Image forming device

Abstract

To provide an image forming apparatus that can save a space and facilitate assembly operations for a gear train that transmits and blocks a turning force to a conveying roller.SOLUTION: An image forming apparatus comprises a gear train that transmits a turning force from a driving force to a conveying roller conveying a sheet, and the gear train includes: a moving gear 33 that is supported movably between a normal position allowing the transmission of the turning force and a processing position blocking the transmission of the turning force and movably in an axial direction, and has a helical gear 41a that generates a force to move in one direction of the axial direction in the movement from the normal position to the processing position; and a leaf spring 61 that buffers the movement of the moving gear 33 in one direction of the axial direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus including a gear train that transmits a rotational force from a motor to a transport roller that transports paper. [Background technology]

[0002] The image forming apparatus includes a pair of transport rollers for transporting paper. The pair of transport rollers includes a drive roller and a driven roller that rotates following the drive roller. The drive roller is connected to a motor via a gear train, and rotates when a torque is transmitted from the motor via the gear train.

[0003] When a paper jam occurs during image formation, the paper may remain sandwiched between the pair of transport rollers. In response to this, one of the gears constituting the gear train may be provided so as to be movable between a normal position that allows the transmission of rotational force to the drive roller and a processing position that blocks the transmission of rotational force to the drive roller. When the gear is moved to the processing position to clear the paper jam, the drive roller rotates freely, allowing the sandwiched paper to be pulled out of the pair of transport rollers without significant resistance.

[0004] For example, the paper feeder described in Patent Document 1 includes a planetary gear mechanism (gear train) between a drive motor and a paper feed roller (drive roller). The planetary gear mechanism includes a sun gear, a planetary gear that meshes with the sun gear, and a first stage gear that meshes with the planetary gear. When a paper jam occurs, the drive motor (motor) is rotated in reverse for a predetermined time to rotate the sun gear in the reverse direction, thereby releasing the meshing between the planetary gear and the first stage gear. This blocks the transmission of rotational force from the drive motor to the paper feed roller. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-125873 Summary of the Invention [Problem to be solved by the invention]

[0006] The gear train described in Patent Document 1 may include, for example, a helical gear. In this case, when the motor is rotated in reverse, a force acts on the helical gear along the axial direction. This may cause the helical gear to fall off or become insufficiently meshed, so the axial movement of the helical gear is restricted by a compression coil spring. However, when using such a compression coil spring, it is necessary to stably support the compression coil spring while ensuring a space for arranging the compression coil spring and a compression allowance, which results in problems such as many design constraints and difficult assembly work.

[0007] In consideration of the above circumstances, an object of the present invention is to provide an image forming apparatus that can reduce space and facilitate assembly work in a gear train that transmits and blocks rotational force to a transport roller. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the image forming apparatus of the present invention is an image forming apparatus equipped with a gear train that transmits a rotational force from a drive source to a transport roller that transports paper, and is supported so as to be movable axially between a normal position that allows the transmission of the rotational force and a processing position that blocks the transmission of the rotational force, and is characterized in that it includes a movable gear having a helical gear that generates a force to move in one axial direction when moving from the normal position to the processing position, and a leaf spring that buffers the movement of the movable gear in one axial direction.

[0009] The image forming apparatus of the present invention may further include an outer plate and an inner plate which support both ends of the rotation shaft of the movable gear so that the movable gear can rotate and move between the normal position and the processing position, and the leaf spring has a fixed portion fixed to the outer plate, a pressing portion which is bent at an acute angle to the fixed portion and contacts the helical gear toward the other direction in the axial direction, and a tip portion which is bent from the tip of the pressing portion toward the fixed portion, and a predetermined clearance is provided between the tip portion and the outer plate.

[0010] In the image forming apparatus of the present invention, the movable gear may be disposed between the transport roller and a drive gear disposed upstream of the transport roller in a transmission direction of the rotational force. Effect of the Invention

[0011] According to the present invention, since a leaf spring is used to cushion the axial movement of the movable gear, the assembly work of the gear train can be facilitated. [Brief description of the drawings]

