INK JET RECORDING HEAD

Abstract

An ink jet recording head includes a nozzle array and discharge energy generation elements. The nozzles include discharge ports to discharge liquid when recording, pressure chambers to communicate with respective discharge ports, and liquid flow paths to supply liquid to the respective pressure chambers. The discharge energy generation elements apply discharge energy to the pressure chambers to discharge liquid from the nozzles in a predetermined order during time-division driving. Arranging intervals of the liquid flow paths take at least two different values. When a drive timing difference average between the adjacent discharge energy generation elements is calculated by a particular expression, a relationship of D≧Y is satisfied between an interval D and an interval Y in a k-th discharge energy generation element and a k+1-th discharge energy generation element positioned adjacent to the k-th discharge energy generation element. The intervals D and Y represent distances between particular liquid flow paths.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink jet recording head that discharges liquid such as ink to various media to perform recording.

2. Description of the Related Art

For an ink jet recording system, there are a method of using an electrothermal conversion element (heater) and a method of using a piezoelectric element as discharge energy generation elements used for discharging liquid droplets.

The ink jet recording head that performs recording by using such a system generally includes a plurality of discharge ports arranged in a raw and pressure chambers communicated with the respective discharge ports. Each pressure chamber includes a discharge energy generation element, and a liquid flow path is connected to the pressure chamber to supply liquid. Liquid is supplied from a common liquid chamber through the liquid flow path.

In the ink jet recording head thus configured, when discharge energy is generated to discharge liquid from a certain discharge port, the energy generates pressure waves not only in a discharge direction but also toward the common liquid chamber through the liquid flow path. The pressure wave generated toward the common liquid chamber is transmitted to an adjacent nozzle to vibrate a liquid surface, causing fluctuation of a discharge amount of ink or unstable discharging.

Recently in particular, a higher density of nozzles, simultaneous driving of the plurality of nozzles for an image of a high recording density, and a higher speed of a recording operation have led to a shorter discharging time interval between adjacent nozzles, making an influence of the pressure wave more conspicuous. Herein, such fluid interaction between the adjacent nozzles is referred to as crosstalk.

Generally, for the nozzles of the ink jet recording head, a time-division drive system is employed. In the system, the nozzles are divided into a predetermined number of groups, in which the nozzles are continuous in position. In the group, the divided nozzles are further divided into drive divisions for respective drive timings, and the time-division drive system drives the discharge energy generation elements in the nozzles at different timings for each drive division (drive block). Employing this drive system enables shifting in drive timing between the adjacent nozzles, and thus crosstalk can be reduced.

There has recently been a request for a higher printing speed of an ink jet recording apparatus. Thus, when drive timings are greatly shifted between the adjacent nozzles to reduce crosstalk, achievement of the higher printing speed is hindered. On the other hand, when an interval in drive timing is set short between the adjacent nozzles to achieve the higher printing speed, a reduction in crosstalk is insufficient, thus affecting printing.

To deal with this problem, Japanese Patent Application Laid-Open No. 5-57890 discusses a method of reducing an influence of crosstalk by appropriately setting resistance of a liquid flow path.

However, the method discussed in Japanese Patent Application Laid-Open No. 5-57890 reduces crosstalk by increasing fluid resistance of a specific nozzle. It consequently takes time to resupply ink, hindering achievement of a higher printing speed.

SUMMARY OF THE INVENTION

The present invention is directed to an ink jet recording head capable of reducing an influence of crosstalk that causes unstable discharging without hindering achievement of a higher printing speed.

