Transmission mechanism and image forming apparatus

Abstract

To provide a transmission mechanism which can easily perform an assembling work to a device main body.SOLUTION: A transmission mechanism 126 comprises: a first sleeve 130 having a first engagement part 162; a second sleeve 132 having a second engagement part 178 engaged with the first engagement part with a clearance in a peripheral direction; and a coil spring 134 arranged between the first sleeve and the second sleeve. The first sleeve has a first lock part 152, and the second sleeve has a second lock part 176 which is engaged with the first lock part in an axial direction. The first sleeve, the second sleeve, and an energization member are unitized by the engagement of the first lock part and the second lock part.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a transmission mechanism and an image forming apparatus, and in particular to a transmission mechanism that is arranged between a first gear and a second gear arranged side by side on the same rotation axis, and transmits the rotational force of the first gear to the second gear, and an image forming apparatus equipped with the same. [Background technology]

[0002] An example of a conventional transmission mechanism (drive transmission unit) is disclosed in Patent Document 1. The drive transmission unit of the technology of Patent Document 1 is a device that transmits drive force from a drive source to a rotating member of a sheet conveying device, and includes a first gear (first ratchet gear) provided with a first engagement portion, a second gear (second ratchet gear) provided with a second engagement portion that engages with the first engagement portion, and a biasing member that biases the first gear and the second gear toward each other. The first gear and the second gear transmit the drive force from the drive source to the rotating member by rotating in a first direction, and the first gear, which rotates in the first direction with the first engagement portion and the second engagement portion engaged, transmits the drive force to the second gear. A first surface of the first engagement portion, which transmits the drive force to the second gear while the first engagement portion rotates in the first direction, is inclined in a direction that allows the first engagement portion or the second engagement portion to retract in a direction against the biasing force of the biasing member and disengage from the other engagement portion while the first engagement portion rotates in the first direction. Then, before the torque applied to the first engagement portion and the second engagement portion by the driving force from the driving source exceeds the allowable torque that would deform or destroy the first gear or the second gear, the engagement between the first engagement portion and the second engagement portion is released. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-26433 Summary of the Invention [Problem to be solved by the invention]

[0004] A relatively large force is required when incorporating a biasing member into the device body, but with the technology of Patent Document 1, the biasing member and gear, etc. are attached separately, so the gear must be attached while pressing down on the biasing member with a large force, which creates assembly problems.

[0005] SUMMARY OF THE INVENTION Therefore, a primary object of the present invention is to provide a novel transmission mechanism and image forming apparatus.

[0006] Another object of the present invention is to provide a transmission mechanism and an image forming apparatus that can be easily assembled to the main body of the apparatus. [Means for solving the problem]

[0007] The first invention is a transmission mechanism disposed between a first gear and a second gear arranged side by side on the same rotation shaft, for transmitting the rotational force of the first gear to the second gear, the transmission mechanism comprising: a first sleeve rotatably disposed about the rotation shaft and having a first engagement portion; a second sleeve rotatably disposed alongside the first sleeve and having a second engagement portion that engages with the first engagement portion with rotational play that allows movement by a predetermined distance in the circumferential direction of the rotation shaft; and a second sleeve sandwiched between the first sleeve and the second sleeve, which is movable in a direction in which the engagement between the first engagement portion and the second engagement portion is released. the first sleeve has a first retaining portion, and the second sleeve has a second retaining portion that engages with the first retaining portion in the axial direction of the rotating shaft, the first sleeve, the second sleeve, and the biasing member are unitized by the engagement between the first retaining portion and the second retaining portion, one of the first retaining portion and the second retaining portion is a locking claw that extends in the axial direction of the rotating shaft, and the other of the first retaining portion and the second retaining portion is a locking hole with which the locking claw engages, and the length of the locking hole in the circumferential direction of the rotating shaft is greater than the length of the locking claw in the circumferential direction of the rotating shaft. The biasing member is a coil spring in which a wire is wound in a spiral shape, the first sleeve has a first restricting portion that contacts one end surface of the wire, the second sleeve has a second restricting portion that contacts the other end surface of the wire, and the coil spring is disposed between the first sleeve and the second sleeve in a state twisted in the radially expanding direction. , transmission mechanism.

[0008] In the first aspect of the present invention, the first and second engagement portions are engaged with a circumferential play, and the first and second sleeves are biased by a biasing member in a direction that disengages the first and second engagement portions, allowing the second sleeve to rotate freely relative to the first sleeve by a circumferential distance equal to the play. Therefore, this transmission mechanism functions as a buffer mechanism that absorbs shock, for example, when meshing another gear with the second gear. Furthermore, one of the first and second retention portions is a locking pawl extending in the axial direction of the rotating shaft, and the other of the first and second retention portions is a locking hole with which the locking pawl engages. The length of the locking hole in the circumferential direction of the rotating shaft is set to a value greater than the length of the locking pawl in the circumferential direction of the rotating shaft. The biasing member is a coil spring in which wire is wound in a spiral shape, the first sleeve has a first restricting portion that contacts one end surface of the wire, and the second sleeve has a second restricting portion that contacts the other end surface of the wire, and the coil spring is disposed between the first sleeve and the second sleeve in a state twisted in the radially expanding direction.

[0009] According to the first aspect of the present invention, the transmission mechanism is unitized by sandwiching the biasing member between the first sleeve and the second sleeve, which makes it easy to assemble the transmission mechanism to the device main body.

