JP4936706B2 - Fixing device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a fixing device for an electrophotographic process such as a copying machine, a printer, and a facsimile, and an image forming apparatus having the same, and more specifically, temperature control and pre-rotation time of a fixing device for fixing a toner image on a recording sheet. The present invention relates to a fixing device and an image forming apparatus having control.

Image forming apparatuses such as copying machines, facsimile machines, printers, and printing machines generally have a fixing device for fixing a toner image on a sheet-like medium on which a toner image as a fixed image is formed. In particular, belt fixing devices are often used for reasons such as energy saving and shortening of start-up time.
However, the ON / OFF control of the heater in the heating roller that heats the belt is performed by detecting the belt temperature on the heating roller, and the belt can maintain a constant temperature during standby. Only the part that is attached, the other belt parts are getting colder. When the print command is received and the fixing device starts to rotate, the cold part of the belt is well below the temperature threshold. This is called temperature drop. If the paper enters the nip where the temperature drop is large, fixing failure or the like occurs.
In order to reduce the temperature drop, there is a method in which the fixing pre-rotation is performed after the printing command is received and before the printing operation is started. After the start of rotation, the belt temperature is detected and the rotation is continued until the dropped temperature recovers to the target temperature, and printing is started after the target temperature is reached. With this method, fixing failure does not occur, but a waiting time is generated for the pre-rotation time. In addition, the target temperature itself at the end of pre-rotation is normally set to a temperature that satisfies all the paper types in a certain range. Therefore, it is unavoidable to use a sheet near the upper limit in the sheet type range, but it is excessive for a user who uses a general sheet.
Accordingly, in view of the above problems, temperature control and pre-rotation time control of the fixing device have been conventionally performed.

  In Patent Document 1, in a fixing device using a fixing belt, in order to stabilize the fixing property at the time of continuous printing and to prevent hot offset, a temperature detecting means for detecting the surface temperature of the fixing belt in the heating process area, and a heating process are disclosed. Temperature control means for controlling the fixing belt surface temperature in the area to a predetermined temperature, having at least two fixing belt surface set temperatures in the heating process area, and after the fixing belt starts rotating upon receiving an image forming operation start signal A technique is disclosed in which, at the start of fixing, the temperature control means switches the fixing belt surface set temperature in the heating process area from the high temperature setting temperature at which fixing is possible to the low temperature setting temperature at which fixing is possible. ing.

  Further, in Patent Document 2, in order to reduce the temperature drop of the fixing belt and obtain a stable image, the set temperature of the pressure roller having the heating roller and the heater of the fixing device is set for each of the heating roller and the pressure roller. The surface temperature is preset to a second set temperature that is higher than the first set temperature necessary for fixing the unfixed image, and the set temperature is gradually changed from the second set temperature to the first set temperature. A control device that lowers is provided. Thus, a technique for preventing an undershoot portion that is lower than the first set temperature that is the target temperature is disclosed.

  Also, in Patent Document 3, even when a fixing belt having an elastic layer is used as a fixing member, accurate temperature control of the fixing member is performed regardless of variations in input voltage and resistance values of the fixing heater. Achieves high-quality images with no image defects and glossy print quality unevenness, high durability and long life, low power consumption, and the same in regions with different rated voltages In order to reduce costs and service costs by providing a fixing device, the maximum supply power to the fixing heater according to the rise time of the detection temperature of the main thermistor or sub-thermistor after the energization of the fixing heater is started. A technique for predicting the value and correcting the output power according to the maximum supply power value when outputting the power value necessary for stable operation of the fixing device is disclosed.

  Patent Document 4 discloses a technique for providing a heat roller temperature control method in which the printing start time is advanced and wrinkles are not generated on the first sheet.

  Further, in Patent Document 5, when the fixing device is started up, the waiting time until the fixing belt and the pressure roller reach a predetermined target temperature is shortened. Energizing the heating means so that the rising temperature is higher than the target temperature, and when the temperature detecting means detects that the temperature of the fixing belt has reached the rising temperature, the fixing belt and the pressure roller Discloses a technique for controlling the rotation of the fixing belt and the pressure roller such that the pre-rotation starts.

  Further, in Patent Document 6, the rotating sound of both the heating and pressurizing rollers during warming-up after turning on the power is reduced to ensure quietness, and good fixability in the first copy after completion of warming-up. In order to ensure the warming up after the power is turned on, only the heating means built in the heating roller is driven without rotating both rollers, and when the first copy start command signal is input, both rollers are turned on. A technique for starting a copying operation after driving for a predetermined time is disclosed.

