JP2005022420A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain a recording quality for a long term by compensating decreases of a jetting speed and a volume of ink due to an increase of the number of driving times. <P>SOLUTION: The number of times for a recording head to jet ink from jetting channels by deformation of a piezoelectric material is counted and stored in a storage means set integrally with the recording head. When the number of times exceeds a predetermined number of times, a wave width of driving pulses to be applied to the piezoelectric material is changed from a value of reduced energy efficiency whereby a pressure wave is displaced with respect to a nearly odd multiple of a time of one-way propagation in the jetting channel to a value of high energy efficiency. A deformation amount decrease due to deterioration of a polarization state of the piezoelectric material is thus compensated, so that the jetting speed and the volume of ink are recovered. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an ink jet recording apparatus that performs a recording operation by ejecting ink.

  As an ink jet recording apparatus, there are an electro-thermal conversion system in which ink is locally heated and boiled and ejected, and an electro-mechanical conversion system in which a piezoelectric material is deformed and ink is ejected. Furthermore, as a material using a piezoelectric material, one side of the ejection channel is covered with a diaphragm, the piezoelectric material is disposed on the diaphragm, and a plurality of grooves serving as the ejection channel are processed on the plate of the piezoelectric material. And the like are separated from each other by piezoelectric material partition walls. They deform the piezoelectric material by applying a voltage to the piezoelectric material parallel or perpendicular to its polarization direction, applying pressure to the ink in the ejection channel and ejecting the ink.

  However, in both the electro-thermal conversion system and the electro-mechanical conversion system, the characteristics deteriorate due to the increase in the number of driving over a long period of time, and the ink ejection speed and volume decrease. As a result, the recording quality is degraded. In particular, when the recording head is mounted on the carriage and scans along the recording medium, the ink landing position is shifted. In particular, the piezoelectric material deteriorates in the polarization state with the increase in the number of times of driving, and the deformation amount is reduced to reach the above state.

  The present invention has been made to solve the above-described problems, and can compensate for a decrease in ink ejection speed and volume due to an increase in the number of times of driving, so that recording quality can be maintained over a long period of time. It is to make.

  In order to achieve this object, an ink jet recording apparatus according to claim 1, wherein a recording head that ejects ink in an ejection channel from a nozzle by deformation of a piezoelectric material, the piezoelectric material is deformed, and the ejection is performed by the deformation. A drive circuit that outputs a drive pulse for ejecting ink by adding the pressure wave generated in the ink in the channel to the pressure generated by the deformation of the piezoelectric material, and a count for counting the number of times the piezoelectric material is driven Means, storage means for storing the count value of the counting means, and change means for changing the drive waveform of the drive pulse output from the drive circuit based on the count value stored in the storage means, The changing means changes the width of the drive waveform from a value with reduced energy efficiency to a value with high energy efficiency based on the count value. And it features.

  An ink jet recording apparatus according to claim 2 is the ink jet recording apparatus according to claim 1, wherein the value obtained by reducing the energy efficiency is shifted with respect to an odd number of times that the pressure wave propagates one way in the ejection channel. It is a value.

  According to a third aspect of the present invention, in the ink jet recording apparatus according to the first or second aspect, the high energy efficiency value is a value that is approximately an odd multiple of a time during which the pressure wave propagates one way through the ejection channel. It is characterized by being.

  An ink jet recording apparatus according to a fourth aspect of the present invention is the ink jet recording apparatus according to any one of the first to third aspects, wherein the changing means is based on the count value before the ink ejection speed falls below a predetermined value. The drive waveform of the drive pulse is changed.

  An ink jet recording apparatus according to a fifth aspect of the present invention is the ink jet recording apparatus according to any one of the first to fourth aspects, wherein the recording head includes the ejection channel by a partition wall that is at least partially polarized. And

  An ink jet recording apparatus according to a sixth aspect of the invention is the ink jet recording apparatus according to any one of the first to fifth aspects, wherein the storage means stores a count value counted by the counting means after a predetermined amount of recording operation is completed. It is characterized by doing.

  An ink jet recording apparatus according to a seventh aspect of the present invention is the ink jet recording apparatus according to any one of the first to sixth aspects, wherein the changing means changes the driving waveform when a recording operation is performed on a different recording medium. It is characterized by doing.

  An ink jet recording apparatus according to an eighth aspect of the present invention is the ink jet recording apparatus according to the seventh aspect, wherein the changing means changes the driving waveform based on a page break signal or a new recording command.

