JP7790211B2 - Fixing device - Google Patents

Description

This disclosure relates to a fixing device.

Some fixing devices used in image forming devices are equipped with a pressure arm that presses the heating unit against the pressure unit. To change or release the pressure applied by the pressure arm, the fixing device is equipped with a cam that acts on the pressure arm and a cam shaft that rotates the cam.

JP 2011-133809 A

If the camshaft is made of a conductive metal, it will act as an antenna. As a result, the camshaft may radiate electromagnetic noise generated inside the image forming device or electromagnetic noise received from outside the image forming device to the inside or outside of the image forming device. This may affect the image forming device and surrounding equipment with radiated noise.

One aspect of the present disclosure aims to realize a fixing device that suppresses the diffusion of radiation noise from a camshaft.

In order to solve the above-mentioned problems, the fixing device disclosed herein is a fixing device that is housed in an image forming apparatus and fixes a toner image on a sheet, and includes: a first rotating body that is rotatable about an axis; a second rotating body that is rotatable about the axis and that sandwiches the sheet between the first rotating body and the second rotating body; a first pressure arm that presses the first rotating body toward the second rotating body, the first pressure arm being conductive and electrically connected to a reference potential section of the image forming apparatus; a first cam that contacts the first pressure arm and rotates to displace the position of the first pressure arm; a conductive cam shaft into which the first cam is fitted and that is rotatable about the axis; a frame that supports the first rotating body, the second rotating body, and the first pressure arm; and a conductive first elastic member that electrically connects the first pressure arm and the cam shaft.

In the fixing device disclosed herein, when the camshaft rotates, the first cam rotates in conjunction with the rotation, displacing the position of the first pressure arm. As a result, the distance between the first pressure arm and the camshaft also changes. Even if the distance between the first pressure arm and the camshaft changes, the elasticity of the first elastic member allows the first elastic member to maintain an electrical connection with the camshaft, ensuring that the potential of the camshaft is at the reference potential. This maintains the potential of the camshaft at the reference potential, thereby suppressing the diffusion of radiated noise generated by the camshaft.

In the fixing device according to the present disclosure, the first elastic member may be a conductive brush made of conductive fibers.

With the above configuration, the fixing device can reduce the friction force between the conductive first elastic member and the cam shaft.

In the fixing device according to the present disclosure, the first elastic member may be a plate-shaped member.

With the above configuration, when the distance between the first pressure arm and the camshaft is short, the first elastic member is electrically connected to the camshaft in a pressed state. When the distance between the first pressure arm and the camshaft is long, the first elastic member is electrically connected to the camshaft in an extended state. As a result, even if the position of the first pressure arm is displaced, the first pressure arm and camshaft remain electrically connected, ensuring that the camshaft maintains a reference potential.

The fixing device according to the present disclosure may further include: the first pressure arm is disposed at one end in the axial direction; a second pressure arm that presses the first rotor and is disposed at the other end in the axial direction; a second cam fitted to the camshaft that contacts the second pressure arm and rotates to displace the position of the second pressure arm; and a second conductive elastic member that electrically connects the second pressure arm and the camshaft.

With the above configuration, the second pressure arm is not directly electrically connected to the reference potential section of the image forming device, as is the first pressure arm. If the second elastic member were attached to the second pressure arm and the camshaft were not electrically connected to the second elastic member, the second pressure arm would not be electrically connected to anything, resulting in the diffusion of radiated noise. Therefore, by electrically connecting the second elastic member to the camshaft, the second pressure arm is electrically connected to the first pressure arm via the second elastic member and the camshaft. Because the first pressure arm is electrically connected to the reference potential section of the image forming device, the second pressure arm can maintain a reference potential. This maintains the potential of the second pressure arm at the reference potential, thereby suppressing the diffusion of radiated noise generated from the second pressure arm.

In the fixing device according to the present disclosure, the cam shaft may be supported on the frame via a resin sliding bearing.

With the above configuration, the fixing device supports the camshaft on the frame using a plastic sliding bearing instead of a metal bearing. Because plastic sliding bearings are inexpensive, this allows for a low-cost fixing device.

In the fixing device according to the present disclosure, the first cam may be integrally molded with the sliding bearing.

With the above configuration, the first cam and sliding bearing of the fixing device are integrally molded. This reduces the number of parts in the fixing device.

