Patent Description:
An inkjet image forming apparatus as a liquid discharge apparatus discharges ink onto a sheet such as paper to form an image.

In an inkjet image forming apparatus, if the position of a sheet conveyed by a conveyance roller or the like deviates from an intended position, the position of ink landing on the sheet also deviates, which degrades image quality. In order to inhibit the positional deviation of the ink with respect to the sheet, there are image forming apparatuses that include a position detector such as an optical sensor that detects the position (positional deviation) of the sheet. For example, <CIT> discloses such a configuration.

The position detector described above needs to be accurately attached to a predetermined position so as to accurately detect the position of the sheet. In general, in order to improve the mounting accuracy of the position detector, there are methods such as improving the dimensional accuracy of components related to the mounting and adjusting the position after the position detector is mounted. However, higher accuracy of component dimensions increases the cost, and adjusting the position after mounting increases the mounting work time, which are not desirable. Therefore, there is a demand for a measure for easily and accurately mounting the position detector.

<CIT>, <CIT>, <CIT>, <CIT>, and <CIT> disclose background art to the invention.

In one aspect, a conveyor includes a conveyance roller to convey a conveyed object, a pair of roller supports opposing to each other and supporting both ends of the conveyance roller in an axial direction of the conveyance roller, a position sensor to detect a position of the conveyed object, and a sensor support supporting the position sensor. Each of the pair of roller supports has an insertion hole into which the sensor support is inserted. The insertion hole determines a position of the sensor support in a direction intersecting an insertion direction of the sensor support. The sensor support includes a positioning portion determining the position of the sensor support with respect to at least one of the pair of roller supports. The positioning portion determines the position of the sensor support in the insertion direction, a direction opposite to the insertion direction, and a rotational direction about an axis along the insertion direction.

In another aspect, a liquid discharge apparatus includes the conveyor described above; and a liquid discharge head to discharge a liquid onto the conveyed object conveyed by the conveyor.

According to aspects of the present disclosure, the position sensor can be mounted easily and accurately.

With reference to drawings, descriptions are given below of embodiments of the present disclosure. In the drawings illustrating embodiments of the present disclosure, elements or components having identical or similar functions or shapes are given similar reference numerals as far as distinguishable, and redundant descriptions are omitted.

First, a configuration of an inkjet image forming apparatus, which is an example of a liquid discharge apparatus according to an embodiment of the present disclosure, is described with reference to <FIG> is a diagram illustrating an overall configuration of an inkjet image forming apparatus <NUM>, and <FIG> is a diagram illustrating a control system of the inkjet image forming apparatus <NUM> (hereinafter simply referred to as the "image forming apparatus <NUM>").

As illustrated in <FIG>, the image forming apparatus <NUM> according to the present embodiment includes a sheet supply device <NUM> that supplies a sheet S for image formation, a conveyor unit <NUM> that conveys the supplied sheet S, a first image forming device <NUM> that forms an image on a front side of the sheet S, a second image forming device <NUM> that forms an image on a back side of the sheet S, a front-back reverse device <NUM> that reverses the sheet S to turn upside down, a first drying device <NUM> and a second drying device <NUM> that dry the sheet S, and a sheet collection device <NUM> that collects the sheet S on which an image has been formed. The image forming apparatus <NUM> according to the present embodiment further includes a controller <NUM> (see <FIG>) that controls the sheet supply device <NUM>, the conveyor unit <NUM>, the first image forming device <NUM>, the second image forming device <NUM>, the front-back reverse device <NUM>, the first drying device <NUM>, the second drying device <NUM>, and the sheet collection device <NUM>.

The sheet supply device <NUM> includes a supply roller <NUM> on which a long sheet S is wound in a roll shape. The supply roller <NUM> is rotatable in the direction indicated by an arrow appended to the supply roller <NUM> in <FIG>, and the sheet S is fed from the supply roller <NUM> as the supply roller <NUM> rotates.

The conveyor unit <NUM> includes a plurality of conveyance devices <NUM> (see <FIG>) each having a plurality of conveyance rollers <NUM>. The sheet S is stretched over the conveyance rollers <NUM>, and the sheet S is conveyed by rotation of the conveyance rollers <NUM>. The conveyance roller may be a pipe, a shaft, or the like having a circular cross section.

The first image forming device <NUM> includes a plurality of head units 12Y, <NUM>, 12C, and <NUM> (also collectively "head units <NUM>") that discharges liquid ink onto the sheet S. Each of the head units <NUM> discharges ink onto the front side of the sheet S to form an image thereon according to, of image data generated by the controller <NUM>, image data representing the image to be formed on the front side of the sheet S. The ink is a liquid containing a colorant, a solvent, and crystalline resin particles dispersed in the solvent. Crystalline resin is a resin that melts to changes a phase thereof from a crystal phase to a liquid phase when heated above a melting point thereof.

The first drying device <NUM> includes a heating drum <NUM> that heats the sheet S to dry the ink on the sheet S. The heating drum <NUM> has a cylindrical shape and rotates while the sheet S is wound around the outer circumferential surface thereof. The heating drum <NUM> includes a heating source such as a halogen heater disposed therein. The heating drum <NUM> is disposed below a conveyance path along which the sheet S is conveyed. In other words, the heating drum <NUM> is on the back side of the sheet S. When the sheet S is conveyed from the first image forming device <NUM>, the bottom face (back side) of the sheet S contacts the outer circumferential surface of the heating drum <NUM>. The heating drum <NUM> conveys the sheet S while heating the sheet S. Accordingly, the drying of the ink on the sheet S is promoted. The rotation speed of the heating drum <NUM> at this time is controlled by the controller <NUM> to be substantially the same as the conveyance speed of the sheet supply device <NUM>, the sheet collection device <NUM>, the conveyor unit <NUM>, and the like. Such control prevents defective conveyance direction of the sheet S being conveyed, such as slipping of the sheet S on the outer circumferential surface of the heating drum <NUM> in the direction in which the sheet S is conveyed (i.e., a sheet conveyance direction).

The front-back reverse device <NUM> has a known structure to reverse the sheet S to turn the sheet S upside down. When the sheet S conveyed from the first drying device <NUM> passes through the front-back reverse device <NUM>, the sheet S is turned upside down and sent to the second image forming device <NUM>. That is, when the sheet S is conveyed with the front side facing up to the front-back reverse device <NUM>, the sheet S is reversed so that the front side faces down (the back side faces up).

The second image forming device <NUM> has a structure similar to that of the first image forming device <NUM> and includes a plurality of head units 14Y, <NUM>, 14C, and <NUM> that discharges ink. The second image forming device <NUM> forms an image on the back side of the sheet S. That is, since the sheet S is conveyed to the second image forming device <NUM> after the sheet S is reversed (turned upside down) by the front-back reverse device <NUM>, the second image forming device <NUM> discharges ink onto the back side of the sheet S to form an image thereon according to, of the image data generated by the controller <NUM>, image data representing the image to be formed on the back side of the sheet S.

Similar to the first drying device <NUM>, the second drying device <NUM> includes a heating drum <NUM> that heats the sheet S. As illustrated in <FIG>, similar to the heating drum <NUM> of the first drying device <NUM>, the heating drum <NUM> of the second drying device <NUM> is disposed below the conveyance path. Since the sheet S is reversed (turned upside down), the front side of the sheet S contacts the outer circumferential surface of the heating drum <NUM>. Even if the front side of the sheet S bears an image (ink is applied thereto), the ink has already been dried by the first drying device <NUM>. Accordingly, the image on the front side is not disturbed by the contact with the heating drum <NUM>.