[0012] [Figure 1] 1 is a side view showing an image forming apparatus (with a cover plate attached) according to one embodiment of the present invention. [Diagram 2] 1 is a side view showing an image forming apparatus (with a cover plate removed) according to one embodiment of the present invention. [Diagram 3] 4 is a perspective view showing a movable gear and a leaf spring in the image forming apparatus according to the embodiment of the present invention; FIG. [Figure 4A] 1 is a side view showing a movable gear moved to a normal position in an image forming apparatus according to an embodiment of the present invention; [Figure 4B] 1 is a side view showing a movable gear that has been moved to a processing position in an image forming apparatus according to an embodiment of the present invention; [Diagram 5] FIG. 2 is a perspective view showing a leaf spring in the image forming apparatus according to the embodiment of the present invention. [Figure 6A]11 is a side view showing a movable gear and a leaf spring that have been moved to normal positions in an image forming apparatus according to an embodiment of the present invention. FIG. [Figure 6B] 11 is a side view showing a movable gear and a leaf spring that have been moved to a processing position in an image forming apparatus according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to an embodiment of the present invention will now be described with reference to the accompanying drawings.

[0014] First, the image forming apparatus 1 will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a side view showing the image forming apparatus 1 with the outer cover removed, and Fig. 2 is a side view showing the image forming apparatus 1 with the outer cover and cover plate removed. Fr, Rr, L, and R shown in each figure indicate the front, rear, left, and right sides of the image forming apparatus 1.

[0015] The image forming apparatus 1 includes a housing 3 having an internal space of a substantially rectangular parallelepiped shape. Inside the housing 3, there are provided a paper feed section for feeding paper, an image forming section for forming a toner image on the paper, a fixing section for fixing the toner image on the paper, and a discharge section for discharging the paper (all of which are not shown). Inside the housing 3, there is formed a paper transport path (not shown) that runs from the paper feed section through the image forming section and the fixing section to the discharge section. At predetermined positions on the transport path, a pair of registration rollers and a pair of transport rollers (both of which are not shown) are provided to transport the paper from the paper feed section to the paper discharge section along the transport path. In addition, a discharge tray (not shown) is formed on the top surface of the housing 3.

[0016] The paper feed unit includes a paper feed roller that rotates to send paper placed in a paper feed cassette or manual feed tray to a transport path. The image forming unit includes an exposure device, a photosensitive drum, a charger, a developing device, a cleaning device, a toner container, etc., and forms a toner image on paper fed from the paper feed unit by electrophotography. The fixing unit includes a heating roller and a pressure roller that rotate to transport the paper and fix the toner image to the paper. The paper discharge unit includes a pair of paper discharge rollers that rotate to discharge the paper with the fixed toner image to a paper discharge tray.

[0017] The above-mentioned plurality of rotating bodies, such as the pair of conveying rollers, the paper feed roller, the heating roller, the pressure roller, and the photosensitive drum, are driven to rotate by a drive mechanism 10 shown in Fig. 2. The drive mechanism 10 is composed of a brushed DC motor 11 capable of forward and reverse rotation, and a gear train 13 made up of drive gears fixed to the rotation shafts of the plurality of rotating bodies. The rotational force of the motor 11 is transmitted to each of the rotating bodies via the gear train 13, so that each rotating body rotates in a predetermined direction at a predetermined number of rotations. The motor 11 is an example of a drive source in this embodiment.

[0018] As shown in FIG. 2, one end (left end) of the output shaft 11a of the motor 11 penetrates the side plate 3L (left side plate) of the housing 3. An output gear 21 is fixed to the end of the output shaft 11a protruding from the side plate 3L. One end (left end) of the rotating shaft of each rotating body also penetrates the side plate 3L (left side plate) of the housing 3. A drive gear is fixed to each end of the rotating shaft protruding from the side plate 3L. Furthermore, as shown in FIG. 1, most of the drive gears are covered with a cover plate 5. That is, most of the drive gears are arranged in the space between the side plate 3L and the cover plate 5.

[0019] Next, referring to FIG. 2, a gear train 13X between the motor 11 and one pair of transport rollers will be described. This pair of transport rollers is disposed in a transport path between the image forming unit and the fixing device, and is composed of a transport drive roller 15 and a driven roller (not shown) that rotates following the transport drive roller 15. In this embodiment, the transport drive roller 15 is an example of a transport roller. As described above, one end (left end) of the rotation shaft of the transport drive roller 15 penetrates the side plate 3L (left side plate) of the housing 3. A transport drive gear 23 is fixed to one end of the rotation shaft protruding from the side plate 3L. A description of drive gears and the like other than this gear train 13X will be omitted.

