JP2000062150A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent recording quality from lowering upon occurrence of paper crease by adjusting the head drive timing depending on the distance between a recording head and a recording sheet. SOLUTION: A reference signal is a head drive timing signal being outputted at a period dependent on the scanning speed of a carriage and the recording density. Head drive delay time is set at 0 when a recording sheet is at a highest position, and a driving waveform (a) is generated at same timing as the reference signal and when the recording sheet is located lower than the highest position, a driving waveform (b) is generated with a time lag for canceling positional variation of the recording sheet behind the reference signal. With such an adjustment, a constant relation is sustained between the reference signal and the position where an ink drop ejected from a recording head adheres to the recording sheet and since the adhering position is not shifted even if the recording sheet creases or the distance between the recording head and the recording sheet is varied, high quality image recording can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus using an on-demand type ink jet recording head.

[0002]

2. Description of the Related Art An on-demand type ink jet recording head is provided with a plurality of nozzle openings and pressure generating chambers communicating with the nozzle openings, and the pressure generating chambers are expanded and contracted in response to a print signal to generate ink drops. Is configured to occur.

In a recording apparatus using this ink jet recording head, improvements such as increasing the number of nozzle openings and increasing the scanning speed of the recording head are generally performed in order to improve the recording speed. . In addition, the recording density is also improved to improve the recording image quality,
Due to the improvement of the recording speed and the recording density, the amount of ink droplets recorded on a certain area per unit time increases, and depending on the type of recording paper, wrinkles may occur on the recording paper due to the water content of the ink droplets. When wrinkles occur on the recording paper, the distance between the recording paper and the recording head changes, and the time it takes for the ink droplets to adhere to the recording paper changes. Unlike the case, there is a phenomenon that the recording image quality is deteriorated due to the deviation.

Therefore, by dividing the area that can be printed by one scan into a plurality of scans and printing over a long time, or by limiting the printing density and reducing the amount of ink droplets on the printing paper. Although it is possible to suppress the generation of wrinkles, it is unavoidable that the recording speed and the recording image quality are deteriorated.

Further, as a method for preventing deterioration of the recording image quality even if paper wrinkles occur, as shown in, for example, Japanese Patent Laid-Open No. 122967/1990, the distance between the recording head and the recording paper is measured by a non-contact sensor, and recording is performed. There has been proposed a method of adjusting the height of the recording head so that the distance between the head and the recording sheet is constant.

[0006]

However, as the recording speed is improved, it is necessary to keep the distance between the recording head and the recording paper mechanically constant in the case of a short period such as paper wrinkling due to recording. It becomes difficult to do so, and the recording image quality deteriorates.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an ink jet recording apparatus capable of preventing the deterioration of the recording image quality when a paper wrinkle occurs due to recording. That is.

[0008]

An ink jet recording apparatus according to claim 1, wherein a recording head capable of ejecting ink droplets, a mechanism for moving the ink jet recording head in a main scanning direction with respect to a recording paper, and a recording paper. And a mechanism for detecting the distance between the recording head and the recording paper, and the head drive timing is adjusted according to the distance between the recording head and the recording paper. .

According to the above arrangement, even if the distance between the recording head and the recording sheet changes during recording due to paper wrinkles, the position of ink droplets on the recording sheet does not change and the deterioration of recording image quality is prevented. Have an effect.

An ink jet recording apparatus according to a second aspect of the invention is characterized in that a sensor for detecting the distance between the recording head and the recording paper detects from the recording surface of the recording paper or the back surface of the recording surface.

An ink jet recording apparatus according to a third aspect of the invention is characterized in that the recording method is changed when a paper wrinkle due to recording of the recording paper is detected.

According to the above construction, there is an effect of suppressing the generation of paper wrinkles due to recording.

An ink jet recording apparatus according to a fourth aspect is characterized in that when a paper wrinkle due to recording on the recording paper is detected, the distance between the recording head and the recording paper is increased.

According to the above construction, even if paper wrinkles occur on the recording paper, the recording head does not rub against the recording paper, and the distance between the recording head and the recording paper can be set small.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a structure around a printing mechanism of an embodiment of a printer of the present invention. In the drawing, reference numeral 1 is a carriage for main scanning, with a timing belt 2 interposed. Is connected to the pulse motor 3 and is configured to be guided by the guide member 4 to reciprocate in the paper width direction of the recording paper 5.

