JP2018008427A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent or inhibit a print head from being displaced in a horizontal surface even in a printer in which the print head is fixed to a movable member which is coupled to a carriage so as to move in a vertical direction.SOLUTION: A printer includes: a print head 21 which makes prints on a printing surface of a sheet (a recording medium); a carriage 23 supported by a carriage shaft 11; a movable member 22 which has a guide member 22a, which rides on the printing surface of the sheet, and a fixing member 22b, which fixes and supports the print head 21, and engages with the carriage 23 so as to move in a vertical direction; coil springs 24 (first elastic members) which press the movable member 22 downward relative to the carriage 23; and a coil spring 25 (a second elastic member) which exerts a load so that a gap formed at a portion, in which the carriage 23 and the movable member 22 are engaged, is drawn in a certain direction.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a printer.

  Some printers print on a recording medium with a print head, and some have a structure that maintains a constant gap between the print head and the recording medium even if the thickness of the recording medium changes (for example, Patent Documents). 1).

  In the printer proposed in Patent Document 1, a print head is fixed to a movable member having a guide plate that rides on a print surface of a recording medium, and the movable member is moved up and down with respect to a carriage that is driven back and forth along a carriage shaft. While being held movably, the movable member is held in a state of being pressed downward (platen side) by an elastic member. That is, this printer has a structure in which the carriage body that supports the print head has a two-body structure of the carriage and the movable member, and these two bodies are coupled so as to be relatively movable up and down.

  According to this printer, the carriage body is maintained at the height position of the carriage shaft. When the guide plate rides on the printing surface of the recording medium, the movable member is moved according to the height position of the printing surface of the recording medium. Moves up and down with respect to the carriage. Thereby, the gap between the print head fixed to the movable member and the print surface of the recording medium can be kept constant.

JP 2001-026159 A

  By the way, a so-called impact dot printer performs printing by a wire (needle) protruding from a print head hitting an ink ribbon disposed between the print head and the recording medium and pressing it against the recording medium. Here, a platen for supporting the recording medium is disposed on the opposite side of the print head across the recording medium. For this reason, the print head receives a reaction force from the platen when the protruding wire presses the ink ribbon against the recording medium.

  In a printer in which the print head is supported by the carriage body having the two-body structure described above, the upward reaction force received by the print head from the platen is suppressed by the elastic member pressing the movable member downward. The print head can be prevented from being pushed upward by the reaction force.

  Here, the fact that the movable member is coupled to the carriage so as to move up and down means that there is a play (gap) between the movable member and the carriage that allows the vertical movement. This gap is a very small amount and is in a direction orthogonal to the vertical direction, that is, in a horizontal plane.

  If the portion where the movable member is coupled to the carriage so as to be movable up and down is disposed at a position shifted from the print head, the reaction force applied by the print head causes the moment of the movable member to the carriage. Acts. At this time, the upward component of the moment can be suppressed by the elastic member described above. On the other hand, the component perpendicular to the vertical direction, that is, the load in the horizontal plane cannot be suppressed, and the print head may be displaced on the print surface by a minute gap in the horizontal plane. If the position of the print head is displaced on the printing surface during the printing operation, the characters or figures to be printed are distorted or deformed, and the printing quality deteriorates.

  The present invention has been made in view of the above circumstances, and even if the print head is a printer fixed to a movable member that is coupled to the carriage so as to move up and down, the print head is displaced in a horizontal plane. It is an object of the present invention to provide a printer that can prevent or suppress the deterioration of print quality.

  The present invention includes a print head that performs printing on a print surface of a recording medium, a carriage that is supported by a carriage shaft, and a guide member that rides on the print surface of the recording medium, and fixes and supports the print head. A movable member that engages with the carriage so as to move up and down, a first elastic member that presses the movable member downward against the carriage, and a portion that engages the carriage and the movable member. And a second elastic member that applies a load so that the gap is moved in a certain direction.

