Image forming apparatus

Abstract

The present invention relates to an image forming apparatus. An image forming apparatus is used, which includes an image bearer, a developing device including a developer bearer that supplies a developer to an electrostatic latent image on a surface of the image bearer, and a developing container that supports the developer bearer and stores the developer, a replenishing container that replenishes the developer to the developing container, and a control unit that controls a replenishing operation, wherein the control unit controls the replenishing operation so that an amount of the developer in the developing container has a predetermined reference value, and when information on a total amount of the developer consumed since a start of use of the developing device exceeds a first threshold value, a target value of the developer stored in the developing container is made larger than the predetermined reference value.

Description

Technical Field

[0001] This invention relates to an image forming apparatus. Background Technology

[0002] Traditionally, image forming apparatuses have been manufactured in which toner is replenished from a toner refill container (toner cartridge) when the amount of toner in the developing container decreases. In particular, many image forming apparatuses have been manufactured in which the toner refill container can be replaced with a new toner refill container. Compared to cartridge-replaceable image forming apparatuses that include a cartridge with an integrated toner container and developing equipment, such cartridge-replaceable image forming apparatuses are advantageous in that they have a smaller amount of discarded cartridges and can reduce cartridge replacement costs.

[0003] Such toner cartridge replaceable image forming apparatuses typically have a configuration in which the remaining amount of toner in the developing unit is calculated and toner is replenished to the developing unit from a toner replenishment container at predetermined time intervals. To calculate the remaining amount of toner in the developing unit, a toner remaining amount detector and a toner usage prediction unit based on printed image information are used.

[0004] Incidentally, toners used with image forming apparatuses typically have a certain particle size distribution. Therefore, toners that are easily developed and toners that are difficult to develop are mixed in the developing equipment.

[0005] To address this situation, Japanese Patent Application Publication No. 2002-287439 and Japanese Patent No. 5118881 propose a configuration in which, when the amount of toner remaining in the developing equipment is small during toner cartridge replacement, the toner in the developing equipment is discharged through the photosensitive drum to, for example, a waste toner container. According to this configuration, when the amount of toner remaining in the developing equipment is small, a high proportion of toners that are difficult to develop (such as large-particle toners) is present, and therefore, these difficult-to-develop toners can be efficiently discharged to a waste toner container, etc.

[0006] However, in configurations like those in related technologies, the discharge operation takes a long time, resulting in extended downtime until the necessary amount of toner is discharged. Furthermore, in configurations where toner discharge and replenishment are performed using new toner cartridges, the timing of the discharge depends on the lifespan of the cartridge being used, thus lacking timing flexibility. Moreover, in configurations where discharge is performed when the remaining toner level is low, the physical properties of the toner change rapidly. Summary of the Invention

[0007] This disclosure is made in view of the above-mentioned disadvantages, and the object of this disclosure is to provide an image forming apparatus that enables the suppression of adverse effects on the image caused by changes in the physical properties of the toner in a configuration that allows replenishment of toner to the processing cartridge.

[0008] This disclosure provides an image forming apparatus, comprising:

[0009] An image carrier having a surface on which an electrostatic latent image is to be formed;

[0010] A developing apparatus, the developing apparatus including a developer carrier and a developing container, the developer carrier being configured to supply developer to the electrostatic latent image, and the developing container being configured to support the developer carrier and store the developer;

[0011] A replenishment container, configured to replenish the developer into the developing container; and

[0012] A control unit configured to control the replenishment operation of the developer from the replenishment container to the developing container.

[0013] in

[0014] The control unit

[0015] The replenishment operation is controlled so that the amount of developer stored in the developing container becomes a predetermined reference value, and

[0016] If the consumption information regarding the total amount of developer consumed since the start of use of the developing equipment exceeds a first threshold, the target value of the amount of developer stored in the developing container will be increased from the predetermined reference value.

[0017] This disclosure also provides an image forming apparatus, comprising:

[0018] A first image carrier and a second image carrier, each having a surface on which an electrostatic latent image is to be formed;

[0019] A first developing apparatus, comprising a first developer carrier and a first developing container, wherein the first developer carrier is configured to supply a first developer to an electrostatic latent image on a first image carrier, and the first developing container is configured to support the first developer carrier and store the first developer.

[0020] The second developing apparatus includes a second developer carrier and a second developing container. The second developer carrier is configured to supply a second developer to an electrostatic latent image on the second image carrier, and the second developing container is configured to support the second developer carrier and store the second developer.

[0021] A first replenishment container, configured to replenish the first developing container with the first developing agent;

[0022] A second replenishment container, configured to replenish the second developer container with the second developer; and

[0023] A control unit configured to control the replenishment operation of the first developer from the first replenishment container to the first developing container and the replenishment operation of the second developer from the second replenishment container to the second developing container.

[0024] in

[0025] The control unit

[0026] The replenishment operation is controlled to bring the amount of the first developer stored in the first developing container to a predetermined reference value, and the replenishment operation is also controlled to bring the amount of the second developer stored in the second developing container to a predetermined reference value.

[0027] If the consumption difference exceeds a third threshold, the target value of the amount of the first developer stored in the first developing container is increased from the predetermined reference value. The consumption difference is obtained by subtracting the total amount of the second developer consumed since the start of use of the second developing device from the first consumption-related information about the total amount of the first developer consumed since the start of use of the first developing device.

[0028] This disclosure also provides an image forming apparatus, comprising:

[0029] A first image carrier and a second image carrier, each having a surface on which an electrostatic latent image is to be formed;

[0030] A first developing apparatus, comprising a first developer carrier and a first developing container, wherein the first developer carrier is configured to supply a first developer to an electrostatic latent image on a first image carrier, and the first developing container is configured to support the first developer carrier and store the first developer.

[0031] The second developing apparatus includes a second developer carrier and a second developing container. The second developer carrier is configured to supply a second developer to an electrostatic latent image on the second image carrier, and the second developing container is configured to support the second developer carrier and store the second developer.

[0032] A first replenishment container, configured to replenish the first developing container with the first developing agent;

[0033] A second replenishment container, configured to replenish the second developer container with the second developer; and

[0034] A control unit configured to control the replenishment operation of the first developer from the first replenishment container to the first developing container and the replenishment operation of the second developer from the second replenishment container to the second developing container.

[0035] in

[0036] The control unit

[0037] The replenishment operation is controlled to bring the amount of the first developer stored in the first developing container to a predetermined reference value, and the replenishment operation is also controlled to bring the amount of the second developer stored in the second developing container to a predetermined reference value.

[0038] If the consumption difference exceeds a third threshold, the target value of the amount of the second developer stored in the second developing container is reduced from the predetermined reference value. The consumption difference is obtained by subtracting the total amount of the second developer consumed since the start of use of the second developing device from the first consumption-related information about the total amount of the first developer consumed since the start of use of the first developing device.

[0039] The features of this disclosure will become clear from the following description of embodiments with reference to the accompanying drawings. The following description of the embodiments is by way of example. Attached Figure Description

[0040] Figure 1 This is a schematic cross-sectional view of the image forming apparatus of Example 1.

[0041] Figure 2 This is a schematic cross-sectional view of the processing box in Example 1.

[0042] Figure 3A This is a schematic diagram of the toner remaining amount detection unit in Example 1.

[0043] Figure 3BThis is a top view of the light-reflecting component of the toner remaining amount detection unit in Example 1.

[0044] Figure 3C It is a graph showing the relationship between the amount of light detected by the light intensity sensor in Example 1 and the amount of toner remaining in the developing container.

[0045] Figure 3D This is a schematic diagram of an exemplary toner remaining amount detection unit of Example 1.

[0046] Figure 4 This is a schematic diagram of the control aspects of the image forming apparatus in Example 1.

