Toner container and image forming apparatus provided with toner container

A toner container adapted to be detachably attached to a developer provided in an apparatus body of an image forming apparatus includes a casing for loading a toner therein. The casing has a bottom wall formed with a replenishing port for replenishing the toner to the developer. A sheet member is placed on the bottom wall. The sheet member has a first end fixed to the casing near the replenishing port, and a second end opposite to the first end. The second end is movable up and down. A first magnet is attached to a lead end of the second end of the sheet member, and a guide to guide the up and down movement of the first magnet. The first magnet is upwardly movable while being guided by the guide by a repulsion force resulting from application of a certain magnetic force to the first magnet.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a toner container detachably attached to a developer provided in an apparatus body of an image forming apparatus, and an image forming apparatus provided with the toner container.

2. Description of the Related Art

An electrophotographic image forming apparatus generally has, in the periphery of a photosensitive drum as an image carrier, a charger, an exposure unit, a developer, a transferer, and a cleaner. An electrostatic latent image is formed on the surface of the photosensitive drum by irradiating light representing image information from the exposure unit onto the surface of the photosensitive drum where uniform electric charges are supplied by the charger. Then, the electrostatic latent image is developed into a toner image by supplying toner i.e. toner particles (hereinafter, toner particles are simply called as “toner”) onto the electrostatic latent image by the developer. Then, the toner image is transferred onto a sheet. The sheet carrying the transferred toner image is transported to a fixing device provided downstream of the photosensitive drum, where the toner image is fixed by heating. After the image fixation, the sheet carrying the fixed toner image is discharged outside of the image forming apparatus.

Normally, a toner container is detachably attached to the developer. A toner replenishing port is formed at an appropriate position in a bottom wall of the toner container so that the toner accommodated in the toner container is replenished to the developer through the replenishing port. When the toner in the toner container is reduced to such an amount that toner replenishment to the developer is incapable as a result of developing process, the toner container is replaced with a new toner container filled with toner.

It is often the case that the bottom wall of the toner container is formed into e.g. a funnel-like shape with a slope tilted toward the replenishing port so as to replenish the toner in possible total amount to the developer. The arrangement is proposed based on an expectation that the toner in the toner container may be guided along the slope, and substantially all the toner in the toner container may be replenished to the developer.

Forming the bottom wall into a funnel-like shape, however, not only leads to a reduced capacity of the toner container, but also leads to forming a waste space corresponding to the funnel portion in the apparatus body of the image forming apparatus. As a result, miniaturization of the image forming apparatus may be hindered.

In view of the above, there is proposed an arrangement of forming the bottom wall of the toner container into a horizontally flat plate (see e.g. Japanese Unexamined Patent Publication No. 2002-278424). Forming the bottom wall of the toner container into a flat plate may be advantageous in increasing the capacity of the toner container by the space corresponding to the funnel portion, and in miniaturizing the image forming apparatus.

Forming the bottom wall of the toner container into the flat plate, however, may obstruct guiding the toner toward the replenishing port, which makes is impossible to replenish all the toner in the toner container to the developer. As a result, the toner container is required to be replaced with a new one, despite toner remainder in the toner container. This is waste of toner.

In other words, the conventional toner container has contradictory problems to be solved: forming the bottom wall of the toner container into a funnel-like shape in an attempt to eliminate toner remainder may obstruct miniaturization of the image forming apparatus; and forming the bottom wall into a flat shape in an attempt to miniaturize the image forming apparatus may increase the amount of toner remainder in the toner container.

SUMMARY OF THE INVENTION

In view of the above problems residing in the conventional examples, it is an object of the present invention to provide a toner container that enables to secure a large capacity of the container, contribute to miniaturization of an image forming apparatus, and to minimize the amount of toner remainder in the container, as well as an image forming apparatus provided with the toner container.

A toner container according to an aspect of the invention comprises: a toner container adapted to be detachably attached to a developer provided in an apparatus body of an image forming apparatus. The toner container comprises: a casing member for loading a toner therein, the casing member including a bottom wall formed with a replenishing port for replenishing the toner to the developer; a sheet member placed on the bottom wall, the sheet member including a first end fixed to the casing member near the replenishing port, and a second end opposite to the first end, the second end being made movable up and down; a first magnet attached to a lead end of the second end of the sheet member; and a guide member for guiding the up and down movement of the first magnet, wherein the first magnet is upwardly movable while being guided by the guide member by a repulsion force resulting from application of a certain magnetic force to the first magnet.

