JP3152274B2 - Cleaning control device for inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer for printing by discharging ink from a nozzle, and more particularly, to measuring a non-printing time and removing nozzle clogging in accordance with the time. The present invention relates to a time measuring means for performing cleaning for prevention.

[0002]

2. Description of the Related Art In an ink-jet printer, since there is a possibility that the nose of a print head is clogged and dots are missing, the non-printing time including the time when the printer is turned off is measured. When the time has reached a certain time, an operation called cleaning is performed in which the minimum necessary ink according to the length of the non-printing time is idle-discharged to prevent dot omission due to nozzle clogging. There is a need.

FIG. 5 is a view for explaining a method employed in a conventional ink jet printer to measure the non-printing time.

Reference numeral 5-1 denotes a clock IC, and a built-in battery 5 set in a battery holder 5-3 separate from a power supply of the printer.
-4, and always counts the reference clock generated by the crystal oscillator 5-2. This watch IC 5-1
Is read by the CPU 5-5 which controls the entire printer, and the non-printing time is grasped.

Reference numeral 5-7 denotes a ROM in which a program for the CPU is written, and reference numeral 5-8 denotes a RAM for writing and reading data required when the CPU executes the program.

Reference numeral 5-9 denotes a nonvolatile memory for storing necessary data so that the data is not lost even when the power of the printer is turned off.
9 stores the updated time every time printing is completed. Thus, when the power is turned off and then turned on, the CPU 5-5 reads the time measured by the clock IC 5-1 and compares it with the final print end time stored in the nonvolatile memory 5-9. Non-printing time can be grasped,
A cleaning method corresponding to the time can be selected.
That is, when the non-printing time is short, a light cleaning method is selected, and when the non-printing time is long, an elaborate cleaning method is selected, so that optimum cleaning can always be performed.

[0007]

However, the prior art shown in FIG. 5 requires a clock IC, a crystal oscillator for generating a reference clock, a dedicated battery, and the like, resulting in an increase in cost. There were problems, such as consideration of heat generation accidents due to accidental short-circuiting of batteries, and consideration of how to dispose of batteries that deal with natural destruction when the printer is discarded after the printer has been used for a while. . To solve these problems,
For example, as can be seen in JP-A-5-254149.
And discharges the accumulated charge of the capacitor with a predetermined time constant.
Set the capacitor to the set voltage value before starting the clocking of the R circuit.
Charge and input the discharge voltage of CR circuit to A / D converter
Timekeeping means has been proposed to time the discharge of the CR circuit.
The voltage is input to an A / D converter which is a circuit at the subsequent stage.
The time that can be measured is short,
Can not be used when measuring a long ink non-ejection period.
No. The present invention has been made in view of such problems.
The purpose is to discharge the CR circuit.
Timer that can accurately measure a long time based on
Cleaning control device for inkjet head with step
Is to provide an installation.

[0008]

Means for Solving the Problems To achieve such a problem
In the present invention, the non-ejection time interval of the ink droplet
Eject ink droplets from the nozzle holes to prevent clogging.
Inkjet head cleaning controller
The capacitor and the resistor are connected in parallel and the capacitor
A CR circuit for discharging the accumulated charge of the
Conducts at the end of each character and charges the capacitor to the set voltage value
And a discharge voltage of the CR circuit.
An A / D converter for converting to a digital value;
A second switch for inputting a discharge voltage to the A / D converter
A second circuit when the power is turned on.
Input the discharge voltage to the A / D converter via the
The ink droplet ejection time interval is detected.

[0009]

【Example】

(Embodiment 1) FIG. 1 is a block diagram of a timer circuit showing a first embodiment of the present invention. Reference numeral 1-1 denotes a SW1 circuit composed of a transistor, which includes a power supply VIN lower than a logic power supply (+5 volts) of a printer and a capacitor 1-8.
To open and close the charging of the capacitor 1-8. This opening and closing operation is controlled by a signal from the output port OUT1 of the CPU 1-4.
The W1 circuit 1-1 is closed and charging is performed. The SW1 circuit 1-1 can be realized using an FET or a relay.

The signal level of the output port OUT1 is at the high level when the power is turned on, and the capacitor 1-8 is not charged unless the signal level of the output port OUT1 is switched by the control program.

Reference numeral 1-2 denotes a CR circuit for discharging the electric charge stored in the capacitor 1-8 through the resistor 1-9 and detecting the elapsed time as a voltage change of the capacitor 1-8. . The product of the capacitor 1-8 and the resistor 1-9 is called a CR time constant, and this value can be freely set to a value corresponding to the time to be measured.

