The output value P is stored in the storage unit 126.

In step S <b> 3, the CPU 111 confirms whether or not the counter number n stored in the storage unit 128 is greater than or equal to the reference value n _K stored in the storage unit 123. When the counter number n is not equal to or greater than the reference value n _K (step S3 No), the process proceeds to step S4. When the counter number n is equal to or greater than the reference value n _K (step S3 Yes), the process proceeds to step S6. .

  In step S4, it is confirmed whether or not the counter number n is zero. When the counter number n is 0 (Yes at Step S4), the process proceeds to Step S5, and when the counter number n is not 0 (No at Step S3), the process proceeds to Step S6.

  In step S5, the CPU 111 proceeds to step S7 when the warm-up is completed (Yes in step S5) based on the result of confirming whether or not the warm-up of the fixing device is completed. When the warm-up is not completed (No at Step S5), the process waits for the warm-up to be completed. When the warm-up is completed (Yes at Step S5), the process proceeds to Step S7.

In step S7, the output value P of the toner density sensor S2 stored in the storage unit 126 is compared with the reference value P _K stored in the storage unit 126, and when the output value P is greater than the reference value P _K (step S7 Yes). To step S8.

  In step S8, the storage unit 126 operates the toner supply unit 61 to supply the toner into the stirring chamber 44, and the process proceeds to step S9.

In step S7, when the output value P is not larger than the reference value P _K (No in step S7), the process proceeds to step S9.

  In step S9, the CPU 111 operates the image forming unit driving unit to execute the image forming operation.

  When one image is formed, the CPU 111 adds 1 to the counter number n in step S10, and sets the counter number n to n = n + 1.

  In step S11, the CPU 111 confirms whether or not the job is finished. If the job is not finished (No in step S11), the process returns to step S3, and the operation from step S3 to step S11 is finished. Run repeatedly until When the job is finished (Yes in step S11), the process proceeds to step S24, and the execution of the job is finished.

When the counter number n is equal to or greater than the reference value n _{K in} step S3 (step S3 Yes) and when the counter number n is not 0 in step S4 (step S4 No), the process proceeds to step S6.

  In step S6, the CPU 111 confirms whether or not the warm-up of the fixing device has been completed. When the warm-up has been completed (Yes in step S6), the CPU 111 proceeds to step S7 and the warm-up is performed. If not completed (No at step S6), the process proceeds to step S12.

  In step S12, the operation mode is switched from the image forming mode to the toner density management mode according to the program stored in the storage unit 121, and the counter number n stored in the storage unit 127 is reset to n = 0. .

  In step S13, the CPU 111 instructs to change the respective rotation speeds so that the ratio of the linear speed of the outer peripheral surface of the developing roller 41 to the linear speed of the outer peripheral surface of the photosensitive drum 1 is 1:10. Control.

  In step S <b> 14, the CPU 111 calls the photometric pattern image data stored in the storage unit 122, instructs the writing unit to write the photometric pattern image data that has been called to the photoconductive drum 1, and causes the photoconductive drum 1 to perform photometry. An electrostatic latent image of the pattern is formed.

  In step S15, the electrostatic latent image is developed, and an electrostatic latent image having a photometric pattern on the photosensitive drum 1 is formed on the toner image. By developing the ratio of the linear velocity of the outer peripheral surface of the developing roller 41 and the linear velocity of the outer peripheral surface of the photosensitive drum 1 to 1:10, all the toner in the developer carried on the developing roller 41 is obtained. Transfer to the photosensitive drum 1 to form a toner image.

  Next, in step S16, the CPU 111 causes the optical sensor S4 to measure the density of the toner image formed on the photosensitive drum 1, obtains the output value A of the measurement result, stores it in the storage unit 124, and stores the magnetic permeability sensor. In S 5, the magnetic permeability of the developer after development carried on the developing roller 41 is measured, and the output value B of the measurement result is acquired and stored in the storage unit 124.

  In step S17, the CPU 111 calls the output value A and the output value B stored in the storage unit 124, and calculates the calculated value C by the calculation formula (C = A / B) stored in the storage unit 121 in the calculation unit 131. The calculated value C is stored in the storage unit 124.

  In step S <b> 18, the CPU 111 refers to the toner density evaluation value conversion table stored in the storage unit 125, calculates the toner density evaluation value Q corresponding to the calculation value C, and stores the toner density evaluation value Q in the storage unit 126. Store.

  In step S19, the CPU 111 calls the output value P of the toner density sensor S2 and the toner density evaluation value Q stored in the storage unit 126, and calculates the calculation formula (D = The calculated value D is calculated by PQ), and the calculated value D is stored in the storage unit 126.

  In step S20, the CPU 111 refers to the control voltage table stored in the storage unit 127 to determine the control voltage value V corresponding to the calculated value D. In step S21, the CPU 111 sends the toner concentration sensor driving unit S21 to the toner concentration sensor. Instruct and control S2 to operate at control voltage V.

