JP2011197104A - Image forming apparatus, image forming method and image formation control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a toner consumption while maintaining irreducible image quality corresponding to characteristics of an image forming apparatus.SOLUTION: The image forming apparatus 1 includes a density detecting unit 23 which detects a toner density of a toner image formed by a photoreceptor, a density correcting unit 103 which performs density correction processing in which control parameters of a developing unit 121 are adjusted based upon a density of a toner image for density correction detected by the density detecting unit 23 so that the density of the toner image formed by the developing unit 121 reaches a target density, a suppression density setting unit 102 which sets a suppression density lower than a standard density in normal operation as the target density, a development characteristic decision unit 105 which decides output characteristics of the developing unit 121 based upon the control parameters adjusted through density correction processing when the suppression density is set as the target density, and an exposure amount adjusting unit 106 which adjusts an exposure amount for formation of a latent image by an exposing unit 123 based upon the determined output characteristics of the developing unit 121.

Description

  The present invention relates to a technique for suppressing toner consumption while maintaining image quality in an image forming apparatus.

  Conventionally, the density of the toner image formed on the photoconductor is adjusted by reducing the density value of the image data or adjusting the light intensity when forming the latent image data image on the photoconductor. An image forming apparatus that suppresses toner consumption is known.

  For example, in Patent Document 1 below, an LUT (LookUp Table) provided for suppressing the color density of an input drawing figure to be a density value determined for each drawing figure such as a character, a line drawing, or a photograph. A technique is described in which the converted drawing figure is printed after conversion to an output density that can save toner consumption by reference.

JP 2001-219626 A

  However, the image formed with the toner consumption suppressed is inevitably deteriorated in image quality as compared with the image formed at the normal time without suppressing the toner consumption. Depending on the characteristics unique to the image forming apparatus, the image quality may be further deteriorated.

  For example, in the technique described in Patent Document 1 described above, in order to avoid deterioration in image quality due to characteristics unique to the image forming apparatus, it takes time to maintain the LUT for each apparatus corresponding to the characteristics unique to the image forming apparatus. It is considered a thing. As described above, it has been difficult to suppress the toner consumption while maintaining the image quality by avoiding the deterioration of the image quality due to the characteristics unique to the image forming apparatus.

  Accordingly, the present invention has been made in view of such circumstances, and provides an image forming apparatus capable of suppressing toner consumption while maintaining the minimum image quality corresponding to the characteristics unique to the apparatus. For the purpose.

The invention described in claim 1
A photoreceptor on which a latent image is formed;
A charging unit for charging the surface of the photoreceptor;
An exposure unit that exposes the surface of the photoreceptor charged by the charging unit to form a latent image;
A developing unit for supplying toner to the latent image on the surface of the photoreceptor to form a toner image;
A density detector for detecting the toner density of a toner image formed by the photoreceptor;
Based on the density of the toner image for density correction detected by the density detection unit, the control parameter of the development unit is set so that the density of the toner image formed by the development unit becomes a preset target density. A density correction unit for performing density correction processing to be adjusted;
A suppression density setting unit that sets a suppression density that is lower than a standard density during normal operation of the developing unit as the target density used in the density correction unit;
When the suppression density is set as the target density by the suppression density setting unit, the output of the developing unit based on the control parameter of the developing unit adjusted by the density correction processing by the density correction unit A development characteristic judging section for judging the characteristics;
An exposure amount adjustment unit that adjusts an exposure amount when the latent image is formed by the exposure unit based on the output characteristics determined by the development property determination unit;
Is an image forming apparatus.

According to a fourth aspect of the present invention, there is provided a photosensitive member on which a latent image is formed, a charging unit that charges the surface of the photosensitive member, and the surface of the photosensitive member that is charged by the charging unit. An image forming method in an image forming apparatus, comprising: an exposure unit that forms a latent image; and a developing unit that supplies toner to the latent image on the surface of the photoreceptor to form a toner image.
A density detecting step for detecting a toner density of a toner image formed by the photoreceptor;
Based on the density of the density correction toner image detected by the density detection step, the control parameter of the developing unit is set so that the density of the toner image formed by the developing unit becomes a preset target density. A density correction step for performing density correction processing to be adjusted;
A suppression density setting step for setting a suppression density that is lower than the standard density during normal operation of the developing unit as a target density used in the density correction step;
When the suppression density is set as the target density by the suppression density setting step, based on the control parameter of the development unit adjusted by the density correction processing by the density correction step, the output of the development unit A development characteristic judging step for judging the characteristics;
An exposure amount adjustment step of adjusting an exposure amount when the latent image is formed by the exposure unit based on the output characteristics determined in the development property determination step;
Is an image forming method.

According to a fifth aspect of the present invention, there is provided a photosensitive member on which a latent image is formed, a charging unit that charges the surface of the photosensitive member, and the surface of the photosensitive member that is charged by the charging unit. A computer built in an image forming apparatus comprising: an exposure unit that forms a latent image; and a developing unit that supplies toner to the latent image on the surface of the photoreceptor to form a toner image;
A density detector for detecting the toner density of a toner image formed by the photoreceptor;
Based on the density of the toner image for density correction detected by the density detection unit, the control parameter of the development unit is set so that the density of the toner image formed by the development unit becomes a preset target density. A density correction unit for performing density correction processing to be adjusted;
A suppression density setting unit that sets a suppression density that is lower than a standard density during normal operation of the developing unit as a target density used by the density correction unit;
When the suppression density is set as the target density by the suppression density setting unit, the output of the developing unit based on the control parameter of the developing unit adjusted by the density correction processing by the density correction unit A development characteristic judging section for judging the characteristics;
An image formation control program that functions as an exposure amount adjustment unit that adjusts an exposure amount when the exposure unit forms the latent image based on output characteristics determined by the development property determination unit.

