JP2006251526A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remarkably shorten a warm-up time and to attain energy-saving in a standby state, in a fixing device of a belt type. <P>SOLUTION: When the power source of the fixing device is turned on, a halogen heater H<SB>2</SB>is turned on, then, a pressure roller 2 is heated up to a set temperature (fixation warm-up state). And the on/off control of the halogen heater H<SB>2</SB>is performed so as to maintain the set temperature of the pressure roller 2 (standby state). When an image formation starting signal is inputted, the halogen heater H<SB>2</SB>is turned off, and also, a halogen heater H<SB>1</SB>is turned on. Simultaneously, the pressure roller 2 and an endless belt 11 are rotated. The endless belt 11 are heated by the halogen heater H<SB>1</SB>, and heated up to a set temperature (170 to 180°C) within 10 seconds. and a fixing processing is performed (fixation operating state). During the fixing processing, the on/off control of the halogen heater H<SB>1</SB>is performed so that the surface temperature of the endless belt 11 is maintained at the set temperature. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device, and more particularly to a fixing device that is mounted on an image forming apparatus such as a copying machine, a printer, or a facsimile machine and melts and fixes unfixed toner on a transfer sheet.

  A fixing device in which a pressure roller is brought into pressure contact with a fixing roller having a built-in heater has been widely used in image forming apparatuses such as copying machines. In this type of fixing device, transfer paper is passed through a nip formed by a fixing roller and a pressure roller, and unfixed toner on the transfer paper is melted and fixed.

  On the other hand, in recent years, it has been strongly desired to shorten the time (warm-up time) until the fixing device reaches the set temperature after turning on the power of the device and to save energy in the standby state. In the fixing device, since the heat capacity of the fixing roller is large, there is a limit to shortening the warm-up time and saving energy in the standby state.

Therefore, various so-called belt-type fixing devices have been proposed so far in which the heat capacity is reduced by using an endless belt. For example, in Patent Document 1, a fixing roller having a pressing member that presses an endless belt against a transfer material, a pressure roller that presses the fixing roller through the endless belt, a guide member that regulates rotation of the endless belt, There has been proposed a fixing device that includes a heating unit that heats an endless belt, and the hardness of the pressing member of the fixing roller is lower than the hardness of the pressure roller.
Japanese Patent Application Laid-Open No. 2002-214953 (Claims, FIGS. 1, 4, and 5)

  However, since the fixing device proposed in Patent Document 1 uses only a device that heats an endless belt as a heating means, although it can be expected that the warm-up time is shortened to some extent by reducing the heat capacity of the fixing roller, Significant shortening was difficult. In addition, since the transfer paper and the pressure roller are deprived of heat during the fixing operation, there is a problem that it takes time for the fixing roller to recover to the set temperature.

  The present invention has been made in view of such a conventional problem. The object of the present invention is to greatly reduce the warm-up time and to remove heat from the transfer paper and the pressure roller during the fixing operation. However, it is an object of the present invention to provide a fixing device in which the fixing roller can quickly recover to a set temperature and can save energy in a standby state.

  According to the present invention, the fixing member includes an endless belt, a pressing member disposed inside the endless belt, for pressing the endless belt against the transfer material, and a first heating unit that heats the endless belt. And a pressure roller that is in pressure contact with the pressing member via the endless belt and includes the second heating means, the set surface temperature of the pressure roller is set to the endless belt in the fixing preparation state and the standby state. There is provided a fixing device characterized in that the set surface temperature of the endless belt is set higher than the set surface temperature of the pressure roller in the fixing operation state. In this specification, the fixing preparation state refers to a period from when the apparatus power is turned on until the surface temperature of the pressure roller reaches a set temperature, and the standby state indicates that the fixing operation is not performed. In addition, it means a state in which the surface temperature of the pressure roller holds the set temperature. The fixing operation state refers to a period from when an image formation start signal is input until a predetermined image formation is completed.

  Here, from the viewpoint of further energy saving while shortening the warm-up time, it is preferable to control the temperature of only the pressure roller in the fixing preparation state and the standby state. It is preferable to turn off the heating means.

  Further, from the viewpoint of maintaining a good fixing process while saving power, the first heating means may be controlled on and off so that the surface temperature of the endless belt becomes a set temperature in the fixing operation state. At this time, it is preferable to control the second heating means so that the surface temperature of the pressure roller becomes the set temperature only when the first heating means is off.

  In the fixing operation state, the first heating unit may be voltage controlled so that the surface temperature of the endless belt becomes a set temperature. At this time, an upper limit is set on the power used for the fixing device, and the second heating unit is set so that the surface temperature of the pressure roller becomes the set temperature with the remaining power obtained by subtracting the power used by the first heating unit from the upper limit. It is preferable to control the voltage.

