JPS60220379A - Recorder - Google Patents

Abstract

PURPOSE:To attain always a stable fixing capacity and prevent surely fixing defects with an inexpensive constitution by providing a temperature sensor which measures the temperature of a fixing means at a prescribed time after the start of recording operation. CONSTITUTION:A fixing means 17 which fixes a developed image has a heating roll 3 incorporating a heater 2 and a roll 4 brought into contact with the heating roll 3. A sensor 5 which detects the temperature of the surface of the heating roll 3 consists of, for example, a thermistor. An electrostatic latent image corresponding to an original image is formed on a photosensitive drum 12, which is electrostatically charged by an electrifier 13, by returning between going and returning of an original platen 15 and is developed by a developing device 16, and the toner image is transferred to a recording paper supplied from a cassette 10. The recording paper where the toner image is formed on the surface is carried to the fixing means 17 and is held between a pair of rolls 3 and 4 and is fixed while carried and is ejected to an eject tray 18.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a recording apparatus, and in particular is an improvement aimed at reducing the power consumption of a fixing means and reliably avoiding the occurrence of fixing failures.

(Prior Art) In recent years, as the speed of copying operations of copying machines, which are typical recording devices, has increased, a large amount of electric power has become necessary in each part of the copying machine. For example, in a fixing device that fixes toner images on recording paper using a heated fixing roller, when a large number of sheets are continuously copied, the surface temperature of the fixing roller decreases, so it is necessary to maintain the surface temperature at the fixing temperature. In addition, the power demand for the heater built into the fixing roller increases. However, in general offices and the like, in most cases, a 100V outlet is used as a power source for the copying machine, so it is necessary to reduce the power distribution to each part of the copying machine as much as possible. Therefore, the power allocated to the fixing device is normally only the minimum amount of power that allows the copying machine to make continuous copies of up to the maximum number of copies, for example, 99 copies if the number of copies is set to 2 digits. .

However, application equipment, such as an automatic document feeder (hereinafter referred to as A
When an ADF (referred to as an ADF) is attached, the copying machine makes continuous copies for the number of originals loaded on the ADF. the result,
If the number of copies greatly exceeds 99, a power shortage occurs in the heater in the fixing roller, and the temperature of the fixing roller drops significantly, resulting in poor toner fixation on the recording paper.

Therefore, it is conceivable to allocate power to the heaters in consideration of the case of continuous copying of a large number of copies using such an ADF.

However, how do you configure a typical office?
Since power cannot be obtained from a 00V outlet, special wiring in the office must be done or a 200V power supply must be used. This not only increases the burden on the user for installing the copying machine, but also increases the running cost of the machine, which is not appropriate.

Furthermore, conventionally, the surface temperature of the fusing roller is detected using a temperature sensor such as a thermistor, and if this surface temperature falls below the fusing temperature, it is determined that fusing is not possible and copying is prohibited. There are problems such as it takes a lot of time for the user to obtain the desired copy and the user feels uncomfortable.

(Objective of the Invention) An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional example, and to enable accurate measurement of the temperature of the fixing means during continuous recording of a large number of sheets, thereby inhibiting recording activity. To provide a recording device that reliably prevents fixing failure without any problems.

(Example) The present invention will be described in detail below with reference to one drawing.

FIG. 1-1 shows a schematic configuration of a copying apparatus to which the present invention can be applied, where lO is a cassette containing recording paper;
12 is a photosensitive drum having a photosensitive member on its surface; 13 is a charger that uniformly charges the photosensitive drum 12 to (+) or (=); 14 is a charger for uniformly charging the photosensitive drum 12 to (+) or (=); an exposure lamp for exposing the document on the document table 15; 33 is a power source for the exposure lamp; 31 is an optical system motor;
16 is a developing device for developing the electrostatic latent image formed on the photosensitive drum 12, 21 is a main motor, and 17 is a fixing stage for fixing the developed image, which includes a heating roller with a built-in heater 2. 3 and a roller 4 in contact with the heating roller 3. Reference numeral 18 denotes an ejection tray for storing the recording paper ejected from the fixing means 17. Further, 5 is a sensor for detecting the temperature of the surface of the heating roller 3, and is constituted by, for example, a thermistor.

An electrostatic latent image corresponding to the original image is formed on the photosensitive drum 12 charged by the charger 13 by the reciprocating movement of the original platen 15, and visualized by the developing device 16, and the toner image is fed from the cassette 10. It is transferred to the fed recording paper. The recording paper on which a toner image has been formed on one surface is conveyed to a fixing means 17, where it is conveyed while being nipped by a pair of rollers 3 and 4, thereby being fixed, and then discharged onto a discharge tray 18.

