JPH049973A - Image recorder provided with heating roller fixing device - Google Patents

Abstract

PURPOSE:To efficiently and consecutively perform the copying of a large number of sheets by switching a set temperature at which a copying action is stopped or lowered by a temperature sensor corresponding to elapsed time from starting or a temperature detected by another temperature sensor. CONSTITUTION:In the case that an atmospheric temperature detected by the temperature sensor S2 is equal to or above the set temperature when the controlled temperature of the temperature sensor S1 is lowered to the 1st slowdown temperature because the copying action is continuously performed, a copying speed is immediately made to slow down by judging that the temperature of a heating roller 10A is detected by the sensor S1 in a normal state and then it is switched to an ordinary speed at the time of recovering to a restored temperature. By judging that the detection of the temperature is not normal when the temperature detected by the sensor S2 is equal to or under the set temperature, the copying action is continued until the temperature is lowered to a 2nd slowdown temperature which is much lower, and a mode is not switched to a copying mode in which the copying speed is caused to slow down until the temperature gets equal to or under the 2nd slowdown temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image recording apparatus equipped with a heat roller fixing device, which creates an electrophotographic image by a recording method.

[Background of the invention]

In an electrophotographic image recording device, an electrostatic latent image is formed on an image carrier, and a toner image and 1. It is then transferred onto recording paper. A rotary roller fixing device is often used to fix the toner image adhered to the recording paper.

This roller fixing device conveys recording paper with a toner image attached between the rotating roller, which has a built-in heat source such as an infrared lamp, and the pressure roller, which presses and rotates in cooperation with the roller. When performing fusing using this heat roller fixing device, the temperature of the heat roller is maintained within a certain range, also known as the control temperature, so that the temperature of the heat roller is kept in contact with or very close to the heat roller. It is controlled by a temperature sensor such as a photo coupler provided.

In the above image recording device, the temperature is controlled at a control temperature of 200°C, for example, and when the copy button is turned on, the toner image or the attached recording paper is carried into the fixing device, fixed, and ejected from the device. . During fixing, the amount of heat on the surface of the heat roller is absorbed by the recording paper. During continuous copying of a large number of sheets using a high-speed printer, the heater lamp inside the heat roller remains on to supply heat, or the temperature on the surface of the heat roller gradually decreases from a control temperature of, for example, 200°C.

If the heat roller surface temperature drops to, for example, about 165° C., the toner image will not be sufficiently fused to the recording paper, and there is a possibility that so-called fixing failure (fixing amplifier) may occur. Therefore, when the heat roller surface temperature drops to, for example, 165°C (this is called the alarm temperature) due to continuous copying, continuous copying is temporarily interrupted and the heat roller surface temperature rises to the control temperature or a separately set return temperature. After that, the process of continuing the previous continuous copy is started again.

Furthermore, a slowdown temperature is also provided separately from the above-mentioned alarm temperature. This is to reduce the copying speed when the heat roller surface temperature drops to the slow town temperature (for example, 170 degrees Celsius), which is higher than the previous alarm temperature (for example, 55 degrees Celsius). minutes 60
If a copy is being made and the copy speed is, for example, 3 per minute.
Switch between 5 copy speeds. By reducing the copying speed at the slow town temperature, the amount of heat taken away is reduced, and after waiting for the surface temperature of the heat roller to rise again to the control temperature or a separately set return temperature, the copying speed can be increased to the previous high speed copying speed (for example, per minute). 60 sheets), or if the heat roller surface temperature continues to decrease even after reducing the copying speed, set the previous alarm temperature (for example, 165°).
Copying is temporarily stopped when the value drops to C).

It is not desirable to temporarily stop copying or reduce the number of copies per minute by setting an alarm temperature or a slowdown temperature from the standpoint of making a large number of copies at high speed. However, copying due to poor fixing (fixing amplifier) should be absolutely prevented.

For this reason, in image recording apparatuses capable of high-speed processing of large-volume copies, an alarm temperature or a slow-down temperature is provided to perform the above-described control.

[Purpose of the invention]

When a temperature sensor is brought into direct contact with the surface of the heat roller to detect the surface temperature of the heat roller, the surface temperature is directly measured. However, if a temperature sensor is brought into contact with the hot roller to detect the temperature, there is a problem that the cured toner may adhere to the temperature sensor and damage the temperature sensor or the part of the hot roller that is in contact, degrading the fixing performance. There is.

In order to avoid this problem, a non-contact temperature sensor is installed slightly away from the surface of the heat roller to detect the temperature. Either the above-mentioned problems with the contact temperature sensor are solved by making it non-contact, or a temperature difference occurs between the surface temperature of the heat roller and the temperature detected by the non-contact temperature sensor.

When a thermocouple with good responsiveness is used as the temperature sensor and the temperature sensor is installed at a distance of 1 mm from the heat roller surface, an example of the relationship between the heat roller surface temperature and the detected temperature is shown in Table 1. It becomes like that.

