JP2001138551A - Ink jet recorder and method for setting actuator drive signal of recording head in ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder in which the effect of nonlinear characteristics of the actuator in a recording head is suppressed. SOLUTION: A drive signal generating circuit 9 for supplying a drive signal to the piezoelectric oscillator 25 of a recording head 8 is mounted on a printer controller 1. The drive signal generating circuit 9 is arranged such that potential information is supplied from a potential information storage means 12 and the middle potential (VC) of a drive signal being inputted to the piezoelectric oscillator 25 is set based on the potential information stored in the potential information storage means. The middle potential is set in a range insusceptible to the effect of nonlinear characteristics of the piezoelectric oscillator 25 thus providing a recorder ensuring a best image quality stably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention includes a piezoelectric vibrator for expanding and contracting a pressure chamber communicating with a nozzle opening, and selectively supplies a driving signal to the piezoelectric vibrator to thereby supply ink from the nozzle opening. The present invention relates to an ink jet type recording apparatus having a recording head for discharging droplets, and a method for setting an actuator drive signal of a recording head in the apparatus.

[0002]

2. Description of the Related Art Ink jet recording apparatuses have been used in many types of printing including color printing in recent years, since noise at the time of printing is relatively small and small dots can be formed at a high density. Such an ink jet recording apparatus is provided with a large number of nozzle openings formed in a row and receives ink supplied from an ink cartridge, and in a main scanning direction (width direction of recording paper). A recording head mounted on a carriage that moves the recording paper in a sub-scanning direction that is orthogonal to the main scanning direction. The image is recorded.

The recording head is provided with a pressure chamber communicating with a nozzle opening and an actuator for expanding and contracting the pressure chamber to change the ink pressure in the pressure chamber, for example, a piezoelectric vibrator. . Such a recording head is configured such that a series of drive signals are supplied to the piezo piezoelectric vibrator to change the ink pressure, whereby an ink droplet can be ejected from a nozzle opening.

For example, print control data sent from a host computer is developed into bitmap data in a pudding controller, and a drive signal is sent to the piezoelectric vibrators arranged in each pressure chamber based on the bitmap data. Is controlled, whereby a predetermined image is printed.

[0005]

Incidentally, in an actuator represented by the above-described piezoelectric piezoelectric vibrator, a mechanical displacement with respect to a drive voltage applied thereto has a non-linear property. For example, FIGS. 8A and 8B show examples of such a case, in which the horizontal axis shows the drive voltage level and the vertical axis shows the mechanical displacement of the actuator.

Generally, most of the piezo elements are, for example, shown in FIG.
As shown in FIG. 3A, the characteristic has a characteristic that the increase in the displacement amount decreases as the drive voltage increases. In some cases, as shown in FIG. 8B, the displacement amount is small when the drive voltage level is low, and the displacement amount sharply increases as the drive voltage level increases. .

As can be understood from these various nonlinear characteristics, even if the drive voltage levels are adjusted, the mechanical displacement of the actuator according to the drive voltage level individually fluctuates. There is a problem that the amount of ink ejected from the unit varies.
This will remain in the product as variations, and even if such variations exist, they are currently kept at an acceptable level.

On the other hand, in this type of ink jet recording apparatus, a technique for ejecting ink droplets of different sizes from the same nozzle opening has been proposed in order to satisfy the opposing requirements of improving image quality and recording speed. I have. For example,
From a series of drive signals formed by connecting a plurality of waveform elements, a necessary waveform element is appropriately selected by a switch means, and the selected waveform element is supplied to the piezoelectric vibrator, whereby a plurality of types of weights having different weights are provided. Ink droplets, for example, ink droplets that form large dots, medium dots, and small dots on the paper surface are selectively ejected. Thus, high-quality multi-tone printing can be realized.

In order to realize such multi-tone printing, a necessary waveform element is appropriately selected by a switch means from a series of drive signals formed by connecting a plurality of waveform elements as described above. Therefore, it is necessary to adjust the terminal potential of the previous drive signal and the start potential applied next to the same level.

That is, an actuator typified by the piezo piezoelectric vibrator generally has the characteristics of a capacitor, and therefore holds the terminal potential of the previous drive signal as a segment voltage. Therefore, when the level of the starting potential applied next does not match the ending potential of the previous drive signal, the segment potential of the piezoelectric vibrator fluctuates instantaneously. Deformation occurs, causing a problem that ink droplets are erroneously ejected.

In addition, a large current exceeding a predetermined value flows through the piezoelectric vibrator, and sometimes the function of the piezoelectric vibrator is deteriorated by the large current, and in extreme cases, the piezoelectric vibrator may be destroyed. I can do it.