Conventionally, especially for high-speed or multi-functional copying machines,
There is a device with a reduction function. When these copying devices perform a reduction function, they generally accomplish this by increasing the speed of optical scanning compared to the case of actual magnification.

However, as the speed of devices has increased, it has often been difficult to increase the speed of optical scanning due to problems such as vibration and insufficient light intensity. In order to solve this problem, reductions have been carried out by, for example, slowing down the circumferential speed of the drum, that is, the paper conveyance speed.

That is, a copying apparatus having the above-mentioned reduction function has a mode in which the paper conveyance speed is lower than the paper conveyance speed during the same-size copying operation. In such a case, the amount of charge and the amount of exposure are controlled in accordance with the change in speed.

Furthermore, there are some conventional products that perform forward rotation during weighting for reasons such as improving fixation in the morning. The speed of this pre-rotation is often slower than that during the copying operation from the standpoint of noise prevention and durability. As shown in examples 1 and 2, there are copying machines that have a slower speed in addition to the normal copying speed.

FIG. 1-2 is a block diagram showing a control section of the copying apparatus shown in FIG. 1-1. 20 is ROM.

This is a well-known one-chip microcomputer (hereinafter referred to as CPU) that includes a built-in RAM and the like. ■1.

f2 is an input port, the sensor 5 is connected to the boat It via an A/D converter 6, and the copy button 8 for outputting a copy command is connected to port 2. INT
An interrupt port is connected to a clock pulse generation circuit 28 that generates a pulse signal according to the rotation of the photosensitive drum 12. Based on the black and white pulses, the CPU 20 controls the copy recording sequence. Also, 0. 07 is an output boat. Boat 01 has a main motor 21 for driving the photosensitive drum 12, paper feed roller 11, etc., and boat 02 has an exposure lamp lighting circuit 22 for lighting the exposure lamp 14. )03 has a paper feed franc 23 for transmitting the drive of the main motor 21 to the paper feed roller 11, the boat 04 has a high voltage source 24 for supplying high voltage to the charger 13, and the boat 05 has a document A forward clutch 25 for controlling the forward movement of the table 15 is connected to the boat 06, a backward clutch 26 for controlling the backward movement of the document table 15 is connected to the boat 06, and a heater drive circuit for driving the heater 2 is connected to the boat 07.

The detection output Sl of the sensor 5 is supplied to the A/D converter 6,
It is converted into an 8-bit digital signal S2. This signal S2 is supplied to the input port I of the CPU 20. C.P.
A copy recording start command signal Sc generated by closing the switch 8 is supplied to the input port 12 of the U20, and the CPU 2
0, this copy recording start command signal Sc and the fixing means 1
A fixing temperature control signal S3 is generated based on a digital signal S2 corresponding to the surface temperature of the roller 3 corresponding to the actual fixing temperature of No. 7, and is supplied to the heater drive circuit 27. The heater drive circuit 27 drives the heater 2 based on the above-mentioned signal S3 to control the fixing temperature of the fixing means 17.

In this embodiment configured in this way, Section 1-1.2-
1. The operation after starting continuous multiple copying will be explained with reference to FIG. 2-2.

First, before the copy recording operation start time t0, the temperature of the fixing means is maintained at To as shown in Figure 2-1. At time 0, the copy recording start command signal Sc is generated, and continuous copying of a large number of sheets starts from lo to A. 1'U2U, the motor is controlled to have the same speed as the drum when compared with a predetermined temperature TL which is higher by the temperature of I at a time after a predetermined time t0 has elapsed from the copy recording start time t0. In the case of T1≦T, as shown in Figure 1-1, the power supply voltage of the main motor 21 is changed to the same speed as the circumferential speed of the drum when the voltage is lower than that for full-scale copying and variable-magnification copying is caused by the dangerous temperature signal as shown in Figure 1-1. Make it. Furthermore, if the temperature of the fixing means rises due to a thermal margin created by switching the amount of light and the amount of charge according to the circumferential speed of the drum using the normal method Q, the predetermined temperature T) ((To≧TH>TL
) and the temperature T'1 of the fixing means at that point. Conventionally, in order to accurately detect that the temperature has fallen below the limit temperature at which fixing failure occurs, for example, a plurality of thermistors have been used. This is because accurate measurements cannot be made using just one thermistor. That is, as shown in Figure 3, the temperature-resistance characteristic of the thermistor is shown by the solid line A.
However, variations occur in the ranges indicated by broken lines B and C. In the figure, To is the temperature of the fixing device held at the start of copying, Ts is the minimum temperature of the fixing device that can perform normal fixing (hereinafter referred to as the fixing limit temperature), and RO
and Rs are resistance values at temperatures T0 and TS, respectively.

