JP2002214967A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain temperature rise at the paper non-passing parts of a heating member and a pressing member in the case of fixing an image on small size transfer material, and the wrinkles of the transfer material and the breakage of the bearing part of a fixing device caused by the temperature rise of the paper non-passing part. SOLUTION: After finishing the consecutive printing of envelopes (S2), a next printing signal and a paper size designating signal are received (S3), and t' is decided according to the paper size in STEP 3 (S4). Decision of t' is made so that t'=ΔT in the case of (the width of the previous printing transfer material)>=(the width of the next printing transfer material), and t'=20 in the case of (the width of the previous printing transfer material)<(the width of the next printing transfer material). After finishing the preparation of image forming, a temperature difference ΔT between a paper passing part and the paper non-passing part on the surface of the heating roller is detected by temperature detection elements 113 and 120 (S7). Only when the width of the next printing transfer material is wide and ΔT>20[ deg.C], requirement on next printing image data is stopped, and when ΔT<=20[ deg.C] is attained, the image data are required (S9) and printing is started (S10).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing a toner carried on a transfer material to the transfer material by heating and pressing, and an image forming apparatus having such a fixing device.

[0002]

2. Description of the Related Art Conventionally, as a fixing device used in an image forming apparatus, a contact heating type fixing device having good thermal efficiency and safety, particularly a heat roller type fixing device formed by a pair of rollers, has been widely used. I have.

This is a pair of rollers, a heating roller having a cylindrical roller and a heater inside, and a pressure roller which is pressed against the heating roller to form a nip between the heating roller and the heating roller. And By heating a heating roller with a heater and passing a transfer material carrying unfixed toner through a nip portion, the toner is heated and pressurized and fixed on the transfer material.

[0004] Transfer materials of various sizes are used as transfer materials for carrying toner. Therefore, there are various widths in the direction perpendicular to the transport direction of these transfer materials, that is, widths when these transfer materials pass through the nip portion (hereinafter referred to as “paper passing width”). Therefore, as for the outer peripheral surfaces of the heating roller and the pressure roller, if the area where the outer peripheral surface makes a full circle with the paper passing width is defined as the paper passing area and the area other than the paper passing area is defined as the non-paper passing area, the heating roller Since the width of the pressure roller in the axial direction (substantially equal to the length of the nip portion) is set in accordance with the transfer material having the largest paper passing width, when a transfer material having a small paper passing width is passed through the nip portion. , The non-sheet passing area is enlarged.

[0005]

According to the prior art,
In some cases, the temperature of the non-sheet passing area becomes higher than the temperature of the sheet passing area, and the transfer material may be wrinkled. That is,
The heating roller is heated by a heater so that the entire outer peripheral surface thereof has a uniform temperature. The paper passing area on the outer peripheral surface of the heating roller is an area where the transfer material is in direct contact. In this area, heat is taken away by the transfer material, and the surface temperature of the outer peripheral surface of the heating roller is reduced, but the non-paper In the region, heat is not taken away by the transfer material, and temperature unevenness occurs on the entire surface of the heating roller. The temperature unevenness on the surface of the heating roller is conspicuous when a transfer material of the same size continuously passes through the nip portion. At this time, if the surface temperature of the heating roller is set in accordance with the sheet area in order to reliably fix the toner on the heating roller, the non-sheet passing area becomes extremely hot.

As described above, when a large temperature difference occurs between the paper passing area and the non-paper passing area of the heating roller, the pressure roller in contact with the heating roller and forming the nip portion similarly generates temperature unevenness. Non-uniform deformation occurs due to thermal expansion, and the contact pressure at the nip changes. The contact pressure in the sheet passing area decreases, and the contact pressure in the non-sheet passing area increases. Therefore, for example, when a wide transfer material is passed after a narrow transfer material is continuously passed, the contact pressure of the wide transfer material at the nip portion in the width direction is determined in the previous pass. The contact pressure on the center side, which is the paper portion, is low, and the contact pressure near the left and right sides, which was the last non-sheet passing area, becomes strong. As a result, wrinkles are generated.

Accordingly, the present invention provides a method for fixing a small-size transfer material, which includes increasing the temperature of a non-sheet passing portion of a heating member and a pressing member and wrinkling of the transfer material caused by the temperature increase of the non-sheet passing portion. It is an object of the present invention to provide an image forming apparatus capable of suppressing damage to a bearing portion of a fixing device.

[0008]

According to a first aspect of the present invention, there is provided a heating member which is maintained at a set temperature, and a pressing member which forms a nip in cooperation with the heating member. In an image forming apparatus having a fixing means for fixing an image through a recording material carrying an image in the nip, a recording material smaller than a predetermined size is continuously passed, and the recording material size of the next print is larger than the predetermined size. If it is larger, the next print command is not accepted until the temperature difference between the sheet passing portion and the non-sheet passing portion becomes equal to or less than a predetermined value.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. Reference examples serving as a technical basis of the present invention will also be described as appropriate.

Reference Example 1 FIG. 3 shows a laser beam printer (image forming apparatus) 21 having a fixing device according to the present invention.
Is schematically illustrated. The configuration and operation will be briefly described below.

A photosensitive drum 22 is rotatably supported substantially at the center of the apparatus main body of the laser beam printer 21. The surface of the photosensitive drum 22 is uniformly charged using the charging roller 25. Next, the image is image-exposed by the laser scanner 23 via the mirror 24 to form a latent image. Next, the toner T in the developing device 26 is developed by the developing roller 27. On the other hand, the transfer material P loaded on the paper cassette 33 is fed by the feed roller 32, the size of the transfer material is detected by the trailing edge detection sensor 34, and is sent to the registration roller 31. The transfer material P is detected by the registration sensor 35 and is in a standby state with its leading end being bitten by the registration roller 31. The transfer material P is sent to the transfer roller 30 so as to be synchronized with the image written on the photosensitive drum 22. Is transferred. The toner T transferred to the transfer material P is fixed by the fixing device 36, and the transfer material P is discharged to the outside of the apparatus main body by the discharge roller 37. On the other hand, after the transfer on the photosensitive drum 22, the remaining toner T is cleaned by the cleaner 29, and the process proceeds to a subsequent process.

