Patent Application
20110116816
This application is based on Japanese Patent Application No. 2009-259728 filed on Nov. 13, 2009, in Japan Patent Office, the entire content of which is hereby incorporated by reference.
The present invention relates to a development apparatus for developing an electrostatic latent image formed on an image carrier, and an image forming apparatus using the same.
There has been extensive use of an image forming apparatus using the electrophotographic process wherein an electrostatic latent image is formed on a photoconductor (image carrier) and is developed with toner. The developed toner image is transferred to a recording medium such as paper and is then fixed on the recording medium.
The development methods for developing an electrostatic latent image using a dry developer includes a one-component development method using toner alone and a two-component development method using both toner and carrier.
In the one-component development method, the toner is passed through the regulating section formed by a toner carrying member and the regulating plate pressed against the toner carrying member, thereby the toner is electrically charged and a desired thin toner layer is obtained. This method provides a simplified configuration, a compact and lightweight structure, and reduces cost of the apparatus. However, toner deterioration is accelerated by the strong stress by the regulating section and the electric charge acceptance of toner tends to be reduced. Further, when the surface of the regulating member as a member for providing the toner with electric charges and the surface of the toner carrying member are contaminated with the toner and external additive agent, the capability of providing the toner with electric charges will be reduced. This will cause a further reduction in toner charge, and will raise fogging or similar problems. For these reasons, the service life of the development apparatus is shorter in general.
In the meantime, in the two-component development method, toner is charged by the frictional charging process through mixture with the carrier. Therefore, this method ensures reduced stress. Further as a surface area of the carrier is large, the carrier has a higher resistance to contamination with the toner and external additive agent. These result in a longer service life of the apparatus. However, when an electrostatic latent image is developed on the image carrier, the image carrier surface is rubbed by the magnetic brush formed by the developer and the marks of the magnetic brush remain on the developed image in the two-component development method. Further, the carrier tends to be deposited on the image carrier. This will cause a problem of image defects.
A so-called hybrid development method is disclosed as a development method (refer to, for example, Unexamined Japanese Patent Application Publication No. H 05-150636), which solves the problems of image defects resulting from the remaining marks of the magnetic brush and others, and realizes high image quality comparable to that of the one-component development method as well as the service life as long as the two-component development. In this hybrid development method, the two-component developer is carried on the developer carrying member. From this two-component developer, only the toner is supplied to the toner carrying member for use in development.
In the hybrid development method, a bias voltage is applied, and toner is supplied onto the toner carrying member from the developer carrying member. The toner layer formed on this toner carrying member is used to develop the latent image on the opposed image carrier.
In the one-component development method or hybrid development method, the amount of the deposited toner in a layer formed on the toner carrying member or specific charge (electric charge per unit mass of the toner layer) depends on the environment where the apparatus is used (temperature, humidity, atmospheric pressure, and others) or number of sheets having been printed. This will cause changes in the state of image formation, particularly in the development characteristics. These changes result in changes in image density, and further in deterioration of the image quality. The solution to this problem requires accurate detection of the changing amount of toner held on the toner carrying member for the purpose of maintaining the image quality.
A method commonly used to minimize the fluctuation in image density is disclosed in the Unexamined Japanese Patent Application Publication No. 2003-173052, for example. In this method, a dummy toner image is developed on the image carrier and the toner amount of the developed toner image is detected at prescribed timings when the toner image (image to be transferred onto the sheet is not formed on the image carrier, for example, before and after image forming operation or during sheet-to-sheet interval in image forming operation. The development bias between the image carrier and toner carrying member is controlled to ensure the toner amount for maintaining the required image density. This method, however, fails to detect the toner amount during the image forming operation.
