JP6913301B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

Conventionally, adjustment control of a charging member that charges on a latent image carrier, an exposure member that exposes a latent image on the latent image carrier, and a developing member that supports toner on the latent image carrier is performed. An image forming apparatus including an adjustment control means is known.

For example, Patent Document 1 discloses an image forming apparatus that controls adjustment of image density as follows. First, in the adjustment control, the development γ is determined from the result of detecting the gradation density of the gradation toner pattern formed on the surface of the photoconductor, and the development potential is determined from the determined development γ. The development potential is the difference between the photoconductor surface potential VL (= constant) and the development bias after exposure at the exposure output (= maximum exposure output) for obtaining a solid density. The development bias is tentatively determined based on the determined development potential. Further, the charge bias is tentatively determined based on the tentatively determined development bias, and the exposure output (exposure intensity) is tentatively determined based on the tentatively determined charge bias.

After completing the first process of tentatively determining the image formation conditions in this way, then, as the second process, the toner patterns for intermediate density and solid density are determined according to the image formation conditions tentatively determined in the first process. Is imaged by area gradation. Then, the image area ratio of the area gradation is corrected so that the toner adhesion amount of the toner pattern for the intermediate density becomes the target value. Further, it is confirmed whether or not the detected toner adhesion amount for the toner pattern for solid density is within the preset target range, and if it is within the target range (allowable range), the image density adjustment control is terminated. On the other hand, if it is out of the target range, the image formation conditions such as the development bias tentatively determined in the first process are corrected so that the toner adhesion amount detected for the toner pattern for solid density approaches the target value. .. Further, since this correction causes the toner adhesion amount of the toner pattern for the intermediate density to shift, the image area ratio of the area gradation for the intermediate density is frequently re-executed as the second process. Is corrected again to prepare for the next printing instruction.

However, depending on the installation environment of the image forming apparatus or the like, the amount of toner adhering to the toner pattern having a solid density may change near the threshold value in the target range. In this case, in the conventional adjustment control, the toner adhesion amount often falls outside the preset target range. Therefore, it is necessary to create a toner pattern and re-detect the amount of toner adhering, and there is a problem that toner is frequently consumed for adjustment control. Further, there is a problem that stable image density cannot be obtained because the image formation conditions are different before and after the adjustment control (for example, before and after the adjustment control during continuous printing).

In order to solve the above-mentioned problems, the present invention supports a charging member that charges the latent image carrier, an exposure member that exposes the latent image on the latent image carrier, and a toner on the latent image carrier. In an image forming apparatus including a developing member to be used, a potential detection member for detecting the potential of the latent image carrier, and an adjustment control means for adjusting the potential of the latent image carrier, the adjustment control means is used. The development conditions of the developing member are determined from the target exposure potential for a solid image determined using the correction value, the exposure conditions of the exposure member are determined from the target exposure potential for halftone adjustment, and the exposure member is determined under the exposure conditions. the exposure potential on the latent image bearing member which is exposed for solid image detected by the potential detecting member from updating the correction value on the basis of a detection potential at said potential detecting member, with said potential detection member When the difference between the detection potential of the above and the target exposure potential for the solid image is within a predetermined range, the difference between the detection potential of the potential detection member and the target exposure potential for the solid image is predetermined in preparation for a printing instruction. When it is out of the range, the target exposure potential for the solid image is corrected to prepare for the printing instruction, and the correction value updated in the current adjustment control is used for the next adjustment control regardless of whether the difference is within or outside the predetermined range. be controlled to the target exposure potential can be used for pre-Symbol solid image determined Te characterized.

According to the present invention, it is possible to suppress a situation in which toner is frequently consumed for adjustment control, and to obtain stable image density before and after adjustment control.

It is explanatory drawing which showed the schematic structure of the main part of the printer which concerns on embodiment. It is explanatory drawing which showed the schematic structure of the image formation part of the printer. It is a block diagram which shows the control system related to the adjustment control in the printer. (A) is an explanatory diagram showing a schematic configuration of an optical sensor constituting an image detection device for black, and (b) is a schematic configuration of an optical sensor constituting an image detection device for another color (color). It is explanatory drawing which shows. It is explanatory drawing which shows the arrangement example of an optical sensor. It is a flowchart which shows the main processing flow of adjustment control in the printer. It is explanatory drawing which shows the setting method of the charge bias Vc and the development bias Vb at the time of making a density patch of 10 gradations in the adjustment control. It is explanatory drawing which shows the setting method of the exposure intensity LDP when creating the density patch of 10 gradations in the adjustment control. It is explanatory drawing which shows the photoconductor potential after exposure at the time of making a density patch of 10 gradations in the adjustment control. It is explanatory drawing which shows the setting method of the charge bias Vc and the development bias Vb when obtaining the Vc-Vd characteristic (first-order approximation formula) for determining the charge bias Vc in the adjustment control. It is explanatory drawing which shows the photoconductor potential after exposure at the time of obtaining the Vc-Vd characteristic (first-order approximation formula) for determining the charge bias Vc in the adjustment control. It is explanatory drawing which shows the setting method of the exposure intensity LDP when obtaining the LDP-VpL characteristic (first-order approximation expression) for determining the exposure intensity LDP in the adjustment control. It is explanatory drawing which shows the photoconductor potential after exposure at the time of obtaining the LDP-VpL characteristic (first-order approximation formula) for determining the exposure intensity LDP in the adjustment control. (A) and (b) are graphs showing the execution result of the adjustment control of the comparative example which does not use the correction value I_VL *. (A) and (b) are graphs showing the execution result of the adjustment control of the embodiment using the correction value I_VL *.