  The ink jet recording apparatus according to claim 9 is the ink jet recording apparatus according to any one of claims 1 to 8, wherein the recording head and the storage unit are detachably mounted on a carriage that can run along the recording medium. It is attached to the head holder.

  As described above, according to the present invention, the drive waveform of the drive pulse is changed from a value with reduced energy efficiency to a value with high energy efficiency even when the polarization state of the piezoelectric material is deteriorated as the number of times of driving increases. Recording quality can be kept.

  In addition, the width of the drive waveform can be a value that is easily reduced in energy efficiency by setting a value that is shifted with respect to almost an odd multiple of the time during which the pressure wave propagates in the injection channel one way, Further, by setting the pressure wave to a value that is approximately an odd multiple of the time during which the pressure wave propagates in the injection channel in one way, a value with high energy efficiency can be easily obtained. Furthermore, even if the polarization state of the piezoelectric material deteriorates, the changing means changes the drive waveform of the drive pulse based on the count value before the ink ejection speed falls below a predetermined value. The recording speed can be recovered, and the recording quality can be maintained without shifting the ink landing position.

  In the ink jet recording apparatus using such a piezoelectric material, the ejection channel is constituted by the partition wall which is at least partially polarized, so that the change of the driving waveform is immediately reflected in the ink ejection.

  Further, by storing the count value in the storage means after the predetermined amount of recording operation is completed, it is not necessary to store the count value frequently in the storage means, and the control can be facilitated.

  Further, by configuring the change means to change the drive waveform when performing a recording operation on a different recording medium, it is assumed that the number of times of driving reaches a predetermined value, and the recording is performed on one recording medium. If the drive waveform is changed immediately during recording, the boundary becomes conspicuous, but such a situation can be avoided and excellent recording quality can be maintained.

  Further, the drive waveform can be changed based on a page break signal or a new recording command. The page break signal is preferable because it can be changed quickly.

  The recording head and the storage means are mounted on a head holder that is detachably mounted on a carriage that can run along the recording medium, so that the memory can be stored when the head holder including the recording head is replaced. The means can also be exchanged together and a new counting of the number of drivings for the new head can be started.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In FIG. 1, the recording head 1 has a plurality of ejection channels 14 and ejects ink supplied from the ink cartridge 5 through the manifold 7 as ink droplets from the nozzle holes on the front surface. The recording head 1 is fixed to the head holder 3 together with the manifold 7 and is covered with a cover 8. A printed wiring board 9 on which a drive circuit for supplying drive pulses to the recording head 1 is mounted is mounted on the head holder 3. The printed wiring board 9 and the recording head 1 are connected by a wiring material (not shown). Further, the printed wiring board 9 is mounted with a non-volatile storage means for recording the number of times the recording head 1 is driven, for example, an EEPROM 10.

  The head holder 3 is detachably mounted on a known carriage (not shown) that can run along the recording medium, and the printed wiring board 9 is connected to a control circuit of the recording apparatus main body via a contact on the carriage. .

  2 to 4 show the configuration of the recording head 1. The recording head of this embodiment includes actuator substrates 2U and 2L, a plate member 4, and a nozzle plate 6. Each actuator substrate 2U, 2L is formed by laminating a plurality of piezoelectric materials as shown in FIG. 4, and the piezoelectric materials of each layer are in opposite directions (thickness direction of the actuator substrates 2U, 2L, respectively, arrow 27U). , 27L). A plurality of channels 14 and 15 that are cut over each layer are formed on the opposing surfaces of the actuator substrates 2U and 2L. Of the plurality of channels, every other channel is used as an ejection channel 14 for ejecting ink, and every other channel between both ends and the ejection channel 14 is used as a dummy channel 15.

  Each ejection channel 14 is formed to penetrate through a predetermined depth from the front end (left end in the figure) to the rear end (right end in the figure) of the actuator substrates 2U and 2L. Each dummy channel 15 is formed to have a predetermined depth from the front end of the actuator substrate 2U, 2L to the vicinity of the rear end side, and the rear end portion 15b of the dummy channel is raised and closed. As a result, the ejection channels 14 and the dummy channels 15 are alternately arranged in parallel via the partition walls 20, and the partition walls 20 are composed of a plurality of layers of piezoelectric materials polarized in opposite directions. Between the actuator substrates 2U and 2L, the plate member 4 is fixed by an adhesive 24, and the open surfaces along the longitudinal direction of the ejection channels 14 and the dummy channels 15 are covered. A nozzle plate 6 is fixed to the front ends of the actuator substrates 2U and 2L and the plate member 4, and nozzle holes 30 corresponding to the ejection channels 14 are formed in the nozzle plate 6. In addition, the manifold 7 is fixed at the rear end, and the ink from the ink cartridge is distributed only to each ejection channel 14.