Therefore, in the case of realizing the multi-tone printing as described above, in order to adjust the terminal potential of the previous drive signal and the start potential applied next to the same level, for example, an intermediate potential of the drive signal is used. Means for managing the potential VC and controlling the intermediate potential VC to be always constant is adopted.

However, as described above, the non-linear characteristic of the actuator in the case of realizing the multi-tone expression for forming large dots, medium dots, and small dots on the paper surface is as follows. This has the problem of affecting the characteristics, making it difficult to accurately control the size of dots required in multi-tone expression, and making it difficult to always stably obtain the best image quality.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and it is possible to suppress a change in image quality caused by a non-linear characteristic of an actuator, and to always obtain the best image quality stably. It is an object of the present invention to provide an ink jet recording apparatus.

It is another object of the present invention to provide a management technique for setting a drive signal to be applied to an actuator of a printhead in order to stably obtain the best image quality in each printing apparatus. Is what you do.

[0016]

In order to achieve the above object, an ink jet recording apparatus according to the present invention has a recording head provided with an actuator for expanding and contracting a pressure chamber communicating with a nozzle opening. And a drive signal generating means for generating a drive signal for driving the actuator; and a drive signal obtained by the drive signal generating means being supplied to the actuator, thereby deforming the actuator and causing ink droplets to flow from the nozzle openings. And a drive signal supply unit for ejecting ink droplets, wherein the drive signal generated by the drive signal generation unit includes a plurality of waveform elements for ejecting ink droplets. A switch for inputting any one or more of the waveform elements to the actuator. Switch means and potential information storage means for providing potential information to the drive signal generation means, wherein the intermediate potential in the drive signal input to the actuator is stored in the potential information stored in the potential information storage means. It is configured to be set based on.

In this case, it is preferable that a series of drive signals formed by connecting a plurality of waveform elements for ejecting ink droplets of different weights are generated by the drive signal generation means, and a starting point of each of the waveform elements is generated. The potential and the termination potential are controlled so as to be substantially the same level of the intermediate potential.

Further, it is desirable that the potential information storage means is constituted by a rewritable nonvolatile memory. Preferably, the apparatus further comprises temperature information acquisition means for acquiring temperature information around the recording head,
The output level of the drive signal generated by the drive signal generation means is controlled based on the temperature information obtained by the temperature information acquisition means.

In any of the above configurations, the actuator can be suitably used in a recording apparatus using a recording head composed of a piezoelectric piezoelectric vibrator as the actuator. Further, in a preferred embodiment, the potential information storage means for storing the information on the intermediate potential is arranged in a printer controller.
On the other hand, a method for setting an actuator drive signal of a recording head in an ink jet recording apparatus according to the present invention includes a displacement characteristic measuring step of measuring a displacement characteristic of an actuator in a recording head mounted on each recording apparatus;
A grouping step of defining individual recording devices into any group according to the displacement characteristics of the actuator; an intermediate potential setting step of setting an optimal intermediate potential for each group according to each group; And a storage step of storing information of the intermediate potential selected in the intermediate potential selection step in the potential information storage means.

In this case, in the displacement characteristic measuring step, the drive signal level is measured so that the ink weight of one dot becomes a predetermined value, and the displacement characteristic of the actuator is obtained according to the drive signal level. You. In the above-described drive signal setting method, the number of the groups may be set to one.

According to the ink jet recording apparatus configured as described above, the potential information is given from the potential information storage means to the drive signal generation means, and the intermediate potential in the drive signal generated by the drive signal generation means is: It is set based on the potential information stored in the potential information storage means.

Therefore, in each recording device, a drive waveform having an intermediate potential specified by the potential information set in the potential information storage means is generated. As a result, it is possible to suppress the influence of the nonlinear characteristic due to the vertical movement of the entire drive waveform.

On the other hand, in the recording apparatus having the above-described configuration, it is preferable to employ the above-described method of setting the actuator drive signal, and measure the displacement characteristics of the actuator in the recording head mounted on each recording apparatus.
According to the displacement characteristics of the actuator, it is possible to set an intermediate potential that is hardly affected by the nonlinear characteristics.

Accordingly, there is provided a recording apparatus which can accurately realize dot size control required particularly in multi-gradation expression and can always stably obtain the best image quality.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an ink jet recording apparatus according to the present invention will be described based on an embodiment shown in the drawings. FIG. 1 is a block diagram showing the overall configuration of the recording apparatus. This ink jet recording apparatus is roughly divided into a printer controller 1 and a print engine 2.

