JPH0557915B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention maintains the gap between the recording paper and the print head (hereinafter referred to as the head gap) at a constant value, thereby improving print quality and durability of the print wire. The present invention relates to an automatic head gap adjustment mechanism for a printer.

[Conventional technology]

Dot impact printers print dots by pressing an ink ribbon against recording paper using a print wire in the print head. In that case,
Since the thickness of recording paper differs depending on the paper used, it is necessary to adjust the head gap each time.
In other words, when the head gap becomes large, the printing pressure becomes weaker, resulting in a thinner print.On the other hand, when the head gap becomes smaller, the printing pressure becomes stronger, which may cause the recording paper to become stained by the ink ribbon, be damaged by the print wire, or cause damage to the wire itself. This is because wear becomes significant. Conventionally, therefore, the head gap is manually adjusted by operating a lever to move the printing head up and down depending on the paper thickness.

[Problem that the invention seeks to solve]

However, such a manual gap adjustment operation has to be performed each time the paper is changed, which is troublesome and can lead to forgetting or incorrect adjustment.

[Means for solving problems]

The automatic head gap adjustment mechanism of the printer according to the present invention was made to solve the above-mentioned problems, and is reciprocated in a direction perpendicular to the feeding direction of the recording paper, and adjusted vertically by an eccentric shaft. a printing head mounted on the carriage that presses an ink ribbon against the recording paper using a print wire to print dots; a spring that applies a rotational force to the eccentric shaft in a direction in which the printing head descends; and a drive. It consists of a motor and a rotation transmission mechanism that transmits the rotation of the drive motor to the eccentric shaft, and the spring rotates the eccentric shaft during a zero position detection operation to lower the print head and press it against the recording paper, The rotation transmission mechanism includes a one-way clutch that transmits the rotation of the drive motor to the eccentric shaft during a head gap setting operation for raising the print head by a certain amount after a zero position detection operation.

[Effect]

In the present invention, the print head is pressed against the recording paper by the spring force, and after the zero position is detected, the print head is raised by a certain amount by a motor drive, so that the head gap can be automatically adjusted. I can do it. Further, since the pressure of the print head against the recording paper is obtained by the spring force of the spring, even if the thickness of the paper differs, the difference is slight and a substantially constant pressure can be obtained.
Therefore, troubles such as impressions and stains on the recording paper can be prevented, and changes in the compression of the recording paper are small, the zero position detection accuracy is improved, and the head gap can be set to a constant value.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a sectional view showing an embodiment of an automatic head gap adjustment mechanism according to the present invention, FIG. 2 is a perspective view of a print head, and FIG. 3 is a sectional view of the head. In these figures, reference numeral 1 indicates a direction perpendicular to the feeding direction of the recording paper 4 (direction of arrow A in FIG. 2) (direction of arrows B and C) along a pair of guide shafts 2 and 3 arranged in parallel in the vertical direction. ), in which a printing head 5, a card holder 6, a timing belt, etc. are disposed, and an ink ribbon 9 fed in the direction of movement of the platen 8 and the carriage 1 is attached to the printing head. 5, and these constitute a printing mechanism.

The print head 5 is of a conventional type, and as shown in FIG. It is generally composed of a plurality of leaf springs 13 that elastically support, a guide plate 14 and a tip guide 15 that guide each print wire 11, and a plurality of coils 16 and magnets 17 that individually drive each print wire 11. It is configured. Twelve print wires 11 are arranged in two rows with a predetermined gap in the direction of movement of the carriage 1, and the wires in each row are arranged in a line in the direction in which the recording paper 4 is fed.

The card holder 6 is made of transparent plastic and is interposed between the recording paper 4 and the ink ribbon 9 by being disposed below the printing head 5. An opening 19 is provided in the center of the card holder 6, which is covered with a mask 20 formed in a thin plate shape (about 0.1 mm thick) from stainless steel or the like. A ribbon hole 22 is formed in the center of the mask 20 to correspond to the print wire 11 .

Therefore, while the carriage 1 is reciprocated along the guide shafts 2 and 3, the coil 16 is energized to selectively drive the armature 12, thereby displacing the print wire 11 downward and projecting it below the case 10. Then, the wire 11 presses the portion of the ink ribbon 9 corresponding to the ribbon hole 22 against the recording paper 4, and desired characters, records, etc. are printed in dots with each reciprocating operation.

