JP5881026B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an inkjet image forming apparatus.

  In general, a printer, a fax machine, a copier, a plotter, or an image forming apparatus that combines a plurality of these functions includes, for example, a liquid ejection head that ejects ink droplets, and ejects ink droplets while conveying a medium. 2. Related Art There is an ink jet recording apparatus that forms an image by adhering to a sheet. The medium here is also referred to as “paper”, but the material is not limited, and a recording medium, a recording medium, a transfer material, a recording paper, and the like are also used synonymously. The image forming apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics. The image formation is not only giving an image having a meaning such as a character or a figure to the medium but also giving an image having no meaning such as a pattern to the medium (simply ejecting a droplet). Also means. The ink is not limited to so-called ink, and is not particularly limited as long as it becomes liquid when ejected. For example, the ink is a generic term for liquids including DNA samples, resists, pattern materials, and the like. Use.

  Such a droplet discharge recording type image forming apparatus includes a serial type ink jet printer, and printing is performed by scanning the print head in a direction perpendicular to the paper conveyance direction, that is, in the main scanning direction by a carriage unit. However, in order to perform accurate printing on the print medium, a mechanism for detecting the position and movement amount of the carriage is required. For example, a method using a linear encoder scale that is long in the carriage movement direction is used. (Patent Document 1 etc.).

FIG. 9 shows a carriage 1 of a general ink jet printer.
A scale is generally printed on the linear encoder scale 7 at intervals of 150 [dpi] or more. The scale is counted by an encoder sensor 8 provided on the carriage 1 to control the position of the carriage 1. Yes. For this reason, it is desirable that the linear encoder scale 7 be positioned in the vicinity of the carriage 1 for accurate position control of the carriage 1.

  However, when the linear encoder scale 7 is provided in the vicinity of the carriage 1, the user touches the encoder scale and scratches it, or the paper dust generated from the paper 10 gets dirty and is discharged for printing called ink mist. The surface of the linear encoder scale may become dirty with fine ink droplets generated as a by-product from the ink droplets and drifting in the machine. If the linear encoder scale 7 is damaged or soiled in this way, the scale printed on the linear encoder scale 7 cannot be counted well by the encoder sensor 8, and the position control of the carriage 1 cannot be performed accurately. End up. For this reason, conventionally, there has been known an image forming apparatus configured such that a service worker or the like can replace a damaged or dirty linear encoder scale.

  In the carriage 1 shown in FIG. 9, the scale drawn on the linear encoder scale 7 is read by the encoder sensor 8, and the encoder sensor 8 has a light receiving portion and a light emitting portion arranged to face each other at a predetermined interval. The scale is read by passing the linear encoder scale 7 between them. That is, the encoder sensor 8 has one open concave shape in cross section viewed from the carriage movement direction, and the linear encoder scale 7 is passed through the slit 81 which is a concave portion. Therefore, since the slit 81 of the encoder sensor 8 is open in one direction, when the user accidentally touches the linear encoder scale 7, the linear encoder scale 7 passes from the encoder sensor 8 through the opening of the slit 81. It may come off. Of course, if the linear encoder scale 7 is removed from the encoder sensor 8, the encoder sensor 8 cannot read the scale of the linear encoder scale 7 and control the position of the carriage 1.

  As a countermeasure, an anti-disengagement hole is provided on the side of the carriage on the same straight line as the slit of the encoder sensor, and the linear encoder scale is passed through the anti-extraction hole and the linear encoder scale is passed through the linear encoder scale. It is possible to pass through the scale. As a result, the linear encoder scale is supported by the inner wall surface of the escape prevention hole provided on the side surface of the carriage, so that the linear encoder scale is not easily detached from the encoder sensor.

  However, since the linear encoder scale has to be inserted from the side into the carriage prevention hole on the side of the carriage, it is difficult to see the carriage prevention hole on the side of the carriage, and it is difficult to attach the elongated encoder scale through the prevention hole. Occurs.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of improving the workability of attaching a linear encoder scale.

