JP2015232655A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of image density control with a single patch by predicting a development start voltage and an image forming part on a photoreceptor drum on the basis of temperature information, the state of deterioration of a developer and a photoreceptor, or the like.SOLUTION: An image forming apparatus forms a single toner patch 110 on an intermediate transfer belt 1 in a predetermined charging condition, developing condition, and exposure condition of a photoreceptor drum 2, detects the density of the toner patch with a toner image detection sensor 30, and adjusts at least one of the charging condition, the developing condition, the exposure condition, and a toner supply condition during the subsequent printing to perform image density control. The image forming apparatus predicts developing performance on the basis of at least one of a developing bias and a detected value of the amount of adhesion of the toner patch during the formation of the toner patch, information on the use of a developing device, information on the use of the photoreceptor, and information on temperature and humidity, and determines an image density control condition on the basis of the predicted developing performance.

Description

  The present invention relates to an electrophotographic image forming apparatus capable of performing image density control.

  In an electrophotographic image forming apparatus, a photosensitive member is uniformly charged and exposed to an image forming unit to form a latent image on the photosensitive member. Then, an image is formed on the photosensitive member by developing the toner on the latent image portion of the photosensitive member. 2. Description of the Related Art Conventionally, a toner density control or a potential control is performed based on the relationship between the toner adhesion amount and the target adhesion amount based on the toner adhesion amount detected using an optical density sensor capable of detecting the toner adhesion amount of an image. ing

  In Patent Document 1, toner replenishment is stopped when the adhesion amount of a toner pattern formed on a photoconductor under a predetermined image forming condition exceeds a predetermined threshold value, and toner replenishment is performed when the adhesion amount falls below a predetermined threshold value. Techniques for performing are described.

  The conventional technology described above calculates a developing ability (development γ) by creating a plurality of toner patches while changing image forming conditions and reading them with an optical density sensor. However, the formation of a plurality of patches has a problem in that a so-called “catch time” occurs and toner yield is poor. Therefore, a technique is known in which only one toner patch is created, development γ is calculated from the one toner patch, and image density control such as potential control and toner density control is performed.

  However, even if the development capability is predicted with one toner patch, the development start voltage and the potential of the image forming portion vary depending on the developer deterioration state and the photoreceptor environment and deterioration state. Cannot be calculated. For this reason, “fogging”, background stains, toner contamination inside the apparatus due to inadequate toner density correction, and image density error due to inadequate potential control occur.

  Further, in the technique described in Patent Document 1, since the developing ability changes depending on the developer, the photoconductor, and the temperature condition, if the toner replenishment amount is uniquely determined, it cannot be adjusted to an appropriate image density.

  The present invention increases the accuracy of image density control with one patch by predicting the development start voltage and the image forming portion on the photosensitive drum based on the deterioration state of the developer and the photosensitive member, temperature information, and the like. With the goal.

  An image forming apparatus according to the present invention includes an image carrier, a charging unit that charges the image carrier, an exposure unit that forms a latent image by exposing the charged image carrier, and a toner and a carrier. And developing means for developing a latent image portion formed on the image carrier with the toner to form a toner image, and recording the toner image on the image carrier with a recording medium. Transfer means for transferring to the toner, a toner storage device for storing the toner, a toner supply device for supplying toner from the toner storage device to the developing device, and a toner concentration detecting means for detecting the toner concentration in the developing device; An optical toner image density sensor for detecting the density of the toner image formed on the image carrier, a temperature / humidity detection means for obtaining temperature / humidity, and a developing device for recording usage information of the developing device. At least one of usage information recording means and photosensitive member state information recording means for recording state information of the photosensitive member, and one toner patch is applied to the photosensitive member under predetermined charging conditions, developing conditions, and exposure conditions. Forming, detecting the density of the toner patch by the optical toner image density sensor, and adjusting at least one of a charging condition, a developing condition, an exposure condition, and a toner replenishment condition at the next image formation. In the image forming apparatus performing density control, development is performed based on the development bias and the density of the toner patch at the time of forming the toner patch, and at least one of the usage information of the developing apparatus, the usage information of the photoconductor, and the temperature and humidity An image forming apparatus comprising: a density control unit that predicts the capability and performs image density based on the predicted development capability. That.

