JP2001199112A - Serial printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a serial printer in which print shift is eliminated even at the time of bi-directional printing. SOLUTION: The serial printer comprises a print medium carrying means, and means for moving a carriage 6 carrying a print head in a direction perpendicular to the carrying direction of a print medium for the purpose of scanning, wherein the carriage moving means is controlled to reciprocate the carriage and print out a line on the print medium, respectively, during going stroke and returning stroke. In parallel with the traveling passage of the carriage, a sensor 7 is disposed oppositely to a scale for linear encoder having indexes 11a, 11b for deciding the starting point of respective prints at the opposite ends and an index 11c of specified pattern between the starting points, and a scale for the carriage 6. Starting points of each print in the going stroke and returning stroke are determined, along with the traveling direction of the carriage, based on a pulse signal obtained by scanning that scale by means of the sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direction (hereinafter, referred to as a main scanning direction) orthogonal to a transport direction of a printing medium.
The present invention relates to a serial printer that prints one line at a time by moving a print head in a sub-scanning direction), and particularly relates to a technique suitable for use in a thermal printer.

[0002]

2. Description of the Related Art As a printer that can be miniaturized, there is a serial thermal printer that has a thermal head composed of a plurality of heating resistors and moves this in a sub-scanning direction to perform printing. In this type of printer, a thermal head opposed to a platen is mounted on a carriage, and while the carriage is moved in the sub-scanning direction by a motor, printing is performed line by line on printing paper, and printing of the line is performed. Each time printing is performed, printing is continuously performed by moving the printing paper by a predetermined amount in the main scanning direction.

There are various types of means for moving the carriage, and a serial screw printer, which has a small number of parts and is easy to miniaturize, is often used.

This feed screw system has a spiral groove on the outer periphery, a feed screw rotated by a stepping motor or the like, and the tip of a pin (head feed pin) fixed to the carriage is inserted into the spiral groove of the feed screw. The carriage is moved along the guide shaft with the rotation of the feed screw.

[0005]

As described above, in a feed screw type serial printer using a stepping motor, a printing signal is output in synchronization with a pulse signal of the stepping motor to perform printing. However, in the case of bidirectional printing in which so-called thrust play occurs and printing is performed on the forward path and the return path of the carriage because a certain degree of asobi is required due to the structure that enables sliding between the groove of the feed screw and the head feed pin. In this case, there arises a problem that the position of printing on the outward path and the position of printing on the return path are separated by the play.

In order to simply avoid such printing deviation, it is sufficient to perform unidirectional printing in which printing is performed only on the outward path of the carriage. However, there is a disadvantage that the printing speed is reduced by half.

Therefore, conventionally, bidirectional printing is actually performed by the printer having the above configuration to measure the amount of print misalignment, and the timing of a signal output to the thermal head is advanced or delayed by the amount of the print misalignment. Therefore, a measure was taken to add a correction pulse corresponding to the drive pulse of the motor.

However, since the correction using the correction pulse is performed digitally instead of continuously (that is, correction can be made only by an integral multiple of one pulse), it is difficult to correct even a small deviation of the printing position. there were.

Further, since the printing characteristics of the printers themselves differ from one another, it is necessary to change the correction amount for each printer. However, setting the correction pulse amount for each printer requires enormous labor and time. However, there is a disadvantage that the cost is increased.

The present invention has been devised in order to solve the above-mentioned problems, and eliminates the need for a print shift correction pulse.
It is an object of the present invention to provide a serial printer that does not cause print misalignment even in bidirectional printing.

[0011]

In order to achieve the above object, the present invention provides a print medium transport means for transporting a print medium in one direction and a carriage having a print head mounted thereon in a direction perpendicular to the transport direction. A serial transfer unit for controlling the carriage transfer unit to reciprocate the carriage so as to print one line each for the print medium in the forward and backward travels. In the printer, in parallel with the traveling path of the carriage, a scale for a linear encoder having an index for determining the starting point of printing at both ends and an index of a predetermined pattern is provided between the starting points, and the scale of the carriage is further provided. A sensor is provided at an opposing position, and based on a pulse signal obtained by scanning the scale with the sensor, the forward path And the origin of each print in the backward path, in which so as to determine the traveling direction of the carriage.

Thus, printing by the print head is started,
The end timing is not affected by the play of the feed screw as in the related art, and the starting point of the forward path and the return path of the carriage based on the pulse signal generated by the linear sensor based on the scanning of the fixed linear encoder scale, and Accurate control can be performed according to the direction determination result, and printing deviation can be effectively reduced. In addition, since a correction pulse for preventing a printing shift is not required, the labor for setting the correction pulse can be omitted, and the manufacturing cost can be reduced.

The traveling direction of the carriage can be determined by counting the number of pulses from a pulse signal indicating the starting point of the outward or return path.