An image forming apparatus according to another aspect of the invention comprises: an apparatus body; an image carrier incorporated in the apparatus body; a developer for forming a toner image by supplying a toner onto a surface of the image carrier; and a toner container detachably attached to the developer, wherein the toner container has the aforementioned arrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a cross-sectional side view showing an embodiment of a printer10to which a toner container30embodying the invention is applied. The printer10, an example of an image forming apparatus, has an apparatus body11. A sheet storage12for storing a stack P1of sheets for printing, an image former13for forming an image on each sheet P which is fed from the sheet stack P1stored in the sheet storage12, and an image fixer14for fixing the image on the sheet P after the image formation are provided in the apparatus body11. The printer10is further provided with a sheet discharger15, at a top part of the apparatus body11, for discharging the sheet P after the image fixation in the image fixer14.

A predetermined number of (in this embodiment, one) sheet cassettes121are detachably provided in the sheet storage12. A pickup roller122is arranged at an upstream end of the sheet cassette121i.e. at a right position inFIG. 1for feeding the sheets P one by one from the sheet stack P1. The sheet P fed from the sheet cassette121by driving the pickup roller122is transported to the image former13along a sheet transport path123and by way of a registration roller pair124provided at a downstream end of the sheet transport path123.

The image former13transfers an image onto the sheet P based on image information electronically transmitted from a computer or a like device. The image former13is provided with a photosensitive drum131, as an image carrier, which is rotatably supported to the apparatus body11about an axis of rotation of the photosensitive drum131extending in a depthwise direction of the apparatus body11i.e. a direction orthogonal to the plane ofFIG. 1. The image former13further includes, along the surface of the photosensitive drum131in clockwise direction in the order from the position immediately above the photosensitive drum131, a charger132, an exposure unit133, a developer20to which the toner container30is detachably attached, a transfer roller134, and a cleaner135.

The photosensitive drum131is adapted to form an electrostatic latent image, and a toner image i.e. a developing agent image on the surface thereof. Preferably, a flat and rigid amorphous silicon layer may be formed on the surface of the photosensitive drum131.

The charger132is adapted to form uniform electric charges on the surface of the photosensitive drum131which is rotated in clockwise direction about the axis of rotation of the photosensitive drum131. The example shown inFIG. 1adopts a technique of applying electric charges to the surface of the photosensitive drum131by corona discharge. A charging roller for applying electric charges, with its surface being rotated in contact with the surface of the photosensitive drum131, may be used as a member for applying electric charges to the surface of the photosensitive drum131, in place of the charger132.

The exposure unit133irradiates, onto the surface of the rotating photosensitive drum131, laser light whose intensity is controlled based on image data electronically transmitted from an external device such as a computer. An electrostatic latent image is formed on the surface of the photosensitive drum131by removing the electric charges corresponding to the area of the drum surface irradiated by the laser light.

The developer20is adapted to magnetically attract toner onto the area of the drum surface where the electrostatic latent image is formed by supplying the toner to the surface of the photosensitive drum131to thereby form a toner image on the surface of the photosensitive drum131. The developer20is constructed by mounting various parts to be described later in a developer body21of the developer20, which is arranged immediately on the right side of the photosensitive drum131. The toner container30is detachably attached to an upper portion of the developer body21at a right position inFIG. 1, and is adapted to replenish a developing agent (in this embodiment, toner) to the developer body21.

There are two types of developing agent: one is a single component developing agent composed of a toner, and the other is a two component developing agent composed of a toner and carrier. The toner is fine particles, with a particle diameter of 6 to 12 μm, obtained by dispersing additives such as a colorant, a charge controlling agent, and a wax in a binder resin. The carrier is magnetic particles, with a particle diameter of 60 to 200 μm, made of magnetite (Fe3O4) or a like material. The carrier is used to charge the toner. Whereas the toner is an expendable which is required to be replenished from the toner container30to the developer20according to needs, the carrier is generally circulatively used without being consumed in a state that a predetermined amount of the carrier is loaded in the developer20.