[0047] Figure 5 It is a graph indicating the relationship between the total amount of toner used and the average particle size in Example 1.

[0048] Figure 6 It is a graph indicating the relationship between the total amount of toner used for each average coverage rate and the average particle size in Example 1.

[0049] Figure 7 It is a schematic graph indicating the target value of light intensity when the remaining amount of toner is changed in Example 1.

[0050] Figure 8 It is a graph indicating the average particle size under multiple total toner usage thresholds in Example 1.

[0051] Figure 9 It is a schematic graph indicating the target value of light intensity under multiple total toner usage thresholds in Example 1.

[0052] Figure 10A It is a graph indicating the change in average particle size for each color in Example 2, showing the average coverage.

[0053] Figure 10B This is a graph indicating the average coverage in Example 2, used to control the amount of remaining material for different colors.

[0054] Figure 10C This is a graph showing the control used to reduce the amount of residue for different cases of average coverage in Example 2 for each color. Detailed Implementation

[0055] In the following, examples of this disclosure will be described in detail with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described in the following examples should be appropriately varied depending on the configuration of the apparatus to which this disclosure is applied and various conditions. Therefore, unless otherwise specified, the scope of this disclosure is not limited. Although multiple features are described in the examples, not all of these multiple features are necessarily essential to the disclosure, and the multiple features can be freely combined.

[0056] Example 1

[0057] Example 1 of this disclosure will be described. The image forming apparatus 1 of this example includes four processing cartridges 3 as developing devices and four toner replenishment units 20 as replenishment containers. The number of processing cartridges 3 and toner replenishment units 20 attached to the image forming apparatus is not limited thereto and can be appropriately arranged as needed. In this example, a laser beam printer is described as an aspect of the image forming apparatus.

[0058] Schematic configuration of image forming apparatus

[0059] Figure 1 This is a schematic cross-sectional view of the image forming apparatus 1. Figure 2 This is a cross-sectional view of the processing box 3 and the toner replenishment unit 20. In this disclosure, the upward direction in the figures is the upward direction in the direction of gravity (the Z direction in the figures).

[0060] The image forming apparatus 1 is a four-color full-color laser printer that uses electrophotographic processing to form color images on a recording medium S. The image forming apparatus 1 is a cartridge type, and each of the cartridges 3 is detachably attached to the main body of the image forming apparatus via a front door 2. In the main body of the image forming apparatus 1, the first to fourth cartridges 3 (3Y, 3M, 3C, and 3K) are arranged in a substantially horizontal direction.

[0061] The first to fourth processing cartridges 3 (3Y, 3M, 3C, and 3K) have the same electrophotographic processing mechanism, and the developer (hereinafter referred to as toner) has a different color than each other. In the following text, unless there is a specific need for differentiation, the suffixes indicating the colors (Y: yellow, M: magenta, C: cyan, and K: black) are omitted. Rotational driving force is transmitted from the drive output unit 121, which is included in the main body of the image forming apparatus, to the processing cartridges 3.

[0062] Bias voltage is supplied from the main body of the image forming apparatus to each element of the processing cartridge 3. For example, charging voltage is applied to charging roller 61 from charging power supply 111. Developing voltage is applied to developing roller 41 from developing power supply 112. Adjusting voltage is applied to developing blade 42 from adjusting power supply 113. Transfer voltage is applied to primary transfer roller 5c and secondary transfer roller 10 from transfer power supply 114.

[0063] like Figure 2 As illustrated, each of the processing cartridges 3 includes a drum unit 60, which includes a photosensitive drum 63 as an image carrier and a charging roller 61 as a charger acting as a processing unit on the photosensitive drum 63. Here, the drum unit 60 may include not only a charger but also a cleaning unit as a processing unit. Additionally, the processing cartridge 3 includes a developing unit 40, which is provided with a developing roller 41 as a developer carrier for developing the electrostatic latent image on the photosensitive drum 63. First to fourth toner replenishment units 20 (20Y, 20M, 20C, and 20K) are connected to the first to fourth processing cartridges 3 (3Y, 3M, 3C, and 3K). The drum unit 60, the developing unit 40, and the toner replenishment unit 20 are connected to each other. A more specific configuration of the processing cartridge 3 will be described later.

[0064] The first processing cartridge 3Y and the first toner replenishment unit 20Y store yellow (Y) toner T in the developing container 44 and form a yellow toner image on the surface of the photosensitive drum 63. The second processing cartridge 3M and the second toner replenishment unit 20M store magenta (M) toner T in the developing container 44 and form a magenta toner image on the surface of the photosensitive drum 63. The third processing cartridge 3C and the third toner replenishment unit 20C store cyan (C) toner T in the developing container 44 and form a cyan toner image on the surface of the photosensitive drum 63. The fourth processing cartridge 3K and the fourth toner replenishment unit 20K store black (K) toner T in the developing container 44 and form a black toner image on the surface of the photosensitive drum 63.

[0065] Each toner remaining quantity detection unit 6, equipped with a toner remaining quantity detection substrate 6a, is deployed near the corresponding developing container 44. The toner remaining quantity detection unit 6 estimates the surface level of the toner to read the remaining amount of toner in the developing container 44. Detailed operation will be described later in the section on the operation of the processing cartridge.

[0066] A laser scanner unit 11, serving as an exposure unit, is provided above the processing box 3. The laser scanner unit 11 outputs a laser beam U corresponding to the image information to scan and expose the surface of each photosensitive drum 63.

[0067] An intermediate transfer unit 5, serving as a transfer component, is provided below the processing cartridge 3. The intermediate transfer unit 5 includes a drive roller 5d, a tension roller 5b, and a flexible transfer belt 5a stretched around the drive roller 5d and the tension roller 5b. The lower surface of the photosensitive drum 63 of the processing cartridge 3 contacts the upper surface of the transfer belt 5a. This contact portion constitutes the primary transfer portion. A primary transfer roller 5c is provided inside the transfer belt 5a and faces the photosensitive drum 63. A secondary transfer roller 10 contacts the drive roller 5d via the transfer belt 5a. The contact portion between the transfer belt 5a and the secondary transfer roller 10 constitutes the secondary transfer portion.

[0068] Feed unit 4 is provided below intermediate transfer unit 5. Feed unit 4 includes a sheet feed tray 4a and a sheet feed roller 4b in which the recording medium S is stacked and stored. Figure 1 A fixing device 7 and a sheet ejection device 8 are provided in the upper left of the main body of the image forming apparatus. The upper part of the main body of the image forming apparatus serves as a sheet ejection tray 9. The toner image on the recording medium S is fixed by the fixing device 7, which is a fixing unit, and ejected into the sheet ejection tray 9. The fixing device 7, which includes a fixing roller 7a and a heating roller 7b, causes the recording medium S to pass through the fixing clamping portion between the fixing roller 7a and the heating roller 7b, and the toner T is melted by heat generated from a heater inside the heating roller 7b, and the toner T is fixed onto the recording medium S.

[0069] The drive output unit 121 is a driver that includes various drive elements, such as a drive source including a motor and transmission elements such as gears and belts. The drive output unit 121 may generate rotational driving force and transmit it to a rotating element included in the image forming apparatus 1, and may also generate driving force and transmit it to an opening / closing element such as a shutter. The drive output unit 121 may be configured to distribute the driving force of a single drive source, or may include multiple drive sources.

[0070] Image forming operations

[0071] The operation for forming a panchromatic image is as follows. The photosensitive drum 63 of the processing cartridge 3 is driven to rotate at a predetermined speed ( Figure 2 (The direction of the middle arrow A1). In the case of the image forming apparatus 1 in this example, the printing rate when continuously passing through A4-sized sheets is 36 sheets per minute, and the peripheral surface of the photosensitive drum 63 rotates at 180 mm / sec.

