Belt conveying apparatus and image forming apparatus

An image forming apparatus includes a belt conveying portion having a movable endless belt provided around at least two supporting members, a cleaning member provided in contact with a surface of the belt, a lubricant supply portion provided below a contact portion between the belt and the cleaning member for supplying lubricant to the contact portion, and an adhered-material storing portion provided below the lubricant supply portion for storing adhered-material scraped off from the belt by the cleaning member.

BACKGROUND OF THE INVENTION

This invention relates to a belt conveying apparatus and an image forming apparatus having a cleaning apparatus for cleaning a surface of a transfer belt of a transfer portion for transferring a toner image.

Recently, a color image forming apparatus such as a color copier has been developed according to colorization of office documents or the like. Further, there is known a four-drum-type image forming apparatus which includes four photosensitive drums (as image bearing bodies) arranged parallel to each other. Such an image forming apparatus is configured to form toner images on the respective photosensitive drums using toners (as developers) of, for example, yellow, magenta, cyan and black. The respective toner images are transferred to a sheet conveyed by a transfer belt (an endless belt) of a transfer portion so that toner images of respective colors are superimposed with each other. Conventionally, the transfer portion of the image forming apparatus has a cleaning blade formed of urethane rubber or the like for removing a toner adhering to a surface of the transfer belt. Such a conventional image forming apparatus is disclosed in, for example, Japanese Laid-Open Patent Publication No. 2004-77607 (paragraphs 0025-0033 and FIG. 10).

SUMMARY OF THE INVENTION

The present invention is intended to provide an image forming apparatus and a belt conveying apparatus capable of stably removing toner adhering to a belt.

The present invention provides an image forming apparatus including a belt conveying portion having a movable endless belt provided around at least two supporting members, a cleaning member provided in contact with a surface of the belt, a lubricant supply portion provided below a contact portion between the belt and the cleaning member, the lubricant supply portion supplying lubricant to the contact portion, and an adhered-material storing portion provided below the lubricant supply portion. The adhered-material storing portion stores adhered-material scraped off from the belt by the cleaning member.

The present invention also provides an image forming apparatus including a toner adhesion member to which a toner adheres, the toner adhesion member causing the toner to move, a cleaning member provided in contact with a surface of the toner adhesion member, a toner accumulation member disposed below a contact portion between the toner adhesion member and the cleaning member so that a part of the toner scraped off from the cleaning member is accumulated on the toner accumulation member, and a toner storing portion provided below the toner accumulation member. The toner storing portion stores the toner scraped off by the cleaning member. The toner accumulated on the toner accumulation member is supplied to the contact portion as lubricant.

The present invention also provides a belt conveying apparatus for conveying recording medium. The belt conveying apparatus includes a belt conveying portion having a movable endless belt provided around at least two supporting members, a cleaning member provided in contact with a surface of the belt, a lubricant supply portion provided below a contact portion between the belt and the cleaning member, the lubricant supply portion supplying lubricant to the contact portion, and an adhered-material storing portion provided below the lubricant supply portion. The adhered-material storing portion stores the adhered-material scraped off from the belt by the cleaning member.

With such an arrangement, when the cleaning blade contacting the belt removes the adhered-material from the belt, any increase of the contact friction can be restricted, and removal of the adhered-material from the belt can be stably performed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1is a schematic view showing a configuration of an image forming apparatus according to Embodiment 1 of the present invention.

The image forming apparatus1000shown inFIG. 1has a configuration of, for example, an electrophotographic color printer. InFIG. 1, a sheet tray100is detachably mounted to a main body of the image forming apparatus1000. Recording sheets (i.e., recording medium)101are stacked in the sheet tray100. The sheet tray100has a sheet placing plate102on which the recording sheets101are placed, and the sheet placing plate102is rotatably supported by a supporting shaft102a. The sheet tray100is provided with not shown guide members for defining a position of the recording sheets101stacked on the sheet placing plate102. The guide members define ends of the stack of the recording sheets101in the sheet feeding direction and in the direction perpendicular to the sheet feeding direction, so as to maintain the constant position of the stack of the recording sheet.

A lift-up lever104is rotatably supported by a shaft104aprovided on the sheet feeding side of the sheet tray100. The shaft104ais disengageably connected to a motor105. When the sheet tray100is mounted to the main body of the image forming apparatus1000, the lift-up lever104is connected to the motor105, and a not shown controller drives the motor105. When the lift-up lever104is rotated, the tip of the lift-up lever104pushes the bottom of the sheet placing plate102upward, and the recording sheets101placed on the sheet placing plate102moves upward. When the recording sheets101reach a predetermined height, an upward movement detecting portion106detects the recording sheets101, and the not shown controller stops the motor105based on the detection signal from the upward movement detecting portion106.

A sheet feeding portion200is disposed on the sheet feeding side of the sheet tray100, for individually feeding the recording sheet101. The sheet feeding portion200includes a pickup roller201provided so as to contact the recording sheet101having moved upward to a predetermined height, and a pair of rollers (i.e., a feed roller202and a retard roller203) for separating the uppermost recording sheet101from next recording sheet101picked up by the pickup roller201. The sheet feeding portion200further includes a sheet existence detecting portion204that detects the existence of the recording sheets101and a sheet remaining amount detecting portion205that detects the remaining amount of the recording sheets101.

The recording sheet101having been separated (from subsequent recording sheets) and fed by the sheet feeding portion200reaches a sheet conveying portion300. In the sheet conveying portion300, the recording sheet101passes a sheet sensor301and reaches a pair of sheet conveying rollers302. The sheet conveying rollers302start conveying the recording sheet101with a predetermined time delay after the recording sheet101is detected by the sheet sensor301. With this, the recording sheet101is pushed into a contact portion of the sheet conveying rollers302so that the recording sheet101is slightly warped, and therefore the skew of the recording sheet101is corrected. The recording sheet101is further conveyed by the conveying rollers302, passes a sheet sensor303, and reaches a pair of conveying rollers304. The conveying rollers304start rotating by a not shown driving portion when the recording sheet101is detected by the sheet sensor303, and convey the recording sheet101without stopping the recording sheet101. The recording sheet101is further conveyed by the conveying rollers302, passes a writing sensor305, and reaches an image forming portion400.

