JP6028648B2 - Image forming apparatus and program - Google Patents

Description

  The present invention relates to an image forming apparatus and a program.

  In Patent Document 1, an electrostatic latent image for a reference toner pattern for detecting toner density is formed on the surface of a rotatable photosensitive member, and the electrostatic latent image is developed by a rotatable developer carrier. Then, in the image forming apparatus provided with the density adjusting unit that detects the reflected light of the developed reference toner pattern and adjusts the toner density using the output value corresponding to the reflected light, the density adjusting unit includes: The length of the reference toner pattern in the rotational movement direction is L when the circumferential length of the developer carrier is L, the linear velocity of the developer carrier is vs, and the linear velocity of the photoconductor is vp. There is described an image forming apparatus configured to be capable of forming a first reference toner pattern longer than x (vp / vs).

  Patent Document 2 discloses a reference density pattern on the photosensitive member in an image control method of an image forming apparatus that forms a latent image on a photosensitive member, develops the latent image, and transfers the developed image to a transfer material. A pattern detection mode that forms a latent image, develops this reference density pattern latent image under a development potential that is the difference between the latent image potential and the development bias potential, to form a reference density pattern, and detects the density of this reference density pattern In this pattern detection mode, the first reference density pattern is formed under the first development potential, the density of the first reference density pattern is detected, and the first image is detected according to the detection result. Forming the second reference density pattern under a second developing potential different from the first developing potential in a state where the first image forming conditions are controlled; Detecting the concentration of the second reference density pattern, in accordance with the detection result, an image control method for an image forming apparatus and controls the second image forming condition is described.

JP 2011-096551 A Japanese Patent No. 2884526

  An object of the present invention is to provide an image forming apparatus and a program that can adjust toner density with high accuracy.

An image forming apparatus according to claim 1 detects a toner image forming unit that forms a toner image on an image holding member according to set image forming conditions, and a density of the toner image formed by the toner image forming unit. The detecting means, the toner image forming means and the detecting means are controlled to set a predetermined image forming condition to form a first toner image on the image carrier, and the density of the formed first toner image detects a first adjusting means for adjusting the image forming condition on the first image forming condition based on the detection result, and controls the toner image forming means and said detection means, it is adjusted by the first adjusting means setting the first image forming condition detecting effective length than the sum of the detection effective length of the first toner image on the image carrier to form a long second toner image was, the concentration of the second toner image formed Detect and based on detection results And a, a second adjusting means for adjusting said first image forming condition in the second image forming condition.

  According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the first adjusting unit sets a different image forming condition and has a potential higher than a predetermined reference value for the image carrier. A plurality of first toner images including an image and a toner image having a low potential are formed.

  According to a third aspect of the present invention, there is provided the image forming apparatus according to the second aspect, wherein the toner image forming unit includes a charging unit that charges the image holding member, and a surface of the image holding member that is charged by the charging unit. An electrostatic latent image forming unit that forms an electrostatic latent image by irradiating light, and an electrostatic latent image formed on the image carrier by the electrostatic latent image forming unit is developed according to an applied voltage. Developing means, and the first adjusting means for each of the first toner images, the charging amount by the charging means, the amount of light irradiated by the electrostatic latent image forming means, and the voltage applied to the developing means The different image forming conditions are set by controlling at least one of the plurality of first toner images.

  According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the second or third aspect, wherein the first adjusting unit detects the density of each of the set different image forming conditions and the plurality of first toner images. Based on the result, an approximate line indicating the relationship between the set different image forming conditions and the density of the toner image is generated, and an image forming condition that is an ideal value of the density of the toner image is generated from the generated approximate line. Derived as image forming conditions, the different image forming conditions are adjusted to the derived first image forming conditions.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the toner image forming unit and the detecting unit are controlled to set the first image forming condition and A third toner image having a density different from that of the second toner image is formed on the image holding member, the density of the formed third toner image is detected, and the density of the second toner image detected by the second adjustment unit is detected. And a tone correction means for correcting the tone of the image formed by the image forming apparatus based on the detection result of the first toner image and the density detection result of the third toner image.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the adjustment by the first adjustment unit and the first adjustment at a timing when the power of the image forming apparatus is turned on. Control means for controlling the adjustment by the two adjustment means is further provided.

  A program according to a fifth aspect causes a computer to function as the first adjustment unit and the second adjustment unit in the image forming apparatus according to any one of the first to sixth aspects.

  According to the first and seventh aspects of the present invention, the toner density can be adjusted with higher accuracy than when the second toner image of the present invention is not used.

  According to the second aspect of the present invention, an error generated when detecting the toner density is reduced as compared with a case where a toner image having a higher potential than a reference value of the present invention and a toner image having a lower potential are not used. Can do.

  According to the third aspect of the present invention, the image forming conditions can be adjusted more finely than when the parameters to be controlled according to the present invention are not used.

  According to the fourth aspect of the present invention, the image forming conditions can be adjusted with higher accuracy than in the case of not using the plurality of first toner images of the present invention.

  According to the fifth aspect of the present invention, the error in correcting the toner density can be reduced as compared with the case where the third toner image of the present invention is not used.

  According to the sixth aspect of the present invention, it is possible to effectively adjust the toner density as compared with the case where the adjustment timing of the present invention is not the timing when the power is turned on.