Hereinafter, an embodiment of an electrophotographic printer will be described as an image forming apparatus to which the present invention is applied.
First, the basic configuration of the printer according to this embodiment will be described.

FIG. 1 is an explanatory diagram showing a schematic configuration of a main part of a printer according to the present embodiment.
As shown in FIG. 1, the printer 100 has image forming portions 102Y (yellow), 102M (magenta), 102C (cyan), and 102K (black) along the intermediate transfer belts 101 stretched on a plurality of tension rollers. ) Is provided. Further, the toner image formed by each image forming unit 102Y, 102M, 102C, 102K is transferred onto the intermediate transfer belt 101 by the primary transfer device 106Y, 106M, 106C, 106K. Further, an image detection device 110 as a toner adhesion amount detecting means for detecting the toner adhesion amount of the toner image transferred on the intermediate transfer belt 101 is provided facing the intermediate transfer belt 101. The toner image on the intermediate transfer belt 101 is transferred to the transfer paper 112 as a recording material by the secondary transfer device 111.

FIG. 2 is an explanatory diagram showing a schematic configuration of the image forming portions 102Y, 102M, 102C, and 102K of FIG. Since the configurations of the image forming units 102Y, 102M, 102C, and 102K are the same, they will be described below without distinguishing them from each other.
Around the photoconductor 202, which is a latent image carrier, there is a charging device 201 as a charging member for charging the surface of the photoconductor, and an exposure member as a latent image forming means for writing an electrostatic latent image on the surface of the photoconductor by writing light L. As a cleaning means for cleaning the writing device 203, the developing device 205 as a developing member for developing an electrostatic latent image with toner, the primary transfer devices 106Y, 106M, 106C, 106K, the transfer residual toner on the photoconductor, and the like. A photoconductor cleaner 209, an erase (static eliminator) 207 as a static eliminator for static eliminating the surface of the photoconductor, and a potential sensor 210 as a potential detection member are provided. The potential sensor 210 is arranged between the writing device 203 and the developing device 205 in the direction of rotation of the photoconductor, and the potential on the photoconductor after passing through the writing device 203 and before reaching the developing device 205. Is detected.

The charging device 201 of the present embodiment is a non-contact charging device including a scorotron charger, and sets the grid voltage (charging bias) Vc of the scorotron charger to a target charging potential (target background potential) (minus potential). By doing so, the potential on the surface of the photoconductor is set as the target charging potential. The charging device 201 is not limited to this, and other non-contact roller chargers, contact roller chargers, and the like can also be used.

The writing device 203 of the present embodiment uses a laser diode (LD) as a light source and irradiates intermittent writing light, that is, repeated pulse-shaped writing light L, so that static electricity for each dot is applied to the surface of the photoconductor. A latent image (1 dot electrostatic latent image) is formed. The writing device 203 irradiates the writing light L according to the set exposure conditions (exposure intensity LDP, exposure spot diameter, etc.), and sets the potential (ground potential) on the uniformly charged photoconductor as the target. It is set to the exposure potential.

The developing apparatus 205 of the present embodiment includes a developing roller as a developing agent carrier arranged on the surface of the photoconductor, and is a two-component developing agent composed of toner charged to a predetermined polarity (minus polarity) and a magnetic carrier. Is supported on a developing roller to supply toner to the surface of the photoconductor. A development bias Vb having an absolute value larger than the exposure potential VL and smaller than the charging potential (ground potential) Vd is applied to the developing roller. As a result, in the developing region where the surface of the photoconductor and the developing roller face each other, the toner is moved toward the electrostatic latent image (exposure portion) on the surface of the photoconductor, and the non-electrostatic latent image on the surface of the photoconductor. An electric field can be formed in the (non-exposed portion) so that the toner does not move, and the electrostatic latent image can be developed with the toner.

When forming an image, first, the surface of the photoconductor is charged by the charging device 201 so that the surface of the photoconductor 202 has a uniform target charging potential (target background potential) Vd * (minus potential). Next, the charged light L corresponding to the image data is exposed to the photoconductor 202Y from the light source (LD) of the writing device 203 on the charged photoconductor surface portion, whereby the potential VL of the exposed portion on the photoconductor surface is exposed. As the (absolute value) decreases, an electrostatic latent image is formed on the surface of the photoconductor. After that, the electrostatic latent image (exposed portion) formed on the photoconductor 202 is developed into a toner image by the toner supported on the developing roller which is the developer carrier of the developing apparatus 205. Specifically, a development bias Vb whose absolute value is larger than the exposed potential VL and smaller than the background potential Vd is applied to the developing roller to electrostatically charge the toner charged to a predetermined polarity (negative polarity). It is developed by adhering it to an electrostatic latent image.

The toner image formed on the photoconductor 202 is transferred onto the intermediate transfer belt 101 (see FIG. 1) by the primary transfer device 106. The transfer residual toner that remains on the photoconductor 202 without being transferred to the intermediate transfer belt 101 is recovered by the photoconductor cleaner 209. Further, the surface of the photoconductor after the toner image is transferred onto the intermediate transfer belt 101 is uniformly irradiated with static electricity elimination light by the erase 207, so that the non-electrostatic latent image portion is statically eliminated and uniformly statically eliminated. It will be in the state of being done.

In this way, the toner images of the respective colors formed by the image forming portions 102Y, 102M, 102C, and 102K of FIG. 1 are primarily transferred onto the intermediate transfer belt 101 so as to overlap each other. After that, each color toner image transferred on the intermediate transfer belt 101 is transferred from the intermediate transfer belt 101 to the transfer paper 112 by the secondary transfer device 111, and the toner image is fixed on the transfer paper 112 by the fixing device to perform a series of printing processes. finish.