As shown in FIG. 4, one electrode 21 is formed on the side surface of the partition wall 20 in each ejection channel 14 of the actuator substrates 2 </ b> U and 2 </ b> L, and the side surface of the partition wall 20 in each dummy channel 15 is Independent electrodes 22 and 22 are formed.
When one ejection channel 14 and the partition walls 20 and 20 on both sides thereof are used as a set of actuators, a drive pulse is applied from the drive circuit to the outer electrodes 22 and 22 of both partition walls 20 and 20, and the inner electrode 21 is grounded. An electric field perpendicular to the polarization directions 27U and 27L is generated on both the partition walls 20 and 20, the both partition walls 20 and 20 are deformed, and the ink in the ejection channel 14 is ejected from the nozzle holes 30.

  Preferably, by applying a driving pulse to the electrodes 22, 22, both the partition walls 20, 20 are deformed in directions away from each other, and pressure wave vibration is generated in the ink in the ejection channel 14. After an odd number of times T during which this pressure wave oscillation propagates in the ejection channel 14 one time, the pressure of the ink decreased due to the expansion between the partition walls 20 and 20 is reversed. Accordingly, the drive to the electrodes 22 and 22 is performed accordingly. When the application of the pulse is stopped and both the partition walls 20 and 20 are restored, the inverted ink pressure and the pressure generated by the restoration of both the partition walls 20 and 20 are added together, and the ink is efficiently ejected. The one-way propagation time T is calculated by L / C from the length L of the ejection channel 14 and the speed of sound C in the ink.

  FIG. 5 shows a configuration for controlling the ink jet recording apparatus. The control circuit 40 includes a known CPU, ROM, and RAM, and outputs recording data received from the outside to the drive circuit 44 as serial data. The drive circuit 44 converts the serial data into parallel data corresponding to each ejection channel 14 of the recording head 1 and outputs the parallel data as a driving pulse corresponding to each ejection channel 14 of the recording head 1. The control circuit 40 is provided in the recording apparatus main body, and the recording head 1, the storage means 10, and the drive circuit 44 are provided integrally with the head holder 3. FIG. 6 shows the control contents of the control circuit related to the number of times the recording head is driven.

  When the power is turned on or a data recording command is received, the control circuit 40 reads the number of times of driving stored in the storage means 10 and stores it in the RAM in the control circuit 40. When the data recording command is received (FIG. 6, S1: Yes), if there is no page break signal (S2: No), the recording data is output to the recording head 1 and the recording operation is executed (S5). At this time, the control circuit 40 causes the counting means 41 in the control circuit to count the number of output recording data, that is, the number of operations of the recording head, by adding to the number of driving times read from the storage means 10. The number of times of driving is counted for each injection channel 14.

  When the page break signal is received (S2: Yes), the determination means 42 in the control circuit determines whether any one of the plurality of ejection channels 14 has exceeded the predetermined number of times of driving, and exceeds it. If not (S3: No), the recording operation is continued as described above (S5). When the number of driving times exceeds the predetermined number (S3: Yes), the changing means 43 in the control circuit changes the driving waveform output to the driving circuit 44. As a result, the drive waveform output from the drive circuit 44 to the recording head 1 also changes. Thereafter, the recording operation is performed with a new drive waveform (S5).

  When the recording operation of the received data is completed (S6: Yes), the number of driving times counted by the counting means 41 is stored in the storage means 10 (S7), and the operation is ended.

  In the recording head using the above-described piezoelectric material, the polarization state of the piezoelectric material deteriorates as the number of times of driving increases, the deformation amount of the partition wall 20 decreases, and the ink droplet ejection speed decreases. The decrease in the injection speed becomes almost linear when the number of times of driving is logarithmic as shown in FIG.

For example, when the ejection speed falls below 7.5 m / s, the landing position of the ink droplets shifts and the deterioration in recording quality becomes unacceptable, and the number of times of driving before the ejection speed falls below 7.5 m / s is 10 ^6. When exceeding the number of times, the drive waveform is changed to increase the drive energy as shown in FIG. 8 to recover the injection speed.

