JP2003011363A - Ink jet head driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink jet head driver in which a head driver is protected against deterioration of characteristics or breakdown. SOLUTION: When a current detector 5 detects a current flowing into a ground line, a driving voltage waveform generator 1 generates a driving voltage waveform having an amplitude smaller than that of the power supply voltage of a head driver 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet head driving device using a piezoelectric element, and more specifically,
The present invention relates to an inkjet head drive device having a drive device that applies a voltage to a piezoelectric element and causes an ink droplet to be ejected from a nozzle hole by the strain force of the piezoelectric element.

[0002]

2. Description of the Related Art Conventionally, in a piezoelectric type ink jet head, a volume change is generated in a piezo element by applying a driving voltage that changes abruptly to a piezo element attached to a nozzle hole, and the volume of the ink chamber changes accordingly. Various types of recording are performed by ejecting ink drops from the nozzle holes onto the paper due to volume changes.

A conventional ink jet head driving device will be described below.

FIG. 7 is a block diagram showing a conventional ink jet head driving device.

In FIG. 7, the ink jet head driving device has a driving voltage waveform Va of a piezoelectric element which is a piezoelectric element.
From the drive voltage waveform generation apparatus 201 via the head driver 203 configured by the drive voltage waveform generation apparatus 201 for generating mp, the control switches SW201, SW202 ... SW20n, and receiving the drive voltage waveform Vamp, and the head driver 203. , P20n to which the drive voltage waveform Vamp of P20, P202 ... P20n is supplied are respectively control switches SW201, SW202 ... SW20.
The drive voltage waveform generator 201 and the head driver 203, and the head driver 203 and the head 204 are connected to each other by a transmission cable 202.

With such an ink jet head driving device, the driving voltage waveform Vamp supplied from the driving voltage generating device 201 passes through the transmission cable 202 and the control switch SW201 in the head driver 203,
Piezo element P20 via SW202 ... SW20n
1, P202 ... P20n, ink droplets are ejected and printing is performed.

[0007]

By the way, in the ink jet head drive device, the waveform is distorted due to factors such as the inductance component due to the length of the transmission cable, the piezo capacitance, the number of drive piezo connections, and the like. Is larger than the set value, or if the amplitude voltage of the drive voltage waveform exceeds the power voltage of the head driver due to a defect in the component parts, etc., current may flow in the parasitic transistor and diode of the head driver. , Leading to deterioration or destruction of the characteristics of the head driver.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ink jet head drive device which prevents the characteristic deterioration or destruction of the head driver.

[0009]

In order to solve this problem, an ink jet head drive device of the present invention is an ink jet head drive device for ejecting ink droplets from a nozzle hole by the distortion force of a piezoelectric element to which a voltage waveform is applied. And a drive voltage waveform generation device that generates a drive voltage waveform for the piezoelectric element, a head driver that is composed of a plurality of control switches and receives the drive voltage waveform, and a drive voltage waveform generation device through the head driver. Heads equipped with piezoelectric elements that are supplied with the drive voltage waveform of each control switch, and the ground line of the head driver when the amplitude voltage of the drive voltage waveform to the piezoelectric element exceeds the power supply voltage of the head driver. If the current detection device has a current detection device that detects the current flowing in the Dynamic voltage waveform generation device is obtained so as to generate a driving voltage waveform of smaller amplitude than the power supply voltage of the head driver.

As a result, it becomes possible to prevent the characteristic deterioration or destruction of the head driver.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is an ink jet head driving device for ejecting ink droplets from a nozzle hole by the strain force of a piezoelectric element to which a voltage waveform is applied, A drive voltage waveform generator that generates a drive voltage waveform, a head driver that is composed of a plurality of control switches and receives the drive voltage waveform, and a drive voltage waveform that is supplied from the drive voltage waveform generator through the head driver. A current that detects the current that flows in the head driver ground line when the amplitude voltage of the drive voltage waveform to the piezoelectric element exceeds the head driver power supply voltage If the current detection device has a detection device and the current detection device detects the current flowing in the ground line, the drive voltage waveform generation device determines the power source of the head driver. An ink jet head driving apparatus for generating driving voltage waveforms of a small amplitude voltage than pressure,
This has the effect of preventing the deterioration or destruction of the characteristics of the head driver.

