JP4168084B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a laser beam printer, a digital copying machine, a plain paper fax machine or the like, or a fixing device mounted on an OA device, and other apparatuses for conveying a recording material and supplying heat. Specifically, the recording material having a fixing member to be heated and a pressure member that is in pressure contact with the fixing member and carrying a toner image to be fixed is set so that the toner image is in contact with the fixing member. The present invention relates to energy saving of a fixing device that passes through a nip portion formed by pressure contact between the fixing member and a pressure member and fixes the toner image on a recording material by the action of heat and pressure.

Conventionally, among fixing devices mounted on electrophotographic image forming apparatuses, particularly in color fixing devices, the surface is coated with a heating roller having a non-adhesive elastic body and a heating source inside, and an elastic body. A heat roller fixing system is used in which a recording sheet on which toner is transferred is fixed between the rollers that are rotated by applying an appropriate pressure. However, in this heat roller fixing method, the heat capacity of the heating roller and the pressure roller is large, and a power saving mode has been studied as an environmental protection measure.
Some black-and-white image forming heat roller fixing devices, which have a relatively short start-up time compared to color image forming, employ a method of shifting to a power saving mode after waiting for a predetermined time after completion of the fixing operation. In this type of fixing device, even when the fixing operation request is received and then the power saving mode returns to the fixing operation mode, the start-up time is short and the print waiting time is short.
However, in the heat roller fixing device for forming a color image, the startup time until returning from the power saving mode to the fixing operation mode is too long. Since the timing of the fixing operation request is not predictable, it is necessary to increase the power in order to shorten the start-up time, and it has been impossible to achieve both shortening of the start-up time and power saving.

Therefore, in recent years, in order to solve these problems, a belt heating method for fixing toner on recording paper on the belt surface has been developed. In the belt heating method, the heat energy necessary for fixing can be obtained simply by heating a fixing belt having a relatively small heat capacity to a predetermined temperature. .
The belt heating system includes an endless fixing belt, a fixing roller that rotatably supports the fixing belt, a heating roller, and a pressure roller that presses the sheet against the fixing belt. The heating means may be installed in the heating roller and further in the pressure roller, and heats the heating roller or the pressure roller, respectively.
There are two methods of starting up the belt heating method: a pre-rotation method and a method of rotating the fixing belt from the time of turning on the power. The pre-rotation method is a method in which when the power is turned on, the fixing belt is heated via a heating roller, and the pre-rotation is started when the temperature of the fixing belt reaches a certain set temperature. In both methods, the fixing is possible when the fixing belt temperature reaches a predetermined set temperature.

In the fixing performance of the heat roller fixing device or the belt heating fixing device, not only the fixing roller or belt temperature but also the pressure roller temperature is important. Glossiness is particularly important for color image fixing, but glossiness is affected by the fixing temperature.
In such a configuration, in order to reduce the power consumption of the fixing device and shorten the start-up time, it is desirable to reduce the heat capacity of the fixing member and increase the output of the heating unit, and further to the fixing member with limited allowable power and It is important to optimize the heating power distribution to the heating member.
In Patent Document 1, as a method of achieving both shortening of startup time and power saving, a fixing temperature detection unit and a control unit are provided, a temperature increase amount per unit time is calculated, and a fixing unit in the power saving mode is calculated. A technique for controlling the temperature so as to be maintained above the minimum temperature is proposed. The minimum temperature is calculated based on the start-up time set by the user and the amount of temperature increase per unit time.
JP 2001-117414 A

In view of the above problems, a first object of the present invention is to reduce the startup time for returning to the fixing operation mode from the power saving mode by reducing the power consumption of the fixing device by having the power saving mode. It is an object of the present invention to provide a fixing device.
A second object of the present invention is to provide an image forming apparatus that includes the above-described fixing device and shortens the copy waiting time.

