This invention relates to an image forming apparatus that applies to a developer bearing member a developing bias in which a DC (direct current) voltage and an AC (alternating current) voltage are superimposed in order to develop an electrostatic latent image formed on an image bearing member with developer including toner.
In an image forming apparatus that forms a toner image on a recording material, well known is the configuration in which a developing bias in which a DC voltage and an AC voltage are superimposed is applied to a developer bearing member that bears developer when developing an electrostatic latent image formed on the image bearing member.
Japanese Patent Application Laid-Open No. 2016-11981 discloses the configuration in which the duty ratio of the components of the side of the polarity (positive polarity) opposite to the polarity of normal charging polarity (negative polarity) is made higher to 50% or more than 50% to improve granularity on the image.
Recently, the image forming apparatus of an electrophotographic system is becoming widespread in the printing industry and the demand for high speed and high quality imaging is becoming rapidly surged. The items of demands concerning high quality imaging include density evenness for an image on the same page, so that reducing image unevenness on the same page as much as possible is becoming placed importance on.
The causes of such image unevenness are various. However, one of the causes is the lack of process precision, such as the eccentricity of a photosensitive drum or a developing sleeve, by which a developing gap is fluctuated to cause image unevenness.
The density unevenness on images in the image processing direction (hereinafter referred to as sub-scanning density unevenness) conspicuously occurs when the charging amount of the toner is large in a case such as low humidity environment. Japanese Patent Application Laid-Open No. 2016-21043 discloses the technology in which the density unevenness on images is reduced irrespective of the charging amount of the toner by changing the duty ration and the peak-to-peak voltage Vpp of the developing bias based on the patch detection density on an intermediate transfer member.
However, when the peak-to-peak voltage Vpp of AC voltage components of the developing bias is made greater in order to improve the sub-scanning density unevenness in a low humidity environment, in which the charging amount of toner is large, the potential difference Vgo between the potential on developing side of AC voltage components and DC voltage components in the developing bias becomes greater so that toner fog may occur.
The purpose of the present invention is to suppress toner fog as well as to suppress density unevenness.
The first aspect of the present invention is an image forming apparatus comprising:
The second aspect of the present invention is an image forming apparatus comprising:
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, with reference to the drawings, preferred embodiments of the present invention will be described in detail. The components of the embodiments described below are only examples and the configurations and various conditions such as functions, sizes, materials, shapes and relative arrangement can be appropriately changed in the range not departing from the gist of the present invention and they are not limited to ones in the following embodiments.
In
Next, the outline of the image forming process of the image forming apparatus 200 will be described. First, in the image forming portions PY, PM, PC, and PK, toner images of the respective colors are formed on the photosensitive drums 13Y, 13M, 13C, and 13K, respectively. The toner images of respective colors formed in this way are transferred on the intermediate transfer belt 10, and subsequently transferred from the intermediate transfer belt 10 to a recording material. The recording material on which an image is transferred is transferred to the fixing device 11 where the toner image is fixed to the image recording material.
Next, the configuration of the image forming apparatus 200 will be described in detail. The four image forming portions PY, PM, PC, and PK have substantially the same configuration as each other except for the developing colors. Therefore, hereinafter the description will be made for the image forming portion PY as the representative, and components of the configurations of the other image forming portions are indicated by replacing the index “Y” of the reference character of the components of the image forming portion PY with “M”, “C”, and “K”, respectively, and the descriptions of the components are omitted.
In the image forming portion PY, the photosensitive drum 13Y is disposed. The photosensitive drum 13Y is a cylindrical photosensitive member as a image bearing member. Around the photosensitive drum 13Y, the charging roller 12Y as a charging device (charging portion), the developing device 1Y as a developer accommodating portion, the primary transfer roller 17Y, and the cleaning device 15Y are disposed. Under the photosensitive drum 13Y in the figure, the laser scanner 14Y as an exposing device (latent image forming portion) is disposed.
