Fixing device and image forming apparatus

Abstract

To make usable a sheet-like member having a uniform thickness as an elastic member, and reduce manufacturing cost compared with a case where a sheet-like member having a non-uniform thickness is used.SOLUTION: A fixing device comprises: an endless belt; fixing means that is in contact with the belt to form a fixing nip part N; and pressing means that is arranged inside the belt, has a shape following an outer peripheral shape of the fixing means, has a holding part holding an elastic member, and presses the belt against the fixing means. When the fixing means is not pressed, the elastic member is deformed to have a shape following the holding part.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Conventionally, techniques relating to fixing devices have already been proposed, for example, as disclosed in Patent Document 1 and the like.

[0003] In Patent Document 1, the surface of the nip forming member on the fixing nip side is made of a metal material, and a gap is formed in the longitudinal end region of this metal material, outside the outer end of the paper passing area for the largest size paper that can pass through, and the vertical side of this gap is configured to extend at an angle to the belt rotation direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-188916 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to enable the use of a sheet-like member having a uniform thickness as the elastic member, thereby reducing manufacturing costs compared to the use of a sheet-like member having a non-uniform thickness. [Means for solving the problem]

[0006] The invention described in claim 1 comprises an endless belt, a fixing means for contacting the belt to form a fixing nip portion; a pressure applying unit that is disposed inside the belt, has a shape following the outer peripheral shape of the fixing unit, has a holding portion that holds an elastic member, and applies pressure to the belt against the fixing unit; Equipped with The fixing device is characterized in that the elastic member is deformed to have a shape conforming to the holding portion when not pressed by the fixing means.

[0007] The invention described in claim 2 is the fixing device described in claim 1, wherein the pressure means has a holding portion having a curved shape and is formed as a pressure adjusting surface that adjusts the pressure applied to the fixing means.

[0008] The invention described in claim 3 is the fixing device described in claim 2, wherein the pressure adjusting surface adjusts the pressure by allowing partial deformation of the elastic member along a thickness direction.

[0009] The invention described in claim 4 is the fixing device described in claim 3, wherein the pressure adjustment surface is a surface including at least one of projections and recesses, slits, and holes.

[0010] The invention described in claim 5 is the fixing device described in claim 1, wherein the elastic member is made of silicone foam.

[0011] The invention described in claim 6 is the fixing device described in claim 5, wherein the pressure means is made of synthetic resin and has a pressing portion at the downstream end along the rotation direction of the belt that directly presses the belt against the fixing means.

[0012] The invention described in claim 7 is the fixing device described in claim 1, wherein the fixing means is a heating roll having a heat source therein.

[0013] An eighth aspect of the present invention is the fixing device according to the seventh aspect, wherein the pressing means presses the belt against the heating roll over the entire area of ​​the fixing nip portion.

[0014] The invention described in claim 9 includes an image forming unit for forming an image on a recording medium, a fixing means for fixing the image on the recording medium; Equipped with The image forming apparatus uses the fixing device according to any one of claims 1 to 8 as the fixing means. Effect of the Invention

[0015] According to the invention described in claim 1, a sheet-like member of uniform thickness can be used as the elastic member, which enables manufacturing costs to be reduced compared to the use of a sheet-like member of non-uniform thickness.

[0016] According to the invention described in claim 2, it becomes easier to adjust the pressure applied to the fixing means, compared to when the holding portion has a flat shape.

[0017] According to the invention described in claim 3, uneven pressure can be avoided compared to a case in which the pressure adjustment surface does not allow partial deformation along the thickness direction of the elastic member.

[0018] According to the invention as recited in claim 4, the pressure adjusting surface makes it easier to adjust the pressure while making the elastic member thinner, compared to when the pressure adjusting surface is formed in a convex shape.

[0019] According to the invention described in claim 5, the elastic member can apply a relatively smaller pressure than when it is made of a silicone foam having a support member.

[0020] According to the invention as recited in claim 6, the pressure applying means can maintain fixation and improve peelability of the recording medium, compared to a case where the pressure applying means does not have a pressing portion.

[0021] According to the invention described in claim 7, the fixing means can have a wider nip area than when it is composed of something other than a heating roll.

[0022] According to the invention as recited in claim 8, the pressing means can increase the area of ​​the fixing nip portion, compared to a case in which the belt is pressed against the heating roll only in a part of the fixing nip portion.

[0023] According to the invention as set forth in claim 9, costs can be reduced compared to when the fixing device as set forth in any one of claims 1 to 8 is not used. [Brief description of the drawings]

[0024] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus to which a fixing device according to a first embodiment of the present invention is applied. [Diagram 2] 1 is a cross-sectional view showing a fixing device according to a first embodiment of the present invention; [Diagram 3] 1 is a cross-sectional view showing a configuration of a main part of a fixing device according to a first embodiment of the present invention. [Figure 4] FIG. [Diagram 5] FIG. 1 is a cross-sectional view showing a conventional fixing device. [Figure 6] 1 is a perspective view showing a configuration of a main part of a fixing device according to a first embodiment of the present invention; [Figure 7] 4 is a perspective configuration diagram showing another main part of the fixing device according to the first embodiment of the present invention; FIG. [Figure 8] 5 is a side view showing another example of the pressure member of the fixing device according to the first embodiment of the present invention. FIG. [Figure 9] 5 is a perspective view showing another example of the pressure member of the fixing device according to the first embodiment of the present invention; FIG. [Figure 10] 4 is a graph showing pressure distribution in the fixing device according to the first embodiment of the present invention. [Figure 11] 4 is a graph showing pressure distribution in the fixing device according to the first embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0026] [Embodiment 1] Fig. 1 shows an overview of an entire image forming apparatus to which a fixing device according to embodiment 1 is applied. In Fig. 1, the symbol X indicates the horizontal direction (width direction) of the image forming apparatus, the symbol Y indicates the depth direction of the image forming apparatus, and the symbol Z indicates the vertical direction of the image forming apparatus.

