JP2008083548A - Image forming apparatus, method for correcting density of developer image and program for controlling image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve image quality by calculating a density correction value corresponding to driving speed even when an image forming apparatus performs printing processing at various driving speeds. <P>SOLUTION: The image forming apparatus 1 is equipped with: a developing device 25 developing a pattern for detecting density and a developer image based on image information; a conveying belt 45 carrying the pattern for detecting density; a density sensor 27 detecting the developer density of the pattern for detecting density; and a printing control part 7 changing an image forming condition on the basis of the result of detection by the density sensor 27. The developing device 25 develops the pattern for detecting density at the second driving speed after developing the pattern for detecting density at the first driving speed. The density sensor 27 detects the developer density of two kinds of patterns for detecting density, and a printing control part 7 changes the image forming condition on the basis of the result of detection by the density sensor 27. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, a developer image density correction method, and an image forming apparatus control program.

  Conventionally, in an electrophotographic image forming apparatus that forms a developer image on a predetermined recording medium, when detecting the developer concentration of the developer image developed by the developing device provided in the image forming apparatus, A density detection pattern is formed on a transfer belt provided in the image forming apparatus. The image forming apparatus detects the developer density of the density detection pattern by the detection unit, and adjusts the density of the developer image by changing the development bias based on the detection result. As an image forming apparatus that adjusts the density of a developer image using such a method, there is an image forming apparatus described in Patent Document 1.

2004-341100 gazette

  However, in the above-described image forming apparatus, the density detection pattern for density adjustment is formed on the transfer belt by executing the printing process at a constant driving speed. The image forming apparatus uses the result of the density adjustment value obtained from the constant driving speed as it is even when the printing process is performed at a driving speed different from the driving speed. There is a problem that an error occurs and the image quality is deteriorated.

  Therefore, the present invention has been made in view of such a situation, and even when the image forming apparatus performs a printing process at various driving speeds, the density correction value corresponding to the driving speed is calculated. An object of the present invention is to provide an image forming apparatus capable of improving the image quality.

  In order to solve the above-described problems, an image forming apparatus includes a developing device that develops a developer image based on a predetermined density detection developer image and input image information, and the density detection developed by the developing device. An image carrier that carries a developer image, a density detector that detects a developer concentration of the developer image for density detection carried by the image carrier, and a detection result of the density detector, An image forming condition changing unit that changes an image forming condition when the developing device develops the developer image based on the image information, and the developing device detects the density detecting developer image at a predetermined first driving speed. And developing the density detection developer image at a second driving speed that is different from the first driving speed, and the density detecting unit is developed at the first driving speed to develop the image. The first developer concentration of the developer image for density detection carried on the carrier and the second developer concentration of the developer image for density detection carried on the image carrier and developed by the second driving speed are set. The image forming condition changing unit detects and changes the image forming condition based on the first developer concentration and the second developer concentration detected by the density detecting unit.

  According to this configuration, the image forming apparatus performs the second development of the first developer density of the density detection developer image printed at the first drive speed and the density detection developer image printed at the second drive speed. Since the image forming conditions can be changed based on the agent concentration, the image forming conditions can be calculated according to the driving speed applicable to the image forming apparatus.

  As described above, according to the image forming apparatus of the present invention, even when the printing process is performed at various driving speeds, the image quality is improved by calculating the density correction value corresponding to the driving speed. be able to.

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

  An image forming apparatus according to an embodiment is an image forming apparatus that performs tandem direct printing. Further, the image forming apparatus performs a printing process at, for example, two types of printing speeds according to the type of the recording medium. Then, the image forming apparatus prints a density detection pattern on a conveyance belt unit that conveys a recording medium such as paper at two printing speeds, detects the developer density of the density detection pattern, and outputs the detection result. Based on this, correction values such as a development bias, a supply bias, and a layer formation bias are calculated. Based on the calculated correction value, the image forming apparatus changes the developing bias, supply bias, and layer forming bias image forming conditions applied to the corresponding units during the printing process.

  As shown in FIG. 1, the image forming apparatus 1 according to the first embodiment configures the image forming apparatus 1 with an interface unit 5 that receives image information transmitted from a host apparatus 3 such as an information processing apparatus. A print control unit 7 that controls the operation of each unit, a memory 9 that stores various types of information, a CPU (Central Processing Unit) 11 that performs various types of arithmetic processing, and a sheet sensor 13 that detects the position of the sheet on the medium conveyance path, An exposure device 15 that exposes a latent image based on image information on a photosensitive drum, which will be described later, and a transfer roller 17 that transfers the developer image onto a sheet. Further, the image forming apparatus 1 uses the charging roller 21 that uniformly charges the surface of the photosensitive drum 19, the developing roller 22, the supply roller 23, and the layer forming blade 24 on the photosensitive drum 19, and the interface unit 5. A developing device 25 for developing a developer image based on the received image information. The image forming apparatus 1 further includes a motor group 26 that supplies a driving force to the developing device 25 and a density sensor 27 that detects the developer concentration of the density detection pattern. In such an image forming apparatus 1, the image information received by the interface unit 5 is converted by the print control unit 7 into image data in a bitmap format, for example. Then, the image forming apparatus 1 exposes the latent image based on the image data converted by the print control unit 7 onto the photosensitive drum 19 by the exposure device 15. Thereafter, the image forming apparatus 1 develops the developer image exposed on the photosensitive drum 19 and transfers the image onto the paper by the transfer roller 17, thereby printing the developer image based on the image information on the paper.

  The interface unit 5 connects the image forming apparatus 1 and the host apparatus 3 via, for example, a LAN (Local Area Network). Such an interface unit 5 is configured by, for example, a USB port formed in the image forming apparatus 1. The image information received by the interface unit 5 is acquired by the print control unit 7.

