JP2009048074A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of appropriately preventing overshoot of the temperature of a fixing member by varying rotating time or rotating speed in turn-off rotation of the fixing member after printing operation to be performed according to a condition in the printing operation in order to prevent the overshoot of the temperature of the fixing member after finishing the printing operation, and an image forming apparatus. <P>SOLUTION: The fixing device which thermally fixes an unfixed toner image on a recording medium conveyed to a fixing nip between the fixing member having a fixing heat source inside and a pressure member pressing the fixing member on the recording medium is equipped with a rotating time change control circuit 30 changing time to rotate the fixing member after turning off the fixing heat source of the fixing member after finishing the printing operation. The rotating time change control circuit 30 changes turn-off rotation time after the printing operation according to the condition in the printing operation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device that heats a fixing member with a fixing heat source, contacts the fixing member with the image surface of the recording medium, and fuses the toner image on the image surface to fix the image on the recording medium. The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof.

2. Description of the Related Art Conventionally, in image forming apparatuses such as printers, copiers, and facsimiles, a toner image formed on a recording medium such as transfer paper, recording material, or paper is heated and melted and pressed to fix the toner image. It is known to use a fixing device.
Generally, a fixing device that fixes an electrophotographic image formed as a toner image on a recording medium supplies electric power to a heater that is a fixing heat source to generate heat in fixing members such as a fixing roller and a fixing belt. Then, the toner image is heated and melted and fixed on the recording medium.
In such a fixing device, in order to make the fixing temperature constant while fixing the electrophotographic image on the recording medium, power is supplied to the heater and the temperature is raised to a predetermined temperature (target control temperature). The fixing state is set, and the recording medium is passed through the fixing device while maintaining the predetermined fixing temperature.
In recent years, a medium having a small heat capacity, such as a thin roller or a fixing belt, has been used for the fixing member from the viewpoint of shortening the temperature rise time (warm-up time) to a fixing enabled state and reducing power consumption. It is getting more.
In the case of such a small heat capacity configuration, the temperature is likely to fluctuate due to the property of being easily heated and cooled, and abnormal temperature rise of the fixing member with respect to the target control temperature, that is, overshoot (hereinafter simply referred to as overshoot) is likely to occur. Can be mentioned.
When such an overshoot occurs, the fixing member temperature becomes high, so that it deteriorates or breaks, or the fixing member temperature is not stable with respect to the target control temperature, so that the image quality after fixing is not stable. There are concerns.

From the above, it is necessary to prevent overshoot by some means. Next, conditions for which overshoot is likely to occur will be described. There are various situations in which overshoot occurs, but it is known that the fixing member that was rotating during the printing operation is likely to occur when the rotation is stopped after the printing operation is completed.
One reason for this is to supply a large amount of power to the heat source to heat the fixing member in order to melt the toner image on the recording medium during the printing operation. On the other hand, less power is required after the printing operation is completed, but even if the temperature controller issues a command to reduce the power supplied to the heat source after the printing operation is completed, the power supply to the heat source and the temperature change of the fixing member Since there is a response delay and is not reflected immediately, the temperature rises after the end of the printing operation.
As another cause, the fixing member rotates during the printing operation, and the amount of heat from the heat source is widely supplied onto the fixing member and the opposing pressure member. Further, electric power is supplied to the heat source by a balance between the amount of heat taken by the recording medium from the fixing member and the amount of heat necessary for maintaining the temperature on the fixing member at the target control temperature. However, since the amount of heat from the heat source is concentrated in a local portion near the heat source due to the stop of the rotation, the temperature of the fixing member in the vicinity of the heat source rapidly increases.
Several techniques have been proposed in the past in order to avoid a temperature rise after the end of the printing operation due to a delay in response to the power supply to the heat source and the temperature change of the fixing member, and a sudden rise in the temperature of the fixing member near the heat source. (For example, see Patent Documents 1 and 2).
In Patent Document 1, the problem of response delay is avoided by turning off the heat source a predetermined time before the time when the trailing edge of the final recording medium in a series of jobs passes through the fixing position.
In Patent Document 2, the temperature rise after the end of the printing operation is avoided by rotating the fixing member while the power supply to the heat source is stopped for a certain time after the end of the printing operation.
JP 2003-76189 A JP-A-6-149122

However, the solution of only Patent Document 1 has a limit in suppressing overshoot. In the technique of Patent Document 2, the time for which the turn-off rotation after the printing operation is continued and the rotation speed are a single value set in advance.
However, the amount of overshoot after the printing operation depends on the conditions during the printing operation because the power supplied to the fixing heat source required during printing varies depending on the conditions during the printing operation (number of sheets passed, thickness of the recording medium, etc.). It depends on.
Further, in the prior art, for example, an appropriate turn-off rotation time after a printing operation or a turn-off rotation speed after a printing operation is set under the condition that the overshoot becomes the largest (condition that the power required for the printing operation is large), It is applied uniformly in all conditions.
Therefore, under conditions where the overshoot is small (conditions where the power required during the printing operation is small), the turn-off rotation is performed after the printing operation at a time and speed more than necessary, and the temperature may drop too much after the printing operation. It was. Further, it has become a factor for shortening the life of the fixing member as the rotational speed increases.
Accordingly, an object of the present invention is to take into consideration the above-described circumstances, and to prevent the overshooting of the temperature of the fixing member after the printing operation is completed, the rotation time or the rotational speed of the turning-off rotation of the fixing member after the printing operation is performed. It is an object of the present invention to provide a fixing device and an image forming apparatus that appropriately prevent overshooting of the temperature of the fixing member by making this variable according to conditions during the printing operation.

