JPH1067101A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize the discharging speeds of ink drops emitted from nozzles within the predetermined range irrespective of the number of ink chambers by a method wherein the number of piezoelectric bodies, to which driving voltage is simultaneously applied for driving, is recognized and, at the same time, the pulse width of the driving voltage is decided in response to the number of recognized piezoelectric bodies. SOLUTION: A CPU decides the pulse width of driving voltage in response to the number of piezoelectric element parts 17 on the basis of the number of the piezoelectric element parts 17 at the retrieval of a data table and, at the same time, the respective piezoelectric element parts 17 are driven by means of the driving voltage having the decided pulse width. Thus, irrespective of the number of ink chambers 12, to which the above-mentioned driving voltage is simultaneously applied, the discharging speeds of the ink drops discharged from nozzles 18 can be set to a near certain discharging speed. The variation of the discharging speeds due to the decrease of the apparent volume modulus of elasticity of ink with the ink chamber 12 through the deflective deformation of a cavity plate 14 caused by the increase of the number of the piezoelectric element parts 17 is dissolved, resulting in realizing favorable printing quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink chamber by applying a driving voltage to a piezoelectric body arranged in a plurality of ink chambers formed in a cavity plate to change the pressure of the ink chamber. In particular, the present invention relates to an ink-jet printer having an ink-jet head that prints characters and the like by discharging ink droplets from a nozzle communicating with a paper, and in particular, recognizes the number of piezoelectric bodies that are driven when a drive voltage is simultaneously applied and recognizes the number By determining the pulse width of the drive voltage in accordance with the number of the piezoelectric bodies, the ejection speed of the ink droplets ejected from the nozzles is determined regardless of the number of ink chambers whose pressure is simultaneously changed via each piezoelectric body. The present invention relates to an ink-jet head that can be made uniform within a range.

[0002]

2. Description of the Related Art Heretofore, in an ink jet head, a driving voltage is applied to a piezoelectric body arranged corresponding to each ink chamber, and the ejection speed of the ink droplet when the ink droplet is ejected from a nozzle communicating with the ink chamber. Various studies have been made on the relationship between the pulse width of the driving voltage applied to the piezoelectric body. In general, it is known that the ejection speed of ink droplets ejected from a nozzle changes periodically according to the pulse width of a drive voltage applied to a piezoelectric body.

For example, when a driving voltage having various pulse widths is applied to a piezoelectric body, and only one ink chamber in an ink jet head is pressurized to discharge an ink droplet from a nozzle, the discharge speed of the ink droplet is reduced. There is a relationship between the pulse width of the driving voltage and a curve S1 (shown by a solid line) shown in FIG. At this time, assuming that the time required for the pressure wave of the ink generated when the ink chamber is pressurized to propagate for the length of the ink chamber is T, the first local maximum K1 in the curve S1 (FIG. 8). Middle, left maximal)
Indicates that the pulse width of the drive voltage corresponds to the time T, and the second maximum K2 (the right maximum in FIG. 8)
Is that the pulse width of the driving voltage is three times the time T, that is, the time 3
It corresponds to T.

In a conventional ink jet head, it is considered that a plurality of ink chambers are simultaneously pressurized based on the relationship between the ejection speed of the ink droplet and the pulse width of the drive voltage applied to the piezoelectric body. Various pulse widths of the drive voltage for driving each piezoelectric body in the ink jet head are selected.

[0005]

The time T required for the ink pressure wave generated when the ink chamber is pressurized to propagate the length of the ink chamber is T = L / √ (E _V / ρ)
Is determined. Here, L is the length of the ink chamber, the volume modulus of apparent ink in E _V is the ink chamber, [rho represents the density of ink. Incidentally, the bulk modulus E _V changes depending on the deformation amount of the ink chamber when the ink chamber is pressurized,
The larger the amount of deformation of the ink chamber, the smaller the value.

Here, as described above, one of the ink chambers in the ink jet head may be independently pressurized, but a plurality of ink chambers may be simultaneously pressurized. As an example opposite to the example (an example in which only one ink chamber is pressurized), consider an example in which all the ink chambers are simultaneously pressurized. When all the ink chambers are simultaneously pressurized via the respective piezoelectric bodies, the cavity plate in which each ink chamber is formed bends and deforms in the pressing direction. The amount of flexural deformation of the cavity plate is smaller than when only one ink chamber is pressurized.
As a result, the apparent bulk modulus E _V of the ink in each ink chamber becomes small. When the volume elastic modulus E _{V of the} ink decreases, the time T increases, as is clear from the above equation. Therefore, when all the ink chambers are simultaneously pressurized, the ejection speed of the ink droplet ejected from the nozzle is: Although the pulse width periodically changes according to the pulse width of the drive voltage applied to the piezoelectric body, the pulse shifts to a larger pulse width as a whole. Specifically, as shown by a curve S2 (shown by a broken line) shown in FIG. 8, the pulse width of the drive voltage at which the same ink droplet ejection speed as that of the curve S1 is obtained is shifted rightward as a whole, K3 (Left local maximum), Local maximum K4
(The right maximum) also shifts to the right.

