Fixing device and image forming apparatus

Abstract

A fixing device capable of preventing the electrode portion of a planar heater from being scraped when a connector is attached. [Solution] The fixing device comprises a cylindrical fixing belt 31, a surface heater 33 that generates heat when electricity is passed through its electrode portion, a heater holder 35 that supports the surface heater 33 so that it is in contact with the inner surface of the fixing belt 31, a connector 25 that is attached in a direction along the surface of the surface heater 33 so as to sandwich the heater holder 35 and the surface heater 33, and whose contact terminal is electrically connected to the electrode portion, and an insulating sheet 39 that has an opening 65 to allow the contact terminal to pass through and covers the electrode portion of the surface heater 33.

Description

[Technical Field]

[0001] The present invention relates to a fixing device that applies heat and pressure to a toner image to fix it on a sheet, and an image forming apparatus that includes the fixing device. [Background technology]

[0002] A planar heater may be used as a heat source for heating a toner image in a fixing device. As described in Patent Document 1, the planar heater is supported on a heater holder by a pair of fixing members.

[0003] The planar heater generates heat when power is supplied via a connector. The connector is attached along the surface of the planar heater so as to sandwich the heater holder and the planar heater, and the contact terminals are electrically connected to the electrodes of the planar heater. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-65301 Summary of the Invention [Problem to be solved by the invention]

[0005] When the connector is attached along the surface of the sheet heater as described above, the contact terminals of the connector slide against the electrodes of the heater, which can cause the anti-sulfuration agent coating the electrodes to be scraped off by the contact terminals or deform the contact terminals, resulting in poor electrical connection between the sheet heater and the connector.

[0006] SUMMARY OF THE INVENTION In consideration of the above circumstances, an object of the present invention is to provide a fixing device that can prevent the electrode portion of the planar heater from being scraped when the connector is attached. [Means for solving the problem]

[0007] In order to solve the above problem, the fixing device of the present invention is characterized by comprising a cylindrical fixing belt, a surface heater that generates heat when electricity is passed through an electrode portion, a heater holder that supports the surface heater so that it contacts the inner surface of the fixing belt, a connector that is attached in a direction along the surface of the surface heater so as to sandwich the heater holder and the surface heater, and whose contact terminal is electrically connected to the electrode portion, and an insulating sheet that has an opening to allow the contact terminal to pass through and covers the electrode portion of the surface heater.

[0008] The present invention may be characterized in that the heater further comprises a stopper that fixes and positions the planar heater to the heater holder, and the insulating sheet is provided integrally with the stopper.

[0009] In the present invention, the heater may further include a stopper that fixes and positions the planar heater to the heater holder, and the insulating sheet may be supported by being sandwiched between the stopper and the heater holder.

[0010] In the present invention, the heater holder may have a recess in which the surface heater is accommodated and an inclined surface inclined from the upstream side of the connector mounting direction toward the recess, and the insulating sheet may have a main body portion covering the electrode portion of the surface heater and a free end portion extending from the main body portion above the inclined surface toward the upstream side of the mounting direction.

[0011] In the present invention, the insulating sheet may be made of a material having better sliding properties than the electrode portions of the planar heater.

[0012] The image forming apparatus of the present invention is characterized by comprising an image forming section that forms a toner image on a sheet of paper, and the fixing device that fixes the toner image on the sheet of paper. [Effects of the Invention]

[0013] According to the present invention, the electrode portion is not scraped by the contact terminal when the connector is attached or detached, thereby suppressing wear on the electrode portion and ensuring that the current supplied to the electrode portion is supplied to the surface heater. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view schematically illustrating an internal configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view schematically illustrating an internal configuration of a fixing device according to an embodiment of the present invention. [Figure 3] FIG. 2 is a perspective view showing a fixing belt assembly of a fixing device according to an embodiment of the present invention. [Figure 4] FIG. 2 is a perspective view showing a heater holder of a fixing belt assembly of a fixing device according to an embodiment of the present invention. [Figure 5] FIG. 2 is a perspective view showing a stopper and an insulating sheet in the fixing device according to the embodiment of the present invention. [Figure 6] FIG. 2 is a perspective view showing a stopper, an insulating sheet, and a connector in the fixing device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] An image forming apparatus and a fixing device according to an embodiment of the present invention will be described below with reference to the drawings.