  In the fixing device of the present invention, in the belt-type fixing device, the pressure roller is also provided with heating means, and when the fixing preparation state is set, the set surface temperature of the pressure roller is higher than the set surface temperature of the endless belt. Compared to this device, the warm-up time can be shortened by about 20 to 30%. Even in the standby state, the set surface temperature of the pressure roller is set higher than the set surface temperature of the endless belt, so that higher energy saving can be achieved as compared with the conventional apparatus. In the fixing operation state, the set surface temperature of the endless belt is set higher than the set surface temperature of the pressure roller, so that excellent fixability can be obtained.

  In the fixing preparation state and standby state, if only the pressure roller is temperature controlled and the first heating means of the fixing member is turned off, further power saving can be achieved while shortening the warm-up time.

  In the fixing operation state, the first heating means is controlled to be turned on and off so that the surface temperature of the endless belt becomes the set temperature. The surface temperature of the pressure roller becomes the set temperature only when the first heating means is turned off. By controlling the second heating means in this way, it is possible to perform a good fixing process while saving power.

  In the fixing operation state, the first heating unit is voltage-controlled so that the surface temperature of the endless belt becomes the set temperature, and an upper limit is set for the power used for the fixing device, and the power used by the first heating unit is subtracted from the upper limit. If the second heating means is voltage-controlled with the remaining electric power so that the surface temperature of the pressure roller becomes the set temperature, it is possible to perform a good fixing process while saving power, as described above.

  Hereinafter, the fixing device according to the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments.

FIG. 1 is a schematic view showing an example of a fixing device according to the present invention. The fixing device shown in FIG. 1 includes a fixing member 1 and a pressure roller 2 that is pressed against the fixing member 1 by a biasing unit (not shown). The fixing member 1 includes a partition member 12 that is attached to the center of the interior surrounded by the endless belt 11 and divides the inner space into upper and lower parts, and a rod-shaped halogen heater (first member) that is attached to the approximate center of the upper space in the axial direction. 1 heating means) H ₁ , a pad member (pressing member) 13a that is in pressure contact with the pressure roller 2 via the endless belt 11 provided in the lower space, and can rotate while applying a predetermined tension to the endless belt 11. It comprises holding guide members 14a, 14b, 15a, and 15b, and a temperature sensor S ₁ for measuring the temperature of the endless belt 11 in. On the other hand, the pressure roller 2 has a rod-shaped halogen heater (second heating means) H ₂ in the axial direction substantially at the center of the inside thereof. The surface temperature of the pressure roller 2 is measured by the temperature sensor S _2.

  The fixing device includes a housing (not shown) including a pair of side walls that are spaced apart in the axial direction, and the fixing member 1 and the pressure roller 2 are rotatable between the pair of side walls. They are supported parallel to each other.

  As shown in FIG. 2, the endless belt 11 is formed by laminating an elastic layer 11b such as 200 μm silicon rubber on a 70 μm base 11a made of polyimide, and further 30 μm of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. It has a structure in which a release layer 11c made of coalescence (PFA) is laminated. Carbon particles are dispersed in the substrate 11a and the elastic layer 11b, respectively, so that the heat absorption efficiency is enhanced. Further, as shown in FIG. 3, the pressure roller 2 is formed by laminating an elastic body layer 2b such as a 0.5 mm silicon foam on a metal core drum 2a having a thickness of 0.5 mm, and further 30 μm thereon. The release layer 2c having excellent heat resistance such as PFA is laminated. In the case where the endless belt 11 is driven by driving the pressure roller 2, in order to efficiently transmit the driving force to the endless belt 11, a grip portion having no release layer 2c at both ends of the pressure roller 2 is used. The frictional force with the endless belt 11 may be mentioned.

The partition member 12 is made of aluminum plate or the like mirror finish is made, at the same time as heat from the halogen heater H ₁ is prevented from directly irradiating the bad member 13a and guide members 14 and 15 or the like, efficiency in the endless belt 11 Is intended to be irradiated.

  The pad member 13a has a heat insulating layer such as a foamed sponge layer so that heat from the endless belt 11 is not released to the outside. In order to ensure the slidability of the endless belt 11, it is desirable to cover the surface of the pad member 11 with a low friction member, or to insert a low friction sheet between the pad member 13 a and the inner surface of the endless belt 11. The pad member 13a is in pressure contact with the pressure roller 2 via the endless belt 11, and forms a nip width that melts and fixes the toner on the transfer paper. For this reason, the hardness and shape of the pad member 13a may be appropriately selected and determined so as to obtain a desired nip width. The pressing force of the pad member 13a against the pressure roller 2 by a biasing means (not shown) is preferably about 300N.