The charging roller 12Y is driven to rotate by the photosensitive drum 13Y during image forming The charging roller 12Y is urged by the pressure spring (not shown) toward the photosensitive drum 13Y. Further, a charging bias is applied to the charging roller 12Y from a high voltage power supply. As a result, the photosensitive drum 13Y is substantially uniformly charged by the charging roller 12Y.
The intermediate transfer belt 10 is disposed opposed to the photosensitive drums 13Y, 13M, 13C, and 13K.
In the positions opposed to the photosensitive drums 13Y, 13M, 13C, and 13K, the primary transfer rollers 17Y, 17M, 17C, and 17K as primary transfer members are respectively disposed via the intermediate transfer belt 10. These configurations respectively form the primary transfer portions T1Y, T1M, T1C, and T1K, which transfer toner images formed on the photosensitive drums 13Y, 13M, 13C, and 13K to the intermediate transfer belt 10.
The intermediate transfer belt 10 is tensioned by the tension rollers and is driven to circularly move by the driving roller which is one of the tension rollers. The secondary transfer outer roller 16 as a secondary transfer member is disposed in the position opposed to the secondary transfer inner roller 18, which is one of the tension rollers, via the intermediate transfer belt 10, which forms the secondary transfer portion T2 that transfers a toner image on the intermediate transfer belt 10 to a recording material. The fixing device 11 is disposed downstream of the secondary transfer portion T2 in the conveying direction of recording material.
At the lower portion of the image forming apparatus 200, a feeding portion (not shown) is disposed. The recording material fed from the feeding portion at the start of the image forming operation is conveyed to the secondary transfer portion T2 at a predetermined timing.
Next, the image forming process of the image forming apparatus 200 configured as described above will be described.
When the image forming operation is started, the surface of the rotating photosensitive drum 13Y is uniformly charged by the charging roller 12Y. Next, the photosensitive drum 13Y is irradiated with a laser beam emanated from the exposing device 14Y corresponding to an image signal. As a result, an electrostatic latent image corresponding to the image signal is formed on the photosensitive drum 13Y. The electrostatic latent image on the photosensitive drum 13Y as an electrostatic latent image bearing member is visualized into a visible image by toner accommodated in the developing device 1Y.
The toner image formed on the photosensitive drum 13Y is primarily transferred onto the intermediate transfer belt 10 by the primary transfer portion T1Y. The toner remaining on the surface of the photosensitive drum 13Y after the primary transfer (after-transfer residual toner) is removed by the cleaning device 15Y. Such an operation is subsequently performed in the image forming portions for the colors, magenta, cyan, and black, so that the four color toner images are superimposed on the intermediate transfer belt 10.
Thereafter, a recording material accommodated in a recording material accommodating cassette (not shown) of the feeding portion is conveyed to the secondary transfer portion T2 in synchronism with the timing of the formation of a toner image and the four-color toner image on the intermediate transfer belt 10 is secondarily transferred on the recording material in a batch. The toner remaining on the intermediate transfer belt 10 that has not been fully transferred at the secondary transfer portion T2 is removed by the intermediate transfer belt cleaner 19.
Then, the recording material is conveyed to the fixing device 11. The fixing device 11 has the fixing roller 20, which has a heat source such as a halogen heater inside, and the pressure roller 21. The fixing roller 20 and the pressure roller 21 form a fixing nip portion. The toner image is fixed when the recording material conveyed to the fixing device 11 passes through the fixing nip portion, and then the recording material is discharged out of the apparatus.
This completes the series of image forming processes. By using only a desired image forming portion or desired image forming portions, a monochrome image with a desired color or a multi-color image with desired colors can be formed.
Next, two-component developing agent used in the present embodiment will be described. The developer to be used contains a mixture of nonmagnetic toner, which has a negative charge polarity, and magnetic carrier, which has a positive charge polarity. In the present embodiment, the charge polarity of the properly charged toner is negative. Non-magnetic toner is made by encapsulating colorants, wax components, etc. in resins such as polyester, styrene acrylic, etc., grinding or polymerizing them into powder, and adding fine powders such as titanium dioxide and silica to the surface. The magnetic carrier is made by coating with resin the surface layer of a core consisting of ferrite particles or resin particles mixed with magnetic powder.
