JP2008207353A - Inkjet recorder, driving method of inkjet head, and inkjet head driving program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder or the like which can simply and highly precisely correct a drive voltage corresponding to each temperature for a plurality of inkjet heads, and can effectively suppress a variation in the ejection performance. <P>SOLUTION: The inkjet recorder is equipped with a difference operation means which calculates a difference between a peculiar drive voltage preliminarily determined peculiarly for every plurality of inkjet heads and a specific temperature reference drive voltage as a peculiar drive voltage of a reference inkjet head, a correction factor operation means which calculates a correction factor, a difference correcting means which corrects the difference by utilizing the correction factor, a correction voltage operation means which calculates a correction voltage by adding the corrected difference to each temperature reference drive voltage preliminarily determined at each temperature to the reference inkjet head, and an input control means which inputs the correction voltage to the predetermined inkjet heads from a voltage generating means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inkjet recording apparatus, an inkjet head driving method, and an inkjet head driving program.

2. Description of the Related Art Conventionally, ink jet recording apparatuses that eject ink and land ink droplets on a recording medium have been used (see, for example, Patent Document 1).
Some of these ink jet recording apparatuses include an ink jet head for ejecting ink. As an ink jet head, a head including a piezoelectric plate having an ink chamber and an electrode portion provided in the ink chamber is known.
Under such a configuration, when a drive voltage is applied to the electrode portion to deform the piezoelectric plate, the volume of the ink chamber changes, thereby ejecting ink contained in the ink chamber.

Here, the viscosity of the ink placed in the ink chamber varies depending on the environmental temperature.
FIG. 21 is a graph showing the relationship between environmental temperature and ink viscosity.
As shown in the figure, the viscosity of the ink has a characteristic that it decreases as the environmental temperature increases. For this reason, if the drive voltage applied to the piezoelectric plate is made constant regardless of the temperature, the ink ejection speed and the amount of ejected droplets (drop volume) differ depending on the temperature. The performance of the piezoelectric plate with respect to the ink ejection speed and ejection droplet amount is referred to as ejection performance. That is, the discharge performance of the piezoelectric plate varies depending on each temperature.

Therefore, a driving voltage that suppresses the discharge performance over a predetermined temperature range is set in advance corresponding to each temperature, and a predetermined driving voltage corresponding to the environmental temperature is applied to the piezoelectric plate to determine the amount of deformation. By adjusting, it is possible to suppress variations in ejection performance of the piezoelectric plate. That is, even if the viscosity of the ink differs due to the difference in environmental temperature, the ink ejection speed and the amount of ejected droplets can always be kept constant, and high-precision recording can be performed.
However, the piezoelectric plates have variations such as the amount of deformation for each individual. Therefore, even if the driving voltage is set in advance for each piezoelectric plate corresponding to each temperature, when the driving voltage that is set in advance is applied to other piezoelectric plates, the piezoelectric plate The discharge performance will be different for each.

Therefore, it is conceivable to absorb variations in the piezoelectric plate by offsetting the correction value uniformly over a predetermined temperature range to a preset driving voltage.
JP 2005-212365 A

  However, if the correction values are uniformly offset as described above, although it contributes to a certain degree of correction as a whole, more accurate correction cannot be performed for each temperature, and the discharge performance is improved over a plurality of piezoelectric plates. There is a problem that variations occur. For this reason, stable and uniform ink ejection cannot be performed across a plurality of piezoelectric plates. On the other hand, the narrower the allowable range of variation such as the deformation amount of the piezoelectric plate is, the more stable the ink discharge is, but the yield is reduced and the cost is increased.

  The present invention has been made in view of such circumstances, and it is possible to easily and accurately correct the driving voltage corresponding to each temperature over a plurality of inkjet heads, and to effectively vary the discharge performance. It is an object of the present invention to provide an ink jet recording apparatus, an ink jet head driving method, and an ink jet head driving program.

In order to solve the above problems, the present invention provides the following means.
The present invention is an ink jet recording apparatus having a plurality of ink jet heads for ejecting ink onto a recording medium, wherein the plurality of ink jets is used to suppress variation in ejection performance over a specific temperature of the plurality of ink jet heads. Difference calculating means for calculating a difference between a specific driving voltage that is uniquely determined in advance for each head and a specific temperature reference driving voltage that is a specific driving voltage of a reference inkjet head that is used as a reference from among the plurality of inkjet heads; Correction coefficient calculation means for calculating a correction coefficient for suppressing variations in ejection performance over the respective temperatures of the inkjet head over a predetermined temperature range including the temperatures and over the plurality of inkjet heads; Correction coefficient calculated by the correction coefficient calculation means Utilizing the difference correction means for correcting the difference calculated by the difference calculation means, and for suppressing variation in ejection performance over each temperature of the reference inkjet head over a predetermined temperature range including each temperature. Correction voltage calculation means for calculating a correction voltage at each temperature of the plurality of inkjet heads by adding the difference corrected by the difference correction means to each temperature reference drive voltage determined in advance according to each temperature And an input control means for inputting a correction voltage calculated by the correction voltage calculation means to a predetermined ink jet head from a voltage generation means for generating a voltage for driving the plurality of ink jet heads. .

In the present invention, the difference calculation means calculates the difference between the specific drive voltage and the specific temperature reference drive voltage, and the correction coefficient calculation means calculates the correction coefficient. Then, the difference correction unit corrects the difference using the correction coefficient, and the correction voltage calculation unit calculates the correction voltage by adding the corrected difference to each temperature reference drive voltage. Further, the input control means inputs a correction voltage from the voltage generating means to a predetermined inkjet head.
As a result, the difference between the specific drive voltage and the specific temperature reference drive voltage can be accurately corrected, and an appropriate correction voltage can be obtained.

  In addition, the present invention includes a temperature detection unit that detects the temperature of each of the plurality of inkjet heads, and the correction voltage calculation unit applies the temperature reference drive voltage corresponding to the temperature detected by the temperature detection unit. The difference corrected by the difference correction means is added to calculate a correction voltage at the detected temperature.

