JP4240971B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus and an image forming method for performing image forming processing using an electrophotographic system such as a copying machine or a laser beam printer, and a cartridge configured to be detachable from an image forming apparatus main body.
[0002]
[Prior art]
FIG. 9 is a schematic diagram illustrating a detailed configuration of a conventional image forming apparatus. In the conventional example shown in FIG. 9, a photosensitive drum 100 is used as an image carrier. The photosensitive drum 100 is formed, for example, by forming a photosensitive material layer such as an organic photosensitive material layer on the surface of an aluminum cylindrical substrate, and is driven to rotate. Around the photosensitive drum 100, a charging roller 101, a laser beam scanning optical system (not shown), a developing device 102 as a developing unit, a transfer roller 108, and a cleaner 109 are sequentially arranged.
[0003]
First, after the photosensitive drum 100 is uniformly charged by the charging roller 101, an electrostatic latent image is formed on the photosensitive drum 100 by laser beam scanning light. Then, a visible image is formed by the toner in the developing device 102 in accordance with the electrostatic latent image.
[0004]
The recording medium, that is, the transfer paper P, is transferred at a substantially contact portion between the photosensitive drum 100 and the transfer roller 108, and the image on the transfer paper P is melted and fixed by the fixing device 110.
[0005]
Further, the developing device 102 includes a developing roller 103 as a developer carrying member, a supply roller 105 that supplies a non-magnetic one-component toner (negative polarity) to the developing roller 103, and an agitation that conveys toner in a container to the vicinity of the supply roller 105. A developing blade 104 is provided as a developer regulating member that regulates the amount of toner on the member 106 and the developing roller 103. Note that the developing roller 103 is in contact with the photosensitive drum 100 and is therefore formed of an elastic body. Further, the developing blade 104 is brought into light pressure contact using the spring elasticity of a thin metal plate.
[0006]
Here, a predetermined potential is supplied to the developing roller 103 by the developing bias power source 107 in order to transfer the toner from the developing roller 103 to the photosensitive drum 100 side. Further, a blade bias power source 108 is connected to the developing blade 104 in order to stabilize the charge amount of the toner (see, for example, Patent Document 1). There are various types of blade bias power supplies 108, such as those having the same potential as the development bias power supply 107 and those supplying different potentials.
[0007]
However, in the image forming apparatus using the non-magnetic one-component toner in the above-described conventional example, toner leakage from the developing device 102 may occur, resulting in toner contamination on the image. In particular, when the blade bias power source 108 is set to the same potential as the developing bias power source 107, toner leakage is remarkable.
[0008]
This is because the toner is carried on the developing roller 103 by the charged charge of the toner itself and the physical adhesion force of the developing roller 103. Therefore, when the toner charge amount is not uniform, the toner with a low charge amount is used. Lowering occurred and toner leakage occurred. Further, a detailed investigation of a toner having a low charge amount that has leaked toner revealed that the reversal toner charged to positive polarity and the regular toner charged to negative polarity were aggregated.
[0009]
In addition, the toner charge amount depends on the use situation. For example, when the toner is used after being left for a long period of time, sufficient chargeability may not be obtained at the initial use stage, and toner leakage may deteriorate. there were. Furthermore, unevenness of the halftone image occurred for the same reason.
[0010]
On the other hand, an image forming apparatus in which a blade bias power source is connected to a developing blade has been devised in order to stabilize the charge amount of toner (see Patent Document 1). That is, in the devised image forming apparatus, for example, the developing roller 103 is always supplied with a voltage of −300 V from the developing bias power source 107, and one developing blade 104 is supplied with −400 V from the blade bias power source 108. As a result, a potential difference of about 100 V is generated between the developing roller 103 and the developing blade 104. This stabilizes the toner charge amount and improves toner leakage. There is also an example in which an AC bias is constantly applied to the developing blade (see, for example, Patent Document 2).
[0011]
[Patent Document 1]
Japanese Patent Laid-Open No. 05-011599.
[0012]
[Patent Document 2]
Japanese Patent Laid-Open No. 58-153972.
[0013]
[Problems to be solved by the invention]
However, when the potential difference is provided as shown in the conventional example, the following problems occur.
[0014]
First, during the use of the image forming apparatus, after the formation of about 1500 images, a solid image has thin density and vertical stripes. This phenomenon also appeared as streaky coating defects on the developing roller 103 that passed through the developing blade 104. As a result of observing the developing blade 104, the toner adhered unevenly in the vicinity of the contact portion of the developing blade 104 with the developing roller 103. Due to the adhesion of the toner, the flow of the toner is blocked, resulting in a defective toner coat on the developing roller 103, causing density thinness and vertical streak density unevenness on the image.
[0015]
FIG. 10 is a schematic diagram illustrating a state of a contact portion between a developing roller and a developing blade in a conventional image forming apparatus. In FIG. 10, a case where the potentials of the developing roller 103 (−300 V) and the developing blade 104 (−400 V) are changed will be described. When the toner T frictionally charged by the supply roller 105 reaches the front of the contact portion between the developing roller 103 and the developing blade 104 (near the portion a), the reversal toner (toner charged positively) mixed in the toner layer ) Is attracted to part a on the surface of the developing blade 104 by the influence of the potential difference.
[0016]
In particular, as the potential difference between the developing roller 103 and the developing blade 104 is increased, the reversal toner is attracted, so that the toner sticking to the portion a of the developing blade 104 becomes worse. As the toner adhesion increases, the amount of toner entering before the contact portion between the developing roller 103 and the developing blade 104 (in the vicinity of the portion a) is blocked, so that the toner layer decreases. As a result, the solid image has a low density. Furthermore, since the amount of toner adhered to the portion a of the developing blade 104 differs in the longitudinal direction, vertical streaks occur in addition to the low density.
[0017]
As described in Patent Document 2, when an AC bias is constantly applied to the developing blade, the AC is provided downstream of the contact portion between the developing roller 103 and the developing blade 104 (for example, a portion in FIG. 10). Toner cloud due to bias occurs. The occurrence of the toner cloud causes toner to be scattered unnecessarily, and the inside of the machine is soiled. When an AC bias is applied to the developing blade, the developing roller 103 and the developing blade 104 are in contact with each other, so that an attack sound due to the AC bias is generated.
[0018]
The present invention has been made in view of such circumstances. In addition to preventing toner leakage during image formation, the toner chargeability is stabilized to prevent toner sticking to the developing blade, and halftone image unevenness is achieved. An image forming apparatus, an image forming method, and a cartridge that can prevent occurrence of image defects such as low density, vertical stripes, and the like, and are particularly suitable for preventing toner leakage and image defects during image formation after being left for a long period of time. The purpose is to do.
