JP2018077410A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can reduce a load on a cleaning blade and efficiently recover lubricant without largely affecting the environment.SOLUTION: An image forming apparatus comprises: photoreceptor drums 41 that respectively carry toner images to be transferred to a sheet; cleaning blades 47 that respectively clean and remove toner attached to the photoreceptor drums by bringing the cleaning blades into contact with the photoreceptor drums; lubricant application mechanisms 48 that respectively supply lubricant to the photoreceptor drums; charging devices 46 that respectively adjust the amount of charge of the toner attached to the photoreceptor drums; prediction means that predicts the amount of lubricant on the surfaces of the photoreceptor drums; determination means that determines whether the amount of lubricant on the surfaces of the photoreceptor drums predicted by the prediction means is larger than a predetermined amount; and control means that, when the amount of lubricant on the surfaces of the photoreceptor drums is determined by the determination means to be larger than the predetermined amount, reduces the output of the charging devices compared with a case where the amount of lubricant on the surfaces of the photoreceptor drums is equal to or less than the predetermined amount and forms an inter-image patch.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, as a means for removing residual toner such as untransferred toner and transfer residual toner on an image carrier, for example, a flat cleaning blade made of an elastic body is used as the image carrier. There is known a blade cleaning type cleaning blade that comes into contact with the surface of the toner and thereby removes residual toner on the image carrier.

  In recent years, in an electrophotographic image forming apparatus, there has been a demand for reducing the particle size of toner particles from the viewpoint of high image quality. Examples of methods for obtaining such toner particles include an emulsion polymerization method and a suspension polymerization method. The polymerization method is used. However, since the adhesion between the toner particles and the image carrier increases as the particle size of the toner particles decreases, it becomes difficult to remove the residual toner on the image carrier. In particular, when a so-called polymerized toner produced by a polymerization method is used, the shape of the toner particles becomes close to a sphere, so that the toner particles roll on the image carrier and pass through a cleaning blade, so-called “suriken”. There is a problem that a cleaning defect called “Frequency” tends to occur, and it becomes more difficult to remove the residual toner on the image carrier. Furthermore, toner aggregates are formed on the image carrier with the toner passing through the blade as a core, and granular white spots (granular noise) may occur in the solid image printing portion.

In order to cope with such quality problems such as “slipping” and “granular noise”, at present, a lubricant is supplied onto the image carrier, and cleaning is performed in a state where adhesion between the toner particles and the image carrier is reduced. ing. As a method of supplying the lubricant onto the image carrier, there is a lubricant coating method in which a brush is brought into contact with a solid lubricant obtained by solidifying the lubricant in a rod shape, the lubricant is scraped off with the brush, and supplied to the surface of the image carrier.
The lubricant application method has a merit that the amount of lubricant supplied to the surface of the image carrier can be easily increased by setting the brush rotation speed high, and quality problems due to lack of lubricant are less likely to occur. On the other hand, if the amount of lubricant on the surface of the image carrier is excessively increased, the adhesion between the cleaning blade and the image carrier is increased, which promotes wear of the cleaning blade and causes a problem that the life of the cleaning blade is shortened. Thus, it is necessary to control the amount of lubricant on the surface of the image carrier to an appropriate amount without excess or deficiency.

By the way, the lubricant applied on the image carrier is polished by particles accumulated in the cleaning device using a cleaning blade or the like by particles accumulated in the toner or external additives detached from the lubricant, and wears from the image carrier. I will do it. For this reason, even if the lubricant is applied evenly on the entire surface of the image carrier from the lubricant application mechanism, there are the following problems.
That is, depending on the image pattern to be formed, if an image with a large amount of white portions continues, the amount of toner and external additives accumulated on the cleaning blade in that portion decreases, and the amount of lubricant on the image carrier increases. Become.
Further, when the cumulative total image area ratio (overall coverage) to be formed is low, the toner consumption amount of the developing device is reduced and the toner replenishment amount is also reduced. Since the supply of new toner is reduced, the same toner is held in the developing unit for a long time. The toner held in the developing unit for a long period of time gradually releases the external additive due to the stress in the developing unit, so that the amount of the external additive held by the toner held for a long period of time decreases. If an image having a low image area ratio is continuously formed, the amount of the external additive held by the toner accumulated in the cleaning blade is reduced and the amount of lubricant wear is reduced. As a result, the amount of lubricant accumulated on the image carrier increases.
Further, the lubricant is easily spread on the image carrier at a high temperature and becomes a layer. In this state, it is difficult to be collected by the cleaning blade as compared with the case where it exists in the form of powder, the wear amount of the lubricant is reduced, and the amount of lubricant on the image carrier is increased.

  In order to solve the problem that the amount of lubricant on the image carrier is excessive as described above, a technique for improving the recoverability of the lubricant by increasing the charge amount of the toner is disclosed (for example, Patent Document 1). In other words, in order to remove the deteriorated lubricant adhering to the image carrier, the charge amount of the toner is increased by the charge amount adjusting means, the electrostatic adhesion force between the image carrier and the toner is increased, and the image is recovered at the time of recovery by the cleaning blade. The frictional force acting between the carrier and the toner is increased. This increases the force acting on the recovery of the lubricant and increases the recovery amount of the lubricant.

Japanese Patent Laid-Open No. 2006-114915

  However, in the configuration in which the charge amount of the toner is increased as in Patent Document 1, the load of the cleaning blade is increased, and there is a possibility that wear of the cleaning blade is promoted. Moreover, since discharge in the charging device is promoted as the amount of charge increases, there is a concern about an increase in the amount of ozone generated.

  The present invention has been made in view of the above problems, and provides an image forming apparatus capable of efficiently recovering a lubricant without reducing the load on the cleaning blade and without greatly affecting the environment. Objective.