In the present invention, the correction voltage calculation means adds the corrected difference to each temperature reference drive voltage corresponding to the detected temperature, and calculates the correction voltage at the detected temperature. A highly accurate correction voltage for each temperature can be obtained.

  In the invention, it is preferable that the correction coefficient is an increase / decrease rate of each of the other temperature reference drive voltages with respect to the one temperature reference drive voltage as a reference.

  According to the present invention, the difference between the specific drive voltage and the specific temperature reference drive voltage can be corrected with high accuracy.

  According to the present invention, the correction coefficient includes a rate of increase / decrease of each other temperature reference drive voltage with respect to each temperature reference drive voltage serving as a reference, and the inherent characteristic for each temperature reference drive voltage serving as a reference. It is calculated using the increase / decrease rate of the drive voltage.

  According to the present invention, the difference between the specific drive voltage and the specific temperature reference drive voltage can be corrected with high accuracy.

  The present invention also relates to an inkjet head driving method in an inkjet recording apparatus having a plurality of inkjet heads for ejecting ink onto a recording medium, and suppressing variations in ejection performance of the plurality of inkjet heads over a specific temperature. In order to do this, a difference between a specific drive voltage that is uniquely determined in advance for each of the plurality of inkjet heads and a specific temperature reference drive voltage that is a specific drive voltage of a reference inkjet head that serves as a reference from among the plurality of inkjet heads. A difference calculating step for calculating and a correction coefficient for suppressing variation in ejection performance over each temperature of the inkjet head over a predetermined temperature range including each temperature and over the plurality of inkjet heads. Correction coefficient calculation step and Using the correction coefficient calculated in the correction coefficient calculation step, the difference correction step for correcting the difference calculated in the difference calculation step, and the variation in ejection performance over each temperature of the reference inkjet head, In order to suppress over a predetermined temperature range including each temperature, a difference corrected by the difference correction step is added to each temperature reference drive voltage predetermined according to each temperature, and each of the plurality of inkjet heads is added. A correction voltage calculated in the correction voltage calculation step is input to a predetermined ink jet head from a correction voltage calculation step for calculating a correction voltage in temperature and voltage generation means for generating a voltage for driving the plurality of ink jet heads. And an input step.

In the present invention, the difference between the specific drive voltage and the specific temperature reference drive voltage is calculated in the difference calculation step, and the correction coefficient is calculated in the correction coefficient calculation step. In the difference correction step, the correction coefficient is used to correct the difference, and in the correction voltage calculation step, the corrected difference is added to each temperature reference drive voltage to calculate the correction voltage. Further, in the input control step, a correction voltage is input from the voltage generating means to a predetermined inkjet head.
As a result, the difference between the specific drive voltage and the specific temperature reference drive voltage can be accurately corrected, and an appropriate correction voltage can be obtained.

  The present invention also provides a computer of an inkjet recording apparatus having a plurality of inkjet heads that eject ink onto a recording medium, in order to suppress variation in ejection performance over a specific temperature of the plurality of inkjet heads. Difference calculation for calculating a difference between a specific drive voltage that is uniquely determined in advance for each inkjet head and a specific temperature reference drive voltage that is a specific drive voltage of a reference inkjet head that is used as a reference from among the plurality of inkjet heads And a correction coefficient calculation step for calculating a correction coefficient for suppressing variation in ejection performance over each temperature of the inkjet head over a predetermined temperature range including each temperature and over the plurality of inkjet heads. And the correction coefficient calculation step Thus, using the calculated correction coefficient, a difference correction step for correcting the difference calculated in the difference calculation step, and a variation in ejection performance over each temperature of the reference ink jet head, a predetermined value including each temperature The difference corrected by the difference correction step is added to each temperature reference drive voltage that is predetermined according to each temperature to suppress over the temperature range, and the correction voltage at each temperature of the plurality of inkjet heads is obtained. A correction voltage calculation step for calculating, and an input step for inputting the correction voltage calculated in the correction voltage calculation step to the predetermined inkjet head from a voltage generating means for generating a voltage for driving the plurality of inkjet heads. It is characterized by making it.

In the present invention, the difference between the specific drive voltage and the specific temperature reference drive voltage is calculated in the difference calculation step, and the correction coefficient is calculated in the correction coefficient calculation step. In the difference correction step, the correction coefficient is used to correct the difference, and in the correction voltage calculation step, the corrected difference is added to each temperature reference drive voltage to calculate the correction voltage. Further, in the input control step, a correction voltage is input from the voltage generating means to a predetermined inkjet head.
As a result, the difference between the specific drive voltage and the specific temperature reference drive voltage can be accurately corrected, and an appropriate correction voltage can be obtained.

  According to the present invention, the difference between the specific drive voltage and the specific temperature reference drive voltage can be accurately corrected, and an appropriate correction voltage can be obtained. Can be effectively suppressed.

(Embodiment 1)
Hereinafter, an ink jet recording apparatus according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows an ink jet recording apparatus as a first embodiment of the present invention.
The ink jet recording apparatus 1 includes an apparatus main body 2 as a main body and a plurality of ink jet heads 3 provided for each color.
The apparatus main body 2 includes a rectangular parallelepiped housing 6. A pair of guide rails 8 extending in the width direction (longitudinal direction) W is provided in the housing 6. These guide rails 8 are provided with a carriage 7 to which a plurality of inkjet heads 3 are fixed. That is, the carriage 7 is supported by the guide rail 8 so as to be able to reciprocate in the width direction W.

  The carriage 7 includes a flat base 7a. The inkjet head 3 is fixed to the base 7a. The base 7a is provided with a rising wall portion 7b raised from the base 7a. A wiring substrate 5 is provided on the rising wall portion 7b. The wiring board 5 is provided with various electronic components for operating the components of the ink jet recording apparatus 1.

A motor 11 is provided at one end of the housing 6 in the width direction W. The output shaft of the motor 11 is directed in the depth direction (short direction) D of the housing 6. A pulley 12 is provided on the output shaft of the motor 11. On the other hand, the pulley 13 is also arranged opposite to the other end portion in the width direction in the housing 6. A timing belt 14 is provided across the pulleys 12 and 13. A carriage 7 is fixed to the timing belt 14.
With such a configuration, when the motor 11 is driven, the carriage 7 reciprocates in the width direction W via the pulleys 12 and 13 and the timing belt 14.

