JP7527938B2 - Fixing device - Google Patents

Description

The present invention relates to a fixing device that applies heat and pressure to an unfixed toner image to fix it.

Fixing devices that apply heat and pressure to unfixed toner to paper are widely known. There are many different types of fixing devices, and they are used according to the environment in which they are used. For example, image forming devices installed in offices often come equipped with a fixing device known as an on-demand fixing device, which has a short start-up time.

Patent Document 1 discloses technology related to an on-demand fixing device. The on-demand fixing device is equipped with a heater with a small heat capacity, a thin film, and a pressure roller. The pressure roller, which is driven to rotate, is pressed against the heater via the film, causing the film to rotate and forming a nip. Unfixed toner transported to the nip is heated by the heater via the film and is thermally fixed.

To supply power to the heater, an electrode is provided at the end of the heater in the longitudinal direction of the film, and a connector extending from the power supply device is connected to this electrode. The fixing device may be replaced by an operator, and to prevent the operator from accidentally touching the parts inside the fixing device, the fixing device is covered in the longitudinal direction of the film with a cover.

Patent Document 1 also discloses a structure for preventing poor power supply to the heater due to poor connection between the connector terminal and the electrode at the end of the heater. Specifically, the connector has a hook that elastically deforms and engages with a flange located at the end of the film.

When assembling the fixing device, there is a possibility that the worker may pull on the wires extending from the connector, unintentionally releasing the engagement between the hook and the flange, causing the connector to come off the flange. For this reason, a plug-in member is inserted between the hook and the connector terminal to limit the elastic deformation of the hook and prevent the connector from coming off the flange.

JP 2004-214056 A

However, the plug-in member protrudes from the connector in the longitudinal direction of the film, and the cover that covers the fixing device must be enlarged in the longitudinal direction.

The present invention aims to reduce the longitudinal size of the fixing device, including the cover, by using an insert member that does not protrude from the connector in the longitudinal direction of the film.

In order to solve the above problems, the fixing device of the present invention comprises a film that contacts the paper, a flange that restricts the movement of the film in the longitudinal direction of the film, a heater that has an electrode at an end of the film that protrudes from the flange in the longitudinal direction and generates heat when a current flows through the electrode, and applies heat to the paper via the film, a pressure roller that contacts the film and is driven to rotate, thereby rotating the film and applying pressure to the heater via the film to form a nip portion where the toner image is fixed, and pressurizes the paper at the nip portion, and a housing member having terminals connected to the electrode. The heater includes a U-shaped connector that protrudes from the housing member, is elastically deformable, and has a hook that engages with an engagement portion provided on the flange, and is inserted into the heater from a direction intersecting the longitudinal direction of the film; an insertion member that is inserted between the terminal and the hook to restrict the elastic deformation of the hook, prevent the engagement between the hook and the flange from being released, and prevent the connector from coming off; and a cover that is positioned outside the connector in the longitudinal direction of the film, and the insertion member is fixed to the connector so as not to protrude from the connector in the longitudinal direction of the film.

According to the present invention, it is possible to reduce the size of the fixing device with the cover attached.

FIG. 1 is a schematic cross-sectional view of an image forming apparatus. FIG. 2 is a schematic cross-sectional view of the fixing device. FIG. 2 is a schematic diagram of a ceramic heater. Schematic diagram of the arrangement of the anchoring flanges. FIG. FIG. 4 is a schematic diagram of a connector in an attached state. FIG. 2 is a schematic diagram of an insert member. FIG. 13 is a schematic diagram after the insertion member is attached. FIG. 13 is a schematic diagram of an insert member according to a modified example. FIG. 13 is a schematic diagram showing an insertion member attached in a modified example. FIG. 11 is a schematic diagram of a modified example after an insert member is attached. FIG. 2 is a schematic diagram of a connector.

Example 1
<Image forming apparatus>
1 is a schematic cross-sectional view of an image forming apparatus 1. As shown in Fig. 1, the image forming apparatus 1 is a full-color printer of a tandem intermediate transfer type in which image forming units PY, PM, PC, and PK for yellow, magenta, cyan, and black are arranged along the moving direction of an intermediate transfer belt 31.

The image forming units PY, PM, PC, and PK are configured identically except for the different colors of toner used in the developing devices 14(Y), 14(M), 14(C), and 14(K).

The image forming unit includes a charging device 12 that charges the surface of the photosensitive drum 11, an exposure device 13, a developing device 14, and a cleaning blade 15.