The fixing device according to the present disclosure may further include a conductive spring that applies pressure to the first pressure arm, one end of the spring being electrically connected to the first pressure arm and the other end of the spring being electrically connected to the reference potential section of the image forming device.

With the above configuration, the first pressure arm is always electrically connected to the reference potential section via the spring. This increases the reliability with which the first pressure arm maintains the reference potential.

The fixing device according to the present disclosure may further include a drive input portion that is fitted onto the cam shaft and applies a rotational drive force to the cam shaft in response to the opening and closing of the cover of the image forming device.

With the above configuration, when the cover is opened or closed, the drive input section applies rotary motor power to rotate the camshaft, changing the pressure exerted by the first and second pressure arms on the first rotor. This allows the first and second pressure arms to apply and release pressure from the first rotor to the second rotor depending on whether the cover is opened or closed.

One aspect of the present disclosure makes it possible to realize a fixing device that suppresses the diffusion of radiation noise from the camshaft.

1 is a diagram illustrating a schematic configuration of a laser printer according to an embodiment of the present disclosure. FIG. 2 is a perspective view of the fixing device according to the embodiment of the present disclosure, viewed from the upper right. FIG. 2 is a cross-sectional view of the right side of the fixing device according to the embodiment of the present disclosure. FIG. 2 is a perspective view of the right side of the fixing device according to the embodiment of the present disclosure, viewed from the inside. FIG. 2 is an enlarged view of the vicinity of a sliding bearing of the fixing device according to an embodiment of the present disclosure. 1A and 1B are diagrams illustrating a sliding bearing of a fixing device according to an embodiment of the present disclosure. FIG. 10 is a right side view of the interlocking mechanism according to an embodiment of the present disclosure. FIG. 10 is a right side view of the interlocking mechanism according to an embodiment of the present disclosure. FIG. 10 is a diagram showing a state in which a first pressure arm presses a heating belt in a fixing device according to an embodiment of the present disclosure. 10 is a diagram showing a state in which the first pressure arm releases pressure from the heating belt in the fixing device according to the embodiment of the present disclosure. FIG. FIG. 1 is a schematic configuration diagram of a fixing device according to an embodiment of the present disclosure. FIG. 10 is a diagram showing a state in which a first pressure arm presses a heating belt in a fixing device according to a first modified example of an embodiment of the present disclosure. FIG. 10 is a diagram showing a state in which the first pressure arm releases pressure from the heating belt in the fixing device according to the first modified example of the embodiment of the present disclosure.

One embodiment of the present disclosure is described in detail below.

<General Configuration of Laser Printer 1>
FIG. 1 is a diagram showing the schematic configuration of a laser printer 1. The laser printer 1 is an example of an image forming apparatus. The left side in FIG. 1 is referred to as the "front" and the right side as the "rear." The front side in FIG. 1 is referred to as the "right" and the back side as the "left." Additionally, the upward direction in FIG. 1 is referred to as the "top" and the downward direction is referred to as the "bottom."

The laser printer 1 comprises a device main body 2 having an opening 6, a process cartridge 3, a scanner unit 4, and a fixing device 5.

The device main body 2 includes a front cover 7, a sheet tray 8, and a discharge tray 9.

The opening 6 is located at the front end of the apparatus main body 2. The opening 6 connects the inside and outside of the apparatus main body 2 in the front-to-rear direction to allow the process cartridge 3 to pass through.

The front cover 7 is located at the front end of the device main body 2. The front cover 7 has a generally plate-like shape that is roughly L-shaped in side cross section. The front cover 7 is supported on the front wall of the device main body 2 so that it can swing around, with its lower end as a fulcrum. The front cover 7 is configured to open or close the opening 6.

The sheet tray 8 is located at the bottom of the device main body 2. The sheet tray 8 is configured to store sheets S.

The discharge tray 9 is located on the top wall of the device main body 2. The discharge tray 9 is recessed downward from the top surface of the device main body 2 so that sheets S can be placed on it.

The process cartridge 3 is housed in approximately the center of the device main body 2 in the vertical direction. The process cartridge 3 is configured to be attached to or detached from the device main body 2 through an opening 6. The process cartridge 3 includes a drum cartridge 10 and a developer cartridge 11.

