JP6727783B2 - Image heating device and image forming device - Google Patents

Description

The present invention relates to an image heating device and an image forming apparatus including the same. This image heating device can be used as a fixing device mounted in an image forming apparatus such as a copying machine of an electrophotographic system or a laser beam printer, for example.

BACKGROUND ART An image heating device (hereinafter, referred to as a fixing device) that heats a recording material (hereinafter, referred to as a paper) carrying a toner image has conventionally been known such as a heat roller system and a film (belt) heating system.

Patent Document 1 discloses a film heating method in which a heat conduction member is provided on the back surface of a heater to suppress so-called non-sheet-passing portion temperature rise (temperature rise in recording material non-passage portion) to improve productivity of small-size paper. A fixing device is described. The heat conducting member is a member made of a material having a higher heat conductivity than the substrate of the heater.

In a film heating type apparatus, a structure in which a protective element as a primary circuit member and a temperature detection element as a secondary circuit member are arranged in a heater is generally adopted. When the heat conducting member is provided on the back surface of the heater, the protective element and the temperature detecting element are arranged for the heat conducting member.

The protection element is connected to a primary circuit, which is a circuit that is directly connected to a commercial power supply that supplies electric power, and when the heating heater has an abnormal temperature rise, it operates due to the abnormal temperature rise, and electricity is supplied from the commercial power supply to the heating heater. Shut off. The temperature detection element is not directly connected to the primary circuit, but is connected to the secondary circuit, which is a circuit to which power is supplied from a device such as a transformer or converter in the equipment. It is used to control the input power.

Therefore, since the primary circuit and the secondary circuit coexist on the back side of the heater, it is desirable to insulate the primary circuit and the secondary circuit. In the configuration where insulation cannot be obtained between the protection element and the heat conduction member, the heat conduction member arranged on the back surface of the heater together with the protection element and the temperature detection element also has the primary circuit side where the protection element is arranged and the second time when the temperature detection element is arranged. It is desirable to secure insulation by dividing the road side.

JP, 2014-238560, A

However, in the configuration in which the heat conduction member is divided and provided on the back surface of the heater, the heat conduction member is in contact with the back surface of the heater and a region that is not in contact with the heat conduction member (distance between the divided heat conduction members). As a result, heat unevenness in the longitudinal direction occurs on the fixing film (fixing belt). In particular, if the area where the heat conductive member is not in contact is large, image defects such as uneven gloss may occur.

On the other hand, if the space between the divided heat conducting members is narrow, there is a possibility that insulation between the heat conducting member on the primary circuit side and the heat conducting member on the secondary circuit side cannot be ensured. Further, the length of the heat conducting member in the longitudinal direction changes due to thermal expansion. The length of the heat conducting member in the longitudinal direction changes depending on the temperature condition of the fixing device and the paper passing condition of the paper. In consideration of these, it is desired to install the divided heat conducting members at a predetermined distance from each other, which makes it difficult to achieve compatibility with image defects such as uneven gloss.

It is an object of the present invention to provide a film heating type image heating device in which heat conduction members are installed in a two-part (divided) manner while ensuring insulation performance between the primary circuit and the secondary circuit, while maintaining thermal uniformity. This is to suppress image defects such as uneven glossiness.

A typical configuration of the image heating apparatus according to the present invention for achieving the above object is,
A heating member having an elongated substrate, and a resistance heating element which is formed on the substrate along the longitudinal direction of the substrate and generates heat by energization;
A holding member for holding the heating member,
A first heat conduction member and a second heat conduction member, which are heat conduction members having a higher heat conductivity in the longitudinal direction than the heat conductivity of the substrate, and are sandwiched between the heating member and the holding member. A conductive member,
A protection element which is in contact with the first heat conduction member, detects an abnormal temperature rise of the resistance heating element via the first heat conduction member, and cuts off the supply of electric power to the resistance heating element;
A temperature detecting element that is in contact with the second heat conducting member and is connected to a control unit that controls the electric power applied to the resistance heating element;
An endless belt capable of rotating while the inner peripheral surface is in contact with and sliding on the surface of the heating member opposite to the side of the heat conducting member,
A rotating body that forms a nip portion with the outer surface of the belt by contacting the heating member with the belt interposed therebetween;
In the image heating device for heating while holding and conveying the recording material carrying an image in the nip portion,
The first heat-conducting member and the second heat-conducting member are arranged along the longitudinal direction at a predetermined interval, and are formed by bending the folding lines extending in the longitudinal direction. A regulation part for regulating movement in the longitudinal direction with respect to the holding member,
The regulating unit is provided at a location corresponding to the inside of the passage region of the recording material of the minimum width size that can be conveyed in said image heating apparatus Rutotomoni, each of said first heat conduction member and the second heat conducting member It is characterized in that one is arranged for each.

According to the present invention, it is possible to suppress image defects such as gloss unevenness due to heat unevenness while ensuring the insulation performance of the primary circuit and the secondary circuit.

