JP2001205798A - Ink jet recorder, and method for driving ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in print quality regardless of variation in the quantity of load on each piezoelectric oscillator constituting an oscillator unit. SOLUTION: The ink jet recorder comprises a means 30 for detecting the temperature of each oscillator unit 2, means 44 for generating a plurality of drive signals depending on the temperature, a switching means 28 for delivering a drive signal to each piezoelectric oscillator 11 in response to a print signal, and a control means 40 for selecting the drive signal of the drive signal generating means 44 based on a temperature signal, wherein a drive signal suitable for driving the piezoelectric oscillator 11 in an optimal state is supplied by detecting the temperature of the oscillator unit 2 with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus using an ink jet recording head which generates ink droplets from nozzle openings by changing ink pressure by a piezoelectric vibrator which expands and contracts in the axial direction. The present invention relates to a technique for preventing a decrease in print quality due to a temperature change of a child.

[0002]

2. Description of the Related Art For example, when a piezoelectric vibrator in a longitudinal vibration mode as disclosed in Japanese Patent Application Laid-Open No. 5-104715 is used for driving an ink jet recording head, the contact area between the piezoelectric vibrator and the diaphragm is extremely reduced. Since the size can be reduced, a resolution of 180 DPI or more can be realized per unit. The piezoelectric vibrators in the longitudinal vibration mode are mounted on a fixed substrate at a constant pitch and assembled into a vibrator unit, and drive signals are individually supplied from a drive circuit to the individual piezoelectric vibrators via a flexible cable. In an ink jet recording head using such a piezoelectric vibrator as a pressure generating means, the piezoelectric constant is affected by the temperature as shown in FIG. 11, and the displacement increases as the temperature rises. In addition, there is a problem that the ejection characteristics of the ink droplets, that is, the ink amount and the flying speed of the ink droplets are greatly affected by the printing load, and the printing quality is degraded. To solve such a problem, Japanese Patent Application Laid-Open No. 6-34
No. 0074, estimating the temperature of the recording head,
It has been proposed to detect and control the drive energy supplied to the piezoelectric vibrator, such as the level of a drive signal, according to the temperature.

[0003]

However, a high-density piezoelectric vibrator unit of a recording head used for high-speed printing has a large number of piezoelectric vibrators mounted on one fixed substrate.
In this case, the temperature of each of the piezoelectric vibrators constituting the vibrator unit increases according to the load, and as a result, the recording head configuration There is a problem in that the ink amount and the flying speed of ink droplets ejected from each other among the plurality of nozzle openings vary, and print quality is degraded. In addition, in a recording head capable of performing color printing, since the plurality of piezoelectric vibrator units having the above-described configuration are accommodated in the same holder, variations occur between these piezoelectric vibrator units, and the print quality deteriorates. There is a problem. The present invention has been made in view of such a problem, and an object of the present invention is to provide a printing unit that has a variation in the amount of load of each of the piezoelectric vibrators constituting a vibrator unit, and further, a print quality due to a variation between the vibrator units. It is an object of the present invention to provide an ink jet recording apparatus capable of preventing fluctuation and reduction of the ink jet recording. Another object of the present invention is to propose a method of driving a recording head in which a plurality of piezoelectric vibrator units are housed in the same holder.

[0004]

According to the present invention, there is provided a piezoelectric vibrator comprising: a plurality of piezoelectric vibrators which expand and contract in the axial direction; and a plurality of piezoelectric vibrators fixed to a fixed substrate serving as a heat conductor of the piezoelectric vibrators. An ink jet recording head configured by fixing a vibrator unit and a flow path unit forming a pressure generating chamber communicating with a nozzle opening to a head holder, and a temperature detecting unit that detects a temperature of each vibrator unit. ,
A drive signal generating means capable of generating a plurality of drive signals corresponding to the temperature, and a switching means for selectively outputting a drive signal of the drive signal generating means to each piezoelectric vibrator in accordance with a print signal, Control means for selecting a drive signal of the drive signal generation means based on a signal from the temperature detection means.

[0005]

The fixed substrate functions as a heat buffer for absorbing the heat generated by each piezoelectric vibrator, and raises the temperature of the piezoelectric element generating a small amount of heat, thereby making the temperature of the entire piezoelectric vibrator uniform, and each vibrator unit. Temperature with high accuracy. Based on the detected temperature, a drive signal suitable for driving the piezoelectric vibrator in an optimal state is selected.

