JP2801225B2 - Image forming device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image forming apparatus that heats and fixes a developed image on a recording material.

[Prior Art] Conventionally, a fixing device used in this type of apparatus has an unfixed state by using a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer and pressing against the heating roller. A heat roller fixing method in which a transfer material on which a toner image is formed is heated while being nipped and conveyed is often used. Also USP
A belt fixing system described in 3,578,797 is known.

[Problems to be Solved by the Invention] However, in the above-described conventional example, since it usually takes a long time to reach a temperature at which a large heat capacity is fixed, the power is always turned on and the fixing unit is heated to a certain temperature or more. A preparation time for the image forming apparatus is provided, which is called "weight-up" or the like. Therefore, there is a drawback that the user is provided immediately after turning on the power or immediately after performing a jam clearance, even when urgently needed. The main disadvantages are described below.

(1) Heat roller fixing method There is a so-called wait time in which the temperature is raised to a predetermined temperature and the image forming operation is prohibited.

Large electric power is required because heat capacity is required.

Since the temperature of the rotating roller is high, a special heat-resistant bearing is required.

There is a danger or a protection member is required because the hand is directly in contact with the roller.

Transfer material is wrapped by constant temperature and curvature of roller
JAM.

[Means for Solving the Problems] The present invention solves the problems of the above-described conventional apparatus, and reduces the heat capacity of the heating element without causing fixing defects and offset. It is an object of the present invention to provide an image forming apparatus which can reduce the standby time, the power consumption, and the temperature rise in the apparatus.

In order to achieve the above object, the present invention provides an image forming unit for forming an unfixed image on a recording material, and heating the unfixed image formed by the image forming unit through a film by a heating element that generates heat by energization. In an image forming apparatus having a fixing unit for fixing a recording material on a recording material and a detection unit for detecting the recording material on the discharge side of the fixing unit, a detection signal generated from the detection unit for each recording material during continuous image formation. The present invention is characterized in that the energization of the heating element is prevented each time.

Thereby, the heat capacity of the heating element can be reduced, and the heating time can be further reduced.

Further, by intermittently heating and driving the recording material in accordance with the feeding interval of the recording material at the time of forming the multi-image, the heating time at the time of forming the multi-image can be greatly reduced.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. First, the schematic structure of the image forming apparatus of the present embodiment will be described with reference to FIG. 1. Reference numeral 1 denotes a document placing table made of a transparent member such as glass, which scans a document by reciprocating in the direction of arrow a. A short-focus small-diameter imaging element array 2 is disposed immediately below the document table, and an image of the document placed on the document table is illuminated by an illumination lamp 3, and a reflected light image is formed on the photosensitive drum by the array 2. 4 is subjected to slit exposure. The photosensitive drum 4 rotates in the direction of arrow b. Reference numeral 5 denotes a charger, which uniformly charges the photosensitive drum 4 covered with, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. On the drum 4 uniformly charged by the charger 5, an electrostatic latent image subjected to image exposure by the element array 2 is formed. The electrostatic latent image is visualized by a developing device 6 using a toner made of a resin or the like that softens and melts when heated. On the other hand, the sheet P stored in the cassette S is pressed by the pair of transport rollers 8 which are pressed and rotated in the vertical direction at timing synchronized with the image on the photosensitive roller 4 and the feed roller 7. It is sent onto the photosensitive drum 4. Then, the toner image formed on the photosensitive drum 4 is transferred onto the sheet P by the transfer discharger 9. Thereafter, the sheet P separated from the photosensitive drum 4 by a known separation unit is guided to a fixing device 11 by a conveyance guide 10 and is heated and fixed, and then discharged onto a tray 13. After the transfer of the toner image, the residual toner on the photosensitive drum 4 is removed by the cleaner 12.

