Patent Grant
8594519
1. Field of the Invention
The present invention relates to an image forming apparatus and a toner supply method.
2. Description of the Related Art
In the related art, a single-component developing apparatus is known. In the single-component developing apparatus, developing is carried out in such a manner that a developing roller, which is a toner carrying member, carries toner that is developer of a non-magnetic or magnetic single component, and the toner on the developing roller is supplied to a latent image on a photosensitive member, in a developing area in which the photosensitive member that is a latent image carrying member and the developing roller face one another.
In the single-component developing apparatus, the developing apparatus is replaced when the toner in the developing apparatus has run out. Therefore, the developing roller for which a replacement time has not been reached yet and thus usage of which can be continued is also replaced. Thus, a resource may be wasted. In a case where the developing apparatus is configured such that a time at which the toner in the developing apparatus runs out and the replacement time of the developing roller are the same as one another, it may be necessary to ensure a space for holding a great amount of toner in the developing apparatus, and thus, the developing apparatus may be increased in size.
Japanese Patent No. 4026977 (patent document 1) describes an image forming apparatus in which a toner container that holds toner is provided separate from a developing apparatus, and a supplying part supplies the toner of the toner container to the developing apparatus. Thereby, in a case where the toner in the toner container runs out, only the toner container is to be replaced, and thus, a developing roller for which usage can be continued is not to be replaced. Further, because an amount of the new toner held by the toner container may be determined without regard to a replacement time of the developing roller, it is possible to reduce a capacity of the toner container to be small, and thus, it is possible to prevent the image forming apparatus from being increased in size.
Further, according to the image forming apparatus of the patent document 1, the toner of the toner container is supplied to the developing apparatus when the toner amount in the developing apparatus becomes less than a lower limit value. Therefore, after the toner is thus supplied to the developing apparatus, the toner having remained in the developing apparatus for a long period of time without being used for developing and the toner newly supplied from the toner container are mixed together.
Japanese Laid-Open Patent Application No. 2009-75244 (patent document 2) describes the following image forming apparatus for preventing fog caused as a result of new toner being supplied to a developing apparatus in which old deteriorated toner remains. The term “fog” means a phenomenon that an image area that is to be a blank has a density increased as a result of toner adhering thereto through a developing process. That is, when a toner amount in the developing apparatus becomes less than a lower limit value, such control is carried out that, before toner is supplied to the developing apparatus, the toner remaining in the developing apparatus is ejected toward an image carrying member. Thereby, the old toner remaining in the developing apparatus is ejected to the image carrying member, and, in a condition in which the developing apparatus has thus become approximately empty of toner, new toner is supplied from a toner container. Therefore, almost all of the toner in the developing apparatus becomes the new toner after the new toner is thus supplied, and thus, it is possible to prevent fog after the new toner is supplied.
A reason why fog occurs when deteriorated old toner and new toner are mixed will now be described concretely.
Old toner remaining in a developing apparatus has suffered stress for a long period of time due to such as stirring. As a result, an external additive that is added externally to surfaces of toner particles for controlling flowability and an electrification property may have been removed or may have been embedded in the particles. Thereby, the toner may not be easily electrified frictionally to, for example, negative polarity that is normal electrification polarity of the toner. On the other hand, new toner supplied to the developing apparatus is not deteriorated and thus, is easily electrified frictionally to the negative polarity. Therefore, when the new toner that is easily electrified to the negative polarity and the old toner that is not easily electrified to the negative polarity are rubbed together, charge separation occurs, and electrons in the old toner move to the new toner. As a result, an electrification amount of the new toner to the negative polarity may increase, an electrification amount of the old toner to the negative polarity may decrease, or the old toner may be electrified to positive polarity. As a result, the toner electrification distribution becomes broad, and also, such a distribution may occur in which two peaks, i.e., an area in which the electrification amount to the negative polarity is large and an area in which the electrification amount is approximately zero, exist. Thus, after the new toner is supplied, the deteriorated toner may become weak electrified toner, or reverse electrified toner. Therefore, in an image forming process after the new toner is supplied, the above-mentioned deteriorated old toner may adhere to an area (other than a latent image area) on a photosensitive member that is an image carrying member for which area no toner is desired to be placed. As a result, fog increases in comparison to a case before the new toner is supplied.
However, there may be case where, for example, a toner consumption rate per a unit period of time in a developing apparatus is high, remaining toner in the developing apparatus becomes equal to or less than a predetermined value within a short period of time, the toner in the developing apparatus has suffered not much stress, and thus, deterioration of the old toner remaining in the developing apparatus is minor. In such a case where deterioration of the old toner remaining in the developing apparatus is minor, the toner has sufficient electrification capability, so that charge separation hardly occurs even when new toner is supplied and the old toner and the new toner are rubbed together. Therefore, in such a case where deterioration of the old toner remaining in the developing apparatus is minor, a toner electrification distribution in the developing apparatus after the new toner is supplied can be maintained as a sharp distribution having a peak of a predetermined electrification amount of the negative polarity. As a result, it is possible to obtain an image in which fog is prevented after the new toner is supplied.
However, according to the above-mentioned patent document 2, although deterioration of old toner remaining in the developing apparatus is minor, and thus, the toner has sufficient electrification capability, the toner is ejected to the image carrying member, and thus, is discarded. As a result, the toner may be wasted.
