JP3552384B2 - Paper transport device and printer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sheet conveying device that sandwiches a sheet supplied from an upstream side between two rollers, and conveys the sheet to a downstream side as the rollers rotate, and a printer including the sheet conveying device. .
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a paper transport device mounted on an ink jet printer, a feed roller that is driven to rotate and a pressure roller that is arranged to press against the feed roller are provided. There is known an apparatus in which a sheet is conveyed downstream by a frictional force between a feed roller and a sheet while the sheet is sandwiched between rollers.
[0003]
In this type of paper transport apparatus, a paper guide is disposed upstream of the pair of rollers, guides the paper along the guide surface of the paper guide, and moves the leading end of the paper transported from a paper cassette or the like to two rollers. Was accurately guided to the contact position.
[0004]
[Problems to be solved by the invention]
However, according to the related art, there are the following problems.
The paper used for printing with an ink-jet printer varies in thickness from relatively thin paper to thick paper such as postcards and envelopes, but when using thick paper, the paper guide guides Immediately before reaching the contact position of the roller pair, the paper guided along the surface cannot smoothly pass through the gap between the paper guide and the feed roller due to the resistance between the paper guide and the paper. Printing is started without feeding, and the margin at the leading end of the paper becomes smaller than expected, which causes a problem that printing cannot be performed at a desired position.
[0005]
Here, if the gap between the paper guide and the feed roller is sufficiently widened according to the thick paper, it is thought that the thick paper will pass through as smoothly as possible. Since the paper can move excessively freely in the gap, there is a possibility that a problem arises that the leading end position of the thin paper cannot be accurately positioned.
[0006]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a paper transport device capable of accurately feeding a paper regardless of the thickness of the paper, and a printer provided with the paper transport device. It is in.
[0007]
[Means for Solving the Problems]
In order to achieve the above-described object, a paper transport device according to the present invention includes a feed roller that is driven to rotate, a pressure roller that is arranged to press the feed roller, and these two rollers. And a first paper guide that guides the paper conveyed from the upstream side along the first guide surface and guides the leading end of the paper to the contact position of the two rollers. A paper transport device that transports the paper downstream by a frictional force between the feed roller and the paper while sandwiching the paper between the feed roller and the pressure roller with the rotation of the feed roller; The first guide surface is formed of an elastic member which is elastically deformed by receiving a pressure from the paper side when the first guide surface comes into contact with the paper conveyed to the downstream side .
[0008]
According to the paper transport device of the present invention, since the first guide surface formed on the first paper guide is formed of the elastic member as described above, the first guide surface contacts the paper transported downstream. At times, the greater the pressure applied from the paper side to the guide surface, the greater the gap between the guide surface and the feed roller. Therefore, thin paper that passes through the gap relatively smoothly is guided along the guide surface with almost no deformation of the elastic member, and when thick paper that normally cannot pass through the gap passes. As a result, the contact pressure from the paper side with respect to the paper guide increases, and the elastic member is compressed. As a result, the gap between the guide surface and the feed roller is pushed and widened, so that the paper becomes smoother due to the widening of the gap. You will be guided along. Therefore, according to the sheet transport device, the sheet can be reliably sent downstream irrespective of the thickness of the sheet, and as a result, the sheet is accurately fed.
[0009]
In addition, the elastic member employed in the present invention does not particularly matter the material or the like as long as it forms a guide surface and changes the distance between the guide surface and the feed roller with elastic deformation. . Specific examples include a rubber- or sponge-shaped synthetic resin material molded into a predetermined shape, a gel-like fluid sealed in a resin film case, a leaf spring-shaped member, and the like. May be elastically deformed, or may be a hard plate or the like forming a guide surface attached via an elastic body. However, a rubber-like or sponge-like synthetic resin material is preferable because it is relatively inexpensive and can be easily processed into an arbitrary shape. Further, the guide surface formed by the elastic member may be in contact with almost the entire surface of the sheet, but, for example, a plurality of strips made of an elastic body are arranged at intervals in parallel with the sheet conveying direction. It may be provided.
[0010]
By the way, if the frictional force generated between the guide surface and the paper is larger than the frictional force generated between the paper and the feed roller, smooth paper feed cannot be realized. It is desirable to reduce the coefficient of friction, but such a material having a small coefficient of friction is not always excellent in elastic deformation characteristics, so it is not easy to select a material that satisfies both characteristics sufficiently. .
[0011]
In this regard, if a film material having a smaller coefficient of friction than the surface of the feed roller is provided on the first guide surface, the surface serving as the base of the first guide surface is elastically deformed. The first guide surface is made of a material with excellent characteristics, and the coefficient of friction of the first guide surface can be reduced by the film material provided on the surface. It is also possible, or it becomes easy to select a material in consideration of cost and the like. Incidentally, as the film material having a small friction coefficient, an arbitrary resin film coated with Teflon or a polyester film can be used.