[0019]
[Means for Solving the Problems]
  The present invention can be realized as an image forming apparatus, for example. The image forming apparatus is in contact with an image carrier, a charging unit that charges the image carrier to a uniform potential, an exposure unit that forms an electrostatic latent image on the charged image carrier, and an image carrier. A rotatable developing roller that forms a toner image using a negative developer on an image carrier on which an electrostatic latent image is formed, and is in contact with the image carrier during image formation; A developing roller having a non-contact state separated from the image carrier during non-image formation, a developing blade for regulating the amount of developer carried on the developing roller, and a bias applied to the developing roller and the developing blade Based on the bias application means, the cumulative number of rotations of the developing roller, and the recording means having an area for recording information of the elapsed time from the time when the developing roller rotated in the previous image formation, and the information recorded in the recording means Bias Setting means for setting a period necessary for uniformly charging the developer by applying a bias by the adding means, and setting by the setting means when the developing roller rotates in a non-contact state before the start of image formation Control means for applying to the bias application means a bias potential difference applied to the developing roller and the developing blade from the bias applying means for a period of time during which the developer is transferred from the developing blade to the developing roller. Features.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0037]
<First Embodiment>
FIG. 1 is a block diagram showing a detailed configuration of the image forming apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the image forming apparatus according to the present embodiment is a reversal development system that visualizes by attaching toner to an exposed portion of an image carrier, and the developer carrier carrying negatively charged toner is imaged. 1 is a one-component image forming apparatus that performs development by contacting a carrier.
[0038]
In FIG. 1, reference numeral 1 denotes a photosensitive drum as an image carrier, which can rotate in the direction of an arrow x. The surface of the photosensitive drum 1 is uniformly charged to a negative polarity by a charging roller 2 that is a primary charger. As the photosensitive drum 1 rotates, the uniformly charged surface is exposed by the exposure device 3. An electrostatic latent image is formed on the exposed portion by eliminating the charged charge.
[0039]
A developing unit 4 transfers toner as a developer to an exposed portion of the electrostatic latent image. As this toner, a non-magnetic one-component toner is used. In this embodiment, a so-called reversal development system for transferring toner to an exposed portion is shown.
[0040]
The toner transferred onto the photosensitive drum 1 is transferred onto the transfer paper P by the transfer roller 5 serving as a transfer charger. The toner remaining on the photosensitive drum 1 without being transferred is removed from the photosensitive drum 1 by the cleaning unit 6. The toner on the transfer paper P is thermally melted by the fixing device 7 and fixed on the transfer paper P to form a permanent image.
[0041]
The developing device 4 includes a developing roller 8 as a developer carrying member, a supply roller 12 that supplies toner to the developing roller 8, a developing blade 9 as a developer regulating member, and a stirring member 13 that conveys toner to the supply roller 12 side. Become.
[0042]
The developing roller 8 can be rotated in the direction of the arrow y by a motor 15 as a driving device. The developing roller 8 performs so-called contact development in which development is performed by contacting the surface of the photosensitive drum 1, but is brought into a non-contact state by a contact / separation mechanism (not shown) during non-image formation. Therefore, it is desirable that the developing roller 8 has elasticity such as rubber. For example, a voltage of about −300 V is supplied to the developing roller 8 from the developing bias power source 10. The toner on the developing roller 8 is transferred to the exposed portion on the photosensitive drum 1 due to the difference between the exposed portion potential on the photosensitive drum 1 and the potential supplied from the developing bias power supply 10.
[0043]
The developing blade 9 is made of a thin metal plate, and is brought into contact contact with the developing roller 8 using the spring elasticity of the thin plate. As the material of the metal thin plate, stainless steel, phosphor bronze, or the like can be used. In this embodiment, a phosphor bronze thin plate having a thickness of 0.1 mm is used as an example. The toner is triboelectrically charged by being rubbed between the developing blade 9 and the developing roller 8 to be charged, and at the same time the layer thickness is regulated. A predetermined voltage is supplied to the developing blade 9 from a blade bias power supply 11.
[0044]
A control device 14 includes a CPU and a ROM, and controls the rotational driving of the developing roller 8 and controls the voltage values of the developing bias power supply 10 and the blade bias power supply 11.
[0045]
Reference numeral 20 denotes an information recording unit for writing and reading information, which is connected to the control device 14 described above. In the information recording unit 20, as the usage status of the developing device 4, the cumulative number of rotations of the developing roller 8 and the time stamp when the developing roller last rotated can be written and updated. FIG. 12 is a configuration diagram of the information storage unit 20 connected to the control device. The information storage unit 20 is configured to have an area for storing information related to the cumulative number of rotations of the developing roller 8 and date / time information that is a time stamp. Further, when the developing device 4 is not in use, the cumulative number of rotations is 0 and the time stamp is not recorded.
[0046]
[toner]
In the one-component developing toner according to the first embodiment of the present invention, the value of the shape factor SF-1 measured by the image analyzer is 100 to 160, and the value of the shape factor SF-2 is 100 to 140. It is preferable. Further, it is more preferable that the value of the shape factor SF-1 is 100 to 140 and the value of the shape factor SF-2 is 100 to 120. Furthermore, by satisfying the above conditions and setting the value of (SF-2) / (SF-1) to 1.0 or less, not only the characteristics of the toner but also matching with the image analysis apparatus is extremely good. It will be something.
[0047]
In addition, SF-1 and SF-2 indicating shape factors used in the present embodiment are randomly sampled 100 toner images enlarged by a magnification of 500 times using FE-SEM (S-800) manufactured by Hitachi, Ltd. Then, the image information is introduced into the image analysis apparatus (Luxex 3) manufactured by Nicole via the interface and analyzed, and the values obtained from the following equations are used as shape coefficients SF-1 and SF-2 in the present embodiment. Defined.
[0048]
SF-1 = {(MXLNG) 2 / AREA} × (π / 4) × 100
SF-2 = {(PERI) 2 / AREA} × (1 / 4π) × 100
Here, AREA indicates the toner projection area, MXLNG indicates the absolute maximum length, and PERI indicates the circumference.
[0049]
Further, the toner shape factor SF-1 indicates the degree of roundness of the toner particles, and gradually becomes indefinite from a spherical shape. SF-2 indicates the degree of unevenness of the toner particles, and the unevenness of the toner surface becomes remarkable.
[0050]
When the above-described shape factor SF-1 exceeds 160, the rolling resistance becomes low, and the torque increases. In addition, since friction increases, frictional heat increases and thermal degradation is likely to occur.
