JPH09186822A - Scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To employ a motor with a small drive torque for the scanner by passing an original between a carrier roller and a close contact image sensor so as to suppress the increase in a load torque when the carrier roller is in direct contact with the image sensor. SOLUTION: A fulcrum B being a turning center of an image sensor 16 is selected to a point toward an upper stream in an original carrying direction from a contact point A between a carrier roller 11 and the image sensor 16 and apart largely upward from a tangential line X-X passing through the contact point A, and when the carrier roller is in direct contact with the image sensor 16 and driven, a friction force F provided to the image sensor 16b acts on the image sensor 16 in a liftup direction thereby decreasing a pressing force between the carrier roller and the image sensor 16, suppressing the increase in the friction force and the increase in the load torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, an image recording apparatus, and the like, and a scanning method for carrying a conveying roller and a sheet by pressing the sheet against the conveying roller to convey the sheet and scanning the sheet for image reading or image recording. And a scanning device having a head.

[0002]

2. Description of the Related Art Conventionally, a scanning device (reading device) using a contact image sensor as this type of scanning head and a scanning device (recording device) using a thermal head are known. A conventional example will be described below by taking a scanning device using a contact image sensor as a scanning head as an example.

FIG. 12 shows a typical conventional image reading apparatus using a contact type image sensor. 1 is a conveying roller arranged at a fixed position, 2 is a sheet (original) to be image read, 3 is a contact-type image sensor, and the support shaft 4
A cover glass 3a is provided so as to be rotatable about the center of the sheet and is in contact with the transport roller 1 on the front side.
A pressing spring 5 presses the contact image sensor 3 against the conveying roller 1. In the image reading apparatus having this configuration,
The contact image sensor 3 is pressed against the conveying roller 1 by the pressing spring 5, and the sheet 2 inserted therebetween is pressed against the conveying roller 1 by the contact image sensor 3, so that The image information on the sheet 2 was conveyed by rotation in the direction of the arrow, and at the same time, the contact image sensor 3 read the image information.

Here, since the sheet 2 slides with respect to the cover glass 3a of the contact type image sensor 3 when the sheet 2 is being conveyed by the sheet conveying roller 1, the rotational load torque applied to the sheet conveying roller 1 at this time. Is mainly due to the frictional force between the paper 2 and the cover glass 3a. But,
While the leading edge of the sheet 2 is fed to the contact point between the transport roller 1 and the cover glass 3a, or while the sheet 2 is discharged past the contact point, the transport roller 1 directly contacts the cover glass 3a. Therefore, the cover roller 3a is rotated in the state of being in contact with the carrier roller 1.
The frictional force between the carrier roller 1 and the conveying roller 1 is applied as a load. Generally, since the surface of the carrying roller 1 is made of a rubber material such as silicon rubber, the coefficient of friction is large, and the coefficient of friction of the carrying roller 1 to the cover glass 3a is 2 to 6 times as large as the coefficient of friction of the paper 2 to the cover glass 3a. Is. Therefore, the rotational load torque applied to the carrying roller 1 is small when the paper 2 is present between the carrying roller 1 and the contact image sensor 3, but when the paper 2 is not present, it is 2 to 6 times as large as when the paper is present. As the stepping motor for driving the roller 1, a powerful one having a large driving torque is used so that the stepping motor does not step out even against a large rotational load torque that acts when the sheet 2 is not present. Was there.

However, since a powerful stepping motor is quite expensive and has a large size, it is a very disadvantageous condition in the construction of the device. Therefore,
A solution to this drawback is proposed in JP-A-63-10968. The one disclosed in this publication is shown in FIG.
As shown in FIG. 3 (a), when the contact image sensor 3 is pressed toward the conveyance roller 1, the conveyance roller 1
A contact member 3b that abuts a bearing 7 supporting the conveying roller 1 is provided at both ends of the contact image sensor 3 so that a minute gap 6 smaller than the sheet thickness is formed between When there is a sheet between the roller 1 and the contact image sensor 3, the contact image sensor 3 presses the sheet against the conveying roller 1 and conveys the sheet without any trouble.
When there is no paper between the two, a minute gap 6 is created between the transport roller 1 and the contact image sensor 3, and the contact image sensor 3 does not apply a friction load to the transport roller 1. The motor load can be reduced to a fraction of the conventional one.

[0006]

However, the one proposed in this publication has the following problems. That is, a small gap of 30 to 40 μm, which is smaller than the thickness of the paper, must be maintained between the contact image sensor and the conveyance roller over the entire width of the paper (original) to be read. , The working accuracy of the contact image sensor and the transport roller must be extremely high,
This becomes a factor that makes the device expensive. Since the paper is pressed against the conveying roller 1 over the entire width thereof with a necessary pressing force, the pressing springs are provided at a plurality of positions in the middle of the back surface of the contact-type image sensor 3 as shown by arrows P in FIG. The pressure applied to the contact type image sensor 3 is 10 to 20 N, and the contact type image sensor 3 is bent in a shape such that the central portion of the front surface is convex. The deflection of the part reaches several tens of μm or more, and contacts the transport roller 1. In order to prevent this, it is necessary to increase the rigidity of the contact image sensor 3, which causes an increase in size of the device and an increase in cost.

If a pressure is applied to both ends of the contact image sensor 3, this deformation will be small, but if a paper having a small width is passed through the center of the contact image sensor 3,
A sufficient pressing force cannot be applied to the paper, which causes a problem such as slippage during paper feeding.

These problems occur not only in the contact type image sensor but also in the case where a recording head such as a thermal head is used as a scanning head.

The present invention has been made in view of the above conventional problems, and when there is no paper between the transport roller and the scanning head pressed against the transport roller, a small gap is not formed between the transport roller and the scanning head. It is an object of the present invention to provide a scanning device that can reduce the rotational load torque of the transport roller while keeping the contact state, and thereby reduce the drive torque of the motor that drives the transport roller.

[0010]

In order to solve the above problems, the present invention has a structure in which a scanning head pressed against a conveying roller is configured to be rotatable around a fulcrum, and the fulcrum position is set to the rotation of the conveying roller. The frictional force applied to the scanning head is selected at a position where a moment in the opposite direction to the conveying roller acts on the scanning head about the fulcrum. According to this configuration, when there is no paper between the scanning head and the conveyance roller, the scanning head is directly pressed against the conveyance roller and tries to exert a large frictional force on the conveyance roller. The force exerts a force on the scan head in the direction away from the transport roller, and therefore, the pressing force of the scan head on the transport roller is automatically reduced, and the frictional force applied to the transport roller by the scan head is increased accordingly. It is suppressed to a small value, the driving torque required for the motor for driving the conveying rollers can be reduced, and the motor having a small driving torque can be used.

