JP4890118B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus.

  Conventionally, as an image forming apparatus capable of changing the density of a developer image developed by a developing apparatus in an electrophotographic image forming apparatus that forms a developer image using a developer, Patent Document 1 discloses the image forming apparatus. Image forming apparatus.

JP 2004-354622 A

  Specifically, this Patent Document 1 discloses a state detection unit that selectively detects a change with time or usage environment of an image forming apparatus, a developer concentration, and sets printing conditions based on the detection result. Printing condition setting means, limit value determining means for determining a limit value of the printing condition based on the detection result of the state detecting means, printing condition set by the printing condition setting means, and limit value determined by the limit value determining means An image forming apparatus including a printing control unit that determines a printing condition setting value based on the comparison result is disclosed.

  In the image forming apparatus, a test pattern is formed on the latent image carrier or the transfer belt in order to keep the density of the developer image printed on the recording medium, which changes with time and environmental changes, constant. Then, the density of the test pattern is detected by the state detection means, and the light amount of the exposure apparatus, the developing bias voltage, the toner supply bias voltage, and the like are controlled based on the detection result.

  In the above-described image forming apparatus, various parameters are corrected according to changes over time and environmental changes. However, there is a problem that a stable density cannot be obtained only by correction based on changes over time or environmental changes.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an image forming apparatus capable of obtaining a stable density.

In order to solve the above-described problems, an image forming apparatus according to the present invention includes a replaceable developer accommodating unit that accommodates a developer, the developer accommodated in the developer accommodating unit, and the developer. A developing means for forming a developer image based on the print information inputted using the printer, a density detecting means for detecting a density value of the developer image formed by the developing means, and a developer accommodating means. A first storage unit for storing first density characteristic information including a first coefficient relating to the density characteristic of the developer, and a second density characteristic including a second coefficient relating to the density characteristic of the developer used in the past. A second storage unit that stores information; and a forming condition changing unit that changes a forming condition of the developer image, wherein the forming condition changing unit stores the first storage unit stored in the first storage unit. Before being included in the density characteristics information The difference between the first coefficient and the second coefficient included in the second density characteristic information stored in the second storage unit, the first coefficient, and the density detecting unit A density value on the paper is calculated from the density value of the developer image, and the density of the developer image developed by the developing unit is calculated from a corrected density value indicating an error between the density value on the paper and a target density value indicating a target density. has a correction value calculation unit for calculating a correction value, the developing means, to form a developer image based on the inputted print information based on the correction value calculated in the correction value calculation section, the It is a feature.

  According to this configuration, the developer image developed by the developing unit becomes a developer image whose formation condition has been changed by the formation condition changing unit. The forming condition changing unit changes the forming condition based on the information on the developer stored in the storage unit and the density of the developer image detected by the density detecting unit. In other words, the image forming apparatus changes the formation conditions of the developer image developed by the developing unit based on the information related to the developer and the density of the developer image, so that the image forming apparatus does not depend on a change with time or an environmental change of the image forming apparatus. A stable developer image can be developed.

  As described above, since the image forming apparatus can develop the developer image based on the information about the developer stored in the storage unit, the image forming apparatus has a stable density regardless of changes over time or environmental changes. The developer image can be formed.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  The embodiment relates to an image forming apparatus that develops a developer image using an image carrier and a developer carrier, and transfers the developer image onto a recording medium. Alternatively, it can be applied to a multifunction machine or the like. Further, in the embodiment, attention is paid to the fact that the density characteristics of the developer housed in the developer cartridge differ depending on the developer cartridge, and the image forming apparatus uses the density characteristics of the developer inside the currently installed developer cartridge. The printing work is performed based on the above. Specifically, the image forming apparatus compares the density characteristics of the developer contained in the currently installed developer cartridge with the density characteristics of the developer contained in the previously installed developer cartridge. Then, it is possible to print a high-quality developer image by performing a printing operation in consideration of the relationship between the two.

  First, the image forming apparatus shown as the first embodiment will be described in detail.

  As shown in FIG. 1, the image forming apparatus 1 uses four primary color developers to develop a developer image based on the latent image exposed by the LED heads 3C, 3M, 3Y, and 3K. A device 5K, a yellow developing device 5Y, a magenta developing device 5M, and a cyan developing device 5C are provided.

  The black developing device 5K, the yellow developing device 5Y, the magenta developing device 5M, and the cyan developing device 5C develop a black, yellow, magenta, or cyan developer image, respectively. The black developing device 5K, the yellow developing device 5Y, the magenta developing device 5M, and the cyan developing device 5C have substantially the same configuration, and hence are collectively referred to as “developing device 5” unless otherwise distinguished below. Detailed explanation is given. Further, each part constituting the developing device 5 is also illustrated by adding any of the characters C, M, Y, or K to the end of each symbol.

  When the image forming apparatus 1 receives print information transmitted from a host apparatus such as an information processing apparatus (not shown), the LED head 3 exposes a latent image based on the print information. The developing device 5 develops the latent image based on the print information exposed by the LED head 3. Such a developing device 5 includes a photosensitive drum 7 that carries a latent image based on print information, a charging roller 9 that applies a charging bias to the surface of the photosensitive drum 7, and a latent roller carried on the photosensitive drum 7. The developing roller 11 that develops the developer image by attaching the developer to the image image, the supply roller 13 that supplies the developer to the developing roller 11, and the developer supplied to the developing roller 11 by the supply roller 13 is thinned. Developing blade 15.

  The photosensitive drum 7 rotates in the direction of arrow A by a driving force supplied from a driving motor (not shown). The photosensitive drum 7 is in contact with the charging roller 9 in order from the upstream in the rotation direction, is opposed to the LED head 3, and is in contact with the developing roller 11.

  The charging roller 9 uniformly charges the surface of the photosensitive drum 7 in contact with the charging roller 9 based on a charging bias applied by a power source (not shown).

  The developing roller 11 adheres the developer supplied from the supply roller 13 to the latent image carried on the surface of the photosensitive drum 7, and develops the developer image on the surface of the photosensitive drum 7. A developing bias is applied to such a developing roller 11 by a power source (not shown). The developing roller 11 carries the developer supplied from the supply roller 13 on the surface by using an electrostatic force generated by the developing bias.

  Here, the density of the developer image developed on the surface of the photosensitive drum 7 depends on the amount of developer carried by the developing roller 11. That is, when the developing roller 11 carries a large amount of developer supplied from the supply roller 13, the density of the developer image developed on the surface of the photosensitive drum 7 by the developing roller 11 becomes high. In addition, when the amount of the developer carried on the developing roller 11 is small, the density of the developer image developed on the surface of the photosensitive drum 7 by the developing roller 11 becomes light.

  In the image forming apparatus 1, it is possible to print a suitable developer image by adjusting the developing bias applied to the developing roller 11 in accordance with the density characteristics of the developer currently mounted on the developing device 5. To do.

  The developing device 5 is mounted with a developer cartridge 19 as developer containing means that is detachable from the developing device 5. The developer cartridge 19 contains a developer for each color and has a structure capable of supplying the developer into the developing device 5.

  The developer cartridge 19 accommodates the developer and is formed to be replaceable from the image forming apparatus 1. Such a developer cartridge 19 includes a wireless communication element 21 as a storage unit that stores information related to the density characteristics of the developer contained in the developer cartridge 19 and can perform wireless communication. The wireless communication element 21 is composed of, for example, an RFID (Radio Frequency Identification) element fixed to the upper surface of the developer cartridge 19. The wireless communication element 21 stores density characteristic information regarding the density characteristics of the developer contained in the developer cartridge 19 to which the wireless communication element 21 is fixed, and identification information for identifying the developer cartridge 19.

