Fixing device and image forming apparatus

Abstract

The invention discloses a fixing device and an image forming apparatus, the fixing device includes: an endless belt; a fixing unit that comes into contact with the belt to form a fixing nip; and a pressing unit that includes a holding portion that holds an elastic member and that presses the belt toward the fixing unit, the holding portion being disposed inside the belt and having a shape that follows the outer peripheral shape of the fixing unit. The elastic member is deformed to have a shape along the holding portion in a state in which the fixing unit is not pressurized.

Description

Technical Field

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

[0002] Conventionally, as a technology related to the fixing device, for example, the technology disclosed in the following patent publications and the like has been proposed.

[0003] Japanese Patent Gazette No. 2016-188916 discloses a technology constructed as follows: the surface of the fixing bite side of the bite forming component is made of a metal material, and a gap is formed in the end area in the longitudinal direction of the metal material and further outward than the outer end of the paper passing area for paper of the maximum size that can pass through, and the longitudinal side of the gap extends obliquely relative to the belt rotation direction. Summary of the invention

[0004] An object of the present invention is to use a sheet member having a uniform thickness as an elastic member, thereby achieving a reduction in manufacturing cost compared to a case where a sheet member having a non-uniform thickness is used.

[0005] According to a first aspect of the present invention, there is provided a fixing device comprising: an annular belt; a fixing unit, the fixing unit being in contact with the belt to form a fixing nip portion; and a pressurizing unit, the pressurizing unit having a retaining portion for retaining an elastic component and pressurizing the belt toward the fixing unit, the retaining portion being arranged inside the belt and having a shape that imitates the outer peripheral shape of the fixing unit, the elastic component being deformed to have a shape along the retaining portion when no pressure is applied to the fixing unit.

[0006] According to a second aspect of the present invention, in the fixing device according to the first aspect, in the pressing unit, the holding portion has a curved surface shape and is formed as a pressing force regulating surface that regulates a pressing force to the fixing unit.

[0007] According to a third aspect of the present invention, in the fixing device according to the second aspect, the pressing force regulating surface regulates the pressing force by allowing local deformation of the elastic member in a thickness direction.

[0008] According to a fourth aspect of the present invention, in the fixing device according to the third aspect, the pressing force regulating surface is formed of a surface including at least any one of concavities and convexities, slits, and holes.

[0009] According to a fifth aspect of the present invention, in the fixing device according to the first aspect, the elastic member is formed of a silicone foam.

[0010] According to a sixth aspect of the present invention, in the fixing device according to the fifth aspect, the pressure unit is made of synthetic resin and has a pressing portion that directly presses the belt toward the fixing unit at an end portion on the downstream side in the rotation direction of the belt.

[0011] According to a seventh aspect of the present invention, in the fixing device according to the first aspect, the fixing unit is constituted by a heating roller having a heating source inside.

[0012] According to an eighth aspect of the present invention, in the fixing device according to the seventh aspect, the pressing unit presses the belt toward the heating roller over all regions of the fixing nip.

[0013] According to the ninth aspect of the present invention, there is provided an image forming device comprising: an image forming unit which forms an image on a recording medium; and a fixing unit which fixes the image to the recording medium, the image forming device using the fixing device of any one of the first to eighth aspects as the fixing unit.

[0014] (Effect)

[0015] According to the first aspect, a sheet member having a uniform thickness can be used as the elastic member, and thus, compared with a case where a sheet member having a non-uniform thickness is used, a reduction in manufacturing cost can be achieved.

[0016] According to the second aspect, compared with a case where the holding portion has a planar shape, it is easier to adjust the pressing force to the fixing unit.

[0017] According to the third aspect, as compared with a case where the pressing force regulating surface does not allow local deformation of the elastic member in the thickness direction, uneven pressing force can be avoided.

[0018] According to the fourth aspect, compared with the case where the pressing force adjustment surface is formed in a convex shape, the elastic member can be made thinner and the pressing force can be easily adjusted.

[0019] According to the fifth aspect, compared with a case where the elastic member is formed of a silicone foam having a supporting member, the pressing force can be relatively reduced.

[0020] According to the sixth aspect, compared with a case where the pressure unit does not have a pressing portion, it is possible to achieve maintenance of fixability and improvement of recording medium detachability.

[0021] According to the seventh aspect, the nip region can be enlarged compared to a case where the fixing unit is composed of components other than the heating roller.

[0022] According to the eighth aspect, compared with a case where the pressing unit presses the belt against the heating roller only in a part of the fixing nip, the area of ​​the fixing nip can be increased.

[0023] According to the ninth aspect, cost reduction can be achieved compared to a case where the fixing device according to any one of the first to eighth aspects is not used. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a diagram showing the overall structure of an image forming apparatus to which a fixing device according to Embodiment 1 of the present invention is applied;

[0025] Figure 2 is a cross-sectional structural diagram showing a fixing device according to a first embodiment of the present invention;

[0026] Figure 3 is a cross-sectional structural diagram showing a main part of a fixing device according to a first embodiment of the present invention;

[0027] Figure 4 is a side view showing a pressurized component;

[0028] Figure 5 is a cross-sectional structural diagram showing a conventional fixing device;

[0029] Figure 6 is a perspective structural diagram showing a main part of a fixing device according to a first embodiment of the present invention;

[0030] Figure 7 is a perspective structural diagram showing other main parts of the fixing device according to the first embodiment of the present invention;

[0031] Figure 8 is a side view showing another example of the pressure member of the fixing device according to the first embodiment of the present invention;

[0032] Fig. 9 is a perspective structural diagram showing another example of the pressure member of the fixing device according to the first embodiment of the present invention;

[0033] Fig.10 is a graph showing pressure distribution of the fixing device according to the first embodiment of the present invention;

[0034] Fig.11 This is a graph showing the pressure distribution of the fixing device according to the first embodiment of the present invention. DETAILED DESCRIPTION

[0035] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be described with reference to the drawings.