[0012]
Further, as described in claim 3, a sheet arranged upstream of the first sheet guide and guiding a sheet conveyed further from the upstream side along a second guide surface, and a leading end of the sheet is set in the first sheet guide. If a second paper guide is provided to guide the paper along the first guide surface, the paper may be guided along the second guide surface first. Paper guide can reliably contact the paper at an angle at a position where the first paper guide is located, so that the first paper guide can be reduced to the minimum necessary size. The first paper guide can be compactly arranged in a limited space near the feed roller, and the second paper guide can be arranged in an appropriate space away from the contact position between the feed roller and the pressure roller. It contributes to miniaturization of the entire apparatus including the location.
[0013]
Further, as described in claim 4, the paper sheet is further rotated at a position where it contacts a sheet stacking section on which a large number of sheets can be stacked and placed and a top surface of the sheet stacked on the sheet stacking section. When a paper feed roller that feeds only one sheet of paper to the downstream side by a frictional force generated between the paper sheet and the paper sheet is provided upstream of the first paper guide, the paper feed roller is driven. By performing the control, the sheets placed on the sheet stacking unit can be sent to the downstream side one by one. In particular, after the paper fed by the paper feed roller is guided by the first paper guide and hits the contact position of the two rollers, the feed roller starts rotating in the forward direction to further downstream the paper. When the feed roller starts to rotate, the leading edge of the paper is sucked between the rollers at the same time that the feed roller starts rotating and the feed roller starts to rotate. The paper feed amount can be accurately controlled by the rotation amount.
[0014]
Still further, when a plurality of the pressure rollers are arranged along the axial direction of the feed roller as described in claim 5, compared to disposing one long pressure roller, each pressure roller has The movement is light, and the paper can be transported more smoothly. In particular, in this case, if a plurality of guide surfaces which are elastically deformed are arranged together with the pressure roller, each guide surface is independently deformed for a wide sheet of paper, and the sheet is further smoothly moved along the guide surface. You will be guided.
[0015]
Next, a printer according to the present invention includes the above-described paper transport device as described in claim 6, and further includes a print head that prints on paper downstream of the transport mechanism. Features. With such a configuration, the paper transport device functions as described above, and the paper can be transported accurately and smoothly to the front of the print head.
[0016]
For such a printer, various more specific configurations are conceivable. For example, when the print head is an ink jet head that ejects ink droplets to perform printing, as described in claim 7, a paper transport function is provided. An excellent ink jet printer can be constructed.
[0017]
It should be noted that the paper transport device of the present invention can be mounted on a printer having a print head of a type other than the ink jet type. Further, the paper transport device of the present invention may be mounted not only on a printer but also on a facsimile machine or the like.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. Note that the specific devices and the like described below are merely examples of the embodiments of the present invention, and the embodiments of the present invention are not limited to the specific examples illustrated below.
[0019]
As shown in FIG. 1, the ink jet printer 2 feeds a plurality of sheets in a stacked state and feeds the sheets one by one to the downstream side from the sheet cassette 4 as the sheet is driven to rotate. A paper feed roller 6, an arm 7 swingably provided above the transport path, and a pressure rotatably provided at the tip of the arm 7 for pressing a sheet passing through the transport path below the arm 7 from above. The printing apparatus includes a roller 8 and a feed roller 10 that sandwiches the sheet between the pressure roller 8 and feeds the sheet to the front of the print head 12 as it is driven to rotate.
[0020]
Of these, the pressure roller 8 is formed of a metal rod having a small coefficient of friction, while the feed roller 10 is formed of ordinary rubber having a large coefficient of friction.
2, the left arm 7L and the right arm 7R, which are symmetrical to each other, form a pair as shown in FIG. 2 (hereinafter, when there is no need to distinguish between left and right, simply Arm 7). Each of the left arm 7L and the right arm 7R includes a bearing 22 serving as a swing fulcrum, a first paper guide 24 extending from the bearing 22, and a bearing 22 opposite to the first paper guide 24. The first paper guide 24 has a bearing portion 24a formed at an end thereof, and both ends of one pressure roller 8 are rotatably supported by both the left arm 7L and the right arm 7R. are doing. The left arm 7L and the right arm 7R can swing independently of each other, and when at least one of them swings, the axial position of the pressure roller 8 is slightly displaced accordingly. I have. Although not shown in FIG. 2, the ink-jet printer 2 is provided with three sets of the left arm 7L and the right arm 7R arranged side by side. Three are supported and arranged along the axial direction of the feed roller 10.
