JP2016114876A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that can eliminate an adverse effect on the device due to damage to a heating element, secure safety of an operator who replaces the heating element, and reduce a running cost of the device.SOLUTION: There is provided a fixing device including: a belt-like fixing member that rotates in contact with an unfixed image; a pressing member that forms a fixing nip part with the belt-like fixing member; a heater member that heats the belt-like fixing member; and holding means for holding the heater member, where the heater member comprises a long base material that extends in a direction orthogonal to a recording medium conveyance direction and a heating element that is formed on the fixing nip part side with respect to the base material, and includes a heat transfer member that transfers a heat from the heater member to the belt-like fixing member; the heater member is surrounded by the holding means and heat transfer member.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, and more particularly to a heating type fixing device mounted on such an image forming apparatus.

  The image forming apparatus forms a toner image on an image carrier based on image information, transfers the toner image onto a recording material such as paper or an OHP sheet, and passes the recording material carrying the toner image through a fixing device. The toner image is fixed on the recording material by heat and pressure.

  As a fixing device that realizes energy saving, a technique of heating a film by a resistance heater in which a resistance heating element is formed on a ceramic or glass substrate has been proposed (for example, see Patent Document 1).

  The fixing device described in Patent Document 1 is sandwiched between a plate-like heating body and a pressure roller that are in contact with a thin-walled cylindrical heat-resistant film so that the film and the recording material are brought into close contact with each other, and gives thermal energy to the recording material. It is a configuration.

  Also, a fixing device is known in which an insulating layer and a resistance heating element are integrally formed on a metal substrate in order, and a thin cylindrical heat-resistant film is heated via the metal substrate (for example, Patent Document 2). reference).

  The fixing devices described in these patent documents can realize energy saving by heating a thin film with a resistance heater in which a heating resistor is formed on a ceramic or glass substrate.

  However, ceramics and glass substrates are easily broken by external force and thermal stress, and it is necessary to replace them. Since the fragments of ceramics and glass substrates have a sharp shape, workers are injured during replacement. There is a risk of doing. Since glass fragments are particularly sharp, there is a high risk of injury to the operator. Furthermore, there is a possibility that fragments of ceramics or a glass substrate may scatter and have an adverse effect on the apparatus.

  Further, in the fixing device described in Patent Document 2, since the metal substrate slides with the heat resistant film, it is necessary to reduce friction between the metal substrate and the heat resistant film and reduce wear of the heat resistant film. Need to be coated. Since this coating deteriorates with time, the fixing device described in Patent Document 2 has a configuration as a heating body in which the resistance heating element and the metal substrate are integrated, and therefore is replaced for each heating body. Since the resistance heating element is an expensive member, it is not preferable to replace the heating element for each heating element from the viewpoint of the running cost of the apparatus.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that eliminates the adverse effects of the apparatus due to breakage of the heating element, ensures the safety of the operator when replacing the heating element, and reduces the running cost of the apparatus.

In order to solve the above-described problem, a fixing device according to a first aspect of the present invention includes:
A belt-like fixing member that rotates in contact with an unfixed image;
A pressing member that forms a fixing nip portion with the belt-shaped fixing member;
In a fixing device comprising: a heater member that heats the belt-shaped fixing member; and a holding unit that holds the heater member.
The heater member includes a long base extending in a direction orthogonal to the recording medium conveyance direction, and a heating element formed on the fixing nip side from the base,
A heat transfer member that transfers heat from the heater member to the belt-shaped fixing member,
The heater member is surrounded by the holding means and the heat transfer member.

  According to the present invention, it is possible to provide a fixing device that eliminates the adverse effects of the apparatus due to the breakage of the heating element, ensures the safety of the operator when replacing the heating element, and reduces the running cost of the apparatus.

1 is a configuration diagram schematically showing an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a configuration diagram schematically illustrating a fixing device of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a configuration diagram schematically illustrating a nip forming member of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a perspective view showing a nip forming member of the image forming apparatus shown in FIG. 1. FIG. 2 is a perspective view showing a nip forming member of the image forming apparatus shown in FIG. 1. FIG. 5 is a configuration diagram schematically showing a nip forming member of an image forming apparatus according to a second embodiment of the present invention.

