JP3214026B2 - Ink jet head and method of driving ink jet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention
The present invention relates to an on-demand type ink jet head that forms dots on recording paper using the ink droplets.

[0002]

2. Description of the Related Art As a conventional ink jet head using a piezoelectric element such as PZT as a pressure generating member, there is Japanese Patent Publication No. 60-8953. This relates to an ink jet head that performs multi-drive using PZT as a piezoelectric element.

[0003]

When a piezoelectric element such as PZT is used as a pressure generating member, or when operation is continued under high humidity or in a dew condensation state, P
Driving characteristics are significantly deteriorated due to moisture absorption of the ZT and a decrease in insulation resistance, and the like, and there is a fear that the printing performance may be reduced and the pressure generating member may be fatally destroyed.

An object of the present invention is to provide a mechanism for preventing a fatal destruction of a pressure generating member under high humidity or in a dew state.

[0005]

According to the present invention, there is provided an ink jet head comprising: a nozzle forming substrate having a nozzle; an ink chamber communicating with the nozzle; and a pressure generating member for pressurizing the ink chamber. It is provided with humidity detecting means provided near the member for detecting humidity near the pressure generating member, and control means for stopping driving of the pressure generating member based on information detected by the humidity detecting means. Further, the inkjet head of the present invention,
In an ink jet head including a nozzle forming substrate having a nozzle, an ink chamber communicating with the nozzle, and a pressure generating member for pressurizing the ink chamber, a humidity detector provided near the pressure generating member and detecting humidity near the pressure generating member. Means, dehumidifying means for dehumidifying the vicinity of the pressure generating member, and control means for driving the dehumidifying means based on information detected by the humidity detecting means. Further, in such an ink jet head, the pressure generating member is made of PZT, and an area outside the driving area of the PZT is used as humidity detecting means. In addition, a method of driving an ink jet head according to the present invention includes a method of driving an ink jet head including a nozzle opening, an ink chamber communicating with the nozzle opening, and a piezoelectric element that generates pressure for discharging ink droplets in the ink chamber. Wherein the driving of the head is stopped when the humidity detected by the humidity detecting means disposed near the piezoelectric element is equal to or higher than a specific value.
Further, the method of driving an ink jet head according to the present invention is directed to a method of driving an ink jet head including a nozzle opening, an ink chamber communicating with the nozzle opening, and a piezoelectric element for generating pressure for discharging ink droplets in the ink chamber. When the humidity detected by the humidity detecting means disposed in the vicinity of the piezoelectric element is equal to or more than a specific value, dehumidification is performed by a dehumidifier.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the entire ink jet head of the present invention. However, in order to explain the inside of the ink jet, it is shown in a partially cut state. FIG. 2 is a cross-sectional view of the front end surface of the inkjet head of FIG.

The outline of the operation of the ink jet head using the present invention is as follows. The configuration of the main part includes a nozzle forming substrate 33 on which the nozzle 34 is formed, a structure 32 forming the ink chamber 51, and the thin film 3 forming a boundary between the ink chamber 51 and the pressure generating member 21.
1, a mounting joint 30 for connecting the pressure generating member 21 and the ink chamber 51, an ink supply port 35 for supplying ink to the ink chamber 51, and a structure 37 for fixing the entire inkjet head of the present invention. Has become.

The operation at the time of discharging ink is as shown in FIGS. Here, 40 is a driving power supply, 41 is a pressure generating member charging switch, 42 is a pressure generating member discharging switch, 20 is an individual electrode corresponding to each nozzle 34, and 22 is a common electrode corresponding to all nozzles. . In the embodiment of the present invention, a laminated PZT is used as the pressure generating member. The displacement direction used is a direction perpendicular to the stacking direction.

FIG. 2 shows a steady state in which no electric field is applied to the pressure generating member 21. Here, when the charging switch 41 is closed and an electric field is applied to the pressure generating member 21, the pressure generating member 21 is displaced in the direction of arrow 66, and simultaneously draws the connected joint 30, and the thin film 31 is moved to the ink chamber 51. In the direction to enlarge. At this time, the ink corresponding to the increased volume of the ink chamber 51 is supplied from the ink supply port 35. Next, as shown in FIG. 4, the charging switch 41 is opened, and the discharging switch 42 is opened.
Close. At this time, the pressure generating member 21 is displaced in the direction of the arrow 65 and acts in the direction of decreasing the volume of the ink chamber 51 at this time. This causes the pressurized ink to fly outside from the nozzle 34. The above is a series of operations for ink ejection.

