JP6086289B2 - Droplet discharge head and image forming apparatus - Google Patents

Description

  The present invention relates to a droplet discharge head and an image forming apparatus employing the droplet discharge head.

  A printer, a fax machine, a copier, a plotter, or an image forming apparatus that combines a plurality of these functions includes, for example, a droplet ejection head that ejects ink droplets, and transports ink droplets while conveying a medium. There is an ink jet recording apparatus that forms an image by adhering to an ink jet recording apparatus. The medium here is also referred to as “paper”, but the material is not limited, and a recording medium, a recording medium, a transfer material, a recording paper, and the like are also used synonymously. The image forming apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics. The image formation is not only giving an image having a meaning such as a character or a figure to the medium but also giving an image having no meaning such as a pattern to the medium (simply ejecting a droplet). Also means. The ink is not limited to so-called ink, and is not particularly limited as long as it becomes liquid when ejected. For example, the ink is a generic term for liquids including DNA samples, resists, pattern materials, and the like. Use.

  The droplet discharge head in the ink jet recording apparatus includes a plurality of nozzles that discharge ink droplets, each pressurizing fluid chamber that communicates with each of the plurality of nozzles, and actuator means that generates energy for boosting each pressurizing fluid chamber; And a common liquid chamber that communicates with each pressurized liquid chamber and supplies ink. The actuator means includes a piezoelectric element corresponding to each pressurized liquid chamber, a drive circuit for driving the piezoelectric element, and a wiring member. In this droplet discharge head, the actuator means applies a voltage to each piezoelectric element from the drive circuit, and deforms each piezoelectric element according to the voltage via a diaphragm that forms one wall surface of the pressurized liquid chamber. It is transmitted to the ink in each pressurized liquid chamber. The pressure-increased ink in the pressurized liquid chamber is ejected from the nozzle. Then, the amount of ink discharged from the common liquid chamber is supplied into the pressurized liquid chamber from which the ink has been discharged.

  When ink is discharged by driving the actuator means with such a droplet discharge head, the electrical loss of the piezoelectric element, the electrical loss of the drive circuit, the electrical loss due to the resistance component of the wiring member, etc. are released as heat, This heat increases the head temperature of the droplet discharge head. When the ink temperature in the head rises as the head temperature rises, the ink viscosity decreases. If the driving waveform for driving the piezoelectric element is constant, there is a problem that the ejection characteristics change due to such a change in the ink viscosity and the image quality deteriorates.

To solve such a problem, the temperature of the droplet discharge head is detected by a temperature sensor, and based on the detected head temperature, a drive waveform for driving the piezoelectric element of the droplet discharge head can be obtained with constant discharge characteristics. There is known a technique for controlling to a driving waveform.
Further, in Patent Document 1, the temperature of the ink jet recording apparatus is detected by a temperature sensor, and the temperature of the droplet discharge head is determined based on the detected temperature in the apparatus, and driving history information on the number of print dots of the image and the print time. An apparatus provided with an arithmetic circuit for estimation is described.

In an actual droplet discharge head, the head temperature is not uniform, and a temperature gradient in the nozzle arrangement direction is generated depending on the image to be formed. Specifically, when the print data of the image is concentrated in a part of the arrangement direction, the driving frequency of the actuator means in that part increases, and the temperature of that part greatly increases.
Further, the temperature gradient in the nozzle arrangement direction is also generated depending on the arrangement positions of the constituent members of the droplet discharge head. For example, in the wiring member that supplies the drive signal of the actuator means to the piezoelectric element, in the portion that is the common wiring of the plurality of piezoelectric elements, the flowing current is large, so the temperature rise in that portion is large. Ink is supplied from an external ink cartridge to the common liquid chamber of the droplet discharge head, but the ink that is supplied from the ink cartridge near the ink supply port flows away from the heat and flows away. The temperature rise is small. On the other hand, at a position away from the ink supply port of the common liquid chamber, the ink supplied from the ink cartridge flows through the common liquid chamber and is warmed. For this reason, the temperature rise is larger than that near the ink supply port.
As described above, in an actual droplet discharge head, a temperature gradient in the arrangement direction is generated depending on the degree of concentration of the image to be formed and the arrangement position of the constituent members.