The image forming portion400includes four toner image forming portions430which are linearly arranged, and a transfer portion460that transfer toner images of the image forming portions430to an upper surface of the recording sheet101by means of Coulomb force. The four toner image forming portions430have the same configurations except colors (black (K), yellow (Y), magenta (M) and cyan (C)) of the toner. Therefore, for facilitating description, parts of only the image forming portions430of black (K) located at the most upstream position (in the conveying direction of the recording sheet101) are shown inFIG. 1. Parts of other three image forming portions430are omitted inFIG. 1, and only photosensitive drums431of the three image forming portions430are shown inFIG. 1.

The toner image forming portion430includes a photosensitive drum431that bears a toner image, a charging roller432that uniformly charges the surface of the photosensitive drum431, an LED head433composed of an LED array that forms a latent image on the charged surface of the photosensitive drum431, a developing roller434that develops the latent image by means of frictional electrification to thereby form a toner image, a toner supply portion436that supplies the toner to the developing roller434, a cleaning blade435that scrapes off the residual toner remaining on the photosensitive drum431after the transferring, and the like.

The transfer portion460includes an endless transfer belt461(i.e., a toner adhesion member) that carries the recording sheet101in a state where the recording sheet101adheres to the transfer belt461by means of electrostatic force. The transfer portion460further includes a drive roller462rotated by a driving portion (not shown) in the direction shown by an arrow to move the transfer belt461, and a tensioning roller463pairing with the driving roller462so that the transfer belt461is wound around the driving roller462and the tensioning roller463. The transfer belt461, the driving roller462and the tensioning roller463constitute a belt conveying portion. The transfer portion460further includes transfer rollers464facing and urged against the photosensitive drums431of the toner image forming portion430, and applied with voltages so that toner images are transferred from the photosensitive drums431to the recording sheet101. The transfer portion460further includes a cleaning blade465as a cleaning member that scrapes off the toner (adhered-material) adhering to the surface of the transfer belt461, and a toner box466as a toner storing portion (or an adhered-material storing portion) in which the toner scraped off from the transfer belt461is accumulated.

The toner image forming portion430and the transfer belt461are driven in synchronization with each other, and the toner images of the respective colors are transferred successively to the recording sheet101fed by the transfer belt461(in a state where the recording sheet101adheres to the transfer belt461with electrostatic force) so that the images of the respective colors are superimposed with each other. The recording sheet101with the toner having been transferred by the image forming portion400is fed to a fixing unit500for fixing the toner image to the recording sheet101with heat and pressure.

The fixing unit500includes an upper roller501and a lower roller502. Each of the upper roller501and the lower roller502has a halogen lamp503as an internal heat source and a surface layer formed of a resilient member. The upper roller501and the lower roller502apply heat and pressure to the toner image formed on the recording sheet101fed from the image forming portion400to thereby fix the toner image to the recording sheet101. Thereafter, the recording sheet101is ejected by a pair of ejection rollers504to a stacker portion505.

InFIG. 1, XYZ coordinate is determined as follows. X-axis is defined in the conveying direction of the recording sheet101when the recording sheet passes the toner image forming portions430. Y-axis is defined in the direction of rotation axes of the photosensitive drums431. Z-axis is defined as being perpendicular to both of the X-axis and the Y-axis. In the subsequent drawings, the X-axis, the Y-axis and the Z-axis indicate the same directions as those shown inFIG. 1. That is, in the subsequent drawings, the X-axis, the Y-axis and the Z-axis indicate directions of component parts in a state where the component parts are assembled into the image forming apparatus1000shown inFIG. 1.

As shown inFIG. 2, the cleaning apparatus480includes the cleaning blade465, the toner box466, a film467, and a toner accumulation member470as a lubricant supply portion. The cleaning blade465extends in the width direction of the transfer belt461. The cleaning blade465is attached to the toner box465by means of a cleaning blade attachment metal plate465ain such a manner that the cleaning blade465is pressed against the transfer belt461, with the transfer belt461being sandwiched by the tensioning roller463and the cleaning blade465. A toner as lubricant is preliminarily coated on the tip of the cleaning blade465so that the transfer belt461moves smoothly. The film467is composed of a resilient member. The film467is attached to the toner box466so that the film467contacts the transfer belt461to thereby prevent the leakage of the waste toner472in the toner box466.

FIG. 3is a perspective view of the cleaning apparatus480as obliquely seen from above.FIG. 4is a plan view of the cleaning apparatus480.FIG. 5is a perspective view showing an external form of the toner accumulation member470of the cleaning apparatus480.FIG. 6is a sectional view showing an internal configuration of the cleaning apparatus480. InFIG. 3, near side wall of the toner box466is omitted so that the positional relationship between the toner box466and the toner accumulation member470can be easily seen.

The toner accumulation member470is a rectangular and elongated plate-like member as shown inFIG. 3. The toner accumulation member470is disposed on the upstream side of the cleaning blade465in the moving direction of the transfer belt461and is disposed on a position lower than the cleaning blade465in the vertical direction. The toner accumulation member470is a shelf-like member provided in the toner box466so that the toner scraped off from the transfer belt461by the cleaning blade465is accumulated on the toner accumulation member470. The toner accumulation member470is fixed to the toner box466using, for example, thermal welding or the like in order to prevent the disengaging of the toner accumulation member470due to the weight of the waste toner472.

Further, as shown inFIG. 6, a space S is formed between the cleaning blade465and the toner accumulation member470. The space S is determined by distances A and B representing the positional relationship between the cleaning blade465and the toner accumulation member470. An end portion (tip)470aof the toner accumulation member470extends parallel to the cleaning blade465in the longitudinal direction of the cleaning blade465. The toner accumulation member470is elongated in the width direction of the transfer belt461, and disposed in parallel to the surface of the transfer belt461. The distances A and B will be described later.

With the above configured cleaning apparatus480, the operation of respective parts will be described.

