JPH04234670A - Ink-jet recording device - Google Patents

Abstract

PURPOSE:To obtain an ink-jet recording device having high reliability by preventing a malfunction and defective printing due to noises when an ink end is detected. CONSTITUTION:The detecting operation of an ink-jet detecting means is conducted when one line is printed, a carriage is decelerated, stopped and re- accelerated and recording-paper carrying operation is performed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording device for recording characters, etc. on recording paper by ejecting ink droplets from a nozzle, and more particularly to an ink end detection device for detecting the end of ink in an ink container. .

0002

[Prior Art] In an inkjet recording device that ejects ink droplets from a nozzle to record and write characters or the like on recording paper according to recording information, when the ink in the ink container is exhausted and the supply is cut off, , it becomes impossible to write records. Furthermore, air enters the ink supply path leading to the nozzle, and even if ink is newly replenished, a problem arises in that it takes a long time before recording can be performed.

[0003]In order to deal with such problems, a structure has been used in which a level detector is disposed within the ink container to detect the ink end before the ink supply is cut off. The signal for detecting ink end is transmitted through an FPC (Flexible Print
It was done by wiring on the circuit (ircuit).

0004

In the conventional example described above, since the ink end detection operation was performed at regular intervals, the print command signal and the ink end detection signal sometimes overlapped. Therefore, there is a problem in that noise is added to the ink end detection signal, resulting in malfunction. When the above-mentioned malfunction occurs, even though there is still sufficient ink in the ink tank, the state becomes the same as the ink-out state, and the recording apparatus stops printing operation. Furthermore, noise is added to the print command signal,
There was a problem that good printing operation could not be performed. Of course, as a means to solve such problems, the above-mentioned FPC
There is a means for wiring a guard pattern between the printing command wiring pattern formed above and the ink end detection pattern. This guard pattern is grounded to GND on the circuit board side. Another method is to increase the width of each pattern and stabilize the individual signals. Another method is to increase the distance between each pattern. In any case, even if the noise countermeasures described above are taken, it is difficult to provide a complete countermeasure. Furthermore, since the FPC becomes larger, the connector and board for connecting the FPC also become larger. Therefore, problems arise in that the cost increases and the overall size of the recording apparatus increases.

SUMMARY OF THE INVENTION Therefore, the present invention is intended to solve the above-mentioned problems, and its purpose is to provide a structure for mounting an ink container on such a carriage and detecting the end of ink in the ink container. An object of the present invention is to provide an extremely reliable inkjet recording device that can perform a reliable ink end detection operation and a good printing operation.

[0006]

[Means for Solving the Problems] An inkjet recording device of the present invention is an inkjet recording device that records on recording paper by ejecting ink droplets from a nozzle of a print head in response to a print command, and the recording paper is conveyed. A recording paper conveying means, a carriage carrying the print head and an ink container for storing ink and moving back and forth, an ink end detection means for detecting the end of ink in the ink container, and transmitting the print command. The apparatus is characterized in that the ink end detection means performs a detection operation only when there is no print command transmitted to the print head. Further, the detection operation of the ink end detection means is performed during or before or after the operation of the recording paper transport means.

Further, the ink end detection means includes an electrode disposed in a part of the ink supply path from the ink container to the print head, including the ink container, and by applying a voltage pulse to the electrode. , is characterized in that it is configured to detect a resistance change between both electrodes that exceeds a set value.

[0008]

[Operation] According to the above structure of the present invention, the ink end detection operation is performed during the so-called recording paper conveyance operation, which is when the carriage reciprocating operation is switched when there is no print command signal transmitted to the print head, so the ink end detection is performed. There is no noise between the signals for printing and the signals for printing commands.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a main sectional view for explaining an embodiment of an inkjet recording apparatus of the present invention, and FIG. 2 is a perspective view of the main parts. Further, FIG. 3 is a block diagram for explaining the ink end detection circuit. A carriage 2 that reciprocates in the direction of arrow B on a guide shaft 2a along a platen 1, which is a recording paper conveying means, rotates in the direction of arrow A to convey the recording paper, and prints near the platen 1. A head 3 is integrally provided. An ink tank 7 is provided above the print head 3 and contains therein a foam 6 made of a porous material such as polyurethane foam. This ink tank 7 is provided with a vent hole 9 in its lid 8 to allow atmospheric air to be taken in, and a platform-shaped protrusion 10 is formed on the bottom surface of the ink tank 7 to ensure close contact with the foam 6. An ink chamber 1 that takes out ink from the form 6 and holds it downward from the center of the protrusion 10.
1 is formed. The end of the ink chamber 11 is sealed with a blind plug 12 made of an elastic member such as rubber. Then, the print head 3 is connected to this blind plug 12 through the filter chamber 4.
The ink impregnated in the ink tank 7 is supplied to the print head 3 by inserting the hollow needle 5 that communicates with the ink tank 7 . Incidentally, the ink chamber 11 is in a sealed state due to the blind plug 12 and the foam 6.