  The identification information is, for example, a serial number unique to the developer cartridge 19 and is constituted by 32-bit information. The serial number indicates, for example, color information regarding the developer color in the upper 2 bits, and a value from 0 to 16777215 in the lower 24 bits. Of the 32-bit serial number, the remaining 6 bits are unused. In the present embodiment, for convenience of explanation, when the upper 2 bits of the serial number are the character string 11, the developer contained in the developer cartridge is cyan, and the upper 2 bits are the character string 10. Indicates that the developer contained in the developer cartridge is magenta, and when the upper 2 bits are the character string 01, the developer contained in the developer cartridge is yellow and the upper 2 bits are the character string 00. In this case, the developer accommodated in the developer cartridge is assumed to be black. In addition, the identification information in the present invention is not limited to the above-described identification information, and it is needless to say that the information may be in any format as long as the information can identify the developer cartridge. . The density characteristic information and the identification information stored in the wireless communication element 21 are read by the RFID reading unit 23.

  The RFID reader 23 is formed at a position where it can communicate with the wireless communication element 21 in a state where the developer cartridge 19 is mounted on the developing device 5. The RFID reading unit 23 communicates with the wireless communication element 21 when the image forming apparatus 1 is turned on and when the image forming apparatus 1 detects opening / closing of the cover by a method described later. The reason why the RFID reading unit 23 communicates with the wireless communication element 21 at this timing is that the operation of replacing the developer cartridge 19 can only be performed by opening and closing the cover of the image forming apparatus 1 and the image forming apparatus 1. This is because the image forming apparatus 1 cannot detect the opening / closing of the cover when the power source is off.

  Such a developing device 5 executes the developing process at the timing when the paper P is transported by the transport device 25.

  The transport device 25 is means for transporting the paper P provided on the medium transport path of the image forming apparatus 1 downstream of the medium transport path.

  A paper cassette 27 that is detachably attached from the image forming apparatus 1 and stores the paper P is formed in the uppermost stream of the medium conveyance path. The paper P stored in the paper cassette 27 is separated one by one by a separation roller 29 that separates the paper P, and is fed downstream by a hopping roller 31 that feeds the paper P downstream in the medium conveyance path. Registration rollers 33 and 35 are formed downstream of the hopping roller 31 in the medium conveyance path. The paper P that has reached the registration rollers 33 and 35 is fed out to the transport device 25 formed in the downstream direction by the registration rollers 33 and 35 at a predetermined timing.

  The transport device 25 transports the paper P transported by the registration rollers 33 and 35 in the downstream direction of the medium transport path in accordance with the timing when the developing process by the developing device 5 is performed. Such a conveying device 25 includes a driving roller 37 that rotates based on a driving force supplied from a driving source (not shown), a driven roller 39 that is disposed substantially in parallel with the driving roller 37 at a predetermined distance, A transfer belt 41 provided between the roller 37 and the driven roller 39.

  The transfer belt 41 is disposed so as to be in contact with the photosensitive drums 7C, 7M, 7Y, and 7K provided in the developing devices 5C, 5M, 5Y, and 5K. Is driven in the direction of arrow B so as to be conveyed downstream of the medium conveyance path. Such a transfer belt 41 is formed of, for example, a black resin having a glossy surface.

  The image forming apparatus 1 also includes a transfer roller 43 that transfers the developer image developed on the photosensitive drum 7 onto the paper P in accordance with the timing at which the paper P is transported on the transport belt 41. The transfer roller 43 is formed so as to be pressed against the photosensitive drum 7 via the transfer belt 41. The transfer roller 43 transfers the developer image developed on the surface of the photosensitive drum 7 onto the sheet P by a transfer bias supplied from a power source (not shown) at the timing when the sheet P is conveyed on the transfer belt 41. To do.

  The image forming apparatus 1 further includes a density sensor 45 that detects the density of a test pattern printed on the transfer belt 41 by a method described later, downstream of the developing device 5C in the driving direction of the transfer belt 41. As shown in FIG. 2, the density sensor 45 includes an LED element 47 that emits light toward the transfer belt 41, a light receiving element 49 that receives specularly reflected light from the transfer belt 41 among the light emitted from the LED element 47, and A light receiving element 51 that receives diffusely reflected light from the transfer belt 41 out of the light emitted from the LED element 47 is provided. In such a density sensor 45, the density of the black developer is detected by the light receiving element 49, and the density of the cyan, magenta, and yellow developer is detected by the light receiving element 51.

  As described above, among the test patterns printed on the transfer belt 41 having black gloss by the method described later, the black developer image attenuates the light intensity of the light emitted from the LED element 47 and emits light. To reflect. The density sensor 45 detects the density of the black developer of the test pattern by receiving the reflected light with the light intensity attenuated by the light receiving element 49. Among the test patterns printed on the transfer belt 41, cyan, magenta, and yellow color developers reflect reflected light according to changes in the developer weight (M / S) per unit area of the developer image. Change the light intensity. The density sensor 45 detects the density of the cyan, magenta, and yellow developer in the test pattern by receiving the light with the changed light intensity by the light receiving element 51.

  Further, the image forming apparatus 1 includes a shutter 53 that can slide between the transfer belt 41 and the density sensor 45 substantially in parallel with the driving direction of the transfer belt 41. The shutter 53 protects the density sensor 45 so that the developer scattered inside the image forming apparatus 1 does not adhere to the density sensor 45 when the image forming apparatus 1 performs printing on the paper P. Further, when the image forming apparatus 1 performs calibration for cyan, magenta, and yellow, the image forming apparatus 1 includes a shutter 53 having a density sensor 45 and a transfer belt 41 as shown in FIG. The shutter 53 is slid in the direction of arrow C so as to be interposed therebetween. Then, the image forming apparatus 1 performs calibration for cyan, magenta, and yellow using the back surface of the shutter 53.

  On the other hand, when the image forming apparatus 1 performs black color calibration, the shutter 53 is moved in the direction of arrow D, and the shutter 53 is moved to a position not interposed between the density sensor 45 and the transfer belt 41.

  The image forming apparatus 1 further includes a cleaning blade 55 that scrapes off a test pattern printed on the transfer belt 41 by a method described later, downstream of the density sensor 45 in the driving direction of the transfer belt 41. The cleaning blade 55 is formed such that one end is fixed to the cleaner container 57 and the other end is in contact with the transfer belt 41. When the test pattern printed on the transfer belt 41 reaches the cleaning blade 55 by driving the transfer belt 41, the test pattern is scraped off by the cleaning blade 55, and the developer that has formed the test pattern Is contained in a cleaner container 57.

  Further, the image forming apparatus 1 fixes the developer image transferred onto the paper P by the developing device 5 and the transfer roller 43 on the paper P downstream of the developing device 5 and the transfer roller 43 in the medium conveyance path. A device 57 is provided. The fixing device 57 includes a fixing roller 61 having a heating element 59 that generates heat by electric power supplied from a power source (not shown), and a pressure roller 63 that rotates while being pressed against the fixing roller 61. The fixing device 57 melts the developer transferred onto the paper P by sandwiching and transporting the paper P transported by the transport device 25 between the fixing roller 61 heated by the heating element 59 and the pressure roller 63. Then, the developer image is fixed on the paper P.

