JP2002072763A - Fixing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make uniform the temperature distribution of a fixation area formed of the press-contact area between a rotary member for heat fixation and a rotary member for pressure fixation in a short time. SOLUTION: This fixing apparatus is equipped with a heater h2 for large-size which is used for large-size sheet fixation and a heater h1 for small-size which is used for small-size sheet fixation, an elapsed time detecting means which measures the elapsed time T from the end of a last job to the input time of a next-time job command signal, and an idling executing means which idles the rotary member Fh for heat fixation and rotary member Fp for pressure fixation by turning on only the heater h1 for small-size according to the elapsed time T when a sheet used for the last job is small-sized and a sheet used for the next-time job is large-sized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
A fixing device that heats and fixes a toner image formed on a recording sheet in an image forming apparatus such as a laser beam printer, particularly, has a heating rotating member and a pressing rotating member that rotate while being pressed against each other, The present invention relates to a fixing device that heats and presses a toner image on a recording sheet that passes through a fixing area to be formed to fix the toner image.

[0002]

2. Description of the Related Art In a fixing device of the type described above, the temperature distribution in a fixing area through which a recording sheet passes is high at one end in the width direction (direction perpendicular to the direction in which the recording sheet is conveyed) and low at the other end. In this case, uniform fixing may not be performed or wrinkles may occur on the recording sheet. Therefore,
In the fixing mounting of the image forming apparatus, the temperature distribution of the heating roll is set within a predetermined temperature range in order to uniformly fix the toner. The following technologies (J01) to (J05) are conventionally known as such a fixing device. (J01) Technology described in JP-A-11-174896 In this publication, the temperature distribution is made uniform by using a large-size lamp and a small-size lamp together and by using a plurality of temperature detecting means. Further, two cooling fans are used to make the temperature distribution uniform. For this reason, for example, when fixing a large-sized sheet after successively fixing small-sized sheets, even if the temperature distribution in the fixing region of the large-sized sheet is not uniform, the temperature distribution can be shortened using the cooling fan in a short time. It is possible to make

(J02) Technology described in Japanese Patent Application Laid-Open No. Hei 10-78728. This publication describes a non-contact sensor to prevent the heating roll from being damaged by contact between the temperature sensor and the heating roll. . (J03) Technology described in Japanese Patent Publication No. 2799602 This patent publication describes a technique in which, when continuous copying is performed for a set number or more, the fixing roll idles after the job is completed. (J04) Technology described in Japanese Utility Model Application Laid-Open No. Sho 60-112260 In this publication, a technology is disclosed in which a heat uniform roll is driven to rotate by pressure contact with a heating roll to uniformize the temperature distribution. (J05) JP-A-8-21779 or JP-A-9
The technology described in JP-A-80968. Using one heater, the idle rotation time for making the heating roll temperature distribution uniform is set according to the paper size and the number of sheets used in the job and the elapsed time from the previous job to the next job. ing.

[0004]

[Problems to be Solved by the Invention]
Problem 1)) In the prior art (J01), since two cooling fans are used, the number of parts increases and the cost increases. In addition, since the temperature detecting means is provided on the heating roll (rotating member for heating and fixing), the heating roll may be worn and the image may be damaged. (Problems of the prior art (J02)) At present, the prior art (J02) cannot be introduced into an inexpensive machine due to its high price and complicated control. Further, the temperature distribution cannot be made uniform in a short time. (Problems of the conventional technology (J03)) In the conventional technology (J03), power and time are wasted regardless of the sheet size of the next job and the elapsed time until the next job. Also,
Since the large-size sheet fixing heater is turned on and idling is performed, an area other than the fixing area of the small-size sheet is heated, and when a small-size sheet is used, power is wasted. (Problems of the conventional technology (J04)) In the conventional technology (J04), the number of parts increases because a heat uniform roll is used.
The device becomes larger and costs increase. (Problem of the conventional technology (J05)) In the conventional technology (J05), since one heater is used, it is not possible to perform idle rotation while heating only a low temperature portion.
The temperature distribution cannot be made uniform in a short time.

The present invention has been made in view of the above circumstances, and has the following (O0
1) and (O02) are to be described. (O01) The temperature distribution in the fixing area formed by the pressure contact area of the heat fixing rotary member and the pressure fixing rotary member can be made uniform in a short time. (O02) The temperature distribution of the fixing area can be made uniform without contacting the contact type sensor for detecting the temperature of the fixing area formed by the pressure contact area of the heat fixing rotating member and the pressure fixing rotating member with the heating fixing member. To do.

[0006]

Next, the present invention devised to solve the above-mentioned problems will be described. The elements of the present invention facilitate the correspondence with the elements of the embodiments described later. For this reason, the elements of the embodiment that are denoted by parentheses are appended. The reason why the present invention is described in correspondence with reference numerals in the embodiments described below is to facilitate understanding of the present invention, and not to limit the scope of the present invention to the embodiments.

(1st invention) In order to solve the aforementioned problem,
The fixing device of the present invention has the following components (A01) to (A06).
It is characterized by having. (A01) A heat-fixing rotating member (Fh) that rotates while being pressed against each other and fixes an unfixed toner image on a recording sheet passing through a fixing area (Q5) formed by the pressed area.
And a rotary member for pressure fixing (Fp), (A02) a large-sized sheet used for fixing a large-sized sheet disposed inside the rotary member for heating and fixing (Fh) and extending in the width direction of the recording sheet. Time use heater (h2; h1 + h
3) and a small-size heater (h1) used when fixing a small-sized sheet compared to the large-sized sheet.
Fixing member (Fh + h1 + h2; Fh + h1 + h3) having the heat fixing fixing rotating member (Fh), and (A)
03) Previous job information storage means (C) for storing the sheet size and the number of recorded images (N) used in the previous job.
1), (A04) Elapsed time detecting means (C2) for measuring the elapsed time (T) from the end of the previous job to the input of the next job command signal, (A05) Detecting and storing the sheet size to be used in the next job (C3), (A06) When the sheet used in the previous job is a small-size sheet and the sheet used in the next job is a large-size sheet, the sheet size is stored in accordance with the elapsed time (T). Idle rotation execution means (C4) for turning on only the small size heater (h1) to execute idle rotation of the heat fixing rotary member (Fh) and the pressure fixing rotary member (Fp).

(Function of the First Invention) In the fixing device having the above-mentioned constitutional requirements, the heating-fixing rotating member (Fh) and the pressure-fixing rotating member (Fp) rotate while being pressed against each other, and are rotated by the pressure contact area. The unfixed toner image on the recording sheet passing through the formed fixing area (Q5) is fixed. Inside the heat fixing rotary member (Fh) of the heat fixing member (Fh + h1 + h2), a large-sized heater (h2; h1 + h3) used for fixing a large-sized sheet and a small-sized sheet compared to the large-sized sheet are used. A small size heater (h1) used at the time of fixing the sheet extends in the width direction of the recording sheet. The previous job information storage means (C1) stores the sheet size and the number of recorded images (N) used in the previous job. The elapsed time detecting means (C2) measures an elapsed time (T) from the end of the previous job to the input of the next job command signal. The next job sheet size storage means (C3) detects and stores the sheet size used in the next job. If the sheet used in the previous job is a small size sheet and the sheet used in the next job is a large size sheet, the idle rotation execution means (C4) performs the small-size use heater (C) according to the elapsed time (T). h1) is turned on, and the heat-fixing rotary member (F
h) and idle rotation of the pressure fixing rotary member (Fp). The fixing area (Q5) can be formed in a short time by the idling.
Of the temperature distribution can be made uniform. When the temperature distribution becomes uniform, it is possible to prevent the occurrence of paper wrinkles on the recording sheet.

(Description of Constituent Requirements of First Invention) The fixing device of the first invention can have the following constituent requirements (A07). (A07) Idle rotation time setting for setting the idle rotation time (Tr) according to the sheet size used in the previous job, the number of sheets recorded in the previous job, the sheet size used in the next job, and the elapsed time (T) The idle rotation execution means (C4) having means (C4a). In the case where the configuration requirement (A07) is provided, the idle rotation time setting means (C4a) uses the idle time according to the sheet size used in the previous job, the sheet size used in the next job, and the elapsed time (T). A small and reasonable idle rotation time (Tr) can be set.

The fixing device according to the first aspect of the present invention can have the following components (A08) and (A09). (A08) A small-size sheet fixing area temperature sensor (SN2) for detecting the temperature of the small-size sheet fixing area (R1) which is a fixing area (Q5) through which the small-size sheet passes, and a fixing area ( Q5) a differential fixing area for detecting the temperature of the large-sized sheet fixing area (R2), which is an area (R2-R1) that does not overlap with the small-sized sheet fixing area (R1). Temperature sensor (SN2 +) having a temperature sensor (SN3)
SN3), (A09) When the elapsed time (T) is within a predetermined time, the small-size sheet fixing area temperature sensor (SN
2) and the idle rotation is performed while controlling the large size use heater (h1 + h3) and the small size use heater (h1) until the temperature detected by the differential fixing area temperature sensor (SN3) reaches a predetermined temperature. Rotation execution means (C
4).

