JP5815621B2 - Image reading device - Google Patents

Description

  Embodiments described herein relate generally to an image reading apparatus that reads image information by reciprocating conveyance of a carriage.

  2. Description of the Related Art Conventionally, in a scanner that reads image information by conveying a carriage while shining light on a document, a timing belt is used as a drive transmission unit of the carriage. The timing belt is engaged with the carriage and drives the carriage in the image reading direction.

  The timing belt and the carriage are fixed. For this reason, the vibration of the stepping motor that drives the timing belt may be transmitted to the carriage and appear as a disturbance in the read image. As a countermeasure against the occurrence of disturbance in the scanned image, it is necessary to prevent the vibration of the stepping motor from being transmitted to the carriage. As a measure for preventing vibration transmission, a vibration isolating member is attached to a portion fixed to the timing belt.

  However, it is necessary to select a material for the vibration isolation member according to the vibration frequency to be transmitted. In the case of a vibration-proof member whose vibration frequency does not match, there is a problem that vibration cannot be suppressed and a new measure is required, resulting in an increase in system cost.

JP 2005-81654 A

  The problem to be solved by the present invention is to provide an image reading apparatus capable of suppressing the influence of vibration of a stepping motor regardless of the selection of the vibration isolation member.

An image reading apparatus according to an embodiment includes an image sensor that reads a document, a carriage that is mounted with the image sensor and reciprocates from a home position, a guide unit that guides reciprocating conveyance of the carriage, and drives reciprocating conveyance of the carriage. a stepping motor for the timing belt for transmitting a driving force from a stepping motor, is formed prior Symbol carriage, connecting portions, and the timing belt having a fitting portion with a movable piece in the longitudinal direction of movement of the carriage A stopper having a fitting piece attached to the fitting piece, the fitting piece is fitted into the fitting portion, and the carriage is driven by the stepping motor so that the fitting piece is moved in the traveling direction side. and a coupling mechanism for conveying butted against, the connecting mechanism section, of the stepping motor When the timing belt is driven in the reverse direction by rolling, a clearance is provided between the movable piece on the reverse side and the fitting piece so that the fitting piece does not hit the movable piece on the reverse side. It is provided.

1 is a schematic configuration diagram viewed from a side surface for explaining a first embodiment of an image reading apparatus. It is the block diagram seen from the upper surface of FIG. It is a principal part expansion perspective view of 1st Embodiment. It is a principal part expansion perspective view of FIG. It is a perspective view which shows the state before the connection of the connection mechanism part of FIG. It is a notional block diagram of a stepping motor. FIG. 6 is an explanatory diagram for explaining an example of a drive signal in FIG. 5. It is explanatory drawing for demonstrating conveyance of a carriage. It is explanatory drawing for demonstrating clearance. 1 is a perspective view for explaining a first embodiment according to an image reading apparatus. FIG. It is a principal part expansion perspective view of FIG. It is a perspective view which shows the state before the connection of the connection mechanism part of FIG.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram viewed from a side surface for explaining the first embodiment of the image reading apparatus. FIG. 2 is a configuration diagram viewed from the top of FIG.

  In this embodiment, the scanner device 100 is taken as an example of the image reading device. In addition to a single unit, the scanner device 100 is mounted on a printer, an all-in-one type multifunction device having a plurality of functions such as copying and FAX. The scanner device 100 uses a CIS (Contact Image Sensor) system as an example of an image sensor.

  In the scanner device 100, a document table 13 made of a transparent member such as glass is placed in the opening 12 of the housing 11. The scanner device 100 is a flat bed type that scans a document on which the document table 13 is placed by scanning the image sensor 14 from the home position and scanning the document table 13.

  In the scanner device 100, the document width direction is read by the element arrangement of the image sensor 14, so-called main scanning direction, and the document length direction is read by moving scanning of the long carriage 15, so-called sub-scanning direction. The entire area can be read (see FIG. 2).

  The CIS type image sensor 14 corresponds to a light receiving element (CCD: Charge Coupled Device or C-MOS: Complementary metal-oxide-semiconductor) arranged at a predetermined pixel density in the main scanning direction. A lens and an exposure lamp that irradiates the original with white light having light emission characteristics of RGB three colors are provided. White light is an LED that emits light with pseudo white light or a fluorescent film having RGB three-wavelength light emission characteristics. Irradiated with. Each light receiving element receives reflected light from the document at predetermined intervals, generates and accumulates electric charges according to the amount of received light, and outputs the electric signals as electrical signals.