The driving roller462is rotated counterclockwise as shown in an arrow inFIG. 1, and the transfer belt462moves in a direction shown by an arrow M inFIG. 1passing through the respective toner image forming portions430. At the respective image forming430, the toner images of the respective colors are transferred to the recording sheet101from the photosensitive drums431. The toner471remaining on the photosensitive drum431without being transferred to the recording sheet101adheres to the surface of the transfer belt461moving in the direction indicated by the arrow M. As shown inFIG. 2, when the transfer belt461moves, the toner471adhering to the surface of the transfer belt461is scraped off therefrom at a contact portion between the transfer belt461and the cleaning blade465. The scraped-off toner471(i.e., waste toner472) is stored in the toner box466.

Here, the assumed operation when the toner accumulation member470is not provided.

At the transfer portion460, when the amount of toner471adhering to the transfer belt461is small (i.e., a minute amount), the cleaning blade465is not applied with sufficient amount of the toner471. In such a case, according to contact of the moving transfer belt461and the cleaning blade465, the amount of the toner (as lubricant) preliminarily coated on the surface of the cleaning blade465gradually decreases, so that the friction between the transfer belt461and the cleaning blade465gradually increases. Due to the increase of the friction, the tip of the cleaning blade465may be bent in the moving direction of the transfer belt461. For example, in the case where the recording sheet of A4 size is fed in the long edge direction, the bending of the tip of the cleaning blade465occurs when approximately 2000 recording sheets are printed, due to the increase of the friction between the cleaning blade465and the transfer belt461.

Next, the operation when the toner accumulation member470is provided in the transfer portion460(FIG. 1) according to the embodiment will be described.

As shown inFIG. 2, a part of the waste toner472scraped off from the surface of the transfer belt461by the cleaning blade465is accumulated on the toner accumulation member470. The waste toner472is accumulated until the waste toner472reaches the surface of the transfer belt461and the tip of the cleaning blade465. The waste toner472accumulated on the toner accumulation member470exceeding a predetermined amount falls from the toner accumulation member470through the space S (FIG. 6), and is stored in the toner box466.

The waste toner472accumulated on the toner accumulation member470contacts and adheres to the transfer belt461and the cleaning blade465. The waste toner472adhering to the transfer belt461and the cleaning blade465is supplied to a contact portion between the transfer belt461and the cleaning blade465as lubricant.

The space S between the toner accumulation member470and the cleaning blade465is adjusted so that the waste toner472(accumulated on the toner accumulation member470) contacts and adheres to the transfer belt461and the cleaning blade465so that the waste toner472(as lubricant) is supplied to the contact portion between the transfer belt461and the cleaning blade465before the preliminarily coated toner (i.e., lubricant toner) on the cleaning blade465runs out, detailed description being given later.

As described above, the cleaning apparatus480according to Embodiment 1 is configured to supply the waste toner472accumulated on the toner accumulation member470to the contact portion between the transfer belt461and the cleaning blade465. With such an arrangement, the increase of the friction between the transfer belt461and the cleaning blade465can be restricted, and therefore the bending of the tip of the cleaning blade465can be prevented.

The space S between the tip of the cleaning blade465and the toner accumulation member470will be described with reference toFIG. 6.

As the space S becomes narrower, the ratio of the amount of the waste toner472accumulated on the toner accumulation member470to the amount of the waste toner472scraped off from the surface of the transfer belt461increases. As the space S becomes wider, the ratio of the amount of the waste toner472accumulated on the toner accumulation member470to the amount of the waste toner472scraped off from the surface of the transfer belt461decreases. Therefore, as the space S becomes narrower, the contact pressure of the waste toner472(accumulated on the toner accumulation member470) urged against the transfer belt461and the cleaning blade465may increase, with the result that the cleaning blade465can not sufficiently scrape off the toner471(FIG. 2) from the surface of the transfer belt461, i.e., a passing-through of the toner471occurs. In contrast, as the space S becomes wider, the waste toner472is not sufficiently supplied to the contact portion between the cleaning blade465and the transfer belt461, and therefore the bending of the tip of the cleaning blade465may occur.

Further, the time after the accumulation of the waste toner472on the toner accumulation member470is started until the accumulated waste toner472reaches the contact portion between the cleaning blade465and the transfer belt461is determined based on the space S.

The space S is determined by distances A and B that represent positional relationship between the toner accumulation member470and the cleaning blade465. The distance A is a distance from the toner accumulation member470to the surface of the transfer belt461, and the distance B is a distance in the moving direction (indicated by the arrow M) of the transfer belt461from the tip of the toner accumulation member470to the contact portion between the cleaning blade465and the transfer belt461.

Further, the toner preliminarily coated as lubricant on the cleaning blade465during the manufacturing runs out when approximately 2000 recording sheets are printed in the case where the recording sheet of A4 size is fed in the long edge direction. Therefore, it is necessary to set the distances A and B so that the waste toner472accumulated on the toner accumulation member270reaches the contact portion between the cleaning blade465and the transfer belt461before the preliminarily coated toner runs out.

Next, a description will be made to an experiment on the relationship between the distances A and B and toner supply performance (i.e., performance for supplying the toner to the cleaning blade465), as well as a cleaning performance (i.e., performance with which the cleaning blade465cleans the transfer belt461).

The printing test is performed while setting the distances A and B in various ways using the image forming apparatus having the cleaning blade465formed of urethane rubber whose thickness is 2 mm and the toner accumulation member470formed of a rigid body. The experimental conditions are as follows:

Length of toner accumulation member470in moving direction of transfer belt: 6 mm (fixed)

Size of recording (printing) sheet: A4 size

Feeding direction: Long edge direction

Number of recording sheets: 2000 sheets

Printing pattern: Ruling pattern (at a low duty)

Regarding the above described printing pattern, “low duty” means that printing density of predetermined area is less than or equal to 5%.