The developer body21includes, in the box-shaped developer body21, a first screw feeder22, a second screw feeder23, and a developing roller24, each of which extends in a direction substantially orthogonal to the plane ofFIG. 1. The first screw feeder22, the second screw feeder23, and the developing roller24are arranged side by side from the right side toward the left side inFIG. 1.

A toner receiving port211is formed in a top wall210of the developer body21immediately above the first screw feeder22to receive the toner from the toner container30into the developer body21. A toner supply port212is formed in a left wall of the developer body21inFIG. 1to supply the toner to the photosensitive drum131. The toner supply port212extends over the substantially entire length of the developer body21in a direction substantially orthogonal to the plane ofFIG. 1.

The toner introduced from the toner container30through the toner receiving port211is circulated inside the developer body21while being stirred by driving rotation of the first and the second screw feeders22and23. A part of the circulating toner is supplied to the surface of the photosensitive drum131by way of the surface of the driving rotating developing roller24.

A layer thickness regulation blade25is provided above the toner supply port212. The layer thickness regulation blade25suspends from the top wall210of the developer body21, with its lower end being opposed to the surface of the developing roller24. As the developing roller24is rotated about its axis of rotation in counterclockwise direction, the toner is supplied from the surface of the developing roller24toward the photosensitive drum131. While the toner is supplied through a clearance between the layer thickness regulation blade25and the surface of the developing roller24, the thickness of the toner is regulated to a predetermined thickness.

The first screw feeder22, the second screw feeder23, and the developing roller24are driven synchronously by transmission of a driving force of an unillustrated drive motor by way of a gear mechanism.

The transfer roller134is adapted to transfer a toner image which is positively charged on the surface of the photosensitive drum131onto a sheet P transported to a position immediately below the photosensitive drum131. The transfer roller134applies negative electric charges, which is opposite to the electric charges of the toner image, to the sheet P.

When the sheet P has reached the position immediately below the photosensitive drum131, the toner image is transferred onto the sheet P which is pressingly held between the transfer roller134and the photosensitive drum131. The transfer process of the sheet P is a process of magnetically attracting the toner image formed on the positively-charged surface of the photosensitive drum131toward the surface of the sheet P which is negatively charged by the transfer roller134.

The cleaner135is adapted to clean the photosensitive drum131after the transfer process by removing toner residuals from the surface of the photosensitive drum131. After the surface of the photosensitive drum131is cleaned by the cleaner135, the photosensitive drum131faces the charger132again.

The image fixer14is adapted to fix the toner image on the sheet P by heating after the transfer process in the image former13. The image fixer14includes a fixing roller141for applying heat to the sheet P, and a pressure roller142which is opposingly arranged below the fixing roller141. After the transfer process, the sheet P is transported toward a nip portion N between the fixing roller141and the pressure roller142. An image fixing process is performed by applying heat to the sheet P from the fixing roller141while the sheet P passes the nip portion N. After the image fixing process, the sheet P is discharged to the sheet discharger15along a sheet discharge path143.

The sheet discharger15is defined by forming the top part of the apparatus body11into a recess. A bottom portion of the recess serves as a discharge tray151for receiving the discharged sheet P.

FIGS. 2 and 3are partially cutaway perspective views showing an embodiment of the toner container30.FIG. 2shows a state that a sheet member32is set to a horizontal position S1, andFIG. 3shows a state that the sheet member32is set to a maximally tilted position S2.FIG. 4is a an enlarged view viewed from the direction IV inFIG. 2. ThroughoutFIGS. 2 through 4, X-X directions are called as left and right directions, and Y-Y directions are called as forward and backward directions. Particularly, −X direction is called as leftward direction, +X direction is called as rightward direction, −Y direction is called as forward direction, and +Y direction is called as backward direction.

As shown inFIGS. 2 and 3, the toner container30basically has a substantially parallelepiped box-like shape, and includes a container body31, as a casing member, for accommodating toner therein, the sheet member32provided in the container body31, a rod member33provided at a rear end, as a second end, of the sheet member32, and a pair of end magnets34, as a first magnet, which are fixed to both ends of the rod member33in the left and right directions.

