JP3979422B2 - Thermal fixing device and image forming apparatus - Google Patents

Description

  The present invention relates to a thermal fixing device and an image forming apparatus.

  In the heat fixing device of an image forming apparatus, a heating roll is excessively heated due to a failure of a temperature detection member or a failure of a control device that controls On / Off of electric power supplied to a heating source or voltage (overheating). ) Is provided in series with a heating source such as a thermostat or a temperature fuse.

  A technique for preventing a sudden overheating by configuring the distance between the heating roll and the overheating prevention device to be closer by softening the bearing or frame that supports the heating roll at the time of overheating is disclosed. . In this technology, when the thickness of the heating roll is reduced, the heat conduction in the axial direction of the heating roll becomes worse as the thickness of the heating roll is reduced. There is a problem that an expected effect cannot be obtained (for example, refer to Patent Documents 1 and 2).

  By installing an over-temperature prevention device at the axial end of the heating roll so that the distance between the heating roll and the over-temperature prevention device is closer when the heating roll is thermally expanded in the axial direction, Techniques for preventing overheating are shown. In this technology, the thinner the heating roll, the worse the heat conduction in the axial direction of the heating roll, so that the temperature at the end of the heating roll is too low and the overheating prevention device does not operate at a sudden overheating. (For example, refer to Patent Document 3).

  The technique of separately having a circuit for performing temperature control and a circuit for cutting off the power to the heater at the time of excessive temperature rise is a problem that leads to an increase in cost (see, for example, Patent Document 4). .

  Generally, a halogen heater is used as a heating source of the heat fixing device of the image forming apparatus. The halogen heater is a heater in which a filament composed of tungsten as a main component is wound into a coil having an appropriate density to form a filament, and this filament is enclosed in a quartz glass column together with a halogen mixed gas.

2. Description of the Related Art In image forming apparatuses, for the purpose of shortening warm-up time at start-up and saving energy, it is advancing to reduce the heat capacity of the heating roll by reducing the thickness of the heating roll. Recently, many heating rolls made of iron have been put into practical use in order to supplement the strength when the thickness is reduced. The thinning and the selection of iron as a material cause the heat conduction of the heating roll to be reduced and increase the temperature unevenness in the axial direction of the heating roll.
Japanese Patent Publication No. 4-39077 Japanese Patent Publication No. 04-77313 Japanese Patent Publication No. 4-77314 JP-A-5-333744

  In order to shorten the warm-up time and save energy in the heating roll of the image forming apparatus, a technique for reducing the heat capacity by making it thin is advancing. Due to the small heat capacity of the heating roll, there is a problem that the temperature rise of the heating roll becomes excessive when the temperature rises abnormally, and it becomes easy to fall into a dangerous state such as ignition before the operation of the excessive temperature rise prevention device.

  One problem when axial temperature irregularities occur in the heating roll is that a temperature detection failure occurs when the relative positional relationship between the filament constituting the halogen heater and the temperature detection member changes. . This is because the surface temperature distribution of the heating roll changes from place to place according to the density of the filament. In the portion where the filament is dense, the surface temperature of the heating roll is higher than the surrounding area, but in the portion where the filament is sparse, the surface temperature of the heating roll is lower than the surrounding area. Therefore, the temperature controlled by the temperature detection member varies as a whole of the heating roll depending on which part of the filament density is present in the portion where the temperature detection member exists. This is a value that cannot be ignored in consideration of variations in the quality of halogen heaters during mass production, variations due to the tolerance of the halogen heater mounting portion, and the like.

  Another problem is that the temperature of the non-sheet passing portion rises too much when a narrow sheet is printed. In order to prevent this, a technique for printing while selectively switching a plurality of halogen heaters having different light distributions is known. However, even with this technique, fixing failure or hot offset may occur when switching between halogen heaters depending on the rotation direction of the heating roll and the relative positional relationship between the temperature detection member and the halogen heater, resulting in image quality problems. .

  The object of the present invention is to provide an excellent heat fixing solution that eliminates the above-described problems by devising the arrangement of the heating source when the heat capacity of the heating roll is reduced by reducing the thickness of the heating roll and causing no problems. An apparatus and an image forming apparatus are realized by improving a simple configuration.

