JP2008052269A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain accurate position control through drive control for a drive source even if the transmission ratio of a drive transmission part is changed by the switching of a gear in the case where drive force from a single drive source is transmitted using a speed change mechanism when driving the reading part of the image reading apparatus in order to move it for scanning. <P>SOLUTION: The speed change mechanism is switched while the drive of the drive source is stopped. A detector is provided for checking that the speed change mechanism has been switched. After the switching of the speed change mechanism is checked by the detector, the position of the reading part is controlled through drive control for the drive source based on a transmission ratio after switching. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image reading apparatus and a reading method for reading an image of a document placed on a document table.

  A conventional image reading apparatus will be described with reference to the drawings. FIG. 9 shows a schematic diagram of a conventional color image reading apparatus (see Patent Document 1).

  In the conventional image reading apparatus, the image on the original 96 is read by causing the reading unit 91 to scan in parallel with the original table glass 94. A linear image sensor is incorporated in the reading unit 91. A timing belt 93 that transmits power from a stepping motor 92 that is a scanning drive source is fixed to the reading unit 91.

  By the forward / reverse rotation of the stepping motor 92, the reading unit 201 can perform reciprocal scanning within the range of the platen glass 94. When the image reading device reads an image on the document 96, the reading unit is moved and scanned by driving the stepping motor 92 at a driving speed corresponding to an arbitrary resolution.

In general, when reading an image on the document 96, the minimum value of the time required for exposure to obtain information of one line of the document is determined by the sensitivity and light quantity of the image sensor. The maximum value of the moving speed of the reading unit can be determined from the minimum value of time required for exposure. When reading at low resolution, the moving speed of the reading unit can be increased, and when reading at high resolution, the moving speed of the reading unit needs to be reduced. Actually, the upper limit value of the moving speed is subject to various restrictions such as the processing time of electric signals.
JP 2000-13564 A

  A stepping motor with easy position control is used to drive the moving scanning of the reading unit of the image reading apparatus, but rotation at a speed corresponding to the reading resolution is required. In the case of an image reading apparatus based on an environment with limited power supply such as USB bus power, a motor with a narrow speed range must be used. In particular, in a high-resolution image reading apparatus, it is difficult to scan at a reading speed corresponding to various resolutions within a speed range of a single drive motor. For this purpose, a speed change mechanism such as a gear change may be used. When the driving force from one drive source is transmitted using a speed change mechanism such as gear switching, the gear state changes at the time of switching, so accurate position control cannot be performed due to the number of steps by a stepping motor or the like. .

  In order to solve the above problems, an image reading apparatus of the present invention has the following configuration.

  An image reading apparatus that scans a reading unit by a scanning drive unit to read an image of an original, and is provided in a driving source and a transmission unit that transmits a driving force from the driving source to the scanning driving unit. A speed change mechanism that selectively connects the second joint to switch the transmission ratio of the transmission portion, a selection portion that biases in a direction in which one of the first and second joints is connected, and a second A detector that detects connection of a joint; and a controller that controls a scanning position of the reading unit based on a drive control signal to the drive source, the controller from the first joint to the second joint. After switching the selection at the selection unit, after the connection of the second joint is detected by the detector, control of the scanning position of the reading unit based on the transmission ratio transmitted by the second joint is started. It is characterized by doing.

  According to the present invention, since the speed change mechanism is used for the scanning drive force transmission portion of the image reading apparatus, a wide range of speeds can be selected according to the reading resolution even when a motor with a narrow speed range is used. Accurate position control can be performed by grasping the state of time with a detector.

  FIG. 1 is a schematic diagram of a color image reading apparatus according to the first embodiment.

  As shown in FIG. 1, an original is set on an original platen glass 2 mounted on the upper surface of the apparatus main body 1, and a contact image sensor 3 is scanned in parallel with the original platen glass 2, whereby an image described on the original Read. The contact image sensor 3 includes a three-color LED, which is a light source for irradiating a document, a rod lens array that forms an image of reflected light from the document on a light receiving element of the image sensor, and an image sensor. And constitutes a reading unit.

