JPH03295662A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To stabilize ink supply by providing ink supply pressure varying means for varying pressure of ink to be supplied to a recording head with respect to a supply system and an ink tank. CONSTITUTION:When recording is started, the temperature of a recording head 1 is detected by temperature detecting means 2A - 2D, and whether a detected temperature TH exceeds a set temperature or not is judged. If it is judged that the detected temperature exceeds the set temperature, a tank base supporting leg 25A is ridden on a cam roller 25 through driving means in response to a signal for reducing a positional difference (h) to enhance the position of an ink tank 13. Then, again whether the temperature TH by the means 2A - 2D is the set temperature or lower or not is judged. If it is judged to be the set temperature or lower, a signal for raising the difference (h) is output to lower the position of the tank 13, and the steps are repeated. Thus, when an ink discharge amount during a recording is increased, it can prevent an unstable discharging operation due to insufficient ink supply.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording apparatus, and more particularly to an inkjet recording apparatus in which ink is supplied from an ink tank to an inkjet recording head via a tube.

[Conventional technology]

2. Description of the Related Art Inkjet recording apparatuses have been known that perform recording by ejecting ink from a recording head toward a recording material. This type of inkjet recording device is a non-impact type recording device with features such as low noise and the ability to easily record color images using multi-colored ink, and has rapidly become popular in recent years. It is becoming popular. However, inkjet recording devices perform printing by ejecting ink directly from fine ejection orifices of the printhead, and therefore require special considerations not found in other printing methods.For example, near the ejection orifices of the printhead A concave surface called a meniscus is formed in the ink liquid due to surface tension, and this meniscus changes depending on the ink supply pressure, which greatly affects the operation when ejecting the ink.

Therefore, in order to obtain stable prints and images, it is necessary to adjust the ink supply pressure so that the amount of ink supplied to the recording head is always appropriate. Especially in the case of the bubble jet method, which uses heat as ejection energy, the amount of ink consumed changes depending on the temperature of the print head during printing.For example, if the temperature rises, the ink viscosity decreases and the amount of ink ejected increases. Therefore, it is necessary to increase the ink supply amount. However, in the conventional case, for example,
It has been considered to adjust the ink supply pressure according to the temperature of the ink, as disclosed in Japanese Patent No. 8-219068.

[Problem to be solved by the invention]

However, in the conventional example described above, when high-density printing is performed, the temperature of the print head rises rapidly, which increases the amount of ink ejection consumed, resulting in a shortage of ink supply and unstable ejection. there were.

SUMMARY OF THE INVENTION An object of the present invention is to focus on the above-mentioned conventional problems, and to solve the problems, it is an object of the present invention to provide an inkjet recording apparatus that can always provide a stable amount of ink supplied to a recording head.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a recording head with a plurality of ink ejection ports, supplies ink from an ink tank to the recording head via a supply system, and supplies the ink to the recording head through a supply system. In an inkjet recording apparatus that performs recording by discharging the ink from an ink discharge port, an ink supply pressure changing means for varying the pressure of ink supplied to the recording head is provided in association with the supply system and/or the ink tank. It is characterized by:

[For production]

According to the present invention, when the amount of ink ejected increases during a printing operation, the pressure of the ink supplied to the print head is changed by the ink supply pressure changing means, and the ink is adjusted to the amount corresponding to the increased amount of ink ejected to the print head. Therefore, recording defects due to insufficient ejection amount can be prevented.

〔Example〕

Embodiments of the present invention will be described in detail and specifically below based on the drawings.

FIG. 1 shows an example of a bubble jet recording apparatus to which the present invention is applied. This example is for a multicolor recording device, where:
Reference numeral 1 denotes a print head unit consisting of a plurality of print heads IA to ID as shown in FIG. 2, and each of the print heads IA to ID ejects ink of a different color. Furthermore, electrothermal transducers (not shown) to which an applied voltage is supplied in order to generate thermal energy for ejecting ink are arranged along the liquid paths of each of the recording heads IA to ID. 2A to 2D are temperature detection means attached to each recording head IA-10, such as temperature sensors such as a thermistor, thermocouple, or varistor;
are the heaters attached to each.

The temperatures detected by these temperature detection means 2A to 2D are supplied to a temperature control device 21, and the heaters 20A to 200 are turned on and off so as to maintain a predetermined set temperature.

3 is a carriage on which the recording head unit 1 is mounted and moves along a guide rail 4; 5 is a timing belt for moving the carriage 4; and 6 is a carriage drive motor. Further, the recording sheet 7 is held at the recording position by a sheet feed roller 9 driven by a sheet feed motor 8 and a holding roller pair 10 that cooperates with the roller 9, -
Each time recording of a line is completed, the sheet is fed in the direction of the arrow. 11 is a supply tube that supplies ink to the recording head IA-10, 12 is a tube that returns ink from the recording head IA-10 to the tank 13, and 14 is a tube that supplies ink to the recording head IA-10 when the carriage 4 is guided to the home position H. This is a non-discharge recovery device for a plurality of recording heads that faces the unit 1 and performs an ink pressurizing operation to be described later on each of the recording heads IA to ID.

