Drive transmission device, fixing device and image forming apparatus

Abstract

To provide a drive transmission device that can easily maintain the constant center distance between gears that mesh with each other.SOLUTION: A drive transmission device 50 comprises: a drive gear 51 that receives a driving force from a drive motor and rotates centered on a drive shaft 52; a transmission gear 53 that meshes with the drive gear 51 and rotates centered on a transmission shaft 42 in association with the rotation of the drive gear 51; a drive contact member 60 that has a drive contact surface 63 curved in a concentric circular shape with the drive gear 51, and is provided non-rotatably on the same axis with the drive shaft 52; a transmission contact member 65 that has a transmission contact surface 67 curved in a concentric circular shape with the transmission gear 53, and is provided non-rotatably on the same axis with the transmission shaft 42 at a position where the transmission contact surface 67 is brought into contact with the drive contact surface 63; and an urging member 54 that urges the transmission shaft 42 toward the drive shaft 52, and maintains a state in which the transmission contact surface 67 and the drive contact surface 63 are in contact with each other.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a drive transmission device that maintains a constant inter-axial distance between meshing gears, a fixing device, and an image forming apparatus. [Background technology]

[0002] An image forming apparatus is disclosed in which the axial distance between gears that rotate a developing sleeve is maintained (Patent Document 1). The rotational shaft of the developing sleeve extends outward from the developer container, and a sleeve gear is fixed to the tip end of the shaft. A development drive gear that is rotatably supported on a drive side plate is engaged with the sleeve gear. The rotational shaft of the developing sleeve extends further outward than the sleeve gear and is supported by a bearing. The bearing is placed on a base formed by cutting out and raising part of the drive side plate, preventing the sleeve gear from moving in a direction away from the development drive gear, and maintaining the axial distance between the sleeve gear and the development drive gear. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-314215 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned technology does not sufficiently consider the movement of the sleeve gear in the direction approaching the development drive gear. Also, in order to accurately maintain the axial distance between the sleeve gear and the development drive gear, it is necessary to form the drive side plate with high precision and accurately position it, including the position where the development drive gear is supported and the position where the base is formed, and there is a problem that the manufacturing of such a drive side plate is very costly.

[0005] SUMMARY OF THE INVENTION In consideration of the above circumstances, the present invention provides a drive transmission device, a fixing device, and an image forming apparatus that can easily maintain a constant inter-axial distance between meshing gears. [Means for solving the problem]

[0006] The drive transmission device of the present invention comprises a drive gear that receives a driving force from a drive source and rotates around a drive shaft, a transmission gear that meshes with the drive gear and rotates around a transmission shaft as the drive gear rotates, a drive contact member that has a drive contact surface that is curved concentrically with the drive gear and is non-rotatable on the same axis as the drive shaft, a transmission contact member that has a transmission contact surface that is curved concentrically with the transmission gear and is non-rotatable on the same axis as the transmission shaft at a position where the transmission contact surface contacts the drive contact surface, and a biasing member that biases either the drive shaft or the transmission shaft toward the other of the drive shaft or the transmission shaft, maintaining the transmission contact surface and the drive contact surface in contact with each other.

[0007] In this case, the drive contact surface may have a curved surface that matches the pitch circle of the drive gear, and the transmission contact surface may have a curved surface that matches the pitch circle of the transmission gear.

[0008] In this case, the drive shaft may be non-rotatably supported by a support member provided on one side of the axial direction, the drive gear may be rotatably supported on the drive shaft at a position opposite the support member, and the drive contact member may be fixed to the drive shaft between a regulating member provided on the other side of the axial direction and the drive gear.

[0009] The fixing device of the present invention comprises the above-mentioned drive transmission device, a fixing member that heats a toner image on a medium while rotating around its axis, a pressure member that forms a pressure area between the fixing member while rotating around its axis and pressurizes the toner on the medium that passes through the pressure area, an ejection roller that rotates around the transmission axis and transports the medium that has passed through the pressure area, and a fixing cover that rotatably supports the transmission axis to which the transmission gear is fixed around its axis, moves in an opening direction to release the transmission gear from engagement with the drive gear, and moves in a closing direction to engage the transmission gear with the drive gear, and the biasing member biases the fixing cover toward the closing direction.