In order to solve the above problem, an image forming apparatus according to claim 1 is provided.
An image carrier for carrying a toner image to be transferred to paper;
Developing means for developing a toner image on the image carrier;
Transfer means for transferring the toner image formed on the image carrier to a sheet;
Cleaning means for cleaning and removing the toner adhering to the image carrier by bringing a cleaning blade into contact with the image carrier;
A charge amount adjusting unit that is arranged on the downstream side of the transfer unit and the upstream side of the cleaning unit in the rotation direction of the image carrier, and adjusts the charge amount of the toner attached to the image carrier;
A collecting unit that is disposed on the downstream side of the charge amount adjusting unit and the upstream side of the cleaning unit in the rotation direction of the image carrier, and collects toner attached to the image carrier;
A supply unit disposed on the downstream side of the transfer unit in the rotation direction of the image carrier and supplying a lubricant to the image carrier;
Predicting means for predicting the amount of lubricant on the surface of the image carrier;
Determining means for determining whether or not the amount of lubricant on the surface of the image carrier predicted by the predicting means is greater than a predetermined amount;
When it is determined by the determining means that the amount of lubricant on the surface of the image carrier is larger than the predetermined amount, the charge amount adjusting means is more than when the amount of lubricant on the surface of the image carrier is not more than the predetermined amount. And a control unit that causes the developing unit to form an inter-image patch.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
The prediction means calculates a cumulative total image area ratio at an arbitrary timing during image formation, predicts a lubricant amount on the surface of the image carrier based on the cumulative total image area ratio,
The determining means determines that the amount of lubricant on the surface of the image carrier is larger than the predetermined amount when the cumulative total image area ratio is smaller than a predetermined value.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect,
The predicting means calculates a partial image area ratio at an arbitrary timing during image formation for each partial image divided in the rotation axis direction of the image carrier, and the image carrier surface based on the partial image area ratio Predict the amount of lubricant
The determination means determines that the amount of lubricant in the region corresponding to the partial image in the surface of the image carrier is larger than the predetermined amount when the partial image area ratio is smaller than a predetermined value;
The control unit causes the developing unit to form the inter-image patch only on an area of the surface of the image carrier on which the determination unit determines that the amount of lubricant is larger than the predetermined amount. Features.

According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects,
A detecting means for detecting a temperature inside the image forming apparatus at an arbitrary timing during image formation;
The predicting means predicts the amount of lubricant on the surface of the image carrier based on the temperature detected by the detecting means,
The determining means determines that the amount of lubricant on the surface of the image carrier is larger than the predetermined amount when the temperature is higher than the predetermined temperature.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects,
The control means stops the output of the charge amount adjusting means and causes the developing means to apply an inter-image patch when the determining means determines that the amount of lubricant on the surface of the image carrier is larger than the predetermined amount. Is formed.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects,
A detecting means for detecting a temperature inside the image forming apparatus at an arbitrary timing during image formation;
The prediction means predicts an increase or decrease in the amount of lubricant on the surface of the image carrier in response to an increase or decrease in temperature detected by the detection means,
The control means increases the image area ratio of the inter-image patch when the predicting means predicts that the amount of lubricant on the surface of the image carrier increases as the temperature rises when the inter-image patch is formed. When the prediction means predicts that the amount of lubricant on the surface of the image carrier has decreased as the temperature decreases, the image area ratio of the inter-image patch is decreased.

  According to the present invention, it is possible to provide an image forming apparatus capable of efficiently recovering a lubricant without reducing the load on the cleaning blade and without greatly affecting the environment.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment to which the present invention is applied. 2 is a block diagram illustrating a main functional configuration of the image forming apparatus. FIG. It is a figure which shows an example of schematic structure of an image formation part. It is a figure which shows an example of a longitudinal belt chart. It is a figure which shows an example of the comparison of the lubricant amount on a photoreceptor drum. It is a figure which shows an example of a mode that the latent image writing area | region on the photoconductive drum was divided | segmented. It is a figure which shows an example of the comparison of the lubricant amount on a photoreceptor drum. It is a figure which shows an example of the comparison of the lubricant amount on a photoreceptor drum. 3 is a flowchart illustrating an operation of the image forming apparatus. It is a figure which shows an example of a partial patch. It is a figure which shows an example of schematic structure of an image formation part. It is a figure which shows an example of schematic structure of an image formation part. It is a figure which shows an example of a horizontal belt chart and a vertical belt chart.

Hereinafter, an embodiment of the image forming apparatus of the present invention will be described with reference to the drawings. In the embodiment of the present invention, a color image forming apparatus will be described as an example. However, the present invention is not limited to this, and can be applied to, for example, a monochrome image forming apparatus.
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a main functional configuration of the image forming apparatus 1.

  As shown in FIGS. 1 and 2, the image forming apparatus 1 includes an automatic document feeder 2, a scanner unit 3, an image forming unit 4, a paper feeding unit 5, a storage unit 6, an operation display unit 7, And a control unit 10.

The automatic document transport unit 2 includes a placement tray on which the document D is placed, a mechanism for transporting the document D, a transport roller, and the like, and transports the document D to a predetermined transport path.
The scanner unit 3 includes an optical system such as a light source and a reflecting mirror. The scanner unit 3 irradiates the document D conveyed on a predetermined conveyance path or the document D placed on the platen glass, and receives reflected light. . The scanner unit 3 converts the received reflected light into an electrical signal and outputs the electrical signal to the control unit 10.

  The image forming unit 4 includes a yellow image forming unit Y, a magenta image forming unit M, a cyan image forming unit C, a black image forming unit K, and a fixing device F.

FIG. 3 is a diagram illustrating a schematic configuration of the image forming unit 4.
Each image forming unit includes a drum-shaped photosensitive drum 41 (image carrier) that is rotationally driven in the direction a in the figure, a charging device 42 that uniformly charges the surface of the photosensitive drum 41, and the charging device. An exposure device 43 that exposes the surface of the photosensitive drum 41 charged by 42 to form an electrostatic latent image, and an electrostatic latent image formed by the exposure device 43 using a developer 442 containing toner. A developing device 44 (developing unit) that makes a visible image, a transfer device 45 (transfer unit) that transfers a toner image formed on the photosensitive drum 41 to a sheet, and charge to the photosensitive drum 41 and the transfer residual toner. The charging device 46 (charge amount adjusting means) to be applied, the cleaning blade 47 (cleaning means) for removing the toner on the photosensitive drum 41 that has passed through the transfer region, and the toner adhering to the surface of the photosensitive drum 41 are collected. While Agents and lubricants applying mechanism 48 for applying the (supply means) provided with a photosensitive drum a toner image formed on 41 to the primary transfer to the intermediate transfer belt 451 to move in the drawing direction b.
The toner image transferred to the intermediate transfer belt 451 is transferred to a recording material at a secondary transfer position (not shown), and then conveyed to the fixing device F and fixed on the recording medium.

