JP2006011033A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus with which the thermal deterioration of a fixing device, such as a pressure roller, by heating up of a non-paper passage section can be surely suppressed. <P>SOLUTION: When a paper width is below a prescribed size, a paper feeding interval is extended and the prescribed temperature is switched when the temperature detected by a second temperature detecting means 5b attains the prescribed temperature or above. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to fixing control of an image forming apparatus such as an electrophotographic copying apparatus or an electrostatic information recording apparatus having a film heating type fixing unit.

  The image forming apparatus includes a transfer unit that forms a toner image charged at a predetermined potential on the surface of a photosensitive drum as an image carrier and transfers the toner image to a transfer material, and a fixing unit that fixes an unfixed toner image by heating or pressing. Image forming apparatuses are well known.

(Film heating type fixing device)
As a fixing means in the image forming apparatus as described above, a film heating type fixing device is often used (for example, Patent Document 1 and Patent Document 2). The film heating type fixing device can reduce the heat capacity of the heating element itself and the members arranged between the heating element and the recording material compared with other well-known fixing devices such as a heat roller method, thus saving power. , Excellent quick start (shortening wait time).

  FIG. 2 shows a schematic diagram of a film heating type fixing device. 1 is a heater as a heating element, 2 is a cylindrical fixing film that slides around the heater 1, 3 is a film guide that guides the rotation of the fixing film 2, and holds the heater 1, 4 is a fixing film 2 A pressure roller 5 that is in pressure contact with the heater 1 through the temperature sensor 5 is a temperature detecting means disposed on the back surface of the heater 1.

  The heater 1 is preferably excellent in heat resistance, high thermal conductivity, and low heat capacity in order to prevent breakage due to thermal stress, suppress non-sheet-passing portion temperature rise, save power, quick start, and the like. Generally, a heater used in a film heating type fixing device has a laminated structure including a heating element, a conductive pattern, and a glass layer on a heater substrate. The heater substrate is preferably made of a material excellent in heat resistance, low heat capacity, thermal conductivity, and electrical insulation, and ceramic such as aluminum nitride or alumina is often used. The heating element is formed by screen-printing and baking an electric resistance material paste such as silver palladium (Ag / Pb) or Ta2N on the heater substrate. The electrode part and the conductive part as the conductive pattern are formed by screen-printing and baking a good conductor material such as silver paste on a substrate. The electrode portion, the conductive portion, and the heating element constitute an electric circuit, and the heater 1 is adjusted to a target temperature by controlling energization to the electric circuit by the control means. The heater 1 is arranged with the direction perpendicular to the conveying direction of the recording material as the longitudinal direction.

  The fixing film 2 is preferably excellent in heat resistance, durability, low heat capacity, and releasability in order to prevent image defects such as thermal deterioration and friction prevention, power saving, quick start property, and offset. For example, a base film such as P1 (polyimide) coated with a heat-resistant resin having releasability such as PFA or Machi is often used.

  The film guide 3 is desirably excellent in heat resistance, insulation and rigidity. For example, a material obtained by molding a material such as PPS (polyphenylene sulfide), PAI (polyamideimide), PI (polyimide), or PEEK (polyetheretherketone) is often used. The heater 1 is fitted and held in a groove provided in the longitudinal direction at the lower center of the film guide 3. Further, the fixing film 2 is fitted on the film guide 3. The pressure roller 4 is composed of a core metal made of iron, stainless steel, or aluminum and a silicon rubber layer excellent in elasticity, heat insulation, and heat resistance. A gear is fitted to the cored bar and is rotated by a drive motor. The heater 1 and the pressure roller 4 form a fixing nip N by pressure contact via the fixing film 2. The recording material P that has entered the fixing nip N is nipped by this pressure contact, and is conveyed in the direction of the arrow by the rotational drive of the pressure roller 4. Further, the driving rotation of the pressure roller 4 causes the fixing film 2 to be driven to rotate.

  The temperature detecting means 5 is disposed on the back surface of the heater 1. As the temperature detection means 5, for example, a thermistor having a temperature detection element 51 whose resistance value changes with temperature can be used. As a temperature detection method, for example, a temperature detection element and a resistor having a known resistance value are incorporated in an electric circuit linked to the control means, a weak constant voltage is applied to the electric circuit, and the resistance value is known. By measuring the partial pressure of the resistor, the temperature detected by the temperature detecting element can be known.