1 is a schematic side view illustrating an overall configuration of an image forming apparatus according to an embodiment. It is a schematic front view which shows the detection area by the density | concentration detection part which concerns on embodiment. 1 is a block diagram illustrating an electrical configuration of an image forming apparatus according to an embodiment. In a plurality of types of image forming apparatuses, the amount of rotation of the photoconductor and the density of a toner image formed with the same image forming conditions and the same density at the central portion in the rotation axis direction of the photoconductor (with respect to a predetermined reference density) It is a graph which shows an example of a relationship with (relative value). It is a graph which shows an example of the relationship between the detection effective length of the patch image which concerns on embodiment, and a density | concentration detection value (relative value with respect to a predetermined reference density). It is a flowchart which shows the flow of a process of the 1st density | concentration adjustment process program which concerns on embodiment. It is a schematic front view showing an example of a patch image formed by the processing of the first density adjustment processing program according to the embodiment. It is a schematic front view which shows another example of the patch image formed by the process of the 1st density adjustment process program which concerns on embodiment. 6 is a graph illustrating an example of a relationship between an image forming condition and a density detection value according to the embodiment. 6 is a graph illustrating an example of a relationship between an image forming condition and a density detection value according to the embodiment. It is a flowchart which shows the flow of a process of the 2nd density adjustment process program which concerns on embodiment. It is a schematic front view which shows an example of the patch image formed by the process of the 2nd density adjustment process program which concerns on embodiment. It is a schematic front view which shows another example of the patch image formed by the process of the 1st density adjustment process program which concerns on embodiment. It is a schematic front view which shows an example of the patch image formed in the conventional image forming apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[First Embodiment]
First, the image forming apparatus according to the present embodiment will be described.

  As shown in FIG. 1, an image forming apparatus 100 according to this embodiment includes an electrophotographic photosensitive member (hereinafter referred to as “photosensitive member”) 10 that rotates in the direction of arrow A. The photoreceptor 10 according to the present embodiment includes a base material made of, for example, cylindrical aluminum, and an organic photosensitive layer formed on the outer peripheral surface of the base material.

  A charger 11 that charges the surface of the photoconductor 10 is provided around the photoconductor 10. The charger 11 is disposed in pressure contact with the photosensitive member 10 so as to be rotatable. The charging roller 11 is driven to rotate as the photosensitive member 10 rotates, and a charging bias having a predetermined value (in this embodiment). , Negative polarity).

  A laser exposure device 12 is provided around the photoconductor 10 to form an electrostatic latent image by irradiating the surface of the photoconductor 10 charged by the charger 11 with the exposure beam Bm. The laser exposure device 12 has a laser (for example, a semiconductor laser) that emits an exposure beam Bm to the photosensitive member 10, and responds to image information input from an image processing device 29 (see FIG. 2) described later. Then, the photosensitive member 10 is irradiated with the exposure beam Bm emitted from the laser. The surface of the photoreceptor 10 is scanned and exposed by the laser exposure device 12, whereby an electrostatic latent image is formed on the photoreceptor 10.

  Further, around the photoconductor 10 is provided a developing device 13 that contains toner and develops an electrostatic latent image on the photoconductor 10 with toner to form a toner image. The developing device 13 according to the present embodiment includes a developer holding body 13a that holds a developer containing toner and a carrier. The electrostatic latent image formed on the surface of the photoreceptor 10 is developed as a toner image by the developing device 13. That is, a voltage composed of a DC voltage or a voltage obtained by superimposing a DC voltage on an AC voltage is applied to the developer holding body 13 a from a power source (not shown), and a developing electric field is formed between the developer holding body 13 a and the photoconductor 10. As a result, the toner on the developer holding member 13a is transferred to a portion corresponding to the electrostatic latent image formed on the photoreceptor 10, and the electrostatic latent image is visualized as a toner image.

  In addition, a density detection unit 13 b that detects the density of the toner image formed on the photoconductor 10 (optical density, hereinafter also referred to as “image density”) is provided around the photoconductor 10. The concentration detection unit 13b according to the present embodiment includes a light emitting element (not shown) and a light receiving element that receives light emitted from the light emitting element and reflected by the surface of the photoconductor 10. In the image forming apparatus 100 according to the present embodiment, the light emitting element is composed of a light emitting diode, and the light receiving element is composed of a photodiode. The density detector 13b utilizes the fact that the amount of light emitted from the light emitting element and reflected on the surface of the photoconductor 10 changes according to the amount of toner attached, and is received by the light receiving element. The density of the toner image formed on the photoconductor 10 is detected based on the amount of light.

  2, the density detection unit 13b has a density in a region within a predetermined range (hereinafter referred to as “detection target range”) with respect to the rotation axis direction D on the surface of the photoconductor 10. Are detected in time series and continuously in accordance with the rotation of the photoconductor 10 in the rotation direction E. In the image forming apparatus 100 according to the present embodiment, as illustrated in FIG. 2, the density detection unit 13 b uses a toner image (hereinafter, referred to as a density adjustment process) in which the detection target range is formed on the photoconductor 10. , Referred to as “patch image”).

  A pre-transfer charger 14 that charges the toner image formed on the photoconductor 10 is provided around the photoconductor 10. The pre-transfer charger 14 according to this embodiment is connected to a current source (not shown) that is a power source capable of adjusting the output current value. Note that charging by the pre-transfer charger 14 is performed prior to electrostatic transfer by a transfer unit 15 described later. The toner image charged by the pre-transfer charger 14 moves to the transfer portion 15 that is transferred to the paper P that is a transfer target as the photosensitive member 10 rotates.

  A transfer unit 20 that transfers the toner image formed on the photoconductor 10 to the paper P in the transfer unit 15 is provided around the photoconductor 10. The transfer unit 20 is bridged with tension by a drive roll 22 and a driven roll 23, and is disposed inside the transfer belt 21 made of an elastic body, and inside the transfer belt 21, and is photosensitive via the transfer belt 21. And a transfer roll 24 pressed against the body 10.

  The transfer roll 24 is configured, for example, by covering the outer periphery of a stainless steel conductive core material with a rubber conductive foam elastic body. In the transfer roll 24, resistance adjustment is performed by mixing a substance having ion conductivity (for example, NBR rubber (nitrile rubber)) into the conductive foamed elastic body. Here, as the transfer roll 24, it is preferable that the volume resistivity in the initial state is set in the range of 105 to 109 Ω · cm and the hardness (Asuka C hardness) is in the range of 30 ° to 50 °. preferable. The transfer roll 24 may be adjusted for resistance by mixing a substance having electron conductivity (for example, carbon black) in addition to the substance having ion conductivity.