[0027] <Overall configuration of image forming apparatus> The image forming apparatus 1 is configured as, for example, a color printer. As shown in FIG. 1, the image forming apparatus 1 includes a plurality of image forming devices 10, an intermediate transfer device 20, a paper feed device 50, and a fixing device 40 as an example of a fixing means according to the first embodiment. The plurality of image forming devices 10 form toner images developed with toner constituting a developer. The intermediate transfer device 20 holds the toner images formed by the image forming devices 10, and transports them to a secondary transfer position where the toner images are finally secondarily transferred onto a recording paper 5 as an example of a recording medium. The paper feed device 50 stores and transports the required recording paper 5 to be supplied to the secondary transfer position of the intermediate transfer device 20. The fixing device 40 fixes the toner image as an example of an image on the recording paper 5 secondarily transferred by the intermediate transfer device 20. In FIG. 1, reference numeral 1a denotes a device main body formed of a supporting structure member, an exterior cover, and the like.

[0028] In this embodiment 1, the image forming means for forming a toner image on a recording medium is made up of a plurality of image forming devices 10 and an intermediate transfer device 20. Note that the image forming means may be configured to include a single image forming device and to directly form a toner image on a recording medium from the image forming device without using the intermediate transfer device.

[0029] The imaging device 10 is composed of four imaging devices 10Y, 10M, 10C, and 10K that are dedicated to forming toner images of four colors, yellow (Y), magenta (M), cyan (C), and black (K), respectively. These four imaging devices 10 (Y, M, C, and K) are arranged in a row along the horizontal direction X in the internal space of the device main body 1a.

[0030] As shown in FIG. 1, each of the image forming devices 10 (Y, M, C, K) includes a photoconductor drum 11 as an example of a rotating image holding means. Around the photoconductor drum 11, the following devices are mainly arranged. The main devices are a charging device 12, an exposure device 13, a developing device 14, a primary transfer device 15, a drum cleaning device 16, and the like. The charging device 12 charges the peripheral surface (image holding surface) of the photoconductor drum 11 on which an image can be formed to a required potential. The exposure device 13 irradiates the charged peripheral surface of the photoconductor drum 11 with light based on image information (signals) to form an electrostatic latent image (for each color) with a potential difference. The developing device 14 develops the electrostatic latent image with toner of the developer of the corresponding color (Y, M, C, K) to form a toner image. The primary transfer device 15 transfers each toner image to the intermediate transfer device 20. The drum cleaning device 16 removes and cleans toner and other adhering matter remaining on the image bearing surface of the photosensitive drum 11 after the primary transfer. Note that reference numerals indicating the photosensitive drum 11, charging device 12, etc. are given only to the yellow (Y) imaging device 10Y and are omitted for the other imaging devices 10 (M, C, K).

[0031] The photoconductor drum 11 has an image bearing surface formed on the peripheral surface of a grounded cylindrical or columnar substrate, the peripheral surface of which has a photoconductive layer (photosensitive layer) made of a photosensitive material. The photoconductor drum 11 is supported so as to rotate in the direction indicated by the arrow A by a driving force transmitted from a driving device (not shown).

[0032] The charging device 12 is composed of a contact-type charging roll that is arranged in contact with the photoconductor drum 11. A charging voltage is supplied to the charging device 12. When the developing device 14 performs reversal development, the charging voltage is a voltage or current of the same polarity as the charging polarity of the toner supplied from the developing device 14. A cleaning roll 121 that cleans the surface of the charging device 12 is arranged in contact with the rear side of the charging device 12.

[0033] The exposure device 13 is composed of an LED print head or the like that irradiates the photosensitive drum 11 with light according to image information using LEDs (Light Emitting Diodes) as a plurality of light emitting elements arranged along the axial direction of the photosensitive drum 11 to form an electrostatic latent image. When it is time to form a latent image, image information (signal) inputted by any means to the image forming apparatus 1 is transmitted to the exposure device 13. Note that the exposure device 13 may be one that irradiates the peripheral surface of the charged photosensitive drum 11 with laser light configured according to the image information inputted to the image forming apparatus 1 to form an electrostatic latent image.

[0034] As shown in FIG. 1, each of the developing devices 14 is configured by arranging a developing roll 141, stirring and conveying members 142 and 143, a layer thickness regulating member 144, and the like inside a housing 140 in which an opening and a developer storage chamber are formed. The developing roll 141 holds the developer and conveys it to a development area facing the photosensitive drum 11. The stirring and conveying members 142 and 143 are made of screw augers or the like that stir the developer while conveying it to pass through the developing roll 141. The layer thickness regulating member 144 regulates the amount (layer thickness) of the developer held by the developing roll 141. In this developing device 14, a developing voltage is supplied between the developing roll 141 and the photosensitive drum 11 from a power supply device (not shown). In addition, the developing roll 141 and the stirring and conveying members 142 and 143 rotate in the required direction by a driving force transmitted from a driving device (not shown). Furthermore, a two-component developer containing a non-magnetic toner and a magnetic carrier is used as the developer of the four colors.

[0035] 1, the primary transfer device 15 is a contact type transfer device equipped with a primary transfer roll that rotates in contact with the circumferential surface of the photoconductor drum 11 via the intermediate transfer belt 21 at the primary transfer position and is supplied with a primary transfer voltage. As the primary transfer voltage, a DC voltage showing a polarity opposite to the charging polarity of the toner is supplied from a power supply device (not shown).