  The sheet on which the developer image has been fixed by the fixing device 57 is further conveyed in the downstream direction of the medium conveying path by a conveying unit (not shown), discharged to a stacker 65 formed on the upper surface of the image forming apparatus 1, and provided to the user. The

  Next, a more specific configuration of the image forming apparatus 1 will be described in detail with reference to FIG.

  The image forming apparatus 1 receives print information transmitted from an information processing apparatus (not shown) or transmits various information to the information processing apparatus, and a command / An image processing unit 103.

  When print information is supplied from the host interface unit 100, the command / image processing unit 103 converts the print information into, for example, image information in a bitmap format. The command / image processing unit 103 also supplies image information based on the print information to the LED head interface unit 105 to expose the latent image.

  Further, when printing information is supplied from the host interface unit 100, the command / image processing unit 103 supplies a command to the printer engine control unit 107 that controls each unit of the image forming apparatus 1 in order to start the printing process.

  The printer engine control unit 107 includes density characteristic information regarding the density characteristics of the developer read from the wireless communication elements 21C, 21M, 21Y, and 21K, identification information for identifying the developer cartridge 19, and the detection result of the density sensor 45. Based on the above, the formation condition of the developer image is changed. In the present embodiment, the printer engine control unit 107 includes density characteristic information regarding the density characteristics of the developer read from the wireless communication elements 21C, 21M, 21Y, and 21K, identification information for identifying the developer cartridge 19, and Based on the detection result of the density sensor 45, the developing bias applied to the developing roller 11 is changed to a developing bias optimum for these conditions. Further, the printer engine control unit 107 supplies a predetermined drive pulse to the LED head interface unit 105. Then, the LED head interface unit 105 supplied with the drive pulse supplies image information to the LED heads 3C, 3M, 3Y, and 3K based on the drive pulse, so that the LED heads 3C, 3M, 3Y, and 3K are supplied. Drive.

  Further, the printer engine control unit 107 supplies control values to the high-voltage control unit 109 that supplies control signals to each unit that uses the high-voltage power supply. The high voltage control unit 109 supplies a voltage control signal to each unit based on the control value supplied from the printer engine control unit 107. Specifically, the high voltage controller 109 includes a charging bias controller 111 that controls the charging bias applied to the charging rollers 9C, 9M, 9Y, and 9K included in the developing devices 5C, 5M, 5Y, and 5K, and the developing devices 5C. , 5M, 5Y, 5K, a developing bias controller 113 for controlling the developing bias applied to the developing rollers 11C, 11M, 11Y, 11K, and a transfer bias applied to each of the transfer rollers 43C, 43M, 43Y, 43K. The transfer bias control unit 115 is supplied with a control signal indicating the voltage value of the charging bias, the voltage value of the developing bias, or the voltage value of the transfer bias.

  The charging bias control unit 111 applies a charging bias to the charging rollers 9C, 9M, 9Y, and 9K based on a control signal supplied from the high voltage control unit 109.

  The developing bias controller 113 applies a developing bias to the developing rollers 11C, 11M, 11Y, and 11K based on the control signal supplied from the high voltage controller 109.

  The transfer bias controller 115 applies a transfer bias to the transfer rollers 43C, 43M, 43Y, and 43K based on the control signal supplied from the high voltage controller 109.

  The printer engine control unit 107 also supplies a hopping motor 117 that supplies driving force to the hopping roller 31, a registration motor 119 that supplies driving force to the registration rollers 33 and 35, and a driving force to the driving roller 37, thereby transferring the transfer belt. Belt motor 121 that drives 41, fixing motor 123 that supplies driving force to, for example, the pressure roller 63 of the fixing device 57, and drum motor 125 that supplies driving force to each of the photosensitive drums 7C, 7M, 7Y, and 7K. To control.

  Further, the printer engine control unit 107 detects the cover state based on the detection result of the cover sensor 127 that detects the open / close state of the cover of the image forming apparatus 1.

  Further, the printer engine control unit 107 is supplied with the detection result of the thermistor 129 formed in the vicinity of the fixing roller 61. Then, the printer engine control unit 107 determines whether the surface temperature of the fixing roller 61 is in a predetermined temperature band based on the detection result of the thermistor 129. Further, the printer engine control unit 107 controls the surface temperature of the fixing roller 61 by controlling on / off of the heating element 59 based on the surface temperature of the fixing roller 61.

  Further, the image forming apparatus 1 includes a field effect transistor (FET) 131 that controls power supplied to the LED element 47. The FET 131 controls the light emission of the LED element 47 based on the output signal supplied from the printer engine control unit 107 via the D / A converter 133. After the LED element 47 emits light, the detection results of the light receiving elements 49 and 51 are supplied to the printer engine control unit 107 via the A / D converter 135. Specifically, these units constitute a circuit as shown in FIG.

  As shown in the figure, the gate terminal of the FET 131 is connected to the output terminal OUT of the D / A converter 133. The first terminal of the FET 131 is grounded through the resistor R1. Further, the second terminal of the FET 131 is connected to the first terminal of the LED element 47 through the resistor R2. The second terminal of the LED element 47 is connected to a power source (not shown).

  The light receiving element 49 is connected to the input terminal IN1 of the A / D converter 135 via the operational amplifier 137. The light receiving element 51 is connected to the input terminal IN2 of the A / D converter 137 via the operational amplifier 139.

  In such a circuit, the detection result of the light receiving element 49 is output to the operational amplifier 137 as a detection signal. This detection signal is adjusted by the operational amplifier 137 and supplied to the A / D converter 135. Similarly, the detection result of the light receiving element 51 is adjusted by the operational amplifier 139 and supplied to the A / D converter 135.

  Here, the D / A converter 133 is a converter that can divide, for example, a voltage of 3.3 V into 10 bits. The A / D converter 135 is, for example, a converter that can divide a voltage of 3.3 V into 12 bits.

  In addition, the image forming apparatus 1 stores the density characteristic information read from the wireless communication element 21 by the RFID reading unit 23 and various information such as identification information as a first storage unit and a second storage unit. Part 141 is provided. The density characteristic information and identification information read by the RFID reading unit 23 are supplied to the printer engine control unit 107. Then, the printer engine control unit 107 stores the density characteristic information and identification information in the storage unit 141. Further, the printer engine control unit 107 reads out density characteristic information and identification information stored in the storage unit 141 in a case described later.

  Next, the operation at the time of calibration of the image forming apparatus 1 having the above-described configuration will be described in detail.

  When performing calibration, the printer engine control unit 107 detects detection signals of the light receiving elements 49 and 51 in a state where the LED elements 47 are turned off. Then, the printer engine control unit 107 stores the dark potential output of the light receiving element 49 in the storage unit 141 as V49 and the dark potential output of the light receiving element 51 as V51. The dark potential output varies depending on the performance of the light receiving element, but is generally about 0.5V to 1V.

  Next, the printer engine control unit 107 outputs from the light receiving elements 49 and 51, is amplified by operational amplifiers 137 and 139, is input to the input terminals IN1 and IN2 of the A / D converter 135, and is converted into a DC voltage. The output value of the output terminal OUT of the D / A converter 133 is raised stepwise so that the potential difference between the voltage and the dark potential stored in the storage unit 141 becomes 2.0V.

