JPH035183A - Automatic regulating mechanism for gap of printing head - Google Patents

Abstract

PURPOSE:To displace a platen in parallel by connecting a rack to one of the platen and a printing head and a pinion gear to the other and bonding the pinion gear with a motor. CONSTITUTION:In a flat platen 31, an opposed section of which to a printing head 20 is formed flatly, both end sections are supported slidably in the vertical direction to the groove sections 32, 33 of side frames 29, 30 while racks 34, 35 are fixed on both outsides. A gear wheel and a pinion are formed integrally in a pinion gear 46, and a boss section 46a is fastened to a shaft 48 by a pin 47. The pinion of a reduction gear 45 is engaged with the gear wheel of the pinion gear 46 and the pinion of the pinion gear 46 with the rack 35. A pinion gear 49 is fixed at the other end of the shaft 48 by setscrews 50a, 50b, and engaged with the rack 34. The shaft 48 is supported rotatably by the side frames 29, 30. The tooth number of the pinion of the pinion gear 46 is made the same as that of the pinion gear 49, and the flat platen 31 is displaced vertically in parallel along the grooves 32, 33 of the side frames 29, 30 when the shaft 48 is turned.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a mechanism for automatically adjusting the gap between the tip of a print stent and a platen.

(Prior art) Conventionally, when performing a printing operation using a wire dot print head,
A drive mechanism within the print head drives the dot wire in response to a print signal, causing the tip of the dot wire to protrude from the front end surface of the print head. At this time, the tip of the dot wire hits the paper on the platen through the ink ribbon, and the dot 1 prints characters, symbols, etc. according to the structure on the paper.

In this type of impact printer, it is necessary to make the operating stroke of the driver l-wire as small as possible in order to speed up the printing operation. However, there are many different types of paper used in impact printers, and their thickness From a thin piece of about 0.05mm to 1.5m
The gap between the tip of the print head and the platen (hereinafter referred to as the "print head gap") needs to be adjusted to an optimal value depending on the thickness of the paper being used. .

In order to automatically adjust the printing radgap for printing papers of various thicknesses, an automatic printing radgap adjustment mechanism as shown in FIG. 6 is provided. In the automatic printing rad gap adjustment mechanism, a linear output device 3 is attached to a carriage 2 on which a print head is mounted, and a pulse motor 5 is rotated clockwise by a control section (not shown).

This rotation causes the cam 4a fixed to both ends of the guide shaft 8 to be rotated through the drive gear 6 and the driven gear 7.
, 4b is rotated, the side frame lla,
A roller 12a rotatably attached to Ilb,]
, 2b, the carriage 2 is moved toward the platen 9 side. Then, when the contact 3a of the linear output device 3 fixed to the carriage 2 contacts the paper 10 and is further pushed in by a stroke S, the output voltage of the linear output device 3 changes from the initial voltage V to ■2. .

The amount of change V in the output voltage is compared with the voltage preset in the control unit, and when they are equal, the stepping motor 5 is rotated a certain amount counterclockwise, and this operation sets the rad gap for printing. Ru.

(Problem to be Solved by the Invention) However, in the printing rad gap automatic adjustment mechanism configured as described above, since the print head is positioned based on the lift amount relative to the rotation angle of the cams 4a and 4b, the rotation angle of the cam and It is necessary to make the relationship between the lift amounts linear, which increases the cost of manufacturing a highly accurate linear cam.

Also, the rotation direction (clockwise) of the stepping motor 5 when the contact 3a of the linear output device 3 is brought into contact with the paper, and the rotation direction (counterclockwise) after the contact 3a is pushed in by a stroke S. ) are reversed, so when the rotation is reversed, the play in the power transmission system (backlash and sliding of the gear train, play in the rotating parts, etc.) is reversed. Therefore, even if a predetermined amount (constant number of pulses) of rotation pulses are applied in the counterclockwise direction, an error occurs due to the reversal of the play, making it difficult to set a stable print head gap.

Further, since the contact 3a of the linear output device 3 is located on the print line, the contact 3a contacts and rubs the paper, where the ink has not yet dried immediately after printing, so that the paper may be stained.

The present invention solves the above-mentioned problems and makes it possible to make the relationship between the rotation angle of the stepping motor and the printing rad gap accurately linear with a simple mechanism, and to print by rotating the stepping motor in the reverse direction. The purpose of the present invention is to provide an automatic adjustment mechanism for the rad gap for printing, which is not affected by play in the power transmission system when setting the rad gap, and can prevent printing smudges caused by contacts of a linear output device. shall be.

