GB2406307A

GB2406307A - Ink jet recoding apparatus

Info

Publication number: GB2406307A
Application number: GB0421235A
Authority: GB
Inventors: Tomohiro Inoue; Yoshiharu Takizawa; Akira Miyao
Original assignee: Hitachi Home and Life Solutions Inc
Current assignee: Hitachi Appliances Inc
Priority date: 2003-09-24
Filing date: 2004-09-23
Publication date: 2005-03-30
Anticipated expiration: 2024-09-23
Also published as: JP4246583B2; GB2406307B; CN1600546A; JP2005096188A; GB0421235D0; CN1309568C

Abstract

An ink jet recording apparatus is provided that can perform stable ink ejection without a position shift occurring between a nozzle (40) in a nozzle plate (31) and a flow path (21, fig 1) in a body (30, fig 1). A nozzle head (6, fig 1) includes a body (30, fig 1), for which a vibration unit (29, fig 1) for vibrating ink is provided, and a nozzle plate (31), which is a single metal member that is detachable from the body (31, fig 1). In the nozzle plate (31), a nozzle (40) is formed by coupling a cylindrical hole (42), which is an ink ejection end (41) a tapered hole (43) and a curved hole (44), and an ink flow path, which is connected to the nozzle (40), is formed by coupling two or more cylindrical holes (37,38,39) for which the inner diameters differ.

Description

INK JET RECORDING APPARATUS

The present invention relates to an ink jet recording apparatus that performs printing by ejecting ink from nozzles.

Example nozzles for an ink jet recording apparatus are disclosed in JP-A10-226070. According to this publication, multiple nozzles are formed in a single metal plate using press machining. The nozzles have a structure wherein cylindrical holes, curved annular holes and tapered holes are connected, and ink is ejected from the tapered holes toward the cylindrical holes. The nozzle plate is fixed to another member wherein flow paths are formed.

For an ink jet recording apparatus, it is important that ink be ejected linearly, at a right angle relative to the nozzle plate. To do this, the nozzles and the flow paths must be precisely machined and assembled in order to prevent an uneven flow of ink. According to the conventional technique, the nozzle plate wherein ink ejection nozzles are formed and a body wherein flow paths, for supplying ink to the nozzles, are formed must be fixed to each other by bonding or using screws. However, according to this method, when the nozzle plate is attached to or removed from the body, the positioning shift between the nozzles and the flow paths, or the overflow of an adhesive occurs, so that an uneven flow of ink results at a step in a portion wherein the nozzles and the flow paths in the body are bonded together. As a result, ink droplets are ejected non-linearly, and the stability for the forming of particles can not be obtained.

It is, therefore, one aim, of the present invention to provide an ink jet recording apparatus that can prevent the positioning shift between nozzles and flow paths, and that can stably eject ink without non-linear trajectory of ink particles.

An ink jet recording apparatus according to the present invention comprises: a body having a vibrating unit for vibrating ink; and a nozzle plate made of a single metal member detachable from the body, wherein the nozzle plate includes nozzles that are formed by connecting cylindrical holes, which serve as ink ejection ends, tapered holes, which are connected to the cylindrical holes and that have a diameter that is reduced in an ink ejection direction, and curved holes, which are connected to the tapered holes, that have a diameter that is reduced in the ink ejection direction. It is preferable that the nozzle plate include ink flow paths, which are connected to the curved holes of the nozzles, that are formed by coupling two cylindrical holes, at the least, the inner diameters of which differ and are reduced in the ink ejection direction.

According to the invention, since the ink ejection nozzles and the flow paths for supplying ink to the nozzles are formed in a single nozzle plate, a positioning shift does not occur between the nozzles and the flow paths. Therefore, even when the nozzle plate is fixed in place by using screws, which ensures that the nozzle plate can be easily detached, stable ink ejection without arcing of the ink trajectory can be performed. Further, since the nozzles can be easily detached, when clogging of the nozzles occurs due to the attachment of a foreign substance or ink to the nozzles, the nozzle plate can be removed and rinsed, using ultrasonic cleaning, and the foreign substance can be quickly removed.

Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings, in which: 4 Fig. 1 is a cross-sectional view of a nozzle head according to one embodiment of the present invention; Fig. 2 is a cross-sectional view of the nozzle plate according to the embodiment of the present invention; Fig. 3 is a front view of the nozzle plate according to the embodiment of the present invention; Fig. 4 is a cross-sectional view of a nozzle according to the embodiment of the present invention; Fig. 5 is a schematic diagram showing a punch whereby the nozzles are formed in accordance with the embodiment of the present invention; Fig. 6 is a schematic diagram showing an ink jet recording apparatus according to the embodiment of the present invention; Fig. 7 is a diagram showing the inside of the main body of the ink jet recording apparatus according to the embodiment of the present invention; Fig. 8 is a diagram showing ink circulation within the ink jet recording apparatus according to the embodiment of the present invention; Fig. 9 is a flowchart showing the processing for the machining of the nozzle plate; Fig. 10 is a crosssectional view of a nozzle according to another embodiment of the present invention; Fig. 11 is an enlarged diagram showing the - 5 joining of body segments constituting the nozzle in accordance with the present invention; Fig. 12 is an enlarged cross-sectional view of the distal end of the body; Fig. 13 is an explanatory diagram for obtaining an axial direction and a resonance frequency for a fluid; and Fig. 14 is an enlarged crosssectional view of a piezoelectric device according to the embodiment of the present invention.

A first embodiment of the present invention will now be described while referring to the accompanying drawings.

Fig. 6 is a schematic diagram showing an ink jet recording apparatus according to the present invention. The ink jet recording apparatus comprises: a main body 600, in which a control system and a circulating system are stored; a print head 610, which has nozzles for forming and ejecting ink particles; and a cable 620, which connects the main body 600 and the circulating system and the control system for the print head 610. The main body 600 includes a liquid crystal touch panel 630 by which a user can enter printing contents and a printing format, and by which control contents and an apparatus operating state can be displayed. The print head 610 is protected with a 6 - cylindrical stainless steel cover, and inside a printing unit is stored for the forming of ink particle and for controlling the flight of ink droplets. A hole 615 formed in the bottom of the cover is used for the passage of ink droplets.

The internal configuration of the main body 600 will now be described while referring to Fig. 7.

Electric parts, such as a control substrate 640, are arranged in the upper portion of the main body 600. In a lower portion 680 of the main body 600, control parts, such as a solenoid valve 650 and a pump unit 655, are arranged, and an ink container 1 in which ink to be supplied to the nozzle is retained is also stored. A door 670 can be opened or closed, and the ink container 1 can be pulled toward the door 670, so that maintenance, such as the replenishment of ink and abandonment of ink, can be easily performed.

The schematic configuration of the ink circulation system and the printing unit of the ink jet recording apparatus will now be described while referring to Fig. 8. An ink supply path 21 includes: the ink container 1, wherein ink is retained; a supply pump, for the transmission of ink under pressure; a pressure control valve 3, for controlling the ink pressure; a pressure gauge 4, for displaying the pressure of the supplied ink; and a filter 5, through which ink is supplied to a nozzle head 6 under a predetermined pressure. A record signal source is connected to an electrifying electrode 7, and by applying a record signal voltage to the electrifying electrode 7, ink particles 8, for regular ejection through the nozzle head 6, are electrified. A high voltage source is connected to an upper deflecting electrode 9, and a lower deflecting electrode 10 is grounded. Therefore, an electrostatic field is formed between the upper deflecting electrode 9 and the lower deflecting electrode 10, and in accordance with the electrification attained by the electrifying electrode 7, the ink particles 8 are deflected and travel through the air and are attached to recording material in order to perform printing. Ink particles 8 that are not electrified by the electrifying electrode 7 and are not used for recording are recovered by an ink collecting path 22, formed of a gutter 11, a filter 12 and a collection pump 14, and the ink so acquired is returned to the ink container 1 and reused.

The nozzle head 6 will now be explained while referring to Fig. 1. The nozzle head 6 is constituted by a vibrating unit 29, a body 30 and a nozzle plate 31. The body and the nozzle plate 31 are made of SUS 304, and the nozzle plate 31 is fixed to the body 30 by screws 28. An ink chamber 36 is formed between the body 30 and the nozzle plate 31, and ink is introduced to the ink chamber 36 through the ink supply path 21 formed in the side of the body 30. An O ring 26 is formed between the body 30 and the nozzle plate 31 to prevent the leakage of ink from the ink chamber 36.

Ink introduced to the ink chamber 36 is passed through cylindrical holes (flow paths) 37, 38 and 39, which are provided at three steps inside the nozzle plate 31 and which have different inner diameters and lengths, and is ejected through a nozzle hole 40. The vibrating unit 29 is constituted by a piezoelectric device 32 and a diaphragm 35 formed in the body 30. The piezoelectric device 32 is vibrated, at a constant cycle, by a vibration source 27 and the vibrations are transmitted through the diaphragm 35 to vibrate the ink in the ink chamber 36.