Then, as described above, the printer engine control unit 107 stores the output value V _OUT of the D / A converter 133 when the potential difference from the dark potential becomes 2.0V in the storage unit 141. Since the output value V _OUT shows different values when the light receiving element 49 is used and when the light receiving element 51 is used, the printer engine control unit 107 stores both values in the storage unit 141. Then, the printer engine control unit 107 stores both output values in the storage unit 141 and ends the calibration operation.

  Next, an operation in which the image forming apparatus 1 detects the density of the developer image formed by the developing device 5 will be described in detail.

  When detecting the density of the developer image, the printer engine control unit 107 prints a test pattern as shown in FIG. 6 on the transfer belt 41. The test pattern is formed by printing a cyan patch image CP, a magenta patch image MP, a yellow patch image YP, and a black patch image KP from the upstream in the driving direction of the transfer belt 41. The cyan patch image CP, magenta patch image MP, yellow patch image YP, and black patch image KP are formed by continuously printing squares of 2 cm each on the transfer belt 41.

  Next, the operation during printing of the image forming apparatus 1 having the above-described configuration will be described in detail.

  When an information processing apparatus (not shown) transmits print information in, for example, PDL (Page Descript Language) format, the image forming apparatus 1 receives the print information through the interface unit 100. The print information received by the interface unit 100 is supplied to the command / image processing unit 103. The command / image processing unit 103 converts the print information into bitmap-format image information that can be printed by the image forming apparatus 1. At this time, the command / image processing unit 103 supplies a command to the printer engine control unit 107 to start the printing process.

  In response to the command, the printer engine control unit 107 controls the temperature of the heating element 59 based on the detection result of the surface temperature of the fixing roller 61 by the thermistor 129, so that the surface temperature of the fixing roller 61 is set to a fixable temperature. maintain.

  Next, the printer engine control unit 107 starts a series of printing operations. First, the printer engine control unit 107 separates the paper P accumulated on the paper cassette 27 by the separation roller 29 and starts driving the hopping motor 117, thereby causing the paper P separated by the hopping roller 31 to follow the medium conveyance path. Transport.

  In addition, the printer engine control unit 107 starts a series of development operations at the timing when the paper P is conveyed under the photosensitive drums 7C, 7M, 7Y, and 7K. First, the printer engine control unit 107 supplies the charging bias control unit 111 with control values of the charging rollers 9C, 9M, 9Y, and 9K. The charging bias controller 111 applies a charging bias to the charging rollers 9C, 9M, 9Y, and 9K based on the supplied control value. The charging rollers 9C, 9M, 9Y, 9K to which the charging bias is applied uniformly charge the surfaces of the photosensitive drums 7C, 7M, 7Y, 7K based on the charging bias.

  Next, the command / image processing unit 103 converts the print information into bitmap format image information, and supplies the image information to the LED head interface unit 105. The LED head interface unit 105 controls the light emission of the LED heads 3C, 3M, 3Y, and 3K based on the image information, and exposes the latent image on the surface of the charged photosensitive drums 7C, 7M, 7Y, and 7K. To do.

  At this time, the printer engine control unit 107 supplies a development bias control value calculated by a method described later to the high-pressure control unit 109. The high voltage controller 109 supplies a control signal to the developing bias controller 113 based on the control value. The development bias controller 113 applies a development bias to the development rollers 11C, 11M, 11Y, and 11K based on the control signal. The developing rollers 11C, 11M, 11Y, and 11K to which the developing bias is applied are supplied with developer from the supply rollers 13C, 13M, 13Y, and 13K, and the developing rollers 11C, 11M, 11Y, and 11K are supplied with the developer. Is adsorbed on its surface using a developing bias. The developing rollers 11C, 11M, 11Y, and 11K supply the developer adsorbed on the surface to the photosensitive drums 7C, 7M, 7Y, and 7K, thereby developing the developer on the surfaces of the photosensitive drums 7C, 7M, 7Y, and 7K. Develop the image.

  Next, the printer engine control unit 107 supplies a transfer bias control value to the high voltage control unit 109. Then, the high voltage controller 109 supplies a transfer bias control signal to the transfer bias controller 115. The transfer bias controller 115 applies a transfer bias to the transfer rollers 43C, 43M, 43Y, and 43K based on the control signal.

  Next, the transfer rollers 43C, 43M, 43Y, and 43K sandwich and convey the paper P conveyed by the conveying device 25 together with the photosensitive drums 7C, 7M, 7Y, and 7K, thereby the photosensitive drums 7C, 7M, 7Y, and The developer image developed on the surface of 7K is transferred onto the paper P.

  Next, the transport device 25 transports the paper P to the fixing device 57. The fixing device 57 fixes the developer image attached on the paper P onto the paper P by nipping and conveying the paper P. Thereafter, the paper P is discharged onto the stacker 65.

  Next, a series of operations of the image forming apparatus 1 when the image forming apparatus 1 determines the bias value of the developing bias applied to the developing roller 11 in the series of operations described above will be described in detail with reference to FIG. do.

  When the image forming apparatus 1 determines the developing bias to be applied to the developing roller 11, the image forming apparatus calculates a predetermined correction value based on the density characteristics of the developer stored in the developer cartridge 19. When the image forming apparatus 1 calculates the correction value, the image forming apparatus 1 determines the density characteristics of the developer stored in the developer cartridge (hereinafter referred to as “lot A”) before the developer cartridge 19 is replaced. And the density characteristics of the developer contained in the developer cartridge after the developer cartridge 19 has been replaced (currently mounted developer cartridge, hereinafter referred to as “lot B”). Note that the developer used in the past refers to the developer contained in the developer cartridge 19 that was mounted when the past correction value was calculated, and preferably the developer cartridge that was mounted when the previous correction value was calculated. The developer accommodated in 19. According to this definition, the developer used in the past includes the case where the developer contained in the currently installed developer cartridge 19 is the same. “Lot” means that the production lots or developers of four developer cartridges 11C, 11M, 11Y, and 11K that contain cyan, magenta, yellow, or black developer can be refilled. Is a developer production lot. In the series of operations, for convenience of explanation, the series of operations of the image forming apparatus 1 when the developer cartridge 19 has not been replaced with reference to the correction value calculation time will be described. A series of operations of the image forming apparatus 1 when the lot B is exchanged will be described.

  When a series of operations starts, in step S1, the RFID reading unit 23 reads the density characteristic information and identification information stored in the wireless communication element 21, and the printer engine control unit 107 stores the read density characteristic information and identification information. Stored in the unit 141. The density characteristic information read here is used for controlling the developing bias, and the identification information is used for the image forming apparatus 1 to identify the developer cartridge 19.

  Here, the density characteristic information includes information as shown in Tables 1 and 2.

  As shown in Table 1, the density characteristic information of lot A is a coefficient of a first-order approximation expression that indicates the relationship between the on-paper density (OD value) of the developer stored in lot A and the sensor detection voltage (V). The coefficient A and the coefficient B, the on-paper density change amount (ΔDB1) when the developing bias changes by 1 V, and the correction value α, the correction value β, and the correction value γ calculated by the method described later are included.

  Similarly, with respect to the density characteristics of lot B, a coefficient A which is a coefficient of a first-order approximation formula indicating the relationship between the density on paper (OD value) of the developer contained in lot B and the sensor detection voltage (V), and The coefficient B, the amount of change in on-paper density (ΔDB1) when the developing bias changes by 1 V, the correction value α, the correction value β, and the correction value γ calculated by the method described later are included.