According to a second aspect of the present invention, there is provided an ink jet head driving device for ejecting an ink droplet from a nozzle hole by a strain force of a piezoelectric element to which a voltage waveform is applied, the driving voltage waveform of the piezoelectric element being A drive voltage waveform generating device for generating, a head driver configured by a plurality of control switches to which the drive voltage waveform is input, and a piezoelectric element to which the drive voltage waveform is supplied from the drive voltage waveform generating device via the head driver. A head provided corresponding to each control switch, a current detection device for detecting a current flowing in the ground line of the head driver when the amplitude voltage of the drive voltage waveform to the piezoelectric element exceeds the power supply voltage of the head driver, Information from the current sensing device when the number of piezoelectric elements that apply the driving voltage waveform simultaneously is increased sequentially by the head driver. A driving voltage waveform generation device that estimates the current flowing in the ground line of the head driver when the driving voltage waveform is applied to all the piezoelectric elements connected to the head driver. Is an inkjet head drive device that generates a drive voltage waveform with an amplitude voltage smaller than the power supply voltage of the head driver, even when the drive voltage waveform is applied to all the piezoelectric elements connected to the head driver. The amplitude voltage of does not exceed the power supply voltage of the head driver, and it is possible to prevent the characteristic deterioration or destruction of the head driver.

According to a third aspect of the present invention, there is provided an ink jet head driving device for ejecting an ink droplet from a nozzle hole by a strain force of a piezoelectric element to which a voltage waveform is applied, wherein the driving voltage waveform of the piezoelectric element is A drive voltage waveform generating device for generating, a head driver configured by a plurality of control switches to which the drive voltage waveform is input, and a piezoelectric element to which the drive voltage waveform is supplied from the drive voltage waveform generating device via the head driver. A head provided corresponding to each control switch, a current detection device for detecting a current flowing in the ground line of the head driver when the amplitude voltage of the drive voltage waveform to the piezoelectric element exceeds the power supply voltage of the head driver, Based on information from the current detection device when the amplitude voltage of the drive voltage waveform to the piezoelectric element is sequentially increased at the power-on stage, the piezoelectric element And a determination device that determines that the amplitude voltage of the drive voltage waveform exceeds the power supply voltage, the determination device determines that the amplitude voltage of the drive voltage waveform to the piezoelectric element exceeds the power supply voltage. If so, it is an inkjet head drive device that does not increase the amplitude voltage of the drive voltage waveform. Even if the power voltage of the head driver is not supplied due to a malfunction of the power supply system, the amplitude voltage of the drive voltage waveform to the piezoelectric element rises. Therefore, it is possible to prevent the characteristic deterioration or destruction of the head driver due to the amplitude voltage of the drive voltage waveform applied to the piezoelectric element exceeding the power supply voltage of the head driver.

According to a fourth aspect of the present invention, in the invention according to the first aspect, the number of times the current detecting device detects the current flowing through the ground line, and the upper limit number of such abnormal state detecting operation are The drive voltage waveform generator is provided with a stored memory, and the drive voltage waveform generator is an inkjet head drive device that does not perform an operation of increasing the amplitude voltage of the drive voltage waveform after the number of detections of an abnormal state exceeds the upper limit number of times.
This has an effect that it is possible to prevent the progressive deterioration of the piezoelectric element due to the repeated occurrence of the abnormal state each time the power is turned on and off.

According to a fifth aspect of the present invention, in the first aspect of the invention, it is determined that the drive voltage waveform generation device performs control for reducing the amplitude voltage of the drive voltage waveform based on information from the current detection device. The inkjet head drive device is provided with a memory that stores the threshold value of the current flowing through the ground line. For each inkjet head drive device having individual differences, the amplitude of the drive voltage waveform is generated only in the abnormal state. It has an effect that the value of the voltage can be reduced.