The drum cartridge 10 includes a photosensitive drum 12, a scorotron charger 13, and a transfer roller 14.

The photosensitive drum 12 is rotatably supported at the rear end of the drum cartridge 10. The photosensitive drum 12 has a generally cylindrical shape that extends in an axial direction. The axial direction of the photosensitive drum 12 is the direction from "left" to "right" in Figure 1, and coincides with the width direction of the sheet S moving along the transport path. Hereinafter, when the term "axial direction" is simply used, this "axial direction" refers to the direction that coincides with the axial direction of the photosensitive drum 12.

The scorotron charger 13 is positioned behind the photosensitive drum 12 at a distance from the photosensitive drum 12.

The transfer roller 14 is positioned below the photosensitive drum 12. The transfer roller 14 is in contact with the lower end of the photosensitive drum 12.

The developer cartridge 11 is attached to the drum cartridge 10 in front of the photosensitive drum 12. The developer cartridge 11 includes a developer roller 15, a supply roller 16, a layer thickness regulating blade 17, a toner storage compartment 18, and an agitator 19.

The developing roller 15 is rotatably supported at the rear end of the developing cartridge 11. The developing roller 15 has a generally cylindrical shape extending axially. The developing roller 15 contacts the front end of the photosensitive drum 12.

The supply roller 16 is positioned below and in front of the developing roller 15. The supply roller 16 is rotatably supported in the developing cartridge 11. The supply roller 16 has a generally cylindrical shape extending axially. The supply roller 16 contacts the lower front end of the developing roller 15.

The layer thickness regulation blade 17 is positioned above and in front of the developing roller 15. The layer thickness regulation blade 17 contacts the front end of the developing roller 15.

The toner storage section 18 is located in front of the supply roller 16 and the layer thickness regulation blade 17. The toner storage section 18 is configured to store toner.

The agitator 19 is rotatably supported within the toner storage section 18.

The scanner unit 4 is located above the process cartridge 3. The scanner unit 4 is configured to emit a laser beam based on image data toward the photosensitive drum 12.

The fixing device 5 is located behind the process cartridge 3. The fixing device 5 includes a heat unit 22 and a pressure roller 21.

The heat unit 22 extends in the axial direction. The heat unit 22 includes a stay cover 51, a stay 52, a reflector 53, a heater 54, a heating plate 55, and a heating belt 56. The heating belt 56 is an example of a first rotating body.

The stay cover 51 is made of a heat-resistant resin material and extends axially. The stay cover 51 has a roughly box-like shape with an open lower end.

The stay 52 is positioned inside the stay cover 51. The stay 52 is made of metal. The stay 52 extends in the axial direction and has a generally rectangular cylindrical shape with an open lower end.

The reflector 53 is positioned inside the stay 52. The reflector 53 is made of a metal material. The reflector 53 extends in the axial direction and has a roughly rectangular cylindrical shape with an open lower end. The inner surface of the reflector 53 is mirror-finished.

The heater 54 is disposed inside the reflector plate 53. The heater 54 has a generally cylindrical shape extending in the axial direction. The heater 54 heats the heating belt 56 via the heating plate 55.

The heating plate 55 is positioned below the heater 54. The heating plate 55 is made of a metal material. The heating plate 55 has a generally flat plate shape extending in the axial direction. The heating plate 55 is supported by the stay 52.

The heating belt 56 is a heat-resistant, flexible film having a generally cylindrical shape extending in the axial direction. The heating belt 56 is wrapped around the stay cover 51, stay 52, reflector plate 53, heater 54, and heating plate 55 so that its inner surface contacts the underside of the heating plate 55. The lower end of the heating belt 56 contacts the upper end of the pressure roller 21. The lower end of the heating belt 56 is sandwiched between the heating plate 55 and the pressure roller 21.

The pressure roller 21 has a generally cylindrical shape extending in the axial direction. The pressure roller 21 is disposed below the heat unit 22. The pressure roller 21 is rotatable. The pressure roller 21 is configured to be driven to rotate by a driving force supplied from a motor (not shown) provided within the device main body 2, and by being driven to rotate, the frictional force with the heating belt 56 (or sheet S) causes the heating belt 56 to rotate. The pressure roller 21 is an example of a second rotating body.