In the present specification, "until the detected temperatures of the small-size sheet fixing area temperature sensor (SN2) and the differential fixing area temperature sensor (SN3) reach predetermined temperatures" in the above (A09) has the following meanings. Have. (1) Until the lower detected temperature reaches the higher temperature (2) Until both detected temperatures reach the predetermined temperature (t1)

In the case where the above-mentioned constitutional requirements (A08) and (A09) are provided, the small size sheet fixing area temperature sensor (SN2) of the temperature sensor determines the fixing area (Q) through which the small size sheet passes.
5), the temperature of the small size sheet fixing area (R1) is detected, and the differential fixing area temperature sensor (SN3) detects the temperature of the large size sheet fixing area (R2) which is the fixing area (Q5) through which the large size sheet passes. Then, the temperature of the differential fixing area (R3), which is an area (R2-R1) that does not overlap with the small size sheet fixing area (R1), is detected. If the elapsed time (T) from the end of the previous job at the time when the next job start command signal is input (input of the copy start key) is within the predetermined time (Trest), the idle rotation execution means (C4) ) Are the small-size sheet fixing area temperature sensor (SN2) and the differential fixing area temperature sensor (SN3).
Until the detected temperature reaches the predetermined temperature (t1), the idle rotation is executed while controlling the large size use heater (h1 + h3) and the small size use heater (h1). In this case, the idle rotation can be terminated when the detected temperatures of the small size sheet fixing area temperature sensor (SN2) and the differential fixing area temperature sensor (SN3) become equal.
Execution of useless idle rotation can be prevented.

In the fixing device according to the first aspect of the present invention, when the components (A08) and (A09) are provided, the following components (A010) and (A011) can be further provided. (A010) An endless thin film-shaped pressure belt (Fp) constituting the pressure-fixing rotating member (Fp), and the pressure belt (Fp) disposed on the back side of the pressure belt (Fp). A pressing pad (11) for pressing the pressing member against the heating / fixing rotary member (Fh), and a belt guide (along the moving path of the pressing belt (Fp) on the back side of the pressing belt (Fp)). (Fp + 3 + 4 + 11), and (A011) the fixing area (Q
Temperature sensors (SN2, SN3) arranged on the back side of the pressure belt (Fp) passing through the fixing area (Q5) for detecting the temperature of 5). The above constituent requirements (A010),
When (A011) is provided, the pressure fixing member (Fp + 3 + 4
+11) is an endless thin-film pressure belt (Fp) constituting the pressure-fixing rotating member (Fp), and the pressure belt (Fp) disposed on the back side of the pressure belt (Fp). ) Against the rotating member (Fh) for heating and fixing, and a belt guide disposed on the back side of the pressing belt (Fp) along the movement path of the pressing belt (Fp). (3, 4). The temperature sensor detects the pressure belt (F) passing through the fixing area (Q5).
It is arranged on the back side of p) and detects the temperature of the fixing area (Q5). The temperature sensor can detect the temperature at a desired position in the fixing area (Q5) without contacting the heating rotary member (Fh). Therefore, the fixing area (Q
5) The temperature at the desired position can be controlled within a predetermined range.

(Second invention) In order to solve the above problems,
The fixing device according to the second aspect of the present invention includes the following components (A01) and (A0).
2), (A05 '), (A08), and (A09). (A01) A heat-fixing rotating member (Fh) that rotates while being pressed against each other and fixes an unfixed toner image on a recording sheet passing through a fixing area (Q5) formed by the pressed area.
And a rotary member for pressure fixing (Fp), (A02) a large-sized sheet used for fixing a large-sized sheet disposed inside the rotary member for heating and fixing (Fh) and extending in the width direction of the recording sheet. Time use heater (h2; h1 + h
3) and a small-size heater (h1) used when fixing a small-sized sheet compared to the large-sized sheet.
Fixing member (Fh + h1 + h2; Fh + h1 + h3) having the heat fixing fixing rotating member (Fh), and (A)
05 ') The next job sheet size storage means (C3) for detecting and storing the sheet size to be used in the next job when the next job command signal is input, and (A08) a fixing area (Q5) through which the small size sheet passes. A small-size sheet fixing area temperature sensor (SN2) for detecting the temperature of the small-size sheet fixing area (R1); and a large-size sheet fixing area (R2) which is a fixing area (Q5) through which the large-size sheet passes. The temperature sensor (SN2 + SN3) having a differential fixing area temperature sensor (SN3) for detecting the temperature of the differential fixing area (R3), which is an area (R2-R1) that does not overlap with the small size sheet fixing area (R1); A09 ')
When the sheet size of the next job is a large-size sheet, the small-size sheet fixing area temperature sensor (SN2)
And the large size heater (h) until the temperature detected by the differential fixing area temperature sensor (SN3) reaches a predetermined temperature.
2; h3) and the idle rotation execution means (C) for executing idle rotation while controlling the small size heater (h1).
4).

(Operation of the Second Invention) The second invention having the above configuration
In the fixing device according to the present invention, the heating-fixing rotating member (Fh) and the pressure-fixing rotating member (Fp) rotate while being pressed against each other, and are formed by the pressed region (Q5).
To fix the unfixed toner image on the recording sheet passing therethrough.
The heat fixing member (Fh + h1 + h2; Fh + h1 + h
A large-size heater (h2) used at the time of fixing a large-size sheet is provided inside the heat-fixing rotary member (Fh) of 3).
A small-size heater (h1) used for fixing a small-sized sheet as compared with the large-sized sheet is arranged to extend in the width direction of the recording sheet. The next job sheet size storage means (C3) detects and stores the sheet size used in the next job when the next job command signal is input. The small size sheet fixing area temperature sensor (SN2) of the temperature sensor (SN2 + SN3) detects the temperature of the small size sheet fixing area (R1), which is the fixing area (Q5) through which the small size sheet passes, and performs a differential fixing area temperature sensor. (SN3) is a large-size sheet fixing area (R2) that is a fixing area (Q5) through which a large-size sheet passes, and is an area (R2-R1) that does not overlap with the small-size sheet fixing area (R1). The temperature of the differential fixing region (R3) is detected. When the sheet size of the next job is a large size sheet, the idle rotation execution means (C4)
Until the detection temperatures of the small-size sheet fixing area temperature sensor (SN2) and the differential fixing area temperature sensor (SN3) reach predetermined temperatures, the large-size use heater (h2;
h3) and idling while controlling the small size heater (h1). In this case, the idle rotation can be terminated when the detected temperature difference between the small size sheet fixing area temperature sensor (SN2) and the differential fixing area temperature sensor (SN3) falls within a predetermined range. Execution can be prevented. That is, the idle rotation time (T
r) can be shortened.

(Third Invention) The following components (A01) to (A)
02), a fixing device provided with (A010) and (A011);
1) A heat-fixing rotating member (Fh) and a pressure-fixing rotating member (Fh) that rotate while being pressed against each other and fix an unfixed toner image on a recording sheet passing through a fixing region (Q5) formed by the pressed region. Fp), (A02) a large-size use heater (h1 + h3) disposed inside the heat-fixing rotary member (Fh) and extended in the width direction of the recording sheet and used for fixing a large-size sheet; A heating fixing member (Fh +) having a heater (h1) used at the time of fixing a small-sized sheet compared with a large-sized sheet and the heating-fixing rotating member (Fh).
h1 + h3), (A010) The pressure fixing rotating member (F
p), an endless thin-film pressure belt (F)
p), a pressing pad (11) disposed on the back side of the pressing belt (Fp) and pressing the pressing belt (Fp) against the heating / fixing rotating member (Fh); A pressure fixing member (Fp + 3 + 4 + 11) having a belt guide (3, 4) arranged along the movement path of the pressure belt (Fp) on the back side of the pressure belt (Fp), (A011)
Temperature sensors (SN2, SN3) arranged on the back side of the pressure belt (Fp) passing through the fixing area (Q5) to detect the temperature of the fixing area (Q5).

(Operation of the Third Invention) The third embodiment having the above-described configuration
In the fixing device according to the present invention, the heating-fixing rotating member (Fh) and the pressure-fixing rotating member (Fp) rotate while being pressed against each other, and are formed by the pressed region (Q5).
To fix the unfixed toner image on the recording sheet passing therethrough.
Inside the heating fixing member (Fh + h1 + h3), there is a large-size heater (h1 + h3) used for fixing a large-size sheet and a small-size sheet fixing compared to the large-size sheet. A small-sized heater (h1) to be used extends in the width direction of the recording sheet. The pressure fixing member (Fp + 3 + 4 + 11) is disposed on an endless thin film pressure belt (Fp) constituting the pressure fixing rotating member (Fp), and on the back side of the pressure belt (Fp). A pressing pad (11) for pressing the pressing belt (Fp) against the heating / fixing rotary member (Fh); And a belt guide (3, 4) arranged in a vertical direction. The temperature sensors (SN2, SN3) are arranged on the back side of the pressure belt (Fp) passing through the fixing area (Q5), and detect the temperature of the fixing area (Q5). The temperature sensor can detect the temperature at a desired position in the fixing area (Q5) without contacting the heating rotary member. Therefore, the temperature at a desired position in the fixing area (Q5) can be easily controlled within a predetermined range.

