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.

<CIT> discloses a printer that forms an image on a disc while transporting the disc placed on a transport table together with the transport table.

<CIT> discloses an additive manufacturing system for producing a 3D part by utilizing electrophotography-based additive manufacturing and molding processes. The additive manufacturing system includes an electrophotographic engine and a deposition unit. The electrophotography unit includes a transfer assembly including a transfer medium, at least one EP engine configured to develop layers of a powder material, and a transfusion assembly configured to build a mold structure having a cavity on a build platform in a layer-by-layer manner by transfusing the developed layers to each other. The deposition unit is configured to deposit molding material into the cavity and form a molded part portion of the 3D part within the cavity.

According to a printing method of transferring an image by bringing a transfer unit into contact with an object, it is difficult to transfer an image onto a circumferential surface of a cylinder, a sphere, or the like along a circumference thereof.

Accordingly, it is an object of the present invention to provide a technique enabling printing of an image on a circumferential surface of a medium along a circumference thereof as compared with a configuration in which a medium fixed to a transport unit is transported and an image is printed thereon.

The present invention is provided by the appended claims. The following disclosure serves a better understanding of the present invention.

According to the invention, there is provided an image forming apparatus including: a transfer unit that transfers an image onto an object by making contact with the object; a holding unit that holds the object having a circumferential surface so that the circumferential surface rotates along a transfer direction of the transfer unit; and a transport unit that transports the holding unit holding the object along a transport path, wherein the transfer unit transfers an image onto the circumferential surface of the object in a circumferential direction as the object rotates, by making contact with the circumferential surface of the object maintained at a transfer position.

According to the invention, the image forming apparatus according to the first aspect is configured such that the holding unit further includes a mobile table part that is moved along the transport path by the transport unit and a support part that is provided on the mobile table part so as to be movable in a direction opposite to the transport direction of the transport unit and rotatably supports the object.

According to the invention, the image forming apparatus according to the second aspect is configured such that the holding unit further includes a driving mechanism that moves the support part relative to the mobile table part at a same speed as a transport speed of the transport unit in the direction opposite to the transport direction of the transport unit.

According to the invention, the image forming apparatus according to any one of the first to third aspects is configured such that the holding unit includes a support table that supports the object placed thereon; and the support table is provided with a roller that has a rotary axis substantially orthogonal to the transport direction of the transport unit and supports the circumferential surface of the object.

According to the invention, the image forming apparatus according to the fourth aspect is configured such that the roller of the support table is provided so as to support the object in a region of the object other than an image region where an image is to be transferred.

According to the invention, the image forming apparatus according to the fourth or fifth aspect is configured such that the support table includes a driving unit that rotates the roller so that the object rotates at a speed corresponding to a transfer speed at which an image is transferred by the transfer unit.

According to the invention, the image forming apparatus according to any one of the first to third aspects is configured such that the holding unit includes a pivotally-supporting part that supports the object so that the object is rotatable about a central axis of the circumferential surface of the object including an image region where an image is to be transferred.

According to the invention, the image forming apparatus according to the seventh aspect is configured to further include a driving unit that drives the pivotally-supporting part so that the object rotates at a speed corresponding to a transfer speed at which an image is transferred by the transfer unit.

According to the invention, an image can be printed on a circumferential surface along a circumference as compared with a configuration in which a medium fixed to a transport unit is transported and an image is printed on the medium.

According to the invention, a position of the object can be maintained at a transfer position when an image is transferred by the transfer unit as compared with a configuration in which a medium is fixed to the transport unit.

According to the invention, the object can be stably held at the transfer position as compared with a configuration in which a driving unit is not used.

According to the invention, an image can be transferred onto the circumferential surface by rotating the object by a roller as compared with a configuration in which a medium is fixed to the transport unit.

According to the invention, an image can be transferred onto the entire circumferential surface of the object unlike a configuration in which a roller is provided at a position corresponding to the image region.

According to the invention, an image can be transferred by stably rotating the object irrespective of a material of the object as compared with a configuration in which the object is rotated in accordance with action of the transfer unit.

According to the invention, an image can be transferred onto the circumferential surface by rotating the object by setting of the rotary axis as compared with a configuration in which a medium is fixed to the transport unit.

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.

<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>. Note that a moving direction of the intermediate transfer belt <NUM> at the transfer position is parallel with a direction in which the attachment table <NUM> is transported by the transport mechanism <NUM> and matches the transport direction during transfer of an image 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. Configuration of Transport Mechanism <NUM> and Attachment Structure for Attachment of Medium <NUM>.

