JPH11348373A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regulate a gap without sacrifice of image quality by disposing a gap regulating member displaceably at a position facing a recording head through a sheet carrying path and providing means for displacing a gap member. SOLUTION: When a sheet is fed, thickness thereof is detected based on a signal from a paper thickness sensor 73 and the gap between the sheet and a recording head 14 is determined based on the detected paper thickness. Rotational direction and amount of a drive motor are then determined based on the determined gap and a current gap and the drive motor is rotary driven in the determined rotational direction by a determined rotary amount. Consequently, an eccentric cam 63 turns through the rotary shaft 62 of a gap regulating mechanism to displace a gap regulating member 24 vertically thus regulating the gap. Since the gap can be regulated while keeping parallelism between the recording head and the sheet, image quality is enhanced.

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, and more particularly to an ink jet recording apparatus capable of adjusting a gap between a recording head and a sheet.

[0002]

2. Description of the Related Art An ink jet recording apparatus used as an image recording apparatus such as a printer, a facsimile, a copying apparatus, etc.
Since an image is recorded on a sheet by ejecting ink droplets from nozzles (ejection ports) of an ink jet head, a gap between the head and the sheet greatly affects the printing quality. For example, if the gap from the head to the paper is too long, the flying ink droplets become unstable, and the landing positions are likely to fluctuate, and the landing dot diameter also fluctuates, deteriorating the image quality. If the gap from the head to the paper is too short, the paper comes into contact with the nozzle surface of the head due to cockling of the paper due to the impact of ink droplets, and the image quality is degraded because the printing surface becomes dirty.

[0003] Therefore, as disclosed in Japanese Patent Application Laid-Open No. 7-314822 and Japanese Patent Application Laid-Open No. 2-41279, it is known to provide means for maintaining a constant distance (gap) between the head and the sheet. Although there are various types of paper such as plain paper, OHP sheet, cardboard, and fabric,
The thickness is not uniform, and if the type of paper is different, the thickness is different and the gap changes.

[0004] Therefore, it has been proposed that a guide rod for supporting a carriage on which a head is mounted can be eccentrically rotated so that a gap between the head and a sheet can be adjusted by displacing the carriage.

[0005]

However, when the carriage on which the head is mounted is displaced as described above, even if the gap can be kept parallel in the main scanning direction of the carriage, it is orthogonal to the main scanning direction. In the sub-scanning direction, only one of the front and rear sides of the carriage is displaced, so that the parallelism between the sheet and the head is reduced and the printing quality is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide an ink jet recording apparatus capable of adjusting a gap without deteriorating image quality.

[0007]

According to a first aspect of the present invention, there is provided an ink jet recording apparatus for printing an image on paper by discharging ink droplets from a recording head. A gap adjusting member is displaceably disposed at a position opposed to the head with the sheet conveyance path interposed therebetween, and a means for displacing the gap adjusting member is provided.

According to a second aspect of the present invention, in the inkjet recording apparatus of the first aspect, the sheet is transported by a transport belt, and the gap adjusting member is located at a position facing the recording head with the transport belt interposed therebetween. It was configured to be displaceable.

According to a third aspect of the present invention, there is provided the ink jet recording apparatus according to the first or second aspect, wherein
The gap adjusting member is displaced based on the detection result of the thickness of the fed paper.

According to a fourth aspect of the present invention, in the inkjet recording apparatus of the first or second aspect,
The gap adjusting member is displaced based on the detection result of the type of the fed paper.

According to a fifth aspect of the present invention, in the inkjet recording apparatus of the first or second aspect,
The gap adjusting member is displaced based on paper thickness information provided from the host side or the operation panel.

According to a sixth aspect of the present invention, in the ink jet recording apparatus according to the first or second aspect,
The gap adjusting member is displaced based on paper type information provided from the host side or the operation panel.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a mechanism section showing an example of an ink jet recording apparatus according to the present invention.
3 is an enlarged view of a main part of FIG. 1, and FIG. 3 is a perspective view showing a gap adjusting mechanism of the recording apparatus.