[0036] [Implementation Method 1]

[0037] Figure 1 This is a diagram showing an overview of the entire image forming apparatus to which the fixing device according to the first embodiment is applied. Figure 1 In the figure, symbol X indicates the horizontal direction (width direction) of the image forming apparatus, symbol Y indicates the depth direction of the image forming apparatus, and symbol Z indicates the vertical direction of the image forming apparatus.

[0038] <Overall Structure of Image Forming Apparatus>

[0039] The image forming device 1 is configured as, for example, a color printer. Figure 1 As shown, the image forming apparatus 1 includes a plurality of image generating devices 10, an intermediate transfer device 20, a paper feed device 50, a fixing device 40 as an example of a fixing unit of the present embodiment 1, and the like. The plurality of image generating devices 10 form a toner image developed using a toner constituting a developer. The intermediate transfer device 20 holds the toner image formed by each image generating device 10 and conveys it to a secondary transfer position where a secondary transfer is finally performed on a recording paper 5 as an example of a recording medium. The paper feed device 50 stores and conveys 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 to the recording paper 5 to which the secondary transfer is performed by the intermediate transfer device 20. Figure 1 In the figure, reference numeral 1a denotes a device main body composed of supporting structural members, an exterior cover, and the like.

[0040] In this embodiment 1, a plurality of image forming devices 10 and an intermediate transfer device 20 constitute an image forming unit for forming a toner image on a recording medium. Alternatively, the image forming unit may be configured such that a single image forming device is provided, and the image forming device directly forms a toner image on a recording medium without passing through an intermediate transfer device.

[0041] The image generating device 10 is composed of four image generating devices 10Y, 10M, 10C, and 10K that form toner images of four colors, namely yellow (Y), magenta (M), cyan (C), and black (K). These four image generating devices 10 (Y, M, C, K) are arranged in a row along the horizontal direction X in the internal space of the device body 1a.

[0042] like Figure 1As shown, each image generating device 10 (Y, M, C, K) is provided with a photosensitive drum 11 as an example of a rotating image holding unit. The following devices are mainly arranged around the photosensitive drum 11. The main devices are a charging device 12, an exposure device 13, a developing device 14, a primary transfer device 15, and a drum cleaning device 16. The charging device 12 charges the peripheral surface (image holding surface) of the photosensitive drum 11 that can form an image to a required potential. The exposure device 13 irradiates the charged peripheral surface of the photosensitive drum 11 with light based on the information (signal) of the image to form an electrostatic latent image (for each color) with a potential difference. The developing device 14 develops the electrostatic latent image using the 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 the toner and other attachments remaining on the image holding surface of the photosensitive drum 11 after the primary transfer. Note that symbols indicating the photosensitive drum 11 , the charging device 12 , and the like are given only to the image generating device 10Y of yellow (Y), and are omitted in the other image generating devices 10 (M, C, K).

[0043] The photosensitive drum 11 is a member having an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material formed on the circumference of a cylindrical or columnar substrate that is grounded. The photosensitive drum 11 is supported to rotate in the direction indicated by arrow A by receiving a driving force from a driving device (not shown).

[0044] The charging device 12 is composed of a contact type charging roller arranged in contact with the photosensitive drum 11. A charging voltage is supplied to the charging device 12. When the developing device 14 is a device that performs reverse development, a voltage or current having the same polarity as the charged polarity of the toner supplied from the developing device 14 is supplied as the charging voltage. On the back side of the charging device 12, a cleaning roller 121 for cleaning the surface of the charging device 12 is arranged in contact.

[0045] The exposure device 13 is composed of an LED print head, etc., which forms an electrostatic latent image by irradiating light corresponding to image information to the photosensitive drum 11 through a plurality of LEDs (Light Emitting Diodes) arranged along the axial direction of the photosensitive drum 11. In the exposure device 13, when the latent image is formed, the information (signal) of the image input by any means is sent to the image forming device 1. In addition, as the exposure device 13, a device that forms an electrostatic latent image by irradiating the peripheral surface of the charged photosensitive drum 11 with a laser beam formed according to the information of the image input to the image forming device 1 can also be used.

[0046] like Figure 1As shown, the developing device 14 is composed of a developing roller 141, stirring and conveying components 142, 143, and a layer thickness limiting component 144, etc., arranged inside a frame 140 having an opening and a developer collection chamber. The developing roller 141 holds the developer and conveys it to a developing area opposite to the photosensitive drum 11. The stirring and conveying components 142, 143 are composed of a spiral agitator, etc., which conveys the developer while stirring it through the developing roller 141. The layer thickness limiting component 144 limits the amount of developer (layer thickness) held by the developing roller 141. In the developing device 14, a voltage for development is supplied between the developing roller 141 and the photosensitive drum 11 from a power supply device not shown in the figure. In addition, the developing roller 141, the stirring and conveying components 142, 143 are rotated in a required direction by the driving force transmitted from a driving device not shown in the figure. In addition, as the developer of the above four colors, a two-component developer including a non-magnetic colorant and a magnetic carrier is used.

[0047] like Figure 1 As shown, the primary transfer device 15 is a contact type transfer device having a primary transfer roller, which rotates while in contact with the peripheral surface of the photosensitive 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 having a polarity opposite to the charged polarity of the toner is supplied from a power supply device (not shown).

[0048] The drum cleaning device 16 is composed of a cleaning blade 161 and a delivery member 162 disposed inside a container-shaped main body 160. The cleaning blade 161 removes and cleans the residual toner and other attached materials. The delivery member 162 is composed of a screw auger and the like, which collects the toner and other attached materials removed by the cleaning blade 161 and conveys them to a recovery system (not shown).