[0072] The transfer belt 5a rotates in the positive direction as the photosensitive drum 63 rotates. Figure 2 The photosensitive drum 63 is rotated at a speed corresponding to the speed of the photosensitive drum 63 in the direction of the middle arrow B. The charging roller 61 contacts the photosensitive drum 63 with a predetermined pressing force and applies a desired charging voltage to uniformly charge the surface of the photosensitive drum 63 to a predetermined potential.

[0073] The laser scanner unit 11 is also driven. Synchronously with the driving of the laser scanner unit 11, in the processing cartridge 3, the charging roller 61 uniformly charges the surface of the photosensitive drum 63 to a predetermined polarity and potential. The laser scanner unit 11 outputs a laser beam U based on the image signal to scan and expose the surface of the photosensitive drum 63. As a result, an electrostatic latent image based on the image signal is formed on the surface of the photosensitive drum 63. The formed electrostatic latent image is developed by a developing roller 41 that is driven to rotate at a predetermined speed.

[0074] Operation of the processing box

[0075] The processing box 3 will then be described in detail. For example... Figure 2 As illustrated, the processing cartridge 3 includes a developing unit 40. The developing unit 40 includes a developing roller 41 carrying developer as a developer carrier, a developing container 44 serving as the container for the developing unit 40, and a supply roller 43 capable of supplying developer to the developing roller 41. The developing roller 41 is rotatably supported by the developing container 44 in the direction of arrow A2. The supply roller 43 is also rotatably supported by the developing container 44 in the direction of arrow A3. The developing roller 41 is positioned in the opening of the developing container 44 and faces the photosensitive drum 63. The supply roller 43 is in contact with the developing roller 41. Toner T, stored in the developing container 44 as developer, is applied to the surface of the developing roller 41 via the supply roller 43.

[0076] The toner replenishment unit 20 is a so-called toner cartridge and contains toner T inside the toner container. The toner replenishment unit 20 is positioned above the developing container 44 and is interconnected with the developing container 44 via a developing opening 25. The toner replenishment unit 20 is replaceable by the user. A toner replenishment baffle 24 is deployed at the connection between the toner replenishment unit 20 and the developing container 44. The toner replenishment baffle 24 is opened or closed at any time by a drive control from the control unit 100, thus maintaining communication between the toner replenishment unit 20 and the developing container 44.

[0077] The toner replenishment stirring shaft 22 and the toner replenishment stirring blade 23 are deployed in the toner replenishment unit 20, and... Figure 2The toner T in the toner replenishment unit 20 rotates counterclockwise as indicated by arrow Z2. The toner T in the toner replenishment unit 20 circulates through the toner replenishment stirring blade 23, and the toner T is transferred from the toner replenishment unit 20 to the developing container 44. In this example, the toner replenishment stirring shaft 22 is configured to rotate continuously during the driving of the processing cartridge 3, and the toner T replenishment operation is controlled by opening or closing the toner replenishment baffle 24. The control unit 100 receives a signal from the toner remaining amount detection substrate 6a, drives the toner replenishment baffle 24 to keep the remaining amount of toner in the developing container 44 constant, and performs the toner T replenishment operation.

[0078] Figure 3A This is a schematic diagram of the toner remaining amount detection unit 6. Figure 3B This is a schematic diagram showing the positional relationship between the toner remaining amount detection substrate 6a, the light reflection member 6d, the developing container 44, and the light L, as seen from above in the direction of gravity of the developing unit 40. Figure 3B The lower part is Figure 2 The front side of the schematic diagram of the processing box 3 in the middle.

[0079] A toner level detection substrate 6a is positioned near the developing container 44 inside the image forming apparatus. An LED light emitting element 6b and a light intensity detection sensor 6c are deployed on the toner level detection substrate 6a; the light emission of the LED light emitting element 6b is controlled by the control unit 100 at any timing. A light reflecting member 6d is fixed to the wall of the developing container 44 facing the toner level detection substrate 6a.

[0080] The LED light emitting element 6b of the toner remaining amount detection substrate 6a emits directional light L in the direction of the light reflecting member 6d. The wall of the developing container 44, located in the light path of the light L emitted from the LED light emitting element 6b, has a transparent window 44a made of, for example, acrylic resin, and the transparent window 44a suppresses the reflection or absorption of light L.

[0081] The emitted light L passes through the interior of the developing container 44 and is reflected on the light-reflecting member 6d towards the light intensity detection sensor 6c on the toner remaining amount detection substrate 6a. The amount of light L reflected and returned is read by the light intensity detection sensor 6c. The detected light intensity varies greatly depending on the surface level of the toner in the developing container 44. When the toner obstructs the light path at a high ratio, the detected light intensity is low; when the toner obstructs the light path at a low ratio, the detected light intensity is high. By reading the intensity of the light, the remaining amount of toner in the developing container 44 can be estimated. The information about the toner detected by the light intensity detection sensor 6c is related to the surface level of the toner.

[0082] Figure 3CThis is a graph indicating the relationship between the remaining amount of toner in the developing container 44 and the surface level of the toner detected by the toner remaining amount detection substrate 6a. If a predetermined surface level of toner is detected based on the detection results, the control unit 100 determines that the amount of toner in the developing container 44 is the target remaining amount of toner.

[0083] In this example, the control unit 100 reads a signal from the toner remaining amount detection substrate 6a and drives the toner replenishment baffle 24, so that the remaining amount of toner T in the developing container 44 is maintained at an average of approximately 40g. Specifically, the control unit 100 initiates a replenishment operation when the amount of toner in the developing container 44 reaches 37g based on the signal from the toner remaining amount detection substrate 6a, and performs the replenishment operation until the amount of toner in the developing container 44 is detected to be 43g. As a result, the amount of toner in the developing container 44 fluctuates between 37g and 43g, and the average remaining amount is maintained at 40g.

[0084] In this example, a toner remaining amount detector, which uses light, is exemplified as a unit for estimating the remaining amount of toner in the developing container 44. However, the unit for estimating the remaining amount of toner is not limited to this. For example, the amount of toner used can be estimated from printed image information, and the remaining amount of toner can be calculated.

[0085] When the amount of toner in the toner replenishment unit 20 decreases and replacement of the toner replenishment unit 20 is imminent, the control unit 100 executes control to notify the user that the toner is LOW. Additionally, when the amount of toner in the toner replenishment unit 20 decreases and replenishment of toner to the developing container 44 is not possible, the control unit 100 executes control to notify the user that the toner is OUT, and executes control to request replacement of the toner replenishment unit 20.

[0086] In this example, the control unit 100 estimates the remaining amount of toner in the toner replenishment unit 20 based on the relationship between the number of toner replenishment operations performed by opening and closing the toner replenishment baffle 24 and the amount of toner added to the developing container 44, and notifies the user of either toner LOW or toner OUT. That is, if the amount of toner added to the developing container 44 relative to the number of toner replenishment operations is less than a predetermined value, it is determined to be toner LOW, and if the amount of toner in the developing container 44 no longer increases due to the number of toner replenishment operations, it is determined to be toner OUT.

[0087] In addition, in order to comprehensively detect the remaining amount of toner in the developing container 44, for example, such as Figure 3DAs illustrated, the two toner remaining amount detection substrates 6a and the two light reflecting members 6d can be longitudinally deployed in the direction of gravity, so that the amount of light L varies with a wider range of changes in the surface level of the toner.

[0088] The method for detecting the remaining amount of toner in the toner replenishment unit 20 is not limited to this, and therefore the remaining amount of toner can be estimated from the image information printed by the user. Additionally, a toner remaining amount detector can be installed on the toner replenishment unit 20.