Next, the adjustment control (process control) of the output image will be described. By performing this adjustment control, the amount of toner adhering to the electrostatic latent image can be stabilized, and the output image can be stabilized. The toner adhesion amount here refers to the toner adhesion amount of 1 dot of the exposure irradiation to the electrostatic latent image. As the image forming conditions, the control for adjusting the charging bias Vc (= Vd) under the charging conditions, the development bias Vb under the developing conditions, and the exposure intensity LDP under the exposure conditions will be mainly described. Further, as the image forming condition, it is also possible to perform adjustment control by changing the conditions of the member around the photoconductor such as the transfer condition and the cleaning condition by controlling the application bias, the member spacing, the moving speed and the like. can.

FIG. 3 is a block diagram showing a control system related to adjustment control in the present embodiment.
In the adjustment control of the present embodiment, first, a density patch 113 which is a toner pattern (toner image) is formed on the intermediate transfer belt 101, and the amount of toner adhered to the density patch 113 is measured for K, which is an optical reflection density sensor, which will be described later. The detection is performed by the image detection device 110 including the optical sensor 301, the Y optical sensor 302Y, the M optical sensor 302M, and the C optical sensor 302C. The control unit 41 as the adjustment control means adjusts the grid voltage (charge bias) Vc of the charging device 201, the development bias Vb of the developing device 205, and the exposure intensity LDP of the writing device 203 based on the detection result of the image detection device 110. do.

FIG. 4A is an explanatory diagram showing a schematic configuration of the optical sensor 301 for K constituting the image detection device 110, and FIG. 4B constitutes an image detection device 110 for another color. It is explanatory drawing which shows the schematic structure of the optical sensor 302. In the following description, the color coding codes K, Y, M, and C will be omitted as appropriate for the explanations common to the colors.

The optical sensor 301 for K includes a light emitting element 303 and a specular light receiving element 304 that receives specular reflected light from the surface of the density patch 113 and the intermediate transfer belt 101. On the other hand, the optical sensors 302 for Y, M, and C include a light emitting element 303, a density patch 113, a specular light receiving element 304 that receives specular reflected light from the surface of the intermediate transfer belt 101, and a density patch 113. It is composed of a diffuse reflection light receiving element 305 that receives diffuse reflection light from the surface of the intermediate transfer belt 101.

As shown in FIG. 5, these optical sensors 301 and 302 are arranged at positions that can face the density patch 113 formed on the intermediate transfer belt 101, respectively. The control unit 41 receives the specular reflection light receiving element 304 and the diffuse reflection light receiving element 305 in accordance with the timing when the density patch 113 reaches the position facing these optical sensors 301 and 302 after the writing of the writing light L is started. By detecting the output voltage of the above and performing the adhesion amount conversion process on the detection result (sensor detection result), the toner adhesion amount of each density patch 113 is derived. Specifically, for example, a conversion table describing the correspondence between the output voltage and the toner adhesion amount is stored in ROM44 (see FIG. 3) in advance, and the toner adhesion amount is derived using this conversion table. Alternatively, for example, the toner adhesion amount may be derived by calculating a conversion formula that converts the output voltage into the toner adhesion amount.

In general, the development γ changes due to environmental changes, deterioration of the photoconductor over time (changes in photosensitive characteristics), and the development potential MaxPot for obtaining a target solid image density (first reference image density) changes. Therefore, it is necessary to confirm the current development γ at a predetermined timing and determine various image formation conditions (charge bias Vc, development bias Vb, exposure intensity LDP, etc.). Therefore, adjustment control is performed at a predetermined timing in order to continue image formation with a stable image density.

FIG. 6 is a flowchart showing a main processing flow of the image density adjustment control in the present embodiment.
FIG. 7 is an explanatory diagram showing a method of setting the charging bias Vc and the developing bias Vb when creating a density patch of 10 gradations in the adjustment control.
FIG. 8 is an explanatory diagram showing a method of setting the exposure intensity LDP when creating a density patch of 10 gradations in the adjustment control.
FIG. 9 is an explanatory diagram showing the photoconductor potential after exposure when creating a density patch of 10 gradations in the same adjustment control.

The adjustment control of the present embodiment is, for example, adjustment control after the preprocessing steps such as calibration and abnormality inspection of the image detection device 110 are completed after the power of the image forming device is turned on. Note that this adjustment control may be performed during continuous printing or after maintenance such as paper jam processing. In the adjustment control, first, a density patch forming process (S1) of 10 gradations is performed. In this process, as shown in FIGS. 7 to 9, a 10-gradation density patch (solid pattern) is applied on the surface of the photoconductor with a constant exposure intensity LDP while shaking the charging bias Vc and the developing bias Vb in 10 steps. (S1). Specifically, the development bias Vb (N) when forming the density patch of the Nth gradation is adjusted with the solid development potential MaxPot (predetermined value at the first time) used at the time of forming the immediately preceding image. It is calculated from the following mathematical formula (1) using the residual exposure potential Vr (predetermined value at the first time), which is the residual potential described later, which is detected during control.
Vb (N) = MaxPot × N / 10 + Vr ・ ・ ・ (1)

Further, the development bias Vb (N) when forming the density patch of the Nth gradation uses the background potential Vd (N) obtained from the following mathematical formula (2), and the Vc-Vd characteristic at the time of the previous adjustment control. From the (first-order approximation formula), the charging bias Vc (N) such that the background potential Vd (N) obtained by the following formula (2) is calculated.
Vd (N) = Vb (N) +100 ... (2)

Next, by detecting the exposed potential VL of each density patch with the potential sensor 210 (S2), the solid development potential of each density patch (hereinafter, simply referred to as “development potential”) MaxPot'= Vb-VL'is set. Calculate (S3). Further, the image detection device 110 detects the toner adhesion amount M / A adhering to these 10 gradation density patches (S4).

