Image forming apparatus

Abstract

To provide an image forming apparatus that can regulate warpage to make the contact pressure of a scraper uniform.SOLUTION: An image forming apparatus comprises, on a surface 5a of an intermediate transfer belt 5, a scraper 11 that is a flexible plate-like member that is orthogonal to a conveyance direction T of the intermediate transfer belt 5 and in contact with the intermediate transfer belt. The image forming apparatus comprises a holding member 15 that mounts the scraper 11 on an image forming apparatus body 1, while bending the scraper 11 so that an intermediate part 12 of the scraper is closer to the intermediate transfer belt 5 than the ends 13.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] 2. Description of the Related Art Conventionally, as a cleaning device used in an image forming apparatus, there is known one in which a scraper is brought into contact with the surface of a member to be cleaned, such as a belt or roller. For example, there is a cleaning device that has a roller as a member to be cleaned, a base having both ends connected to both ends of the roller, and a scraper attached to the base (see, for example, Patent Document 1). In such a scraper, an edge for scraping off toner is formed at the leading edge of a flat scraper, and the leading edge is formed in a gently convex curved shape by projecting further forward at the center in the width direction. The scraper is pressed against the outer peripheral surface of the roller with a predetermined pressure, so that the edge scrapes off the toner adhering to the surface of the member to be cleaned. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-126493 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional image forming apparatuses, the base on which the scraper is attached has dimensional errors due to manufacturing variations, and therefore the deformation of the scraper caused by the force pressing the edge against the roller is not uniform. In addition, the belt sags and deforms. As a result, the desired contact pressure P cannot be obtained, particularly in the middle of the belt width direction. Due to this uneven contact, the parts where the contact pressure P is low cannot be cleaned sufficiently. Furthermore, the parts where the contact pressure P is high wear quickly and uneven wear occurs on the edges. Therefore, in order to maintain good cleaning performance for a long period of time, further improvements are desired.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an image forming apparatus capable of regulating the warp and making the contact pressure of the scraper uniform. [Means for solving the problem]

[0006] That is, the above-mentioned object of the present invention is achieved by the following configuration. (1) An image forming apparatus includes a scraper, which is a flexible plate-like member that contacts a surface of an intermediate transfer belt in a direction perpendicular to the transport direction of the intermediate transfer belt, and a holding member that holds the scraper in a warped manner so that a center portion of the scraper is closer to the intermediate transfer belt than an end portion of the scraper, and that mounts the scraper to an image forming apparatus main body.

[0007] (2) The image forming apparatus according to (1), wherein the tip edge of the scraper abuts against the front surface of the intermediate transfer belt between a pair of roller members supporting the intermediate transfer belt from the back surface.

[0008] (3) The image forming apparatus according to (1), wherein the holding member includes a first holding member and a second holding member that hold the scraper in an out-of-plane direction.

[0009] (4) An image forming apparatus as described in (3), wherein the first retaining member has a surface contact portion that supports the intermediate portion of the scraper from the opposite side of the intermediate transfer belt and is set to have a higher rigidity than the second retaining member.

[0010] (5) The image forming apparatus according to (1), wherein the rigidity of the scraper is set to be higher than that of the intermediate transfer belt and lower than that of the holding member, so that the scraper conforms in shape to the holding member when held by the holding member.

[0011] (6) The image forming apparatus described in (1), in which the amount of warping δ of the holding member set to warp the middle portion of the scraper is defined by the following formula (1) so as to be within a cleanable range between a lower limit value based on the deflection of the holding member (calculated as uniformly distributed load) and taking into account the slack of the intermediate transfer belt, and an upper limit value based on the deflection of the holding member (calculated as concentrated load) and taking into account that the contact angle α is appropriate for cleaning.

number

[0012] (7) An image forming apparatus as described in (1), further comprising an elastic loading mechanism that includes an elastic member formed as a separate member from the scraper and that contacts the scraper against the intermediate transfer belt using the elastic force of the elastic member.

[0013] (8) The elastic load mechanism of the image forming apparatus described in (7) has a regulating portion that regulates the contact force.

[0014] (9) A fixing portion for fixing the holding member to the image forming apparatus body

[0015] (10) The image forming apparatus according to (1), wherein the scraper has a metal member.

[0016] (11) The image forming apparatus according to (1), wherein a front end edge of the scraper is straight when viewed in a plane of the scraper.

[0017] (12) The image forming apparatus according to (1), wherein the front end edge of the holding member is straight when viewed in a plan view of the scraper.

[0018] (13) The holding member has warpage regulation parts that hold the middle part of the scraper on the inside of the left and right ends in the width direction to regulate the warpage shape, and the holding member has rigidity improving parts formed on the outside of the warpage regulation parts closer to the intermediate transfer belt than the warpage regulation parts and farther from the intermediate transfer belt than the center part that holds the middle part of the scraper.

[0019] (14) The image forming apparatus according to (1), wherein the holding member has a plastic range that is large enough not to be plastically deformed by a contact force of the scraper against the intermediate transfer belt. Effect of the Invention

