Patent Description:
In recent years, there are cases where an image is printed on any of media having various thicknesses and shapes such as metal, glass, and tile. A printing process includes a step of fixing an image that has been formed on a print surface of an object with the use of an image forming material by performing heating treatment and pressure treatment.

<CIT> discloses a method for forming a particle image with particles including powder particles having a thermosetting property, which are an image forming material, and fixing the particle image attached to an object by heating the particle image by a heat source. <CIT> discloses a fixing device providing a casing which surrounds a high-frequency generating means and a shielding member which opens and closes the recording-material entrance of this casing at the entrance. A fixing function part consisting of an oscillator, a waveguide and a cooling device is surrounded with a shielding box, and a shielding member opening and closing an entrance for paper as a recording material and a couple of rollers made of microwave absorbers at a discharge opening are formed.

In a case where thermal fixation is performed inside a fixing device, it is required to keep a decrease in temperature inside the fixing device small when an object is transported into the fixing device.

The following disclosure serves a better understanding of the present invention. Accordingly, it is an object of the present disclosure to provide a technique of keeping a decrease in temperature inside a fixing device small when an object is transported into the fixing device as compared with a configuration in which an object is transported into the fixing device through an opening of the fixing device.

According to claim <NUM>, there is provided an image forming apparatus including, among other features: a transport unit that transports an object along a transport path; a transfer unit that transfers an image onto the object on the transport path; and a fixing unit that has a heat source for increasing a temperature inside the fixing unit, into which the object onto which the image has been transferred is carried along the transport path, and includes a first opening and closing member that opens a carry-in opening when the object is carried into the fixing unit and closes the carry-in opening after the object is carried into the fixing unit.

According to a first preferred embodiment, the image forming apparatus is configured such that a height of the carry-in opening opened to a maximum extent is substantially same as a height of a position where the transfer unit transfers an image onto the object.

According to a second preferred embodiment, the image forming apparatus is configured such that the first opening and closing member of the fixing unit is a shutter that opens the carry-in opening by moving up from a lower end of the carry-in opening, and a maximum height to which the shutter moves up is substantially same as the height of the position where the transfer unit transfers an image onto the object.

As defined by claim <NUM>, the image forming apparatus is further configured such that the fixing unit includes a second opening and closing member that opens a carry-out opening through which the object is carried out of the fixing unit after fixing of the image transferred onto the object and closes the carry-out opening after the object is carried out of the fixing unit.

As defined by claim <NUM>, the image forming apparatus is further configured such that the fixing unit further includes a covering unit that covers the heat source when the second opening and closing member opens the carry-out opening and exposes the heat source when the second opening and closing member closes the carry-out opening.

According to claim <NUM>, a decrease in temperature inside the fixing unit during a process of carrying the object into the fixing unit can be kept small as compared with a configuration in which the object is carried into the fixing unit through an opening that does not have an opening and closing unit.

According to the first preferred embodiment, a decrease in temperature inside the fixing unit during a state in which the carry-in opening is opened can be kept small as compared with a configuration in which the height of the carry-in opening is not limited.

According to the second preferred embodiment, a decrease in temperature inside the fixing unit during a state in which the carry-in opening is opened can be kept small as compared with a configuration in which a position to which the shutter moves up is not limited.

According to claim <NUM>, a decrease in temperature inside the fixing unit during a process of carrying the object out of the fixing unit can be kept small as compared with a configuration in which the object is carried out of the fixing unit through an opening that does not have an opening and closing unit.

According to claim <NUM>, a decrease in temperature inside the fixing unit during a process of carrying the object out of the fixing unit can be further kept small as compared with a configuration in which the heat source is exposed irrespective of whether the carry-out opening is opened or closed.

An exemplary embodiment of the present disclosure is described in detail below with reference to the attached drawings. An image forming apparatus according to the present exemplary embodiment is an image forming apparatus employing digital printing. Although an electrophotographic system, an inkjet system, and the like are known as digital printing systems, the electrophotographic system is assumed in the present exemplary embodiment. In the electrophotographic system, a transfer unit and a medium are brought into contact with each other when an image is transferred onto the medium. Furthermore, in the present exemplary embodiment, any of media having various thicknesses and shapes such as metal, glass, and tile is assumed as an object on which an image is to be printed. Apparatus Configuration.

