Image forming device

Abstract

To reduce noise generated when a rotating member returns from a second position to a first position.SOLUTION: An image forming device 201 includes: a rotating member that can rotate between a first position and a second position; a conveyance guide 2 that rotatably holds the rotating member; a pressing member 4 held by the conveyance guide so as to be movable in an axial direction AD of the rotating member; and a spring member 5 that biases the pressing member so that the pressing member biases the rotating member in the axial direction. The pressing member includes: a first contact surface 4e and a second contact surface 4f that can come into contact with a protrusion 3c provided on the rotating member, in which the first contact surface is configured to have a first inclined surface shape so as to contact the protrusion and increase a biasing force applied to the rotating member when the rotating member rotates from the first position to the second position, and the second contact surface is configured to have a second inclined surface shape that is inclined so as to come into contact with the protrusion and increase the biasing force applied to the rotating member when the rotating member rotates from the first position in an opposite direction to the second position.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an image forming apparatus including a rotating member that rotates.

Background Art

[0002] Conventionally, as a technique for detecting the conveyance position of a sheet (recording medium) in an image forming apparatus, there is known a configuration including a sensor flag disposed in a conveyance path, a biasing spring that biases the sensor flag, and a sensor such as a photointerrupter. The sensor flag is directly contacted by the leading edge of the sheet and is swung against the biasing force of the biasing spring. The movement of the swing of the sensor flag is detected by a sensor such as a photointerrupter, and the position information of the sheet is generally detected from the ON / OFF signal information of the sensor. In such a contact-type sensing configuration, when the swinging sensor flag returns to the standby position, it collides with the positioning member at the opposing standby position. As a result, the kinetic energy of the sensor flag is abruptly converted into sound energy and is released to the outside as a collision sound, so that a sound is generated every time the sheet is conveyed.

[0003] To reduce this noise, Patent Document 1 proposes a method to weaken the force with which the sensor flag 10 contacts the positioning member 12, by providing an impact absorbing member 11 on the positioning member 12 that receives the sensor flag 10, as shown in Figure 9. Figure 9 is a perspective view of a conventional sensor flag 10 and impact absorbing member 11. The sensor flag 10 is provided with a contact portion 10a and a contact portion 10b. The impact absorbing member 11 is fixed to the positioning member 12. Figure 9(a) is a perspective view of the sensor flag 10 located at the standby position WP. Figure 9(b) is a perspective view of the sensor flag 10 located at the detection position DP. The sensor flag 10 is rotated from the standby position WP to the detection position DP when the conveyed sheet pushes the contact portion 10a. When the sheet passes the contact portion 10a, the sensor flag 10 returns from the detection position DP to the standby position WP. According to Patent Document 1, when the sensor flag 10 returns from the detection position DP to the standby position WP, the contact portion 10b of the sensor flag 10 collides with the shock-absorbing member 11 fixed to the positioning member 12. The shock-absorbing member 11 mitigates the impact when the sensor flag 10 is positioned by the positioning member 12.

[0004] Patent Document 2 proposes a method to reduce the force with which the sensor flag contacts the receiving part by integrally providing a leaf spring to the sensor flag. Furthermore, Patent Document 3 discloses that when the rotating part moves from the detection position to the standby position, the positioning contact part slides against the sliding contact part while the rotating part moves axially, thereby dispersing the kinetic energy when the positioning contact part lands on the positioning surface. This reduces the collision noise when the positioning contact part collides with the positioning surface in the standby position. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-94444 [Patent Document 2] Japanese Patent Publication No. 2000-335783 [Patent Document 3] Japanese Patent Publication No. 2012-188288 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, as shown in Figure 9, Patent Document 1 mitigates the impact of the sensor flag 10 collision by having the contact portion 10b of the sensor flag 10 collide with an impact absorbing member 11 fixed to the positioning member 12 when the sensor flag 10 returns to the standby position WP. Patent Document 2 mitigates the impact of the rotational member collision by using a leaf spring, but the rotational member collides with the positioning member at the opposing standby position. Patent Document 3 disperses the kinetic energy of the collision, but the rotational member collides with the positioning member at the opposing standby position. In all of the prior arts, in order to stop the rotational member in the standby position, the rotational member collides with the positioning member at the standby position, so there is a problem that a collision sound is generated each time the rotational member returns from the detection position to the standby position.