In order to solve the above problems, the invention described in claim 1 includes a fixing member having a fixing heat source therein, and a pressure member that presses the fixing member, and the fixing member and the pressure member In a fixing device for thermally fixing an unfixed toner image on a recording medium conveyed to the fixing nip to the recording medium, the power supply to the fixing heat source is turned off after the printing operation is completed, and the fixing member is rotated. A rotation time change control circuit for changing the power supply off rotation time is provided, and the rotation time change control circuit is characterized by a fixing device that changes the power supply off rotation time according to a condition during a printing operation.
The invention according to claim 2 is characterized in that the rotation time change control circuit changes the power supply off rotation time after the printing operation of the fixing member according to the number of printed sheets. And

According to a third aspect of the present invention, the rotation time change control circuit sets the power supply off rotation time after the printing operation set by the number of printed sheets according to the thickness of the recording medium during the printing operation. The fixing device according to claim 2, wherein correction is performed.
According to a fourth aspect of the present invention, the rotation time change control circuit corrects the power supply off rotation time after the printing operation determined by the number of printed sheets according to the temperature of the environment during the printing operation. A fixing device according to claim 2 is characterized.
According to a fifth aspect of the present invention, the rotation time change control circuit sets the power supply off rotation time after the printing operation determined by the number of printed sheets according to a set temperature of the fixing member during the printing operation. The fixing device according to claim 2, wherein the fixing device is corrected.
According to a sixth aspect of the present invention, there is provided a fixing unit in which a toner image formed on a recording medium is thermally fixed on the recording medium by a fixing member having a fixing heat source therein and a pressure member that presses the fixing member. The apparatus includes a rotation speed change control circuit that changes a cutting rotation speed for turning off the power supply to the fixing heat source and rotating the fixing member after the printing operation is finished, and the power supply off rotation speed is set at the time of the printing operation. It features a fixing device that changes according to conditions.

According to a seventh aspect of the invention, there is provided the fixing device according to the sixth aspect, wherein the rotation speed change control circuit changes the power supply off rotation speed after the printing operation according to the number of printed sheets.
Further, in the invention according to claim 8, the rotation speed change control circuit determines the power supply off rotation speed after the printing operation determined by the number of printed sheets according to the thickness of the recording medium at the time of the printing operation. The fixing device according to claim 6 is corrected.
According to a ninth aspect of the present invention, the rotational speed change control circuit corrects the power supply off rotational speed after the printing operation determined by the number of printed sheets according to the temperature of the environment during the printing operation. A fixing device according to claim 6 is characterized.

According to a tenth aspect of the present invention, the rotation speed change control circuit determines the rotation speed of the power supply off after the printing operation determined by the number of printed sheets according to a set temperature of the fixing member during the printing operation. The fixing device according to claim 6, wherein the fixing device is corrected.
According to an eleventh aspect of the present invention, there is provided a detection mechanism capable of detecting the timing when the recording medium passes through the fixing nip, and the amount of heat supplied from the fixing heat source to the fixing member is increased from the time when the timing is detected. The fixing during a printing operation is performed using feed forward control that supplies a reduced amount of heat supplied from the fixing heat source to the fixing member before the trailing edge of the recording medium passes through the fixing nip. The fixing device according to claim 1, wherein the fixing heat source of the member is controlled.
According to a twelfth aspect of the present invention, the electrostatic latent image formed on the image carrier is visualized by developing with toner, the toner image is transferred onto a recording medium, and the toner image on the recording medium is transferred. An image forming apparatus for fixing the toner image on the recording medium by heat and pressure, wherein the fixing apparatus according to any one of claims 1 to 11 is mounted as the fixing apparatus for fixing the toner image on the recording medium. Features a forming device.

  According to the present invention, it is possible to prevent deterioration and breakage of the fixing member as a result of suppressing overshoot, and it is also possible to stabilize the image quality after fixing by stabilizing the temperature. Furthermore, the life of the fixing member can be improved by optimizing the turn-off rotation time or speed of the fixing member and eliminating unnecessary rotation.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing an overall configuration of an internal mechanism of an image forming apparatus to which a fixing device according to the present invention can be applied.
The image forming apparatus A shown in FIG. 1 employs an electrophotographic system, and is configured by installing an image reading device 2 above the image forming apparatus main body 1 and attaching a duplex unit 3 on the right side.
An intermediate transfer device 4 is provided in the image forming apparatus main body 1. The intermediate transfer device 4 includes an endless intermediate transfer belt 5 that is stretched around a plurality of rollers. The intermediate transfer belt 5 is stretched almost horizontally in the image forming apparatus main body 1 so as to run counterclockwise. Provided.
Under the intermediate transfer device 4, cyan, magenta, yellow, and black image forming devices 12 c, 12 m, 12 y, and 12 k are arranged in a quadruple tandem manner along the stretch direction of the intermediate transfer belt 5.
Each of the image forming devices 12c, 12m, 12y, and 12k includes a charging device, a developing device, a transfer device, and the like around a photosensitive drum 6c, 6m, 6y, and 6k that is a drum-shaped image carrier that rotates clockwise in the drawing. Install and configure a cleaning device. An exposure device 7 is provided below the image forming devices 12c, 12m, 12y, and 12k.

A sheet feeding device 8 is provided below the exposure device 7. The paper feeding device 8 is provided with a paper feeding cassette 9 (in this embodiment, two stages) that stores recording media (paper) P. At the upper right of each paper feed cassette 9, there is provided a paper feed roller 11 that feeds out the recording medium P, which is a recording material in each paper feed cassette 9, one by one and puts it into the recording medium transport path 10.
The recording medium conveyance path 10 is formed on the right side in the image forming apparatus main body 1 from the lower side to the upper side, and leads to the in-body paper discharge unit 14 formed between the image reading apparatus 2 and the image forming apparatus main body 1. It is provided to communicate.
On the recording medium conveyance path 10, there are formed a registration roller (conveyance roller) 15, a secondary transfer device 16 facing the intermediate transfer belt 5, a fixing device 17, and a paper discharge device 18 including a pair of paper discharge rollers. They are provided in order from the bottom to the top on the right side in the apparatus body 1.
Upstream of the registration roller 15, a sheet feeding path 20 that re-feeds from the duplex unit 3 or manually feeds from the manual sheet feeding device 19 across the duplex unit 3 to the recording medium transport path 10. Is provided. In addition, a refeed conveyance path 22 to the duplex unit 3 is branched downstream of the fixing device 17.