The sheet collection device <NUM> includes a collection roller <NUM> that winds and collects the sheet S. The collection roller <NUM> is rotatable in the direction indicated by an arrow appended thereto in <FIG>, and the sheet S is wound in a roll shape around the collection roller <NUM> as the collection roller <NUM> rotates. The sheet collection device <NUM> may include a post-processing unit that performs post-processing such as cutting the sheet S to a predetermined length and aligning the cut sheet S.

The controller <NUM> is implemented by an information processing apparatus such as a personal computer (PC). The controller <NUM> generates image data representing images to be formed on the front side and the back side of the sheet S, and controls various operations of the sheet supply device <NUM>, the first image forming device <NUM>, the second image forming device <NUM>, the front-back reverse device <NUM>, the first drying device <NUM>, the second drying device <NUM>, and the sheet collection device <NUM>. For example, the controller <NUM> controls, in addition to the rotation speeds of the supply roller <NUM>, the collection roller <NUM>, and the conveyance rollers <NUM>, the temperatures of the heating sources that heat the heating drums <NUM> and <NUM>.

Next, with reference to <FIG>, a description is given of the configuration of the image forming devices according to the present embodiment. In the present embodiment, the first image forming device <NUM> and the second image forming device <NUM> has similar configurations. Accordingly, the configuration of the first image forming device <NUM> is described, and the description of the configuration of the second image forming device <NUM> is omitted.

As illustrated in <FIG>, in the first image forming device <NUM> according to the present embodiment, the four head units <NUM>, 12C, <NUM>, and 12Y that discharge black (K), cyan (C), magenta (M), and yellow (Y) inks, respectively, are disposed in that order from the upstream side in the direction indicated by arrow A (hereinafter "sheet conveyance direction A") in which the sheet S is conveyed. The order of the head units <NUM>, 12C, <NUM>, and 12Y of the respective colors is not limited to the illustrated order. The color of the ink to be used may be a color other than yellow, magenta, cyan, and black.

Each of the head units <NUM>, 12C, <NUM>, and 12Y includes four liquid discharge heads <NUM>. Each liquid discharge head <NUM> has a plurality of nozzles <NUM> and discharges ink (liquid) onto the sheet S from each nozzle <NUM>. The liquid discharge heads <NUM> are alternately arranged to cover an image formation area of the sheet S entirely in the width direction of the sheet S. When the sheet S is conveyed to the position facing the head units <NUM>, 12C, <NUM>, and 12Y, the liquid discharge heads <NUM> discharge ink, and an image is formed on the sheet S.

In this specification, the term "width direction" of the sheet S is a direction parallel to a conveyance plane on which the sheet is conveyed and orthogonal to the sheet conveyance direction A. The width direction is indicated by arrow B in <FIG>. Further, the term "conveyance plane" is a plane through which the conveyed sheet passes. The conveyance plane includes, for example, an imaginary plane connecting contact portions between the sheet and a plurality of conveyance rollers to convey the sheet, or a face of a conveyance belt on which the sheet is placed and conveyed. The "width direction" of the sheet may be referred to "sheet width direction" in the following description.

With reference to <FIG>, a description is given of a configuration of the conveyance device <NUM> (serving as a conveyor) of the conveyor unit <NUM> disposed in the first image forming device <NUM>.

As illustrated in <FIG>, the conveyance device <NUM> includes the plurality of conveyance rollers <NUM>. The plurality of the conveyance rollers <NUM> illustrated in <FIG> includes drive roller pairs 17A and 17B, a drive roller 17C, and a plurality of driven rollers 17d to <NUM>. The drive roller pair 17A disposed extreme upstream in the sheet conveyance direction A and the drive roller pair 17B disposed extreme downstream in the sheet conveyance direction A are two drive roller pairs that convey the sheet S while sandwiching the sheet S from the front side and the back side. In addition to the drive roller pairs 17A and 17B (drive roller pairs), the drive roller 17C (not paired with another roller) disposed adjacent to and downstream from the upstream drive roller pair 17A conveys the sheet S.

The plurality of driven rollers 17d to <NUM> is disposed between the drive roller 17C on the upstream side and the drive roller pair 17B on the downstream side. Instead of the driven rollers 17d to <NUM>, a plurality of drive rollers may be disposed. In <FIG>, the head units <NUM>, 12C, <NUM>, and 12Y discharge ink at liquid discharge positions <NUM>, 10C, <NUM>, and 10Y (also collectively "liquid discharge positions <NUM>"), respectively. The driven rollers 17d to <NUM> are disposed such that each liquid discharge position <NUM> is interposed between two of the driven rollers 17d to <NUM> in the sheet conveyance direction. With the arrangement in which the driven rollers 17d to <NUM> are respectively disposed on upstream and downstream from the liquid discharge positions <NUM>, 10C, <NUM>, and 10Y, fluttering of the sheet S particularly at the liquid discharge positions <NUM>, 10C, <NUM>, and 10Y is inhibited, and the sheet S can be stably conveyed.

When the conveyance roller <NUM> is eccentric or thermally expanded, as illustrated in <FIG>, the conveyed sheet S may be displaced in the width direction indicated by arrow B, and the sheet S may be conveyed in a meandering manner. When such meandering of the sheet S occurs, the position of the ink landing on the sheet S also deviates, and image quality deteriorates. Therefore, in the present embodiment, in a case where meandering of the sheet S occurs, the head units 12C, <NUM>, and 12Y for cyan, magenta, and yellow are movable in the width direction of the sheet S indicated by arrow B, so as to follow the meandering (positional deviation in the width direction). In <FIG>, chain double-dashed lines indicate the move of the head units 12C, <NUM>, and 12Y.

In order to move the head units 12C, <NUM>, and 12Y to follow the meandering of the sheet S, it is necessary to grasp a positional deviation (the direction in which the position deviates and the amount of deviation) in the width direction indicated by arrow B of the sheet S. For that, as illustrated in <FIG>, the conveyance device <NUM> according to the present embodiment is provided with a plurality of position sensors <NUM> (first to fourth position sensors 30A to 30D) serving as a position detector to detect the position of the sheet S.

Each position sensor <NUM> is disposed opposite the corresponding head unit <NUM> (on the lower side of the sheet S in <FIG>) relative to the conveyance path through which the sheet S is conveyed, and in the vicinity of the liquid discharge position <NUM> at which the head unit <NUM> discharges ink. That is, each position sensor <NUM> is disposed between, out of the driven rollers 17d to <NUM>, two driven rollers respectively disposed upstream and downstream from the corresponding one of the liquid discharge positions <NUM>, 10C, <NUM>, and 10Y. The "liquid discharge position" in this specification refers to a liquid discharge position in a state where the sheet does not meander, that is, a state where the head unit does not move in the sheet width direction and is disposed at a reference position (initial position) set in advance.

The position sensor <NUM> is an optical sensor or the like that detects surface information of a conveyed object to be conveyed. Examples include a charge-coupled device (CCD) camera and a complementary metal oxide semiconductor (CMOS) camera using air pressure, photoelectricity, ultrasonic wave, or light such as visible light, laser, or infrared light.

<FIG> is a block diagram illustrating a control system of the position sensors and the head units according to the present embodiment. With reference to <FIG>, a description is given below of control of the position sensors <NUM> and the head units <NUM> using an example of a combination of the first position sensor 30A and the second position sensor 30B. The first position sensor 30A detects the position of the sheet S at the position of the head unit <NUM> for black. The second position sensor 30B detects the position of the sheet S at the position of the head unit 12C for cyan.

As illustrated in <FIG>, the controller <NUM> includes a calculation unit <NUM>. Each of the first position sensor 30A and the second position sensor 30B includes an imaging device <NUM>, an image capture controller <NUM>, and an image storage unit <NUM>.