JP-A-11-002982 JP 2004-184696 A JP 2004-191966 A JP 08-314322 A JP 2002-082570 A Japanese Patent Laid-Open No. 02-029769

However, any of the disclosed techniques of Patent Documents 1 to 6 does not take into account the printing state, the power-on time of the image forming apparatus, and the like as countermeasures for the temperature drop, and the mobility is not sufficient.
The present invention is capable of reliably detecting a temperature drop in consideration of the printing state, the power-on time of the image forming apparatus, and the pre-rotation time, and can turn on the heater quickly. Even if the value is set high, the influence on the next printing can be reduced, and further, a fixing device capable of selecting a temperature detection pre-rotation method and a constant second pre-rotation method, and an image forming apparatus provided with the same It is an issue to provide.

In order to solve the above problems, the present invention has the following features.
The present invention is provided with a fixing auxiliary member, a heating member, a fixing member stretched between the fixing auxiliary member and the heating member, and provided to face the fixing auxiliary member via the fixing member. In the fixing device provided with a pressure member for forming a heating member and a heater inside the heating member, the fixing device is set to perform pre-rotation before the start of printing according to an image forming linear speed, and Rotation is a temperature detection pre-rotation that detects the temperature of each member during pre-rotation according to the state of the apparatus and starts printing after rotating the fixing device until the temperature of each member reaches a predetermined temperature. One of a method and a fixed second pre-rotation method in which printing is started after the fixing device is rotated to a predetermined time by setting the pre-rotation time to a fixed time is selected. It is a fixing device.
The fixing device according to the present invention is further characterized in that control is performed to change a fixed time of the constant second pre-rotation method.
The present invention further includes a mode for switching to the temperature detection pre-rotation method when high fixability cannot be obtained by the constant second rotation even when the control is performed with the constant second pre-rotation method selected. The fixing device is characterized.
The present invention is, in addition, a signal of the scan Tatoki press time or print data received during it is determined that the print request signal, selects the constant Byopu les rotating system, the signal at the document setting or during panel operation , it is determined that print preparation request, Ru fixing device der, wherein the control to select the temperature detecting preliminary rotation scheme is made.
The fixing device according to the present invention is further characterized in that control is performed so that the target temperature of the non-rotating standby heating member is higher than the set temperature of the heating member in all modes during printing.
According to another aspect of the present invention, there is provided a fixing device characterized in that control is performed such that the target temperature of the pressure member that is not rotating and waiting is higher than the set temperature of the pressure member in all modes during printing. .
The present invention is an image forming apparatus including any one of the fixing devices described above.

By means for solving the above problems, the present invention can detect the temperature drop reliably and turn on the heater quickly in consideration of the printing state, the power-on time of the image forming apparatus, and the pre-rotation time. In addition, by setting the time for setting the temperature threshold of the set temperature high until the next sheet enters the fixing nip, it is possible to reduce the influence on the next printing. In addition, by making it possible to select the constant second pre-rotation method, convenience can be improved, and a fixing device capable of obtaining stable fixing properties, and an image forming apparatus including the fixing device can be provided.
Further, since the temperature drop is reduced when the entire fixing device is warmed up, an excessive amount of heat as a side effect can be prevented.

  The best mode for carrying out the present invention will be described below with reference to the drawings. The following description is an example of the best mode of the present invention, and it is easy for a person skilled in the art to make other embodiments within the scope of the claims by making changes and modifications within the scope of the claims. However, this does not limit the scope of the claims.

FIG. 1 is a diagram illustrating an image forming apparatus including a fixing device according to the present invention. The configuration will be described below. The image forming apparatus shown in FIG. 1 is used as a copier or printer capable of forming a full color image by a quadruple tandem method. Other image forming apparatuses include a facsimile apparatus that can perform the same image forming process as the above-described copying machine and printer based on a received image signal. Note that the image forming apparatus includes not only the above-described color image but also an apparatus that targets a single color image.
The image forming apparatus 20 shown in FIG. 1 forms a color image directly from a latent image carrier onto a recording sheet by superimposing and transferring an image for each color separation onto a recording sheet such as paper adsorbed to a transfer belt used as a transfer body. Is used. In FIG. 1, an image forming apparatus 20 includes the following apparatuses. A document image is provided with photoconductors 25Y, 25M, 25C, and 25BK, developing devices 26Y, 26M, 26C, and 26BK, charging rollers 27Y, 27M, 27C, and 27BK, and photoconductor cleaning devices 28Y, 28M, 28C, and 28BK. The image forming devices 21Y, 21M, 21C, and 21BK that form images corresponding to the respective colors, the transfer device 22 arranged to face these image forming devices, and these image forming devices and the transfer device 22 face each other. A manual feed tray 23 as a sheet supply means for supplying a recording sheet to a transfer area to be performed, a first paper feed cassette 24A and a second paper feed cassette 24B provided in the paper feed device 24, and the manual feed tray 23 or the paper feed cassette The recording sheet conveyed from 24 is supplied in accordance with the image forming timing by the image forming devices 21Y, 21M, 21C, and 21BK. And Jisutorora 30, and a fixing device 1 for fixing the sheet-shaped medium after transferred in the transfer area.
Further, the image forming apparatus 20 includes a control unit (not shown). The temperature control and pre-rotation time control of the fixing device 1 are performed by the control means (not shown).