[0051]
In order to increase the transfer efficiency of the toner image, it is desirable that the shape factor SF-2 of the toner particles is 100 to 140, and the value of (SF-2) / (SF-1) is 1.0 or less. . Further, when the shape factor SF-2 of the toner particles is larger than 140 and the value of (SF-2) / (SF-1) exceeds 1.0, the surface of the toner particles is not smooth and a large number of irregularities are formed on the toner. The particles have a tendency to reduce the transfer efficiency from the photosensitive drum to the transfer paper or the like.
[0052]
In particular, when the shape factor SF-1 is 160 or less and the shape factor SF-2 is 140, when a potential difference is provided between the developing blade and the developing sleeve, the toner can be easily separated from the developing blade, preventing blade fusion. Is effective.
[0053]
Further, as the toner particles used in the present embodiment, it is preferable to use a toner particle whose surface is coated with an external additive so that the toner has a desired charge amount. In this sense, the external additive coverage on the toner surface is preferably 5 to 99%, more preferably 10 to 99%.
[0054]
As for the external additive coverage on the toner surface, 100 toner images were randomly sampled using FE-SEM (S-800) manufactured by Hitachi, Ltd., and the image information was sent to the image analysis device (Luxex 3 manufactured by Nicole) via the interface. ). The obtained image information is binarized since the brightness of the toner particle surface portion and the external additive portion are different, and the area SG of the external additive portion and the area of the toner particle portion (including the area of the external additive portion) are also obtained. Divide into ST. And the external additive coverage is
External additive coverage (%) = (SG / ST) × 100
Is calculated by
[0055]
The external additive used in this embodiment preferably has a particle size of 1/10 or less of the weight average diameter of the toner particles from the viewpoint of durability when added to the toner. The particle size of the additive means the average particle size obtained by observing the surface of the toner particles with an electron microscope. As the external additive, for example, the following are used.
[0056]
Metal oxide (aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, zinc oxide, etc.), nitride (silicon nitride, etc.), carbide (silicon carbide, etc.), metal salt (sulfuric acid) Calcium, barium sulfate, calcium carbonate, etc.), fatty acid metal salts (zinc stearate, calcium stearate, etc.), carbon black, silica, etc.
[0057]
In this embodiment, auxiliary particles are externally added to the toner particles (100 parts by weight). The externally added auxiliary particles added 1 part by weight of silica as a negative-polarity external additive and 0.1 part by weight of titanium oxide as a positive-polarity external additive. In particular, when a positive external additive is added, it is possible to adjust the fluidity of the toner and impart chargeability to the toner.
[0058]
These external additives are used in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the toner particles. These external additives may be used alone or in combination. Further, those subjected to hydrophobic treatment are more preferable.
[0059]
When the amount of the external additive is less than 0.01 parts by weight, the fluidity of the one-component developer is deteriorated, and the efficiency of transfer and development is lowered. So-called scattering occurs in which toner is scattered. On the other hand, when the amount of the external additive exceeds 10 parts by weight, an excessive amount of the external additive adheres to the photosensitive drum or the developing roller and deteriorates the chargeability of the toner or disturbs the image.
[0060]
The toner according to the exemplary embodiment is substantially spherically or spindle-shaped and dispersed in islands in a state where the wax component is not compatible with the binder resin in the tomographic observation of the toner particles using a transmission electron microscope (TEM). Preferably it is. By dispersing the wax component as described above and encapsulating it in the toner, it is possible to prevent deterioration of the toner, contamination of the image forming apparatus, and the like. Thereby, it is possible to maintain a good chargeability and form a toner image excellent in dot reproduction over a long period of time. Further, since the wax component acts efficiently during heating, the low-temperature fixability and offset resistance are satisfied.
[0061]
In the present embodiment, as a specific method for observing the tomographic plane of the toner particles, the toner particles can be sufficiently dispersed in a room temperature curable epoxy resin and then cured in an atmosphere at a temperature of 40 ° C. for 2 days. After the effected material was dyed with ruthenium tetroxide and, if necessary, osmium tetroxide, a flaky sample was cut out using a microtome equipped with diamond teeth, and a toner particle fault was measured using a transmission electron microscope (TEM). Observe the morphology. In the present embodiment, it is preferable to use a ruthenium tetroxide dyeing method in order to provide a contrast between materials by utilizing a slight difference in crystallinity between the wax component to be used and the resin constituting the outer shell. It was observed that the toner particles used in the examples of this embodiment had the wax component encapsulated with the outer shell resin.
[0062]
As the wax component according to the present embodiment, a wax component having a maximum endothermic peak in the region of 40 to 130 ° C. at the time of temperature rise in the DSC curve measured by a differential scanning calorimeter is used. Having a maximum endothermic peak in the above temperature range greatly contributes to low-temperature fixing, and effectively exhibits releasability.
[0063]
And when the said maximum endothermic peak is less than 40 degreeC, the self-cohesion force of a wax component will become weak, as a result, high temperature offset resistance will deteriorate and gloss will become high too much. On the other hand, if the maximum endothermic peak exceeds 130 ° C., the fixing temperature becomes high and it becomes difficult to appropriately smooth the surface of the fixed image. It is not preferable. Further, in the case where granulation and polymerization are carried out in an aqueous medium and a toner is directly obtained by the polymerization method, if the maximum endothermic peak temperature is high, problems such as precipitation of a wax component mainly during granulation are not preferable.
[0064]
The maximum endothermic peak temperature of the wax component is measured according to “ASTM D 3418-8”. For the measurement, for example, DSC-7 manufactured by PerkinElmer is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, and an empty pan is set as a control. After the temperature is raised and lowered once to obtain a previous history, measurement is performed at a rate of temperature rise of 10 ° C./min.
[0065]
Specific examples of the wax component include paraffin wax, polyolefin wax, Fischer tropish wax, amide wax, higher fatty acid, ester wax and derivatives thereof, or graft / block compounds thereof.
[0066]
Next, an image forming process performed by the image forming apparatus having the above-described configuration will be described. FIG. 2 is a flowchart for explaining an image forming process procedure of the image forming apparatus according to the first embodiment.
[0067]
First, the image forming apparatus according to the present embodiment is in a print standby state, and receives a print signal from a personal computer (not shown) or the like (step S201). Thereby, the control device 14 reads the cumulative number of rotations of the developing roller 8 from the information recording unit 20 (step S202). Then, the read accumulated rotational speed is compared in the control device 14 (step S203). As a result, when the cumulative number of rotations is 0 (Yes), the process proceeds to the image forming process 1 (step S204).
