JPH0858150A - Multineedle recording head - Google Patents

Abstract

PURPOSE: To reduce an electrostatic stray-capacitance and reduce the deterioration of an applied voltage to prevent the lowering in image density. CONSTITUTION: Conductors 8,...,8 which constitute recording electrodes 1,2 are arranged at a specified pitch and are firmly encapsulated in an electrode supporting block 5. Then the conductor 8 which constitutes each recording electrode is drawn out of the electrode supporting block 5. Further, these conductors 8 which can be grouped are bundled together and connected to a wiring substrate 6, and are connected to an external drive circuit. In this case, the conductors 8,...,8 for the electrode are loosened and connected to the wiring substrate 6 in such a way that the conductors are loosely arched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-needle recording head suitable as an electrostatic recording type recording head. More specifically, the present invention relates to an improvement in the connection structure of recording electrodes of a multi-needle recording head to a wiring board.

[0002]

2. Description of the Related Art A multi-needle recording head used in an electrostatic recording system, for example, a same-plane control multi-needle recording head is generally
As shown in FIGS. 6 and 7, two rows of recording electrodes 101 and 102, which are composed of conducting wires 108 arranged in a zigzag pattern at high density in a constant pitch, and two rows of control electrodes 10 corresponding thereto.
3 and 104 are electrode supporting blocks 1 made of an electrically insulating resin or the like.
It is composed by being hardened at 05. For example, M (= 128) sets of N (= 55) sets of M × N (= 7040) first recording electrodes 101 are formed.
And M × N arranged at a predetermined interval in parallel with this
(= 7040) second recording electrodes 102 and the first recording electrodes 102
And the control electrodes 103 and 104, which are respectively arranged outside the columns along the columns of the second recording electrodes 101 and 102, expose their end faces to the surface of a resin block / electrode support block 105 made of an insulating resin. Is provided.

Here, the first and second recording electrodes 101,
102 is usually formed by the tip portion of the conductive wire 108. In order to simplify the drive circuit, the conductor lines 108 of the recording electrodes that can be grouped are grouped together, then once connected to the wiring board 106, and each group is connected to the drive circuit. For example, the above M × N
In the case of the first recording electrode 101 of the book, N lead wires 108 of the recording electrode belonging to the same group are collected from the N sets of recording electrode groups by N, and each of the terminals 10 of the wiring board 106 is
7 are soldered to each of the M terminals 107, ... On the other hand, the second recording electrode 102
Are similarly grouped and soldered to the opposite side surface of the wiring board 106 (not shown). In addition, each terminal 107,
, 107 are connected to a drive circuit via a connector (not shown), and a voltage can be applied to any of the recording electrodes 101 ,.

Although not shown, such a multi-needle recording head utilizes a drum-shaped winding jig and a winding machine having a casting recess as shown in Japanese Patent Laid-Open No. 2-239953. Manufactured. That is, the conductor wire for the electrode supplied from the winding machine is distributed to the drum-shaped winding jig having the casting concave portion while applying a constant back tension so that the conductor wire is bundled into groups at a constant pitch. Wrap around. Then, the winding jig wound with the ODD side electrode lead wire and the winding jig wound with the EVEN side electrode lead wire are abutted against each other, and an electrically insulating resin is cast into the opposing recesses to form a lead wire or the like. It solidifies to form an electrode support block.

The recording electrodes of the multi-needle recording head thus manufactured and the terminals of the wiring board are wired in a relationship as shown in FIG. Note that in FIG. 8, for convenience of description, the recording electrodes are replaced with the winding grooves that determine the positional relationship of the recording electrodes of the winding jig, and the terminals on the wiring board are replaced with the pins that bundle the conductor wires to be grouped in the drive circuit. Are respectively replaced to describe the wiring relationship. That is, in the conducting wire 108, for example, the first recording electrode 101 at the left end is connected to the first terminal 107, and
The first recording electrode is sequentially connected to the second terminal 107, the third recording electrode 101 is connected to the third terminal 107, and
The recording electrodes from the 1st to 128th are the 1st to 128th
After being connected to the first terminals 107, the 129th to 256th recording electrodes are sequentially connected to the first to 128th terminals 107, ..., 107 again. By repeating this N times, the total number of recording electrodes 101 is M × N (= 7040).
Wiring is distributed to the terminals 107, ..., 107 at 28 locations. A large number of conducting wires 108 wired in this way,
, 108 cross each other and come into close contact with each other as they approach the terminal 107.

The lead-out portion 109, which is drawn out of the electrode support block 105 and is led to a predetermined terminal 107 of the wiring board 106, may be caught by a tool or the like at the time of head assembling work and cause a wire breakage or the like. Therefore, the terminals 107, ..., 1 corresponding to the wiring substrate 106 are fixed by wire bonding or the like so as not to fall apart while being pulled and in tension.
It is connected to 07.