[0006]

FIG. 1 shows an embodiment of an ink jet recording head used in an ink jet recording apparatus according to the present invention. In this embodiment, five nozzle opening rows 1 are formed. The five piezoelectric vibrator units 2 are accommodated in the head holder 3 so as to correspond to the respective nozzle opening rows.

FIG. 2 shows a cross-sectional structure of one of the nozzle openings described above. The flow channel unit 4 communicates with the nozzle plate 6 in which the nozzle openings 5 are formed at a constant pitch and the nozzle openings 5. The pressure generating chamber 7, a flow path forming substrate 10 having a reservoir 9 for supplying ink to the pressure generating chamber 7 via an ink supply port 8, and the front end of each piezoelectric vibrator 11 in the vertical vibration mode of the piezoelectric vibration unit 2 are brought into contact with each other. An elastic plate 12 for expanding and reducing the volume of the pressure generating chamber 7 is integrally laminated.

The flow path unit 4 is connected to an opening surface 14 of the head holder 3 formed by injection molding of a polymer material, and the piezoelectric vibration unit 2 is connected to a flexible cable 15 for transmitting an external drive signal. Above accommodation room 16
The recording head is formed by inserting a frame 17 which also serves as a shield material on the nozzle plate side, with a contact surface with each head holder 3 fixed by an adhesive.
The head holder 3 is formed with an ink guide path 18 communicating with an external ink tank, and the tip thereof is connected to an ink inlet 19 of the flow path unit 4.

In the embodiment, the piezoelectric vibrator 11 of the longitudinal vibration mode constituting the vibrator unit 2 has an internal electrode 20 as one pole and an internal electrode 21 as the other pole via a piezoelectric material 22 in this embodiment. One having a piezoelectric constant d31 which is laminated in a sandwich shape and has one internal electrode 20 exposed on the front end side and the other internal electrode 21 exposed on the rear end side, and connected to the segment electrode 23 and the common electrode 24 at each end face. Configured as
The pressure generating chambers 5 are fixed to a fixed substrate 25 so as to match the arrangement pitch of the pressure generating chambers 5 and are assembled in the unit 2 as shown in FIG.

In such a piezoelectric vibrator 11, 11 ', one piezoelectric vibrating plate is fixed at one end to a fixed substrate 25, and is fixed at a predetermined pitch by a cutting tool such as a dicing saw so as to leave a fixed area. It is manufactured by forming a slit S. In FIG. 3, reference numerals 11 ′ and 11 ′ denote dummy piezoelectric vibrators for positioning the piezoelectric vibrator unit 2 at a predetermined position of the flow path unit 4.

As shown in FIG. 4, the slit S is formed so that the front end of the cutting tool D is on the fixed substrate 25 side and the rear end is on the upper side, so that the adjacent piezoelectric vibrator 11 is buffered. In addition to this, good heat conduction with the fixed substrate 25 can be ensured.

The piezoelectric vibrator unit 2 configured as described above applies an adhesive to the tip of the piezoelectric vibrator 11 and then comes into contact with the flow path unit 4 to fix the fixed substrate 25 to the adhesive layer 26.
To form a recording head fixed to the head holder 3.

The flexible cable 15 is provided with switching means 28 such as a transmission gate for selectively applying a drive signal from the drive signal generating means to each of the piezoelectric vibrators 11 in accordance with a print signal. A drive signal is supplied to each of the piezoelectric vibrators 11 via. The switching means 28 is disposed and fixed such that the exposed surface thereof forms a heat conductive relationship with the fixed substrate 25 via a mold agent or an adhesive layer 29 having high thermal conductivity.

These piezoelectric vibrators 11 are fixed to the fixed substrate 25 with an adhesive having a high thermal conductivity, and the fixed substrate 25 quickly absorbs heat due to dielectric loss or the like when ejecting ink droplets. On the other hand, the fixed substrate 25 is made of at least a material having a higher thermal conductivity than the material constituting the head holder 3 or the piezoelectric material 22, for example, a metal, and the heat capacity thereof is higher than that of all the piezoelectric vibrators 11. The temperature of the piezoelectric vibrator 11 is detected at a position where the temperature of the piezoelectric vibrator 11 can be detected.
0 are fixed via an adhesive layer 31 so as to form a heat conductive relationship.