[0049] The intermediate transfer device 20 is configured to be located above each image generating device 10 (Y, M, C, K) along the vertical direction Z. The intermediate transfer device 20 is mainly composed of an intermediate transfer belt 21, a plurality of belt support rollers 22 to 25, a belt cleaning device 26, and a secondary transfer device 30. The intermediate transfer belt 21 is an example of an intermediate transfer unit that circulates in the direction indicated by the arrow B while passing through the primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roller). The plurality of belt support rollers 22 to 25 maintain the intermediate transfer belt 21 in a desired state from its inner periphery and support it so that it can circulate. The secondary transfer device 30 is configured on the outer peripheral surface (image holding surface) side of the intermediate transfer belt 21 supported by the belt support rollers 25, and performs secondary transfer of the toner image on the intermediate transfer belt 21 onto the recording paper 5. The belt cleaning device 26 removes and cleans toner, paper dust and other adhering materials remaining on the outer peripheral surface of the intermediate transfer belt 21 after passing through the secondary transfer device 30 .

[0050] As the intermediate transfer belt 21, 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, polyamideimide resin, etc. is used. In addition, the belt support roller 22 is configured as a driving roller. The belt support roller 23 is configured as a surface forming roller that maintains the stroke position of the intermediate transfer belt 21. The belt support roller 24 is configured as a tension applying roller that applies tension to the intermediate transfer belt 21. The belt support roller 25 is configured as a support roller for secondary transfer.

[0051] The secondary transfer device 30 includes a secondary transfer roller 31 that rotates at a secondary transfer position. The secondary transfer position is the outer peripheral surface portion of the intermediate transfer belt 21 supported by the belt support roller 25 in the intermediate transfer device 20. A DC voltage having a polarity opposite to or having the same polarity as the charged polarity of the toner is supplied to the secondary transfer roller 31 or the belt support roller 25 of the intermediate transfer device 20 as a secondary transfer voltage.

[0052] The fixing device 40 is composed of a pressure belt 42 as an example of an endless belt and a heating roller 41 as an example of a fixing unit that contacts the pressure belt 42 to form a fixing nip N. The heating roller 41 is heated by the heating unit so that the surface temperature is maintained at a preset temperature. The pressure belt 42 contacts the heating roller 41 with a required pressure and rotates. In the fixing device 40, the contact portion between the heating roller 41 and the pressure belt 42 becomes the fixing nip N for performing the fixing process (heating and pressing) required for fixing the unfixed toner image to the recording paper 5. In addition, the fixing device 40 will be described in detail later.

[0053] The paper supply device 50 is arranged to be present at a position below the image generating device 10 (Y, M, C, K). The paper supply device 50 is mainly composed of one (or more) paper storage bodies 52 and a feeding device 53 that feeds out the recording paper 5 one by one from the paper storage body 52. ​​The paper storage body 52 stores the recording paper 5 of a desired size, type, etc. in a state of being loaded on the loading plate 51. In addition, the paper storage body 52 is installed, for example, so that it can be pulled out to the front side (the side that the user faces when operating) of the device body 1a, that is, the left side in the example shown in the figure.

[0054] As the recording paper 5, for example, there can be mentioned thin paper such as plain paper, tracing paper, etc. used in electronic photographic copiers and printers, or OHP sheets made of transparent film-like media made of synthetic resin (PET, etc.). In order to further improve the smoothness of the image surface after fixing, it is preferred that the surface of the recording paper 5 is as smooth as possible. As the recording paper 5, for example, coated paper formed by coating the surface of plain paper with resin, so-called thick paper with a relatively large basis weight such as coated paper for printing, etc. can also be used.

[0055] A paper feed conveying path 57 is provided between the paper feed device 50 and the secondary transfer device 30. The paper feed conveying path 57 is composed of one (or more) paper conveying roller pairs 54 that convey the recording paper 5 fed from the paper feed device 50 to the secondary transfer position, and conveying guide materials 55 and 56. The paper conveying roller pair 54 disposed at a position before the secondary transfer position in the paper feed conveying path 57 is configured as a roller (registration roller) that adjusts the conveying timing of the recording paper 5, for example.

[0056] 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 and the like that transports the recording paper 5 sent out from the secondary transfer device 30 to the fixing device 40.

[0057] A discharge conveying path 65 is provided on the downstream side of the fixing device 40. The discharge conveying path 65 includes a paper conveying roller pair 61 and a paper discharge roller pair 62, conveying guide materials 63 and 64, etc., for discharging the recording paper 5 on which the toner image is fixed by the fixing device 40 to a paper discharge unit 60 disposed at the upper part of the apparatus body 1a.

[0058] Figure 1 In the figure, reference numeral 100 denotes a control device as an example of a control unit that performs overall control of the operation of the image forming apparatus 1. The control device 100 includes a CPU (Central Processing Unit) and a ROM (Read Only Memory), a RAM (Random Access Memory), or a bus or a communication interface that connects the CPU and ROM, etc. (not shown).

[0059] <Basic Operation of Image Forming Device>

[0060] Next, a basic image forming operation performed by the image forming apparatus 1 will be described.

[0061] Here, the image forming operation 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) will be described. In addition, the image forming operation when forming an image composed of a combination of toner images of single or multiple colors using any one or more of the four image forming devices 10 (Y, M, C, K) is basically the same.

[0062] When the image forming apparatus 1 receives the instruction information of the print request, the control device 100 starts 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.

[0063] In each image forming device 10 (Y, M, C, K), first, each photosensitive drum 11 rotates in the direction indicated by arrow A. The surface of each photosensitive drum 11 is charged to a required polarity (negative polarity in Embodiment 1) and potential by each charging device 12. Next, the exposure device 13 irradiates the surface of the charged photosensitive drum 11 with light based on a signal of an image obtained by converting the information of the image input to the image forming device 1 into each color component (Y, M, C, K). Then, an electrostatic latent image of each color component formed with a required potential difference is formed on the surface of the photosensitive drum 11.

