JPH10240357A - Heater, fixation device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the heater of better responsiveness capable of accurately detecting a temperature by providing a temperature detection element for detecting a heating temperature by a heating element and providing the temperature detection element on a substrate on the same surface side provided with the heating element. SOLUTION: On the surface of the substrate 17 formed by alumina or the like, the heating element 18 composed of an electric resistance material such as silver palladium or the like for instance is applied by screen printing or the like and glass or fluororesin or the like is coated on it as a protective layer 19. Further, a thermister 20 which is the temperature detection element for detecting the heating temperature by the heating element 18 is attached so as to perform the temperature control of this heater. For the thermister 20, a thermister material 20a and an electrode 20b are formed by printing near the heating element 18 on the substrate 17 on the same surface side provided with the heating element 18 and the upper surface is coated with the protective layer 19. By the constitution, since the temperature is detected on the same surface as the heating element, regardless of the thickness of the substrate or the like, the temperature is directly and more accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater capable of accurately detecting a heating temperature of a heating element, a fixing device using the heater, and an image forming apparatus.

[0002]

2. Description of the Related Art Many printers, copiers and the like form an image by an electrophotographic recording method. In the electrophotographic recording method, a toner image is transferred to a recording medium, and heat and pressure are applied to the recording medium. Is applied to fix the toner image.

As a fixing device for fixing the toner image, a heat roller system has been conventionally used. This method is based on a metal roller with a heater inside and a pressure roller with elasticity that comes into pressure contact with it.
The toner image is heated and pressed and fixed by introducing a recording medium as a member to be heated into the nip portion of the roller pair, nipping, conveying and passing the recording medium.

However, in such a heat roller type fixing device, it takes a very long time to raise the surface of the roller to the fixing temperature because the heat capacity of the roller is large. For this reason, in order to quickly execute the image output operation, there is a problem that the roller surface must be kept at a certain temperature even when the apparatus is not used.

In order to solve the above-mentioned problems, a film heating type heating device for heating and fixing a film has been proposed (JP-A-63-313182;
No. -1557878).

This film heating type fixing device is usually
A heat-resistant film of a book, a heating element (heater) fixedly supported and disposed on one side of the film, and a heater disposed on the other side of the film opposite to the heater via a film. It is composed of a pressure member for bringing the member to be heated into close contact.

When this is used as a fixing device, a recording medium on which a toner image is formed and carried is introduced into a press-contact nip formed by press-contact between a heater and a pressing member with the film interposed therebetween. By passing the recording medium, the surface of the visible image carrier of the recording medium is heated by the heater via the film, heat energy is applied to the unfixed image, the toner is softened and melted, and the image is heated and fixed.

The heater has a resistance heating element that generates heat when energized, and a ceramic substrate having good thermal conductivity on which the resistance heating element is provided. The resistance heating element is provided by an output of a temperature detecting element for detecting the temperature of the substrate. Is controlled.

Conventionally, upon detecting the temperature, a thermistor composed of thermistor beads protected by glass is attached to the back surface of the heating element including the resistance heating element, and the resistance value of the thermistor beads is measured by a lead wire. The temperature of the body is detected and the power applied to the resistance heating element of the heating body is controlled to control the temperature of the heating body to a predetermined value.

[0010] In order to eliminate the variation in the contact state between the thermistor and the heating element and improve the responsiveness, FIG.
As shown in FIG. 5, a heater in which a chip-type thermistor is mounted on the back surface of a heater substrate 55 provided with a heating element 57 has been produced. This chip type thermistor is made of alumina base
A thermistor material 51 and an electrode 52 are laminated on 50 and are coated with glass as a moisture-proof layer 53. Then, the chip-type thermistor is bonded to an electrode provided on the back surface of the heater substrate 55 with a conductive adhesive 54 having high heat resistance.

In order to further improve the assemblability and improve the responsiveness, it has been proposed to form the thermistor 56 directly on the heater substrate 55 by printing as shown in FIG. Since the printing thermistor has no gap with the heater substrate 55 and is printed directly on the substrate 55, the responsiveness variation is reduced, and more accurate temperature detection becomes possible.

