JPH04239648A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To enhance printing quality by preventing the relative reduction of a recording dot size to resolving power at the time of the advance of ink consumption or at the time of draft mode recording and the change of the recording dot size due to the kind of recording paper in an ink jet recording apparatus equipped with a liquid level height control mechanism controlling the height of the liquid level of the ink in an ink reservoir supplying ink to a recording head. CONSTITUTION:A liquid level height control mechanism 11 detecting the lowering of the liquid level of the ink in an ink reservoir 2 supplying ink to a recording head and controlling the height of said liquid level corresponding to the detection result is provided. By this mechanism, the jet amount of the ink from the recording head is controlled to make it possible to control the size of the dot recorded on a recording medium.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus equipped with a liquid level adjustment mechanism for adjusting the level of ink in an ink reservoir that supplies ink to a recording head.

0002

2. Description of the Related Art FIG. 6 is a side view showing the main structure of an ink jet recording apparatus. In the figure, 1 is a recording head, 2 is an ink reservoir, and 100 is recording paper.

The recording head 1 includes an ink passage 3, a plurality of nozzles 4 that communicate with the ink passage 3 and open to a nozzle surface 1a, and a plurality of ink jets that generate pressure in the ink passage corresponding to each nozzle 4. means (piezoelectric element, etc.) 5, and a nozzle surface 1a is provided on the recording paper 100 conveyed through the conveyance path.
are arranged to face each other at a predetermined distance.

The ink reservoir 2 is connected to the recording head 1 through an ink supply path 6, and the liquid level of the ink 7 stored therein is lower than that in the ink passage 3. This stored ink 7 is supplied to the ink passage 3 through the common ink passage 6 by capillary force.

During printing, the recording head 1 is moved in a direction perpendicular to the plane of the paper in FIG. 6, and the ink ejecting means 5 corresponding to a predetermined nozzle 4 is activated at a predetermined time. This results in
Pressure is generated in the ink passage 3 facing the ink ejecting means 5, and ink is ejected from the nozzle 4. The ejected ink adheres to the recording paper 100 in the form of dots to perform recording.

[0006] In an inkjet recording device having such a configuration and operation, the size of dots recorded on the recording paper changes due to a decrease in the amount of ink particles as ink is consumed, or resolution decreases during draft mode recording. Therefore, the dot diameter becomes relatively smaller than the optimum value. Further, the dot diameter changes depending on the type of recording medium used. Conventionally, this problem has been dealt with by adjusting the ink particle diameter by adjusting the driving conditions.

[0007]

However, the above-mentioned conventional system has the disadvantage that the drive circuit and its control become complicated and the cost increases.

[0008] The present invention provides an inkjet recording device that can improve printing quality by preventing a decrease in recording dot size during ink consumption and draft mode recording, or a change in recording dot size depending on the type of recording paper. is intended to provide.

[0009]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes a recording head that ejects ink to perform recording, and an ink reservoir that supplies ink to the recording head. In an inkjet recording device,
A configuration (first configuration) comprising a liquid level height adjusting means for detecting a drop in the liquid level of ink in the ink reservoir as the ink is consumed and adjusting the liquid level accordingly; do.

[0010] Furthermore, in an inkjet recording apparatus equipped with a recording head that ejects ink to perform recording, and an ink reservoir that supplies ink to the recording head,
A configuration (second configuration) includes a liquid level adjustment mechanism that adjusts the level of ink in the ink reservoir in accordance with the resolution of a recorded image.

Furthermore, in an inkjet recording apparatus that includes a recording head that ejects ink to perform recording, and an ink reservoir that supplies ink to the recording head, the ink reservoir may be adjusted depending on the type of recording paper. A configuration with a liquid level adjustment mechanism that adjusts the liquid level of the ink inside (
Third configuration).

0012

[Operation] In the present invention, the height of the ink level in the ink reservoir is adjusted depending on the drop in the ink level in the ink reservoir due to ink consumption, the resolution of the recorded image, or the type of recording paper. A liquid level adjustment mechanism is provided to adjust the liquid level. Therefore, it is possible to adjust the size of dots recorded on the recording paper by controlling the amount of ink ejected from the recording head, and it is possible to perform high-quality recording.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 5.

The present invention is based on the discovery that the size of ejected ink particles can be adjusted by adjusting the height of the ink liquid level in the ink reservoir, and this principle is applied. This principle was discovered as a result of various studies, and its contents are as follows.