  FIG. 1 shows a monochrome printer as an example of an image forming apparatus according to the first embodiment of the present invention, which will be described based on this. Naturally, the present invention applies to a known color image forming apparatus. Is applicable. As is known, a monochrome printer is provided with predetermined devices necessary for forming an image around a photosensitive member 8 as an image carrier, such as a charging unit, an exposure unit, and a developing unit. That is, a charging roller 18 as a charging means, a mirror 20 constituting an exposure means, a developing device 22 having a developing roller 22a as a developing means, a transfer device 10, a cleaning device 24 having a cleaning blade 24a, and the like are arranged. Yes. Then, between the charging roller 18 and the developing device 22, exposure light Lb is irradiated to the exposure unit 26 on the photoconductor 8 via the mirror 20 and scanned. A sheet feeding unit 4 is disposed below the printer, and a registration roller pair (positioning roller pair) 6 is provided in the middle of the sheet conveyance path to the image forming unit. At the end of the sheet conveyance path, a fixing device 12 including a fixing belt 28, a heater member 56, and a pressure roller 30 as main components is provided.

  The paper feed means 4 feeds the paper P as a recording medium stored in a stacked state and the paper P stored in the paper feed tray 14 one by one in order from the top. It has a paper roller 16 and the like. The paper P sent out by the paper supply roller 16 is temporarily stopped by the registration roller pair 6. Then, after correcting the posture deviation, at the timing synchronized with the rotation of the photoconductor 8, that is, the front end of the toner image formed on the photoconductor 8 coincides with the predetermined position of the front end of the sheet P in the transport direction. At timing, it is sent to the transfer portion N by the registration roller pair 6.

  The image forming operation in this printer is performed in the same manner as before. That is, when the photosensitive member 8 starts to rotate, the surface of the photosensitive member 8 is uniformly charged by the charging roller 18, and the exposure light Lb is irradiated and scanned on the exposure unit 26 based on the image information to correspond to an image to be created. An electrostatic latent image is formed. The electrostatic latent image is moved to a position facing the developing device 22 by the rotation of the photosensitive member 8, where toner is supplied to be visualized to form a toner image. The toner image formed on the photoreceptor 8 is transferred onto the paper P that has entered the transfer portion N at a predetermined timing by applying a transfer bias of the transfer device 10. The paper P carrying the toner image as an unfixed image is conveyed toward the fixing device 12, fixed by the fixing device 12, and then discharged and stacked on a paper discharge tray outside the apparatus. Residual toner remaining on the photosensitive member 8 without being transferred at the transfer portion N reaches the cleaning device 24 as the photosensitive member 8 rotates. Then, while passing through the cleaning device 24, it is scraped off and cleaned by the cleaning blade 24a. Thereafter, the residual potential on the photoconductor 8 is removed by a known charge eliminating means, and is prepared for the next image forming step.

Next, the configuration of the fixing device according to the present embodiment will be described with reference to FIG.
The fixing device 12 includes an endless fixing belt (belt-shaped fixing member; hereinafter, simply referred to as a fixing belt) 28 that is a flexible heat-resistant film, and a pressure roller 30 as a pressing member that comes into contact with the outer peripheral surface thereof. And a heater member 56. The heater member 56, together with a first heat transfer member 50 as a heat transfer member for heat equalization in the axial direction (longitudinal direction) of the fixing belt 28, and a sliding member that reduces friction between the fixing belt 28, A nip forming member that forms the fixing nip SN with the pressure roller 30 is formed.

  A thermistor 34 that detects the surface temperature of the fixing belt 28 is provided downstream of the fixing nip SN. Based on the detection information of the thermistor 34, the heating control means 42 controls the power supply 40 that supplies power to the heater member 56. The heating control means 42 means a microcomputer including a CPU, ROM, RAM, I / O interface and the like.

  The fixing belt 28 has a nickel base having an outer diameter of 30 mm and a thickness of 10 to 70 μm, an elastic layer coated on the surface of the base, and a release layer formed on the surface. The elastic layer is made of silicone rubber and has a thickness of 50 to 150 μm. The release layer that enhances the durability and secures the release property is formed of a fluorine-based resin such as PFA or PTFE, and is provided with a thickness of 5 to 50 μm. The material of the substrate is not limited to nickel, and may be formed of a heat resistant resin material such as SUS or polyimide (PI).

  The pressure roller 30 has an outer diameter of 30 mm, and includes a hollow iron core 30a, an elastic layer 30b formed on the surface of the core 30a, and a release layer 30c formed on the surface thereof. ing. The elastic layer 30b is made of silicone rubber and has a thickness of 5 mm. The release layer 30c is formed of a fluororesin (PFA or PTFE) layer having a thickness of about 40 μm and ensures release properties. As is known, the pressure roller 30 is pressed against the nip forming member 55 via the fixing belt 28 by an urging unit. The pressure roller 30 is rotated by a driving force transmitted from a driving source such as a motor provided in the image forming apparatus via a gear. The fixing belt 28 is rotated by the pressure roller 30.