  On the other hand, in a device that detects the temperature of the droplet discharge head by the temperature sensor and controls the drive waveform based on the detected head temperature, the temperature is usually detected by using one temperature sensor. Then, based on only the detected temperature at the temperature sensor installation position, the drive waveform of the entire droplet discharge head is controlled to a drive waveform that provides a certain discharge characteristic. That is, this apparatus does not take into consideration the actual temperature gradient of the droplet discharge head. For this reason, the controlled driving waveform is not optimal for suppressing the change in the ejection characteristics due to the temperature rise for the entire droplet ejection head, and there is a risk of degrading the image quality.

  In order to actually perform control in consideration of the temperature gradient of the droplet discharge head, a plurality of temperature sensors are arranged in the arrangement direction, and the drive waveform of the entire droplet discharge head is based on the temperatures detected by the plurality of temperature sensors. It is conceivable to control. However, this method requires a plurality of temperature sensors, detection circuits, and wirings to be mounted in the droplet discharge head, leading to an increase in cost.

  The apparatus of Patent Document 1 estimates the head temperature based on the in-machine temperature detected by the temperature sensor and the drive history information of the number of print dots and the print time of the entire formed image. The head temperature is not estimated in consideration of the concentration degree of the image data and the temperature gradient in the arrangement direction due to the arrangement of the constituent members. For this reason, even if the drive waveform of the entire droplet discharge head is controlled based on the estimated head temperature, the controlled drive waveform suppresses a change in discharge characteristics due to a temperature rise in the entire droplet discharge head. It will not always be optimal.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a purpose thereof is a droplet discharge head and image formation that can satisfactorily suppress a change in discharge characteristics due to a temperature rise due to driving of the droplet discharge head at a low cost. Is to provide a device.

In order to achieve the above object, the invention of claim 1 is characterized in that a plurality of nozzles for ejecting ink droplets, each pressurized liquid chamber communicating with the plurality of nozzles, and energy for pressurizing each pressurized liquid chamber are provided. Actuating actuator means, a common liquid chamber communicating with the pressurized liquid chamber for supplying ink, a temperature sensor for detecting the head temperature, and a driving waveform of the actuator means are controlled so as to obtain a certain discharge performance. In a droplet discharge head provided with a control unit,
The droplet discharge head is divided into a plurality of areas in the nozzle arrangement direction, and includes a counting unit that counts the number of print dots for each of the divided areas, and the control unit detects a head temperature detected by the temperature sensor. And the number of printed dots for each of the plurality of areas counted by the counting means, and the drive waveform is controlled, and the temperature rise in each area is estimated from the number of printed dots in each area counted by the counting means. When the difference in the magnitude of the temperature rise exceeds a predetermined value, the control unit decreases the frequency of the voltage driven by the actuator .

  In the present invention, the actuator means so as to obtain a constant discharge performance based on the head temperature detected by the temperature sensor and the number of print dots for each of the plurality of regions divided in the arrangement direction counted by the counting means. To control the driving waveform. In this way, the control unit uses not only the head temperature detected by the temperature sensor but also the data of the number of print dots for each of the plurality of regions divided in the arrangement direction, so that the actual arrangement direction of the droplet discharge heads The drive waveform can be controlled in consideration of the temperature gradient. According to this, it becomes possible to control the drive waveform suitable for the actual temperature rise of the droplet discharge head, as compared with the device that controls the drive waveform using only the head temperature detected by the conventional temperature sensor. In addition, this apparatus is advantageous in terms of cost because it is not necessary to provide a plurality of temperature sensors for detecting a temperature gradient.

  According to the present invention, there is an excellent effect that it is possible to satisfactorily suppress a change in ejection characteristics due to a temperature rise due to driving of a droplet ejection head at a low cost.

FIG. 3 is a perspective view of a droplet discharge head according to the present embodiment. FIG. 4 is a schematic diagram of a heat generating portion that accompanies driving of a liquid discharge head. Explanatory drawing of the counting means which counts the number of printing dots for every group. FIG. 2 is a side view illustrating the overall configuration of the inkjet recording apparatus according to the embodiment. FIG. 2 is a plan view of a main part of the ink jet recording apparatus according to the embodiment.