[0007] Therefore, the present invention provides an image forming apparatus that can reduce the generation of noise when a rotating member returns from a second position to a first position. [Means for solving the problem]

[0008] An image forming apparatus for forming an image on a recording medium according to one embodiment of the present invention is: A rotating member that can rotate between a first position and a second position, A holding member that rotatably holds the aforementioned rotating member, A pressing member held by the holding member so as to be movable in the rotational axis direction of the rotating member, A pressing member that biases the pressing member such that the pressing member biases the rotating member in the direction of the rotating axis, Equipped with, The pressing member has a first contact surface and a second contact surface that can contact the projection provided on the rotating member, The first contact surface is configured to have a first inclined shape such that it contacts the projection when the rotating member rotates from the first position to the second position, thereby increasing the biasing force applied to the rotating member. The second contact surface is characterized by being configured as a second inclined surface shape that is inclined so as the rotating member rotates from the first position in the direction opposite to the second position, it contacts the projection and increases the biasing force applied to the rotating member. [Effects of the Invention]

[0009] According to the present invention, it is possible to reduce the generation of noise when the rotating member returns from the second position to the first position. [Brief explanation of the drawing]

[0010] [Figure 1] Cross-sectional view of an image forming apparatus. [Figure 2] A perspective view of the sheet detection unit of the first embodiment. [Figure 3] Cross-sectional view of the sheet detection unit of the first embodiment. [Figure 4] A perspective view of the sensor flag of the first embodiment. [Figure 5] A perspective view of the pressing member of the first embodiment. [Figure 6] An explanatory diagram showing the movement of the pressing member due to the rotation of the sensor flag. [Figure 7] Perspective view of the sensor flag of the second embodiment. [Figure 8] A perspective view of the pressing member of the second embodiment. [Figure 9] A perspective view of a conventional sensor flag and shock-absorbing member. [Modes for carrying out the invention]

[0011] The embodiments for carrying out the present invention will be described below with reference to the attached drawings. Unless otherwise specifically stated, the dimensions, materials, shapes, and relative positions of the components are not intended to limit the scope of this invention. In the following description, the positional relationships of the image forming apparatus (up, down, left, right, and front / back) will be described based on a view of the image forming apparatus from the front (viewpoint in Figure 1). [Examples]

[0012] (Image forming apparatus) FIG. 1 is a cross-sectional view of an image forming apparatus 201. The image forming apparatus 201 is an electrophotographic copying machine (e.g., a digital copying machine) that forms a full-color image on a recording medium (hereinafter referred to as a sheet) using an electrophotographic method. In this embodiment, the image forming apparatus 201 will be described by taking an electrophotographic copying machine as an example, but the image forming apparatus 201 is not limited thereto. The image forming apparatus 201 may be an electrophotographic printer (e.g., a color laser beam printer, a color LED printer), an MFP (multifunction peripheral), a facsimile apparatus, or a printing machine. Further, the image forming apparatus 201 may be an inkjet printer that forms an image on a recording medium not limited to the electrophotographic method but using an inkjet method.

[0013] The image forming apparatus 201 includes a device main body 201A, an image forming unit 201B, an intermediate transfer unit 201C, a reverse conveyance unit 201D, and a sheet feeding unit 201E. An image reading device 202 for reading an image of a document is provided above the device main body 201A of the image forming apparatus 201. The image forming unit 201B as an image forming means is provided inside the device main body 201A and forms a toner image on the sheet P in cooperation with the intermediate transfer unit 201C. The toner image formed on the sheet P by the image forming unit 201B is fixed to the sheet P by a fixing unit 220 provided inside the device main body 201A, and an image is formed on the sheet P. The sheet P on which the image is formed is discharged to a discharge space DS provided in the device main body 201A between the image reading device 202 and the image forming unit 201B. A discharge tray 230 on which the discharged sheet P is stacked is provided in the discharge space DS.

[0014] The sheet feeding unit 201E as the sheet feeding means feeds the sheet P to the image forming unit 201B. The sheet feeding unit 201E includes a plurality of cassette feeding devices arranged at the lower part of the apparatus main body 201A and a manual feeding device 100M arranged at the right side part of the apparatus main body 201A. The plurality of cassette feeding devices include a first feeding cassette 100A, a second feeding cassette 100B, a third feeding cassette 100C, and a fourth feeding cassette 100D. The first feeding cassette 100A, the second feeding cassette 100B, the third feeding cassette 100C, and the fourth feeding cassette 100D are arranged in this order from the top.

[0015] The image forming unit 201B is a so-called tandem type intermediate transfer system including a laser scanner 210, four process cartridges 211, and an intermediate transfer unit 201C. The four process cartridges 211 respectively form a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image. Each of the process cartridges 211 includes a photosensitive drum 212, a charger 213, a developer 214, and a cleaner (not shown). Above the image forming unit 201B, four toner cartridges 215 respectively containing yellow toner, magenta toner, cyan toner, and black toner are detachably attached to the apparatus main body 201A. [[ID=*]] [[ID=*]]

[0016] [[ID=*]] The intermediate transfer unit 201C has an intermediate transfer belt 216 wound around a driving roller 216a and a tension roller 216b. The intermediate transfer belt 216 is arranged above the four process cartridges 211. The intermediate transfer belt 216 is arranged so as to contact the photosensitive drums 212 of the four process cartridges 211. The intermediate transfer belt 216 is rotated in the counterclockwise direction (the direction indicated by the arrow Q) by the driving roller 216a driven by a driving unit (not shown). The intermediate transfer unit 201C includes four primary transfer rollers 219 that contact the inner peripheral surface of the intermediate transfer belt 216 at positions facing the four photosensitive drums 212. Four primary transfer portions T1 are formed as nip portions between the intermediate transfer belt 216 and the photosensitive drums 212.