(Means for Solving the Problems) For this purpose, the present invention provides at least one of the platen and the print head with a drive device for changing the relative position between them, and adjusts the thickness of the paper to be printed on the platen. In an automatic print head gap adjustment mechanism that can adjust the gap between them accordingly, a rack is connected to one of the platen and print head, a pinion gear is connected to the other, and the pinion gear is connected to a motor.

In addition, in the above print head gap automatic adjustment mechanism,
A linear output device is mounted on the print head so as to face the paper, and a contact element that can be retracted when it comes into contact with the paper is disposed at the tip of the linear output device, and means for detecting the surface position of the paper based on the amount of change in the output of the paper; means for driving the driving device in a direction that reduces the gap between the platen and the print head until the surface position of the paper is detected; and the surface position of the paper. means for driving the drive device in a direction to increase the gap and then again in a direction to decrease the gap to form a gap of a predetermined amount between the platen and the print head. ing.

Furthermore, the printing surface of the platen is flat, and the contact position of the contactor to the paper is provided outside the printing area of the print head.

(Function) As explained above, according to the present invention, at least one of the platen and the print head is provided with a drive device for changing the relative position between the two, and the print head is adjusted according to the thickness of the paper to be printed on the platen. In the printing rad gap automatic adjustment mechanism that makes it possible to adjust the gap between the two, a rack is connected to one of the platen and the print head, a pinion gear is connected to the other, and the pinion gear is connected to the motor. There is no need to manufacture highly accurate linear cams.

In addition, in the above-mentioned printing rad gap automatic adjustment mechanism,
A linear output device is attached to the print head so as to face the paper, and a contact element that can be retracted when the paper comes into contact is provided at the tip of the linear output device. means for detecting the surface position of the paper based on the amount of change; means for driving the driving device in a direction that reduces the gap between the platen and the print head until the surface position of the paper is detected; After that, the drive device is driven in a direction to increase the gap, and then in a direction to decrease the gap again,
Since a means for forming a certain amount of gap between the platen and the print head is provided, play in the power transmission system is prevented from reversing between the time when the surface position of the paper is detected and the time when the drive device is stopped. , errors caused by this can be suppressed.

Furthermore, since the printing surface of the platen is flat and the contact position of the contactor to the paper is provided outside the printing area of the print head, it is difficult to contact and rub the paper immediately after printing when the ink is not yet dry. Things will disappear.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Figure 1 is a plan view of a printer that employs the automatic print head gap adjustment mechanism of the present invention, Figure 2 is a right side view of the printer, and Figure 3 is a right side view of the printer.
4 is a block diagram of the automatic print head gap adjustment mechanism of the present invention, and FIG. 5 is an explanatory diagram of the operation of the automatic print head gap adjustment mechanism of the present invention.

1 to 3, 20 is a print head, and 21 is a carriage on which the print head 20 is mounted.

A linear output device 22 is provided on the arm portion 21 a of the carriage 21 so as to face the paper 23 .

The contact 22a of the linear output device 22 is attached to a nut 24a so as to slightly protrude from the print head tip 20a.
, adjusted and attached by 24b,
It comes into contact with the surface of the paper 23.

When the contact 22a is pushed in the direction of the arrow in FIG. 3, the linear output device 22 generates an output voltage that changes in proportion to the amount of push. For example, a permanent magnet is fixed to the contactor 22a, a Hall element is built in the frame 22b, and an output voltage is obtained from the Hall element depending on the relative positional relationship. Further, the contactor 22a is connected to the frame 22b.
It is slidably supported in the axial direction. The operating force of the contactor 22a can be arbitrarily set by a spring provided within the frame 22b. Further, the tip of the contactor 22a is formed into a hemispherical shape so that it can make good contact with the paper 23.

25 is a guide shaft that penetrates and engages with the front part of the carriage 21; 26 is a slide beam that engages with a bearing 27 and a guide 28 provided at the rear of the carriage 21; Both ends are fixed to side frames 29, 30. The carriage 21 is driven by a drive source (not shown) via a power transmission mechanism,
It is movable along the guide shaft 25.