Accordingly, as shown in FIG. 8, for example, the ink droplet discharge speed when the pulse width of the drive voltage applied to the piezoelectric body when set to P _A is pressurized only one ink chamber Is V _A , while the ink droplet ejection speed when all the ink chambers are pressurized drops to V _B. Each of these ink drop ejection velocity V _A, for V _B, both each having a constant value greater than, but the difference between V _A and V _B are required to be within a predetermined tolerance, V _A is V _B not have a certain level of value as, also, when the difference between the both is not within the predetermined tolerance, the ink droplet ejection velocity V _a as the number of ink chambers to be pressurized, V _B And the print quality is seriously affected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and recognizes the number of piezoelectric bodies driven by simultaneous application of a driving voltage, and corresponds to the recognized number of piezoelectric bodies. By determining the pulse width of the drive voltage, the ejection speed of the ink droplets ejected from the nozzles is made uniform within a predetermined range irrespective of the number of ink chambers whose pressure is simultaneously changed via each piezoelectric body. It is an object of the present invention to provide an ink jet printer provided with an ink jet head having good print quality.

[0009]

According to an aspect of the present invention, there is provided an ink jet printer, comprising: a cavity plate having a plurality of ink chambers formed thereon; a sheet material covering an upper surface of each ink chamber; A piezoelectric body disposed on a sheet material corresponding to the chamber; and a nozzle plate having nozzles formed so as to communicate with the respective ink chambers. In an ink jet printer in which an ink jet head that prints characters or the like on paper by ejecting ink droplets from nozzles by changing the number of piezoelectric elements and the pulse width of the drive voltage to which the drive voltage is applied simultaneously is used. And a recognizing means for recognizing the number of the piezoelectric bodies, when a drive voltage is applied to the piezoelectric bodies to change the pressure of the ink chamber. It has a configuration for driving the piezoelectric element while determining the pulse width of the reference drive voltage to said storage means based on piezoelectric number recognized by said recognizing means.

In the ink jet printer according to the first aspect,
When a drive voltage is applied to each piezoelectric body to change the pressure in the ink chamber, ink droplets are ejected from the nozzles and characters or the like are printed on paper, the number of piezoelectric bodies to which the drive voltage is simultaneously applied is recognized. At the same time, the storage means is searched based on the recognized number of piezoelectric bodies. At this time, the number of piezoelectric bodies to which the drive voltage is simultaneously applied and the pulse width of the drive voltage are stored in the storage unit in association with each other, and the number of piezoelectric bodies and the pulse width of the drive voltage are stored between the number of piezoelectric bodies and the pulse width of the drive voltage. Also, a correspondence is provided such that the ink ejection speed of the ink droplet ejected from the nozzle is within a predetermined range even when the number of piezoelectric bodies changes. Then, at the time of searching the storage means, based on the number of piezoelectric bodies recognized through the recognition means, the pulse width of the drive voltage corresponding to the number of piezoelectric bodies is selected and determined, and the drive voltage having the pulse width is used. Each piezoelectric body is driven.

According to the first aspect of the present invention, the number of piezoelectric bodies driven by simultaneously applying the driving voltage is recognized, and the pulse width of the driving voltage is selected according to the recognized number of piezoelectric bodies. Since it is determined, it is possible to equalize the ejection speed of the ink droplets ejected from the nozzles within a predetermined range regardless of the number of ink chambers in which the pressure is simultaneously changed via each piezoelectric body, Therefore, it is possible to print characters and the like with good printing quality.

According to a second aspect of the present invention, there is provided an ink jet printer according to the first aspect.
The storage means stores the drive voltage by changing the pulse width every time the number of piezoelectric bodies increases by one. In the ink jet printer according to the second aspect, the storage means changes and stores the pulse width of the drive voltage every time the number of piezoelectric bodies increases by one, so that the storage means can be precisely defined according to the number of piezoelectric bodies recognized by the recognition means. The pulse width of the drive voltage can be controlled.

Further, an ink jet printer according to claim 3 is the ink jet printer according to claim 1,
The storage unit divides the number of piezoelectric bodies into a predetermined number of groups, and stores the pulse width of the drive voltage corresponding to each of the divided groups, and the recognition unit stores the group to which the recognized number of piezoelectric bodies belongs. It is characterized by specifying. In the ink-jet printer according to the third aspect, the storage unit stores the pulse width of the driving voltage corresponding to each group by dividing the number of piezoelectric bodies into a predetermined number of groups, and the recognition unit stores the recognized piezoelectric voltage. Since the group to which the number of bodies belongs is specified, the pulse width of the drive voltage corresponding to the group to which the number of piezoelectric bodies recognized by the recognition unit belongs may be selected at the time of searching the storage means. Selection can be easily performed.

According to a fourth aspect of the present invention, there is provided an ink jet printer, comprising: a cavity plate in which a plurality of ink chambers are formed; a sheet material covering an upper surface of each ink chamber; and a sheet material corresponding to each ink chamber. And a nozzle plate in which nozzles are formed so as to communicate with the respective ink chambers. By applying a drive voltage to each piezoelectric body to change the pressure in the ink chamber, ink droplets are ejected from the nozzles. In an ink jet printer provided with an ink jet head for discharging and printing characters or the like on paper, the number of piezoelectric bodies to which the drive voltage is applied simultaneously is recognized, and the number of piezoelectric bodies is divided into a predetermined number of groups. A recognition unit for specifying a group to which the number of piezoelectric bodies belongs, and a pulse width of the drive voltage for each group of the number of piezoelectric bodies recognized and specified by the recognition unit. Calculating means for applying a drive voltage to the piezoelectric body to change the pressure of the ink chamber, and driving each piezoelectric body according to the pulse width of the drive voltage calculated via the calculation means. Have.

