JPH0414878B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of coupling a drive arm and a movable yoke in a spring-release print head.

[Conventional technology]

For example, a spring-release type printing head is
As disclosed in Japanese Patent No. 154178, the drive arm that drives the printing element is biased backward by a permanent magnet against its elastic force, and the magnetic field of the permanent magnet is canceled by the excitation of the drive coil to create a biased state. The drive arm is released, and the drive arm moves forward with its own elastic force, thereby driving the printing element.

Normally, the drive arm is equipped with a movable yoke at a position facing the core around which the drive coil is wound, but conventionally, this movable yoke was mechanically connected directly to the drive arm by caulking or press-fitting. or by using adhesive.

[Problem that the invention seeks to solve]

If the movable yoke is directly connected to the drive arm by mechanical connection by caulking or press-fitting, the connection strength between the two is sufficient, but the drive arm may be deformed such as warping due to processing distortion during connection. Sometimes. When the drive arm is warped, the positional relationship of the movable yoke with respect to the core end surface varies, which results in variation in response characteristics for each drive arm.

When the movable yoke is directly fixed to the drive arm with an adhesive, the drive arm is less likely to warp, but there is a problem in that the bonding strength is insufficient. This is because, according to the conventional simple adhesive structure, the adhesive surface between the drive arm and movable yoke is parallel to the plate surface of the drive arm, so the deformation of the drive arm during the printing operation causes the adhesive on the adhesive surface to come off. This is because the adhesive is repeatedly subjected to the force of trying to separate, and the adhesive area itself is small.

Furthermore, in known spring-release type print heads, the movable yoke moves in an arc around the support portion of the drive arm, so that when the movable yoke is drawn to the core, the edge of the rear end surface locally touches the core end surface. comes into contact with. This has resulted in decreased magnetic efficiency and durability.

SUMMARY OF THE INVENTION An object of the present invention is therefore to provide a bonding method that uses both mechanical bonding by caulking or press-fitting and bonding by adhesive to take advantage of the respective advantages of both.

Another object of the present invention is to provide a coupling method that allows the movable yoke to be easily coupled into a mounting relationship in which the rear end surface of the movable yoke is in substantial surface contact with the end surface of the core.

[Means for solving problems]

The method of coupling the drive arm and movable yoke according to the present invention is characterized by the combination of mechanical coupling by caulking or press-fitting and bonding by adhesive. First, a bushing having a through hole is fixed by caulking or press fitting into a through hole of a drive arm supported in a cantilevered manner. The movable yoke fixed to the bush has a shaft portion smaller in diameter than the through hole formed in advance on the surface facing the bush, and this shaft portion is loosely fitted into the through hole of the bush. Then, the movable yoke, which is in a loose state with respect to the bushing, is held in a desired mounting posture via a jig, and in this state, adhesive is injected into the through hole, so that the movable yoke is held in a loose state with respect to the bushing. It is glued.

〔Example〕

First, the structure of a print head to which the bonding method of the present invention is applied will be explained.

In FIG. 1, a printing wire 1 is slidably passed through a wire guide 2. As shown in FIG. It goes without saying that a plurality of printing wires 1 are actually provided and are supported by a plurality of wire guides. A printing pin 3 is fixed to the rear end of the printing wire 1, and a return spring 4 inserted between the printing pin 3 and the wire guide 2 causes the printing wire 1 to move backward (lower side in FIG. 1). is being energized.

Behind the printing wire 1, a drive arm assembly consisting of a stopper plate 5, a drive arm 6, a spacer ring 7, and a yoke plate 8 is arranged. The yoke plate 8 is integrated by a screw 9 that passes through the yoke plate 8 and screws into the yoke plate 8. The stopper plate 5, drive arm 6 and spacer ring 7 are made of non-magnetic material, and the yoke plate 8 is made of magnetic material. A bush 10 is fixed to the intermediate portion of the drive arm 6, and a movable yoke 11 made of a magnetic material is fixed to the bush 10 via an adhesive 12.
The bush 10 has a through hole 10a formed in its center, and the movable yoke 11 is cylindrical and has a shaft portion 11a having a smaller diameter than the through hole 10a projecting from one end surface thereof. . Further, a peripheral wall portion 11b is provided protruding from the outer peripheral portion of the movable yoke 11, and the outflow of the adhesive 12 is restricted by this peripheral wall portion 11b.