  An image sensor 14 is mounted on the carriage 15 serving as a transported means on the surface facing the document table 13. A bar-shaped guide shaft 16 is disposed along the conveyance direction of the carriage 15 at a position facing the vicinity of the middle in the longitudinal direction of the carriage 15. In addition, guide rails 17 are arranged at intervals in positions parallel to the guide shaft 16. The carriage 15 is transported in a direction perpendicular to the longitudinal direction by transporting on the guide shaft 16 and the guide rail 17. The guide shaft 16 and the guide rail 17 serve as guide members, and the carriage 15 is accurately conveyed in parallel with the document. A sliding portion (not shown) is provided on the lower surface side of one end of the carriage 15, and this sliding portion slides on the guide rail 17.

  3 is an enlarged view of a portion of the carriage 15 viewed from the surface opposite to the surface opposite to the document table 13. A slider 18 that slides on the guide shaft 16 is integrally formed in a direction orthogonal to the longitudinal direction of the carriage 15 on the surface opposite to the document table 13 of the carriage 15. The slider 18 includes slide pieces 18 a and 18 b sandwiching the guide shaft 16 on the carriage 15.

  Protrusions 18c and 18d are formed in parallel with each other in the direction orthogonal to the carriage 15 surface of the opposed surfaces of the slide pieces 18a and 18b. The protrusions 18c and 18d can reduce the contact area between the slider 18 and the guide shaft 16 to eliminate rattling and achieve smooth sliding.

  Further, the carriage 15 and an annular timing belt 19 as a transmission portion are connected by a connecting mechanism portion 20. The coupling mechanism unit 20 can transport the carriage 15 along the guide shaft 16 in the sub-scanning direction by running the timing belt 19.

  4 and 5 show the coupling mechanism portion 20. 4 is an enlarged perspective view showing the main part of FIG. 3, and FIG. 5 is a perspective view showing a state before the connection mechanism 20 is connected.

  The connecting mechanism 20 includes a connecting part 21 formed integrally with the carriage 15 and a stopper 22 to which a timing belt 19 connected to the connecting part 21 is attached.

  The connecting portion 21 includes a slide portion 211 having a concave section with movable pieces 211f and 211r on the opposite surface of the carriage 15 to which the image sensor 14 is attached, and a support portion 212 at a concave open portion of the slide portion 211. Is formed. The support portion 212 and the bottom portion 213 of the slide portion 211 have a gap s1. The bottom surface 213 has a width of w1 and is arranged in a direction orthogonal to the longitudinal direction of the carriage 15. A space surrounded by the slide part 211 and the support part 212 is formed as a fitting part 214.

  Moreover, the stopper 22 is comprised from the U-shaped clamping part 221 of the integrally formed U-shaped clamping part 221 and the reverse direction. Ribs 223 and 224 are formed in the holding portion 221 in parallel to both ends. The ribs 223 and 224 are formed at intervals at which the valley portions 191 of the tooth surfaces of the timing belt 19 coincide.

  The fitting piece 222 is formed so that the surface facing the clamping part 221 has an interval of s2, and the opposite surface has an interval of s3. The interval s2 is formed to be slightly wider than the thickness of the bottom surface 213 of the slide portion 211. The interval s3 is formed slightly narrower than the interval s1 between the support part 212 and the bottom part 213. The width w2 of the fitting piece 222 is formed to be narrower than the width w1 of the bottom surface 213 of the slide portion 211.

  The coupling mechanism unit 20 performs a coupling function by engaging the fitting piece 222 of the stopper 22 to which the timing belt 19 is attached with the fitting portion 214 of the coupling unit 21. The stopper 22 can move the fitting portion 214 by a difference (w1−w2) between the width w1 of the connecting portion 21 of the connecting mechanism portion 20 and the width w2 of the stopper 22. w1-w2 is the amount of displacement.

  An annular timing belt 19 that transports the carriage 15 in the sub-scanning direction along the guide shaft 16 is attached to the stopper 22. The timing belt 19 converts the rotation operation of the stepping motor 23 as a driving source into a reciprocating motion, and conveys the carriage 15.

  As shown in FIG. 2, the stepping motor 23 conveys the image sensor 14 along the sub-scanning direction. The drive gear 24 is fixed to the shaft 231 of the stepping motor 23. The drive gear 24 is meshed with the driven gear 25.