  The thermistor mainly includes a heater integrated type and an external contact type, both of which are widely used. FIG. 3A shows a schematic diagram of a thermistor integrated with a heater, and FIG. 3B shows a schematic diagram of an external contact type thermistor. The heater-integrated thermistor is obtained by mounting a temperature detection element 51, an electrode portion 52 made of silver paste or the like, and a conductive portion 53 on the heater 1. The temperature detection element 51 is bonded to the conductive portion 53 and the heater 1 with solder 54 or the like. A voltage is applied to the temperature detection element 51 from the outside via the electrode part 52 and the conductive part 53. The external contact type thermistor is a thermistor unit independent of the heater 1, and includes a temperature detection element 51, an electric circuit 55 using a dumet wire or the like, a ceramic paper 56 having heat insulation, insulation and elasticity, and a support for a heat resistant resin. 57, an insulating film 58 such as a Kapton sheet, and an adhesive 59 such as a gasket. The temperature detecting means 5 is arranged at a location that becomes a paper passing area at the heater longitudinal position in recording materials of all sizes that can be passed. The temperature detection means 5 monitors the temperature of the sheet passing area, transmits the detected temperature to the control circuit, and feeds it back to the energization control to the heater 1 for the purpose of always obtaining good fixability.

(Non-paper passing part temperature rise)
Incidentally, the above-described fixing device has a problem of so-called “non-sheet passing portion temperature rise”. This is because when a recording material having a narrow width in the direction orthogonal to the paper passing direction, that is, a so-called small size paper (for example, A4 size: B5 size paper in an image forming apparatus capable of printing 210 mm in width: 182 mm in width) is passed through a heater. This is a phenomenon in which the temperature rises in one heating element region and a non-sheet passing region. FIG. 4 shows a state of temperature rise of the non-sheet passing portion in the longitudinal direction of the heating element. The temperature of the sheet passing portion is controlled to be a constant temperature by the amount of heat supplied from the heater while the amount of heat is taken away by the recording material. On the other hand, in the non-sheet passing region, the amount of heat is not lost and the amount of heat is supplied from the heater, so that the temperature is raised above the fixing control temperature. When the non-sheet passing portion becomes high temperature, components of the fixing device, such as a pressure roller, are thermally deteriorated. Or, after passing a small size paper and passing a plain paper size recording material in a state where the non-sheet passing portion is at a high temperature, in the area where the small size paper was passed, Image defects such as edge hot offset, gloss unevenness, and fixing unevenness due to being too high, or conveyance failures such as paper wrinkles occur.

(Conventional solution for temperature rise in non-sheet passing area)
As a method for solving such a problem, when it is determined that the recording material is a small size, for example, by the following paper width detecting means, the width of the recording material in the direction orthogonal to the paper passing direction is a predetermined dimension, for example, 200 mm or less. If it is determined that there is a method, there is a method of relaxing the temperature rise of the non-sheet passing portion by extending the sheet feeding interval. Furthermore, in order to increase the throughput speed at the initial stage of paper feeding, a method of extending the paper feeding interval stepwise during continuous paper feeding is widely used.

-Paper Width Detection Means Any paper width detection means may be used as long as the paper width can be detected. As an example, a paper width regulating means serving as a paper width detection means is described in the paper position regulating member of the paper feed tray.

  FIG. 5 shows a schematic diagram of an example of the paper width detecting means. In this example, it is assumed that the recording material is conveyed with a central reference. Reference numeral 40 denotes a paper feed tray. Reference numeral 44 denotes a tray base on which a recording material is set. Reference numerals 41 and 42 are paper position regulating members which can slide as indicated by arrows. By sliding, the recording material is sandwiched from both sides, and the setting position of the recording material in the direction perpendicular to the conveyance direction is regulated, so that normal feeding and conveyance can be performed without any abnormality such as a jam. Reference numeral 43 denotes a variable resistor as paper width detecting means. When the paper position regulating members 41 and 42 slide to sandwich the recording material, the resistance value of the variable resistor 43 changes, and the resistance value is detected by a fixed power source and voltage detection means (not shown), thereby making the paper width of the recording material. Can be detected.

