JP5037891B2 - Image fixing device - Google Patents

Description

  The present invention relates to an image heating apparatus suitable for use as an image heating and fixing apparatus (fixing device) mounted on an image forming apparatus such as an electrophotographic printer or an electrophotographic copying machine.

  As a fixing device mounted on an electrophotographic printer or copying machine, a fixing roller, a pressure roller that forms a nip by contacting with the outer peripheral surface (surface) of the fixing roller, and a surface that contacts the surface of the fixing roller are heated. And a heater that forms a nip portion. Patent Document 1 describes this type of fixing device. The surface of the fixing roller is heated by a heater through a heating nip portion. Then, the recording material carrying the unfixed toner image is nipped and conveyed at the nip portion, and the toner image is heated and fixed on the recording material by the heat and nip pressure on the surface of the fixing roller.

In the above fixing device, the heater has a plate shape with a low heat capacity, and is a type that generates heat when energized by rubbing against the surface of the fixing roller at the heating nip portion. With this configuration, the energy density at the heating nip can be made higher than that of a fixing device configured to heat the surface of the fixing roller with a heat roller that contacts the surface of the fixing roller. It becomes possible to do.
JP 2002-236426 A

  The present invention is a further development of the above prior art. SUMMARY OF THE INVENTION An object of the present invention is to provide an image heating apparatus that can increase the amount of heat supplied to the surface of a rotating body that heats an image on a recording material, and can efficiently heat the surface of the rotating body.

Typical structure of the image heating apparatus according to the present invention includes a rotating member, a heat conducting member in contact with the rotating surface, and the surface opposite to the contact surface between the rotating body before Kinetsu conductive member A heating body that contacts and heats the surface of the rotating body via the heat conducting member, and heats the image on the recording material by the heat of the surface of the rotating body, wherein the heat conducting member Is formed by connecting a plurality of plate members, is in contact with the surface of the rotating body at a position corresponding to the contact position between the heat conducting member and the heating body, and at a position other than the contact position, the contact area between the heat transfer member and the rotating member surface S1, when the contact area between the heat transfer member and the heating member S2, you characterized in that it has a relationship of S1> S2.

  According to the present invention, the amount of heat supplied to the surface of the rotating body that heats the image on the recording material can be increased, and the surface of the rotating body can be efficiently heated.

Hereinafter, the present invention will be described in detail with reference to the drawings.
[Reference Example 1]

(1) Example of Image Forming Apparatus FIG. 1 is an overall model diagram of an example of an image forming apparatus in which the image heating apparatus according to the present invention can be mounted as a heat fixing apparatus (fixing device).

The image forming apparatus shown in FIG. 1 is a laser beam printer that forms an image on a recording material such as recording paper, an OHP sheet, or cloth using an electrophotographic image forming system.

Images forming apparatus 1, the process cartridge 2 is detachably attached to the image forming apparatus main body 1A constituting the housing of the image forming apparatus 1. The process cartridge 2 includes a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 3 as an image carrier, and a charging unit 4, a developing unit 5, and a cleaning unit 6 that act on the photosensitive drum 3. The photosensitive drum 3 is rotationally driven in the direction of the arrow at a predetermined peripheral speed. The outer peripheral surface (surface) of the photosensitive drum 3 is uniformly charged to a predetermined polarity and potential by a charging roller 4 as a charging means.

  An exposure device 7 as an optical unit irradiates the surface of the photosensitive drum 3 with a laser beam L corresponding to image information. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 3. This latent image is developed as a toner image (developed image) by a developer (hereinafter referred to as toner) by a developing roller 5 as a developing means.

  On the other hand, in synchronization with the formation of the toner image, the recording material P set in the feeding cassette 8 is conveyed to the transfer position one by one by the pickup roller 9, the feed roller 10, the retard roller 11, and the registration roller 12. . A transfer roller 13 as a transfer unit is disposed at the transfer position. The toner image on the surface of the photosensitive drum 3 is transferred to the recording material P by applying a voltage to the transfer roller 13.