The image formation process will be explained using image forming unit PY as an example.

First, the surface of the photosensitive drum 11Y is uniformly charged by the charging device 12Y. Then, the exposure device 13Y irradiates the photosensitive drum surface with a laser according to image data to form an electrostatic latent image. Then, the developing device 14Y attaches toner of each color to the electrostatic latent image to form a toner image on the surface of the photosensitive drum 11Y. The formed toner image is primarily transferred to the intermediate transfer belt 31 by applying a voltage to the primary transfer blade 17Y. After the primary transfer, any toner remaining on the photosensitive drum 11 that has not been transferred is scraped off and removed by the cleaning blade 15.

This series of processes is repeated for PM, PC, and PK to form a full-color toner image on the intermediate transfer belt 31.

The recording material P is taken out one by one from the recording material cassette 20 and waits at the pair of registration rollers 23. Specific examples of the recording material P include plain paper, resin sheet, coated paper, cardboard, and overhead projector sheet.

The recording material P is fed to the secondary transfer section T2 by the registration roller pair 23 in time with the toner image on the intermediate transfer belt 31. The fed toner image is secondarily transferred from the intermediate transfer belt 31 to the recording material P. The recording material P with the toner image secondarily transferred is transported to the fixing device 40, where it is fixed by heat and pressure. The recording material P with the fixed toner image is discharged to the external tray 64 by the discharge roller pair 63.

On the other hand, when toner images are formed on both sides of the recording material P, the recording material P, on which the toner image on one side has been fixed by the fixing device 40, is guided upward by the flapper 61. The recording material P is conveyed in a switchback manner on the conveying path 73. The switched-back conveyed recording material P is conveyed on the double-sided conveying path 70 and waits at the registration roller pair 23. The toner image is then secondarily transferred to the other side at the secondary transfer section T2. The recording material P, on which the toner image on the other side has been fixed by the fixing device 40, is then discharged onto the external tray 64.

<Fixing Device>
Fig. 2 is a schematic cross-sectional view of the fixing device, Fig. 3 is a schematic diagram of a ceramic heater which is a heating member, and Fig. 4 is a schematic diagram of the arrangement of a fixing flange which is an example of a regulating member.

As shown in the schematic cross-sectional view of the fixing device in FIG. 2, the fixing device 40 has a ceramic heater 100, a fixing film 101, and a pressure roller 106.

The ceramic heater 100, which is a heat-generating member, is a planar heater, one side of which is in contact with the fixing film 101. A heating resistor 100b is disposed on the surface in contact with the ceramic heater, and heat is generated when a current flows through the heating resistor 100b.

The fixing film 101 is a cylindrical endless film, and a ceramic heater is disposed inside the fixing film 101. The fixing film 101 is thin and has a small amount of heat. Therefore, the heat of the ceramic heater 100 is transferred almost directly to the outer surface of the fixing film 101, which is the heating section. Therefore, the heating section reaches a temperature exceeding the toner melting point temperature in a short time. This eliminates the need to constantly raise the temperature of the heating section, and achieves power saving. In addition, because the heating section reaches a temperature exceeding the toner melting point temperature in a short time, the time from when printing is requested to when the recording material is discharged is shortened.

The guide member 103 is disposed penetrating the fixing film 101 in the longitudinal direction and contacts the inner surface of the fixing film 101. The guide member 103 is formed in a beam shape using a synthetic resin material that is heat resistant, has a low coefficient of friction, and has low thermal conductivity. Examples of synthetic resin materials include phenolic resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, and LCP resin.

The stay 102 supports the entire guide member 103 in the longitudinal direction inside the fixing film 101 and applies pressure to the pressure roller 106. The stay 102 ensures the strength of the guide member 103. The stay 102 is formed into a beam shape using steel material with a U-shaped cross section.

As shown in the explanatory diagram of the arrangement of the fixing flange, which is a restricting member, in FIG. 4, the fixing flange 104 is fitted into both ends of the stay 102. The fixing flange 104 fitted into both ends of the stay 102 restricts the movement of the fixing film 101 in the longitudinal direction of the fixing film.

The pressure roller 106 is driven by the drive mechanism 120 to rotate at approximately the same peripheral speed as the conveying speed of the recording material P carrying the toner image conveyed from the secondary transfer section (T2: Figure 1). The pressure roller 106 has an outer diameter of φ25 mm. The pressure roller 106 has an outer diameter of φ20 mm, a 1.3 mm thick aluminum cylindrical material on the outside of which is formed an elastic layer 106b of 2.5 mm thick made of soft silicone rubber with an Asker hardness of 64°. The surface of the elastic layer 106b is covered with a release layer 106c made of a 50 μm thick PFA tube.