[0036] The drum cleaning device 16 is composed of a cleaning blade 161 and a sending member 162 arranged inside a container-shaped main body 160. The cleaning blade 161 cleans by removing residual toner and other adhering matter. The sending member 162 is composed of a screw auger or the like that collects the toner and other adhering matter removed by the cleaning blade 161 and conveys it to a collection system (not shown).

[0037] The intermediate transfer device 20 is disposed so as to be located above each of the image forming devices 10 (Y, M, C, K) in the vertical direction Z. The intermediate transfer device 20 is mainly composed of an intermediate transfer belt 21, a plurality of belt support rolls 22-25, a belt cleaning device 26, and a secondary transfer device 30. The intermediate transfer belt 21 is an example of an intermediate transfer means that moves in a circular manner in the direction indicated by the arrow B while passing through a primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roll). The plurality of belt support rolls 22-25 support the intermediate transfer belt 21 so as to be able to move in a circular manner while maintaining the intermediate transfer belt 21 in a desired state from its inner circumference. The secondary transfer device 30 is disposed on the outer circumferential surface (image bearing surface) side of the intermediate transfer belt 21 supported by the belt support roll 25, and performs a second transfer of the toner image on the intermediate transfer belt 21 to the recording paper 5. The belt cleaning device 26 removes and cleans toner, paper powder, and other deposits that remain on and adhere to the outer circumferential surface of the intermediate transfer belt 21 after passing through the secondary transfer device 30.

[0038] The intermediate transfer belt 21 is an endless belt made of a material in which a resistance adjusting agent such as carbon black is dispersed in a synthetic resin such as polyimide resin, polyamide resin, or polyamideimide resin. The belt support roll 22 is configured as a drive roll. The belt support roll 23 is configured as a surface adjustment roll that maintains the running position of the intermediate transfer belt 21. The belt support roll 24 is configured as a tension applying roll that applies tension to the intermediate transfer belt 21. The belt support roll 25 is configured as a backup roll for secondary transfer.

[0039] The secondary transfer device 30 includes a secondary transfer roll 31 that rotates at a secondary transfer position. The secondary transfer position is an outer peripheral surface portion of the intermediate transfer belt 21 supported by the belt support roll 25 in the intermediate transfer device 20. A DC voltage having a polarity opposite to or the same as the charging polarity of the toner is supplied to the secondary transfer roll 31 or the belt support roll 25 of the intermediate transfer device 20 as a secondary transfer voltage.

[0040] The fixing device 40 includes a pressure belt 42 as an example of an endless belt, and a heating roll 41 as an example of a fixing means that contacts the pressure belt 42 to form a fixing nip N. The heating roll 41 is heated by a heating means so that the surface temperature of the heating roll 41 is maintained at a predetermined temperature. The pressure belt 42 rotates in contact with the heating roll 41 at a required pressure. In the fixing device 40, the contact area between the heating roll 41 and the pressure belt 42 becomes the fixing nip N where a required fixing process (heating and pressure) is performed to fix an unfixed toner image to the recording paper 5. The fixing device 40 will be described in detail later.

[0041] The paper feeder 50 is disposed so as to be located below the imaging devices 10 (Y, M, C, K). This paper feeder 50 is mainly composed of one (or more) paper containers 52 and a delivery device 53 that delivers recording paper 5 one sheet at a time from the paper container 52. The paper container 52 receives recording paper 5 of a desired size, type, etc., stacked on a stacking plate 51. The paper container 52 is attached so as to be able to be pulled out, for example, from the front side (the side the user faces during operation) of the device main body 1a, or in the illustrated example, from the left side.

[0042] Examples of the recording paper 5 include thin paper such as plain paper or tracing paper used in electrophotographic copiers and printers, or OHP sheets made of a transparent film-like medium made of synthetic resin (PET, etc.). In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper 5 is as smooth as possible. Examples of the recording paper 5 that can be used include coated paper in which the surface of plain paper is coated with resin or the like, and so-called thick paper with a relatively large basis weight such as art paper for printing.

[0043] A paper feed path 57 is provided between the paper feed device 50 and the secondary transfer device 30. The paper feed path 57 is made up of one (or more) paper transport roll pairs 54 and transport guide members 55, 56 that transport the recording paper 5 sent out from the paper feed device 50 to the secondary transfer position. The paper transport roll pair 54, which is disposed in the paper feed path 57 at a position immediately before the secondary transfer position, is made up of, for example, rolls (registration rolls) that adjust the transport timing of the recording paper 5.

[0044] In addition, a paper transport path 59 is provided between the secondary transfer device 30 and the fixing device 40. The paper transport path 59 is composed of a transport guide member 58 that transports the recording paper 5 sent out from the secondary transfer device 30 to the fixing device 40, etc.

[0045] A discharge conveying path 65 is provided downstream of the fixing device 40. The discharge conveying path 65 includes a paper conveying roll pair 61, a paper discharging roll pair 62, conveying guide members 63 and 64, and the like for discharging the recording paper 5 on which the toner image has been fixed by the fixing device 40 to a paper discharging section 60 disposed at the top of the apparatus main body 1a.

[0046] 1, reference numeral 100 denotes a control device as an example of a control means for comprehensively controlling the operation of the image forming apparatus 1. The control device 100 is configured to include a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), or a bus for connecting the CPU, the ROM, etc., a communication interface, etc. (not shown).

[0047] <Basic operations of image forming device> Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.

[0048] Here, the image forming operation will be described when forming a full-color image composed of a combination of toner images of four colors (Y, M, C, K) using the four image forming devices 10 (Y, M, C, K). Note that the image forming operation when forming an image by combining single-color or multiple-color toner images using one or more of the four image forming devices 10 (Y, M, C, K) is basically the same.