This ink jet recording apparatus comprises a carriage movable in the main scanning direction inside the recording apparatus main body 1, a recording head including an ink jet head mounted on the carriage, an ink cartridge for supplying ink to the recording head, and the like. A paper feed cassette (or a paper feed tray) 4 capable of loading a large number of sheets 3 from the front side is detachably attached to a lower portion of the apparatus main body 1. A manual tray 5 is mounted on the front side so as to be openable and closable, and the paper fed from the paper feed cassette 4 or the paper 3 set in the manual tray 5 is taken in. Is recorded, and the sheet is discharged to the sheet discharge tray 6 mounted on the rear side. An upper cover 7 is mounted on the upper part so as to be openable and closable.

The printing mechanism 2 holds a carriage 13 slidably in a main scanning direction (a direction perpendicular to the paper surface in FIG. 1) by a main guide rod 11 and a sub guide rod 12 which are mounted on left and right side plates (not shown). On the lower surface side of the carriage 13, a recording head 14 composed of an ink jet head having nozzles for discharging ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk) is ejected. The ink tank (ink cartridge) 15 for supplying each color ink to the recording head 14 is exchangeably mounted on the upper side of the carriage 5.

As the recording head 14, a plurality of heads for ejecting ink droplets of each color may be arranged side by side in the main scanning direction, or a single head having a nozzle for ejecting ink droplets of each color may be used. The used one may be used. The ink cartridge 15 is held on the carriage 13 by a cartridge holding lever 16.

On the other hand, in order to convey the sheet 3 in the sub-scanning direction with respect to the printing position by the recording head 14, the sheet 3 is electrostatically attracted and conveyed between the conveyance roller 21 and the conveyance driven roller 22. A gap adjusting member 24 is provided at a position facing the recording head 14 with the conveyance belt 23 interposed therebetween, in this case, on the back side of the conveyance belt 23.
Is provided, the gap adjusting member 24 is displaceably disposed at a position facing the recording head 14 across the sheet transport path. The transport roller 21 has a transport belt 23.
, A tip roller 25 that defines the feed angle of the paper 3 is pressed and disposed.

It is preferable that the transport roller 21 has a diameter which does not separate the curvature, for example, a diameter of 30 mm or more, which secures the paper adhesion at the time of double-sided printing. It is preferable to use a medium resistor. Also, the gap adjusting member 2
Numeral 4 has a length in the main scanning direction as shown in FIG. 3, and both ends are slidably held as holding members (not shown) so as to be vertically displaceable without tilting in the sub scanning direction. doing.

On the other hand, in order to feed the paper 3 from the paper feed cassette 4 onto the conveyor belt 23, a paper feed roller 26 and a friction pad 27 which separate and feed the paper 3 one by one,
A guide member 29 is provided to guide the fed sheet 3 to the intermediate roller 28 disposed in contact with the transport roller 21. The paper feed cassette 4 includes a bottom plate 32 and an extended bottom portion 33 that forms a sheet mounting surface together with the bottom plate 32 on the cassette body 31.
And the length of the sheet mounting surface can be selected by changing the mounting position of the extension bottom 33, so that the cassette body 3
Large-size papers exceeding one can be used. Further, an end fence 34 for regulating the rear end of the sheet is mounted on the extension bottom 33 so as to be movable in the lengthwise direction in a stepless manner.

In order to feed the paper 3 from the manual tray 5 to the transport belt 23, a pickup roller 35 for picking up the paper 3 from the manual tray 5, a feed roller 36 for feeding the paper 3, and a feed roller 37 , Paper 3
And a guide member 38 for guiding the intermediate roller 28 to the intermediate roller 28.

A guide member 41 for guiding the paper 3 in order to discharge the printed paper 3 to the paper output tray 6.
And a paper discharge roller 42 for feeding the paper 3 to the paper discharge tray 6
And a paper discharge driven roller 43.