TABLE 1 shows evaluation results of the toner supply performance to the cleaning blade465and the cleaning performance of the cleaning blade465for cleaning the transfer belt461according to the experimental. In TABLE 1, evaluation criteria of determining whether the result is excellent (O) or not (X) are as follows:

The toner supply performance is evaluated to be excellent (O) in the case where the waste toner472on the toner accumulation member470reaches the tip of the cleaning blade465as shown inFIG. 2after the printing of 2000 recording sheets. The toner supply performance is evaluated to be not-excellent (X) in the case where the waste toner472on the toner accumulation member470does not reach the tip of the cleaning blade465after the printing of 2000 recording sheets.

Further, the cleaning performance is evaluated to be excellent (O) in the case where no contamination is present on the back surface of the recording sheet after the printing of 2000 recording sheets. The cleaning performance is evaluated to be not-excellent (X) in the case where contamination is present on the back surface of the recording sheet after the printing of 2000 recording sheets. In this regard, when the cleaning failure occurs, the toner adhering to the surface of the transfer belt461is not scraped off by the cleaning blade465, so that the contamination (toner) is present on the back side of the recording sheet.

According to the experimental result shown in TABLE 1, it is possible to determine that the waste toner can effectively be supplied to the contact portion between the cleaning blade465and the transfer belt461in the case where the distances A and B (representing the positional relationship between the toner accumulation member470and the cleaning blade465) satisfy the following condition (1), (2) or (3):
2.0 mm≦B≦3.0 mm and 3.0 mm≦A≦8.0 mm,   (1)
0.0 mm≦B≦1.0 mm and 5.0 mm≦A≦9.0 mm, and   (2)
B=0.0 mm and A=10.0 mm.   (3)

As described above, according to the image forming apparatus of Embodiment 1, the toner accumulation member470is provided at a predetermined distance from the cleaning blade465so that the waste toner472is accumulated on the toner accumulation member470and is supplied (as lubricant) to the contact portion between the transfer belt461and the cleaning blade465. Therefore, the increase of the friction between the cleaning blade465and the transfer belt461can be restricted. Accordingly, it becomes possible to prevent the bending of the tip of the cleaning blade465, and to prevent the failure in removing the toner471(FIG. 2) from the surface of the transfer belt461.

FIG. 7shows a specific example of Embodiment 1 designed in consideration of productivity. In this specific example, a toner accumulation member470′ has a substantially Z-shaped cross section (cut along a plane perpendicular to the longitudinal direction of the toner accumulation member470′). The space S between the toner accumulation member470′ and the cleaning blade465is wider than that of the toner accumulation member470shown inFIG. 6, and the length C of the toner accumulation member470′ (specifically, set to 6.3 mm) in the moving direction of the transfer belt461is longer than that of the toner accumulation portion470shown inFIG. 6. With such dimensions, the same advantages as the above described Embodiment 1 are obtained, although the sectional shape of the toner accumulation member470′ is different from the sectional shape of the toner accumulation member470.

FIG. 8is an enlarged view showing a cleaning apparatus680having a cleaning blade465and a toner box466of an image forming apparatus according to Embodiment 2 of the present invention and surroundings thereof.FIG. 9is a perspective view showing an external configuration of the cleaning apparatus680as obliquely seen from above.FIG. 10is a plan view showing the cleaning apparatus680.FIG. 11is a perspective view showing an external form of a toner accumulation member670of the cleaning apparatus680. InFIG. 9, near side wall of the toner box466is omitted so that the positional relationship between the toner box466and the toner accumulation member670can be easily seen.

The difference between the image forming apparatus having the cleaning apparatus680of Embodiment 2 and the image forming apparatus1000having the cleaning apparatus480(FIG. 2) of Embodiment 1 is in the shape of the toner accumulation member670(470). Therefore, components of the image forming apparatus (having the cleaning apparatus680) of Embodiment 2 which are the same as those of the image forming apparatus1000of Embodiment 1 are assigned the same reference numerals or omitted in drawings, and duplicate descriptions thereof are omitted. The description is emphasized on the difference between the image forming apparatus of Embodiment 2 and the image forming apparatus of Embodiment 1. The components of the image forming apparatus of Embodiment 2 except the toner accumulation member670are the same as those of the image forming apparatus1000of Embodiment 1, and thereforeFIG. 1is referred as necessary.

As shown inFIGS. 8 through 11, the toner accumulation member670of Embodiment 2 has a plate-like shape as the toner accumulation member470(FIG. 5) of Embodiment 1. However, the toner accumulation member670has a cutaway concave portion670bformed on the side of the toner accumulation member670facing the cleaning blade465. The cutaway concave portion670bis formed at the center of the toner accumulation member670. The cutaway concave portion670bis. Convex portions670care formed at both sides of the cutaway concave portion670b, and protrude toward the cleaning blade465. Each convex portion670chas a tip portion670a.

FIG. 12is a sectional view showing an internal configuration of the cleaning apparatus680according to Embodiment 2. As shown inFIG. 12, a space S is formed between the cleaning blade465and the tip portions670aof the convex portions670cof the toner accumulation member670. The space S is determined by the dimensions A and B representing the positional relationship between the cleaning blade465and the toner accumulation member670. The toner accumulation member670is disposed so that the tip portions670aof the convex portions670care parallel to the cleaning blade465in the longitudinal direction. In other words, the toner accumulation member670extends in the width direction of the transfer belt461, and is disposed parallel to the surface of the transfer belt461.

In this regard, the distance A is a distance from the toner accumulation member670to the surface of the transfer belt461, and the distance B is a distance in the moving direction of the transfer belt461from the tip portions670aof the convex portions670cof the toner accumulation member670to the contact portion between the cleaning blade465and the transfer belt461. The details of the distances A and B are the same as those described in Embodiment 1, and therefore duplicate descriptions thereof are omitted.

Here, the reason for providing the cutaway concave portion670bon the toner accumulation member670in Embodiment 2 will be described.

For example, if the cleaning apparatus680shown inFIG. 8has no toner accumulation member670, a bending of the cleaning blade465easily occurs at a contact portion between the cleaning blade465and the transfer belt461as described above. Particularly, it is known that both ends of the cleaning blade465in the longitudinal direction are easily bent.