[0049] When the image forming apparatus 1 receives command information requesting printing, the four image forming devices 10 (Y, M, C, K), the intermediate transfer device 20, the secondary transfer device 30, the fixing device 40, etc. are started under the control of the control device 100.

[0050] In each imaging device 10 (Y, M, C, K), first, each photoconductor drum 11 rotates in the direction indicated by arrow A. The surface of each photoconductor drum 11 is charged to a required polarity (negative polarity in the first embodiment) and potential by each charging device 12. Next, exposure device 13 irradiates the charged surface of photoconductor drum 11 with light emitted based on an image signal obtained by converting image information input to image forming device 1 into each color component (Y, M, C, K). Then, an electrostatic latent image of each color component, constituted by a required potential difference, is formed on the surface of photoconductor drum 11.

[0051] Next, each developing device 14 (Y, M, C, K) supplies toner of the corresponding color (Y, M, C, K) charged to the required polarity (negative polarity) to the electrostatic latent image of each color component formed on the photoconductor drum 11, electrostatically attaching it to the electrostatic latent image, thereby developing it. Through this development, the electrostatic latent image of each color component formed on each photoconductor drum 11 is visualized as a toner image of four colors (Y, M, C, K) developed with the toner of the corresponding color.

[0052] Next, the toner images of each color formed on the photoconductor drums 11 of the imaging devices 10 (Y, M, C, K) are transported to a primary transfer position. Then, the primary transfer device 15 performs primary transfer of the toner images of each color onto the intermediate transfer belt 21 of the intermediate transfer device 20 rotating in the direction indicated by the arrow B, in such a manner that the toner images are superimposed in order.

[0053] In addition, in each of the imaging devices 10 (Y, M, C, K) where the primary transfer has been completed, the drum cleaning device 16 scrapes off any adhering matter to clean the surface of the photosensitive drum 11. This makes each of the imaging devices 10 (Y, M, C, K) ready for the next image formation operation.

[0054] Next, the intermediate transfer device 20 conveys the primary transferred toner image to the secondary transfer position by the rotation of the intermediate transfer belt 21. Meanwhile, the paper feeder 50 sends out the required recording paper 5 to a paper feed path 57 in accordance with the image creation operation. In the paper feed path 57, a pair of paper feed rolls 54 as registration rolls feeds and supplies the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

[0055] At the secondary transfer position, the secondary transfer roll 31 performs secondary transfer of the toner images on the intermediate transfer belt 21 all at once onto the recording paper 5. After the secondary transfer is completed, the belt cleaning device 26 in the intermediate transfer device 20 removes and cleans the surface of the intermediate transfer belt 21 to remove any toner or other deposits remaining thereon after the secondary transfer.

[0056] Next, the recording paper 5 onto which the toner image has been secondarily transferred is peeled off from the intermediate transfer belt 21 and the secondary transfer roll 31, and then transported along a paper transport path 59 to the fixing device 40. The fixing device 40 introduces the recording paper 5 carrying the unfixed toner image after the secondary transfer into the fixing nip portion N between the rotating heating roll 41 and the pressure belt 42, and passes it through. As a result, the fixing device 40 performs the necessary fixing process (heating and pressure) to fix the unfixed toner image to the recording paper 5. After fixing is completed, the recording paper 5 is discharged by a paper discharge roll pair 62 via a discharge transport path 65 to a paper discharge section 60 provided at the top of the device main body 1a.

[0057] Through the above operations, a full-color image is output, which is formed by combining toner images made of four colors of toner (Y, M, C, K).

[0058] <Configuration of the fixing device> 2 is a cross-sectional view showing the configuration of the fixing device according to the first embodiment. The fixing device 40 according to the first embodiment is integrally configured as a fixing unit. As shown in FIG. 1, the fixing device 40 as a fixing unit can be independently attached and detached from the main body 1a of the image forming apparatus 1 by opening and closing a rear cover 1b located on the right side in the figure in a clockwise direction.

[0059] As shown in Fig. 2, the fixing device 40 includes a device housing 43 as an example of a case. The device housing 43 is composed of a frame (not shown) that supports the heating roll 41 and the pressure belt 42, a main body (not shown) that holds the frame, and an exterior cover that covers the outer periphery of the main body and the frame. Inside the device housing 43, the heating roll 41 and the pressure belt 42 are arranged in a pressure-contact state. As described above, the pressure belt 42 is an example of an endless belt. The heating roll 41 is an example of a fixing means that contacts the pressure belt 42 to form a fixing nip N.

[0060] The device housing 43 has an inlet 431 at its lower end surface for introducing the recording paper 5 onto which the unfixed toner image Ti has been transferred. Inside the inlet 431, a guide plate 432 is arranged in a state of inclining obliquely upward, for guiding the recording paper 5 to the fixing nip portion N where the heating roll 41 and the pressure belt 42 are in pressure contact. The device housing 43 also has an outlet 433 at the left end of its upper end surface for discharging the recording paper 5 which has been subjected to the fixing process by the heating roll 41 and the pressure belt 42 to the outside. The outlet 433 is provided with an exit roll (not shown) that can rotate to discharge the recording paper 5 to the outside of the device housing 43 as necessary. The recording paper 5 is transported with the center along the depth direction Y intersecting with the transport direction as a reference (so-called center register).

[0061] A rod-shaped actuator 435 is provided in a conveying passage 434 formed between the fixing nip portion N of the fixing device 40 and the discharge port 433 so as to be rotatable in a clockwise direction about a fulcrum 435a. The actuator 435 is an example of a detection means for detecting the passage of the leading edge of the recording paper 5. The rotational movement of the actuator 435 is detected as the passage of the recording paper 5 by an optical sensor (not shown) or the like.

[0062] As shown in FIG. 2, the fixing device 40 is roughly divided into a heating roll 41 and a pressure unit 44 that holds a pressure belt 42 that is provided so as to be movable toward and away from the heating roll 41 .