According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the current detecting device is an ink jet head driving device incorporated in a head driver, and is small in size. The inkjet head driving device can be obtained.

FIG. 1 shows an embodiment of the present invention.
From now on, description will be made with reference to FIG. In addition, in these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

(Embodiment 1) FIG. 1 is a block diagram showing an ink jet head drive device according to a first embodiment of the present invention, and FIG. 2 shows an example of an amplitude voltage of a drive voltage waveform in the ink jet head drive device of FIG. It is a waveform diagram.

In FIG. 1, the ink jet head driving device of the present embodiment ejects ink droplets from a nozzle hole by the strain force of a piezoelectric element to which a voltage waveform is applied, and a driving voltage waveform of a piezoelectric element which is a piezoelectric element. Vamp
Voltage waveform generator 1 for generating
1, SW2 ... SWn, and the driving voltage waveform Va
The head driver 3 to which mp is input, and the piezo elements P1, P2, ... To which the drive voltage waveform Vamp from the drive voltage waveform generation device 1 is supplied via the head driver 3.
Pn has a head 4 provided corresponding to each control switch SW1, SW2 ... SWn, and the drive voltage waveform generator 1 and the head driver 3 and the head driver 3 and the head 4 are connected by a transmission cable 2. Connected to each other.

Then, by turning on / off the control switches SW1, SW2 ... SWn of the head driver 3, the drive voltage waveform Vamp from the drive voltage waveform generator 1 is applied to the piezo elements P1, P2 ... Pn. Is controlled.

Further, the ink jet head driving device of this embodiment is provided with a current detecting device 5 for detecting the current flowing through the ground line of the head driver 3. That is, in the current detection device 5, the power supply voltage of the head driver 3 exceeds the amplitude voltage of the drive voltage waveform Vamp to the piezo elements P1, P2, ...
The current flowing through the ground line of is detected. When the current detection device 5 detects the current, the drive voltage waveform generation device 1 described above generates the drive voltage waveform Vamp having an amplitude voltage smaller than the power supply voltage of the head driver 3.

The operation of the ink jet head driving device thus constructed will be described below with reference to FIGS. 1 and 2.
Will be explained.

Here, FIG. 2A shows a drive voltage waveform Vamp set as the head driver power supply voltage, and FIG. 2B shows a drive voltage waveform Va including the head driver power supply voltage and distortion.
mp is shown respectively.

The set drive voltage waveform V shown in FIG.
When the amp is input to the head driver 3, distortion occurs due to factors such as the inductance component due to the length of the transmission cable 2, the piezo capacitance, the number of drive piezo connections, and the like, as shown in FIG. The amplitude voltage of the drive voltage waveform Vamp becomes larger than the set value.

When the amplitude voltage of the drive voltage waveform Vamp exceeds the power supply voltage of the head driver 3, an abnormal current flows through the parasitic transistor and the parasitic diode formed inside the head driver 3, and the characteristic of the head driver 3 deteriorates. Or destruction occurs.

Here, when the amplitude voltage of the drive voltage waveform Vamp exceeds the power supply voltage of the head driver 3, the current flowing through the ground line of the head driver 3 increases, and the current value is determined by the current detecting device 5 as described above. The detected information is transmitted to the drive voltage waveform generation device 1.

Then, the drive voltage waveform generator 1 reduces the amplitude voltage of the drive voltage waveform Vamp to be smaller than the power supply voltage of the head driver 3. As a result, it is possible to prevent the characteristic deterioration or destruction of the head driver 3 from occurring.

(Second Embodiment) FIG. 3 is a block diagram showing an ink jet head driving device according to a second embodiment of the present invention.

In the present embodiment, in addition to the ink jet head driving device having the structure of the first embodiment,
The piezo element P1 connected to the head driver 3 is obtained from the information from the current detection device 5 when the number of the piezo elements P1, P2, ... Pn to which the head driver 3 applies the drive voltage waveform Vamp at the same time is sequentially increased. , P
An estimating device 6 is provided for estimating the current flowing through the ground line of the head driver 3 when the drive voltage waveform Vamp is applied to all the numbers 2 ... Pn.