The imaging device <NUM> captures an image of the sheet S being conveyed.

The image capture controller <NUM> includes a shutter control unit <NUM> and an image acquisition unit <NUM>. The shutter control unit <NUM> controls the timing at which the imaging device <NUM> captures an image. The image acquisition unit <NUM> acquires data of an image captured by the imaging device <NUM>.

The image storage unit <NUM> stores the image data obtained by the image capture controller <NUM>.

The sheet S has diffusiveness on or inside thereof. Accordingly, when the sheet S is irradiated with laser beam from a laser light source of the position sensor 30A or 30B, the reflected light is diffused. The diffuse reflection creates a pattern on the sheet S. The pattern is made of spots called "speckles" and called a "speckle pattern," which is an example of the surface information. When an image of the sheet S is captured, image data representing the speckle pattern is obtained. From the image data, the position of the pattern is known, and the position of a specific portion of the sheet S is detected.

That is, when the sheet S is conveyed, the pattern of the sheet S is also conveyed. Therefore, by detecting the same pattern at different times, the movement amount or the movement speed of the sheet S can be obtained.

The image data obtained by the first position sensor 30A and image data obtained by the second position sensor 30B are sent to the calculation unit <NUM> of the controller <NUM>. The calculation unit <NUM> calculates how much the predetermined portion on the sheet S has moved in the sheet width direction based on the image data sent from the first position sensor 30A and the second position sensor 30B. By moving the head unit 12C for cyan in the sheet width direction based on the movement amount (positional deviation amount) of the sheet S calculated by the calculation unit <NUM>, the discharge position in the sheet width direction is controlled. In other combinations of the position sensors <NUM>, the positional deviation of the sheet S is detected in the same manner, and the magenta and yellow head units <NUM> and 12Y are moved in the sheet width direction based on the detected positional deviation amount, thereby controlling the respective discharge positions in the sheet width direction.

Based on the image data obtained by each position sensor <NUM>, in addition to the positional deviation in the sheet width direction, the positional deviation in the sheet conveyance direction is also detected. For example, the calculation unit <NUM> calculates how much the predetermined portion on the sheet S has moved in the sheet conveyance direction based on the image data sent from the first position sensor 30A and the second position sensor 30B, so as to calculate the positional deviation amount of the sheet S in the sheet conveyance direction. In other combinations of the position sensors <NUM>, the positional deviation in the sheet conveyance direction is similarly detected. The sheet S may extend in the sheet conveyance direction due to permeation of the ink. In such a case, the discharge timing of each of the head units <NUM>, 12C, <NUM>, and 12Y is controlled based on the calculated positional deviation amount in the sheet conveyance direction. Thus, the discharge position in the sheet conveyance direction can be controlled.

In order to improve the detection accuracy of each position sensor <NUM>, as illustrated in <FIG>, each position sensor <NUM> is preferably disposed between rollers such as the driven rollers 17d to <NUM>. Since the conveyance speed of the sheet S is relatively stable between the rollers, the position sensors <NUM> disposed between the rollers can accurately detect the movement amount or the movement speed of the sheet S in at least one of the sheet conveyance direction and the sheet width direction.

Preferably, the position of the position sensor <NUM> is close to the corresponding liquid discharge position <NUM> where ink is discharged. That is, the shorter the distance between the position sensor <NUM> and the liquid discharge position <NUM>, the smaller the detection error. Therefore, the positional deviation of the sheet S can be detected with high accuracy.

Further, the position sensor <NUM> is preferably disposed upstream from the liquid discharge position <NUM>. When the position sensor <NUM> is disposed upstream from the liquid discharge position <NUM>, the movement or discharge timing of the head unit <NUM> can be controlled after the position of the sheet S is detected by the position sensor <NUM> and before the sheet S is conveyed to the liquid discharge position <NUM>.

By contrast, in a case where the position sensor <NUM> is disposed directly below the liquid discharge position <NUM>, there is a concern that the landing position of the ink deviates due to a delay by the amount of the control operation. If the control operation is performed quickly, as the position of the position sensor <NUM>, directly below the liquid discharge position <NUM> is preferred to upstream from the liquid discharge position <NUM> for accurately detecting the movement amount of the sheet S directly below the liquid discharge position <NUM>. Alternatively, when the error by the amount of the control operation is allowable, the position sensor <NUM> may be disposed downstream from the liquid discharge position <NUM>.

In the present embodiment, intervals D1 to D3 (see <FIG>) between the position sensors <NUM> in the sheet conveyance direction A are set to be integral multiples of a circumferential length X of the drive roller that conveys the sheet S (for example, the lower drive roller of the drive roller pair 17B disposed extreme downstream in the sheet conveyance direction A in <FIG>). That is, in <FIG>, the respective distances D1 to D3 from the extreme upstream position sensor 30A to the position sensors 30B to 30D downstream from the position sensor 30A are respectively set to one, two, and three multiples of the circumferential length X of the drive roller (D1=X, D2=2X, D3=3X).

Setting the intervals D1 to D3 between the position sensors <NUM> to integral multiples of the circumferential length X of the drive roller is advantageous as follows. Even if the drive roller is eccentric, this setting can cancel out the speed unevenness of the sheet S due to the eccentricity at the detection positions of the position sensors <NUM>. Therefore, each position sensor <NUM> can accurately detect the positional deviation of the sheet S.

Similarly, intervals E1 to E3 between the head units <NUM>, 12C, <NUM>, and 12Y in the sheet conveyance direction A are set to one, two, and three multiples of the circumferential length X of the drive roller (E1=X, E2=2X, and E3=3X). This setting can cancel out the speed unevenness of the sheet S due to the eccentricity of the drive roller at each of the liquid discharge positions <NUM>, 10C, <NUM>, and 10Y, thereby securing accurate discharge of ink from the head units <NUM>, 12C, <NUM>, and 12Y to the sheet S.

To improve the detection accuracy of each position sensor <NUM>, the position of the position sensor <NUM> relative to the liquid discharge position is set as described above, and, preferably, the mounting accuracy of the position sensor is improved. For improving the mounting accuracy of the sensor, generally, there is a method of increasing the dimensional accuracy of a mounting component or performing position adjustment after mounting. However, higher accuracy of component dimensions increases the cost, and adjusting the position after mounting increases the mounting work time, which are not desirable. Therefore, in the present embodiment, the following configuration is adopted to easily and accurately mount the position sensor. Hereinafter, a sensor mounting structure according to the present embodiment will be described.

<FIG> is a perspective view of a part of the conveyance device <NUM> including the sensor mounting structure according to the present embodiment.

As illustrated in <FIG>, the position sensor <NUM> is attached between a pair of side plates 21A and 21B via two support shafts <NUM> and a sensor holder <NUM>. The pair of side plates 21A and 21B serves as a pair of roller supports to support both ends (or the vicinity thereof) of each of the plurality of conveyance rollers <NUM>. The side plates 21A and 21B are disposed in parallel with each other with an interval therebetween. The sensor holder <NUM> holds the position sensor <NUM>. The sensor holder <NUM> extends across the two support shafts <NUM> and is attached to the two support shafts <NUM>. Each support shaft <NUM> is a component of a sensor support that supports the position sensor <NUM> held by the sensor holder <NUM>, and is attached between the pair of side plates 21A and 21B. On the side plate 21A, a flat fixing plate <NUM> serving as a fixing member that fixes each support shaft <NUM> is attached. The flat fixing plate <NUM> is another component of the sensor support. That is, the sensor support includes the pair of support shafts <NUM> and the fixing plate <NUM>. As described above, the conveyance device <NUM> according to the present embodiment includes the pair of side plates 21A and 21B, the two support shafts <NUM>, the sensor holder <NUM>, and the fixing plate <NUM> as the sensor mounting structure for mounting the position sensor <NUM>.