As shown in the figure, near the temperature To, the thermistor shows a resistance value corresponding to the temperature TO, and as a result, temperature can be measured with high accuracy. ) etc., it is not possible to accurately measure the temperature in areas other than the temperature TO. Therefore, considering the variation shown by the broken lines B and C, the relationship between the limit temperature Ts and the resistance value Rs is
It will vary from B. As a result, even though the temperature of the fixing means is lower than the fixing limit temperature Ts, the speed mode does not change due to an error in the detected temperature, and there is a possibility that the toner image on the recording paper will not be fixed properly. was there.

Therefore, another example of a more preferable speed mode control method will be explained with reference to FIG.

After the copy recording start command signal Se is generated at time () and continuous copying of many copies is started, the fixing temperature gradually decreases from T as the number of copies increases.CPU
At time 1.20, a predetermined period of time has elapsed from the copy recording start time t0. The fixing temperature T at t2 is calculated from the detection output of the sensor 5, and then the fixing temperature T2 at time t2 after a predetermined time has elapsed is similarly calculated. The average temperature change rate ΔT/l from the fixing temperature calculated in this way from time t1 to time t2 = (T2-T1)/(
t2 t+) is calculated. Based on this value, the fixing limit temperature T
The time ts when the temperature reaches 's is calculated, and the time Δts=ts-t2 until the temperature of the fixing means reaches Ts is calculated.

In addition, since the temperature drops rapidly immediately after copying and recording starts, Δt
It is difficult to calculate s accurately. Therefore, it is desirable to reduce Δts after the sudden temperature change ends. This can be achieved by starting the measurement, for example, 10 seconds after the predetermined time t' has elapsed, or by starting the measurement when the temperature falls below a certain predetermined temperature T' (T o >T'> T s). Here t'
, T' may be determined appropriately depending on each recording device. After Δts becomes smaller than a predetermined time ti, the copying operation is switched to the low speed mode and the copying operation is performed in the low speed mode until the temperature of the fixing means recovers to a certain predetermined temperature TA (To≧TA>TS). After the temperature of the fixing means has recovered to TA, normal copying operation is resumed and the same process is repeated. Here, the time t until reaching the fixing limit temperature T3
It has been confirmed through experiments that predicting s by linear approximation can be done with high accuracy by appropriately setting time Ll+t2.The system is equipped with a temperature sensor that can measure the temperature of the fixing means at a predetermined time after the start of the process. By doing this, it is possible to accurately measure or predict when the temperature of the fixing means approaches the fixing limit temperature, so with the fixing limit hot water stop 1, stable fixing performance can be obtained at all times for any type of copying, and fixing can be performed with an inexpensive configuration. It has become possible to reliably prevent defects.

[Brief explanation of drawings]

1-1 is a block diagram showing an outline of a copying apparatus to which the present invention can be applied, FIG. 1-2 is a block diagram showing a control section of the copying apparatus shown in FIG. 1-1, and 2-2 Ship It It is a diagram showing the temperature-temporal deformity of Uchi means in the poem 'E'. 2---Heater, 3.4-11 roller, 5-11 sensor, 6---A/D converter, 8-m-copying switch, 10
-m-cassette, 11--1 paper feed roller, 12-11 photosensitive drum, 13-m-charger, 14-m-exposure lamp,
15-m-document table, 16--developing device, 17--constant fixing means, 18-m-discharge tray, 20-m-microcomputer, 21--main motor, 22--1-exposure lamp lighting circuit , 23-m-paper feed clutch, 24-m-high pressure source, 25-m
- Forward clutch, 26 - Reverse clutch, 27 - Heater drive circuit, 28 - Drum clock generation circuit. 31-m-Optical system motor. 33--One exposure lamp power supply. tatltz Tls abbreviation

Claims (1)

[Claims] In a recording apparatus having a heating roller fixing means for fixing a toner image onto a recording material by passing it between a pair of rollers, and having a multi-speed mode, the temperature of at least one of the L rollers is lower than or equal to a predetermined temperature. A recording device characterized in that it performs a recording operation in a low speed mode when