  The recording material P that has received the transfer of the toner image is conveyed to the fixing device 14. The recording material P receives heat and pressure in the fixing device 14. As a result, the toner image is heat-fixed on the recording material P. The recording material P exiting the fixing device 14 is discharged by a discharge roller 15 to a discharge tray 16 provided on the upper portion of the apparatus main body 1A.

  Residual toner remaining on the surface of the photosensitive drum 3 after the transfer of the toner image is removed by a cleaning blade 6 as a cleaning unit. As a result, the photosensitive drum 3 is used for the next image formation.

(2) Fixing Device FIG. 2 is a structural model diagram of an example of the fixing device 14. 3 is a cross-sectional view of the fixing device 14 shown in FIG.

  In the following description, with respect to the fixing device and its constituent members, the longitudinal direction refers to a direction orthogonal to the recording material conveyance direction on the surface of the recording material. The short direction refers to the recording material conveyance direction on the surface of the recording material. The width means a dimension in the recording material conveyance direction.

  The fixing device 14 includes a fixing roller 31 as a rotator (fixing rotator), a heat transfer plate 35 as a heat conductive member, a heater 33 as a heater, and a pressure as a pressure rotator (backup member). And a roller 32. Further, the fixing device 14 includes a first holder 34 as a first holding member and a second holder 30 as a second holding member. These members are all members elongated in the longitudinal direction.

  The fixing roller 31 has an elastic layer 31b made of silicone rubber or the like on the outer periphery of an aluminum or iron core 31a. Therefore, the outer peripheral surface (surface) of the fixing roller 31 is elastic by the elastic layer 31b.

  A heater 33, a heat transfer plate 35, and a fixing roller 31 are attached to a first holder 34 that is held on the apparatus main body 1A so as to be movable up and down. A pressure roller 30 is attached to a second holder 30 that is held by the apparatus main body 1A so as to be vertically movable so as to face the first holder 34 in the width direction. The first holder 34 and the second holder 30 are each formed of a heat resistant plastic such as a liquid crystal polymer.

  The heater 33 is a ceramic heater or a carbon heater, for example, and generates heat when energized from a power source. Further, the heater 33 is bonded and fixed to the holder 34 with an adhesive, for example.

  The heat transfer plate 35 is a metal plate such as copper, for example, and has a thermal conductivity better than at least the fixing roller 31. The heat transfer plate 35 has a spring property. The heat transfer plate 35 is fixed to the holder 34 so as to be in pressure contact with the heater 33 in a plane.

In this reference example , the heater 33 is fixed to a recess provided in the center in the width direction on the lower surface of the first holder 34. The outer central surface of the heat transfer plate 35 bent into a U shape having a width slightly smaller than the diameter of the fixing roller 31 is brought into contact with the heater 33 by a single metal plate, and the heat transfer plate is brought into contact with the heater 33. 35 is fixed to the first holder 34. Then, both ends of the cored bar 31 a of the fixing roller 31 are in contact with the first holder 34 in a state where the surface of the fixing roller 31 is in contact with the inner surface of the longitudinal center, the inner surface of the longitudinal left plate, and the inner surface of the longitudinal right plate. It is supported so that it can rotate freely.

The pressure roller 32 has an elastic layer 32b made of silicone rubber or the like on the outer periphery of an aluminum or iron cored bar 32a. Therefore, the outer peripheral surface (surface) of the pressure roller 32 is elastic by the elastic layer 32b. Both ends of the metal core 32a of the pressure roller 32 are rotatably supported by the second holder 30 via bearings 39. In this reference example , a roller having an elastic layer 32 b is used as the pressure roller 32. Instead of the pressure roller 32, a roller that does not have the elastic layer 32 b can be used as the pressure roller 32.

