JPH11258943A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent transfer blurring from occurring due to irregularities of an unfixed image even when large size paper passes after small size paper consecutively passes, to simplify structure, to facilitate production and to prevent cost from rising by shifting a job to a next job after a standby time for a specified time in accordance with the size of passing paper and the number of sheets of passing paper in one job. SOLUTION: The width of passing paper and the number of sheets of the passing paper are compared with reference values (S21 and S22) at the same time as the start of image forming operation. When both or either value is equal to or under the reference value, the device is brought into a standby (S27) as the transfer blurring does not occur even when the large size paper passes after finishing the image forming operation (S23). When both or either value is equal to or above the reference value, the device is put into a standby (S27) after the standby state is started and continued for a specified time (S24, S25 and S26) after finishing the image forming operation. When the next job is inputted, whether or not the width of the passing paper is of the reference value is judged (S28 and S29). When the width of the passing paper is equal to or above the reference value, the device is put into a standby (S29, S26 and S27) after the specified time elapses in the standby state. When it is equal to or under the reference value, the image forming operation is started (S30).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a fixing device in a printer, a facsimile, a copying machine, or the like.

[0002]

2. Description of the Related Art This type of conventional image forming apparatus includes a fixing device having substantially the same configuration as the fixing device of the present invention shown in FIG. 1, and this fixing device will be described with reference to FIG.
The fixing roller 1 having a built-in heater 2 and a pressure roller 4 rotatably pressed to the fixing roller 1 by a pressure lever 3 apply an unfixed toner image to a transfer sheet at a nip portion formed by heat. This is to fuse and fix. In the figure, 6 is a pressing spring of the pressure lever 3, 7 is a thermistor, 8 is an entrance guide plate, 9 is a separation claw, and 11 and 12 are paper discharge rollers.

In such a fixing device, the fixing roller 1 is controlled to a predetermined temperature by a thermistor 7 and control means (not shown). The transfer paper carrying the unfixed toner image is passed through the nip formed by the fixing roller 1 and the pressure roller 4 of such a fixing device, so that the toner image is fixed.

In such a printer, the heat of the paper passing portion of the fixing roller 1 is removed by the paper when the small size paper is passed, but the heat of the non-paper passing portion is not removed by the paper. A large temperature difference occurs between the paper section and the non-paper passing section. As a result, the difference in thermal expansion between the fixing roller 1 and the pressure roller 4 causes a difference in the diameter, so that the nip width of the non-sheet passing portion is significantly larger than the nip width of the sheet passing portion. When large-size paper is passed into such a state, a difference in transport speed occurs between the large nip portion at both ends and the small width nip portion at the center, the paper flaps, the unfixed image is disturbed, and transfer blur occurs. There is a problem.

[0005]

In order to solve such a problem, two heaters having different light distributions (light emission lengths) are provided in the fixing roller 1, and both ends and a central portion of the fixing roller 1 are provided. A method has been proposed in which the temperature is detected by different thermistors to individually control the temperature. However, such a device has to use a plurality of heaters, thermistors, control drivers, and the like, and has a problem that the cost is high because the structure is complicated and manufacturing is difficult.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional image forming apparatus, and to continuously feed small-sized paper through a fixing device and then pass large-sized paper. Occasionally, the paper does not flutter and unfixed images are disturbed, causing no transfer blurring. Further, since there is no need to use a plurality of heaters, thermistors, control drivers, etc., the structure is simple and the manufacturing is easy. An object of the present invention is to provide a fixing device that does not increase costs.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a fixing roller having a built-in heater and a pressure roller rotatably pressed against the fixing roller. In an image forming apparatus provided with a fixing device for hot-melt fixing an unfixed toner image on a transfer sheet at a nip portion, the invention according to claim 1 according to a sheet passing size and a sheet passing number of one job, After waiting for a predetermined time, the process shifts to the next job.

According to a second aspect of the present invention, after the fixing roller is rotated for a predetermined time in accordance with the sheet passing size and the number of sheets passed in one job, the process shifts to the next job.