The container body31includes a bottom wall311which has a rectangular shape in plan view and is formed substantially horizontally, a replenishing port310which is formed at a front end, as a first end portion, of the bottom wall311, and extends over the substantially entire length of the container body31in the left and right directions, a front wall312which is formed upright from a front end of the replenishing port310, a pair of side walls313which are formed upright from both ends of the bottom wall311in the left and right directions, a rear wall314extending upwardly from a rear end, as a second end portion, of the bottom wall311, and a top wall315which extends to the side wall pair313and an upper end of the front wall312.

An engaging portion316which extends downwardly from the bottom wall311, with a vertically through hollow, is formed at a position below the replenishing port310. Engaging grooves316aextending over the substantially entire length of the engaging portion316are formed in an outer surface of a front wall and in an outer surface of a rear wall of the engaging portion316, respectively. Atop wall213of the developer body21has an attachment support214which is detachably engageable with the engaging portion316in the left and right directions.

The attachment support214defines the toner receiving port211for receiving the toner from the toner container30into the developer body21through the replenishing port310. Engaging ribs211a, extending in the left and right directions, are formed at upper ends of the attachment support214so that the engaging ribs211aare engaged in the engaging grooves316ain sliding contact therewith. The toner container30is detachably attached to the developer20by slidably drawing the engaging ribs211ain and out of the engaging grooves316a.

A lower opening of the engaging portion316is covered by an unillustrated cover sheet e.g. an adhesive sheet to prevent the toner in the container body31from falling through the replenishing port310before the toner container30is attached to the developer20. A user is allowed to attach the toner container30to the developer20by slidably engaging the engaging portion316with the attachment support214while peeling off the cover sheet. Thereby, the toner container30is attached to the developer20, while preventing toner leakage.

The sheet member32has an effective surface, i.e. a surface where the toner is loaded, whose area is substantially the same as the area of the bottom wall311. With this arrangement, substantially all the toner in the container body31is loaded on the sheet member32except for an area corresponding to the replenishing port310. The sheet member32has a front end321, as a first end, which is fixedly supported to an end portion of the replenishing port310i.e. an inner surface of the rear walls of the engaging portion316by adhesion or a like technique.

The rod member33extends in a cylindrical portion322which is defined by winding the rear end, as the second end, of the sheet member32. The rod member33has a length slightly larger than the length of the cylindrical portion322. With this arrangement, the rod member33is slightly protruded from both ends of the cylindrical portion322in a state that the rod member33extends in the cylindrical portion322.

The end magnets34each has a spherical shape, as shown inFIGS. 2 and 3. The end magnet34has a north pole at an outer portion thereof, and a south pole at a central portion thereof i.e. an inner portion through which the rod member33extends.

The rear wall314has an inner surface formed into an arc-shape, with an upper corner position of the front end321of the sheet member32i.e. a position316bwhere an inner corner portion of the engaging portion316is bent by about 90 degrees, serving as a center of curvature; and with a distance between the front end321and the rear end of the sheet member32, serving as a radius of curvature. Also, the side walls313each has an arc-shaped guide rail313a, as a guide member, at a position slightly forward of the rear wall314. The guide rail313aprojects outwardly in sliding contact with a front end of the end magnet34, with the upper corner position of the front end321serving as a center of curvature, and with the distance between the front end321and the front end of the end magnet34serving as a radius of curvature.

The guide rails313aproject outwardly from the side walls313, respectively. The length of the rear wall314in the left and right directions is set slightly larger than the outer distance between the side walls313so as to install the guide rails313a. With this arrangement, there is defined a guide space V between each of the guide rails313aand the rear wall314, in which the end magnet34is moved up and down while being guided along the corresponding guide rail313a. In other words, arc-shaped projections projecting outwardly in the left and right directions are formed on the rear end of the container body31for defining the guide spaces V.

The sheet member32is movable between the horizontal position S1shown inFIG. 2and the maximally tilted position S2shown inFIG. 3by way of the rod member33, as the end magnets34are moved up and down while being guided in the guide spaces V.

The sheet member32has such dimensions that end portions thereof in the left and right directions are slidably contacted with the side walls313of the container body31, and a rear portion of the cylindrical portion322is slidably contacted with the rear wall314of the container body31in a state that the sheet member32is placed on the bottom wall311of the container body31. The dimension setting enables to prevent the toner on the sheet member32from falling onto the bottom wall311.