A recording head 6 to be described later is attached to the surface of the carriage 1 that faces the recording paper 5, that is, the lower surface in this embodiment. The recording head 6 receives ink replenishment from an ink cartridge 7 mounted on the upper portion of the carriage 1, ejects ink droplets onto the recording paper 5 in accordance with the movement of the carriage 1, forms dots, and forms the recording paper 5 Print images and characters on.

Reference numeral 33a is a distance sensor attached to the side surface of the carriage 1, and detects the gap between the recording head 6 and the recording paper 5 by measuring the distance to the recording paper 5. A distance sensor 33b similar to the distance sensor 33a (not shown) is attached to the side surface of the carriage 1 facing the distance sensor 33a to detect the distance between the recording paper 5 and the recording head 6.

In the distance sensor 33a, the carriage 1 is in the direction A.
When the carriage 1 moves in the direction B, the distance sensor 33b detects the distance between the recording head 6 and the recording sheet 5 when the carriage 1 moves to 1. There is.

Reference numeral 8 denotes a capping device, which is provided in the non-printing area and seals the nozzle opening of the recording head 6 during the pause of printing, while ink drops from the recording head 6 due to the flushing operation performed during the printing operation. To receive.

A cleaning means 9 is provided in the vicinity of the capping device 8 and is configured to wipe the surface of the nozzle plate of the recording head 6 with a blade or the like to wipe off the ink residue and paper dust on the surface of the nozzle plate. .

A pulse motor 10 for sub-scanning conveys the recording paper 5 in accordance with the operation of the carriage 1 via a reduction gear (not shown).

FIG. 2 shows an embodiment of a control device for controlling the above-mentioned ink jet recording apparatus.
Reference numeral 0 denotes a control unit that receives a print command signal and print data from the host and an output from the distance sensor 33, and receives a buffer memory 31, a timing adjustment circuit 32, a head drive circuit 41, a carriage drive circuit 42, and a paper, which will be described later. The conveyance drive circuit 43 is controlled to execute the printing operation.

The buffer memory 31 is a memory for temporarily storing print data from the host, and outputs the print data stored by the print timing signal to the head drive circuit 41.

The timing adjusting circuit 32 is a distance sensor 33.
It is a circuit that delays a timing pulse to a drive circuit 41 that drives the recording head 6 according to the output voltages of a and b.

The drive circuit 41 is configured to selectively apply a drive voltage to the piezoelectric vibrator 21 that drives the nozzles of the recording head 6 that eject ink droplets in accordance with recording data.

FIG. 3 is a diagram showing details of the distance sensors 33a and 33b of the above-mentioned ink jet recording apparatus, and FIG. 4 is a circuit diagram of the distance sensors 33a and 33b. Reference numeral 331 is a light emitting diode whose emission wavelength is in the infrared region, and emits light toward the recording paper 5. Reference numeral 332 is a phototransistor, and when infrared light reflected by the recording paper 5 enters, a current flows and a voltage is generated at the sensor output V.

The position of the recording sheet 5 is physically regulated so as to be contained between the lowest position D and the highest position U.

FIG. 5 is a graph showing the relationship between the distance d between the recording head 6 and the recording paper 5 and the sensor output V of the distance sensors 33a and 33b.

The sensor output V is the recording paper 5 and the distance sensor 3.
When the distance d from 3a and 3b is small, the voltage is high, and as the distance d increases, the voltage decreases, but at some point the voltage becomes the minimum, and thereafter the voltage rises again. Therefore, the distance between the recording paper 5 and the distance sensors 33a and 33b is set so as to exclude the position where the sensor output V is the lowest.

When paper wrinkles occur due to recording, the sensor output V periodically fluctuates as the carriage 1 scans. In order to perform printing with as few paper wrinkles as possible, when this variation is detected, the control unit 30 prints by scanning in either one direction when the previous printing method was to scan the carriage 1 in both directions. Switch to. Next, if a paper wrinkle is detected during printing by the carriage 1 scanning in one direction, the scanning speed of the carriage 1 is reduced to perform printing. That is, paper wrinkles are prevented by reducing the amount of ink droplets attached to the recording paper 5 per unit time.

FIG. 6 is a diagram showing the relationship between the distance d between the recording head 6 and the recording paper 5 detected by the distance sensors 33a and 33b and the head drive timing delay time t.

Regarding the head drive timing delay time t, the head drive timing delay time t is set to 0 when the recording sheet 5 is at the highest position, that is, closest to the recording head 6. When the recording paper 5 is below the highest position, the head drive timing delay time t becomes a value obtained by dividing the difference between the position of the recording paper 5 and the highest position by the flight speed of the ink droplet, and the recording paper 5 is the lowest. Almost straight to the position.