Further, the paper 3 having passed the printing position by the recording head 4 is used to discharge the printed paper 3 once out of the apparatus main body 1 and then feed the paper 3 again to the conveyor belt 23 to perform double-sided printing. A guide member 45 for guiding the sheet 3 obliquely downward between the discharge tray 6 and the paper feed cassette 4 is provided, and near the entrance between the guide member 45 and the guide member 41 on the discharge side, the paper 3 A first branch claw 46 for branching the discharge path is swingably provided.

In the vicinity of the terminal end of the guide member 45,
A switchback roller 47 and a switchback driven roller 48 for discharging the paper 3 toward the upper surface of the paper feed cassette 4 outside the apparatus main body 1 and feeding the paper 3 into the apparatus main body 1 again are provided. This switchback roller 4
Reference numeral 7 denotes a normal rotation when the paper 3 having been printed on one side is conveyed in the discharge direction, a reverse rotation when the paper 3 is re-fed, and a rear end in the discharge direction of the paper 3 when the paper 3 is discharged. It is stopped at a predetermined timing in order to pinch.

Further, on the upstream side of the switchback roller 47 and the switchback driven roller 48 in the sheet discharging direction,
A second branching claw 49 for switching the transport path of the sheet 3 between a discharge path to the outside of the apparatus main body 1 and a path for re-feeding the sheet 3 into the apparatus main body 1 is provided swingably. In order to feed the paper 3 fed into the apparatus main body 1 by the reverse rotation of the paper to the transport belt 23, a guide member 51 for guiding the paper 3, a double-sided relay roller 52 for transporting the paper 3 and a double-sided relay roller driven roller 53 and transport roller 2
1 and a transport roller driven roller 54 that feeds the sheet 3 to the intermediate roller 28 following the first roller 1.

Here, a gap adjusting mechanism for displacing the gap adjusting member 24 will be described with reference to FIG.
In the gap adjusting mechanism 61, eccentric cams 63 fixed to a rotating shaft 62 are disposed below both ends of the gap adjusting member 24 in the main scanning direction, and a driving shaft 65 of a driving motor 64 is connected to the rotating shaft 62. doing.

A drive shaft 65 of the drive motor 64 is provided with an encoder 66 having slits 66a formed at predetermined intervals in a peripheral portion thereof, and a transmissive photosensor comprising a light emitting element and a light receiving element opposed to each other with the encoder 66 interposed therebetween. Is provided. Therefore, the gap adjusting member 24 is vertically displaced by driving the drive motor 64 to rotate the eccentric cams 63, 63 via the rotary shaft 62.

Further, in order to detect the thickness of the sheet, as shown in FIG. 2, a detection filler 72 having a detection end abutting against the tip roller 25 and swingably supported at a swing fulcrum 71, and a detection filler 72. And a paper thickness sensor 73 using a transmission type photosensor including a light emitting element and a light receiving element which are opposed to each other with the filler section interposed therebetween. Therefore, the fine movement of the tip roller 25 is detected by the paper thickness sensor 73 via the detection filler 72 in accordance with the thickness of the fed paper, and a signal of a level corresponding to the paper thickness is output from the paper thickness sensor 73.

Next, an outline of a control section of the ink jet recording apparatus will be described with reference to FIG. The control unit includes a microcomputer (hereinafter, referred to as a “CPU”) 80 that controls the entire recording apparatus, a ROM 81 that stores necessary fixed information, a RAM 82 that is used as a working memory, and the like. An image memory 83 for storing processed data, and a parallel input / output (PIO)
A port 84, an input buffer 85, and a gate array (G
A) or a parallel input / output (PIO) port 86, a head drive circuit 88, drivers 89 and 90, and the like.

Here, in addition to image information from the host side, information indicating whether or not to perform double-sided printing,
Various instruction information including information indicating the type of paper or the thickness of the paper, information indicating the type of paper or the thickness of the paper from an operation panel (not shown), a gap sensor 67
, A paper thickness detection signal from the paper thickness sensor 73, signals from various sensors such as a home position sensor for detecting the home position (reference position) of the carriage 13, and the like. Necessary information is transmitted to the host side and the operation panel side via the interface.