[0064] Next, each developing device 14 (Y, M, C, K) supplies a toner of a corresponding color (Y, M, C, K) charged to a required polarity (negative polarity) to the electrostatic latent image of each color component formed on the photosensitive drum 11, and electrostatically adheres the toner to develop the electrostatic latent image. Through this development, the electrostatic latent image of each color component formed on each photosensitive drum 11 is visualized as a toner image of four colors (Y, M, C, K) developed by the toner of the corresponding color.

[0065] Next, the toner images of each color formed on the photosensitive drums 11 of the image generating devices 10 (Y, M, C, K) are conveyed to the primary transfer position. Then, the primary transfer device 15 transfers the toner images of each color to the intermediate transfer belt 21 of the intermediate transfer device 20 rotating in the direction indicated by the arrow B in a sequentially superimposed state.

[0066] In addition, in each image generating device 10 (Y, M, C, K) where the primary transfer is completed, the drum cleaning device 16 removes the attached matter by scraping, and cleans the surface of the photosensitive drum 11. Thus, each image generating device 10 (Y, M, C, K) is in a state where it can perform the next image generating operation.

[0067] Next, in the intermediate transfer device 20, the toner image after the primary transfer is held and conveyed to the secondary transfer position by the rotation of the intermediate transfer belt 21. On the other hand, in the paper feeding device 50, the required recording paper 5 is fed to the paper feeding and conveying path 57 in accordance with the image generation operation. In the paper feeding and conveying path 57, the paper conveying roller pair 54 as a registration roller feeds the recording paper 5 in accordance with the transfer timing and supplies it to the secondary transfer position.

[0068] At the secondary transfer position, the secondary transfer roller 31 secondary transfers the toner image on the intermediate transfer belt 21 to the recording paper 5. In the intermediate transfer device 20 after the secondary transfer, the belt cleaning device 26 removes and cleans the toner and other attached materials remaining on the surface of the intermediate transfer belt 21 after the secondary transfer.

[0069] Next, the recording paper 5 to which the toner image is secondarily transferred is peeled off from the intermediate transfer belt 21 and the secondary transfer roller 31, and is then conveyed to the fixing device 40 along the paper conveying path 59. The fixing device 40 guides the recording paper 5 holding the unfixed toner image after the secondary transfer into the fixing nip N between the rotating heating roller 41 and the pressure belt 42 and passes it. Thus, the fixing device 40 performs the necessary fixing process (heating and pressurizing) to fix the unfixed toner image on the recording paper 5. The recording paper 5 after the fixing is completed is discharged to the paper discharge section 60 provided at the upper part of the device body 1a via the discharge conveying path 65 and the paper discharge roller pair 62.

[0070] Through the above-described operation, a full-color image formed by combining toner images composed of four color toners (Y, M, C, and K) is output.

[0071] <Structure of the fixing unit>

[0072] Figure 2 FIG. 4 is a cross-sectional view showing the fixing device of the first embodiment. The fixing device 40 of the first embodiment is integrally formed as a fixing member. Figure 1 As shown, the fixing device 40 as a fixing member can be independently attached to and detached from the apparatus body 1 a of the image forming apparatus 1 by opening and closing the rear cover 1 b located on the right side in the figure in the clockwise direction and the counterclockwise direction.

[0073] like Figure 2 As shown in the figure, the fixing device 40 has a device housing 43 as an example of a frame. The device housing 43 is composed of a frame (not shown) supporting the heating roller 41 and the pressure belt 42, a main body (not shown) holding the frame, or an outer cover covering the outer periphery of the main body and the frame. The heating roller 41 and the pressure belt 42 are arranged inside the device housing 43 in a state of being pressed. As described above, the pressure belt 42 is an example of an endless belt. The heating roller 41 is an example of a fixing unit that contacts the pressure belt 42 to form a fixing nip N.

[0074] The device housing 43 has an inlet 431 at its lower end surface for introducing the recording paper 5 to which the unfixed toner image Ti is transferred. Inside the inlet 431, a guide plate 432 for guiding the recording paper 5 to the fixing nip N where the heating roller 41 and the pressure belt 42 are pressed is arranged in a state of being inclined upward. In addition, the device housing 43 has an outlet 433 at the left end of its upper end surface for discharging the recording paper 5 to the outside after the fixing process by the heating roller 41 and the pressure belt 42 is performed. As needed, an outlet roller (not shown) is rotatably provided at the outlet 433 as needed, and the outlet roller discharges the recording paper 5 to the outside of the device housing 43. In addition, the recording paper 5 is transported with the center along the depth direction Y intersecting the transport direction as a reference (so-called center registration).

[0075] In the conveying path 434 formed between the fixing nip N of the fixing device 40 and the discharge port 433, a rod-shaped actuator 435 is provided, which can rotate in the clockwise direction around a fulcrum 435a. The actuator 435 is an example of a detection unit that detects the passage of the leading end of the recording paper 5. The rotation of the actuator 435 is detected as the passage of the recording paper 5 by an optical sensor (not shown) or the like.

[0076] like Figure 2 As shown, the fixing device 40 is roughly divided into a heating roller 41 and a pressure unit 44 that holds a pressure belt 42 that is provided to be contactable and separable from the heating roller 41 .