[0068]
FIG. 3 is a diagram illustrating a sequence between the units in the image forming apparatus performed in the image forming process 1 of step S204 in the flowchart of FIG. As shown in FIG. 3, when the pre-preparation rotation is started, first, the developing roller starts to rotate (step S301). Here, the pre-preparation rotation indicates a state in which the developing roller immediately before image formation is rotating (during non-image formation). In the present embodiment, at the time of non-image formation, the photosensitive drum 1 and the developing roller 8 are separated from each other and are in a non-contact state.
[0069]
As the developing roller rotates in step S301, a DC bias of −300 V is applied to the developing roller 8 from the developing bias power source (step S302). In the blade bias power source, a DC bias of −600 V is applied to the developing blade 9 (step S303).
[0070]
In this embodiment, as an example, by applying −600 V to the developing blade 9 and −300 V to the developing roller 8 at the start of the rotation of the developing roller, the positive polarity reversal toner that causes toner leakage is applied. A potential difference that can be transferred from the developing roller 8 to the developing blade 9 side is supplied. Thereby, the charging uniformity of the toner coated on the surface of the developing roller 8 can be improved, and toner leakage at the start of rotation of the developing roller 8 can be prevented.
In other words, the image forming apparatus according to the present embodiment is characterized in that the potential difference between the developer carrier and the developer regulating unit applied at the start of rotation of the developer carrier is 60 to 500V.
[0071]
After −600 V is applied to the developing blade 9 and −300 V to the developing roller 8 for a moment, the voltages of the developing bias power supply 10 and the blade bias power supply 11 are set to −300 V, which are substantially the same potential, from the rotation before preparation to the image forming area. The process proceeds (step S304).
[0072]
In this embodiment, as an example, the rotation time before preparation in the image forming process 1 is set to 6 seconds, which is longer than the image forming process 2 described later. Also, the time for providing the potential difference was set to 4 sec. This pre-preparation rotation time is a necessary and sufficient value to raise the toner chargeability even after being left for a long period of time so that it can be charged uniformly, thereby further increasing the uniformity of the toner charge amount. It is possible to obtain a good image such as a halftone image having a uniform density. Of course, the pre-preparation rotation time is not limited to this value, and can be freely set in the image forming apparatus to be used. Further, the DC bias applied to the developing blade 9 and the developing roller 8 is not limited to the above value.
[0073]
In the image forming area, image formation is performed by exposure on the photosensitive drum and formation of a toner image (step S305). During this image formation, since the developing roller 8 and the developing blade 9 are substantially at the same potential, some negative polarity external additive is transferred by the charge of the toner layer. However, reversal toner that causes low density and vertical stripes does not adhere to the developing blade.
[0074]
When the exposure to the photosensitive drum is turned off and the image forming area is finished (step S306), the rotation of the developing roller is turned off after entering the rotation after preparation (step S307), the developing bias power is turned off (step S308), and the blade bias power is turned on. The image forming process 1 is completed by turning OFF (step S309).
[0075]
After the image forming process 1 as described above, in step S205 of the flowchart shown in FIG. 2, the information on the accumulated rotation speed and time stamp of the developing roller 8 is updated and written in the information recording unit 20, and then the print standby is performed again. A state is reached (step S206), and a series of image forming processes is completed.
[0076]
If the cumulative number of rotations of the developing roller 8 is other than 0 in step S203 (No), the time stamp when the developing roller 8 is rotated in the previous image forming process stored in the information recording unit 20 is read (step S207). . Then, it is determined whether or not this time stamp is more than 6 hours before the current time (step S208). As a result, when it is determined that it is six hours or more before the current time (Yes), the process proceeds to the image forming process 1 in step S204, the above-described sequence is performed, and the series of flowcharts is completed.
[0077]
In this embodiment, the value to be compared in step S208 is set to 6 hours. However, the value is not limited to this, and can be freely set to 3 hours according to the characteristics of the image forming apparatus to be used and the toner. May be.
[0078]
On the other hand, in step S208, when the time stamp read from the information recording unit 20 is within 6 hours from the current time (No), the process proceeds to the pre-preparation rotation of the image forming process 2 starting from step S209.
[0079]
FIG. 4 is a diagram illustrating a sequence between the units in the image forming apparatus performed in the image forming process 2 in step S209 in the flowchart of FIG. In the sequence of FIG. 4, the rotation time before preparation in the image forming step 1 is about 2 seconds, and the time when the bias potential difference between the developing roller 8 and the developing blade 9 applied at the start of the rotation before preparation is provided is about 500 msec. It is a thing. Further, other bias setting values, conditions at the time of image formation region and rotation after preparation, and the like were the same as those in the image forming step 1.
[0080]
The pre-preparation rotation time in this image forming step 2 is the minimum necessary time before reaching the image forming area, and the time when the potential difference is provided also corresponds to this. Of course, the rotation time before preparation and the time for providing the potential difference are not limited to this, but it is desirable to make them as short as possible. As a result, it is possible to avoid unnecessarily increasing the printing time when the toner chargeability is sufficient and the risk of toner leakage is small.
[0081]
After the image forming process 2 in step S209 is completed, the information about the cumulative rotation speed of the developing roller 8 and the time stamp is updated and written in the information recording unit 20 (step S205), and the print standby state is again entered (step S205). Step S206), a series of image forming processing is completed.
[0082]
In the image forming process 1 in step S204 and the image forming process 2 in step S209 in the present embodiment, a non-image forming area called “inter-sheet space” between image formations when printing a plurality of sheets is also the same bias as the image forming area. The voltage was set to approximately the same potential by applying −300 V from each of the developing bias power source and the blade bias power source. This value is not limited to this value. For example, the potential difference may be provided by applying −300 V from the developing bias power source and −600 V from the blade bias power source as in the case of the rotation before preparation. As a result, the negative-polarity external additive that can adhere to the developing blade 9 in the image forming area can be transferred again to the developing roller 8.
[0083]
That is, in the image forming apparatus according to the present embodiment, the potential difference between the developer carrying member provided at the start of rotation of the developer carrying member and the developer regulating member is such that the developer regulating member has a larger amount of developer than the developer carrying member. It is characterized by being large on the same polarity side as the charging polarity.
[0084]
Similarly, during the rotation after preparation, a potential difference may be provided between the developing roller and the developing blade by changing the developing bias power source and the blade bias power source. In step S204, the blade bias power source is instantaneously switched from −600 V to −300 V. However, the switching is not limited to this as long as the blade bias power source is switched within the non-image forming time, and the blade bias power source may be switched in a slope shape. Also good. The timing at which the potential difference is provided between the developing blade 9 and the developing roller 8 is set at the time of non-image formation. When the potential difference is applied from the same potential, the toner carrying amount regulated on the developing roller 8 changes. This is because a density step occurs on the image.