According to an embodiment, an ink jet recording head includes a nozzle array and discharge energy generation elements. The nozzle array includes nozzles arranged in an array, where the nozzles include discharge ports to discharge liquid when recording, pressure chambers to communicate with respective discharge ports, and liquid flow paths to supply liquid to the respective pressure chambers. The discharge energy generation elements apply discharge energy to the pressure chambers to discharge liquid from the nozzles in a predetermined order during time-division driving. Arranging intervals of the liquid flow paths take at least two different values. When a drive timing difference average X between the adjacent discharge energy generation elements is calculated by the following expression:

$\frac{n_1-n_2+n_2-n_3+n_3-n_4+\dots +n_{N-1}-n_N+n_N-n_{N+1}}{N}=X$

a relationship of D≧Y is satisfied between an interval D and an interval Y in a k-th discharge energy generation element and a k+1-th discharge energy generation element that is adjacent to the k-th discharge energy generation element. In the above expression, N indicates as a quantity that number of divisions for the time-division driving. Here, drive timings of adjacent N discharge energy generation elements are set to n₁ for a first discharge energy generation element, n₂ for a discharge energy generation element adjacent to the first discharge energy generation element, and similarly set for n₃ to n_N, where n=1 to N. In the above relationship, the interval D is a distance between a liquid flow path corresponding to a k-th discharge energy generation element where |n_k−n_k+1|<X is satisfied, and a liquid flow path corresponding to the k+1-th discharge energy generation element. Moreover, the interval Y is a distance between a liquid flow path corresponding to the k-th discharge energy generation element where |n_k−n_k+1|>X is set, and a liquid flow path corresponding to the k+1-th discharge energy generation element.

Further features and aspects of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 is a perspective view of a recording head according to an exemplary embodiment.

FIG. 2 is a sectional view of the recording head taken along the line A-A′ illustrated in FIG. 1.

FIG. 3 illustrates drive timing when the number of time divisions is four according to the exemplary embodiment.

FIG. 4A illustrates a conventional nozzle arrangement when the number of time divisions is four according to the exemplary embodiment. FIG. 4B schematically illustrates a meniscus vibration state of nozzles n3 and n5 caused by discharging of ink from a nozzle n4 in the conventional nozzle arrangement when the number of time divisions is four according to the exemplary embodiment.

FIG. 5A illustrates a nozzle arrangement when the number of time divisions is four according to the exemplary embodiment. FIG. 5B schematically illustrates a meniscus vibration state of nozzles n3 and n5 caused by discharging of ink from a nozzle n4 in the nozzle arrangement when the number of time divisions is four. FIG. 5C schematically illustrates meniscus vibration states of the nozzle n3 in a case where ink is discharged from a nozzle n2 in the nozzle arrangement according to the exemplary embodiment when the number of time division is four, and a case where ink is discharged from a nozzle n4 according to a comparative example.

FIG. 6 illustrates drive timing when the number of time divisions is sixteen according to an exemplary embodiment.

FIG. 7 illustrates a nozzle arrangement when the number of time divisions is sixteen according to the exemplary embodiment.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view of a recording head according to an exemplary embodiment. FIG. 2 is a sectional view of the recording head taken along the line A-A′ illustrated in FIG. 1.

A flow path component 4 and a discharge port plate 8 are provided on a substrate 34. An ink supply chamber 10 is connected to a common liquid chamber 6 and a liquid flow path 7 of a discharge portion illustrated in FIG. 4A via an ink supply port 3 of an opening formed on a surface of the substrate 34.

As illustrated in FIG. 1, on one surface of the substrate 34, electrothermal conversion elements 1, which are discharge energy generation elements operated to discharge ink, and a thin and long rectangular ink supply port 3 are formed. The ink supply port 3 is a long groove-shaped opening formed on the surface of the substrate 34, and corresponds to an opening at an end of the ink supply chamber 10. The ink supply chamber 10 is a through-hole provided toward a surface opposite to the surface of the substrate 34 where the electrothermal conversion elements 1 are formed, and connected to the discharge portion via the ink supply port 3.

The electrothermal conversion elements 1 are laid out in a line on each of both sides of the ink supply port 3 in a longitudinal direction at intervals of 600 dots per inch. The flow path component 4 is provided on one surface of the substrate 34, and the discharge port plate 8 is joined onto the flow path component 4. The discharge port plate 8 includes discharge ports 2 corresponding to the electrothermal conversion elements 1.