[0089] The developing unit 40 in this example uses a contact developing method. That is, the toner layer carried on the developing roller 41 is brought into contact with the photosensitive drum 63 in the developing portion (developing area) where the photosensitive drum 63 and the developing roller 41 face each other. A developing voltage is applied to the developing roller 41. Under the applied developing voltage, the toner carried on the developing roller 41 is transferred from the developing roller 41 to the surface of the photosensitive drum 63 based on the electrostatic latent image on the surface of the photosensitive drum 63, thus developing the toner image.

[0090] In this example, the developing voltage is -300V. A reverse developing method is used in this example. That is, the surface of the photosensitive drum 63 is charged by the charging roller 61, and then the surface of the photosensitive drum 63 is exposed in the exposure step. Toner from the developing roller 41 adheres to the exposed areas of the surface of the photosensitive drum 63, where the amount of charge decays with exposure, thereby forming a toner image. After the toner image is transferred to the transfer belt 5a, the surface of the photosensitive drum 63 is neutralized by the pre-exposure member 62 to ensure a uniform potential. Thereafter, the photosensitive drum 63 is charged again by the charging roller 61.

[0091] Furthermore, in this example, a value of 7 is used. The toner T has a particle size and a negative normal charging polarity. As toner T, for example, a polymeric toner generated by a polymerization method can be used. Toner T does not contain magnetic components and is a so-called non-magnetic single-component developer in which toner T is carried on the developing roller 41 mainly by intermolecular forces or electrostatic forces (mirror forces).

[0092] The toner particles contain various waxes used to adjust the melting characteristics of toner T during the fixing process and its adhesion to the recording material and fixing roller. Tiny particles formed from silica particles with submicron-sized grains are added to the surface of the toner particles to adjust the flowability and rechargeability of toner T. In this example, the toner T with added tiny particles is defined as a developer.

[0093] In this example, although a non-magnetic single-component developer is used as an example, a single-component developer containing a magnetic component can be used. As a developer, a two-component developer consisting of a non-magnetic toner and a magnetic carrier can be used. In the case of using a magnetic developer, for example, a cylindrical developing sleeve in which a magnet is deployed can be used as the developer carrier.

[0094] A stirring member 45, serving as a stirring unit, is provided inside the developing container 44. The stirring member 45 is driven to rotate in the direction of arrow Z1, thereby stirring the toner T in the developing container 44 and feeding the toner T toward the developing roller 41 and the supply roller 43. Furthermore, the stirring member 45 has the function of circulating any toner T that is not used for development but has fallen off the developing roller 41 within the developing container, thereby ensuring the toner T is homogenized within the developing container.

[0095] Furthermore, a developing blade 42, made of stainless steel, is deployed in the developing container 44 through an opening in which the developing roller 41 is positioned, to adjust the amount of toner carried on the developing roller 41. A voltage 200V greater than the absolute value of the negative polarity side of the developing roller 41 is applied to the developing blade 42 from a regulating power supply 113. That is, a voltage 200V greater than the normal polarity side of the toner T is applied to the developing blade 42.

[0096] The developer supplied to the surface of the developing roller 41 passes over the portion facing the developing blade 42 as the developing roller 41 rotates, causing the developer to become evenly thinned. At the same time, the toner becomes charged through friction with the developing blade 42 and through the potential difference provided between the developing blade 42 and the developing roller 41, and is charged to the negative polarity, which is the normal polarity of the toner.

[0097] In this example embodiment, a so-called cleaner-less configuration is employed, in which residual toner left on the photosensitive drum 63 that was not transferred to the recording medium S is recovered to the developing unit 40 and reused. The residual toner is reused in subsequent steps. The residual toner comprises a mixture of toner T charged with a positive polarity (opposite to the normal polarity in this example) and toner T charged with a negative polarity but lacking sufficient charge. The toner T is uniformly charged to a negative polarity by discharging the bias of the negative side of the charging roller 61 during the charging step of the photosensitive drum 63.

[0098] The residual toner, charged to a negative polarity, reaches the developing area as the photosensitive drum 63 rotates. Here, the behavior of the residual toner that has reached the developing area will be described separately for the exposed and unexposed areas of the photosensitive drum 63. In the unexposed area (i.e., the dark potential portion) of the photosensitive drum 63, the surface potential of the photosensitive drum 63 on the negative polarity side is greater than the developing voltage applied to the developing roller 41. Therefore, the residual toner with a sufficiently negative charge moves to the developing roller 41 by the Coulomb force caused by the electric field and is recovered into the developing container 44. Here, the dark potential portion of the photosensitive drum 63 is not limited to the unexposed area, and weak exposure can be performed when the surface potential of the photosensitive drum 63 on the negative polarity side is greater than the developing voltage applied to the developing roller 41.

[0099] The toner recovered in the developing container 44 is stirred together with the toner in the developing container 44 by the stirring member 45 and dispersed in the toner in the developing container 44, and is carried by the developing roller 41 for reuse in the developing process.

[0100] On the other hand, in the exposure zone of the photosensitive drum 63, because the surface potential of the photosensitive drum 63 on the negative polarity side is less than the developing voltage applied to the developing roller 41, the residual toner remains on the surface of the photosensitive drum 63 and is not transferred from the photosensitive drum 63 to the developing roller 41 in the developing zone. The residual toner remaining on the surface of the photosensitive drum 63, along with other toner transferred from the developing roller 41 to the exposure zone, is carried on the photosensitive drum 63, moves to the transfer unit, and is transferred to the recording medium S in the transfer unit.

[0101] In this example, the dark potential portion is -500V, and the exposure potential portion is -50V. As mentioned above, because the developing voltage is -300V, the background contrast is as follows: The background contrast is determined by the potential difference between the dark potential portion of the photosensitive drum 63 (which has already passed through the portion adjacent to the charging roller 61) and the developing voltage (the surface potential of the developing roller 41). V. Furthermore, the development contrast, which is the potential difference between the exposure area of ​​the photosensitive drum 63 and the developing voltage (the surface potential of the developing roller 41), is... V.

[0102] Through the aforementioned electrophotographic image forming processing operations, a yellow toner image corresponding to the yellow component of the panchromatic image is formed on the photosensitive drum 63 of the first processing cartridge 3Y. The toner image is transferred once to the transfer belt 5a. Similarly, a magenta toner image corresponding to the magenta component of the panchromatic image is formed on the photosensitive drum 63 of the second processing cartridge 3M. The toner image is transferred once to be overlaid on the yellow toner image that has already been transferred to the transfer belt 5a. Similarly, a cyan toner image corresponding to the cyan component of the panchromatic image is formed on the photosensitive drum 63 of the third processing cartridge 3C. The toner image is transferred once to be overlaid on the yellow and magenta toner images that have already been transferred to the transfer belt 5a. Similarly, a black toner image corresponding to the black component of the panchromatic image is formed on the photosensitive drum 63 of the fourth processing cartridge 3K. The toner image is transferred once to be overlaid on the yellow, magenta, and cyan toner images that have already been transferred to transfer belt 5a.

[0103] In this way, a panchromatic unfixed toner image in four colors—yellow, magenta, cyan, and black—is formed on the transfer belt 5a.

[0104] On the other hand, the recording media S are separated and fed one after another at predetermined control timings. The recording media S are introduced into the secondary transfer section at predetermined control timings, which is the adjacent part between the secondary transfer roller 10 and the transfer belt 5a.

[0105] As a result, while the recording medium S is being transferred to the secondary transfer section, the four-color overlay toner image on the transfer belt 5a is sequentially and collectively transferred onto the surface of the recording medium S.

