Patent Description:
Patent Literature <NUM> discloses a configuration where a transfer member is fed by a feeding member configured by an endless wire, and an unfixed toner image transferred to the transfer member is thermally fused by radiation heat.

In the case where a feeding section that is in contact with the rear surface of a recording medium such as a sheet is used as a feeding section that feeds the recording medium in a heating section which heats in a non-contact manner the front surface of the recording medium, the feeding section is gradually heated with the operation of the heating section, and the rear surface of the recording medium is heated by the heated feeding section. With respect to the degree by which the rear surface of the recording medium is heated by the feeding section, the degree in the initial stage of the operation of the heating section is different from that in a stage where the operation of the heating section is continued. Therefore, the control of the heating temperature of the heating section is sometimes complicated.

At least one embodiment of the invention reduces the influence of heat that is received from the rear surface of a recording medium when the recording medium is fed while the front surface is opposed to a heating section, as compared with the case where the rear surface in an image region of the recording medium is in contact with a component of a device. At least one embodiment of the invention reduces the influence of heat that is applied to a fixed image on the rear surface of the recording medium, as compared with a configuration where the rear surface of the recording medium to which the image is fixed is in contact with a component of the device. At least one embodiment of the invention reduces the influence of heat that is received from the rear surface of the recording medium when the recording medium is fed while the front surface is opposed to the heating section, as compared with a configuration where a no-wind condition in which air is not blown to the rear surface of the recording medium is produced. At least one embodiment of the invention feeds the recording medium to a pressurizing section with enabling the influence of heat that is received from the rear surface of the recording medium, to be reduced as compared with a configuration where, when the recording medium is fed while the front surface is opposed to the heating section, the front-end side of the recording medium is not held and is in a free state.

Further details of the invention are defined by the dependent claims <NUM>-<NUM>.

According to an example, the influence of heat that is received from the rear surface of the recording medium can be reduced as compared with a configuration where, when the recording medium is fed while the front surface is opposed to the heating section, the rear surface in the image region of the recording medium is in contact with a component of the device.

According to an example, the influence of heat that is applied to a fixed image on the rear surface of the recording medium can be reduced as compared with a configuration where the rear surface of the recording medium on which the image is fixed is in contact with a component of the device.

According to an example, the recording medium can be held and fed from the heating section to the pressurizing section that is disposed downstream of the heating section.

According to an example, the influence of heat that is received from the rear surface of the recording medium can be reduced as compared with a configuration where, when the recording medium is fed while the front surface is opposed to the heating section, the recording medium is in a free state.

According to an example, the influence of heat that is received from the rear surface of the recording medium can be reduced as compared with a configuration where, when the recording medium is fed while the front surface is opposed to the heating section, a no-wind condition in which air is not blown to the rear surface of the recording medium is produced.

According to an aspect of the present invention, an image on the recording medium can be prevented from being disturbed, as compared with a configuration where an air blowing section that is disposed so that a blow-out port is opposed to the front surface of the recording medium is used.

According to an example, before the recording medium is fed to the heating section, the attitude of the recording medium can be stabilized as compared with a configuration where the air blowing section is disposed downstream of the upstream position of the heating section in the feeding direction.

According to an example, before the recording medium is heated by the heating section, the attitude of the recording medium can be stabilized as compared with a configuration where the air blowing section is disposed downstream of the upstream position of the upstream side reflector in the feeding direction that partitions a heating region of the heating section.

According to an example, the temperature of the recording medium in the pressurizing section is not excessively lowered, and, before the recording medium is fed to the pressurizing section, the attitude of the recording medium can be stabilized, as compared with the case where the distance between the pressurizing section and the heating section is set to be longer than that between the pressurizing section and the air blowing section.

According to an example, the temperature of the recording medium in the pressurizing section is not excessively lowered, and, before the recording medium is fed to the pressurizing section, the attitude of the recording medium can be stabilized, as compared with the case where the distance between the pressurizing section and a starting position of the blowing region is set to be longer than that between the pressurizing section and the air blowing section.

According to an example, the influence of heat that is received from the rear surface of the recording medium can be reduced while the recording medium is stably fed, as compared with a configuration where the front-end side of the recording medium is not held and is in a free state.

According to an example, air that is blown from the air blowing section can be prevented from unevenly hitting the rear surface of the recording medium, as compared with a configuration where the air directly hits the rear surface of the recording medium without passing through the ventilation holes.

According to an example, the influence of heat that is received from the rear surface of the recording medium can be reduced and fed to the pressurizing section, as compared with a configuration where, when the recording medium is fed while the front surface is opposed to the heating section, the front-end side of the recording medium is not held and is in a free state.

According to an example, the distance between the front-end side of the recording medium and the heating section, and that between the rear-end side of the recording medium and the heating section can be less dispersed, as compared with a configuration where, when the recording medium is fed while the front surface is opposed to the heating section, the holding section holds only the front-end side of the recording medium.

According to an example, the holding section hardly hinders the pressurization of the recording medium as compared with a configuration where the recording medium is pressurized between a pressurizing member in which a recess is not formed, and the heating member.

According to an example, the pressure that pressurizes the recording medium can be prevented from varying, as compared with a configuration where the recording medium is pressurized between the pressurizing section and heating section the axis-to-axis distance between which is not maintained.

According to an example, the attitude of the rear-end side of the recording medium can be stabilized as compared with the case where the distance between the heating section and the pressurizing section is larger than the length of the used recording medium in the feeding direction of the recording medium.

According to an example, it is possible to provide a fixing device in which, even when dry toner is used, the image quality can be prevented from being lowered.

According to an example, a fixed image that is formed on the rear surface of the recording medium can be prevented from fusing.

Hereinafter, an exemplary embodiment of the invention will be described with reference to the drawings. The arrow H shown in the figures indicates the vertical direction or the upward and downward direction of an apparatus, the arrow W indicates the horizontal direction or the width direction of the apparatus, and the arrow D indicates the anteroposterior direction (depth direction) of the apparatus.

The configuration of an image forming apparatus <NUM> of the exemplary embodiment will be described. <FIG> is a schematic diagram showing the configuration of the image forming apparatus <NUM> of the exemplary embodiment.

The image forming apparatus <NUM> shown in <FIG> is an example of the image forming apparatus that forms an image on a recording medium. Specifically, the image forming apparatus <NUM> is an electrophotographic image forming apparatus that forms a toner image on a sheet P which is an example of the recording medium. As shown in <FIG>, more specifically, the image forming apparatus <NUM> has sheet accommodating sections <NUM>, a sheet discharging section <NUM>, an image forming section <NUM>, a feeding mechanism <NUM>, a reversing mechanism <NUM>, a fixing device <NUM>, and a cooling section <NUM>.

The accommodating sections <NUM> shown in <FIG> have a function of accommodating sheets P. The image forming apparatus <NUM> includes a plurality (for example, two) of accommodating sections <NUM>, and is configured so as to feed a sheet P selectively from the plural accommodating sections <NUM>. As the sheet P that is an example of the recording medium, a single sheet (cut sheet) having a predetermined size is used. The sheet P has the front surface PA (see <FIG>) functioning as the one surface, and the rear surface PB (see <FIG>) functioning as the other surface. The front surface PA of the sheet P has an image region GR (see <FIG>) to which a toner image is to be transferred, i.e., the image region GR in which an unfixed image is to be formed.