(Description of Constituent Requirements of First to Third Inventions) In the fixing device of the first to third inventions, the following constitutional requirements (A
012) can be provided. (A012) The large size heater (h2) is provided corresponding to the entire length of the large size sheet in the width direction, and the small size use heater (h1) is provided corresponding to the width of the small size sheet in the width direction. Heat fixing member (Fh + h1 + h2).
In the case where the above-described configuration requirements are satisfied, the heater (h
2) is provided corresponding to the entire length of the large size sheet in the width direction, and the heater (h1) used in the small size sheet is provided corresponding to the entire length of the small size sheet in the width direction. Therefore, all the recording sheets whose length is smaller than the width of the small size heater (h1) in the width direction can be fixed by turning on / off only the small size use heater (h1). Further, a recording sheet longer than the width of the small size heater (h1) and not more than the width of the large size heater (h2) is turned on only the large size heater (h2). Heating and fixing can be performed by turning off or by alternately turning on the small size heater (h1) and the large size heater (h2) at a fixed ratio according to the paper size. That is, the ON / OFF control of the fixing heaters (h1, h2) at the time of job execution may be performed for only one of the heaters h1 or h2, and thus the control is easy.

Further, the fixing device according to the first to third aspects of the present invention can have the following configuration requirement (A013). (A013) The small size heater (h1) is provided corresponding to the entire length of the small size sheet in the width direction, and the large size use heater (h1 + h3) is provided in the width direction of the large size sheet and the width direction of the small size sheet. A region (R2-R) having a difference length (R3 = R2-R1) of the total length (R1) and not overlapping the heater (h1) in the small size in the width direction.
The heating / fixing member (Fh + h1 + h3) including the differential heater (h3) disposed in the differential fixing region (R3), which is 1), and the small-size-use heater (h1). When the above-mentioned constitutional requirements are satisfied, the small-size sheet is heated and fixed by controlling ON / OFF of only the small-size use heater (h1). (H3) can be controlled to perform heat fixing.

[0020]

Embodiments of the present invention will now be described with reference to the drawings, but the present invention is not limited to the following embodiments. (Embodiment 1) FIG. 1 is an explanatory view of a color image forming apparatus having a fixing device according to Embodiment 1 of the present invention. In FIG. 1, the image forming apparatus U includes an automatic document feeder U1 and an image forming apparatus main body (copier) U2 having a platen glass PG for supporting the same. The automatic document feeder U1 includes a document feed tray TG1 on which a plurality of documents Gi to be copied are stacked, and a document feed tray T
A document discharge tray TG2 for discharging a document Gi conveyed from G1 through a copy position (document reading position) on the platen glass PG.

The image forming apparatus main body U2 has a UI (user interface) through which a user inputs an operation command signal such as copy start, an exposure optical system A, and the like.
Reflected light from a document conveyed on the platen glass PG by the automatic document feeder U1 or a document (not shown) manually placed on the platen glass PG is transmitted through the exposure optical system A to the CCD (CCD). R (red), G
(Green) and B (blue). An IPS (Image Processing System) converts the RGB electrical signals into Y (yellow), M (magenta), C (cyan), and K (black) image data and temporarily stores the image data. Output to the laser drive circuit DL at a predetermined timing.

The surface of the image carrier (rotating member) PR that rotates in the direction of the arrow Ya is uniformly charged by the charging roll CR, and the latent image writing position Q1, the developing area Q2, and the primary transfer area Q3 are moved. Pass sequentially. The ROS (latent image writing device) driven by the laser driving circuit DL causes an image carrier PR at the latent image writing position Q1 by the laser beam L.
The surface is exposed and scanned to form an electrostatic latent image on the surface of the image carrier PR. When a full-color image is formed, electrostatic latent images corresponding to four color images of Y (yellow), M (magenta), C (cyan), and K (black) are sequentially formed. Only the electrostatic latent image corresponding to the (black) image is formed.

The rotary type developing device G rotates in the developing area Q2 sequentially with the rotation of the rotating shaft Ga.
(Yellow), M (magenta), C (cyan), K
It has developing units GY, GM, GC, and GK for four colors (black). Each of the developing units GY, GM, GC, and GK has a developing roll GR that conveys a developer to the developing area Q2. Develop into a toner image Tn.

Below the image carrier PR, a slide frame F1 is provided by a pair of left and right slide rails SR, SR.
(Indicated by a two-dot chain line) is supported so as to be slidable back and forth (in a direction perpendicular to the paper surface). Slide frame F1
, A belt frame F2 of the belt module BM is supported so as to be rotatable up and down around a hinge axis F2a. The belt module BM includes a plurality of belt support rolls (Rd, Rd) that rotatably support the intermediate transfer belt B.
Rt, Rf, T2a), a primary transfer roll T1, a contact roll T2c, and the belt frame F2 that supports them. The plurality of belt support rolls (Rd, Rt, Rf, T2a) include a belt drive roll Rd, a tension roll Rt, an idler roll (free roll) Rf, and a backup roll T2a,
The backup roll T2a has the contact roll T
2c is in contact.

The belt module BM is rotatable up and down around the hinge shaft F2a. When the belt module BM is rotated downward, the belt module BM does not come into frictional contact with the image carrier PR together with the slide frame F1 to form an image. Device body U
2 can go in and out. The primary transfer unit T1 is supplied with a primary transfer voltage having a polarity opposite to that of the toner by a power supply circuit E controlled by a controller C, and transfers the toner image Tn on the surface of the image carrier PR to a primary transfer area Q3. , The primary transfer is performed on the intermediate transfer belt B. In the case of a full-color image, Y, M, C, and K are sequentially formed on the surface of the image carrier PR.
The toner images Tn of the respective colors are primary-transferred sequentially onto the surface of the intermediate transfer belt B in the primary transfer area Q3, and a full-color multiple toner image is finally formed on the intermediate transfer belt B. When a single-color mono-color image is formed, only one developing unit is used, and a single-color toner image is primarily transferred onto the intermediate transfer belt B. After the primary transfer, the image carrier P
On the R surface, the residual toner is cleaned by the image carrier cleaner CLp, and the charge is eliminated by the charge eliminating roll JR.

Below the backup roll T2a, a secondary transfer slide frame Fs slidable back and forth (in a direction perpendicular to the paper surface) by a pair of left and right slide rails SR, SR is provided with respect to the image forming apparatus main body U2. It is detachably supported in the front-rear direction. A secondary transfer lifting frame Ft of the secondary transfer unit Ut is supported on the secondary transfer slide frame Fs so as to be rotatable up and down around a hinge axis Fta. When the secondary transfer unit Ut is rotated downward, the secondary transfer unit Ut can enter and exit the image forming apparatus main body U2 without making frictional contact with the belt module BM. The secondary transfer unit Ut includes a secondary transfer roll T2b.
, A secondary transfer roll cleaner CLt, a roll support lever Lr, a post-transfer sheet guide SG2, a sheet transport belt BH, and the secondary transfer lift frame Ft that supports them.

The roll support lever Lr is a lever that supports the secondary transfer roll T2b and the secondary transfer roll cleaner CLt, and is rotated around a hinge axis La by a motor (not shown) to rotate the secondary transfer roll T2b. The intermediate transfer belt B is moved between a secondary transfer position in contact with the intermediate transfer belt B and a standby position separated from the intermediate transfer belt B. A secondary transfer area Q4 is formed by the contact area between the secondary transfer roll T2b and the intermediate transfer belt B, and a secondary transfer unit T2 is formed by the secondary transfer roll T2b, the backup roll T2a, and the contact roll T2c. I have.

The recording sheets S stored in the paper feed tray TR1 are taken out by a pickup roll Rp at a predetermined timing, separated one by one by a separating roll Rs, and conveyed to a registration roll Rr. The registration roll Rr
The recording sheet S conveyed to the pre-transfer sheet guide S is synchronized with the timing at which the primary-transferred multi-toner image or single-color toner image moves to the secondary transfer area Q4.
The sheet is transported from G1 to the secondary transfer area Q4. When the recording sheet S passes through the secondary transfer area Q4, a secondary transfer voltage having the same polarity as the toner charging polarity is applied to the contact roll T2c of the secondary transfer unit T2 from the power supply circuit E controlled by the controller C. Is done. The secondary transfer unit T2 collectively applies the color toner image primarily transferred onto the intermediate transfer belt B onto the recording sheet S in the secondary transfer area Q4.
Next transfer. The residual toner is removed from the intermediate transfer belt B after the secondary transfer by the belt cleaner CLb. Further, the secondary transfer roll T2b is a secondary transfer roll cleaner CLt.
As a result, the toner adhered to the surface is collected.

The secondary transfer roll T2b and the belt cleaner CLb are arranged so as to be able to freely contact (separate and contact) with the intermediate transfer belt B, and when a color image is formed, the final color is not fixed. It is separated from the intermediate transfer belt B until the toner image is primarily transferred to the intermediate transfer belt B. The secondary transfer roll cleaner CLt
Is the secondary transfer roll T2 with respect to the intermediate transfer belt B.
Move away from and move with b. The recording sheet S on which the toner image has been secondarily transferred is conveyed to a fixing area Q5 by a post-transfer sheet guide SG2 and a sheet conveying belt BH. And pressure roll (rotating member for pressure fixing) Fp
Is fixed by a fixing device F having a pair of fixing rolls (Fh + Fp). The recording sheet S on which the toner image has been fixed is discharged to the recording sheet discharge tray TR2. The codes Rp, Rs, Rr, SG1, SG
The sheet conveying device SH is constituted by the elements indicated by 2, BH.