<FIG> illustrates a configuration of an image forming apparatus to which the present exemplary embodiment is applied. The image forming apparatus <NUM> includes a transfer unit <NUM>, a fixing unit <NUM>, a medium attaching detaching unit <NUM>, and a transport mechanism <NUM>. Furthermore, the image forming apparatus <NUM> includes a controller (not illustrated) having one or more processors, which are computing units, a memory serving as a working region in data processing, and a storage device that holds a program and data. The controller may be a single controller that controls operation of the whole image forming apparatus <NUM> or may be controllers individually provided in units such as the transfer unit <NUM>, the fixing unit <NUM>, and the transport mechanism <NUM>.

The transfer unit <NUM> is a unit that transfers an image formed with particles such as toner onto a medium <NUM>. The fixing unit <NUM> is a unit that fixes, on a surface of the medium <NUM>, an image transferred by the transfer unit <NUM> by heating the medium <NUM>. The medium attaching detaching unit <NUM> is a unit in which a user of the image forming apparatus <NUM> attaches the medium <NUM> to an attachment table (described later) provided in the transport mechanism <NUM>. The transport mechanism <NUM> is provided across the transfer unit <NUM>, the fixing unit <NUM>, and the medium attaching detaching unit <NUM>, and transports the medium <NUM> on which an image is to be printed to the units <NUM>, <NUM>, and <NUM> as indicated by the arrow in <FIG>.

The medium attaching detaching unit <NUM> is a housing having an opening through which the medium <NUM> can be carried into and out of the medium attaching detaching unit <NUM>. In the medium attaching detaching unit <NUM>, one end portion of a transport rail <NUM> that constitutes the transport mechanism <NUM> is located, and a transport start position and a transport end position are set. This will be described in detail later. In the present exemplary embodiment, the transport start position and the transport end position are set at the same position. In an initial state, an attachment table <NUM> that constitutes the transport mechanism <NUM> is disposed at the position of the transport rail <NUM> set as the transport start position and the transport end position. The user attaches a jig <NUM> holding the medium <NUM> to the attachment table <NUM> by putting the jig <NUM> into the housing of the medium attaching detaching unit <NUM> through the opening, thereby making the medium <NUM> transportable by the transport mechanism <NUM>. After an image is transferred onto the medium <NUM> by the transfer unit <NUM> and fixed by the fixing unit <NUM>, the attachment table <NUM> on which the medium <NUM> is placed moves along the transport rail <NUM> and reaches the transport end position. In this state, the user detaches the jig <NUM> holding the medium <NUM> from the attachment table <NUM> and takes the jig <NUM> out through the opening of the housing of the medium attaching detaching unit <NUM>.

<FIG> illustrates a configuration of the transfer unit <NUM>. The transfer unit <NUM> forms an image with charged particles and transfers the image onto the medium <NUM> by generating an electric field. The transfer unit <NUM> includes a developing device <NUM>, a first transfer roll <NUM>, and an intermediate transfer belt <NUM>. The intermediate transfer belt <NUM> is tensioned between the developing device <NUM> and a position where an image is transferred onto the medium <NUM> by rollers <NUM> and <NUM> and a backup roll <NUM>. Furthermore, the transfer unit <NUM> includes a cleaning device <NUM> for removing particles attached to the intermediate transfer belt <NUM>.

The developing device <NUM> is a unit that forms, on a photoreceptor, an electrostatic latent image of an image to be transferred and develops the image by attaching charged particles to the electrostatic latent image on the photoreceptor. As the developing device <NUM>, an existing device used in an electrophotographic image forming apparatus can be used. <FIG> illustrates an example of a configuration employed in a case where color image formation processing is performed by using four colors, that is, three colors: yellow, magenta, and cyan, and an additional one color: black. The developing device <NUM> is provided for each of these colors, and the developing devices <NUM> for yellow, magenta, cyan, and black are given suffixes Y, M, C, and K indicative of the colors in <FIG>. In the following description, the suffixes are omitted in a case where the colors of the developing devices <NUM> need not be distinguished although the suffixes Y, M, C, and K are given to the reference signs in a case where the colors are distinguished.

