JP2843865B2 - Image recording apparatus with heat roller fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus that is used in an electrophotographic image recording apparatus and includes a heat roller fixing device that fuses and fixes a toner image on a transfer material. Things.

[Conventional technology]

FIG. 5 is an overall configuration diagram of an image recording apparatus such as a copying machine provided with a heat roller fixing device, which is known, for example, from Japanese Patent Application Laid-Open No. 55-81378.

In the figure, 1 is a heat roller composed of a hollow roller made of aluminum having a thickness of 4 mm to 5 mm and coated with 20 μm to 60 μm of Teflon, 52 is a heating element such as an infrared lamp (halogen heater), and 54 is a thermocouple or thermistor A temperature sensor for detecting the surface temperature of the heat roller 51; and 53, a pressure roller for pinching the recording paper between the heat roller 1 and the recording paper. It is a roller coated with silicone rubber.

The recording paper on which the toner image is formed is continuously inserted between the heat roller 51 and the pressure roller 53, and is nipped and pressed while receiving heat. As a result, the toner is fused and fixed on the recording paper. In this way, the toner is fixed. In order to keep the surface temperature of the heat roller 51 constant, the surface temperature of the heat roller 51 is detected and converted into a signal for control.

[Problems to be solved by the invention]

In an image recording apparatus (copier) having a fixing device using the heat roller, generally, when the copying speed is continuously increased, the amount of heat taken by the recording paper from the heat roller increases in proportion to the copying speed. The surface temperature of the roller 51 decreases. Further, the decrease in the surface temperature of the heat roller 51 is also caused by the room temperature, a change in the power supply voltage, and the type (length, paper quality, etc.) of the recording paper. When the surface temperature of the heat roller 51 falls below a certain value, a high-quality fixed image cannot be obtained, and in some cases, there are problems such as occurrence of uneven fixing and feeding of unfixed recording paper. Was.

For this reason, in order to maintain a sufficient temperature for fixing, a large-capacity heat source device is prepared and temperature control is performed. Nevertheless, there is a problem that it is difficult to stably fix the heat roller, and the device and the power supply become large.

[Means for solving the problem]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus which eliminates these drawbacks and always stably fixes a toner image by a heat roller.

A heat roller fixing device for nipping and transporting a transfer material between a heat roller rotating with built-in heating means and a pressure roller pressing the heat roller and fixing a toner image attached to the transfer material is provided. In the image recording apparatus, a detecting means for directly or indirectly detecting the temperature of the heat roller, a first set temperature value for setting a fixing upper limit, and a second set temperature value for setting a lower fixing limit. And when the detected surface temperature of the heat roller reaches the second set temperature value, the outer peripheral linear speed of the heat roller is increased to a second speed higher than the outer peripheral linear speed at the first set temperature value. An image recording apparatus provided with a heat roller fixing device, comprising a control mechanism configured to execute thermal fixing by switching to an outer peripheral linear velocity.

Further, the present invention also provides a heat roller for nipping and transporting a transfer material between a heat roller rotating with a built-in heating means and a pressure roller pressing the heat roller, and fixing a toner image attached to the transfer material. In an image recording apparatus having a roller fixing device, a detection device that directly or indirectly detects the temperature of the heat roller,
It has three set reference values, a first set temperature value for setting a fixing upper limit, a second set temperature value for setting a lower fixing limit, and a third set temperature value, and the detected surface temperature of the heat roller is When the second set temperature value is reached, the outer peripheral linear speed of the heat roller is switched to a second outer peripheral linear speed that is higher than the outer peripheral linear speed at the first set temperature value, and thermal fixing is performed. Further, the surface temperature of the heat roller is lowered and the third
And a control mechanism configured to stop the copying function when the set temperature value is reached.

〔Example〕

Hereinafter, an embodiment of a heat roller fixing device of the present invention will be described with reference to the drawings.

FIG. 5 is a configuration diagram of an image recording apparatus (copier) equipped with the heat roller fixing device of the present invention. First, an outline of steps up to a fixing device in a copying machine will be described. The image carrier 10 is charged by the charger 11, and the photoconductive surface on the surface of the image carrier 10 rotates while holding the charge uniformly, and reaches the exposure unit 20. In the exposure unit 20, the reflected light of the document irradiated by the light source is scanned by an optical system such as a mirror and a lens, and is incident on the photoconductive surface of the image carrier 10, thereby forming an electrostatic latent image of the document image. This electrostatic latent image is developed in the developing section 30, and a toner image of the latent image is formed. In the transfer section 40, the toner image is transferred onto the transfer paper fed in synchronization. The transfer paper on which the toner image has been transferred is separated from the image carrier 10 by the separation electrode 41, conveyed by the conveyance belt 42, further thermally fixed by the heat roller fixing device 50 according to the present invention, and discharged out of the machine.

