Patent Application
20170227889
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-020500 filed Feb. 5, 2016.
The present invention relates to a developing device and an image forming apparatus.
According to an aspect of the invention, there is provided a developing device including: a developing container that accommodates a two-component developer; a toner concentration detecting unit that detects a toner concentration of the developer by a detecting unit exposed to an inner wall of the developing container; a transport member that is disposed within the developing container and stirs and transport the developer with a transport blade having a pitch that is equal to or less than a size of the detecting unit of the toner concentration detecting unit; and a plurality of gap holding members that is provided at a position facing the toner concentration detecting unit of the transport member and holds a gap such that a tip thereof is abutted against the inner wall of the developing container.
Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein:
Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.
An image forming apparatus 1 according to exemplary embodiment 1 is configured as, for example, a monochrome copier. The image forming apparatus 1 may include, on an upper portion of an apparatus body 1a, an automatic document feeder 2 that feeds a document (not illustrated) in a state where the document is separated one by one, and an image reader 3 that reads an image of the document fed by the automatic document feeder 2 or a document loaded on platen glass (not illustrated). Further, the image forming apparatus 1 includes, within the apparatus body 1a, an imaging device 10 that forms a toner image developed by toner constituting a developer, a transfer device 15 that transfers the toner image formed by the imaging device 10 to a recording sheet 5 as an example of a recording medium, a sheet feeding device 50 that receives and feeds a required recording sheet 5 which is to be fed to a transfer location of the transfer device 15, a fixing device 40 that fixes the toner image to the recording sheet 5 transferred by the transfer device 15, and so on. Further, the apparatus body 1a is formed of a support structure member, an exterior cover, or the like.
As illustrated in
The photoconductor drum 11 forms an image holding surface having a photoconductive layer (photosensitive layer) that is made of a photosensitive material on a peripheral surface of a grounded cylindrical or columnar base. The photoconductor drum 11 is supported to be rotated in a direction illustrated by arrow A when power is transmitted thereto from a driving device (not illustrated).
The charging device 12 is configured as a contact-type charging roll placed to be in contact with the photoconductor drum 11. A charging voltage is supplied to the charging device 12. In a case where the developing device 14 is configured to perform reversal development, a voltage or current having the same polarity as the charged polarity of the toner supplied from the developing device 14 is supplied as the charging voltage. Further, a cleaning roll 121 is disposed on the charging device 12 to come into contact therewith, thereby cleaning the surface of the charging device. The charging device 12 may use a non-contact type charging device, such as, a scorotron, which is placed on the surface of the photoconductor drum 11 in a non-contact state.
The exposure device 13 irradiates light that is configured depending on image information of document read by the image reader 3 or image information input from an external personal computer to the image forming apparatus 1, onto the charged peripheral surface of the photoconductor drum 11, thus forming an electrostatic latent image. When the latent image is formed, the image information of the document read by the image reader 3 or image information (signal) input to the image forming apparatus 1 by any unit is transmitted to the exposure device 13.
The exposure device 13 is constituted with an LED print head that irradiates light corresponding to the image information to the photoconductor drum 11 by LEDs (Light Emitting Diodes) as plural light emitting elements arranged in an axial direction of the photoconductor drum 11, thus forming an electrostatic latent image. Further, an exposure device configured to perform deflection scanning of laser beams configured according to the image information in the axial direction of the photoconductor drum 11 may be used as the exposure device 13.
As illustrated in
The transfer device 15 is a contact-type transfer device provided with a transfer roll, which rotates and comes into contact with a periphery of the photoconductor drum 11 and is supplied with a transfer voltage. As the transfer voltage, a DC voltage exhibiting a polarity that is reverse to the charged polarity of the toner is supplied from a power source device (not illustrated).
As illustrated in
The fixing device 40 is configured by arranging a belt-type or roll-type heating rotary body 41 heated by a heating unit such that a surface temperature is kept at a required temperature, a roll-type or belt-type pressurizing rotary body 42 configured to be rotated by coming in contact with the heating rotary body 41 in a state of substantially following the axial direction of the heating rotary body 41 with a predetermined pressure, and so on. The fixing device 40 includes a fixing treatment section configured to perform required fixing treatments (heating and pressurizing) by a contact portion that is in contact with the heating rotary body 41 and the pressurizing rotary body 42.