[0015] In the ink jet printer of the fourth aspect,
When a drive voltage is applied to each piezoelectric body to change the pressure in the ink chamber, ink droplets are ejected from the nozzles and characters or the like are printed on paper, the number of piezoelectric bodies to which the drive voltage is simultaneously applied is recognized. The group to which the number of piezoelectric bodies belongs is specified while dividing the number of piezoelectric bodies into a predetermined number of groups, and the pulse width of the drive voltage is calculated for each group of the recognized and specified number of piezoelectric bodies. At this time, the calculation means calculates the pulse width of the drive voltage according to a predetermined calculation formula such that the ink discharge speed of the ink droplets discharged from the nozzles is within a predetermined range even when the number of piezoelectric bodies changes. Then, each piezoelectric body is driven by the drive voltage having the pulse width calculated through the calculation means as described above.

According to the ink jet printer of the fourth aspect, the number of piezoelectric bodies to which the driving voltage is simultaneously applied and driven is recognized, the group to which the number of piezoelectric bodies belongs is specified, and the recognized and specified piezoelectric body is identified. Since the pulse width of the driving voltage is calculated and determined for each group of the number of inks, regardless of the number of ink chambers whose pressure is simultaneously changed via each piezoelectric body, the ink droplets ejected from the nozzles are It is possible to make the discharge speed uniform within a predetermined range, and therefore,
It is possible to print characters and the like with good printing quality.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an ink jet printer according to the present invention will be described in detail based on an embodiment embodying the present invention with reference to the drawings. First, a schematic configuration of the ink jet printer according to the first embodiment will be described with reference to FIG. FIG. 1 is a perspective view showing a main part of the ink jet printer.

In FIG. 1, a pair of frames 1 (FIG. 1)
A platen 3 is rotatably mounted via a shaft 2 between the two frames (only one of the frames 1 is shown). The platen 3 is rotated by a motor 4. A piezoelectric ink jet head 5 is arranged opposite to the platen 3. The inkjet head 5 is mounted on a carriage 7 together with the ink supply device 6. The carriage 7 is slidably supported by two guide rods 8 arranged in parallel with the axis of the platen 3, and the carriage 7 is provided with a timing belt 10 stretched over a pair of pulleys 9. Be linked. One of a pair of pulleys 9 (FIG. 1)
The middle and right pulleys 9) are fixed to the drive shaft of the CR motor 11, and therefore the timing belt 1 is rotated based on the rotation of the right pulley 9 via the CR motor 11.
0 is sent, and the carriage 7 is reciprocated along the platen 3.

Next, the structure of the ink jet head 5 will be described with reference to FIGS. FIG. 2 is a side sectional view of the inkjet head 5, and FIG. 3 is a front view of the inkjet head 5 excluding a nozzle plate.

In FIG. 2 and FIG. 3, the ink-jet head 5 has a plurality of ink pressure chambers 12 having a length L by cutting an alumina sintered body, and an ink manifold 13 communicating with each ink pressure chamber 12. Is formed. Each ink manifold 13 is supplied with ink from an ink supply device 6 attached to the ink jet printer, and ink is supplied from the ink manifold 13 to the ink pressure chamber 12. A vibration sheet 15 formed of an aramid film is bonded and fixed to the upper surface of the cavity plate 14. The vibration sheet 15 closes the upper surfaces of the ink pressure chambers 12 and the ink manifold 13.

A piezoelectric plate 16 made of a piezoelectric material such as PZT is provided on the upper surface of the vibration sheet 15 above the cavity plate 14. While responding,
The piezoelectric element portion 17 is formed such that its lower end portion is in contact with the vibration sheet 15. Each of the piezoelectric element portions 17 is provided with a predetermined electrode pattern (not shown). When a driving voltage is applied to the electrode pattern, the piezoelectric element portion 17 is positioned at a lower position in FIGS. Vibrating sheet 15
To press the ink pressure chamber 12. The configurations of the piezoelectric plate 16 and the piezoelectric element 17 are known, and a detailed description thereof will be omitted.

The front end face of the ink jet head 5 (FIG. 1)
A nozzle plate 19 in which nozzle holes 18 are formed corresponding to the respective ink pressure chambers 12 is fixed to the middle and left end surfaces. As described above, when the vibrating sheet 15 is pressed from the nozzle holes 18 of the nozzle plate 19 to apply the driving voltage to the piezoelectric element section 17 and the ink pressure chamber 12 is pressed, Drops are ejected at a predetermined ejection speed. As a result, printing of characters and the like is performed on the paper arranged opposite to the ink jet head 5.

Although only six ink pressure chambers 12 are shown in FIG. 2 for the sake of convenience for easy understanding, the actual ink jet head 5 has a head unit as shown in FIG. 120 are provided in a staggered arrangement. Also, 120 head units are 6
It is composed of two heads each of which is integrally formed with 0 heads, and each head is separately controlled.

Next, a control system of the ink jet printer equipped with the ink jet head 5 configured as described above will be described with reference to FIG. FIG. 4 is a block diagram showing a control system of the ink jet printer. In FIG. 4, the ink jet printer is configured with a CPU 20 as a core, and is connected to a host computer 22 via an interface 21.