[0085]
That is, the image forming apparatus according to the present embodiment includes an image carrier (photosensitive drum 1), a charging unit (charging roller 2) that charges the image carrier to a uniform potential, and a charged image carrier. An exposure means (exposure device 3) for forming an electrostatic latent image; a developing means (developing device 4) for forming a toner image using a developer on the image carrier on which the electrostatic latent image is formed; and a toner image A recording unit (information recording unit 20) having an area for recording predetermined information referred to when the toner image is formed, and control for controlling a toner image forming process by the developing unit based on the predetermined information recorded in the recording unit Means (control device 14).
[0086]
In the image forming apparatus according to the present embodiment, the developing unit regulates the rotatable developer carrying member (developing roller 8) carrying the developer and the amount of developer carried on the developer carrying member. Developer regulating means (developing blade 9) and bias applying means (developing bias power supply 10, blade bias power supply 11) for applying a bias to the developer carrying member and developer regulating means are provided, and the control means is developer carrying At the start of rotation of the body, for a period based on predetermined information recorded in the recording means (for example, whether 6 hours or more have passed since the previous rotation), the developer carrying body and the developer regulating means with respect to the bias applying means A bias having a predetermined potential difference is applied between the two.
[0087]
Next, in the image forming apparatus according to the first embodiment, a comparative example in the case of the following configuration will be shown.
[0088]
[Comparative Example 1]
In the processing by the image forming apparatus according to the first embodiment, the developing roller 8 is set to −300V and the developing blade 9 is set to −400V during image formation and non-image formation in the image forming process 1 and the image forming process 2. A potential difference was provided.
[0089]
[Comparative Example 2]
In the processing by the image forming apparatus according to the first embodiment, the bias applied to the developing roller 8 and the developing blade 9 is all set to the same potential (−300 V) during image formation and non-image formation.
[0090]
[Comparative Example 3]
In the processing by the image forming apparatus according to the first embodiment, reference to the information recording unit 20 is not performed, and the sequence of the image forming process 2 is used at the time of all image formation.
[0091]
With respect to the first embodiment and Comparative Examples 1 to 3, the presence or absence of toner leakage was evaluated using the image forming apparatus after being left for one week in a high-temperature and high-humidity environment with an air temperature of 30 ° C. and a humidity of 80%. At the same time, image defects (half-tone density unevenness, image density thinness and verticalness) when 2000 sheets are output under normal usage conditions (temperature 23 ° C., humidity 50%, 4% printing rate image 200 sheets / day). The occurrence of streak) was evaluated.
[0092]
FIG. 11 is a diagram illustrating a comparison result of the occurrence of an image defect due to an image forming process under other conditions with the image forming apparatus according to the first embodiment. As shown in FIG. 11, the comparative evaluation result is indicated by “◯” when there is no toner leakage and image defect (halftone density unevenness, thin image density and vertical stripe), and “X” when toner leakage and image defect respectively occur.
[0093]
From these comparison results, in the image processing apparatus according to the first embodiment, toner leakage did not occur even in the initial state or image output after being left for one week. In addition, a good image with uniform density was obtained even with a halftone image. Even in the case of continuous print output, a good print image was obtained without unnecessarily increasing the rotation time before preparation.
[0094]
On the other hand, in Comparative Example 1, there was no occurrence of toner leakage, but an image defect with low density and vertical stripes occurred. In Comparative Example 2, there was no occurrence of light density and vertical stripes, but toner leakage occurred. As for Comparative Example 3, only the halftone density unevenness occurred in the initial image and the print output after being left for 6 hours or more.
[0095]
Regarding the result of Comparative Example 1, since a potential difference is provided between the developing roller 8 and the developing blade 9 during image formation and non-image formation, the reverse toner is attracted and fixed to the developing blade, and the toner is blocked. As a result, thin density and vertical streaks occurred.
[0096]
As for the result of Comparative Example 2, toner fixing did not occur because the developing roller 8 and the developing blade 9 were at the same potential. However, the toner charge amount was uneven and contained a large amount of reversal toner, and was left for one week. Toner leakage occurred after or during initial use.
[0097]
Further, as for the result of Comparative Example 3, since the toner chargeability did not rise sufficiently at the time of initial use and at the time of print output after being left for 6 hours or more, no toner leakage occurred. Image defects occurred as unevenness.
[0098]
As described above, in this embodiment, in the image forming apparatus including the information recording unit 20 for recording and referring to information, the developing roller 8 and the developing blade 9 are applied by bias application at least when the developing roller 8 starts to rotate. And the elapsed time from the previous image formation is referred to by the information recording unit 20, and the rotation time of the developing roller 8 during non-image formation is made variable according to the elapsed time.
[0099]
This makes it possible to adopt a sequence that reliably prevents toner leakage in the most severe situation with respect to toner leakage, which is image formation after standing for a long time, and avoids unnecessarily prolonging image formation time. Can do. Further, even after being left for a long period of time, uniform toner chargeability can be obtained and a good image can be provided. Further, by preventing the toner from sticking to the developing blade 9, it is possible to prevent the occurrence of a vertical streak image due to this.
[0100]
<Second Embodiment>
Next, an image forming apparatus and the like according to the second embodiment of the present invention will be described.
[0101]
FIG. 5 is a schematic cross-sectional view of a cartridge (process cartridge) that can be attached to and detached from the image forming apparatus according to the second embodiment of the present invention. In FIG. 5, the same parts as those in the image forming apparatus according to the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0102]
The feature of this embodiment is that, in the image forming apparatus described in the first embodiment, at least the developing device 4 and the information recording unit 20 are integrally incorporated in the cartridge container, and the image forming apparatus main body is The process cartridge 99 is detachable. In FIG. 5, the photosensitive drum 1, the charging roller 2, the developing unit 4, and the cleaning unit 6 are integrated to form a process cartridge 99.
[0103]
This process cartridge 99 is mounted on an image forming apparatus main body (not shown) provided with a motor 15 and a control device 14 for rotationally driving the photosensitive drum 1 and the developing roller 8, an exposure device 3, a transfer roller 5, a fixing device 7, and the like. Installed.
[0104]
An electrostatic latent image is formed on the photosensitive drum 1 uniformly charged by the charging roller 2 in the process cartridge 99 by the exposure device 3 provided in the main body of the image forming apparatus, and then the toner image is developed by the developing device 4. Is formed. The toner image formed on the photosensitive drum 1 is transferred onto the transfer paper P by the transfer roller 5 provided in the image forming apparatus main body, and is fixed by the fixing device 7 to become a permanent image. The transfer residual toner that is not transferred onto the transfer paper P and remains on the photosensitive drum 1 is removed by the cleaning unit 6 in the process cartridge 99.