[0021]
On the other hand, springs 28 are respectively arranged on the plurality of cylindrical spring receiving portions 26 a provided on the spring receiving plate 26 of each arm 7. As shown in FIG. 3, the spring 28 is compressed between the spring support plate 32 and the spring receiving plate 26, and the spring 28 urges the spring receiving plate 26 in the direction of arrow P in the drawing. . The arm 7 is swingably supported by a shaft 34 fixed to the printer main body, and the pressure roller 8 on the opposite side to the spring receiving plate 26 is fed by a moment generated by the repulsive force of the spring 28. It is pressed against the peripheral surface of the roller 10. The concave side surface 24b of the first paper guide 24 is provided with a plurality of ribs 24c for reinforcing the first paper guide 24.
[0022]
Further, as shown in FIG. 3, a second paper guide 36 is provided on the upstream side of the contact position S between the pressure roller 8 and the feed roller 10 so that the paper 40 sent out by the paper feed roller 6 can be moved downward. And guided in the direction of the contact position S. An opening (not shown) for manual paper feed is provided above the second paper guide 36, and the manually fed paper 41 abuts on the second paper guide 36 to change its course. Are similarly guided in the direction of the contact position S.
[0023]
Further, a third paper guide 38 is provided at a printing position downstream of the contact position S, and the paper 40 sent from the contact position S is supported from below by a reference surface 38a on the surface thereof, and the printing is performed during printing. Sheet 40 is positioned.
As shown in FIG. 3, the surface of the first paper guide 24 on the supply side is a guide surface 24d which is convex as a whole, and the leading end portion of the guide surface 24d (that is, the contact position). A concave guide surface 24e, which is curved and concaved, is formed in a portion immediately before the upstream side of S). That is, the concave guide surface 24e is formed so as to form a substantially arc shape having a center on the paper 40 side when viewed in a cross section in the feed direction of the paper 40. The feed roller 10 forms a narrow passage with the concave guide surface 24e. When the concave guide surface 24e is formed at the distal end of the guide surface 24d, the leading end of the paper 40 guided to the distal end of the guide surface 24d is guided by the concave guide surface 24e, and the feed roller 10 and the pressure roller 8 are guided. When the paper 40 is pinched between the contact position S and the paper 40, the shape of the paper 40 becomes a shape along the concave guide surface 24e. When coming, the tendency to move away from the reference plane 38a is reduced. This suppresses the tendency of the paper 40 to move away from the reference surface 38a as compared with a case where the approach angle of the paper 40 to the contact position S is simply guided linearly or convexly, and makes the paper 40 more closely contact the reference surface 38a. The tendency is strengthened, and high-precision printing becomes possible.
[0024]
The concave guide surface 24e is formed by adhering a film material 53 having a smaller coefficient of friction than the surface of the feed roller 10 to the surface of an elastic body 51 elastically deformed by receiving a pressure from the paper side. Therefore, when the sheet abutting on the concave guide surface 24e is relatively thin, the sheet enters the space between the feed roller 10 and the pressure roller 8 without substantially deforming the elastic body 51, while the sheet is relatively thick. In this case, the contact pressure of the sheet against the concave guide surface 24e increases, and the elastic body 51 is compressed. As a result, the gap between the concave guide surface 24e and the feed roller 10 is expanded, and the gap is expanded. The paper more smoothly enters between the feed roller 10 and the pressure roller 8. Therefore, regardless of the thickness of the sheet, the sheet can be appropriately guided to the contact position S between the feed roller 10 and the pressure roller 8, and the sheet can be reliably sent to the print head 12 side.
[0025]
In the ink jet printer 2 configured as described above, when a printing operation is started, first, the paper feed roller 6 rotates and only one sheet is fed from the paper feed cassette 4. Then, the paper fed by the paper feed roller 6 comes into contact with the first paper guide 24 and is guided by the first paper guide 24 as it is, and as described above, the elastic body 51 is compressed as necessary to form the concave guide. The gap between the surface 24e and the feed roller 10 is expanded, and the sheet reaches the contact position S between the pressure roller 8 and the feed roller 10. At this time, the feed roller 10 is rotating in the reverse direction or has stopped, and the sheet only hits the contact position S and is not sucked. Then, at a timing after the sheet has definitely hit the contact position S, the feed roller 10 starts rotating in the forward direction, and conveys the sheet further downstream. Therefore, the leading edge of the sheet is reliably sucked in at the timing when the feed roller 10 starts to rotate in the forward direction. Therefore, it is possible to grasp the transport amount of the sheet based on the rotation amount of the feed roller 10 and control the print start position and the like. Can be implemented accurately.