  In these inventions, a suppression density that is lower than the standard density during normal operation of the developing unit is set as a target density by the suppression density setting unit, and control parameters of the developing unit are adjusted by density correction processing by the density correction unit. Then, the development characteristic determination unit determines the output characteristic of the development unit accompanying the change in the state of the development unit such as aged deterioration based on the control parameter of the development unit adjusted by the density correction processing by the density correction unit, and exposure The amount adjustment unit adjusts the exposure amount when the latent image is formed by the exposure unit based on the output characteristics.

  Therefore, even when the developing unit exhibits output characteristics that make it difficult to form a toner image with the above-mentioned suppression density, the toner density is compensated for by adjusting the exposure amount. Deterioration can be avoided.

  Further, after the exposure amount is adjusted by the exposure amount adjustment unit, when density correction processing is performed by the density correction unit, development is performed based on the toner image whose toner density is adjusted by the exposure amount according to the output characteristics of the development unit. The control parameter of the unit is changed to an appropriate control parameter.

  For this reason, for example, since the output characteristics of the developing unit have deteriorated, when performing density correction processing after adjusting the exposure amount to be high by the exposure amount adjustment unit, in order to maintain the toner density of the toner image at the suppression density, The control parameter of the developing unit is adjusted so as to lower the toner density compared to the previous density correction process, and the burden on the developing unit can be reduced.

  On the other hand, since the output characteristics of the developing unit were not deteriorated, when the density correction processing is performed after the exposure amount is adjusted to be low by the exposure amount adjustment unit, the toner density of the toner image should be set to the suppression density. The control parameters of the developing unit are adjusted so as to increase the toner density as compared with the previous density correction process, and the burden on the developing unit can be increased. That is, in these inventions, the toner density can be adjusted by the developing unit and the exposure unit, and the output characteristics of the developing unit can be adjusted.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the development characteristic determining unit is configured such that the control parameter adjusted by the density correction processing by the density correction unit is the development parameter. When the upper limit value or the lower limit value allowable in the part is close, it is determined that the developing unit has an output characteristic capable of adjusting the exposure amount by the exposure amount adjustment unit,
The exposure amount adjusting unit forms the latent image by the exposing unit when the developing property determining unit determines that the developing unit has an output characteristic capable of adjusting an exposure amount by the exposure amount adjusting unit. Adjust the exposure amount.

  In this invention, when the control parameter adjusted by the density correction processing by the density correction unit is close to the upper limit value or the lower limit value allowable in the development unit, the output characteristics of the development unit are degraded or not degraded, respectively. Therefore, as described above, the toner density of the toner image formed on the surface of the photoreceptor can be adjusted to be increased or decreased by adjusting the exposure amount based on the output characteristics. Therefore, it is possible to avoid the deterioration of the image quality or to further suppress the toner consumption.

  The invention according to claim 3 is the image forming apparatus according to claim 1 or 2, wherein the suppression density is preset for each drawing figure of the image to be formed.

  According to the present invention, since a toner image can be formed with an appropriate suppression density for each drawing figure of the image, the image quality can be maintained flexibly and appropriately according to the drawing figure.

  According to the present invention, it is possible to provide an image forming apparatus capable of suppressing the toner consumption while maintaining the minimum image quality corresponding to the characteristic unique to the apparatus.

1 is a cross-sectional view illustrating an overall configuration of a printer according to an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating an intermediate transfer belt on which a density correction toner pattern is formed and a density toner density detection sensor. FIG. 2 is a block diagram illustrating an example of a schematic configuration of a printer. It is a figure which shows the density correction process by a density correction part. FIG. 10 is a diagram illustrating that the development characteristic determination unit determines the output characteristic of the development unit based on the control parameter adjusted by the density correction processing, and (a) determines that the output characteristic of the development unit is deteriorated. (B) is a diagram illustrating a case where it is determined that the output characteristics of the developing unit have not deteriorated. 3 is a flowchart showing a flow of image forming processing by the printer 1.

  An outline of the internal structure of a printer 1 as an example of an image forming apparatus according to the present invention will be described with reference to FIG. In FIG. 1, the left-right direction of the paper surface is referred to as the left-right direction, the front-back direction of the paper surface is referred to as the front-rear direction, and in particular, the −X direction in FIG. The direction is called backward.

  As shown in FIG. 1, the printer 1 has a device body 11 having a box shape. Inside the apparatus main body 11, an image forming unit 12 that forms an image based on image data transmitted from an external device such as a computer connected to a network, and the like is formed by the image forming unit 12. Are provided with a fixing unit 13 that performs a fixing process on the image transferred to the sheet, and a sheet storage unit 14 that stores recording paper for transfer. Formed on the upper portion of the apparatus main body 11 is a paper discharge portion 15 for discharging the recording paper P after the fixing process.

