JPH0242863A - Original reading device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a document reading device using a contact type image sensor.

2. Description of the Related Art Conventionally, as an H document reading device using a contact type image sensor, the one shown in FIG. 6 or FIG. 7 is common.

In the document reading device shown in FIG. 6, first, a contact image sensor 5 is provided, which includes a transparent protective glass 1, an array of LEDs 2, an array of rod lenses 3, an array of photoelectric conversion elements 4, etc. ing. Further, a platen roller 6 is provided which is pressed against the surface of the protective glass 1 at the document reading position n A tp of the contact type image sensor 5 and is driven to rotate around its axis.

Note that the outer peripheral portion of the platen roller 6 is formed of a white elastic member. Then, by rotationally driving the platen roller 6, the document 7 is fed while being held between the protective glass 1 and the platen roller 6.
Reading of the original 7 is performed when the original 7 passes through the original reading position LI A I+.

In the document reading device shown in FIG. 7, a white guide plate 8 is provided facing the surface of the protective glass 1 of the contact type image sensor 5 with a gap of a predetermined size. Also, a contact image sensor 5 on the conveyance route of the document 7 is provided.
A pair of document transport rollers 9 are located at the front and rear of the
, 10 are provided. Then, the document 7 is fed between the white guide plate 8 and the protective glass 1 by the document transport roller 9 on the front side, and the document 7 is read at the document reading position "A". The original 7 is ejected by the original transport roller 10 on the back side.

Problems to be Solved by the Invention First, in the document reading device shown in FIG. 6, the outer peripheral surface of the platen roller 6, which is formed of an elastic member, is easily soiled by contact with the document 7, and the adhered dirt cannot be removed. Hateful. For this reason, the shading correction of the contact type image sensor 5, which is performed using the white surface of the platen roller 6, cannot be performed accurately, resulting in a decrease in reading accuracy. Also, manuscript 7
Before reaching the platen roller 6, the platen roller 6 is pressed against the surface of the protective glass 1,
The rotational load when rotating the platen roller 6 is increased.

Next, in the document reading device shown in FIG.
shading correction can be performed accurately.

However, the original 7 tends to rise from the surface of the protective glass 1, which tends to cause out-of-focus. In order to prevent such a focus shift, it may be possible to lightly press the white guide plate 8 against the surface of the protective glass 1, but in that case, the transportability of the original, which is thin and weak, will deteriorate. and jams are more likely to occur. Furthermore, the white guide plate 8 is rubbed and soiled by the original 7, making it impossible to perform shading correction accurately.

Means for Solving the Problem A hard platen roller is provided that faces the document reading position of the contact type image sensor and is pressed in the direction of the contact type image sensor, and the outer peripheral surface of this platen roller is painted in a white color. The platen roller is surface-treated and is movable toward and away from the contact image sensor, and is provided with a rotational drive mechanism that rotates the platen roller at a circumferential speed substantially equal to the conveyance speed of the document along the conveyance direction of the document. Ta.

Furthermore, in a state where the platen roller is closest to the contact image sensor, a small gap is provided between the platen roller and the contact image sensor at least within the document reading width.

Further, bearings having a diameter larger than that of the platen roller were provided at both ends of the platen roller, and the outer peripheral surface of the bearing was brought into contact with the surface of the contact type image sensor outside the range of the document reading width.

The working platen roller is rotated by a rotary drive mechanism along the document conveyance direction at a circumferential speed that is approximately equal to the document conveyance speed, which assists the document conveyance and improves conveyance even for thin documents. This prevents jamming from occurring immediately in front of the platen roller. In addition, since the platen roller is pressed in the direction of the contact type image sensor, the original is prevented from lifting up when reading the original, thereby preventing out-of-focus. Furthermore, since the platen roller can move toward and away from the contact image sensor, if the document is thick, the platen roller will move away from the contact image sensor, reducing the paper thickness. Even if the document is thick, jamming is prevented. The outer circumferential surface of the hard platen roller, which has been surface-treated in a white color, makes it difficult for dirt to adhere to the outer circumferential surface of the platen roller. You can perform accurate shading correction.

Further, by providing a small gap between the platen roller and the contact type image sensor, the conveyance of the document is further improved, and furthermore, the platen roller is prevented from being soiled or scratched due to rubbing with the document.