  According to the present invention, an image can be obtained by creating only one toner patch by predicting the development start voltage and the image forming portion on the photosensitive drum based on the deterioration state of the developer and the photosensitive member, temperature information, and the like. The accuracy of density control can be increased.

1 is a schematic diagram illustrating an image forming apparatus to which an embodiment of the present invention is applied. The partial perspective view which shows an example of the installation condition of a toner image detection sensor The block diagram which shows the principal part of the control system of the image forming apparatus Schematic diagram showing density adjustment pattern and optical sensor formed on the intermediate transfer belt Graph showing an example of calculating development γ using a toner patch created with a developer in an initial state Graph showing an example of calculating development γ with a toner patch created by a deteriorated developer Flow chart showing image adjustment operation Table showing the relationship between total development travel time and cumulative average image area ratio Graph showing the relationship between toner density and development γ when the toner density is experimentally changed A graph showing the amount of change in toner density necessary for developing γ when the target adhesion amount is reached The graph which shows the effect by the correction in Embodiment 1 A graph showing the actual development potential when the image area potential changes 10 is a flowchart illustrating an image adjustment operation in the second embodiment. Table showing image part potential shift amount determined by the number of inserted sheets and temperature The graph which shows the effect by the correction in Embodiment 2 10 is a flowchart illustrating an image adjustment operation according to the third embodiment. FIG. 6 is a schematic diagram showing a density adjustment pattern and an optical sensor formed on an intermediate transfer belt in Embodiment 3. Table showing the development start voltage determined by the amount of dirt attached

  In the present invention, one toner patch is detected to control the image density, and the image forming conditions are optimally corrected based on the developer, the photoreceptor, and the temperature and humidity information.

  Hereinafter, an image forming apparatus according to an embodiment for carrying out the present invention will be described. First, an image forming apparatus to which an embodiment of the present invention is applied will be described. FIG. 1 is a schematic view showing an image forming apparatus to which an embodiment of the present invention is applied. The image forming apparatus 100 is a quadruple tandem type intermediate transfer type full color image forming apparatus. An electrophotographic image forming apparatus may be a full-color image forming apparatus such as a 4-drum tandem direct transfer system or a 1-drum intermediate transfer system, or a monochrome image forming apparatus such as a 1-drum direct transfer system. However, the present invention is applied.

  In the image forming apparatus 100, image forming stations 40Y, 40M, 40C, and 40K are disposed along the extended surface of the intermediate transfer belt 1 that is an image carrier and is an intermediate transfer member. In each of the image forming stations 40Y, 40M, 40C, and 40K, photosensitive drums 2Y, 2M, 2C, and 2K that are image carriers are arranged in parallel. Note that Y added to the reference numeral indicates yellow, M indicates magenta, C indicates cyan, and K indicates black. Since the image forming stations 40Y, 40M, 40C, and 40K have the same structure, the yellow image forming station 40Y will be described below. In the image forming station 40Y, a charging charger 3 as a charging unit, a writing unit 4Y, a developing unit 5Y as a developing device, and a primary transfer roller 6Y as a primary transfer unit are arranged around the photosensitive drum 2Y in the order of rotation. A photoreceptor cleaning unit 7Y and a quenching lamp 8Y are arranged. The same applies to imaging stations of other colors. The developing unit 5 stores a two-component developer composed of toner and carrier. The toner of the developer in the developing unit is replenished from a toner storage device (not shown) in which replenishment toner is stored. The toner density in the developing unit is detected by the toner density detecting means, and based on the detection result, the replenishing toner is replenished from the toner replenishing device (not shown) to the developing unit by the toner replenishing device.

