JP4479385B2 - 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-described 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 and 2 below describe control methods for solving such problems. In the control method of Patent Literature 1, when the accumulated rotation time of the pressure roller 13 is smaller than a predetermined value, the initial operation waiting time is shortened by increasing the set temperature of the heating roller 15. Further, according to the control method of Patent Document 2, the amount of heat stored in the pressure roller 13 is estimated from the accumulated time of rotation of the pressure roller 13, and the set temperature of the heating roller 15 is changed in accordance with the estimated amount of heat supply. The amount of heat is adjusted.
Japanese Patent No. 3123291 Japanese Patent No. 3422339

  However, if the fixing device is turned off and then restarted before it is sufficiently cooled, the temperature of the pressure roller 13 becomes higher than the temperature estimated from the accumulated time of rotation and stop of the pressure roller 13. There was a problem that wasteful energy was consumed.

  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, the recording paper on which an image of unfixed toner is formed is passed between a heating device having a heater and a pressure device not having a heater, and the recording paper is heated while being moved. In the fixing device for fixing the unfixed toner to the recording paper, if the cumulative value of the rotation of the pressure device 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, the pressure roller is rotated intermittently for a predetermined time every predetermined time , and if the accumulated value is equal to or greater than the predetermined value, A control method that does not rotate the pressure device in the standby state, or if the cumulative value of rotation of the pressure device after the heating device reaches a predetermined fixing temperature is large, the heating device and the pressure device Equipment and In the standby state for maintaining the recording sheet the heating device immediately after fixing the toner of the unfixed on the recording paper by fed to the fixing temperature during fixing of the temperature is increased by rotating the pressure device A control method for shortening the post-rotation time, wherein the cumulative value is stored in the storage device when the cumulative value is stored in the storage device and the fixing device is restarted. The value is calculated from the value and the temperature of the heating device.

  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. Further, if the pressure roller is not completely cooled when the power of the fixing device is shut off, a value calculated from the temperature when the fixing device is started and the accumulated value stored in the storage device is set to the initial value of the accumulated value. By setting the value, the rotation procedure for heating the pressure roller can be appropriately changed according to the temperature state of the pressure roller. As a result, since the rotation time for heating the pressure roller is shortened, the fixing device has a short initial operation waiting time from the standby state until the toner is fixed on the first recording paper, and the pressure roller is more than necessary. Low energy consumption because it is not heated.

  In the fixing device control method of the present invention, when the temperature of the heating device when the fixing device is restarted is lower than a lower limit temperature, the initial value may be set to zero. When the temperature of the heating device when restarted is higher than the boundary temperature, the initial value of the cumulative value may be set to the same value as the cumulative value stored in the storage device.

  According to this method, when the temperature of the heating device is lower than the lower limit temperature, it can be determined that the pressure roller is completely cooled, so the pressure roller is required by setting the initial value of the cumulative value to zero. The rotation procedure of the pressure roller that can be heated to the minimum can be selected. Further, when the temperature of the heating device is higher than the upper limit temperature, the heating device and the pressurizing device are hardly cooled, and the accumulated value is integrated as the initial value with the same value as the accumulated value stored in the storage device. Thus, it is possible to select the rotation procedure of the pressure roller that can be performed with the minimum necessary heating in consideration of the heat applied to the pressure roller during the previous operation. As a result, since the rotation time for heating the pressure roller is shortened, the fixing device has a short initial operation waiting time from the standby state until the toner is fixed on the first recording paper, and the pressure roller is more than necessary. Low energy consumption because it is not heated.

  In the fixing device control method of the present invention, the storage device may store a value indicating which of the plurality of predetermined temperature bands has the accumulated value.

  According to this method, since it is not necessary to frequently rewrite the value stored in the storage device, the life of the storage device is extended. As a result, the fixing device with a short initial movement waiting time from the standby state until the toner is fixed on the first recording sheet and with low energy consumption has a long life.

