Patent Description:
<CIT> discloses a printer that forms an image on an image formation surface of a disc transported by a transport device. In this printer, a toner image given to a transfer belt is electrically transferred onto the image formation surface of the disc by bringing an electrode of a transfer device into contact with the image formation surface and supplying an electric charge. <CIT> discloses a a method and a system for printing predefined prints on a metal plate. The prints are received as instructions by the system and, based on the instruction, a print transfer unit is electrically charged in specific areas corresponding to the instructions. Further, the metal plate is electrically biased, and by using positive and negative bias it is possible to electrostatically transfer powder via the print transfer unit to the metal plate in a pattern similar to the predefined print. The metal plate is placed on a printing table being adjustable to ensure a contact between the print transfer unit and the metal plate. Further, the printing table comprises means for generating a vacuum between the surface of the printing table and the metal plate to ensure that the metal plate lies plane on the printing table. <CIT> discloses an image forming apparatus in which the transport table may be entirely made of a conductive material to be an electrode.

Some image forming apparatuses bring a transfer unit into contact with an image formation surface of a recording medium transported by a transport unit and transfer a toner image onto the image formation surface by a transfer electric field applied between the image formation surface and the transfer unit. In such image forming apparatuses, in a case where a member such as an electrode or a grounding member is brought into contact with the image formation surface in order to form the transfer electric field, it is difficult to transfer an image onto a portion where this member makes contact.

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 forming a transfer electric field between a transfer unit and an image formation surface of a recording medium without bringing a member into contact with the image formation surface.

According to a first aspect of the present disclosure, there is provided an image forming apparatus including, among other features, a transport unit that transports a recording medium whose image formation surface has electric conductivity; a transfer unit that makes contact with the image formation surface of the recording medium transported by the transport unit and transfers an image formed with particles onto the image formation surface by an electric field formed between the transfer unit and the image formation surface; and a support unit that has electric conductivity, supports the recording medium so as to be conductive with the image formation surface of the recording medium, and is transported to the transfer unit together with the recording medium by the transport unit.

According to a second aspect of the present disclosure, the image forming apparatus according to the first aspect is configured such that the support unit becomes conductive with the image formation surface by making contact with the recording medium.

According to a third aspect of the present disclosure, the image forming apparatus according to the first or second aspect is configured such that the support unit becomes conductive with the image formation surface by making contact with a peripheral edge of the recording medium surrounding a periphery of the image formation surface.

According to a fourth aspect of the present disclosure, the image forming apparatus according to any one of the first to third aspects is configured such that the support unit becomes conductive with the image formation surface through a front end or a rear end of the recording medium in a transport direction in which the recording medium is transported by the transport unit by making contact with the front end or the rear end of the recording medium.

According to a fifth aspect of the present disclosure, the image forming apparatus according to the first or second aspect is configured such that the support unit becomes conductive with the image formation surface by making contact with a portion of the recording medium other than a peripheral edge surrounding a periphery of the image formation surface.

According to a sixth aspect of the present disclosure, the image forming apparatus according to any one of the first to fifth aspects is configured such that the image formation surface of the recording medium is connected to ground with the support unit interposed therebetween.

According to a seventh aspect of the present disclosure, the image forming apparatus according to any one of the first to sixth aspects is configured such that the transport unit includes a table part to which the support unit is attached and moves along a transport path; and the support unit is conductive with the table part of the transport unit.

According to an eighth aspect of the present disclosure, the image forming apparatus according to the seventh aspect is configured such that the support unit is connected to ground with the table part of the transport unit interposed therebetween.

According to the first aspect of the present disclosure, a transfer electric field can be formed between the transfer unit and the image formation surface without bringing a member into contact with the image formation surface of the recording medium.

According to the second aspect of the present disclosure, the support unit and the image formation surface can be made conductive with each other with more certainty than in a case where the support unit does not make contact with the image formation surface.

According to the third aspect of the present disclosure, a conduction path between the support unit and the image formation surface can be shortened as compared with a case where the support unit makes contact with a portion of the recording medium other than the peripheral edge surrounding the periphery of the image formation surface.