Then, from the development potential MaxPot'of each density patch detected in the processing step S3 and the toner adhesion amount M / A of each density patch detected in the processing step S4, the current development γ (gamma) and development are performed. The starting voltage Vk is calculated (S5). In this calculation, the development potential MaxPot'is taken on the horizontal axis, the toner adhesion amount M / A is taken on the vertical axis, the detection result of each density patch is plotted to obtain a linear approximation formula, and the slope is taken as the development γ. , The horizontal axis intercept is calculated as the development start voltage Vk.

In the present embodiment, after the development γ is calculated in the processing step S5, the currently set charging bias Vc0 and the developing bias Vb0 (values adjusted by the previous adjustment control) are applied and are currently set. The surface of the photoconductor is exposed with an exposure intensity LDP'1.8 times (180%) of the exposure intensity LDP0. Then, the potential of the electrostatic latent image (exposed portion) formed thereby is detected by the potential sensor 210 as the residual exposed portion potential Vr (S6).

Next, in the present embodiment, the development potential MaxPot * required to obtain the first target toner adhesion amount M / A * corresponding to the target solid image density (first reference image density) is calculated (S7). Specifically, the solid development potential MaxPot * that satisfies M / A * = development γ × (MaxPot * −Vk) is calculated. Further, at this time, the development potential HtPot * required to obtain the second target toner adhesion amount corresponding to the target halftone image density (second reference image density) is HtPot * (= Vb-VpL) = 0. It can be calculated from 435 × MaxPot * -55 (S7). The coefficients included in this equation are numerical values set by prior experiments and the like and are stored in the ROM 44 of FIG. Further, in order to satisfy both the target halftone development potential HtPot * and the target solid development potential MaxPot * with the same exposure intensity LDP, the target value of the solid exposure potential (first target electrostatic latent image potential) VL *. May be set so as to satisfy VL * = 0.262 × MaxPot + 74 + Vr.

From the above, using the development γ and the development start voltage Vk calculated in the processing step S5 and the residual exposure portion potential Vr detected in the processing step S6, first, the target value VL * of the solid exposure portion potential is set as follows. It is determined from the mathematical formula (3) of (S8). However, in the present embodiment, as shown in the following mathematical formula (3), the target value VL * of the solid exposed portion potential is determined by using the correction value I_VL * described later. The coefficients included in this equation are numerical values set by prior experiments and the like.
VL * = 0.262 × MaxPot * + 74 + Vr + I_VL * ・ ・ ・ (3)

Next, the development bias Vb is determined from the following mathematical formula (4) (S9).
Vb = MaxPot * + VL *
= 1.262 × MaxPot * + 74 + Vr + I_VL * ・ ・ ・ (4)

Next, using the predetermined skin potential (100V), the target value Vd * of the skin potential is determined from the following mathematical formula (5) (S10).
Vd * = Vb + 100
= 1.262 × MaxPot * + 174 + Vr + I_VL * ・ ・ ・ (5)

Next, the target value VpL * of the halftone exposed portion potential is determined from the following mathematical formula (6) (S11).
VpL * = 0.565 x MaxPot * + 55 + VL *
= 0.827 × MaxPot * + 129 + Vr + I_VL * ・ ・ ・ (6)

Next, in the adjustment control of the present embodiment, the scalp potential Vd is detected by the potential sensor 210 while swinging the charging bias Vc, and the detected scalp potential Vd is the target value Vd of the scalp potential determined in the processing step S10. The charging bias Vc is determined so as to match * (S12).

Specifically, the charging bias Vc is switched in three stages as shown in FIGS. 10 (a) to 10 (c), and each background potential Vd is detected by the potential sensor 210 as shown in FIG. The Vc-Vd characteristic is calculated from the detection result by a linear approximation formula, and the charging bias Vc is set so as to match the target value Vd * of the background potential. To explain a specific example, the charging bias Vc of the first stage is set to the charging bias Vc so as to be the target value Vd * of the background potential using the Vc-Vd characteristic (first-order approximation formula) at the time of the previous adjustment control. do. The second-stage charging bias Vc is a value obtained by adding 100 [V] to the first-stage charging bias Vc. The third-stage charging bias Vc is a value obtained by subtracting 100 [V] from the first-stage charging bias Vc.

The development bias Vb at this time is set to the development bias Vb determined in the processing step S9 for the first stage development bias Vb, and the second stage development bias Vb is 100 to the first stage development bias Vb. [V] is added, and the third-stage development bias Vb is a value obtained by subtracting 100 [V] from the first-stage development bias Vb. At this time, no exposure is performed.

Next, in the adjustment control of the present embodiment, the development bias Vb determined in the processing step S9 and the charging bias Vc determined in the processing step S12 are fixed, and the exposure intensity LDP is shaken to obtain a predetermined area gradation. A halftone pattern is formed, and the exposed portion potential (average value) VpL of the halftone pattern is detected by the potential sensor 210. Then, the exposure intensity LDP is determined so that the detected halftone exposure portion potential VpL matches the target value VpL * of the halftone exposure portion potential determined in the processing step S11 (S13).

