Fixing device

Abstract

The objective is to provide a new type of fixing device that builds upon conventional technology. [Solution] A fixing device mounted on an apparatus body of an image forming apparatus, the apparatus body having an electrically groundable main body conductor, the fixing device comprising: a heating unit comprising an endless belt and a heater for heating the belt; a pressure roller for forming a nip portion; a pressure arm for pressing the heating unit against the pressure roller; a conductive pressure spring for biasing the pressure arm so that the heating unit is pressed against the pressure roller; a frame for supporting the heating unit, the frame being made of resin; a conductive brush member in contact with the belt; a first conductor portion in contact with the brush member and the pressure spring respectively, and providing electrical conductivity between the brush member and the pressure spring; and a second conductor portion in contact with the pressure spring and the main body conductor respectively, and providing electrical conductivity between the pressure spring and the main body conductor.

Description

Technical Field

[0001] The present invention relates to a fixing device provided in an electrophotographic image forming apparatus.

Background Art

[0002] The fixing device described in Patent Document 1 includes a heating unit having a heater that heats the inner surface of a belt, and a pressure roller that forms a nip portion together with the heater via the belt, and fixes the toner on the recording material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a new form of fixing device that develops conventional technology.

Means for Solving the Problems

[0005] One aspect of the present invention is as follows.

[0006] A fixing device mounted on a device main body of an image forming apparatus, the device main body having a main body conductor portion that can be electrically grounded, for fixing toner to a recording material, a heating unit including an endless belt and a heater provided on a side of the inner surface of the belt for heating the belt, a pressure roller that forms a nip portion together with the heater via the belt, a pressure arm for pressing the heating unit against the pressure roller, a pressure spring having conductivity for biasing the pressure arm so that the heating unit is pressed against the pressure roller, A frame for supporting the heating unit, comprising a frame made of resin, A brush member that is in contact with the belt and is conductive, A first conductor portion that contacts the brush member and the pressure spring, and provides electrical conductivity between the brush member and the pressure spring, A second conductor portion that contacts the aforementioned pressure spring and the aforementioned main body conductor portion, and provides electrical conductivity between the pressure spring and the aforementioned main body conductor portion, A fixing device characterized by having the following features. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a new form of fixing device that is an advancement of the conventional technology. [Brief explanation of the drawing]

[0008] [Figure 1] Perspective views (a, b) of the fixing device according to Example 1. [Figure 2] Cross-sectional view of the fixing device according to Example 1. [Figure 3] Cross-sectional view of the fixing device according to Example 1. [Figure 4] Cross-sectional view of the fixing device according to Example 1. [Figure 5] An exploded perspective view of the fixing device according to Example 1. [Figure 6] Perspective views (a, b) of the fixing device according to Example 1. [Figure 7] Top view of the fixing device according to Example 1. [Figure 8] A perspective view of the fixing device according to Example 1. [Figure 9] Cross-sectional view of the fixing device according to Example 1. [Figure 10] Front view and top view (a, b) of the contact spring according to Example 1. [Figure 11] Front view and cross-sectional view (a, b, c, d) of the fixing device according to Example 1. [Figure 12] Cross-sectional views (a, b) of the fixing device according to Example 1. [Figure 13] An exploded perspective view of the fixing device according to Example 1. [Figure 14] Top view of the fixing device according to Embodiment 1. [Figure 15] Top view of the fixing device according to Modification 1. [Figure 16] Schematic views (a, b) of the fixing device according to Modification 2.

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described based on the drawings. Note that the dimensions, materials, shapes, relative arrangements, etc. of the components described in the following embodiments may be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless otherwise specifically described, the scope of the present invention is not limited to this example.

[0010] FIG. 2 is a cross-sectional view of an electrophotographic image forming apparatus 1 to which the fixing device in this embodiment is applied. In the following description, as shown in FIG. 2, when the image forming apparatus 1 is installed on a horizontal plane, the vertical direction is defined as the z direction. The direction intersecting the z direction is defined as the y direction. The y direction is a direction parallel to the rotation axis direction of the pressure arm 652 described later. The direction intersecting both the z direction and the y direction is defined as the x direction. The x direction is a direction parallel to the direction in which the heating unit 61 described later conveys the recording material located at the nip portion. The x direction and the y direction are preferably horizontal directions. Also, the x direction, the y direction, and the z direction are preferably orthogonal to each other. Further, if necessary, the directions of the arrows x, y, z shown in each drawing are respectively represented as the +x side, the +y side, and the +z side, and the opposite sides are respectively represented as the -x side, the -y side, and the -z side. In the following description, the direction in which the recording material is conveyed in the nip portion np1 described later is referred to as the recording material conveyance direction (+x direction). Also, the rotation axis direction of the pressure arm 652 described later is referred to as the axial direction. In the axial direction, the direction from the heating unit 61 described later toward the electrical contact 668b1 is referred to as the first axial direction (+y direction). In the axial direction, the direction opposite to the first axial direction is referred to as the second axial direction (-y direction). The Y direction is also the longitudinal direction of the heating unit 61. Also, the Y direction is the generatrix direction of the belt 614.

[0011] <Example 1> The fixing device 6 in Example 1 will be described.

[0012] [Configuration of the image forming apparatus] The configuration of the image forming apparatus 1 will be described using FIG. 2. The image forming apparatus 1 includes an apparatus main body 2, a process cartridge 10, and a fixing device 6. The process cartridge 10 is detachably attached to the apparatus main body 2. The fixing device 6 is detachably attached to the apparatus main body 2. It can also be said that the fixing device 6 is mounted on the apparatus main body 2. Note that the fixing device 6 may be non-detachably attached.

[0013] The apparatus main body 2 includes a paper feed tray 3, a sheet feeding unit 4, a conveyance path P, a transfer roller 51, a sheet discharge unit 7, a paper discharge tray 8, a laser scanner 9, and an opening / closing door 21. The process cartridge 10 includes a photosensitive drum 11 and a developing roller 12 as a developer carrier. Further, the process cartridge 10 houses a developer therein. The opening / closing door 21 is supported so as to be rotatable about a rotation axis 21a, and is configured to be movable between a closed position for closing the opening 2a and an open position for opening the opening 2a. When the opening / closing door 21 is in the open position where the opening 2a is released, the process cartridge 10 can be attached to and detached from the apparatus main body 2 through the opening 2a.