The first transfer roll <NUM> is a unit used to transfer (first transfer) an image formed by the developing device <NUM> onto the intermediate transfer belt <NUM>. The first transfer roll <NUM> is disposed so as to face the photoreceptor of the developing device <NUM>, and the intermediate transfer belt <NUM> is located between the developing device <NUM> and the first transfer roll <NUM>. The first transfer roll <NUM> is provided corresponding to each of the developing devices 110Y, <NUM>, 110C, and <NUM>. In <FIG>, the first transfer rolls <NUM> corresponding to the developing devices 110Y, <NUM>, 110C, and <NUM> of the respective colors are given suffixes Y, M, C, and K indicative of the colors. In the following description, the suffixes are omitted in a case where the colors of the first transfer rolls <NUM> need not be distinguished although the suffixes Y, M, C, and K are given to the reference signs in a case where the colors are distinguished.

The intermediate transfer belt <NUM>, the rollers <NUM> and <NUM>, and the backup roll <NUM> are units used to transfer an image formed by the developing device <NUM> onto the medium <NUM>. As illustrated in <FIG>, the intermediate transfer belt <NUM> rotates in a direction indicated by the arrows in <FIG> (a counterclockwise direction in the example illustrated in <FIG>) while being suspended around the rollers <NUM> and <NUM> and the backup roll <NUM> in a tensioned state. For example, one or both of the rollers <NUM> and <NUM> is (are) a roller(s) that is (are) driven to rotate, and the intermediate transfer belt <NUM> is pulled by rotation of this(these) roller(s). In this way, the intermediate transfer belt <NUM> rotates.

An outer surface of the intermediate transfer belt <NUM> in the example of the configuration in <FIG> is a surface (hereinafter referred to as a "transfer surface") on which an image is held. An image is transferred from the photoreceptor of the developing device <NUM> onto the transfer surface of the intermediate transfer belt <NUM> when the intermediate transfer belt <NUM> passes between the developing device <NUM> and the first transfer roll <NUM>. In the example of the configuration illustrated in <FIG>, images of the respective colors: yellow (Y), magenta (M), cyan (C), and black (K) are superimposed on the transfer surface by the developing devices 110Y, <NUM>, 110C, and <NUM> and the first transfer rolls 120Y, <NUM>, 120C, and <NUM>, and thus a multi-color image is formed.

The backup roll <NUM> transfers (second transfer) the image onto the medium <NUM> by bringing the transfer surface of the intermediate transfer belt <NUM> into contact with the medium <NUM>. A predetermined voltage is applied to the backup roll <NUM> when the image is transferred. This generates an electric field (hereinafter referred to as a "transfer electric field") in a range including the backup roll <NUM> and the medium <NUM>, thereby transferring the image formed with charged particles from the intermediate transfer belt <NUM> onto the medium <NUM>. As described above, to transfer an image from the intermediate transfer belt <NUM> onto the medium <NUM>, an electric current need to flow from the backup roll <NUM> to the medium <NUM> through the intermediate transfer belt <NUM>. In a case where the medium <NUM> is a conductor such as a metal, an electric current flows through the medium <NUM> itself, and therefore an image is transferred onto a surface of the medium <NUM> by generating a transfer electric field. On the other hand, in a case where the medium <NUM> is not a conductor, no electric current flows through the medium, and therefore an image cannot be transferred in this state. In view of this, in a case where the medium <NUM> is not a conductor, an electric current is passed through the medium <NUM> by taking a measure such as forming a layer made of an electrically conductive material (hereinafter referred to as an "electrically conductive layer") in advance in at least a region on the surface of the medium <NUM> where an image is to be formed.

A procedure of transfer of an image by the intermediate transfer belt <NUM> is described. When the intermediate transfer belt <NUM> rotates, images of the respective colors: yellow (Y), magenta (M), cyan (C), and black (K) are sequentially superimposed on the transfer surface (outer surface in <FIG>) of the intermediate transfer belt <NUM> by the developing devices 110Y, <NUM>, 110C, and <NUM> and the first transfer rolls 120Y, <NUM>, 120C, and <NUM>, and thus a multi-color image is formed. When the intermediate transfer belt <NUM> further rotates, the image formed on the transfer surface of the intermediate transfer belt <NUM> reaches a position (hereinafter referred to as a "transfer position") where the intermediate transfer belt <NUM> makes contact with the medium <NUM>. As described above, a voltage is applied to the backup roll <NUM>. This generates a transfer electric field, thereby transferring the image from the intermediate transfer belt <NUM> onto the medium <NUM>.

