JP4479384B2 - Fixing device control method and image forming apparatus - Google Patents

Description

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

  The recording paper on which an image is formed with unfixed toner is sandwiched between a heating device having a heater and a pressure roller, and heated while the recording paper is moved by rotation of the heating device and the pressure roller. 2. Description of the Related Art Fixing devices that fix toner are used in image forming apparatuses such as copiers and printers.

  The heating device and the pressure roller that pinch the recording paper need to be at a predetermined temperature or higher in order to heat the toner and the recording paper by the heat to fix the toner to the recording paper. For this reason, each of the heating device and the pressure roller may be heated by a heater. However, in order to reduce the cost, the pressure roller is not provided with a heater, and a predetermined temperature is generated by heat transmitted from the heating device. In many cases, it is designed to maintain

  FIG. 4 shows a configuration of a conventional fixing device 11. The conventional fixing device 11 includes a heating device 12 and a pressure roller 13 that is in pressure contact with the heating device 12. The heating device 12 includes an endless sheet-shaped fixing belt 14 that is stretched between a heating roller 15 and a fixing roller 16. The heating roller 15 is provided with a heater 17 inside, and a thermistor 18 is in contact with the outer surface. Is provided. The thermistor 19 is also provided on the pressure roller 13 so as to be in contact with the outer surface.

  In the fixing device 11 having the above configuration, the thermistor 18 detects the temperature of the heating roller 15 and controls the heater 17 to be ON / OFF so that the heating roller 15 maintains a predetermined temperature. A portion of the fixing belt 14 that is in contact with the heating roller 15 is heated by the heating roller 15. The pressure roller 13 rotates in the direction indicated by the arrow, so that the fixing belt 14 rotates in the direction indicated by the arrow, and the heating roller 15 and the fixing roller 16 are also rotated. The pressure roller 13 and the fixing roller 16 are indirectly heated by receiving heat from the fixing belt 14 heated by the heating roller 15, but the rotation of the pressure roller 13 is stopped when the thermistor 19 detects a predetermined temperature. Then the heat supply is cut off. In this manner, in the fixing device 11, the temperature of the fixing belt 14 and the pressure roller 13 can be maintained at a predetermined temperature.

  In the fixing device 11, the recording paper P on which an image is formed with the toner T on one side is fed in the direction of the arrow, nipped between the fixing belt 14 and the pressure roller 13, and sent out by their rotation. At this time, the toner T is heated and fixed on the recording paper P by the fixing belt 14.

  Further, in order to reduce the cost, it is considered that the thermistor 19 for detecting the temperature of the pressure roller 13 is omitted from the fixing device 11. Even if the temperature of the pressure roller 13 is not known, the temperature of the heating roller 15 is set high so that the temperature of the pressure roller 13 is equal to or higher than that required under any conditions, or the heating device 12 is heated. It is possible to fix the toner T on the recording paper P without any problems if the rotation before the fixing is sufficient to heat the pressure roller 13 immediately before the recording paper P is passed between the recording paper P and the pressure roller 13. is there. However, in this case, there are problems that the initial operation waiting time from the standby state to the first fixing (first print) becomes long, the energy consumption increases, and the life of the fixing device 11 becomes short.

Patent Documents 1 to 3 below describe control methods for solving such problems. Patent Document 1 describes a control method in which a decrease in the temperature of the heating roller 15 during pre-fixing rotation is measured, and the pre-fixing rotation is performed for a longer time as the temperature decrease increases. In Patent Documents 2 and 3, a temperature drop of the pressure roller 13 is estimated based on the accumulated time of rotation and stop of the pressure roller 13, and the set temperature of the heating roller 15 is changed accordingly. A control method for adjusting the amount of heat is described.
Japanese Patent No. 3255247 Japanese Patent No. 3123291 Japanese Patent No. 3422339

  However, in these control methods, since it is necessary to detect the temperature change of the heating roller 15 in detail with the thermistor 18 or to detect a plurality of set temperatures, the temperature control of the heating roller 15 becomes complicated. there were.

  In view of the above problems, an object of the present invention is to provide a fixing device with a simple configuration, a short initial waiting time, and low energy consumption, and an image forming apparatus using the same.

  In order to solve the above-mentioned problems, the present inventor has repeatedly conducted intensive experiments. As a result, the temperature of the pressure roller that has been stopped after a certain period of rotation has reached a certain minimum temperature, and then released heat from the heating device. It has been found that the temperature rises gradually and that the aforementioned minimum temperature is related to the aforementioned rotation time.

