Fixation device and image forming apparatus

Abstract

To provide a fixation device that can stabilize contact pressure between a heating member and a pressurizing member with a simple configuration that achieves miniaturization and low cost.SOLUTION: A fixation device 30 includes a fixation belt 32, a pressurizing roller 33, a pressurizing mechanism 40, and a fixation frame 31. The pressurizing mechanism 40 includes a pressurizing plate 41, pressurizing springs 42, a cam member 43, and a support member 44. The pressurizing plate 41 oscillates in a direction toward and away from the fixation belt 32. The pressurizing springs 42 energize the pressuring plate 41 in a direction of approaching the fixation belt 32. The cam member 43 is brought into contact with the pressuring plate 41 from an opposite side of the pressurizing springs 42, and rotates to make the pressurizing plate 41 oscillate. The support member 44 is fixed to the fixation frame 31 to support one end of the pressurizing springs 42 and an oscillation fulcrum 41a of the pressurizing plate 41. The support member 44 has a through-hole 44h into which a revolving shaft 43x of the cam member 43 is inserted.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In electrophotographic image forming devices such as copiers and printers, a fixing device employing a thermal fixing method is widely used to fix an unfixed toner image formed on a sheet-like recording medium to the recording medium. The recording medium is heated and pressurized as it passes through a fixing nip formed by contact between a heating member and a pressure member, thereby fixing the unfixed toner image. Such fixing devices include a pressure mechanism that forms the fixing nip between the heating member and the pressure member.

[0003] For example, the conventional fixing device disclosed in Patent Document 1 is equipped with a pressure mechanism including a lever member that is rotatably mounted on a support frame and that presses the fixing film against a pressure roller, a pressure spring that applies a pressing force to the lever member, and a cam member that acts on the lever member to reduce the pressure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-201357 Summary of the Invention [Problem to be solved by the invention]

[0005] In the pressure mechanism of the above-mentioned prior art, the lever member, pressure spring, and cam member, which are components, are directly arranged and positioned on a support frame that supports the fixing film and pressure roller. As a result, the positional relationship of each component of the pressure mechanism depends on the dimensional accuracy of the support frame, making position adjustment difficult. For this reason, the pressure mechanism of the prior art requires an adjustment member to ensure that the biasing force of the pressure spring is at a predetermined pressure, which raises concerns about an increase in the number of parts required for pressure adjustment and an increase in the size of the device.

[0006] The present invention has been made in consideration of the above points, and aims to provide a fixing device and an image forming apparatus that can stabilize the contact pressure between the heating member and the pressure member with a simple configuration that is compact and low cost. [Means for solving the problem]

[0007] To solve the above problems, the fixing device of the present invention includes a heating member, a pressure member, a pressure mechanism, and a fixing frame. A recording medium is inserted into a fixing nip portion and heated and pressurized to fix a toner image formed on the recording medium to the recording medium. The pressure member contacts the heating member and applies pressure to form the fixing nip portion. The pressure mechanism adjusts the contact pressure of the fixing nip portion. The fixing frame supports the heating member, the pressure member, and the pressure mechanism. The pressure mechanism includes a pressure plate, a biasing member, a cam member, and a support member. The pressure plate swings toward or away from either the heating member or the pressure member. The biasing member biases the pressure plate toward either the heating member or the pressure member. The cam member contacts the pressure plate from the opposite side of the biasing member and rotates to swing the pressure plate. The support member is fixed to the fixing frame and supports one end of the biasing member and the swing fulcrum of the pressure plate. The support member has a through hole into which the rotation shaft of the cam member is inserted. [Effects of the Invention]