  The drive waveform can be changed by increasing the pulse peak value, that is, the voltage, or changing the pulse width. As described above, when the pulse width is an odd multiple of the one-way propagation time (L / C) of the pressure wave in the injection channel, the most efficient injection can be performed. As shown in FIG. 9A, the energy efficiency is slightly reduced to 1.3 L / C, and after the number of driving times reaches a predetermined value, as shown in FIG. As C, energy efficiency can be improved.

  In addition to the above, the drive waveform may be changed by adding a preliminary pulse that gives vibration that does not cause ejection to ink before the drive pulse.

  When any one of the plurality of injection channels 14 exceeds the predetermined number of times, the drive waveform of only the corresponding injection channel may be changed. However, the drive waveform may be changed for all the injection channels. Good.

  Further, the number of times of driving may be determined in a plurality of stages, the driving waveform may be changed in each stage, and further, in the final stage, it may be notified that the recording head has reached the end of its life.

  Even if the head holder 3 including the recording head 1 is removed from the carriage for repair or inspection, the contents of the storage means 10 are maintained even if the head holder 3 is mounted again, and there is no problem in counting the number of times of driving. When the head holder 3 including the recording head 1 is replaced with a new one, a new count value for the recording head is stored.

  Since the control circuit 40 determines the page break signal in S2 of FIG. 6 and changes the waveform based on exceeding the number of times of driving, the boundary due to the waveform change is not formed in the middle of one recording medium. . In this case, since a new data recording command is used for recording on a different recording medium instead of the page break signal, the problem caused by the waveform change can be solved.

  Although the description has been given of the case in which the partition wall constituting the ejection channel 14 is formed of the piezoelectric material, the present invention can be similarly applied to the case where the piezoelectric material is attached to the diaphragm.

FIG. 3 is a cross-sectional view of a state in which a recording head, an ink cartridge, a head holder, and the like are combined. FIG. 3 is an exploded perspective view of a recording head. FIG. 2 is a longitudinal sectional view of a recording head. FIG. 3 is an enlarged cross-sectional view of a recording head. It is a block diagram which shows the structure for control of an inkjet recording device. FIG. 6 is a flowchart showing the contents of control related to the number of times the recording head is driven in the ink jet recording apparatus. FIG. 6 is a relationship diagram between the number of times the recording head is driven and the ink droplet ejection speed. In FIG. 7, it is explanatory drawing when the drive waveform is changed. It is a wave form diagram which shows the example of a change of a drive waveform.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording head 3 Head holder 10 Memory | storage means 14 Injection channel 40 Control circuit 41 Counting means 42 Discriminating means 43 Changing means 44 Drive circuit

Claims (9)

A recording head for ejecting ink in the ejection channel from the nozzle by deformation of the piezoelectric material;
A drive circuit that deforms the piezoelectric material and outputs a drive pulse for ejecting ink by adding the pressure wave generated in the ink in the ejection channel to the pressure wave generated by the deformation of the piezoelectric material. When,
Counting means for counting the number of times the piezoelectric material is driven;
Storage means for storing the count value of the counting means;
A change means for changing a drive waveform of the drive pulse output from the drive circuit based on the count value stored in the storage means, and the change means reduces the width of the drive waveform to reduce energy efficiency. An ink jet recording apparatus, wherein the value is changed to a value with high energy efficiency based on the count value.   2. The ink jet recording apparatus according to claim 1, wherein the value obtained by reducing the energy efficiency is a value deviated from an approximately odd multiple of a time during which the pressure wave propagates one way through the ejection channel.   The inkjet recording apparatus according to claim 1, wherein the high energy efficiency value is a value that is approximately an odd multiple of a time during which the pressure wave propagates one way through the ejection channel.   4. The ink jet recording apparatus according to claim 1, wherein the changing unit changes a drive waveform of the drive pulse based on the count value before the ink ejection speed falls below a predetermined value. 5.   5. The ink jet recording apparatus according to claim 1, wherein the recording head includes the ejection channel by a partition wall which is at least partially polarized.   6. The ink jet recording apparatus according to claim 1, wherein the storage unit stores a count value counted by the counting unit after a predetermined amount of recording operation is completed.   The inkjet recording apparatus according to claim 1, wherein the changing unit changes the driving waveform when a recording operation is performed on a different recording medium.   8. The ink jet recording apparatus according to claim 7, wherein the changing unit changes the driving waveform based on a page break signal or a new recording command. 9. The inkjet recording according to claim 1, wherein the recording head and the storage unit are attached to a head holder that is detachably mounted on a carriage that can run along a recording medium. apparatus.

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