Fixing device

Abstract

To provide a fixing device that allows a user to visually check the phase of a cam for changing a nip pressure, and can prevent the user from touching the cam.SOLUTION: A fixing device 1 is removably mounted in a body housing of an image forming apparatus. The fixing device 1 comprises a heating member, a pressure member, a first arm, a first cam 7A, and an exterior cover 11. The heating member and the pressure member extend in a longitudinal direction. The first arm applies a nip pressure for nipping a sheet between the heating member and the pressure member. The first cam 7A rotates about a cam axis. The first cam 7A has, on its peripheral surface, a first cam surface 71A that acts on the first arm. The exterior cover 11 covers the first cam surface 71A of the first cam 7A. The exterior cover 11 has a first opening 11A that exposes part of the first cam surface 71A of the first cam 7A.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a fixing device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there is known a fixing device that is detachable from the image forming apparatus main body, has a cam for changing nip pressure, and has the circumferential surface and side surface of the cam exposed (Patent Document 1).

[0003] Also known is a fixing device in which the cam is located inside the housing of the fixing device and is not exposed (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-232442 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-085238 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the cam is exposed as in the structure of Patent Document 1, there is a problem that the user may touch the cam when replacing the fixing device, which may change the cam phase. On the other hand, when the cam is not exposed as in the structure of Patent Document 2, there is a problem that the cam phase cannot be visually confirmed when replacing the fixing device or assembling it in the manufacturing process.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a fixing device that allows the phase of a cam for changing nip pressure to be visually confirmed and that can be prevented from being touched by a user. [Means for solving the problem]

[0007] In order to solve the above problems, the fixing device of the present invention, which is detachable from the main body of an image forming apparatus, includes a heating member, a pressure member, a first arm, a first cam, and an exterior cover. The heating element and the pressure element extend in a longitudinal direction. The first arm provides a nip pressure that nip the sheet between the heating member and the pressure member. The first cam rotates around a cam shaft and has a first cam surface on its circumferential surface that acts on the first arm. The exterior cover covers the first cam surface of the first cam and has a first opening that exposes a portion of the first cam surface of the first cam.

[0008] Since the exterior cover that covers the first cam surface of the first cam has the first opening, the phase of the first cam can be visually confirmed and the user can be prevented from touching it.

[0009] The first cam may be configured not to protrude from the first opening to the outside of the exterior cover regardless of the phase of the first cam.

[0010] Regardless of the phase of the first cam, the first cam does not protrude from the first opening to the outside of the exterior cover, and therefore, the user is prevented from touching the first cam.

[0011] The exterior cover may cover a side surface of the first cam facing the camshaft.

[0012] By covering the side surface of the first cam with the exterior cover, it is possible to prevent the user from touching the side surface of the first cam that faces the direction of the cam shaft.

[0013] The fixing device may further include a shaft and a cam gear. The shaft may be rotatable about a cam axis extending in the longitudinal direction and to which the first cam is fixed. The cam gear may be fixed to the shaft. The cam gear may have a gear with gear teeth and a cylindrical flange extending in the longitudinal direction from the gear. The flange extends in a part of the rotation direction. The mark may have a shape different from that of the other portions. The first opening may expose the flange.

[0014] The flange portion is exposed from the first opening, so that the phase of the first cam can be visually confirmed.

[0015] The fixing device may further include a side frame that rotatably supports the shaft and is positioned between the first cam and the cam gear.

[0016] The side frame that rotatably supports the shaft is positioned between the first cam and the cam gear, so that the camshaft is stably supported when a driving force is input to the shaft.

[0017] The exterior cover may cover a portion of the gear teeth of the gear and may further have a second opening that exposes another portion of the gear teeth from the exterior cover.

[0018] By covering a portion of the cam gear with an exterior cover, the exposure of the cam gear can be reduced, and the user can be prevented from touching it.

[0019] The fixing device may include a cam sensor that detects the phase of the first cam.

[0020] The exterior cover may cover the cam sensor.

[0021] The exterior cover covers the cam sensor, preventing damage to the cam sensor and preventing malfunction.