Next, the structure of the fixing device 36 is shown in FIG. The heating roller (fixing roller) 40 disposed on the upper side is a pipe-shaped pipe made of aluminum, iron or the like covered with a release layer such as PFA or PTFE, having a thickness of 2.0 mm and an outer diameter of 25 mm.
mm roller.

A pressure roller 41 disposed in pressure contact with the heating roller 40 at a total pressure of 7 kg has a hardness of 45 formed by forming a layer of a heat-resistant elastic material such as silicon rubber or fluorine rubber on a cored bar.
A roller having a degree (Asker C), a cored bar diameter of 8 mm, and an outer diameter of 20 mm. The transfer material P is passed between the heating roller 40 and the pressure roller 41, and the toner T on the transfer material P is heated and pressed between the heating roller 40 and the pressure roller 41 to be fixed. A heater 42 is provided inside the heating roller 40 and heats the heating roller 40 from the inside.
The surface of the heating roller 40 is in contact with a temperature detecting element 43 as a temperature detecting means, and detects the temperature of the heating roller 40. The heater 42 is connected to a heater driving means 44 for turning the heater 42 on and off. Heater driving means 4
The control means 45 controls the heater driving means 44 on the basis of the data from the temperature detecting element 43 to intermittently drive (turn on and off) the heater 42 and to change the surface temperature of the heating roller 40 to a predetermined fixing temperature (printing temperature). Temperature) or the non-fixing standby temperature (standby temperature).

Further, as shown in FIG. 2, the fixing device 36 of the present invention has a temperature detecting element 43 disposed in a non-image area on the transfer material, and a point a on the heating roller 40 regardless of the size of the transfer material P. Is a one-side reference configuration through which the transfer material end passes.

FIG. 5 shows a temperature control (temperature control) when printing plain paper (A4 size or the like) according to the present invention. The present invention is detected by sensor sheet size L ₁ of the conveying direction, L ₁
If ≧ 245 mm, it is determined that the paper is plain paper (A4 size or the like). In this reference example, when an image forming apparatus having a process speed (paper feed speed) of 50 mm / sec determines that the paper size is plain paper (A4 size or the like), the throughput (paper feed timing) is set to 8 (sheets) when A4 paper is passed. / Min), and the paper interval at this time (at the time of paper conveyance) is L
₂ ′, the paper size L ₁ when L ₁ ≧ 245 mm
Sheet interval L ₂ regardless of is always constant at L _{2 '.}

If L ₁ <245 mm, the envelope size is determined, and the throughput is always 8 (sheets / minute) regardless of the paper size L ₁ . Sheet interval L ₂ at this time varies according to the paper size L _1. These paper size L ₁ , paper interval L
_{The second} detecting means will be described later.

FIG. 6 shows the temperature distribution on the surface of the heating roller 40 when A4 paper (210 × 297 mm) is continuously passed at a printing temperature of 185 ° C. and a throughput of 8 (sheets / minute). As can be seen from the drawing, the temperature distribution on the surface of the heating roller when the plain paper having a wide transfer material width is continuously passed is substantially flat. However, in the fixing device 36 in which the temperature detecting element 43 is arranged in the non-image area on the transfer material in the one-side reference configuration shown in FIG. As a result, the surface temperature of the non-sheet-passing portion of the heating roller, which does not lose heat energy, rises. This situation is shown in FIGS. 2-a in FIG. 7 shows a print temperature of 185 ° C., a throughput of 8 (sheets / min), which is wider than that of plain paper, and a surface of the heating roller when an envelope (106 × 241 mm) is continuously passed. It is a temperature distribution. FIG. 8 shows the temperature rise of the bearing at the non-sheet-passing portion of the heating roller at this time.
As can be seen from FIGS. 7 and 8, when the envelope is continuously passed at a print temperature of 185 ° C. and a throughput of 8 (sheets / minute), the temperature of the heating roller bearing reaches approximately 233 ° C.
Exceeds the heat resistant temperature of the heated roller bearing. The bearing of the heating roller 40 is usually based on PPS (polyphenylene sulfide) resin, and its heat-resistant temperature is around 230 ° C. Therefore, the printing temperature is 185 ° C,
If an envelope or the like having a narrow transfer material width is continuously passed at a throughput of 8 (sheets / minute), the bearing of the heating roller 40 may be damaged.

As in the present invention, if the throughput at the time of passing the envelope with the one-sided reference machine is 8 (sheets / minute), the temperature detecting element 43 is used.
The surface temperature of the heating roller at the thermistor contact portion is lower than the surface temperature of the heating roller at the non-sheet passing portion because the temperature is controlled during printing in a state where thermal energy is deprived by the paper. Further, since the surface temperature of the heating roller in the non-paper passing portion where the energy is not directly taken away by the paper becomes high, the thermal energy moves to the portion where the temperature is low. However, when the throughput is 8 (sheets / minute), the thermal energy supplied from the heater is greater than the moving thermal energy due to the temperature control during printing, so that thermal energy is accumulated in the non-sheet passing portion of the heating roller 40. As a result, the surface temperature of the heating roller in the non-sheet passing portion is higher than the surface temperature of the heating roller in the sheet passing portion. At this time, the temperature difference between the surface temperature of the heating roller of the thermistor portion which is in contact with the paper passing portion and performs temperature detection and the temperature difference between the heating roller bearing portion of the non-paper passing portion is approximately 48 ° C.