[0106] Control

[0107] Figure 4 This is a schematic block diagram illustrating the control aspects of the main parts of the image forming apparatus 1 according to this example. The image forming apparatus 1 includes a control unit 100. The control unit 100 includes a CPU 101 (which is the central element for performing arithmetic processing) as an arithmetic control unit, storage elements such as ROM 102, RAM 103 or non-volatile memory 104 as storage units, and input / output units (not shown) that control the transmission and reception of signals between various elements connected to the control unit 100. RAM 103 stores sensor detection results, calculation results, etc., and ROM 102 stores control programs, pre-obtained data tables, etc.

[0108] The control unit 100 is a controller that comprehensively controls the operation of the image forming apparatus 1. The control unit 100 executes a predetermined image forming sequence by controlling the transmission and reception of various electrical information signals, driving timing, etc. Each unit of the image forming apparatus 1 is connected to the control unit 100. For example, in the context of this example, the charging power supply 111, developing power supply 112, regulating power supply 113, transfer power supply 114, exposure device 115, toner replenishment baffle 24, drive output unit 121, LED light emitting element 6b, toner remaining amount detection substrate 6a, etc., are connected to the control unit 100.

[0109] Replacement of each unit box

[0110] When the remaining toner in the toner replenishment unit 20 is low, the control unit 100 notifies the user to replace it with a new product. Furthermore, the developing unit 40 and the drum unit 60 are integrated into the processing cartridge 3, and the processing cartridge 3 is detachably attached to the image forming apparatus 1. In this example, the toner replenishment unit 20 and the processing cartridge 3 can be separated and replaced independently.

[0111] The developing roller 41, developing blade 42, supply roller 43, photosensitive drum 63, charging roller 61, toner T, etc., deteriorate during user use and become difficult to provide sufficient image quality after a certain amount of use. In the image forming apparatus 1 according to this example, the deterioration of each component and toner T is predicted based on the rotational speed of the developing roller 41 and photosensitive drum 63. That is, when a threshold is exceeded, the control unit 100 performs control to notify the user of the end of the life of the processing cartridge 3 and the replacement with a new product. In this example, for example, if the user performs continuous printing on average every two sheets, and a total of 50,000 sheets are printed, the control unit 100 notifies the user of the prediction of the end of the life of the processing cartridge 3 and the replacement with a new cartridge.

[0112] Increase in the particle size of the toner

[0113] Toner T used in image forming apparatus consists of particles with an average particle size of approximately 7. The powder has a certain particle size distribution. Therefore, it is impossible to make the physical properties (e.g., particle size, shape, and charge) of each particle of toner T completely identical. As a result, toner T that is easy to develop and toner T that is difficult to develop are mixed in the developing container 44. For example, in a single-component contact developing system, toner T with a small particle size is generally likely to be developed, while toner T with a large particle size is unlikely to be developed.

[0114] The following phenomenon is generally known as a reason why toner T with a small particle size is more easily developed. In single-component contact development as in this example, toner T is charged on the surface, a mirror force is generated on the developing roller 41, and it is conveyed to the conditioning section via the developing blade 42. The conveyed toner is conditioned by the developing blade 42 to have a constant layer thickness. In order to conditioned the toner T to have a constant layer thickness, the developing blade 42 is abutted against the developing roller 41 with a certain pressure, and the developing roller 41 rotates while maintaining a constant gap with the developing blade 42.

[0115] Therefore, when toner T passes through the gap between the developing roller 41 and the developing blade 42, toner T with smaller particle size is more likely to pass through the gap in terms of shape, while toner T with larger particle size is less likely to pass through the gap. As a result, the toner T passing through the adjustment section of the developing blade 42 has a large number of small particles, and the toner T to be developed and consumed also has a high proportion of small particles.

[0116] As the preferential consumption of toner T with small particle size continues and the amount of toner used increases, the proportion of toner T with large particle size in the developing container 44 is higher than the initial proportion. As a result, due to the increase in the average particle size of the toner T in the developing container 44, fixing properties and other properties change, and image quality deteriorates. Note that in this example, the amount of toner in the developing container 44 is controlled to fall within the range of 37g to 43g, and the average amount of toner is approximately 40g.

[0117] Figure 5This is a graph illustrating the relationship between the total amount of toner used in processing cartridge 3 at the end of its lifespan and the change in the average particle size of the toner in the developing container. The horizontal axis represents the total amount of toner used, and the vertical axis represents the average particle size. In the graph, curve D1 indicates the case with an average coverage of 2%, curve D2 indicates the case with an average coverage of 5%, and curve D3 indicates the case with an average coverage of 10%. The starting point of each curve (the left end in the graph) indicates the average particle size of the new toner, and the ending point (the right end) indicates the average particle size at the end of the processing cartridge's lifespan. Under this condition, "at the end of the lifespan" is considered to be when the value related to the rotational speed of the developing roller 41 exceeds the lifespan value (i.e., the predetermined threshold). The total amount of toner used is the total amount of toner T used from the time the processing cartridge 3 is in a new state until the calculated time point, and can be referred to as the cumulative amount of developer consumed. The total amount of toner used is also information about the total amount of toner T consumed since the start of use of the processing cartridge 3, and can be referred to as consumption-related information. It should be noted that the consumption-related information may include not only the specific weight of the toner, but also the amount of light obtained by the light intensity detection sensor 6c and the current or voltage value converted from the light intensity. Additionally, the consumption calculated from image information used during image formation can also be considered as included in the consumption-related information.

[0118] Here, it is assumed that the use of the new processing cartridge 3 has begun, and the start time of use is defined as the starting point for calculating the total amount of toner used. However, the starting point for calculation is not limited to the state where the processing cartridge 3 is completely unused. For example, the timing at which the processing cartridge 3 is attached to the image forming apparatus 1 for actual use after performing pre-shipment testing, forming a sample image, etc., can be defined as the timing of the start of use of the processing cartridge 3.

[0119] Although the number of development rotations of processing cartridge 3 at the end of the development life is the same in all curves D1, D2, and D3, the total amount of toner used at the end of the development life increases in the order of D1, D2, and D3 because the average coverage differs from one another. In curve D1, which has a low average coverage, the total amount of toner used at the end of the life is small, and the total amount of toner used at the end of the life increases with the increase of average coverage.

[0120] like Figure 5 As indicated, the average particle size of the toner T in the developing container 44 increases with the total amount of toner used in the processing cartridge 3. Therefore, considering the lifespan of the processing cartridge 3, the average particle size of the toner in the developing container 44 at the end of its lifespan increases with the increase in average coverage. For example, in the case of the processing cartridge 3K of the image forming apparatus 1 in this example, the average coverage during normal use is approximately 5%, and the average particle size increases according to… Figure 5The curve D2 transformation in the image.

[0121] Depend on Figure 5 The vertical axis represents the average particle size E, a value that, in this example of the image forming apparatus 1, may cause fixing failure if the average particle size exceeds this value. In this example, the average particle size of the new toner is 7. The average particle size E that may be associated with fixing failure is 10. .

[0122] At this point, when the average coverage, as indicated by curve D2, is 5%, even if the processing cartridge 3 is at the end of its lifespan, the average particle size of the toner in the developing container does not exceed E, and no fixing failure image is formed. However, as indicated by curve D3, when the average coverage is 10%, the average particle size of the toner in the developing container exceeds E before the end of the lifespan of the processing cartridge 3, and fixing failure may occur.

[0123] Countermeasures to address the increase in toner particle size caused by changes in the remaining amount of toner.

[0124] In this example, the control unit 100 performs a replenishment operation by driving the toner replenishment baffle 24 while referencing a signal from the toner remaining amount detection substrate 6a, so that the average remaining amount of toner in the developing container 44 becomes a predetermined reference value (40g in this case).