As shown in FIG. 1, the head gap automatic adjustment mechanism 30 for adjusting the head gap G has an eccentric shaft 32 which is rotatably disposed on a side plate 31 and supports the guide shaft 3, and another side plate 33. A pulse motor 34 provided and a rotation transmission mechanism 35 that transmits the rotation of the pulse motor 34 to the eccentric shaft 32.
and a spring 36 that applies a rotational force to the eccentric shaft 32 in the direction in which the printing head 5 descends. The rotation transmission mechanism 35 includes a drive gear 41 that is press-fitted and fixed to the output shaft 40 of the pulse motor 34, a first intermediate gear 44 that integrally has a sleeve 43 and is rotatably disposed on a shaft 42, and a slip gear. 45 and a one-way clutch 46 fitted to the distal end of the sleeve 43;
A second intermediate gear 48 is rotatably disposed on the shaft 47 and meshes with the slip gear 45; intermediate gear 49
is interposed between the second and third intermediate gears 48 and 49, and the rotation of the second intermediate gear 48 is controlled by the third intermediate gear 4.
9, and a friction transmission plate 51 that transmits data to the friction transmission plate 9. During the zero position detection operation (pressing operation) of the print head 5, the one-way clutch 46
Sleep 4 occurs during a head gap setting operation (returning operation) in which the print head 5 is raised by a certain amount after detecting the zero position while being free with respect to the first intermediate gear 44.
3 and transmits the rotation of the first intermediate gear 44 to the slip gear 45.

The spring 36 is a torsion coil spring fitted around the outer periphery of the eccentric shaft 32, one end 36a of which is locked to the side plate 31, and the other end fixed to the eccentric shaft 32 with screws. In this case, the spring 36 is attached to the eccentric shaft 32 in a twisted state.
By being attached to the eccentric shaft 32, a rotational force is normally applied to the eccentric shaft 32 in the direction in which the print head 5 descends, and when the eccentric shaft 32 is rotated when the zero position is detected, the spring force is weakened.

The pulse motor 34 normally operates as the spring 3.
The rotation transmission mechanism 35 is locked by supplying a holding current sufficient to generate a driving force balanced with the spring force of the rotation transmission mechanism 35. This is to prevent the spring 36 from rotating the eccentric shaft 32 when the pulse motor 34 is stopped and the output shaft 40 is left free. In this case, it is also possible to lock the eccentric shaft 32 by engaging a pawl operated by a solenoid or the like with the driven gear 50 without supplying a holding current to the pulse motor 34.
The pulse motor 34 is driven when the head gap is set and when the print head 5 is pushed up to the highest position.

Next, the operation of the head gap automatic adjustment mechanism 30 having such a configuration will be explained.

First, the pulse motor 34 is driven by a signal from the control circuit to raise the print head 5 to its maximum height position. At this time, the rotation of the pulse motor 34 is as follows: drive gear 41 - first intermediate gear 44 - one-way clutch 46 - slip gear 45 - second intermediate gear 4
8-Friction transmission plate 51-The friction is transmitted to the driven gear 50 via the third intermediate gear 49, and rotates the eccentric shaft 32 in the direction in which the print head 5 rises. Therefore, when the spring 36 is compressed, it accumulates spring force. When the print head 5 reaches the highest position, the driven gear 30
The pin 60 provided in the second intermediate gear 48 comes into contact with a stopper (not shown) and stops. After that, the friction transmission plate 51 slips, so that the rotation of the second intermediate gear 48 is not transmitted to the third intermediate gear 49, and the pulse motor 34 Also, damage to the rotation transmission mechanism 35 is prevented. When the print head 5 reaches the highest position and a certain period of time has elapsed, a holding current is supplied to the pulse motor 34 to lock the rotation transmission mechanism 35. At this time, recording paper 4
has not yet been fed to the lower part of the print head 5.

Next, the recording paper 4 is fed to the lower part of the print head 5, and the zero position of the print head 5 is detected. At this time,
The supply of the holding current is stopped, and the pulse motor 34 is stopped. Then, since the rotation transmission mechanism 35 becomes free from the pulse motor 34, the spring 36 rotates the eccentric shaft 32 with its spring force. As a result, the guide shaft 3 rotates integrally with the eccentric shaft 32 and at the same time gradually descends, so that the print head 5 is pressed against the recording paper 4 via the card holder 6 and the ink ribbon 9. FIG. 4 shows this state.