  Above the writing unit 4, a scanner unit 9, an ADF (Auto Documents Feeder) 10, and the like are provided. The intermediate transfer belt 1 is rotatably supported by a plurality of rollers 11, 12, and 13, and an intermediate transfer belt cleaning unit 15 as a cleaning unit is provided at a portion facing the rollers 12. A secondary transfer roller 16 as a transfer unit is provided at a portion facing the roller 13. A plurality of paper feed trays 17 are provided at the lower part of the main body of the image forming apparatus 100. The recording paper 20 as a recording medium accommodated in these paper feeding trays 17 is fed by a pickup roller 21 and a paper feeding roller 22, conveyed by a conveying roller pair 23, and is transferred by a registration roller pair 24 at a predetermined timing. It is sent to the next transcription site.

  A fixing unit 25 as a fixing unit is provided downstream of the secondary transfer portion in the sheet conveyance direction. In FIG. 1, reference numeral 26 denotes a paper discharge tray, and 27 denotes a switchback roller pair.

  Next, an image forming operation of the image forming apparatus 100 will be described. When a print start command is input, the rollers around the photosensitive drum, the intermediate transfer belt, and the paper feed path start to rotate at a predetermined timing, and the recording paper feed starts from the lower paper feed tray. Is done. On the other hand, the surface of each photosensitive drum 2 is charged to a uniform potential by the charging charger 3, and the surface is exposed according to the image data by the writing light emitted from the writing unit 4. The potential pattern after exposure is called an electrostatic latent image (latent image portion). The photosensitive drum 2 carrying the electrostatic latent image on the surface thereof is supplied with toner from the developing unit 5, The carried electrostatic latent image is developed to a specific color.

  In this image forming apparatus 100, since the photosensitive drums 2 have four colors, toner images of yellow, magenta, cyan, and black (color order varies depending on the system) are developed on each photosensitive drum. . The toner image developed on each photosensitive drum 2 is intermediated by a primary transfer bias and a pressing force applied to a primary transfer roller 6 disposed opposite to the photosensitive drum at a contact point with the intermediate transfer belt 1. Transferred onto the transfer belt 1. A full color toner image is formed on the intermediate transfer belt 1 by repeating the four colors while matching the timing of the primary transfer operation. The full-color toner image formed on the intermediate transfer belt 1 is transferred to the recording paper 20 conveyed at the timing by the registration roller pair 24 in the secondary transfer roller portion.

At this time, the secondary transfer is performed by the secondary transfer bias applied to the secondary transfer roller 16 and the pressing force. The recording paper 20 to which the full-color toner image has been transferred passes through the fixing unit 25, whereby the toner image carried on the surface is heated and fixed. If it is single-sided printing, it is conveyed straight as it is to the paper discharge tray 26, and if it is double-sided printing, the conveyance direction is changed downward and conveyed to the paper reversing unit. The recording paper 20 that has reached the paper reversing section is reversed in the conveying direction by the switchback roller pair 27 and exits the paper reversing section from the rear end of the paper.
This is called a switchback operation, and the front and back of the recording paper can be reversed by this operation.

  The recording paper that has been turned upside down does not return to the fixing unit, but passes through the refeed conveyance path and joins the original paper feed path. Thereafter, the toner image is transferred in the same manner as the front surface printing, and is discharged through the fixing unit 25. Thereby, the double-sided printing operation is completed.

  The subsequent operation of each unit will be described. The photosensitive drum 2 that has passed through the primary transfer portion carries the primary transfer residual toner on the surface thereof, and this is removed by the photosensitive member cleaning unit 7 constituted by a blade and a brush. Thereafter, the surface is uniformly discharged by the quenching lamp 8 to prepare for charging for the next image. The intermediate transfer belt 1 that has passed through the secondary transfer portion also carries secondary transfer residual toner on its surface, which is also removed by an intermediate transfer belt cleaning unit 15 composed of blades and brushes. Removed and ready for transfer of next toner image. By repeating such an operation, single-sided printing or double-sided printing is performed.