  The print control unit 7 acquires the image information received by the interface unit 5 from the interface unit 5. Then, the print control unit 7 converts the image information acquired from the interface unit 5 into image data of, for example, bitmap format that can be printed by the image forming apparatus 1. Thereafter, the print controller 7 supplies an image signal based on the image data to the process controller 28 so that the exposure device 15 exposes the latent image based on the image data. In addition, after starting a series of printing processes for printing image information, the print control unit 7 instructs the development voltage control unit 29 on the value of the development bias, and supplies the supply voltage control unit 31 with the value of the supply bias. And instructing the layer formation voltage control unit 33 to specify the value of the layer formation bias, and instructing the motor control unit 35 to start driving the motor group 26 that supplies driving force to each unit that is driven during the printing process. To do. In addition, when the image forming apparatus 1 changes the image forming condition of the developer image, for example, when the power of the image forming apparatus 1 is turned on, the print control unit 7 notifies the density sensor control unit 37 of the detection result of the density sensor 27. Instruct acquisition. Then, the print control unit 7 stores the detection result acquired by the density sensor control unit 37 from the density sensor 27 in the memory 9 so that the CPU 11 can calculate the image forming conditions. Thereafter, the print controller 7 notifies the developing voltage controller 29 of the setting value of the developing bias to be applied to the developing roller 22 based on the image forming conditions calculated by the CPU 7. Further, the print control unit 7 notifies the supply voltage control unit 31 of the voltage value of the supply bias to be applied to the supply roller 23 based on the image forming conditions calculated by the CPU 7. Further, the print control unit 7 notifies the supply roller 23 of the voltage value of the supply bias to the layer formation voltage control unit 33 based on the image forming condition calculated by the CPU 7.

  The memory 9 includes a ROM (Read Only Memory) 39 that stores a control program for performing various operations of the image forming apparatus 1, a RAM (Random Access Memory) 41 that temporarily stores various information during calculation processing by the CPU 11, and And a pattern storage unit 43 for storing image data of the density detection developer image.

  The ROM 39 stores a control program for the image forming apparatus 1 in advance in the manufacturing stage of the image forming apparatus 1. The control program for the image forming apparatus 1 stored in the ROM 39 is executed by the print control unit 7 and the CPU 11 when the print control unit 7 performs various controls and when the CPU 11 calculates image formation conditions. In addition, the ROM 39 stores a reference value for the setting value of the developing bias, the setting value of the supply bias, and the setting value of the layer forming bias, which are used when the CPU 11 calculates the image forming conditions.

  The RAM 41 temporarily stores information used by the CPU 11 when the CPU 11 performs a calculation process. The information stored in the RAM 41 is erased when the image forming apparatus 1 is turned off. Specifically, the RAM 41 stores calculation results for changing image forming conditions such as a developing bias, a supply bias, and a layer forming bias, and various values accompanying the calculation.

  The pattern storage unit 43 is configured by a nonvolatile memory such as a ROM, for example, and stores image data of a density detection developer image to be printed when the image forming apparatus 1 changes image forming conditions.

  The CPU 11 executes a control program for the image forming apparatus 1 stored in the ROM 39, and based on the detection result of the development density of the developer image acquired by the print control unit 7 from the density sensor 27 via the density sensor control unit 37. To calculate image forming conditions. Specifically, the CPU 11 determines, based on the detection result of the developer density of the developer image, at least one set value or all of the set value of the developing bias, the set value of the supply bias, and the set value of the charging bias. Is set, and the calculation result is supplied to the print control unit 7. The print control unit 7 then instructs the development voltage control unit 29 to change the development bias setting value to the development bias setting value calculated by the CPU 11 based on the setting value supplied from the CPU 11. Supply. Similarly, the print control unit 7 supplies an instruction to the supply voltage control unit 31 to change the supply bias setting value to the supply bias setting value calculated by the CPU 11, thereby controlling the layer formation voltage control. An instruction to change the setting value of the layer forming bias to the setting value of the layer forming bias calculated by the CPU 11 is supplied to the unit 33. That is, in the image forming apparatus 1, the CPU 11, the print control unit 7, the development voltage control unit 29, the supply voltage control unit 31, and the layer formation voltage control unit 33 constitute an image formation condition changing unit.

  As shown in FIG. 2, the sheet sensor 13 is a plurality of sensors provided on the medium conveyance path R, and detects the position of the sheet P on the medium conveyance path R. The detection result of the paper sensor 13 is supplied to the print control unit 7. Then, the print control unit 7 measures the timing for performing the printing operation based on the detection result of the paper sensor 13.

  The exposure device 15 is provided corresponding to the plurality of developing devices 25, and exposes latent image images corresponding to the respective colors in accordance with the color of the developer image developed by the developing device 25. The image forming apparatus 1 includes four exposure devices 15 corresponding to the respective colors, the exposure device 15C corresponds to a latent image corresponding to a cyan developer image, and the exposure device 15M corresponds to a magenta developer image. The exposure device 15Y has a latent image corresponding to the yellow developer image, the exposure device 15K has the latent image corresponding to the black developer image, and the development devices 25C and 25M corresponding to the latent image. , 25Y, 25K, the photosensitive drum 19 is exposed. Such an exposure apparatus 15 includes, for example, an LED array in which LED (Light Emitting Diode) elements are arranged and a Selfox lens array, emits light according to an image of one line of image data, and generates a latent image as a photoconductor. The drum 19 is exposed.

  The charging roller 21 is provided corresponding to each of the developing devices 25C, 25M, 25Y, and 25K, is applied with a set value controlled by the process control unit 28, and the surface of the photosensitive drum 19 is applied using the applied bias. Charge uniformly.

  The transfer roller 17 is formed corresponding to each of the developing devices 25C, 25M, 25Y, and 25K via a conveyance belt 45 that conveys the paper P. The transfer roller 17 is applied with a bias controlled by the process control unit 28, and transfers the developer image developed on the photosensitive drum 19 onto the paper P using the applied bias. Further, when the image forming apparatus 1 performs a series of processes for changing image conditions, the transfer roller 17 transfers the developer image of the density detection pattern developed on the photosensitive drum 19 onto the conveyance belt 45. To do.

