Fixing device and image forming apparatus including the same

Abstract

To provide a fixing device comprising a heat roller body having a driven gear attached to its one end, and prevent the generation of unusual sound caused by advanced rotation of the heat roller body.SOLUTION: A fixing device has a notch part 33a that is formed at an end of a heat roller body 33, a pair of projection plate parts 33b, 33c that are connected to two edges of the notch part 33a, and a transmission projection part 36e that is formed on a driven gear 36 and inserted into the notch part 33a. The transmission projection part 36e is in contact with one projection plate part 33b to transmit a rotation power of the driven gear 36 to the heat roller body 33. The driven gear 36 has a contact part 33g that is located on the front side in a roller rotation direction with respect to one projection plate part 33b. An interval k1 in the roller rotation direction between the contact part 33g and one projection plate part 33b is narrower than an interval k2 in the roller rotation direction between the transmission projection part 36e and the other projection plate part 33c.SELECTED DRAWING: Figure 8A

Description

Technical Field

[0001] The present invention relates to a fixing device and an image forming apparatus including the fixing device.

Background Art

[0002] For example, an image forming apparatus such as a laser printer has an image forming unit and a fixing device. The image forming unit has a photosensitive drum, a developing unit, a transfer roller, and a laser scanning unit (LSU).

[0003] The laser scanning unit irradiates the photosensitive drum with laser light based on image information. As a result, an electrostatic latent image is formed on the photosensitive drum. Next, the developing unit supplies toner to the photosensitive drum, thereby forming a toner image on the photosensitive drum. The toner image on the photosensitive drum is transferred onto a sheet by the transfer roller. The toner image transferred onto the sheet is fixed to the sheet by the fixing device.

[0004] Here, the fixing device has a heat roller disposed in a housing and a pressure roller extending along the heat roller. The heat roller has a tubular heat roller body made of a metal material and a heater provided inside the heat roller body. Then, with the heat roller body heated by the heater, the sheet onto which the toner image has been transferred is supplied between the heat roller and the pressure roller, whereby the toner image is fixed to the sheet.

[0005] A driven gear for rotating the heat roller body about its axis is mounted on the outer peripheral surface of one end side of the heat roller body. A driving gear meshes with the driven gear.

[0006] As described in Patent Document 1, usually, protrusions are formed on the inner peripheral surface of the driven gear, while a slit-shaped notch is formed at the end of the heat roller body. Then, the driven gear is mounted on the heat roller body by inserting the protrusions of the driven gear into the notch of the heat roller body.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In the fixing device shown in Patent Document 1, since the protrusion (transmission protrusion) provided on the driven gear is only inserted into the notch provided in the heat roller body, there is a risk that the end face of the notch hits the transmission protrusion and loses, resulting in a decrease in the power transmission function.

[0009] In order to avoid this problem, a pair of protruding plate portions are formed from the two axially extending edges in the notch portion of the heat roller body toward the inner side of the roller, and the power transmission function can be improved by bringing the transmission protrusion into contact with the side surface of the protruding plate portion when the driven gear rotates.

[0010] FIG. 9A is a cross-sectional view perpendicular to the axial direction showing a state in which the driven gear 102 is attached to the heat roller body 101 provided with a pair of protruding plate portions 101a in this way. The interval between the pair of protruding plate portions 101a is preferably set larger than the width of the transmission protrusion 102a of the driven gear 102 in consideration of thermal expansion. However, in this case, for example, when the driven gear 102 stops instantaneously due to backlash or the like generated between the driven gear 102 and a driving gear (not shown), as shown in FIG. 9B, the heat roller body 101 rotates forward and the protruding plate portion 101a located on the front side in the rotation direction collides with the end face of the transmission protrusion 102a. Since this collision occurs every time the driven gear rotates, there is a problem that abnormal noise associated with the collision occurs in the rotation cycle of the driven gear.

