JPH04326387A - Fixing device - Google Patents

Abstract

PURPOSE:To obtain a fixing device where the unbalance of temperature is not caused inside a heating roller and which is excellent in fixing performance and has high energy efficiency by providing the temperature detection part and the temperature control part of a heating element. CONSTITUTION:This device is provided with the heating roller 1 equipped with the heating elements 5-1, 5-2 and 5-3 which are constituted of heating element groups and which are obtained by being divided into at least two or more in an axial direction on its surface, and a pressuring roller 2 which press- contacts and interlocks with the heating roller 1. Then, the temperature detection part 8 for detecting the temperatures of the respective heating elements 5-1, 5-2 and 5-3 and the temperature control part 9 for controlling the temperatures of the heating elements 5-1, 5-2 and 5-3 by supplying energy to the respective heating element groups in accordance with an output signal from the detection part 8 are provided. Therefore, the unbalance of temperature inside the heating roller 1 is restrained even in the case of consecutive fixing, and the energy is supplied only to a part which needs heat, so that the fixing device which is excellent in fixing performance and has high energy efficiency is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an image forming apparatus such as a copying machine or a printer using an electrophotographic process.

0002

2. Description of the Related Art A fixing device is used in an image forming apparatus as a device for fixing an unfixed toner image formed on a support such as paper. A heat roller that is equipped with a heat roller whose surface is a heat-conductive metal pipe coated with a heat-resistant release layer such as tetrafluoroethylene, and a pressure roller whose metal core is coated with a heat-resistant elastic layer such as silicone rubber. Type heat fixing devices are widely used.

An example of the above-mentioned conventional fixing device will be described below with reference to the drawings. FIG. 9 is a schematic cross-sectional view showing an example of a conventional fixing device. In FIG. 9, 1 is a heating roller, 2 is a pressure roller, and 3 is a support that supports the toner image 4. The heating roller 1 is formed by covering the surface of a metal pipe 31 having a heat source 30 such as a halogen lamp therein with a heat-resistant release layer 32 . On the other hand, the pressure roller 2 has a heat-resistant elastic layer 2b formed on a metal core 2a. Further, the heating roller 1 and the pressure roller 2 are pressed against each other by a pressure mechanism (not shown), and a predetermined contact width is formed at the pressed portion. A temperature detector 33 is attached to a support plate 35 via a leaf spring 34 so as to be in contact with the surface of the heating roller 1.

The operation of the fixing device configured as described above will be explained below. First, heat is supplied to the heating roller 1 by supplying power to the heat source 30, the temperature at that time is detected by the temperature detector 33, and the power supply is turned on and off by a temperature regulator (not shown). Keep the temperature of 1 at a constant temperature. Then, by rotating the heating roller 1 in the direction of the arrow shown in the figure by a driving means (not shown), the pressure roller 2 follows the heating roller 1 and rotates in the direction of the arrow shown in the figure. At this time, since the heat-resistant elastic layer 2b of the pressure roller 2 is deformed by the pressure, a pressure contact portion having a predetermined width is formed. By passing the support 3 holding the toner image 4 through this pressure contact portion by a conveying means (not shown), the toner image 4 is melted by the heat from the heating roller 1 and fixed by cooling.

[0005]

[Problems to be Solved by the Invention] However, in the above configuration, the width of the support such as paper holding the toner image is smaller than the length of the heating roller or the pressure roller, and for example, the support is continuous only around the center. When the support passes through the support, the temperature of the central portion decreases because the heat from the heating roller is absorbed by the support. At this time, if the temperature detection section is provided at the end of the heating roller, it will not be able to detect a drop in temperature at the center, and the amount of heat necessary for fixing will not be supplied, resulting in defective fixing. Furthermore, even if a temperature sensor is installed in the center, the temperature in the center will recover by continuing to supply power to the heat source to raise the temperature that has dropped, but the temperature at the edges will rise too much, resulting in safety concerns or material problems. This will lead to unfavorable conditions such as impact on the environment and energy loss. Further, in this case, when a support of a different size passes next and part of it passes through this high temperature section, undesirable phenomena such as offset to the heating roller may occur. These problems occur not only when the support passes through the center, but also when the width of the support is small and heat does not move uniformly in the axial direction of the heating roller, in other words, thermal imbalance occurs. or overheating of the heating roller,
This has led to problems such as a decrease in energy efficiency.