  The image forming apparatus 100 includes a toner image detection sensor 30 as an optical toner image density detection unit configured by an optical sensor as a density detection unit that detects the density of a toner image formed on the outer peripheral surface of the intermediate transfer belt 1. It has. The toner image detection sensor 30 can detect the density of the toner image of the image pattern formed on the surface of the intermediate transfer belt 1 so as to be used for correction control of image unevenness. In this example, a toner image detection sensor 30 is arranged at a position P1 (position before secondary transfer) facing the portion of the intermediate transfer belt 1 that is wound around the roller 11. When the toner image detection sensor 30 is disposed on the downstream side of the secondary transfer portion, a roller 14 for preventing shaking is provided inside the intermediate transfer belt 1, and the toner image is opposed to the roller 14. A detection sensor 30 is provided.

  In the image forming apparatus 100, the control toner pattern image is formed on the photosensitive drum 2 and reaches the transfer position to the downstream belt (the intermediate transfer belt 1 or the transfer conveyance belts 28a and 29a).

  FIG. 2 is a partial perspective view showing an example of the installation state of the toner image detection sensor. The toner image detection sensor 30 is obtained by installing a toner image detection sensor (optical sensor unit) 30 at a position P1 before secondary transfer in the image forming apparatus 100. The toner image detection sensor 30 is a four-head type (four-head toner image detection sensor 30) in which sensor heads (optical sensors) 31a, 31b, 31c, and 31d as three density detection means are mounted on a sensor substrate 32. is there. That is, the toner adhesion amounts at four locations on the toner image detection sensor 30 in which four sensor heads (optical sensors) are installed in the main scanning corresponding direction (axial direction of the photosensitive drum 2) orthogonal to the recording paper conveyance direction are measured simultaneously. it can.

  The number of sensor heads in the toner image detection sensor 30 is not limited to the above four. For example, a configuration including one or two sensor heads or a configuration including four to seven heads including sensor heads dedicated to each color may be used.

  Next, control of the image forming apparatus 100 will be described. FIG. 3 is a block diagram showing the main part of the control system of the image forming apparatus. The control unit 200 as a control unit is configured by, for example, a microcomputer, and includes a CPU (Central Processing Unit) 201 as an arithmetic processing unit, a RAM (Random Access Memory) 202 as a storage unit, and a ROM (Read Only Memory). ) 203 or the like. The control unit 200 is electrically connected to the image forming stations 40Y, 40M, 40C, and 40K, the writing unit 4, the toner image detection sensor 30, and the like.

  And the control part 200 controls these various apparatuses based on the control program memorize | stored in RAM202. The RAM 202, which is a non-volatile memory, stores output conversion data (conversion table), which will be described later, as output conversion information used when calculating the toner density (toner adhesion amount) from the detection value of each optical sensor of the toner image detection sensor 30. The output conversion formula (algorithm) is stored.

<Embodiment 1>
In the image forming apparatus 100 having the above-described configuration, a case where only one image density adjustment pattern (toner patch) (one patch) is formed and the detection sensor is one head will be described. FIG. 4 is a schematic diagram showing a density adjustment pattern and an optical sensor formed on the intermediate transfer belt 1. The toner patch 110 is disposed at the center of the image in the image area width of the intermediate transfer belt 1 and is detected by the toner image detection sensor 120. This is because the central portion is least affected by the density deviation within the image forming width in the main scanning direction. These image density adjustment patterns are created with a predetermined charging bias, developing bias, and LD power.

  However, if the developing ability (hereinafter referred to as “development γ”) is calculated with one patch in this way, the optimum image forming condition cannot be determined with only one patch due to the deterioration state of the developer. This is because uncharged toner increases due to the deterioration of the developer, and therefore the development start voltage Vk decreases.