  Further, the drive pulley 26 is rotatably supported coaxially with the driven gear 25. The drive pulley 26 rotates by the same amount as the driven gear 25. The idler pulley 27 is rotatably installed. The timing belt 19 is disposed outside the drive pulley 26 and the idler pulley 27 so as to apply an appropriate tension.

  With such a drive system configuration, the stepping motor 23 can drive the timing belt 19 via the drive gear 24, the driven gear 25, and the drive pulley 26, and can reciprocate the carriage 15 in the sub-scanning direction.

  By the way, the stepping motor 23 increases its vibration when the frequency characteristic of the rotation step angle of the internal rotor angle and the frequency characteristic of the number of teeth of the drive gear 24 match the natural vibration of the carriage. This vibration appears as generation of a vibration sound or generation of an abnormal image due to vibration of the image sensor 14.

  Here, consider a case where vibration is generated in the stepping motor 23 that drives the timing belt 19. The vibration of the stepping motor 23 is also transmitted to the stopper 22 of the coupling mechanism unit 20 via the timing belt 19.

  However, the stopper 22 and the timing belt 19 are connected in a loosely fitted state. For this reason, the vibration transmitted to the stopper 22 is not transmitted to the connecting portion 21 and the influence on the carriage 15 on which the image sensor 14 is mounted can be prevented. It is possible to prevent the reading image from being disturbed when the vibration of the stepping motor 23 is generated.

  An example of the stepping motor 23 used in the scanner device 100 will be described with reference to FIG.

  The stepping motor 23 causes a current to flow through the coils of the stators 232 and 233 to generate a magnetic force, and attracts and rotates the rotor 234. The stator 232 is composed of X and x coils, and the stator 233 is composed of Y and y coils. A power source + DC is sequentially supplied to each coil from an intermediate tap of each coil so that the angle determined in one step is rotated. For example, the stepping motor 23 can be rotated by 1.8 degrees in one step and can be rotated once by 200 pulses.

  FIG. 7 shows an example of a drive signal for the stepping motor 23. FIG. 6 shows an example of a driving method in which one-phase excitation and two-phase excitation are alternately repeated. As a result, the pulse width of each phase is 3, and the driving method is such that excitation is performed by shifting by 2 pulses from the next phase. In the case of this drive, since the angle of rotation for each pulse is halved compared to the one-phase excitation and the two-phase excitation, fine motor control can be realized.

  The stepping motor 23 is controlled to rotate by the control unit 28 of the scanner device 100 (see FIG. 1). The RGB data acquired by the image sensor 14 is sent to the control unit 28. The control unit 28 controls the operation of the scanner device 100 according to a command from a data processing unit (not shown), and transmits data acquired by the scanner device 100 to the data processing unit.

  By the way, the stepping motor 23 rotates finely by repeating energization and stopping of a predetermined pulse at the rotation angle. Depending on the stop position (rotation angle) at that time, there is a characteristic of rotating slightly in the reverse direction without stopping at the position where the energization is stopped.

  FIG. 8 is a diagram for explaining the movement of the slide portion 211 and the fitting piece 222 accompanying the driving of the timing belt 19 when the rotation of the stepping motor 23 is reversed.

  FIG. 8A shows that the stepping motor 23 is in a non-driven state. In this case, the fitting piece 222 is located between the movable pieces 211f and 211r of the U-shaped slide portion 211, and the stopper 22 is at the position P1 in the sub-scanning direction.

  FIG. 8B shows a state where the stepping motor 23 is driven and the movable piece 211 f of the slide portion 211 is moved against the fitting piece 222. As a result, the stopper 22 moves from P1 to P2 in the sub-scanning direction.

  FIG. 8C shows a state in which the stepping motor 23 has stopped and returned by a distance L1 due to reverse rotation. At this time, the timing belt 19 is also driven in the reverse direction. Thereby, the stopper 22 moves to a position where the sub-scanning direction returns from P2 to P3.

  FIG. 8D shows a state in which the stepping motor 23 is driven again and the movable piece 211 f of the slide portion 211 is moved against the fitting piece 222. As a result, the stopper 22 moves from P3 to P4 in the sub-scanning direction.

  The carriage 15 is conveyed in the sub-scanning direction according to the procedure shown in FIGS. Note that the operation shown in FIG. 8C caused by the reverse rotation of the stepping motor 23 does not occur in every stop operation of the stepping motor 23.

  Incidentally, as shown in FIG. 8C, the width w1 of the bottom surface 213 and the width w2 of the fitting piece 222 with respect to the return amount L1 of the stepping motor 23 are designed with clearance. That is, w1-w2 is designed to be equal to or longer than the distance L2 ((w1-w2) / 2-L1) between the fitting piece 222 and the movable piece 211r.