In order to reduce the temperature difference on the surface of the heating roller between the paper passing portion and the non-paper passing portion, the supply of the heat energy from the heater 42 may be smaller than the transfer of the heat energy. In order to reduce the supply of thermal energy from the heater 42, the print temperature may be reduced to reduce the number of times the heater is turned on.

Accordingly, in the present invention, when continuously passing an envelope or the like having a narrow transfer material width, control is performed to lower the printing temperature when continuous printing reaches a certain number of sheets. The reason why the print temperature can be lowered by the number of continuous prints is that when the paper is passed, the pressure roller 41
This is because the fixing property is improved by heating. Moreover, in this reference example, the throughput is 8
(Sheets / min), the space between the sheets is wider than that of the normal-size paper, and this effect is enhanced. Further, as can be seen from FIG. 7, the surface temperature of the heating roller at the central portion of the roller where the nip width is narrow and the fixing property is reduced is increased by the rise in the temperature of the non-sheet passing portion, and the fixing property is improved.

FIG. 1 shows the temperature control performed in the present invention when continuously passing an envelope or the like having a narrow transfer material width. T ₂ the heating roller surface temperature Turn on the main body became 175 ° C. at time t ₁
More standby temperature control is performed at 175 ° C. Upon starting the envelope printing at time t _2, t ₄ the number of fed sheets is 25 sheets
Until performs print temperature control at 185 ° C., t ₄ thereafter to be performed print temperature control at 180 ° C..

9 and 10 show the rise in the surface temperature of the heating roller in the non-sheet passing portion when continuous printing is performed under the above-described temperature control. 4-a in FIG. 9 is a temperature distribution of the heating roller surface of time t _{4 (FIG.} 1), 4-b is a temperature distribution of the heating roller surface at the time t ₄ after. FIG. 10 shows the temperature rise of the bearing on the non-sheet-passing portion side of the heating roller at this time. As can be seen from these figures, the temperature of the heating roller bearing is about 228 ° C. when the envelope is continuously fed by the temperature control of the present invention.
However, the temperature does not exceed the heat-resistant temperature of the heating roller bearing and does not damage the fixing device 36.

In the present embodiment, the size of the transfer material P is measured by the trailing edge detection sensor 34, and the size of the plain paper and the size of the envelope are switched based on the measured size. The size of the transfer material P is measured by measuring a time t (sec) from when the front end of the transfer material enters the rear end detection sensor 34 until the rear end of the transfer material is removed, and this value and the process speed Vp = 50 (mm / sec) Thus, the length L ₁ (mm) of the paper in the transport direction can be obtained by L ₁ = 50 × t. The size of the long envelope in the transport direction is approximately (106 × 241 mm). Therefore, L ₁ ≦ 241
(Mm), it can be determined to be an envelope, but in view of the measurement error, it is determined to be an envelope when L ₁ <245 (mm). In the present embodiment, the transfer material size is determined by the trailing edge detection sensor 34, but the same can be performed by using the registration sensor 35. In the present embodiment, the throughput is fixed at 8 (sheets / minute), but this is performed by controlling the sheet interval using the trailing edge detection sensor 34. FIG. 11 shows how to obtain the sheet interval. In the conveying direction of the paper length _L 1 (mm), a sheet interval _L 2 to obtain (mm),
When the process speed Vp = 50 and (mm / sec), when the throughput 8 (sheets / min), the sheet interval is _{L 2 = (50 × 60-8 ×} L 1) / 7.

As described above, the length of the transfer material in the transport direction is detected by the trailing edge detection sensor 34 or the registration sensor 35 to determine whether or not the width of the transfer material is smaller than the envelope size. Thus, it is possible to determine whether the size is an envelope size without a width detection sensor. The count of the number of envelopes printed is counted as continuous printing when a print signal is received while the main motor for paper transport is rotating, and when the print signal is received after the main motor is stopped, the temperature of the pressure roller 41 is counted. Since there is a possibility that the temperature has decreased, the number of sheets is counted again from 0 and the temperature control is performed from the first sheet.

By performing the above control, even when an envelope or the like having a narrow transfer material width is continuously passed, the rise in the surface temperature of the non-paper-passing portion of the heating roller can be suppressed, and damage to the heating roller bearing can be prevented.

REFERENCE EXAMPLE 2 The fixing device 36 of this reference example has a heating roller thickness of 1.8 m for the purpose of cost reduction and size reduction.
m, an outer diameter of 20 mm, and a heating roller 40 smaller in diameter than Reference Example 1 is used. On the other hand, the pressure roller 41 has the same configuration as in the first embodiment. When the thickness of the heating roller 40 is thin, the thermal conductivity in the longitudinal direction of the heating roller is reduced.
Therefore, when continuous printing is performed on an envelope or the like having a narrow transfer material width, heat transfer is unlikely to occur, and a large temperature distribution difference occurs between the envelope passing portion and the non-sheet passing portion. The process speed is set to 50 mm / sec as in the first embodiment.