  One example will be described below. FIG. 5 is a graph showing an example in which development γ is calculated with a toner patch created with a developer in an initial state. In this case, since the development start voltage Vk is substantially zero, the development γ can be calculated from the slope of the straight line connecting the zero point, the development potential of one patch portion, and the adhesion amount.

  FIG. 6 is a graph showing an example of calculating development γ using a toner patch created with a deteriorated developer. In this case, the development start voltage Vk is shifted from zero, and when the development ability is calculated from the slope of the straight line connecting the zero point, the development potential of one patch portion, and the adhesion amount, the development ability is seen to be low. End up. For this reason, when charging, development, exposure conditions, and toner density target values are corrected based on the erroneously observed developing ability, the correction amount is insufficient and the target adhesion amount is set. I can't.

  It is known that the shift of the development start voltage Vk occurs due to developer deterioration. Therefore, in the image forming apparatus according to the first embodiment, the control unit 200 is operated as a density control unit, the shift amount of the development start voltage Vk is predicted based on the deterioration information of the developer, the development capability is corrected, and the optimum image is obtained. Set the formation conditions. Therefore, the image forming apparatus 100 includes a developing device usage information recording device that records usage information of the developing unit 5 and a photoreceptor state information recording device that records state information of the photosensitive drum 2.

  Hereinafter, the image quality adjustment operation of the image forming apparatus 100 according to the first embodiment will be described. FIG. 7 is a flowchart showing the image adjustment operation. The image adjustment operation is performed according to the following procedure.

[S101] Execution Determination of Image Quality Adjustment Operation First, execution determination of the image quality adjustment operation is performed. The execution determination of the image quality adjustment operation is performed based on the number of images. When the predetermined number of images (100 in this embodiment) is reached from the previous image quality adjustment operation, the image quality adjustment operation execution flag is set, and the image quality adjustment operation is performed at the end of printing. Executed. Further, when the number of continuous paper passes reaches a predetermined number (100 in this embodiment), the image density fluctuation during continuous paper passing may be suppressed by inserting an image quality adjustment operation during printing.

[S102] Pattern Creation When the image quality adjustment operation execution flag is set in [S101], the image quality adjustment operation is executed when printing is completed. In the image quality adjustment operation, a toner patch as shown in FIG. 4 is created. At the end of printing, a charging bias as a predetermined charging condition, a developing bias as a developing condition, and an exposure light amount are set, and a pattern is created under the conditions. The pattern is created with a thin analog halftone by intentionally narrowing the development potential (difference between the development bias and the exposure portion potential). In this embodiment, since a monochrome machine is assumed, an analog halftone is used in which the adhesion amount can be detected with the regular reflection light output of the toner image detection sensor 30. However, in a color machine, the amount of adhesion can be detected with an optical toner density sensor even if the amount of adhesion is higher than the diffuse reflected light output, so it is not necessary to be halftone and the amount of solid adhesion may be used.

[S103] Pattern Detection The toner patch created in [S102] is detected by an optical toner density sensor.

[S104] Calculation of Adhesion Amount The toner adhesion amount is calculated from the pattern detection result in [S103]. This is calculated by converting the output value obtained by detecting the toner patch 110 with the toner image detection sensor 120 into a toner adhesion amount (see JP-A-2006-139180).

[S105] Calculation of development start voltage Vk The development start voltage Vk is calculated from the developer usage information. The shift of the development start voltage Vk is caused by the toner being peeled off due to the deterioration of the developer or the toner having the changed charging characteristics due to the increase in the amount of fine powder. Changes in these charging characteristics can be predicted from the total development running time (total driving time) and the cumulative average of image area ratios (cumulative average image area ratio). Therefore, the shift amount of the development start voltage Vk is calculated from the total development running time and the image area ratio cumulative average table (see FIG. 8). The image area ratio cumulative average is calculated based on the total number of pixels and the number of sheets passed in a predetermined number of sheets. calculate. In this embodiment, the number is 300.