[0010] The second invention is dependent on the first invention. ,Ko Ilba Neha The restoring force against torsion urges the first sleeve and the second sleeve in a direction that disengages the first engaging portion from the second engaging portion, and the restoring force against compression urges the first sleeve and the second sleeve in a direction that separates them from each other in the axial direction of the rotation shaft.

[0013] A third invention is according to the first or second invention, wherein one of the first engaging portion and the second engaging portion is a protrusion that extends along the axial direction of the rotating shaft and has a length in the circumferential direction of the rotating shaft that is a first width, and the other of the first engaging portion and the second engaging portion is a groove that extends along the axial direction of the rotating shaft and has a length in the circumferential direction of the rotating shaft that is a second width that is greater than the first width. ,Ko Ilba Neha The first sleeve and the second sleeve are biased so that the protrusions come into contact with one of the two side surfaces that form the grooves.

[0014] No. 4 The inventions are the first to3 The image forming apparatus includes the transmission mechanism according to any one of the above aspects, and transmits a rotational force to the fixing unit using the transmission mechanism. [Effects of the Invention]

[0015] According to this invention, the transmission mechanism is unitized by sandwiching the biasing member between the first sleeve and the second sleeve, so that the assembly work of the transmission mechanism to the device main body can be easily performed.

[0016] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments, which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic cross-sectional view showing the internal structure of an image forming apparatus including a transmission mechanism according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing the image forming apparatus with the fixing unit removed. [Figure 3] FIG. 2 is a schematic cross-sectional view showing a fixing unit. [Figure 4] FIG. 2 is a perspective view showing a fixing unit driving device. [Figure 5] FIG. 2 is a perspective view showing a rotational force transmission device. [Figure 6] FIG. 2 is an exploded perspective view showing the configuration of the rotational force transmission device. [Figure 7] FIG. 2 is a perspective view showing a ratchet member provided in the rotational force transmission device. [Figure 8] FIG. [Figure 9] FIG. 2 is an exploded perspective view showing the configuration of a transmission mechanism included in the rotational force transmission device. [Figure 10] FIG. [Figure 11] FIG. 4 is a perspective view showing a first sleeve included in the transmission mechanism. [Figure 12] FIG. 4 is a first perspective view showing a second sleeve included in the transmission mechanism. [Figure 13] FIG. 10 is a second perspective view showing the second sleeve. [Figure 14] 3 is a diagram illustrating the internal structure of the torque transmission device in a state in which the first ratchet portion and the second ratchet portion are engaged with each other. FIG. [Figure 15] 4 is a diagram illustrating the internal structure of the torque transmission device in a state where the engagement between the first ratchet portion and the second ratchet portion is released. FIG. [Figure 16] 10 is a diagram illustrating a buffering operation of the torque transmission device. FIG. [Figure 17] FIG. 4 is an exploded perspective view showing the configuration of a transmission mechanism provided in a torque transmission device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] [First Example] 1 and 2, an image forming apparatus 10 according to an embodiment of the present invention forms a multicolor or monochrome image on paper (recording medium) by electrophotography. As will be described in detail later, the image forming apparatus 10 includes a rotational force transmission device 104 provided in an apparatus main body 12. The rotational force transmission device 104 includes an input gear 122, an output gear 124, a transmission mechanism 126, and the like (see FIG. 6), and transmits the driving force (rotational force) from the motor 102 to a fixing unit 46, which is an example of a removable unit.

[0019] First, a brief description will be given of the basic configuration of the image forming apparatus 10. In this specification, the front side (front) is defined as the surface facing the user's standing position, i.e., the surface on which the operation unit 26 is provided, and the front-rear direction (depth direction) of the image forming apparatus 10 and its components is defined. The left-right direction (horizontal direction) of the image forming apparatus 10 and its components is defined based on the state in which the image forming apparatus 10 is viewed from the user.

[0020] 1 and 2, in this embodiment, the image forming apparatus 10 is a multifunction peripheral (MFP) having a copying function, a printer function, a scanner function, a facsimile function, etc. The image forming apparatus 10 includes a device main body 12 equipped with an image forming unit 30, etc., and an image reading device 14 disposed above the device main body 12.

[0021] The image reading device 14 includes a document table 16 made of a transparent material. A document retaining cover 18 is attached above the document table 16 via a hinge or the like so that it can be opened and closed freely. This document retaining cover 18 is provided with an ADF (automatic document feeder) 24 that automatically feeds documents placed on a document tray 20 one by one to an image reading position 22. In addition, on the front side of the document table 16, an operation unit 26 is provided that accepts input operations such as printing instructions from the user. This operation unit 26 is appropriately provided with a display such as a touch panel display, various operation buttons, etc.

[0022] The image reading device 14 also includes an image reading unit 28 equipped with a light source, multiple mirrors, an imaging lens, a line sensor, and the like. The image reading unit 28 exposes the surface of the document to light, and directs the light reflected from the document surface to the imaging lens via multiple mirrors. The imaging lens then forms an image of the reflected light on the light-receiving elements of the line sensor. The line sensor detects the luminance and chromaticity of the reflected light that forms an image on the light-receiving elements, and generates image data based on the image of the document surface. A CCD (Charge Coupled Device) or a CIS (Contact Image Sensor) is used as the line sensor.

[0023] The device main body 12 incorporates a control unit (not shown) including a CPU and memory, and an image forming unit 30. The control unit transmits control signals to each part of the image forming device 10 in response to input operations by a user to the operation unit 26, causing the image forming device 10 to perform various operations.