Furthermore, in the event that a discharge failure occurs in the print head 3, the suction pump 15 is operated via the cap 13 and piping 14 to suck ink from the print head 3, thereby recovering the discharge failure. An action is taken. The sucked ink is sent to a waste ink reservoir 17 through a pipe 16. In the present invention, the waste ink reservoir 17 and the ink tank 7 are separate bodies, and the waste ink reservoir 17 is disposed within the main body of the recording apparatus, so that it is not normally replaced.

Reference numerals S1 and S2 in the figure are electrodes for ink end detection, one of which, S1, is provided on the inner wall surface of the ink tank 7 so as to be in contact with the foam 6, and the other electrode, S2, is provided on the inner wall surface of the ink tank 7. , the hollow needle 5 in contact with the ink also serves as an electrode. Then, as shown in FIG. 3, a reference voltage Vcc is applied to one of the electrodes S1 and S2. Further, the other electrode S2 is grounded. Further, a resistance change detection circuit including a differentiation circuit 19 and a comparison circuit 20 is connected to the electrode S1 on the side to which the reference voltage Vcc is applied. and,
It is configured to generate an output signal when the amount of resistance change exceeds a certain level.

A print command signal for ejecting ink droplets applied to the print head 3 is transmitted by the FPC 18, which is a flexible signal transmission means. A signal line for ink end detection is integrally wired on the FPC 18 and connected to the electrodes S1 and S2. In addition, instead of FPC18, FFC (Flexible FPC) is used as a signal transmission means.
It goes without saying that a lat cable or the like may also be used. Furthermore, it goes without saying that instead of using one FPC, a structure of two stacked FPCs may be used.

Next, the state before and after the ink in the ink tank 7 containing the foam 6 used in this example is depleted,
The change in electrical resistance will be explained using FIG. 4.

[0014] When a porous material B such as polyurethane foam is brought into pressure contact with the upper part of the ink chamber A whose upper end serves as an ink outlet, the ink i impregnated into this porous material B is consumed. The ink is sequentially supplied into the ink chamber A by capillary action to fill the ink chamber A. (Figure 4(a)). Under this condition, the two electrodes S1 and S2 disposed in the porous material B and the ink chamber A, respectively,
The resistance between them is small and remains almost constant. (Area a in Figure 5). On the other hand, the ink in the porous material B gradually depletes, and as a result, air g enters into the porous material B to replace the ink i. Then, a part of the air g that has entered reaches the bottom of the porous material B while encountering great resistance, and comes to appear in a part of the ink outlet. Therefore, a partial break begins to occur between the ink i in the porous material B and the ink i in the ink chamber A, which were communicating at this portion (FIG. 4(b)). The resistance between both electrodes S1 and S2 increases by an amount corresponding to this decrease in communication area (
Area b) in Figure 5. As the ink i in the porous material B further depletes, the communication area further decreases, and finally the ink i in the porous material B and the ink i in the ink chamber A are separated. Along with this, the resistance between both electrodes S1 and S2 becomes maximum (
Area c) in Figure 5.