  A coefficient A and a coefficient B, which are coefficients of a first-order approximation expression showing the relationship between the density (OD value) of the developer contained in the lot A or the lot B and the sensor detection voltage (V), are the lot A or the lot. Calculated and stored for each color included in B. For example, the coefficient A and the coefficient B are values calculated by paying attention to the density characteristics of the developer of each color. The coefficients A and B are approximations obtained by experimentally determining the OD value when the developing bias shows an arbitrary value and the sensor detection voltage at that time and then plotting them on orthogonal coordinates. Calculated based on a straight line.

  For example, when the developer bias of lot A is used and the developing bias is changed, the OD value and sensor detection value at each developing bias value are experimentally obtained by transferring the developer onto paper. Suppose that the results are as shown in Table 3. As shown in the table, when the developing bias is −140V, the OD value is 1.19, the sensor detection voltage is 1.24V, and when the developing bias is −200V, the OD value is 1.43. The sensor detection voltage is 1.52 V. When the developing bias is −260 V, the OD value is 1.68 and the sensor detection voltage is 1.79 V. Then, as shown in FIG. 8, the result is plotted on orthogonal coordinates where the OD value is taken on the y axis and the sensor detection voltage is taken on the x axis. Further, using the cyan developer of lot B, the developing bias was changed, and the OD value and sensor detection value at each developing bias value were experimentally obtained by transferring the developer onto paper. The results are as shown in Table 4 and are plotted in the figure.

The black squares in the figure plot the results of lot A, and the black circles plot the results of lot B. And these also show substantially linear so that it may understand also from the arrangement | sequence of a black painting square or a black painting circle. And when obtaining a linear first-order approximation represented by a black square,
y _A = 0.8907x + 0.0824 (Formula 1)
Is derived. In addition, when obtaining a linear first-order approximation represented by a black circle,
y _B = 0.8234x + 0.1741 (Formula 2)
Is derived. The coefficient A and the coefficient B included in the density characteristic information of the lot A are values indicating the parameters of the expression 1, and the coefficient A and the coefficient B included in the density characteristic information of the lot B are the parameters of the expression 2. Value.

  In the same manner, the coefficients A and B for the magenta, yellow, and black developers of lot A and lot B are obtained. For example, the relationship between the OD value of the magenta color of Lot A and the sensor detection value shows the result shown in Table 5, and the relationship between the OD value of the magenta color of Lot B and the sensor detection value shows the result as shown in Table 6. When these are plotted, the relationship shown in FIG. 9 is shown. Further, for example, the relationship between the OD value of the yellow color of lot A and the sensor detection value shows the result as shown in Table 7, and the relationship between the OD value of the yellow color of lot B and the sensor detection value shows the result as shown in Table 8. When these are plotted, the relationship shown in FIG. 10 is shown. Further, for example, the relationship between the OD value of the yellow color of the lot A and the sensor detection value shows the result as shown in Table 9, and the relationship between the OD value of the yellow color of the lot B and the sensor detection value shows the result as shown in Table 10. When these are plotted, the relationship as shown in FIG. 11 is shown. The coefficients A and B are determined on the basis of the values shown in Tables 3 to 10 and the linear parameters shown in FIGS. 8 to 10, and the developers of lot A and lot B are determined. It is stored in each wireless communication element 21 of the cartridge 19.

Further, the on-paper density change amount ΔDB1 is a value indicating the change amount of the on-paper density per 1 V of the developing bias.
ΔDB1 = (OD value at DB260V−OD value at DB140V) ÷ (260−140) (Formula 3)
Is calculated based on

  Further, the correction value α, the correction value β, and the correction value γ indicate differences in density characteristics between the currently installed developer cartridge 19 and the developer cartridge 19 that was mounted at the time of the previous correction value calculation. The image forming apparatus 1 calculates a correction value α, a correction value β, and a correction value γ every time the development bias voltage value is determined. That is, when determining the voltage value of the developing bias, if the developer cartridge 19 that was mounted at the time of the previous correction value calculation is mounted in the image forming apparatus 1, the correction value α, the correction value β, and the correction The values γ are all 0. On the other hand, when a developer cartridge 19 that is different from the developer cartridge 19 that was mounted at the time of the previous correction value calculation is mounted in the image forming apparatus 1, the correction value α, the correction value β, and the correction value γ are: A coefficient A, a coefficient B, and ΔDB1 specific to the developer stored in the developer cartridge 19 mounted at the time of the previous correction value calculation, and a specific to the developer stored in the currently mounted developer cartridge 19 Is calculated based on the coefficient A, the coefficient B, and ΔDB1. Specifically, the correction value α, the correction value β, and the correction value γ are calculated by the difference between the coefficient A, the coefficient B, and ΔDB1, and according to this, the development is performed after the previous correction value calculation. When calculating the correction value without exchanging the agent cartridge 19, the coefficient A, the coefficient B, and ΔDB1 read from the wireless communication element 21 indicate the same value, so that the correction value α, the correction value β, and the correction value γ takes the value 0. On the other hand, when the correction value is calculated immediately after the developer cartridge 19 is replaced, the correction value α, the correction value β, and the correction value are corrected because the coefficients A, B, and ΔDB1 of all the developers are different. The value γ indicates a predetermined value.

In the above example, the correction value α, the correction value β, and the correction value γ read from the lot A all indicate the value 0. On the other hand, the cyan correction value α read from the lot B is a value obtained by calculating the difference between the cyan coefficient A of the lot A and the cyan coefficient A of the lot B and multiplying it by 100. The cyan correction value β read out from the lot B is a value obtained by calculating the difference between the cyan coefficient B of the lot A and the cyan coefficient B of the lot B and multiplying it by 100. Further, the cyan correction value γ read from the lot B is a value obtained by multiplying the difference between the cyan ΔDB1 coefficient B of the lot A and the cyan ΔDB1 of the lot B by 10,000. These correction values are stored in the wireless communication element 21 as 8-bit data between values -128 and 127, for example. Then, the image forming apparatus 1 corrects the on-paper density DP and ΔDB1 values of the developer image transferred onto the paper P using the correction value α, the correction value β, and the correction value γ. Specifically, the on-paper density DP is
On-paper density DP = (coefficient A + correction value α / 100) × (sensor detection value) + (coefficient B + correction value β / 100) (Formula 4)
And ΔDB1 after correction is
ΔDB1 ′ = (ΔDB1 of lot A) + (correction value γ / 10000) (Formula 5)
Is calculated by

After storing the serial number, the correction value α, the correction value β, and the correction value γ in the storage unit 141 in step S1, the image forming apparatus 1 performs calibration in step S2. The result of calibration is used when controlling the development bias. The printer engine control unit 107, of the output value _{V OUT} of the D / A converter 133, and stores the output value _{V OUT} based on the light receiving result of the light receiving element 49, the storage unit 141 as a control value VblkCAL. The printer engine control unit 107, of the output value _{V OUT} of the D / A converter 133, and stores the output value _{V OUT} based on the reception result of the light receiving element 51, the storage unit 141 as a control value VcolorCAL.

  Next, in step S <b> 3, the printer engine control unit 107 prints a test pattern on the transfer belt 41. The test pattern is detected by the density sensor 45, and the detection result is used for controlling the developing bias. Then, when developing the test pattern, the developing bias applied to the developing roller 11 is, for example, −200V.