  The following two methods are practically used for the control for extending the paper feed interval during continuous paper feeding.

(1) Control to extend the paper feed interval according to the number of sheets passed (number switching control)
This is a control (so-called sheet number switching control) in which the paper feed interval is extended stepwise depending on the number of recording material sheets to be passed. The number of sheets to extend the paper feed interval is set so that the paper feed interval is extended by the number of paper passes that does not cause thermal degradation in the fixing device even when continuous recording materials with severe temperature rise in the non-sheet passing area are passed. ing. The recording material with severe temperature rise in the non-sheet passing portion is a recording material having a narrow width in the sheet passing direction, a long length in the sheet passing direction, and a large thickness. For example, a COM10 size ( An envelope having a width of 104.8 mm and a length of 241.3 mm.

-Means for counting the number of sheets to be passed As a means for counting the number of sheets to be passed through the recording material, a photo interrupter can be used. A photo interrupter is comprised by the transmission part, the receiving part, and the rod-shaped rocking | fluctuation member. The transmitter and the receiver face each other, and the transmitter is applied with a voltage from the control circuit and transmits an optical signal from the transmitter to the receiver. Between the transmitting part and the receiving part, one end of the shaking member can be moved back and forth. The other end of the oscillating portion protrudes into the recording material conveyance path, and oscillates the entire oscillating member by contacting the recording material passing therethrough. The movement of the oscillating unit blocks the optical signal transmitted from the transmitting unit to the receiving unit, or does not block it, thereby detecting the passage of the recording material. The detected passage of the recording material is transmitted to the control means by an electric signal, and the control means counts the number of sheets passed.

  FIG. 6 shows a flowchart of the conventional sheet number switching control. In S <b> 201, the image forming apparatus that has received the print signal resets the count of the sheet passing number Q in S <b> 202 (Q = 0), and stores the scheduled printing number R in S <b> 203.

  In S204, for example, the paper width L is detected by the paper width detecting means. If L <200 mm is not satisfied in S205, normal control is performed in S206. If L <200 mm, it is determined that the size is small, and the paper feed interval switching control in S207 to S211 is performed. In S207, an initial paper feed interval is determined. Here, Table 1 shows an example of each set value of the conventional sheet number switching control.

  In this example, four stages K of paper feed intervals are provided, and the stage K of paper feed intervals is set to be switched from K1 → K2 → K3 → K4 according to the number Q of sheets to be passed. Paper is fed in S208. In step S209, the sheet passing number Q is counted by the photo interrupter or the like (Q = Q + 1). If the sheet passing number Q has not reached the scheduled printing number R in S210, the sheet feeding interval K is determined from Table 1 based on the sheet passing number Q in S211, and the sheet feeding is performed again (S211 → S208). When Q = R in S210, all control is terminated after the recording material is discharged from the image forming apparatus (S212).

  In this way, by extending the paper feed interval in stages according to the number of papers to be passed, even if small-size papers are passed continuously, the temperature rise at the non-sheet passing part is suppressed and thermal deterioration of the pressure roller and the like is suppressed. It is possible to prevent the occurrence of image defects due to non-sheet passing portion temperature rise.

  However, in such sheet number switching control, even in the case of continuous passing of small size paper where the non-sheet passing portion temperature rise is relatively slow, the same number of sheets as the small size paper where the non-sheet passing portion temperature rise is abrupt and stepwise. The paper feed interval is extended. Here, the non-sheet passing portion temperature rise is relatively small and the recording material is a recording material that has a wide width in the sheet passing direction, a small thickness, and a short length in the sheet passing direction. For example, a commonly used recording material having a B5 size basis weight of 64 g / m can be used.

(2) Switching the paper feed interval by detecting the temperature of the non-sheet passing portion (temperature switching control)
In the market, paper such as the above-mentioned COM10 envelope has a much lower general-purpose frequency than B5 size recording materials. Therefore, there is no thermal deterioration, image defect, or conveyance defect even if the COM10 envelope is passed through, and the non-sheet passing part depends on the type of recording material for the purpose of speeding up the throughput in B5 size continuous sheet passing. Focusing on the difference in the temperature rise, a control for switching the paper feed interval step by step by detecting the temperature rise in the non-sheet passing portion by the second temperature detecting means, so-called temperature switching control is disclosed in, for example, Patent Document 3 below. Proposed and practical.