[S106] Calculation of Development γ Development γ is calculated based on the development potential Pot at the time of pattern creation in [S102], the adhesion amount detection result in [S104], and the development start voltage Vk in [S105]. The development potential Pot at the time of pattern creation in [S102] can be calculated from the development bias Vb at the time of pattern creation and the image portion potential Vl by the following formula.

  Here, the image portion potential Vl is fixed to 50 [−V]. This image portion potential varies depending on the state of the photoreceptor (in the second embodiment, development γ is calculated in consideration of the variation). From the above, the development γ can be calculated by the following equation.

[S107] Calculation of Correction Value of Potential Control Condition The charging bias, development bias, and exposure light amount are corrected from the development γ calculated in [S106]. From correction bias Vc, development bias Vb, exposure light quantity LDP, development γ, acquisition amount M / A at the time of process control, and target adhesion amount M / A ′ (here, 0.55 [mg / cm 2]) Then, the corrected charging bias Vc ′, developing bias Vb ′, and exposure light quantity LDP ′ are calculated. The calculation formula is shown below.

Here, ε and η are coefficients, and in this embodiment, Vl = 50 [−V].

[S108] Calculation of correction value of target toner density The target toner density TCref is corrected based on the development γ calculated in [S106]. First, an adhesion amount M / A at the time of image formation (at the time of image formation) is calculated from development γ. The calculation formula is shown below.

  Subsequently, a difference Δγ between the development γ ′ and the development γ, which is a target value of the development γ used when the toner replenishment condition is adjusted to derive the development γ, is calculated by the following equation.

  The TC correction amount necessary for inducing the Δγ is calculated from the following equation.

  Here, “a” is an experimentally obtained slope of the TC-development gamma correlation. FIG. 9 is a graph showing the relationship between the toner density and the development γ when the toner density is experimentally changed, and FIG. 10 shows the amount of change in the toner density necessary to obtain the development γ when the target adhesion amount is reached. It is a graph to show. FIG. 9 shows the correlation of the development γ when the TC is experimentally changed stepwise. From this slope, the development γ change amount with respect to the TC change amount can be found. For this reason, as shown in FIG. 10, it is possible to calculate the amount of TC change necessary for developing γ when the target adhesion amount is reached.

[S109] Potential Control Condition, Weighting of Target Toner Density Correction Value Potential Control Conditions (Charging Bias Vc ′, Development Bias Vb ′, Exposure Light Amount LDP ′) Calculated in [S107] and [S108] and Target Toner The correction value of the density TCref is applied. At this time, the correction of the potential control condition and the target toner density is performed at the same time, resulting in overcorrection. Therefore, weighting is performed on the correction amount of the potential control condition and the correction amount of the target toner density so as not to overcorrect by the following expression. In the following, recorrected charging bias Vc ″, developing bias Vb ″, exposure light quantity LDP ″, and target toner density TCref ″ are calculated.

  The potential control affects the image density immediately after the image quality adjustment operation, and the toner density control gradually affects the image density immediately after the image quality adjustment operation. In this embodiment, by setting α = 0.5 and β = 0.5, image quality adjustment by potential control and toner density control is performed in half. Further, both potential control and toner density control may be achieved by gradually changing α and β according to the number of sheets passed through the image quality adjustment operation.

[S110] Application of potential control condition and target TC re-correction amount The imaging condition correction amount calculated in [S109] is applied.
This is the end of the density adjustment. At the next image formation, image formation is performed based on this adjustment.

  The image forming apparatus 100 according to the first embodiment has the following effects. FIG. 11 is a graph showing the effect of correction in the first embodiment. In the image forming apparatus 100 according to the first embodiment, as shown in FIG. 11, an error in image density control due to a development γ calculation error accompanying a shift in the development start voltage Vk can be reduced.