  Next, in step S4, the density sensor 45 detects the density of the developer image of the test pattern. At this time, the power supplied to the LED element 47 of the density sensor 45 is input based on the control value VblkCAL when the LED element 47 irradiates a black patch. On the other hand, the power supplied to the LED element 47 when the LED element 47 irradiates the cyan, magenta, and yellow patches is input based on the control value VcolorCAL. The detection result by the density sensor 45 is converted into a digital signal by the A / D converter 135 and stored in the storage unit 141 as the sensor detection value SD. When the detection of the density sensor 45 is completed, the shutter 53 is quickly closed. At this time, the cyan sensor detection value SDC is 1.50 V, the magenta sensor detection value SDM is 1.80 V, the yellow sensor detection value SDY is 1.60 V, and the black sensor The detection value SDK is assumed to be 0.180V.

Next, in step S <b> 5, the printer engine control unit 107 calculates the on-paper density DP based on the sensor detection value SD stored in the storage unit 141. Specifically, the printer engine control unit 107 sets the sensor detection value SD, the coefficient A of lot A, the correction value α of lot A, the coefficient B and the correction value β stored in the storage unit 141 to the above equation 4. Substituting and calculating the on-paper density DPC, DPM, DPY, DPK of each color of lot A. Specifically, the on-paper density DPC is
DPC = (0.8907 + 0/100) × CMV + (0.0824 + 0/100) (Formula 6)
The on-paper density DPM is calculated based on
DPM = (0.8813 + 0/100) × CMV + (0.0411 + 0/100) (Formula 7)
The on-paper density DPY is calculated based on
DPY = (0.9421 + 0/100) × CMV + (0.0079 + 0/100) (Formula 8)
The on-paper density DPK is calculated based on
DPK = (− 2.1614 + 0/100) × CMV + (1.8841 + 0/100) (Formula 9)
Is calculated based on Substituting the above-mentioned values of paper density DPC, DPM, DPY, DPK into these results in paper density DPC = 1.41845, paper density DPM = 1.62774, paper density DPY = 1.52626, and paper density. DPK = 1.49505.

In step S6, the printer engine control unit 107 calculates a corrected density value ΔD based on the on-paper densities DPC, DPM, DPY, DPK calculated in step S5 and the target density value DT. Specifically, the corrected density value ΔD is represented by the difference between the on-paper density DPC, DPM, DPY, DPK and the target density value DT. Thus, by calculating the difference between the two, the difference between the target value and the current state can be clarified. For example, if the target density value DT is 1.5 for each color, the corrected density value ΔDC for cyan is
ΔDC = DPC−1.5 (Formula 10)
The corrected density value ΔDM for magenta color is
ΔDM = DPM−1.5 (Formula 11)
The corrected density value ΔDY for the yellow color is
ΔDY = DPY−1.5 (Formula 12)
The corrected density value ΔDK of black is
ΔDK = DPK−1.5 (Formula 13)
Is calculated by Then, according to the above formulas 10 to 13, the corrected density value ΔDC becomes the value −0.08155, the corrected density value ΔDM becomes the value 0.12744, the corrected density value ΔDY becomes the value 0.01526, and the corrected density value ΔDK. Becomes the value -0.00495. Note that the larger the target density value DT, the wider the gamut range as the reproduction region can be. However, if this value is too high, poor fixing occurs or the consumption of the developer increases. In consideration of such circumstances, the target density value DT is preferably set between the value 1.2 and the value 1.7.

In step S7, the printer engine control unit 107 calculates a development bias correction value DBR based on the corrected density value ΔD calculated in step S6. The development bias correction value DBR indicates a bias voltage value necessary to correct an error between the target density value DT and the corrected density value ΔD. The development bias correction value DBR is
DBR = ΔDC / (ΔDB1 + correction value γ / 10000) (Formula 14)
Is calculated by Then, by substituting each value into the formula 14, the development bias correction value DBRC of the cyan developer of lot A is
DBRC = ΔDC / (0.0041 + 0/10000) (Formula 15)
The development bias correction value DBRM of the magenta developer is calculated as follows:
DBRM = ΔDM / (0.0025 + 0/10000) (Formula 16)
The development bias correction value DBRY of the yellow color developer is calculated as follows:
DBRY = ΔDY / (0.0039 + 0/10000) (Formula 17)
The development bias correction value DBRK of the black developer calculated by
DBRK = ΔDK / (0.0024 + 0/10000) (Formula 18)
Is calculated by According to the above formulas 15 to 18, the development bias correction value DBRC is −20V, the development bias correction value DBRM is 51V, the development bias correction value DBRY is 4V, and the development bias correction value DBRK is a value. -2V. Here, since the development bias correction value DBR is an integer, the decimal part is rounded off.

Next, in step S8, the printer engine control unit 107 changes the setting value of the developing bias based on the developing bias correction value DBR. Specifically, the development bias setting value DB is determined by calculating the sum of the initial value of the development bias and the development bias correction value DBR. If the initial value of the developing bias is −200 V, the developing bias setting value DBC applied to the developing roller 11C is
DBC = −200V + DBRC (Formula 19)
The development bias setting value DBM determined based on the above and applied to the development roller 11M is:
DBm = −200V + DBRM (Formula 20)
The development bias setting value DBY determined based on the above and applied to the development roller 11Y is:
DBY = −200V + DBRY (Formula 21)
The development bias setting value DBK determined based on the above and applied to the development roller 11K is:
DBK = −200V + DBRK (Formula 22)
To be determined. According to the above equations 19 to 22, the development bias setting value DBC is -220V, the development bias setting value DBM is -149V, the development bias setting value DBY is -196V, and the development bias setting value. DBK has a value of -202V. The development bias setting value DB determined here is used as a control value supplied to the high voltage controller 109 until the next development bias density correction operation is performed. Then, by applying the developing bias to the developing roller 11 based on the setting value DB of the developing bias determined in this way, a developer image having substantially the same density as the above-described target density value DT can be obtained. It becomes.

  In step S <b> 9, the printer engine control unit 107 determines whether a new density correction instruction is transmitted from an information processing apparatus (not shown) via the interface unit 100. When the printer engine control unit 107 determines that a new density correction instruction has been supplied, the density correction operation configured by the processing from step S2 to step S8 is performed again.

  Next, in step S10, the printer engine control unit 107 has transmitted a density correction invalid command that is an instruction not to reflect the density correction value calculated from the information processing apparatus (not shown) via the interface unit 100 during printing. Judge whether or not. If the printer engine control unit 107 determines that the density correction invalid command has not been transmitted, the series of processing ends. On the other hand, if the printer engine control unit 107 determines that the density correction invalid command has been transmitted, the process of step S11 is executed.

  In step S <b> 11, the printer engine control unit 107 determines whether the cover has been opened or closed in order to detect replacement of the developer cartridge 19. If the printer engine control unit 107 determines that the cover has not been opened or closed, the printer engine control unit 107 determines that the developer cartridge 19 has not been replaced, and executes the process of step S9 again. On the other hand, if the printer engine control unit 107 determines that the cover has been opened and closed, the developer cartridge 19 may have been replaced, so the process of step S12 is executed to determine this.

  In step S <b> 12, the printer engine control unit 107 reads the identification information stored in the wireless communication element 21 and compares the read identification information with the identification information stored in the storage unit 141.

  In step S <b> 13, the printer engine control unit 107 determines whether the identification information is equal. If even one piece of identification information does not match, the processing of step S14 is executed assuming that the developer cartridge 19 has been replaced. On the other hand, when the printer engine control unit 107 determines that the identification information is the same, the process of step S9 is executed again.