  Next, the nip forming member will be described with reference to FIG.

  The nip forming member 55, together with the heater member 56, the first heat transfer member 50 for heat equalizing in the axial direction (longitudinal direction) of the fixing belt 28, and a sliding member that reduces friction between the fixing belt 28 and the nip forming member 55. The fixing nip SN is formed with the pressure roller 30. The heater member 56 heats the fixing belt 28 via the first heat transfer member 50 to increase the temperature of the fixing belt 28 and heat and fix the unfixed image conveyed to the fixing nip portion SN. .

  The heater member 56 is a plate composed of a long base material 56b extending in the axial direction of the fixing belt 28, and a resistance heating element 56a as a heating element disposed on the fixing nip SN side from the base material 56b. It is a heating element in the shape. For example, a resistance heating element 56a made of ruthenium oxide or the like is printed on a low thermal conductivity base material 56b made of ceramic such as glass or alumina, and fired, and an overcoat (OC) layer is formed thereon. Is further formed. The OC layer located on the fixing nip SN side from the base material 56b is formed of glass or the like, and is thinner than the base material 56b, and is more likely to transfer heat to the OC layer side than heat transfer to the base material 56b side. It plays a role as an insulating layer.

  The heater member 56 is in contact with the fixing belt 28 via the first heat transfer member 50. The first heat transfer member 50 is made of copper, aluminum, or the like, which has a higher thermal conductivity than ceramics such as glass or alumina, and efficiently transfers the heat of the heater member 56 to the fixing belt 28. In addition, the first heat transfer member 50 contributes to an improvement in heat transfer in the heater longitudinal direction, and can reduce a temperature deviation in the longitudinal direction of the fixing belt 28.

  By the way, since both the heater member 56 and the first heat transfer member 50 are composed of highly rigid members, it is difficult to uniformly contact the entire longitudinal direction due to the influence of surface roughness, warpage, and waviness. . In order to avoid such a problem, a second heat transfer auxiliary member between the heater member 56 and the first heat transfer member 50 is used as a heat transfer auxiliary member having a lower rigidity than the rigidity of the heater member 56 and the first heat transfer member 50. By interposing the heat member 51, the heat from the heater member 56 can be efficiently transmitted to the first heat transfer member while maintaining the adhesion between the heater member 56 and the first heat transfer member 50. For the second heat transfer member 51, heat conductive grease, a heat conductive sheet (TIM: Thermal Interface Material), or the like can be used. In addition, the heat transfer member is not limited to an aspect constituted by two parts, and may be constituted by a plurality of parts of three or more parts. In this case, among the plurality of heat transfer members, a member disposed at a position closest to the heater member 56 is a heat transfer auxiliary member that is lower than the rigidity of the other heat transfer members and the heater member 56.

  The first heat transfer member 50 slides in contact with the fixing belt 28 and wears the fixing belt 28. Therefore, the surface of the first heat transfer member 50 that is in sliding contact with the fixing belt 28 is subjected to a surface treatment such as a low friction coating as a sliding member. That is, the surface of the heater member 56 with which the fixing belt 28 contacts is covered by surface treatment. As a result, wear of the fixing belt 28 can be reduced. As a material for the surface treatment, DLC (diamond-like carbon), PTFE (polytetrafluoroethylene) or the like having a low friction coefficient is suitable. Considering the heat transfer performance from the first heat transfer member 50 to the fixing belt 28, the surface treatment layer is preferably a thin layer of about 2 to 50 μm. The portion to be surface-treated is not limited to the portion that is in sliding contact with the fixing belt 28.

  A heater holder 57 as a holding means for holding the heater member 56 is supported by a stay (support member) 61 connected to the apparatus side plate, prevents the member from being bent by the pressure received from the pressure roller 30, and is uniform in the longitudinal direction. The nip width can be obtained.

  By the way, the heater holder 57 easily receives a heat from the heater member 56 and becomes high temperature, and may be damaged. Therefore, the heater holder 57 is formed of a resin having high heat resistance such as LCP (liquid crystal polymer), PPS (poniphenylene sulfide), PAI (polyamideimide), PI (polyimide), PEEK (polyetheretherketone). As a result, the heater holder 57 can be prevented from being damaged. Moreover, the heater holder 57 can improve heat insulation performance by being formed with resin with low thermal conductivity. Furthermore, the heater holder 57 is a position that is not adjacent to each other via the resistance heating element 56a and the base material 56b, and is contacted at two locations, thereby reducing the amount of heat flowing from the first heat transfer member 50 to the heater holder 57, and heat. Can be efficiently transmitted to the first heat transfer member 50 and the second heat transfer member 51 on the high heat conduction side, and thus to the fixing belt 28. In addition, the location where the heater holder 57 contacts the heater member 56 is not limited to two modes.

