JP4611276B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an inkjet recording apparatus that ejects ink from a plurality of nozzles.

  2. Description of the Related Art In recent years, inkjet recording apparatuses that eject ink from a plurality of nozzles and perform printing on a recording medium such as paper have been widely marketed because of their advantages such as small size, low cost, and quietness during operation.

  FIG. 5 is an explanatory diagram of the operation principle of such an ink jet recording apparatus. The ink chamber 501 is always filled with ink from an ink tank (not shown), and the inside of the pressure chamber 502 communicating with the ink chamber 501 through the flow path 505 is always filled with ink. A nozzle 503 is perforated at the lower end of the pressure chamber 502, but the ink in the ink chamber 501 and the pressure chamber 502 has a balance between the negative pressure from the ink tank and the force with which the ink tries to exit from the nozzle due to capillary action. In general, no ink leaks from the nozzle 503 because it is maintained (FIG. 5 (a)).

  A pressure element 504 is disposed at the upper end of the pressure chamber 502, and when there is an instruction for printing, the pressure element 504 pressurizes the ink in the pressure chamber 502. Then, ink 506 is ejected from the nozzle 503 and adheres to the recording medium P to perform printing (FIG. 5 (b)). Various elements have been developed as the pressurizing element 504, but a representative example is a piezoelectric element, and an ink jet recording apparatus using the piezoelectric element is called a piezo method.

  Based on this operating principle, as shown in FIG. 4 (a), by constructing a head unit 402 in which about 400 to 500 pressure chambers 502 and pressurizing elements 504 (indicated by points 401) are arranged, for example, 600 dpi Printing with a resolution of 1 is possible. When printing, it is possible to scan the head unit 402 in a direction perpendicular to the paper conveyance direction for printing, but recently, in order to meet the demand for high-speed printing, without performing such scanning, As shown in FIG. 4B, an ink jet recording apparatus including a head bar 403 in which a head unit 402 is fixedly arranged over the entire width of the recording medium P has been proposed.

  At this time, as shown in FIG. 4C, an ink jet recording apparatus that employs a head bar 406 in which the trapezoidal head units 405 are arranged in a staggered manner has also appeared. Compared with the head bar 403 employing the rectangular head unit 402 of FIG. 4 (b), the head bar 406 can be smaller in width W, which can contribute to downsizing of the entire apparatus.

  Here, as shown in FIG. 4 (d), when the rectangular head units 402 are arranged in a row, the nozzle to be used is suddenly switched to the nozzles of other head units at the joint between the head units 402. For this reason, there are problems that streaks occur in printing (particularly in the case of image printing) and characteristic differences between the head units 402 become obvious. In this regard, if the trapezoidal head units 405 are arranged in a staggered manner as shown in FIG. 4 (c), the trapezoidal hypotenuse passes twice in the conveyance direction A of the recording medium, so that such a problem can be avoided. It is.

  An ink jet recording apparatus employing such a trapezoidal head unit is disclosed, for example, in Patent Document 1 below. In an inkjet recording apparatus that performs color printing, the head bar 403 includes four head bars (illustrated) that eject black (K), cyan (C), magenta (M), and yellow (Y) ink, respectively. Not).

  On the other hand, as a general problem of the ink jet recording apparatus, there is an increase in viscosity that exceeds a specified value of ink in the nozzle. That is, as described with reference to FIG. 5, the nozzle 503 is always filled with ink, but if this nozzle is not used for a long period of time, the water in the ink evaporates from the nozzle 503. Depending on the situation, the viscosity of the ink rises and it becomes difficult for the ink to come out of the nozzles, resulting in poor printing.

In order to prevent this, a technique has been developed in which the ink in the vicinity of the nozzle 503 is swung (flushed) at regular time intervals. In the case of the piezo method described above, the piezoelectric element 504, which is a pressure element, is applied with a voltage that does not cause ink to be ejected from the nozzle 503 to vibrate the piezoelectric element, and thereby the ink in the nozzle 503 is swung. Technology. This swing can prevent an increase in the viscosity of the ink in the nozzle 503 beyond a specified value. An ink jet recording apparatus that employs such an ink swing technique is disclosed, for example, in Patent Document 2 below.
JP 2006-88568 A JP 2004-42314 A

  However, the above technique has the following problems.

  As described above, the ink in the nozzle 503 is oscillated by oscillating the pressure element 504 such as a piezoelectric element. If this oscillation is frequently performed, the life of the pressure element 504 is remarkably reduced. For this reason, it is desirable to perform the oscillation only when it is the minimum necessary.