  The photosensitive drum 41 is made of an organic photoreceptor in which a photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of a drum-shaped metal substrate, for example, as a resin constituting the photosensitive layer, for example, polycarbonate Resins, silicone resins, polystyrene resins, acrylic resins, methacrylic resins, epoxy resins, polyurethane resins, vinyl chloride resins, melamine resins, and the like.

As the charging device 42, a charging roller is used to charge the photosensitive drum 41 to a constant potential. As the charging device 42, a corotron charger, a scorotron charger, or the like can be used.
After charging by the charging device 42, an electrostatic latent image is formed on the surface of the photosensitive drum 41 by an exposure device 43 such as a laser.

The developing device 44 includes a developing sleeve 441 disposed so as to face the photosensitive drum 41 with a developing area interposed therebetween. For example, a DC developing bias having the same polarity as the charging polarity of the charging device 42 or a developing bias in which a DC voltage having the same polarity as the charging polarity of the charging device 42 is superimposed on the AC voltage is applied to the developing sleeve 441. Thus, reversal development is performed in which toner is attached to the electrostatic latent image formed by the exposure device 43.
The developer 442 used in the developing device 44 includes toner and a carrier for charging the toner. The toner is not particularly limited, and a commonly used toner can be used, and a colorant and, if necessary, a charge control agent or a release agent are contained in the binder resin, and an external additive is used. Can be used. The particle size of the toner is not particularly limited but is preferably 3 to 15 μm.
The toner image formed on the photosensitive drum 41 by the developing device 44 is conveyed to a transfer region formed between the intermediate transfer belt 451 and the toner image. In the transfer area, a voltage having a polarity opposite to that of the toner is applied to the transfer roller 452, and the toner image on the photosensitive drum 41 is transferred onto the intermediate transfer belt 451.

  The toner remaining on the photosensitive drum 41 without being transferred onto the intermediate transfer belt 451 in the transfer region is conveyed to the charging device 46. The charging device 46 is constituted by a corotron charger, for example, and applies a charge to the photosensitive drum 41 and the transfer residual toner. That is, by aligning the polarity of the transfer residual toner including the weakly charged / reversely charged toner and charging the surface of the photosensitive drum 41 to the same polarity, an electrostatic repulsive force is generated between the photosensitive drum 41 and the residual transfer toner. Work and make it easier to collect. At this time, a DC bias having the same polarity as the charging polarity of the charging device 42 or a bias in which a DC voltage having the same polarity as the charging polarity of the charging device 42 is superimposed on an AC voltage can be applied. The effect of aligning the polarity of the transfer residual toner is excellent.

The untransferred toner after passing through the charging device 46 is collected by a flat cleaning blade 47 made of an elastic material. The photosensitive drum 41 from which the toner on the surface has been collected by the cleaning blade 47 is charged again by the charging device 42 to repeat the formation of the next electrostatic latent image and the toner image.
As physical properties of the cleaning blade 47, the rebound resilience and hardness are important. The rebound resilience is preferably 10 to 80% at a temperature of 25 ° C., more preferably 30 to 70%. The JIS A hardness is preferably 20 to 90 °, particularly preferably 60 to 80 °. When the JIS A hardness is less than 20 °, the cleaning blade 47 is too soft and the blade is likely to turn up. On the other hand, when the JIS A hardness is greater than 90 °, it becomes difficult to follow slight irregularities and foreign matter on the photosensitive drum 41, and toner particles are likely to be “slipped”.

In the rotational direction of the photosensitive drum 41, a lubricant application mechanism 48 for applying a lubricant to the photosensitive drum 41 is installed downstream of the contact portion with the intermediate transfer belt 451 and upstream of the cleaning blade 47. . The lubricant application mechanism 48 includes at least a lubricant application brush 481 and a solid lubricant 482.
The lubricant application brush 481 is installed in contact with both the solid lubricant 482 and the photoreceptor drum 41, and supplies lubricant particles scraped from the solid lubricant 482 to the photoreceptor drum 41. At that time, it also serves as a collecting means for collecting the toner on the surface of the photosensitive drum 41 by the contact pressure. Note that a sponge or the like can be used instead of the lubricant application brush 481.

The rotation direction of the lubricant application brush 481 may be either the width direction (direction in which the surface moves in the same direction) or the counter direction (direction in which the surface moves in the reverse direction) with respect to the photosensitive drum 41. From the viewpoint of spreading the lubricant particles on the photosensitive drum 41 as much as possible, the counter direction is preferable. FIG. 3 shows a configuration in the counter direction.
The rotational speed of the lubricant application brush 481 is controlled by changing the rotational speed of the motor. Increasing the rotation speed increases the coating amount, and decreasing it decreases the coating amount. When the number of rotations is increased, the amount of toner / external additive recovered from the photosensitive drum 41 is increased, and when the number of rotations is decreased, the amount of toner / external additive recovered is decreased.

A lubricant application part cleaning member 483 may be provided downstream of the contact position with the photosensitive drum 41 and upstream of the contact position with the solid lubricant 482 in the rotational direction of the lubricant application brush 481. The lubricant application part cleaning member 483 recovers the toner and external additives collected from the photosensitive drum 41 by the lubricant application brush 481 by contact with the photoreceptor from the surface of the lubricant application brush 481. By cleaning the surface of the lubricant application brush 481, the next scraping from the solid lubricant 482 and the recovery of the toner / external additive from the photosensitive drum 41 are surely executed.
The lubricant application portion cleaning member 483 in FIG. 3 has a blade shape, but is not limited thereto. What is necessary is just to be able to clean the surface of the lubricant application brush 481, and for example, a rotary member that contacts the lubricant application brush 481 and a scraper that peels off the toner / external additive from the surface of the rotary member may be used.

  As the material of the solid lubricant 482, a material that can be applied to the surface of the photosensitive drum 41 and that can reduce the surface energy to reduce the adhesion between the toner and the photosensitive drum 41 is selected. Examples include fatty acid metal salts, fluorine-based resins and the like, and these can be used alone or in admixture of two or more. In particular, fatty acid metal salts are preferred. As the fatty acid metal salt, as the fatty acid, a linear hydrocarbon is preferable, and for example, myristic acid, palmitic acid, stearic acid, oleic acid and the like are preferable, and stearic acid is more preferable. Examples of the metal include lithium, magnesium, calcium, strontium, zinc, cadmium, aluminum, cerium, titanium, and iron. Of these, zinc stearate, magnesium stearate, aluminum stearate, iron stearate and the like are preferred, and zinc stearate is most preferred. The above material is melted and molded, or particles of the above material are compression molded to prepare a shape that can be scraped off by the lubricant application brush 481 and used as a solid lubricant 482.