[0017] The image forming unit 201B includes a secondary transfer roller 217 that contacts the outer circumferential surface of the intermediate transfer belt 216 at a position opposite to the drive roller 216a. A secondary transfer section T2 is formed as a nip between the secondary transfer roller 217 and the intermediate transfer belt 216, where the toner image supported on the intermediate transfer belt 216 is transferred to the sheet P.

[0018] In each process cartridge 211, the charger 213 uniformly charges the surface of the rotating photosensitive drum 212. The laser scanner 210 emits laser light of each color onto the uniformly charged surface of the photosensitive drum 212 to form an electrostatic latent image on the surface of the photosensitive drum 212. The developer 214 supplies toner to the surface of the photosensitive drum 212 to form negatively charged toner images of each color. Each toner image is transferred sequentially to the intermediate transfer belt 216 in each primary transfer section T1 (primary transfer) by applying a positive transfer bias voltage to the primary transfer roller 219. The toner images of each color are superimposed on the intermediate transfer belt 216 to form a full-color toner image on the intermediate transfer belt 216.

[0019] In parallel with this toner image formation process, the sheet P fed from the sheet feeding unit 201E is transported to the registration roller pair 240. The registration roller pair 240 corrects the skewness of the sheet P. Subsequently, the registration roller pair 240 starts transporting the sheet P so that it reaches the secondary transfer unit T2 at the same time as the full-color toner image formed on the intermediate transfer belt 216 reaches the secondary transfer unit T2. The full-color toner image supported on the intermediate transfer belt 216 is transferred to the sheet P in the secondary transfer unit T2 (secondary transfer) by applying a positive transfer bias voltage to the secondary transfer roller 217.

[0020] The sheet P onto which the toner image has been transferred is heated and pressurized by the fixing unit 220 to fix the color image onto the sheet P. The sheet P with the fixed image is discharged to the discharge tray 230 by the discharge roller pair 225 and stacked. In the case of double-sided printing, where an image is formed on both sides of the sheet P, the sheet P, which has passed through the fixing unit 220 and has an image formed on the front surface (first surface), is switched back by the reversible reversible roller pair 222 provided in the reversal transport unit 201D. The sheet P is then transported again to the image forming unit 201B through the re-transport passage R, where an image is formed on the back surface (second surface) opposite to the front surface. The sheet P with images formed on both sides is discharged to the discharge tray 230 by the discharge roller pair 225.

[0021] (Sheet detection unit) The sheet detection unit 1 will be described below with reference to Figures 1, 2, and 3. Figure 2 is a perspective view of the sheet detection unit 1 of the first embodiment. Figure 3 is a cross-sectional view of the sheet detection unit 1 of the first embodiment. The sheet detection unit 1 is located at the junction 33 of the transport path 31 from the first feed cassette 100A located at the top and the transport paths 32 from the second feed cassette 100B, third feed cassette 100C, and fourth feed cassette 100D located at the bottom. A transport roller pair 7 is located at the junction 33 to transport the sheet P to the registration roller pair 240 through the transport path 34. The transport roller pair 7 consists of a transport roller 7a located on the side of the first feed cassette 100A with respect to the transport path 34 and a transport roller 7b located on the side opposite to the first feed cassette 100A with respect to the transport path 34. The sheet detection unit 1 is located on the side of the transport roller 7a at the junction 33. The sheet detection unit 1 detects sheets P being transported from the transport path 31 to the merging section 33 and sheets P being transported from the transport path 32 to the merging section 33.

[0022] The sheet detection unit 1 includes a transport guide 2 (holding member) that guides the transport of the sheet P, a sensor flag 3 (rotating member), a pressing member 4 (cam member), a spring member 5 (pressing member), and a photosensor 6. The transport guide 2 defines a portion of the transport path 31 between the transport roller pair 17 and the transport roller pair 7 that transport the sheet P fed from the first feed cassette 100A. The transport guide 2 holds the sensor flag 3 so that it can rotate (oscillate) around the rotation axis RA (rotation axis) which is perpendicular to the transport direction CD of the sheet P. The transport guide 2 holds the pressing member 4 so that it can move in the axial direction AD (rotation axis direction) along the rotation axis RA.

[0023] Figure 4 is a perspective view of the sensor flag 3 of the first embodiment. The sensor flag 3 has a contact portion 3a, a shielding portion 3b, a projection portion 3c, a pivoting shaft portion 3d, abutment portion 3e, and a shaft portion 3f. The contact portion 3a and the shielding portion 3b extend radially from the shaft portion 3f. The projection portion 3c, the pivoting shaft portion 3d, and the abutment portion 3e are provided at one end of the shaft portion 3f.