[0077] like Figure 3 As shown, the heating roller 41 has a cylindrical core rod 411, an elastomer layer 412, and an anti-sticking layer 413. The core rod 411 is made of metal such as stainless steel or aluminum, or iron (thin-walled high-tensile steel pipe). The core rod 411 is formed into a relatively thin-walled cylindrical shape, and the heat capacity is set to be significantly small. The elastomer layer 412 is made of a heat-resistant elastomer such as silicone rubber or fluororubber coated on the outer periphery of the core rod 411. The elastomer layer 412 is also formed into a relatively thin-walled cylindrical shape, which helps to reduce the heat capacity of the heating roller 41. The anti-sticking layer 413 is made of polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), etc., which are thinly coated on the surface of the elastomer layer 412. As shown in FIG. Figure 2 As shown, two halogen lamps 414a and 414b are arranged inside the heating roller 41 as an example of a heating unit. The two halogen lamps 414a and 414b are configured so that the heating areas along the depth direction Y orthogonal to the drawing are different from each other. In addition, the number of halogen lamps 414a and 414b is not limited to two, and may be only one or more than three.

[0078] like Figure 2As shown, both ends of the heating roller 41 along its longitudinal direction (axial direction) are supported rotatably inside the device housing 43 via bearing components (not shown). The heating roller 41 is driven to rotate at a required speed in the direction of arrow C by a drive motor (not shown) on the device body 1a side via a driving force transmission gear 415 meshing with a drive gear (not shown) installed at one end along the axial direction. The drive motor is an example of a drive source. In addition, the pressure belt 42 is driven to rotate by being pressed against the rotationally driven heating roller 41 at the fixing nip portion N.

[0079] The rotation speed of the heat roller 41 , that is, the fixing speed, may be set to a plurality of speeds such as high speed, medium speed, and low speed according to the basis weight and material of the recording paper 5 .

[0080] The surface temperature of the heating roller 41 is detected by a temperature sensor (not shown). In the heating roller 41, the power supply to the halogen lamps 414a and 414b is controlled by a temperature control circuit using a triac (not shown) based on the detection result of the temperature sensor. As a result, the heating roller 41 is heated so that its surface reaches the required fixing temperature.

[0081] On the other hand, Figure 2 As shown, the pressurizing unit 44 includes a pressurizing belt 42, a pressurizing member 45 as an example of a pressurizing unit, a sheet metal member 48, a pair of guide members 49, and a sliding sheet or felt member (not shown). Figure 3 As shown, the pressure member 45 includes an elastic member 46 and a retaining member 47, and the retaining member 47 is arranged inside the pressure belt 42, holds the elastic member 46 and makes the pressure belt 42 pressurized against the heating roller 41. The sheet metal member 48 is an example of a mounting unit that mounts the retaining member 47 of the pressure member 45 in a fixed state. A pair of guide members 49 is an example of a guide unit that guides the pressure belt 42 in a rotatable manner, and the two ends along the length direction of the sheet metal member 48 are arranged in a fixed state respectively. The sliding sheet not shown is an example of a sheet interposed between the pressure belt 42 and the pressure member 45 to reduce the sliding resistance. The felt member not shown is arranged inside the pressure belt 42, and is an example of a lubricant retaining unit that retains the lubricant applied to the inner peripheral surface of the pressure belt 42.

[0082] The pressure belt 42 is made of a flexible material and is formed into an endless belt whose free shape before installation is a thin-walled cylindrical shape. The pressure belt 42 has a substrate layer, an elastomer layer coated on the surface of the substrate layer, and an anti-sticking layer coated on the surface of the elastomer layer. In addition, the pressure belt 42 can also be composed of a substrate layer and an anti-sticking layer directly coated on the surface of the substrate layer. The substrate layer is formed of a heat-resistant synthetic resin such as polyimide, polyamide, polyimide amide, or a metal such as stainless steel, nickel, and copper. The elastomer layer is composed of an elastomer such as heat-resistant silicone rubber or fluororubber. The anti-sticking layer is formed of polytetrafluoroethylene (PTFE) or perfluoroalkoxyalkane (PFA), etc. As for the pressure belt 42, for example, its thickness can be set to about 50 to 200 μm.

[0083] As described above, the pressure member 45 includes the elastic member 46 and the holding member 47. The holding member 47 is disposed inside the pressure belt 42, holds the elastic member 46, and makes the pressure belt 42 pressed against the heating roller 41 in the entire region of the fixing nip N. Figure 3 and Figure 4 As shown, the holding member 47 is a member that holds the elastic member 46 in the region of the fixing nip N and presses the pressure belt 42 toward the surface of the heating roller 41 .

[0084] The sheet metal component 48 is formed by, for example, bending a sheet metal of a metal such as stainless steel, aluminum, or iron. In the illustrated example, only one sheet metal component 48 is illustrated, but other sheet metal components arranged in parallel with the sheet metal component 48 may be provided as sheet metal components in addition to the sheet metal component 48. The sheet metal component 48 fixes the holding component 47 of the pressurizing component 45, thereby determining the direction in which the holding component 47 is pressed against the outer peripheral surface of the heating roller 41. The direction in which the holding component 47 is pressed against the outer peripheral surface of the heating roller 41 is set, for example, in the direction toward the center O of the heating roller 41.

[0085] A felt member (not shown) is provided over the entire length of the outer surface of the sheet metal member 48 by bonding or the like. The felt member is formed to be relatively thick so that when tension acts on the pressure belt 42, it elastically deforms to support the pressure belt 42.

[0086] The felt member is impregnated with a lubricant in a predetermined amount for supplying in a state of being applied to the inner peripheral surface of the pressure belt 42. As the lubricant, for example, amino-modified silicone oil with a viscosity of 100 to 350 cs is used. The lubricant is applied to the inner peripheral surface of the pressure belt 42 by being impregnated in the felt member in advance. However, the lubricant is not limited to this, and the lubricant may be supplied in a state of being applied to the inner peripheral surface of the pressure belt 42 at the initial stage.