The head drive circuit 88 is an energy generating element (an electromechanical device such as a piezoelectric element) corresponding to each nozzle of the recording head (inkjet head) 6 based on various data and signals provided via the PIO port 86. A driving waveform is applied to an energy generating element of a driving nozzle (a nozzle for discharging ink droplets) corresponding to image information in a conversion element or an electrothermal conversion element such as a heating resistor. In addition, as a driving waveform, a rectangular pulse, a triangular waveform, and other shapes such as a sin (sine) waveform can be used.

Further, the driver 89 includes the PIO port 8
6 according to the drive data given through the
Motor 91 for scanning the scanning roller 3 in the main scanning direction,
Motor 9 for rotating 1 in the paper transport direction (sub-scanning direction)
2. Drive motor 64 for displacing gap adjusting member 24
Are respectively driven and controlled. Further, the driver 90 drives and controls a solenoid (not shown) that swings the first branch claw 46 and the second branch claw 49.

Next, the operation of the ink jet recording apparatus thus configured will be described with reference to FIG. Referring to FIG. 3, when paper 3 is fed, a paper thickness detection signal from paper thickness detection sensor 73 is taken in to feed paper 3
Of the recording head 1 based on the detected paper thickness.
The gap amount between the sheet 4 and the sheet 3 to be conveyed is determined. The gap amount can be determined, for example, by previously storing the relationship between the paper thickness and the gap amount as table data in the ROM 81 and reading out the gap amount data according to the detection signal.

The rotation direction and the rotation amount of the drive motor 64 are determined based on the determined gap amount and the current gap amount, and the drive motor 64 is driven to rotate in the determined rotation direction by the determined rotation amount. Thereby, the eccentric cams 63, 63 are rotated via the rotating shaft 62 of the gap adjusting mechanism 61.
Rotates, and the gap adjusting member 24 is displaced up and down to adjust the gap. After the predetermined gap amount is obtained in this way, the drive motor 64 is stopped and the gap adjustment ends.

As described above, the gap adjusting member is displaceably disposed at a position opposed to the recording head with the sheet conveying path interposed therebetween, and the means for displacing the gap adjusting member is provided. The gap can be adjusted while maintaining the parallelism, and the image quality is improved. In this case, the paper can be transported by the transport belt, and the gap adjustment member moves the transport belt up and down, whereby the gap can be adjusted more easily and accurately.

Further, by displacing the gap adjusting member based on the detection result of the thickness of the sheet, an appropriate gap corresponding to the sheet thickness can be automatically set. Instead of detecting the paper thickness, the type of the fed paper is detected, and the gap adjusting unit is displaced based on the detection result, thereby automatically setting an appropriate gap according to the paper type. be able to. The detection of the paper type can be dealt with, for example, by using a transmission type photosensor to determine a plain paper and an OHP sheet from the amount of transmitted light.

Next, another example of the gap adjusting process will be described with reference to FIG. In this process, the paper type information provided from the host side or the operation panel is read, and
The gap amount corresponding to the designated paper type is read from a predetermined table and determined, and based on this and the current gap amount, the rotation direction and rotation amount of the drive motor 64, that is, the displacement direction and displacement of the gap adjusting member 24. Determine the amount.

By providing the means for displacing the gap adjusting member based on the paper type information provided from the host side or the operation panel, the gap can be automatically adjusted to an appropriate one according to the paper type. In this case, the supply of the paper type information from the host may be performed using the paper type setting function of the printer driver. In the case where the paper type information from the host and the operation panel conflict with each other, it is possible to deal with this by performing a process of giving priority to either one. It should be noted that, by providing information of the paper thickness itself from the host side or the operation panel side in place of the paper type information and providing a means for displacing the gap adjusting member based on the paper thickness information, the paper thickness is automatically adjusted according to the paper thickness. Can be adjusted to an appropriate gap.

Next, another example of the gap adjusting member will be explained with reference to FIG. 8. In this example, two rollers 75, 75 are arranged at intervals corresponding to the width of the recording head in the sheet conveying direction.
75, and these rollers 75, 75 are disposed so as to be integrally displaceable up and down. Even when such a gap adjusting member is used, the same operation and effect as the above embodiment can be obtained.