According to the fourth aspect of the present disclosure, conduction between the support unit and the image formation surface of the recording medium is less likely to be cut off when the recording medium makes contact with the transfer unit than in a case where the support unit is not conductive through the front end or the rear end of the recording medium.

According to the fifth aspect of the present disclosure, contact of the transfer unit with the image formation surface is less hindered by the support unit than in a case where the support unit makes contact with the peripheral edge surrounding the periphery of the image formation surface.

According to the sixth aspect of the present disclosure, a configuration of the support unit can be simplified as compared with a case where a voltage is applied to the support unit without connecting the image formation surface to ground with the support unit interposed therebetween.

According to the seventh aspect of the present disclosure, the configuration of the support unit can be simplified as compared with a case where the support unit is not conductive with the table part.

According to the eighth aspect of the present disclosure, the configuration of the support unit can be simplified as compared with a case where the support unit is not connected to ground with the table part interposed therebetween.

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 recording medium <NUM> (hereinafter simply referred to as 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>.

<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>. Furthermore, the transfer unit <NUM> includes a power source <NUM> that applies a predetermined voltage to the backup roll <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 alphabets (color signs) 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 alphabets 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> by the power source <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 <NUM>, 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 bring the intermediate transfer belt <NUM> into contact with the medium <NUM> in a predetermined relation 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 adjuster 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, a jig <NUM> that holds the medium <NUM> on the table part <NUM> is attached to the table part <NUM>.

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>. Then, 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.

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 table part <NUM> according to the present exemplary embodiment is made of an electrically conductive material. Furthermore, the table part <NUM> is in contact with a grounding member (not illustrated) and is connected to ground with the grounding member interposed therebetween.

The jig <NUM> is an example of a support unit and is a device that holds 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 jig <NUM> according to the present exemplary embodiment is made of an electrically conductive material. Furthermore, the portion of the jig <NUM> attached to the table part <NUM> is conductive with the table part <NUM>. Furthermore, the jig <NUM> supports the medium <NUM> so as to be conductive with a surface (an image formation surface, which will be described later) of the medium <NUM> including a region where an image is to be formed. In this way, the image formation surface of the medium <NUM> supported by the jig <NUM> is connected to ground with the jig <NUM> and the table part <NUM> interposed therebetween.

Note that a relationship between the jig <NUM> and the medium <NUM> will be described in detail later.

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.

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 fixing unit <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. Configuration of Medium Attaching Detaching Unit <NUM>.

See <FIG> again. As described above, the medium attaching detaching unit <NUM> is a unit that is located at the transport start position and the transport end position, which are an end portion of the transport rail <NUM>. In the medium attaching detaching unit <NUM>, the jig <NUM> is attached and detached to and from the attachment table <NUM> or the medium <NUM> is attached and detached to and from the jig <NUM> attached to the attachment table <NUM>.

Furthermore, the medium attaching detaching unit <NUM> according to the present exemplary embodiment includes a cleaning device <NUM> for removing particles attached to an upper surface <NUM> (see <FIG>, which will be described later) of the jig <NUM>. The cleaning device <NUM> has, for example, a brush, a web, or the like that makes contact with the upper surface <NUM> of the jig <NUM>.

After an image is fixed on the medium <NUM> in the fixing unit <NUM>, the attachment table <NUM> on which the jig <NUM> holding the medium <NUM> is placed moves to the transport end position of the medium attaching detaching unit <NUM>. At the transport end position of the medium attaching detaching unit <NUM>, the medium <NUM> is removed from the jig <NUM> attached to the attachment table <NUM>. Then, the particles attached to the upper surface <NUM> of the jig <NUM> are removed by the cleaning device <NUM>.

Then, a new medium <NUM> is placed on the jig <NUM>, and image formation operation on this new medium <NUM> is performed.