[0125] Here, the smaller the target value of the remaining toner in the developing container 44, the less toner T in the developing container 44 needs to be discarded at the end of the life of the processing cartridge 3, which is advantageous in terms of cost. However, if the developing container 44 is not filled with a certain amount of toner, it is difficult to achieve the appropriate concentration when printing patterns (such as solid images) that consume a large amount of toner T. In view of the above, the amount of toner in the developing container 44 is set to an appropriate value for each product.

[0126] Here, as the amount of toner in the developing container 44 increases, the change in the average particle size of the toner due to the increase in the total amount of toner used, as described in the section "Increase in Toner Particle Size," becomes more gradual. This is because when the amount of toner in the developing container 44 is large, even if the amount of toner with large particle size generated in the adjustment section of the developing blade 42 is the same, the proportion of toner with large particle size is unlikely to increase, and therefore the change in the average particle size relative to the total amount of toner used is gradual.

[0127] Figure 6This is a graph indicating the relationship between the average particle size of the toner and the remaining amount of toner in the developing container 44 at each average coverage level in Example 1 until the end of the life of the processing cartridge 3. In the graph, curve D2 indicates the number of sheets with an average coverage of 5% and printing continuing until the end of the life, while maintaining an average remaining amount of toner in the developing container 44 at 40g. In the graph, curve D3 indicates the case with an average coverage of 10% and an average remaining amount of toner in the developing container 44 of 40g. In the graph, curve D4 indicates the case with an average coverage of 5% and an average remaining amount of toner in the developing container 44 of 60g. In the graph, curve D5 indicates the case with an average coverage of 10% and an average remaining amount of toner in the developing container 44 of 60g. In each of curves D2 to D5, the number of developing rotations of the processing cartridge 3 at the end of its life is equal. However, because the average coverage differs from one another, the total amount of toner used at the end of the developing life is greater in curves D3 and D5 than in curves D2 and D4.

[0128] As from Figure 6 As can be seen, compared with curves D2 and D3 indicating that the remaining amount of toner in the developing container 44 is 40g, curves D4 and D5 indicating that the remaining amount of toner is 60g have a smoother change in the average particle size of the toner in the developing container 44 relative to the total amount of toner used.

[0129] However, in curve D3, which indicates an average coverage of 10% and a remaining amount of toner in the developing container 44 of 40g, the average particle size of the toner in the developing container 44 exceeds E before the end of the life of the processing cartridge 3, and fixing failure may occur.

[0130] Therefore, when the total amount of toner T used exceeds the first threshold F, the control unit 100 of this example increases the remaining amount of toner in the developing container 44 from a predetermined reference value of 40g to 60g. As described above, controlling the replenishment operation based on the total amount of toner T used is a feature of this example. Here, the first threshold F is set to a value slightly smaller than the total amount of toner used when the average particle size of the toner reaches the threshold E in which fixing failure occurs.

[0131] By changing the remaining amount of toner in the developing container 44 from 40g to 60g, the transition in toner particle size, represented by curve D3, shifts to curve D5. That is, by increasing the remaining amount of toner when the total toner usage is F, the subsequent change in average particle size shifts to curve D5. In this way, even at an average coverage of 10%, the average particle size of the toner in the developing container 44 does not exceed E until the end of the life of the processing cartridge 3. Therefore, fixing failures are suppressed. In this example, the first threshold F for the total toner usage is set at 300g.

[0132] In this example, when the remaining toner amount is changed from 40g to 60g, the control unit 100 drives the toner replenishment baffle 24 and performs toner replenishment during the image forming operation after the total toner usage exceeds a first threshold F. In this way, by performing the toner replenishment operation during the image forming operation, the remaining amount of toner in the developing container 44 can be changed without causing downtime for the user.

[0133] Figure 7 The relationship between the remaining amount of toner in the developing container 44 and the amount of light detected by the light intensity detection sensor 6c is indicated. Figure 7 This diagram schematically illustrates the target value of the light intensity detected by the light intensity sensor 6c when the remaining amount of toner in the developing container 44 is changed. When the remaining amount of toner in the developing container 44 is 40g, the control unit 100 performs a toner replenishment operation based on the light intensity 6c1 detected by the light intensity sensor 6c. When the remaining amount of toner in the developing container 44 is changed from 40g to 60g, the toner replenishment operation is performed based on the light intensity 6c2 detected by the light intensity sensor 6c.

[0134] change

[0135] Figure 8 Example 1 shows an example of a product with a further extended lifespan for processing box 3. Figure 8 This indicates the change in the average particle size of the toner in the developing container 44 of the processing cartridge 3 at each average coverage, and also indicates the change given multiple total toner usage thresholds. Curves D3, D5, and D6 each indicate the change in the average particle size of the toner in the developing container 44 relative to the total toner usage of the processing cartridge 3 until the end of the lifetime of the processing cartridge 3.

[0136] In the graphs, compared to curve D3, curves D5 and D6 each indicate the case where the lifespan of the long-life processing cartridge 3 is 1.5 times longer than that of curve D3. As described above, in the graphs, curve D3 indicates the case where the average coverage is 10% and the remaining toner in the developing container 44 is 40g. In the graphs, curve D5 indicates the case where the average coverage is 10%, the remaining toner in the developing container 44 is 60g, and the lifespan of the processing cartridge 3 is 1.5 times longer than that of the processing cartridge 3 in curve D3. In the graphs, curve D6 indicates the case where the average coverage is 10%, the remaining toner in the developing container 44 is 80g, and the lifespan of the processing cartridge 3 is 1.5 times longer than that of the processing cartridge 3 in curve D3.

[0137] In curves D5 and D6, which indicate the case of long-life processing cartridge 3, the total amount of toner used at the end of its life increases. Therefore, even if the remaining amount of toner in the developing container 44 is changed from 40g to 60g according to the method of Example 1 and a transition to curve D5 is performed when the total amount of toner used exceeds the first threshold F, the average particle size of the toner may again exceed E depending on the life of processing cartridge 3.

[0138] In this modification, the control unit 100 sets a second threshold G for the total amount of toner used and performs a toner replenishment operation, changing the amount of remaining toner in the developing container 44 to a third remaining amount of toner, which is 80g. As a result, the average particle size of the toner in the developing container 44 is prevented from exceeding E again, thereby suppressing fixing failures.

[0139] When control is executed based on the second threshold G of this change, such as Figure 9 As indicated in the document, the toner replenishment baffle 24 is operated based on the light quantity 6c3 detected by the light quantity detection sensor 6c. Figure 9 This is a schematic diagram illustrating the target value of the light intensity of the light intensity detection sensor 6c when the remaining amount of toner in the developing container is varied, given multiple total toner usage thresholds in Example 1.

[0140] The third and fourth thresholds can be set for the total amount of toner used based on the lifespan of the processing cartridge 3. In this case, a toner replenishment operation is performed, so that the remaining amount of toner in the developing container 44 is also changed to the third and fourth remaining amounts of toner.

[0141] Comparison Examples

[0142] As a comparative example, the case where the remaining amount of toner in developer container 44 is initially set to a larger value of 60g will be described. Assuming the remaining amount of toner in developer container 44 is 60g, the average particle size of the toner in developer container 44 at 5% and 10% average coverage is as follows... Figure 6 The changes are as indicated by curves D4 and D5. That is, when the remaining amount of toner is 60g, the average particle size of the toner in the developing container 44 does not exceed E in both cases of 5% average coverage and 10% average coverage until the end of the life of the processing cartridge 3, and thus suppresses the occurrence of fixing failure.

[0143] However, when using an average coverage of 5%, where no fixing failure image occurs even when the remaining amount of toner in the developing container 44 is 40g, if the remaining amount of toner is set to 60g, then an overfill of 20g of toner increases the amount of toner to be discarded.