The cleaning device <NUM> is a unit that removes particles attached to the transfer surface of the intermediate transfer belt <NUM>. The cleaning device <NUM> is provided at a position on a downstream side relative to the transfer position and an upstream side relative to the developing device 110Y and the first transfer roll 120Y in a direction in which the intermediate transfer belt <NUM> rotates. With this configuration, particles remaining on the transfer surface of the intermediate transfer belt <NUM> are removed by the cleaning device <NUM> after the image is transferred from the intermediate transfer belt <NUM> onto the medium <NUM>. In a next operation cycle, an image is newly transferred (first transfer) onto the transfer surface from which particles have been removed.

An attachment structure for attachment of the medium <NUM> is described. In the present exemplary embodiment, it is assumed that the medium <NUM> can have various thicknesses and shapes. In a case where the medium <NUM> directly placed on a transport path constituted by a belt and a roller is transported, it is difficult to appropriately bring the intermediate transfer belt <NUM> into contact with the medium <NUM> since a height of the medium <NUM> relative to the transport path varies at the transfer position of the transfer unit <NUM> in a case where a thickness and a shape of the medium <NUM> vary. Specifically, such a situation can occur in which the medium <NUM> does not make contact with the intermediate transfer belt <NUM> in a case where the height of the medium <NUM> is low, and a strong shock is caused when the medium <NUM> makes contact with the intermediate transfer belt <NUM> in a case where the height of the medium <NUM> is high. In view of this, the transport mechanism <NUM> according to the present exemplary embodiment has the attachment table <NUM> having a height controller and transports the medium <NUM> placed on the attachment table <NUM> together with the attachment table <NUM>.

The transport mechanism <NUM> includes the transport rail <NUM> that specifies a transport path for the medium <NUM> and the attachment table <NUM> that moves on the transport rail <NUM> (see <FIG>). The attachment table <NUM> includes a leg part <NUM> attached to the transport rail <NUM> and a table part <NUM> on which the medium <NUM> is to be placed. Furthermore, the jig <NUM> that holds the medium <NUM> on the table part <NUM> is attached to the table part <NUM>. The transport mechanism <NUM> is an example of a transport unit.

In the example of the configuration illustrated in <FIG>, the transport rail <NUM> is disposed so as to extend from the medium attaching detaching unit <NUM> to the transfer unit <NUM> while passing the fixing unit <NUM>. An end portion of the transport rail <NUM> on a medium attaching detaching unit <NUM> side is the transport start position and the transport end position. The attachment table <NUM> is transported leftward in <FIG> from the transport start position of the medium attaching detaching unit <NUM>, and an image is transferred onto the medium <NUM> in the transfer unit <NUM>. After the image transfer, the attachment table <NUM> is transported rightward in <FIG>, and reaches the transport end position of the medium attaching detaching unit <NUM> after the image is fixed on the medium <NUM> in the fixing unit <NUM>.

The leg part <NUM> is attached to the transport rail <NUM> and moves on the transport rail <NUM>. A mechanism for moving the leg part <NUM> on the transport rail <NUM> is not limited in particular. For example, the leg part <NUM> may be provided with a driving device so as to be movable on its own or the transport rail <NUM> may be provided with a unit that pulls the leg part <NUM>. Furthermore, the leg part <NUM> has a height controller that controls a height of the table part <NUM>. The leg part <NUM> is an example of a height adjuster. A configuration of the height controller is not limited in particular. For example, the table part <NUM> may be moved up and down by rack and pinion and a drive motor. Alternatively, the height of the table part <NUM> may be controlled by manually operating a gear that is linked with the height of the table part <NUM>. Furthermore, various methods can be used as an operation method for controlling the height. For example, an input interface for input to a controller of the drive motor may be prepared, and an operator of the image forming apparatus <NUM> may manually input and set height data by using the input interface. Alternatively, the height of the medium <NUM> attached to the attachment table <NUM> may be automatically detected by using a sensor, and the drive motor may be controlled so that the medium <NUM> is located at an appropriate height.