In order to solve the above problems, a fixing device of the present invention includes a fixing member having a first heating unit and a pressure member in contact with the fixing member and having a second heating unit, and is a toner to be fixed. The recording material carrying the image is passed through the nip formed by the pressure contact between the fixing member and the pressure member so that the toner image is in contact with the fixing member, and the toner image is recorded by the action of heat and pressure. In the fixing device that performs the fixing operation on the material, the fixing member is a fixing belt that is stretched around at least two guide members, and the fixing device is an oil that does not apply oil to the surface of the fixing belt. a-less fixing device, the fixing belt and the pressure member, after the fixing operation is completed, and shifts to the power saving mode, when receiving a fixing operation request is controlled to return to the printable mode, the fixing belt Among the pressure members, the member with the larger heat capacity is controlled at a temperature higher than the temperature during the fixing operation of the member with the larger heat capacity in the power saving mode, and the member with the smaller heat capacity is controlled in the power saving mode. Sometimes, the temperature is controlled at a temperature lower than the temperature during the fixing operation of the member having the smaller heat capacity.
The fixing device of the present invention includes a fixing member having a first heating unit, and a pressure member having a second heating unit in pressure contact with the fixing member, and carrying a toner image to be fixed. An operation in which the toner image is fixed to the recording material by the action of heat and pressure by passing the nip portion formed by the pressure contact between the fixing member and the pressure member in a direction in which the toner image is in contact with the fixing member. The fixing member is a fixing belt that is stretched around at least two guide members, and the fixing device is an oilless fixing device that does not apply oil to the surface of the fixing belt. , the fixing belt and the pressure member, after the fixing operation is completed, waiting a predetermined time to transition to the power saving mode, when receiving a fixing operation request is controlled to return to the printable mode, and the fixing belt Of the pressure members, the member with the larger heat capacity is controlled at a temperature higher than the temperature during the fixing operation of the member with the larger heat capacity in the power saving mode, and the member with the smaller heat capacity is controlled in the power saving mode. Further, the temperature of the member having the smaller heat capacity is controlled at a temperature lower than the temperature at the time of fixing operation.

The fixing device according to the present invention is further characterized in that a member having a smaller heat capacity among the fixing member and the pressure member is in a non-energized state in the power saving mode. Further, the fixing device of the present invention, furthermore, the larger member of the heat capacity is a pressure member, the smaller member of the thermal capacity you wherein it is fixing member.

Also, the fixing device of the present invention, further, among the two guide members, one is a fixed member, said fixing member is characterized in that contact with the pressure member via the fixing belt. In the fixing device of the present invention, the two guide members are rollers, and a fixing member is in contact with the pressure member via the fixing belt.
The fixing device of the present invention is further characterized in that the fixing member and the pressure member have substantially the same time until returning from the power saving mode to the fixing operation mode.
The fixing device of the present invention is further characterized in that the fixing belt is pre-rotated when the fixing device starts up.

An image forming apparatus of the present invention includes a feeding unit that feeds a recording material, an image forming unit that forms a toner image on the recording material, and a fixing device that fixes the toner image on the recording material to the recording material. In the image forming apparatus, the fixing device is any of the above-described fixing devices.

As described above, according to the present invention, it is possible to save power by providing a power saving mode, and to efficiently reduce the time for returning from the power saving mode to the fixing operation mode. It is possible to provide a fixing device capable of uniform fixing without gloss unevenness and good separation of recording paper from a fixing member.
In particular, in the case of a heat roller type fixing device, it is possible to provide a fixing device having a simple configuration and stable image quality and conveyance of recording paper. In the case of a belt fixing type fixing device, it is possible to provide a fixing device that realizes a faster start-up time.
In addition, by mounting such a fixing device, it is possible to provide an image forming apparatus that can save power and can shorten the print waiting time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a vertical sectional view schematically showing an image forming apparatus according to the present application. Note that the fixing device of the present invention is not limited to the image forming apparatus having the configuration shown in FIG. 1, and can be adopted in other types of image forming apparatuses.
The image forming apparatus 1 includes an image forming unit 2 that forms a toner image on a recording material, a feeding unit 3 that feeds the recording material to the image forming unit, and a fixing that fixes a toner image formed on the recording material. Device 4.
First, the outline of the image forming unit 2 will be clarified.
The image forming unit 2 illustrated here has a drum-shaped photoconductor 5 which is an example of an image carrier, and when the photoconductor 5 rotates clockwise, the surface of the photoconductor 1 is predetermined by the charging device 6. Charged to polarity. The surface of the charged photoconductor 1 is irradiated with a light-modulated laser beam L emitted from a laser writing unit 7 which is an example of an exposure apparatus, whereby an electrostatic latent image is formed on the surface of the photoconductor 1. The electrostatic latent image is visualized as a toner image by the developing device 8, and the toner image is transferred onto the recording material fed from the feeding unit 3 by the action of the transfer device 9.
The transfer residual toner adhering to the surface of the photoreceptor 1 after the toner image transfer is removed by the cleaning device 10.