On the other hand, the image carrier 10 from which the transfer paper has been separated by the separation electrode 41 enters the cleaning device 43 while carrying the untransferred residual toner, where the residual toner on the image carrier 10 is removed,
A new copy cycle is prepared.

FIG. 1 is a sectional view of a heat roller fixing device 50 according to the present invention. In the figure, reference numeral 51 denotes a heat roller. Inside the heat roller 51, a halogen heater 52 is provided. Heat roller above
A pressure roller 53 is provided below the heat roller 51 so as to be pressed against the heat roller 51 as an opposing roller. The transfer paper having the toner image is fed between the pair of rollers from the conveyor belt 42 side and passes the toner image toward the heat roller 51, so that the toner image on the transfer paper is fixed.

The heat roller 51 has a thickness outside the pipe-shaped metal core bar.
This roller covers a tube of about 30 μm tetrafluoroethylene / perfluoroalkylvinyl ether copolymer (PFA) and has an outer diameter of about 60 mm.

The halogen heater 52 built in the heat roller 51 is a 1500-watt and 600-watt heater located substantially at the center of the heat roller 51. The amount of heat generated is controlled so that the temperature of the peripheral surface of the heat roller 51 is maintained at about 200 ° C. during copying by detecting the temperature of a temperature measuring unit (temperature sensor) 54 disposed close to the peripheral surface of the heat roller 51. Have been.

An oil application roller 55 is provided above the peripheral surface of the heat roller 51.
However, the oil is applied to the peripheral surface of the heat roller 51 while being pressed against the heat roller 51 by its own weight and a spring and driven to rotate. Reference numeral 56 denotes oil supply means for constantly supplying oil to the oil application roller 55, and an oil impregnated pad 56B built in the box-shaped frame 56A is slidably in contact with the peripheral surface of the oil application roller 55 to supply oil. Reference numeral 57 denotes a cleaning roller made of foamed silicone rubber, which adsorbs and removes toner and the like attached to the peripheral surface of the heat roller 51.

The pressure roller 53 comes into pressure contact with the heat roller 51 from immediately below and rotates counterclockwise. An auxiliary heating means 58 is provided near the peripheral surface of the pressure roller 53. The auxiliary heating means 58 has a built-in heater using a heating element and controls the surface temperature of the pressure roller 53.

Toward the pressure contact portion between the heat roller 51 and the pressure roller 53,
The transfer paper having the toner image transferred on its upper surface is carried in from the direction of arrow A by the guides 501 and 502. The transfer paper is held between the heat roller 51 and the pressure contact portion of the pressure roller 53,
It is transported in the direction of arrow B. At this time, the toner on the transfer paper is melted by the calorific value of the halogen heater 52 built in the heat roller 51 and fixed on the transfer paper. The transfer paper on which the toner image is fixed is transferred to the heat roller 51 and the pressure roller 5.
The roller is carried out from the pressure contact portion 3 and is separated from both roller peripheral surfaces by the separation claws 503, 504, and is discharged to the outside of the heat roller fixing device 50 in the direction of arrow B through the guides of the guide members 505, 506.

FIG. 2 is a diagram showing a temperature change on the surface of the heat roller when the first and second temperature set values are provided.

FIG. 2 is a diagram showing the temperature change on the surface of the heat roller. As described above, when the recording paper is continuously inserted between the heat roller 51 and the pressure roller 53 and the fixing is performed, the recording is performed. Since the paper takes heat, the temperature of the heat roller surface decreases. The temperature of the heat roller surface is usually about 160 ° C. to 200 ° C. Therefore, within the temperature range in which fixing is possible, the first
The set temperature TH is set, and the second set temperature TL is set in the low temperature section. The line speed of the heat roller can be switched between a low-speed LS1 and a high-speed LS2 in order to change the transport speed of the recording paper in accordance with the two set values (temperatures).

Assuming that the fixing is started at the set temperature TH and the line speed LS1 at the point S as shown in FIG. 2, as the recording paper is continuously fixed, the temperature of the surface of the heat roller gradually decreases.
Eventually, the temperature reaches the second set temperature TL. Then, at the point C, the line speed is switched to the high speed of LS2. By doing so, the time required for the recording paper to pass between the heat roller and the pressure roller is reduced, so that the temperature drop on the heat roller surface is interrupted and the temperature on the heat roller surface rises again. Therefore, the image can be fixed to the end (point F) at the line speed LS2.

The line speeds LS1 and LS2 are, of course, constant speeds and require the condition of LS2 ≧ LS1.

Actually, for example, LS2 ≧ (1.2 × LS1) is practical.

FIG. 3 is a diagram showing a temperature change on the surface of the heat roller when the first, second, and third set temperature values are provided.