[0024] Figure 5 is a perspective view of the pressing member 4 of the first embodiment. The pressing member 4 has a bearing portion 4a, a first sliding shaft portion 4b, a second sliding shaft portion 4c, an anti-rotation portion 4d, a first contact surface 4e, a second contact surface 4f, and a spring receiving portion 4g. The bearing portion 4a is provided on the first sliding shaft portion 4b. The two first contact surfaces 4e and the two second contact surfaces 4f are provided point-symmetrically at one end of the first sliding shaft portion 4b. The anti-rotation portion 4d is provided on the outer circumference of the first sliding shaft portion 4b. The spring receiving portion 4g is provided between the other end of the first sliding shaft portion 4b and one end of the second sliding shaft portion 4c.

[0025] Referring to Figure 2, the first sliding shaft portion 4b of the pressing member 4 is held so as to be movable in the axial direction AD by the first bearing portion 2b of the transport guide 2. The second sliding shaft portion 4c of the pressing member 4 is held so as to be movable in the axial direction AD by the second bearing portion 2c of the transport guide 2. The anti-rotation portion 4d of the pressing member 4 fits into a groove portion 2d formed in the first bearing portion 2b of the transport guide 2 to restrict the rotation of the pressing member 4 around the rotation axis RA. One surface of the spring receiving portion 4g of the pressing member 4 is configured to be able to contact the first contact surface 2g of the first bearing portion 2b. However, in this embodiment, when the pressing member 4 and the sensor flag 3 are assembled into the transport guide 2, the spring receiving portion 4g does not contact the first contact surface 2g. The spring member 5 is attached to the second sliding shaft portion 4c. The spring member 5 in the first embodiment is a compression spring, but it may be another elastic material such as rubber. One end of the spring member 5 is in contact with the second bearing portion 2c. The other end of the spring member 5 is in contact with the other surface of the spring receiving portion 4g. The spring member 5 biases the pressing member 4 in the direction indicated by arrow A (biasing direction) along the axial direction AD.

[0026] The pivot shaft portion 3d of the sensor flag 3 is inserted into the bearing portion 4a of the pressing member 4, and the sensor flag 3 is held rotatably with respect to the pressing member 4. One end of the shaft portion 3f of the sensor flag 3 is held rotatably by the third bearing portion 2f of the transport guide 2. The other end of the shaft portion 3f of the sensor flag 3 is held rotatably by the fourth bearing portion 2h of the transport guide 2. The abutment portion 3e of the sensor flag 3 is configured to abut against the second contact surface 2e of the third bearing portion 2f of the transport guide 2. Movement of the sensor flag 3 in the direction indicated by arrow A (biasing direction) is restricted by the abutment portion 3e abutting against the second contact surface 2e (movement restricting portion) of the third bearing portion 2f.

[0027] Two projections 3c are provided that protrude radially from the pivot shaft portion 3d of the sensor flag 3, arranged point-symmetrically with respect to the rotation axis RA. When the sensor flag 3 is rotated with the pivot shaft portion 3d of the sensor flag 3 inserted into the bearing portion 4a of the pressing member 4, the two projections 3c can contact (make contact with) the first contact surface 4e or the second contact surface 4f of the pressing member 4 according to the rotational position of the sensor flag 3. As the sensor flag 3 rotates, the projections 3c ride up onto the first contact surface 4e, pushing the first contact surface 4e and causing the pressing member 4 to move along the axial direction AD in the direction indicated by arrow B. On the other hand, the projections 3c receive a rotational force and a force along the axial direction AD in the direction indicated by arrow A from the pressing member 4 according to the inclined shape of the first contact surface 4e. The pivot shaft portion 3d extends from the projections 3c and is inserted into the bearing portion 4a of the pressing member 4, and is rotatably supported. The sensor flag 3 receives a force from the first contact surface 4e or the second contact surface 4f along the axial direction AD in the direction indicated by arrow A, and the abutment portion 3e of the sensor flag 3 abuts against the second contact surface 2e of the third bearing portion 2f of the transport guide 2. The abutment portion 3e of the sensor flag 3 abuts against the second contact surface 2e of the third bearing portion 2f of the transport guide 2 restricts the movement of the sensor flag 3 in the direction indicated by arrow A.

[0028] The transport guide 2 is equipped with a light-transmitting photosensor 6 having a light-emitting part and a light-receiving part. When a sheet P being transported from the transport path 31 or transport path 32 comes into contact with the contact part 3a of the sensor flag 3 and presses the contact part 3a, the sensor flag 3 rotates and the shielding part 3b blocks the light path of the light-emitting and light-receiving parts of the photosensor 6. When the light path of the photosensor 6 is blocked, the output of the photosensor 6 is turned OFF. When the sheet P passes the contact part 3a, the biasing force of the spring member 5 (biasing member) rotates the sensor flag 3 and the shielding part 3b retracts from the light path of the light-emitting and light-receiving parts of the photosensor 6, allowing light to pass through the photosensor 6. When light passes through the photosensor 6, the output of the photosensor 6 is turned ON. The photosensor 6 outputs a detection signal in accordance with the rotation of the sensor flag 3 to the detection position. The passage state of the sheet P is detected by switching the ON / OFF of the detection signal of the photosensor 6.