[0024] Image forming section 30 includes an exposure unit 32, a developing device 34, a photosensitive drum 36, a cleaner unit 38, a charger 40, an intermediate transfer belt unit 42, a secondary transfer roller 44, and a fixing unit 46, and forms an image on paper conveyed from a paper feed tray 48 or a manual paper feed tray 50, and discharges the paper with the image formed on it to a paper discharge tray 52. ​​Image data used to form an image on paper is image data read by image reading section 28 or image data sent from an external computer.

[0025] The image data handled by the image forming apparatus 10 corresponds to color images of four colors: black (K), cyan (C), magenta (M), and yellow (Y). Therefore, four of each of the developing device 34, photosensitive drum 36, cleaner unit 38, and charger 40 are provided so as to form four types of latent images corresponding to each color, and these constitute four image stations.

[0026] The photosensitive drum 36 is an image carrier having a photosensitive layer formed on the surface of a cylindrical conductive base, and the charger 40 is a member that charges the surface of the photosensitive drum 36 to a predetermined potential. The exposure unit 32 is configured as a laser scanning unit (LSU) equipped with a laser emitter and a reflecting mirror, etc., and exposes the charged surface of the photosensitive drum 36 to light, thereby forming an electrostatic latent image on the surface of the photosensitive drum 36 according to image data. The developer 34 visualizes the electrostatic latent image formed on the surface of the photosensitive drum 36 with four-color (YMCK) toner. The cleaner unit 38 removes toner remaining on the surface of the photosensitive drum 36 after development and image transfer.

[0027] The intermediate transfer belt unit 42 includes an intermediate transfer belt 54, a drive roller 56, a driven roller 58, and four intermediate transfer rollers 60, and is disposed above the photosensitive drums 36. The intermediate transfer belt 54 is a flexible, endless belt that is stretched by a plurality of rollers, including the drive roller 56 and the driven roller 58, and is disposed so that its surface (outer periphery) abuts against the surface of the photosensitive drums 36. The intermediate transfer belt 54 rotates (circularly moves) in a predetermined direction as the drive roller 56 rotates. The intermediate transfer rollers 60 are disposed at positions facing each of the photosensitive drums 36 across the intermediate transfer belt 54. During image formation, the intermediate transfer rollers 60 are used to sequentially transfer the toner images of each color formed on each photosensitive drum 36 onto the intermediate transfer belt 54, superimposing them one on top of the other, thereby forming a multi-color toner image on the intermediate transfer belt 54.

[0028] The secondary transfer roller 44 is disposed opposite the drive roller 56 with the intermediate transfer belt 54 sandwiched therebetween. When a sheet of paper passes through the secondary transfer nip between the secondary transfer roller 44 and the intermediate transfer belt 54, the toner image formed on the intermediate transfer belt 54 is transferred onto the sheet of paper.

[0029] The fixing unit 46 (fixing device) includes a fixing belt 62, a pressure roller 64, and the like, and is disposed above the secondary transfer roller 44 (downstream in the paper transport direction). The fixing unit 46 is detachable from the apparatus main body 12. The fixing belt 62 includes a fixing pad 76, a heat source 82, and the like (see FIG. 3), and the fixing belt 62 is heated by the heat source 82 to a predetermined fixing temperature. The pressure roller 64 is also disposed so as to press the fixing belt 62 between itself and the fixing pad 76. When paper passes through the fixing nip N between the pressure roller 64 and the fixing belt 62, the toner image transferred to the paper is melted, mixed, and pressed against the paper, thereby thermally fixing the toner image to the paper.

[0030] Furthermore, a fixing unit drive device 100 is fixedly provided on the rear side of the fixing unit 46 (at the rear right part of the device body 12) in the device body 12. When the fixing unit 46 is attached to the device body 12, the fixing unit 46 and the fixing unit drive device 100 are connected, and the pressure roller 64 receives a rotational drive force from the fixing unit drive device 100 and is driven to rotate. The specific configurations of the fixing unit 46 and the fixing unit drive device 100 will be described later.

[0031] Within the device main body 12, a first paper transport path L1 is formed for sending paper from the paper feed tray 48 or manual paper feed tray 50 to the paper output tray 52 via the registration rollers 68, secondary transfer roller 44, and fixing unit 46. In addition, when performing double-sided printing on the paper, a second paper transport path L2 is formed for returning the paper, after single-sided printing is completed and the paper has passed through the fixing unit 46, to the first paper transport path L1 upstream in the paper transport direction of the secondary transfer roller 44. A plurality of transport rollers 66 for applying auxiliary propulsion force to the paper are appropriately provided in the first paper transport path L1 and the second paper transport path L2.

[0032] Next, the configuration of the fixing unit 46 will be described with reference to Fig. 3. The fixing unit 46 includes a fixing belt 62 and a pressure roller 64, and fixes a toner image onto the paper by passing the paper through a fixing nip N formed between them.

[0033] 3, the fixing unit 46 includes a heater unit 70 having a fixing belt 62 and the like, and a pressure roller 64. The members of the heater unit 70 and the pressure roller 64 are integrally held in a predetermined arrangement by a fixing frame (not shown).

[0034] The heater unit 70 includes a fixing belt 62 that is formed in a generally cylindrical shape and extends in the front-to-rear direction (the width direction of the paper). The fixing belt 62 is typically made of a strip-shaped base material made of a synthetic resin such as polyimide or a metal such as nickel, with a release layer provided on the surface. The fixing belt 62 is rotatable about its axis and has an inner diameter of, for example, 30 mm. Inside the fixing belt 62, a fixing pad 76, a support member 78, a reflector 80, a heat source 82, and the like are also provided.