[0063] As shown in FIG. 3, the heating roll 41 has a cylindrical core metal 411, an elastic layer 412, and a release layer 413. The core metal 411 is made of metal such as stainless steel, aluminum, or iron (thin-walled high-tensile steel pipe). The core metal 411 is formed in a relatively thin-walled cylindrical shape, and its heat capacity is set to be significantly small. The elastic layer 412 is made of a heat-resistant elastic material such as silicone rubber or fluororubber that is coated on the outer periphery of the core metal 411. The elastic layer 412 is also formed in a relatively thin-walled cylindrical shape, and contributes to reducing the heat capacity of the heating roll 41. The release layer 413 is made of polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), or the like that is thinly coated on the surface of the elastic layer 412. Inside the heating roll 41, as shown in FIG. 2, two halogen lamps 414a and 414b are arranged as an example of a heating means. The two halogen lamps 414a, 414b are configured, for example, to have different heat generating regions along the depth direction Y perpendicular to the drawing. The number of halogen lamps 414a, 414b is not limited to two, and may be one or three or more.

[0064] As shown in Fig. 2, both ends of the heating roll 41 along its longitudinal direction (axial direction) are rotatably supported inside the device housing 43 via bearing members (not shown). The heating roll 41 is driven to rotate at a required speed in the direction of arrow C by a drive motor (not shown) on the device main body 1a via a drive force transmission gear 415 that meshes with a drive gear (not shown) attached to one end along the axial direction. The drive motor is an example of a drive source. The pressure belt 42 is pressed against the rotationally driven heating roll 41 at the fixing nip N, and thus rotates.

[0065] The rotation speed of the heating roll 41, that is, the fixing speed, may be set to a number of speeds such as high speed, medium speed, and low speed depending on the basis weight and material of the recording paper 5, etc.

[0066] The surface temperature of the heating roll 41 is detected by a temperature sensor (not shown). The heating roll 41 controls the power supply to the halogen lamps 414a and 414b by a temperature control circuit (not shown) using a triac or the like based on the detection result of the temperature sensor. As a result, the heating roll 41 is heated so that its surface reaches a required fixing temperature.

[0067] On the other hand, as shown in FIG. 2, the pressure unit 44 includes the pressure belt 42, a pressure member 45 as an example of a pressure means, a sheet metal member 48, a pair of guide members 49, and a sliding sheet, a felt member, etc. (not shown). As shown in FIG. 3, the pressure member 45 includes an elastic member 46 and a holding member 47 that is arranged inside the pressure belt 42 and holds the elastic member 46 to press the pressure belt 42 against the heating roll 41. The sheet metal member 48 is an example of a mounting means that mounts the holding member 47 of the pressure member 45 in a fixed state. The pair of guide members 49 are arranged in a state where both ends along the longitudinal direction of the sheet metal member 48 are fixed, and are an example of a guide means that rotatably guides the pressure belt 42. The sliding sheet (not shown) is an example of a sheet that is interposed between the pressure belt 42 and the pressure member 45 to reduce sliding resistance. The felt member (not shown) is an example of a lubricant holding means that is arranged inside the pressure belt 42 and holds a lubricant applied to the inner circumferential surface of the pressure belt 42.

[0068] The pressure belt 42 is made of a flexible material and is configured as an endless belt whose free shape before installation is a thin cylindrical shape. The pressure belt 42 includes a base layer, an elastic layer coated on the surface of the base layer, and a release layer coated on the surface of the elastic layer. The pressure belt 42 may also be configured of a base layer and a release layer directly coated on the surface of the base layer. The base layer is made of a heat-resistant synthetic resin such as polyimide, polyamide, or polyimideamide, or a metal such as stainless steel, nickel, or copper. The elastic layer is made of an elastic material such as heat-resistant silicone rubber or fluororubber. The release layer is made of polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), or the like. The pressure belt 42 can be set to a thickness of, for example, about 50 to 200 μm.

[0069] As described above, the pressure member 45 includes the elastic member 46 and the holding member 47 that is disposed inside the pressure belt 42 and holds the elastic member 46 to bring the pressure belt 42 into pressure contact with the heating roll 41 over the entire area of ​​the fixing nip portion N. As shown in Figures 3 and 4, the holding member 47 is a member that holds the elastic member 46 and presses the pressure belt 42 toward the surface of the heating roll 41 in the area of ​​the fixing nip portion N.

[0070] The sheet metal member 48 is formed by bending a metal plate material such as stainless steel, aluminum, or iron. Although only one sheet metal member 48 is shown in the illustrated example, the sheet metal member may include another sheet metal member arranged parallel to the sheet metal member 48 in addition to the sheet metal member 48. The sheet metal member 48 is attached in a fixed state to the holding member 47 of the pressure member 45, thereby determining the direction in which the holding member 47 presses against the outer circumferential surface of the heating roll 41. The direction in which the holding member 47 presses against the outer circumferential surface of the heating roll 41 is set, for example, to a direction facing the center O of the heating roll 41.

[0071] A felt member (not shown) is attached to the outer surface of the sheet metal member 48 over the entire length thereof by means of adhesion or the like. The felt member is formed to be relatively thick so as to elastically deform and support the pressure belt 42 when tension is applied to the pressure belt 42.

[0072] The felt member is impregnated with a predetermined amount of lubricant to be supplied in a coated state to the inner circumferential surface of the pressure belt 42. As the lubricant, for example, amino-modified silicone oil having a viscosity of 100 to 350 cs is used. The lubricant is preliminarily impregnated into the felt member, and is then applied to the inner circumferential surface of the pressure belt 42. However, the present invention is not limited to this, and the lubricant may be configured to be initially applied to the inner circumferential surface of the pressure belt 42.