[0012]

In today's image forming apparatuses and the like, with the increase in the process speed, it is required to secure good fixability and to realize a quick start. For that purpose, it is necessary to use a material having high thermal conductivity and low heat capacity for each member of the heat fixing device.

However, when the heat capacity of the heater is reduced,
If the response time of the temperature detecting element is long because the temperature of the heater rises and falls quickly, the temperature ripple becomes large and the control to the target temperature becomes complicated. Therefore, a heater that has a higher responsiveness and that can accurately detect a heating temperature is desired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a heater having better responsiveness and capable of accurately detecting a temperature, and a fixing device and an image using the heater. An object of the present invention is to provide a forming apparatus.

[0015]

To achieve the above object, a typical configuration according to the present invention comprises a substrate, a heating element provided on one side of the substrate, which generates heat when energized, and a heating element. And a temperature detecting element for detecting a heating temperature of the heating element, wherein the temperature detecting element is provided on a substrate on the same surface on which the heating element is provided.

In the above configuration, since the temperature is detected on the same surface as the heating element, the temperature can be directly and accurately detected regardless of the thickness of the substrate.
Therefore, when the fixing device and the image forming device are configured using the heater, it is easy to control the fixing temperature with higher accuracy, and it is possible to obtain a high-quality image.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an image forming apparatus using a fixing device according to the present invention will be described with reference to the drawings.

First Embodiment FIGS. 1 to 4 show a first embodiment, FIG. 1 is an explanatory view of a configuration of a heater, FIG. 2 is an overall schematic explanatory view of an image forming apparatus, and FIG. FIG. 3 is an explanatory diagram of a configuration of a fixing device.

Here, as the order of the description, first, the overall configuration of the image forming apparatus will be described, and then the configuration of the fixing device and the heater used therein will be described.

<< Overall Configuration of Image Forming Apparatus >> As shown in FIG. 2, this image forming apparatus (laser beam printer) A transmits information light (laser light) based on image information from an optical unit 1 to a drum-shaped image. A latent image is formed on the photoconductor by irradiating the photoconductor, which is a carrier, and the latent image is developed to form a toner image. Then, in synchronization with the formation of the toner image, a recording medium P, which is a recording medium, is transported by a transport unit,
An image is formed on the recording medium P by an image forming unit.

In the present embodiment, an electrophotographic method is used as an image forming means, and the photosensitive drum 2, which is an electrophotographic photosensitive member, a charging means, a developing means, and a cleaning means (not shown) are formed into cartridges. The cartridge 3 is detachable from the apparatus main body. The image forming unit uniformly charges the surface of the rotating photosensitive drum 2 by the charging unit, and then forms a latent image on the photosensitive drum 2 by irradiating light from the optical unit 1, and this latent image is developed by the developing unit. A visible image is formed by developing the toner. Then, the toner image is transferred to the recording medium P conveyed by the transfer means 4, and the transferred image is fixed by the fixing means 5 which is a fixing device.

On the other hand, the sheet transport means for transporting the recording medium P includes a pickup roller 7 and a separation claw 6a for separating and feeding one by one from a recording medium cassette 6 mounted on the bottom of the apparatus main body. 8 and a pinch roller 9 which rotates by being pressed against the sheet, and is conveyed to the image transfer section by U-turn.

By applying a voltage to the transfer roller 4 constituting the transfer means, the recording medium P on which the toner image formed on the photosensitive drum 2 has been transferred is guided by the driving rotation of the transport roller 8 and the transfer roller 4. The sheet is conveyed along the conveyance guide member 10 constituting the means and reaches the fixing means 5. Further, the recording medium P on which the transfer toner image is fixed by applying heat and pressure by the fixing unit 5 is discharged to the discharge roller pair 11, 12.
And discharged to the discharge section 13 in the upper part of the apparatus main body.

{Structures of Fixing Device and Heater} Next, the structure of the fixing means (fixing device) 5 for fixing the toner image transferred to the recording medium P and the structure of the heater used for this will be described.

The fixing means 5 according to the present embodiment is a tensionless type film heating and fixing device. As shown in FIG. 3, the heat-resistant film 14, which is a rotatable cylindrical member, generates heat. It is externally fitted to the support 15 of the heater H which is also a film guide member including the body. The inner peripheral length of the film 14 and the outer peripheral length of the support 15 are the same as those of the film 14,
For example, the film 14 is made larger by about 3 mm.