FIG. 3 is a configuration explanatory diagram of a main part of the first embodiment. Schematic of an example of an image forming apparatus Explanatory drawing of main part of fixing device Block diagram of control system Assembly drawing to assemble the heat conduction member and the heater to the heater holder Configuration explanatory drawing of the principal part of the comparative example 1. Illustration of other configurations FIG. 3 is an explanatory diagram of a configuration of a main part of Example 2

<<Example 1>>
(Body structure of image forming apparatus)
FIG. 2 is a schematic diagram of the image forming apparatus 50 in this embodiment. The image forming apparatus 50 is an electrophotographic monochrome laser printer that directly transfers a toner image formed on the photosensitive drum 1 serving as an image carrier to a sheet-shaped recording material (hereinafter referred to as a sheet) P. .. Around the photosensitive drum 1, a charging device 2, an exposure device 3 that irradiates the photosensitive drum 1 with a laser beam B, a developing device 5, a transfer roller 10, and a photosensitive drum cleaner in order along the drum rotation direction (arrow R1 direction). 16 are arranged.

The surface of the rotating photosensitive drum 1 is negatively charged by the charger 2, and the charged surface is exposed by laser scanning by the exposure device 3. The laser beam B is modulated according to the image information, and an electrostatic latent image corresponding to the scanning exposure pattern is formed on the surface of the photosensitive drum 1 (the surface potential of the exposed portion rises). The electrostatic latent image is developed as a toner image by the developing device 5 containing black toner. The toner of this embodiment is negatively charged, and the negative toner adheres only to the electrostatic latent image portion on the photosensitive drum 1 to form a toner image on the photosensitive drum 1.

The sheet P is fed by the feed roller 4 and is conveyed by the conveying roller 6 to the transfer nip N which is the contact portion between the photosensitive drum 1 and the transfer roller 10. A transfer bias of a positive polarity, which is the reverse polarity of the toner, is applied to the transfer roller 10 from a power source (not shown), and the toner image on the photosensitive drum 1 is transferred onto the paper P at the transfer nip portion N. .. After the transfer, the transfer residual toner on the surface of the photosensitive drum 1 is removed by a photosensitive drum cleaner 16 having an elastic blade.

The sheet P carrying the toner image is conveyed and introduced into the fixing device 100 as an image heating device, and the toner image on the surface is heated and fixed. Then, it is discharged onto the tray 11 as an image-formed product.

(Outline of fixing device)
The fixing device 100 of this embodiment is a film (belt) heating type image heating device (OMF: on-demand fixing device) for the purpose of shortening the startup time and reducing power consumption.

FIG. 3A is a cross-sectional view of the main part showing the outline of the fixing device 100 in this embodiment. FIG. 3B is a schematic view of a main part in the longitudinal direction of the fixing device 100 as seen from the upstream side (sheet introduction side) of the sheet conveyance direction (recording material conveyance direction: arrow A1 direction). In FIG. 3B, the fixing film 112 and the heater holder 130 are transparent so that the states of the heater 113, which is an internal member of the fixing film 112, and the first and second heat conducting members 140 and 141 can be easily understood. Shown by state.

The fixing device 100 includes a film unit (belt unit) 101 and a pressure roller 110 as a rotating body having elasticity. The film unit 101 and the pressure roller 110 are arranged substantially in parallel, and the fixing film 112 and the pressure roller 110 of the film unit 101 form a nip portion (fixing nip) No.

The film unit 101 has a fixing film 112 that is a rotatable endless belt that is loosely fitted onto an internal member. Inside the fixing film 112, there are a heater 113 as a heating member, first and second heat conducting members 140, 141, and a heater holder 130 as a holding member for holding the heater 113 and the heat conducting members 140, 141. It is arranged. Similarly, a protective element 114 as a primary circuit member, a temperature detecting element 115 as a secondary circuit member, a stay 120 supporting the heater holder 130, and flange members 150 on one end side and the other end side are arranged.

The flange members 150 on the one end side and the other end side are fitted and fixedly installed on the one end side and the other end side of the stay 120, respectively. The fixing film 112 is located between the collar seats 150a of the flange member 150 on the one end side and the other end side.

The heater holder 130 is a holding member that fixes and holds the heating heater 113, and is preferably made of a material having a low heat capacity so as not to easily remove the heat of the heating heater 113. In this embodiment, a liquid crystal polymer (LCP) which is a heat resistant resin is used. Using. The heater holder 130 is supported by an iron stay 120 from the side opposite to the heater 113 to have strength.

One end side and the other end side of the core metal 117 of the pressure roller 110 are rotatably supported by bearings 132 with respect to the apparatus housing (not shown). The film unit 101 is installed in the apparatus casing with the internal heater 113 facing the pressure roller 110 so as to be substantially parallel to the pressure roller 110. Then, a predetermined pressing force in the direction of arrow A2 by the pressure spring 133 is applied to the flange members 150 on the one end side and the other end side, respectively. The stay 120 is pressed and urged in the direction toward the pressure roller 110 by this pressing force.

Therefore, the surface (first surface) of the heater 113 held by the heater holder 130 and a part of the surface of the heater holder 130 sandwich the fixing film 112 and the elastic layer of the pressure roller 110 with respect to the pressure roller 110. It is pressed against the elastic layer of 116. The front side of the heater 113 contacts the inner surface of the fixing film 112, and forms an inner surface nip Ni that heats the fixing film 112 from the inner surface. Then, the pressure roller 110 is pressed against the heater 113 so as to sandwich the fixing film 112, and a fixing nip (nip portion) No is formed between the outer surface of the fixing film 112 and the pressure roller 110. ..