  The developing device 25 develops a developer image corresponding to the color of the developer included in the developing device 25. Such a developing device 25 includes a developing roller 22 that develops the developer image by attaching the developer to the latent image carried on the photosensitive drum 19, and a supply roller that supplies the developer to the developing roller 22. And a layer forming blade 24 for forming a developer layer by thinning the developer carried on the supply roller 23.

  The surface of the photosensitive drum 19 is uniformly charged by the charging roller 21. The photosensitive drum 19 carries the latent image on the surface by irradiating the charged portion with the exposure device 15 to remove the charge. Such a photosensitive drum 19 is rotationally driven based on the driving force supplied from the motor group 26.

  The developing roller 22 is applied with a developing bias controlled by the developing voltage control unit 29 and carries the developer using the applied voltage. The developing roller 22 is rotationally driven based on the driving force supplied from the motor group 26 to attach the carried developer to the latent image carried on the photosensitive drum 19. A developer image is developed on the surface. The amount of developer carried by the developing roller 22 changes according to the value of the developing bias.

  The supply roller 23 is applied with a supply bias controlled by the supply voltage control unit 31 and attaches the developer to itself using the applied voltage. The developer attached to the supply roller 23 is supplied to the development roller 22 when the supply roller 23 is driven to rotate.

  The motor group 26 is constituted by a plurality of motors, and the individual motors constituting the motor group 26 are individually driven under the control of the motor control unit 35, and the developing roller 22, the supply roller 23, and the photosensitive drum 19 are respectively driven. , And supply power to the conveyor belt 45 and the like. Such a motor group 26 is composed of, for example, a plurality of pulse motors whose driving speed changes based on a signal supplied from the motor control unit 35.

  The density sensor 27 detects the developer density of the developer image of the density detection pattern transferred onto the transport belt 45 under the control of the density sensor control unit 37. Such a density sensor 27 is arranged on the downstream side of the developing devices 25C, 25M, 25Y, and 25K in the driving direction of the conveyance belt 45, and is configured by a light emitting element and a light receiving element (not shown). The density sensor 27 emits the density detection pattern by causing the light emitting element to emit light, and the reflected light is received by the light receiving element. The density sensor 27 detects the developer density of the density detection pattern based on the attenuation rate of the reflected light.

  The conveyance belt 45 drives the sheet P conveyed from the upstream side of the medium conveyance path R in the direction of arrow A while adsorbing the sheet P by electrostatic force, and moves the sheet P to the medium conveyance path when the developer image is transferred onto the sheet P. It is transported in the downstream direction. The conveyance belt 45 carries a developer image having a density detection pattern when the image forming apparatus 1 detects the density of the developer image. Such a conveyor belt 45 is formed of a glossy black resin on the surface, and is installed substantially parallel to the driving roller 45a that rotates based on the driving force supplied from the layer forming blade 24 and the driving roller 45a. It is stretched between the idle rollers 45b. The conveyor belt 45 is driven in the direction of the arrow A in accordance with the operation in which the driving roller 45a is rotationally driven by the driving force supplied from the motor group 26.

  The image forming apparatus 1 also includes a cleaning blade 47 that peels off the developer image of the density detection pattern carried by the transport belt 45 from the transport belt 45 and a waste developer container that stores the developer peeled off by the cleaning blade 47. 49. The cleaning blade 47 has one end in contact with the transport belt 45 and the other end fixed to a waste developer container 49. The cleaning blade 47 and the waste developer container 49 are disposed on the downstream side of the density sensor 27 in the driving direction of the transport belt 45.

  The image forming apparatus 1 further includes a fixing device 51 that fixes the developer image transferred onto the paper P by the developing devices 25C, 25M, 25Y, and 25K and the transfer rollers 17C, 17M, 17Y, and 17K onto the paper P. . The fixing device 51 is disposed on the downstream side of the developing devices 25C, 25M, 25Y, and 25K and the transfer rollers 17C, 17M, 17Y, and 17K in the medium conveyance path R. The fixing device 51 fixes the developer image on the paper P by nipping and conveying the paper P by the fixing roller 53 incorporating a heat source (not shown) and the pressure roller 55 pressed against the fixing roller 53.

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

  First, an operation when the image forming apparatus 1 performs a printing process will be described.

  When image information is transmitted from the host apparatus 3 to the image forming apparatus 1, the image forming apparatus 1 receives the image information at the interface unit 5. Then, the print control unit 7 acquires the image information received by the interface unit 5 and converts the image information into image data. The print control unit 7 instructs the process control unit 28, the development voltage control unit 29, the supply voltage control unit 31, the layer formation voltage control unit 33, and the motor control unit 35 to execute the print process. In addition, the print control unit 7 supplies the converted image data to the process control unit 28. Further, the print control unit 7 refers to the RAM 41 and reads the setting value of the developing bias, the setting value of the supply bias, and the setting value of the layer forming bias stored in the RAM 41 in the image forming condition calculation process described later. Then, the print control unit 7 supplies the read development bias setting value to the development voltage control unit 29, supplies the supply bias setting value to the supply voltage control unit 31, and sets the layer formation bias setting value to the layer formation voltage. It supplies to the control part 33.

  The process control unit 28 supplies the image data supplied from the print control unit 7 to the exposure device 15 line by line and supplies power to the charging roller 21 from a power source (not shown). Then, the charging roller 21 supplied with electric power uniformly charges the surface of the photosensitive drum 19 based on the supplied electric power. The process control unit 28 supplies power to the transfer roller 17 from a power source (not shown) to charge the transfer roller 17.

  When an instruction to execute a printing process is supplied from the printing control unit 7, the motor control unit 35 starts driving a pulse motor that drives the conveyance belt 45 and a pulse motor that drives each unit of the developing device 25. At this time, for example, according to the instruction of the print control unit 7, the motor control unit 35 according to the instruction of the print control unit 7, the developing roller 22, the supply roller, and the like included in the image information transmitted from the host device 3 23 and the photosensitive drum 19 are driven at a printing speed of 10 PPM (Paper Per Minute) or a printing speed of 30 PPM.