In order to solve the above problems, the present invention provides a print head for forming an image on a recording medium, a carriage mounted with the print head and scanned in a main scanning direction, and a carriage for detecting the position of the carriage. A linear encoder scale that is long in the moving direction, and an encoder sensor that is provided on the carriage and has one open concave groove in a cross section viewed from the carriage moving direction, and reads the linear encoder scale that has passed through the groove In the image forming apparatus having a communication hole provided in the carriage and through which the linear encoder scale passes, an outer peripheral portion of the communication hole is disposed above a part of the carriage and the encoder sensor. is formed with a communication hole forming member has a portion covering the substrate, the communication hole forming member before By leaving upward relative movement or the carriage upwardly relative to the carriage, characterized in that the openable part of the outer peripheral portion of the communication hole.

In the present invention, the outer peripheral portion of the communication hole is formed by a part of the carriage and a communication hole forming member having a portion that is disposed above the encoder sensor and covers the substrate of the encoder sensor. Since a part of the outer peripheral portion of the communication hole can be opened by moving upward with respect to the carriage or detaching upward with respect to the carriage, the communication hole forming member is opened with respect to the carriage to open the communication hole. As a result, the encoder sensor can be easily viewed, and the linear encoder scale can be easily attached to the encoder sensor. Therefore, workability can be improved compared with the case where the linear encoder scale is inserted into the groove of the encoder sensor by visually observing the communication hole from the side of the carriage.

  As described above, according to the present invention, there is an excellent effect that the mounting workability of the linear encoder scale can be improved.

2 is a schematic diagram of a carriage according to Configuration Example 1. FIG. 1 is a perspective view showing an ink jet printer that is an example of an image forming apparatus to which the present invention is applied. The side view of the mechanism part of an inkjet printer. 1 is a schematic configuration diagram of a serial inkjet printer viewed from above. FIG. 2 is a schematic configuration diagram when a serial carriage is viewed from the side. FIG. 6 is a schematic diagram of a carriage according to Configuration Example 2. FIG. 9 is a schematic diagram of a carriage according to Configuration Example 3. The schematic diagram of the carriage which concerns on a modification. The perspective view which showed the carriage of the general inkjet printer.

  FIG. 2 is a perspective view showing an ink jet printer as an example of an image forming apparatus to which the present invention is applied, and FIG. 3 is a side view of a mechanism portion of the ink jet printer shown in FIG. An ink jet printer in the illustrated example includes a carriage 1 that can move in the main scanning direction inside a printer main body 100, a print head 2 that includes an ink jet head mounted on the carriage, and a sub tank (ink cartridge) 12 that supplies ink to the print head 2. A paper feed cassette 40 (or paper feed tray) capable of stacking a large number of sheets 10 from the front side is detachably attached to the lower part of the printer main body 100. The paper 10 fed from the paper feed cassette 40 is taken in, and after a required image is recorded by the printing mechanism unit 20, the paper 10 is discharged to a paper discharge tray 46 mounted on the rear side.

  The printing mechanism unit 20 holds the carriage 1 slidably in the main scanning direction (in the direction perpendicular to the paper in FIG. 3) by guide rods 4 which are guide members provided on left and right side plates (not shown). A print head 2 composed of an inkjet head that ejects ink droplets of each color (Y), cyan (C), magenta (M), and black (Bk) is mounted with the ink droplet ejection direction facing downward. On the upper side, each sub tank 12 for supplying ink of each color to the print head 2 is mounted.

  Each color sub-tank 12 is connected to an ink tank 15 of each color that is mounted so as to be replaceable via an ink supply tube 16, and receives ink from the ink tank 15. The carriage 1 is slidably fitted to the guide rod 41 on the rear side (downstream side in the paper conveyance direction). In order to move and scan the carriage 1 in the main scanning direction, a timing belt 5 is stretched between a driving pulley 18 and a driven pulley 19 that are rotationally driven by the main scanning motor 6, and the timing belt 5 is attached to the carriage 1. It is fixed to.

  On the other hand, in order to convey the paper 10 set in the paper feed cassette 40 to the lower side of the print head 2, the paper feed roller 21 and the friction pad 22 for separating and feeding the paper 10 from the paper feed cassette 40 and the paper 10 are guided. A guide member 23 for conveying, a conveying roller 24 for reversing and conveying the fed paper 10, a conveying roller 25 pressed against the peripheral surface of the conveying roller 24, and a feeding angle of the paper 10 from the conveying roller 24. A tip roller 26 is provided. The transport roller 24 is rotationally driven by a sub-scanning motor 27 through a gear train.