  The paper feed unit 5 includes a plurality of paper feed trays 51 to 53, and stores a plurality of different types of paper P in the paper feed trays 51 to 53. The paper feed unit 5 feeds the paper P stored in a predetermined transport path to the image forming unit 4.

  The storage unit 6 includes an HDD (Hard Disk Drive), a semiconductor memory, and the like, and stores data such as program data and various setting data in a readable / writable manner from the control unit 10. In addition, the storage unit 60 stores a partial image area ratio Cn (partial coverage) for each segment C1 to Cn (see FIG. 6) in a past fixed period, which will be described later, a minimum value Cmin of an image ratio for each segment C1 to Cn, and a segment C1 to C1. The accumulated total image area ratio Call (total coverage) calculated by the total sum of Cn, various threshold values, and the like are stored.

The operation display unit 7 is configured by, for example, a liquid crystal display (LCD) with a touch panel, and functions as the display unit 71 and the operation unit 72.
The display unit 71 displays various operation screens, operation states of functions, and the like according to a display control signal input from the control unit 10. In addition, a touch operation by the user is received and an operation signal is output to the control unit 10.
The operation unit 72 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 10. The user can operate the operation display unit 7 to perform settings relating to image formation such as image quality setting, magnification setting, application setting, output setting, and paper setting, a paper conveyance instruction, and a device stop operation.

  The control unit 10 includes a CPU, a RAM, a ROM, and the like. The CPU expands various programs stored in the ROM to the RAM, and cooperates with the expanded various programs, so that the automatic document conveying unit 2, The operation of each unit of the image forming apparatus 1 such as the scanner unit 3, the image forming unit 4, the paper feeding unit 5, the storage unit 6, the operation display unit 7 and the like is comprehensively controlled (see FIG. 2). For example, the control unit 10 receives the electrical signal from the scanner unit 3 and performs various image processing, and outputs the image data Dy, Dm, Dc, Dk of each color of YMCK generated by the image processing to the image forming unit 4. . The control unit 10 controls the operation of the image forming unit 4 to form an image on the paper P.

Next, a method for predicting the amount of lubricant on the photosensitive drum 41 will be described.
The image forming apparatus 1 according to the present embodiment accumulates the image area ratio / image pattern information in the storage unit 6 and predicts the amount of lubricant on the photosensitive drum 41 based on accumulated data for a certain period.
The amount of lubricant on the photosensitive drum 41 after 3000 sheets of the vertical band chart as shown in FIG. 4 was printed on A4 paper was measured. The amount of lubricant was substituted by the ratio of zinc in zinc stearate determined by an X-ray photoelectron spectrometer. FIG. 5 shows the measurement results obtained by changing the vertical band width of FIG. 4 according to each image area ratio. As is clear from FIG. 5, when the amount of lubricant in the vertical belt portion and the non-longitudinal belt portion is compared, the amount of lubricant on the photosensitive drum 41 in the white portion is large. Further, comparing the low image area ratio (low coverage) and the high image area ratio (high coverage) in FIG. 5, it can be seen that the low image area ratio has a larger amount of lubricant.
Therefore, the amount of lubricant on the photosensitive drum 41 can be predicted by calculating the image area ratio. As the image area ratio, there are two ways of thinking: a partial image area ratio and a cumulative total image area ratio.

  In this embodiment, the latent image writing area on the image carrier is divided in the main scanning direction, that is, the direction orthogonal to the rotation direction of the surface of the photosensitive drum 41, and a plurality of divided areas (segments) (C1 to Cn). ) The image ratio is calculated every time. FIG. 6 shows an example of division into N segments in the main scanning direction. The image ratio is calculated from the latent image writing information for each of the divided segments. For example, in the case of an image as shown in FIG. 6, the image ratio is 100% in the segments Ci to Cj, and the image ratio is 50% in the other segments. In this way, the partial coverage of each segment may be calculated from the image ratio of each segment in the image forming area.

  In order to control with higher accuracy, between the images, the development unit regardless of the area including the outside of the image forming area such as various printing modes to maintain the image quality, that is, the image portion / background portion It is preferable that the image ratio is calculated for the entire region during the period in which is operating, and this is used as the partial coverage. What is counted as the image portion is not limited to the image forming area, but includes image patches that are printed for various purposes during various printing modes and between images.

The overall coverage Call is an image ratio obtained from the sum of all the segments C1 to CN. The total coverage is preferably calculated from the entire area including the outside of the image forming area.
Although it is possible to predict the average amount of lubricant on the photoconductor from the accumulated total image area ratio Call and to control the average amount of lubricant on the photoconductor drum 41, it is more preferable that the rotation direction of the photoconductor is determined by the partial image area ratio Cn. It is preferable to predict the amount of lubricant in each of the plurality of segments divided in the direction orthogonal to the control and control the amount of lubricant in each segment on the photosensitive member, that is, to control not for the entire photosensitive drum 41 but for each segment.

As the threshold value Ca for determining whether or not Cn is a low image area ratio, an area ratio of 15% or less, more preferably 5% or less is suitable. The larger the value, the more reliably the amount of lubricant can be suppressed, and the smaller the value, the more the toner consumption can be saved. As the number of segments N increases, the amount of lubricant can be reliably suppressed even if Ca is reduced. What is necessary is just to set suitably according to the number N of segments, and the state of an actual apparatus.
The timing of image-to-image patch formation based on the image area ratio may be controlled every predetermined number of sheets, but it is preferable to always control.