Next, the operation up to ink end in this embodiment will be explained. When ink is sufficiently stored in the form 6 in the ink tank 7 and the electrodes S1 and S2 are connected through the ink, the resistance between the electrodes S1 and S2 is small and stable. This state continues as long as the foam 6 is wetted, even if the ink is reduced and the electrode S1 is no longer in direct contact with the ink. As the recording device continues recording and writing operations, the ink in the form 6 is further reduced, and the intruded air is allowed to reach the upper open end of the ink chamber 12. Then, due to the air that has entered, the area of the ink entanglement connecting the foam 6 and the ink chamber 12 begins to decrease. Accordingly, the resistance between the electrodes S1 and S2 increases rapidly. This resistance change is immediately detected by the differentiating circuit 19 as a change amount. Then, when this amount of change exceeds the value of the set voltage input to the comparison circuit 20, a signal is output from the comparison circuit 20. The printing operation is stopped by the output signal, and the carriage 2
returns to the cap 13 position and closes the cap 13 to cover the nozzle portion of the print head 3. Then, on a panel surface (not shown), a message indicating that the ink is out is displayed.

FIG. 8 is a circuit diagram of the ink end detection circuit in this embodiment. Ink end detection trigger pulse 3
01 is input to the detection pulse generation unit 302, it outputs a detection pulse 303 having a certain pulse width. The detection pulse 303 is input to the ink end detection section 304 and turns on the transistor Q1 through the delay driver IC1.
/off. The detection pulse 303 is at high level (H
), the transistor Q1 is in the off state, and a voltage pulse is applied between the electrode input terminals 305a and 305b. Electrodes S1 and S2 are connected to the electrode input ends 305a and 305b.
are connected to each other via the FPC 18. The electrode input terminal 305b is grounded. Transistor Q1
While in the off state, the voltage V(-) at the electrode input terminal 305a is divided by the resistor R1 and the resistance value R inside the form 6, and is input to the (-) input terminal of the comparator IC2 through the resistor R5. On the other hand, comparator IC2 (
A voltage V(+) equal to the preset value of V(-) at the end of ink is applied to the input terminal of resistors R2 and R.
It is realized and input by 3. Comparator IC2
is V(-) by comparing V(-) and V(+).
<High level (H) when V(+), V(-)>
When the voltage is V(+), a low level (L) is output, and the ink end signal output section 307 outputs the detected level signal 306.
give to The ink end signal output section 307 latches the detection level signal 306 into the D-flip-flop IC4 at the rising edge of the sampling pulse 308, and outputs an ink end signal 309.

Next, the operation of the ink end detection circuit will be explained using the waveform diagram of FIG. The rising edge of the ink end detection trigger pulse 301 generates a detection pulse 303 that remains at a high level (H) for a certain period of time. The delay driver IC1 applies the delayed and inverted detection pulse 303 to the base of the transistor Q1. The transistor Q1 is turned off, and the resistance value R between the electrodes S1 and S2 and the resistance R are input to the electrode input terminal 305a.
1, a divided voltage V(-) appears. When the amount of ink held in the form 6 in the ink tank 7 is sufficient, the resistance value R between the electrodes S1 and S2 is small, so that the voltage V(+) indicating the ink end state is
)>V(-), and it is latched at the rising edge of the sampling pulse 308. and ink end signal 309
becomes a high level (H) indicating a non-ink-end state.

When the ink held in the form 6 is consumed due to a printing operation or the like, the resistance value R between the electrodes S1 and S2 increases. As a result, when V(+)<V(-), the detection level signal 306 becomes low level (L). The time during which the detection level signal 306 is at low level (L) is
It is governed by the off-state time of transistor Q1 by delay driver IC1. Therefore, the detection level signal 306
is reliably latched at the rising edge of the sampling pulse 308. Then, the ink end signal 309 becomes low level (L) indicating the ink end state. With the above configuration, the voltage V(+) indicating the ink end state
The set value of the ink end detection level can be set arbitrarily by appropriately selecting the resistors R2 and R3 that provide the voltage V(-) to be detected, and R1 that provides the detected voltage V(-). In this embodiment, the ink end detection operation is not performed during the printing operation for one line. Therefore, the ink end detection level is set so that even if all the nozzles print for one line and the number of digits is printed, enough ink remains to prevent air from entering the hollow needle 5. In this embodiment, as shown in FIG. 10, the period of the detection pulse is 1 KHz, the energization time is 100 to 200 μsec, and 3 to 5 pulses are used per ink end detection operation. The reason why the number of pulses per ink end detection operation is plural is to correct the malfunction so that even if one pulse malfunctions due to noise or the like, the ink end state does not occur.