<Embodiment 2>
In Example 1, correction was performed based on the usage state of the developer. However, the calculation of the development γ varies not only with the development start voltage Vk but also with the image portion potential Vl even if the toner adhesion amount is the same when the state of the image forming apparatus is the initial state. For example, when the image portion potential V1 increases by 50 [−V], the development potential actually decreases by 50 [−V]. FIG. 12 is a graph showing the actual development potential state when the image portion potential changes. Therefore, in the second embodiment, by predicting the image portion potential Vl from the usage state of the photoconductor, the development potential calculation error is suppressed, and the development γ is calculated more accurately. For this reason, a photoconductor usage history is recorded.

  Hereinafter, an image adjustment operation of the image forming apparatus 100 according to the second embodiment will be described. FIG. 13 is a flowchart showing an image adjustment operation in the second embodiment.

[S201] to [S205]
[S201] to [S205] are the same as the processes of [S101] to [S105] in the first embodiment.

[S206]
The image portion potential Vl is calculated from the photoreceptor usage information. The shift of the image portion potential Vl at the start of development is caused by a change in the charge characteristic on the photosensitive member due to a change in the thickness of the photosensitive member or a temperature. Therefore, the change in charge characteristics can be predicted from the correlation between the total number of sheets passing and the temperature. Therefore, the shift amount of the image portion potential Vl is calculated from a table of the total number of sheets passed and the temperature. For this reason, the image forming apparatus 100 is provided with temperature / humidity detection means (not shown) for acquiring temperature / humidity. FIG. 14 is a table showing the shift amount of the image portion potential determined by the number of inserted sheets and the temperature.

[S207] to [S211]
[S207] to [S211] are the same as the processes of [S101] to [S105] in the first embodiment.

  The image forming apparatus according to the second embodiment has the following effects. FIG. 15 is a graph showing the effect of correction in the second embodiment. As shown in FIG. 15, the image forming apparatus 100 according to the second embodiment can reduce an error in image density control due to a development γ calculation error due to a shift of the image portion potential Vl on the photoconductor.

<Embodiment 3>
Next, an image forming apparatus according to Embodiment 3 will be described. In the first embodiment, the correction is performed based on the usage state of the developer. However, in the image forming apparatus 100 according to the third embodiment, the actual development start voltage Vk is used as the development start voltage Vk.

  Hereinafter, an image adjustment operation of the image forming apparatus 100 according to the third embodiment will be described. FIG. 16 is a flowchart illustrating an image adjustment operation according to the third embodiment.

[S302] Creation of Patch Pattern / Budget Pattern FIG. 17 is a schematic diagram showing a density adjustment pattern and an optical sensor formed on the intermediate transfer belt in the third embodiment.
In addition to the patch pattern creation in [S <b> 102], the gap between the charging bias and the developing bias is intentionally narrowed, and the scumming toner is deposited on the photosensitive drum 2. The pattern creation example shown in FIG. 17 can be employed. In addition to the toner patch 110, a ground toner 130 is attached to the intermediate transfer belt 1. At this time, scumming is also formed in a toner adhesion region where the image carrier is not exposed under predetermined charging and developing conditions.

[S303] Patch Pattern / Border Pattern Detection In addition to patch pattern detection, a ground pattern is detected in the same manner as [S103].

[S304] Calculation of Adhesion Amount As in [S104], the adhesion amount of the patch pattern and the adhesion amount of the background pattern are calculated.

[S305] Calculation of Development Start Voltage Vk The development start voltage Vk is calculated from the amount of background toner adhesion acquired in [S304]. Experimentally, the correlation between the background stain amount and the development start voltage Vk is obtained. As the developer deteriorates, the amount of uncharged toner increases and the amount of background stain tends to increase. Similarly, since the development start voltage Vk shifts in the negative direction due to an increase in uncharged toner, the development start voltage Vk tends to increase with an increase in the amount of background contamination. From this characteristic, the development start voltage Vk can be calculated from a table based on the amount of background contamination. FIG. 18 is a table showing the development start voltage determined by the amount of background dirt adhesion.