The feeding unit 3 includes a paper feeding cassette 11 that contains a recording material P made of, for example, transfer paper or a resin sheet, and the uppermost recording material P is fed out of the cassette by the rotation of the feeding roller 12. The fed recording material P is fed to the transfer portion between the photosensitive member 1 and the transfer device by the rotation of the registration roller pair 13, and the toner image on the photosensitive member 5 is transferred to the recording material as described above. Transferred onto P.
The recording material carrying the toner image in this way passes through the fixing device 4, and at this time, the toner image on the recording material P is fixed as described later. The recording material P that has passed through the fixing device 4 is discharged onto a discharge tray 14 outside the apparatus.

FIG. 2 is a schematic cross-sectional view showing a belt heating type fixing device 4 as an example.
The fixing member 15 is an endless fixing belt stretched between a fixing roller 17 and a heating roller 18. The fixing member 15 is heated by a heating roller 18 including a first heating unit. The pressure member 16 is a pressure roller and includes a second heating unit. The fixing member 15 and the pressure member 16 are pressed to form a nip portion, and the recording material P carrying the unfixed toner image T is fixed by heating and pressing. The belt heating method has a short rise time and can save power, and has an effect of preventing toner belt offset, and can be applied oil-less or with a small amount of oil. A thermistor S1 is installed at the center of the belt width of the fixing member 15, and detects the temperature of the fixing belt. Further, a thermistor S2 is installed at the center of the roller width of the pressure member 16, and detects the temperature of the pressure roller.

The fixing belt used for the fixing member 15 is preferably a thin endless belt formed of a heat resistant resin such as polyimide, nickel, carbon steel, stainless steel or the like. The endless belt is formed seamlessly by a nickel electroforming method or a polyimide molding method.
Since the surface layer of the fixing belt is on the side in contact with the unfixed toner, the fixing belt is configured to be coated with a heat-resistant release layer such as a fluorine resin or silicon rubber. The heat-resistant release layer preferably has a rubber hardness of 25 to 65 degrees (JIS A hardness meter) and a thickness in the range of 100 to 300 μm as a condition for obtaining good fixability and thermal responsiveness. Moreover, the structure which provides a heat resistant elastic layer as an intermediate | middle layer may be sufficient.

The fixing roller 17 has a cored bar at the center, and a heat insulating elastic layer is formed on the outer periphery thereof. As the core metal, a conductive member such as aluminum, stainless steel, or carbon steel can be used. The heat insulating elastic layer is made of a soft heat resistant material for making the nip width sufficiently wide. For example, foamed silicon rubber or the like can be used. The heat insulating elastic layer has a sufficient thickness to form the nip portion, and is preferably about 15% to 20% of the diameter of the fixing roller 17.
The heating roller 18 is a hollow metal cylindrical thin roller made of aluminum, carbon steel, stainless steel or the like. The heating roller 18 includes a heater H1 as a first heating means. A halogen heater can be used as the heater H1.
The fixing member 15 has a smaller heat capacity of the fixing belt in order to shorten the start-up time of the fixing device 4 and to achieve a predetermined fixing temperature faster. Further, since it is on the side in contact with the unfixed toner, the amount of heat supplied to the heating roller 18 during the fixing operation is the heat for heating the pressure member 16 so that the fixing temperature does not decrease even during continuous paper feeding. It is sufficiently larger than the supply amount.