When the laser printer 1 begins image formation, the scorotron charger 13 uniformly charges the surface of the photosensitive drum 12. The scanner unit 4 exposes the surface of the photosensitive drum 12 based on the image data. As a result, an electrostatic latent image based on the image data is formed on the surface of the photosensitive drum 12.

The agitator 19 agitates the toner in the toner storage section 18 and supplies it to the supply roller 16. The supply roller 16 supplies the toner supplied by the agitator 19 to the development roller 15. At this time, the toner is positively charged by friction between the development roller 15 and the supply roller 16, and is carried by the development roller 15. The layer thickness regulation blade 17 regulates the layer thickness of the toner carried by the development roller 15 to a constant thickness.

The toner carried by the developing roller 15 is then supplied to the electrostatic latent image on the surface of the photosensitive drum 12. As a result, a toner image is carried on the surface of the photosensitive drum 12.

Sheets S are fed one by one from the sheet tray 8 at a predetermined timing by the rotation of various rollers between the photosensitive drum 12 and the transfer roller 14. The toner image on the surface of the photosensitive drum 12 is transferred to the sheet S as it passes between the photosensitive drum 12 and the transfer roller 14.

The sheet S is then heated and pressurized as it passes between the pressure roller 21 and the heat unit 22. This causes the toner image on the sheet S to be thermally fixed to the sheet S.

The sheet S is then placed on the discharge tray 9.

<Details of Fixing Device 5>
Fig. 2 is a perspective view of the fixing device 5 as seen from the upper right. Fig. 3 is a cross-sectional view of the right side of the fixing device 5. Fig. 4 is a perspective view of the right side of the fixing device 5 as seen from the inside. Fig. 5 is an enlarged view of the area around the sliding bearing 31B of the fixing device 5.

The fixing device 5 further includes a frame 31, a first pressure arm 33R, a second pressure arm 33L, a first cam 35R, a second cam 35L, a cam shaft 34, a spring 36, a spring 37, a drive input portion 32, a conductive brush 39R, a sliding bearing 31B, a ground spring 41, a leaf spring 42, a main frame 40, and a support shaft 31A.

The frame 31 is made of a resin material and has a generally box-like shape extending in the axial direction. The frame 31 supports the heating belt 56, the pressure roller 21, the first pressure arm 33R, and the second pressure arm 33L. The heat unit 22 is supported by the frame 31 in a state in which it can slide up and down. As shown in FIG. 5, the frame 31 supports the cam shaft 34 via a resin sliding bearing 31B. The resin sliding bearing 31B is low-cost. By using the resin sliding bearing 31B instead of a metal bearing, the fixing device 5 can be realized at low cost.

Figure 6 shows the plain bearing 31B. The plain bearing 31B is molded integrally with each of the first cam 35R and the second cam 35L. Figure 6 shows the plain bearing 31B molded integrally with the second cam 35L. The plain bearing 31B has a D-cut inner peripheral portion 31C and an outer peripheral portion 31D whose outer periphery slides against the frame 31. The tip of the camshaft 34 is D-cut. The tip of the camshaft 34 is inserted into the inner peripheral portion 31C. The plain bearing 31B, the first cam 35R, and the second cam 35L are made of POM (polyacetal).

This allows for a reduction in the number of parts compared to when the sliding bearing 31B is a separate part from each of the first cam 35R and the second cam 35L.

The first pressure arm 33R is located on the right end side in the axial direction. More specifically, the first pressure arm 33R is located at the right end above the heat unit 22. The first pressure arm 33R is made of a conductive metal material. The first pressure arm 33R contacts the stay cover 51 at the contact portion 38.

The first pressure arm 33R is rotatably supported by the frame 31 and the support shaft 31A. This allows the first pressure arm 33R to rotate around the support shaft 31A.

The support shaft 31A has a rod shape extending in the axial direction.

The second pressure arm 33L is located on the left end side in the axial direction. More specifically, the second pressure arm 33L is located at the left end above the heat unit 22. The second pressure arm 33L is made of a conductive metal material. The second pressure arm 33L comes into contact with the stay cover 51 at a contact portion (not shown).

The second pressure arm 33L is rotatably supported by the frame 31 and the support shaft 31A. This allows the second pressure arm 33L to rotate around the support shaft 31A, which extends in the axial direction.