  On the left side of the upper part of the apparatus main body 11, an unillustrated operation panel for inputting an output condition of the recording paper P and the like is provided. The operation panel includes a power key, a start button, and a toner consumption required for a normal image forming mode in which a normal image forming operation is performed and an image forming operation based on the same image data as in the normal image forming mode. Various keys for inputting output conditions, such as alternatively setting a toner suppression mode for suppressing the amount, are provided. In addition, a display unit (not shown) is provided on the operation panel, and the display unit displays the operation status and state of the printer 1.

  The image forming unit 12 forms a toner image on the recording paper P fed from the paper storage unit 14. In the present embodiment, the image forming unit 12 uses a magenta unit 12M that uses magenta toner, which is sequentially arranged from the upstream side to the downstream side (from right to left), and cyan toner. It includes a cyan unit 12C, a yellow unit 12Y that uses yellow toner, and a black unit 12K that uses black toner.

  Each unit 12M, 12C, 12Y, and 12K is provided with a photosensitive drum 120 and a developing unit 121 as the photosensitive member in the present invention. The photosensitive drum 120 forms an electrostatic latent image and a toner image along the electrostatic latent image on the peripheral surface, and an amorphous silicon layer is laminated on the peripheral surface. The photosensitive drum 120 of each unit receives supply of toner from the developing unit 121 while rotating counterclockwise in FIG.

  A charging unit 122 is provided immediately below each photoconductor drum 120, and an exposure unit 123 is provided further below each charging unit 122.

  Each photosensitive drum 120 is charged uniformly by the charging unit 122, and corresponds to each color based on image data input from the computer or the like on the charged peripheral surface of the photosensitive drum 120. Laser light is emitted from each exposure unit 123. As a result, the electric charge in the portion irradiated with the laser beam is erased according to the intensity (exposure amount) of the laser beam, and an electrostatic latent image is formed on the peripheral surface of each photosensitive drum 120.

  The developing unit 121 supplies toner to a developing roller (not shown) from a toner container (not shown) in which toner is stored, and applies a predetermined developing bias voltage to the developing roller. At this time, since a potential difference is generated between the photosensitive drum 120 and the developing roller, the toner adhering to the developing roller moves toward the surface of the photosensitive drum 120. In this manner, toner is supplied from the developing unit 121 to the electrostatic latent image formed on the peripheral surface of the photosensitive drum 120, and a toner image is formed on the peripheral surface of the photosensitive drum 120.

  An intermediate transfer belt 124 stretched between a driving roller 124a and a driven roller 124b is provided above the photosensitive drum 120. The intermediate transfer belt 124 is provided in contact with each photosensitive drum 120.

  The intermediate transfer belt 124 is pressed against the peripheral surface of the photosensitive drum 120 by a primary transfer roller 125 serving as a transfer unit according to the present invention provided corresponding to each photosensitive drum 120. Circulates between the driving roller 124a and the driven roller 124b (endless rotation) in synchronization with the rotation.

  When the intermediate transfer belt 124 circulates, the primary transfer roller 125 transfers the magenta toner image onto the peripheral surface of the intermediate transfer belt 124 by the photosensitive drum 120 of the magenta unit 12M. The cyan toner toner image is transferred onto the transfer belt 124 at the same position by the photoconductor drum 120 of the cyan unit 12C, and then at the same position of the intermediate transfer belt 124 by the photoconductor drum 120 of the yellow unit 12Y. The transfer of the yellow toner image is performed in an overlapping manner, and finally the transfer of the black toner image by the photosensitive drum 120 of the black unit 12K is performed. As a result, a color toner image is formed on the peripheral surface of the intermediate transfer belt 124.

  The color toner image formed on the peripheral surface of the intermediate transfer belt 124 is transferred to the recording paper P conveyed from the paper storage unit 14.

  Each unit of the image forming unit 12 forms a toner pattern as a toner image for density correction in the present invention described later on the intermediate transfer belt 124 under the control of the pattern formation control unit 104 described later.

  A secondary transfer roller 113 is provided at a position facing the driving roller 124 a of the intermediate transfer belt 124 while being in contact with the peripheral surface of the intermediate transfer belt 124. A sheet conveyance path 111 extending in the vertical direction is formed at a nip portion between the driving roller 124 a and the secondary transfer roller 113 with the intermediate transfer belt 124 interposed therebetween.

  The sheet conveying path 111 is provided with a pair of conveying rollers 112 at an appropriate position, and the recording sheet from the sheet storage unit 14 is driven by the conveying roller pair 112 to nip the intermediate transfer belt 124 and the secondary transfer roller 113. It is conveyed toward.

  At the nip portion between the intermediate transfer belt 124 and the secondary transfer roller 113 in the paper conveyance path 111, the recording paper P conveyed through the paper conveyance path 111 is pressed and clamped by the intermediate transfer belt 124 and the secondary transfer roller 113; The toner image on the intermediate transfer belt 124 is transferred to the recording paper P by the transfer bias of the secondary transfer roller 113.

  The fixing unit 13 performs a fixing process on the recording paper P with the toner image transferred to the recording paper P at the nip portion between the intermediate transfer belt 124 and the secondary transfer roller 113.