[0020] According to the present invention, there is provided an image forming apparatus capable of regulating the warp and making the contact pressure of the scraper uniform. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a side view showing a state in which a scraper is in contact with an intermediate transfer belt in the image forming apparatus according to the first embodiment of the present invention. [Diagram 2] FIG. 2 is a side view showing the configuration of the scraper and the holding member in the scraper of the first embodiment. [Diagram 3] 3 is a front view showing the configuration of the scraper and the holding member of the first embodiment, taken along the line III in FIG. 2. [Figure 4] 4 is a cross-sectional view taken along line IV-IV in FIG. 2, showing the configuration of a scraper and a holding member according to the first embodiment. FIG. [Diagram 5] 1 is a graph showing the contact pressure P when the amount of warping δ in the width direction is changed in the scraper of the first embodiment. [Figure 6] FIG. 2 is a side view showing the configuration of the main part of the scraper of the first embodiment. [Figure 7] 7 is a front view showing the overall configuration of the scraper of the first embodiment, as viewed from the direction of the arrow VII in FIG. 6. [Figure 8]8 is a front view showing the overall configuration of the scraper of the first embodiment, as viewed from the direction of the arrow VIII in FIG. 6. [Figure 9] 3 is a plan view of the vicinity of the tip of the scraper as viewed in the direction of the arrow IX in FIG. 2. [Figure 10] FIG. 11 is a side view showing the configuration of the main part of the scraper of the second embodiment. [Figure 11] FIG. 11 is a side view showing the configuration of the main part of the scraper of the third embodiment. [Figure 12] 3 is a front view of the scraper of the fourth embodiment as seen from the direction of the arrow III in FIG. 2. [Figure 13] 11 is a graph comparing the amount of warpage δ in the width direction and the contact pressure P of the scraper of the fourth embodiment with those of the scraper of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, each embodiment of the present invention will be described in detail. For ease of understanding, in each embodiment, the manufacturing variation of the holding member 15 described later is defined as the “dimensional error”, and the curved shape of the holding member 15 that causes the holding member 15 to warp the scraper 11 is defined as the “specified warping shape”. The curved shape of the holding member 15 has a "warping amount (δ)" in a direction approaching or receding toward the intermediate transfer belt 5. The warping amount (δ) of the holding member 15 will be described as being equal to the "warping amount (δ)" of the front edge 14 of the scraper 11.

[0023] Furthermore, the curved shape of the scraper 11, which is determined by the curved shape of the holding member 15, is defined as the "warping of the scraper 11." When the scraper 11 comes into contact with the intermediate transfer belt 5, the scraper 11 and the holding member 15 are flexed and deformed by the reaction force from the intermediate transfer belt 5. The amount of deformation of the front end edge 14 of the scraper 11 due to these flexing deformations is described as the "deflection of the scraper 11," and the amount of deformation of the holding member 15 is described as the "deflection of the holding member 15." Furthermore, the bending or slack deformation of the intermediate transfer belt 5 is unified and defined as "slack of the intermediate transfer belt 5."

[0024] 1 shows an image forming apparatus according to a first embodiment, which includes an image forming apparatus main body 1 having a first roller member 3, a second roller member 4, and an intermediate transfer belt 5 supported by the first roller member 3 and the second roller member 4. The image forming apparatus main body 1 includes a cleaning unit 10 that cleans toner 6 adhering to the intermediate transfer belt 5.

[0025] 2, the cleaning unit 10 has a scraper 11 that abuts a front edge 14 in a width direction W (see FIG. 3) on the surface 5a of the intermediate transfer belt 5, perpendicular to the transport direction T of the intermediate transfer belt 5. The cleaning unit 10 has a holding member 15 that holds the scraper 11 and is attached to the image forming apparatus main body 1.

[0026] Of these, the scraper 11 is made of a metal member. 3, the scraper 11 of the first embodiment is made of a flexible plate-like member. This allows the scraper 11 to be warped so that the middle portion 12 located between the ends 13, 13 is closer to the intermediate transfer belt 5 than the left and right ends 13, 13 in the width direction W when viewed in the transport direction T of the intermediate transfer belt 5. Therefore, while the scraper 11 is held by the holding member 15, the scraper 11 is fixed with a curved shape that is convex downward at the center in the width direction W. Furthermore, the front end edge 14 of the scraper 11 is formed so as to be linear along the width direction W in a plan view of the scraper 11 (see FIG. 9).

[0027] As shown in FIG. 2, the holding member 15 has a first holding member 16 and a second holding member 17 that hold the scraper 11 in the out-of-plane direction. The first retaining member 16 has a curved flat plate portion 16a and a reinforcing flange portion 16b that extends integrally from the upper side of the flat plate portion 16a in the out-of-plane direction at the base end side of the flat plate portion 16a. As a result, the first retaining member 16 is formed to be substantially L-shaped in side view. The first holding member 16 is fixed to the image forming apparatus main body 1 via a fixing portion 7 such as a bracket (not shown) at a connection portion where the flat plate portion 16a and the reinforcing flange portion 16b intersect substantially at right angles.

[0028] The second holding member 17 has a flat plate portion 17a curved along the flat plate portion 16a and a reinforcing flange portion 17b integrally formed on the base end side of the flat plate portion 17a, so that the second holding member 17 is formed in a substantially L-shape in side view. As shown in FIG. 3, the first holding member 16 and the second holding member 17 are stacked in the vertical direction with substantially the same width W dimension. This increases the moment of inertia of area of ​​the holding member 15. Therefore, the holding member 15 can improve the bending rigidity and torsional rigidity in the width direction W compared to when it is configured from a single flat plate or a single rod material.

[0029] Furthermore, as shown in FIG. 4, the scraper 11 is sandwiched between the first holding member 16 and the second holding member 17 in the out-of-plane direction. The scraper 11 is detachably fixed by a plurality of screws 19 that pass through and fasten the first holding member 16 and the second holding member 17. As a result, the scraper 11 is fixed and held in a state where it is sandwiched between the flat plate portion 16a of the first holding member 16 and the flat plate portion 17a of the second holding member 17.

[0030] The screw insertion holes formed in the scraper 11 of the first embodiment have an inner diameter dimension that is slightly larger than the screw holes formed in the first holding member 16 or the second holding member 17. This allows the scraper 11 to move in the width direction W due to warping deformation when it is positioned and fixed between the first holding member 16 and the second holding member 17.