The nozzle plate 31 will now be described in detail while referring to the cross-sectional view in Fig. 2 and the front view in Fig. 3. Externally, the nozzle plate 31 has a three-step shape, and is so formed that it is cylindrical at a first step 50 and a second step 51 and, as is shown in Fig. 3, is rectangular at a third step 52, in the four corners of which screw holes 25 are formed. In the nozzle plate 31, the cylindrical hole 37 (inner diameter 2 mm), the cylindrical hole (inner diameter 1 mm) and the cylindrical hole 39 (inner diameter 0.5 mm), all of which have different inner diameters, are positioned in the named order with the cylindrical hole 37 nearest the ink chamber 36. Since a drill is used to bore the cylindrical holes 37, 38 and 39, a seam 33 between the cylindrical holes 37 and 38 and a seam 34 between the - 9 - cylindrical holes 38 and 39 are formed and tapered at an angle of 120 by the distal end of the drill. The cylindrical holes 37, 38 and 39 form an ink flow path for supplying ink to the nozzle hole 40, and constitute a step structure with each step having a different inner diameter. This design is employed to prevent the occurrence of fluid resonance in the ink supply path.

The frequency of the fluid resonance in the ink supply path is obtained by employing the following expression (1).

fr = nVl/{4(1 + k2)} (1) In this expression, n denotes an integer value determined by a resonance mode; Vi denotes a wave velocity in ink; l denotes the length of an ink flow path; and k denotes a correction coefficient. Since the diameter of the nozzle hole 40 is considerably smaller than the diameter of the cylindrical hole 39, a boundary condition wherein one end is closed and the other end is open is employed, and n = 1 in a first mode, n = 3 in a second mode and n = 5 in a third mode.

Further, since a boundary condition wherein both ends are open is employed for the cylindrical holes 37 and 38, n = 2 in the first mode, n = 4 in the second mode and n = 6 in the third mode are established. While at a normal temperature the wave velocity in ink is generally 1200 to 1400 m/s, changes in the wave - 10 - velocity depend on the temperature. In an operating temperature range of O to 45 C for the ink jet recording apparatus, there is a +10% change in the wave velocity in ink. Therefore, in this embodiment, in order to prevent fluid resonance from affecting the formation of particles, the length l of the flow path is adjusted, so that the fluid resonance frequency is set so it differs considerably from a drive frequency of 70 kHz.

That is, in this embodiment, a fluid resonance frequency of 90 kHz or higher is set for the first mode in which the fluid resonance frequency in each ink flow path is the lowest. Further, in this embodiment, the lengths of the cylindrical holes 37, 38 and 39 in the ink ejection direction are set to 2 to 3 mm, while the depth L of the nozzle plate 31 is set to 7 mm. With this structure, since the affect of fluid resonance, which changes greatly in consonance with the temperature, is prevented, and since vibration amplification using mechanical vibration, which changes less and is less dependent on the temperature, is employed, stable particle formation can be performed.

Fig. 9 is a flowchart showing the processing for machining the nozzle plate 31. Eirst, at step 11, the external shape of the nozzle plate 31 is formed, and at steps 12 to 14, by using a drill, the cylindrical holes 37, 38 and 39 are formed in order beginning with the one having the largest inner diameter. At step 15, the nozzle 40 is formed by press - 11 machining. Finally, at step 16, the SUS material and flash remaining in the nozzle 40 are removed by etching. As a result, a nozzle 40 having high circularity, in which there are no scratches and to which no foreign substances are attached, is obtained.

The nozzle 40 will now be explained in detail while referring to Fig. 4. The nozzle 40 includes: a cylindrical hole 42, in which an opening (orifice) 41 is formed on the ink ejection side; a tapered hole 43, the diameter of which is reduced in the ink ejection direction; and a horn shaped curved hole 44, the diameter of which is reduced in the ink ejection direction. The nozzle 40 is formed by inserting a punch 60, shown in Fig. 5, through the cylindrical hole 39, and then performing press machining. Since a shaft 64 of the punch 60 has a small, 0.4 mm diameter and is easily broken, the shaft 64 of the punch 60 is used by inserting it into the cylindrical hole 39, while a shaft 65 of the punch 60, which has a large, 0.9 mm diameter, is used by inserting it into the cylindrical holes 37 and 38. With this structure, the service life of the punch 60 can be extended. A distal end 62 of the punch 60 is a cylindrical member having a diameter of 0.065 mm and a length of 0.06 mm, and an angle 3 of a conical portion 61 is 40 . The remaining SUS material or flash that blocks the nozzle hole 40 is removed by polishing or etching the surface on the opening 41 side. The shape of the punch 60 is transferred to the - 12 shapes of the cylindrical hole 42 and the tapered hole 43.