The CPU 20 also includes a switch panel 2
3, a ROM 24 and a RAM 25 are connected to each other. The switch panel 23 is a panel for setting and displaying a paper size and other various parameters. R
The OM 24 is a storage device for storing various programs necessary for controlling the ink jet printer.
The data table 26 shown in FIG. 5 is stored in M24. The RAM 25 is a memory for temporarily storing various data calculated by the CPU 20 when controlling the inkjet printer.

Here, the data table 26 shown in FIG. 5 will be described with reference to FIG. FIG. 5 shows a piezoelectric element section 17 to which a drive voltage is simultaneously applied in the inkjet 5.
FIG. 4 is an explanatory diagram showing a data table 26 in which the numbers of the driving voltages and the pulse widths of the driving voltages correspond to each other. In the data table 26 shown in FIG. 5, the left column shows the number of the piezoelectric elements 17 to which the driving voltage is simultaneously applied, and the right column shows the number of the piezoelectric elements 17 corresponding to the number of the simultaneously driven piezoelectric elements 17. 5 shows a pulse width of a drive voltage applied to the unit 17. For example, when only one piezoelectric element unit 17 is driven, the number of simultaneously driven piezoelectric element units 17 is 1. Therefore, the pulse width P1 of the drive voltage applied to the piezoelectric element unit 17 at this time is 7.50 μs. Similarly, when the drive voltage is simultaneously applied to the 60 piezoelectric element sections 17, the number of simultaneously driven piezoelectric element sections 17 is 60, and accordingly, at this time, the number of piezoelectric element sections 17 is applied to each piezoelectric element section 17. Drive voltage pulse width P
60 becomes 9.50 μs. In the data table 26, the pulse width P of the drive voltage is changed so as to increase by 0.03 μs each time the number of piezoelectric elements 17 driven simultaneously increases by one.

The number of the piezoelectric elements 17 driven by the application of the driving voltage at the same time is recognized through the CPU 20 according to a predetermined recognition program.

Next, the control system of the ink jet printer will be described with reference to FIG. 4. The CPU 20 controls the LF through an LF drive circuit 27 and a CR drive circuit 28, respectively.
The drive of the motor 29 and the CR motor 11 is controlled. here,
The LF motor 29 basically drives a paper feed mechanism, and the CR motor 11 drives a carriage mechanism including the above-described carriage 7 and the like. The CPU 20
Is connected to the head drive circuit 31 via the flexible cable 30, and drives the inkjet head 5 for printing.

Using the ink jet printer configured as described above, when the driving voltage is simultaneously applied and the number of piezoelectric element units driven is 10, 20, and 3, and
0, the data table 26
The relationship between the pulse width P and the ejection speed of the ink droplet was measured while changing the pulse width P of the drive voltage based on the above. The measurement result is shown in FIG. FIG. 6 shows the pulse width P and the ink drop of the ink droplets measured while changing the pulse width P of the drive voltage based on the data table 26 for each of the ten, twenty, and thirty piezoelectric elements 17 that are simultaneously driven. 6 is a graph showing a relationship with a discharge speed V. In the graph of FIG. 6, the horizontal axis represents the pulse width P (microsecond: μS) expressed with time, and the vertical axis represents the ink discharge speed V (m / s).
Is shown.

Referring to FIG. 6, the measurement results when the number of simultaneously driven piezoelectric element portions 17 is 10 will be described. The measurement result in this case is shown by a curve S3 (shown by a solid line) in FIG.
The pulse width P10 at this time is 7.80 μs from the data table 26. In such a case, the ink ejection speed V becomes the first peak value K5 (about 10 m / s) at the pulse width P10. Also, it can be seen that the second peak value K6 (about 8.7 m / s) is obtained when the pulse width P10 is three times the value (3P10).

Next, if the number of simultaneously driven piezoelectric element portions 17 is 2
A description will be given of the measurement result in the case of zero. The measurement result in this case is shown by a curve S4 (shown by a dashed line) in FIG. 6, and the pulse width P20 at this time is 8.10 μs from the data table 26. In such a case, each of the piezoelectric element portions 17 of the piezoelectric plate 16 in the inkjet head 5 is extended via the vibration sheet 15 in the direction of the ink chamber 12, and the cavity plate 14 is pressurized in the twenty ink chambers 12. Therefore, it is deformed so as to bend downward. Thus, the cavity plate 14
Is deformed, the apparent bulk modulus of the ink present in the ink chamber 12 becomes smaller, so that the first peak value K7 (about 10 m / s) and the second peak value K8 ( (About 8.7 m / s) shifts rightward from the peak values K5 and K6 in the curve S3, respectively.

That is, the curve S4 is similar to the curve S3 in that the ink discharge speed V periodically changes according to the pulse width P. However, the ink discharge speed V becomes the first at the pulse width P20. Peak value K7 (about 10m / s)
Becomes Also, when the pulse width P20 is three times that (3P2
0), the second peak value K8 (about 8.7 m / s) is obtained.