The sheet discharging section <NUM> shown in <FIG> is a portion onto which the sheet P on which an image is formed is discharged. Specifically, the apparatus is configured so that the sheet P to which an image is fixed by the fixing device <NUM>, and which is then cooled by the cooling section <NUM> is discharged onto the sheet discharging section <NUM>.

The image forming section <NUM> shown in <FIG> is an example of the image forming section that forms an image on the recording medium. Specifically, the image forming section <NUM> has a function of forming a toner image on the sheet P by using the electrophotographic method. As shown in <FIG>, more specifically, the image forming section <NUM> has toner image forming portions <NUM> that form toner images, respectively, and a transferring device <NUM> that transfers the toner images formed by the toner image forming portions <NUM>, to the sheet P.

Plural toner image forming portions <NUM> are provided so as to form toner images of respective colors. In the image forming apparatus <NUM>, toner image forming portions <NUM> for a total of four colors of yellow (Y), magenta (M), cyan (C), and black (K) are provided. The characters (Y), (M). (C), and (K) shown in <FIG> indicate constituting portions corresponding to the colors, respectively.

The toner image forming portions <NUM> for the respective colors are configured in a basically similar manner except the used toner. As shown in <FIG>, specifically, each of the toner image forming portions <NUM> for the respective colors has a photosensitive drum <NUM> (photosensitive member) that is rotated in the direction of the arrow A in <FIG>, and a charging device <NUM> that charges the photosensitive drum <NUM>. Each of the toner image forming portions <NUM> for the respective colors further has an exposing device <NUM> that exposes the photosensitive drum <NUM> which is charged by the charging device <NUM>, thereby forming an electrostatic latent image on the photosensitive drum <NUM>, and a developing device <NUM> that develops the electrostatic latent image which is formed on the photosensitive drum <NUM> by the exposing device <NUM>, thereby forming a toner image.

The transferring device <NUM> shown in <FIG> has a function of primarily transferring the toner images on the photosensitive drums <NUM> for the respective colors to an intermediate transfer member to be superimposed on one another, and secondarily transferring the superimposed toner images to the sheet P. As shown in <FIG>, specifically, the transferring device <NUM> includes a transfer belt <NUM> functioning as an intermediate transfer member, primary transfer rollers <NUM>, and a transferring section <NUM>.

Each of the primary transfer rollers <NUM> has a function of transferring the toner image that is formed on the photosensitive drum <NUM> for the corresponding color, to the transfer belt <NUM> at a primary transfer position T (see <FIG>) which is between the photosensitive drum <NUM> and the primary transfer roller <NUM>.

As shown in <FIG>, the transfer belt <NUM> has an endless shape, and is wound around plural rollers <NUM>, whereby the attitude of the transfer belt is determined. The transfer belt <NUM> is caused to circulate in the direction of the arrow B, by rotationally driving at least one of the plural rollers <NUM>, to feed the primarily transferred images to a secondary transfer position NT.

The transferring section <NUM> has a function of transferring the toner images which are transferred onto the transfer belt <NUM>, to the sheet P. Specifically, the transferring section <NUM> has a secondary transferring portion <NUM> and an opposing roller <NUM>.

The opposing roller <NUM> is placed below the transfer belt <NUM> so as to be opposed to the transfer belt <NUM>. As shown in <FIG>, the secondary transferring portion <NUM> is placed inside the transfer belt <NUM> so that the transfer belt <NUM> is placed between the secondary transferring portion and the opposing roller <NUM>. Specifically, the secondary transferring portion <NUM> is configured by a corotron. In the transferring section <NUM>, the toner images that are transferred to the transfer belt <NUM> are transferred to the sheet P which passes through the secondary transfer position NT, by an electrostatic force which is generated by the discharge of the secondary transferring portion <NUM>.

The feeding mechanism <NUM> shown in <FIG> is a mechanism that feeds the sheet P. Specifically, the feeding mechanism <NUM> has a function of feeding the sheet P that is accommodated in one of the accommodating sections <NUM>, to the secondary transfer position NT. The feeding mechanism <NUM> has a further function of feeding the sheet P from the secondary transfer position NT to a fixing unit <NUM> that will be described later (configured by a heating roller <NUM> and pressurizing roller <NUM> which will be described later). In other words, the feeding mechanism <NUM> has a function of, in the fixing device <NUM>, feeding the sheet P to which toner images are transferred.

As shown in <FIG>, specifically, the feeding mechanism <NUM> has feed out rollers <NUM>, plural feeding rollers <NUM>, and a chain gripper <NUM>. The feed out rollers <NUM> are rollers for feeding out the sheet P that is accommodated in corresponding one of the accommodating sections <NUM>. The plural feeding rollers <NUM> are rollers for feeding the sheet P that is fed out by one of the feed out rollers <NUM>, to the chain gripper <NUM>.

The chain gripper <NUM> is a feeding section that feeds the sheet P while holding the front-end side (tip-end side) of the sheet P as shown in <FIG> and <FIG>. Specifically, the chain gripper <NUM> includes a pair of chains <NUM>, and grippers <NUM> that function as the holding member (gripping member).

As shown in <FIG>, the pair of chains <NUM> are formed into an annular shape. The pair of chains <NUM> are placed at an interval in the anteroposterior direction (the direction D in <FIG>) of the apparatus (see <FIG>). The pair of chains <NUM> are wound respectively around a pair of sprockets (not shown) that are placed on one and other end sides in the axial direction of the opposing roller <NUM> and pressurizing roller <NUM> which will be described later, and a pair of sprockets <NUM> that are placed at an interval in the anteroposterior direction of the apparatus. When one of the pairs of sprockets is rotated, the chains <NUM> are circulated in the direction of the arrow C (see <FIG>).

As shown in <FIG>, attachment members <NUM> to which the grippers <NUM> are attached bridge between the pair of chains <NUM> in in the anteroposterior direction of the apparatus. Plural attachment members <NUM> are secured to the pair of chains <NUM> at predetermined intervals in the circumferential direction (circular direction) of the chains <NUM>. In the figures, in order to illustrate the chains <NUM> in a simplified manner, portions constituting the chains <NUM> are shown in a rectangular shape.

As shown in <FIG>, plural grippers <NUM> are attached to each of the attachment members <NUM>, at predetermined intervals in the anteroposterior direction of the apparatus. The grippers <NUM> have a function of holding (gripping) a front-end portion of the sheet P. When the front-end portion of the sheet P is held, the position of the sheet P in the feeding direction of the sheet is easily determined, and the positioning (registration) between the sheet P and images in the transferring section <NUM> is facilitated. As shown in <FIG> and <FIG>, specifically, each of the grippers <NUM> has a claw 76A and a claw rest 76B. The gripper <NUM> is configured so that the front-end portion of the sheet P is clamped between the claw 76A and the claw rest 76B, whereby the sheet P is held. Specifically, the grippers <NUM> hold the front-end portion of the sheet P outside the image region GR (see <FIG>) in the front surface PA to which the toner images are to be transferred. In each of the grippers <NUM>, for example, the claw 76A is pressed against the claw rest 76B by a spring or the like, and opened or closed with respect to the claw rest 76B by the action of a cam or the like. Sometimes, marks that are called register marks are formed outside the image region GR in order to, when a printed matter is to be produced, indicate positions where an operation of cutting the printed matter into the finished dimensions is to be performed, or to perform registration for multicolor printing. In the case where the register marks are to be formed, the marks may be formed at positions where the grippers <NUM> overlap with the marks in the plan view shown in <FIG>. The grippers <NUM> may be allowed to partly overlap with the image region GR, but the image is formed so as not to overlap with the grippers.

