JPH11138928A - Ink jet recording device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] The image quality is degraded due to contact with the head due to cockling or bending of paper. SOLUTION: A nip position changing means 14 for displacing a nip position A of a sheet by a roller 11 and a spur 12.
With.

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 changing the nip position of a sheet after printing.

[0002]

2. Description of the Related Art An ink jet recording apparatus used for a printer, a facsimile, a copying machine, etc. includes a plurality of nozzles for ejecting ink droplets, and an actuator such as an electromechanical conversion element or a heating resistor provided for each nozzle. Using an inkjet head equipped with a recording head, an ink droplet is ejected from a nozzle of the recording head onto a sheet according to a recording signal while conveying the fed sheet to record an image, and the recorded sheet is printed. The paper is output to the paper output tray. In the present specification, “paper” means that ink droplets are attached, and is not limited to paper.
OHP sheets and the like are included.

In such an ink jet recording apparatus, the number of nozzles of the head increases with the speeding up, and the width (printing width) that can be printed in one scan is widened. As the amount increases, cockling of paper tends to occur. Here, cockling refers to a phenomenon in which the ink adhering surface side of the paper instantaneously expands due to the swelling action of the ink adhering to the paper. This cockling depends on the amount of ink ejected at once and the paper type,
Generally, the amount of ink is large, and the thinner the paper, the greater the amount of cockling (the amount of swelling of the paper).

In the ink jet recording apparatus, when this cockling occurs, the paper rubs against the head, and a rub mark of the ink remains. Even if the rubbing is not reached, the distance from the head to the paper changes and the image deteriorates. Will be.

Therefore, conventionally, Japanese Patent Application Laid-Open No. 7-285251
And Japanese Patent Application Laid-Open No. 7-323622, while slightly increasing the speed of a roller disposed immediately after the printing section to apply tension to the sheet, and moving the roller in the printing section. The paper is conveyed while being pulled downward by being disposed obliquely downward in the paper conveyance direction.

[0006] For example, as shown in FIG.
3 is sent out to the paper receiving table 104, an image is recorded by the ink jet head 101, and then conveyed in the paper discharging direction while being pulled by a nip portion A formed between the paper discharging roller 105 and the spur 106. Here, a discharge roller 105 and a spur 106 serving as a sheet discharge conveyance unit for conveying the sheet in the sheet discharge direction are provided on a conveyance path P2 obliquely downward with respect to the same horizontal conveyance path P1 as the sheet conveyance direction in the printing unit. , So that the nip portion A is positioned higher than the upper surface of the paper receiving table 104, and the paper discharge rollers 1
05 is slightly increased with respect to the conveying roller 102.

[0007]

However, there are various types of paper used in the ink jet recording apparatus, such as plain paper, thick paper (thick paper), OHP sheet, and the like. The optimal position slightly differs depending on the amount of ink to be attached and the type of paper. Moreover,
When the position of the nip portion is fixed downward as in the above-described conventional ink jet recording apparatus, and when strong paper such as thick paper is used, as shown in FIG. The same result as cockling occurs, for example, the sheet is curved before the cradle 104 and comes into contact with the inkjet head 101, and the image quality is reduced.

For this reason, in the conventional ink jet recording apparatus, usable paper types are limited.
When rubbing with the head occurs due to the use of paper of another paper type, the gap between the inkjet head and the paper is widened by a gap adjusting means or the like, and there is no choice but to leave some image deterioration as unavoidable. .

[0009] The present invention has been made in view of the above points, and has as its object to improve image quality.

[0010]

According to a first aspect of the present invention, there is provided an ink jet recording apparatus which records an image on a sheet using an ink jet head, and interposes the sheet on which the image is recorded in a discharge direction. An ink jet recording apparatus provided with a paper discharging and conveying means for feeding paper to the printer is provided with means for changing a nip position of a sheet by the paper discharging and conveying means.

According to a second aspect of the present invention, there is provided the ink jet recording apparatus according to the first aspect, further comprising: means for displaceably supporting the sheet discharging and conveying means; and driving means for displacing the sheet discharging and conveying means. Configuration.

According to a third aspect of the present invention, in the inkjet recording apparatus of the first or second aspect,
The nip position of the paper by the paper discharging / conveying means is changed according to the specified paper type or the detected paper type.

According to a fourth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to third aspects, the nip position of the sheet by the sheet discharging and conveying means is changed according to a type of an image to be recorded on the sheet. The configuration was adopted.