The amplitude voltage of the drive voltage waveform Vamp changes due to variations in the length of the transmission cable 2, variations in piezo capacitance, etc., and the amount of change in the amplitude voltage of the drive voltage waveform Vamp is connected to the head driver 3. It becomes maximum when the drive voltage waveform Vamp is applied to the piezo, that is, when all pins are turned on. Then, the estimation device 6 estimates the value of the current flowing through the ground line of the head driver 3 when all pins are on, based on the amount of increase in the current detected by the current detection device 5 when the number of piezos applied simultaneously is sequentially increased. To do. It is estimated from the estimated current value whether or not the amplitude voltage of the drive voltage waveform Vamp exceeds the power supply voltage of the head driver 3 when all pins are turned on. As a result, the drive voltage waveform generation device 1 reduces the amplitude voltage of the drive voltage waveform Vamp within a range that does not affect the print quality, and generates the drive voltage waveform Vamp having an amplitude voltage smaller than the power supply voltage of the head driver 3.

As a result, even if there are variations in the length of the transmission cable 2 and the piezo capacitance, when the drive voltage waveform Vamp is applied to all the piezo elements P1, P2 ... Pn connected to the head driver. But drive voltage waveform Va
The amplitude voltage of mp never exceeds the power supply voltage of the head driver 3. Therefore, it becomes possible to prevent the characteristics of the head driver 3 from being deteriorated or destroyed.

(Third Embodiment) FIG. 4 is a block diagram showing an ink jet head driving device according to a third embodiment of the present invention.

In the present embodiment, in addition to the ink jet head driving device having the structure of the first embodiment,
Piezo elements P1, P2 ... Pn at power-on stage
Information from the current detection device 5 when the amplitude voltage of the drive voltage waveform Vamp to the piezo element P is sequentially increased.
A judging device 7 is provided for judging that the amplitude voltage of the driving voltage waveform Vamp to 1, P2 ... Pn exceeds the power supply voltage of the head driver 3 and is not in the normal power-on sequence.

In such a structure, when the power is normally turned on, the drive voltage waveform Vamp is applied after the power supply voltage is supplied to the head driver 3.

If there is a defect in the power supply voltage supply system of the head driver 3 at the power-on stage, the drive voltage waveform Vam is supplied without the power supply voltage of the head driver 3 being supplied.
p will be applied.

That is, the amplitude voltage of the drive voltage waveform Vamp exceeds the power supply voltage of the head driver 3,
An abnormal current flows through a parasitic transistor parasitic diode formed inside the head driver 3, causing characteristic deterioration or destruction of the head driver 3. Therefore, in the power-on stage, by gradually increasing the drive voltage waveform Vamp, the determination device 7 determines from the information from the current detection device 5 that the amplitude voltage of the drive voltage waveform Vamp exceeds the power supply voltage of the head driver 3. That is, it can be determined that there is a problem in the power supply system.

When it is determined that there is a defect in the supply system of the power supply voltage, it is possible to avoid the characteristic deterioration or destruction of the head driver 3 by not increasing the amplitude voltage of the drive voltage waveform Vamp. .

(Embodiment 4) FIG. 5 is a block diagram showing an ink jet head drive apparatus according to Embodiment 4 of the present invention.

In the present embodiment, in addition to the ink jet head driving device having the structure of the first embodiment,
The threshold value of the current flowing through the ground line of the head driver 3 that determines that the drive voltage waveform generation device 1 performs control for reducing the amplitude voltage of the drive voltage waveform Vamp, the number of times the current detection device 5 detects the current flowing through the ground line, A memory 8 is provided for storing the upper limit number of times of such abnormal state detection operation.

