JPH01219520A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To enable the correction for making a head gap constant and to improve the printing accuracy by providing a control means which supplies a signal to a moving means so that the head gap is constant. CONSTITUTION:The control means for the head gap consists of a plate 12 where both ends of a guide shaft 4 are fixed and the upper end is supported, a plate drawing roller 13 arranged on the reference-position-HP side plate 12 on the side of a recording sheet 3, and a spring 14 which is positioned on the opposite side from the roller 13 interposing the plate 12 between them and has one end fixed and the other end connected to the lower end part of the external plate 12. Consequently, if the head gap varies owing to the thickness and swelling of a sheet 3, a sensor roll 19 moves and its movement quantity is detected in real time as the resistance value of a continuously variable resistance 17. The movement quantity of a recording head 6 is calculated by a control box 15 from the resistance value and information is supplied to a driving means which drives the roller 13 so that the head gap is constant.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an inkjet recording device.

[Prior Art] (Technical Background) In recent years, the use of OA has progressed more and more, and the amount of information processed by computers has become increasingly diverse.

Conventionally, a recording device such as a printer has been used to output the results of information processing by the computer as a hard copy.

The above-mentioned recording devices include those using various recording (printing) methods such as a wire tod type, a thermal transfer type, and an inkjet type.

Among the above-mentioned recording methods, the wire tod method generates a large amount of noise during the recording operation, so it is necessary to keep the approximate number of devices used in one office below a certain level.

Further, although the thermal transfer type is quiet, it has drawbacks such as slow recording speed and high running costs.

Compared to the wire tod type and thermal transfer type described above, the inkjet type has advantages such as high-speed printing, quiet operation, and low running costs.

(Latest Prior Art) By the way, as an inkjet recording apparatus, an apparatus having the configuration shown in FIG. 9 is conventionally known.

That is, in FIG. 9, the recording sheet 3 is conveyed by a paper feed roller 11 to sheet feed rollers 1.2 installed vertically at a predetermined interval, and is fed in the direction of arrow A.

Further, a carriage 5 that moves along a guide shaft 4.4 is provided on the front surface of the recording sheet 3. An inkjet recording head 6 (hereinafter simply referred to as a recording head 6) is mounted on the carriage 5. This recording head 6
has an ink chamber inside, and ink is supplied under pressure from an inkjet cartridge (not shown) mounted on the carriage 5 or a tank provided outside the carriage.

A nozzle is formed at the tip of the ink chamber toward the recording sheet 3, and ink droplets are ejected as a result of the vibration of an electro-mechanical conversion element provided in contact with the ink chamber.

A hot plate 7 is provided on the back side of the recording sheet 3 in order to improve the fixing (drying) properties of the ink droplets flying onto the surface of the recording sheet 3.

A plurality of ink ejection ports for forming dots are formed on the front surface of the recording head 6.

The carriage 5 is reciprocated by a carriage drive motor (not shown) via a belt transmission mechanism 9.

During recording, the width direction m of the sheet 3 of the carriage 5 is
Recording is performed while forming flying ink droplets from each ink ejection port of the recording head 6 toward the recording sheet 3 in synchronization with the motion. After recording is completed, the recording head 6 moves to a reference position HP outside the recording range. A pump suction type ink recovery device 10 is provided at the reference position HP, and the recovery device 1
0 eliminates clogging of ink ejection ports caused by dust, thickened ink adhesion, air bubbles, etc., and maintains image quality.

[Problems to be solved by the invention] However, in the above-mentioned conventional inkjet recording device,
In each of the following cases, (1) When the recording sheet absorbs water and swells under high temperature and high humidity conditions, (2) When the recording sheet swells due to heat for fixing ink, (3) When a difference in head gap occurs due to a difference in paper thickness, there is a problem in that the head gap fluctuates.

In the above cases, conventional inkjet recording apparatuses have had problems with printing.

FIG. 10 is a diagram showing the path of ink droplets flying onto a recording sheet in an inkjet recording apparatus. When the inkjet recording head 6 is moving in the B direction, ink droplets ejected at the PA position land on the recording sheet 3 at the PB position. This is because the flying ink droplets are the first
As shown in Figure 1, the velocity vector V in the direction of the recording sheet,
This is because the inkjet recording head flies in the direction of the composite speed vector C+e of the vector V and the speed vector v2 in the main scanning direction of the inkjet recording head in the perpendicular direction.