According to this embodiment, when a print signal is input from a host or the like and applied to the piezoelectric vibrator 1, the piezoelectric vibrators 11, 11, 11... The chamber 7 is expanded. This allows the reservoir 9
Flows into the pressure generating chamber 7 through the ink supply port 8. When the electric charge of the piezoelectric vibrator 11 is discharged at the stage when a predetermined time has elapsed, the piezoelectric vibrator 11 expands to its original state,
The ink droplets are ejected from the nozzle openings 5 by restoring and contracting the pressure generating chamber 7.

When the piezoelectric vibrator 11 repeatedly charges and discharges, the piezoelectric material 22 constituting the piezoelectric vibrator generates heat in accordance with the drive duty due to dielectric loss, and the temperature rises. The heat generated by each piezoelectric vibrator 11 is conducted to the fixed substrate 25.

Since the thermal conductivity of the head holder 3 to which the fixed substrate 25 is fixed is kept lower than that of the fixed substrate 25, the heat generated by each piezoelectric vibrator 11 flows more than the heat flowing into the head holder 3. Is uniformed in the arrangement direction by the conductive action of the fixed substrate 25. Accordingly, since the fixed substrate 25 functions as a kind of heat buffer, the piezoelectric vibrator 11 having a low drive duty and a low temperature receives the supply of heat from the fixed substrate 25 and increases in temperature. 2, all the piezoelectric vibrators 11, 1
The temperatures of 1, 11, and ‥‥ are made as uniform as possible.

Therefore, each of the piezoelectric vibrators 11, 11, 1
(1) Variation in characteristics among each other becomes as small as possible. Therefore, the temperature of the piezoelectric vibrator can be detected with high accuracy even if a single temperature detecting means 30 is used.

By adjusting the drive signal in accordance with the temperature of each transducer unit 2 by the temperature detecting means 30 provided on the fixed substrate 25, all of the drive signals can be adjusted regardless of the temperature change and the drive duty variation. Printing can be performed with high quality by uniformly discharging ink droplets from the nozzle opening row.

The individual piezoelectric vibrators 11, 11, 1
The heat generated in (1) and (2) is transmitted to the head holder 3 after being made uniform by the fixed substrate 25, and is radiated from the surface of the head holder 3 to the atmosphere, and the ink guide path 18 of the head holder 3 is used for printing. It is absorbed by the ink that flows with it and prevents the entire recording head from overheating.

FIG. 5 shows an embodiment of a driving device suitable for a recording head having the above-described configuration.
1, a RAM 42, and a print control unit 40 composed of a CPU 43 are provided with a signal from a temperature detection unit 30 provided on each of the fixed substrates 25 of the plurality of transducer units 2, 2, 2 # constituting the recording head. And a plurality of drive signal generation means 4 in which a plurality of drive signals are previously set to be selectable.
4, a drive signal optimal for each of the transducer units 2, 2, 2,... Is selected and output.

The drive signal generating means 44 is provided as shown in FIG.
As shown in FIG. 7B, the voltage for ejecting the ink droplet is set to be higher than the low-temperature voltage V1 than the high-temperature voltage V2, or as shown in FIGS. 7A and 7B. The drive signal has different durations T1 and T2, that is, different pulse widths. Furthermore, the displacement characteristics of the piezoelectric vibrator 11 can be adjusted even when the voltage change rate of the rise or fall of each signal is changed.

With such a configuration, even if the load amount varies among the vibrator units constituting the same recording head, the vibrator unit is driven based on the signal of the temperature detecting means 30 of each vibrator unit 2. An optimal driving signal is selected from the signal generating means 44 and supplied to the switching means 28, and the individual piezoelectric vibrators 11 are displaced in accordance with a print signal from a host (not shown), so that ink droplets are formed in a prescribed state. Discharge. If the temperature of the vibrator unit 2 exceeds the specified upper limit temperature, the print control unit 40
Stops the printing operation to prevent the piezoelectric vibrator or the like from being damaged.

