JP2006330252A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain uniform temperature distribution without causing uneven temperature distribution on the width of recording material and the actuation state of an image forming apparatus or the like. <P>SOLUTION: In addition to information on the width of the recording material, by combining at least a piece of information out of (a) whether it is before or after starting a temperature control state or elapsed time from starting image forming, (b) the temperature of a pressure member with the information on the width of the recording material, a power supply ratio for a plurality of heating means is changed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on a recording material by an electrophotographic process, and more particularly, to a fixing device that fixes a toner image on a recording material and includes an induction heating type fixing device. .

  In recent years, development of energy-saving image forming apparatuses has been strongly demanded. In an electrophotographic image forming apparatus, since a considerable amount of power consumption is consumed by the fixing device, the development of a technique for reducing the power consumption of the fixing device is a major issue for energy saving of the image forming apparatus. It has become.

  Since the fixing device needs to start up and operate within a short time when the copy button is pressed or a print command is issued from a network device, the temperature is raised to a fixing temperature or a temperature close to the fixing temperature even during standby. For this reason, there is power consumption by the fixing device even during standby, and this standby power consumption accounts for a large proportion of the power consumption of the image forming apparatus.

  Therefore, there is a need for a fixing device that can eliminate or reduce the power supply to the fixing device during standby, and that can rise to a fixing temperature in a short time. It has been.

  In the induction heating method, as in the case where a halogen lamp is used as a heat source, it is not heating by radiant heat, but heating by heating in the object, and the object itself generates heat and becomes a heat source. The heating member can be heated to the fixing temperature.

  On the other hand, since the size of the recording material, that is, the width in the direction orthogonal to the conveyance direction of the recording material passed through the fixing device is various, the temperature distribution in the recording material width direction of the heating member becomes non-uniform. There's a problem.

Patent Document 1 proposes a fixing device that controls energization to a plurality of heat sources in accordance with the size of the recording material. In Patent Document 2, in the induction heating type fixing device, a plurality of coils are used as means for solving the temperature non-uniformity caused by the difference in the width of the recording material, and according to the amount of power supplied to the first coil. Thus, it has been proposed to perform control to change the power supply amount to other coils.
JP 2005-93351 A Japanese Patent Laid-Open No. 2000-206913

  Since the temperature distribution of the heating member in the width direction of the recording material varies depending on the width of the recording material passed through the fixing device and varies depending on various states of the image forming apparatus, as in the invention of Patent Document 1, The control based only on the information on the size of the recording material does not sufficiently eliminate the uneven temperature.

  The same applies to the invention of Patent Document 2, and the temperature distribution cannot be sufficiently maintained uniformly by control in a single mode as in Patent Document 2.

  In a fixing device using a thinned heating member in order to reduce the heat capacity, the temperature distribution of the heating member is likely to be non-uniform. It is particularly difficult to keep it uniform.

  An object of the present invention is to provide an image forming apparatus that solves the above-described problems in the prior art, always maintains sufficient uniformity of the temperature distribution, and stably maintains proper fixing. .

The object is achieved by the following invention.
(Claim 1)
A heating member for heating and fixing a toner image, a pressure member, and a coil divided into a plurality of portions in a direction perpendicular to the conveyance direction of the recording material, and heated by the induction current flowing in the coil An image forming apparatus comprising a fixing device that clamps and conveys a recording material between a heating member and the pressure member, and fixes a toner image onto the recording material, wherein the plurality of coils are formed in accordance with the width of the recording material. In an image forming apparatus that controls energization to each separately,
The control means for controlling the energization of the coils determines the ratio α of the power supplied to the plurality of coils based on the combination of at least one of the following information a and b and the recording material width information. An image forming apparatus characterized by performing control to change.
a. Elapsed time before or after entering the temperature control state or from the start of image formation b. The temperature of the pressure member (Claim 2)
The plurality of coils have a center coil and an end coil, and the ratio α = (amount of power supplied to the center coil / amount of power supplied to the end coil) is supplied to the end coil. The control means controls the power to be less than or equal to the power supplied to the central coil, and the ratio α is larger in the case of a narrow width recording material than in the case of a wide width recording material. The image forming apparatus according to claim 1.
(Claim 3)
The plurality of coils include a center coil and an end coil, and the ratio α = (amount of power supplied to the center coil / amount of power supplied to the end coil). 3. The image forming apparatus according to claim 1, wherein before the temperature control state is entered, the ratio α is controlled to be larger than after the temperature control state is entered.
(Claim 4)
The plurality of coils include a center coil and an end coil, and the ratio α = (amount of power supplied to the center coil / amount of power supplied to the end coil). 4. The image forming apparatus according to claim 1, wherein after the predetermined time has elapsed from the image formation start time, the ratio α is controlled to be smaller than before the time has elapsed.
(Claim 5)
The plurality of coils include a center coil and an end coil, and the ratio α = (amount of power supplied to the center coil / amount of power supplied to the end coil). The image forming apparatus according to claim 1, wherein when the temperature of the pressure member is high, the ratio α is controlled to be small.
(Claim 6)
The said control means performs control which changes the said ratio (alpha) based on the difference of the temperature of the center part of the said heating member, and the temperature of the edge part of the said heating member. 2. The image forming apparatus according to item 1.
(Claim 7)
The image forming apparatus according to claim 1, wherein the heating member is a roller having a thickness of 0.4 to 2.0 mm.