Next, a description is given of details of the sensor mounting structure and a mounting method according to the present embodiment with reference to the exploded perspective views of <FIG>. In the following description, of the side plates 21A and 21B illustrated in <FIG>, the side plate 21A on the near side in the drawing is also referred to as a "first side plate 21A," and the side plate 21B on the far side is also referred to as a "second side plate 21B. " In addition, the side on which the side plates 21A and 21B face each other (face a center in the sheet width direction) is referred to as an "inner side" or "opposing side," and an opposite side thereof is referred to as an "outer side.

As illustrated in <FIG>, each of the first side plate 21A and the second side plate 21B has two insertion holes <NUM> into which the respective support shafts <NUM> are inserted. Each insertion hole <NUM> has a circular cross section. The insertion holes <NUM> are positioned at the same height and at the same interval so that the support shafts <NUM> inserted in the insertion holes <NUM> are horizontal and parallel to each other.

As illustrated in <FIG>, each support shaft <NUM> is inserted from the outer side of the first side plate 21A toward the second side plate 21B in the direction indicated by arrow C (also "insertion direction C"). A front end of each support shaft <NUM> in the insertion direction C includes a protruding portion <NUM> having a circular cross section. The protruding portion <NUM> is to be inserted into the insertion hole <NUM> of the second side plate 21B. The protruding portion <NUM> has a smaller diameter than other portion (a large-diameter portion <NUM>) of the support shaft <NUM>. As illustrated in <FIG>, when the protruding portion <NUM> is inserted into the insertion hole <NUM> of the second side plate 21B, an end-side portion (on the protruding portion <NUM> side) of the large-diameter portion <NUM> of the support shaft <NUM> is also inserted into the insertion hole <NUM> of the second side plate 21B.

After the support shafts <NUM> are inserted into the insertion holes <NUM> of the first and second side plates 21A and 21B, the fixing plate <NUM> is attached to the first side plate 21A. Then, the movement of the support shafts <NUM> in the insertion direction C and the direction opposite thereto and the rotation of the support shafts <NUM> about the axes along the insertion direction C are restricted.

Specifically, as illustrated in <FIG>, a rear end (an end opposite to a front end in the insertion direction C) of each support shaft <NUM> includes a rotation prevention protrusion <NUM>. The rotation prevention protrusion <NUM> has a D-shaped cross section and restricts rotation of the support shaft <NUM>. Relating to this, the fixing plate <NUM> has fitting holes <NUM>, each having a D-shaped cross section, into which the rotation prevention protrusions <NUM> of the support shafts <NUM> fit. As the rotation prevention protrusion <NUM> of the support shaft <NUM> is inserted and fitted into the fitting hole <NUM> of the fixing plate <NUM>, the rotation of the support shaft <NUM> with respect to the fixing plate <NUM> is restricted. The shape of the cross section of the rotation prevention protrusion <NUM> and the fitting hole <NUM> is not limited to a D-shape but may be another non-circular shape such as a quadrangular shape, a polygonal shape, or an elliptical shape.

Further, as illustrated in <FIG>, a screw hole <NUM> is provided in the rotation prevention protrusion <NUM>. The support shaft <NUM> is screwed to the fixing plate <NUM> by a screw <NUM> inserted into the screw hole <NUM> from the outer side of the fixing plate <NUM>. Further, the fixing plate <NUM> has a screw insertion hole <NUM> for attaching the fixing plate <NUM> to the first side plate 21A. Relating to this, the first side plate 21A has a screw hole <NUM> for attaching the fixing plate <NUM>. A screw <NUM> is inserted into the screw insertion hole <NUM> of the fixing plate <NUM> and screwed in the screw hole <NUM> of the first side plate 21A. Then, the fixing plate <NUM> is attached to the outer face of the first side plate 21A.

As illustrated in <FIG>, in a state in which the support shaft <NUM> is secured to the fixing plate <NUM> and the fixing plate <NUM> is secured to the first side plate 21A, movement of the support shaft <NUM> in the insertion direction C and the direction opposite thereto with respect to the first side plate 21A is restricted. Further, in this state, since the respective rotation prevention protrusions <NUM> of the support shafts <NUM> are fitted to the fitting holes <NUM> of the fixing plate <NUM>, the rotation of the support shafts <NUM> with respect to the first side plate 21A is also restricted.

<FIG> is an exploded perspective view of the sensor holder <NUM>, the position sensor <NUM>, and the support shafts <NUM> in a state before the sensor holder <NUM> is attached to the support shafts <NUM>.

As illustrated in <FIG>, each support shaft <NUM> includes a mounting face <NUM> for mounting the sensor holder <NUM> on the surface thereof. The mounting face <NUM> is a flat face. In a state in which rotation of the support shaft <NUM> with respect to the first side plate 21A is restricted, the mounting face <NUM> faces upward (conveyance path side) and is disposed horizontally.

The mounting face <NUM> includes two positioning recesses 226a and 226b as positioning portions for positioning the sensor holder <NUM>. Of the two positioning recesses 226a and 226b, the positioning recess 226a has a round shape and serves as a main reference for positioning. The other positioning recess 226b has a slot shape and serves as a sub-reference for positioning. The mounting face <NUM> further has two screw holes <NUM> for mounting the sensor holder <NUM>.

As illustrated in <FIG>, the sensor holder <NUM> includes a base portion <NUM> attached to the mounting face <NUM> of the support shaft <NUM>, and a sensor mounting portion <NUM> to which the position sensor <NUM> is mounted. The base portion <NUM> and the sensor mounting portion <NUM> are orthogonal to each other. When the base portion <NUM> is disposed horizontally, the sensor mounting portion <NUM> extends vertically downward from the base portion <NUM>. The base portion <NUM> includes two positioning projections <NUM>, as positioning portions, to be inserted into the positioning recesses 226a and 226b in the mounting face <NUM>. When the positioning projections <NUM> are inserted into the positioning recesses 226a and 226b, the sensor holder <NUM> is prevented from moving horizontally (in a direction parallel to the mounting face <NUM>) with respect to the support shaft <NUM>. At this time, since the base portion <NUM> is placed on the mounting face <NUM> of the support shaft <NUM>, movement of the sensor holder <NUM> in a downward direction (a direction perpendicular to the mounting face <NUM>) with respect to the support shaft <NUM> is also restricted.

In the present embodiment, the positioning recesses 226a and 226b are provided in both of the support shafts <NUM> for commonality of components. However, the positioning projections <NUM> of the sensor holder <NUM> are inserted into the positioning recesses 226a and 226b of only one of the support shafts <NUM>. In this manner, the sensor holder <NUM> is positioned with reference to the positioning recesses 226a and 226b of at least one of the support shafts <NUM>. Alternatively, the sensor holder <NUM> may be positioned with reference to the positioning recesses 226a and 226b of both support shafts <NUM>. In addition, the projection-recess relationship between the positioning portions of the sensor holder <NUM> and the support shaft <NUM> may be opposite to that in the present embodiment. That is, the sensor holder <NUM> may have positioning recesses, and the mounting face <NUM> of the support shaft <NUM> may have positioning projections.

As illustrated in <FIG>, the base portion <NUM> of the sensor holder <NUM> has a plurality of screw insertion holes <NUM> for attaching the sensor holder <NUM> to the support shafts <NUM>. In a state in which the sensor holder <NUM> is positioned with respect to the mounting faces <NUM> of the support shafts <NUM>, screws <NUM> are inserted into the screw insertion holes <NUM> of the sensor holder <NUM> and screwed to the screw holes <NUM> in the mounting faces <NUM>. Then, the sensor holder <NUM> is mounted to the mounting faces <NUM> of the support shafts <NUM>.