Next, the operation of the charging device 46 will be described.
Using the image forming apparatus 1 of FIG. 1, the effect of the charging device 46 on the toner recoverability in the lubricant application mechanism 48 and the amount of lubricant on the photosensitive drum 41 was tested.
FIG. 7 shows the recovery rate of the toner on the photosensitive drum 41 of the lubricant application brush 481.
The amount of toner remaining on the photosensitive drum 41 before and after contacting the lubricant application brush 481 is adjusted when the transfer device is adjusted and the transfer residual toner adhesion amount is about 1.5 g / m ² and the charging device 46 is turned on and off. Measured and calculated the toner recovery rate of the lubricant application brush 481.
When the charging device 46 is turned on in this experiment, the photosensitive member surface potential is about −350 V, and the negatively charged toner can obtain a high recovery rate due to the bias effect with the lubricant application brush 481. On the other hand, when the charging device 46 is turned off, the surface potential of the photosensitive member becomes + ten or less V and the bias effect with the lubricant application brush 481 is small and the toner recovery rate remains low.

FIG. 8 shows the amount of lubricant in the area corresponding to the solid portion of the photosensitive drum 41 after the A4 / 3000 sheets of the vertical band chart as shown in FIG.
The amount of lubricant on the photoreceptor was substituted by the ratio of zinc in zinc stearate obtained by an X-ray photoelectron spectrometer. It can be seen that the amount of lubricant on the photoconductor in the solid portion is smaller when the charging device 46 is turned off than when the charging device 46 is turned on. As shown in FIG. 7, the toner recovery rate of the lubricant application brush 481 is reduced by turning off the charging device 46, and the amount of toner reaching the cleaning blade 47 is increased. By improving.

Further, in order to increase the amount of toner reaching the cleaning blade 47, it is desirable to form an inter-image patch.
In the image forming apparatus 1 according to the present invention, the image forming apparatus 1 is provided in an area different from the normal image forming area corresponding to the original image (between the image forming area and the next image forming area) or different from the normal image forming area. In the operation mode, a control mechanism (not shown) having a patch image forming function for forming a toner image (patch image) can be provided. However, in consideration of the influence on productivity, a normal image is obtained. It is desirable to form patch images (inter-image patches) between the formed images. The toner used for forming the normal toner image and the patch image has the same configuration.

Specifically, with respect to the patch image forming method, the exposure device 43 selectively irradiates light onto a region on the surface of the photosensitive drum 41 that is uniformly charged by the charging device 42 and should be developed. It is assumed that a solid image is formed by attaching toner to the exposure area by the device 44.
The patch image to be formed on the photoconductive drum 41 is preferably at least the same as or larger than the image forming area in the normal image forming process in the axial direction of the photoconductive drum 41.

  Furthermore, as shown in FIG. 8, the amount of lubricant on the photosensitive member varies depending on the environmental temperature, so it is desirable to change the image area ratio of the patch between images according to the environmental temperature. L and H indicate environmental temperatures. In this example, the L environment indicates 10 ° C. and the H environment indicates 30 ° C. When the particulate lubricant supplied to the photosensitive member is spread on the photosensitive member, the higher the temperature, the lower the lubricant hardness and the spreading property, so that the amount of lubricant on the photosensitive drum 41 is higher. Will increase. That is, it is possible to predict the amount of lubricant on the photoreceptor by measuring the in-machine temperature.

Therefore, in the present invention, when it is predicted that the amount of lubricant on the photosensitive drum 41 is large using the effect of the charging device 46 on the amount of lubricant on the photosensitive drum 41, an inter-image patch is formed, The output of the charging device 46 is reduced or stopped. As a result, the amount of toner reaching the cleaning blade 47 is increased, and the amount of lubricant on the photosensitive drum 41 is more effectively reduced.
Further, the image area ratio of the inter-image patch is controlled according to the in-machine temperature detected by the temperature sensor A (detection means) disposed in the vicinity of the photosensitive drum 41, and the higher the temperature, the more the inter-image patch. Control to increase the image area ratio.

Next, the lubricant recovery control of the image forming apparatus 1 according to the first embodiment will be described using the flowchart of FIG.
When printing is started, the control unit 10 calculates a partial image area ratio (partial coverage) for each of the segments C1 to CN as a prediction unit (step S901), and based on this, the accumulated total image area ratio (total coverage: Call) is calculated (step S902). Next, the temperature sensor A detects the in-machine temperature T (step S903).

  Next, the control unit 10 determines whether or not the overall coverage Call is equal to or less than a predetermined threshold value CA (step S904). When it is determined that the overall coverage Call is not CA or less (Step S904: No), the control unit 10 proceeds to Step S909, but when it is determined that the entire coverage Call is CA or less (Step S904: Yes), The control unit 10 turns off the charging device 46 as a control means (step S905).

  Next, in step S906, the control unit 10 determines whether or not the detected temperature T is equal to or higher than a predetermined threshold value Ta. If it is determined that the detected temperature T is equal to or higher than Ta (step S906: Yes), the control unit 10 serves as a determination unit. It is determined that the amount of lubricant on the drum is large, and an inter-image patch (horizontal band patch) having an image area ratio C ′ = C′a is formed as control means (step S907), and the process proceeds to step S914. When the control unit 10 determines that the detected temperature T is lower than the threshold Ta (step S906: No), the control unit 10 forms a horizontal band patch with an image area ratio C ′ = C′b as a control unit (step S908). ), The process proceeds to step S914. The horizontal band patch is a type of inter-image patch, and is a toner image formed over substantially the entire length of the photosensitive drum 41 in the axial direction of the photosensitive drum 41. Further, C′a> C′b.

  When the control unit 10 determines in step S904 that Call ≦ CA is not satisfied (step S904: No), the control unit 10 determines, as a determination unit, the partial coverage Cn of each segment of C1 to CN that is equal to or less than a predetermined threshold value Ca. It is determined whether or not (step S909). When the control unit 10 determines that the partial coverage Cn is not equal to or less than the threshold value Ca for all segments (step S909: No), the process proceeds to step S914, but it is determined that there is a segment satisfying the partial coverage Cn ≦ Ca. When it does (step S909: Yes), the control part 10 turns off the charging device 46 as a control means (step S910).

  Next, in step S911, the control unit 10 determines whether or not the detected temperature T is equal to or higher than a predetermined threshold value Ta, and if it is determined that Ta ≦ T (step S911: Yes), the control unit 10 as a determination unit, It is determined that the amount of lubricant in the region corresponding to the segment where the partial coverage Cn on the photosensitive drum 41 is equal to or less than Ca is large, and an image-to-image patch (partial patch) having an image area ratio C ″ = C ″ a as control means. Is formed in the area (step S912), and the process proceeds to step S914. When the control unit 10 determines that Ta ≦ T is not satisfied (step S911: No), the control unit 10 forms a partial patch with an image area ratio C ″ = C ″ b in the above-described region as a control unit (step S911). S913), the process proceeds to step S914. The partial patch is a kind of inter-image patch, and is a toner image formed on only a part of the photosensitive drum 41 in the axial direction as shown in FIG. C ″ a> C ″ b.

