JP2013230932A - Paper feeder and printer - Google Patents

Abstract

To provide a paper feeding device and a printer capable of keeping a paper pressing force constant regardless of the paper thickness and suppressing a decrease in printing quality due to variations in paper feeding amount.
A paper feeding device of a printer includes a pressing device that biases a paper pressing roller toward the paper feeding roller. The pressing device 9 energizes the coil spring 13 that biases the swing lever 11 attached with the paper pressing roller 8 from above, the assist coil spring 14 that biases the swing lever 11 from below, and the assist coil spring 14. An energizing device 15 is provided. The assisting coil spring 14 is made of a shape memory alloy, and when it is energized, it generates heat internally and its free length changes. By energizing according to the paper thickness of the recording paper and increasing / decreasing the urging force by the assisting coil spring 14, the fluctuation of the urging force of the coil spring 13 caused by the fluctuation of the paper thickness is offset and the paper pressing force is kept constant. To do.
[Selection] Figure 1

Description

  The present invention relates to a paper feeding device that transports recording paper by pressing it against a paper feeding roller, and a printer including the paper feeding device.

  Conventionally, as a paper feeder for printers, a pair of transport rollers (paper feed roller and paper press roller) is placed in the recording paper transport path, and the paper press roller is pressed against the paper feed roller so that the recording paper is placed between both rollers. A device that generates a conveying force by being sandwiched is used. Such a paper feeding device generally presses the paper pressing roller against the paper feeding roller by a biasing member such as a spring.

  Patent Document 1 discloses a paper feeding device that sandwiches and conveys recording paper by a paper feeding roller (driving roller) and a paper pressing roller (idler roller). In this paper feeding device, in the case of thin recording paper (thin paper), the recording paper is pressed against the driving roller only by the weight of the idler roller. On the other hand, when the recording paper is thicker than this, the elastic force of the spring is applied to the idler roller by pushing up the idler roller, and a paper pressing force stronger than that of the thin paper is applied. In this way, when the thin paper is conveyed, the pressing force by the idler roller can be reduced, so that it is possible to prevent the thin paper from being marked with a roller.

JP 05-186085 A

  In the structure in which the paper pressing roller is urged toward the paper feed roller side by a spring as in Patent Document 1, the length of the spring changes according to the paper thickness. The pressure (nip pressure / paper pressing force) pressed against the roller fluctuates. When the paper pressing force fluctuates, there is a problem in that the conveyance force fluctuates accordingly and the paper feed amount varies, resulting in a decrease in print quality.

  SUMMARY OF THE INVENTION In view of the above-described problems, the present invention provides a paper feeding device that can keep the paper pressing force constant even when the paper thickness changes, and can suppress deterioration in print quality due to variations in the paper feeding amount. And to propose a printer equipped with the same.

In order to solve the above problems, the paper feeding device of the present invention is:
A paper feed roller disposed in the conveyance path of the recording medium;
A paper holding member disposed opposite to the paper feed roller;
Biasing means for biasing the paper pressing member toward the paper feed roller;
The biasing means is
An urging member for urging the paper pressing member with an urging force corresponding to the paper thickness of the recording medium;
A biasing force adjusting member made of a shape memory alloy that biases the paper pressing member together with the biasing member,
The biasing force adjusting member is
When deformed by the expression of the shape memory effect, the urging force applied from the urging force adjusting member to the paper pressing member is changed.

  In the present invention, when the urging force of the urging member that urges the recording medium fluctuates with the variation of the paper thickness, the variation in the urging force is detected by the shape memory alloy urging force adjusting member. It can be offset by deforming. Accordingly, even when the paper thickness changes, the recording medium can always be pressed with a constant force (paper pressing force), and the recording medium can be conveyed with a constant conveyance force. Therefore, variation in the paper feed amount can be suppressed, and deterioration in print quality can be suppressed.

  In the present invention, a first spring member that biases the paper pressing member is used as the biasing member, and the paper pressing member is biased together with the first spring member as the biasing force adjusting member. The 2nd spring member which is arrange | positioned and the free length changes with expression of the shape memory effect can be used. If it does in this way, since the free length of the 2nd spring member can be changed and the urging | biasing force can be adjusted, the fluctuation | variation of the urging | biasing force of a 1st spring member can be canceled.