The table part <NUM> is a table that is attached to the leg part <NUM> and on which the medium <NUM> is placed with the jig <NUM> interposed therebetween. The table part <NUM> is provided with a fastener (not illustrated) for positioning the jig <NUM>. Any jigs <NUM> compatible with this fastener can be positioned and attached to the table part <NUM> irrespective of shapes thereof.

Furthermore, the table part <NUM> is attached so as to float up and sink down with respect to the leg part <NUM> in accordance with a pressure applied from an upper side. The configuration in which the table part <NUM> floats up and sinks down is, for example, realized by interposing an elastic body at a portion where the table part <NUM> and the leg part <NUM> are joined. By employing such a configuration, a shock caused when the medium <NUM> held by the jig <NUM> attached to the table part <NUM> makes contact with the intermediate transfer belt <NUM> of the transfer unit <NUM> is lessened.

The jig <NUM> is a device for holding the medium <NUM> and is attached to the table part <NUM>. A portion of the jig <NUM> attached to the table part <NUM> has a shape and a structure compatible with the fastener of the table part <NUM>. Furthermore, the jig <NUM> has a shape for holding the medium <NUM>. Therefore, media <NUM> having various shapes and sizes can be placed on the attachment table <NUM> by preparing jigs <NUM> compatible with the shapes and sizes of the media <NUM>.

The image forming apparatus <NUM> according to the present exemplary embodiment has the transport mechanism <NUM> configured as above and therefore can print an image on any of the media <NUM> having various shapes and sizes. However, before start of image transfer operation, the height of the table part <NUM> is controlled in order to prevent a strong shock from being caused by contact of the medium <NUM> with the intermediate transfer belt <NUM> of the transfer unit <NUM> or prevent failure to bring the medium <NUM> into contact with the intermediate transfer belt <NUM> when an image is transferred onto the medium <NUM>.

<FIG> illustrate operation of the transport mechanism <NUM> before start of image formation by the transfer unit <NUM>. <FIG> illustrates how the height is controlled, <FIG> illustrates a state where the attachment table <NUM> has retreated to a preparation position after the height control, and <FIG> illustrates a state where the transfer unit <NUM> starts transfer of an image.

In a case where an image is formed on the medium <NUM>, first, the medium <NUM> held by the jig <NUM> is placed on the attachment table <NUM> at the transport start position of the medium attaching detaching unit <NUM>. Then, the medium <NUM> is lowered to a height at which the medium <NUM> does not make contact with the intermediate transfer belt <NUM> of the transfer unit <NUM> by the height controller of the attachment table <NUM>, and then the attachment table <NUM> on which the medium <NUM> is placed is moved to a position below the transfer position of the transfer unit <NUM>.

Next, the height of the attachment table <NUM> is controlled so that the medium <NUM> makes contact with the intermediate transfer belt <NUM> with a strength appropriate for transfer of the image at the transfer position (arrow a in <FIG>). When the height is controlled, information on an appropriate height (hereinafter referred to as a "transfer execution height") thus obtained is held, for example, in the memory of the controller. Then, the attachment table <NUM> is lowered to a height where the medium <NUM> does not make contact with the intermediate transfer belt <NUM> and moves to the preparation position for transfer operation (arrow b in <FIG>).

When the attachment table <NUM> moves to the preparation position, the height of the attachment table <NUM> is adjusted to the transfer execution height on the basis of the information obtained in the height control. Then, the attachment table <NUM> moves to the transfer position (arrow c in <FIG>), and transfer of the image starts when the medium <NUM> makes contact with the intermediate transfer belt <NUM> at the transfer position (<FIG>).

After the image is transferred onto the medium <NUM> in the transfer unit <NUM>, the image is fixed in the fixing unit <NUM>. In the present exemplary embodiment, an image is formed on any of the media <NUM> having various thicknesses and shapes, and therefore the fixing processing is performed by a non-contact-type device. The fixing unit <NUM> melts particles forming the image transferred onto the medium <NUM> by heating the particles and thereby fixes the particles on the surface of the medium <NUM>.