Second temperature detection means FIG. 7 shows the arrangement of two temperature detection means. The first temperature detecting means 5a is arranged in the paper passing area for all sizes of recording materials that can be passed. The second temperature detecting means 5b is arranged in a portion that becomes a non-sheet passing region for a recording material having a minimum sheet passing width that can be passed.

  FIG. 8 shows a flowchart of conventional temperature switching control. Table 2 shows an example of each set value of the conventional temperature switching control used in this example.

In this example, a threshold temperature of 210 ° C. is provided with respect to the detection temperature of the second temperature detection means. It is set to be. S301 to S303 are the same controls as S201 to S203 in the above-described number switching (FIG. 6). In S304, temperature detection by the second temperature detection means is started. Here, the detected temperature is T. The paper width L is detected in S305, and if L <200 mm is not satisfied in S306, normal control is performed in S307. When L <200 mm, the process proceeds to the paper feed interval switching control in S308 to S315. In S308, the initial paper feeding interval is set to K1, and in S309, paper feeding is started. In S310, the number of sheets to be passed is counted by the photo interrupter or the like (Q = Q + 1). If it is determined in S311 that the sheet passing number Q has not reached the scheduled printing number R, and the sheet feed interval stage K is not K4 in S312, the detected temperature T is compared with the threshold temperature 210 ° C. in S313. If T> 210 ° C., the paper feed interval is extended in S314 (K = K + 1). If T> 210 ° C., the paper feed interval is not changed in S315. In S312, K = K4, that is, when the paper feed interval is the longest in the set paper feed interval stage, the paper feed interval is not extended (S315). The paper feeding is started again according to the paper feeding interval determined in S314 and S315. (S314, S315 → S309). If Q = R in S313, after the recording material is discharged from the image forming apparatus, all control is terminated (S316).
JP-A-4-44075 JP-A-4-204980 JP 2002-169413 A

  FIG. 9 shows the temperature distribution in the longitudinal direction of the heating element when the recording materials having different widths in the direction perpendicular to the sheet passing direction are continuously passed and the detected temperatures of the second temperature detecting means are the same. Thus, the position where the non-sheet passing temperature rise is maximum in the longitudinal direction of the heating element varies depending on the paper size. This is because the non-sheet-passing area of the heating element varies depending on the paper width, and the range in which the heat accumulation during non-sheet-passing temperature rises is different.

  Therefore, it is an irregular recording material (for example, a recording material created by the user), and especially when a recording material whose temperature rises rapidly at the non-sheet passing portion is passed, the maximum temperature at the non-sheet passing portion is even higher. Therefore, there is a possibility that the fixing device such as the pressure roller is thermally deteriorated. Or, after passing a small size paper and passing a plain paper size recording material in a state where the non-sheet passing portion is at a high temperature, in the area where the small size paper was passed, There is a possibility that edge hot offset due to being too high, image defects such as fixing unevenness and gloss unevenness due to uneven temperature distribution, or conveyance failure such as paper wrinkles may occur. Alternatively, particularly when a recording material having a moderate temperature rise in the non-sheet passing portion is passed, there is a possibility that the throughput may be lowered more than necessary.

  Therefore, it is proposed to provide multiple temperature detectors to be placed in the non-sheet passing area, and to extend the paper feed interval when the highest detected temperature of these multiple temperature detectors exceeds the threshold temperature. Has been. In such a case, the temperature close to the maximum temperature of the non-sheet-passing temperature rise can be detected, but depending on the dimensions of the temperature detection means, the dimensions required for the support of the temperature detection means and the wiring of the electric signal circuit, Since the place and the number of places that can be placed are limited, it is not possible to reliably detect the maximum temperature of the non-sheet passing portion temperature rise, and the above problem when an irregularly shaped recording material is passed has not been solved before. is there. Further, it is not preferable because the cost increases due to the increase in the number of temperature detection means and the wiring of the electric signal circuit of the temperature detection means becomes complicated.