This is because, when the printing is performed on the recording sheet101, both ends of the cleaning blade465in the longitudinal direction are positioned outside a printable area, and therefore are not supplied with sufficient amount of the toner471(as lubricant) from the photosensitive drum431(FIG. 1) via the transfer belt461. Further, since both end surfaces of the cleaning blade465in the longitudinal direction are not supported, the end portions of the cleaning blade465have lower strength than the center portion (which continues to both end portions), with the result that the end portions of the cleaning blade465tend to be easily bent. In the portion of the cleaning blade465corresponding to the printable area, sufficient amount of toner471(adhering to the surface of the transfer belt461) is supplied to the contact portion between the cleaning blade465and the transfer belt461, and therefore it is not likely that the toner runs out.

For these reasons, the cleaning blade465of the cleaning apparatus680of Embodiment 2 has the cutaway concave portion670bformed at the center portion to have a depth d so as to supply the sufficient amount of waste toner472(accumulated on the toner accumulation member670) to both end portions of the cleaning blade465, while limiting the amount of waste toner472supplied to the contact portion of the cleaning blade465corresponding to the printable area.

Next, the operation of the above configured cleaning apparatus680will be described.

The driving roller462is rotated counterclockwise as shown by an arrow inFIG. 1, and the transfer belt462moves in a direction shown by an arrow M inFIG. 8. The toner471remaining on the photosensitive drum431without being transferred to the recording sheet101adheres to the surface of the transfer belt461moving in the direction indicated by the arrow M. As shown inFIG. 8, when the transfer belt461moves, the toner471adhering to the surface of the transfer belt461is scraped off at a contact portion between the transfer belt461and the cleaning blade465, and the scraped-off toner471(i.e., waste toner472) is stored in the toner box466.

A part of the waste toner472scraped off from the surface of the transfer belt461by the cleaning blade465is accumulated on the toner accumulation member670. The waste toner472is accumulated until the waste toner472reaches the surface of the transfer belt461and the tip of the cleaning blade465. The waste toner472accumulated on the toner accumulation member670exceeding a predetermined amount falls through a space including the cutaway concave portion670bto be stored in the toner box466, and a part of the waste toner472on the toner accumulation member670moves in the longitudinal direction, for example, from the center portion to both end portions (i.e., the convex portions670c) of the toner accumulation member670.

Since the toner accumulation member670has the cutaway concave portion670bon the side facing the cleaning blade465, the waste toner472accumulated on the convex portions670c(on both sides of the cutaway concave portion670b) adheres to the transfer belt461and the cleaning blade465, and is supplied to the contact portion between the cleaning blade465and the transfer belt461as lubricant. At the center portion where the cutaway concave portion670bis formed, the accumulating amount of the waste toner472is relatively small, and the distance from the cleaning blade465is relatively long, with the result that the amount of waste toner472supplied to the corresponding portion of the cleaning blade465is limited.

Since the toner471tends to less adhere to the end portions of the transfer belt461as described above, the waste toner472tends to be less accumulated on the end portions of the convex portions670cin the longitudinal direction of the toner accumulation member670. However, the accumulation of the waste toner472on the end portions of the toner accumulation member670is supplemented by the waste toner472moving from the inner side (i.e., center side) of the toner accumulation member670toward the outer side (i.e., the end side) of the toner accumulation member670.

If the amount of the waste toner472(as lubricant) supplied to the contact portion between the cleaning blade465and the transfer belt461is too large, a large load is applied to the cleaning blade465, so that the passing-through of the waste toner472occurs. Therefore, the cutaway concave portion670bis formed at the center portion of the toner accumulation member670corresponding to the center portion of the cleaning blade465where a relatively large amount of the toner471is supplied (i.e., where the bending of the cleaning blade465is less likely to occur). The distance from the cutaway portion670bto the cleaning blade465is relatively large, and the amount of the waste toner472supplied to the cleaning blade465is reduced.

FIG. 13is a plan view showing a modification of the toner accumulation member according to Embodiment 2 of the present invention.

Both end portions of the cleaning blade465have relatively low strength as described above, and therefore, if the waste toner472is excessively accumulated on the convex portions670c, the passing-through of the waste toner472may occur. Further, the waste toner472accumulated on the convex portions670cis prevented from moving further outward in the longitudinal direction of the toner accumulation member670by the toner box466, although the waste toner472is able to move inward (i.e., toward the space S including the concave portion670b). Therefore, the waste toner472tends to be continuously accumulated on the end portions of the toner accumulation member670, and may cause the passing-through of the waste toner472.

For solving this problem, the dimensions of the toner accumulation member670′ of the modification shown inFIG. 13are determined so that spaces Sb are formed between the toner box466and both ends (in the longitudinal direction) of the toner accumulation member670′. With such a configuration, the waste toner472on the convex portion670ccan move further outward and fall through the spaces Sb. Therefore, the excessive accumulation of the waste toner472on the convex portion670ccan be prevented.

As described above, according to the image forming apparatus of Embodiment 2, it becomes possible to supply suitable amount of waste toner (as lubricant) to both end portions of the cleaning blade465corresponding to the outside of the printable area where an insufficient amount of toner adhering to the transfer belt is supplied. Further, it becomes possible to prevent the supply of excessive amount of waste toner to the center portion of the cleaning blade where sufficient amount of toner is supplied (i.e., where the bending is less likely to occur). In this way, the waste toner is supplied in a balanced manner, and therefore it becomes possible to prevent the deterioration in cleaning performance at the center portion of the cleaning blade due to the passing-through of the waste toner, and to prevent the bending of the cleaning blade at both ends of the cleaning blade.

FIG. 14is an enlarged view showing a cleaning apparatus780having a cleaning blade465and a toner box466of an image forming apparatus of Embodiment 3 of the present invention and surroundings thereof.FIG. 15is a perspective view showing an external configuration of the cleaning apparatus780as obliquely seen from above.FIG. 16is a plan view showing the cleaning apparatus780.FIG. 17is a perspective view showing an external form of a toner accumulation member770of the cleaning apparatus780. InFIG. 15, near side wall of the toner box466is omitted so that the positional relationship between the toner box466and the toner accumulation member770can be easily seen.