The printer controller 1 includes an interface 3 for receiving print data and the like from a host computer (not shown) and a RAM for storing various data.
4, a ROM 5 storing control routines and the like for various data processing, a control unit 6 including a CPU, etc., an oscillation circuit 7, and a drive signal generation for generating a drive signal to be supplied to a recording head 8 described later. A circuit 9, an interface 10 for transmitting print data, drive signals, and the like developed into dot pattern data (bitmap data) to the print engine 2, and a sensor for acquiring temperature information around a recording head described later. A / D conversion circuit 11 that converts the detection signal into digital data and outputs the digital data to the control unit 6, and supplies potential information to the drive signal generation circuit 9, and the drive output from the drive signal generation circuit 9 Potential information storage means 12 for setting an intermediate potential of a signal. Note that the drive signal generation circuit 9 and the control section 6 constitute a drive signal generation means in the present invention.

The interface 3 receives, for example, any one of character code, graphic function, and image data or print data including a plurality of data from a host computer or the like. The interface 3 is busy (BU) to the host computer.
SY) signal or acknowledge (ACK) signal.

The RAM 4 is used as a reception buffer 4a, an intermediate buffer 4b, an output buffer 4c, a work memory (not shown), and the like. Receive buffer 4
In a, print data from the host computer received by the interface 3 is temporarily stored. The intermediate buffer 4b stores the intermediate code data converted into the intermediate code by the control unit 6. Further, dot pattern data is developed on the output buffer 4c as described later.

The ROM 5 stores various control routines, font data, graphic functions, and the like executed by the control unit 6 as described above. The control unit 6 has a function of reading the print data in the reception buffer 4a, converting the print data into an intermediate code, and storing the converted intermediate code data in the intermediate buffer 4b. The control unit 6 has a function of expanding the intermediate code data read from the intermediate buffer 4b into dot pattern data with reference to font data and graphic functions in the ROM 5. The developed dot pattern data is stored in the output buffer 4c after necessary decoration processing is performed.

When dot pattern data corresponding to one line of printing by the recording head 8 is obtained,
The dot pattern data for the line is
Is transmitted serially to the recording head 8 via the. When one line of dot pattern data is output from the output buffer 4c, the contents of the intermediate buffer 4b are erased, and the development for the next intermediate code is performed. Here, the print data developed into the dot pattern data is composed of, for example, 4 bits as gradation data for each nozzle as described later.

Further, the control unit 6 refers to a data table stored in the ROM 5 based on the sensor output (temperature information around the recording head) output from the A / D conversion circuit 11, and generates the drive signal. It is configured to control the output level of the drive signal generated by the means 9.

On the other hand, the print engine 2 comprises a recording head 8, a paper feed mechanism 14, and a carriage mechanism 15. The paper feed mechanism 14 includes a paper feed motor, a paper feed roller, and the like, and acts to sequentially feed the recording paper. That is, the paper feed mechanism 14 performs the sub-scan in the recording operation. Further, the carriage mechanism 15 includes a carriage on which the recording head 8 is mounted, a pulse motor for moving the carriage via a timing belt, and the like. The carriage mechanism 15 performs main scanning in a printing operation.

The recording head 8 is, for example, 64
It has a number of nozzle openings 16 (see FIG. 2), and functions to discharge ink supplied from an ink cartridge (not shown) from each nozzle opening 16 as ink droplets.

The print data developed into the dot pattern data is transmitted to the shift register 2 through the interface 10 in synchronization with the clock signal (CK) from the oscillation circuit 7.
1 is serially transmitted. The serially transferred print data (SI) is temporarily latched by the latch circuit 22. The latched print data is boosted by a level shifter 23 as a voltage amplifier to a voltage at which a switch circuit 24 as a switch unit can be driven, and the boosted switching signal is supplied to the switch circuit 24. I have.

A drive signal (COM) from the drive signal generation circuit 9 is input to the input side of the switch circuit 24, and a piezoelectric vibrator 25 composed of a piezo element is connected to the output side of the switch circuit 24. ing.

The print data described above is transmitted to the switch circuit 24.
Control the operation of. For example, during a period in which the print data applied to the switch circuit 24 is “1”, a drive signal is supplied to the piezoelectric vibrator 25, and the piezoelectric vibrator 25 is deformed according to the drive signal. On the other hand, while the print data applied to the switch circuit 24 is “0”, the supply of the drive signal to the piezoelectric vibrator 25 is cut off. With the deformation of the piezoelectric vibrator 25, ink droplets are ejected from the nozzle openings 16.

The recording head 8 is provided with a temperature sensor 26 as temperature information acquiring means, and a detection signal from the temperature sensor 26 is A / A as described above.
The driving signal generating means 9
Is configured to control the output level (VH) of the drive signal generated by the controller. Thereby, the change in the viscosity of the ink based on the temperature change is corrected, and the weight of each ink droplet when performing multi-tone printing as described below is suppressed from being dependent on the environmental temperature. .