In the pressure roller 110, the driving force of the motor (driving source) M controlled by the control unit 500 ((a) of FIG. 4) with respect to the driving gear 131 provided on the core metal 117 is a power transmission mechanism (not shown). ) Is transmitted via. As a result, the pressure roller 110 is rotationally driven at a predetermined speed in the counterclockwise direction indicated by the arrow R1 in FIG. In this embodiment, the pressure roller 110 rotates at a surface moving speed of 150 mm/sec.

As the pressure roller 110 is driven to rotate, the fixing film 112 is driven to rotate. That is, the inner peripheral surface of the fixing film 112 is in contact with the surface of the heater 113 and a part of the surface of the heater holder 130 in the fixing nip No and slides while the heater 113, the heater holder 130, and the stay 120 are outside. The surroundings are rotated in the clockwise direction of arrow R2.

The flange seats 150a of the flange members 150 on the one end side and the other end side respectively receive the end faces of the fixing film and thereby regulate the shift of the fixing film 112 in the longitudinal width direction due to the rotation. Further, the film inner surface guide portions 150b of the flange members 150 on the one end side and the other end side respectively support both ends of the fixing film 112 from the inside of the film and guide the rotation of the fixing film 112 (rotation orbit determination).

The heater 113 receives power from the primary circuit (AC circuit) 502 of the power supply circuit 501 ((a) of FIG. 4) controlled by the control unit 500, generates heat, and is rapidly heated. Then, the temperature of the heater 113 is detected by the temperature detection element 115 of the secondary circuit (DC circuit) 505. The control unit 500 controls the power supply control circuit 504 so that the temperature of the heating heater 113 is raised to a predetermined temperature and regulated based on the temperature information fed back from the temperature detecting element 115, and the power is supplied to the heating heater 113. Adjust the power. The power supply circuit 501 for supplying electric power to the heater 113 shown in FIG. 4A will be described later.

In a state where the pressure roller 110 is rotationally driven and the heater 113 is raised to a predetermined temperature and is temperature-controlled, the sheet P on which the unfixed toner image T is formed is fixed in the direction of arrow A1 in the image forming unit. It is conveyed to the nip No and introduced. The sheet P is introduced so that the image side faces the fixing film 112. Then, the paper P is nipped and conveyed at the fixing nip No and is heated and pressed by the heat of the fixing film 112 heated by the heater 113 and the nip pressure, and the unfixed toner image T is fixed on the paper P as a fixed image. It

In the apparatus according to the present embodiment, the paper P of various sizes, large and small, is passed by the so-called center reference conveyance centered on the width of the paper. In FIG. 3B, Wg is the longitudinal width of the elastic layer 116 of the pressure roller 110. X is the width of the passage area of the maximum width size sheet (large size sheet) usable (transportable) in the apparatus, that is, the maximum sheet passage width. The maximum sheet passing width X in this embodiment is a letter size width of 216 mm. Wg>X. Xm is the width of the passage area of the minimum width size paper (small size paper) usable in the apparatus, that is, the minimum paper passage width. The minimum sheet passing width Xm in this embodiment is 76 mm. The longitudinal width of the fixing film 112 is larger than Wg.

The inner surfaces on one end side and the other end side of the fixing film 112 are supported by the film inner surface guide portions 150b of the flange members 150 on the one end side and the other end side, respectively, outside the maximum sheet passing width X.

(Fixing film)
The fixing film 112 of this embodiment is a flexible, heat-resistant member that is elastic and has a thin cylindrical shape with an outer diameter of 20 mm in a substantially cylindrical shape when it is not deformed by an external force. It has a multilayer structure in the thickness direction. The layer structure of the fixing film 112 includes a base layer 126 for maintaining the strength of the film and a release layer 127 for reducing the adhesion of dirt to the surface.

The material of the base layer 126 is required to have heat resistance because it receives the heat of the heater 113. Further, since it slides on the heater 113, strength is also required. Therefore, it is preferable to use a metal such as SUS (Stainless Used Steel: stainless steel) or nickel, or a heat resistant resin such as polyimide. Since metal is stronger than resin and can be made thin, and also has high thermal conductivity, heat of the heater 113 is easily transferred to the surface of the fixing film 112. On the other hand, since resin has a smaller specific gravity than metal, it has an advantage that it has a small heat capacity and is easily heated. Further, the resin can be molded at low cost because a thin film can be molded by coating molding.

In this embodiment, a polyimide resin is used as the material of the base layer 126 of the fixing film 112, and a carbon-based filler is added to improve the thermal conductivity and strength. The thinner the base layer 126, the easier it is to transfer the heat of the heater 113 to the surface of the fixing film, but the strength is lowered, so that the thickness is preferably about 15 μm to 100 μm, and in this embodiment, it is set to 50 μm.

As a material of the release layer 127 of the fixing film 112, it is preferable to use a fluororesin such as perfluoroalkoxy resin (PFA), polytetrafluoroethylene resin (PTFE), and tetrafluoroethylene-hexafluoropropylene resin (FEP). In this embodiment, PFA, which has excellent releasability and heat resistance, is used among the fluororesins.

The release layer 127 may be formed by coating a tube, but may be formed by coating the surface with a paint. In this example, the release layer 127 was formed by a coating excellent in thin-wall molding. The thinner the release layer 127 is, the easier it is to transfer the heat of the heater 113 to the surface of the fixing film 112. However, if the release layer 127 is too thin, the durability is deteriorated.