In the chain gripper <NUM>, in the state where the grippers <NUM> hold the front-end portion of the sheet P, the chains <NUM> are circulated in the direction of the arrow C to feed the sheet P. The chain gripper <NUM> feeds the sheet P in the attitude in which the front surface PA is oriented upward, to the secondary transfer position NT, then causes the sheet P to pass through a heating section <NUM> that will be described later, and thereafter feeds the sheet to the fixing unit <NUM> that will be described later. As described above, the chain gripper <NUM> has a function of causing the sheet P to pass through the heating section <NUM>, and feeding the sheet from the heating section <NUM> to the fixing unit <NUM>, and functions also as the fixing device <NUM>. In <FIG>, a part of the feeding path along which the sheet P is fed in the feeding mechanism <NUM> is indicated by the dash-dot line.

The reversing mechanism <NUM> shown in <FIG> is an example of the reversing mechanism that reverses the front and rear surfaces of the recording medium on which an image is fixed by the fixing device. Specifically, the reversing mechanism <NUM> is a mechanism for reversing the sheet P to which the images are fixed by the fixing device <NUM>. As shown in <FIG>, more specifically, the reversing mechanism <NUM> has a plurality (for example, two) of feeding rollers <NUM>, a reversing device <NUM>, and a plurality (for example, seven) of feeding rollers <NUM>.

The plural feeding rollers <NUM> feed the sheet P that is sent from the fixing device <NUM>, to the reversing device <NUM>.

In the reversing device <NUM>, for example, the sheet P is twisted like a Mobius strip by feeding the sheet P while being folded plural times so that the feeding direction of the sheet P is changed by an increment of, for example, <NUM> degrees, whereby the sheet P are reversed.

The plural feeding rollers <NUM> feed the sheet P in which the front and rear surfaces are reversed by the reversing device <NUM>, to the chain gripper <NUM>. Namely, the plural feeding rollers <NUM> have a function of delivering the sheet P in which the front and rear surfaces are reversed, to the chain gripper <NUM>.

When, as described above, the reversing mechanism <NUM> reverses the sheet P, and delivers the sheet to the chain gripper <NUM>, the chain gripper <NUM> feeds the delivered sheet P as the sheet P in which the toner images are fixed to the rear surface PB.

In <FIG>, a part of the feeding path along which the sheet P is fed in the reversing mechanism <NUM> is indicated by the dash-dot line. Alternatively, the reversing mechanism <NUM> may be a mechanism in which the sheet P is reversed by switch backing the sheet,.

The fixing device <NUM> shown in <FIG> is an example of the fixing device that fixes an image which is formed by the image forming section, to the recording medium. Specifically, the fixing device <NUM> is a device that fixes the toner images which are transferred by the transferring device <NUM>, to the sheet P.

As shown in <FIG>, the fixing device <NUM> is placed downstream of the secondary transfer position NT in the feeding direction of the sheet P. As shown in <FIG>, the fixing device <NUM> has the heating section <NUM>, the chain gripper <NUM> that is described above, air blowers <NUM>, a ventilation plate <NUM>, and the fixing unit <NUM> (fixing section).

The heating section <NUM> shown in <FIG> is an example of the heating section that heats in a non-contact manner the front surface of the recording medium. Specifically, the heating section <NUM> has a function of heating in a non-contact manner the front surface PA of the sheet P that is fed by the chain gripper <NUM>,.

The heating section <NUM> is placed downstream of the secondary transfer position NT (see <FIG>) in the feeding direction of the sheet P, so as to be opposed to the front surface PA of the sheet P that is fed by the chain gripper <NUM>. Specifically, the heating section <NUM> includes a reflection plate <NUM>, plural heaters <NUM> (heating source), and a wire mesh <NUM>.

The reflection plate <NUM> has a function of reflecting infrared beams emitted from the heaters <NUM>, toward the lower side of the apparatus (the side of the sheet P that is fed by the chain gripper <NUM>). The reflection plate <NUM> is formed by using, for example, a metal plate such as an aluminum plate. The reflection plate <NUM> is formed into a box-like shape in which the lower side of the device is opened. Specifically, the reflector <NUM> includes: an upper reflector <NUM> that covers the upper side of the heater <NUM> of the heating section <NUM>; an upstream side reflector <NUM> extending downward from the upper reflector <NUM> and covering the upstream side surface of the heater <NUM> on the upstream side of the reflector <NUM> in the feeding direction of the sheet P; an downstream side reflector <NUM> extending downward from the upper reflector <NUM> and covering the downstream side surface of the heater <NUM>; and a pair of side reflectors extending downward from the upper reflector <NUM> at both side ends of the reflector <NUM> in a direction intersecting the transport direction of the sheet P and covering both side surfaces of the heater <NUM>.

The heaters <NUM> are infrared heaters having a columnar shape that is elongated in the anteroposterior direction of the apparatus. A plurality (for example, <NUM>) of heaters <NUM> are arranged inside the reflection plate <NUM> in the width direction of the apparatus. Specifically, each of the heaters <NUM> includes a carbon filament <NUM>, and a cylindrical quartz tube <NUM> in which the carbon filament <NUM> is accommodated. A black infrared radiation film is formed on the front surface of the quartz tube <NUM>. Since the black infrared radiation film is formed on the front surface of the quartz tube <NUM> in this way, the heater <NUM> may efficiently radiate infrared beams as compared with the case where, for example, a white film is formed. In the exemplary embodiment, black is a color in which, when the deviation in chromaticity from an achromatic point (x = <NUM>, y = <NUM>, Y = <NUM>) is indicated by the color difference ΔE, the color difference ΔE is equal to or smaller than <NUM>. In <FIG>, in order to specifically illustrate the configuration of each of the heaters <NUM>, the heater <NUM> is enlargedly shown in the upper left side of the heating section <NUM>. In the heaters <NUM> in the exemplary embodiment, the peak of the radiation wavelength of the infrared beams is set to be equal to or larger than <NUM> [µm] and equal to or smaller than <NUM> [µm], or in the so-called far-infrared region. The surface temperature of the heaters <NUM> of the heating section <NUM> is set to a predetermined temperature which is equal to or higher than <NUM> [°C] and equal to or lower than <NUM>,<NUM> [°C]. In the exemplary embodiment, moreover, the heaters <NUM> which efficiently radiate far-infrared beams are arranged in the width direction of the apparatus at a density of <NUM> or more and <NUM> or less per <NUM> [m] of the length of the reflection plate <NUM> in the width direction of the apparatus, and therefore an excellent heating distribution is obtained.