[0029] As shown in Figure 2, the pressing member 4 is supported by the transport guide 2 on the same axis as the rotation axis RA of the sensor flag 3. The pressing member 4 is supported by the transport guide 2 so as to be able to translate in the axial direction AD of the sensor flag 3, and its rotation in the rotational direction RD (Figure 3(a)) is restricted. The pivot shaft portion 3d of the sensor flag 3 is inserted into the bearing portion 4a of the pressing member 4, and the pressing member 4 rotatably supports the sensor flag 3 and is movable in the axial direction AD relative to the sensor flag 3.

[0030] The pressing member 4 is biased by the spring member 5 along the axial direction AD in the direction indicated by arrow A, so that the first contact surface 4e, the second contact surface 4f, or the first contact surface 4e and the second contact surface 4f contact the projection 3c of the sensor flag 3. The movement of the pressing member 4 in the direction indicated by arrow A by the spring member 5 is restricted by the contact between the first contact surface 4e, the second contact surface 4f, or the first contact surface 4e and the second contact surface 4f with the projection 3c of the sensor flag 3. Figure 3(a) shows the state in which the sensor flag 3 is in the standby position WP (first position). Figure 3(b) shows the state in which the sensor flag 3 is in the detection position DP (second position). When the sensor flag 3 rotates from the standby position WP to the detection position DP, the projection 3c of the sensor flag 3 pushes the first contact surface 4e, causing the pressing member 4 to move in the direction indicated by arrow B (Figure 2) against the biasing force of the spring member 5. The first contact surface 4e is configured as a first inclined surface that contacts the projection 3c when the sensor flag 3 rotates from the standby position WP to the detection position DP, thereby increasing the biasing force applied to the sensor flag 3. On the other hand, when the sensor flag 3 rotates in the opposite direction from the standby position WP to the detection position DP, the projection 3c of the sensor flag 3 pushes against the second contact surface 4f, moving the pressing member 4 in the direction indicated by arrow B (Figure 2) against the biasing force of the spring member 5. The second contact surface 4f is configured as a second inclined surface that contacts the projection 3c when the sensor flag 3 rotates in the opposite direction from the standby position WP to the detection position DP, thereby increasing the biasing force applied to the sensor flag 3.

[0031] Figure 6 is an explanatory diagram of the movement of the pressing member 4 due to the rotation of the sensor flag 3. Figure 6(a) shows the position of the pressing member 4 when the sensor flag 3 is in the standby position WP (first position). Figure 6(b) shows the position of the pressing member 4 when the sensor flag 3 is in the detection position DP (second position). Figure 6(c) shows the position of the pressing member 4 when the sensor flag 3 has rotated in the opposite direction from the detection position DP (second position) and is in the return position RP (third position).

[0032] The movement of the pressing member 4 when the sensor flag 3 rotates from the standby position WP shown in Figures 3(a) and 6(a) to the detection position DP shown in Figures 3(b) and 6(b) will be explained. When the sheet P is transported while the sensor flag 3 is in the standby position WP shown in Figures 3(a) and 6(a), the leading edge of the sheet P comes into contact with the contact portion 3a of the sensor flag 3. As the sheet P is transported, the contact portion 3a is pushed by the sheet P, and the sensor flag 3 rotates counterclockwise around the rotation axis RA in Figure 3. As the sensor flag 3 rotates counterclockwise, the projection 3c of the sensor flag 3 pushes the first contact surface 4e of the pressing member 4 in the direction indicated by arrow B, as shown in Figure 6(b). Since the rotation of the anti-rotation portion 4d of the pressing member 4 is restricted by the groove portion 2d (rotation restricting portion) of the transport guide 2, the pressing member 4 is moved along the axial direction AD in the direction indicated by arrow B, against the biasing force of the spring member 5 by the projection portion 3c of the sensor flag 3. As the pressing member 4 moves in the direction indicated by arrow B, the biasing force (restoring force) of the spring member 5 is increased.

[0033] When the tip of sheet P further presses against the contact portion 3a of sensor flag 3, sensor flag 3 reaches the detection position DP shown in Figure 6(b). When the tip of sheet P leaves the contact portion 3a of sensor flag 3, the contact portion 3a comes into contact with the surface of sheet P, and sensor flag 3 is held in the detection position DP without being further rotated by sheet P, as shown in Figure 3(b). Sensor flag 3 can also rotate further counterclockwise from the detection position DP as shown in Figure 3(b). This further counterclockwise rotation of sensor flag 3 allows the pressing member 4 to move further in the direction indicated by arrow B in Figure 6(b). Therefore, during the rotation of sensor flag 3 from standby position WP to detection position DP, sensor flag 3 does not collide with other members.

