JP2007216472A - Image input device and reference position detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly and accurately set the reference position of a carriage in an image input device equipped with a carriage moving mechanism. <P>SOLUTION: The image input device has a control means to control the movement of the carriage and a holding back member to hold back the movement of the carriage. The carriage is moved at least twice to the holding member and the speed after the second movement is made slower than the initial movement speed. When the carriage moves to the holding back member and stops by a movement following the second, the position of the carriage is detected as the reference position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image input apparatus, and more particularly to a reference position detection technique for an image input apparatus having a mechanism for transporting a carriage.

  Patent Document 1 describes a flatbed scanner device that reads an image while moving a carriage on which an image sensor is mounted along a document table in the sub-scanning direction. The carriage is attached to a timing belt that is rotated by a motor, and moves as the motor rotates.

  Such a scanner device detects the reference position of the carriage in the initialization operation, and obtains the position of the carriage during the reading operation based on the reference position. For example, the carriage is moved to a wall (carriage restraining member) which is the movement limit, and is collided and stopped. Then, the position is detected as a reference position.

JP 2001-8029 A

  However, in the conventional scanner device, the accuracy of the reference position to be detected is not always sufficient. For example, in the conventional scanner device, the carriage collides against the wall at the same high speed as when reading an image. Therefore, the timing belt is easily pulled back, and a position deviated from the original reference position is detected as the reference position. .

  On the other hand, if the carriage is moved to the wall at a low speed from the beginning, it takes time to collide with the wall.

  The present invention has been made to solve the above-described problems, and an object thereof is to quickly and accurately detect the reference position of a carriage.

In order to solve the above problems, the first aspect of the present invention is:
An image input device comprising: a carriage; a control unit for controlling movement of the carriage; a stop member for stopping movement of the carriage; and a reference position detection unit for detecting a reference position of the carriage. I have. Then, the control means moves the carriage to the stop member at least twice and makes the speed of the second and subsequent movements slower than the speed of the first movement. The reference position detection means detects the reference position of the carriage after the carriage has moved to the stop member and stopped by the second and subsequent movements.

  The control means moves the carriage to the stop member at a first speed, then returns the position of the carriage by a predetermined distance, and moves the carriage to the stop member at a second speed slower than the first speed. It can be moved.

  The image input apparatus may include a motor, a timing belt for transmitting the driving force of the motor to the carriage, and an encoder for outputting the rotation amount of the motor. The control means periodically increases the drive current applied to the motor at a predetermined increase rate, and decreases the drive current applied to the motor at a predetermined decrease rate each time the encoder detects a predetermined rotation amount. When the current exceeds a predetermined threshold value, it can be determined that the carriage has moved to the stopping member.

  Hereinafter, an embodiment of the present invention will be described.

  FIG. 1 is a schematic configuration diagram of a scanner device 1 which is an example of an image input device of the present invention.

  The scanner device 1 is a so-called flatbed scanner device having a document table on the upper surface of a housing. The scanner device 1 scans a carriage 300 on which a CIS (Contact Image Sensor) type image sensor is mounted, and reads an image of a document fixed on a document platen of a transparent plate.

  The scanner device 1 includes a carriage 300 on which a light source and a CCD image sensor are mounted, a drive mechanism 20 that controls the reciprocation of the carriage 300, and a control unit 100 that controls the entire scanner device 1.

  Furthermore, a wall (carriage restraining member) 400 for determining the reference position of the carriage 300 is provided in the housing of the scanner device 1. As a result, the carriage 300 can move to the position of the wall 400 in the direction of the dotted arrow, but cannot move any more when it collides with the wall 400.

  The carriage 300 carries the light source and the image sensor in the sub-scanning direction. The carriage 300 is slidably locked to a guide shaft or the like parallel to the surface of the platen of the document table, and is pulled and reciprocated by a timing belt 224 rotated by the motor 200 of the drive mechanism 20.