[0016] First, the overall configuration of image forming apparatus 1 will be described with reference to Fig. 1. Fig. 1 is a front view that schematically shows the internal configuration of image forming apparatus 1. The symbols Fr, Rr, L, R, Up, and Lo used in the following drawings represent front, rear, left, right, top, and bottom, respectively.

[0017] The device body 3 of the image forming device 1 is provided with a paper feed cassette 5 that stores paper, a paper feed device 7 that feeds paper from the paper feed cassette 5, an image forming unit 9 that forms a toner image on paper using an electrophotographic method, a fixing device 11 that fixes the toner image on the paper, a discharge device 13 that discharges paper, and a discharge tray 15 on which the discharged paper is stacked. In addition, a pair of registration rollers 17 is arranged between the paper feed device 7 and the image forming unit 9.

[0018] The paper feed cassette 5 is housed in a cassette housing section provided at the bottom inside the device main body 3. The paper feed device 7 is located above the front end of the cassette housing section. The registration roller pair 17 is located above the paper feed device 7. The image forming section 9 is located behind the registration roller pair 17. The fixing device 11 is located behind the image forming section 9. The discharge device 13 is located above the fixing device 11. The discharge tray 15 is provided on the top surface of the device main body 3.

[0019] Furthermore, a main transport path 19a and a duplex transport path 19b along which paper is transported are formed in the device body 3. The main transport path 19a is formed along the transport direction from the paper feed device 7, through the image forming unit 9 and the fixing device 11, toward the discharge device 13. The duplex transport path 19b branches off from the main transport path 19a downstream of the fixing device 11 in the transport direction, and merges with the main transport path 19a upstream of the registration roller pair 17 in the transport direction.

[0020] Next, a brief description of the image forming operation will be given. In the case of single-sided printing, the paper fed from paper cassette 5 by paper feed device 7 is transported along main transport path 19a, and after skew is corrected by registration roller pair 17, it is transported to image forming unit 9. In image forming unit 9, a toner image is formed on the paper. The paper with the toner image formed is transported along main transport path 19a to fixing device 11, where the toner image is fixed to the paper. The paper with the fixed toner image is discharged by discharge device 13 onto discharge tray 15.

[0021] During double-sided printing, after a toner image has been fixed on one side of the paper by fixing device 11, the paper passes through fixing device 11, switches back, and is transported to double-sided conveying path 19b. The paper passes through double-sided conveying path 19b and is transported along main conveying path 19a. After the pair of registration rollers 17 corrects the skew of the paper, the toner image is transferred to the other side of the paper in image forming unit 9. The paper with the transferred toner image is transported along main conveying path 19a to fixing device 11, where the toner image is fixed to the other side of the paper. The paper with the fixed toner image is transported along main conveying path 19a to discharge device 13, and is discharged by discharge device 13 onto discharge tray 15.

[0022] Next, the fixing device 11 will be described with reference to Fig. 2. Fig. 2 is a cross-sectional view showing the internal configuration of the fixing device 11. The fixing device 11 includes a belt assembly 21, a pressure roller 23, and two connectors 25 (not shown in Fig. 2, see Fig. 3).

[0023] First, the belt assembly 21 will be described with reference to Fig. 3. Fig. 3 is a perspective view showing the belt assembly 21. The belt assembly 21 includes a fixing belt 31, a heater 33 that heats the fixing belt 31, a heater holder 35 that houses the heater 33, two stoppers 37 that support the heater 33 on the heater holder 35, an insulating sheet 39 fixed to the stoppers 37, and left and right end holders 41 that support the heater holder 35.