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. The attachment table <NUM> is an example of a holding 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>. 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. The leg part <NUM> and the table part <NUM> are an example of a mobile table part.

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>. In the present exemplary embodiment, it is assumed that an image is to be formed on a medium <NUM> having a circumferential surface, and the transfer unit <NUM> transfers an image onto the circumferential surface of the medium <NUM> along a circumferential direction. Accordingly, a jig having a function of bringing the circumferential surface of the medium <NUM> into contact with the intermediate transfer belt <NUM> of the transfer unit <NUM> along the circumferential direction is used as the jig <NUM>. Details of such a jig <NUM> will be described later. The jig <NUM> is an example of a support part, a support table and a pivotally-supporting part.

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> illustrate a configuration and operation of the fixing unit <NUM>. <FIG> illustrates a state where openings of the fixing unit <NUM> are closed, and <FIG> illustrates a state where the openings of the fixing unit <NUM> are opened. 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>, roll-up shutters <NUM> and <NUM> are provided as the opening and closing members of the carry-in opening <NUM> and the carry-out opening <NUM>. The shutters <NUM> and <NUM> are closed (see <FIG>) except when the medium <NUM> is carried into and out of the fixing unit <NUM> and thereby prevent a decrease in internal temperature. The shutter <NUM> of the carry-in opening <NUM> opens when the medium <NUM> is carried into the fixing unit <NUM>, and the shutter <NUM> of the carry-out opening <NUM> opens when the medium <NUM> is carried out of the fixing unit <NUM> (see <FIG>).

In the example illustrated in <FIG>, a roll-up shutter <NUM> is provided as the covering member that covers the heat source <NUM>. The shutter <NUM> closes in a case where the shutter <NUM> of the carry-in opening <NUM> and/or the shutter <NUM> of the carry-out opening <NUM> open(s) (see <FIG>). This may keep a decrease in temperature of the heat source <NUM> small even in a case where the carry-in opening <NUM> and/or the carry-out opening <NUM> open(s) and the internal temperature decreases.

In the example illustrated in <FIG>, a state where both of the shutter <NUM> of the carry-in opening <NUM> and the shutter <NUM> of the carry-out opening <NUM> are opened is illustrated for convenience of description. In actual operation, the shutter <NUM> of the carry-out opening <NUM> remains closed when the medium <NUM> is carried into the fixing unit <NUM>, and the shutter <NUM> of the carry-in opening <NUM> remains closed when the medium <NUM> is carried out of the fixing unit <NUM>. This keeps a decrease in internal temperature small.

The shutters <NUM>, <NUM>, and <NUM> illustrated in <FIG> are an example of the opening and closing members of the carry-in opening <NUM> and the carry-out opening <NUM> and the covering member of the heat source <NUM>. The opening and closing members and covering member are not limited to the above configuration, as long as the opening and closing members and covering member keep a decrease in internal temperature of the fixing unit <NUM> and temperature of the heat source <NUM> small. For example, an opening and closing door may be provided instead of the shutters <NUM>, <NUM>, and <NUM> illustrated in <FIG>. As the opening and closing member of the carry-out opening <NUM> through which the medium <NUM> passes after the fixing processing is finished, a curtain made of a heat insulating material or air curtain may be used to prevent leakage of internal air.

<FIG> illustrate a method for transferring an image onto the medium <NUM> having a circumferential surface. <FIG> illustrates a state at the start of the transfer, <FIG> illustrates a state during the transfer, and <FIG> illustrates a state at the end of the transfer. In the example illustrated in <FIG>, an image T is transferred onto a side surface of a cylindrical medium <NUM> over a half of a circumference in a circumferential direction.

To form the image T on the side surface that is the circumferential surface of the medium <NUM> along the circumferential direction, it is necessary to move a portion of the side surface of the medium <NUM> that makes contact with the intermediate transfer belt <NUM> of the transfer unit <NUM> as the intermediate transfer belt <NUM> moves while stopping the medium <NUM> at the transfer position of the transfer unit <NUM>. For this purpose, the jig <NUM> holds the medium <NUM> so that a central axis of the circumferential surface of the medium <NUM> is orthogonal to the moving direction (hereinafter referred to as a "transfer direction") of the intermediate transfer belt <NUM> at the transfer position, and rotates the medium <NUM> about the central axis. A direction of rotation of the medium <NUM> is such a direction that movement of the circumferential surface matches the transfer direction of the intermediate transfer belt <NUM> at a position where the intermediate transfer belt <NUM> and the circumferential surface of the medium <NUM> make contact with each other. In the example illustrated in <FIG>, the medium <NUM> is illustrated in such a posture that the central axis of the circumferential surface is perpendicular to the paper on which <FIG> are drawn. The intermediate transfer belt <NUM> moves from left to right in <FIG>, and the medium <NUM> rotates in a clockwise direction in <FIG> (see the arrows in <FIG>).

