JPH07191571A - Heating device and image forming device - Google Patents

Abstract

PURPOSE:To efficiently prevent the generation of the wrinkles of a material to be heated by executing preprocessing for making the temperature in the width direction of the material to be heated of a heating member uniform before the material to be heated is fed/heated, only when there is a possibility that a heating roller is thermally expanded. CONSTITUTION:The CPU of a laser printer judges whether the previously set time lapses from the previous image forming action or not and when the specified time lapses, a printing action is taken (the step 1). When the specified time does not lapse, it is judged whether the previous printing action is continued by a prescribed number of paper sheets or more or not When the previous printing action is within a prescribed number of papers, the printing action is taken (the step 2). When the pervious printing action is continued by a prescribed number of papers or more, it is judged whether the size of the paper printed in this time is larger than that in the previous time or not. When the size is smaller, it is judged that the wrinkles are not generated and the printing action is continued and when the size is larger, a prerotation is attained for a specified time in a standby state to relax the thermal deformation of the heating roller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a heater that generates heat when energized, and heats a heating member heated by the heat generated by the heater and a pressure-contact nip portion between a pressure member pressed against the heating member. The present invention relates to a heating device that feeds a material and heats it. The present invention also relates to an image forming apparatus including the heating device as an image heating and fixing device.

[0002]

2. Description of the Related Art Specific examples of the heating device described above include electrophotographic, electrostatic recording, magnetic recording in image forming apparatuses such as copiers, laser printers, facsimiles, microfilm printers, image display devices and recording machines. A recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) as an image support is formed by using a toner made of a heat-meltable resin or the like by an appropriate image forming process means such as recording. An unfixed toner image (fixed image) corresponding to the target image information formed on the surface of the recording medium by a direct method or an indirect (transfer) method is heated as a permanent image on the surface of the recording material carrying the image. An image heating and fixing device of a heat roller type for fixing processing can be mentioned.

An image heating and fixing device of this heat roller type will be described below as an example. FIG. 9 is a sectional view showing a schematic configuration of an example of the apparatus. Reference numeral 1 is a fixing roller as a heating member, and 2 is a pressure roller as a pressing member, which are vertically arranged in parallel with each other and are brought into pressure contact with a predetermined pressing force.
Both ends are rotatably supported by bearings between side plates (not shown) of the apparatus frame.

As an example of the fixing roller 1, a releasable resin layer 4 such as PFA or PTFE is provided on the outer peripheral surface of a hollow core metal 3 such as aluminum or iron, and a halogen as a heating source is provided in the hollow core metal 3. A heater 15 is inserted and provided, and a temperature detecting element 9 such as a thermistor is brought into contact with the roller surface. As an example of the pressure roller 2, a roller-shaped sponge layer 7 having heat resistance and low hardness is concentrically provided on a metal core 6 made of aluminum, iron, or the like, and a P-shaped sponge layer 7 is formed on the outer peripheral surface thereof.
The coating layer 8 is formed of a resin having a high releasability such as FA.

Reference numeral N denotes a mutual pressure contact nip portion (fixing nip portion) between the fixing roller 1 and the pressure roller 2. The fixing roller 1 is rotationally driven in the arrow direction at a predetermined peripheral speed by a drive system (not shown), and the pressure roller 2 is driven by the fixing roller 1 to rotate.

The fixing roller 1 is heated by the halogen heater 15 being energized from an energizing circuit (not shown) to generate heat, and the surface temperature of the fixing roller 1 is detected by the temperature detecting element 9. The detected temperature information is fed back to a temperature control circuit (not shown), and the energization of the halogen heater 15 by the energizing circuit is controlled so that the detected temperature output of the temperature detecting element 9 becomes a predetermined value. That is, the halogen heater 15 is used so that the surface temperature of the fixing roller 1 is maintained at a predetermined fixing temperature.
Is energized.

