JPH03217886A - Fixation processing method - Google Patents

Abstract

PURPOSE:To prevent fixation processing from being interrupted by controlling fixing speed after measurement point temperature is reached according to the remaining number of sheets in continuous image formation and the temperature drop rates of a fixing device. CONSTITUTION:A sensor S1 for form detection is installed on the paper discharge side of the fixing device 13 and a temperature sensor Th is provided on the peripheral surface of an upper roller 13a. When copy processing is started, fixation is carried out at a constant fixing speed and fixation temperature drops at a constant decrease rate. The copy processing is possible by as many sheet as so far until the temperature T drops to lower-limit temperature T2 and the processing is performed at the same speed as before when the remaining number of sheets is less than that obtained so far. When the remaining number of sheets is larger than that processed so far, the temperature T possibly falls below T2 to interrupt the copy processing. In such a case, the subsequent copying speed is increased to decrease the temperature drop rate, so that the copy processing can be carried on without being interrupted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Al Industrial Field of Application) The present invention relates to a fixing method for fixing an image by heating a sheet on which an image has been formed in an image forming apparatus.

(bl) Conventional technology For example, in the case of an image forming apparatus that forms an image using toner made of a mixture of resin and colorant, the resin in the toner is softened or melted by heat in order to fix the toner transferred onto paper. Therefore, in this case, the fixing process must be performed at a temperature higher than the temperature at which the resin softens or melts. However, if the toner temperature is raised too much, there is a problem that offset will occur. Therefore, in the fixing device, offset will not occur. The upper limit temperature was set as the target temperature, and the lower limit temperature at which the toner softened and melted was set as the low limit temperature, and fixing processing was permitted only within the range of both temperatures.

However, if image forming processing (fixing processing) is performed continuously, the temperature of the fixing device may drop beyond the above-mentioned lower limit, resulting in defective fixing. Conventionally, even during continuous image forming processing, if the temperature of the fixing device exceeds a low limit, the image forming processing is interrupted and the fixing device waits for the temperature to return to a predetermined temperature. In this case, some apparatuses have been designed to reduce the rate of decrease in fixing temperature by lowering the fixing processing speed at a temperature slightly higher than the lower limit temperature, thereby extending the time until the lower limit temperature is reached.

(C) Problems to be Solved by the Invention However, in the conventional apparatus as described above, the fixing process was performed regardless of the number of images to be processed. If the temperature exceeds the fixing temperature, it may be necessary to wait until the fixing temperature reaches a predetermined temperature in order to process only one sheet. In addition, in a device that lowers the fixing speed when the temperature drops to a certain degree, even if processing continues at a high speed, all sheets may be processed before the lower temperature limit is reached. However, the speed was sometimes reduced.

An object of the present invention is to provide a fixing processing method that prevents the above-mentioned wastage of time by controlling the fixing processing speed while taking into account the rate of temperature decrease of the fixing device and the number of sheets remaining for image formation processing. (d) Means for Solving the Problem The present invention provides a fixing method that sets a target temperature and a low limit temperature of a fixing device, and permits fixing of paper within this temperature range. and a low limit temperature, and during continuous image forming processing, detect the number of fixed sheets processed while the fixing device temperature decreases from the target temperature to the measurement point temperature, and detect the number of sheets processed at the measurement point. Measurement is performed from the ratio of the number of sheets remaining in the continuous image forming process at the time the temperature is reached and the temperature difference from the target temperature to the measurement point temperature, and the number of fixed sheets and the temperature difference from the measurement point temperature to the low limit temperature. The fixing processing speed is determined after the point temperature is reached.

(In the 81 action fixing device, the temperature of the device decreases when the paper is fixed. This lowering rate is approximately proportional to the number of sheets to be fixed.

Therefore, if you count the number of sheets processed while the fixing device's temperature drops by a predetermined value (from the target temperature to the measurement point temperature), the temperature will drop at approximately the same rate during the subsequent fixing process.

Therefore, if processing is performed at the same speed as before, the number of remaining sheets will also decrease in temperature at the same rate, and it is possible to see whether it is possible to process all remaining sheets before reaching the lower temperature limit. . If all processing is possible, it is sufficient to continue processing at the same speed, and conversely, if it is not possible, the fixing processing speed may be lowered. Therefore, if the fixing processing speed is determined according to the rate of decrease in fixing temperature and the number of remaining sheets, processing can be carried out according to the situation, and wasted time can be prevented.

(f) Examples FIG. 3 is a schematic front view of a copying machine equipped with a fixing device.

A cylindrical photoreceptor l is provided approximately at the center of the copying machine body. A charger 2, a developer 3, a transfer device 4, a stripper 5, a cleaner 6, and a static eliminator 7 are provided around the photoconductor 1 in the above order. Further, an upper part of the copying machine main body is provided with a document table 8 on which a document to be copied is placed, and an optical system 9 including a light source, a mirror, and a lens is provided below the document table 8.

Further, the right side of the copying machine main body is provided with a paper storage set 10 containing sheets, and the left side is provided with a paper ejection tray 11. A paper transport path is formed between the paper cassette 10 and the paper discharge tray 11 via the photoreceptor 1 . A fixing device 13 is provided within this paper transport path.

The fixing device 13 includes an upper roller 13a that is internally equipped with a heater such as a halogen lamp, and a lower roller 13b that comes into pressure contact with the upper roller 13a.

Further, a temperature sensor Th is provided on the circumferential surface of the upper roller 13a, and a sensor S for detecting paper is provided on the ejecting side of the fixing device l3.
1 is provided.