<FIG> illustrates a configuration and operation of the fixing unit <NUM>. The fixing unit <NUM> includes a carry-in opening <NUM>, which is an opening through which the medium <NUM> is carried into the fixing unit <NUM>, and a carry-out opening <NUM>, which is an opening through which the medium <NUM> is carried out of the fixing unit <NUM>. Furthermore, the carry-in opening <NUM> and the carry-out opening <NUM> of the fixing unit <NUM> according to the present exemplary embodiment are provided with an opening and closing member and are configured to be opened when the medium <NUM> is carried into or out of the fixing unit <NUM> and be closed when the fixing processing is performed.

In this example, an opening on a side where the medium <NUM> is carried into the fixing unit <NUM> when image fixing processing is performed by the fixing unit <NUM> is the carry-in opening <NUM>, and an opening on a side where the medium <NUM> is carried out of the fixing unit <NUM> is the carry-out opening <NUM>. In other words, an opening in a side surface that faces the transfer unit <NUM> is the carry-in opening <NUM>, and an opening in a side surface that faces the medium attaching detaching unit <NUM> is the carry-out opening <NUM>. In the example illustrated in <FIG>, an opening on a left side is the carry-in opening <NUM>, and an opening on a right side is the carry-out opening <NUM>. In the image forming apparatus <NUM> according to the present exemplary embodiment, the medium <NUM> passes through the fixing unit <NUM> when the medium <NUM> is transported from the transport start position of the medium attaching detaching unit <NUM> to the transfer unit <NUM>. In this case, the medium <NUM> enters the fixing unit <NUM> through the carry-out opening <NUM> and exits the fixing unit <NUM> through the carry-in opening <NUM>, in a manner opposite to the case where the fixing processing is performed. However, in the present exemplary embodiment, the carry-in opening <NUM> and the carry-out opening <NUM> are set as described above on the basis of operation performed when the fixing processing is performed in the fixing unit <NUM>.

The fixing unit <NUM> includes a heat source <NUM> for thermal fixation. The heat source <NUM> can be, for example, any of various existing heat sources such as a halogen lamp, a ceramic heater, and an infrared lamp. Instead of the heat source <NUM>, a device that heats particles forming the image by emitting infrared laser may be used. The fixing unit <NUM> according to the present exemplary embodiment is provided with a member that can cover the heat source <NUM>, and is configured so that the heat source <NUM> is exposed when the fixing processing is performed.

In the example illustrated in <FIG>, the carry-in opening <NUM> and the carry-out opening <NUM> are provided with roll-up shutters <NUM> and <NUM>, respectively. The shutter <NUM> is an example of a first opening and closing member, and the shutter <NUM> is an example of a second opening and closing member. The shutters <NUM> and <NUM> are provided above the carry-in opening <NUM> and the carry-out opening <NUM>, respectively. When the shutters <NUM> and <NUM> are rolled up, the shutters <NUM> and <NUM> move up from lower ends of the carry-in opening <NUM> and the carry-out opening <NUM> and open the carry-in opening <NUM> and the carry-out opening <NUM>, respectively. Furthermore, a roll-up shutter <NUM> is provided inside the fixing unit <NUM> as a covering member that covers the heat source <NUM>. The shutter <NUM> is an example of a covering member that covers the heat source <NUM>. The shutters <NUM>, <NUM>, and <NUM> may be made of any material that endures a temperature inside the fixing unit <NUM> and has a certain level of heat insulating effect or higher. In the present exemplary embodiment, the shutters <NUM>, <NUM>, and <NUM> are individually operated in accordance with a timing such as a timing of carrying in of the medium <NUM> or a timing of carrying out of the medium <NUM>. In this way, a decrease in temperature inside the fixing unit <NUM> resulting from opening of the carry-in opening <NUM> and the carry-out opening <NUM> is kept small.

<FIG> are views for explaining operation of the shutters <NUM>, <NUM>, and <NUM> of the fixing unit <NUM>. <FIG> illustrates a state where the medium <NUM> is being carried into the fixing unit <NUM>, <FIG> illustrates a state during execution of fixing processing, and <FIG> illustrates a state where the medium <NUM> is being carried out of the fixing unit <NUM>. In a case where the medium <NUM> onto which an image has been transferred by the transfer unit <NUM> is carried into the fixing unit <NUM>, only the shutter <NUM> of the carry-in opening <NUM> is opened, and the shutter <NUM> of the carry-out opening <NUM> is closed, as illustrated in <FIG>. This keeps a decrease in temperature inside the fixing unit <NUM> small as compared with a configuration in which the openings are not provided with an opening and closing member. Furthermore, in a case where the shutter <NUM> is closed, a decrease in temperature of the heat source <NUM> resulting from a decrease in temperature inside the fixing unit <NUM> caused by opening of the shutter <NUM> is kept small.