  An ink cartridge 17 that supplies ink is provided at the other end in the housing 6. The ink cartridge 17 is connected to the inkjet head 3 attached to the carriage 7 via an ink supply pipe 18 made of a flexible tube. Various inks are supplied from the ink cartridge 17 to the inkjet head 3 via the ink supply pipe 18.

Further, an opening (not shown) arranged to face each other is provided on the front surface and the rear back surface of one end portion of the housing 6. A pair of carry-out rollers 22 extending in the longitudinal direction W is provided at a position facing one end of the housing 6 facing the opening on the front surface. On the other hand, a pair of carry-in rollers 21 extending in the longitudinal direction W are provided at positions facing the rear rear opening.
With such a configuration, the sheet (recording medium) S is inserted from the opening on the rear back surface, and the carry-in roller 21 and the carry-out roller 22 are driven so that the sheet S is discharged from the opening on the front surface. It has become.

  Moreover, the inkjet head 3 is provided with the rectangular attachment base 25 as shown in FIG. The mounting base 25 is attached to the base 7a of the carriage 7 via screws (not shown). An inkjet head chip 26 to be described later is attached to the upper surface of the attachment base 25. On the upper surface of the inkjet head chip 26, a rectangular channel substrate 27 extending over the entire length in the longitudinal direction is provided. A connecting portion 30 is provided at the center of the upper surface of the flow path substrate 27 in the longitudinal direction.

  Further, the mounting base 25 is provided with a rectangular base plate 31 raised from the mounting base 25. The base plate 31 is made of aluminum or the like. A wiring substrate 35 is provided on one main surface of the base plate 31 (the main surface disposed on the inkjet head chip 26 side). A control circuit 32 that performs various controls of the inkjet head chip 26 is mounted on the wiring board 35.

The base plate 31 is provided with a support portion 37 at the upper end, extending to one main surface side. The support portion 37 is provided with a pressure adjusting portion 38 having a storage chamber for storing ink. An ink communication tube 39 that communicates with the storage chamber is provided below the pressure adjustment unit 38. The ink communication tube 39 is connected to the connecting portion 30 of the flow path substrate 27 via an O-ring.
On the other hand, an ink intake port 42 that communicates with the storage chamber is provided in the upper portion of the pressure adjustment unit 38. The ink supply pipe 18 is attached to the ink intake port 42.
With this configuration, when ink is supplied from the ink cartridge 17 via the ink supply pipe 18, the ink is taken into the storage chamber in the pressure adjustment unit 38 via the ink intake 42. Further, a predetermined amount of ink is supplied to the inkjet head chip 26 via the ink communication tube 39 and the flow path substrate 27.

As shown in FIGS. 3 and 4, the inkjet head chip 26 includes a rectangular piezoelectric ceramic plate 44. The piezoelectric ceramic plate 44 is made of PZT (lead zirconate titanate). A long groove 45 extending in the short direction is formed on the upper surface of the piezoelectric ceramic plate 44. The long grooves 45 have a rectangular cross section, and a plurality of long grooves 45 are arranged over the entire length of the piezoelectric ceramic plate 44 in the longitudinal direction. That is, the long groove 45 is divided by the side wall 46. As shown in FIG. 4, the bottom surface of the long groove 45 has a front flat surface 44a extending from the front side of the piezoelectric ceramic plate 44 to a substantially central portion in the short side direction, and a depth from the rear portion of the front flat surface 44a toward the rear side. It is composed of an inclined surface 44b that gradually becomes shallower and a rear flat surface 44c that extends rearward from the rear portion of the inclined surface 44b.
The rear end portion of the long groove 45 is sealed with a sealing portion (not shown).

A drive electrode portion 50 extending in a plate shape is provided in the long groove 45. That is, the drive electrode portions 50 are provided by vapor deposition at the upper end portions of both main surfaces of the side wall 46, respectively. The drive electrode unit 50 is electrically connected to the control circuit 32 by a wire 47 (shown in FIG. 5).
A nozzle plate 51 made of polyimide is provided on the front surface of the piezoelectric ceramic plate 44. One main surface of the nozzle plate 51 is a bonding surface to the piezoelectric ceramic plate 44, and the other main surface is coated with a water repellent film having water repellency for preventing adhesion of ink and the like.

  The nozzle plate 51 is formed with a plurality of nozzle openings 52 at predetermined intervals (intervals equal to the pitch of the long grooves 45) in the longitudinal direction. The nozzle opening 52 is formed in the nozzle plate 51 such as a polyimide film using, for example, an excimer laser device. These nozzle openings 52 are arranged in alignment with the long grooves 45, respectively.

Further, a rectangular ink chamber plate 55 is provided on the upper surface of the piezoelectric ceramic plate 44. The length of the ink chamber plate 55 in the short direction is shorter than the length of the piezoelectric ceramic plate 44 in the short direction. The front end surface of the ink chamber plate 55 and the front end surface of the piezoelectric ceramic plate 44 are flush with each other.
The ink chamber plate 55 is formed with a rectangular opening 56 extending in the longitudinal direction. The opening 56 extends over the entire long groove 45 in the longitudinal direction of the piezoelectric ceramic plate 44. That is, all the long grooves 45 are opened outward through the openings 56.
In addition, a rectangular nozzle support plate 57 is fitted and bonded to the rear back surface of the piezoelectric ceramic plate 44.

  With such a configuration, when a predetermined amount of ink is supplied from the storage chamber in the pressure adjusting unit 38 to the flow path substrate 27 through the ink communication tube 39 and the connection unit 30, the ink is It is fed into the long groove 45 through 56. That is, the long groove 45 functions as an ink chamber into which ink is put.