[0008] According to the configuration of the present invention, the pressure mechanism is composed of a pressure plate, a biasing member, a cam member, and a support member, and the pressure plate, biasing member, and cam member are arranged and positioned on the support member. The support member is a separate member from the fixing frame and is not affected by the dimensional accuracy of the fixing frame. In other words, the pressure mechanism can improve dimensional accuracy independently of the fixing frame, and the contact pressure between the heating member and the pressure member can be easily adjusted. Therefore, a simple configuration that is compact and low cost makes it possible to stabilize the contact pressure between the heating member and the pressure member. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional side view of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of a fixing device of the image forming apparatus of FIG. [Figure 3] 3 is a cross-sectional side view showing the periphery of a pressure mechanism of the fixing device in FIG. 2. [Figure 4] 4 is a cross-sectional side view showing the periphery of a pressure mechanism of the fixing device in FIG. 3, illustrating a pressure-released state. FIG. [Figure 5] 3 is a perspective view of a fixing frame around a pressure mechanism in FIG. 2. FIG. [Figure 6] 6 is a perspective view of a support member of a pressure mechanism fixed to the fixing frame of FIG. 5. FIG. [Figure 7] 3 is a perspective view of a pressure plate and a support member of the pressure mechanism of FIG. 2. FIG. [Figure 8] 3 is a cross-sectional perspective view of a pressure plate and a support member of the pressure mechanism of FIG. 2. FIG. [Figure 9] FIG. 8 is a perspective view of a support member of the pressure mechanism of FIG. 7. [Figure 10] FIG. 8 is a perspective view of a pressure plate of the pressure mechanism of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following.

[0011] 1 is a schematic cross-sectional side view of an image forming apparatus 1 according to an embodiment. An example of the image forming apparatus 1 according to this embodiment is a so-called printer that receives image data and a print command related to a print job from an external computer and executes printing.

[0012] As shown in FIG. 1, the image forming apparatus 1 includes a main body 2, which includes a sheet supply unit 3, a sheet conveying unit 4, an exposure unit 5, an image forming unit 20, a transfer unit 6, a fixing device 30, a sheet discharge unit 8, and a control unit 9.

[0013] The sheet supply unit 3 is located at the bottom of the main body 2. The sheet supply unit 3 stores multiple sheets (recording media) S and separates and sends out the sheets S one by one during printing. The sheet transport unit 4 transports the sheets S sent out from the sheet supply unit 3 to the transfer unit 6 and the fixing device 30, and then discharges the fixed sheets S from the sheet discharge port 4D to the sheet discharge unit 8. The exposure unit 5 irradiates the image forming unit 20 with laser light controlled based on image data.

[0014] Image forming unit 20 is disposed above sheet supply unit 3. Image forming unit 20 includes a photosensitive drum 21 that is supported so as to be rotatable in a predetermined direction (counterclockwise in FIG. 1). Image forming unit 20 further includes a charging unit 22, a developing unit 23, and a cleaning unit 24 that are disposed around photosensitive drum 21 along the direction of rotation of photosensitive drum 21. Note that transfer unit 6 is disposed between developing unit 23 and cleaning unit 24.

[0015] The photosensitive drum 21 has a photosensitive layer on its outer circumferential surface. The charging unit 22 charges the outer circumferential surface of the photosensitive drum 21 to a predetermined potential. The exposure unit 5 exposes the outer circumferential surface of the photosensitive drum 21 charged by the charging unit 22 to light, forming an electrostatic latent image of the original image on the outer circumferential surface of the photosensitive drum 21. The developing unit 23 develops this electrostatic latent image by attaching toner to it, thereby forming a toner image.

[0016] The transfer unit 6 is disposed above the sheet supply unit 3 and below the image forming unit 20. The transfer unit 6 transfers the toner image formed on the outer peripheral surface of the photosensitive drum 21 onto the sheet S. After the toner image is transferred to the sheet S, the cleaning unit 24 removes toner and the like remaining on the outer peripheral surface of the photosensitive drum 21, thereby cleaning it.

[0017] The fixing device 30 is disposed downstream in the sheet conveying direction of the sheet conveying section 4 from the image forming section 20 and the transfer section 6. The fixing device 30 fixes the toner image transferred (formed) on the sheet S to the sheet S by inserting the sheet S into a fixing nip section, which will be described later, and applying heat and pressure.

