Development agent container, process cartridge, and image forming apparatus

A development-agent container includes a development-agent containing unit for containing development agents for developing latent images formed on an image carrier; a light-transmission window formed at a frame of the development-agent containing unit for detecting a remaining amount of the development agents in the development-agent containing unit and a stirring member disposed in the development agent containing unit for stirring the development agents. The stirring member has a light-shielding flexible sheet for rubbing the light-transmission window.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention relates to a development-agent container for containing
 development agents in a development apparatus in an electrophotographic
 image forming apparatus, a process cartridge, and an image forming
 apparatus.
 2. Related Background Art
 In an image forming apparatus of an electrophotographic system, in other
 words, in an apparatus for obtaining images by developing with development
 agents, electrostatic latent images on an image carrier, such as a
 photosensitive drum or the like, it is required to supply development
 agents as expendables. As a method for supplying development agents, there
 are the following methods.
 First of all, a development-agent receiving container is installed in an
 image forming apparatus body, such as a photocopier or the like, and a
 development-agent supplying container, filled with development agents in
 advance for supplying development agents, is prepared as another
 expendable, independent from the image forming apparatus, and when the
 development-agent receiving container comes to have the smaller remaining
 amount of the development agents, the development agents in the
 development-agent supplying container are supplied, as a supplying method,
 in the whole amount at once to the development-agent receiving container.
 As another method, there is a method using a stationary container, in
 which, though a development-agent supplying container is prepared in the
 same way as the above method, after a development-agent supplying
 container is attached to the image forming apparatus body without
 supplying the agents in the whole amount, the development-agent supplying
 container is left over as it is in the image forming apparatus body, and
 the development agents are gradually delivered toward a development
 apparatus by operating a development-agent stirring apparatus until the
 development agents are used up.
 In addition, there is a process cartridge method in which a photosensitive
 drum, a cleaning apparatus, and a development apparatus filled in advance
 with development agents, are formed unitedly and in which those elements
 are detachably attached to the image forming apparatus body. In this
 method, development agents are delivered gradually to a development sleeve
 and a photosensitive drum from a development-agent containing section
 formed in the cartridge by operating a development-agent stirring
 apparatus until the incorporated development agents are used up where the
 cartridge is attached once in the image forming apparatus body.
 However, in all the methods, it is required to detect the remaining amount
 of the development agents in the development-agent container, and the
 remaining amount is detected by a light transmission method, an antenna
 method, and like.
 FIG. 5 is an illustration of a development apparatus performing detection
 of the development-agent remaining amount through a light transmission
 method; FIG. 6 is a diagram illustrating the relation between a
 toner-remaining amount and a light-transmission time. A development
 apparatus 100 shown in FIG. 5 is structured of a development unit 107 in
 which a development sleeve 105, a development agent supplying roller 106,
 and so on are installed, and a development-agent container 104 welded
 thereto for containing the development agents. Light-transmission windows
 101, 102 for detecting the development-agent remaining amount are attached
 to the development-agent container 104. A stirring member 103 is
 rotatively attached to the interior of the development-agent container 104
 to stir the toners T serving as development agents, and is driven in an
 arrow AA direction by a drive means, not shown. The stirring member 103 is
 constituted of a stirring stay 103a connected to the drive means and a
 flexible stirring sheet 103b for removing the toners clinging to the
 light-transmission windows 101, 102.
 In the image forming apparatus body, a light-emitting portion 108 and a
 light-receiving portion 109 are arranged, and the detection light L is
 emitted from the light emitting portion 108, transmitted through the light
 transmission windows 101, 102, and received at the light-receiving portion
 109 to detect the remaining amount of the development agents T in the
 development agent container 104. More specifically, the detection light L
 is emitted for a period while the stirring member 103 rotates for one
 turn, and time t that light transmits in the development-agent container
 104 is detected during this period. When this amount exceeds a prescribed
 threshold t1, it is judged as toners remain in a small amount, and the
 apparatus notifies it to the users.