Next, if the number of simultaneously driven piezoelectric element portions 17 is 3
A description will be given of the measurement result in the case of zero. The measurement result in this case is shown by a curve S5 (shown by a broken line) in FIG. 6, and the pulse width P30 at this time is set in the data table 26.
To 8.40 μs. In such a case, similar to the case where the number of the simultaneously driven piezoelectric elements 17 is 20, the cavity plate 14 is flexed and deformed, and the apparent bulk modulus of the ink existing in the ink chamber 12 is further reduced. , The first peak value K9 (about 1
0 m / s) and the second peak value K10 (about 8.7 m
/ S) are the peak values K7 and K in the curve S4, respectively.
Shift from 8 to the right.

That is, the curve S5 is similar to the curves S3 and S4 in that the ink discharge speed V periodically changes according to the pulse width P. However, the ink discharge speed V becomes the first at the pulse width P30. The second peak value K9 (about 10 m
/ S). When the pulse width P30 is three times as large (3P30), the second peak value K10 (about 8.7 m) is obtained.
/ S).

Here, when the relationship between the pulse width P and the ink discharge speed V in each of the curves S3, S4, and S5 is mutually examined, as is clear from FIG. Data table 26
, The pulse width P10 (7.80 μs) is selected in accordance with the above equation. If the number of simultaneously driven piezoelectric element sections 17 is 20, the pulse width P20 (8.10 μs) is selected in the same manner. If the number of the sections 19 is 30, if the pulse width P30 (8.40 μs) is selected in the same manner, the curve S3
, The peak value K7 of the curve S4, and the peak value K9 of the curve S5, the ejection speed V of about 10 m / s.
Can be obtained, and the peak value K6 of the curve S3, the peak value K8 of the curve S4, and the peak value K1 of the curve S5
At 0, a discharge speed V of about 8.7 m / s can be obtained.

As described in detail above, in the ink jet printer according to the present embodiment, a drive voltage is applied to each piezoelectric element portion 17 to pressurize the ink chamber 12 so that ink droplets are ejected from the nozzle holes 18 and printed on paper. A piezoelectric element 1 to which a drive voltage is simultaneously applied when characters or the like are printed on
The number 7 is recognized via the CPU 20, and the data table 26 is searched based on the recognized number of piezoelectric elements 17. At this time, the data table 26 stores the number of piezoelectric elements 17 to which the drive voltage is simultaneously applied and the pulse width P of the drive voltage in association with each other.
Further, between the number of the piezoelectric elements 17 and the pulse width P of the drive voltage, the ink ejection speed V of the ink droplet ejected from the nozzle hole 18 is substantially the same even when the number of the piezoelectric elements 17 changes. Is established so that the value of the relation is obtained. At the time of searching the data table 26, the CPU 20 selects and determines the pulse width P of the drive voltage corresponding to the number of the piezoelectric elements 17 based on the number of the piezoelectric elements 17, and uses the drive voltage having the pulse width P to determine each pulse. The piezoelectric element section 17 is driven.

Therefore, the number of piezoelectric elements 17 driven by simultaneous application of the drive voltage is recognized, and the pulse width P of the drive voltage is selected and determined according to the recognized number of piezoelectric elements 17. Therefore, the ejection speed V of the ink droplet ejected from the nozzle hole 18 is set to be substantially the same ejection speed V regardless of the number of the ink chambers 12 which are simultaneously pressed through the respective piezoelectric element portions 17. In addition, as the number of simultaneously driven piezoelectric elements 17 increases, the cavity plate 14 bends and deforms, and the apparent bulk modulus of ink existing in the ink chamber 12 decreases, thereby causing ejection. Variations in the speed V can be eliminated, so that characters and the like can be printed with good print quality.

The data table 26 stores the pulse width P of the drive voltage so that the pulse width P increases by a predetermined value each time the number of piezoelectric elements 17 increases by one.
It is possible to precisely control the pulse width P of the drive voltage according to the number of the piezoelectric elements 17 recognized by the PU 20.

Next, an ink jet printer according to a second embodiment will be described with reference to FIG. FIG. 7 is an explanatory diagram schematically showing the contents of the data table stored in the ROM 24 in the ink jet printer of the second embodiment. The ink jet printer according to the second embodiment has basically the same configuration as the ink jet printer according to the first embodiment. In the data table 26 according to the first embodiment, the piezoelectric elements 17 that are simultaneously driven are provided. The number and pulse width of the simultaneously driven piezoelectric element portions 17 are stored in such a manner that the pulse width P of the drive voltage is increased by a predetermined time every time the number increases by one. The data table according to the second embodiment is different from the first embodiment in that the piezoelectric element unit 17 is divided into a predetermined number of groups, and the pulse width of the driving voltage is stored corresponding to each of the divided groups. different.

In the data table 32 shown in FIG.
The left column shows the groups of the piezoelectric elements 17 to which the driving voltage is applied simultaneously, and the right column shows the driving applied to each piezoelectric element 17 in each group corresponding to the number of the piezoelectric elements 17 to be driven simultaneously. Indicates the pulse width of the voltage. As shown in FIG. 7, each of the piezoelectric element sections 17 in the 60 head units that constitute one head section is divided into groups each including 10 piezoelectric element sections 17. Divided into two groups. For example, if the number of the piezoelectric element units 17 that are simultaneously driven is nine, it belongs to the first group (1 to 10), and the pulse of the driving voltage applied to each of the nine piezoelectric element units 17 Width P is 7.7μ
s. Similarly, when the number of piezoelectric elements 17 simultaneously driven is 51, the sixth group (51
60), and each of the 51 piezoelectric element portions 1
The pulse width P of the drive voltage applied to 7 is 9.2 μs. In the data table 32, the pulse width P of the driving voltage is 0.3 μs every time the number of piezoelectric elements 17 driven simultaneously increases by 10, that is, from the first group to the sixth group. It is changed so as to increase in increments.