The invention described in claim 3 is the first or second invention.
In the invention described in (1), when a next job is input while waiting for a predetermined time or during rotation of the fixing roller, the amount of applied toner is changed for a predetermined time according to the sheet passing size of the input job. Is what you do.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In each embodiment of the present invention shown in the drawings, the same parts as those of the above-mentioned conventional example are denoted by the same reference numerals, and the description thereof will be omitted. The thermistor 7 of these embodiments is provided within the minimum size paper passing range. In these embodiments, the conditions under which the temperature rise at the end of the fixing roller 1 causes the transfer blur, that is, the paper passing width and the number of paper passing as the reference values are different from each other. Is calculated in advance by experiments for each embodiment.

FIG. 2 shows a flowchart of the first embodiment. In this embodiment, the reference value is such that the sheet passing width is 216 mm and the number of sheets passed is 100. In such a case, at the same time as the start of the image forming operation (step 21), the set sheet passing width and sheet passing number are compared with the reference values of 216 mm and 100 sheets (step 22). If both or one of the values is determined to be equal to or smaller than the reference value N, the image forming operation ends (step 2).
3) Even if large-size paper is passed immediately afterward, no transfer blur occurs, so that the printer immediately enters the standby state as usual (step 27).

On the other hand, in the case of Y where both or one of the values is determined to be equal to or more than the reference value, the temperature distribution of the fixing roller 1 is changed to the area where no transfer blur occurs after the end of the image forming operation (step 24). It takes a predetermined time to enter. Therefore, after the end of this (step 24), the image forming apparatus starts a standby state (step 25), and for a predetermined time 30 seconds in this embodiment.
During this period, the standby state is continued (step 26). After this time elapses, no transfer blur occurs even when the paper is passed, so that the standby state is established as usual (step 27). At this time, the predetermined time of 30 seconds differs for each embodiment, and such a predetermined time is calculated in advance for each embodiment by experiments.

In the standby state as described above, when the next job is input (step 28), the sheet passing width is set to the reference value of 216 m.
m is determined (step 29). If Y is determined to be equal to or greater than the reference value, a standby state for a predetermined time of 30 seconds is made in the same manner as described above (step 26). Standby state as usual (Step 2
7). On the other hand, if N is determined to be equal to or smaller than the reference value, the image forming operation is started as it is even during standby (step 30). In this way, even if large-size paper is passed after the small-size paper is continuously passed through the fixing device, the unfixed image is not disturbed due to fluttering of the paper, and transfer blur does not occur.

FIG. 3 shows a flowchart of the second embodiment. In this embodiment, instead of the standby state (steps 25 and 26) of the first embodiment, the fixing roller 1 is rotated (steps 35 and 36), and the rotation time of the fixing roller 1 is calculated in advance by experiments. Except for the predetermined time of 15 sec (step 36), the same operation as that of the first embodiment is performed, so only the operation in these (steps 35 and 36) will be described.

After the end of the image forming operation (step 24), the rotation of the fixing roller 1 is started (step 35), and the rotation of the fixing roller 1 is continued for the predetermined time 15 seconds (step 3).
6) After this time elapses, even if the paper is passed, no transfer blur occurs, so that the printer enters the standby state as usual (step
27).

When the next job is input while the fixing roller 1 is rotating as described above (step 28), it is determined whether or not the sheet passing width is equal to or larger than the reference value of 216 mm in (step 29). , In the case of Y determined to be equal to or greater than the reference value,
As described above, the fixing roller 1 rotates for 15 seconds (step 3).
6) After this time has elapsed, the device enters the standby state as usual (step 27).

On the other hand, if N is determined to be less than the reference value, the image forming operation is started as it is while the fixing roller 1 is rotating (step 30). In this way, even if large-size paper is passed after the small-size paper is continuously passed through the fixing device, the unfixed image is not disturbed due to fluttering of the paper, and transfer blur does not occur.