The cylindrical hole 42 has a diameter of 0.065 mm and a length of 0.05 mm in the ink ejection direction, and a seam 46 between the tapered hole 43 and the cylindrical hole 42 is a sharp edge having a curvature of 0.001 mm or smaller. The tapered angle of the tapered hole 43 is 40+5 , and the diameter at the seam between the tapered hole 43 and the curved hole 44 is about 0.17 mm. Further, the length of the tapered hole 43 in the ink ejection direction is about 0.14 mm.

The inner diameter of the curved hole 44 gradually increases toward the cylindrical hole 39, with an inclination smaller than the tapered angle of the tapered hole 43, and the curved hole 44 is connected to the cylindrical hole 39. The curved hole 44 is obtained by plastic deformation when the punch 60 is driven in, and the shape and the curvature of the curved hole 44 can be adjusted in accordance with the hardness of the material and the thickness of the plate used during press machining.

While referring to Fig. 10, a nozzle 6 according to another embodiment of the present invention will now be described. Fig. 10 is a cross sectional view of the nozzle 6 for the embodiment. Big differences from the preceding embodiment are that an ink flow path associated with the nozzle is formed in one direction, that a vibrating unit directly vibrates - 13 the ink flow path, and that a body 30 is separated into two segments, which are used as a nozzle plate 31.

That is, the nozzle 6 is constituted by the body 30, a piezoelectric device 32 and a protective cover 72 that are arranged outside the body 30, and a joint 21a that is located at one end of the body 30. In this embodiment, the body 30 can be separated into bodies 30a and 30b, the joint 21a is attached to the body 30 by an adhesive, and the protective cover 72 is fixed to the body 30 by a screw 28a. A hole 73 formed in the protective cover 72 is used to extract a lead line for transmitting a signal to the piezoelectric device 32.

Ink is supplied from the joint 21a to the body 30, and is passed through ink flow paths 37, 38 and 39, the diameters of which are gradually reduced at three steps in the body 30, and is ejected from an orifice (distal opening) 41 located forward. The body is made of stainless steel, the ink flow paths, the diameters of which are gradually reduced at three steps, are obtained by drill machining, and the orifice 41 located forward is formed by press machining. An explanation will be given later for the reason that the diameters of the ink flow paths 37, 38 and 39 are reduced at three steps.

A method for manufacturing the orifice 41 will now be described while referring to Fig. 12.

Basically, the orifice 41 is manufactured in the same manner as in the previous embodiment.

However, in this embodiment, since only the portions of the body segments on the front side need be formed, only a short tool is required, compared with the previous embodiment wherein the three-step flow path is formed in the nozzle plate, and the opening (orifice) 41 is bored using the punch. Further, the process is simplified and the machining accuracy is increased.

That is, after the cylindrical ink flow path 39 is formed by drilling, tapered portions 80 and 82 are obtained at tapered angles of about 120 , which is equivalent to the angle of the distal end of the drill.

Thereafter, using a punch having the same shape as the distal end of the orifice 41, the tapered portion 80 is removed by press machining, and a tapered portion 81, having a shape that matches the shape of the distal end of the punch, and the orifice 41, the diameter of which is about 65 um, are obtained.

The piezoelectric device 32 will now be described in detail while referring to Fig. 14. The piezoelectric device 32 has a cylindrical shape, and an electrode is formed on the internal and external surface. An inner electrode 55 of the piezoelectric device 32 entirely covers the inner walls and the end faces of the cylindrical portion, and a non- electrode portion 54 is provided on the outer surface of the piezoelectric device 32 to furnish insulation between an outer electrode 56 and the inner electrode 55. The inner electrode 55 is adhered to the body 30, so that 15 - the vibration of the piezoelectric device 32 can be efficiently transmitted to the body 30. Since the inner electrode 55 of the piezoelectric device 32 contacts the body 30, the body 30 and the inner electrode 55 can be conductive, and thus, when a transmitter for generating an electric signal as a sine wave is connected to the outer electrode 56 and the body 30, the piezoelectric device 32 can be vibrated.