  Further, a conveyance belt 9 is provided for guiding the sheet 10 fed from the conveyance roller 24 on the lower side of the print head 2 corresponding to the movement range of the carriage 1 in the main scanning direction. The conveyance belt 9 sucks the sheet 10 conveyed by being charged by the charger 30 and plays a role of keeping the sheet surface and the print head surface in parallel. A paper discharge roller 33 for sending the paper 10 to the paper discharge tray 46 is disposed downstream of the transport belt 9 in the paper transport direction.

  The printer main body 100 can be attached with a paper reversing unit 43 and a paper feeding unit 50 as necessary. The sheet reversing unit 43 includes a second conveying roller 34 and a third conveying roller 35, and after printing on the surface of the sheet 10 by the print head 2, the conveying roller 24 is reversed to pull the sheet 10 into the printer main body 100. The print head is reversed and fed to the conveyance roller 24 by passing through the second conveyance roller 34 and the third conveyance roller 35 in the sheet reversing unit 43, and the back surface of the sheet 10 faces the print head 2 side. 2 is transported below and printing on the back side. The paper feed unit 50 includes a second paper feed roller 36, a friction pad 37, a carry-out roller 38, and the like, and can accommodate a large amount of paper of the same size or different size from the paper stored in the paper feed cassette 40. Any one of the sheets can be appropriately selected and used.

  FIG. 4 is a diagram illustrating a configuration when a serial type ink jet printer (hereinafter simply referred to as a printer) according to the present embodiment is viewed from above. FIG. 5 is a diagram illustrating a configuration when the carriage 1 used in the printer according to the present embodiment is viewed from the side.

  A plurality of print heads 2 for ejecting ink are mounted on the carriage 1. An endless timing belt 5 is attached to the carriage 1, and the timing belt 5 is driven to rotate by a main scanning motor 6, whereby the carriage 1 moves along the guide rod 4 in the main scanning direction. At that time, the encoder sensor 8 provided on the carriage 1 scans the carriage 1 by reading the scale of the linear encoder scale 7 which is long in the carriage movement direction and is set at least in the scanning range of the carriage 1 in the main scanning direction. The position can be detected. Each time the paper 10 is transported by a certain distance in the sub-scanning direction by the transport belt 9, ink is ejected from the print head 2 while the carriage 1 is scanned to form an image on the paper 10. The linear encoder scale 7 is provided in the vicinity of the carriage 1 that can be read by the encoder sensor 8. The linear encoder scale 7 is provided so as to be exposed along the scanning range of the carriage 1.

  The encoder sensor 8 has a slit 81 which is a groove part for allowing the linear encoder scale 7 to pass therethrough. A light emitting part and a light receiving part are provided on both sides of the inner surface facing each other with a predetermined interval between the slits 81, and the light emission thereof. The position of the carriage 1 is detected by reading the scale by passing the linear encoder scale 7 between the light receiving portion and the light receiving portion.

  4 and 5, the linear encoder scale 7 is drawn with a thickness for the sake of clarity. Generally, a linear encoder scale 7 in which a scale is printed on a transparent film material is used. Then, the encoder sensor 8 counts the scale by using the non-transparent portion where the scale of the linear encoder scale 7 is printed and the transparent portion where the scale is not printed.

As described above, the scale drawn on the linear encoder scale 7 is read by the encoder sensor 8, and the encoder sensor 8 has a light receiving portion and a light emitting portion arranged to face each other with a predetermined interval therebetween. The scale is read by passing through the linear encoder scale 7. That is, the encoder sensor 8 cross section viewed from the carriage moving direction is a concave shape, a slit 81 is recessed portion through the linear encoder scale 7. Therefore, since the slits 81 of the encoder sensor 8 is opened, when the user had touched the linear encoder scale 7 by mistake, the linear encoder scale 7 from the encoder sensor 8 through the opening of the slit 81 is disengaged May end up. Therefore, in this embodiment, provided with a communication hole 70 through which the linear encoder scale 7 on the side surface of the carriage 1 and the slit 81 on the same straight line of the encoder sensor 8, an encoder sensor while passing the linear encoder scale 7 to the communicating hole 70 It is through the linear encoder scale 7 the slit 81 of 8. Thus, even touched linear encoder scale 7 incorrectly Yu Za, are easily as the linear encoder scale 7 from the encoder sensor 8 does not come off configuration.