<FIG> is an exploded perspective view of the sensor holder <NUM> and the position sensor <NUM> to be attached to the sensor holder <NUM>.

As illustrated in <FIG> and <FIG>, the sensor mounting portion <NUM> of the sensor holder <NUM> includes a plurality of positioning projections <NUM> as positioning portions for positioning the position sensor <NUM>. As indicated by a chain double-dashed line in <FIG>, the position sensor <NUM> is restricted from moving downward and rightward in the drawing by the contact with the positioning projections <NUM> of the sensor holder <NUM>. Specifically, the position sensor <NUM> includes a main body <NUM> including the imaging device <NUM>, a lens unit <NUM>, and an illumination unit <NUM>, and the main body <NUM> has a hexahedral shape (a cubic shape or a rectangular parallelepiped shape). As the positioning projections <NUM> contact two planes (the bottom face and the right face in <FIG>) of the main body <NUM> orthogonal to each other, movement of the position sensor <NUM> in a direction orthogonal to the two planes of the main body <NUM> is restricted.

Further, the sensor mounting portion <NUM> of the sensor holder <NUM> includes a plurality of screw insertion holes <NUM> for mounting the position sensor <NUM>. Relating to this, the main body <NUM> of the position sensor <NUM> has a plurality of screw holes <NUM>. In a state in which the position sensor <NUM> is positioned with respect to the sensor holder <NUM>, screws <NUM> are inserted into the screw insertion holes <NUM> of the sensor mounting portion <NUM> and screwed to the screw holes <NUM> in the position sensor <NUM>. Then, the position sensor <NUM> is mounted to the sensor holder <NUM>. In the present embodiment, the two screw insertion holes <NUM> and the two positioning projections <NUM> are provided in the sensor mounting portion <NUM> so that the number of position sensors <NUM> attached to the sensor holder <NUM> can be increased to two or the mounting position can be selected.

In the above-described structure according to the present embodiment, in order to mount the position sensor <NUM> between the side plates 21A and 21B, first, as illustrated in <FIG>, the two support shafts <NUM> are inserted into the insertion holes <NUM> from the outer side of the first side plate 21A. Further, the front ends (the protruding portions <NUM>) of the support shafts <NUM> in the insertion direction C are inserted into the insertion holes <NUM> of the second side plate 21B. In the present embodiment, the diameter of the insertion holes <NUM> of the first side plate 21A are larger on the near side than on the far side in the insertion direction C (see <FIG>). Therefore, for example, even when the positions of the insertion holes <NUM> of the side plates 21A and 21B are slightly shifted from each other, the support shaft <NUM> can be smoothly inserted from the insertion hole <NUM> of the first side plate 21A into the insertion hole <NUM> of the second side plate 21B when the support shaft <NUM> is inclined in the insertion hole <NUM> of the first side plate 21A.

Next, the mounting faces <NUM> of the support shafts <NUM> inserted into the insertion holes <NUM> are aligned so as to face upward, and the fixing plate <NUM> is attached from the outer side of the first side plate 21A. At this time, as illustrated in <FIG>, the fixing plate <NUM> is disposed such that the rotation preventing protrusions <NUM> of the support shafts <NUM> fit in the fitting holes <NUM> of the fixing plate <NUM>. Then, the screw <NUM> is screwed to the screw insertion hole <NUM> in the fixing plate <NUM>, and the screws <NUM> are screwed to the screw holes <NUM> in the rotation prevention protrusions <NUM> of the support shafts <NUM>. Thus, the fixing plate <NUM> is secured to the first side plate 21A, and the support shafts <NUM> are secured to the fixing plate <NUM>.

Subsequently, as illustrated in <FIG>, the position sensor <NUM> is mounted to the sensor holder <NUM>.

First, the position sensor <NUM> is brought into contact with the plurality of positioning projections <NUM> of the sensor holder <NUM> to be positioned. While this state is maintained, the screws <NUM> are screwed to the screw holes <NUM> of the position sensor <NUM> through the screw insertion holes <NUM> of the sensor holder <NUM>. Thus, the position sensor <NUM> is mounted to the sensor holder <NUM>.

Then, the sensor holder <NUM> to which the position sensor <NUM> is mounted is mounted on the support shafts <NUM> secured between the pair of side plates 21A and 21B. First, as illustrated in <FIG>, the positioning projections <NUM> of the sensor holder <NUM> are inserted into the positioning recesses 226a and 226b in the mounting face <NUM> of one of the support shafts <NUM>, to determine the position thereof. Next, the screws <NUM> are screwed to the screw holes <NUM> in the mounting face <NUM> through the screw insertion holes <NUM> of the sensor holder <NUM>, and the sensor holder <NUM> is mounted on each support shaft <NUM>. Thus, the mounting operation of the position sensor <NUM> is completed.

As described above, in the present embodiment, the position sensor <NUM> can be mounted while the position of each member is determined. Accordingly, the position sensor <NUM> can be easily and accurately mounted without strict dimension management of components or position adjustment after the mounting.

That is, in the present embodiment, as the support shafts <NUM> supporting the position sensor <NUM> are inserted into the insertion holes <NUM> in the pair of side plates 21A and 21B, the positions of the support shafts <NUM> in a direction (radial direction) intersecting the insertion direction C are determined. In addition, in a state in which the support shafts <NUM> are inserted into the insertion holes <NUM>, the support shaft <NUM> are secured to the first side plate 21A via the fixing plate <NUM>. Then, the positions of the support shafts <NUM> with respect to the first side plate 21A in the insertion direction C and the direction opposite thereto (axial direction) are determined. Further, the rotation prevention protrusions <NUM> at the rear ends of the support shafts <NUM> are fitted into the fitting holes <NUM> of the fixing plate <NUM>. This fitting determines the position of the support shafts <NUM> with respect to the first side plate 21A in the rotational direction about the axes along the insertion direction C.

As described above, in the present embodiment, the paired side plates 21A and 21B have the insertion holes <NUM> into which the support shafts <NUM> are inserted to position the support shafts <NUM> in the direction intersecting the insertion direction C. Additionally, the fixing plate <NUM> functions as a positioning portion for positioning the support shafts <NUM> in the insertion direction C and the direction opposite thereto and in the rotational direction about the axis along the insertion direction C with respect to the first side plate 21A. With this structure, the positions of the support shafts <NUM> can be easily determined by inserting the support shafts <NUM> into the insertion holes <NUM> and attaching the fixing plate <NUM> to the first side plate 21A.

In addition, in the present embodiment, each support shaft <NUM> is inserted into the insertion hole <NUM> from the outer side of the first side plate 21A. This configuration is advantageous in reducing the number of attachment components and facilitating the mounting work as compared with a configuration in which each support shaft <NUM> is inserted into the insertion hole <NUM> from the inner side (opposing side) of the first side plate 21A as illustrated in <FIG>. Specifically, in the comparative example illustrated in <FIG>, the support shaft <NUM> is inclined, and the front end thereof is inserted into the insertion hole <NUM> from the inner side of the first side plate 21A. After that, as illustrated in <FIG>, the support shaft <NUM> is disposed horizontal, and the rear end thereof is inserted into the insertion hole <NUM> of the second side 21B. In such a mounting method, the insertion hole <NUM> in the first side plate 21A has a diameter larger than that of the support shaft <NUM> since the support shaft <NUM> is inserted into the insertion hole <NUM> in an inclined posture. Therefore, in a state in which the support shaft <NUM> is horizontally disposed, as illustrated in <FIG>, another member such as a bearing <NUM> for supporting the rear end of the support shaft <NUM> with respect to the insertion hole <NUM> of the first side plate 21A is used. By contrast, in the present embodiment, since the support shaft <NUM> is inserted into the insertion hole <NUM> from the outer side of the first side plate 21A, the insertion hole <NUM> of the first side plate 21A can have the same size as the support shaft <NUM>, and there is no need to separately provide a bearing or the like. Therefore, the support shaft <NUM> can be easily attached with a small number of parts. Note that the present disclosure does not exclude a configuration in which the support shaft <NUM> is inserted from the inner side of the first side plate 21A as illustrated in <FIG>. A member such as the bearing <NUM> may be provided, or such a configuration may be adopted.