[0006] Furthermore, the heat of the heating roller is mainly absorbed by the support such as toner or paper at the pressure roller and the pressure roller, so that the temperature of the pressure roller becomes low and temperature imbalance occurs inside the heating roller. It is difficult to provide a temperature sensor in the press-contact part, and a difference occurs between the temperature of the press-contact part and the temperature of the detection part. This becomes especially noticeable when the film is passed through the support continuously. If this detected temperature is directly compared with the necessary set temperature of the heating roller and the power supply is controlled by a temperature regulator, the temperature of the pressure contact portion becomes low, resulting in defective fixing. Furthermore, if the set temperature is set high in consideration of this, areas other than the pressure welded parts will be heated unnecessarily, resulting in problems such as a decrease in energy efficiency.

In view of the above-mentioned problems, the present invention provides a fixing device that does not cause temperature imbalance inside the heating roller, has good fixing properties, and is energy efficient.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the fixing device of the present invention provides a heating roller having a heating element on its surface that is composed of a group of heating elements divided into at least two heating elements in the axial direction. a pressure roller that presses and interlocks with the heating roller; a temperature detection unit that detects the temperature of each heating element; and a temperature detection unit that supplies energy to each of the heating element groups in accordance with an output signal of the temperature detection unit. The heating element is equipped with a temperature adjustment section that adjusts the temperature of the heating element.

[0009]

[Function] The present invention uses the above-described configuration to independently detect and control the temperature of the heating elements that are provided on the surface of the heating roller in an axial direction. Even if only a section is continuously cooled and the temperature decreases, by supplying power and controlling the temperature only to the heating element in that section, the temperature imbalance in the axial direction can be eliminated and the above-mentioned problems can be solved.

0010

[Embodiment] The following is a fixing device according to an embodiment of the present invention.
This will be explained with reference to the drawings. FIG. 1 shows a schematic front view of a fixing device in a first embodiment of the present invention. An object of the present invention is to provide a fixing device that suppresses temperature imbalance within the roller even when the width of the support is smaller than the length of the heating roller and that heat transfer within the roller is uneven, and that has good fixing performance and high energy efficiency. Our goal is to provide the following.

In FIG. 1, 1 is a heating roller, 2 is a pressure roller having a heat-resistant elastic layer formed on a metal core, and 5-
1 to 5-3 are heating elements divided in the axial direction on the surface of the heating roller 1, and 6-1a, b to 6-3a, b are heating elements 5-
Electrodes for feeding power to 1 to 5-3, 7-1a, b to 7-
3a, b are brushes that slide in contact with the electrodes 6-1a, b to 6-3a, b to supply power; 8 is a brush 7-1a, b to 7-3
temperature detection unit connected to a and b; 9 is a brush 7-1a;
This is a temperature control unit connected to b to 7-3a and b. Further, the heating roller 1 and the pressure roller 2 are pressed against each other by a pressure mechanism (not shown), and a predetermined contact width is formed at the pressed portion.

The operation of the fixing device constructed as described above will be explained below with reference to FIGS. 1 and 2.

First, FIG. 2 is a half-sectional view taken along the line A-A in FIG.
The electrode 6-1b passes under the heating elements 5-2 and 5-3 while maintaining insulation and is electrically connected to the heating element 5-1. It is conducting. The electrodes 6-2a, b, 6-3a, and b are also electrically connected to the heating elements 5-2 and 5-3, respectively, in different cross sections. With this configuration, it becomes possible to independently supply power to each of the heating elements 5-1 to 5-3. Further, FIG. 3 is a detailed explanatory diagram of the temperature detection section 8 and the temperature adjustment section 9. 8-1 to 8-3
are connected to 7-1a, b to 7-3a, b, respectively, to detect the resistance values of the heating elements 5-1 to 5-3, and calculate the temperature using the calibration curve of the resistance value of the heating element determined in advance against the temperature. Temperature calculation units 9-1 to 9-3 calculate and output temperature signals to the heating elements 5-1 to 5-3 by comparing the calculated and detected temperature signals with a set temperature signal (not shown). This is a temperature adjustment unit that can control the power supply to the heating element and independently control the temperature of the heating element. Therefore, even if a support such as paper carrying a toner image passes only through the center of the heating roller 1 and heat is taken away only from the heating element 5-2, the temperature of each heating element is controlled independently. Heat can be supplied only to the heating element 5-2 in that part to maintain the temperature, and good fixing performance can be maintained. At this time, excessive heat is not supplied to the other parts, that is, the heating elements 5-1 and 5-3, and an imbalance in the temperature distribution in the axial direction of the heating roller 1 does not occur. Therefore, it is only necessary to supply the minimum necessary energy to each part, and the energy efficiency is high.