The substrate 34 functions as a part of the flow path component 4, and any material can be used as long as the material allows the substrate 34 to function as a support member of a material layer on which a discharge energy generation unit, the discharge ports 2, and a flow path described below are formed. For example, glass, ceramics, plastic, or a metal can be used. In the present exemplary embodiment, a silicon substrate is used for the substrate 34.

As illustrated in FIG. 2, the liquid flow path 7 is formed to guide ink from the ink supply port 3 to a pressure chamber 5 on each electrothermal conversion element 1. In the present exemplary embodiment, the pressure chamber 5 is 30 micrometers square. The discharge port plate 8 includes the discharge port 2 formed as an opening to communicate the pressure chamber 5 with the outside. Ink is discharged from the discharge port 2. Herein, the discharge port 2, the pressure chamber 5, and the liquid flow path 7 constitute a nozzle. In the present exemplary embodiment, similar members are used for the discharge port plate 8 and the flow path component 4. However, similar effects can be obtained even when different members are used.

An embodiment is described below. The recording head according to the present exemplary embodiment is described by way of case where the number of time divisions is sixteen, more specifically a case where ink is discharged by time-division driving for each of drive blocks 1 to 16. First, referring to FIG. 3, FIGS. 4A and 4B, and FIGS. 5A to 5C, a mechanism of suppressing crosstalk when the number of time divisions is four is described.

FIG. 3 illustrates nozzle numbers n1 to n5 for five nozzles, and block numbers indicating drive timings of discharge energy generation elements provided corresponding to the respective nozzles. The drive timing indicates an order of driving. FIG. 3 illustrates, below the table, a difference in drive timing between each nozzle and an adjacent nozzle, the drive timing of the adjacent nozzle having been calculated from a drive timing of the discharge energy generation element of each nozzle.

Time intervals for driving the blocks are set equal, and a difference in driving time between adjacent nozzles is determined based on the intervals (block intervals) and the difference in drive timing. The drive timing is repeated for every four nozzles. In FIG. 3, drive timings of the nozzles n1 and n5 are equal.

FIG. 4A illustrates nozzle front view according to a comparative example. Each nozzle includes the discharge port 2, the pressure chamber 5, and the liquid flow path 7, and has a liquid flow path length of 34 micrometers (length from a center of the discharge port to a common liquid chamber) and a liquid flow path width of 14 micrometers. The nozzle is communicated with the common liquid chamber. The liquid flow paths 7 are arranged at equal intervals with a distance d (42 micrometers) between the liquid flow paths, and the intervals are equal to arranging intervals of the pressure chambers 5. These nozzles are driven at the drive timings illustrated in FIG. 3.

In FIGS. 3 and 4A, focusing on the nozzles n3 to n5, ink is discharged in order of n4, n5 and n3. In the configuration illustrated in FIG. 4A, the nozzles are formed at equal intervals of d. Thus, a pressure wave generated by the ink discharging from the nozzle n4 is transmitted almost equally to the nozzles n3 and n5, generating equal meniscus vibrations.

FIG. 4B illustrates this state. A horizontal axis indicates a period of elapsed time from a start of a discharge operation from the nozzle n4, and a vertical axis indicates meniscus amplitudes of the nozzles n3 and n5. Meniscus amplitude behaviors are similar between the nozzles n3 and n5. A timing of ink discharging from the nozzle n5 is a one-block interval (T) later after discharging from the nozzle n4, and a timing of ink discharging from the nozzle n3 is a two-block interval (2T) later. This difference in discharge timing causes ink to be discharged from the nozzle n5 in a convex meniscus state. On the other hand, in the nozzle n3, the vibration has been sunk down, and ink is discharged in an almost flat meniscus state.

FIG. 5A illustrates nozzle shapes according to the present exemplary embodiment. Drive timings are similar to those illustrated in FIG. 3. In FIG. 5A, intervals of pressure chambers in a nozzle array illustrated in FIG. 5A are substantially equal.