In this embodiment, an elevating mechanism40is provided in the apparatus body11of the printer10to move the end magnet pair34up and down. As shown inFIGS. 2 through 4, the elevating mechanism40includes a shaft41which is arranged at a position immediately below the toner container30in the apparatus body11and extends in the left and right directions in parallel with the rod member33; a pair of magnet rollers42, as a second magnet, which are concentrically mounted on the shaft41to be integrally rotatable, and are arranged opposing to the respective corresponding end magnets34; a drive gear43which is concentrically mounted on one end of the shaft41to be integrally rotatable; and a drive motor44for transmitting a driving force thereof to the drive gear43via a gear mechanism441.

The magnet rollers42each has, as shown inFIG. 4, plural unit magnets on a peripheral portion thereof, with its north pole and a south pole being alternately arranged with a phase interval of 90°. The magnet rollers42are integrally rotated about the axis of rotation of the shaft41via the gear mechanism441and the drive gear43by driving the drive motor44. The end magnets34each generates a repulsing magnetic force when the north pole of the corresponding magnet roller42faces the end magnet34, and is magnetically attracted to the magnet roller42when the south pole of the magnet roller42faces the end magnet34.

In this embodiment, a magnetic field sensor35, as a sensor, is provided to detect one of the end magnets34. The magnetic field sensor35is provided at a position on the outer surface of the rear wall314, corresponding to one of the guide spaces V, and corresponding to a predetermined maximal height of the end magnet34. The magnetic field sensor35is a measuring device capable of detecting a magnetic flux density of the end magnet34. For instance, data representing a magnetic flux density when the end magnet34is set to the maximal height may be stored in an unillustrated controller. Then, the controller may compare a magnetic flux density detected by the magnetic field sensor35with the pre-stored input value representing the magnetic flux density at the maximal height, and judge that the end magnet34has reached the maximal height when these values are identical to each other.

The maximal height of the end magnet34is a selected height position which enables to set the sheet member32to such a tilt angle as to fall substantially all the toner from the sheet member32. With this arrangement, when the magnetic field sensor35detects the end magnet34, the toner in the container body31is almost entirely consumed, in other words, the container body31is empty. Then, the toner container30is replaced with a new one based on the detection result of the magnetic field sensor35.

FIGS. 5A through 5Bare cross-sectional side views of the toner container30for describing an operation of the elevating mechanism40.FIG. 5Ashows a state that the toner is full in the container body31.FIG. 5Bshows a state that toner remainder in the container body31is in a medium level.FIG. 5Cshows a state that the toner in the container body31is almost entirely consumed.

First, as shown inFIG. 5A, in a state that the toner is full in the container body31, a certain weight corresponding to a large amount of toner is applied to the sheet member32. Accordingly, even if the north poles of the magnet rollers42face the respective corresponding end magnets34, there is no likelihood that the end magnets34are moved upward against the weight of the toner. Thus, the sheet member32is set to the horizontal position S1.

As the toner is consumed by a developing process in the developer20, the toner in the container body31is replenished into the developer body21(seeFIG. 1) through the replenishing port310. Thereby, the amount of toner on the sheet member32is decreased. As a result, the weight of the toner on the sheet member32is gradually decreased against the repulsion force of the magnet rollers42. Then, as shown inFIG. 5B, when the north poles of the magnet rollers42face the respective corresponding end magnets34, the end magnets34are moved upward while being guided in the guide spaces V by a repulsion force between the magnet rollers42and the end magnets34. Thereby, the sheet member32attached with the end magnets34at the rear end thereof is tilted by a certain angle with respect to the bottom wall311, with the front end321being set to a lowest position.

Then, as the south poles of the magnet rollers42face the respective corresponding end magnets34by rotation of the magnet rollers42about the axis of rotation of the shaft41, the end magnets34are magnetically attracted to the magnet rollers42, and, as a result, the sheet member32is returned to the horizontal position S1. Since the magnet rollers42are rotated about the axis of rotation of the shaft41by driving the drive motor44, the end magnets34are repeatedly repulsed away from and attracted to the magnet rollers42at a predetermined cycle. With this arrangement, the sheet member32is flutteringly moved via the rod member33. The fluttering movement of the sheet member32causes the toner on the sheet member32to be securely moved toward the replenishing port310.