  In step S914, the next page is printed, and the process returns to step S901, and the same control is performed for the page.

As described above, the image forming apparatus 1 according to the present embodiment divides a toner image to be formed into a plurality of segments in the direction of the rotation axis of the photosensitive drum 41, and calculates overall coverage and partial coverage. If the overall coverage is less than or equal to a predetermined threshold, a horizontal band patch is formed.
Therefore, according to the image forming apparatus 1 of the present embodiment, when it is determined that the overall coverage is small and the amount of lubricant on the photoconductive drum 41 is large, the recovery efficiency of the lubricant is improved by forming the horizontal band patch. Can be improved. Further, the amount of toner in the inter-image patch necessary for suppressing the cleaning blade wear can be reduced, which is economical.

  Further, when there is a segment in which the overall coverage exceeds a predetermined threshold and the partial coverage is equal to or less than the predetermined threshold, a partial patch is formed only in a portion where the partial coverage is small. Accordingly, it is possible to prevent the lubricant from being excessively collected in the portion where the lubricant on the photosensitive drum 41 is small, and to efficiently recover the portion where the amount of the lubricant is large.

  In this embodiment, the amount of lubricant recovered is changed depending on the temperature. That is, the higher the temperature in the machine, the easier the lubricant is spread and applied onto the photosensitive drum 41. Therefore, the higher the temperature is, the larger the image area ratio of the patch between images can be to improve the recovery efficiency of the lubricant. .

  In the present embodiment, the charging device 46 is turned off when forming the inter-image patch. As a result, the amount of toner collected by the lubricant application brush 481 can be suppressed, and the amount of lubricant collected by the cleaning blade 47 can be increased.

  Further, in the present embodiment, the formation control of the inter-image patch is performed every time one sheet is printed. Thus, the lubricant is calculated by calculating the image area ratio for each sheet and performing the control corresponding thereto. The collection accuracy can always be kept high.

[Other Embodiments]
As mentioned above, although concretely demonstrated based on embodiment which concerns on this invention, said embodiment is a suitable example of this invention, and is not limited to this.

  For example, in the above-described embodiment, the charging device 46 is turned off when forming the patch between images. However, the present invention is not limited to this, and a configuration in which the output reduction rate is changed according to the image area ratio may be used.

  In the above-described embodiment, the threshold temperature Ta for the in-machine temperature is provided, and the image area ratio of the inter-image patch can be adjusted in two stages by comparison with the threshold Ta. However, the present invention is not limited to this. . For example, a configuration in which a plurality of threshold values are provided and control is possible in multiple stages, and a control table that increases the image area ratio of the inter-image patch in proportion to the temperature is created in advance, and the image area ratio is determined according to the detected temperature. It is good also as a structure.

In the above embodiment, the lubricant application mechanism 48 is provided on the upstream side of the cleaning blade 47 in the rotation direction of the photosensitive drum 41 as shown in FIG. 3, but the photosensitive drum of the cleaning blade 47 is shown in FIG. A lubricant application mechanism 48 may be provided on the downstream side in the rotational direction of 41.
In this case, a fixing blade 484 is generally provided on the downstream side of the photosensitive drum 41 of the lubricant application mechanism 48. The fixing blade 484 is installed for the purpose of spreading and applying the lubricant supplied onto the photosensitive drum 41 by the lubricant applying mechanism 48 on the photosensitive drum 41 and eliminating excessive lubricant particles. As the material of the fixing blade 484, like the cleaning blade 47, a flat blade made of an elastic body is representative. In this case, a toner collection brush 491 (collection means) made of the same material as the lubricant application brush 481 and a toner collection unit cleaning member 492 are installed on the upstream side of the cleaning blade 47, so that the upstream side of the cleaning blade 47. Toner recovery can be assisted.
Alternatively, as shown in FIG. 12, a developer 442 obtained by externally adding lubricant particles to toner may be used to supply the lubricant particles together with the toner to the photosensitive drum 41 by the developing device 44. Similarly in this case, it is desirable to install a toner collection brush 491 (collection means) and a toner collection unit cleaning member 492.

  In order to confirm the effect of the present invention, the effect was verified using the image forming apparatus 1 shown in FIG.

(Device configuration)
(1) Photosensitive drum 41
As the photoreceptor drum 41, a drum-shaped organic photoreceptor having a photosensitive layer made of polycarbonate resin and having a thickness of 25 μm formed on the outer peripheral surface of a drum-shaped metal substrate made of aluminum was used. The photosensitive drum 41 rotates at 40 mm / sec.
(2) Developing device 44
The developing device 44 includes a developing sleeve 441 that is rotationally driven at a linear velocity of 600 mm / min. A bias voltage having the same polarity as the surface potential of the photosensitive drum 41 is applied to the developing sleeve 441 and is reversed by a two-component developer. What was developed was used.
(3) Transfer device 45
As an intermediate transfer member, an endless intermediate transfer belt 451 made of a polyimide resin imparted with conductivity is used. The intermediate transfer belt 451 is pressed against the photosensitive drum 41 via the intermediate transfer belt 451. A transfer roller 452 for applying a voltage is provided.
(4) Charging device 46
Using a corotron charger utilizing corona discharge, AC: 6000 V / 1 kHz was superimposed on DC: -2000 V.
(5) Cleaning blade 47
The cleaning blade 47 was made of urethane rubber having a rebound resilience of 50% (25 ° C.), a JIS A hardness of 70 °, a thickness of 2.00 mm, a free length of 10 mm, and a width of 324 mm. The cleaning blade 47 was set so that the contact load with respect to the photosensitive drum 41 was 20 N / m and the contact angle was 15 °.
(6) Lubricant application mechanism 48
The lubricant application brush 481 uses a conductive fur brush: conductive polyester fiber, the brush hair length is 3 mm, and the diameter of the roller is 14 mm. It rotates in the same direction (with direction) with respect to the photosensitive drum 41, and the relative speed θ is 0.5.
The solid lubricant 482 is pressed and held against the lubricant application brush 481 by a compression spring. For the solid lubricant 482, zinc stearate is used.
(7) Toner The toner constituting the two-component developer is composed of toner particles having a volume average particle diameter of 6.5 μm produced by an emulsion polymerization method, and has negative chargeability. Silica and titania fine particles are externally treated.