Reference numeral 1-3 denotes a SW2 circuit, and a CR circuit 1-
The terminal voltage of the capacitor 1-8, which is the output of the
-4 is input only when necessary to the analog input terminal A / DIN, and the control is performed by the signal of the output port OUT2. To make the SW2 circuit 1-3 conductive, the signal level of the output port OUT2 is set to Low.
At this time, the terminal voltage of the capacitor 1-8 is electrically connected to the analog input terminal A / DIN. VH in the figure is the power supply voltage of the driving system of the printer.
This is a voltage sufficient to turn on the gate of the ET.

By the SW2 circuit 1-3, the analog input terminal A /
The input impedance of DIN is very low,
It is possible to prevent such a problem that the terminal voltage of the capacitor 1-8 decreases very quickly with respect to the R time constant.

The SW2 circuit 1-3 can be realized by using a relay. Reference numeral 1-6 denotes a CPU.
ROM in which the operation program of 1-4 is written,
Reference numeral 1-7 is a RAM.

FIG. 2 is a discharge characteristic diagram of a CR circuit which is the main part of the cleaning control device of the present invention. In the present invention, CR
After charging the circuit 1-2 with a constant voltage Vfull,
The SW1 circuit 1-1 for supplying the electric charge is turned off, and the electric charge stored in the capacitor 1-8 is discharged by the resistor 1-9.
The elapsed time is calculated by the CPU from the change in the terminal voltage.

Equation (2-1) in FIG. 2 is a CR circuit 1-2.
Shows the relationship between the terminal voltage Vt of the capacitor 1-8 and the elapsed time t when the electric charge stored in the capacitor 1 is discharged. As can be seen from this equation, the capacitor terminal voltage Vt after t seconds is C
It is related to the R time constant, and the larger this value is, the slower the voltage drops. Further, the elapsed time t is calculated by the equation (2-
In 2), the required CR time constant can be calculated by equation (2-3).

FIG. 6 summarizes the program operations of the first embodiment and a later-described second embodiment. Process 1 is performed when the power of the printer is turned on.

When the power is turned on, first, a signal for turning on the FET of the SW2 circuit 1-3 is output to the output port OUT2, and the terminal voltage of the capacitor 1-8 is input to the analog input terminal ADIN. At -4, the analog voltage is converted into a digital value and read. Then, the expression (2-
2) Alternatively, the elapsed time is obtained by referring to a relative relationship table between the voltage value and the elapsed time stored in advance in the ROM 1-6, and the signal level of the output port OUT2 is switched to inhibit the input to the analog input terminal ADIN. I do. The empty cleaning is performed a number of times corresponding to the obtained elapsed time, and the initial cleaning is completed.

NO. The process 2 is performed at the end of printing and at the end of the initial cleaning. A signal for turning on the transistor of the SW1 circuit 1-1 is output to the output port OUT1 for a certain period of time, and the capacitor 1-8 is charged to the voltage Vfull. The measurement time until is reset, and the measurement of the non-printing time thereafter is restarted.

Incidentally, the charging of the capacitor 1-8 may be started at the same time as the printing is started, and may be stopped by switching the signal level of the output port OUT1 to High after the printing is completed. In this case, since the capacitor 1-8 can be charged in advance during the printing time, there is no need to provide a new charging time after printing is completed.

As described above, the optimum cleaning operation can be performed by reading the voltage of the CR circuit to calculate the time and controlling the charging timing of the CR circuit.

(Embodiment 2) FIG. 3 is a circuit block diagram showing a second embodiment of the present invention. As shown in this figure, the difference between the second embodiment and the first embodiment is that the discharge resistance of the CR circuit is omitted. That is, in the second embodiment, the discharge of the capacitor 3-8 is left to the self-discharge due to the leakage current.

As a result, a longer elapsed time can be measured as compared with the first embodiment.

(Embodiment 3) FIG. 4 is a circuit block diagram showing a third embodiment of the present invention. In this circuit block diagram, the difference from the first or second embodiment is
4-3 has a built-in timer counter 4-12, and a time counter 4 for storing an elapsed time in a RAM.
−8, and furthermore, a nonvolatile memory 4-9.

In the third embodiment, the number of constituent elements is increased as compared with the above-mentioned embodiment. However, a CPU used in a normal printer has a plurality of timer counters built therein, and one of them is used. This does not increase the cost. As the nonvolatile memory 4-9, a memory conventionally used for storing default settings and user settings of the printer even after the power is turned off can be used. Next, the processing flow will be described with reference to FIG.

