JP7124457B2 - Fixing device, manufacturing method of fixing device, and image forming apparatus - Google Patents

Description

The present invention relates to a fixing device, a method for manufacturing a fixing device, and an image forming apparatus.

For example, International Publication No. 2016/104759 (hereinafter referred to as “Patent Document 1”) discloses a heat transport structure including a plurality of graphite sheets and an adhesive layer that bonds the graphite sheets together. there is The heat-transporting structure includes a fixed portion in which an adhesive layer is arranged between the graphite sheets adjacent to each other in the stacking direction of the plurality of graphite sheets, and an adhesive layer between the graphite sheets adjacent to each other in the stacking direction. and a heat transfer part arranged so as to face each other with a gap therebetween.

WO2016/104759

2. Description of the Related Art A fixing device that heats and presses a recording medium such as a sheet of paper with a fixing belt to fix a toner image on the recording medium is known. In such a fixing device, when small size paper such as A6 or A5 is continuously passed through the fixing device, the heat transfer from the fixing belt to the paper does not progress in the paper non-passing area of the fixing belt. For this reason, a phenomenon occurs in which the temperature of the fixing belt rises locally, which may cause variations in the fixability of the toner image and impair the uniformity of the image quality.

On the other hand, in order to promote heat transfer from the non-sheet-passing area, it is conceivable to arrange a plurality of graphite sheets to improve the heat uniformity of the fixing belt. When a plurality of graphite sheets are integrated with an adhesive such as a double-sided tape, damage to each graphite sheet is suppressed and handling is facilitated, which is preferable.

However, due to the heat generated by the driving of the fixing device, the adhesive volatilizes to generate gas, and the adhesive thermally shrinks, causing the graphite sheet to peel off. There is a concern that it will be difficult to ensure heat conductivity.

In addition, since the thermal conductivity of the adhesive is smaller than that of the graphite sheet, that is, the adhesive acts as a thermal resistance, the graphite sheet is arranged on the farthest side of the plurality of graphite sheets from the fixing belt. The amount of heat transferred to the sheet is reduced. Therefore, the amount of heat transferred in the surface direction within the sheet is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device capable of ensuring high heat conductivity due to a graphite sheet, a method for manufacturing the fixing device, and an image forming apparatus having such a fixing device.

A fixing device according to the present invention includes an endless fixing belt, a heat source for heating the fixing belt, a pad member disposed on the inner peripheral side of the fixing belt, and a pad member facing the pad member via the fixing belt. A pressure rotating member arranged to rotate while pressing the fixing belt against the pad member; a plurality of graphite sheets laminated between the pad member and the fixing belt; A holder for holding the plurality of graphite sheets together so that the mating graphite sheets are in contact with each other.

In this fixing device, a plurality of graphite sheets are integrally held by a holder, so that the graphite sheets adjacent to each other in the stacking direction come into contact with each other, so that high heat conductivity can be secured by the graphite sheets.

Further preferably, the fixing device further includes a fixing portion provided integrally with the holder for fixing the plurality of graphite sheets to the pad member.

In this way, the operation of fixing the plurality of graphite sheets to the pad member can be facilitated.

Further, preferably, the holder is configured to hold the plurality of graphite sheets over the full width of the pressure rotating member in the axial direction.

By doing so, the stress generated in the graphite sheet due to the holding by the holder can be distributed over the axial direction of the pressurizing rotary member. As a result, breakage of the graphite sheet can be suppressed.

Also preferably, the holder is made of an elastic body that biases the plurality of graphite sheets from both sides in the stacking direction.

By doing so, it is possible to hold a plurality of graphite sheets integrally with a simple structure.

Also preferably, a fixing nip portion is formed between the fixing belt and the pressure rotating member. The holder is provided upstream of the fixing nip portion in the passage direction of the recording medium.

In this way, the sheet closest to the fixing belt among the plurality of graphite sheets is less likely to accompany the fixing belt. As a result, it is possible to suppress the occurrence of wrinkles on the sheet.

Also preferably, a fixing nip portion is formed between the fixing belt and the pressure rotating member. The plurality of graphite sheets has overhanging portions that overhang from the holder on the side opposite to the fixing nip portion with respect to the holder.

In this way, the heat transfer area of each graphite sheet is increased by the amount of the projecting portion, so that the graphite sheet can be heated uniformly.

Further preferably, the pad member is provided with a recess. The fixed part has a protrusion that engages with the recess.

In this way, each graphite sheet is effectively fixed to the pad member via the retainer due to the engagement of the projections and recesses.

Also preferably, a fixing nip portion is formed between the fixing belt and the pressure rotating member. The holder and the fixing portion are provided at a portion of the pad member separated from the trajectory of the recording medium passing between the fixing belt and the pressure rotating member.

This prevents the recording medium passing through the fixing nip portion from interfering with the holder and the fixing portion.

More preferably, the holder and the fixing portion are provided behind the fixing nip portion with the pad member interposed therebetween.

In this way, the above effect can be obtained more reliably.
A method for manufacturing a fixing device according to the present invention comprises a step of integrating a plurality of graphite sheets by a holding fixture, and a step of integrating a plurality of graphite sheets by a fixing portion, after which the plurality of graphite sheets are integrated by a fixing portion. to the pad member.

In this fixing device manufacturing method, a fixing device capable of ensuring high heat conductivity due to the graphite sheet is easily manufactured.

An image forming apparatus according to the present invention includes any one of the fixing devices described above.
According to the image forming apparatus configured in this way, it is possible to suppress the occurrence of variations in the fixability of the toner image by ensuring high heat conductivity due to the graphite sheet. Thereby, uniformity of image quality can be improved.

As described above, according to the present invention, there are provided a fixing device capable of ensuring high heat conductivity due to a graphite sheet, a method for manufacturing this fixing device, and an image forming apparatus equipped with such a fixing device. can provide.