  The fixing unit 13 includes a heat roller 134 having an energization heating element (fixing heater) as a heating source therein, a fixing roller 130 disposed opposite to the heat roller 134, and between the fixing roller 140 and the heat roller 134. The fixing belt 133 is stretched, and the pressure roller 132 is disposed so as to face the heat roller 134 with the fixing belt 133 interposed therebetween.

  The recording paper P supplied to the fixing unit 13 with the toner image transferred is subjected to a fixing process by obtaining heat from the heat roller 134 while passing between the pressure roller 132 and the high-temperature fixing belt 133. Is done. The recording paper P for which the fixing process has been completed passes through a paper discharge conveyance path 114 extending from the upper part of the fixing unit 13 and is discharged toward a paper discharge tray 151 of a paper discharge unit 15 provided at the top of the apparatus main body 11. Is done.

  The paper storage unit 14 includes a manual feed tray 141 that can be freely opened and closed on the right side wall of the apparatus main body 11, and a paper tray 142 that is removably mounted at a position below the exposure unit 123 in the apparatus main body 11. I have. A sheet bundle is stored in the sheet tray 142.

  The paper tray 142 includes a box body whose upper surface is open on the entire surface, and can store a paper bundle P1 in which a plurality of recording papers P are stacked. The uppermost recording sheet P of the sheet bundle P1 stored in the sheet tray 142 is fed out from the sheet bundle P1 toward the sheet conveyance path 111 by driving the pickup roller 143 from the sheet bundle P1, and is fed out one by one. The paper P is fed through the paper conveyance path 111 to the nip portion between the secondary transfer roller 113 and the intermediate transfer belt 124 in the image forming unit 12 by driving the conveyance roller pair 112.

  The intermediate transfer belt 124 faces the circumferential surface of the intermediate transfer belt 124 at a position downstream of the nip portion between the secondary transfer roller 113 and the intermediate transfer belt 124 (left side) in the running direction of the intermediate transfer belt 124. A toner concentration detection sensor 23 is provided at the position.

  The toner density detection sensor 23 is a sensor that detects the toner density on the circumferential surface of the intermediate transfer belt 124. The toner concentration detection sensor 23 outputs light with a predetermined amount of light toward the toner image formed on the peripheral surface of the intermediate transfer belt 124, and an electric signal (voltage value) proportional to the amount of reflected light is output from the toner concentration detection sensor. 23 is output to a later-described toner concentration detection unit 101 serving as a drive control unit.

  The toner density detection sensors 23 are provided at two different locations in the length direction (rotational axis direction) of the drive roller 124a of the intermediate transfer belt 124 (however, the number of toner density detection sensors 23 is limited to two. Not the purpose.)

  For example, as shown in FIG. 2, each toner density is spaced from the peripheral surface of the intermediate transfer belt 124 by a predetermined distance so as to face both ends of the intermediate transfer belt 124 in the width direction (length direction of the driving roller 124a). A detection sensor 23 is provided.

  The toner density detection unit 101 calculates the density of toner attached to the peripheral surface of the intermediate transfer belt 124 based on the output voltage value of the toner density detection sensor 23. In other words, the toner density detection sensor 23 and the toner density detection unit 101 described above constitute a density detection unit in the present invention.

  A cleaning roller (cleaning unit) 35 for removing toner on the intermediate transfer belt 124 is provided at a position facing the driven roller 124b with the intermediate transfer belt 124 interposed therebetween.

  FIG. 3 is a block diagram illustrating an example of a schematic configuration of the printer 1. The printer 1 includes a control unit 100 that controls the entire printer 1.

  The control unit 100 includes a ROM 112 that stores an operation program for the entire apparatus, such as an image formation control program according to an embodiment of the present invention, and a RAM 113 that temporarily stores image data and the like and functions as a work area. It is connected. Further, the control unit 100 includes a CPU (not shown), and the operation of the image forming control program and the like stored in the ROM 112 is executed by the CPU, whereby the entire apparatus is controlled.

  Further, the image forming units 12M, 12C, 12Y, and 12K for the respective colors are connected to the control unit 100. The control unit 100 transfers the toner image on the photosensitive drum 120 to the recording sheet, the charging unit 122, the exposure unit 123, and the developing unit 121 provided in the image forming units 12M, 12C, 12Y, and 12K, respectively. In addition, a transfer bias unit 182 that applies a transfer bias to the primary transfer roller 125 and a drum motor 115 that is a driving source of the photosensitive drum 120 are controlled.

  In FIG. 3, each image forming unit for magenta, cyan, yellow, and black is shown as one image forming unit. However, in actuality, each image forming unit is connected to the control unit 100 for each color. It is controlled.

  Further, a toner density detection sensor 23 is connected to the control unit 100, and the toner density detection sensor 23 sends a detection signal (voltage value) indicating the density of the toner pattern to be detected to the control unit 100.

  The fixing motor 130 rotationally drives the heat roller 134 and the pressure roller 132 (FIG. 1), and is controlled by the control unit 100 via a driver 130a. The fixing heater 131 is provided in the heat roller 134 (FIG. 1), and ON / OFF is controlled by the control unit 100.