  The contact image sensor 3 is supported on a carriage 5 that slides on a guide shaft 4 fixed to the apparatus main body 1. A timing belt 15 that transmits power to the reading unit as a scanning drive unit is fixed to the carriage 5 via a gear drive train 16 as a transmission unit from a motor 17 that is a drive source. The gear drive train 16 includes a speed change mechanism by changing gears. A flexible cable (not shown) for electrical input / output of the contact image sensor 3 is connected to the contact image sensor 3 on one side and connected to the control board (not shown) of the main body of the image reader. It is connected.

  In addition to the above, the image reading apparatus includes an electrical component including a control board and a power source. These components are arranged in the apparatus main body 1 that fixedly supports the platen glass.

  A document cover 6 as a cover member for pressing the document onto the glass is mounted on the document table glass 2 through a hinge 7 so as to be openable and closable. A document pressing sheet 8 is affixed to the surface of the document cover inner surface facing the document table glass 2.

  FIG. 2 is a block diagram showing an electrical configuration of an image input apparatus that implements the image processing method of the present embodiment. The contact image sensor 3 includes a light source 31 that is a light source for reflection originals and an image sensor 32. The home position sensor 18 connected to the system controller 20 aligns the initial position of the motor 17 that is a stepping motor that drives the carriage 5 for scanning. The light source 31 is controlled by the system controller 20.

  The image sensor 32 is controlled by the system controller 20, and the signal output from the image sensor 32 is processed by the analog processing circuit 21, converted to a digital signal by the A / D conversion circuit 22, and processed by the image processing circuit 23. And stored in the buffer memory 24. The system controller 20, the buffer memory 24, and the interface 25 are connected, and mutual data communication is possible. The signal stored in the buffer memory 24 is sent to the external device 26 through the interface 25 as image data.

  The system controller 20 is connected to the motor 17, the gear change motor 114, and the gear change sensor 116 for control. The gear change sensor 116 detects the gear connection state, and the system controller 20 controls the position of the carriage 5 using the motor 17.

  Next, the gear drive train 16 as a transmission unit will be described. Among these, as a speed change mechanism, two joint portions are switched.

  The reduction ratio, which is the ratio of the number of revolutions of the motor 17 and the number of revolutions of the pulley 107c that drives the timing belt, is 1/15 for low resolution for high speed movement and 1/60 for high resolution for low speed movement. These are transmission ratios that transmit driving force from the motor 17 to the moving scanning of the reading unit. That is, the amount of advance of the carriage 5 by one pulse of the motor 17 that is a stepping motor by a gear drive train for low resolution is four pulses of the motor 17 that is a stepping motor by a gear drive train for high resolution. . In the high resolution gear train, reading can be performed four times finer in the moving direction of the carriage 5.

  In this embodiment, it is assumed that an image is read at a maximum of 4800 scanning lines per inch. Accordingly, the distance traveled by one pulse of the motor 17 when a high-resolution gear with a large reduction ratio is used is the length of one pixel when an image is read at 4800 dpi. When this gear drive train is used, 2 pulses are 2400 dpi and 3 pulses are 1600 dpi.

  Also, the low resolution gear drive train with a small reduction ratio is 1/4 times the gear ratio of the high resolution gear drive train with a large reduction ratio. The distance traveled by one pulse of the motor 17 when a gear drive train with a small reduction ratio is used is the length of one pixel when an image is read at 1200 dpi.

  3, 4 and 5 are general views of the gear drive train. FIG. 6 is a cross-sectional view taken along line A-A ′ in FIG. 3.

  The gear drive trains with a small reduction ratio are the drive gear 17a, the gear 101, the idler gear 102, the gear 103, the gear 104, the gear 105, and the gear 107a on the motor 17. The gear drive train having a large reduction ratio is common to the drive gear 17a to the gear 104 on the motor 17, and further includes the gear 106 and the gear 107b.

  The two gear drive trains have different gear ratios at the final stage, the gear ratio between the gear 105 and the gear 107a is 2, and the gear ratio between the gear 106 and the gear 107b is ½.

  The gear 104, the gear 105, and the gear 106 are coaxial with the shaft 130, and the gear 104 is always meshed with the gear 103 and can move in the axial direction (vertical direction in FIG. 6). A gear 103a on the small diameter side 103 has a thickness corresponding to the movement of the gear 104 in the axial direction.