  The development voltage control unit 29 causes the development roller 22 to be supplied with the voltage indicated by the setting value of the development bias supplied from the print control unit 7 from a power source (not shown). Similarly, the supply voltage control unit 31 and the layer formation voltage control unit 33 use the power supply (not shown) to set the supply bias set value supplied from the print control unit 7 and the voltage shown in the layer formation bias set value. To the supply roller 23 and the layer forming blade 24.

  When a supply bias is applied to the supply roller 23, the developer inside the developing device 25 is attracted to the supply roller 23 by the supply bias and adheres to the surface of the supply roller 23. At this time, the amount of developer adhering to the supply roller 23 depends on the set value of the supply bias. Then, the developer attached to the surface of the supply roller 23 by the supply roller 23 having the developer attached to the surface thereof rotated by the driving force supplied from the motor group 26 is leveled by the layer forming blade 24. At this time, since a layer forming bias is applied to the layer forming blade 24, a predetermined bias is applied to the developer in contact with the layer forming blade 24. Thereafter, when the supply roller 23 further rotates, the developer is conveyed to a contact portion between the supply roller 23 and the development roller 22.

  At this time, a developing bias is applied to the developing roller 22, and the developer adhering to the supply roller 23 is removed from the surface of the supply roller 23 by the difference in the set values of the developing roller 22 and the supply roller 23. Move to the 22 surface. At this time, the amount of the developer adhering to the surface of the developing roller 22 depends on the setting value of the developing bias. Thereafter, the developing roller 22 further rotates, and the developer attached to the surface of the developing roller 22 is attracted by the exposure device 15 to the photosensitive drum 19 on which a latent image is formed. Then, when the developer adheres to the surface of the photosensitive drum 19, a developer image based on the latent image is developed on the surface of the photosensitive drum 19.

  The print controller 7 performs such a development process while detecting the timing at which the paper is transported by the paper sensor 13. The developer image carried on the photosensitive drum 19 is caused by the difference between the set values of the photosensitive drum 19 and the transfer roller 17 at the timing when the paper P is conveyed to the lower part of the developing devices 25C, 25M, 25Y, and 25K. Transferred onto the paper P. Thereafter, the sheet P on which the developer image has been transferred is conveyed in the direction of the fixing device 51, and the developer image is attached by the fixing device 51 and discharged onto a stacker (not shown) of the image forming apparatus 1.

  Next, a method for changing the image forming condition by the image forming apparatus 1 will be described in detail with reference to FIGS. Specifically, the image forming apparatus 1 detects the density of the developer image of the density detection pattern printed at different printing speeds, and based on the detection result, the development bias, the supply bias, the layer formation bias, etc. Change the image forming conditions. In the present embodiment, it is assumed that the image forming apparatus 1 prints the density detection pattern at two types of printing speeds.

  For example, when the user turns on the power of the image forming apparatus 1, the image forming apparatus 1 executes a series of image forming condition calculation processes by executing a control program stored in the ROM 39.

  When a series of processes starts, the image forming apparatus 1 causes the motor control unit 35 to change the setting of the printing speed when printing the density detection pattern in step S1. The image forming apparatus 1 sets the printing speed to one of two predetermined printing speeds. Specifically, in the present embodiment, the image forming apparatus 1 first prints the density detection pattern at a printing speed of 10 PPM, and then prints the density detection pattern at a printing speed of 30 PPM. In this step immediately after the start of a series of processes, the image forming apparatus 1 sets the printing speed to a speed of 10 PPM.

  In step S2, the image forming apparatus 1 prints a developer image having a density detection pattern. Specifically, the print control unit 7 reads the lower image data of the density detection pattern from the pattern storage unit 43, and prints an image based on the image data at a printing speed of 10 PPM and a developer concentration of 100%. Print on top. At this time, the print control unit 7 reads the voltage reference value stored in the ROM 39, and at time t0, the motor drive speed is increased to 10 PPM, and the voltage applied to the charging roller 21 is increased to a voltage value of −1000 V. The developing bias applied to the developing roller 22 is lowered to a voltage value of −200 V, the developing bias applied to the supply roller 23 and the layer forming bias applied to the layer forming blade 24 are lowered to a voltage value of −300 V, The voltage applied to the transfer roller 17 is raised to a voltage value of 4000V. Thereafter, the print control unit 7 drives the exposure device 15 based on the image data of the density detection pattern at time t1 to form a latent image of the density detection pattern on the photosensitive drum 19. When the formation of the latent image of the density detection pattern is completed, the print control unit 7 stops driving the exposure device 15 at time t2.

  Next, in step S3, the print control unit 7 determines whether it is necessary to change the printing speed. Specifically, the print control unit 7 determines that the print speed needs to be changed when the currently set print speed is 10 PP, while the currently set print speed is 30 PPM. If there is, it is determined that there is no need to change the printing speed. If the print control unit 7 determines that the print speed needs to be changed, the process of step S1 is executed again. In step S1, the printing control unit 7 sets the printing speed of the density detection pattern to the printing speed of 30 PPM. Then, at time t3, the printing control unit 7 raises the driving speeds of the conveying belt 45, the developing roller 22, the supply roller 23, and the photosensitive drum 19 to the printing speed 30PPM, and executes the process of step S2 again.

  When the processing so far is executed by the image forming apparatus 1, as shown in FIG. 5, the density detection patterns PC10, PM10, PY10, PK10 and the printing speed of 30 PPM printed at the printing speed of 10 PPM are formed on the conveyor belt 45. The density detection patterns PC30, PM30, PY30, and PK30 printed in (1) are continuously printed.