The pressure member 16 forms a heat-resistant release layer on the surface layer of the cored bar. As the core metal, a conductive member such as aluminum, stainless steel, or carbon steel can be used. As the heat-resistant release layer, fluorine resin, silicon rubber, or the like can be used. The pressurizing member 16 has a core metal that is hollow, and has a heater H2 that is a second heating means. A halogen heater can be used as the heater H2.
In FIG. 2, in order to improve the peelability of the recording material P from the fixing member 15, a downward nip shape is formed. That is, the hardness of the pressure member 16 is increased. The pressure member 16 has a heat-insulating release layer that is a surface layer with a thickness of less than 7% of the diameter of the pressure member 16 and a hardness of 20 degrees or more according to JIS A.
The pressure member 16 may not be provided with a heating means, but in the present invention, the heating means is provided for the following reason. Since the heat of the fixing member 15 is taken away by the toner or the recording material P at the time of fixing, the temperature is likely to change depending on the situation, such as at the start of the fixing operation or at the time of continuous paper feeding. Can be kept at temperature. In particular, in order to make the color image uniform glossiness, it is important that the fixing temperature is maintained and controlled at a predetermined constant temperature, and it is preferable to provide a heating means on the pressure member 16. Further, in the fixing nip portion, the toner is affected not only from the front surface but also from the back surface of the recording material P, so this configuration is preferable.
The ratio of the heat supply amount is set so that the fixing member 15 is larger than the pressure member 16.

The fixing device 4 of the present invention may be a heat roller system. FIG. 3 is a schematic cross-sectional view showing a heat roller fixing type fixing device 4 as an example.
The fixing member 15 is a fixing roller having a hollow metal cylindrical core, a heat insulating elastic layer formed on the outer periphery thereof, and a heat-resistant release layer such as a fluorine-based resin or silicon rubber as a surface layer. It has become. The cored bar contains the heater H1. The heat insulating elastic layer can be the same as the fixing roller described in the belt heating method, but a thin roller is preferable for reducing the heat capacity.
The pressure member 16 may be the same as a belt heating type pressure roller, but in order to form a sufficient fixing nip portion with the fixing member 15 of the thin roller, the heat insulating release layer is thickened.

Next, start-up time setting according to the fixing device 4 of the present invention will be described.
FIG. 4 is a graph showing gloss characteristics during toner fixing. In this embodiment, the glossiness needs to be 10% or more, and the set temperatures of the fixing member and the pressure member are determined from the glossiness. The fixing member 15 employs a belt heating method, the pressure member 16 is a pressure roller, and the pressure member 16 has a larger heat capacity. The fixing belt linear velocity during fixing was 200 mm / s.
In order to obtain a glossiness of 10% or more, the pressure member 16 needs to be about 120 ° C. or more when the fixing member 15 is 150 ° C., and the pressure member 16 needs to be about 105 ° C. or more when the fixing member 15 is 160 ° C. there were.
In addition, since the fixing member 15 and the pressure member 16 are in contact with each other, it is actually difficult to keep the temperature difference between the fixing member 15 and the pressure member 16 at about 25 ° C. or more. The temperature difference between the fixing member 15 and the pressure member 16 is desirably set to 20 ° C. or less. In this embodiment, the fixing member 15 is set to 150 ° C., and the pressure member 16 is set to about 130 ° C.

Next, operation control of the fixing device 4 will be described. Here, a description will be given of when the power is turned on.
FIG. 5 is a graph showing operation control and start-up time (s) of a conventional belt heating type fixing device. As described above, the fixing member 15 has a set temperature of 150 ° C. and the pressure member 16 has a set temperature of 130 ° C., and each heater is controlled by the temperature control circuit.
When the power is turned on, each heater is turned on. When the power is turned on, driving is not started, and pre-rotation is started when the temperature of the fixing member 15 reaches 150 ° C. Immediately after the pre-rotation, the fixing member 15 is deprived of heat by the pressurizing member 16, so that the temperature rapidly decreases. Thereafter, when the pressure member 16 reaches 130 ° C. before the fixing member 15 reaches 150 ° C., the temperature control circuit turns off the heater H2 of the pressure member 16, and then the pressure member 16 reaches 130 ° C. On / off control of the heater H2 is started so as to be maintained. The time from when the power is turned on until the fixing member 15 reaches 150 ° C. is defined as a start-up time A (s).
When the fixing member 15 reaches 150 ° C., the temperature control circuit turns off the heater H1 of the fixing member 15 and starts ON / OFF control of the heater H1 so that the fixing member 15 maintains 150 ° C. Similarly, the time when the pressure member 16 reaches 130 ° C. is defined as the rising time T (s).
When the pressure member 16 reaches 130 ° C., the temperature control circuit turns off the heater H2, and starts ON / OFF control of the heater H2 so that the pressure member 16 maintains 130 ° C. When the heat source is only the heater H1, only the heater H1 is controlled similarly.