  According to the invention of any one of claims 1 to 7, the ratio of the power supplied to the plurality of coils is changed according to not only the difference in the width of the recording material but also various states of the image forming apparatus. It becomes possible to always keep it stable and uniform.

  According to the invention of claim 2, uniform fixing is performed on recording materials having various widths.

  In the initial stage of image formation immediately after the start of image formation, the temperature tends to decrease in the region through which the recording material passes, i.e., in the central portion. Well prevented. Further, when a considerable time has elapsed from the start of image formation, the rate of heat release from the end portion increases, but the invention according to claim 3 or claim 4 is favorable for the heat release at the end portion. Temperature correction is performed.

  When the temperature of the pressurizing member increases, the heat capacity of the pressurizing member increases and the temperature does not easily drop. According to the invention of claim 5, when the temperature of the heating member rises, an excessive increase in the temperature of the central portion of the heating member is prevented.

  According to the seventh aspect of the present invention, an image forming apparatus is realized in which fixing is performed under a uniform temperature distribution and the rise time is short.

  Although the present invention will be described with reference to the illustrated embodiment, the present invention is not limited to the embodiment.

  FIG. 1 is an overall view of an image forming apparatus according to an embodiment of the present invention, which includes an image forming apparatus main body A, an image reading apparatus SC, and an automatic document feeder DF.

  The image forming apparatus main body A shown in the figure is an image forming apparatus comprising a drum-shaped photoconductor 1, a charging device 2, an exposure device (image writing means) 3, a developing device 4, a transfer device 5, a separating device 6, a cleaning device 8, and the like. Section, a fixing device 20, and a paper transport system.

  The paper transport system includes a first transport unit including a paper feed cassette 10, a first paper feed unit 11, a second paper feed unit 12, a transport unit 13, a paper discharge unit 14, and a manual paper feed unit 15; It is composed of a circulation refeeding section that circulates and refeeds paper.

  The paper feed cassette 10 and the first paper feed means 11 are formed by a plurality of paper feed means (three stages in the figure), and accommodate and feed a plurality of types of paper P. The paper size is input by setting by an operator or automatic paper size setting by a paper size detection means.

  The sheet P that has passed through the conveying unit 13 and has been fixed by the fixing device 20 is conveyed by the conveying path switching unit 16 to a straight discharge path conveying path r1, a reverse discharging path conveying path r2, and a double-sided circulation path conveying path. One of r3 is selected and conveyed.

  The paper P passing through the transport path r1 is discharged with the image forming surface facing up (face up). The paper P passing through the transport path r2 advances to the transport paths r3 and r4 of the double-sided circulation path, and is then transported in reverse, passes through the transport path r2, and is discharged with the image forming surface facing down (face down). .

  The second transport unit branches the paper P on which the image has been formed by the image forming unit, before the paper discharge unit 14 by the transport path switching unit 16, transports the paper P along the circulation refeeding path, and recirculates the paper. The paper P is reversed by the reverse conveying roller 17 in the middle of the paper path, and then fed again to the image forming unit via the second paper feeding unit 12.