1 is a diagram schematically showing the overall configuration of an image forming apparatus according to a first embodiment of the invention; FIG. 2 is a diagram showing a fixing device of the image forming apparatus shown in FIG. 1; FIG. It is a perspective view which shows roughly a pad member, a holder, and a fixing|fixed part. FIG. 4 is a front view schematically showing each graphite sheet, holders and fixtures; FIG. 5 is a plan view of FIG. 4; 3 is a diagram for explaining how heat is transmitted in the fixing device in FIG. 2; FIG. FIG. 5 is a diagram schematically explaining the amount of heat transfer in the thickness direction when an adhesive layer is interposed in the entire area between graphite sheets (comparative example). FIG. 5 is a diagram schematically illustrating the amount of heat transferred in the axial direction when an adhesive layer is interposed in the entire area between graphite sheets (comparative example). 8 is an image before use of the comparative example shown in FIG. 7; Figure 8 is an image after use of the comparative example shown in Figure 7; It is a perspective view which shows the modification of a fixing|fixed part. It is a figure which shows the relationship between the modification of a fixing|fixed part, and a pad member. It is a figure which shows the relationship between a fixing|fixed part, a fixing member, and a pad member. FIG. 8 is a plan view schematically showing a graphite sheet and a holder of a fixing device according to a second embodiment of the invention; 15 is a front view showing a state in which the graphite sheet and the holder shown in FIG. 14 are fixed to the pad member by the fixing portion; FIG. FIG. 11 is a front view schematically showing a holder of a fixing device according to a third embodiment of the invention; FIG. 17 is a plan view of FIG. 16; FIG. 17 is a front view showing a modification of the holder shown in FIG. 16; FIG. 19 is a plan view of FIG. 18; FIG. 11 is a front view schematically showing a holder of a fixing device according to a fourth embodiment of the invention; FIG. 21 is a plan view of FIG. 20; FIG. 11 is a front view schematically showing a holder of a fixing device according to a fifth embodiment of the invention;

An embodiment of the present invention will be described with reference to the drawings. In the drawings referred to below, the same or corresponding members are given the same numbers.

(First embodiment)
FIG. 1 is a diagram schematically showing the overall configuration of an image forming apparatus according to the first embodiment of the invention. This image forming apparatus 1 is an intermediate transfer type color image forming apparatus using an electrophotographic process technology. The image forming apparatus 1 primarily transfers each color toner image of Y (yellow), M (magenta), C (cyan), and K (black) formed on the photosensitive drum 413 onto the intermediate transfer belt 21 . The image forming apparatus 1 superimposes the toner images of four colors on the intermediate transfer belt 21, and then secondary-transfers them onto the conveyed recording medium to form an image. The recording medium is plain paper, for example.

The image forming apparatus 1 employs a tandem system. In the tandem system, the photosensitive drums 413 corresponding to the four colors of YMCK are arranged along the running direction of the intermediate transfer belt 21 (the direction indicated by the arrow A in FIG. 1). In the tandem method, four-color toner images of YMCK are sequentially transferred onto the intermediate transfer belt 21 in one procedure.

The image forming apparatus 1 has an image reading section 10 , an image processing section 30 , an image forming section 40 , a conveying section 50 and a fixing device 60 .

The image reading unit 10 has an automatic document feeder 11 called an ADF (Auto Document Feeder) and a document image scanning device 12 (scanner). The automatic document feeder 11 transports the document J placed on the document tray by the transport mechanism and sends it to the document image scanning device 12 . The automatic document feeder 11 makes it possible to continuously read images (including both sides) of a large number of documents J placed on the document tray at once.

The document image scanning device 12 optically scans the document conveyed from the automatic document feeder 11 onto the contact glass or the document placed on the contact glass. The document image scanning device 12 forms an image of light reflected from the document on the light receiving surface of a CCD (Charge Coupled Device) sensor 12a to read the document image. The image reading unit 10 generates input image data based on the result of reading by the document image scanning device 12 . Predetermined image processing is performed on the input image data in the image processing section 30 .

The image processing section 30 has a circuit or the like for performing digital image processing on the input image data generated by the image reading section 10 in accordance with initial settings or user settings. For example, the image processing unit 30 performs tone correction based on tone correction data (tone correction table).

The image processing unit 30 performs various types of correction processing such as color correction, shading correction, compression processing, etc., on the input image data, in addition to tone correction. The image forming section 40 is controlled based on the image data subjected to these processes.

The image forming section 40 has image forming units 41 Y, 41 M, 41 C, and 41 K, and an intermediate transfer unit 42 . The image forming units 41Y, 41M, 41C, and 41K and the intermediate transfer unit 42 form toners of Y, M, C, and K components based on the image data processed by the image processing section 30. to form an image by

Image forming units 41Y, 41M, 41C, and 41K have the same configuration. For convenience of illustration and description, common constituent elements are denoted by the same reference numerals, and Y, M, C, and K are added to the reference numerals to distinguish them. In FIG. 1, only the components of the image forming unit 41Y for the Y component are denoted by reference numerals, and the components of the other image forming units 41M, 41C, and 41K are omitted.

The image forming unit 41 has an exposure device 411 , a developing device 412 , a photosensitive drum 413 , a charging device 414 and a drum cleaning device 415 . The photoreceptor drum 413 is a negatively charged organic photoreceptor (OPC: Organic Photo-conductor) having an aluminum conductive cylindrical body (aluminum base tube). The drum diameter of the photosensitive drum 413 is, for example, 80 [mm]. An undercoat layer (UCL), a charge generation layer (CGL), and a charge transport layer (CTL) are sequentially laminated on the outer peripheral surface of the photosensitive drum 413 . The photoreceptor drum 413 rotates when power is transmitted from a drive motor (not shown).

The charge generating layer is an organic semiconductor comprising a charge generating material (eg phthalocyanine pigment) dispersed in a resin binder (eg polycarbonate). The charge generating layer is exposed by exposure device 411 to generate a pair of positive and negative charges.

The charge-transporting layer comprises a hole-transporting material (electron-donating nitrogen-containing compound) dispersed in a resin binder (eg, polycarbonate). The charge transport layer transports positive charges generated in the charge generation layer to the surface of the charge transport layer.

