JPH03162965A - Temperature compensator for liquid jet recording head - Google Patents

Abstract

PURPOSE:To realize high quality of image by detecting a temperature based on an output waveform from an integrator comprising the electrostatic capacity of a piezoelectric element and a resistor, and switching a heater attached to a recording head according to the detected result. CONSTITUTION:A pulse signal source 1 for generating detecting pulse group to a piezoelectric element, an integrator 2 comprising the electrostatic capacity of the element and a resistor, and a temperature detector 5 for detecting a temperature according to an output waveform from the integrator 2 are provided. A heater controller 6 for switching a heater attached to a recording head according to a detected result by the detector 5 is provided. Accordingly, a specific temperature sensor is not provided, an ambient temperature or ink temperature can be simply and inexpensively detected, and compensated. Thus, ink jet characteristic stable against temperature change is obtained, and high quality of an image can be always obtained irrespective of the environmental temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature compensation device for a liquid jet recording head.
For example, it is used in inkjet printers.

In general, in an inkjet recording device, the ink ejection characteristics at the environmental temperature are largely dependent on the ink's viscosity and surface tension. Above all,
Since the ink viscosity is highly dependent, when the ink temperature changes, the ink viscosity also changes, and therefore the ink jetting characteristics also change. This is one of the major causes of deterioration of image quality when printed on recording paper.6 Conventionally, several temperature compensation devices have been proposed for the above-mentioned temperature changes. For example, in JP-A-55-101473, in order to adjust the control voltage, a voltage divider provided in each control circuit includes an adjustable resistance, and this resistance is common to all control circuits. is connected to a regulating circuit, and the regulating circuit is a temperature-related resistance (a thermal conductor with a negative temperature coefficient).
It is disclosed that an output voltage that varies with ambient temperature is delivered through the air conditioner.

Further, JP-A-56-63464 discloses that the ink temperature is detected by a temperature sensing element (for example, a thermistor), and the output voltage is controlled by configuring the resistance value to change depending on the ink temperature. ing.

? Furthermore, Japanese Patent Application Laid-open No. 57-47666 discloses a device that detects the ambient temperature using a temperature sensing element and changes the electric signal applied to the ink droplet ejecting device according to the detected temperature. It is disclosed that the changes correspond to changes in the minimum drop forming voltage of the ink drop ejector.

However, all of the conventional techniques described in the above-mentioned publications require the installation of a special device for detecting the ambient temperature or ink temperature, such as a thermistor or a resistor with a negative temperature coefficient.

Therefore, the number of assembly steps increases and the configuration is restricted due to installation, which is disadvantageous to lower costs or higher integration.

The present invention was made to solve the above-mentioned drawbacks, and provides a means for simply and inexpensively detecting ambient temperature or ink temperature without providing a special temperature sensing element, and a method for temperature compensation. By providing a control means for this, stable ink ejection characteristics can be obtained against temperature changes, and the ink jetting characteristics can be maintained regardless of the environmental temperature. The object of this invention is to provide a temperature compensation device for a liquid jet recording head that can always ensure high image quality.

In order to achieve the above-mentioned objects, the present invention provides (1) a flow system that accommodates the recording liquid to be introduced and is attached with an energy acting section that generates pressure waves in the recording liquid using a piezoelectric element; an orifice that communicates with the flow path and causes the recording liquid to be ejected as droplets by the acting force; and a liquid chamber that communicates with the flow path and introduces the recording liquid into the flow path. , a liquid jet recording head comprising an introduction means for introducing recording liquid into the liquid chamber, comprising a pulse signal source for generating a detection pulse group in the piezoelectric element, and a capacitance and a resistance of the piezoelectric element. a temperature detection device that detects temperature based on an output waveform output by the integration circuit; and a heater control circuit that switches a heater attached to the recording head based on the detection result of the temperature detection device. Prepared or (2
)? In the liquid jet recording head, a pulse signal source that generates a group of detection pulses in the piezoelectric element, an integrating circuit composed of a capacitance and a resistance of the piezoelectric element, and an output waveform outputted by the integrating circuit (3) In the liquid ejecting recording head, the piezoelectric element a pulse signal source that generates a group of detection pulses; an integrating circuit configured of the capacitance and resistance of the piezoelectric element; a temperature detection device that detects temperature based on an output waveform output by the integrating circuit; The present invention is characterized by comprising a control circuit that controls the pulse width of a pulse waveform for driving the recording head based on the detection result by the temperature detection device. Hereinafter, the present invention will be explained based on examples.