  The document d placed on the document table of the automatic document feeder DF is transported by the paper feeding means, and one or both side images of the document d are read by the optical system of the image reading device SC and read by the image sensor CCD. It is. The analog signal photoelectrically converted by the image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit (not shown), and then sent to the exposure device 3. .

  In the exposure device 3, the output light from the semiconductor laser is irradiated onto the photoconductor 1 of the image forming unit to form a latent image. In the image forming unit, processes such as charging, exposure, development, transfer, separation, and cleaning are performed. An image is transferred to the paper P fed from the paper feed cassette 10 and the manual paper feed means 15 by the transfer device 5. The paper P carrying the image is fixed by the fixing device 20 and discharged from the paper discharge means 14.

  Alternatively, the single-sided image processed paper P sent to the circulation refeed unit by the conveyance path switching unit 16 is reversed by the reverse conveyance roller 17 and then subjected to double-sided image processing in the image forming unit, and then fixed by the fixing device 20. The paper is processed and discharged by the paper discharge means 14.

  FIG. 2 is a diagram showing a dielectric heating type fixing device 20, and FIG. 3 is a sectional view taken along the axis of the heating roller.

  Reference numeral 21 denotes a heating roller as a heating member, which is made of a metal such as iron or stainless steel that generates Joule heat by an induced current generated in the roller, as will be described later. A release layer such as a fluororesin is preferably formed on the surface of the heating roller. A heating roller having a heat-resistant elastic layer can also be used.

  In order to reduce the heat capacity, the heating roller 1 is desirably thin with a thickness of about 0.4 to 2.0 mm. If it is thinner than 0.4 mm, the mechanical strength is lowered. Moreover, as a heating member, it can replace with a roller and can also use the resin belt which consists of resin, such as a metal belt or a polyimide. For example, a belt as disclosed in JP-A-2002-148982 can be used as the heating member.

  Reference numeral 22 denotes a pressure roller as a pressure member that press-contacts the heating roller 1, and press-contacts the heating member 21 by a spring (not shown). The pressure roller 22 has a shaft 22a made of metal and a heat-resistant elastic body layer 22b such as silicon rubber formed thereon. A release layer may be formed on the heat resistant elastic layer 22b. As the pressure member, a belt can be used instead of the roller.

  Reference numeral 23 denotes a coil that generates a magnetic field that generates an induced current in the heating roller 21.

  This embodiment has a plurality of coils, and the energization of the central coil 23A for heating the central part in the width direction and the end coil 23B for heating the end part are separately controlled.

  The recording material P is nipped and conveyed by the heating roller 21 and the pressure roller 22 and is fixed by heating of the heating roller 21, but the direction perpendicular to the conveying direction of the conveyed recording material P, that is, the recording material. The central coil 23A of the coil divided in the width direction X of P heats the central portion of the recording material P in the width direction, and the end coil 23B heats the end of the recording material P in the width direction. In the following, the width direction refers to a direction orthogonal to the conveyance direction of the recording material P, in other words, the axial direction of the heating roller 21 (direction X in FIG. 2).

  Then, as will be described later, the ratio α of the power supplied to the central coil 23A and the power supplied to the end coil 23B = (power supplied to the central coil 23A / end coil 23B The power supplied) is changed according to the width of the recording material P and the like.

  Reference numeral 24 is an upper entry guide plate, 25 is an lower entry guide plate, 26 is an upper discharge guide plate, and 27 is a lower discharge guide plate. Reference numeral 28 denotes an upper separation claw for separating the recording material P from the heating roller 21, and reference numeral 29 denotes a lower separation claw for separating the recording material P from the pressure roller 2.

  A cleaning web 30 for cleaning the surface of the heating roller 21 is fed from the original winding shaft 31, wound on the winding shaft 32, and pressed against the heating roller 21 by the pressing roller 33.

  SE1 is a temperature sensor that detects the surface temperature of the central portion in the width direction of the pressure heating roller 1, SE2 is a temperature sensor that detects the surface temperature of the end portion in the width direction of the heating roller 1, and SE3 detects the temperature of the pressure member. It is a temperature sensor.

  The heating roller 1 is supported by a bearing (not shown) and is driven to rotate by a motor (not shown). The pressure roller 2 is in pressure contact with the heating roller 1 and is driven to rotate by the heating roller 1.