In such a configuration, when taking a copy, the image reading device 2 reads the original image and writes it with the exposure device 7, and the photosensitive drums that are the respective image carriers of the image forming devices 12c, 12m, 12y, and 12k. Each color toner image is formed on 6c, 6m, 6y, and 6k, and the toner image is sequentially transferred by primary transfer devices 21c, 21m, 21y, and 21k to form a color image on the intermediate transfer belt 5.
On the other hand, one of the paper feeding rollers 11 is selectively rotated to feed the recording medium P from the corresponding paper feeding cassette 9 into the recording medium conveyance path 10 or manually from the manual paper feeding device 19. P is put into the paper feed path 20.
The recording medium P is conveyed by the registration roller 15 through the recording medium conveying path 10 and sent to the secondary transfer position in a timely manner, and the color image formed on the intermediate transfer belt 5 as described above is transferred by the secondary transfer device 16. Transfer to the recording medium P. The recording medium P after the image transfer is fixed by the fixing device 17, discharged by the paper discharge device 18, and stacked on the in-body paper discharge unit 14.
When an image is also formed on the back side of the recording medium P, it is placed in the refeed conveyance path 22, reversed by the duplex unit 3, then fed again through the feed path 20, and separately formed on the intermediate transfer belt 5. After the image is secondarily transferred to the recording medium P, the image is fixed again by the fixing device 17 and discharged to the in-body discharge portion 14 by the discharge device 18.

FIG. 2 is a schematic diagram showing the configuration of the fixing device according to the present invention. The fixing device 17 according to the present invention includes a fixing roller 23 that is a roller-shaped fixing member and a pressure roller 24 that is a roller-shaped pressing member.
Of these rollers 23 and 24, the rotation shaft of one roller (for example, fixing roller 23) is fixed, and the rotation shaft of the other roller (for example, pressure roller 24) is movable.
The other roller (for example, pressure roller 24) is supported so as to be able to come into contact with and separate from one roller (for example, fixing roller 23), and the other roller (for example, pressure roller 24) is not shown. Is biased toward one of the rollers (for example, the fixing roller 23) by a spring or other elastic member.
A fixing nip n is formed between the fixing roller 23 and the pressure roller 24. A fixing heat source 25 is built in the fixing roller 23, and the fixing roller 23 is heated by the fixing heat source 25.
In this embodiment, a heater such as a halogen heater or a carbon heater is used as the fixing heat source 25. However, the heater is not limited to a heater, and for example, a heat source that generates heat using electromagnetic induction may be used. Good.

In the present embodiment, as the temperature detecting means, the fixing roller 23 is provided with a temperature detecting means 26 for detecting the temperature of the fixing roller 23 in close proximity, and the temperature detecting means 26 detects the temperature of the fixing roller 23. taking measurement.
The temperature controller 27 passes through the PWM drive circuit 28 based on the information on the temperature deviation between the target control temperature designated in advance and the temperature of the fixing roller 23 detected by the temperature detecting means 26, and the fixing power source 25 of the fixing roller 23. The power applied to is controlled.
In the illustrated fixing device 17, a fixing roller 23 is heated by a fixing heat source 25, and the fixing roller 23 contacts an image surface of a recording medium passing through a fixing nip n between the fixing roller 23 and the pressure roller 24. The toner image on the image surface is melted by heat from the fixing roller 23 to be fixed on the recording medium.

FIG. 3 is a timing chart showing the state transition of the operation of the fixing device together with the transition of the fixing roller temperature in a general usage method. FIG. 3 shows the state of operation of the fixing device 17 (FIG. 2), which is changed in a general usage method, together with the temperature change of the fixing roller 23.
2 and 3, in the start-up state, the temperature is raised while the fixing roller 23 and the pressure roller 24 are rotated, and the printable state is obtained. If there is no print request from the user at this point, the rotation of the fixing roller 23 and the pressure roller 24 is stopped in a standby state.
In this standby state, the temperature of the fixing roller 23 is maintained at a constant temperature so that the printing operation can be immediately started when a printing request is received. When a print request is received from the user, the rotation is started and the printing operation is performed. After the printing is finished, the rotation is stopped, and the state again enters the standby state.

FIG. 4 is a timing chart showing the difference in overshoot amount depending on whether or not the turn-off rotation is performed after the printing operation. As shown in FIG. 4, when the fixing roller 23 is turned off after the printing operation, an overshoot of the temperature of the fixing roller 23 when the printing state is shifted to the standby state can be prevented.
FIG. 4 shows a comparison of the magnitude of the overshoot of the temperature of the fixing roller 23 as a fixing member when the turning-off rotation of the fixing roller 23 is performed after paper passing and when it is not performed. By performing the turn-off rotation after the printing operation, the overshoot can be reduced.