  A current source 26 that is a power source capable of adjusting an output current value is connected to the transfer roll 24. On the other hand, the base material of the photoreceptor 10 is grounded. The current source 26 supplies constant current control to the transfer roll 24 by supplying a bias (positive polarity) opposite to the toner charging polarity (negative polarity in this embodiment) to the transfer roll 24. (Hereinafter referred to as “transfer current”). Then, when a transfer current is supplied from the current source 26 to the transfer roll 24, a current flows through the transfer roll 24, the transfer belt 21, and the photoconductor 10. As a result, an electric field is formed between the photoconductor 10 and the transfer belt 21, and a charge having a polarity opposite to the charge polarity of the toner on the photoconductor 10 is applied from the transfer roll 24 to the paper P.

  On the other hand, in the transfer unit 15, the sheet P conveyed in time with the movement of the toner image is sandwiched between the photoconductor 10 and the transfer roll 24 via the transfer belt 21 of the transfer unit 20. As a result, the toner image held on the photoconductor 10 is electrostatically transferred onto the paper P in the transfer unit 15 pressed by the photoconductor 10 and the transfer roll 24.

  The sheet P on which the toner image has been electrostatically transferred is peeled off from the photoreceptor 10 by being electrostatically attracted to the transfer belt 21, and is provided by the transfer belt 21 on the downstream side in the transport direction of the sheet P of the transfer unit 20. Further, it is conveyed to the vicinity of a fixing device 60 described later.

  At this time, at the end of the transfer belt 21 on the fixing device 60 side, the sheet P is peeled from the transfer belt 21 due to the curvature when the transfer belt 21 is wound around the driving roll 22 and the stiffness of the sheet P. Then, the paper P is guided to the fixing inlet guide 56 and conveyed to the fixing device 60.

  Further, the transfer unit 20 is provided with a cleaning blade 25 that scrapes off deposits on the surface of the transfer belt 21 after the paper P has passed the position where the drive roll 22 is disposed.

  In some cases, the paper P is not peeled off from the photoconductor 10 and remains adsorbed on the photoconductor 10. In this case, the paper P is separated from the photoconductor 10 by a separation claw (not shown) disposed in the vicinity of the surface of the photoconductor 10 on the downstream side of the transfer portion 15 in the conveyance direction of the paper P, and the transfer belt 21 is fixed to the transfer belt 21. Electroadsorbed.

  Further, the top of the sheet P side is formed in the shape of a saw blade when viewed from the direction of arrow F in FIG. A static elimination unit 27 composed of a body is provided. The static elimination unit 27 is sandwiched between blocks so that the top portion is not exposed, and is provided so as not to contact the paper P.

  The neutralization unit 27 is connected to a neutralization power source (not shown) that applies a voltage to the neutralization unit 27. In this embodiment, the toner image is transferred by adjusting the voltage applied to the charge removal unit 27 from the charge removal power source, and the potential difference between the charged paper P and the charge removal unit 27 is adjusted. The charge removal amount of the paper P (that is, the charge amount of the paper P) is adjusted. The neutralization unit 27 is provided to assist the separation of the paper P from the transfer belt 21.

  Further, the image forming apparatus 100 according to the present embodiment includes a fixing device 60 that fixes the toner image transferred onto the paper P to the paper P. The unfixed toner image on the paper P conveyed to the fixing device 60 is fixed on the paper P by being subjected to fixing processing by heat and pressure in the fixing device 60. The paper P on which the fixed image is formed is conveyed to a discharge unit (not shown) of the image forming apparatus 100.

  On the other hand, a pre-cleaning charger 28 for charging the surface of the photoconductor 10 is provided around the photoconductor 10 in order to remove the positive charge attached to the photoconductor 10 after the transfer of the toner image onto the paper P. ing. Further, on the downstream side of the pre-cleaning charger 28 around the photoconductor 10, a cleaning blade 17 a that removes toner remaining on the photoconductor 10 and a fibrous member 16 that supplies a lubricant 16 a to the surface of the photoconductor 10. A cleaning unit 17 is provided.

  In addition, the image forming apparatus 100 according to the present embodiment has, as a paper transport system, a paper tray 50 that stores the paper P, and a pickup roll that picks up and transports the paper P accumulated in the paper tray 50 at a predetermined timing. 51 is provided. Further, the image forming apparatus 100 includes, as a paper transport system, a transport roll 52 that transports the paper P taken out by the pickup roll 51, and a registration roll 54 that feeds the transported paper P to the transfer unit 15 at a predetermined timing. I have. Further, the image forming apparatus 100 serves as a paper conveyance system, a conveyance guide 55 that guides the paper P sent out from the registration roll 54 to the transfer unit 15, and guides the paper P to which the toner image is transferred and conveyed to the fixing device 60. The fixing entrance guide 56 described above is provided.

  The paper P taken out by the pickup roll 51 is transported in the direction of arrow C by the transport roll 52 and reaches the registration roll 54. The transport roll 52 and the registration roll 54 are temporarily stopped when the paper P reaches the position where the registration roll 54 is disposed, and are rotated again in accordance with the movement timing of the toner image formed on the photoconductor 10. . As a result, the position of the sheet P and the position of the toner image are aligned, and the sheet P is sent out from the transport guide 55 to the transfer unit 15.

  Next, an electrical configuration of the image forming apparatus 100 according to the present embodiment will be described.

  As shown in FIG. 3, the image forming apparatus 100 according to the present embodiment includes a control unit 30 that comprehensively controls the entire apparatus.