  Next, in step S <b> 4, the print control unit 7 detects the developer concentration of the density detection pattern carried on the conveyance belt 45. Specifically, the print control unit 7 supplies an instruction to the density sensor control unit 37 to drive the density sensor 27 to detect the developer density of the density detection pattern. Under this instruction, the density sensor control unit 35 drives the density sensor 27 at time t4 to detect the developer density of the density detection patterns PC10, PM10, PY10, and PK10. The print control unit 7 lowers the driving speed of the motor group 26 to the printing speed 10 PPM so that the developer density of the density detection patterns PC10, PM10, PY10, and PK10 can be detected in accordance with the operation, and the conveyance belt. 45 drive speed is changed. When the print control unit 7 determines that the density detection patterns PC10, PM10, PY10, and PK10 carried on the transport belt 45 have passed the density sensor 27 after a certain time has elapsed, the print control unit 7 at time t5. 7 raises the driving speed of the motor group 26 to the printing speed 30 PPM, and changes the driving speed of the conveyor belt 45. When the driving speed of the conveyor belt 45 changes, the density detection patterns PC30, PM30, PY30, and PK30 pass through the density sensor 27 at a printing speed of 30 PPM, and the developer density is detected by the density sensor 27. Then, after the density detection patterns PC30, PM30, PY30, and PK30 pass through the density sensor 27, the print control unit 7 stops driving the motor group 26 at time t6, and applies the voltage applied to the charging roller 21. The voltage is raised to 0 V, the developing bias applied to the developing roller 22 is raised to 0 V, the supply bias applied to the supply roller 23 and the layer forming bias applied to the layer forming blade 24 are set to the voltage. The voltage is raised to 0V, the voltage applied to the transfer roller 17 is lowered to 0V, and the driving of the density sensor 27 is stopped.

  Next, in step S5, the print controller 7 displays the detection results of the developer concentrations of the density detection patterns PC10, PM10, PY10, PK10 and the density detection patterns PC30, PM30, PY30, PK30 detected by the density sensor 27. It is stored in the RAM 41.

  Next, in step S6, the CPU 11 executes the control program stored in the ROM 39 and develops the density detection patterns PC10, PM10, PY10, PK10 and the density detection patterns PC30, PM30, PY30, PK30 stored in the RAM 41. Image forming conditions are calculated based on the agent concentration. Specifically, the CPU 11 develops the development bias to be applied to the developing roller 22 during the printing process based on the density detection patterns PC10, PM10, PY10, PK10 and the density detection patterns PC30, PM30, PY30, PK30. , The voltage value of the supply bias to be applied to the supply roller 23, and the voltage value of the layer formation bias to be applied to the layer forming blade 24 are calculated.

According to the inventors' experiment, the relationship between the developer image density value (OD value) and the developing bias voltage value (V) at a printing speed of 30 PPM and a printing speed of 10 PPM is as shown in FIG. It becomes a relationship. Then, when an approximate straight line is obtained based on each value plotted on the coordinate axis, the relationship between the OD value at the printing speed of 30 PPM and the voltage value of the developing bias is as follows:
y ₁ = −0.003 × ₁ +0.8 (Formula 1)
Represented by On the other hand, the relationship between the OD value at the printing speed of 30 PPM and the voltage value of the developing bias is as follows:
y ₂ = −0.003 × ₂ +0.9 (Formula 2)
Represented by That is, according to Equations 1 and 2, when the printing speed is 10 PPM, and when the printing speed is 30 PPM, the slope between the density value (OD value) and the developing bias voltage value (V) is The value is -0.003. The variables x ₁ and x ₂ indicate the development bias voltage value, and the variables y ₁ and y ₂ are values indicating the OD value of the developer image. Therefore, if the target OD value is determined, the OD value is set. It is possible to derive the voltage value of the developing bias to be applied to the developing roller 22 in order to obtain it.

Specifically, the ROM 39 of the image forming apparatus 1 has
Development bias correction value = (detected OD value−target OD value) /0.003 (formula 3)
Is stored, and the CPU 11 calculates the correction value of the developing bias using Equation 3. In Expression 3, a developing bias necessary for correcting the difference between the target OD value and the actual OD value of the density detection pattern printed by the developing device 25 is calculated. For example, when the OD value to be targeted is 1.5 and the OD value detected by the detection sensor S and stored in the RAM 41 is 1.6, the CPU 11 determines that the OD value is 0.1 as an error. Substituting these values into Equation 3 to calculate the development bias required to correct
Correction value of developing bias = (1.6−1.5) /0.003=33V (Formula 4)
Is derived. The density detection pattern detected by the detection sensor S is printed with the developing bias set to a voltage value of −200 V, and is a detected value. Therefore, the CPU 11 uses the developing bias correction value 33 V calculated by Equation 4 as the detected value. A set value -167 V after development bias correction is derived by adding to the voltage value -200 V of development bias at the time of printing.

  Thereafter, in step S7, the CPU 11 refers to such a calculation method and the OD values of the density detection patterns PC10, PM10, PY10, PK10 stored in the RAM 41, and executes the printing process at a printing speed of 10 PPM. The corrected setting value of the developing bias to be applied to the developing rollers 22C, 22M, 22Y, and 22K is calculated and stored in the RAM 41. The CPU 11 refers to the above-described calculation method and the OD values of the density detection patterns PC30, PM30, PY30, and PK30 stored in the RAM 41, and the developing rollers 22C when executing the printing process at the printing speed of 30 PPM. Set values after correction of the developing bias to be applied to 22M, 22Y, and 22K are calculated and stored in the RAM 41.

In step S <b> 6, the CPU 11 sets the setting value of the supply bias to be applied to the supply roller 23 and the setting value of the layer formation bias to be applied to the layer forming blade 24 based on the set value after the correction of the developing bias. calculate. Specifically, the CPU 11 calculates a setting value for the supply bias and a setting value for the layer formation bias based on the calculation formula stored in the ROM 39. For example,
Setting value of supply bias = Setting value after development bias correction−100V (Formula 5)
as well as,
Setting value of layer forming bias = Setting value of supply bias (Formula 6)
Are stored in the ROM 39 as calculation formulas for the supply bias setting value and the layer formation bias setting value, the CPU 11 reads out these equations stored in the ROM 39, and sets the supply bias setting value and the layer formation bias value. Calculate the set value. To explain with the above example, the CPU 11 reads Formula 5 from the ROM 39, substitutes the set value after correction of the developing bias stored in the RAM 41 into Formula 5, and calculates the set value -267V after correction of the supply bias. . Further, the CPU 11 calculates a set value −267V after correction of the calculated supply bias and a set value −267V after correction of the layer formation bias based on Equation 6.