The case will be considered where a recording medium that has an A2 or larger size or a large width is fed in a manner that the long side of the recording medium extends in the feeding direction of the recording medium, and a toner on the recording medium is heated. When the heating operation is performed by the far-infrared heaters <NUM> which are arranged at a density less than <NUM> per meter, the voltage that is to be applied to the carbon filaments is raised in order to increase the output of each of the heaters <NUM>. When the voltage is raised, however, the temperature of the black infrared radiation film is raised, and the fusion of the toner is dominantly caused by heat conduction from the surrounding air that is heated by the near-infrared component rather than the far-infrared component. As a result, uneven fusion occurs between the vicinity of the heaters <NUM> and the heaters <NUM>. When the density is set to be <NUM> or greater per meter, by contrast, far-infrared radiation from the carbon filaments may be made dominant, and therefore far-infrared beams that show a weak dependence on distance from the radiation source may be efficiently used in fusion of the toner as compared with the case where the density is less that <NUM> per meter, so that fusion unevenness among the heaters <NUM> is reduced. When the number of the heaters is larger than <NUM>, far-infrared beams are excessively radiated, and therefore it is difficult to control the temperature of the irradiated member to a degree at which the toner fuses. Furthermore, the fixing device that is in the subsequent stage is heated by the heat of the toner, and the temperature control becomes difficult. Therefore, the number of the heaters is preferably <NUM> or less. In the case where a recording medium having a B2 or larger size is fed in a manner that the long side of the recording medium extends in the feeding direction of the recording medium, particularly, the number of the heaters is preferably <NUM> or more and <NUM> or less.

The wire mesh <NUM> is secured to the edge portion of the lower opening of the reflection plate <NUM>. According to the configuration, the interior and exterior of the reflection plate <NUM> are separated from each other by the wire mesh <NUM>. The wire mesh <NUM> prevents the sheet P that is fed by the chain gripper <NUM>, from being in contact with the heaters <NUM>.

The chain gripper <NUM> shown in <FIG> is an example of the feeding section that feeds the recording medium while the front surface of the recording medium is opposed to the heating section. The grippers <NUM> provided in the chain gripper <NUM> are an example of the holding section that holds at least the front-end side of the recording medium. The front-end side of the recording medium means a portion of the recording medium which is downstream (on the front side) of the middle in the feeding direction.

In the chain gripper <NUM>, specifically, the chains <NUM> are circulated in the direction of the arrow C as described above in the state where the chain gripper <NUM> holds the front-end portion of the sheet P, thereby feeding the sheet P while the front surface PA of the sheet P is opposed to the heaters <NUM> of the heating section <NUM>. Namely, the chain gripper <NUM> has a function of causing the sheet P to pass through the heating region of the heating section <NUM>. In the feeding by the chain gripper <NUM>, the rear-end side of the sheet P is not held and is in a free state.

The chain gripper <NUM> has a further function of feeding the sheet P from the heating section <NUM> to the fixing unit <NUM>. In the portion having the function of causing the sheet P to pass through the heating region of the heating section <NUM>, and that of feeding the sheet from the heating section <NUM> to the fixing unit <NUM>, as described above, the chain gripper <NUM> functions as an example of the feeding section of the fixing device <NUM>.

The air blowers <NUM> shown in <FIG> are an example of the maintaining section that, in order to enable the recording medium to be fed by the feeding section in a state where the rear surface that is opposite to the front surface, and that is in an image region where an unfixed-image is formed on the front surface is in a non-contact state, maintains the non-contact state. The air blowers <NUM> are also an example of the air blowing section that blows air to the rear surface of the recording medium that is fed by the feeding section. Alternatively, a configuration that functions both as the feeding section and the air blowing section may be employed, and the sheet P may be fed while the non-contact state is maintained by using only the air blowing section.

Plural air blowers <NUM> are placed inside (on the inner circumferential side) of the chains <NUM> as seen in the anteroposterior direction of the apparatus, and below the heating section <NUM>. As shown in <FIG> and <FIG>, the plural air blowers <NUM> are placed in a two-dimensional pattern (matrix-like pattern) along the direction of feeding the sheet P and the anteroposterior direction of the apparatus. In order to simplify the illustration of the air blowers <NUM>, the blades of a part of the air blowers <NUM> are not shown in <FIG>.

As shown in <FIG>, the air blowers <NUM> are upward directed, and configured so as to blow air to the upper side. Namely, the air blowers are configured so as to blow air in the thickness direction of the sheet P to only the rear surface PB of the sheet P that is in the state where the rear surface is opposed to the heating section <NUM>. In other words, the air blowers <NUM> are placed so as to be opposed to the rear surface PB of the sheet P that is fed by the chain gripper <NUM>. In other words, furthermore, the chain gripper <NUM> is configured so as to feed the sheet P while causing the rear surface PB of the sheet P to be opposed to the air blowers <NUM>.

For example, axial flow air blowers that blow air in the axial direction are used as the air blowers <NUM>. Alternatively, centrifugal air blowers that blow air in the centrifugal direction, such as multi-blade air blowers (for example, sirocco fans) may be used as the air blowers <NUM>.

When the air blowers <NUM> blow air to the rear surface PB of the sheet P that is fed by the chain gripper <NUM>, the sheet P rises from the ventilation plate <NUM>. This causes the rear surface PB of the sheet P to be in the non-contact state. Specifically, at least the rear surface PB in the image region GR of the sheet P is set to the non-contact state. More specifically, at least the rear surface PB in the image region GR of the sheet P is set to the non-contact state with respect to the ventilation plate <NUM>. Therefore, the air blowers <NUM> have a function of maintaining the non-contact state so that the sheet P is fed by the chain gripper <NUM> in the state where the rear surface PB in the image region GR of the sheet P is in the non-contact state. The rear surface PB outside the image region GR of the sheet P is allowed to be in contact with the ventilation plate <NUM>. It is necessary to prevent the air which is blown from blow-out ports of the air blowers <NUM>, from being supplied directly to the front surface PA of the sheet P. This is because the image forming apparatus <NUM> of the exemplary embodiment is an image forming apparatus of the type in which an image is formed by using dry toner, and, when air is supplied directly to the front surface of the sheet P from the blow-out ports, unfixed toner images may be disturbed. When air is supplied only to the rear surface PB, moreover, the toner which is transferred to the front surface PA is prevented from being cooled.

The ventilation plate <NUM> shown in <FIG> is an example of the ventilating section having plural ventilation holes through which the air that is blown from the air blowing section toward the rear surface of the recording medium may pass. Specifically, the ventilation plate <NUM> is configured by a plate in which plural ventilation holes <NUM> through which the air that is blown from the air blowers <NUM> toward the rear surface PB of the sheet P may pass are formed.

The ventilation plate <NUM> is placed inside (on the inner circumferential side) of the chains <NUM> as seen in the anteroposterior direction of the apparatus, below the heating section <NUM>, and above the air blowers <NUM> so that the thickness direction coincides with the vertical direction of the apparatus. Namely, the ventilation plate is placed so as to cover the air blowers <NUM> on the side of the blowing direction of the air blowers <NUM>. In other words, it may be said also that the ventilation plate <NUM> is an example of the placement member that is placed so as to be opposed to the rear surface PB of the sheet P which is fed by the chain gripper <NUM>.