A method for shortening the start-up time using this control method will be described.
FIG. 6 shows a case where the fixing member 15 reaches 150 ° C. in A1 (s) before the pressure member 16 reaches 130 ° C. As described above, the heater H1 is turned off at A1 (s), and thereafter ON / OFF control is performed during Δt1 (s). Since the lighting rate of the heater H1 is reduced during Δt1 (s) during ON / OFF control, the heat supply rate from the heater H1 is reduced. Therefore, the longer Δt1 (s), the worse the heat supply rate, and the startup time T1 (s) is delayed. Conversely, the shorter the Δt1 (s), the better the heat supply rate and the shorter the startup time T1 (s).
If the pressure member 16 reaches 130 ° C. before the fixing member 15 reaches 150 ° C., the heat supply rate of the heater H2 decreases, and the start-up time for the same reason as described above. T1 (s) becomes long.
That is, in order to shorten the start-up time T1 (s), the heating rate of the fixing member 15 and the pressure member 16 is adjusted, Δt1 (s) is shortened, and the heat supply rate from the heater H1 is increased. good. In short, if the fixing member 15 and the pressure member 16 reach their respective set temperatures almost simultaneously, the OFF time of the heaters H1 and H2 is shortened from the time of power-on to the completion of startup, and the allowable power at startup is reduced. Since it can be utilized to the maximum extent, the time to reach the fixing operation mode is shortened.

Therefore, one means for shortening Δt1 (s) for shortening the startup time will be described.
In the state of FIG. 6, in order to shorten Δt <b> 1 (s), the power of the heater H <b> 2 may be increased and the temperature increase rate of the pressure member 16 may be increased.
FIG. 7 shows a case where the power of the pressure member 16 is increased. In this case, the temperature raising rate of the pressure member 16 is increased, and the time for reaching the set temperature 130 ° C. of the pressure member 16 is shortened. In exchange, since the power of the heater H2 is increased, the power of the heater H1 is decreased, so that the heating rate of the heater H1 is decreased and the time for the fixing member 15 to reach the set temperature of 150 ° C. is delayed.
However, since the difference between the time for the pressurizing member 16 to reach the set temperature 130 ° C. and the time for the fixing member 15 to reach the set temperature 150 ° C. is reduced, the ON / OFF time Δt2 (s) of the heater H1 is Δt1 (s The heat supply rate of the heater H1 is improved as compared with the case of FIG.
Therefore, the heater ON / OFF time shortening (Δt1−Δt2) is larger than the delay of the fixing member 15 reaching 150 ° C. (A2−A1), and the startup time T2 (s) is shortened.
Although the method for shortening the startup time after power-on has been described above, the same can be said for the startup time from the power saving mode.
As another method for shortening Δt1, the fixing quality is not affected.
There are a method by power distribution of the heater H1 and the heater H2, a method by temperature setting of the fixing member 15 temperature setting and the pressure member temperature 16 setting, a method by heat capacity distribution of the fixing member 15 and the pressure member 16

Next, specific examples of the startup time and power saving from the power saving mode will be described. In the belt heating type fixing device 4, the heat capacity of the pressure member 16 is larger than that of the fixing member 15. On the other hand, the heater output is larger than that of the heater H2 in order to obtain good fixability in continuous printing.
Paying attention to the heat capacity of the belt fixing and the configuration of the heater output, the time for the fixing member 15 and the pressure member 16 to reach a predetermined fixing temperature when returning from the energy saving and power saving mode to the fixing operation mode is shortened. As one of the methods for achieving both, the heater H2 is turned on to maintain the pressure member 16 at a desired temperature, while the heater H1 is turned on / off to maintain the fixing member 15 at a desired temperature. Here, the desired temperature is a temperature that satisfies both the above-described energy saving and shortening of the startup time.

Next, temperature control of the fixing device of the present invention will be described.
The fixing device 4 of the present invention allows the recording material P carrying the toner image to be fixed to pass through the fixing nip portion so that the toner image is in contact with the fixing member 15, and records the toner image by the action of heat and pressure. Fix to material P. After the fixing operation is completed, the control unit (not shown) is controlled to shift to the power saving mode when waiting for a predetermined time and to return to the fixing operation mode when receiving the fixing operation request.
A feature of the fixing device 4 of the present invention is that, when shifting to the power saving mode, at least the member having the larger heat capacity among the heat capacities of the fixing member 15 and the pressure member 16 is always controlled below a predetermined fixing temperature. Is Rukoto. The member having a large heat capacity is the pressing member 16 in FIGS. 2 and 3. Thereby, power saving of the fixing device 4 in the power saving mode can be achieved.