By performing pulse detection as shown in this embodiment, the amount of electrical energy given to the ink can be minimized. Thereby, changes in the components due to electrolysis of the ink and formation of a polarized film on the electrodes can be suppressed.

The ink end detection operation during the printing operation will be explained in detail with reference to FIG. Carriage (CR)
2 performs a printing operation within the printing area 101 in response to a printing command signal. The carriage 2 then passes through the deceleration area 102 and comes to a stop. If the print command continues, the carriage 2 moves to the acceleration area 1 without stopping time 103.
04, and the printing operation is performed again within the printing area 101. The recording paper conveyance operation (PF) starts within the carriage deceleration area 102 and ends within the carriage acceleration area 104. Note that the ink end detection operation may be performed anywhere between the carriage deceleration area 102 and the carriage acceleration area 104. however,
In this embodiment, the ink end detection operation is performed at the end of the recording paper conveyance operation. By configuring the recording paper transport operation and the ink end detection operation so that they do not overlap in this way, it is more effective in terms of control processing and noise countermeasures.

FIG. 7 shows an operational flowchart of the ink end detection operation during the printing operation.

At step 201, carriage (CR) 2
performs a printing operation for one line in response to a printing command signal. Next, in step 202, the carriage 2 is decelerated in the carriage deceleration area, and the carriage 2 is stopped. After a recording paper conveyance operation is performed in step 203, an ink end detection operation is performed in step 204. Then, in step 205, it is determined whether or not the ink has run out. If the ink has not run out, the carriage 2 is accelerated in the acceleration region in step 206, and the printing operation for the next line is performed again in step 207. Repeat this operation below. If step 205
If it is the ink end, the process advances to step 208 and subsequent steps. At step 208, the carriage 2 is moved to the cap 13 position. Next, in step 209, the nozzle portion of the print head 3 is covered with the cap 13. Then, in step 210, a message that the ink is out is displayed on the panel, and the recording apparatus stops the printing operation.

[0023]

According to the present invention, the ink end detection operation signal is transmitted during the so-called recording paper transport operation, when the carriage reciprocating operation is switched from the carriage deceleration to the carriage acceleration operation, when the print command signal is not transmitted. Therefore, it is possible to provide a highly reliable inkjet recording apparatus that is free from malfunctions and printing defects due to noise.

[Brief explanation of the drawing]

FIG. 1 is a main sectional view for explaining an embodiment of an inkjet recording apparatus of the present invention.

FIG. 2 is a perspective view of main parts.

FIG. 3 is a block diagram for explaining an ink end detection circuit.

FIG. 4 is an explanatory diagram showing states before and after running out of ink.

FIG. 5 is a diagram showing the relationship between ink consumption and electrical resistance.

FIG. 6 is a diagram illustrating in detail an ink end detection operation during a printing operation.

FIG. 7 is an operational flowchart of an ink end detection operation during a printing operation.

FIG. 8 is a circuit diagram of an ink end detection circuit.

FIG. 9 is a waveform diagram for explaining the operation of the ink end detection circuit.

FIG. 10 is a diagram illustrating a detection pulse for ink end detection.

[Explanation of symbols]

1 Platen 2 Carriage 3 Print head 5 Hollow needle 7 Ink tank 13 Cap 15 Suction pump 17 Waste ink reservoir 18 FPC 19 Differential circuit 20 Comparison circuit

Claims (3)

[Claims] 1. An inkjet recording device that records on recording paper by ejecting ink droplets from a nozzle of a print head in response to a print command, comprising: a recording paper conveying means for conveying the recording paper; and a recording paper conveying means for conveying the recording paper; A carriage that carries an ink container therein and moves back and forth, an ink end detection means for detecting the end of the ink in the ink container, and a flexible signal transmission means for transmitting the printing command. An ink jet recording apparatus, characterized in that the ink end detection means performs a detection operation only when there is no print command transmitted to the print head. 2. The inkjet recording apparatus according to claim 1, wherein the detection operation of the ink end detection means is performed during or before or after the operation of the recording paper transport means. 3. The ink end detection means includes an electrode disposed in a part of the ink supply path from the ink container to the print head, including the ink container, and applies a voltage pulse to the electrode. 2. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is configured to detect a change in resistance between both electrodes that exceeds a set value.