The ventilation holes <NUM> pass through the ventilation plate <NUM> in the thickness direction. As shown in <FIG>, the plural ventilation holes <NUM> are placed in a two-dimensional pattern (matrix-like pattern) along the direction of feeding the sheet P and the anteroposterior direction of the apparatus. In order to simplify the illustration of the ventilation plate <NUM>, a part of the ventilation holes <NUM> is not shown in <FIG>.

The ventilation plate <NUM> is configured so that air that is blown from the air blowers <NUM> is caused to pass through the plural ventilation holes <NUM> to hit against the rear surface PB of the sheet P which is fed by the chain gripper <NUM>. In other words, a configuration is employed where the air blowers <NUM> blow air to the rear surface PB of the sheet P that is fed by the chain gripper <NUM>, through the ventilation plate <NUM> in which the plural ventilation holes <NUM> are formed.

The ventilation plate <NUM> is configured by a metal plate. The ventilation plate <NUM> functions also as a reflection plate that reflects the infrared beams emitted from the heaters <NUM>, toward the upper side of the apparatus (the side of the sheet P that is fed by the chain gripper <NUM>).

In the exemplary embodiment, in a configuration where the length of each of the heaters <NUM> in the width direction of the apparatus is set to <NUM> [m], a recording medium to be fed is preferably used in which the length in the width direction of the apparatus is equal to or larger than the length of the A2 size. When a recording medium which is smaller than the A2 size is used, the area where the air blown by the air blowers <NUM> is blocked by the recording medium is so small that most of the air is supplied to the infrared heaters <NUM>, with the result that there is a possibility that the heated air in the periphery of the heating section <NUM> may be diffused in the apparatus. When a recording medium having an A2 or larger size is fed, the recording medium occupies about <NUM> or more percent of the length of the infrared heaters <NUM> in the width direction of the apparatus, and therefore this is preferable also in the viewpoint of suppression of the temperature rise in the apparatus.

In the exemplary embodiment, the blowing region that is set by the air blowers <NUM> and the ventilation plate <NUM> is set to be longer upstream in the feeding direction of the sheet P than the heating region that is set by the above-described heating section <NUM>. Before the sheet P that has passed through the transferring section <NUM> enters the heating section <NUM>, namely, the rear surface PB is air blown by the air blowers <NUM>. This causes the sheet P to be carried to the heating section <NUM> in the state where the attitude of the sheet is stabilized. More preferably, the blowing region may be set while a point that is immediately behind the transferring section <NUM>, and that does not overlap with the transfer belt <NUM> in the gravitational direction is used as the starting point, and the region is directed downstream in the feeding direction of the sheet P. More preferably, the blowing region set by the air blowers <NUM> and the ventilation plate <NUM> is set to be longer upstream in the feeding direction of the sheet P than the upstream reflector <NUM> located on the upstream side in the feeding direction of the sheet P in the reflector <NUM>. That is, the sheet P after passing through the transferring section <NUM> is air blown by the air blowers <NUM> on the rear surface PB before the upstream side reflector <NUM> that partitions the heating region set by the heating section <NUM>. Another point of view may be said that the contact position between the transfer belt <NUM> which is the transfer unit <NUM> and the paper P, the upstream end of the blowing region, and the upstream end of the heating region by the heating unit <NUM> are arranged in this order toward the downstream in the feeding direction of the sheet P.

Preferably, the relative positional relationship between the heating region and the blowing region on the downstream side of the heating section <NUM> may be set in a manner that the heating region is closer to the fixing unit <NUM> that will be described later, more specifically, a contact position between the heating roller <NUM> and the pressurizing roller <NUM> in the fixing unit <NUM>, than the blowing region. Namely, the sheet P which is being fed has a portion which is heated by the heating section <NUM> until just before the sheet enters the fixing unit <NUM>, but the rear surface PB of which is not subjected to the air blowing of the air blowers <NUM>. More specifically, the position of the downstream reflector <NUM> on the reflector <NUM> is set longer toward the downstream in the feeding direction of the sheet P than the blowing region. More preferably, the position of the downstream end of the heater <NUM> as the heating source constituting the heating section <NUM> in the feeding direction of the sheet P is set longer toward downstream of the blowing region formed by the blowers <NUM> in the feeding direction of the sheet P. Another viewpoint may be said that the downstream end of the blowing region, the downstream end of the heater <NUM>, and the contact position between the heating roller <NUM> and the pressure roller <NUM> in the fixing unit <NUM> are arranged in this order toward the downstream side in the feeding direction of the sheet P. This is because, when the blowing region is set up to a position that is close to the fixing unit <NUM>, there is a possibility that the air blowing may exert an influence on the sheet P which enters the fixing unit <NUM>, for example, that the attitude of the sheet P that enters the fixing unit may be disturbed.

The fixing unit <NUM> shown in <FIG> is a fixing section that fixes an image on the sheet P to the sheet P. Specifically, the fixing unit <NUM> has a function of contacting with the sheet P to heat and pressurize the sheet P, thereby fixing the toner images to the sheet P. Although the exemplary embodiment having the heating section <NUM> that performs heating and pressurization will be described, heating is not always necessary. In the case where the object of the process is to improve the surface property of the toner which is fused by the heating section <NUM> in the previous step, such as the adjustment of the gloss, even a mode where only the pressurization is performed by a pressurizing section may be employed in the invention.

As shown in <FIG>, the fixing unit <NUM> is placed downstream of the heating section <NUM> in the feeding direction of the sheet P. Specifically, the fixing unit <NUM> has the heating roller <NUM>, the pressurizing roller <NUM>, and a driven roller <NUM>.

The heating roller <NUM> shown in <FIG> is an example of the heating member that is placed downstream of the heating section in the feeding direction, and that heats the recording medium. Specifically, the heating roller <NUM> is placed downstream of the heating section <NUM> in the feeding direction, and has a function of contacting with the sheet P to heat the sheet P. The heating roller <NUM> is placed while making the anteroposterior direction of the apparatus coincident with the axial direction so that the heating roller is in contact with the front surface PA of the sheet P.

The heating roller <NUM> has: a cylindrical base member <NUM>; a rubber layer <NUM> that is formed on the outer circumference of the base member <NUM>; a release layer <NUM> that is formed on the outer circumference of the rubber layer <NUM>; and a heater <NUM> (heating source) that is accommodated in the base member <NUM>. The heater <NUM> is configured by, for example, a single or plural halogen lamps.

In the heating roller <NUM>, as shown in <FIG>, butted portions <NUM> that are butted against butting portions <NUM> that will be described later, and that are disposed in the pressurizing roller <NUM> are disposed. The butted portions <NUM> are an example of a butted portion that is disposed in the heating roll. Specifically, each of the butted portions <NUM> is formed into a cylindrical shape having an outer diameter that is equivalent to that of the heating roller <NUM>. Moreover, the butted portions <NUM> are disposed respectively in one and other end portions in the axial direction of the heating roller <NUM> so that the butted portions are coaxial with the heating roller <NUM>, and rotated integrally with the heating roller <NUM>.