The sheet feeding device 50 is placed at a position below the imaging device 10. The sheet feeding device 50 mainly includes a singular (plural) sheet storage body (bodies) 51 that receive(s) recording sheets 5 of a desired size and kind in a stacked state, and sending devices 52 and 53 that send the recording sheets 5 from the sheet storage body 51 one by one. For example, the sheet storage body 51 is attached to be withdrawn to the front side (the side where a user faces during the operation) of the apparatus body 1a.
As the recording sheets 5, a thin paper (e.g., a plain paper, an OHP sheet, or a tracing paper), which is used in an electrophotographic copier, a printer, or the like may be exemplified. In order to further improve the smoothness of an image surface after the fixing, it is preferable that the surfaces of the recording sheets 5 are as smooth as possible, and a so-called thick paper or the like that has a relatively heavy basis weight (e.g., a coated paper obtained by coating a surface of the plain paper with a resin or the like, a printing art paper).
Between the sheet feeding device 50 and the transfer device 15, a sheet feeding transport path 56 is provided which includes a singular (or plural) sheet transport roll pair(s) 54 and 55 or a transport guide (not illustrated) to transport the recording sheets 5 sent from the sheet feeding device 50 to a transfer location. The sheet transport roll pair 55 includes, for example, a roll (registration roll) that regulates a transport time of the recording sheets 5. Further, a sheet transport path 57 is provided between the transfer device 15 and the fixing device 40 so as to transport the recording sheets 5 sent from the transfer device 15 after the transfer to the fixing device 40. In addition, a sheet exit roll pair 59 is arranged in a portion near an exit port of the recording sheet 5 formed in the apparatus body 1a so as to discharge the recording sheets 5, which are sent from an outlet roll 43 of the fixing device 40 after the fixing, to a sheet discharge portion 58 installed in an upper portion of the apparatus body 1a.
A switching gate (not illustrated) is provided between the fixing device 40 and the sheet exit roll pair 59 to switch sheet transport paths. The sheet exit roll pair 59 is configured to switch its rotating direction between a forward rotation direction (discharge direction) and a reverse rotation direction. In the case of forming an image on both sides of the recording sheet 5, the rear end of the recording sheet 5, which is formed with an image on one side thereof, passes through the switching gate (not illustrated), and then the rotating direction of the sheet exit roll pair 59 is switched from the forward rotation direction (discharge direction) to the reverse rotation direction. The recording sheet 5 transported by the sheet exit roll pair 59 in the reverse direction is subjected to the switching of the transport path thereof by the switching gate (not illustrated), and is transported to a duplex transport path 60 that is formed along a side of the apparatus body 1a in a substantially vertical direction. The duplex transport path 60 includes plural sheet transport roll pairs 61 configured to transport the recording sheets 5 to the sheet transport roll pair 55 in the state where the a front and a back of the sheet are reversed, a transport guide (not illustrated), and so on.
Further, above the fixing device 40, a sheet exit roll pair 64 and a sheet exit roll pair 67 are provided, in which the sheet exit roll pair 64 discharges, through the sheet transport roll pair 62, the recording sheets 5, which are sent from the exit roll 43 of the fixing device 40 after the fixing, to the second sheet discharge portion 63 installed at the upper portion of the apparatus body 1a for face-down discharge, and the sheet exit roll pair 67 switches the transport direction by the switching gate 65 to discharge the recording sheet 5 after the fixing to the third sheet discharge portion 66 installed at a side of the upper portion of the apparatus body 1a for face-up discharge.
In
Further, reference numeral 145 of
In addition, reference numeral 100 of
As illustrated in
Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.
When the image forming apparatus 1 receives instruction information that requests an image forming operation (print), the imaging device 10, the transfer device 15, the fixing device 40, and so on are started. In the image forming operation, if necessary, an image (not illustrated) of a document fed by the automatic document feeder 2 or an image (not illustrated) of a document positioned on platen glass is read by an image reader 3.
In addition, in the imaging device 10, first, the photoconductor drum 11 is rotated in a direction indicated by arrow A so that the charging device 12 charges the surface of the photoconductor drum 11 with a required polarity (negative polarity in exemplary embodiment 1) and potential. Subsequently, the exposure device 13 converts image information of document read by the image reader 3 or image information input to the image forming apparatus 1 into black and white components, and irradiates emitted light based on the signal of the image obtained by the conversion to the charged surface of the photoconductor drum 11, thereby forming, on the surface, an electrostatic latent image that is configured by a required potential difference.
