JPH07329320A - Wire dot print head - Google Patents

Abstract

PURPOSE:To provide a wire dot print head in which stable printing characteristics are obtained by reducing unevenness of the spring force of a leaf spring. CONSTITUTION:A spot facing 42 is formed on the surface of a spacer 15 of one member for holding a leaf spring 14 of a magnet yoke 21 side. Members for forming a print head 11 are held under pressure contact by a clamp 33. A holding force P of the clamp 33 is divided into forces P1, P2 at the outer peripheral pressure contact part 43 and the inner peripheral pressure contact part 44 of the spacer 15 between the spacer 15 and the yoke 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire dot print head used in a serial impact printer, and more particularly to the structure thereof.

[0002]

2. Description of the Related Art Conventionally, as a wire dot print head used in a serial impact printer, there is one described in Japanese Utility Model Publication No. 4-36275. In the print head according to this publication, a permanent magnet, a base plate, a spacer, a leaf spring, a yoke, and a guide are sequentially laminated on a base,
It is clamped and fixed by a clamp. The leaf spring is supported like a cantilever, and has an armature having a printing wire fixed to the tip thereof.

The armature is biased toward the electromagnet, and the leaf spring is biased accordingly. Due to the bias of the leaf spring, spring force is stored, and when the armature is released by operating the electromagnet, printing is performed by the stored spring force.

[0004]

However, the above-mentioned conventional wire dot print head has the following problems. It will be described with reference to FIG. FIG. 7 is an explanatory diagram showing a conventional problem.

In FIG. 7, a print wire 2 is fixed to the tip of an armature 1, and the armature 1 is provided with a leaf spring 3
Is fixed to the free end 3a. The fixed end 3b of the leaf spring 3 is sandwiched between the yoke 4 and the spacer 5, and is fixed by the sandwiching force P of a clamp (not shown). At the time of non-printing, the free end 3a of the leaf spring 3 is attracted to the core 7 of the electromagnet 6 by the magnetic flux of a permanent magnet (not shown) together with the armature 1 and is biased. When printing, the free end 3 of the leaf spring 3
The a is released from the magnetic flux of the permanent magnet by the electromagnet 6, and is bent upward in the figure by the stored spring force. A notch 8 is formed in the inner peripheral portion of the spacer 5, and the free end 3a of the leaf spring 3 is biased around the fixed end A. Since the clamping force P by the clamp presses each member by the surface, the stress against the bias of the leaf spring 3 in the spacer 5 is dispersed, and the stress at the fixed end portion 5a of the spacer 5 is weak. In addition, variations in stress occur at the fixed ends 5a of the spacers 5 corresponding to the respective armatures 1. As a result, the spring force of each print wire varies, and the print quality may deteriorate. The stress at the fixed end portion 5a of the spacer 5 serves to suppress the vibration of the leaf spring 3, and if this stress is weak, the leaf spring 3 and the spacer 5 may be separated from each other.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, according to the present invention, a leaf spring having an armature having a print wire attached to the tip thereof is sandwiched by a sandwiching member, and further pressed by a spring member to sandwich the armature. By biasing the leaf spring by attracting to, the wire dot print head that conducts printing by energizing the coil attached to the core to release the armature, of the holding member on the side where the leaf spring is biased,
A force receiving portion that intensively receives the clamping force of the spring member is provided at a portion corresponding to the base portion where the leaf spring is biased.

[0007]

According to the present invention having the above structure, since the force receiving portion is provided at the portion of the holding member for holding the leaf spring, which corresponds to the base portion where the leaf spring is biased, the stress against the bias or vibration of the leaf spring is reduced. It becomes stronger and the variation in stress is reduced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. Note that elements common to the drawings are given the same reference numerals. FIG. 1 is a sectional view showing a wire dot print head according to a first embodiment of the present invention, and FIG. 2 is a partial side sectional view showing the wire dot print head according to the first embodiment. First, the entire print head will be described with reference to FIG.

In FIG. 2, a wire dot print head 1
Reference numeral 1 denotes a spring charge type print head, which is a spring assembly including a guide frame 12, an armature yoke 13, a biasing leaf spring 14, a magnetic spacer 15, an armature 16, a guide nose 17, a print wire 18 and a wire guide 19. 20, magnet yoke 21, permanent magnet 22, yoke 23, base yoke 2
4, an electromagnet 25, a printed circuit board 26, a thermistor 27, and a magnet assembly 29 including a radiation fin 28. The electromagnet 25 includes a rod-shaped core 30 having a substantially trapezoidal cross section and an exciting coil 32 wound around a bobbin 31. A filler 36 is filled inside the print head 11.