[0010] The image forming apparatus of the present invention includes the fixing device described above. [Effects of the Invention]

[0011] According to the present invention, the distance between the axes of the gears that mesh with each other can be easily maintained constant. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view (front view) showing an outline of the inside of an image forming apparatus according to one embodiment of the present invention. [Figure 2] 1 is a cross-sectional view (front view) showing a fixing device, a conveying device, and the like of an image forming apparatus according to an embodiment of the present invention. [Figure 3] FIG. 1 is a perspective view showing a fixing device according to an embodiment of the present invention. [Figure 4] FIG. 2 is a plan view showing the rear part of the fixing device according to the embodiment of the present invention. [Figure 5] FIG. 2 is a perspective view showing a drive contact member of the drive transmission device according to the embodiment of the present invention. [Figure 6A] 1 is a front view showing a drive transmission device according to an embodiment of the present invention; [Figure 6B] 1 is an enlarged front view showing a portion of a drive transmission device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that Fr, Rr, L, R, U, and D shown in the drawings indicate front, rear, left, right, top, and bottom. Terms indicating directions and positions are used in this specification, but these terms are used for convenience of explanation and do not limit the technical scope of the present invention.

[0014] An image forming apparatus 1 according to an embodiment will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view (front view) showing an outline of the interior of the image forming apparatus 1. Figure 2 is a cross-sectional view (front view) showing a fixing device 12, a conveying device 13, etc.

[0015] [Image forming device] The image forming apparatus 1 is a color printer that forms an image by transferring a full-color toner image formed by electrophotography onto paper S (medium). As shown in FIG. 1, the image forming apparatus 1 includes an apparatus main body 2 having a substantially rectangular parallelepiped appearance. A cassette 3 that stores paper S is removably provided at the bottom of the apparatus main body 2, and a paper output tray 4 onto which paper S with an image formed thereon is output is provided on the top surface of the apparatus main body 2. Four toner containers 5 that store replenishment toner (developer) of four colors (magenta, cyan, yellow, and black) are removably attached below the paper output tray 4. The medium is not limited to paper paper S, and may be a resin sheet or the like.

[0016] On the right side inside the device main body 2, a transport path 6 and a reverse transport path 7 are formed as paths for transporting the paper S. The transport path 6 is formed in a roughly S-shape along the vertical direction, and is a path for transporting the paper S from the cassette 3 to the paper output tray 4. The reverse transport path 7 branches off to the right on the downstream side of the transport path 6, extends downward, and merges with the upstream side of the transport path 6. The reverse transport path 7 is a path for reversing the paper S and transporting it again to the image forming device 11, which will be described later. In this specification, the terms "upstream" and "downstream" refer to "upstream" and "downstream" in the transport direction of the paper S (medium).

[0017] Also provided inside the apparatus main body 2 are a paper feeder 10, an image forming device 11, a fixing device 12, and a conveying device 13. The paper feeder 10 is provided at the upstream end of the conveying path 6, and has the function of separating and sending out the paper sheets S stored in the cassette 3 one by one onto the conveying path 6. The fixing device 12 is provided downstream of the conveying path 6, and has the function of thermally fixing a toner image onto the paper sheet S by passing the paper sheet S between a fixing belt 25 that rotates around an axis and a pressure roller 26. The image forming device 11 is provided midway between the paper feeder 10 and the fixing device 12 on the conveying path 6. The conveying device 13 is provided in the conveying path 6 or the reverse conveying path 7, and has the function of conveying the paper sheet S.

[0018] <Imaging device> The imaging device 11 has an intermediate transfer belt 14, four drum units 15, and an optical scanning device 16. The intermediate transfer belt 14 is provided below the toner container 5, is stretched over multiple rollers, and rotates in the direction indicated by the arrow in FIG. 1. The four drum units 15 are aligned in the left-right direction below the intermediate transfer belt 14, and the optical scanning device 16 is provided below the drum units 15. The four drum units 15, which correspond to the four colors of toner, have the same structure, so the following description will focus on one drum unit 15.

[0019] The drum unit 15 has a photosensitive drum 20, a charging device 21, a developing device 22, a primary transfer roller 23, and a cleaning device 24. The photosensitive drum 20 rotates around its axis while contacting the underside of the intermediate transfer belt 14. The charging device 21, the developing device 22, the primary transfer roller 23, and the cleaning device 24 are arranged around the photosensitive drum 20 in the order of the image formation process. The primary transfer roller 23 faces the photosensitive drum 20 from above, with the intermediate transfer belt 14 sandwiched between them.

[0020] <Conveyor equipment> As shown in FIGS. 1 and 2, the transport device 13 includes a transport main body 30, a pair of registration rollers 31, a secondary transfer roller 32, and a plurality of pairs of transport rollers 33 to .

[0021] The transport main body 30 is provided between the transport path 6 and the reverse transport path 7, and constitutes part of the transport path 6 and the reverse transport path 7, and has the function of guiding the transported paper S. An open / close cover 17 is provided on the device main body 2 so as to be openable and closable. The open / close cover 17 is provided, for example, so as to be rotatable about an axis on one rear side (not shown). When the open / close cover 17 is closed, it forms the right side of the device main body 2, and constitutes the reverse transport path 7 between the open / close cover 17 and the transport main body 30. By opening the open / close cover 17, paper S jammed in the transport path 6 or the reverse transport path 7 can be removed (jam clearance can be performed). The open / close cover 17 may also be provided so as to be rotatable about an axis on one lower side, for example.