[0018] The sheet discharge section 8 is disposed on the top surface of the main body 2. The sheet S on which the toner image has been fixed and printing has been completed is transported to the sheet discharge section 8. The sheet discharge section 8 takes out the printed sheet (printed material) from above the main body 2.

[0019] The control unit 9 includes a CPU, an image processing unit, a memory unit, and other electronic circuits and electronic components (all not shown). The CPU controls the operation of each component provided in the image forming apparatus 1 based on control programs and data stored in the memory unit to perform processing related to the functions of the image forming apparatus 1. The sheet supply unit 3, the sheet conveying unit 4, the exposure unit 5, the image forming unit 20, the transfer unit 6, and the fixing unit 30 each receive individual commands from the control unit 9 and work together to print on the sheet S. The memory unit is configured by a combination of a non-volatile storage device such as a program ROM (Read Only Memory) or a data ROM, and a volatile storage device such as a RAM (Random Access Memory).

[0020] Next, the configuration of the fixing device 30 will be described with reference to Fig. 2, Fig. 3, and Fig. 4 in addition to Fig. 1. Fig. 2 is a perspective view of the fixing device 30 of the image forming apparatus 1 of Fig. 1. Fig. 3 is a cross-sectional side view showing the periphery of the pressure mechanism 40 of the fixing device 30 of Fig. 2. Fig. 4 is a cross-sectional side view showing the periphery of the pressure mechanism 40 of the fixing device 30 of Fig. 3, and is a view showing a pressure-released state.

[0021] As shown in FIGS. 2, 3, and 4, the fixing device 30 includes a fixing frame 31, a fixing belt (heating member) 32, a pressure roller (pressure member) 33, and a pressure mechanism 40.

[0022] The fixing frame 31 is formed as a box having a substantially rectangular parallelepiped shape. A fixing belt 32 and a pressure roller 33 are housed inside the fixing frame 31. The fixing frame 31 has an entrance 31E and an exit 31D for the sheet S. The fixing frame 31 also has a pair of side plates 311.

[0023] The pair of side plates 311 are disposed at both ends of the fixing frame 31 in the axial direction of the fixing belt 32 and the pressure roller 33, and at both ends in the sheet width direction perpendicular to the sheet conveying direction. The pair of side plates 311 are formed in the shape of flat plates extending in the vertical direction and the sheet conveying direction. The pair of side plates 311 support both ends of the axial direction of the fixing belt 32 and the pressure roller 33. The pair of side plates 311 also support the pressure mechanism 40.

[0024] The fixing belt 32 is endless and formed in a cylindrical shape. The fixing belt 32 is supported by a pair of side plates 311 of the fixing frame 31 via a belt holder 34 arranged radially inward. The fixing belt 32 is rotatable along the sheet conveyance direction around an axis extending in the sheet width direction. The belt holder 34 is supported by a pair of side plates 311 arranged outside the axial direction of the fixing belt 32, ensuring strength sufficient to apply pressure between the belt holder 34 and the pressure roller 33.

[0025] The fixing belt 32 has a laminated structure in which an elastic layer and a release layer are provided on the outer periphery of a base layer. The base layer is made of, for example, a metal film such as nickel or a polyimide film. The elastic layer is made of, for example, silicone rubber. The release layer is made of, for example, a fluorine-based resin such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer).

[0026] A heat source 35 is disposed radially inward of the fixing belt 32. The heat source 35 is supported by a belt holder 34. The heat source 35 is disposed inside the fixing belt 32, facing the pressure roller 33 across the fixing belt 32. The heat source 35 is constituted by a planar heater (e.g., a resistance heating element) extending over the entire axial direction of the fixing belt 32. The heat source 35 comes into contact with the fixing belt 32, thereby directly heating the fixing belt 32 at the fixing nip N. The operation of the heat source 35 is controlled by the control unit 9.