The difference between the image forming apparatus having the cleaning apparatus780of Embodiment 2 and the image forming apparatus having the cleaning apparatus480(FIG. 2) of Embodiment 1 is in the shape of the toner accumulation member770. Therefore, components of the image forming apparatus (having the cleaning apparatus780) of Embodiment 3 which are the same as those of the image forming apparatus1000of Embodiment 1 are assigned the same reference numerals or omitted in drawings, and duplicate descriptions thereof are omitted. The description is emphasized on the difference between the image forming apparatus of Embodiment 3 and the image forming apparatus of Embodiment 1. The components of the image forming apparatus of Embodiment 3 except the toner accumulation member770are the same as those of the image forming apparatus1000of Embodiment 1, and thereforeFIG. 1is referred as necessary.

As shown inFIGS. 14 through 17, the toner accumulation member770of Embodiment 3 has a plate-like shape as the toner accumulation member470(FIG. 5) of Embodiment 1. However, the toner accumulation member770has a cutaway concave portion770bformed at a center of a side facing the cleaning blade465, and cutaway end portions770dformed at both ends of the side facing the cleaning blade465. Convex portions770care formed on the side of the toner accumulation member470facing the cleaning blade465except where the cutaway concave portion770band the cutaway end portions770dare formed. The convex portions770chave tip portions770afacing the cleaning blade465.

FIG. 18is a sectional view showing an internal configuration of the cleaning apparatus780according to Embodiment 3. As shown inFIG. 18, a space S is formed between the cleaning blade465and the tip portions770aof the convex portion770cof the toner accumulation member770. The space S is determined by dimensions A and B representing the positional relationship between the cleaning blade465and the toner accumulation member770. The toner accumulation member770is disposed so that the tip portions770aof the convex portions770care parallel to the cleaning blade465in the longitudinal direction. In other words, the toner accumulation member770extends in the width direction of the transfer belt461, and is disposed parallel to the surface of the transfer belt461.

In this regard, the distance A is a distance from the toner accumulation member770to the surface of the transfer belt461, and the distance B is a distance in the moving direction of the transfer belt461from the tip portion770aof the convex portion770cof the toner accumulation member770to the contact portion between the cleaning blade465and the transfer belt461. The details of the distances A and B are the same as those described in Embodiment 1, and therefore duplicate descriptions thereof are omitted.

Here, the reason for providing the cutaway concave portion770band cutaway end portions770don the toner accumulation member770in Embodiment 3 will be described.

For example, if the cleaning apparatus780shown inFIG. 14has no toner accumulation member770, a bending of the cleaning blade465easily occurs at a contact portion between the cleaning blade465and the transfer belt46.1as described above. Particularly, if continuous printing is performed on the recording sheets101of a particular size, it is known that bending tends to occur at portions of the cleaning blade465corresponding to the ends portions of the recording sheet101in the width direction.

The reason of the occurrence of bending is as follows: In the case where printing is performed on large number of recording sheets101having the same size, the toner471or paper particle is not likely to adhere to portions on the transfer belt461corresponding to end portions of the recording sheet101in the width direction. This is considered to be because the end portions of the recording sheet101in the width direction are outside a printable area, and because there are noncontact portion (where the photosensitive drum431does not contact the transfer belt461) in the vicinity of the end portions of the recording sheet101according to the thickness of the recording sheet101. Therefore, when the transfer belt461moves to the contact portion, the toner471is not sufficiently supplied to portions of the cleaning blade465corresponding to the end portions of the recording sheet101in the width direction. As a result, at the portions of the cleaning blade465corresponding to the end portions of the recording sheet101, the preliminarily coated toner on the surface of the cleaning blade465decreases, and the friction between the transfer belt461and the cleaning blade465increases, with the result that a bending of the cleaning blade465tends to occur at the portions corresponding to the end portions of the recording sheet101.

In this regard, at other portions of the cleaning blade465than those corresponding to the end portions of the recording sheet101, the toner471adhering to the surface of the transfer belt461is supplied to the contact portion between the cleaning blade465and the transfer belt461as lubricant, and therefore the toner is not likely to run out.

For these reasons, the cleaning apparatus780according to Embodiment 3 is configured to supply sufficient amount of waste toner472(accumulated on the toner accumulation member770) to the portions of the cleaning blade465corresponding to the end portions of the recording sheet101as lubricant, and to limit the amount of the waste toner472supplied to other portions of the cleaning blade465. Therefore, the cutaway convex portion770band the cutaway end portions770dare formed on the toner accumulation member770to have the depth d so that the center lines cc (FIGS. 17 and 18) of the convex portions770care substantially aligned with ends of the recording sheet101in the width (W) direction of the recording sheet101.

Next, the operation of the above configured cleaning apparatus780will be described.

The driving roller462is rotated counterclockwise as shown by an arrow inFIG. 1, and the transfer belt462moves in a direction shown by an arrow M inFIG. 14. The toner471remaining on the photosensitive drum431without being transferred to the recording sheet101adheres to the surface of the transfer belt461moving in the direction indicated by the arrow M. As shown inFIG. 14, when the transfer belt461moves, the toner471adhering to the surface of the transfer belt461is scraped off at the contact portion between the transfer belt461and the cleaning blade465, and the scraped-off toner471(i.e., waste toner472) is stored in the toner box466.

A part of the waste toner472scraped off from the surface of the transfer belt461by the cleaning blade465is accumulated on the toner accumulation member770. The waste toner472is accumulated until the toner waste472reaches the surface of the transfer belt461and the tip of the cleaning blade465. The waste toner472accumulated on the toner accumulation member770exceeding a predetermined amount falls through a space including the cutaway concave portion770band the cutaway end portions770dto be stored in the toner box466, and a part of the waste toner472on the toner accumulation member770moves in the longitudinal direction, for example, from the center portion to both end portions of the toner accumulation member770.

The toner accumulation member770has the cutaway concave portion770band the cutaway end portions770dat the side facing the cleaning blade465, and the waste toner472accumulated on the convex portions770con both sides of the cutaway concave portion770badheres to the transfer belt461and the cleaning blade465, and is supplied to the contact portion between the cleaning blade465and the transfer belt461as lubricant. At the portions where the cutaway concave portion770band the cutaway end portions70care formed, the amount of the accumulated waste toner472is relatively small, and the distance from the cleaning blade465is relatively long, with the result that the amount of waste toner supplied to the corresponding portions of the cleaning blade465is limited.