FIG. 4 shows a flowchart of the third embodiment. In this embodiment, in step 29 of the first embodiment, it is determined whether or not the sheet passing width is equal to or larger than the reference value of 216 mm.
A decrease in the amount of toner adhesion is started (step 31). 15 seconds, the time of decrease in the amount of adhesion calculated in advance by experiments
In the case of Y exceeding step (step 31), the amount of adhered toner becomes normal and transfer blur does not easily occur, and the original amount of adhered toner is restored. In this way, even if large-size paper is passed after the small-size paper is continuously passed through the fixing device, the unfixed image is not disturbed due to fluttering of the paper, and transfer blur does not occur.

FIG. 5 shows a flowchart of the fourth embodiment. In this embodiment, in step 29 of the second embodiment, it is determined whether or not the sheet passing width is equal to or more than the reference value of 216 mm.
A decrease in the amount of toner adhesion is started (step 31). In the case of Y (step 32), in which the decrease time of the attached amount exceeds 15 seconds, the attached amount of the toner becomes normal and the transfer blur does not easily occur, and the original attached amount is returned. In this way, even if large-size paper is passed after the small-size paper is continuously passed through the fixing device, the unfixed image is not disturbed due to fluttering of the paper, and transfer blur does not occur.

[0020]

According to the present invention, as described above, an unfixed toner image is formed in a nip formed by a fixing roller having a built-in heater and a pressure roller rotatably pressed against the fixing roller. An image forming apparatus provided with a fixing device for performing heat-fusion fixing on transfer paper. The image forming apparatus waits for a predetermined time according to the sheet passing size and the number of sheets passed in one job, and then shifts to the next job. After passing large-size paper continuously, large-size paper does not flutter, unfixed images are disturbed and transfer blur does not occur, and multiple heaters, thermistors, control drivers, etc. are used. There is an effect that the structure is simple, the manufacturing is easy, and the cost is not increased.

According to the second aspect of the invention, after the fixing roller is rotated for a predetermined time in accordance with the sheet passing size and the number of sheets passed in one job, the process shifts to the next job. After continuous paper passing, even if large-size paper is passed, the paper will not flutter and the unfixed image will not be disturbed, causing transfer blurring.Moreover, it is possible to use multiple heaters, thermistors, control drivers, etc. There is an effect that the structure is simple, the manufacturing is easy, and the cost is not increased.

According to a third aspect of the present invention, when a next job is input while waiting for a predetermined time or rotating the fixing roller,
Since the amount of applied toner is changed for a predetermined time in accordance with the paper passing size of the input job, the paper flaps even when large paper is passed after continuous feeding of small paper through the fixing device. Unfixed images are not disturbed and transfer blur does not occur.
Moreover, there is an effect that a plurality of heaters, thermistors, control drivers, and the like are not used, and the structure is simple, the manufacturing is easy, and the cost is not increased.

[Brief description of the drawings]

FIG. 1 is a front view of a fixing device used in the present invention.

FIG. 2 is a flowchart according to the first embodiment of the present invention.

FIG. 3 is a flowchart of a second embodiment of the present invention.

FIG. 4 is a flowchart of a third embodiment of the present invention.

FIG. 5 is a flowchart of a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Heater 3 Pressure lever 4 Pressure roller 6 Pressing spring 7 Thermistor 8 Inlet guide plate 9 Separation claw 11 Discharge roller 12 Discharge roller

Claims (3)

[Claims] 1. A fixing device for fixing an unfixed toner image on a transfer sheet by fusing a non-fixed toner image at a nip formed by a fixing roller having a built-in heater and a pressure roller rotatably pressed against the fixing roller. In an image forming apparatus provided with
An image forming apparatus that waits for a predetermined time according to a sheet passing size and a sheet passing number of a job and shifts to a next job. 2. A fixing device for fixing an unfixed toner image to a transfer sheet by fusing a non-fixed toner image at a nip formed by a fixing roller having a built-in heater and a pressure roller rotatably pressed against the fixing roller. In an image forming apparatus provided with
An image forming apparatus comprising: rotating a fixing roller for a predetermined time according to a sheet passing size and a sheet passing number of a job; 3. When a next job is input while waiting for a predetermined time or rotating the fixing roller, the amount of toner adhered is changed for a predetermined time in accordance with the sheet passing size of the input job. The image forming apparatus according to claim 1.