Power transmission mechanism, sheet transport device, image forming apparatus

Abstract

To provide a drive force transmission mechanism, a sheet transport device, and an image forming apparatus capable of suppressing the generation of vibration and noise. [Solution] In the drive force transmission mechanism, the first planetary gear 52 is provided so as to be movable between a first meshing position in which it meshes with the inner circumferential gear portion of the first output side gear 54 along the rotation axis 51C due to its rotation, and a first non-meshing position which is on the side surface 51E side of the first meshing position and does not mesh with the inner circumferential gear portion. When the rotation of the first sun gear 53 is not locked, the first planetary gear 52 revolves by the rotation of the first input side gear 51 and rotates the first sun gear 53 without rotating itself.

Description

Technical Field

[0004] ,

[0005]

[0001] The present invention relates to a driving force transmission mechanism, a sheet conveying device, and an image forming apparatus.

Background Art

[0002] An image forming apparatus including a driving force transmission mechanism that transmits a rotational driving force input from a motor is known. For example, the driving force transmission mechanism including an input gear, an output gear, a first planetary gear mechanism, a second planetary gear mechanism, and a switching unit is known as a related art (see Patent Document 1). The rotational driving force of the motor is input to the input gear. The output gear outputs the rotational driving force input to the input gear. The first planetary gear mechanism rotates the output gear in a first direction by receiving the rotational driving force transmitted from the input gear. The second planetary gear mechanism rotates the output gear in a second direction opposite to the first direction by receiving the rotational driving force transmitted from the input gear via the first planetary gear mechanism. The switching unit switches the planetary gear mechanism that rotates the output gear between the first planetary gear mechanism and the second planetary gear mechanism.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the driving force transmission mechanism according to the above-described related art, vibration and noise occur in the planetary gear mechanism that does not rotate the output gear.

[0005] An object of the present invention is to provide a driving force transmission mechanism, a sheet conveying device, and an image forming apparatus capable of suppressing the generation of vibration and noise.

Means for Solving the Problems

[0006] A driving force transmission mechanism according to one aspect of the present invention comprises an input gear, an output gear, a first planetary gear mechanism, a second planetary gear mechanism, and a switching unit. The input gear receives the rotational driving force of a motor. The output gear outputs the rotational driving force received by the input gear. The first planetary gear mechanism receives the rotational driving force transmitted from the input gear and rotates the output gear in a first direction. The second planetary gear mechanism receives the rotational driving force transmitted from the input gear via the first planetary gear mechanism and rotates the output gear in a second direction opposite to the first direction. The switching unit switches the planetary gear mechanism that rotates the output gear between the first planetary gear mechanism and the second planetary gear mechanism. The first planetary gear mechanism includes a first input-side gear, a first planetary gear, a first sun gear, and a first output-side gear. The first input gear meshes with the input gear. The first planetary gear is supported so as to be rotatable on the first side surface of the first input gear. The first sun gear is mounted coaxially with the first input gear and meshes with the first planetary gear. The first output gear has a first inner gear portion that meshes with the first planetary gear, is mounted coaxially with the first input gear and meshes with the output gear. The second planetary gear mechanism includes a second input gear, a second planetary gear, a second sun gear, and a second output gear. The second input gear meshes with the first input gear. The second planetary gear is supported so as to be rotatable on the second side surface of the second input gear. The second sun gear is mounted coaxially with the second input gear and meshes with the second planetary gear. The second output gear has a second inner gear portion that meshes with the second planetary gear, is mounted coaxially with the second input gear, and meshes with the output gear. The switching portion has a locking portion. The locking portion locks the rotation of either the first sun gear or the second sun gear. The first planetary gear is provided to be movable between a first meshing position in which it meshes with the first inner gear portion along the rotation axis of the first planetary gear by its rotation, and a first non-measuring position which is on the first side surface side of the first meshing position and does not mesh with the first inner gear portion.The second planetary gear is provided so as to be movable between a second meshing position, in which it meshes with the second inner gear portion along the rotation axis of the second planetary gear due to its rotation, and a second non-meshing position, which is on the second side portion side of the second meshing position and does not mesh with the second inner gear portion. The first planetary gear revolves by the rotation of the first input gear and rotates the first sun gear without rotating itself when the rotation of the first sun gear is not locked by the locking portion. The second planetary gear revolves by the rotation of the second input gear and rotates the second sun gear without rotating itself when the rotation of the second sun gear is not locked by the locking portion.

[0007] A sheet conveying device according to another aspect of the present invention comprises a conveying member and a drive force transmission mechanism. The conveying member is used for conveying sheets. The drive force transmission mechanism transmits the rotational drive force to the conveying member.

[0008] An image forming apparatus according to another aspect of the present invention comprises a sheet transport device and an image forming unit. The image forming unit forms an image on a sheet transported by the sheet transport device. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress the generation of vibration and noise. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view showing the configuration of the image forming unit of an image forming apparatus according to an embodiment of the present invention. [Figure 3] Figure 3 is a perspective view showing the configuration of the driving force transmission mechanism of an image forming apparatus according to an embodiment of the present invention. [Figure 4] Figure 4 is a right side view showing the configuration of the driving force transmission mechanism of an image forming apparatus according to an embodiment of the present invention. [Figure 5]Figure 5 is a right side view showing the configuration of the driving force transmission mechanism of an image forming apparatus according to an embodiment of the present invention. [Figure 6] Figure 6 is a left side view showing the configuration of the driving force transmission mechanism of an image forming apparatus according to an embodiment of the present invention. [Figure 7] Figure 7 is a rear view showing the configuration of the drive force transmission mechanism of an image forming apparatus according to an embodiment of the present invention. [Figure 8] Figure 8 is a right side view showing the configuration of the first planetary gear mechanism and the second planetary gear mechanism of an image forming apparatus according to an embodiment of the present invention. [Figure 9] Figure 9 is a cross-sectional view taken along the line IX-IX in Figure 8. [Figure 10] Figure 10 is an exploded view of the first planetary gear mechanism and the second planetary gear mechanism shown in Figure 9. [Figure 11] Figure 11 is an exploded view of the first planetary gear mechanism and the second planetary gear mechanism of an image forming apparatus according to an embodiment of the present invention. [Figure 12] Figure 12 is an exploded view of the first and second planetary gear mechanisms of a conventional drive force transmission mechanism. [Figure 13] Figure 13 is an exploded view of the first and second planetary gear mechanisms of a conventional drive force transmission mechanism. [Figure 14] Figure 14 is a perspective view showing the configuration of the ratchet teeth of the first input side gear of an image forming apparatus according to an embodiment of the present invention. [Figure 15] Figure 15 is a cross-sectional view showing the configuration of the first planetary gear of an image forming apparatus according to an embodiment of the present invention. [Figure 16] Figure 16 is a cross-sectional view showing the configuration of the first planetary gear of an image forming apparatus according to an embodiment of the present invention. [Figure 17] Figure 17 is a cross-sectional view showing the configuration of the second planetary gear of an image forming apparatus according to an embodiment of the present invention. [Figure 18] Figure 18 is a cross-sectional view showing the configuration of the second planetary gear of an image forming apparatus according to an embodiment of the present invention. [Figure 19]FIG. 19 is an exploded view of the first planetary gear mechanism and the second planetary gear mechanism of the image forming apparatus according to an embodiment of the present invention. [Figure 20] FIG. 20 is an exploded view of the first planetary gear mechanism and the second planetary gear mechanism of the image forming apparatus according to an embodiment of the present invention. [Embodiments for Carrying Out the Invention]

[0011] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments are merely examples of embodying the present invention and do not limit the technical scope of the present invention.