[0020] The gear train 13X is composed of an output gear 21, first to fourth drive gears 25, 27, 29, 31, a moving gear 33, and a conveying drive gear 23. The output gear 21 meshes with the first drive gear 25. The first drive gear 25 meshes with the second drive gear 27. The second drive gear 27 meshes with a third drive gear 29. The third drive gear 29 meshes with a fourth drive gear 31. The fourth drive gear 31 meshes with the conveying drive gear 23 via the moving gear 33.

[0021] The movable gear 33 is provided so as to be movable between a normal position where it meshes with the transport drive gear 23 and a processing position where it is separated from the transport drive gear 23. When the movable gear 33 moves to the normal position, the transmission of rotational force from the fourth drive gear 31 to the transport drive gear 23 via the movable gear 33 is permitted, and when the movable gear 33 moves to the processing position, the transmission of rotational force from the fourth drive gear 31 to the transport drive gear 23 is prevented.

[0022] However, if a paper jam occurs while the paper is being transported along the transport path, the rotation of the transport roller pair is stopped, and the paper may remain sandwiched between the transport roller pair. In this case, even if you try to pull out the sandwiched paper, the rotation of the transport drive roller 15 is stopped, so the friction between the transport drive roller 15 and the paper makes it difficult to pull out the paper. Therefore, when clearing a paper jam, the moving gear 33 is moved to the processing position to cut off the transmission of rotational force from the motor 11 to the transport drive roller 15, allowing the transport drive roller 15 to rotate freely. This makes it possible to pull out the sandwiched paper without much resistance.

[0023] The movable gear 33 will be described with reference to Fig. 3, Fig. 4A, and Fig. 4B. Fig. 3 is a perspective view showing the movable gear and a leaf spring, and Fig. 4A and Fig. 4B are views showing the movable gear before and after movement. The side plate 3L is omitted in Fig. 3.

[0024] 3, the movable gear 33 includes a gear portion 41 and a rotating shaft 43, and both ends of the rotating shaft 43 are supported by the side plate 3L (see FIGS. 1 and 2) and the cover plate 5. The gear portion 41 of the movable gear 33 includes a large-diameter helical gear 41a that meshes with the fourth drive gear 31, and a small-diameter plain gear 41b that can mesh with the conveying drive gear 23.

[0025] The side plate 3L and the cover plate 5 are formed with a long hole 51 (only the long hole 51 of the cover plate 5 is shown in FIG. 3, the long hole of the side plate 3L is omitted) along the circumferential direction of a circle centered on the axis of the fourth drive gear 31. One end of the rotating shaft 43 of the movable gear 33 is inserted into the long hole of the side plate 3L, and the other end is inserted into the long hole 51 of the cover plate 5. In this manner, both ends of the rotating shaft 43 are supported rotatably and movably along the circumferential direction of a circle centered on the axis of the fourth drive gear 31. In this embodiment, the side plate 3L is an example of an inner plate, and the cover plate 5 is an example of an outer plate.

[0026] 4A and 4B, when the fourth drive gear 31 rotates clockwise, the movable gear 33 rotates counterclockwise and moves clockwise along the long hole 51. The movable gear 33 moves until the end of the rotating shaft 43 is engaged with one end (rear end) of the long hole 51 (see FIG. 4A). At this position, the plain gear 41b (see FIG. 3) of the movable gear 33 meshes with the conveying drive gear 23. In other words, the position where the end of the rotating shaft 43 of the movable gear 33 is engaged with one end (rear end) of the long hole 51 is the normal position.

[0027] On the other hand, when the fourth drive gear 31 rotates counterclockwise, the movable gear 33 moves counterclockwise along the long hole 51 while rotating clockwise. The movable gear 33 moves until the end of the rotating shaft 43 engages with the other end (front end) of the long hole 51 (see FIG. 4B). At this position, the plain gear 41b of the movable gear 33 moves away from the transport drive gear 23. In other words, the position where the end of the rotating shaft 43 of the movable gear 33 engages with the other end (front end) of the long hole 51 is the processing position.

[0028] 1 and 3, a hook portion 53 formed by cutting out a side edge of the cover plate 5 and a rectangular opening 55 (see FIG. 1) are formed adjacent to the long hole 51 of the cover plate 5. A boss 57 (see FIG. 3) is provided on the inner surface of the cover plate 5 between the hook portion 53 and the opening 55.

