JPH046581A - Heat roller fixing device - Google Patents

Abstract

PURPOSE:To stably obtain a clear copy by providing first and second set- temperatures, detecting each of the set-temperatures, and controlling the prelimi nary rotation of a heat roller. CONSTITUTION:As temperatures for which fixing is initiated, the first set- temperature T1 and the second set-temperature T2, which is higher that the first one, are set. When a power source is turned on, the heat roller 51 is heated, and the heating of the heat roller 51 is stopped when its surface temperature reaches the first set-temperature T1; however, the surface temperature of the roller rises higher and soon reaches the second set-temprature T2, and a tempera ture sensor 54 detects this. When the heat roller 51 is preliminarily rotated at the time of t2, the heat of the roller 51 is taken away with a pressure roller 53, so that the temperature of the heat roller 51 began to fall and soon is lowered to the first set-temperature T1 again. Here, the heating of the heat roller 51 is started again, but its temperature still is lowered to the low temp. When the heat roller 51 and the pressure roller 53 are warmed, the temperature of the roller 51 rises again and reaches the first set-temperature T1, therefore the preliminary rotation of the heat roller 51 is stopped. Thus, the stable fixing of a toner image is always achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat roller fixing device used in an electrophotographic image recording apparatus, which fuses and fixes a toner image on a transfer material.

[Conventional technology]

FIG. 4 is a sectional view showing an example of a silent roller fixing device of an image recording apparatus such as a copying machine.

In the figure, 51 has a wall thickness of 4mm to 51I coated with 10μm to 60μm of tare-on (manufactured by DuPont) on the surface.
11 a heat roller consisting of an aluminum pipe-shaped roller, 52 a heating element consisting of an infrared lamp (halogen heater), etc., 54 a temperature sensor consisting of a thermocouple or thermistor, etc., for detecting the surface temperature of the heat roller 51; Reference numeral 53 denotes a pressure roller for sandwiching and passing the recording paper between it and the heat roller 51, and is usually a roller coated with silicone rubber or silicone rubber.

The recording paper on which the toner image has been formed is continuously inserted between the heat roller 51 and the pressure roller 53, and is held and pressed while receiving heat. As a result, the toner is fused to the surface of the recording paper and fixed. In this way, the toner is fixed, but the heat roller 51
In order to keep the surface temperature constant,
As described in Japanese Patent No. 384, the heat roller 5
The surface temperature of the heat roller is detected and converted into a signal, and the heat roller is controlled to pre-rotate or stop in response to the signal. Also, Special Publication No. 1-36106, Special Publication No. 1-36106, Special Publication No. 1-36106,
As described in each publication of No. 31463, a set temperature is set, and the preliminary rotation is controlled by the time counting signal until the set temperature is reached after the power supply official, the temperature change during that time, and the detection signal of arrival. There are some that have been.

[Problem that the invention seeks to solve]

In a heat roller fixing device in an image recording apparatus such as a copying machine, when the above-described control is performed, it takes time for the heat roller to reach a certain temperature after the power is turned on because the heat roller constantly rotates. Furthermore, the reduction in the surface temperature of the heat roller also varies depending on the indoor temperature, changes in power supply voltage, and the type of recording paper (thickness, paper quality, etc.).

For this reason, efforts are being made to shorten the time by preparing a heat source device with a large capacity or by using another preheating means. Even so, it is difficult to obtain stable heat roller fixing, and there are problems such as the device and power source are large and the cost increases.

[Means for solving problems]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate these drawbacks and provide an apparatus in which a toner image is fixed by a heated roller at a constant temperature.

To achieve the above object, the present invention is a heat roller fixing device that fixes a toner image attached to a transfer material using a rotating heat roller having a built-in heating means and a pressure roller rotating while pressing the heat roller. , a temperature detection means for detecting the temperature of the heat roller; and two reference values: a first set temperature for setting the fixing temperature of the toner image, and a second set temperature for setting the temperature higher than the first set temperature. is provided, and when the heat roller surface temperature detected by the temperature detection means reaches the second set temperature reference value, the heat roller and the pressure roller start rotating, and then the heat roller and the pressure roller are restarted. The heat roller fixing device is characterized in that the roller is controlled to stop rotating when the roller reaches a first set temperature.

〔Example〕

Embodiments of the heat roller fixing device of the present invention will be described below with reference to the drawings.

First, an outline of the steps up to the fixing device in a copying machine is that an image is exposed on the photoconductive surface of the surface of a charged image carrier to form an electrostatic latent image of the original image. This electrostatic latent image is developed to form a toner image that transfers the toner image onto the transfer paper. The transfer paper on which the toner image has been transferred is separated from the image carrier, conveyed, further thermally fixed by the heat roller fixing device 50 according to the present invention, and discharged outside the machine.