Since the toner471tends to less adhere to the portions of the transfer belt461corresponding to the end portions of the recording sheet101as described above, the waste toner472tends to be less accumulated on the end portions of the convex portions770cin the longitudinal direction. However, the accumulation of the waste toner472on the end portions of the toner accumulation member770is supplemented by the waste toner472moving from the inner side (i.e., the center side) of the toner accumulation member770to the outer side (i.e., the end side) of the toner accumulation member770.

If the amount of the waste toner472(as lubricant) supplied to the contact portion between the cleaning blade465and the transfer belt461is too large, a large load is applied to the cleaning blade465, so that the passing-through of the waste toner472may occur. Therefore, the cutaway concave portion770band the cutaway end portions770dare formed at the portions of the toner accumulation member770corresponding to portions of the cleaning blade465where a relatively large amount of the waste toner472is supplied (i.e., where the bending of the cleaning blade465is less likely to occur). The distances from the cutaway concave portion770band the cutaway end portions770dto the cleaning blade465to the cleaning blade465are relatively large, and therefore the supplying amount of the waste toner472is restricted.

FIG. 19is a plan view showing a modification of the toner accumulation member according to Embodiment 3 of the present invention.

In the case where various kinds of recording sheets are used, it is also possible to use a toner accumulation member770′ shown inFIG. 19. The toner accumulation member770′ ofFIG. 19has convex portions770cformed on both sides of the center of the toner accumulation member770′ in the width direction. Centers of respective convex portions770care substantially aligned with centers (for example, centers “aa” and “bb”) of ends of a plurality of kinds of recording sheets in the width direction. With such a configuration, suitable amount of waste toner472is supplied to the contact portion between the cleaning blade465and the transfer belt461at portions corresponding to the end portions of the respective recording sheets in the width direction. In the example shown inFIG. 19, convex portions770care formed corresponding to the end portions of two kinds of recording sheets101aand101bin the width direction.

The shape of the toner accumulation member770′ of Embodiment 3 can be combined with the shape of the toner accumulation member670of Embodiment 2 capable of supplying the waste toner to both end portions of the cleaning blade465in the longitudinal direction of the cleaning blade465. With such a combination, the bending of the cleaning blade465at portions corresponding to the end portions of the recording sheet101(in the width direction of the recording sheet101) can be prevented, and the bending of the end portions of the cleaning blade465(in the longitudinal direction of the cleaning blade465) can also be prevented.

As described above, according to the image forming apparatus of Embodiment 3, it becomes possible to supply suitable amount of waste toner to portions of the cleaning blade corresponding to both end portions of the recording sheet where the supply of toner adhering to the surface of the transfer belt is insufficient. Further, it becomes possible to prevent excessive supply of waste toner to the center portion of the cleaning blade where a sufficient amount of toner is supplied (i.e., where the bending is less likely to occur). Therefore, the waste toner is supplied in a balanced manner, with the result that it becomes possible to prevent the deterioration in cleaning performance at the center portion of the cleaning blade do to the passing-through of the waste toner, and to prevent the bending of the cleaning blade at both end portions of the cleaning blade in the width direction of the recording sheet.

FIG. 20is an enlarged view showing a cleaning apparatus880having a cleaning blade465and a toner box466of an image forming apparatus of Embodiment 4 of the present invention and surroundings thereof.

The difference between the image forming apparatus having the cleaning apparatus880of Embodiment 4 and the image forming apparatus having the cleaning apparatus480(FIG. 2) of Embodiment 1 is in the shape of the toner accumulation member870. Therefore, components of the image forming apparatus (having the cleaning apparatus880) of Embodiment 4 which are the same as those of the image forming apparatus1000of Embodiment 1 are assigned the same reference numerals or omitted in drawings, and duplicate descriptions thereof are omitted. The description is emphasized on the difference between the image forming apparatus of Embodiment 4 and the image forming apparatus of Embodiment 1. The components of the image forming apparatus of Embodiment 4 except the toner accumulation member870are the same as those of the image forming apparatus1000of Embodiment 1, and thereforeFIG. 1is referred as necessary.

The toner accumulation member870of Embodiment 4 is formed of a resilient member such as, for example, Mylar (trademark) film made of PET (Poly Ethylene Terephthalate). An end of the toner accumulation member870is fixed to a predetermined position inside the toner box466using, for example, a double-sided adhesion tape or the like. The fixing position and the shape of the toner accumulation member870are determined in accordance with the space S and the distances A and B presenting the fixing position and the shape of the toner accumulation member770having been described with reference toFIG. 18in Embodiment 3.

The toner accumulation member870is configured so that the deflection amount thereof increases and the space S is enlarged according to the amount of the waste toner472accumulated on the toner accumulation member870. The operation of the above configured cleaning apparatus880will be described.

The driving roller462is rotated counterclockwise as shown by an arrow inFIG. 1, and the transfer belt462moves in a direction shown by an arrow M inFIG. 20. The toner471remaining on the photosensitive drum431without being transferred to the recording sheet101adheres to the surface of the transfer belt461moving in the direction indicated by the arrow M. As shown inFIG. 20, when the transfer belt461moves, the toner471adhering to the surface of the transfer belt461is scraped off at the contact portion between the transfer belt461and the cleaning blade465, and the scraped-off toner471(i.e., waste toner472) is stored in the toner box466.

A part of the waste toner472scraped off from the surface of the transfer belt461by the cleaning blade465is accumulated on the toner accumulation member870. The waste toner472is accumulated until the waste toner472reaches the surface of the transfer belt461and the tip of the cleaning blade465. The waste toner472accumulated exceeding a predetermined amount on the toner accumulation member870falls from the toner accumulation member870through the space S, and is stored in the toner box466.