Further, the image forming apparatus according to the present embodiment has a one-side reference configuration as in the first embodiment. With such a configuration, when continuously passing an envelope or the like having a narrow transfer material width, the surface temperature of the non-sheet-passing portion of the heating roller at which the transfer material P does not lose heat energy increases. This situation is shown in FIGS. 12A uses the fixing device 36 of the present embodiment,
The print temperature is 185 ° C, the throughput is 8 (sheets / min), the paper interval is wider than that of plain paper, and the envelope (106 x 24)
1 mm) is a temperature distribution on the surface of the heating roller when paper is continuously passed. FIG. 13 shows the temperature rise of the bearing at the non-sheet passing portion side of the heating roller at this time. As can be seen from FIGS. 12 and 13, when the fixing device 36 of the present embodiment is used and the envelope is continuously passed at a print temperature of 185 ° C. and a throughput of 8 (sheets / minute), the temperature of the heating roller bearing reaches approximately 240 ° C. As a result, the temperature exceeds the heat-resistant temperature of the heating roller bearing. The bearing of the heating roller 40 is usually based on PPS (polyphenylene sulfide) resin, and its heat-resistant temperature is around 230 ° C. For this reason, when the fixing device 36 of the present embodiment is used to continuously feed an envelope or the like having a narrow transfer material width at a printing temperature of 185 ° C. and a throughput of 8 (sheets / minute), the heating roller bearing may be damaged.

As in the present invention, when the throughput at the time of passing the envelope in the one-sided reference machine is 8 (sheets / min), the temperature detecting element 43 is used.
The surface temperature of the heating roller at the thermistor contact portion is lower than the surface temperature of the heating roller at the non-sheet passing portion because the temperature is controlled during printing in a state where the thermal energy is deprived by the paper. Further, since the surface temperature of the heating roller in the non-sheet passing portion where the heat energy is not directly taken away by the paper becomes high, the heat energy moves to the portion where the temperature is low. However, the throughput is 8
(Sheets / minute), the heater 4 depends on the temperature control during printing.
2 is greater than the moving heat energy, the heat energy is accumulated in the non-sheet passing portion of the heating roller 40, and the heat energy of the non-sheet passing portion is higher than the heating roller surface temperature of the sheet passing portion. The heating roller surface temperature is higher. At this time, the temperature difference between the surface temperature of the heating roller of the thermistor that is in contact with the paper passing portion and performing temperature detection and the temperature of the bearing of the heating roller in the non-paper passing portion is approximately 55 ° C.

In order to reduce the temperature difference between the surface of the heating roller in the paper passing portion and the non-paper passing portion, it is necessary to reduce the temperature of the heater 4 rather than the transfer of thermal energy.
It is sufficient to reduce the supply of heat energy from the second. In order to reduce the supply of thermal energy from the heater 42, the print temperature may be reduced, or the throughput may be reduced to reduce the number of times the heater 42 is turned on.

Therefore, in the present invention, when continuously passing an envelope or the like having a narrow transfer material width, the paper interval is controlled so as to be slower than the throughput of the maximum transfer material size (in this embodiment, the legal size (215. 9 × 355.6mm)
Min) and the throughput is fixed at 6 (sheets / min). For this reason, when the envelope is passed, the space between the sheets is wider than when the normal size paper is passed, and the fixing property is improved by the pressure roller 41 warming up between the sheets. Further, as can be seen from FIG. 15, the surface temperature of the heating roller at the central portion of the roller where the nip width is narrow and the fixing property is reduced is increased by increasing the temperature of the non-sheet passing portion, and the fixing property is improved. Further, since the throughput is set to 6 (sheets / minute), the heat energy taken away from the heating roller 40 per hour is reduced, so that the printing temperature can be lowered stepwise according to the number of prints. Therefore, in the present invention, when continuously passing an envelope or the like, control for switching the print temperature is performed according to the number of prints.

FIG. 14 shows the temperature control performed in the present invention when continuously passing an envelope or the like having a narrow transfer material width. Turn on the main body at the time t _1, the heating roller surface temperature is carried out a standby temperature control than t ₂ became 175 ° C. at 175 ° C.. T the number of fed sheets When you start the envelope of print at time t ₃ is 25 sheets
_The print temperature control is performed at 185 ° C. up to ₄ and the print temperature control is performed at 180 ° C. after t ₄ .

FIGS. 15 and 16 show the rise in the surface temperature of the heating roller in the non-sheet passing portion when continuous printing is performed under the above-described temperature control. In FIG. 15, 8-a is the temperature distribution on the heating roller surface at time t ₄ (FIG. 14), and 8-b is the temperature distribution on the heating roller surface after t ₄ . FIG. 16 shows the temperature rise of the bearing on the non-sheet-passing portion side of the heating roller at this time.
As can be seen from these figures, the temperature of the heating roller bearing is reduced by about 22 when continuous feeding of envelopes is performed with the temperature control of the present invention.
The temperature rises to 3 ° C.
It does not fall within 30 ° C. and does not damage the fixing device 36.

In the present embodiment, the throughput was fixed at 6 (sheets / min), but this was performed by controlling the sheet interval using the trailing edge detection sensor 34. FIG. 11 shows how to obtain the sheet interval. The length in the paper transport direction is L ₁ (mm), the required paper interval is L ₂ (mm), and the process speed Vp = 50 (mm).
When / sec) to, when the throughput 6 (sheets / minute), the sheet interval is, _L 2 = (a _{50 × 60-4 × L 1) /} 5.

The count of the number of prints on the envelope is performed by counting the number of sheets as continuous printing when a print signal is received while the main motor for conveying paper is rotating, and pressurizing the print signal after stopping the main motor. Roller 4
Since there is a possibility that the temperature of No. 1 has decreased, counting is restarted from 0 sheets and the temperature control is performed from the first sheet.

By performing the above control, even when the thin heat roller 40 is used to continuously feed an envelope or the like having a narrow transfer material width, the rise in the surface temperature of the non-paper passing portion of the heat roller 40 is suppressed. Thus, damage to the bearing of the heating roller 40 can be prevented.

<Embodiment 3> The image forming apparatus and the fixing device 36 used in this embodiment have the same configuration as that used in Embodiment 2.