Although the above embodiment has been described with a configuration in which the gap adjusting member is automatically displaced,
Means for manually displacing the gap adjusting member may be provided.

[0040]

As described above, according to the ink jet recording apparatus of the first aspect, the gap adjusting member is displaceably disposed at a position opposed to the recording head with the sheet conveying path conveyed therebetween. Since the means for displacing the gap adjusting member is provided, the gap can be adjusted without deteriorating the image quality.

According to the ink jet recording apparatus of claim 2, in the ink jet recording apparatus of claim 1,
The paper is transported by the transport belt, and the gap adjusting member is displaceably disposed at a position facing the recording head with the transport belt interposed therebetween, so that the gap can be adjusted by displacing the transport belt. The mechanism for adjusting the gap is simplified, and an accurate gap can be easily obtained.

According to the ink jet recording apparatus of the third aspect, in the ink jet recording apparatus of the first or second aspect, the gap adjusting member is displaced based on the detection result of the sheet thickness. Can automatically adjust to the appropriate gap.

According to the ink jet recording apparatus of the fourth aspect, in the ink jet recording apparatus of the first or second aspect, the gap adjusting member is displaced based on the detection result of the paper type. Can automatically adjust to the appropriate gap.

According to a fifth aspect of the present invention, there is provided the ink jet recording apparatus of the first or second aspect, wherein a means for displacing the gap adjusting member based on paper thickness information provided from the host side or the operation panel is provided. Therefore, an appropriate gap can be automatically adjusted according to the paper thickness.

According to the ink jet recording apparatus of claim 6, in the ink jet recording apparatus of claim 1 or 2, the means for displacing the gap adjusting member based on the paper type information provided from the host side or the operation panel is provided. Therefore, an appropriate gap can be automatically adjusted according to the type of paper.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a mechanism section showing an example of an ink jet recording apparatus according to the present invention.

FIG. 2 is an enlarged explanatory view of a main part of FIG. 1;

FIG. 3 is a perspective view showing a gap adjusting mechanism of the recording apparatus.

FIG. 4 is a schematic block diagram of a control unit of the recording apparatus.

FIG. 5 is a schematic flowchart illustrating an example of a gap adjustment process of the recording apparatus.

FIG. 6 is a schematic flowchart illustrating another example of the gap adjustment processing of the recording apparatus.

FIG. 7 is an enlarged explanatory view of a main part showing another example of the gap adjusting member of the recording apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Device main body, 2 ... Printing mechanism part, 3 ... Paper, 4 ... Paper feed cassette, 5 ... Manual feed tray, 6 ... Discharge tray, 13 ... Carriage, 14 ... Recording head, 21 ... Transport roller, 23
... Conveying belt, 24 ... Gap adjusting member, 61 ... Gap adjusting mechanism, 63 ... Eccentric cam, 64 ... Drive motor, 67
... gap sensor, 73 ... paper thickness sensor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masumi Sato 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Genichi Yasui 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd.

Claims (6)

[Claims] 1. An ink jet recording apparatus which prints an image on a sheet by ejecting ink droplets from a recording head, wherein a gap adjusting member is displaceably disposed at a position facing the recording head with a sheet conveying path interposed therebetween. An ink jet recording apparatus comprising means for displacing the gap adjusting member. 2. The ink jet recording apparatus according to claim 1, wherein the sheet is conveyed by a conveyance belt, and the gap adjusting member is displaceably disposed at a position facing the recording head with the conveyance belt interposed therebetween. An ink jet recording apparatus comprising: 3. The ink jet recording apparatus according to claim 1, wherein the gap adjusting member is displaced based on a detection result of a thickness of the fed sheet. 4. The ink jet recording apparatus according to claim 1, wherein the gap adjusting member is displaced based on a detection result of a type of the fed paper. 5. The ink jet recording apparatus according to claim 1, wherein the gap adjusting member is displaced based on paper thickness information provided from a host or an operation panel. 6. The ink jet recording apparatus according to claim 1, wherein the gap adjusting member is displaced based on sheet type information provided from a host side or an operation panel.