Table 1: Using a non-contact temperature sensor, the inventor set the control temperature to 185°C, the slow town temperature to 163°C, and the alarm temperature to 158°C, and performed a large amount of high-speed copying. Although it is an image recording device, compared to when a contact temperature sensor is used, it has been found that the temperature can reach an alarm temperature or a slow-down temperature, causing the copying operation to stop or the number of copies per hour to decrease. It was done. This situation in which the number of sheets to be processed decreases even though fixability is ensured is not desirable for an image recording apparatus that performs high-speed processing.

The inventor investigated the cause and found that Table 1 shows the temperature relationship in a steady state. Before the steady state, the difference between the heat roller surface temperature and the temperature detected by the non-contact temperature sensor was It is clear that this is the cause of the alarm temperature reaching Yaslowtown temperature even though the above fixing performance is secured before the steady state is reached.

The present invention is an image forming apparatus that detects the temperature of the surface of a heat roller using a non-contact temperature sensor.Fixing performance is always ensured even immediately after warming up or in a steady state, and fixing performance is maintained at an appropriate time. It is an object of the present invention to provide an image recording device equipped with a heat roller fixing device that can temporarily stop copying operations or reduce the number of copies per hour.

[Structure of the invention]

The above object is to provide a heat roller with a built-in heat source, a pressure roller that is in pressure contact with the heat roller and rotate together with the heat roller, and a nearby non-contact temperature sensor that detects the temperature of the heat roller, and is controlled by the temperature sensor. In an image recording apparatus equipped with a heat roller fixing device, the copying operation is temporarily stopped or the number of copies per hour is reduced when the temperature drops to a certain set temperature due to continuous copying. The temperature is achieved by an image recording device equipped with a heat roller fixing device characterized in that the main switch is controlled to be switched in response to the elapsed time from 01 or the temperature detected by a separately provided temperature sensor. Ru.

〔Example〕

Embodiments of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 shows the main parts of an image recording apparatus according to the present invention, in which a photoreceptor drum l rotates in the direction of the arrow and a charger 2 applies a potential to the photoreceptor on the outer periphery. A latent image is formed by projecting the image.

The latent image is developed into a toner image by the developing device 4, and transferred to the paper feed cassette 6A or 6B in the transfer device 5.
, 6C onto the recording paper fed therefrom. When feeding the recording paper, the timing roller 7 is operated to adjust the alignment with the toner image.

The recording paper to which the toner image has been transferred is separated from the circumferential surface of the photoreceptor drum 1 by a separator 8, and is transported via a transport belt 9 to a heat roller fixing device IO.

The fixing device IO is composed of a heat roller IOA that has a built-in heat source H such as an infrared lamp, and a pressure roller IOB that presses against the heat roller IOA from directly below. The toner image is melted and fixed while conveying the recording paper.

A temperature sensor S1 for detecting the temperature of the circumferential surface of the heat roller IOA is disposed in a non-contact state on the circumferential surface of the heat roller IOA.

A thermocouple is used as the temperature sensor S1, and its temperature detecting portion is fixed in the axial center of the heat roller IOA at a position spaced within a range of l±0-15 mm from the roller circumferential surface.

The temperature detected by the temperature sensor Sl is fed back to the control unit of the recording apparatus main body, and the control unit operates the heat lamp power supply via the drive system according to the temperature data, and the heat source H1: the current is intermittent. The temperature of the heat roller IOA is controlled, and in parallel with this, the fixing motor power source is operated to rotate or stop the heat roller IOA.

Further, the rotation of the photosensitive drum 1 and the feeding and conveyance of the recording paper are also controlled via the drive system in accordance with the setting of the number of copies or the selection of the recording paper size.

In the first embodiment, the fixing device 10 or one temperature sensor S
Control of the fixing temperature in the case where only 1 is incorporated will be explained with reference to FIG.

The temperature sensor S1 detects a predetermined control temperature TC.
The time period for which the heat source H is energized is controlled so that the heat source H can be detected at all times, thereby maintaining the temperature of the circumferential surface of the heat roller IOA suitable for fixing.

As copying continues, the temperature detected by the temperature sensor S1 changes to the lower limit of the first column temperature TA(I) that enables fixing.
) and a second alarm temperature TA (n
) and when the temperature rises again to a return temperature TR that sufficiently enables practical fixing, respective detection signals are fed back to the control section.

The above-mentioned detected temperatures are the peripheral surface temperature of the heat roller 10A in a steady state and the control temperature T C = 186°C on the condition that it is maintained at 200°C, for example, the alarm temperature T
A (I) - 158°C Alarm temperature T A (n') = 147°C
Return temperature T R is set to 170°C.

The seven steps of temperature control will be explained below with reference to the flowchart shown in FIG. 2(a).

When the main switch MSW of the recording device is turned on and the copy button is turned on, continuous copying will start, and if the original size is A4 or 85, the copying speed will be 60 sheets per minute, 8 sheets per minute.
40 sheets per minute for 4 size, 35 sheets per minute for A3 size
Copying continues at the same speed.