The driven roller <NUM> shown in <FIG> is placed while making the anteroposterior direction of the apparatus coincident with the axial direction so that the driven roller is in contact with a region of the outer circumferential surface of the heating roller <NUM> that is other than the region with which the sheet P is contacted. The driven roller <NUM> has a cylindrical base member <NUM>, and a heater <NUM> (heating source) that is accommodated in the base member <NUM>. The driven roller <NUM> is drivenly rotated by the heating roller <NUM>, and heats the heating roller <NUM>. Since the heating roller <NUM> is heated by the driven roller <NUM>, and the heating roller <NUM> itself has the heater <NUM>, the surface temperature of the heating roller <NUM> is a predetermined temperature of <NUM> [°C] or higher and <NUM> [°C] or lower.

The pressurizing roller <NUM> shown in <FIG> is an example of the pressurizing member that cooperates with the heating roller to pressurize the recording medium, and that has a recess into which the holding section enters is formed in the outer circumferential surface. Specifically, the pressurizing roller <NUM> has a function of cooperating with the heating roller <NUM> to clamp the sheet P, and pressuring the sheet. The pressurizing roller <NUM> is placed below the heating roller <NUM> while making the anteroposterior direction of the apparatus coincident with the axial direction.

The pressurizing roller <NUM> has: a cylindrical base member <NUM>; a rubber layer <NUM> that is formed on the outer circumference of the base member <NUM>; and a release layer <NUM> that is formed on the outer circumference of the rubber layer <NUM>.

The circumferential length of the pressurizing roller <NUM> is made equal to the placement interval at which the grippers <NUM> are arranged on the chains <NUM>. As shown in <FIG> and <FIG>, the recess <NUM> that extends in the anteroposterior direction of the apparatus is formed in the outer circumferential surface of the pressurizing roller <NUM>.

The pressurizing roller <NUM> is configured so that, when the grippers <NUM> that hold the front-end side of the sheet P passes between the pressurizing roller <NUM> and the heating roller <NUM>, the grippers <NUM> enter the recess <NUM>.

In the pressurizing roller <NUM>, as shown in <FIG>, the butting portions <NUM> that butt respectively against the butted portions <NUM> of the heating roller <NUM> are disposed. The butting portions <NUM> are an example of the butting portions that are disposed axially outside the recess of the pressurizing roll, and that butt respectively against the butted portions <NUM> to maintain the axis-to-axis distance between the heating roller <NUM> and the pressurizing roller <NUM>.

The butting portions <NUM> are formed into a cylindrical shape having an outer diameter that is equivalent to that of the pressurizing roller <NUM>. The butting portions <NUM> are placed axially outside the recess <NUM> of the pressurizing roller <NUM>. Specifically, the butting portions <NUM> are disposed respectively in one and other end portions in the axial direction of the pressurizing roller <NUM> so that the butting portions are coaxial with the pressurizing roller <NUM>, and rotated integrally with the pressurizing roller <NUM>,.

Even when the case where the heating roller <NUM> and the pressurizing roller <NUM> are rotated in the state where the butting portions <NUM> butt against the butted portions <NUM>, and, as a result, the recess <NUM> is opposed to the heating roller <NUM>, the axis-to-axis distance between the heating roller <NUM> and the pressurizing roller <NUM> is maintained. Consequently, the surface pressure of the load at which the pressurizing roller <NUM> is urged toward the heating roller <NUM> by an urging member that is not shown is about <NUM> [kPa] or lower and <NUM> [kPa] or higher. In the prior art, the surface pressure in a usual fixing device is about <NUM> [kPa].

In the fixing unit <NUM>, the pressurizing roller <NUM> is rotated by a driving section (not shown), the heating roller <NUM> is drivenly rotated by the pressurizing roller <NUM>, and the driven roller <NUM> is drivenly rotated by the heating roller <NUM>.

As shown in <FIG>, the cooling section <NUM> is placed downstream of the fixing unit <NUM> in the feeding direction of the sheet P. The cooling section <NUM> includes plural (for example, two) of cooling rollers <NUM> that are juxtaposed in the width direction of the apparatus.

Each of the cooling rollers <NUM> is configured by a cylindrical roller that is made of a metal or the like. The cooling roller <NUM> has a configuration where air flows through the interior of the roll, and the sheet P is cooled by the air (heat exchange with the air).

The sheet P that is sent out from one of the accommodating sections <NUM> shown in <FIG> is fed by the plural feeding rollers <NUM>, and delivered to the chain gripper <NUM>. The sheet P that is delivered to the chain gripper <NUM> is fed to the secondary transfer position NT by the chain gripper <NUM> in the state where the front-end portion is held by the grippers <NUM>, and the toner images are transferred from the transfer belt <NUM> to the front surface PA. As shown in <FIG>, the sheet P to which the toner images are transferred is fed by the chain gripper <NUM> to the heaters <NUM> of the heating section <NUM> in the state where the front surface PA is opposed to the heaters <NUM>, and the toner images are heated. In the exemplary embodiment, the movement speed of the chain gripper <NUM> is <NUM> [mm/sec] or lower and <NUM> [mm/sec] or higher.

The sheet P in which the toner images are heated by the heating section <NUM> is further fed to the fixing unit <NUM> by the chain gripper <NUM>, and pressurized and heated while being clamped between the heating roller <NUM> and the pressurizing roller <NUM>. This causes the toner images to be fixed to the sheet P. In the case where an image is to be formed on only the front surface PA of the sheet P, the sheet P to which the toner images are fixed is cooled by the cooling rollers <NUM> of the cooling section <NUM> shown in <FIG>, and then discharged onto the sheet discharging section <NUM>.

In the configuration, the relative positions of the fixing unit <NUM> and the heating section <NUM> are determined so that the time period when the sheet P that is fed by the chain gripper <NUM> is moved from the downstream end of the heating section <NUM> to a nipping section N is <NUM> [sec] or shorter and <NUM> [sec] or longer. Specifically, the relative positions of the fixing unit <NUM> and the heating section <NUM> are determined so that the time period from the passage of the front end of the sheet P through the end portion of the heating section <NUM> on the side of the fixing unit <NUM>, to the arrival of the front end of the sheet P to the nipping section N is <NUM> [sec] or shorter and <NUM> [sec] or longer.

In another view, the relative distance between the downstream end of the heating section <NUM> and the nipping section N of the heating section <NUM> is set to be shorter than the feeding direction length of the sheet P that is used in the image forming apparatus. Therefore, the attitude in which the rear-end side of the sheet P is stabilized is maintained until the sheet P arrives at the nipping section N.

The feeding speed of the sheet P is determined so that the time period when the sheet P to which the toner images are transferred is heated in the nipping section N is <NUM> [msec] or shorter and <NUM> [msec] or longer. Specifically, the feeding speed of the sheet P is determined so that the time period from the arrival of a predetermined reference point on the sheet P to the nipping section N, to the passage of the reference point through the nipping section N is <NUM> [msec] or shorter and <NUM> [msec] or longer.

In the case where images are to be formed on the both surfaces of the sheet P, the sheet P in which an image is fixed to the front surface PA is reversed by the reversing mechanism <NUM> shown in <FIG>, and then again delivered to the chain gripper <NUM>. The sheet P that is delivered to the chain gripper <NUM> is fed to the secondary transfer position NT as the sheet P in which the fixed toner images are formed on the rear surface PB, and toner images are transferred from the transfer belt <NUM> to the front surface PA.