  In this way, the width w1 of the bottom surface 213 and the width w2 of the fitting piece 222 are made different so that the distance L2 is secured with respect to the return distance L1 of the stepping motor 23. Thereby, the movable piece 211r and the fitting piece 222 do not collide with each other, and the influence of vibration of the stepping motor 23 can be suppressed.

  In the above conveying method, the carriage 15 is displaced by the clearance. However, since the scanning direction that requires positional accuracy is always only in one direction and means for correcting the reference position of the carriage 15 for each scanning is used in combination, the displacement of the reciprocating motion does not affect the function. Can be.

Further, the clearance between the stopper 22 of the timing belt 19 and the connecting portion 21 of the carriage 15 is not limited to any size. As a clearance, it is necessary to absorb at least the magnitude of vibration of the drive system of the apparatus.

  The required clearance will be described by taking the case where the vibration system of the carriage 15 is a linear vibration as an example. Here, the maximum amplitude amount of the vibration system is obtained by measuring the frequency and acceleration and converting them into a displacement amount D of the following equation.

D = A / (2πf) ²
Where D is the displacement (m), A is the maximum acceleration (m / s ² ), and f is the frequency (Hz).
If a clearance larger than the maximum amplitude is provided, vibration in the system can be released. In short, the clearance relationship between the slide portion 211 integrally formed with the carriage 15 and the stopper 22 attached to the timing belt 19 may be satisfied by w1−w2 ≧ D (see FIG. 8C). The displacement amount D corresponds to the distance L1 that the stepping motor 23 has returned by reverse rotation.

  Here, a specific example will be described.

As shown in FIG. 9, when the vibration acceleration of 40.5 Hz is 4.54 m / s ² from the vibration measurement result of the carriage 15, the result of the following expression is obtained by calculating with the above formula.

D = 4.54 / (2 × 3.14 × 40.5)
= 7.01 × 10 ⁻⁵ (m) = 0.07 (mm)
In this vibration system, the minimum clearance is 0.07 mm.

  In this way, by optimizing the clearance between the stopper 22 attached to the timing belt 19 and the slide portion 211 formed integrally with the carriage 15, transmission of any vibration can be suppressed, and abnormal noise can be suppressed. In addition, the occurrence of abnormal images such as image blur can be suppressed.

  In this embodiment, the coupling mechanism portion 20 that couples the timing belt 19 and the carriage 15 is provided with a certain clearance. As a result, it is possible to suppress the transmission of vibrations and to suppress the occurrence of abnormal images such as abnormal sounds and image blurring.

(Second Embodiment)
10 to 12 are perspective views for explaining a second embodiment according to the image reading apparatus. FIG. 10 is a perspective view corresponding to FIG. 3 of the first embodiment. FIG. 11 is an enlarged perspective view of the main part of FIG. FIG. 12 is a perspective view showing a state before the connection mechanism 200 is connected. In addition, the same code | symbol is attached | subjected to the component same as the said embodiment, and it demonstrates centering on a different part here.

  The connection mechanism unit 200 includes a connection unit 210 and a stopper 220. In the connecting portion 210, holding portions 215 and 216 are integrally formed with the carriage 15 on both sides of the slide portion 211. Claw portions 217 and 218 are formed at the open ends of the holding portions 215 and 216.

  The stopper 220 is integrally formed with guide portions 225 and 226 for guiding the width direction of the timing belt 19 on both sides of the ribs 223 and 224 of the holding portion 221. The guide portions 225 and 226 are formed with engaging portions 227 and 228 opposite to the ribs 223 and 224, respectively. Guide portions 229 and 230 to which the claw portions 217 and 218 can be locked are formed on the back surfaces of the guide portions 225 and 226.

  Here, the connection of the carriage 15 and the timing belt 19 by the engagement between the connecting portion 210 of the connecting mechanism portion 200 and the stopper 220 will be described.

The ribs 223 and 224 of the holding portion 221 of the stopper 220 are engaged with the valley portions 191 of the belt tooth surface of the timing belt 19 . At this time, the claw portions 217 and 218 of the holding portions 215 and 216 warp so as to escape from the timing belt 19. Then, in a state where the ribs 223 and 224 and the valley portion 191 of the belt tooth surface are engaged, the warpage of the claw portions 217 and 218 is returned and the timing belt 19 is engaged with the stopper 220 .