The present invention has been made to achieve the above object, and includes a heating roll incorporating a plurality of halogen heaters, a pressure member installed so as to be in pressure contact with the heating roll, and a temperature for detecting the surface temperature of the heating roll. In a thermal fixing device including a detection member and a temperature control device that controls electric power supplied to the halogen heater based on the temperature detected by the temperature detection member.
The halogen heaters are disposed upstream and downstream in the rotation direction of the heating roll as viewed from the surface of the heating roll detected by the temperature detection member, and the halogen heater on the upstream side is locally localized in the axial direction. the root of the Do light distribution ripple disposed at a position corresponding to the temperature sensing member, the halogen heater in the downstream, to the arrangement of the summit of the local light distribution ripple in the axial direction at a position corresponding to the temperature detection member Is a heat fixing device.

Furthermore, the present invention provides an image forming apparatus comprising the above-described heat fixing device.

  According to the present invention, when lighting control is performed while selectively switching a plurality of halogen heaters having different light distributions, the rotation direction of the heating roll and the relative positional relationship between the temperature detection member and the halogen heater are optimized. In addition, it has become possible to prevent the occurrence of fixing failure and hot offset when switching halogen heaters.

  Furthermore, when a heating source with a difference in light emission in the longitudinal direction is used and the thickness of the heating roll is made thin, even if the mounting accuracy of the heating source includes some errors, temperature control of the heating roll Can be within the proper range.

  In the present invention, as means for controlling the power supplied to the heating source based on the temperature detected by the temperature detecting member, for example, means for controlling On / Off of the power source, voltage or duty, etc. may be used.

Since the halogen heater is composed of filaments that are dense in the longitudinal direction, there is a phenomenon in which the external temperature corresponding to this has a wave-like distribution in the longitudinal direction of the heater . The longitudinal direction of the local light distribution ripple Ha Rogenhita, refers to the distribution shape of the temperature. The top of the wave is called the mountain peak, and the lower part between the waves is called the valley bottom .

Referring to hereinafter drawings illustrating the embodiments of the present invention.

  FIG. 17 is an explanatory diagram showing the entire image forming apparatus 200 to which the present invention is applied. The image forming apparatus 200 applies static electricity to the photosensitive drum 202 from the electrostatic roll 204 to charge the photosensitive drum 202, and irradiates light such as a laser from the exposure apparatus 206 to form a latent image on the photosensitive drum 202. The powder is supplied by the developing roll 210 of 208, and an image appears on the photosensitive drum 202. The paper supplied through the paper supply path 228 is passed between the photosensitive drum 202 and the transfer roll 212 to transfer the image onto the paper, and then the fixing roll 214 fixes the image on the paper. In the paper supply path, the paper is pulled out from the paper feed cassette 220, advanced by the feed rolls 222 and 224, positioned by the registration roll 226, and passed between the photosensitive roll 202 and the transfer roll 212 via the paper supply path 228 at the paper feed timing. To supply. The paper onto which the image has been transferred is fixed by the fixing roll 214 and discharged by the discharge roll 240. Reference numerals 230 and 232 denote paper feed levers. The present invention provides an invention characterized by the thermal fixing device 250 of the image forming apparatus 200.

  FIG. 16 is a circuit diagram showing a system to which the present invention is applied. A heating roll 10 incorporating a halogen heater 12 as a heating source, a pressure member 20 installed so as to be in pressure contact with the heating roll 10, and a heating roll The temperature detection member 22 for detecting the temperature, the power supply connector 32 for supplying power to the heating source, and the heating roll 10 are prevented from being excessively heated, and coupled in series with the heating source (halogen heater 12). This is a thermal fixing device provided with an excessive temperature rise prevention device 30. The temperature detection member 22 includes a temperature control device (not shown) that controls electric power supplied to the heating source based on the detected temperature. In the first aspect of the present invention, the heating source (halogen heater 12) is installed closer to the overheat prevention device 30 than the center of the heating roll 10.

FIG. 2 is an explanatory diagram of a conventional example, in which a halogen heater 10, a heating roll 214 incorporating the halogen heater, and a curve 120 (light distribution ripple 120) showing a surface temperature distribution graph along the axial direction thereof are drawn. It is. In the surface temperature graph, the longitudinal direction of the halogen heater 10 is taken on the horizontal axis, the direction perpendicular thereto is taken on the vertical axis, and the vertical axis shows the temperature level in E (%). In the halogen heater 10, a filament 92 in which a tungsten wire is wound in a dense and spiral manner is enclosed in an enclosure tube 94 and sealed together with a halogen gas 96, and the end of the filament 92 is connected to the power supply terminal 100. A curve 120 (light distribution ripple) is a graph showing the surface temperature distribution (light distribution ripple 120) along the axial direction of the heating roll containing the halogen heater. The light distribution ripple 120 locally rises and falls, and a peak 122 and a valley 124 are formed. In FIG. 2, the temperature detection member 110 is in contact with the outer surface of the heating roll 214 and detects the surface temperature of the heating roll 214. In FIG. 2, the position of the temperature detection unit 112 of the temperature detection member 110 is at a position that does not correspond to either the peak 122 or the valley 124 of the light distribution ripple 120.

