JPH04234669A - Ink-jet recording device - Google Patents

Abstract

PURPOSE:To obtain an ink-jet recording device, in which no malfunction or defective recording by noises is generated and which has high reliability, by conducting positive ink-end detecting operation in the irreducible minimum of a demand. CONSTITUTION:In an ink-jet recording device having the discharge defective recovery means of a nozzle, ink-end detecting operation is conducted once during recovery operation, ink is sucked when ink is not ended, and ink-end detecting operation is further 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 tank. .

0002

2. Description of the Related Art In an inkjet recording device that records and writes characters, etc. according to recording information on recording paper by ejecting ink droplets from a nozzle, ink is ejected from minute nozzles to form ink droplets. If foreign matter such as paper powder or dust adheres to the nozzle, the flight of ink droplets will be disturbed. If the flight is disturbed, it becomes impossible to write a good record. Ink droplets are formed by rapidly changing the volume of a pressure chamber provided inside the recording head using an electrostrictive vibrator or the like to generate ejection pressure. Therefore,
If air gets mixed into the ink supply path, the ejection pressure will not be generated satisfactorily, making recording and writing impossible.

Further, when the ink in the ink tank is completely consumed and the supply is cut off, recording and writing become impossible. 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.

[0004]In order to deal with such problems, a structure has been used in which a level detector is disposed within the ink tank to detect the ink end before the ink supply is cut off. If the ink tank is mounted on a carriage and performs printing operations while reciprocating integrally with the print head, an ink end detection means is also mounted on the carriage, and a signal for ink end detection is sent. The transmission is performed using an FPC (Flexible Print), which is a signal transmission means for transmitting a recording command for ejecting ink droplets.
It was done by wiring on the t circuit.

[0005]

In the conventional example described above, the ink end detection operation was performed at regular intervals. Therefore, in the ink end detection operation during the printing operation, the print command signal and the ink end detection signal may overlap. Therefore, there is a problem in that the recording command signal is superimposed on the ink end detection signal as noise, resulting in a 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, there is a problem in that noise is added to the recording command signal, making it impossible to perform a good recording operation. Of course, as a means to solve such a problem, there is a means for wiring a guard pattern between the printing command wiring pattern formed on the FPC 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. however,
Even if the above-mentioned noise countermeasures 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.

[0006]Furthermore, ejection failure occurs when air enters the ink supply path as described above or when foreign matter adheres to the nozzle portion of the print head, but when ejection failure occurs, good printing operation cannot be continued. It disappears. Therefore, conventionally, this type of recording apparatus has been provided with an ejection failure recovery means to recover from this ejection failure. Then, the cause of the ejection failure is removed by operating the ejection failure recovery means and forcibly consuming ink from the nozzle. During this recovery operation, the amount of ink consumed is much greater than during the recording operation, and in the conventional ink end detection operation that is performed at regular intervals, air may get mixed in from the hollow needle.

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and its purpose is to provide a structure in which an ink end detection means is mounted on such a carriage to detect the end of ink in an ink container. The purpose of the present invention is to provide an extremely reliable inkjet recording device that can perform reliable ink end detection operations and good printing operations in all conditions during recording and recovery operations. .

[0008]

[Means for Solving the Problems] An inkjet recording apparatus of the present invention is an inkjet recording apparatus that records on recording paper by ejecting ink droplets from a nozzle of a recording head according to a recording command, and the recording paper is conveyed. a recording paper conveying means, a carriage carrying the recording head and moving back and forth, an ink end detection means for detecting the end of ink in an ink container disposed on the carriage and containing ink, and the recording command. and an ejection failure recovery means for performing a recovery operation to recover from an ejection failure of the nozzle, and a detection operation of the ink end detection means during the recovery operation. The cycle T1 and the detection operation cycle T2 of the ink end detection means during the recording operation by the recording head are T.
It is characterized in that 1<T2.

[0009]Furthermore, the ink end detection means is characterized in that the detection operation is carried out during or before and after the operation of the recording paper transport means.

[0010] The ink end detection means includes an electrode disposed in a part of the ink supply path from the ink tank to the recording head, including the ink tank, 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.

[0011]

[Operation] According to the above structure of the present invention, since the ink end detection operation is performed only when there is no print command signal transmitted to the print head, the ink end detection signal and the print command signal are mutually connected. , there is no noise.

Furthermore, by configuring the ink end detection operation cycle to be changed between the recording operation and the recovery operation, the ink end detection operation can be performed reliably even during the recovery operation which consumes a large amount of ink. No air is mixed in from the hollow needle.

[0013]

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 that rotates in the direction of arrow A to convey recording paper, has a recording medium close to the platen 1. A head 3 is integrally provided. An ink tank 7 is provided above the recording head 3 and contains 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 recording 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 recording 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.

In addition, in the event that an ejection failure occurs in the recording head 3, the suction pump 15 is operated via the cap 13 and piping 14 to suck ink from the recording head 3, thereby recovering the ejection 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.

By the way, the symbols 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 recording command signal for ejecting ink droplets applied to the recording head 3 is transmitted by the FPC 18, which is a flexible signal transmitting 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.

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 the 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 enough ink is stored in the form 6 in the ink tank 7 and both electrodes S1 and S2 are connected via ink, both electrodes S1 and S2
The resistance between them 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. Along with this, both electrodes S1, S2
The resistance between them 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 recording 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 recording head 3. Then, on a panel surface (not shown), a message indicating that the ink is out is displayed.