(Fixing Device) FIG. 2 is an enlarged view of the fixing device shown in FIG. FIG. 3 is a sectional view taken along the line III-III of FIG. 2 and 3, the heating roll Fh incorporates therein a heater h1 for use in small size and a heater h2 for use in large size paper.
It is rotatably supported by a frame (not shown) via ha and Fha. Further, both ends in the roll axis direction of the pressure roll Fp are rotatably supported by a frame (not shown) via bearings Fpa, Fpa. The heater h1 is A4
A heater for fixing SEF (A4 short edge feed, that is, a conveyance sheet whose front and rear ends in the conveyance direction are short edges of an A4 size sheet), and the length thereof is almost the same as the length of the short edge of the A4 sheet. Or a slightly longer length. The heater h1 has the same width as the small-size sheet fixing area R1 (see FIG. 3), which is an area through which a small-size sheet (a sheet having a sheet width of A4 SEF or less in the direction perpendicular to the sheet conveyance direction) passes. In FIG. 3, the heater h1 is A4SEF and B
When a 5 SEF sheet is fixed, ON / OFF control is performed to maintain the temperature of the small-size sheet fixing region R1 at the fixing temperature.

The heater h2 is used for fixing A4 LEF (A4 long edge feed, that is, a transport sheet whose front and rear ends in the transport direction are long edges of an A4 size sheet). Is approximately the same as or slightly longer than the length of the long edge of the A4 sheet. The heater h2 is a large-size sheet (the sheet width in the direction perpendicular to the sheet conveyance direction is A4SEF).
It has the same width as the large-size sheet fixing area R2 (see FIG. 3), which is an area through which a longer sheet passes. A4LEF, A3SEF as the large size sheet
(A3 short edge feed), B4SEF, B5L
There is an EF sheet or the like, and fixing is performed using the heater h2. In FIG. 3, the heater h2 is turned on and off to maintain the temperature of the large-size sheet fixing region R2 at the fixing temperature. In FIG. 3, a differential fixing area R3 (= R2-R1), which is a difference area between the large-size sheet fixing area R2 and the small-size sheet fixing area R1, is heated only at the time of fixing the large-size sheet. Is an area that is not heated during fixing.

(Explanation of Control Unit of First Embodiment) FIG. 4 is a block diagram (functional block diagram) showing each function provided in the control unit of the fixing device according to the first embodiment of the present invention. . In FIG. 4, a controller C is an I / O for performing input / output of signals with the outside, adjustment of input / output signal levels, and the like.
(Input / output interface), ROM (read only memory) storing programs and data for performing necessary processing, RAM (random access memory) for temporarily storing necessary data, and storage in the ROM (A central processing unit) that performs processing in accordance with the programmed program, and a computer having a clock oscillator and the like. By executing the program stored in the ROM, various functions can be realized. it can.

(Signal Input Element Connected to Controller C) The controller C includes a UI (user interface) and a heating roll temperature sensor SN1 (FIGS. 2 to 4).
Signals from other signal input elements are input. The UI includes a display UI1, a copy start key UI2, a copy number setting key UI3, and a magnification setting key UI.
4, numeric keypad UI5, etc.

(Control elements connected to the controller C) The controller C includes an IPS (image processing system, that is, an image processing system), a DL
(Laser driver or laser drive circuit), power supply circuit E, heating roller drive circuit D1 and heater drive circuit D2 of the fixing device, and other control elements, and output operation control signals for them. The power supply circuit E supplies power to various drive circuits, motors, heaters, and the like. The heating roll driving circuit D1 rotationally drives the heating roll Fh via a heating roll driving motor M1. The heater driving circuit D2 drives the heaters h1 and h2 built in the heating roll Fh.

(Function of Controller C) The controller C has a function of executing a process according to an input signal from the signal output element and outputting a control signal to each control element. That is, the controller C has the following functions. C0: Job Executing Unit The job executing unit C0 executes copying in response to the input of the copy start key UI2. C1: Previous Job Information Storage Unit The previous job information storage unit has a sheet size storage unit C1a of the previous job (previous copy operation) and a recording number (copy number) storage unit of the previous job, and stores information of the previous job. Is stored. C1a: Sheet size storage unit of the previous job The sheet size storage unit C1a of the previous job is a recording sheet (copy paper) of the previous job (previous copy operation).
(The length of the front edge of the sheet in the transport direction) is stored. C1b: Recording Number Storage Unit of Previous Job The recording number storage unit C1b of the previous job stores the number of recording sheets (copy number) of the previous job (previous copy operation).

C2: Elapsed Time Counter (Elapsed Time Detecting Means) The elapsed time counter C2 measures the elapsed time from the end of the previous job. Fr1: elapsed time determination flag Fr1 has an initial value of “0”,
It becomes "1" at the start of counting of the measurement time of the elapsed time counter C2, and becomes "0" when the elapsed time reaches 180 sec. Fr2: idle rotation executing determination flag The initial value of the idle rotation executing determination flag Fr2 is "0", "1" during the idle rotation execution period, and "0" at the end of the idle rotation. Fr3: Judgment flag during job execution The initial value of the judgment flag Fr3 during job execution is "0", "1" during the job execution period, and "0" at the end of the job.

C3: Sheet Size Detection and Storage Unit for Next Job The sheet size detection and storage unit C2 for the next job is used for the next job when a command signal for the next job is input (input of the copy start key UI2). The size of the recording sheet to be detected is detected and stored. C4: Idling rotation execution means Idling rotation executing means C4 has idling rotation time setting means C4a, and executes idling for a time set by the idling rotation time setting means C4a. The idle rotation time setting means C4
a has an idle rotation time calculation expression setting table C4a1 and a calculation expression parameter setting table C4a2, and sets the idle rotation time. C4a1: idle rotation time calculation formula setting table FIG. 5 is an explanatory diagram of the idle rotation time calculation formula setting table C4a1. In FIG. 5, the idle rotation time calculation expression setting table C4a1 includes an idle rotation time calculation expression for calculating the idle rotation time based on the sheet sizes G1 to G4 of the previous job and the sheet sizes G1 to G4 of the next job (see FIG. 2) are stored. C4a2: Calculation formula parameter setting table FIG. 6 is an explanatory diagram of the idling time calculation formula setting table C4a2. 6, the calculation formula parameter setting table C4a2 includes an idle rotation time calculation expression Tr corresponding to the numerical values 0 to 3 (see FIG. 5) specifying the idle rotation time calculation expression (see FIG. 2 in FIG. 6). And a table for storing values of the parameters a and b of the idle rotation time calculation formula Tr corresponding to the numerical values 0 to 3, wherein the parameters a and b are determined corresponding to the numerical values 0 to 3. I have.

C5: Heating Roll Rotation Control Means The heating roll rotation control means C5 is
0 and the operation of the heating roll driving circuit D1 is controlled in accordance with the output signal of the idle rotation execution means C4 and the like.
To rotate. C6: Fixing Heater Control Unit The fixing heater control unit C6 includes the job executing unit C0.
The operation of the heater drive circuit D2 is controlled according to the output signal of the idle rotation execution means C4 and the like, and the heaters h1 and h2 incorporated in the heating roll Fh are turned on and off.

FIG. 7 shows the elapsed time (the rest of the fixing device) from the end of the previous job to the start of the next job without idling with respect to the number of prints N of the previous job when the sheet size of the next job is larger than the previous job. Time) T
5 is a graph showing a rest time Trest which is a set value of the above. In FIG. 7, when the sheet size of the recording sheet of the next job is larger than that of the previous job, and when the number of prints in the previous job is N, the elapsed time from the previous job can be started without idle rotation ( The set value Trest of the fixing device rest time) T is as follows. In the case of N <150, Trest ≧ 1.2N (sec) or more. When N ≧ 150, Trest ≧ 180 (sec) or more. Therefore, when the elapsed time T satisfies T ≧ Trest and the next job start command signal is input (input of the copy start key), the next job is started immediately without idling. .

FIG. 8 shows the case where the next job start command is input (input of the copy start key) when the sheet size of the next job is larger than the previous job, and when the next job start command signal is transmitted from the previous job. 11 is a graph showing a set value Trev (sec) of the idle rotation execution time Tr with respect to the number N of prints of the previous job when the elapsed time T until the input (input of the copy start key) is T <Trest. In FIG. 8, when the sheet size of the recording sheet of the next job is larger than that of the previous job and the number of prints in the previous job is N, the elapsed time (resting time of the fixing device) T from the previous job is The set value Trev of the idle rotation time Tr executed when the input of the next job start command signal (copy start key) is input when T <Trest is as follows. If N ≦ 50, Trev = 0 (sec). When 50 <N <150, Trev = 0.6 (N-50) (sec). When N ≧ 150, Trev = 60 (sec).

The set value Trev of the idle rotation time Tr in the case of 50 <N <150 can be determined, for example, as follows. Trev = 0.6 (N−50) × ｛(Trest−T) / Tres
t)｝ (sec).

(Operation of the First Embodiment) FIG. 9 is a time chart of a heating roll temperature control showing a general example of the heater ON / OFF control performed by the fixing heater control means C6.
In FIG. 9, when the image forming apparatus is turned on, the heater h2 is turned on by the fixing heater control unit C6, and the temperature of the heating roll rises. Heating roll temperature sensor SN1
The heater h2 is turned off when the temperature of the heating roll detected by the heater becomes equal to or higher than the standby temperature t0 and the standby temperature t
It turns on when it becomes less than 0. Thus, the temperature of the heating roll Fh is maintained at t0 until the copy start key (job start signal input key) is turned on. When the copy start key is turned on, one of the heaters h1 and h2 corresponding to the sheet size on which the image is to be recorded is turned on, and at the same time, the heating roll Fh starts rotating. The job can be started when the temperature of the heating roll Fh reaches the copy temperature t1, but the job (copy operation) is started after the idle rotation is performed for a necessary time.