As described above, the ink level in the ink reservoir is set to be lower than the nozzle position so that the ink does not flow out from the nozzles of the recording head.
Ink is supplied to the ink passage of the recording head by capillary force. Ink liquid level at the nozzle (meniscus)
The position of 7a is recessed toward the ink passage 3 as shown in FIG. is proportional to the size of Figure 4 (A) shows the case when the ink level is at the standard height, Figure 4 (B) shows the case when the ink level is lower than the standard height, and Figure 4 (C) shows the case when the ink level is higher than the standard height. As shown, as the position of the mechanical gas 7a recedes from the nozzle 4 toward the ink passage 3, the amount of ink ejected from the nozzle 4 due to the action of the ink ejecting means 5 decreases, and the diameter of the ink particles also becomes smaller.

This relationship is clear from FIG. 5, which shows the relationship between the height difference between the ink levels of the nozzle and the ink reservoir and the diameter of ejected ink particles.

A liquid level height adjustment mechanism 11 used in the present invention to which this principle is applied is shown in FIG. FIG. 1(A) is a front view, and FIG. 1(B) is a side view.

The liquid level height adjustment mechanism 11 is connected to the ink reservoir 2.
It is composed of a stage 12 on which the stage 12 is placed, and an elevating means 13 for elevating and lowering the stage 12. The elevating means 13 includes a pinion 14 supported by a fixed bearing (not shown) and a rack 16 that is fixed to an elevating plate 15 that is movable up and down and meshes with the pinion 14, and the stage 12 is moved up and down. It is fixed to the plate 15. 17 is a handle for rotating the pinion 14. The action of this liquid level height adjustment mechanism 11 is as follows.

The height of the ink liquid level in the ink reservoir 2 is:
This value is detected by a detection means (not shown), but if this value becomes lower than the standard height due to ink consumption, the handle 17 is rotated clockwise in FIG. Adjust the liquid level to the standard height. Also,
If the ink level is higher than the standard level, the handle 17 is rotated counterclockwise to adjust the ink level. Thereby, the ink level in the ink reservoir 2 can be maintained constant and stable quality can be ensured.

Although the above explanation deals with an example in which the ink level is adjusted manually, it is also possible to automatically adjust the ink level using a motor. This type of liquid level adjustment mechanism 21 includes a motor 22, a position sensor 23, and a control section 24, as shown in FIG. The other stage 12, pinion 14, and elevating plate 15 are the same as those shown in FIG. The motor 22 is connected to the pinion 14, the position sensor 23 is attached to the lifting plate 15, and the control unit 24
is connected to the motor 22 and position sensor 23.

In this case, the height of the ink liquid level can be detected by the position sensor 23. Information regarding the height of the ink liquid level is input to the control unit 23, and upon receiving a signal from the position sensor 23, the motor 22 is rotated to automatically adjust the height of the stage 12, that is, the height of the ink liquid level. . The information input to the control unit 24 is to keep the ink level at a constant level, or to receive a signal from a switch on the control panel indicating that it is in draft mode.
It raises the ink liquid level to a predetermined height, or there is a recording paper selection key provided on the control panel, etc. (for selecting recording paper, recording paper that spreads ink particles easily, recording paper that does not spread easily, etc.) switch),
It raises and lowers the ink level. The liquid level adjustment in the draft mode and the liquid level adjustment depending on the type of recording paper are as follows.

First, liquid level adjustment in the draft mode will be explained. In the recording apparatus, thinning recording is performed in order to increase the printing speed. For example, resolution 360d
In a recording device that outputs A4 paper in 1 minute at pi, if you record at 180 dpi in draft mode, the time required for output will be halved to 30 seconds, and the printing speed can be doubled. However, since the dots to be recorded are thinned out, white spots may appear in the print, resulting in a decrease in print quality. To prevent this, as the resolution decreases,
It is necessary to increase the amount of ink to be ejected to increase the size of the dots. Therefore, by increasing the liquid level of the ink in the ink reservoir, the amount of ink ejected can be increased to prevent the print quality from deteriorating.