As described above, in the image forming apparatus <NUM> according to the present exemplary embodiment, an image formed with particles is transferred from the transfer surface of the intermediate transfer belt <NUM> onto the medium <NUM> by bringing the transfer surface of the intermediate transfer belt <NUM> into contact with the medium <NUM> held by the jig <NUM>. During this process, the transfer surface of the intermediate transfer belt <NUM> and the upper surface <NUM> of the jig <NUM> sometimes make contact with each other, and particles are sometimes attached from the intermediate transfer belt <NUM> to the upper surface <NUM> of the jig <NUM>. In a case where particles are attached to the upper surface <NUM> of the jig <NUM>, the particles are sometimes attached to a new medium <NUM> and smear the new medium <NUM> when the new medium <NUM> is placed on the jig <NUM> after image formation operation on the medium <NUM> is finished.

In the present exemplary embodiment, the particles attached to the jig <NUM> are removed by the cleaning device <NUM>, and therefore it is less likely that the particles are attached to and smear the medium <NUM> placed on the jig <NUM>. Conduction of Medium <NUM>
As described above, at least the region of the medium <NUM> where an image is to be formed has electric conductivity. In the following description, a surface of the medium <NUM> including the region where an image is to be formed is referred to as an image formation surface of the medium <NUM>. It is desirable to connect the image formation surface of the medium <NUM> to ground in order to allow an electric current to flow from the backup roll <NUM> to the image formation surface of the medium <NUM> while passing through the intermediate transfer belt <NUM> when a voltage is applied to the backup roll <NUM> by the power source <NUM>. In the present exemplary embodiment, the jig <NUM> of the transport mechanism <NUM> and the image formation surface of the medium <NUM> are conductive with each other. The image formation surface of the medium <NUM> is connected to ground with the jig <NUM> and the table part <NUM> conductive with the jig <NUM> interposed therebetween.

The following describes in detail conduction of the medium <NUM>, mainly a relationship between the jig <NUM> of the transport mechanism <NUM> and the medium <NUM>.

<FIG> and <FIG> are views for explaining a relationship between the jig <NUM> and the medium <NUM>. <FIG> is a perspective view of the jig <NUM> and the medium <NUM>, <FIG> is a view of the transport mechanism <NUM> and the medium <NUM> viewed from an upper side (intermediate transfer belt <NUM> side), and <FIG> is a cross-sectional view of the transport mechanism <NUM> and the medium <NUM> taken along line VIB-VIB illustrated in <FIG>. In <FIG>, description of the table part <NUM> of the transport mechanism <NUM> is omitted.

The medium <NUM> according to the present exemplary embodiment has a front surface <NUM> and a rear surface <NUM> that are rectangular, a pair of first side surfaces <NUM> that connect the front surface <NUM> and the rear surface <NUM> and face each other, and a pair of second side surfaces <NUM> that connect the front surface <NUM> and the rear surface <NUM> and face each other, and has a rectangular parallelepiped shape as a whole. In this example, the front surface <NUM> of the medium <NUM> is the image formation surface including the region where an image is to be formed.

Furthermore, the medium <NUM> according to the present exemplary embodiment has a medium body <NUM> made of a non-conductive material and an electrically conductive layer <NUM> that is made of an electrically conductive material and is laminated on the medium body <NUM>. In this example, the front surface <NUM> of the medium <NUM> is constituted by the electrically conductive layer <NUM>. Furthermore, each of the first side surfaces <NUM> of the medium <NUM> includes a non-electrically-conductive part <NUM> constituted by the medium body <NUM> and an electrically conductive part <NUM> constituted by the electrically conductive layer <NUM>. Similarly, each of the second side surfaces <NUM> of the medium <NUM> includes a non-electrically-conductive part <NUM> constituted by the medium body <NUM> and an electrically conductive part <NUM> constituted by the electrically conductive layer <NUM>.

In this example, the electrically conductive parts <NUM> of the first side surfaces <NUM> and the electrically conductive parts <NUM> of the second side surfaces <NUM> are a peripheral edge surrounding a periphery of the front surface <NUM>, which is the image formation surface.