[0012] [Configuration of Image Forming Apparatus 100] First, the configuration of the image forming apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. Here, FIG. 2 is a cross-sectional view showing the configuration of the image forming unit 14. FIG. 3 is a perspective view showing the configuration of the paper discharge roller 36B and the driving force transmission mechanism 3.

[0013] For convenience of explanation, in the installation state (the state shown in FIG. 1) in which the image forming apparatus 100 can be used, the vertical direction is defined as the up-down direction D1. Also, with the left side surface of the paper surface of the image forming apparatus 100 shown in FIG. as the front (front surface), the front-rear direction D2 is defined. Further, with reference to the front surface of the image forming apparatus 100 in the installation state, the left-right direction D3 is defined.

[0014] The image forming apparatus 100 is a printer having a printing function of forming an image based on image data on a sheet. Note that the image forming apparatus of the present invention is not limited to a printer, and any apparatus having the printing function may be used.

[0015] As shown in FIG. 1, the image forming apparatus 100 includes an image forming unit 1 and a sheet conveying unit 2.

[0016] The image forming unit 1 implements the printing function. Specifically, the image forming unit 1 forms a color or monochrome image on the sheet supplied from the sheet transport unit 2 according to an electrophotographic method. The image forming unit 1 may also form an image on the sheet using an image forming method other than electrophotographic, such as an inkjet method.

[0017] As shown in Figure 1, the image forming unit 1 comprises a plurality of image forming units 11 to 14, an optical scanning device 15, an intermediate transfer belt 16, a secondary transfer roller 17, a fixing device 18, and a paper output tray 19.

[0018] Image forming unit 11 uses yellow (Y) toner to form a toner image on the intermediate transfer belt 16. Image forming unit 12 uses cyan (C) toner to form a toner image on the intermediate transfer belt 16. Image forming unit 13 uses magenta (M) toner to form a toner image on the intermediate transfer belt 16. Image forming unit 14 uses black (K) toner to form a toner image on the intermediate transfer belt 16. As shown in Figure 1, image forming units 11 to 14 are arranged along the front-to-back direction D2 of the image forming apparatus 100, in the order of yellow, cyan, magenta, and black from the front side of the image forming apparatus 100.

[0019] As shown in Figure 2, the image forming unit 14 comprises a photoreceptor drum 21, a charging roller 22, a developing device 23, a primary transfer roller 24, and a drum cleaning unit 25. Each of the image forming units 11 to 13 has the same configuration as the image forming unit 14. Each of the image forming units 11 to 14 also comprises a toner container 26 as shown in Figure 1.

[0020] An electrostatic latent image is formed on the photoreceptor drum 21. The photoreceptor drum 21 receives rotational driving force supplied from a motor (not shown) and rotates in the drum rotation direction D4 shown in Figure 2. This causes the photoreceptor drum 21 to transport the electrostatic latent image formed on its surface.

[0021] The charging roller 22 receives a preset charging voltage and charges the surface of the photoreceptor drum 21. The surface of the photoreceptor drum 21, which has been charged by the charging roller 22, is irradiated with light based on image data emitted from the optical scanning device 15. As a result, an electrostatic latent image is formed on the surface of the photoreceptor drum 21.

[0022] The developing device 23 develops the electrostatic latent image formed on the surface of the photoreceptor drum 21. The developing device 23 includes a pair of agitators and a developing roller. The pair of agitators agitate the toner and carrier contained inside the developing device 23. This agitation causes the toner and carrier to become triboelectrically charged. The developing roller scoops up the toner agitated by the pair of agitators and transports the scooped-up toner to the area opposite the photoreceptor drum 21. The developing roller also receives a preset developing bias voltage and supplies the toner transported to the area opposite the photoreceptor drum 21 to the photoreceptor drum 21. As a result, toner is selectively supplied to the exposure area on the photoreceptor drum 21 that has been irradiated with light emitted from the light scanning device 15, and the electrostatic latent image formed on the surface of the photoreceptor drum 21 is developed. The developing device 23 is supplied with toner from the toner container 26.

[0023] The primary transfer roller 24 receives a preset primary transfer current and transfers the toner image formed on the surface of the photoreceptor drum 21 to the intermediate transfer belt 16.

[0024] The drum cleaning unit 25 removes toner remaining on the surface of the photoreceptor drum 21 after the toner image has been transferred by the primary transfer roller 24.

[0025] The optical scanning device 15 emits light based on image data toward the surface of the photosensitive drum 21 of each of the image forming units 11 to 14.

[0026] The toner images formed on the surface of the photoreceptor drums 21 of each of the image forming units 11 to 14 are transferred to the intermediate transfer belt 16. The intermediate transfer belt 16 is stretched at a predetermined tension by a drive roller, a tension roller, and four primary transfer rollers 24. The intermediate transfer belt 16 rotates in the belt rotation direction D5 shown in Figures 1 and 2, as the drive roller rotates in response to rotational driving force supplied from a motor (not shown). In this way, the intermediate transfer belt 16 transports the transferred toner images.

[0027] The secondary transfer roller 17 receives a preset secondary transfer current and transfers the toner image transferred to the surface of the intermediate transfer belt 16 to the sheet being transported by the sheet transport unit 2. The secondary transfer roller 17 is positioned opposite the drive roller, with the intermediate transfer belt 16 in between. The secondary transfer roller 17 is biased toward the drive roller by a biasing member (not shown). This forms a transfer nip portion between the intermediate transfer belt 16 and the secondary transfer roller 17 that grips the sheet. The secondary transfer roller 17 is positioned between the paper feed path 35 and the paper discharge path 36 and presses against the sheet passing through the transfer nip portion, transporting the sheet in the second transport direction D7 (see Figure 1).

[0028] The fixing device 18 fixes the toner image transferred to the sheet by the secondary transfer roller 17 to the sheet. The fixing device 18 comprises a fixing member and a pressurizing member. The fixing member is a roller-shaped or belt-shaped member that heats the toner image transferred to the sheet. The temperature of the fixing member is maintained at a predetermined target temperature by a heater (not shown). The pressurizing member is a roller-shaped member that pressurizes the sheet. The pressurizing member is biased toward the fixing member by a biasing member (not shown). This forms a fixing nip portion that grips the sheet between the fixing member and the pressurizing member. The pressurizing member is provided in the paper discharge path 36 and presses against the sheet passing through the fixing nip portion to transport the sheet in the second transport direction D7 (see Figure 1).