The index of the scale for the linear encoder is formed by a printing layer of a slit-shaped line pattern having different reflectances, and the linear sensor is constituted by a light reflection type sensor. it can.

Further, the indices for determining the starting points at both ends of the scale for the linear encoder are formed of printed layers having different reflectivities, and the indices for determining the starting points are wider than the slit-like indices. It should be a width.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic plan view showing an embodiment of a serial printer according to the present invention, FIG. 2 is a schematic perspective view showing a main part of the serial printer according to the present invention, and FIG. FIG. 3 is a schematic side view illustrating a configuration of a linear encoder unit.

As shown in FIG. 1, a serial thermal printer P as a kind of serial printer is constructed by incorporating various members into a frame 1 made of an injection molded product of a plastic such as polycarbonate.

The frame 1 has a pair of frame side walls 2 and 3 opposed to each other at a predetermined interval in the paper width direction. In FIG. 1, an arrow D1 indicates a direction in which a thermal paper (not shown) as a recording medium is carried out (ie, a main scanning direction).
, And an arrow D2 indicates a moving direction of the carriage (that is, a sub-scanning direction) described later.

A platen 4 is provided between the pair of frame side walls 2 and 3, and a carriage 6 on which a thermal head 5 is mounted is disposed to face the platen 4. Flexible wiring (not shown) is connected to the thermal head 5, and a print signal is input from an external control device. The print signal is input in synchronization with a pulse signal of a stepping motor M described later.

A reflection type linear sensor 7 is provided on the side of the carriage 6 opposite to the position where the thermal head 5 is arranged. The linear sensor 7 includes a light-emitting unit and a light-receiving unit (both not shown), irradiates light from the light-emitting unit to a scale 11 for a linear encoder, which will be described later, A signal is generated. Although not shown, a flexible wiring is connected to the linear sensor 7 to supply power to the linear sensor 7 and output a pulse signal generated by this sensor to an external print control device. .

The carriage 6 is supported in such a manner that a guide shaft 8 and a head feed screw 9 provided between the frame side walls 2 and 3 are inserted into engagement holes 6a and 6b formed in the carriage itself. I have. The guide shaft 8 is fixed to the frame side walls 2 and 3. On the other hand, the head feed screw 9 is rotatably supported.

On the outer peripheral surface of the head feed screw 9, two spiral grooves 9 for reciprocating the carriage 6 in the longitudinal direction are provided.
a is engraved, and the tip of the head feed pin 10 fitted into the engagement hole 6c formed in the upper part of the carriage 6 is engaged with the spiral groove 9a. The head feed pin 10 is guided along the spiral groove 9a with the rotation of the head feed screw 9, so that the carriage 6 reciprocates in the sub-scanning direction D2.

The head feed screw 9 is configured so that a driving force is transmitted by a stepping motor M provided in the frame 1 and a gear transmission mechanism G connected thereto, and the head feed screw 9 is rotated.

The linear sensor 7 provided on the carriage 6
A scale 11 for a linear encoder is provided along the sub-scanning direction at a position immediately below the axis.

The scale 11 is made of, for example, a transparent plastic film such as PET (polyethylene terephthalate). The scale 11 is formed by printing various indexes with black ink on the back surface, and is fixed so as to be attached to a part of the frame 1. ing.

Incidentally, the mounting position of the scale 11 is as follows.
In terms of accuracy, it is desirable to be as close to the guide shaft 8 as possible.
However, if a separate space is provided for this purpose, the size may be increased. Therefore, the size may be appropriately determined in consideration of the use of the printer, cost, and the like.

At both ends of the scale 11, starting points of a forward path (defined as a rightward direction in FIG. 2 in this embodiment) and a return path (defined as a leftward direction in FIG. 2 in this embodiment) are shown. Indicators 11a and 11b are formed. In the present embodiment, as shown in FIG. 2, the starting point 11a of the outward path is formed by a black (low reflectance) printing portion, and the starting point 11b of the return path is a white (high reflectance) non-printing portion. . The starting point 11b of the return path may be printed with white ink or metallic ink in order to increase the reflectance.

The starting point 11a of the forward path and the starting point 11 of the return path
As shown in FIG. 2, slit-like indices 11 c are formed at regular intervals by printing black ink. The range in which the index 11c is formed corresponds to the printing range of the thermal paper.

By sequentially scanning these indices 11a to 11c with the linear sensor 7 (in this example, scanning from left to right), a pulse signal having a waveform as shown in FIG. 4 can be obtained. .

That is, when the linear sensor 7 scans the index 11a, the low state S1 on the left end side in FIG. 4 continues for a predetermined time, and based on this state, the print control device (not shown) operates based on this state. It can be determined that the carriage 6 is at the starting point of moving from left to right.