[0022] The fixing device may further include a second arm located on the opposite side of the heating member from the first arm in the longitudinal direction, and a second cam having a second cam surface acting on the second arm. The exterior cover may cover the second cam surface of the second cam.

[0023] The fixing device may further include a shaft connecting the first cam and the second cam, and the exterior cover may cover the shaft. [Effects of the Invention]

[0024] According to the fixing device of the present invention, it is possible to provide a fixing device that allows the phase of the cam for changing the nip pressure to be visually confirmed and that is prevented from being touched by the user. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view of a fixing device according to an embodiment, showing a state in which a first cam is located at a first position. [Figure 2] 4 is a cross-sectional view of the fixing device according to the embodiment, showing a state in which the first cam is located at a second position. FIG. [Figure 3] FIG. 2 is a perspective view of a fixing frame of the fixing device according to the embodiment. [Figure 4] FIG. 2 is a perspective view of the fixing device according to the embodiment, seen from the downstream side in the installation direction. [Figure 5] FIG. 2 is a perspective view of the fixing device according to the embodiment, seen from the upstream side in the installation direction. [Figure 6] 2 is a diagram showing one end portion of the fixing device according to the embodiment as viewed from above in the longitudinal direction; FIG. [Figure 7] FIG. 2 is a diagram illustrating a state in which the fixing device is attached to the main body housing of the image forming apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0026] Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. As shown in Fig. 1, the fixing device 1 is a device that fixes a toner image on a sheet S. The fixing device 1 is detachable from a main body housing MB (see Fig. 7) of an image forming apparatus PR such as a printer. The fixing device 1 includes a heating roller 2 as an example of a heating member, a pressure roller 3 as an example of a pressure member, a fixing frame 4, an arm 5, a spring 6, a cam 7, and an exterior cover 11.

[0027] The heating roller 2 extends in the longitudinal direction and rotates around a rotation axis X (see FIG. 3). The heating roller 2 rotates by receiving a driving force from a motor (not shown) provided in the image forming apparatus PR. The heating roller 2 has a roller 2A and a heater H. In this embodiment, the heating roller 2 has two heaters H1 and H2. The roller 2A is a metal tube and is heated by the heater H. The heater H is disposed inside the roller 2A. The heater H is, for example, a halogen heater.

[0028] In the following description, the longitudinal direction of the heating roller 2 will be simply referred to as the longitudinal direction. The longitudinal direction is also the direction of the rotation axis X of the heating roller 2. The arrow indicating the longitudinal direction in the drawings points to one side in the longitudinal direction, and the direction opposite to the arrow points to the other side in the longitudinal direction. The direction in which the fixing device 1 is attached to the main body housing MB will be referred to as the attachment direction. The fixing device 1 is attached by moving from the rear to the front of the main body MB. The front-to-rear and up-to-down directions of the fixing device 1 are the front-to-rear and up-to-down directions of the main body housing MB when the fixing device 1 is attached to the main body housing MB. The sheet S is transported from the front to the rear of the fixing device 1 and passes through the fixing device 1. After passing through the fixing device 1, the sheet S is transported upward of the fixing device 1.

[0029] The pressure roller 3 extends in the longitudinal direction (see FIG. 3). The pressure roller 3 rotates following the rotation of the heat roller 2, and nips the sheet S between the pressure roller 3 and the heat roller 2. The pressure roller 3 has a shaft 3A and a roller body 3B. The shaft 3A is made of, for example, metal. The roller body 3B is made of, for example, rubber, and is provided so as to cover the periphery of the shaft 3A.

[0030] 3, the fixing frame 4 includes a pair of side frames 4A and 4B and a connecting frame 4C. The side frames 4A and 4B are located at both ends in the longitudinal direction of the heating roller 2 and the pressure roller 3. The side frames 4A and 4B support the heating roller 2 rotatably. The connecting frame 4C is a metal plate that extends in the longitudinal direction and connects the side frame 4A on one side in the longitudinal direction to the side frame 4B on the other side in the longitudinal direction. The cam 7 includes a first cam 7A and a second cam 7B. The first cam 7A is located close to the side frame 4A. The second cam 7B is located close to the side frame 4B. The first cam 7A and the second cam 7B are connected by a shaft 8 extending in the longitudinal direction. The shaft 8 is rotatably supported by the side frames 4A and 4B.

