JPH0452222B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a wire dot head, and more particularly to a wire dot head that, after driving the armature that drives the wire for dot printing, is moved back by the biasing force of a restoring spring and brought into contact with a stopper to return to its initial position. Regarding the head.

Prior Art In this type of wire dot head, an electromagnet housed in the head body attracts and operates an armature, and this armature drives the wire into pressure contact with the print paper via the ink ribbon, thereby producing the desired print using the dot matrix. is going on.

In other words, if m×n dot matrices are arranged as shown in Fig. 1, the vertical direction is
Use a print head with n wires arranged in a row at a pitch of P ₂ , and shift the print head to the right or left m times at a pitch of P ₁ so that the wires can be driven at each pitch. Therefore, an m×n dot matrix can be constructed.

Immediately after each dot is printed, the armature moves back due to the biasing force of the restoring spring, contacts the stopper, and returns to the initial position.

Wire dot printers that print using such wire dot heads have the advantage of being able to make copies at the same time because they print by impact, but they have the disadvantage of making a lot of noise when they are driven.

The first cause of noise is impact sound when dots are printed on printing paper. The impact sound quality in this case is determined by the material and hardness of the platen, the mounting state of the printing paper, and the impact force of the wire.

The second cause of noise is the contact sound generated when the armature contacts the stopper when returning to its initial position. The quality of this contact sound is determined by the material and hardness of the stopper, its surrounding members, and the exterior condition of the head.

However, in the conventional wire dot head, the stopper is made of a hard material such as plastic, so the above-mentioned contact noise is loud.

In addition, if the stopper is hard, the repulsive force that the armature receives will be large when it comes into contact with the stopper.
The operation of the armature becomes unstable, and as a result, the printing quality deteriorates.

Purpose The present invention has been made in view of the above points, and an object of the present invention is to provide a wire dot head that minimizes the contact noise when the armature returns and improves printing quality by stabilizing the operation of the armature. The purpose is

Embodiments Hereinafter, the basic structure and operation of a wire dot head to which the present invention is applied will be explained with reference to the accompanying drawings.

FIG. 2 is a longitudinal sectional view of an embodiment of a wire dot head to which the present invention is applied, and FIG. 3 is an exploded perspective view thereof.

In Fig. 2, 1 is a plurality of wires 2 for printing.
This is a tip guide that supports and guides 2. Further, reference numeral 2 denotes an intermediate guide that similarly supports and guides the wire 22, and both guides have a hole in which the wire 22 is inserted, with the tips thereof located approximately in the center. The intermediate guide 2 is attached to a bag holder 21, which will be described later, with screws 23 or the like via a positioning engagement portion (not shown). Further, the intermediate guide 2 is provided with a U-shaped groove 2a for attachment to a carriage (not shown) via a screw. 3 is a flexible cable for supplying current to the electromagnet coil 7, which will be described later; 4 is a heat dissipation plate that makes surface contact with the yoke 5 of the electromagnet, which will be described later, and the back holder; and also serves as a spacer between the flexible cable 3 and the yoke. ing. Reference numeral 5 designates a yoke of an electromagnet, which is formed in an elliptical shape as shown in FIG. 4, and uniformizes the sliding resistance of the wire to prevent density unevenness between dots formed on the printing paper.

A core 6 is connected to the yoke 5, and a bobbin 8 on which a coil 7 is wound is fitted onto the core 6. This bobbin 8 is provided with two terminals 8a, and the winding start and winding end portions of the coil 7 are soldered.These two terminals are also soldered to the aforementioned flexible cable 3, and the coil 7 is connected to the coil 7 by soldering. energization is performed.

Reference numeral 9 denotes a rear guide that supports and guides the wire 22 through a hole formed at its tip. Between this rear guide 9 and the armature 14, there is a restoring spring 10 for returning the armature to its initial position after being driven. equipped. Armature 1 is restored by restoring spring 10.
4 is always biased in the right direction in the figure, that is, in the backward direction.

Also, behind the armature 14 is a stopper 15.
is arranged, and when the armature 14 comes into contact with this stopper 15, it stops moving backward.
The stopper 15 is formed into a disk shape, and grooves into which the armature fits are radially bored on the front side. In addition, in this embodiment, the stopper 15 has a hardness
It is made of acrylic rubber with an angle of about 95 degrees. The surface is also subjected to fluorine substitution treatment using fluorine gas.

Further, in the figure, 11 is an auxiliary yoke arranged in parallel with the yoke 5, and 12 is an auxiliary yoke that prevents wear due to rotation due to line contact with the auxiliary yoke 11, residual magnetism, etc. of the auxiliary yoke 11, which is a problem when forming a closed magnetic path. A spacer such as a polyester film is interposed between the auxiliary yoke 11 and the armature 14 in order to prevent the movement of the armature 14 from becoming unstable.