(Pressure roller)
The pressure roller 110 of the present embodiment has an outer diameter of 20 mm, and an iron core metal 117 of 12 mm in diameter is formed with an elastic layer 116 (foamed rubber) having a thickness of 4 mm obtained by foaming silicone rubber. When the pressure roller 110 has a large heat capacity and a high thermal conductivity, the heat of the surface of the pressure roller 110 is easily absorbed inside, and the surface temperature of the pressure roller 110 is unlikely to rise. That is, a material having a low heat capacity, a low thermal conductivity, and a high heat insulating effect can shorten the rise time of the surface temperature of the pressure roller 110.

The thermal conductivity of the foamed rubber obtained by foaming the silicone rubber is 0.11 to 0.16 W/m·K, which is lower than that of the solid rubber of about 0.25 to 0.29 W/m·K. Further, the specific gravity related to the heat capacity is about 1.05 to 1.30 for the solid rubber, while it is about 0.45 to 0.85 for the foamed rubber, which is a low heat capacity. Therefore, this foamed rubber can shorten the rise time of the surface temperature of the pressure roller 110.

The smaller the outer diameter of the pressure roller 110 is, the more the heat capacity can be suppressed. In this example, the outer diameter was φ20 mm. Regarding the wall thickness of the elastic layer 116, if it is too thin, heat escapes to the metal cored bar, and therefore an appropriate thickness is required. In this embodiment, the elastic layer 116 has a thickness of 4 mm.

A release layer 118 made of perfluoroalkoxy resin (PFA) is formed on the elastic layer 116 as a toner release layer. Similar to the release layer 127 of the fixing film 112, the release layer 118 may be a tube-coated surface or a surface-coated surface. However, in this embodiment, a tube having excellent durability was used.

As the material of the release layer 118, in addition to PFA, a fluororesin such as PTFE or FEP, or a fluororubber or silicone rubber having a good releasability may be used. As for the surface hardness of the pressure roller 110, the lower the surface hardness of the fixing nip No, the lighter pressure and the wider width can be obtained, but if the surface hardness is too low, the durability is lowered. Load) was set to 40°.

(Heating heater)
The heater 113 of this embodiment is a general heater used in a film heating type image heating apparatus. That is, it is a ceramic heater having an elongated ceramic substrate and a resistance heating element that is formed along the length of the substrate and that generates heat when energized.

The configuration of the heater 113 in this embodiment will be described with reference to FIGS. 3 and 1. FIG. 1A is a schematic view of the heater 113 seen from the direction of arrow A3 in FIG. 3A (a schematic view of the surface of the heater 113).

The substrate 207 of the heater 113 is an alumina substrate having a width (short width) Wh=6 mm in the sheet transport direction A1 and a thickness H=1 mm. Two parallel resistance heating elements 201 and 202 are formed on the surface of the substrate 207 along the length of the substrate. The resistance heating elements 201 and 202 are formed by coating Ag/Pd (silver palladium) with a predetermined width and a thickness of 10 μm by screen printing. A glass is covered thereon with a thickness of 50 μm as a heating element protective layer 209. The heating element protective layer 209 is shown only in FIG. 1A and is omitted in FIGS. 1C and 1D.

In this embodiment, in the heater 113, the side on which the glass layer 209 is formed as the heating element protective layer is the first surface (front surface) on which the inner peripheral surface of the fixing film 112 contacts and slides, and the substrate on the opposite side. The surface is the second surface (back surface) with which the heat conducting member 140 contacts in the longitudinal direction.

The longitudinal width W of the resistance heating elements 201 and 202 is 218 mm, which is 1 mm longer at each end so that a letter size sheet having a width of 216 mm corresponding to the maximum sheet passing width X can be sufficiently heated in the apparatus of the present embodiment.

One end side of the two resistance heating elements 201 and 202 on the substrate 207 is connected in series via the conductor 203 and is electrically connected. Conductive electrodes 204 and 205 are provided on the other ends of the resistance heating elements 201 and 202, respectively. The resistance heating elements 201 and 202 generate heat when electricity is supplied from the electrode portions 204 and 205. The longitudinal width Wb of the substrate 207 of the heater 113 was set to 270 mm so that the resistance heating elements 201 and 202, the conductor 203, the electrode portions 204 and 205 and the heating element protective layer 209 could be accommodated.

(Power supply circuit)
The power supply circuit 501 that supplies power to the heater 113 shown in FIG. 4A will be described. The power supply circuit 501 includes a commercial power supply (commercial AC power supply) 503, a power supply control circuit (triac) 504, a protective element 114, an electrode portion 205, a resistance heating element 202, a conductor 203, a resistance heating element 201, and an electrode portion 204 in series. It has a connected primary circuit (AC circuit) 502. The power supply control circuit 503 is controlled by the control unit 500. Further, the power supply circuit 501 has a secondary circuit (DC circuit) 505 in which the temperature detection element 115 is connected to the control unit 500.

The protection element 114 is a primary circuit member that operates when the temperature of the heater 113 rises abnormally and shuts off the power supply to the primary circuit 502, that is, shuts off the power supply from the commercial power source 503 to the heater 113. For example, it is an energization cutoff member that has a switch inside such as a thermal fuse, a thermoswitch, and a thermostat, and that operates by an abnormal temperature rise of the heater 113 to cut off energization.