  The control unit 30 includes a CPU (Central Processing Unit) that executes various processes including a first density adjustment process and a second density adjustment process described later, and a RAM (Random Access) that temporarily stores various information as a work area of the CPU. Memory). In addition, the control unit 30 includes storage means such as a ROM (Read Only Memory) and a HDD (Hard Disk Drive) that store various information used for execution of processing by the CPU for a long period of time.

  A user interface 31 is electrically connected to the control unit 30. The user interface 31 includes a display unit such as a display for displaying information and an operation input unit such as an operation button for inputting information according to a user operation. The control unit 30 receives input of various types of information including information indicating an execution instruction for image forming processing via the operation input unit. The control unit 30 is connected to each part such as the charger 11, the laser exposure unit 12, the developing unit 13, the density detection unit 13b, and controls the operation of each part.

  Further, the image forming apparatus 100 according to the present embodiment includes an image processing apparatus 29 that performs various types of image processing on an image to be formed on the paper P. In the image forming apparatus 100 according to the present embodiment, the control unit 30 inputs image information output from an image reading device or a personal computer (not shown) to the image processing device 29. Then, an electrostatic image is formed on the photosensitive member 10 by the laser exposure device 12 based on the image information subjected to the image processing by the image processing device 29.

  Incidentally, the image forming apparatus 100 according to the present embodiment performs density adjustment processing for adjusting the image density by adjusting the image forming conditions. In this density adjustment processing, the image forming apparatus 100 according to the present embodiment forms a patch image K indicating an image having a uniform density on the photoconductor 10, and the density detection unit 13b detects the density of the formed patch image K. To do. Furthermore, the image forming apparatus 100 according to the present embodiment compares the detection value (hereinafter referred to as “density detection value”) of the patch image K obtained thereby and a predetermined target value. The image forming apparatus 100 according to the present embodiment adjusts the image density by adjusting the image forming conditions so that the density of the patch image K matches the target value. In the image forming apparatus 100 according to the present embodiment, information indicating the target value is stored in advance in the ROM of the control unit 30.

  However, as described above, the image forming apparatus 100 according to the present embodiment adjusts the image forming conditions so that the density of the patch image K matches the target value in the density adjustment processing. The target value does not always match. That is, when the image forming conditions are adjusted, a difference between the adjusted image density and the target value (hereinafter referred to as “adjustment error”) may occur.

  Here, the adjustment error mainly includes a step of detecting the density of the patch image K (hereinafter referred to as “detection step”) and a step of calculating an adjustment amount when adjusting the image forming conditions (hereinafter referred to as “calculation”). It is called "process"). Hereinafter, the adjustment error generated by these detection process and calculation process will be described.

  First, in the detection step, an adjustment error occurs due to a difference in density detection value depending on a position to be detected. That is, even when toner images are formed on the photoconductor 10 under the same image forming conditions, the image density varies depending on the position of the photoconductor 10. Note that the image processing conditions in the image forming apparatus 100 according to the present embodiment are such that the potential of the toner attached to the photoreceptor 10 (hereinafter referred to as “toner potential”) is a target value. This is a condition for controlling each part. This toner potential is determined depending on the parameters of the voltage applied to the charger 11, the amount of light irradiated by the laser exposure device 12, and the voltage applied to the developing device 13. Hereinafter, the charger 11, the laser exposure device 12, and the developing device 13 are collectively referred to as a control target portion.

  As an example, as shown in FIG. 4, it is assumed that a toner image having the same density is formed in the central portion in the rotation axis direction D of the photoconductor 10 under the same image forming conditions. Even in this case, the image density at each position with respect to the rotation direction E is often different. This is because even when toner is adhered to the photoconductor 10 under the same image forming conditions, the light emitted from the light emitting element of the density detector 13b is reflected on the reflection surface for each position of the surface of the photoconductor 10. This is thought to be due to the different rates. Further, the toner image density unevenness due to the variation in the toner adhesion amount on the photoconductor 10, the sensor sensitivity variation in the detection target area by the density detection unit 13b, and the like are considered to be the factors.

  On the other hand, in the above calculation step, when calculating the adjustment value of each parameter used for adjusting the image forming condition, an adjustment error occurs due to a complicated entanglement of a plurality of factors that cause an error in the final calculation result. In the image forming apparatus 100 according to the present embodiment, the voltage applied to the charger 11, the amount of light irradiated by the laser exposure device 12, and the voltage applied to the developing device 13 are used as the above parameters. Further, as a factor for generating the calculation result, there is an error that occurs due to a disorder in the relationship between the toner adhesion amount and the density detection value. In addition, this is caused by an error generated due to a disorder in the relationship between the toner adhesion amount and the toner potential, and a disorder in the relationship between the toner potential and the potential characteristic of the photoconductor 10. There are also errors. Further, as this factor, there is an error generated due to the disorder of the relationship between the potential characteristics of the photoconductor 10 and the irradiation light quantity of the laser exposure unit 12. Further, as this factor, there is an error that occurs due to the disorder of the relationship between the irradiation light quantity of the laser exposure device 12 and the bias applied to the laser exposure device 12.

  It should be noted that the above-mentioned disturbance in the relationship is caused by errors caused by inherent characteristics of each part such as the photoconductor 10, the charger 11, the laser exposure unit 12, and the developing unit 13, environmental conditions such as temperature and humidity, Due to deterioration and the like.

  In this way, the relationship of each factor causing an error in the calculation result is not a simple linear relationship, but presents a complicated state. Therefore, the adjustment error generated in the calculation process is accurately grasped, It is difficult to adjust the image density so as to cancel the adjustment error. In particular, the larger the difference between the detected density value and the target value, the greater the adjustment error in the calculation process.

  In the calculation step, the relationship between the parameters for adjusting the toner potential also changes depending on the difference between the detected density value and the target value. Therefore, in the conventional image forming apparatus, the image density is adjusted based on a standard relationship prepared in advance as each relationship between the parameters.