A thermistor (temperature detecting means) 61 (shown in FIG. 5) is provided on the lower surface of the piezoelectric ceramic plate 44. The thermistor 61 outputs a voltage corresponding to the temperature of the piezoelectric ceramic plate 44. The thermistor 61 is electrically connected to the control circuit 32.
As shown in FIG. 5, the control circuit 32 includes a control unit (difference calculating means, correction coefficient calculating means, difference correcting means, correction voltage calculating means, and input control means) 63. A head temperature detector (temperature detector) 64 connected to the thermistor 61 is connected to the controller 63. The head temperature detector 64 detects the temperature of the piezoelectric ceramic plate 44 from the voltage output from the thermistor 61 and outputs it as a temperature information signal.

  The control unit 63 is connected to a storage unit 65 that stores various types of information. The storage unit 65 includes a temperature-voltage table 65a in which each temperature of a later-described reference piezoelectric ceramic plate 44A and each temperature reference drive voltage value are associated with each other by actual ink. The storage unit 65 stores the specific temperature reference drive voltage value and the unique drive voltage value for each of the plurality of piezoelectric ceramic plates 44.

Here, the specific drive voltage value, the specific temperature reference drive voltage value, and each temperature reference drive voltage value will be described.
The piezoelectric ceramic plate 44 has variations such as a deformation amount for each individual. Therefore, when the same voltage is applied to the plurality of piezoelectric ceramic plates 44, the amount of deformation varies for each piezoelectric ceramic plate 44, and as a result, the ejection performance also varies. For this reason, high-precision recording cannot be performed.
In view of this, a drive voltage that suppresses variations in ejection performance over a plurality of piezoelectric ceramic plates 44 at a specific temperature (for example, 25 ° C.) is uniquely determined in advance for each of the plurality of piezoelectric ceramic plates 44. . That is, a specific drive voltage for each of the plurality of piezoelectric ceramic plates 44 is determined using the reference liquid. Thereby, the deformation amount of the plurality of piezoelectric ceramic plates 44 and the like can be adjusted, and variation in ejection performance over the plurality of piezoelectric ceramic plates 44 can be suppressed at 25 ° C.
As described above, the drive voltage uniquely determined in advance so as to suppress the variation in the ejection performance over the plurality of piezoelectric ceramic plates 44 at 25 ° C. is referred to as “specific drive voltage”. These intrinsic drive voltages are called head ranks.

  One piezoelectric ceramic plate 44 serving as a reference is selected from the plurality of piezoelectric ceramic plates 44, and the selected piezoelectric ceramic plate 44 is referred to as a “reference piezoelectric ceramic plate” 44A. The inherent drive voltage of the reference piezoelectric ceramic plate 44A is referred to as “specific temperature reference drive voltage”. That is, among the plurality of piezoelectric ceramic plates 44, the specific drive voltage of the remaining piezoelectric ceramic plates 44 other than the reference piezoelectric ceramic plate 44A is used as the specific drive voltage as it is, and the specific drive voltage of the reference piezoelectric ceramic plate 44A is used as the specific temperature reference drive. We will use them as voltages. Here, the specific temperature reference drive voltage is 21.5V, for example.

By applying the specific drive voltage and the specific temperature reference drive voltage, it is possible to suppress variations in the discharge performance of the plurality of piezoelectric ceramic plates 44 at 25 ° C. However, as described above, the viscosity of the ink changes depending on the temperature. Therefore, when the temperature of the piezoelectric ceramic plate 44 is not 25 ° C., the ejection performance of the piezoelectric ceramic plate 44 changes depending on the temperature. Therefore, a reference liquid is used in advance to correspond to each temperature so that the variation in the discharge performance of the reference piezoelectric ceramic plate 44A selected from the plurality of piezoelectric ceramic plates 44 is suppressed over a predetermined temperature range. Determine the drive voltage. For example, when the temperature of the reference piezoelectric ceramic plate 44A is 20 ° C., each temperature reference drive voltage corresponding to 20 ° C. is applied, and when it is 50 ° C., each temperature reference drive corresponding to 50 ° C. Apply voltage. Thus, by applying a driving voltage corresponding to each temperature, in the reference piezoelectric ceramic plate 44A, variation in ejection performance can be suppressed over a predetermined temperature range.
As described above, the drive voltage determined in advance corresponding to each temperature so as to suppress the variation in the discharge performance of the reference piezoelectric ceramic plate 44A over a predetermined temperature range is referred to as “each temperature reference drive voltage”.

  It should be noted that a predetermined drive voltage must be applied to the remaining piezoelectric ceramic plates 44 other than the reference piezoelectric ceramic plate 44A in order to suppress variations in ejection performance when the temperature is not 25 ° C. A method for obtaining an appropriate drive voltage when the temperature is not 25 ° C. with respect to the ceramic plate 44 will be described later.

FIG. 6 is a diagram illustrating a temperature-voltage table 65 a included in the storage unit 65.
In the figure, “reference head temperature (° C.)” indicates the temperature of the reference piezoelectric ceramic plate 44A, and “drive voltage (V)” indicates each temperature reference drive voltage. The temperature-voltage table 65a is a correspondence table in the case where actual ink is used instead of the reference liquid. Therefore, at 25 ° C., each temperature reference drive voltage is 24.8 V, which is different from the specific temperature reference drive voltage (21.5 V) when the above-described reference liquid is used, but the same ink in each. Needless to say, the reference driving voltages are equal at 25 ° C.

  As shown in FIG. 5, the controller 63 is connected to a drive voltage generator (voltage generator) 66 that generates a drive voltage for driving the piezoelectric ceramic plate 44. The control unit 63 inputs an appropriate drive voltage to the predetermined piezoelectric ceramic plate 44 at an appropriate timing via the drive voltage generation unit 66.