The film 14 need not have a cylindrical shape, but may have a configuration in which the film 14 is sequentially fed from a supply roller to a take-up roller as long as the film 14 moves in accordance with the conveyance of the recording medium.

The film 14 has a heat capacity of 100 μm or less, preferably 50 μm or less and preferably 20 μm or more and has a heat resistance of PTFE (polytetrafluoroethylene) to reduce the heat capacity and improve the quick start property of the apparatus. P
FA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer) monolayer,
Alternatively, it is preferable to use a composite film such as polyimide, polyamideimide, PEEK (polyetheretherketone), PES (polyethersulfone), or PPS (polyphenylenesulfide), which is coated with PTFE, PFA, FEP, or the like on its outer peripheral surface. . In the present embodiment, a polyimide film having an outer peripheral surface coated with PTFE is used.

Reference numeral 16 denotes a rotating member that forms a nip N with the heater H sandwiching the film 14, presses the recording medium P against the film 14, and applies a conveying force to the recording medium P. It is a pressure roller. This pressure roller 16
In FIG. 3, a heat-resistant rubber roller portion 16b having good releasability such as silicon rubber is integrally provided on a core 16a and a driving force is transmitted to a gear (not shown) attached to an end of the core 16a. It is driven and rotated in the direction of arrow A. As a result, the recording medium P is transported in the direction of arrow B, and
Rotates in the direction of arrow C.

A heater H for heating the film 14 is attached to the support 15, and by heating the recording medium P passing through the nip N, the toner image transferred by the image forming means is permanently applied to the recording medium P. Establish.

Here, the configuration of the heater H will be described. FIG.
As shown in the schematic sectional view of FIG. 1, a heating element 18 made of an electric resistance material such as Ag / Pd (silver palladium) is coated on a surface of a substrate 17 made of alumina or the like with a thickness of about 10 μm and a width of 1 mm.
3 mm is applied by screen printing or the like, and a protective layer 19 is coated thereon with glass, fluororesin or the like.
Further, a thermistor 20, which is a temperature detecting element for detecting a heating temperature of the heating element 18 for controlling the temperature of the heater, is attached.

The thermistor 20 has a thermistor material 20 a and an electrode 20 b formed by printing on the same surface of the substrate 17 on which the heating element 18 is provided and near the heating element 18. It is configured with a coat.

The temperature of the heater H is detected by the thermistor 20, the output is A / D converted, and the CPU shown in FIG.
The temperature is controlled by controlling the AC voltage applied to the heating element 18 by pulse width modulation such as phase and frequency control based on the signal.

The temperature control is performed by controlling the temperature of the heating element 18 in the fixing nip and the thermistor 20 as the process speed increases.
Are required to have no error in the detected temperature, to have good responsiveness, and to have small variations in temperature ripple. In this regard, in the present embodiment, since the thermistor 20 is disposed in the fixing nip on the same surface as the heating element 18, the heating element in the actual fixing nip is provided more than when the thermistor is provided on the back side of the substrate 17. An error between the temperature of 18 and the temperature detected by the thermistor 20 is suppressed, and the response is improved. For this reason, a high-speed device (in this embodiment, a process speed of 50 mm / sec)
However, the fixing temperature can be accurately controlled,
A good image free from defective fixing, offset, gloss unevenness, etc. can be obtained.

Here, the heater H having the configuration according to this embodiment is used.
2 shows experimental results when an image is formed by controlling the fixing temperature by using a heater, and when an image is formed by controlling the fixing temperature by using a heater provided with a thermistor on the back surface of a heater substrate.

The table shown in FIG. 4A shows the actual surface temperature of the heating element in the fixing nip with respect to the thermistor output (temperature controlled) of a heater having a thermistor on the back surface of the heater substrate. Indicates the value of the temperature ripple ΔT at that time.

As can be seen from the values shown in FIGS. 4 (a) and 4 (b), the actual heater surface temperature when monitoring the temperature on the back surface of the heater and controlling the temperature indicates a temperature higher than the thermistor output.
Temperature ripple ΔT on the front surface rather than temperature ripple ΔT on the back surface
Is larger.