  The drive mechanism 20 includes a motor 200 that is a DC motor, a motor driver 230 that controls the motor 200, a worm gear 220 joined to the output shaft of the motor 200, a spur gear 221 that meshes with the worm gear 220 and rotates at a predetermined reduction ratio. And a driven pulley 223 attached to the spur gear 221, a driven pulley 222 on the opposite side, and a timing belt 224 stretched between the pulleys 222 and 223 and attached with the carriage 300. With such a mechanism, when the motor 200 rotates in a predetermined direction, the carriage 300 moves in the direction of the dotted arrow (or the reverse direction).

  The motor driver 230 includes a power control transistor, and controls the drive current applied to the motor 200 by so-called PWM (Pulse Width Modulation) control that changes the ratio (duty ratio) of the ON period to the switching period of the transistor. . That is, by reducing the duty ratio, the ON time is shortened and the drive current is reduced. On the contrary, by increasing the duty ratio, the on-time is extended and the drive current is increased.

  In addition, an encoder 210 is attached to the motor 200. The encoder 210 outputs a pulse (encoder pulse) corresponding to the rotation amount of the motor 200.

  The control unit 100 includes a duty ratio generation unit 111, a wall determination unit 112, a motor control unit 120, and a timer 130 as characteristic function units. Each functional unit can be realized by software or hardware. A description of the functions related to the image reading operation, which is the original basic operation of the scanner device 1, is omitted.

  The duty ratio generation unit 111 periodically generates a duty ratio for driving the motor 200. Specifically, the duty ratio is increased at a predetermined increase rate for each interrupt of the timer 130. On the other hand, every time an encoder pulse output is received, the duty ratio is reduced at a predetermined reduction rate. Then, the adjusted duty ratio is sent to the motor control unit 120. Note that the rate of increase in duty ratio due to timer interruption and the rate of decrease in duty ratio due to encoder pulses are determined in advance corresponding to the moving speed of the carriage 300.

  With the duty ratio adjusted in this way, the carriage 300 can usually move at a constant speed. That is, as the duty ratio increases, the drive current to the motor 200 increases, the motor 200 rotates faster, and the carriage 300 tends to move at high speed. However, the fact that the motor 200 rotates quickly means that the encoder pulse is output in a short cycle, so that the duty ratio is reduced accordingly. Therefore, the duty ratio is kept substantially constant when averaged over a predetermined period, so that the carriage 300 moves at a constant speed.

  The wall determination unit 112 determines whether or not the carriage 300 has collided with the wall 400. If it is determined that the carriage 300 has collided with the wall 400, the position of the carriage 300 at that time is detected as a reference position. The collision with the wall 400 is performed by monitoring the duty ratio determined by the duty ratio generation unit 111 and determining whether the duty ratio exceeds a predetermined threshold.

  Note that the position of the carriage 300 at the time of image reading is represented by the number of encoder pulses counted from the reference position. Therefore, when the reference position is detected, the encoder pulse counter is initialized to zero.

  The motor control unit 120 acquires the duty ratio from the duty ratio generation unit 111 and sends it to the motor driver 230. Therefore, the motor control unit 120 includes a register for storing the duty ratio.

  Such a control unit 100 includes a CPU 110 that is a main control device, a ROM in which programs and the like are recorded, a RAM that temporarily stores data and the like as a main memory, and an interface that controls input and output with a host and the like. And a system bus serving as a communication path between the devices. In addition, you may be comprised by ASIC (Application Specific Integrated Circuit) designed so that each process may be performed exclusively.

<Description of operation>
Next, a characteristic operation of the scanner device 1 configured as described above will be described.

  The scanner device 1 configured as described above moves the carriage 300 to the wall 400 and collides with it in order to set the reference position in the initial operation. Then, the collision position is detected as a reference position.

  Here, the collision with the wall 400 is determined based on whether the duty ratio exceeds a predetermined threshold value (a value that does not exceed normal movement). However, when the threshold value is exceeded once, the reference position is not detected immediately, but the reference position is detected after the carriage 300 is made to collide with the wall 400 again at a lower speed than the speed at which it was first collided.

  FIG. 2 is a flowchart of the reference position detection process of the scanner device 1. FIG. 3 is a diagram showing how the carriage 300 moves in this processing in relation to the wall 400.