[0007]

However, in this conventional wiring structure, the electrode lead wire 108 is fixed by the resin electrode support block 105 in a tensioned state with a certain back tension, and the lead wire of the lead-out portion 109 is fixed. Since they are solidified by wire bonding, there is a problem that the inter-line stray capacitance of the adjacent electrode conducting wires 108, 108 increases. In particular, since the wiring lead-out portion 109 near the terminal 107 of the wiring board is fixed in a state of being closely adhered by wire bonding, the distance between the adjacent conducting wires is only a few dozen μm due to the thickness of the insulating film, and the electrostatic capacitance is large. Will increase rapidly. The line capacitance decreases logarithmically as the line distance increases, and the change is remarkable especially in the range where the line distance is small.

It is widely known that if the electrostatic stray capacitance is large, the applied voltage is reduced or the drive voltage waveform is blunted, and good recording cannot be performed. In particular, as shown in FIG. 9, in a recording pattern called an intermediate screen in which about half of the electrodes alternately perform recording / non-recording (ON / OFF), the influence of the stray capacitance is greatly affected.

Here, the decline of the applied voltage means that from the recording electrode side which is on to the recording electrode side which is off.
That is, the current flows along the path of the floating capacitive coupling. That is, the fall of the applied voltage occurs by the following mechanism. 1) The recording electrodes 101, ..., 101 of the multi-needle recording head and the drive circuit thereof have a so-called push-pull circuit system as shown in FIG. 10. For example, when the recording electrode 101 is off (no printing), The upper driver IC 111 is turned on, the lower driver IC 112 is turned off, and the recording electrode 101 is held at the ground potential. When the adjacent recording electrode 101 is on (prints), the upper driver IC 113 is turned off, the lower driver IC 114 is turned on, and a voltage of, for example, -260 V is applied to the recording electrode 101. 2) At this time, both recording electrodes 101, 101 and both conducting wires 10
A voltage difference is generated between 8 and 108, and a current route that flows so as to charge a kind of capacitor 115 that is electrostatic stray capacitance formed between them is created. 3) Then, an excessive current flows at the rising edge of the driver pulse, and this current causes the capacity of the applied power source to be exceeded, causing the applied voltage to decline.

The decrease of the applied voltage increases as the floating electrostatic capacity increases, as shown in FIG. 11, which shows the dependency of the effective applied voltage on the floating electrostatic capacity of the "0011" drawing pattern. As shown in FIG. 12 showing the dependency of the optical density on the effective applied voltage (at the time of "0011" drawing pattern), the applied voltage is small (from -260 V to -80 V due to the decline of the applied voltage). The optical density decreases, and the image density decreases. For this reason,
Since the conventional multi-needle recording head has a large floating electrostatic capacity, it can cope with a line image having a small print rate, but cannot at all cope with screen recording having a relatively large print rate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multi-needle recording head in which the stray capacitance is reduced, the applied voltage is not greatly reduced, and the driving voltage waveform is not blunted.

[0012]

In order to achieve the above object, the invention of claim 1 constitutes each recording electrode by arranging a large number of conducting wires constituting the recording electrode at a fixed pitch and fixing them by an electrode supporting block. In a multi-needle recording head in which conductors can be grouped by pulling them out from the electrode support block and connected to a wiring board collectively, and then connected to an external drive circuit, the conductors for electrodes are loosened and connected to the wiring board. ing.

According to the second aspect of the present invention, the portion of the electrode lead wire pulled out from the electrode support block is loosened and connected to the wiring board.

Further, according to the invention of claim 3, the electrode lead wire is slackened as a whole except for the vicinity of the head surface constituting the recording electrode in the electrode support block.

[0015]

The floating capacitance C increases as the distance between adjacent conductors decreases when the length and cross-sectional radius of the conductors are determined as expressed by the following mathematical formula 1.

## EQU1 ## C = (. Pi..epsilon.L) / ln {(d-r) / r} where .pi. Is the circular constant, .epsilon. Is the relative permittivity of the substance between the conductors, and L is The length of the conducting wire, d is the distance between the conducting wires, and r is the cross-sectional radius of the conducting wire.

Therefore, in the multi-needle recording head according to the first aspect, when the tension applied to the electrode lead wire is released and the slack is applied, each wire rod shrinks or deforms in a different direction, and becomes a fluff. It expands into a shape and the distance between adjacent wire rods is widened. Therefore, the stray capacitance in the most severe recording pattern that causes a voltage drop, that is, the “0101” pattern in which ON and OFF are alternately repeated is also reduced.

Further, in the multi-needle recording head according to a second aspect of the present invention, tension is applied to the electrode conducting wire during the molding of the electrode supporting block to keep the distance between the wire materials constant, and when the electrode supporting block is connected to the wiring substrate, Only the pulled out part is loosened so as to bulge into a proper shape.