  Thereafter, in step S7, the CPU 11 stores the calculated supply bias and layer formation bias in the RAM 41, and ends a series of processes.

  Then, the setting value after the correction of the developing bias, the setting value after the correction of the supply bias, and the setting value after the correction of the layer forming bias stored in the RAM 41 in this way are processed by the image forming apparatus 1 in the printing process. When executing, it is referred to by the print control unit 7, and the set value is changed by the development voltage control unit 29, the supply voltage control unit 31, and the layer formation voltage control unit 33 under the instruction of the print control unit 7.

  As described above, the image forming apparatus 1 can change the printing speed according to the type of the recording medium included in the image information, and the image forming apparatus 1 prints the density detection pattern accordingly. Even at this time, printing is continuously performed at two speeds of a printing speed of 10 PPM and a printing speed of 30 PPM. Then, the image forming apparatus 1 detects the developer concentrations of the two types of density detection patterns printed at these two types of speeds at the same speed as the printing speed. As a result, the image forming apparatus 1 uses the developer concentration detected based on the two types of density detection patterns to set the development bias setting value, the supply bias setting value, or the layer formation bias setting used during the printing process. In order to calculate the value, it is possible to calculate image forming conditions corresponding to two types of printing speeds. The image forming apparatus 1 calculates the image forming conditions corresponding to each printing speed, and changes the image forming conditions according to the printing speed at the time of the printing process, so that the optimum image forming conditions for each printing speed are obtained. Thus, it is possible to print a developer image with higher image quality than that of a conventionally used image forming apparatus.

  Further, since the image forming apparatus 1 continuously prints the density detection pattern corresponding to each printing speed and performs density detection, the image forming condition calculation process can be performed quickly.

  Next, a second embodiment of the image forming apparatus to which the present invention is applied 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, detailed description thereof will be omitted, and detailed description will be given only for a portion having a difference. I do.

  As shown in FIG. 7, the image forming apparatus 57 according to the second embodiment includes an input unit 59 for inputting information on the type and thickness of the paper P in addition to the configuration of the image forming apparatus 1. Prepare.

  The input unit 59 is an operation panel formed on the image forming apparatus 57, for example, and relates to the type of recording medium and the thickness of the recording medium to be used for the image forming apparatus 57 during the printing process when operated by the user. Enter information. Then, the input unit 59 supplies the print control unit 7 with information regarding the input type of recording medium and the thickness of the recording medium. Information about the type of recording medium and the thickness of the recording medium supplied to the print control unit 7 is stored in the RAM 41.

  Further, the control program for the image forming apparatus 57 stored in the ROM 39 of the image forming apparatus 57 is different from the control program stored in the ROM 39 of the image forming apparatus 1. Specifically, the control program stored in the ROM 39 of the image forming apparatus 57 is input to the input unit 59 and stored in the RAM 41 and the recording medium when determining the printing speed during the printing process. The printing speed is determined by referring to the information regarding the thickness of the printing. The image forming apparatus 1 controls each unit so that the printing speed decreases as the thickness of the recording medium increases.

  Hereinafter, a method for changing the image forming condition by the image forming apparatus 57 will be described in detail with reference to FIG. Specifically, the image forming apparatus 57 detects developer images of density detection patterns printed at different printing speeds, and forms image formation such as development bias, supply bias, and layer formation bias based on the detection results. Change the condition. Then, the image forming apparatus 57 sets the printing speed of the density detection pattern based on the information regarding the type and weight of the paper used at the time of printing.

  When a series of processing starts, in step S10, the image forming apparatus 57 detects the type and weight of the paper used for printing. Specifically, the image forming apparatus 57 requests the user to input information regarding the type and weight of the paper using a display unit (not shown). When information regarding the paper type and weight is input to the input unit 59, the image forming apparatus 57 causes the RAM 41 to store information regarding the paper type and weight.

Next, in step S <b> 11, the image forming apparatus 57 sets the printing speed for printing the density detection pattern based on the information on the paper type and weight stored in the RAM 41. For example, the image forming apparatus 1 stores a table as shown in Table 1 in the RAM 41. The image forming apparatus 1 refers to the RAM 41 during the printing process, and sets the printing speed to 30 PPM when the continuous amount of paper is 55 kg to 77 kg, for example.

  Next, in step S12, the image forming apparatus 57 prints the developer image of the density detection pattern at the set printing speed. Specifically, the print control unit 7 controls each unit based on the printing speed set in step S11 and prints the density detection pattern.

  Next, in step S13, the print control unit 7 determines whether it is necessary to change the printing speed. Specifically, the print control unit 7 determines whether or not it is necessary to change the printing speed according to the type of paper used for printing. For example, when the user designates using normal paper and OHP paper for printing, the print control unit 7 sets the printing speed used when printing normal paper and the printing speed used when printing OHP paper. It is determined that it is necessary to print at two printing speeds. Then, the print control unit 7 executes the processes of step S11 and step S12 according to the number of types of paper.

  Next, in step S14, the print control unit 7 detects the developer concentration of the density detection pattern carried on the conveyor belt 45, and stores the detection result in the RAM 41 in step S15.

  Next, in step S16, the print controller 7 executes the control program stored in the ROM 39, calculates the image forming conditions based on the developer concentration of the density detection pattern stored in the RAM 41, and in step S17. The image forming conditions are stored in the RAM 41, and the series of processes is terminated.

  After that, the image forming apparatus 57 controls the development voltage control unit 29, the supply voltage control unit 31, and the layer formation voltage control unit 33 based on the image forming conditions in the same manner as the image forming apparatus 1, and prints the print data. The developer image based on is printed on the paper.