[0029] Generally, a force (thrust load) that moves the helical gear in the axial direction of the rotating shaft acts on the helical gear depending on the direction of rotation. In this embodiment, when the movable gear 33 moves to the processing position, a force that moves the helical gear 41a along the axial direction from the side plate 3L to the cover plate 5 acts on the helical gear 41a. When such a force acts, one end of the rotating shaft 43 may come out of the long hole of the side plate 3L, or the meshing between the helical gear 33 and the third drive gear 31 may become insufficient. Therefore, the gear train 13X includes a leaf spring 61 that buffers the axial movement of the movable gear 33.

[0030] Next, the leaf spring 61 will be described with reference to Fig. 5 in addition to Fig. 3. Fig. 5 is a perspective view showing the leaf spring 61.

[0031] As shown in FIG. 5, the leaf spring 61 is made of sheet metal and has a fixed portion 63 which is fixed to the cover plate 5 (see FIG. 3), a pressing portion 65 which is bent at an acute angle relative to the fixed portion 63, and a tip portion 67 which is bent from the tip of the pressing portion 65.

[0032] The fixing portion 63 has a substantially rectangular base portion 69 and a pair of hook portions 71 provided on opposing sides of the base portion 69. A circular opening 69a is formed near the center of the base portion 69. The pair of hook portions 71 are formed so as to bend from the sides of the base portion 69 at substantially right angles in the same direction relative to the base portion, and further bend at substantially right angles in opposite directions to each other. The pressing portion 65 is a long plate-like piece, and is bent from one part of the remaining sides of the base portion 69 in a substantially 180-degree arc shape in a direction opposite to the bending direction of the pair of hook portions 71, and extends longer than the base portion 69. In this way, the pressing portion 65 is bent so as to form an acute angle with respect to the fixing portion 63. The pressing portion 65 is formed so that the portion on the side of the base portion 69 is wide and the portion on the side of the tip portion 67 is narrow. The tip portion 67 is bent from the tip of the pressing portion 65 at substantially right angles toward the fixing portion 63. The tip of the tip portion 67 is formed in an arc shape. In a free position where no compressive force is applied to the leaf spring 61, the tip of the tip portion 67 does not reach a plane including the base portion 69.

[0033] As shown in FIG. 3, the leaf spring 61 is attached to the cover plate 5 by fitting the boss 57 of the cover plate 5 into the opening 69a of the base portion 69 and engaging the pair of hook portions 71 with the hook portion 53 of the cover plate 5 and the opening 55 (see FIG. 1). The pressing portion 65 contacts the helical gear 41a of the gear portion 41 with a predetermined pressure in the direction from the cover plate 5 toward the side plate 3L. A clearance C is provided between the tip of the tip portion 67 and the cover plate 5. The clearance C is set to a distance equal to or less than a distance at which one end of the rotating shaft 43 does not come out of the opening of the side plate 3L when the movable gear 33 moves in the direction from the side plate 3L toward the cover plate 5 until the tip portion 67 abuts against the cover plate 5. The clearance C is, for example, 0.4 mm.

[0034] In the image forming apparatus 1 having the above configuration, the gear train 13X during paper jam processing will be described with reference to Figures 2, 3, 4A, 4B, and 6A and 6B. Figures 6A and 6B are diagrams showing the moving gear 33 before and after movement.

[0035] First, the gear train 13X in the normal state will be described. In the normal state, the motor 11 rotates in one direction, and the output gear 21 fixed to the output shaft 11a of the motor 11 rotates in the clockwise direction in FIG. 2. Then, the fourth drive gear 31 rotates in the clockwise direction via the first to third drive gears 25, 27, and 29. With the rotation of the fourth drive gear 31, the moving gear 33 moves in the clockwise direction while rotating in the counterclockwise direction. The moving gear 33 moves to the normal position, and continues to rotate in the counterclockwise direction there (see FIG. 4A and FIG. 6A). By the moving gear 33 moving to the normal position in this way, the rotational force of the motor 11 is transmitted to the transport drive gear 23, and the transport drive roller 15 rotates to transport the paper.

[0036] When a paper jam occurs, the motor 11 rotates in the other direction. This causes the fourth drive gear 31 to rotate counterclockwise via the first to third drive gears 25, 27, and 29. As the fourth drive gear 31 rotates, the moving gear 33 moves counterclockwise while rotating clockwise. The moving gear 33 moves to the processing position, where it continues to rotate clockwise (reverse rotation, see Figures 4B and 6B). By moving the moving gear 33 to the processing position in this way, the transmission of the rotational force of the motor 11 to the transport drive gear 23 is interrupted.