As described above, the jig <NUM> holds the medium <NUM> and is attached to the table part <NUM>.

The jig <NUM> according to the present exemplary embodiment has the rectangular upper surface <NUM> that faces the intermediate transfer belt <NUM> when transported to the transfer position and a rectangular lower surface <NUM> opposite to the upper surface <NUM>, and has a rectangular parallelepiped shape as a whole. The jig <NUM> is attached to the table part <NUM> so that the lower surface <NUM> faces the table part <NUM>, and the jig <NUM> is conductive with the table part <NUM> through the lower surface <NUM>.

Furthermore, the jig <NUM> has, in a central part thereof in the transport direction of the transport mechanism <NUM>, a recessed part <NUM> that is recessed from the upper surface <NUM> toward the lower surface <NUM>. The medium <NUM> is inserted into a space formed inside the recessed part <NUM> of the jig <NUM>, and thus the medium <NUM> is supported in the recessed part <NUM>. In this example, the medium <NUM> is inserted into the recessed part <NUM> of the jig <NUM> so that the pair of first side surfaces <NUM> extend along the transport direction in which the medium <NUM> is transported by the transport mechanism <NUM> and the pair of second side surfaces <NUM> extend along a width direction of the medium <NUM> orthogonal to the transport direction.

The recessed part <NUM> of the jig <NUM> has an inner peripheral surface that matches the shape of the medium <NUM>. Specifically, the recessed part <NUM> has a pair of first inner peripheral surfaces <NUM> that extend along the transport direction of the transport mechanism <NUM> and face each other with the space in the recessed part <NUM> interposed therebetween and a pair of second inner peripheral surfaces <NUM> that extend along the width direction orthogonal to the transport direction of the transport mechanism <NUM> and face each other with the space in the recessed part <NUM> interposed therebetween. Furthermore, the recessed part <NUM> has a bottom surface <NUM> extending from lower ends of the first inner peripheral surfaces <NUM> and the second inner peripheral surfaces <NUM> along the transport direction and the width direction.

In the recessed part <NUM>, a length of each of the first inner peripheral surfaces <NUM> along the transport direction, in other words, an interval between the second inner peripheral surfaces <NUM> that face each other is equal to a length of the medium <NUM> in the transport direction. Furthermore, in the recessed part <NUM>, a length of each of the second inner peripheral surfaces <NUM> along the width direction, in other words, an interval between the first inner peripheral surfaces <NUM> that face each other is equal to a length of the medium 500along the width direction.

When the medium <NUM> is inserted into the recessed part <NUM> of the jig <NUM>, the jig <NUM> and the electrically conductive layer <NUM> of the medium <NUM> make contact with each other, and thereby the jig <NUM> and the electrically conductive layer <NUM> of the medium <NUM> become conductive with each other.

Specifically, the first inner peripheral surfaces <NUM> of the recessed part <NUM> of the jig <NUM> and the first side surfaces <NUM> of the medium <NUM> make contact with each other. In this way, the jig <NUM> and the electrically conductive parts <NUM> of the first side surfaces <NUM> of the medium <NUM> become conductive with each other.

Furthermore, the second inner peripheral surfaces <NUM> of the recessed part <NUM> of the jig <NUM> and the second side surfaces <NUM> of the medium <NUM> make contact with each other. In this way, the jig <NUM> and the electrically conductive parts <NUM> of the second side surfaces <NUM> of the medium <NUM> become conductive with each other.

Since the jig <NUM> and the electrically conductive layer <NUM> of the medium <NUM> become conductive with each other, the jig <NUM> and the front surface <NUM> of the medium <NUM>, which is the image formation surface, become conductive with each other. As a result, the front surface <NUM> of the medium <NUM>, which is the image formation surface, is connected to ground with the jig <NUM> and the table part <NUM> conductive with the jig <NUM> interposed therebetween.