 With the development apparatus thus structured, though the stirring sheet
 103b is structured to wipe the surfaces of the light-transmission windows
 101, 102 by a rotation of the stirring member 103 during the detection
 operation, the stirring sheet 103b is at a position shielding the
 detection light L from starting wiping the light-transmission window 101
 to ending wiping the light-transmission window 102. Although a flexible
 sheet, such as PET, is frequently used for a material of the stirring
 sheet, such a conventional sheet is generally transparent or
 semitransparent, which has low light-shielding property.
 Where the toner-remaining amount is relatively large in the
 development-agent container 104, toners clings to the surface of the
 stirring sheet 103b in a large amount, and when the stirring sheet 103b is
 on a beam axis of the detection light L, the stirring sheet 103b also
 shields the detection light L. However, if the toner-remaining amount
 become small, situations that the sheet can shield the light and cannot
 shield the light may occur, depending on the toner amount clinging to the
 stirring sheet 103b. In addition to the toner-clinging degree on the
 stirring sheet, situations that the sheet can shield the light and cannot
 shield the light may occur depending on differences in the light emitting
 of the detection light and sensitivity of the light receiving sensor.
 FIG. 6 is a graph showing a relation between a toner amount in the
 development-agent container 104 and the transmission time t of the
 detection light. If the toner amount M is reduced, the transmission time t
 increases, and when the time t exceeds the threshold t1, the apparatus
 issues a warning of "empty of toner amount." However, as described above,
 with the conventional structure, where the toner amount is small, the
 stirring sheet 103b may shield light in some case but may not shield light
 in other cases, and when the light is shielded, it becomes a curve as
 shown with numeral S1, whereas when the light is not shielded, it becomes
 a curve as shown with numeral S2. The toner-remaining amount M where the
 transmission time t exceeds the threshold t1 is M1 when the light is
 shielded and M2 when the light is not shielded, and generates large
 differences.
 SUMMARY OF THE INVENTION
 It is an object of the invention to provide a development-agent container,
 a process cartridge, and an image forming apparatus capable of detecting
 toner-remaining amounts stably and surely without being affected by toners
 clinging to a stirring sheet.
 A representative structure of a development agent container according to
 the invention to accomplish the above object includes a development-agent
 containing unit for containing development agents for developing latent
 images formed on an image carrier; a light-transmission window formed at a
 frame of the development agent containing unit for detecting a remaining
 amount of the development agents in the development-agent containing unit;
 and a stirring member disposed in the development-agent containing unit
 for stirring the development agents, the stirring member having a
 light-shielding flexible sheet for rubbing the light-transmission window.
 Where the flexible sheet is made of a synthetic resin sheet having
 flexibility, with a carbon coating thereon, the flexible sheet can be
 structured to have an adequate light-shielding property.
 As another structure of the invention, a development cartridge includes, at
 least, developing means for developing latent images on an image carrier
 with development agents; and a development-agent container including: a
 development-agent containing unit for containing development agents for
 developing latent images formed on an image carrier; a light-transmission
 window formed at a frame of the development-agent containing unit for
 detecting a remaining amount of the development agents in the
 development-agent containing unit; and a stirring member formed in the
 development-agent containing unit for stirring the development agents, the
 stirring member having a light-shielding flexible sheet for rubbing the
 light transmission window.
 As yet another structure of the invention a process cartridge includes, at
 least, an image carrier for carrying latent images; developing means for
 developing latent images on an image carrier with development agents; a
 housing for supporting the image carrier and the developing means; and a
 development-agent container including: a development-agent containing unit
 for containing development agents for developing latent images formed on
 an image carrier; a light-transmission window formed at a frame of the
 development-agent containing unit for detecting a remaining amount of the
 development agents in the development-agent containing unit; and a
 stirring member formed in the development-agent containing unit for
 stirring the development agents, the stirring member having a
 light-shielding flexible sheet for rubbing the light-transmission window.