  Between the second holder 30 provided with the pressure roller 32 and the apparatus main body 1A, and between the first holder 34 provided with the heater 33, the heat transfer plate 35 and the fixing roller 31, and the apparatus main body 1A, respectively, pressure means. The heater springs 36 and 37 are arranged. The corresponding first holder 34 and second holder 30 are pressed by the heater springs 36 and 37 so as to approach each other to bring the surface of the fixing roller 31 and the surface of the pressure roller 32 into contact with each other in a pressurized state. Thus, a nip portion (fixing nip portion) N having a predetermined width is formed at the contact portion between the surface of the fixing roller 31 and the surface of the pressure roller 32.

  Further, by pressing the corresponding first holder 34 and the second holder 30 in the direction approaching each other by the heater springs 36 and 37, the inner surface of the longitudinal center of the heat transfer plate 33 presses the surface of the fixing roller 31 in the first holder 34. Touch the state. Here, since the fixing roller surface 31 has elasticity, the inner surface of the longitudinal center of the heat transfer plate 35 contacts the fixing roller surface 31 with an area of a predetermined width. Further, since the fixing roller surface 31 has elasticity and the heat transfer plate 35 has a spring property, the inner surface of the long left plate and the inner surface of the right right plate of the heat transfer plate 35 have a predetermined area. Contact with. That is, the heat transfer plate 35 is in contact with the fixing roller surface 31 at the position corresponding to the contact position between the heat transfer plate 35 and the heater 33 at the long center outer surface. Hereinafter, the position where the inner longitudinal inner surface of the heat transfer plate 35 contacts the fixing roller surface 31 is referred to as an X portion. Further, the heat transfer plate 35 is in contact with the fixing roller surface 31 on the inner surface of the left and right long plates at a position other than the contact position between the heater 33 and the central outer surface of the heat transfer plate 35. Hereinafter, in the heat transfer plate 35, a position where the long left inner surface contacts the fixing roller surface 31 is referred to as α portion, and a position where the long right inner surface contacts the fixing roller surface 31 is referred to as β portion.

  FIG. 4 is a structural model diagram of the heater 33. The heater 33 has a thin plate-like substrate 33a whose main component is ceramics typified by alumina. On the surface (surface on the nip portion N side) of the substrate 33a, a resistance heating element 33b mainly composed of Ag / Pd (silver palladium) or the like is applied by screen printing or the like along the longitudinal direction of the substrate 33a. It is formed. In addition, electrode portions 33c1 and 33c2 for energizing the heating element 33b are formed on the surface of the substrate 33a. The heating element 33b is covered with a protective layer 33d mainly composed of glass or fluorine. The protective layer 33d is formed on the surface of the substrate 33a so as to cover the heating element 33b.

In the heater 33, the thermistor 21 as temperature detecting means is provided on the back surface of the substrate 33a (surface opposite to the surface on the nip portion N side). The thermistor 21 is arranged in a region through which the recording material P of all sizes usable in the image forming apparatus passes in the heater 33.

(3) Heat Fixing Operation of Fixing Device In the fixing roller 31, the driving gear G provided at the end of the core 31a is rotated in the direction of the arrow at a predetermined peripheral speed (process speed) by a fixing motor 24 as a fixing driving means. Is done. Although the fixing motor 24 is not shown, the driving is controlled by an MPU (micro processor unit) 22 (FIG. 4) as a control means. A rotational force acts on the pressure roller 32 by the pressure friction force in the nip portion N between the surface of the fixing roller 31 and the surface of the pressure roller 32 due to the rotation of the fixing roller 31. With this rotational force, the pressure roller 32 is driven to rotate in the direction of the arrow along with the fixing roller 31.

  In the rotation state of the fixing roller 31 and the pressure roller 32, the MPU 22 starts driving the heater driving unit 23 as a power supply unit. The heater driving unit 23 energizes the heating element 33 b through the electrode portions 33 c 1 and 33 c 2 of the heater 33. As a result, the heating element 33b generates heat and the heater 33 quickly rises in temperature. Since the heat transfer plate 35 that is in contact with the heater 33 is heated by the heater 33 and has a higher thermal conductivity than the fixing roller 31, the entire heat transfer plate 35 has a higher temperature than the fixing roller 31. Accordingly, the heat of the heater 33 is transmitted to the fixing roller 31 via the heat transfer plate 35. That is, the heat of the heat transfer plate 35 is transmitted to the surface of the fixing roller 31 that is rotating through the X portion, the α portion, and the β portion.