[0011]

According to the invention of claim 1, the scanning head, which is pressed against the carrying roller by the pressing means, is rotatable about a fulcrum in a plane perpendicular to the axis of the carrying roller. The fulcrum position is located on the scanning head side with respect to the tangent line drawn to the contact point on the upstream side in the paper transport direction with respect to the contact point between the scanning head and the transport roller, and on the transport roller side on the downstream side. Further, the angle (θ) formed by the straight line connecting the fulcrum and the contact point with respect to the tangent line is set to 20 ° or more.

In the apparatus having the above-mentioned structure, the scanning head is constantly pressed against the conveying roller by the pressing means, and when there is a sheet between them, the conveying roller conveys the sheet, and when there is no sheet, the conveying roller does not move. Spins idle while in contact with the scanning head. Since the coefficient of friction of the carrying roller with respect to the scanning head is much larger than the coefficient of friction of the paper, when the scanning head directly contacts the carrying roller, the frictional force acting on the carrying roller tends to be extremely large. . However, the frictional force applied to the scanning head by the carrying roller in the paper carrying direction causes the scanning head to exert a moment in the direction of separating the scanning head from the carrying roller about the fulcrum, and the pressing force by the pressing means is applied. A force that opposes to, and the opposition force increases as the frictional force increases. For this reason,
When the scanning head comes into direct contact with the carrying roller and the friction coefficient increases, the pressing force of the scanning head on the carrying roller is automatically greatly reduced, and eventually, the increase in the frictional force applied to the carrying roller by the scanning head is suppressed to be small. To be done. Thus, when the scanning head comes into direct contact with the conveying roller, the frictional force applied to the conveying roller by the scanning head does not increase so much as compared with the case of conveying the sheet, and therefore, the increase of the rotational load torque of the conveying roller can be suppressed to a small value. The driving torque of can be reduced. Here, the effect that the frictional force of the transport roller reduces the pressing force of the scanning head increases as the angle (θ) formed by the straight line connecting the fulcrum and the contact point with respect to the tangent line increases. A larger value is preferable, and in the present invention, this angle is set to 20 ° or more.

According to a second aspect of the present invention, the scanning head, which is pressed by the pressing means against the transport roller that can rotate in the normal and reverse directions, is located in a plane perpendicular to the axis of the transport roller, and is the first when the transport roller is normally rotated. Centering on one fulcrum,
At the time of reverse rotation, it is arranged so as to be rotatable around the second fulcrum, and the position of the first fulcrum is located at the contact point on the upstream side in the regular paper transport direction from the contact point between the scanning head and the transport roller. The drawn tangent is located on the scanning head side and on the downstream side on the transport roller side, and the angle (θ) formed by the straight line connecting the first fulcrum and the contact point with respect to the tangent is 20 ° or more, Further, the position of the second fulcrum is located on the transport roller side with respect to the tangent line drawn at the contact point on the upstream side in the regular paper transport direction with respect to the contact point between the scan head and the transport roller, and on the scan head on the downstream side. The angle (α) formed by the straight line located on the side and connecting the second fulcrum and the contact point to the tangent line is 20 ° or more.

In the apparatus having the above-mentioned structure, when the transport roller is rotating in the forward direction, the scanning head is rotatable about the first fulcrum, and in this state, the paper is placed between the scanning head and the transport roller. Therefore, when the carrying roller idles in a state where it is in contact with the scanning head, a large frictional force acting on the scanning head by the carrying roller causes the scanning head to separate from the carrying roller about the first fulcrum. Directional moment is applied to automatically reduce the pressing force of the scanning head on the transport roller.
When the carrying roller is rotating in the opposite direction, the scanning head is rotatable about the second fulcrum, and in this state, there is no paper between the scanning head and the carrying roller, and therefore the carrying roller is the scanning head. The large frictional force exerted on the scanning head by the carrying roller when it spins in contact with the moving head causes a moment in the direction of separating the scanning head from the carrying roller about the second fulcrum to act on the scanning head. Automatically reduces the pressing force on the conveyance roller. Thus, even when the transport roller is rotating in either the forward or reverse direction, even if the scan head comes into direct contact with the transport roller and the frictional force with respect to the scan head increases, the frictional force will increase. It can be suppressed to a small value, and thus the drive torque of the motor can be decreased.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention shown in the drawings will be described below.

FIG. 1 is a schematic sectional view showing a scanning device according to a first embodiment in which the present invention is applied to an image reading device, taken along a plane perpendicular to an axis of a conveying roller, and FIG. 2 is a scanning diagram of the embodiment. FIG. 3 is a schematic perspective view showing main parts of the apparatus, and FIG. 3 is a schematic sectional view showing the scanning apparatus cut along a vertical plane including the axis of the scanning roller. 1 to 3, reference numeral 11 denotes a carrying roller having an outer periphery made of a rubber material, and 12 denotes a carrying roller 11.
Is a bearing that rotatably holds, and 13 is a side plate.
By supporting 2, the conveying roller 11 is held at a fixed position. The transport roller 11 is connected to a stepping motor (not shown) via a gear train and is driven to rotate.

Reference numeral 14 is a sheet or original having an image to be read, and 16 is a scanning head, that is, a contact type image sensor for pressing the original 14 to convey it and conveying it, and scanning the original. The contact image sensor 16 includes a cover glass 16a, a case 16b, and an LED as a light source arranged inside the cover glass 16a.
16c, a lens array 16d, a light receiving element 16e, etc., and a reading point A on the cover glass 16a in FIG.
The reading point A is arranged to be pressed against the conveying roller 11 while reading the image of the document 14.
Therefore, the point A is a reading point as well as a contact point between the contact image sensor 16 and the conveying roller 11.