[0014] The sheet feeding unit 4 is composed of a paper feed roller 41, a separation roller 42, a separation pad 42a, and a pair of conveyance rollers 43. Based on a print start signal, the sheet S stored in the paper feed tray 3 is sent out to the conveyance path P by the sheet feeding unit 4 and conveyed toward the transfer roller 51 via a pair of registration rollers 44.

[0015] When the sheet S is transported to a predetermined position, an image formation start signal is issued, and the image formation process begins. The photosensitive drum 11, which is rotated by a drive source (motor) (not shown), is uniformly charged to a predetermined potential by a charging means (not shown). The surface of the charged photosensitive drum 11 is exposed by a laser scanner 9 based on image information, and an electrostatic image is formed in which the charge of the exposed area is removed. The toner in the process cartridge 10 is carried on the developing roller 12 and supplied to the photosensitive drum 11 according to the electrostatic latent image, developing the latent image. As a result, the latent image is made visible on the photosensitive drum 11 as a toner image.

[0016] The transfer roller 51 is positioned opposite the photosensitive drum 11 of the process cartridge 10. When the sheet S, conveyed by the registration roller pair 44, passes through the nip between the photosensitive drum 11 and the transfer roller 51, a voltage is applied to the transfer roller 51 from the main unit 2 of the device, and the toner image on the photosensitive drum 11 is transferred to the sheet S as an unfixed image. Subsequently, the sheet S with the transferred toner image is conveyed to the fuser 6, which is equipped with a heating unit 61 and a pressurizing rotating body 62. The fuser 6 is a fixing device that fixes toner (developer) to the recording material. When the sheet S passes through the nip of the heating unit 61 and the pressurizing rotating body 62, the unfixed image transferred on the sheet S is heated and pressurized and fixed to the surface of the sheet S. The sheet S with the fixed toner image is discharged to the output tray 8 via the sheet discharge unit 7.

[0017] [Fuser configuration] Next, the configuration of the fuser unit will be described. Figure 3 is a plan view of the fuser unit 6. As shown in Figure 3, the heating unit 61 comprises a heater 611, a holder 612, a stay 613, and a belt 614. The heater 611 is provided on the inner surface side of the belt 614 and heats the belt 614. The heater 611 extends in the direction of the generatrix (Y direction) of the belt 614, and the shape of the heater 611 is flat. The heater 611 has a first surface 611a and a second surface 611b opposite to the first surface 611a, and the first surface 611a is supported by the holder 612.

[0018] The holder 612 is made of a heat-resistant resin such as PPS or liquid crystal polymer, and has a guide surface 612a and a support wall 612b. The guide surface 612a contacts the inner circumferential surface 614a of the belt 614 to guide the belt 614, and the support wall 612b has a support surface 612b1 that supports the heater 611. The support surface 612b1 of the support wall 612b is in contact with the first surface 611a of the heater 611. The stay 613 is a member that supports the holder 612, and is formed by bending a plate material with greater rigidity than the holder 612, for example, a steel plate with a thickness of 1.6 mm, into a roughly U-shape.

[0019] The belt 614 is an endless belt that is heat-resistant and flexible, and is composed of, for example, a metal sleeve such as stainless steel coated with fluororesin, or a laminate of polyimide resin, silicone rubber, fluororesin, etc. A heater 611, a holder 612, and a stay 613 are arranged inside the belt 614, and the belt 614 is configured to rotate around these. The inner circumferential surface 614a of the belt 614 is in contact with the second surface 611b of the heater 611.

[0020] The pressurizing rotating body 62 (pressurizing roller) has a metal shaft 62a and a roller 62b made of an elastic material that covers the shaft 62a, and is pressed against the heater 611 via a belt 614. The pressurizing rotating body 62 sandwiches the belt 614 between itself and the heater 611, forming a nip portion np1 for nipping, heating, and pressurizing the sheet S. In other words, the pressurizing rotating body 62 (pressurizing roller) can be said to form a nip portion np1 together with the heater 611 via the belt 614. That is, the pressurizing rotating body 62 heats and pressurizes the sheet S together with the heater 611 at the nip portion np1.

[0021] The pressurized rotating body 62 is configured to rotate when a driving force is transmitted from a drive source provided by the image forming apparatus 1. As the pressurized rotating body 62 rotates, the belt 614 rotates in response. The sheet S on which the toner image has been transferred is transported between the pressurized rotating body 62 and the heated belt 614, thereby thermally fixing the toner image.

[0022] Next, the frame configuration of the fuser 6 will be described using Figure 4. Figure 4 is a plan view of the fuser 6. The fuser 6 has an upper frame 64 and a lower frame 63. The lower frame 63 can also be called the first frame and the upper frame 64 can be called the second frame. The lower frame 63 is the frame that supports the heating unit 61 and the pressurizing rotating body 62. The upper frame 64 is located above the lower frame 63 and covers the heating unit 61. The lower frame 63 and the upper frame 64 are resin components formed by non-conductive molded members (resin members). The upper frame 64 has an upper guide surface 64a located downstream of the heating unit 61 in the recording material transport direction (+X). The upper guide surface 64a guides the upper surface of the sheet S being transported in the recording material transport direction. The lower frame 63 has a lower guide surface 64a located downstream of the heating unit 61 in the recording material transport direction. The lower guide surface 64a guides the lower surface of the sheet S being transported in the recording material transport direction.

[0023] Next, the configuration of the lower frame 63 that supports the pressurized rotating body 62 will be described using Figure 5. Figure 5 is an exploded perspective view of the fixing unit 6. The lower frame 63 has rails 63b at its ends in the first axial direction and the second axial direction, respectively. The rails 63b extend vertically and support the holder 612 so that it can move vertically. The two rails 63b face each other in the axial direction. The rails 63b engage with grooves 617a1 and 617b1 provided in the transmission members 617a and 617b, respectively.

[0024] The fixing unit 6 is equipped with a bearing 62c. The end of the shaft 62a in the first axial direction and the end in the second axial direction are supported by bearings 62c and 62d, respectively. Bearing 62c is positioned by fitting into a recess 63d1 provided in the lower frame 63. Similarly, bearing 62d is positioned by fitting into a recess 63d2 provided in the lower frame 63. Bearing 62c is electrically conductive. In this configuration, bearings 62c and 62d are provided with protrusions, and the lower frame 63 is provided with recesses 63d1 and 63d2, but the relationship between the protrusions and recesses may be reversed. Also, the means for fixing bearings 62c and 62d to the lower frame 63 does not have to be of a protrusion-recess shape.