Also, to explain liquid level adjustment depending on the type of recording paper, ink particles ejected from the head adhere and become fixed on the surface of a recording medium such as recording paper. During this fixing process, the ink particles spread on the recording medium by evaporation or penetration into the recording medium, forming dots. The spread of the ink particles, that is, the dot diameter, varies depending on the characteristics of the recording medium used. When using ink with a certain composition,
The types of recording paper and the spread of ink (dot diameter/ink particle diameter) are as follows. Recording paper type Xerox 4024; dot diameter 155μ
mRecording paper type Spicabond; Dot diameter 165μmRecording paper type PPC paper;
Dot diameter: 180 μm However, ink particle diameter: 77 μm Therefore, by adjusting the height of the ink level in the ink reservoir depending on the type of recording medium used, uniform printing quality can be obtained for various recording media.

An example of application of the liquid level height adjustment mechanism shown in FIG. 2 is shown in FIG. The liquid level height adjustment mechanism 31 of this example uses an ink passage pressure sensor 32 instead of a position sensor as a means for detecting the ink level height in the ink reservoir.
33 is a control section.

The ink passage pressure sensor 32 is provided in the ink passage (not shown), and its output signal is sent to the control unit 33.
is input. When the ink level in the ink reservoir decreases, the height difference between the nozzle and the nozzle increases, and the pressure within the ink passage decreases. Therefore, by measuring the pressure inside the ink passage with the ink passage pressure sensor 32, the height of the ink liquid level can be detected. The control unit 33 calculates the level of ink in the ink reservoir based on the magnitude of this signal, and operates the motor 22 in a predetermined direction for a predetermined time to move the stage 12.
automatically adjust the height.

The control unit 33 also maintains the ink level at a constant level, or receives a signal from a switch on the control panel indicating that the ink level is in the draft mode and raises the ink level to a predetermined level. or in response to the output of the recording paper selection key (switch for selecting the type of recording paper, recording paper that spreads ink particles easily, recording paper that does not spread easily, etc.) provided on the control panel, etc. Information for raising and lowering the liquid level is input. Note that a means for detecting the pressure inside the ink passage with a pressure sensor and detecting the liquid level position of the ink in the ink reservoir based on the measured value is disclosed in, for example, Japanese Patent Application No. 2-188 filed by the present applicant.
No. 124 "Ink Remaining Amount Detection Device".

[0027]

As described above, according to the present invention, the size of dots recorded on a recording medium can be adjusted by controlling the amount of ink ejected by adjusting the liquid level of the ink in the ink reservoir. Therefore, high-quality recording can be performed.

[Brief explanation of the drawing]

FIG. 1 is a structural explanatory diagram of a liquid level height adjustment mechanism according to an embodiment of the present invention, with FIG. 1(A) being a front view and FIG. 1(B) being a side view.

FIG. 2 is a side view showing another example of the liquid level height adjustment mechanism according to the embodiment of the present invention.

FIG. 3 is a side view showing an application example of FIG. 2;

FIG. 4 is an explanatory diagram of the ink droplet jetting mechanism of the embodiment of the present invention, in which FIG. 4(A) shows when the ink liquid level is at the standard height, and FIG. 4(B) shows when the ink liquid level is lower than the standard height. , Figure 4 (
C) shows when the ink liquid level is higher than the standard height.

FIG. 5 is an explanatory diagram of the relationship between ink particle diameter and ink liquid level height difference in an example of the present invention.

FIG. 6 is a side view showing the main structure of the inkjet recording device.

[Explanation of symbols]

1 Recording head 2 Ink reservoir 3 Ink passage 4 Nozzles 11, 21, 31 Liquid level height adjustment mechanism 23
Position sensor 32 Ink passage pressure sensor

Claims (3)

[Claims] 1. In an inkjet recording apparatus comprising a recording head that ejects ink to perform recording, and an ink reservoir that supplies ink to the recording head, the ink in the ink reservoir decreases as the ink is consumed. An inkjet recording apparatus comprising a liquid level height adjustment mechanism that adjusts the height of the liquid level in response to a drop in the liquid level. 2. In an inkjet recording apparatus comprising a recording head that ejects ink to perform recording, and an ink reservoir that supplies ink to the recording head, the ink reservoir An inkjet recording device characterized by being provided with a liquid level adjustment mechanism for adjusting the liquid level of ink within the inkjet recording device. 3. In an inkjet recording apparatus comprising a recording head that ejects ink to perform recording, and an ink reservoir that supplies ink to the recording head, the ink reservoir An inkjet recording device characterized by being provided with a liquid level adjustment mechanism for adjusting the liquid level of ink within the inkjet recording device.