[0031] Furthermore, face contact portions 16c, 17c are formed on the side surfaces of the first holding member 16 and the second holding member 17 facing the scraper 11. Among these, the face contact portion 16c of the first holding member 16 supports the middle portion 12 of the scraper 11 from the side opposite to the intermediate transfer belt 5. As a result, when the screws 19 are fastened, the scraper 11 is pressed against the face contact portions 16c, 17c. Therefore, the front end edge 14 can be made to follow the curved shapes of the face contact portions 16c, 17c. In the first embodiment, as shown in Fig. 3, a plurality of screws 19 are fastened through the holding member 15 in the out-of-plane direction in a state where the scraper 11 is sandwiched between the first holding member 16 and the second holding member 17 (see Fig. 4). Therefore, at the front end edge 14 of the scraper 11, the middle portion 12 is curved in a downward convex shape close to the intermediate transfer belt 5, in comparison with the left and right end portions 13, following the curved shape of the face contact portion 16c of the first holding member 16.

[0032] 5 shows the relationship between the amount of warping δ in the width direction W at the front edge 14 of the scraper 11 and the contact pressure P. In the first embodiment, the amount of warping δ of the holding member 15 is described as being equal to the amount of warping δ of the front edge 14 of the scraper 11. 5, the upper graph shows the amount of warping δ in the width direction W, with the upper side being the + side approaching the intermediate transfer belt 5 and the lower side being the - side away from the intermediate transfer belt 5. In addition, in FIG. 5, the lower graph shows the contact pressure P in the width direction W, with the upper side being the higher (+) side of the contact pressure P and the lower side being the lower (-) side of the contact pressure P.

[0033] For example, when the amount of warping δ in the intermediate transfer belt 5 at the intermediate portion is away from the intermediate transfer belt 5 (− side in the upper graph) (δ1, δ2), the contact pressures P1 and P2 decrease near the intermediate portion in the width direction W (− side in the lower graph). It is known that the intermediate transfer belt 5 slackens due to its own weight or due to tension being placed on multiple inner rollers, and in the width direction W, the vicinity of the middle portion is positioned lower than both the left and right ends. For this reason, even if the amount of warping δ of the scraper 11 is uniform (δ3) in the width direction W, the contact pressure decreases near the middle part in the width direction W (negative side in the graph below) as indicated by a contact pressure P3.

[0034] For this reason, in this embodiment, the scraper 11 is warped in advance by the holding member 15 so that the center portion of the scraper 11 is closer to the intermediate transfer belt 5 than the ends of the scraper 11. That is, when the amount of warp δ in the middle portion is close to the intermediate transfer belt 5 (+ side in the upper graph) (δ4), the contact pressure P in the width direction W approaches uniformity as shown by P4 (+ side in the lower graph). Theoretically, when the amount of warp δ in the middle portion is closer to the intermediate transfer belt 5 (on the positive side in the upper graph) (δ5), it is possible to obtain a substantially uniform contact pressure P5 in the width direction W. This is believed to be because the amount of bending caused by the reaction force from the intermediate transfer belt 5 is offset by defining the positive warp.

[0035] Therefore, the holding member 15 of the first embodiment has a warp-defined shape that holds the scraper 11 in a warped state such that the middle portion 12 is closer to the intermediate transfer belt 5 than the end portion 13 of the scraper 11. The holding member 15 mounts the scraper 11 to the image forming apparatus main body 1 while holding the scraper 11.

[0036] In this state, as shown in FIG. 1, the front end edge 14 of the scraper 11 is abutted against the front surface 5a of the intermediate transfer belt 5 between a pair of roller members 3.4 that support the intermediate transfer belt 5 from the back surface 5b. Therefore, even if the intermediate transfer belt 5 is bent and deformed due to contact with the scraper 11, the contact pressure P can be made uniform in the width direction W. Therefore, by appropriately setting the curved shape of the holding member 15 that determines the amount of warping δ in the width direction W at the front end edge 14 of the scraper 11, a desired contact pressure P that is uniform in the width direction W can be obtained. For example, in order to approach the contact pressure P4 in FIG. 5, or more preferably, the contact pressure P5, the curved shape of the holding member 15 is set so that the front end edge 14 of the scraper 11 has a warp amount δ4 or δ5. This cancels out and balances the amount of warping δ and the amount of bending caused by the reaction force from the intermediate transfer belt 5. This allows the scraper 11 to be brought into almost uniform contact with the intermediate transfer belt 5 with a desired contact pressure P that allows good cleaning performance to be achieved.

[0037] In addition, the first holding member 16 has a surface contact portion 16c that supports the middle portion 12 of the scraper 11 from the opposite side of the intermediate transfer belt 5, and is set to have higher rigidity than the second holding member 17. The holding member 15 has a plastic range that is large enough not to be plastically deformed by the contact force of the scraper 11 against the intermediate transfer belt 5. The front end edge 18 of the holding member 15 is configured to be linear along the width direction W in the plan view of the scraper 11 shown in FIG.

[0038] For example, a lower limit (5×F×L3) / (384×E×I) is set in consideration of the deflection caused by the reaction force of the scraper 11 and the slackness of the intermediate transfer belt 5. Also, the amount of warping δ is set to an upper limit (F×L3) / 48×E×I) including a coefficient assumed to provide an appropriate contact angle α with the contact pressure P of the intermediate portion 12 as a concentrated load. The amount of warping δ is defined by the following formula (1) so that it falls within a cleanable range between the lower limit (5×F×L3) / (384×E×I) and the upper limit (F×L3) / 48×E×I).