Specifically, as shown in FIGS. 12 (a) to 12 (e), the halftone pattern (out of the 8 × 8 dot matrix) in which the area gradation is 24/64 while swinging the exposure intensity LDP in 5 steps. A pattern of striking 24 dots) is formed, and the exposed portion potential VpL of each halftone pattern as shown in FIG. 13 is detected by the potential sensor 210. Then, the LDP-VpL characteristic is calculated from the detection result by a first-order approximation formula, and the exposure intensity LDP that matches the target value VpL * of the halftone exposure portion potential is determined. For example, 60 [%], 70 [%], 80 [%], 90 [%], and 100 [%] are used for the five-step exposure intensity LDP. After that, the halftone pattern is recreated with the determined exposure intensity LDP, the halftone exposure part potential is detected by the potential sensor 210, and it is confirmed that the detection result matches the target value VpL *. You may.

Next, in the adjustment control of the present embodiment, the solid pattern is formed by using the development bias Vb determined in the processing step S9, the charging bias Vc determined in the processing step S12, and the exposure intensity LDP determined in the processing step S13. The potential sensor 210 detects the exposed potential VL of the solid pattern formed and to which the toner is not attached (S14). Then, it is confirmed whether or not the detected solid exposure portion potential VL matches the target value VL * of the solid exposure portion potential determined in the processing step S8.

Specifically, as described above, the calculation formula of VL * = 0.262 × MaxPot + 74 + Vr is a formula designed with parameters so as to satisfy VpL * and VL * at the same time. The part potential VL should match the target value VL * of the solid exposed part potential determined in the processing step S8. However, due to individual differences in the photoconductor characteristics, environmental changes, etc., they may not completely match and may be misaligned.

Therefore, in the adjustment control of the present embodiment, the error | VL-VL * | between the solid exposed portion potential VL detected in the processing step S14 and the target value VL * of the solid exposed portion potential determined in the processing step S8 is calculated. (S15). Then, the correction value is updated from the mathematical formula (5) described below according to the error | VL-VL * | (S16). As a result, the error | VL-VL * | calculated in the processing step S15 at the time of the next adjustment control can be reduced, the image formation conditions do not differ significantly before and after the adjustment control, and a stable image density can be obtained. In the present embodiment, as this correction value, a correction value I_VL * that corrects the target value VL * of the solid exposure portion potential determined in the processing step S8 is used, but in the case of a new product such as at the time of shipment, the correction value I_VL * is used. Uses a zero value or a predetermined value stored in the ROM 44 or the like in FIG.

In the present embodiment, when the target value VL * of the solid exposure portion potential is lowered by 4.64 [V], the error | VL-VL * | calculated in the processing step S15 becomes +1 in advance from the parameter design. It is known. Therefore, the correction value I_VL * can be calculated from the following mathematical formula (5) using the previous correction value I_VL *'.
I_VL * = I_VL *'+ 0.3 × 4.64 × (VL-VL *) ・ ・ ・ (5)

The reason why the gain of 0.3 is applied in the mathematical formula (5) is that the solid exposure portion potential VL detected in the processing step S14 varies depending on the position in the circumferential direction of the photoconductor. This is to prevent the potential VL from fluctuating significantly with each adjustment control. In the present embodiment, by applying a gain of 0.3, the target value VL * of the solid exposure potential is corrected in the direction in which the error | VL-VL * | is reduced by 30% for each adjustment control, and in the long term. , The center of the distribution of the error | VL-VL * | including the variation of the detected solid exposed potential VL approaches zero.

Next, in the adjustment control of the present embodiment, whether or not the error | VL-VL * | calculated in the processing step S15 is within the permissible range, specifically, the error | VL-VL * | is predetermined. It is determined whether or not it is equal to or less than the VL adjustment threshold value (S17). In this determination, if it is determined that the error | VL-VL * | is equal to or less than the predetermined VL adjustment threshold value (Yes in S17), it is determined that the image formation condition can be adjusted almost as intended, and the adjustment control is terminated. , The image formation operation is possible (print standby state).

On the other hand, if it is determined that the error | VL-VL * | exceeds the predetermined VL adjustment threshold value (No in S17), it means that the solid exposure portion potential VL deviates from the target value VL * beyond the permissible range. Judge and reset the image formation conditions. In this resetting, first, the target value VL *'of the solid exposure portion potential is reset from the following mathematical formula (6) so that the error | VL-VL * | becomes zero (S18).
VL *'= VL * + 4.64 x (VL-VL *) ... (6)

Further, while maintaining the solid development potential MaxPot * and the halftone development potential HtPot * calculated in the processing step S7, the development bias Vb and the background portion are used in the same manner as in the above method using the reset VL *'. The target value Vd * of the potential and the target value VpL * of the halftone exposure portion potential are reset (S19). In this resetting, the development bias Vb, the target value Vd * of the background potential, and the target value VpL * of the halftone exposure potential are set before the reset so as to maintain the difference from the VL *'after the reset. It is translated by the amount of movement of VL *'after resetting from VL *. After that, the processing steps S12 to S17 are executed again to reset each image formation condition.

Here, for example, under a situation where the developing ability is high, the required developing potential MaxPot * is small, so even if the error | VL-VL * | is small, the effect on the solid image density is large, and the image formation conditions are reset. The need increases. Therefore, the VL adjustment threshold value in the present embodiment may be changed according to the development potential MaxPot *. As a result, even when the development potential fluctuates, the VL adjustment threshold value can be appropriately changed in conjunction with this.