The camshaft 34 is disposed at the upper rear end of the frame 31. The camshaft 34 is made of a conductive metal material and has a generally cylindrical shape extending in the axial direction. The right end of the camshaft 34 is rotatably supported at the upper rear end of the right side of the frame 31. The left end of the camshaft 34 is rotatably supported at the upper rear end of the left side of the frame 31. This allows the camshaft 34 to rotate around an axis extending in the axial direction.

The first cam 35R is fitted onto the right end of the camshaft 34. More specifically, the first cam 35R is attached to the right end of the camshaft 34 so as not to rotate relative to it. In addition, the drive input portion 32 is fitted onto the right end of the first cam 35R.

The second cam 35L is fitted onto the left end of the camshaft 34. More specifically, the second cam 35L is attached to the left end of the camshaft 34 so as not to rotate relative to it.

The spring 36 is arranged in a generally vertical direction. The spring 36 is made of a conductive metal material. The upper end of the spring 36 is fixed to the first pressure arm 33R. The lower end of the spring 36 is fixed to the rear end of the frame 31. This applies downward tension to the spring 36. That is, as shown in FIG. 3, tension is applied to the first pressure arm 33R in a direction that rotates it downward. Due to the downward tension of the spring 36, the first pressure arm 33R presses the stay cover 51 at the contact portion 38. The stay cover 51 is in contact with the stay 52 and presses the stay 52. The stay 52 is in contact with the heating plate 55 and presses the heating plate 55. The heating plate 55 is in contact with the heating belt 56 and presses the heating belt 56. The heating belt 56 then presses against the pressure roller 21. Note that the direction indicated by F in Figure 3 and subsequent figures is the direction in which the first pressure arm 33R presses the heating belt 56.

The upper end of the first pressure arm 33R and the spring 36 are electrically connected. The lower end of the spring 36 is further connected to the upper end of the ground spring 41. The ground spring 41 is made of a conductive metal material. This electrically connects the spring 36 and the ground spring 41. The lower end of the ground spring 41 is connected to the upper end of the leaf spring 42. The leaf spring 42 is made of a conductive metal material. This electrically connects the ground spring 41 and the leaf spring 42. The lower end of the leaf spring 42 is connected to the main frame 40. The main frame 40 is made of a conductive metal material. The potential of the main frame 40 is the frame ground of the laser printer 1. The main frame 40 is an example of a reference potential section of an image forming device. The frame ground of the main frame 40 is an example of a reference potential. The leaf spring 42 and the main frame 40 are electrically connected.

The first pressure arm 33R is always electrically connected to the main frame 40 via the spring 36, the ground spring 41, and the leaf spring 42. This increases the reliability with which the first pressure arm 33R secures the frame ground of the main frame 40.

The spring 37 is arranged in a generally vertical direction. The spring 37 is made of a conductive metal material. The upper end of the spring 37 is fixed to the second pressure arm 33L. The lower end of the spring 37 is fixed to the rear end of the frame 31. This applies downward tension to the spring 37. In other words, tension is applied to the second pressure arm 33L in a direction that rotates it downward. The downward tension of the spring 37 causes the second pressure arm 33L to pressurize the stay cover 51 at the contact point. The stay cover 51 is in contact with the stay 52 and presses the stay 52. The stay 52 is in contact with the heating plate 55 and presses the heating plate 55. The heating plate 55 is in contact with the heating belt 56 and presses the heating belt 56. The heating belt 56 applies pressure toward the pressure roller 21.

The conductive brush 39R is made of, for example, multiple conductive fibers. The conductive brush 39R is an example of a first elastic member. As shown in Figures 3, 4, and 5, the upper end of the conductive brush 39R is fixed to the inner side of the first pressure arm 33R with conductive tape 43 so that the lower end of the conductive brush 39R contacts the cam shaft 34. The conductive brush 39R electrically connects the first pressure arm 33R and the cam shaft 34.

Figure 7 is a right side view of the interlocking mechanism 60 when the front cover 7 is closed. Figure 8 is a right side view of the interlocking mechanism 60 when the front cover 7 is open. The interlocking mechanism 60 is provided inside the device main body 2 and is configured to rotate the drive input portion 32 in conjunction with the opening operation of the front cover 7.