Next, the operation of the inkjet recording apparatus 1 in the present embodiment configured as described above will be described.
When printing is instructed from a personal computer or the like connected to the ink jet recording apparatus 1, the control unit 63 calculates a correction voltage value as will be described later, and performs a predetermined ink jet head 3 operation via the drive voltage generation unit 66. A correction voltage is selectively input to the piezoelectric ceramic plate 44.
As a result, the side wall 46 shown in FIG. 3 is distorted, and the volume of the long groove 45 is increased. Accordingly, the ink temporarily stored in the storage chamber in the pressure adjusting unit 38 is sent into the long groove 45 through the flow path substrate 27.
Then, when the control unit 63 selectively inputs a correction voltage to the predetermined drive electrode unit 50, the volume of the long groove 45 is reduced, and the ink fed into the long groove 45 is ejected through the nozzle opening 52. The As a result, ink droplets land on the surface of the paper S.
That is, while the paper S is sent in the depth direction D from the rear side to the front side of the apparatus main body 2, the carriage 7 is moved in the width direction W, and ink is ejected at an appropriate timing, whereby predetermined printing is performed on the paper S. Is done.

Here, since the deformation amount of the piezoelectric ceramic plate 44 differs depending on the temperature, in order to improve the discharge accuracy, it is necessary to correct the driving voltage input to each piezoelectric ceramic plate 44 according to each temperature. Therefore, as described above, the specific drive voltage value, the specific temperature reference drive voltage value, and each temperature reference drive voltage value are determined in advance.
That is, variation in ejection performance over a plurality of piezoelectric ceramic plates 44 at 25 ° C. is suppressed by the specific drive voltage value and the specific temperature reference drive voltage value. In addition, each temperature reference drive voltage value suppresses variation in ejection performance over a predetermined temperature range in the reference piezoelectric ceramic plate 44A.
However, in the remaining piezoelectric ceramic plate 44, when the temperature is not 25 ° C., the variation in ejection performance becomes large.

Therefore, conventionally, a uniform correction value is added to each temperature reference drive voltage value to correct the input drive voltage.
FIG. 7 is a table showing the correspondence between the temperature reference drive voltage of the conventional piezoelectric ceramic plate as a reference, the correction voltage of the other piezoelectric ceramic plate, and the temperature.
FIG. 8 is a graph of the table of FIG. 7 and 8, “head temperature (° C.)” indicates the temperature of the piezoelectric ceramic plate.
In FIG. 8, symbol A1 is a reference temperature-voltage curve showing each temperature reference drive voltage value of the reference piezoelectric ceramic plate having a specific temperature reference drive voltage of 21.5 V for each temperature.
Reference symbol A2 is a corrected temperature-voltage curve showing, for each temperature, the correction voltage of the piezoelectric ceramic plate having a specific drive voltage of 18V.
Reference symbol A3 is a corrected temperature-voltage curve showing, for each temperature, the corrected voltage of the piezoelectric ceramic plate whose intrinsic drive voltage is 25V.

Conventionally, the difference obtained by subtracting the specific temperature reference drive voltage value VG from the specific drive voltage value VF is used as the correction value. Then, the difference is uniformly added to each temperature reference drive voltage value of the reference piezoelectric ceramic plate to obtain a correction voltage value.
That is, as shown in FIG. 7, for a piezoelectric ceramic plate having a specific drive voltage value of 18V, for example, −3.5, which is obtained by subtracting the specific temperature reference drive voltage value 21.5 from the specific drive voltage value 18V, is used as the correction value. . Then, for example, at 25 ° C., a correction value of −3.5 is added to each temperature reference drive voltage value of 24.8 V of the reference piezoelectric ceramic plate to obtain a correction voltage value of 21.3 V. For example, for a piezoelectric ceramic plate having a specific drive voltage value of 25V, +3.5, which is obtained by subtracting the specific temperature reference drive voltage value 21.5 from the specific drive voltage value 25V, is used as the correction value. For example, at 25 ° C., the correction value +3.5 is added to each temperature reference drive voltage value 24.8V to obtain a correction voltage value 28.3V.

Thus, as shown in FIGS. 7 and 8, conventionally, for the remaining piezoelectric ceramic plates, a correction voltage is obtained by uniformly offsetting a correction value as a difference from the reference temperature-voltage curve A1. It was.
However, if the correction value is uniformly offset, the offset ratio with respect to each temperature reference drive voltage changes for each temperature. For example, the ratio at 15 ° C. is 3.5 / 29.0 = 0.12, but the ratio at 50 ° C. is 3.5 / 19.1 = 0.18. That is, when the specific drive voltage value is larger than the specific temperature reference drive voltage value, the correction value becomes positive. Therefore, the higher the temperature of the piezoelectric ceramic plate, the larger the ratio of the correction value to be added. As a result, the correction voltage value becomes larger than the appropriate drive voltage. Therefore, the higher the temperature of the piezoelectric ceramic plate, the larger the discharge speed and the amount of discharged droplets. In contrast, when the specific drive voltage value is smaller than the specific temperature reference drive voltage value, the correction value becomes negative. Therefore, the higher the temperature of the piezoelectric ceramic plate, the larger the ratio of the correction value to be added. As a result, the correction voltage value becomes smaller than the appropriate drive voltage. Therefore, the higher the temperature of the piezoelectric ceramic plate, the smaller the discharge speed and the amount of discharged droplets.

FIG. 9 is a graph showing a difference in discharge speed between the specific drive voltage and the specific temperature reference drive voltage (21.5 V) with respect to the specific drive voltage.
FIG. 10 is a graph showing the difference in ejected droplet amount between the specific drive voltage and the specific temperature reference drive voltage (21.5 V) with respect to the specific drive voltage.
9 and 10, each difference is 0 (zero) and ideally a straight line parallel to the horizontal axis. However, conventionally, since the ratio of correction values changes, turn into.

According to the ink jet recording apparatus 1 in the present embodiment, the control unit 63 can calculate the correction voltage value with high accuracy by performing the processing as follows.
FIG. 11 is a flowchart showing the processing of the control unit 63.
When printing is instructed from a personal computer or the like connected to the inkjet recording apparatus 1, the control unit 63 reads a temperature information signal from the head temperature detection unit 64 (step S1). When it is determined that the temperature information signal is not active (step S2: NO), the controller 63 repeats the process of step S1. On the other hand, when it is determined that the temperature information signal is active (step S2: YES), the control unit 63 reads the specific temperature reference drive voltage value from the storage unit 65 (step S3). The specific temperature reference drive voltage value (21.5 V) is input in advance by the user via an operation unit (not shown) and stored in the storage unit 65.
Then, the control unit 63 substitutes 1 for the variable N (step S4). That is, the control unit 63 secures a predetermined area of a memory (not shown) as a variable N, and writes 1 in the predetermined area.