Next, the detailed configuration of the developing device 1Y will be described. The developing devices 1M, 1C, and 1K have the same configuration as that of the developing device 1Y.
In
The developing container 2 is divided by the partition wall 51 into the first conveying path (agitating chamber) 52 as a first chamber and the second conveying path (developing chamber) 53 as a second chamber. The first conveying path 52 and the second conveying path 53 are communicated with each other by communicating openings at both end portions. As a result, the first conveying path 52 and the second conveying path 53 form a circulating path of the developer.
In the developing container 2, two screw members are provided as conveying members that convey the developer while agitating it. The first conveying screw 58 (first conveying portion) is provided on the first conveying path 52 and the second conveying screw 59 (second conveying portion) is provided on the second conveying path 53. The first conveying screw 58 and the second conveying screw 59 respectively have the rotating shafts 58a, 59a and the blades 58b, 59b spirally provided around the rotating shafts 58a, 59a (on the rotating shafts).
When the first conveying screw 58 rotates around the rotating shaft 58a, the spiral blade 58b conveys the developer in the first conveying path 52 in the direction of arrow α (first direction), which is one of the longitudinal directions of the developing device 1Y (axial directions of the rotating shaft 58a). When the second conveying screw 59 rotates around the rotating shaft 59a, the spiral blade 59b conveys the developer in the second conveying path 53 in the direction of arrow β (second direction), which is the other of the longitudinal directions of the developing device 1Y (axial directions of the rotating shaft 59a). As a result, the developer is circulated between the first conveying path 52 and the second conveying path 53.
The developer in the second conveying path 53 is scooped up to within the range of magnetic force of the pole S2 by the second conveying screw 59 provided in the second conveying path 53 under the developing sleeve 54 to be borne on the surface of the developing sleeve 54. The borne developer is conveyed with the rotation of the surface of the developing sleeve 54. The restricting blade 55 is disposed distanced from the surface of the developing sleeve 54 for a predetermined gap in the vicinity of the magnetic pole Ni of the developing sleeve 54 as a member for forming a thin layer of the developer. The gap between the developing sleeve 54 and the restricting blade 55 is generally set to 200 to 500 μm and the wider the gap is, more developer is borne on the developing sleeve 54.
The conveyed developer forms the magnetic brush at the pole N1 and the desired amount of developer is formed as a thin layer on the surface of the developing sleeve 54 by the restricting blade 55 provided with a predetermined gap from the developing sleeve 54. Thereafter, the developer conveyed to the opposing portion of the photosensitive drum 13Y forms the magnetic brush again at the pole S1 and forms a developing nip between the photosensitive drum 13Y and the developing sleeve 54.
The surface of the photosensitive drum 13Y is charged by the charging roller 12Y to a predetermined potential while the image portion is exposed by the exposure device 14Y to form the exposure potential. Further, a developing bias is applied to the developing sleeve 54 by a high voltage circuit (not shown). The developing bias to be applied to the developing device 54 will be described in detail later.
The toner charged in the developing device 1Y receives a driving force by the potential difference between the developing bias and the drum surface in the developing nip so that the toner adheres to the exposed portion. This completes the developing process.
The carrier and the toner that is not used for development are conveyed further downstream of the developing sleeve 54 in the rotating direction, lose a magnetic binding force in the zero-gauss area (area in which magnetic flux density is zero) formed between the pole S2 and the pole S3, and are collected in the second conveying path 53.
The image forming apparatus 200 according to the present embodiment is configured to develop an electrostatic latent image by AC development in which a developing bias consisting of DC voltage components and AC voltage components, obtained from AC voltage being superimposed to DC voltage is applied to the developing sleeve 54.