In addition, by providing large-diameter bearings at both ends of the platen roller and bringing the outer circumferential surface of the bearings into contact with the surface of the contact image sensor outside the range of document reading width, the gap between the platen roller and the contact image sensor is improved. Ensure a small gap.

Embodiment A first embodiment of the present invention will be explained based on FIGS. 1 and 2. Incidentally, the same parts as those explained in FIGS. 6 and 7 are indicated by the same reference numerals, and the description thereof will be omitted. first,
A contact type image sensor 5 including a protective glass 1, an array of LEDs 2, an array of rod lenses 3, an array of photoelectric conversion elements 4, etc. is provided. There is a rotation axis 1 in front and behind the
1.12 and document transport rollers 13 and 14 fixed to these rotating shafts 11.12 are installed.

An arm 1 is attached to the document transport rollers 13 and 14.
Pressure rollers 17 and 18 held by the rollers 5 and biased by a spring 16 are resiliently abutted. Note that driving pulleys 19 and 20 are fixed to the rotating shafts 11 and 12, respectively.
a small-diameter drive pulley 22 fixed to a rotating shaft 21 installed in a triangular position with respect to the drive pulley 19;
A drive belt 23 is wound between the drive belt 20 and the drive belt 20 .

Furthermore, a large diameter pulley 24 fixed to the rotating shaft 21
A drive belt 27 is wound between the drive pulley 26 of the drive motor 25 and the drive pulley 26 of the drive motor 25.

Next, a pair of guide plates 28 and 29 are installed with a gap of a predetermined size between the protective glass 1 and the surface of the protective glass 1. original reading position 11
A platen roller 3o facing the API is provided. Bearings 32 are attached to support shafts 31 at both ends of the platen roller 30, and these bearings 32 are attached to a housing (
(not shown) is vertically movably engaged with a long groove 33 formed in the vertical direction. Note that the longitudinal direction of the long groove 33 and the conveyance direction of the document 7 are set to be perpendicular to each other.

Bearings 34 are attached to both ends of the platen roller 30, and a diameter "D" of the bearings 34 is set larger than a diameter "D" of the platen roller 30. Further, an actuator 35 is attached to the housing so as to be freely rotatable in the vertical direction around the axis of a support shaft 36, and this actuator 35 is elastically pushed against the lower outer circumferential surface of the bearing 34 by the biasing force of a spring 37. is in contact with the On the other hand, the upper outer peripheral surface of the bearing 34 is in contact with the surface of the protective glass 1 outside the range of the document reading width. Therefore, there is a minute dimension "δ" between the surface of the protective glass 1 and the platen roller 30 within the document reading width.
” (δ=D1-D, /2=o, ・05~0.15+m
) is provided.

A gear 38 is fixed to the tip of one of the support shafts 31,
This gear 38 meshes with an idle gear 39. The idle gear 39 is disposed at a position where it meshes with the gear 38 approximately on a pitch circle when the platen roller 30 moves to the position farthest from the contact image sensor 5.

Furthermore, a gear 40 fixed to the rotating shaft 21 meshes with the idle gear 39. These gears 38, 40, the idle gear 39, the drive motor 25, and the like provide a rotational drive mechanism that rotates the platen roller 30 along the conveyance direction of the document 7 at a circumferential speed approximately equal to the conveyance speed of the document 7. 41 are configured.

The platen roller 30 is made of a hard member such as metal or plastic, and its outer peripheral surface is painted or plated in a white color.

In such a configuration, when the power is turned on and the start button for document reading is pressed, the drive motor 2 is first turned on.
5 rotates, and this rotation is transmitted via the drive belt 27.23 and drive pulleys 26, 24, 22, 19.20, etc., and the document conveyance roller 13.14 rotates in the direction of arrow a. Furthermore, the gear 40 rotates integrally with the drive pulleys 24 and 22.

The rotation of gear 40 is transmitted to gear 3 via idle gear 39.
8, and the platen roller 30 rotates together with the gear 38 in the direction of arrow a'.

On the other hand, when the leading edge of one document 7 separated by a document separation and conveyance mechanism (not shown) reaches between document conveyance roller 13 and pressure roller 17 .