As described above, in the adjustment control of the present embodiment, the correction value I_VL * is updated in the processing step S16 regardless of the error | VL-VL * |. As a result, the error | VL-VL * | calculated in the processing step S15 at the time of the next adjustment control can be reduced, the image formation conditions do not differ significantly before and after the adjustment control, and a stable image density can be obtained.
14 (a) and 14 (b) are graphs showing the execution results of adjustment control of a comparative example in which the correction value I_VL * is not used.
15 (a) and 15 (b) are graphs showing the execution result of the adjustment control of the present embodiment using the correction value I_VL *.
Note that FIGS. 14 (a) and 15 (a) show an error | VL-VL * | at the time of each adjustment control, and FIGS. 14 (b) and 15 (b) show each adjustment. It shows the image density after control.

In the adjustment control of the comparative example in which the correction value I_VL * is not used, when the error | VL-VL * | is in the vicinity of the VL adjustment threshold value, as shown in FIG. 14A, the error for each adjustment control ( Depending on the variation), the error | VL-VL * | may be equal to or less than the VL adjustment threshold value or exceed the VL adjustment threshold value. As a result, the resetting of the image forming conditions (S18, S19) may or may not be carried out, and the image density varies depending on whether or not the resetting is carried out for each adjustment control.

On the other hand, according to the adjustment control of the present embodiment using the correction value I_VL *, the correction value I_VL * of the target value VL * of the solid exposure portion potential is corrected (updated) every time the adjustment control is performed. The error | VL-VL * | will converge to near zero. As a result, the situation in which the resetting of the image forming conditions (S18, S19) is performed or not performed is eliminated, and the image density becomes stable in the vicinity of the target image density.

What has been described above is an example, and has a unique effect in each of the following aspects.
(Aspect A)
The charging member such as the charging device 201 that charges the latent image carrier such as the photoconductor 202, the exposure member such as the writing device 203 that exposes the latent image on the latent image carrier, and the latent image carrier. A developing member such as a developing device 205 that carries toner, a potential detecting member such as a potential sensor 210 that detects the potential of the latent image carrier, and a control unit 41 that adjusts and controls the potential of the latent image carrier. In the image forming apparatus provided with the adjustment control means, the adjustment control means has the development conditions (development bias Vb, linear velocity) of the developing member from the target exposure potential for a solid image (target value VL * of the solid exposure portion potential). Etc.), and the exposure conditions (exposure intensity LDP, exposure spot diameter, etc.) of the exposure member are determined from the target exposure potential for halftone (target value VpL * of the halftone exposure portion potential), and the above exposure conditions are used. The exposure potential (solid exposure portion potential VL) on the latent image carrier exposed from the exposure member for a solid image is detected by the potential detection member, and the detection potential VL of the potential detection member and the solid image are used. When the difference from the target exposure potential VpL * | VL-VL * | is within a predetermined range (below the VL adjustment threshold), the detection potential of the potential detection member and the target exposure potential for the solid image are prepared in preparation for printing instructions. When the difference | VL-VL * | is out of the predetermined range (exceeds the VL adjustment threshold), the target exposure potential VL * for the solid image is corrected to prepare for the printing instruction, and the difference is within or outside the predetermined range. However, the next adjustment control is characterized in that the target exposure potential for the solid image corrected based on the detected potential can be used.
According to this aspect, the target exposure potential for the solid image modified based on the detected potential is used for the next adjustment control. As a result, in the next adjustment control, the difference | VL-VL * | between the detection potential VL of the potential detection member and the target exposure potential VL * for the solid image becomes smaller, and the difference | VL-VL * | becomes smaller. The frequency of falling out of the predetermined range decreases. As a result, it is possible to suppress a situation in which toner is frequently consumed for adjustment control. Further, since the situation where the difference | VL-VL * | is within or outside the predetermined range is eliminated, stable image density can be obtained before and after the adjustment control.

(Aspect B)
The charging member such as the charging device 201 that charges the latent image carrier such as the photoconductor 202, the exposure member such as the writing device 203 that exposes the latent image on the latent image carrier, and the latent image carrier. A developing member such as a developing device 205 that carries toner, a potential detecting member such as a potential sensor 210 that detects the potential of the latent image carrier, and a control unit 41 that adjusts and controls the potential of the latent image carrier. In the image forming apparatus provided with the adjustment control means, the adjustment control means determines the development bias Vb of the developing member from the target exposure potential for the solid image (target value VL * of the solid exposure portion potential), and performs intermediate adjustment. The exposure intensity LDP of the exposure member is determined from the target exposure potential (target value VpL * of the halftone exposure portion potential), and the latent image carrier exposed from the exposure member for a solid image at the exposure intensity. The potential (solid exposure portion potential VL) is detected by the potential detection member, and the difference | VL-VL * | between the detection potential VL and the target exposure potential VL * for the solid image is within a predetermined range (VL-VL * | When it is (below the VL adjustment threshold), the difference | VL-VL * | between the detection potential of the potential detection member and the target exposure potential for the solid image is out of the predetermined range (exceeds the VL adjustment threshold) in preparation for the printing instruction. ), The target exposure potential VL * for the solid image is corrected to prepare for the printing instruction, and the solid image corrected based on the detected potential in the next adjustment control regardless of whether the difference is within a predetermined range or not. It is characterized in that the target exposure potential for use is controlled so that it can be used.
According to this aspect, the target exposure potential for the solid image modified based on the detected potential is used for the next adjustment control. As a result, in the next adjustment control, the difference | VL-VL * | between the detection potential VL of the potential detection member and the target exposure potential VL * for the solid image becomes smaller, and the difference | VL-VL * | becomes smaller. The frequency of falling out of the predetermined range decreases. As a result, it is possible to suppress a situation in which toner is frequently consumed for adjustment control. Further, since the situation where the difference | VL-VL * | is within or outside the predetermined range is eliminated, stable image density can be obtained before and after the adjustment control.