Further, the control unit 63 reads the first (Nth) unique drive voltage value from the storage unit 65 (step S5). The unique drive voltage value is input in advance by the user via an operation unit (not shown) according to the inkjet head 3 to be attached, and stored in the storage unit 65.
Then, the control unit 63 calculates a difference value SS between the first (Nth) specific drive voltage value VF and the specific temperature reference drive voltage value VG from the following equation (1) (step S6).
SS = VF-VG (1)
That is, the control unit 63 subtracts the specific temperature reference drive voltage value VG from the specific drive voltage value VF.
Specifically, for example, as shown in FIG. 12, when the specific temperature reference drive voltage value VG is 21.5V and the specific drive voltage value VF is 18V or 25V, the result is as follows. That is, the correction value SS when the specific drive voltage value VF is 18V is 18-21.5 = −3.5. Further, the correction value SS when the inherent drive voltage value VF is 25 V is 25-21.5 = 3.5.

  Further, the control unit 63 reads each temperature reference drive voltage value corresponding to the temperature detected by the head temperature detection unit 64 from the temperature-voltage table 65a of the storage unit 65 (step S7). Each temperature reference drive voltage value read at this time is referred to as “detected each temperature reference drive voltage value”. For example, from the temperature-voltage table 65a shown in FIG. 6, if the detected temperature is 15 ° C. (or 50 ° C.), the temperature reference drive voltage value 29.0V (or 19.1V: The numerical value at 50 ° C. is read out. At this time, 29.0 V (or 19.1 V) is the detected temperature reference drive voltage value.

Furthermore, the control unit 63 reads out each temperature reference drive voltage value corresponding to the reference temperature for calculating the correction coefficient from the temperature-voltage table 65a. Each temperature reference drive voltage value read at this time is referred to as “each temperature reference drive voltage value as a reference”. For example, from the temperature-voltage table 65a shown in FIG. 6, if the reference temperature is 25.0 ° C., the control unit 63 reads each temperature reference drive voltage value 24.8V corresponding thereto. At this time, 24.8V is a reference temperature reference drive voltage value.
And the control part 63 calculates the correction coefficient k by the following (2) Formula from each detected temperature reference drive voltage value VD and each temperature reference drive voltage value VS used as a reference (step S8).
k = VD / VS (2)
That is, the control unit 63 divides each detected temperature reference drive voltage value VD by each temperature reference drive voltage value VS used as a reference. That is, the correction coefficient k is an increase / decrease rate of each detected temperature reference drive voltage value VD with respect to each temperature reference drive voltage value VS used as a reference.
Specifically, as shown in FIG. 12, the correction coefficient k is 29.0 V (or 19.1 V) /24.8 V≈1.16 (or 0.77).

Then, the control unit 63 calculates a difference correction value SC from the difference value SS calculated in step S6 and the correction coefficient k according to the following equation (3) (step S9).
SC = SS · k (3)
That is, the control unit 63 multiplies the difference value SS and the correction coefficient k.
Specifically, as shown in FIG. 12, when the specific drive voltage value VF is 18V, the difference correction value SC is −3.5 × 1.16 (or 0.77) ≈−4.06 (or − 2.69), and the differential correction value SC when the specific drive voltage value VF is 25 V is 3.5 × 1.16 (or 0.77) ≈4.06 (or 2.69).

Further, the control unit 63 calculates a correction voltage value VC from the detected temperature reference drive voltage value VD and the difference correction value SC according to the following equation (4) (step S10).
VC = VD + SC (4)
That is, the control unit 63 adds each detected temperature reference drive voltage value VD and the difference correction value SC.
Specifically, as shown in FIG. 12, when the specific drive voltage value VF is 18 V, the correction voltage value VC is 29.0 (or 19.1) −4.06 (or −2.69) ≈24. .9V (or 16.4V), and the correction voltage value VC when the specific drive voltage value VF is 25V is 29.0 (or 19.1) +4.06 (or +2.69) ≈33.0V (or 21.7V).

Further, the control unit 63 outputs a control signal to the drive voltage generation unit 66, and outputs the correction voltage of the correction voltage value VC calculated in step S10 via the drive voltage generation unit 66 to the first (Nth) head. At an appropriate timing (step S11). As a result, ink is ejected from the inkjet head 3 and landed on the paper S.
Further, the control unit 63 increments the variable N by one (step S12), and determines whether or not the variable N is larger than the total number of heads input in advance (step S13). When determining that the variable N is smaller than the total number of heads (step S13: NO), the control unit 63 returns to step S5 and repeats the process. As a result, appropriate correction voltage values are similarly input to the remaining nozzles. On the other hand, when the control unit 63 determines that the variable N is larger than the total number of heads (step S13: YES), the process ends.

  As described above, according to the ink jet recording apparatus 1 of the present embodiment, the difference value SS can be appropriately corrected by the correction coefficient k, so that a more appropriate correction voltage value VC can be obtained. Therefore, an appropriate drive voltage corresponding to each temperature can be input to the predetermined piezoelectric ceramic plate 44, and the dispersion of the discharge performance can be accurately performed across the plurality of piezoelectric ceramic plates 44 and over a predetermined temperature range. Can be suppressed.

That is, the ratio of the difference correction value at 15 ° C. to each detected temperature reference drive voltage is 4.06 / 29.0≈0.14, and the ratio at 50 ° C. is 2.69 / 19.1≈. 0.14. That is, the ratio of the difference correction value can be made equal over the temperatures. In other words, when the specific drive voltage value is larger than the specific temperature reference drive voltage value, the higher the temperature of the piezoelectric ceramic plate 44, the smaller the difference correction value to be added. On the other hand, when the specific drive voltage value is smaller than the specific temperature reference drive voltage value, the difference correction value to be added can be increased as the temperature of the piezoelectric ceramic plate 44 is higher.
Therefore, as shown in FIG. 13, the range at the reference temperature is 3.5 + 3.5 = 7V, whereas the range at 15 ° C. is 4.06 + 4.06≈8.2V, and the range at 50 ° C. Is 2.69 + 2.69≈5.4V.
As a result, as shown in FIG. 14 and FIG. 15, the slopes of the discharge speed difference and the discharge droplet amount difference can be made gentle, and the characteristics of the discharge speed difference and the discharge droplet amount difference can be changed over the predetermined temperature range. It can be close to an ideal straight line (0 (zero)) parallel to the axis. Therefore, variation in discharge performance can be suppressed, and the discharge performance can be made substantially constant.