In addition, the fixing device 4 of the present invention is characterized in that when shifting to the power saving mode, the member having the larger heat capacity is always controlled below the predetermined fixing temperature and the member having the smaller heat capacity is fixed to the predetermined fixing temperature. It may be controlled at a temperature lower than the temperature.
FIG. 8 is a model diagram showing a change in heat capacity when the fixing member 15 and the pressure member 16 return from the power saving mode to the fixing operation mode in this case.
Since the fixing member 15 has a large heater H1 output during the fixing operation, power saving can be achieved by controlling the fixing member 15 at a temperature lower than that during the fixing operation in the power saving mode. Further, since it is a member having a small heat capacity, the start-up is quick and the time for returning to the fixing operation mode upon receiving the fixing operation request is also fast.

Further, the fixing device 4 according to the present invention is characterized in that when shifting to the power saving mode, the member having the larger heat capacity is always controlled below the predetermined fixing temperature and the member having the smaller heat capacity is in the non-energized state. It may be controlled.
FIG. 9 is a model diagram showing a change in heat capacity when the fixing member 15 and the pressure member 16 return from the power saving mode to the fixing operation mode in this case.
When the mode is shifted to the power saving mode, the heater of the member having the smaller heat capacity is set in a non-energized state, whereby in addition to more effective power saving, it is possible to prevent a decrease in durability due to thermal degradation.

Alternatively, the fixing device 4 of the present invention is characterized in that when the mode is shifted to the power saving mode, the member having the larger heat capacity is always controlled at a temperature higher than the predetermined fixing temperature, and the member having the smaller heat capacity is set to the predetermined value. It may be controlled at a temperature lower than the fixing temperature.
FIG. 10 is a model diagram showing a change in heat capacity when the fixing member 15 and the pressure member 16 return from the power saving mode to the fixing operation mode in this case.
Power saving can be achieved by controlling the member having the smaller heat capacity at a temperature lower than the fixing temperature. In addition, even when the member having a smaller heat capacity is lower than the fixing temperature, the member having the larger heat capacity is controlled to a temperature higher than the fixing temperature, so that the time for returning to the fixing operation mode can be shortened. it can.

  In this case, the member having the smaller heat capacity may be in a non-energized state. Thereby, in addition to the more effective power saving, the fall of durability by thermal degradation can be prevented. Even when the member having the smaller heat capacity is set in the non-energized state, the member having the larger heat capacity is controlled to a temperature higher than the fixing temperature, so that the time for returning to the fixing operation mode can be shortened.

In the above description, as an example, the member having the smaller heat capacity is described as the fixing member 15, and the member having the larger heat capacity is described as the pressing member 16.
However, in the relationship shown in FIGS. 8 to 10, the member having the smaller heat capacity can be used as the pressing member 16, and the member having the larger heat capacity can be used as the fixing member 15. An example of the heat roller system is shown in FIG. 11, and an example of the belt heating system is shown in FIG.
In this configuration, the surface hardness of the fixing member 15 is sufficiently soft and the pressure member is used in order to improve the fixing performance such as uniform fixing without gloss unevenness and separation of the recording material P from the fixing member 15. It is desirable to form the fixing nip portion with a relatively hard surface hardness of 16.

In order to obtain such a configuration, there is a method of changing the hardness or thickness of the elastic layer formed on the core metal of the fixing member 15 and the pressure member 16, but in this case, the thickness of the elastic layer is made constant. It is desirable in terms of the roller method to change the angle. This is because the rubber kneading process is easier when the rubber hardness is not changed, and the cost can be suppressed.
Therefore, the fixing member 15 having a thick elastic layer has a larger heat capacity. In this case, when the mode is shifted to the power saving mode, the member having the larger heat capacity among the heat capacity of the fixing member and the pressure member, that is, the fixing member 15 is always controlled to a predetermined fixing temperature by the heater H1, and the heat capacity. The smaller member, that is, the pressure member, is always controlled at a temperature lower than a predetermined fixing temperature by the heating means. Thereby, the time for returning to the fixing operation mode is shortened.