[0034] Next, we will explain the movement of the pressing member 4 when the sensor flag 3 rotates from the detection position DP shown in Figures 3(b) and 6(b) to the standby position WP shown in Figures 3(a) and 6(a). When the sheet P is further transported and the rear end of the sheet P passes the contact portion 3a of the sensor flag 3, the contact portion 3a is no longer pressed by the sheet P. The sensor flag 3 is rotated to the standby position WP by the rotational moment due to the center of gravity of the sensor flag 3 and the rotational force that the projection 3c receives from the first contact surface 4e due to the biasing force of the spring member 5. At that time, the projection 3c of the sensor flag 3 receives a force in the clockwise direction and a force in the direction indicated by arrow A along the axial direction AD from the first contact surface 4e of the pressing member 4. Even if the projection 3c of the sensor flag 3 receives a force from the first contact surface 4e of the pressing member 4 in the direction indicated by arrow A along the axial direction AD, the abutment portion 3e of the sensor flag 3 contacts the second contact surface 2e of the transport guide 2, so the sensor flag 3 does not move in the direction indicated by arrow A. Therefore, as the pressing member 4 moves in the direction indicated by arrow A due to the biasing force (restoring force) of the spring member 5, the first contact surface 4e rotates the projection 3c, and the sensor flag 3 rotates clockwise in Figure 3(b). When the projection 3c of the sensor flag 3 reaches the valley (inflection point) between the first contact surface 4e and the second contact surface 4f of the pressing member 4, the sensor flag 3 returns to the standby position WP.

[0035] However, when the sensor flag 3 returns from the detection position DP to the standby position WP, the kinetic energy of the sensor flag 3 does not become 0 (zero). In the conventional technology, as explained in Figure 9, the sensor flag 10 is stopped at the standby position WP when the contact portion 10b of the sensor flag 10 collides with the shock-absorbing member 11 fixed to the positioning member 12. Therefore, in the conventional technology, a collision sound is generated when the contact portion 10b collides with the shock-absorbing member 11. In contrast, in the first embodiment, in order to prevent the generation of a collision sound, the sensor flag 3 passes through the standby position WP without the contact portion 10b colliding with the shock-absorbing member 11.

[0036] As the sensor flag 3 rotates past the standby position WP and in the opposite direction to the detection position DP, the projection 3c rides up onto the second contact surface 4f of the pressing member 4. The projection 3c of the sensor flag 3 pushes the second contact surface 4f in the direction indicated by arrow B, as shown in Figure 6(c). The pressing member 4 is moved along the axial direction AD in the direction indicated by arrow B, against the biasing force of the spring member 5 due to the projection 3c of the sensor flag 3. As the pressing member 4 moves in the direction indicated by arrow B, the biasing force (restoring force) of the spring member 5 increases. In this way, the rotational kinetic energy of the sensor flag 3 as it returns from the detection position DP to the standby position WP is converted into elastic energy of the spring member 5, which is translated along the axial direction AD by the second contact surface 4f, and is attenuated. The sensor flag 3 stops temporarily at the return position RP shown in Figure 6(c). After that, the sensor flag 3 is rotated in the return direction from the return position RP by the biasing force (restoring force) of the spring member 5 and returns to the standby position WP, where it stops.

[0037] The sensor flag 3 can rotate further clockwise in Figure 3 from the return position RP where its clockwise rotational kinetic energy switches to counterclockwise rotational kinetic energy. This further clockwise rotation of the sensor flag 3 allows the pressing member 4 to move further in the direction indicated by arrow B in Figure 6(c). Therefore, in the operation of the sensor flag 3 returning from the detection position DP to the standby position WP, the sensor flag 3 does not collide with any other members. In this way, the sensor flag 3 can be returned from the detection position DP to the standby position WP and stopped without providing any members on the transport guide 2 that would collide with the sensor flag 3. Thus, the impact when positioning the sensor flag 3 to the standby position WP can be mitigated, and the generation of collision noise when the sensor flag 3 returns to the standby position WP can be prevented.

[0038] According to the first embodiment, when the sensor flag 3 returns from the detection position DP to the standby position WP, if the sensor flag 3 rotates in the opposite direction to the detection position DP beyond the standby position WP, a force is generated in the reverse rotation direction that returns the sensor flag 3 to the standby position WP. Due to this force in the reverse rotation direction, the sensor flag 3 can return to the standby position WP without colliding with other members. According to the first embodiment, the rotational kinetic energy of the sensor flag 3 is converted into elastic energy translated in the axial direction AD along the rotation axis RA and attenuated. As a result, the sensor flag 3 stops at the standby position WP without colliding with other members. According to the first embodiment, the generation of noise when the sensor flag 3 returns from the detection position DP to the standby position WP can be reduced. [Examples]

[0039] The second embodiment will now be described. In the second embodiment, the same reference numerals are used for structures similar to those in the first embodiment, and their descriptions will be omitted. The image forming apparatus 201 of the second embodiment is the same as the image forming apparatus 201 of the first embodiment, so its description will be omitted. In the first embodiment, the sensor flag 3 is provided with a projection 3c, and the pressing member 4 is provided with a first contact surface 4e and a second contact surface 4f. In contrast, in the second embodiment, the sensor flag 8 (rotating member) is provided with a first contact surface 8e and a second contact surface 8f, and the pressing member 9 is provided with a projection 9e. The differences from the first embodiment will be mainly described below.