[0087] The sliding sheet not shown in the figure is composed of a thin and long flat rectangular sheet. As the sliding sheet, for example, a component having a base layer and a structure composed of a textile or woven fabric laminated on the surface or both sides of the base layer is used. The base layer is composed of a fluororesin such as polytetrafluoroethylene (PTFE). The structure composed of the textile or woven fabric is composed of glass fiber or aramid fiber. In addition, as a sliding sheet, it can also be a sheet composed of only a single layer, and the single layer is composed of a textile or woven fabric composed of glass fiber or aramid fiber. As for the sliding sheet, its thickness can be set to about 100 to 200 μm.

[0088] However, in the conventional fixing device 40, Figure 5 As shown, in order to press the pressure belt 42 against the outer peripheral surface of the heating roller 41 at the fixing nip portion N, an elastic body such as silicone rubber having a rectangular cross section held by a holding member 47 is used as an elastic member 46. Considering the workability when holding the elastic body by the holding member 47, the elastic body composed of silicone rubber or the like is vulcanized and fixed to the surface of a metal plate T composed of a thin stainless steel plate or the like.

[0089] Therefore, the conventional fixing device 40 has the following technical problems: in order to reduce the pressure that presses the pressure belt 42 against the outer peripheral surface of the heating roller 41 and realize low surface pressure, it is necessary to strictly manage the elastic modulus and the tolerance of the thickness or width of the elastic body that determines the amount of flattening (bite amount) of the elastic component 46 caused by pushing, which inevitably increases the manufacturing cost of the pressure body.

[0090] Therefore, the fixing device of this embodiment is configured to include a pressure unit, which is a unit arranged inside the belt and holds the elastic member and presses the belt toward the fixing unit. The elastic member in the state of not pressurizing the fixing unit is configured to imitate the outer peripheral shape of the fixing unit in the fixing nip portion.

[0091] That is, Figure 3 and Figure 4 As shown, the fixing device 40 of the first embodiment includes a pressure member 45 as an example of a pressure unit, which is arranged inside the pressure belt 42 and presses the pressure belt 42 against the heating roller 41 while holding the elastic member 46 .

[0092] As described above, the pressure member 45 includes the elastic member 46 and the holding member 47. The holding member 47 is disposed inside the pressure belt 42, holds the elastic member 46, and brings the pressure belt 42 into pressure contact with the heating roller 41. Figure 3 and Figure 4 As shown, the holding member 47 is a member that holds the elastic member 46 in the region of the fixing nip N and presses the pressure belt 42 toward the surface of the heating roller 41 .

[0093] The elastic member 46 is made of, for example, heat-resistant silicone rubber, EPDM or other foam. Figure 6 As shown, the elastic member 46 is obtained by cutting out a sheet-shaped member having a uniform thickness into a desired width and length, for example.

[0094] As the elastic member 46, a foamed body of silicone rubber, i.e., silicone sponge, is used. The elastic member 46 is not bonded to the sheet metal, but is used as it is in the form of a long strip. Figure 8 and Fig. 9 As shown, in order to fix the elastic member 46 at a desired position of the holding member 47 or to adjust the pressing force, one or more sheet members 70 to 72 may be interposed between the elastic member 46 and the holding member 47 .

[0095] In the present 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 compressive residual strain of 5.0% when the thickness is 3 mm.

[0096] The holding member 47 is composed of, for example, a heat-resistant synthetic resin integrally molded into a desired cross-sectional shape by injection molding, etc. Examples of the heat-resistant synthetic resin include liquid crystal polymer (LCP), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyethersulfone (PES), polyamideimide (PAI), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), or composite materials thereof.

[0097] like Figure 4 Side view of Figure 6 As shown, the holding member 47 has a pressurizing portion 471 which is directly pressed against the surface of the heating roller 41 without sandwiching the elastic member 46 at the outlet of the fixing nip N. The pressurizing portion 471 has a cross-sectional shape that is a substantially flat shape formed by bending the outlet side end of the fixing nip N, or a shape in which the outlet of the fixing nip N is bent into a convex shape toward the heating roller 41 side.

[0098] like Figure 4 As shown, with respect to the retaining member 47, the portion marked with reference numeral 472 located on the upstream side of the fixing nip portion N relative to the pressure portion 471 is formed to imitate the outer peripheral shape of the heating roller 41 at the fixing nip portion N as an example of a fixing unit, that is, it is bent into a substantially arc shape that is concave toward the heating roller 41. Here, the portion 472 of the retaining member 47 located on the upstream side of the fixing nip portion N relative to the pressure portion 471 is not necessarily an arc shape that completely imitates the outer peripheral shape of the heating roller 41, and may also have a flat portion or a curved portion whose curvature is different from the arc of the heating roller 41. In addition, Figure 4 In the figure, the portion denoted by reference numeral 473 indicates a chamfered portion formed at an end portion along the longitudinal direction of the holding member 47. Reference numeral 474 indicates a mounting portion of a second sheet metal member (not shown) fixed to the holding member 47.

[0099] The portion of the holding member 47 marked with a reference numeral 472 located on the upstream side of the fixing nip N relative to the pressurizing portion 471 is formed as a pressurizing force regulating surface, which is an example of a holding portion that holds the elastic member 46 and regulates the pressurizing force applied to the heating roller 41. The pressurizing force regulating surface 472 is arranged at a position farther from the outer peripheral surface of the heating roller 41 than the pressurizing portion 471.

[0100] The pressure regulating surface 472 of the holding member 47 holds the elastic member 46. Figure 4 As shown, the elastic member 46 held by the holding member 47 is arranged in a substantially arc shape following the outer peripheral shape of the heating roller 41 in the fixing nip N when not pressed against the heating roller 41 .