Next, by applying the present invention, the first set temperature T1 and the second set temperature T2 are set within the temperature range in which the fixing can be performed in the same manner as described above, and the line speeds LS1 and LS2 of the heat roller corresponding to each of them are set. Further, a third temperature is set as a temperature at which fixing becomes impossible.
Set the set temperature T3. Assuming that the fixing is started at the first set temperature T1 and the line speed LS1 of the heat roller as shown by a point S in FIG. 3, the temperature of the surface of the heat roller is lowered by the continuous fixing of the recording paper. Then, when the point C is reached and the fixing is continued at the line speed of LS1 as it is, the point D is reached immediately and the fixing becomes impossible. However, when the line speed according to the present invention is switched to LS2, the fixing can be further continued. Even in this case, if the amount of recording paper is too large,
Eventually, as shown by the dotted line in the figure, the temperature reaches the point F, the third set temperature T3, and the fixing becomes impossible. That is, when the temperature reaches the third set temperature T3, the fixing is stopped immediately, a warning such as an alarm is issued, and the recording paper inserted in the transfer unit 40 or the heat roller fixing device 50 is discharged out of the device. To control the image recording apparatus.

As described above, the image recording apparatus controls the line speed in accordance with the fixing temperature, performs the uniform heat roller fixing, and obtains a clear copy.

Although the drive system of the image recording apparatus is entirely performed by the CPU, as shown in FIGS. 4 and 5, the motor M1 for driving the image carrier 10 and the motor M2 for driving the heat roller are independent of each other. The timing is controlled by the CPU. The switching and control of the line speed of the heat roller are also controlled by the CPU by detecting the size of the recording paper and the surface temperature of the heat roller.

〔The invention's effect〕

As described above, the heat roller fixing device of the present invention provides the first set temperature and the second set temperature in accordance with the temperature change of the heat roller, and switches the line speed of the roller according to each set temperature. You can always get consistent, clean copies. Further, by providing the third set temperature, it is possible to provide an image recording apparatus having a heat roller fixing device for stopping copying immediately when copying is impossible and preventing the recording paper from being unfixed. Became.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a heat roller fixing device according to the present invention, FIG. 2 is a diagram showing a temperature change on a heat source roller surface when first and second temperature set values are provided, Figure 3 shows the first
FIG. 4 shows a temperature change on the surface of the heat source roller when the second and third temperature set values are provided, FIG. 4 shows a control system by the CPU, and FIG. 5 shows a conventional heat roller fixing device. 1 is an overall configuration diagram illustrating an example of an image recording apparatus according to an embodiment. 50: Heat roller fixing device 51: Heat roller, 52: Halogen heater 53: Pressure roller, 54: Temperature measuring unit M1, M2: Drive motor TH, T1: First set temperature TL, T2 … Second set temperature T3… Third set temperature, S… Copy start point C… Speed switch point, D… Copy impossible point F… Copy stop point

Continuation of front page (56) References JP-A-62-44785 (JP, A) JP-A-57-79975 (JP, A) JP-A-62-288876 (JP, A) JP-A-61-186976 (JP, A) JP-A-58-121057 (JP, A) JP-A-54-80135 (JP, A) (58) Fields studied (Int. Cl. ⁶ , DB name) G03G 13/20 G03G 15/20

Claims (2)

(57) [Claims] 1. A heat roller rotating with a built-in heating means,
In an image recording apparatus provided with a heat roller fixing device for nipping and transporting a transfer material between the transfer roller and a pressing roller pressed against the transfer material and fixing a toner image attached to the transfer material, the temperature of the heat roller is directly controlled. Or a detection device for indirectly detecting the surface of the heat roller having two set reference values of a first set temperature value for setting a fixing upper limit and a second set temperature value for setting a fixed lower limit. When the temperature reaches the second set temperature value, the heat fixing is performed by switching the outer circumferential linear speed of the heat roller to a second outer circumferential speed higher than the outer circumferential linear speed at the first set temperature value. An image recording apparatus provided with a heat roller fixing device, comprising the control mechanism configured as described above. 2. A heat roller rotating with built-in heating means,
In an image recording apparatus provided with a heat roller fixing device for nipping and transporting a transfer material between the transfer roller and a pressing roller pressed against the transfer material and fixing a toner image attached to the transfer material, the temperature of the heat roller is directly controlled. Or a detection device for indirectly detecting, a first set temperature value for setting a fixing upper limit, and three setting reference values of a second set temperature value and a third set temperature value for setting a fixing lower limit, When the detected surface temperature of the heat roller reaches the second set temperature value, the outer linear speed of the heat roller is switched to a second outer linear speed higher than the outer linear speed at the first set temperature value. To perform heat fixing, and further, the surface temperature of the heat roller is lowered to reduce the third temperature.
An image recording apparatus provided with a heat roller fixing device, comprising a control mechanism configured to stop the copying function when the set temperature value is reached.