When the amplitude voltage of the drive voltage waveform Vamp exceeds the power supply voltage of the head driver 3 due to an abnormality of the elements constituting the ink jet head drive device, the drive voltage waveform is obtained from the current value detected by the current detection device 5. It is detected that the amplitude voltage of Vamp exceeds the power supply voltage of the head driver 3, and the drive voltage waveform generation device 1 can reduce the amplitude voltage of the drive voltage waveform Vamp to avoid an abnormal state.

However, since the elements forming the ink jet head driving device are abnormal, the power is turned on / off.
Each time it is turned off, the amplitude voltage of the drive voltage waveform Vamp is repeatedly controlled to avoid the abnormal state. Then, the drive voltage waveform Vamp is calculated from the current value detected by the current detection device 5.
Is detected to exceed the power supply voltage of the head driver 3, and the drive voltage waveform generator 1 detects the drive voltage waveform V
Since it takes a certain period of time to reduce the amplitude voltage of amp, deterioration of the elements constituting the inkjet head driving device including the head driver 3 progresses every time the power is turned on / off.

Therefore, when an abnormal state in which the amplitude voltage of the drive voltage waveform Vamp exceeds the power supply voltage of the head driver 3 is detected from the current value detected by the current detection device 5, the drive voltage waveform generation device 1 drives. Voltage waveform Vamp
The memory 8 for storing the number of times the control of reducing the amplitude voltage of is performed is provided so that the operation of increasing the amplitude voltage of the drive voltage waveform Vamp is not started after the number of times the abnormal state is detected exceeds the set value. As a result, the abnormal state does not occur more than the set number of times, so that it is possible to prevent the deterioration of the element that progresses due to the repeated abnormal state each time the power is turned on and off.

Here, since each element forming the ink jet head driving device has variations, when the amplitude voltage of the driving voltage waveform Vamp exceeds the power supply voltage of the head driver 3 and the characteristics of the head driver 3 are deteriorated or destroyed. The value of the current flowing through the ground line of the head driver 3 varies depending on each inkjet head driving device.

Therefore, if the threshold value of the current flowing through the ground line of the head driver 3 that determines that the control for reducing the amplitude voltage of the drive voltage waveform Vamp is set for all ink jet head drive devices,
Drive voltage waveform Vamp even though it is not in an abnormal state
It is conceivable to perform control to reduce the value of the amplitude voltage of.

Therefore, the threshold value of the current flowing through the ground line of the head driver 3 that determines that the control for reducing the amplitude voltage value of the drive voltage waveform Vamp that is optimum for each inkjet head driving device is performed. By storing in the memory of each inkjet head driving device having individual differences,
It is possible to reduce the value of the amplitude voltage of the drive voltage waveform Vamp only in the abnormal state.

(Fifth Embodiment) FIG. 6 is a block diagram showing an ink jet head driving device according to a fifth embodiment of the present invention.

In this embodiment, the ink jet head driving device having the structure of the first embodiment is
The current detection device 5 is built in the head driver 3.

By thus incorporating the current detection device 5 inside the head driver 3, the area occupied by the current detection device 5 composed of individual parts can be reduced, and a small ink jet head drive device. Can be obtained.

Incidentally, such a structure is adopted in the second to fourth embodiments.
It can also be used in the inkjet head driving device shown in FIG.

[0050]

As described above, according to the present invention, if the current detection device detects the current flowing through the ground line, the drive voltage waveform generation device causes the drive voltage waveform having an amplitude voltage smaller than the power supply voltage of the head driver. Is generated, it is possible to prevent the deterioration or destruction of the characteristics of the head driver.

[Brief description of drawings]

FIG. 1 is a block diagram showing an inkjet head driving device according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing an example of an amplitude voltage of a drive voltage waveform in the inkjet head drive device of FIG.

FIG. 3 is a block diagram showing an inkjet head driving device according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing an inkjet head driving device according to a third embodiment of the present invention.

FIG. 5 is a block diagram showing an inkjet head driving device according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram showing an inkjet head driving device according to a fifth embodiment of the present invention.

FIG. 7 is a block diagram showing a conventional inkjet head driving device.