FIGS. 5 and 6 are views for explaining the displacement direction of the laminated PZT used as the pressure generating member 21. FIG.

FIG. 5 is a diagram showing a state where the pressure generating member 21 is charged. By closing the charging switch 41 and opening the discharging switch 42, the driving power supply 40 is connected between the individual electrode 20 and the common electrode 22. At this time, the pressure generating member 21 is deformed to become thicker in the direction of the arrow 61 from its piezoelectricity and polarization direction. At this time, it is deformed in the direction of contraction in the direction of arrow 62 at a ratio determined by the Poisson ratio. In the embodiment of the present invention, the displacement in the direction of the arrow 62 is used.

FIG. 6 is a diagram showing a state in which the pressure generating member 21 is being discharged. By opening the charging switch 41 and closing the discharging switch 42, the individual electrode 20 is opened.
And the common electrode 22 are connected to discharge the electric charge in the pressure generating member 21. At this time, a thinning deformation occurs in the direction of the arrow 64, and at the same time, it deforms in a direction extending in the direction of the arrow 63 and returns to the original state.

FIG. 7 is a perspective view when the pressure generating section 21 is taken out alone. FIG. 8 shows a configuration in which a humidity detecting unit 70 is attached as means for detecting the humidity near the pressure generating unit 21. Reference numeral 71 denotes a sensor electrode for extracting a signal from the humidity detector 70.

FIGS. 9 and 10 show internal cross-sectional views of the humidity detecting section 70. FIG.

FIG. 9 shows an example in which the humidity detecting section 70 is formed directly on the pressure generating member 21. In advance, the pressure generator 2
A nickel chromium-gold electrode is formed on the surface of 1 by a sputtering method or the like, and a sensor electrode 71 is formed by a photolithography method. This is the individual electrode 20
And the same material and construction method. Further, the humidity detecting section 70 can be formed by applying the water absorbing resin 73 containing the conductive particles 72. By employing this method, the humidity at a position closer to the pressure generating section 21 can be detected, and the reliability of the detected value has been improved. In addition, since it can be formed integrally, it can be downsized as a whole,
The simplification of the manufacturing process was also realized.

FIG. 10 shows a structure in which an electrode 75 and a water-absorbent resin 73 containing conductive particles 72 are previously drawn on a substrate 74 such as alumina.
A humidity detecting section 70 is formed and attached to a sensor electrode 71 formed on the pressure generating member 21 so as to maintain electrical continuity. In this case, since the pressure generating member 21 and the humidity detecting unit 70 are separated, the highly accurate humidity detecting unit 7 is not affected by the pressure generating member 21.
0 could be obtained.

FIG. 11 is a connection diagram for reading signals from the humidity detector 70 of the type shown in FIGS. The humidity information extracted by the sensor electrode 71 is input to the sensor reading unit 80. In this case, the individual drive electrode 20 and the drive unit 81, the wiring 83 connecting the drive unit 81 and the individual drive electrode, and the wiring 84 connecting the common electrode 22 and the common terminal of the drive unit 81 are different from the system for reading the humidity information. , Completely independent. Therefore, the control system for driving the pressure generating member 21 and the control system for reading the humidity information need not be synchronized, and both can be easily controlled.

FIGS. 16 and 17 show examples of a circuit manufactured as the sensor reading section 80. FIG.

FIG. 16 shows, using a comparator 90, whether or not the humidity exceeds the humidity determined by the value set by the comparison variable resistor 95. Normally, driving for a long time at a humidity exceeding 80% may cause fatal damage to the pressure generating member 21. Therefore, when the humidity exceeds the threshold value, it is necessary to suspend the driving of the head, or to activate a device for dehumidifying the vicinity of the head, such as a heating device or a blowing device. This series of controls is performed by a control device using a CPU. Humidity information 91 to be given to the control device is created in this circuit.