The present invention has been devised in consideration of the above-mentioned problem, and an object of the present invention is to provide an image forming apparatus and a toner supply method in which it is possible to prevent fog after new toner is supplied and also developer is prevented from being wasted.
According to an aspect of the present invention, an image forming apparatus includes a latent image carrying member that carries a latent image; an electrifying part that electrifies a surface of the latent image carrying member; a latent image writing part that writes the latent image on the latent image carrying member; a developing part that develops the latent image on the latent image carrying member by using toner and obtains a toner image; a transferring part that transfers the toner image on the latent image carrying member to a surface of an endless moving member in which the surface is moved in an endless manner or a recording member held on the surface of the endless moving member; a toner container that holds the toner to be supplied to the developing part; a remaining amount detecting part that detects a toner remaining amount in the developing part; a toner supplying part that supplies the toner to the developing part from the toner container when the remaining amount detecting part detects that the toner remaining amount in the toner developing part is equal to or less than a predetermined toner amount value; a fog detecting part that detects fog of an image; and a determining part that, when the remaining amount detecting part detects that the remaining toner amount in the developing part is equal to or less than the predetermined toner amount value, forms a fog detecting image, detecting the fog detecting image by the fog detecting part, and determines, based on a detection result of the fog detecting part for the fog detecting image, whether a toner ejecting process of ejecting the toner remaining in the developing part to the latent image carrying member is carried out before supplying the toner to the developing part by the toner supplying part.
According to another aspect of the present invention, a toner supply method for supplying toner from a toner container to a developing part that causes toner to adhere to a latent image formed on a latent image carrying member and develops the latent image, includes detecting a toner amount in the develop part as being equal to or less than a predetermined toner amount value; forming a fog detecting image in a case where the toner amount in the developing part is equal to or less than the predetermined toner amount value, and detecting fog; and determining based on the detected fog whether to execute a toner ejecting process of ejecting the toner remaining in the developing part toward the latent image carrying member before supplying the toner to the developing part from the toner container.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.
According to an embodiment of the present invention, it is determined whether a toner ejecting process is to be carried out, based on a detection result of detection by a fog detecting part. Thereby, it is possible to prevent fog after new toner is supplied, and also, it is possible to prevent developer from being wasted. That is, in a case where fog is equal to or more than a predetermined fog value as a result of the detection by the fog detecting part, toner is supplied to a developing part after the toner ejecting process is carried out. On the other hand, in a case where fog is less than the predetermined fog value as a result of the detection by the fog detecting part, toner is supplied to the developing part without carrying out the toner ejecting process. In a case where deterioration of old toner remaining in the developing part has developed, friction electrification is not sufficiently carried out in the toner, and thereby, fog becomes equal to or more than the predetermined fog value. Therefore, in a case where fog is equal to or more than the predetermined fog value, the toner ejecting process is carried out, old toner remaining in the developing apparatus is thus ejected, and, in a condition in which the inside of the developing apparatus becomes almost empty of toner, new toner is supplied to the developing apparatus. Thereby, it is possible to prevent fog after the new toner is supplied.
On the other hand, in a case where deterioration of the old toner remaining in the developing apparatus is minor and the toner has sufficient friction electrification capability, fog becomes less than the predetermined fog value. Therefore, in this case, the ejecting process is not carried out and new toner is supplied to the developing apparatus. Thereby, it is possible to prevent useless consumption of toner, and also, it is possible to prevent fog after new toner is supplied.
Below, an embodiment of an electrophotographic printer (simply referred to as a printer, hereinafter) as an image forming apparatus according to the present invention will now be described.
First, a basic configuration of a printer 100 will now be described.
The electrifying apparatus 2K as an electrifying part is configured so that a high voltage of a core metal of an electrification roller (2K) which is in contact with a surface of the photosensitive member 1K and thus is rotated along with rotation of the photosensitive member 1K is applied to the surface of the photosensitive member 1K, and the surface of the photosensitive member 1K is uniformly electrified. Instead of the electrification roller (2K), a corotron-type or a scorotron type electrification unit that discharges electricity as a result of a high voltage being applied to a charging wire, an electrification brush, an electrification sheet, a stylus electrode, or such, may be used. These are advantageous in that they can electrify the surface of the photosensitive member 1K in a non-contact manner, and thus, are not easily affected by a cleaning property. However, an amount of discharge product such as ozone, NOx or such generated along with discharging is particularly larger than the case of using the electrification roller, and therefore, a problem may arise concerning durability of the photosensitive member 1K.
The developing apparatus 4K is a single-component developing apparatus, and includes a developing roller 41K as a toner carrying member, and a toner supply roller 42K as a toner supply member that supplies toner to the developing roller 41K. Above the developing apparatus 4K, a toner container 7K is provided. In the toner container 7K are included a toner storage part 71K that stores new toner and a waste toner receiving part 72K that is provided above the toner storage part 71K and receives waste toner. In the toner storage part 71K, an agitator 71aK that is driven and rotated by a driving part not shown, and a conveying member 71bK that includes a screw or a coil and conveys the new toner from the inside of the toner storage part 71K toward a toner supply port not shown acting as a connection part connecting between the developing apparatus 4K and the toner storage part 71K, are provided. The conveying member 71bK is driven and rotated by a driving part not shown. It is preferable that the agitator 71aK is at any time driven and rotated to stir the new toner in the inside of the toner storage part 71K for the purpose of maintaining flowability of the new toner in the inside of the toner storage part 71K.