[0025] [Configuration of the pressurizing mechanism] Next, the configuration of the pressure mechanism of the fuser 6 will be described. Figure 11(a) is a front view of the fuser 6. Figures 11(b) to (d) are cross-sectional views of Figure 11(a), respectively.

[0026] As shown in Figure 11, the fuser 6 has a pressurizing mechanism 65 that presses the heating unit 61 against the pressurizing rotating body 62. The pressurizing mechanism 65 is provided at both the end of the lower frame 63 in the first axial direction and the end in the second axial direction. In other words, it can be said that the pressurizing mechanism 65 is supported by the lower frame 63. The structure of the pressurizing mechanism 65 provided on the end of the lower frame 63 in the first axial direction and the pressurizing mechanism 65 provided on the end of the lower frame 63 in the second axial direction are substantially the same. Therefore, the explanation of the pressurizing mechanism 65 provided on the first axial direction side also applies to the pressurizing mechanism 65 provided on the second axial direction side, so the explanation is omitted.

[0027] The pressurizing mechanism 65 includes a transmission member 651, a pressurizing arm 652, and a pressurizing spring 653. The pressurizing arm 652 is supported by a lower frame 63. More specifically, the pressurizing arm 652 is supported by a support portion 64d of the lower frame 63 and is rotatably supported around the central axis x1 of the support portion 64d. The support portion 64d is a substantially cylindrical projection.

[0028] The pressure arm 652 presses the transmission member 651 from above, moving the transmission member 651 downward. This causes the transmission member 651 to press the stay 613 downward. The transmission member 651 presses the stay 613, moving the stay 613 downward. As the stay 613 moves downward, the heating unit 61, which includes the stay 613, is pressed toward the pressure rotating body 62. The pressure spring 653 is a conductive tension coil spring that biases the pressure arm 652 so that the heating unit 61 is pressed toward the pressure rotating body 62. The pressure spring 653 engages with the lower frame 63 and the pressure arm 652. The biasing of the pressure arm 652 by the pressure spring 653 causes the pressure arm 652 to move the transmission member 651 downward. That is, the pressure arm 652 presses the heating unit 61 toward the pressure rotating body 62 (pressure roller).

[0029] [Configuration of the pressure release mechanism] Next, the configuration of the pressure release mechanism provided in the fuser 6 will be described using Figures 12 and 13. Figure 12 is a cross-sectional view of the fuser 6. Figure 12(a) shows the pressurized state with the pressure release mechanism 67 pressurized. Figure 12(b) shows the depressurized state with the pressure release mechanism 67 released. Figure 13 is an exploded perspective view of the upper frame 64, lower frame 63 and camshaft 671, with some parts such as the heating unit 61 and pressurizing rotating body 62 omitted. The pressure release mechanism 67 is a nip pressure release mechanism that changes the nip pressure in the nip section np1 between the heating unit 61 and the pressurizing rotating body 62. The pressure release mechanism 67 includes a camshaft 671 and a cam 672.

[0030] As shown in Figure 12, the camshaft 671 is rotatable about axis x2. The camshaft 671 extends axially and is made of a conductive metal. As shown in Figure 13, cams 672 are fixed (supported) to the first axial end and the second axial end of the camshaft 671, respectively. The cams 672 are supported so as to rotate together with the camshaft 671. The cams 672 are provided on the first axial end side and the second axial end side of the lower frame 63, respectively. The structure of the cam 672 provided on the first axial end side and the cam 672 provided on the second axial end side of the lower frame 63 are substantially the same.

[0031] The cam 672 presses against the pressurizing arm 652 against the biasing force of the pressurizing spring 653. That is, the rotation of the cam 672 changes the pressing force applied by the pressurizing arm 652 to the pressurizing rotating body 62 of the heating unit 61. The cam 672 is rotatable between the pressurizing position shown in Figure 12(a) and the release position shown in Figure 12(b).

[0032] To release the pressurized state, the camshaft 671 is rotated, causing the cam 672 to rotate. When the cam 672 rotates, the pressurizing arm 652, which is in contact with the cam 672, moves away from the transmission member 651 in the opposite direction to the direction in which the stay 613 is pressed against the transmission member 651. As a result, the pressure pressing the heating unit 61 toward the pressurizing rotating body 62 decreases.

[0033] Next, the support configuration of the camshaft 671 will be described using Figure 13. The lower frame 63 has a support wall 63l that rotatably supports the camshaft 671. The support wall 63l extends in the vertical direction (Z direction). The support wall 63l has a hole 631h that rotatably supports the camshaft 671. The camshaft 671 passes through the hole 631h. In other words, the support wall 63l can also be called a shaft support portion that supports the camshaft 671. The support walls 63l are provided on the end side in the first axial direction of the lower frame 63 and on the end side in the second axial direction of the lower frame 63. In addition, substantially the same hole 631h is provided in each support wall 63l.

[0034] The upper frame 64 has a support wall 64l that rotatably supports the camshaft 671. The support wall 64l extends vertically. The support wall 64l has a hole 641h that rotatably supports the camshaft 671. The camshaft 671 passes through the hole 641h. The support wall 64l is provided on the end side of the upper frame 64 in the first axial direction and on the end side of the lower frame 63 in the second axial direction. In addition, substantially the same hole 641h is provided in each support wall 64l.

[0035] [Grounding configuration of the fuser] Next, the grounding configuration of the fuser 6 will be described. In this embodiment, the fuser 6 is equipped with a grounding configuration for removing static electricity generated in the heating unit 61 of the fuser 6. Static electricity generated in the fuser 6 flows to the main body of the device 2 via the static electricity remover 66.

[0036] <Static electricity remover> The configuration of the electrostatic discharger 66 will be explained using Figures 1, 6 to 9. Figures 1(a) and 1(b) are perspective views of the fuser 6. Figure 6(a) is a perspective view of the fuser 6. Figure 6(b) is a perspective view of the fuser 6 when the cover 661 shown in Figure 6(a) is omitted. Figure 7 is a top view of the fuser 6. Figure 8 is a perspective view of the fuser 6. Figure 9 is a cross-sectional view of the fuser 6.