[0029] The output tray 19 receives a sheet on which the toner image has been fixed by the fuser unit 18.

[0030] The sheet transport unit 2 transports the sheet on which the image is formed by the image forming unit 1. The sheet transport unit 2 is an example of the sheet transport device of the present invention.

[0031] As shown in Figure 1, the sheet transport unit 2 includes a paper feed cassette 31, a pickup roller 32, a paper feed roller 33, a separation roller 34, a paper feed path 35, a paper discharge path 36, and a reversing transport path 37. The sheet transport unit 2 also includes a drive force transmission mechanism 3 and a motor 4, as shown in Figure 3.

[0032] The paper feed cassette 31 houses the sheets on which images are formed by the image forming unit 1. For example, the paper feed cassette 31 can hold sheets such as paper, coated paper, postcards, envelopes, and OHP sheets. A lift plate 31A (see Figure 1) is provided at the bottom of the paper feed cassette 31. The lift plate 31A lifts the bundle of sheets housed in the paper feed cassette 31 to a position where it contacts the pickup roller 32.

[0033] The pickup roller 32 is located above the paper feed cassette 31. The pickup roller 32 contacts the top sheet in the sheet stack lifted by the lift plate 31A and transports the sheet to the paper feed roller 33.

[0034] The paper feed roller 33 is located in the paper feed path 35 and contacts the upper surface of the sheet being transported by the pickup roller 32, thereby transporting the sheet in the first transport direction D6 (see Figure 1).

[0035] The separation roller 34 is located below the paper feed roller 33. The separation roller 34 is biased toward the paper feed roller 33 by a biasing member (not shown). This forms a paper feed nip between the paper feed roller 33 and the separation roller 34, which grips the sheets. When multiple sheets are conveyed to the nip, the separation roller 34 separates the sheets that are in contact with the paper feed roller 33 from the other sheets.

[0036] The paper feed path 35 is the passage through which the sheet moves from the paper feed cassette 31 to the transfer nip section where the toner image is transferred by the secondary transfer roller 17. In the paper feed path 35, the sheet is transported in the first transport direction D6 shown in Figure 1.

[0037] The paper discharge path 36 is a passage for the movement of sheets from the transfer nip section, through the fixing nip section, to the paper discharge tray 19. In the paper discharge path 36, the sheets are transported in the second transport direction D7 shown in Figure 1. A sheet discharge port 36A (see Figure 1) is provided at the downstream end of the paper discharge path 36 in the second transport direction D7. The sheet discharge port 36A opens in the sheet discharge direction D9 shown in Figure 1. The sheet discharge port 36A discharges the sheets on which the toner image has been fixed by the fixing device 18. Specifically, the sheet discharge port 36A is provided with a pair of paper discharge rollers consisting of a paper discharge roller 36B (see Figure 1) and a driven roller 36E (see Figure 1). The paper discharge roller 36B transports the sheets to the paper discharge tray 19. The paper discharge roller 36 is an example of a transport member of the present invention.

[0038] The inversion transport path 37 is used to invert the sheet after it has passed through the secondary transfer roller 17 and the fixing device 18, and to re-transport the sheet to the secondary transfer roller 17 and the fixing device 18. The inversion transport path 37 branches off from the paper discharge path 36 at a branching position P1 (see Figure 1) downstream of the fixing device 18 in the second transport direction D7. The inversion transport path 37 also merges with the paper feed path 35 at a merging position P2 (see Figure 1) upstream of the secondary transfer roller 17 in the first transport direction D6. In the inversion transport path 37, the sheet is transported in the third transport direction D8 shown in Figure 1.

[0039] As shown in Figure 1, a movable guide member 36C is provided at the branching position P1 in the paper discharge path 36. The movable guide member 36C is provided so as to be able to change its posture between a first posture (see Figure 1) in which sheets being transported in the second transport direction D7 are guided to the sheet discharge port 36A, and a second posture in which sheets being transported in the opposite direction to the second transport direction D7 by the paper discharge roller 36B are guided to the reverse transport path 37.

[0040] In the image forming apparatus 100, when an image is formed on both sides of a sheet, the paper discharge roller 36B and the movable guide member 36C are used to send the sheet with an image formed on one side to the reverse transport path 37. Specifically, in the image forming apparatus 100, after the rear end of the sheet being transported in the second transport direction D7 has passed the branching position P1 and before the sheet is discharged to the paper discharge tray 19, the rotation direction of the paper discharge roller 36B is switched. As a result, the sheet is transported in the opposite direction to the second transport direction D7. Also, in the image forming apparatus 100, the posture of the movable guide member 36C is switched from the first posture to the second posture. As a result, the sheet being transported in the opposite direction to the second transport direction D7 is guided to the reverse transport path 37.

[0041] Motor 4 rotates the paper discharge roller 36B. In this embodiment, motor 4 rotates in only one direction.

[0042] The power transmission mechanism 3 transmits the rotational power of the motor 4 to the paper discharge roller 36B. Furthermore, the power transmission mechanism 3 can switch the rotation direction of the paper discharge roller 36B.

[0043] [Configuration of the drive force transmission mechanism 3] Next, the configuration of the drive force transmission mechanism 3 will be described with reference to Figures 3 to 6. Here, Figure 4 is a right side view showing the configuration of the drive force transmission mechanism 3 when the output gear 45 is rotated by the first planetary gear mechanism 43. Figure 5 is a right side view showing the configuration of the drive force transmission mechanism 3 when the output gear 45 is rotated by the second planetary gear mechanism 44. Figure 6 is a left side view showing the configuration of the drive force transmission mechanism 3 when the output gear 45 is rotated by the first planetary gear mechanism 43. Note that in Figures 4 to 6, the transmission path of rotational drive force from the input gear 42 to the third transmission gear 49 is shown by a dashed line.

[0044] As shown in Figures 3 and 4, the drive force transmission mechanism 3 comprises a pair of support walls 41A and 41B, an input gear 42, a first planetary gear mechanism 43, a second planetary gear mechanism 44, an output gear 45, a switching section 46, a first transmission gear 47, a second transmission gear 48, and a third transmission gear 49.

[0045] A pair of support walls 41A and 41B rotatably support each of the gears included in the drive force transmission mechanism 3. Support walls 41A and 41B are each flat plate-shaped members and are arranged opposite each other in the left-right direction D3. Each of the gears included in the drive force transmission mechanism 3 is positioned in the space between the pair of support walls 41A and 41B.

[0046] The rotational driving force of the motor 4 is input to the input gear 42.

[0047] The output gear 45 outputs the rotational driving force of the motor 4, which is input to the input gear 42.

[0048] The first planetary gear mechanism 43 receives the rotational driving force from the motor 4 transmitted from the input gear 42 and rotates the output gear 45 in the first direction D21 shown in Figure 4.

[0049] The second planetary gear mechanism 44 receives the rotational driving force of the motor 4 transmitted from the input gear 42 via the first planetary gear mechanism 43, and rotates the output gear 45 in the second direction D22 (see Figure 5), which is opposite to the first direction D21.

