JPH07242015A - Ultrasonic vibration applying device of printing head - Google Patents

Abstract

PURPOSE:To normally control a developer in each of developer through-holes by uniformizing vibration in the vicinity of all of the developer through-holes of a printing head. CONSTITUTION:An ultrasonic vibration applying device applying ultrasonic vibration to a printing head 100 consists of an ultrasonic vibration generating source 70 and the ultrasonic vibration transmission plate 80 having the ultrasonic vibration generating source 70 fixed thereto and transmitting the ultrasonic vibration generated from the ultrasonic vibration generating source 70 to the printing head 100. The ultrasonic vibration transmission plate 80 has comb tooth-shaped projections 81 extending toward a matrix electrode part 40 and fixed to the printing head 100 at the tips thereof. When the wavelength of the ultrasonic vibration generated from the ultrasonic vibration generating source 70 to be transmitted to the ultrasonic vibration transmission plate 8 is set to lambda1 and the thickness of the plate 80 is set to (t), the width W of each of the comb tooth-shaped projections 81 satisfies conditions of W< lambda1/2 and W>=t.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head ultrasonic vibration imparting device for imparting ultrasonic vibration to a print head of a powder jet image forming apparatus.

[0002]

2. Description of the Related Art The present applicant has already developed a powder jet image forming apparatus as shown in FIG. This powder jet image forming apparatus has a print head 2 that controls passage of toner charged with a predetermined polarity, for example, negative polarity.
A toner supply roller 1 for supplying toner to the print head 2, a recording paper transport roller 3 for guiding the recording paper P to the print head 2, and a toner transferred onto the recording paper P. And a fixing roller 4 for fixing.

As shown in FIG. 6, the print head 2 includes an insulating substrate 20, and frame members 31 and 32 provided at both front and rear ends of the insulating substrate 20 in the recording paper conveying direction (direction indicated by arrow A).
And a matrix-shaped electrode portion 40 formed on the rear half of the insulating substrate 20 in the recording paper conveyance direction, and an ultrasonic vibration source 50 provided on the first half of the insulating substrate 20 in the recording paper conveyance direction. .

As shown in FIGS. 7 and 8, the matrix-shaped electrode section 40 includes a plurality of first electrodes 21 formed on the surface of the toner supply roller 1 of the insulating substrate 20 and recording paper of the insulating substrate 20. The transport roller 3 is provided with a plurality of second electrodes 22 formed on the surface of the cotton. The plurality of first electrodes 21 and the plurality of second electrodes 22 form a matrix electrode portion. A toner passage hole 23 penetrating the print head 2 is formed at each intersection of each first electrode 21 and each second electrode 22.

An on-voltage (for example -100V) and an off-voltage (for example + 300V) are selectively applied to each first electrode 21. Each second electrode 22 has an on-voltage (for example, 0 V) and an off-voltage (for example, -200 V).
V) and are selectively applied. FIG. 9 shows each first electrode 21.
Of the applied voltage V1-0 to V1-7. As shown in FIG. 9, each of the first electrodes 21 is subjected to the dimic scan control, and the applied voltage is sequentially turned on at predetermined unit time intervals. Then, only when the applied voltage to both the first electrode 21 and the second electrode 22 is the on-voltage, the toner passes through the toner insertion hole 23 at the intersection thereof, and the dot printing is performed.

The recording paper P is moved in the direction perpendicular to the first electrode 21 by the recording paper conveying roller 3 and in the direction in which control by dynamic scanning of the first electrode 21 proceeds (direction shown by arrow A in FIGS. 6 and 7). Be transported. A voltage of +500 V is applied to the recording paper carrying roller 3. The toner supply roller 1 is grounded and its surface potential is 0V.

The ultrasonic vibration generating source 50 includes a toner insertion hole 2
Ultrasonic vibration is applied to the print head 2 in order to prevent the toner from being clogged in 3 and to allow the toner to smoothly pass through the toner insertion hole 23. The ultrasonic vibration generation source 50 is composed of four ultrasonic vibrators 50a. The vibration frequency of each ultrasonic transducer 50a is about 300.
It is about 500 KHz.