  However, the viscosity increase above the specified value of the ink in the nozzle 503 is various, such as the room temperature and humidity of the room where the ink jet recording apparatus is placed, or the temperature rise inside the recording apparatus caused by using the ink jet recording apparatus. Caused by various factors.

  For this reason, if the rocking is performed at a constant time interval as described above, this time interval must be set short in consideration of all the factors. It is the cause of further shortening.

  The present invention has been made in view of such problems, and by actually measuring the increase in viscosity above the specified value of the ink in the nozzle 503, the viscosity increase above the specified value of the ink can be actually increased. An object of the present invention is to provide an ink jet recording apparatus that can keep the life of a pressurizing element long by performing only when it occurs.

  In order to achieve the above object, the present invention employs the following means.

  The applicant of the present application has paid attention to the fact that the end nozzle 408 outside the maximum width of the recording medium P is not used for printing in the ink jet recording apparatus having the head bar as shown in FIG. That is, although the end nozzle 408 is always filled with ink, it is not used for printing, so the corresponding pressure element is not driven at all. For this reason, an increase in viscosity that exceeds the specified value of ink is most likely to occur in the end nozzle group 408.

  Therefore, first, as shown in FIG. 4 (c), the present invention provides an inkjet including a head bar in which a head unit including a plurality of nozzles that eject ink is disposed in a direction perpendicular to the recording medium conveyance direction. A recording device is assumed.

  Next, in such an ink jet recording apparatus, there are provided ejection means for ejecting ink to end nozzles not used for printing on the head bar, and detection means for detecting ejection of ink from the end nozzles. And when the said detection means does not detect the said discharge, the rocking | fluctuation means which rocks | swiveles all the said nozzles is provided. As a result, at the end nozzle where the viscosity increase more than the specified value of ink is most likely to occur, all nozzles are swung (flushing) only when a viscosity increase exceeding the specified value is actually observed. Can do.

  Further, a light emitting element for irradiating light to the ink ejected by the ejection means and an imaging element for observing the shadow of the ink are provided, and the detection means detects the ejection of the ink from the end nozzle based on the shadow. You may make it do.

  If the user deems necessary, such as when the power is turned on, the ejection unit can be configured to eject ink based on the user's instruction. In particular, in an ink jet recording apparatus that performs color printing, the head bar, the ejection unit, and the swing unit are provided for each color type, and the swing can be controlled for each color type. .

  As described above, according to the present invention, in the end nozzle group in which the viscosity increase more than the specified value of the ink is most likely to occur, the increase in viscosity exceeding the specified value of the ink in the nozzle is measured and the oscillation is actually defined. By performing only when the viscosity increase of more than the value occurs, it is possible to provide an ink jet recording apparatus that can keep the life of the pressure element long.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an internal structure diagram of an embodiment of an ink jet recording apparatus 100 according to the present invention.

  The ink jet recording apparatus 100 includes a paper feed cassette 111 disposed at a lower portion, an ink tank 112 disposed above the paper feed cassette 111, and a conveyance belt 113 disposed above the ink tank 112. Further, a recording head 114 disposed above the transport belt 113 and a sheet transport path 116 disposed at the right end of the apparatus are provided.

  The paper feed cassette 111 stores a recording medium P on which printing is performed. In the paper feed cassette 111, a paper feed roller 121 for feeding paper is arranged at an end portion on the paper transport path 116 side. Yes. The paper transport path 116 is configured by a guide plate that guides the recording medium P fed from the paper feed cassette 111 to the transport belt 113. In this paper transport path 116, a transport roller pair 122 for transporting the fed paper is disposed on the paper feed cassette 111 side, and a registration roller pair 123 for performing secondary paper feed is disposed on the transport belt 113 side. .

  The ink tank 112 includes ink tanks 112K, 112C, 112M, and 112Y arranged in parallel in the left-right direction, and stores black (K), cyan (C), magenta (M), and yellow (Y) ink, respectively. is doing.

  The conveyor belt 113 conveys the recording medium P, which has been secondarily fed by the registration roller pair 123, to the left, and to the left and right outer sides (downstream and upstream in the sheet conveyance direction) of the recording head 114. The pair of transport rollers 124 and the transport rollers 125 are stretched.