[0050] The switching unit 46 switches the planetary gear mechanism that rotates the output gear 45 between the first planetary gear mechanism 43 and the second planetary gear mechanism 44.

[0051] As shown in Figure 6, the first transmission gear 47 is provided in mesh with the output gear 45 and the second transmission gear 48. The first transmission gear 47 transmits the rotational driving force of the motor 4 transmitted from the output gear 45 to the second transmission gear 48.

[0052] As shown in Figure 6, the second transmission gear 48 is provided in mesh with the first transmission gear 47 and the third transmission gear 49. The second transmission gear 48 transmits the rotational driving force of the motor 4 transmitted from the first transmission gear 47 to the third transmission gear 49.

[0053] As shown in Figure 3, the third transmission gear 49 is provided at one end of the rotating shaft 36D (see Figure 3) of the paper discharge roller 36B. The third transmission gear 49 is rotatably mounted integrally with the paper discharge roller 36B and the rotating shaft 36D. As shown in Figure 6, the third transmission gear 49 is meshed with the second transmission gear 48.

[0054] The third transmission gear 49 receives rotational driving force from the motor 4 transmitted from the second transmission gear 48 and rotates in the third direction D11 shown in Figure 4, or the fourth direction D12 shown in Figure 5. Specifically, when the output gear 45 rotates in the first direction D21 (see Figure 4), the third transmission gear 49 rotates in the third direction D11 (see Figure 4). As a result, the paper discharge roller 36B transports the sheet in the sheet discharge direction D9 (see Figure 3). Also, when the output gear 45 rotates in the second direction D22 (see Figure 5), the third transmission gear 49 rotates in the fourth direction D12 (see Figure 5). As a result, the paper discharge roller 36B transports the sheet in the opposite direction to the sheet discharge direction D9 (see Figure 3).

[0055] [Configuration of the first planetary gear mechanism 43] Next, the configuration of the first planetary gear mechanism 43 will be explained with reference to Figures 4 to 11.

[0056] As shown in Figures 8 to 10, the first planetary gear mechanism 43 comprises a first input gear 51, two first planetary gears 52, a first sun gear 53, and a first output gear 54.

[0057] As shown in Figure 6, the first input gear 51 meshes with the input gear 42. As shown in Figures 10 and 11, the first input gear 51 comprises a rotating shaft 51A, a gear section 51B, two rotating shafts 51C, and a connecting section 51D. The rotating shaft 51A rotatably supports the first sun gear 53 and the first output gear 54. The gear section 51B is a disc-shaped portion that rotates around the rotating shaft 51A, and has teeth formed on its outer circumference that mesh with the input gear 42. The gear section 51B is formed to be rotatable integrally with the rotating shaft 51A. The two rotating shafts 51C are provided protruding from positions on either side of the center of one side portion 51E (see Figure 11) of the gear section 51B. Each of the rotating shafts 51C rotatably supports the first planetary gear 52. The connecting portion 51D is provided as a hollow cylindrical projection from a circular opening formed in the center of the side portion 51E. The connecting portion 51D connects the rotating shaft 51A and the gear portion 51B. The connecting portion 51D forms a housing space for housing the sun gear portion 53B (see Figure 11) of the first sun gear 53. The connecting portion 51D also includes a pair of window portions 51F (see Figure 11) that face the teeth of the sun gear portion 53B toward each of the rotating shafts 51C.

[0058] Each of the first planetary gears 52 is supported so as to be able to rotate on the side portion 51E (an example of the first side portion of the present invention) of the first input gear 51. Each of the first planetary gears 52 has an axial hole portion 52A (see Figure 10) through which it is inserted onto the rotating shaft 51C of the first input gear 51. Each of the first planetary gears 52 also has a tooth portion 52B (see Figure 10) that meshes with the sun gear portion 53B (see Figure 10) of the first sun gear 53 and the inner circumference gear portion 54C (see Figure 10) of the first output gear 54.

[0059] The first sun gear 53 is mounted coaxially with the first input gear 51 and meshes with each of the first planetary gears 52. As shown in Figures 10 and 11, the first sun gear 53 comprises a cylindrical portion 53A, a sun gear portion 53B, and a engaged gear portion 53C. The cylindrical portion 53A is formed so that the rotation shaft 51A of the first input gear 51 can be inserted through it. The sun gear portion 53B is the outer circumference of the cylindrical portion 53A that forms teeth that mesh with each of the first planetary gears 52. The sun gear portion 53B is formed at one end of the cylindrical portion 53A in its longitudinal direction. The engaged gear portion 53C is formed at the other end of the cylindrical portion 53A in its longitudinal direction. The engaged gear portion 53C is a disc-shaped part that rotates around the cylindrical portion 53A, and has teeth formed on its outer circumference that engage with the engaging portion 72C (see Figure 4) of the switching portion 46.

[0060] As shown in Figure 6, the first output gear 54 meshes with the output gear 45. As shown in Figure 6, the first output gear 54 is mounted coaxially with the first input gear 51. As shown in Figures 10 and 11, the first output gear 54 comprises a gear portion 54A, a cylindrical portion 54B, and an inner circumferential gear portion 54C (an example of the first inner circumferential gear portion of the present invention). The gear portion 54A is a disc-shaped portion having an axial hole that is inserted through the rotating shaft 51A of the first input gear 51, and has teeth formed on its outer circumference that engage with the output gear 45. The cylindrical portion 54B is formed as a cylinder with a larger diameter than the gear portion 54A and is open at one end. The gear portion 54A is formed on one side surface of the cylindrical portion 54B. The cylindrical portion 54B rotates integrally with the gear portion 54A around the rotation axis 51A of the first input gear 51. The cylindrical portion 54B houses the two first planetary gears 52. The inner circumference gear portion 54C is formed on the inner circumference of the cylindrical portion 54B. The inner circumference gear portion 54C meshes with each of the first planetary gears 52.

[0061] [Configuration of the second planetary gear mechanism 44] Next, the configuration of the second planetary gear mechanism 44 will be explained with reference to Figures 4 to 11.

[0062] As shown in Figures 8 to 10, the second planetary gear mechanism 44 comprises a second input gear 61, two second planetary gears 62, a second sun gear 63, and a second output gear 64.

[0063] As shown in Figure 6, the second input gear 61 meshes with the first input gear 51 of the first planetary gear mechanism 43. As shown in Figures 10 and 11, the second input gear 61 comprises a rotating shaft 61A, a gear section 61B, two rotating shafts 61C, and a connecting section 61D. The rotating shaft 61A rotatably supports the second sun gear 63 and the second output gear 64. The gear section 61B is a disc-shaped portion that rotates around the rotating shaft 61A, and has teeth formed on its outer circumference that mesh with the first input gear 51 of the first planetary gear mechanism 43. The gear section 61B is formed to be rotatable integrally with the rotating shaft 61A. The two rotating shafts 61C are provided protruding from positions on either side of the center of one side portion 61E (see Figure 11) of the gear section 61B. Each of the rotating shafts 61C rotatably supports the second planetary gear 62. The connecting portion 61D is provided projecting in a hollow cylindrical shape from a circular opening formed in the center of the side portion 61E. The connecting portion 61D connects the rotating shaft 61A and the gear portion 61B. The connecting portion 61D also includes a pair of window portions 61F (see Figure 11) that face the teeth of the sun gear portion 63B toward each of the rotating shafts 61C.