Subsequently, the developing device 14 supplies toner charged with the required polarity (negative polarity) from the developing roll 141 to the electrostatic latent image formed on the photoconductor drum 11 to electrostatically attach the toner to the electrostatic latent image, thereby performing the development. By the development, the electrostatic latent image formed on the photoconductor drum 11 is developed as a monochrome toner image that is developed by black toner.
Subsequently, when the toner image formed on the photoconductor drum 11 of the imaging device 10 is transported to the transfer location, the transfer device 15 transfers the toner image to the recording sheet 5.
Further, in the imaging device 10 where the transfer has been completed, the drum cleaning device 16 scrapes out and remove the attached matter, such as the toner to clean the surface of the photoconductor drum 11. Thus, the imaging device 10 is ready to form a next image. The toner or the like scraped by the drum cleaning device 16 is transported to the developing device 14 by the reuse device 180, and used for development again.
Meanwhile, the sheet feeding device 50 sends the required recording sheets 5 to the sheet feeding transport path 56, according to the image forming operation. In the sheet feeding transport path 56, the sheet transport roll pair 55 as the registration roll sends and supplies the recording sheets 5 to the transfer location according to a transfer time.
Subsequently, the recording sheets 5 to which a toner image is transferred from the photoconductor drum 11 are transported to the fixing device 40 through the transport guide (not illustrated). The fixing device 40 performs a required fixing treatment (heating and pressurizing) by introducing the transferred recording sheets 5 into the contact portion between the rotating heating rotary body 41 and the pressurizing rotary body 42, thereby fixing an unfixed toner image to the recording sheets 5. Finally, after the fixation is terminated, the recording sheets 5 are discharged to the sheet discharge portion 58 or the like installed in the upper portion of the apparatus body 1a by the sheet exit roll pair 59 or the like, in the case of an image forming operation of forming an image on one side.
Further, when an image is formed on both sides of a recording sheet 5, while the rear end of the recording sheet 5, which is formed with an image on one side thereof, is maintained by the sheet exit roll pair 59 without being discharged by the sheet exit roll pair 59, the rotating direction of the sheet exit roll pair 59 is switched to the reverse rotation direction. The recording sheet 5 transported in the reverse rotation direction by the sheet exit roll pair 59 passes through the switching gate (not illustrated), and then is transported again to the sheet transport roll pair 55 in the state where the a front and a back of the sheet are reversed, through the duplex transport path 60 that is provided with the sheet transport roll pair 61, the transport guide (not illustrated), or the like. The sheet transport roll pair 55 sends and supplies the recording sheet 5 to the transfer location according to a transfer time, an image is formed on the back of the recording sheet 5, and the sheet 5 is discharged to the sheet discharge portion 58 installed in the upper portion of the apparatus body 1a or the like by the sheet exit roll pair 59 or the like.
By the above-described operation, the recording sheet 5 formed with a monochrome image is output.
The developing device 14 includes a device housing 140 as an example of the developing container. The device housing 140 is generally constituted with a lower housing 140a disposed in a lower portion of the developing device 14 and an upper housing 140b disposed in an upper portion of the developing device 14. The lower housing 140a and the upper housing 140b are joined via a spacer member 150. A developer accommodation chamber 151 formed within the device housing 140 to accommodate the two-component developer 4 consisting of a non-magnetic toner and a magnetic carrier. An opening 152 is formed in an area of the device housing 140 which faces the photoconductor drum 11. As an example of the developer holding member, the developing roll 141 is placed within the device housing 140 to be rotatable in a direction indicated by an arrow such that the developing roll is partially exposed to the opening 152. The developing roll 141 includes a magnet roll 141a that is fixedly disposed therein and has plural magnetic poles of required polarities arranged at required positions in a peripheral direction thereof, and a developing sleeve 141b that is disposed on an outer circumference of the magnet roll 141a to be rotatable in a direction indicated by an arrow at a required rotating speed. The developing sleeve 141b is formed from a non-magnetic material (e.g., aluminum or non-magnetic stainless steel) in a cylindrical shape.