[0027] The pressure roller 33 is formed in a cylindrical shape. A rotation shaft of the pressure roller 33 is supported by a pair of side plates 311 of the fixing frame 31. The pressure roller 33 is rotatable along the sheet conveyance direction around an axis extending in the sheet width direction.

[0028] The pressure roller 33 has a laminated structure in which an elastic layer and a release layer are provided on the outer periphery of a core metal. The core metal is made of metal such as iron or aluminum. The elastic layer is made of silicone rubber, for example. The release layer is made of fluorine-based resin such as PFA, for example.

[0029] The pressure roller 33 is connected to a drive source (not shown) including, for example, a motor, and receives power from the motor to rotate clockwise in FIGS. 1, 3, and 4. The pressure roller 33 contacts the outer peripheral surface of the fixing belt 32 and applies a rotational driving force to the fixing belt 32. In other words, the fixing belt 32 is rotated by contact with the pressure roller 33. The operation of the pressure roller 33 is controlled by the control unit 9.

[0030] A predetermined pressure is applied to the fixing belt 32 by the pressure mechanism 40 toward the pressure roller 33. As a result, the fixing belt 32 comes into contact with the outer circumferential surface of the pressure roller 33 and is pressed against it. A fixing nip N is formed between the fixing belt 32 and the pressure roller 33. In other words, the pressure roller 33 comes into contact with the fixing belt 32 and applies pressure to form the fixing nip N.

[0031] The pressure mechanisms 40 are disposed on the outer sides of the pair of side plates 311 of the fixing frame 31. That is, a pair of pressure mechanisms 40 are provided at both axial ends of the fixing belt 32 and the pressure roller 33. The pair of pressure mechanisms 40 adjusts the contact pressure between the fixing belt 32 and the pressure roller 33, i.e., the contact pressure at the fixing nip N.

[0032] Each of the pair of pressure mechanisms 40 includes a pressure plate 41, a pressure spring (biasing member) 42, a cam member 43, and a support member 44.

[0033] The pressure plate 41 is disposed opposite a pair of belt holders 34 that support both axial ends of the fixing belt 32, and is located above the belt holders 34 shown in FIGS. 3 and 4. The pressure plate 41 has a longitudinal shape extending along the sheet conveying direction Dc (the left-right lateral direction in FIGS. 3 and 4), which is perpendicular to the axial direction of the fixing belt 32. The pressure plate 41 is supported by a support member 44 at a swing fulcrum 41a, which is one end (left end in FIGS. 3 and 4) on the upstream side of the sheet conveying direction Dc, and at a swing end 41b, which is the other end (right end in FIGS. 3 and 4) on the downstream side of the sheet conveying direction Dc. The pressure plate 41 swings toward and away from the belt holders 34 (fixing belt 32).

[0034] The pressure spring 42 is a compression coil spring and is disposed between the pressure plate 41 and the support member 44, and is located above the pressure plate 41 shown in FIGS. 3 and 4. Specifically, one end of the pressure spring 42 is supported by a spring receiving portion 44a formed on the support member 44. The other end of the pressure spring 42 is supported by a boss portion 34a of the belt holder 34 that protrudes through a through hole 41c formed in the pressure plate 41, and is in contact with the pressure plate 41. The outer diameter of the pressure spring 42 is larger than the inner diameter of the through hole 41c. As the pressure plate 41 swings, the pressure spring 42 contracts between the pressure plate 41 and the support member 44. In other words, the pressure spring 42 biases the pressure plate 41 in a direction toward the belt holder 34 (the fixing belt 32).

[0035] The cam member 43 is disposed on the same side of the pressure plate 41 as the belt holder 34, below the pressure plate 41 as shown in Figures 3 and 4. In other words, the cam member 43 contacts the pressure plate 41 from the side opposite the pressure spring 42. The cam member 43 is disposed near the swing end 41b of the pressure plate 41, with the belt holder 34 and the pressure spring 42 spaced apart, relative to the swing fulcrum 41a of the pressure plate 41.