Next, when the pressing operation is completed, a predetermined head gap G is applied to the pulse motor 34 by the corresponding number of pulses to drive the motor 34. Then,
Since the rotation of the output shaft 40 is transmitted to the driven gear 50 by the rotation transmission mechanism 35, the eccentric shaft 32 rotates together with the gear 50, twisting the spring 36 and simultaneously pushing up the guide shaft 3. When the guide shaft 3 is pushed up, the print head 5 also moves up together with the carriage 1, so that a predetermined head gap is set between the print head 5 and the recording paper 4. After the pulse motor 34 is held in a driven state with a holding current and the rotation transmission mechanism 35 is locked, the above-described printing operation is performed.

Thus, according to the head gap automatic adjustment mechanism 30 having such a configuration, the head gap G can be automatically set, so the operation is easy and there is no possibility of erroneous adjustment or forgetting the adjustment.
In addition, since the print head 5 is pressed against the recording paper 4 by the spring force of the spring 36, even if the paper thickness differs, the difference is only about 1 to 2 mm at most, so the pressure force against the paper does not change significantly. , the print head 5 can be pressed against the recording paper 4 with a substantially constant pressure contact force. In this case, if the spring force of the spring 36 is set in consideration of the weight of the print head 5, carriage 1, guide shaft 3, etc. and the frictional load of the bearing, it is possible to obtain an appropriate contact force and record the data. There is no dirt on the surface of the paper 4 as an impression, that is, a trace of the opening shape of the ribbon hole 22, or there is no dirt on the surface of the paper 4, and the print quality is not adversely affected.

Furthermore, if the pressure contact force is approximately constant and an appropriate pressure contact force is obtained, there will be little compression change in the paper even in the case of multiple sheets of copy paper, and the detection accuracy of the origin position of the paper surface and the precision of the head gap G will be improved. In other words, if the pressing force is too strong, the print head 5 will dig in, causing a large change in the compression of the paper, resulting in poor detection accuracy of the origin position on the paper surface, and if the print head 5 is returned from this biting state. , the head gap G is reduced by the amount of penetration of the printing head 5. In this case, the card holder 6 and the paper may come into contact with each other during the printing operation, and the ink ribbon 9 may protrude below the ribbon hole 22, which may stain the paper. This causes problems such as making holes in the paper and causing the wire 11 to wear out quickly. In this regard, in the present invention, since an appropriate pressure contact force is obtained, the above-mentioned problems do not occur, and the printing quality and durability of the print wire are improved.

〔Effect of the invention〕

As described above, according to the automatic head gap adjustment mechanism in a printer according to the present invention, the head gap can be automatically adjusted with a relatively simple structure, and operability can be improved. In addition, the print head can be pressed against the recording paper with an approximately constant appropriate pressure regardless of its thickness, and problems such as impressions and stains can be prevented, and if the pressing force is approximately constant, the gap between the heads can be reduced. It not only allows for highly accurate settings and prevents uneven printing, but also has great effects, such as less wear on the print wire and no holes in the paper.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an embodiment of the head gap adjustment mechanism according to the present invention, Fig. 2 is a perspective view of the print head, Fig. 3 is a cross-sectional view of the print head, and Fig. 4 is the state at the time of zero position detection. FIG. 1... Carriage, 2, 3... Guide shaft, 4... Recording paper, 5... Print head, 9...
Ink ribbon, 11...Print wire, 32...
... Eccentric shaft, 34 ... Pulse motor, 35 ... Rotation transmission mechanism, 36 ... Spring, 46 ... One-way clutch.

Claims (1)

[Claims] 1 A carriage that is reciprocated in a direction perpendicular to the feeding direction of the recording paper and adjusted vertically by an eccentric shaft, and an ink ribbon mounted on this carriage that presses the ink ribbon against the recording paper using a print wire to print dots. It consists of a print head, a spring that applies a rotational force to the eccentric shaft in the direction in which the print head descends, a drive motor, and a rotation transmission mechanism that transmits the rotation of the drive motor to the eccentric shaft, and the spring During the zero position detection operation, the print head is lowered and pressed against the recording paper by rotating the eccentric shaft, and the rotation transmission mechanism raises the print head by a certain amount after the zero position detection. An automatic head gap adjustment mechanism for a printer, comprising a one-way clutch that transmits rotation to the eccentric shaft.