[0035] The fixing pad 76 is a fixed member fixedly provided so as to be in sliding contact with the inner peripheral surface of the fixing belt 62, and is formed in the shape of a long plate extending along the axial direction of the fixing belt 62. The fixing pad 76 has a sliding contact sheet 76a on its outer peripheral surface (at least the surface that comes into sliding contact with the fixing belt 62), and sliding oil is applied to this sliding contact sheet 76a to reduce frictional force with the fixing belt 62. The length of the fixing pad 76 is the same as the axial length (width) of the fixing belt 62.

[0036] The support member 78 supports the fixing pad 76 while pressing it against the inner circumferential surface of the fixing belt 62, and both ends of the support member 78 are fixed to the fixing frame. In this embodiment, the support member 78 has a generally L-shaped cross section and includes a long plate-like fixing portion 78a to which the fixing pad 76 is fixed, and a long plate-like standing portion 78b standing from the widthwise end of the fixing portion 78a. In addition, a thin plate-like reflecting plate 80 is attached to the support member 78 so as to cover the surface facing the heat source 82.

[0037] The heat source 82 is a member for heating the fixing belt 62, and is provided so as to extend along the axial direction of the fixing belt 62. A lamp heater such as a halogen lamp is used as the heat source 82. In this embodiment, the heat source 82 includes a first lamp heater 82a that heats the central portion of the fixing belt 62 in the axial direction, and a second lamp heater 82b that heats both end portions of the fixing belt 62 in the axial direction.

[0038] The pressure roller 64 is disposed in a position facing the fixing pad 76 with the fixing belt 62 sandwiched therebetween. The pressure roller 64 is provided to extend parallel to the axial direction of the fixing belt 62, and presses the fixing belt 62 between itself and the fixing pad 76, thereby forming a fixing nip N between itself and the fixing belt 62.

[0039] A gear (not shown) is provided at the rear end of the roller shaft (not shown) of the pressure roller 64. An output gear 124 of a torque transmission device 104 (described later) is connected to this gear, thereby connecting a motor 102 (see FIG. 4) to the roller shaft of the pressure roller 64, and the pressure roller 64 is rotated by receiving driving force from the motor 102. In addition, as the pressure roller 64 is rotated, the fixing belt 62 is rotated in the direction opposite to the rotation direction of the pressure roller 64. That is, the pressure roller 64 abuts against the outer peripheral surface of the fixing belt 62 to form a fixing nip N between the pressure roller 64 and the fixing belt 62, and transmits a rotational driving force to the fixing belt 62 via the fixing nip N, thereby rotating the fixing belt 62.

[0040] The fixing unit 46 also includes a temperature sensor 94 such as a thermopile that detects the surface temperature of the fixing belt 62. Furthermore, a peeling plate 96 is provided downstream of the fixing nip N in the paper transport direction to prevent the paper from wrapping around the fixing belt 62.

[0041] Next, the configuration of the fixing unit drive device 100 will be described. As shown in Fig. 4, the fixing unit drive device 100 is a device for applying a rotational drive force to the fixing unit 46, and includes a motor 102, which is an example of a drive source, and a rotational force transmission device 104. The rotational force transmission device 104 is connected to the motor 102 via a pinion gear 106 and an intermediate gear 108, and the motor 102, rotational force transmission device 104, pinion gear 106, intermediate gear 108, etc. are held in a predetermined arrangement by a frame 110. The drive force from the motor 102 is transmitted to the pressure roller 64 of the fixing unit 46 via the pinion gear 106, intermediate gear 108, and rotational force transmission device 104.

[0042] 5 and 6, the rotational force transmission device 104 includes an input gear 122 (first gear) and an output gear 124 (second gear) made of synthetic resin and arranged side by side on the same rotation shaft 120 (support shaft). When the fixing unit 46 is attached to the apparatus main body 12, a gear provided at the rear end of the roller shaft of the pressure roller 64 meshes with the output gear 124 of the rotational force transmission device 104. The input gear 122 and the output gear 124 rotate about the rotation shaft 120 in the first direction X (positive rotation direction) due to the driving force from the motor 102, whereby the rotational force transmission device 104 transmits rotational force to the pressure roller 64 of the fixing unit 46.

[0043] Here, it is preferable to provide a torque limiter mechanism to prevent damage to the gears due to a high load being applied to the fixing unit drive device 100 when the fixing unit 46 is locked due to damage to the fixing belt 62, etc. Furthermore, to prevent damage to the gears due to the impact when the gear of the pressure roller 64 and the output gear 124 of the rotational force transmission device 104 mesh together when the fixing unit 46 is attached to the device main body 12, it is preferable to provide a buffer mechanism to absorb this impact.

[0044] Therefore, in this embodiment, the following configuration is adopted for the rotational force transmission device 104, thereby reducing the number of parts and reducing costs by sharing parts, and allowing the rotational force transmission device 104 to function as a torque limiter mechanism and a buffer mechanism. In addition, by unitizing the biasing member with other parts, the ease of assembly to the device main body 12 is improved. The configuration of the rotational force transmission device 104 will be described in detail below.