[0036] The cam member 43 is connected to a drive unit (not shown) including a motor and receives rotational power from the drive unit. The cam member 43 rotates around the axis of a rotation shaft 43x extending in the sheet width direction. The cam member 43 has a long diameter portion and a short diameter portion with different radial lengths from the central axis of rotation, and as the cam member 43 rotates, the distance from the central axis to the point of contact with the pressure plate 41 changes. As a result, the cam member 43 rotates and causes the pressure plate 41 to swing.

[0037] 3 and 4 are diagrams showing the pressurized and unpressurized states of the fixing nip N by the pressure mechanism 40. When the minor diameter portion of the cam member 43 faces the pressure plate 41 as shown in Fig. 3, a constant pressure is applied to the belt holder 34 via the pressure plate 41 due to the biasing force of the pressure spring 42. As a result, the pressure roller 33 is pressed against the fixing belt 32, forming the fixing nip N between the pressure roller 33 and the fixing belt 32.

[0038] 3 rotates a predetermined amount, and when the major diameter portion of the cam member 43 comes into contact with the pressure plate 41 as shown in FIG. 4, the pressure plate 41 is displaced (swings) in a direction away from the belt holder 34 against the biasing force of the pressure spring 42. As a result, the pressure spring 42 is compressed between the pressure plate 41 and the support member 44, and the pressure acting on the belt holder 34 via the pressure plate 41 decreases. In other words, the contact pressure between the fixing belt 32 and the pressure roller 33, i.e., the contact pressure at the fixing nip N, decreases.

[0039] Next, the arrangement and configuration of the pressure mechanism 40 will be described in detail with reference to FIGS. 5 to 10. FIG. 5 is a perspective view of the fixing frame 31 around the pressure mechanism 40 in FIG. 2. FIG. 6 is a perspective view of the support member 44 of the pressure mechanism 40 fixed to the fixing frame 31 in FIG. 5. FIGS. 7 and 8 are a perspective view and a cross-sectional perspective view of the pressure plate 41 and support member 44 of the pressure mechanism 40 in FIG. 2. FIGS. 9 and 10 are perspective views of the support member 44 and pressure plate 41 of the pressure mechanism 40 in FIG. 7. Note that FIG. 5 shows the pressure mechanism 40 removed. FIG. 6 depicts only the support member 44 of the components of the pressure mechanism 40, omitting the pressure plate 41 and pressure spring 42.

[0040] The support member 44 is fixed to the side plate 311 of the fixing frame 31. The support member 44 has a lower wall portion 44b, a front wall portion 44c, a side wall portion 44d, an upper wall portion 44e, and a rear wall portion 44f. All of these wall portions are formed in a flat plate shape.

[0041] The lower wall portion 44b is located on the most upstream side in the sheet conveying direction Dc of the support member 44 and extends in a substantially horizontal direction. The support member 44 is fixed to the side plate 311 via the lower wall portion 44b.

[0042] The front wall portion 44c is located upstream of the belt holder 34 and the pressure spring 42 in the sheet conveying direction Dc. The front wall portion 44c extends substantially perpendicularly in the sheet width direction and the up-down direction, continuing from the lower wall portion 44b. The front wall portion 44c has a support hole 44g into which the swing fulcrum 41a of the pressure plate 41 is inserted and which supports the pressure plate 41.

[0043] The side wall portion 44d is located downstream of the front wall portion 44c in the sheet conveying direction Dc. The side wall portion 44d extends continuously from the front wall portion 44c substantially perpendicularly in the sheet conveying direction and the up-down direction. The side wall portion 44d is disposed opposite the rear wall portion 44f in the sheet width direction (axial direction of the belt holder 34), across the arrangement space of the pressure plate 41 and the pressure spring 42.