(Image pattern)
As shown in FIG. 13, charts having different total image area ratio: Call and difference between the maximum value and the minimum value of the partial image area ratio: ΔC were created and divided with the number of segments N = 12. In the case of the horizontal band chart as shown in FIG. 13A, ΔC is 0%, and in the case of the vertical band chart as shown in FIG. 13B, ΔC is 100%.
The cumulative total image area ratio was set to 5%, 10%, and 15%, and 20000 sheets were run on each side of A4. In the case of a horizontal band chart such as ΔC: 0%, the accumulated total image area ratio is changed by the width in the photosensitive member rotation direction, and in the case of a vertical band chart such as ΔC: 100%, it is orthogonal to the photosensitive member rotation direction. Changed in the width of the direction. A half image was printed after running 5000 sheets, and the presence or absence of occurrence of lubricant pattern noise (image noise) was evaluated according to the evaluation criteria described later.
Furthermore, the wear width (BL wear) of the cleaning blade was measured after the end of running 20000 sheets, the life of the cleaning blade was calculated from the value, and evaluated according to the evaluation criteria described later.

(Evaluation criteria)
For image noise, the in-plane density difference in the half image was measured. In the transmission density, a density difference of 0.1 or less was marked with ◯, and a density exceeding 0.1 was marked with x. X-Rite 310TR was used for image density measurement.
Regarding the BL wear, the BL wear width after the end of running 20000 sheets was evaluated as “○” when the width was 10 μm or less, and “×” when it exceeded 10 μm. When the lifetime of the cleaning blade is 500,000 prints and the upper limit of the BL wear width that can ensure cleaning is 50 μm, the BL wear width when printing 20000 sheets is 10 μm.

(Experiment 1)
<Comparative Example 1>
Does not form patch between images.
The environment is N environment: 20 ° C.
<Comparative example 2>
When the cumulative total image area ratio is 15% or less, an inter-image patch (horizontal band patch) is formed. The image area ratio of the patch between images was equivalent to 5% and equivalent to 10%.
When the inter-image patch is formed, the charging device 46 is operated in the same manner as in the normal image formation.
The environment is N environment: 20 ° C.
<Example 1>
When the cumulative total image area ratio is 15% or less, an inter-image patch (horizontal band patch) is formed. The image area ratio of the patch between images was equivalent to 5% and equivalent to 10%.
When the inter-image patch is formed, the charging device 46 is stopped.
The environment is N environment: 20 ° C.

As shown in Table I, in Comparative Example 1, both of Call = 5% and Call = 10%, lubricant pattern noise and cleaning blade wear occurred at ΔC: 100%, and cleaning blade wear occurred at ΔC: 0%. .
In Comparative Example 2, when the toner from the inter-image patch is supplied to the cleaning blade 47 and the lubricant recoverability is improved, when Call = 5%, the image area ratio of the inter-image patch is equivalent to 10%, and ΔC: 0% The wear of the cleaning blade can be suppressed. Further, when Call = 10%, the cleaning blade wear of ΔC = 0% can be suppressed when the image area ratio between images is equivalent to 5%.
In the first embodiment, due to the effect of increasing the amount of toner reaching the cleaning blade 47 by stopping the charging device 46 during the patch between images, when Call = 5%, the image area ratio between images is equivalent to 5%. ΔC: 0% cleaning blade wear can be suppressed, and compared with Comparative Example 2, the amount of toner consumed in patch between images for the cleaning blade wear suppression can be reduced. Further, when the image-to-image patch image area ratio is 10%, the cleaning blade wear can be suppressed even when ΔC is 100%.

(Experiment 2)
<Comparative Example 3>
Partial image area ratio: An inter-image patch (partial patch) as shown in FIG. 10 was formed on a segment of 15% or less. The image area ratio of the patch between images was equivalent to 5%, equivalent to 10%, and equivalent to 15%.
When the inter-image patch is formed, the charging device 46 is operated in the same manner as in the normal image formation.
The environment is N environment: 20 ° C.
<Example 2>
Partial image area ratio: Inter-image patches (partial patches) were formed on segments of 15% or less. The image area ratio of the patch between images was equivalent to 5% and equivalent to 10%.
When the inter-image patch is formed, the charging device 46 is stopped.
The environment is N environment: 20 ° C.

As shown in Table II, in Comparative Example 3, when Call = 5%, the partial image area ratio: 0% to 100% is formed by forming an inter-image patch only on the 0% portion. Since the difference in the amount of lubricant is small, when the image area ratio between images is 15%, lubricant pattern noise and cleaning blade wear can be suppressed even when ΔC is 100%.
In Example 2, when Call = 5%, due to the effect of increasing the amount of toner reaching the cleaning blade 47 by stopping the charging device 46 at the time of patching between images, the image area ratio between images is equivalent to 10%. Even at ΔC: 100%, lubricant pattern noise and cleaning blade wear could be suppressed. Therefore, compared to Comparative Example 3, the amount of toner consumed in the patch between images with respect to the lubricant pattern noise could be reduced.

(Experiment 3)
<Comparative Example 4>
Does not form patch between images.
The environment is H environment: 30 ° C.
<Comparative Example 5>
When the in-machine temperature is 30 ° C. or higher, an inter-image patch (horizontal band patch) is formed. The image area ratio of the patch between images was equivalent to 5% and equivalent to 10%.
When the inter-image patch is formed, the charging device 46 is operated in the same manner as in the normal image formation.
The environment is H environment: 30 ° C.
<Example 3>
When the in-machine temperature is 30 ° C. or higher, an inter-image patch (horizontal band patch) is formed. The image area ratio of the patch between images was equivalent to 5%, equivalent to 10%, and equivalent to 15%.
When the inter-image patch is formed, the charging device 46 is stopped.
The environment is H environment: 30 ° C.