[0045] As shown in FIGS. 5 and 6 , a transmission mechanism 126 and a ratchet member 128 are provided on the same rotary shaft 120 between the input gear 122 and the output gear 124. The transmission mechanism 126 is attached to the front surface of the input gear 122 (the side surface on the output gear 124 side). As will be described in detail later, the transmission mechanism 126 is composed of three members: a first sleeve 130, a second sleeve 132, and a coil spring 134, which is an example of a biasing member. These three members are combined together to form a unit. A fitting protrusion 160 is formed on the rear end of the transmission mechanism 126 (specifically, the rear end of the first sleeve 130) to fit into a fitting hole 122a formed in the input gear 122. The transmission mechanism 126 is connected and fixed to the input gear 122 by fitting the fitting protrusion 160 into the fitting hole 122a, and rotates together with the input gear 122 around the rotary shaft 120. Furthermore, a first ratchet portion 190 is formed at the front end portion of the transmission mechanism 126 (the end portion on the input gear 122 side, specifically the front end portion of the second sleeve 132).

[0046] 7 and 8 as well as Fig. 6, the ratchet member 128 is made of synthetic resin and is attached to the rear surface of the output gear 124 (the side surface on the input gear 122 side). The ratchet member 128 has a circular plate-shaped base 140 with an insertion hole 140a formed in the center, through which the rotation shaft 120 is inserted. Four fitting protrusions 142 with a generally trapezoidal cross section are formed on the front surface of the base 140 and fit into fitting holes 124a formed in the output gear 124. The ratchet member 128 is connected and fixed to the output gear 124 by fitting the fitting protrusions 142 into the fitting holes 124a, and rotates together with the output gear 124 around the rotation shaft 120. In addition, a short cylindrical portion 144 that protrudes rearward from the peripheral edge is formed on the rear surface of the base 140, and a second ratchet portion 146 that engages with the first ratchet portion 190 is formed on the rear end surface of the short cylindrical portion 144 (i.e., the end portion of the ratchet member 128 on the input gear 122 side).

[0047] The second ratchet portion 146 is configured with a plurality of saw-tooth teeth 146a arranged in the circumferential direction. Each of the plurality of teeth 146a has a third inclined surface 146b and a fourth inclined surface 146c that engage with a first inclined surface 190b and a second inclined surface 190c, respectively, of the first ratchet portion 190, which will be described later. That is, the second ratchet portion 146 in this embodiment has a plurality of third inclined surfaces 146b that are inclined at a first inclination angle θ1 with respect to the axial direction of the rotating shaft 120 and that engage with each of the plurality of first inclined surfaces 190b, and a plurality of fourth inclined surfaces 146c that are inclined at a second inclination angle θ2 with respect to the axial direction of the rotating shaft 120 and that engage with each of the plurality of second inclined surfaces 190c.

[0048] 9 and 10, the transmission mechanism 126 is made up of three members: a first sleeve 130 arranged on the input gear 122 side; a second sleeve 132 arranged on the output gear 124 side; and a coil spring 134 arranged between the first sleeve 130 and the second sleeve 132. These three members are unitized in advance before being attached to the device main body 12. By unitizing the members by sandwiching the coil spring 134 between the first sleeve 130 and the second sleeve 132 in this way, the attachment (assembly) of the transmission mechanism 126 to the device main body 12 becomes easier.

[0049] 9 and 10 , and referring to FIG. 11 , the first sleeve 130 is made of synthetic resin and includes a short cylindrical base 150 having a central insertion hole 150a through which the rotary shaft 120 is inserted. Two locking claws 152, which are an example of a first retaining portion, are formed at the front end of the base 150. The locking claws 152 are formed to protrude forward from the front end of the base 150 and extend in the axial direction of the rotary shaft 120, and have a hook portion 152a protruding outward at their tip ends. The first sleeve 130 also includes a cylindrical tubular portion 154 formed to surround the base 150, and a cylindrical first retaining portion 156 formed to surround the tubular portion 154. The rear ends of the base 150, the tubular portion 154, and the first retaining portion 156 are connected by a connecting portion 158 in the shape of an annular ring. Furthermore, two fitting protrusions 160 having a generally trapezoidal cross section are formed on the rear surface of the connecting portion 158 to be fitted into fitting holes 122 a formed in the input gear 122 .

[0050] A first engagement portion 162 is formed on the outer peripheral surface of the cylindrical portion 154. In this embodiment, the first engagement portion 162 is configured by a plurality of generally rectangular plate-shaped protrusions that are arranged at predetermined intervals around the circumference of the rotary shaft 120 and extend in the axial direction of the rotary shaft 120. A flange-shaped first locking portion 164 that protrudes outward beyond the first holding portion 156 is formed on the peripheral edge of the connecting portion 158, and a short cylindrical return portion 166 that protrudes forward is formed on the peripheral edge of the first locking portion 164. Furthermore, a first restriction portion 168 that has a rectangular cross section and protrudes forward is formed on the front surface of the first locking portion 164.

[0051] 9 and 10 as well as 12 and 13, second sleeve 132 is made of synthetic resin and includes a short cylindrical base portion 170 having an insertion hole 170a formed in the center thereof through which rotation shaft 120 is inserted. Second sleeve 132 also includes a cylindrical tubular portion 172 formed to surround base portion 170, and the rear end of base portion 170 and the center of tubular portion 172 are connected by a connecting portion 174 in the shape of an annular ring.