[0011] The present invention has been made in view of such a point, and an object thereof is to prevent the generation of abnormal noise caused by the forward rotation of a heat roller body in a fixing device provided with a heat roller body having a driven gear attached to one end, while sufficiently ensuring the power transmission function by the driven gear.

Means for Solving the Problems

[0012] The fixing device according to the present invention includes a heat roller body formed in a cylindrical shape, a driven gear attached to an end of the heat roller body and meshing with a driving gear, a notch formed at an end of the heat roller body and recessed inward in the axial direction, a pair of protruding plate portions extending from two edges extending in the axial direction in the notch toward the inner side of the roller and facing each other in the width direction of the notch orthogonal to the axial direction, and a transmission protrusion formed on the driven gear, which is inserted into the notch when the driven gear is attached to the end of the heat roller body and transmits the rotational power of the driven gear to the heat roller body by contacting one of the pair of protruding plate portions when the driven gear rotates. The dimension of the transmission protrusion along the width direction of the notch is set smaller than the interval in the width direction of the pair of protruding plate portions. The driven gear is located on the front side in the roller rotation direction with respect to one of the protruding plate portions in the heat roller body and has a contact portion that contacts the one protruding plate portion when the heat roller body rotates forward. The interval in the roller rotation direction between the contact portion and the one protruding plate portion is set to be narrower than the interval in the roller rotation direction between the transmission protrusion and the other protruding plate portion in a state where the transmission protrusion contacts the one protruding plate portion.

Effects of the Invention

[0013] According to the present invention, in a fixing device provided with a heat roller body having a driven gear attached to one end, it is possible to prevent the generation of abnormal noise caused by the forward rotation of the heat roller body while sufficiently ensuring the power transmission function by the driven gear.

Brief Description of the Drawings

[0014]

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8A

Fig. 8B

Fig. 9A

Fig. 9B

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments.

[0016] 《Embodiment》 FIG. 1 is a cross-sectional view showing the schematic configuration of the image forming apparatus 1 in the present embodiment. As shown in FIG. 1, the image forming apparatus 1 includes a housing 2, a cassette paper feeding unit 7, an image forming unit 8, a fixing device 9, and a paper discharging unit 10. Then, the image forming apparatus 1 is configured to form a toner image on a sheet while transporting the sheet along a transport path in the housing 2 based on image data transmitted from a terminal (not shown) or the like.

[0017] The cassette paper feeding unit 7 is provided at the bottom of the housing 2. The cassette paper feeding unit 7 includes a paper feeding cassette 11 that houses a plurality of sheets stacked on top of each other, and a pick-up roller 12 that takes out the sheets in the paper feeding cassette 11 one by one.

[0018] The image forming unit 8 is provided above the cassette paper feeding unit 7 in the housing 2. The image forming unit 8 includes a photosensitive drum 16 which is an image carrier rotatably provided in the housing 2, a charging roller 17 disposed around the photosensitive drum 16, a developing unit 18, a transfer roller 19 and a cleaning unit 20, and a laser scanner unit (LSU) 30 which is an optical scanning device disposed on the side of the photosensitive drum 16. Then, the image forming unit 8 is configured to form an image on the sheet supplied from the cassette paper feeding unit 7.

[0019] A pair of registration rollers 15 are provided in the transport path to temporarily hold the fed sheet and then supply it to the image forming unit 8 at a predetermined timing.

[0020] The fixing device 9 is disposed above the image forming unit 8. The fixing device 9 includes a heat roller 22 and a pressure roller 23 that are pressed against each other and rotate. Then, the fixing device 9 is configured to fix the toner image transferred to the sheet by the image forming unit 8 onto the sheet.

[0021] The paper discharge unit 10 is provided on the side of the fixing device 9. The paper discharge unit 10 includes a paper discharge tray 3, a paper discharge roller 24 for transporting the paper to the paper discharge tray 3, and a transport guide rib 25 for guiding the paper to the paper discharge roller 24. The paper discharge tray 3 is formed in a concave shape on the upper part of the housing 2.