  According to the printer of the present invention, even when the print head is fixed to a movable member that is coupled to the carriage so as to be movable up and down, the print head is prevented from being displaced in a horizontal plane and deteriorating print quality. Or it can be suppressed.

1 is a perspective view showing a main part of an impact dot printer which is an embodiment of a printer according to the present invention. It is sectional drawing which shows the cross section by the II line | wire in FIG. It is a perspective view of a printing part. It is a disassembled perspective view of a printing part. It is a front view of a printing part. It is a side view of a printing part. It is typical sectional drawing which shows the clearance gap in the part which a guide shaft and a guide hole engage. It is typical sectional drawing which shows the state which brought the clearance gap shown in FIG. 7 to the downstream of the conveyance direction. FIG. 7 is a side view corresponding to FIG. 6, illustrating an example of a printing unit in which a leaf spring bent in a substantially L shape applies an elastic force that pushes the movable member fixed member toward the carriage.

  Embodiments of a printer according to the present invention will be described below with reference to the drawings.

<Configuration of impact dot printer>
FIG. 1 is a perspective view showing a main part of an impact dot printer 1 (hereinafter simply referred to as a printer 1) which is an embodiment of a printer according to the present invention, and FIG. FIG. Note that FIG. 2 also includes the range not shown in FIG. The main part of the printer 1 of FIG. 1 includes two pairs of conveying rollers 13 and 14 and a printing unit 20. Although not shown, the printer 1 also includes a control unit that controls operations of the conveyance roller pairs 13 and 14, the printing unit 20, and the like.

  The conveyance roller pairs 13 and 14 convey a sheet 200 bound in a booklet form, which is an example of a recording medium, in a direction Y (hereinafter referred to as a conveyance direction Y) in a conveyance path 15 (conveyance roller pair 13, platen 12, and conveyance roller pair). 14). The transport roller pair 13 and the transport roller pair 14 are arranged side by side along the transport direction Y of the paper 200, and the transport roller pair 13 is disposed upstream of the transport roller pair 14.

  As shown in FIG. 2, the conveyance roller pair 13 includes a rubber roller 13b disposed on the lower side in the vertical direction Z and a resin roller 13a disposed on the upper side in the vertical direction Z. As shown in FIG. 1, a pair of rubber rollers 13b and resin rollers 13a, which are provided in contact with each other on the surface, is formed in a direction X (hereinafter referred to as a scanning direction X) orthogonal to the transport direction Y. 6 pairs are provided along the line. These six pairs of rubber rollers 13b and resin rollers 13a are provided coaxially.

  As shown in FIG. 2, the conveying roller pair 14 includes a rubber roller 14b disposed below the vertical direction Z and a resin roller 14a disposed above the vertical direction Z. 6 pairs of the rubber roller 14b and the resin roller 14a are also provided along the scanning direction X, and the six pairs of rubber roller 14b and the resin roller 14a are made of resin. The made rollers 14a are coaxially provided.

  The shaft provided with the six rubber rollers 13b of the conveying roller pair 13 and the shaft provided with the six rubber rollers 14b of the conveying roller pair 14 are each driven by a stepping motor.

  The printing unit 20 is provided between the conveyance roller pair 13 and the conveyance roller pair 14 in the conveyance direction Y. The printing unit 20 is provided to be movable along the carriage shaft 11 extending in the scanning direction X, and moves (scans) in the scanning direction X by driving a stepping motor. The printing unit 20 can perform printing on the entire surface of the paper 200 by printing on the paper 200 moving in the transport direction Y while moving in the scanning direction X.

  3 is a perspective view of the printing unit 20, FIG. 4 is an exploded perspective view of the printing unit 20, FIG. 5 is a front view of the printing unit 20, and FIG. 6 is a side view of the printing unit 20. As shown in FIGS. 3 and 4, the printing unit 20 includes a print head 21, a carriage 23, and a movable member 22.