Figure 1 is an explanatory view for explaining an embodiment of the present onset Akira shows a light distribution ripple 120 showing the surface temperature distribution of the same halogen heater 10 and the heating roll and described in FIG. Each reference number is the same as in FIG. In FIG. 1, the position of the temperature detection member 110 coincides with the position corresponding to the valley bottom 124 of the light distribution ripple 120. If it does in this way, when temperature control of a heating roll is performed by the detection temperature of the temperature detection member 110, it becomes clear what the detected temperature measures. Therefore, the accuracy of temperature control can be improved. In FIG. 1, the portion corresponding to the position of the temperature detection member 110 coincides with the valley bottom 124 of the local light distribution ripple 120 in the axial direction of the halogen heater, but may coincide with the mountain top 122.

  In the portion corresponding to the peak 122 or the valley bottom 124 of the light distribution ripple 120, the temperature change in the heating roll axis direction is small. For this reason, as in the present invention, the halogen heater 10 is configured to be positioned at the peak 122 or the valley bottom 124 of the local light distribution ripple 120 in the longitudinal direction at the position of the temperature detection member 110, so Therefore, even if the position of the peak 122 or the valley bottom 124 of the light distribution ripple 120 of the halogen heater 10 varies somewhat, the heating roll temperature detected by the temperature detection element 110 is not easily affected by the light distribution ripple 120.

Next, using a halogen heater of multiple, rows cormorants If the fixing while switching the halogen heater in accordance with the printing conditions such as sheet size or the number of prints will now be described with reference to FIG. FIG. 3 is a cross-sectional view of the heating roll 130 and the pressure member 140. The heating roll 130 incorporates two halogen heaters 90A and 90B. For example, the halogen heater 90A has a narrow heating area and corresponds to a narrow paper, and the halogen heater 90B has a wide heating area and corresponds to a wide paper. Then, the halogen heaters 90A and 90B are switched and used according to the printing conditions. The heating roll 130 rotates in the direction of the rotation direction 132, and the pressure member 140 follows this. The heating roll 130 and the pressure member 140 are pressure-bonded, and the sheet is sandwiched between the two nips (the heating roll 130 and the pressure member 140) with the nip 134 interposed therebetween. The toner is thermally fixed on the paper. The temperature detection member 110 makes the temperature detection part 112 contact the outer surface of the heating roll 130. In such an arrangement, when the temperature sensor 110 is installed in the valley of the light distribution ripple in both the halogen heaters 90A and 90B as in the prior art, the temperature 114 at the nip 134 is as shown in FIG. In other words, when the halogen heater 90B is used, the temperature 114 at the nip portion becomes high because the portion having the lowest roll circumferential temperature (upstream of the halogen heater) is monitored and controlled. On the contrary, when the halogen heater 90A is used, the temperature at the nip portion 116 is lowered because the highest temperature on the roll circumference (downstream of the halogen heater) is monitored and controlled as shown in FIG.

In the above SL arrangement, the halogen heater 90A in the rotation direction upstream side of the heating roll 130 as seen from the temperature sensing member 110 is positioned at a position corresponding to the valley bottom in the axial direction of the local light distribution ripple temperature detecting member, The halogen heater 90B on the downstream side is positioned at a position corresponding to the peak of the local light distribution ripple in the axial direction.

  FIG. 5 shows a temperature unevenness curve 126 caused by a light distribution ripple created by the halogen heater 90A. The position of the temperature sensor 110 corresponds to the bottom of the valley and is controlled by the control temperature 127. Accordingly, the entire roll has an average higher angle than the temperature measured by the temperature sensor 110. FIG. 4 shows a temperature unevenness curve 128 due to a light distribution ripple created by the halogen heater 90B. The position of the temperature sensor 110 corresponds to the peak, and the nip temperature is controlled by the control temperature 127. Accordingly, the entire roll is on average lower than the temperature measured by the temperature sensor 110. That is, the temperature of the upstream halogen heater 90A is generally low, and the heating roll reaches the nip after passing through the temperature detection member. The downstream halogen heater 90B generally has a high temperature, and the heating roll immediately reaches the nip. Therefore, by using the peak and valley bottom of the light distribution ripple as described above, the effects described in FIGS. 5 and 6 are synergistic and the nip temperature is optimized. As a result, the detected temperature acts in the direction of optimizing the control temperature, fixing failure can be prevented, and optimization of the nip temperature can be achieved.