  In the present invention, in view of the above-mentioned problems, even in an irregular recording material, it is possible to prevent thermal deterioration, image failure, and conveyance failure of a pressure roller against a recording material whose temperature is not rapidly increased. An object of the present invention is to provide an image forming apparatus that can achieve a high throughput for a recording material having a relatively slow non-sheet-passing temperature, is inexpensive, and does not complicate the wiring of an electric signal circuit. And

  In order to solve the above problems, the present invention comprises the following configurations (1) to (5).

(1) A heating element arranged with the direction intersecting the sheet passing direction of the recording material as a longitudinal direction, a fixing film that slides and rotates around the heating element, and a fixing nip that presses against the heating element via the fixing film A pressure member that forms a sheet, a first temperature detection unit disposed in a portion that is a sheet passing region for all the recording materials that can be passed, and a recording material having a minimum sheet passing width that can be passed. A second temperature detecting means disposed in a portion that becomes a non-sheet passing area, and a fixing means having
Means for energizing the heating element according to the temperature detected by the first temperature detecting means;
Means for detecting the paper width of the recording material in the direction orthogonal to the paper passing direction;
In the case where the paper width is less than or equal to a predetermined dimension, control for extending the paper feed interval when the temperature detected by the second temperature detection means is equal to or higher than the predetermined temperature;
In an image forming apparatus having
Control for changing the predetermined temperature according to the detected paper width;
An image forming apparatus comprising:

(2) A heating element arranged with the direction intersecting the sheet passing direction of the recording material as a longitudinal direction, a fixing film that slides and rotates around the heating element, and a fixing nip that presses against the heating element via the fixing film A pressure member that forms a sheet, a first temperature detection unit disposed in a portion that is a sheet passing region for all the recording materials that can be passed, and a recording material having a minimum sheet passing width that can be passed. A second temperature detecting means disposed in a portion that becomes a non-sheet passing area, and a fixing means having
Means for energizing the heating element according to the temperature detected by the first temperature detecting means;
Means for detecting the paper width of the recording material in the direction orthogonal to the paper passing direction;
In the case where the paper width is equal to or smaller than a predetermined dimension, control for shortening the paper feed interval when the temperature detected by the second temperature detecting means is equal to or lower than the predetermined temperature;
In an image forming apparatus having
Control for changing the predetermined temperature according to the detected paper width;
An image forming apparatus comprising:

(3) In the image forming apparatus according to (1) or (2),
The image forming apparatus, wherein the predetermined temperature is selected from a plurality of values set in advance corresponding to a paper width.

(4) In the image forming apparatus according to (1) or (2),
The image forming apparatus, wherein the predetermined temperature is a value calculated based on a paper width.

(5) In the image forming apparatus described in (1) to (4),
The image forming apparatus according to claim 1, wherein the control changes the predetermined temperature when a paper feed interval is switched.

  According to the present invention, the paper feed interval switching control at the time of small-size paper feeding is a control for changing the threshold temperature according to the paper width, so that the temperature rise of the non-paper-passing portion is whatever the paper width of the recording material. It is possible to reliably suppress the thermal deterioration of the fixing device such as the pressure roller.

  Alternatively, edge hot offset due to non-sheet-passing temperature rise, image defects such as fixing unevenness and gloss unevenness, and conveyance defects such as paper wrinkles can be reliably suppressed. In addition, since the temperature detecting means arranged in the non-sheet passing portion can be made one, the above-described effect can be obtained without increasing the cost and complication of the wiring.

  The best mode for carrying out the present invention will be described below based on examples.

  The image forming apparatus used in the present embodiment is an image forming apparatus using the above-described conventional film heating type fixing means and includes the controls of the following embodiments (see FIG. 2).

(Outline of fixing device)
The heater 1 was screen-printed with an electric resistance material paste such as silver palladium (Ag / Pd) on an aluminum nitride substrate having a width of 7 mm, a length of 235 mm, and a thickness of 1.0 mm so as to have a resistance value of 11Ω. .