[0039]

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[0040] In this manner, measurements obtained in advance from tests and specified values ​​indicating the physical properties of various materials are substituted into formula (1). Then, the amount of warping δ within the range obtained from formula (1) is given to the holding member 15. As a result, even if the intermediate transfer belt 5 is warped due to contact with the middle portion 12, the scraper 11 can be made to contact evenly between the ends 13, 13, making the contact pressure P uniform. Therefore, poor cleaning does not occur due to uneven wear of the scraper 11. Furthermore, the scraper 11 held by the holding member 15 having such a warp amount δ wears evenly, and can maintain good cleaning performance for a long period of time.

[0041] Furthermore, when the scraper 11 comes into contact with the intermediate transfer belt 5, it applies pressure to the surface 5a while bending the leading edge 14 upward in the out-of-plane direction (see FIG. 6). This allows the leading edge 14 of the scraper 11 to come into contact with the intermediate transfer belt 5 at an appropriate contact angle α. This allows the toner 6 and the like adhering to the surface 5a to be scraped off evenly, improving cleaning performance.

[0042] Furthermore, in the image forming apparatus of the first embodiment, the first holding member 16 is made of a highly rigid material such as stainless steel. This allows the first holding member 16 to have a higher rigidity than the material such as an iron material (e.g., chromeless steel plate) constituting the second holding members 17 and 27. Also, for example, in the first embodiment, the plate thickness of the flat portion 16a may be set to be greater than the plate thickness of the flat portion 17a so that the rigidity of the first holding member 16 is higher than the rigidity of the second holding member 17. For this reason, the curved shapes of the scraper 11 and the second holding member 17 depend on the curved shape of the face contact portion 16c of the first holding member 16. Therefore, by appropriately forming the face contact portion 16c of the first holding member 16, it is possible to easily give the scraper 11 a desired curved shape.

[0043] 6 to 8 show the elastic load mechanism 50 (see FIG. 2) used in the image forming apparatus according to the first embodiment of the present invention. As shown in FIG. 7, the elastic load mechanism 50 has a pair of left and right arm portions 53 each rotatably supported on a shaft portion 54 protruding from a wall surface of the image forming apparatus main body 1 . A spring member 51 serving as an elastic member formed as a separate member from the scraper 11 is connected to the upper portion of each arm portion 53 of the elastic load mechanism 50. The spring member 51 has an elastic force, and brings the scraper 11 into contact with the intermediate transfer belt 5 by using this elastic force. 7, the spring members 51 are omitted. Each spring member 51 biases the arm portion 53 forward along the conveying direction T, that is, in the opposite direction to the conveying direction.

[0044] The left and right arm portions 53 are fixed to the left and right end surfaces, respectively, of a first holding member 16 constituting the holding member 15. As a result, when each arm portion 53 rotates in the front-rear direction around the shaft portion 54 as the center of rotation, the scraper 11 held by the holding member 15 can move the front end edge 14 toward or away from the surface 5a of the intermediate transfer belt 5.

[0045] Furthermore, the elastic load mechanism 50 is provided with a pair of stoppers 52 as regulating parts at the front and rear of each arm part 53, spaced apart by a predetermined distance. The left and right stoppers 52 are fixed to protrude from the image forming apparatus main body 1. As a result, when the arm portion 53 rotates in the front-rear direction around the shaft portion 54 as the center of rotation, the front and rear side surfaces of the arm portion 53 can be abutted against the respective stoppers 52, thereby regulating the range of rotation.

[0046] The elastic load mechanism 50 configured in this manner brings the scraper 11 into contact with the intermediate transfer belt 5 using the elastic force of the spring member 51. The spring member 51 of the elastic load mechanism 50 can adjust the biasing force to bring the front edge 14 of the scraper 11 into contact with the surface 5a of the deflecting intermediate transfer belt 5 with a desired contact force.

[0047] Furthermore, as shown in FIGS. 7 and 8, the elastic load mechanism 50 biases a pair of arms 53, which are fixed to the left and right end faces, respectively, of the holding member 15 that holds the scraper 11, by means of spring members 51. This allows the elastic load mechanism 50 to distribute the set spring load in the width direction W to obtain the desired contact pressure P.

[0048] Furthermore, the spring member 51 may be replaced with another spring member 51 having a different spring rate. By replacing the spring member 51, it is possible to easily accommodate both color toners used in a color mode, which have different adhesion to the intermediate transfer belt 5, and monochrome toners used in a monochrome mode. This provides good versatility and allows the efficiency of maintenance work to be improved.

[0049] Furthermore, the elastic load mechanism 50 has a stopper 52 as a regulating part for regulating the contact force. The stopper 52 regulates the rotation angle of the arm part 53 about the shaft part 54. Therefore, the contact angle α at which the front end edge 14 contacts the surface 5a can be stopped within a desired angle range. Therefore, there is no risk that the contact angle α of the scraper 11 will become too large.

[0050] 10 shows a cleaning unit 20 used in an image forming apparatus according to a second embodiment of the present invention. Note that the same or equivalent parts as those in the first embodiment will be described with the same reference numerals. In the cleaning unit 20 of the second embodiment, the second holding member 27 is not provided with a reinforcing flange (see reinforcing flange portion 17b shown in FIG. 2) so that the rigidity of the first holding member 16 is higher than the rigidity of the second holding member 27. This allows the first holding member 16 and the second holding member 27 in the cleaning unit 20 to have different rigidities even if they are made of materials with the same thickness.

[0051] A surface contact portion 16c curved in the width direction (front-rear direction on the paper) is formed on the first holding member 16, which is set to have higher rigidity than the second holding member 27. The surface contact portion 16c supports the middle portion 12 of the scraper 11 from the opposite side of the intermediate transfer belt 5. Therefore, the scraper 11 can be warped into a desired curved shape by being pressed against the surface contact portion 16c by the second holding member 27. As a result, even if the intermediate transfer belt 5 is bent by the contact of the scraper 11, the contact pressure P at which the front end edge 14 of the scraper 11 contacts the intermediate transfer belt 5 in the width direction W can be made uniform. The other configurations and effects are the same as those of the first embodiment, so the description will be omitted.