To solve these problems, Unexamined Japanese Patent Application Publication No. 2008-176236 discloses a method of using the detecting means to detect the toner amount in the toner layer formed on the toner carrying member instead of the toner amount held on the image carrier. This method uses an LED or LD as a light emitting means, which applies light to the toner layer. The reflected light is detected by the light-receiving element such as a photoelectric conversion element, and the absolute amount of the toner layer is obtained from the intensity of this reflected light.
Unexamined Japanese Patent Application Publication No. H06-258949 discloses a method of controlling and maintaining the toner amount held on the toner carrying member at a prescribed level. This control is based on the charge amount of the toner supplied from the developer carrying member to the toner carrying member. This charge amount is obtained by analyzing the current value flowing through the closed loop circuit made up of the toner carrying member, the developer carrying member and an electric power supply apparatus for bias connected to each of them.
In the method disclosed in Unexamined Japanese Patent Application Publication No. 2008-176236, the amounts of light reflected from the toner layer and the toner carrying member surface are measured, therefore, the changes in the amount of the toner cannot be detected in the area where there is too much absolute amount of toner on the toner carrying member. This results in poor detection accuracy and poor image quality. Further, in Unexamined Japanese Patent Application Publication No. H06-258949, the specific charge of toner itself depends on the working environment or the number of sheets having been printed. Thus, an appropriate toner amount cannot be obtained when control is provided based on the result of analysis of the detected current value, and satisfactory image quality cannot be obtained. For example, control is provided in such a way that, when there is an increase in the specific charge of the toner, the toner amount held on the toner carrying member will be reduced. This results in reduced image density.
The present invention is intended to solve the aforementioned problems. It is accordingly an object of this invention to provide a development apparatus, and image forming apparatus wherein, high-precision detection of the toner amount is ensured, and stable image quality is provided accordingly.
In view of the foregoing, one embodiment according to one aspect of the present invention is a development apparatus, comprising:
a toner carrying member configured to hold and carry toner on a surface thereof and convey the toner to an image carrier facing the toner carrying member to develop an electrostatic latent image formed on the image carrier, wherein the toner is carried on a toner carrying area on the surface of the toner carrying member, said toner carrying area being broader in the direction of an axis of rotation of the toner carrying member than an image forming area on a surface of the image carrier in the direction of an axis of rotation thereof;
a detecting roller provided facing the toner carrying member, the detecting roller configured to hold and carry the toner transferred from a non-facing part of the toner carrying area on the surface of the toner carrying member, said part not facing the image forming area of the image carrier; and
a toner detecting device configured to detect optically quantity of the toner transferred to and held on said detecting roller, or quantity of the toner remaining on said non-facing part on the surface of the toner carrying area without being transferred to said detecting roller.
Another embodiment according to another aspect of the present invention is a development apparatus, comprising:
a toner carrying member configured to hold and carry toner on a surface thereof and convey the toner to an image carrier facing the toner carrying member to develop an electrostatic latent image formed on the image carrier, wherein the toner is carried on a toner carrying area on the surface of the toner carrying member, said toner carrying area being broader in the direction of an axis of rotation of the toner carrying member than an image forming area on a surface of the image carrier in the direction of the axis of rotation thereof;
a detecting roller provided facing the toner carrying member, the detecting roller configured to hold and carry the toner transferred from a non-facing part of the toner carrying area on the surface of the toner carrying member, said non-facing part not facing the image forming area of the image carrier;
a toner detecting device configured to detect optically quantity of the toner transferred to and held on said detecting roller; and
a controller configured to control transfer of the toner from the toner carrying member to the detecting roller so that a thickness of a toner layer formed on the detecting roller is smaller than a thickness of a toner layer formed on the toner carrying member before the toner being transferred to the detecting roller.