As described above, according to this embodiment, a heating element divided into three parts is provided on the surface of the heating roller, and the pressure roller is brought into pressure contact with the toner image to pass through the support holding the toner image. By providing a temperature detecting section that detects the temperature of the temperature detecting section, and a temperature adjusting section that supplies energy to each of the heating element groups according to the output signal of the temperature detecting section and independently adjusts the temperature of each heating element. , the width of the support is smaller than the width of the heating roller, and even if there is an imbalance in heat transfer in the axial direction of the heating roller during continuous fixing, energy can be supplied independently to each heating element, so the temperature imbalance in the axial direction can be avoided. It has effects such as good fixing properties and good energy efficiency.

Next, a second embodiment of the present invention will be described with reference to the drawings. SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device with good fixing performance and high energy efficiency by suppressing temperature imbalance inside the roller due to heat leakage from the pressure contact portion of the heating roller during continuous fixing.

FIG. 4 is a schematic sectional view of a fixing device showing a second embodiment of the present invention. In FIG. 4, 1 is a heating roller, 2 is a pressure roller having a heat-resistant elastic layer 2b formed on a metal core 2a, and 10-1 to 10-10 are heating rollers 1.
3 is a support for supporting a toner image 4; The heating roller 1 and the pressure roller 2 are pressed against each other by a pressure mechanism (not shown), and a predetermined contact width is formed at the pressed portion.

The operation of the fixing device constructed as described above will be explained below with reference to FIGS. 4 and 5.

First, FIG. 5 is a schematic front view of the heating roller 1 in FIG.
-1a, b~7-10a, b are electrodes 6-1a, b~6-
A brush 8 is connected to the brushes 7-1a, b to 7-10a, b, and a brush 9 is connected to the brushes 7-1a, b to 7-10a, b. This is the connected temperature control section. Here, the electrode 6-1a is the electrode 6-2
pass under 6-10a while maintaining insulation and are electrically connected to the heating element 10-1, and the electrode 6-2b is connected to the electrode 6-1.
It passes under the electrodes 6-3a, . . . , 6-10a while maintaining insulation properties at a position different from a, and is electrically connected to the heating element 10-2. The following electrodes 6-4a to 6-10a, 6-1b to 6-
Heat generating elements 10-1 to 10-1 are similarly applied to 10b.
Conducted with 0. With this configuration, it becomes possible to independently supply power to each of the heating elements 10-1 to 10-10. As a result, as in the first embodiment, the temperature adjustment section 9 uses the temperature signal calculated by the temperature calculation section 8 to compare it with a set temperature signal (not shown),
By controlling the power supply to 0, the temperature of each heating element is independently controlled.

As described above, by providing heating elements divided in the circumferential direction on the surface of the heating roller and controlling the temperature of each heating element independently, heat is removed from the pressure contact portion of the heating roller 1 during continuous fixing. Even if the temperature drops, a temperature drop in the pressure welding part can be detected and energy can be supplied only to that part without powering (supplying energy) to other parts, so temperature imbalance does not occur. Therefore, a fixing device with good fixing performance and high energy efficiency can be realized.

Next, a third embodiment of the present invention will be described with reference to the drawings. An object of the present invention is to provide a fixing device that maintains fixing performance and has high energy efficiency by supplying energy only to the pressure contact portion of the heating roller.

FIG. 6 is a sectional view of the vicinity of the power supply section of a fixing device showing a third embodiment of the present invention. In FIG. 6, 1 is a heating roller, 11-1 to 11-10 are electrodes that are electrically connected to the heating elements 10-1 to 10-10 in FIG. 4, and 12a,
12b (installed at the opposite shaft end with the same mounting angle as 12a, not shown) is a brush provided so as to be electrically connected to the heating element near the pressure contact part with the pressure roller 2 in FIG. Similar to FIG. 5, they are a temperature detection section and a temperature adjustment section, respectively.

The operation of the fixing device constructed as described above will be explained below with reference to FIGS. 4 and 6.