 An image forming apparatus according to the invention includes: an image
 carrier for carrying latent images; developing means for developing latent
 images on an image carrier with development agents; a housing for
 supporting the image carrier and the developing means; a development agent
 container including: a development-agent containing unit for containing
 development agents for developing latent images formed on an image
 carrier; a light-transmission window formed at a frame of the development
 agent containing unit for detecting a remaining amount of the development
 agents in the development-agent containing unit; and a stirring member
 formed in the development-agent containing unit for stirring the
 development agents, the stirring member having a light-shielding flexible
 sheet for rubbing the light-transmission window; and remaining amount
 detecting means for development agents having a light-emitting portion and
 a light-receiving portion of light transmitting through the
 light-transmission window.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Hereinafter, referring to the drawings, an embodiment of a
 development-agent container and a development apparatus according to the
 invention is described. FIG. 1 is a structural diagram showing a
 development apparatus according to an embodiment; FIG. 2 is a view showing
 the whole structure of an image forming apparatus according to an
 embodiment; FIG. 3 is a view illustrating a stirring member; FIG. 4 is a
 diagram showing the relation between the toner-remaining amount of the
 development-agent container and transmission time.
 [Whole Structure]
 The image forming apparatus shown in FIG. 2 is a laser beam printer as an
 embodiment of an image forming apparatus for forming color images in use
 of an electrophotographic method. A charging means 2 uniformly charges the
 surface of the electrophotographic photosensitive body (hereinafter
 referred to as "photosensitive (drum 1") as an image carrier in a drum
 shape rotating at a constant rate, and latent images are formed by
 projecting a laser beam corresponding to the image information from
 exposing means 3. These latent images are developed by four development
 apparatuses 12m, 12c, 12y, 12b (hereinafter, referred to as "development
 apparatuses 12" collectively), and color images are produced by
 sequentially transferring images made of visualized development agents
 (hereinafter referred to as toners 22) onto an intermediate transfer body
 4 in a belt shape.
 These color images are transferred by transferring means 6 onto a recording
 medium P (e.g., recording paper, OHP sheet or the like) conveyed by
 conveying means from a feeding section. The recording medium P is conveyed
 to fixing means 7 to fix the color images and delivered onto a delivery
 portion 8 on a top of the apparatus.
 [Process Cartridge]
 Next, structures of respect portions are described. The photosensitive drum
 1 is structured, as a process cartridge, unitedly with the charging means
 2 and a cleaning means 9, and detachably attached to the image forming
 apparatus body. The user can replace it according to the life span of the
 photosensitive drum.
 The photosensitive drum 1 is structured with a coating of an organic
 photoconductive layer on an outer surface of an aluminum cylinder having a
 diameter of about 50 mm. The photosensitive drum 1 is rotatively supported
 to a frame 9a in a shape of a container for the cleaning means 9 also
 serving as a holder for the photosensitive drum 1, and is rotatively
 driven in a counterclockwise direction in FIG. 1 by drive force of a drive
 motor, not shown.
 The charging means 2 is disposed on a round surface of the photosensitive
 drum 1. The charging means 2 according to this embodiment uses a so-called
 contact charging method, and charges uniformly the surface of the
 photosensitive drum 1. In the exposing means 3 for exposing the
 photosensitive drum 1 thus charged, a laser diode, not shown, radiates to
 a polygon mirror 3a image light corresponding to an image signal where the
 image signal is fed to the laser diode. The polygon mirror 3a rotates at a
 high speed by means of a scanner motor, and image light reflected on the
 polygon mirror selectively exposes the surface of the photosensitive drum
 1 that rotates at a constant rate via a reflection mirror 3b to form
 latent images.
 The cleaning means 9 is similarly disposed on the round surface of the
 photosensitive drum 1. The cleaning means 9 is constituted of the frame
 9a, the cleaning blade 9b, and the waste toner container 9c, and toners 22
 that remain on the photosensitive drum 1 are wiped out by a cleaning blade
 9b and thereby stored in the waste toner container 9c. The waste toner
 container 9c is formed with a capacity that will not be filled before the
 photosensitive drum 1 reaches the end of the life span and is replaced
 unitedly with the process cartridge 10 when the process cartridge 10 is
 replaced upon reaching the end of the life span.
 [Intermediate Transfer Body]
 The latent images thus formed are developed by the development apparatuses
 12 with respect to each color, and the toner images thus visualized are
 transferred onto an intermediate transfer body 4. As described above, the
 respective color toner images are overlapped on an intermediate transfer
 belt 4a of the intermediate transfer body 4, thereby forming color images.