[0008]

By the way, when the ultrasonic transducer 50a is applied to the print head 2 to apply vibration of a constant frequency, a standing wave is generated. The generation mechanism of this standing wave will be described. Assuming that the ultrasonic vibration sources (excitation points) are present at two points A and B as shown in FIG. 10A, the vibrations from the excitation points A and B are transmitted to the point C. To be done. At this time, if there is a difference in the distance between A and C and the distance between B and C, even if the oscillations at both excitation points A and B have the same phase, at the time when they are transmitted to the point C. , A phase difference occurs between the vibrations from the excitation points A and B.

If the phase difference is 180 degrees like vibration A1 and vibration B2 in FIG. 10B, the vibration (A1 in FIG.
The vibrations cancel each other out, as in + B2). Therefore, in this case, the node portion of the standing wave corresponds to the point C. The phase difference at the point C of the vibration from each of the excitation points A and B is 0 as shown by the vibration A1 and the vibration B1 in FIG.
When the degree is the same (in phase), the vibrations are mutually strengthened like the vibration (A1 + B1) in the figure. Therefore, in this case, the antinode portion of the standing wave corresponds to the point C.

On the actual print head 2, not a combination of two vibrations but a large number of vibrations including a reflected wave at the end face of the print head 2 are combined to generate a standing wave.

As described above, when a standing wave is generated in the print head 2 by the ultrasonic transducer 50a, in the matrix electrode portion 40 of the print head 2, there are places where vibration is strong and places where vibration is weak. In a place with strong vibration, toner control is performed smoothly, but in a place with weak vibration,
The toner will not be controlled normally. As a result, the image density decreases in a place where vibration is weak, or in the worst case,
The toner may fall into a state where it cannot pass through the toner insertion hole.

The present invention provides an ultrasonic vibration imparting device for a print head, wherein the vibration can be made uniform in the vicinity of all the developer insertion holes of the print head, and the developer is normally controlled in each developer insertion hole. The purpose is to do.

[0013]

An ultrasonic vibration imparting device for a first print head according to the present invention comprises one or a plurality of ultrasonic vibrators formed on one surface of an insulating substrate and extending in a direction orthogonal to a recording paper conveying direction. Of the first electrode and a plurality of second electrodes formed on the other surface of the insulating substrate form a matrix electrode part, and a developer insertion hole is formed at each intersection of the first electrode and the second electrode. Ultrasonic vibration applying device for applying ultrasonic vibration to a print head that is provided with an ultrasonic vibration generating source that generates ultrasonic vibration, and the ultrasonic vibration generating source is fixed and generates ultrasonic vibration. The ultrasonic vibration transmission plate for transmitting the ultrasonic vibration generated from the source to the print head. The ultrasonic vibration transmission plate has comb-shaped teeth whose tip extends toward the matrix-like electrode part and whose tip is fixed to the print head. Ridges Assuming that the wavelength when the ultrasonic vibration generated from the ultrasonic vibration generating source is transmitted through the ultrasonic vibration transmitting plate is λ1 and the thickness of the ultrasonic vibration transmitting plate is t, It is characterized in that the width W satisfies the conditions of W <λ1 / 2 and W ≧ t.

An ultrasonic vibration imparting device for a second print head according to the present invention is insulated from one or a plurality of first electrodes formed on one surface of an insulating substrate and extending in a direction orthogonal to the recording paper conveyance direction. A matrix-shaped electrode portion is formed by a plurality of second electrodes formed on the other surface of the substrate, and a developer insertion hole is formed at each intersection of the first electrode and the second electrode. In an apparatus for applying ultrasonic vibrations to a print head for applying ultrasonic vibrations, an ultrasonic vibration source for generating ultrasonic vibrations and ultrasonic waves generated from the ultrasonic vibration source are fixed. And an ultrasonic vibration transmission plate for transmitting vibrations to the print head.The ultrasonic vibration transmission plate has comb-shaped projections whose tips extend toward the matrix-like electrode section and whose tips are fixed to the print head. Cage, super sound The wavelength when the ultrasonic vibration generated from the vibration source is transmitted through the print head is λ2, and in two adjacent comb tooth-shaped protrusions, from the tip of one comb tooth-shaped protrusion to the developer insertion hole closest to it. If the distance is L1 and the distance from the developer insertion hole closest to the tip of the one comb tooth-shaped projection to the tip of the other comb tooth-shaped projection is L2, the pitch P of the comb tooth-shaped projections is (L2- L1) ≦ λ2 / 4 is set so as to satisfy the condition.