[0144] Therefore, in Example 1, assuming general use with an average coverage of approximately 5%, the remaining amount of toner was initially set to as low as 40g. Furthermore, with continued use at a low frequency (i.e., an average coverage of 10%) and an increase in the total amount of toner used, the remaining amount of toner was changed to 60g.

[0145] Table 1 compares Example 1, Comparative Example 1 (with a uniform toner remaining amount of 40g), and Comparative Example 2 (with a uniform toner remaining amount of 60g). Table 1 lists the average coverage (5% or 10%), whether fixing-related problems were found, and whether the amount of unused toner was small or large (i.e., cost-performance) for Example 1, Comparative Example 1, and Comparative Example 2.

[0146] First, let's examine Comparative Example 1. With an average coverage rate of 5% and relatively high usage frequency in the market, "no problems were found." However, with an average coverage rate of 10%, despite relatively low usage frequency in the market, the likelihood of fixing-related problems increases. Therefore, "problems were found."

[0147] Next, we will examine Comparative Example 2. No fixing-related issues are found. However, there is a cost-performance problem due to the increased amount of toner discarded in the unused state.

[0148] Finally, as in Example 1, the configuration in which the remaining amount of toner in the developing container 44 is increased from 40g to 60g when the total amount of toner used exceeds the threshold F will be examined. In this case, fixing-related problems can be suppressed at any average coverage, and the amount of unused toner can be suppressed.

[0149] [Table 1]

[0150]

[0151] Example 2

[0152] In Example 2, if the difference in the total amount of toner used in the multiple processing cartridges 3 installed on the image forming apparatus 1 exceeds a certain threshold, the control unit 100 performs a toner replenishment operation, thereby changing the remaining amount of toner in the developing container 44. Since the configuration, except for the threshold setting for the total amount of toner used and the control of the toner replenishment operation, is the same as in Example 1, it is not described further.

[0153] In Example 1, the number of processing boxes 3 included in the image forming apparatus 1 can be one or more. In the case of multiple processing boxes 3 provided in Example 1, a supplementary operation is performed, causing the remaining amount of toner to be changed for each processing box 3. On the other hand, in Example 2, the image forming apparatus 1 includes at least two processing boxes 3, and the control unit 100 performs supplementary control based on the difference in the total amount of toner used between the processing boxes.

[0154] The image forming apparatus 1 according to this example includes multiple processing cartridges 3 for yellow (Y), magenta (M), cyan (C), and black (K), thereby enabling full-color printing. As described in the section on image forming operation, processing cartridges 3Y, 3M, 3C, and 3K sequentially develop the toner T of each color onto a transfer belt 5a. The toner of each color developed on the transfer belt 5a is transferred onto a sheet by a secondary transfer roller 10 and fixed by a fixing device 7.

[0155] Because each toner T is transferred onto the transfer belt 5a in the order of Y, M, C, and K, the yellow toner T is on the bottom layer of the transfer belt 5a, followed by the magenta and cyan toner T, and the black toner T is on the top layer. When each toner T is transferred onto the sheet by the secondary transfer roller 10, the order of the top and bottom layers of toner T is reversed, so that the yellow toner T is on the top layer and the black toner T is on the bottom layer on the sheet. The fixing device 7 of this example includes a heating roller 7b with a heater on the printing surface side of the sheet. Therefore, on the sheet, the heat from the heater is easily transferred to the top layer of toner T (yellow), and the heat from the heater is difficult to transfer to the bottom layer of toner T (black).

[0156] Generally, as the particle size of toner T increases, greater heat energy is required for melting. If toner T is not properly melted, the adhesion between the toner T and the film after fixing will be weak. Therefore, with an increase in the particle size of toner T, it is necessary to properly melt the toner T by, for example, increasing the fixing temperature. However, if excessive heat energy is applied to the toner T, it will over-melt, and the over-melted toner T will adhere to the fixing roller side or excessively penetrate the film, making it impossible to obtain the appropriate concentration in some cases. Considering the above, the heat energy applied to the toner T by the fixing device 7 is set within an appropriate range.

[0157] Figures 10A to 10C These are graphs showing how the average particle size of the toner in the developing container 44 changes when the toner is used in a manner with significantly different average coverage for each color. Here, the yellow processing cartridge 3Y is defined as the first developing device, the photosensitive drum 63Y for yellow is defined as the first image carrier, the developing roller 41Y is defined as the first developer carrier, and the developing container 44Y is defined as the first developing container. The toner replenishment unit 20Y storing the yellow toner T (first developer) is defined as the first replenishment container. The cyan processing cartridge 3C is defined as the second developing device, the photosensitive drum 63C for cyan is defined as the second image carrier, the developing roller 41C is defined as the second developer carrier, and the developing container 44C is defined as the second developing container. The toner replenishment unit 20C storing the cyan toner T (second developer) is defined as the second replenishment container.

[0158] Figure 10A The diagram illustrates the relationship between the total toner usage and the change in average particle size when 5000 sheets pass through the yellow processing cartridge 3Y with an average coverage of 5% (curve H1) and the cyan processing cartridge 3C with an average coverage of 10% (curve H2). That is, it indicates the case where an image with higher coverage is printed in cyan compared to yellow. The remaining toner in each of the developing containers 44 is 40g.

[0159] exist Figure 10A In this example, the usage difference J indicates the difference in the total amount of toner used between the yellow treatment box 3Y and the cyan treatment box 3C. The usage difference (consumption difference) is calculated by subtracting the total amount of cyan toner used (second consumption-related information) from the total amount of yellow toner used (first consumption-related information).

[0160] Particle size difference This indicates the difference in average particle size of the toner between the yellow developing container 44Y and the cyan developing container 44C when the usage difference is J. In other words, the average particle size of the yellow toner is smaller than that of the cyan toner. .

[0161] In this case, because the average particle size of the cyan toner T is larger than that of the yellow toner T, the heat energy required for proper melting also increases. However, when the heat energy required to melt the cyan toner T is applied by the fixing device 7, the yellow toner T, which has a smaller particle size, may be over-melted. More specifically, this refers to the particle size difference, which is the difference between the average particle sizes of the first toner T and the second toner T. If the value exceeds the predetermined value, it may be impossible to set the heat energy for properly fixing both the first toner T and the second toner T.

[0162] Therefore, in this example, the particle size difference is estimated from the difference in total toner usage J. And in particle size difference Before the value exceeds the threshold that could cause fixing-related problems, implement supplementary controls to reduce grain size difference. Specifically, the control unit 100 performs a toner replenishment operation, changing the target value of the remaining amount of toner in the cyan developing container 44, which has a large total toner usage, from a first reference value (40g) to a second reference value (60g) that is greater than the first reference value.

[0163] Figure 10B This is a graph illustrating the control of the remaining amount of toner in this example. Figure 10B In the middle, curves H1 and H2 are... Figure 10A The same applies to curves H1 and H2. Curve H1 indicates the relationship between the total amount of toner used and the average particle size when the yellow toner T is present and the average coverage is 5%. Curve H2 indicates the relationship between the total amount of toner used and the average particle size when the cyan toner T is present and the average coverage is 10%. In both curves H1 and H2, the remaining amount of toner in the developing container is set to 40g when the developing container is new. Curve H3 indicates the relationship between the total amount of toner used and the average particle size when the cyan toner T is present, the average coverage is 10%, and the remaining amount of toner is 60g.

[0164] As mentioned above, when the average particle size difference exceeds A fixing failure occurs under certain circumstances. Therefore, in this example, when the difference in toner usage J exceeds a threshold (the third threshold), the control unit 100 changes the remaining amount of toner in the cyan developing container 44 from 40g to 60g. As a result, the relationship between the toner particle size change and the total amount of toner used shifts from curve H2 to curve H3. At this time, the particle size difference between yellow and cyan changes from... (and Figure 10A In Same) change to By reducing particle size difference in this way, fixing failures can be suppressed.