When the pressure roller 2 is driven to rotate counterclockwise in FIG. 1 by a motor (not shown), the endless belt 11 is driven clockwise. At this time, since the pad member 13a is fixed, the endless belt 11 slides on the surface of the pad member 13a. Radiant heat from the halogen heater H ₁ is applied to the rotating endless belt 11 to heat the endless belt 11. Since the endless belt 11 is not in contact with anything other than the pad member 13a and the guide members 14 and 15, the temperature rises rapidly. On the other hand, the paper P on which unfixed toner is placed is conveyed substantially horizontally from right to left in FIG. Then, when the nip between the pad member 13a and the pressure roller 2 the sheet P passes, the paper P by the pressure roller 2 even heated by the endless belt and the halogen heater H ₂ that is heated by the halogen heater H ₁ The unfixed toner is melted and fixed on the paper P.

An example of control of the halogen heaters H ₁ and H ₂ of this fixing device is shown in FIG. FIG. 4 shows changes with time in the surface temperature of the endless belt 11 and the pressure roller 2 with the temperature as the vertical axis and the time as the horizontal axis. This fixing device is mounted on a printer of A4 equivalent to 20 ppm, and the maximum power consumption of the halogen heaters H ₁ and H ₂ is 700 W, respectively.

First, when the apparatus is turned on, the fixing apparatus is in a fixing preparation state, the halogen heater H ₂ is turned on, and the pressure roller 2 is heated to a set temperature (for example, 140 to 150 ° C.). At this time, the pressure roller 2 is not rotationally driven. In the conventional fixing device, since the fixing roller is heated, it is necessary to heat the toner to a temperature necessary for fixing the toner (for example, 170 to 180 ° C.). However, in the fixing device of the present invention, the pressure roller 2 is heated. Therefore, a setting temperature lower than that of the conventional fixing roller is sufficient. As a result, the warm-up time is remarkably shortened compared to the conventional case. In the fixing device of the present invention, the endless belt is not heated, which contributes to energy saving.

When the surface temperature of the pressure roller 2 reaches the set temperature, the fixing heater enters a standby state, and the halogen heater H ₂ is on / off controlled so that the pressure roller 2 maintains the set temperature. When an image formation start signal is input, the fixing operation state is entered, the halogen heater H ₂ is turned off, and the halogen heater H ₁ is turned on. At the same time, the pressure roller 2 starts to rotate, and thereby the endless belt 11 also rotates. The endless belt 11 is heated by the halogen heater H ₁ and heated to a set temperature (170 to 180 ° C.) within 10 seconds. Therefore, the fixing device is in a state in which the fixing process can be performed after the paper feeding operation is started until the paper P is conveyed to the fixing device. As a result, there is no waiting time for image formation due to the fixing device, and rapid image formation processing can be performed.

While the fixing process is being performed by the fixing device, the halogen heater H ₁ is on / off controlled so that the surface temperature of the endless belt 11 maintains the set temperature. During the fixing operation state, when the halogen heater of H ₂ pressure roller 2 may also be turned off, but the halogen heater H ₁ is the surface temperature of and the pressure roller 2 in the off is equal to or less than a predetermined lower limit surface temperature, It is recommended to heat the pressure roller 2 with the halogen heater H ₂ turned on. As a result, the fixing property can be improved while providing a power saving effect. The lower limit surface temperature of the pressure roller 2 during the fixing operation state may be about 100 ° C., but it is preferably about 120 ° C. in consideration of various actual use states.

When a series of fixing processes is completed, the fixing device enters a standby state, and the halogen heater H ₂ is controlled to be turned on and off so that the pressure roller 2 maintains the set temperature, and the halogen heater H ₁ is turned off. As described above, since the set temperature (for example, 140 to 150 ° C.) of the pressure roller 2 is lower than the set temperature (for example, 170 to 180 ° C.) of the endless belt 11, the endless belt 11 is maintained at a predetermined temperature. High energy savings can be achieved compared to the above devices. Although the halogen heater H ₁ is turned off at the same time as the fixing process is completed, if the rotational driving of the endless belt 11 is stopped simultaneously with this, the surface temperature of the endless belt 11 rises abnormally. It is desirable to continue for a while after the fixing process is completed. As a result, the remaining heat of the endless belt 11 can be transmitted to the pressure roller 2 and heat loss can be avoided.