  The gear 105 and the gear 106 are gears whose positions in the axial direction are fixed. The gear 105 is always meshed with the gear 107a and the gear 106 is meshed with the gear 107b.

  As shown in FIG. 6, joint portions 104 a and 106 a for coupling each other are provided on the upper surface of the gear 104 and the lower surface of the gear 106. Similarly, joints 104b and 105a are provided on the lower surface of the gear 104 and the upper surface of the gear 105 to couple each other. The shaft of the gear 104 serves as an output shaft that transmits the driving force from the motor 17 to one of the two joint portions.

  In this embodiment, this joint portion is made of an internal gear and a spur gear having the same number of teeth, 104a and 104b are internal gears, and 105a and 106a are spur gears (tooth shape is not shown). The spur gears are engaged with each other by inserting a spur gear into the internal gear, and two parts are coupled to each other.

  In addition, a change arm 110 is disposed on the same axis as the shaft 130 between the gear 104 and the gear 105. The gear 104 is urged against the lower change arm 110 of FIG. The change arm is urged upward in FIG. 6 by the spring 112, and is further constantly urged by the gear change wheel 115 along the shaft 131.

  In the free state, the resultant force of the springs 112 and 113 is greater than the force of the spring 111, and the gear 104 is coupled to the gear 106 by the joint portions 104a and 106a.

  Cam surfaces 110 a and 115 a are provided on the change arm 110 and the gear change wheel 115, respectively, on the surface on which the change arm 110 is pressed and urged against the gear change wheel 115. By rotating the change motor 114, a gear change worm gear 114a, which is a drive gear provided on the change motor 114, rotates the gear change wheel 115. Thereby, the height of the change arm 110 can be changed by pushing down the cam surface 110a while the helical cam surface 115a is engaged. By selecting the rotation direction of the change motor 114 by the selection unit configured as described above, it is possible to select which joint unit is to be connected. Since the gear 104 is biased to the change arm 110 by the spring 111 in the downward direction in FIG. 6, the gear 104 moves in the downward direction in FIG. 6 as the change arm 110 moves. In FIG. 3, the joint portion 104b of the gear 104 and the joint portion 105a of the gear 105 are coupled in a state where the change arm 110 and the gear 104 are on the lower side of FIG. A column is selected. In FIG. 4, the joint 104a of the gear 104 and the joint 106a of the gear 106 are coupled with the change arm 110 and the gear 104 in the axial direction of the shaft 130 in FIG. A drive train is selected.

  The position of the change arm 110 in the axial direction can be detected by the gear change sensor 116. When the joint 104a of the gear 104 and the joint 106a of the gear 106 are coupled, the gear change sensor 116 detects the gear change by the light shielding plate 116a provided on the change arm 110 shielding the photo interrupter 116b of the fixed portion. Configure the detector to detect.

  The gear 107a, the gear 107b, and the pulley 107c are coupled and rotate together in the forward and reverse directions. A timing belt 15 is attached to the pulley 107c, and a scanning drive unit is configured to transmit the driving force from the motor 17 to the scanning drive of the reading unit by transmitting the rotation of the pulley 107c to the carriage 5.