The contact type image sensor 16 includes a case 16
A central fulcrum member 18a is provided at the center of the upper surface of b, and end fulcrum members 19a having U-shaped grooves are provided at both ends of the upper surface. On the other hand, a stay 20 is passed over the side plates 13 on both sides, and a central fulcrum receiver 18b is attached to the center of the stay 20 to support the central fulcrum member 18a of the contact image sensor 16. Also,
Each side plate 13 is attached with a fulcrum pin 19b at a position facing the end fulcrum member 19a, and the fulcrum pin 19b is inserted into the U-shaped groove of the corresponding end fulcrum member 19a. Thus, in FIG. 1, the central fulcrum member 18a is supported by the central fulcrum receiver 18b to prevent downward movement,
Further, the movement in the horizontal direction is restricted by the engagement between the end fulcrum member 19a and the fulcrum pin 19b. Here, as can be seen clearly from FIG. 1, the engagement point between the central fulcrum member 18a and the central fulcrum receiver 18b, the end fulcrum member 19a and the fulcrum pin 1
The engagement point with 9b is arranged so as to be close to each other in a plane perpendicular to the axis of the transport roller 11. Therefore, the contact type image sensor 16 has a position determined by these engagement points, that is, a fulcrum B. It can be rotated around. The structure of the fulcrum for allowing the contact-type image sensor 16 to rotate about the fulcrum B is not limited to that shown in the illustrated embodiment, and can be changed as appropriate. Alternatively, a fulcrum pin provided on the side plate may be used so as to be rotatably held.

The position of the fulcrum B is on the upstream side of the contact point A between the contact type image sensor 16 and the conveying roller 11 in the document conveying direction, and on the tangent line X--X drawn at the contact point A.
With respect to the contact type image sensor 16, it is arranged at a position largely separated from the tangent line XX. Therefore, the angle θ formed by the straight line connecting the contact point A and the fulcrum B with respect to the tangent line XX
Is larger and is set to 45 ° in this embodiment.

Reference numeral 22 is a pressing spring which constitutes a pressing means for pressing the contact type image sensor 16 against the conveying roller 11, and its upper end is supported by the stay 20. As can be seen from FIGS. 2 and 3, the pressing springs 22 are arranged at symmetrical positions on both sides of the central fulcrum member 18a. As described above, the contact image sensor 16
Since the central fulcrum member 18a provided at the center thereof is supported by the central fulcrum receiver 18b, and the left and right can be swung up and down, by pushing the back surface thereof with the two pressing springs 22, The entire length of the die image sensor 16 in the longitudinal direction can be uniformly pressed against the transport roller 11. Therefore, the mounting position accuracy of the contact image sensor 16 in the height direction is not so required. Further, the contact-type image sensor 16 is used in a state of being constantly pressed against the conveying roller 11 as will be described later, so that a gap as proposed in JP-A-63-10968 is formed. It does not require the high precision and high rigidity that are required in some cases, and it is possible to use the one having the strength conventionally used conventionally.

Reference numeral 24 is a document guide for guiding the document 14 to a contact point A between the transport roller 11 and the contact image sensor 16, 25 is a paper detection sensor for detecting the presence / absence of a document, and 26 is the transport roller 11. A discharge roller for discharging the document 14 and an idler roller 27 for pressing the document 14 against the discharge roller 26. Both the discharge roller 26 and the idler roller 27 are positioned and attached to the side plate 13 by bearings 29, similarly to the transport roller 11. The discharge roller 26 is connected to the transport roller 11 by a drive system such as a gear (not shown), and the discharge roller 26 and the transport roller 11 both rotate in the same direction to transport the document 14.

The operation of the scanning device (image reading device) configured as described above will be described below. When the document 14 is inserted between the document guides 24 and the tip of the document 14 is inserted to the contact point A between the conveyance roller 11 and the contact image sensor 16, the paper detection sensor 25 detects the inserted document 14. After a waiting time of about 1 second after the detection of the original, a stepping motor (not shown) which is a drive source of the conveying roller 11 is activated to move the conveying roller 11 by a small angle in the counterclockwise direction indicated by an arrow in FIG. Rotate. By this operation, the original 1
The front end of 4 is the contact roller 11 and the contact type image sensor 16
Sandwiched between.

Thereafter, the contact image sensor 16 is driven by a driver (not shown) of the contact image sensor 16.
Is driven, and the transport roller 11 and the discharge roller 2 are driven.
6 is rotated counterclockwise, so that the original 14
While being transported, the image information is sequentially read. The image signal output from the contact image sensor 16 is transmitted to a printer unit (not shown) or a modem unit that controls signal output to a line.

Further, the paper detection sensor 25 detects the trailing edge of the document 14 as the transport roller 11 rotates counterclockwise. After detecting the trailing edge of the document 14, the apparatus continues the reading operation by the amount corresponding to the distance between the paper detection position and the reading point A of the contact image sensor 16. After that, the driving driver of the contact image sensor 16 is the contact image sensor 1.
Although the driving of No. 6 is stopped, the stepping motor continues to rotate the conveying roller 11 and the discharge roller 26 counterclockwise for a predetermined time so that the trailing end of the document 14 surely passes through the discharge roller 26.

The reading operation is performed as described above. Next, the rotational load torque that acts on the transport roller 11 during this operation will be described with reference to FIGS. 4A and 4B and in comparison with the conventional example. FIG. 4B shows the relationship of forces acting on the conventional contact image sensor 3. The contact image sensor 3 has a fulcrum C on or near the tangent line X-X drawn to the contact point A between the conveyance roller 1 and the contact image sensor 3. Therefore, the angle formed by the straight line connecting the fulcrum C and the contact point A with respect to the tangent line XX is almost 0.
°. Contact image sensor 3 is pressed against the conveying roller 1 mainly by the force P ₁ by the pressing spring, as a reaction force, the reaction force R ₁ to the conveying roller 1, the reaction force S ₁ is generated in the fulcrum C. However, the reaction force S ₁ is extremely small and can be omitted. Therefore, in a state where the transport roller 1 does not rotate, the force P ₁ due to the pressing spring and the reaction force R ₁ of the transport roller ₁ have substantially the same value.