In the developing apparatus 4K, a toner transporting member 44K that includes a screw or such for conveying the new toner of the toner storage part 71K supplied from the toner supply port to the entire area in an axis direction of the developing apparatus 4K, an agitator 43K that stirs toner in the developing apparatus 4K, and the developing roller 41K that is the toner carrying member, are provided. Further, a lamellation blade 45K, an extending end of which is in contact with the developing roller 41K and which makes thinner a toner layer that is carried by the developing roller 41K, and a toner supply roller 42K that is in contact with the developing roller 41K and supplies toner to the developing roller 41K, are provided.
The toner supply roller 42K is in contact with the developing roller 41K, is rotated along with rotation of the developing roller 41K or is rotated in a rotation direction reverse or counter to a rotation direction of the developing roller 41K, and supplies toner that adheres to the toner supply roller 42K to the toner developing roller 41K. The surface of the toner supply roller 42K is coated by a formed material having cells, thus, efficiently takes in by causing the toner in the inside of the developing apparatus 4K to adhere to the formed material, and also, prevents deterioration of the toner otherwise occurring because of concentration of pressure at a part at which the toner supply roller 42K is in contact with the developing roller 41K. To the toner supply roller 42K, a voltage of normal electrification polarity (negative polarity) of toner is applied by the power source 110 as a voltage applying part. The voltage is a negative voltage lower than a voltage (negative voltage) applied to the developing roller 41K, that is, a negative voltage having an absolute value larger than an absolute value of the negative voltage applied to the developing roller 41K. Thereby, at the part at which the toner supply roller 42K is in contact with the developing roller 41K, an electric field is generated. Friction electrification of the toner in the inside of the developing apparatus 4K is promoted as the toner is stirred by the agitator 43K and the toner is electrified in the normal electrification polarity (negative polarity). Thereby, the toner held by the toner supply roller 42K and conveyed to the part at which the toner supply roller 42K is in contact with the developing roller 41K moves from the toner supply roller 42K to the developing roller 41K by the influence of the electric field, and statically adheres to the developing roller 41K. A layer thickness of the K toner adhering to the developing roller 41K on the surface of the developing roller 41K is controlled by the lamellation blade 45K when the K toner on the developing roller 41K passes a position along with rotation of the developing roller 41K at which the developing roller 41K is in contact with the lamellation blade 45K. The K toner, after the layer thickness thereof is thus controlled, adheres to an electrostatic latent image for the color K formed on the photosensitive member 1K for the color K at a developing area that is a part at which the developing roller 41K is in contact with the photosensitive member 1K. As a result of the adhesion, the electrostatic latent image for the color K is developed by the K toner into a K toner image.
At an end of the process cartridge 10K, a waste toner conveyance part 64K that extends from the drum cleaning apparatus 6K to a waste toner receiving part 72K of the toner container 7K (not shown in
Toner removed from the photosensitive member 1K by the drum cleaning apparatus 6K is, as waste toner, conveyed to the bottom end of the waste toner conveyance part 64K at an end part of the process cartridge 10K, by a waste toner conveying member 62K. The waste toner thus conveyed to the bottom of the waste toner conveyance part 64K is raked up by the protrusion parts 63aK of the waste toner collecting belt 63K. The waste toner that has been thus raked up by the protrusion parts 63aK is held, as shown in
The toner container 7K is provided detachably from the apparatus body of the developing apparatus 4K, and, after the new toner in the toner storage part 71K runs out, the toner container 7K is removed from the apparatus body of the developing apparatus 4K, and is replaced with another toner container 7K in which new toner is held. At the same time, the waste toner stored in the waste toner receiving part 72K of the toner container 7K is also collected.
Further, the developing apparatus 4K has a detecting window 46K made from transparent material and protruding from a case of the developing apparatus 4K (see
The control part 90 drives and rotates the conveying member 71bK (see
The above-mentioned drum cleaning apparatus 6K includes a cleaning blade 61K, an extending end of which is in contact with the surface of the photosensitive member 1K and which is made of an elastic body, and the waste toner conveying member 62K for conveying the waste toner removed by the cleaning blade 61K from the surface of the photosensitive member 1K to the waste toner conveyance part 64K (see
The process cartridge 10K has been described above with reference to
As shown in
In this configuration, in a case where image forming is carried out in a negative positive way (in which an absolute value of an electrical potential at an exposed part is lower than an absolute value of an electrical potential at a non-exposed part, and toner adheres to the exposed part), surfaces of the respective photosensitive members 1Y, 1M, 1C and 1K are uniformly electrified by the respective electrifying apparatuses 2Y, 2M, 2C and 2K in negative polarity. Next, from an exposure apparatus 130 as a latent image forming part disposed above in the vertical direction of the photosensitive members 1Y, 1M, 1C and 1K, light 3Y, 3M, 3C and 3K according to given image information is emitted to the respective photosensitive members 1Y, 1M, 1C and 1K, and thereby, latent images of the respective colors are formed on the respective photosensitive members 1Y, 1M, 1C and 1K. As the exposure apparatus 130, a laser beam scanner using laser diodes or such may be used. Next, as a result of developing biases in negative polarity having absolute values larger than the electrical potentials at the exposed parts being applied to the developing rollers 41Y, 41M, 41C and 41K of the respective developing apparatus 4Y, 4M, 4C and 4K from the power source 110, the toners carried by the developing rollers 41Y, 41M, 41C and 41K are moved to the latent images on the photosensitive members 1Y, 1M, 1C and 1K, and are made to adhere to the latent images. Thereby, toner images corresponding to the latent images are formed on the photosensitive members 1Y, 1M, 1C and 1K.