  FIG. 5 is an explanatory diagram showing the relationship between the X portion, α portion, and β portion of the heat transfer plate 35 and the surface of the fixing roller 31.

  In FIG. 5, the heat transfer plate 35 indicated by a solid line represents the shape in contact with the surface of the fixing roller 31. A heat transfer plate 35 indicated by a two-dot chain line represents a shape in a free state that is not in contact with the surface of the fixing roller 31. The heat transfer plate 35 has a free state width that is not in contact with the surface of the fixing roller 31 smaller than the diameter of the fixing roller 31 and has a spring property. For this reason, the heat transfer plate 35 is in contact with the surface of the fixing roller 31 having elasticity in the α and β portions other than the X portion with a predetermined area. Here, if the contact area obtained by adding the areas of the X part, the α part, and the β part is S1, and the contact area between the heat transfer plate 35 and the heater 33 is S2, S1> S2. That is, the contact area S 1 between the heat transfer plate 35 and the surface of the fixing roller 31 is larger than the contact area S 2 between the heat transfer plate 35 and the heater 33. As a result, the amount of heat supplied to the surface of the fixing roller 31 is increased as compared with the case where the surface of the fixing roller 31 is directly heated by the heater 33 from one of the X, α, and β portions. That is, in the rotation direction of the fixing roller 31, only three locations excluding the nip portion N where heat is taken away by the recording material P, that is, the downstream side (α portion), the upstream side (β portion), and the downstream side of the nip portion N The surface of the fixing roller 31 can be heated between the upstream sides (X portion). As a result, the amount of heat supplied to the surface of the fixing roller 31 that heats the unfixed toner image 38a on the recording material P can be increased, and the surface of the fixing roller 31 can be efficiently heated.

  Further, the MPU 22 takes in temperature information detected by the thermistor 21 in real time. The MPU 22 controls the heater drive unit 23 based on the temperature information, and the energization amount to the heater 33 so that the heater 33 maintains a predetermined set temperature (target temperature) (hereinafter, the set temperature is referred to as a fixing temperature). To control.

In a state where the heater 33 is maintained at the fixing temperature, the recording material P carrying the unfixed toner image 38a is introduced into the nip portion N (FIG. 3). The recording material P is nipped and conveyed at the nip portion N by the fixing roller 31 and the pressure roller 32. In the conveying process, heat is applied from the surface of the fixing roller 31 to the unfixed toner image 38a on the recording material P. As a result, the unfixed toner image 38a is heated and fixed on the recording material P as a fixed image 38b by receiving heat and nip pressure. The recording material P that has exited the nip N is separated from the surface of the fixing roller 31 by the curvature, and is discharged to the discharge roller 15 (FIG. 1).
[Example 1]

The fixing device shown in this embodiment has the same configuration as the fixing device 14 of Reference Example 1 except for the heat transfer plate 35. In this embodiment, the same reference numerals are given to members / portions common to the fixing device 14 of Reference Example 1 , and the description thereof is omitted. The same applies to Reference Example 2 .

  FIG. 6 is an explanatory view showing a main part of the fixing device 14 shown in this embodiment.