Next, the principle of AC development used when the image forming apparatus 200 according to the present embodiment develops an electrostatic latent image formed on the photosensitive drum 13Y will be described referring to
The ratio of the application time of the maximum voltage value V2 in one AC voltage cycle (hereinafter referred to as “duty ratio”) is calculated by T2/(T1+T2), where T1 (s) is the application time of the minimum voltage value V1 and T2 (s) is the application time of the maximum voltage value V2.
In this case, the potential difference Vgo between the minimum voltage value V1 of the AC voltage and the DC voltage Vdc, the potential difference Vre between the maximum voltage value V2 of the AC voltage and the DC voltage Vdc, the duty ratio, and the peak-to-peak voltage Vpp have the relationship that satisfies the following two formulae to offset the effect on the DC voltage even when the peak-to-peak voltage Vpp is changed. The application time T1 of the minimum voltage value V1 of the AC voltage corresponds to the application time of the potential difference Vgo in one AC voltage cycle. The application time T2 of the maximum voltage value V2 of the AC voltage corresponds to the application time of the potential difference Vre in one AC voltage cycle.
As shown in
As shown in
Further, it is preferable that the Duty ratio is 50% or larger, because less potential difference Vre weaken the forces for returning toner adhered to the photosensitive drum 13Y, which increases reproductivity of the shallow highlighted portion of the latent image so that the image roughness is improved. When the duty ratio is too large, the fog may greatly deteriorate. Therefore, it is more preferable that the duty ratio is between 50% and 90%.
The distance between the surface of the developing sleeve 54 and the surface of the photosensitive drum 13Y in the developing region is referred to as a developing gap. This developing gap periodically fluctuates with the rotation of the developing sleeve 54 and the photosensitive drum 13Y due to the eccentricity of the developing sleeve 54 and the photosensitive drum 13Y. With the gap fluctuating in this way, the electric field generated by the developing bias applied to the developing sleeve 54 becomes strong when the gap is small and weak when the gap is large.
Accordingly, in the image forming apparatus in which the developing gap fluctuates, when the developing gap is small, an amount of toner moving toward the latent image increases and the density of the image corresponding to that portion becomes high, whereas, when the developing gap is high, an amount of toner moving toward the latent image decreases and the density of the image corresponding to that portion becomes low. As a result, in the image forming apparatus in which the developing gap fluctuates, there is a problem that a periodic image density unevenness occurs with the gap fluctuating.
As shown in the graph of
As the technology to suppress the periodic density unevenness, which becomes apparent in the low humid environment, it is generally for the peak-to-peak voltage Vpp to be increased in the low humidity environment as compared with in the high humidity environment.
When the peak-to-peak voltage Vpp of the developing bias increases, the potential difference Vgo increases accordingly, which deteriorates the fog as shown in the graph of
Therefore, in the present embodiment, as shown in the graph of
As shown in
In the comparative example 2, the duty ratio is fixed at 75%, but the peak-to-peak voltage Vpp is controlled in response to the environmental humidity such that the less the environmental humidity becomes, the greater the peak-to-peak voltage Vpp becomes. Therefore, different from the comparative example 1, the periodic density unevenness is suppressed irrespective of the environmental humidity, but the potential difference Vgo becomes large and the fog worsens.
In contrast, the present embodiment adopts the configuration in which the less the environmental humidity becomes, the greater the peak-to-peak voltage Vpp and less the duty ratio become, so that the potential difference Vgo is maintained constant at 1050 (V). As a result, the periodic density unevenness and the fog are suppressed simultaneously.
As shown in
The control portion 70 includes the CPU (Central Processing Unit) 71 as an arithmetic control means, the ROM (Read Only Memory) 72, the RAM (Random Access Memory) 72 and so on. The CPU 71 controls the respective portions of the image forming apparatus 200 while reading out the program corresponding to the working procedures, stored in the ROM 72. The working data and the input data are stored in the RAM 73 and the CPU 71 performs the controls while referring to the data stored in the RAM 73 based on the above described programs and so on.