In a case where the transfer unit <NUM> transfers the image T onto the medium <NUM>, first, the image T is formed on the intermediate transfer belt <NUM> by the developing devices <NUM> of the respective colors as the intermediate transfer belt <NUM> moves. Then, when the intermediate transfer belt <NUM> further moves and the image T formed on the intermediate transfer belt <NUM> reaches the transfer position, the image T is transferred from the intermediate transfer belt <NUM> onto the medium <NUM>, as illustrated in <FIG>. When the intermediate transfer belt <NUM> further moves, the medium <NUM> rotates accordingly, and transfer of the image T is executed while the contact portion of the medium <NUM> moves along the circumferential direction. Accordingly, the image T on the intermediate transfer belt <NUM> is transferred onto the circumferential surface of the medium <NUM> along the circumferential direction, as illustrated in <FIG>.

Next, the jig <NUM> for the medium <NUM> having the circumferential surface is described. In the present exemplary embodiment, the jig <NUM> that rotates the medium <NUM> and continuously brings the circumferential surface of the medium <NUM> into contact with the intermediate transfer belt <NUM> of the transfer unit <NUM> along the circumferential direction is used, as described with reference to <FIG>. A configuration of such a jig <NUM> is described below by giving specific examples.

<FIG> illustrate an example of a configuration of the jig <NUM> that rotatably holds the medium <NUM>. <FIG> illustrates the jig <NUM> and the medium <NUM> viewed in a direction parallel with a rotary axis of the medium <NUM>, and <FIG> illustrates a relationship between the medium <NUM> and rollers 423b of the jig <NUM> viewed in a direction perpendicular to the rotary axis of the medium <NUM>. In <FIG>, only the medium <NUM> and the rollers 423b are illustrated. The jig <NUM> illustrated in <FIG> includes a base 423a and the rollers 423b. The base 423a includes a driving device 423c for rotating the rollers 423b. In the jig <NUM> illustrated in <FIG>, the base 423a has a structure that fits with the fastener of the table part <NUM> and is fixed to the table part <NUM>.

The rollers 423b make contact with the circumferential surface of the medium <NUM> and rotatably supports the medium <NUM>. The rollers 423b are disposed on the base 423a so that rotary axes thereof are orthogonal to the transfer direction of the intermediate transfer belt <NUM> and the medium <NUM> is placed on the rollers 423b. In the example illustrated in <FIG>, two rollers 423b are spaced apart from each other by an appropriate distance so that rotary axes thereof are parallel with each other, and the medium <NUM> is placed between the two rollers 423b. Although it seems that two rollers 423b are disposed in <FIG>, it is assumed that two rollers 423b are disposed for each of two rotary axes, as illustrated in <FIG>. A rotary surface of each of the rollers 423b is, for example, made of a member having a high coefficient of friction such as rubber.

The image forming apparatus <NUM> according to the present exemplary embodiment rotates the medium <NUM> at the transfer position when an image is formed on the medium <NUM>, as described with reference to <FIG>. Accordingly, in some cases, a portion of the circumferential surface of the medium <NUM> onto which the image has been transferred moves downward and reaches a position corresponding to the rollers 423b as the medium <NUM> rotates. An example of such cases is a case where an image is transferred over a half of the circumference or an entire circumference of the circumferential surface of the medium <NUM>. In such a case, it is necessary to avoid contact between the image transferred onto the circumferential surface of the medium <NUM> and the rollers 423b. In view of this, the rollers 423b are configured to support the medium <NUM> in regions other than a region where an image is to be transferred on the circumferential surface of the medium <NUM>.

In the example illustrated in <FIG>, a region R where an image is to be transferred is set in a central part of the circumferential surface of the medium <NUM> in a central axis direction. Two rollers 423b whose rotary axes match each other are disposed on both sides of the region R so as to support the medium <NUM> at positions that do not make contact with the region R. Note that the configuration illustrated in <FIG> is an example of a configuration in which the rollers 423b do not make contact with the region R of the medium <NUM>, and shapes of the rollers 423b are not limited to the configuration illustrated in <FIG>. For example, a roller 423b whose portion corresponding to the region R is thinner than portions thereof on both sides and does not make contact with the region R may be used instead of disposing the plural rollers 423b as illustrated in <FIG>.