  In the present invention, there is provided energization means for energizing the second spring member, and control means for controlling the energization means, and the control means corresponds to the second thickness according to the thickness of the recording paper to be conveyed. The free length of the second spring member can be adjusted by controlling the energization time and current value of the spring member. By doing this, the free length of the second spring member can be adjusted to a desired length and its urging force can be adjusted, so that the recording medium can always be pressed with a constant paper pressing force even when the paper thickness changes. .

  In this case, the control means stores a plurality of energization patterns corresponding to a plurality of preset paper thicknesses, and the energization pattern corresponding to the paper thickness of the recording paper conveyed from the plurality of energization patterns. It is desirable that the second spring member is energized according to the energization pattern. If it does in this way, a suitable energization pattern can be set up beforehand and the free length of the 2nd spring member can be adjusted precisely according to this. Therefore, the variation in the paper feeding force can be effectively suppressed by simple control.

  Here, the biasing means includes a swing lever having the paper pressing member attached to one end thereof, and the swing lever includes a paper pressing direction in which the paper pressing member approaches the paper feeding roller, and The paper pressing member is arranged to swing in a backward direction away from the paper feed roller, and at least one of the first spring member and the second spring member moves the swing lever in the paper pressing direction. It is desirable to arrange it to be energized. As described above, by adopting a structure in which the paper pressing member is urged through the swing lever, various spring arrangements can be accommodated. Therefore, the degree of freedom in design increases.

  In this case, the first spring member is attached to the swing lever so that the swing lever is urged in the paper pressing direction, and the second spring member is mounted on the first spring member. It is desirable to attach to the rocking lever in the opposite direction. Thus, the posture of the swing lever can be stabilized by attaching the two spring members to the swing lever in opposite directions.

Next, the printer of the present invention is
A print head;
And a paper feeding device that transports a recording medium along a transport path that passes through the print head.

  According to the present invention, when the urging force of the urging member that urges the recording medium varies with the variation in the paper thickness, the variation in the urging force is changed by deforming the urging force adjusting member made of shape memory alloy. Can be offset. Accordingly, even when the paper thickness changes, the recording medium can always be pressed with a constant force (paper pressing force), and the recording medium can be conveyed with a constant conveyance force. Therefore, variation in the paper feed amount can be suppressed, and deterioration in print quality can be suppressed.

It is explanatory drawing which shows the longitudinal cross-sectional structure of the principal part of the printer to which this invention is applied. It is explanatory drawing which shows the correspondence of the attachment length of a coil spring, and the paper thickness of a recording paper. 2 is a block diagram illustrating a control system of the printer. FIG. 6 is a flowchart illustrating control of the paper feeding device when printing is performed.

  Hereinafter, an embodiment of a printer including a paper feeding device to which the present invention is applied will be described with reference to the drawings.

  FIG. 1 is an explanatory view showing a longitudinal sectional configuration of a main part of a printer to which the present invention is applied. The printer 1 includes a print head 2 and a paper feeding device 5 that transports a recording paper 4 (recording medium) along a transport path 3 that passes through a printing position A by the print head 2. The printing position A is defined by the platen 6 disposed below the conveyance path 3. The paper feeding device 5 includes a paper feeding roller 7 disposed on the upstream side of the printing position A, a paper pressing roller 8 (paper pressing member) disposed to face the paper feeding roller 7, and the paper pressing roller 8 as a paper feeding roller. 7 is provided with a pressing device 9 (biasing means) for urging toward the paper 7 and a paper feed motor 10 for driving the paper feed roller 7.

  The pressing device 9 includes a rocking lever 11 disposed above the transport path 3. The swing lever 11 is supported so as to be swingable about a fulcrum 11a provided at the bent portion. The swing lever 11 includes a swing piece 11b extending from the fulcrum 11a along the transport path 3, and a paper pressing roller 8 is rotatably attached to the tip of the swing piece 11b. Further, the swing lever 11 includes a drive piece 11c extending upward from the fulcrum 11a. At the tip of the drive piece 11c, a spring mounting portion 11d is formed that protrudes in the opposite direction to the swing piece 11b. The swing lever 11 is arranged so that when the swing lever 11 swings around the fulcrum 11a, the tip of the swing piece 11b moves up and down, and the paper pressing roller 8 attached thereto moves up and down. That is, the swing lever 11 is disposed so as to swing in the paper pressing direction B1 in which the paper pressing roller 8 approaches the paper feeding roller 7 and in the backward direction B2 in which the paper pressing roller 8 moves away from the paper feeding roller 7. Has been.