 The intermediate transfer belt 4a is a belt having a peripheral length of
 about 440 mm and is tensioned by three rollers: a drive roller 4b, a
 secondary transfer opposing roller 4c, and a driven roller 4d, and travels
 in an arrow D direction as shown in FIG. 2. A belt pushing roller 4g is
 provided near the drive roller 4d and is structured to urge the
 intermediate transfer belt 4a toward the photosensitive drum 1 and to
 release urging the belt.
 A cleaning unit 4e, capable of contacting to and separating from the
 surface of the intermediate transfer belt 4a, is formed at a predetermined
 position of the outside of the intermediate transfer belt 4. The cleaning
 unit 4 removes post-transfer remaining toners that remain after being
 secondarily transferred at a time onto a recording medium P as described
 below. The cleaning unit 4e gives the toners 22 charges that are reverse
 to those during transfer by contacting the charging roller to the
 intermediate transfer belt 4a, and thereby, the toners 22 are adhered
 electrostatically to the photosensitive drum 1 and subsequently collected
 by the cleaning means 9 for the photosensitive drum 1. It is to be noted
 that as a method for cleaning the intermediate transfer belt 4a, not only
 an electrostatic cleaning method as described above, but also a mechanical
 method, such as a blade or a fur blush or a combination of those, can be
 used.
 [Transferring Means]
 The transferring means 6, for transferring to the recording medium P the
 toner images multiply transferred onto the intermediate transfer body 4,
 is structured of a roller in this embodiment. The roller is formed of a
 metal shaft wound by a foamed elastic body having an intermediate
 resistance and is arranged as to be movable in a vertical direction in the
 drawing.
 The transferring means 6 takes a lower position as shown with a solid line
 in FIG. 2 and is separated from the intermediate transferring body 4 so as
 not to disturb the images while the four color toner images are formed on
 the intermediate transfer body 4, or namely while the intermediate
 transfer body 4 rotates multiple times.
 The transferring means 6 moves to an upper position as shown with a broken
 line by means of a cam, not shown, in meeting with a timing when the color
 images are transferred onto the recording medium P after the color images
 are formed on the intermediate transfer body 4 upon overlapping the toner
 images. The transferring means 6 then comes in pressurized contact with
 the intermediate transfer body 4 via the recording medium P. A bias
 voltage is fed to the transferring means 6 at the same time, and thereby
 the toner image on the intermediate transfer body 4 is transferred on the
 recording medium P.
 [Conveying Means]
 The conveying means for conveying the recording medium P includes a feeding
 cassette 5a for containing recording media P of multiple sheets, a pickup
 roller 5b, a feeding roller pair 5c composed of a feeding roller and a
 retard roller, a conveyance roller pair 5d, a register roller pair 5e, a
 delivery roller pair 5f, and so on.
 When images are formed, the recording media P are sent from the feeding
 cassette 5a by the pickup roller 5b and are conveyed upon separating the
 recording media sheet by sheet by means of the feeding roller pair 5c to
 the register roller pair 5e by way of the conveyance roller pair 5d. The
 register roller pair 5e performance non-rotation operation and a rotation
 operation with a predetermined sequence synchronously with the
 intermediate transfer body 4 and corrects oblique feeding of the recording
 medium P, as well as transfers the color images by sending the recording
 medium P to the nip portion between the intermediate transfer body 4 and
 the transferring means 6.
 [Fixing Means]
 The recording medium P on which the color images are transferred is
 transferred to the fixing means 7 made of a fixing roller 7a for applying
 heat on the recording medium P and a pressure roller 7b for pressing the
 recording medium P to the fixing roller 7a, and toner images are fixed to
 the recording medium P. The fixing roller 7a and the pressure roller 7b
 are hollow rollers, in which respective heaters are provided, and are
 driven rotatively. The toner images are fixed to the recording medium P by
 conveyance in applying heat and pressure to the recording medium P. The
 recording medium P on which the images are fixed is delivered to the
 delivery portion 8 by the delivery roller pair 5f constituting the
 conveying means.
 [Development Apparatus]
 Next, the structure of the development apparatus for developing latent
 images formed on the photosensitive drum 1 is described. The image forming
 apparatus requires development of respective colors: yellow, magenta,
 cyan, and black, to form full color images, and has development
 apparatuses 12y, 12m, 12c, 12b (hereinafter referred to as "development
 apparatuses 12" collectively) for respective colors.