Next, when the transport roller 1 rotates counterclockwise as indicated by the arrow, friction occurs with the cover glass 3a of the document 2 during transport of the document 2, and when there is no document 2, the cover glass of the transport roller 1 is present. The frictional force F ₁ is applied to the contact point A of the contact image sensor 3 due to the friction with respect to 3a.
Works. This frictional force F ₁ acts on the tangent line XX, and therefore acts almost in the same direction as the straight line connecting the contact point A and the fulcrum C, so that the contact type image sensor 3 is provided around the fulcrum C. No moment is generated and fulcrum C
It is supported by the reaction force of T ₁ . Therefore, the reaction force R ₁ of the conveying roller ₁ is almost always the force P _{1 of the} pressing spring regardless of the rotation of the conveying roller 1 and the magnitude of the frictional force F ₁ acting on the contact image sensor 3. Equal and constant. The frictional force F ₁ acting on the contact image sensor 3 is
Since it is the product of the coefficient of friction against the cover glass 3a and the pressing force by the transport roller 1, that is, the reaction force R ₁ , the cover glass 3a
When the coefficient of friction of the document with respect to a is μ (paper) and the coefficient of friction of the transport roller 1 is μ (rubber), the frictional force during document transport and when the transport roller idles is F ₁ (during document transport) = R ₁・ Μ (paper) F ₂ (roller idle) = R ₁ · μ (rubber) In general, μ (rubber) is several times as large as μ (paper), so the frictional force when the transport roller 1 directly contacts the contact image sensor 3 and idles is several times greater than when the document is transported. Therefore, the rotational load torque acting on the transport roller 11 naturally increases several times.

On the other hand, in this embodiment, as shown in FIG. 4A, the fulcrum B of the contact image sensor 16 is a straight line connecting the fulcrum B and the contact point A with respect to the tangent line XX. It is arranged so that the angle θ is about 45 °. In this configuration, the contact image sensor 16 is pressed against the conveying roller 1 mainly by the force P _{2 of the} pressing spring, and the reaction force R ₂ to the conveying roller 11 is a reaction force thereof.
Occurs. This reaction force R ₂ is a value substantially equal to the force P ₂ by the pressing spring when the transport roller 1 is not rotating, as in the conventional example.

Next, when the conveying roller 11 rotates counterclockwise as indicated by the arrow and a frictional force F ₂ acts on the contact point A of the contact image sensor 3, this frictional force F ₂ is a reaction force generated at the fulcrum B. not only it is supported by T _2, the contact type causing moment in the clockwise direction about the fulcrum B to the image sensor 16, acts to lift the contact image sensor 16, and the reaction force of the upward fulcrum B Gives rise to S ₂ . Therefore, the reaction force R ₂ generated on the transport roller 11 is reduced, and the reduction amount of the reaction force R ₂ at that time is the frictional force F ₂
The larger is, the larger. Therefore, during conveyance of the document 14, the frictional force F ₂ acting on the contact image sensor 16 is applied.
Is not so large, the frictional force F ₂ thereof is small to lift the contact image sensor 16, and the reaction force R ₂ of the conveying roller 11 is maintained at a large value, so that the pressing force required for conveying the original document is kept. Is maintained, but the original is gone,
When the transport roller 11 is in direct contact with the cover glass 16a of the contact-type image sensor 16 and idles, a large friction coefficient F _{2 due to} a large friction coefficient with the cover glass.
Tends to act, which acts to lift the contact-type image sensor 16, greatly reducing the reaction force R ₂ and reducing the friction force F ₂ . Thus, the transport roller 1
Even when 1 touches the cover glass 16a of the contact type image sensor 16 and rotates idly, the frictional force F ₂ does not become so large, and becomes considerably smaller than the frictional force F ₁ (when the roller is idling) in the conventional example. As described above, the frictional force F ₂
Corresponds to the rotational load torque on the conveyance roller 11, so in the present embodiment, even when there is no document between the conveyance roller 11 and the contact image sensor 16 and the friction coefficient with respect to the cover glass 16a becomes extremely large, the conveyance is performed. The amount of increase in the rotational load torque applied to the roller 11 can be suppressed to a small amount, and therefore the rotational load torque is considerably smaller than in the conventional case. Therefore, a stepping motor with a small drive torque can be driven without step out.

Next, in this embodiment, the frictional force acting on the contact image sensor 16 and the rotational load torque acting on the conveying roller 11 will be described more specifically. In FIG. 5, the pressing force acting to press the contact image sensor 16 against the contact point A with the conveying roller 11 by a pressing spring or the like is P, the reaction force of the conveying roller 11 is R, and when the conveying roller 11 rotates. If the frictional force acting on the contact image sensor 16 is F, the friction coefficient on the contact image sensor 16 is μ, and the distance from the fulcrum B to the line on which the pressing force P and the friction force F act is L ₁ and L ₂ , respectively. , Fulcrum B
The following equation holds from the balance of moments around.

PL ₁ = RL ₁ + FL ₂ Here, F = μR. Therefore, if the above equation is transformed, PL ₁ = RL ₁ + μRL ₂ = R (L ₁ + μL ₂ ) and if further transformed, R = PL ₁ / (L ₁ + μL ₂ ) = P / (1 + μL ₂ / L ₁ ) = P / (1 + μtan θ) Therefore, the frictional force F acting on the contact image sensor 16 is F = μR = μP / (1 + μtan θ), and the frictional force F is a function of the friction coefficient μ and the angle θ. The rotational load torque that acts on the transport roller 11 is a value proportional to the frictional force F.

FIG. 6 shows the relationship between the frictional force F (or rotational load torque) and the friction coefficient μ when the pressing force P for pressing the contact image sensor 16 against the conveying roller 11 is constant.
6 is a graph showing a plurality of angles θ calculated from the above formula. In FIG. 6, what is indicated by a straight line 50 is shown in FIG.
This corresponds to the conventional example (angle θ = 0 °) shown in (b), and in this case, the friction force F is proportional to the friction coefficient μ. On the other hand, when the position of the fulcrum B is separated from the tangent line XX and the straight line connecting the fulcrum B and the contact point A is inclined with respect to the tangent line XX, θ = 15 ° in FIG. Two
As can be seen from the curves corresponding to 6.6 °, 45 °, and 70 °, the increase in the friction force F is suppressed as the friction coefficient μ increases, and the friction force F decreases as the angle θ increases. Become. In the figure, 51 is the characteristic of this embodiment in which the angle θ is set to 45 °.

Here, the actual value of the friction coefficient μ is 0 .. in the combination of the paper (original 14) and the cover glass 16a.
It is about 2 to 0.5, and in the combination of the silicone rubber which is the surface material of the transport roller 11 and the cover glass 16a, it is about 0.8 to 1.4 due to dirt on the roller surface.