In the embodiment, the protection element 114 is inserted through the hole 130c provided in the heater holder 130 as shown in FIG. 4B, and a first heat conducting member to be described later on the back surface of the substrate 207 of the heater 113. It is abutted via 140. That is, the protection element 114 detects the temperature of the heater 113 via the first heat conduction member 140.

The temperature detection element 115 is a primary circuit member for controlling the temperature of the heater 113, and is, for example, a thermistor. The temperature detecting element 115 is also inserted from a hole 130d provided in the heater holder 130 and is in contact with the back surface of the substrate 207 of the heater 113 via a second heat conducting member 141 described later. That is, the temperature detecting element 115 also detects the temperature of the heater 113 via the second heat conducting member 141.

The control unit 500 controls the power supply control circuit 504 according to the detected temperature information of the temperature detection element 115, and appropriately controls the current flowing from the electrode units 204 and 205 to the resistance heating elements 201 and 202 in the power supply circuit 501. Therefore, the temperature of the heater 113 is adjusted.

The above-mentioned protection element 114 and temperature detection element 115 are both installed at a position within the width of the minimum sheet passing width Xm with respect to the heater 113 in order to detect the temperature in the sheet passing state to the apparatus. .. In addition, in order to avoid complication of the drawings, the protection element 114 and the temperature detection element 115 are omitted from the drawings other than FIGS. 3 and 4.

(Heat conduction member)
As shown in (b) to (d) of FIG. 1, on the back surface (second surface) of the heater 113, two first and second heat conduction members 140 for equalizing the temperature of the heater 113 are provided. , 141 are provided. That is, the heat conducting members 140 and 141 are divided into a first portion and a second portion at the central portion in the longitudinal direction in the conveyance region of the paper P. The first and second heat conduction members 140 and 141 are arranged side by side in the longitudinal direction of the back surface of the heater at a position substantially corresponding to the longitudinal width W of the resistance heating elements 201 and 202.

The heat-conducting members 140, 141 are members having a heat conductivity higher than that of the substrate 207 of the heater 113 at least in the direction parallel to the plane, and are placed between the heater 113 and the holder 130. Has been done.

FIG. 5 shows an assembly view (exploded perspective view) when the heat conducting members 140 and 141 and the heater 113 are assembled to the heater holder 130. The heater holder 130 is provided with a groove 130b so that the heat conducting members 140 and 141 and the heater 113 are sufficiently accommodated. After the two heat conducting members 140 and 141 are fitted into the groove 130b of the heater holder 130, the heater 113 is fitted therein.

Further, the heat conducting members 140, 141 are provided with restricting portions 140a, 141a for restricting a shift in the longitudinal direction from the heater holder 130. The restriction portions 140a and 141a of the heat conducting members 140 and 141 are formed by bending a part of the heat conducting members 140 and 141 as shown in FIG.

On the other hand, the heater holder 130 is provided with a restriction groove 130a so that the restriction portions 140a and 141a of the heat conduction members 140 and 141 are fitted therein. The heat conduction members 140, 141 and the heater holder 130 are regulated in the longitudinal direction by fitting the regulation portions 140a, 141a of the heat conduction member into the regulation grooves 130a of the heater holder 130.

As for the material of the heat conducting members 140 and 141, the higher the heat conductivity than the material of the substrate 207 of the heater 113, the more the effect of leveling the temperature of the members such as the heater 113, the fixing film 112, and the pressure roller 118. high. The heat conducting members 140 and 141 may be provided by applying a silver paste having high heat conductivity, or may be in contact with a graphite sheet or a metal plate such as an aluminum plate.

When a sheet or a metal plate is used as the heat conducting members 140 and 141, there is an advantage that the heat capacity of the heat conducting member 140 can be easily adjusted by the thickness thereof. In the present embodiment, aluminum (aluminum) plates, which have relatively high heat conduction among metals and can be installed at low cost, were used as the heat conduction members 140 and 141. As the thickness of the heat conducting members 140 and 141 is higher, the effect of leveling the temperature is higher. Therefore, as described above, in a job of continuously passing small size paper narrower than the longitudinal width W of the resistance heating elements 201 and 202. Productivity is improved.

However, since the heat capacity becomes large, the rise time of the heater 113 is delayed. Therefore, it is desirable to adjust the material and the thickness of the heat conducting member 140 by balancing the productivity of the small size sheets during continuous sheet feeding and the rising time of the heater 113.

The heat conducting members 140 and 141 of this embodiment are made of an aluminum plate having a thickness t of 0.5 mm and a width (short width) in the sheet conveying direction A1 that is the same as the short width Wh of the substrate 207 of the heater 113. I was there.

As described above, the protection element 114, which is the primary circuit member, and the temperature detection element 115, which is the secondary circuit member, are in contact with the first and second heat conducting members 140 and 141, respectively. Therefore, the first heat conduction member 140 on the protection element 114 side is treated as a primary circuit, and the second heat conduction member 141 on the temperature detection element 115 side is treated as a secondary circuit.

Therefore, in order to ensure insulation between the first heat conduction member 140 and the second heat conduction member 141, it is desirable to arrange them at a predetermined distance. FIG. 1B is a schematic view of the heater 113 and the first and second heat conducting members 140 and 141 as seen from the direction of arrow A2 in FIG. 3A (first and second heat conducting members 140). , 141 is a schematic view on the back surface side of the heater 113 in which the heaters 141 are installed. As shown in FIG. 1B, the first and second heat conducting members 140, 141 are installed (placed at a predetermined interval) apart from each other by a predetermined distance Y in the longitudinal center portion of the heater 113. There is. In this embodiment, the predetermined distance Y is 4 mm.