Fig. 13 is a detailed diagram showing the body 30. The body 30a and 30b are cylindrical members, and the total length of the two is LO. The ink flow paths 38 and 39, having lengths L2 and L3, are formed inside the body 30, and when the joint 21a, the length of which is determined to be L1, is inserted and adhered to the body 30, the flow path 37 is obtained.

The outer diameter of the body 30a is designated in accordance with the internal diameter of the piezoelectric device 32 located at a root portion 75.

An explanation will now be given for the state wherein, when the body 30 (the assembly comprising the bodies 30a and 30b) is vibrated by applying a high frequency voltage to the piezoelectric device 32, the vibration is transmitted to ink flowing in the body 30. The vibration occurring within the range of a voltage that can be applied to the piezoelectric device 32 is very small and is not appropriate for the formation of particles. Therefore, in this embodiment, a resonance frequency fb (mechanical - 16 resonance) in the axial direction of the body 30 is set so it is close to a nozzle drive frequency fn, and the vibration is amplified by the body 30. The resonance frequency fb in the axial direction can be obtained by the following expression (2).

fb = nVb/4(L + k1) (2) In this expression, n denotes an integer value determined by a resonance mode; L denotes the length of the body 30; Vb denotes a wave velocity in the body 30; and kit denotes a correction coefficient determined through experimentation. In this embodiment, the body 30 is made of a stainless steel, and Vb = 5000 m/s. For the nozzle drive frequency fn, an optimal value is substantially determined in accordance with the diameter of the orifice 41 (A = 0.065 mm in this embodiment), and in this embodiment, En = 70 kHz. In the calculation, the length L, for which fn is the first resonance frequency fb (n = 1), is about 22 mm; however, actually, the appropriate length L is about 22 to 26 mm because the first resonance frequency varies depending on the shape of the joint 21a. With this structure, since ink is vibrated by the vibration of the piezoelectric device 32, which is amplified by the body 30, particles can be formed efficiently.

The ink flow path in the body 30 will now be explained. The orifice 41 (the hole diameter of 0.065 mm) for ink ejection is formed in one end of the body 30.

The ink flow paths 37, 38 and 39 constitute a step structure wherein their inner diameters differ, i.e., the inner diameters of the paths are reduced toward the orifice 41. This is because when the fluid resonance frequency occurring in the ink flow path is increased, the occurrence of fluid resonance similar to the drive frequency can be prevented. As well as in the previous embodiment, the fluid resonance frequency of the ink flow path is obtained by the following expression (3).

fr = nV/4(1 + k2) (3) In this expression, n denotes an integer value determined by a resonance mode; Vl denotes a wave velocity in ink; l denotes the length of an ink flow path; and k2 denotes a correction coefficient. Since the diameter of the orifice 41 is considerably smaller than the hole diameter of the ink flow path 39, the boundary condition wherein one end is closed and the other end is open is employed, and n = 1 in a first mode, n = 3 in a second mode and n = 5 in a third mode are established. Further, since the boundary condition wherein both ends are open is employed for the ink flow paths 37 and 38, n = 2 in the first mode, n = 4 in the - 18 second mode and n = 6 in the third mode are established. Furthermore, the wave velocity in ink is generally 1200 to 1400 m/s at a normal temperature; however, the wave velocity in ink varies in consonance with the temperature, and fluctuation of the wave velocity is about +10% at 0 C to 45 C, which is an operating temperature range for the ink jet recording apparatus. Therefore, in this embodiment, in order to prevent the affect of the fluid resonance on particle formation, the length l of the ink flow path is set, so that the fluid resonance frequency is considerably higher than the drive frequency. Specifically, the diameter of the flow path is divided into three or more segments, and the length l of each flow path segment is set shorter than 1/2 the flow path length L. The lengths l of the flow path segments are shown as L1, L2 and L3 in Fig. 13. With this arrangement, the resonance frequency of ink flowing along each ink flow path can be higher than the drive frequency. The ink flow path 39 is shorter than the ink flow paths 37 and 38, so that the fluid resonance frequency for the ink flow path 39 is higher than the frequency for the ink flow paths 37 and 38. This is because the fluid resonance characteristic of the ink flow path 39, which is nearest the orifice 41, affects the formation of particles.

According to this arrangement, since the affect of the fluid resonance, which changes greatly in - 19 - consonance with the temperature, can be avoided and since the vibration can be amplified by using mechanical resonance, which changes less relative to the temperature, the stable formation of particles can be performed.