  In order to suppress the above adjustment error, the image forming apparatus 100 according to the present embodiment performs rough adjustment, which is rough adjustment of image density, as density adjustment processing, and then performs the rough adjustment according to the result of rough adjustment. Fine adjustment, which is finer than coarse adjustment, is performed.

  At this time, the image forming apparatus 100 uses the length of the patch image K used in the fine adjustment with respect to the rotation direction E (hereinafter referred to as “detection effective length”) that can be detected by the density detection unit 13b in the coarse adjustment. It is longer than the effective detection length of the patch image K.

  That is, the adjustment error that occurs in the detection step becomes smaller as the effective detection length of the patch image K becomes longer. Therefore, in order to reduce the adjustment error that occurs in the detection step, the effective detection length of the patch image K It is desirable to lengthen. The graph shown in FIG. 5 shows an example of the relationship between the effective detection length of the patch image K and the image density. In the graph shown in FIG. 5, the relationship between the effective detection length of the patch image K and the image density is represented by a point for each of a plurality of image forming apparatuses (denoted as apparatuses A to D in the figure). . In the graph shown in FIG. 5, the target value of the image density at each detection effective length of the devices A, B, and D is represented by a curve m, and the target value of the device C is represented by a curve n. As an example, as shown in FIG. 5, it can be seen that the longer the effective detection length, the closer the image density approaches the target value and the smaller the image density variation.

  On the other hand, the longer the effective detection length of the patch image K is, the more toner is consumed when the patch image K is formed on the photoreceptor 10. When the amount of toner consumption increases, it becomes necessary to increase the amount of toner collected at the time of toner cleaning, or the life cycle of a waste toner bottle (not shown) for collecting used toner is shortened. Further, when the toner consumption increases, the wear amount of the photoconductor 10 increases, and the sagging time of each part such as the fixing device 60 may be prolonged.

  Therefore, in the image forming apparatus 100 according to the present embodiment, the detection effective length of the patch image K used in the rough adjustment is a predetermined ratio (about 8% in the present embodiment) with respect to the circumferential length of the photoreceptor 10. The length (hereinafter referred to as “first length”) (in this embodiment, 20 mm). In the image forming apparatus 100 according to the present embodiment, the effective detection length of the patch image K used in the fine adjustment is longer than the effective detection length of the patch image K used in the coarse adjustment (hereinafter, “second length”). ("In this embodiment, 60 mm)".

  Further, in the image forming apparatus 100 according to the present embodiment, in order to reduce the adjustment error generated in the calculation process, the rough adjustment is performed under a plurality of types (two types in the present embodiment) of image forming conditions. The image density is adjusted using the patch image K. At this time, in the image forming apparatus 100 according to the present embodiment, an image forming condition for making the toner potential larger than the toner potential indicated by the image forming condition adopted immediately before the density adjustment processing, and an image forming condition for making the toner potential smaller. The coarse adjustment is performed using the two types of image forming conditions. In this way, by adjusting the image forming strip a plurality of times, even when the difference between the density detection value and the target value is relatively large, compared with the case where the image forming condition is a single type. The image forming conditions are adjusted with high accuracy.

  Note that the coarse adjustment may be performed using a single patch image K under a single type of image forming condition.

  Here, the image forming apparatus 100 according to the present embodiment executes the density adjustment processing at the timing when the power is turned on and the timing at which the execution of the job is started. Note that a job here refers to a single image forming process request or a plurality of related image forming process requests that are input at one time by the user via the operation input unit of the user interface 31 described above. This process is executed according to the requested group. When the control unit 30 receives an input of information indicating the request or the request group via the operation input unit of the control unit 30 described above, or when the information is received from an external device such as the personal computer described above. The job execution is started. Hereinafter, the density adjustment process that is executed when the power is turned on is referred to as a first density adjustment process, and the density adjustment process that is executed when the job is started is referred to as a second density adjustment process.

  Next, the operation of the image forming apparatus 100 when performing the first density adjustment process will be described with reference to FIG. FIG. 6 is a flowchart showing the flow of processing of the first density adjustment processing program executed by the control unit 30 of the image forming apparatus 100 according to the present embodiment. The program is stored in advance in the ROM of the control unit 30. The patch images K2 to K6 formed by the first density adjustment processing program will be described with reference to FIGS. 7A and 7B.

  First, in step S101, the concentration detection unit 13b is controlled to detect the concentration, and information indicating the concentration obtained thereby is stored in the RAM of the control unit 30. Since no toner image is formed on the photoconductor 10 at this stage, in the process of this step S101, as shown in FIG. 7A, the density of the region R where the toner image is not formed on the surface of the photoconductor 10 is increased. Detected and stored.

  In the next step S103, it is determined whether or not the density detection is completed. If a negative determination is made, the process returns to step S101. If an affirmative determination is made, the process proceeds to step S105. At this time, in the image forming apparatus 100 according to the present embodiment, it is determined whether or not the end has been detected in an area corresponding to a predetermined length with respect to the rotation direction E (30 mm in the present embodiment). This is performed by determining whether or not the detection of the concentration of the liquid has ended.

  In step S105, information indicating the image forming condition at this time is acquired from the HDD of the control unit 30. In the image forming apparatus 100 according to the present embodiment, information indicating the image forming conditions includes the above parameters (in this embodiment, the voltage applied to the charger 11, the amount of light irradiated by the laser exposure device 12, and the developing device 13. This is information indicating the value of applied voltage. Note that the information indicating the image forming conditions is stored by the process of step S137 described later. Therefore, when the first density adjustment processing program is executed for the first time, the information indicating the direct image forming conditions is stored. Absent. In this case, in the image forming apparatus 100 according to the present embodiment, information indicating values set as default for the control target part at this time as the parameters is acquired as information indicating the image forming conditions. And

  In the next step S107, the above-described control is performed so that the image forming condition becomes the image forming condition based on the image forming condition (hereinafter referred to as “reference condition”) indicated by the information acquired by the processing in step S105. Control the target area.