An average drive timing difference X of the four nozzles is calculated from FIG. 3. Herein, the average drive timing difference means an average value of drive timing differences between the adjacent nozzles. In the four nozzles, the average drive timing difference X can be calculated by the following expression:

$\frac{n_1-n_2+n_2-n_3+n_3-n_4+n_4-n_5}{4}=X$

X=2 is acquired from the expression.

Thus, at the drive timings illustrated in FIG. 3, when a timing difference from an adjacent nozzle is larger than 2, a liquid inter-flow-path distance between the adjacent nozzles is approximated to d because a meniscus vibration is small and an influence of crosstalk is small. When a timing difference is smaller than 2, a liquid inter-flow-path distance between the adjacent nozzles is set large from d because a meniscus vibration is relatively large and an influence of crosstalk is large.

When a timing difference from an adjacent nozzle is equal to 2, a liquid inter-flow-path distance between the adjacent nozzles is set equal to d. FIG. 5A illustrates liquid flow paths arranged under such conditions. In FIG. 5A, only a distance between the liquid flow paths is changed while a length and a width of the liquid flow path are not changed at each nozzle.

Focusing on the nozzles n3, n4, and n5, in FIG. 5A, a liquid inter-flow-path distance d between the nozzles n3 and n4 is not changed, while a liquid inter-flow-path distance D (50 micrometers) between the nozzles n4 and n5 is larger than the distance d. As illustrated in FIG. 5B, when ink is discharged from the nozzle n4, a meniscus amplitude in the nozzle n3 is not different from that of the comparative example. However, in the nozzle n5, because of the far liquid inter-flow-path distance, a meniscus amplitude is smaller and a vibration cycle is shorter.

A period of time from discharging from the nozzle n4 to discharging from the nozzle n5 is equal to that of the conventional case. However, since the meniscus vibration has been suppressed, ink can be discharged in a near flat meniscus state of both of the nozzles n3 and n5. Thus, the ink can be discharged in a reduced state of a crosstalk influence.

On the other hand, at the nozzles n2 and n3, an inter-flow-path distance is smaller than the distance d. Thus, as illustrated in FIG. 5C, when ink is discharged from the nozzle n2, a meniscus amplitude in the nozzle n3 is larger than the distance d, and a vibration cycle is longer. However, since a discharge timing from the nozzle n3 is a three-block interval (3T) after the discharging from the nozzle n2, a meniscus vibration is suppressed over time, and the ink is discharged in a near flat meniscus state.

Thus, in the liquid flow path arrangement of the equal intervals according to the comparative example, there is fluctuation of ink discharging in the array of nozzles. For example, ink is discharged from one nozzle in an unsuppressed meniscus vibration state, while ink is discharged from another nozzle in a sufficiently suppressed meniscus vibration state. As a result, especially crosstalk between nozzles where discharge timings are close causes unstable discharging.

However, employing the liquid flow path arrangement suitable for the drive timings according to the present exemplary embodiment enables a stable operation.

FIGS. 6 and 7 illustrate drive timings and a liquid flow path arrangement respectively when the number of time divisions is sixteen. FIG. 6 illustrates drive timings of discharge energy generation elements of seventeen adjacent nozzles n1 to n17. An average drive timing difference X of the sixteen nozzles in FIG. 6 is calculated by the following expression:

$\frac{n_1-n_2+n_2-n_3+n_3-n_4+\dots +n_{15}-n_{16}+n_{16}-n_{17}}{16}=X$

The average driving timing difference X=7.5 is acquired.

Thus, in FIG. 6, when a drive timing difference between discharge energy generation elements of the adjacent nozzles is larger than 7.5, a liquid inter-flow-path distance between the adjacent nozzles is set shorter. When the drive timing difference is smaller than 7.5, liquid inter-flow-path distances between the adjacent nozzles are set farther to each other. FIG. 7 illustrates this flow path arrangement. Only the liquid inter-flow-path distance is changed while a length and a width of a liquid flow path are not changed at each nozzle.