  The fixing film 2 was coated with 10 μm of PTFE on the outer surface of a cylindrical polyimide film having a length of 226 mm, an inner diameter of 24 mm, and a thickness of 55 μm.

  The pressure roller 4 was formed by providing a silicon rubber layer with a thickness of 5 mm on an aluminum core with an outer diameter of 8 mm.

  The first temperature detection means 5a and the second temperature detection means 5b were arranged at positions of 15 mm and 103 mm, respectively, on the opposite side of the heater 1 from the center of the heating element in the longitudinal direction of the heater 1. In this case, an external contact type thermistor is used for both temperature detection means, but a heater integrated type may be used if a setting value for switching a paper feed interval to be described later is optimized.

  The heater 1 and the two temperature detection means 5a and 5b were fixed to the film guide 3, and the temperature detection means 5a and 5b were pressed against the heater with a spring pressure of about 1N.

  The image forming apparatus of the present embodiment has the paper width detecting means (see FIG. 5) shown in the section of the conventional example, the recording material having a paper width of 200 mm or less is made small, and the recording material arranged in the paper feed tray When the paper width is 200 mm or less, the paper feed interval switching control is performed by the temperature detection of the second temperature detection means.

(First embodiment)
FIG. 1 shows a flowchart of sheet feeding interval switching control according to the first embodiment. The image forming apparatus that has received the print signal in S1 resets the count of the number of sheets to be passed Q (Q = 0) in S2, and records the scheduled print number R in S3. In S4, temperature detection by the second temperature detection means 5b is started. Here, the detected temperature is T. In S5, the paper width detecting means detects the paper width of the recording material, more specifically, the size of the recording material in the direction perpendicular to the conveying direction. Here, let L be the detected paper width.

  In S6, when L ≧ 200 mm, normal sheet passing control is performed in S7. When L <200 mm, the process shifts to sheet passing control having sheet feeding interval switching control described in S8 to S16. In S8, the initial paper feed interval stage is set to K1. Here, Table 3 shows setting values of the paper feed interval switching control according to the first embodiment.

  The paper feed interval stage K is set to 4 stages (K = K1, K2, K3, K4), and the paper feed intervals at each stage are set as shown in the table, and the paper feed intervals K1 → K2 → K3 → K4 by continuous paper feeding. Stage K is repeated.

  In S9, a threshold temperature Ta for extending the paper feed interval with respect to the detected temperature T is determined from Table 3 based on the paper width L. The threshold temperature Ta is set so that the maximum temperature of the non-sheet passing temperature does not reach the heat deterioration temperature of the fixing device even when a recording material having any paper width is passed, or the image defect shown in the problem section The temperature was set in advance so as not to reach the temperature at which it occurred.

  Paper is fed in S10. In S11, the number of sheets passed Q is counted by detecting the conveyance of the recording material by the paper detection means described in the section of the conventional example (Q = Q + 1). If the sheet passing number Q has not reached the scheduled printing number R in S12, the sheet feed interval stage K is confirmed in S13. If K = K4 is not satisfied, it is determined in S14 whether the detected temperature of the second temperature detecting means 5b has exceeded the threshold temperature. If T> Ta, the paper feed interval is extended in S15 (K = K + 1). If T> Ta is not satisfied, the paper feed interval is not changed (S16). In S13, if K = K4, that is, if the set paper feed interval is the largest, the paper feed interval is not extended (S13 → S16). Paper feeding is performed again at the paper feeding interval determined in S15 and S16 (S15, S16 → S10). When the sheet passing number Q reaches the scheduled printing number R in S12, all the control is ended after the recording material is discharged from the image forming apparatus.

  As described above, the paper feed interval switching control at the time of small-size paper passing is a control for detecting the paper width and changing the threshold temperature according to the paper width, so that the temperature rise of the irregular shape, particularly the non-paper passing portion, is abrupt. When the recording material is passed, the temperature rise of the non-sheet passing part is suppressed, the heat deterioration of the fixing device such as the pressure roller, the image defect such as edge hot offset, gloss unevenness, fixing unevenness, or paper Conveyance defects such as wrinkles can be reliably suppressed. Alternatively, when an irregularly shaped recording material with a particularly slow increase in temperature of the non-sheet passing portion is passed, continuous feeding can be performed without unnecessarily slowing the throughput. In addition, since the temperature detecting means arranged in the non-sheet passing portion can be made one, the above-described effect can be obtained without increasing the cost and complication of the wiring.