31 is a flat platen in which the part facing the print head 20 is formed flat, and both ends thereof are connected to the side frame 29.
．． 30 so as to be slidable in the vertical direction, and racks 3435 are fixed to both outer sides thereof. The rack 34.35 has a boss) 36.37
is implanted and is slidably supported by elongated sections 38 and 39 provided on the side frame 2930. 40.41
is the rack 34. , 35 and side frames 29, 30
A spring tensioned between the flat platen and the flat platen urges the flat platen downward.

42 is a stepping motor, which is attached to the side frame 30 via a bracket (not shown).

A drive gear 43 is fixed to the shaft of the stepping motor 42.

Reduction gears 44 and 45 are integrally formed with large and small gears, and are rotatably supported by the bracket (not shown).

The drive gear 43 meshes with a large gear of a reduction gear 44, and the small gear of the reduction gear 44 meshes with a large gear of a reduction gear 45, respectively.

The pinion gear 46 is formed by integrally forming large and small gears, and a boss portion 46a is fixed to a shaft 48 by a pin 47. The small gear of the reduction gear 45 meshes with the large gear of the pinion gear 46, and the small gear of the pinion gear 46 meshes with the rack 35. Further, a pinion gear 49 is fixed to the other end of the shaft 48 by a push screw 50a50b, and meshes with the rack 34.

The shaft 48 is rotatably supported by the side frames 29, 30. Further, the number of teeth of the small gear of the pinion gear 46 is the same as the number of teeth of the pinion gear 49, and when the shaft 48 rotates, the flat platen 31 moves vertically in parallel along the grooves 32, 33 of the side frames 291-30.

The paper 23 can be moved in the direction of the arrow in FIG. 2 by a feed roller (not shown).

51 is an ink ribbon cassette.

Next, in FIG. 4, 52 is a stepping motor drive circuit, which drives the stepping motor 42 according to commands from a control section 53. 54 is linear output device 2
A-D converts the analog signal from 2 into a digital signal
It is a converter, and the control unit 53 converts the digital signal.
Output to.

Next, the operation of the printing rad gap automatic adjustment mechanism of the present invention having the above-described configuration will be explained.

When the power of the printer is turned on, as an initial operation, a reverse signal is output from the control unit 53 to the stepping motor drive circuit 52 to rotate the stepping motor 42 clockwise in FIG. 2, regardless of whether or not a medium is loaded. . When the stepping motor 42 rotates clockwise, the rotation is transmitted via the drive gear 43 and reduction gears 44 and 45, the second vinyl gear 46 and shaft 48 rotate counterclockwise, and the pinion gear 49 also rotates counterclockwise. Rotate. shaft 48
When the pinion gears 46.49 attached to both ends of the pinion gears 46.49 rotate together counterclockwise, the rack 34.35 meshing with them lowers, and the flat platen 31 moves along the groove 32.33 of the side frame 29.30. The print head moves in parallel in a direction that widens the gap.

At this time, the stepping motor drive circuit 52 outputs a preset number of reverse pulses to the stepping motor 42. The number of pulses is determined when the post 36.37 installed on the rack 34.35 comes into contact with the lower end of the long side 38.39 installed on the side frame 29.30, and the pulse motor 42
It is assumed that the number of pulses is a constant enough to cause a loss of synchronization.

That is, no matter where the flat platen 31 is located, the stepping motor 42 is always caused to step out of step, and further, the step-out of the stepping motor 42 is ignored and a preset constant pulse is sent. In this state, the print head gear supply is sufficient to load paper and replace the ink ribbon cassette.

Next, when the paper 23 is mounted on the flat platen 31 and print data is transmitted from a host computer (not shown), etc., a forward signal is sent from the control section 53 to the stepping motor drive circuit as shown in FIGS. 4 and 5. 52 to rotate the stepping motor 42 counterclockwise. Due to this rotation, the stepping motor 42
, move the flat platen 31 from the initial position to the print head 2.
Translate to the 0 side.

Here, the rotation angle (number of pulses) of the stepping motor 42
The amount of vertical movement of the flat platen 31 is the rack 3.
4.35 and pinion gear 49.46. If the parallelism of the flat platen 31 is poor within the range of movement of the carriage 21, loosen the push screws 50a and 50b of the pinion gear 49, and adjust the rotational phases of the pinion gears 49 and 46 by shifting them from each other. , can be easily adjusted.