The interlocking mechanism 60 includes a rear cover 69, a first slide member 61, a first link 62, a second link 63, a second slide member 68, and a third cam 67. The front cover 7 and the rear cover 69 are examples of covers.

The front cover 7 can swing back and forth around the pivot point 66.

As shown in Figure 7, the first slide member 61 is a rod-shaped member extending in the front-rear direction and is disposed between the front cover 7 and the drive input portion 32. An abutment portion 65 that abuts against the drive input portion 32 is formed on the rear end of the first slide member 61, which is the end opposite the front cover 7. The front end, which is the end on the front cover 7 side, is connected to the front cover 7 via a first link 62 and a second link 63.

The first link 62 is elongated and rotatably connected to the front cover 7.

The second link 63 is rotatably supported on the device main body 2 between the first link 62 and the first slide member 61, and is rotatably connected to both the first link 62 and the first slide member 61. Specifically, the second link 63 has a link shaft 64 at its center that rotatably supports the second link 63, an arm portion (number omitted) extending diagonally upward and forward from the link shaft 64 and connecting to the first link 62, and an arm portion (number omitted) extending diagonally downward and forward from the link shaft 64 and connecting to the first slide member 61.

As shown in Figure 8, when the front cover 7 is opened, the first link 62 and second link 63 configured as described above move forward, causing the second link 63 to rotate counterclockwise as shown. This pushes the first slide member 61 rearward. On the other hand, when the front cover 7 is closed, the first link 62 moves rearward, causing the second link 63 to rotate clockwise as shown. This causes the first slide member 61 to move forward.

The first slide member 61 is a member that rotates the drive input portion 32 in conjunction with the opening and closing of the front cover 7. When the front cover 7 is opened, the first slide member 61 slides rearward, and the abutment portion 65 presses the tip of the drive input portion 32 rearward. This causes the drive input portion 32 to rotate counterclockwise as shown. Furthermore, when the front cover 7 is closed from this state, the first slide member 61 moves forward, causing the drive input portion 32 to rotate clockwise as shown, returning to its original position.

The drive input portion 32 has its center attached to the right end of the camshaft 34 so that it cannot rotate relative to the camshaft 34. The drive input portion 32 rotates in conjunction with the opening and closing of the front cover 7, providing a rotational drive force to the camshaft 34. The drive input portion 32 rotates the camshaft 34.

As shown in Figure 7, the second slide member 68 is a rod-shaped member that extends generally vertically. It is disposed between the third cam 67 and the drive input portion 32 and is supported on the device main body 2 so that it can slide longitudinally.

The third cam 67 converts and transmits the rotational movement of the rear cover 69 into the sliding movement of the second slide member 68.

When the rear cover 69 is opened, the lower end of the second slide member 68 engages with the third cam 67 and is pushed up. At this time, the upper end of the second slide member 68 engages with the drive input portion 32 and pushes the drive input portion 32 upward, causing it to rotate counterclockwise as shown. Furthermore, when the rear cover 69 is closed from this state, the engagement between the second slide member 68 and the third cam 67 is released, and the drive input portion 32 and second slide member 68 move downward and return to their original positions.

The drive input portion 32 rotates in conjunction with the opening and closing of the rear cover 69, providing a rotational drive force to the camshaft 34. The drive input portion 32 rotates the camshaft 34.

<Operation of the first pressure arm 33R>
9 is a diagram showing the first pressure arm 33R pressing the heating belt 56. As shown in FIG. 9, the first cam 35R rotates in conjunction with the rotation of the cam shaft 34. When the protrusion P of the first cam 35R is in a downward position, the tension of the spring 36 causes the first pressure arm 33R to press the heating belt 56. As the first pressure arm 33R presses the heating belt 56, the heating belt 56 moves toward and contacts the pressure roller 21. As a result, the heating belt 56 presses the pressure roller 21. At this time, the cam shaft 34 is electrically connected to the main body frame 40 via the conductive brush 39R, the first pressure arm 33R, and the spring 36.

Figure 10 shows the first pressure arm 33R releasing pressure from the heating belt 56. As shown in Figure 10, when the protrusion P of the first cam 35R is in the upward position, the first cam 35R is pushing up the first pressure arm 33R, causing the first pressure arm 33R to release pressure from the heating belt 56. As a result, the heating belt 56 releases pressure from the pressure roller 21. At this time, the cam shaft 34 is electrically connected to the main frame 40 via the conductive brush 39R, the first pressure arm 33R, and the spring 36. Note that when pressure from the heating belt 56 is released, the heating belt 56 and the pressure roller 21 may be in contact.