By the way, when the fulcrum B is arranged at a position inclined with respect to the tangent line XX as shown in the embodiment, the original is fed (the friction coefficient μ is 0.2 to 0.5). Also in the region (1), the reaction force R is reduced. For this reason,
The frictional force between the transport roller 11 and the document 14 may be insufficient, which may hinder document feeding. Therefore, in order to reliably feed the document, it is necessary to increase the pressing force P so as to compensate for the decrease in the reaction force R. In FIG. 7, the friction coefficient μ of the original is set to 0.5, and under that condition, the reaction force R is constant with respect to each value of the angle θ (thus, the friction force F is also constant).
6 is a graph showing the characteristics obtained by setting the pressing force P so that The vertical axis shows the rotational load torque proportional to the frictional force F, and the numerical value shows the frictional force F when the reference friction coefficient μ = 0.5 as 100. Further, reference numeral 52 indicates the characteristic of the conventional example (θ = 0 °), and reference numeral 53 indicates the characteristic of the present embodiment (θ = 45 °).

As can be seen from FIG. 7, the conventional example (θ =
0 °), the conveyance roller 11 is attached to the contact image sensor 1
When the cover glass 16a of No. 6 was brought into direct contact with the cover glass 16a and was allowed to idle, the friction coefficient μ = 1.
So that T _G1 corresponding to 4 is expected and can be supported,
The driving torque of the motor is set to T _{M1 in} consideration of the safety factor. On the other hand, in this embodiment (θ = 45 °), the maximum value of the rotational load torque is expected to be T _G2 which is considerably lower than that of the conventional example T _G1 , and correspondingly the driving torque of the motor is also considerably low T _G2. It can be set as _M2 . Thus, in the present embodiment, it is possible to employ a motor having a smaller drive torque than the conventional one, and it is possible to reduce the size and cost.

Further, this embodiment can cope with the case where the friction coefficient μ becomes higher. That is, when the apparatus is left warm for a long period of time or the like, the silicone rubber on the surface of the transport roller 11 may be activated while sticking to the cover glass 16a.
Becomes extremely large (for example, about μ = 2.5), but when the friction coefficient μ is 3 or less, the drive torque T _M2 of the motor exceeds the rotational load torque shown by the curve 53, and the motor is disconnected. It is started without any adjustment and normal reading is performed. On the other hand, in the conventional example, when the friction coefficient μ is slightly increased, the rotational load torque exceeds the drive torque T _M1 of the motor, causing the motor to step out. To prevent this, it is necessary to employ a motor with a larger drive torque, but this embodiment also eliminates this drawback.

In the embodiment described above, the angle θ is 45
However, the present invention is not limited to this case, and the angle θ can be appropriately increased or decreased. FIG. 8 is a rewrite of the characteristics shown in the graph of FIG. 7 with the horizontal axis as the angle θ and the vertical axis as the rotational load torque, and the curve 55 shows the friction coefficient μ =
In the case of 1.4 (the state where the transport roller directly contacts the cover glass and rotates), the curve 56 shows a friction coefficient μ = 2.5.
It shows the case where the rubber is in close contact with the cover glass. As can be seen from FIG. 8, the rotational load torque decreases as the angle θ increases from 0 °, and in particular 0
It decreases sharply from 0 to 20 °. Therefore, in the present invention, this angle θ is set to 20 ° or more. When this angle θ approaches 90 °, the reduction of the rotational load torque becomes gentle, while it is difficult to position the reading point A of the contact image sensor 16 so as to coincide with the contact point with the conveyance roller 11. Become. Therefore, the angle θ is 7
It is preferably 0 ° or less. Also, this angle θ is 9
When the range is 0 ° to 180 °, the frictional force F applied to the contact image sensor 16 by the rotation of the transport roller 11
Acts to press the contact-type image sensor 16 against the transport roller 11, so that the reaction force of the transport roller 11 increases and the frictional force further increases. Therefore, this area cannot be used.

Further, in the above embodiment, the fulcrum B of the contact type image sensor 16 is located at the tangent line X passing through the contact point A upstream of the contact point A between the contact type image sensor 16 and the conveying roller 11 in the document conveying direction. Although the fulcrum B is arranged above -X (on the contact image sensor side), the fulcrum B is symmetrical with respect to the contact point A, that is, a tangent line that is downstream of the contact point A in the document transport direction and passes through the contact point A. The same effect can be obtained by arranging it below XX (on the side of the transport roller). Therefore, the arrangement area of the fulcrum B usable in the present invention is shown in FIG.
In the present invention, a region sandwiched by a straight line 60 passing through the contact point A and inclined at an angle θ = 20 ° with respect to the tangent line XX and a vertical straight line YY passing through the contact point A is a fulcrum B in the present invention. Is a region that can be used for the arrangement of the fulcrum B, and the region between the straight line 60 and the straight line 62 that passes through the contact point A and is inclined at an angle θ = 70 ° with respect to the tangent line XX is the fulcrum B arrangement. This area is suitable for.

In the embodiment described above, the transport roller 1
The case where 1 rotates only in one direction has been described. by the way,
Depending on the location where the transport roller is used, it may rotate in the forward and reverse directions. In that case, when the contact type image sensor is in contact with the transport roller and the transport roller rotates in the reverse direction in the configuration of the above-described embodiment, the transport roller is excessively rotated. Load torque is applied, which causes inconvenience. Therefore, an example of a configuration that can be used for the transport roller 11 that rotates in the forward and reverse directions will be described.

