JP2973262B2 - Drive circuit for inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates are those which relate to the driving circuits of the ink jet head.

[0002]

2. Description of the Related Art Conventionally, there is a method for driving an ink jet head as disclosed in Japanese Patent Publication No. 2-50867. This driving method will be specifically described with reference to FIGS. FIG. 6A shows the transistor 5
FIG. 6B shows the on / off state of the transistor 52, and FIG. 6C shows the on / off state of the transistor 52.
FIG. 6 is a diagram showing an applied voltage of No. 3; Further, the magnitude relationship between the resistance value RP of the parallel equivalent resistance of the piezoelectric element 53 and the respective resistance values (R54, R55, R56) of the resistors 54, 55, 56 is as follows: Rp >> R54 >> R55 >> R56 It is set as follows.

Before time t1 shown in FIG. 6a, that is, in a standby state, the transistors 51, 52, and 57 are off, and the piezoelectric element 53 is charged via the resistors 54 and 56 as shown in FIG. When ink droplet ejection is required,
As shown in FIG. 6A, the transistor 51 is turned on and the piezoelectric element 53 is turned on.
Is discharged through the resistor 55. Next, the transistor 51 is turned off and the transistor 52 is turned on as shown in FIG.
Ink droplets are ejected.

[0004]

However, in the above method, a discharge control signal (signal input to the transistor 51 in FIG. 5) for controlling discharge is applied to one nozzle drive.
And a charge control signal for controlling charging (the transistor 5 in FIG. 5)
2), a drive control circuit (not shown) for controlling the drive of the drive circuit shown in FIG. 5 becomes complicated and costs increase. Had.

An object of the present invention is to provide a low-cost ink jet head driving circuit and a driving method thereof.

[0006]

According to the present invention, there is provided a drive circuit for an ink jet head for applying pressure to a pressure chamber by charging and discharging a piezoelectric element and ejecting ink droplets from nozzles.
A first switching element and a second switching element are connected in series between a pair of power terminals to form a switching circuit.
And a first series circuit composed of a first resistor and a first rectifier element and a second series circuit composed of a second resistor and a second rectifier element are connected to the first and second rectifiers. A piezoelectric element drive in which the elements are connected in parallel so that they are opposite to each other to form a parallel circuit, and the piezoelectric element is connected in series to the parallel circuit.
An operating condition setting circuit is connected in parallel to the second switching element, and the first rectifying element is connected to the piezoelectric element by the first switching element.
In the direction of charging the electric charge via the resistor of
Rectifying element Yes place the charge stored in the piezoelectric element in the direction of discharging through the second resistor, the upper Symbol first switching element and the second switching element, is one Control is performed so that when it is on, the other is off .

In a driving circuit of an ink jet head for applying pressure to a pressure chamber by charging and discharging a piezoelectric element and ejecting ink droplets from a nozzle, a first switching element and a second switching element are connected between a pair of power terminals. To form a switching circuit, and connect a first series circuit including a first resistor and a first rectifying element and a second resistor in parallel to form a parallel circuit. A piezoelectric element driving condition setting circuit in which the piezoelectric element is connected in series to a circuit is connected in parallel to the second switching element, and the first rectifying element is connected to the piezoelectric element by the first resistor. Yes disposed in a direction in which electric charge through the upper Symbol first switching element and the second switching element, one the other when on is controlled to be off.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to one embodiment shown in the drawings.

In FIG. 1, reference numeral 1 denotes a piezoelectric element which is fixed to the wall of a pressure chamber (not shown) filled with ink, and ejects ink droplets by deformation. 2, 3, and 4 are transistors. Transistors 2 and 3 constitute a first and second switching elements, respectively, the transistors
A switching circuit is composed of the switching circuits 2 and 3 . 5,6,7,
Reference numeral 8 denotes a resistor, and the resistors 5 and 6 constitute first and second resistors, respectively. Reference numerals 9 and 10 denote diodes constituting first and second rectifying elements, respectively. 11 is a first series circuit,
It comprises a resistor 5 and a diode 9. Reference numeral 12 denotes a second series circuit, which includes the resistor 6 and the diode 10. Reference numeral 13 denotes a parallel circuit, which includes serial circuits 11 and 12. Parallel with piezoelectric element 1
The path 13 constitutes a piezoelectric element driving condition setting circuit.

