JP3224267B2 - Document reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading apparatus having a scanning section of a reading optical system driven by a stepping motor or the like.

[0002]

2. Description of the Related Art Conventionally, a scanning unit of a reading optical system has a CC unit.
2. Description of the Related Art A document reading device that includes a D image sensor, reads an image from a document by scanning, converts the image into an electric signal, and outputs the signal to a recording device such as a copying machine or a printer has been widely used. By the way, in such a document reading apparatus, for example, FIG.
A scanning unit (not shown) equipped with a CCD sensor 200 having a short reading length of about 16 mm as shown in FIG. 0 scans the original 201 in the main scanning direction indicated by an arrow Y to read an image corresponding to the width. Each time one main scan is completed, the scanning unit is moved in the sub-scanning direction (indicated by an arrow X).
, Where reading by main scanning is performed again,
By repeating the above, the image has been read from the entire surface of the document 201.

[0003]

However, in such a conventional example, reading of the original 201 is performed as follows.
Each area to be read when the CCD sensor 200 serving as the reading means is scanned in the arrow Y direction must be accurately connected in the sub-scanning direction. For this reason, conventionally, in this type of apparatus, a reading unit and the like are driven by an easily controllable stepping motor so as to perform accurate scanning.

However, the range of the speed at which the stepping motor rotates smoothly is narrow due to its characteristics. Therefore, the scanning speed cannot be largely changed when performing variable-magnification reading such as enlargement or reduction. However, there is a problem that the variable magnification range cannot be widened.

That is, the vibration caused by the stepwise rotation of the motor at the time of low-speed rotation is particularly severe in a stepping motor, and the vibration is transmitted to the reading means via a drive transmission means such as a wire. Reproducibility is deteriorated, and a change in scanning speed causes a reduction in reading accuracy.

Further, when scanning the reading means at a steady speed, the reading position accuracy is deteriorated due to transient vibration when accelerating from the stopped state to the steady speed or when shifting from the accelerated state to the steady speed. Therefore, in order to prevent such adverse effects due to the transient vibration, it is necessary to start reading after the vibration is sufficiently attenuated, which causes a problem that the size of the apparatus is increased.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a document reading apparatus capable of smoothly moving a scanning unit even when a motor that easily generates vibrations is used, and improving the reading accuracy of a document with a simple configuration. Is to do.

[0008]

A document reading apparatus according to the present invention has a scanning unit for optically scanning a document, and a guide rail for guiding the movement of the scanning unit. In a document reading apparatus that moves earlier when moving backward than before, a sliding member rotatable in a direction of approaching and separating from the guide rail around a fulcrum on the scanning unit, and the sliding member is attached to the guide rail. An urging member that urges the scanning unit in the pressing direction, wherein the fulcrum is provided on the upstream side in the forward movement direction of the scanning unit from a contact position between the sliding member and the guide rail. During the forward movement, a larger braking force is applied than during the backward movement.

[0009]

[0010]

According to the document reading apparatus of the present invention, the scanning unit is provided with a sliding member for generating a frictional load between the scanning unit and the guide rail. The friction load is made larger than the friction load at the time of return.

[0011]

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. here,
Reference numeral 1 denotes a main scanning table on which a reading optical system including a CCD reading sensor 2 is mounted, and which is driven by main scanning in directions of arrows A and B along guide rails 3A and 3B, and 4 supports the main scanning table 1 movably. And a sub-scanning table that moves along the sub-scanning rails 5A and 5B. 6A and 6B are side plates provided at both ends of the sub-scanning table 4 to support the ends of the guide rails 3A and 3B, 7 is a main scanning drive system attached to the side plate 6A, and 8 is connected to the main scanning table 1. And a wire stretched between the pulleys 9A and 9B and driven by the motor 10 of the main scanning drive system 7 .

Both ends of the sub-scanning rails 5A and 5B for guiding the sub-scanning table 4 are supported by a document reading apparatus main body (not shown). Reference numeral 11 denotes a driving motor for the sub-scanning table 4 ;
Is a drive shaft driven by the motor 11, 13 is its pulley, 14 is a drive belt stretched between the pulley 11A and the pulley 13 of the motor 11, 15A and 15B are both ends sealed to the sub-scanning table 4. Endless wire 16 which is stopped and driven by the motor 11 via the drive shaft 12;
A is a deflection pulley for the wire 15A, and a wire 15B
Is also provided with a deflection pulley (not shown).

In the image reading apparatus thus configured, the reading sensor 2 reads a document placed on a document table (not shown) while the main scanning table 1 is moving in the main scanning direction indicated by the arrow A. , The main scanning table 1 indicates the arrow B for each main scanning.
The sub-scanning table 4 is returned to the home position (hereinafter referred to as HP) by the movement in the direction, and the sub-scanning table 4 is sub-scanned by the sub-scanning table driving motor 11 in the direction of arrow C by a distance corresponding to the reading width. Here, the arrow D indicates the direction in which the sub-scanning table 4 is returned when reading of one document is completed.