That is, according to the present invention, a recording sheet on which an image is formed with unfixed toner is passed between a heating device having a heater and a pressure roller not having a heater, and the recording sheet is heated while being moved. In the fixing device for fixing the unfixed toner to the recording paper, if the cumulative value of rotation of the pressure roller after the heating device reaches a predetermined fixing temperature is smaller than a predetermined value, In a standby state in which the heating device is maintained at the fixing temperature, intermittent rotation is performed by rotating the pressure roller for a predetermined time every predetermined time , and if the accumulated value is equal to or greater than the predetermined value, the addition is performed in the standby state. If the pressure roller does not rotate, or if the accumulated value of rotation of the pressure roller after the heating device reaches a predetermined fixing temperature is large, the pressure roller is interposed between the heating device and the pressure roller. In the standby state for maintaining the heating device immediately after and passed the serial recording paper was fixing the toner of the unfixed on the recording paper to the fixing temperature, the rotation after the fixing to increase in temperature by rotating the pressure roller This is a method of shortening the time.

  According to this method, the longer the rotation time from the start of the fixing device, the more the heat is transferred from the heating device to the pressure roller, and the pressure roller is heated. The temperature of the roller can be estimated. Therefore, even if the fixing device has a simple configuration in which a thermistor or the like for detecting the temperature of the pressure roller is not provided, the rotation procedure is changed according to the cumulative value so that the pressure roller is recorded with a minimum rotation. It can be heated to a predetermined temperature at which unfixed toner can be fixed on the paper. As a result, the fixing device has a short initial operation waiting time from the standby state until the toner is fixed to the first recording paper, and does not heat the pressure roller more than necessary, so that the energy consumption is small.

According to the above method , the temperature of the pressure roller during standby can be maintained at a predetermined temperature by the intermittent rotation, and even if the temperature of the pressure roller decreases during standby, the rotation before fixing is performed. The pressure roller can be heated to a substantially predetermined temperature, and the amount of heat dissipated while optimizing the amount of heat supplied to the pressure roller by the post-fixing rotation so that the temperature does not fall too low until the next fixing. As little as possible. As a result, the fixing device can reduce the rotation before fixing required when fixing toner on the first recording paper from the standby state, so that the initial operation waiting time is short and the amount of heat to be supplied to the pressure roller is reduced. Since it can be reduced, it consumes less energy.

  In the fixing device control method of the present invention, the cumulative value may be a cumulative time of the rotation, a cumulative value of a value obtained by multiplying the rotational time by a rotational speed, The cumulative value may not include the time during which the recording paper is passed between the heating device and the pressure roller.

  According to this method, if the rotation speed of the fixing device is constant, the amount of heat transferred from the heating device to the pressure roller can be estimated based on the accumulated time of rotation of the pressure roller. The higher the rotation speed of the fixing device, the greater the amount of heat transferred from the heating device to the pressure roller. However, the amount of heat transferred from the heating device to the pressure roller by the cumulative value of the rotation time multiplied by the rotation speed. Can be guessed. Further, if the time during which the recording paper is passed is excluded, an error due to the amount of heat that the recording paper takes from the pressure roller can be eliminated. Thereby, a rotation procedure can be changed appropriately, the initial operation waiting time can be shortened, and energy consumption can be reduced.

  In the fixing device control method of the present invention, the rotation procedure may differ depending on the environmental temperature and / or the environmental humidity.

  According to this method, the amount of heat dissipated from the pressure roller changes depending on the environmental humidity and the environmental humidity. Therefore, select an appropriate rotation procedure according to the environmental humidity and the environmental humidity, and shorten the initial waiting time. , Energy consumption can be reduced.

  In the fixing device control method of the present invention, when the fixing device is restarted, the accumulated value may be returned to the initial value.

  According to this method, the temperature of the pressure roller reaches a predetermined temperature even in a predetermined rotation procedure due to cooling of the pressure roller when the heater of the heating device is not operating due to power interruption or paper jam handling. The trouble of not doing can be prevented.

  The image forming apparatus according to the present invention includes a fixing device controlled by the control method.

  According to this configuration, the configuration of the fixing device is simple, the initial operation waiting time is short, and the image forming apparatus consumes little energy.