The driving device 423c is a driving unit for rotating the rollers 423b. The rollers 423b rotate by receiving power from the driving device 423c and thereby rotates the medium <NUM>. Any of various existing mechanisms can be used as the driving device 423c, and a specific structure of the driving device 423c is not limited. For example, a motor and a driving roller that rotates by receiving power from the motor may be used, and rotation of the driving roller may be transmitted to the rollers 423b by bringing the driving roller into contact with the rollers 423b. The driving device 423c rotates the rollers 423b so that a rotation speed of the medium <NUM> rotated by the rollers 423b becomes equal to a moving speed of the intermediate transfer belt <NUM> at the contact position with the intermediate transfer belt <NUM> of the transfer unit <NUM>.

Note that the configuration in which the driving device 423c is provided in the jig <NUM> and the jig <NUM> dynamically rotates the medium <NUM> in synchronization with action of the intermediate transfer belt <NUM> of the transfer unit <NUM> while using the rollers 423b as driving wheels has been described above. However, it is also possible to employ a configuration in which the jig <NUM> merely rotatably supports the medium <NUM> and the medium <NUM> rotates in accordance with action of the intermediate transfer belt <NUM> while the rollers 423b are used as driven wheels. For example, in a case where the medium <NUM> is made of a material having a high coefficient of friction with the intermediate transfer belt <NUM>, the medium <NUM> is rotated without the need for driving by the rollers 423b by being pulled by the intermediate transfer belt <NUM> at the contact position.

<FIG> illustrate another example of the configuration of the jig <NUM> that rotatably holds the medium <NUM>. <FIG> illustrates the jig <NUM> and the medium <NUM> viewed in a direction parallel with the rotary axis of the medium <NUM>, and <FIG> illustrates the jig <NUM> and the medium <NUM> viewed in a direction perpendicular to the rotary axis of the medium <NUM>. The jig <NUM> illustrated in <FIG> supports the medium <NUM> so that the medium <NUM> is rotatable about the central axis of the circumferential surface of the medium <NUM>. The jig <NUM> has fastening parts 423d that rotatably fasten the medium <NUM>. The jig <NUM> includes a driving device 423e for rotating the medium <NUM>. The jig <NUM> has a structure that fits with the fastener of the table part <NUM> and is fixed to the table part <NUM>.

The jig <NUM> illustrated in <FIG> fastens positions where the central axis of the circumferential surface of the medium <NUM> passes from both sides of the axis by using the fastening parts 423d. The driving device 423e is a driving unit for rotating the fastening parts 423d. The fastening parts 423d receives power from the driving device 423e and rotate the medium <NUM> about the central axis of the circumferential surface while fastening the medium <NUM>. Any of various existing mechanisms can be used as the driving device 423e, and a specific structure of the driving device 423e is not limited. For example, the fastening parts 423d may be directly driven to rotate by a motor. The driving device 423e rotates the fastening parts 423d so that a rotation speed of the medium <NUM> becomes equal to a moving speed of the intermediate transfer belt <NUM> at the contact position with the intermediate transfer belt <NUM> of the transfer unit <NUM>.

Note that the configuration in which the driving device 423e is provided in the jig <NUM> and the jig <NUM> dynamically rotates the medium <NUM> in synchronization with action of the intermediate transfer belt <NUM> of the transfer unit <NUM> while using the fastening parts 423d as driving wheels has been described. However, it is also possible to employ a configuration in which the jig <NUM> merely rotatably supports the medium <NUM> and the medium <NUM> rotates in accordance with action of the intermediate transfer belt <NUM> while the fastening parts 423d are used as driven wheels. For example, in a case where the medium <NUM> is made of a material having a high coefficient of friction with the intermediate transfer belt <NUM>, the medium <NUM> is rotated without the need for driving by the fastening part 423d by being pulled by the intermediate transfer belt <NUM> at the contact position.

Since the jig <NUM> illustrated in <FIG> rotates while fastening the central axis of the circumferential surface of the medium <NUM>, media <NUM> having various shapes having a circumferential surface can be held by fastening the central axis of the circumferential surface. Furthermore, the jig <NUM> illustrated in <FIG> can hold the medium <NUM> so that an image is transferred onto a circumferential surface of the medium <NUM> even in a case where the circumferential surface of the medium <NUM> has an uneven portion.