[0105]
The information recording unit 20 is connected to the control device 14 by being mounted in the main body of the image forming apparatus, and can write and read information.
[0106]
By performing the sequence described in the first embodiment on the image forming apparatus main body and the process cartridge 99 described above, the image density due to toner leakage at the start of rotation of the developing roller 8 and toner adhesion to the developing blade. Thin and vertical stripes can be prevented, and a good image can be stably obtained.
[0107]
In addition, since the structure is detachable from the main body of the image forming apparatus, it is possible to provide a process cartridge having excellent maintainability.
[0108]
<Third Embodiment>
FIG. 6 is a schematic diagram showing the configuration of an image forming apparatus according to the third embodiment of the present invention. The image forming apparatus according to the third embodiment is capable of color image formation, and mainly includes a photosensitive drum 1 as an image carrier, a charging roller 2 as a charging unit, an exposure device 3 for providing image information, and a photosensitive drum 1. The image forming apparatus includes a developing unit 22 that visualizes the upper electrostatic latent image and an intermediate transfer member 24.
[0109]
The developing device 22 includes a rotary 22x as a rotating support, a yellow developing device 22a, a magenta developing device 22b, a cyan developing device 22c, and a black developing device 22d, and each includes information recording units 20a, 20b, 20c, and 20d. .
[0110]
That is, the image forming apparatus according to the present embodiment is an electrophotographic color printer, and includes four colors of yellow Y, magenta M, cyan C, and black Bk based on image data from a personal computer (not shown) or a workstation. The toner images of each color are sequentially formed from the separated image data based on the separated image data, and the toner images are superimposed on an intermediate transfer member and transferred onto a transfer material (recording medium) such as paper to obtain a full color image. Note that the image forming apparatus (color printer) in the present embodiment is a so-called rotary type color printer that employs a developing device in which a plurality of developing means, that is, developing devices are mounted in a rotary.
[0111]
In FIG. 6, the color printer includes a photoconductive organic photosensitive drum 1 as an image carrier, and the photosensitive drum 1 is rotationally driven in the direction of an arrow q. The surface of the photosensitive drum 1 is uniformly charged to a predetermined dark portion potential by applying a bias to the core of the charging roller 2 as a contact charging unit. Next, scanning exposure is performed with a laser beam that is ON / OFF controlled by the exposure device 3 in accordance with yellow (Y) image data of the first color, and a first electrostatic latent image is formed as a bright portion potential. Is done.
[0112]
The electrostatic latent image formed in this way is developed and visualized by developing means (developing device) mounted in the rotary 22x of the developing device 22. The rotary 22x includes a first developing device 22a in which yellow (Y) toner is included as a first color toner, a second developing device 22b in which magenta (M) toner is included as a second color toner, A third developing device 22c containing cyan (C) toner as a third color toner and a fourth developing device 22d containing black (Bk) toner as a fourth color toner are integrated and integrated. Thus, when an image of each color is formed, it is rotated to the position opposite to the photosensitive drum (in the direction of arrow r in FIG. 6).
[0113]
In the developing unit located at the developing position facing the photosensitive drum 1, a developing roller as a developer carrying member carrying toner regulated to a predetermined layer thickness is rotationally driven by a motor 23. Development is performed by applying a predetermined bias to the core metal. The Y, M, C, and Bk developing devices 22a, 22b, 22c, and 22d are detachable from the color printer as a single cartridge (developing cartridge), and are individually provided by consumption of toner contained therein and consumption of each member. It is possible to replace it.
[0114]
First, the first electrostatic latent image is developed and visualized by the first developing cartridge 22a containing Y toner as the first color toner. Any developing method can be used regardless of contact or non-contact. In this embodiment, as in the first embodiment, image exposure and reversal development are combined, and contact with nonmagnetic one-component toner having high sphericity is achieved. Development method is used.
[0115]
This visualized toner image of the first color is a surface layer having releasability from the conductive elastic layer on the cylinder at the first transfer site which is the nip portion with the intermediate transfer member 24 as the second image carrier. Electrostatic transfer (primary transfer) to the surface of the intermediate transfer member 24 formed from
[0116]
The intermediate transfer member 24 has a peripheral length longer than the length of the maximum transfer material that can be passed, and is approximately in contact with the peripheral speed of the photosensitive drum 1 while being pressed against the photosensitive drum 1 with a predetermined pressing force. The photosensitive drum 1 is rotationally driven in a direction opposite to the rotation direction of the photosensitive drum 1 (each in the direction of arrow s in FIG. 6 and in the same direction at the contact portion) with a high peripheral speed. As described above, the toner image formed on the surface of the photosensitive drum 1 is applied with a voltage (primary transfer bias) having a polarity opposite to the charging polarity of the toner to the cylinder portion of the intermediate transfer member 24. As a result, electrostatic transfer (primary transfer) is performed on the surface of the intermediate transfer member 24.
[0117]
The toner remaining on the surface of the photosensitive drum 1 after the primary transfer is removed by the cleaning unit 6 to prepare for the next latent image formation.
[0118]
Thereafter, the same process is repeated, and each time, the second color toner image developed with M toner, the third color toner image developed with C toner, and the fourth color toner image developed with Bk toner. However, a color toner image is formed by sequentially transferring and laminating on the surface of the intermediate transfer body 24.
[0119]
Thereafter, the transfer belt 18 that has been separated from the surface of the intermediate transfer member 24 is pressed against the surface of the intermediate transfer member 24 with a predetermined pressing force and is driven to rotate. A transfer roller 17 is included in the transfer belt 18. By applying a voltage (secondary transfer bias) having a polarity opposite to the charging polarity of the toner to the transfer roller 18, the surface of the intermediate transfer body 24 is transferred to the surface of the transfer paper P conveyed at a predetermined timing. The color toner images stacked on the sheet are collectively transferred (secondary transfer), and the transfer paper P is conveyed to the fixing device 7.
[0120]
The transfer paper P is discharged to the outside after the toner image is fixed as a permanent image by the fixing device 7, and a desired color print image is obtained. Further, the toner remaining on the surface of the intermediate transfer member 24 after the secondary transfer is removed by the intermediate transfer member cleaning device 16 that comes into contact with the surface of the intermediate transfer member 24 at a predetermined timing.