However, when the fixing roller 1 and the pressure roller 2 are rotating and the fixing roller 1 is temperature-controlled to a predetermined fixing temperature, the unfixed toner image 12 is fed from the image forming mechanism (not shown). Paper 13 as a material to be heated carrying paper
Is conveyed and guided by the inlet guide 14 to the fixing nip portion N which is a pressure contact portion between the fixing roller 1 and the pressure roller 2, and the fixing nip portion N is nipped and conveyed, so that the sheet at the fixing nip portion N is conveyed. The unfixed toner image 12 on 13 is fixed as a permanent image on the surface of the paper 13 by heat and pressure. Then, the sheet 13 that has undergone the image heating and fixing process exits the apparatus and is output as an image formed product (copy, print). Reference numeral 5 denotes a sheet separating claw that prevents the sheet 13 that has passed through the fixing nip portion N from being caught in the fixing roller 1.

FIG. 10 shows an example of the light distribution of the halogen heater. In order to correct heat escape from the vicinity of the opening of the fixing roller 1 in the longitudinal direction, the ratio is set to be higher than in the vicinity of the center, and when the maximum size paper is passed as the surface temperature of the fixing roller 1. , Is designed to have a uniform temperature in the longitudinal direction.

In the image forming apparatus using the heating and fixing device having the above-described structure, when a large number of sheets having a size smaller than the maximum width that can be passed are continuously passed, a sheet passing area and a sheet non-passing area As a result, a difference gradually occurs in the surface temperature of the fixing roller 1. This is because the heat carried out by the paper in the paper passing area appears as an increase in the surface temperature in the non-paper passing area. This phenomenon is more remarkable when the thickness of the fixing roller 1 is thin (when the heat capacity is small).
Due to this phenomenon, the pressure roller 2 facing the pressure contact has a difference in thermal expansion due to the surface temperature difference of the fixing roller 1, and the roller shape is distorted, which hinders sheet conveyance and causes wrinkles.

In order to solve this problem, the length of the surface of the fixing roller is conventionally increased by prolonging the time of the post-process (post-rotation) of the printing work and lowering the temperature-controlled temperature of the post-process lower than during printing. A measure is taken to alleviate the temperature difference in the direction and even the expansion of the pressure roller 2.

[0011]

However, in the above-mentioned conventional example, it is useful if the next sheet passing is performed immediately after performing a series of continuous sheet passing, but otherwise, it is a waste of energy. Also, it is disadvantageous to the device life. Further, according to experiments, it has been found that the above-mentioned trouble occurs immediately after a series of continuous paper passages when a paper of a larger size than the paper that has been passed up to then is passed.

The present invention solves the above problems and provides a heating device and an image forming apparatus which can make the surface temperature difference between the paper passing area and the non-paper passing area uniform without wasting energy. The purpose is to do.

[0013]

According to the present invention, the first object of the present invention is to provide a heating device, which has a heater that generates heat when energized, and a heating member that is heated by the heat generated by the heater, and a heating member. In a heating device that heats a material to be heated by feeding the material to be heated to a pressure contact nip portion with a pressure member that has been pressure contacted, when the material to be heated is fed and heated, the elapsed time from the end of the previous feeding and heating operation. At least one of the number of materials to be heated fed during the previous feeding and heating operation, and the size comparison result between the materials to be heated fed during the previous feeding and heating operation and the material to be heated to be fed and heated this time. One of them is achieved by selecting whether or not to perform a pretreatment for equalizing the temperatures of the heating member and the pressing member in the width direction of the material to be heated before the feeding and heating operation.

Next, the image forming apparatus has a heater that generates heat when energized, and the pressure contact nip portion between the heating member that is heated by the heat generated by the heater and the pressure member that is pressed against the heating member is covered. In an image forming apparatus equipped with a heating device for feeding a heating material to perform heat treatment, when feeding and heating the material to be heated, the elapsed time from the end of the previous feeding and heating operation, the previous feeding and heating operation At least one of the number of materials to be heated fed at this time and the size comparison between the materials to be heated fed at the previous feeding and heating operation and the material to be heated to be fed at this time is used to supply This is achieved by selecting whether or not to perform a pretreatment for equalizing the temperatures of the heating member and the pressing member in the width direction of the material to be heated before the feeding and heating operation.