[S306] to [S310]
Since it is the same as [S106] to [s310], it is omitted. Further, as in the second embodiment, the Vl correction may be performed based on the photoreceptor information and the temperature.

  The image forming apparatus according to the third embodiment has the following effects. That is, by calculating the development start voltage Vk from the amount of background contamination of the background contamination pattern, Vk correction by feedback can be performed, and Vk can be calculated more accurately than predicted.

1: Intermediate transfer belt 2: Photosensitive drum (image carrier)
3: Charging charger 4: Writing unit (exposure means)
5: Developing unit (developing device)
6: Primary transfer roller 7: Photoconductor cleaning unit 8: Quenching lamp 9: Scanner unit 10: ADF
11, 12, 13: Roller 14: Roller 15: Intermediate transfer belt cleaning unit 16: Secondary transfer roller 17: Paper feed tray 20: Recording paper 21: Pickup roller 22: Paper feed roller 23: Conveying roller pair 24: Registration roller Pair 25: Fixing unit 26: Paper discharge tray 27: Switchback roller pair 28a, 29a: Transfer conveyance belt 30: Toner image detection sensor (optical toner image density detection means)
32: Sensor substrates 40Y, 40M, 40C, 40K: Image forming station 100: Image forming apparatus 110: Toner patch 120: Toner image detection sensor 130: Toner 200: Control unit 201: CPU
202: RAM
203: ROM

JP-A-62-164066

Claims (7)

An image carrier;
Charging means for charging the image carrier;
Exposure means for forming a latent image by exposing the charged image carrier;
Developing means for containing a two-component developer composed of a toner and a carrier and developing a latent image portion formed on the image carrier with the toner to form a toner image;
Transfer means for transferring the toner image on the image carrier to a recording medium;
A toner storage device storing the toner;
A toner supply device for supplying toner from the toner storage device to the developing device;
Toner density detecting means for detecting the toner density in the developing device;
Optical toner image density detection means for detecting the density of the toner image formed on the image carrier,
At least one of temperature / humidity detection means for acquiring temperature / humidity, developing device usage information recording means for recording usage information of the developing device, and photosensitive member state information recording means for recording state information of the photosensitive member; ,
Forming a single toner patch on the photosensitive member under predetermined charging conditions, development conditions, and exposure conditions;
Detecting the density of the toner patch by the optical toner image density detecting means;
In an image forming apparatus that performs image density control by adjusting at least one of charging conditions, development conditions, exposure conditions, and toner replenishment conditions at the time of the next image formation,
The development capability is predicted based on the development bias at the time of forming the toner patch, the density of the toner patch, the usage information of the developing device, the usage information of the photoconductor, and the temperature and humidity, and the predicted development. An image forming apparatus comprising density control means for performing image density based on the capability.   2. The density control unit corrects at least one of the charging condition, the developing condition, the exposure condition, and the toner replenishment condition by a developing ability corrected based on usage information of the developing device. The image forming apparatus described in 1.   The image forming apparatus according to claim 1, wherein the usage information of the developing device is at least one of a total driving time of the developing device and a cumulative average image area ratio.   The density control unit corrects at least one of the charging condition, the developing condition, the exposure condition, and the toner replenishment condition based on the developing ability corrected based on the state information of the photoconductor. The image forming apparatus according to 1.   5. The image forming apparatus according to claim 1, wherein the photoconductor state information is a photoconductor use history.   5. The image forming apparatus according to claim 1, wherein the photoconductor state information is temperature / humidity information. Forming a non-exposure toner adhering area on the image carrier under predetermined charging and developing conditions;
The image forming apparatus according to claim 1, wherein the developing capability of the toner adhesion area is corrected based on a detection result of the optical toner image density detection unit.