[0064] Each of the second planetary gears 62 is supported so as to be able to rotate on the side portion 61E (an example of the second side portion of the present invention) of the second input gear 61. Each of the second planetary gears 62 is provided with an axial hole portion 62A (see Figure 10) through which the rotation axis 61C of the second input gear 61 is inserted. Each of the second planetary gears 62 is also provided with teeth portion 62B (see Figure 10) that mesh with the sun gear portion 63B (see Figure 10) of the second sun gear 63 and the inner circumference gear portion 64C (see Figure 10) of the second output gear 64.

[0065] The second sun gear 63 is mounted coaxially with the second input gear 61 and meshes with each of the second planetary gears 62. As shown in Figures 10 and 11, the second sun gear 63 comprises a cylindrical portion 63A, a sun gear portion 63B, and a engaged gear portion 63C. The cylindrical portion 63A is formed so that the rotation shaft 61A of the second input gear 61 can be inserted through it. The sun gear portion 63B is the outer circumference of the cylindrical portion 63A that forms teeth that mesh with each of the second planetary gears 62. The sun gear portion 63B is formed at one end of the cylindrical portion 63A in its longitudinal direction. The engaged gear portion 63C is formed at the other end of the cylindrical portion 63A in its longitudinal direction. The engaged gear portion 63C is a disc-shaped part that rotates around the cylindrical portion 63A, and has teeth formed on its outer circumference that engage with the engaging portion 72C (see Figure 4) of the switching portion 46.

[0066] As shown in Figure 6, the second output gear 64 meshes with the output gear 45. As shown in Figure 6, the second output gear 64 is mounted coaxially with the second input gear 61. As shown in Figures 10 and 11, the second output gear 64 comprises a gear portion 64A, a cylindrical portion 64B, and an inner circumferential gear portion 64C (an example of the second inner circumferential gear portion of the present invention). The gear portion 64A is a disc-shaped portion having an axial hole that is inserted into the rotating shaft 61A of the second input gear 61, and has teeth formed on its outer circumference that engage with the output gear 45. The cylindrical portion 64B is formed as a cylinder with a larger diameter than the gear portion 64A and is open at one end. The gear portion 64A is formed on one side surface of the cylindrical portion 64B. The cylindrical portion 64B rotates integrally with the gear portion 64A around the rotation axis 61A of the second input gear 61. The cylindrical portion 64B houses the two second planetary gears 62. The inner circumference gear portion 64C is formed on the inner circumference of the cylindrical portion 64B. The inner circumference gear portion 64C meshes with each of the second planetary gears 62.

[0067] [Configuration of switching unit 46] Next, the configuration of the switching unit 46 will be described with reference to Figures 4 and 5.

[0068] As shown in Figure 4, the switching unit 46 includes a solenoid 71 and a rotating arm 72.

[0069] The rotating arm 72 is rotatably mounted around the rotation axis 45A (see Figure 4) of the output gear 45. As shown in Figure 4, the rotating arm 72 comprises a first arm 72A, a second arm 72B, and an engaging portion 72C. The first arm 72A extends radially from the rotation axis 45A toward the solenoid 71. The second arm 72B extends radially from the rotation axis 45A toward the space between the engaged gear portion 53C (see Figure 4) of the first planetary gear mechanism 43 and the engaged gear portion 63C (see Figure 4) of the second planetary gear mechanism 44. The engaging portion 72C is provided at the extended end of the second arm 72B so as to be engageable with the engaged gear portion 53C or the engaged gear portion 63C. The first arm 72A, the second arm 72B, and the engaging portion 72C are formed to be rotatable as a single unit around the rotation axis 45A (see Figure 4).

[0070] The solenoid 71 rotates the rotating arm 72 between a first position (see Figure 4) in which the engaging portion 72C engages with the engaged gear portion 53C (see Figure 4) of the first planetary gear mechanism 43, and a second position (see Figure 5) in which the engaging portion 72C engages with the engaged gear portion 63C (see Figure 5) of the second planetary gear mechanism 44. As shown in Figure 4, the solenoid 71 includes a plunger 71A. The plunger 71A is connected to the extended end of the first arm 72A of the rotating arm 72. The solenoid 71 rotates the rotating arm 72 between the first position and the second position by moving the plunger 71A forward and backward.

[0071] The engaging portion 72C of the rotating arm 72 engages with the engaged gear portion 53C of the first planetary gear mechanism 43 when the rotating arm 72 is positioned in the first position, thereby locking the rotation of the first sun gear 53. Furthermore, the engaging portion 72C of the rotating arm 72 engages with the engaged gear portion 63C of the second planetary gear mechanism 44 when the rotating arm 72 is positioned in the second position, thereby locking the rotation of the second sun gear 63. The engaging portion 72C is an example of a locking portion of the present invention.

[0072] Here, the operation of a conventional drive force transmission mechanism will be explained with reference to Figures 12 and 13. Figure 12 shows the operation of the first planetary gear mechanism 43 and the second planetary gear mechanism 44 when the rotation of the first sun gear 53 is locked. Figure 13 shows the operation of the first planetary gear mechanism 43 and the second planetary gear mechanism 44 when the rotation of the second sun gear 63 is locked.

[0073] First, referring to Figure 12, we will explain the operation of the conventional drive force transmission mechanism when the rotation of the first sun gear 53 is locked.

[0074] The first input gear 51 of the first planetary gear mechanism 43, which meshes with the input gear 42 (see Figure 4), rotates in the direction of the arrow shown in Figure 12 when the rotational driving force of the motor 4 is input to the input gear 42. As a result, each of the first planetary gears 52 revolves around the rotation axis 51A of the first input gear 51 in the same direction as the rotation of the first input gear 51. In addition, the second input gear 61 of the second planetary gear mechanism 44, which meshes with the first input gear 51, rotates in the direction of the arrow shown in Figure 12. In addition, each of the second planetary gears 62 revolves around the rotation axis 61A of the second input gear 61 in the same direction as the rotation of the second input gear 61.

[0075] Here, in the first planetary gear mechanism 43, the rotation of the first sun gear 53 is locked. Therefore, the rotational driving force of the motor 4 is transmitted to each of the first planetary gears 52 via the sun gear portion 53B of the first sun gear 53, whose rotation is locked. As a result, the rotational driving force of the motor 4 is transmitted to the output gear 45 via each of the first planetary gears 52 and the first output gear 54. Consequently, each of the first planetary gears 52 and the first output gear 54 rotate in the direction of the arrow shown in Figure 12. In addition, the output gear 45 rotates in the first direction D21 (see Figure 12).

[0076] On the other hand, in the second planetary gear mechanism 44, the rotation of the second sun gear 63 is not locked. Therefore, the rotational driving force of the motor 4 is not transmitted to each of the second planetary gears 62. As a result, the second sun gear 63, each of the second planetary gears 62, and the second output gear 64 rotate in the direction of the arrows shown in Figure 12, receiving the rotational driving force of the motor 4 transmitted via the output gear 45.