Next, the details of the main scanning drive system 7 having means for transmitting the driving force will be described with reference to FIG.

Here, the motor 10 is provided with pulleys 21A and 21B at both ends thereof. 22, an electromagnetic clutch; and 23, a pulley coaxial with the electromagnetic clutch 22. 24 is a motor pulley 21B and a pulley 23
And a belt stretched between them. Similarly, 25 is an electromagnetic clutch provided with a pulley 25A at one end, 26 is a belt stretched between the pulley 21A and the pulley 25A, 2
Reference numeral 7 denotes an idler for adjusting the tension of the belt 26. Reference numeral 28 denotes the electromagnetic clutches 22 and 25.
Is provided with a main scanning table at one end.
A pulley 9B for driving a wire 8 for reciprocating the wire 1
Are provided integrally.

Here, in the drive system including the pulley 21B, the belt 24 and the pulley 23, the motor 10 and the drive shaft 28
And a drive system including a pulley 21A, a belt 26, and a pulley 25A so that
The drive shaft 28 is configured as a reduction system in which the rotation of the drive shaft 28 is slower than the rotation of 0, and the reduction ratio is set to about 3 in this embodiment. At the time of main scanning, only one of the electromagnetic clutches 22 and 25 is selectively energized, and either the constant speed system or the deceleration system is selected. This selection is determined according to the reading magnification, the scanning direction, the reading sequence, and the like, as described later.

In the case of this embodiment, the influence of vibration occurs when the driving frequency of the motor 10 is 500 pps or less. Therefore, the driving system is switched from the constant velocity system to the deceleration system when the driving frequency is lower than 500 pps. As a result, a high-precision read image could always be obtained.

In the case of this example, as described above,
The speed reduction ratio between the speed reduction system and the constant speed system is set to about 3, but is not limited to this, and is appropriately selected from the scanning speed and the driving frequency of the motor.

Next, the configuration of the main scanning table 1 will be described in detail with reference to FIGS.

An illumination system 31 includes a lamp for illuminating the original, a mirror (not shown), and the like. A projection lens 32 projects an original image illuminated by the illumination system onto the CCD sensor 2. The projected original image is CC
The signal is sequentially converted into an electric signal by the D (read) sensor 2.
Reference numeral 34 denotes a shield case that covers a driver substrate (not shown) for driving the CCD sensor. Reference numeral 35 denotes a detection piece that is drilled from the main scanning table housing 1A for HP detection. Reference numeral 36 denotes a sub scanning table side. It is a photo interrupter for HP detection,
This is for detecting the HP in the main scanning direction. 37 is a fan for cooling the illumination system 31, and 38 is a cover having a deflecting plate 38A for deflecting the cooling air from the fan 37 toward the illumination system 31 and the platen glass (not shown). Together with 37, it is fixed on the main scanning table housing 1A.

Further, as shown in FIG. 4, the main scanning table 1 is provided on one guide rail 3B by bearings 41A and 41B provided on the housing 1A and a bearing 41C provided on the urging unit 42, and by a bearing 41D. It is held movably in the main scanning direction with respect to the other rail 3A.

As shown in FIG. 5, one end of the wire 8 is connected to a hook 43 formed on a part of the housing 1A by a spring 44.
And the other end of the wire 8 is connected to a hook 45
Is fixed via a buffer member 46. The buffering member 46 is formed of an elastic material such as rubber, so that the main scanning table 1 is adversely affected by vibrations generated when the motor 10 of the drive system 7 rotates and vibrations of the wires 8 during the main scanning. And the reciprocating movement by the main scanning table 1 is smoothly performed.

Next, details of the urging unit 42 will be described with reference to FIG.

Here, 51 is a base member fixed to the main scanning table housing 1A, and 52 is an arm member having a roller 53 at one end and rotatably attached to the base member 51 by a support pin 54. , The spring 55 is biased so as to bias the roller 53 at its tip toward the rail 3B. 56 has a roller 57 at one end, and a support pin 58
The arm member is rotatably attached to the base member 51, and is urged by a spring 59 to bias the roller 57 toward the rail 3B.

An arm member 60 has a pad 61 at one end, and is rotatably attached to the base member 51 by a support pin 62. The arm member 60 is biased by a spring 63 to bias the pad 61 toward the rail 3B. It is being rushed. Here, the pad 61 applies an appropriate frictional load to the main scanning table 1 by abutting on the rail 3B. When the main scanning table 1 scans, an impact vibration accompanying acceleration is applied between the pad 61 and the rail 3B. Can be attenuated by friction.

