JPH0469268A - Automatic adjustment device for head gap of printer - Google Patents

Abstract

PURPOSE:To ensure that the gap value of a print head is made constant by storing the detected rotary oscillation value of a platen due to an eccentricity and correcting the variation of a print head gap value caused by the oscillation value of the platen by adjustment of a print head position. CONSTITUTION:Data on a distance from a ribbon protector 6 (the tip of a print head 1) to a sheet surface on the platen 3 is stored in a head gap value storage part 3 each time the platen makes the specified number of rotations. Then the rotary oscillation value, that is, the offset position (sigma) of the platen 3 is detected. On the other hand, after the detection and storage of the offset value (sigma), the platen 3 is driven by a stepping motor 30 for sheet feed and each time the sheet is fed, a print head gap adjustment drive device 25 iscontrolled by a value corresponding to the offset value, in a routine printing process. Next the gap value for the rotating position of the platen 3 is corrected and thus the gap value registered during the single rotation of the platen 2 is maintained at a constant level.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an automatic print head gap adjustment device for a printer.

<Prior Art> FIG. 5 is a side view showing the main structure of a conventional serial printer.

In FIG. 5, in this printer, a roller-shaped platen 51 and a print head 52 are arranged between a ribbon 10 and a print head 52.
They are arranged opposite to each other with 3 interposed therebetween. Then, the continuous printing paper 54 is passed between the platen 51 and the print head 52 in a state in which it is brought into close contact with the platen 51, and the continuous printing paper 54 is conveyed by the drive of a tractor 55 that is synchronized with the rotation of the platen 51. .

In this type of printer, the tip of the print head 52 (in this structure, the ribbon protector 53) and the continuous printing paper 5
When the print head gap between the print head and the print head 4 changes, the print pressure changes and the density also changes. For this reason, it is necessary to always keep the print head gap constant.

Therefore, depending on the thickness of the paper used, the print head 5
2 in a direction perpendicular to the platen 51 and automatically corrects the print head gap to keep it constant, as can be seen in, for example, Japanese Patent Laid-Open No. 63-233871. , has already been proposed.

In the print head gap adjustment structure in this conventional printer, the print head 52 (in this embodiment, the ribbon protector 53) is pressed against the surface of the paper 54, and then moved back a predetermined distance, and the amount of this back movement is adjusted. This is the print head gap amount after adjustment. therefore,
The surface of the platen 16 serves as a reference surface when establishing a print head gap.

<Problems to be Solved by the Invention> For this reason, in the printing bed gap adjustment structure of conventional printers, if the platen 16 is eccentric due to manufacturing errors, rotational runout occurs when the platen 16 rotates, and this rotation The print head gap amount also varies in proportion to the runout. This fluctuation causes the print density to become uneven, resulting in a problem of deterioration of print quality.

The present invention has been made in view of the above problems, and its purpose is to provide an automatic print head gap adjustment device for a printer that can reduce fluctuations in the print head gap and improve print quality. be.

Means for Solving the Problems> In order to achieve the above object, the automatic print head gap adjustment device for a printer according to the present invention includes a drive means for adjusting the print head gap that moves the print head away from and into contact with the platen. , control for controlling the rotation of the platen and the driving means, detecting and storing the rotational shake amount of the platen, and controlling the driving means in accordance with the rotational position of the platen to correct the print head gap amount; It is equipped with means.

According to this configuration, the amount of rotational run-out of the platen due to eccentricity is detected and stored, and during subsequent printing, the driving means is controlled according to the rotational position of the platen, and the position of the print head is adjusted to adjust the rotational deviation of the platen. Since the variation in the print head gap amount due to the amount of runout is corrected, a constant print head gap amount, that is, a constant printing pressure can always be obtained.

<Example> Hereinafter, an example of the present invention will be described in detail using the drawings.

FIG. 1 is a schematic layout diagram of the main parts of a printer to which an embodiment of the present invention is applied.

In FIG. 1, in this printer, a print head 1 is mounted on a carriage 2, and a platen 3 is arranged opposite to this print head 1. The platen 3 is integrated with a platen shaft 4, and both ends of the platen shaft 4 are rotatably supported by side frames (not shown) provided on the left and right sides. Furthermore, a ribbon protector 6 is provided in front of the print head 1.