 Those development apparatuses 12 are cartridges (development cartridge)
 detachably attached to a rotary unit 11 that rotates around a shaft 13 as
 a center, and when images are formed, the development apparatuses 12 are
 rotatively driven around the shaft 13 as held by the rotary unit 11. The
 development apparatus 12 containing toners 22 of a prescribed color is
 stopped at a position opposite to the photosensitive drum 1, and latent
 images are developed by supplying toners 22 corresponding to the
 electrostatic latent images of the photosensitive drum 1 after a
 development sleeve as described below is positioned so as to oppose to the
 photosensitive drum 1 and keep a very small gap (about 300 microns).
 When a color image is formed, the rotary unit 11 rotates at one rotation of
 the intermediate transfer body 4, and a development step is made in the
 order of the yellow development apparatus 12y containing yellow color
 toners, the magenta development apparatus 12m containing magenta color
 toners, the cyan development apparatus 12c containing cyan color toners,
 and the black development apparatus 12b containing black color toners.
 FIG. 1 shows a state that any one of the development apparatuses 12 is
 immovably positioned at a development position opposing to the
 photosensitive drum 1. The development apparatus 12 is structured by
 unitedly connecting, by ultrasound wielding or the like, the development
 agent container 21 for containing toners 22 as development agents with a
 development unit 24 in which a development sleeve 23, an elastic blade 25,
 an elastic roller, and the like are mounted.
 The development unit 24 has the development sleeve 23 as a development
 agent carrier at an opening extending in a longitudinal direction, and the
 electrostatic latent images thereon are developed and visualized where the
 unit 24 is arranged to face to the photosensitive drum 1. The development
 sleeve 23 is provided transversely in exposing about a half of the round
 surface, faces to the photosensitive drum with a very small gap, and is
 drive rotatively in the arrow B direction during the development
 operation. The elastic roller 27 rotatively contacts about a half of the
 round surface of the development sleeve 23 located in the development unit
 24. The elastic roller 27 has a structure that a sponge is adhered to a
 core metal, is rotatively driven in a direction the same as the
 development sleeve 23, and operates to feed the toners 22 to the
 development sleeve 23 and remove undeveloped toners.
 The elastic blade 25 is urged on a downstream side with respect to the
 elastic roller 27 in the rotational direction of the development sleeve
 23. The elastic blade 25 is made of a rubber material such as urethane,
 silicone, or using a thin metal plate such as SUS or phosphor bronze
 having spring elasticity as a base in which a rubber material is adhered
 to a contacting surface to the development sleeve 23. The elastic blade 25
 is supported by a blade supporting plate 26 and is attached so that a tip
 and vicinity on a free end side of the elastic blade 25 is in contact with
 an outer round surface of the development sleeve 23 with an area contact,
 thereby controlling the layer thickness of the toners on the development
 sleeve 23, and applying charges to the toner 22 by a rubbing motion.
 Light transmission windows 28, 29 are secured by ultrasound wielding or the
 like to the frame of the development agent container 21 to provide a light
 path of the detection light for detecting toner-remaining amount. As a
 material for the light transmission windows 28, 29, a material such as,
 e.g., transparent polystyrene such as GP-PS, in which the transmission
 rate of infrared light of wavelength 900 to 940 nm is guaranteed to be
 about 80% or higher, and which can be wielded well by ultrasound to the
 development agent container 21 but hardly receives cracks during wielding,
 is preferably used, and more preferably added with flame retarders.
 A stirring member 30 is formed in the development-agent container 21 to
 stir the contained toners 22 and to convey the toners 22 toward the
 development unit 24. The stirring member 30 is made, as shown in FIG. 1
 and FIG. 3, of a stirring stay 30a and a stirring sheet 30b. Opposite ends
 of the stirring stay 30a are supported by a stirring gear 31 and a
 stirring support member 32. The stirring gear 31 and the stirring support
 member 32 are rotatively supported by sliding portions 21a, 21b of the
 development-agent container 21, respectively, and the stirring member 30
 rotates in the arrow C direction where the stirring gear 31 receives the
 drive force, thereby stirring and conveying the toners 22.