In a manner similar to that described above, the sheet P to which the toner images are transferred is heated in the heating section <NUM>, and then pressurized and heated while being clamped between the heating roller <NUM> and the pressurizing roller <NUM>, whereby the toner images are fixed to the sheet P. The sheet P to which the toner images are fixed is cooled by the cooling rollers <NUM> of the cooling section <NUM>, and then discharged onto the sheet discharging section <NUM>.

In the exemplary embodiment, as shown in <FIG>, the air blowers <NUM> blow air to the rear surface PB of the sheet P that is fed by the chain gripper <NUM>, in the heating section <NUM>, and therefore the air blowers <NUM> maintain the non-contact state of the rear surface PB in the image region GR of the sheet P so that the sheet P is fed in the non-contact state.

Here, a configuration (first configuration) where, when the sheet P is fed while the front surface PA is opposed to the heating section <NUM>, the rear surface PB in the image region GR of the sheet P is in contact with a portion constituting the apparatus is considered. In the first configuration, in the case where the operation of the fixing device <NUM> is continued, and therefore the constituting portion (for example, the ventilation plate <NUM>) with which the sheet P is in contact is heated by the heating section <NUM>, the sheet P is heated by the constituting portion, and the fusion of the toner is advanced.

Therefore, the fusibility of the toner in the initial stage of the operation of the fixing device <NUM> is varied from that in the stage where the operation of the fixing device <NUM> is continued. Therefore, the heating temperatures of the heating section <NUM> and the heating roller <NUM> are changed between the initial stage of the operation of the fixing device <NUM> and the stage where the operation of the fixing device <NUM> is continued. As a result, the control of the heating temperature is complicated.

In the exemplary embodiment, by contrast, the air blowers <NUM> maintains the non-contact state of the rear surface PB in the image region GR of the sheet P so that the sheet P is fed in the non-contact state. As compared with the above-described first configuration, therefore, the rear surface PB of the sheet P is not heated, and the influence caused by the heat (for example, conductive heat) that is received from the rear surface PB of the sheet P is reduced. In other words, the temperature control of the heating performed by the heating section <NUM> and the heating roller <NUM> is prevented from becoming complicated.

In the case where images are to be formed on the both surfaces of the sheet P, even when the sheet P in which the fixed toner images are formed on the rear surface PB is fed in the heating section <NUM> by the chain gripper <NUM>, particularly, the rear surface PB of the sheet P is not heated, and, as compared with the first configuration, the fixed toner images are prevented from being fused. In order to, in the case where images are to be formed on the both surfaces of the sheet P, prevent the fixed toner images from being fused, particularly, the feeding section and the air blowing section are controlled so that, when the sheet P in which the fixed toner images are formed on the rear surface PB passes through the heating section <NUM>, the rear surface PB is in the non-contact state. In the case where the sheet P in which fixed toner images are not formed on the rear surface PB, and unfixed toner images are formed only on the front surface PA, the feeding operation may be performed while the ventilation plate <NUM> and the like are always contacted with the rear surface PB.

In the exemplary embodiment, in the heating section <NUM>, the air blowers <NUM> blow air to the rear surface PB of the sheet P that is fed by the chain gripper <NUM>, through the ventilation plate <NUM> in which the plural ventilation holes <NUM> are formed. Therefore, the air is prevented from unevenly hitting the rear surface PB of the sheet P, as compared with a configuration (second configuration) where air blown from the air blowers <NUM> directly hits the rear surface PB of the sheet P without passing through the ventilation holes <NUM>. Consequently, the attitude of the sheet P is hardly varied as compared with the above-described second configuration.

In the exemplary embodiment, in the case where the grippers <NUM> that hold the front-end side of the sheet P pass between the pressurizing roller <NUM> and the heating roller <NUM>, as shown in <FIG>, the grippers <NUM> enter the recess <NUM>. Therefore, the grippers <NUM> hardly hinder the pressurization of the sheet P as compared with a configuration where the sheet P is pressurized between the pressurizing roller <NUM> in which the recess <NUM> is not formed, and the heating roller <NUM>.

In the exemplary embodiment, even when the state where the recess <NUM> is opposed to the heating roller <NUM> is formed by rotating the heating roller <NUM> and the pressurizing roller <NUM> in the state where the butting portions <NUM> shown in <FIG> are butted against the butted portions <NUM>, the axis-to-axis distance between the heating roller <NUM> and the pressurizing roller <NUM> is maintained. Therefore, the pressure that pressurizes the sheet P may be prevented from varying, as compared with a configuration where the sheet P is pressurized between the pressurizing roller <NUM> and heating roller <NUM> the axis-to-axis distance between which is not maintained.

In the exemplary embodiment, when the sheet P is fed while the front surface PA is opposed to the heating section <NUM>, the attitude of the sheet P may be changed. Namely, the sheet P may be fed in the state where the rear-end side of the sheet P hangs down. The heating section <NUM> heats the sheet P by using infrared electromagnetic waves. Even when the attitude of the sheet P is changed, therefore, the sheet P is heated.

Furthermore, for example, a configuration may be employed where the rear surface PB in the image region GR of the sheet P is temporarily contacted with the ventilation plate <NUM>. In the exemplary embodiment, even in the case where the rear surface PB in the image region GR of the sheet P is temporarily contacted with the ventilation plate <NUM>, the configuration where the air blowers <NUM> blow air to the rear surface PB of the sheet P fed by the chain gripper <NUM> performs the following functions.

According to the configuration, in the heating section <NUM>, the air blowers <NUM> blow air to the rear surface PB of the sheet P fed by the chain gripper <NUM>, and therefore the sheet P rises. When the sheet P is fed while the front surface PA is opposed to the heating section <NUM>, therefore, the rear surface PB of the sheet P is hardly contacted with the ventilation plate <NUM> as compared with a configuration (third configuration) where a calm state in which air is not blown against the rear surface PB of the sheet P is set. Consequently, the rear surface PB of the sheet P is hardly heated as compared with the above-described third configuration, and the influence caused by the heat that is received from the rear surface PB of the sheet P is reduced.

In the exemplary embodiment, a configuration where the air blowers <NUM> and the ventilation plate <NUM> are not disposed may be employed. This configuration performs the following functions in the configuration where the grippers <NUM> of the chain gripper <NUM> hold the front-end side of the sheet P.

According to the configuration, since the front-end side of the sheet P is held, the attitude of the sheet P is hardly changed, and the rear-end side is made difficult to hang down, by the stiffness of the sheet P, as compared with a configuration (fourth configuration) where the front-end side of the sheet P is not held, and is in the free state.

Therefore, the rear surface PB of the sheet P is hardly contacted with the ventilation plate <NUM> as compared with the above-described fourth configuration. As compared with the above-described fourth configuration, consequently, the rear surface PB of the sheet P is hardly heated, and the influence caused by the heat that is received from the rear surface PB of the sheet P is reduced.

Although, in the chain gripper <NUM> in the exemplary embodiment, the grippers <NUM> that are an example of the holding section hold the front-end side of the sheet P, the invention is not limited to this. The holding section may have a configuration where, as shown in <FIG>, the section holds the front- and rear-end sides of the sheet P. The rear-end side of the sheet P means a portion which is upstream (the rear side) of the middle of the sheet P in the feeding direction.