Therefore, if the head gap is not constant, the landing point position of the ejected ink will not be constant, making it difficult to expect further improvement in printing accuracy. Further, there was a problem that the amount of bulge was too large, causing the head and recording sheet to come into contact with each other.

To explain specifically, lV+l-5m/sea.

lv': 1-0, 6 m/sec, if the head gap changes by only 0.5 mm, the landing point position of the flying ink will change by 6 points in the main scanning direction of the inject recording head.
A change of 0 μm has occurred.

[Means for Solving the Problems] The gist of the present invention is to cause an inkjet recording head to main scan in the width direction of a recording sheet, and to print ink droplets from the inkjet recording head in accordance with recording information sent from the outside. In an inkjet recording apparatus that performs recording by ejecting the inkjet onto a sheet, a measuring means for measuring the distance from the inkjet recording head to the printing surface of the recording sheet, and an inkjet recording head and/or the recording sheet are attached to the recording sheet. On the other hand, it has a moving means for moving in the front-back direction, and a control means that reads a measured value of the head gap measured by the measuring means and gives a signal to the moving means so that the head gap becomes a constant value. An inkjet recording device characterized by:

[Function] With the above configuration, the present invention makes it possible to correct the head gap to a constant value in any case, and to significantly improve printing accuracy.

[Example] (First example) The present invention will be specifically described below with reference to the drawings.

FIG. 1 is a perspective view showing a recording apparatus according to a first embodiment, and FIG. 2 is a right side view of FIG. 1.

Note that explanations of parts common to the conventional example shown in FIG. 9 will be omitted.

In this embodiment, measurement of the head cap and its control are performed in parallel with recording.

FIG. 3 is a perspective view showing a mechanism for measuring the head gap. When the head gap changes due to the thickness or bulge of the sheet, the sensor roller 19 moves. That is, the head gap is converted into the amount of movement of the sensor roller 19, and this amount of movement is detected as the resistance value of the variable resistor 17 in real time and continuously. The amount of movement of the recording head is calculated and controlled by the control box 15 according to the resistance value.

The variable resistor 17 is connected to the control box 15, and the resistance value of the variable resistor 17 is input to the control box.

The control box 15 is connected to drive means (not shown) for driving the plate roller 13 shown in FIGS. That is, the control box 15 provides information to the driving means in response to the measured value from the variable resistor 17 so that the bed gap is constant.

In this example, as a means for controlling the helad gap, both ends of the guide shaft 4 are fixed, and a plate 1 whose upper end is supported is used.
2, a plate puller disposed on the recording sheet side of the plate 12 on the reference position HP side is a roller 13, and the roller 1
The spring 14 is located on the opposite side of the outer plate 12 across the roller 12, and has one end fixed and the other end connected to the lower end of the outer plate 12. Note that the roller 13 is continuous with the lower end of the plate 12. Therefore, when the roller 13 is driven, the plate 12 is attracted toward the recording sheet against the spring 14, and the head cap is controlled.

Note that the measurement and control of the head gap are continuously performed until the conveyance of the recording sheet is completed.

Furthermore, in this example, the recording head was moved by moving the plate 12 to adjust the head cap, but control can also be achieved by moving the sheet feed roller 1.degree. 2 back and forth.

(Second Embodiment) FIG. 4 is a sectional view of the measuring means for the helad cap of this embodiment.

In this embodiment, a detection rod 20 is used in place of the sensor roller 19, and the resistance value of the variable resistor 21 is measured by the rotational force of the moment. Accurate measurement is possible, and when selecting a variable resistor, even one with large sliding resistance can be used.

The other configurations and operations are the same as those of the previous embodiment.

(Third Example) In this example, the sensor roller 9 was made of a material with good absorbency. Examples of such materials include nonwoven fabrics.

The difference from the first embodiment is that in the first embodiment, the sensor roller 1
9, when the printed surface is rubbed and the printed surface is not completely fixed, ink droplets are transferred to the sensor roller 19, and then transferred again to the recording sheet, staining the recording sheet. Although problems may occur, in this example,
The sensor roller 22 is made of a material that has good ink absorption properties, and there is no possibility of retransfer.

Other configurations and operations are similar to those of the first embodiment.