FIG. 10 is a flowchart of idle rotation and job execution processing. Each ST in the flowchart of FIG.
The processing of (step) is performed according to a program stored in the ROM of the controller C. This process is executed by multitasking in parallel with other various processes of the image forming apparatus. The flowchart of the idle rotation and job execution processing shown in FIG. 10 is started when the power is turned on. In step ST1 of FIG. 10, it is determined whether the copy start key has been turned on. ST if no (N)
Step 1 is repeated. If yes (Y), the process moves to ST2. In ST2, it is determined whether or not an elapsed time determination flag Fr1 indicating whether or not the elapsed time T from the end of the previous job is within the upper limit of 180 seconds or more is "1". The elapsed time determination flag Fr1 has an initial value “0”, becomes “1” at the end of the job, and has an elapsed time upper limit of 180.
This flag is set to “0” when the time exceeds sec.

If no (N) in ST2, ST1
3 and if yes (Y), then to ST3. ST3
In the above, the elapsed time T is T <Trest (Trest = 1.
It is determined whether 2N (see FIG. 6) and N is the number of recordings of the previous job. If no (N), the process moves on to ST13, and if yes (Y), the process moves on to ST4. In ST4, the sheet size is detected and stored in the next size storage means C3 (see FIG. 4). Next, in ST5, using the values stored in the sheet size storage means C1a of the previous job and the sheet size detection storage means C3 of the next job, and the idle rotation time calculation formula setting table C4a1 in Table 1 of FIG. The rotation time calculation formulas 0 to 3 are set. That is, chart 1 in FIG.
, One of the calculation formulas 0 to 3 (see FIGS. 5 and 6) is set. Next, in ST6, the set value Trev of the idling time Tr is set using the parameter setting table C4a2 in FIG.

Next, in ST7, it is determined whether or not Tr> 0. If no (N), the process moves on to ST13, and if yes (Y), the process moves on to ST8. Next, in ST8, Tr
= A (N−b) ≦ 60 (sec). If no (N), the process moves on to ST9, and if yes (Y), S
Move to T10. In ST9, the set value Trev of the idling time Tr is set to 60 sec. In ST10, the idling execution determination flag Fr2 is set to "1". Next, ST11
, The small-size heater h1 used in the previous job is turned on, and idle rotation is performed Trev (sec). The on / off control of the heaters h1 and h2 will be described later with reference to FIGS.
This will be described below. After the idling is completed, in ST12, the idling execution determination flag Fr2 is set to "0".

Next, in ST13, the job execution determination flag Fr3 is set to "1". Next, in ST14, execution of a job (next job) is started. Next, in ST15, it is determined whether or not the job has been completed. If no (N), ST15 is repeatedly executed. If yes (Y), the process moves to ST16. Next, in ST16, the job execution determination flag Fr3 is set to "0". Next, in ST1
Return to

FIG. 11 is a flowchart of idling execution determination data storage processing. The processing of each ST (step) in the flowchart of FIG.
This is performed according to the program stored in M. This process is executed by multitasking in parallel with other various processes of the image forming apparatus. The flowchart of the idle rotation execution determination data storage processing shown in FIG. 11 is started when the power is turned on. In step ST21 of FIG. 11, it is determined whether or not the job execution has been started. ST if no (N)
Step 21 is repeatedly executed. ST2 if yes (Y)
Move to 2. In ST22, the sheet sizes G1 to G4
(See FIG. 5) is stored in the previous size storage means C1a.
Next, in ST23, it is determined whether or not the job has been completed. If no (N), the process moves to ST24. In ST24, it is determined whether or not one copy (image recording) has been made. If no (N), the process returns to ST23. If yes (Y), the process moves to ST25. In ST25, the number of copies N
Is set to N = N + 1. Next, the process proceeds to ST23.

If the answer is YES (Y) in ST23, the process moves to ST26. In ST26, N is stored in the previously recorded number storage means C1b. Next, in ST27, counting of the elapsed time T after the end of the job is started. Then S
At T28, the elapsed time determination flag Fr1 is set to Fr1 =
"1" is stored. The elapsed time determination flag Fr1 is 0 ≦ T
This flag is set to “1” only in a period of ≦ 180 (sec) and set to “0” in other periods. Next, in ST29,
It is determined whether or not T ≧ 180. ST if yes (Y)
The process moves to ST31, and if no (N), the process moves to ST30. ST
At 30, it is determined whether idle rotation has started. This determination is based on the idling execution determination flag Fr2 (S11 in FIG. 10).
Judgment is made based on whether Fr2 = "1" in T10 to ST12). If no (N), the process returns to ST29; if yes (Y), the process moves to ST31. In ST31, the following processing is performed. (1) Assuming T = 0, the counting of T is stopped. (2) The elapsed time determination flag Fr1 is set to “0”. (3) It is assumed that the number of recordings N = 0. Next, the process returns to ST21.

FIG. 12 is a main flow chart of a fixing heater control process according to the first embodiment of the present invention.
The flowchart of FIG. 12 is a flowchart common to the second and third embodiments described later. The processing of each ST (step) in the flowchart of FIG. 12 is performed according to a program stored in the ROM of the controller C. This process is executed by multitasking in parallel with other various processes of the image forming apparatus. The flowchart of the idle rotation execution determination data storage processing shown in FIG. 12 is started when the power is turned on. In step ST41 of FIG. 12, it is determined whether or not the apparatus is on standby. This determination is made based on whether or not both the idling execution determination flag Fr2 and the job execution determination flag Fr3 are "0". When both the idling-in-execution determination flag Fr2 and the job-in-execution determination flag Fr3 are 0, the idle rotation is not being executed and the job is not being executed. If yes (Y), the process moves to ST42. The subroutine of ST42 will be described later with reference to FIG. After ST42, the process returns to ST41. No (N) in ST41
In the case of, the process moves to ST43.

In step ST43, it is determined whether or not idle rotation is being performed. This determination is based on the idling running determination flag Fr2.
= “1”. If yes (Y), the process moves to ST44. The subroutine of ST44 will be described later with reference to FIG. After ST44, the process returns to ST41. If no (N) in ST43, the process moves to ST45.
In step ST45, it is determined whether or not the job is being executed. This determination is based on the job execution determination flag Fr3 = "1".
It is determined by whether or not. If yes (Y), ST46
Move on to The subroutine of ST46 will be described later with reference to FIG. After ST46, the process returns to ST41. ST45
If the result is NO (N), the process returns to ST41.

FIG. 13 is a flowchart of the standby heater control process, and is a flowchart of the subroutine of ST42. In ST42-1 in FIG. 13, it is determined whether or not the heating roll temperature t satisfies t ≧ t0 with respect to the standby temperature set value t0. If yes (Y), all heaters h1 and h2 are turned off, and the process returns to ST41 in FIG. 12, and no (N)
In this case, the heater h2 is turned on in ST42-3, and the process returns to ST41. That is, during standby, the temperature of the heating roll Fh is controlled by turning on and off the heater h2.

FIG. 14 is a flowchart of the idling-time heater control process, which is a flowchart of the subroutine of ST44. In ST44-1 in FIG. 14, it is determined whether or not the heating roll temperature t satisfies t ≧ t1 with respect to the set value t1 of the fixing temperature. If no (N), the process moves to ST44-2. S
At T44-2, the heater used in the previous job (small size sheet fixing heater h1) is turned on,
It returns to ST41 of No. 2. In the case of YES (Y) in ST44-1, the process moves to ST44-3. In ST44-6, all heaters are turned off. Next, ST41 of FIG.
Return to

FIG. 15 is a flowchart of the heater control process at the time of job execution, and is a flowchart of the subroutine of ST46. In ST46-1 in FIG. 15, it is determined whether or not the heating roll temperature t satisfies t ≧ t1 with respect to the set value t1 of the fixing temperature at the time of job execution. In the case of Yes (Y), all heaters h1 and h2 are turned off, and then ST4 in FIG.
Returning to 1, if no (N), the heater corresponding to the sheet size used in the job is turned on in ST46-3, and then the process returns to ST41 in FIG. That is, during the execution of the job, the temperature of the heating roll Fh is controlled by turning on and off the heater corresponding to the sheet size used in the job.