(Second embodiment)
In the control of Example 1, a threshold temperature that differs depending on the paper width L was set. The control of the second embodiment is characterized in that a mathematical formula for determining the threshold temperature Tb is set by the paper width L. By doing so, it is possible to perform the paper feed interval control corresponding to the paper width of the recording material as compared with the first embodiment.

  FIG. 10 is a flowchart of the paper feed interval switching control according to the second embodiment. Here, the steps other than S9-1 and S14-1 are the same as those in the first embodiment. In S9-1, the threshold temperature Tb is determined from the mathematical formulas set as shown in Table 4 and the paper width L detected by the paper width detecting means. In S14-1, it is determined whether or not to switch the paper feed interval from the detected temperature T and the threshold temperature Tb of the second temperature detecting means 5b.

(Third embodiment)
The control in the first and second embodiments is a control to extend the paper feed interval when the temperature of the non-sheet passing portion is high, but the temperature of the non-sheet passing portion is considerably suppressed by extending the paper feed interval. If the recording material is changed to a relatively slow recording material with a non-sheet passing temperature rise during continuous paper feeding, it is better to shorten the paper feeding interval by the second temperature detection means. This is preferable because the throughput can be increased. Thus, the third embodiment is characterized in that the threshold temperature Tc that varies depending on the paper width L is set in the paper feed interval switching control in which the detected temperature T is shortened by the threshold temperature Tc.

  FIG. 11 is a flowchart of the paper feed interval switching control according to the third embodiment. Here, S1 to S8 are the same as in the first embodiment. In S9-2, based on the paper width L, the threshold temperature Tc is determined from Table 5.

  The threshold temperature Tc is set in advance so as not to reach the heat deterioration temperature of the fixing device even if the paper feed interval is shortened, or not to reach the temperature at which the image defect or the like shown in the problem section occurs. .

  S10 to S12 are the same as those in the first embodiment. If the paper feed interval stage K is K1 in S13, the paper feed interval is not shortened because K1 is the shortest paper feed interval among the set paper feed intervals (S13 → S16). If K = K1, the detected temperature T of the second temperature detecting means 5b is compared with the threshold temperature Tc in S14-2. If T <Tc, the paper feed interval is shortened in S15 (K = K). -1). If T <Tc, the paper feed interval is not shortened in S16.

  Note that the image forming apparatus may have the control of the first or second embodiment in addition to the control of the third embodiment.

(Fourth embodiment)
In Example 3, a different threshold temperature was set depending on the paper width L. The control of the fourth embodiment is characterized in that a mathematical expression for determining the threshold temperature Td by the paper width L is set in order to achieve control corresponding to the paper width.

  FIG. 12 is a flowchart of the paper feed interval switching control according to the fourth embodiment. Here, the steps other than S9-3 and S14-3 are the same as in the third embodiment. In S9-3, the threshold temperature Td is determined from the mathematical formula set in advance as shown in Table 6 and the paper width L detected by the paper width detecting means.

  In S14-3, it is determined whether to switch the paper feed interval from the detected temperature T and the threshold temperature Td of the second temperature detecting means 5b.

  Note that the image forming apparatus may have the control of the first or second embodiment in addition to the control of the fourth embodiment.

(Fifth embodiment)
When the paper feeding interval is increased, the heat amount of the non-sheet passing portion is radiated and the temperature in the heater longitudinal direction is made uniform. Therefore, the temperature difference between the maximum temperature of the non-sheet-passing temperature rise shown in FIG. 9 and the detection temperature of the second detection detection unit varies depending on the length of the paper feed interval. Therefore, it is preferable to have different threshold temperatures when the paper feed interval is switched.

  FIG. 13 is a flowchart of the paper feed interval switching control according to the sixth embodiment. Except for S9-4 and S14-4, the process is the same as that of the first embodiment. In S9-4, the threshold temperature Te is determined from Table 7 based on the stage K of the paper feed interval and the paper width L.