[0165] change

[0166] In the above example, the control unit 100 performs a toner replenishment operation, changing the target value of the remaining toner in the cyan developing container 44, which has a large total toner usage, from a first reference value (40g) to a second reference value (60g) that is greater than the first reference value. However, the present invention is not limited to such control, as long as the particle size difference can be reduced. That is, for example, the control unit 100 can perform a toner replenishment operation, so that the target value of the remaining amount of toner in the yellow developing container 44, which has a small total amount of toner used, is changed from a first reference value (40g) to a third reference value (30g), which is less than the first reference value.

[0167] Figure 10C The diagram illustrates the control of this change. Figure 10C In the figure, curve H4 indicates the relationship between the total amount of toner used and the average particle size when the target value of the remaining amount in the yellow developing container 44 is changed to 30g.

[0168] When the target value of the remaining toner in the developing container 44 of the processing cartridge 3Y is changed to 30g and a toner replenishment operation is performed, the change in the average particle size of the toner shifts to curve H4. Through this replenishment operation, the average particle size of the toner is larger compared to the case of curve H1. At this time, the particle size difference between yellow and cyan changes from... (and Figure 10A In Same) change to By reducing particle size difference in this way, fixing failures can be suppressed.

[0169] Because the fixing device 7 in this example includes a heating unit on the printing surface side of the sheet, over-melting may occur if the particle size of the toner (yellow) on the uppermost side of the sheet is smaller than that of other toner colors. On the other hand, if the particle size of the toner (cyan or black) on the lowermost side of the sheet is larger than that of other toner colors, the heat energy required for melting becomes insufficient, and fixing problems due to insufficient melting may occur. Based on this consideration, the state where the average particle size of the toner T closer to the heating unit is larger than the average particle size of the toner T further away from the heating unit is more preferable than the reverse. Therefore, based on the particle size difference... When the average particle size of the toner T for each color is controlled by supplementary operation, the control unit 100 can change the particle size difference for each combination of colors. .

[0170] The difference in the total amount of toner used can be set for each color, which is greater than the difference in the total amount of toner used J, and the control of changing the remaining amount of toner in the developing container 44 can be performed multiple times.

[0171] In this example, the average particle size of the cyan toner T is 1 larger than that of the yellow toner T. In more cases, fixing-related problems may occur. In such cases, particle size difference... It can be set to 1 In this example, at the particle size difference 1 The difference J in the total amount of toner used is 300g. Therefore, the control unit 100 monitors whether the difference in the total amount of toner used exceeds 300g, and performs the supplementary control of this example if the difference in the total amount of toner used exceeds 300g.

[0172] The control in Example 2 can be executed in combination with the control in Example 1, or the control in Example 2 can be executed independently. To execute Example 2, multiple thresholds can be provided as described in Example 1, and the remaining amount of toner can be gradually changed.

[0173] According to this disclosure, an image forming apparatus can be provided that enables the suppression of adverse effects on the image caused by changes in the physical properties of the toner in a configuration that allows for the replenishment of toner to a processing cartridge.

[0174] While this disclosure has been described with reference to embodiments, it is to be understood that this disclosure is not limited to the disclosed examples. The scope of the appended claims is to be interpreted in the broadest possible sense to cover all such modifications and equivalent structures and functions.

Claims

1. An image forming apparatus, comprising: An image carrier having a surface on which an electrostatic latent image is to be formed; A developing apparatus, the developing apparatus including a developer carrier and a developing container, the developer carrier being configured to supply developer to the electrostatic latent image, and the developing container being configured to support the developer carrier and store the developer; A replenishment container configured to replenish the developer into the developing container; as well as A control unit configured to control the replenishment operation of the developer from the replenishment container to the developing container. in The control unit The replenishment operation is controlled so that the amount of developer stored in the developing container becomes a predetermined reference value, and If the consumption information regarding the total amount of developer consumed since the start of use of the developing equipment exceeds a first threshold, the target value of the amount of developer stored in the developing container will be increased from the predetermined reference value.

2. The image forming apparatus according to claim 1, wherein If the consumption-related information exceeds a second threshold greater than the first threshold after the target value of the amount of developer stored in the developing container is increased from the predetermined reference value, the control unit further increases the target value of the amount of developer stored in the developing container.

3. An image forming apparatus, comprising: A first image carrier and a second image carrier, each having a surface on which an electrostatic latent image is to be formed; A first developing apparatus, comprising a first developer carrier and a first developing container, wherein the first developer carrier is configured to supply a first developer to an electrostatic latent image on a first image carrier, and the first developing container is configured to support the first developer carrier and store the first developer. The second developing apparatus includes a second developer carrier and a second developing container. The second developer carrier is configured to supply a second developer to an electrostatic latent image on the second image carrier, and the second developing container is configured to support the second developer carrier and store the second developer. A first replenishment container, configured to replenish the first developing container with the first developing agent; A second replenishment container is configured to replenish the second developer to the second developing container; as well as A control unit configured to control the replenishment operation of the first developer from the first replenishment container to the first developing container and the replenishment operation of the second developer from the second replenishment container to the second developing container. in The control unit The replenishment operation is controlled to bring the amount of the first developer stored in the first developing container to a predetermined reference value, and the replenishment operation is also controlled to bring the amount of the second developer stored in the second developing container to a predetermined reference value. If the consumption difference exceeds a third threshold, the target value of the amount of the first developer stored in the first developing container is increased from the predetermined reference value. The consumption difference is obtained by subtracting the total amount of the second developer consumed since the start of use of the second developing device from the first consumption-related information about the total amount of the first developer consumed since the start of use of the first developing device.

4. An image forming apparatus, comprising: A first image carrier and a second image carrier, each having a surface on which an electrostatic latent image is to be formed; A first developing apparatus, comprising a first developer carrier and a first developing container, wherein the first developer carrier is configured to supply a first developer to an electrostatic latent image on a first image carrier, and the first developing container is configured to support the first developer carrier and store the first developer. The second developing apparatus includes a second developer carrier and a second developing container. The second developer carrier is configured to supply a second developer to an electrostatic latent image on the second image carrier, and the second developing container is configured to support the second developer carrier and store the second developer. A first replenishment container, configured to replenish the first developing container with the first developing agent; A second replenishment container is configured to replenish the second developer to the second developing container; as well as A control unit configured to control the replenishment operation of the first developer from the first replenishment container to the first developing container and the replenishment operation of the second developer from the second replenishment container to the second developing container. in The control unit The replenishment operation is controlled to bring the amount of the first developer stored in the first developing container to a predetermined reference value, and the replenishment operation is also controlled to bring the amount of the second developer stored in the second developing container to a predetermined reference value. If the consumption difference exceeds a third threshold, the target value of the amount of the second developer stored in the second developing container is reduced from the predetermined reference value. The consumption difference is obtained by subtracting the total amount of the second developer consumed since the start of use of the second developing device from the first consumption-related information about the total amount of the first developer consumed since the start of use of the first developing device.

5. The image forming apparatus according to claim 1 or 2, wherein The developing device is a processing box that can be attached to the main body of the image forming apparatus.

6. The image forming apparatus according to claim 5, wherein The replenishment container is a toner cartridge that can be attached to the developing equipment.

7. The image forming apparatus according to claim 1 or 2, further comprising a detector configured to detect the amount of developer stored in the developing container; The control unit performs a supplementary operation based on the detection result of the detector, such that the amount of developer stored in the developing container becomes the predetermined reference value.

8. The image forming apparatus according to claim 1 or 2, wherein The control unit calculates the amount of developer consumed based on image information about the image developed by the developing equipment.

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