The longer the longitudinal widths of the first and second heat conducting members 140 and 141, the higher the effect of smoothing the heat in the longitudinal direction. However, when a paper having a large width such as a letter size is passed, the heat of the end portions is reduced. Since the heat is easily dissipated, the fixing property of the widthwise end portion of the paper having a large width may deteriorate. Therefore, it is desirable to adjust the positions of the longitudinal width end portions of the first and second heat conducting members 140 and 141 by balancing the productivity of the small size sheet and the fixability of the end portion in the width direction of the large size sheet.

In this embodiment, the entire longitudinal width (positions on one end side and the other end side) of the first and second heat conducting members 140, 141 is made equal to the longitudinal width W of the resistance heating elements 201, 202 of the heater 113. .. Since the longitudinal width W of the heating resistors 201 and 202 is 218 mm and the distance Y between the first and second heat conducting members 140 and 141 is 4 mm, the first and second heat conducting members 140 and 141 respectively. Has a longitudinal width Wa of 107 mm.

(Position of the control part of the heat conducting member)
In this embodiment, restriction portions 140a and 141a for restricting the positions of the heat conducting members 140 and 141 in the longitudinal direction are provided at locations corresponding to the inner side of the minimum sheet passing width Xm in the longitudinal direction, and the heat conducting members 140 and 141 are provided. It is characterized by suppressing the deviation in the longitudinal direction.

FIG. 1C shows a schematic sectional view in the longitudinal direction in which the first and second heat conduction members 140 and 141 and the heater 113 are fitted in the heater holder 130. The restriction portions 140a and 141a of the first and second heat conduction members 140 and 141 are installed inside the minimum sheet passing width Xm, and the distance L from the inner end of the heat conduction members 140 and 141 is 4 mm, respectively. ..

FIG. 1D shows the expansion of the first and second heat conducting members 140 and 141 when the paper is passed to the minimum paper passing width Xm. When a sheet having the minimum sheet-passing width Xm is passed, the temperature of the first and second heat-conducting members 140, 141 is the fixing controlled temperature within the sheet-passing area, but the sheet is not passed. In the section, the temperature rises due to the temperature rise in the non-sheet passing area.

Since the expansion due to thermal expansion is proportional to the temperature rise, the expansion due to thermal expansion of the first and second heat conducting members 140 and 141 is large in the non-paper passing portion and small in the paper passing portion. Therefore, as shown by the arrow in (d) of FIG. 1, the first and second heat conducting members 140 and 141 respectively have a large elongation toward the outer end in the longitudinal direction, but expand toward the inner end. Is small. Therefore, the predetermined separation distance Y between the first heat conduction member 140 and the second heat conduction member 141 of 4 mm is substantially maintained.

Here, Comparative Example 1 shown in FIG. 6A will be described. FIG. 6A corresponds to FIG. 1D in this embodiment, and includes the restriction portions 140a and 141a of the first and second heat conduction members 140 and 141 and the restriction groove 130a of the heater holder 130. The configuration is the same as that of the present embodiment except for the position in the longitudinal direction, and the same reference numerals are used and the description thereof is omitted.

In the configuration of the comparative example 1 of FIG. 6A, the expansion due to the thermal expansion of each of the first and second heat conducting members 140 and 141 is on the outer end side and the inner end side in the longitudinal direction of the member. The regulating portions 140a and 141a are installed near the longitudinal center of the heat conducting member so as to be substantially even. Therefore, the distance L between the inner end of the first heat conduction member 140 and the restriction portion 140a and the distance L between the inner end of the second heat conduction member 141 and the restriction portion 140a are each 70 mm. The separation distance Y between the first and second heat conducting members 140 and 141 is 4 mm, as in the present embodiment.

In the configuration of Comparative Example 1, the restricting portions 140a and 141a of the first and second heat conducting members 140 and 141 are provided outside the minimum sheet passing width Xm. Therefore, when a sheet corresponding to the minimum sheet passing width Xm is passed, the first and second heat conducting members 140 and 141 expand due to the temperature rise in the non-sheet passing portion as shown in FIG. 6B. Also extends to the inner end side. That is, the distances between the inner ends of the first heat conducting member 140 and the second heat conducting member 141 become short.

As a result, the predetermined separation distance Y between the first heat conduction member 140 and the second heat conduction member 141 of 4 mm is not maintained, and the distance is shortened further than that, and the distance between the first and second heat conduction members is reduced. Insulation performance, that is, the insulation performance of the primary circuit and the secondary circuit deteriorates.

(Verification of effect)
With respect to the configuration of the present Example 1 and the configuration of Comparative Example 1, thermal unevenness evaluation and evaluation as to whether insulation between the first and second heat conducting members 140 and 141 is ensured were performed.

The evaluation of heat unevenness was made by passing 10 sheets of 100% printing pattern on the entire surface, because when printing with an image pattern that is uniform and has a large amount of applied toner, image defects such as gloss unevenness due to heat unevenness are likely to occur. When there was no gloss unevenness, it was evaluated as ◯, and when even one sheet had gloss unevenness, it was evaluated as x.