FIGS. 9 to 11 show a scanning device provided in a facsimile machine as a scanning device according to the embodiment in that case, and the same or similar parts as those of the embodiment shown in FIGS. The same reference numerals are given and shown, and description thereof is omitted.
Also in the embodiment shown in FIGS. 9 to 11, the transport roller 11 is used.
The contact-type image sensor 16 is arranged so as to be pressed against the central fulcrum member 18c provided at the center of the upper surface of the contact type image sensor 16 and attached to the stay 20.
U of the end fulcrum member 19c which is placed on d and provided at both ends
The fulcrum pin 19d attached to the side plate is inserted into the groove. Here, as can be seen from FIG. 9, the contact portion between the center fulcrum member 18c and the center fulcrum receiver 18d is inclined upward to the left, and the U-shaped groove of the end fulcrum member 19c is considerably wider than the fulcrum pin 19d. With this configuration, the conveying roller 11 rotates in the forward direction, that is, the counterclockwise direction as shown by the arrow in FIG.
When the leftward frictional force F is applied to the center fulcrum member 18c is supported by the center fulcrum receiver 18d, and the end fulcrum member 19c abuts the fulcrum pin 19d, the horizontal movement is blocked, and the contact type image is obtained. The sensor 16 is rotatable about the first fulcrum B defined by the central fulcrum member 18c, the central fulcrum receiver 18d, the end fulcrum member 19c, and the fulcrum pin 19d. The transport roller 11 is indicated by an arrow in FIG. As described above, when the contact type image sensor 16 is rotated in the opposite direction, that is, clockwise, and a rightward frictional force F is applied to the contact type image sensor 16, the central fulcrum member 18c is separated from the central fulcrum receiver 18d and the end fulcrum member 18c is moved. 19c separates from the fulcrum pin 19d and becomes movable.

The contact-type image sensor 16 is further provided with a second end fulcrum member 30a extending downward at both ends thereof.
A groove 31 is formed at the lower end of the second end fulcrum member 30a. A second fulcrum pin 30b is attached to the side plate, and is inserted into the groove 31 of the second fulcrum pin 30b. here,
The positions and shapes of the second fulcrum pin 30b and the groove 31 are shown in FIG.
10, the second fulcrum pin 30b does not come into contact with the second end fulcrum member 30a when the contact roller type image sensor 16 is supported at the first fulcrum B by rotating the conveying roller 11 in the positive direction, as shown in FIG. As shown in FIG. 3, when the conveyance roller 11 rotates in the opposite direction indicated by the arrow, that is, in the clockwise direction, and the contact type image sensor 16 is moved to the right, the second fulcrum pin 30b abuts the second end fulcrum member 30a. To the right and downward. At this time, the upper center fulcrum member 18c and the center fulcrum receiver 18d are separated from each other, and the end fulcrum member 19c is also separated from the fulcrum pin 19d. Thus, in this state, the contact image sensor 1
6 is rotatable about the second fulcrum pin 30b,
In other words, the second fulcrum pin 30b constitutes the second fulcrum which is the center of rotation of the contact image sensor 16. Hereinafter, the second fulcrum will be indicated by the symbol D.

Here, the position of the first fulcrum B described above is arranged in an area usable for the arrangement of the fulcrum B described with reference to FIG. 5, preferably in a suitable area, and in the present embodiment. An upstream side (right side in the drawing) with respect to the regular paper transport direction from a tangent line XX passing through the contact point A between the contact image sensor 16 and the transport roller 11 and above the tangent line XX (contact image sensor side). ), And a straight line connecting the first fulcrum B to the contact point A passes through the contact point A and is a tangent line X-
The angle θ formed with respect to X is set to 45 °.
The position of the second fulcrum D (second fulcrum pin 30b) is also arranged in the area usable for the arrangement of the fulcrum B described in FIG. 5, preferably in a suitable area. However, since the second fulcrum D is a fulcrum when the transport roller 11 rotates in the opposite direction, when the area shown in FIG. 5 is applied when setting the position of the second fulcrum D, that area is rotated by the rotation of the transport roller 11. If the direction is reversed, it must be modified and applied. Therefore, the position of the second fulcrum D is reversed on the upstream side and the downstream side when the normal paper transport direction by the transport roller 11 is used as a reference. In the present embodiment, as shown in FIG. 10, the position of the second fulcrum D is on the upstream side (on the right side in the drawing) of the tangent line XX passing through the contact point A in the regular paper transport direction and at the tangent line XX. The angle α formed by the straight line connecting the second fulcrum to the contact point A with respect to the tangent line XX passing through the contact point A is set to 25 °. .

In FIGS. 9 to 11, 33 is a paper sheet which is an original or recording paper, and 34 is a scanning head for pressing the paper sheet 33 against the carrying roller 11 to carry it and scanning the paper sheet for recording. It is a thermal head. The thermal head 34 has a fulcrum member 35a provided with a groove at both ends thereof, and the fulcrum member 35a is fitted to the fulcrum pin 35b fixed to a side plate (not shown), thereby forming a fulcrum. It is rotatable about the pin 35b. In other words, the fulcrum pin 35b constitutes a fulcrum about which the thermal head 34 rotates. The position of this fulcrum (fulcrum pin 35b) is also arranged in a region that can be used for arranging the fulcrum B described in FIG. 5, preferably in a suitable region, and in this embodiment, it is shown in FIG. The angle θ'is set to 45 °. Reference numeral 36 is a pressing spring that presses the thermal head 34 against the transport roller 11, and 37 is a stay that holds one end of the pressing spring 36, which is fixed to both side plates.

Sheets 40a, 40b, 40c and 40d are paper 3
A paper guide for guiding 3 along a predetermined path, 41
Is an entrance paper sensor on the entrance side of the paper for detecting the presence or absence of paper, and 42 is an exit paper sensor for detecting the presence or absence of paper on the exit side of the paper.

The operation of the scanning device configured as described above will be described. In the present scanning device, whether the paper 33 is an original or a recording paper, the paper is conveyed by the conveyance roller 11 along the same conveyance path, and reading or recording is performed in the middle thereof. The reading operation is the same as that in the first embodiment, so the description thereof is omitted. next,
The recording operation will be described. When the paper 33, which is a recording paper, is inserted between the paper guides 40a and 40b and the tip of the paper 33 is inserted near the contact point H between the transport roller 11 and the thermal head 34, the entrance paper sensor 41 detects the paper 33. . After a waiting time of about 1 second after the detection of the paper 33, a stepping motor (not shown) which is a drive source of the conveyance roller 11
Operates to rotate the transport roller 11 by a small angle in the counterclockwise direction indicated by the arrow in FIG. By this operation, the leading edge of the sheet 33 is sandwiched between the transport roller 11 and the thermal head 34.