In addition, since the ink jet recording apparatus 1 according to the present embodiment includes the thermistor 61 and the head temperature detection unit 64, the temperature of the piezoelectric ceramic plate 44 can be detected with high accuracy, and the ejection performance can be improved with higher accuracy. Can be suppressed.
Further, since the correction coefficient is the increase / decrease rate of each detected temperature reference drive voltage value relative to each reference temperature reference drive voltage value, the difference value can be corrected with high accuracy.

(Embodiment 2)
Next, a second embodiment of the present invention will be described.
16 to 20 show a second embodiment of the present invention.
16 to 20, the same components as those shown in FIGS. 1 to 15 are denoted by the same reference numerals, and the description thereof is omitted.
This embodiment and the first embodiment have the same basic configuration, and only the differences will be described here.

The present embodiment differs from the first embodiment in the way of calculating the correction coefficient. That is, as shown in FIG. 16, the control unit 63 increases / decreases the detected temperature reference drive voltage value with respect to each reference temperature reference drive voltage value (correction for temperature change) and each reference temperature reference. The correction coefficient k1 is calculated using the increase / decrease rate of the Nth specific drive voltage value with respect to the drive voltage value (correction for the specific drive voltage). The increase / decrease rate (correction for temperature change) indicates the correction coefficient k in the first embodiment.
That is, in step S8a, the control unit 63 calculates the following from the Nth specific drive voltage value, the specific temperature reference drive voltage value, each detected temperature reference drive voltage value, and the specific temperature reference drive voltage value: The correction coefficient k1 is calculated by the equation (5). As described above, VF is the Nth specific drive voltage value, VG is the specific temperature reference drive voltage value, VD is the detected temperature reference drive voltage value, and VS is the reference temperature reference drive voltage value. Show.
k1 = {1- (VF / VG) · (1-VD / VS)} (5)

Specifically, as shown in FIG. 17, assuming that the Nth unique drive voltage value is 18 V, the specific temperature reference drive voltage value is 21.5 V, the detected temperature is 15 ° C., and the reference temperature is 25 ° C., {1 − (18.0V / 21.5V) · (1-29.0V / 24.8V)} ≈1.14.
From the equation (3), the difference correction value SC is −3.5 × 1.14≈−3.99. Further, from the equation (4), the correction voltage value VC is 29.0-3.99≈25.0.

Further, as shown in FIG. 18, the range at the reference temperature is 3.5 + 3.5 = 7V, whereas the range at 15 ° C. is 8.0V, and the range at 50 ° C. is 5.7V. Become.
As a result, as shown in FIGS. 19 and 20, the gradients of the discharge speed difference and the discharge droplet amount difference can be made more gradual, and the characteristics of the discharge speed difference and the discharge droplet amount difference can be maintained over a predetermined temperature range. Further, it can be made closer to an ideal straight line (0 (zero)) parallel to the horizontal axis. That is, variation in ejection performance can be suppressed with higher accuracy over a plurality of piezoelectric ceramic plates 44 and over a predetermined temperature range.
Further, since the correction coefficient k is further corrected by a predetermined increase / decrease rate (correction with respect to the specific drive voltage), a more accurate correction coefficient k1 can be obtained.

  In the first and second embodiments, ink is put into all the long grooves 45 of the piezoelectric ceramic plate 44. However, the present invention is not limited to this, and ink is put into only the predetermined long grooves 45. May be. That is, when water-based ink or the like is used, the water-based ink is electrolyzed when a voltage is applied to the drive electrode unit 50 in a state where the water-based ink is placed in the long groove 45, and thereby the drive electrode in the long groove 45. The parts 50 are short-circuited. Therefore, ink is put in every other long groove 45, and a voltage is applied only to the drive electrode portion 50 of the long groove 45 where ink cannot be put, so that the drive electrode portion 50 of the long groove 45 into which ink is put is connected to the ground. What is necessary is just to make it connect.

  Further, a program for calculating a correction voltage value and realizing a function of inputting the correction voltage to the piezoelectric ceramic plate 44 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is stored in the computer system. Various controls may be performed by reading and executing. Here, the “computer system” includes an OS and hardware such as peripheral devices.

Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.
The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