In this exemplary embodiment, the rotating direction of the developing sleeve 141b is set in a direction opposite to the rotating direction of the photoconductor drum 11. That is, as illustrated in
Within the device housing 140, a supply and transport member 142, which includes, for example, a screw auger (supply auger) configured to draw up the developer 4 accommodated in the developer accommodation chamber 151 and supply the developer 4 to the developing roll 141, is disposed obliquely downward from the developing roll 141. The supply and transport member 142 is rotationally driven in the clockwise direction by a driving device (not illustrated). On a side of the developing roll 141 a columnar layer thickness regulating member 144 is disposed to regulate an amount (layer thickness) of the developer held on the developing roll 141. Further, within the device housing 140, a stirring and transport member 143, which includes, for example, a screw auger (admix auger) configured to stir and transport the developer 4 supplied into the device housing 140, is disposed on the rear side of the supply and transport member 142. The stirring and transport member 143 is also rotationally driven in the clockwise direction by the driving device (not illustrated).
The supply and transport member 142 and the stirring and transport member 143 are configured to be similar to each other. Here, the configuration of the stirring and transport member 143 will be representatively described. As illustrated in
In this exemplary embodiment, in order to enhance the productivity that is determined by the number of the recording sheets 5 on which an image may be formed per unit time in the image forming apparatus 1, the photoconductor drum 11, and the developing roll 141, the supply and transport member 142, and the stirring and transport member 143 of the developing device 14 are configured to relatively increase a rotating speed to achieve a high rotating speed.
More specifically, the pitch P of the transport blade 143b of the supply and transport member 142 or the stirring and transport member 143 is set to be relatively small such that the developer 4 may be stably transported in the axial direction even in the case where the supply and transport member 142 and the stirring and transport member 143 arrives at the high rotating speed. As will be described later, the pitch P of the transport blade 143b of the supply and transport member 142 and the stirring and transport member 143 is set to be equal to or less than a diameter D of a detecting unit 172 of the toner concentration sensor 170. In this exemplary embodiment, as illustrated in
As illustrated in
As illustrated in
As illustrated in
Further, while the toner supplied into the device housing 140 from the supply port 158a is transported by the stirring and transport member 143, the toner is stirred with the developer 4 accommodated in the device housing 140.
However, in this exemplary embodiment, as described above, the attached matter such as the toner removed by the drum cleaning device 16 is transported to the developing device 14 by the reuse device 180, and is used again for developing in the developing device 14. In this regard, the attached matter removed by the drum cleaning device 16 includes foreign matter, such as fiber or paper debris, of the recording sheet 5 attached to the surface of the photoconductor drum 11 in the transfer location of the photoconductor drum 11, in addition to the transfer residual toner remaining on the surface of the photoconductor drum 11. When the foreign matter circulates in the developing device 14 and is transported by the developing roll 141 to the developing area with the developer 4, the toner may not be developed only in an area where the foreign matter exits on the surface of the developing roll 141, and as a result an image defect such as a white spot may occur.
Therefore, in this exemplary embodiment, as illustrated in
The cleaning member 192 rubs the developer 4 against the foreign matter removing screen member 190 according to the rotation of the stirring and transport member 143, thereby causing the developer 4 to pass through the first passage 156 such that only the developer 4, which passes through the plural slits 191 of the foreign matter removing screen member 190, is filtered. The foreign matter such as fiber or paper debris of the recording sheet 5 entrained in the developer 4 or the agglomerated developer 4 is not able to pass through the foreign matter removing screen member 190, thereby being captured by the foreign matter removing screen member 190. The foreign matter captured by the foreign matter removing screen member 190 is scraped up to the upper portion of the developer 4 according to the rotation of the cleaning member 192, and stays in the upper portion of the layer of the developer 4 because the specific gravity of the foreign matter is smaller than that of the developer 4. Further, in the foreign matter, the foreign matter having a small particle diameter (e.g., paper debris of the recording sheets 5) may pass through the foreign matter removing screen member 190. However, because the specific gravity of the foreign matter such as paper debris or the like of the recording sheets 5 is considerably smaller than that of the developer 4, the foreign matter is scraped up to the upper portion of the foreign matter removing screen member 190 by the cleaning member 192, and is suppressed from passing through the foreign matter removing screen member 190.