FIG. 16 is a graph for explaining the operation and effect of the first embodiment. A solid roll (a rubber pressure roll or a rubber pressure roll whose surface is coated with a tube such as PFA) is shown in FIG. Immediately after 100 consecutive copies of A4 SEF sheets (small size sheets)
FIG. 7 is a diagram illustrating the occurrence rate of paper wrinkles and the grade of paper wrinkles of the large-size sheet (A3 SEF sheet) when 50 SEF sheets (large-size sheets) are copied, for each type of fixing device. In FIG. 16, “no countermeasure”, “improved heating roll”, “large-size heater idle rotation”, and “first embodiment idle rotation” have the following meanings. (1) "No countermeasure": A case where the next job is executed without idle rotation after a rest time of 50 sec using a heating roll having the same configuration as that of the first embodiment. (2) "Improved heater" ... heater h1 of the first embodiment
And a case where the next job is executed without idle rotation after a rest time of 50 sec by using a heater that reduces the calorific value distribution of h2 on the large-size sheet transfer area side (right side in FIG. 3). (3) "Large-size heater idle rotation": The heating roll Fh of the first embodiment is used, the idle rotation execution time is determined in the same manner as in the first embodiment, and the large-size heater (heater used in the next job) h2 is set. When turning on and idling (idle rotation for 30 sec after a rest time of 20 sec). (4) “Small size heater idle rotation”: Small size heater according to the method of the first embodiment (the heater used in the previous job)
h1 is turned on and idling (30 sec after resting time 20 sec)
(Second idle rotation).

In FIG. 16, G1 to G5 are indices of the degree of wrinkles, G1 indicates a small wrinkle and a small wrinkle, and G5 indicates a large wrinkle and a large wrinkle. As can be seen from FIG. 16, in the first embodiment of the present invention, generation of wrinkles is small and small as compared with the other embodiments.

FIG. 17 is a graph for explaining the operation and effect of the first embodiment. FIG.
Continuously copy 100 sheets of EF sheets (small size sheets) and A3SEF sheets (large size sheets) in the next job
Rest time when copying 50 sheets (elapsed time from end of previous job to start of next job) and A3S
FIG. 17B is a view showing the relationship between the grade of paper wrinkles generated on the EF sheet and FIG. 17B shows a case where 100 sheets of A4 SEF sheets (small size sheets) are continuously copied in the previous job, and A
FIG. 9 is a diagram showing a relationship between idle rotation time when 50 sheets of No. 3 (large size sheet) are copied and the grade of paper wrinkles generated on the A3SEF sheet. FIG. 17A, FIG.
As can be seen from the comparison of FIG. 7B, the occurrence of paper wrinkles can be prevented in a short time by performing the idle rotation. Therefore, by performing the idle rotation, the temperature distribution of the heating roll Fh is made uniform in a short time. It is considered possible.

FIG. 18 is a graph showing the rate of occurrence of paper wrinkles by grade for the sponge roll and the solid roll.
A used A4SEF in the previous job using sponge roll
100 sheets (small size sheet) of the
A3 SEF sheet (large sheet) 50 for next job
Rest time when copying on a sheet (the elapsed time from the end of the previous job to the start of the next job) and the A3SEF
A diagram showing the relationship between the grade of paper wrinkles generated in the sheet,
FIG. 18B shows A4 in the previous job using the solid roll.
Rest time when 100 consecutive copies of SEF sheets (small size sheets) and 50 A3 SEF sheets (large size sheets) in the next job and A3S
It is a figure which shows the relationship with the grade of the paper wrinkle which generate | occur | produced in EF sheet. FIG. 19 is a graph showing a change in a nip width (a length of a press-contact area of a heating roll and a pressure roll in a sheet conveying direction) between a sponge roll and a solid roll. FIG. Change in nip width, position in the roll axis direction, and rest time when 100 consecutive A4 SEF sheets (small size sheets) are copied in a job (time elapsed since the end of the previous job)
FIG. 19B is a diagram showing the relationship between FIG. 19B and FIG. 19B. Using a tube solid roll (a roll obtained by coating a solid roll with a tube made of a material having good releasability), 100 sheets of A4 SEF sheets (small size sheets) are continuously copied in the previous job. FIG. 9 is a diagram showing a relationship between a change in nip width, a position in a roll axis direction, and a rest time when the nip width is changed.

In FIG. 19, O / B means the out side (front side or outside) of the image forming apparatus, and I / B means in (rear side or back side). The front side (O / B) is the left side portion of FIG.
Side. The rear side (I / B) is the right side of FIG. 3 and is the differential fixing area R3 side (the area where only the fixing of the large size sheet is performed and the fixing of the small size sheet is not performed). As can be seen by comparing FIGS. 19A and 19B, the nip width of the solid roll greatly changes in the large-size sheet fixing region R2 side (the side where the temperature rise is large during continuous running of the small-size sheet) as compared to the sponge roll. (To increase. Further, as can be seen from FIG. 18, the solid roll is more likely to generate poor-grade paper wrinkles than the sponge roll, but this has a large change in the nip width in the heating roll axial direction as shown in FIG. 19. That is one reason.

In the first embodiment, the heating roll Fh using the solid roll in which the paper wrinkles easily occur is used.
Is used, the temperature distribution in the width direction of the fixing region Q5 can be made uniform in a short time, so that the nip width at each position in the axial direction of the heating roll can be made uniform. For this reason, the occurrence of paper wrinkles can be prevented.

(Embodiment 2) FIG. 20 is a flowchart of a heater control process during idling of a color image forming apparatus having a fixing device according to Embodiment 2 of the present invention, and corresponds to FIG. 14 of Embodiment 1 described above. FIG.
It is a flowchart of a subroutine. In the description of the second embodiment, components corresponding to the components of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. The second embodiment differs from the first embodiment in the idling-time heater control process, but is otherwise the same as the first embodiment. The idling-time heater control process (see FIG. 20) according to the second embodiment includes the heater h1 for fixing the small-size sheet of the previous job.
This embodiment differs from the first embodiment shown in FIG. 14 in which only the small-size sheet fixing heaters are turned on and off by alternately turning on the large-size sheet fixing heaters h2 for the next job and performing idle rotation.

In ST44-11 of FIG. 20, it is determined whether or not the heating roll temperature t satisfies t ≧ t1 with respect to the fixing temperature set value t1. If no (N), the process moves to ST44-12. In ST44-12, the heater selection flag Fr
It is determined whether 4 = “0”. The initial value of Fr4 is F
r4 = "0". If yes (Y), ST44-
Move to 13. In ST44-13, the heater used for the previous job (small-size sheet fixing heater) h1 is turned on, and the process returns to ST41 in FIG. ST44-
If No (N) in 12 (Fr4 = “1”), the process moves to ST44-14. In ST44-14, the heater for the next job (the large-size sheet fixing heater) h2 is turned on, and the process returns to ST41 in FIG.

In the above ST44-11, yes (Y)
In the case of, the process moves to ST44-15. In ST44-15, it is determined whether or not heaters h1 and h2 are on. If yes (Y) (if any), the process moves to ST44-16. In ST44-16, all heaters are turned off. Next, in ST44-17, the heater selection flag Fr4
= "0" is determined. If yes (Y) (if Fr4 = "0") in ST44-17, ST44-
In ST44-18, the heating heater selection flag Fr4 is set to "1", and the flow returns to ST41 in FIG. If no (N) (if Fr4 = "1") in ST44-17, the process moves to ST44-19, and
At T44-19, the heater selection flag Fr4 =
After "0", the process returns to ST41 in FIG. Said S
In the case of No (N) in T44-15, the process returns to ST41 of FIG. In the second embodiment, the small-size sheet fixing heaters h1 and the large-size sheet fixing heaters h2 are alternately turned on during idling, but they can be configured to be turned on and off at a preset duty ratio. is there.

(Embodiment 3) FIG. 21 is an explanatory view of a color image forming apparatus having a fixing device according to Embodiment 3 of the present invention. FIG. 22 is an enlarged view of the fixing device shown in FIG. FIG. 23 is a sectional view taken along the line XXIII-XXIII in FIG. In the description of the third embodiment, components corresponding to the components of the first embodiment are denoted by the same reference numerals, and a detailed description thereof will be omitted. The third embodiment differs from the first embodiment in the following points, but has the same configuration as the first embodiment in other points. Image forming apparatus U including fixing device of Embodiment 3
Uses a pressure belt (pressure-fixing rotating member) Fp instead of the pressure roll Fp of the first embodiment. The pressure belt Fp is formed by a thin-film endless belt, and a frame support shaft 1 extending in the width direction of the pressure belt Fp is disposed inside the endless pressure belt Fp. The frame support shaft 1 has both ends in the belt width direction connected to a pair of rotation levers (not shown), and a position separated from a position close to the heating roll Fh when the rotation lever (not shown) rotates. To move between.

A belt support frame 2 extending in the axial direction is fixed to the frame support shaft 1, and belt guides 3 and 4 are connected to side surfaces of the belt support frame 2. , A plurality of cylindrical members 6 are fixed at intervals in the axial direction of the heating roll Fh. A column 7 is supported on each cylindrical member 6 so as to be slidable up and down, and a pad support member 8 extending in the axial direction of the heating roll is fixed to the upper end of the column 7. An outer end of a pin (not shown) penetrating the column 7 has an elongated hole (not shown) formed in a side wall of the cylindrical member 6 and extending in the axial direction.
And the column 7 is movable within a range in which the pin (not shown) can move in the axial direction within the elongated hole (not shown). A rigid belt pressing member 9 is fixed to a side surface of the pad supporting member 8 fixed to the upper end of the column 7, and a pressing pad 11 having elasticity is supported on an upper surface of the pad supporting member 8. A compression spring 12 is disposed outside the cylindrical member 6, and the compression spring 12 constantly presses the pad support member 8 toward the heating roll Fh.
The pressure fixing members (Fp, 1 to 12) according to the third embodiment are constituted by the elements indicated by the reference numerals Fp, 1 to 12, and the like.