Another embodiment according to another aspect of the present invention is a development apparatus, comprising:
a toner carrying member configured to hold and carry toner on a surface thereof and convey the toner to an image carrier facing the toner carrying member to develop an electrostatic latent image formed on the image cannier, wherein the toner is carried on a toner carrying area on a surface of the toner carrying member, said toner carrying area being broader in the direction of an axis of rotation of the toner carrying member than the image forming area on a surface of the image carrier in the direction of the axis of rotation thereof;
a detecting roller provided facing the toner carrying member, the detecting roller configured to hold and carry the toner transferred from a non-facing part of the toner carrying area on the surface of the toner carrying member, said non-facing part not facing the image forming area on the surface of the image carrier; and
a toner detecting device configured to detect optically quantity of the toner remaining on said non-facing part of the toner carrying area without being transferred to the detecting roller.
Another embodiment according to another aspect of the present invention is a development apparatus, comprising:
a toner carrying member configured to hold and carry toner on a surface thereof and convey the toner to an image carrier facing the toner carrying member to develop an electrostatic latent image formed on the image carrier, wherein the toner is carried on a toner carrying area on the surface of the toner carrying member, said area being broader in the direction of an axis of rotation of the toner carrying member than an image forming area on a surface of the image carrier in the direction of the axis of rotation thereof;
a detecting roller provided facing the toner earning member, the detecting roller configured to hold and carry the toner transferred from a non-facing part of the toner carrying area on the surface of the toner carrying member, said non-facing part not facing the image forming area on the surface of the image carrier, said detecting roller having translucency; and
a toner detecting device configured to detect optically quantity of the toner transferred to and held on the detecting roller by measuring amount of light transmitted through the detecting roller and the toner layer formed on a surface of the detecting roller.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not serve to limit the invention, for which reference should be made to the appended claims.
The following describes an embodiment of the present invention with reference to the drawings.
The following description refers to an example of the image forming apparatus equipped with a development apparatus based on the hybrid development method. To be more specific, a developer carrying member is used as a toner supply member. As is obvious, a development method should not be restricted to this method. Another development method such as a one-component development method can also be utilized.
(Structure and Operation of the Image Forming Apparatus)
Referring to
This image forming apparatus is a printer wherein the toner image formed on the image carrier (photoconductor) 1 by the electrophotographic process is transferred onto a transfer medium P such as a paper sheet to form an image thereon.
This image forming apparatus is equipped with an image carrier 1 for carrying an image. Around the image carrier 1, a charging member 3 for electrically charging the image carrier, a development apparatus 2 for developing the electrostatic latent image on the image carrier 1 with the toner, a transfer roller 4 for transferring the toner image on the image carrier 1 to the transfer medium P, and a cleaning blade 5 for removing the remaining toner from the image carrier 1 are arranged in that order in the rotating direction A of the image carrier 1.
After having been charged by the charging member 3, the image carrier 1 is exposed to light by the exposure device 6 equipped with a laser light-emitting device, for example, and thereby an electrostatic latent image is formed on the surface of the image carrier. The development apparatus 2 uses a toner to develop this electrostatic latent image and forms a toner image. After transferring the toner image on the image carrier 1 to the transfer medium P, the transfer roller 4 conveys the transfer medium P in the arrow-marked direction C of the drawing.
The toner image on the transfer medium P is fixed by the fixing apparatus (not illustrated). After that, the transfer medium P is ejected. The toner remaining on the image carrier 1 subsequent to the transfer is removed by the mechanical force of the cleaning blade 5.
A conventional technique based on the electrophotographic process can be used, as required, for the image carrier 1, the charging member 3, the exposure device 6, the transfer roller 4, and the cleaning blade 5 used in the image forming apparatus. For example, a charging roller is illustrated as a charging member 3 in the drawing, but instead, it may be a charging device which is not in contact with the image carrier 1. Further, the cleaning blade 5 may not be used.
The detailed description of the structure example of the development apparatus 2 will be introduced later.
(Developer Structure)
A hybrid development method is used in the present embodiment. An appropriate two-component developer can be used. To be more specific, the developer 22 used in the present embodiment includes toner and carrier for charging the toner.