Further, in the multi-needle recording head according to the third aspect, tension is applied to the conductive wire near the head surface forming the electrode to keep the distance between the wire materials constant, and except for this portion, the electrode support block is excluded. The entire part including the conducting wire that is pulled out to the wiring board is loosened, and the distance between the wires is widened.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to the embodiments shown in the drawings.

1 and 2 show an embodiment in which the present invention is applied to a multi-needle recording head of the same surface control type. This multi-needle recording head comprises first and second recording electrodes 1, which are composed of the tip portions of two rows of conducting wires arranged at high density with a constant pitch.
2 and two corresponding control electrodes 3 and 4 are fixed by an electrode supporting block 5 made of an electrically insulating resin or the like. The recording electrodes 1 and 2 are M × N (= 704) consisting of N (= 55) sets, for example, M (= 128) sets.
0) first recording electrodes 1 and M × N (=) arranged in a zigzag pattern at regular intervals with respect to the first recording electrodes 1.
7040) recording electrodes 2.

Here, the first and second recording electrodes 1 and 2 are
In order to simplify the drive circuit, the conductors 8 are grouped for each recording electrode that can be grouped and connected to the terminals 7 of the wiring board 6, and then the drive circuit is provided for each group via a connector (not shown). It is provided to connect to. For example, the above-mentioned M × N first recording electrodes 1
In this case, the conductors 8 of the recording electrodes belonging to the same group are gathered from the N recording electrode groups and connected to the corresponding terminals 7 of the wiring board 6 by N, respectively.
Are summarized in. The second recording electrode 2 has the same structure. As the recording electrode conducting wire 8, a wire material having an electrically insulating coating, for example, a urethane coated wire is generally used.

The conductive wires 8 drawn out from the electrode support block 5 are bundled in groups and soldered to the terminals 7 of the wiring board 6. At that time, the conductor 8 is connected in a non-tensioned form, that is, in a loosened form. For this reason, as shown in FIG. 2, the entire portion corresponding to the wiring routing portion 9 bulges into a narrow shape, and the distance between adjacent wire rods becomes long. Each terminal 7 is connected to a drive circuit (not shown) to form a circuit as shown in FIG.
A voltage, for example -260 V, can be applied to the recording electrodes 1 and 2. In addition, such a multi-needle recording head 10
The recording electrode 1 is formed in the winding order similar to that of the conventional one shown in FIG.

Next, another embodiment of the present invention will be described with reference to FIG. In addition, the members indicated by the same reference numerals as those in FIG. 1 represent the same members as those in FIG. In this example, as shown in FIG. 3A, the lead wires 8 drawn out from the electrode supporting blocks 5 of the recording electrodes 1 and 2 are formed to be parallel, and thereafter, the lead wires 8 every M number are collected. , N bundles, and the bundle is soldered to one terminal.
The final shape is the same as in FIG. After the state of FIG. 3A, the recording electrode 1 is formed as shown in FIG.
The conducting wire 8 and the conducting wire 8 of the recording electrode 2 are distributed right and left in a loosened form. After that, it is soldered to the terminals.
The sectional shape of the completed multi-needle recording head 10 is similar to that shown in FIG.

Next, a third embodiment of the present invention will be described with reference to FIG.
It will be explained based on. In this embodiment, not only the wiring lead-out portion 9 but also the portion of the conductive wire 8 in the electrode support block 5 other than the portion forming the electrode is loosened. That is, as shown in FIG. 4 (A), at least the conductive wire 8 in a range and depth that sufficiently functions as a recording electrode is tensioned and hardened with an electrically insulating resin, and other portions are loosened. It is hardened with an electrically insulating resin. For example, a winding jig around the first recording electrode lead wire and a second winding jig.
Butt against the winding jig around which the conductor for the recording electrode of
The electrically insulative resin is cast into the opposite resin casting groove (recess) at a depth of about half (at least in the range where the conductive wire sufficiently functions as a recording electrode) and is once cured (primary casting). Next, the lead wire 8 is loosened by removing the pin plate of the winding jig, pushed into the partial electrode support block 5 ′ side formed by the primary casting, and the lead wire 8 is covered as shown in FIG. 4 (B). Let it relax. Then, the remaining resin is cast (secondary casting) to form a complete electrode support block 5. The multi-needle recording head 10 produced by this method is shown in FIG.
As shown in (C), the slack portion of the conductor wire 8 is not limited to the wiring lead-out portion 9, but also the electrode support block 5 of the recording electrodes 1 and 2.
Extends to the inside. According to this embodiment, the stray capacitance is further reduced.