Next, a specific structure of the recording head 8 will be described with reference to a sectional view shown in FIG. The recording head 8 illustrated in FIG. 2 is a recording head to which a piezoelectric vibrator 25 in a flexural vibration mode is attached. The recording head 8 is formed on the actuator unit 32 in which the pressure chamber 31 is formed, the flow path unit 33 joined to the front surface of the actuator unit 32, and the rear surface of the actuator unit 32 corresponding to the pressure chamber 31. A piezoelectric vibrator 25.

The actuator unit 32 includes the pressure chamber 3
1, a cover member 35 joined to the front surface of the pressure chamber forming substrate 34, and a back side opening surface of the pressure chamber 31 joined to the back surface of the pressure chamber forming substrate 34. And a vibration plate 36. Diaphragm 36
Is made of, for example, a thin ceramic plate having elasticity. The lid member 35 has a first ink flow path 37 and a second ink flow path 38 communicating with the pressure chamber 31.

The flow path unit 33 includes the ink chamber forming substrate 4
0, a nozzle plate 41 joined to the front surface of the ink chamber forming substrate 40, and a supply port forming plate 42 joined to the back surface of the ink chamber forming substrate 40.

The ink chamber forming substrate 40 has a common ink chamber 4
3 and a nozzle communication port 44 are formed, and a large number of nozzle openings 16 are formed in the nozzle plate 41 in a state of being arranged in a row. And each nozzle opening 1
Numerals 6 communicate with corresponding nozzle communication ports 44, respectively. The supply port forming plate 42 has a common ink chamber 43.
An ink supply port 45 is formed which communicates with the first ink channel 37, and a communication port 46 which communicates with the nozzle communication port 44 and the second ink channel 38 is formed.

In the recording head 8 having the above-described structure, the ink supply port 45, the first ink flow path 37, the pressure chamber 31, the second ink flow path 38,
A series of ink flow paths reaching the nozzle opening 16 through the communication port 46 and the nozzle communication port 44 is formed.

The piezoelectric vibrator 25 is disposed on the back side of the pressure chamber 31 with the vibration plate 36 interposed therebetween. This piezoelectric vibrator 2
5, a lower electrode 50 is formed on the front surface, and an upper electrode 51 is formed on the back surface so as to cover the piezoelectric vibrator 25.

At both ends of the actuator unit 32, connection terminals 52 whose base ends are electrically connected to the upper electrode 51 of each piezoelectric vibrator 25 are provided. A flexible circuit board 53 is joined to the distal end surface of the connection terminal 52, and a drive signal is supplied to the piezoelectric vibrator 25 via the connection terminal 52 and the upper electrode 51.

In the recording head 8 configured as described above, when a driving signal described later is supplied, a potential difference occurs between the upper electrode 51 and the lower electrode 50. Due to this potential difference, the piezoelectric vibrator 25 contracts, for example, in a direction orthogonal to the electric field, and the piezoelectric vibrator 25 and the vibration plate 36 bend so as to protrude toward the pressure chamber 31 to contract the pressure chamber 31.

When ejecting ink droplets from the nozzle openings 16, for example, the pressure chamber 31 is rapidly contracted. That is, when the pressure chamber 31 is suddenly contracted, the ink pressure in the pressure chamber 31 increases, and an ink droplet is ejected from the nozzle opening 16 with the increase in the pressure. After ejection of the ink droplets, the upper electrode 51 and the lower electrode 50
Is eliminated, the piezoelectric vibrator 25 and the diaphragm 36 return to the original state. Thereby, the inside of the contracted pressure chamber 31 expands, and the pressure chamber 31 passes from the common ink chamber 43 through the ink supply port 45 and the first ink flow path 37.
Is supplied with ink.

Next, the electrical configuration of the recording head will be described. As shown in FIG. 1, the recording head 8 includes a shift register 21, a latch circuit 22, and a level shifter 2.
3, a switch circuit 24, a piezoelectric vibrator 25, and the like. More specifically, as shown in FIG. 3, these shift register 21, latch circuit 22, level shifter 23, switch circuit 24, and piezoelectric vibrator 25
The shift registers 21a to 21n and the latch circuits 22a to 21n correspond to the nozzle openings 16, respectively.
22n, level shifters 23a to 23n, switch circuit 2
4a to 24n and piezoelectric vibrators 25a to 25n.

In this embodiment, the print data is
As described later, like "1010", "0100", etc.
Each nozzle is composed of a total of 4-bit data from the most significant bit 3 to the least significant bit 0.

Then, in synchronization with the clock signal (CK) from the oscillation circuit 7, the print data (SI) constituting the dot pattern data is serially transmitted from the output buffer 4c and sequentially set in each of the shift registers 21a to 21n. You. In this case, first, the data of the most significant bit in the print data of all the nozzle openings 16 is serially transmitted, and when the serial transmission of the data of the most significant bit is completed, the data of the second most significant bit is serially transmitted. . Similarly, the data of the lower bits are sequentially transmitted in a serial manner.