A transition from a state of operating with a gear with a small reduction ratio to a state of operating with a gear with a large reduction ratio will be described. In the state of operating with a gear having a small reduction ratio, the joint portions 104 b and 105 a are coupled, and the power of the gear 104 is transmitted to the gear 105. At this time, the photo interrupter of the gear change sensor 116 is not shielded from light.
1) First, the home position of the carriage 5 is detected, and a control counter for the motor 17 in the system controller 20 is initialized. Thereby, the scanning position of the reading unit is initialized. The home position is on the upstream side of the scanning with respect to the document, and is detected while moving the carriage 5 in the scanning direction by the rotation of the motor 17 in the forward direction.
2) Next, the gear with the smallest reduction ratio is moved to the position before the reading start position, and the motor 17 is stopped.
3) When a gear having a large reduction ratio is selected, the gear change motor 114 is rotated forward, and the gear change wheel 115 is rotated in the direction b in FIG. As a result, the engagement surface between the spiral cam surface 115a and the cam surface 110a gradually shifts, the change arm moves upward in FIG. 6, and the gear 104 also moves in the axial direction upward in FIG. . As the gear 104 moves, the coupling portions 104b and 105a are uncoupled.
4) When the gear change wheel 115 is further rotated in the same direction, the lower surface of the joint portion 104a collides with the upper surface of 106a. When the gear teeth are well in phase, the joints 104a and 106a are well coupled, but usually collide because they are out of phase.
5) The gear change wheel 115 is further rotated in the same direction to a position where the joint portions 104a and 106a can be sufficiently coupled when the phases are in phase. Usually, since the phases are not matched, the surface where the spiral cam surface 115a and the cam surface 110a are engaged is separated, and the cam surface 115a is separated upward. At this time, if the phases match, the photo interrupter of the gear change sensor 116 is shielded from light, a gear change to a gear with a large reduction ratio is detected, and the gear change ends.
6) When the gear change cannot be detected by the gear change sensor 116, the lower surface of the joint 104a and the upper surface of 106a collide with each other. The transmission gear 104 is biased upward via the change arm 110 by the upward resultant force of the springs 112 and 113 that is greater than the downward force of the spring 111. Here, the rotation of the motor 17 in the positive direction is resumed.
7) When the joint portion 104a rotates with the lower surface of the joint portion 104a in contact with the upper surface of 106a and the gear teeth are in phase, the transmission gear 104 moves upward, and the transmission gear 104 and the first object A gear 106 as a transmission gear is coupled by joint portions 104a and 106a. At this time, the gear change is detected by the gear change sensor 116 and the gear change is completed.

  Thereafter, the rotation of the motor 17 is transmitted to 107c via gears 106 and 107b. At this time, 105 rotates idly by 107a rotating integrally with 107b and 107c.

  Conversely, when selecting a gear with a small reduction ratio, the rotation of the motor 17 is first stopped. Next, the gear change motor is rotated in the reverse direction, and the gear change wheel 115 rotates in the direction a in FIG. As a result, when the change arm 110 moves downward in FIG. 6, the gear 104 moves in the axial direction downward in FIG. 6 due to the force of the spring 111, and the coupling between the joint portions 104 a and 106 a is released. At this time, the light interruption of the photo interrupter of the gear change sensor 116 is released, but the joint portions 104b and 105a are not yet coupled. As the gear change wheel 115 further rotates in the direction a, the change arm 110 moves downward. Since the phase is not normally matched, the lower surface of the joint 104b and the upper surface of 105a collide. With further rotation of the gear change wheel 115 in the direction a, the change arm 110 moves downward, and moves to a position where the joint portions 104b and 105a can be sufficiently coupled when the phases are matched. Thereafter, when the motor 17 is rotated, the joint portion 104a rotates in a state where the lower surface of the joint portion 104b and the upper surface of 105a are in contact with each other. When the gear teeth are in phase, the transmission gear is moved downward by the force of the spring 111, and the joint portions 104b and 105a are coupled. Thereafter, the rotation of the motor 17 is transmitted to the 107c through the gears 105 and 107a. At this time, 106 rotates idly by 107b rotating integrally with 107a and 107c.

  Thus, changing the axial position of the change arm 110 also changes the axial position of the gear 104, and the two gear drive trains can be selectively used by changing the axial position of the gear 104. it can.

Next, the operation of the apparatus in this embodiment will be described separately when reading at high resolution and when reading at low resolution.
First, a case where a document is read at a low resolution will be described.

  First, at the initial position of the carriage 5, it is confirmed by the gear change sensor 116 that the gear 104 is coupled to the gear 105. Then, the motor 17 is rotated to move from the initial position to the reading start position. Since the speed of movement of the carriage 5 to the reading position can be increased, a low-resolution gear drive train with a small reduction ratio is used. As it is, reading is started using a gear drive train with a small reduction ratio. After the reading is completed, the motor 17 is rotated in the reverse direction using the gear drive train on the low resolution side as it is, and the carriage is moved to the initial position.