  The transfer belt drive motor 190 is a drive source of a drive roller that travels the intermediate transfer belt 124, and is controlled by the control unit 100 via a driver 125a.

  The operation unit 127 includes an operation panel for inputting various operation instructions from the user and the display unit. The control unit 100 is connected to a PC (personal computer) 130 via an interface 129. The printer 1 forms an image based on the image data input from the PC 130.

  The registration motor 183 rotates a registration roller (not shown), and is controlled by the control unit 100 via the driver 183a.

  The secondary transfer motor 129 rotates the secondary transfer roller 113 (FIG. 1), and is controlled by the control unit 100 via the driver 129a.

  Further, a secondary transfer bias unit 138 that applies a transfer bias to the secondary transfer roller 113 is connected to the control unit 100.

  The control unit 100 also functions as a toner density detection unit 101, a suppression density setting unit 102, a pattern formation control unit 104, a density correction unit 103, a development characteristic determination unit 105, and an exposure adjustment unit 106. .

  The toner density detection unit 101 controls the driving of the toner density detection sensor 23 and is transferred to the intermediate transfer belt 124 by the image forming units 12M, 12C, 12Y, and 12K under the control of the pattern formation control unit 104 described later. The toner pattern density is calculated based on a detection signal (voltage value) output from the toner density detection sensor 23.

  For example, when the suppression density setting unit 102 receives an instruction to input the toner suppression mode from the above-described operation panel, a suppression density that is lower than the standard density during the normal operation of the developing unit 121 is set to a density correction unit 103 described later. Set as the target density used in.

  Here, the standard density during normal operation of the developing unit 121 is an image density that is optimal in terms of image quality when an image forming operation is performed with new toner in the printer 1 that has never been used when the printer 1 is shipped from the factory. These are determined for each model of the printer 1 and stored in the ROM 112 in advance.

  In addition, when the printer 1 is shipped from the factory, the suppression density, which is lower than the standard density, can maintain a minimum image quality when an image forming operation is performed with new toner in the printer 1 that has never been used. The image density lower than the standard density is determined for each model of the printer 1 and stored in the ROM 112 in advance.

  Upon receiving an input instruction from the operation panel, the suppression density setting unit 102 reads the suppression density stored in the ROM 112 and stores the suppression density in the RAM 113 as a target density used by the density correction unit 103 described later. When the printer 1 is started up after the power is turned on, the standard density stored in the ROM 112 is stored in the RAM 113 as the target density by the control unit 100.

  That is, when the toner image forming operation is performed at the suppression density in the developing unit 121, the toner image density becomes lower than the standard density, so that the toner consumption amount is reduced.

  The pattern formation control unit 104 performs processing and control necessary for forming a toner pattern, which is a toner image for density correction, on the image forming units 12M, 12C, 12Y, and 12K for each color.

  For example, as shown in FIG. 2, the pattern formation control unit 104 develops a developing bias voltage to be applied to the developing roller provided in each unit with respect to the image forming units 12M, 12C, 12Y, and 12K for each color. The toner pattern PM1-4, PC1-4, PY1-4, and PK1-4 on the peripheral surface of the photosensitive drum 120 are changed in several steps (for example, four steps) from the lower limit value to the upper limit value that are acceptable in the unit 121. When the toner image is formed, the toner image is transferred to the intermediate transfer belt 124 by the primary transfer roller 125 and the changed development bias voltage values are stored in the RAM 113.

  Based on the density of the toner pattern detected by the toner density detection sensor 23, the density correction unit 103 develops the developing unit so that the density of the toner image formed by the developing unit 121 becomes a target density set in advance in the RAM 113. Density correction processing for adjusting 121 control parameters is performed.

  The density correction unit 103 controls the toner density of the toner patterns PM1 to 4, PC1 to 4, PY1 to 4, and PK1 to 4 (FIG. 2) formed on the intermediate transfer belt 124 under the control of the pattern formation control unit 104. The toner density detection sensor 23 detects the toner density of the detected toner pattern and the development bias voltage value stored in the RAM 113 when the toner pattern is formed and stored in the RAM 113.

  Next, as shown in FIG. 4, the density correction unit 103 is detected by the toner density detection sensor 23 stored in the RAM 113 in a two-dimensional coordinate system in which the horizontal axis is the development bias voltage and the vertical axis is the toner density. For the points P1 to P4 corresponding to the combinations of the toner density and the development bias voltage of the toner patterns PK1 to PK4, an approximate straight line L that minimizes the sum of the distances from the points P1 to P4 is used, for example, bounce regression It is calculated by a predetermined calculation method such as

  Next, the density correction unit 103 selects the development bias voltage value corresponding to the target density preset in the RAM 113 among the calculated points P1 to P4 on the approximate straight line L (the development bias voltage value at the point P5 in the figure). And the obtained development bias voltage value is set as the development bias voltage value during the image forming operation by the development unit 121.

  Here, if the development bias voltage value set by the density correction unit 103 is lower than the lower limit value or higher than the upper limit value allowable in the development unit 121, the lower limit value or the upper limit value is set to the image by the development unit 121, respectively. It is set as the developing bias voltage value during the forming operation.

  The density correction unit 103 adjusts the developing bias voltage values for the other image forming units 12M, 12C, and 12Y in the same manner as the adjustment of the developing bias voltage value in the image forming unit 12K. That is, the development bias voltage value is an example of a control parameter in the present invention.