As in the aforementioned case, focusing on the nozzles n5 to n7, in the nozzles n5 and n6 where discharge timings are close, liquid inter-flow-path distances are set far from each other to reduce the influence of crosstalk. In the nozzles n6 and n7 where discharge timings are sufficiently shifted, liquid inter-flow-path distance is set close to each other. As a result, the influence of crosstalk can be reduced at the entire nozzles, thus realizing a stable operation.

A change amount of the liquid inter-flow-path distance can be set, in view of flow resistances of the nozzles and ink physical properties, to enable a stable operation at the entire nozzles. Basically, whether to set the inter-flow-path distance close to or far from each other is determined based on an average value of discharge timings or a discharge timing difference between the adjacent nozzles.

In the present exemplary embodiment, all the liquid inter-flow-path distances corresponding to the case where the drive timing difference from the adjacent discharge energy generation element is larger than the average value X are set close to one another, while all the liquid inter-flow-path distances corresponding to the case where the drive timing difference is smaller than the average value X are set far from one another. However, all the liquid inter-flow-path distances may not be set close to or far from one another. Setting far from one another the liquid inter-flow-path distances corresponding to the case where the drive timing difference from the adjacent discharge energy generation element is smaller than the average value X enables reduction of crosstalk between the adjacent nozzles corresponding to the liquid flow paths thereof.

It is desirable to set the drive timing difference of at least the adjacent discharge energy generation element to be separated farther than the liquid inter-flow-path distance of the nozzles corresponding to a minimum discharge energy generation element in the nozzle array.

A value A smaller than the average drive timing X can be set. Liquid inter-flow-path distances corresponding to a case where a drive timing difference is smaller than X−A can be set far from each other, liquid inter-flow-path distances corresponding to a case where a drive timing difference is larger than X+A can be set close to each other, and all liquid inter-flow-path distances corresponding to a case where a discharge energy generation element of drive timing difference X±A, can be set equal.

The present exemplary embodiment is applied to the ink jet recording head where the liquid flow paths of nozzles in the same drive section are equal in length, width, and flow resistance. However, the present invention can be applied to an ink jet recording head where such factors are different. When necessary, a noise filter can be provided.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures, and functions.

This application claims priority from Japanese Patent Application No. 2010-025866 filed Feb. 8, 2010, which is hereby incorporated by reference herein in its entirety.

Claims

1. An ink jet recording head, comprising: a nozzle array including nozzles arranged in an array, the nozzles including discharge ports to discharge liquid when recording, pressure chambers configured to communicate with respective discharge ports, and liquid flow paths configured to supply liquid to the respective pressure chambers; anddischarge energy generation elements configured to apply discharge energy to the pressure chambers to discharge liquid from the nozzles in a predetermined order during time-division driving,wherein arranging intervals of the liquid flow paths take at least two different values, andwherein, when a drive timing difference average X between the adjacent discharge energy generation elements is calculated by the following expression:

2. The ink jet recording head according to claim 1, wherein, when a value A is smaller than the drive timing difference average X of the discharge energy generation elements, relationships of D1≧D2≧Y2≧Y1, D1>Y2, and D2>Y1 are satisfied among (i) an interval D1 between a liquid flow path corresponding to the k-th discharge energy generation element where |nk−nk+|<X−A<X is satisfied and the liquid flow path corresponding to the k+1-th discharge energy generation element, (ii) an interval D2 between a liquid flow path corresponding to the k-th discharge energy generation element where X−A<|nk−nk+1|<X is satisfied and the liquid flow path corresponding to the k+1-th discharge energy generation element, (iii) an interval Y1 between the liquid flow path corresponding to a k-th discharge energy generation element where |nk−nk+1|>X+A>X is satisfied and the liquid flow path corresponding to the k+1-th discharge energy generation element, and (iv) an interval Y2 between a liquid flow path corresponding to the k-th discharge energy generation element where X+A>|nk−nk+1|>X is satisfied and the liquid flow path corresponding to the k+1-th discharge energy generation element.

3. The ink jet recording head according to claim 1, wherein intervals of the pressure chambers in the nozzle array are equal.