When printing is performed by using the nozzle in Fig. 10, the orifice 41 may be closed because the solvent used in ink is highly volatile, and tiny particles, which can not be removed by using a filter, may clog the ink circulating path. In this case, the nozzle is removed from the ink jet recording apparatus, is immersed in a solvent, and is rinsed by ultrasonic cleaning. When the nozzle is long, it tends to take much time to rinse the inside of the nozzle using ultrasonic cleaning. In addition, when the body having the shape shown in Fig. 13 is to be manufactured, the length of the punch required to form the orifice 41 at the front of the flow path 39 using press machining is equal to the sum of the length LO of the body and the length of a portion that is to be attached to a press machine. In this case, the length of the punch reaches about 35 mm, and a reduction in the manufacturing precision provided by the punch becomes a problem. In addition, since a tiny boring portion is present at the tip of the long punch, as another problem, the punch tends to be easily broken. Therefore, as is shown in Fig. 11, when the body 30 is formed using the separate bodies 30a and 30b, cleaning can be easily performed, - 20 and the precision with which the orifice 41 is machined and the service life of the press machining punch can be increased. The structure of the body segments will now be described while referring to Fig. 11.

Fig. 11 is an enlarged diagram showing the distal end of the nozzle in Fig. 10. The bodies 30a and 30b are separate members that are engaged by external and internal threads that are formed in the inner walls to serve as a screw 50. A rubber plate 70, which is an ink leakage prevention member, is attached at the boundary between the ink flow paths 38 and 39, so that ink flowing from the flow path 38 to the flow path 39 is prevented from leaking.

With this arrangement, the size of the nozzle is reduced compared with the nozzle in the previous embodiment, and a nozzle is provided for which the level of maintenance that can be performed is excellent and by which ink particles can be stably formed without being affected by temperature changes.

It should be further understood by those skilled in the art that although the foregoing

description has been made on embodiments of the

invention, the invention is not limited thereto and various changes and modifications may be made without departing from the scope of the appended claims. - 21

Claims

CLAIMS: 1. An ink jet recording apparatus, for ejecting ink from a nozzle

to perform printing, comprising: a body having a vibrating unit for vibrating ink; and a nozzle plate made of a single metal member detachable from the body, wherein the nozzle plate includes nozzles that are formed by connecting cylindrical holes, which serve as ink ejection ends, tapered holes, which are connected to the cylindrical holes and that have a diameter that is reduced in an ink ejection direction, and curved holes, which are connected to the tapered holes, that have a diameter that is reduced in the ink ejection direction.
2. An ink jet recording apparatus according to claim 1, wherein the nozzle plate includes ink flow paths, which are connected to the curved holes of the nozzles, that are formed by coupling two cylindrical holes, at the least, the inner diameters of which differ and are reduced in the ink ejection direction.
3. An ink jet recording apparatus according to claim 1 or 2, further comprising: an electrifying electrode for electrifying ink particles that are ejected from a nozzle in the nozzle plate; and a deflecting electrode for deflecting the ink particles that are electrified. - 22
4. A method for manufacturing a nozzle plate for an ink jet recording apparatus according to claim 2, comprising the steps of: using a drill to bore in the nozzle plate a cylindrical hole to be used as a flow path; and inserting a punch, which is so structured that the shaft has two or more outer diameters, into and through the cylindrical hole bored in the nozzle plate and performing press machining for the cylindrical hole used as the ink ejection end.
5. An ink jet recording apparatus according to claim 1, wherein the vibrating unit is positioned on the outer portion of the ink flow path; wherein, instead of the nozzle plate, an ink flow path having a stepped structure is formed in the body by coupling cylindrical holes having different inner diameters; and wherein the body is separable into segments at a step position whereat the inner diameter of the ink flow path differs.
6. An ink jet recording apparatus according to claim 5, which is separable along a boundary between an ink flow path, communicating with an orifice, and a flow path, the inner diameter of which differs from the inner diameter of the ink flow path.
7. An ink jet recording apparatus according to claim 5, wherein the diameter of the ink flow path is reduced toward the orifice.
8. An ink jet recording apparatus according to - 23 claim 5, wherein coupling of the segments of the body is accomplished by using a screw.
9. An ink jet recording apparatus according to claim 8, further comprising: an ink leakage prevention member being provided along the boundary of an ink flow path joint for the segments of the body.
10. An ink jet recording apparatus as herein described with reference to, and as illustrated in, Figs. 1 to 14.
11. A method of manufacturing a nozzle plate for an ink jet recording apparatus as herein described with reference to, and as illustrated in, Figs. 1 to 14.