In step S14, the printer engine control unit 107 calculates a correction value α, a correction value β, and a correction value γ. For example, assume that when the cover is opened and closed, the mounted lot A is removed and the lot B is mounted, so that it is determined in step S13 that the identification information does not match. Since the lot B is newly installed, the information stored in the wireless communication element 21 of the lot B includes, in addition to the identification information, a coefficient A corresponding to the developer inside the developer cartridge 19, and The coefficient B and the on-paper density variation ΔDB1, and the correction value α, the correction value β, and the correction value γ are stored as a value 0, for example. Therefore, the printer engine control unit 1 reads out the coefficient A and coefficient B of the lot A read from the wireless communication element 21 of the lot A and stored in the storage unit 141, the on-paper density change ΔDB1, and the lot B read from the lot B. The correction value α, the correction value β, and the correction value γ are calculated based on the coefficient A, the coefficient B, and the on-paper density change amount ΔDB1. Specifically, the correction value α is
α = (coefficient A of lot B−coefficient A of lot A) × 100 (Equation 23)
The correction value β is calculated based on
β = (coefficient B of lot B−coefficient B of lot A) × 100 (Equation 24)
The correction value γ is calculated based on
γ = (ΔDB of lot B1−ΔDB1 of lot A) × 10000 (Formula 25)
Is calculated based on According to the above equations 23 to 25, the cyan correction value α of lot B is −6, the magenta correction value α is −5, the yellow correction value α is −27, black The color correction value α is −55. Further, the cyan correction value β of lot B is the value 9, the magenta correction value β is the value −3, the yellow color correction value β is the value −3, and the black color correction value β is the value 38. Become. In addition, the cyan correction value γ of lot B is −6, the magenta correction value γ is 0, the yellow correction value γ is −16, and the black correction value γ is 0. . The correction value α, the correction value β, and the correction value γ calculated here are stored in the wireless communication element 21 by the RFID control unit 23. Thereafter, the printer engine control unit 107 executes the processing from step S2 to step S8 again, and calculates the development bias setting value for lot B.

  As described above, according to the image forming apparatus 1, the development bias is changed in accordance with the density characteristics of the mounted developer cartridge 19. An image can be printed.

  Further, by correcting the setting value of the developing bias based on the density characteristics of the developer, errors such as the infrared reflectance of the developer, the transfer efficiency difference between the transfer belt 41 and the paper P, and the developer charging difference, etc. It becomes possible to absorb the factors.

  Next, the second embodiment of the present invention will be described in detail.

  Since the image forming apparatus according to the second embodiment has a portion having the same configuration as that of the image forming apparatus 1 described above, detailed description of the portion is omitted, and detailed description is given only for a portion having a difference. I do.

  In the image forming apparatus according to the second embodiment, the correction value stored in the wireless communication element 21 of the currently installed developer cartridge 19 is made to correspond to the color of the developer stored in the developer cartridge 19. Are stored in the storage unit 141 as αN_C, αN_M, αN_Y, αN_K, βN_C, βN_M, βN_Y, βN_K, and γN_C, γN_M, γN_Y, γN_K. Further, the image forming apparatus uses the correction values stored in the wireless communication element 21 of the developer cartridge 19 mounted immediately before replacing the developer cartridge 19 as αO_C, αO_M, αO_Y, αO_K, βO_C, βO_M, The data are stored in the storage unit 141 as βO_Y, βO_K, and γO_C, γO_M, γO_Y, and γO_K.

In such an image forming apparatus, during the development process, the developer is supplied from the developer cartridge 19 to the developing device 5. Even after all the developer in the developer cartridge 19 is supplied to the developing device 5, the developing device is supplied. The developer remains inside 5. Normally, when the developer in the developer cartridge 19 runs out, the user is prompted to replace the developer cartridge 19. When the developer cartridge 19 is replaced, the developing process is continued, but when the developer cartridge 19 is not replaced, the developing device 5 is emptied to prevent the photosensitive drum 7 from being damaged. Accordingly, the operation of the developing device 5 is stopped. However, even in such a case, a predetermined number of sheets can be printed because the developer remains in the developing device 5 as described above. When the developer weight that can be accommodated in the developing device 5 is TC, TM, TY, TK, and the developer consumption amount per dot of each color is EC, EM, EY, EK, the developing devices 5C, 5M. , 5Y, 5K The dot count value DC that can be printed with the developer remaining in the interior is
DC_C = TC / EC (Formula 26)
DC_M = TM / EM (Formula 27)
DC_Y = TY / EY (Formula 28)
DC_K = TK / EK (Formula 29)
It becomes. The dot count values DC_C, DC_M, DC_Y, and DC_K calculated based on these equations 26 to 29 are stored in the storage unit 141. This dot count value is calculated based on the result of an experiment performed in a state where printing at a ratio of 5% to 15% with respect to the sheet area is corrected to a solid density of 1.5 by density correction.

Further, the image forming apparatus 1 calculates the dot count value of the used developer for each color, and stores the calculated dot count value in the storage unit 141 as UC_C, UC_M, UC_Y, and UC_K.

In this case, the correction value α used during the development process by the image forming apparatus is
α = αO_C + (αN_C−αO_C) × (UC_C / DC_C) (Equation 30)
α = αO_M + (αN_M−αO_M) × (UC_M / DC_M) (Formula 31)
α = αO_Y + (αN_Y−αO_Y) × (UC_Y / DC_Y) (Formula 32)
α = αO_K + (αN_K−αO_K) × (UC_K / DC_K) (Expression 33)
The correction value β is calculated based on
β = βO_C + (βN_C−βO_C) × (UC_C / DC_C) (Formula 34)
β = βO_M + (βN_M−βO_M) × (UC_M / DC_M) (Formula 35)
β = βO_Y + (βN_Y−βO_Y) × (UC_Y / DC_Y) (formula 36)
β = βO_K + (βN_K−βO_K) × (UC_K / DC_K) (Expression 37)
The correction value γ is calculated based on
γ = γO_C + (γN_C−γO_C) × (UC_C / DC_C) (Formula 38)
γ = γO_M + (γN_M−γO_M) × (UC_M / DC_M) (formula 39)
γ = γO_Y + (γN_Y−γO_Y) × (UC_Y / DC_Y) (Formula 40)
γ = γO_K + (γN_K−γO_K) × (UC_K / DC_K) (Formula 41)
Is calculated based on Since the values calculated by such equations 30 to 41 are values that take into consideration the ratio between the use count value UC and the dot count value DC, the mixing ratio of the new developer and the old developer is taken into consideration. It becomes possible to change the developing bias.

  As described above, the dot count value DC and the usage amount count value UC are calculated in advance by experiments and stored in the storage unit 141. However, the remaining amount of developer in the developer cartridge 19 is detected. It may be calculated based on the result of calculating the ratio between the old developer and the new developer in the developing device 5 by the detecting means.

  Hereinafter, the operation of the image forming apparatus will be described.

  As shown in FIG. 12, when a series of operations starts, in step S <b> 21, the printer engine control unit 107 reads the identification information stored in the wireless communication element 21, and the read identification information and the identification information stored in the storage unit 141. And compare.

  In step S22, the printer engine control unit 107 determines whether or not both identification information are equal. If even one piece of identification information does not match, the process of step S23 is executed assuming that the developer cartridge 19 has been replaced.

  Next, in step S23, the printer engine control unit 107 inputs a new correction value to the old correction value. Specifically, the printer engine control unit 107 inputs the correction value αN, the correction value βN, and the correction value γN as the correction value αO, the correction value βO, and the correction value γO for each color.