The original 7 is conveyed in the direction of the arrow between the protective glass 1 and the guide plate 28 by the rotation of the original conveyance roller 13, and eventually reaches the original reading position "A''. Original reading position II A ty The original 7 that has reached this stage advances between the protective glass 1 and the platen roller 3o, during which reading of the original is performed.After the original reading has been completed, the original 7 is continuously conveyed in the direction indicated by the arrow, and passes between the protective glass 1 and the guide. Board 2
9 and reaches between the document conveyance roller 14 and the pressure roller 18, and is discharged to a paper discharge section (not shown) by the rotational drive of the document conveyance roller 14.

Here, a gap with a microscopic dimension "δ" is formed between the protective glass 1 and the platen roller 30 at the document reading position "1A", and the platen roller 30 is moved in the conveyance direction of the document 7 (arrow Since the document rotates in the same direction (direction of arrow a') as in the direction of the platen roller 30, it prevents jamming in front of the platen roller 30 even when the paper is thin and has a weak texture, improving conveyance. In addition, if the paper thickness of the document is thicker than the gap dimension "δ", the platen roller 30 moves along the long groove 33 in a direction away from the protective glass 1 according to the thickness. Even if the document is thick, jamming in front of the platen roller 30 is prevented, and conveyance performance is improved.

On the other hand, the platen roller 30 is pressed in the direction of the protective glass 1 by the actuator 35, and a minute gap dimension "5δ" is maintained between the platen roller 30 and the protective glass 1 in the normal state.

Therefore, when reading the document, the platen roller 30
comes into contact with the back surface of the original 7, the original 7 is prevented from lifting off the surface of the protective glass 1, and a shift in focus due to the lifting of the original 7 is prevented. If the document is thick and the platen roller 30 moves in a direction away from the protective glass 1, the pressing force of the platen roller 30 against the back surface of the document 7 increases, so the paper pressure becomes thicker.
Even if the document is stiff, it is prevented from rising from the surface of the protective glass 1, and the out-of-focus is prevented.

Next, consider uneven illumination, variations in sensitivity of the photoelectric conversion element 4,
Furthermore, if the ambient light is at its lowest level, the reading accuracy will deteriorate.

Therefore, in order to improve reading accuracy, a white member serving as a reference is usually read before reading starts, and shading correction is performed in which the photoelectric conversion elements 4 are electrically corrected one by one based on the output waveform. Here, since the outer circumferential surface of the platen roller 30 has been surface-treated in a white color, shading correction can be performed by reading the outer circumferential surface of the platen roller 30. Moreover, the platen roller 30
Since it is made of a hard material rather than the conventional white elastic material, it is difficult for dirt to adhere to it, and even if dirt does adhere to it, it can be easily removed. Therefore, the outer peripheral surface of the platen roller 30 is maintained in a white state suitable for shading correction for a long period of time, and shading correction can always be performed with high precision. Furthermore, when the document 7 is conveyed between the platen roller 30 and the protective glass 1, a gap of minute dimension "1δ" is provided between the platen roller 30 and the protective glass 1, and Since the platen roller 30 rotates at approximately the same circumferential speed as the transport speed of the original 7, the platen roller 30 is not rubbed by the original M7 and becomes dirty or scratched, making the platen roller 30 even more suitable for shading correction. can be maintained in the same condition.

Next, a second embodiment of the present invention will be explained based on FIG. Note that the same parts as those explained in FIGS. 1 and 2 are indicated by the same reference numerals, and the description thereof will be omitted (the same applies below). In this embodiment, the installation position of the idle gear 39 is changed, and the center of the platen roller 30 and the idle gear 3
The straight line connecting the centers of the originals 9 and the conveyance direction of the original 7 is approximately parallel to each other. Therefore, it is possible to increase the amount of movement of the platen roller 30 in the direction away from the protective glass 1, and it is possible to smoothly read thicker originals.

Next, a third embodiment of the present invention will be described based on FIG. 4. In this embodiment, gear 38.40 and idle gear 3
A drive pulley 42 replaces the rotary drive mechanism 41 consisting of 9 etc.
, 43 and a drive belt 44, etc.
It uses

First, a drive pulley 42 is fixed to the rotating shaft 11.