According to a fifth aspect of the present invention, in the ink jet recording apparatus of the first aspect, the nip position of the sheet by the sheet discharging / conveying means is changed in conjunction with an operation member for adjusting a gap.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic side view of a main part of a printing mechanism of an ink jet recording apparatus according to the present invention, FIG. 2 is an explanatory view of a nip position changing means of the printing mechanism, and FIG. 3 is a nip position of the printing mechanism. FIG. 7 is an explanatory diagram of a state in which is changed.

The printing mechanism of the ink jet recording apparatus includes a guide rod 1 laid between left and right side plates (not shown).
The carriage 2 is slidably held in a main scanning direction (a direction perpendicular to the paper surface of FIG. 1) by a guide plate (not shown), and a recording head 3 composed of an ink jet head is placed on the lower surface side of the carriage 2 in the ink droplet ejection direction. The ink cartridge 4 for supplying ink to the recording head 3 is mounted on the upper surface side of the carriage 2. The carriage 2 is moved and scanned in the main scanning direction by using a main scanning motor (not shown) as a driving source.

The recording head 3 comprises, for example, four heads arranged in the main scanning direction for discharging yellow (Y) ink, magenta (M) ink, cyan (C) ink and black (Bk) ink, respectively. Similarly, the ink cartridge 4 also includes four ink cartridges for supplying each color ink.

On the other hand, on the lower side of the carriage 2, a paper feed roller 6 for feeding the paper 5 set in the paper feed cassette is provided.
And a transport roller 7 having one cylindrical surface in the main scanning direction for transporting the paper fed by the paper feed roller 6 in reverse.
A pinch roller 8 for defining an angle at which the sheet 5 is sent from the conveying roller 7; a guide member 9 having a rib 10 for guiding the sheet 5 sent from the conveying roller 7 to a lower side of the recording head 3; And a spur 12 abutting against the roller, and a paper discharge tray 13 mounted in an inclined state for storing the discharged paper.

The spur 12 is usually made of a thin metal plate, and has a star-like shape with a plurality of sharp edges, which are discharged from the printing unit (head 3). This is for transporting the paper 5 without rubbing the undried ink on the paper 5. The spurs 12 and the rollers 11 constitute a paper discharging and conveying means for conveying the paper 5 in the paper discharging direction, and a contact portion between the spurs 12 and the rollers 11 becomes a nip portion A (hereinafter, the position of the nip portion A is referred to as a nip portion A). Simply referred to as “nip position A”).

Then, as shown in FIGS. 2 and 3, the nip position A of the sheet by these rollers 11 and spurs 12
Nip position changing means 14 for displacing the nip position. The variable nip position means 14 includes a movable lever 16 pivotally supported by a support shaft that rotatably holds the roller 11, a stepping motor 17, a gear 18 mounted on the rotation shaft of the stepping motor 17, and a gear 18. And an idler gear 19 that meshes with a rack 16a of the movable lever 16. When the stepping motor 17 is driven, the movable lever 16 swings to displace the roller 11 and the spur 12 up and down. Note that the spur 12 is displaced by moving along with the roller 11 by a connecting plate (not shown). Also,
The movable lever 16 constitutes means for supporting the roller 11 and the spur 12 in a displaceable manner, and the stepping motor 17 and the like constitute drive means for displacing the roller and the spur 12.

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”) 20 for controlling the entire printing apparatus, a ROM 21 storing necessary fixed information, a RAM 22 used as a working memory, and the like, and a processor for processing image information. An image memory 23 for storing the converted data, a nip position table 24 for storing nip position information corresponding to the paper type, a parallel input / output (PIO) port 25, an input buffer 26,
Gate array (GA) or parallel input / output (PIO) port 27, head drive circuit 28 and drivers 29, 3
0 and so on.

In the PIO port 24, in addition to image information from the host, information such as paper type designation data indicating the type of paper, and a paper type designation from a paper type designation switch 31 provided on an operation panel (not shown). In addition to various kinds of designated information including information, a detection signal from a paper presence / absence sensor for detecting the start and end of the paper, a signal from various sensors such as a home position sensor for detecting a home position (reference position) of the carriage 2 and the like are input. This PIO port 24
Required information is transmitted to the host and the operation panel via the PC. Note that the paper type designation switch 31 may be either a single unit or a designation unit using a menu selection method.

Further, the head drive circuit 28 is configured to control, based on various data and signals given via the PIO port 27, an energy generating element (such as a piezoelectric element or a heating resistor) corresponding to each nozzle of the recording head 3. A required drive waveform is applied to an energy generating element of a drive nozzle (a nozzle for ejecting ink droplets) corresponding to the image information.