[0052] 11 shows a cleaning unit 30 used in an image forming apparatus according to a third embodiment of the present invention. The same or equivalent parts as those in the first or second embodiment will be described with the same reference numerals. In the cleaning section 30, the first holding member 26 is formed in a thick block shape having a substantially trapezoidal cross section. For this reason, the rigidity of the first holding member 26 is set to be higher than the rigidity of the second holding member 27.

[0053] In the cleaning unit 30 of the third embodiment configured as described above, the face contact portion 26c is formed on the first holding member 26 that is set to have higher rigidity than the second holding member 27. The face contact portion 26c supports the middle portion 12 of the scraper 11 from the opposite side of the intermediate transfer belt 5. Therefore, the scraper 11 can be pressed against the surface contact portion 16c and warped into a desired shape. As a result, even if the intermediate transfer belt 5 is warped by the contact of the scraper 11, the contact pressure P at which the front end edge 14 of the scraper 11 contacts the intermediate transfer belt 5 in the width direction W can be made uniform. The other configurations and effects are similar to those of the first or second embodiment, and therefore the description thereof will be omitted.

[0054] 12 and 13 are diagrams illustrating a cleaning unit 60 used in an image forming apparatus according to a fourth embodiment of the present invention. Note that the same or equivalent parts as those in the first embodiment are denoted by the same reference numerals and will be described. In a cleaning unit 60 of the fourth embodiment shown in FIG. 12, the scraper is held and fixed in place by a holding member 21 so as to have a desired warped shape, similar to the holding member 15 (see FIG. 2) of the first embodiment.

[0055] That is, the holding member 21 has a pair of warp regulating portions 40 on the inside of the left and right end portions 13, 13 in the width direction W. As a result, the intermediate portion 12 of the scraper that is sandwiched between the warp regulating portions 40, 40 from the out-of-plane direction has a curved shape that is warped so as to be convex toward the intermediate transfer belt 5. 13, the upper graph shows the amount of warping δ in the width direction W, with the upper side being the + side approaching the intermediate transfer belt 5 and the lower side being the - side away from the intermediate transfer belt 5. 13, the lower graph shows the contact pressure P in the width direction W, with the upper side being the higher + side of the contact pressure P and the lower side being the lower - side of the contact pressure P. Among these, the line shown by the contact pressure P5 shows the ideal case where the intermediate transfer belt 5 can be contacted in a substantially uniform state.

[0056] 13, the contact pressure Pc at the intermediate portion 12 of the scraper of the fourth embodiment is set to a value equivalent to the contact pressure Pa at the intermediate portion 12 of the scraper 11 of the first embodiment. In addition, the rigidity improving portions 42, 42 provided on the outer sides in the width direction W of the holding member 21 are brought closer to the intermediate transfer belt 5 due to the amount of warping caused by the left and right warp regulating portions 40. As a result, the cleaning unit 60 of the fourth embodiment comes into contact with the intermediate transfer belt 5 in the width direction W in a substantially uniform state with a contact pressure Pc that is close to the desired contact pressure P5, thereby further improving the cleaning performance.

[0057] Furthermore, the holding member 21 is provided with a pair of left and right rigidity enhancing portions 42, 42 symmetrically on the left and right outside of each warp regulating portion 40 in the width direction W. 12, each of the rigidity improving portions 42 is set to be closer to the intermediate transfer belt 5 than the warpage regulating portion 40. Also, each of the rigidity improving portions 42 is formed to be farther from the intermediate transfer belt 5 than the center portion 41 that holds the intermediate portion 12 of the scraper. For this reason, the scraper has two protrusions extending upward in the out-of-plane direction along the warp regulating portion 40. Thus, together with the portion of the intermediate portion 12 extending downward in the out-of-plane direction, a plurality of peaks and valleys are arranged in an uneven pattern, thereby improving the bending rigidity of the scraper.

[0058] The holding member 21 of the fourth embodiment thus configured can set the protruding dimension of the scraper protruding toward the intermediate transfer belt 5 to a desired size. Even if the protruding dimension of the scraper is large, the scraper can obtain sufficient bending rigidity in the out-of-plane direction to maintain the desired warped shape.

[0059] Furthermore, for example, if the warp amount δ6 closer to the intermediate transfer belt 5 than the warp amount δ5 in the middle portion shown in FIG. 5 is set excessively (to the + side in the upper graph), the contact pressure P6 in the middle portion increases but decreases at the ends.

[0060] In contrast to this, the rigidity-improved portions 42 of the holding member 21 of the fourth embodiment are formed so as to be close to the intermediate transfer belt 5 and have a size that is approximately 1 / 3 to 1 / 2 of the size of the intermediate portion 12 at both outermost ends. For this reason, the contact pressure Pc of the scraper in the fourth embodiment is on the positive side on both the left and right sides from the vicinity of the warp determining portion 40 toward the outside. It is also known that when the integral value of the total contact pressure P in the width direction W is low, the deflection of the holding member 21 is small, the contact pressure P in the center is high, and the contact pressure P at the ends is low. In contrast to this, in the holding member 21 of the fourth embodiment, the contact pressure Pc equivalent to that in the vicinity of the intermediate portion 12 can be obtained even on the outer side of the warp restricting portion 40 . Therefore, the holding member 21 can obtain a uniform contact pressure P in the width direction W while keeping the integral value in the width direction W, which is the total pressure of the contact pressure P, similarly low. This makes it possible to further reduce uneven cleaning caused by the slack in the intermediate transfer belt 5 in the fourth embodiment or the bending of the scraper and the holding member.