FIG. 8 shows another embodiment of the present invention. In this embodiment, the switching means 28 is used.
9 is connected to the timing adjusting means 45 at the preceding stage, and as shown in FIG.
The configuration is such that the switching signal 28 is output after delaying the drive signal for low temperature of FIG.

As a result, the ink amount of the ink droplet is corrected by the temperature change of the piezoelectric vibrator 11, and the flying speed of the ink droplet fluctuates due to the temperature. By correcting the position fluctuation, it is possible to reliably prevent the print quality from deteriorating.

In the above-described embodiment, the piezoelectric vibrators are arranged and fixed on one surface of the fixed substrate.
As shown in FIG. 0, the same effect can be obtained by arranging the piezoelectric vibrators 11 on both surfaces and attaching the temperature detecting means temperature 30 to only one surface of the fixed substrate 25.

In the above-described embodiment, the temperature of the piezoelectric vibrator is detected by attaching the temperature detecting means to the fixed substrate. As described above, the piezoelectric vibrator 11 has a piezoelectric multiplier depending on the temperature. Therefore, the value of the current flowing into the piezoelectric vibrator and the rate of change change according to the piezoelectric constant, that is, the capacitance temperature. Therefore, the temperature can be indirectly measured by detecting the change form of the current of the piezoelectric vibrator 11.

Further, the transmission gate constituting the switching means 28 is usually constructed as a semiconductor integrated circuit, and a diode for detecting the temperature is also provided therein, so that the temperature characteristic of the diode is detected. By doing so, the temperature of the vibrator unit 2 can be detected.

In the above-described embodiment, an example has been described in which the internal electrodes 21 and 22 have the piezoelectric constant d31 formed in the expansion and contraction direction. However, the internal electrodes are provided in a direction orthogonal to the expansion and contraction direction. A similar effect can be obtained when applied to a vibrator unit using a piezoelectric vibrator having a piezoelectric constant d33.

In the above-described embodiment, the switching means 28 such as a transmission gate is mounted on the flexible cable 15 and the switching means 28 is arranged on the fixed substrate 25 so as to form a heat conduction relationship. The same operation can be achieved even if the drive signal generating means composed of a semiconductor circuit for converting a signal into a drive signal is mounted in the same manner as the switching means 28 and is arranged and fixed on the fixed substrate 25 so as to form a heat conduction relationship. Play.

[0031]

As described above, according to the present invention, a plurality of vibrator units each having a plurality of piezoelectric vibrators which expand and contract in the axial direction fixed to a fixed substrate serving as a heat conductor of the piezoelectric vibrator, and a nozzle opening An ink jet recording head configured by fixing a flow path unit forming a pressure generating chamber communicating with a head holder to a head holder, temperature detecting means for detecting the temperature of each vibrator unit, and a plurality of drives corresponding to the temperature A driving signal generating means capable of generating a signal, a switching means for selectively outputting a driving signal of the driving signal generating means to each piezoelectric vibrator corresponding to a print signal, and a signal from the temperature detecting means. Control means for selecting the drive signal of the drive signal generation means, so that the temperature of the entire piezoelectric vibrator is made uniform by the good heat conduction characteristics of the fixed substrate,
The temperature of each transducer unit is detected with high accuracy, and a drive signal suitable for driving the piezoelectric transducers in an optimal state is selected, and the piezoelectric constant between the piezoelectric transducer units and between the piezoelectric transducers is determined. Variations in the ink droplet ejection characteristics due to the variations can be prevented.

[Brief description of the drawings]

FIG. 1 is an assembled perspective view showing one embodiment of an ink jet recording head used in a recording apparatus of the present invention.

FIG. 2 is a diagram showing the recording head in a cross-sectional structure in one pressure generating chamber.

FIG. 3 is a perspective view showing one embodiment of a vibrator unit constituting the recording head.

FIG. 4 is a diagram illustrating a severance line when a slit for separating a piezoelectric vibrator is formed.

FIG. 5 is a block diagram showing an embodiment of the recording apparatus of the present invention.

FIGS. 6A and 6B are waveform diagrams showing an example of a drive signal suitable for driving at a low temperature and at a high temperature, respectively.

FIGS. 7A and 7B are waveform diagrams showing an embodiment of a drive signal suitable for driving at a low temperature and at a high temperature, respectively.