表１には、印刷枚数と印刷動作後の消灯回転時間を予め関連付けて纏めて示している。 FIG. 5 is a block diagram showing an outline of a rotation time change control circuit for changing the turn-off rotation time after the fixing roller print operation. In FIG. 5, the rotation time change control circuit 30 includes a rotation time setting unit 31, a correction unit 32, a control unit 33, and a printing operation condition input unit 34.
Hereinafter, means for appropriately adjusting the overshoot amount by changing the rotation time of the turning-off rotation of the fixing roller after the printing operation according to the conditions during the printing operation will be described. For example, in the fixing device 17 shown in FIG. 2, after the printing operation is completed, the power supply to the fixing heat source 25 of the fixing roller 23 is turned off (extinguishes), and then the time for rotating the fixing roller 23 (hereinafter, the extinction after the printing operation ( Power supply off) Rotation time) is changed according to the conditions during printing operation.
As an example, in response to a print request from the user, the number of printed sheets is counted by the printing operation condition input unit 34 in FIG. 5 and corrected by the control means 33 and the correcting unit 32 according to the counted number of printed sheets to set the rotation time. In part 31, the turn-off rotation time after the printing operation is determined.
However, in the present invention, the determination method of the turn-off rotation time after the printing operation is referred to the table of the number of printed pages and the turn-off (power supply off) rotation time after the printing operation as shown in Table 1 in advance. This is determined by operating the rotation time change control circuit 30.
[Table 1]

Table 1 collectively shows the number of printed sheets and the turn-off rotation time after the printing operation in association with each other.

FIG. 6 is a timing chart showing a comparison result of the overshoot of the temperature of the fixing roller when the turn-off rotation time after the printing operation is a constant value and when it is variable depending on the number of printed sheets.
In FIG. 6A, the overshoot of the temperature of the fixing roller 23 when the turn-off rotation time after the printing operation is set to a constant value is shown in FIG. The overshoot of the temperature of the fixing roller 23 is shown as a comparison result.

Referring to FIGS. 2 and 6, as shown by a solid line in FIG. 6A, the conventional method is optimized in advance when, for example, the number of printed sheets is large (300 in the figure). The turn-off rotation time t1 after the printing operation is uniformly used. For this reason, when the number of printed sheets is small (10 sheets in the figure), the turn-off rotation time t1 of the fixing roller 23 after the printing operation is too long.
For this reason, after the rotation is completed, it takes a long time until the temperature of the fixing roller 23 (FIG. 2) decreases too much and then reaches the standby target temperature. Therefore, when a user issues a print command in succession, printing cannot be performed immediately, causing a waiting time.
On the other hand, when the turn-off rotation time of the fixing roller 23 after the printing operation is variable according to the number of printed sheets as in the present invention, the rotation is performed at the turn-off rotation time t1 when the number of printed sheets is 300 sheets. Since it rotates at t2 when there are 10 sheets, overshoot can be appropriately prevented according to the number of printed sheets, as shown by the broken line in FIG.
In this embodiment, an example of association between the number of printed sheets by the table and the turn-off rotation time after the printing operation is shown. However, the relationship between the two may be described by an experimentally obtained mathematical expression. Absent.
In the fixing device according to the present invention, the turn-off rotation time after the printing operation determined by the number of prints described above can be set to be corrected according to the thickness of the recording medium at the time of the printing operation.

印刷動作後の消灯回転時間を補正するために用いる、記録媒体の厚さ（坪量）に対する重み係数を示している。
例えば、印刷枚数が６０枚、記録媒体の坪量が９０ｇ／ｍ^２の場合は、印刷動作後消灯回転時間ｔは、
ｔ＝２．０×１．２＝２．４［ｓ］
となる。
このように、図５の回転時間変更制御回路３０の印刷動作条件入力部３４に表２の重み計数を含む記録媒体の厚さを入力し、記録媒体の厚さを測定し、厚さに応じて、制御手段３３及び補正部３２で印刷動作後の消灯回転時間を補正することにより、印刷動作後のオーバーシュート量を最適化することが可能となる。 Hereinafter, the correction procedure will be described. First, the printing operation condition input unit 34 in FIG. 5 determines the thickness of the recording medium. The thickness can be determined by physical measurement using a micro displacement sensor or the like. If the type of recording medium (paper) to be used is known in advance, the user inputs the thickness of the recording medium. You may keep it.
Next, a procedure for correcting the turn-off rotation time after the printing operation according to the thickness of the recording medium will be described. As the recording medium is thicker, more electric power is required to be input to the fixing heat source 25 (FIG. 2) during the printing operation. Therefore, as described above, the temperature overshoot of the fixing roller 23 after the printing operation increases.
As the thickness of the recording medium, a basis weight or a continuous amount is often used as a unit indicating the thickness. Therefore, in the present embodiment, the thickness of the recording medium at the time of printing is expressed by basis weight (g / m ² ), and the thickness of the recording medium is weighted as shown in Table 2, and the number of printed sheets in Table 1 is calculated. The turn-off rotation time after the printing operation is determined by multiplying the determined turn-off rotation time of the fixing roller 23 after the printing operation by a weight.
[Table 2]

The weighting coefficient with respect to the thickness (basis weight) of the recording medium used for correcting the turn-off rotation time after the printing operation is shown.
For example, when the number of printed sheets is 60 and the basis weight of the recording medium is 90 g / m ² , the turn-off rotation time t after the printing operation is
t = 2.0 × 1.2 = 2.4 [s]
It becomes.
As described above, the thickness of the recording medium including the weighting factor in Table 2 is input to the printing operation condition input unit 34 of the rotation time change control circuit 30 in FIG. 5, the thickness of the recording medium is measured, and according to the thickness. Thus, the amount of overshoot after the printing operation can be optimized by correcting the turn-off rotation time after the printing operation by the control means 33 and the correction unit 32.