When the first cam 35R rotates, the position of the first pressure arm 33R changes, and the distance between the first pressure arm 33R and the camshaft 34 also changes. When the distance between the first pressure arm 33R and the camshaft 34 is short, the conductive brush 39R is pressed and electrically connected to the camshaft 34. When the distance between the first pressure arm 33R and the camshaft 34 is long, the conductive brush 39R is extended and electrically connected to the camshaft 34. In this way, even if the distance between the first pressure arm 33R and the camshaft 34 changes due to the rotation of the first cam 35R, the elasticity of the conductive brush 39R ensures that the lower end of the conductive brush 39R is always in contact with the camshaft 34. Therefore, even if the distance between the first pressure arm 33R and the camshaft 34 changes, the camshaft 34 remains electrically connected to the first pressure arm 33R via the conductive brush 39R.

This ensures that the camshaft 34 is always electrically connected to the main frame 40. The potential of the camshaft 34 is maintained at the frame ground of the main frame 40, thereby suppressing the spread of radiated noise generated by the camshaft 34.

<Electrical Connection of Second Pressurizing Arm 33L>
FIG. 11 is a schematic diagram of the fixing device 5. The fixing device 5 further includes a conductive brush 39L. The conductive brush 39L is made of, for example, a plurality of conductive fibers. The conductive brush 39L is an example of a second elastic member. As shown in FIG. 11 , the upper end of the conductive brush 39L is fixed to the inner side surface of the second pressure arm 33L with a conductive tape 43 so that the lower end of the conductive brush 39L contacts the cam shaft 34. The conductive brush 39L electrically connects the second pressure arm 33L and the cam shaft 34.

Unlike the first pressure arm 33R, the second pressure arm 33L is not electrically connected to the main frame 40 via a ground spring and a leaf spring. If the upper end of the conductive brush 39L were fixed to the second pressure arm 33L and electrically connected, and the camshaft 34 and conductive brush 39L were not electrically connected, the second pressure arm 33L would not be electrically connected to anything and would diffuse radiated noise. Therefore, the second pressure arm 33L is electrically connected to the camshaft 34 via the conductive brush 39L. The camshaft 34 is electrically connected to the main frame 40 via the conductive brush 39R, the first pressure arm 33R, and the spring 36. The second pressure arm 33L can ensure frame grounding for the main frame 40.

This maintains the potential of the second pressure arm 33L at the frame ground of the main frame 40, thereby suppressing the spread of radiated noise generated from the second pressure arm 33L.

[Variation 1]
Modifications of the embodiments of the present disclosure will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiments, and the description thereof will not be repeated.

Figure 12 shows how the first pressure arm 33R presses the heating belt 56. The fixing device 5A is equipped with a leaf spring 39RA. For example, the leaf spring 39RA is a plate-shaped member. The leaf spring 39RA is an example of a first elastic member. The upper end of the leaf spring 39RA is fixed to the inner side of the first pressure arm 33R. The leaf spring 39RA is electrically connected to the first pressure arm 33R. The lower end of the leaf spring 39RA is in contact with the cam shaft 34. As a result, the leaf spring 39RA is electrically connected to the cam shaft 34. The spring 36 is electrically connected to the main body frame 40.

As shown in Figure 12, the first cam 35R rotates in conjunction with the rotation of the cam shaft 34. When the protrusion P of the first cam 35R is in a downward position, the tension of the spring 36 causes the first pressure arm 33R to pressurize the heating belt 56. As the first pressure arm 33R presses the heating belt 56, the heating belt 56 moves toward and contacts the pressure roller 21. As a result, the heating belt 56 presses the pressure roller 21. At this time, the cam shaft 34 is electrically connected to the main frame 40 via the leaf spring 39RA, the first pressure arm 33R, and the spring 36.