The drive arms 6 are arranged radially at equal angular intervals as shown in the third figure, and are connected together at their respective rear ends. A through hole 6 for attaching a bush 10 is provided in the middle of the drive arm 6.
A is perforated. The yoke plate 8 has a movable yoke 11 corresponding to this arrangement of the drive arm 6.
A through hole 8a is formed concentrically through which a through hole 8a can be penetrated. The stopper plate 5 also has a shape substantially similar to the yoke plate 8 shown in FIG.

Behind the drive arm assembly, a U-shaped core 13 is arranged such that one end surface 13a thereof faces the movable yoke 11. A permanent magnet 14, a magnet plate 15, and a spacer ring 16 are sandwiched between the other end surface 13b of the core 13 and the yoke plate 8. Further, a drive coil 17 is wound around a part of the core 13. The core 13, magnet plate 15 and spacer ring 16 are made of magnetic material. Therefore, the magnetic plate 15 and the spacer ring 1
6. A magnetic path 18 for the permanent magnet 14 is formed by the movable yoke 11 and the core 13, and the movable yoke 11 is attracted to the end surface 13a against the elastic force of the drive arm 6 when no current is applied. When the drive coil 17 is energized, the permanent magnet 14 passes through the magnetic path 18.
The magnetic flux from is canceled out. As a result, the magnetic attraction of the movable yoke 11 to the core end surface 13a is released, and the drive arm 6 moves forward by its own elastic force to move the printing wire 1 forward against the spring force of the return spring 4. Dots are formed on a print medium (not shown).

Here, a method of coupling the drive arm 6 and the movable yoke 11 according to the present invention will be described in detail.

First, as shown in FIG. 5a, the bush 10 is fixed to the through hole 6a of the drive arm 6 by caulking or press fitting. Next, in this embodiment, as shown in FIG. 5B, the stopper plate 5, the drive arm 6, the spacer ring 7, and the yoke plate 8 are laminated and integrated with screws 9. Thereafter, the movable yoke 11 is passed through the through hole 8a side of the yoke plate 8, and the shaft portion 11a is inserted into the through hole 10 of the bush 10. At this stage, the shaft portion 11a of the movable yoke 11 is attached to the bush 10.
can move relatively freely relative to the through hole 10a. Therefore, as shown in FIG. 5c, the drive arm assembly is mounted on a jig 19 with the movable yoke 11 inserted.
Set it on top. The jig 19 includes a movable yoke 11
A mounting surface 19a for mounting the rear end surface is formed, and this mounting surface 19a is inclined at an angle θ with respect to the horizontal plane. Therefore, the movable yoke 11
The axial center line L2 is the axial center line L1 of the bush 10.
It is held in an attitude tilted by an angle θ relative to the target. Then, while the movable yoke 11 is held in the above-described position via the jig 19, the adhesive 1 is applied.
2 into the through hole 10a of the bush 10. The adhesive 12 injected into the through hole 10a
0a and the shaft portion 11a, the bottom surface of the bush 10, and the top surface of the movable yoke 11. The outflow to is regulated.

As the adhesive 12 hardens, the movable yoke 11 is fixed so that its rear end surface forms an angle θ with respect to the plate surface of the drive arm 6, as shown in FIG. The angle θ is set to be substantially equal to the swing angle of the drive arm 6, so that when the movable yoke 11 is in the retracted state when no current is applied, the rear end surface is aligned with the end surface 13a of the core 13.
(See Figure 1).

FIG. 6 shows a movable yoke 20 according to another embodiment, in which a groove 20c is formed on the outer peripheral surface of the shaft portion 20a.
is formed. According to this movable yoke 20,
Since the adhesive enters the groove 20c, it becomes difficult to peel off. Note that 20b is a peripheral wall for controlling the outflow of adhesive.