Hereinafter, a droplet discharge head according to an embodiment of the present invention will be described.
FIG. 1 is an exploded perspective view of a droplet discharge head according to the present embodiment. 1 mainly includes a nozzle plate 11, an actuator substrate 12, a common liquid chamber substrate 13, a housing 14, an FPC 15, and the like.

The nozzle plate 11 has a plurality of nozzles 16 perforated in two rows.
The actuator substrate 12 includes a plurality of pressurized liquid chambers (not shown) that supply ink to the nozzles 16. Specifically, the partition wall of the pressurizing liquid chamber is formed by a method of etching the Si substrate, and the pressurizing liquid chamber is formed by laminating a diaphragm on the Si substrate. On this diaphragm, electrodes, piezoelectric elements 5 and the like as actuator means for generating energy for individually raising the pressure in each pressurized liquid chamber are laminated and formed corresponding to each individual liquid chamber. Further, a drive circuit 3 for driving each piezoelectric element 5 and a wiring member 20 for inputting a drive signal to the drive circuit 3 are provided.
The common liquid chamber substrate 13 includes a common liquid chamber 18 that supplies ink to each pressurized liquid chamber via the communication path 17.
The housing 14 includes an ink supply path 19 that supplies ink from an ink cartridge (not shown) into the common liquid chamber 18.

  Further, the liquid discharge head is provided with a connector substrate (not shown) having an electrical pad that is electrically connected to a connector arranged in an inkjet recording apparatus, which will be described later, and transmits an electrical signal corresponding to a recorded image. Yes. Furthermore, a drive circuit 3 for driving the piezoelectric element 5 provided on the actuator substrate 12, and an FPC 15 for electrically connecting the wiring member 20 connected to the drive circuit 3 and the connector substrate are provided. An electrical signal transmitted from the ink jet recording apparatus in accordance with the recorded image is supplied to the piezoelectric element 5 of the actuator substrate 12 via a connector substrate (not shown) and the FPC 15. The mechanical vibration converted by the piezoelectric element 5 pressurizes the ink in the pressurized liquid chamber via the diaphragm, and the ink is ejected from the nozzle onto the recording paper with high accuracy. Then, the amount of ink discharged from the common liquid chamber 18 is supplied into the pressurized liquid chamber from which the ink has been discharged.

FIG. 2 is a schematic view of a heat generating portion that accompanies driving of the liquid discharge head. The drive signal for the droplet discharge head is supplied from the control device 1 to the drive IC (drive circuit) 3 via the drive signal wiring member 2 and applied to each piezoelectric element 5 from the drive IC 3 via the individual wiring member 4. It is connected to the control device 1 via the common electrode 6. The drive IC 3 selects a drive signal so that a drive waveform is applied only to the piezoelectric element 5 to be driven.
In this droplet discharge head, an ink supply path 19 (see FIG. 1) for supplying ink from an ink cartridge (not shown) into the common liquid chamber 18 is provided at the center of the nozzle arrangement direction. Ink is supplied from the ink supply port, which is the outlet of the ink supply path 19, to the central portion of the common liquid chamber 18 in the arrangement direction of the nozzles. Further, a temperature sensor (not shown) for detecting the head temperature is installed at the center of the nozzle arrangement direction.

In the present embodiment, as shown in FIG. 2, the droplet discharge heads are divided into the following three groups (regions) A, B, and C in the nozzle arrangement direction.
Group A is a region away from the central portion, and is a region where the temperature rises greatly as the ink supplied from the central ink supply port flows while flowing.
The B group is an area near the ink supply port in the central portion, and the temperature rise is small because unwarmed ink is supplied.
The group C is a region away from the center, and has a large temperature rise as in the group A, and the region where the temperature rise is the largest because the supply currents to the heads of the drive signal wiring 2 and the common electrode wiring 6 are concentrated. It is.

FIG. 3 is an explanatory diagram of counting means for counting the number of print dots for each of the three groups A, B, and C. The number of print data corresponding to the groups A, B, and C is counted from image data transferred to the head from the control device 1, and the number of dots printed in a predetermined time immediately before the head temperature is determined is obtained. For example, when obtaining the number of dots at time T1, the number of dots is counted by a counter every time T2 (T1> T2), and the value is written to the ring buffer. Then, by calculating the total value of the data in the ring buffer when determining the number of dots for T1, the number of print dots for a certain time T1 can be easily determined.