As the toner on the sheet member32is significantly decreased, as shown inFIG. 5C, the weight of the toner is significantly decreased. When the north poles of the magnet rollers42face the respective corresponding end magnets34in this state, the sheet member32is set to the maximally tilted position S2. Thereby, a meager amount of toner left on the sheet member32is gathered on an area near the replenishing port310.

In addition to the above operation, the sheet member32is oscillatingly moved between the horizontal position S1and the maximally tilted position S2in accordance with the up and down movements of the end magnets34in response to rotation of the magnet rollers42. This enables to sweep off the toner remainder from the sheet member32, and substantially all the toner on the sheet member32is replenished to the developer20through the replenishing port310.

Thus, unlike the conventional arrangement, the above arrangement enables to efficiently use the toner, without likelihood that the toner container30may be replaced with a new one, with the toner remainder in the container body31.

As described above in detail, the toner container30of the embodiment is detachably attached to the developer20for supplying the toner to the surface of the photosensitive drum131of the printer10. The toner container30includes; the container body31having the bottom wall311formed with the replenishing port310through which the toner loaded in the container body31is replenished to the developer20; the sheet member32which is placed over the substantially entire surface of the bottom wall311except for the replenishing port310, and has the front end321fixed to the end portion of the replenishing port310; the end magnets34arranged at the rear end of the sheet member32; and the guide spaces V for guiding the end magnets34up and down. Further, the magnet rollers42are provided outside of the container body31to apply a repulsion force to the end magnets34so that the end magnets34are moved upward along the guide spaces V.

In the thus-constructed toner container30, in a state that the toner is full in the container body31of the toner container30, the sheet member32placed on the bottom wall311is firmly contacted with the bottom wall311against a repulsion force between the end magnets34and the magnet rollers42due to the weight of the toner. This state is defined as an initial state. As the toner is replenished from the toner container30into the developer body21from the initial state, the amount of toner in the toner container30is gradually decreased. As a result, the repulsion force between the end magnets34and the magnet rollers42is gradually dominant, as compared with the weight of the toner in the toner container30. Thereby, the end magnets34are moved upward in the guide spaces V.

When the end magnets34are moved upward in the guide spaces V, the rear end of the sheet member32is moved upward together with the end magnets34. As a result, the sheet member32is gradually tilted, with the replenishing port310being set to a lowest position. The tilt angle of the sheet member32is maximum immediately before the toner in the toner container30is gone. With this arrangement, the toner remainder on the sheet member32is moved toward the replenishing port310while being guided on the sheet member32at the maximally tilted angle position. This enables to efficiently use substantially all the toner in the toner container30in replacing with a new toner container, without likelihood that the toner may be left in the toner container30before the replacement.

Since the sheet member32is tilted, as the amount of toner in the toner container30is decreased, it is possible to set the bottom wall311of the toner container30for supporting the sheet member32to a horizontal position in the initial state. This arrangement not only enables to increase the capacity of the toner container30, as compared with the conventional arrangement, in which the bottom wall corresponding to the bottom wall311is formed into the funnel-like shape, but also contributes to miniaturization of the apparatus body11of the printer10in the case where the toner container30substantially with the same capacity as the conventional toner container is used in the printer10.

Thus, the toner container30of the embodiment is advantageous in increasing the capacity of the toner container30, in contributing to miniaturization of the apparatus body11of the printer10, and in eliminating toner remainder in the container body31. This enables to use substantially all the toner in the container body31without waste, thereby contributing to running cost reduction of the printer10.

In the embodiment, the magnet rollers42are rotatable about the axis of rotation of the shaft41by driving the drive motor44, and the unit magnets are arranged on the peripheral portion of each of the magnet rollers42in such a manner that the north pole and the south pole are circumferentially and alternately arranged. With this arrangement, the north poles and the south poles of the magnet rollers42are alternately acted on the respective corresponding end magnets34by rotating the magnet rollers42. Thereby, the end magnets34are oscillatingly moved up and down, as being repulsed away from the north poles of the magnet rollers42and attracted to the south poles of the magnet rollers42. As a result, the sheet member32is flutteringly moved in response to the oscillatory up and down movements of the end magnets34, and the toner remainder on the sheet member32is shaken off from the sheet member32toward the replenishing port310. This securely enables to eliminate likelihood that toner may be left in the toner container.