A drive pulley 43 is fixed to the support shaft 31 of the platen roller 30. And these drive pulleys 42, 43
A drive belt 44 is wound between them. Furthermore, long groove 3
A tensioner 46 is provided to maintain the tension of the drive belt 44 in a substantially constant state even if the distance between the centers of the drive pulleys 42 and 43 changes due to the movement of the platen roller 30 along the axis 3. In addition, since the vertical component of the tension acting on the drive belt 44 acts in a direction that urges the platen roller 30 in the direction of the protective glass 1, the platen roller 30 is rotationally driven.
0 is prevented from moving away from the back surface of the document 7.

Next, a fourth embodiment of the present invention will be described based on FIG. In this embodiment, the contact type image sensor 5 is arranged below and the platen roller 30 is arranged above. Furthermore, the tension roller 30 is rotated by a rotary drive mechanism 49 consisting of an idle gear 47 that meshes with a gear 46 fixed to the rotating shaft 11, an idle gear 48 that meshes with the idle gear 47, a gear 38 that meshes with the idle gear 48, a drive motor 25, etc. It is being driven. A straight line connecting the center of the platen roller 30 and the center of the idle gear 48 is substantially parallel to the conveying direction of the original 7. Therefore, when a jam occurs, the platen roller 30 is opened upward to remove the jam, and then when the platen roller 30 is closed, the gear 38 and the idle gear 48 can be smoothly engaged.

Effects of the Invention According to the present invention, as described above, the platen roller is rotationally driven along the document conveying direction by the rotation drive mechanism at a circumferential speed that is approximately equal to the document conveying speed, so that the platen roller assists in conveying the document. Therefore, it is possible to improve the conveyance of documents with thin and weak paper and prevent jams from occurring just before the platen roller, and also to press the platen roller toward the contact image sensor. By doing so, it is possible to prevent the document from lifting up when reading the document and prevent the focus from being out of focus.
By providing the platen roller so that it can move in the direction toward and away from the contact image sensor, when the document is thick, the platen roller moves in the direction away from the contact image sensor. Even if the paper is thick, it can be read without jamming.Furthermore, the platen roller is made of a hard material and the outer circumferential surface is surface-treated in a white color, so that the outer circumferential surface of the platen roller can be used for a long time. It is possible to maintain a white state over a long period of time and perform shading correction accurately.
By creating a small gap between the platen roller and the contact image sensor, it is possible to further improve the conveyance of thin originals, and it is also possible to further maintain the white state of the outer peripheral surface of the platen roller. This has the effect of further increasing the accuracy of shading correction.

[Brief explanation of the drawing]

Fig. 1 is a side view showing a first embodiment of the present invention, Fig. 2 is a perspective view showing a part thereof, Fig. 3 is a side view showing a second embodiment of the invention, and Fig. 4 is a side view showing a first embodiment of the invention. FIG. 5 is a side view showing a fourth embodiment of the present invention, FIG. 6 is a side view showing a conventional example, and FIG. 7 is a side view showing another conventional example. FIG. 5...Contact image sensor, 7...Document, 3o.
...Platen roller, 34...Bearing, 41...Rotation drive mechanism, 45...Rotation drive mechanism, 49...Rotation drive mechanism applicant Ricoh Co., Ltd."

Claims (1)

[Claims] 1. A hard platen roller is provided that faces the original reading position of the contact image sensor and is pressed in the direction of the contact image sensor, and the outer circumferential surface of the platen roller is painted in a white color. In addition to surface treatment, the platen roller is provided so as to be movable in the direction toward and away from the contact image sensor, and the platen roller is rotated along the conveying direction of the document, and the platen roller is rotated at a speed corresponding to the conveyance speed of the document. A document reading device characterized by being provided with a rotational drive mechanism that rotates at approximately the same circumferential speed. 2. According to claim 1, in a state where the platen roller is closest to the contact image sensor, a minute gap is provided between the platen roller and the contact image sensor at least within a document reading width. manuscript reading device. 3. Bearings with a diameter larger than the diameter of the platen roller are provided at both ends of the platen roller, and the outer peripheral surface of the bearings is brought into contact with the surface of the contact type image sensor outside the range of the document reading width. The document reading device according to claim 2.