The toner images of the respective colors thus developed by the developing apparatuses 4Y, 4M, 4C and 4K, respectively, are primarily transferred to the intermediate transfer belt 15 as an intermediate transfer member, in such a manner that the respective toner images are superposed to form a color image. The toners not having been transferred to the intermediate transfer belt 15 and remaining after the transfer process on the respective photosensitive members 1Y, 1M, 1C and 1K are removed from the surfaces of the photosensitive members 1Y, 1M, 1C and 1K by cleaning belts 61Y, 61M, 61C and 61K of the respective cleaning apparatuses 6Y, 6M, 6C and 6K.
Further, a paper supply cassette (not shown) is provided below in the vertical direction of the intermediate transfer belt 15 in the printer 100. Transfer paper fed from the paper supply cassette is conveyed by a conveyance belt (not shown) as being guided by a conveyance guide (not shown), and is sent to a temporary stopping position at which a registration roller (not shown) is provided. Then, at a predetermined timing, the transfer paper is supplied by the registration roller to a secondary transfer part between a part of the intermediate transfer belt 15 at which the intermediate transfer belt 15 is wound on the secondary transfer facing roller 21 and a secondary transfer roller 22. Then, as a result of a predetermined secondary bias being applied to the secondary transfer roller 22 by the power source 110, the color image (toner images) formed on the intermediate transfer belt 15 is secondarily transferred to the transfer paper, and the color image is thus formed on the transfer paper. The color image (toner images) formed on the transfer paper is fixed by a fixing unit 26, and after that, the transfer paper is ejected to a paper ejecting tray (not shown). Further, the toners remaining on the intermediate transfer belt 15 after the secondary transfer process are removed by the belt cleaning apparatus 33. The toners thus removed by the belt cleaning apparatus 33 are, as waste toners, conveyed to a waste toner receiving part (not shown and corresponding to the waste toner receiving part 72K of the toner container 7K) of the toner container 7Y from the belt cleaning apparatus 33, through a conveyance part not shown.
Further, the printer 100 has a contact/apart mechanism 50 as a contact/apart part which causes the intermediate transfer belt 15 to come into contact with and be removed from the photosensitive members 1Y, 1M and 1C.
As shown in
Below, for the sake of convenience, description will be made only for the developing apparatus 4K for example. However, also to the other developing apparatuses 4Y, 4M and 4C, the same description is applicable, and duplicate description will be omitted. In the present embodiment, when a toner remaining amount in the developing apparatus 4K becomes less than the predetermined toner amount value, the conveying member 71bK (see
Therefore, in the related art, before new toner is supplied to a developing apparatus from a toner storage part, a toner ejecting process of ejecting old toner remaining in the developing apparatus to a photosensitive member is carried out.
It is noted that, in a case where deterioration of old toner remaining in the developing apparatus is minor, the old toner has a property such that the toner is sufficiently electrified to negative polarity, and therefore, charge separation does not easily occur even when the old toner and new toner are rubbed together. Therefore, in such a case where deterioration of the old toner remaining in the developing apparatus is minor, a toner electrification distribution in the developing apparatus after the new toner is supplied can be maintained as a sharp distribution having a peak of a predetermined electrification amount. Therefore, in a case where deterioration of old toner remaining in the developing apparatus is minor, it is possible to obtain a satisfactory image in which no fog occurs even after new toner is supplied.
However, according to the related art, although deterioration of old toner remaining in the developing apparatus is minor, the toner is ejected to the image carrying member, and thus, is discarded. As a result, the toner may be wasted. Therefore, according to the present embodiment, when a remaining toner amount in the developing apparatus becomes less than the predetermined toner amount value, fog in an image is detected. Then, in a case where detected fog is equal to or more than a predetermined fog amount, a toner ejecting process is carried out. Then, after that, new toner is supplied to the developing apparatus. On the other hand, in a case where detected fog is less than the predetermined fog amount, no toner ejecting process is carried out, and new toner is supplied to the developing apparatus. Below, this point of the present embodiment will be described concretely.