The charging device 414 uniformly charges the surface of the photosensitive drum 413 having photoconductivity to a negative polarity. The exposure device 411 is composed of, for example, a semiconductor laser. The exposure device 411 irradiates the photosensitive drum 413 with laser light corresponding to the image of each color component.

A positive charge is generated in the charge generation layer of the photoreceptor drum 413 and transported to the surface of the charge transport layer, thereby neutralizing the surface charge (negative charge) of the photoreceptor drum 413 . An electrostatic latent image of each color component is formed on the surface of the photosensitive drum 413 due to a potential difference with the surroundings.

The developing device 412 is a two-component developing device. The developing device 412 visualizes the electrostatic latent image by attaching toner of each color component to the surface of the photosensitive drum 413 to form a toner image.

The drum cleaning device 415 has a drum cleaning blade that slides on the surface of the photosensitive drum 413 . A drum cleaning device 415 removes toner remaining on the surface of the photosensitive drum 413 after the primary transfer.

The intermediate transfer unit 42 has an intermediate transfer belt 21 , a primary transfer roller 422 , a plurality of support rollers 423 , a secondary transfer section 23 and a belt cleaning device 426 . The intermediate transfer belt 21 is endless. The intermediate transfer belt 21 is stretched in a loop shape around a plurality of support rollers 423 . At least one of the plurality of supporting rollers 423 is configured as a driving roller, and the others are configured as driven rollers.

For example, it is preferable that the roller 423A arranged downstream in the traveling direction of the intermediate transfer belt 21 from the primary transfer roller 422K for the K component is the drive roller. This makes it easier to keep the running speed of the intermediate transfer belt 21 constant. As the roller 423A rotates, the intermediate transfer belt 21 runs in the arrow A direction at a constant speed.

The intermediate transfer belt 21 has conductivity and elasticity. Intermediate transfer belt 21 has a high-resistivity layer having a volume resistivity of, for example, 8 to 11 [logΩ·cm] on its surface. The material, thickness and hardness of the intermediate transfer belt 21 are not limited as long as they have conductivity and elasticity.

The primary transfer roller 422 is arranged on the inner circumferential surface side of the intermediate transfer belt 21 . A primary transfer roller 422 is arranged to face the photosensitive drum 413 . The primary transfer roller 422 is pressed against the photosensitive drum 413 with the intermediate transfer belt 21 interposed therebetween. Thereby, the primary transfer nip portion N1 is formed.

When the intermediate transfer belt 21 passes through the primary transfer nip portion N1, the toner images on the photosensitive drum 413 are sequentially superposed on the intermediate transfer belt 21 and primarily transferred. Specifically, a primary transfer bias is applied to the primary transfer roller 422 to impart an electric charge having a polarity opposite to that of the toner to the back side of the intermediate transfer belt 21 (the side in contact with the primary transfer roller 422). Thereby, the toner image is electrostatically transferred to the intermediate transfer belt 21 .

The toner image electrostatically transferred onto the intermediate transfer belt 21 is then conveyed to the secondary transfer portion 23 . When the recording medium passes through the secondary transfer portion 23, the toner image on the intermediate transfer belt 21 is secondarily transferred onto the recording medium. Specifically, a secondary transfer bias is applied to the secondary transfer roller 33 to impart an electric charge having a polarity opposite to that of the toner to the side of the recording medium that contacts the secondary transfer roller 33 . As a result, the toner image is electrostatically transferred to the recording medium.

The belt cleaning device 426 contacts the outer peripheral surface of the intermediate transfer belt 21 . A belt cleaning device 426 removes toner remaining on the surface of the intermediate transfer belt 21 after secondary transfer.

The recording medium onto which the toner image has been transferred is conveyed to the fixing device 60 after passing through the secondary transfer section 23 . The fixing device 60 heats and presses the recording medium to which the toner image has been secondarily transferred, thereby fixing the toner image to the recording medium. Details of the fixing device 60 will be described later.

The transport unit 50 transports the recording medium. The transport section 50 has a paper feed section 51 , a paper discharge section 52 and a transport path section 53 . The paper feed section 51 has paper feed tray units 51a, 51b, and 51c. The paper feed tray units 51a, 51b, and 51c store paper S (standard paper, special paper) identified based on basis weight, size, etc. for each preset type.

The paper sheets S accommodated in the paper feed tray units 51 a , 51 b , 51 c are delivered one by one from the top and transported to the transport path section 53 . The transport path portion 53 has a plurality of transport roller pairs including a registration roller pair 53a. The registration roller section in which the registration roller pair 53a is arranged corrects the inclination and deviation of the recording medium. The recording medium is transported to the secondary transfer portion 23 through the transport path portion 53 . In the secondary transfer section 23 , the toner images on the intermediate transfer belt 21 are collectively secondary-transferred onto one surface of the paper S, and then subjected to a fixing process in the fixing device 60 .

The recording medium that has passed through the fixing device 60 is conveyed to the paper discharge section 52 . The paper ejection section 52 has a transport roller pair (paper ejection roller pair) 52a. The recording medium on which the image has been formed is discharged to the outside through the conveying roller pair 52a.

Next, the structure of the fixing device 60 will be described in detail. FIG. 2 is a diagram showing a fixing device of the image forming apparatus shown in FIG.

As shown in FIGS. 1 and 2, the fixing device 60 includes an endless fixing belt 61, a heat source 62, a pad member 63, a pressure rotating member 64, and a plurality of laminated graphite sheets 65. , a holder 66 , a fixing portion 67 , a sliding sheet 69 , and a support member 72 . The fixing device 60 is of a direct heating (heating rollerless) type in which heat generated from a heat source 62 is directly transferred to the fixing belt 61 . It should be noted that FIG. 2 shows the plurality of graphite sheets 65 as a single layer.