In this embodiment, in order to improve the fixing property of the envelope immediately after the main switch of the image forming apparatus is turned on (in the morning), the fixing temperature in the morning is set higher than the normal temperature control.
In a low-temperature environment where the room temperature is 10 ° C. or less, the fixing property until the pressure roller 41 sufficiently warms becomes unstable. This is because the heat energy of the heating roller 40 is given to the pressure roller 41, so that it is impossible to give sufficient heat energy to fix the toner on the transfer material P. Such a phenomenon is conspicuous when the envelope is thicker than plain paper (such as A4 paper) and the envelope has poor surface properties. Therefore, in this reference example, the transfer material size is detected in order to improve and stabilize the fixing property when the envelope is passed in the morning in a low-temperature environment, and if this is an envelope, the transfer material size is detected until the pressure roller 41 is sufficiently warmed. And increase the fixing temperature. The method for detecting the size of the transfer material is the same as that in the first embodiment.

FIG. 17 shows the temperature control when the envelope is passed according to this embodiment. At time _{t 1,} than _{t 2} when _the heat roller 40 surface temperature Turn on the main body became 175 ° C. The standby temperature control 17
Perform at 5 ° C. Time between at t ₂ to t ₄ when starting the envelope print number of fed sheets is 20 sheets performs printing temperature control at 190 ° C., t ₄ thereafter perform printing temperature control at 180 ° C.. The throughput sheet interval at this time is the same as in Reference Example 2. Further, the temperature control temperature and throughput paper interval when passing normal-size paper (A4 or the like) are the same as in Reference Example 2.

In this embodiment, the print temperature is controlled to 190 ° C. when the envelope is passed in the morning. For this reason, when temperature control is performed only with the number of continuous prints as in Reference Example 2,
If intermittent printing is performed such that printing is stopped for a short time before the predetermined number of prints is reached and printing is started again, the number of continuous prints is re-counted, and control is performed again as the first print. Would. When such intermittent printing of an envelope or the like is repeatedly performed, the temperature of the bearing portion on the non-paper-passing portion side of the heating roller at which the thermal energy is not deprived by the paper becomes 6 (sheets / min) as shown in FIG. However, the temperature is about 233 ° C., which exceeds the heat-resistant temperature of the bearing of 230 ° C.

Therefore, in the present embodiment, control is performed to ensure the safety of the heating roller bearing regardless of intermittent or continuous printing. For this reason, in the present reference example, the number of prints is integrated regardless of continuous or intermittent printing within a predetermined time after the start of printing, and the printing temperature is switched when the predetermined number of prints have been performed within this predetermined time. ,
If the predetermined number of prints have not been performed within the predetermined time, the count of the number of prints is cleared, re-counting is started, and control from the first sheet is performed again.

FIG. 18 shows an envelope (10) at a printing temperature of 190 ° C. (no temperature control switching) and a throughput of 6 (sheets / minute).
(6 × 241 mm) indicates the temperature rise of the heating roller bearing when continuous paper is passed. As can be seen from this figure, the temperature of the heating roller bearing is supplied from the heater 42 and the heating roller 4
When the thermal energy stored in the storage area is saturated, the temperature is settled to a constant temperature, the throughput is 6 (sheets / minute), and the printing temperature is 19
If it is 0 ° C., it will be about 233 ° C. When the temperature of the heating roller bearing reached 233 ° C., the paper passing of the envelope was stopped, the envelope was left in a standby state (temperature control: 175 ° C.), and the temperature was measured. Decreased to about 175 ° C., at which the temperature became almost flat. From the above results, in this reference example, the time required for continuous 20 sheets of envelopes at a throughput of 6 (sheets / min) and the time required for the temperature of the heated roller bearing portion to reach a maximum of 233 ° C. to fall to the normal standby temperature If the number of prints reaches 20 within 6 minutes after the start of printing, the print temperature is set to 1
The temperature is switched from 90 ° C. to 180 ° C., and if 20 prints are not performed within 6 minutes, the count of the number of prints is returned to 0 and the temperature is controlled again from the first print.

By performing the above control, when printing is performed in a mode in which the number of prints becomes 20 within six minutes after the start of printing, the heating roller 4
From 0, sufficient heat is supplied to the pressure roller 41. When the pressure roller 41 is sufficiently warmed, sufficient heat can be applied to the paper even when the temperature control temperature is switched, and stable fixing performance can be secured. When printing is performed in a mode in which 20 prints are not performed within six minutes from the start of printing, the heating roller 40 and the pressure roller 4
1 is small, and the temperature of the pressure roller 41 is insufficient to switch the temperature control temperature. In addition, when printing an envelope in such a mode, the temperature of the heating roller bearing rises substantially the same as when only a few sheets are printed, and there is no need to switch the temperature adjustment temperature.

FIG. 19 shows the temperature rise of the heating roller bearing when the envelope is passed under the control of the present embodiment. As can be seen from this figure, when the envelope is fed under the control of this embodiment, the temperature of the heating roller bearing rises up to a maximum of 228 ° C, but this falls within the heat-resistant temperature of the heating roller bearing and the fixing device is damaged. I will not do it.

As described above, by performing the control of the present invention, even if the envelope is passed in the morning in a low-temperature environment, the pressure roller 41 can be continuously or intermittently printed. Since the temperature control is switched in a sufficiently warmed state, stable fixing properties can be secured. Moreover, even when a thin-walled heating roller 40 is used to continuously feed a narrow envelope or the like, a rise in the surface temperature of the heating roller non-sheet passing portion can be suppressed, and damage to the heating roller bearing can be prevented.