First, FIG. 2 shows the temperature characteristics of the capacitance C of the piezoelectric element. Now, the temperature of the piezoelectric element is from T■ to T2
When the capacitance increases to 7-? Increase to 2. The present invention has focused on this point, and is characterized by comprising a control means for detecting temperature from changes in capacitance of the piezoelectric element and for temperature compensation.

FIG. 1 is a configuration diagram for explaining a temperature compensation device for a liquid jet recording head according to the present invention. In the figure, l is a pulse source, 2 is an integrating circuit, 3 is a resistor R, and 4 is a capacitance C 5 is a detection circuit, and 6 is a control circuit. As shown in FIG. 3(a), the pulse signal source l has a pulse width of PWI (
Two pulses (first pulse) and Pw2 (second pulse) are generated. The integrating circuit 2 is composed of three resistors R and four capacitors C. The capacitance C is a piezoelectric element attached to the flow path for generating pressure waves. The detection circuit 5 is
It detects the input pulse voltage value. The control circuit 6 controls the drive voltage of the heater control circuit and the head based on the results of the detection circuit 5. Pulse now
When two pulse waveforms, PW■ and Pw2 (first pulse, second pulse), are input to the integrating circuit 2, the output waveform is the 8th -? An integral waveform with a slow rise and a slow fall is output as shown in FIG. 3(b). Here, as shown in FIG. 2, as the temperature T rises, the value of the capacitance C of the piezoelectric element 4 rises, and as the value of the time constant CR increases, the waveform output from the integrating circuit 2 becomes The result will be as shown in Figure 3 (c). At this time, the first
If the pulse (pulse width pwx) is sufficiently CR>>Pwe with respect to the value of the time constant CR of the integrating circuit 2, the pulse peak voltage VP■ will be low because the pulse rise time is slow. 1; I will. Next, the detection circuit 5
In this case, a threshold voltage V■ is provided, and when the input voltage VP is Vp≧■8, it is detected, and when V p <V Il, it is not detected. Therefore, the detection circuit 5 does not detect the first pulse, but only the second pulse.

As the temperature further increases, the first
Peak voltage VP■, VPz for both pulse and second pulse
becomes lower than the threshold voltage V}l, and the detection circuit 5 does not detect either of them.

In this way, by utilizing the temperature characteristics of the piezoelectric element 4, the waveform output from the integrating circuit 2 changes as shown in FIGS. Temperature detection can be performed in three stages: (1) first and second pulses, (2) second pulse only, and (2) no detection pulse.

The control circuit 6 uses the known technology as described above to control the head fluctuation voltage or heater switching according to the state of the detection pulse detected by the detection circuit 5, and performs temperature compensation for the ink ejection characteristics. It is something that does.

Furthermore, the pulse widths Pw1 and p of the first pulse and the second pulse are
w, is the threshold voltage V. in the detection circuit 5 with respect to the time constant CR of the integrating circuit 12. (For example, at TTL level V.=2.
4V). To determine such pulses @Pw,, Pw2, CR>>(d▼
It is sufficient if it is m.

The detection pulses input to the integrating circuit 2 are not limited to two pulses as described above, but if a plurality of pulse groups are used, temperature detection can be performed in multiple stages and accuracy can be increased. For a group of n pulses, the pulse width Pwn is Pwx-t<
P Wx (k=2 to n).