  Next, the fitting piece 222 of the stopper 220 is fitted into the fitting portion 214 of the connecting portion 210. At this time, the holding portions 215 and 216 are warped, the guide portions 229 and 230 of the stopper 220 are overcome, and the claw portions 217 and 218 are engaged with the guide portions 229 and 230. The guide portions 229 and 230 and the claw portions 217 and 218 are related to each other with dimensions that allow the guide portions 229 and 230 to slide on the claw portions 217 and 218.

  The stopper 220 of the coupling mechanism part 200 in which the coupling part 210 and the stopper 220 are engaged with each other is the fitting part 214 by the difference (w1-w2) between the width w1 of the coupling part 210 of the coupling mechanism part 200 and the width w2 of the stopper 220. Can be moved.

  Therefore, the coupling mechanism 200 that couples the timing belt 19 and the carriage 15 has a structure with a certain clearance. As a result, it is possible to suppress the transmission of vibration and to suppress the occurrence of abnormal images such as abnormal sounds and image blurring.

  Furthermore, as shown in FIG. 11, the carriage 15 may be acted on by the forces in the rotational directions indicated by the arrows Rr and Rl in the drawing when the timing belt 19 is driven. With respect to the rotation of the arrow Rr, the guide portion 229 hits the holding portion 215 to prevent the rotational force. With respect to the rotation of the arrow Rl, the guide portion 230 comes into contact with the holding portion 216 to prevent the rotational force.

  Thereby, the rotational force can be distributed as compared with the case where the rotational force of the carriage 15 directly acts on the slide portion 211 and the fitting piece 222. For this reason, it becomes possible to prevent the slide part 211 and the fitting piece 222 from being damaged.

This embodiment, the coupling mechanism 20 0 for connecting the timing belt 19 and the carriage 15, by providing a certain clearance, to suppress the transmission of vibrations, suppress generation of abnormal images such as abnormal sound and image blurring be able to. Furthermore, it is possible to improve the strength against mechanical action exerted on the coupling mechanism unit 20 0.

  It is not limited to the above-described embodiments. For example, the fitting portion 214 of the connecting portion 21 is an area surrounded by the slide portion 211 and the support portion 212, but a cylindrical connecting portion having the inside as a fitting portion is integrally formed with the carriage 15. Also good.

  Although several embodiments have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, combinations, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 100 Scanner apparatus 14 Image sensor 15 Carriage 16 Guide shaft 17 Guide rail 18 Slider 19 Timing belt 191 Valley part 20,200 of a belt tooth surface Connection mechanism part 21,210 Connection part 211 Slide part 211f, 211r Movable piece 212 Support part 213 Bottom part 214 fitting parts 215, 216 holding parts 217, 218 claw parts 22, 220 stopper 221 clamping part 222 fitting pieces 223, 224 ribs 225, 226 guide parts 227, 228 engaging parts 229, 230 guide part 23 stepping motor 24 drive Gear 25 Driven gear 26 Drive pulley 27 Idler pulley 28 Control unit

Claims (4)

An image sensor that reads the document;
A carriage mounted with the image sensor and reciprocatingly conveyed from a home position;
A guide portion for guiding reciprocal conveyance of the carriage;
A stepping motor for driving reciprocating conveyance of the carriage;
A timing belt for transmitting a driving force from the stepping motor ;
Formed prior Symbol carriage, and composed of a stopper having a connecting portion, and the fitting piece is attached to the timing belt having a fitting portion with a movable piece in the moving direction before and after the carriage, said fitting piece the fitted into the fitting portion, and a coupling mechanism for conveying abutted against the fitting piece to the movable piece in the traveling direction by the driving of the carriage said stepping motor
When the timing belt is driven in the reverse direction due to the reverse rotation of the stepping motor, the coupling mechanism portion has a clearance that prevents the fitting piece from contacting the movable piece on the reverse direction side. An image reading apparatus provided between the movable piece and the fitting piece . The fitting part of the connecting part is constituted by a slide part having a concave cross section and a support part arranged in a concave open part of the slide part,
The image reading apparatus according to claim 1, wherein the fitting piece of the connecting portion is integrally formed with the stopper attached to the timing belt . Before hear Riaran scan is the width of the fitting pieces, and narrower than the movable pieces in the moving direction before and after the carriage, the image reading apparatus according to claim 1. The clearance scan has the vibration system of the carriage, and the above displacement amount calculated from the relationship between a frequency and acceleration, the image reading apparatus according to one of claims.

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