  The development characteristic determination unit 105 is based on the development bias voltage value of the development unit 121 adjusted by the density correction processing by the density correction unit 103 when the suppression density is set in the RAM 113 as the target density by the suppression density setting unit 102. Thus, it functions as a device for judging the output characteristics of the developing unit 121.

  The exposure amount adjustment unit 106 adjusts the exposure amount when the exposure unit 123 forms a latent image based on the output characteristics determined by the development characteristic determination unit 105.

  For example, the output characteristic of the developing unit 121 indicates a distribution of the developing bias voltage value in a predetermined past certain period. As shown in FIG. 5A, when the development bias voltage value adjusted by the density correction processing by the density correction unit 103 is close to the upper limit value P4, the development characteristic determination unit 105 uses the printer 1 to control the image with the suppression density. In order to form the image, it is necessary to apply the developing bias voltage value to the developing roller of the developing unit 121 at a value close to the upper limit value. It is judged that it exhibits difficult characteristics.

  When the development characteristic determination unit 105 determines that the output characteristic of the development unit 121 has deteriorated, the exposure amount adjustment unit 106 sets the intensity of the laser beam applied to the peripheral surface of the photosensitive drum 120 from the conventional level. The exposure amount of the exposure unit 123 is adjusted by setting the density value of the image data to be formed high at a predetermined ratio.

  That is, the exposure amount adjustment unit 106 can form an image in which the image quality is not deteriorated as compared with the image formed with the suppression density even if the output characteristics of the developing unit 121 are deteriorated due to aging deterioration or the like. The potential of the latent image formed on the photosensitive drum 120 can be adjusted by adjusting the exposure amount when the latent image is formed by the exposure unit 123 to be high.

  On the other hand, as shown in FIG. 5B, when the development bias voltage value adjusted by the density correction processing by the density correction unit 103 is close to the lower limit value P1, the development characteristic determination unit 105 uses the suppression density in the printer 1. In order to form an image, it is only necessary to apply the developing bias voltage value to the developing roller of the developing unit 121 at a value close to the lower limit value. It is judged that it is very easy to form.

  When the development characteristic determination unit 105 determines that the output characteristic of the development unit 121 has not deteriorated, the exposure amount adjustment unit 106 sets the intensity of the laser light applied to the peripheral surface of the photosensitive drum 120 from the conventional level. The exposure amount of the exposure unit 123 is adjusted by setting the density value component of the image data of the image to be formed to a low value or by setting the density value component low at a predetermined ratio.

  That is, when the output characteristic of the developing unit 121 is not deteriorated, the exposure amount adjusting unit 106 forms a latent image by the exposing unit 123 so that the amount of toner consumed for forming an image with a suppressed density can be reduced. The potential of the latent image formed on the photosensitive drum 120 can be adjusted by adjusting the exposure amount when the exposure is performed.

  Next, the flow of image forming processing by the printer 1 will be described. The image forming units 12C, 12M, and 12Y are assumed to perform the same processing as the image forming unit 12K. Hereinafter, the image forming processing performed for the image forming unit 12K will be described.

  In the following description, the density correction process by the density correction unit 103 is described as being periodically executed after a predetermined time has elapsed or after printing a predetermined number of sheets. However, the execution time of the density correction process is not limited thereto. It may be when the printer 1 is turned on or when an instruction to execute density correction processing is received from the operation panel, or may be appropriately changed as a design matter.

  As shown in FIG. 6, after the printer 1 is turned on, when an input instruction of the suppression density setting unit 102 from the operation panel is received (S1; YES), the suppression density setting unit 102 sets the suppression density preset in the ROM 112. Is set in the RAM 113 as a target density used by the density correction unit 103 (S2, suppression density setting step). If the input instruction of the suppression density setting unit 102 is not accepted after the printer 1 is turned on (S1; NO), the control unit 100 sets the standard density as the target density in the RAM 113.

  Next, when it is time to execute the above density correction processing (S3; YES), the pattern formation control unit 104 causes the image forming unit 12K to form a toner pattern on the intermediate transfer belt 124 (S4).

  Next, the toner density detection unit 101 drives the toner density detection sensor 23 to detect the density of the toner pattern based on a signal (voltage value) obtained from the toner density detection sensor 23 (S5, density detection step). The density correction unit 103 sets the density of the toner image formed by the development unit 121 to a preset target density based on the density of the density correction toner image detected in the density detection step (S5). Thus, the above-described density correction processing for adjusting the control parameter of the developing unit 121 is performed (S6, density correction step).

  When the suppression density is set as the target density in the suppression density setting step (S2), the development characteristic determination unit 105 adjusts the development bias voltage value of the development unit 121 adjusted by the density correction processing in the density correction step (S6). Based on the above, the output characteristic of the developing unit 121 is determined.

  For example, when the development bias voltage value is close to the upper limit value and the lower limit value allowable in the development unit 121 as described above, the development characteristic determination unit 105 determines that the output characteristic of the development unit 121 is the exposure amount by the exposure unit 123. If it is determined that the output characteristic needs to be adjusted (S7, development characteristic determination step; YES), the exposure amount adjustment unit 106 adjusts the exposure amount when the exposure unit 123 forms a latent image (S8). , Exposure amount adjustment step).