During execution of the fixing processing, the shutter <NUM> of the carry-in opening <NUM> and the shutter <NUM> of the carry-out opening <NUM> are closed, and the shutter <NUM> is opened, as illustrated in <FIG>. This increases the temperature inside the fixing unit <NUM>, heats the medium <NUM>, and thereby fixes an image. Then, in a case where the medium <NUM> that has been subjected to the fixing processing is carried out from the fixing unit <NUM>, only the shutter <NUM> of the carry-out opening <NUM> is opened, and the shutter <NUM> of the carry-in opening <NUM> is closed, as illustrated in <FIG>. This keeps a decrease in temperature inside the fixing unit <NUM> small as compared with a configuration in which the openings are not provided with an opening and closing member. Furthermore, in a case where the shutter <NUM> is closed, a decrease in temperature of the heat source <NUM> resulting from a decrease in temperature inside the fixing unit <NUM> caused by opening of the shutter <NUM> is kept small.

The carry-in opening <NUM> and the shutter <NUM> are further described below. In the present exemplary embodiment, an upper limit is set on a height of the carry-in opening <NUM>. <FIG> is referred to again to explain limitation on the height of the carry-in opening <NUM>. In <FIG>, the transfer unit <NUM>, the fixing unit <NUM>, and the medium attaching detaching unit <NUM> of the image forming apparatus <NUM> are illustrated as blocks. However, these units are merely expressed as blocks divided according to their functions in <FIG>, and it is not intended that the transfer unit <NUM>, the fixing unit <NUM>, and the medium attaching detaching unit <NUM> each have an individual housing. Actually, the transfer unit <NUM> and the fixing unit <NUM> may be provided adjacent to each other in a single housing.

When the carry-in opening <NUM> of the fixing unit <NUM> is opened, heat inside the fixing unit <NUM> leaks out. In such a case, in a case where the transfer unit <NUM> and the fixing unit <NUM> are adjacent to each other, there is a possibility that an image formed on the developing device <NUM> or the intermediate transfer belt <NUM> of the transfer unit <NUM> is influenced by the heat leaking out from the fixing unit <NUM>. In the present exemplary embodiment, the influence of the heat leaking out from the fixing unit <NUM> on the transfer unit <NUM> is kept small by limiting the height of the carry-in opening <NUM> of the fixing unit <NUM>.

<FIG> illustrates limitation on the height of the carry-in opening <NUM> of the fixing unit <NUM>. In the example illustrated in <FIG>, a lower end of the shutter <NUM> of the carry-in opening <NUM> rolled up to a highest position is located at a same height as the transfer position of the transfer unit <NUM>. By thus setting the height of the carry-in opening <NUM> opened to a maximum extent equal to or lower than the height of the transfer position, transmission of heat inside the fixing unit <NUM> to members such as the intermediate transfer belt <NUM> of the transfer unit <NUM> is kept small. Although <FIG> illustrates the height of the lower end of the shutter <NUM> rolled up to the highest position, a mode of limitation on the height of the carry-in opening <NUM> is not limited to the one illustrated in <FIG>. For example, opening closing operation of the shutter <NUM> may be controlled so that a maximum height to which the shutter <NUM> is rolled up does not exceed the height of the transfer position irrespective of a position where the shutter <NUM> is provided. Alternatively, the height of the carry-in opening <NUM> itself may be set equal to or lower than the height of the transfer position of the transfer unit <NUM>.