  The first heat transfer member 50 extends in a direction opposite to the direction toward the pressure roller 30 from the bottom 50a that forms the fixing nip SN via the fixing belt 28 and the peripheral edge of the bottom 50a in the recording medium conveyance direction. And provided side portion 50b. The first heat transfer member 50 can be made inexpensive by forming a thin copper plate by bending or extrusion molding.

  At the tip of the side portion 50 b, there is a hook portion 50 c as an engaging means that hooks on the heater holder 57. A plurality of hooks 50 c are provided across the longitudinal direction of the first heat transfer member 50.

  As shown in FIG. 4, the hook portion 50 c is configured to have an engagement piece in the longitudinal direction of the first heat transfer member 50. Then, by inserting the hook portion 50c into the hole portion 57a of the heater holder 57 and sliding (moving) the first heat transfer member 50 in the longitudinal direction of the first heat transfer member 50, as shown in FIG. The first heat transfer member 50 can be assembled to the heater holder 57.

  Since the heater member 56 is accommodated in the first heat transfer member 50 and is surrounded by the heater holder 57 and the first heat transfer member 50, the heater member 56 is damaged when the heater member 56 is damaged. Can prevent the debris from scattering. Therefore, when the heater member 56 is replaced, the worker can work safely. In addition, the damage to the heater member 56 does not adversely affect the apparatus.

  On the other hand, when the first heat transfer member 50 is removed from the heater holder 57, the first heat transfer member 50 is slid in the longitudinal direction of the first heat transfer member 50 in the direction opposite to the sliding direction, and is pulled out. The heat member 50 can be removed from the heater holder 57.

  Since the first heat transfer member 50 can be configured to be detachable from the heater member 56, when surface treatment such as coating applied to the first heat transfer member 50 requires replacement due to deterioration over time, The first heat transfer member 50 can be individually replaced without replacing the heater member 56. Therefore, the running cost of the apparatus can be reduced.

  By the way, when the heat transfer grease is used as the second heat transfer member 51, the viscosity of the heat transfer grease 51 decreases when heated. In such a case, the second heat transfer member 51 may flow out from between the heater member 56 and the first heat transfer member 50.

  In the present embodiment, the second heat transfer member 51 is covered with the heater member 56 and the first heat transfer member 50 as shown in FIG. Therefore, the second heat transfer member 51 does not flow out between the heater member 56 and the first heat transfer member 50.

  In addition, when heat transfer grease is used as the second heat transfer member 51, bubbles are mixed in the heat transfer grease 51, so that an appropriate amount of heat transfer grease 51 is transferred to the heater member 56 and the first heat transfer grease. It becomes difficult to fill the space between the heat member 50 and the heat member 50. Moreover, after filling the heat transfer grease 51, the heat transfer grease 51 can be expanded to some extent by pressing the heater member 56 and the first heat transfer member 50 in the thickness direction. However, sufficient adhesion between the heater member 56 and the first heat transfer member 50 cannot be maintained, and heat from the heater member 56 cannot be efficiently transferred to the first heat transfer member 50.

  In the present embodiment, the hook portion 50 c is configured in a shape having an engagement piece in the longitudinal direction of the first heat transfer member 50.

Specifically, an example of an assembly procedure around the heater member will be described.
First, the heater member 56 is placed on the heater holder 57. Next, the heat transfer grease 51 is applied to the surface of the heater member 56. Next, the first heat transfer member 50 is assembled to the heater holder 57 so as to cover the heater member 56 to which the heat transfer grease 51 is applied.

  When assembling the first heat transfer member 50 to the heater holder 57, the hook portion 50 c is inserted into the hole 57 a of the heater holder 57, and the first heat transfer member 50 is slid in the longitudinal direction of the first heat transfer member 50. (Move).

  By sliding the first heat transfer member 50 against the heater member 56, the heat transfer grease 51 is expanded and unevenness is eliminated. In addition, an appropriate amount of heat transfer grease 51 can be disposed between the first heat transfer member 50 and the heater member 56.

  Subsequently, an image forming apparatus according to a second embodiment of the present invention will be described. Note that components common to those in the image forming apparatus according to the first embodiment are denoted by corresponding reference numerals and detailed description thereof is omitted, and different components are described in detail with reference to the drawings.