(Aspect C)
In the aspect A or B, the exposed member exposes a latent image by area gradation control.
According to this, it is not necessary to change the exposure intensity LDP for each image density, and stable control of the image density is easy.

(Aspect D)
In any of the embodiments A to C, the adjustment control means detects the residual potential (residual exposure portion potential Vr) of the latent image carrier with the potential detection member, and the residual detected by the potential detection member. It is characterized in that the target exposure potential VL * for the solid image is set so that the potential Vr and the target exposure potential VL * for the solid image become predetermined set values (the equation (3)). ..
According to this, even when the residual potential Vr fluctuates due to a temperature / humidity environment or deterioration (wear, etc.) of the photoconductor over time, it is easy to achieve the target image density over a wide range from low image density to high image density.

(Aspect E)
In any of the embodiments A to D, the difference between the target exposure potential VpL * for halftone adjustment and the development bias Vb becomes a linear equation (the equation (3)) of the development potential MaxPot * for the solid image. It is characterized in that the target exposure potential VpL * for the halftone adjustment is set so as to be.
According to this, even when the development potential fluctuates, it is easy to achieve the target image density over a wide range from low image density to high image density.

(Aspect F)
In any of the embodiments A to E, the predetermined range is set according to the development potential MaxPot * for the solid image.
According to this, even when the development potential fluctuates, the predetermined range can be appropriately changed in conjunction with the fluctuation.

(Aspect G)
In an image forming apparatus provided with adjustment control means such as a control unit 41 that controls adjustment of a plurality of image formation conditions such as a charge bias Vc, a development bias Vb, and an exposure intensity LDP according to a predetermined adjustment rule, the plurality of images are produced. As the image conditions, a common set value is used at the time of image formation of the first reference image density such as solid image density and the second reference image density such as halftone image density, which have different image densities, and both image densities are used. The adjustment control means adjusts the reference image density (halftone image density) of one of the two reference image densities in the adjustment control, including common image formation conditions such as exposure intensity LDP having different optimum set values. A predetermined evaluation value VL at the other reference image density (solid image density) at the set value of the common image formation condition, and an optimum evaluation value VL corresponding to the optimum set value at the other reference image density. The amount of deviation from * | VL-VL * | is grasped, and in the next adjustment control, the adjustment rule corrected by using the amount of deviation (the equations (3) and (5)) is used as the adjustment rule. It is characterized by that.
In the above embodiment, the adjustment control performed by the adjustment control means includes a development potential determination step, an image formation condition provisional determination step, an image formation condition correction step, an image formation condition confirmation step, and an image formation condition confirmation step.
In the development potential determination step, the result of detecting the amount of toner adhered to a toner pattern such as a 10-gradation density patch formed on the surface of the photoconductor (development γ, development start voltage Vk) is used to determine the solid image density and the like. The first development potential (solid development potential MaxPot *) for obtaining the first reference image density and the second development potential (halftone development potential HtPot *) for obtaining the second reference image density such as halftone image density are Determine (S1 to S7).
In the image formation condition tentative determination step, the image formation condition is tentatively determined based on the determined first development potential (S8 to S10, S12). The image formation conditions adjusted by the adjustment control of the present embodiment are three: charging bias Vc, development bias Vb, and exposure intensity LDP. In the processing step corresponding to the image formation condition tentative determination step of the present embodiment, the image formation condition for realizing the first development potential is tentatively determined so that the first reference image density (solid image density) can be obtained. In the present embodiment, the target value Vd * of the background potential for determining the charge bias Vc, the development bias Vb, and the target value VL * of the solid exposure potential for determining the exposure intensity LDP are determined.
In the image formation condition correction step, the tentatively determined image formation condition is corrected based on the second development potential (S11, S13). In the processing step corresponding to the image formation condition correction step in the present embodiment, the exposure intensity LDP is corrected, but a common work in which a common set value is used for both the first reference image density and the second reference image density at the time of printing. As long as it is an image condition, not only the exposure intensity LDP but also the charging bias Vc, the development bias Vb, and the like may be modified.
In the image formation condition confirmation step, there is a discrepancy between the toner adhesion amount when an image having the first reference image density is imaged under the modified image formation condition and the first target toner adhesion amount corresponding to the first reference image density. It is confirmed whether or not the amount is within a predetermined allowable range (below the VL adjustment threshold value) (S17). In the image formation condition correction step of the present embodiment, the image formation conditions other than the exposure intensity LDP, which is the image formation condition to be corrected, are not corrected. Therefore, in the processing step corresponding to the image formation condition confirmation step in the present embodiment, this may be directly detected as the amount of toner adhered when an image having the first reference image density is imaged under the modified image formation condition. Instead, a solid exposed portion potential VL that correlates with this can be substituted, and accordingly, the target value VL * of the solid exposed portion potential is substituted as the first target toner adhesion amount, and the deviation amount is | VL-VL * | can be used.
In the correction value calculation step, the correction value I_VL * for reducing the deviation amount used in the subsequent image formation condition confirmation step during adjustment control is calculated (S16). Then, in the image formation condition provisional determination step, the image formation condition using the correction value I_VL * is provisionally determined. In the present embodiment, as a correction value for reducing the deviation amount, the target value VL * (parameter used for determining the image formation condition) of the solid exposure portion potential used for calculating the deviation amount is corrected. Although the correction value I_VL * is used, it may be another parameter such as the residual potential Vr as long as it is a parameter used for determining the image formation condition and the parameter changes the amount of deviation.
As described above, in the present embodiment, in the adjustment control, the common image is adjusted for one of the reference image densities (solid image density and halftone image density) of both reference image densities (halftone image density). A predetermined evaluation value (solid exposure part potential VL) at the other reference image density (solid image density) under the set value of the condition (exposure intensity LDP) and the optimum at the other reference image density (solid image density). The amount of deviation | VL-VL * | from the optimum evaluation value (target value VL * of the solid exposed part potential) corresponding to the set value is grasped, and in the next adjustment control, this amount of deviation | VL is used as the adjustment rule. The adjustment rule modified using −VL * | (the above equations (3) and (5)) is used.
Depending on the installation environment of the image forming apparatus and the like, the amount of toner adhered when creating an image having the first reference image density may change near the threshold value of the allowable range. In this case, the deviation amount | VL-VL * | is in the vicinity of the boundary of the predetermined allowable range. In this situation, in the conventional adjustment control (conventional adjustment control that does not use the correction value) in which the adjustment rule of the next adjustment control is not modified by using this deviation amount | VL-VL * |, the variation (detection) for each adjustment control is used. The amount of deviation may be within a predetermined allowable range or out of a predetermined allowable range due to an error, a slight change in the environment, or the like). When the deviation amount is out of the predetermined allowable range, the image formation condition is reset so that the deviation amount approaches zero. However, when the deviation amount is within the predetermined allowable range, the image formation condition is not reset and the deviation amount is reduced. It remains. Therefore, the actual image density differs depending on whether the amount of deviation is within the predetermined allowable range or outside the predetermined allowable range. As a result, in the situation where the deviation amount is within the predetermined allowable range or outside the predetermined allowable range as described above, the image density changes frequently and irregularly, and a stable image density is obtained. I can't.
According to this aspect, even if the deviation amount is near the boundary of a predetermined allowable range, the adjustment rule of the next adjustment control is modified by using this deviation amount, so that the adjustment control in the subsequent adjustment control is performed. The amount of deviation can be reduced. As a result, the situation in which the deviation amount falls within the predetermined permissible range or goes out of the predetermined permissible range is eliminated, and a stable image density can be obtained.