FIG. 7 shows the relationship between the rail 3B and the arm 60. Now, when the main scanning table 1 is scanned in the image reading direction (the direction of arrow A in the drawing), the pad 61 and the rail 3B are thus scanned.
Frictionally force F _A is generated in the direction shown, a large braking force between a result of the frictional force F _A is to bias the arm 60 in the counterclockwise direction, the pad 61 and the rail 3B between the Let it. On the other hand, the main scanning stage 1 after scan end direction read image, the frictional force F _B between when it is scanned in the return direction (arrow B direction) and the pad 61 and the rail 3B occurs in the direction shown in the figure, the friction force F _B is for biasing the arm 60 in the clockwise direction, so that the braking force generated between the pad 61 and the rail 3B is weakened. That is, the frictional force acts strongly during the scanning in the reading direction in which the vibration of the main scanning table 1 is required to be quickly attenuated, and the frictional force acting as the load is reduced in the scanning in the return direction, in which the quick scanning is required.

FIG. 8 shows the configuration of a circuit according to the present invention. 1
Reference numeral 01 denotes a CCD driver for driving a CCD sensor 2 provided in the main scanning table 1 ; and 103, an image processing unit that performs the following processing on an output signal of the sensor 2. The image processing unit 103 amplifies the output of the CCD sensor 2, an A / D converter 105 that sequentially A / D converts the output signal amplified by the amplifying unit 104, and the information stored in the memory 106. A shading correction unit 107 for correcting illumination unevenness and sensor bit unevenness, an input masking unit 108 for performing color correction by performing a 3 × 3 matrix operation on an input signal, a Log conversion unit 109 for performing gradation conversion, and an edge. The processing unit 110 includes an emphasis masking UCR process, and a main scanning scaling interpolating unit 111 that performs interpolation processing at the time of reduced or enlarged scaling reading.

Reference numeral 112 denotes a CPU having a RAM and a ROM, and further controlling the CCD driver 101, the image processing unit 103, and an I / O unit 113 described later. An I / O 113 manages information I / O based on the CPU 112.
Reference numeral 114 denotes a controller for controlling the driving of the main scanning motor 10 and the sub-scanning motor 11; 117, clutch switching means for switching the electromagnetic clutches 22, 25 of the driving system 7 ;
An HP 118 detects home positions of the main and sub scanning.
A sensor 119, an operation unit 120, an editor 120 for inputting an area designation and the like, and a CVR power supply 121 for controlling lighting of a lamp 122 of the illumination system 31.

Next, a typical reading sequence of the image reading apparatus according to the present invention will be described with reference to the flowchart of FIG.

First, when the reading start key is pressed, power is supplied to the constant speed clutch 22 in step S1, and the constant speed system is selected in the main scanning drive system 7 . Thus, the main scanning table 1 is driven by the main scanning motor 10 in the direction of arrow B in FIG. 1, and the sub-scanning table 4 is driven by the sub-scanning motor 11 in the direction of arrow D. In step S2, the HP detection operation is performed.
Initial positioning of the main scanning table 1 and the sub-scanning table 4 is performed. The reason why the constant velocity system is selected during the HP detection operation is to shorten the time required for HP detection.

Next, at this position, the standard white plate located on the platen glass (not shown) is read. At step S3, the lighting voltage of the lamp 122 and the amplifier gain are determined. 10
6 is performed. Then, in step S4, it is determined whether or not the minimum output value is equal to or smaller than a predetermined value, for example, to determine whether or not the read output is uneven. Then, in the next step S6, it is determined whether or not the reading magnification is equal to or less than a predetermined value. If the reading magnification is equal to or less than the predetermined value, the process proceeds to step S7, where the main scanning table 1 is scanned in the reading direction and the original reading operation is performed.

After reading one line by main scanning, the process proceeds to step S8, where the main scanning table 1 is returned to the start position.
In step S9, the sub-scanning table 4 is moved by a predetermined sheet feed amount. In step S10, it is determined whether or not the operations from steps S7 to S9 have been repeated a predetermined number of times for one page. After the predetermined number of readings, the process proceeds to step S11, where the main scanning table 1 and the sub-scanning table 4 are reset. After returning to the HP position, a series of reading operations is completed.

Further, if the reading magnification is equal to or more than the predetermined magnification in step S6, the flow branches to step S12, where the power is supplied to switch to the side of the reduction clutch 25, and the main scanning drive system 7 selects the reduction system. .

Thus, the process proceeds to step S13, where the main scanning table
1 is scanned in the reading direction to read the original, and after reading one line, in step S14, the clutch is switched to the constant speed clutch 22.
The process proceeds to step S15, where the main scanning table 1 is returned to the HP, and in the next step S16, the sub-scanning table 4 is moved by a predetermined sheet feed amount. It is determined whether or not the operations from steps S12 to S16 have been repeated a predetermined number of times in step S17. After reading the document a predetermined number of times and determining that the operation has been completed, the process returns to step S11 and returns to main scanning table 1 and sub-scanning table 4. Is returned to the HP position, and a series of reading operations is completed.