  As will be described in detail later, the fixing device 1 employs a belt fixing system in which a fixing belt 6 as a fixing member heated on the side facing the image is disposed. For this reason, the fixing device 1 includes a fixing roller 2 as a fixing auxiliary member, a heating roller 10 as a heating member, a fixing belt 6 stretched between the fixing roller 2 and the heating roller 10, and the fixing belt. 6, a pressure roller 3 as a pressure member that is provided opposite to the fixing roller 2 and forms a nip portion, and heaters 5 and 7 inside the heating roller 10 and the pressure roller 3. It has a configuration with.

FIG. 2 is a schematic view of a belt fixing type fixing device. FIG. 2A shows an example in the case where there is no support roller for holding the tension on the fixing belt 6, and FIG. 2B shows an example in the case where there is a support roller for holding the tension on the fixing belt 6. . In the fixing device 1, the fixing belt 6 is suspended from the fixing roller 2 and the heating roller 10, and the fixing roller 2 and the pressure roller 3 form a nip. In addition, it includes an inlet guide plate 4, heaters 5 and 7, a temperature detection device 8 that detects the temperature of the surface of the heating roller 10, and a temperature detection device 9 that detects the temperature of the surface of the pressure roller 3.
Here, in this configuration, the pressure roller 3 includes the heater 7, but the pressure roller 3 may not include the heater 7. Further, when the heater 7 is not included in the pressure roller 3, the temperature detection device 9 may or may not be provided, but the temperature detection device 9 is more reliably combined with the temperature detection device 8. Can detect the temperature drop.

FIG. 3 is a view showing a peripheral view of a belt fixing type fixing device. In this configuration, the recording sheet 11 is temporarily stopped by the registration roller 30 at the time of printing, and at the same time when the sheet feeding is started again, the fixing device 1 starts to rotate, so that the fed recording sheet 11 has an appropriate set temperature (temperature threshold). The heater lighting is controlled by a control means (not shown) so that the value becomes (value). The recording sheet 11 passes through the nip portion which is a fixing region while being nipped and conveyed.
The timing for changing the fixing temperature threshold is synchronized with the start of rotation of the fixing device 1. The temperature threshold value is not changed before the fixing device 1 starts rotating. The pre-rotation temperature threshold is as is.

Simultaneously with the rotation of the fixing device 1, the temperature detecting device 8 in the fixing device 1 detects the temperature drop because the cold part of the belt rotates, and immediately turns on the heater when the temperature falls below the temperature threshold. However, at the start of rotation, when the belt temperature did higher than temperature threshold by control ripple takes time falls below the temperature threshold starts rotating, is delayed for the heater is turned on, the paper nip The temperature may not recover before reaching the part.
Therefore, by increasing the temperature threshold value by a certain time (here, one revolution of the belt, the time is set in advance) from the start of rotation of the fixing device 1, the ripple is absorbed and always The paper can be picked up while the heater is on.
After a certain time, even if the temperature threshold value is returned to the normal value, the belt temperature falls below the temperature threshold value, and the heater continues to be lit.

FIG. 4 is a flowchart showing temperature control of the fixing device when the temperature threshold value of the fixing temperature is set high at the start of printing. In FIG. 4, the temperature threshold value of the fixing temperature is set high at the start of printing, and the temperature threshold value is exceeded earlier than the time when the second sheet of continuous printing enters the fixing nip portion, exceeding the time for one week of the belt. Is returned to the normal value.
Specifically, with respect to the original target temperature threshold value of 190 ° C., the temperature threshold value was increased by 30 ° C. immediately after the fixing device 1 started to rotate. Since the time for increasing the temperature threshold is assumed even when the next sheet is a different sheet type, the temperature threshold before the next sheet enters the fixing nip is restored.