In addition, in the present embodiment, since the support shafts <NUM> can be inserted from the insertion holes <NUM> of the same one (the first side plate 21A) of the pair of side plates 21A and 21B to the insertion hole <NUM> of the other side plate (the second side plate 21B), the support shafts <NUM> can be attached easily. For example, there may an obstacle on the second side plate 21B side that makes it difficult to insert the support shafts <NUM> and screwing the support shafts <NUM> from the second side plate 21B side. In such a case, the mounting work is facilitated by inserting and screwing the support shafts <NUM> from the first side plate 21A side. In addition, since it is not necessary to change the insertion direction for each support shaft <NUM>, work efficiency is also improved.

Further, in the present embodiment, as the support shafts <NUM> are secured to the first side plate 21A via the fixing plate <NUM>, the support shafts <NUM> are positioned with respect to the first side plate 21A in the insertion direction C and the direction opposite thereto (positioning in the axial direction). By contrast, with respect to the second side plate 21B, since only the front end of each support shaft <NUM> is inserted into the insertion hole <NUM> (see <FIG>), positioning of each support shaft <NUM> in the insertion direction C and the direction opposite thereto (positioning in the axial direction) is not performed. Thus, in the present embodiment, the support shafts <NUM> are not positioned in the insertion direction C and in the direction opposite thereto (positioned in the axial direction) with respect to the second side plate 21B and are allowed to move in the axial direction with respect to the second side plate 21B. With this structure, even if the support shafts <NUM> expand or contract in the axial direction due to a temperature rise after attachment, the side plates 21A and 21B are less likely to be directly affected by the expansion and contraction of the support shafts <NUM>. This feature can inhibit deformation such as bending of the side plates 21A and 21B caused by expansion and contraction of the support shafts <NUM>, thereby improving positional accuracy of the support shafts <NUM>.

Further, as described above, since the support shafts <NUM> are positioned with respect to the same side plate (the first side plate 21A) via the fixing plate <NUM>, the positioning accuracy of the support shafts <NUM> improves. That is, since the positioning of the support shafts <NUM> in the insertion direction C and the direction opposite thereto is performed with reference to the same side plate (first side plate 21A), the accuracy of positioning can be high compared with a case in which the positioning is performed with reference to different side plates. As described above, in the present embodiment, since the support shafts <NUM> can be positioned with high accuracy, the mounting accuracy of the position sensor <NUM> supported by the support shafts <NUM> are also improved.

In addition, the sensor mounting structure of the present embodiment facilitates installation of an additional position sensor <NUM>, maintenance work, and the like. For example, additional insertion holes <NUM> for the additional position sensor are provided in advance in each of the side plates 21A and 21B so that, when necessary, another support shaft <NUM> is inserted into the additional insertion holes <NUM> from the outer side of the first side plate 21A and easily attached. Further, since the sensor holder <NUM> can be screwed and secured to the added support shaft <NUM> from above, the mounting work can be easily performed. Similarly, the position sensor <NUM> can be easily replaced or rearrangement from above the support shafts <NUM>.

Further, as in the example illustrated in <FIG>, fitting holes <NUM> (positioning portions in the rotational direction) having a D-shaped cross section to be fitted to the rotation prevention protrusions <NUM> of the support shafts <NUM> may be directly provided in one (the side plate 21A) of the pair of side plates 21A and 21B. In this case, the rotation prevention protrusion <NUM> on each of the support shafts <NUM> and the fitting hole <NUM> in the side plate 21A together serve as the positioning portion for positioning the support shaft <NUM> in the rotational direction. In the example illustrated in <FIG>, the support shaft <NUM> is inserted into the fitting hole <NUM> in the direction indicated by arrow C1 (insertion direction C1) from the inner side of the side plate side 21A. Each fitting hole <NUM> in the side plate 21A serves as both the positioning portion for the rotational direction and the positioning portion for the radial direction (the insertion hole <NUM>). In other words, each fitting hole <NUM> fits with the rotation prevention protrusion <NUM> in the support shaft <NUM> to restrict the rotation of the support shaft <NUM>, and supports the support shaft <NUM> in the direction intersecting the insertion direction C1. In this case, when the rotation prevention protrusion <NUM> of the support shaft <NUM> is inserted into the fitting hole <NUM> from the inner side of the side plate side 21A, the position of the support shaft <NUM> is determined in the rotational direction and in a direction (radial direction) intersecting the insertion direction C1. Further, as the front end face of the support shaft <NUM> in the insertion direction C1 contacts the side plate side 21A, the position of the support shaft <NUM> is determined also in the insertion direction C1 (axial direction). In this case, at least one of the pair of side plates 21A and 21B is movable toward and away from the other. After the front end of each support shaft <NUM> in the insertion direction C1 is inserted into the fitting hole <NUM> of the side plate 21A, the other side plate 21B is moved toward the rear end of each support shaft <NUM>, so as to insert the rear end of each support shaft <NUM> into the insertion hole <NUM> of the side plate 21B. Thus, each support shaft <NUM> is sandwiched between the pair of side plates 21A and 21B, and the support shafts <NUM> are positioned with respect to the side plates 21A and 21B in the insertion direction C1 and the direction opposite thereto.

Alternatively, the position of each support shaft <NUM> in the in the insertion direction C may be determined as in another example illustrated in <FIG>. Specifically, in <FIG>, when the protruding portion <NUM> at the front end of each support shaft <NUM> in the insertion direction C is inserted into the insertion hole <NUM> of the second side plate 21B, the end face of the large-diameter portion <NUM> on the front end side (the protruding portion <NUM> side) of each support shaft <NUM> contacts the rim of the insertion hole <NUM> of the second side plate 21B (the inner face of the second side plate 21B enclosing the insertion hole <NUM>), thereby determining the position of each support shaft <NUM> in the insertion direction C. In this case, each insertion hole <NUM> of the second side plate 21B has a diameter larger than the diameter of the projecting portions <NUM> and smaller than the diameter of the end face of the large-diameter portion <NUM> so that the end face of the large-diameter portions <NUM> of the support shaft <NUM> contacts the rim of the insertion hole <NUM>.

Further, as in the example illustrated in <FIG>, the support shaft <NUM> may include a plurality of mounting faces <NUM> at different positions in the axial direction of the support shaft <NUM>. For example, in a configuration in which the width-direction reference position for determining the width-direction position of the sheet S in the first image forming device <NUM> is on the near side (left side in <FIG>), in the second image forming device <NUM>, in which the sheet S is thereafter reversed and conveyed, the width-direction reference position for the sheet S is on the far side (right side in <FIG>). Accordingly, the sensor holder <NUM> of the first image forming device <NUM> may be attached to the mounting face <NUM> on the near side of the support shaft <NUM>, and the sensor holder <NUM> of the second image forming device <NUM> may be attached to the mounting face <NUM> on the far side of the support shaft <NUM>. In this manner, since the support shaft <NUM> includes the plurality of mounting faces <NUM>, it is possible to appropriately select the position of the position sensor <NUM> according to the width-direction reference position of the sheet S or the like.