[0037] As shown in Figure 6(a), an electrostatic discharger 66 is attached to the upper frame 64 to remove static electricity generated in the fuser 6. The electrostatic discharger 66 is located downstream of the midpoint 614m of the belt 614 in the first axial direction.

[0038] As shown in Figures 6 to 9, the electrostatic discharger 66 comprises a brush 660, a first conductive plate 662, a resistive member 663, a second conductive plate 664, a cover 661, screws 665 and 666, and a first conductive spring 667.

[0039] The brush 660 is in contact with the heating unit 61 and the first conductive plate 662. The first conductive plate 662 is in contact with the resistance member 663. The second conductive plate 664 is in contact with the first conductive spring 667. Furthermore, the brush 660, the first conductive plate 662, the resistance member 663, and the second conductive plate 664 are all conductive. Therefore, static electricity generated in the heating unit 61 is transmitted from the brush 660 to the first conductive spring 667.

[0040] The cover 661 is a cover that covers the brush 660, the first conductive plate 662, and the second conductive plate 664 from above. As shown in Figures 6(a) and 6(b), screws 665 secure the first conductive plate 662 to the upper frame 64 together with the cover 661. Screws 666 also secure the second conductive plate 664 to the upper frame 64 together with the cover 661.

[0041] The configuration of the brush 660 (brush member) will now be described. As shown in Figure 8, the brush 660 is fixed inside the upper frame 64. As shown in Figure 9, the brush 660 is a conductive member that contacts the belt 614 from above. The brush 660 comprises a brush body 660a and a base plate 660b. The brush body 660a is made of a conductive resin. The base plate 660b is made of SUS, a metal, and is conductive. The brush body 660a is in contact with the surface 614b of the belt 614, and the brush body 660a and the belt 614 are electrically connected. That is, the brush 660 and the heating unit 61 are electrically connected. In this embodiment, the brush body 660a is in contact with the surface 614b of the belt 614, but a conductive member may be placed between the brush body 660a and the belt 614 to make the brush body 660a and the belt 614 electrically connected. The base plate 660b is a plate fixed to the brush body 660a and the upper frame 64. That is, the brush body 660a is fixed to the upper frame 64 via the base plate 660b. As shown in Figure 8, the base plate 660b is in contact with the contact portion 662b of the first conductive plate 662, which will be described later. That is, the base plate 660b and the first conductive plate 662 are electrically connected. As shown in Figure 7, the brush body 660a is in contact with the transmission member 617a. More specifically, when viewed in the vertical direction (Z direction), the brush body 660a overlaps with the transmission member 617a in the first axial direction, at least in part.

[0042] Next, the configuration of the first conductive plate 662 will be described. As shown in Figure 7, the first conductive plate 662 is a conductive member located upstream of the brush 660 in the first axial direction. As shown in Figure 6, a first hole 662d is formed in a part of the first conductive plate 662, and the screw 665 passes through the first hole 662d. Therefore, the first conductive plate 662 is fixed (supported) to the upper frame 64 by the screw 665. As shown in Figure 7, the first conductive plate 662 has contact portions 662a, 662b, and 662c. Contact portion 662a is in contact with the resistor member 663, which will be described later. That is, the first conductive plate 662 is electrically connected to the resistor 663. As shown in Figures 7 and 8, contact portion 662b is in contact with the base plate 660b. That is, contact portion 662b and the base plate 660b are electrically connected. Therefore, since the first conductive plate 662 is electrically connected to the brush 660 and the resistive member 663, static electricity can be passed from the brush 660 towards the resistive member 663.

[0043] Next, the configuration of the resistor 663 will be described. The grounding configuration in this embodiment includes the resistor 663. By slowly grounding the current through the resistor 663, it is possible to prevent the protective layer formed on the surface of the heater 611 from being damaged. As shown in Figure 7, the resistor 663, which has a predetermined electrical resistance, is pressed toward the upper frame 64 by the contact portion 662a of the first conductive plate 662 and the contact 664a of the second conductive plate 664, and is fixed to the upper frame 64.

[0044] Resistor 663 is in contact with contact portion 662a, and resistor 663 and the first conductive plate 662 are electrically connected. Also, resistor 663 is in contact with contact 664a of the second conductive plate 664, which will be described later, and resistor 663 and the second conductive plate 664 are electrically connected. Therefore, since resistor 663 is electrically connected to both the first conductive plate 662 and the second conductive plate 664, static electricity can be passed from the first conductive plate 662 to the second conductive plate 664.

[0045] Next, the configuration of the second conductive plate 664 will be described. As shown in Figure 6, the second conductive plate 664 has a second hole 664d formed therein, and the screw 666 passes through the second hole 664d. Therefore, the second conductive plate 664 is fixed to the upper frame 64 by the screw 665.

[0046] As shown in Figure 7, the second conductive plate 664 is a conductive material and includes contact portions 664a, 664b, and 664c. Contact portion 664a is in contact with the resistor 663. That is, the resistor 663 and the second conductive plate 664 are electrically connected. A third hole 664h is formed in contact portion 664b. The hook 667a of the first conductive spring 667, which will be described later, passes through the third hole and engages with the contact portion 664b. Contact portion 664b is in contact with the hook 667a of the first conductive spring 667, which will be described later. That is, the second conductive plate 664 and the first conductive spring 667 are electrically connected. Therefore, since the second conductive plate 664 is electrically connected to the resistor 663 and the first conductive spring 667, static electricity can flow from the resistor 663 to the first conductive spring 667.

[0047] As shown in Figure 7, when viewed vertically, the contact portion 664b has an overlapping portion 664bo that overlaps with the camshaft 671. The overlapping portion 664bo is located below the camshaft 671. By positioning the second conductive plate 664 below the camshaft 671 in this way, the second conductive plate 664 is less likely to be interfered with by the rotational movement of the camshaft 671 compared to a configuration in which the second conductive plate 664 is positioned above the camshaft 671.

[0048] Furthermore, the contact portion 664c is in contact with the camshaft 671 from above. The contact portion 664c can be called the camshaft contact portion. With this configuration, the charge accumulated on the camshaft 671 can be discharged via the second conductive plate 664.