Next, a case where a document is read at a high resolution will be described.
First, it is confirmed that the gear 104 is coupled to the gear 105 by the gear change sensor 116 at the initial position of the carriage 5. Then, the motor 17 is rotated to move from the initial position to the reading start position. At this time, a low-resolution gear drive train with a small reduction ratio is used as in the low-resolution reading. Here, the drive control signal of the motor 17 is controlled by the number of pulses used for low resolution control.

  Thereafter, the motor 17 is rotated forward, the carriage 5 is moved to the reading start position which is the switching position, and then temporarily stopped.

  Thereafter, the gear change motor 114 is reversely rotated by the gear change sensor 116 until the gear 104 is confirmed to be coupled to the gear 106. The gear change wheel 115 is rotated in the direction of FIG. As a result, the change arm moves in the upward direction in FIG. 6, and the gear 104 is moved in the axial direction in the upward direction in FIG. 6 in synchronization therewith. The gear 104 is coupled with the gear 106, and the coupling with the gear 105 is released. Thereafter, the motor 17 is rotated to start reading with high resolution. After the reading is completed, the gear 104 is switched to the low resolution side, the motor 17 is rotated in the reverse direction, and the carriage 5 is moved to the initial position.

  FIG. 7 is a schematic diagram of the speed range of a gear drive train with one different reduction ratio. According to this figure, the speed range A of the gear drive train having a reduction ratio of 1/15 and C having the reduction ratio of 1/60 can be selectively used as in this embodiment, and therefore the usable speed range is A + C. It becomes the range. In contrast, for example, a single gear drive train with a reduction ratio of 1/30 between 1/15 and 1/60 has a very small speed range.

Next, an image reading apparatus according to a second embodiment of the present invention will be described.
In the image reading apparatus of the second embodiment, when switching from the low resolution reading gear to the high resolution reading gear, the low resolution gear is continuously connected until the high resolution gear is connected. It has become the composition which is. For this reason, after selecting the switching from the low resolution gear to the high resolution gear, the carriage moves when the motor 17 is driven even before the high resolution gear is connected. The rest is the same as in the first embodiment.

  The operation of the second embodiment will be described below with reference to the flowchart of FIG.

  In step 1, the gear switching sensor 116 checks whether the gear is connected for high resolution or low resolution, and if the high resolution is connected, the gear change motor 114 is rotated so that the connection is changed for low resolution. Let

  In step 2, the initial position of the carriage is detected by a home position sensor (not shown), and the initial position of position control is adjusted.

In step 3, it moves to the switching position before the reading position. Instead of moving to the exact reading position, the distance L when moving to the gear change is stopped in anticipation.
In step 4, the gear change motor 114 is rotated to switch to a high resolution connection.
In step 5, the motor 17 is rotated by a small step.

In step 6, the gear change sensor 116 is checked, and if high resolution is connected, the process proceeds to step 7; otherwise, the process proceeds to step 5.
In step 7, the distance traveled by the carriage for gear switching can be determined according to how many step feeds in step 5 are performed. In step 3, the distance is stopped by a distance L. If the distance moved in step 5 is subtracted, the remaining moving distance to the reading position can be found. As a result, the number of pulses as a drive control signal of the motor 17 is controlled to move the remaining moving distance.
In step 8, the image is read.
In step 9, the gear change motor 114 is rotated to return the gear to the low resolution.

In step 10, the motor 17 is rotated back to the initial position. At this time, when the rotation of the carriage drive motor is started, the gear is switched from high resolution to low resolution.
In step 11, when the carriage is detected by the home position sensor, the carriage drive motor is decelerated and stopped.

  In the above description, a stepping motor is used, but a DC motor with a rotary encoder can also be used. In this case, the drive control of the DC motor is performed based on the output pulse of the rotary encoder. In addition to the contact image sensor, a reduction optical system composed of a plurality of mirrors, lenses, and line image sensors that fold the optical path can be used as the reading unit.