When the linear sensor 7 scans the index 11c, the pulse signal becomes a state S2 in which a low state and a high state occur alternately and continuously as shown in FIG. While the state from S2 to S2 continues, it can be determined that the carriage 6 is moving from left to right.

Next, when the linear sensor 7 scans the index 11b, the high state S3 continues for a predetermined time, and based on this state, the printing control device causes the carriage 6 to move from left to right.
It can be determined that the end point that moves to the right (that is, the right-to-left starting point) has been reached.

Further, the carriage 6 has a head feed screw 9
When the moving direction is changed from right to left by being guided by the spiral groove 9a, the linear sensor 7 scans the index 11c, and the output pulse signal again becomes the state S2 in which the low state and the high state are generated alternately and continuously. Become. At this time, the print control device sets
While the high state continues, it can be determined that the thermal head 5 has not reached the printing range.

Thus, the printing start position and printing direction of the thermal head 5 mounted on the carriage 6 can be accurately determined, and a print signal can be input to the thermal head 5 at an appropriate timing based on this. As a result, it is possible to effectively avoid a printing shift at the end portion due to backlash between the head feed screw 9 and the head feed pin 10 as in the related art. Therefore, even when performing so-called bidirectional printing in which printing is performed in the forward scan and the return scan in the sub-scanning direction of the carriage 6, accurate and clean printing can be performed without occurrence of print deviation for each line. Further, unlike the related art, there is no need to apply a pulse for correcting a print misalignment, so that it is not necessary to set a correction pulse, and the manufacturing cost can be reduced.

Although illustration and detailed description are omitted, the printer P is provided with a transporting means for transporting thermal paper as a recording medium in the main scanning direction D1 in addition to the above configuration.

The above is the schematic configuration of the serial printer according to the present embodiment.

Next, an outline of the operation will be described.

When printing is to be performed by the printer P, first, thermal paper as a recording medium is inserted into the printer P in the main scanning direction D1, and the space between the platen 4 and the thermal head 5 is inserted to start printing. Prepare for. It should be noted that the insertion of the thermal paper can be performed by operating the above-mentioned transporting means.

Next, when printing by the printer P is started under the control of the printing control device, the stepping motor M is driven, and the head feed screw 9 is driven via the gear transmission mechanism G.
Starts rotating.

When the head feed screw 9 rotates, the head feed pin 10 of the carriage 6 is guided along the groove 9a and moves in the sub-scanning direction D2.

For example, in FIG. 1, when the left end is the home position of the carriage 6, movement from the left end to the right is first started. At this time, the carriage 6
The linear sensor 7 has indexes 11a and 11c of the scale 11.
Is started, and a pulse signal as shown in FIG. 4 is generated and output to the print control device.

The print control device is configured to output the signal S in the low state shown in FIG.
The starting point and the moving direction of the forward path (left to right in FIG. 1) of the carriage 6 are determined based on 1 and the pulse signal S2 at a predetermined interval, and a print signal is input to the thermal head 5 at a predetermined timing. As a result, printing for one line is performed on the thermal paper.

Next, when the carriage 6 reaches the right end, the linear sensor 7 generates a high-state signal S3 in FIG. 4 based on the scanning of the index 11b, and the print control device outputs the signal S3 of the high state based on the signal. (Left to right direction in Fig. 1)
(That is, the starting point in the right-to-left direction) is output, and a control signal is output to the thermal paper conveying means to feed the paper by one line in the main scanning direction D1.

When the paper is fed by one line, the carriage 6
Starts moving from right to left by being guided by the groove 9a of the head feed screw 9. At this time, the linear sensor 7 scans the indicators 11b and 11c to generate a high-state signal S3 and a pulse signal S2.
And S2, the return path of the carriage 6 (FIG. 1,
A starting point (right-to-left direction) and a moving direction are determined, and a print signal is input to the thermal head 5 at a predetermined timing. As a result, the next one line is printed on the thermal paper.

By repeating the above operation,
Printing is performed in both the forward and backward directions of the carriage 6.

As described above, the serial printer according to the present embodiment determines the starting point and the moving direction of the forward and backward paths of the carriage 6 based on the signal generated by the linear encoder including the linear sensor 7 and the scale 11. The print signal can be input to the thermal head 5 at an appropriate timing based on the determination result. Accurate and clear printing can be performed without causing printing displacement. Further, unlike the related art, there is no need to apply a pulse for correcting a print misalignment, so that it is not necessary to set a correction pulse, and the manufacturing cost of the printer can be reduced.

In this embodiment, a reflection type linear sensor 7 and a reflection type scale 11 are used as linear encoders.
However, the present invention is not limited to this. For example, magnets having different polarities are disposed at the ends for discriminating the starting points of the forward path and the backward path, and magnets are arranged at predetermined intervals therebetween. Alternatively, a magnetic sensor using a Hall element or the like may be mounted on the carriage to obtain a desired signal.