The embodiments of the present disclosure have been described above using an example of the conveyor mounted in an inkjet image forming apparatus. However, aspects of the present disclosure are applicable to, in addition to the above-described inkjet image forming apparatus, a conveyor mounted in an electrophotographic image forming apparatus as illustrated in <FIG>. Hereinafter, a configuration of an electrophotographic image forming apparatus to which aspects of the present disclosure are applied will be described.

An image forming apparatus <NUM> illustrated in <FIG> is a tandem image forming apparatus including four process units 61Y, 61C, <NUM>, and 61Bk as image forming units (image forming devices).

Each of the process units 61Y, 61C, <NUM>, and 61Bk includes a drum-shaped photoconductor <NUM> serving as a latent image bearer, a charging roller <NUM> serving as a charger that charges the photoconductor <NUM>, a developing device <NUM> that forms a toner image on the photoconductor <NUM>, and a cleaning blade <NUM> serving as a cleaning device that cleans the surface of the photoconductor <NUM>.

In <FIG>, an exposure device <NUM> is disposed above the process units 61Y, 61C, <NUM>, and 61Bk. The exposure device <NUM> includes a light source, a polygon mirror, an f-θ lens, and reflection mirrors to irradiate the surfaces of the photoconductors <NUM> with laser beams according to the image data.

In <FIG>, a transfer device <NUM> is disposed below the process units 61Y, 61C, <NUM>, and 61Bk. The transfer device <NUM> includes an intermediate transfer belt <NUM> formed of an endless belt as a transfer member, primary transfer rollers <NUM> each of which is disposed in contact with corresponding one of the photoconductors <NUM>, forming a primary transfer nip therebetween, and a secondary transfer roller <NUM> disposed in contact with the intermediate transfer belt <NUM>, forming a secondary transfer nip therebetween.

The image forming apparatus <NUM> includes sheet feeding trays <NUM> that store sheets S as recording media, sheet feeding rollers <NUM> that feed the sheets S from the sheet feeding trays <NUM>, and a timing roller pair <NUM> that conveys the fed sheets S to the secondary transfer nip at a predetermined timing. The image forming apparatus <NUM> further includes a fixing device <NUM> that fixes images on the sheets S, a cooling device <NUM> that cools the sheets S, an ejection roller pair <NUM> that discharges the sheets S to the outside of the apparatus, and an output tray <NUM> on which the ejected sheets S are placed.

The image forming apparatus <NUM> illustrated in <FIG> operates as follows.

When an image forming operation is started, the photoconductors <NUM> of the process units 61Y, 61C, <NUM>, and 61Bk rotate in a counterclockwise direction in <FIG>, and the charging rollers <NUM> uniformly charge the surfaces of the photoconductors <NUM> to a predetermined polarity. Then, the exposure device <NUM> directs laser beams onto the charged surfaces of the photoconductors <NUM> according to image data of a document read by a scanner. Thus, electrostatic latent images are formed on the photoconductors <NUM>. Note that the image data according to which each photoconductor <NUM> is exposed is single-color image data obtained by separating full-color image data into individual color components of yellow, cyan, magenta, and black. The electrostatic latent images formed on the photoconductors <NUM> are developed into toner images with toner of respective colors supplied by the developing devices <NUM>.

In the transfer device <NUM>, one of a plurality of rollers 69A to 69D that supports the intermediate transfer belt <NUM> rotates as a drive roller, thereby rotating the intermediate transfer belt <NUM> in the direction indicated by an arrow appended to the transfer device <NUM> in <FIG>. Each primary transfer roller <NUM> is applied with a voltage having a polarity opposite a charging polarity of the toner, in constant-voltage or constant-current control, so as to generate a transfer electrical field in each primary transfer nip between the primary transfer roller <NUM> and the corresponding photoconductor <NUM>. The transfer electric fields generated at the primary transfer nips sequentially transfer and superimpose the respective toner images from the photoconductors <NUM> one on another on the intermediate transfer belt <NUM>. Thus, a full-color toner image is formed on the intermediate transfer belt <NUM>. Residual toner on the photoconductor <NUM> not transferred onto the intermediate transfer belt <NUM> is removed by the cleaning blade <NUM>.

In accordance with rotation of the intermediate transfer belt <NUM>, the full-color toner image transferred onto the intermediate transfer belt <NUM> reaches the secondary transfer nip (position of the secondary transfer roller <NUM>) and is transferred, at the secondary transfer nip, onto the sheet S conveyed by the timing roller pair <NUM>. The sheet S is supplied from the sheet feeding tray <NUM>. In the sheet feeding tray <NUM>, after an instruction to start a printing operation is given, the sheets S are fed one by one as the sheet feeding roller <NUM> rotates. The timing roller pair <NUM> halts the supplied sheet P and then conveys the sheet P to the secondary transfer nip timed to coincide with arrival, at the secondary transfer nip, of the full-color toner image on the intermediate transfer belt <NUM>. At this time, the secondary transfer roller <NUM> is applied with a transfer voltage having a polarity opposite to the charging polarity of the toner image on the intermediate transfer belt <NUM>, and the transfer electrical field generated in the secondary transfer nip transfers the toner image from the intermediate transfer belt <NUM> onto the sheet S.

Thereafter, the sheet S is conveyed to the fixing device <NUM>. The fixing device <NUM> heats and presses the toner image to the sheet S with a fixing roller <NUM> and a pressure roller <NUM>, thereby fixing the toner image on the sheet S. Then, the sheet S is conveyed to the cooling device <NUM> and cooled, after which the ejection roller pair <NUM> ejects the sheet S to the output tray <NUM>. Thus, a series of image forming operations is completed.

The cooling device <NUM> in the image forming apparatus <NUM> has the following configuration.

As illustrated in <FIG>, the cooling device <NUM> includes a pair of conveyor belts 51A and 51B. Each of the conveyor belts 51A and 51B is an endless belt and is stretched by a pair of conveyance rollers <NUM>. At least one of the conveyance rollers <NUM> is a drive roller that is rotated by a drive source such as a motor. As the conveyance rollers <NUM>, the conveyor belts 51A and 51B rotate. As a result, the sheet S is conveyed while being nipped by the conveyor belts 51A and 51B.

As illustrated in <FIG>, inside the pair of conveyor belts 51A and S 1B, cooling members 53A and 53B are disposed, respectively. The cooling members 53A and 53B are pressed against the inner peripheral surfaces of the conveyor belts 51A and 51B by springs <NUM> serving as pressing members. With this configuration, the sheet S conveyed between the conveyor belts 51A and S 1B, is cooled from both sides by the cooling members 53A and 53B while being conveyed by the rotating conveyor belts 51A and 51B.

In the cooling device <NUM> including the pair of conveyor belts 51A and 51B as described above, when one or more of the conveyance rollers <NUM> respectively supporting the conveyor belts 51A and 51B are eccentric, there is a concern that the conveyor belts 51A and 51B may meander (deviate in the sheet width direction). Therefore, the cooling device <NUM> illustrated in <FIG> includes position sensors <NUM> respectively disposed inside the conveyor belts 51A and 51B, to detect the positions of the conveyor belts 51A and 51B. These position sensors <NUM> detect the surfaces of the conveyor belts 51A and 51B to determine the presence or absence of meandering of the conveyor belts 51A and 51B. When the conveyor belts 51A and 51B meander, the positions (positions in the sheet width direction) of the conveyor belts 51A and 51B are corrected by meandering correction units <NUM> provided to the conveyance rollers <NUM>.