 To make stirring and conveying stable, the inner surface 21c of the
 development-agent container 21 has a shape extending along the stirring
 orbit. The light-transmission window 28 located upward of the container is
 formed with a curved face extending along the stirring orbit to effectuate
 the wiping by the stirring member 30. This is because the toner-remaining
 amount may not be detected accurately if the wiping effect is not so good.
 [Operation of Toner Remaining Amount Detection]
 Next, the operation for toner-remaining amount detection is described. In
 the image forming apparatus body, a light guide for guiding the LED light
 from a body light-emitting portion, not shown, to the development
 apparatuses 12, and a light guide 34 for guiding the light that has passed
 through the interior of the development agent container 21 to a
 body-light-receiving portion, not shown, are arranged at positions
 corresponding to the light transmission windows 28, 29. With such a
 structure, when the amount of the toners 22 is not so much in the
 development-agent container 21, the stirring sheet 30b wipes out the
 toners on the light-transmission windows 28, 29 to ensure the light path,
 so that the light guided by the light guide 33 to the development
 apparatuses 12 transmits through the container and is introduced to the
 light-receiving portion by the light guide 34.
 When the amount of the toner 22 is higher in the development agent
 container 21, the light transmission window 29 is covered soon by the
 toner even where cleaned by the stirring sheet 30b, and therefore, the
 light is not transmitted through the window. However, the time that the
 light transmitted through the development-agent container 21 becomes
 longer as the toners 22 remain less. In this embodiment, the LED light is
 emitted for a time that the stirring member 30 turns once, and the
 transmission time t that the light is transmitted through the
 development-agent container 21 during this turn is detected.
 FIG. 4 is a diagram showing the relation between the toner-remaining amount
 M in the development-agent container 21 and transmission time t per unit
 time (the stirring member 30 turns once). In this embodiment, a time
 required for the stirring member 30 to make one turn is one second, but a
 maximum value of the transmission time t is about 0.7 sec. because the
 stirring sheet 30b shields the light path for about 0.3 sec. From the
 starting of wiping the light-transmission window 28 to the ending of
 wiping the light-transmission window 29. In this apparatus, the threshold
 of the toner-remaining amount detection is set to 0.6 sec., and it is set
 so that when the transmission time t exceeds this, or namely when the
 toner-remaining amount M is about 40 g as shown in FIG. 4, a warning
 "empty of toner amount" is to be issued.
 Herein, as a material for the stirring sheet 30b, a completely
 light-shielding flexible sheet having a film thickness of about 70
 microns, in which a carbon coating is made on a polyester base, is used.
 In a prior art, since the LED light may transmit through the stirring
 sheet 30b, the timing of the toner-remaining amount detection becomes
 unstable when the amount of the toner becomes less as described above, and
 it may causes fluctuations in a range of 30 g or the like. In this
 embodiment, by use of the completely light shielding sheet, such
 fluctuations are reduced to 5 g or less.
 The material of the stirring sheet 30b according to the invention is not
 limited to the material shown in the embodiment, and this invention is
 applicable by using a material such as urethane rubber or the like having
 a low clarity or being mixed with pigments having a light reflecting
 property as far as it ensures the required light-shielding property.
 Although in this embodiment, the structure that the invented
 development-agent container is incorporated as a part of a detachable
 cartridge in the image forming apparatus body is exemplified, it may be a
 sole structure of the development-agent container or a structure in which
 the invented development agent container is incorporated as a part of a
 process cartridge, and furthermore, the development-agent container is
 incorporated in the image forming apparatus body where the toner can be
 supplied by another container.
 In addition, although in this embodiment the color image forming apparatus,
 in which plural development apparatuses having cartridges are
 incorporated, is exemplified, this invention is applicable to a monochrome
 image forming apparatus having a single cartridge as a matter of course.
 As described above, with the development-agent container and the
 development apparatus according to the invention, by use of the completely
 light-shielding sheet for a flexible sheet rubbing the light transmission
 window for the stirring member, it is possible to provide the
 development-agent container and the development apparatus, which can
 stably detect the toner-remaining amount.