Then, each shift register 2 has a print data of the bit corresponding to all the nozzle openings 16.
When set to 1a to 21n, the control unit 6 outputs a latch signal (LAT) to each of the latch circuits 22a to 22n at a predetermined timing. With this latch signal, each of the latch circuits 22a to 22n latches the print data set in each of the shift registers 21a to 21n.

The print data latched by each of the latch circuits 22a to 22n is stored in the corresponding level shifter 2
3a to 23n. This level shifter 23a-
In 23n, when the print data is, for example, "1", a voltage value at which the switch circuits 24a to 24n can be driven, for example,
This print data is boosted to several tens of volts. The boosted print data is supplied as switching signals to switch circuits 24a to 24n functioning as analog switches, and the switch circuits 24a to 24n to which print data "1" is supplied are connected (ON) by the print data. State.

Each of the switch circuits 24a to 24n has a drive signal (C) supplied from the drive signal generation circuit 9.
OM) is also input, and the switch circuits 24a to 24n
Are turned on, the piezoelectric vibrators 25a to 25n connected to the switch circuits 24a to 24n are turned on.
n is supplied with a drive signal.

As described above, in the recording head 8, whether or not a drive signal is input to each of the piezoelectric vibrators 25a to 25n can be controlled by the print data. For example, when the print data is "1", the corresponding switch circuits 24a to 24n are turned on, so that the drive signal is supplied to the corresponding piezoelectric vibrators 25a to 25n. Then, the piezoelectric vibrator 2 is driven by this drive signal.
5a to 25n are deformed.

When the print data is "0", the corresponding switch circuits 24a to 24n
Are disconnected (off), and the piezoelectric vibrators 25a to 25
The supply of the drive signal to n is cut off.

Next, a drive signal supplied to the recording head,
An example of a method of expressing the ink droplets ejected and the gradation will be described with reference to FIG. FIG. 4 shows the waveforms of the drive signals and the method of controlling the gradation expression based on the application timing of each of these waveforms. Drive signal generation circuit 9
The generated drive signal includes a first pulse including a waveform element as a first drive signal, a second pulse including a waveform element as a second drive signal, and a waveform as a third drive signal. It is composed of a third pulse including an element and a fourth pulse including a waveform element as a fourth drive signal.

Here, the first pulse and the third pulse have the same pulse shape, for example, for ejecting a medium ink droplet of 10 ng. The second pulse is located between the first pulse and the third pulse, and is for discharging a small ink droplet of, for example, 2 ng. The fourth pulse positioned between the third pulse and the first pulse is for applying a slight vibration to the ink near the nozzle opening 16 to prevent the ink viscosity from increasing. Some ink droplets are not ejected.

The voltage of the first pulse shown in FIG. 4 starts from the intermediate potential VC (P11), drops from the intermediate potential VC to the first minimum potential VLM with a predetermined voltage gradient θDM (P12), The minimum potential VLM is maintained for a predetermined time (P13). Next, the voltage value of the first pulse is the lowest potential VLM.
To a maximum potential VH with a predetermined voltage gradient θCM (P14).

The voltage gradient θCM during charging is set to be larger than the voltage gradient θDM during discharging. The time required for the voltage value of the first pulse to rise from the lowest potential VLM to the highest potential VH is set substantially equal to the natural oscillation period TA of the piezoelectric vibrator 17. Note that the lowest potential VLM is preferably the same as the reference potential (0 V) or a positive potential in order to prevent the polarization reversal of the piezoelectric vibrator 17.

The first pulse voltage value is the highest potential VH
Is held for a predetermined time (P15), and then falls again to the intermediate potential VC (P16). Here, the time from the start of the voltage rise from the lowest potential VLM to the end of the maintenance of the highest potential VH is set to be substantially the same as the natural cycle (Helmholtz cycle) of the ink.

Subsequently, the voltage value of the second pulse starts from the intermediate potential VC as in the case of the first pulse (P21), and falls to the second lowest potential VLS with a predetermined voltage gradient θDS (P22). The potential level of the lowest potential VLS of the second pulse is set higher than the lowest potential VLM of the first pulse. Then, after the voltage value of the second pulse is maintained at the lowest potential VLS for a predetermined time (P23),
The voltage rises to the intermediate potential VC with a predetermined voltage gradient θCS (P24). In the second pulse, the voltage gradient θDS at the time of discharging is set to be larger than the voltage gradient θCS at the time of charging.