  Note that in the image forming apparatus 100 according to the present embodiment, the processes in steps S107 to S113 are performed a plurality of times (in this embodiment, twice) using a plurality of image forming conditions based on the reference conditions. In the first processing of step S107, the image forming conditions are adjusted so that the toner potential becomes a potential obtained by subtracting a predetermined potential change amount α from the toner potential obtained by the reference condition. . In the second process of step S107, the image forming conditions are adjusted so that the toner potential becomes a potential obtained by adding the change amount α to the toner potential obtained by the reference condition.

  As described above, the toner potential is adjusted by adjusting at least one of the parameters of the voltage applied to the charger 11, the amount of light irradiated by the laser exposure device 12, and the voltage applied to the developing device 13. Adjusted. In the image forming apparatus 100 according to this embodiment, the voltage applied to the charger 11 and the voltage applied to the developing device 13 are set to predetermined fixed values, and the toner potential is adjusted by adjusting the amount of irradiation light. Adjust. However, the method of adjusting the image forming condition (toner potential) is not limited to this, and may be a method of adjusting either the voltage applied to the charger 11 or the developing device 13. The image forming condition (toner potential) adjustment method is a method of adjusting a combination of a plurality of voltages applied to the charger 11, an irradiation light amount by the laser exposure device 12, and a voltage applied to the developing device 13. May be.

  In the next step S109, the patch images K2 and K3 are formed on the photoconductor 10 with the density being a predetermined first density (100% in the present embodiment) and the effective detection length being the first length. The laser exposure device 12 and the developing device 13 are controlled so as to start the operation.

  In the next step S111, the concentration detection unit 13b is controlled to detect the concentration, and information indicating the concentration obtained thereby is stored in the RAM of the control unit 30. As a result, the densities of the patch images K2 and K3 formed on the photoconductor 10 in step S109 are detected and stored.

  In the next step S113, whether or not the detection of the density of the patch image is completed by detecting whether or not the length of the patch image formed on the photoconductor 10 by this time has reached the first length. Determine whether or not. If a negative determination is made in step S113, the process returns to step S111. If an affirmative determination is made, the process proceeds to step S115.

  Note that in the image forming apparatus 100 according to the present embodiment, the processes in steps S107 to S113 are performed a plurality of times (in this embodiment, twice) using a plurality of image forming conditions based on the reference conditions. In the first processing of step S107, the image forming conditions are adjusted so that the toner potential becomes a potential obtained by subtracting a predetermined change amount α from the toner potential obtained by the reference condition. In the second process of step S107, the image forming conditions are adjusted so that the toner potential becomes a potential obtained by adding the change amount α to the toner potential obtained by the reference condition. It is confirmed that the displacement amount α is larger than the displacement amount of the toner potential assumed by experience or simulation, for example, and that it is possible to correct the image density with accuracy equal to or higher than a predetermined reference value by experience or simulation. The value is smaller than the displacement.

  As described above, in the image forming apparatus 100 according to the present embodiment, the toner potential used in the coarse adjustment is obtained by adding and subtracting the displacement amount α from the toner potential obtained by the reference condition, but is not limited thereto. . For example, the toner potential used in the coarse adjustment may be obtained by adding the displacement amount β from the toner potential obtained by the reference condition and the potential obtained by subtracting the displacement amount γ.

  As described above, the toner potential is adjusted by adjusting at least one of the parameters of the voltage applied to the charger 11, the amount of light irradiated by the laser exposure device 12, and the voltage applied to the developing device 13. Adjusted. In the image forming apparatus 100 according to the present embodiment, the toner potential is adjusted by adjusting the amount of irradiation light after setting the voltage applied to the charger 11 and the voltage applied to the developing unit 13 to fixed values. However, the method of adjusting the image forming conditions is not limited to this, and may be a method of adjusting either the voltage applied to the charger 11 or the developing device 13. The image forming condition adjustment method may be a method of adjusting a combination of a plurality of the above parameters.

  As described above, in the image forming apparatus 100 according to the present embodiment, two patch images K2 and K3 are formed as patch images for coarse adjustment. However, the number of patch images for coarse adjustment is not limited to this. May be one (see FIG. 7B) or three or more. In the case of using three or more sheets, the image forming conditions are adjusted using a plurality of toner potentials including both a toner potential larger than a toner potential obtained by the reference condition and a toner potential smaller than the toner potential.

  As described above, when the processes of steps S107 to S113 are performed twice, as shown in FIG. 7A, the patch image K2 is formed by the first process of step S109, and the patch image is generated by the second step S109. K3 is formed.

  In step S115, it is determined whether or not the detection of the density of the patch images K2 and K3 for coarse adjustment has been completed. As described above, when the processes in steps S107 to S113 are performed twice, the patch image K2 for coarse adjustment is determined by determining whether or not the detection of the density of the two patch images K2 and K3 is completed. It is determined whether or not the detection of the concentration of K3 is completed. If a negative determination is made in step S115, the process returns to step S107, whereas if an affirmative determination is made, the process proceeds to step S117.

  In step S117, image forming conditions for fine adjustment are derived based on the detected density values of a plurality of patch images (in the present embodiment, patch images K2 and K3) formed on the photoconductor 10 by the rough adjustment. First, the control unit 30 stores the density detection value stored in the process of step S101 (hereinafter referred to as “first density detection value”) and a plurality of density detection values stored in the process of step S111 (hereinafter referred to as “first detection value”). Each of “2 concentration detection values”) is read out. Next, the control unit 30 subtracts the first density detection value from each of the plurality of second density detection values.