The control portion 70 includes the image processing portion 74 which processes image information and generates driving signals to the respective portions, the image forming control portion 75 which controls the respective portions, and the replenishing control portion 76 which controls toner replenishment in the developing devices 1Y, 1M, 1C, and 1K.
The temperature and humidity sensor 79 as a humidity detecting means for detecting an environmental humidity and the bias power source 80 which supplies developing biases to the developing devices 1Y, 1M, 1C, and 1K are connected to the control portion 70. The temperature and humidity sensor 79 is provided, for example, at a part of the wall portion of the first conveying path (agitating chamber) 52 to detect information concerning the temperature and humidity inside the developing device 1. The control portion 70 calculates the absolute moisture content inside the developing device 1 based on the information concerning the temperature and humidity inside the developing device 1, which is the detection results of the temperature and humidity sensor 79. Namely, the temperature and humidity sensor 79 detects the information concerning the absolute moisture contents inside the developing container 2.
In the present embodiment, the control portion 70 calculates the information concerning volumetric humidity as the information concerning the absolute moisture content. However, the information concerning the absolute moisture content is not limited to the information concerning volumetric humidity and the control portion 70 may calculate the information concerning the weight absolute humidity.
The control portion 70 determines the developing bias based on the calculated information concerning the absolute moisture content. The bias power supply 80 outputs the developing bias determined by the control portion 70.
The density detecting sensor 22 as a density detecting means for detecting the density of the toner image for adjusting the image density formed on the intermediate transfer belt 10 is connected to the control portion 70. The density detecting sensor 22 irradiates respective patch images formed on the intermediate transfer belt 10 in the image forming portions PY, PM, PC, and PK with a measuring light, and detects the light amount reflected from the respective patch images. The detection result is transmitted to the control portion 70 as a light reception output signal.
An optical sensor having a light emitting element, such as an LED (Light Emitting Diode) and a light receiving element, such as a PD (Photo Diode) is generally used as the density detecting sensor 22. In measuring the toner adhering amount on the intermediate transfer belt 10, when a measuring light is emitted to the toner image from the light emitting element, the measuring light enters the light receiving element as the light reflected from the toner and the light reflected from the belt surface. When the amount of adhering toner is large, the light amount received by the light receiving element decreases since the light reflected from the toner is blocked by the toner. In contrast, when the amount of adhering toner is small, the light amount received by the light receiving element increases as a result the increase of the amount of the light reflected from the belt surface.
The density correction for each color is performed by detecting with the density detecting sensor 22 the density of the patch image for each color based on the output value of the light reception signal, which is based on the received reflected light amount, by comparing the detected density of the patch image with the predetermined reference density, and by adjusting the settings of the exposure device 14. The image density adjustment with the density detecting sensor 22 is performed each time image forming is performed for a predetermined number of sheets. In the present embodiment, the image density adjustment control is performed each time image forming is performed for 500 A4-size sheets.
A developing bias determining procedure in the present embodiment will be described according to the flowchart of
When an image forming operation signal is input, the information concerning the absolute moisture content inside the developing container 2 is detected by the temperature and humidity sensor 79 (step S101), and based on this information, the CPU 71 calculates the information concerning the volumetric humidity (step S102).
Next, the peak-to-peak voltage Vpp and the duty ratio of the developing bias are determined such that the potential difference Vgo becomes constant regardless of the environmental humidity as shown in the table 1 of
Next, an instruction to output the developing bias with the peak-to-peak voltage Vpp and the duty ratio having been stored in the RAM 73 in step S104 is given to the bias power source 80 (step S105) and an image forming operation is performed (step S106).
In the present embodiment, the two-component developer is exemplarily used as developer, however, the mono-component developer may also be used in applying the present invention.
Next, the second embodiment of the present invention will be described.