[0015]

In the ultrasonic vibration imparting device for the first print head according to the present invention, the ultrasonic vibration generated from the ultrasonic vibration generating source is transmitted in the protruding direction of the comb-shaped projection. Therefore, the ultrasonic vibration output from each comb tooth-shaped projection slightly interferes with the ultrasonic vibration output from the adjacent comb tooth-shaped projection, but is output from the other comb tooth-shaped projections. It is transmitted to the matrix electrode portion without interfering with ultrasonic vibration. As a result, the standing wave is not generated and the vibrations in the vicinity of all the developer insertion holes of the matrix-shaped electrode portion become uniform, so that the developer control is normally performed in each developer insertion hole.

Further, in this ultrasonic vibration imparting device, the wavelength at which the ultrasonic vibration generated from the ultrasonic vibration generating source is transmitted through the ultrasonic vibration transmitting plate is λ1, and the thickness of the ultrasonic vibration transmitting plate is Assuming t, the width W of each comb-shaped projection is
Since the conditions of W <λ1 / 2 and W ≧ t are satisfied, the ultrasonic vibration generated from the ultrasonic vibration generating source is transmitted only in the length direction of each comb-toothed protrusion, It will not be transmitted in the width direction. Therefore, a standing wave is not generated inside each comb-toothed protrusion, and variations in vibration among the comb-toothed protrusions are reduced, so that vibrations in the vicinity of all the developer insertion holes of the matrix electrode portion are reduced. It becomes more uniform.

In the ultrasonic vibration applying device for the second print head according to the present invention, the ultrasonic vibration generated from the ultrasonic vibration generating source is transmitted in the protruding direction of the comb-shaped projection. Therefore, the ultrasonic vibration output from each comb tooth-shaped projection slightly interferes with the ultrasonic vibration output from the adjacent comb tooth-shaped projection, but is output from the other comb tooth-shaped projections. It is transmitted to the matrix electrode portion without interfering with ultrasonic vibration. As a result, the standing wave is not generated and the vibrations in the vicinity of all the developer insertion holes of the matrix-shaped electrode portion become uniform, so that the developer control is normally performed in each developer insertion hole.

Further, in this ultrasonic vibration imparting device, the wavelength at which the ultrasonic vibration generated from the ultrasonic vibration source is transmitted to the print head is λ2, and one of the two adjacent comb-teeth-like protrusions is The distance from the tip of the comb tooth-shaped protrusion to the developer insertion hole closest to it is L1, and the distance from the developer insertion hole closest to the tip of one of the comb tooth-shaped protrusions to the tip of the other comb tooth-shaped protrusion is L2. Then, the pitch P of the comb-shaped projections is set so as to satisfy the condition of (L2-L1) ≦ λ2 / 4, so that the two adjacent comb-shaped projections are transmitted to the developer insertion hole. The ultrasonic vibrations generated do not weaken each other. Therefore, uniform vibration can be obtained near the developer insertion hole.

[0019]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows an ultrasonic vibration applying device for applying ultrasonic vibration to a print head.

In the print head 100 shown in FIG. 1, the matrix-shaped electrode portion 40 is formed in the rear half of the insulating substrate 20 in the recording paper conveyance direction (the direction indicated by arrow A). The structure of the matrix-shaped electrode portion 40 is the same as that shown in FIG. 6, and therefore its explanation is omitted.

The ultrasonic vibration imparting device 60 includes an ultrasonic vibration generating source 70 and an ultrasonic vibration transmitting plate 80 having a rectangular shape when seen from a plane for transmitting the vibration generated from the ultrasonic vibration generating source 70 to the print head 100. Consists of. Ultrasonic vibration transmission plate 8
A comb-shaped projection 81 is formed at the rear end of the recording paper conveyance direction 0. At the front end of the ultrasonic vibration transmitting plate 80 in the recording paper conveyance direction, a vibration reflecting portion 82 protruding upward is integrally formed over the entire length of the front edge.

Comb-shaped projection 8 on the upper surface of ultrasonic vibration transmission plate 80
The ultrasonic vibration generation source 70 is fixed between 1 and the vibration reflection portion 82. The ultrasonic vibration generation source 70 is composed of four rectangular ultrasonic vibrators 70a arranged in a straight line in a direction perpendicular to the recording paper conveyance direction A.