As mentioned above, for the sake of convenience, description is made only for the developing apparatus 4K for example. However, also to the other developing apparatuses 4Y, 4M and 4C, the same description is applicable, and duplicate description is omitted. As shown in
When the fog detecting process is thus carried out, a blank paper image as a fog detecting image is formed on the intermediate transfer belt 15. Specifically, in a case where the toner remaining amount in the developing apparatus 4K for the color K becomes less than the predetermined toner amount value, the electrifying apparatus 2K of the process cartridge 10K including the developing apparatus 4K uniformly electrifies the surface of the photosensitive member 1K, no exposure is carried out by the exposure apparatus 130, and the predetermined developing bias is applied to the developing roller 41K. Thereby, a blank paper image is formed on the photosensitive member 1K. In a case where deterioration of old toner remaining in the developing apparatus 4K is minor, and the old toner is sufficiently electrified, the toner hardly moves to the photosensitive member 1K, and fog hardly occurs. On the other hand, in a case where toner in the developing apparatus 4K is deteriorated, and an electrification amount in the toner is small, a force operating on the toner such that the toner is prevented from moving from the developing roller 41K because of an electric field between the developing roller 41K and the photosensitive member 1K, becomes weaker. Therefore, the deteriorated weak-electrified toner adheres to the photosensitive member 1K. As a result, fog in the blank paper image becomes worse. Then, the blank paper image is transferred to the intermediate transfer belt 15, and the blank paper image is then detected by the reflection optical sensor 150 disposed on the downstream side in the moving direction of the intermediate transfer belt 15 with respect to the process cartridge 10K for the color K as shown in
By using the reflection optical sensor 150, it is possible to detect a toner adhesion amount on the intermediate transfer belt 15. Specifically, the surface of the intermediate transfer belt 15 is so smooth as to behave as a mirror surface, and therefore, specular reflection light is dominant in light obtained from being emitted by the light emitting device 151 and then being reflected by the surface of the intermediate transfer belt 15. On the other hand, a part at which toner adheres to the intermediate transfer belt 15 has a coarse surface, and therefore, diffuse reflection light becomes dominant over specular reflection light. Accordingly, by measuring a ratio between specular reflection light and diffuse reflection light reflected by the intermediate transfer belt 15, it is possible to estimate a toner adhesion amount by estimating a ratio between an area in which toner adheres and an area in which no toner adheres (bare or exposed surface area) on the intermediate transfer belt 15.
To the specular reflection light receiving device 152 of the reflection optical sensor 150, reflected light (specular reflection) from the surface of the intermediate transfer belt 15 and reflected light (diffuse reflection) from the toner surface are given. To the diffuse reflection light receiving device 153 of the reflection optical sensor 150, reflected light (diffuser reflection) from the surface of the intermediate transfer belt 15 and reflected light (diffuse reflection) from the toner surface are given. Output of the specular reflection light receiving device 152 becomes maximum at a bare surface part of the intermediate transfer belt 15 and decreases as the toner adhesion amount increases. Output of the diffuse reflection light receiving device 153 becomes minimum at the bare surface part of the intermediate transfer belt 15 and increases as the toner adhesion amount increases.
When a blank paper image having a little fog is detected by the reflection optical sensor 150, the output value of the specular reflection light receiving device 152 is approximately maximum and the output value of the diffuse refection light receiving device 153 becomes approximately minimum, since toner hardly adheres to the intermediate transfer belt 15. On the other hand, when a blank paper image having remarkable fog is detected by the reflection optical sensor 150, the output value of the specular refection light receiving device 152 decreases and the output value of the diffuse refection light receiving device 153 increases, since much toner (weak-electrified toner) adheres to the intermediate transfer belt 15.
In the present embodiment, the control part 90 determines whether the output value Vsp of the diffuse light receiving device 153 exceeds a threshold when detecting in the blank paper image that is the fog detecting image (step S3 in
When the toner ejecting process is carried out, the electrifying apparatus 2K uniformly electrifies the surface of the photosensitive member 1K, and the exposure apparatus 130 exposes the entire surface of the photosensitive member 1K. Thereby, the old toner remaining in the developing apparatus 4K adheres to the entire area of an image forming area of the photosensitive member 1K, and thus, it is possible to effectively eject the toner remaining in the developing apparatus 4K to the photosensitive member 1K. The old toner thus having been ejected to the surface of the photosensitive member 1K is transferred to the intermediate transfer belt 15, and is removed by the belt cleaning apparatus 33 from the intermediate transfer belt 15. Then, the toner is conveyed to the waste toner receiving part of the toner container 7Y of the color Y as waste toner by the conveyance part from the belt cleaning apparatus 33. It is noted that, at this time, the secondary transfer roller 21 is caused to be apart from the intermediate transfer belt 15.
Further, such a control method may be used that the voltage applied to the electrifying apparatus 2K is turned off, the surface of the photosensitive member 1K is not electrified, and the old toner remaining in the developing apparatus 4K is ejected. In this control method, the electrification electric potential on the surface of the photosensitive member 1K is zero and the predetermined developing bias of negative polarity is applied to the developing roller 41K. Therefore, between the photosensitive member 1K and the developing roller 41K, toner of negative polarity on the developing roller 41K electrostatically moves to the photosensitive member 1K. Thus, also in this control method, it is possible that the old toner remaining in the developing apparatus 4K adheres to the entire surface of the image forming area of the photosensitive member 1K. Further, in the case where the control method is used, it is not necessary to expose the surface of the photosensitive member 1K for a long time by the exposure apparatus 130, and it is advantageous that deterioration of the photosensitive member 1K because of light-induced fatigue can be avoided.
Further, such a control method may be used that at a time of carrying out the toner ejecting process, the power source 110 is controlled so that such a voltage is applied to the toner supply roller 42K that an absolute value of the voltage applied to the toner supply roller 42K becomes larger, and an electric potential difference between the developing roller 41K and the toner supply roller 42K becomes larger. Thereby, the old toner remaining in the developing apparatus 4K easily moves to the developing roller 41K from the toner supply roller 42K electrostatically. Further, the lamellation blade 45K may be made to be apart from the developing roller 41K. Thereby, a toner layer on the developing roller 41K becomes thicker, and thus, it is possible to move the toner from the developing apparatus 4K to the photosensitive member 1K within a shorter time period.