  As described above, according to the image forming apparatus 57, it is possible to perform the density correction of the developer image according to the type of the medium used at the time of printing. Therefore, the density correction can be performed efficiently.

  In the above-described embodiment, when the developer density of the developer image printed on the conveyance belt 45 is detected using the density sensor 27, the print control unit 7 determines the drive speed of the motor group 26 as follows: Although control was performed according to the printing speed of the density detection pattern to be detected, printing was performed at different printing speeds while maintaining the driving speed of the conveyor belt 45 at a constant speed without performing such control. It is also possible to detect the developer concentration of the density detection pattern. Specifically, when detecting the developer concentration of the density detection pattern, the image forming apparatuses 1 and 57 determine the length of the density detection pattern in the medium conveyance path R direction, whichever of the two printing speeds. Either one is changed corresponding to the printing speed. For example, the image forming apparatus 1 prints the density detection pattern at the printing speed of 10 PPM and the printing speed of 30 PPM, but the density detection patterns PC30, PM30, and PY30 when the density detection pattern is printed at the printing speed of 30 PPM. , PK30 in the medium transport path R direction is X, and the lengths of the density detection patterns PC10, PM10, PY10, PK10 in the medium transport path R direction are “actual printing speed / original printing speed”. By setting the value 3X multiplied by X, the image forming apparatus can perform printing of different density detection patterns at a constant printing speed and processing for detecting the developer density of the density detection patterns.

  In this case, the image forming apparatus 1 executes the control program stored in the ROM 39, and first prints the density detection patterns PC10, PM10, PY10, and PK10 on the transport belt 45 at a printing speed of 10 PPM. Then, after printing of all the density detection patterns PC10, PM10, PY10, and PK10 is completed, the printing speed is increased from when the density detection patterns PC10, PM10, PY10, and PK10 start to be detected. Switch to 30 PPM. Then, after switching the printing speed to the printing speed 30 PPM, the image forming apparatus 1 starts exposure of the latent image of the density detection patterns PC30, PM30, PY30, and PK30. At this time, as shown in FIG. 9, the image forming apparatus 1 prevents the density detection process from starting before switching the printing speed to the printing speed 30 PPM in the direction of the arrow A of the density detection pattern PK10. A distance D1 from the front end portion to the rear end portion in the direction of arrow A of the density detection pattern PC10 is detected from the nip portion between the photosensitive drum 19C and the transfer roller 17C of the developing device 25C located on the most downstream side. The density detection patterns PC10, PM10, PY10, and PK10 are printed so as to be shorter than the distance D2 to the position SS.

  When printing such density detection patterns PC10, PM10, PY10, and PK10, the image forming apparatus 1 uses the control program stored in the ROM 39 to drive the motor at speed t10 as shown in FIG. To 10PPM. Then, the image forming apparatus 1 starts driving the exposure device 15K at time t11 to form a latent image on the photosensitive drum 19K. Then, after forming the density detection pattern PK10 corresponding to the length 3X on the photosensitive drum 19K, the image forming apparatus 1 lowers the driving of the exposure device 15K at time t12. Then, the image forming apparatus 1 measures the timing at which the density detection pattern PY10 should be printed, starts the exposure device 15Y at time t13, and lowers the exposure device 15Y at time t14, thereby generating the density detection pattern PY10. Print. Further, the image forming apparatus 1 repeats the same operation from time t15 to time t18, and prints the density detection patterns PM10 and PC10 on the transport belt 45.

  Next, at time t19, the image forming apparatus 1 raises the drive speed of the motor to 30 PPM, raises the drive of the exposure device 15K, and raises the drive of the density sensor 27. The timing at time t19 is after the developer image of the density detection pattern PC10 formed on the photosensitive drum 19C at time t18 has been completely transferred onto the conveyance belt 45. The image forming apparatus 1 forms the latent image of the density detection pattern PK30 on the photosensitive drum 19K by lowering the driving of the exposure device 15K at time 20 while maintaining the motor driving speed at 30 PPM. To do. At this time, the time from time t19 to time t20 corresponds to approximately 1/3 of the time from time t11 to time t12. The image forming apparatus 1 repeats the same operation from time t21 to time t26, and prints the density detection patterns PY30, PM30, and PC30 on the transport belt 45.

  Note that it is not necessary to start up the exposure device 15K and the density sensor 27 at time t19. At this timing, it is sufficient that at least the motor drive speed is 30 PPM. And the timing which starts the drive of the exposure apparatus 15 and the density sensor 27 should just be after time t19.

  Thereby, the image forming apparatus 1 can perform the density detection processing of the density detection patterns PC10, PM10, PY10, and PK10 while executing the printing process of the density detection patterns PC30, PM30, PY30, and PK30. Then, by simultaneously performing the printing process of the density detection patterns PC30, PM30, PY30, and PK30 and the density detection process of the density detection patterns PC10, PM10, PY10, and PK10 in this manner, the image forming apparatus 1 is useless. It is possible to speed up the process of changing the image forming conditions without performing an operation.

  In the above description, the length of the density detection pattern is changed according to the printing speed. However, the length of the density detection pattern is made the same, and the detection cycle of the density sensor 27 is changed according to the printing speed. The same effect can be obtained by changing it.

  Further, in the above-described embodiment, the density detection pattern is changed from the upstream side in the medium transport path R direction to the cyan density detection patterns PC10 and PC30, the magenta density detection patterns PM10 and PM30, and the yellow density. Although the detection patterns PY10 and PY30 and the black color density detection patterns PK10 and PK30 are sequentially printed, the order may be reversed. In this case, the density detection pattern includes black density detection patterns PK10 and PK30, yellow density detection patterns PY10 and PY30, and magenta density detection pattern PM10 from the upstream side in the medium conveyance path R. Printing is performed on the conveyance belt 45 in the same manner as the PM 30 and the cyan density detection patterns PC 10 and PC 30.