<Embodiment 4> FIG. 20 is a sectional view showing the structure of an image forming apparatus of the present invention, for example, in the case of a laser beam printer 91. Hereinafter, the configuration and operation will be described.

The surface of a photosensitive drum 92 as an image carrier is uniformly charged using a charging roller 95. Next, the image is image-exposed by a laser scanner 93 via a mirror 94 to form a latent image. Next, the latent image is developed with the toner T by the developing roller 97 of the developing device 96. On the other hand, the transfer material P loaded on the paper cassette 103 is
02, the size of the transfer material is detected by a trailing edge detection sensor (size detection unit) 104, and is sent to a registration roller 101.

The transfer material P is detected by the registration sensor 105, and stands by with its leading end being bitten by the registration roller 101. The transfer material P is synchronized with the image written on the photosensitive drum 92 so as to synchronize with the transfer roller 100. And the image is transferred. The toner T transferred to the transfer material P is fixed by a fixing device (fixing means) 106, and the transfer material P is discharged outside the apparatus by a discharge roller 107.

On the other hand, the toner T remaining on the photosensitive drum 92 after the transfer is cleaned by the cleaner 99, and the process proceeds to a subsequent process.

Next, the configuration of the fixing device 106 is shown in FIG. In the figure, reference numeral 110 denotes a heating roller (fixing roller), and PFA and PTFE are formed on the surface of an aluminum pipe material.
A roller having a pipe material thickness of 2.5 mm and an outer diameter of 25 mm covered with a release layer. A pressure roller 111 disposed in pressure contact with the heating roller 110 at a total pressure of 7 kg has a roller hardness of 45 degrees (Asker C) in which a layer of a heat-resistant elastic material such as silicon rubber or fluoro rubber is formed on a cored bar. Core diameter 12
mm and an outer diameter of 25 mm. Heating roller 1 described above
A transfer material P is passed through a nip portion N between the roller 10 and the pressure roller 111, and the toner T on the transfer material P is heated and pressed at the nip portion N and fixed. A heater 112 is provided inside the heating roller 110, and the heating roller 110
Is heated from the inside. The surface of the heating roller 110 is in contact with a temperature detecting element 113 as a temperature detecting means.
The temperature of the heating roller 110 is detected. Heater driving means 1
The control means 115 controls the heater driving means 114 on the basis of the data from the temperature detecting element 113 to drive the heater 112 intermittently, and adjusts the surface temperature of the heating roller 110 to a predetermined set temperature (print temperature). Alternatively, the temperature is maintained at a standby temperature (standby temperature) during non-fixing. The control means 115 is connected to a CPU 116, which is further connected to a rear end detection sensor 104, a registration sensor 105, a cassette size detection means 117, and a paper feeding section driving means (transfer material supply means) 118. The paper feeding unit driving means 118 is for continuously feeding the transfer material to the fixing device 106. In this reference example,
The CPU 116 functions as a print operation delay unit. That is, the next print operation is delayed according to the temperature state of the fixing device 106 as described later.

Further, as shown in FIG. 26, the fixing device 106 of the present invention includes a temperature detecting element 113 in a non-image area on the transfer material.
And the heating roller 110 regardless of the size of the transfer material P.
It has a one-sided reference configuration in which the end of the transfer material always passes through point a above.

In a fixing device in which the temperature detecting element 113 is arranged in the paper passing portion (paper passing area) on the heating roller in the one-side reference configuration, when the envelope or the like having a narrow transfer material width is passed, the transfer material P The surface temperature of the heating roller non-sheet passing portion (non-sheet passing region) where heat energy is not deprived increases. Print temperature 180
Envelope (106 × 24) at 8 ° C., throughput 8 (sheets / min)
1 mm) when the paper is passed through the heating roller 110,
FIG. 22 shows the temperature change in the non-sheet passing portion. The surface temperature of the heating roller non-sheet passing area is 230 ° C about 10 minutes after the start of printing.
Reaches and saturates. At this time, the surface temperature of the heating roller paper passing portion is 180 ° C., and the temperature difference between the paper passing portion and the non-paper passing portion is about 50 ° C. The elastic layer of the pressure roller 111 disposed in pressure contact with the heating roller 110 thermally expands due to the heat given from the heating roller 110. Since the temperature is higher than the temperature, the outer diameter of the pressure roller 111 in the non-paper passing portion becomes larger than the outer diameter of the pressure roller 111 in the paper passing portion. Immediately after this, when a wide sheet of plain paper is passed, the pressure roller 111
Wrinkles occur due to the deformation of.

In order to prevent wrinkles from occurring, it is necessary to reduce the difference in the outer diameter of the pressure roller 111 between the paper passing portion and the non-paper passing portion. In order to reduce the outer diameter difference between the pressure roller 111 between the paper passing portion and the non-paper passing portion, a period during which printing is not accepted is provided for a fixed time, and excessive heat energy from the heater 112 is supplied to the non-paper passing portion. The operation may be stopped to make the surface temperature of the heating roller 110 uniform.

In this embodiment, the size (including the thickness) of the transfer material P was measured by the trailing edge detection sensor 104. The size of the transfer material P is determined by the time T (sec) from when the leading end of the transfer material enters the trailing end detection sensor 104 to when the trailing end of the transfer material comes off.
c) is measured, and this value and the process speed Vp = 50
(Mm / sec), the paper length L ₁ (m
m) can be obtained by L ₁ = 50 × T. The size of the long envelope in the transport direction is almost (106 × 241 m).
m). Therefore, it can be determined that the envelope if _{L 1} ≦ 241 (mm), in anticipation of measurement error _{L 1}
An envelope was determined when ≦ 245 (mm).
The size detection of the transfer material P is not limited to this.
0 The size in the longitudinal direction may be detected, or the size may be determined from the sheet cassette 103 by the cassette size detecting means 117 (see FIG. 21). In the present embodiment, the transfer material size is determined by the trailing edge detection sensor 104, but the same can be performed by using the registration sensor 105.