  In S14-4, it is determined whether to extend the paper feed interval from the detected temperature T and the threshold temperature Te.

  By doing as described above, it is possible to perform the paper feed interval switching control corresponding to the temperature distribution of the non-sheet passing portion which varies depending on the difference in the paper feed intervals.

  In this example, the control is performed to change the threshold temperature when the paper feed interval is switched based on the control of the first embodiment. However, the same control may be applied to the second to fourth embodiments.

Flowchart of paper feed interval switching control according to the first embodiment. Schematic of film heating type fixing device Schematic of thermistor The figure which shows the mode of temperature rise of the non-sheet passing part in the heat generation length Schematic diagram of an example of paper width detection means Flow chart of conventional number switching control The figure which shows arrangement | positioning of two temperature detection means The figure which shows the conventional temperature switching means Figure showing the temperature distribution in the longitudinal direction of the heating element, depending on the paper width Flowchart of paper feed interval switching control in embodiment 2 Flowchart of paper feed interval switching control of embodiment 3 Pro-chart of paper feed interval switching control in embodiment 4 Flowchart of paper feed interval switching control in embodiment 5

Explanation of symbols

1 Heating element (heater)
2 fixing film 3 film guide 4 pressure roller 5 temperature detecting means 5a first temperature detecting means 5b second temperature detecting means 40 paper feed trays 41, 42 paper position regulating member 43 variable resistance (paper width detecting means)
44 Tray base 51 Temperature detection element 52 Thermistor electrode 53 Thermistor conductive portion 54 Solder 55 Dumet wire (electric circuit)
56 Ceramic paper 57 Support 58 Insulating film 59 Adhesive N Fixing nip P Recording material R Planned number of printed sheets Q Number of sheets to be passed K Current feed interval K1, K2, mm, K4 Stage T of set feed interval T Second Detected temperatures Ta, Tb, Tc, Td, Te of each temperature detecting means Threshold temperature L in each embodiment Width of the recording material in the direction orthogonal to the sheet passing direction detected by the paper width detecting means

Claims (5)

A heating element arranged with the direction intersecting the sheet passing direction of the recording material as a longitudinal direction, a fixing film that slides and rotates around the heating element, and the heating element through the fixing film are pressed into contact with the heating element to form a fixing nip. The pressurizing member, the first temperature detecting means arranged in a portion that is a paper passing area for all the recording materials that can be passed, and the recording material with the minimum paper passing width that can be passed are not passed. A fixing unit having a second temperature detecting unit disposed in a portion to be a paper region;
Means for energizing the heating element according to the temperature detected by the first temperature detecting means;
Means for detecting the paper width of the recording material in the direction orthogonal to the paper passing direction;
In the case where the paper width is less than or equal to a predetermined dimension, control for extending the paper feed interval when the temperature detected by the second temperature detection means is equal to or higher than the predetermined temperature;
In an image forming apparatus having
Control for changing the predetermined temperature according to the detected paper width;
An image forming apparatus comprising: A heating element arranged with the direction intersecting the sheet passing direction of the recording material as a longitudinal direction, a fixing film that slides and rotates around the heating element, and the heating element through the fixing film are pressed into contact with the heating element to form a fixing nip. The pressurizing member, the first temperature detecting means arranged in a portion that is a paper passing area for all the recording materials that can be passed, and the recording material with the minimum paper passing width that can be passed are not passed. A second temperature detecting means arranged in a portion to be a paper region;
Fixing means having
Means for energizing the heating element according to the temperature detected by the first temperature detecting means;
Means for detecting the paper width of the recording material in the direction orthogonal to the paper passing direction;
In the case where the paper width is equal to or smaller than a predetermined dimension, control for shortening the paper feed interval when the temperature detected by the second temperature detecting means is equal to or lower than the predetermined temperature;
In an image forming apparatus having
Control for changing the predetermined temperature according to the detected paper width;
An image forming apparatus comprising: The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the predetermined temperature is selected from a plurality of values set in advance corresponding to a paper width. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the predetermined temperature is a value calculated based on a paper width. The image forming apparatus according to claim 1, wherein
The image forming apparatus according to claim 1, wherein the control changes the predetermined temperature when a paper feed interval is switched.