  In the above-described embodiment, the tandem type image forming apparatus has been described in detail. However, the present invention relates to an intermediate transfer type image forming apparatus, an MFP (Multi Function Peripherals), a fax machine, and a copying machine. It can also be applied to machines.

1 is a block diagram illustrating a configuration of an image forming apparatus according to a first embodiment. FIG. 2 is an elevation view schematically illustrating the structure of the image forming apparatus. FIG. 6 is a flowchart showing the operation of the image forming apparatus. 6 is a graph showing a transition of operation of each unit of the image forming apparatus. It is a figure which shows the example of the pattern for density detection printed by the image forming apparatus. It is a graph which shows the relationship between the density value and bias voltage value by experiment of this inventor. It is a block diagram which shows the structure of the image forming apparatus concerning 2nd Embodiment. FIG. 6 is a flowchart showing the operation of the image forming apparatus. FIG. 10 is an elevational view showing an outline of the structure of an image forming apparatus as a modification. 6 is a graph showing a transition of operation of each unit of the image forming apparatus.

Explanation of symbols

1,57 Image forming apparatus 3 Host apparatus 5 Interface section 7 Print control section 9 Memory 11 CPU
13 Paper sensor 15 Exposure devices 15C, 15M, 15Y, 15K Exposure devices 17C, 17M, 17Y, 17K Transfer rollers 19C, 19M, 19Y, 19K Photosensitive drums 21C, 21M, 21Y, 21K Charging rollers 22C, 22M, 22Y, 22K Developing roller 23C, 23M, 23Y, 23K Supply roller 24C, 24M, 24Y, 24K Layer forming blade 25C, 25M, 25Y, 25K Developing device 26 Motor group 27 Density sensor 28 Process control unit 29 Development voltage control unit 31 Supply voltage control unit 33 Layer formation voltage control unit 35 Motor control unit 37 Density sensor control unit 43 Pattern storage unit 45 Conveying belt 47 Cleaning blade 49 Waste developer container 51 Fixing device 53 Fixing roller 55 Pressure roller 57 Image forming device 59 Input unit PC10, PM10, PY 0, PK10 density detection pattern PC30, PM30, PY30, PK30 density detection pattern S detection sensor R medium transportation path

Claims (7)

A developing device for developing a developer image based on a predetermined density detection developer image and input image information;
An image carrier that carries the developer image for density detection developed by the developing device;
A density detector for detecting a developer density of the density detection developer image carried by the image carrier;
An image forming condition changing unit that changes an image forming condition when the developing device develops a developer image based on the image information based on a detection result of the density detecting unit;
The developing device includes:
After developing the developer image for density detection at a predetermined first drive speed, the developer image for density detection is developed at a second drive speed different from the first drive speed,
The density detector is developed at the first developer density and the second drive speed of the developer image for density detection developed at the first driving speed and carried on the image carrier and carried on the image carrier. A second developer concentration of the density-development developer image is detected,
The image forming condition changing unit changes the image forming condition based on the first developer concentration and the second developer concentration detected by the density detecting unit;
An image forming apparatus. The developing device changes the length in the driving direction of the image carrier of the density detection developer image according to the driving speed of either the first driving speed or the second driving speed,
The density detection unit is configured to adjust the density detection image according to the drive speed of the first drive speed or the second drive speed according to the length of the density detection image changed by the developing device. Detecting the first developer concentration and the second developer concentration;
The image forming apparatus according to claim 1. The developing device detects the density detected after the density detection developer image is carried on the image carrier at the first drive speed and developed at the first drive speed carried on the image carrier. Switching the driving speed to the second driving speed before the developer image reaches a position that can be detected by the density detection unit;
The image forming apparatus according to claim 2. The length at the driving speed of the developer image for density detection carried on the image carrier by the first driving speed is the distance from the developing device to the density detector in the circumferential direction of the image carrier. Shorter than,
The image forming apparatus according to claim 3. The developing device includes:
A developer carrier that adsorbs the developer using the applied developing bias;
A developer supply body that adsorbs the developer using an applied supply bias and supplies the adsorbed developer to the developer carrier;
A developer for charging the developer using the applied charging bias; and a layer forming member for forming a developer layer on the surface of the developer supply body by thinning the developer adsorbed on the developer supply body. ,
The image forming condition changing unit includes a developer supplying body having a developing bias applied to the developer carrying body based on the first developer concentration and the second developer concentration detected by the density detecting unit. Changing the value of the supply bias applied to and / or the charging bias applied to the layer forming member,
The image forming apparatus according to claim 1. A developing device that develops a developer image based on a predetermined density detection developer image and input image information is driven at a predetermined first drive speed to provide an image carrier that carries the density detection developer image. A first image carrying step for carrying the developer image for density detection;
A second image carrying step of driving the developing device at a second driving speed different from the first driving speed to carry the density detection developer image on the image carrier;
A detection step of detecting developer concentrations of the two types of developer images for density detection carried on the image carrier in the first image carrying step and the second image carrying step;
An image forming condition changing step of changing an image forming condition when the developing device develops a developer image based on the image information based on a detection result in the detecting step;
A density correction method for a developer image, comprising: An image forming apparatus control program executable on an image forming apparatus for forming a developer image,
In the image forming apparatus,
First development control means for developing a first density detecting developer image in a developing device that develops the developer image at a predetermined first driving speed;
First image carrying control means for carrying the first density detection developer image developed at the first driving speed on an image carrier carrying a developer image;
A second development control means for causing the developing device to develop a second density detection developer image at a second driving speed different from the first driving speed;
Second image carrying control means for carrying the second density detecting developer image developed at the second driving speed on the image carrier;
The developer density of the developer image for the first density detection carried on the image carrier and the developer density of the developer image for the second density detection are set in a density detection unit that detects the development density of the developer image. A density detection control unit to detect, and an image formation condition changing unit that changes an image formation condition based on a developer density of the first density detection developer image and a developer density of the second density detection developer image. Functioning as an image formation condition change control means for changing the image formation conditions;
A program for controlling an image forming apparatus.