The toner ejecting process is terminated in such a manner that, by using the reflection optical sensor 150, a toner density of an image (referred to as an ejected image, hereinafter) formed by the toner ejected from the developing apparatus 4K and transferred to the surface of the intermediate transfer belt 15 is detected, and when the detected toner density of the ejected image becomes equal to or less than a predetermined toner density value because of lack of a toner amount remaining in the developing apparatus 4K, the developing bias is turned off, and the toner ejecting process is terminated. However, in this case, since the position at which the detection is carried out by the reflection optical sensor 150 is to the downstream side in the image moving direction with respect to the developing area, the toner ejecting process is continued for a predetermined time period under the condition of the lack of the toner amount remaining in the developing apparatus 4K. As a result, a time period required for the toner on the intermediate transfer belt 15 being completely removed by the cleaning apparatus 33 becomes longer, and deterioration between the members which rub one another such as rubbing between the photosensitive member 1K and the intermediate transfer belt 15 may cause anxiety. Therefore, because a toner consumption amount per unit time period during the toner ejecting process and a toner remaining amount in the developing apparatus 4K at a time when the toner ejecting process is started are previously known, such a control method may be used that an apparatus driving time is previously calculated therefrom and is stored in a memory (not shown), and, the toner ejecting process is terminated when the apparatus driving time is reached after the toner ejecting process is started. Thereby, the toner ejecting process is terminated at an expected time when the toner density at the developing area becomes equal to or less than the predetermined toner density value. Therefore, it is possible to shorten the time period required for the toner on the intermediate transfer belt 15 being removed in comparison with the case where the toner ejecting process is terminated when the decrease in the toner density of the ejected image transferred to the surface of the intermediate transfer belt 15 is detected by the reflection optical sensor 150. Thereby, it is possible to reduce rubbing between the photosensitive member 1K and the intermediate transfer belt 15 in comparison with the case where the toner ejecting process is terminated when the decrease in the toner density of the ejected image transferred to the surface of the intermediate transfer belt 15 is detected by the reflection optical sensor 150, and thus, it is possible to reduce deterioration between the members that rub one another.
Then, after the toner ejecting process is thus terminated and the toner of the ejected image on the intermediate transfer belt 15 is removed by the belt cleaning apparatus 33, new toner is supplied from the toner storage part 71K to the developing apparatus 4K (step S5). Thus, before the new toner is thus supplied, almost all of the old deteriorated toner in the developing apparatus 4K has been removed through the toner ejecting process, and therefore, it is possible to prevent fog from occurring in a formed image after new toner is supplied.
On the other hand, in a case where the output value Vsp of the diffuse light receiving device 153 is equal to or less than the threshold (step S3 NO), the control part 90 determines that fog is equal to or less than the predetermined fog value, and therefore, does not carry out the toner ejecting process, and supplies new toner to the developing apparatus 4K from the toner storage part 71K (step S5). Thus, in a case where deterioration of the toner remaining in the developing apparatus 4K is minor, and fog hardly occurs, the toner ejecting process is not carried out, and therefore, it is possible to avoid useless toner consumption.
Description has been made for the developing apparatus 4K for the color K for example. As mentioned above, the same toner supply control of
Further, in the above-mentioned configuration, the toner supply control of
Further, a gloss level on the surface of the intermediate transfer belt 15 may vary as a result of the surface of the intermediate transfer belt 15 being deteriorated because of having been used for a long time period. When the gloss level on the surface of the intermediate transfer belt 15 varies, the output value of the reflection optical sensor 150 varies, and precise fog detection may not be able to be carried out. Therefore, a second reflection optical sensor 150A (see
Further, in a case where the toner ejecting process for the developing apparatus 4K of the color K is carried out, the photosensitive members 1Y, 1M and 10 of the colors Y, M and C are made to be apart from the intermediate transfer belt 15 by means of the contact/apart mechanism 50 (see
Further, a second contact/apart mechanism may be provided by which the intermediate transfer belt 15 can be apart from and come into contact with the photosensitive member 1K of the color K. The second contact/apart mechanism includes a supporting member that supports the primary transfer roller 5K of the color K and moves the primary transfer roller 5K in directions of causing the primary transfer roller 5K to be apart from and come into contact with the photosensitive member 1K, and a moving part such as a solenoid or such to move the supporting member in the directions of causing the primary transfer roller 5K to be apart from and come into contact with the photosensitive member 1K. By the configuration, it is possible that at a time of the toner ejecting process for the developing apparatus 4K of the color K, the intermediate transfer belt 15 is made to be apart from the photosensitive member 1K. Thereby, it is possible that driving of the intermediate transfer belt 15 is stopped, and the toner ejected from the developing apparatus 4K is not transferred to the intermediate transfer belt 15, but is conveyed to the drum cleaning apparatuses 6K, and is removed by the drum cleaning apparatus 6K. Thereby, it is possible to avoid deterioration of the intermediate transfer belt 15. Further, in a case of configuring as described above so that all the photosensitive members 1Y, 1M, 1C and 1K can be apart from and come into contact with the intermediate transfer belt 15, and the toner ejected by each of the developing apparatuses 4Y, 4M, 4C and 4K is collected by the respective one of the drum cleaning apparatuses 6Y, 6M, 6C and 6K, the mechanism for causing the secondary transfer roller 22 to be apart from and come into contact with the intermediate transfer belt 15 is not necessary.