  The print head 21 includes a plurality of wires for performing printing on the printing surface (upper surface illustrated in the present embodiment) of the paper 200, and a wire protruding downward from the central portion in the scanning direction X is an ink whose illustration is omitted. This is a so-called impact dot type print head that performs printing by hitting a ribbon and pressing it against the paper 200.

The carriage 23 is supported by the carriage shaft 11 and is movable in the scanning direction X by passing the carriage shaft 11 through two holes 23a formed coaxially. A guide plate 23c is fixed to the carriage 23 with screws 29c.
The guide plate 23c is fixed to a belt 11a that moves in the scanning direction X by driving a stepping motor. Thus, when the stepping motor is driven, the carriage 23 moves along the carriage shaft 11 via the belt 11a and the guide plate 23c.

  The carriage 23 is provided with two cylindrical guide shafts 23b extending in the vertical direction Z shown in the figure. The two guide shafts 23b are arranged side by side along the scanning direction X. Further, the guide shaft 23b is disposed upstream of the hole 23a through which the carriage shaft 11 is passed in the transport direction Y.

  The movable member 22 includes a guide member 22a and a fixed member 22b. The guide member 22a rides on the printing surface of the paper 200 and presses the paper 200 against the platen 12 (see FIGS. 1 and 2) disposed below the guide member 22a in the vertical direction Z. The guide member 22a is, for example, a plastic molded product such as polycarbonate, and an opening is provided in the center of the bottom surface, and a ribbon mask is disposed in the opening.

  The ribbon mask is a pressed product of a thin plate made of stainless steel, for example, and is drawn into a convex shape so that the bottom surface protrudes about 0.08 to 0.1 [mm] from the bottom surface of the guide member 22a. Yes. A print hole 22e as an opening through which the wire of the print head 21 projects is formed on the bottom surface. The ribbon mask and the guide member 22a are connected by adhesion, press-fitting, or insert molding.

  The fixing member 22b supports the print head 21 by fixing it with two screws 29b. The guide member 22a and the fixing member 22b are integrally coupled by two screws 29a. In this coupled state, the position of the wire of the print head 21 is adjusted so as to protrude from the print hole 22e. .

  Further, guide holes 22c through which the two guide shafts 23b of the carriage 23 are respectively passed are formed on both sides of the fixed print head 21 along the scanning direction X of the fixed member 22b. As shown in FIG. 3, the printing unit 20 is engaged with each guide hole 22c in a state where the guide shaft 23b is passed. Thus, the print head 21 is fixed to the carriage via the movable member 22.

  That is, the print head 21 is fixed to a two-body carriage body of the movable member 22 and the carriage 23 that are engaged with each other by the guide shaft 23b and the guide hole 22c. As shown in FIG. 6, the guide hole 22 c is formed at a position biased to the downstream side in the transport direction Y with respect to the portion facing the platen 12 of the print head 21.

  Here, the outer diameter of the guide shaft 23b is slightly smaller than the inner diameter of the guide hole 22c. Thereby, the guide hole 22c can slide along the direction (vertical direction Z) in which the guide shaft 23b extends with respect to the guide shaft 23b. And since it is slidable, there is a slight gap between the guide shaft 23b and the guide hole 22c.

  In addition, a coil spring 24 (an example of a first elastic member) is disposed on each guide shaft 23b. The coil spring 24 is disposed so that one end thereof is in contact with the carriage 23 and the other end thereof is in contact with the fixed member 22 b of the movable member 22 in a state of being contracted from the natural length. Thereby, the coil spring 24 presses the movable member 22 downward against the carriage 23 and presses the guide member 22 a against the printing surface of the paper 200.