  As an example, as shown in FIG. 8, the control unit 30 uses the relationship between the plurality of second density detection values subjected to the subtraction and the toner potential used to obtain the second density detection values. By inserting, an approximate line p indicating the relationship between the toner potential and the detected value of the image density is created. Then, the control unit 30 derives the toner potential (image forming condition) at which the density detection value becomes the target value, using the created approximate line p.

  In the next step S119, the image forming apparatus 100 forms the toner image on the photoconductor 10 so that the image forming conditions for the fine adjustment are derived in the same manner as in step S107. Control the control target part. In other words, the image forming apparatus 100 according to the present embodiment derives the adjustment amount of each parameter for obtaining the derived toner potential, and controls the control target portion using the derived adjustment amount.

  In the next step S121, the laser exposure unit 12 and the developing unit 13 are started so as to start the formation of the patch image K4 having the density of the first density and the effective detection length of the second length on the photoconductor 10. To control. As shown in FIG. 7A, a patch image K4 having a detection effective length longer than that of the patch image K2 is formed on the photoconductor 10.

  In the next step S123, the concentration detection unit 13b is controlled to detect the concentration, and information indicating the concentration obtained thereby is stored in the RAM of the control unit 30. Thereby, the density of the patch image K4 formed on the photoconductor 10 in step S121 is detected and stored.

  In the next step S125, the detection of the density of the patch image K4 is completed by detecting whether or not the length of the patch image formed on the photoconductor 10 by this time has reached the second length. It is determined whether or not. If a negative determination is made in step S125, the process returns to step S123. If an affirmative determination is made, the process proceeds to step S127.

  In step S127, patch images K5 and K6 having a density different from the first density and the detection effective length having a predetermined length (the first length in the present embodiment) are applied to the photoconductor 10. The laser exposure device 12 and the developing device 13 are controlled so as to start the formation. Although the number of patch images formed in step S127 is arbitrary, the image forming apparatus 100 according to the present embodiment forms two patch images K5 and K6. Further, when a plurality of patch images K5 and K6 are formed in this step S127, the density of each of the patch images K5 and K6 is different from the first density and different from each other (this embodiment). Then, 55% and 60%). As shown in FIG. 7A, patch images K5 and K6 are formed on the photoconductor 10.

  The patch images K5 and K6 formed by the process of step S127 are used for tone adjustment when forming the toner image, together with the patch image K4 formed by the process of step S121.

  In the next step S129, the density detector 13b is controlled to detect the density of the surface of the photoconductor 10, and information indicating the density obtained thereby is stored in the RAM of the controller 30. As a result, the densities of the patch images K5 and K6 formed on the photoconductor 10 in step S127 are detected and stored.

  In the next step S131, the density of the patch images K5 and K6 is detected by detecting whether or not the length of the patch image formed on the photoconductor 10 by this time has reached the first length. It is determined whether or not it has been completed. If a negative determination is made in step S131, the process returns to step S129. If an affirmative determination is made, the process proceeds to step S133.

  In step S133, it is determined whether or not the detection of the density of the patch images K5 and K6 for gradation adjustment has been completed. In the image forming apparatus 100 according to the present embodiment, the density detection of the patch images K5 and K6 for gradation adjustment is performed by determining whether or not the density detection of the two patch images K5 and K6 is completed. It is determined whether or not it has been completed. If a negative determination is made in step S133, the process returns to step S127. If an affirmative determination is made, the process proceeds to step S135.

  In step S135, based on the detected density value of the patch image K4, the image forming conditions used when performing the image forming process are derived. At this time, for example, as shown in FIG. 9 as an example, the control unit 30 intersects the approximate line p created in the process of step S117 with the toner density used when obtaining the density detection value of the patch image K4. Is moved in the direction of the axis of the density detection value to the position where the Then, the toner potential (image forming condition) at which the density detection value becomes the target value is derived using the approximated line p that has been translated.

  In the next step S137, information indicating the derived image forming conditions is stored in the HDD of the control unit 30, and the first density adjustment processing program is terminated. The stored information indicating the image forming conditions is used at the next execution of the first density adjustment processing program.

  As described above, in the image forming apparatus 100 according to the present embodiment, by increasing the effective detection length of the patch image K4 used for the fine adjustment, the adjustment error generated in the detection process is reduced, and the image density adjustment is performed. Improve accuracy.

  That is, the adjustment error that occurs in the detection step is less dependent on the difference between the detected value of the image density and the target value than the adjustment error that occurs in the calculation step. For this reason, if the difference is smaller than a predetermined reference value, the image density may be moved away from the target value due to an adjustment error when performing the density adjustment process. However, in the image forming apparatus 100 according to the present embodiment, the effective detection length of the fine adjustment patch image K4 is longer than the effective detection length of the conventional fine adjustment patch image shown in FIG. This prevents the image density from moving away from the target value.

  In the image forming apparatus 100 according to the present embodiment, the density detection values of a plurality of patch images (patch images K2 and K3 in the present embodiment) formed under different image forming conditions in the rough adjustment are used to generate an image. The formation conditions are adjusted. As a result, the adjustment error in the calculation process is reduced, and the accuracy of image density adjustment is improved. When a plurality of patch images K2 and K3 are used in the coarse adjustment, the image forming conditions are adjusted as shown in FIG. 8, but when a single patch image K2 is used, as shown in FIG. The image forming conditions may be adjusted.

  In the image forming apparatus 100 according to the present embodiment, in the rough adjustment, the adjustment amount of each parameter may be corrected according to various conditions such as the use period and the use environment of each control target part described above. Thereby, the adjustment error generated in the calculation step is further reduced, and the accuracy of image density adjustment is improved.

  In the image forming apparatus 100 according to the present embodiment, the first density adjustment processing program is executed at a timing when the power is turned on, but the execution timing of the first density adjustment processing program is not limited to this. That is, when the power source of the image forming apparatus 100 is turned off after the power source is turned off for a relatively long time, the power source of the image forming apparatus 100 is operated for a relatively long time. As a result, the amount of change in the image density with respect to the target value increases. In view of this, the first density is applied only when the power of the image forming apparatus 100 is turned on after being continuously turned off for a predetermined time (for example, 4 hours). The adjustment processing program may be executed.