  As described above, according to the present invention, it is possible to provide a fixing device having a simple configuration in which the pressure roller does not include a heater or thermistor, a short initial waiting time, and low energy consumption, and an image forming apparatus using the same.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a configuration of a fixing device 1 according to an embodiment of the present invention. The fixing device 1 includes a heating device 2 and a pressure roller 3 that is in pressure contact with the heating device 2. The heating device 2 is stretched between a heating roller 5 on which an endless sheet-like fixing belt 4 can rotate and a nip forming member 6 fixed so as not to rotate. The heating roller 5 is in contact with the heater 7 and the outer surface. Thus, a thermistor 8 is provided. The nip forming member 6 is supported by the reinforcing member 9 and sandwiches the fixing belt 4 together with the pressure roller 3.

  Next, the operation of the fixing device 1 having the above configuration will be described.

  In the fixing device 1, the thermistor 8 detects the temperature of the heating roller 5, and controls the heater 7 on / off so that the heating roller 5 maintains, for example, 190 ° C. A portion of the fixing belt 4 that is in contact with the heating roller 5 is heated by the heating roller 5. The fixing device 1 rotates the pressure roller 3 in the direction indicated by the arrow, thereby rotating the fixing belt 4 in the direction indicated by the arrow and rotating the heating roller 5 as well. The pressure roller 3 and the nip forming member 6 are indirectly heated by receiving heat from the fixing belt 4 heated by the heating roller 5.

  If the pressure roller 3 is equal to or higher than a predetermined temperature, the recording paper P on which an image is formed with unfixed toner T on one side is fed in the direction of the arrow and passed between the fixing belt 4 and the pressure roller 3. The toner T can be heated and fixed on the recording paper P by the fixing belt 4 while the recording paper P is sent out by the rotation of the pressure roller 3. At this time, if the temperature of the pressure roller 3 is low, the pressure roller 3 takes heat from the recording paper P and the toner T, and the fixing of the toner T to the recording paper P is obstructed. Therefore, as a method for controlling the temperature of the pressure roller 3 by its rotation, the pressure roller 3 is set at intervals during the standby until the fixing device 1 receives a fixing signal instructing the passage of the recording paper P. Intermittent rotation that compensates for the heat dissipated by rotating for a short time, pre-fixing rotation that rotates the pressure roller 3 to a temperature at which the toner T can be fixed immediately before passing the recording paper, and passing the recording paper There is a post-fixing rotation in which the pressure roller 3 is rotated afterward to give heat that will be dissipated during standby.

  In the fixing device 1 of the present embodiment, the rotation before fixing is always constant, for example, 11 seconds, but this time, the toner T is recorded immediately after the heating roller 5 reaches 190 ° C. after the fixing device 1 is started. This is the time required to heat the pressure roller 3 to a temperature at which it can be fixed to the paper P. On the other hand, between the intermittent rotation of the pressure roller 3 and the rotation after fixing, the rotation procedure including the rotation time and the presence / absence of rotation is changed according to the situation. The rotation procedure is changed by using, as the cumulative value of the rotation of the pressure roller 3, the cumulative time th obtained by integrating the rotational time excluding the rotation for fixing after the fixing device 1 has been warmed up. , Based on the value of th.

  When the fixing device 1 does not perform fixing immediately after starting, the fixing device 1 enters a standby state after rotating for 25 seconds immediately after the heating roller 5 reaches 190 ° C. At the time of this standby, in order to prevent the temperature of the pressure roller 3 from being excessively lowered, for example, intermittent heat for 5 seconds is performed every 60 seconds to compensate for the dissipated heat. As a result, the pressure roller 3 repeats heating and heat dissipation, and the temperature of the central portion rises, so that the temperature can be maintained without intermittent rotation. Whether or not the fixing device 1 requires intermittent rotation is determined by the accumulated time th and the environmental temperature Ta as shown in Table 1 below. The environmental temperature Ta is information that can be obtained without adding new components because it is usually provided with an environmental temperature sensor and an environmental humidity sensor as long as it is an apparatus such as an image forming apparatus using a fixing device. Further, since the environmental humidity also affects the heat dissipation of the pressure roller 3, it may be classified according to the environmental temperature Ta and the environmental humidity.

  Further, the post-fixing rotation that is performed immediately after the recording paper P is passed between the fixing belt 4 and the pressure roller 3 and the toner T is fixed is short as the cumulative rotation time th increases, as in the intermittent rotation. It will take time. In the fixing device 1, as shown in the following Table 2, the post-fixing rotation time is determined by the accumulated time th and the environmental temperature Ta.