[0040] Figure 7 is a perspective view of the sensor flag 8 of the second embodiment. The sensor flag 8 has a contact portion 8a, a shielding portion 8b, abutment portion 8c, a pivot shaft portion 8d, a first contact surface 8e, a second contact surface 8f, and a shaft portion 8g. The contact portion 8a and the shielding portion 8b extend radially from the shaft portion 8g. The abutment portion 8c, the pivot shaft portion 8d, the first contact surface 8e, and the second contact surface 8f are provided at one end of the shaft portion 8g. The two first contact surfaces 8e and the two second contact surfaces 8f are provided on the outer circumference of the pivot shaft portion 8d in a point-symmetrical manner.

[0041] Figure 8 is a perspective view of the pressing member 9 of the second embodiment. The pressing member 9 has a bearing portion 9a, a first sliding shaft portion 9b, a second sliding shaft portion 9c, an anti-rotation portion 9d, a projection portion 9e, and a spring receiving portion 9f. The bearing portion 9a is provided on the first sliding shaft portion 9b. The anti-rotation portion 9d is provided on the outer circumference of the first sliding shaft portion 9b. The two projection portions 9e protrude from one end of the first sliding shaft portion 9b in the direction indicated by arrow A along the axial direction AD. The spring receiving portion 9f is provided between the other end of the first sliding shaft portion 9b and one end of the second sliding shaft portion 9c.

[0042] The sensor flag 8 and pressing member 9 of the second embodiment are attached to the transport guide 2 and operate in the same manner as the sensor flag 3 and pressing member 4 of the first embodiment, producing the same effect. According to the second embodiment, the generation of noise when the sensor flag 8 returns from the detection position DP to the standby position WP can be reduced.

[0043] In the first and second embodiments, the sensor flag 3 and sensor flag 8 were described as rotating members, respectively. However, the rotating members are not limited to the sensor flag 3 and sensor flag 8, as long as they rotate between a first position and a second position. Also, in the first and second embodiments, a first contact surface 4e was provided on the pressing member 4 and a first contact surface 8e on the sensor flag 8 in order to apply rotational force to the rotating members to return them from the second position to the first position. However, the rotating members may be configured to return from the second position to the first position by their own weight. In that case, the first contact surface 4e of the pressing member 4 and the first contact surface 8e of the sensor flag 8 may be omitted. [Explanation of symbols]

[0044] 2: Transport guide / 3: Sensor flag / 3c: Protrusion / 4: Pressing member / 4e: First contact surface / 4f: Second contact surface / 5: Spring member / 201: Image forming apparatus / P: Sheet / WP: Standby position / DP: Detection position / AD: Axial axis

Claims

1. An image forming apparatus for forming an image on a recording medium, a rotating member that is rotatable about a rotation axis between a first position and a second position and that is rotatable from the first position in a direction opposite to the second position; a holding member that guides the sheet and rotatably holds the rotating member; a pressing member provided on the holding member, the pressing member contacting the rotating member to move the rotating member in a rotation axis direction of the rotating member; a pressing member that biases the pressing member so that the pressing member moves the rotating member in the rotation axis direction; Equipped with The pressing member rotates the rotating member in a return direction by the axial force received from the pressing member, the return direction is a direction in which the rotating member returns to the first position when the rotating member rotates from the first position in a direction opposite to the second position; 1. An image forming apparatus comprising:

2. The pressing member has a contact surface capable of contacting a protrusion provided on the rotating member, The contact surface is configured to have an inclined surface shape that is inclined so that the contact surface comes into contact with the protrusion and the biasing force applied to the rotating member becomes large when the rotating member rotates in the opposite direction from the first position to the second position.

2. The image forming apparatus according to claim 1,

3. the holding member has a restricting portion that restricts movement of the rotating member in a biasing direction in which the pressing member biases the pressing member, 3. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

4. The holding member has a rotation restricting portion that restricts rotation of the pressing member.

4. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

5. The pressing member has a first contact surface and a second contact surface capable of contacting a protrusion provided on the rotating member, the first contact surface is configured to have a first inclined surface shape that is inclined so as to come into contact with the protrusion and increase a biasing force applied to the rotating member when the rotating member rotates from the first position to the second position, the second contact surface is configured to have a second inclined shape that is inclined so that the second contact surface comes into contact with the protrusion and the biasing force applied to the rotating member becomes large when the rotating member rotates from the first position to the direction opposite to the second position.