And between the ribbon protector 6 and platen 3,
The printing paper 5 is set in close contact with the platen 3. Note that if the printing paper 5 is continuous paper, it is moved by a tractor (not shown) that rotates in synchronization with the platen 3, and if it is cut paper, it is moved by a tractor (not shown) that rotates in synchronization with the platen instead of the tractor. The paper is moved by the paper feed roller. In addition, these platen 3 and the tractor,
The driving force for rotating the paper feed rollers and the like is applied from a paper feed stepping motor 30 via pulleys, belts, etc. (not shown), and this paper feed stepping motor 30 is attached to a side frame (not shown). It is being

Next, the carriage 2 has a guide shaft 7 on its distal end side.
The rear end side is movably engaged via a bearing 9 with a slide beam 8 installed between the left and right side frames. Further, both ends of the guide shaft 7 are movably and rotatably inserted into and engaged with horizontally elongated holes 10 provided in the left and right side frames, respectively. Note that the horizontally elongated hole 10 is formed to extend horizontally along the bottom surface 20 of the frame. Therefore, the carriage 2 has a guide shaft 7
The print head 1 can be moved in a direction parallel to the platen axis 4, that is, in the spacing direction, guided by the slide beam 8, and in a direction perpendicular to the platen axis 4, that is, the print head 1 can be moved in the direction perpendicular to the platen axis 4, guided by the horizontally elongated hole 10. It is supported so that it can move integrally with the guide shaft 7 in directions that allow it to move away from and approach the guide shaft 7.

Further, on both sides of the guide shaft 7, as the guide shaft 7 is rotated in the direction of arrow B in FIG.
A cam 11 having a cam surface 11a whose distance from the center 21 of the guide shaft 7 gradually increases is fixed. Further, a cam follower 12 is provided on the side frame side corresponding to the cam surface 11a of the cam 11, and the cam surface 11a of the cam 11 is brought into contact with the cam follower 12 by the biasing force of a spring 13. Note that the cam surface 11a of the cam 11 and the cam follower 12 come into contact on the slide beam 8 side opposite to the platen 3 with the guide shaft 7 in between. On the other hand, one end of the spring 13 is engaged with an engagement pin 22 fixed to the center of the guide shaft 7, and the other end is engaged with an engagement pin 23 implanted in the side frame. The print head 1 is always urged in a direction away from the platen 3 by a spring 13.

In addition, although not shown, a print head gap stepping motor 31 (second
(see diagram) is power connected. On the other hand, a slit disk 14 is fixed to the other end of the guide shaft 7.

A portion of the slit disk 14 is bulged into a substantially fan-like shape, and a plurality of slits 15 are provided at equal intervals along the circumference of the bulged fan-shaped portion 14a. Further, a photosensor 16 is fixed to the side frame in correspondence with the slit disk 14. The photosensor 16 detects the slit 15 on the slit disk 14 when the slit disk 14 rotates together with the side shaft 7, and outputs a signal every time it detects the slit 15.

Next, FIG. 2 shows a control circuit block diagram of the print bed gap automatic adjustment system of this printer.

This control circuit is composed of a control means 23, a paper feed drive means 24, a print head gap adjustment drive means 25, etc. connected to the control means 23, respectively.

Further, the control means 23 is mainly configured with a microprocessor 32, and the microprocessor 32 includes a storage section 33. The photo sensor 16, paper feed stepping motor drive circuit 34 and print head gap drive circuit 35 are connected. Furthermore, microprocessor 3
2, a page break command signal 3 from a host computer, etc.
6. A print data signal 37 and the like are input. In addition, the storage unit 33 detects the rotational runout amount (eccentricity σ) of the platen 3 detected as described later,
A control program section 38 that calculates the print head gap amount according to the rotational position of the platen 3 and instructs the control of the print head gap adjustment driving means 25, and a head that stores the value calculated by the control program section 38. It is composed of a gap amount storage section 39.

The paper feed stepping motor drive means 24 includes the paper feed stepping motor 30 whose drive is controlled by a paper feed stepping motor drive circuit 34, and a platen 3.0 driven by the paper feed stepping motor 30. The paper feed mechanism 40 includes a tractor (not shown) and a paper feed roller. Note that the platen 3 here is set to rotate once when the paper feed stepping motor 30 takes 15 steps.

The print head gap adjustment driving means 25 is driven by the print gap stepping motor 31 which is rotatable in two directions, forward and reverse, and whose drive is controlled by a print head gap stepping motor drive circuit 35. Guide shaft 7, cam 11. It is composed of a printing gap setting mechanism 41 consisting of a cam follower 12 and the like.

Next, the paper thickness detection operation of the print head gap automatic adjustment device of the printer configured as described above will be explained with reference to the operation diagram shown in FIG. 3 and the schematic diagram shown in FIG. 4. Note that the paper thickness detection here is performed at the time of printer manufacturing or maintenance inspection.
The rotational run-out amount (eccentricity σ) of the platen 3 unique to this printer
), and is different from the paper thickness detection that is normally performed when replacing paper. Further, in the printer of this embodiment, the detection operation is performed every time the platen 3 rotates 24 degrees and stops, that is, 15 times per -round, and the operation diagram shown in FIG. Only the operation is shown, the Y-axis direction indicates the rotation direction of the guide shaft 7, and the X-axis direction indicates the elapsed time t.