  In step S24, the printer engine control unit 107 stores the correction value in the storage unit 141. Specifically, the correction values stored in the storage unit 141 here are the correction value αO, the correction value βO, and the correction value γO to which new values are input in step S23.

  Next, in step S <b> 25, the printer engine control unit 107 resets the use count value DC stored in the storage unit 141 to a value of 0. Then, the use count value DC whose value has been reset is stored in the storage unit 141.

  Next, in step S26, the printer engine control unit 107 calculates the correction value α, the correction value β, and the correction value γ based on the above-described Expressions 30 to 41.

  Next, calibration is performed in step S27.

  Next, in step S <b> 28, the printer engine control unit 107 prints a test pattern on the transfer belt 41.

  Next, in step S29, the density sensor 45 detects the density of the developer image of the test pattern.

  Next, in step S <b> 30, the printer engine control unit 107 calculates the on-paper density DP based on the sensor detection value SD stored in the storage unit 141.

  Next, in step S31, the printer engine control unit 107 calculates a corrected density value ΔD based on the on-paper densities DPC, DPM, DPY, DPK calculated in step S5 and the target density value DT.

  In step S32, the printer engine control unit 107 calculates a development bias correction value DBR based on the corrected density value ΔD calculated in step S6.

  Next, in step S33, the printer engine control unit 107 changes the setting value of the developing bias based on the developing bias correction value DBR.

  In step S <b> 34, the printer engine control unit 107 determines whether a new density correction instruction is transmitted from the information processing apparatus (not shown) via the interface unit 100. If the printer engine control unit 107 determines that a new density correction instruction has been supplied, the density correction operation configured by the processing from step S26 to step S33 is performed again.

  In step S <b> 35, the printer engine control unit 107 determines whether a density correction invalid command has been transmitted from an information processing apparatus (not shown) via the interface unit 100. If the printer engine control unit 107 determines that the density correction invalid command has not been transmitted, the series of processing ends. On the other hand, when the printer engine control unit 107 determines that the density correction invalid command has been transmitted, the process of step S36 is executed.

  In step S <b> 36, the printer engine control unit 107 determines whether the cover has been opened or closed to detect the replacement of the developer cartridge 19. If the printer engine control unit 107 determines that the cover has not been opened or closed, the printer engine control unit 107 determines that the developer cartridge 19 has not been replaced, and executes the process of step S34 again. On the other hand, if the printer engine control unit 107 determines that the cover has been opened and closed, the developer cartridge 19 may have been replaced, so the process of step S21 is executed again to determine this.

  If it is determined in step S22 that the identification information is equal, the printer engine control unit 107 determines whether density correction has been performed after the power is turned on. If the printer engine control unit 107 determines that the density correction has been executed, the process of step S34 is executed. On the other hand, when the printer engine control unit 107 determines that the density correction is not executed, the process of step S26 is executed.

  As described above, according to the second embodiment, even when the old developer and the new developer that are generated when the developer cartridge 19 is replaced are mixed, the development bias is considered in consideration of the ratio of these developers. Therefore, a good developer image can be obtained.

  In the above-described embodiment, the developing bias applied to the developing roller is changed based on the difference in the density characteristics of the developer. However, the present invention is not limited to this configuration. Any configuration may be used as long as a correction value calculated based on a difference in the density characteristics of the developer is applied to an element that affects the density of the developer image to be printed.

  In the above-described embodiment, the correction value α, the correction value β, and the correction value γ are expressed by three significant digits, but the resolution of the 12-bit A / D converter 135 is 3.3 / 4096V. Therefore, the case of 3 significant digits is an example expressed for the purpose of speeding up the arithmetic processing. If the purpose is not to speed up the arithmetic processing, the effective number may be increased.

1 is a schematic sectional view of an image forming apparatus shown as a first embodiment to which the present invention is applied. FIG. 2 is an elevation view illustrating an outline of a density sensor provided in the image forming apparatus. FIG. 2 is an elevation view illustrating an outline of a density sensor provided in the image forming apparatus. 2 is a block diagram illustrating the image forming apparatus. FIG. FIG. 2 is a circuit diagram illustrating a part of a circuit system of the image forming apparatus. It is a figure which shows the example of the test pattern printed by the image forming apparatus. FIG. 6 is a flowchart showing a series of operations of the image forming apparatus. 4 is a graph showing developer characteristics of a cyan developer cartridge provided in the image forming apparatus. 4 is a graph showing developer characteristics of a magenta developer cartridge provided in the image forming apparatus. 6 is a graph showing developer characteristics of a yellow developer cartridge provided in the image forming apparatus. 4 is a graph showing developer characteristics of a black developer cartridge provided in the image forming apparatus. FIG. 10 is a flowchart showing a series of operations of the image forming apparatus according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming device 3 LED head 5Y Yellow developing device 5C Cyan developing device 5K Black developing device 5M Magenta developing device 5 Developing device 7 Photosensitive drum 9 Charging roller 11 Developing roller 13 Supplying roller 15 Developing blade 19 Developer cartridge 21 Wireless communication element 23 RFID control unit 25 Conveying device 27 Paper cassette 29 Separating roller 31 Hopping rollers 33 and 35 Registration roller 37 Drive roller 39 Drive roller 41 Transfer belt 43 Transfer roller 45 Density sensor 61 Fixing roller 107 Printer engine control unit 109 High pressure control unit 113 Development Bias control unit 141 storage unit

Claims (4)

A replaceable developer containing means for containing the developer;
Developing means for receiving the developer contained in the developer containing means and forming a developer image based on print information input using the developer;
Density detecting means for detecting a density value of the developer image formed by the developing means;
A first storage unit that stores first density characteristic information including a first coefficient related to the density characteristic of the developer stored in the developer storage unit;
A second storage unit for storing second density characteristic information including a second coefficient related to the density characteristic of the developer used in the past;
Forming condition changing means for changing the forming condition of the developer image,
The forming condition changing means includes
The first coefficient included in the first density characteristic information stored in the first storage unit and the second coefficient included in the second density characteristic information stored in the second storage unit. A density value on the paper is calculated from the difference from the coefficient, the first coefficient, and the density value of the developer image detected by the density detection means, and the target density indicating the density value on the paper and the target density A correction value calculation unit that calculates a correction value of a developer image developed by the developing unit from a corrected density value indicating an error from the value,
The developing unit forms a developer image based on the input print information based on the correction value calculated by the correction value calculation unit;
An image forming apparatus. A storage unit that is provided in the developer storage unit and stores identification information for identifying the developer storage unit;
When the forming condition changing unit determines that the currently installed developer containing unit is different from the previously installed developer containing unit based on the identification information, the correction value calculating unit sets the correction value to the correction value calculating unit. Let me calculate
The developing unit forms a developer image based on the input print information based on the correction value calculated by the correction value calculation unit;
The image forming apparatus according to claim 1. The developing means includes a latent image carrier that carries a latent image based on the input print information;
A developer carrying member that carries a developer by electrostatic force and develops the latent image carried on the latent image carrier by the carried developer;
The value of the electrostatic force applied to the developer carrier is a value determined based on the correction value calculated by the correction value calculation unit;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. A developer amount storage unit for storing the amount of developer accommodated in the developer accommodating means;
A developer usage amount storage unit that stores the usage amount of the developer used by the developing means,
The correction value calculation unit
Calculating the correction value based on a ratio between the amount of the developer stored in the developer amount storage unit and the usage amount of the developer stored in the developer usage amount storage unit;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.