  The second embodiment is different from the first embodiment in that the shape of the first heat transfer member is different. This will be specifically described below.

  By the way, since the base material 56b is comprised from ceramics, such as glass and alumina which are low heat conductive materials from the 1st heat-transfer member 50, the heat | fever from the resistance heating element 56a is 1st from the base material 56b. It is easy to conduct to the heat transfer member 50. In other words, the resistance heating element 56a locally heats the first heat transfer member 50. The first heat transfer member 50 conducts heat to the fixing belt 28 to raise the temperature of the fixing belt 28. The fixing belt 28 rotates counterclockwise in FIG. 6, and the portion heated by the resistance heating element 56a moves downstream in the sheet conveying direction.

  Then, the heat of the heated portion of the fixing belt 28 is transmitted to the first heat transfer member 50 on the downstream side in the sheet conveyance direction, and further transmitted to the heater member 56. Therefore, after all, the whole heater member 56 is heated, and it takes time to warm up.

  As shown in FIG. 6, the first heat transfer member 150 of the present embodiment is a downstream side in the sheet conveyance direction, and includes a bottom portion 150 a that forms a fixing nip portion SN via the fixing belt 28, and a heater member 56. A gap CL is provided between them.

  By providing a gap CL between the first heat transfer member 150 and the heater member 56 on the downstream side in the paper conveyance direction, the heat of the heated portion of the fixing belt 28 is changed to the first downstream side in the paper conveyance direction. Transmission to the heat transfer member 150 can be suppressed. Therefore, the warm-up time can be shortened.

  Further, the first heat transfer member 150 may be provided with a protruding portion 150d that protrudes toward the pressure roller 30 on the downstream side in the sheet conveying direction.

  By providing the projecting portion 150d on the downstream side in the paper transport direction, the paper is discharged downstream in the paper transport direction, so that the peelability between the fixing belt 28 and the paper is improved.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this. It should be noted that the materials and dimensions of each component introduced in the above-described embodiment are merely examples, and it is needless to say that various materials and dimensions can be selected within a range where the effects of the present invention can be exhibited.

28 fixing belt (an example of a belt-like fixing member)
30 Pressure roller (an example of a pressing member)
50 1st heat-transfer member (an example of heat-transfer member)
50c Hook (an example of engagement means)
51 2nd heat transfer member (an example of heat transfer auxiliary member)
56 Heater member 56a Resistance heating element (an example of a heating element)
56b Base material 57 Heater holder (an example of holding means)
SN Fixing nip CL clearance

JP-A-6-95540 JP-A-8-272240

Claims (11)

A belt-like fixing member that rotates in contact with an unfixed image;
A pressing member that forms a fixing nip portion with the belt-shaped fixing member;
A heater member for heating the belt-shaped fixing member;
A fixing device comprising: a holding unit that holds the heater member;
The heater member includes a long base extending in a direction orthogonal to the recording medium conveyance direction, and a heating element formed on the fixing nip side from the base,
A heat transfer member that transfers heat from the heater member to the belt-shaped fixing member,
The fixing device, wherein the heater member is surrounded by the holding means and the heat transfer member. The heat transfer member is in contact with the belt-shaped fixing member and forms a fixing nip portion, and a side extending from the periphery of the bottom portion in the recording medium conveyance direction in a direction opposite to the direction toward the pressing member. And
The fixing device according to claim 1, wherein the heater member is housed in the heat transfer member and is surrounded by the heat transfer member and the holding unit.   The fixing device according to claim 2, wherein at least one engaging unit that engages with the holding unit is provided at a tip of the side portion.   The fixing device according to claim 3, wherein the engaging unit includes an engaging piece extending in a longitudinal direction of the heat transfer member.   The fixing device according to claim 1, wherein the heat transfer member has a protruding portion protruding toward the pressing member on the downstream side in the recording medium conveyance direction.   6. The fixing device according to claim 1, wherein a gap is provided between the heat transfer member and the heater member and downstream in the recording medium conveyance direction.   The heat transfer member and the heater member include a heat transfer auxiliary member having rigidity lower than that of the heat transfer member and the heater member, according to any one of claims 1 to 6. Fixing device.   The fixing device according to claim 7, wherein the heat transfer auxiliary member is a heat transfer grease.   The fixing device according to claim 7, wherein the heat transfer auxiliary member is a heat conductive sheet.   The fixing device according to claim 1, wherein a surface of the heat transfer member contacting the belt-shaped fixing member is subjected to a surface treatment.   An image forming apparatus comprising the fixing device according to claim 1.

Images