[0077] Next, referring to Figure 13, the operation of the conventional drive force transmission mechanism when the rotation of the second sun gear 63 is locked will be described.

[0078] The first input gear 51 of the first planetary gear mechanism 43, which meshes with the input gear 42 (see Figure 4), rotates in the direction of the arrow shown in Figure 13 when the rotational driving force of the motor 4 is input to the input gear 42. As a result, each of the first planetary gears 52 revolves around the rotation axis 51A of the first input gear 51 in the same direction as the rotation of the first input gear 51. In addition, the second input gear 61 of the second planetary gear mechanism 44, which meshes with the first input gear 51, rotates in the direction of the arrow shown in Figure 13. In addition, each of the second planetary gears 62 revolves around the rotation axis 61A of the second input gear 61 in the same direction as the rotation of the second input gear 61.

[0079] Here, in the second planetary gear mechanism 44, the rotation of the second sun gear 63 is locked. Therefore, the rotational driving force of the motor 4 is transmitted to each of the second planetary gears 62 via the sun gear portion 63B of the second sun gear 63, whose rotation is locked. As a result, the rotational driving force of the motor 4 is transmitted to the output gear 45 via each of the second planetary gears 62 and the second output gear 64. Consequently, each of the second planetary gears 62 and the second output gear 64 rotate in the direction of the arrow shown in Figure 13. In addition, the output gear 45 rotates in the second direction D22 (see Figure 13).

[0080] On the other hand, in the first planetary gear mechanism 43, the rotation of the first sun gear 53 is not locked. Therefore, the rotational driving force of the motor 4 is not transmitted to each of the first planetary gears 52. As a result, the first sun gear 53, each of the first planetary gears 52, and the first output gear 54 rotate in the direction of the arrow shown in Figure 13, receiving the rotational driving force of the motor 4 transmitted via the output gear 45.

[0081] Incidentally, in conventional drive force transmission mechanisms, in the planetary gear mechanism on the side where the rotation of the sun gear is not locked, each planetary gear rotates in the opposite direction to the rotation direction of the input gear. Therefore, in conventional drive force transmission mechanisms, vibration and noise are generated in the planetary gear mechanism on the side where the output gear 45 is not rotated.

[0082] In contrast, the image forming apparatus 100 according to the embodiment of the present invention can suppress the generation of vibration and noise, as will be explained below.

[0083] Specifically, each of the first planetary gears 52 is provided to be movable between a first meshing position (see Figure 16) in which it meshes with the inner circumferential gear portion 54C along the rotation axis 51C of the first planetary gear 52 due to its rotation, and a first non-meshing position (see Figure 15) which is on the side surface 51E side of the first meshing position and does not mesh with the inner circumferential gear portion 54C.

[0084] More specifically, the first input gear 51 of the first planetary gear mechanism 43 has ratchet teeth 51G (see Figure 14) formed on its side surface 51E around the rotation axis 51C of each of the first planetary gears 52. Each of the first planetary gears 52 also has ratchet teeth 52C (see Figure 15) that mesh with the ratchet teeth 51G. The ratchet teeth 52C are formed on the side surface of the first planetary gear 52 that faces the side surface 51E. As a result, each of the first planetary gears 52 can rotate in only one direction, and this rotation causes it to oscillate along the rotation axis 51C.

[0085] Furthermore, the first planetary gear mechanism 43 includes a coil spring 81 (see Figure 15) and a spring support portion 51H (see Figure 15) corresponding to each of the first planetary gears 52. The coil spring 81 is inserted through the rotation shaft 51C of the first planetary gear 52. The spring support portion 51H is provided at the tip of the rotation shaft 51C. The spring support portion 51H supports one end of the coil spring 81. The coil spring 81 is compressed between the first planetary gear 52 and the spring support portion 51H. The coil spring 81 biases each of the first planetary gears 52 in the direction from the first meshing position to the first dismeeting position. The coil spring 81 is an example of the first biasing portion of the present invention.

[0086] Furthermore, in the first planetary gear mechanism 43, each of the first planetary gears 52, when the rotation of the first sun gear 53 is not locked by the engaging portion 72C, revolves by the rotation of the first input gear 51 and rotates the first sun gear 53 without rotating on its own axis.

[0087] Furthermore, each of the second planetary gears 62 is provided to be movable between a second meshing position (see Figure 18) in which it meshes with the inner circumferential gear portion 64C along the rotation axis 61C of the second planetary gear 62 due to its rotation, and a second non-meshing position (see Figure 17) which is on the side surface 61E side of the second meshing position and does not mesh with the inner circumferential gear portion 64C.

[0088] More specifically, the second input gear 61 of the second planetary gear mechanism 44 has ratchet teeth 61G (see Figure 17) formed on its side surface 61E around the rotation axis 61C of each of the second planetary gears 62. Each of the second planetary gears 62 also has ratchet teeth 62C (see Figure 17) that mesh with the ratchet teeth 61G. The ratchet teeth 62C are formed on the side surface of the second planetary gear 62 that faces the side surface 61E. As a result, each of the second planetary gears 62 can rotate in only one direction, and this rotation causes it to oscillate along the rotation axis 61C.

[0089] Furthermore, the second planetary gear mechanism 44 includes a coil spring 82 (see Figure 17) and a spring support portion 61H (see Figure 17) corresponding to each of the second planetary gears 62. The coil spring 82 is inserted through the rotation shaft 61C of the second planetary gear 62. The spring support portion 61H is provided at the tip of the rotation shaft 61C. The spring support portion 61H supports one end of the coil spring 82. The coil spring 82 is compressed between the second planetary gear 62 and the spring support portion 61H. The coil spring 82 biases each of the second planetary gears 62 in the direction from the second meshing position to the second dismeshing position. The coil spring 82 is an example of the second biasing portion of the present invention.

[0090] Furthermore, in the second planetary gear mechanism 44, each of the second planetary gears 62, when the rotation of the second sun gear 63 is not locked by the engaging portion 72C, revolves by the rotation of the second input gear 61 and rotates the second sun gear 63 without rotating on its own axis.

[0091] Here, the operation of the drive force transmission mechanism 3 of the image forming apparatus 100 of the present invention will be described with reference to Figures 19 and 20. Figure 19 shows the operation of the first planetary gear mechanism 43 and the second planetary gear mechanism 44 when the rotation of the first sun gear 53 is locked. Figure 20 shows the operation of the first planetary gear mechanism 43 and the second planetary gear mechanism 44 when the rotation of the second sun gear 63 is locked.

[0092] First, referring to Figure 19, the operation of the drive force transmission mechanism 3 when the rotation of the first sun gear 53 is locked will be explained.