In the experiment, the temperature of the heater of this embodiment was set such that the same fixing property as that of the heater having the thermistor on the back surface of the heater substrate was obtained. Temperature control temperature 200 ℃, 190
℃ and 180 ℃, whereas the heater of this embodiment
0 ° C, 200 ° C, and 190 ° C. FIG. 4C shows the temperature ripple at this time, and it can be seen that the ripple of the heater surface temperature is clearly smaller than that of FIG. 4B.

FIG. 4D shows the results of image evaluation (fixing unevenness, offset, and gloss unevenness) when an image is formed by using the heater provided with a thermistor on the back surface of the substrate and the heater of the present embodiment.良, ○, △, and × were evaluated in four stages. Here, each of the ten samples was evaluated in consideration of measurement errors, variations, and the like.

As can be seen from this result, when temperature control is performed by detecting the temperature on the back surface of the heater, the actual surface temperature of the heater varies considerably more than the temperature on the back surface of the heater. There are variations.

Also, when the temperature control is performed by detecting the temperature of the heater surface, the temperature profile of the heater surface is more uniform than when the temperature control is performed by detecting the back surface temperature. It can be seen that there are few variations and ripples with respect to temperature, and image defects such as poor fixing, uneven fixing, offset and gloss unevenness are less likely to occur.

[Second Embodiment] In the above-described embodiment, an example is shown in which the thermistor member 20a is arranged near the heating element 18, but as shown in FIG. 5, the printing thermistor member 20a is connected to the heating element.
It may be formed by laminating on 18. 5A is a schematic explanatory view of the heater H in the longitudinal direction, and FIG. 5B is a schematic sectional explanatory view.

The heater H includes an insulating layer 21 on the heating element 18.
Is provided, a printing thermistor material 20a is provided thereon, and an accurate temperature in the nip can be monitored in the longitudinal direction,
The thermistor member 20a is arranged outside the transport area of the recording medium P so as not to disturb the image.

FIG. 6 shows a comparison experiment result in the case where the heater H is used, similarly to the above-described first embodiment, in comparison with the case where an image is formed using a heater provided with a thermistor on the back surface of the heater. In this case, similarly to the first embodiment, a thermistor is provided on the back surface of the substrate so that the heater temperature control temperature of the present embodiment can obtain the same fixing property as the heater having the thermistor on the back surface of the heater substrate. Adjust the heater temperature to 200
C., 190.degree. C., and 180.degree. C., whereas 220.degree. C., 210.degree. The results were 210 ° C., 200 ° C., and 190 ° C. for the heater according to the present embodiment. FIG. 6A shows the temperature ripple of the heater according to the present embodiment at this time. Compared with the result of the heater in which the thermistor is provided on the back surface of the substrate in FIG. It can be seen that the size is smaller than that of the embodiment, and the response is improved.

FIG. 6B shows image evaluation results of the heater provided with a thermistor on the back surface of the substrate and the heater of the present embodiment. The evaluation is divided into four stages as in the case of the first embodiment. evaluated.

As is apparent from the results, by arranging the thermistor material 20a on the heating element 18, the fixing temperature can be controlled more accurately, and a high-quality image can be obtained.

[Third Embodiment] In the first and second embodiments described above, the main purpose is to detect the temperature of the heater. However, in the fixing device, the temperature of the recording medium P conveyed reaches a predetermined temperature. Whether or not it has reached a problem is inherently a problem.

Therefore, as shown in FIG. 7, if the temperature of the fixing film 14 close to the temperature of the recording medium being conveyed can be detected, a better image can be obtained.

FIG. 7A is an explanatory sectional view of the heater H, and FIG. 7B is an explanatory plan view partially cut away in the longitudinal direction.

The heater H shown in FIG. 7 is the same as the first embodiment in that a thermistor member 20a as a temperature detecting element is provided on the substrate 17 on the same side as the heating element 18, but its position is the same as that of the first embodiment. It is arranged downstream of the recording medium transport direction 18. Then, printing is performed on the thermistor member 20a without providing the protective layer 19 by glass coating.

Since the printing thermistor is a sintered material containing glass, it has a much higher hardness than the resin film 14 and does not wear even when rubbed against the film 14 (thermistor material 20a). A protective layer 19 may be provided thereon).