There is no particular restriction concerning toner. A commonly used conventional toner can be used. The binder resin can include colorant and, if required, a charge controlling agent or mold releasing agent. Further, an external additive agent can also be added and processed. There is no particular restriction to the particle size of the toner. The particle size in the range from 3 through 15 μm is preferred in general.
This toner can be produced according to the conventional known method. For example, a pulverization method, emulsion polymerization method, and suspension polymerization method can be utilized.
The commonly used conventional binder resin, colorant, charge control agent, and mold-releasing agent can also be used for toner.
The conventional known agent can also be used as the aforementioned external additive agent. The opposite polarity particles having the charging polarity opposite to that of the toner can be used as the external additive agent.
There is no particular restriction to carrier. A conventional known carrier can be used. A binder type carrier or coating type carrier can be employed. There is no particular restriction to the particle size of the carrier. The preferred particle size is in the range of 15 through 100 μm.
The binder type carrier is obtained by dispersing magnetic fine particles in the binder resin. Positively or negatively charging particles can be fixed to the carrier surface. A surface coating layer can be provided.
The conventional known binder resin and magnetic fine particles can be used in the binder type carrier.
In the meantime, the coating type carrier is produced by coating the carrier core particles made of magnetic substances with resin. For the coating type carrier, positively or negatively charging particles can be fixed to the carrier surface, similarly to the case of the binder type carrier.
The mixture ratio of the toner and the carrier may be adjusted to get a desired amount of toner charge. The mixture ratio of toner is generally 3 through 50% by mass, preferably 6 through 30% by mass with respect to the total amount of the toner and the carrier.
(Structure and Operation of Development Apparatus 2)
Referring to
As described above, the development apparatus of this embodiment has a toner carrying member and a developer carrying member for supplying toner to the toner carrying member. In the development apparatus used in this embodiment, development is performed with the toner layer formed on the toner carrying member opposed to the image carrier. A plurality of toner carrying members can be used, or a plurality of developer carrying members can be used.
The developer 22 used in the development apparatus 2 is made of a toner and a carrier as described above, and is stored in a developer reservoir 16.
The developer reservoir 16 is formed of a developing device enclosure 19, and normally incorporates mixing and agitating members 17 and 18. The mixing and agitating members 17 and 18 mix and agitate the developer 22, and supply the developer 22 to the developer carrying member 11. An ATDC (Automatic Toner Density Control) sensor 20 for toner density detection is preferably arranged in the developing device enclosure 19 at a position opposed to the mixing and agitating member 18.
The development apparatus 2 normally has a supply section 14 so that the amount of toner to be consumed in the development area 8 is supplied in the developer reservoir 16. In the supply section 14, the supply toner 21 fed from a hopper (not illustrated) accommodating the same is supplied into the developer reservoir 16.
The developer carrying member 11 includes a magnetic member 25 fixedly arranged inside, and a freely rotatable sleeve roller 26 including the same. The developer 22 supplied to the developer carrying member 11 is retained on the surface of the sleeve roller 26 by the magnetic force of the magnetic member 25 inside the developer carrying member 11. The developer 22 is conveyed by the rotation of the sleeve roller 26, and the amount of the developer 22 to be passed is regulated by the regulating member (regulating blade) 15 arranged opposed to the developer carrying member 11.
The magnetic member 25 has five magnetic poles—N1, S1, N2, N3, and S2 (refer to
Of these magnetic poles, the main magnetic pole N1 is arranged in the toner supply area 7 to face the toner carrying member 23. Further, north poles N2 and N3 having the same polarity for generating the repulsive magnetic field for separating the developer 22 from the sleeve roller 26 are arranged to face the internal side of the developer reservoir 16.
The toner supply bias voltage Vs for supplying toner to the toner carrying member 23 is applied to the developer carrying member 11 by the supply bias electric power supply 29 for the developer carrying member.