Table 1 shows the effect of raising the temperature threshold.

As shown in Table 1, as a result, the time from when the fixing device 1 started to rotate until the heater was turned on was shortened, and the temperature drop was improved by 4 ° C. from 168 ° C. to 172 ° C. It should be noted that an appropriate range for raising the temperature threshold is about 5 to 40 ° C.
As described above, in order to obtain the effect, it is necessary to continuously increase the temperature threshold, and by continuing the time for one belt or more, it is possible to reliably detect a temperature drop and turn on the heater quickly, and Since the time for increasing the temperature threshold of the set temperature is until the next sheet enters the fixing nip portion, the influence on the next printing can be reduced.

5 and 6 are flowcharts showing temperature control of the fixing device different from the above-described embodiment.
FIG. 5 is a flowchart showing temperature control of the fixing device when the time from power-on is counted. In FIG. 5, the time from power-on is counted, and the temperature threshold is returned to the normal value when it is determined that the fixing unit has been sufficiently warmed.
FIG. 6 is a flowchart showing temperature control of the fixing device when the number of printed sheets is counted from the start of sheet passing. In FIG. 6, the number of printed sheets from the power-on (from the start of paper feeding) is counted, and the temperature threshold value is returned to the normal value when it is determined that the fixing unit is sufficiently warmed.
Further, the combination of FIG. 5 and FIG. 6, that is, the control for increasing the temperature threshold may be terminated when a certain time or a certain number of sheets pass, and the normal temperature threshold may be returned.
As described above, when the entire fixing device is warmed, the temperature drop is reduced, so that an excessive amount of heat as a side effect can be prevented.

In the fixing device of the above embodiment, the temperature detection pre-rotation method and the constant second pre-rotation method can be selected by a control unit (not shown). As a result, the fixing device of the present invention can sufficiently exhibit mobility in consideration of the printing state, the power-on time of the image forming apparatus, and the pre-rotation time.
Table 2 shows experimental results when control is performed so that the temperature detection pre-rotation method and the constant second pre-rotation method can be selected.

In this experiment, the image forming apparatus was provided with two or more types of image forming linear speeds and paper settings, and as an additional condition classification, the printing state of the image forming apparatus was classified into one in the morning, when left unattended, and others. Mass of the paper, was used for 75~105g / ^{m 2} at 64~74g / ^{m 2,} of medium thickness paper on plain paper. Table 2 shows the experimental results separately for the case of image forming linear velocity H (maximum) and image forming linear velocity L (minimum).
As shown in Table 2, pre-rotation is performed depending on the image forming linear velocity, the type of paper, and the printing state of the image forming apparatus. Among them, the constant rotation pre-rotation can be selected when the image forming linear velocity H of plain paper is left most frequently used. In this embodiment, the fixed second time is 4 seconds by default, but can be selected between 2 and 9 seconds.
However, under strict conditions for fixing properties, the risk of fixing failure increases if the fixed time is set, so even when the fixed second pre-rotation method is selected, the control means (not shown) has a mode for switching to the temperature detection pre-rotation method. I tried to make it.
Normally, the setting is changed by a serviceman, and can be finely adjusted to the minimum time satisfying the fixing property in accordance with the sheet normally used by the user. As a result, the convenience can be improved, and a fixing device capable of obtaining a stable fixing property and an image forming apparatus including the fixing device can be provided.

温度検出プレ回転方式を選択した場合にはプリントタイム（印刷開始から印刷終了までの時間）は１０〜１７秒要する。一方、定秒プレ回転方式を選択して定秒時間をデフォルトの４秒に設定した場合にはプリントタイムは１０秒となり、温度検出プレ回転方式を選択した場合と比べると、最大７秒の待ち時間の短縮になる。 Table 3 shows the effect of shortening the print time under conditions where pre-rotation is performed.

When the temperature detection pre-rotation method is selected, the print time (time from the start of printing to the end of printing) takes 10 to 17 seconds. On the other hand, when the fixed second pre-rotation method is selected and the fixed second time is set to the default of 4 seconds, the print time is 10 seconds, which is a maximum of 7 seconds waiting compared to the case where the temperature detection pre-rotation method is selected. Save time.

回転していない待機中の加熱ローラの目標温度（待機温度）を、印刷時の全てのモードの加熱ローラの設定温度（印刷温度ＭＡＸ）より高くすることで、定着回転時の温度落ち込みを最小限にし、それによる待ち時間を少なくすることができる。
また、回転していない待機中の加圧ローラの目標温度（待機温度）を、印刷時の全てのモードの加圧ローラの設定温度（印刷温度ＭＡＸ）より高くすることで、定着回転時の温度落ち込みを最小限にし、それによる待ち時間を少なくすることができる。 Table 4 shows the relationship between the set temperature during normal standby and the set temperature during printing.