Further, in order to use the count value for temperature correction as will be described later, it is preferable to perform the weighting according to the droplet size (according to the input energy to the head) for counting.
In the above example, the counter means uses a timer to count the number of print dots in each group for a fixed time, but may count the number of print dots per page of the image.

  Then, based on the head temperature detected by the temperature sensor and the print dot count data of each group counted by the counting means, the drive waveform of the piezoelectric element 5 is controlled so as to obtain a certain discharge performance. Hereinafter, a specific example of drive waveform control based on the head temperature and the print dot count data of each group will be described.

In the liquid droplet ejection head of this embodiment, the number of print dots is counted for each of the three groups A, B, and C divided above, and the number of print dots for each group is weighted by the position in the arrangement direction of each group, Rank as the degree of influence on head temperature rise. Then, the head temperature detected by the temperature sensor is corrected based on the combination of the influence values, and the drive waveform is selected based on the corrected temperature.

Table 1 is an example of a table showing the relationship between the counted number of printed dots in each group and the degree of influence on the head temperature. According to the table of Table 1, the counted number of print dots in each group for a certain period of time is weighted according to the position of each group in the arrangement direction, and ranked as an influence on the head temperature rise.

In this table, the degree of influence on the head temperature is ranked into 0 to 3, and the number of print dots per second of each group is weighted so that the degree of influence on the head temperature of each rank is the same. doing. For example, group B has an ink supply port, and unheated ink passes, so heat is taken from the head. For this reason, in group B, compared with group A and group C, the number of print dots showing the same temperature rise is the largest. In Group C, since the common wiring portion generates heat, the number of print dots showing the same temperature rise is reduced.

温度センサの補正値は、上記テーブルでの印刷を実行したときにヘッド内に発生する温度勾配の場合に、最適印刷ができる駆動波形が選択される補正値とする。この温度センサ補正テーブルは、予め実験により各影響度の組み合わせでのグループ毎のインク温度上昇値を求め、値を決定しておく。 Table 2 is an example of a temperature sensor correction table showing the relationship between the combination of the degree of influence on the head temperature and the correction value. With reference to the table in Table 2, a correction value for correcting the detected temperature detected by the temperature sensor is determined by a combination of ranks having an influence degree of 0 to 3 on the head temperature. In this embodiment, a temperature sensor (not shown) is installed at a position for detecting the temperature of group B, which is the central portion in the arrangement direction.

The correction value of the temperature sensor is a correction value for selecting a drive waveform that can be optimally printed in the case of a temperature gradient generated in the head when printing is performed using the above table. In this temperature sensor correction table, an ink temperature increase value for each group in a combination of each degree of influence is obtained in advance by experiment, and the value is determined.

Hereinafter, detailed description will be given with specific numbers.
The correction value is determined based on the temperature of the group in which the temperature sensor is mounted. For example, when the temperature sensor is mounted at the position of group B, if the temperature rise is (1 ° C., 0 ° C., 1 ° C.) with the influence degree (1, 0, 0), the drive waveform is The correction value is set to “+ 0.5 ° C.” so that a waveform having a median value of 0.5 ° C. is selected. If the temperature rise is (2 ° C., 1 ° C., 3 ° C.) with the influence level (1, 1, 1), the correction value is similarly set to “+ 1 ° C.”.

<Waveform selection example 1>
When the temperature sensor is 27 ° C., the influence degree is (1, 0, 0), and the correction value is + 0.5 ° C., the selected drive waveform is 27.5 ° C. The sensor detection temperature indicates the temperature of group B, and the waveform having the median value of 27.5 ° C. is selected assuming that the temperature of each group is (28 ° C., 27 ° C., 28 ° C.).
<Waveform selection example 2>
When the temperature sensor is 28 ° C., the influence is (1, 1, 1), and the correction value is + 1 ° C., the selected drive waveform is 29 ° C. The sensor detection temperature indicates the temperature of group B, and the waveform with the median value of 29 ° C. is selected assuming that the temperature of each group is (29 ° C., 28 ° C., 30 ° C.).