<FIG> illustrate an example of the medium <NUM> having a circumferential surface. <FIG> illustrates a medium <NUM> having a spherical shape, and <FIG> illustrates a medium <NUM> having a truncated cone shape. <FIG> illustrate the medium <NUM> viewed in a direction perpendicular to the rotary axis of the medium <NUM> from a front side in the transport direction in which the medium <NUM> is transported.

In a case where the medium <NUM> has a spherical shape, the circumferential surface is bulged not only in a circumferential direction, but also in a direction parallel with the central axis. Accordingly, an image is transferred onto a thin region where the medium <NUM> and the intermediate transfer belt <NUM> make contact with each other due to warpage of the intermediate transfer belt <NUM>, as illustrated in <FIG>. However, an image of this width can be transferred over an entire circumference of the spherical medium <NUM>. In <FIG>, a band-shaped image T is formed on a portion of the surface of the medium <NUM> that makes contact with the intermediate transfer belt <NUM>.

In a case where the medium <NUM> has a truncated cone shape, the circumferential surface is inclined with respect to the central axis. In this case, as illustrated in <FIG>, the jig <NUM> holds the medium <NUM> by inclining the central axis in accordance with the inclination of the circumferential surface so that the circumferential surface of the medium <NUM> corresponds to a surface of the intermediate transfer belt <NUM> of the transfer unit <NUM>. In <FIG>, an image T that is inclined with respect to the central axis of the circumferential surface is formed corresponding to the circumferential surface of the medium <NUM>.

In the example illustrated in <FIG>, image transfer in a case where the circumferential surface of the medium <NUM> has curvature also in a direction parallel with the central axis (<FIG>) and a case where the circumferential surface of the medium <NUM> is inclined with respect to the central axis (<FIG>) has been described. As described above, in a case where the jig <NUM> illustrated in <FIG> is used, an image can be transferred onto media <NUM> having various circumferential surfaces. Furthermore, an image can be formed even on a medium <NUM> having a protruding portion on a circumferential surface thereof such as a glass with a handle by rotating the medium <NUM> within such a range that the protruding portion does not make contact with the intermediate transfer belt <NUM> and the jig <NUM> although the image can be transferred only onto a part of the circumferential surface.

In a case where an image is transferred onto a circumferential surface of the medium <NUM> in the transfer unit <NUM>, the medium <NUM> itself needs to stop at the transfer position while the image is being transferred although the medium <NUM> is rotated in synchronization with movement of the intermediate transfer belt <NUM> of the transfer unit <NUM>, as described above. One example of a method for stopping movement of the medium <NUM> during transfer of an image is that the transport mechanism <NUM> stops transport of the attachment table <NUM> on which the medium <NUM> is placed when the medium <NUM> moves to the transfer position. Another example of the method is that the position of the medium <NUM> relative to the transfer position of the transfer unit <NUM> is stopped by moving the jig <NUM> relative to the table part <NUM> of the attachment table <NUM> in a direction opposite to the direction in which the attachment table <NUM> is transported.

In the configuration described with reference to <FIG>, the jig <NUM> is fixed to the attachment table <NUM> with the use of the fastener provided on the table part <NUM>. On the other hand, in a case where the jig <NUM> is moved relative to the table part <NUM>, the table part <NUM> is provided with a movement path, and the jig <NUM> has a unit for movement that moves along the movement path. The movement path of the table part <NUM> and the unit for movement of the jig <NUM> are not limited to a specific configuration, provided that the jig <NUM> can move along a predetermined movement path. One example is a configuration in which the table part <NUM> is provided with a groove or a rail as the movement path and the jig <NUM> has, as the unit for movement, a wheel for travelling in the groove or on the rail. More specifically, a rack and pinion in which a rack is used as a rail of the movement path and a pinion gear is used as a wheel of the jig <NUM> may be used, and the jig <NUM> may be moved by controlling rotation of the pinion gear of the jig <NUM>. The jig <NUM> may be provided with a driving unit such as a motor, and the jig <NUM> may travel on its own on the movement path of the table part <NUM>. Alternatively, the movement path of the table part <NUM> may be provided with a unit for pulling the jig <NUM>.

The movement path is provided parallel with the transport direction in which the attachment table <NUM> is transported. The jig <NUM> is movable only in a direction along the movement path, and movement thereof in a width direction of the movement path is restricted. Furthermore, in a case where the jig <NUM> is moved relative to the table part <NUM>, the movement path needs to be long enough for the jig <NUM> to move while an image is being transferred onto the medium <NUM>. This leads to an increase in size of the table part <NUM> relative to the jig <NUM> as compared with a configuration in which the jig <NUM> is fixed to the table part <NUM> such as the configuration described with reference to <FIG>.