As shown in FIG. 6, the brush that supplies power to the heating element only supplies power to the heating element near the press-contact area where the support 3 holding the toner image 4 passes and the heat necessary for fixing is supplied. In other words, even when the heating roller 1 rotates, the electrodes also rotate with the heating roller 1, so the heating element to which power is supplied is switched one after another, and in the end, power is supplied only to the heating element located near the pressure welding part at that time. . Therefore, energy is supplied only to the parts originally required for fixing and not to other parts, resulting in high energy efficiency.

[0024] As described above, by arranging the brush at a position where power is supplied only to the electrodes divided in the circumferential direction and the electrode corresponding to the heating element near the press-contact part, fixing can be performed with the minimum amount of energy necessary. be able to.

Next, a fourth embodiment of the present invention will be described with reference to the drawings. An object of the present invention is to provide a fixing device that can suppress temperature imbalance inside a heating roller with high reliability, has good fixing performance, and is highly energy efficient.

FIG. 7 is a partial front view of the vicinity of the shaft end of a fixing device showing a fourth embodiment of the present invention. In FIG. 7, 1 is a heating roller, electrodes 6-1a, b to 6-10a, b are electrically connected to heating elements 10-1 to 10-10, respectively, and 13-1a, b to 13-10a, b are electrodes. 6-1a,
b ~ 6-10a, one end is soldered to b, and the other end is soldered to Fig. 5
14a and 14b are flange portions for preventing wires from getting caught; 15 is a spiral spring connected to the drive shaft of the heating roller 1; 16 is a spiral spring connected to the drive shaft of the heating roller 1; 17 is a support portion; 18 is a clutch 1 that switches transmission between a drive means (not shown) for driving the heating roller 1 and a drive shaft of the heating roller 1;
6 is a clutch control unit that outputs connection/disconnection command signals.

The operation of the fixing device constructed as described above will be explained below with reference to FIGS. 4 and 7.

First, wiring cables 13-1a, b to 13-10a, for supplying power to the heating elements 10-1 to 10-10,
b has a length sufficient to wrap around the portion regulated by 14a and 14b without interfering with the rotation of the heating roller 1 while the heating roller 1 rotates to fix at least one support; It is in a state where it is not wrapped around the end of the roller 1 at all. Immediately before the support starts passing through the fixing section, the clutch 16 is connected by the clutch control section 18 to rotate the heating roller 1. Along with this, the spiral spring 15 is wound up from its neutral state, and at the same time, the distribution cables 13-1a, b to 13-10a, b are also wound around. When the time elapses from when the clutch is connected until at least one support body finishes passing, the clutch control unit 18 operates the clutch 16 to disconnect the driving force. At that time, the heating roller 1 rotates in the opposite direction to that during fixing due to the spring force stored by the spiral spring 15 and returns to the neutral position (initial state), and the wiring 13-
1a, b to 13-10a, b are unwound.

As described above, by using a wiring cable having a length that supplies the heating roller without hindering its rotation during fixing, a clutch for switching transmission of driving force, and a spiral spring for return operation, It is more reliable than the energy supply by the sliding of the electrode part and the brush in the first to third embodiments of the present invention, or the switching operation while supplying power in the third embodiment, and The same effect as in the embodiment can be achieved.

Next, a fifth embodiment of the present invention will be described with reference to the drawings. An object of the present invention is to provide a fixing device that quickly eliminates temperature imbalance inside a heating roller during continuous fixing with a simple configuration, has good fixing performance, and is highly energy efficient.

FIG. 8 is a sectional view of a fixing device showing a fifth embodiment of the present invention. In FIG. 8, 1 is a heating roller, 2 is a pressure roller, and 3 is a support that supports the toner image 4. The heating roller 1 has a metal layer 2 with high thermal conductivity on an insulating core 22 with low thermal conductivity such as resin.
1 is formed, and a heating element 20 is further formed on the surface thereof.

The operation of the fixing device configured as described above will be explained below. During fixing operation, support 3
As the toner image 3 passes through the pressure contact portion and absorbs heat, the temperature of the pressure contact portion decreases. However, a thin metal layer with high thermal conductivity 2
1 on the insulating core 22 suppresses heat diffusion into the interior and quickly supplies heat from a heating element other than the pressure welding part, reducing the temperature drop in the pressure welding part, resulting in heating. Temperature imbalance within the roller 1 can be alleviated.