  In accumulating the accumulated time th, the time from the start of passing the first recording sheet P between the fixing belt 4 and the pressure roller 3 to the end of passing the last continuous recording sheet P is: Do not add to accumulated time th. This is because, in the fixing device 1, the amount of heat transmitted from the fixing belt 4 and the amount of heat taken away by the recording paper P of the pressure roller 3 while the recording paper P is passing are substantially equal. Under different conditions, it may be better to add the rotation time between sheets between the recording sheet P and the next recording sheet P to the accumulated time th.

  Here, as an example, the rotation procedure when fixing is performed immediately after startup in the fixing device 1 when the environmental temperature Ta is 20 will be described.

  When the fixing device 1 is activated, the accumulated time th is reset to 0, and the pressure roller 3 rotates while the heater 7 is energized to generate heat, and warm-up is started. If the fixing command signal is received that indicates that the toner T should be fixed by passing the recording paper P before the temperature of the heating roller 5 reaches 190 ° C., the thermistor 8 has reached 190 ° C. As soon as it is detected, the rotation procedure for fixing is started.

  In the rotation procedure for fixing, first, the pre-fixing rotation is performed for 11 seconds, and the temperature of the pressure roller 3 is sufficiently increased. At this time, the accumulated time th is 11 seconds. Subsequently, the sheet passing rotation is performed to fix the toner T by passing the recording sheet P, and when fixing a plurality of recording sheets P, for example, the next sheet passing through the rotation between sheets to open a sheet interval of 60 mm is inserted. Repeat the paper rotation. The sheet passing rotation and the sheet rotation for fixing are not added to the accumulated time th. When the last recording paper P has been passed, rotation after fixing is performed for a predetermined number of seconds according to Table 2. Here, since the accumulated time th is 11 seconds and the environmental temperature Ta is 20 ° C., rotation after fixing is performed for 12 seconds. When the rotation after the fixing is completed, th is added to the 12 seconds, so that it becomes 23 seconds, and the fixing device 1 stops the pressure roller 3 and enters a standby state.

  At the time of standby, it is determined according to Table 1 whether to perform intermittent rotation for 5 seconds every 60 seconds. Here, since the accumulated time th is 23 seconds and the environmental temperature Ta is 20 ° C., intermittent rotation is performed. When intermittent rotation is performed, the rotation time is added to the accumulated time th. When the fourth intermittent rotation is performed after the fixing device 1 enters the standby state, the cumulative time th reaches 43 seconds, and thereafter, the intermittent rotation is not performed as defined in Table 1.

  Further, when performing the next fixing, the recording paper P is passed after rotating for 11 seconds before fixing and adding 11 seconds to the accumulated time th. Subsequently, since the cumulative time th at that time is 53, the post-fixing rotation of 12 seconds defined in Table 2 is performed, and the post-fixing rotation of 12 seconds is added to the cumulative time th. Thereafter, the fixing device 1 again enters the standby state, but the accumulated time th is 65 seconds, and the intermittent rotation is no longer performed as defined in Table 1.

  Thereafter, each time the fixing device 1 performs fixing, 11 seconds of pre-fixing rotation and post-fixing rotation time defined in Table 2 are added to the cumulative time th, and the cumulative time th continues to increase. However, when the power of the fixing device 1 is turned off or the operation current to the fixing device 1 is cut off by detecting that the housing of the image forming apparatus has been opened due to a paper jam processing, etc. The temperature of the roller 3 will fall. When the temperature of the pressure roller 3 is lowered, the toner T cannot be fixed on the recording paper P. Therefore, it is necessary to supply extra heat from the heating roller 5, but in this state, a rotation procedure for supplying a necessary amount of heat is performed. It cannot be determined. Therefore, in such a case, the accumulated time th is once returned to the initial value of zero and restarted from the warm-up. At this time, the temperature of the pressure roller 3 may be higher than usual, but there is no problem in fixing the toner T to the recording paper P.

  As described above, the advantage of the control method of changing the rotation procedure according to Tables 1 and 2 will be described in comparison with the case of operating in the same rotation procedure.

  If the fixing device 1 is operated in an unchanging rotation procedure, the environmental temperature Ta is low, and immediately after the fixing device 1 is started, it can be heated to a temperature at which fixing can be performed even when the pressure roller 3 is cooled down. It is necessary to perform intermittent rotation at all times during standby, and always to perform rotation after fixing for, for example, 17 seconds after passing paper. These rotations consume a lot of motive energy and extra energy consumption due to the heat generated by the heater 7 because the pressure roller 3 becomes hot and dissipates a lot of heat. However, in this embodiment, the intermittent rotation is canceled depending on the accumulated time th, and the post-fixing rotation is shortened to, for example, 7 seconds, so that energy consumption can be reduced.