  Immediately after the power of the droplet discharge head is turned on, the number of printing dots within a certain period of time immediately before is zero, so there is no difference between the temperature detected by the temperature sensor and the head temperature. For this reason, the control unit selects a driving waveform using the temperature detected by the temperature sensor as the head temperature, and drives the head by applying it to the piezoelectric element. On the other hand, when printing is performed and the head temperature rises, a temperature gradient is formed in the head, but by correcting the temperature detected by the temperature sensor using the temperature sensor correction value obtained from the tables in Tables 1 and 2. The optimum driving waveform is selected. At this time, even if there is a temperature difference between the ink temperature and the temperature sensor, which has the greatest effect on the ejection characteristics, the difference between the ink temperature and the detected value at the temperature sensor can be determined in advance by taking a correction value into consideration. Can also be corrected.

  As described above, in the above embodiment, the droplet discharge head is divided into a plurality of areas in the nozzle arrangement direction, the number of print dots for each area is counted, and the counted number of print dots for each group is calculated. Weighted by position, ranked as the degree of influence on head temperature rise. Then, the head temperature detected by the temperature sensor is corrected based on the combination of the influence values, and the drive waveform is selected based on the corrected temperature. The degree of influence on the head temperature rise is an estimation of the magnitude of the temperature rise in each area in consideration of the degree of image concentration in each area and the ease of temperature rise due to the arrangement position of each area. Then, since the head temperature detected by the temperature sensor is corrected based on the combination of weighted values, the corrected temperature becomes the head temperature in consideration of the concentration degree of the image and the temperature gradient depending on the arrangement position of each region. By controlling the drive waveform of the actuator means using such a head temperature, an actual liquid droplet can be obtained as compared with a conventional device that controls the drive waveform using a head temperature that does not consider the temperature gradient in the head. The drive waveform can be controlled to suit the temperature of the ejection head.

  Here, the difference in the value of the influence of each group represents the difference in the temperature rise in each group, that is, the temperature gradient in the droplet discharge head. When the difference between the influence values is greater than or equal to a predetermined value, it indicates that the temperature gradient in the head is greater than the predetermined value. In such a case, the temperature gradient is too large, and it is determined that good ejection performance cannot be obtained if the entire droplet ejection head is driven with one drive waveform. For this reason, when the difference between the influence values becomes equal to or greater than a predetermined value, the control unit stops driving the actuator and stops image formation. Thereby, it is possible to prevent the quality of the output image from being deteriorated.

  Further, when the difference between the influence values becomes equal to or greater than a predetermined value, the control unit may restrict the actuator to be driven only in a region where the difference between the influence values is equal to or less than the predetermined value. Thus, when the temperature gradient in the head becomes large, printing is performed only with nozzles in a range where the temperature gradient is small, and it is possible to prevent a decrease in print quality.

  Further, when the difference between the influence values becomes a predetermined value or more, the control unit may reduce the frequency of the voltage driven by the actuator. Thereby, printing can be continued while suppressing a temperature rise.

Next, an ink jet recording apparatus as an image forming apparatus equipped with the above-described droplet discharge head will be described.
FIG. 4 is a side view for explaining the overall configuration of the ink jet recording apparatus, and FIG. 5 is a plan view of the main part of the apparatus. In this ink jet recording apparatus, a carriage 103 is slidably held in a main scanning direction by a guide rod 101 and a guide rail 102 which are horizontally disposed on left and right side plates (not shown). Then, the main scanning motor 104 moves and scans in the arrow direction (main scanning direction) in FIG.

The carriage 103 includes, for example, an inkjet head 107 serving as a droplet ejection head that ejects ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). Are arranged in a direction crossing the main scanning direction. The ink droplet is ejected in the downward direction. The carriage 103 is equipped with ink cartridges 108 for each color for supplying ink of each color to the inkjet head 107.
On the other hand, a paper feeding unit for feeding paper 112 loaded on a paper stacking unit (pressure plate) 111 such as a paper feeding cassette 110 is provided. The paper feed unit is provided with a half-moon roller (paper feed roller) 113 that separates and feeds paper 112 one by one from the paper stacking unit 111 and a paper feed roller 113, and a separation pad 114 made of a material having a large friction coefficient, The separation pad 114 is urged toward the paper feed roller 113 side.