As illustrated in
As illustrated in
In addition, the stirring and transport member 143 is integrally provided with flat plate-shaped stirring members 173 configured to stir the developer 4 is integrally installed at a position corresponding to the detecting unit 172 of the toner concentration sensor 170. As illustrated in
In the developing device 14 configured as described above, as illustrated in
When the stirring and transport member 143 is bent, it is difficult to maintain a gap between the toner concentration sensor 170 and the stirring member 173 of the stirring and transport member 143 at a required value, and as the stirring and transport member 143 rotates, the gap between the toner concentration sensor 170 and the stirring member 173 of the stirring and transport member 143 fluctuates.
As is evident from
Therefore, in a case where the gap between the toner concentration sensor 170 and the stirring member 173 of the stirring and transport member 143 is wider than the normal value, when the toner concentration within the developing device 14 is controlled based on the output value of the toner concentration sensor 170, the toner concentration detected by the toner concentration sensor 170 is detected to be relatively lower than an original value (in the case where the gap is normal), and a rise in toner concentration resulting from the supply of the toner is also detected to be lower than an actual gradient. Consequently, the developer may be supplied to the inside of the developing device 14 an excessive amount than the actual toner concentration so that the blow-out of the toner from the developing device 14 may occur under certain circumstances.
Therefore, this exemplary embodiment is provided with plural (two) gap holding members 175 that are installed at a position facing the toner concentration sensor 170 of the stirring and transport member 143 and abutted against the inner wall of the device housing 140 of the developing device 14 at the tips thereof so as to hold the gap between the toner concentration sensor 170 and the stirring members 173 of the stirring and transport member 143 at a required value.
As illustrated in
As illustrated in
At that time, the developer 4 accommodated in the device housing 140 of the developing device 14 suffers from the consumption of the toner due to the developing process in which the toner is supplied from the developing roll 141 to the electrostatic latent image formed on the circumferential surface of the photoconductor drum 11 to electrostatically attach the toner to the electrostatic latent image. The toner concentration of the developer 4 accommodated in the device housing 140 is detected by the toner concentration sensor 170 disposed on the downstream side in the transport direction of the developer 4 of the stirring and transport member 143.
When it is determined that the toner concentration of the developer 4 in the device housing 140 detected by the toner concentration sensor 170 becomes less than a required threshold value, the controller 100 supplies the toner from the toner cartridge 145 through the transport member 159 into the device housing 140. As illustrated in
In this exemplary embodiment, since the gap holding members 175 are installed on the stirring and transport member 143, the gap between the detecting unit 172 of the toner concentration sensor 170 and the stirring members 173 of the stirring and transport member 143 is always maintained at a required value.
Therefore, a signal as illustrated in
In
In contrast, in
Further, in
When the stirring and transport member 143 of the exemplary embodiment has the gap holding members 175 as described above, it has been found that the toner concentration of the developer 4 in the device housing 140 may be precisely detected.
In contrast, when the stirring and transport member 143 does not have the gap holding members 175 and the gap between the toner concentration sensor 170 and the stirring member 173 of the stirring and transport member 143 is wider than the normal value, it has been found that the output waveform of the toner concentration sensor 170 exhibits a relatively large value, compared to a proper case, and thus, the toner concentration of the developer 4 in the device housing 140 is erroneously detected as a value that is lower than an actual value.
Therefore, the exemplary embodiment attaches the magnetic member to the stirring and transport member so as to constitute a gap detecting unit for detecting the gap between a detecting surface of the toner concentration detecting unit and the stirring and transport member, which improves the detecting precision of the toner concentration without using the magnetic member, compared to the case of suppressing the detection error in toner concentration which is caused by a variation in the gap between the detected surface of the toner concentration detecting unit and the stirring and transport member.
In the foregoing exemplary embodiment, descriptions have been made with reference to the case of forming a monochrome image with the image forming apparatus. However, the descriptions may also be applied to an image forming apparatus that has plural imaging devices that forms a full color image.
Further, in the foregoing exemplary embodiment, descriptions have been made with reference to the case of installing two gap holding members at the positions different by 180 degrees on the outer circumference of the stirring and transport member, respectively. However, three or more gap folding members may be disposed on the outer circumference of the stirring and transport member. For example, three gap holding members may be installed, respectively, at positions different by, for example, 120 degrees.
The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-020500 | Feb 2016 | JP | national |