Next, the operation will be described with reference to FIG. FIGS. 2A and 2B are diagrams showing ON and OFF states of the transistors 3 and 4. FIG.

At the time of standby, that is, at the time when ink droplet ejection is not required (before t1 in FIG. 2), the transistor 4 is turned on as shown in FIGS.
Is turned on, and the transistor 3 is turned off. Therefore,
The piezoelectric element 1 continues to be charged by the current flowing through the diode 9 via the resistor 5. However, since the piezoelectric element 1 is a capacitive element, the resistance R5 of the resistor 5 and the piezoelectric element 1
Time R determined by the time constant determined by the capacitance C of
After the passage of 5 · C, the potential almost reaches the same level as the high-voltage power supply VH, and thereafter, only the current that supplements the self-discharge current of the minute piezoelectric element 1 continues to flow. In this state, the wall of the pressure chamber is displaced inward due to the deformation of the piezoelectric element 1.

At time t1 (immediately before the ejection of ink droplets), the transistors 4 and 2 are turned off, and at the same time, the transistor 3 is turned on. Therefore, the electric charge charged in the piezoelectric element 1 is discharged through the diode 10, the resistor 6 and the transistor 3, and the time constant R6 .times. Determined by the resistance value R6 of the resistor 6 and the capacitance C of the piezoelectric element 1. After elapse of C, the potential of the piezoelectric element 1 becomes equal to the GND level. At this time, the displacement of the wall of the pressure chamber is canceled by the release of the deformation of the piezoelectric element 1, and the ink flows into the pressure chamber.

At time t2 (at the time of ink droplet ejection), the transistors 4 and 2 are turned on and the transistor 3 is turned off, the piezoelectric element 1 is charged as described above, and the wall of the pressure chamber is moved inward again. It is displaced, and ink droplets are ejected from a nozzle (not shown).

As described above, since the signal for controlling the on / off of the transistor 3 is an inverted signal of the signal for controlling the on / off of the transistor 4, the driving signal of the ink jet head can be simplified, and the driving can be performed at low cost. You .

[0015] The contact may be used as shown in FIG. 3 as a driving circuit of the ink jet head. In the figure,
1 are the same as those in FIG. FIG. 3 is FIG.
In this case, the diode 10 is omitted. In this case, the charge completion time is determined by the combined resistance value of the resistors 5 and 6, and the discharge completion time is determined by the resistance value of the resistor 6 . In this case, the diode 10 can be omitted, the cost can be suppressed.

When the above two examples are applied to a multi-nozzle head, the above circuits may be provided simply according to the number of nozzles. In this case, the charging current is always supplied to the nozzles that do not eject ink, so that there is no voltage drop of the piezoelectric element even for nozzles that do not eject ink for a long time, and stable ink ejection is performed. be able to.

In the above, an example of the pulling drive of the ink jet has been described. Next, an example of the push driving will be described with reference to FIG. Note that the driving circuit of the inkjet head shown in FIG. 1 is used. FIGS. 4A and 4B are diagrams showing ON and OFF states of the transistors 3 and 4. FIG.

At the time of standby, that is, at the time when ink droplet ejection is not required (before t3 in FIG. 4), the transistors 4 and 2 are turned off and the transistor 3 is turned on as shown in FIGS. Therefore, the electric charge charged in the piezoelectric element 1 is continuously discharged through the resistor 6 and the diode 10. At this time, the piezoelectric element 1 is not deformed, and the wall of the pressure chamber is not displaced.

At time t3 (at the time of ink droplet ejection), the transistors 4 and 2 are turned on and the transistor 3 is turned off. Therefore, the piezoelectric element 1 is charged by current flowing through the resistor 5 and the diode 9, the wall of the pressure chamber is displaced inward, and ink droplets are ejected from the nozzle.