Bearing members (not shown) made of heat-resistant resin such as PEEK, PPS, or liquid crystal polymer are attached to both ends of the shaft member 106a, and the shaft member 106a is held rotatably by side plates (not shown). The release layer 106c is made of a material with excellent release properties and heat resistance, such as fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, PTFE, or FEP.

The fixing device 40 sandwiches a fixing film 101 between a ceramic heater 100 and a pressure roller 106 to form a nip portion N. The fixing device 40 applies heat from the ceramic heater 100 to the unfixed toner image conveyed to the nip portion N through the fixing film 101. At the same time, the ceramic heater 100 and the pressure roller 106 pressurize the unfixed toner image through the fixing film 101 to fix it.

Although not shown, a cover covers the fixing device from the longitudinal direction of the fixing device. The fixing device may be replaced by the user, and there is a risk that the user may come into contact with the fixing member when replacing the fixing device. For this reason, the fixing device is covered from the longitudinal direction by a cover.

<Pressure mechanism>
Fig. 5 is a schematic diagram of the pressure mechanism 130. A pair of the pressure mechanisms 130 are provided corresponding to the pair of fixing flanges 104 shown in Fig. 4. In Fig. 5, (a) shows a pressurized state, and (b) shows a pressure-released state.

The following describes how the pressure mechanism 130 switches between the pressurized state (a) and the unpressurized state (b).

The pressure lever 133 can rotate around the support shaft 117, and the rotating end is pressed by the pressure spring screw 134 to apply pressure to the pressure-receiving portion 104b of the fixing flange. The pressure spring screw 134 is fixed by the pressure screw fixing portion 135. When the motor 137 rotates the drive shaft 131, the eccentric cam 132 rotates around the drive shaft 131, raising and lowering the rotating end of the pressure lever 133.

The pressure mechanism 130 presses the fixing film 101 in the pressure direction by releasing the eccentric cam 132 pushing up the pressure lever 133, forming a nip portion of the recording material between the fixing film 101 and the pressure roller 106. The eccentric cam 132 rotates, and the pressure lever 133 operates in a direction to press the pressure-receiving portion 104b of the fixing flange, creating a pressurized state in which a pressure force f is applied between the fixing film 101 and the pressure roller 106.

As shown in FIG. 5B, the pressure mechanism 130 releases the pressure on the fixing film 101 by pushing up the pressure lever 133 with the eccentric cam 132, and separates the fixing film 101 from the pressure roller 106. When the eccentric cam 132 rotates and the pressure lever 133 separates from the pressure-receiving portion 104b of the fixing flange, a pressure-released state is created in which no pressure is applied between the fixing film 101 and the pressure roller 106.

The purpose of releasing the pressure is to prevent deformation of the pressure roller 106 when the power is turned off or in sleep mode.

<Connector>
12 is a schematic diagram of the connector for explaining the connector, which has a U-shaped housing member 110e and a hook 104d.

The U-shaped housing member 110e has a current terminal 110A and a current terminal 110B on the inside, and current flows to the ceramic heater 100 via the current terminals 110a and 110b.

The housing member 110e will be described in detail. The housing member 110e is composed of a bottom 211 and a pair of extensions 210 extending from both ends of the bottom 211. The bottom 211 and the pair of extensions 210 form a general U-shape. Electrical terminals are provided on the inside of the pair of extensions 210 so as to face each other. In other words, when the connector is inserted into the electrode 100d arranged at the end of the ceramic heater 100, the ceramic heater 110 is sandwiched between electrical terminals A and B. The connector 110 is attached to the ceramic heater 100 in a direction intersecting the longitudinal direction of the fixing device. In FIG. 6, the connector 110 is attached from the direction of arrow A as a representative example.

A hook extends from the outside of the extension part 210t on the side where the current-carrying terminal 110a is formed (the side where the current-carrying terminal b is formed is referred to as extension part 210b) of the pair of extension parts 210. The hook extends from the tip side of extension part 210t toward the bottom. In other words, a gap G is formed between hook 104d and the outer surface of extension part 210t.

When the connector 110 is inserted into the ceramic heater 100, the hook 110d is pressed against the engagement portion 104a of the fixing flange, and the hook 110d elastically deforms toward the extension portion 210t so as to narrow the gap G. When the connector 110 is inserted further, the elastic deformation of the hook 110d is released, and the engagement between the engagement portion 104a of the fixing flange and the hook 110d is completed.