[0101] That is, the pressure regulating surface 472 of the retaining component 47 not only performs the function of retaining the elastic component 46, but also plays the following role: by allowing local deformation of the elastic component 46 along the thickness direction, the pressure applied to the heating roller 41 is adjusted along the axial direction of the heating roller 41 or in at least one direction intersecting the axial direction.

[0102] like Figure 6 As shown, the pressure regulating surface 472 holds, for example, an elastic member 46 formed in a sheet shape with a uniform thickness, and generates a pressure on the fixing nip portion N by elastically deforming the elastic member 46 in the thickness direction. The pressure generated by the elastic deformation of the elastic member 46 basically depends on the elastic coefficient of the material constituting the elastic member 46 and the elastic deformation amount of the elastic member 46.

[0103] The pressure regulating surface 472 of the retaining member 47 can set the pressure generated by elastic deformation of the elastic member 46 to a desired state along its longitudinal direction and the direction intersecting the longitudinal direction by appropriately setting the shape along its longitudinal direction and the direction intersecting the longitudinal direction.

[0104] The pressure regulating surface 472 of the holding member 47 may be a curved surface or a curved surface including a flat surface in part. In addition, the pressure regulating surface 472 of the holding member 47 may be a surface including at least one of concavities and convexities, slits, and holes.

[0105] like Figure 7As shown, a plurality of small recesses 475, 475, ..., for example, having a rectangular or circular planar shape, are provided on the pressure regulating surface 472 of the holding member 47. The recesses 475, 475, ... are formed by holes or through holes that are recessed from the pressure regulating surface 472. A plurality of recesses 475, 475, ... are arranged along the length direction of the holding member 47 and the width direction intersecting the length direction.

[0106] The recesses 475, 475, ... are arranged along the length direction of the holding member 47 in a manner that they are symmetrical to both sides with respect to the center S in the direction intersecting the conveying direction of the recording paper 5 as a reference, and the intervals thereof gradually narrow as they approach the ends. In addition, the recesses 475, 475, ... are arranged in two rows only on the entrance side of the fixing nip N in the direction intersecting the length direction of the holding member 47. The two ends of the holding member 47 in the length direction are supported by the frame of the device housing 43 (not shown) via the sheet metal member 48, so there is a tendency that the pressure applied to the heating roller 41 by the two ends is greater than that of the central portion. Therefore, the recesses 475, 475, ... of the holding member 47 are arranged in a manner that the intervals thereof gradually narrow as they approach the two ends in the length direction of the holding member 47, thereby making it possible to make the pressure applied to the two ends of the holding member 47 in the length direction smaller than that of the central portion, and as a result, the pressure applied to the holding member 47 in the length direction can be made uniform.

[0107] In addition, the arrangement of the recesses 475, 475, ... is not limited to this, and is arbitrary. By arbitrarily setting the arrangement of the recesses 475, 475, ..., the pressure generated by the deformation of the elastic member can be set with a high degree of freedom. In addition, in addition to the recesses, projections and depressions, slits, holes, etc. can also be used.

[0108] The recessed parts 475, 475, ... of the holding member 47 partially reduce the area of ​​the surface supporting the back surface of the elastic member 46 on the pressure regulating surface 472. The recessed parts 475, 475, ... can also be appropriately set in depth, and can be set in a non-contact state in which they do not contact the back surface of the elastic member 46 at all, or can be set in a contact state so that they contact when the elastic member 46 is deformed to a certain extent.

[0109] In addition, in this embodiment 1, if Figure 3 As shown, the fixing nip N where the holding member 47 holds the elastic member 46 and brings the pressure belt 42 into pressure contact with the heating roller 41 is set to have a relatively larger area than that of the conventional fixing device.

[0110] That is, the holding member 47 is configured to form a relatively large central angle θ close to about 90 degrees over the outer circumference of the heating roller 41. Figure 5As shown in FIG. 1 , the center angle θ′ is greatly reduced, and the length of the fixing nip portion N along the outer circumference of the heating roller 41 is about 8 mm. In contrast, in the fixing device 40 of the first embodiment, as shown in FIG. Figure 3 As shown in FIG. 1 , an example of the length of the fixing nip portion N along the outer circumference of the heating roller 41 is about twice as long as 15 mm.

[0111] The holding member 47 holds the elastic member 46 to form a fixing nip N that is in pressure contact with the outer peripheral surface of the heating roller 41 , and the central angle θ is preferably 45 degrees or more, and more preferably 60 degrees to 90 degrees.

[0112] When the length of the pressure belt 42 along the axial direction is set to be the same as that of the surface of the heating roller 41, the central angle θ of the fixing nip portion N formed by the holding member 47 is equivalent to the area of ​​the fixing nip portion N. When the central angle θ of the holding member 47 is twice that of the conventional one, when the total pressure of the pressure belt 42 and the heating roller 41 is set to be constant, the pressure per unit area of ​​the pressure belt 42 pressed against the heating roller 41 by the holding member 47 can be reduced to 1 / 2, and the pressure can be reduced. The reduction of the pressure of the holding member 47 also contributes to the thinning of the core rod 411 and the elastic layer 412 of the heating roller 41.

[0113] <Function of the fixing device>

[0114] In the above configuration, in the fixing device of the first embodiment, a sheet member having a uniform thickness can be used as the elastic member by the following configuration, and thus the manufacturing cost can be reduced compared to the case of using a sheet member having a non-uniform thickness.

[0115] That is, Figure 2 As shown, the fixing device 40 of this embodiment 1 has the elastic member 46 of the pressure member 45 that presses the pressure belt 42 against the surface of the heating roller 41 so that the shape of the elastic member 46 when not pressurized against the surface of the heating roller 41 is a substantially arc shape that imitates the outer peripheral shape of the heating roller 41.