By setting the target temperature (standby temperature) of the non-rotating standby heating roller higher than the setting temperature (printing temperature MAX) of the heating roller in all modes during printing, the temperature drop during fixing rotation is minimized. And the waiting time due to this can be reduced.
In addition, the target temperature (standby temperature) of the non-rotating standby pressure roller is set higher than the set temperature (printing temperature MAX) of the pressure roller in all modes during printing, so that the temperature during fixing rotation is set. It is possible to minimize depression and thereby reduce waiting time.

The fixing device according to the present invention determines the signal when the machine is operated for printing or when the print data is transmitted as a print request signal when the start key is pressed or when the print data is received, and is set to a fixed time. Select the pre-rotation method, and the signal when no other printing is performed (for example, when an original is set or the panel is operated) is judged as a print preparation request, and the temperature detection pre-rotation method is selected. You can also choose.
Since there is no waiting for the user when printing is not actually performed, heat can be stored by sufficient pre-rotation. As a result, stable fixability can be obtained.

Further, the fixing device of the present invention, control is control that combines a plurality, but also enables the control is performed.
As a result, the fixing device of the present invention takes into account the paper normally used by the user, the printing state, the power-on time of the image forming apparatus, and the pre-rotation time, and sets the control means (not shown) according to the user usage situation. These are arbitrarily selected and combined, and control can be performed by the control means (not shown). By making it possible to customize the setting of the fixing device according to the usage situation of the user, it was possible to fully demonstrate mobility.

1 is a diagram illustrating an image forming apparatus including a fixing device according to the present invention. 1 is a schematic view of a belt fixing type fixing device. FIG. 3 is a view showing a peripheral view of a belt fixing type fixing device. 6 is a flowchart showing temperature control of the fixing device when a temperature threshold value of the fixing temperature is set high when printing is started. 6 is a flowchart illustrating temperature control of the fixing device when the time from power-on is counted. 6 is a flowchart illustrating temperature control of the fixing device when the number of printed sheets is counted from the start of sheet passing.

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Fixing roller 3 Pressure roller 4 Entrance guide plate 5 Heater 6 Fixing belt 7 Heater 8, 9 Temperature detection device 10 Heating roller 11 Recording sheet 20 Image forming device 21 Image forming device 22 Transfer device 22A Paper conveyance unit 23 Manual feed Tray 24 Paper feed cassette 25 Photoconductor 26 Developing device 27 Charging roller 28 Photoconductor cleaning device 30 Registration roller 31 Electrostatic adsorption roller

Claims (7)

A fixing auxiliary member, a heating member, a fixing member stretched between the fixing auxiliary member and the heating member, and a fixing member provided to face the fixing auxiliary member via the fixing member and forming a nip portion. In a fixing device including a pressure member and a heater inside the heating member,
The fixing device is set to perform pre-rotation before starting printing according to the image forming linear speed,
The pre-rotation is a temperature detection that detects the temperature of each member during pre-rotation according to the state of the apparatus, and starts printing after rotating the fixing device until the temperature of each member reaches a predetermined temperature. A pre-rotation method,
Any one of a fixed-second pre-rotation method in which printing is started after the fixing device is rotated to a predetermined time by setting the pre-rotation time to a fixed time is selected. The fixing device according to claim 1, wherein the fixing device is controlled to change a fixed time of the constant second pre-rotation method. The fixing device has a mode for switching to the temperature detection pre-rotation method when high fixability cannot be obtained by the constant second rotation even when the constant second pre-rotation method is selected. The fixing device according to claim 1 or 2 . The fixing device, a signal or when the print data received at the scan Tatoki pressed determines that print request signal, selects the constant Byopu les rotation system,
The fixing according to any one of claims 1 to 3 , wherein a signal for setting a document or operating a panel unit is determined as a print preparation request, and control is performed to select the temperature detection pre-rotation method. apparatus. The fixing device includes a fixing according to the target temperature of the heating member during standby not rotating, to claim 1, characterized in that control of higher than the set temperature of the heating member for all modes when printing is performed apparatus. 2. The fixing device according to claim 1, wherein the fixing device is controlled so that a target temperature of the non-rotating standby pressure member is higher than a set temperature of the pressure member in all modes during printing. Fixing device. The fixing device according to claim 1 is provided.
An image forming apparatus.

Images