[0022] The registration roller pair 31 is provided downstream of the junction of the reverse conveying path 7 and upstream of the secondary transfer roller 32. The registration roller pair 31 temporarily blocks the sheet S being conveyed through the conveying path 6 to correct any inclination of the sheet S (skew correction). The secondary transfer roller 32 is supported by the conveying main body 30 and contacts the right end of the intermediate transfer belt 14 to form a transfer nip N1. The conveying roller pairs 33 to 35 are disposed at appropriate positions on the reverse conveying path 7. One roller of the conveying roller pair 34, 35 is supported by the conveying main body 30, and the other roller is supported by the opening / closing cover 17.

[0023] [Image formation processing] Here, a description will be given of the operation of the image forming apparatus 1. For example, a control unit (not shown) executes image forming processing as follows based on image data input from an external terminal.

[0024] The charging device 21 charges the surface of the photosensitive drum 20. The optical scanning device 16 exposes the photosensitive drum 20 to light, forming an electrostatic latent image corresponding to the image data on the surface of the photosensitive drum 20. The developing device 22 develops the electrostatic latent image on the photosensitive drum 20 into a toner image using toner supplied from the toner container 5. The four-color toner images carried on the four photosensitive drums 20 are sequentially transferred (primary transfer) onto the rotating intermediate transfer belt 14 by primary transfer rollers 23 to which a primary transfer bias is applied. As the intermediate transfer belt 14 rotates, it carries a full-color toner image in which the four-color toner images are superimposed. The cleaning device 24 removes any toner remaining on the surface of the photosensitive drum 20 after the primary transfer.

[0025] The paper feeder 10 takes out the paper S stored in the cassette 3 and sends it out to the conveying path 6. The pair of registration rollers 31 sends the skew-corrected paper S downstream. A secondary transfer roller 32 to which a secondary transfer bias is applied performs a second transfer of the toner image on the intermediate transfer belt 14 onto the surface of the paper S passing through the transfer nip N1. The fixing device 12 applies pressure to the toner image transferred to the paper S and heats it to thermally fix it onto the paper S. In the case of single-sided printing, the paper S with the fixed toner image (image formed) is discharged to the paper output tray 4.

[0026] When double-sided printing is performed, the paper S that has passed through the fixing device 12 switches back at the downstream end of the conveying path 6 and is sent to the reverse conveying path 7. A plurality of conveying roller pairs 33 to 35 convey the paper S along the reverse conveying path 7, and the paper S re-enters the conveying path 6 from the reverse conveying path 7. Then, an image is formed on the back side of the paper S in the same procedure as in the single-sided printing described above.

[0027] [Fixing device] Next, the fixing device 12 will be described with reference to Figures 2 to 4. Figure 3 is a perspective view showing the fixing device 12. Figure 4 is a plan view showing the rear part of the fixing device 12.

[0028] As shown in FIGS. 2 and 3, the fixing device 12 includes a fixing belt 25, a pressure roller 26, a heat generating section 27, a pair of fixing conveying rollers 40, and a drive transmission device 50.

[0029] <Fixing belt> The fixing belt 25, which is an example of a fixing member, is made of a laminated material of metal and synthetic resin and is formed in a generally cylindrical shape that is long in the front-rear direction. As shown in FIG. 2, a support member 25A, a pressure pad 25B, and a belt guide 25C are provided inside the fixing belt 25. The support member 25A penetrates the fixing belt 25 in the axial direction, and both ends thereof are supported by the fixing frame 36 (see FIG. 1). The pressure pad 25B is made of heat-resistant synthetic resin and is fixed to the support member 25A so as to face the pressure roller 26 across the fixing belt 25. The belt guide 25C is made of metal and is formed in a generally semi-cylindrical shape that is long in the axial direction. The belt guide 25C is fixed to the support member 25A on the opposite side from the pressure pad 25B and contacts the inner surface of the fixing belt 25 to maintain the fixing belt 25 in a generally cylindrical shape.

[0030] 3, fixing belt 25 is rotatably supported by support member 25A via a pair of caps 25D attached to both front and rear ends. A gear (not shown) is integrally formed with cap 25D, and fixing belt 25 rotates by receiving a driving force from a motor (not shown) connected to the gear.