With the above configuration, the average value of the temperature of the film 14 heated in the nip and the temperature of the heater can be obtained as the output of the thermistor 20, so that more accurate temperature control can be performed.

As shown in FIG. 8, when a glass layer for heat insulation (which also serves as the protective layer 19 in this embodiment) is provided between the heater substrate 17 and the printing thermistor material 20a, the thermistor material 20a In addition, since the heat transfer from the substrate 17 is reduced, more accurate temperature control can be performed, which is preferable.

[0053]

The present invention is constructed as described above.
Since the temperature is detected on the same surface as the heating element, the temperature can be directly and accurately detected regardless of the thickness of the substrate.

Therefore, when the fixing device and the image forming apparatus are configured using the heater, it is easy to control the fixing temperature with higher accuracy, and it is possible to obtain a high-quality image.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the configuration of a heater.

FIG. 2 is an overall schematic diagram of the image forming apparatus.

FIG. 3 is an explanatory diagram of a configuration of a fixing device.

FIG. 4 is a table showing temperature ripples and image evaluation results of a heater in which a thermistor is disposed on the substrate surface on the same side as the heating element, a heater in which a thermistor is disposed on the rear surface of the substrate.

FIG. 5 is an explanatory diagram of an embodiment in which a thermistor is arranged on a heating element.

FIG. 6 shows a temperature ripple between a heater having a thermistor disposed on a heating element and a heater having a thermistor disposed on the back surface of a substrate;
It is a table | surface figure which shows an image evaluation result.

FIG. 7 is an explanatory diagram of a configuration of a heater for detecting a film temperature by heating of the heater and performing temperature control.

FIG. 8 is a structural explanatory view of a heater for detecting and controlling the film temperature by heating the heater and having a heat insulating layer provided between the substrate and the thermistor.

FIG. 9 is a diagram illustrating a configuration of a heater that detects a temperature by using a thermistor chip provided on the back surface of the heater substrate.

FIG. 10 is a configuration explanatory view of a heater that detects a temperature using a printing thermistor provided on the back surface of the heater substrate.

[Explanation of symbols]

 H ... Heater P ... Recording medium 1 ... Optical means 2 ... Photoreceptor drum 3 ... Process cartridge 4 ... Transfer means 5 ... Fixing means 6 ... Recording paper cassette 6a ... Separation claw 7 ... Pickup roller 8 ... Convey roller 9 ... Pinch roller 10 ... Conveyance guide member 11 ... Discharge roller pair 12 ... Discharge roller pair 13 ... Discharge part 14 ... Film 15 ... Support 16 ... Pressure roller 16a ... Core 16b ... Roller part 17 ... Substrate 18 ... Heat generating element 19 ... Protective layer 20 ... Thermistor 20a ... Thermistor material 20b ... Electrode 21 ... Insulating layer

Claims (6)

[Claims] 1. A temperature detecting element comprising: a substrate; a heating element provided on one surface side of the substrate for generating heat when energized; and a temperature detecting element for detecting a heating temperature of the heating element. Is provided on a substrate on the same surface side on which the heating element is provided. 2. A temperature detecting element, comprising: a substrate; a heating element provided on one surface side of the substrate for generating heat by energization; and a temperature detecting element for detecting a heating temperature of the heating element. And a heating element formed by laminating the heating element and the heating element. 3. The heater according to claim 1, wherein said temperature detecting element is constituted by a printing thermistor. 4. A fixing device for heating and fixing an image transferred to a recording medium, comprising: a film member that moves following the conveyance of the recording medium; and a recording medium that is pressed against the film member and conveyed to the recording medium. 4. A rotating member for applying a force, and a heater for heating the recording medium via the film member, wherein the heater is used as the heater.
A fixing device characterized by using the heater described in (1). 5. The fixing device according to claim 4, wherein the temperature detecting element is disposed outside a passage area of the image transferred to the recording medium. 6. An image forming apparatus for transferring an image to a recording medium and fixing the image by heating, a conveying unit for conveying the recording medium, an image forming unit for transferring the image to the recording medium, An image forming apparatus comprising: a fixing unit configured to fix a transferred image on a recording medium; and the fixing device according to claim 4 or 5 is used as the fixing unit.