[0049] Next, the configuration of the first conductive spring 667 will be described. The first conductive spring 667 is a conductive component. As shown in Figure 6, the first conductive spring 667 has a main spring 667c, a hook 667a, and a hook 667b.

[0050] Hook 667a is one end of the first conductive spring 667, and hook 667b is the other end of the first conductive spring 667. As described above, hook 667a engages with contact portion 664b via third hole 664h. Hook 667b engages with upper hook 653a of the pressure spring 653, which will be described later. That is, the first conductive spring 667 contacts and conducts electricity with the second conductive plate 664 and the pressure spring 653, respectively. The main spring 667c extends from hook 667a in the first axial direction and is connected to hook 667b. That is, the first conductive spring 667 (first spring) extends in the direction of the rotation axis of the pressure arm 652 and is electrically connected to the pressure spring 653.

[0051] Next, the positional relationship between the main spring 667c and the frame will be explained using Figure 6(a). A groove shape 641c is formed in the support wall 64l of the upper frame 64. The groove shape 641c is designed to allow the main spring 667c to pass through the support wall 63l from upstream to downstream in the first axial direction. The first conductive spring 667 passes through the groove shape 641c and extends in the first axial direction.

[0052] The end of the support wall 63l of the lower frame 63 in the recording material transport direction is called the downstream support end 631e. As shown in Figure 6(a), in the recording material transport direction, the downstream support end 631e is located between the camshaft 671 and the first conductive spring (first spring). The downstream support end 631e contacts the first conductive spring 667, guiding it to restrict its movement toward the camshaft 671. This configuration reduces the possibility of the first conductive spring 667 being interfered with by the rotation of the camshaft 671. In this embodiment, the first conductive spring 667 is configured to contact the downstream support end 631e, but the first conductive spring 667 may be positioned further downstream in the recording material transport direction than the downstream support end 631, so that the first conductive spring 667 and the downstream support end 631e do not come into contact.

[0053] Next, the electrical connection of the pressure spring 653 will be explained using Figures 1, 7, and 12. The pressure spring 653 comprises an upper hook 653a, a lower hook 653b, and a main spring 653c. One end of the pressure spring 653 is the upper hook 653a, and the other end is the lower hook 653b. The main spring 653c is connected to the upper hook 653a and the lower hook 653b and extends downward (vertically). In other words, the pressure spring 653 can be said to extend downward from the upper hook 653a toward the lower hook 653b. The upper hook 653a engages with the hook 667b of the first conductive spring 667. The hook 669b of the second conductive spring 669, which will be described later, engages with the lower hook 653b. Therefore, the pressure spring 653 is in contact with and electrically connected to the first conductive spring 667 and the second conductive spring 669, respectively.

[0054] As shown in Figure 12, the pressure arm 652 has a groove, which is an arm engagement portion 652a. The upper hook 653a is supported by engaging with the arm engagement portion 652a. That is, the pressure spring 653 is in contact with and supported by the pressure arm 652. The lower frame 63 also has a groove, which is a frame engagement portion 63e1. The lower hook 653b is supported by engaging with the frame engagement portion 63e1.

[0055] The conductivity configuration of the second conductivity spring 669 will be explained using Figure 1. The second conductivity spring 669 has a hook 669a, a hook 669b, and a main spring 669c. One end of the second conductivity spring 669 is the hook 669a, and the other end is the hook 669b. The main spring 669c is connected to the hooks 669a and 669b. The second conductivity spring 669 extends from the hook 669a toward the hook 669b in the direction of recording material transport. The hook 669a engages with the contact spring 668, which will be described later. Also, as mentioned above, the hook 669b engages with the lower hook 653b. Therefore, the second conductivity spring 669 is in contact with and electrically connected to the compression spring 653 and the contact spring 668, respectively.

[0056] Next, the electrical configuration of the contact spring 668 will be described using Figures 1 and 10. Figure 10(a) is a front view of the contact spring 668. Figure 10(b) is a top view of the contact spring 668. The contact spring 668 is a torsion coil spring made of a single metal wire. The contact spring 668 has a coil portion 668a, a first arm 668b extending from one end of the coil portion 668a, and a second arm 668c extending from the other end in a direction different from that of the first arm 668b. The first arm 668b has a spring-hanging portion 668b2, an extension portion 668b3, a hook portion 668b4, and a bent portion 668b5, and has an electrical contact 668b1 at its tip that contacts the main body conductor portion 2a of the device body 2, which will be described later. When the electrical contact 668b1 comes into contact with the main body conductor 2a, static electricity flows from the fuser 6 towards the main body 2 of the device.

[0057] The spring attachment portion 668b2 extends from one end of the coil portion 668a in the axial direction of the coil portion 668a. The extension portion 668b3 bends from the spring attachment portion 668b2 and extends in a direction intersecting the axial direction of the coil portion 668a. The hook portion 668b4 bends from the extension portion 668b3 at the bent portion 668b5 and extends in a direction perpendicular to the axial direction of the coil portion 668a. The electrical contact 668b1 is the tip of the first arm 668b and consists of the shape of a metal wire as it is after being cut, without any rounding or other processing, and has a sharp edge. In Figure 10, the metal wire is depicted as having been neatly cut at a right angle, but it may have an irregular shape, such as a shape that has been transferred from the blade of a cutting tool.

[0058] The second arm 668c has a second extension 668c1, a third extension 668c2, a retaining portion 668c3, and a pressed portion 668c4. The second extension 668c1 extends from the other end of the coil portion 668a in a direction intersecting the axial direction of the coil portion 668a. The pressed portion 668c4 is the portion that bends from the second extension 668c1 to the third extension 668c2. The third extension 668c2 extends in a direction perpendicular to the axial direction of the coil portion 668a and in a direction different from that of the second extension 668c1. The retaining portion 668c3 extends from the end of the third extension 668c2 furthest from the coil portion 668a in the axial direction of the coil portion 668a.

[0059] One end 669a of the second conductive spring 669 engages with the spring attachment portion 668b2. The second conductive spring 669 is a tension spring. The other end 669b of the second conductive spring 669 engages with the lower hook 653b of the compression spring 653. As a result, as shown in Figure 1, the contact spring 668 is biased by the second conductive spring 669 to rotate around the axis B of the boss 63e (in the direction of arrow C).