[Explanation of symbols]

1 Drive voltage waveform generator 3 head driver 4 heads 5 Current detector 6 Estimator 7 Judgment device 8 memory

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masafumi Tomita             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Hidetoshi Matsuo             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 2C057 AF65 AG12 AG44 AL13 AM16                       AR04

Claims (6)

[Claims] 1. An inkjet head drive device for ejecting ink droplets from a nozzle hole by a strain force of a piezoelectric element to which a voltage waveform is applied, the drive voltage waveform generation device generating a drive voltage waveform of the piezoelectric element, Each of the control switches includes a head driver including a plurality of control switches to which the drive voltage waveform is input, and the piezoelectric element to which the drive voltage waveform is supplied from the drive voltage waveform generation device via the head driver. And a current detection device for detecting a current flowing through the ground line of the head driver when the amplitude voltage of the drive voltage waveform to the piezoelectric element exceeds the power supply voltage of the head driver. If the current detection device detects a current flowing in the ground line, the drive voltage waveform generation device Inkjet head driving apparatus characterized by generating the driving voltage waveform of smaller amplitude than the power supply voltage of Ddodoraiba. 2. An ink jet head drive device for ejecting ink droplets from a nozzle hole by a strain force of a piezoelectric element to which a voltage waveform is applied, the drive voltage waveform generating device generating a drive voltage waveform of the piezoelectric element. Each of the control switches includes a head driver including a plurality of control switches to which the drive voltage waveform is input, and the piezoelectric element to which the drive voltage waveform is supplied from the drive voltage waveform generation device via the head driver. A head provided corresponding to, a current detection device for detecting a current flowing in the ground line of the head driver when the amplitude voltage of the drive voltage waveform to the piezoelectric element exceeds the power supply voltage of the head driver, In the case where the number of the piezoelectric elements that simultaneously apply the drive voltage waveform is sequentially increased by the head driver From the information from the current detection device, having an estimation device that estimates the current flowing in the ground line of the head driver when the drive voltage waveform is applied to all of the piezoelectric elements connected to the head driver, The drive voltage waveform generation device generates the drive voltage waveform having an amplitude voltage smaller than a power supply voltage of the head driver based on information from the estimation device. 3. An ink jet head drive device for ejecting ink droplets from a nozzle hole by a strain force of a piezoelectric element to which a voltage waveform is applied, the drive voltage waveform generation device generating a drive voltage waveform of the piezoelectric element. Each of the control switches includes a head driver including a plurality of control switches to which the drive voltage waveform is input, and the piezoelectric element to which the drive voltage waveform is supplied from the drive voltage waveform generation device via the head driver. A head provided corresponding to, a current detection device for detecting a current flowing in the ground line of the head driver when the amplitude voltage of the drive voltage waveform to the piezoelectric element exceeds the power supply voltage of the head driver, From the current detection device when the amplitude voltage of the drive voltage waveform to the piezoelectric element is sequentially increased at the power-on stage And a determination device for determining that the amplitude voltage of the drive voltage waveform to the piezoelectric element exceeds the power supply voltage, the drive voltage waveform generation device, the determination device to the piezoelectric element The inkjet head drive device, wherein if the amplitude voltage of the drive voltage waveform exceeds the power supply voltage, the amplitude voltage of the drive voltage waveform is not increased. 4. A memory for storing the number of times the current detecting device has detected the current flowing in the ground line and the upper limit number of times of the detection operation of such an abnormal state is provided, and the drive voltage waveform generating device is 2. The inkjet head drive device according to claim 1, wherein the operation of increasing the amplitude voltage of the drive voltage waveform is not performed after the number of times of detecting an abnormal state exceeds the upper limit number of times. 5. A memory storing a threshold value of a current flowing through the ground line, which is determined by the information from the current detection device to determine that the drive voltage waveform generation device controls to reduce the amplitude voltage of the drive voltage waveform. The inkjet head drive device according to claim 1, wherein the inkjet head drive device is provided. 6. The ink jet head drive device according to claim 1, wherein the current detection device is incorporated in the head driver.