In the embodiment, since the magnet rollers42are arranged in the apparatus body11of the printer10, there is no need of arranging the magnet rollers42in the toner container. This enables to simplify the construction of the toner container.

Further, the magnetic field sensor35for detecting the end magnet34is arranged at such a position that the sheet member32is set to a tilt angle position capable of falling substantially all the toner remainder from the sheet member32. This enables to judge that the container body31is empty based on a detection result of the magnetic field sensor35for detecting the end magnet34. Thus, an appropriate time for replacing the toner container30with a new one can be easily determined based on the judgment result.

The invention is not limited to the foregoing embodiment, but may embrace the following modifications and/or alterations.

(1) In the embodiment, the printer10is described as an example of the image forming apparatus. The invention may be applicable to other image forming apparatus such as a copier or a facsimile machine.

(2) In the embodiment, the magnet rollers42facing the respective corresponding end magnets34are provided in the apparatus body11of the printer10. Alternatively, the magnet rollers42may be provided in the toner container30. In the modification, the toner container30is applicable to a well-known printer, in which magnet rollers42are not provided in an apparatus body. This enables to expand the versatile use of the toner container30.

(3) In the embodiment, the magnet rollers42serve as the second magnet, and the magnet rollers42are rotatable about the axis of rotation of the shaft41by driving the drive motor44. Alternatively, a single magnet with a pole opposite to the pole of the end magnet34may be provided as the second magnet.

In the modification, the second magnet applies a repulsion force against the end magnet34, and does not attract the end magnet34. Accordingly, unlike the embodiment in which the magnet rollers42are used as the second magnet, the end magnet is not oscillatingly moved up and down. However, the modification exhibits a function that the tilt angle of the sheet member32is gradually increased as the amount of toner in the container body31is decreased, because a constant repulsion force is generated on the end magnet34.

Also, unlike the embodiment that the magnet rollers42are used as the second magnet, providing the single magnet as the second magnet eliminates the need of providing the elevating mechanism40for elevating the end magnets34by rotating the magnet rollers42in response to driving of the drive motor44. This enables to simplify the arrangement of the printer.

(4) In the embodiment, the replenishing port310of the toner container30is formed in one end of the bottom wall311. Alternatively, the replenishing port may be formed in the middle or an appropriate position of the bottom wall311. In the modification, however, it is necessary to provide at least two sheet members32facing each other with respect to the replenishing port30, end magnet pairs34each of which is provided for each of the sheet members32, and plural second magnets for elevating the respective end magnet pairs34.

(5) In the embodiment, the bottom wall311of the container body31is set horizontally. Alternatively, the bottom wall311may be tilted downwardly toward the replenishing port310in the initial state. The modification enables to increase the falling effect by tilting the sheet member32relative to the tilted bottom wall311, in addition to the advantage that the bottom wall311has a function of falling the toner toward the replenishing port310. This is further advantageous in eliminating likelihood that toner may be left in the toner container30.

(6) Alternatively, a bag-like member loaded with a toner, having a part thereof facing the replenishing port310being formed into an opening, may be used in place of the sheet member32. In the modification, the peripheral end of the opening of the bag-like member is fixed to the inner end of the replenishing port310with no clearance. Thereby, the toner in the bag-like member is allowed to fall exclusively into the replenishing port310. This is advantageous in securely preventing the toner from falling onto the bottom wall311through a clearance between the end portion of the sheet member32and the inner wall of the container body31, which may occur in the embodiment.

The aforementioned embodiment primarily includes the inventions having the below-mentioned arrangements.

A toner container according to an aspect of the invention comprises: a casing member for loading a toner therein, the casing member including a bottom wall formed with a replenishing port for replenishing the toner to the developer; a sheet member which is placed on the bottom wall, the sheet member including a first end fixed to the casing member near the replenishing port, and a second end opposite to the first end, the second end being made movable up and down; a first magnet which is attached to a lead end of the second end of the sheet member; and a guide member for guiding the up and down movement of the first magnet, wherein the first magnet is upwardly movable while being guided by the guide member by a repulsion force resulting from application of a certain magnetic force to the first magnet.