  The flow shown in FIG. 2 is started when the reference position needs to be detected as an initial operation before image reading such as when the power is turned on or when power saving is canceled.

  The wall determination unit 112 sets an initial moving speed V1 of the carriage 300. For example, the moving speed during normal image reading can be set to the moving speed V1. Then, the duty ratio generation unit 111 is instructed to generate a duty ratio for moving the carriage 300 in the direction of the wall 400 at the moving speed V1 (S11).

  In response to this, the duty ratio generator 111 generates a duty ratio for moving the carriage 300 in the direction of the wall 400 at the moving speed V1.

  FIG. 4A is a diagram showing the relationship between the time and the duty ratio in such a case. As shown in the figure, the duty ratio generation unit 111 increases the duty ratio at an increase rate corresponding to the moving speed V1 every time a timer interrupt is received. On the other hand, every time an encoder pulse is received, the duty ratio is decreased at a decrease rate corresponding to the moving speed V1.

  Thus, as shown in FIG. 3, the carriage 300 moves to the wall 400 at the moving speed V1.

  During this time, the wall determination unit 112 monitors the duty ratio set by the duty ratio generation unit 111 (S12), and determines whether or not the duty ratio exceeds a predetermined threshold (S13).

  The determination method here will be specifically described. When the carriage 300 moves to the wall 400 and is stopped by the wall 400, the rotation of the timing belt 224 is stopped. Then, the rotation of the motor 200 is also stopped. Then, the encoder pulse is not output. However, the duty ratio continues to increase due to the timer interrupt. Therefore, the wall determination unit 112 can determine the collision with the wall based on whether or not a predetermined threshold value is exceeded. The predetermined threshold value is set to a duty ratio that does not exceed the normal movement of the carriage 300.

  When the duty ratio exceeds a predetermined threshold (Y in S13), the wall determination unit 112 performs a process of rotating the motor 200 in the reverse direction and returning the position of the carriage 300 by a predetermined distance (see FIG. 3). That is, the wall determination unit 112 instructs the duty ratio generation unit 111 to generate a duty ratio for returning a predetermined distance.

  The predetermined distance here may be a distance sufficient for accelerating the carriage 300 to a moving speed V2 described later in the second movement of the carriage 300 described later. If it is too short, it cannot be accelerated to the speed V2, but if it is too long, the carriage 300 is moved uselessly. Such a distance is experimentally determined in advance.

  Next, the wall determination unit 112 determines the second moving speed V <b> 2 of the carriage 300. The moving speed V2 is set to be slower than the initial moving speed V1. The moving speed 2 can be set to an experimentally determined speed in order to accurately determine the reference position.

  Then, the duty ratio generating unit 111 is instructed to generate a duty ratio for moving the carriage 300 in the direction of the wall 400 at the moving speed V2 (S15).

  In response to this, the duty ratio generator 111 generates a duty ratio for moving the carriage 300 in the direction of the wall 400 at the moving speed V1.

  FIG. 4B is a diagram showing the relationship between the time and the duty ratio in such a case. As shown in the figure, the duty ratio generator 111 increases the duty ratio at an increase rate corresponding to the moving speed V2 every time a timer interrupt is received. On the other hand, every time an encoder pulse is received, the duty ratio is decreased at a decrease rate corresponding to the moving speed V2. As shown in FIG. 4B, since the moving speed V2 <the moving speed V1, the increase rate due to the timer interruption is smaller than the change in the duty ratio shown in FIG. Thus, as shown in FIG. 3, the carriage 300 moves to the wall 400 at a moving speed V2 that is slower than the moving speed V1.

  During this time, the wall determination unit 112 monitors the duty ratio set by the duty ratio generation unit 111 (S16), and determines whether the duty ratio exceeds the above-described predetermined threshold value (S17).

  When the duty ratio exceeds a predetermined threshold (Y in S17), the wall determination unit 112 detects the position where the carriage 300 is present as the reference position. That is, the encoder pulse counter is initialized to zero. Then, the reference position setting process ends.