In the configuration shown in <FIG>, a total of six grippers <NUM> or pairs of grippers <NUM>, <NUM>, <NUM> are configured as one set. In each of the pairs, the two grippers are placed on the pair of chains <NUM>, respectively. On each of the chains <NUM>, the corresponding grippers <NUM>, <NUM>, <NUM> are arranged at predetermined intervals in the circumferential direction (circular direction) of the chain <NUM>.

The grippers <NUM> clamp and hold respectively the front-end sides of the side portions of the sheet P, and the grippers <NUM> clamp and hold respectively the rear-end sides of the side portions of the sheet P. Moreover, the grippers <NUM> which are between the grippers <NUM>, <NUM> clamp and hold respectively parts that are in the side portions of the sheet P, and that are in the middle portion in the feeding direction. Alternatively, the grippers <NUM> may be omitted, and a total of four grippers <NUM>, <NUM> may be configured as one set. Alternatively, only the grippers <NUM> may clamp the front-end portions of the front-end sides of the sheet P in a similar manner as <FIG>.

According to the configuration shown in <FIG>, when the sheet P is fed while the front surface PA is opposed to the heating section <NUM>, the distance between the front-end side of the sheet P and the heating section <NUM>, and that between the rear-end side of the sheet P and the heating section <NUM> are less dispersed as compared with the case where the grippers <NUM> hold only the front-end side of the sheet P.

The modification may have a configuration where the air blowers <NUM> and the ventilation plate <NUM> are not used. In the modification, the grippers <NUM>, <NUM> may hold the sheet P, whereby the non-contact state is maintained so that the sheet P is fed in the state where the rear surface PB in the image region GR of the sheet P is in the non-contact state. In this case, the grippers <NUM>, <NUM> function as an example of the maintaining section. A configuration may be employed where the rear surface PB in the image region GR of the sheet P is temporarily contacted with a constituting portion of the apparatus.

In the modification, the recess <NUM> is formed at positions that are in the outer circumferential surface of the pressurizing roller <NUM>, and that correspond to the grippers <NUM>, <NUM>, <NUM>. Therefore, plural recesses <NUM> are formed at positions that are in the outer circumferential surface of the pressurizing roller <NUM>, and on the both axial end sides, and at intervals in the circumferential direction of the pressurizing roller <NUM> in accordance with the intervals of the grippers <NUM>, <NUM>, <NUM> in the circumferential direction (circular direction) of the chain <NUM>.

Although, in the exemplary embodiment, the sheet P is used as an example of the recording medium, the invention is not limited to this. For example, a film or the like may be used as an example of the recording medium. A sheet-like member that is other than the sheet P, and that is formed into a sheet-like shape (a paper-like shape or a film-like shape) may be used as an example of the recording medium.

Although, in the exemplary embodiment, the chain gripper <NUM> that is used as an example of the feeding section feeds the sheet P to the secondary transfer position NT, causes the sheet P to pass through the heating section <NUM>, and then feeds the sheet to the fixing unit <NUM>, the invention is not limited to this. A feeding section such as a chain gripper to which the sheet P that has passed through the secondary transfer position NT is delivered, which causes the sheet P to pass through the heating section <NUM>, and which then feeds the sheet to the fixing unit <NUM> may be used as an example of the feeding section. In this case, the sheet is fed to the secondary transfer position NT by another feeding section (for example, feeding rollers).

Although, in the exemplary embodiment, the air blowers <NUM> blow air to the rear surface PB of the sheet P in the thickness direction of the sheet P, the invention is not limited to this. For example, the air blowers <NUM> may blow air to the rear surface PB of the sheet P in a direction obliquely toward the upstream in the feeding direction of the sheet P (the obliquely upper right side in <FIG>).

A further configuration may be employed where, as shown in <FIG>, the air blowers <NUM> are placed in the outer sides in the width direction of the sheet P, and air is blown from the sides of the both side ends of the sheet P to the rear surface PB of the sheet P. In other words, a configuration where air is supplied to the rear surface PB of the sheet P so that the sheet P rises may be employed.

Although, in the exemplary embodiment, air is supplied only to the rear surface PB of the sheet P, the invention is not limited to this. The case where air is supplied to the front surface PA of the sheet P may be allowed from the following viewpoints.

The example shown in <FIG> is Modification <NUM> in which air is supplied to the front surface PA from the viewpoint of stable feeding of the sheet P. In addition to the configuration of the exemplary embodiment shown in <FIG>, Modification <NUM> has air blowers <NUM> that are placed so to be opposed to the front surface PA of the sheet P, and that are used for supplying air to the front surface PA. The relative air volume between the air blown from the air blowers <NUM> and that blown from the air blowers <NUM> is adjusted, and the attitude of the sheet P is maintained in parallel with the feeding direction. In this case, from the viewpoint that dry toner is used, the volume of the air blown by the air blowers <NUM> is set to a value which is smaller than the volume of the air blown by the air blowers <NUM>, and at which the toner is not scattered by the air blown by the air blowers <NUM>.

In Modification <NUM> shown in <FIG>, in order to ventilate the air in the vicinity of the heating section <NUM>, an air blower <NUM> is disposed so as to be directed in a direction perpendicular to the blowing direction of the air blowers <NUM>. That is, the air blower <NUM> is disposed so that the blow-out port of the air blower is opened in the direction along the front surface PA of the sheet P, and not directed to the front surface PA of the sheet P. There is a possibility that air blown from the air blower <NUM> flows in the direction along the front surface PA of the sheet P, and the air blown by the air blower <NUM> is supplied to the front surface PA of the sheet P. Also in this case, similarly with Modification <NUM>, the volume of the blown air is preferably set to a value at which scattering of the toner does not occur.

The exemplary embodiment has been described by means of the mode where the air blowers <NUM> blow air to the rear surface PB of the sheet P in the thickness direction of the sheet P. In the case where a recording medium does not exist between the heating section <NUM> and the air blowers <NUM>, when the air blowing is performed by the air blowers <NUM>, there arises a problem that the warmed air in the periphery of the heating section <NUM> is distributed in the apparatus. As a countermeasure against this, the air blowers <NUM> are controlled so as to blow air at the timing when the recording medium is opposed to the air blowers <NUM>, and the blown air is blocked by the recording medium. In other words, in the interval between preceding and succeeding recording media, the air blowing is weakened or stopped, whereby the volume of the air that is blown by the air blowers <NUM>, and that is supplied to the heating section <NUM> is reduced, with the result that the warmed air is prevented from being distributed in the apparatus. The driving of the air blowers <NUM> may be controlled as described above, or the plural air blowers <NUM> are individually driven controlled.

The invention is not limited to the above-described exemplary embodiment, various modifications, changes, and improvements may be made. For example, an appropriate combination of plural the above-described modifications may be configured.

Claim 1:
A fixing device (<NUM>) including:
a heating section (<NUM>) that heats in a non-contact manner a front surface of a recording medium;
a feeding section (<NUM>) that feeds the recording medium while causing the front surface to be opposed to the heating section (<NUM>); and
an air blowing section (<NUM>) that blows air to a rear surface of the recording medium that is fed by the feeding section (<NUM>),
wherein the air blowing section (<NUM>) is disposed so that a blow-out port is opposed only to the rear surface of the recording medium, and not opposed to the front surface.