When the control temperature TC of the temperature sensor St drops to the first alum temperature TA(I) as shown in FIG. 2(b) due to a decrease in the peripheral surface temperature of the heat roller IOA as copying continues, Main switch MS in the control section
The elapsed time since the W or ON state is calculated. For example, if it exceeds a preset one hour, it is assumed that the temperature of the heat roller IOA is detected by the temperature sensor S1 or is being carried out in a steady state. The copy operation will be stopped immediately.

However, if the above elapsed time has not reached 1 hour,
Assuming that the temperature detection of the heat roller IOA by the temperature sensor S1 has not yet been carried out in a steady state, the control temperature TC or a lower second alarm temperature TA (n
), the copying operation continues until the value drops to below 100%, at which point the copying operation is stopped.

The supply of electricity to the heat wH is continued even when the copying operation is stopped,
As a result, when the temperature detected by the temperature sensor S1 rises and reaches the return temperature TR, the copying operation is automatically started again and the previously set continuous copying is resumed.

Next, as a second embodiment, control of the fixing temperature in a case where the fixing device 10 includes a built-in temperature sensor S2 together with the temperature sensor Sl will be explained with reference to FIG.

The temperature sensor Sl detects a first slow-down temperature TS, which is the lower limit of fixing at a normal copying speed.
(1), when the temperature drops to the second slow town temperature TS (n), which is even lower than that, and when the temperature rises again to the return temperature TR, which sufficiently enables fixing at the normal copying speed, the respective detection signals are detected. Feed/
＼・inked.

For example, the temperature sensor S2 is located at a position in contact with the circumferential surface of the pressure roller 10B, detects the ambient temperature inside the fixing device IO, and feeds back the detection signal to the control to control the temperature of the heat roller IOA. It is determined whether temperature detection is being performed in a steady state.

Each of the above detected temperatures is based on the condition that the peripheral surface temperature of the heat roller 10A in a steady state is maintained at 200°C, and for example, the control temperature TC = 186°.
C Slow Town Temperature T S (I) = 162°C Slow Town Temperature T S (It) = 150°C
Return temperature T R is set to 170°C.

The temperature control sequence will be explained below with reference to the flowchart shown in FIG. 3(a).

By turning on the copy button, continuous copying operations are started under exactly the same conditions as in the first embodiment.

For example, when the control temperature TC of the temperature sensor Sl decreases to the first slow town temperature TS (1) as shown in FIG. 3(b) due to the continuation of the copy operation, the ambient temperature detected by the temperature sensor S2 is If the temperature exceeds 100°C, the temperature sensor Sl detects the heat roller IOA.
It is determined that the temperature detection is being carried out in a steady state, and the copying speed is immediately switched to a slow-down copy mode, and if the document size is A4 or 85, it prints 35 pages per minute, or 84 pages per minute. 1 is 20 per minute for A3 size
The copying operation continues, and after the temperature detected by the temperature sensor Sl has recovered to the return temperature T1, H, the copying operation is switched to continuous copying at the normal copying speed described above.

On the other hand, whether the ambient temperature detected by the temperature sensor S2 is 100
If the temperature has not reached °C, it is determined that the temperature detection of the heat roller IOA by the temperature sensor Sl is not performed in a steady state, and the control temperature TC is set to a second slowdown temperature TS (n The copying operation continues until the speed drops to ), at which point the copying speed is switched to a slowed-down copy mode.

〔Effect of the invention〕

The present invention provides non-contact temperature detection even when it is difficult to perform temperature detection in a steady state, such as when the mature roller fixing device is insufficiently warmed up or immediately after a large number of copies have been made continuously. This technology uses a sensor to accurately detect the temperature range suitable for practical use of the heat roller, and as a result, it is possible to efficiently and continuously copy a large number of copies without fear of damaging the heat roller. An image forming apparatus including a roller fixing device is now provided.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of main parts of an image forming apparatus of the present invention, and FIG. 2 (
a), (b) and FIGS. 3(a) and 3(b) are a flowchart and a graph thereof showing temperature control of a heat roller fixing device in the apparatus according to the first and second embodiments of the present invention. l... Photosensitive drum 2... Charger 3... Exposure section 4... Developing device 5 Transfer units 6A, 6B, 6C, paper feed cassette 7... Timing roller 8... Separator 9... Conveyance Belt 10... Fixing device 10A... Heat roller 10B... Pressure roller H... Heat source 51, 52... Temperature sensor

Claims (1)

[Scope of Claims] A heat roller with a built-in heat source, a pressure roller that is in pressure contact with the heat roller and rotates together, and an adjacent non-contact temperature sensor that detects the temperature of the heat roller are provided. In an image recording apparatus equipped with a heat roller fixing device that is controlled so that when the temperature drops to a certain set temperature due to continuous copying, the copying operation is temporarily stopped or the number of copies per hour is reduced. An image recording apparatus equipped with a heat roller fixing device, characterized in that the temperature is controlled so as to be switched in accordance with the elapsed time after turning on the main switch or the temperature detected by a separately provided temperature sensor.