2. The image forming apparatus according to claim 1,

6. The pressing member is A bearing portion that rotatably holds the rotating member; a first sliding portion and a second sliding portion held by the holding member so as to be movable in the rotation axis direction; a rotation restricting portion provided on an outer periphery of the first sliding portion and fitted into a groove of the holding member to restrict rotation of the pressing member about the rotation axis; The first contact surface and the second contact surface provided at one end of the first sliding portion; a biasing force receiving portion provided between the other end of the first sliding portion and the one end of the second sliding portion and receiving the biasing force of the pressing member; 6. The image forming apparatus according to claim 5,

7. A sensor having a light emitting unit and a light receiving unit, The rotating member is A shaft portion rotatably held by the holding member; a contact portion extending in a radial direction from the shaft portion and capable of contacting the recording medium being conveyed; a shielding portion extending in a radial direction from the shaft portion and capable of shielding an optical path between the light emitting portion and the light receiving portion of the sensor when the conveyed recording medium presses the contact portion to rotate the rotating member; the protrusion portion capable of contacting the first contact surface and the second contact surface of the pressing member; a rotation shaft portion provided at one end of the shaft portion, the rotation shaft portion being inserted into the bearing portion of the pressing member and being held rotatably relative to the pressing member; abutting portion provided on the shaft portion and abutting against a contact surface of the holding member to restrict movement of the rotating member in the rotation axis direction, 7. The image forming apparatus according to claim 6,

8. The contact portion of the rotating member in the first position is pressed by the recording medium being transported, whereby the rotating member rotates from the first position to the second position, when the rear end of the recording medium being conveyed passes through the contact portion, the rotating member rotates from the second position to the first position by the biasing force of the pressing member, further rotates from the first position in the direction opposite to the second position against the biasing force of the pressing member, and then returns to the first position by the biasing force of the pressing member; 8. The image forming apparatus according to claim 7,

9. The rotating member has a contact surface capable of contacting a protrusion provided on the pressing member, The contact surface is configured to have an inclined surface shape that is inclined so that the contact surface comes into contact with the protrusion and the biasing force applied to the rotating member becomes large when the rotating member rotates from the first position to the second position in the opposite direction.

2. The image forming apparatus according to claim 1,

10. The rotating member has a first contact surface and a second contact surface that can come into contact with a protrusion portion provided on the pressing member, the first contact surface is configured to have a first inclined surface shape that is inclined so that the first contact surface comes into contact with the protrusion and a biasing force applied to the rotating member becomes large when the rotating member rotates from the first position to the second position, the second contact surface is configured to have a second inclined surface shape that is inclined so that the second contact surface comes into contact with the protrusion and the biasing force applied to the rotating member becomes large when the rotating member rotates from the first position to the direction opposite to the second position.

2. The image forming apparatus according to claim 1,

11. The pressing member is A bearing portion that rotatably holds the rotating member; a first sliding portion and a second sliding portion held by the holding member so as to be movable in the rotation axis direction; a rotation restricting portion provided on an outer periphery of the first sliding portion and fitted into a groove of the holding member to restrict rotation of the pressing member around the rotation axis; The protrusion; a biasing force receiving portion provided between the other end of the first sliding portion and one end of the second sliding portion, the biasing force receiving portion receiving the biasing force of the pressing member; Equipped with The protrusion is provided at one end of the first sliding portion.

11. The image forming apparatus according to claim 10.

12. A sensor having a light emitting unit and a light receiving unit, The rotating member is A shaft portion rotatably held by the holding member; a contact portion extending in a radial direction from the shaft portion and capable of contacting the recording medium being conveyed; a shielding portion extending in a radial direction from the shaft portion and capable of shielding an optical path between the light emitting portion and the light receiving portion of the sensor when the conveyed recording medium presses the contact portion to rotate the rotating member; a rotation shaft portion provided at one end of the shaft portion, the rotation shaft portion being inserted into the bearing portion of the pressing member and being held rotatably relative to the pressing member; abutment portion provided on the shaft portion and abutting against a contact surface of the holding member to restrict movement of the rotating member in the rotation axis direction, The first contact surface and the second contact surface are capable of coming into contact with the protrusion portion of the pressing member.

12. The image forming apparatus according to claim 11.

13. The contact portion of the rotating member at the first position is pressed by the recording medium being transported, whereby the rotating member rotates from the first position to the second position; when the rear end of the recording medium being conveyed passes through the contact portion, the rotating member rotates from the second position to the first position by the biasing force of the pressing member, further rotates from the first position in the direction opposite to the second position against the biasing force of the pressing member, and then returns to the first position by the biasing force of the pressing member; 13. The image forming apparatus according to claim 12.

14. 14. The image forming apparatus according to claim 1, wherein the rotating member is a sensor flag.

Images