[0022] When the image forming apparatus 1 receives image data, in the image forming unit 8, the photosensitive drum 16 is rotationally driven and the charging roller 17 charges the surface of the photosensitive drum 16.

[0023] Then, based on the image data, laser light is emitted from the laser scanner unit 30 to the photosensitive drum 16. An electrostatic latent image is formed on the surface of the photosensitive drum 16 by the irradiation of the laser light. On the other hand, toner is supplied from the toner container 21 to the developing unit 18. The electrostatic latent image formed on the photosensitive drum 16 is developed in the developing unit 18 to become a visible image as a toner image.

[0024] Thereafter, the paper passes between the transfer roller 19 and the photosensitive drum 16, and the toner image on the photosensitive drum 16 is transferred to the paper by the transfer bias applied to the transfer roller 19 during this passage. The paper onto which the toner image has been transferred is heated and pressurized by the heat roller 22 and the pressure roller 23 in the fixing device 9. As a result, the toner image is fixed to the paper.

[0025] <Fixing device> FIG. 2 is a side view of the fixing device 9 as viewed from the heat roller 22 side, and FIG. 3 is a cross-sectional view showing an enlarged view of the heat roller main body 33 to which the driven gear 36 is attached.

[0026] As shown in FIG. 2, the fixing device 9 has a housing 31 and a heat roller 22 rotatably supported by the housing 31. The housing 31 is formed of a resin material or the like. Further, the fixing device 9 includes a pressure roller 23 (shown only in FIG. 1) extending along the heat roller 22.

[0027] The heat roller 22 has a heat roller body 33 formed in a cylindrical shape, a heater 34 which is a heat source disposed inside the heat roller body 33, and a driven gear 36 attached to an end of the heat roller body 33 and meshing with a drive gear 35.

[0028] The heat roller body 33 is made of a metal material such as aluminum, for example, and has a cylindrical shape. The thickness of the heat roller body 33 is, for example, about 1 mm or less. The heater 34 is inserted inside the heat roller body 33. The heater 34 is configured to generate heat when energized and heat the heat roller body 33 to a predetermined temperature.

[0029] The heat roller body 33 is supported by the housing 31 via a plurality of bushing 37, 38 which are cylindrical bearing members. The bushings 37, 38 are formed of a resin material, for example.

[0030] Flange portions 37a, 38a are respectively formed on the outer peripheral surfaces of the bushings 37, 38. The flange portions 37a, 38a are respectively fitted into grooves 31a formed in the housing 31. Thereby, the bushings 37, 38 are prevented from moving in the axial direction of the heat roller body 33.

[0031] FIG. 4 and FIG. 5 are respectively a perspective view and a side view seen from the axial direction showing an enlarged end portion of the heat roller body 33, and FIG. 6 and FIG. 7 are respectively a perspective view and a side view seen from the axial direction showing the driven gear 36.

[0032] As shown in FIGS. 4 and 5, a notch 33a is formed at the end of the heat roller body 33. The notch 33a is formed to be recessed inward in the axial direction from the end face of the heat roller body 33 when viewed from the radial direction of the heat roller body 33.

[0033] On the inner peripheral edge of the notch portion 33a, a U-shaped wall portion protruding radially inward of the heat roller body 33 is formed. This U-shaped wall portion includes a pair of protruding plate portions 33b and 33c facing each other in the width direction of the notch portion 33a. When one of the protruding plate portions 33b located on the front side in the rotational direction of the transmission protrusion 36e is pressed against the transmission protrusion 36e, a rotational driving force is transmitted from the driven gear 36 to the heat roller body 33.

[0034] As shown in FIG. 7, the driven gear 36 is formed with a transmission protrusion 36e that is inserted into the notch portion 33a when the driven gear 36 is attached to the end portion of the heat roller body 33.