Regarding the insulation performance between the first and second heat conduction members 140 and 141, it was confirmed whether or not discharge occurred when a voltage assuming a lightning surge was applied. In the evaluation, the voltage of 6 kV was applied to the primary circuit 6 times while the paper was being passed, and the presence or absence of discharge was confirmed. The case where there is no discharge between the first and second heat conduction members 140 and 141 was marked with ◯, and the case where there was discharge was marked with x.

In each evaluation, when a letter size Xerox 4200 (basis weight is 75 g/m ² ) having a maximum paper feed width X of 216 mm and a paper sheet cut from the Xerox 4200 to have a minimum paper feed width Xm of 76 mm are used, Was evaluated in.

The fixing temperature was adjusted so that the temperature detecting element 115 reached 180° C., and the paper was passed at 25 ppm for the letter size paper having the maximum paper passing width X. With respect to the paper having the minimum paper-passing width Xm, the paper was passed at a speed of 15 ppm so as not to exceed the heat resistant temperature of the heater holder 130 and the pressure roller 110 due to the temperature rise in the non-paper-passing portion.

In addition, as Comparative Example 2, the same configuration as in Comparative Example 1 was also evaluated in the case where the inner portions of the first and second heat conductive members 140 and 141 were shortened and the separation distance Y was set to 5 mm. The evaluation results are shown in Table 1.

As shown in Table 1, in the configuration of Example 1, uneven gloss due to uneven heat and discharge could be suppressed.

In Comparative Example 1, although the uneven gloss could be suppressed, the discharge occurred only when the paper having the minimum width was passed. It is considered that this is because the distance Y between the first and second heat conduction members 140 and 141 is shorter than 4 mm due to the thermal expansion due to the temperature rise due to the temperature rise in the non-sheet passing portion due to the minimum width sheet passing. To be

In Comparative Example 2, since the initial separation distance Y between the first and second heat conduction members 140 and 141 was set to 5 mm and lengthened, discharge could be suppressed. However, gloss unevenness occurs in letter-size paper that has a small inward expansion due to thermal expansion of the first and second heat conductive members 140 and 141.

As described above, by providing the restriction portions 140a and 141a of the first and second heat conducting members 140 and 141 inside the minimum sheet passing width Xm, even if sheets of various sizes having different widths are passed, the heat conducting member is provided. It is possible to suppress changes in the amount of thermal expansion inward of 140 and 141. Therefore, it is possible to suppress image defects such as uneven gloss due to uneven heat and ensure insulation between the heat conductive members 140 and 141.

In the first embodiment, the restriction portions 140a, 141a in the longitudinal direction of the first and second heat conduction members 140, 141 are limited to one place. This is because if the restriction portions are provided at two or more locations, a force may be applied to the heat conducting members 140 and 141 to cause deformation due to the difference in expansion amount between the heater holder 130 and the heat conducting members 140 and 141. Is.

Further, if the friction coefficient of the first and second heat conducting members 140 and 141, the heater 113, and the heater holder 130 is high, the heat conducting members 140 and 141 are regulated other than the regulating portions 140a and 141a, and thus, similarly. Deformation may occur.

For this purpose, for example, it is effective to apply a lubricant such as lubricating grease to the first and second heat conducting members 140 and 141. Further, as shown in FIG. 7, a recess 130e is provided on the contact surface of the heater holder 130 with the first and second heat conducting members 140, 141. Accordingly, it is effective to reduce the contact area between the heater holder 130 and the heat conducting members 140 and 141.

Although the protection element 114 and the temperature detection element 115 are in contact with the first and second heat conducting members 140 and 141, respectively, in the first embodiment, they may not be in contact with each other. That is, the protection element 114 as a primary circuit member, which is directly connected to the commercial power source 502, may be in the vicinity of the first heat conduction member 140, or the temperature detection element 115 as a secondary circuit member is second. It may be close to the heat conduction member 141. This embodiment is effective when the insulation between the primary circuit member 114 and the first heat conducting member 140 and the insulation between the secondary circuit member 115 and the second heat conducting member 141 are not ensured.

Therefore, in the present invention, the proximity of the primary circuit member to the first heat conducting member includes the case where the primary circuit member is in contact with the first heat conducting member and the case where the primary circuit member is not in contact with the first heat conducting member. Be done. The approach of the secondary circuit member to the second heat conducting member includes the case where the secondary circuit member is in contact with the second heat conducting member and the case where it is not in contact with the second heat conducting member.

<<Example 2>>
The second embodiment will be described below. The second embodiment is characterized by directly fixing the first and second heat conducting members 140 and 141 to the heater holder 130 with an adhesive as a method of regulating the first and second heat conducting members 140 and 141. There is.

In the second embodiment, the image forming apparatus that forms an unfixed toner image, the method of the fixing device, the fixing film, the pressure roller, and the heater are the same as those in the first embodiment, and thus the description thereof is omitted.

(Heat conduction member)
This will be described with reference to FIG. In this embodiment, the adhesive 160 is used as a method of regulating the first and second heat conduction members 140 and 141. As shown in FIG. 8B, the adhesive 160 is applied to the first and second heat conductive members 140 and 141 and bonded to the heater holder 130. Although the protective element 114 and the temperature detecting element 115 are omitted, they are similar to those of the fixing device of the first embodiment. Is the same as.