FIG. 2 is an enlarged view of the fixing device 11 of the present embodiment. Reference numeral 21 denotes a low-heat-capacity linear heating element fixedly supported by the apparatus, and is, for example, an alumina substrate having a thickness of 1.0 mm, a width of 10 mm, and a length of 240 mm.
22 is coated with a resistance material 23 to a width of 1.0 mm, and is energized from both ends in the longitudinal direction. The energization is performed by applying a pulse corresponding to a desired amount of temperature energy release controlled by the temperature detecting element 24 in a pulse-like waveform of DC 100 V and a cycle of 20 mSec, changing the pulse width. The approximate pulse width is 0.5 mSec to 5 mSec. In this way, the fixing film 25 moves in the direction of the arrow in the drawing while coming into contact with the heating element 21 whose energy and temperature are controlled. As an example of this fixing film, a heat-resistant film having a thickness of 20 μm,
For example, it is an endless film in which polyimide, polyetherimide, PES, and PFA are coated at least on the image contacting surface side with a release layer formed by adding a conductive material to a fluororesin such as PTFE or PAF to a thickness of 10 μm. Generally, the total thickness is preferably 100 μm, more preferably 40
It is less than μm. The film is driven by the driving roller 26 and the driven roller 27 and by tension, and moves without wrinkles in the direction of the arrow. 28 is a pressure roller having a rubber elastic layer with good release properties such as silicone rubber, and a total pressure of 4 to 7K.
The heating body is pressurized through the film with g and pressed against the film to rotate. The unfixed toner (T) on the transfer material (P) is guided to a fixing unit by an entrance guide 29, and a fixed image is obtained by the above-described heating. The endless belt has been described above, but the fixing film may be an edged film as shown in FIG. 2 (b). As an image forming apparatus, a copying machine,
The present invention is applicable to all fixing devices such as a printer and a facsimile which form an image using toner.

Next, FIG. 3 shows a block diagram of the control unit. First, reference numeral 40 denotes a control means, which in this embodiment is constituted by a microcomputer, a logic element and the like. The paper detection signal S1 from the paper detection means 14 for feeding paper is input to the input terminal IN1 of the control means 40. Input terminal IN2
Paper detection means 15 at the entrance side of the fixing device in the paper conveyance direction.
And a paper detection signal S3 from the paper detection means 16 on the paper discharge side of the fixing device in the paper transport direction is input to the input terminal S3. Also, the input terminal IN4
An image signal R generated when the image detecting means 45 detects an image timing member (not shown) attached to the document table 1 is input. From the OUT1 terminal of the control means 40, a temperature control means 41 for controlling the temperature of the heating element 21 is provided.
And outputs a fixing heater temperature control permission signal H to the heater. From the OUT2 terminal, the main motor that drives the image forming apparatus
The transport drive signal M to 42 is output. The OUT3 terminal outputs a paper feed drive signal SL1 to the paper feed drive unit 43. The OUT4 terminal outputs a transport roller drive signal SL2 to the transport roller drive unit 44. (Each output from the output terminal is “H” and turned ON (ACTIVE) and “L” is turned OFF.) The transport roller drive signal SL2 is output based on the input of the image destination signal R. is there.

In the present image forming apparatus configured as described above, focusing on the fixing unit, a fixed image can be obtained by the control described below.

FIG. 4 is a timing chart for two-sheet copying. M is a transport drive signal, SL1 is a paper feed drive signal, SL2 is a transport roller drive signal, S1 is a paper feed detection signal, S
As described above, reference numeral 2 denotes an entrance-side paper detection signal, S3 denotes a discharge-side paper detection signal, and H denotes a fixing heater temperature control permission signal. The control means (40) sets the transport drive signal M to "H" at the copy ON timing to drive the transport drive system.
To "H" and feed the sheet P. Sheet P fed
Is detected by the paper detecting means 14 and sufficiently hits the transport roller 8, after which the control means 40 sets the transport roller drive signal SL 2 to “H” to drive the transport roller 8 at the timing of adjusting the position of the leading edge of the image. The position of the leading end of the image is adjusted by synchronizing with the optical system. Next, after the unfixed image is transferred from the drum 4 by high-pressure control, the sheet P is transported to the fixing device 11 by the transport drive system. Then, when paper is detected by the above-described paper detection means 14, the control means 40 validates H, which is a heater temperature control permission signal. That is, if the entrance-side paper detection signal S2 from the paper detection means 15 rises at the timing, the temperature control of the heating element 21 is started at the subsequent timing. Next, the entrance side paper detection signal S2 is "L".
The sheet P has not completely passed through the fixing device 11 even if the temperature of the fixing heater 11 is lowered.
I'm leaving. And falls to the paper discharge side sheet detection signal S ₃ is "L" from the paper detection unit 16, the control unit 40 detects that the paper has passed through the fixing device 11, the fixing heater temperature control permission signal "L" And the temperature control of the heating body 21 is stopped.
That is, the fixing heater temperature control permission signal is realized by calculating the logical sum of the signals S2 and S3. As described above, by providing 15 and 16 paper detections, a completely fixed image can be obtained with a necessary and minimum temperature adjustment time. Further, in FIG. 3, the control means 40 does not set the fixing heater temperature control permission signal to "H" during the interval between the second and the last sheet. In other words, during multi-printing during continuous image formation, the power supply to the heating element 21 is stopped each time based on the discharge side paper detection signal S3 generated from the paper detection unit 16 for each sheet, and according to the sheet conveyance interval. The temperature of the heating body 21 is intermittently controlled. FIG. 5 shows a flowchart for realizing the above. That is, the entrance-side paper detection signal S2 or the discharge-side paper detection signal S3
If either of them is “H” (steps 1 and 2), the control means 40 controls the temperature of the fixing device (step 4). However, both the inlet side sheet detecting signal S ₂ and the paper discharge side sheet detection signal in the case of "L", the control unit 40 stops the temperature control of the heater 21.