A plunger 13 is fixed to the armature 14, and a wire 22 is connected to the tip of the armature 14 by brazing. Further, the other end of the armature 14 is provided with a hole (not shown) into which the engaging portion of the bobbin 8 described above is fitted, and the armature 14 rotates about this engaging portion as a fulcrum. Reference numeral 16 denotes an armature holder, which stabilizes the rotation of the armature 14 by pressing and holding the pivot portion from the rear when the armature 14 rotates. Also, this armature holder 1
6 is fitted with the stopper 15 described above.
A leaf spring 17 is provided in contact with the armature holder 16, and the elastic displacement of the leaf spring 17 uniformly presses the armature holder 16. These auxiliary yoke 11, armature 1
4. The arrangement relationship between the armature holder 16 and the leaf spring 17 is shown in FIG.

Reference numeral 18 denotes a damper for vibration isolation provided on the leaf spring 17, and this damper 18 is held in pressure contact with a back holder 21 via a washer 19 and a spring washer 20. This damper 18 is swingably provided by a leaf spring 17 and a spring washer 20 in order to enhance the vibration-proofing effect. Here, the washer 19 prevents the spring washer 20 from biting into the damper 18.

Next, the operation of the wire dot head constructed as described above will be explained.

When the coil 7 of the wire dot head is energized, the yoke 5, the auxiliary yoke 11, and the plunger 1
3. Since a closed magnetic path is formed by the core 6, the plunger 13 of the armature 14 is attracted to the core 6, and the armature 14 rotates so as to push out the wire 22 while compressing the restoring spring 10. At this time, the tip of the wire 22 hits the ink ribbon on the printing paper to print a dot. At this moment of printing, the coil 7 is de-energized and the wire 22 is affected by the repulsive force from the platen and the compressed restoring spring 10.
The armature 14 is pushed back by the urging force of
It comes into contact with the stopper 15 and stops at the initial position before suction. Along with this movement of the armature 14, the tip of the wire 22 also moves back and then stops at the initial position.

In the above operation, the movement of the armature 14, that is, the movement of the wire 22, is determined by the material and hardness of the stopper 15 and the spring constant of the restoring spring 10.

The details of the operation of the armature when the spring constant is inappropriate and the stopper 15 is hard as in a conventional wire dot printer will be explained below with reference to FIGS. 6A and 6B.

Here, FIG. 6A shows the relationship between time and the displacement x of the tip of the wire 22 linked to the armature 14, which is made dimensionless by x/c using the clearance c between the printing paper and the tip of the head. Ori x/c
Printing is performed when = 1.0. Further, FIG. 6B shows the relationship between the voltage of the electric signal applied to the coil 7 and time. Here, FIG. 6A and FIG. 6B correspond on the time axis, and the signal period is T and the energization time is τ.

When an electric signal is applied, the armature 14 is attracted to the core 6, and in conjunction with this, the wire 22 begins to move from point a and reaches the paper surface at point b to print. Immediately before this, the electrical signal becomes 0. Therefore, immediately after printing, the armature 14 is rotated in the backward direction by the repulsive force from the platen and the biasing force of the restoring spring 10, so that the wire 22 returns to point c, and the armature 14 comes into contact with the stopper 15.

However, since the hardness of the stopper 15 is high, a large sound is generated due to the impact of the contact, and the repulsive force of the contact is large.
4 rebounds, and the tip of the wire 22 moves up to point d.

At this point, the armature 10 is pushed back again by the biasing force of the restoring spring 10, but just before it returns, the energization signal is applied again and the core 6 is attracted.
In conjunction with this, the tip of the wire 22 once returns from point d to point e, then reverses and reaches point f, whereupon printing is performed again.

Here, the suction force of the core 6 is relatively weakened by the inertial force when the wire 22 returns from point d to point e, so that at point f of printing, the pressure contact force for printing decreases and the printed dots become thinner.

In order to prevent the occurrence of a large contact noise and destabilization of the operation of the armature as in the above-mentioned operation, in this embodiment, the restoring spring 10 having an appropriate spring constant is used, and the stopper 15 is used as described above. is made of acrylic rubber with a hardness of approximately 95°, and its surface is further subjected to fluorine substitution treatment using fluorine gas.

Here, acrylic rubber and its fluorine substitution treatment will be explained.

Acrylic rubber is an elastic material containing three components of acrylic acid alkyl ester (CH ₂ = CHCOOR), and is usually a copolymer with a second component having an active group that serves as a cross-linking point, and its structural formula is as follows. .