[0015]

According to the present invention, it is determined that the temperature difference between the heated material passing region and the non-passing region in the heating member and the pressing member has decreased when a predetermined time has elapsed since the end of the previous feeding and heating operation. If the number of heated materials fed during the previous feeding / heating operation does not exceed the specified number, it is determined that the temperature difference is small, and the heating material fed during the previous feeding / heating operation is When the material to be heated to be fed and heated is smaller, it is judged that the above temperature difference does not pose a problem, and before the feeding and heating operation, before uniformizing the temperature of the heating member and the pressing member in the width direction of the material to be heated. Do not process. However, when at least one of the conditions is not satisfied, it is determined that the temperature difference occurs, and the pretreatment is performed. In this way, the pretreatment is performed only when there is a risk of thermal expansion due to the temperature difference, and the wrinkles of the non-heated material are efficiently prevented.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a schematic configuration of a laser printer using a transfer type electrophotographic process, which is an image forming apparatus equipped with a heat fixing device of the present invention.

In FIG. 1, reference numeral 21 is a rotary drum type OP.
It is a C photoconductor (hereinafter referred to as a photoconductor drum), and is rotationally driven in a direction of an arrow at a predetermined peripheral speed (process speed).
A charging roller 22 as a charging member is disposed in contact with the photosensitive drum 21, and the surface of the photosensitive drum 21 is
After being uniformly negatively charged by the charging roller 22, the laser scanner 23 receives a laser beam scanning exposure L of the target image information to form an electrostatic latent image. Then, the latent image is subjected to reversal development by the negative polarity toner in the developing device 24 and visualized as a toner image.

On the other hand, the paper 13 is fed one by one from the paper cassette 28 by the pickup roller 29, and the photosensitive drum 21 and the transfer roller 2 to which a positive transfer bias is applied via the paper feed roller 30 and the registration roller 31.
5 is fed to the pressure contact nip portion (transfer portion) 26 at a predetermined timing, and the photosensitive drum 21 is fed to the fed paper 13.
Side toner images are sequentially transferred.

Then, the sheet 13 to which the toner image has been transferred in this way passes through the conveyance guide 32 and passes through the fixing device 50.
When the toner image is introduced, the toner image is subjected to heat fixing processing and is output as an image formed product (print, copy).

The photosensitive drum 21 after the transfer of the toner image onto the paper 13 is cleaned by a cleaning device 27 to remove adhering residual substances such as transfer residual toner, and is subjected to repeated image formation. In the image forming apparatus according to the present exemplary embodiment, the paper 13 is fed and conveyed in the inside of the apparatus with reference to the center.

The structure of the fixing device 50 is shown in FIG.
The device shown in FIG. 10 has the same light distribution as the device shown in FIG. Temperature sensing element 9
Is arranged in the central portion (position 0).

The CPU 40 controls all of the above-described laser printers. Particularly, regarding the fixing device 50, the switch circuit 41 is controlled by the temperature of the fixing roller surface read from the temperature detecting element 9. , Controls the energization of the halogen heater 15 from the power supply 42. It also controls the rotation of the pair of fixing rollers.

Further, the CPU 40 has a clock function for counting the elapsed time from the end of the previous image forming operation, and further has a memory for storing the number of continuously passed sheets and the paper size in the previous image forming operation. The elapsed time from the end of the previous image forming operation is such that the pressure roller deformation shown in the conventional example does not cause paper wrinkles even if any image forming operation is performed in a standby state (standby state) for a certain time. It is the time to compare with the predetermined time to relax. Further, the number of continuous sheets to be passed is a number for comparison with a predetermined number of sheets to be continuously passed, which may cause deformation of the pressure roller due to temperature rise in the non-sheet passing portion.