(Position of the control part of the heat conducting member)
The restriction portions 140a and 141a of the first and second heat conduction members are at positions (adhesion portions) where they are adhered by the adhesive 160. In the first heat conduction member 140, the distance L from the end of the inner end of the heat conduction member 140 at the position (adhesion portion) where the regulation member 140a is adhered is 4 mm, as in the first embodiment. .. The distance L from the end of the inner end of the heat conductive member 141 at the position where the second heat conductive member 141 is bonded with the adhesive 160, which is the restriction portion 141a, is also 4 mm, as in the first embodiment. Further, the predetermined separation distance Y between the restriction portions 140a and 141a of the first and second heat conduction members is also set to 4 mm as in the first embodiment.

(Verification of effect)
With respect to the configuration of the present Example 2, the thermal unevenness and the insulation between the first and second heat conductive members 140 and 141 were evaluated by using the same evaluation method as in Example 1. As for the evaluation results, neither gloss unevenness nor discharge occurred.

In Example 2 as well, it was possible to suppress gloss unevenness due to heat unevenness and ensure insulation between the first and second heat conductive members 140 and 141. As in the first embodiment, the restriction portions 140a and 141a are provided at locations corresponding to the inner side of the minimum sheet passing width Xm. Therefore, even when a sheet corresponding to the minimum sheet passing width X is passed, it is possible to prevent the first and second heat conducting members 140 and 141 from thermally expanding and extending inward in the longitudinal direction. is there.

Further, in the second embodiment, the first and second heat conducting members 140 and 141 are adhered to the heater holder 130, but the same effect can be obtained when the heat conducting members 140 and 141 are adhered to the heater 113. be able to.

In Embodiments 1 and 2 described above, the image heating device has been described by taking the fixing device that heats and fixes the unfixed toner image formed on the sheet (recording material) as an example, but is not limited thereto. The present invention can also be applied to an apparatus that reheats a toner image fixed or supposedly attached to the paper P to increase the gloss (glossiness) of the image.

100.. Image heating device (fixing device), 113.. Heating member (heating heater), 209.. Substrate, 201, 202.. Resistance heating element, 130.. Holding member (heater holder), 140.. Heat conducting member 141, second heat conducting member 112, belt (fixing film) 110, rotating body (pressurizing roller), No. nip portion (fixing nip) 140a, 141a. Restriction part, Y, interval, Xm, minimum sheet width (passage area of recording material of minimum width size)

Claims (11)

A heating member having an elongated substrate, and a resistance heating element which is formed on the substrate along the longitudinal direction of the substrate and generates heat by energization;
A holding member for holding the heating member,
A first heat conduction member and a second heat conduction member, which are heat conduction members having a higher heat conductivity in the longitudinal direction than the heat conductivity of the substrate, and are sandwiched between the heating member and the holding member. A conductive member,
A protection element which is in contact with the first heat conduction member, detects an abnormal temperature rise of the resistance heating element via the first heat conduction member, and cuts off the supply of electric power to the resistance heating element;
A temperature detecting element that is in contact with the second heat conducting member and is connected to a control unit that controls the electric power applied to the resistance heating element;
An endless belt capable of rotating while the inner peripheral surface is in contact with and sliding on the surface of the heating member opposite to the side of the heat conducting member,
A rotating body that forms a nip portion with the outer surface of the belt by contacting the heating member with the belt interposed therebetween;
In the image heating device for heating while holding and conveying the recording material carrying an image in the nip portion,
The first heat-conducting member and the second heat-conducting member are arranged along the longitudinal direction at a predetermined interval, and are formed by bending the folding lines extending in the longitudinal direction. A regulation part for regulating movement in the longitudinal direction with respect to the holding member,
The regulating unit, the image heating apparatus is provided at a position corresponding to the inside of the passage region of the recording material of the minimum width size that can be conveyed in Rutotomoni, said first heat conduction member and the second heat conducting member An image heating device, characterized in that one is provided for each . A primary circuit member directly connected to a commercial power source is adjacent to the first heat conducting member, and a secondary circuit member is adjacent to the second heat conducting member. Item 1. The image heating device according to item 1. The image heating apparatus according to claim 2, wherein the primary circuit member is a protection element that operates due to an abnormal temperature rise of the heating member to shut off the energization of the primary circuit. The image heating apparatus according to claim 2, wherein the secondary circuit member is a temperature detecting element that detects the temperature of the heating member. The image heating apparatus according to any one of claims 1 to 4, wherein the heating member is a ceramic heater. The image heating device according to claim 1, wherein the first heat conducting member and the second heat conducting member are made of aluminum. Image heating apparatus according to any one of claims 1 to 6, characterized in that lubricating grease is applied to the first thermally conductive member and the second heat conducting member. The holding member has a contact area between the first heat conducting member and the second heat conducting member by providing a recessed portion on a contact surface between the first heat conducting member and the second heat conducting member. The image heating device according to any one of claims 1 to 7 , wherein Image heating apparatus according to any one of claims 1 to 8 wherein the regulating unit is characterized in that fitted into the restricting groove provided in the holding member. 9. The restricting portion is an adhesive portion made of an adhesive material to each of the holding members of the first heat conducting member and the second heat conducting member, and the regulating portion is any one of claims 1 to 8. The image heating device described. An image forming apparatus, comprising an image heating apparatus according to any one of claims 1 to 10.