JPH11167308A - Thermal fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal fixing device having a surface temperature detection means constituted so that the increase of friction with a movably heating member may prevented by uniformizing the pressure distribution at a contact part to the surface shape of the movable heating member such as a roller or a belt whose surface is soft. SOLUTION: This thermal fixing device is provided with a thermistor unit provided with a thermistor 501, a heat resistant sponge 502 elastically holding the thermistor 501, a polyimide film 506 insulating the thermistor 501 from a roller 401 and also conducting heat to the thermistor 501 while sliding on the surface of the roller 401, and a pressure spring 504 integrally holding and pressing the thermistor 501, the sponge 502 and the film 506 to the roller 401. Relating to the device, the thermistor unit is provided with hardening resin 101 which is solidified and formed along the surface shape of the roller 401 so as to integrally fix the thermistor 501 on the sponge 502.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device incorporated in an image forming apparatus such as a laser beam printer, a copying machine, etc. It relates to means for detecting.

[0002]

2. Description of the Related Art As a thermal fixing device of an image forming apparatus, a recording material on which a toner image is formed is passed through a movable heating member such as a roller or a belt to heat and press to fix the toner image on the recording material. Is widely used. In this heat fixing device, the surface temperature of the movable heating member is appropriately controlled in order to obtain a good fixed image.

An example of a conventional heat fixing device will be described below with reference to FIG. The heat fixing device shown in FIG. 4 is for a monochrome printer.

The fixing roller 401 and the fixing roller 40
1 and a pressure roller 402 pressed against it.
Only the fixing roller 401 has a built-in halogen heater 405. A thermistor unit 403 is slidably disposed on the surface of the fixing roller 401, and converts the surface temperature of the fixing roller 401 into an electric signal and detects the electric signal. The electric signal from the thermistor unit 403 is input to the CPU 404.

On the other hand, a halogen heater 405 of the fixing roller 401 is connected to a triac 406. The triac 406 has a gate input connected to the output side of the CPU 404 via a phototriac 407.

The CPU 404 includes a thermistor unit 40
The detected temperature input from Step 3 is compared with the fixing target temperature, and the temperature of the halogen heater 405 is feedback-controlled so that the surface temperature of the fixing roller 401 becomes a predetermined fixing target temperature.

Next, the structure of the contact portion between the thermistor unit 403 and the fixing roller 401 will be described with reference to FIG.

The thermistor unit 403 includes a thermistor 501, a heat-resistant sponge 502 for holding the thermistor 501, a pressing leaf spring 504 to which the heat-resistant sponge 502 is attached via a polyimide film 503,
Thermistor lead 5 extending from the thermistor 501 and wired between the pressing leaf spring 504 and the heat-resistant sponge 502
05, and a polyimide film 506 integrally covering the heat-resistant sponge 502 and the thermistor 501. The thermistor 501 is formed by a dip process for sealing a ceramic component with molten glass.

On the other hand, the fixing roller 401 has a metal core 507 made of an aluminum pipe, and a Teflon layer 508 provided on the surface of the metal core 507 to improve the releasability of the toner.

The thermistor unit 403 of the type shown in FIG. 5 has no problem when it is mounted on a roller having a hard surface such as the heat fixing device of a black-and-white printer shown in FIG. When the roller is mounted on a soft roller such as a fixing device, the roller is deformed as described below.

In a color printer, it is necessary to apply sufficient heat and pressure in order to sufficiently melt and mix toners of a plurality of colors at the time of fixing. Therefore, a heat fixing device as shown in FIG. 6 is used. .

In this thermal fixing device for a color printer, a fixing roller 401 and a pressure roller 402 are provided with a heat-resistant silicone rubber layer extending up to 2 mm between a core made of aluminum pipe and a 50 μm Teflon layer. Are formed. FIG. 7 shows a core metal 507, a Teflon layer 508, and a heat-resistant silicone rubber layer 701 of the fixing roller 401. The heat-resistant silicone rubber layer increases the width (nip) of the contact surface between the rollers 401 and 402 by elastic deformation, increases the adhesion of the recording paper to the toner image, and improves the heat application property.

A halogen heater 405 of the fixing roller 401 and a halogen heater 6
01 is incorporated to improve the fixing performance. The temperature of the halogen heater 601 is controlled by a triac 602 and a photo triac 603.

FIG. 7 shows a state where the thermistor unit shown in FIG. 5 is mounted on the heat fixing device of the color printer.