  The recording material P carrying an unfixed toner image passes through the nip between the heating roller 21 and the pressure roller 22, and when passing, the toner image is heated and fixed on the recording material P.

  The surface temperature of the heating roller 21 is controlled by the control means CR based on the temperature detected by the temperature sensor SE1 and is maintained at an appropriate fixing temperature. Such temperature control is performed by the power supplied to the central coil 23A and the coil 23B. The electric power supplied to is controlled separately, whereby a uniform temperature distribution in the width direction is maintained.

  In addition, as is well known, the control means CR performs alternating energization in the central coils 23A and 23B in a time-sharing manner in order to suppress the instantaneous power, and controls the ratio of the division time in the alternate energization to thereby control the central coil. The ratio α of the supplied power supplied to 23A and 23B is controlled.

  The heating roller 21 has a maximum size, that is, a length capable of passing a recording material P having a maximum length in the width direction, for example, A3 or A4 vertical recording material P.

  When the recording material P having a narrow width such as the A4 size side and the B5 size side is passed, the recording material P is increased by increasing the ratio α between the energizing time for the central coil 23A and the energizing time for the coil 23B. The temperature drop at the center due to the heat taken away by P is corrected.

The control means CR controls the ratio α of the energizing time to the central coil 23A and the energizing time to the end coil 23B based on the recording material width information based on the recording material size information. The size information is combined with at least one of the following information a and b for use in control.
a. Time before or after entering the temperature control state, or elapsed time from the start of image formation b. Temperature of Pressurizing Member Control using the control means CR will be described with reference to FIG.

  FIG. 4 is a time chart for fixing temperature control.

  At time t1, the copy button is pressed or a star and a signal ST are generated by an image forming signal from an external device, and the main power supply and fixing power supplies EA and EB are started by the start signal ST.

  When the fixing power sources EA and EB are turned on, the temperature of the heating roller 21 rises, and a temperature control state in which the fixing power sources EA and EB are turned on and off by the temperature of the heating roller 21 is entered from the time t2 when the fixing roller reaches the predetermined fixing temperature. In the temperature control state, the control means CR performs control to turn on and off the fixing power sources EA and EB by feedback control based on the temperature detected by the heating member temperature sensor SE1.

  When image formation is completed, the main power supply is turned off at time t4. The fixing power sources EA and EB are turned off when the image formation is completed immediately after the temperature control is turned off at time t3.

  In the central part in the width direction through which recording materials of all sizes pass, the amount of heat lost by the recording material is larger than that in the end part in the width direction, so that the temperature tends to be lower than at the end part. In addition, when a recording material having a narrow width is passed, the temperature lowering tendency in the central portion becomes stronger. Therefore, basically, the ratio α = (the energizing time to the central coil 23A / the energizing time to the coil 23B) between the energizing time to the central coil 23A and the energizing time to the coil 23B is higher than 1. For the recording material having a narrow width, control for increasing the ratio α is performed.

  The information “a. Before or after temperature control” is first fixed by feedback control for turning ON / OFF the fixing power sources EA and EB based on the temperature detected by the temperature sensor SE1 after the image formation start time t1. It is before or after the time t2 when the heat sources EA and EB are turned off.

  The information “b. Elapsed time from start of image formation” is a time length from the rising time t1 of the start signal ST.

  The information “c. Temperature of heating member” is a temperature detected by a temperature sensor SE3 that detects the temperature of the pressure roller 22.

  In the initial stage of image formation immediately after the start of image formation, the temperature tends to decrease. Therefore, as described above, a temperature drop is likely to occur in the central portion as compared with the end portion. In order to correct this tendency at the initial stage of image formation, the ratio α is set larger. That is, before the time t2 when the temperature control state is entered, the previous period ratio α is set larger, and in the initial stage where the elapsed time from the image formation start time t1 is short, the ratio α is set larger. As the value becomes longer, control to reduce the ratio is performed.

  Furthermore, when the temperature of the pressure roller 22 is high, the temperature of the heating member 21 is difficult to decrease. Therefore, by setting the ratio α larger when the temperature of the heating roller 22 is low and setting the ratio α smaller when the temperature is low, the temperature drop of the central portion is suppressed, and the temperature distribution of the heating roller 21 is changed. It can be made uniform.