That is, according to the present invention, the temperature control of the fixing member 15 and the pressure member 16 can be determined as needed depending on which is a member having a large heat capacity or a member having a small heat capacity, and as described above, the shape of the fixing member 15 is limited. Not.
The belt heating method in which the fixing member 15 is formed of a fixing belt can reduce the heat capacity of the fixing member 15 and can realize a significant reduction in the time for returning to the fixing operation mode. Further, the belt heating method can have various layouts. For example, a configuration using a fixing member and a heat-resistant elastic member as shown in FIGS.
The heat roller system in which the fixing member 15 is constituted by a fixing roller can obtain a fixing performance such as a stable image quality and a recording paper conveyance property with a simple configuration.

Further, the fixing device 4 according to the present invention is characterized in that the time required to return from the power saving mode to the fixing operation mode in response to the fixing operation request is 30 seconds or less, preferably 10 seconds or less.
The inventors conducted a satisfaction survey regarding the operation when the user outputs a copy, taking a copying machine as an example in the image forming apparatus, and found that the waiting time until the copy can be performed from the power saving mode. Obtained a result of 30 seconds or less, preferably 10 seconds or less. Among the image forming apparatuses, the one that requires the most startup time is the fixing device, and the copy waiting time can be shortened by shortening the time until returning to the fixing operation mode.
For example, in order to achieve energy saving by setting the copy waiting time to 10 seconds or less and the power consumption in the power saving mode to 1/3 or less of the conventional one by the fixing device 4 of the present invention, fixing with a small heat capacity. The configuration of the member 15 is a condition.

In addition, since the time required for the fixing member 15 and the pressure member 16 to reach a predetermined fixing temperature is substantially the same, the time for returning from the power saving mode to the fixing operation mode can be efficiently shortened. .
In order to speed up the start-up time after the power is turned on or from the power saving mode, the heater power uses the maximum input power within the allowable range of the apparatus. As described above, when either the fixing member 15 or the pressure member 16 rises earlier at this time, the heating means provided on the member that rises earlier is turned off once, and then turned on to maintain the set temperature. Repeat / OFF control. In such a state, the heat supply amount of the member that has not yet started up decreases, and the startup effect is halved. That is, the fastest startup condition is that the fixing member 15 and the pressure member 16 are simultaneously started up at a predetermined temperature, which is the most efficient method. This is because each heater is lit 100% until the apparatus starts up.

  FIG. 15 is a model diagram showing a change in heat capacity when the fixing member 15 and the pressure member 16 return from the power saving mode to the fixing operation mode in this case. The time for returning from the power saving mode to the fixing operation mode is related to the heat capacities of the fixing member 15 and the pressure member 16 and the outputs of the heaters H1 and H2. A predetermined temperature is calculated from these and set as shown in FIG. By doing so, the fixing member 15 and the pressure member 16 can be started up substantially simultaneously.

(Example)
The start-up time and power consumption were investigated using a belt heating type fixing device. As experimental conditions, the pressure member was 40 CPM (200 mm / S), the fixing belt heater was 800 W, the pressure roller heater was 400 W, and the fixing temperature setting and the pressure roller setting temperature were 150 ° C. and 130 ° C., respectively. . As an example of the power saving mode during standby, the fixing belt heater was turned off and the pressure roller heater was turned on / off at 130 ° C.
As a result, the waiting time for printing from the power saving mode was 10 seconds. Further, it was found that the power consumption can be reduced to about 1/3 in the power saving mode as compared with the conventional method having no power saving mode.