The fixing roller 401 for a color printer includes:
Since the heat-resistant silicone layer 701 is provided, the surface is soft. Therefore, the surface of the polyimide film 506 sinks in the shape of the thermistor 501 and the fixing roller 401
Deform the surface of

Next, a conventional example of a thermistor unit of a type different from that shown in FIGS.
This is shown in FIG. FIG. 8 shows a perspective view of the thermistor unit, and FIG. 9 shows a mounted state of the thermistor unit.

As shown in FIGS. 8 and 9, the thermistor unit includes a chip-type thermistor 801, a lead frame 802 to which the thermistor 801 is adhered and also serves as a pressure spring, and the thermistor 801 and the lead frame 80.
2, a protective resin 804 for protecting the wire bonding 803, and a polyimide film 805 bonded to the lead frame 802 on the side opposite to the thermistor 801 (the side facing the roller). And a polyimide film 806 provided on the thermistor 801 side of the lead frame 802 so as to allow the protective resin 804 to escape therefrom, and a fixed mold 807 for integrally insert-molding the base end side of the lead frame 802.

A thermistor mounting portion 902 is provided on a housing 901 of the heat fixing device. This thermistor mounting portion 90
The fixing mold 807 of the thermistor unit is screw 9
03 is fixed. This thermistor unit is
Fixing roller 401 by the spring force of lead frame 802
Is pressed against.

[0019]

However, the two types of thermistor units shown in FIGS. 7 and 9 have the following problems.

First, in the thermistor unit 403 of the type using the thermistor 501 obtained by the above-described dip process shown in FIG. 7, the fixing roller 40 having a soft surface like a heat fixing device for a color printer is used.
The following problem occurs when the camera is mounted on the camera.

Since the thermistor 501 is formed by a dipping process in which a ceramic component is sealed in molten glass, the thermistor 501 has a non-uniform and irregular shape. for that reason,
This thermistor 501 is held flexibly by a heat-resistant sponge 502. The thermistor 501 is in contact with the fixing roller 401 via a polyimide film 506 as an electrically insulating sliding member. The thermistor 501 is pressed by a pressing leaf spring 504.

In a thermal fixing device for a black and white printer,
Since the surface of the fixing roller 401 is hard, the surface of the polyimide film 506 follows the surface of the fixing roller 401 (see FIG. 5). On the other hand, in the thermal fixing device for a color printer, since the surface of the fixing roller 401 is soft, the surface of the polyimide film 506 becomes thermistor 501.
, And a strong resistance is generated between the surface of the fixing roller 401 and the Teflon layer 508 on the surface of the fixing roller 401. Teflon layer 5
When 08 is lost, the releasability of the portion is impaired, so that the toner is offset to the fixing roller 401, causing a problem that the fixed image is impaired.

On the other hand, in the thermistor unit of the type using a chip-shaped thermistor 801 as shown in FIG. 9, the lead frame 802 is interposed between the thermistor 801 and the fixing roller 401, so that the contact portion The pressure distribution can be made uniform, and the fixing roller 401 does not deform.

However, on the other hand, there is a restriction that the thickness of the lead frame 802 cannot be too large in order to prevent heat from escaping to the lead frame 802 and to prevent a decrease in response due to an increase in heat capacity. If the lead frame 802 is thin, the lead frame 802 may be removed when the paper is wound around the rollers 401 and 402 due to a jam or the like.
2 is easily plastically deformed.
This problem occurs regardless of whether the surface of the roller is soft or hard. That is, the same problem occurs in both the thermal fixing devices of the monochrome printer and the color printer.

A first object of the present invention is a surface temperature detecting means of a type in which a temperature detecting means obtained by a dipping step is held by an elastic holding means, wherein a contact portion of a movable heating member having a soft surface with a surface shape is provided. Another object of the present invention is to provide a heat fixing device having a surface temperature detecting means for preventing an increase in friction with a movable heating member by making the pressure distribution uniform.