The number of piezoelectric elements 17 driven by application of the driving voltage at the same time is the same as that of the first embodiment in that the number is recognized through the CPU 20 according to a predetermined recognition program. Further, in the ink jet printer of the second embodiment, the relationship between the pulse width P and the ejection speed of the ink droplet was measured while changing the pulse width P of the drive voltage based on the data table 32. It was confirmed that similar measurement results were obtained.

In the ink jet printer according to the second embodiment, a drive voltage is applied to each piezoelectric element section 17 to pressurize the ink chamber 12, thereby ejecting ink droplets from the nozzle holes 18 to print characters and the like on paper. When printing, CP
The number of piezoelectric elements 17 to which the drive voltage is simultaneously applied is recognized via U20, and the data table 32 is searched based on the recognized number of piezoelectric elements 17 to which the number of piezoelectric elements 17 belongs. A group is specified. At this time, the data table 32 divides the number of the piezoelectric element portions 17 to which the drive voltage is applied simultaneously into six groups every ten, and the divided groups correspond to the pulse width P of the drive voltage. The piezoelectric element portion 17 is provided between each group and the pulse width P of the drive voltage.
The corresponding relationship is established so that the ink ejection speed V of the ink droplet ejected from the nozzle hole 18 has substantially the same value even when the group of. And CPU
Reference numeral 20 denotes the piezoelectric element unit 1 when the data table 32 is searched.
The pulse width P of the driving voltage corresponding to the group is selected and determined based on the group to which the number 7 belongs, and each of the piezoelectric element sections 17 is driven by the driving voltage having the pulse width P.
Is driven.

As described above, the number of the piezoelectric elements 17 to which the driving voltage is simultaneously applied and driven and the group to which the number belongs are recognized, and the pulse width P of the driving voltage is selected corresponding to the recognized group. As a result, the ejection speed V of the ink droplets ejected from the nozzle holes 18 is set to substantially the same ejection speed V regardless of the number of the ink chambers 12 that are simultaneously pressurized via the respective piezoelectric elements 17. In addition, as the number of piezoelectric elements 17 driven simultaneously increases, the cavity plate 14 bends and deforms, and the apparent bulk modulus of the ink existing in the ink chamber 12 decreases. As a result, it is possible to prevent the ejection speed V from fluctuating, thereby printing characters and the like with good printing quality.

The data table 32 of the ROM 24 stores the pulse width of the drive voltage corresponding to each group by dividing the number of the piezoelectric element sections 17 into a predetermined number (six). Since the CPU 20 specifies the group to which the number of the recognized piezoelectric elements 17 belongs,
At the time of searching the data table 32, the pulse width of the drive voltage corresponding to the group to which the number of the piezoelectric elements 17 recognized by the CPU 20 belongs may be selected, and therefore, the pulse width can be easily selected.

Next, an ink jet printer according to a third embodiment will be described. Here, the ink jet printer of the third embodiment has basically the same configuration as the ink jet printers of the first and second embodiments, and the data table 26 of the first embodiment has a simultaneous drive. The number and the pulse width of the piezoelectric elements 17 that are simultaneously driven so that the pulse width P of the driving voltage increases by a predetermined time each time the number of the piezoelectric elements 17 to be increased by one are stored in correspondence with each other. In the data table 32 of the second embodiment, the number of piezoelectric elements 17 that are simultaneously driven is one.
While the pulse width of the drive voltage is stored corresponding to each of the divided groups, the piezoelectric elements 17 that are simultaneously driven are stored in the third embodiment. The second embodiment is different from the first and second embodiments in that a predetermined number of groups are divided, and the pulse width of the drive voltage is obtained by calculation based on a predetermined arithmetic expression for each of the divided groups.

In the ink jet printer of the third embodiment, each of the piezoelectric element sections 17 in the 60 head units constituting one head section is divided into three groups of 20 piezoelectric elements 17 (first group: simultaneously driven piezoelectric elements). Part 17
, The second group: the number of piezoelectric elements 17 simultaneously driven is 21 to 40, and the third group: the number of piezoelectric elements 17 simultaneously driven is 41 to 60). The CPU 20 recognizes the number of the simultaneously driven piezoelectric element sections 17 and specifies each group to which the recognized number of the piezoelectric element sections 17 belongs. Then, the CPU 20 determines whether the group to which the number of the piezoelectric elements 7 to be simultaneously driven belongs to the first group, the second group, or the third group according to the operation formula set for each group. The pulse width P of the voltage is calculated.

Here, the pulse width calculation formula corresponding to the first group is defined by the following formula. Pulse width P = A × N (number of piezoelectric element portions 17) + B (operational expression 1) Here, N is in the range of 1 to 20, and A and B are constants specific to the first group.

The pulse width calculation formula corresponding to the second group is defined by the following formula. Pulse width P = C × N (number of piezoelectric element portions 17) + D (arithmetic expression 2) Here, N is in the range of 21 to 40, and C and D are constants specific to the second group.