Next, when a printing operation is selected by operating an operation panel (not shown), the apparatus further rotates the conveying roller 11 counterclockwise to convey the sheet 33, and the leading edge of the sheet 33 is detected by the discharged sheet sensor 42. The motor stops at the point of time. Next, the motor is rotated in the reverse direction, and the conveying roller 11 is rotated in the reverse direction by a predetermined amount, so that the leading edge of the sheet 33 is accurately aligned with the contact point H. Thereafter, recording is performed by a drive driver (not shown) of the thermal head 34 according to the image signal sent from the memory section or the modem section.
The transport roller 11 rotates counterclockwise and transports the paper 33 in the regular direction. Recording is continued until the image signal data ends or the trailing edge of the sheet 33 is detected by the entrance sheet sensor 41. Even after the recording is completed, the transport roller 11 continues to rotate in the counterclockwise direction, and after the trailing edge of the sheet 33 is detected by the entrance sheet sensor 41, the trailing edge of the sheet 33 can surely pass the contact point A. After continuing the rotation for the required time, the transport roller 11 is stopped. Thus, the recording operation is completed.

Next, the frictional force acting on the contact type image sensor 16 and the thermal head 34 and the rotational load torque acting on the conveying roller 11 during the above operation will be described. When the transport roller 11 rotates in the forward direction, that is, the counterclockwise direction as shown in FIG.
6 is moved to the left by the frictional force F acting on the contact point A, and is rotatable about the first fulcrum B on the upper right side. Therefore, as in the first embodiment, the sheet 33 is placed between the contact image sensor 16 and the conveying roller 11.
When the frictional force F with respect to the contact-type image sensor 16 is increased and the frictional force F is about to increase, the frictional force F acts in the direction of pushing up the contact-type image sensor 16 and the conveyance roller 11 and the contact-type image sensor 16. By reducing the pressing force with the image sensor 16, an increase in the frictional force F is suppressed. Further, since the thermal head 34 is also rotatable around the fulcrum pin 35b, as in the case of the contact type image sensor 16, the thermal head 34 can be rotated.
When the paper 33 does not exist between the transfer roller 11 and the conveyance roller 11 and the friction coefficient with respect to the thermal head 34 increases and the friction force is about to increase, the friction force acts in the direction of separating the thermal head 34, and the conveyance roller By reducing the pressing force between 11 and the thermal head 34, an increase in frictional force is suppressed. Thus, the increase of the rotational load torque applied to the transport roller 11 is suppressed to be small.

Next, the conveying roller 11 is rotated in the reverse direction so that the paper 3
When pulling back 3, the frictional force F acts on the contact image sensor 16 in the opposite direction. At this time, if the contact-type image sensor 16 is rotatable around the first fulcrum B, the frictional force acts in the direction of pressing the contact-type image sensor 16 against the conveying roller 11, and the frictional force is significantly increased. . However, in this embodiment, as shown in FIG. 10, when the conveyance roller 11 is rotated in the reverse direction and rotated in the clockwise direction, the rotation causes the contact image sensor 1 to rotate.
The frictional force F acting on 6 slightly moves the contact-type image sensor 16 to the right so that the contact-type image sensor 16 is supported by the second fulcrum pin 30b at the lower right and the central fulcrum member 18c located at the upper right. Central support 18d,
The end fulcrum member 19c and the fulcrum pin 19d are separated from each other. As a result, the contact-type image sensor 16 can rotate about the second fulcrum D (second fulcrum pin 30b), and the force shown in FIG. 11 is applied, and the horizontal reaction force T is applied to the second fulcrum D. An upward reaction force S is generated. In this state, when the paper 33 does not exist between the contact image sensor 16 and the conveyance roller 11, the friction coefficient F with respect to the contact image sensor 16 increases, and when the friction force F is about to increase, the friction force is increased. F is a contact image sensor 1
6 is pushed up to reduce the pressing force (reaction force R of the transport roller 11) between the transport roller 11 and the contact image sensor 16, thereby suppressing an increase in the friction force F. Thus, in this case as well, it is possible to suppress an increase in the rotational load torque applied to the transport roller 11.

In FIG. 10, the thermal head 34 is rotatable about the fulcrum pin 35b at the same position as in the normal rotation even when the transport roller 11 is rotated in the reverse direction. The frictional force acting on the head 34 acts in the direction of pressing the thermal head 34 against the transport roller 11. However, since the conveyance roller 11 is rotated in the reverse direction in order to pull the paper 33 back to the contact point H, the thermal head 3 is rotated when the conveyance roller 11 is rotated in the reverse direction.
The sheet 33 is always present between the sheet 4 and the conveying roller 11, and a large frictional force does not act on the thermal head 34. Therefore, the thermal head 34 does not apply an excessive rotational load torque to the transport roller 11 when the transport roller 11 is rotated in the reverse direction.

As described above, in the second embodiment, the contact type image sensor 16 is used not only when the transport roller 11 is rotated in the forward direction but also when it is rotated in the opposite direction to pull back the recording sheet. It is possible to suppress an increase in the rotational load torque when the roller directly contacts the transport roller 11, and therefore, it is possible to reduce the drive torque of the motor for driving the transport roller and to downsize the motor.

[0050]

As described above, according to the first aspect of the present invention, the scanning head, which is pressed against the conveying roller by the pressing means, has the fulcrum in the plane perpendicular to the axis of the conveying roller. It is arranged rotatably as a center, and its fulcrum position is located on the scanning head side with respect to the tangent line drawn to the contact point on the upstream side in the paper transport direction from the contact point between the scanning head and the transport roller, and on the downstream side. In the case where the conveying roller is placed on the side of the conveying roller and the straight line connecting the fulcrum and the contact point forms an angle of 20 ° or more with respect to the tangent line, the conveying roller idles in direct contact with the scanning head. As described above, when the coefficient of friction with respect to the scanning head increases and the frictional force is about to increase, the large frictional force causes a force in the direction of separating the scanning head from the conveyance roller. It is possible to suppress an increase in frictional force to a small extent. Therefore, it is possible to suppress an increase in the rotational load torque of the carry roller, and it becomes possible to drive the carry roller with a motor having a small driving torque without any trouble, and it is possible to reduce the size and size of the apparatus. This has the effect of reducing costs. Further, in the present invention, it is not necessary to form a minute gap between the scanning head and the carrying roller as proposed in Japanese Patent Laid-Open No. 63-10968, so that the apparatus can be operated with high accuracy and high rigidity. Since it is not necessary to make the device, the cost of the device can be reduced also from this point.