Heat source 62 is, for example, a halogen heater. The heat source 62 is arranged inside the fixing belt 61 . The heat source 62 heats the fixing belt 61 from the inside by emitting light. The fixing belt 61 is held by holding members at both ends. A temperature sensor (not shown) is provided on the outer peripheral side of the fixing belt 61, and the heat source 62 is set so as to achieve a predetermined temperature target (for example, a fixing temperature within the range of 150° C. to 180° C.). controlled.

The heat source 62 has a long heater 62A and a short heater 62B. The length (heat source length) of the long heater 62A in the axial direction of the pressure rotating member 64 is greater than the length (heat source length) of the short heater 62B in the axial direction of the pressure rotating member 64. The heat source 62 is controlled so that the long heater 62A generates heat in the process of fixing large size paper, and the short heater 62B generates heat in the process of fixing small size paper (for example, A6 and A5 size paper). .

The pad member 63 is arranged on the inner peripheral side of the fixing belt 61 . The pad member 63 is made of a resin material. Pad member 63 is made of, for example, PPS (polyphenylene sulfide). Details of the structure of the pad member 63 will be described later.

The pressure rotating member 64 is, for example, a pressure roller. The pressurizing rotating member 64 has an elastic layer made of silicone rubber on its outer peripheral surface. The pressure rotating member 64 is arranged on the outer peripheral side of the fixing belt 61 . The pressure rotating member 64 is arranged to face the pad member 63 with the fixing belt 61 interposed therebetween. The pressurizing rotating member 64 is driven to rotate by a driving source (not shown). Specifically, the pressure rotating member 64 presses the fixing belt 61 toward the pad member 63 so that the fixing belt 61 moves relative to the pad member 63 while the fixing belt 61 is pressed against the pad member 63 . rotate while As a result, a fixing nip portion N is formed between the fixing belt 61 and the pressure rotating member 64, as shown in FIG. The fixing belt 61 and the pressure rotating member 64 are pressed against each other at the fixing nip portion N. As shown in FIG. The pressure rotating member 64 conveys the recording medium 110 by rotating the fixing belt 61 .

The support member 72 is arranged on the inner peripheral side of the fixing belt 61 . The support member 72 has a shape extending in the axial direction of the pressure rotating member 64 . The support member 72 supports the pad member 63 . As shown in FIG. 1, the support member 72 may be provided with a reflective member 74 . The reflecting member 74 is provided at a portion of the supporting member 72 facing the heat source 62 . Reflecting member 74 is configured to reflect radiant heat from heat source 62 toward fixing belt 61 .

Here, the pad member 63 will be described in detail. FIG. 3 is a perspective view schematically showing a pad member, a retainer and a fixing portion; As shown in FIGS. 2 and 3, the pad member 63 has a curved first surface 63A, a flat second surface 63B, a flat third surface 63C, a flat fourth surface 63D, and a flat surface. It has a fifth surface 63E and a flat sixth surface 63F.

The first surface 63A is the surface forming the fixing nip portion N. As shown in FIG. The first surface 63A has a curved shape that is convex toward the second surface 63B. The second surface 63B is the surface of the pad member 63 opposite to the first surface 63A. The third surface 63C connects the first surface 63A and the second surface 63B on the upstream side in the passage direction of the recording medium 110 . A boundary portion between the third surface 63C and the first surface 63A is curved. The fourth surface 63D connects the first surface 63A and the second surface 63B on the downstream side in the passage direction of the recording medium 110 . A boundary portion between the fourth surface 63D and the first surface 63A is formed at an acute angle. The area of the fourth surface 63D is larger than the area of the third surface 63C. The fifth surface 63E is connected to one end of each of the first to fourth surfaces 63A to 63D in the axial direction of the pressure rotating member 64. As shown in FIG. The sixth surface 63F is connected to the other end of each of the first to fourth surfaces 63A to 63D in the axial direction of the pressure rotating member 64 .

The second surface 63B is provided with a recess 63b having a shape recessed toward the first surface 63A. The concave portion 63b has a shape extending along the axial direction of the pressure rotating member 64. As shown in FIG. Specifically, the concave portion 63b has a shape extending from one end (fifth surface 63E) of the pad member 63 to the other end (sixth surface 63F) in the axial direction of the pressure rotating member 64 .

As shown in FIG. 3, the recess 63b has a pair of opposing walls 63b1 and an upper wall 63b2. The pair of opposing wall portions 63b1 are opposed to each other in the passage direction of the recording medium 110 . Each opposing wall portion 63b1 has a shape rising from the second surface 63B toward the first surface 63A. Each opposing wall portion 63b1 is formed flat. The upper wall portion 63b2 connects the ends of the opposing wall portions 63b1 on the first surface 63A side (the upper side in FIG. 3). The upper wall portion 63b2 is formed flat. The dimension of the upper wall portion 63b2 in the passing direction of the recording medium 110 is larger than the dimension of each opposing wall portion 63b1 in the direction orthogonal to the second surface 63B. However, the shape of the recess 63b is not limited to this.

Each graphite sheet 65 is a sheet made of graphite having a high thermal conductivity compared to aluminum, copper, or the like. Each graphite sheet 65 has a characteristic that the smaller the thickness (sheet thickness), the higher the thermal conductivity in the surface direction. Each graphite sheet 65 is arranged between the pad member 63 and the fixing belt 61 . Each graphite sheet 65 is a member that promotes heat transfer from a non-paper-passing area (relatively high-temperature area) of the area facing the heat source 62 in the fixing belt 61 . In other words, each graphite sheet 65 is a member for improving the heat uniformity of the fixing belt 61 . As shown in FIG. 2, each graphite sheet 65 has a shape that covers the first surface 63A of the pad member 63. As shown in FIG. Each graphite sheet 65 is fixed to the pad member 63 .

FIG. 4 is a front view schematically showing each graphite sheet, holder and fixture. As shown in FIG. 4, the holder 66 integrally holds a plurality of graphite sheets 65 so that the graphite sheets 65 adjacent to each other in the stacking direction of the plurality of graphite sheets 65 are in contact with each other. The holder 66 is made of a heat-resistant material such as resin, metal, or ceramic.