Furthermore, the electrostatic capacitance C constituting the integrating circuit 2 uses a piezoelectric element for ejecting ink, but in the case of a head having multiple nozzles, the integrating circuit 2 is configured in all the piezoelectric elements of each nozzle, and The output waveform may be input to the detection circuit 5, but from the viewpoint of space saving and low cost, an integral circuit may be configured using the piezoelectric element of any one of the multiple nozzles for temperature detection, and all the nozzles It is preferable to perform temperature compensation for all the nozzles, or to provide one dummy nozzle and configure an integration circuit using the piezoelectric element for temperature detection to perform temperature compensation for all nozzles.

FIG. 4(a) is a schematic diagram of an on-demand 1-type inkjet I head using laminated PZT. In the figure, 7 is a substrate, 8 is a laminated PZT, 9 is a channel plate, 10 is a common liquid chamber, 1 is a nozzle plate, 12 is a nozzle joint, 13 is a copper wire, and 4 is an FPC.

Further, FIG. 2B is an enlarged view of the nozzle joint 12, in which 15 is a filler, 16 is a flow path, and 171l? A channel plate, 18 is ink, 19 is an electrode, and 8 - 84 are laminated PZT (6N) attached to each nozzle.

Figure 5 is a diagram showing the structure of a temperature compensation device using a heater in the on-demand inkjet head.

In the figure, 20 is a pulse diagnosis source, 21 is a resistor Ro, 22 is a capacitance CO, 23 is an integrating circuit, 24 is a counter, 25 is a comparison circuit, 26 is a heater operating circuit, and 27 is a heater. It is a pulse signal source 20 and generates the detection pulse group shown in FIG. 3(a) (V p 1 = V p 2 =
5V. P w x = 2 μs. Pw2=5μ
s). The integrating circuit 23 is an arbitrary one of the laminated PZT attached to each of the plurality of nozzles (for example, 82 in FIG. 4(b)).
capacitance CO (Go=10nF) and resistance Ro (Ro=
10KΩ). The counter 24 is a counter that counts a group of pulses output from the integrating circuit 23, and V++=2 . 4V. The comparison circuit 25 compares the number of pulses NB counted by the counter 24 with the reference 12.
−? Compare the number 1 and the number NA, and if NA < NB, it is High. When NA≧NB, LO is 1bi
Outputs the t signal.

The heater drive circuit 26 receives the output signal from the comparator circuit 25, and when it is Illight, turns the heater ON and LoI.
When it is 1, the heater is switched off.

A heater 27 for temperature compensation is installed on the back surface of the substrate 7 in FIG. 4(a).

FIG. 6 is a flowchart 1 for explaining the operation of the first embodiment. Now, when the lower limit temperature of the ink temperature is T■, if the ink temperature T<T■, the integration circuit 23
The output waveform from is as shown in Figure 3(b), therefore,
It is counted as NB=2. On the other hand, for reference, NA=
If you set the count number to 1, N B > N A
Therefore, the heater switch is turned on and the ink temperature becomes Δ
T increases, and the ink temperature becomes T=T1+ΔT. next,
The detection pulses are again input to the integrating circuit 23 to count the pulses. At this time, if NB≦NA, the heater switch is turned off, and if N n > NA still? The switch of the heater 27 is in the ON state.

If the above cycle is performed periodically, the ink temperature T will always be T.
≧T is maintained.

Furthermore, although the waveform shown in FIG. 3(.) is used as the detection pulse output from the pulse signal source 20, two pulses are not necessarily required. It is sufficient to set the reference count 1 to NA=0 using only the pulse (however, Pw<<CR).

Lost 1. - Figure 7 shows that the head shown in Figure 4 has a laminated PzT
FIG. 2 is a configuration diagram of a temperature compensation device using dynamic voltage control.