[0052] Two locking holes 176, which are an example of a second locking portion that engages with the first locking portion (locking claw 152) of the first sleeve 130 in the axial direction of the rotating shaft 120, are formed in the base 170 and the connecting portion 174. The locking holes 176 are holes with a rectangular cross section that are formed by cutting out the rear portion of the base 170 and the inner peripheral edge of the connecting portion 158 in the thickness direction of the base 170. In this embodiment, the length W2 of the locking holes 176 in the circumferential direction of the rotating shaft 120 is set to a value greater than the length W1 of the locking claw 152 in the circumferential direction of the rotating shaft 120. In other words, the locking claw 152 and the locking hole 176 are provided with a rotational play that allows the locking claw 152 to move in the circumferential direction of the rotating shaft 120 by the difference between W1 and W2. In other words, the locking claw 152 is attached to the locking hole 176 with a rotational play that allows the locking claw 152 to move within a range within the difference between W1 and W2, that is, a predetermined distance in the circumferential direction of the rotating shaft 120.

[0053] Then, the locking claw 152 is fitted into the locking hole 176, and the hook portion 152a of the locking claw 152 is locked to the inner peripheral edge portion of the connecting portion 174, whereby the second sleeve 132 is integrated (unitized) with the first sleeve 130 in a state where it is prevented from coming off in the axial direction (front side) of the rotating shaft 120. Also, by making the length of the locking hole 176 in the axial direction of the rotating shaft 120 larger than the length of the hook portion 152a of the locking claw 152, the second sleeve 132 is integrated with the first sleeve 130 so as to be movable in the axial direction of the rotating shaft 120.

[0054] Additionally, a second engagement portion 178 that engages with the first engagement portion 162 of the first sleeve 130 is formed on the inner peripheral surface of the rear portion of the cylindrical portion 172. In this embodiment, the second engagement portion 178 is configured with a plurality of grooves that are arranged at predetermined intervals in the circumferential direction of the rotating shaft 120 and extend in the axial direction of the rotating shaft 120. Each of the grooves is formed by two protrusions 180. The rotational force of the first sleeve 130 is transmitted to the second sleeve 132 by engaging the first engagement portion 162 with the second engagement portion 178.

[0055] In this embodiment, the length W4 (second width) of the second engagement portion 178 in the circumferential direction of the rotary shaft 120 is set to a value larger than the length W3 (first width) of the first engagement portion 162 in the circumferential direction of the rotary shaft 120. That is, the first engagement portion 162 and the second engagement portion 178 are engaged with each other with a rotational play that allows them to move in the circumferential direction of the rotary shaft 120 by the difference between W3 and W4. The magnitude α of this rotational play (see FIG. 16 ) is set to a value equivalent to one to three pitches of the output gear 124. That is, the second engagement portion 178 engages with the first engagement portion 162 with a rotational play that allows them to move a predetermined distance in the circumferential direction of the rotary shaft 120. The magnitude of the circumferential play between the locking claw 152 and the locking hole 176 is set to a value equal to or slightly larger than α. Therefore, it can be said that the magnitude α of the rotational play is determined by the difference in length between the first engagement portion 162 and the second engagement portion 178 in the circumferential direction.

[0056] A short cylindrical second holding portion 182 is provided on the outer peripheral surface of the front end of the tubular portion 172. A flange-shaped second locking portion 184 that protrudes outward is formed at the front end of the second holding portion 182, and a short cylindrical return portion 186 that protrudes rearward is formed on the periphery of the second locking portion 184. Furthermore, a second restricting portion 188 that has a rectangular cross section and protrudes rearward is formed on the rear surface of the second locking portion 184.

[0057] A first ratchet portion 190 is formed at the front end of the cylindrical portion 172. The first ratchet portion 190 is composed of a plurality of sawtooth-shaped teeth 190a arranged in the circumferential direction. Each of the plurality of teeth 190a has a first inclined surface 190b formed on the surface that presses the second ratchet portion 146 when the transmission mechanism 126 is rotated in the first direction X to transmit the driving force from the motor 102 to the ratchet member 128, and a second inclined surface 190c formed on the opposite side. A second inclination angle θ2 of the second inclined surface 190c with respect to the axial direction of the rotation shaft 120 is set to a value greater than the first inclination angle θ1 of the first inclined surface 190b. That is, the first ratchet portion 190 of this embodiment has a plurality of first inclined surfaces 190b inclined at a first inclination angle θ1 with respect to the axial direction of the rotating shaft 120, and a plurality of second inclined surfaces 190c formed between the plurality of first inclined surfaces 190b and inclined at a second inclination angle θ2 larger than the first inclination angle θ1 with respect to the axial direction of the rotating shaft 120. The first inclination angle θ1 is preferably set to a value of, for example, 2 degrees or more and 15 degrees or less, and the second inclination angle θ2 is preferably set to a value of, for example, 60 degrees or more and 80 degrees or less.

[0058] 9 and 10 , coil spring 134, an example of a biasing member, is a general-purpose compression coil spring in which metal wire is wound spirally at predetermined intervals in the axial direction, and is provided so as to be sandwiched between first sleeve 130 and second sleeve 132. Specifically, a rear end of coil spring 134 is fitted onto first retaining portion 156 of first sleeve 130 and held by first retaining portion 156, and a front end of coil spring 134 is fitted onto second retaining portion 182 of second sleeve 132 and held by second retaining portion 182. At this time, rear end 134a of coil spring 134 abuts against first locking portion 164 of first sleeve 130, and front end 134b of coil spring 134 abuts against second locking portion 184 of second sleeve 132. The first sleeve 130 and the second sleeve 132 are biased in directions away from each other in the axial direction of the rotating shaft 120 by the restoring force of the coil spring 134 against compression. In other words, the coil spring 134 biases the second sleeve 132 toward the ratchet member 128.