[0031] Returning to FIG. 1 , the arm 5, spring 6, and cam 7 constitute a pressure change mechanism that changes the nip pressure between the heating roller 2 and the pressure roller 3. The pressure change mechanism can change the nip pressure by moving at least one of the heating roller 2 and the pressure roller 3 relative to the other. In this embodiment, the pressure change mechanism changes the nip pressure by moving the pressure roller 3 relative to the heating roller 2.

[0032] 1 and 3, the arm 5 includes a first arm 51 and a second arm 52. The first arm 51 is provided on one side frame 4A in the longitudinal direction. The second arm 52 is provided on the other side frame 4B in the longitudinal direction. The second arm 52 has a configuration that is bilaterally symmetrical to the first arm 51, so only the first arm 51 will be described here, and a description of the second arm 52 will be omitted. The first arm 51 has one end 5A, the other end 5B, a first portion 5C, and a second portion 5D. The first arm 51 is rotatable about an arm axis 1X extending in the longitudinal direction.

[0033] One end 5A is rotatably supported by a side frame 4A on one side in the longitudinal direction via a shaft 5E. The other end 5B has a cam follower 5F. The cam follower 5F is capable of coming into contact with the cam 7.

[0034] The first portion 5C and the second portion 5D are located between the one end 5A and the other end 5B. The first portion 5C supports the pressure roller 3. The second portion 5D is a portion to which a spring 6 is connected. One end of the spring 6 is hooked to the second portion 5D, and the other end of the spring 6 is hooked to the side frame 4A. The spring 6 presses the pressure roller 3 against the heating roller 2 via the arm 5.

[0035] The first cam 7A is fixed to a shaft 8. The shaft 8 is rotatably supported by the side frame 4A on one side in the longitudinal direction around a cam axis 2X extending in the longitudinal direction. That is, the first cam 7A is rotatably supported by the side frame 4A via the shaft 8. The first cam 7A has a first cam surface 71A on its peripheral surface that acts on the first arm 51. The first cam 7A moves the pressure roller 3 by rotating, thereby changing the nip pressure that nips the sheet S. The first cam 7A is rotatable between a first position shown in FIG. 1 and a second position shown in FIG. 2.

[0036] In the first position, the nip pressure between the heating roller 2 and the pressure roller 3 becomes a first nip pressure. At this time, the first cam surface 71A does not contact the cam follower 5F. In the second position, the nip pressure between the heating roller 2 and the pressure roller 3 becomes a second nip pressure that is smaller than the first nip pressure. At this time, the first surface 71A contacts the cam follower 5F. The first cam 7A can rotate counterclockwise from the first position shown in FIG. 1 to the second position shown in FIG. 2. When the first cam 7A rotates from the first position to the second position, the first arm 51 rotates clockwise about the arm axis 1X, moving the pressure roller 3.

[0037] The spring 6 and the second cam 7B have a configuration that is bilaterally symmetrical to the spring 6 and the first cam 7A, and therefore a detailed description thereof will be omitted.

[0038] 3, the fixing device 1 further includes a cam gear 9, a fixing gear 10, and a cam sensor CS. The cam gear 9 is fixed to the end of the shaft 8. The side frame 4A is located between the cam gear 9 and the first cam 7A.

[0039] The cam gear 9 is connected to the cam 7 via a shaft 8 and transmits a driving force to the cam 7. The cam gear 9 is located on one side in the longitudinal direction with respect to the longitudinal center CL of the heating roller 2. The cam gear 9 has a plurality of gear teeth 9A, a flange 9B extending from near the base of the gear teeth 9A to one side in the longitudinal direction, and a cylindrical flange 9D extending to the other side in the longitudinal direction. The flange 9B has a notch 9C for detecting the phase of the cam 7 with a cam sensor CS. The flange 9D has a notch 9E in part of its rotational direction for checking the phase of the cam 7 through a first opening 11A, which will be described later.