(Fourth Embodiment) FIG. 5 is a sectional view of a helad gap measuring means of a fourth embodiment.

In this example, first, a substantially triangular sensor body 23 is used in place of the sensor roller of the first example. The sensor body 23 is pivotally supported at one vertex, and the other vertex is in contact with the recording sheet 3.

On the other hand, the variable resistor 24 in this example is of a rotary type, and its variable operating section 25 is pivotally supported, and the end of the variable operating section 25 is connected to the vicinity of the apex of the sensor body 23 via an appropriate member. It is.

In other words, the difference from the first embodiment is that in this embodiment, the amount of change θR in the resistance value of the variable resistor is amplified and can be detected with respect to the amount of bulge θd of the recording sheet.
), the head gap can be measured with higher sensitivity.

The other configurations and operations are the same as those of the previous embodiment.

(Fifth Example) FIG. 6 is a perspective view of an apparatus according to a fifth example, and FIG.
The figure is a right side view of the sixth device, and FIG. 8 is a view taken in one direction of FIG. 7.

The difference from the above four embodiments is that the plate 12 of the moving means in the above embodiment is pulled by a roller 1.
When attracted by 3, it moves forward and backward in an arc. Therefore, if the amount of movement is large, the vertical displacement of the recording head may become so large that it cannot be ignored.

However, in this embodiment, the arrangement is such that the carriage does not shift in the vertical direction when the head gap is adjusted. That is, the adjustment width of the head gap is transmitted to the binion 27 via the power transmission gear 28, and by moving the rack 26 forward and backward, the carriage stand 25 attached to the upper part of the rack 26 is moved forward and backward. The recording head 6 is mounted on the carriage stand 26, and the forward/backward mechanism of the carriage moving stand 25 serves as a moving means.

Note that the head gap measuring means may be any of the methods of the above four embodiments.

The other configurations and operations are the same as those of the previous embodiment.

[Effects of the Invention] As is clear from the above description, according to the present invention, the bed gap can be controlled to be constant, and (1) the accuracy of the recording position on the recording sheet is improved.

(2) The recording head comes into contact with the recording sheet, further reducing stains on the recording sheet.

(3) There is no need for surface-to-paper contact between the recording head and the ink ejection characteristics are improved.

An inkjet recording device capable of the above can be provided.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the ink jet recording apparatus of the first embodiment, and FIG. 2 □ is a side view thereof. FIG. 3 is a side view of the helad gap measuring means of the above device. Moreover, FIG. 4 is a side view of the head gap measuring means of the apparatus according to the second embodiment. FIG. 5 is a side view of the helad gap measuring means of the apparatus according to the fourth embodiment. Moreover, FIG. 6 is a perspective view of the apparatus according to the fifth embodiment, and FIG. 7 is a side view thereof. 8th
The figure is a view taken in one direction in FIG. 7. FIG. 9 is a perspective view showing a conventional example. FIG. 10 is a plan view showing the state of ink flying from the ink head to the recording paper.
Figure 1 is the vector diagram. 1... Sheet feed roller 1.2... Sheet feed roller 2.3... Recording sheet, 4... Guide shaft, 5...
・Carriage, 6... Recording head, 7... Hot plate, 9
...Belt transmission mechanism, 10...Ink recovery device, 1
1...Paper feed roller, 12...Plate, 13...
Plate puller is roller, 14-...spring, 15...
Control box, 16... Spring, 17-... Variable resistor 1
．． 19...sensor roller, 20...detection rod, 21...
・Variable resistance 2.23...Sensor body, 24...Variable resistance 3゜Figure 1Figure 2Figure 3Figure 7Figure 8Figure 9Figure 1QFigure 11

Claims (1)

[Claims] (1) In an inkjet recording apparatus that performs recording by main scanning an inkjet recording head in the width direction of a recording sheet and causing ink droplets to fly from the inkjet recording head to the recording sheet in accordance with recording information sent from the outside, a measuring means for measuring the distance from the inkjet recording head to the printing surface of the recording sheet (hereinafter this distance is referred to as head gap); and an inkjet recording head and/or the recording sheet in the front-rear direction with respect to the recording sheet. The apparatus is characterized by comprising a moving means for moving the head, and a control means for reading a measured value of the head gap measured by the measuring means and giving a signal to the moving means so that the head gap becomes a constant value. Inkjet recording device.