41 Control unit 100 Printer 101 Intermediate transfer belt 102 Image forming unit 110 Image detection device 201 Charging device 202 Photoreceptor 203 Writing device 205 Developing device 209 Photoreceptor cleaner 207 Erase 210 Potential sensor 301, 302 Optical sensor

Japanese Unexamined Patent Publication No. 2014-119665

Claims (6)

The charging member that charges on the latent image carrier, the exposure member that exposes the latent image on the latent image carrier, the developing member that supports the toner on the latent image carrier, and the potential of the latent image carrier. In an image forming apparatus including a potential detection member for detection and an adjustment control means for adjusting and controlling the potential of the latent image carrier.
The adjustment control means
The development conditions of the developing member are determined from the target exposure potential for the solid image determined by using the correction value.
The exposure conditions of the exposed member are determined from the target exposure potential for halftone adjustment, and the exposure conditions are determined.
By detecting the exposure potential on the latent image bearing member which is exposed for solid image from the exposure member at the exposure condition by said potential detection member, updating the correction value on the basis of a detection potential at said potential detection member death,
When the difference between the detection potential of the potential detection member and the target exposure potential for the solid image is within a predetermined range, prepare for printing instructions.
When the difference between the detection potential of the potential detection member and the target exposure potential for the solid image is out of the predetermined range, the target exposure potential for the solid image is corrected to prepare for the printing instruction.
Said difference regardless of the predetermined range and out, the next adjustment control controls to the target exposure potential can be used for pre-Symbol solid image determined using the correction value updated in the current regulation control An image forming apparatus as a feature. The charging member that charges on the latent image carrier, the exposure member that exposes the latent image on the latent image carrier, the developing member that supports the toner on the latent image carrier, and the potential of the latent image carrier. In an image forming apparatus including a potential detection member for detection and an adjustment control means for adjusting and controlling the potential of the latent image carrier.
The adjustment control means
The development bias of the developing member is determined from the target exposure potential for a solid image determined using the correction value.
The exposure intensity of the exposed member is determined from the target exposure potential for halftone adjustment, and the exposure intensity is determined.
The potential on the latent image carrier exposed from the exposed member for a solid image with the exposure intensity is detected by the potential detecting member, and the correction value is updated based on the detected potential by the potential detecting member. ,
When the difference between the detection potential of the potential detection member and the target exposure potential for the solid image is within a predetermined range, prepare for printing instructions.
When the difference between the detection potential of the potential detection member and the target exposure potential for the solid image is out of the predetermined range, the target exposure potential for the solid image is corrected to prepare for the printing instruction.
Said difference regardless of the predetermined range and out, the next adjustment control controls to the target exposure potential can be used for pre-Symbol solid image determined using the correction value updated in the current regulation control An image forming apparatus as a feature. In the image forming apparatus according to claim 1 or 2.
The exposure member is an image forming apparatus that exposes a latent image by controlling area gradation. In the image forming apparatus according to any one of claims 1 to 3.
The adjustment control means detects the residual potential of the latent image carrier with the potential detection member, and the residual potential detected by the potential detection member and the target exposure potential for the solid image become predetermined set values. As described above, an image forming apparatus characterized by setting a target exposure potential for the solid image. In the image forming apparatus according to any one of claims 1 to 4.
An image forming apparatus characterized in that the target exposure potential for halftone adjustment is set so that the difference between the target exposure potential for halftone adjustment and the development bias becomes a linear expression of the development potential for the solid image. In the image forming apparatus according to any one of claims 1 to 5,
An image forming apparatus, characterized in that the predetermined range is set according to the development potential for the solid image .

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