FIG. 8 is a block diagram showing another embodiment of the recording apparatus of the present invention.

FIGS. 9A and 9B are waveform diagrams showing an example of a driving signal suitable for driving at a low temperature and at a high temperature, respectively.

FIG. 10 is a view showing another embodiment of the present invention in the structure of a piezoelectric vibrator unit.

FIG. 11 is a diagram illustrating an example of a relationship between a temperature and a displacement amount of a piezoelectric vibrator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle opening row 2 Piezoelectric vibrator unit 3 Head holder 4 Flow path unit 11 Piezoelectric vibrator 15 Flexible cable 25 Fixed substrate 28 Switching means 30 Temperature detecting means 40 Printing control means

Claims (16)

[Claims] 1. A flow forming a plurality of piezoelectric vibrators extending and contracting in an axial direction, a plurality of vibrator units fixed to a fixed substrate serving as a heat conductor of the piezoelectric vibrators, and a pressure generating chamber communicating with a nozzle opening. An ink jet recording head configured by fixing a path unit to a head holder; temperature detecting means for detecting a temperature of each of the vibrator units; a drive signal capable of generating a plurality of drive signals corresponding to the temperature Generating means; switching means for selectively outputting a drive signal of the drive signal generating means to each piezoelectric vibrator in accordance with a print signal; driving of the drive signal generating means based on a signal from the temperature detecting means An ink jet recording apparatus comprising: a control unit for selecting a signal. 2. An ink jet recording apparatus according to claim 1, wherein said drive signal generating means generates a drive signal having any one of a voltage value, a pulse width, and a voltage change rate corresponding to a temperature. 3. A timing adjusting means for adjusting timing for outputting the drive signal for each of the transducer units based on a signal from the temperature detecting means.
3. The ink jet recording apparatus according to claim 1. 4. The switching means is mounted on a film-like cable for supplying a drive signal to each of the piezoelectric vibrators of each of the vibrator units, and is fixed to the fixed substrate so as to form a heat conduction relationship. 2. The ink jet recording apparatus according to 1. 5. An ink jet recording apparatus according to claim 1, wherein said temperature detecting means comprises a temperature sensor attached to said fixed substrate. 6. An ink jet recording apparatus according to claim 5, wherein said temperature detecting means comprises a diode built in said switching means. 7. An ink jet recording apparatus according to claim 1, wherein said temperature detecting means comprises circuit means for detecting a current value flowing into said piezoelectric vibrator. 8. An ink jet recording apparatus according to claim 1, wherein said printing control means stops a recording operation when a temperature equal to or higher than a specified value is detected by said temperature detecting means. 9. The ink jet recording apparatus according to claim 1, wherein the fixed substrate is configured to have a larger heat capacity than the whole of the plurality of piezoelectric vibrators. 10. The ink jet recording apparatus according to claim 1, wherein the fixed substrate is made of a material having a higher thermal conductivity than the piezoelectric vibrator. 11. The piezoelectric vibrator according to claim 1, wherein one of the piezoelectric vibrating plates is divided so that an end of the piezoelectric vibrator on the fixed substrate side is continuous. Ink jet recording device. 12. The ink jet recording apparatus according to claim 1, wherein a plurality of piezoelectric vibrators are fixed on both surfaces of the fixed substrate. 13. A plurality of piezoelectric vibrators which expand and contract in the axial direction,
An ink jet recording head configured by fixing a plurality of vibrator units fixed to a fixed substrate serving as a heat conductor of the piezoelectric vibrator and a flow path unit forming a pressure generating chamber communicating with a nozzle opening to a head holder The method according to claim 1, further comprising: selecting a drive signal corresponding to the temperature of each of the vibrator units; and selectively outputting the selected drive signal to each of the piezoelectric vibrators in accordance with a print signal. A method for driving an ink jet recording head. 14. The method according to claim 13, wherein the drive signal changes one of a voltage value, a pulse width, and a voltage change rate according to the temperature of the vibrator unit. 15. The method according to claim 13, further comprising the step of adjusting the timing of outputting the drive signal to the piezoelectric vibrator in accordance with the temperature for each of the vibrator units. 16. The temperature of the vibrator unit is detected based on a current value flowing into the piezoelectric vibrator.
4. The method for driving an inkjet recording head according to item 3.