The ultrasonic vibration transmitting plate 80 has a comb-shaped projection 81.
Is placed on the front end of the insulating substrate 20 in the recording paper conveyance direction so that the tip of the comb-shaped protrusion 81 faces the matrix electrode part 40, and the tip of the comb-shaped protrusion 81 is on the upper surface of the insulating substrate 20. It is attached to the print head 100 by being fixed to.

The ultrasonic vibration generated from the ultrasonic vibration source 70 is transmitted through the comb-shaped projection 81 of the ultrasonic vibration transmission plate 80. Let λ1 be the wavelength at which the ultrasonic vibration generated from the ultrasonic vibration generating source 70 is transmitted through the ultrasonic vibration transmitting plate 80, and t be the thickness of the portion other than the vibration reflecting portion 82 of the ultrasonic vibration transmitting plate 80. , The width W of each comb-shaped projection 81
Is set to a length that satisfies the two conditions represented by the following formulas 1 and 2.

[0026]

[Equation 1] W <λ1 / 2

[0027]

(2) W ≧ t

The wavelength λ1 when the ultrasonic vibration generated from the ultrasonic vibration source 70 is transmitted through the ultrasonic vibration transmission plate 80.
Is calculated from the following Equation 3 based on the transmission speed v1 and the vibration frequency f when the ultrasonic vibration is transmitted through the ultrasonic vibration transmission plate 80.

[0029]

## EQU3 ## λ1 = v1 / f

When the ultrasonic vibration transmission plate 80 having a thickness t of 1 mm is used and the vibration frequency f is 300 kHz, the vibration transmission speed v1 becomes 1600 mm / s, and the vibration wavelength λ
1 becomes 5.3 mm. In such a case, as an example of the comb-tooth-shaped protrusion 81 that satisfies the conditions expressed by the above mathematical expressions 1 and 2, the width W of the comb-tooth-shaped protrusion 81 is 1.5 mm and the pitch P of the comb-tooth-shaped protrusion 81 is P. Is 2.0 mm.

In such an ultrasonic vibration imparting device 60, the ultrasonic vibration generated from the ultrasonic vibration generating source 70 is transmitted in the protruding direction of the comb-shaped projection 81.
Therefore, the ultrasonic vibration output from each comb-tooth-shaped projection 81 slightly interferes with the ultrasonic vibration output from the adjacent comb-tooth-shaped projection 81, but from the other comb-tooth-shaped projections 81. It is transmitted to the matrix-shaped electrode portion 40 without interfering with the output ultrasonic vibration. As a result, the standing wave is not generated and the vibrations in the vicinity of all the toner insertion holes 23 of the matrix-shaped electrode portion 40 are made uniform, so that the toner control is normally performed in each toner insertion hole 23.

Further, in the ultrasonic vibration imparting device 60, since the width W of each comb tooth-shaped protrusion 61a satisfies the conditions shown in the above mathematical formulas 1 and 2, the ultrasonic vibration generating source 70 The generated ultrasonic vibration is applied to each comb-shaped projection 81.
Is transmitted only in the lengthwise direction of the comb tooth-shaped projections 81 and is not transmitted in the widthwise direction of each comb-tooth-shaped projection 81. Therefore, each comb-shaped protrusion 81
Since a standing wave is not generated inside and the variation in vibration among the comb-shaped projections 81 is reduced, the vibration in the vicinity of all the toner insertion holes 23 of the matrix electrode portion 40 becomes more uniform.

The pitch of the comb-shaped projections 81 of the ultrasonic vibration transmitting plate 80 is preferably set as follows. That is, the wavelength when the ultrasonic vibration generated from the ultrasonic vibration generation source 70 is transmitted through the insulating substrate 20 is set to λ2, and FIG.
As shown in, the pitch of the comb-shaped projections 81 is set to P (= ab).
In two adjacent comb tooth-shaped projections 81, the toner insertion hole 2 closest to the tip of one comb tooth-shaped projection 81 is located.
3 is L1 (= ac), and one comb tooth-shaped protrusion 81
Is L2 (= bc), the pitch P of the comb-tooth-shaped protrusions 81 is defined by the following formula 4. Set to be satisfied.

[0034]

## EQU00004 ## L2-L1.ltoreq..lambda.2 / 4

When the pitch P of the comb-toothed protrusions 81 is set in this way, the toner is inserted from the tips (points a and b) of two adjacent comb-toothed protrusions 81 shown in FIG. 2 to the point c. Since the phase difference of the ultrasonic vibrations transmitted to the hole 23 is much smaller than the phase difference λ2 / 2 that cancels the vibrations of each other, the toner insertion hole 23 from the two adjacent comb tooth-shaped projections 81. The ultrasonic vibrations transmitted to each other will not weaken each other. Therefore, uniform vibration can be obtained near the toner insertion hole 23.