When the medium <NUM> is transported to the transfer position by the transport mechanism <NUM> and a voltage is applied to the backup roll <NUM> by the power source <NUM> (see <FIG>), an electric current flows from the intermediate transfer belt <NUM> to the jig <NUM> and the table part <NUM> by passing through the front surface <NUM> of the medium <NUM>, which is the image formation surface, as illustrated in <FIG>. This forms a transfer electric field between the backup roll <NUM> and the front surface <NUM> of the medium <NUM>, thereby transferring an image from the intermediate transfer belt <NUM> onto the medium <NUM>.

As described above, in the image forming apparatus <NUM> according to the present exemplary embodiment, the jig <NUM> supports the medium <NUM> so as to be conductive with the front surface <NUM> of the medium <NUM>, which is the image formation surface. This allows the front surface <NUM> of the medium <NUM> to be connected to ground without bringing another member into contact with the front surface <NUM>, thereby forming a transfer electric field between the backup roll <NUM> and the front surface <NUM> of the medium <NUM>.

Furthermore, since it is unnecessary to bring another member into contact with the front surface <NUM> of the medium <NUM>, a region where an image is formed on the front surface <NUM> may be increased as compared with a case where another member is brought into contact with the front surface <NUM>. In addition, since it is unnecessary to bring another member into contact with the front surface <NUM> of the medium <NUM>, an image may be transferred over the whole front surface <NUM> of the medium <NUM>. It is therefore easier to form an image without a frame (frameless image) on the front surface of the medium <NUM>.

Furthermore, as described above, the jig <NUM> according to the present exemplary embodiment becomes conductive with the image formation surface of the medium <NUM> by making contact with the medium <NUM>. More specifically, the jig <NUM> becomes conductive with the front surface <NUM> of the medium <NUM>, which is the image formation surface, by making contact with the electrically conductive parts <NUM> of the first side surfaces <NUM> and the electrically conductive parts <NUM> of the second side surfaces <NUM> of the medium <NUM>.

This allows the jig <NUM> and the front surface <NUM> of the medium <NUM> to be conductive with each other with more certainty as compared with a case where the jig <NUM> does not make contact with the medium <NUM>.

Furthermore, the jig <NUM> according to the present exemplary embodiment becomes conductive with the image formation surface of the medium <NUM> by making contact with the peripheral edge surrounding the periphery of the image formation surface of the medium <NUM>. More specifically, the jig <NUM> becomes conductive with the front surface <NUM> of the medium <NUM>, which is the image formation surface, by making contact with the electrically conductive parts <NUM> of the first side surfaces <NUM> and the electrically conductive parts <NUM> of the second side surfaces <NUM> that surround the periphery of the front surface <NUM> of the medium <NUM>, which is the image formation surface.

This allows a conduction path for making the jig <NUM> and the front surface <NUM> of the medium <NUM> conductive with each other to be shortened as compared with a case where the jig <NUM> becomes conductive with the front surface <NUM> by making contact with a portion of the medium <NUM> other than the peripheral edge surrounding the periphery of the front surface <NUM>.

In the present exemplary embodiment, the jig <NUM> need not necessarily make contact with the electrically conductive parts <NUM> of the first side surfaces <NUM> or the electrically conductive parts <NUM> of the second side surfaces <NUM> of the medium <NUM> as long as the jig <NUM> and the front surface <NUM> of the medium <NUM> are conductive with each other. In other words, a gap may be present between the jig <NUM> and the electrically conductive parts <NUM> of the first side surfaces <NUM> or the electrically conductive parts <NUM> of the second side surfaces <NUM> of the medium <NUM> as long as an electric current flows from the backup roll <NUM> to the image formation surface of the medium <NUM> by passing through the intermediate transfer belt <NUM> when a voltage is applied to the backup roll <NUM> by the power source <NUM>.

However, from a viewpoint of making the jig <NUM> and the front surface <NUM> of the medium <NUM> conductive with more certainty, it is desirable that the jig <NUM> make contact with the electrically conductive parts <NUM> of the first side surfaces <NUM> or the electrically conductive parts <NUM> of the second side surfaces <NUM> of the medium <NUM>, as described above.