A second object of the present invention is a surface temperature detecting means of a type in which a tip-shaped temperature detecting means is fixed to a pressure contact spring means, wherein the surface temperature detecting means prevents plastic deformation of the pressure contact spring means. An object of the present invention is to provide an image forming apparatus having:

[0027]

According to a first aspect of the present invention, the first object is to allow a recording material on which a toner image is formed to pass through a movable heating member such as a roller or a belt. The temperature detecting device detects the surface temperature of a movable heating member of a heat fixing device that fixes a toner image on a recording material by heating and pressing. The temperature detecting device converts temperature information into an electric signal. Elastic holding means for holding the temperature detecting means electrically insulated from the movable heating member and a film-shaped film insulating means for transferring heat to the temperature detecting means while closely sliding on the surface of the movable heating member; In a thermal fixing apparatus having a surface temperature detecting means having a temperature detecting means, an elastic holding means, and a pressure contact spring means for integrally holding a film insulating means and pressing against a movable heating member, Temperature detection means is achieved by having a solidification means for integrally fixed to the elastic holding means temperature sensing means by being formed and solidified to fit the surface shape of the movable heating element.

According to the second aspect of the present invention,
A second object of the present invention is to provide a heat-fixing device in which a recording material on which a toner image is formed is passed through a movable heating member such as a roller or a belt to apply heat and pressure to fix the toner image on the recording material. Thermal fixing device for detecting a surface temperature, comprising: a temperature detecting means for converting temperature information into an electric signal; and a pressing spring means for holding the temperature detecting means and pressing against a movable heating member. In the device, the surface temperature detecting means is achieved by having a regulating means disposed behind the pressure contact spring means with a space in which the pressure contact spring is elastically deformable.

According to the third aspect of the present invention,
The second object is achieved when the regulating means is made of an electrically insulating material.

[0030] In the fourth invention according to the present application, the second object is achieved by the restriction means being made of an elastic material.

That is, in the first invention according to the present application, the solidifying means solidifies in accordance with the surface shape of the movable heating member, thereby integrally fixing the temperature detecting means to the elastic holding means, and The detection means is maintained in the shape of the surface of the movable heating member to prevent deformation. As a result, the pressure distribution at the contact portion of the surface temperature detecting means with respect to the movable heating member is made uniform, the friction between the movable heating member and the movable heating member is prevented from increasing, and the Teflon layer on the surface of the movable heating member is scraped off to release the mold. Is prevented from lowering, thereby preventing the toner from being offset to the movable heating member.

Further, in the second invention according to the present application, the regulating means is arranged with a space capable of being elastically deformed behind the pressure contact spring means to prevent plastic deformation of the pressure contact spring means. Since the appropriate pressing force of the press-contact spring means is not impaired, it is possible to prevent the temperature detection performance of the thermistor unit from being lowered.

Further, in the third invention according to the present application, the regulating means of the second invention is made of an electrically insulating material, and prevents the detected electric signal from short-circuiting through the regulating means. I do.

According to the fourth aspect of the present invention,
The restricting means of the second or third invention is made of an elastic material, and prevents the contacted surface temperature detecting means from being damaged or deformed.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to FIGS.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a state where the thermistor unit (surface temperature detecting means) of the present embodiment is mounted on a fixing roller of a heat fixing device. 2A to 2C show a process of manufacturing the thermistor unit in FIG. The entire thermal fixing device for a color printer to which the thermistor unit is attached is as shown in FIG. The thermistor unit of this embodiment is an improvement of the thermistor unit of FIG. 7 which is a conventional example.

The manufacturing process of the thermistor unit according to this embodiment will be described with reference to FIGS.

First, FIG. 2A shows a state immediately after the thermistor unit of the present embodiment is assembled.

This thermistor unit comprises a thermistor 5
01, a heat-resistant sponge 502 for holding the thermistor 501, a pressure leaf spring 504 in which the heat-resistant sponge 502 is attached via a polyimide film 503, and a pressure leaf spring 504 extending from the thermistor 501 and the heat-resistant sponge 502. Thermistor lead 50 wired between
5, a polyimide film 506 integrally covering the heat-resistant sponge 502 and the thermistor 501; a thermistor 501, the heat-resistant sponge 502 and the polyimide film 5
06 and the curable resin 101 filled between them.

Here, the thermistor 501 is a temperature detecting means, the heat-resistant sponge 502 is an elastic holding means, the polyimide film 506 is a film insulating means, and the pressing leaf spring 504 is used.
Corresponds to a pressing spring means. The curable resin 101 corresponds to a solidifying unit.

The most significant feature of the present embodiment resides in that the curable resin 101 as a solidifying means is filled. In this embodiment, as the curable resin 101, a heat-resistant silicone resin such as Toray SE4420 having a relatively high thermal conductivity after solidification is used. In the state of FIG. 2A, the curable resin 101 has not yet been solidified immediately after filling, and thus the state where the thermistor 501 is extruded toward the polyimide film 506 by the pressure of the heat-resistant sponge 502 is shown.