[0031] <Pressure roller> As shown in FIG. 2, pressure roller 26, an example of a pressure member, is formed in a generally cylindrical shape that is long in the front-rear direction and is disposed on the right side of fixing belt 25. Pressure roller 26 is formed, for example, by laminating synthetic resin elastic layer 26B on the outer peripheral surface of metal core 26A. Both axial ends of pressure roller 26 (core 26A) are rotatably supported by a pair of movable frames (not shown). The movable frames are supported by fixing frame 36 (see FIG. 1) so as to be swingable in the left-right direction and are connected to a pressure adjustment unit (not shown) that includes a spring, an eccentric cam, etc.

[0032] When the pressure adjustment unit rotates the movable frame toward the fixing belt 25, the pressure roller 26 is pressed against the fixing belt 25, forming a pressurized pressure region N2 between the fixing belt 25 and the pressure roller 26. With the pressure region N2 in a pressurized state, the pressure roller 26 rotates in response to the fixing belt 25. On the other hand, when the pressure adjustment unit rotates the movable frame in a direction away from the fixing belt 25, the pressure roller 26 is released from pressing against the fixing belt 25, forming a pressure region N2 in which the pressure is reduced. Note that with the pressure region N2 formed, the fixing belt 25 is deformed by being pressed by the pressure roller 26. The pressure region N2 refers to the region extending from an upstream position where the pressure is 0 Pa, through a position where the pressure is maximum, to a downstream position where the pressure returns to 0 Pa.

[0033] <Heat generating part> Heat generating unit 27 is disposed to the left of fixing belt 25 across a gap. Heat generating unit 27 is an induction heater that generates a magnetic field to cause fixing belt 25 to self-heat. Belt guide 25C described above absorbs leakage magnetic flux that has passed through fixing belt 25, thereby generating heat and assisting in heating fixing belt 25. Note that, although induction heating type heat generating unit 27 is disposed on the outside of fixing belt 25 as a heat source, a halogen heater, carbon heater, or the like may be disposed inside fixing belt 25 instead.

[0034] <Fixing conveyance roller pair> 2, the fixing conveying roller pair 40 is disposed downstream (above) of the pressure roller 26 (pressure region N2). As shown in FIGS. 2 and 4, the fixing conveying roller pair 40 includes a discharge roller 41 and a driven roller 45.

[0035] (ejection roller) The discharge roller 41 is supported by a fixation cover 37 provided on the upper part of the fixation frame 36. The discharge roller 41 is formed, for example, by laminating a synthetic resin roller body 43 on the outer peripheral surface of a metal transmission shaft 42. Both the front and rear sides of the transmission shaft 42 are rotatably supported by the fixation cover 37 via bearings 66 (see FIG. 6A described later). The roller body 43 is fixed to the transmission shaft 42 and rotates integrally with the transmission shaft 42 around the axis.

[0036] (driven roller) The driven roller 45 is supported on the upper part of the fixing frame 36. The driven roller 45 is formed, for example, by laminating a roller body 47 made of synthetic resin on the outer peripheral surface of a metal driven shaft 46. Both front and rear ends of the driven shaft 46 are rotatably supported by the fixing frame 36 via bearings (not shown). The roller body 47 is fixed to the driven shaft 46 and rotates integrally with the driven shaft 46 around the axis.

[0037] (fixing cover) 2, the fixing cover 37 is swingably supported on the upper part of the fixing frame 36 via a pair of front and rear support shafts 37A. When the opening / closing cover 17 is open, the fixing cover 37 swings between a separation position where the discharge roller 41 is separated from the driven roller 45 in an opening direction (to the right in FIG. 2) and a closing position where the discharge roller 41 is rotated in a closing direction (to the left in FIG. 2) to come into close contact with the driven roller 45.

[0038] <Drive transmission device> 4, the drive transmission device 50 is disposed behind the fixing conveying roller pair 40. As shown in FIGS. 3 and 4, the drive transmission device 50 includes a drive gear 51, a transmission gear 53, and a biasing member 54.

[0039] (Drive gear) The drive gear 51 is a so-called spur gear (involute gear) that rotates around a drive shaft 52, and is disposed at the upper rear of the fixing frame 36. The (rear end of) the drive shaft 52 is non-rotatably supported (fixed) by a support member 38A that is erected at the upper rear of the fixing frame 36 (on one axial side). The drive gear 51 is rotatably supported by the drive shaft 52 at a position facing (the front surface of) the support member 38A. The drive gear 51 is connected to the drive motor 28 (drive source) via another gear train or the like (not shown) (see FIG. 3). The drive gear 51 receives driving force from the drive motor 28 and rotates around its axis.

[0040] The portion of drive shaft 52 that rotatably supports drive gear 51 has a circular cross section, and the portion of drive shaft 52 that protrudes forward from drive gear 51 (hereinafter also referred to as the "D-cut portion") has a substantially D-shaped cross section (see FIG. 6A, which will be described later). Note that, on the upper portion of fixing frame 36, restricting member 38B is erected forward of support member 38A (on the other side in the axial direction). Restricting member 38B is erected facing the front of support member 38A across a space for arranging drive gear 51.