[0073] The sliding sheet (not shown) is made of a long and narrow flat rectangular sheet. For example, the sliding sheet has a base layer and a structure made of woven fabric, knitted fabric, etc. laminated on the surface or both sides of the base layer. The base layer is made of a fluororesin such as polytetrafluoroethylene (PTFE). The structure made of woven fabric, knitted fabric, etc. is made of glass fiber, aramid fiber, etc. The sliding sheet may be made of only a single layer made of woven fabric, knitted fabric, etc. made of glass fiber, aramid fiber, etc. The sliding sheet can be set to a thickness of about 100 to 200 μm.

[0074] 5, in the conventional fixing device 40, in order to press the pressure belt 42 against the outer circumferential surface of the heating roll 41 in the fixing nip portion N, an elastic body such as silicone rubber having a rectangular cross section is used as the elastic member 46 held by a holding member 47. Taking into consideration the workability when holding the elastic body on the holding member 47, the elastic body made of silicone rubber or the like is provided in a state of being vulcanized and fixed to the surface of a metal plate T made of a thin stainless steel plate or the like.

[0075] Therefore, in the conventional fixing device 40, in order to reduce the pressure that presses the pressure belt 42 against the outer peripheral surface of the heating roll 41 and thereby achieve a low surface pressure, it was necessary to strictly control the elastic modulus of the elastic body, which determines the amount of crushing (amount of penetration) caused by the pressing of the elastic member 46, as well as the tolerances of the thickness, width, etc., and this posed a technical problem in that the manufacturing cost of the pressure body was inevitably increased.

[0076] Therefore, the fixing device of this embodiment is configured to include a pressure means which is disposed inside the belt, holds an elastic member, and presses the belt against the fixing means, and the elastic member when not pressed against the fixing means is disposed in a shape that conforms to the outer peripheral shape of the fixing nip portion of the fixing means.

[0077] That is, as shown in Figures 3 and 4, the fixing device 40 of this embodiment 1 is equipped with a pressure member 45 as an example of a pressure means that is disposed inside the pressure belt 42, holds an elastic member 46, and presses the pressure belt 42 against the heating roll 41.

[0078] As described above, the pressure member 45 includes the elastic member 46 and the holding member 47 that is disposed inside the pressure belt 42 and holds the elastic member 46 to press the pressure belt 42 against the heating roll 41. As shown in Figures 3 and 4, the holding member 47 is a member that holds the elastic member 46 and presses the pressure belt 42 toward the surface of the heating roll 41 in the region of the fixing nip portion N.

[0079] The elastic member 46 is made of, for example, heat-resistant silicone rubber, EPDM foam, etc. As shown in Fig. 6, the elastic member 46 is, for example, a sheet-like member formed to a uniform thickness, cut to a required width and length, and used as is.

[0080] A silicone sponge, which is a foam of silicone rubber, is used as the elastic member 46. The elastic member 46 is formed into a strip shape and used as is without being bonded to a metal plate. However, as shown in Fig. 8 and Fig. 9, one or more sheet-like members 70 to 72 may be interposed between the elastic member 46 and the holding member 47 for the purpose of fixing the elastic member 46 at a required position on the holding member 47 or adjusting the pressure force.

[0081] In this embodiment, the elastic member 46 has a tensile strength of 1.0 MPa, an elongation of 50 to 70%, a 25% compression load of 0.03 MPa, and a compression residual strain of 5.0% when the thickness is 3 mm.

[0082] The holding member 47 is made of, for example, a heat-resistant synthetic resin integrally molded into a required cross-sectional shape by injection molding, etc. Examples of heat-resistant synthetic resins include liquid crystal polymer (LCP), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyether sulfone (PES), polyamide imide (PAI), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), and composite materials thereof.

[0083] 4 and 6, the holding member 47 has a pressure applying section 471 that is pressed directly against the surface of the heating roll 41 at the exit of the fixing nip N without the interposition of the elastic member 46. The cross-sectional shape of the pressure applying section 471 is formed in a substantially flat shape with a curved end on the exit side of the fixing nip N, or in a shape in which the exit of the fixing nip N is curved in a convex shape toward the heating roll 41 side.

[0084] As shown in FIG. 4, the holding member 47 has a portion with a reference numeral 472 located upstream of the fixing nip N from the pressure unit 471, which is formed in a shape following the outer peripheral shape of the fixing nip N of the heating roll 41 as an example of a fixing means, that is, in a substantially arc shape concavely curved toward the heating roll 41. Here, the portion 472 located upstream of the fixing nip N from the pressure unit 471 of the holding member 47 does not necessarily have to be an arc shape completely following the outer peripheral shape of the heating roll 41, and may have a flat portion or a curved portion whose curvature is different from that of the heating roll 41. In FIG. 4, the portion with a reference numeral 473 indicates a chamfered portion formed at an end portion along the longitudinal direction of the holding member 47. Also, reference numeral 474 indicates an attachment portion of a second sheet metal member (not shown) fixed to the holding member 47.

[0085] A portion indicated by reference numeral 472, which is located upstream of the pressure section 471 of the holding member 47 in the fixing nip N, is formed as a pressure adjusting surface which is an example of a holding section that holds the elastic member 46 and adjusts the pressure applied to the heating roll 41. The pressure adjusting surface 472 is disposed at a position farther away from the outer circumferential surface of the heating roll 41 than the pressure section 471.

[0086] The pressure adjusting surface 472 of the holding member 47 holds the elastic member 46. The elastic member 46 held by the holding member 47 is arranged in a substantially arc shape following the outer circumferential shape of the heating roll 41 at the fixing nip portion N when not pressed by the heating roll 41, as shown in FIG.