[0061] Furthermore, the rigidity-improved portions 42 of the holding member 21 are spaced apart from the intermediate transfer belt 5 near the left and right outermost ends in the width direction W of the intermediate transfer belt 5 compared to the central portion 41. Therefore, the scraper can obtain a more uniform contact pressure Pc in the width direction W. For example, the holding member 21 of the fourth embodiment has rigidity improving portions 42 on both the left and right sides, each of which is close to the intermediate transfer belt 5. This enables the scraper to obtain a distribution of the contact pressure Pc in the width direction W that is closer to the theoretically ideal (contact pressure P5 in FIG. 5) than the scraper 11 of the first embodiment (e.g., contact pressure P4 in FIG. 5) shown by the imaginary line a in FIG. 13. In this way, the holding member 21 of the fourth embodiment is set to have the same warpage as the scraper, which reduces uneven cleaning caused by slack in the intermediate transfer belt 5 and provides a practically beneficial effect of maintaining good cleaning performance for a long period of time.

[0062] As described above, the image forming apparatus of the embodiment includes a first roller member 3, a second roller member 4, an intermediate transfer belt 5, and a cleaning unit 10 having a scraper 11, as shown in FIG. The image forming apparatus also includes a scraper 11, which is a flexible plate-like member that contacts the surface 5a of the intermediate transfer belt 5 perpendicular to the transport direction T of the intermediate transfer belt 5. The image forming apparatus also includes a holding member 15 that holds the scraper 11 in a warped manner so that a middle portion 12 of the scraper 11 is closer to the intermediate transfer belt 5 than an end portion 13 of the scraper 11, and mounts the scraper 11 on the image forming apparatus main body 1.

[0063] According to the image forming apparatus of this embodiment configured as above, the contact pressure P of the scraper 11 can be made uniform. That is, the scraper 11 is held in a curved manner and attached to the image forming apparatus main body 1 so that the holding member 15 brings the middle portion 12 closer to the intermediate transfer belt 5 than the end portion 13 . Therefore, even if the intermediate transfer belt 5 is bent due to contact with the intermediate portion 12, the scraper 11 can be made to contact evenly between the ends 13, 13 to make the contact pressure P uniform. Therefore, poor cleaning due to uneven wear of the scraper 11 does not occur. Furthermore, the wear progresses evenly, making it possible to maintain good cleaning performance for a long period of time.

[0064] Further, the front edge 14 of the scraper 11 comes into contact with the front surface of the intermediate transfer belt 5 between a pair of roller members 3.4 that support the intermediate transfer belt 5 from the back surface 5b. As a result, even if the intermediate transfer belt 5 is bent due to contact of the front end edge 14 between the pair of roller members 3.4, the scraper 11 can be brought into contact with the intermediate transfer belt 5 evenly, making the contact pressure P uniform.

[0065] Furthermore, as shown in FIG. 2, the holding member 15 has a first holding member 16 and a second holding member 17 that hold the scraper 11 in the out-of-plane direction. 3 or 4, the holding member 15 that holds the scraper 11 is fastened at multiple locations between the first holding member 16 and the second holding member 17 by screws 19. Even in this case, the contact pressure P at which the scraper 11 contacts the intermediate transfer belt 5 is smoothed as shown in FIG. 5, thereby enabling the intermediate transfer belt 5 to exhibit even better cleaning performance.

[0066] For example, if a configuration is adopted in which the scraper 11 is screwed using only one of the holding members, the parts other than the screw-fastened parts will float. This causes variation in the contact pressure P between the screw-fastened parts and the parts other than the screw-fastened parts. Similarly, if the scraper 11 is attached to one of the holding members by an adhesive, double-sided tape, or welding, the non-adhered portion or the portion with low adhesive strength will float. This causes uneven adhesion, uneven attachment, uneven welding, etc., resulting in variation in the contact pressure P. Therefore, in a configuration using one holding member, regardless of whether the scraper 11 is attached to the front or back side, variation in the contact pressure will occur. In contrast, in the cleaning unit 10 of the embodiment, the scraper 11 is clamped in the out-of-plane direction between the first holding member 16 and the second holding member 17. Therefore, there is no floating portion, and the contact pressure P of the scraper 11 can be made uniform.

[0067] The first holding member 16 has a surface contact portion 16 c that supports the middle portion 12 of the scraper 11 from the opposite side of the intermediate transfer belt 5 , and is set to have a higher rigidity than the second holding member 17 . As a result, the scraper 11 is pressed against the surface contact portion 16c formed in a curved shape on the first holding member 16, and can be warped into a desired shape.

[0068] Further, the rigidity of the scraper 11 is set to be higher than that of the intermediate transfer belt 5 and lower than that of the holding member 15 so that the scraper 11 conforms in shape to the holding member 15 when held by the holding member 15 . That is, the intermediate transfer belt 5 is made of polyimide. Therefore, the rigidity of the intermediate transfer belt 5 can be set lower than that of the scraper 11.

[0069] The thickness direction dimension of the scraper 11 may be set to be smaller than the thickness direction dimensions of the first holding member 16 and the second holding member 17. Therefore, the scraper 11 is less susceptible to the reaction force from the intermediate transfer belt 5 and can maintain a desired shape.

[0070] In addition, because the bending deformation is reduced, deterioration of the holding member 15 is suppressed, and the holding member 15 can be used for a long period of time. Therefore, in maintenance work, worn scraper 11 is removed from the holding member 15 and replaced. This allows a new scraper 11 to be held on the holding member 15 with the specified warpage δ with good workability. Therefore, the desired cleaning performance can be maintained for a long period of time.