[0035] Here, as shown in FIGS. 6 and 7, the driven gear 36 has a large-diameter cylindrical portion 36a formed with a gear portion on the peripheral surface, and a small-diameter cylindrical portion 36b integrally formed coaxially with the large-diameter cylindrical portion 36a. A driving gear 35 (shown only in FIG. 2) meshes with the outer peripheral surface of the large-diameter cylindrical portion 36a. The outer diameter of the small-diameter cylindrical portion 36b is smaller than the outer diameter of the large-diameter cylindrical portion 36a. Near the boundary between the large-diameter cylindrical portion 36a and the small-diameter cylindrical portion 36b of the driven gear 36, a ring-shaped flange surface protruding radially inward is formed, and the end surface of the heat roller body 33 abuts against this flange surface. A C-shaped rib 36d having a C-shaped cross section extending in the roller axis direction is connected to the inner peripheral edge of the flange surface.

[0036] The C-shaped rib 36d is a columnar portion having a C-shaped cross section with one portion in the circumferential direction missing, and functions as a reinforcing rib of the driven gear 36. Further, although details will be described later, the C-shaped rib 36d also has a function of preventing the heat roller body 33 from rotating ahead.

[0037] On the inner peripheral surface of the driven gear 36, a transmission protrusion 36e extending in the axial direction across the large-diameter cylindrical portion 36a and the small-diameter cylindrical portion 36b is formed. The transmission protrusion 36e axially penetrates the missing portion of the C-shaped rib 36d. As shown in FIG. 7, the transmission protrusion 36e protrudes radially inward from the inner peripheral surface of the driven gear 36 and has a substantially rectangular shape when viewed from the axial direction. The width of the transmission protrusion 36e is smaller than the width of the missing portion of the C-shaped rib 36d. Note that the reference numeral 36f in the figure is a sink mark hole for preventing sink marks during molding.

[0038] When inserting the driven gear 36 into the end of the heat roller body 33, the position of the transmission protrusion 36e (see FIG. 6) formed on the driven gear 36 is aligned with the position of the notch 33a (see FIG. 4) formed on the heat roller body. Then, while fitting the inner peripheral surface of the driven gear 36 to the outer peripheral surface of the end of the heat roller body 33, it is moved from the outer side to the inner side in the axial direction, and the movement is completed when the end face of the heat roller body 33 abuts against the flange surface of the driven gear 36.

[0039] FIG. 8A is a cross-sectional view perpendicular to the axial direction showing a state where the mounting of the driven gear 36 to the end of the heat roller body 33 is completed. In the mounted state of the driven gear 36, the ring-shaped portion of the end of the heat roller body 33 excluding the pair of protruding plate portions 33b and 33c is inserted into the gap between the inner peripheral surface of the driven gear 36 and the outer peripheral surface of the C-shaped rib 36d, and the transmission protrusion 36e of the driven gear 36 is inserted between the pair of protruding plate portions 33b and 33c.

[0040] In this state, when the driven gear 36 is rotationally driven in a predetermined direction (clockwise direction in FIG. 8A) around its axis by the driving gear, the end face on the front side in the rotation direction of the transmission protrusion 36e abuts against one of the protruding plate portions 33b. Then, when this one of the protruding plate portions 33b is pushed by the transmission protrusion 36e, the heat roller body 33 rotates in the same direction as the driven gear 36. In this example, a noise prevention structure is adopted so that the heat roller body 33 does not rotate ahead of time and generate abnormal noise when the driven gear 36 rotates.

[0041] That is, in this abnormal noise prevention structure, as shown in FIG. 8A, with the transmission protrusion 36e protruding from the one protruding plate portion 33b, the distance k1 in the roller rotation direction between one end portion 36g of the C-shaped rib 36d facing the protruding plate portion 33b and the protruding plate portion 33b is set to be narrower than the distance k2 in the roller rotation direction between the transmission protrusion 36e and the other protruding plate portion 33c.