The third pulse has the same waveform as the first pulse as described above, and the description thereof is omitted. However, the total time of the first pulse and the third pulse is half the printing cycle. That is, when the first pulse and the third pulse are selected to form a large dot on a recording sheet, ink droplets corresponding to medium dots are ejected at regular intervals in time. Specifically, for example, the printing cycle is set to 14.4 kHz.
Then, the ejection cycle of the ink droplet corresponding to the medium dot is 28.
It is set to 8 kHz. Therefore, the total time of the first pulse and the third pulse is set to the maximum driving cycle of the recording head 8.

The voltage of the fourth pulse also starts from the intermediate potential VC in the same manner as in the first to third pulses (P41).
(P42). Then, after maintaining this minimum potential VLN for a predetermined time (P43), it rises to the intermediate potential VC. Here, since the fourth pulse gives a minute vibration that does not eject ink droplets,
The lowest potential VLN of the fourth pulse is set to a level closer to the intermediate potential VC than the lowest potential VLS of the second pulse. Further, the voltage gradient at the time of discharging by the fourth pulse and the voltage gradient at the time of charging are set to be substantially equal.

Next, the first pulse (medium dot), the second pulse (small dot), the third pulse (medium dot),
A method of selecting one or a plurality of pulses (micro vibrations) to express multiple gradations will be described with reference to FIGS.

As described above, each shift register 21a
21 to 21n, via the latch circuits 22a to 22n, etc., while the bit of the print data applied to the switch circuits 24a to 24n is "1", the driving signal is applied to the piezoelectric vibrators 25a to 2n.
5n, the piezoelectric vibrators 25a to 25n expand and contract according to the waveform of the drive signal. On the other hand, while the bit of the print data is "0", the supply of the drive signal to the piezoelectric vibrators 25a to 25n is cut off.

Therefore, as shown in FIG. 4, in accordance with the generation timing of a series of drive signals repeatedly generated,
By setting the bit of the print data to “1” or “0”, one or more of the first to fourth pulses can be selected. For example,
When no dots are not formed (gradation value 1), when only small dots are formed (gradation value 2), when only one medium dot is formed (gradation value 3), two middle dots are formed. If dots are formed on recording paper in four patterns of large dots formed by dots (gradation value 4), four levels of dot gradation can be obtained.

In the case of four gradations as described above, FIG.
As shown in the figure, the gradation value 1 is "00" and the gradation value 2 is "0".
Each gradation value can be represented by 2-bit data, such as "1", gradation value 3 "10", and gradation value 4 "11".

Non-dot dot gradation value 1 that does not eject ink droplets
In the case of (4), the fourth pulse for generating only a slight vibration may be supplied to the piezoelectric vibrators 25a to 25n as shown by the circles in FIG. Therefore, when the gradation value is 1, "0" is applied to the switch circuits 24a to 24n during the generation periods of the first to third pulses, while "1" is synchronized with the generation timing of the fourth pulse. Is applied, only the fourth pulse can be applied to the piezoelectric vibrators 25a to 25n.

That is, by translating (decoding) 2-bit data “00” indicating a gradation value 1 into 4-bit data “0001”, only the fourth pulse that does not eject ink droplets is output to the piezoelectric vibrators 25a to 25n. , Thereby realizing a dot value of 1 without dots.

Similarly, "0" is given to the switch circuits 24a to 24n during the generation period of the first pulse, the third pulse, and the fourth pulse, and similarly, the generation of the second pulse If "1" is applied in synchronization with the timing, only the second pulse is supplied to the piezoelectric vibrators 25a to 25n. Similarly, by translating 2-bit data “01” indicating the gradation value 2 into 4-bit data “0100”, only the second pulse for forming a small dot is applied to the piezoelectric vibrators 25a to 25n. Thus, the gradation value 1 of the small dot can be realized.

Similarly, by translating 2-bit data "10" indicating the gradation value 3 into 4-bit data "1000" and supplying this to the switch circuits 24a to 24n, only the first pulse is applied to the piezoelectric vibrator 25a. To 25n, one medium dot is formed on the recording paper, and a gradation value of 3 is realized.

Further, by translating 2-bit data "11" indicating the gradation value 4 into 4-bit data "1010" and supplying the same to the switch circuits 24a to 24n, the first pulse for forming the medium dot and the first pulse are outputted. Only three pulses are applied to the piezoelectric vibrators 25a to 25n. As a result, it is possible to realize a gradation value of 4 in which ink droplets corresponding to medium dots are ejected twice successively on the recording paper, and the respective inks are mixed to form substantially one large dot on the paper surface. it can.

FIGS. 5 and 6 show one or more of the first pulse (medium dot), the second pulse (small dot), the third pulse (medium dot), and the fourth pulse (fine vibration) as described above. FIG. 9 shows the application timing of the drive signal applied to one actuator in the case of expressing multiple gradations.

First, FIG. 5A shows a case where a large dot is formed on the paper surface by discharging the first pulse and the third pulse twice in one cycle of printing. As described above, in this case, the switch circuits 24a to 24a
n is turned on.