  Next, the image forming unit 12K generates a latent image on the photosensitive drum 120 whose peripheral surface is uniformly charged by the charging unit 122 with a predetermined exposure amount by the exposure unit 123 based on image data input from a computer or the like. A toner image is formed on the photosensitive drum 120 by applying a predetermined developing bias voltage value to the developing roller provided in the developing unit 121, and the intermediate transfer belt 124 is used as a transfer unit by a primary transfer roller 125. The toner image is transferred to the intermediate transfer belt 124 by being pressed against the peripheral surface of the photosensitive drum 120, and a toner image is formed on the peripheral surface of the intermediate transfer belt 124 (S9).

  If it is not time to execute the density correction process (S3; NO), or if the suppression density is set as the target density in the suppression density setting step (S2), the density in the density correction step (S6). If it is determined that the output characteristic of the developing unit 121 indicates an output characteristic that does not require adjustment of the exposure amount by the exposure unit 123 based on the development bias voltage value of the developing unit 121 adjusted by the correction process (S7; NO) ), Without performing the density correction process, the image forming unit 12K performs a series of image forming processes shown in step S9.

  That is, according to this configuration, the developing unit 121 compensates for the toner density by adjusting the exposure amount even when the developing unit 121 exhibits output characteristics that make it difficult to form a toner image with the above-described suppression density. It is possible to avoid the deterioration of the image quality due to the aging of 121.

  On the other hand, when the output characteristic of the developing unit 121 is not deteriorated and the output characteristic is easy to form a toner image with the above-described suppression density, the toner density is lowered by adjusting the exposure amount to be low. The toner consumption can be further suppressed by adjusting.

  Further, after the exposure amount is adjusted by the exposure amount adjustment unit 106, when density correction processing is performed by the density correction unit 103, the toner density is adjusted based on the exposure amount according to the output characteristic of the developing unit 121. Thus, the control parameter of the developing unit 121 is changed to an appropriate control parameter.

  For this reason, for example, since the output characteristics of the developing unit 121 have deteriorated, when the density correction processing is performed after the exposure amount is adjusted to be high by the exposure amount adjustment unit 106, the toner density of the toner image is maintained at the suppression density. Therefore, the control parameter of the developing unit is adjusted so as to lower the toner density compared to the previous density correction process, and the burden on the developing unit 121 can be reduced.

  On the contrary, since the output characteristics of the developing unit 121 have not deteriorated, when the density correction processing is performed after the exposure amount is adjusted to be low by the exposure amount adjustment unit 106, the toner density of the toner image is set to the suppression density. Therefore, the control parameter of the developing unit 121 is adjusted so as to increase the toner density as compared with the previous density correction process, and the burden on the developing unit 121 can be increased. That is, the toner density can be adjusted by the developing unit 121 and the exposure unit 123, and the output characteristics of the developing unit 121 can be adjusted.

  In addition to the above-described configuration, for example, a suppression density may be set in the ROM 112 in advance for each drawing figure of an image to be formed, such as a character image or an image image such as a photograph or a line drawing.

  In this configuration, the operation panel is configured so that an instruction can be input for the type of drawing figure, such as whether the image to be formed is a character image or an image image, and when the control unit 100 receives the instruction input, the input drawing This can be realized by reading the suppression density corresponding to the figure from the ROM 112 and setting the read suppression density in the RAM 113 as the target density.

  According to this configuration, for example, even when an image is formed with a suppressed density so as to suppress toner consumption, it is desirable to maintain readability without degrading image quality when forming a character image. The required image quality differs depending on the drawing figure, such as the appearance can be understood even if the image quality is lowered when forming the image, but the suppression density can be preset for each drawing figure, so depending on the drawing figure Image quality can be maintained flexibly and appropriately.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, when the development bias voltage value is close to an upper limit value and a lower limit value allowable in the development unit 121, the development characteristic determination unit 105 requires the exposure unit 123 to adjust the exposure amount when the output characteristic of the development unit 121 is close. However, the present invention is not limited to this, and a predetermined threshold value is provided, and when the developing bias voltage value is adjusted to the upper limit side with respect to the threshold value by the density correction process, the developing unit 121 is deteriorated. On the other hand, when the developing bias voltage value is adjusted to the lower limit side with respect to the threshold value, it may be determined that the developing unit 121 has not deteriorated. In accordance with this, when it is determined that the developing unit 121 is deteriorating, the exposure amount adjusting unit 106 adjusts to increase the exposure amount and determines that the developing unit 121 is not deteriorating. In some cases, the exposure amount may be reduced.

  In the above embodiment, the toner density detection sensor 23 is provided at a position facing the circumferential surface of the intermediate transfer belt 124 and configured to detect the toner density on the circumferential surface of the intermediate transfer belt 124. However, the present invention is not limited to this, and the toner density on the circumferential surface of the photosensitive drum 120 may be detected by being provided at a position facing the circumferential surface of the photosensitive drum 120. In accordance with this, the toner density detection unit 101 is configured to calculate the density of the toner pattern formed on the photosensitive drum 120 based on the detection signal (voltage value) output from the toner density detection sensor 23. can do. That is, the present invention can also be applied to a primary transfer type image forming apparatus configured to directly transfer a toner image formed on a photosensitive drum to a recording sheet without using an intermediate transfer belt.