  Spring support frames 12a and 12b fixed to the main body frame of the printer 1 are arranged above and below the spring mounting portion 11d. The pressing device 9 includes a steel coil spring 13 (biasing member / first spring member) disposed in a tensioned state between the upper spring support frame 12a and the spring mounting portion 11d, and a lower spring mounting portion. An assist coil spring 14 (biasing force adjusting member / second spring member) made of a shape memory alloy disposed between 11d and the spring support frame 12b is provided. The upper coil spring 13 urges the swing lever 11 in the paper pressing direction B1 by pulling the drive piece 11c upward. As a result, the paper pressing roller 8 attached to the tip of the swing piece 11 b is biased toward the paper feeding roller 7, and the recording paper 4 is pressed against the paper feeding roller 7.

  On the other hand, the assisting coil spring 14 is arranged in a free length state or in a compressed state between the spring mounting portion 11d and the lower spring support frame 12b. When the assisting coil spring 14 is in a free length state, the recording paper 4 is pressed only by the urging force of the upper coil spring 13. When the assisting coil spring 14 is in the compressed state, the recording paper 4 is pressed by the resultant force of the biasing force from the upper coil spring 13 and the biasing force from the assisting coil spring 14.

  The pressing device 9 includes an energizing device 15 (energizing means) for energizing the assisting coil spring 14. A current-carrying cable 15 a for connection to the current-carrying device 15 is connected to both ends of the assisting coil spring 14. The assisting coil spring 14 is made of a shape memory alloy such as a TiNi alloy or an FeMnSi alloy. When energized, the assist coil spring 14 generates heat internally and exhibits a shape memory effect, and returns to a previously memorized shape. The assisting coil spring 14 has an initial shape such that its free length is L0 in a state where current is not applied. On the other hand, the shape stored in the assisting coil spring 14 is a shape having a free length Lmax. The free length Lmax is set to a dimension longer than the free length L0 in the initial shape. The assist coil spring 14 can be deformed to an arbitrary length in the range from L0 to Lmax by controlling the amount of heat generated by the energization device 15 and controlling the internal heat generation amount of the assist coil spring 14. By adjusting the free length of the assisting coil spring 14, it is possible to adjust the urging force applied from the assisting coil spring 14 to the paper pressing roller 7 via the swing lever 11. The energization amount can be controlled by a combination of energization time and current value.

  FIG. 2 is an explanatory diagram showing a correspondence relationship between the attachment length of the coil spring and the paper thickness of the recording paper. FIG. 2A shows the case where the paper thickness is the thickest, and FIG. FIG. 2C shows the case where the paper thickness is the thinnest. The initial shape of the assisting coil spring 14 is set based on the assumed paper thickness d0 (see FIG. 2A) of the thickest paper type. In this example, the assisting coil spring 14 is attached so that the attachment length La0 of the assisting coil spring 14 matches the free length L0 when the recording paper 4a having the paper thickness d0 is sandwiched between the paper feeding roller 7 and the paper pressing roller 8. The initial shape of the coil spring 14 is set. When the recording paper 4a having the paper thickness d0 is conveyed, the paper feeding device 5 is used in its initial shape without energizing the assisting coil spring 14. In this case, since the biasing force is not generated from the assisting coil spring 14 having the free length L0, the recording paper 4 is pressed only by the biasing force of the upper coil spring 13. The upper coil spring 13 presses the recording paper 4 with an urging force corresponding to the attachment length Ls0.