The movable yoke 21 shown in FIG. 7 has a rear end face cut obliquely at an angle θ, and the movable yoke 21 is fixed in a posture in which its axial center line substantially coincides with that of the bush 10. It turns out. The other configurations are completely the same as the movable yoke 11.

In addition, in the above embodiment, the drive arm 6 is
Integration with the stopper plate 5, spacer ring 7, or yoke plate 8 is not an essential requirement of the present invention. Moreover, in order to increase adhesive strength, a groove may be formed in the through hole 10a of the bush 10.

〔Effect of the invention〕

According to the above-described method of coupling the drive arm and movable yoke according to the present invention, the following effects can be achieved.

Although the drive arm is deformed in an arched manner during operation, since the adhesive is formed between the rigid bush and the movable yoke, the adhesive will not come off due to this effect. The adhesive surface between the through hole of the bush and the shaft of the movable yoke is parallel to the load acting on the movable yoke (the force that pulls the movable yoke backwards. This is the force that tries to peel off the adhesive). , and the adhesive area increases accordingly.
Sufficiently high adhesive strength can be obtained.

When the bushing is connected to the drive arm by caulking or press-fitting, the drive arm may warp, but this accuracy error is completely absorbed during bonding, and the movable yoke is fixed to the bushing with its rear end surface uniformly aligned. Ru. This makes the response characteristics of each drive arm constant.

Furthermore, if the mounting surface of the jig that receives the rear end surface of the movable yoke is inclined at an angle substantially equal to the swing angle of the drive arm, the rear end surface of the movable yoke will be substantially aligned with the end surface of the core when no power is applied. As a result, the drive efficiency and durability of the print head are improved.

If a concave groove is formed on the outer circumferential surface of the shaft portion of the movable yoke or on the inner circumferential surface of the bush, the bonding strength of the adhesive can be further improved.

Furthermore, if the peripheral wall is formed to protrude from the outer periphery of the end surface of the movable yoke, troubles due to adhesive leakage will not occur.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a main part of a printing head in which a movable yoke is fixed to a drive arm by the coupling method according to the present invention, Fig. 2 is a side view showing the mounting posture of the movable yoke with respect to the drive arm, and Fig. 3 4 is a reduced front view of the drive arm, FIG. 4 is a reduced plan view of the stopper plate, FIGS. The front view and FIG. 7 are sectional views showing a structure for attaching a movable yoke to a drive arm according to still another embodiment. 6... Drive arm, 6a... Through hole, 10... Bush, 10a... Through hole, 11, 20, 21...
...Movable yoke, 11a, 20a, 21a...shaft part, 11b, 20b, 21b...peripheral wall part, 20c
...Concave groove, 19...Jig, 19a...Placement surface, θ
...Inclination angle of the mounting surface.

Claims (1)

[Scope of Claims] 1. A bushing having a through hole is fixed to a through hole of a drive arm supported in a cantilever shape, and a shaft having a smaller diameter than the through hole is attached to a surface of the movable yoke opposite to the bushing. The shaft portion of the movable yoke is loosely engaged with the through hole of the bushing, and the movable yoke that is loosely engaged with the bushing is held in a desired mounting posture via a jig. . A method for coupling a drive arm and a movable yoke, comprising: injecting an adhesive into the through hole in such a state, and fixing the movable yoke to the bushing with the adhesive. 2. The jig has a mounting surface for mounting the rear end surface of the movable yoke, and the mounting surface is inclined at an angle substantially equal to the swing angle of the drive arm. A method of coupling a drive arm and a movable yoke according to claim 1. 3. The method of coupling a drive arm and a movable yoke according to claim 1, wherein a groove is formed in at least one of the outer circumferential surface of the shaft portion of the movable yoke or the inner circumferential surface of the bush. 4. The drive arm and movable yoke according to claim 1, wherein the movable yoke is integrally formed with a peripheral wall portion protruding from the peripheral edge of the opposing surface to prevent the adhesive from flowing out. How to join. 5. The method of coupling a drive arm and a movable yoke according to claim 1, wherein a plurality of the drive arms are arranged radially and connected together at their outer peripheral portions.