An image forming apparatus according to another aspect of the invention comprises: an apparatus body; an image carrier incorporated in the apparatus body; a developer for forming a toner image by supplying a toner onto a surface of the image carrier; and a toner container detachably attached to the developer, wherein the toner container has the aforementioned arrangement.

In the above arrangements, as the toner in the toner container is gradually decreased, the repulsion force generated on the first magnet is dominant, as compared with the weight of the toner. Thereby, the first magnet is moved upward along the guide member. Then, the second end of the sheet member is moved upward together with the first magnet, and the sheet member is gradually tilted, with the first end thereof near the replenishing port being set to a lowest position. Immediately before the toner in the toner container is gone, the tilt angle of the sheet member is maximum. With this arrangement, the toner remainder on the sheet member is moved toward the replenishing port, as being guided on the sheet member at the maximally tilted angle position. Thus, the arrangement is advantageous in efficiently using substantially all the toner in the toner container, without toner remainder in the toner container.

Since the sheet member is gradually tilted, as the amount of toner in the toner container is decreased, it is possible to set the bottom wall of the toner container horizontally. This not only enables to increase the capacity of the toner container, as compared with the conventional toner container, in which the bottom wall is formed into a funnel-like shape, but also contributes to miniaturization of the apparatus body of the image forming apparatus, in the case where the toner container with the same capacity as the conventional toner container is used.

Preferably, a second magnet for applying the certain magnetic force to the first magnet may be provided in the casing member. This arrangement enables to readily provide the operation and the effect of the invention, even if the inventive toner container is used in a well-known image forming apparatus, in which the second magnet is not provided in the apparatus body. Thereby, versatile use of the toner container is expanded.

Preferably, a second magnet for applying the certain magnetic force to the first magnet may be provided in the apparatus body. This arrangement enables to eliminate the need of providing a member for applying a certain magnetic force in the toner container, thereby simplifying the construction of the toner container.

Preferably, the second magnet may be a cylindrical magnet roller which is rotatable about a horizontal axis, and the magnet roller may have a peripheral portion where a north pole and a south pole are alternately arranged in a circumferential direction thereof.

In the above arrangement, the north pole and the south pole of the second magnet are alternately acted on the first magnet, as the magnet roller is rotated. Thereby, the first magnet is attracted to and repulsed away from the second magnet, and the first magnet is oscillatingly moved up and down. With this arrangement, since the sheet member is flutteringly moved by the oscillatory up and down movements of the first magnet, the toner remainder on the sheet member is moved toward the replenishing port by the fluttering movement of the sheet member. This enables to eliminate likelihood that the toner may be left in the toner container.

Preferably, the first end of the sheet member may be fixed to an end portion of the replenishing port. Particularly preferably, the sheet member may be placed over a substantially entire surface of the bottom wall except for the replenishing port, and a portion of the sheet member corresponding to an end portion of the replenishing port may be fixed to the end portion of the replenishing port.

In the above arrangement, the end portion of the sheet member except for the first end facing the replenishing port is firmly contacted with the inner wall of the casing member with no clearance in a state that the sheet member is placed over the bottom wall. This arrangement enables to prevent the toner from falling onto the bottom wall through a clearance between the end portion of the sheet member and the inner wall of the casing member, even if the sheet member is tilted.

Preferably, the bottom wall may have a rectangular shape in plan view, and may be set to a substantially horizontal position, the first end of the bottom wall may be formed with the replenishing port, the first magnet may be arranged on the second end opposite to the first end, the sheet member may be placed over a substantially entire surface of the bottom wall except for the replenishing port, and the sheet member may be tilted by a predetermined angle with respect to the bottom wall in such a manner that the first end of the sheet member is set to a lowest position, as the second end of the sheet member is raised by the upward movement of the first magnet.

Preferably, a sensor may be provided in the casing member for detecting whether the first magnet has reached a predetermined height position. In this case, preferably, the sensor may be so constructed as to detect the first magnet when the toner in the casing member is substantially consumed.

The above arrangement enables to determine that the toner in the casing member is empty based on a detection result of the sensor for detecting the end magnet.

This application is based on Japanese Patent Application No. 2006-139029 filed on May 18, 2006, the contents of which are hereby incorporated by reference.