[0059] Furthermore, when the coil spring 134 is mounted on the first sleeve 130 and the second sleeve 132, it is slightly twisted in the radially expanding direction. In this state, one end 134c (one end face) of the wire material forming the coil spring 134 abuts against the first restricting portion 168 of the first sleeve 130 in the circumferential direction of the rotating shaft 120, thereby restricting the circumferential position of the one end 134c. Furthermore, the other end 134d (other end face) of the wire material forming the coil spring 134 abuts against the second restricting portion 188 of the second sleeve 132 in the circumferential direction of the rotating shaft 120, thereby restricting the circumferential position of the other end 134d. As a result, the coil spring 134 biases the first sleeve 130 and the second sleeve 132 by its restoring force against torsion in a direction in which the engagement between the first engagement portion 162 and the second engagement portion 178 is released, that is, in a direction in which the first engagement portion 162 (protrusion) abuts against one side surface 178a of both side surfaces forming the second engagement portion 178 (groove) (see FIG. 16 ). Note that the side surface 178a is the side surface opposite the side surface 178b with which the first engagement portion 162 abuts when the first sleeve 130 rotates in the first direction X. Therefore, it can be said that the coil spring 134 biases the first sleeve 130 and the second sleeve 132 by its restoring force against torsion so that rotational play with the second engagement portion is generated on the first direction X side relative to the first engagement portion 162.

[0060] 14, in the rotational force transmission device 104 described above, when the fixing unit 46 is driven, the input gear 122 receives a driving force from the motor 102 and rotates in the first direction X. Accordingly, the transmission mechanism 126 rotates in the first direction X, and the first inclined surface 190b of the first ratchet portion 190 presses the third inclined surface 146b of the second ratchet portion 146, causing the ratchet member 128 and the output gear 124 to rotate in the first direction X. As a result, the driving force of the motor 102 is transmitted to the pressure roller 64 of the fixing unit 46, causing the pressure roller 64 to rotate in the forward direction (the direction in which the paper is conveyed toward the paper output tray 52).

[0061] 15 , when the fixing unit 46 is locked while the motor 102 is running and a rotational load of a predetermined value or greater acts between the first ratchet portion 190 and the second ratchet portion 146, the second sleeve 132 moves in a direction away from the ratchet member 128 (rearward) against the biasing force of the coil spring 134, thereby disengaging the first ratchet portion 190 and the second ratchet portion 146. When a rotational load of a predetermined value or greater acts between the first ratchet portion 190 and the second ratchet portion 146, the second sleeve 132 moves in a direction away from the ratchet member 128 because the first ratchet portion 190 and the second ratchet portion 146 have the first inclined surface 190b and the third inclined surface 146b. That is, in this embodiment, the torque limiter mechanism is configured by three components: the ratchet member 128, the second sleeve 132, and the coil spring 134.

[0062] 16 , the first engagement portion 162 and the second engagement portion 178 are engaged with each other with rotational play in the circumferential direction of the rotating shaft 120, and the coil spring 134 biases the first sleeve 130 and the second sleeve 132 in a direction that disengages the first engagement portion 162 and the second engagement portion 178, causing the first engagement portion 162 to abut against one side surface 178a of the second engagement portion 178. As a result, in a free state in which the motor 102 is stopped, a non-transmission section is formed in which no rotational force is transmitted over a circumferential distance equivalent to the magnitude α of the rotational play, and the second sleeve 132 is able to rotate freely in the second direction Y relative to the first sleeve 130. Therefore, when the fixing unit 46 is attached to the apparatus main body 12, that is, when the gear of the pressure roller 64 and the output gear 124 of the rotational force transmission device 104 mesh together while the motor 102 is stopped and free, the second sleeve 132, the ratchet member 128, and the output gear 124 can rotate freely relative to the first sleeve 130, thereby mitigating the impact caused by this meshing. That is, in this embodiment, a buffer mechanism is made up of the three components of the transmission mechanism 126: the first sleeve 130, the second sleeve 132, and the coil spring 134. Furthermore, even if the fixing unit 46 becomes locked (the pressure roller 64 does not rotate) for some reason, the fixing unit 46 can be easily removed from the apparatus main body 12 because of the rotational play.

[0063] As described above, according to this embodiment, the coil spring 134 is sandwiched between the first sleeve 130 and the second sleeve 132 to form a unit, which facilitates the assembly of the transmission mechanism 126 to the device main body 12. In other words, the assembly performance is excellent.

[0064] Furthermore, according to this embodiment, the transmission mechanism 126 functions as a buffer mechanism, so that damage to the gears when the fixing unit 46 is attached can be appropriately prevented.

[0065] Furthermore, according to this embodiment, the coil spring 134 functions as a compression spring in the torque limiter mechanism (and ratchet mechanism) and as a torsion spring in the buffer mechanism, so that one coil spring 134 is shared by both mechanisms. Also, the second sleeve 132 is shared as a component of both the torque limiter mechanism and the buffer mechanism. This allows for fewer parts, lower costs, and a smaller size.

[0066] [Second Example] Next, a rotational force transmission device 104 according to a second embodiment of the present invention will be described with reference to Fig. 17. In this second embodiment, the configuration of the coil spring 134 of the transmission mechanism 126 included in the rotational force transmission device 104 differs from that of the first embodiment described above. Since the other parts are similar, the same reference numerals are used for parts common to the first embodiment described above, and duplicated descriptions will be omitted or simplified.