表３には、印刷動作後消灯回転時間を補正するために用いる、環境温度に対する重み係数を示している。
例えば、印刷枚数が１２０枚、環境温度が２０℃であった場合は、印刷動作後の消灯回転時間ｔは、
ｔ＝ ４．０×２．５＝１０．０［ｓ］
となる。
以上のように、印刷動作時の環境温度を考慮し、印刷動作後のオーバーシュート量を最適化することができる。 In the fixing device according to the present invention, the turn-off rotation time after the printing operation determined by the number of prints described above is input to the printing operation condition input unit 34 of the rotation time change control circuit 30 as the environmental temperature, and the printing operation is performed. Correct according to the ambient temperature. Hereinafter, the correction procedure will be described.
First, the temperature of the environment is measured. In general, a temperature / humidity sensor or the like is often attached to an image forming apparatus. Therefore, they may be used, or a temperature sensor may be separately attached for the present invention. They may be input to the printing operation condition input unit 34 of the rotation time change control circuit 30.
Next, a procedure for correcting the turn-off rotation time after the printing operation based on the measured environmental temperature will be described. When the temperature of the environment is low, the temperature of the recording medium is also low, and a large amount of electric power is required to be input to the fixing heat source 25 (FIG. 2) during the printing operation. For this reason, as described above, the temperature overshoot of the fixing roller 23 (FIG. 2) after the printing operation increases.
Therefore, the environmental temperature at the time of printing is weighted as shown in Table 3, and the post-printing turn-off rotation time determined from the number of printed sheets shown in Table 1 is multiplied by the weighting coefficient to obtain the post-printing operation. Determine the turn-off rotation time of.
[Table 3]

Table 3 shows weighting factors for the environmental temperature used for correcting the turn-off rotation time after the printing operation.
For example, when the number of printed sheets is 120 and the environmental temperature is 20 ° C., the turn-off rotation time t after the printing operation is
t = 4.0 × 2.5 = 10.0 [s]
It becomes.
As described above, the amount of overshoot after the printing operation can be optimized in consideration of the environmental temperature during the printing operation.

表４には、印刷動作後の消灯回転時間を補正するために用いる、定着ローラ２３の設定温度に対する重み係数を示している。
例えば、印刷枚数が３０枚、定着ローラ２３の目標制御温度が１６０℃であった場合は、印刷動作後の消灯回転時間ｔは、
ｔ＝１．０×３．０＝３．０［ｓ］
となる。
以上のように、印刷時の定着ローラ２３の設定温度を考慮することで、印刷動作後のオーバーシュート量をさらに最適化することができる。
一般には、定着ローラ２３の設定温度は、記録媒体の厚さ、環境の温度などを考慮して予め決定されているため、表４の重み係数には、表２、表３に示した、記録媒体の厚さ及び、環境の温度の重み情報が含まれていると考えられる。
しかし、必要に応じて、記録媒体の厚さ、環境の温度、定着ローラ２３の印刷動作時の設定温度の情報を併用して（つまり、表２、表３、表４の重み係数を併用して、）印刷動作後の消灯回転時間を補正してもよい。 Further, in the fixing device according to the present invention, the turn-off rotation time after the printing operation determined by the number of printed sheets described above is corrected according to the set temperature (target control temperature) of the fixing roller 23 (FIG. 2) during the printing operation. . When the set temperature of the fixing roller 23 during the printing operation is high, the maximum overshoot reaching point after the printing operation is also high because the temperature is high during the printing operation.
Therefore, the set temperature of the fixing roller 23 during the printing operation is weighted as shown in Table 4, and the weighting is multiplied with the turn-off rotation time after the printing operation determined from the number of printed sheets in Table 1. Thus, the rotation time change control circuit 30 determines the turn-off rotation time after the printing operation.
[Table 4]

Table 4 shows weighting factors for the set temperature of the fixing roller 23 used for correcting the turn-off rotation time after the printing operation.
For example, when the number of printed sheets is 30 and the target control temperature of the fixing roller 23 is 160 ° C., the turn-off rotation time t after the printing operation is
t = 1.0 × 3.0 = 3.0 [s]
It becomes.
As described above, the amount of overshoot after the printing operation can be further optimized by considering the set temperature of the fixing roller 23 during printing.
In general, since the set temperature of the fixing roller 23 is determined in advance in consideration of the thickness of the recording medium, the temperature of the environment, and the like, the weighting factors in Table 4 are the recording factors shown in Tables 2 and 3. It is considered that the weight information of the thickness of the medium and the temperature of the environment is included.
However, if necessary, the information on the thickness of the recording medium, the temperature of the environment, and the set temperature information during the printing operation of the fixing roller 23 are used together (that is, the weighting factors of Tables 2, 3, and 4 are used together). ) The turn-off rotation time after the printing operation may be corrected.

FIG. 7 is a block diagram showing an outline of a rotation speed change control circuit for changing the rotation speed of the turn-off rotation after the printing operation of the fixing roller. In FIG. 7, the rotation speed change control circuit 35 includes a rotation speed setting unit 36, a correction unit 37, a control unit 38, and a printing operation condition input unit 39.
In the fixing device according to the present invention, the rotational speed of the extinguishing (cutting) rotation after the printing operation is changed according to the conditions during the printing operation. As an example, the fixing device 17 (FIG. 2) according to the present invention counts the number of prints in response to a print request from the user using the rotation speed change control circuit 35 of FIG. Determine the turn-off speed afterwards.
Hereinafter, means for appropriately adjusting the overshoot amount by changing the rotation speed of the turn-off rotation after the printing operation according to the conditions during the printing operation will be described. First, the case where the rotational speed is changed by inputting the number of prints to the printing operation condition input unit 39 of the rotational speed change control circuit 35 of FIG. 7 will be described.