  A transport belt 121 for electrostatically adsorbing and transporting the paper 112 is provided as a transport unit for transporting the paper 112 fed from the paper feed unit below the inkjet head 107. In addition, a counter roller 122 for transporting the paper 112 fed from the paper supply unit via the guide 115 with the transport belt 121 interposed therebetween, and a transport guide 123 for following the transport belt 121 are provided. ing. Further, a tip pressure roller 125 urged toward the conveying belt 121 by the pressing member 124 and a charging roller 126 as a charging unit for charging the surface of the conveying belt 121 are provided.

  Here, the conveyance belt 121 is an endless belt, and is stretched between the conveyance roller 127 and the tension roller 128, and the conveyance roller 127 rotates from the sub-scanning motor 131 via the timing belt 132 and the timing roller 133. Is done. Thus, the belt is configured to circulate in the belt conveyance direction (sub-scanning direction) in FIG. Note that a guide member 129 is disposed on the back surface side of the conveyance belt 121 corresponding to the image forming area by the ink jet head 107.

In the image forming apparatus configured as described above, the sheets 112 are separated and fed one by one from the sheet feeding unit, and the sheet 112 fed substantially vertically upward is guided by the guide 115, and includes the conveyance belt 121 and the counter roller 122. It is sandwiched between and conveyed. Further, the front end is guided by the transport guide 123 and pressed against the transport belt 121 by the front end pressure roller 125, and the transport direction is changed by about 90 °.
At this time, a positive voltage and a negative output are alternately applied to the charging roller 126 from a high voltage power source by a control circuit (not shown), that is, an alternating voltage is applied. As a result, the charging voltage pattern in which the conveyor belt 121 alternates, that is, plus and minus are alternately charged in a band shape with a predetermined width in the sub-scanning direction that is the circumferential direction. When the paper 112 is fed onto the conveyance belt 121 charged alternately with plus and minus, the paper 112 is attracted to the conveyance belt 121 by electrostatic force, and the paper 112 is conveyed in the sub-scanning direction by the circular movement of the conveyance belt 121. Is done.

  Therefore, by driving the inkjet head 107 according to the image signal while moving the carriage 103, ink droplets are ejected onto the stopped paper 112 to record one line, and after the paper 112 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 112 has reached the recording area, the recording operation is finished, and the paper 112 is discharged onto the paper discharge tray 154.

  Note that the image forming apparatus according to the present invention can also be applied to a printer, a facsimile machine, a copying machine, a multi-function machine thereof, and the like. Further, the present invention can also be applied to a droplet discharge head or a droplet discharge device that discharges a liquid other than ink, such as a DNA sample, a resist, or a pattern material, or an image forming apparatus that includes these.

What has been described above is merely an example, and the present invention has specific effects for each of the following aspects.
(Aspect A)
A plurality of nozzles for ejecting ink droplets, each pressurizing liquid chamber communicating with the plurality of nozzles, actuator means for generating energy for boosting each pressurizing liquid chamber, and supplying ink to the pressurizing liquid chamber The liquid droplet ejection head includes a common liquid chamber, a temperature sensor that detects the head temperature, and a control unit that controls the drive waveform of the actuator means so as to obtain a certain ejection characteristic. The droplet discharge head is divided into a plurality of areas such as the A, B, and C groups with respect to the nozzle arrangement direction, and a counting unit 8 that counts the number of print dots for each divided area is provided. The control unit controls the drive waveform based on the head temperature detected by the temperature sensor and the number of print dots for each of the plurality of areas counted by the counting means. According to this, as described in the above embodiment, it is possible to satisfactorily suppress the change in the ejection characteristics due to the temperature rise due to the driving of the droplet ejection head at a low cost.

(Aspect B)
In (Aspect A), the counter means counts the number of print dots within a predetermined time for each divided area. According to this, as described in the above embodiment, it is possible to satisfactorily suppress the change in the ejection characteristics due to the temperature rise due to the driving of the droplet ejection head at a low cost.

(Aspect C)
In (Aspect A), the counter means counts the number of print dots per page of the image for each of the divided areas. According to this, as described in the above embodiment, it is possible to satisfactorily suppress the change in the ejection characteristics due to the temperature rise due to the driving of the droplet ejection head at a low cost.

(Aspect D)
In any one of (Aspect A), (Aspect B), and (Aspect C), the control unit has a temperature correction table that indicates a relationship between a preset number of print dots in each region and a temperature correction value. The head temperature detected by the temperature sensor is corrected with reference to the temperature correction table, and the drive waveform is controlled based on the corrected value. According to this, as described in the above embodiment, it is possible to obtain the head temperature in consideration of the temperature gradient of the droplet discharge head.