<Insertion parts>
When assembling the fixing device, the wiring 110c connected to the connector may be pulled by an operator, which may unintentionally release the engagement between the engagement portion 104a of the fixing flange and the hook 110d, causing the connector 110 to come off from the fixing flange 104. Conventionally, therefore, an insert member is inserted into the gap G. The presence of the insert member in the gap G limits the elastic deformation of the hook portion 110d in the direction of the extension portion 210t. This prevents the engagement between the fixing flange 104 and the hook portion 110d from being released. However, by attaching the insert member from the longitudinal direction of the fixing device, the insert member protrudes outward from the connector 110 in the longitudinal direction of the fixing device. Therefore, the cover that covers the fixing device from the longitudinal direction had to be enlarged in the longitudinal direction of the fixing device. Therefore, by using an insert member 111 that does not protrude outward from the connector 110 in the longitudinal direction of the film, the cover can be made smaller. A detailed explanation of this is given below.

7 is a schematic diagram of the shape of the plug member 111 and how the plug member 111 is attached to the connector 110. FIG. 8 is a schematic diagram of the plug member after attachment, where FIG. 8(a) is a view from the longitudinal direction, FIG. 8(b) is a view from the conveying direction, and FIG. 8(c) is a cross-sectional view taken along line A-A of FIG. 8(b). As shown in FIG. 7, the plug member 111 has a plug portion 111a that limits the elastic deformation of the hook portion 110d of the connector 110, and an engagement portion 111b with the connector 110. The plug portion 111a is inserted between the hook portion 110d of the connector 110 and the housing member 110e in the S1 direction of FIG. 7. The inserted plug portion 111a is inserted in a position facing the engagement portion 104a of the fixing flange. The engagement portion referred to here refers to the portion where the hook portion 110d and the engagement portion 104a are in contact. In other words, when the plug-in member 111 is plugged into the connector 110, the plug-in portion 111a faces the engagement portion 104a via the hook portion 110d. In FIG. 8(a), the plug-in portion 111a supports the hook portion 110d at a position where it faces the engagement portion 104a via the hook portion 110d, but the hook portion 110d may be supported further back in the plug-in direction of the connector 110.

The inserted plug portion 111a restricts the elastic deformation of the hook portion 110d into the housing member 110e. As a result, the engagement between the engagement portion 104a of the fixing flange and the hook portion 110d of the connector 110 is prevented from being released. As a representative example, in FIG. 7, the plug portion 111a has a protrusion. However, for example, the plug portion 111a may have a thick shape that restricts the elastic deformation of the hook portion 110d.

As shown in FIG. 8B, the inserted plug member 111 does not protrude from the connector in the longitudinal direction. This allows the cover that covers the fixing device to be prevented from being enlarged in the longitudinal direction, and the space required for the fixing device, including the cover, can be reduced in the longitudinal direction.

The engaging portion 111b of the insertion member 111 is structured so that it can bend inward with 111c as a fulcrum when it is attached to the hollow portion 111f of the connector 110. The insertion member 111 is attached to the hollow portion 110f of the connector 110 in the direction of the arrow S1, which is the transport direction. The height h1 of the hollow portion 110f of the connector 110 and the height h2 of the engaging portion 111b of the insertion member 111 correspond to the pressure direction. When the insertion member is attached to the connector, h1 and h2 correspond to each other, so the insertion member is fixed in the pressure direction. As mentioned above, the engaging portion 111b of the insertion member 111 is in a state where it can bend with 111c as a fulcrum, and in the natural state, the relationship between the width d2 of the insertion member and the width d1 of the connector is d2 ≧ d1. When the plug-in member 111 is attached, the width d2 of the plug-in member bends to match the width d1 of the cavity of the connector, and the plug-in member 111 is fixed to the connector member 110 in the longitudinal direction. The cavity 110f of the connector 110 has protrusions 110g protruding inward from both ends in the longitudinal direction. When the plug-in member 111 is attached, the two engagement parts 111b bend inward and overcome the protrusions 110g, and the plug-in member 111 is fixed in the conveying direction by engaging with the engagement parts 111b and the protrusions 110g. The plug-in member is shown in the attached state in Figure 8. When the plug-in member is inserted into the gap G in this way, the plug-in member is fixed to the connector. This configuration makes it possible to omit the process of fixing the plug-in member, simplifying the assembly process for the worker.