When the forward signal is continued to be sent, the contact 22a of the linear output device 22 fixed to the carriage 21 and the paper 2
The gap on the surface of paper 23 becomes narrower, and the contactor 22a comes into contact with the surface of paper 23. If you continue to send forward signals,
The contactor 22a is pushed in by a stroke S, and the output voltage from the linear output device 22 changes from the initial voltage (2) to (2). The amount of change in this output voltage is converted into a digital signal by an A-D converter, and when it is compared with the voltage set in advance in the control unit 53 and becomes equal, the output signal to the stepping motor drive circuit 52 is changed from the forward direction. Can be switched to reverse direction.

Here, α is used to ensure a predetermined print head gap.
When a reverse pulse is required, the control unit 53 once sends a reverse pulse of α and β pulses, and then sends forward pulses for β pulses to stop the stepping motor 42 in the forward direction.

That is, without rotating the print head in the same forward direction as when the surface position of the paper 23 was detected, it is possible to obtain a print head gap of a predetermined amount corresponding to the α pulse.

Therefore, even if the thickness of the paper 23 differs or the play in the power transmission system changes over time, it is possible to always ensure a constant rad gap for printing.

Also, the print head gap is usually 0.3 rra+ ~ 0
．． It is very narrow at 5 mm, and if the paper 23 lifts up from the platen 31, the contact 22a will come into contact with the paper immediately after printing and the ink has not yet dried, and as the carriage 21 moves left and right, blurring will occur. Sometimes.

Therefore, as shown in FIG. 1, if the position outside the print area of the print head, that is, the print width in the paper feeding direction, is B, then the position of the contact 22a of the linear output device 22 is shifted from the center of the print head. It is shifted by A (A>1/2 B).

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) 6 As explained above, according to the present invention, the platen is moved in parallel by the rack and pinion, so the rotation angle of the pulse motor is completely proportional to the amount of movement of the platen, which is expensive and expensive. It is possible to eliminate the need for a precise linear cam.

Also, after detecting the paper surface using a forward pulse,
Since the printing gap is formed by sending a certain number of extra reverse pulses than the number of pulses required to form the printing gap, and then sending forward pulses, it is possible to stop the stepping motor in the forward direction. This eliminates the influence of play in the power transmission system and always provides a stable rad gap for printing.

Furthermore, by locating the contact of the linear output device outside the printing area of the print head, it is possible to prevent printing stains even when the ink has not yet dried immediately after printing.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a printer that employs the printing head gap automatic adjustment mechanism of the present invention, Fig. 2 is a right side view of the printer, Fig. 3 is a front view of the main parts, and Fig. 4 is a printer using the printing head gap automatic adjustment mechanism of the present invention. FIG. 5 is a block diagram of the automatic adjustment mechanism, FIG. 5 is an operation time chart of the automatic print head gap adjustment mechanism of the present invention, and FIG. 6 is a side view of the conventional automatic print head gap adjustment mechanism. 1.20...Print head, 2,21...Carriage, 322...Linear output device, 3a, 22a...
Contactor, 5, 42...Stepping motor, 25...
・Guide shaft, 31...Flat platen, 34
．． 35...Rack, 46.49...Pinion gear.

Claims (3)

[Claims] (1) At least one of the platen and the print head is provided with a drive device for changing the relative position between them, making it possible to adjust the gap between them according to the thickness of the paper on which printing is to be performed on the platen. In the automatic print head gap adjustment mechanism, (a) a rack is installed on one of the platen and the print head;
A print head gap automatic adjustment mechanism, characterized in that a pinion gear is connected to the other end, and (b) the pinion gear is connected to a motor. (2) At least one of the platen and the print head is provided with a drive device for changing the relative position between the two, making it possible to adjust the gap between them according to the thickness of the paper to be printed on the platen. In the print head gap automatic adjustment mechanism, (a) a linear output device is attached to the print head so as to face the paper, and (b) a contact that can be retracted at the tip of the linear output device when it comes into contact with the paper is provided. (c) means for detecting the surface position of the paper based on the amount of change in the output from the linear output device; and (d) a gap between the platen and the print head until the surface position of the paper is detected. (e) after the surface position of the sheet is detected, driving the drive device in a direction to increase the gap and then again in a direction to decrease the gap; , means for forming a predetermined amount of gap between the platen and the print head. (3) The print head gap automatic adjustment mechanism according to claim 2, wherein the print surface of the platen is flat, and the contact position of the contactor with the paper is outside the print area of the print head.