Here, when the reading magnification is equal to or more than a predetermined value, the scanning is performed in the reading direction by switching to the deceleration clutch 25 so that the main scanning drive system 7 is selected to be decelerated. Thus, the drive frequency of the stepping motor 10 in the main scanning drive system 7 is increased to obtain a smooth rotation of the motor 10.

When returning the main scanning table 1 to the start position, the constant speed system is selected in order to increase the scanning speed of the main scanning table 1 and shorten the reading time. Further, when the drive system 7 is switched in each of steps S12 and S14, while the motor 10 is completely stopped, the clutch that is already energized is kept as it is and the other clutch that is not energized is energized. Then, it is desirable that a sequence in which the energization of the clutch that has been in the energized state be cut off thereafter. As a result, at least one of the clutches of the drive system 7 is always energized, so that the drive system 7
And the main scanning table 1 are always integrated, so the main scanning table
1, the position reproducibility is guaranteed, and the reading accuracy is not adversely affected.

[0039]

[0040]

[0041]

In each of the embodiments described above, the scanning section of the original reading apparatus has been described. However, the present invention is not limited to this, and may be applied to, for example, a scanning section of a printer. Needless to say.

Further, in the above embodiment, the switching by the main scanning drive system 7 is the constant speed system and the deceleration system.
However, the present invention is not limited to this, and the main scanning speed may be appropriately selected from the driving frequency of the motor 10 according to the reading magnification, such as a speed increasing system, a constant speed system, and a deceleration system. Also, the original is scanned by an optical system that scans a mirror or the like.
Of course, the same effect can be obtained even when the present invention is applied to a mirror scanning drive system in a reading device configured to project onto a D sensor.

[0044]

As described above, according to the present invention,
A sliding member for generating a frictional load between the guide rail and the guide rail is provided in the scanning unit, and the frictional load in the forward movement of the scanning unit is made larger than the frictional load in the backward movement in accordance with the movement of the sliding member. This allows the scanning unit to quickly attenuate the vibration of the scanning unit due to a large friction load when the scanning unit reads the original in a forward movement, and to quickly return the operation unit due to the small friction load when the scanning unit moves back. Can be. As a result, original reading accuracy can be improved with a simple configuration.

[0045]

[0046]

Further, since the frictional load generated between the guide rail and the guide rail can be appropriately changed depending on the scanning direction and the scanning speed, the durability of the sliding member can be improved, and the drive motor of the main scanning unit can be downsized. It is also possible to aim.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration example of a main part of a document reading apparatus of the present invention.

FIG. 2 is a perspective view showing a configuration example of a scanning drive system according to the present invention.

FIG. 3 is a perspective view showing a configuration example of a main scanning table according to the present invention.

FIG. 4 is a front view of the main scanning table shown in FIG. 3;

FIG. 5 is a plan view of the main scanning table shown in FIG. 3;

FIG. 6 is a plan view showing a configuration example of an urging unit according to the present invention.

FIG. 7 is an explanatory diagram of an operation by the urging unit shown in FIG. 6;

FIG. 8 is a block diagram showing a circuit configuration of a document reading apparatus according to the present invention.

FIG. 9 is a flowchart illustrating an example of a control operation procedure of the document reading apparatus according to the present invention.

FIG. 10 is an explanatory diagram of a reading operation.

[Description of Signs] 1 main scanning table 2 CCD reading sensor 3A, 3B guide rail 4 sub-scanning table 10 main scanning system driving motor 11 sub-scanning table driving motor 21 motor 22, 25 clutch 24, 26 belt 28 driving shaft 31 illumination system 42 urging unit 51 base member 52, 56, 60 arm 53, 57 roller 54, 58, 62 support pin 55, 59, 63 spring 61 pad 71 solenoid

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1/04-1/207 G03B 27/50 G03G 15/04-15/04 120

Claims (2)

(57) [Claims] A scanning unit for optically scanning a document; a guide rail for guiding the movement of the scanning unit;
A document reading device in which the scanning unit moves faster when moving backward than when moving forward, a sliding member rotatable in a direction of approaching and separating from the guide rail around a fulcrum on the scanning unit. An urging member that urges the sliding member in a direction of pressing the sliding member against the guide rail, wherein the fulcrum is moved in a forward direction of the scanning unit with respect to a contact position between the sliding member and the guide rail. A document reading apparatus provided on the upstream side, wherein a larger braking force is applied during forward movement of the scanning unit than during backward movement. 2. The document reading apparatus according to claim 1, wherein the urging member is a spring that pulls a portion of the sliding member opposite to the contact point with respect to the fulcrum.