<FIG> illustrate movement of the jig <NUM>. <FIG> illustrates a state at the start of transfer, <FIG> illustrates a state during the transfer, and <FIG> illustrates a state at the end of the transfer. In a case where an image is transferred by the transfer unit <NUM>, when the medium <NUM> reaches the transfer position as a result of transport of the attachment table <NUM>, the jig <NUM> starts moving on the table part <NUM> in a direction opposite to the transport direction in which the attachment table <NUM> is transported, as illustrated in <FIG>. The jig <NUM> moves on the table part <NUM> and keeps the medium <NUM> at the transfer position as illustrated in <FIG> as the image is transferred onto the medium <NUM>. After the transfer of the image onto the medium <NUM> ends, the movement of the jig <NUM> ends, and the medium <NUM> is transported toward the fixing unit <NUM> together with the attachment table <NUM>, as illustrated in <FIG>.

The unit for movement of the jig <NUM> is controlled in terms of timings of start and end of movement of the jig <NUM> and a movement speed. Specifically, the unit for movement of the jig <NUM> is controlled so as to start movement of the jig <NUM> at a timing at which the medium <NUM> reaches the transfer position as a result of transport of the attachment table <NUM>, move the jig <NUM> at a same speed as a transport speed of the attachment table <NUM> in a direction opposite to the transport direction in which the attachment table <NUM> is transported, and stop movement of the jig <NUM> at a timing at which transfer of an image onto the medium <NUM> ends. A controller is, for example, realized by a processor that controls operation of the driving unit of the jig <NUM> and a memory in which a control program to be executed by the processor and control data are stored. The controller may be mounted in the jig <NUM> or operation of the jig <NUM> may be controlled by an external control device. In the latter case, it is necessary to provide a signal path, for example, by connecting a signal cable to the jig <NUM> in order to transmit a control signal to the driving unit of the jig <NUM> during transport of the attachment table <NUM>. The positions of the medium <NUM> and the jig <NUM> may be, for example, specified on the basis of a detection signal of a sensor provided in a housing of the image forming apparatus <NUM> or may be, for example, calculated on the basis of the position of the attachment table <NUM> on the transport rail <NUM>. The position of the attachment table <NUM> on the transport rail <NUM> can be specified from information used for transport control in the transport mechanism <NUM>. Furthermore, a length of the movement path of the table part <NUM> may be set to such a length that after start of movement of the jig <NUM>, the jig <NUM> reaches an end on a side where the movement ends at a timing of end of transfer of an image onto the medium <NUM>.

Although the exemplary embodiment of the present disclosure has been described, the technical scope of the present disclosure is not limited to the above exemplary embodiment. For example, the mechanism for moving the medium <NUM> and the mechanism for moving the jig <NUM> relative to the table part <NUM> are not limited to those described in the above exemplary embodiment and can have various configurations according to kind and shape of the medium <NUM>. Various changes and substitution of the configurations are encompassed within the present disclosure without departing from the scope of the appended claims.

Claim 1:
An image forming apparatus (<NUM>) comprising:
a transfer unit (<NUM>) configured to transfer an image onto an object (<NUM>) by making contact with the object (<NUM>);
a holding unit (<NUM>) configured to hold the object (<NUM>) having a circumferential surface so that the circumferential surface rotates along a transfer direction of the transfer unit (<NUM>);
a fixing unit (<NUM>) configured to fix on the circumferential surface of the object (<NUM>), the image transferred by the transfer unit (<NUM>) by heating the object (<NUM>); and
a transport unit (<NUM>) configured to transport the holding unit (<NUM>) holding the object (<NUM>) along a transport path,
wherein the holding unit (<NUM>) includes a jig (<NUM>) configured to support the object (<NUM>) placed thereon,
the image forming apparatus (<NUM>) being characterized in that:
the transfer unit (<NUM>) is configured to transfer the image onto the circumferential surface of the object (<NUM>) in a circumferential direction as the object (<NUM>) rotates about a central axis of the circumferential surface of the object (<NUM>), by making contact with the circumferential surface of the object (<NUM>) maintained at a transfer position, and that the jig (<NUM>) holds the object (<NUM>) so that the central axis of the circumferential surface of the object (<NUM>) is orthogonal to the transfer direction of the transfer unit (<NUM>) at the transfer position.