Theoretically, two adjacent comb-shaped projections 81
Not only one comb tooth-shaped protrusion 81 and the other comb tooth-shaped protrusion 8
1 and the toner insertion hole 23 and the comb-shaped projections 8
It is preferable to set the distance from 1 to λ2 / 4 or less,
Actually, the transmission range of the ultrasonic vibration output from the tip of one comb-tooth-shaped protrusion 81 is considered to be up to the width of the adjacent comb-tooth-shaped protrusion 81. In the relationship, the condition of the above-mentioned formula 4 should be satisfied.

In the toner insertion hole 23, the toner insertion hole 2 closest to the tip of one comb tooth-shaped projection 81 is located.
3 is set by using the distances L1 and L2 between the two adjacent comb-teeth protrusions 81 at a position farther from the tip of one of the comb-teeth protrusions 81 than the toner insertion hole 23 closest thereto (recording). Toner insertion hole 23 in the direction opposite to the upper conveying direction)
And the distance L1 ′, L between two adjacent comb-tooth-shaped protrusions 81
In the relationship with 2 ', (L2'-L1') is (L2'-L1 ')
This is because the value is smaller than 2-L1).

The wavelength λ2 when the ultrasonic vibration generated from the ultrasonic vibration generating source 70 is transmitted through the insulating substrate 20 is based on the transmission speed v2 and the vibration frequency f when the ultrasonic vibration is transmitted through the insulating substrate 20. , Is calculated from the following Equation 5.

[0039]

[Formula 5] λ2 = v2 / f

When a glass epoxy having a thickness of 0.2 mm is used as the insulating substrate 20 and copper having a thickness of 35 μm is used as the first and second electrodes, when the vibration frequency f is 300 kHz, the vibration transmission speed is v2 is 700 mm
/ S, and the vibration wavelength λ2 is 2.3 mm. Also,
The distance L1 (= ac) in FIG. 2 is 5.0 mm. In such a case, as an example of the comb-shaped portion 61 that satisfies the condition represented by the above-mentioned mathematical formula 4, the width W of the comb-teeth-shaped protrusion 81 is 1.5.
For example, the pitch P of the comb-shaped projections 81 is 2.0 mm.

That is, L2 in FIG. 2 is (5.0 ² +
2.0 ^{2) 1/2} = 5.385 next, L2-L1 = 0.
It becomes 385. On the other hand, since λ2 / 4 = 0.575, L2-L1 ≦ λ2 / 4.

Incidentally, as shown in FIG.
If the shape of the tip is curved, the radiation range of the ultrasonic vibration output from the comb-shaped projection 81 can be changed.
That is, if the tip shape of the comb-toothed projection 81 is a convex curve, the radiation range of the ultrasonic vibration output from the comb-toothed projection 81 is widened, and the tip shape of the comb-toothed projection 81 is concave. The curved line narrows the radiation range of the ultrasonic vibration output from the comb-shaped projection 81.

For example, assuming that the tip of the comb-toothed projection 81 is straight and the vibration radiation angle is 20 °, the tip of the comb-toothed projection 81 has a convex curve with a curvature of 0.8 mm. The vibration radiation angle spreads to about 50 °, and the comb-shaped projections 8
When the tip shape of No. 1 is a concave curve having a curvature of 0.8 mm, the vibration radiation angle is narrowed to about 10 °.

Therefore, according to the width and pitch of each comb-tooth-shaped projection 81, the tip shape of the comb-tooth-shaped projection 81 is made to be a convex or concave curve so that each comb-tooth can be formed as shown in FIG. The radiation range of the ultrasonic vibrations output from the tips of the projections 81 is set to a radiation range in which the minimum is MIN and the maximum is MAX, and the ultrasonic vibrations output from the tips of the comb-shaped projections 81 separated from each other are mutually It is preferable to apply vibration to the entire matrix-shaped electrode portion 40 without any interference and without gaps. The radiation range of ultrasonic vibrations in FIGS. 3 and 4 indicates the range until the vibration velocity becomes 1/2.