The humidity sensor of the type manufactured in FIGS. 9 and 10 has a resistance value with respect to the relative humidity as shown in FIG. Therefore, in order to give a threshold value to the humidity of 80%, the voltage dividing resistor 94 is set to 100
Ω, the comparison variable resistor 95 is set at the middle point. Here, by closing the measurement voltage application switch 93, the comparator 90 compares the measurement voltage 92 divided by the resistance ratio of the voltage dividing resistor 94 and the sensor 96 with the output voltage of the comparison variable resistor 95. . At this time, if the humidity is higher than the set threshold value, the divided voltage on the sensor side becomes higher, so that the output 91 of the comparator 70 outputs a true logical value. If the humidity is lower than the set threshold, the output 91 outputs a false logical value. The control device using the CPU reads this logical value, and stops driving the head or activates the dehumidifying means near the head.

FIG. 17 shows an example in which the comparator 90 is replaced with A
This is an example using the / D conversion unit 98. By using the A / D converter 98, the control unit using the CPU can know the current relative humidity as an absolute value. Therefore, by knowing the temporal displacement of the humidity, it is predicted in advance that the humidity will enter the inoperable region of the ink jet head, and the driving of the head is stopped by activating the head dehumidifying means in advance. And continuous operation was possible in the safe operation area.

FIGS. 12 and 13 show an example in which PZT itself used as the pressure generating unit 21 is used as humidity detecting means by utilizing the hygroscopicity of the PZT itself. The sensor electrode 76 formed simultaneously with the individual electrode 20 by a sputtering method or the like.
And a change in the resistance value between the common electrode 22 to detect the humidity and the dew state. FIG. 20 shows the change in the resistance value of PZT used in this example with respect to the relative humidity.
As shown in FIG. As the circuit of the sensor reading section 80, the circuits shown in FIGS. 16 and 17 can be used as they are. However, since the change characteristic of the resistance value with respect to humidity is as shown in FIG. 20, the output 91 of the comparator 90 is a false logical value in the operable region, and the output 91 of the comparator 90 is in the non-operable region. Output 91 will indicate a true logical value. FIG. 14 is an example in which the humidity is detected by measuring the current flowing between the common electrode 22 and the common terminal of the drive unit 81. In this case, when an arbitrary individual electrode 20 is driven by the driving unit 81, the current flowing through the wiring 84 connecting the common electrode 22 and the common terminal of the driving unit 81 is detected, thereby detecting the resistance between the driven electrodes. This is a method of calculating a value. As an example of the current detection unit 86, a circuit manufactured in FIG. 18 is shown. A current detection resistor 101 is inserted in the middle of the wiring 84, a voltage generated at both ends of the current detection resistor 101 is amplified by an operational amplifier 102, and the voltage value 88 is converted into a digital value by an A / D converter 103. Thus, the resistance value of PZT can be obtained by reading and calculating by the control unit using the CPU. From this result, the driving of the head is stopped or the head dehumidifying means is activated. Further, what is measured by the method shown in FIG. 14 is a portion of PZT that is actually used for printing. Therefore, by knowing the resistance value, it is possible to know the disconnection, short-circuit, and abnormal resistance value of the drive circuit, and it is also possible to notify the user of a failure of the head to the outside. As a result, it is possible to notify the time of head replacement and the like.

FIG. 15 shows an example in which a changeover switch 87 for selectively connecting the drive unit 81 and the sensor reading unit 85 is provided for each drive electrode 20. this is,
This is an example in which a portion of PZT that is actually used for printing is used as a humidity sensor, similarly to the configuration described with reference to FIG. In this case, the circuits shown in FIGS. 16 and 17 can be used as the sensor reading unit 85, and both the humidity detection and the abnormality detection of the head itself can be realized with a simpler circuit.

[0025]

As described above, the ink jet head according to the present invention comprises an ink jet head having a nozzle forming substrate having a nozzle, an ink chamber communicating with the nozzle, and a pressure generating member for pressurizing the ink chamber. By providing a humidity detecting means provided near the pressure generating member and detecting humidity near the pressure generating member, and a control means for stopping the driving of the pressure generating member based on information detected by the humidity detecting means, In the case of high humidity that may cause performance degradation or catastrophic damage, by restricting the operation of the pressure generating member, it is possible to prevent deterioration and damage of the pressure generating member. Can be provided. In addition, an ink jet head according to the present invention includes a nozzle forming substrate having a nozzle, an ink chamber communicating with the nozzle, and a pressure generating member that pressurizes the ink chamber. By having a humidity detecting means for detecting humidity near the member, a dehumidifying means for dehumidifying the vicinity of the pressure generating member, and a control means for driving the dehumidifying means based on information detected by the humidity detecting means, the pressure generating member has remarkable performance. In a high-humidity condition that may cause deterioration or fatal damage, dehumidifying means can prevent the pressure-generating member from deteriorating and damaging, thereby providing a long-term highly reliable inkjet head. It has the effect of being able to.
Further, in such an ink jet head, the pressure generating member is made of PZT, and by using a region outside the driving region of the PZT as a humidity detecting unit, the resistance value of the pressure generating member is measured in addition to the above-mentioned effects. This makes it possible to check the function of the head itself, which has the effect of further improving the long-term reliability of the ink jet head.