[0087] In other words, the pressure adjustment surface 472 of the holding member 47 does not simply have the function of holding the elastic member 46, but also serves to adjust the pressure applied to the heating roll 41 along at least one direction, either the axial direction of the heating roll 41 or a direction intersecting the axial direction, by allowing partial deformation of the elastic member 46 along the thickness direction.

[0088] 6, the pressure adjustment surface 472 holds, for example, an elastic member 46 formed in a sheet shape having a uniform thickness, and generates a pressure force in the fixing nip portion N by elastically deforming the elastic member 46 along the thickness direction. The pressure force generated by the elastic deformation of the elastic member 46 is basically determined by the elastic coefficient of the material constituting the elastic member 46 and the amount of elastic deformation of the elastic member 46.

[0089] By appropriately setting the shape of the pressure adjustment surface 472 of the holding member 47 along its longitudinal direction and a direction intersecting the longitudinal direction, it is possible to set the pressure generated by the elastic deformation of the elastic member 46 to a desired state along its longitudinal direction and a direction intersecting the longitudinal direction.

[0090] The pressure adjusting surface 472 of the holding member 47 may be a curved surface or a curved surface including a flat surface in part. The pressure adjusting surface 472 of the holding member 47 may be configured to have a surface including at least one of projections and recesses, slits, and holes.

[0091] 7, a plurality of small recesses 475, 475... each having a rectangular or circular planar shape, for example, are provided on the pressure adjustment surface 472 of the holding member 47. The recesses 475, 475... are formed as holes or through holes recessed from the pressure adjustment surface 472. A plurality of recesses 475, 475... are arranged along the longitudinal direction of the holding member 47 and along the width direction intersecting with the longitudinal direction.

[0092] The recesses 475, 475... are arranged symmetrically on both sides of the holding member 47 with respect to the center S along the direction intersecting the conveying direction of the recording paper 5, and the interval between the recesses becomes gradually narrower toward the ends along the longitudinal direction of the holding member 47. The recesses 475, 475... are arranged in two rows only on the entrance side of the fixing nip N along the direction intersecting the longitudinal direction of the holding member 47. Since both ends along the longitudinal direction of the holding member 47 are supported by the frame of the device housing 43 (not shown) via the sheet metal member 48, the pressure applied to the heating roll 41 tends to be larger than that in the central portion. Therefore, the recesses 475, 475... of the holding member 47 are arranged so that the interval between the recesses becomes gradually narrower toward both ends along the longitudinal direction of the holding member 47, so that the pressure applied to both ends along the longitudinal direction of the holding member 47 can be made smaller than that in the central portion, and as a result, the pressure applied to the both ends along the longitudinal direction of the holding member 47 can be made uniform along the longitudinal direction of the holding member 47.

[0093] The arrangement of the recesses 475, 475... is not limited to this and can be any arrangement. By arbitrarily setting the arrangement of the recesses 475, 475..., it becomes possible to set the pressure force generated by the deformation of the elastic member with a high degree of freedom. Also, other than the recesses, unevenness, slits, holes, etc. may be used.

[0094] The recesses 475, 475... of the holding member 47 partially reduce the area of ​​the surface that supports the rear surface of the elastic member 46 on the pressure force adjustment surface 472. The depth of the recesses 475, 475... may be set appropriately, and may be in a non-contact state where they do not come into contact at all with the rear surface of the elastic member 46, or in a contact state where they come into contact when the elastic member 46 is deformed to a certain extent.

[0095] In addition, in this embodiment 1, as shown in FIG. 3, the fixing nip portion N where the holding member 47 holds the elastic member 46 and presses the pressure belt 42 against the heating roll 41 is set to have a relatively large area compared to conventional fixing devices.

[0096] That is, the holding member 47 is configured to form a relatively large central angle θ close to approximately 90 degrees around the outer periphery of the heating roll 41. As shown in Fig. 5, a conventional equivalent fixing device 40 has a significantly smaller central angle θ', and an example of the length of the fixing nip portion N along the outer periphery of the heating roll 41 is approximately 8 mm. In contrast, as shown in Fig. 3, the fixing device 40 according to the first embodiment has a length of the fixing nip portion N along the outer periphery of the heating roll 41 of approximately 15 mm, which is approximately twice as long.

[0097] The central angle θ of the fixing nip N where the holding member 47 holds the elastic member 46 and is in pressure contact with the outer circumferential surface of the heating roll 41 is preferably 45 degrees or more, and more preferably 60 degrees to 90 degrees.

[0098] The central angle θ of the holding member 47 forming the fixing nip N corresponds to the area of ​​the fixing nip N, assuming that the length along the axial direction where the pressure belt 42 is in pressure contact with the surface of the heating roll 41 is the same. If the central angle θ of the holding member 47 is twice as long as in the past, assuming that the total pressure force of the pressure belt 42 and the heating roll 41 is constant, the pressure force per unit area where the pressure belt 42 is in pressure contact with the heating roll 41 by the holding member 47 can be halved, making it possible to reduce the pressure. Reducing the pressure of the holding member 47 also contributes to making the core metal 411 and the elastic layer 412 of the heating roll 41 thinner.

[0099] <Function of the Fixing Device> In the above-described configuration, the fixing device according to embodiment 1 makes it possible to use a sheet-like member of uniform thickness as the elastic member, thereby enabling manufacturing costs to be reduced compared to the case where a sheet-like member of non-uniform thickness is used.

[0100] In other words, in the fixing device 40 according to this embodiment 1, as shown in FIG. 2, the elastic member 46 of the pressure member 45 that presses the pressure belt 42 against the surface of the heating roll 41 is configured so that when not pressed against the surface of the heating roll 41, the elastic member 46 has an approximately arc shape that follows the outer peripheral shape of the heating roll 41.