1 is a schematic configuration diagram of an image forming apparatus according to a fixing device of the present invention. FIG. 2 is a schematic configuration diagram of a belt heating type fixing device. FIG. 2 is a schematic configuration diagram of a heat roller fixing type fixing device. 6 is a graph showing the relationship between the fixing temperature and the glossiness of an image. 6 is a graph showing a relationship between operation control of the fixing device and start-up time. 6 is a graph showing a relationship between operation control of the fixing device and start-up time. 6 is a graph showing an example in which the start-up times of the fixing member and the pressure member are almost the same. It is a model figure which shows the heat capacity change of a fixing member and a pressurization member. It is a model figure which shows the heat capacity change of a fixing member and a pressurization member. It is a model figure which shows the heat capacity change of a fixing member and a pressurization member. It is a schematic block diagram showing an example of a heat roller system when a member having a smaller heat capacity is a pressure member and a member having a larger heat capacity is a fixing member. It is a schematic block diagram which shows an example of a belt heating system when a member with a smaller heat capacity is a pressure member and a member with a larger heat capacity is a fixing member. It is a schematic block diagram which shows an example of a belt heating system when a member with a smaller heat capacity is a fixing member and a member with a larger heat capacity is a pressure member. It is a schematic block diagram which shows an example of a belt heating system when a member with a smaller heat capacity is a fixing member and a member with a larger heat capacity is a pressure member. It is a model figure which shows the heat capacity change of a fixing member and a pressurization member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 3 Feeding means 4 Fixing device 5 Photoconductor 6 Charging device 7 Laser writing unit 8 Developing device 9 Transfer device 10 Cleaning device 11 Paper feed cassette 12 Feeding roller 13 Registration roller pair 14 Paper discharge tray 15 Fixing member 16 Pressing member 17 Fixing roller 18 Heating roller H1, H2 Heater L Laser beam P Recording material S1, S2 Thermistor T Toner image

Claims (9)

A recording member having a fixing member having a first heating unit and a pressure member in contact with the fixing member and having a second heating unit, and carrying a toner image to be fixed. In the direction of contact, pass through the nip formed by the pressure contact between the fixing member and the pressure member,
In a fixing device that performs an operation of fixing a toner image to a recording material by the action of heat and pressure,
The fixing member is a fixing belt configured to be stretched around at least two guide members,
The fixing device is an oilless fixing device that does not apply oil to the surface of the fixing belt,
The fixing belt and the pressure member shift to a power saving mode after completion of the fixing operation, and are controlled to return to a printable mode upon receiving a fixing operation request. The larger member is controlled at a temperature higher than the temperature during the fixing operation of the member having the larger heat capacity in the power saving mode, and the member having the smaller heat capacity is controlled in the smaller one of the smaller heat capacity in the power saving mode. The fixing device is characterized in that it is controlled at a temperature lower than the temperature during the fixing operation of the member. A recording member having a fixing member having a first heating unit and a pressure member having a second heating unit in pressure contact with the fixing member, the toner image being a fixing member. In the direction of contact with the fixing member and the pressure member between the nip formed by the pressure contact,
In a fixing device that performs an operation of fixing a toner image to a recording material by the action of heat and pressure,
The fixing member is a fixing belt configured to be stretched around at least two guide members,
The fixing device is an oilless fixing device that does not apply oil to the surface of the fixing belt,
The fixing belt and the pressure member are controlled to shift to a power saving mode when waiting for a predetermined time after completion of the fixing operation, and to return to a printable mode when receiving a fixing operation request. The member with the larger heat capacity is controlled at a temperature higher than the temperature during the fixing operation of the member with the larger heat capacity during the power saving mode, and the member with the smaller heat capacity is controlled with the heat capacity during the power saving mode. The fixing device is controlled at a temperature lower than the temperature at the time of fixing operation of the smaller member. The fixing device according to claim 1, wherein a member having a smaller heat capacity among the fixing member and the pressure member is in a non-energized state in a power saving mode. The fixing device according to claim 1, wherein the member having the larger heat capacity is a pressure member, and the member having the smaller heat capacity is a fixing member. The fixing device according to claim 1, wherein one of the two guide members is a fixing member, and the fixing member is in contact with the pressure member via the fixing belt. The fixing device according to claim 1, wherein the two guide members are rollers, and a fixing member is in contact with the pressure member via the fixing belt. The fixing device according to claim 1, wherein the fixing member and the pressure member have substantially the same time until returning from the power saving mode to the fixing operation mode. The fixing device according to claim 1, wherein the fixing belt is pre-rotated when the fixing device starts up. An image forming apparatus comprising: a feeding unit that feeds a recording material; an image forming unit that forms a toner image on the recording material; and a fixing device that fixes the toner image on the recording material to the recording material. Is an image forming apparatus according to any one of claims 1 to 8.

Images