表５には、印刷枚数と印刷動作後消灯回転速度の関連付けを示している。本発明では、表５のように、予め関連付けておいた印刷枚数と印刷動作後の消灯回転速度のテーブル情報を基に回転速度を決定する。 FIG. 8 is a timing chart showing a comparison result of overshoot when the turn-off rotation speed after the printing operation is a constant value and when it is variable depending on the number of printed sheets. In FIG. 8A, the overshoot of the temperature of the fixing roller 23 (FIG. 2) when the turn-off rotation speed after the printing operation is set to a constant value is made variable according to the number of printed sheets in FIG. 8B. In this case, the temperature overshoot of the fixing roller 23 (FIG. 2) is shown as a comparison result.
FIG. 8 shows a comparison result of overshoot when the turn-off rotation speed after the printing operation is set to a constant speed v1 and when it is variable depending on the number of printed sheets (v1 and v2).
The faster the rotation speed, the faster the heat of the fixing roller 23 is transferred to the opposing pressure roller 24 (FIG. 2). Therefore, if the turn-off rotation is performed for the same time, the overshoot amount of the temperature of the fixing roller 23 is rotated. The faster the speed, the smaller.
[Table 5]

Table 5 shows the association between the number of printed sheets and the turn-off rotation speed after the printing operation. In the present invention, as shown in Table 5, the rotation speed is determined based on the table information of the number of printed sheets and the turn-off rotation speed after the printing operation associated in advance.

In the present embodiment, the rotation speed of the fixing roller 23 can be selected and driven from three rotation speeds of 50 [mm / s], 100 [mm / s], and 150 [mm / s]. Table 5 is used to determine which of the three rotational speeds is used.
In the present embodiment, three rotational speeds are used. However, the rotational speeds may be divided more finely according to the purpose, or continuously depending on the configuration of the fixing drive used. When the speed can be changed, the relationship between the number of printed sheets and the rotational speed may be described by a mathematical formula, and the rotational speed may be continuously changed with respect to the number of printed sheets. As described above, the amount of overshoot after the printing operation can be optimized by changing the turn-off rotation speed after the printing operation in accordance with the number of printed sheets.
In the fixing device according to the present invention, the turn-off rotation speed after the printing operation determined by the number of prints described above is corrected according to the thickness of the recording medium. The correction procedure is described below. First, the method of determining the thickness of the recording medium is omitted because the same method as described above with reference to FIG. 5 can be used.

表６に示す回転速度の補正の数値の意味は、「＋１」が表５により印刷枚数に応じて決定された回転速度に対して、所有している回転速度の中で１段階速い回転速度へ補正することを意味し、「＋２」であれば２段階速い回転速度へ補正することを意味する。
例えば、印刷枚数が６０枚、記録媒体の厚さが９５［ｇ／ｍ^２］であった場合には、表５から決定される印刷枚数６０枚に対する回転速度１００［ｍｍ／ｓ］に対して、＋1の補正であるから、１段階速い回転速度にシフトさせ、１５０［ｍｍ／ｓ］で回転させる。
また、例えば、印刷枚数が６０枚、転写紙の厚さが２００［ｇ／ｍ^２］であった場合には、印刷枚数６０枚に対する回転速度１００［ｍｍ／ｓ］に対して、＋２の補正であるため、２段階速い回転速度へシフトを行なうことを意味する。しかし、本実施の形態では、所有している回転速度が１５０［ｍｍ／ｓ］を上限としているため、１５０［ｍｍ／ｓ］を選択することになる。
このように回転速度だけでの補正では頭打ちとなってしまう場合には、図５に示した回転時間偏向制御回路３０により回転時間も同時に調節することによって、さらに、高精度にオーバーシュートを防ぐこともできる。
以上のように、記録媒体の厚さを考慮し、印刷動作後の消灯回転速度を決定することによって、印刷動作後のオーバーシュート量を最適化することが可能である。
また、本発明による定着装置では、前述した印刷枚数により決定された印刷動作後の消灯回転速度を、図７の回転時間変更制御回路３５において印刷動作時の環境の温度により補正する。補正の手順において、環境の温度の判断方法などは、表３に関連して説明したのと同様であるため、割愛する。 Next, means for correcting the turn-off rotation speed after the printing operation from the measured thickness of the recording medium will be described. As the recording medium is thicker, a larger electric power is required during the printing operation, so that the temperature overshoot of the fixing roller 23 after the printing operation increases as described above.
Therefore, the rotational speed correction is performed using the table in Table 6 for the thickness of the recording medium during printing. This rotational speed correction is performed in the rotational time change control circuit 35 of FIG.
[Table 6]

The meaning of the numerical value of the rotational speed correction shown in Table 6 is that “+1” is a rotational speed that is one step faster than the rotational speed that is determined according to the number of printed sheets according to Table 5. This means that correction is made, and if “+2”, it means that the rotation speed is corrected by two steps faster.
For example, when the number of printed sheets is 60 and the thickness of the recording medium is 95 [g / m ² ], the rotational speed is 100 [mm / s] for 60 printed sheets determined from Table 5. +1, so that the rotation speed is shifted by one step and rotated at 150 [mm / s].
Further, for example, when the number of printed sheets is 60 sheets and the thickness of the transfer paper is 200 [g / m ² ], correction of +2 is performed with respect to a rotational speed of 100 [mm / s] with respect to 60 printed sheets. Therefore, this means that the shift is made to a two-stage faster rotation speed. However, in the present embodiment, since the owned rotation speed has an upper limit of 150 [mm / s], 150 [mm / s] is selected.
In this way, when the correction is made only by the rotation speed, the rotation time is simultaneously adjusted by the rotation time deflection control circuit 30 shown in FIG. 5 to prevent overshoot with higher accuracy. You can also.
As described above, it is possible to optimize the overshoot amount after the printing operation by determining the turn-off rotation speed after the printing operation in consideration of the thickness of the recording medium.
Further, in the fixing device according to the present invention, the turn-off rotation speed after the printing operation determined by the number of prints described above is corrected by the temperature of the environment during the printing operation in the rotation time change control circuit 35 of FIG. In the correction procedure, the method for determining the temperature of the environment is the same as that described with reference to Table 3, and is therefore omitted.