Next, the ink supply system and circulation system according to the present invention will be explained with reference to FIG. Here, the ink supply system is such that during normal recording, ink is supplied from the ink tank 13 to the recording heads IA to ID through the supply pipe 11, and is returned from the recording head to the ink tank 13 via the return pipe 12. It is constructed as a closed type, and the ink in the head is maintained at a negative pressure due to the height difference between the ejection opening 22 and the position of the ink liquid level 13A in the head. Therefore, the higher the position difference is, the more the ink supply amount can be reduced.Conversely, if the position difference is lowered and, for example, h=O, the ink supply pressure will be eliminated except for the pipe resistance, and the ink supply amount will be increased. can be done.

Therefore, when the ink in the head LA-10 is normally maintained at negative pressure and high-density recording is to be performed, it is necessary to bring the positional difference as close to zero as possible from the negative pressure side. , it becomes possible to increase the amount of ink supplied, and there is no possibility of non-ejection due to insufficient supply. In this case, the ink liquid level height 13A is the supply path 11.
The position may be such that the ink inside is maintained at atmospheric pressure.

Furthermore, in FIG. 3, 23 is a waste ink tank for storing ink discharged into the recovery device 14, and 24 is an ink cartridge for replenishing the ink tank 13 with ink. Further, in this example, a tank stand 25 is provided at the bottom of the ink tank 13 to receive it, and the cam roller 2
6 is moved in the direction of the arrow by a drive means (not shown) in response to a command from the control circuit 27, and the support leg 25A of the tank stand 25 is moved onto the cam roller 26 from the state of (A) to the state of (B). Raise the ink tank 13 to the tank stand 25
It is possible to lift it up and reduce the positional difference.

Therefore, the control operation in the inkjet recording apparatus configured as described above will be explained with reference to FIG. 4. First, when recording is started in step Sl, the temperature of the recording head 1 is detected by the temperature detection means 2A to 2D in step S2. ,
In step S3, it is determined whether the detected temperature TH exceeds the set temperature. Note that the set temperature here refers to the limit temperature at which the ink supply starts to become insufficient when performing high-density recording, and if it is determined in step S3 that the detected temperature exceeds the set temperature, the process proceeds to step S4. In step S5, the tank stand support leg 25 is moved onto the cam roller 26 via a driving means (not shown) in response to a signal to advance and reduce the position difference.
Move A onto the vehicle to raise the position of the ink tank 13.

(The amount of ink supplied can be increased by reducing the ink negative pressure, so insufficient ejection can be prevented. Then, in step S6, the temperature TH detected by the temperature detection means 2A to 2D is checked again. Determine whether the temperature has fallen below the set temperature.

If it is determined that the temperature has fallen below the set temperature, the process proceeds to step S7, where a signal is issued to increase the position difference, and step S
Lower the position of the ink tank 13 in step 8 and repeat the steps from step 82 onward. As a specific example, the ejection port density is 400 dpi.
, When all ejection is performed at a frequency of 2.5 KHz using a bubble jet recording head having 128 ejection ports,
By changing the positional difference from 10 cm to 2 cm, the recording head IA-10 could be kept below the set temperature as described above, and stable ejection could be continued.

In the embodiment described above, by moving the ink tank 13 up and down, the ink negative pressure inside the head is changed based on the position difference, and the amount of ink supplied to the recording head IA-ID is increased or decreased. Instead, for example, as shown in FIG. 3, a supply pump 30 is provided in connection with the supply pipe 11, and this pump 30 applies a minute pressure to the ink in the supply pipe 11 to supply ink. The amount may be controlled depending on the head temperature.

Furthermore, although not shown, for example, the diameter of the ink supply pipe can be expanded by forming the ink supply pipe 11 from shape memory resin or by providing a throttle valve as the temperature of the ink increases as the temperature of the recording head 1 rises. It is also possible to increase the amount of ink supplied by doing so. Note that when the ink supply tube 11 is formed of a shape-memory resin, it is desirable to treat the inner surface of the tube with Teflon, for example, in consideration of its wettability with ink.

(Others) The present invention brings about excellent effects particularly in a bubble jet type recording head and recording apparatus among inkjet recording types.

This is because such a system can achieve higher recording density and higher definition.