The operation of the CPU 40 when it receives an image forming operation request (print signal reception) will be described below with reference to the flow chart shown in FIG. First, in Step 1,
It is determined whether or not a predetermined time period has elapsed since the previous image forming operation (print operation). If the predetermined time period has elapsed, wrinkles do not occur, so the process directly proceeds to the print operation. However, if the predetermined time has not elapsed, the process proceeds to Step 2, and it is determined whether the previous print operation has continued for a predetermined number of sheets or more by comparing with the memory for the number of continuously passed sheets. If the wrinkles do not continue for the predetermined number of sheets or more, the wrinkles do not occur, and the process proceeds to the printing operation. On the other hand, if the number of sheets exceeds the predetermined number, the process proceeds to Step 3 and it is determined whether the paper size to be printed this time is larger than the previously used paper size. If it is small, it means that wrinkles do not occur, so the process proceeds to the printing operation, but if it is large, S
Proceed to step 4 to perform a print pre-processing routine.

In the print pre-processing routine Step 100, the pre-rotation is repeated for a predetermined time in the standby state to alleviate the thermal deformation of the pressure roller 2. By proceeding to the printing operation, wrinkles are prevented.

(Experimental Example) The core metal 3 of the fixing roller 1 has a thickness of 2
mm aluminum, 50 μm thick on the surface
The PFA tube 4 of is covered with an outer diameter of 30 mm and a length of 2
A 40 mm fixing roller 1 was formed. As the pressure roller 2, a foamed silicone rubber layer 7 having a thickness of 7 mm is concentrically integrated with a stainless steel core 6 in a roller shape, and the surface thereof is covered with a PFA tube 8 having a thickness of 30 μm. The outer diameter and the length were substantially the same. The hardness of the pressure roller 2 was 50 degrees according to ASKER-C.

The total pressure of the fixing roller 1 and the pressure roller 2 is 10 k.
The contact was made with g, and a nip portion N having a width of about 4 mm was formed.
The halogen heater 15 was rated at 750 W, and the temperature control temperature was 180 ° C. for standby temperature control and 190 ° C. for print temperature control.

The process speed is 95 mm / se.
c. Under the above-described conditions, first, the conditions under which the pressure roller 2 is deformed due to the temperature rise in the non-sheet passing portion due to the continuous passing of the small size and the wrinkles occur immediately after the passing of the large size are searched. At this time, A5 vertical feed was used as the small size, and A4 vertical feed was used as the large size. As a result, it was found that wrinkles occurred when 30 or more sheets were continuously fed.

Next, when the standby state is continued in the state where the wrinkles are generated, it is examined as to how long time has elapsed, the deformation of the pressure roller 2 is alleviated and the state where the wrinkles are not generated is reached. I knew that I should do it.

Further, when the standby temperature was adjusted and the fixing roller pair was rotated in the state where the wrinkle occurred, the time until the wrinkle did not occur was examined, and it was found that 10 seconds or more should pass. In this case, it is considered that the heat relaxation of the pressure roller 2 is promoted by rotating the pressure roller 2 rather than simply being in the standby state.

From the above results, the parameters which are the judgment criteria in the flow chart shown in FIG. 2 are set as follows in consideration of the safety side.

Predetermined time in Step 1; 25 seconds Predetermined number of sheets in Step 2; 25 sheets Predetermined time in Step 100; 12 seconds

It is needless to say that when this embodiment was carried out using the above parameters, good results regarding wrinkles were obtained. In the present embodiment, the Ste
The order of p1, Step2, and Step3 need not be in this order, and it is not necessary to perform all Steps, and there may be omitted Steps.

Further, in this embodiment, the standby temperature control state is set as the standby state for waiting for printing, but a so-called sleep state in which the temperature control is off may be set. This can be dealt with by changing the parameter.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is the same as Embodiment 1 except that Step 200 shown in FIG. 3 is executed instead of the print preprocessing routine Step 100 shown in Embodiment 1 above.