FIG. 9 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/off the transistor Q1 through the delay driver IC1 (LS31). While the detection pulse 303 is at a high level (H), the transistor Q1 is turned off, 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, respectively, via the FPC 18. The electrode input terminal 305b is grounded. While the transistor Q1 is in the off state, the electrode input terminal 305a
The voltage V(-) at 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, a voltage V(+) equal to a preset value of V(-) at the end of ink is input to the (+) input terminal of the comparator IC2, which is realized by resistors R2 and R3. By comparing V(-) and V(+), comparator IC2 outputs a high level (H) when V(-)<V(+), and a low level (H) when V(-)>V(+). L) is output and given to the ink end signal output section 307 as a detection level signal 306. Ink end signal output section 307
Now, the detection level signal 306 is converted to the sampling pulse 30.
By the rising edge of 8, the D-flip-flop IC4 (LS74A) is latched and the ink end signal 3 is output.
Outputs 09.

[0021] Here, IC3 is LS04, and IC5 is LS04.
It is 221.

Next, the operation of the ink end detection circuit will be explained using the waveform diagram shown in 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. Delay driver IC1 causes transistor Q1
A detection pulse 303 is delayed and inverted and applied to the base of the . The transistor Q1 is turned off, and a voltage V(-) that is divided by the resistance value R between the electrodes S1 and S2 and the resistor R1 appears at the electrode input terminal 305a. 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 V(
+)>V(-), and is latched at the rising edge of the sampling pulse 308. and ink end signal 30
9 is a high level (H) indicating a non-ink-end state.

When the ink held in the form 6 is consumed by a recording 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 recording 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 recorded, enough ink remains to prevent air from entering the hollow needle 5. Further, in this embodiment, the voltage pulse for detection has a period of 1 kHz, as shown in FIG.
The current application time was set to 100 to 200 μs, and 3 to 5 pulses were used for each 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 recording operation within the recording area 101 in response to a recording command signal. The carriage 2 then passes through the deceleration area 102 and comes to a stop. If the recording command continues, the carriage 2 moves to the acceleration area 1 without stopping time 103.
04, and the recording operation is performed again within the recording 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 as long as no recording signal is transmitted. 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 operation flowchart of the ink end detection operation during the recording operation.

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

FIG. 8 shows an operational flowchart of the ink end detection operation during the recovery operation.

[0029] In step 401, it is determined whether the recording device is off-line or not, and if it is off-line, the process advances to step 403. If it is not offline, the process proceeds to step 402, where the on-offline changeover switch is pressed to set it offline. Next, in step 403, the recovery operation switch is pressed and a recovery operation command is input. When the recovery operation command is input, the process advances to step 404. In step 404, it is determined whether the recording head is at the cap position. If the print head is not at the cap position, the process advances to step 413, and the print head is moved to the cap position. If the recording head is in the cap position, the process advances to step 405 and the cap is closed. Then, in step 406, one ink end detection operation is performed. In step 407, it is determined whether or not the ink has run out. If the ink is out, step 41
Proceed to step 5. If the ink is not exhausted, the process advances to step 408, where the suction pump is operated and ink suction is started. Next, in step 409, an ink end detection operation is started. If it is determined in step 410 that the ink has run out, the process proceeds to step 414, the suction pump is stopped, and step 415
When the ink is out is displayed on the panel, the printing apparatus stops. If it is determined in step 410 that the ink is not exhausted, the process proceeds to step 411, where it is determined whether the elapsed time has exceeded the set value T0. If the set value is not exceeded,
Repeat steps 409, 410, and 411. When the elapsed time exceeds the set value, the process proceeds to step 412, where the suction pump is stopped and the recovery operation is ended.

The ink end detection operation during the recovery operation consumes a large amount of ink, so it is necessary to repeat the detection operation continuously. In this embodiment, a detection pulse is continuously applied once every 0.001 seconds during ink suction. In addition, since the ink end detection operation during the recording operation is performed every one line of recording operation, the ink end detection operation is approximately 0.01 seconds to 0.0 seconds.
．． The detection operation is performed once every 5 seconds or more.

[0031]

According to the present invention, since the ink end detection period is suitable for each operation during the recording operation and the recovery operation, the ink end detection operation can be performed to the minimum necessary level in all operations. As a result, during recording operation, the ink end detection operation signal is transmitted only when the recording command signal is not transmitted, so it is possible to provide a highly reliable inkjet recording device that is free from malfunctions and recording defects due to noise. It has this effect. Also, during the recovery operation, unlike during the recording operation, the ink end detection operation is performed continuously, so air is not mixed into the ink supply path, and the ink end can be detected reliably. It has this effect.

[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 the main parts of the present invention.

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 an operation flowchart of an ink end detection operation during a recovery operation.

FIG. 9 is a circuit diagram of an ink end detection circuit.

FIG. 10 is a waveform diagram for explaining the operation of the ink end detection circuit.

FIG. 11 is a diagram illustrating voltage pulses 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 apparatus that records on a recording paper by ejecting ink droplets from a nozzle of a recording head in accordance with a recording command, the apparatus comprising: a recording paper transport means for transporting the recording paper; and the recording head. A reciprocating carriage, an ink end detection means for detecting the end of ink in an ink tank disposed on the carriage and containing ink, and a flexible signal transmission means for transmitting the recording command. and an ejection failure recovery means that performs a recovery operation to recover from the ejection failure of the nozzle,
Inkjet recording characterized in that a detection operation cycle T1 of the ink end detection means during the recovery operation and a detection operation cycle T2 of the ink end detection means during the recording operation of the printhead satisfy T1<T2. Device. 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 an ink supply path from the ink tank to the recording head, including the ink tank, 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.