Figure 13 shows the first pressure arm 33R releasing pressure from the heating belt 56. As shown in Figure 13, when the protrusion P of the first cam 35R is in the upward position, the first cam 35R is pushing up the first pressure arm 33R, causing the first pressure arm 33R to release pressure from the heating belt 56. As a result, the heating belt 56 releases pressure from the pressure roller 21. At this time, the cam shaft 34 is electrically connected to the main frame 40 via the leaf spring 39RA, the first pressure arm 33R, and the spring 36. Note that when pressure from the heating belt 56 is released, the heating belt 56 and the pressure roller 21 may be in contact.

When the first cam 35R rotates, the position of the first pressure arm 33R changes, and the distance between the first pressure arm 33R and the camshaft 34 also changes. When the distance between the first pressure arm 33R and the camshaft 34 is short, the leaf spring 39RA is pressed and electrically connected to the camshaft. When the distance between the first pressure arm 33R and the camshaft 34 is long, the leaf spring 39RA is extended and electrically connected to the camshaft 34.

As a result, even if the position of the first pressure arm 33R changes, the first pressure arm 33R and the cam shaft 34 remain electrically connected, ensuring that the cam shaft 34 is frame grounded to the main frame 40.

Here, an example has been described in which the first elastic member 39RA is a leaf spring, but the second elastic member may also be a leaf spring.

[Variation 2]
Modifications of the embodiments of the present disclosure will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiments, and the description thereof will not be repeated.

In the above embodiment, an example was described in which the sliding bearing 31B is molded integrally with each of the first cam 35R and the second cam 35L, but the sliding bearing 31B may also be a separate part from each of the first cam 35R and the second cam 35L. In that case, the sliding bearing 31B may be configured so that the inner peripheral portion 31C of the sliding bearing 31B is in sliding contact with the cam shaft 34.

Other embodiments
In the above embodiment, the heating belt 56 is used as an example of the first rotating body, but the first rotating body is not limited to this and may be a heating roller or a pressure roller. The first rotating body may also be a pressure belt in contact with the heating roller. The pressure roller 21 is used as an example of the second rotating body, but the second rotating body is not limited to this and may be a heating roller or heating belt heated by the heater 54, or a pressure belt in contact with the heating roller.

This disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure.

REFERENCE SIGNS LIST 1 laser printer 5 fixing device 21 pressure roller 22 heat unit 33R first pressure arm 33L second pressure arm 34 cam shaft 35R first cam 35L second cam 36 spring 37 spring 39R conductive brush 39L conductive brush 40 main body frame 56 heating belt

Claims (8)

A fixing device that is housed in an image forming apparatus and fixes a toner image on a sheet,
a first rotor that is rotatable around an axial direction;
a second rotating body that is rotatable around the axial direction and that sandwiches the sheet between the second rotating body and the first rotating body;
a first pressure arm that presses the first rotating body toward the second rotating body, the first pressure arm being conductive and electrically connected to a reference potential portion of the image forming apparatus;
a first cam that comes into contact with the first pressure arm and rotates to displace the position of the first pressure arm;
a conductive cam shaft into which the first cam is fitted and which is rotatable about the axial direction;
a frame that supports the first rotating body, the second rotating body, and the first pressure arm;
a first conductive elastic member electrically connecting the first pressure arm and the cam shaft; The fixing device according to claim 1, wherein the first elastic member is a conductive brush made of conductive fibers. The fixing device according to claim 1, wherein the first elastic member is a plate-shaped member. the first pressure arm is disposed on one end side in the axial direction,
a second pressure arm that applies pressure to the first rotor, the second pressure arm being disposed on the other end side in the axial direction;
a second cam fitted to the camshaft, the second cam being in contact with the second pressure applying arm and rotating to displace the position of the second pressure applying arm;
a conductive second elastic member that electrically connects the second pressure arm and the camshaft;
The fixing device according to claim 1 , further comprising: A fixing device according to any one of claims 1 to 4, wherein the cam shaft is supported on the frame via a resin sliding bearing. The fixing device described in claim 5, wherein the first cam is integrally molded with the sliding bearing. a conductive spring that applies pressure to the first pressure arm;
One end of the spring is electrically connected to the first pressure arm,
The fixing device according to claim 1 , wherein the other end of the spring is electrically connected to the reference potential portion of the image forming apparatus. The fixing device described in any one of claims 1 to 7, further comprising a drive input portion fitted to the cam shaft and applying a rotational drive force to the cam shaft in conjunction with opening and closing of a cover of the image forming device.