In the example illustrated in <FIG> and <FIG>, the shutters <NUM>, <NUM>, and <NUM> are used as the opening and closing members for the carry-in opening <NUM> and the carry-out opening <NUM> and the covering member that covers the heat source <NUM>. However, these opening and closing members and covering member are not limited to the above configuration, as long as a decrease in temperature inside the fixing unit <NUM> and a decrease in temperature of the heat source <NUM> are kept small. For example, opening and closing doors may be provided instead of the shutters <NUM>, <NUM>, and <NUM>. In particular, as for the carry-out opening <NUM>, movement of air into and from the fixing unit <NUM> may be blocked by a curtain using a heat insulating material, an air curtain, or the like instead of providing an opening and closing member. Since the medium <NUM> that has been subjected to the fixing processing passes through the carry-out opening <NUM>, an image formed on the medium <NUM> is not affected by contact with the curtain or a wind pressure of the air curtain.

<FIG> illustrates an example in which an air curtain is used to open and close the carry-out opening <NUM>. In the fixing unit <NUM> illustrated in <FIG>, the heat source <NUM> and the shutters <NUM> and <NUM> are similar to those illustrated in <FIG>. In the fixing unit <NUM> illustrated in <FIG>, the carry-out opening <NUM> is provided with an air outlet <NUM> of the air curtain, instead of the shutter <NUM> illustrated in <FIG>. In the configuration illustrated in <FIG>, the air outlet <NUM> is provided above the carry-out opening <NUM> and blows out air downward. This flow of air blocks movement of air into and from the fixing unit <NUM>, thereby keeping leak of heat inside the fixing unit <NUM> small.

Although the exemplary embodiment of the present disclosure has been described above, the technical scope of the present disclosure is not limited to the above exemplary embodiment. For example, in the above exemplary embodiment, the shutter <NUM> that covers the heat source <NUM> is closed when the medium <NUM> is carried into the fixing unit <NUM> (see <FIG>). However, the shutter <NUM> may be opened when the medium <NUM> is carried into the fixing unit <NUM>. This maintains a state where the heat source <NUM> is exposed, and therefore keeps a decrease in temperature inside the fixing unit <NUM> small even when the opening and closing member of the carry-out opening <NUM> is opened. Furthermore, various changes and substitutions of the configurations are encompassed within the present disclosure without departing from the scope of the appended claims.

The foregoing description of the exemplary embodiments of the present disclosure has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical applications, thereby enabling others skilled in the art to understand the disclosure for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims.

According to the image forming apparatus according to claim <NUM>, a decrease in temperature inside the fixing unit during a process of carrying the object into the fixing unit can be kept small as compared with a configuration in which the object is carried into the fixing unit through an opening that does not have an opening and closing unit.

According to the image forming apparatus according to claim <NUM>, a decrease in temperature inside the fixing unit during a state in which the carry-in opening is opened can be kept small as compared with a configuration in which the height of the carry-in opening is not limited.

According to the image forming apparatus according to claim <NUM>, a decrease in temperature inside the fixing unit during a state in which the carry-in opening is opened can be kept small as compared with a configuration in which a position to which the shutter moves up is not limited.

According to the image forming apparatus according to claim <NUM>, a decrease in temperature inside the fixing unit during a process of carrying the object out of the fixing unit can be kept small as compared with a configuration in which the object is carried out of the fixing unit through an opening that does not have an opening and closing unit.

Claim 1:
An image forming apparatus (<NUM>) comprising:
a transport unit (<NUM>) that transports an object along a transport path (<NUM>);
a transfer unit (<NUM>) that transfers an image onto the object on the transport path (<NUM>); and
a fixing unit (<NUM>) that has a heat source (<NUM>) for increasing a temperature inside the fixing unit (<NUM>) , into which the object onto which the image has been transferred is carried along the transport path (<NUM>), and includes a first opening and closing member (<NUM>) that opens a carry-in opening when the object is carried into the fixing unit (<NUM>) and closes the carry-in opening after the object is carried into the fixing unit (<NUM>),
wherein the fixing unit (<NUM>) includes a second opening and closing member (<NUM>) that opens a carry-out opening through which the object is carried out of the fixing unit (<NUM>) after fixing of the image transferred onto the object and closes the carry-out opening after the object is carried out of the fixing unit (<NUM>) ,
the image forming apparatus (<NUM>) being characterized in that
the fixing unit (<NUM>) further includes a covering unit (<NUM>) that covers the heat source (<NUM>) when the second opening and closing member (<NUM>) opens the carry-out opening and exposes the heat source (<NUM>) when the second opening and closing member (<NUM>) closes the carry-out opening.