In this embodiment, the print temperature is adjusted as the pre-printing process, and the pre-printing process is repeated for a predetermined number of times. As a result, the temperature ripple that accompanies the rise of the temperature control from the standby state can be used to alleviate the thermal deformation of the pressure roller 2, so that the pre-printing processing time can be shortened compared to the first embodiment.

(Experimental Example) Under the conditions used in Experimental Example 1, when the print temperature was adjusted under the condition that wrinkles were generated and the fixing roller pair was rotated, the time until the occurrence of wrinkles was examined. It turned out that it would be good if seven seconds or more passed.

From the above results, 9 seconds was set as the predetermined time which is the judgment criterion in the flowchart shown in FIG. When this example was carried out using this, good results regarding wrinkles were obtained.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, instead of the preprocessing routine Step 100 shown in the first embodiment, the Step shown in FIG.
The procedure is the same as in Example 1 except that step 300 is performed.

In this embodiment, as a pre-printing process, a standby state is waited for a predetermined time. This is Example 1
As shown in, it is known that wrinkles do not occur due to thermal relaxation of the pressure roller 2 after a predetermined time even in the standby state. Therefore, in Step 300,
The standby time is set to the time obtained by subtracting the elapsed time up to the present time from the predetermined time shown in Step 1 of the first embodiment. This will not cause wrinkles.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 5 shows an example in which a heat fixing device 51 having two halogen heaters 16 and 17 is used instead of the heat fixing device used in the laser printer shown in FIG.

In the figure, 43 and 44 are halogen heaters 16 and 1, respectively.
7 is a switch circuit for controlling energization to 7. The same numbers are the same as above. In addition, this embodiment also uses paper 13.
Are fed and transported in the device on a central basis.

The halogen heaters 16 and 17 have the light distribution shown in FIG. 6, and the temperature detecting element 9 is arranged in the central portion (position 0). Such a halogen heater 1
By blinking 6 and 17 as appropriate, it is possible to reduce the temperature rise in the non-sheet-passing area even when paper of various sizes is passed.
Wrinkles due to deformation of the pressure roller can be reduced, but it is not perfect. Therefore, the application of the present invention is effective. Further, when the heat capacity of the fixing roller is reduced to reduce the thickness, the effect becomes remarkable.

FIG. 7 is a diagram showing a lighting cycle of the halogen heaters 16 and 17. Depending on the size of the paper, t0,
Set t1, t2, t3 to appropriate values.

The present embodiment is the same as the first embodiment except that Step 400 shown in FIG. 8 is executed instead of the print preprocessing routine Step 100 shown in the first embodiment. In Step 400, as pre-printing processing, multiple rotations are performed for a predetermined time while the print temperature is adjusted at a lighting ratio according to the previously printed size. This allows
It is possible to compensate for the degree of heating at the non-sheet passing portion and the sheet passing portion in the previous printing operation, and it is possible to reduce thermal deformation of the pressure roller.

(Experimental Example) The core metal 3 of the fixing roller has a thickness of 0.
9mm aluminum, halogen heaters 16, 1
7 is the same as the experimental example of Example 1 except that the ratings of No. 7 are 400 W and 350 W, respectively. At this time, the lighting ratio of the halogen heater depending on the paper size was set as shown in Table 1.

[0051]

[Table 1]

Under the above conditions, the pressure roller 2 is deformed due to the temperature rise of the non-sheet passing portion due to the continuous feeding of the small size (A5 size), and the wrinkles are generated after the passing of the large size (A4 size). I searched. As a result, it was found that wrinkles occurred when 50 or more sheets were continuously fed.

Next, when the standby state was continued in the state where the wrinkles were generated, it was examined how long time passed before the deformation of the pressure roller 2 was alleviated and the wrinkles were not generated. As a result, it was found that 20 seconds or more should pass.

Further, when the wrinkle is not generated and the time before the wrinkle is generated when the fixing roller pair is rotated while lighting in the A5 paper mode in the state where the wrinkle is generated, it is found that 5 seconds or more may be elapsed. . From the above results, the parameters that are the judgment criteria in the flowcharts shown in FIGS. 2 and 8 are set as follows in consideration of the safety side.