In the present embodiment, in addition to the control in the first embodiment in which the peak-to-peak volage Vpp and duty ratio of the developing bias is changed such that the potential difference Vgo is maintained as constant in response to a change in environmental humidity, the potential difference Vback between the charging potential Vd (i.e., the surface potential of the non-image portion) and the DC volage Vdc (i.e. the potential difference Vback that is the absolute value of the difference between the charging potential Vd and the DC volage Vdc) is changed simultaneously. The other configuration is the same as that of the first embodiment and should refer to the first embodiment.
The phenomenon may occur in which the carrier is separated from the developing sleeve 54 and adheres to the photosensitive drum 13Y during application of the developing bias (hereinafter referred to as carrier adhesion). It is desirable that the carrier adhesion does not occur since an occurrence of the carrier adhesion may lead to abrasion of the photosensitive drum 13′ so that the endurance may deteriorate.
The carrier adhesion is greatly correlated with the duty ratio and the potential difference Vback of the developing bias.
As shown in
It is desirable for the potential difference Vback to be set between 50 (V) to 200 (V). The reason why the potential difference Vback should be 50 (V) or higher is that there is a possibility that the fog may easily occur when the potential difference Vback is lower than 50 (V) (for example 0 (V)), taking into consideration the potential stability of non-image portion. On the other hand, the reason why the potential difference Vback should be 200 (V) or lower is that there is a concern of the above described carrier adhesion when the potential difference Vback is higher than 200 (V).
The number of carrier adhesion becomes higher when the duty ratio becomes lower as described above. Therefore, in the first embodiment in which the duty ratio becomes less when the environmental humidity becomes lower, the carrier adhesion deteriorates more when the environmental humidity becomes lower. In contrast, in the present embodiment, the CPU 71 of
Next, the third embodiment of the present invention will be described.
In the first and second embodiments, even if the settings of the peak-to-peak voltage Vpp and the duty ratio, and the DC voltage Vdc of the developing bias are changed in response to a change in the environmental humidity, the charging amount of the toner is not immediately changed, but it gradually changed to the value being adapted to the environment by being agitated in the developing device. Therefore, when the settings of the developing bias are changed, only the developing characteristics are changed with the toner charging amount being the same, so that the densities of respective tones are changed.
For example, when the humidity in the developing device 1 changes from 50% to 30%, while the developing device 1 is in the halt state, the peak-to-peak voltage Vpp and the duty ratio are changed in the settings of the developing bias in next operation state, but the toner in the developing device in the state where the operation is halted is not agitated and the toner charging amount is maintained at the value for the humidity of 50% before the humidity changes.
Therefore, only the settings of developing bias are changed with the toner charging amount being not changed and the developing characteristics of the toner to the photosensitive drum 13 is changed. As a result, the densities of respective tones of the output recording material are changed as shown in the graph of
Therefore, in the present embodiment, the occurrence of a change of tint in a case where the settings of the developing bias are changed is intended to be suppressed. The other configuration is the same as those of the first and second embodiment and should refer to those embodiments.
Even in the first and second embodiments, for example, when the image forming apparatus operates longer in a room in which the humidity is 50%, the temperature in the apparatus rises and the humidity in the developing device gradually changes from 50% to 30%. In this case, the settings of the developing bias are gradually changed according to the change in humidity. Therefore, the density change ΔD is small when the bias is changed. However, when the apparatus is not used at night, for example, the apparatus does not operate for a long time. In such a case, the humidity in the developing device returns to 50% and when the settings of the developing bias are greatly changed at one time in the next operation state, the density change ΔD becomes greater because the toner amount does not change during the operation halt time.
In the present embodiment, the maximum values of the ranges of change in peak-to-peak voltage Vpp and the duty ratio of the developing bias for a single time. When the ranges of change in the developing bias according to the humidity change are greater than the maximum values, the developing bias is changed in multiple times, so that the density change ΔD is reduced when the developing bias is changed.