In the above embodiment, the control method of the halogen heaters H ₁ and H ₂ is the on / off control. However, the temperature ripple may increase in the on / off control mainly due to the small heat capacity of the endless belt 11. Therefore, it is also effective to control the electric power of the halogen heaters H ₁ and H ₂ . In this case, for example, an upper limit is set on the total power consumption of the halogen heaters H ₁ and H ₂ (for example, 700 W), and in the fixing operation state, the remaining power obtained by subtracting the power used by the halogen heater H ₁ from the total power consumption. The voltage of the halogen heater H ₂ may be controlled within the range of electric power. By fixing the maximum power consumption (700 W) in this way, it is possible to avoid that the two halogen heaters H ₁ and H ₂ generate the maximum output at the same time, and energy saving can be achieved.

Similarly, in the standby state, the voltage of the halogen heater H ₁ may be controlled within the range of the remaining power obtained by subtracting the power used by the halogen heater H ₂ from the total power consumption. By warming the endless belt 11 to some extent in the standby state, the time from the input of the image formation start signal to the start of image formation can be further shortened. Since the pressure roller 2 does not rotate and the endless belt 11 does not rotate in the standby state, the heating area of the endless belt 11 is limited to the upper half area of the endless belt 11 by the partition member 12. Therefore, the set surface temperature of the endless belt 11 in the standby state is preferably set to be equal to or lower than the set temperature of the pressure roller.

In the above embodiment, the halogen heaters H ₁ and H ₂ are used as the heating means. However, a conventionally known heating means such as a resistance heating element or electromagnetic induction heating may be used. Of these, the non-contact heating method is desirable.

  FIG. 5 is a schematic diagram showing another embodiment of the fixing device according to the present invention. The fixing device of FIG. 5 is different from the fixing device described so far in that a roller member 13b is used as a pressing member. Since other configurations are substantially the same as those of the fixing device shown in FIG. 1, the description thereof is omitted here.

  When the pad member 13a is used as the pressing member, the pad member 13a is consumed due to friction with the endless belt 11, and the rotational load of the endless belt 11 increases. On the other hand, when the roller member 13b is used as the pressing member, the roller member 13b rotates with the rotation of the endless belt 11, so that the wear and rotational load of the roller member 13b are remarkably reduced as compared with the pad member 13a. On the other hand, in the case of the roller member 13b, the shaft is easily bent and the nip width is narrowed. Therefore, the roller member 13b is used in an apparatus with a low image forming speed capable of maintaining fixability even if the nip width is small, and the pad member 13a is used in an apparatus having a medium or high image forming speed where securing of the nip width is important. Thus, it is recommended to select and use the shape of the pressing member depending on the image forming speed.

1 is a schematic diagram illustrating an example of a fixing device according to the present invention. It is a schematic diagram which shows the structure of the endless belt used in FIG. It is a schematic diagram which shows the structure of the pressure roller used in FIG. FIG. 2 is a diagram illustrating a temperature control example of the fixing device in FIG. 1. FIG. 6 is a schematic diagram illustrating another example of a fixing device according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing member 2 Pressure roller 11 Endless belt 12 Partition member 13a Pad member (pressing member)
13b Roller member (pressing member)
14a, 14b, 15a, 15b Guide member H ₁ halogen heater (first heating means)
H ₂ halogen heater (second heating means)
P paper S ₁ and S ₂ temperature sensors

Claims (7)

A fixing member provided with an endless belt, a pressing member disposed inside the endless belt, for pressing the endless belt against the transfer material, and a first heating means for heating the endless belt;
In a fixing device including a pressure roller that is in pressure contact with a pressing member via an endless belt and includes a second heating unit,
In the fixing preparation state and standby state, set the pressure roller set surface temperature higher than the endless belt set surface temperature,
A fixing device, wherein a set surface temperature of an endless belt is set higher than a set surface temperature of a pressure roller in a fixing operation state.   The fixing device according to claim 1, wherein the temperature of only the pressure roller is controlled in a fixing preparation state and a standby state.   The fixing device according to claim 2, wherein the first heating unit of the fixing member is turned off in the fixing preparation state and the standby state.   The fixing device according to claim 1, wherein the first heating unit is on / off controlled so that the surface temperature of the endless belt becomes a set temperature in the fixing operation state.   The fixing device according to claim 4, wherein the second heating unit is controlled so that the surface temperature of the pressure roller becomes a set temperature only when the first heating unit is off.   The fixing device according to any one of claims 1 to 3, wherein the voltage of the first heating unit is controlled so that the surface temperature of the endless belt becomes a set temperature in the fixing operation state.   An upper limit is set for the power used for the fixing device, and the voltage of the second heating unit is controlled so that the surface temperature of the pressure roller becomes the set temperature with the remaining power obtained by subtracting the power used by the first heating unit from the upper limit. The fixing device according to claim 6.

Images