FIG. 4 is a sectional view of a heat roller fixing device 50 according to the present invention. In the figure, 51 is a heat roller, and a halogen heater 52 is disposed inside the heat roller 51. A heat roller 51 is provided below the heat roller 51 as an opposing roller.
A pressure roller 53 is provided in pressure contact with. The transfer paper carrying the toner image passes between the pair of rollers with the toner image directed toward the roller 51, thereby fixing the toner image on the transfer paper.

The heat roller 51 is a roller having an outer diameter of about 40 mm and has a pipe-shaped metal core coated with tetrafluoroethylene (PTFE) about 20 μm thick on the outside.

The halogen heater 52 built into the roller 51 is an 850W heater located approximately at the center of the heat roller 51. The amount of heat generated is controlled by temperature detection by a temperature sensor 54 placed in contact with the surface of the heat roller 51 so that the temperature of the shoulder surface of the heat roller 51 is maintained at around 200° C. during copying.

An oil application roller 5 is placed above the shoulder surface of the heat roller 51.
5 applies oil to the circumferential surface of the heat roller 51 while being pressed against the heat roller 51 by its own weight and spring and rotates as a result. Reference numeral 56 denotes an oil supply means for constantly supplying oil to the oil application roller 55, and an oil-impregnated pad slides on the circumferential 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 adhering to the circumferential surface of the heat roller 51.

The pressure roller 53 is in pressure contact with the heat roller 51 from directly below and rotates counterclockwise.

A transfer paper with a toner image transferred onto its upper surface is carried toward the pressure contact portion between the heat roller 51 and the pressure roller 53 from the direction of arrow A under the guidance of guide plates 501 and 502.

The transfer paper is held between the pressure contact portions of the rollers 51 and 53 and conveyed in the direction of arrow B. At this time, the toner on the transfer paper is melted by the amount of heat generated by the heater 52 built into the heat roller 51 and fixed on the transfer paper. The transfer paper on which the toner image has been fixed is carried out from the pressure contact portion of both rollers 51 and 52, peeled off from the circumferential surfaces of both rollers by separation claws 503 and 504, and guided by guide members 505 and 506, and then transferred to the direction indicated by arrow B. It is discharged to the outside of the heat roller fixing device 50 in both directions.

Generally, when the power is turned on, the heat roller is rapidly heated and its temperature rises, but it takes time for the heat roller to reach a uniform fixing temperature. The CPU then maintains a predetermined temperature.
controlled by Further, when recording paper is continuously inserted between the heat roller 51 and the pressure roller 53 and fixing is performed,
Since the recording paper absorbs heat, the temperature of the surface of the heat roller 51 decreases. The temperature of this heat roller surface is usually 160'C~2
00'C is used.

In FIG. 1, the power is turned on and the heat roller 51 reaches the first set temperature T.
A diagram showing the relationship between the temperature change on the surface of the heat roller 51 and time when the heat roller 51 starts preliminary rotation when the heat roller 51 reaches temperature T2 and then reaches the vg2 set temperature T2. It is a diagram showing the relationship between the temperature on the surface of the heat roller 51 and time when temperature control is performed after reaching the first set temperature T1 immediately. Further, FIG. 3 is a diagram showing these control systems by the CPU 6.

As shown in FIG. 1, a first set temperature TI and a second set temperature T2 higher than the first set temperature TI are set as the temperature at which fixing is started. When the power is turned on, the heat roller 51 is heated, its surface temperature rises, and when it reaches the first set temperature TI (tl), heating to the heat roller 51 is stopped, but the roller surface temperature further increases. The temperature rises and eventually reaches the second set temperature T2 (t2), and the temperature sensor 54 detects this. At this time t2, the silent roller 51 is pre-rotated. In this case, heat is taken away by the pressure roller 53, so the heat roller 5
The temperature of temperature 1 begins to decrease and eventually decreases again to the first set temperature TI (t3). Here, heating of the heat roller 51 is started again, but the temperature of the heat roller 51 is further lowered to a lower temperature.

and heat roller 51. As the pressure roller 53 is warmed up, the temperature rises again and reaches the first set temperature TI (t4
). The temperature sensor 54 detects this time t4 as described above, and the preliminary rotation of the heat roller 51 is stopped. Thereafter, control is continued to stand by at the first set temperature TI, and a constant fixing temperature is always maintained.