Predetermined time in Step 1; 25 seconds Predetermined number of sheets in Step 2; 60 sheets Predetermined time in Step 400; 7 seconds

Needless to say, when the present embodiment was carried out using the above parameters, good results were obtained regarding wrinkles. Further, in the present embodiment, the lighting mode in the previous printing is selected as the lighting mode in the pre-printing process, but the present invention is not limited to this, and it is possible to extend two halogen heaters at various ratios. There is a nature.

[0057]

As described above, according to the present invention,
Paper wrinkles caused by thermal deformation of the pressure roller due to small-sized continuous paper passage can be easily prevented without increasing the cost. Further, it is more effective that the wrinkle prevention sequence is not always performed even when it is not necessary as in the conventional example.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a laser printer according to first to third embodiments of the present invention.

FIG. 2 is a flowchart illustrating processing before starting a printing operation according to the first exemplary embodiment of the present invention.

FIG. 3 is a flowchart illustrating pre-processing in Example 2 of the present invention.

FIG. 4 is a flowchart illustrating pre-processing in Example 3 of the present invention.

FIG. 5 is a schematic configuration diagram of a laser printer to which a fourth embodiment of the present invention is applied.

FIG. 6 is a diagram showing a light distribution of a halogen heater in Example 4 of the present invention.

FIG. 7 is a diagram showing a method for lighting a halogen heater according to a fourth embodiment of the present invention.

FIG. 8 is a flowchart illustrating pre-processing in Example 4 of the present invention.

FIG. 9 is a sectional view of a conventional heat fixing device.

10 is a diagram showing a light distribution of a halogen heater mounted in the heat fixing device of FIG.

[Explanation of symbols]

 1 Fixing film (heating member) 2 Pressure roller (pressure member) 13 Recording material (non-heating material) 15,16,17 Halogen heater

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroto Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Minoru Matsukuma 3-30-2 Shimomaruko, Ota-ku, Tokyo Kyano (72) Inventor Hiroaki Sakai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kazuro Ono 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yasunari Obara, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (8)

[Claims] 1. A heating member having a heater that generates heat when energized is supplied to a heating nip portion between a heating member that is heated by the heat generation of the heater and a pressing member that is pressed against the heating member. When heating and heating the material to be heated in a heating device for heat treatment, the elapsed time from the end of the previous feeding and heating operation, the number of materials to be heated fed during the previous feeding and heating operation, the previous feeding At least one of the comparison results of the sizes of the material to be heated fed during the feeding and heating operation and the material to be heated to be fed and heated this time is used, and at least one of them is used to cover the heating member and the pressing member before the feeding and heating operation. A heating device, characterized in that it is selected whether or not to perform a pretreatment for equalizing the temperature in the width direction of the heating material. 2. The heating device according to claim 1, wherein the pretreatment is a treatment for holding a standby state for a predetermined time. 3. The heating device according to claim 2, wherein the standby state involves heating. 4. The heating apparatus according to claim 1, wherein the pretreatment is a feeding heating operation treatment that does not involve a material to be heated. 5. A material to be heated is fed to a pressure contact nip portion between a heating member heated by the heat generation of the heater and a pressure member pressed against the heating member. In an image forming apparatus equipped with a heating device for heat treatment, when feeding and heating the material to be heated, the time elapsed from the end of the last feeding and heating operation, the material to be heated fed at the last feeding and heating operation Number of sheets, and the result of comparison of the size of the heated material fed during the previous feeding and heating operation and the size of the heated material to be fed and heated this time, using at least one of the And an image forming apparatus for selecting whether or not to perform a pretreatment for equalizing the temperature of the pressure member in the width direction of the material to be heated. 6. The image forming apparatus according to claim 5, wherein the pre-processing is processing for holding a standby state for a predetermined time. 7. The image forming apparatus according to claim 6, wherein the standby state involves heating. 8. The image forming apparatus according to claim 5, wherein the pre-processing is a feeding heating operation processing with a material to be heated.