At time t4 (at the end of ink droplet ejection), the transistors 4 and 2 are turned off and the transistor 3 is turned on, the piezoelectric element 1 is discharged as described above, and the wall displacement of the pressure chamber is released. Then, the ink droplets are cut off.

In this case, the transistor 3
A signal for controlling ON and OFF of the transistor 4
Since the signal is an inverted signal of the signal for controlling the turning off, the driving of the inkjet head can be simplified, and the driving can be performed at low cost.

Incidentally, as shown above, the circuit shown in FIG. 3 may be used as a driving circuit for the ink jet head.

As described above, the operation of the ink jet head
The switching conditions for controlling the
The piezoelectric element drive condition setting circuit for
This switching circuit is connected at the connection point of
It can be applied to various piezoelectric element drive condition setting circuits.
You. In other words, it is necessary to make the switching circuit
Can be. Also, since it is connected at one connection point,
Becomes easier.

[0024]

According to the present invention, the driving signal of the ink jet head can be simplified, and the driving can be performed with an inexpensive configuration.

Also, the operation of the ink jet head is controlled.
The switching circuit and the driving condition of the piezoelectric element
Configure the piezoelectric element drive condition setting circuit separately and connect one
This switching circuit is connected to various points.
This can be applied to a piezoelectric element driving condition setting circuit. You
In other words, the switching circuit can have versatility.
Wear. Also, since it is connected at one connection point, manufacturing is easy.
become.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing one embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of FIG. 1;

FIG. 3 is an electric circuit diagram showing another embodiment of the present invention.

FIG. 4 is a timing chart for explaining the operation of FIGS. 1 and 3;

FIG. 5 is an electric circuit diagram showing a driving circuit of a conventional inkjet head.

FIG. 6 is a timing chart for explaining the operation of FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 1st switching element 3 2nd switching element 2 and 3 Switching circuit 5 1st resistance 6 2nd resistance 9 1st rectification element 10 2nd rectification element 11 1st series circuit 12th 2 series circuit 13 parallel circuit 1 and 13 piezoelectric element drive condition setting circuit

Claims (2)

(57) [Claims] 1. A driving circuit for an ink jet head for applying pressure to a pressure chamber by charging and discharging a piezoelectric element and ejecting ink droplets from a nozzle, wherein a first switching element and a second switching element are connected between a pair of power terminals. Connected in series to form a switching circuit.
Forming a first series circuit including a first resistor and a first rectifier element and a second series circuit including a second resistor and a second rectifier element into the first and second rectifiers. A piezoelectric element in which the elements are connected in parallel so that they are opposite to each other to form a parallel circuit, and the piezoelectric element is connected in series to the parallel circuit
A driving condition setting circuit is connected in parallel to the second switching element, the first rectifying element is arranged in the piezoelectric element in a direction in which electric charges are charged through the first resistor, and the second rectifying element is connected to the piezoelectric element. element a charge stored in the piezoelectric element Yes disposed in a direction of discharging through the second resistor, the upper Symbol first switching element and the second switching element, one is on A driving circuit for controlling the other side to be turned off. 2. A driving circuit for an ink jet head for applying pressure to a pressure chamber by charging and discharging a piezoelectric element to eject ink droplets from a nozzle, wherein a first switching element and a second switching element are connected between a pair of power terminals. Connected in series to form a switching circuit.
A first series circuit comprising a first resistor and a first rectifier element and a second resistor are connected in parallel to form a parallel circuit, and the piezoelectric element is connected in series to the parallel circuit. Piezoelectric element
The drive condition setting circuit is connected in parallel to said second switching element, the first rectifying element is Yes and oriented so as to charge the electric charge via said first resistor to said piezoelectric element, the upper Symbol first A drive circuit for an ink jet head, wherein one of the first switching element and the second switching element is controlled such that when one is on, the other is off.