  Further, the ratio α is controlled based on the difference between the temperature at the central portion and the temperature at the end, that is, the difference between the detected temperature of the temperature sensor SE1 and the detected temperature of the temperature sensor SE2, and the central portion is controlled. When the temperature is lower than the temperature at the end portion, the temperature distribution is made uniform by increasing the previous ratio α.

  Tables 1 to 3 show control examples of the ratio α (the energization time to the central coil 23A / the energization time to the coil 23B). As shown in Table 1, Tables 1 to 8 shown in Tables 2 and 3 were assigned and applied to each size of the recording material before and after entering the temperature control state. Through the control shown in Tables 1 to 3, intermittent image formation, continuous image formation, double-sided image formation, image formation in these mixed modes, and recording materials of various sizes are used in which one or a few image forming jobs are repeated. In the image formation, good fixing could be stably performed.

  Note that the pressure roller temperature TP in Tables 1 and 2 is the temperature detected by the temperature sensor SE3, and the energization time ratio α is the amount of power supplied to the power source E2A of the central coil 23A and the power source E2B of the coil 23B in FIG. The middle-end temperature difference ΔT is the difference between the temperature detected by the temperature sensor SE1 and the temperature detected by the temperature sensor SE2, and positive (+) is the end at the center. The negative (-) indicates that the central part is cooler than the end part.

  In Table 1, information before or after temperature control is used, but the temperature distribution is made uniform by using information on the elapsed time from the start of image formation instead of the information. be able to.

1 is an overall view of an image forming apparatus. It is a figure which shows the fixing apparatus of a dielectric heating system. It is sectional drawing along the axis | shaft of a heating roller. It is a time chart of fixing temperature control.

Explanation of symbols

20 Fixing device 21 Heating roller 22 Pressure roller 23, 23A, 23B Coil CR control means EA, EB Fixing power source SE1, SE2, SE3 Temperature sensor

Claims (7)

A heating member for heating and fixing a toner image, a pressure member, and a coil divided into a plurality of portions in a direction perpendicular to the conveyance direction of the recording material, and heated by the induction current flowing in the coil An image forming apparatus comprising a fixing device that clamps and conveys a recording material between a heating member and the pressure member, and fixes a toner image onto the recording material, wherein the plurality of coils are formed in accordance with the width of the recording material. In an image forming apparatus that controls energization to each separately,
The control means for controlling the energization of the coils determines the ratio α of the power supplied to the plurality of coils based on the combination of at least one of the following information a and b and the recording material width information. An image forming apparatus characterized by performing control to change.
a. Elapsed time before or after entering the temperature control state or after the start of image formation b. Temperature of the pressure member The plurality of coils have a center coil and an end coil, and the ratio α = (amount of power supplied to the center coil / amount of power supplied to the end coil) is supplied to the end coil. The control means controls the power to be less than or equal to the power supplied to the central coil, and the ratio α is larger in the case of a narrow width recording material than in the case of a wide width recording material. The image forming apparatus according to claim 1. The plurality of coils include a center coil and an end coil, and the ratio α = (amount of power supplied to the center coil / amount of power supplied to the end coil). 3. The image forming apparatus according to claim 1, wherein before the temperature control state is entered, the ratio α is controlled to be larger than after the temperature control state is entered. The plurality of coils include a center coil and an end coil, and the ratio α = (amount of power supplied to the center coil / amount of power supplied to the end coil). 4. The image forming apparatus according to claim 1, wherein after the predetermined time has elapsed from the image formation start time, the ratio α is controlled to be smaller than before the time has elapsed. The plurality of coils include a center coil and an end coil, and the ratio α = (amount of power supplied to the center coil / amount of power supplied to the end coil). The image forming apparatus according to claim 1, wherein when the temperature of the pressure member is high, the ratio α is controlled to be small. The said control means performs control which changes the said ratio (alpha) based on the difference of the temperature of the center part of the said heating member, and the temperature of the edge part of the said heating member. 2. The image forming apparatus according to item 1. The image forming apparatus according to claim 1, wherein the heating member is a roller having a thickness of 0.4 to 2.0 mm.

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