[0101] Therefore, the fixing device 40 can use a sheet-like highly expanded silicone foam having a uniform thickness as the elastic member 46. As shown in Fig. 10 and Fig. 11, unlike those made of silicone rubber or the like, the elastic member 46 made of highly expanded silicone foam or the like has a low elastic modulus and, even when the elastic member 46 is formed thin to reduce pressure, it is possible to accurately and easily achieve a desired low surface pressure by controlling the shape of the pressure adjusting surface 472 of the holding member 47, providing recesses 475, 475... on the pressure adjusting surface 472, and controlling the thickness of the elastic member 46.

[0102] Therefore, an increase in the cost of the fixing device 40 due to an increase in the manufacturing cost of the elastic member 46 can be avoided.

[0103] In the above embodiment, the case where the present invention is applied to a full-color image forming apparatus has been described, but it is needless to say that the present invention can also be applied to a monochrome image forming apparatus in the same manner.

[0104] (Additional Note) (((1))) An endless belt; a fixing means for contacting the belt to form a fixing nip portion; a pressure applying unit that is disposed inside the belt, has a shape following the outer peripheral shape of the fixing unit, has a holding portion that holds an elastic member, and applies pressure to the belt against the fixing unit; Equipped with The fixing device according to claim 1, wherein the elastic member is deformed to conform to the holding portion when the elastic member is not pressed by the fixing means. (((2))) 2. The fixing device according to claim 1, wherein the pressure means has a holding portion having a curved shape, and is formed as a pressure adjusting surface for adjusting the pressure applied to the fixing means. (((3))) The fixing device according to (((2))), wherein the pressure adjusting surface adjusts the pressure by allowing partial deformation of the elastic member along a thickness direction. (((4))) In the fixing device according to (((3))), the pressure adjustment surface is a surface including at least one of projections and recesses, slits, and holes. (((5))) The fixing device according to (((1))), wherein the elastic member is made of silicone foam. (((6))) The pressure applying means is made of synthetic resin and has a pressing portion at a downstream end in the rotation direction of the belt for directly pressing the belt against the fixing means. (((7))) The fixing device according to (((1))), wherein the fixing means is a heating roll having a heat source therein. (((8))) The fixing device according to ((7))), wherein the pressure means presses the belt against the heating roll over the entire area of ​​the fixing nip portion. (((9))) an image forming means for forming an image on a recording medium; a fixing means for fixing the image on the recording medium; Equipped with An image forming apparatus using the fixing device according to any one of ((1))) to (((8))) as the fixing means.

[0105] According to the fixing device of (((1))), it is possible to use a sheet-like member having a uniform thickness as the elastic member, thereby enabling reduction in manufacturing costs compared to the use of a sheet-like member having a non-uniform thickness. According to the fixing device of (((2))), it is easier to adjust the pressure applied to the fixing means, compared to when the holding portion has a flat shape. According to the fixing device of (((3))), it is possible to avoid uneven pressure compared to a case in which the pressure adjustment surface does not allow partial deformation along the thickness direction of the elastic member. According to the fixing device of (((4))), the pressure adjustment surface makes it easier to adjust the pressure while making the elastic member thinner, compared to when the pressure adjustment surface is formed in a convex shape. According to the fixing device of (((5))), the elastic member can apply a relatively small pressure compared to when it is made of a silicone foam having a support member. According to the fixing device of (((6))), the pressure applying means can maintain the fixing performance and improve the peelability of the recording medium, compared to a case where the pressure applying means does not have a pressing portion. According to the fixing device of (((7))), the fixing means can have a wider nip area than when it is composed of something other than a heating roll. According to the fixing device of (((8))), the pressure means can increase the area of ​​the fixing nip portion, compared to a case in which the belt is pressed against the heating roll only in a portion of the fixing nip portion. According to the image forming apparatus of (((9))), costs can be reduced compared to when the fixing device described in any one of (((1))) to (((8))) is not used. [Explanation of symbols]

[0106] 1...Image forming device 1a…Device body 11...Photoconductor drum 40...Fixing device 41…Heated roll 42...Compression belt 45...Pressure member 46...Elastic member 47...Retaining member 472…Pressure adjustment surface

Claims

1. An endless belt; a fixing means for contacting the belt to form a fixing nip portion; a pressure applying unit that is disposed inside the belt, has a shape following the outer peripheral shape of the fixing unit, has a holding portion that holds an elastic member, and applies pressure to the belt against the fixing unit; Equipped with The fixing device according to claim 1, wherein the elastic member is deformed to conform to the holding portion when the elastic member is not pressed by the fixing means.

2. 2. The fixing device according to claim 1, wherein the pressure applying means has a curved holding portion formed as a pressure adjusting surface for adjusting the pressure applied to the fixing means.

3. The fixing device according to claim 2 , wherein the pressure adjusting surface adjusts the pressure by allowing partial deformation of the elastic member along a thickness direction.

4. The fixing device according to claim 3 , wherein the pressure adjusting surface is a surface including at least one of projections and recesses, slits, and holes.

5. 2. The fixing device according to claim 1, wherein the elastic member is made of a silicone foam.

6. 6. The fixing device according to claim 5, wherein the pressure means is made of synthetic resin and has a pressing portion at a downstream end in the rotation direction of the belt for directly pressing the belt against the fixing means.

7. 2. The fixing device according to claim 1, wherein the fixing means comprises a heating roll having a heat source therein.

8. 8. The fixing device according to claim 7, wherein the pressing means presses the belt against the heating roll over the entire fixing nip portion.

9. an image forming means for forming an image on a recording medium; a fixing means for fixing the image on the recording medium; Equipped with 9. An image forming apparatus using the fixing device according to claim 1 as the fixing means.

Images