[0024] First, the fixing belt 31 will be described. The fixing belt 31 is formed in a cylindrical shape with a predetermined inner diameter and a width greater than the width of the paper. The fixing belt 31 is made of a flexible material and has a base layer, an elastic layer provided on the outer surface of the base layer, and a release layer provided on the outer surface of the elastic layer. The base layer is made of resin. The elastic layer is made of silicone rubber or the like. The release layer is made of a PFA tube or the like.

[0025] Next, a description will be given of the heater 33. The heater 33 is a rectangular plate-shaped planar heater 33. The planar heater 33 includes a base material, a heat insulating layer, a heating resistor layer, and a coating layer.

[0026] The substrate has a rectangular plate shape with a length longer than the width of the fixing belt 31. The heat insulating layer is made of an electrically insulating material with low thermal conductivity, such as ceramics or glass, and is formed on one surface of the substrate. The heating resistor layer is made of an electrically conductive material, such as a metal with high resistance, and is laminated on the surface of the heat insulating layer. The length of the heating resistor layer (length along the width direction of the fixing belt) is slightly longer than the width of the fixing belt 31 and shorter than the length of the substrate. In other words, the resistive heating layer is not formed on both ends of one surface of the substrate. Electrode portions connected to the heating resistor layer are formed on both ends of one surface of the substrate. The electrode portions are coated with an anti-sulfuration agent. The heating resistor layer generates heat when current is applied to the electrode portions. The coating layer is made of an electrically insulating material, such as ceramics, that has low sliding friction resistance against the fixing belt, and covers the heating resistor layer.

[0027] Next, the heater holder 35 will be described with reference to FIG. 4. FIG. 4 is a perspective view of the heater holder 35. The heater holder 35 is formed in a substantially semi-cylindrical shape along the circumferential direction of the inner circumferential surface of the fixing belt 31, and has a width wider than that of the fixing belt 31. The heater holder 35 has a flat portion 51 and a curved portion 53. The curved portions 53 are formed on both sides of the flat portion 51 in the circumferential direction. The length of the flat portion 51 is longer than the lengths of the curved portions 53. Therefore, both ends of the flat portion 51 protrude outward beyond the curved portions 53. A recess 55 is formed on the outer surface 51a of the flat portion 51 to accommodate the planar heater 33. In addition, side surfaces 51b (side surfaces in the circumferential direction) of both ends of the flat portion 51 are inclined toward the outer surface 51a of the flat portion 51 so as to approach each other (referred to as inclined surfaces). The heater holder 35 is formed of a heat-resistant resin such as a liquid crystal polymer.

[0028] As shown in FIG. 2, the heater holder 35 is fixed to the lower surface of a stay 57 that passes through the hollow portion of the fixing belt 31 .

[0029] Next, the stopper 37 will be described with reference to Figure 5. Figure 5 is a perspective view showing the stopper 37 and the insulating sheet 39. The stopper 37 secures both ends of the sheet heater 33 housed in the recess 55 of the heater holder 35 to the heater holder 35. The stopper 37 has a curved shape that follows the outer surface 51a and both inclined surfaces 51b of the end of the flat portion 51 of the heater holder 35. The stopper 37 is made of resin. The stopper 37 can be attached to the end of the flat portion 51 of the heater holder 35 by elastically deforming.

[0030] Next, the insulating sheet 39 will be described with reference to Fig. 5. The insulating sheet 39 is provided integrally with the stopper 37. The insulating sheet 39 is made of a material (e.g., polyimide) that has electrical insulation properties and good heat resistance, and has a substantially rectangular shape. The thickness of the insulating sheet 39 is, for example, 0.1 to 0.2 mm.