5 is a plan view of FIG. 4. FIG. As shown in FIG. 5, the holder 66 is configured to hold a plurality of graphite sheets 65 across the entire width of the pressure rotating member 64 in the axial direction (vertical direction in FIG. 5). Specifically, the holder 66 holds the ends of the plurality of graphite sheets 65 on the upstream side (the right side in FIG. 5) in the passage direction of the recording medium 110 over the entire width of the pressure rotating member 64 in the axial direction. is doing. In this embodiment, as shown in FIG. 3, the holder 66 is connected to a holder main body 661 that opens in one direction (upward in FIG. 3) and the holder main body 661 so as to close the opening. and a lid portion 662 .

As shown in FIGS. 3 and 5, the width of the holder body 661 in the direction parallel to the axial direction of the pressure rotating member 64 (vertical direction in FIG. 5) is greater than the width of each graphite sheet 65 in the same direction. set large. The lid portion 662 is connected to the holder main body 661 by a fastening member 80 such as a screw. By connecting the lid portion 662 to the holder main body 661 by the fastening member 80, the holder main body 661 and the lid portion 662 sandwich the plurality of graphite sheets 65 from both sides in the stacking direction. Thereby, the displacement of each graphite sheet 65 with respect to the holder 66 is restricted.

The fixing portion 67 is provided integrally with the holder 66 . The fixing portion 67 fixes the plurality of graphite sheets 65 to the pad member 63 via the holders 66 . The fixed portion 67 is fixed to a portion of the pad member 63 that positions the holder 66 upstream of the fixing nip portion N in the passage direction of the recording medium 110 . The fixed portion 67 is fixed to a portion of the pad member 63 that separates the holder 66 and the fixed portion 67 from the trajectory of the recording medium 110 . In this embodiment, the fixing portion 67 is fixed to the recess 63b of the pad member 63. As shown in FIG. The fixed portion 67 is configured by a convex portion having a shape that corresponds to and engages (is press-fitted into) the concave portion 63b. Specifically, as shown in FIG. 3 , the fixing portion 67 has a shape that continuously extends along the direction parallel to the width direction of the holder body 661 . 2, the holder 66 and the fixing portion 67 are positioned upstream of the fixing nip portion N in the passage direction of the recording medium 110. and is provided at a position separated from the trajectory of the recording medium 110 passing through the fixing nip portion N. FIG. The fixing portion 67 is fixed to the concave portion 63b after the plurality of graphite sheets 65 are held by the holder 66. As shown in FIG. The end of the plurality of graphite sheets 65 on the side opposite to the side held by the holder 66 (left side in FIG. 4) may be adhered to the fourth surface 63D of the pad member 63 or the like.

A sliding sheet 69 is provided between each graphite sheet 65 and the fixing belt 61 . Sliding sheet 69 is provided to reduce the frictional force between each graphite sheet 65 and fixing belt 61 . The sliding sheet 69 is fixed to the pad member 63 .

A specific example of the fixing device 60 will now be described. Considering heat resistance, strength and surface smoothness, the fixing belt 61 is composed of a 60 μm thick PI substrate (base material), a 200 μm thick rubber layer (elastic layer), and a 30 μm thick PFA tube (releasing layer). ) and three layers (diameter 25 mm).

The pressurizing rotating member 64 consists of a pressurizing roller with a diameter of 25 mm. The pressurizing rotary member 64 has a rubber layer (thickness 3 mm) disposed on its outer peripheral surface and a PFA tube (release layer) having a thickness of 30 μm.

The heat source 62 consists of a halogen heater with a tube diameter of 5.5 mm. The heat source 62 has a long heater that emits light from the entire width and a short heater that emits light from the central portion.

The pad member 63 is made of liquid crystal polymer. The support member 72 is made of a SECC plate (thickness: 2 mm). The reflecting member 74 is made of a highly reflective sheet.

FIG. 6 is a diagram for explaining how heat is transmitted in the fixing device in FIG. FIG. 6 schematically shows an endless fixing belt 61, a heat source 62, a support member 72, a pad member 63, and a plurality of graphite sheets 65 arranged inside the fixing belt 61 with both ends thereof. are being taught. DR1 indicates the rotational axis direction of the pressure rotating member 64, and is hereinafter referred to as "axial direction DR1".

Referring to FIG. 6, heat source 62 has a length H (hereinafter referred to as "heat source length H") in axial direction DR1. The heat source 62 heats the fixing belt 61 from its inner peripheral side over the heat source length H (arrow Z in FIG. 6).

The width of a recording medium such as paper passing through the fixing nip portion N is defined as D (hereinafter referred to as "paper width D"). A dotted line shown in FIG. 6 is an area through which the paper passes through the fixing nip portion N (hereinafter referred to as a "paper passing area"). Since the heat of the fixing belt 61 is transferred to the paper in the paper passing area, the temperature of the fixing belt 61 (area F in FIG. 6) in the paper passing area rises significantly even if the paper is continuously passed. do not do.

However, the heat source length H must be greater than the paper width D so that the entire maximum paper width can be heated during the fixing process. In this case, a region of the fixing belt 61 that is heated over the heat source length H (hereinafter referred to as a “heating region”) and is also a non-paper-passing region (hereinafter referred to as an “edge region R”). ) will exist. Even if the temperature of the end region R rises significantly due to continuous paper feeding, the heat is not transferred to the paper, so the temperature of the end region R rises significantly. Such a temperature rise in the end area R is likely to occur when printing on a sheet of small width, such as A5 or A6.

In the fixing device 60 of the present embodiment, a highly thermally conductive graphite sheet 65 is arranged between the pad member 63 and the fixing belt 61 in order to suppress the temperature rise in the end region R.

The heat of the fixing belt 61 in the end region R is transferred to the graphite sheet 65 (arrow C in FIG. 6). The heat transferred to the graphite sheet 65 diffuses toward the outside of the region F of the graphite sheet 65 in the axial direction DR1 (arrow E in FIG. 6). The diffused heat is transmitted to the low-temperature portion I (the non-sheet-passing, non-heating region) of the fixing belt 61 (arrow G in FIG. 6).