  Here, in order to pass the linear encoder scale 7 through the slit 81 of the encoder sensor 8, the linear encoder scale 7 is inserted into the encoder sensor 8 from the lateral direction of the carriage 1 on the front side of the sheet as shown by an arrow A in FIG. It is possible. However, when the guide rod 4 or the timing belt 5 which is the point of operation of the carriage 1 is located, it is possible to perform accurate control or the possibility of being touched by the user is reduced. As shown, the encoder sensor 8 is generally attached to the rear of the carriage 1 in many cases. Since there is a frame member 3 or the like in the lateral direction of the carriage 1, an operator generally removes the linear encoder scale 7 from the front side of the carriage 1, and the encoder sensor 8 is visually recognized by the carriage 1 or the like. It becomes work in the state that cannot.

[Configuration example 1]
FIG. 1 is a schematic diagram of a carriage according to Configuration Example 1. FIG.
In the present configuration example, a sensor that is a communication hole forming member that is provided in the carriage 1 and that communicates with the side surface of the carriage 1 so as to cover the encoder sensor 8 and communicate with the side surface of the carriage 1 through the linear encoder scale 7. The cover 60 is provided so as to be openable and closable with respect to the carriage 1 by rotating around the hinge 1 serving as a rotation shaft.

The normal time, such as when performing the printing operation, the sensor cover 60 as shown in FIG. 1 (a) kept closed with respect to the carriage 1, even as the user touches the linear encoder scale 7 by mistake, encoder easily The linear encoder scale 7 is not removed from the sensor 8.

On the other hand, when the linear encoder scale 7 is replaced, as shown in FIG. 1B, the sensor cover 60 is rotated counterclockwise in the drawing around the hinge 1 to be opened with respect to the carriage 1 for communication. The hole 70 is opened. Accordingly , the linear encoder scale 7 can be attached to the encoder sensor 8 in a state where the encoder sensor 8 can be viewed with the encoder sensor 8 facing outside. Therefore, even if the operator has performed the installation of the linear encoder scale 7 from the front side of the carriage 1, since it is possible to attach the linear encoder scale 7 the concave shape of the slit 81 of the encoder sensor 8, a front side carriage The workability can be improved as compared with the case where the linear encoder scale 7 is inserted into the slit 81 of the encoder sensor 8 by visually observing the communication hole 70 from the lateral direction 1.

  At this time, it is easier to attach the linear encoder scale 7 to the encoder sensor 8 from above the encoder sensor 8. Therefore, the slit 81 of the encoder sensor 8 has an upper section when viewed from the carriage moving direction as shown in FIG. It is desirable to have an open concave shape (upward slit).

[Configuration example 2]
FIG. 6 is a schematic diagram of a carriage according to Configuration Example 2.
In this configuration example, provided on the carriage 1, a communication hole 70 communicating with the carriage movement direction by the linear encoder scale 7 is passed, is communicating hole forming member to cover the encoder sensor 8 which forms with the side surface of the key Yarijji 1 A sensor cover 62 is detachably attached to the carriage 1.

In normal times, such as when performing printing operation, the linear encoder from Figure 6 the sensor cover 62 as shown in (a) Leave mounted on the carriage 1, even users Tsu touch accidentally, the encoder sensor 8 easily Keep the scale 7 from coming off.

On the other hand, when replacing the linear encoder scale 7, the sensor cover 62 is lifted upward from the carriage 1 to open the communication hole 70 as shown in FIG. 6B. Accordingly , the linear encoder scale 7 can be attached to the encoder sensor 8 in a state where the encoder sensor 8 can be viewed with the encoder sensor 8 facing outside. Therefore, even if the operator has performed the installation of the linear encoder scale 7 from the front side of the carriage 1, since it is possible to attach the linear encoder scale 7 the concave shape of the slit 81 of the encoder sensor 8, a front side carriage The workability can be improved as compared with the case where the linear encoder scale 7 is inserted into the slit 81 of the encoder sensor 8 by visually observing the communication hole 70 from the lateral direction 1.