表７には、印刷時の環境温度に対して行なう回転速度補正を表６に示す回転速度の補正の数値の意味において示している。
そこで、印刷時の環境温度に対して、表７のテーブルを用いて回転速度補正を行なう。表５の印刷枚数から決定される印刷動作後の消灯回転速度に対して、図７の回転速度変更制御回路３５で、表７のテーブルを考慮して、回転速度補正を行なうことにより、印刷動作後の消灯回転速度を決定する。
例えば、印刷枚数が３５枚、環境の温度が１８℃で合った場合には、表５から決定される印刷枚数に対する回転速度５０［ｍｍ／ｓ］に対して、表７のテーブルにより「＋１」の回転速度補正がなされるので、１００［ｍｍ／ｓ］の回転速度にて印刷動作後の消灯回転を行なう。
以上のように、印刷動作時の環境温度を考慮し、図７の回転時間変更制御回路３５において、印刷動作後の消灯回転速度を決定することにより、印刷動作後のオーバーシュート量を最適化することができる。 Next, a procedure for correcting the turn-off rotation speed after the printing operation according to the temperature of the environment will be described. When the temperature of the environment is low, the temperature of the recording medium is low, and a large amount of power is required during the printing operation, so that the overshoot after the printing operation is increased as described above.
[Table 7]

Table 7 shows the rotational speed correction performed for the environmental temperature during printing in terms of numerical values for rotational speed correction shown in Table 6.
Therefore, the rotational speed is corrected using the table in Table 7 for the environmental temperature during printing. The rotational speed correction after the printing operation determined from the number of printed sheets in Table 5 is corrected by the rotational speed change control circuit 35 in FIG. Determine the turn-off speed afterwards.
For example, when the number of printed sheets is 35 and the environmental temperature is 18 ° C., “+1” is obtained from the table of Table 7 with respect to the rotational speed 50 [mm / s] for the number of printed sheets determined from Table 5. Since the rotation speed is corrected, the turn-off rotation after the printing operation is performed at a rotation speed of 100 [mm / s].
As described above, the overshoot amount after the printing operation is optimized by determining the turn-off rotation speed after the printing operation in the rotation time change control circuit 35 in FIG. 7 in consideration of the environmental temperature during the printing operation. be able to.

表８には、印刷動作時の定着ローラ２３の設定温度に対して行なう回転速度補正を表６に示す回転速度の補正の数値の意味において示している。
そこで、印刷動作時の定着ローラ２３の設定温度に対して、表８のテーブルを用いて回転速度補正を行なう。表５の印刷枚数から決定される印刷動作後の消灯回転速度に対して、回転速度補正を行なうことにより、印刷動作後の消灯回転速度を決定する。
一般には、定着ローラ２３の設定温度は、記録媒体の厚さ、環境の温度などを考慮して決定されるため、表８の回転速度補正の値には、表６、表７に示した、記録媒体の厚さ及び、環境の温度による回転速度補正の情報が含まれていると考えられる。
しかし、必要に応じて、記録媒体の厚さ、環境の温度、定着ローラ２３の印刷動作時の設定温度の情報を併用して、図７の回転時間変更制御回路３５で印刷動作後の消灯回転速度を補正してもよい。
以上のように、印刷動作時の定着ローラ２３の印刷動作時の設定温度を考慮し、印刷動作後の消灯回転速度を決定することにより、印刷動作後のオーバーシュート量を最適化することができる。 Further, in the fixing device according to the present invention, the turn-off rotation speed after the printing operation determined by the number of printed sheets described above is corrected with respect to the set temperature of the fixing roller 23 (FIG. 2) during the printing operation. When the set temperature of the fixing roller 23 during the printing operation is high, the maximum overshoot reaching point after the printing operation is also high because the temperature is high during the printing operation.
[Table 8]

Table 8 shows the rotational speed correction performed with respect to the set temperature of the fixing roller 23 during the printing operation in the meaning of numerical values for rotational speed correction shown in Table 6.
Therefore, the rotational speed is corrected using the table in Table 8 for the set temperature of the fixing roller 23 during the printing operation. The turn-off rotation speed after the printing operation is determined by correcting the rotation speed with respect to the turn-off rotation speed after the printing operation determined from the number of printed sheets in Table 5.
In general, since the set temperature of the fixing roller 23 is determined in consideration of the thickness of the recording medium, the temperature of the environment, and the like, the rotational speed correction values in Table 8 are shown in Tables 6 and 7. It is considered that information on the rotational speed correction according to the thickness of the recording medium and the temperature of the environment is included.
However, if necessary, the rotation time change control circuit 35 in FIG. 7 uses the information on the thickness of the recording medium, the temperature of the environment, and the set temperature information during the printing operation of the fixing roller 23 together to turn off the light after the printing operation. The speed may be corrected.
As described above, the overshoot amount after the printing operation can be optimized by determining the turn-off rotation speed after the printing operation in consideration of the set temperature during the printing operation of the fixing roller 23 during the printing operation. .