As shown in Table III, in Comparative Example 4, since the environmental temperature was higher than that in Comparative Example 1, there was no problem when Call = 15% due to the influence of the amount of lubricant on the photosensitive drum 41 as described above. Was only the lubricant pattern noise at ΔC: 0%.
In Comparative Example 5, when Call = 15% as compared to Comparative Example 4, the cleaning blade wear at ΔC: 0% was able to be suppressed when the image area ratio between images was equivalent to 5%. Compared with Comparative Example 2, the required image area ratio is increasing.
In the third embodiment, the required image area ratio tends to increase as compared with the first embodiment due to the influence of the environmental temperature. When the image-to-image patch image area ratio is equivalent to 10%, the cleaning blade wear of ΔC = 0% can be suppressed, and compared with Comparative Example 5, the image-to-image patch toner consumption for suppressing the cleaning blade wear can be reduced.

(Experiment 4)
<Example 4>
Partial image area ratio: Inter-image patches (partial patches) were formed on segments of 15% or less. The image area ratio of the patch between images was equivalent to 5%, equivalent to 10%, and equivalent to 15%.
When the inter-image patch is formed, the charging device 46 is stopped.
The environment is H environment: 30 ° C.

  As shown in Table IV, in Example 4, the control itself is the same as in Example 2, but the ambient temperature is different. As described above, the higher the ambient temperature, that is, the in-machine temperature, the direction in which the amount of lubricant on the photoreceptor increases in terms of the spreadability of the lubricant. In the case of Call = 5%, in the N environment, the patch image area ratio was equivalent to 10%, and both ΔC = 0% and ΔC: 100% were able to suppress both lubricant pattern noise and cleaning blade wear. As the amount of lubricant on the body increases, it is necessary to further improve the lubricant recoverability by the cleaning blade 47. Therefore, when the image area ratio between images is equivalent to 10%, the lubricant pattern noise and cleaning are obtained when ΔC is 100%. Although blade wear occurred, it was possible to suppress both by increasing the image area ratio between images to 15%.

  Although specific description has been made based on the embodiment according to the present invention, the detailed configuration of each apparatus constituting the image forming apparatus and the detailed operation of each apparatus are within the scope not departing from the gist of the present invention. It can be changed as appropriate.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Automatic document conveyance part 3 Scanner part 4 Image forming part 41 Photosensitive drum (image carrier)
42 Charging device 43 Exposure device 44 Developing device (developing means)
441 Development sleeve 442 Developer 45 Transfer device (transfer means)
451 Intermediate transfer belt 452 Transfer roller 46 Charging device (charge amount adjusting means)
47 Cleaning blade (cleaning means)
48 Lubricant application mechanism (supply means)
481 Lubricant application brush (recovery means)
482 Solid lubricant 483 Lubricant application part cleaning member 484 Immobilization blade 491 Toner recovery brush (collection means)
492 Toner recovery unit cleaning member 5 Paper supply unit 6 Storage unit 7 Operation display unit 10 Control unit (prediction unit, determination unit, control unit)
A Temperature sensor (detection means)

Claims (6)

An image carrier for carrying a toner image to be transferred to paper;
Developing means for developing a toner image on the image carrier;
Transfer means for transferring the toner image formed on the image carrier to a sheet;
Cleaning means for cleaning and removing the toner adhering to the image carrier by bringing a cleaning blade into contact with the image carrier;
A charge amount adjusting unit that is arranged on the downstream side of the transfer unit and the upstream side of the cleaning unit in the rotation direction of the image carrier, and adjusts the charge amount of the toner attached to the image carrier;
A collecting unit that is disposed on the downstream side of the charge amount adjusting unit and the upstream side of the cleaning unit in the rotation direction of the image carrier, and collects toner attached to the image carrier;
A supply unit disposed on the downstream side of the transfer unit in the rotation direction of the image carrier and supplying a lubricant to the image carrier;
Predicting means for predicting the amount of lubricant on the surface of the image carrier;
Determining means for determining whether or not the amount of lubricant on the surface of the image carrier predicted by the predicting means is greater than a predetermined amount;
When it is determined by the determining means that the amount of lubricant on the surface of the image carrier is larger than the predetermined amount, the charge amount adjusting means is more than when the amount of lubricant on the surface of the image carrier is not more than the predetermined amount. An image forming apparatus comprising: control means for reducing the output of the image forming means and causing the developing means to form an inter-image patch. The prediction means calculates a cumulative total image area ratio at an arbitrary timing during image formation, predicts a lubricant amount on the surface of the image carrier based on the cumulative total image area ratio,
2. The determination unit according to claim 1, wherein when the cumulative total image area ratio is smaller than a predetermined value, the determination unit determines that the amount of lubricant on the surface of the image carrier is larger than the predetermined amount. Image forming apparatus. The predicting means calculates a partial image area ratio at an arbitrary timing during image formation for each partial image divided in the rotation axis direction of the image carrier, and the image carrier surface based on the partial image area ratio Predict the amount of lubricant
The determination means determines that the amount of lubricant in the region corresponding to the partial image in the surface of the image carrier is larger than the predetermined amount when the partial image area ratio is smaller than a predetermined value;
The control unit causes the developing unit to form the inter-image patch only on an area of the surface of the image carrier on which the determination unit determines that the amount of lubricant is larger than the predetermined amount. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. A detecting means for detecting a temperature inside the image forming apparatus at an arbitrary timing during image formation;
The predicting means predicts the amount of lubricant on the surface of the image carrier based on the temperature detected by the detecting means,
The determination unit determines that the amount of lubricant on the surface of the image carrier is larger than the predetermined amount when the temperature is higher than the predetermined temperature. The image forming apparatus described in the item.   The control means stops the output of the charge amount adjusting means and causes the developing means to apply an inter-image patch when the determining means determines that the amount of lubricant on the surface of the image carrier is larger than the predetermined amount. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed. A detecting means for detecting a temperature inside the image forming apparatus at an arbitrary timing during image formation;
The prediction means predicts an increase or decrease in the amount of lubricant on the surface of the image carrier in response to an increase or decrease in temperature detected by the detection means,
The control means increases the image area ratio of the inter-image patch when the predicting means predicts that the amount of lubricant on the surface of the image carrier increases as the temperature rises when the inter-image patch is formed. 6. The image area ratio of the inter-image patch is decreased when it is predicted by the prediction means that the amount of lubricant on the surface of the image carrier is decreased as the temperature decreases. The image forming apparatus according to any one of the above.

Images