  In the fixing device 14 of the present embodiment, the heat transfer plate 35 includes three elongated plate members: a central plate member 35P, a left side plate member 35Q, and a right side plate member 35R. The central plate member 35P, the left side plate member 35Q, and the right side plate member 35R are metal plates having good thermal conductivity such as copper. Then, the center plate member 35P and the left side plate member 35Q are rotatably connected by the first connecting shaft 35F, and the center plate member 35P and the right side plate member 35R are rotatably connected by the second connecting shaft 35G. ing. These connecting shafts 35F and 35G have both longitudinal ends held by the apparatus main body 1A. The heater 33 is in contact with the surface of the central plate member 35P. The back surface of the central plate member 35P is in contact with the fixing roller surface 31 (X portion). The left side plate member 35Q is pressed against the fixing roller surface 31 by a heater spring 36 provided between the apparatus main body 1A and is in contact with the fixing roller surface 31 (α portion). The right side plate member 35R is also pressed against the fixing roller surface 31 by a heater spring 36 provided between the apparatus main body 1A and is in contact with the fixing roller surface 31 (β portion). Therefore, if the contact area obtained by adding the areas of the X part, the α part, and the β part is S1, and the contact area between the heat transfer plate 33 and the heater 33 is S2, S1> S2.

Also in the fixing device 14 of the present embodiment, the central plate member 35P, the left side plate member 35Q, and the right side plate member 35R of the heat transfer plate 35 are provided on the downstream side (α portion), the upstream side (β portion) of the nip portion N, and The surface of the fixing roller 31 can be heated between the downstream side and the upstream side (X portion). Therefore, the same effect as that of the fixing device of Reference Example 1 can be obtained.

In the fixing device 14 of the reference example 1 and the present embodiment , the material of the heat transfer plate 35 is a metal plate having good heat conductivity such as copper. However, the material of the heat transfer plate 35 is not limited to this, and is higher than that of the fixing roller 31. It may be a plastic (synthetic resin) having good heat conduction and spring properties.
[Reference Example 2]

The fixing device shown in this reference example has the same configuration as the fixing device 14 of Reference Example 1 except for the heat transfer plate 35.

FIG. 7 is an explanatory view showing a main part of the fixing device 14 shown in this reference example .

In the fixing device 14 of this reference example , the heat transfer plate 35 is formed wider than the heater 33 by a metal block having good heat conduction or a plastic having good heat conduction. A heater 33 is in contact with the surface of the heat transfer plate 35. The back surface of the heat transfer plate 35 is formed on a contact surface 35a having the same curvature as that of the fixing roller surface 31, and the contact surface 35a is in contact with the surface of the fixing roller 31 (X portion). Therefore, if the contact area of the X part is S1, and the contact area between the heat transfer plate 35 and the heater 33 is S2, S1> S2. As a result, the amount of heat supplied from the heater 33 to the surface of the fixing roller 31 increases.

Therefore, the fixing device 14 of this reference example can achieve the same effect as the fixing device of Reference Example 1 .

Overall model diagram of an example of an image forming apparatus Structural model diagram of an example of fixing device of Reference Example 1 MM sectional view of the fixing device of FIG. Heater configuration model diagram Explanatory drawing showing the relationship between the X part, α part and β part of the heat transfer plate and the fixing roller surface Explanatory drawing showing the principal part of the fixing device of Embodiment 1 . Explanatory drawing showing the principal part of the fixing device of Reference Example 2 .

14: fixing device, 31: fixing roller, 32: pressure roller, 33: heater, 35: heat transfer plate

Claims (3)

A rotating body,
A heat conducting member in contact with the rotating body surface;
A heating element for heating the surface opposite the contact surface of the rotating member through said heat conducting member and the contact surface between the rotating body before Kinetsu conductive member,
Have
An image heating apparatus for heating an image on a recording material by heat of the rotating body surface,
The heat conducting member is formed by connecting a plurality of plate members, and contacts the surface of the rotating body at a position corresponding to a contact position between the heat conducting member and the heating body, and at a position other than the contact position. And
An image heating apparatus having a relationship of S1> S2, where S1 is a contact area between the heat transfer member and the surface of the rotating body, and S2 is a contact area between the heat transfer member and the heating body. .   The image heating apparatus according to claim 1, wherein the surface of the rotating body has elasticity.   The image heating apparatus according to claim 1, wherein a material of the heat conducting member is a metal or a synthetic resin.