The toner carrying member 23 is arranged to face both the developer carrying member 11 and image carrier 1. The development bias voltage for developing the electrostatic latent image on the image carrier 1 is applied to the toner carrying member 23 by the development bias electric power supply 30 for the toner carrying member.
The detecting roller 27 is opposed to the circumference of the toner carrying member 23, and is located between the area where the toner carrying member 23 faces the developer carrying member 11 as a toner supply member, and the area where the toner carrying member 23 is opposed to the image carrier 1. In
Similarly, referring to
The developer 22 inside the developer reservoir 16 is mixed and agitated by the rotation of the mixing and agitating members 17 and 18. Through the mixing and agitation, the developer 22 is frictionally charged, and circulated and conveyed inside the developer reservoir 16. Then the developer 22 is fed to the sleeve roller 26 on the surface of the developer carrying member 11.
This developer 22 is maintained on the surface of the sleeve roller 26 by the magnetic force of the magnetic member 25 inside the developer carrying member 11. The developer 22 is rotated and transferred on the sleeve roller 26 The amount of the developer 22 thus transferred on the surface of the sleeve roller 26 is regulated by the regulating member 15 arranged to face the developer carrying member 11.
The developer 22, having been regulated by the regulating member 15, is conveyed to the toner supply area 7 facing the toner carrying member 23.
In the toner supply area 7 where the toner carrying member 23 and the developer carrying member 11 face each other, the developer 22 is bristled by the main magnetic pole N1 of the magnetic member 25. The toner in the developer 22 is supplied to the toner carrying member 23 by the force which is applied to the toner and generated by the toner supply electric field having been formed according to the potential difference between the development bias Vb applied to the toner carrying member 23 and the toner supply bias Vs applied to the developer carrying member 11.
The development bias Vb obtained by superimposition of the AC voltage to the DC voltage is applied to the toner carrying member 23. The toner supply bias Vs obtained by superimposition of the AC voltage to the DC voltage is applied to the developer carrying member 11 as well. Then the electric field obtained by superimposition of the AC electric field to the DC electric field is formed in the toner supply area 7. The development bias Vb and/or toner supply bias Vs can be a DC voltage.
In the toner supply area 7, the toner layer supplied onto the toner carrying member 23 from the developer carrying member 11 is conveyed to the development area 8 by the rotation of the toner carrying member 23, and is supplied for development by the electric field formed by the development bias Vb applied to the toner carrying member 23 and the latent image potential on the image carrier 1.
In the development area 8, development is performed by the transfer of the toner by electric field through the development gap formed between the toner carrying member 23 and image carrier 1. After toner has been consumed in the development area 8, the remaining toner layer which has not been consumed in the development area 8 is conveyed to the toner supply area 7 by the rotation of the toner carrying member 23.
In the toner supply area 7, the toner remaining on the toner carrying member 15 subsequent to development is mechanically scraped off by the bristled developer 22 on the developer carrying member 11.
The developer 22 having passed through the toner supply area 8 is conveyed toward the developer reservoir 16 with the rotation of the sleeve 26. The developer 22 is separated from the developer carrying member 11 by the repulsive magnetic field formed by the magnetic poles N2 and N3 of the magnetic member 25, and is recovered into the developer reservoir 16.
When the supply control section (not illustrated) has detected from the output value of the ATDC sensor 20 that the toner density in the developer 22 has been reduced below the minimum toner density for ensuring image density, the supply toner 21 stored in the hopper is supplied into the developer reservoir 16 through the toner supply section 14 by the toner supply device (not illustrated).
(Method of Detecting the Amount of the Toner Held on the Toner Carrying Member)
The following describes the method of detecting the amount of the toner held on the toner carrying member.
In the development apparatus of this embodiment, it is important to stabilize the toner amount on the toner carrying member 23. To achieve this objective, it is essential to ensure accurate measurement of the toner amount supplied from the developer carrying member 11.