Then, as shown in FIG. 5A, in the generation period of the second pulse and the generation period of the fourth pulse,
The switch circuits 24a to 24n are turned off, and each pulse signal as a drive signal for the recording head is not selected.

Next, FIG. 5B shows a case where the first pulse is ejected once in one cycle of printing to form a medium dot on the paper surface. In this case, at the generation timing of the first pulse, the switch circuits 24a to 24a-2
4n is turned on. Then, in the generation period of the second pulse, the third pulse, and the fourth pulse, the switch circuits 24a to 24n are turned off, and each pulse signal as the drive signal of the recording head is not selected.

FIG. 6A shows the second cycle in one cycle of printing.
A case is shown in which a pulse is ejected once to form a small dot on the paper surface. In this case, at the generation timing of the second pulse, the switch circuits 24a to 24n
Is turned on. Then, in the generation period of the first pulse, the third pulse, and the fourth pulse, the switch circuits 24a to 24n are turned off, and each pulse signal as a drive signal of the recording head is not selected.

FIG. 6B shows a case where the fourth pulse is applied in one cycle of printing to apply a slight vibration to the ink near the nozzle opening of the recording head. In this case, at the generation timing of the fourth pulse,
The switch circuits 24a to 24n are turned on. Then, in the generation period of the first pulse, the second pulse, and the third pulse, the switch circuits 24a to 24n are turned off, and each pulse signal as the drive signal of the recording head is not selected.

In this embodiment, FIG.
As shown in FIG. 6B and FIGS. 6A and 6B, the starting potential and the ending potential of each pulse as the drive signal are controlled to be substantially the same level of the intermediate potential (VC). . This is set based on the potential information stored in the potential information storage unit 12 shown in FIG. 1 in each recording device as described later.

Accordingly, when the drive pulse is applied to the actuator intermittently as described above, the end potential (VC) of the previous drive pulse and the start potential (VC) of the next drive pulse are applied. Is substantially the same level as above, and by controlling the switching circuits 24a to 24n, it is possible to prevent a problem such as an abrupt deformation of the piezoelectric vibrator and erroneous ejection of ink droplets.

Next, FIG. 7 explains a procedure for setting a drive signal to be applied to the actuator of the recording head in each recording apparatus having the above-described configuration. In the recording apparatus shown in the above-described embodiment, the potential information is supplied from the potential information storage means 12 to the drive signal generation circuit 9 and the drive signal generated by the drive signal generation circuit 9 based on the potential information is supplied to the drive signal generation circuit 9. The intermediate potential (VC) is configured to be controlled.

Since the actuator has variations due to non-linearity as already described with reference to FIG. 8, the optimum intermediate potential (VC) of the drive signal applied to the actuator in each recording apparatus is set.
The effect of the variation due to the nonlinearity of the actuator is suppressed.

Therefore, a step is executed in which the potential information is stored in the potential information storage means 12 according to the displacement characteristics of the actuators, and the information of the intermediate potential (VC) is written into each. Therefore, it is desirable that the potential information storage means 12 is constituted by a rewritable nonvolatile memory. As this nonvolatile memory, for example, a programmable ROM (PROM) can be used, and in addition, an EEPROM, a flash memory, or the like can be used.

The procedure will be described with reference to FIG. First, displacement characteristics of an actuator in a recording head in each recording apparatus are measured. This can be determined, for example, by measuring the drive signal level so that the ink weight of one dot becomes a predetermined value.
That is, when the drive signal level at which the ink weight of one dot takes a predetermined value is small, the displacement characteristic of the actuator is large, and when the drive signal level at which the ink weight of one dot takes a predetermined value is large, It can be said that the displacement characteristics of the actuator are small.

The displacement characteristics of the actuators are individually obtained by such a method, and the individual recording devices are defined in any group (grouping step). In FIG. 7, for convenience, G1, G2, G3,.
It is indicated by the sign of Gn. Subsequently, an optimum intermediate potential (VC) is set according to each group grouped as described above (intermediate potential setting step). In this case, the intermediate potential (VC) is set according to the group from the large displacement amount to the small group (or, conversely, the small displacement amount to the large group). In FIG. 7, for convenience, the intermediate potentials are denoted by VC-1, VC-2, VC-3,... VC-n.

In this case, a relatively high level of the intermediate potential is set for the recording devices in the group having the large displacement characteristic, and
A relatively high level of intermediate potential is set. This allows
A potential setting that is not easily affected by the nonlinearity of the actuator can be performed.

Subsequently, according to the intermediate potential set as described above, the operation of installing the potential information of the intermediate potential in each potential information storage means 12 in the recording device corresponding to the group (storage step). Is executed,
Thereby, the potential information storage means 1 in each recording device
The writing of the potential information to 2 is completed.