When a detection instruction is given from the control program section 38, the print head gap stepping motor 31 is driven in reverse. Further, due to the rotation of the print head gap stepping motor 31, the guide shaft 7 is rotated in the direction of arrow A in FIG. 1, and the slit 14 is moved from the position shown by the solid line in FIG. Immediately after the position, that is, the edge portion 114 of the slit disk 14 is detected by the photosensor 16 (third
The carriage 2 is then moved in the direction of arrow C in FIG. 1 under the control of the cam 11, which rotates together with the guide shaft 7 while contacting the cam follower 12. Ribbon protector 6 is also the 4th
0 away from the platen 3 to the position indicated by the dotted line in the figure.
A signal is then applied to drive the print head gap stepping motor 31 in the forward direction. Further, as the print head gap stepping motor 31 rotates, the guide shaft 7 is rotated in the direction of arrow B in FIG. 1, and the carriage 2 is also rotated in the direction of the arrow in FIG. Start moving in the direction of contact.

Then, when the edge portion 14 of the slit disk 14 crosses in front of the fort sensor 16 again and the first slit 15 is detected (the position already indicated by the symbol in FIG. 3), this signal is input into the storage section 33. The slits 15 that will be detected thereafter are also sequentially input.Thus, as the slit disk 14 rotates, the carriage 2 is moved in the direction of the arrow in FIG. When the carriage 2 comes into contact with the paper surface and no longer moves, this is detected and the print head gap stepping motor 31 is stopped. The number of slits detected between the position indicated by the symbol C in FIG. Then, the print head gap stepping motor 31 is driven in reverse, and this drive rotates the guide shaft 7 in the direction of arrow A in FIG. 1, and also rotates the carriage 2 in the direction of arrow C in FIG. When the carriage 2 is moved back by a certain amount (symbol d in FIG. 3), a print gap suitable for this platen surface is obtained. Information about the distance dimension (jl) between the ribbon protector 6 and the paper surface on the platen 3 at this time is stored in the head gap amount storage section 39.
This operation is performed every 24 degrees of rotation,
This is sequentially stored in the head gap amount storage section 39. Then, by knowing the distance (jl)~115) between the ribbon protector 6 and the paper surface on the platen 3 detected for each rotational position of the platen 2 during this detection, the amount of rotational runout of the platen 2, that is, the eccentric position can be determined. (σ) is detected.

On the other hand, after being detected and memorized, during normal printing operation,
Each time the platen 3 is driven by the paper feed stepping motor 3o and the paper is fed, the print head gap adjustment drive means 25 is controlled by an amount corresponding to the offset position. Then, the gap amount with respect to the rotational position of the platen 3 is corrected,
This keeps the gap amount constant during one revolution of the platen. Therefore, the print head gap automatic adjustment device of this printer can always obtain a constant printing pressure without being affected by the amount of rotational runout of the platen. , printing quality can be improved.

<Effects of the Invention> As explained above, according to the printing bed gap automatic adjustment device of the printer according to the present invention, the amount of rotational runout of the platen due to eccentricity is detected and stored, and during subsequent printing, Since the drive means is controlled by the printer and the position of the print head is adjusted to compensate for fluctuations in the print head gap due to platen shake, a constant print head gap, or in other words, a constant printing pressure, is always obtained. . As a result, print quality improves.

[Brief explanation of drawings]

Fig. 1 is a schematic layout diagram of the main parts of a printer to which an embodiment of the present invention is applied; Fig. 2 is a control circuit block diagram of the print head gap automatic adjustment system of the same printer shown in Fig. 1; Fig. 3; is an operation diagram for explaining the paper thickness detection operation in the printer shown in FIGS. 1 and 2, and FIG. FIG. 5 is a side view showing the main structure of a conventional serial printer. DESCRIPTION OF SYMBOLS 1... Print head, 2... Carriage, 3... Platen, 5... Print paper, 6... Ribbon protector, 23... Control means, 25... Print head gap adjustment drive means .

Claims (1)

[Claims] In an automatic print head gap adjustment device for a printer that feeds print paper between a platen and a print head in synchronization with the rotation of the platen, the print head moves the print head away from and into contact with the platen. a drive means for gap adjustment; controlling the rotation of the platen and the drive means; detecting and storing the amount of rotational runout of the platen; and controlling the drive means according to the rotational position of the platen to print. 1. A print head gap automatic adjustment device for a printer, comprising: a control means for correcting a head gap amount.