In the present embodiment, high-precision detection of the toner amount is ensured by installation of a detecting roller 27. The detecting roller 27 is placed facing the circumference of the toner carrying member 23. To be more specific, the detecting roller 27 is located between the area wherein the toner carrying member 23 faces the developer carrying member 11, and the area wherein the toner carrying member 23 faces the image carrier 1. In
The following describes the operation of the detecting roller. The toner supplied to the toner carrying member 23 by the developer carrying member 11 is transferred onto the detecting roller 27 by the bias formed by superimposition of the AC voltage onto the DV voltage applied between the toner carrying member 23 and detecting roller 27. The DC voltage bias can be used to transfer the toner from the toner carrying member 23 to the detecting roller 27.
To explain one of the embodiments of the present invention,
The toner amount m0 on the toner carrying member 23 is required to ensure a sufficient image density. Accordingly, the toner amount is often set at a level that is too large to be directly detected by a conventional optical device for detecting the toner amount by the light reflected from the toner layer on the toner carrying member 23. This conventional device has failed to provide high-precision detection.
However, in the present embodiment, when the toner is transferred to the detecting roller 27, the value is converted into the toner amount m1 that can be detected by the optical toner detecting device 28a. This arrangement makes it possible to measure the toner amount on the detecting roller 27, and to identify the toner amount on the toner carrying member 23 in a simple and accurate manner.
A still further embodiment is represented by an example of the structure shown in
In the meantime, in the detecting roller 27, a substrate of high translucency may be used for the detecting roller 27, which is not subjected to many of such restrictions. This allows detection of a greater amount of toner by the transmission toner detecting device 28. Further, in
As shown in
The following notes the positional relationship among the image carrier 1, toner carrying member 23, and detecting roller 27 in the longitudinal direction.
The present embodiment is characterized in that a toner carrying area on the surface of the toner carrying member is broader in the direction of rotating axis of the toner carrying member 23 than an image forming area on a surface of the image carrier, and that the toner is transferred to the detecting roller from a part of the toner carrying area on the surface of the toner carrying member, which part does not face the image forming area of the image carrier.
In all of the embodiments described with reference to
If the toner transferred to the detecting roller 27 is transferred from a part of the toner carrying area w1 on the toner carrying member 23, which part faces the image forming area w0 on the image carrier 1, the toner amount on the toner carrying member 23 is reduced. This makes it difficult to develop an electrostatic latent image on the image carrier 1 with sufficient density. To solve this problem, detection of the toner amount and the image forming operation must be performed at different time point. The timings for detecting the toner amount will be restricted to the time of non-image formation. However, these problems are solved by the structure of the present embodiment.
Examples of the structures of the detecting roller 27 according to the present embodiment include: the roller having a smaller diameter in the non-detection area (the area facing the image forming area w0 of the image carrier 1) to avoid contact with the toner carrying member 23; the roller having only the width of the detection area (area w2 not facing the image forming area); and the roller wherein the electric field for causing a substantial toner transfer is prevented from being formed in the image forming area w0 by insulating the part of the roller facing the image forming area w0 or applying a reverse bias thereto so that a bias to transfer the toner is applied only to the detecting area of the detecting roller 27. As described above, these structures ensure that toner is not transferred to the detecting roller 27 from the part of the toner layer on the toner carrying member 23, which part faces the image forming area w0.
The following describes the structure of the toner amount control system. This control system controls the detection of the toner amount held on the toner carrying member 23, and controls the amount of toner held on the toner carrying member 23 to an appropriate level based on the data obtained from the result of this detection.
The detecting roller 27 is connected with the electric power supply apparatus 31 for transferring the toner on the toner carrying member 23. This electric power supply apparatus 31 is capable of controlling the timings for turning on or off the bias to transfer the toner from the toner carrying member 23, or the timings of turning on or off the bias to ensure that the toner having been transferred to the detecting roller 27 will go back to the toner carrying member 23. This electric power supply apparatus 31 is controlled by the CPU. The toner detecting device 28a as an optical sensor for detecting the toner amount on the detecting roller 27 is installed in the vicinity of the circumference of the detecting roller 27 on a non-contact basis. After having been amplified by a preamplifier, these signals are fed to the A/D converter, and are then input into the CPU as values representing the amount of reflected light.