[Brief description of the drawings]

FIG. 1 is a perspective view of an inkjet head according to the present invention.

FIG. 2 is a longitudinal sectional view of the inkjet head of the present invention.

FIG. 3 is a longitudinal sectional view of the inkjet head of the present invention,
It is a figure in the state where the pressure generating member was contracted.

FIG. 4 is a longitudinal sectional view of the inkjet head of the present invention,
It is a figure in the state where the pressure generating member was extended.

FIG. 5 is an operation explanatory diagram when the pressure generating member contracts.

FIG. 6 is an operation explanatory diagram when the pressure generating member is extended.

FIG. 7 is a perspective view of a pressure generating unit.

FIG. 8 is an explanatory diagram when a humidity detecting unit is attached to the pressure generating unit.

FIG. 9 is a diagram illustrating an example of forming a humidity detection unit.

FIG. 10 is a diagram illustrating an example of mounting a humidity detecting unit.

FIG. 11 is a connection diagram of a humidity detector.

FIG. 12 is an enlarged cross-sectional view of a humidity detector.

FIG. 13 is an explanatory diagram in the case where PZT is used as a humidity detector.

FIG. 14 is a connection diagram when humidity is measured by a current detector.

FIG. 15 is a connection diagram of an example in which a driving unit and a sensor reading unit are switched and operated.

FIG. 16 is a diagram illustrating a circuit example of a sensor reading unit using a comparator.

FIG. 17 is a diagram illustrating a circuit example of a sensor reading unit using an A / D converter.

FIG. 18 is a diagram illustrating a circuit example of a sensor reading unit using current detection.

FIG. 19 is a diagram showing resistance characteristics of a humidity detector formed of conductive particles.

FIG. 20 shows resistance characteristics of a humidity detector when PZT is used.

[Explanation of symbols]

 20 individual electrode 21 pressure generating part 22 common electrode 31 thin film 33 nozzle forming substrate 34 nozzle 35 ink supply port 40... Drive power supply 41... Charge switch 42... Discharge switch 50... Ink droplet 51... Ink chamber

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-90248 (JP, A) JP-A-4-284431 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/045

Claims (5)

(57) [Claims] 1. An ink jet head comprising : a nozzle forming substrate having a nozzle; an ink chamber communicating with the nozzle; and a pressure generating member for pressurizing the ink chamber, wherein the pressure generating member is provided near the pressure generating member. Wet
Humidity detecting means for detecting the temperature, the humidity detecting means detects
Driving of the pressure generating member is stopped according to the obtained information.
A control means.
Good. 2. An ink jet head comprising : a nozzle forming substrate having a nozzle; an ink chamber communicating with the nozzle; and a pressure generating member for pressurizing the ink chamber, wherein the vicinity of the pressure generating member is provided near the pressure generating member. Wet
Humidity detecting means for detecting the temperature,
Dehumidifying means for dehumidifying, and information detected by the humidity detecting means
Control means for driving the dehumidifying means by means of
An ink jet head, characterized in that: 3. The ink jet head according to claim 1, wherein the pressure generating member is made of PZT, and an area outside a driving area of the PZT is used as a humidity detecting unit. 4. A method for driving an ink jet head, comprising: a nozzle opening; an ink chamber communicating with the nozzle opening; and a piezoelectric element for generating a pressure for ejecting ink droplets in the ink chamber. A method for driving the ink jet head, wherein the driving of the head is stopped when the humidity detected by the humidity detecting means provided in the printer is equal to or more than a specific value. 5. A method for driving an ink jet head, comprising: a nozzle opening; an ink chamber communicating with the nozzle opening; and a piezoelectric element for generating a pressure for ejecting ink droplets in the ink chamber. A method for driving an ink-jet head, characterized in that when the humidity detected by the disposed humidity detecting means is equal to or higher than a specific value, dehumidification is performed by a dehumidifier.