Further, the pulse width calculation expression corresponding to the third group is defined by the following expression. Pulse width P = E × N (the number of piezoelectric element portions 17) + F (arithmetic expression 3) Here, N is in the range of 41 to 60, and E and F are constants specific to the third group.

The number of the piezoelectric elements 17 driven by the application of the driving voltage at the same time is the same as in the first and second embodiments in that they are recognized through the CPU 20 according to a predetermined recognition program. It is. In addition, in the ink jet printer of the third embodiment, the relationship between the pulse width P of the driving voltage and the ejection speed of the ink droplet was measured while changing the number of piezoelectric elements 17 driven simultaneously. It was confirmed that substantially the same measurement results were obtained.

In the ink jet printer according to the third embodiment, a drive voltage is applied to each piezoelectric element portion 17 to pressurize the ink chamber 12, thereby ejecting ink droplets from the nozzle holes 18 to print characters and the like on paper. When printing, CP
The number of piezoelectric elements 17 to which the driving voltage is simultaneously applied via U20 is recognized, and the group to which the recognized number of piezoelectric elements 17 belongs is specified. And
When the number of the piezoelectric element units 17 belongs to the first group,
The pulse width P of the drive voltage is calculated based on the above-described arithmetic expression 1, and each piezoelectric element unit 17 is driven by the drive voltage having the calculated pulse width P. Similarly, when the number of the piezoelectric element units 17 belongs to the second group, the pulse width is calculated based on the arithmetic expression 2. When the number of the piezoelectric element units 17 belongs to the third group, the pulse width is calculated based on the arithmetic expression 3. P is calculated and each piezoelectric element unit 17 is driven.

As described above, in the ink jet printer according to the third embodiment, the number of the piezoelectric element portions 17 to which the drive voltage is simultaneously applied and driven and the group to which the number belongs are recognized, and the group corresponding to the recognized group is recognized. The pulse width P of the driving voltage is determined by calculation, so that the ink droplets ejected from the nozzle holes 18 can be ejected regardless of the number of the ink chambers 12 that are simultaneously pressurized through the respective piezoelectric elements 17. The speed V can be set to substantially the same ejection speed V. In addition, as the number of simultaneously driven piezoelectric element portions 17 increases, the cavity plate 14 bends and deforms so that the ink present in the ink chamber 12 is apparently deformed. Of the discharge speed V caused by the decrease of the bulk modulus of the character can be eliminated. It is capable of printing.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various improvements and modifications can be made without departing from the gist of the present invention. For example, in each of the above embodiments, the ink chamber 1 is
The ink jet head 5 of the so-called push-in type, which ejects ink droplets by pressurizing the ink jet head 2, has been described as an example. Ejecting drops,
It is apparent that the present invention is also applicable to a so-called pull-down type ink jet head.

[0054]

As described above, in the ink jet printer according to the first aspect, by applying a drive voltage to each piezoelectric body and changing the pressure of the ink chamber, ink droplets are ejected from the nozzles to form characters on paper. At the time of printing, the number of piezoelectric bodies to which the drive voltage is simultaneously applied is recognized, and the storage means is searched based on the recognized number of piezoelectric bodies.
At this time, the number of piezoelectric bodies to which the drive voltage is simultaneously applied and the pulse width of the drive voltage are stored in the storage unit in association with each other, and the number of piezoelectric bodies and the pulse width of the drive voltage are stored between the number of piezoelectric bodies and the pulse width of the drive voltage. Also, a correspondence is provided such that the ink ejection speed of the ink droplet ejected from the nozzle is within a predetermined range even when the number of piezoelectric bodies changes. Then, at the time of searching the storage means, based on the number of piezoelectric bodies recognized through the recognition means, the pulse width of the drive voltage corresponding to the number of piezoelectric bodies is selected and determined, and the drive voltage having the pulse width is used. Each piezoelectric body is driven.

Therefore, according to the ink jet printer of the first aspect, the number of piezoelectric bodies driven by simultaneously applying the driving voltage is recognized, and the pulse width of the driving voltage corresponding to the recognized number of piezoelectric bodies is determined. Is selected and determined, so that the ejection speed of the ink droplets ejected from the nozzles can be made uniform within a predetermined range regardless of the number of ink chambers whose pressure is simultaneously changed via each piezoelectric body. Therefore, printing of characters and the like can be performed with good printing quality.

Further, in the ink jet printer according to the second aspect, the storage means changes and stores the pulse width of the drive voltage every time the number of piezoelectric bodies increases by one. The pulse width of the driving voltage can be precisely controlled according to the number.

Further, in the ink jet printer according to the third aspect, the storage means stores the pulse width of the drive voltage corresponding to each group by dividing the number of piezoelectric bodies into a predetermined number of groups. Since the means specifies the group to which the recognized number of piezoelectric bodies belong, it is sufficient to select the pulse width of the drive voltage corresponding to the group to which the number of piezoelectric bodies recognized and specified by the recognition unit belongs when searching the storage means. Therefore, the pulse width can be easily selected.