  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 over a heating roller 5 on which an endless sheet-like fixing belt 4 can rotate and a nip forming member 6 fixed in a non-rotatable manner. The heating roller 5 has an internal heater 7 and an outer surface. The thermistor 8 is provided so as to contact. 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 200 ° C., for example. A portion of the fixing belt 4 that is in contact with the heating roller 5 is heated by the heating roller 5. In the fixing device 1, by rotating the pressure roller 3 in the direction indicated by the arrow, the fixing belt 4 is rotated in the direction indicated by the arrow, and the heating roller 5 is also rotated. 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 at, for example, 11 seconds, but this time, after the fixing device 1 is started, the toner T is immediately applied after the heating roller 5 reaches 200 ° C. This is the time required to heat the pressure roller 3 to a temperature at which it can be fixed to the recording 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. This rotation procedure is changed by adding the rotation time excluding the rotation for fixing after the fixing device 1 has been warmed up to the initial value th ₀ as the cumulative value of the rotation of the pressure roller 3. The time th is used, and based on the value of th.

  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.

The initial value th ₀ is determined by the cumulative time ti stored in a storage device (not shown) and the temperature Ti of the heating roller 5 detected by the thermistor 8 when the fixing device 1 is started.

In the fixing device 1, as shown in Table 1 below, nine bands are set for the cumulative time th, and the status indicating which cumulative time th is included in the cumulative time th is stored even when the power is turned off. The content is stored in a storage device including a non-volatile memory such as a flash memory. This storage of status may be stored in the memory by setting any one of nine bits corresponding to each accumulated time band to 1 or 0, and expressed as a binary number by a memory of 5 bits or more. Also good. This storage is updated by rewriting the status of the storage device when the accumulated time th reaches the lower limit value of each time band. Then, when determining the initial value th ₀ cumulative time th uses the lower limit of the time band as a representative value of the cumulative time ti.

When the temperature Ti of the heating roller 5 when the fixing device 1 is started is lower than the lower boundary value T _r1 , the initial value th _{0 is set} to 0 as shown in the following formula 1. When the temperature Ti is not less than the lower boundary value T _{r1 and not} more than the upper boundary value T _r2 , the representative value ti of the accumulated time th is stored in the correction formula of the order n _r as shown in the following equation 2, and the temperature Ti the value obtained by correcting the set as an initial value th _0. Further, when the temperature Ti is higher than the upper boundary value T _r2, as shown in Equation 3 below, a representative value ti and as the initial value th _0.

In the present embodiment, the lower boundary value T _r1 , the upper boundary value T _r2, and the correction order n _r are set as shown in Table 2 below.

  When the fixing device 1 does not perform fixing immediately after the start-up, the fixing device 1 enters a standby state immediately after the heating roller 5 reaches 200 ° C., for example, after being warmed up for 25 seconds. 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 3 below. The environmental temperature Ta is information that can be obtained without adding any components because an environmental temperature sensor and an environmental humidity sensor are usually provided in 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 Table 4 below, the post-fixing rotation time is determined by the accumulated time th and the environmental temperature Ta.

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

When the fixing device 1 is started from a completely cooled state, the temperature of the heating roller 5 is 20 ° C. which is the same as the environmental temperature, and the initial value th ₀ of the cumulative time th is set to ₀ according to Equation 1, status t ₁ is stored in the storage device. Then, while the heater 7 is energized and generates heat, the pressure roller 3 rotates to start warming up. When the fixing command signal instructing that the toner T should be fixed by passing the recording paper P before the temperature of the heating roller 5 reaches 200 ° C., the thermistor 8 has reached 200 ° 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, the post-fixing rotation is performed for a predetermined number of seconds according to Table 4. Here, since the accumulated time th is 11 seconds and the environmental temperature Ta is 20 ° C., the fixing device 1 rotates after fixing for 12 seconds and then stops the pressure roller 3 and enters a standby state. During after fixing rotating, th status t ₂ is stored in the storage device so reaches 20 seconds, the rotation is terminated after fixing, th is 23 seconds by adding 12 seconds.

  At the time of standby, it is determined according to Table 3 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 3.

When performing the next fixing after the intermittent rotation of the fourth time, it performs the pre-rotation fixing of 11 seconds, the status t ₃ is recorded in the storage device when the accumulated time th has reached 45 seconds. The recording paper P is passed after the rotation before fixing, and the accumulated time th is 53 seconds. Subsequently, the post-fixing rotation of 12 seconds defined in Table 4 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 3.