[0067] 17, in this embodiment, a first extension portion 134e and a second extension portion 134f extending in the axial direction are formed at both ends of the wire material forming the coil spring 134. Meanwhile, a fitting hole 164a (another example of a first restricting portion) extending in the axial direction and having a circular cross section is formed in the first locking portion 164 of the first sleeve 130, and a fitting hole 184a (another example of a second restricting portion) extending in the axial direction and having a circular cross section is formed in the second locking portion 184 of the second sleeve 132. The first extension portion 134e is fitted into the fitting hole 164a and engaged with the fitting hole 164a, thereby restricting the circumferential position of the first extension portion 134e. The second extension portion 134f is fitted into the fitting hole 184a and engaged with the fitting hole 184a, thereby restricting the circumferential position of the second extension portion 134f.

[0068] In this second embodiment, the same effects as those of the first embodiment can be achieved, and damage to the gears when the fixing unit 46 is attached can be appropriately prevented.

[0069] In the above-described embodiment, the output gear and the second ratchet member are formed as separate parts, and the second ratchet member is attached to the output gear, but the output gear and the second ratchet member may be integrally molded in advance. Similarly, the input gear and the first sleeve may be integrally molded in advance.

[0070] In the above-described embodiment, the first engagement portion formed on the first sleeve is a ridge and the second engagement portion formed on the second sleeve is a groove, but the first engagement portion may be a groove and the second engagement portion may be a ridge. Also, the first removal prevention portion formed on the first sleeve is a locking claw and the second removal prevention portion formed on the second sleeve is a locking hole, but the first removal prevention portion may be a locking hole and the second removal prevention portion may be a locking claw.

[0071] Furthermore, in the above-described embodiment, a multifunction machine that combines a copier, a facsimile, a printer, etc., is exemplified as the image forming apparatus, but the image forming apparatus may be any one of a copier, a facsimile, a printer, etc., or a multifunction machine that combines at least two of these. Also, the image forming apparatus may be a monochrome machine.

[0072] Furthermore, in each of the above-described embodiments, the transmission mechanism is applied to a fixing unit drive device, but the transmission mechanism can also be applied to other rotational force transmission units of an image forming device, or to rotational force transmission units provided in devices other than an image forming device.

[0073] Furthermore, the specific numerical values ​​and materials given above are merely examples and can be changed as appropriate according to the needs of the product specifications, etc. [Explanation of symbols]

[0074] 10...Image forming device 12...Device body 30...Image forming unit 46...Fuser unit (detachable unit) 64...Pressure roller 100...Fuser unit drive device 102...Motor (drive source) 104 ...Rotational force transmission device 120...rotation axis 122...Input gear (1st gear) 124...Output gear (2nd gear) 126...Transmission mechanism 128 ... Ratchet member 130...1st sleeve 132...Second sleeve 134... Coil spring (biasing member) 146...Second ratchet part 152 ... Locking claw (first locking portion) 162 ... First engagement portion 178 ... Second engagement portion 190 ... Locking hole (second locking portion)

Claims

1. A transmission mechanism is disposed between a first gear and a second gear arranged side by side on the same rotation shaft, and transmits a rotational force of the first gear to the second gear, a first sleeve rotatably provided around the rotation axis and having a first engagement portion; a second sleeve provided alongside the first sleeve so as to be rotatable about the rotation axis, the second sleeve having a second engaging portion that engages with the first engaging portion with rotational play that allows the second sleeve to move a predetermined distance in a circumferential direction of the rotation axis; and a biasing member that is sandwiched between the first sleeve and the second sleeve and biases the first sleeve and the second sleeve in a direction in which the engagement between the first engaging portion and the second engaging portion is released, the first sleeve has a first retaining portion, and the second sleeve has a second retaining portion that engages with the first retaining portion in the axial direction of the rotation shaft, and the first sleeve, the second sleeve, and the biasing member are unitized by the engagement between the first retaining portion and the second retaining portion, one of the first retaining portion and the second retaining portion is a locking claw extending in the axial direction of the rotation shaft, and the other of the first retaining portion and the second retaining portion is a locking hole with which the locking claw engages, a length of the locking hole in the circumferential direction of the rotation shaft is greater than a length of the locking claw in the circumferential direction of the rotation shaft; The biasing member is a coil spring in which a wire is wound in a spiral shape, the first sleeve has a first restricting portion that abuts against one end surface of the wire, the second sleeve has a second restricting portion that abuts against the other end surface of the wire, The coil spring is disposed between the first sleeve and the second sleeve in a state twisted in a radially expanding direction.

2. 2. The transmission mechanism according to claim 1, wherein the coil spring biases the first sleeve and the second sleeve in a direction disengaging the first engaging portion and the second engaging portion by a restoring force against torsion, and biases the first sleeve and the second sleeve in a direction separating them from each other in the axial direction of the rotating shaft by a restoring force against compression.

3. one of the first engagement portion and the second engagement portion is a protrusion that extends along the axial direction of the rotating shaft and has a length in the circumferential direction of the rotating shaft that is a first width, the other of the first engaging portion and the second engaging portion is a groove portion that extends along the axial direction of the rotating shaft and has a length in the circumferential direction of the rotating shaft that is a second width that is greater than the first width, 3. The torque transmission device according to claim 1, wherein the coil spring biases the first sleeve and the second sleeve so that the protrusion contacts one of the two side surfaces that define the groove.

4. A transmission mechanism according to any one of claims 1 to 3, an image forming apparatus that transmits a rotational force to a fixing unit using the transmission mechanism;

Images