[0071] 2. The image forming apparatus according to claim 1, wherein the amount of warping δ of the holding member 15 set to warp the intermediate portion 12 of the scraper 11 is defined by the following formula (1) so as to be within a cleanable range between a lower limit value taking into consideration the deflection of the intermediate transfer belt 5 and an upper limit value including a coefficient assumed to provide an appropriate contact angle α with the contact pressure P of the intermediate portion 12 as a concentrated load.

number

[0072] For this reason, various specified values, such as actual values ​​of load F obtained in advance from tests, are applied to formula (1) to give the holding member 15 a warp amount δ. As a result, even if the holding member 21 is warped, the scraper 11 can be brought into contact evenly between the ends 13, 13, making the contact pressure P uniform. Therefore, poor cleaning due to uneven wear of the scraper 11 does not occur. Furthermore, the progress of wear is even, and a cleaning part 10 capable of maintaining good cleaning performance for a long period of time can be obtained.

[0073] More specifically, the lower limit is set based on a general beam (holding member) and a deflection formula (uniformly distributed load). The reason is that the intermediate transfer belt 5 is in a tensioned state, and even if it is continuously molded with the same thickness dimension, it is known that the tension force is low in the center of the width direction W. For this reason, it is necessary to set the tension force to a value larger than the value required for cleaning in the center. Note that tolerances are not taken into consideration here.

[0074] More specifically, the upper limit is set based on a general beam and deflection formula (concentrated load) assuming a state in which the intermediate transfer belt 5 is most deflected. Furthermore, the upper limit is determined by multiplying the load F by a coefficient. The coefficient is determined by the contact angle α at which the scraper 11 contacts the intermediate transfer belt 5, which is necessary to ensure cleaning performance. For example, when the contact pressure P becomes high, a reaction force is applied to the scraper 11 from the intermediate transfer belt 5, and the scraper 11 is bent upward in the out-of-plane direction, thereby decreasing the contact angle α. Conversely, when the contact pressure P is low, the contact angle α is large because less force is applied to the scraper 11. It is known that in cleaning the intermediate transfer belt 5, whether the contact angle α is high or low, the cleaning performance is deteriorated. For this reason, in the scraper 11 of the first embodiment, the variation in the contact pressure P is calculated from the maximum allowable variation in the contact angle α, and the ratio of the variations in the contact pressure P is used as a coefficient. In the first embodiment, a margin of about 1.5 times the normal value is provided.

[0075] Furthermore, the image forming apparatus has an elastic load mechanism 50 that causes the scraper 11 to abut against the intermediate transfer belt 5 by using the elastic force of a spring member 51, as shown in FIGS. The elastic load mechanism 50 thus configured can bring the scraper 11 into contact with the surface 5a of the intermediate transfer belt 5 at a desired contact pressure P.

[0076] Further, the elastic load mechanism 50 has a stopper 52 as a restricting portion for restricting the contact force. The elastic load mechanism 50 configured in this manner can prevent the contact pressure P of the scraper 11 contacting the surface 5a of the intermediate transfer belt 5 from becoming too large. Therefore, the elastic load mechanism 50 can further make the contact pressure P of the scraper 11 closer to uniform, thereby maintaining good cleaning performance for a long period of time.

[0077] As shown in FIG. 2, the image forming apparatus has a fixing portion 7 for fixing the holding member 15 to the image forming apparatus main body 1. As shown in FIG. Therefore, the scraper 11 can be brought into contact with the intermediate transfer belt 5 at a stable contact angle α and contact pressure P by the holding member 15 fixed by the fixed portion 7.

[0078] Specifically, a fixing portion may be provided instead of the elastic load mechanism 50 of the first embodiment shown in Fig. 2. As a result, the portion where the flat plate portion 16a and the reinforcing flange portion 16b of the first holding member 16 are connected is fixed to the image forming apparatus main body 1 via the fixing portion 7. The fixing portion 7 has a small number of parts and is inexpensive. In addition, it saves space and can be made compact.

[0079] Furthermore, the fixing portion fixes the first holding member 16 of the holding member 15 to the image forming apparatus main body 1. Therefore, when the screws 19 of the holding member 15 are released, the second holding member 17 can be removed from the first holding member 16 and a new scraper 11 can be easily replaced. Even in such a case, the replaced new scraper 11 is held in a similar curved state with the front end edge 14 following the curved shapes of the face contact portions 16c, 17c of the first holding member 16 and the second holding member 17. Therefore, the contact pressure P when the new scraper 11 contacts the intermediate transfer belt 5 is equal to the contact pressure P of the removed scraper 11. Therefore, the contact pressure P is uniform before and after maintenance, and better cleaning performance can be achieved.

[0080] In addition, the scraper 11 has a metal member, so that the uniform contact pressure P can further slow down the progress of wear.

[0081] The front end edge 14 of the scraper 11 is straight when the scraper 11 is viewed from above. Therefore, the scraper 11 can be manufactured inexpensively and easily provides good dimensional accuracy to the leading edge 14. Therefore, the manufacturing cost of the scraper 11 can be suppressed while effectively suppressing cleaning unevenness. Furthermore, the cleaning ability is better than that of a conventional scraper edge in which the widthwise center portion of the tip end of the scraper is protruded further forward to form a gentle convex curve. That is, the scraper 11 of the present invention, which is curved out of the plane, has a straight front edge 14 perpendicular to the transport direction T and uniformly abuts on the surface 5a of the intermediate transfer belt 5 in the width direction W. This prevents the scraped toner 6 from spreading, and provides good dust collection. Therefore, the straight front edge 14 of the scraper 11 can further improve cleaning performance.

[0082] Furthermore, the front end edge 18 of the holding member 15 is linear when viewed from above the scraper 11. Therefore, the holding member 15 can be manufactured inexpensively and can easily provide good dimensional accuracy to the front end edge 14 of the scraper 11. Therefore, the holding member 15 can effectively suppress cleaning unevenness while suppressing manufacturing costs.