[0041] (Transmission gear) The transmission gear 53 is a so-called spur gear (involute gear) that rotates around the transmission shaft 42 and meshes with the drive gear 51 from the right side. The transmission shaft 42 of the discharge roller 41 extends rearward beyond the roller body 43, and the transmission gear 53 is supported (fixed) to the rear portion of the transmission shaft 42 so as not to be rotatable. In other words, the transmission gear 53 is supported by the fixing cover 37 via the transmission shaft 42. The fixing cover 37 moves (rotates) in the opening direction (rightward in FIGS. 3 and 4) to release the meshing of the transmission gear 53 with the drive gear 51, and moves (rotates) in the closing direction (leftward in FIGS. 3 and 4) to mesh the transmission gear 53 with the drive gear 51. By meshing with the drive gear 51, the transmission gear 53 rotates around its axis in accordance with the rotation of the drive gear 51.

[0042] (biasing member) As shown in FIG. 4, the biasing member 54 is, for example, a compression coil spring and is provided at the upper rear of the fuser cover 37. When the fuser cover 37 is in the closed position and the open-close cover 17 is closed (hereinafter simply referred to as the "closed state"), the biasing member 54 is pushed leftward by the open-close cover 17 and compressed. The compressed biasing member 54 biases the fuser cover 37 in the closing direction (leftward). As a result, the discharge roller 41, which is supported by the fuser cover 37 via the transmission shaft 42, is pressed against the right side of the driven roller 45, forming the discharge nip N3 (see FIG. 2). Furthermore, the transmission gear 53, which is supported by the fuser cover 37 via the transmission shaft 42, is firmly engaged with the drive gear 51.

[0043] [Fixing process] Here, a description will be given of the operation of the fixing device 12. The control unit executes the fixing process while appropriately controlling the fixing device 12 during the image forming process described above.

[0044] More specifically, the heat generating unit 27 heats the fixing belt 25. The fixing belt 25 heats the toner image on the paper S as it passes through the pressure region N2 while rotating about its axis. The pressure roller 26 pressurizes the toner on the paper S as it passes through the pressure region N2 while rotating about its axis. As the paper S passes through the pressure region N2, the toner image on the paper S melts and is fixed to the paper S.

[0045] The drive transmission device 50 transmits the driving force (rotational force) of the drive motor 28 to the transmission shaft 42 (discharge roller 41). The discharge roller 41 rotates around the transmission shaft 42 due to the driving force of the drive motor 28, and the driven roller 45 rotates around the driven shaft 46, driven by the discharge roller 41. The pair of fixing and conveying rollers 40 (discharge roller 41, driven roller 45) conveys the paper S that has passed through the pressure region N2 by rotating around the shaft. If the paper S becomes jammed in the pressure region N2 or the discharge nip N3, the jammed paper S can be removed (jam clearance) by rotating the fixing cover 37 from the closed position to the separated position. The pressure adjustment unit is configured to move in conjunction with the fixing cover 37. When the fixing cover 37 is rotated from the closed position to the separated position, the movable frame rotates away from the fixing belt 25, reducing the pressure in the pressure region N2 (not shown). Conversely, when the fixing cover 37 is rotated from the separated position to the closed position, the movable frame rotates in a direction approaching the fixing belt 25, and pressure is applied to the pressure region N2 (not shown).

[0046] Incidentally, in order to properly transmit the driving force of the drive motor 28 to the discharge roller 41, it is necessary to maintain a specified center distance D between the drive gear 51 and the transmission gear 53. For example, if the center distance D is longer than the specified center distance D, tooth skipping occurs, making it impossible to ensure normal transmission of the driving force. Also, for example, if the center distance D is shorter than the specified center distance D, the gears 51 and 53 cannot rotate normally. Therefore, the drive transmission device 50 according to this embodiment has a structure for maintaining a constant center distance D between the drive gear 51 and the transmission gear 53.

[0047] The structure for maintaining a constant inter-axial distance D will be specifically described with reference to Figures 4, 5, 6A, and 6B. Figure 5 is a perspective view showing a driving contact member 60. Figure 6A is a front view showing a drive transmission device 50, and Figure 6B is an enlarged front view showing a portion of the drive transmission device 50. 6A and 6B, the tip circles of the drive gear 51 and the transmission gear 53 are indicated by solid or dashed lines, and the pitch circles P1 and P2 of the drive gear 51 and the transmission gear 53 are indicated by dashed-dotted lines. Needless to say, the pitch circles P1 and P2 refer to circles that pass through the intersection (pitch point P0) of the locus of contact points between the tooth surfaces of the drive gear 51 and the transmission gear 53 and the line segment connecting the rotation centers of both gears 51 and 53, and that are coaxial with both gears 51 and 53.