[0116] Therefore, the fixing device 40 can use a sheet of highly expanded silicone foam or the like having a uniform thickness as the elastic member 46. Fig.10 and Fig.11 As shown, the elastic component 46 composed of high-foaming silicone foam or the like is different from the elastic component composed of silicone rubber or the like, has a low elastic modulus, and even when it is formed to be thin to achieve low pressure, the desired low surface pressure can be easily and with high precision by maintaining the shape of the pressure regulating surface 472 of the component 47, providing recesses 475, 475, etc. on the pressure regulating surface 472, and managing the thickness of the elastic component 46.

[0117] This can avoid an increase in the cost of the fixing device 40 due to an increase in the manufacturing cost of the elastic member 46 or the like.

[0118] Furthermore, in the above-described embodiment, the case where the invention is applied to a full-color image forming apparatus is described, but it is of course also possible to apply the invention to a black-and-white image forming apparatus in the same manner.

[0119] (Note) (((1)))

[0121] A fixing device, characterized in that:

[0122] have:

[0123] Annular band;

[0124] a fixing unit that contacts the belt to form a fixing nip; and

[0125] a pressurizing unit having a holding portion for holding an elastic member and pressurizing the belt toward the fixing unit, the holding portion being arranged inside the belt and having a shape that follows the outer peripheral shape of the fixing unit,

[0126] The elastic member is deformed so as to have a shape along the holding portion when not applying pressure to the fixing unit. (((2)))

[0128] The fixing device according to (((1))), wherein:

[0129] In the pressurizing unit, the holding portion has a curved surface shape and is formed as a pressurizing force regulating surface for regulating a pressurizing force applied to the fixing unit. (((3)))

[0131] The fixing device according to (((2))), wherein:

[0132] The pressing force regulating surface regulates the pressing force by allowing local deformation of the elastic member in the thickness direction. (((4)))

[0134] The fixing device according to (((3))), wherein:

[0135] The pressure regulating surface is composed of a surface including at least one of projections and recesses, slits, and holes. (((5)))

[0137] The fixing device according to (((1))), wherein:

[0138] The elastic member is made of a silicone foam. (((6)))

[0140] The fixing device according to (((5))), wherein:

[0141] The pressing unit is made of synthetic resin and has a pressing portion that directly presses the belt toward the fixing unit at an end portion on a downstream side in a rotation direction of the belt. (((7)))

[0143] The fixing device according to (((1))), wherein:

[0144] The fixing unit is composed of a heating roller having a heating source inside. (((8)))

[0146] The fixing device according to (((7))), wherein:

[0147] The pressing unit presses the belt toward the heating roller over all areas of the fixing nip. (((9)))

[0149] An image forming device,

[0150] have:

[0151] an image forming unit that forms an image on a recording medium; and

[0152] a fixing member that fixes the image onto the recording medium,

[0153] The image forming apparatus uses the fixing device described in any one of (((1))) to (((8))) as the fixing unit.

[0154] According to the fixing device of (((1))), a sheet member having a uniform thickness can be used as the elastic member, and thus, compared with a case where a sheet member having a non-uniform thickness is used, a reduction in manufacturing cost can be achieved.

[0155] According to the fixing device of (((2))), it is easier to adjust the pressing force to the fixing unit than in the case where the holding portion has a planar shape.

[0156] According to the fixing device of (((3))), unevenness in the pressing force can be avoided compared with a case where the pressing force regulating surface does not allow local deformation of the elastic member in the thickness direction.

[0157] According to the fixing device of (((4))), compared with the case where the pressing force adjustment surface is formed in a convex shape, the elastic member can be made thinner and the pressing force can be easily adjusted.

[0158] According to the fixing device of (((5))), the pressing force can be relatively reduced compared to a case where the elastic member is formed of a silicone foam having a supporting member.

[0159] According to the fixing device of (((6))), compared with a case where the pressure unit does not have a pressing portion, it is possible to achieve maintenance of fixing performance and improvement of recording medium peeling performance.

[0160] According to the fixing device of (((7))), the nip region can be enlarged compared to a case where the fixing unit is composed of a part other than the heating roller.

[0161] According to the fixing device of (((8))), the area of ​​the fixing nip portion can be increased compared to a case where the pressing unit presses the belt against the heating roller only in a part of the fixing nip portion.

[0162] According to the image forming apparatus of (((9))), cost reduction can be achieved compared to a case where the fixing device described in any one of (((1))) to (((8))) is not used.

Claims

1. A fixing device, characterized in that: have: Annular band; a fixing unit that contacts the belt to form a fixing nip; and a pressurizing unit having a holding portion for holding an elastic member and pressurizing the belt toward the fixing unit, the holding portion being arranged inside the belt and having a shape that follows the outer peripheral shape of the fixing unit, The elastic member is deformed so as to have a shape along the holding portion when not applying pressure to the fixing unit.

2. The fixing device according to claim 1, wherein: In the pressurizing unit, the holding portion has a curved surface shape and is formed as a pressurizing force regulating surface for regulating a pressurizing force applied to the fixing unit.

3. The fixing device according to claim 2, wherein: The pressing force regulating surface regulates the pressing force by allowing local deformation of the elastic member in the thickness direction.

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

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

6. The fixing device according to claim 5, wherein: The pressing unit is made of synthetic resin and has a pressing portion that directly presses the belt toward the fixing unit at an end portion on a downstream side in a rotation direction of the belt.

7. The fixing device according to claim 1, wherein: The fixing unit is composed of a heating roller having a heating source inside.

8. The fixing device according to claim 7, wherein: The pressing unit presses the belt toward the heating roller over all areas of the fixing nip.

9. An image forming device, characterized in that: have: an image forming unit that forms an image on a recording medium; and a fixing member that fixes the image onto the recording medium, The image forming apparatus uses the fixing device according to any one of claims 1 to 8 as the fixing unit.

Images