It goes without saying that other configurations can be appropriately changed without departing from the technical scope of the present invention.

For example, in this embodiment, the case where the stepping motor M is used as the driving source has been described, but a direct current (DC) motor may be used instead. At that time, since printing can be performed based on a signal obtained by the linear encoder, the conventional DC
The timing generator (tag generator) provided for acquiring the print timing in the motor system becomes unnecessary, and the configuration can be simplified and the cost can be reduced.

Further, in the present embodiment, the pattern of the index 11c of the scale 11 is formed in a slit shape at a constant interval.
A pattern with a different pitch may be provided on the way so that the scanning direction can be identified.

The arrangement of the linear sensor and the scale is as follows.
3, a linear sensor 7 'is provided at a position corresponding to the position above the engagement hole 6a of the guide shaft of the carriage 6, and is opposed to the linear sensor 7'. The scale 11 'may be arranged. In this case, the pulse signal can be obtained with high accuracy without being easily affected by vibration or blur due to backlash between the guide shaft 8 and the engagement hole 6a, and the printing accuracy can be further improved.

Further, the scales 11 and 1 are provided to the printer P.
Instead of providing 1 ', it is also possible to print an index on the printing paper with a special ink which is invisible to the naked eye and which is sensitive to ultraviolet or infrared rays, and detects this with an ultraviolet or infrared sensor to detect the printing range. is there.

Further, in this embodiment, the case where the present invention is applied to a serial thermal printer has been described. However, the present invention is not limited to this. It can also be applied to serial printers.

[0055]

As described above, in the serial printer according to the present invention, the print medium transport means for transporting the print medium in one direction, and the carriage on which the print head is mounted are scanned by traveling in the direction perpendicular to the transport direction. A serial printer that includes at least a carriage transfer unit that controls the carriage transfer unit to reciprocate the carriage and print one line each on the print medium during forward and backward travels. In parallel with the carriage traveling path, a scale for a linear encoder having an index for discriminating the starting point of printing at both ends and an index of a predetermined pattern is provided between the starting points, and further opposed to the scale of the carriage. A sensor is provided at the position, and based on a pulse signal obtained by scanning the scale with the sensor, The starting point of each printing and the traveling direction of the carriage are determined on the return path, so that the timing of starting and ending printing by the thermal head is not affected by the feed screw as in the past, and the fixed linear encoder is used. It is possible to accurately control the starting point of the forward path and the backward path of the carriage based on the pulse signal generated by the linear sensor based on the scanning of the scale for use, and the result of the determination of the traveling direction, thereby effectively reducing the printing deviation. This has the effect. In addition, since a correction pulse for preventing printing displacement is not required, there is an effect that the trouble of setting the correction pulse can be omitted, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an embodiment of a serial printer to which the present invention is applied.

FIG. 2 is a schematic perspective view showing a main part of a serial printer to which the present invention is applied.

FIG. 3 is a schematic side view illustrating a configuration of a linear encoder unit of the serial printer according to the present invention.

FIG. 4 is an explanatory diagram illustrating a pulse signal generated by a linear encoder section of the serial printer according to the present invention.

FIG. 5 is a schematic side view showing another configuration of the linear encoder of the serial printer according to the present invention.

[Explanation of symbols]

 P Serial printer 1 Frame 2, 3 Frame side wall 4 Platen 5 Thermal head 6 Carriage 7, 7 'Linear sensor 8 Guide shaft 9 Head feed screw 9a Guide groove 10 Head feed pin 11, 11' Scale 11a Index for starting point 11b Index for starting point of return 11c Index for determining traveling direction M Stepping motor G Gear transmission mechanism D1 Main scanning direction D2 Sub scanning direction

Claims (3)

[Claims] 1. A print medium transport means for transporting a print medium in one direction, and a carriage transport means for traveling and scanning a carriage on which a print head is mounted in a direction orthogonal to the transport direction. A serial printer that controls the carriage to reciprocate and print one line each for the print medium during forward and backward travels. The serial printer is provided at both ends in parallel with the carriage travel path. A scale for a linear encoder having an index of a predetermined pattern is provided between the start points and an index for determining the starting point of printing, and a sensor is further provided at a position facing the scale on the carriage, and the scale is scanned by the sensor. The starting point of each print and the traveling direction of the carriage are determined in the forward path and the return path based on the pulse signal obtained by A serial printer. 2. The scale index for the linear encoder is formed by a printed layer of a slit-shaped line pattern having different reflectivity, and the linear sensor is constituted by a light reflection type sensor. The serial printer according to claim 1, wherein: 3. An index for determining a starting point at both ends of the scale for the linear encoder is formed by a printed layer having different reflectance, and the index for determining the starting point is wider than the slit-like index. 3. The serial printer according to claim 2, wherein the width is a width.