  As shown in FIG. 2B, when the recording paper 4b having the paper thickness d1 thinner than the paper thickness d0 is conveyed, the paper pressing roller 8 is lowered by the dimensional difference between the paper thickness d0 and the paper thickness d1. Thus, the swing lever 11 turns in the paper pressing direction B1. Accordingly, the attachment length Ls of the upper coil spring 13 changes to a dimension Ls1 shorter than that when the paper thickness d0 is set, and the attachment length La of the lower assist coil spring 14 is longer than that when the paper thickness d0. The dimension changes to La1. When the paper feeding device 5 conveys the recording paper 4b having the paper thickness d1, the fluctuation of the urging force from the coil spring 13 (in this case, the mounting length of the upper coil spring 13 is changed from Ls0 to Ls1). In order to offset the decrease in the urging force and maintain the paper pressing force constant, the energizing device 15 is controlled to energize the assisting coil spring 14, and the assisting coil spring 14 is extended to increase the urging force. .

  That is, the paper feeding device 5 extends the assisting coil spring 14 until the free length L1 of the assisting coil spring 14 after deformation becomes longer than the attachment length La1 of the assisting coil spring 14 in this state. As a result, the biasing force in the paper pressing direction B <b> 1 is applied from the assisting coil spring 14 to the swing lever 11. Then, the assisting coil spring 14 is extended until the fluctuation (decrease) in the urging force from the upper coil spring 13 is just offset by the fluctuation (increase) in the urging force from the assisting coil spring 14. Thereby, the urging force applied to the recording paper 4b can be made the same as in the case of the paper thickness d0.

  As shown in FIG. 2C, when the recording paper 4c having the thinnest paper thickness d2 is conveyed, the attachment length Ls2 of the upper coil spring 13 is further shortened and the attachment length of the lower assisting coil spring 14 is provided. The length La2 is further increased. Therefore, when the recording paper 4c having the paper thickness d2 is conveyed, the paper feeding device 5 cancels the further decrease of the urging force due to the further contraction of the upper coil spring 13 and maintains the paper pressing force constant. Then, the energizing device 15 is controlled to further energize the assisting coil spring 14. Then, the assisting coil spring 14 is extended until the free length = Lmax. When the free length of the assisting coil spring is Lmax, the biasing force from the assisting coil spring 14 is offset by the amount that offsets the decrease in the biasing force from the coil spring 13 due to the fact that the mounting length Ls2 of the upper coil spring 13 is further shortened. Will increase. Thereby, the urging force applied to the recording paper 4c can be made the same as in the case of the paper thickness d0.

(Control system)
FIG. 3 is a block diagram showing a control system of the printer 1. The control system of the printer 1 is configured around a control unit 20 (control means) including a CPU, a ROM, a RAM, and the like. The control unit 20 receives a print command from a host device (not shown) and signals from various detectors such as a paper detector provided in the printer 1. The print head 2 is connected to the output side of the control unit 20 via a head driver (not shown). A paper feed motor 10 is connected via a motor driver (not shown). Furthermore, an energization device 15 is connected to the output side of the control unit 20.

  The control unit 20 includes a printing control unit 21 and a paper pressing force control unit 22. In this example, the control unit 20 functions as a control unit for performing overall control of the paper feeding device 5. The ROM of the control unit 20 stores in advance an energization pattern (combination of current value and energization time) for obtaining an internal heat generation amount necessary for extending the free length of the assist coil spring 14 from L0 to L1 or Lmax. ing. Such an energization pattern can be determined in advance by experiments or calculations. When recording paper 4 having a paper thickness other than d0, d1, and d2 is used, an energization pattern corresponding to each paper thickness can be set and stored in advance.

(Paper feeder control)
FIG. 4 is a flowchart showing the control of the paper feeding device during printing. The control unit 20 starts the process of this flowchart based on the reception of the print command from the upper apparatus. First, in step S1, the paper pressing force control means 22 extracts paper information (for example, the type of paper specified by the user) from the print command, and determines the paper thickness of the recording paper 4 based on the extracted paper information. To do. For example, a correspondence table between the paper type and the paper thickness is created in advance and stored in the ROM of the control unit 20, and the paper thickness is determined based on the correspondence table. When the paper pressing force control means 22 determines that the paper thickness is smaller than the maximum value d0 (step S1: No), the paper pressing force control means 22 proceeds to step S2. On the other hand, if it is determined that the paper thickness is the maximum value d0 (step S1: Yes), the process proceeds to step S3.