As described above, in the cooling device <NUM> including the position sensors <NUM> to detect the meandering of the conveyor belts 51A and 51B, the mounting accuracy of the position sensors <NUM> affects the detection accuracy of the meandering. For this reason, it is preferable to apply one of the sensor mounting structures (illustrated in <FIG> and <FIG>) according to the present disclosure to the cooling device <NUM> as well as the conveyance device <NUM> according to the above-described embodiment. Thus, the position sensors can be easily and accurately mounted, and the detection accuracy of meandering is also improved. Further, aspects of the present disclosure are applicable to, in addition to the conveyance device functioning as the cooling device <NUM>, a conveyance device other than the cooling device, such as a transfer device <NUM> including an intermediate transfer belt <NUM> illustrated in <FIG>.

The term "liquid discharge apparatus" used in this specification also represents an apparatus including a liquid discharge head or a liquid discharge device to discharge liquid by driving the liquid discharge head. The term "liquid discharge apparatus" used in this specification includes, in addition to apparatuses to discharge liquid to materials to which the liquid adheres, for example, apparatuses to discharge the liquid into gas (air) or liquid.

The "liquid discharge apparatus" may include at least one of devices for feeding, conveying, and ejecting a material to which liquid adheres. The "liquid discharge apparatus" may further include at least one of a device for pre-processing (or pretreatment) and a device for post-processing (or aftertreatment). The liquid discharge apparatus may be, for example, an image forming apparatus to form an image on a sheet by discharging ink, or a three-dimensional fabricating apparatus (solid-object fabricating apparatus) to discharge a fabrication liquid to a powder layer in which powder material is formed in layers, so as to form a three-dimensional fabrication object (solid fabrication object).

The "liquid discharge apparatus" is not limited to an apparatus to discharge liquid to visualize meaningful images, such as letters or figures. For example, the liquid discharge apparatus may be an apparatus to form meaningless images, such as meaningless patterns, or fabricate three-dimensional images.

The term "liquid discharge apparatus" may represent an apparatus to relatively move the liquid discharge head and the material onto which liquid can adhere. However, the liquid discharge apparatus is not limited to such an apparatus. Specific examples include a serial-type liquid discharge apparatus including a liquid discharge head that ejects liquid while moving in the sheet width direction, and a line-type liquid discharge apparatus (see <FIG>) including a liquid discharge head that ejects liquid without moving in the sheet width direction.

In addition, the "liquid discharge apparatus" includes a treatment liquid application apparatus that discharges a treatment liquid onto a surface of a sheet for the purpose of modifying the surface of the sheet, and an injection granulation apparatus that injects a composition liquid in which a raw material is dispersed in a solution through a nozzle to granulate fine particles of the raw material.

In addition, the term "liquid discharge head" refers to a functional component that discharges or ejects liquid from a nozzle. The liquid to be discharged from the nozzle of the liquid discharge head is not limited to a particular liquid as long as the liquid has a viscosity or surface tension to be discharged from the liquid discharge head. However, preferably, the viscosity of the liquid is not greater than <NUM> mPa·s under ordinary temperature and ordinary pressure or by heating or cooling. Examples of the liquid include a solution, a suspension, or an emulsion including, for example, a solvent, such as water or an organic solvent, a colorant, such as dye or pigment, a functional material, such as a polymerizable compound, a resin, a surfactant, a biocompatible material, such as DNA, amino acid, protein, or calcium, and an edible material, such as a natural colorant. Such a solution, a suspension, or an emulsion can be used for, e.g., inkjet ink, surface treatment solution, a liquid for forming components of electronic element or light-emitting element or a resist pattern of electronic circuit, or a material solution for three-dimensional fabrication.

Examples of a source for generating energy to discharge liquid include a piezoelectric actuator (a laminated piezoelectric element or a thin-film piezoelectric element), a thermal actuator that employs an electrothermal transducer element, such as a heat element, and an electrostatic actuator including a diaphragm and opposed electrodes.

In this specification, the term "head unit" refers to an assembly in which functional components and mechanisms are integral with the liquid discharge head, and includes an assembly of components related to liquid discharge. For example, the "head unit" includes a combination of the head and at least one of a head tank, a carriage, a supply unit, a maintenance unit, a main-scanning moving mechanism, and a liquid circulator. The "head unit" may include one liquid discharge head or a plurality of liquid discharge heads as in the above-described embodiment.

In present specification, the terms "combined" or "integrated" mean attaching the liquid discharge head and the functional parts (or mechanism) to each other by fastening, screwing, binding, or engaging and holding one of the liquid discharge head and the functional parts to the other movably relative to the other. The liquid discharge head and the functional part(s) or device(s) may be detachably attached to each other.

For example, the liquid discharge head and the head tank are integral parts of the head unit. Alternatively, the liquid discharge head may be coupled with the head tank through a tube or the like to become one unit. A unit including a filter can be added at a position between the head tank and the liquid discharge head of the head unit. In yet another example, the liquid discharge head and the carriage are combined as the "head unit. " As yet another example, in the head unit, the liquid discharge head and the main scanning moving unit are combined into a single unit. The liquid discharge head is movably held by a guide that is a part of the main-scanning moving mechanism. The liquid discharge head, the carriage, and the main-scanning moving mechanism may be integral parts of a single unit.

As yet another example, in the head unit, a cap that is a part of the maintenance unit is secured to the carriage mounting the liquid discharge head such that the liquid discharge head, the carriage, and the maintenance unit are integral parts of the head unit. As yet another example, a tube is coupled to the liquid discharge head to which either the head tank or a channel member is attached such that the liquid discharge head and the supply unit are integral parts of the head unit.

The main-scan moving mechanism may be a guide only. The supply unit can be a tube(s) only or a loading unit only.

The term "material onto which liquid adheres" denotes, for example, a conveyed object that is a material to which liquid adheres at least temporarily, a material to which liquid adheres and is fixed, or a material to which liquid adheres and permeates. Examples of the "material to which liquid can adhere" include recording media, such as paper, recording paper, recording sheets, film, and cloth; electronic components, such as electronic substrate and a piezoelectric element; and media, such as a powder layer, an organ model, and a testing cell. The "material to which liquid can adhere" includes any material to which liquid adheres, unless otherwise specified.

The above-mentioned "material to which liquid adheres" may be any material, such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, or the like, as long as liquid can temporarily adhere.

Claim 1:
A conveyor (<NUM>) comprising:
a conveyance roller (<NUM>) configured to convey a conveyed object;
a pair of roller supports (21A, 21B) opposing to each other and supporting both ends of the conveyance roller (<NUM>) in an axial direction of the conveyance roller (<NUM>);
a position sensor (<NUM>) configured to detect a position of the conveyed object; and
a sensor support (<NUM>) supporting the position sensor (<NUM>),
wherein each of the pair of roller supports (21A, 21B) has an insertion hole (<NUM>; <NUM>) into which the sensor support (<NUM>) is inserted, the insertion hole (<NUM>; <NUM>) determining a position of the sensor support (<NUM>) in a direction intersecting an insertion direction of the sensor support (<NUM>), and
the sensor support (<NUM>) includes a positioning portion (<NUM>) determining the position of the sensor support (<NUM>) with respect to at least one of the pair of roller supports (21A, 21B), the positioning portion (<NUM>) determining the position of the sensor support (<NUM>) in the insertion direction, a direction opposite to the insertion direction, and a rotational direction about an axis along the insertion direction, characterized in that
the position of the sensor support (<NUM>) with respect to one of the pair of roller supports (21A, 21B) is determined only in the direction intersecting the insertion direction, and
wherein the positioning portion (<NUM>) of the sensor support (<NUM>) is at an end of the sensor support (<NUM>) and determines the position of the sensor support (<NUM>) with respect to the other of the pair of roller supports (21A, 21B) in the insertion direction, the direction opposite to the insertion direction, and the rotational direction.