In the figure, 30 is a pulse signal source, 3 is a resistor, 32 is a capacitance, 33 is an integrating circuit, 34 is a counter, 35 is a comparison circuit, 36 is a multi-nozzle drive circuit, and 37 is a laminated PZT. Note that the arrangement from the pulse signal source 30 to the counter 34 is exactly the same as from the pulse signal source 20 to the counter 24 shown in FIG. When ゛≦T2, the product? When the output waveform of the circuit 33 is T<T■, it is as shown in FIG. 3(b), when T■≦T≦T2, it is as shown in FIG. 3(c), and when T:>T2, the same Resistor 3 as shown in figure (d)
The value of engineering is set. The comparator circuit 35 has an output of 3b
It exists, and the first bit 1~ is NA < NB. 2nd bit 1. is NA-NB, 3rd bit 1. is NA > N
It is divided into n.

FIG. 8 is a flowchart 1 for explaining the operation of the second embodiment. Now, if the reference counter number is set to N = l, when T < T, it will be counted as N, = 2, and in the comparator circuit 35, only the No.
Therefore, the multi-nozzle drive circuit 36 drives the nozzle at a voltage higher than the normal voltage. When T>T2, it is counted as NB=O, and in the comparator circuit 35, only the third bit 1- is Hi.
gh, and the multi-nozzle drive circuit 36 drives the nozzle at a lower voltage than usual. When T≦T≦T2, N
Since B=NA=1, only the second bit of the comparator circuit 35 becomes illumination, and is driven with a normal operating voltage.

Absent J1 ■5? In the multi-nozzle drive circuit 36, temperature compensation can be performed by controlling the pulse width Pwo of the pulse pulse instead of controlling the drive voltage.

FIG. 9 shows a configuration diagram of a temperature compensating device using pulse width control of the navel 1- having eight nozzles. In the figure, 40 is a pulse signal source, 41 is a resistor, 42 is a capacitance, 43 is an integrating circuit, 44 is a counter, 45 is a comparison circuit,
46 to 48 are resistors r■ to r3, 49 is a capacitor, 50
51 is an OR circuit, 51 is a monostable multivibrator, 52 is an 8-bit applied signal, 53 is a multi-nozzle fluctuating circuit, 5
4 is a laminated PZT.

FIG. 10 is a timing chart 1 for explaining the operation of the third embodiment. In general, the jetting characteristics of an inkjet head using laminated PZT are such that the jetting speed (4) changes depending on the voltage value and pulse width of the driving pulse, and particularly for the pulse width Pwo, the jetting characteristics are as shown in FIG. 1l. Therefore, when the ink temperature T is T<T■, P
wo=P WO3, 16? If yo≦T≦T2, Pwo=Pwo2, T>T2
In the case of Pwo=Pwo. And it is sufficient.

In FIG. 9, the signal from the pulse signal source 40 is as shown in FIG.
A detection pulse group as shown in is output, and in Examples 1 and 2,
Similarly, after passing through the integrating circuit 43, it is counted by the counter 44, and as a result, N1 is input to the comparator circuit 45 in 2 bits. Here, the standard count number NA (2 bits)
If NB>NA, resistor r3, N n
If = NA, resistor r2 is selected; if N B < NA, resistor r2 is selected (however, r■<r2<
r・3). In the monostable multivibrator 51, the pulse width of the output pulse is determined by the resistor and capacitor 49 selected by the comparator circuit 45. That is, when the resistance r is the pulse width Pwo■, when the resistance r2 the pulse width is 'fti
When P w o z and resistance r3, pulse intensity Pwo3 is determined. On the other hand, an 8-bit print signal 52 is input to the OR circuit 50, and when there is a print signal in at least one of the 8 bits, a 1-register signal is input to the monostable multivibrator 51. At this time, what is the determined pulse width? w o (P WO■Or P WO20r
The pulse waveform of P wo, ) is the multi-nozzle active circuit 53
The driving voltage Vpo is amplified to a driving voltage Vpo and applied to each of the laminated layers P Z T 5 4 to be driven in accordance with the print signal 52 .

Incidentally, ① to ② in the timing chart of FIG. 10 correspond to ① to ② marked on the signal lines in FIG. 9.