The clamp 33 has its one end 33a hooked on the hooking portion 34 of the outer wall of the guide frame 12, and the fin 2
The hook portion 35 of No. 8 is engaged with a hole (not shown) of the other end 33b to clamp the entire print head 11 and fix it integrally. The clamps 33 are provided at four locations around the print head 11.

In FIG. 1, the leaf spring 14 is sandwiched between an armature yoke 13 and a spacer 21. A counterbore portion 41 is formed on the inner peripheral portion of the spacer 15 on the leaf spring 14 side, and the leaf spring 14 is biased around an end portion 41 a facing the end portion of the counterbore portion 41. A counterbore 42 is formed on the spacer 15 on the side of the magnet yoke 21. Therefore, the spacer 15 is in contact with the magnet yoke 21 at the outer peripheral pressure contact portion 43 and the inner peripheral pressure contact portion 44.

FIG. 3 is a plan view showing the spacer of the first embodiment, and FIG. 4 is a partially enlarged view of FIG.
FIG. 5 is a view of 5 viewed from the magnet yoke side. 5 is a sectional view taken along line BB of FIG. In these drawings, the spacer 15 has a ring shape as a whole, and the counterbore 4
1 are formed on the inner peripheral portion 15a at equal intervals. The free end 14a of the leaf spring 14 is arranged so as to face the spot facing portion 41. The counterbore portions 41 are provided in the same number as the armatures 16. The spot facing portion 42 is formed in a ring shape along the shape of the spacer 15. Inner peripheral portion 15a of the spot facing portion 42
The inner peripheral pressure contact portion 44 is formed on the side, and the outer peripheral pressure contact portion 43 is formed on the outer peripheral portion 15b side of the spot facing portion 42. The counterbore 42 occupies approximately a half of the total surface area of the spacer 15 facing the magnet yoke 21.

An escape hole 45 is formed on the inner peripheral side of the spot facing portion 42. The escape hole 45 is provided to escape the protrusion to the spacer 15 side when the armature 16 and the leaf spring 14 are fixed by laser welding. Further, a spot hole 46 for welding the spacer 15 and the leaf spring 14 is formed between the spot facing portion 42 and the spot facing portion 41.

In FIG. 1, the print head 1 after assembly is shown.
1 is fixed by the clamping force P of the clamp 33. The sandwiching force P between the spacer 15 and the magnet yoke 21 is the force P1 on the inner peripheral pressure contact portion 44 and the outer peripheral pressure contact portion 4.
The force P2 for 3 is divided. That is, the sandwiching force P is concentrated on the inner peripheral pressure contact portion 44 and the outer peripheral pressure contact portion 43 between the spacer 15 and the magnet yoke 21. Inner circumference pressure contact part 4
The pinching force P1 concentrated on 4 becomes a stress against the external force due to the bias of the leaf spring 14, and becomes a force for pressing the fixed end portion 41a of the leaf spring 14. By concentrating the clamping force P on the inner peripheral pressure contact portion 44, the variation in spring force can be reduced, and stable spring characteristics can be obtained.

Since the counterbore 42 occupies approximately a half of the total surface area of the spacer 15 facing the magnet yoke 21, the clamping force P1 against the inner peripheral pressure contact portion 44 is as follows.
It is about twice as strong as the conventional one.

As described above, according to the first embodiment, since the counterbore 42 is provided on the side of the magnet yoke 21 of the spacer 15, the stress on the fixed end portion 41a of the leaf spring 14 increases, so that the spacer 15 and the leaf spring are increased. It is not necessary to fix it by laser welding with 14, and it can be expected to reduce the assembly process.
Further, by providing the counterbore 42, it is possible to significantly reduce the occurrence of defects due to foreign matter adhering between the spacer 15 and the magnet yoke 21.

In the above embodiment, the counterbore 42 is provided on the surface of the spacer 15 on the side of the magnet yoke 21, but the counterbore may be provided on the plate spring 14 side of the spacer 15. Further, instead of the spot facing, a similar effect can be obtained by forming a hole penetrating from the leaf spring 14 side to the magnet yoke 21 side.