[0044] The upper wall portion 44e is located above the front wall portion 44c and downstream in the sheet conveying direction Dc, and further above the pressure spring 42 located above the pressure plate 41. The upper wall portion 44e extends continuously from the side wall portion 44d in the sheet conveying direction Dc. The upper wall portion 44e has a spring bearing portion 44a that supports one end of the pressure spring 42. That is, the support member 44 supports one end of the pressure spring 42 and the swing fulcrum 41a of the pressure plate 41.

[0045] The rear wall portion 44f is located downstream of the belt holder 34 and the pressure spring 42 in the sheet conveying direction Dc. The rear wall portion 44f extends continuously from the upper wall portion 44e substantially perpendicularly downward in the sheet conveying direction and the up-down direction. The rear wall portion 44f is disposed opposite the side wall portion 44d in the sheet width direction (axial direction of the belt holder 34), across the arrangement space of the pressure plate 41 and the pressure spring 42. The rear wall portion 44f is also disposed adjacent to and opposite the side plate 311.

[0046] The rear wall portion 44f has a through hole 44h. The through hole 44h penetrates the rear wall portion 44f in the axial direction of the rotation shaft 43x at the location where the rotation shaft 43x of the cam member 43 is arranged, and the rotation shaft 43x is inserted into the through hole 44h. In other words, the support member 44 has the through hole 44h into which the rotation shaft 43x of the cam member 43 is inserted.

[0047] According to the above configuration, the pressure mechanism 40 is made up of the pressure plate 41, the pressure spring (biasing member) 42, the cam member 43, and the support member 44, and the pressure plate 41, the pressure spring 42, and the cam member 43 are disposed on and positioned on the support member 44. The support member 44 is a separate member from the fixing frame 31 and is not affected by the dimensional accuracy of the fixing frame 31. In other words, the pressure mechanism 40 can have high dimensional accuracy independently of the fixing frame 31, and can easily adjust the contact pressure between the fixing belt 32 and the pressure roller 33. Therefore, a simple configuration that is compact and low cost can stabilize the contact pressure between the fixing belt 32 and the pressure roller 33.

[0048] The side plates 311 of the fixing frame 31 also have fixing portions 311f and positioning holes 311h for fixing the support members 44 of the pressure mechanism 40.

[0049] The fixed portion 311f is disposed upstream of the belt holder 34 in the sheet conveying direction Dc. The fixed portion 311f is disposed opposite the lower wall portion 44b of the support member 44. The upper surface of the fixed portion 311f faces the lower surface of the lower wall portion 44b and extends adjacent to it in the approximately horizontal direction. In other words, the fixed portion 311f is formed adjacent to the swing fulcrum of the pressure plate 41. The fixed portion 311f is fixed to the lower wall portion 44b, which is one end side of the support member 44 on the upstream side in the sheet conveying direction Dc, by a fastening member 36 such as a screw.

[0050] The positioning hole 311h is disposed downstream of the belt holder 34 in the sheet conveying direction Dc. The positioning hole 311h penetrates the side plate 311 in the axial direction of the rotation shaft 43x at the location where the rotation shaft 43x of the cam member 43 is disposed. That is, the positioning hole 311h is formed at a position overlapping with a through-hole 44h formed on the other end of the support member 44 on the downstream side in the sheet conveying direction Dc. The rotation shaft 43x of the cam member 43 is inserted into the positioning hole 311h.

[0051] According to the above configuration, the support member 44 of the pressure mechanism 40 is positioned and fixed to the side plate 311 via the positioning hole 311h and the fixing portion 311f. More specifically, the support member 44 is positioned on the plane of the side plate 311 by the positioning hole 311h. Furthermore, the support member 44 is fixed by the fixing portion 311f to prevent the support member 44 from rotating around the rotation axis 43x of the cam member 43 inserted into the positioning hole 311h. This allows the pressure mechanism 40 to be appropriately positioned with respect to the fixing frame 31, and stabilizes the contact pressure between the fixing belt 32 and the pressure roller 33.