As described above, the distance L1 (= a in FIG.
c) is set to 5.0 mm, and the width W of the comb-shaped projection 81 is 1.5.
When the pitch P of the comb-tooth-shaped protrusions 81 is 2.0 mm and the tip shape of the comb-tooth-shaped protrusions 81 is, for example, a convex curve with a curvature of 2.0 mm, it is preferable as shown in FIG. A wide oscillating radiation range was obtained.

[0046]

According to the present invention, the vibration can be made uniform in the vicinity of all the developer insertion holes on the print head, and the developer can be normally controlled in each developer insertion hole.

[Brief description of drawings]

FIG. 1 is a perspective view showing an ultrasonic vibration applying device attached to a print head.

FIG. 2 is a partially enlarged plan view for explaining a condition for setting a pitch of comb-teeth-like protrusions.

FIG. 3 is a partially enlarged plan view showing a vibration radiation range in the case where the tip shape of the comb-teeth-like projection is curved.

FIG. 4 is a partially enlarged plan view showing an example in which the vibration emission range is set to a suitable range by making the tip shape of the comb-teeth-like protrusion into a curve.

FIG. 5 is a configuration diagram showing a schematic configuration of a powder jet image forming apparatus.

FIG. 6 is a schematic perspective view showing a conventional print head.

7 is a plan view showing a matrix-shaped electrode portion of FIG.

8 is a sectional view taken along line VIII-VIII in FIG.

FIG. 9 is a time chart showing changes in the voltage applied to the first electrode.

FIG. 10 is an explanatory diagram for explaining a mechanism of a standing wave.

[Explanation of symbols]

 20 Insulating Substrate 21 First Electrode 22 Second Electrode 23 Toner Insertion Hole 40 Matrix Electrode 60 Ultrasonic Vibration Giving Device 70 Ultrasonic Vibration Source 70a Ultrasonic Transducer 80 Ultrasonic Vibration Transmission Plate 81 Comb-like Protrusion 100 Printing head

Claims (2)

[Claims] 1. One or a plurality of first electrodes formed on one surface of an insulating substrate and extending in a direction orthogonal to a recording paper conveyance direction, and a plurality of second electrodes formed on the other surface of the insulating substrate. The matrix-shaped electrode portion is formed by and the ultrasonic vibration is applied to the print head in which the developer insertion hole is formed at each intersection of the first electrode and the second electrode. The device consists of an ultrasonic vibration source that generates ultrasonic vibration, and an ultrasonic vibration transmission plate that is fixed to the ultrasonic vibration source and that transmits the ultrasonic vibration generated from the ultrasonic vibration source to the print head. , The ultrasonic vibration transmission plate has comb-teeth-like protrusions whose tips extend toward the matrix-like electrode section and whose tips are fixed to the print head. Sound wave vibration transmission plate When the wavelength when reaching is λ1 and the thickness of the ultrasonic vibration transmitting plate is t, the width W of each comb tooth-shaped protrusion satisfies the conditions of W <λ1 / 2 and W ≧ t. A device for applying ultrasonic vibration to the print head. 2. One or a plurality of first electrodes formed on one surface of the insulating substrate and extending in a direction orthogonal to the recording paper conveyance direction, and a plurality of second electrodes formed on the other surface of the insulating substrate. The matrix-shaped electrode portion is formed by and the ultrasonic vibration is applied to the print head in which the developer insertion hole is formed at each intersection of the first electrode and the second electrode. The device consists of an ultrasonic vibration source that generates ultrasonic vibration, and an ultrasonic vibration transmission plate that is fixed to the ultrasonic vibration source and that transmits the ultrasonic vibration generated from the ultrasonic vibration source to the print head. , The ultrasonic vibration transmission plate has comb-teeth-shaped protrusions that extend toward the matrix-shaped electrode part and are fixed to the print head, and the ultrasonic vibration generated from the ultrasonic vibration source is printed. Transmit head The wavelength at this time is λ2, and in two adjacent comb tooth-shaped projections, the distance from the tip of one comb tooth-shaped projection to the developer insertion hole closest to it is L1, and the distance between the tip of one comb tooth-shaped projection is the largest. Letting L2 be the distance from the near developer insertion hole to the tip of the other comb tooth-shaped protrusion, the pitch P of the comb tooth-shaped protrusions is set so as to satisfy the condition of (L2-L1) ≦ λ2 / 4. A device for applying ultrasonic vibration to a print head, which is characterized in that