[0048] As shown in FIG. 4, the drive transmission device 50 further includes a drive contact member 60 and a transmission contact member 65.

[0049] (Drive contact member) The driving contact member 60 is made of, for example, a resin material or a metal material, and is provided coaxially with the driving shaft 52 so as not to rotate. The driving contact member 60 is disposed in front of the driving gear 51 (see FIG. 4). As shown in FIG. 5, the driving contact member 60 has a sleeve portion 61 formed in a cylindrical shape and a protruding portion 62 protruding from the sleeve portion 61.

[0050] An insertion hole 61A is formed in the sleeve portion 61 so as to penetrate in the front-rear direction. The rear end of the insertion hole 61A is formed in a substantially circular shape, and the portion excluding the rear end of the insertion hole 61A is formed in a substantially D shape. The D-cut portion of the drive shaft 52 is inserted into the insertion hole 61A of the sleeve portion 61, so that the drive contact member 60 is supported (fixed) to the drive shaft 52 so as not to rotate. The drive contact member 60 is fixed to the drive shaft 52 between the restricting member 38B and the drive gear 51 (see FIG. 4).

[0051] The protrusion 62 is formed integrally with the sleeve portion 61 from the right side to the lower side. A drive contact surface 63 that is curved concentrically with the drive gear 51 is formed on the right side of the protrusion 62. As shown in Fig. 6A, the drive contact surface 63 has a curved surface that coincides with the pitch circle P1 of the drive gear 51 when viewed from the front (axial direction). In other words, the drive contact surface 63 has the same curvature as the pitch circle P1.

[0052] As shown in Fig. 5, an engagement recess 62A cut out in a substantially triangular shape is formed on the lower front side of the protrusion 62. With the drive shaft 52 passing through the drive contact member 60, the drive contact member 60 is sandwiched between the regulating member 38B and the drive gear 51, and the right end of the regulating member 38B fits into the engagement recess 62A (see Fig. 4). This restricts movement of the drive gear 51 in the front-rear direction (axial direction).

[0053] (Transmission contact member) The transmission contact member 65 is formed of, for example, a resin material or a metal material, and is non-rotatably provided coaxially with the transmission shaft 42. The transmission contact member 65 is disposed in front of the transmission gear 53 (see FIG. 4). As shown in FIG. 6A, the transmission contact member 65 is formed in a substantially U-shape that is open on the left side when viewed from the front, and is fitted (fixed) into a fitting recess 37B formed in the fuser cover 37. The fitting recess 37B is formed at the left end of the fuser cover 37, forward of the transmission gear 53. A bearing portion 66 is fitted (fixed) into the U-shaped portion of the transmission contact member 65, and the transmission shaft 42 passes through the bearing portion 66 and is rotatably supported by the transmission contact member 65 via the bearing portion 66.

[0054] A transmission contact surface 67 is formed on the upper left side surface of the transmission contact member 65, and is curved concentrically with the transmission gear 53. The transmission contact surface 67 has a curved surface that coincides with the pitch circle P2 of the transmission gear 53. In other words, the transmission contact surface 67 has the same curvature as the pitch circle P2.

[0055] Incidentally, the fact that both contact surfaces 63, 67 coincide with the pitch circles P1, P2 (have the same curvature) does not mean that they must coincide strictly (be identical), but means that manufacturing errors are allowed.

[0056] 6A and 6B, in the closed state, the transmission contact member 65 is positioned so that the transmission contact surface 67 contacts the drive contact surface 63. Also, in the closed state, the biasing member 54 biases the transmission shaft 42 toward the drive shaft 52 via the fixation cover 37 (see arrow F in FIG. 6A), maintaining the transmission contact surface 67 and the drive contact surface 63 in contact with each other. The transmission contact surface 67 and the drive contact surface 63 contact each other at a single point when viewed from the front (approximately a single line when viewed from above). This contact portion (contact point) substantially coincides with the pitch point P0 of both gears 51 and 53 when viewed from the front.

[0057] In the drive transmission device 50 according to the present embodiment described above, the transmission shaft 42 is biased toward the drive shaft 52 via the fuser cover 37, maintaining partial contact between the curved transmission contact surface 67 and the drive contact surface 63. This configuration prevents the drive gear 51 and the transmission gear 53 from moving toward or away from each other. Furthermore, because the drive contact member 60 and the transmission contact member 65 are mounted on the shafts 42 and 52, respectively, the manufacturing cost of the drive transmission device 50 can be reduced compared to when separate components supporting the contact members 60 and 65 are formed with high precision and positioned accurately. This allows the center distance D between the meshing gears 51 and 53 to be easily maintained constant. Furthermore, because the drive contact member 60 and the transmission contact member 65 do not rotate, friction and wear between the transmission contact surface 67 and the drive contact surface 63 can be prevented. This allows the center distance D to be maintained constant over a long period of time.