According to the recording apparatus thus obtained, since the intermediate potential of the drive signal is individually set according to the displacement characteristics of the actuator, it is possible to suppress the influence of the variation due to the non-linearity of the actuator.

[0088]

According to the ink jet recording apparatus employing the actuator drive signal setting method according to the present invention, the drive signal generating means is provided with the potential information from the potential information storage means, and the drive generated by the drive signal generating means is provided. The intermediate potential in the signal is set based on the potential information stored in the potential information storage means. Therefore, in each recording device, a drive waveform having an intermediate potential specified by the potential information set in the potential information storage means is generated, thereby suppressing the influence of the nonlinear characteristic due to the entire drive waveform moving up and down. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an ink jet recording apparatus according to the present invention.

FIG. 2 is a sectional view showing a mechanical structure of a recording head.

FIG. 3 is a block diagram showing a main part of a recording head drive circuit.

FIG. 4 is a waveform diagram showing an example of a series of drive signals supplied to a recording head.

FIG. 5 is a timing chart when a large dot drive signal and a medium dot drive signal are supplied to a recording head.

FIG. 6 is a timing chart when a small dot drive signal and a minute vibration signal are supplied to a recording head.

FIG. 7 is a diagram illustrating a procedure for setting an intermediate potential of a drive signal applied to an actuator of a print head in each printing apparatus.

FIG. 8 is a characteristic diagram showing a relationship between a drive voltage of a recording head actuator and a mechanical displacement amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer controller 2 Print engine 3 Interface 4 RAM 5 ROM 6 Control part 7 Oscillation circuit 8 Recording head 9 Drive signal generation circuit 10 Interface 11 A / D conversion circuit 12 Potential information storage means 14 Paper feed mechanism 15 Carriage mechanism 16 Nozzle opening DESCRIPTION OF SYMBOLS 21 Shift register 22 Latch circuit 23 Level shifter 24 Switch circuit 25 Piezoelectric vibrator 26 Temperature sensor 31 Pressure chamber 32 Actuator unit 33 Flow path unit 34 Pressure chamber forming substrate 35 Cover member 36 Vibration plate 41 Nozzle plate 44 Nozzle communication port 45 Ink supply port 50 lower electrode 51 upper electrode

Claims (8)

[Claims] A recording head having an actuator for expanding and contracting a pressure chamber communicating with a nozzle opening;
A drive signal generating means for generating a drive signal for driving the actuator, and a drive signal obtained by the drive signal generating means is supplied to the actuator, thereby deforming the actuator and ejecting ink droplets from a nozzle opening. And a drive signal supply unit for causing the drive signal to be generated by the drive signal generation unit.
A switch means for inputting any one or more of the waveform elements to the actuator, including a plurality of waveform elements for ejecting ink droplets; and Potential information storage means for providing potential information by means of an ink jet type, wherein an intermediate potential in a drive signal input to the actuator is set based on the potential information stored in the potential information storage means. Recording device. 2. A series of drive signals formed by connecting a plurality of waveform elements for ejecting ink droplets of different weights from said drive signal generation means, and a starting end potential of each of said waveform elements and 2. The ink jet recording apparatus according to claim 1, wherein the terminal potential is controlled to be substantially the same level of an intermediate potential. 3. The ink jet recording apparatus according to claim 1, wherein said potential information storage means is constituted by a rewritable nonvolatile memory. 4. A driving signal generated by the driving signal generating means based on the temperature information obtained by the temperature information obtaining means, further comprising temperature information obtaining means for obtaining temperature information around the recording head. 4. An apparatus according to claim 1, wherein said output level is controlled.
An ink jet recording apparatus according to any one of the above. 5. The ink jet recording apparatus according to claim 1, wherein a potential information storage unit for storing the information on the intermediate potential is provided in a printer controller. 6. A method for setting an actuator drive signal of a recording head in an ink jet type recording apparatus according to claim 1, wherein the displacement of the actuator in the recording head mounted on each recording apparatus. A displacement characteristic measuring step of measuring characteristics; a grouping step of defining individual recording devices into any group according to the displacement characteristics of the actuator; and an optimal intermediate potential for each group according to each group. Setting an intermediate potential setting step of setting the intermediate potential information selected in the intermediate potential selecting step in the potential information storage means, and sequentially performing a storing step of storing the information of the intermediate potential in the potential information storing means. Method. 7. In the displacement characteristic measuring step,
7. The recording head according to claim 6, wherein the drive signal level is measured so that the ink weight of one dot becomes a predetermined value, and the displacement characteristic of the actuator is obtained according to the drive signal level. Actuator drive signal setting method. 8. The method according to claim 6, wherein the number of the groups is one.