In FIG. 22, the belt pressing member 9 and the pressing pad 11 press the pressing belt Fp against the heating roll Fh from the back side by the compression spring 12. Since the belt pressing member 9 is formed of a harder material than the heating roll Fh, a portion of the surface of the heating roll Fh pressed by the hard belt pressing member 9 is deformed into a concave shape. Due to this deformation, the recording sheet passing through the fixing area Q5 which is a pressure contact area between the heating roll Fh and the pressure belt Fp is easily peeled off from the surface of the heating roll Fh. As shown in FIG. 23, a small-size sheet fixing area temperature sensor SN2 for detecting the temperature of the fixing area, and a large-size sheet Passing through the fixing area Q5
A differential fixing area temperature sensor SN3 for detecting a temperature of a differential fixing area R3 (= R2-R1) which is an area (R2-R1) which is a large size sheet fixing area R2 which is not overlapped with the small size sheet fixing area R1. Is arranged.

(Explanation of Control Unit of Third Embodiment) FIG. 24 is a block diagram (functional block diagram) showing functions of a control unit of a fixing device according to a third embodiment of the present invention. . (Signal input element connected to controller C) The controller C includes a small-size sheet fixing area temperature sensor SN2 and a differential fixing area temperature sensor SN instead of the heating roll temperature sensor SN1 shown in FIG.
3. Signals from other signal input elements are input. SN2: Small-size sheet fixing area temperature sensor The small-size sheet fixing area temperature sensor SN2 detects a small-size sheet fixing area temperature ts. SN3: Differential fixing area temperature sensor Differential fixing area temperature sensor SN3 is a large-size sheet fixing area R2 that is a fixing area Q5 through which a large-size sheet passes.
And a differential fixing area R3 (= R2-R) which is an area (R2-R1) that does not overlap with the small-size sheet fixing area R1.
1, that is, the temperature tm of the area through which only the large-sized sheet passes). (Control Elements Connected to Controller C) The controller C is connected to the same control elements as those in the first embodiment shown in FIG. 4 and outputs their operation control signals.

(Function of Controller C) The controller C has a function of executing a process according to an input signal from the signal output element and outputting a control signal to each control element. That is, the controller C has the following functions. C0: Job execution means Job execution means, ie, C0 is copy start key U
The copy is executed according to the input of I2. Fr2: idle rotation executing determination flag The initial value of the idle rotation executing determination flag Fr2 is "0", "1" during the idle rotation execution period, and "0" at the end of the idle rotation. Fr3: Judgment flag during job execution The initial value of the judgment flag Fr3 during job execution is "0", "1" during the job execution period, and "0" at the end of the job.

C4: idle rotation executing means The idle rotation executing means C4 has a fixing area temperature difference detecting means C4a, and when the start signal input key (copy start key UI2) of the next job is input, If the detected temperature difference between the small size sheet fixing area temperature sensor SN2 and the large size sheet fixing area temperature sensor SN3 is not within the predetermined range, the idle rotation is performed until the detected temperature difference falls within the predetermined range. C5: Heating Roll Rotation Control Means The heating roll rotation control means C5 controls the operation of the heating roll drive circuit D1 in accordance with output signals from the job execution means C0 and the idle rotation execution means C4, and rotates the heating roll Fh. . C6: Fixing Heater Control Unit The fixing heater control unit C6 controls the operation of the heater driving circuit D2 according to output signals from the job executing unit C0 and the idle rotation executing unit C4, and is built in the heating roll Fh. The heaters h1 and h2 are turned on and off.

(Operation of Third Embodiment) FIG. 25 is a flowchart of idle rotation and job execution processing according to the third embodiment, and corresponds to FIG. 10 of the first embodiment. The processing of each ST (step) in the flowchart of FIG.
This is performed according to a program stored in the ROM of the controller C. This process is executed by multitasking in parallel with other various processes of the image forming apparatus. FIG.
The flowchart of the idle rotation and job execution processing shown in FIG. The processing shown in FIG.
ST2 to ST7 and ST9 in FIG. 10 of the first embodiment are omitted, and ST8 'is provided instead of ST8 in FIG. 10 and ST11-1 is added. FIG.
In step ST1, it is determined whether the copy start key has been turned on. If no (N), ST1 is repeatedly executed. If yes (Y), the process moves to ST8 '. In ST8 ', it is determined whether or not the difference (tm-ts) between the differential fixing area temperature (temperature of the fixing area through which only the large size sheet passes) tm and the small size sheet fixing area temperature ts is larger than the allowable temperature difference ta. . If no (N), the process moves to ST13, and if yes (Y), the process moves to ST10.

In ST10, the idling-in-progress discrimination flag Fr2 is set to "1". Next, in ST11, the small-size sheet fixing heater h1 is turned on to start idling. Next, in ST11-1, it is determined whether or not the difference (tm-ts) between the large-size sheet fixing area temperature tm and the small-size sheet fixing area temperature ts is equal to or smaller than the allowable temperature difference ta. If no (N), the process repeats ST11-1. If yes (Y), the process moves to ST12. Next, ST1
In step 2, the idling execution determination flag Fr2 is set to "0".

Next, in step ST13, the job execution determination flag Fr3 is set to "1". Next, in ST14, execution of a job (next job) is started. Next, in ST15, it is determined whether or not the job has been completed. If no (N), ST15 is repeatedly executed. If yes (Y), the process moves to ST16. Next, in ST16, the job execution determination flag Fr3 is set to "0". Next, in ST1
Return to

The main flow of the fixing heater control process according to the third embodiment is exactly the same as that in FIG. 12 of the first embodiment. Also, a flowchart of the standby heater control process (flowchart of the subroutine of ST42 in FIG. 12) of the third embodiment will be described.
This is exactly the same as FIG. 13 of the first embodiment. The flowchart of the heater control process at the time of job execution of the third embodiment (the flowchart of the subroutine of ST46 in FIG. 12) is exactly the same as that of FIG. 15 in the first embodiment. FIG. 26 is a flowchart of the idle rotation heater control process of the third embodiment, which is a flowchart corresponding to FIG. 14 of the first embodiment, and is a flowchart of the subroutine of ST44 in FIG. ST4 in FIG.
In 4-21, it is determined whether or not tm−ts ≧ ta. If yes (Y), the process moves to ST44-22. ST44-2
In 2, the small size sheet fixing heater h1 is turned on, and the process returns to ST41 in FIG. ST44
In the case of No (N) at -21, all heaters are turned off at ST44-23, and then at ST41 of FIG.
Return to

In each of the first to third embodiments, when the temperature of the fixing area Q5 formed by the pressure contact area of the heat fixing rotary member Fh and the pressure fixing rotary member Fp is detected, the contact type sensor is heated and fixed. It can be detected without making contact with the sheet passing area on the surface of the rotating member Fh. For this reason,
Since it is possible to prevent the surface of the heating / fixing rotary member Fh from being damaged, it is possible to prevent the image quality from being degraded due to the damage to the surface of the heating / fixing rotary member.

(Modification) Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, but includes the gist of the present invention described in the claims. Various changes can be made within the scope. Modified embodiments of the present invention will be exemplified below. (H01) The present invention can be applied to an image forming apparatus other than a copying machine, such as a printer and a facsimile. (H02) In the first embodiment, when the next job start signal is input (input of the copy start key), the elapsed time T from the previous job is T <T with respect to Trest.
In the case of rest, the idle rotation time Tr is set by the calculation formula Tr = a (N−b) shown in Table 2 in FIG. 6, but the following formula or the like can be used as the calculation formula. Tr = a (N−b) × (Trest−T) / Trest (H03) An arbitrary number of temperature sensors can be arranged in the fixing area Q5 and various places near the fixing area Q5.

[0075]

The above-described image forming apparatus of the present invention can provide the following effect (E01). (E01) The temperature distribution in the fixing region formed by the pressure contact region of the heat fixing rotary member and the pressure fixing rotary member can be made uniform in a short time. For this reason, occurrence of paper wrinkles, offsets, and the like can be prevented. In particular, in order to shorten the warm-up time, a heating roll having a reduced thickness is effective because the temperature distribution tends to be non-uniform. In addition, in order to overcome the disadvantage that the sponge roll is easily degraded for high-speed machines that need to reduce the total load applied to the heating roll and increase the Nip width from the limit value of the allowable bending stress by making it thinner. This is effective when using a solid roll. (E02) The contact type sensor for detecting the temperature of the fixing region formed by the pressure-contact region of the heat-fixing rotating member and the pressure-fixing rotating member makes the temperature distribution of the fixing region uniform without contacting the heating-fixing member. It is possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a color image forming apparatus having a fixing device for an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of the fixing device shown in FIG.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a block diagram (functional block diagram) illustrating functions provided in a control unit of the fixing device according to the first embodiment of the present invention;

FIG. 5 is an idle rotation time calculation formula setting table C4a;
FIG.

FIG. 6 is an idle rotation time calculation formula setting table C4a;
FIG. 2 is an explanatory diagram of FIG.

FIG. 7 illustrates the number of prints N of the previous job when the sheet size of the next job is larger than the previous job.
14 is a graph showing a set value Trest of an elapsed time (resting time of the fixing device) T in which the next job can be started without idle rotation from the end of the previous job.