  In step S22, the CPU 111 switches the operation mode from the toner density sensor correction mode to the image forming mode according to the program stored in the storage unit 121, and rotates the developing roller 41 and the photosensitive drum 1 in the image forming mode. Rotate at speed.

  After completing step S22, the CPU 111 returns to step S2, acquires the output value P of the toner density sensor S2 that is output under the condition of the control voltage V in step S2, and then executes the operations after step S3. When the job ends in step S11 (step S11 Yes), the process proceeds to step S23, and the job execution is ended.

  As described above, in the second embodiment of the invention, even when the image forming mode is being executed, the toner density is measured by the toner density sensor disposed in the stirring chamber, and the toner density management is executed. Then, when the image formation in the image formation mode is executed a predetermined number of times, or when the image forming mode is less than the predetermined number of times, the fixing device has not been warmed up. The control voltage of the toner density sensor is corrected based on the output value of the sensor and the output value of the second sensor, and the toner density management by the toner density sensor is changed at a high temperature and high humidity or at a low temperature and low humidity. Thus, toner density management that is not affected by image quality can be performed with less influence on the image forming operation.

It is a schematic diagram explaining the process of acquiring the information value corresponding to the toner density in the present invention. FIG. 6 is data and a diagram for explaining a correspondence between a developer toner density and a calculated value; FIG. 3 is a diagram showing an example of an image forming apparatus to which the present invention is applied. FIG. 6 is a schematic diagram illustrating a process for performing toner density management in the embodiment of the invention. 2 is a block diagram illustrating an outline of a toner density management control system in the image forming apparatus according to the present exemplary embodiment. FIG. 6 is a flowchart illustrating a flow of an operation for performing toner density management in a toner density management mode. FIG. 10 is a schematic diagram illustrating a process for correcting an output level of a toner density sensor according to a second embodiment. FIG. 10 is a block diagram illustrating an outline of a toner density sensor correction control system in an image forming apparatus according to a second embodiment. 10 is a flowchart illustrating a flow of an operation in which the image forming apparatus of the second embodiment performs toner density correction in a toner density sensor correction mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging means 3 Exposure means 4 Developing apparatus 5 Cleaning means 6 Intermediate transfer body 7 Primary transfer means 9 Secondary transfer means 10 Image forming means 11 Control means 111 CPU
121 to 129 Storage unit 131 Calculation unit 141 Comparison unit 150 Interface 20 Paper feed conveyance unit 21 Paper feed cassette 22 Paper feed unit 23 to 26 Paper feed roller 27 Registration roller 28 Paper discharge roller 29 Paper discharge tray 41 Developing roller 44 Stirring chamber 50 Image processing section 60 Toner storage means 61 Toner supply means 70 Fixing device 90 Transfer material S2 Toner density sensor S21 Toner density sensor driving means S4 Optical sensor S5 Magnetic permeability sensor 100 Image forming apparatus 200 Image reading apparatus 201 Automatic document feeder 202 Document image Scanning exposure equipment

Claims (6)

An image forming apparatus using a developer containing toner and carrier,
Toner storage means for storing the toner;
A developer storage section for storing the developer;
A toner replenishing means for supplying toner stored in the toner storage means to the developer storage section; and a developing device having a developer carrier for carrying the developer;
A photoreceptor carrying an electrostatic latent image;
And an image forming apparatus that develops a latent image carried on the photoconductor at a position facing the photoconductor and the developer carrying body into a toner image with the developer carried on the developer carrying body. In
A first sensor that outputs an output value corresponding to the density of a toner image formed on the surface of the photoreceptor;
A second sensor that outputs an output value corresponding to the magnetic permeability of the developer remaining on the surface of the developer carrying member after development;
Control means for controlling the operation of the toner replenishing means based on the output value of the first sensor and the output value of the second sensor;
An image forming apparatus comprising: The control unit calculates a calculated value from an output value of the first sensor and an output value of the second sensor, and controls the operation of the image forming apparatus based on the calculated value. The image forming apparatus described in 1. The calculated value is calculated by the equation C = A / B where C is the calculated value, A is the output value of the first sensor, and B is the output value of the second sensor. The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus. 4. The image forming apparatus according to claim 2, wherein the control unit controls the operation of the toner replenishing unit based on a comparison result between the calculated value and a preset reference value. Based on the results of the measurement by the first sensor and the second sensor and the output of the output value, the calculation of the calculated value by the control means, the comparison of the calculated value with the reference value, and the comparison result 5. The image forming apparatus according to claim 1, wherein the operation of the toner replenishing unit is controlled after a developing operation performed under conditions different from those in normal image formation. . The image forming apparatus according to claim 1, further comprising: a toner density sensor having a variable output level for measuring a toner density of the developer housed in the developer housing section.
The image forming apparatus, wherein the control unit controls an output level of the toner density sensor based on an output value of the first sensor and an output value of the second sensor.

Images