Also, the sensor cover 62 by detachable from the carriage 1, it is possible to increase the degree of freedom in the opening of the communication hole 70.

[Configuration example 3]
FIG. 7 is a schematic diagram of the carriage 1 according to Configuration Example 3.
Generally, a carriage cover, which is a cover member that covers the inside of the carriage, is detachably attached to the carriage 1 in order to perform replacement and maintenance of parts inside the carriage. Therefore, the sensor cover 64 that is a communication hole forming member that can be attached to and detached from the carriage 1 and that forms the communication hole 70 of the linear encoder scale 7 together with the side surface of the carriage 1 is also used as the carriage cover. It is possible to reduce the number of attachment / detachment mechanisms, thereby reducing costs.

  The carriage cover is not removed by the user for the original purpose and is removed by the service worker during parts replacement or maintenance. Similarly, the carriage cover can be removed during replacement of the linear encoder scale 7 performed by the service worker. But there is no functional problem.

  Further, even when the sensor cover can be opened and closed by rotating about the rotation axis as shown in the configuration example 1, the sensor cover and the carriage cover can be used together. The same effects as described above can be obtained.

[Modification]
Here, board the encoder sensor 8 provided on the carriage 1 is fixed, to contain a mechanism for transmitting a signal other to the carriage 1 is almost. Therefore, to perform the maintenance of the substrate encoder sensor 8 is fixed easily, to configured to allow access to the sensor cover 66 also serving as a carriage cover to the base plate by removing from the carriage 1 as shown in FIG. 8 Is desirable.

As described above, according to the present embodiment, the print head 2 for forming an image on the paper 10 as a recording medium, the carriage 1 on which the print head 2 is mounted and scanned in the main scanning direction, and the position of the carriage 1 are detected. A linear encoder scale 7 that is long in the carriage movement direction, and a slit 81 that is provided on the carriage 1 and that is one open concave groove in a cross section viewed from the carriage movement direction. In an image forming apparatus having an encoder sensor 8 that reads the linear encoder scale 7 and a communication hole 70 that is provided in the carriage 1 and through which the linear encoder scale 7 passes, an outer peripheral portion of the communication hole 70 is a part of the carriage 1 and an encoder sensor. it is disposed above the 8 a passage forming member having a portion overlying the substrate of the encoder sensor 8 Sensaka It is formed in the over, that the sensor cover is moved upward relative to the carriage 1, and openable part of the outer peripheral portion of the communication hole 70. Thus, by the sensor cover is moved upward relative to the carriage 1, a portion of the outer peripheral portion of the communication hole 70 is openable, the communication hole 70 by opening the sensor cover relative to the carriage 1 is opened Thus, the encoder sensor 8 can be easily viewed, and the linear encoder scale 7 can be easily attached to the encoder sensor 8. Therefore, workability can be improved as compared with the case where the linear encoder scale 7 is inserted into the slit 81 of the encoder sensor 8 by visually observing the communication hole 70 from the side of the carriage 1.
Further, according to the present embodiment, the print head 2 for forming an image on the paper 10 as a recording medium, the carriage 1 to which the print head 2 is mounted and scanned in the main scanning direction, and the position of the carriage 1 are detected. A linear encoder scale 7 that is long in the carriage movement direction, and a slit 81 that is provided on the carriage 1 and that is one open concave groove in a cross section viewed from the carriage movement direction. In an image forming apparatus having an encoder sensor 8 that reads the linear encoder scale 7 and a communication hole 70 that is provided in the carriage 1 and through which the linear encoder scale 7 passes, an outer peripheral portion of the communication hole 70 is a part of the carriage 1 and an encoder sensor. it is disposed above the 8 a passage forming member having a portion overlying the substrate of the encoder sensor 8 Sensaka It is formed in the over, that the sensor cover is disengaged upward with respect to the carriage 1, and openable part of the outer peripheral portion of the communication hole 70. Thus, by the sensor cover is disengaged upward with respect to the carriage 1, a portion of the outer periphery of the communication hole 70 is openable, communication holes 70 are opened by opening the sensor cover to the carriage 1 Thus, the encoder sensor 8 can be easily seen, and the linear encoder scale 7 can be easily attached to the encoder sensor 8. Therefore, workability can be improved as compared with the case where the linear encoder scale 7 is inserted into the slit 81 of the encoder sensor 8 by visually observing the communication hole 70 from the side of the carriage 1.
Further, according to the present embodiment, the hinge 1 that is a shaft member that pivotally supports the sensor cover with respect to the carriage 1 is provided, so that the sensor cover 60 is rotated around the hinge 1. Thus, it can be opened with respect to the carriage 1, and the removal prevention hole 70 can be opened.
In addition, according to the present embodiment, the sensor covers 64 and 66 also serve as a carriage cover that covers at least a part of the inside of the carriage, thereby integrating the sensor cover and the carriage cover, the number of parts, and attaching / detaching the cover. Therefore, it is possible to reduce the number of mechanisms used, and it is possible to reduce the cost.
Further, according to the present embodiment, the carriage cover covers the substrate on which the encoder sensor 8 is fixed. Accordingly, the substrate can be accessed by removing the sensor cover 66 that also serves as the carriage cover from the carriage 1, and the substrate can be easily maintained.
Further, according to the present embodiment, the slit 81 of the encoder sensor 8 has a concave shape opened upward in a cross section viewed from the carriage movement direction. Since the linear encoder scale 7 can be easily attached to the encoder sensor 8 from above the encoder sensor 8, the slit 81 of the encoder sensor 8 has an open concave shape with an upward cross section when viewed from the carriage movement direction (upward slit). ) Is desirable.