[Other Embodiments] Instead of providing the paper detection unit 15 without changing the 16 paper detection units 16 in the previous embodiment, the time from the timing of adjusting the position of the leading edge of the image to the entrance of the fixing device by the timer ( The T) shown in FIG.
By inputting the value to 0), the temperature control can be started before the sheet P enters the fixing unit, and the fixing heater temperature control permission signal H can be lowered at the falling of the sheet discharge side sheet detection signal S3. is there.

FIGS. 6A and 6B are flowcharts for realizing this control. The configuration of the control unit in this case is as follows:
It is the same as FIG. Therefore, it will be described. In FIG. 6 (a), a flag HEAT2 for intermittent driving is a flag which is set when the sheet detecting means 16 on the discharge side of the fixing device detects a sheet, and HEAT1 is an image signal on as described later. This flag is set when a predetermined time T has elapsed since the start of the process. First, at step 10, it is determined whether or not the flag HEAT2 is "L". In the case of “L”, that is, until the sheet reaches the paper detecting means 16, the process proceeds to step 11. In the case of not “L”, that is, after the sheet reaches the paper detecting means 16, the process proceeds to step 15. In step 11, it is determined whether or not the flag HEAT1 is "H". In the case of "H", that is, after a lapse of T seconds from the turning on of the image signal, the process proceeds to steps 12 to 14, and the temperature of the heating body 21 is adjusted until the paper detecting means 16 detects a sheet (steps 12, 1).
Four). When the paper detection unit 16 is a signal S ₃ detected the sheet becomes "H", the to the flag HEAT2 "H" (Step 1
3). Then, after the flag HEAT2 becomes “H”, step 15 is performed.
The paper detection means 16 detects the passage of the sheet and outputs a signal
Until S ₃ becomes "L", the process proceeds from step 15 to step 14,
The temperature of the heating body 21 is adjusted. The signal S ₃ becomes "L" when the processing proceeds to step 16 and 17, the flag HEAT2, HEAT1 to "L",
The temperature control of the heating element 21 is stopped.

FIG. 6 (b) is a flowchart of a timer interrupt process executed when an interrupt is input at a fixed time interval. In step 20, it is determined whether or not the image signal R has been input to the input terminal IN4. If not, the process returns to the main routine. Upon receiving the image signal, it is determined in step 21 whether the flag HEAT is "L". Then, in the case of "L", it is determined whether or not T seconds have elapsed, and when T seconds have elapsed, the flag HEAT1 is set to "H".
And return to the main routine. In this embodiment, the case where the recording material is heated by the heating element via the heat-resistant film has been described. However, the present invention is not limited to this, and can be applied to various types of devices that perform immediate fixing.

[Effects of the Invention] As described above, according to the present invention, since the recording material is heated and fixed by heating with the heating element, the heat capacity of the heating element can be reduced without causing a fixing defect or offset. it can. Also, since it is only necessary to control the temperature until the recording material passes through the fixing device, energy saving is achieved, and further energy saving can be achieved by starting heating the fixing means immediately before entering the fixing device. ,
In addition, the so-called wait-up time for waiting up can be omitted. Further, it is possible to prevent the temperature inside the machine from rising, which is often a problem in design.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an image forming apparatus to which the present invention is applied, and FIG.
3A and 3B are enlarged views of the fixing device, FIG. 3 is a block diagram of a control unit, FIG. 4 is a timing chart of each signal in the present embodiment, and FIG. 5 is for realizing the present embodiment. 6 (a) and 6 (b) are flowcharts for realizing another embodiment. 11 ... fixing device, 14, 15, 16 ... paper detection means, 21 ... heating element, 23 ... resistance material, 25 ... fixing film, 40 ... control means

Claims (1)

(57) [Claims] An image forming means for forming an unfixed image on a recording material, and an unfixed image formed by the image forming means is heated via a film by a heating element which generates heat when energized, and is fixed on the recording material. An image forming apparatus comprising: a fixing unit for detecting a recording material on the discharge side of the fixing unit; and a detection unit for each recording material based on a detection signal generated for each recording material during continuous image formation. An image forming apparatus, wherein the power supply to a heating element is stopped.