Further, in the fog detection, the intermediate transfer belt 15 is made to be apart from the photosensitive member 1K in the example of the toner supply control of the developing apparatus 4K for the color K, after the blank paper image is formed on the intermediate transfer belt 15. Then, after the blank paper image on the intermediate transfer belt 15 is detected by the reflection optical sensors 150, an area of the intermediate transfer belt 15 after being apart from the photosensitive member 1K (which area has moved as passing the belt cleaning apparatus 33 and after that, not coming into contact with the photosensitive member 1K) is detected by the reflection optical sensor 150. This area has not come into contact with the photosensitive member 1K and thus, no toner adheres to the area of the intermediate transfer belt 15. Therefore, it is possible to precisely detect a variation, if any, of the gloss level of the surface of the intermediate transfer belt 15 by detecting the area by the reflection optical sensor 150. A difference value (Vsp_dif′−Vsp_dif) is calculated between the value Vsp_dif obtained when the reflection optical sensor 150 detects the blank paper image and the value Vsp_dif′ obtained when the reflection optical sensor 150 detects the above-mentioned area of the intermediate transfer belt 15 after being apart from the photosensitive member 1K. Then, in a case where an absolute value of the difference value (Vsp_dif′−Vsp_dif) exceeds a threshold, it is determined that fog exceeds the predetermined fog value, and the toner ejecting process is carried out. Also by such a control method, it is possible to carry out precise fog detecting through aging. Further, in this control method, it is possible to precisely detect a variation in the gloss level on the surface of the intermediate transfer belt 15 merely by providing the reflection optical sensor 150 at the image forming area (A1 in
Further, in the above description, the reflection optical sensor 150 is provided at a position facing the immediate transfer belt 15. However, instead, as shown in
Next, a verification experiment will be described.
Materials of toner used in the verification experiment are as follows:
Polyester resin A (softening point: 131° C., AV value (acid value): 25) . . . 68 parts
Polyester resin B (softening point: 116° C., AV value (acid value): 1.9) . . . 32 parts
Master batch of cyan (containing 50 parts of Pigment Blue 15:3) . . . 8 parts
Carnauba wax . . . 8 parts
The above-mentioned toner materials were sufficiently mixed by a Henschel mixer; after that, by using a two-axis kneading and extruding machine (PCM-30 manufactured by IKEGAI CORPORATION) after an ejecting part thereof was removed, were melted and kneaded, then, the obtained mixture was rolled by using a cooling press roller into 2 mm thickness, was cooled by a cooling belt, and after that, was crushed coarsely by a feather mill. After that, a mechanical grinder (KTM manufactured by KAWASAKI HEAVY INDUSTRY LTD.) was used to crush the material into an average grain size of 10 through 12 μm. Further, a jet grinder (IDS manufactured by NIPPON PNEUMATIC MFG. CO., LTD.) was used to crush the material, and classify and remove coarse grains from the material, and after that, a rotor classifier (Teeplex classifier, type: 100ATP, manufactured by HOSOKAWA MICRON CORPORATION) was used to classify the classified fine grains, and thus, a toner parent body A having a volume mean grain size (volume mean diameter) of 7.9 μm and having an average circularity of 0.910 was obtained. 1 part of silica (RX200) was added to 100 parts of the toner parent body A, a Henschel mixer was used to carry out mixing the material at a circumferential velocity of 40 m/s, for 5 minutes, and thus, toner was produced.
The thus-produced toner was supplied to a printer, Ipsio C220; an endurance test was carried out, at a room temperature, in a manner of 1 sheet/1 job, 3 seconds intermittent, and 3000 sheets/5000 sheets. After that, the toner was extracted from a developing apparatus. The extracted toner was used as the old toner in the developing apparatus, the new toner was used as toner being supplied, plural mixed toners were produced having mutually different mixture ratios, a blank paper image was formed on a photosensitive member, and a toner amount level (fog amount) on the photosensitive member was measured. The result is shown in
As shown in
Further, in the above description, the example in which the present invention is applied to the image forming apparatus according to the intermediate transfer system (see
Thus, the image forming apparatus according to the present embodiment includes the photosensitive members 1Y, 1M, 1C and 1K that are latent image carrying members for carrying latent images; the electrifying apparatuses 2Y, 2M, 2C and 2K that are electrifying parts for electrifying the surfaces of the photosensitive members 1Y, 1M, 1C and 1K; the exposure apparatus 130 that is a latent image writing part for writing the latent images to the photosensitive members 1Y, 1M, 1C and 1K; the developing apparatuses 4Y, 4M, 4C and 4K that are developing parts for obtaining toner images by developing the latent images on the photosensitive members 1Y, 1M, 1C and 1K by respective toners; and the intermediate transfer belt 15 that is an endless moving member for moving a surface thereof in an endless manner or the transfer unit 30 as a transferring part for transferring the toner images on the photosensitive members 1Y, 1M, 1C and 1K to transfer paper as a recording member held on the surface of the paper conveyance belt 91. Further, the image forming apparatus further includes the toner containers 7Y, 7M, 7C and 7K that hold new toners to be supplied to the developing apparatuses 4Y, 4M, 4C and 4K; the remaining amount detecting parts (including the combinations of the transmission optical sensors (81K in the example of the developing apparatus 4K) and the control unit 90) for detecting toner remaining amounts in the developing apparatuses 4Y, 4M, 4C and 4K; and the toner supplying parts (including the control part 90 and the conveying parts (71bK in the example of the developing apparatus 4K)) for supplying the new toners from the toner storage parts (71K in the example of the developing apparatus 4K) to the developing apparatuses 4Y, 4M, 4C and 4K when the remaining amount detecting parts detect that the toner amounts in the developing apparatuses 4Y, 4M, 4C and 4K are equal to or less than the predetermined toner amount values. Further, when the remaining amount detecting parts detect that the toner amounts in the developing apparatuses 4Y, 4M, 4C and 4K are equal to or less than the predetermined toner amount values, blank paper images that are fog detecting images are formed, and the fog detecting part (including the reflection optical sensor 150 and the control part 90) detects in the blank paper images. Then, in cases where fog in the blank paper images exceeds the predetermined fog values, the control part 90 as a determining part carries out the toner ejecting processes of ejecting old toners remaining in the developing apparatus 4Y, 4M, 4C and 4K to the photosensitive members 1Y, 1M, 1C and 1K, before supplying the new toners to the developing apparatuses 4Y, 4M, 4C and 4K. On the other hand, in cases where fog in the blank paper images is equal to or less than the predetermined fog values, the control part 90 does not carry out the toner ejecting processes, and supplies the new toners to the developing apparatuses 4Y, 4M, 4C and 4K.