As is clear from the above explanation, according to the present invention, even if the ink ejection characteristics change due to changes in the ink temperature of the liquid ejection recording head or the ambient temperature, the ink ejection characteristics can be changed without installing a special temperature sensing element. , the ink temperature is detected, and from the result, the ink temperature can be kept constant by heater control in claim 1, the pulse voltage can be controlled in claim 2, and the pulse width of the vibration pulse can be controlled in claim 3. Can be done. Therefore, stable ink jetting characteristics can be obtained, so high image quality can be achieved, and space and cost can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the temperature compensation device for a liquid jet recording head according to the present invention, FIG. 2 is a diagram showing the temperature characteristics of the capacitance C of a piezoelectric element, and FIGS. (d) is a diagram showing the detection pulse waveform, Figures 4 (a) and (b) are a schematic diagram and partially enlarged view of the on-demand inkjet head, and Figure 5 is the temperature of the first embodiment. 6 is a flow chart for explaining the operation of the first embodiment shown in FIG. 5, and FIG. 7 is a diagram showing the structure of the temperature compensator according to the second embodiment. is a flowchart for explaining the operation of the second embodiment shown in FIG. 7, FIG. 9 is a block diagram of the temperature compensation device of the third embodiment, and FIG. 10 is a flowchart for explaining the operation of the second embodiment shown in FIG. Timing chart 1-, 1st to explain the operation
FIG. 1 is a diagram showing the ejection characteristics of an inkjet head. DESCRIPTION OF SYMBOLS 1...Pulse signal source, 2...Integrator circuit, 3...Resistor, 4...Capacitance, 5...Detection circuit, 6...Control circuit.

Claims (1)

[Scope of Claims] 1. A flow path that accommodates the recording liquid to be introduced and is provided with an energy acting section that generates pressure waves in the recording liquid using a piezoelectric element, and a flow path that is connected to the flow path and that contains the recording liquid. an orifice for ejecting the recording liquid as a droplet by the acting force; a liquid chamber for communicating with the flow path and introducing the recording liquid into the flow path; and an introduction means for introducing the recording liquid into the liquid chamber. A liquid jet recording head comprising: a pulse signal source that generates a group of detection pulses in the piezoelectric element;
an integrating circuit made up of the capacitance and resistance of the piezoelectric element; a temperature detecting device that detects temperature based on the output waveform outputted by the integrating circuit; 1. A temperature compensation device for a liquid jet recording head, comprising: a heater control circuit for switching a heater. 2. A flow path that accommodates the recording liquid to be introduced and is provided with an energy acting section that generates pressure waves in the recording liquid using a piezoelectric element, and a flow path that communicates with the flow path to cause the recording liquid to be liquidized by the acting force. A liquid jet recording head comprising an orifice for ejecting droplets, a liquid chamber for communicating with the flow path and introducing the recording liquid into the flow path, and an introduction means for introducing the recording liquid into the liquid chamber. a pulse signal source that generates a group of detection pulses in the piezoelectric element;
an integrating circuit made up of the capacitance and resistance of the piezoelectric element; a temperature detecting device that detects temperature based on the output waveform output by the integrating circuit; and driving of the recording head based on the detection result of the temperature detecting device. 1. A temperature compensation device for a liquid jet recording head, comprising: a control circuit for controlling voltage. 3. A channel that accommodates the recording liquid to be introduced and is provided with an energy acting section that generates pressure waves in the recording liquid using a piezoelectric element, and a channel that communicates with the channel and causes the recording liquid to be liquidized by the acting force. A liquid jet recording head comprising an orifice for ejecting droplets, a liquid chamber for communicating with the flow path and introducing the recording liquid into the flow path, and an introduction means for introducing the recording liquid into the liquid chamber. a pulse signal source that generates a group of detection pulses in the piezoelectric element;
an integrating circuit composed of a capacitance and a resistance of the piezoelectric element; a temperature detecting device that detects temperature based on an output waveform outputted by the integrating circuit; and driving the recording head based on the detection result of the temperature detecting device. 1. A temperature compensation device for a liquid jet recording head, comprising: a control circuit for controlling a pulse width of a pulse waveform.