(Aspect E)
In any one of (Aspect A), (Aspect B), (Aspect C) or (Aspect D), the magnitude of the temperature rise in each area is estimated from the number of printed dots in each area, and the magnitude of the temperature rise When the difference is equal to or greater than a predetermined value, the control unit stops driving the actuator. According to this, as described in the above embodiment, when it is determined that the temperature gradient is too large and the entire droplet discharge head is driven with one drive waveform, good discharge performance cannot be obtained. Image formation can be stopped to prevent degradation of the output image quality.

(Aspect F)
In any one of (Aspect A), (Aspect B), (Aspect C) or (Aspect D), the magnitude of the temperature rise in each area is estimated from the number of printed dots in each area, and the magnitude of the temperature rise is calculated. When the difference is greater than or equal to a predetermined value, the control unit drives the actuator only in a region where the difference in magnitude of the temperature rise is less than or equal to the predetermined value. According to this, as described in the above embodiment, when it is determined that the temperature gradient is too large and the entire droplet discharge head is driven with one drive waveform, good discharge performance cannot be obtained. Image formation can be performed only with nozzles in a range where the temperature gradient is small, and deterioration in the quality of the output image can be prevented.

(Aspect G)
In any one of (Aspect A), (Aspect B), (Aspect C) or (Aspect D), the magnitude of the temperature rise in each area is estimated from the number of printed dots in each area, and the magnitude of the temperature rise is calculated. When the difference exceeds a predetermined value, the control unit decreases the frequency of the voltage driven by the actuator. According to this, as described in the above embodiment, printing can be continued while suppressing a temperature rise.

(Aspect H)
In an image forming apparatus that forms an image by adhering droplets ejected by droplet ejection means to the medium while transporting the medium, the liquid ejection heads of (Aspect A) to (Aspect G) are used as the droplet ejection means. Is adopted. According to this, as described in the above embodiment, a high-quality image can be obtained stably.

1 Control Device 2 Drive Signal Wiring Member 3 Drive IC
4 Individual wiring member 5 Piezoelectric element 6 Common electrode 8 Count means 11 Nozzle plate 12 Actuator substrate 13 Common liquid chamber substrate 14 Housing 15 FPC
16 Nozzle 18 Common liquid chamber 19 Ink supply path 107 Inkjet head

Japanese Patent Laid-Open No. 7-242404

Claims (5)

A plurality of nozzles for ejecting ink droplets; pressure fluid chambers communicating with the plurality of nozzles; actuator means for generating energy for boosting the pressure fluid chambers; and ink communicating with the pressure fluid chambers In a liquid droplet ejection head comprising a common liquid chamber for supplying a liquid, a temperature sensor for detecting a head temperature, and a control unit for controlling a drive waveform of the actuator means so as to obtain a constant ejection characteristic,
The droplet discharge head is divided into a plurality of areas in the nozzle arrangement direction, and includes a counting unit that counts the number of print dots for each of the divided areas, and the control unit detects a head temperature detected by the temperature sensor. And the number of printed dots for each of the plurality of areas counted by the counting means, and the drive waveform is controlled, and the temperature rise in each area is estimated from the number of printed dots in each area counted by the counting means. When the difference in the magnitude of the temperature rise exceeds a predetermined value, the control unit reduces the frequency of the voltage driven by the actuator . In the liquid droplet ejection head according to claim 1, said count means, the droplet discharge head, characterized by counting the number of print dots within a certain time of the divided each region. In the liquid droplet ejection head according to claim 1, said count means, the droplet discharge head, characterized by counting the number of print dot images per page of the divided each region. 4. The droplet discharge head according to claim 1, wherein the control unit has a temperature correction table indicating a relationship between the number of printed dots in each region and a temperature correction value, and refers to the temperature correction table. Then, the head temperature detected by the temperature sensor is corrected, and the drive waveform is controlled based on the corrected head temperature . While conveying the medium body, in with the droplet ejected by the liquid droplet discharge means is attached to the medium image forming apparatus for performing image formation, the droplet droplet-dispensing of claims 1 to 4 as a discharge means An image forming apparatus using a head.

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