  A hooking portion 22d (see FIG. 4) protruding upward is formed at a position on the upper portion of the fixing member 22b that coincides with the center of the print head 21 in the scanning direction X. On the other hand, an opening 23e (see FIG. 3) penetrating in the transport direction Y is formed in a portion of the carriage 23 corresponding to the hook portion 22d. Further, at a position corresponding to the center of the print head 21 in the scanning direction X at the upper portion of the guide plate 23c fixed to the carriage 23, a hook portion 22d is provided at a height corresponding to the hook portion 22d of the fixing member 22b. A hook portion 23d similar to the above is formed.

  Each end of a coil spring 25 (an example of a second elastic member) that is extended to be longer than the natural length is hooked on the hook 22d of the fixing member 22b and the hook 23d of the guide plate 23c. ing. Therefore, the coil spring 25 is provided at a position that coincides with the center of the print head 21 in the scanning direction X. Further, due to the elastic force of the coil spring 25 being extended beyond the natural length, the upper part (the hook part 22d) of the movable member 22 to which the print head 21 is fixed is pulled toward the hook part 23d of the guide plate 23c. It is done.

  Thereby, a slight gap existing between the guide shaft 23b and the guide hole 22c is brought close to the guide plate 23c side (downstream side in the transport direction Y), and on the upstream side in the transport direction Y, the guide shaft 23b and There is no gap between the guide hole 22c and the guide shaft 23b and the guide hole 22c are kept in contact with each other.

<Operation of impact dot printer>
As shown in FIG. 2, the printer 1 transfers a sheet 200 inserted in the conveyance path 15 on the left side of the drawing in the conveyance direction Y with respect to the conveyance roller pair 13 arranged on the upstream side, into the conveyance roller pair 13. Between the rubber roller 13b and the resin roller 13a. When the paper detection sensor (not shown) provided in the printer 1 detects the paper 200, the control unit drives the stepping motor based on the detection result, and the rubber roller 13b rotates and is sandwiched between the conveyance roller pair 13. The sheet 200 is fed by a predetermined amount along the conveyance path 15 in the conveyance direction Y. The feeding amount of the paper 200 is an amount in which a predetermined portion of the paper 200 is disposed between the print head 21 and the platen 12 of the printing unit 20, and is set by a step amount driven by the stepping motor. It is remembered.

  The control unit controls the printing head 21 to protrude the wire for printing, the control to drive the stepping motor that moves the printing unit 20 in the scanning direction X, and the paper 200 by the conveyance roller pairs 13 and 14 in the conveyance direction Y. Control is performed to drive a stepping motor for conveyance. Accordingly, the printing unit 20 performs printing on the paper 200 while moving in the scanning direction X, and the transport roller pairs 13 and 14 transport the paper 200 in the transport direction Y to perform predetermined printing at a predetermined position on the paper. .

  Here, if the paper sheet 200 is bound in a booklet, such as a bank passbook of a financial institution, the thickness of the paper sheet 200 changes depending on the page to be printed (the thickness of each paper sheet). The thickness does not change, but the thickness changes due to the difference in the number of sheets stacked on the expanded page).

  In the printer 1 of this embodiment, the height position of the platen 12 is fixed, and the height position of the carriage 23 supported by the carriage shaft 11 is also fixed. However, the print head 21 is supported by a two-body carriage body that can be displaced in the thickness direction (vertical direction Z) of the paper 200.

  That is, as shown in FIG. 5, the print head 21 is fixed to the movable member 22 that can move up and down along the guide shaft 23 b with respect to the carriage 23, and the guide member 22 a runs on the paper surface of the paper 200. The movable member 22 moves upward relative to the carriage 23 against the elastic force of the coil spring 24. Therefore, the print head 21 moves up and down according to the thickness of the paper 200 on which the print head 21 prints, and the gap between the print head 21 and the paper surface of the paper 200 is always kept constant.

  Incidentally, the printer 1 performs printing by the wire protruding from the print head 21 hitting an ink ribbon disposed between the print head 21 and the paper 200 and pressing it against the paper 200. When the ink wire presses the ink ribbon against the paper 200, a reaction force directed upward in the vertical direction Z is received from the platen 12 disposed below the print head 21, as shown in FIG.