  In step S2, the paper pressing force control means 22 adjusts the dimensions of the assist coil spring 14 according to the determined paper thickness. That is, an energization pattern corresponding to the determined paper thickness is read from the ROM, and the energization device 15 is controlled according to the read energization pattern to energize the assisting coil spring 14. As a result, the free length of the assisting coil spring 14 changes to a dimension corresponding to the paper thickness, and the urging force fluctuates, and the fluctuation of the paper pressing force accompanying the fluctuation of the paper thickness is corrected. Accordingly, the pressing device 9 can press the recording paper 4 with the same paper pressing force as that when the paper thickness is the maximum value d0 and the assisting coil spring 14 has the initial shape. The paper pressing force control means 22 proceeds to step S3 when the dimension adjustment in step S2 is completed. In step S <b> 3, the print control unit 21 drives the paper feed motor 10 based on the print command to start the rotation of the paper feed roller 7. The print control unit 21 controls the printing operation by the print head 2 in conjunction with the conveyance operation of the recording paper 4 by the conveyance force of the paper feed roller 7 and performs printing on the recording paper 4.

(Function and effect)
In the printer 1 of this example, as described above, the current-carrying device 15 is connected to the assist coil spring 14 made of the shape memory alloy, and the paper press roller 8 is biased by combining the assist coil spring 14 and the steel coil spring 13. Thus, the pressing device 9 is configured. In such a configuration, the shape memory effect can be expressed by controlling the energization time and the current value to the assisting coil spring 14, and the shape (free length) can be adjusted to a desired length. Therefore, the size of the assisting coil spring 14 is adjusted according to the paper thickness of the recording paper 4 when printing is performed, whereby the urging force applied from the pressing device 9 to the paper pressing roller 8 can always be adjusted to a constant value. Therefore, even if the paper thickness changes, the recording medium can always be pressed with a constant paper pressing force, and the recording paper 4 can always be conveyed with a constant conveyance force. Therefore, variation in the paper feed amount can be suppressed, and deterioration in print quality can be suppressed. Further, by performing the energization control based on a preset energization pattern, the paper pressing force can be adjusted with high accuracy with simple control. Further, in this example, a structure is employed in which coil springs are attached and urged on the upper and lower sides of the swing lever 11, so that the degree of freedom of component placement is high and the movement is stable.

(Modification example)
(1) In the above embodiment, the energization of the assist coil spring 14 is only performed before the start of printing. However, when the printing operation is performed for a long time, the temperature of the assist coil spring 14 decreases during printing. As a result, the shape may return to its original shape and the paper pressing force may fluctuate. Thus, in this example, the assist coil spring 14 is energized intermittently even after printing is started. For example, an energization pattern for energizing a predetermined energization amount every predetermined time is stored in the control unit 20, and energization of the assisting coil spring 14 is performed according to the energization pattern after printing is started. In this way, the fluctuation of the paper pressing force can be suppressed within a fluctuation range that does not deteriorate the print quality. Therefore, variation in the paper feed amount can be suppressed, and deterioration in print quality can be suppressed.

(2) In the above embodiment, the paper pressing force is adjusted by determining the paper thickness from the paper type set by the user. However, a pressure sensor is provided in the pressing device 9 to adjust the paper pressing force (paper pressing roller 8 or The urging force applied to the swing lever 11 is directly monitored, and the assist coil spring 14 is energized to adjust the dimension of the assist coil spring 14 when the detected value of the pressure sensor is out of the preset range. You may comprise as follows. In this way, it is possible to adjust the paper pressing force with higher accuracy, and it is possible to more effectively suppress a decrease in print quality.

(3) In the above embodiment, the coil spring 13 is disposed on the upper side of the swing lever 11 and the assisting coil spring 14 is disposed on the lower side. However, they can be disposed upside down. In this case, the assist coil spring 14 can compensate for a decrease in the urging force from the coil spring 13 by using the assist coil spring 14 formed so that the free length is reduced by energization. Further, both the coil spring 13 and the assisting coil spring 14 can be arranged on the upper side or the lower side of the swing lever 11. Alternatively, the assisting coil spring 14 is arranged so as to bias the swing lever 11 in the backward direction B2, and the assisting coil spring 14 is deformed according to the variation in the paper thickness, whereby the biasing force of the assisting coil spring 14 is increased. It may be configured to weaken.