All of these controls are controlled by the CPU 6, but in reality, the temperature of the heat roller 51 starts changing as soon as the power is turned on, and the number of times the temperature reaches the first set temperature TI is counted by a counter function. That is, the time cl when the temperature of the heat roller 51 starts to rise and the temperature sensor 54 detects the first set temperature TI is counted as one time by the counter function. and,
Furthermore, the temperature of the hot opening/-ra 51 rises, and the second set temperature T2
The temperature sensor 54 detects that the temperature has reached t.
At step 2, the heat roller 51 and the pressure roller 53 start preliminary rotation. As a result, the temperature of the heat roller 51 begins to decrease, and the temperature sensor detects that it has reached the first set temperature TI again, and heats the heat roller 51 again, counting this time t3 as two times. Then, the temperature of the heat roller 51 further decreases, and eventually begins to rise at a point slightly lower than the first set temperature TI, as shown in FIG.

Shortly thereafter, the temperature sensor 54 detects that the first set temperature TI has been reached for the third time. This time point t4 is counted as three times, and the preliminary rotation of the heat roller 51 and pressure roller 53 is stopped. Here, the temperature of the heat roller 51 is uniformly high enough to fix the image, and the CPU 6 detects that the first set temperature TI has been reached (passed) three times and is in a standby state (copyable state). ) to perform steady temperature control.

In the standby state, the heat roller 51 is at the desired fixing temperature, so the temperature sensor 54 is set to maintain this temperature.
The CPU 6 is in a copyable state by performing steady temperature control.

Next, as shown in FIG. 2, if the heat roller 51 is heated in advance and the heating of the heat roller 51 starts from a temperature closer to the first set temperature TI, the heat roller 51
At the time tl when the temperature sensor 54 detects that the temperature has risen and reached the first set temperature TI, the heating of the heat roller 51 is stopped and counted as one time as described above. However, although the temperature of the heat roller 51 further rises, the temperature of the heat roller 51 drops before reaching the second set temperature T2, so the pre-rotation of the heat roller 51 and the pressure roller 53 is not performed. Then, at time t3 when the temperature sensor 54 detects that the heat roller 51 has reached the first set temperature TI again, heating of the heat roller 51 is started again, and the heating is counted twice. In reality, due to thermal inertia, the temperature starts to rise at a temperature slightly lower than the first set temperature TI.

From this time point t3, steady temperature control may be performed to put the device in a standby state (copyable state). Alternatively, the temperature sensor 54 may detect the time t4 when the first set temperature TI is reached for the next third time, count three times, and set it in a steady standby state (copyable state).

These control systems are shown in FIG. 1 is the power switch, 2 is the motor that drives the heat roller, and the C
Controlled by PU6. Further, 3 is an interface for the temperature sensor and halogen heater to the CPU 6, and 4 is a counter function, which may be configured by software of the CPU.

5 is a copy start button.

Further, the image recording apparatus is configured such that the CPU performs all controls of the image recording apparatus, such as the size and timing of recording paper. Therefore, it is also possible to share these controls with one CPU.

In this way, by pre-rotating the heat roller according to the temperature of the heat roller and the power supply voltage after the power is turned on, stable fixing is possible under any conditions.

〔Effect of the invention〕

As described above, the heat roller fixing device of the present invention provides a first set temperature and a second set temperature, detects each set temperature, and controls the preliminary rotation of the heat roller to approximately maintain the surface temperature of the heat roller. It is now possible to consistently obtain clean, even and clean copies. In addition, if the heat roller is preheated when the power is turned on, it takes less time to reach the copy-ready state, and the image recording device is equipped with a heat roller fusing device that constantly adapts the temperature control and performs stable fusing. can now be provided.

Furthermore, by performing preliminary rotation at the second set temperature, the surface temperature of the roller did not rise above the second set temperature, ensuring safety.

53... Pressure roller 54... Temperature measuring unit (temperature sensor) tl, t3.
t4... Time when the first set temperature is reached t2... Time when the vg2 set temperature is detected

Claims (1)

[Claims] In a heat roller fixing device that fixes a toner image attached to a transfer material using a rotating heat roller having a built-in heating means and a pressure roller rotating while pressing the heat roller, the temperature of the heat roller is detected. and two reference values, a first set temperature for setting the fixing temperature of the toner image and a second set temperature set higher than the first set temperature, which are detected by the temperature detecting means. When the heat roller surface temperature reaches the second set temperature reference value, the heat roller and pressure roller start rotating, and then the heat roller and pressure roller reach the first set temperature again. A heat roller fixing device characterized in that the rotation is controlled to stop when the rotation is stopped.