[0052] Furthermore, the pressure spring 42, which is a compression coil spring, is disposed opposite the belt holder 34 (fixing belt 32) across the pressure plate 41. The pressure spring 42 urges the fixing belt 32 toward the pressure roller 33 via the pressure plate 41 and the belt holder 34. As shown in FIG. 3 , the central axis of the coil portion of the compression coil spring (pressure spring 42) is disposed so as to overlap with a straight line L1 that passes through the rotation center C1 of the fixing belt 32 adjacent to the pressure plate 41.

[0053] The above configuration allows the necessary pressure to be applied along the appropriate pressure direction (the direction of straight line L1), thereby suppressing variations in the contact pressure between the fixing belt 32 and the pressure roller 33 caused by the pressure mechanism 40 and tilting of the fixing belt 32 biased by the pressure spring 42.

[0054] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and various modifications can be made without departing from the spirit of the invention.

[0055] For example, in the above embodiment, the pressure plate 41 is attached to the belt holder 34 (the fixing belt 32). Although they are arranged adjacent to each other, the pressure plate 41 may be arranged adjacent to the pressure roller 33. That is, in the above embodiment, the pressure spring 42 urges the pressure plate 41 in a direction approaching the belt holder 34 (fixing belt 32), but the pressure plate 41 may be urged in a direction approaching the pressure roller 33.

[0056] In the above embodiment, the image forming apparatus 1 is an image forming apparatus for monochrome printing, but is not limited to such a model. The image forming apparatus may be, for example, an image forming apparatus for color printing. [Industrial Applicability]

[0057] The present invention can be used in fixing devices and image forming apparatuses. [Explanation of symbols]

[0058] 1. Image forming device 2 Main unit 30 Fixing device 31 Fixing Frame 32 Fixing belt (heating member) 33 Pressure roller (pressure member) 34 Belt holder 35 Heating source 36 Fastening members 40 Pressure Mechanism 41 Pressure plate 41a Swing fulcrum 42 Pressure spring (biasing member) 43 Cam member 43x rotation axis 44 Support member 44h through hole 311 Side panel 311f Fixed part 311h Positioning hole C1 Rotation center L1 straight line N Fixing nip S seat

Claims

1. A heating element; a pressure member that contacts the heating member and is pressed to form a fixing nip portion; a pressure mechanism for adjusting the contact pressure of the fixing nip portion; a fixing frame supporting the heating member, the pressure member, and the pressure mechanism; a fixing device for fixing a toner image formed on a recording medium to the recording medium by inserting the recording medium into the fixing nip portion and applying heat and pressure to the recording medium, The pressure mechanism includes: a pressure plate that swings toward and away from one of the heating member and the pressure member; a biasing member that biases the pressure plate in a direction toward one of the heating member and the pressure member; a cam member that contacts the pressure plate from the opposite side of the biasing member and rotates to swing the pressure plate; a support member fixed to the fixing frame and supporting one end of the biasing member and a swing fulcrum of the pressure plate; Equipped with The fixing device is characterized in that the support member has a through hole into which a rotation shaft of the cam member is inserted.

2. The fixing frame is a fixing portion formed adjacent to the swing fulcrum of the pressure plate, to which one end side of the support member is fixed by a fastening member; a positioning hole formed at a position overlapping with the through hole formed on the other end side of the support member, into which the rotation shaft of the cam member is inserted; 2. The fixing device according to claim 1, further comprising:

3. the biasing member is a compression coil spring, 2. The fixing device according to claim 1, wherein the central axis of the compression coil spring is arranged to overlap a line passing through a rotation center of one of the heating member and the pressure member adjacent to the pressure plate.

4. an image forming unit that forms a toner image on the recording medium; a fixing device according to any one of claims 1 to 3, which heats and pressurizes the recording medium on which the toner image has been formed by the image forming unit to fix the toner image to the recording medium; An image forming apparatus comprising:

Images