[0031] The insulating sheet 39 has a main body 61 and a free end 63. The main body 61 has a rectangular shape with dimensions larger than the electrode portions of the sheet heater 33. One side edge of the main body 61 is fixed to the stopper 37. Two openings 65 are formed in the center of the main body 61. The free end 63 extends from a side edge (one side edge in the circumferential direction) adjacent to the side edge fixed to the stopper 37. The free end 63 is not fixed to the stopper 37. Each corner of the insulating sheet 39 is rounded in an arc shape.

[0032] The planar heater 33 housed in the recess 55 of the heater holder 35 is fixed to the heater holder 35 by the stopper 37 as described above. More specifically, the end of the planar heater 33 (the portion between the resistance heating layer and the electrode portion) is sandwiched between the stopper 37 and the recess 55. This allows the planar heater 33 to be housed in the recess 55, and restricts movement in the length direction (the width direction of the fixing belt 31) and in a direction intersecting the length direction (the circumferential direction of the fixing belt 31).

[0033] Furthermore, when the sheet heater 33 is fixed to the heater holder 35 by the stopper 37 in this manner, the main body 61 of the insulating sheet 39 comes into contact with the upper surface of the electrode portion, and the free end 63 covers the upper side of the inclined surface 51b at the end of the flat portion 51. Furthermore, the electrode portion of the sheet heater 33 is exposed from the opening 65 of the main body 61.

[0034] Next, we will explain the left and right end holders 41. Each end holder 41 supports one end of the fixing belt 31 and one end of the stay 57. The left and right end holders 41 are supported by the left and right side plates of the fixing housing (not shown) via pressure change units (not shown).

[0035] Next, a description will be given of the pressure roller 23. The pressure roller 23 has a rotating shaft, an elastic layer provided on the outer peripheral surface of the rotating shaft, and a release layer provided on the outer peripheral surface of the elastic layer.

[0036] Both ends of the rotation shaft of the pressure roller 23 are rotatably supported by the left and right side plates of the fixing housing below the belt assembly 21. The pressure roller 23 faces the planar heater 33 with the fixing belt 31 of the belt assembly 21 sandwiched therebetween. This forms a fixing nip N between the fixing belt 31 and the pressure roller 23. A drive gear (not shown) is fixed to one end of the rotation shaft of the pressure roller 23. The drive gear is connected to a motor (not shown) via a gear train (not shown).

[0037] When the motor is driven, the drive gear rotates in the clockwise direction in FIG. 2 (see the arrow in FIG. 2) via the gear train, causing the pressure roller 23 to rotate in one direction (clockwise in this example). This causes the fixing belt 31, which is in contact with the pressure roller 23 at the fixing nip N, to rotate in the other direction (counterclockwise in this example). This causes the paper to be transported from the fixing nip N.

[0038] Next, connector 25 will be described. As shown in FIG. 3, a recess 71 is formed on one end face of connector 25 along the longitudinal direction of the connector. Two contact terminals are supported on each of the opposing side faces of recess 71. Each contact terminal is a leaf spring-like member shaped like an arc along the longitudinal direction, and can be elastically deformed into a flat shape when pressed. Each contact terminal is connected to a power source via wiring 73.

[0039] In the fixing device 11 having the above configuration, the process of connecting the connector 25 to the electrode portion of the sheet heater 33 will be described with reference to Fig. 6. Fig. 6 is a perspective view of the stopper 37, the insulating sheet 39, and the connector 25 as seen from below.

[0040] The connector 25 is attached to the heater holder 35 (the end of the flat portion 51) in a direction along the surface of the sheet heater 33 (in this example, the transport direction, the direction from the front to the rear). More specifically, the connector 25 is attached from the side where the free end 63 of the insulating sheet 39 is provided, with the end surface where the recess 71 is formed first. As the connector 25 is attached in this manner, the end of the flat portion 51 of the heater holder 35 begins to be inserted into the recess 71 of the connector 25.