Since the heat transfer function of the graphite sheet 65 is exhibited in this manner, the heat in the end region R is dispersed to the low temperature portion I of the fixing belt 61, and as a result, the fixing belt 61 has a uniform heat effect. be.

When the laminated type graphite sheets 65 shown in FIGS. 3 and 4 are used, each graphite sheet 65 has a characteristic that the smaller the thickness thereof, the higher the thermal conductivity in the plane direction. High thermal conductivity can be obtained in the graphite sheet 65 while keeping the thickness (heat capacity) of the graphite sheet 65 small. As a result, the heat soaking effect of the fixing belt 61 by the graphite sheet 65 can be enhanced.

FIG. 7 is a diagram schematically explaining the amount of heat transferred in the thickness direction when an adhesive layer is interposed in the entire area between graphite sheets (comparative example). FIG. 8 is a diagram schematically explaining the amount of heat transferred in the axial direction when an adhesive layer is interposed in the entire area between graphite sheets (comparative example). As shown in FIG. 7, in the comparative example, since the adhesive layer 165 has a thermal resistance (because the heat transfer coefficient of the adhesive layer 165 is smaller than that of the graphite sheet 65), the heat source 62 and the pad member 63, the amount of heat transferred to the pad member 63 through the graphite sheet 65 (the amount of heat transferred in the thickness direction of the graphite sheet 65) gradually decreases. Therefore, as shown in FIG. 8, the amount of heat transferred in the axial direction (horizontal direction in FIG. 8) of the pressure rotating member 64 gradually decreases as the pad member 63 is approached. As a result, the graphite sheet 65 does not exhibit a sufficient heat soaking effect.

FIG. 9 is an image before use of the comparative example shown in FIG. FIG. 10 is an image after use of the comparative example shown in FIG. As shown in FIGS. 9 and 10, it can be seen that there are gaps between the graphite sheets after use (heat transfer is reduced) compared to before use. This is due to volatilization and heat shrinkage of the adhesive.

In contrast, in the present embodiment, the ends of the plurality of graphite sheets 65 on the upstream side in the passage direction of the recording medium 110 are held (nipped) by the holder 66 and are in contact with each other. Moreover, the portions of the plurality of graphite sheets 65 that overlap the fixing nip portion N in the stacking direction come into contact with each other along the first surface 63A of the pad member 63 by being pressed by the pressure rotating member 64. there is Therefore, good heat conductivity of the graphite sheet 65 is ensured.

Furthermore, unlike the conventional case in which a plurality of graphite sheets are bonded together with an adhesive, peeling of the graphite sheet 65 due to gas generation from the adhesive can be avoided. In addition, since no volatile components are generated from the adhesive, it is also environmentally friendly.

Further, since the holder 66 is configured to hold the plurality of graphite sheets 65 over the entire width of the pressure rotating member 64 in the axial direction, one of the graphite sheets 65 is held by the holder 66 . The stress generated in the vicinity of the portion where the pressure is applied is distributed over the entire axial width of the pressure rotating member 64 . Therefore, breakage of the graphite sheet 65 is suppressed.

Further, since the holder 66 is provided on the upstream side of the fixing nip portion N in the passage direction of the recording medium 110 , the sheet closest to the fixing belt 61 among the plurality of graphite sheets 65 is attached to the fixing belt 61 . By being accompanied, the occurrence of wrinkles in the sheet is suppressed.

In addition, since the fixed portion 67 has a convex portion that engages with the concave portion 63b of the pad member 63, the engagement of the convex portion and the concave portion 63b allows each graphite sheet 65 to be effectively attached to the pad member via the holder 66. 63.

Further, since the holding member 66 and the fixing portion 67 are provided at a portion of the pad member 63 separated from the trajectory of the recording medium 110 passing between the fixing belt 61 and the pressure rotating member 64, the fixing nip portion N is formed. Interference of the passing recording medium 110 with the holder 66 and the fixing portion 67 is avoided. Specifically, since the fixing portion 67 is fixed to the second surface 63B of the pad member 63 having a relatively large area, the fixing portion 67 is firmly fixed to the pad member 63 .

In addition, the manufacturing method of the fixing device 60 includes a step of integrating a plurality of graphite sheets 65 with a holder 66, and a step of integrating a plurality of graphite sheets 65. and fixing the graphite sheet 65 to the pad member 63 . With this manufacturing method, the fixing device 60 capable of ensuring high heat conductivity due to the graphite sheet 65 is easily manufactured.

Note that the holder 66 and the fixing portion 67 are provided upstream of the fixing nip portion N in the passage direction of the recording medium 110 and at a position separated from the trajectory of the recording medium 110 passing through the fixing nip portion N. If so, the fixing portion 67 may be fixed to the third surface 63C of the pad member 63 instead of the recess 63b provided on the second surface 63B of the pad member 63. FIG. In this aspect, since the portion of each graphite sheet 65 sandwiched by the holder 66 (the portion having a high heat transfer rate) is positioned closer to the fixing nip portion N than in the above-described embodiment, the temperature uniformity of the fixing belt 61 is improved. is higher.

Alternatively, the fixing portion 67 may be omitted, and the holder 66 may be adhered to the pad member 63 by an adhesive member (heat-resistant double-sided tape or the like). However, when the holder 66 is fixed to the pad member 63 by the fixing portion 67 as in the above-described embodiment, heat deterioration is suppressed compared to the case where an adhesive member is used, so durability is improved. Furthermore, the occurrence of wrinkles in the graphite sheet 65 when connecting the graphite sheet 65 to the pad member 63 is suppressed.

It should be noted that the fixed portion 67 is not limited to a shape that extends continuously along the axial direction of the pressure rotating member 64 . FIG. 11 is a perspective view showing a modification of the fixing portion. As shown in FIG. 11 , the fixed portion 67 may be composed of a plurality of projections arranged with gaps along the axial direction of the pressure rotating member 64 . In this aspect, less material is used to manufacture the fixing portion 67 than in the above embodiment.