(4) In the above embodiment, the coil spring is used as the urging member and the urging force adjusting member, but other forms of urging member and urging force adjusting member such as a leaf spring may be used. At this time, the urging force adjusting member may be configured such that the urging force applied to the paper pressing roller 8 changes due to the expression of the shape memory effect. For example, in the above embodiment, the urging force is applied by pressing one end of the oscillating lever 11. However, the urging member and the urging force adjusting member capable of applying the urging force in the rotation direction to the fulcrum 11 a of the oscillating lever 11 are used. be able to. Further, without using the swing lever 11, the rotary shaft of the paper pressing roller 8 is supported so as to be movable in the vertical direction, and the rotary shaft is biased downward by the biasing member and the biasing force adjusting member. You can also.

DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Print head, 3 ... Conveyance path 4, 4a, 4b, 4c ... Recording paper, 5 ... Paper feeding apparatus, 6 ... Platen, 7 ... Paper feeding roller, 8 ... Paper pressing roller (paper pressing member) ), 9 ... Pressing device (biasing means), 10 ... Motor, 11 ... Oscillating lever, 11a ... Supporting point, 11b ... Oscillating piece, 11c ... Drive piece, 11d ... Spring mounting portion, 12a ... Spring support frame, 12b ... Spring support frame, 13 ... Coil spring (biasing member / first spring member), 14 ... Assisting coil spring (biasing force adjusting member / second spring member), 15 ... Energizing device (energizing means), 15a ... Energizing Cable, 20 ... control unit (control means), 21 ... printing control means, 22 ... paper pressing force control means, A ... printing position, B1 ... paper pressing direction, B2 ... reverse direction, d0, d1, d2 ... paper thickness, L0, L1, Lmax ... Free length La0, La1, La2 ... mounting length, Ls0, Ls1, Ls2 ... mounting length

Claims (7)

A paper feed roller disposed in the conveyance path of the recording medium;
A paper holding member disposed opposite to the paper feed roller;
Biasing means for biasing the paper pressing member toward the paper feed roller;
The biasing means is
An urging member for urging the paper pressing member with an urging force corresponding to the paper thickness of the recording medium;
A biasing force adjusting member made of a shape memory alloy that biases the paper pressing member together with the biasing member,
The biasing force adjusting member is
A paper feeding device configured to change an urging force applied to the paper pressing member from the urging force adjusting member when the shape memory effect is deformed. In claim 1,
The biasing member is
A first spring member for biasing the paper pressing member;
The biasing force adjusting member is
A paper feeding device, wherein the paper feeding device is a second spring member that is arranged so as to urge the paper pressing member together with the first spring member, and whose free length is changed by expression of a shape memory effect. In claim 2,
Energization means for energizing the second spring member;
Control means for controlling the energization means,
The control means is
A paper feeding device characterized in that the free length of the second spring member is adjusted by controlling the energization time and current value to the second spring member in accordance with the thickness of the recording paper to be conveyed. . In claim 3,
The control means includes
A plurality of energization patterns corresponding to a plurality of preset paper thicknesses are stored,
A paper feeding device that reads an energization pattern corresponding to the thickness of the recording sheet conveyed from the plurality of energization patterns and energizes the second spring member according to the energization pattern. In any one of claims 2 to 4,
The biasing means is
Provided with a swing lever with the paper pressing member attached to one end,
The swing lever
The paper pressing member is disposed so as to swing in a paper pressing direction in which the paper pressing member approaches the paper feeding roller, and in a backward direction in which the paper pressing member is separated from the paper feeding roller,
At least one of the first spring member and the second spring member is disposed so as to urge the swing lever in the paper pressing direction. In claim 5,
The first spring member is
It is attached to the swing lever in such a direction as to bias the swing lever in the paper pressing direction.
The second spring member is
A paper feeding device, wherein the paper feeding device is attached to the swing lever in a direction opposite to the first spring member. A print head;
A printer comprising the paper feeding device according to claim 1, wherein the recording medium is transported along a transport path that passes through the print head.

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