The waste toner472accumulated on the toner accumulation member870contacts and adheres to the transfer belt461and the cleaning blade465, and is supplied to the contact portion between the transfer belt461and the cleaning blade465as lubricant.

Here, in the case where a flowability of the waste toner472decreases due to environmental changes or the like, the waste toner472accumulated on the toner accumulation member870becomes less movable into the inside of the toner box466via the space S. Therefore, the waste toner472tends to be excessively accumulated on the toner accumulation member870. If the toner accumulation member870has no resiliency, the excessively accumulated waste toner472causes an excessively large pressure applied to the cleaning blade475, which may cause the passing-through of the waste toner472.

In contrast, the toner accumulation member870of Embodiment 4 is formed of a resilient member such as Mylar film. Therefore, when a large amount of the waste toner472is accumulated on the toner accumulation member870to start applying a pressure to the cleaning blade465, the toner accumulation member870deflects as shown inFIG. 21due to a reaction force from the cleaning blade465and due to the weight of the waste toner472. Accordingly, the pressure applied to the cleaning blade465decreases, and the passing-through of the waste toner472due to the excessive accumulation can be prevented.

Further, since the space S is enlarged by the deflection of the toner accumulation member870, the waste toner472is more likely to fall in the toner box466. Therefore, the exceedingly accumulated waste toner472falls in the toner box466and is stored therein. Therefore, the amount of the waste toner472accumulated on the toner accumulation member870can be restricted within a suitable range, and suitable amount of waste toner472is supplied to the contact portion between the cleaning blade465and the transfer belt461.

As described above, according to the image forming apparatus of Embodiment 4, the toner accumulation member870is formed of a resilient member such as Mylar film. Therefore, even when the amount of the waste toner472accumulated on the toner accumulation member870increases, the pressure applied to the cleaning blade465can be reduced, with the result that the passing-through of the waste toner472due to the excessive accumulation of the waste toner472can be prevented. Moreover, since a suitable amount of waste toner472is supplied to the contact portion between the cleaning blade465and the transfer belt461, the bending of the cleaning blade465can be prevented.

FIG. 22is an enlarged view showing a cleaning apparatus980having a cleaning blade465and a toner box466of an image forming apparatus of Embodiment 5 of the present invention and surroundings thereof.

The image forming apparatus having the cleaning apparatus980of Embodiment 5 is different from the image forming apparatus having the cleaning apparatus480(FIG. 2) of Embodiment 1 is that an agitating apparatus990(as lubricant supply portion) is provided instead of the toner accumulation member470. Therefore, components of the image forming apparatus (having the cleaning apparatus980) of Embodiment 5 which are the same as those of the image forming apparatus1000of Embodiment 1 are assigned the same reference numerals or omitted in drawings, and duplicate descriptions thereof are omitted. The description is emphasized on the difference between the image forming apparatus of Embodiment 5 and the image forming apparatus of Embodiment 1. The components of the image forming apparatus of Embodiment 5 except the agitating apparatus990are the same as those of the image forming apparatus1000of Embodiment 1, and thereforeFIG. 1is referred as necessary.

The cleaning apparatus980of Embodiment 5 is configured to have the agitating apparatus990in the toner box466as shown inFIG. 22. The agitating apparatus990includes a shaft990aextending in the direction of the toner box466(i.e., the Y direction) and rotated by a not shown driving unit, and a plurality of agitation films990belongated in the Y direction. One of longitudinal sides of each agitation film990bis fixed to the shaft990a. When the shaft990arotates clockwise in the direction shown by an arrow inFIG. 22, the respective agitation films990bagitate the waste toner472stored in the toner box466and stir up the waste toner472.

In the example shown inFIG. 22, a plurality of agitation films990bare fixed to the shaft990a, in order to efficiently agitate the waste toner472in a large toner box466. However, in the case where the toner box466is small, the agitating apparatus990is able to efficiently agitate the waste toner472even when only one agitation film990bis fixed to the shaft990a.

As described above, according to the image forming apparatus of Embodiment 5, a part of the waste toner472stirred up by the agitating apparatus990is supplied to the contact portion between the cleaning blade465and the transfer belt461as lubricant. Therefore, it becomes possible to prevent the increase of the friction between the transfer belt461and the cleaning blade465, and to prevent the bending of the cleaning blade465. As a result, it becomes possible to prevent a deterioration of cleaning performance for removing the toner471(FIG. 2) from the transfer belt461.

FIG. 23is an enlarged view showing a modification of the cleaning apparatus1010according to Embodiment 5 and surroundings thereof.FIG. 24is an enlarged view showing an internal configuration of the cleaning apparatus1010. InFIG. 24, a contour of the cleaning blade465is shown by a dashed line for the sake of simplicity.

In the above described cleaning apparatus980shown inFIG. 22, the shaft990ato which the agitation films990bare fixed is rotated so as to supply the waste toner472in the toner box466to the transfer belt461and the cleaning blade465. However, it is also possible to obtain the same effect by mounting agitation film1012on a spiral (i.e., a spring)1011for conveying the waste toner472as shown inFIGS. 23 and 24.

In this case, the spiral1011driven by an external driving means (not shown) causes the waste toner472accumulated in the toner box466to move in a predetermined direction. When the waste toner472moved by the spiral1011and accumulated contacts the agitating film1012, the agitating film1012fixed to the spiral1011and rotating together with the spiral film1011supplies the waste toner472to the transfer belt461and the cleaning blade465.

The above described agitation film1012can be disposed at a position so as to supply the waste toner472to a desired position of the cleaning blade465. In other words, the agitation film1012can be configured to supply the waste toner472to the entire area of the transfer belt461as described in Embodiment 1, or can be configured to supply the waste toner472to predetermined portion(s) of the transfer belt461in the Y-direction as described in Embodiments 2 through 4.

The embodiments are described with reference to an example in which the present invention is used to clean the transfer belt in the color electrophotographic printer, but the present invention is also applicable to, for example, an apparatus for cleaning the residual toner on the image bearing body using the cleaning blade.

While the preferred embodiments of the present invention have been illustrated in detail, it should be apparent that modifications and improvements may be made to the invention without departing from the spirit and scope of the invention as described in the following claims.