  A recovery port 126 having an opening on the upper surface for recovering excess ink during printing is disposed below the transport roller 124, and a waste ink tank 127 is disposed below the recovery port 126. Has been placed. The collection port 126 and the waste ink tank 127 communicate with each other through a communication pipe 128 to constitute a collection ink storage unit.

  Further, a discharge roller pair 129 is disposed on the left side of the conveyor belt 113, and a discharge port 130 is formed in the left side wall of the device on the left side of the discharge roller pair 129. A discharge tray 131 protruding outside is disposed.

  In the recording head 114, the nozzle surface 141 on the lower surface is supported at a printing position at a minute interval from the paper conveyance surface of the conveyance belt 113. The recording head 114 includes head bars 114K, 114C, 114M, and 114Y that are similar to the head bar 406 of FIG. Each of the head bars 114K, 114C, 114M, and 114Y ejects black (K), cyan (C), magenta (M), and yellow (Y) ink with the following structure.

  On the nozzle surface 141 of the recording head 114, for each head bar 114K, 114C, 114M, 114Y, a large number of nozzles are formed in the paper width direction so as to be larger than the paper width (see FIG. 4). Each of these nozzles communicates with a pressurizing chamber (not shown) formed in the head bar corresponding to each nozzle, and each pressurizing chamber is further formed in each head bar 114K, 114C, 114M, 114Y. The ink chamber communicates with the ink chamber (not shown). The head bar 114K, 114C, 114M, and 114Y ink liquid chambers communicate with the ink tanks 112K, 112C, 112M, and 112Y through ink supply tubes (not shown).

  Further, a drying device 115 for drying ink ejected from the head bars 114K, 114C, 114M, 114Y to the recording medium P is disposed downstream of the recording head 114.

  FIG. 2 is a schematic configuration diagram relating to control of the inkjet recording apparatus 100 in the present embodiment.

  The ink jet recording apparatus 100 includes a CPU (Central Processing Unit) 201, a RAM (Random Access Memory) 202, a ROM (Read Onl4 Memory) 203, an HDD (Hard Disk Drive) 204, a conveyance belt 113, a paper feed roller 121, and the like for printing. A driver 205 corresponding to each drive unit is connected via an internal bus 206. The CPU 201 uses, for example, the RAM 202 as a work area, executes a program stored in the ROM 203, the HDD 204, and the like, and exchanges data and commands with the driver 205 based on the execution result, thereby allowing each of the drive units to Control the behavior. Further, each means (shown in FIG. 3) to be described later other than the above-described drive unit operates as each means when the CPU 201 executes the program.

  FIG. 3 is a software configuration diagram of the ink jet recording apparatus according to the present embodiment.

  As described above with reference to FIG. 4, the end nozzle group 408 outside the maximum width of the recording medium P is not used for printing. That is, although the end nozzle group 408 is always filled with ink, it is not used for printing, so the corresponding pressure element 504 is not driven at all during printing. For this reason, among all the nozzles of each of the head bars 114K, 114C, 114M, 114Y, an increase in viscosity that exceeds the specified value of ink is most likely to occur in the end nozzle group 408.

  Therefore, the ejection unit 301 drives the pressurizing element 504 corresponding to the end nozzle group 408 at a timing instructed by the user, for example, when the ink jet recording apparatus 100 is turned on. Ink 307 is discharged.

  On the other hand, a light emitting diode 304, which is a light emitting element, is disposed on the ink 307 ejection side of the end nozzle group 408, and irradiates the ink 307. In addition to the light emitting diode, a light bulb (ultra-small type) or the like can be used as the light emitting element. An imaging element 305 such as a CCD (Charge Coupled Device) is provided at a position facing the light emitting diode 304 and the ink 307, and a shadow caused by the irradiation of the ink 307 is observed.

  When this shadow is observed, the detection unit 302 determines that ink has actually been ejected from the end nozzle group 408. Then, when the ink ejection from the end nozzle group 408 is actually measured in this way, it is considered that the viscosity has not increased beyond the specified value of the ink, and therefore no special operation is performed.

  On the other hand, when the discharge means 301 is activated and the detection means 302 has not actually measured ink discharge from any of the nozzles in the end nozzle group 408, any of the nozzles in the end nozzle group 408 is not used. The increase in viscosity exceeds the specified value of the ink. Only in this case, the swinging means 303 swings (flushes) all the nozzles of the head bars 114K, 114C, 114M, 114Y.