[0093] The first input gear 51 of the first planetary gear mechanism 43, which meshes with the input gear 42 (see Figure 4), rotates in the direction of the arrow shown in Figure 19 when the rotational driving force of the motor 4 is input to the input gear 42. As a result, each of the first planetary gears 52 revolves around the rotation axis 51A of the first input gear 51 in the same direction as the rotation of the first input gear 51. In addition, the second input gear 61 of the second planetary gear mechanism 44, which meshes with the first input gear 51, rotates in the direction of the arrow shown in Figure 19. In addition, each of the second planetary gears 62 revolves around the rotation axis 61A of the second input gear 61 in the same direction as the rotation of the second input gear 61.

[0094] Here, in the first planetary gear mechanism 43, the rotation of the first sun gear 53 is locked. Therefore, the rotational driving force of the motor 4 is transmitted to each of the first planetary gears 52 via the sun gear portion 53B of the first sun gear 53, whose rotation is locked. As a result, each of the first planetary gears 52 rotates in the direction of the arrow shown in Figure 19, and each of the first planetary gears 52 moves from the first non-meshing position (see Figure 15) to the first meshing position (see Figure 16). Therefore, each of the first planetary gears 52 meshes with the inner gear portion 54C, and the rotational driving force of the motor 4 is transmitted to the output gear 45 via each of the first planetary gears 52 and the first output gear 54. Consequently, the first output gear 54 rotates in the direction of the arrow shown in Figure 19. Also, the output gear 45 rotates in the first direction D21 (see Figure 19). Furthermore, when the first planetary gear 52 and the inner gear portion 54C mesh, the frictional force acting between them prevents the first planetary gear 52 from moving towards the first non-mesh position due to the biasing force of the coil spring 81. Therefore, the meshed state between the first planetary gear 52 and the inner gear portion 54C is maintained.

[0095] On the other hand, in the second planetary gear mechanism 44, the rotation of the second sun gear 63 is not locked. Therefore, the rotational driving force of the motor 4 is not transmitted to each of the second planetary gears 62. In other words, each of the second planetary gears 62 rotates the second sun gear 63 without rotating on its own axis. As a result, each of the second planetary gears 62 does not move from the second non-meshing position (see Figure 17) and does not mesh with the inner circumference gear portion 64C. Therefore, the rotational driving force of the motor 4 is not transmitted to each of the second planetary gears 62 via the output gear 45 and the second output side gear 64.

[0096] When the object to be locked by the engaging portion 72C switches from the first sun gear 53 to the second sun gear 63, each of the first planetary gears 52 receives the rotational driving force of the motor 4 via the first output gear 54 instead of the first sun gear 53, and rotates in the opposite direction to the arrows shown in Figure 19. Due to this rotation and the biasing force of the coil spring 81, each of the first planetary gears 52 moves from the first meshed position to the first dismeshed position.

[0097] Next, referring to Figure 20, the operation of the drive force transmission mechanism 3 when the rotation of the second sun gear 63 is locked will be described.

[0098] The first input gear 51 of the first planetary gear mechanism 43, which meshes with the input gear 42 (see Figure 4), rotates in the direction of the arrow shown in Figure 20 when the rotational driving force of the motor 4 is input to the input gear 42. As a result, each of the first planetary gears 52 revolves around the rotation axis 51A of the first input gear 51 in the same direction as the rotation of the first input gear 51. In addition, the second input gear 61 of the second planetary gear mechanism 44, which meshes with the first input gear 51, rotates in the direction of the arrow shown in Figure 20. In addition, each of the second planetary gears 62 revolves around the rotation axis 61A of the second input gear 61 in the same direction as the rotation of the second input gear 61.

[0099] Here, in the second planetary gear mechanism 44, the rotation of the second sun gear 63 is locked. Therefore, the rotational driving force of the motor 4 is transmitted to each of the second planetary gears 62 via the sun gear portion 63B of the second sun gear 63, whose rotation is locked. As a result, each of the second planetary gears 62 rotates in the direction of the arrow shown in Figure 20, and each of the second planetary gears 62 moves from the second non-meshing position (see Figure 17) to the second meshing position (see Figure 18). Therefore, each of the second planetary gears 62 meshes with the inner gear portion 64C, and the rotational driving force of the motor 4 is transmitted to the output gear 45 via each of the second planetary gears 62 and the second output gear 64. Consequently, the second output gear 64 rotates in the direction of the arrow shown in Figure 20. Also, the output gear 45 rotates in the second direction D22 (see Figure 20). Furthermore, when the second planetary gear 62 and the inner gear portion 64C mesh, the frictional force acting between them prevents the movement of the second planetary gear 62 toward the second non-meshing position due to the biasing force of the coil spring 82. Therefore, the meshed state between the second planetary gear 62 and the inner gear portion 64C is maintained.

[0100] On the other hand, in the first planetary gear mechanism 43, the rotation of the first sun gear 53 is not locked. Therefore, the rotational driving force of the motor 4 is not transmitted to each of the first planetary gears 52. In other words, each of the first planetary gears 52 rotates the first sun gear 53 without rotating on its own axis. As a result, each of the first planetary gears 52 does not move from the first non-meshing position (see Figure 15) to the first meshing position (see Figure 16) and does not mesh with the inner circumference gear portion 54C. Therefore, the rotational driving force of the motor 4 is not transmitted to each of the first planetary gears 52 via the output gear 45 and the first output side gear 54.

[0101] When the object to be locked by the engaging portion 72C switches from the second sun gear 63 to the first sun gear 53, each of the second planetary gears 62 receives the rotational driving force of the motor 4 via the second output gear 64 instead of the second sun gear 63, and rotates in the opposite direction to the arrows shown in Figure 20. Due to this rotation and the biasing force of the coil spring 82, each of the second planetary gears 62 moves from the second meshing position to the second dismeshed position.

[0102] Thus, in the image forming apparatus 100, when the rotation of the second sun gear 63 is not locked, each of the second planetary gears 62 does not mesh with the inner gear portion 64C. Similarly, in the image forming apparatus 100, when the rotation of the first sun gear 53 is not locked, each of the first planetary gears 52 does not mesh with the inner gear portion 54C. Therefore, in the planetary gear mechanism where the rotation of the sun gear is not locked, it is avoided that each planetary gear rotates in the opposite direction to the rotation direction of the input gear. Consequently, in the image forming apparatus 100, it is possible to suppress the generation of vibration and noise in the planetary gear mechanism where the output gear 45 is not rotated.

[0103] Each of the first planetary gears 52 may be biased by its own weight in the direction from the first meshed position to the first dismeshed position. Similarly, each of the second planetary gears 62 may be biased by its own weight in the direction from the second meshed position to the second dismeshed position. In this case, the drive force transmission mechanism 3 does not need to be equipped with coil springs 81 and 82.

[0104] Furthermore, each of the first planetary gears 52 may be permitted to rotate in both directions. For example, the first input gear 51 may have a first undulating surface that periodically undulates along the circumferential direction of the rotation axis 51C instead of ratchet teeth 51G. Also, each of the first planetary gears 52 may have a second undulating surface that can come into close contact with the first undulating surface.