Next, FIG. 2B shows a curing step of the curable resin 101 of the thermistor unit.

The jig 102 has the same curvature as the surface (see FIG. 1) of the fixing roller 401 to which the thermistor unit is mounted. In FIG. 2A, the curable resin 10
1 is filled in the thermistor unit shown in FIG.
In the above, the cured resin 101 is cured while being pressed against the jig 102 under the same pressure conditions as during use.

Next, FIG. 2C shows the thermistor unit separated from the jig 102 after the curing step. When the curable resin 101 is cured, the thermistor 501, the curable resin 101, and the heat-resistant sponge 502
And the polyimide film 506 are integrally fixed. In particular, the surface of the polyimide film 506 serving as the contact surface of the thermistor unit with the fixing roller 102 is formed with the same curvature as the fixing roller 401.

FIG. 1 shows a state in which the cured thermistor unit shown in FIG. 2C is mounted on a fixing roller 102 of a thermal fixing device for a color printer.

Since the sliding surface of the thermistor unit is the same as the curvature of the fixing roller 401, the pressure distribution becomes uniform, and the surface of the soft fixing roller 401 used in the heat fixing device of the color printer is prevented from changing. An increase in frictional resistance due to deformation is prevented, so that the fixing roller 40
The wear of the one Teflon layer 508 can be minimized.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows a state where the thermistor unit is mounted on a thermal fixing device for a color printer. Here, the case where the image forming apparatus is mounted on a heat fixing device for a color printer is shown, but the image forming apparatus may be mounted on a heat fixing device having a hard roller for a black and white printer.

The thermistor unit shown in FIG. 3 is of a type having a chip-shaped thermistor 801 as temperature detecting means. The thermistor unit includes a leaf spring-shaped lead frame 802 which also serves as a pressure contact spring means to which the thermistor 801 is adhered and a lead wire;
01 and the lead frame 802, and the wire bonding 803
3, a polyimide film 805 bonded to the lead frame 802 on the side opposite to the thermistor 801 (the side facing the fixing roller 401), and the protective resin 804 on the lead frame 802 on the side of the thermistor 801. Polyimide film 806 provided in the area where
02 and a fixed mold 807 for integrally insert-molding the base end side. This thermistor unit is
The housing 90 of the heat fixing device via the thermistor mounting portion 902
Attach to 1. The regulating member 30 is spaced apart from the thermistor unit on the side opposite to the fixing roller 401 about the lead frame 802 of the thermistor unit.
1 is arranged. The point that the regulating member 301 is provided in this way is the greatest feature of the present embodiment. In the present embodiment, the regulating member 301 is provided on the inner surface of the housing 901.

The back of the thermistor unit (fixing roller 4
The distance between the apex of the protective resin 804 provided on the side opposite to (01) and the regulating surface (lower surface) of the regulating member 301 is set in the elastic deformation area of the lead frame 802. When the lead frame 802 of the thermistor unit is bent to the side opposite to the fixing roller 401 in order to remove the paper jam generated on the rollers 401 and 402 of the heat fixing device, the thermistor unit comes into contact with the regulating member 301. No more turns. Thus, the lead frame 8
02 is only elastically deformed (because it is not plastically deformed), so that the pressing force (for example, a light pressing force of about 10 g) of the lead frame 802 as the pressure contact spring means is not impaired, and the temperature sensing performance of the thermistor unit is reduced. Nothing to do.

The regulating member 301 of this embodiment is made of heat-resistant silicone rubber. Since the heat-resistant silicone rubber has elasticity, it does not damage or deform the contacted thermistor unit. Further, since the heat-resistant silicone rubber is an electrically insulating material, short circuit of the lead frame 802 through which the thermistor detection signal flows is prevented.

The present invention is not limited to the above-described embodiment, and various modifications can be made.

For example, in the above-described embodiment, the case where the thermistor unit is mounted on the fixing roller 401 is shown. However, the present invention is not limited to this, and the thermistor unit may be mounted on the pressure roller 402 side.

In the above-described embodiment, a roller is shown as the movable heating member. However, the present invention is not limited to this, and a belt or the like may be used.