[0060] When the fuser 6 is not mounted on the main body 2, the bending portion 668b5 of the first arm 668b contacts the abutment surface 63f provided on the lower frame 63 due to the biasing force of the second conductive spring 669, and its orientation is determined. The lower frame 63 also has a first protective wall 63h located on one side of the hook portion 668b4 in the axial direction b of the coil portion 668a, and a second protective wall 63k located on the other side of the hook portion 668b4. That is, the hook portion 668b4 is located in the gap between the first protective wall 63h and the second protective wall 63k. At this time, the electrical contact 668b1 does not protrude from the first protective wall 63h and the second protective wall 63k, or protrudes only slightly. As a result, when the fuser 6 is not mounted on the main body 2, the electrical contact 668b1 is protected by the first protective wall 63h and the second protective wall 63k, making it less likely to get caught on other objects.

[0061] On the other hand, when the fuser 6 is not mounted on the main body 2, the pressed portion 668c4 is bent so as to protrude from the lower frame 63. The lower frame 63 has a slit 63g and a retaining wall 63n downstream of the boss 63e in the direction opposite to the recording material transport direction. The slit 63g extends in a direction perpendicular to the axis of the boss 63e. More specifically, the slit 63g extends in the recording material transport direction. The retaining wall 63n is positioned adjacent to the slit 63g. The third extension portion 668c2 of the second arm 668c enters the slit 63g. The retaining portion 668c3 is located upstream of the retaining wall 63n in the first axial direction and faces the retaining wall 63n. As a result, when the second conductive spring 669 rotates in the direction of arrow c, which is the direction in which the pressed portion 668c4 protrudes, the retaining portion 668c3 comes into contact with the retaining wall 63n.

[0062] Next, the conductivity configuration of the main body of the device 2 will be explained using Figure 14. Figure 14 is a top view of the fuser 6. The main body of the device 2 has a conductive main body conductor part 2a. In this embodiment, the main body conductor part 2a is an electrode. The main body conductor part 2a is a metal plate that also serves as the frame of the main body of the device 2. The main body conductor part 2a is configured to be electrically groundable. The main body conductor part 2a is in contact with the electrical contact 668b1 and is conductive. Therefore, it is possible to drain static electricity flowing from the electrical contact 668b1 to the ground from the main body conductor part 2a.

[0063] The grounding configuration of the fuser has been explained above. As previously stated, the brush body 660a is in contact with the surface 614b of the belt 614, and the brush body 660a and the belt 614 are electrically connected. The brush 660 is in contact with the first conductive plate 662 and is electrically connected. The resistor 663 is in contact with the second conductive plate 664 and is electrically connected. The second conductive plate 664 is in contact with the first conductive spring 667 and is electrically connected. The first conductive spring 667 is in contact with the pressure spring 653 and is electrically connected. The pressure spring 653 is in contact with the second conductive spring 669 and is electrically connected. The second conductive spring 669 is in contact with the contact spring 668 and is electrically connected. The electrical contact 668b1 of the contact spring 668 is in contact with the main body conductor portion 2a of the device body 2 and is electrically connected. The main conductor portion 2a is configured to be electrically groundable.

[0064] Here, the first conductive plate 662, the resistor 663, the second conductive plate 664, and the pressure spring 653 can be collectively referred to as the first conductor section 600a. In other words, the first conductor section 600a includes the first conductive plate 662, the resistor 663, the second conductive plate 664, and the first conductive spring 667 (first spring). The first conductor section 600a contacts the brush 660 (brush member) and the pressure spring 653, respectively, and provides electrical conductivity between the brush 660 (brush member) and the pressure spring 653.

[0065] The second conductive spring 669 and the contact spring 668 can be collectively referred to as the second conductor section 600b. In other words, the second conductor section 600b includes the second conductive spring 669 and the contact spring 668. The second conductor section 600b contacts the pressure spring 653 and the main conductor section 2a, and provides electrical conductivity between the pressure spring 653 and the main conductor section 2a.

[0066] Therefore, the charge generated in the heating unit 61 is grounded via the brush 660, the first conductor part 600a, and the second conductor part 600b. With this configuration, the charge accumulated in the heating unit 61 can be removed.

[0067] Furthermore, in the fuser unit 6 of this embodiment, since the upper frame 64 and lower frame 63 are made of resin, it is difficult to use the upper frame 64 and lower frame 63 as part of the grounding configuration. However, as described above, by connecting the brush 660, the first conductor section 600a, and the second conductor section 600b to the main body conductor section 2a, it is possible to dissipate the charge generated in the heating unit 61.

[0068] Furthermore, in the fuser 6 of this embodiment, the upper frame 64 (second frame) supports the first conductive plate 662, the resistor 663, and the second conductive plate 664. In other words, it can be said that the upper frame 64 supports the first conductor portion 600a. It can also be said that the upper frame 64 guides the first conductor portion 600a. By supporting the first conductor portion 600a with the upper frame 64 in this way, the stability of the first conductor portion 600a against external forces can be improved.

[0069] <Example 1> Next, Modification 1 will be explained using Figure 15. Figure 15 is a top view of the fuser 6. In Embodiment 1, the grounding configuration was such that static electricity was discharged via the brush 660, the first conductor section 600a, and the second conductor section 600b, but the pressure arm 652 may be included as part of the grounding configuration. That is, the pressure arm 652 may be made of a conductive material, and the brush 660, the pressure arm 652, and the pressure spring 653 may be electrically connected. In this case, the grounding configuration from the pressure spring 653 to the main conductor section 2a is the same as in Embodiment 1, so the explanation will be omitted.

[0070] The fuser 6 includes a conductive intermediate conductor 658. The intermediate conductor 658 is a metal component, but any conductive component may be used. As shown in Figure 15, the intermediate conductor 658 is in contact with and electrically connected to the brush 660 and the pressure arm 652, respectively. In this modified example, the intermediate conductor 658 is electrically connected to the belt 614 via the brush 660. This allows for stable contact with a weak force without damaging the belt 614.

[0071] Alternatively, the brush 660 may be omitted, and the intermediate conductor portion 658 may be brought into direct contact with the belt 614 to establish electrical conductivity between the intermediate conductor portion 658 and the belt 614. In this case, since the brush 660 is not provided, an inexpensive grounding configuration can be created. The intermediate conductor portion 658 is separate from the transmission member 617 or the pressure arm 652, but the intermediate conductor portion 658 may be integrally configured with the transmission member 617 or the pressure arm 652.