FIG. 23 shows the transition of the surface temperature of the heating roller 110 when continuously passing an envelope or the like having a narrow transfer material width in the configuration of the present embodiment. Put the main power supply at time _{t 1,} than _{t 2} when _the heating roller 110 surface temperature became 180 ° C., 18
When the envelope is continuously passed at a temperature of 0 ° C. and a throughput of 8 (sheets / minute), the surface temperature of the non-sheet passing portion increases. According to the experiment results of the inventor, t after about 3 minutes from the start of the paper feeding of the envelope.
_{After 2} (approximately 25 continuous papers), the continuous paper passing of the envelope is terminated, and the transfer is performed in a state where the temperature difference between the paper passing portion and the non-paper passing portion on the surface of the heating roller exceeds 20 ° C. Wrinkles occur when plain wide paper is passed. When the temperature of the non-sheet passing portion on the heating roller surface reaches the maximum temperature of 230 ° C., the time required for the temperature of the non-sheet passing portion to drop to 200 ° C. or less (t ₅ −
t ₄ ) is about 25 seconds, and this time is the same even when idling is performed.

FIG. 24 shows a paper passing method in this embodiment. After the print signal is ready to be accepted (S
1) When a print signal for envelope passing is input, 180 ° C
At a temperature control and a throughput of 8 (sheets / minute), continuous paper feeding of envelopes is started (S2), and at the same time, the number of envelope papers is counted (S3). When continuous printing of envelopes is completed (S4), ST
If the number N of continuous prints counted in EP3 is 25 or more (N ≧ 25) (S5), the process enters a state where the next print is not accepted (S6). If the time after entering STEP 6 becomes 30 seconds or more (wait time T ≧ 30), the process enters a ready state (S1) for receiving the next print.

By performing the above-described size detection and setting the next print acceptance prohibition time based on the number of continuous prints of the envelope, when an envelope or the like having a narrow transfer material is passed, and then a plain paper or the like having a wide transfer material is passed. The generation of wrinkles can be prevented. Further, in this embodiment, the surface temperature of the heating roller 110 is made uniform without idling, so that the drum surface is not excessively shaved.

<Embodiment 5> The image forming apparatus used in the present embodiment has the same one-side reference configuration as the image forming apparatus used in Embodiment 4.

In Reference Example 4, in order to prevent the generation of wrinkles in the case where a wide transfer material plain paper is passed immediately after the continuous transfer of an envelope or the like having a narrow transfer material width, the envelopes or the like must have a certain number of sheets or more. After the continuous paper passing and between the paper passing with the plain paper, a fixed time during which the print was not accepted was provided.

In this embodiment, the request for the image data of the next print is made according to the number of continuous sheets passed through an envelope or the like having a narrow transfer material width, the time until the preparation of the image formation for the next print is completed, and the paper size of the next print. For a certain period of time.

In the present embodiment, similarly to Embodiment 4, the fixing device 106 has a one-side reference configuration, and the temperature detecting element 113 is disposed in the paper passing portion on the heating roller 110. When the paper is continuously passed at a printing temperature of 180 ° C. and a throughput of 8 (sheets / minute), the change in the surface temperature of the paper passing portion and the non-paper passing portion of the heating roller 110 is the same as that in FIG. is there.

FIG. 25 shows a paper passing method according to this embodiment. At the same time as the continuous paper passing of the envelope is started (S1), the number of envelopes passed is counted (S2). At the end of continuous envelope printing,
If the number of continuous prints N counted in STEP 2 is 25 or more (N ≧ 25), the timer starts counting (S
5) A next print signal and a paper size designation signal are received (S6). T is determined based on the paper size received in STEP 6 (S7). t is t = 0 when (transfer material width of previous print) ≧ (transfer material width of next print), and t = 20 when (transfer material width of previous print) <(transfer material width of next print). Next, the next print transfer material P is fed (S8),
After completion of preparation for forming the next print image (S9), the image data of the next print is requested when T ≦ t (S1).
1) Printing is started (S12).

By performing the above-described paper passing method, the next print is delayed to prevent wrinkles only when the transfer material width of the next print is larger than the transfer material width of the previous print.
If the width of the transfer material is narrow and it is not necessary to prevent wrinkles, the next print can be continued.

<Embodiment 1> The image forming apparatus used in the present embodiment has the same one-side reference configuration as the image forming apparatus used in Reference Example 4.

In Reference Examples 4 and 5, a period during which printing on plain paper is not accepted is provided in accordance with the number of continuous sheets passed through an envelope or the like having a narrow transfer material width. In the present embodiment, the temperature of the non-sheet passing portion when the transfer material P having a narrow transfer material width is passed is monitored by a temperature sensor, and before the transfer material P having a wide transfer material width is printed in accordance with the temperature. Then, a time is provided for waiting for the image data request for the next print.

In this embodiment, similarly to the fourth embodiment, the fixing device 106 has a one-side reference configuration, and the temperature detecting element 113 is disposed in the paper passing portion on the heating roller 110. Print temperature 180 ° C, throughput 8
The change in the surface temperature of the sheet passing portion and the non-sheet passing portion of the heating roller 110 when the sheet is continuously passed at (sheets / minute) is the same as that in FIG. In order to completely prevent the occurrence of wrinkles of plain paper after continuous paper passing through the envelope, it is necessary to suppress the temperature difference between the paper passing portion and the non-paper passing portion in experiments conducted by the inventor to 20 ° C or less.