[0083] The holding member 15 also has warp regulating portions 40 that hold the intermediate portion 12 on the inside of the left and right ends 13, 13 in the width direction W to regulate the warp shape. The holding member 15 has rigidity improving portions 42 formed on the outside of the warp regulating portions 40, closer to the intermediate transfer belt 5 than the warp regulating portions 40 and farther from the intermediate transfer belt 5 than a central portion 41 that holds the intermediate portion 12. Therefore, the intermediate portion 12 of the scraper, which has sufficient bending rigidity due to the rigidity improving portion 42, can be brought into uniform contact with the intermediate transfer belt 5, thereby improving the cleaning performance of the toner 6 adhering to the bending intermediate transfer belt 5.

[0084] Furthermore, the holding member 15 has a plastic range that is large enough so that the holding member 15 is not plastically deformed by the contact force of the scraper 11 against the intermediate transfer belt 5 . Therefore, the holding member 15 returns to its original shape even if it is deformed by contact with the scraper 11. Therefore, it is possible to achieve a practically beneficial effect of maintaining good cleaning performance for a long period of time.

[0085] Although the embodiments of the present invention have been described above, these embodiments are merely illustrative and do not limit the technical scope of the present invention. The present invention can take various other embodiments, and various modifications such as omissions and substitutions can be made without departing from the gist of the present invention. These embodiments and their modifications are included in the scope and gist of the invention described in this specification, etc., and are included in the scope of the invention described in the claims and their equivalents.

[0086] In the embodiment, the scraper 11 is configured as a flexible plate-like member made of a metal member. However, this is not particularly limited. For example, the scraper 11 may be configured of other metal members such as phosphor bronze, or synthetic resin materials, etc. In other words, the scrapers 11 may be configured in any shape, number, material, or combination.

[0087] In the embodiment, the holding member 15 has the first holding members 16, 26 and the second holding members 17, 27 that hold the scraper 11 in the out-of-plane direction. However, this is not particularly limited. For example, the holding member 15 may be composed of three or more members. Furthermore, the first holding members 16, 26 may be made of another metal, and the second holding members 17, 27 may be made of a low-rigidity metal material such as an iron material (eg, chromeless steel plate) or a synthetic resin material. That is, the holding member 15 holds the scraper 11 in a warped manner so that the middle portion 12 is closer to the intermediate transfer belt 5 than the end portion 13 of the scraper 11. The holding member 15 may be any member that mounts the scraper 11 to the image forming apparatus main body 1. In this manner, the shape, number, material, and combination of the holding members 15 may be configured in any manner. [Explanation of symbols]

[0088] 5 Intermediate transfer belt 12 Middle section 13 End 15 Retaining member T Transport direction

Claims

1. a scraper, which is a flexible plate-like member that contacts the surface of the intermediate transfer belt in a direction perpendicular to the conveying direction of the intermediate transfer belt; a holding member for holding the scraper in a warped state so that a middle portion of the scraper is closer to the intermediate transfer belt than an end portion of the scraper, and mounting the scraper to the image forming apparatus body; An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, wherein the tip edge of the scraper abuts against the front surface of the intermediate transfer belt between a pair of roller members supporting the intermediate transfer belt from the rear surface thereof.

3. The image forming apparatus according to claim 1 , wherein the holding member includes a first holding member and a second holding member that hold the scraper in an out-of-plane direction.

4. The image forming apparatus according to claim 3 , wherein the first holding member has a surface contact portion that supports the middle portion of the scraper from an opposite side of the intermediate transfer belt, and is set to have a rigidity higher than that of the second holding member.

5. 2 . The image forming apparatus according to claim 1 , wherein the scraper has a rigidity set to be higher than that of the intermediate transfer belt and lower than that of the holding member, so that the scraper conforms to the shape of the holding member when held by the holding member.

6. 2. The image forming apparatus according to claim 1, wherein the amount of warping δ of the holding member set to warp the intermediate portion of the scraper is defined by the following formula (1) so as to be within a cleanable range between a lower limit value taking the deflection of the holding member as a base (equally distributed load in calculation) and taking into consideration slack in the intermediate transfer belt, and an upper limit value taking the deflection of the holding member as a base (concentrated load in calculation) and taking into consideration a contact angle α appropriate for cleaning. [0010] F: Load applied to the holding member L: Length of the holding member E: Young's modulus of the holding member L: Moment of inertia of the two holding members δ: Amount of warping of the holding member

7. 2. The image forming apparatus according to claim 1, further comprising an elastic load mechanism for contacting the scraper with the intermediate transfer belt by using an elastic force of an elastic member formed as a separate member from the scraper.

8. The image forming apparatus according to claim 7 , wherein the elastic load mechanism has a restricting portion that restricts the contact force.

9. The image forming apparatus according to claim 1 , further comprising a fixing portion for fixing the holding member to the image forming apparatus main body.

10. The image forming apparatus according to claim 1 , wherein the scraper has a metallic member.

11. The image forming apparatus according to claim 1 , wherein a front edge of the scraper is linear in a plan view of the scraper.

12. The image forming apparatus according to claim 1 , wherein the front end edge of the holding member is linear in a plan view of the scraper.

13. The holding member includes a warp regulating portion that holds the middle portion of the scraper at the inside of the left and right ends in the width direction to regulate the warp shape; 2. The image forming apparatus according to claim 1, further comprising: a rigidity improving portion formed on the outer side of the warp regulating portion, the rigidity improving portion being closer to the intermediate transfer belt than the warp regulating portion and farther from the intermediate transfer belt than a central portion that holds the intermediate portion of the scraper.

14. 2. The image forming apparatus according to claim 1, wherein the holding member has a plastic range that is large enough not to be plastically deformed by a contact force of the scraper against the intermediate transfer belt.

Images