As described above, the heating roller was provided with an insulating core made of resin or the like with low thermal conductivity, a metal layer with high thermal conductivity was formed on the core, and a heat generating layer was further formed on the metal layer. With this structure, temperature imbalance within the heating roller during fixing can be alleviated, resulting in good fixing performance and high energy efficiency.

Although the first embodiment shows an example in which the heating element is divided into three parts, the present invention is not limited to this, and a different number of divisions may be used.

Furthermore, although the second and third embodiments show examples in which the heating element is divided into 10 parts, the number of divisions is not necessarily limited to this number, and other numbers of divisions may be used.

Furthermore, although a spiral spring and a clutch are used as the return means in the fourth embodiment, the present invention is not limited to this, and other methods such as using a return motor may also be used. Furthermore, although the configuration here is based on the second and third embodiments, the same effect can be obtained even if the configuration is based on the first embodiment.

Further, in the fifth embodiment, a resin layer is used for the heat insulating core and a metal is used for the heat carrier layer, but the material is not necessarily limited to these materials, and there is a sufficient difference in thermal conductivity between the two, so that heat can be diffused into the interior. Other materials may be used as long as they can suppress heat and quickly supply heat.

[0038]

Effects of the Invention As described above, the present invention provides a heating roller having a heating element on its surface that is composed of at least two groups of heating elements divided in the axial direction, and a pressurizing roller that is interlocked with the heating roller in pressure contact with the heating roller. a roller, a temperature detection section that detects the temperature of each heating element, and a temperature adjustment section that supplies energy to each of the heating element group according to an output signal of the temperature detection section to adjust the temperature of the heating element. By providing this, even during continuous fixing, temperature imbalance inside the heating roller can be suppressed and energy can be supplied only to the portions that require heat supply, resulting in good fixing performance and high energy efficiency.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a half-sectional view of FIG. 1;

FIG. 3 is a detailed explanatory diagram of a temperature detection section and a temperature adjustment section in FIG. 1;

FIG. 4 is a schematic cross-sectional view of a fixing device according to a second embodiment of the present invention.

FIG. 5 is a schematic front view of FIG. 4;

FIG. 6 is a sectional view of a fixing device according to a third embodiment of the present invention.

FIG. 7 is a partial front view of a fixing device according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view of a fixing device according to a fifth embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view of a conventional fixing device.

[Explanation of symbols]

1 Heating roller 2 Pressure roller 3 Support 4 Toner image 5-1, 5-2, 5-3 Heating element 8 Temperature detector 9 Temperature controller

Claims (6)

[Claims] 1. A heating roller having a heating element on its surface, and a pressure roller interlocking with the heating roller, wherein the heating element is divided into at least two parts in the axial direction of the heating roller. a temperature detection unit that detects the temperature of each heating element; and a temperature detection unit that supplies energy to each of the heating element groups according to an output signal of the temperature detection unit to adjust the temperature of the heating element. A fixing device characterized by having an adjustment section. 2. A heating roller having a heating element on its surface, and a pressure roller interlocking with the heating roller, the heating element being divided into at least two parts in the circumferential direction of the heating roller. a temperature detection unit that detects the temperature of each heating element; and a temperature detection unit that supplies energy to each of the heating element groups according to an output signal of the temperature detection unit to adjust the temperature of the heating element. A fixing device characterized by having an adjustment section. 3. A switching section for supplying energy to at least one or more heating elements located near a pressure contact portion with the pressure roller as the heating roller rotates, and a temperature adjustment section adjusts the temperature of the heating element. The fixing device according to claim 2, characterized in that: 4. A heating roller returning means for rotating the heating roller in the opposite direction to the rotational position at the start of fixing after the fixing operation is completed, and a heating roller return means having one end fixed to a heating element group to prevent heating during fixing. Claim 1, claim 2, or claim 3, further comprising a wiring cable having a length that allows energy to be supplied from the temperature control unit without interfering with rotation of the roller. Fusing device. 5. A heating roller provided with a heating layer made of a heating element on its surface, and a pressure roller interlocked with the heating roller, wherein the heating roller is arranged on a heat insulating layer made of a material with low thermal conductivity. A fixing device comprising: a heat conductive layer made of a material with high thermal conductivity; and a heat generating layer formed on the heat conductive layer. 6. The heating element is a conductive resistance layer, and the temperature detection section detects the temperature of the resistance layer using the temperature characteristic of the resistance value of each resistance layer. 2,
The fixing device according to claim 3, claim 4, or claim 5.