FIG. 5 shows the dependency of the optical density on the floating capacitance and the effect of the present invention in the case of the "0011" drawing pattern. A multi-needle recording head 10 according to the present invention shown in FIGS. 1 and 2.
As shown in FIG. 5, the optical density is about 1.3 times higher than that of the conventional product. In addition to the increase in optical density, the decrease in the floating capacitance has the effect that the drive voltage waveform becomes dull and an appropriate voltage can be applied. As a result, it becomes possible to draw various plane drawing patterns (patterns for drawing an image like a painting rather than printing characters). Further, an excessive current does not flow at the rising edge of the driver pulse, the load on the driver IC is reduced, the degree of freedom of the used element is increased, and the cost can be reduced and the quality can be improved stably.

Even when a multiplexing driving method is employed in which one driver IC is driven in accordance with the timing of time-division scanning to operate a plurality of recording electrode needles, vertical stripe drawing unevenness caused by stray capacitance is reduced. High image quality can be obtained. Further, by adopting this multiplexing drive system, the number of driver ICs can be reduced, and cost reduction and quality stability can be improved.

The above-described embodiments are examples of preferred embodiments of the present invention, but the present invention is not limited thereto and various modifications can be made without departing from the gist of the present invention. For example, the recording electrodes are not in two rows but in one row or three rows.
It is also applicable to more than rows. Alternatively, the wiring board 6 may be eliminated by directly connecting the conductor 8 to the connector without using the wiring board 6. In addition, the multi-needle recording head 10
It is also possible to connect the part that is the tip of the and the part corresponding to the routing part 9 as separate members and connect them. Further, the portion to be loosened may be limited to the inside of the electrode support block 5.

[0028]

As is apparent from the above description, in the multi-needle recording head according to the first aspect of the invention, since the electrode lead wires are slackened and connected to the wiring board, the electrode lead wires shrink or contract in different directions. It deforms and swells into a flat shape, widening the distance between adjacent wire rods, and reducing stray capacitance.
For this reason, the drive waveform is not blunted and the applied voltage is not reduced, and high-quality and high-density drawing can be performed.

Further, in the multi-needle recording head of the second aspect, since the portion of the recording electrode wire rod pulled out from the electrode supporting block is loosened and connected to the wiring substrate, the space between the electrode supporting block and the wiring substrate is formed. Can be effectively used to easily widen the distance between adjacent conductors.

Further, in the multi-needle recording head of the third aspect, tension is applied to the conductor wire near the head surface forming the electrode to keep the distance between the wire materials constant, and except for this portion, the inside of the electrode support block is kept. Since the entire distance between the wiring board and the wiring board is loosened and the distance between the wirings is widened, the floating capacitance can be minimized without lowering the pitch accuracy of the recording electrodes.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a multi-needle recording head of the present invention.

FIG. 2 is a side sectional view of an embodiment of the present invention.

FIG. 3 is a perspective view showing another embodiment of the present invention,
(A) shows the situation before the present invention is applied, and (B) shows the situation where the present invention is applied.

FIG. 4 is a side sectional view showing a third embodiment of the present invention, (A) showing a primary casting stage, (B) a conducting wire pushing stage before the secondary casting, and (C) a two stage. Each of the next casting stages is shown.

FIG. 5 is a graph showing the dependency of optical density on the floating capacitance by taking the floating capacitance on the X axis and the optical density on the Y axis.

FIG. 6 is a perspective view showing an example of a conventional multi-needle recording head.

FIG. 7 is a side sectional view of a conventional multi-needle recording head.

FIG. 8 is a wire wiring diagram for explaining how to wind a wire of a conventional multi-needle recording head.

FIG. 9 is a diagram showing a drawing pattern in which a decrease in applied voltage is likely to occur.

FIG. 10 is a circuit diagram for explaining a decline in applied voltage.

FIG. 11 is a graph showing the dependence of the effective applied voltage on the stray capacitance, where the X axis is the stray capacitance and the Y axis is the effective value of the applied voltage.

FIG. 12 is a graph showing the dependency of optical density on the effective applied voltage by plotting the effective applied voltage on the X axis and the optical density on the Y axis.

[Explanation of symbols]

 1, 2 Recording electrode 5 Electrode support block 6 Wiring board 7 Terminal 8 Conductor 9 Conductor lead

Claims (3)

[Claims] 1. A plurality of conducting wires constituting a recording electrode are arranged at a constant pitch and fixed by an electrode supporting block, and conducting wires constituting each recording electrode are led out from the electrode supporting block and are grouped for each conducting wire. A multi-needle recording head which is connected to an external drive circuit after being connected to a substrate, wherein the electrode lead wire is loosened and connected to the wiring substrate. 2. The multi-needle recording head according to claim 1, wherein a portion of the electrode lead wire pulled out from the electrode support block is loosened and connected to the wiring board. 3. The multi-needle recording head according to claim 1, wherein the electrode lead wire is slack in the entire electrode supporting block except for the vicinity of the head surface constituting the recording electrode.