According to the second aspect of the present invention, the scanning head, which is pressed by the pressing means against the transport roller capable of rotating in the normal and reverse directions, is arranged in the plane perpendicular to the axis of the transport roller when the transport roller is normally rotated. Centering on one fulcrum,
At the time of reverse rotation, it is arranged so as to be rotatable around the second fulcrum, and the position of the first fulcrum is located at the contact point on the upstream side in the regular paper transport direction from the contact point between the scanning head and the transport roller. The drawn tangent is located on the scanning head side and on the downstream side on the transport roller side, and the angle (θ) formed by the straight line connecting the first fulcrum and the contact point with respect to the tangent is 20 ° or more, Further, the position of the second fulcrum is located on the transport roller side with respect to the tangent line drawn at the contact point on the upstream side in the regular paper transport direction with respect to the contact point between the scan head and the transport roller, and on the scan head on the downstream side. Even if the transport roller rotates in the forward direction, the reverse roller is located on the side and the straight line connecting the second fulcrum and the contact point forms an angle (α) with respect to the tangent line of 20 ° or more. When rotating in the direction When the scanning head comes into direct contact with the conveying roller and the friction coefficient with respect to the scanning head increases, the frictional force acting on the scanning head exerts a force in the direction of separating the scanning head from the conveying roller, thereby suppressing an increase in the frictional force. Therefore, the increase of the rotational load torque of the carrying roller is suppressed to a small level, and the carrying roller can be driven by the motor having a small driving torque without any trouble, and the size and cost of the apparatus can be reduced. It has the effect of being able to.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a scanning device according to an embodiment in which the present invention is applied to an image reading device, taken along a plane perpendicular to an axis of a conveyance roller.

FIG. 2 is a schematic perspective view showing main components of the scanning device shown in FIG.

FIG. 3 is a schematic cross-sectional view showing the scanning device shown in FIG. 1 taken along a plane perpendicular to the axis of the scanning roller.

4A is a schematic cross-sectional view showing how a force is applied to the contact image sensor in the embodiment shown in FIG. 1, and FIG. 4B is a schematic cross-sectional view showing how a force is applied to the contact image sensor in the conventional example.

5 is a schematic cross-sectional view showing how the force is applied to the contact-type image sensor and an arrangement area of a fulcrum B in the embodiment shown in FIG.

FIG. 6 is a graph showing the relationship between the friction force acting on the contact image sensor and the friction coefficient under the condition that the pressing force P is constant.

FIG. 7 is a graph showing the relationship between the friction force acting on the contact image sensor and the friction coefficient under the condition that the pressing force P is set so that the rotational load torque is constant when the friction coefficient is 0.5.

FIG. 8 is a graph showing the relationship between rotational load torque and angle θ.

FIG. 9 is a schematic cross-sectional view showing a scanning device according to a second embodiment of the present invention, taken along a plane perpendicular to the axis of the transport roller when the transport roller is in the normal rotation state.

FIG. 10 is a schematic cross-sectional view showing a scanning device according to a second embodiment of the present invention in a state in which the transport roller is in the reverse rotation state, taken along a plane perpendicular to the axis of the transport roller.

11 is a schematic cross-sectional view showing how to apply force in the state shown in FIG.

FIG. 12 is a schematic sectional view showing an example of a conventional scanning device.

13A is a schematic front view showing another example of the conventional scanning device in a state where no pressing force is applied to the contact type image sensor, and FIG. 13B is a schematic front view showing the scanning device in which the pressing force is applied to the contact type image sensor. Schematic front view with the addition of

[Explanation of symbols]

 11 Conveyor Roller 12 Bearing 13 Side Plate 14 Document 16 Contact Image Sensor (Scanning Head) 16a Cover Glass 18a Central Support Point Member 18b Central Support Point Support 18c Central Support Point Member 18d Central Support Point Support 19a End Support Point Member 19b Support Point Pin 19c End Support Point Member 19d Support Point Pin 20 Stay 22 Pressing spring 30a Second end fulcrum member 30b Second fulcrum pin 33 Paper 34 Thermal head (scan head) 35a fulcrum member 35b fulcrum pin 36 Pressing spring 37 Stay A Contact point B fulcrum, first fulcrum C fulcrum D Two fulcrum XX tangent

Claims (3)

[Claims] 1. A scanning head comprising: a carrying roller; a scanning head that presses a sheet against the carrying roller to carry the sheet and scans the sheet; and a pressing unit that acts to press the scanning head against the carrying roller. Is rotatably provided about a fulcrum in a plane perpendicular to the axis of the carrying roller, and the fulcrum position is located in the sheet carrying direction rather than the contact point between the scanning head and the carrying roller. On the upstream side, an angle (θ) formed by a straight line located on the scan head side with respect to the tangent line drawn to the contact point and connecting the fulcrum and the contact point with respect to the tangent line.
Is 20 ° or more. 2. A scanning head comprising: a carrying roller; a scanning head that presses the paper against the carrying roller to carry the paper and scans the paper; and a pressing unit that acts to press the scanning head against the carrying roller. Is rotatably provided about a fulcrum in a plane perpendicular to the axis of the carrying roller, and the fulcrum position is located in the sheet carrying direction rather than the contact point between the scanning head and the carrying roller. On the downstream side, it is located on the conveying roller side with respect to the tangent line drawn to the contact point, and the angle (θ) formed by the straight line connecting the fulcrum and the contact point with respect to the tangent line is 20 ° or more. A scanning device characterized by. 3. A forward / reverse rotatable conveyance roller, a scanning head that presses the conveyance roller to convey the sheet and scans the sheet, and a pressing unit that presses the scanning head against the conveyance roller. The scanning head is provided so as to be rotatable about a first fulcrum during normal rotation of the transportation roller and a second fulcrum during reverse rotation in a plane perpendicular to the axis of the transportation roller, The position of the first fulcrum is on the scanning head side with respect to the tangent line drawn to the contact point on the upstream side in the regular paper transport direction from the contact point between the scanning head and the transport roller, and on the transport roller side on the downstream side. And the straight line connecting the first fulcrum and the contact point forms an angle (θ) of 20 ° or more with respect to the tangent line, and the position of the second fulcrum is the position of the scanning head and the conveyance. The upstream side of the regular paper transport direction from the contact point with the roller is on the transport roller side with respect to the tangent line drawn to the contact point, and on the downstream side is on the scan head side, and the second fulcrum and the A scanning device, wherein an angle (α) formed by a straight line connecting the contact point with the tangent line is 20 ° or more.