To briefly explain the image forming process, first, the photoreceptor 1 is charged by the charger 1, and reflected light from the original is guided to it by the optical system 9. Then, a portion of the charged charge is removed by light, and a latent image is formed on the photoreceptor 1. Then, toner is attached to this latent image by the developing device 3, and this toner is further transferred by the transfer device 4 onto the paper l2 fed from the paper cassette 1o. This paper is peeled off by a peeler 5 and conveyed to a fixing device 13 where it is subjected to a fixing process.

FIG. 2 is a diagram showing an example of a temperature change state of the fixing device.

In the figure, T1 indicates the target temperature, T2 indicates the low limit temperature, and T indicates the measurement point temperature. The target temperature T1 is set to the upper limit temperature at which the toner on the paper does not offset, T2 is set to the lower limit temperature at which the toner is sufficiently softened or melted, and T is set to an intermediate value between the two temperatures T1 and T2. In order to simplify the explanation, we use “T:I = ('r,
+Tg)/2".

On/off control of the heater is performed so that the temperature of the heater of the fixing device is T during standby when copy processing is not being performed. When the copy process is started, the following control is performed. FIG. 1 is a flowchart showing the fixing processing procedure during copy processing.

When the print switch is operated, copy processing is started (nl→n2). The measurement end flag n3 is a flag that is set when the temperature of the fixing device drops to T3. When this flag is in the reset state, the process advances to n4 and it is determined whether or not the sensor S1 at the rear of the fixing device has detected paper. And every time this sensor S1 detects paper (
The temperature T of the fixing device is detected by the sensor Th each time one sheet of fixing processing is performed (n5). Then, the detected temperature T is compared with the target temperature T, and if it has fallen below the target temperature T, it is further compared with the measurement point temperature T3 (n6→n7). If the T1 temperature and T2 temperature are maintained at n6 and n7, the number of copies A and B processed from the start of copying to that time is stored (
n8, n9). These addition operations are performed when the temperature of the fixing device is T.
Repeat until it reaches 3, and when the heater temperature drops below T3, calculate the remaining number of copies Y (nlo)
. Here, N is the total number of copies and is a value input from the operation unit at the time of starting copying. And the number of remaining copies Y,
Compare the number of copies (B-A) processed while the fixing temperature drops from T to T3 (nil), and if the remaining number of copies Y is less, set the measurement end flag at nl3. , the copy process is performed at the same copy speed as before until the copy process is completed (nl4). However, if the remaining number of copies is greater, the subsequent copy speed is adjusted in nl2.

As shown in FIG. 2, at the start of the copy process, the fixing process is performed at a fixing speed (copy speed) S+. As long as the copying process is performed at the same speed S, the fixing temperature T decreases at a constant rate. Therefore, if the fixing process continues at the same speed even below the T3 temperature, the fixing temperature will decrease at the same rate of decline (see Figure 2).
I[)), by the time the fixing temperature reaches T2, the same number of copies can be processed as before (T
3 = ('r+ +Tz) /2). Therefore, when the remaining number of sheets Y is less than the number of sheets processed so far (B-A), processing can be performed at the same speed as before.

However, the number of remaining sheets Y is the number of sheets done so far (B-
If the amount is higher than A), the fixing temperature may become lower than T2 by the time the copying process is completed, and the copying process may be interrupted. Therefore, the copy speed S2 after T3 is lowered to alleviate the temperature drop rate and prevent the copy process from being interrupted. If the copy speed S2 is lowered, it will become as shown in (1) and (n) in FIG. 2, for example, and the remaining number of copies can be processed without interrupting copying.

When the copy process is completed (n14), the measurement end flag is reset (nl5) and the processing speed is reduced only when it is necessary to return to the standby state, thereby preventing unnecessary speed reduction and interruption of the copy process. be able to.

In this embodiment, the measurement point temperature T3 is set to the target temperature T. This temperature is set to be exactly the middle temperature between T1 and T2, but this temperature may be any temperature between T1 and T2, and in that case, the temperature decrease rate c = ” ( T ITs ) / (
B-A)", and compare the number of sheets of paper that can be processed until the fixing temperature reaches T2 D1'"(T3T2)/C"゜ with the remaining number of sheets Y, and if D≧Y, copy as is. Continue processing at the same speed, and if D≦Y, reduce the copy speed and perform the subsequent processing.Also, set multiple points for the measurement point temperature, and calculate the rate of temperature decrease between the measurement points. The copy speed may also be controlled while watching.

(Effects of the Invention As described above, according to the present invention, the fixing speed after reaching the measurement point temperature is controlled based on the number of sheets remaining in the continuous image forming process and the rate of temperature decrease of the fixing device. The fixing speed is not lowered, and by lowering the fixing speed, interruption of the fixing process can also be prevented.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing an example of the processing procedure related to the fixing process of a copying machine that is an embodiment of the present invention, FIG. 2 is a diagram showing an example of the state of change in the fixing temperature, and FIG. 1 is a schematic front view of a copying machine provided with the present invention. 13 constant fixing device, Th1 temperature sensor, S1 paper detection sensor.

Claims (1)

[Claims] (1) In a fixing method that sets a target temperature and a low limit temperature of a fixing device and permits fixing of paper within this temperature range, a measurement point temperature is set between the target temperature and the low limit temperature. At the same time, during the continuous image forming process, the number of fixed sheets processed while the fixing device temperature decreases from the target temperature to the measurement point temperature is detected, and the remaining number of sheets of the continuous image forming process is detected when the temperature reaches the measurement point temperature. The fixing processing speed after reaching the measurement point temperature is determined from the ratio of the number of sheets and the temperature difference from the target temperature to the measurement point temperature and the number of sheets already fixed and the temperature difference from the measurement point temperature to the low limit temperature. A fixing processing method characterized by: