Liquid ejection head
In an embodiment, a liquid ejection head includes a nozzle plate, a pressure chamber, an actuator, and a drive circuit. The actuator varies a volume of the pressure chamber in response to a driving signal from the drive circuit. The driving signal includes an ejection waveform for ejecting liquid from a nozzle and a cancellation waveform for suppressing residual oscillation after ejection of the liquid. The ejection waveform includes voltage changes in stages and the cancellation waveform includes two waveform portions for suppressing residual oscillations and higher harmonic acoustic resonance frequencies.
1 . A liquid ejection head, comprising:
a nozzle plate including a nozzle;
a pressure chamber fluidly connected to the nozzle;
an actuator configured to vary a volume of the pressure chamber in response to a driving signal; and
a drive circuit configured to generate the driving signal for driving the actuator, wherein
the driving signal generated by the drive circuit includes an ejection waveform for ejecting liquid from the nozzle and a cancellation waveform for suppressing residual oscillation after the ejection of the liquid,
the cancellation waveform includes a first waveform portion and a second waveform portion, and the second waveform portion cancels oscillation that has an acoustic resonance frequency higher than a main acoustic resonance frequency of the liquid in the pressure chamber and is caused by the first waveform portion, and
when a cycle of the acoustic resonance frequency higher than the main acoustic resonance frequency is λn, a time interval Tm 2 of the first and second waveform portions satisfies:
(
kkk
/
2
-
1
/
6
)
λ
n
≤
T
m
2
≤
(
kkk
/
2
+
1
/
6
)
λ
n
,
where kkk is an odd number of 1 or more.
2 . The liquid ejection head according to claim 1 , wherein the first waveform portion and the second waveform portion have the same shape.
3 . The liquid ejection head according to claim 1 , wherein the ejection waveform includes a first potential change in at least two stages and a second potential change in at least two stages, the first and second potential changes being with opposite polarities.
4 . The liquid ejection head according to claim 3 , wherein a time width between a start of the first potential change and a start of the second potential change is approximately equal to an acoustic length of the main acoustic resonance frequency.
5 . The liquid ejection head according to claim 1 , wherein
the first waveform portion includes first and second potential changes with opposite polarities, and
the second waveform portion includes third and fourth potential changes with opposite polarities.
6 . The liquid ejection head according to claim 1 , wherein
the drive circuit includes a switching circuit that connects an electrode and a voltage source, and
potential changes in the driving signal are generated by switching of the switching circuit.
7 . The liquid ejection head according to claim 1 , wherein the actuator is a piezoelectric actuator.
8 . A liquid ejection head, comprising:
a nozzle plate including a nozzle;
a pressure chamber fluidly connected to the nozzle;
an actuator configured to vary a volume of the pressure chamber in response to a driving signal; and
a drive circuit configured to generate the driving signal for driving the actuator, wherein
the driving signal generated by the drive circuit includes an ejection waveform for ejecting liquid from the nozzle and a cancellation waveform for suppressing residual oscillation after the ejection of the liquid,
the cancellation waveform includes a first waveform portion and a second waveform portion, and the second waveform portion cancels oscillation that has an acoustic resonance frequency higher than a main acoustic resonance frequency of the liquid in the pressure chamber and is caused by the first waveform portion,
the first waveform portion includes first and second potential changes with opposite polarities,
the second waveform portion includes third and fourth potential changes with opposite polarities,
the ejection waveform includes a first potential change in at least two stages and a second potential change in at least two stages, the first and second potential changes being with opposite polarities, and
a time width between a midpoint between a start of the first stage of the first potential change and a start of the second stage of the second potential change in the ejection waveform and a midpoint between a start of the first potential change in the first waveform portion and a start of the fourth potential change in the second waveform portion is a multiple of an acoustic length of the main acoustic resonance frequency.
9 . The liquid ejection head according to claim 8 , wherein the polarity of the first potential change in the ejection waveform is the same as the first potential change in the first waveform portion of the cancellation waveform.
10 . The liquid ejection head according to claim 9 , wherein the time width is an odd multiple of the acoustic length.
11 . The liquid ejection head according to claim 9 , wherein the time width is approximately three times the acoustic length.
12 . The liquid ejection head according to claim 8 , wherein the polarity of the first potential change in the ejection waveform is the opposite of the first potential change in the first waveform portion of the cancellation waveform.
13 . The liquid ejection head according to claim 12 , wherein the time width is an even multiple of the acoustic length.
14 . The liquid ejection head according to claim 12 , wherein the time width is approximately two times the acoustic length.
15 . The liquid ejection head according to claim 8 , wherein a time width of each stage in the ejection waveform is greater than a time width between the first and second potential changes in the first waveform portion of the cancellation waveform.
16 . An image forming apparatus, comprising:
a liquid ejection head; and
a sheet conveyor configured to convey a sheet to the liquid ejection head, wherein
the liquid ejection head includes:
a nozzle plate including a nozzle;
a pressure chamber fluidly connected to the nozzle;
an actuator configured to vary a volume of the pressure chamber in response to a driving signal; and
a drive circuit configured to generate the driving signal for driving the actuator,
the driving signal generated by the drive circuit includes an ejection waveform for ejecting liquid from the nozzle and a cancellation waveform for suppressing residual oscillation after the ejection of the liquid,
the cancellation waveform includes a first waveform portion and a second waveform portion, and the second waveform portion cancels oscillation that has an acoustic resonance frequency higher than a main acoustic resonance frequency of the liquid in the pressure chamber and is caused by the first waveform portion, and
when a cycle of the acoustic resonance frequency higher than the main acoustic resonance frequency is λn, a time interval Tm 2 of the first and second waveform portions satisfies:
(
kkk
/
2
-
1
/
6
)
λ
n
≤
T
m
2
≤
(
kkk
/
2
+
1
/
6
)
λ
n
,
where kkk is an odd number of 1 or more.
17 . The image forming apparatus according to claim 16 , wherein
the first waveform portion includes first and second potential changes with opposite polarities, and
the second waveform portion includes third and fourth potential changes with opposite polarities.
18 . The image forming apparatus according to claim 17 , wherein
the ejection waveform includes a first potential change in at least two stages and a second potential change in at least two stages, the first and second potential changes being with opposite polarities, and
a time width between a midpoint between a start of the first stage of the first potential change and a start of the second stage of the second potential change in the ejection waveform and a midpoint between a start of the first potential change in the first waveform portion and a start of the fourth potential change in the second waveform portion is a multiple of an acoustic length of the main acoustic resonance frequency.