Here, R ₁ =CmH ₂ m−, R ₂ =CnH _2o+1 .

As described above, acrylic rubber is composed of saturated carbon bonds and has excellent heat resistance that can withstand temperatures of 200°C or more when used continuously or for a short time. The internal temperature of a wire dot head rises to around 150°C when used for a long period of time, and there are only a limited number of rubbers that can withstand this temperature, so acrylic rubber is ideal in this respect.

Furthermore, acrylic rubber has resistance to aliphatic hydrocarbon lubricating oil used inside the head due to the polarity of the carbonyl group, and is excellent in this respect as well.

However, the disadvantage of acrylic rubber is that it is highly sticky. If the stopper is highly adhesive, the armature will stick to the stopper when it comes into contact with the stopper, resulting in a delay in response to the drive electric signal or malfunction.
As a result, the dots are misaligned and the high-speed operation of the head is hindered.

Therefore, in this embodiment, in order to remove the stickiness of the acrylic rubber, the acrylic rubber is subjected to surface treatment by fluorine substitution. Specifically, for example, after holding an acrylic rubber molded into the shape of the stopper 15 in a fluorine gas stream at a temperature of 10° to 150°,
Wash sequentially with aqueous alkali metal salt solution and water.

By performing the surface treatment in this manner, the stickiness of the acrylic rubber stopper can be removed, and the above-mentioned response operation of the armature can be prevented from being delayed and malfunction can be prevented, allowing accurate high-speed operation.

Next, details of the operation of the armature 14 of the wire dot head of this embodiment using the stopper 15 made of acrylic rubber subjected to the surface treatment as described above will be explained with reference to FIGS. 7A and 7B.

Here, FIGS. 7A and 7B illustrate the operation of the tip of the wire 22 in conjunction with the armature 14, similar to FIGS. 6A and 6B.

When an electric signal is applied, the core 6 of the armature 14 is attracted, and in conjunction with this, the wire 22 moves from point a', reaches point b', contacts the platen, and prints. Immediately before this, the electrical signal becomes 0 level. Therefore, the suction force of the core 6 is deenergized, and the armature 14 rotates and retreats due to the repulsive force of the platen at the time of contact and the biasing force of the restoring spring 10, and comes into contact with the stopper 15.

The impact force of this contact is absorbed by the elastic force of the acrylic rubber of the stopper 15, so the contact noise is very small, and the repulsive force is small, so the restoring spring 10
The biasing force overcomes this, and the armature 14 stops at the same time as the contact without rebounding. That is, the tip of the wire 22 moves from point b' to point c' and stops.

An electrical signal is then applied and the above operation is repeated.

As mentioned above, armature 14 and stopper 15
Since the armature 14 does not bounce back when it makes contact, it operates in response to an electrical signal, so the wire 22 can also operate in response to an electrical signal. Moreover, the contact noise between the armature 14 and the stopper 15 is very small. This reduces the overall noise of the head. Incidentally, noise tests showed that the noise level was approximately 10 dB lower than before.

Effects As is clear from the above explanation, according to the present invention, the stopper for returning the armature to the initial position in the wire dot head is formed from acrylic rubber, and the acrylic rubber is surface-treated by fluorine substitution. Therefore, by reducing the contact noise when the armature returns, the noise of the entire head can be reduced, and the stable operation of the armature can improve printing quality.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the structure of a dot matrix, FIG. 2 is a longitudinal sectional view showing an example of a wire dot head to which the present invention is applied, and FIG. 3 is an exploded perspective view of the wire dot head shown in FIG. , Fig. 4 is a view taken along the line A-A' in Fig. 2, and Fig. 5 is a view taken along the line B- in Fig. 2.
Figure 6 is a diagram showing the movement of the armature using a conventional stopper; Figure 6A is a diagram showing the operation of the wire tip; Figure 6B is a timing chart of electrical signals; FIG. 7 explains the operation of the armature by the stopper of the present invention. FIG. 7A is a diagram showing the operation of the tip of the wire, and FIG. 7B is a timing chart of electric signals. 5... Yoke, 6... Core, 7... Coil, 1
0... Restoration spring, 13... Plunger, 14...
Armature, 15... Stoppa, 22... Wire.

Claims (1)

[Claims] 1. In a wire dot head that performs desired printing using a plurality of wires that are driven into pressure contact with a printing target in response to a plurality of armatures that are attracted and operated by electromagnets housed in the head body, the armature after being driven has a restoring spring. 1. A wire dot head, characterized in that a stopper that comes into contact when returning to a non-operating initial position is made of acrylic rubber, and the acrylic rubber of the stopper is surface-treated by fluorine substitution.