  In the printer 1, since the print head 21 is supported by the two-body carriage described above, the upward reaction force received by the print head 21 from the platen 12 presses the movable member 22 downward. It is possible to prevent the print head 21 from being pushed up by the reaction force by being pressed by the coil spring 24.

  7 is a schematic cross-sectional view showing a gap K at a portion where the guide shaft 23b and the guide hole 22c are engaged. FIG. 8 shows the gap K shown in FIG. It is typical sectional drawing which shows a state.

  A portion where the guide shaft 23b and the guide hole 22c, which join the carriage 23 and the movable member 22 so as to be movable up and down, are engaged with the platen 12 of the print head 21, as shown in FIG. On the other hand, it is eccentric to the downstream side in the transport direction Y. Therefore, the upward reaction force received by the print head 21 from the platen 12 generates a moment M that causes the guide shaft 23b and the guide hole 22c to rotate in the clockwise direction in FIG.

  A gap K exists as shown in FIG. 7 at the portion where the guide shaft 23b and the guide hole 22c are engaged. Therefore, unlike the printer 1 of the present embodiment, in the printer without the coil spring 25 (see FIG. 6), the gap K is closer to the upstream side in the transport direction Y when the moment M is not acting. The position where the gap K exists is not specified uniformly, such as when it is close to the downstream side, or when it is close to any of the scanning directions X.

  On the other hand, in a state where the moment M is applied, the movable member 22 tries to rotate with respect to the carriage 23 by the amount of play due to the gap K. When the movable member 22 is rotated by the moment M, the movable member 22 is moved to the carriage 23 (guide shaft 23b) so that the gap K shown in FIG. 7 is moved to the downstream side in the transport direction Y as shown in FIG. It is displaced with respect to it.

  As described above, in the printer having the configuration without the coil spring 25, the movable member 22 is displaced in the horizontal plane according to the presence or absence of the moment M, so that the print position by the print head 21 may be shifted in the transport direction Y. Since the print head 21 moves only in the scanning direction X during the original printing operation, if the position of the print head 21 is displaced in the transport direction Y, the characters and figures to be printed are distorted and deformed. Print quality deteriorates.

  On the other hand, in the printer 1 of this embodiment, the coil spring 25 (see FIG. 6) pulls the movable member 22 (fixed member 22b) in a certain direction, specifically, the carriage 23 (guide plate 23c) side. The direction in which the coil spring 25 applies a pulling load to the movable member 22 is such that the gap K is reduced by the moment M generated in the movable member 22 by the load that the guide member 22a rides on the printing surface of the paper 200 and is displaced upward. It matches the direction to do.

  Therefore, in the printer 1 according to the present embodiment, regardless of the presence of the moment M, the gap K is always moved toward the downstream side in the transport direction Y as shown in FIG. As a result, the movable member 22 is not displaced in the horizontal plane, and there is no possibility that the printing position by the print head 21 is shifted in the transport direction Y.

  Further, in the printer 1 of the present embodiment, the wire protrudes downward from the center portion of the print head 21 in the scanning direction X, so that a reaction force acts on the center of the print head 21 in the scanning direction X. Since the coil spring 25 is disposed at a position coincident with the center of the print head 21 in the scanning direction X, the position of the moment M acting on the print head 21 in the scanning direction X and the load that the coil spring 25 pulls. The working position can be matched.

  As shown in FIG. 8, the printer 1 of this embodiment is one in which an elastic force is applied to the movable member 22 by a coil spring 25 in the direction in which the gap K is approached by the moment M. In such a printer, the load applied to the movable member is not limited to the direction in which the gap K is approached by the moment M.