FIG. 8 is a diagram illustrating a case where a next job start command is input (input of a copy start key) when a sheet size of the next job is larger than a previous job, and a next job start command signal from the previous job; 9 is a graph showing a set value Trev (sec) of the idle rotation execution time Tr with respect to the number N of prints of the previous job when the elapsed time T until the input of the first job (input of the copy start key) is T <Trest.

FIG. 9 is a time chart of heating roll temperature control showing a general example of heater on / off control performed by a fixing heater control unit C6.

FIG. 10 is a flowchart of idle rotation and job execution processing.

FIG. 11 is a flowchart of idling execution determination data storage processing.

FIG. 12 is a flowchart of a fixing heater control process according to the first embodiment of the present invention.

FIG. 13 is a flowchart of a standby heater control process, and is a flowchart of a subroutine of ST42.

FIG. 14 is a flowchart of an idle rotation heater control process, and is a flowchart of a subroutine of ST44.

FIG. 15 is a flowchart of a heater control process at the time of job execution, and is a flowchart of the subroutine of ST46.

FIG. 16 is a graph for explaining the operation and effect of the first embodiment. 500 sheets of A4 SEF sheets (small size sheets) are continuously copied using a solid roll (a heating roll having a hard surface). A3SEF immediately after
FIG. 7 is a diagram showing the paper wrinkle occurrence rate and paper wrinkle grade of the A3SEF sheet when copying is performed on the sheet (large size sheet) for each type of fixing device.

FIG. 17 is a graph for explaining the operation and effect of the first embodiment. FIG. 17A shows A4S in the previous job.
Rest time (elapsed time from the end of the previous job to the start of the next job) when 500 continuous copies of EF sheets (small size sheets) are made and the next job is copied to A3SEF sheets (large size sheets). A3SE
FIG. 17B is a diagram showing the relationship between the grade of the paper wrinkles generated on the sheet F and 100 sheets of A4 SEF sheets (small size sheets) in the previous job, and A in the next job.
FIG. 7 is a diagram showing a relationship between idle rotation time and the grade of paper wrinkles generated on the A3SEF sheet when 50 consecutive copies of 3SEF sheets (large-size sheets) are made.

FIG. 18 is a graph showing the rate of occurrence of paper wrinkles in sponge rolls and solid rolls by grade.
A used A4SEF in the previous job using sponge roll
100 sheets (small size sheet) of the
The rest time (elapsed time from the end of the previous job to the start of the next job) when 50 consecutive copies of A3 SEF sheets (large sheets) are made in the next job and the A3
FIG. 18B is a diagram showing the relationship between the grade of the paper wrinkles generated on the SEF sheet and FIG. 18B shows a case where 100 sheets of A4 SEF sheets (small size sheets) are continuously copied in a previous job using a solid roll, and A3 SEF sheets are used in the next job. FIG. 7 is a diagram showing a relationship between a rest time when 50 sheets (large size sheets) are continuously copied and a grade of paper wrinkles generated on the A3SEF sheet.

FIG. 19 is a graph showing a change in a nip width (a length of a pressure contact area of a heating roll and a pressure roll in a sheet conveying direction) between a sponge roll and a solid roll.
9A is A4SE in previous job using sponge roll
FIG. 19B is a diagram showing the relationship between the change in the nip width, the position in the roll axis direction, and the rest time (elapsed time from the end of the previous job) when 100 sheets of the F sheet (small size sheet) are continuously copied. Nip width change and roll when 100 A4SEF sheets (large size sheets) were continuously copied in the previous job using a tube solid roll (a roll in which the solid roll was covered with a tube made of a material with good release properties) It is a figure which shows the relationship between the position of an axial direction, and a rest time.

FIG. 20 is a flowchart of a heater control process during idle rotation of the color image forming apparatus having the fixing device according to the second embodiment of the present invention, and is a diagram corresponding to FIG. 14 of the first embodiment; It is a flowchart of the subroutine of ST44 of FIG.

FIG. 21 is an explanatory diagram of a color image forming apparatus having a fixing device according to a third embodiment of the present invention.

FIG. 22 is an enlarged view of the fixing device shown in FIG. 21.

FIG. 23 is a sectional view taken along line XXIII-XXIII in FIG. 22.

FIG. 24 is a fixing device according to a third embodiment of the present invention;
FIG. 3 is a block diagram (functional block diagram) showing each function of the control unit of FIG.

FIG. 25 is a flowchart of idle rotation and job execution processing according to the third embodiment, and corresponds to FIG. 10 of the first embodiment.

FIG. 26 is a flowchart of a heater control process during idling according to the third embodiment.
12 is a flowchart corresponding to ST4 in FIG.
14 is a flowchart of a subroutine of No. 4;

[Explanation of symbols]

C1: previous job information storage means, C2: elapsed time detection means (elapsed time counter), C3: sheet size storage means of the next job, C4: idle rotation execution means, C4a: idle rotation time setting means, Fh: heat fixing Rotating member, Fp: rotating member for pressure fixing, h1: heater used in small size, h2;
h1 + h3: Large size heater, N: Number of recorded images, Q5: Fixing area, SN2: Small size sheet fixing area temperature sensor, SN3: Differential fixing area temperature sensor, T: Input of next job command signal from the end of previous job Elapsed time until time, Tr: idle rotation time, Trest: rest time, which is a set value of elapsed time (resting time of the fixing device) T from which the next job can be started without idle rotation from the end of the previous job, 3, 4, ... Belt guide, 11 ... Press pad, (Fh
+ H1 + h2; Fh + h1 + h3): heat fixing member,
(Fp + 3 + 4 + 11) ... pressure fixing member,

Continued on front page F-term (reference) 2H033 AA03 BA11 BA12 BA25 BA27 BA32 BB18 BB37 CA01 CA07 CA17 CA19 CA21 CA27 CA40 CA48 3K058 AA02 AA86 BA18 CA23 DA01 GA06

Claims (4)

[Claims] 1. A fixing device having the following constitutional requirements (A01) to (A06): (A01) an unfixed toner on a recording sheet that rotates while pressing against each other and passes through a fixing region formed by the pressing region. A heat-fixing rotating member and a pressure-fixing rotating member for fixing an image, (A02) used for fixing a large-sized sheet disposed inside the heat-fixing rotating member and extending in the width direction of the recording sheet; A large-sized heater to be used and a small-sized used heater to be used when fixing a small-sized sheet compared to the large-sized sheet; and a heat-fixing member having the heat-fixing rotating member,
(A03) Previous job information storage means for storing the sheet size and the number of recorded images used in the previous job, (A04)
Elapsed time detection means for measuring the elapsed time from the end of the previous job to the input of the next job command signal, (A05) the sheet size storage means for the next job which detects and stores the sheet size used in the next job, (A06) If the sheet used in the previous job is a small-size sheet and the sheet used in the next job is a large-size sheet, only the small-size use heater is turned on in accordance with the elapsed time, and the heat-fixing rotating member and Idle rotation executing means for performing idle rotation of the pressure fixing rotary member. 2. The method according to claim 1, wherein the following components (A07) are provided.
(A07) idle rotation time setting means for setting the idle rotation time according to the sheet size used in the previous job, the number of sheets recorded in the previous job, the sheet size used in the next job, and the elapsed time The idle rotation execution means having: 3. The following components (A01), (A02), (A
05 ′), (A08), (A09)
1) a heat-fixing rotating member and a pressure-fixing rotating member that rotate while pressing each other and that fix an unfixed toner image on a recording sheet passing through a fixing region formed by the pressing region; (A02) the heat fixing; A large-size heater used for fixing a large-sized sheet, which is disposed inside the rotating member for use and is arranged to extend in the width direction of the recording sheet, and is used for fixing a small-sized sheet as compared with the large-sized sheet. (A05 ') The sheet size of the next job, which detects and stores the sheet size to be used in the next job when the next job command signal is input, Means (A08) Small size sheet fixing area temperature sensor for detecting the temperature of the small size sheet fixing area which is the fixing area through which the small size sheet passes And a differential fixing area temperature sensor for detecting a temperature of a differential fixing area that is a fixing area for a large size sheet that is a fixing area through which the large size sheet passes and that does not overlap with the fixing area for the small size sheet. (A09) When the sheet size of the next job is a large size sheet, the large size heater is used until the detection temperatures of the small size sheet fixing area temperature sensor and the differential fixing area temperature sensor reach predetermined temperatures. And the idle rotation execution means for executing idle rotation while controlling the heater used at the time of small size. 4. The following constituent requirements (A01), (A02), (A02)
010) and (A011), (A01) a heat-fixing rotating member that rotates while pressing against each other, and fixes an unfixed toner image on a recording sheet passing through a fixing area formed by the pressing area; Rotating member for pressure fixing, (A0
2) A large-size heater used for fixing a large-size sheet, which is disposed inside the heat-fixing rotary member and extends in the width direction of the recording sheet, and has a small size compared to the large-size sheet. A heating / fixing member having a small-size heater to be used at the time of sheet fixing and the heating / fixing rotating member; (A010) an endless thin-film-shaped pressure belt constituting the pressing / fixing rotating member; A pressure pad disposed on the back side of the pressure belt and pressing the pressure belt against the heating / fixing rotating member; and a belt guide disposed on the back side of the pressure belt along a movement path of the pressure belt. A pressure fixing member having
(A011) A temperature sensor disposed on the back surface side of the pressure belt passing through the fixing region to detect the temperature of the fixing region.