[0041] When the end is inserted into the recess 71 of the connector 25, the contact terminal of the connector 25 first comes into contact with the free end 63 of the insulating sheet 39. The contact terminal is pushed by the insulating sheet 39 and slides from the free end 63 into the main body 61 while elastically deforming. When the contact terminal eventually reaches the opening 65 of the main body 61, it elastically returns to its original shape and electrically connects with the electrode portion of the sheet heater 33 through the opening 65. This makes it possible to supply power to the sheet heater 33 via the connector 25.

[0042] As described above, according to the present invention, when the connector 25 is attached to the heater holder 35, the contact terminals of the connector 25 move along the upper surface of the insulating sheet 39, so that the electrode portion does not come into contact with the contact terminals. In this way, the electrode portion is not scraped by the contact terminals when the connector 25 is attached or detached, so wear and scraping of the electrode portion is suppressed and power can be reliably supplied to the sheet heater 33 via the connector 25.

[0043] Furthermore, when the connector 25 is attached, the contact terminal slides from the free end 63 of the insulating sheet 39 to the main body 61, so the contact terminal can be guided to the electrode portion without getting caught on the inclined surface 51b of the heater holder 35.

[0044] The mounting direction of connector 25 is not limited to the above direction, and it may be the opposite direction or a direction perpendicular to the above direction. Even in this case, since the electrode portion is covered with main body 61 of insulating sheet 39, the electrode portion does not come into contact with the contact terminal when connector 25 is mounted.

[0045] Furthermore, the insulating sheet 39 does not necessarily have to be provided integrally with the stopper 37. For example, the insulating sheet 39 may be fixed to the electrode portion with an adhesive. Alternatively, a holding portion may be provided adjacent to the main body portion 61 of the insulating sheet 39, and the holding portion may be sandwiched between the heater holder 35 and the stopper 37. Furthermore, the stopper 37 and the heater holder 35 may be provided with projections or openings that engage with each other. In this case, by engaging the two, the stopper 37 can be more securely attached to the heater holder 35, allowing the sheet heater 33 to be positioned more accurately.

[0046] Furthermore, it is preferable that the insulating sheet 39 be made of a material that has better sliding properties than the electrode portion, in order to reduce the resistance between the contact terminals and the insulating sheet 39 when the connector 25 is attached.

[0047] Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the above embodiments, and those skilled in the art may modify the above embodiments without departing from the scope and spirit of the present invention. [Explanation of symbols]

[0048] 1. Image forming device 9 Image forming unit 11 Fixing device 25 connectors 31 Fixing belt 33 Planar heater 35 Heater holder 37 Stopper 39 Insulation sheet 51b Slope 55 recess 61 Main body 63 Free end 65 Aperture

Claims

1. a cylindrical fixing belt; a surface heater that generates heat when electricity is applied to the electrode portion; a heater holder that supports the planar heater so as to contact the inner circumferential surface of the fixing belt; a connector that is attached along a direction along the surface of the planar heater so as to sandwich the heater holder and the planar heater, and whose contact terminals are electrically connected to the electrode portions; an insulating sheet having an opening through which the contact terminal passes and covering the electrode portion of the planar heater.

2. a stopper for fixing the planar heater to the heater holder and positioning the heater; 2. The fixing device according to claim 1, wherein the insulating sheet is provided integrally with the stopper.

3. a stopper for fixing the planar heater to the heater holder and positioning the heater; 2. The fixing device according to claim 1, wherein the insulating sheet is supported by being sandwiched between the stopper and the heater holder.

4. The heater holder is a recess in which the planar heater is accommodated; an inclined surface inclined from the upstream side in the mounting direction of the connector toward the recess, The insulating sheet is a main body portion covering the electrode portion of the planar heater; 2. The fixing device according to claim 1, further comprising: a free end portion extending from the main body portion toward the upstream side in the mounting direction above the inclined surface.

5. 2. The fixing device according to claim 1, wherein the insulating sheet is made of a material having better sliding properties than the electrode portion of the planar heater.

6. an image forming unit that forms a toner image on a sheet; a fixing device according to claim 1 for fixing the toner image onto a sheet of paper; An image forming apparatus comprising:

Images