[0072] Alternatively, the intermediate conductor section 658 may be omitted, and the transmission member 617 shown in Figure 5 may be made of a conductive material. In this case, the transmission member 617 contacts and conducts electricity with the belt 614 and the pressure arm 652, respectively.

[0073] <Modification 2> Next, a modified example 2 will be explained using Figure 16. Figure 16 is a schematic diagram showing a part of the belt 614. The surface 614b of the belt 614 that the brush body 660a contacts may remain as is with the coating layer of fluororesin or the like, but if the belt 614 is made of a conductive material such as a metal sleeve, for example, the coating layer may be partially removed to expose the metal layer (conductive layer).

[0074] As shown in Figure 16(a), the belt 614 has a conductive layer 614d and an insulating layer 614c that covers the conductive layer 614d from the outer surface side of the belt 614. For example, the conductive layer 614d is the base layer of the belt 614. The conductive layer 614d has an exposed portion 614cc that is not covered by the insulating layer 614c and is exposed on the outer surface side of the belt 614. The brush 660 is in contact with the exposed portion 614cc, thereby dissipating the charge of the heating unit 61 to the earth via the grounding configuration described above.

[0075] Figure 16(b) shows the sheet S positioned at the nip portion np1 and the toner image being fixed by the fuser 61. Figure 16(b) also shows the case where the toner image I formed on the sheet S is at its maximum in the busbar direction (Y) of the belt 614. The portion of the belt 614 that is in the same position as the toner image I in the busbar direction (Y) of the belt 614 is called the first belt portion 614I. At least a portion of the exposed portion 614cc is located outside the first belt portion 614I in the busbar direction of the belt 614. Similarly, at least a portion of the brush 660 is located outside the first belt portion 614I in the busbar direction of the belt 614. By configuring the exposed portion 614cc in this way, the impact on fixing quality can be reduced compared to a configuration where the exposed portion 614cc is in the same position as the first belt portion 614I in the busbar direction of the belt 614.

[0076] The above describes Example 1 and Modifications 1 and 2. In this embodiment, the brush body 660a is made of conductive resin, but this is not necessarily required. For example, a brush made of thin metal, a weak torsion coil spring, or a thin metal foil would suffice, as long as it is conductive and can make stable contact with a weak force so as not to damage the belt 614.

[0077] In summary, the disclosure of this embodiment includes the following configuration.

[0078] (Item 1) An image forming apparatus, comprising an apparatus body equipped with an electrically groundable main body conductor, and a fixing device for fixing toner to a recording material, A heating unit comprising an endless belt and a heater provided on the inner surface side of the belt for heating the belt, A pressure roller that forms a nip portion together with the heater via the belt, A pressure arm for pressing the heating unit against the pressure roller, The heating unit biases the pressurizing arm so that it is pressed against the pressurizing roller, and a conductive pressurizing spring is provided. A frame for supporting the heating unit, comprising a frame made of resin, A brush member that is in contact with the belt and is conductive, A first conductor portion that contacts the brush member and the pressure spring, and provides electrical conductivity between the brush member and the pressure spring, A second conductor portion that contacts the aforementioned pressure spring and the aforementioned main body conductor portion, and provides electrical conductivity between the pressure spring and the aforementioned main body conductor portion, A fixing device characterized by having the following features.

[0079] (Item 2) The fixing device according to item 1, characterized in that the first conductor portion includes a resistor.

[0080] (Item 3) The belt has a conductive layer and an insulating layer that covers the conductive layer from the outer surface side of the belt. The conductive layer has an exposed portion that is not covered by the insulating layer so as to be exposed on the outer surface side of the belt, The brush member contacts the exposed portion of the conductive layer, When the recording material is located at the nip portion and the toner image formed on the recording material is at its maximum in the direction of the belt's generatrix, the portion of the belt that is at the same position as the toner image in the direction of the generatrix is ​​defined as the first portion of the belt. The fixing device according to item 1 or 2, characterized in that at least a portion of the exposed portion is located outside the first part of the belt in the direction of the belt's busbar.

[0081] (Item 4) A camshaft rotatably supported on the frame, A cam supported on the camshaft so as to rotate together with the camshaft, the cam that rotates to change the pressing force applied by the pressurizing arm to the pressurizing roller of the heating unit, A fixing device according to any one of items 1 to 3, characterized by having the following features.

[0082] (Item 5) Viewed in the vertical direction, the first conductor portion has an overlapping portion that overlaps with the camshaft, and the overlapping portion is located below the camshaft. The fixing device described in item 4, characterized by the features described herein.

[0083] (Item 6) When the aforementioned frame is designated as the first frame, The system further comprises a second resin frame that supports the camshaft, A fixing device according to either item 4 or 5, characterized by the features described in item 4 or 5.

[0084] (Item 7) The fixing device according to item 6, characterized in that the first conductor portion is supported by the second frame.

[0085] (Item 8) The first conductor portion includes a first spring, The first spring extends in the direction of the rotation axis of the pressurizing arm and is electrically connected to the pressurizing spring. A fixing device according to any one of items 1 to 7, characterized by the features described in item 1 to 7.

[0086] (Item 9) The first conductor section includes the first spring, The frame supports the camshaft and has a shaft support portion extending vertically. When the direction in which the recording material is transported in the aforementioned nip section is defined as the recording material transport direction, The downstream end of the shaft support in the recording material transport direction is defined as the downstream support end. The fixing device according to item 4 or 5, characterized in that, in the direction of transporting the recording material, the downstream end of the support is located between the camshaft and the first spring.

[0087] (Item 10) The downstream end of the support guides the first spring so as to restrict its movement toward the camshaft. The fixing device according to item 9, characterized in that it is a fixing device.

[0088] (Item 11) The conductive layer is the base layer of the belt. The fixing device according to item 3, characterized in that it is a fixing device.

[0089] (Item 12) The second conductor portion includes a torsion coil spring. The torsion coil spring contacts the main body conductor portion. A fixing device according to any one of items 1 to 11, characterized by the features described above.

[0090] (Item 13) The aforementioned main body conductor portion is an electrode. A fixing device according to any one of items 1 to 12, characterized by the features described above.