FIG. 12 is a diagram showing the relationship between a modified example of the fixing portion and the pad member. As shown in FIG. 12, the fixing portion 67 may be formed in a shape in which the dimension in the direction orthogonal to the width direction of the fixing portion 67 (left and right direction in FIG. 12) gradually decreases as the distance from the holder 66 increases. good. In this aspect, the ease of inserting the fixing portion 67 into the pad member 63 is enhanced, and the ease of assembly is improved.

FIG. 13 is a diagram showing the relationship between the fixing portion, the fixing member, and the pad member. As shown in FIG. 13 , the fixing device 60 may further include a fixing member 70 that fixes each graphite sheet 65 to the pad member 63 via a holder 66 . The fixing member 70 is fixed to the second surface 63B of the pad member 63 while passing through each graphite sheet 65 . A screw is preferably used as such a fixing member 70 . In this aspect, the holder 66 is fixed to the pad member 63 more firmly than in the above-described embodiment, thereby improving durability.

(Second embodiment)
Next, the graphite sheet 65 in the fixing device 60 of the second embodiment of the invention will be described with reference to FIGS. 14 and 15. FIG. In the second embodiment, only parts different from the first embodiment will be described, and descriptions of the same structures, functions and effects as those of the first embodiment will not be repeated.

FIG. 14 is a plan view schematically showing a graphite sheet and a holder of the fixing device according to the second embodiment of the invention. 15 is a front view showing a state in which the graphite sheet and the holder shown in FIG. 14 are fixed to the pad member by the fixing portion; FIG. As shown in FIGS. 14 and 15, each graphite sheet 65 has a projecting portion 65a projecting from the holder 66 on the side opposite to the fixing nip portion N with respect to the holder 66. As shown in FIG. That is, the projecting portion 65a extends from the holder 66 toward the side (right side in FIG. 14) of each graphite sheet 65 opposite to the side on which the portion 65b that is superimposed on the first surface 63A of the pad member 63 is located. It has a shape that pulls out.

In this aspect, the heat transfer area of each graphite sheet 65 is increased by the extension portion 65a as compared with the above-described embodiment, so that the graphite sheet 65 is improved in heat uniformity.

(Third embodiment)
Next, the holder 66 in the fixing device 60 of the third embodiment of the invention will be described with reference to FIGS. 16 and 17. FIG. In addition, in the third embodiment, only the parts different from the first embodiment will be described, and descriptions of the same structures, functions and effects as those of the first embodiment will not be repeated.

FIG. 16 is a front view schematically showing a holder of a fixing device according to the third embodiment of the invention. 17 is a plan view of FIG. 16. FIG. As shown in FIGS. 16 and 17, the holder 66 of this embodiment is made of an elastic body that clamps a plurality of graphite sheets 65 while urging them from both sides in the stacking direction. Specifically, the holder 66 includes a first wall 663 that supports the fixing portion 67, a second wall 664 that faces the first wall 663 in the stacking direction, and a second wall 664 that connects the first wall 663 and the second wall 664. 3 walls 665 . The third wall 665 connects the first wall 663 and the second wall 664 with the free end of the second wall 664 biased toward the free end of the first wall 663 . ing. 17 indicate portions of each graphite sheet 65 sandwiched between the first wall 663 and the second wall 664. As shown in FIG.

In this aspect, with a simple configuration, it is possible to integrally hold a plurality of graphite sheets 65 so that the graphite sheets 65 are in contact with each other.

18 is a front view showing a modification of the holder shown in FIG. 16; FIG. 19 is a plan view of FIG. 18. FIG. In the third embodiment, as shown in FIGS. 18 and 19, the first wall 663 and the second wall 664 sandwich the graphite sheets 65 from both sides in the stacking direction while the graphite sheets 65 are bent. It may have holding portions 663a and 664a. Each of the sandwiching portions 663a and 664a has a shape that is bent so as to protrude toward one side in the stacking direction (lower side in FIG. 18).

(Fourth embodiment)
Next, a holder 66 in a fixing device 60 according to a fourth embodiment of the invention will be described with reference to FIGS. 20 and 21. FIG. In addition, in the fourth embodiment, only the parts different from the first embodiment will be described, and descriptions of the same structures, functions and effects as those of the first embodiment will not be repeated.

FIG. 20 is a front view schematically showing a holder of a fixing device according to the fourth embodiment of the invention. 21 is a plan view of FIG. 20. FIG. As shown in FIGS. 20 and 21, the holder 66 of the present embodiment is composed of clamping members that clamp the graphite sheets 65 from both sides in the stacking direction. Specifically, the holder 66 includes a first wall 671 that supports the fixing portion 67, a second wall 672 that faces the first wall 671 in the stacking direction, and a second wall that connects the first wall 671 and the second wall 672. 3 walls 673, a clamping plate 674 that clamps each graphite sheet 65 with the first wall 671 between the first wall 671 and the second wall 672, and at least one clamp 675 that presses the clamping plate 674 toward the first wall 671. and A screw is preferably used as the at least one clamp 675 . As shown in FIG. 21, at least one clamp 675 includes a plurality of (five in this example) clamps 675 arranged along the width direction of the second wall 672 (vertical direction in FIG. 21). have.

Also in this mode, the graphite sheets 65 are integrally held so that the graphite sheets 65 are in contact with each other.

(Fifth embodiment)
Next, a holder 66 in a fixing device 60 according to a fifth embodiment of the invention will be described with reference to FIG. In addition, in the fifth embodiment, only parts different from the first embodiment will be described, and descriptions of the same structures, functions and effects as those of the first embodiment will not be repeated.