[0105] Furthermore, each of the second planetary gears 62 may be permitted to rotate in both directions. For example, the second input gear 61 may have a third undulating surface that periodically undulates along the circumferential direction of the rotation axis 61C instead of ratchet teeth 61G. Also, each of the second planetary gears 62 may have a fourth undulating surface that can come into close contact with the third undulating surface.

[0106] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0107] <Appendix 1> The first planetary gear mechanism comprises an input gear to which the rotational driving force of a motor is input, an output gear to which the rotational driving force input to the input gear is output, a first planetary gear mechanism that receives the rotational driving force transmitted from the input gear and rotates the output gear in a first direction, a second planetary gear mechanism that receives the rotational driving force transmitted from the input gear via the first planetary gear mechanism and rotates the output gear in a second direction opposite to the first direction, and a switching unit that switches the planetary gear mechanism that rotates the output gear between the first planetary gear mechanism and the second planetary gear mechanism, wherein the first planetary gear mechanism The first input gear has a first input side gear that meshes with the input gear, a first planetary gear that is rotatably supported on the first side portion of the first input side gear, a first sun gear that is coaxial with the first input side gear and meshes with the first planetary gear, and a first output side gear that has a first inner circumference gear portion that meshes with the first planetary gear and is coaxial with the first input side gear and meshes with the output gear, and the second planetary gear mechanism has a second input side gear that meshes with the first input side gear, a second planetary gear that is rotatably supported on the second side portion of the second input side gear, and the second input side gear The first planetary gear is provided coaxially with the second planetary gear and has a second sun gear that meshes with the second planetary gear, and a second output gear that has a second inner gear portion that meshes with the second planetary gear and is provided coaxially with the second input gear and meshes with the output gear, and the switching unit has a locking portion that locks the rotation of either the first sun gear or the second sun gear, and the first planetary gear is movable by its rotation between a first meshing position in which it meshes with the first inner gear portion along the rotation axis of the first planetary gear and a first non-measuring position which is on the first side portion side of the first meshing position and does not mesh with the first inner gear portion The second planetary gear is provided so as to be movable between a second meshing position in which it meshes with the second inner gear portion along the rotation axis of the second planetary gear by its rotation and a second non-meshing position which is on the second side portion side of the second meshing position and does not mesh with the second inner gear portion, and the first planetary gear revolves by the rotation of the first input side gear and rotates the first sun gear without rotating itself when the rotation of the first sun gear is not locked by the locking portion, and the second planetary gear is provided so as to be movable between a second meshing position in which it meshes with the second inner gear portion along the rotation axis of the second planetary gear by its rotation and a second non-meshing position which is on the second side portion side of the second planetary gear and does not mesh with the second inner gear portion, and the first planetary gear revolves by the rotation of the first input side gear and rotates the first sun gear without rotating itself when the rotation of the second sun gear is not locked by the locking portion,A power transmission mechanism that rotates the second sun gear without rotating itself, while simultaneously revolving due to the rotation of the second input gear.

[0108] <Note 2> The drive force transmission mechanism according to Appendix 1, wherein the first planetary gear mechanism has a first biasing portion that biases the first planetary gear in a direction toward the first dismeet position from the first meshing position, and the second planetary gear mechanism has a second biasing portion that biases the second planetary gear in a direction toward the second dismeet position from the second meshing position.

[0109] <Note 3> A sheet conveying device comprising a conveying member used for conveying sheets, and a drive force transmission mechanism described in Appendix 1 or 2 for transmitting the rotational driving force to the conveying member.

[0110] <Note 4> An image forming apparatus comprising a sheet conveying device as described in Appendix 3, and an image forming unit that forms an image on a sheet conveyed by the sheet conveying device. [Explanation of symbols]

[0111] 1 Image forming unit 2 Sheet transport section 3. Power transmission mechanism 4 motors 36B Paper output roller 42 Input Gear 43. First planetary gear mechanism 44. Second planetary gear mechanism 45 Output gear 46 Switching section 47 First transmission gear 48 Second transmission gear 49 Third transmission gear 51 First input side gear 52 First Planetary Gear 53 First Solar Gear 54 First output side gear 61 Second input side gear 62 Second Planetary Gear 63 Second Solar Gear 64 Second output gear 71 Solenoid 72 Rotating Arms 81 Coil spring 82 Coil springs 100 Image forming apparatus

Claims

1. The input gear to which the rotational driving force of the motor is input, An output gear that outputs the rotational driving force input to the input gear, A first planetary gear mechanism that receives the rotational driving force transmitted from the input gear and rotates the output gear in a first direction, A second planetary gear mechanism receives the rotational driving force transmitted from the input gear via the first planetary gear mechanism and rotates the output gear in a second direction opposite to the first direction, A switching unit that switches between the first planetary gear mechanism and the second planetary gear mechanism for rotating the output gear, Equipped with, The first planetary gear mechanism is, A first input-side gear that meshes with the aforementioned input gear, A first planetary gear is supported so as to be able to rotate on the first side surface of the first input gear, A first sun gear is provided coaxially with the first input gear and meshes with the first planetary gear, A first inner gear portion that meshes with the first planetary gear, a first output gear that is provided coaxially with the first input gear and meshes with the output gear, It has, The second planetary gear mechanism is, A second input gear that meshes with the first input gear, A second planetary gear is supported on the second side portion of the second input gear so as to be rotatable, A second sun gear is provided coaxially with the second input gear and meshes with the second planetary gear, A second inner gear portion that meshes with the second planetary gear, a second output gear that is provided coaxially with the second input gear and meshes with the output gear, It has, The switching unit has a locking unit that locks the rotation of either the first sun gear or the second sun gear. The first planetary gear is provided so as to be movable between a first meshing position in which it meshes with the first inner circumferential gear portion along the rotation axis of the first planetary gear by rotation, and a first non-meshing position which is on the first side surface side of the first meshing position and does not mesh with the first inner circumferential gear portion. The second planetary gear is provided so as to be movable between a second meshing position, in which it meshes with the second inner circumferential gear portion along the rotation axis of the second planetary gear due to its rotation, and a second non-meshing position, which is on the second side surface side of the second meshing position and does not mesh with the second inner circumferential gear portion. When the rotation of the first sun gear is not locked by the locking portion, the first planetary gear revolves by the rotation of the first input gear and rotates the first sun gear without rotating on its own axis. The second planetary gear, when the rotation of the second sun gear is not locked by the locking portion, revolves by the rotation of the second input gear and rotates the second sun gear without rotating on its own axis. Power transmission mechanism.

2. The first planetary gear mechanism has a first biasing unit that biases the first planetary gear in the direction from the first meshing position to the first dismeeting position, The second planetary gear mechanism has a second biasing unit that biases the second planetary gear in the direction from the second meshing position to the second dismeeting position. The driving force transmission mechanism according to claim 1.

3. A conveying member used for transporting sheets, A drive force transmission mechanism according to claim 1 or 2 for transmitting the rotational drive force to the transport member, A sheet transport device equipped with the following features.

4. A sheet conveying device according to claim 3, An image forming unit that forms an image on a sheet conveyed by the sheet conveying device, An image forming apparatus equipped with the following features.

Images