FIG. 7 is a partial view of a halogen heater 90 as a heating source. In the halogen heater 90, a filament 92 is enclosed in an enclosure tube 94. In the filament 92, light emitting portions 150 and non-light emitting portions 152 are alternately arranged at substantially equal intervals along the longitudinal direction of the heater 90. There is a difference in the amount of light emitted. In the embodiment, the heater longitudinal dimension of the light emitting unit 150 and the non-light emitting unit 152 is about 10 mm. A temperature detection member 110 is disposed at a substantially central portion in the longitudinal direction of the halogen heater 90. The position is at a certain distance 154 from one terminal 100. The temperature detection member 110 detects the temperature of the outer surface of the heating roll incorporating the heater 90. A temperature control device is provided for controlling the power of the heater based on this detection.

  FIG. 8 is a diagram in which the halogen heater 90 and a temperature distribution curve 160 along its longitudinal direction are shown. The temperature distribution is displayed in E (%). The temperature distribution in a certain section at the center of the halogen heater 90 is set to a certain value 162, and a temperature detection member is arranged at the center.

  FIG. 9 is a cross-sectional view showing a cross section of the sheet passing area at the center of the heating roll 130. In recent years, a technique for reducing the warm-up time and saving energy has been adopted for the cylindrical body 136 in the paper passing area of the heating roll 130 with a reduced thickness 138. The thickness 138 of the heating roll 130 has been about 0.7 mm in the past, but the thickness of the thinnest part in the paper passing area is 0.5 mm or less, and recently, the thickness has been reduced to about 0.2 mm. . This thickness is such that a temperature gradient appears based on the difference in the amount of light emitted from the heating source (halogen heater) in the longitudinal direction of the heating roll in the vicinity where the temperature detection member is disposed.

  10 and 11 schematically show an enlarged positional relationship between the position of the halogen heater 90 in the longitudinal direction of the filament 92 and the temperature detection member 110, and correspond to the light-emitting portion 150 and the non-light-emitting portion 152 of the filament 92. It is explanatory drawing which showed collectively the light distribution ripple 120 to do. In FIG. 10, the temperature detection member 110 faces the light emitting portion 150 of the filament 92 and faces the peak 122 of the light distribution ripple 120. In FIG. 11, the temperature detection member 110 is opposed to the position of the filament 92 that is off the light emitting portion 150, and is opposed to the peak 122 and the valley bottom 124 of the light distribution ripple 120. The temperature gradient along the longitudinal direction of the filament 92 is gentle at the peak 122 and the valley bottom 124 of the light distribution ripple 120, and the temperature gradient along the longitudinal direction of the filament 92 changes suddenly between the peak 122 and the valley bottom 124.

  12 to 15 are charts showing changes in roll temperature change over time. The roll temperature transitions 172 and 174 when the same pulse input 170 is applied to the same halogen heater are shown. In the drawing, “Lamp” indicates a halogen heater, and the pulse input 170 indicates the ON / OFF operation. The upper side is ON and the lower side is OFF.

FIG. 12 shows a reference example. When the thickness of the heating roll is 0.2 mm, the temperature detection member is arranged to face the peak of the light distribution ripple, and the facing position matches the peak (deviation = The temperature transition 172 on the surface of the heating roll at 0 mm) and the temperature transition 174 on the surface of the heating roll when displacement occurs from this (displacement = 3 mm) are shown.

FIG. 13 shows a reference example, in which the thickness of the heating roll is 0.2 mm, the temperature detection member is arranged facing the middle of the light distribution ripple (middle of the peak and valley bottom), and the facing position is the same as the middle. A temperature transition 172 on the surface of the heating roll when it is offset (deviation = 0 mm) and a temperature transition 174 on the surface of the heating roll when a positional deviation occurs from this (displacement = 3 mm) are shown.

  FIG. 14 and FIG. 15 show conventional examples corresponding to FIG. 12 and FIG. 13, respectively, where the thickness of the heating roll is 0.7 mm and the temperature detection member is arranged facing the peak of the light distribution ripple. When the opposed positions coincide with each other (displacement = 0 mm), the temperature transition 172 of the surface of the heating roll and the heating roll when misalignment occurs (displacement = 3 mm). The temperature transition 174 of the surface is shown. As shown in FIGS. 14 and 15, when the thickness of the heating roll is 0.7 mm, that is, when it is thick, even if the temperature detection member is installed with a deviation from a predetermined position, a large change in the detected temperature is observed. I can't.