[0054]

According to the first aspect of the present invention described above, the temperature detecting means is integrally fixed to the elastic holding means by solidifying the solidifying means in accordance with the surface shape of the movable heating member. The surface temperature detecting means is maintained in the surface shape of the movable heating member to prevent deformation. As a result, the pressure distribution of the contact portion of the surface temperature detecting means with respect to the movable heating member is made uniform, and an increase in friction with the movable heating member is prevented. Therefore, it is possible to prevent the Teflon layer on the surface of the movable heating member from being scraped off, thereby reducing the releasability, and thereby preventing the toner from being offset to the movable heating member.
The quality of the fixed image can be improved.

According to the second invention of the present application,
The restricting means is arranged behind the press-contact spring means with an elastically deformable space to prevent plastic deformation of the press-contact spring means. Since the appropriate pressing force of the press-contact spring means is not impaired, it is possible to prevent the temperature detection performance of the thermistor unit from being lowered.

According to the third aspect of the present invention,
Since the regulating means of the second invention is made of an electrically insulating material, it is possible to prevent a short circuit of the detected electric signal through the regulating means.

According to the fourth invention of the present application,
Since the regulating means of the second invention or the third invention is made of an elastic material, it is possible to prevent the contacting surface temperature detecting means from being damaged or deformed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a mounting state of a surface temperature detecting unit of a heat fixing device according to a first embodiment of the present invention.

2A and 2B are diagrams showing a manufacturing process of the temperature detecting means of FIG. 1, wherein FIG. 2A shows a state immediately after assembling, FIG. 2B shows a state in which the temperature detecting means is in contact with a jig, and FIG. ing.

FIG. 3 is a cross-sectional view illustrating a surface temperature detecting unit of a heat fixing device according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing the entire heat fixing device for a black and white printer.

5 is a cross-sectional view showing a state in which an example of a conventional surface temperature detecting unit is mounted on the monochrome fixing device of FIG.

FIG. 6 is a schematic configuration diagram illustrating an entire heat fixing device for a color printer.

7 is a cross-sectional view showing a state in which the conventional surface temperature detecting means shown in FIG. 5 is mounted on the color heat fixing device shown in FIG.

FIG. 8 is a perspective view showing another example of the conventional temperature detecting means.

9 is a cross-sectional view showing a state in which the surface temperature detecting unit of FIG. 8 is mounted on a thermal fixing device.

[Explanation of symbols]

 Reference Signs List 101 Curable resin (solidifying means) 301 Control member (control means) 401 Fixing roller (movable heating member) 501 Thermistor (temperature detecting means) 502 Heat-resistant sponge (elastic holding means) 504 Pressing spring (press-contact spring means) 506 Polyimide film (Film insulating means) 507 Core 508 Teflon layer 701 Heat-resistant silicone rubber layer 801 Thermistor (Temperature detecting means) 802 Lead frame (Press-contact spring means) 901 Housing of heat fixing device

Claims (4)

[Claims] 1. A surface temperature of a movable heating member of a heat fixing device for fixing a toner image to a recording material by heating and pressing the recording material having a toner image formed thereon by passing the recording material through a movable heating member such as a roller or a belt. Temperature detecting means for converting the temperature information into an electric signal,
Elastic holding means for elastically holding the temperature detecting means,
A film-shaped film insulating unit that electrically insulates the temperature detecting unit from the movable heating member and conducts heat to the temperature detecting unit while closely sliding on the surface of the movable heating member; a temperature detecting unit and an elastic holding unit; In a heat fixing device having a surface temperature detecting means having a pressure contact spring means for integrally holding a film insulating means and pressing against a movable heating member,
The heat fixing device, wherein the surface temperature detecting means has a solidifying means which is solidified and formed in accordance with the surface shape of the movable heating member to thereby integrally fix the temperature detecting means to the elastic holding means. . 2. A surface temperature of a movable heating member of a heat fixing device for fixing a toner image to a recording material by heating and pressing the recording material having a toner image formed thereon by passing the recording material through a movable heating member such as a roller or a belt. Temperature detecting means for converting the temperature information into an electric signal,
In a heat fixing device having surface temperature detecting means having pressure contact spring means pressed against the movable heating member while holding the temperature detecting means, the surface temperature detecting means has a pressure contact spring elastically deformable on the back surface of the pressure contact spring means. A heat fixing device comprising a regulating means arranged with a space. 3. The heat fixing device according to claim 2, wherein the regulating means is made of an electrically insulating material. 4. The heat fixing device according to claim 2, wherein the regulating means is made of an elastic material.