FIG. 7 is a diagram showing a head drive timing adjusting method, and the reference signal is a head drive timing signal output in a cycle determined by the scanning speed and recording density of the carriage. When the recording paper 5 is at the above-mentioned highest position, the head drive delay time is set to 0 and the head drive circuit 41 generates the waveform indicated by the drive waveform (a) at the same timing as the reference signal. When the recording paper 5 is below the highest position, the head drive circuit 41 is driven at the timing when the delay time for canceling the change in the position of the recording paper 5 is canceled in the reference signal.
Drive waveform (b) is generated. By adjusting as described above, the relationship between the reference signal and the position where the ink droplets ejected from the recording head 6 are attached to the recording paper 5 is kept constant.

FIG. 8 is a diagram showing a control block of another embodiment of the present invention. In the figure, reference numeral 44 denotes a carriage height adjusting drive circuit for driving the carriage height adjusting motor 11, which measures the distance between the recording head 6 and the recording paper 5 by the distance sensors 33a and 33b, and the recording head is generated by the occurrence of paper wrinkles due to recording. When the distance between the recording sheet 5 and the recording sheet 5 becomes smaller than the set limit value, the recording head 6 may rub against the recording sheet 5, and therefore the control unit 30 controls the carriage height adjustment drive circuit 44. A signal is output and the carriage height adjusting motor 11 is driven to control the distance between the recording head 6 and the recording paper 5 to be separated. These controls are performed for each main scan so that the distance between the recording head 6 and the recording paper 5 is within a range where there is no problem. In addition to these controls, the drive timing of the recording head 6 is adjusted at each ink droplet ejection timing.

[0035]

As described above, the distance between the recording head and the recording paper is detected by the light reflection type sensor, and the drive timing of the recording head is adjusted according to the distance, so that the recording paper is printed. Even if the distance between the recording head and the recording paper changes due to the occurrence of blistering, there is an effect that high-quality image recording can be performed without shifting the ink droplet adhesion position on the recording paper. In addition, even if the paper thickness of the recording paper is different, there is an effect that the displacement of the ink droplet attachment position does not occur.

Furthermore, since the distance between the recording head and the recording paper can be made as short as possible, there is an effect that the influence of the flight conditions of the ink droplets of the recording head can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an inkjet recording apparatus to which the present invention is applied.

FIG. 2 is a block diagram of an apparatus showing an embodiment of the present invention.

FIG. 3 is a diagram showing a sensor for detecting a distance between a recording head and recording paper according to the present invention.

FIG. 4 is a diagram showing a circuit of a sensor for detecting a distance between a recording head and a recording sheet of the present invention.

FIG. 5 is a diagram showing a relationship between a distance between a recording head and a recording sheet of the present invention and a sensor output voltage.

FIG. 6 is a diagram showing a relationship between a distance between a recording head and a recording sheet of the present invention and head drive timing adjustment time.

FIG. 7 is a diagram showing a method for adjusting head drive timing according to the present invention.

FIG. 8 is a block diagram of an apparatus showing another embodiment of the present invention.

[Explanation of symbols]

5 recording paper 6 recording head 8 capping device 9 Cleaning device 21 Piezoelectric vibrator 33a, b Distance sensor

Claims (4)

[Claims] 1. A recording head having a nozzle plate provided with a plurality of nozzle openings and a pressure generating chamber formed by a vibrating plate that is deformed by expansion and contraction of a piezoelectric vibrator, capable of ejecting ink droplets, and the recording head. An inkjet recording apparatus comprising a mechanism for moving a recording sheet in a main scanning direction with respect to a recording sheet, and a mechanism for moving the recording sheet in a sub-scanning direction different from the main scanning direction. A mechanism is provided that includes a distance sensor that moves to measure the distance between the recording head and the recording paper, and that adjusts the timing of driving the piezoelectric vibrator of the recording head according to the distance between the recording head and the recording paper. An inkjet recording apparatus comprising: 2. The distance sensor applies an infrared light source to the recording surface of the recording paper or the back surface of the recording surface, detects the reflected light with a photo sensor, and measures the distance between the recording head and the recording paper. The ink jet recording apparatus according to claim 1, wherein 3. The method according to claim 1, wherein when a wrinkle of the recording paper is detected during recording on the recording paper by the recording head, the recording method on the recording paper is changed. Inkjet recording device. 4. The method according to claim 1, wherein a distance between the recording head and the recording paper is increased when a paper wrinkle of the recording paper is detected during recording on the recording paper by the recording head. 2. The inkjet recording device according to 2.