Further, in the fixing device according to the present invention, control is performed using a so-called feedforward described below as control means of the fixing heat source 25 (FIG. 2) during the printing operation. There is a time lag (dead time) before the heat input from the fixing heat source 25 is supplied to the fixing device 17 (FIG. 2).
Therefore, the time when the recording medium passes through the fixing device 17 is predicted, and the heat input supply from the fixing heat source 25 is started or amplified before the recording medium passes through the fixing device 17. Then, before the rear end of the recording medium passes through the fixing device 17, the heat input supply from the fixing heat source 25 is blocked or reduced in advance.
As a method for detecting the timing at which the recording medium P (see FIG. 1) passes to the fixing device 17, for example, with respect to the time when the rotation of the registration roller (conveying roller) 19 (see FIG. 1) is turned on from off. Considering the time required for passing, which is determined from the transport distance and transport speed between the registration roller 19 and the fixing device 17, the timing at which the recording medium passes through the fixing device 17 can be grasped.
The capturing of the timing at which the recording medium passes through the fixing device 17 is referred to as a sign, and the sign that the recording medium P passes through the fixing nip is detected. Therefore, from the transport distance and the transport speed between the registration roller 19 and the fixing device 17. Determining the timing in consideration of the time required for passing is described as a detection mechanism that can detect a sign. Note that the timing detection method is not limited to this.
By using the above feedforward control, the amount of heat supplied from the fixing heat source 25 can be reduced in advance before the end of the printing operation, so the amount of overshoot after the printing operation is reduced. In this state, if the rotation time and rotation speed of the fixing roller after the printing is turned off are optimized, the overshoot amount can be controlled more precisely.

1 is a schematic diagram illustrating an overall configuration of an internal mechanism of an image forming apparatus to which a fixing device according to the present invention can be applied. 1 is a schematic diagram illustrating a configuration of a fixing device according to the present invention. 6 is a timing chart showing a state transition of the operation of the fixing device in a general usage method together with a transition of the temperature of the fixing roller. It is a timing chart which shows the difference in the amount of overshoot by the presence or absence of execution of light extinction rotation after printing operation. It is a block diagram which shows the outline of the rotation time change control circuit which changes the rotation time of the turn-off rotation after the printing operation of the fixing roller. 10 is a timing chart showing a comparison result of the temperature overshoot of the fixing roller when the turn-off rotation time after the printing operation is set to a constant value and when it is made variable according to the number of printed sheets. It is a block diagram which shows the outline of the rotational speed change control circuit which changes the rotational speed of the light extinction rotation after the printing operation of a fixing roller. 6 is a timing chart showing a comparison result of overshoot when the turn-off rotation speed after the printing operation is set to a constant value and when it is made variable according to the number of printed sheets.

Explanation of symbols

A image forming apparatus, n fixing nip, P recording medium (paper, transfer paper, recording material), 4 transfer apparatus, 5 intermediate transfer belt, 6c image carrier (photosensitive drum), 8 paper supply apparatus, 12c image forming apparatus , 17 fixing device, 23 fixing member (fixing roller), 24 pressure roller, 25 fixing heat source, 26 temperature detecting means, 27 temperature controller, 28 PWM drive circuit, 30 rotation time change control circuit, 31 rotation time setting unit, 32 Correction unit, 33 control means, 34 printing operation condition input unit, 35 rotation speed change control circuit, 36 rotation speed setting unit, 37 correction unit, 38 control means, 39 printing operation condition input unit

Claims (12)

  A fixing member having a fixing heat source therein, and a pressure member that presses the fixing member; and an unfixed toner image on a recording medium conveyed to a fixing nip between the fixing member and the pressure member A fixing device for heat-fixing on a recording medium, comprising: a rotation time change control circuit for changing a power supply off rotation time for turning off the power supply to the fixing heat source and rotating the fixing member after completion of a printing operation; The time change control circuit changes the power supply off rotation time according to a condition during a printing operation.   The fixing device according to claim 1, wherein the rotation time change control circuit changes the cutting rotation time of the fixing member according to the number of printed sheets.   The fixing device according to claim 2, wherein the rotation time change control circuit corrects the power supply off rotation time set by the number of printed sheets based on a thickness of the recording medium during a printing operation.   3. The fixing device according to claim 2, wherein the rotation time change control circuit corrects the power supply off rotation time determined by the number of printed sheets based on an environmental temperature during a printing operation.   3. The fixing device according to claim 2, wherein the rotation time change control circuit corrects the power supply off rotation time determined by the number of printed sheets based on a set temperature of the fixing member during a printing operation.   In a fixing device that thermally fixes a toner image formed on a recording medium onto a recording medium by a fixing member having a fixing heat source therein and a pressure member that presses the fixing member, the fixing heat source is supplied to the fixing heat source after a printing operation is completed. A rotation speed change control circuit for changing the power supply off rotation speed for turning off the power supply and rotating the fixing member, and changing the power supply off rotation speed according to a condition during a printing operation. Fixing device to do.   The fixing device according to claim 6, wherein the rotation speed change control circuit changes the power supply off rotation speed according to the number of printed sheets.   The fixing device according to claim 6, wherein the rotation speed change control circuit corrects the power supply off rotation speed determined by the number of printed sheets based on a thickness of the recording medium during a printing operation.   The fixing device according to claim 6, wherein the rotation speed change control circuit corrects the power supply off rotation speed determined by the number of printed sheets based on an environmental temperature during a printing operation.   The fixing device according to claim 6, wherein the rotation speed change control circuit corrects the power supply off rotation speed determined by the number of printed sheets based on a set temperature of the fixing member during a printing operation.   A detection mechanism capable of detecting a timing at which the recording medium passes through the fixing nip, and supplying an increased amount of heat supplied from a fixing heat source to the fixing member from the time when the timing is detected; Controlling the fixing heat source of the fixing member during a printing operation using feedforward control in which the amount of heat supplied from the fixing heat source to the fixing member is reduced before passing through the fixing nip. The fixing device according to claim 1, wherein the fixing device is a fixing device.   The electrostatic latent image formed on the image carrier is visualized by developing with toner, the toner image is transferred onto a recording medium, and the toner image on the recording medium is fixed on the recording medium with heat and pressure. 12. The image forming apparatus according to claim 1, wherein the fixing device according to claim 1 is mounted as a fixing device for fixing the toner image on the recording medium.

Images