  On the other hand, when the thickness of the heating roll is 0.2 mm, that is, when it is thin, a large error occurs in the detected temperature due to the position of the temperature detecting member and the halogen heater. As shown in FIG. 13, when the temperature detection member is installed in the middle of the ripple (a position where the gradient of the temperature gradient is large), if the temperature detection member is installed with a deviation from a predetermined position, a large change in the detected temperature is observed. It is done. In FIG. 13, when the temperature detection member is shifted by 3 mm to the ripple peak side (the higher temperature side), the detection temperature of the temperature detection member is high. In this case, since temperature control is performed based on a high detection temperature of the temperature detection member, the actual surface temperature of the heating roll is lowered. On the other hand, when the temperature detection member deviates to the ripple valley side (the lower temperature side), the actual surface temperature of the heating roll is controlled to a higher temperature than when the deviation = 0 mm.

On the other hand , as shown in FIG. 12, if the temperature detecting member is installed at a position where the gradient of the temperature gradient is small, that is, facing the peak of the light distribution ripple, the temperature detecting member is shifted from a predetermined position. Even if it is done, a big change is not seen in detection temperature. Even if the temperature detection member is installed facing the valley of the ripple, the same result is obtained because the gradient of the temperature gradient is small.

  As described above, even if the relative mounting position accuracy between the temperature detecting member and the halogen heater deviates by 3 mm from a predetermined installation-related position due to manufacturing or mounting errors, etc., temperature detection is possible. If the member is placed facing a position where the gradient of the temperature gradient of the light distribution ripple of the halogen heater is low, the surface temperature of the heating roll will be set to the target temperature without causing a large difference in the detection temperature of the temperature detection member. Can be controlled.

It is explanatory drawing of an Example. It is explanatory drawing of a prior art example. It is sectional drawing of a heating roll and a pressurization member. It is a graph which shows the temperature transition of a nip part. It is a graph which shows the temperature nonuniformity of a light distribution ripple. It is a graph which shows the temperature nonuniformity of a light distribution ripple. It is a block diagram of a halogen heater. It is explanatory drawing which shows the light distribution intensity | strength of a halogen heater. FIG. It is an arrangement relation figure of a heater and a sensor. It is an arrangement relation figure of a heater and a sensor. It is a surface temperature transition figure (reference example) of a heating roll. It is a surface temperature transition figure (reference example) of a heating roll. It is a surface temperature transition figure (reference example) of a heating roll. It is a surface temperature transition figure (reference example) of a heating roll. It is a circuit diagram of a temperature rising and heating prevention device. 1 is an overall explanatory diagram of an image forming apparatus.

Explanation of symbols

10 Halogen heater 90, 90A, 90B Halogen heater (heating source)
92 Filament 94 Encapsulated tube 96 Halogen gas 98 Lid 100 Terminal 110 Temperature detection member 112 Temperature detection part 114, 116 Temperature of nip part 120 Light distribution ripple (curve)
122 mountain top 124 valley bottom 126 temperature unevenness curve 127 control temperature 128 temperature unevenness curve 130 heating roll 132 rotation direction 134 nip 136 cylinder 138 thickness 140 pressure member 150 light emitting part 152 non-light emitting part 154 constant distance 160 temperature distribution curve 162 constant value 170 Pulse input 172, 174 Temperature transition 200 Image forming apparatus 202 Photosensitive drum 204 Electrostatic roll 206 Exposure apparatus 208 Developer 210 Development roll 212 Transfer roll 214 Heating roll 220 Paper feed cassette 222, 224 Feed roll 226 Registration roll 228 Paper supply path 230, 232 Paper feed lever 240 Discharge roll 250 Thermal fixing device

Claims (2)

A heating roll containing a plurality of halogen heaters, a pressure member installed so as to be in pressure contact with the heating roll, a temperature detection member for detecting the surface temperature of the heating roll, and the halogen based on the temperature detected by the temperature detection member In a thermal fixing device including a temperature control device that controls electric power supplied to a heater,
The halogen heaters are disposed upstream and downstream in the rotation direction of the heating roll as viewed from the surface of the heating roll detected by the temperature detection member, and the halogen heater on the upstream side is locally localized in the axial direction. the root of the Do light distribution ripple disposed at a position corresponding to the temperature sensing member, the halogen heater in the downstream, to the arrangement of the summit of the local light distribution ripple in the axial direction at a position corresponding to the temperature detection member A heat fixing device characterized by the above.   An image forming apparatus comprising the heat fixing device according to claim 1.

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