[0121]
FIG. 7 is a configuration diagram illustrating developing cartridges 22a, 22b, 22c, and 22d that respectively store Y, M, C, and Bk toners that are developing units in the image forming apparatus according to the third embodiment. The developing cartridges 22a to 22d can be attached to and detached from the rotary color printer as the image forming apparatus shown in FIG. 6 by opening and closing a developing cartridge replacement cover (not shown). In FIG. 6, it is assumed that the cyan developing cartridge 22c at the take-out position can be taken out in the upward arrow D direction.
[0122]
In the rotary type color printer shown in FIG. 6, it is necessary to attach and detach the developing cartridge at the take-out position, and 22a, 22b and 22d which are Y, M and Bk developing cartridges other than the cyan developing cartridge 22c in FIG. When exchanging the developing cartridge, it is necessary to rotate the rotary 22x to rotate the developing cartridge to be taken out to the attachment / detachment position (position 22c in FIG. 6).
[0123]
The configuration of the image forming apparatus and the image forming operation according to the present embodiment will be described below with reference to FIGS.
[0124]
The developing cartridge 22a in the image forming apparatus of the present embodiment shown in FIG. 7 is a reversal developing device that contains a non-magnetic one-component Y toner as a developer. The developing cartridge 22a is in contact with the photosensitive drum 1 and rotates in the direction of arrow e in FIG. 7 to perform development while rotating, and the toner is rotated in the direction f in FIG. 7 by the developing roller 8a. A supply roller 12a as a toner supply means supplied by the toner, a developing blade 9a as a toner regulating means for regulating the toner application amount and the charge amount on the developing roller 8a, an agitating member 13a for agitating and supplying toner to the supply roller 12a It has. An information recording unit 20a that records the cumulative number of rotations of the developing roller and the time stamp of the previous image formation is provided on the outer surface of the developing cartridge 22a. The developing cartridges 22b, 22c, and 22d have the same configuration.
[0125]
FIG. 8 is a flowchart for explaining an image forming process procedure in the image forming apparatus (color printer) of the third embodiment.
[0126]
First, when a print output request is received from a personal computer (not shown), the color printer in the print standby state receives a print signal (step S401). Then, from the information recording units 20a, 20b, 20c, and 20d included in the developing cartridges 22a to 22d, as information on the usage status of the developing cartridges 22a to 22d, the cumulative number of rotations of the developing roller is the control device of the image forming apparatus body. 21 is read and referred to (step S402).
[0127]
Next, as a result of referring to the cumulative number of rotations of each developing roller (step S403), for a developing cartridge whose cumulative number of rotations is 0 (Yes), a toner start-up sequence is performed (step S404).
[0128]
The toner start-up sequence in step S404 is to rotate the developing roller of the developing cartridge during non-image formation and apply a bias that provides a potential difference between the developing roller and the developing blade at least when the developing roller starts rotating by bias applying means. It is. In this embodiment, the rotation time of the developing roller is 10 seconds, and the potential difference between the developing roller and the developing blade starts to be applied in synchronization with the rotation of the developing roller, and is continuously applied for 8 seconds. However, the rotation time of the developing roller and the time for providing the potential difference are not limited to this time. Thereafter, a temporary standby is performed to synchronize with other developing cartridges (step S405).
[0129]
If the cumulative number of rotations is not 0 (No) as a result of referring to the cumulative number of rotations of the developing roller in step S403, the time stamp when the previous developing roller rotated stored in the information recording unit is read (step S409). Then, it is determined whether or not the time stamp is at least 8 hours before the current time (step S410). As a result, when it is determined that the previous time is 8 hours or more (Yes), the process proceeds to the toner start-up sequence in step S404, and the same sequence as the above-described process is performed. Thereafter, a temporary standby is performed to synchronize with other developing cartridges (step S405).
[0130]
On the other hand, if the time stamp read from the information recording unit in step S410 is within 8 hours from the current time (No), the process directly proceeds to the standby state in step S405.
[0131]
In this embodiment, the value to be compared is set to 8 hours in step S410. However, the value is not limited to this time, and can be set freely according to the characteristics of the image forming apparatus to be used and the toner. Good.
[0132]
These toner start-up sequences can set an arbitrary developing roller rotation time for each developing device even when it is necessary to synchronize the image formation timing in each developing device of a full-color printer, and the difference in toner chargeability Can be adjusted. Further, by providing a potential difference between the developing roller and the developing blade at the start of rotation of the developing roller, toner leakage can be prevented even after leaving for a long time.
[0133]
Note that the processing from step S402 to S405 is performed for each developing cartridge. Thereafter, when all the developing cartridges are in a standby state (step S405), an image forming process is performed (step S406).
[0134]
Here, the image forming process in step S406 in the present embodiment uses the sequence of the image forming process 2 in the first embodiment described above for each developing device.
[0135]
That is, the photosensitive drum 1 rotates, and the rotary revolution is started so that the developing device 22a for the first color is brought to face the photosensitive drum 1. When the first color (yellow) developing device 22a comes to the position opposite the photosensitive drum, the developing roller 8a starts pre-preparation rotation, and the first color image forming process is started. Simultaneously with the start of the pre-preparation rotation of the developing roller 8a, voltage is supplied from the developing bias power source 25 and the blade bias power source 26, and a potential difference is provided between the developing roller 8a and the developing blade 9a.
[0136]
At this time, a voltage of about −300 V is applied from the developing bias power source 25 and a voltage of −600 V is applied from the blade bias power source. The time for applying −600 V to the blade bias power source is 500 msec, and thereafter, the blade bias power source is switched to −300 V, which is the same potential as the developing bias power source.
[0137]
Note that the pre-preparation rotation time in the image forming process of the present embodiment is 2 sec, which is the minimum necessary time before reaching the image forming area.
[0138]
In addition, image formation on the photosensitive drum 1 is performed during the start and end of on-drum exposure by the exposure device 3, and the developing roller and the developing blade are substantially at the same potential in the image forming area.
[0139]
When the first color image forming area is completed, the developing device is rotated after preparation, and then the rotation of the developing roller 8a is stopped, the first color image forming process is completed, and the process proceeds to the second color (magenta) image forming process. Rotary revolution to do. Note that, after the preparation, as for the voltages from the rotating developing bias power supply and blade bias power supply, the same bias as that in the image forming area is continuously applied, and the rotation of the developing roller 8a is stopped and the bias application is also 0V.
[0140]
Next, the revolution of the rotary is completed, and the second color (magenta) developing device 22 b stops at the position facing the photosensitive drum 1. Then, the developing roller 8b starts pre-preparation rotation, and the second color image forming process is performed in the same manner as the first color image formation. Thereafter, the above operation is performed up to the fourth color.