[0058] Furthermore, in the drive transmission device 50 according to this embodiment, the contact surfaces 63, 67 are formed on the pitch circles P1, P2 of the gears 51, 53, so that the drive contact surface 63 and the transmission contact surface 67 come into contact with each other at approximately the pitch point P0 when viewed from the front (axial direction) (see FIGS. 6A and 6B). With this configuration, the component force Fc (see FIG. 6B) of the biasing force F of the biasing member 54 can be directed in the normal direction to the contact portion between the contact surfaces 63, 67. As a result, the force Fc is applied in a direction perpendicular to the contact portion between the contact surfaces 63, 67, so that the state in which the contact surfaces 63, 67 come into contact with each other can be stabilized.

[0059] Furthermore, according to the drive transmission device 50 of this embodiment, the drive contact member 60 is fixed to the drive shaft 52 between the restricting member 38B and the drive gear 51, and therefore the drive contact member 60 can also be used as a retainer for the drive gear 51. This allows for a reduction in the number of parts compared to when a separate part is provided to retain the drive gear 51, thereby enabling a reduction in the manufacturing cost of the drive transmission device 50.

[0060] If the drive shaft 52 and the transmission shaft 42 were supported on a single support plate (not shown), the positions of the shafts 42 and 52 would be fixed, and the inter-shaft distance D would be kept constant. However, if the shafts 42 and 52 were supported on a single support plate, the gears 51 and 53 would not be able to disengage from each other. Therefore, in a structure such as the fixing device 12 described above, which requires the fixing cover 37 to be opened to disengage the gears 51 and 53 for jam clearance, a structure in which two shafts 42 and 52 are supported on a single support plate cannot be adopted. In contrast, according to the fixing device 12 of this embodiment, even if the transmission shaft 42 moves together with the fixing cover 37, the contact surfaces 63 and 67 come into contact with each other by placing the fixing cover 37 in the closed position, and the inter-shaft distance D between the meshing gears 51 and 53 can be kept constant.

[0061] In the drive transmission device 50 according to this embodiment, the drive contact surface 63 of the drive contact member 60 has the same curvature as the pitch circle P1 of the drive gear 51, but the present invention is not limited to this. For example, the drive contact surface 63 may be a curved surface having a curvature greater or smaller than the curvature of the pitch circle P1 (not shown). Similarly, the transmission contact surface 67 of the transmission contact member 65 may be a curved surface having a curvature greater or smaller than the curvature of the pitch circle P2 (not shown). In other words, it is sufficient that both contact surfaces 63, 67 are formed generally along the pitch circles P1, P2 of the gears 51, 53.

[0062] In the drive transmission device 50 according to the present embodiment, the drive contact member 60 is a separate member from the fixation frame 36 and the restricting member 38B, but this is not limiting, and for example, the drive contact member 60 may be formed integrally with the restricting member 38B or the like (not shown). Similarly, for example, the transmission contact member 65 may be formed integrally with the fixation cover 37 (not shown).

[0063] Furthermore, in the drive transmission device 50 according to this embodiment, the drive gear 51 is rotatably supported on the drive shaft 52, but this is not limiting and the drive gear 51 may be fixed to the drive shaft 52. In this case, the drive contact member 60 is arranged coaxially with the drive shaft 52, but is not in contact with the drive shaft 52 and may be fixed to the fixing frame 36 or the like (not shown).

[0064] Furthermore, in the drive transmission device 50 according to this embodiment, the biasing member 54 is a compression coil spring, but the present invention is not limited to this. For example, the biasing member 54 may be an elastic body such as rubber, or a tension spring that biases the fuser cover 37 toward the closed position. Alternatively, a torsion coil spring may be provided on the support shaft 37A. Furthermore, in the drive transmission device 50 according to this embodiment, the biasing member 54 biases the transmission shaft 42 toward the drive shaft 52 via the fuser cover 37, but the present invention is not limited to this. For example, the biasing member 54 may be provided to bias the drive shaft 52 toward the transmission shaft 42 (not shown).

[0065] Furthermore, although the drive transmission device 50 according to this embodiment is provided to transmit drive force to the discharge roller 41 of the fixing device 12, the present invention is not limited to this. The drive transmission device 50 can be applied as long as it has a structure that transmits drive force to a rotating body using two or more gears. Furthermore, if the transmission shaft 42 is not used as a rotation shaft for another member, the transmission gear 53 may be rotatably supported on the transmission shaft 42 without being fixed to the transmission shaft 42.