[0040] The cam sensor CS is a sensor that can detect the phase of the cam 7. The cam sensor CS is a photointerrupter that has a light-emitting element and a light-receiving element. A flange 9B is located between the light-emitting element and the light-receiving element. When the notch 9C is located between the light-emitting element and the light-receiving element, the cam sensor CS can detect that the cam 7 is in a specified phase by the light-receiving element receiving the light emitted by the light-emitting element.

[0041] The fixing gear 10 has a plurality of gear teeth 10A. The fixing gear 10 is fixed to an end of the roller 2A in the longitudinal direction. The fixing gear 10 is provided coaxially with the heating roller 2. The fixing gear 10 transmits driving force to the heating roller 2.

[0042] 4 and 5, the exterior cover 11 is a cover that covers the fixing device 1. The exterior cover 11 covers the fixing frame 4, the cam sensor CS, the cam 7, the shaft 8, the cam gear 9, and the fixing gear 10. Specifically, the exterior cover 11 covers the side surface of the first cam 7A facing the cam shaft 2X and a portion of the first cam surface 71A. On the other hand, the exterior cover 11 does not have an opening on the other side in the longitudinal direction, and as shown by the dashed lines in Figures 4 and 5, the second cam surface 71B of the second cam 7B on the other side is covered by the exterior cover 11 and is not exposed. In addition, the exterior cover 11 covers a portion of the gear teeth 9A of the cam gear 9 and a portion of the gear teeth 10A of the fixing gear 10.

[0043] As shown in FIG. 4, the exterior cover 11 has a first opening 11A, a second opening 11B, and a third opening 11C on one side in the longitudinal direction.

[0044] 6, the first opening 11A is located directly above the first cam 7A. The first opening 11A exposes a part of the first cam surface 71A of the first cam 7A, a part of the flange 9D, and a part of the side frame 4A.

[0045] In Figure 1, as shown by the circle drawn with a two-dot chain line indicating the maximum diameter of the first cam 7A, the first cam 7A does not protrude outside the exterior cover 11 from the first opening 11A regardless of the phase of the first cam 7A.

[0046] Returning to FIG. 4, the second opening 11B is located on one side of the first opening 11A in the longitudinal direction. The second opening 11B exposes a portion of the gear teeth 9A of the cam gear 9. The second opening 11B opens toward the downstream side and upward in the mounting direction. A portion of the cam gear 9 protrudes from the second opening 11B to the outside of the exterior cover 11.

[0047] The third opening 11C is located on one side of the first opening 11A in the longitudinal direction. The third opening 11C is located downstream in the mounting direction relative to the second opening 11B. The third opening 11C exposes a portion of the gear teeth 10A of the fixing gear 10. The third opening 11C opens toward the downstream side and upward in the mounting direction. A portion of the fixing gear 10 protrudes from the third opening 11C to the outside of the exterior cover 11.

[0048] 6, the first opening 11A is provided so that the flange 9D can be seen. The notch 9E of the flange 9D is located at a position that is visible from the first opening 11A when the first cam 7A is located at the first position.

[0049] As shown in FIG. 7, the main body housing MB includes a fixing drive gear 91 that transmits driving force to the fixing gear 10 to drive the heating roller 2, a cam drive gear 92 that transmits driving force to the cam gear 9 to drive the cam 7, and a cover CR. The fixing drive gear 91 and the cam drive gear 92 are driven by a motor (not shown). The cover CR can open and close an opening on one side of the main body housing MB at the rear. An image forming unit 100 that forms a toner image on a sheet S is provided inside the main body housing MB. The image forming unit 100 supplies the sheet S on which the toner image has been formed to the fixing device 1.

[0050] When the fixing device 1 is attached to the main body housing MB of the image forming apparatus PR, the cover CR on the side of the main body housing MB is opened, and the fixing device 1 is inserted into the main body housing MB in the attachment direction. Then, the cam gear 9 exposed from the second opening 11B of the exterior cover 11 meshes with the cam drive gear 92. Also, the fixing gear 10 exposed from the third opening 11C of the exterior cover 11 meshes with the fixing drive gear 91.