By providing the configuration, it is possible to prevent fog occurring after new toner is supplied, and also, it is possible to avoid useless toner consumption.
Further, the fog detecting part may detect fog in the fog detecting image based on a detection result (Vsp_dif) of the blank paper image that is the fog detecting image obtained by the reflection optical sensor 150 as a first optical detecting part that is disposed to face the image forming area (A1 shown in
It is also possible to detect fog based on a detection result (Vsp_dif) of the blank paper image that is the fog detecting image obtained by the reflection optical sensor 150 as an optical detecting part that is disposed to face the image forming area (A1 shown in
Further, the voltage applying part (power source 110) is controlled so that the electric potential difference, at a time of the toner ejecting process, between the toner supply roller (42K in the example of the developing apparatus 4K) as a toner supply member and the developing roller (41K in the example of the developing apparatus 4K) as a toner carrying member becomes larger than the electric potential difference at a time of a developing operation. Thereby, it is possible to increase a toner amount to be supplied to the developing roller from the toner supply roller at a time of the toner ejecting process, and it is possible to effectively eject old toner remaining in the developing apparatus from the developing roller.
Further, the intermediate transfer belt may be made to be apart from the photosensitive members by the contact/apart mechanism at a time when the toner ejecting process is carried out. Thereby, at a time when the toner ejecting process is carried out, the intermediate transfer belt is prevented from rubbing on the cleaning member of the belt cleaning apparatus and the photosensitive members, and thus, it is possible to avoid deterioration of the intermediate transfer belt occurring because of rubbing.
Further, in the toner containers (7Y, 7M, 7C, 7K), the waste toner receiving parts (72K in the example of the toner container 7K) as removed toner containers are provided for holding waste toners that are removed toners removed by the drum cleaning apparatuses that are toner removing parts. Thereby, when new toners in the toner containers run out, it is possible to collect waste toners at the same time when the toner containers are replaced by other toner containers that hold new toners.
Further, it is possible to terminate the toner ejecting process at a timing at which a shortage of toner occurs in the developing area, as a result of the toner ejecting process being terminated based on a driving time period of the developing apparatus elapsing since the toner ejecting process is started. In this control method, it is possible to prevent deterioration of the photosensitive members and the intermediate transfer belt 15 occurring because of rubbing, in comparison to the case where the reflection optical sensor 150 is used to detect a density of toner of an ejected image adhering to the intermediate transfer belt 15, and when a detection result of the density of toner of the ejected image becomes equal to or less than the predetermined toner density value, the toner ejecting process is terminated.
Further, it is not necessary to carry out an electrifying process of the surface of the photosensitive member by the electrifying apparatus at a time when the toner ejecting process is carried out. Although the electrifying process of the surface of the photosensitive member by the electrifying apparatus is not carried out, it is possible to create an electric field such that toner on the developing roller electrostatically moves to the photosensitive member, as a result of a developing bias being applied to the developing roller. Thus, it is possible to eject old toner remaining in the developing apparatus from the developing roller to the photosensitive member. Thereby, it is possible to prevent deterioration occurring because of light-induced fatigue, in comparison to a case where, at a time when the toner ejecting process is carried out, the photosensitive member is electrified by the electrifying apparatus, the entire surface of the photosensitive member is exposed by the exposure apparatus, and toner on the developing roller is caused to move to the photosensitive member.
Further, it may be determined that a toner amount in the developing apparatus is equal to or less than the predetermined toner amount value when, after the transmission optical sensor that is a height detecting part that detects a height of toner held in the developing apparatus detects that the height of the toner becomes equal to or less than the predetermined height value, the number of dots included in an image to be output is counted, and the counted number becomes equal to or more than the predetermined number value. By the control method, it is possible to reduce the remaining toner in the developing apparatus to just such an amount that an image density becomes equal to or less than the predetermined density value because of lack of the toner amount remaining in the developing apparatus, and thus, it is possible to reduce the ejected toner amount to the minimum necessary amount.
The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.
The present application is based on Japanese Priority Application No. 2010-026413, filed on Feb. 9, 2010, the entire contents of which are hereby incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-026413 | Feb 2010 | JP | national |
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