[0042] Therefore, for example, even if the heat roller main body 33 rotates ahead due to the backlash or the like that occurs between the driven gear 36 and the driving gear 35 (only shown in FIG. 2) and stops instantaneously, as shown in FIG. 8B, when one protruding plate portion 33b abuts against one end portion of the C-shaped rib 36d, it is possible to prevent the other protruding plate portion 33c from colliding with the end face of the transmission protrusion 36e. Therefore, it is possible to prevent the generation of abnormal noise due to the collision between the other protruding plate portion 33c and the transmission protrusion 36e.

[0043] Here, although a slight sound is generated even when one protruding plate portion 33b abuts against one end portion of the C-shaped rib 36d, since the distance k1 between one protruding plate portion 33b and one end portion of the C-shaped rib 36d is smaller than the distance k2 between the transmission protrusion 36e and the other protruding plate portion 33c, the collision energy is also reduced, and the generated sound is negligibly small. In addition, in order to reduce the collision sound between one protruding plate portion 33b and one end portion of the C-shaped rib 36d, as in this example, one end portion of the C-shaped rib 36d may be slightly sharpened so as to collide with one protruding plate portion 33b in a line contact or point contact. Thereby, the contact surface area during the collision can be reduced, and the generation of the collision sound can be surely suppressed.

[0044] Also, in this example, the C-shaped rib 36d not only functions as a pre-rotation prevention portion of the heat roller main body 33 but also functions as a reinforcing rib of the driven gear 36. Therefore, there is no need to separately provide a reinforcing rib, and the driven gear 36 can be made smaller, lighter, and more compact.

[0045] [Other Embodiments] In the above embodiment, one end portion 36g of the C-shaped rib 36d is used as the contact portion, but the present invention is not limited thereto. For example, a rectangular block having the same size as the transmission protrusion 36e may be simply arranged.

[0046] In the above embodiment, a printer has been described as an example of the image forming apparatus. However, the present invention is not limited thereto, and other image forming apparatuses such as a copying machine, a scanner device, or a multifunction peripheral may be used.

Industrial Applicability

[0047] As described above, the present invention is useful for a fixing device, and particularly useful when applied to an image forming apparatus such as a printer, a copying machine, a scanner device, or a multifunction peripheral.

Explanation of Reference Numerals

[0048] 1 Image forming apparatus 9 Fixing device 22 Heat roller 33 Heat roller body 33a Notch 33b One protruding plate portion 33c The other protruding plate portion 35 Driving gear 36 Driven gear 36d C-shaped rib 36e Transmission protrusion 36g One end portion (contact portion) 101 Heat roller body 101a Protruding plate portion 102 Driven gear 102a Transmission protrusion

Claims

1. A heat roller body formed in a cylindrical shape, A driven gear attached to an end of the heat roller body and meshing with a drive gear, A notch formed at an end of the heat roller body and recessed inward in the axial direction, A pair of protruding plate portions extending from two axially extending edges in the notch toward the inner side of the roller and facing each other in the width direction of the notch perpendicular to the axial direction, A transmission protrusion formed on the driven gear, inserted into the notch when the driven gear is attached to the end of the heat roller body, and transmitting the rotational power of the driven gear to the heat roller body by contacting one of the pair of protruding plate portions when the driven gear rotates, The dimension of the transmission protrusion along the width direction of the notch is set to be smaller than the interval in the width direction between the pair of protruding plate portions, The driven gear is located on the front side in the roller rotation direction with respect to the one protruding plate portion of the heat roller body and has a contact portion that contacts the one protruding plate portion when the heat roller body rotates forward, A fixing device, wherein the interval in the roller rotation direction between the contact portion and the one protruding plate portion is set to be narrower than the interval in the roller rotation direction between the transmission protrusion and the other protruding plate portion of the pair of protruding plate portions in a state where the transmission protrusion contacts the one protruding plate portion.

2. In the fixing device according to Claim 1, The contact portion is formed by one end of a C-shaped rib with a portion corresponding to the transmission protrusion missing when viewed from the axial direction of the heat roller body. A fixing device.

3. An image forming apparatus including the fixing device according to Claim 1 or 2.

Images