[0051] As described above, the following effects can be obtained in this embodiment.

[0052] Since the exterior cover 11 that covers the first cam surface 71A of the first cam 7A has the first opening 11A, the phase of the first cam 7A can be visually confirmed and the user is prevented from touching it.

[0053] Regardless of the phase of the first cam 7A, the first cam 7A does not protrude from the first opening 11A to the outside of the exterior cover 11, and therefore, the user is prevented from touching the first cam 7A.

[0054] The exterior cover 11 covers the side surface of the first cam 7A, thereby preventing the user from touching the side surface of the first cam 7A that faces the direction of the camshaft 2X.

[0055] The flange 9D is exposed from the first opening 11A, so that the phase of the first cam 7A can be visually confirmed.

[0056] By covering a part of the cam gear 9 with the exterior cover 11, the exposure of the cam gear 9 can be reduced, and the user can be prevented from touching it.

[0057] The side frame 4A, which rotatably supports the shaft 8, is positioned between the first cam 7A and the cam gear 9, so that the camshaft 2X is stably supported when a driving force is input to the shaft 8.

[0058] By covering the cam sensor CS with the exterior cover 11, damage to or malfunction of the cam sensor CS can be suppressed.

[0059] The present invention is not limited to the above-described embodiment, but can be used in various forms as exemplified below.

[0060] In the above-described embodiment, the flange 9D has the notch 9E. However, for example, the mark indicating the phase of the cam 7 may be a step, a protrusion, a groove, a line, or the like provided on the flange. Furthermore, the mark does not have to be provided on the flange, and may be a protrusion protruding from the side surface of the cam. Furthermore, the exterior cover 11 may have an opening that exposes the second cam 7B. In this case, it is preferable to provide a mark indicating the phase of the second cam 7B on or near the second cam 7B.

[0061] The elements described in the above-described embodiment and modifications may be implemented in any combination. [Explanation of symbols]

[0062] 1 Fixing device 2 Heating roller 3 Pressure roller 2X camshaft 7A First Cam 11 Exterior cover 11A 1st opening 51 First Arm 71A First cam surface MB main body case PR Image forming equipment

Claims

1. A fixing device detachable from a main body housing of an image forming apparatus, a longitudinally extending heating element and pressure element; a first arm that applies a nip pressure to nip a sheet between the heating member and the pressure member; a first cam that rotates around a cam shaft and has a first cam surface on its circumferential surface that acts on the first arm; an exterior cover that covers the first cam surface and has a first opening that exposes a portion of the first cam surface; A fixing device comprising:

2. 2. The fixing device according to claim 1, wherein the first cam does not protrude from the first opening to the outside of the exterior cover regardless of the phase of the first cam.

3. 2. The fixing device according to claim 1, wherein the exterior cover covers a side surface of the first cam that faces the cam shaft.

4. a shaft rotatable about the cam shaft to which the first cam is fixed, the shaft extending in the longitudinal direction; a cam gear fixed to the shaft, a gear having gear teeth; a cam gear having a cylindrical flange extending from the gear in the longitudinal direction, the flange having a mark in a part of the rotational direction that has a shape different from that of the other part; Furthermore, The fixing device according to claim 1 , wherein the first opening exposes the flange.

5. Further provided is a side frame that rotatably supports the shaft, 5. The fixing device according to claim 4, wherein the side frame is positioned between the first cam and the cam gear.

6. The exterior cover further has a second opening, the exterior cover covers a portion of the gear teeth of the gear; The fixing device according to claim 4 , wherein the second opening exposes another part of the gear teeth from the exterior cover.

7. 5. The fixing device according to claim 4, further comprising a cam sensor for detecting the phase of the first cam.

8. The fixing device according to claim 7 , wherein the exterior cover covers the cam sensor.

9. a second arm positioned on the opposite side of the first arm across the heating member in the longitudinal direction; a second cam having a second cam surface acting on the second arm, The fixing device according to claim 1 , wherein the exterior cover covers the second cam surface.

10. a shaft connecting the first cam and the second cam; The fixing device according to claim 9 , wherein the exterior cover covers the shaft.

Images