[0066] Furthermore, in the fixing device 12 according to this embodiment, the discharge roller 41 and the driven roller 45 constitute the fixing conveying roller pair 40, but this is not limited thereto, and the discharge roller 41 may be configured to come into contact with the platen plate on which the paper S slides instead of the driven roller 45 (not shown).

[0067] Furthermore, in the fixing device 12 according to the present embodiment, the fixing belt 25 is used as an example of a fixing member, but this is not limiting, and a roller member similar to the pressure roller 26 may be used (not shown). Furthermore, the pressure roller 26 is used as an example of a pressure member, but this is not limiting, and a belt member similar to the fixing belt 25 may be used (not shown).

[0068] Furthermore, the image forming apparatus 1 according to the present embodiment is a color printer, but is not limited to this, and the present invention may also be applied to, for example, a monochrome printer, a copying machine, a facsimile machine, a multifunction machine, or the like.

[0069] The above-described embodiment shows one aspect of the drive transmission device, fixing device, and image forming apparatus according to the present invention, and the technical scope of the present invention is not limited to the above-described embodiment. The present invention may be variously changed, substituted, or modified within the scope of the technical concept, and the claims include all embodiments that may fall within the scope of the technical concept. [Explanation of symbols]

[0070] 1. Image forming device 12 Fixing device 25 Fixing belt (fixing member) 26 Pressure roller (pressure member) 28 Drive motor (drive source) 37 Fixing cover 38A Support member 38B Regulatory member 41 Discharge roller 42 Transmission shaft 50 Drive transmission device 51 Drive gear 52 Drive shaft 53 Transmission gear 54 biasing member 60 driving contact member 63 Drive contact surface 65 Transmission contact member 67 Transmission contact surface N2 pressure area P1, P2 pitch circle S Paper (medium)

Claims

1. a drive gear that receives a driving force from a drive source and rotates around a drive shaft that is supported non-rotatably; a transmission gear that meshes with the drive gear and rotates about a transmission shaft in accordance with the rotation of the drive gear; a drive contact member having a drive contact surface curved concentrically with the drive gear and non-rotatably provided coaxially with the drive shaft; a transmission contact member having a transmission contact surface curved concentrically with the transmission gear, the transmission contact member being non-rotatably provided coaxially with the transmission shaft at a position where the transmission contact surface contacts the drive contact surface; a biasing member that biases one of the drive shaft and the transmission shaft toward the other of the drive shaft and the transmission shaft, and maintains the transmission contact surface and the drive contact surface in contact with each other.

2. a drive gear that receives a driving force from a drive source and rotates around a drive shaft; a transmission gear that meshes with the drive gear and rotates about a transmission shaft in accordance with the rotation of the drive gear; a drive contact member having a drive contact surface curved concentrically with the drive gear and non-rotatably provided coaxially with the drive shaft; a transmission contact member having a transmission contact surface curved concentrically with the transmission gear, the transmission contact member being non-rotatably provided coaxially with the transmission shaft at a position where the transmission contact surface contacts the drive contact surface; a biasing member that biases one of the drive shaft and the transmission shaft toward the other of the drive shaft and the transmission shaft, and maintains the transmission contact surface and the drive contact surface in contact with each other, The drive shaft is supported non-rotatably by a support member provided on one side in the axial direction, the drive gear is rotatably supported on the drive shaft at a position facing the support member, The drive transmission device according to claim 1, wherein the drive contact member is fixed to the drive shaft between a restricting member provided on the other side in the axial direction and the drive gear.

3. the drive contact surface has a curved surface that matches the pitch circle of the drive gear; 3. The drive transmission device according to claim 1, wherein the transmission contact surface has a curved surface that coincides with the pitch circle of the transmission gear.

4. The drive shaft is supported non-rotatably by a support member provided on one side in the axial direction, the drive gear is rotatably supported on the drive shaft at a position facing the support member, 2. The drive transmission device according to claim 1, wherein the drive contact member is fixed to the drive shaft between a restricting member provided on the other side in the axial direction and the drive gear.

5. The drive transmission device according to claim 2 or 4; a fixing member that heats the toner image on the medium while rotating around its axis; a pressure member that rotates around an axis to form a pressure region between itself and the fixing member, and that pressurizes the toner on the medium that passes through the pressure region; an ejection roller that rotates around the transmission shaft and transports the medium that has passed through the pressure area; a fixation cover that supports the transmission shaft to which the transmission gear is fixed so as to be rotatable about the axis, moves in an opening direction to release the transmission gear from meshing with the drive gear, and moves in a closing direction to mesh the transmission gear with the drive gear, The fixing device, wherein the biasing member biases the fixing cover in the closing direction.

6. An image forming apparatus comprising the fixing device according to claim 5.

Images