  Thus, the reference position is set in the initial operation before image reading.

  When obtaining the position of the carriage 300 in the image reading operation, the control unit 1 uses the reference position set as described above. That is, the distance from a reference position at a certain position is represented by the number of encoder pulses counted while the carriage 300 moves from the reference position to that position.

  The embodiment of the present invention has been described above.

  According to the above embodiment, in detecting the reference position, the carriage 300 is first caused to collide with the wall 400 at a high speed (for example, a speed at the time of image reading). Then, it is made to collide with the wall 400 again at low speed, and the position is detected as a reference position. Thereby, it is possible to reduce a deviation in the detection of the reference position due to the mechanism of the drive mechanism. That is, when the carriage 300 is moved at a high speed, the motor torque is large, so that the influence of the pullback due to the elasticity of the timing belt is increased. However, the influence can be reduced by reducing the speed. The reference position can be set more accurately.

  The present invention is not limited to the above embodiment. The above embodiment can be variously modified.

  For example, the collision at low speed may be performed more than once. In addition, when performing a plurality of times, the speed may be set slower each time the number is repeated. When the detected reference position no longer changes (for example, when the encode pulse counted when the position is returned after the collision is equal to the encode pulse until the next collision), the reference position setting process is performed. You may make it complete | finish. In this way, the reference position can be detected with higher accuracy.

  The present invention is not limited to a CIS image scanner. For example, the present invention can be applied to a CCD scanner device in which an image sensor is fixed and a light source and a reflection mirror are moved by a carriage.

  The present invention can also be applied to an apparatus (for example, a printer) having a mechanism for transporting a carriage using a DC motor.

  Further, the image input apparatus of the present invention is not limited to the scanner apparatus, and may be a complex machine with a printer, a copier, a facsimile, or the like.

1 is a schematic configuration diagram of a scanner device. The flowchart of a reference position detection process. The figure for demonstrating the movement of a carriage. The figure which shows the relationship between time and a duty ratio. FIG. 4A shows the first collision. FIG. 4B shows the second collision.

Explanation of symbols

1 ... Scanner device,
DESCRIPTION OF SYMBOLS 100 control part 110 ... CPU, 111 ... duty ratio generation part, 112 ... wall determination part, 120 ... motor control part, 130 ... timer 20 ... drive mechanism, 200 ... motor, 210 ... encoder, 220 ... worm gear, 231 ... flat Gears, 223, 222 ... pulley, 224 ... timing belt, 230 ... motor driver 300 ... carriage,
400 ... wall

Claims (4)

An image input device,
A carriage,
Control means for controlling movement of the carriage;
A restraining member for restraining the movement of the carriage;
A reference position detecting means for setting a reference position of the carriage,
The control means includes
Moving the carriage at least twice to the stop member and making the speed of the second and subsequent movements slower than the speed of the first movement;
The reference position detecting means includes
An image input device that detects a position where the carriage has moved to the stop member and stopped by the second and subsequent movements as a reference position of the carriage. The image input device according to claim 1,
The control means includes
After moving the carriage to the stop member at a first speed,
Return the carriage position by a predetermined distance,
An image input apparatus, wherein the carriage is moved to the stopping member at a second speed that is slower than the first speed. The image input device according to claim 1,
A motor,
A timing belt for transmitting the driving force of the motor to the carriage;
An encoder for outputting the rotation amount of the motor;
The control means includes
While the drive current applied to the motor is periodically increased at a predetermined increase rate, the encoder is decreased at a predetermined decrease rate each time the encoder detects a predetermined rotation amount,
An image input apparatus, wherein when the drive current exceeds a predetermined threshold value, it is determined that the carriage has moved to the stop member. A reference position detection method for an image input device,
The image input device includes:
A carriage,
A restraining member for restraining the movement of the carriage,
The carriage is moved at a speed that is lower than the speed of the first movement after the second movement, and is moved to the stop member at least twice.
A reference position detection method for an image input apparatus, wherein a position where the carriage has moved to the stop member and stopped by the second and subsequent movements is detected as a reference position of the carriage.

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