It is a figure which shows 1st Embodiment of the inkjet recording device which concerns on this invention, Comprising: It is a perspective view which shows a mode that the housing | casing was seen through. It is a perspective view which expands and shows the inkjet head of FIG. It is the figure which expanded and showed the inkjet head chip | tip of FIG. 2, Comprising: It is a disassembled perspective view which shows a mode that a part of longitudinal direction was fractured | ruptured. It is a disassembled perspective view which expands and shows a part of inkjet head chip of FIG. It is a block diagram which shows the inkjet recording device in this embodiment for every function. It is a figure which shows the temperature-voltage table a which the memory | storage part of FIG. 5 has. It is a table | surface which shows the response | compatibility with each temperature reference drive voltage of the conventional piezoelectric ceramic plate used as a reference | standard, and the correction voltage of other piezoelectric ceramic plates, and temperature. FIG. 8 is a graph of the table of FIG. It is a graph which shows the difference of the discharge speed of these specific drive voltage and specific temperature reference drive voltage with respect to the specific drive voltage in FIG. It is a graph which shows the difference of the ejection droplet amount of these specific drive voltage and specific temperature reference drive voltage with respect to the specific drive voltage in FIG. It is a flowchart which shows the process of the control part of FIG. In this embodiment, it is a table | surface which shows the response | compatibility with each temperature reference drive voltage of the piezoelectric ceramic plate used as a reference | standard, the correction voltage of another piezoelectric ceramic plate, a correction coefficient, and temperature. 13 is a graph of the table of FIG. It is a graph which shows the difference of the discharge speed of these specific drive voltage and specific temperature reference drive voltage with respect to the specific drive voltage in FIG. It is a graph which shows the difference of the droplet amount of these specific drive voltages and specific temperature reference drive voltage with respect to the specific drive voltage in FIG. It is a figure which shows a part of 2nd Embodiment of the inkjet recording device which concerns on this invention, Comprising: It is a flowchart which shows the process of a control part. In this embodiment, it is a table | surface which shows the response | compatibility with each temperature reference drive voltage of the piezoelectric ceramic plate used as a reference | standard, the correction voltage of another piezoelectric ceramic plate, a correction coefficient, and temperature. FIG. 17 is a graph of the table of FIG. It is a graph which shows the difference of the discharge speed of these specific drive voltage and specific temperature reference drive voltage with respect to the specific drive voltage in FIG. It is a graph which shows the difference of the discharge droplet amount of these specific drive voltage and specific temperature reference drive voltage with respect to the specific drive voltage in FIG. It is a graph which shows the relationship between environmental temperature and the viscosity of an ink.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 3 Inkjet head 61 Thermistor (temperature detection means)
64 Head temperature detector (temperature detection means)
63 control unit (difference calculation means, correction coefficient calculation means, difference correction means, correction voltage calculation means, input control means)
66 Drive voltage generator (voltage generator)
S paper (recording medium)

Claims (6)

An inkjet recording apparatus having a plurality of inkjet heads for ejecting ink onto a recording medium,
In order to suppress variation in ejection performance at a specific temperature across the plurality of ink jet heads, a specific driving voltage that is uniquely determined in advance for each of the plurality of ink jet heads and a reference among the plurality of ink jet heads. Difference calculating means for calculating a difference with a specific temperature reference driving voltage that is a specific driving voltage of the reference inkjet head;
Correction coefficient calculating means for calculating a correction coefficient for suppressing variation in ejection performance over each temperature of the inkjet head over a predetermined temperature range including each temperature and over the plurality of inkjet heads;
Difference correction means for correcting the difference calculated by the difference calculation means using the correction coefficient calculated by the correction coefficient calculation means;
In order to suppress variations in ejection performance over the respective temperatures of the reference ink jet head over a predetermined temperature range including the respective temperatures, the difference correction means is applied to each temperature reference driving voltage determined in advance according to each temperature. A correction voltage calculating means for calculating a correction voltage at each temperature of the plurality of inkjet heads by adding the difference corrected by
Input control means for inputting a correction voltage calculated by the correction voltage calculation means from a voltage generation means for generating a voltage for driving the plurality of ink jet heads to the predetermined ink jet head. Recording device. Temperature detecting means for detecting the temperature of each of the plurality of inkjet heads;
The correction voltage calculation means includes
The correction voltage at the detected temperature is calculated by adding the difference corrected by the difference correction unit to each temperature reference drive voltage corresponding to the temperature detected by the temperature detection unit. The ink jet recording apparatus according to claim 1.   3. The ink jet recording apparatus according to claim 1, wherein the correction coefficient is an increase / decrease rate of each other temperature reference drive voltage with respect to one temperature reference drive voltage as a reference. 4. The correction factor is
Increase / decrease rate of each other temperature reference drive voltage with respect to one temperature reference drive voltage as a reference,
The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is calculated using an increase / decrease rate of the specific drive voltage with respect to each of the temperature reference drive voltages as a reference. An inkjet head driving method in an inkjet recording apparatus having a plurality of inkjet heads that eject ink onto a recording medium,
In order to suppress variation in ejection performance at a specific temperature across the plurality of inkjet heads, a specific driving voltage that is uniquely determined in advance for each of the plurality of inkjet heads and a reference from the plurality of inkjet heads. A difference calculation step for calculating a difference with a specific temperature reference drive voltage that is a specific drive voltage of the reference inkjet head;
A correction coefficient calculation step for calculating a correction coefficient for suppressing variations in ejection performance over each temperature of the inkjet head over a predetermined temperature range including each temperature and over the plurality of inkjet heads;
A difference correction step for correcting the difference calculated by the difference calculation step using the correction coefficient calculated by the correction coefficient calculation step;
In order to suppress variation in ejection performance over each temperature of the reference ink jet head over a predetermined temperature range including each temperature, the difference correction step is performed to each temperature reference drive voltage predetermined according to each temperature. A correction voltage calculating step of calculating the correction voltage at each temperature of the plurality of inkjet heads by adding the difference corrected by
An inkjet head drive comprising: an input step of inputting a correction voltage calculated in the correction voltage calculation step to a predetermined inkjet head from a voltage generation means for generating a voltage for driving the plurality of inkjet heads. Method. In a computer of an ink jet recording apparatus having a plurality of ink jet heads for discharging ink onto a recording medium,
In order to suppress variation in ejection performance at a specific temperature across the plurality of ink jet heads, a specific driving voltage that is uniquely determined in advance for each of the plurality of ink jet heads and a reference among the plurality of ink jet heads. A difference calculation step for calculating a difference from a specific temperature reference drive voltage that is a specific drive voltage of the reference inkjet head;
A correction coefficient calculation step for calculating a correction coefficient for suppressing variations in ejection performance over each temperature of the inkjet head over a predetermined temperature range including each temperature and over the plurality of inkjet heads;
A difference correction step for correcting the difference calculated by the difference calculation step using the correction coefficient calculated by the correction coefficient calculation step;
In order to suppress variation in ejection performance over each temperature of the reference ink jet head over a predetermined temperature range including each temperature, the difference correction step is performed to each temperature reference drive voltage predetermined according to each temperature. A correction voltage calculating step of calculating the correction voltage at each temperature of the plurality of inkjet heads by adding the difference corrected by
An input step of inputting a predetermined correction voltage calculated by the correction voltage calculation step to the predetermined inkjet head from a voltage generation unit that generates a voltage for driving the plurality of inkjet heads. Driving program.

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