  In addition, if the rotation after fixing is fixed in a short time, it is necessary to lengthen the rotation before fixing, so the initial waiting time becomes long. However, in this embodiment, the rotation after fixing is lengthened only when necessary. The rotation is always as short as 11 seconds, and the initial waiting time is short.

  In the present embodiment, the control method based on the assumption that the rotation speed of the pressure roller 3 of the fixing device 1 is constant has been described. However, the rotation speed of the pressure roller 3 depends on the thickness and material of the recording paper P. It is also possible to switch between. If the rotational speed is doubled, the amount of heat received by the pressure roller 3 from the heating roller 5 via the fixing belt 4 is also almost doubled. Correspondingly, each boundary value of the cumulative time th in Tables 1 and 2 may be changed according to the rotational speed, but instead of the cumulative time th, the rotational time is multiplied by the rotational speed of the pressure roller 3. If Table 1 and Table 2 are defined for the cumulative value (also expressed as the cumulative rotational speed or the cumulative distance converted into the recording paper feed amount), different rotational speeds can be handled, and the rotational speed is switched in the middle. Sometimes optimal control can be performed.

  In the fixing device 1, the fixing belt 4 is sandwiched between the nip forming member 6 and the pressure member 3. However, like the fixing device 1 ′ shown in FIG. 2, the rotatable fixing roller 10 and the pressure roller 3. Thus, a device that sandwiches the fixing belt 4 spanned between the heating roller 5 and the fixing roller 10 may be used. Further, as in the fixing device 1 ″ shown in FIG. 3, a device that fixes the toner T by passing the recording paper P between the heating roller 5 and the pressure roller 3 that are in direct pressure contact with each other may be used. 2 and 3, the same components as those of the fixing device 1 of FIG.

  By using the fixing device controlled by the control method as described above as a component, an image forming apparatus such as a copying machine or a printer can have a simple configuration, a short initial waiting time, and low energy consumption. .

1 is a schematic view of a fixing device of the present invention. FIG. 3 is a schematic view of a fixing device having a different configuration according to the present invention. FIG. 3 is a schematic view of a fixing device having a further different configuration according to the present invention. Schematic of a conventional fixing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Heating device 3 Pressure roller 7 Heater 8 Thermistor P Recording paper T Toner

Claims (8)

The recording paper on which an image is formed by unfixed toner is passed between a heating device having a heater and a pressure roller not having a heater, and heated while moving the recording paper to move the unfixed toner. In a fixing device for fixing toner on the recording paper,
If the cumulative value of rotation of the pressure roller after the heating device reaches a predetermined fixing temperature is smaller than a predetermined value, the pressure roller is moved in a standby state in which the heating device is maintained at the fixing temperature. A fixing device control method, wherein intermittent rotation is performed at predetermined time intervals for a predetermined time , and the pressure roller is not rotated in the standby state if the accumulated value is equal to or greater than the predetermined value. The recording paper on which an image is formed by unfixed toner is passed between a heating device having a heater and a pressure roller not having a heater, and heated while moving the recording paper to move the unfixed toner. In a fixing device for fixing toner on the recording paper,
If the accumulated value of the rotation of the pressure roller after the heating device reaches a predetermined fixing temperature is large, the recording paper is passed between the heating device and the pressure roller to the recording paper. In a standby state in which the heating device is maintained at the fixing temperature immediately after fixing the unfixed toner, the fixing device is configured to shorten a post-fixing rotation time for rotating the pressure roller to increase the temperature. Control method. The accumulated value, the control method of the fixing device according to claim 1 or 2, wherein the a cumulative time of rotation. 3. The fixing device control method according to claim 1, wherein the cumulative value is a cumulative value of a value obtained by multiplying the rotation time by a rotation speed. The accumulated value, the control method of the fixing device according to claim 3 or 4, characterized in that does not include the recording paper time that passed the between the pressure roller and the heating device. The environmental temperature and / or humidity, the control method of the fixing device according to any one of claims 1 5, characterized in that said rotating steps are different. Wherein when the fixing device has restarted, the control method of the fixing device according to any one of claims 1 to 6, characterized in that returning the accumulated value to an initial value. An image forming apparatus, comprising a fixing device for controlling by a control method according to any one of claims 1 to 7.

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