Furthermore, in a case where the jig <NUM> makes contact with the medium <NUM>, it is desirable that the jig <NUM> become conductive with the front surface <NUM> of the medium <NUM> by making contact with at least a front end or a rear end of the medium <NUM> in the transport direction. In this example, it is desirable that the jig <NUM> make contact with the electrically conductive part <NUM> of the second side surface <NUM>, which is the front end or the rear end of the medium <NUM> in the transport direction.

In a case where the jig <NUM> becomes conductive with the front surface <NUM> of the medium <NUM> by making contact with the front end or the rear end of the medium <NUM>, the conduction between the jig <NUM> and the medium <NUM> is less likely to be cut off even in a case where the medium <NUM> is pushed in the transport direction by a shock caused when the medium <NUM> is transported to the transfer position and makes contact with the intermediate transfer belt <NUM>.

Furthermore, the jig <NUM> according to the present exemplary embodiment is conductive with the table part <NUM> that is connected to ground. If the jig <NUM> is not conductive with the table part <NUM>, the jig <NUM> that varies depending on the shape and size of the medium <NUM> needs to be connected to ground in order to connect the front surface <NUM> of the medium <NUM> held by the jig <NUM> to ground. In this case, it is likely that the configuration of the jig <NUM> becomes complicated.

On the other hand, in a case where the jig <NUM> is conductive with the table part <NUM> and the front surface <NUM> of the medium <NUM> is connected to ground with the table part <NUM> interposed therebetween as in the present exemplary embodiment, the configuration of the jig <NUM> may be simplified.

Next, a modification of the present exemplary embodiment is described. In the above example, a case where the medium <NUM> in which the electrically conductive layer <NUM> made of an electrically conductive material is laminated on the medium body <NUM> that is not a conductor is used has been described. The following describes a case where a medium <NUM> that is entirely made of a conductor such as a metal is used.

<FIG> are views for explaining the modification of the present exemplary embodiment. <FIG> is a diagram illustrating an example of a configuration of the medium <NUM> that is entirely made of a conductor, and <FIG> illustrates an example of a cross section of the transport mechanism <NUM> in which the medium <NUM> has been attached to the jig <NUM>. Note that <FIG> illustrates a cross section of the transport mechanism <NUM> and the medium <NUM> taken along the transport direction of the transport mechanism <NUM> at a central part of the medium <NUM> in the width direction. In <FIG>, similar constituent elements to those illustrated in <FIG> are given identical reference signs, and detailed description thereof is omitted.

As described above, the medium <NUM> according to the modification is entirely made of a conductor. This medium <NUM> includes a flat plate part <NUM> having a flat plate shape and having a front surface <NUM> and a rear surface <NUM> that are rectangular and a base part <NUM> having a rectangular parallelepiped shape and protruding from a central part of the rear surface <NUM> of the flat plate part <NUM>. The flat plate part <NUM> and the base part <NUM> of the medium <NUM> are made of a conductor, and therefore the entire medium <NUM> has electric conductivity. In this example, the front surface <NUM> of the flat plate part <NUM> of the medium <NUM> is an image formation surface including a region where an image is to be formed.

As in the above example, a jig <NUM> according to the modification holds the medium <NUM> and is attached to the table part <NUM>. The jig <NUM> has a recessed part <NUM>. The base part <NUM> of the medium <NUM> is inserted into a space formed inside the recessed part <NUM> of the jig <NUM>, and the medium <NUM> is supported in the recessed part <NUM>.

In this example, an inner peripheral surface <NUM> of the recessed part <NUM> has a shape that matches an outer peripheral surface <NUM> of the base part <NUM> of the medium <NUM>.

With this configuration, when the base part <NUM> of the medium <NUM> is inserted into the recessed part <NUM> of the jig <NUM>, the inner peripheral surface <NUM> of the recessed part <NUM> of the jig <NUM> and the outer peripheral surface <NUM> of the base part <NUM> of the medium <NUM> make contact with each other, and thereby the jig <NUM> and the base part <NUM> of the medium <NUM> become conductive with each other.