[0026]
As described above, according to the ink jet printer 2, since the concave guide surface 24e formed on the first paper guide 24 is formed by the elastic body 51 as described above, regardless of the thickness of the paper, The paper can be reliably sent to the front of the print head 12.
[0027]
Further, since the film material 53 having a smaller coefficient of friction than the surface of the feed roller 10 is provided on the concave guide surface 24e, the frictional resistance of the concave guide surface 24e is reduced regardless of the frictional resistance of the surface of the elastic body 51 itself. As a result, the paper can be transported more smoothly.
[0028]
Further, since the second paper guide 36 is provided, the paper can be reliably brought into contact at an angle at a position where the first paper guide 24 is located. Thus, the first paper guide 24 can be compactly arranged in a limited space near the feed roller 10, and the second paper guide 36 can be disposed at an appropriate distance from the contact position S between the feed roller 10 and the pressure roller 8. And the entire inkjet printer 2 can be reduced in size.
[0029]
Further, after the paper fed by the paper feed roller 6 is guided by the first paper guide 24 and hits the contact position S between the pressure roller 8 and the feed roller 10, the feed roller 10 starts rotating in the forward direction and Is further conveyed to the downstream side, so that the feed roller 10 starts rotating and at the same time the leading edge of the paper is sucked between the pressure roller 8 and the paper feed amount is accurately determined by the rotation amount of the feed roller 10. Can be controlled.
[0030]
Furthermore, since three pressure rollers 8 are arranged along the axial direction of the feed roller 10, the movement of each pressure roller 8 becomes lighter than when one long pressure roller is provided, Smooth paper conveyance can be realized.
[0031]
As mentioned above, although the specific example of the present invention has been described, various specific configurations of the present invention other than the above specific example can be considered.
For example, in the above specific example, an example is shown in which the paper transport apparatus of the present invention is mounted on an ink jet printer. ).
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a schematic configuration of a main part of an ink jet printer equipped with a paper transport device of the present invention.
FIG. 2 is a perspective view around a pressure roller and a feed roller.
FIG. 3 is a cross-sectional view around a pressure roller and a feed roller.
[Explanation of symbols]
2 Inkjet printer, 4 Paper feed cassette, 6 Paper feed roller, 7 Arm, 8 Pressure roller, 10 Feed roller, 12 Print head , 22 ... bearing part, 24 ... first paper guide, 26 ... spring receiving plate, 28 ... spring, 32 ... spring support plate, 34 ... shaft, 36 ... 2 paper guide, 38 ... third paper guide, 40, 41 ... paper, 51 ... elastic body, 53 ... film material.

Claims (7)

A feed roller that is driven to rotate, a pressure roller that is arranged to press against the feed roller, and a sheet that is arranged upstream of these two rollers and that conveys the paper conveyed from the upstream further along the first guide surface. And a first paper guide for guiding the leading end of the paper to the contact position of the two rollers, and holding the paper between the feed roller and the pressure roller with the rotation of the feed roller. Meanwhile, in a paper transport device that transports the paper downstream by a frictional force between the feed roller and the paper,
The paper transport device according to claim 1, wherein the first guide surface is formed of an elastic member that is elastically deformed by receiving pressure from the paper side when the first guide surface comes into contact with the paper transported downstream . The paper transport device according to claim 1,
A sheet conveying device, wherein a film material having a smaller coefficient of friction than a surface of the feed roller is provided on the first guide surface. The paper transport device according to claim 1 or 2,
A sheet arranged on the upstream side of the first sheet guide and guided further from the upstream side is guided along the second guide surface, and a leading end of the sheet is guided in a direction in which the sheet comes into contact with the first sheet guide. A sheet conveying device provided with a second sheet guide. The paper transport device according to any one of claims 1 to 3,
Further, the sheet is rotated between a sheet stacking section on which a large number of sheets can be stacked and placed, and a position in contact with the upper surface of the sheet stacked on the sheet stacking section, and the rotation is generated between the sheet and the sheet. A paper feed roller for feeding only one sheet of paper downstream by frictional force is provided upstream of the first paper guide;
After the paper fed by the paper feed roller is guided by the first paper guide and hits the contact position of the two rollers, the feed roller starts rotating in the forward direction to move the paper further downstream. A sheet transport device configured to transport. The paper transport device according to any one of claims 1 to 4,
A paper transport device, wherein a plurality of the pressure rollers are arranged along an axial direction of the feed roller. A paper transport device according to any one of claims 1 to 5,
Further, a printer is provided with a print head for printing on paper downstream of the feed roller and the pressure roller. The printer according to claim 6,
The printer according to claim 1, wherein the print head is an ink jet head that ejects ink droplets to perform printing.

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