FIG. 6 is a cross-sectional view of an essential part showing a wire dot print head according to the second embodiment of the present invention. Next, the second embodiment will be described. In the print head of the second embodiment, the magnet yoke facing the spacer is provided with a counterbore to concentrate the clamping force by the clamp on the inner peripheral portion of the spacer.

In FIG. 6, the leaf spring 14 is sandwiched between the armature yoke 13 and the spacer 14, and the spacer 15
Is sandwiched between the leaf spring 14 and the magnet yoke 21. On the surface of the magnet yoke 21 on the spacer 15 side,
A spot facing 51 is formed. The spot facing 51 occupies about 4/5 of the surface of the magnet yoke 21 facing the spacer 15. The clamping force P by the clamp 33 is equal to the spacer 1
5 and the magnet yoke 21, the clamping force P3 against the outer peripheral pressure contact portion 53 of the spacer 15 facing the outer peripheral portion 52 located outside the counterbore 51 and the inner peripheral portion 54 located inside the counterbore 51 are opposed. The clamping force P4 is exerted on the inner peripheral pressure contact portion 55, and this clamping force P is applied to the outer peripheral pressure contact portion 53.
And the inner peripheral pressure contact portion 55 is concentrated. The clamping force P4 at the inner peripheral pressure contact portion 55 is about 5 times that of the conventional one.

In the second embodiment, the magnet yoke 2 facing the spacer 15 on the opposite side of the leaf spring 14 is provided.
Since the counterbore 51 is provided in 1, the region where the counterbore 51 is formed can be widened. That is, when the spacer 15 is provided with a spot facing, the size of the spot facing is limited because the spacer 15 has the escape hole 45 and the spot hole 46 as described in the first embodiment. Since these holes are not provided, the spot facing can be enlarged. The counterbore is increased, the stress against the bias of the leaf spring 14 is increased, and the variation of the spring force is reduced accordingly.
Stable printing characteristics can be obtained. Further, the increase in the stress further reduces the laser welding process for fixing the spacer 15 and the leaf spring 14 to each other. Further, in the second embodiment, in the step of polishing the magnet yoke 21 so that the upper surface of the magnet yoke 21 and the upper surface of the core are flush with each other, the polishing area is reduced by forming the counterbore 51, so that the number of polishing steps is reduced. There is an effect.

[0021]

As described in detail above, according to the present invention, the clamping force of the spring member is concentrated on the portion of the clamping member on the side where the leaf spring is biased, corresponding to the base portion where the leaf spring is biased. Since the force receiving portion for receiving is provided, the stress against the bias of the leaf spring is increased, the variation in spring force is reduced, and stable printing characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a print head according to a first embodiment of the present invention.

FIG. 2 is a partial side sectional view showing a wire dot print head according to the first embodiment.

FIG. 3 is a plan view showing a spacer of the first embodiment.

FIG. 4 is a partially enlarged view of FIG.

FIG. 5 is a sectional view taken along line BB.

FIG. 6 is a cross-sectional view of essential parts showing a print head according to a second embodiment.

FIG. 7 is an explanatory diagram showing a conventional problem.

[Explanation of symbols]

 11 Wire dot print head 13 Armature yoke 14 Leaf spring 15 Spacer 16 Armature 21 Magnet yoke 33 Clamp 42 Counterbore 41a Fixed end 44 Inner peripheral pressure contact P P clamping force

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takanori Mimura 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (3)

[Claims] 1. A leaf spring, to which an armature having a printing wire attached at its tip is fixed, is sandwiched by a sandwiching member, and is further pressed and sandwiched by a spring member, and the leaf spring is biased by attracting the armature to the core and attached to the core. In a wire dot print head that energizes the coil to release the armature for printing, concentrate the clamping force of the spring member on the part of the clamping member on the side where the leaf spring is biased, corresponding to the base part where the leaf spring is biased. The wire dot print head is characterized in that it is provided with a force receiving portion that receives the force. 2. The wire dot print head according to claim 1, wherein the force receiving portion is formed by forming a spot facing on the side opposite to the plate spring side of the holding member. 3. The wire dot print head according to claim 1, wherein the force receiving portion is formed by forming a counterbore on a member facing the plate spring side of the holding member.