Since both of the base part <NUM> and the flat plate part <NUM> of the medium <NUM> have electric conductivity, the jig <NUM> and the front surface <NUM> of the flat plate part <NUM>, which is the image formation surface, become conductive with each other when the jig <NUM> and the base part of the medium <NUM> become conductive with each other. As a result, the front surface <NUM> of the flat plate part <NUM>, which is the image formation surface, is connected to ground with the jig <NUM> and the table part <NUM> conductive with the jig <NUM> interposed therebetween.

When the medium <NUM> is transported to the transfer position by the transport mechanism <NUM> and a voltage is applied to the backup roll <NUM> (see <FIG>) by the power source <NUM> (see <FIG>), an electric current flows from the intermediate transfer belt <NUM> (see <FIG>) to the jig <NUM> and the table part <NUM> by passing through the front surface <NUM> of the flat plate part <NUM>, which is the image formation surface. This forms a transfer electric field between the backup roll <NUM> and the front surface <NUM> of the medium <NUM>, thereby transferring an image from the intermediate transfer belt <NUM> onto the medium <NUM>.

As described above, in a case where the entire medium <NUM> has electric conductivity, the jig <NUM> may become conductive with the image formation surface of the medium <NUM> by making contact with a portion of the medium <NUM> other than a peripheral part surrounding a periphery of the image formation surface. In a case where the jig <NUM> becomes conductive with the image formation surface by making contact with the portion other than the peripheral edge of the image formation surface, transfer of an image onto the image formation surface by the intermediate transfer belt <NUM> is less likely to be hindered by the jig <NUM> as compared with a case where the jig <NUM> makes contact with the peripheral edge of the image formation surface of the jig <NUM>.

Note that as in the above example, in a case where the entire medium <NUM> has electric conductivity, the jig <NUM> need not necessarily make contact with the medium <NUM> as long as the jig <NUM> is conductive with any portion of the medium <NUM>. In other words, a gap may be present between the medium <NUM> and the jig <NUM> as long as an electric current flows from the backup roll <NUM> to the image formation surface of the medium <NUM> by passing through the intermediate transfer belt <NUM> when a voltage is applied to the backup roll <NUM> by the power source <NUM>.

The exemplary embodiment of the present disclosure has been described above, but the technical scope of the present disclosure is not limited to the above exemplary embodiment.

For example, although the image forming apparatus <NUM> is configured such that a transfer electric field is formed between the backup roll <NUM> and the image formation surface of the medium <NUM> by connecting the image formation surface of the medium <NUM> to ground with the jig <NUM> interposed therebetween and applying a predetermined voltage to the backup roll <NUM> by the power source <NUM> in the above exemplary embodiment, this is not restrictive. For example, the image forming apparatus <NUM> may form a transfer electric field between the backup roll <NUM> and the image formation surface of the medium <NUM> by connecting the backup roll <NUM> to ground and applying a voltage to the jig <NUM> or the table part <NUM>.

Claim 1:
An image forming apparatus (<NUM>) comprising:
a transport unit (<NUM>) configured to transport a recording medium (<NUM>) whose image formation surface has electric conductivity;
a transfer unit (<NUM>) configured to make contact with the image formation surface of the recording medium (<NUM>) transported by the transport unit (<NUM>) and to transfer an image formed with particles onto the image formation surface by an electric field formed between the transfer unit (<NUM>) and the image formation surface; and
a support unit (<NUM>) that has electric conductivity, configured to support the recording medium (<NUM>) so as to be conductive with the image formation surface of the recording medium (<NUM>), and to be transported to the transfer unit (<NUM>) together with the recording medium (<NUM>) by the transport unit (<NUM>), wherein
the image formation surface of the recording medium (<NUM>) is connected to ground with the support unit (<NUM>) interposed therebetween;
the transport unit (<NUM>) includes a table part (<NUM>) which is connected to ground and to which the support unit (<NUM>) is attached and which moves along a transport path;
and
the support unit (<NUM>) is conductive with the table part (<NUM>) of the transport unit (<NUM>).