FIG. 26 is a diagram showing the fixing device 106 of the present embodiment. Temperature sensing element (thermistor) 113, 1
Numeral 20 is installed in a non-image area outside the maximum sheet passing width. FIG.
Is a temperature detection circuit used in the fixing device 106 of the present invention. The CPU 116 detects a change in the resistance value of the temperature detection elements (thermistors 113 and 120) due to a change in the temperature of the surface of the heating roller using the circuit shown in FIG. The temperature difference between the temperature detecting elements 113 and 120 is detected as a voltage difference in the CPU.

FIG. 28 shows a paper passing method according to this embodiment. After the continuous printing of the envelope (S2), the next print signal and the paper size designation signal are received (S3), and STEP3 is performed.
T 'is determined based on the paper size (S4). t 'is t' = ′ T when (previous print transfer material width) ≧ (next print transfer material width), and t '= 20 when (previous print transfer material width) <(next print transfer material width). After the completion of the image forming preparation, the temperature difference ΔT between the paper passing portion and the non-paper passing portion on the surface of the heating roller is detected by the temperature detecting elements 113 and 120 (S7).
The transfer material width of the next print is wide, and ΔT> 20
Only in the case of [° C.], the request for the image data for the next print is stopped, and when ΔT ≦ 20 [° C.] or less, the image data is requested (S9), and printing is started (S10).

By performing the above-described sheet passing, it is possible to reliably and efficiently prevent wrinkles of the transfer material P having a wide transfer material width, which are generated after continuous sheet passing such as an envelope having a narrow transfer material width.

[0069]

As described above, according to the present invention,
When fixing a small-size transfer material, the temperature of the non-sheet passing portion of the heating member and the pressure member may be increased, and the wrinkling of the transfer material and the damage of the bearing portion of the fixing device caused by the temperature increase of the non-sheet passing portion. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing temperature control of a heating roller of Reference Example 1.

FIG. 2 is a diagram illustrating a configuration of a fixing device according to a first embodiment.

FIG. 3 is a cross-sectional view of the image forming apparatus of Reference Example 1.

FIG. 4 is a diagram illustrating a configuration of a fixing device according to a reference example 1.

FIG. 5 is a diagram showing temperature control of a heating roller of Reference Example 1.

FIG. 6 is a diagram showing the surface temperature of the heating roller of Reference Example 1.

FIG. 7 is a diagram showing the surface temperature of the heating roller of Reference Example 1.

FIG. 8 is a diagram showing the surface temperature of the heating roller of Reference Example 1.

FIG. 9 is a diagram showing the surface temperature of the heating roller of Reference Example 1.

FIG. 10 is a view showing the surface temperature of the heating roller of Reference Example 1.

FIG. 11 is a diagram showing a paper passing state in Reference Example 1.

FIG. 12 is a diagram showing the surface temperature of a heating roller of Reference Example 2.

FIG. 13 is a diagram showing the surface temperature of a heating roller of Reference Example 2.

FIG. 14 is a diagram showing a temperature control of a heating roller of Reference Example 2.

FIG. 15 is a diagram showing the surface temperature of the heating roller of Reference Example 2.

FIG. 16 is a view showing the surface temperature of the heating roller of Reference Example 2.

FIG. 17 is a diagram showing a temperature control of a heating roller of Reference Example 2.

FIG. 18 is a diagram showing the surface temperature of the heating roller of Reference Example 3.

FIG. 19 is a diagram showing the surface temperature of the heating roller of Reference Example 3.

FIG. 20 is a cross-sectional view schematically illustrating an image forming apparatus of Reference Example 4.

FIG. 21 is a cross-sectional view illustrating a configuration of a fixing device according to a fourth embodiment.

FIG. 22 is a diagram illustrating a heating roller surface temperature in Reference Example 4.

FIG. 23 is a diagram showing a heating roller surface temperature in Reference Example 4.

FIG. 24 is a flowchart illustrating a paper passing method according to a fourth embodiment.

FIG. 25 is a flowchart illustrating a paper passing method according to a fifth embodiment.

FIG. 26 is a front view illustrating the configuration of the fixing device according to the first embodiment;

FIG. 27 is a diagram illustrating a temperature detection circuit of the fixing device according to the first embodiment;

FIG. 28 is a flowchart illustrating a paper passing method according to the first embodiment.

[Explanation of symbols]

 Reference Signs List 40 heating roller (fixing roller) 41 pressure roller 42 heater 43 temperature detecting element (thermistor) 44 heater driving means 45 control means 104 size detecting means (rear end detecting sensor) 105 size detecting means (registration sensor) 106 fixing means (fixing) Device, fixing device) 110 heating roller 111 pressure roller 113 temperature detection means (temperature detection element) 116 printer operation delay means (CPU) 118 transfer material supply means (paper feed section drive means) N nip portion P transfer material

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Masahiro Goto 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Koichi Suwa 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Non-corporation (72) Inventor Yuko Tanaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Tetsuo Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. F term (reference) 2C061 AQ06 AS02 AS04 HK07 HN15 2H027 DA12 DA36 DA38 DA46 DA50 DC03 DC10 ED17 ED25 EE02 EE07 EF06 ZA07 2H033 AA03 AA15 BA08 BA30 BB01 CA07 CA17 CA19 CA30 CA35

Claims (1)

[Claims] 1. An image fixing device comprising: a heating member that is maintained at a set temperature; and a pressing member that forms a nip in cooperation with the heating member. A recording material having a size smaller than a predetermined size is continuously passed, and when the size of the recording material for the next print is larger than the predetermined size, the paper passing portion and the non-paper passing portion are separated. An image forming apparatus, wherein a next print command is not received until the temperature difference becomes equal to or less than a predetermined value.