[0037] When the movable gear 33 rotates clockwise in this manner, a force acts on the movable gear 33, moving it along the axial direction from the side plate 3L toward the cover plate 5. However, as shown in Fig. 3, the pressing portion 65 of the leaf spring 61 contacts the gear portion 41 in the direction from the cover plate 5 toward the side plate 3L, so that the axial movement of the movable gear 33 is buffered. The movable gear 33 can move until the tip portion 67 of the leaf spring 61 abuts against the cover plate 5. The movable gear 33 moves from the normal position to the processing position while being pressed by the leaf spring 61.

[0038] Thereafter, the paper that has been pinched between the pair of transport rollers is pulled out. Because the transport drive roller 15 is in a free state, the paper can be pulled out from the pair of transport rollers without much resistance.

[0039] As is clear from the above description, according to the image forming apparatus 1 of this embodiment, the leaf spring 61 is used to cushion the axial movement of the movable gear 33, so that it can be easily installed in a narrow space, and the assembly work of the gear train can be easily performed. That is, it is only necessary to pass the opening 69a of the leaf spring 61 through the boss 57 of the cover plate 5, and to hook the pair of hook portions 71 of the leaf spring 61 into the opening 55 and the hook portion 53. In addition, the tip portion 67 of the leaf spring 61 can appropriately secure the space between the movable gear 33 and the cover plate 5, so that deformation of the leaf spring 61 when assembling the leaf spring 61 can be prevented.

[0040] Furthermore, since the contact area between the pressing portion 65 of the leaf spring 61 and the gear portion 41 of the movable gear 33 is relatively wide, the pressing portion 65 can be stably brought into contact with the movable gear 33 even when the movable gear 33 moves. Therefore, the leaf spring 61 can stably buffer the movement of the movable gear 33. Therefore, even if the movable gear 33 rotates in the reverse direction when moving from the normal position to the processing position, it is possible to prevent the rotation shaft 43 of the movable gear 33 from falling off the side plate 3L and the helical gear 41a of the movable gear 33 from becoming insufficiently engaged with the fourth drive gear 31.

[0041] Moreover, the movable gear 33 is disposed between the conveying drive gear 23 and the fourth drive gear 31. That is, the movable gear 33 is disposed between the conveying drive gear 23 and the fourth drive gear 31, which is disposed upstream of the conveying drive gear 23 in the direction of transmission of the rotational force. By disposing the movable gear 33 in this manner, the number of parts in the gear train can be minimized.

[0042] In this embodiment, the transport drive roller 15 of the transport roller pair has been described as an example of a transport roller, but the transport roller is not limited to the transport drive roller 15. The transport roller may be a drive roller that is driven to rotate among a pair of rollers that rotate to transport paper. For example, the transport roller may be one of the heating roller and pressure roller of a fixing device that is driven to rotate, or one of a pair of registration rollers that is driven to rotate.

[0043] Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the above embodiments, and those skilled in the art may modify the above embodiments without departing from the scope and spirit of the present invention. [Explanation of symbols]

[0044] 1. Image forming device 3L Side plate (inner plate) 5 Cover plate (outer plate) 13X Gear Train 21 Motor (drive source) 23 Transport drive roller (transport roller) 33 Moving Gear 41a Hasbage Gear 61 Leaf Spring 63 Fixed part 65 Pressing part 67 Tip

Claims

1. An image forming apparatus including a gear train that transmits a rotational force from a drive source to a transport roller that transports paper, The gear train includes: a movable gear having a helical gear supported so as to be movable in an axial direction between a normal position that allows transmission of the rotational force and a processing position that blocks transmission of the rotational force, and which generates a force for moving in one axial direction when moving from the normal position to the processing position; a leaf spring that buffers movement of the movable gear in one axial direction; an outer plate and an inner plate that rotatably support both ends of the rotation shaft of the movable gear and moveably between the normal position and the processing position; The leaf spring is A fixing portion fixed to the outer plate; a pressing portion bent at an acute angle with respect to the fixing portion and contacting the helical gear toward the other direction in the axial direction; a tip portion bent from a tip of the pressing portion toward the fixing portion, An image forming apparatus, comprising: a first end portion and a second end portion of the outer plate;

2. 2 . The image forming apparatus according to claim 1 , wherein the movable gear is disposed between the transport roller and a drive gear disposed upstream of the transport roller in a transmission direction of the rotational force.

Images