Thereafter, each time the fixing device 1 performs fixing, 11 seconds of pre-fixing rotation and post-fixing rotation time defined in Table 4 are added to the cumulative time th, and the cumulative time th continues to increase. When the cumulative time th reaches 240 seconds, the status of the storage device is rewritten to t _4, when the cumulative time th is further reached at different times bands, status corresponding to the storage device is recorded.

Here, when restarting after the power of the fixing device 1 is turned off, any one of the formulas 1, 2 and 3 is applied depending on the temperature Ti of the heating roller 5 at the same time as the restarting, and stored before the power is turned off. by correcting the representative value ti of the status of the accumulated time th to determine the initial value th ₀ cumulative time th was.

For example, if the accumulated time th has off the power of the fixing device 1 when 700 seconds, statuses storage device has stored this time is t _5. When the temperature of the heating roller 5 is 100 ° C. when the fixing device 1 is restarted, the representative value ti = 540 seconds, so that the initial value th ₀ is calculated as 60 seconds according to Equation 2. Therefore, the cumulative time th at the time of re-starting becomes 60 seconds, the stored contents of the storage device is updated in the status t _3.

  The re-started fixing device 1 warms up until the temperature of the heating roller 5 reaches 200 ° C. and then enters a standby state after rotating for 25 seconds after warming up, but the accumulated time th is already 60 seconds. Therefore, intermittent rotation is not performed. Thereafter, the fixing device 1 determines the post-fixing rotation time according to the accumulated time th according to Table 4.

  As described above, the advantages of the control method of changing the rotation procedure according to Tables 1 to 4 and Formulas 1 to 3 will be described in comparison with the case of operating with the unchanged 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, since the post-fixing rotation is lengthened only when necessary, the pre-fixing rotation is always as short as 11 seconds and the initial waiting time is short. Further, when the fixing device is activated, an initial value th ₀ corresponding to the cooling state of the pressure roller 3 is calculated from the temperature of the heating roller 5 at the time of activation and the status ti of the accumulated time th stored at the previous operation. Since the accumulated time th is changed, the optimum rotation procedure of the pressure roller 3 can be selected in consideration of the remaining amount of heat accumulated in the previous operation held by the pressure roller 3. For this reason, the fixing device 1 has a short initial operation waiting time under any conditions and does not consume more energy than necessary.

  In addition, even if a storage device such as a flash memory that does not have a large number of rewritable times (about 1 million times) is used, the status of the accumulated time th is stored, so that the storage device does not need to be frequently rewritten and fixed. Equipment life is long.

  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 Table 3 and Table 4 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, Table 3, and Table 4 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 accommodated, Optimum control can be performed even when is switched.

  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 (6)

The recording paper on which an image of unfixed toner is formed is passed between a heating device having a heater and a pressurizing device 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 rotation of the pressure device 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 control method in which intermittent rotation is performed for a predetermined time every predetermined time , and the pressure device is not rotated in the standby state if the cumulative value is equal to or greater than the predetermined value,
Storing the accumulated value in a storage device;
When the fixing device is restarted, the initial value of the cumulative value is set to a value calculated from the cumulative value stored in the storage device and the temperature of the heating device. Method. The recording paper on which an image of unfixed toner is formed is passed between a heating device having a heater and a pressurizing device 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 device after the heating device reaches a predetermined fixing temperature is large, the recording paper is passed between the heating device and the pressure device to the recording paper. A control method for shortening a post-fixing rotation time for rotating the pressure device to increase the temperature in a standby state in which the heating device is maintained at the fixing temperature immediately after fixing the unfixed toner,
Storing the accumulated value in a storage device;
When the fixing device is restarted, the initial value of the cumulative value is set to a value calculated from the cumulative value stored in the storage device and the temperature of the heating device. Method. 3. The fixing device control method according to claim 1, wherein when the temperature of the heating device when the fixing device is restarted is lower than a lower limit temperature, the initial value of the cumulative value is set to zero. . The initial value of the cumulative value is set to the same value as the cumulative value stored in the storage device when the temperature of the heating device when the fixing device is restarted is higher than an upper limit temperature. Item 4. The fixing device control method according to any one of Items 1 to 3 . In the storage device, control of the fixing device according to any one of claims 1 to 4, characterized in that storing a value indicating whether there is the accumulated value to any band of the plurality of temperature bands predetermined Method. An image forming apparatus, comprising a fixing device for controlling by a control method according to any one of claims 1 to 5.

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