In the present embodiment, the CPU 71 of
In the second embodiment, the duty ratio is greatly changed in response to the humidity change the next day after the 3000 sheets are output, whereas in the third embodiment, the duty ratio is changed stepwise. In the graph of
Next, the fourth embodiment of the present invention will be described.
In the present embodiment, the change in tint when the settings of the developing bias are changed is intended to be suppressed by changing the settings of the developing bias in response to the environmental humidity only immediately before the image density adjustment control using the density detecting sensor. The other configuration is the same as those of the first, second, and third embodiments and should refer to those embodiments.
The operation of the present embodiment will be described referring to the flowchart of
After outputting a sheet of image (step S201), the humidity in the developing device is detected using the temperature and humidity sensor 79 (step S202). Whether it is necessary to change the settings of the developing bias in response to the humidity in the developing device detected by the temperature and humidity sensor 79 is judged (step S203). When it is judged that it is necessary to change the settings of the developing bias (step S203), whether the present time is immediately before the image density adjustment control, which is performed every 500 sheets is judged (step S204). When it is judged that the present time is immediately before the image density adjustment control (step S204), the settings of the developing bias are changed (step S205), and then the image density adjustment control is performed (step S206).
On the other hand, when it is judged that the present time is not immediately before the image density adjustment control (step S204), the sequence returns to step S202 without changing the developing bias and the humidity in the developing device is detected by the temperature and humidity sensor 79.
Further, when it is judged that it is not necessary to change the settings of the developing bias (step S203), the sequence goes to step S207 where whether the present time is immediately before the image density adjustment control is judged. When it is judged that the present time is immediately before the image density adjustment control (step S207), the sequence goes to step S206 where only the image density adjustment control is performed.
Next, the fifth embodiment of the present invention will be described.
In the third and fourth embodiments, the change in tint when the developing bias is changed can be reduced, however, the influence on the change of the developing bias does not disappear. The problem of the periodic density unevenness is conspicuous when an image with high image printing ratio is output. In contrast, when images with low image printing ratio is dominant, the necessity for changing developing bias is low.
Therefore, the present embodiment has the tint change priority mode, in which the developing bias is not changed even if the humidity in the developing device changes, and the on-surface density unevenness priority mode, in which the developing bias is changed if the humidity in the developing device changes. One of these modes can be freely selected. The other configuration is the same as those of the first, second, third and fourth embodiments and should refer to those embodiments.
In the present embodiment, a button for a user to freely select one of the tint change priority mode and the on-surface density unevenness priority mode is provided on the operation portion of the image forming apparatus 200. The CPU 71 in
In the above respective embodiments, the description is made when the image forming apparatus is a printer. However, the present invention can be applied to a copying machine, a facsimile device, or a multi-function machine with these multiple functions.
In the above respective embodiments, the case where the potential difference Vgo is 1050 (V) is exemplarily described. However, even if the potential difference Vgo is not 1050 (V), as long as the potential difference Vgo is constant regardless of the environmental humidity, the similar effects can be expected. The meaning that the potential difference Vgo is constant regardless of the environmental humidity includes the case where the potential difference Vgo fluctuates with ±5% with respect to the reference value in response to a change in the environmental humidity as long as the relationship is met in which the less the environmental humidity is, the greater the peak-to-peak voltage Vpp is set and the less the duty ratio is set.
For example, in the above first embodiment, the case is exemplarity described in which when the environmental humidity is 80%, the peak-to-peak voltage Vpp is 1400 (V), the potential difference Vgo is 1050 (V), and the duty ratio is 75% (refer to
In the above respective embodiments, the combinations of the environmental humidity, the peak-to-peak voltage Vpp, the duty ratio, and the potential difference Vback are not limited to those indicated in
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Applications No. 2023-096154, filed Jun. 12, 2023 and No. 2024-035619, filed Mar. 8, 2024, which are hereby incorporated by reference herein in their entirety.
Number | Date | Country | Kind |
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2023-096154 | Jun 2023 | JP | national |
2024-035619 | Mar 2024 | JP | national |