In this way, the plug-in member 111 of this embodiment prevents the connector from coming loose, reduces the size of the fixing device including the cover, and simplifies the assembly process for the worker.

<Modification>
9, 10, and 11, a fixing device according to the second embodiment and an image forming apparatus including the same will be described. Note that the configuration of the image forming apparatus is the same as that of the first embodiment, so the description will be omitted, and only the configuration of the fixing device will be described here. In the fixing device, the same parts as those in the first embodiment will also be omitted.

9 is a schematic diagram of the insertion member in the modified example. FIG. 10 is a schematic diagram of the insertion member when attached in the modified example. FIG. 11 is a schematic diagram of the insertion member after attachment in the modified example, where FIG. 10(a) is a view from the longitudinal direction and FIG. 10(b) is a view from the transport direction. As shown in FIG. 9, the insertion member 112 has an insertion portion 112a that fixes the hook portion 110d of the connector 110 so that it does not deform, an engagement portion 112b with the connector 110, and a fitting portion 112c that positions the connector in the longitudinal direction. As shown in FIG. 10, the insertion member 112 is positioned in the longitudinal direction by attaching the width d4 of the fitting portion 112c of the insertion member 112 to the width d3 of the fitting groove 110i of the connector in the direction of S1, which is the transport direction. At that time, the engagement portion 112b of the insertion member 112 is attached over the protrusion portion 110h, so that the engagement portion 112b and the protrusion portion 110g engage with each other. The pressure direction of the insertion member 112 is fixed by sandwiching the outer shape h3 of the connector 110 between the engagement portion 112b of the insertion member 112 and the height h4 of the insertion portion 112a, and is attached as shown in FIG. 10. The inserted insertion portion 112a limits the elastic deformation of the hook portion 110a of the connector 110 in the direction of the conductive terminal 110a, as in the first embodiment. As a result, the engagement between the engagement portion 104a of the fixing flange and the hook portion 110d of the connector 110 is prevented from being released. In addition, as shown in FIG. 11(b), the inserted insertion member 112 does not protrude from the connector in the longitudinal direction. Therefore, as in the first embodiment, there is no need to enlarge the cover that covers the connector in the longitudinal direction, and the fixing device including the cover can be made more space-saving.

REFERENCE SIGNS LIST 1 Image forming apparatus 40 Fixing apparatus 100 Ceramic heater 100a Ceramic substrate 100b Resistance heating element 100c Glass protective body 100d Electrode 101 Fixing film 102 Stay 103 Guide member 103a Fitting groove 104 Fixing flange 104a Engagement portion 104b Pressured portion 106 Pressure roller 106a Core metal 106b Elastic layer 107 Cover 110 Connector 110a Current-carrying terminal (upper portion)
110b Current-carrying terminal (bottom)
110c Wiring 110d Hook portion 110e Housing member 210 Extension portion 211 Bottom portion 110f Hollow portion 110g Projection portion 110h Projection portion 110i Fitting groove 111 Insert member 111a Insert portion 111b Engagement portion 112 Insert member 112a Insert portion 112b Engagement portion 112c Fitting portion G Gap

Claims (4)

An endless film in contact with the recording material ;
a heater having electrodes at ends of the film in the longitudinal direction, the heater being disposed inside the film, and generating heat when a current flows therethrough to heat the film;
a pressure roller that contacts the outer peripheral surface of the film and forms a fixing nip portion together with the film;
The pressure roller conveys the recording material together with the film while applying heat and pressure to the recording material, thereby fixing the toner image on the recording material.
a flange that restricts movement of the film in a longitudinal direction of the film;
a U-shaped connector including a housing having terminals connected to the electrodes, and a hook protruding from the housing and elastically deformable to engage with the flange, the U-shaped connector being inserted into the heater in a direction intersecting the longitudinal direction;
an insertion member that is inserted between the terminal and the hook to limit elastic deformation of the hook;
The plug member is fixed to the connector so as not to protrude from the connector in the longitudinal direction.
A fixing device comprising: The plug member is inserted between the terminal and the hook in a direction perpendicular to the longitudinal direction.
2. The fixing device according to claim 1, a cover that covers the connector from an outer side of the connector in the longitudinal direction.
3. The fixing device according to claim 1, wherein the fixing member is a fixing member having a fixing roller. The heater contacts the inner circumferential surface of the film.
4. The fixing device according to claim 1, wherein the fixing member is a fixing member having a fixing roller.

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