[0091] (Item 14) The first conductor portion has a camshaft contact portion that contacts the camshaft. A fixing device according to any one of items 4 to 13, characterized by the features described above.

[0092] (Item 15) The heating unit sets the direction in which it transports the recording material located at the nip portion as the recording material transport direction. The frame is provided with an upper guide surface located downstream of the heating unit in the recording material transport direction. The upper guide surface guides the upper surface of the recording material as it is transported in the direction of the recording material transport. A fixing device according to any one of items 1 to 5, characterized by the above.

[0093] (Item 16) A fixing device for fixing toner to a recording material, which is attached to the main body of an image forming apparatus, the main body having an electrically groundable main body conductor, A heating unit comprising an endless belt and a heater for heating the inner surface of the belt, A pressure roller that forms a nip portion together with the heater via the belt, A conductive pressurizing arm presses the heating unit toward the pressure roller, A conductive pressure spring that contacts the pressure arm, the pressure spring biasing the pressure arm in a direction that causes the pressure arm to press against the heating unit, A frame made of resin, comprising a frame that supports the heating unit, A brush member that is in contact with the belt and is conductive, An intermediate conductor portion that contacts the brush member and the pressure arm, and provides electrical conductivity between the brush member and the pressure arm, A conductor portion that contacts the pressure spring and the main body conductor portion, and provides electrical conductivity between the pressure spring and the main body conductor portion, A fixing device characterized by having the following features. [Explanation of Symbols]

[0094] 2. Main unit of the device 6. Fuser 61 Heating Unit 62 Pressure rollers 652 Pressure Arm 653 Compression spring 63 Lower frame 660 brushes 600a First Conductor Section 600b Second conductor section

Claims

1. An image forming apparatus, comprising an apparatus body equipped with an electrically groundable main body conductor, and a fixing device for fixing toner to a recording material, A heating unit comprising an endless belt and a heater provided on the inner surface side of the belt for heating the belt, A pressure roller that forms a nip portion together with the heater via the belt, A pressure arm for pressing the heating unit against the pressure roller, The heating unit biases the pressurizing arm so that it is pressed against the pressurizing roller, and a conductive pressurizing spring is provided. A frame for supporting the heating unit, comprising a frame made of resin, A brush member that is in contact with the belt and is conductive, A first conductor portion that contacts the brush member and the pressure spring, and provides electrical conductivity between the brush member and the pressure spring, A second conductor portion that contacts the aforementioned pressure spring and the aforementioned main body conductor portion, and provides electrical conductivity between the pressure spring and the aforementioned main body conductor portion, A fixing device characterized by having the following features.

2. The fixing device according to claim 1, characterized in that the first conductor portion includes a resistor.

3. The belt has a conductive layer and an insulating layer that covers the conductive layer from the outer surface side of the belt. The conductive layer has an exposed portion that is not covered by the insulating layer so as to be exposed on the outer surface side of the belt, The brush member contacts the exposed portion of the conductive layer, When the recording material is located at the nip portion and the toner image formed on the recording material is at its maximum in the direction of the belt's generatrix, the portion of the belt that is at the same position as the toner image in the direction of the generatrix is ​​defined as the first portion of the belt. The fixing device according to claim 1, characterized in that at least a portion of the exposed portion is located outside the first part of the belt in the direction of the belt's busbar.

4. A camshaft rotatably supported on the frame, A cam supported on the camshaft so as to rotate together with the camshaft, the cam that rotates to change the pressing force applied by the pressurizing arm to the pressurizing roller of the heating unit, The fixing device according to claim 1, characterized by having the following features.

5. Viewed in the vertical direction, the first conductor portion has an overlapping portion that overlaps with the camshaft, and the overlapping portion is located below the camshaft. The fixing device according to feature 4.

6. When the aforementioned frame is designated as the first frame, The system further comprises a second resin frame that supports the camshaft, The fixing device according to feature 4.

7. The fixing device according to claim 6, characterized in that the first conductor portion is supported by the second frame.

8. The first conductor portion includes a first spring, The first spring extends in the direction of the rotation axis of the pressurizing arm and is electrically connected to the pressurizing spring. The fixing device according to feature 1.

9. The first conductor section includes the first spring, The frame supports the camshaft and has a shaft support portion extending vertically. When the direction in which the recording material is transported in the aforementioned nip section is defined as the recording material transport direction, The downstream end of the shaft support in the recording material transport direction is designated as the downstream support end. The fixing device according to claim 4, characterized in that, in the direction of transporting the recording material, the downstream end of the support is located between the camshaft and the first spring.

10. The downstream end of the support guides the first spring so as to restrict its movement toward the camshaft. The fixing device according to feature 9.

11. The conductive layer is the base layer of the belt. The fixing device according to feature 3.

12. The second conductor portion includes a torsion coil spring. The torsion coil spring contacts the main body conductor portion. The fixing device according to feature 1.

13. The aforementioned main body conductor portion is an electrode. The fixing device according to feature 12.

14. The first conductor portion has a camshaft contact portion that contacts the camshaft. The fixing device according to feature 4.

15. The heating unit sets the direction in which it transports the recording material located at the nip portion as the recording material transport direction. The frame is provided with an upper guide surface located downstream of the heating unit in the recording material transport direction. The upper guide surface guides the upper surface of the recording material as it is transported in the direction of the recording material transport. The fixing device according to feature 1.

16. A fixing device for fixing toner to a recording material, which is attached to the main body of an image forming apparatus, the main body having an electrically groundable main body conductor, A heating unit comprising an endless belt and a heater for heating the inner surface of the belt, A pressure roller that forms a nip portion together with the heater via the belt, A conductive pressurizing arm presses the heating unit toward the pressure roller, A conductive pressure spring that contacts the pressure arm, the pressure spring biasing the pressure arm in a direction that causes the pressure arm to press against the heating unit, A frame made of resin, comprising a frame that supports the heating unit, A brush member that is in contact with the belt and is conductive, An intermediate conductor portion that contacts the brush member and the pressure arm, and provides electrical conductivity between the brush member and the pressure arm, A conductor portion that contacts the pressure spring and the main body conductor portion, and provides electrical conductivity between the pressure spring and the main body conductor portion, A fixing device characterized by having the following features.

Images