[0141]
Thereafter, the rotation of the developing roller is turned off, and the developing bias power supply and blade bias power supply are also turned off, and the image forming process up to the fourth color is completed.
[0142]
In the flowchart shown in FIG. 8, when the image forming process in the color printer in step S406 is completed, the intermediate transfer member 24, the photosensitive drum 1 and the like are rotated rearward of the main body for the next printing (not shown). Further, the cumulative number of rotations of the developing roller and the time stamp are updated in the information recording units 20a, 20b, 20c, and 20d provided in the developing cartridges 22a to 22d, and new writing is performed (step S407). Thereafter, when the post-rotation of the main body is finished, the photosensitive drum 1 is stopped and is again in a print standby state (step S408), and a series of image forming processes is finished.
[0143]
As a result of performing the sequence in the image forming apparatus (full color printer) according to the present embodiment described above, it is possible to prevent toner leakage at the start of rotation of the developing roller and image density thinning and vertical stripes due to toner adhesion to the developing blade, A stable and good image can be obtained. Further, among the components of the image forming apparatus, the developing means including toner, which is relatively exhausted, is a process cartridge that can be attached to and detached from the image forming apparatus main body, thereby reducing the labor of the user involved in various maintenance operations. Can be achieved.
[0144]
<Other embodiments>
Note that the present invention can be applied to a system constituted by a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), but an apparatus (for example, a copying machine, a facsimile machine, etc.) comprising a single device. You may apply to.
[0145]
Also, an object of the present invention is to supply a recording medium (or storage medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and a computer (or CPU or CPU) of the system or apparatus. Needless to say, this can also be achieved when the MPU) reads and executes the program code stored in the recording medium. In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiment, and the recording medium on which the program code is recorded constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.
[0146]
Further, after the program code read from the recording medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the card or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.
[0147]
When the present invention is applied to the recording medium, program code corresponding to the flowchart described above is stored in the recording medium.
[0148]
【The invention's effect】
  As explained above, according to the present invention,In the system in which development is performed with the developing roller in contact with the image carrier, the developing roller is rotated in a non-contact state with the image carrier, and based on the information recorded on the recording means. A bias having a predetermined potential difference is applied between the developing roller and the developing blade for the set period. As a result, the charging uniformity of the developer coated on the surface of the developing roller is improved, and the initial use of the developing roller and after being left for a long timeToner leakage during image formationTheWhile preventingCurrentPrevents image blades from sticking toner and prevents image defects such as uneven halftone image, low density, and vertical stripes.The Further, when the toner is sufficiently charged and the risk of toner leakage is small, it is possible to avoid unnecessarily lengthening the image formation time.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a detailed configuration of an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a flowchart for explaining an image forming process procedure of the image forming apparatus according to the first embodiment;
FIG. 3 is a diagram showing a sequence between respective units in the image forming apparatus performed in image forming step 1 in step S204 in the flowchart of FIG.
4 is a diagram showing a sequence between respective units in the image forming apparatus performed in image forming step 2 in step S209 in the flowchart of FIG.
FIG. 5 is a schematic sectional view of a process cartridge that can be attached to and detached from an image forming apparatus according to a second embodiment of the present invention.
FIG. 6 is a schematic diagram illustrating a configuration of an image forming apparatus according to a third embodiment of the present invention.
FIG. 7 is a configuration diagram illustrating developing cartridges 22a, 22b, 22c, and 22d that respectively store Y, M, C, and Bk toners that are developing units in an image forming apparatus according to a third embodiment.
FIG. 8 is a flowchart for explaining an image forming process procedure in an image forming apparatus (color printer) according to a third embodiment;
FIG. 9 is a schematic diagram illustrating a detailed configuration of a conventional image forming apparatus.
FIG. 10 is a schematic diagram illustrating a state of a contact portion between a developing roller and a developing blade in a conventional image forming apparatus.
FIG. 11 is a diagram showing a comparison result of occurrence of image defects due to image forming processing under other conditions with the image forming apparatus according to the first embodiment.
FIG. 12 is a configuration diagram of an information storage unit 20 connected to the control device.
[Explanation of symbols]
1 Photosensitive drum
2 Charging roller
3 Exposure unit
4, 22 Developer
8 Development roller
9 Development blade
10 Development bias power supply
11 Blade bias power supply
14 Control device
20, 20a, 20b, 20c, 20d Information recording section
22a Yellow developer
22b Magenta developer
22c Cyan developer
22d Black developer
99 process cartridge

Claims (8)

An image carrier;
Charging means for charging the image bearing member to a uniform potential;
Exposure means for forming an electrostatic latent image on the charged image carrier;
A rotatable developing roller that forms a toner image by using a negative developer on the image carrier on which the electrostatic latent image is formed in contact with the image carrier, and at the time of image formation A developing roller having a contact state in contact with the image carrier and a non-contact state in which the image carrier is separated during non-image formation ;
A developing blade for regulating the amount of developer carried on the developing roller;
Bias applying means for applying a bias to the developing roller and the developing blade;
A recording unit having an area for recording information on an accumulated rotational speed of the developing roller and information on an elapsed time from the time when the developing roller was rotated in the previous image formation ;
Setting means for setting a period necessary for uniformly charging the developer by applying a bias by the bias applying means based on information recorded in the recording means ;
When the developing roller rotates in the non-contact state before the start of image formation, a bias potential difference applied to the developing roller and the developing blade from the bias applying unit for the period set by the setting unit. An image forming apparatus comprising: a control unit that causes the bias applying unit to apply a bias of a potential difference at which the developer transfers from the developing blade to the developing roller . 2. The image according to claim 1, further comprising a developing device including the developing roller, the developing blade, and the recording unit, the developing device being detachable from an apparatus main body of the image forming apparatus. Forming equipment. A process cartridge comprising a photosensitive drum as the image carrier, the charging unit, the developing roller, the developing blade, and the recording unit, and further comprising a process cartridge that is detachable from the apparatus main body of the image forming apparatus. The image forming apparatus according to claim 1, further comprising: A plurality of developing rollers ;
Yellow, magenta, with cyan and 4 colors of developer black, image forming apparatus according to claim 1 or 2, characterized in that to form a toner image for each color. The developer, an image forming apparatus according to any one of the things nonmagnetic is a component toner from claim 1 to 4. The image forming apparatus according to claim 1 , wherein the bias applied by the bias applying unit is larger on the negative side of the developing blade than the developing roller . Said potential difference, the image forming apparatus according to claim 1 or 6, characterized in that it is 60～500V. Said bias application means, during image formation, the image forming apparatus according to claim 1, wherein the bias applied the developing roller to said developing blade is substantially the same potential.

Images