  As described above, in the end nozzle group 408 where the viscosity increase more than the specified value of the ink is most likely to occur, the oscillation is performed by oscillating all the nozzles only when the increase in the viscosity exceeding the specified value of the ink is actually measured. It can be done only when it is necessary.

  The above-described embodiment is an example embodying the present invention, and is not intended to limit the technical scope of the present invention.

  Therefore, in the above-described embodiment, the head bar is configured by four corresponding to each color of black (K), cyan (C), magenta (M), and yellow (Y), but is not limited thereto. For example, the present invention can be applied to monochrome printing, that is, when there is only one head bar. Further, by providing a receiving tray 306 for catching the ink ejected by the activation of the ejection means 301 at the ink ejection destination of the end nozzle 408 group, it is possible to prevent the inside of the ink jet recording apparatus 100 from being stained.

  Furthermore, in the above-described embodiment, the ejection unit 301 is activated based on a user instruction, but may be activated at regular time intervals. Even if the ejection unit 301 is activated at a constant time interval, in the present invention, all the nozzles are oscillated only when the ejection of ink from any nozzle in the end nozzle group 408 is not actually measured. . Therefore, unlike the above-described background art, the oscillation is not performed at regular time intervals, and the life of the piezoelectric element 504 can be kept long.

  In the embodiment described above, as shown in FIG. 4C, the head bar includes the trapezoidal head unit 405, but the head unit is not limited to the trapezoid. As shown in FIG. 4 (b) and FIG. 4 (d), the present invention is applied to any ink jet recording apparatus in which the head bar is arranged beyond the width of the recording medium P and there is an end nozzle not used for printing. There is application of.

  Furthermore, all the nozzles in the end nozzle group 408 are caused to discharge ink from all the nozzles in the end nozzle group 408 by confirming the viscosity increase and solidification exceeding the specified value of the ink once, and either of them as described above. All nozzles may be swung when no ink is ejected from one nozzle, or all nozzles are swung when ink discharge from a specified number of nozzles is not observed. May be performed.

  In addition, when the individual nozzles in the end nozzle group 408 are used in order and ink is ejected in order at regular time intervals, and there is no ejection from any of the nozzles, the nozzles in the end nozzle group 408 All nozzles may be swung including the above. In this way, the amount of ink used for confirmation can be reduced, and it is possible to check at short time intervals, so environmental fluctuations, etc., compared to using all the nozzles of the end nozzle group 408, etc. It can respond by.

  The ink jet recording apparatus according to the present invention is useful as a printer, a copier, a multi-function machine, etc., by keeping ink pressurizing (flushing) in the nozzle only when it is necessary and keeping the life of the pressure element long. It is.

1 is an internal structure diagram of an embodiment of an ink jet recording apparatus of the present invention. FIG. 3 is a schematic configuration diagram relating to control of the ink jet recording apparatus of the present invention. FIG. 2 is a software configuration diagram of the inkjet recording apparatus according to the invention. The block diagram of a head unit and a head bar. Explanatory drawing of the operation principle of an inkjet recording device.

Explanation of symbols

100 Inkjet recording device
112 Ink tank
113 Conveyor belt
114 recording head
112K, 112C, 112M, 112Y Ink tank
114K, 114C, 114M, 114Y line head
141 Nozzle surface
201 CPU
202 RAM
203 ROM
301 Discharge means
302 Detection means
303 Swing means
304 light emitting diode
305 CCD image sensor
307 ink
402,405 head unit
403,406,407 head bar
408 End nozzle
501 Ink chamber
502 nozzles
503 pores
504 Pressure element

Claims (4)

In an inkjet recording apparatus provided with a head bar in which a head unit including a plurality of nozzles each ejecting ink includes a head bar arranged in a direction orthogonal to the conveyance direction of the recording medium,
Discharge means for discharging ink to the end nozzle group not used for printing on the head bar;
Detecting means for detecting ejection of ink from the end nozzle;
Oscillating means for oscillating ink in the nozzle when the detecting means does not detect the ejection;
An ink jet recording apparatus comprising: A light emitting element that emits light to the ink ejected by the ejection means, and an imaging element that observes the shadow of the ink,
The inkjet recording apparatus according to claim 1, wherein the detection unit detects ejection of ink from the end group nozzles based on the shadow. The inkjet recording apparatus according to claim 1, wherein the ejection unit ejects ink based on a user instruction. For each color type, the head bar, the ejection means, the swing means,
The inkjet recording apparatus according to claim 1, wherein the oscillation is controlled for each color type.

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