No. Reference numeral 1 describes a process performed when the power of the printer is turned on.

When the power is turned on, first, a signal for turning on the FET of the SW2 circuit 4-3 is output to the output port OUT2, and the terminal voltage of the capacitor 4-10 is input to the analog input terminal ADIN. At -4, the analog voltage is converted into a digital value and read. Then, the elapsed time is obtained by substituting the time constant of the CR circuit stored in the non-volatile memory described later and the voltage Vfull of the capacitor at the time of initial charging into the equation (2-2), and then switching the signal level of the output port OUT2. Therefore, input to the analog input terminal ADIN is prohibited. Then, the initial cleaning is performed by performing the empty ink discharge the number of times corresponding to the obtained elapsed time. Thereafter, a signal for turning on the transistor of the SW1 circuit 4-1 is output to the output port OUT1 for a certain period, and the capacitor 4
-10 is charged to the voltage Vfull, and the SW2 circuit 4-3 is again operated for a certain period of time as described above to
10 is read and the value is read from the nonvolatile memory 4
-9, and finally, the time counter 4 of the RAM 4-7.
8 is initialized to 0. The stored value of the time counter 4-8 is incremented and updated by one by an overflow signal or an interrupt signal from a timer counter 4-12 built in the CPU 4-4, and the stored value is changed from the cleaning or the immediately preceding printing end point. This indicates the non-printing time.

NO. The process of No. 2 is performed at the end of printing, except that there is no cleaning operation. This is the same as the processing of step 1.

NO. Reference numeral 3 denotes a CR time constant calculation routine which is a feature of the third embodiment. As described above, the time counter 4-8 measures the elapsed time of the discharge of the capacitor 4-10.
The terminal voltage of −10 is read, the time of the time counter 4-8 is measured, and the initial charging voltage Vf stored in the nonvolatile memory 4-9 is read.
The CR time constant is calculated according to the formula (2-3) with reference to the ull, it updates the CR time constant values stored in the nonvolatile memory 4-9. Thus, the time can be accurately grasped even if the capacitance and the resistance value of the capacitor vary. Further, even if the capacity of the capacitor is lost due to a change over time, the time can be accurately managed.

[0030]

As described above, in the present invention ,
Capacitor and resistor are connected in parallel, capacitor accumulation
A CR circuit that discharges electric charges at a predetermined time constant, and every time printing is completed
, And charges the capacitor to the set voltage value.
Convert discharge voltage of switch circuit and CR circuit to digital value
A / D converter and A / D conversion of discharge voltage of CR circuit
And a second switch circuit for inputting to the switch, when the power is turned on.
The discharge voltage through the second switch circuit to the A / D
Input to the converter to detect the non-ink drop ejection time interval.
The driving power based on the discharge voltage of the CR circuit.
When ejecting non-ink droplets for a long time even when ink is not supplied
The interval can be measured accurately .

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a discharge characteristic diagram of a CR circuit.

FIG. 3 is a block diagram of a second embodiment of the present invention.

FIG. 4 is a block diagram of a third embodiment of the present invention.

FIG. 5 is a block diagram illustrating a conventional example.

FIG. 6 is a view for explaining program processing according to the first and second embodiments.

FIG. 7 is a diagram illustrating a program process according to a third embodiment.

[Explanation of symbols]

 1-1: Switch circuit 1-2: CR circuit 1-3: Switch circuit 1-4: CPU 1-5: Crystal oscillator 1-6: ROM 1-7 ... RAM 1-8 ... Capacitor 1-9 ... Resistance

Claims (2)

(57) [Claims] 1. A cleaning control device for an ink jet head which discharges ink droplets from nozzle holes in accordance with a non-discharge time interval of ink droplets, wherein a capacitor and a resistor are connected in parallel, , A first switch circuit that conducts each time printing is completed and charges the capacitor to a set voltage value, and an A / D converter that converts the discharge voltage of the CR circuit into a digital value. And a second switch circuit for inputting the discharge voltage of the CR circuit to the A / D converter. When the power is turned on, the discharge voltage is supplied to the A / D converter via the second switch circuit. A cleaning control device for an ink jet head which detects a non-ink droplet ejection time interval by inputting to a converter. 2. A means for reading the voltage of the capacitor after a lapse of a predetermined time after the power is turned on, calculating a time constant of the CR circuit from a voltage fluctuation from an initial charging voltage, and calculating a time constant of the latest CR circuit. The cleaning control device for an inkjet head according to claim 1, further comprising the nonvolatile memory that stores the information.