The following relationship holds between the amount of light reflected by the detecting roller 27 and captured by the toner detecting device 28a and the toner amount on the detecting roller 27. When the toner amount is smaller, the amount of reflected light is greater and the output of the toner detecting device 28a is higher. When the toner amount is greater, the amount of reflected light is smaller and the output of the toner detecting device 28a is lower.
In the next step, the toner amount on the detecting roller 27 for the purpose of detection is measured by the toner detecting device 28. The output value and Table 2 are compared to read out the toner amount on the detecting roller 27. The toner amount having been read out is compared with Table 1, and whereby the toner amount on the toner carrying member 23 prior to toner transfer is read out. Based on the toner amount held on the toner carrying member 23 obtained in this manner, if the toner amount is lower than a prescribed level, for example, the electric power supply apparatus 29 connected to the developer carrying member 11 may be controlled by the CPU in order to increase the amount of toner supplied from the developer carrying member 11. Alternatively, the rotating speed of the developer carrying member 11 may be changed under the control of the CPU to change the amount of toner supplied to the toner carrying member 23. Further, the method of detecting the toner amount on the toner carrying member 23 in the present embodiment enables the toner amount on the toner carrying member 23 to be detected even during the image forming operation. Thus, based on the result of detecting toner amount on the toner carrying member 23, the electric power supply apparatus 30 connected to the toner carrying member 23 is feedback-controlled, whereby appropriate developing conditions is formed.
Further, as the toner amount can be detected during the image forming operation, the detection may be conducted at any desired timing, and whereby high quality images are obtained quickly.
To ensure more stable maintenance of the toner amount on the toner carrying member 23, the toner amount is preferably detected frequently. As a preferred timing for detecting and controlling the toner amount at a higher frequency, the following equation should be satisfied, wherein the rotating cycle of the detecting roller 27 is T1; the toner transfer direction switching cycle for transfer from the toner carrying member 23 to the detecting roller 27 (a cycle of switching the direction of electric field between the transfer of toner from the toner carrying member 23 to the detecting roller 27 and the transfer of toner in the reverse direction) is T2; and the time ratio of toner transfer in each direction (time ratio required for toner transfer) is 1:
T1={n+(½)}T2 (wherein “n” is an integer)
If this equation is satisfied, the ratio between the time period required for the toner to be transferred from the toner carrying member 23 to the detecting roller 27 and the time period for the toner not to be transferred (ON/OFF ratio) is 1. The toner carrying areas and non-carrying areas move on the surface of the detecting roller 27 in a striped pattern at an equally spaced interval.
As is apparent from the above description, the present embodiment ensures that the amount of toner held on the toner carrying member 23 can be detected at a higher frequency even in the image forming operation. By controlling the conditions of forming the toner layer on the toner carrying member 23, the amount of toner held on the toner carrying member 23 can be maintained at a stable level. This allows the development characteristics to be maintained at a stable level, and ensures a stable supply of high-quality images.
In each of the above embodiments, after at least a portion of the toner on a non-facing part of the toner carrying area, which non-facing part does not face the image-forming area, has been transferred onto the detecting roller, detection is conducted by the toner detecting devices. This method enhances detection accuracy and increases detection frequency. This technique provides a development apparatus capable of stable supply of high-quality images and an image forming apparatus using the same, wherein the toner amount held on the toner tallying member, which toner amount has a serious impact on the image quality, can be controlled to a high level of precision, based on the result of the detection thereof.
The aforementioned embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2009-259728 | Nov 2009 | JP | national |