As for typical configurations and principles thereof, it is preferable to use the basic principles disclosed in, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740,796. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, it is necessary to arrange the liquid (ink) in accordance with the sheet and liquid path that hold it. The electrothermal converter that is
Generating thermal energy in the electrothermal transducer and producing film boiling on the thermally active surface of the recording head by applying at least one drive signal that corresponds to recorded information and provides a rapid temperature rise above nucleate boiling. As a result, bubbles in the liquid (ink) can be formed in a one-to-one correspondence with this drive signal, which is effective. The growth and contraction of this bubble causes the liquid (ink) to be ejected through the ejection opening to form a small droplet (at least one droplet).If this drive signal is in the form of a pulse, the growth and contraction of the bubble will occur immediately and appropriately. Because you will be exposed to
Particularly responsive liquid (ink) ejection can be achieved,
More preferable pulse-shaped drive signals include those described in U.S. Pat. Nos. 4,463,359 and 4,345,262.
Those described in the specification are suitable. Furthermore, if the conditions described in US Pat. No. 4,313,124 concerning the invention regarding the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be performed.

The configuration of the recording head includes, in addition to the combination configuration of ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, a heat acting section. The present invention also includes configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose configurations in which the wafer is placed in a bending region. In addition, Japanese Patent Application Laid-Open No. 1989-5 discloses a configuration in which a common slit is used as a discharge part of a plurality of electrothermal converters.
No. 9-123670 and Japanese Patent Application Laid-Open No. 59/1989 which discloses a configuration in which a discharge portion is made to correspond to an opening that absorbs pressure waves of thermal energy.
The effects of the present invention are also effective even if the structure is based on the publication No.-138461. In other words, regardless of the form of the printhead, printing can be performed reliably and efficiently.

Furthermore, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium that can be recorded by a recording apparatus.

Such a recording head may have either a configuration in which the length is satisfied by a combination of a plurality of recording heads, or a configuration as a single recording head formed integrally. In addition, even the serial type shown above can be installed on the main body of the device, allowing for electrical connection to the main body of the device and supply of ink from the main body of the device.Replaceable chip type recording heads. Alternatively, the present invention is also effective when using a cartridge type recording head that is integrally provided with the recording head itself.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc., which are provided as a configuration of the recording apparatus, to the present invention, because the effects of the present invention can be further stabilized. Specifically, these include capping means for the recording head, cleaning means, pressure or suction means, preheating means using an electrothermal transducer or another heating element, or a combination thereof; It is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order to perform stable printing.

In addition, regarding the type and number of recording heads installed, for example, in addition to one type that corresponds to single-color ink, there is also a plurality of recording heads that correspond to multiple inks with different recording colors and densities. It may be something that can be done.

In addition, the inkjet recording apparatus of the present invention can be used as an image output terminal for information processing equipment such as a computer, or as a copying apparatus combined with a reader or the like, or as a facsimile apparatus having a transmitting and receiving function. It may also be one that takes

〔Effect of the invention〕

As described above, according to the present invention, a means for changing the pressure of ink supplied to the recording head is provided in connection with the supply system and/or the ink tank, so that when the amount of ink discharged during recording increases. Furthermore, it is now possible to prevent unstable ejection operations due to insufficient ink supply.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a bubble jet recording device to which the present invention is applied. FIG. 2 is a configuration diagram of a recording head temperature control device according to the present invention. FIG. 3 is an ink supply system and circulation system according to the present invention. and a block diagram of the recovery system. FIG. 4 is a flowchart of the ink supply amount control operation according to the present invention. DESCRIPTION OF SYMBOLS 1... Recording head unit, IA-ID... Recording head, 28-2D... Temperature detection means, 3... Carriage 11... Ink supply pipe, 12... Return pipe, 13 ... Ink tank, 13A ... Ink liquid level, 14 ... Recovery device, 21 ... Temperature control device, 25 ... Tank stand, 25A ... Support leg, 26 ... Cam roller, 27 ...Control circuit.

Claims (1)

[Claims] 1) A recording head is provided with a plurality of ink ejection ports, ink is supplied from an ink tank to the print head via a supply system, and recording is performed by ejecting the ink from the ink ejection ports. An inkjet recording apparatus, characterized in that an ink supply pressure changing means for changing the pressure of ink supplied to the recording head is provided in association with the supply system and/or the ink tank. 2) The ink jet recording apparatus according to claim 1, wherein the ink supply pressure changing means is a means for changing the relative height of the liquid level in the ink tank with respect to the ink ejection opening. 3) The inkjet recording apparatus according to claim 1, wherein the ink tank supply pressure changing means is provided in the supply system. 4) The ink jet recording apparatus according to claim 1, wherein the ink supply pressure changing means is driven when the temperature of the recording head reaches a predetermined temperature or higher. 5) The recording head has an electrothermal conversion element that generates thermal energy that is used as ejection energy for ejecting the ink from the ink ejection opening. The inkjet recording device described in .