1 is a perspective view of an image reading apparatus according to an embodiment of the present invention with a document cover opened. FIG. Block diagram for describing an embodiment of the present invention Gear drive train When selecting a gear drive train with a small reduction ratio Gear drive train When selecting a gear drive train with a large reduction ratio Schematic diagram showing the configuration of the gear drive train Cross section of transmission mechanism Schematic diagram of speed range Flowchart for explaining the embodiment of the present invention Conventional image reading apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reader main body 3 Contact image sensor 15 Timing belt 16 Gear drive train 17 Motor 20 System controller 104a, 106a, 104b, 105a Joint part 114 Gear change motor 115 Gear change wheel 110 Change arm 116 Gear change sensor

Claims (11)

An image reading apparatus that scans a reading unit by a scanning drive unit and reads an image of a document,
A driving source;
A transmission mechanism that is provided in a transmission unit that transmits the driving force from the drive source to the scanning drive unit, and that selectively connects the first and second joints to switch the transmission ratio of the transmission unit;
A selector that biases in a direction in which one of the first and second joints is connected;
A detector for detecting the connection of the second joint;
A controller for controlling a scanning position of the reading unit by a drive control signal to the drive source,
The controller, after switching the selection by the selection unit from the first joint to the second joint, after detecting the connection of the second joint by the detector, Control of the scanning position of the reading unit based on the transmission ratio to be transmitted is started. The image reading apparatus according to claim 1,
The first joint has a first member and a second member;
The second joint has a third member and a fourth member;
The transmission unit transmits a driving force from the first member to the scanning drive unit, and transmits a driving force from the fourth member to the scanning drive unit, and the first transmission unit. And a second transmission part having a different transmission ratio,
The selection unit selectively biases an output shaft coupled with the second member and the third member and outputting a driving force transmitted from the first driving source in the axial direction. The image reading apparatus according to claim 1,
The connection of the first joint is released when the selection in the selection unit is switched from the first joint to the second joint;
The controller does not scan the scanning drive unit with the drive control signal to the drive source until the detector detects the connection of the second joint after switching the selection by the selection unit. Thus, the scanning position of the reading unit is controlled. The image reading apparatus according to claim 1,
The first connection is continued until the second joint is connected when the selection in the selection unit is switched from the first joint to the second joint,
The controller switches the first drive by the drive control signal to the drive source until the detector detects the connection of the second joint after switching the selection by the selection unit. The scanning position of the reading unit is controlled by being driven by the transmission unit. The image reading apparatus according to claim 1,
It has a home position sensor that detects the home position,
A transmission ratio in the first transmission unit is larger than a transmission ratio in the second transmission unit;
The controller performs alignment at the home position in a state where the first joint is connected. The image reading apparatus according to claim 5,
The controller moves the reading unit from the home position to the switching position in a state where the first joint is connected, and stops the driving source.
After switching to the second joint by the selection unit at the switching position, driving of the drive source is started, and the image of the original is read by the reading unit. The image reading apparatus according to claim 5,
The controller performs control to switch the first joint to the first joint by the selection unit after the reading of the image of the original by the reading unit, and then return the reading unit to the home position. The image reading apparatus according to claim 1,
The drive source is a stepping motor, and the position of the reading unit is controlled using a drive pulse of the stepping motor as the drive control signal. The image reading apparatus according to claim 1,
The drive source is a DC motor, and the DC motor has a rotary encoder, and controls the position of the reading unit using an output pulse of the rotary encoder as the drive control signal. The image reading apparatus according to claim 2,
The selection unit includes a worm gear driven by a switching motor;
A cam connected to a gear driven by the worm gear;
A switching arm that engages with the cam and moves the output shaft in the axial direction;
A spring that biases the output shaft toward the switching arm. A method for controlling an image reading apparatus that scans a reading unit by a scanning drive unit to read an image of an original, wherein the image reading device is a transmission mechanism that transmits a driving force from a drive source to the scanning drive unit. The transmission mechanism selectively selects a first and second joint for selectively connecting a driving force from the driving source and transmitting the driving force to the driving unit; and a selection for selecting the first and second joints. And a detector for detecting the connection of the second joint, and the control method includes:
A switching step of stopping driving of the drive source and switching the selection from the first to the second joint in the selection unit;
A detection step of detecting connection of the second joint by the detector after the switching step;
A position control step of starting control of the scanning position of the reading unit by a drive control signal of the drive source based on transmission of drive force at the second joint after detection in the detection step. It is characterized by.

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