Further, in the ink jet printer according to the fourth aspect, when a drive voltage is applied to each piezoelectric body to change the pressure in the ink chamber, ink droplets are ejected from nozzles to print characters or the like on paper. The number of piezoelectric bodies to which the drive voltage is simultaneously applied is recognized, and the group to which the number of piezoelectric bodies belongs is specified while dividing the number of piezoelectric bodies into a predetermined number of groups. The pulse width of the drive voltage is calculated for each group of. At this time,
The calculating means calculates the pulse width of the drive voltage according to a predetermined calculation formula so that the ink discharge speed of the ink droplets discharged from the nozzles is within a predetermined range even when the number of piezoelectric bodies changes. Then, each piezoelectric body is driven by the drive voltage having the pulse width calculated through the calculation means as described above.

Therefore, according to the ink jet printer of the fourth aspect, the number of piezoelectric bodies to which the driving voltage is simultaneously applied and driven is recognized, the group to which the number of piezoelectric bodies belongs is specified, and the recognition and specification are performed. Because the pulse width of the drive voltage is calculated and determined for each group of the number of piezoelectric bodies, the ink ejected from the nozzles regardless of the number of ink chambers whose pressure is simultaneously changed via each piezoelectric body The droplet discharge speed can be made uniform within a predetermined range, and therefore,
Printing of characters and the like can be performed with good printing quality.

As described above, the present invention recognizes the number of piezoelectric bodies driven by simultaneous application of the drive voltage, and determines the pulse width of the drive voltage in accordance with the recognized number of piezoelectric bodies. An ink jet head that can make the ejection speed of ink droplets ejected from the nozzle uniform within a predetermined range regardless of the number of ink chambers that are simultaneously pressurized via each piezoelectric body, thereby providing an ink jet head with good print quality. Provided can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of an ink jet printer.

FIG. 2 is a side sectional view of the inkjet head.

FIG. 3 is a front view of the inkjet head shown without a nozzle plate.

FIG. 4 is a block diagram illustrating a control system of the inkjet printer.

FIG. 5 is an explanatory diagram showing a data table in which the number of piezoelectric elements to which a driving voltage is simultaneously applied and the pulse width of the driving voltage correspond to each other in the ink jet printer of the first embodiment.

FIG. 6 shows that the number of simultaneously driven piezoelectric element units is 10, 20,
7 is a graph showing the relationship between the pulse width P and the ejection speed V of the ink droplet measured while changing the pulse width P of the drive voltage based on the data table for each of 30 pieces.

FIG. 7 is an explanatory diagram schematically showing the contents of a data table stored in a ROM in the ink jet printer of the second embodiment.

FIG. 8 shows a relationship between a pulse width obtained when only one ink chamber is pressurized and an ink ejection speed in a conventional inkjet head, and a pulse width obtained when all ink chambers are pressurized. 6 is a graph showing a relationship between the speed and the ink ejection speed.

[Explanation of symbols]

 5 Ink Head 12 Ink Chamber 13 Ink Manifold 14 Cavity Plate 16 Piezoelectric Plate 17 Piezoelectric Element 18 Nozzle Hole 19 Nozzle Plate 20 CPU 26, 32 Data Table

Claims (4)

[Claims] A cavity plate in which a plurality of ink chambers are formed; a sheet material covering an upper surface of each ink chamber;
A piezoelectric body disposed on a sheet material corresponding to each ink chamber; and a nozzle plate having nozzles formed therein so as to communicate with each ink chamber. In the ink jet printer provided with an ink jet head that prints characters and the like on paper by discharging ink droplets from nozzles by changing the pressure of the nozzle, the number of piezoelectric bodies and the pulse of the drive voltage to which the drive voltage is applied simultaneously Storage means for storing the width in correspondence with each other; and recognition means for recognizing the number of piezoelectric bodies. When a drive voltage is applied to the piezoelectric bodies to change the pressure of the ink chamber, the recognition is performed by the recognition means. An ink jet printer wherein each of the piezoelectric bodies is driven while determining the pulse width of the drive voltage with reference to the storage means based on the number of piezoelectric bodies thus obtained. 2. The ink-jet printer according to claim 1, wherein said storage means changes the pulse width of the drive voltage each time the number of piezoelectric bodies increases by one and stores the drive voltage. 3. The storage unit divides the number of piezoelectric bodies into a predetermined number of groups, and stores a pulse width of a driving voltage corresponding to each of the divided groups, and the recognition unit stores the recognized piezoelectric body. 2. The ink jet printer according to claim 1, wherein a group to which the number belongs is specified. 4. A cavity plate in which a plurality of ink chambers are formed, a sheet material covering an upper surface of each ink chamber,
A piezoelectric body disposed on a sheet material corresponding to each ink chamber; and a nozzle plate having nozzles formed therein so as to communicate with each ink chamber. In an ink jet printer provided with an ink jet head that prints characters and the like on paper by discharging ink droplets from nozzles by changing the pressure of the nozzle, the number of piezoelectric bodies to which the driving voltage is simultaneously applied is recognized, and A recognition unit that divides the number of piezoelectric bodies into a predetermined number of groups and specifies a group to which the number of piezoelectric bodies belongs; and calculates a pulse width of the drive voltage for each group of the number of piezoelectric bodies recognized and specified by the recognition unit. When a drive voltage is applied to the piezoelectric body to change the pressure of the ink chamber, a calculation unit is provided according to the pulse width of the drive voltage calculated through the calculation unit. Jet printer, characterized in that for driving the piezoelectric element.