DESCRIPTION OF SYMBOLS 1 Carriage 2 Print head 3 Frame member 4 Guide rod 5 Timing belt 6 Main scanning motor 7 Linear encoder scale 8 Encoder sensor 9 Conveying belt 10 Paper 12 Sub tank 15 Ink tank 16 Ink supply tube 18 Drive pulley 19 Driven pulley 20 Printing mechanism part 21 Feed roller 22 Friction pad 23 Guide member 24 Transport roller 25 Transport roller 26 Front roller 27 Sub-scanning motor 30 Charger 33 Paper discharge roller 34 Second transport roller 35 Third transport roller 36 Second paper feed roller 37 Friction pad 38 Transport roller 40 the paper feed cassette 43 sheet reversing unit 46 discharge tray 50 the sheet feeding unit 60 the sensor cover 61 hinge 62 sensor cover 64 sensor cover 66 sensor cover 70 communication holes 8 1 Slit 100 Printer body

JP 2006-187905 A

Claims (5)

A print head for forming an image on a recording medium;
A carriage mounted with the print head and scanning in the main scanning direction;
A linear encoder scale elongated in the carriage movement direction for detecting the position of the carriage;
An encoder sensor provided on the carriage, having one open concave groove in a cross section viewed from the carriage movement direction, and reading the linear encoder scale passed through the groove;
In the image forming apparatus provided in the carriage and having a communication hole through which the linear encoder scale passes,
An outer peripheral portion of the communication hole is formed by a part of the carriage and a communication hole forming member having a portion that is disposed above the encoder sensor and covers a substrate of the encoder sensor, and the communication hole forming member is the carriage. The image forming apparatus is characterized in that a part of the outer peripheral portion of the communication hole can be opened by moving upward . A print head for forming an image on a recording medium;
A carriage mounted with the print head and scanning in the main scanning direction;
A linear encoder scale elongated in the carriage movement direction for detecting the position of the carriage;
An encoder sensor provided on the carriage, having one open concave groove in a cross section viewed from the carriage movement direction, and reading the linear encoder scale passed through the groove;
In the image forming apparatus provided in the carriage and having a communication hole through which the linear encoder scale passes,
An outer peripheral portion of the communication hole is formed by a part of the carriage and a communication hole forming member having a portion that is disposed above the encoder sensor and covers a substrate of the encoder sensor, and the communication hole forming member is the carriage. An image forming apparatus characterized in that a part of the outer peripheral portion of the communication hole can be opened by separating upward . The image forming apparatus according to claim 1.
An image forming apparatus comprising a shaft member that pivotally supports the communication hole forming member with respect to the carriage. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the communication hole forming member covers a part of the carriage . The image forming apparatus according to any one of claims 1 to 4,
The image forming apparatus according to claim 1, wherein the groove portion of the encoder sensor has a concave shape opened upward in a cross section viewed from a carriage moving direction.

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