  In the above embodiment, the printer 1 including the image forming units 12M, 12C, 12Y, and 12K for each color for color image formation is shown as an example of the image forming apparatus according to the present invention. The apparatus is not limited to this, and may be a monochrome printer, a multifunction machine having a scanner function, a facsimile function, a printer function, a copy function, or the like.

  In the above embodiment, the configurations and settings shown in FIGS. 1 to 6 are merely examples, and the present invention is not limited to the embodiment.

1 Printer (image forming device)
12 Image forming units 12M, 12C, 12Y, 12K Image forming unit 120 Photosensitive drum (photosensitive member)
121 Developing unit 122 Charging unit 123 Exposure unit 124 Intermediate transfer belt 125 Primary transfer roller 23 Toner concentration detection sensor (density detection unit)
100 control unit 101 toner density detection unit (density detection unit)
102 Suppression Density Setting Unit 103 Density Correction Unit 104 Pattern Formation Control Unit 105 Development Characteristic Determination Unit 106 Exposure Amount Adjustment Unit S2 Suppression Density Setting Step S5 Density Detection Step S6 Density Correction Step S7 Development Characteristic Determination Step S8 Exposure Amount Adjustment Step

Claims (5)

A photoreceptor on which a latent image is formed;
A charging unit for charging the surface of the photoreceptor;
An exposure unit that exposes the surface of the photoreceptor charged by the charging unit to form a latent image;
A developing unit for supplying toner to the latent image on the surface of the photoreceptor to form a toner image;
A density detector for detecting the toner density of a toner image formed by the photoreceptor;
Based on the density of the toner image for density correction detected by the density detection unit, the control parameter of the development unit is set so that the density of the toner image formed by the development unit becomes a preset target density. A density correction unit for performing density correction processing to be adjusted;
A suppression density setting unit that sets a suppression density that is lower than a standard density during normal operation of the developing unit as the target density used in the density correction unit;
When the suppression density is set as the target density by the suppression density setting unit, the output of the developing unit based on the control parameter of the developing unit adjusted by the density correction processing by the density correction unit A development characteristic judging section for judging the characteristics;
An exposure amount adjustment unit that adjusts an exposure amount when the latent image is formed by the exposure unit based on the output characteristics determined by the development property determination unit;
An image forming apparatus comprising: The development characteristic determination unit is configured to determine whether the development unit is the exposure amount adjustment unit when the control parameter adjusted by the density correction processing by the density correction unit is close to an upper limit value or a lower limit value allowable in the development unit. Judge that the exposure amount by the output characteristics can be adjusted,
The exposure amount adjusting unit forms the latent image by the exposing unit when the developing property determining unit determines that the developing unit has an output characteristic capable of adjusting an exposure amount by the exposure amount adjusting unit. The image forming apparatus according to claim 1, wherein an exposure amount at the time of adjustment is adjusted.   The image forming apparatus according to claim 1, wherein the suppression density is set in advance for each drawing figure of an image to be formed. A photosensitive member on which a latent image is formed; a charging unit that charges the surface of the photosensitive member; an exposure unit that exposes the surface of the photosensitive member charged by the charging unit to form a latent image; An image forming method in an image forming apparatus comprising: a developing unit that supplies toner to a latent image on a surface of a photoreceptor to form a toner image;
A density detecting step for detecting a toner density of a toner image formed by the photoreceptor;
Based on the density of the density correction toner image detected by the density detection step, the control parameter of the developing unit is set so that the density of the toner image formed by the developing unit becomes a preset target density. A density correction step for performing density correction processing to be adjusted;
A suppression density setting step for setting a suppression density that is lower than the standard density during normal operation of the developing unit as a target density used in the density correction step;
When the suppression density is set as the target density by the suppression density setting step, based on the control parameter of the development unit adjusted by the density correction processing by the density correction step, the output of the development unit A development characteristic judging step for judging the characteristics;
An exposure amount adjustment step of adjusting an exposure amount when the latent image is formed by the exposure unit based on the output characteristics determined in the development property determination step;
An image forming method comprising: A photosensitive member on which a latent image is formed; a charging unit that charges the surface of the photosensitive member; an exposure unit that exposes the surface of the photosensitive member charged by the charging unit to form a latent image; A computer built in an image forming apparatus comprising: a developing unit that supplies toner to a latent image on the surface of the photoreceptor to form a toner image;
A density detector for detecting the toner density of a toner image formed by the photoreceptor;
Based on the density of the toner image for density correction detected by the density detection unit, the control parameter of the development unit is set so that the density of the toner image formed by the development unit becomes a preset target density. A density correction unit for performing density correction processing to be adjusted;
A suppression density setting unit that sets a suppression density that is lower than a standard density during normal operation of the developing unit as a target density used by the density correction unit;
When the suppression density is set as the target density by the suppression density setting unit, the output of the developing unit based on the control parameter of the developing unit adjusted by the density correction processing by the density correction unit A development characteristic judging section for judging the characteristics;
An image formation control program that functions as an exposure amount adjustment unit that adjusts an exposure amount when the latent image is formed by the exposure unit based on output characteristics determined by the development property determination unit.

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