  In other words, the printer according to the present invention can set the load applied to the movable member in a direction opposite to the direction in which the gap K is approached by the moment M. However, in this case, even if the moment M acts on the movable member, a large load that does not displace the movable member in the direction in which the gap K is approached by the moment M (the downstream direction of the transport direction Y) is reversed. It is necessary to act in the direction (upstream side of the transport direction Y).

  Even when the moment M is applied, the gap K is always kept at the upstream side in the transport direction Y, so that the movable member is not displaced in the horizontal plane, and the print position by the print head is transported. There is no risk of shifting in the direction Y. However, as a load to be applied to the movable member, it is necessary to apply a larger load than the case in which the load is applied in the direction in which the gap K is approached by the moment M (the direction downstream from the transport direction Y). Therefore, the sliding resistance between the guide shaft 23b and the guide hole 22c may be increased.

  In the printer 1 of this embodiment, the coil spring 25 pulls the movable member 22 toward the carriage 23. However, the second elastic member in the printer according to the present invention is not limited to the coil spring. Other types of springs (eg, leaf springs) can be applied. In addition, the second elastic member in the printer according to the present invention is not limited to a spring, and a member formed of an elastic material such as rubber can also be applied.

  In the printer 1 of the present embodiment, the coil spring 25 applies an elastic force that pulls the movable member 22 toward the carriage 23. However, the second elastic member in the printer according to the present invention is a movable member. The movable member is not limited to one that pulls toward the carriage side, and an elastic force that pushes toward the carriage side may be applied to the movable member.

  FIG. 9 shows an example of a printing unit 20 ′ in which a leaf spring 26 (an example of a second elastic member) bent in a substantially L shape applies an elastic force pushing the fixed member 22 b of the movable member 22 toward the carriage 23. FIG. 7 is a side view corresponding to FIG. 6. In the illustrated printing portion 20 ′, the upper portion of the leaf spring 26 bent to the L shape is screwed to the carriage 23, and the lower portion of the bent portion of the L bent portion is fixed. The member 22b is pressed downstream in the transport direction Y, thereby applying an elastic force that pushes the movable member 22 toward the carriage 23 side. In FIG. 9, the description of the guide shaft 23b and the guide hole 22c shown in FIG. 6 is omitted.

  Also by the printer 1 of the embodiment provided with the printing unit 20 ′ configured in this way instead of the printing unit 20, the same operation and effect as the printer 1 of the above-described embodiment can be obtained.

  Note that the above-described printing unit 20 and printing unit 20 ′ are a guide member 22 a that is a portion that generates a moment M in the guide shaft 23 b and the guide hole 22 c that are engaged with each other (below the engaged portion). On the other hand, the second elastic member (coil spring 25 or leaf spring 26) is arranged on the upper side which is the opposite side, and the degree of freedom of arrangement can be increased as compared with the one arranged below.

DESCRIPTION OF SYMBOLS 1 Impact dot printer 11 Carriage shaft 12 Platen 20 Printing part 21 Print head 22 Movable member 22a Guide member 22b Fixing member 22c Guide hole 23 Carriage 23b Guide shaft 24 Coil spring 25 Coil spring 200 Paper K Clearance M Moment X Scanning direction Y Conveyance direction Z Vertical direction

Claims (3)

A print head for printing on the print surface of the recording medium;
A carriage supported by a carriage shaft;
A movable member that has a guide member that rides on the print surface of the recording medium, and that fixes and supports the print head and engages the carriage in a vertically movable manner;
A first elastic member that presses the movable member downward against the carriage;
A printer comprising: a second elastic member that applies a load so that a gap formed in a portion engaged with the carriage and the movable member is moved in a certain direction.   The second elastic member applies a load to the movable member in a direction in which the gap is reduced by a moment generated in the movable member due to a load that the guide member rides on the printing surface of the recording medium and is displaced upward. The printer according to claim 1.   The printer according to claim 1, wherein the second elastic member is provided at a position coinciding with the print head in a direction in which the print head moves along the carriage shaft.