  Next, the operation of the image forming apparatus 100 when performing the second density adjustment process will be described with reference to FIG. FIG. 10 is a flowchart showing the flow of processing of the second density adjustment processing program executed by the control unit 30 at the timing when the image forming apparatus 100 according to the present embodiment starts execution of a job. The program is stored in advance in the ROM of the control unit 30. Here, a case where an image is formed by the print function will be described.

  First, in step S102, it is determined whether or not the job is completed. If the determination is affirmative, the process proceeds to step S104. If the determination is negative, the process proceeds to step S106 described later.

  In step S104, it is determined whether or not the number of sheets P on which image formation has been performed since the previous image density adjustment is equal to or greater than a predetermined first threshold (80 sheets in the present embodiment). . If the determination in step S104 is affirmative, the process proceeds to step S121 described above. If the determination is negative, the second density adjustment processing program is terminated.

  In step S106, it is determined whether or not image formation on one sheet P is completed by executing the job. Note that, regarding the paper P that is the object when the affirmative determination is made in this step S106, the negative determination is made in this step S106 even if the image formation is completed. If a negative determination is made in step S106, the process returns to step S102, whereas if an affirmative determination is made, the process proceeds to step S108.

  In step S108, it is determined whether or not the number of sheets P on which image formation has been performed since the previous image density adjustment is equal to or greater than a predetermined second threshold value (100 sheets in the present embodiment). . If the determination in step S108 is affirmative, the process proceeds to step S121 described above. If the determination is negative, the process returns to step S102.

  Since the processing of steps S121 to S137 is the same as the processing of steps S121 to S137 in the first density adjustment processing program, detailed description thereof is omitted here. In the present embodiment, the patch image K4, the patch image K5, and the patch image K6 are sequentially formed on the photoconductor 10 as shown in FIG. 11 as an example by the processes in steps S121 to S137.

  In the image forming apparatus 100 according to the present embodiment, the patch images K2 to K6 are formed in a central portion with respect to the rotation axis direction D of the photoconductor 10 so as to form a line along the rotation direction E. However, the arrangement of the patch images K2 to K6 is not limited to this, and the patch images K2 to K6 are formed in two rows along the rotation direction E at both ends with respect to the rotation axis direction D of the photoconductor 10. Also good. Also, as shown in FIG. 12, the patch images K2 to K6 may be formed in three rows along the rotation direction E at the center and both ends with respect to the rotation axis direction D of the photoconductor 10.

10 Photoconductor (image carrier)
11 Charger (toner image forming means, charging means)
12 Laser exposure device (toner image forming means, electrostatic latent image forming means)
13 Developer (toner image forming means, developing means)
13b Concentration detector (detection means)
15 Transfer unit 24 Transfer roll 30 Control unit (first adjustment unit, second adjustment unit, control unit)
100 Image forming apparatus P Paper

Claims (7)

Toner image forming means for forming a toner image on the image holding member according to the set image forming conditions;
Detecting means for detecting the density of the toner image formed by the toner image forming means;
Controlling the toner image forming means and the detecting means to set a predetermined image forming condition to form a first toner image on the image carrier, and to detect the density of the formed first toner image; First adjusting means for adjusting the image forming condition to the first image forming condition based on a detection result;
By controlling the toner image forming unit and the detecting unit, the first image forming condition adjusted by the first adjusting unit is set, and the total effective detection length of the first toner image is set on the image carrier. A second adjusting unit that forms a second toner image having a long detection effective length, detects a density of the formed second toner image, and adjusts the first image forming condition to the second image forming condition based on a detection result; ,
An image forming apparatus. The first adjusting means sets a plurality of first toner images including a toner image having a potential higher than a predetermined reference value and a toner image having a low potential by setting different image forming conditions. The image forming apparatus according to claim 1. The toner image forming unit includes:
Charging means for charging the image carrier;
An electrostatic latent image forming unit that forms an electrostatic latent image by irradiating light onto the surface of the image carrier charged by the charging unit;
Developing means for developing the electrostatic latent image formed on the image carrier by the electrostatic latent image forming means according to an applied voltage;
The first adjusting unit controls at least one of a charging amount by the charging unit, an irradiation light amount by the electrostatic latent image forming unit, and a voltage applied to the developing unit for each of the first toner images. The image forming apparatus according to claim 2, wherein the plurality of first toner images are formed by setting the different image forming conditions. The first adjusting means determines whether the different image forming conditions and the density of the toner image are set based on each of the set different image forming conditions and the detection result of the density of each of the plurality of first toner images. An approximate line indicating a relationship is generated, an image forming condition that is an ideal value of the density of the toner image is derived from the generated approximate line as the first image forming condition, and the different image forming condition is derived from the derived first image. The image forming apparatus according to claim 2, wherein the image forming apparatus is adjusted to a forming condition. The toner image forming unit and the detecting unit are controlled to set the first image forming condition, and form and form a third toner image having a density different from that of the second toner image on the image holding member. The density of three toner images is detected and formed by the image forming apparatus based on the detection result of the density of the second toner image detected by the second adjustment unit and the detection result of the density of the third toner image. The image forming apparatus according to claim 1, further comprising a gradation correction unit that performs gradation correction of an image to be processed. 6. The apparatus according to claim 1, further comprising a control unit that controls the adjustment by the first adjustment unit and the adjustment by the second adjustment unit at a timing when the power of the image forming apparatus is turned on. The image forming apparatus according to claim 1.   A program for causing a computer to function as the first adjustment unit and the second adjustment unit in the image forming apparatus according to any one of claims 1 to 6.