FIG. 22 is a front view schematically showing a holder of a fixing device according to the fifth embodiment of the invention. As shown in FIG. 22, the holder 66 of this embodiment includes a first wall 681 that supports the fixing portion 67, a second wall 682 that faces the first wall 681 in the stacking direction, the first wall 681 and It has a third wall 683 that connects the second walls 682, and at least one penetrating member 684 fixed to the first wall 681 and the second wall 682 while penetrating the graphite sheets 65 in the stacking direction. there is The dimension between the first wall 681 and the second wall 682 is set substantially equal to the overall thickness of the multiple graphite sheets 65 . Therefore, displacement of each graphite sheet 65 in the stacking direction between the first wall 681 and the second wall 682 is suppressed. Note that the at least one penetrating member 684 may have multiple (eg, five) penetrating members 684, similar to the multiple clamps 675 shown in FIG.

Also in this mode, the graphite sheets 65 are integrally held so that the graphite sheets 65 are in contact with each other.

It should be noted that the embodiments disclosed this time are illustrative in all respects and should not be considered restrictive. The scope of the present invention is indicated by the scope of the claims rather than the description of the above-described embodiments, and includes all modifications within the meaning and scope equivalent to the scope of the claims.

The present invention is applied to fixing devices and image forming apparatuses.

Reference Signs List 1 image forming apparatus 10 image reading section 30 image processing section 40 image forming section 50 conveying section 60 fixing device 61 fixing belt 62 heat source 63 pad member 63A first surface 63B second surface 63b Recessed portion 63b1 Opposing wall portion 63b2 Upper wall portion 64 Pressure rotating member 65 Graphite sheet 66 Holder 67 Fixed portion 69 Sliding sheet 70 Fixed member 72 Supporting member N Fixing nip portion.

Claims (10)

an endless fixing belt;
a heat source for heating the fixing belt;
a pad member arranged on the inner peripheral side of the fixing belt;
a pressure rotating member arranged at a position facing the pad member with the fixing belt interposed therebetween, and rotating while pressing the fixing belt toward the pad member;
a plurality of graphite sheets laminated between the pad member and the fixing belt;
a holder that integrally holds the plurality of graphite sheets so that the graphite sheets that are adjacent to each other in the stacking direction of the plurality of graphite sheets are in contact with each other ;
The fixing device , wherein the holder comprises an elastic body that biases the plurality of graphite sheets from both sides in the stacking direction . an endless fixing belt;
a heat source for heating the fixing belt;
a pad member arranged on the inner peripheral side of the fixing belt;
a pressure rotating member arranged at a position facing the pad member with the fixing belt interposed therebetween, and rotating while pressing the fixing belt toward the pad member;
a plurality of graphite sheets laminated between the pad member and the fixing belt;
a holder that integrally holds the plurality of graphite sheets so that the graphite sheets that are adjacent to each other in the stacking direction of the plurality of graphite sheets are in contact with each other;
A fixing nip portion is formed between the fixing belt and the pressure rotating member,
The fixing device according to claim 1, wherein the plurality of graphite sheets have projecting portions projecting from the holder on a side opposite to the fixing nip portion with respect to the holder. an endless fixing belt;
a heat source for heating the fixing belt;
a pad member arranged on the inner peripheral side of the fixing belt;
a pressure rotating member arranged at a position facing the pad member with the fixing belt interposed therebetween, and rotating while pressing the fixing belt toward the pad member;
a plurality of graphite sheets laminated between the pad member and the fixing belt;
a holder for integrally holding the plurality of graphite sheets so that the graphite sheets adjacent to each other in the stacking direction of the plurality of graphite sheets are in contact with each other;
a fixing part that is provided integrally with the holder and fixes the plurality of graphite sheets to the pad member;
The pad member is provided with a recess,
The fixing device, wherein the fixing portion has a convex portion that engages with the concave portion. an endless fixing belt;
a heat source for heating the fixing belt;
a pad member arranged on the inner peripheral side of the fixing belt;
a pressure rotating member arranged at a position facing the pad member with the fixing belt interposed therebetween, and rotating while pressing the fixing belt toward the pad member;
a plurality of graphite sheets laminated between the pad member and the fixing belt;
a holder for integrally holding the plurality of graphite sheets so that the graphite sheets adjacent to each other in the stacking direction of the plurality of graphite sheets are in contact with each other;
a fixing part that is provided integrally with the holder and fixes the plurality of graphite sheets to the pad member;
A fixing nip portion is formed between the fixing belt and the pressure rotating member,
The fixing device, wherein the holder and the fixing portion are provided at a portion of the pad member separated from a trajectory of the recording medium passing between the fixing belt and the pressure rotating member. 5. The fixing device according to claim 4 , wherein the holder and the fixing portion are provided behind the fixing nip portion with the pad member interposed therebetween. an endless fixing belt;
a heat source for heating the fixing belt;
a pad member arranged on the inner peripheral side of the fixing belt;
a pressure rotating member arranged at a position facing the pad member with the fixing belt interposed therebetween, and rotating while pressing the fixing belt toward the pad member;
a plurality of graphite sheets laminated between the pad member and the fixing belt;
a holder that integrally holds the plurality of graphite sheets so that the graphite sheets that are adjacent to each other in the stacking direction of the plurality of graphite sheets are in contact with each other;
The fixing device, wherein the holder has a shape surrounding upstream ends of the plurality of graphite sheets in the passage direction of the recording medium, and sandwiches the plurality of graphite sheets from both sides in the stacking direction. The fixing device according to any one of claims 1 to 6, wherein the holder is configured to hold the plurality of graphite sheets over the full width of the pressure rotating member in the axial direction. A fixing nip portion is formed between the fixing belt and the pressure rotating member,
The fixing device according to any one of claims 1 to 7 , wherein the holder is provided upstream of the fixing nip portion in the direction in which the recording medium passes. A method for manufacturing a fixing device according to any one of claims 3 to 5 ,
a step of integrating a plurality of the graphite sheets with the holder;
and fixing the plurality of graphite sheets to the pad member by the fixing portion after the step of integrating the plurality of graphite sheets. An image forming apparatus comprising the fixing device according to claim 1 .

Images