Further, the driver 29 includes a PIO port 2
7 according to the drive data given through
The carriage 2 is moved and scanned in the main scanning direction by controlling the driving of the main scanning motor 32 for scanning the main scanning direction in the main scanning direction and the sub-scanning motor 33 for rotating the conveying roller 7 in the sub-scanning direction. By rotating the transport roller 7, the paper 5
Is transported by a predetermined amount. The driver 30 is connected to the PIO port 2
The driving of the stepping motor 17 is controlled according to the driving data given through the control unit 6 to displace the nip position A of the sheet by the roller 11 and the spur 12.

The nip position variable control in the ink jet recording apparatus configured as described above will be described with reference to FIG. First, as shown in FIG. 5, the control unit fetches paper type designation information given from the host side or paper type designation information given from the paper type designation switch 31 of the main body of the recording apparatus. When the paper type designation information is given from both the host side and the paper type designation switch 31, a process of giving priority to the paper type designation information from one of them, for example, the host side may be performed.

The fetched sheet type designation information is converted into nip position data using the nip position table 24, and the driving amount of the stepping motor 17 according to the difference between the current nip position and the nip position obtained as a result of the conversion. Is calculated, and the stepping motor 17 is rotationally driven via the driver 30. As a result, the movable lever 16 moves in the vertical direction, the roller 11 and the spur 12 are displaced, and the nip position A for sandwiching the sheet is displaced to a required position.

For example, when using paper 5 that is not very strong, such as plain paper, the stepping motor 17 is driven (or set as an initial position) to move the movable lever 16.
In the state shown in FIG. 2, the roller 11 and the spur 1
2, the nip position A of the sheet is located below the sheet conveying direction (the guide surface of the guide member 9) in the printing section. As a result, the paper 5 is sandwiched between the guide member 9 and the roller 11 and the spur 12 located diagonally downward, and is conveyed in a paper discharging direction under tension while the roller 11 is slightly accelerated. Therefore, cockling of the paper is suppressed, and contact with the head 3 is prevented even if cockling occurs.

On the other hand, when a stiff paper 5 such as a thick paper or an OHP sheet is used, the stepping motor 17 is driven and the movable lever 16 is displaced to the state shown in FIG. The nip position A of the sheet by the spur 12 is displaced to an extended nip position A ′ which extends the sheet conveying direction in the printing portion in a substantially horizontal direction. As a result, the paper 5 is directly sandwiched between the guide member 9 and the rollers 11 and spurs 12 located on the extension line, and is conveyed in a paper discharging direction under tension while the rollers 11 are slightly accelerated. Therefore,
Since the paper 5 does not bend due to the stiffness of the paper 5 and is prevented from contacting the head 3, the image quality only changes within the range of the gap variation between the head 3 and the paper 5. Reduce.

Here, the nip position A is displaced in two stages according to relatively thin paper such as plain paper and stiff paper such as thick paper or OHP sheet. Therefore, the nip position A can be displaced in three or more stages according to the paper type. As the paper type information, the specification information from the host side or the specification information from the specification switch of the main body of the recording apparatus is used. The paper type is detected based on the amount of transmitted light by emitting a laser beam or the like to the paper. Comprising detection means,
The nip position can be displaced by controlling the drive of the stepping motor in accordance with the type of paper detected by the detection means.

Next, another example of the nip position variable control by the control unit will be described with reference to FIG. In this example, the control unit identifies whether the image data to be printed is text or graphic, that is, the image type, converts the identification result into a nip position using a nip position table, and obtains the current nip position and the conversion result. The difference from the nip position is converted into a driving amount of the stepping motor 17, and the stepping motor 17 is rotationally driven via the driver 30. As a result, the movable lever 16 is displaced in the vertical direction, the roller 11 and the spur 12 are also displaced in the vertical direction according to the type of image to be printed, and the nip position A for sandwiching the paper is displaced to a required position.

Therefore, when printing an image having a relatively small amount of ink such as a text image, for example, the nip position A of the sheet by the roller 11 and the spur 12 is used.
For example, as shown in FIG. 2, it is positioned below the sheet conveying direction (the guide surface of the guide member 9) in the printing section. On the other hand, when printing an image in which the amount of ink is large and cockling is likely to occur, such as a graphic image, the nip position A of the sheet by the roller 11 and the spur 12 is printed.
Is positioned slightly below the position shown in FIG. 2, for example.
In this manner, the nip position can be displaced to the optimum position according to the image type, that is, the amount of ink to be hit on the sheet.

Next, another example of the nip position changing means will be described with reference to FIG. In this example, a roller 1 is attached to the tip of a movable lever 42 pivotally supported by a support shaft 41.
1 is rotatably supported, a tension coil spring 43 is interposed between the movable lever 42 and the upper fixed portion, and a solenoid 44 is disposed on the lower side. A tension coil spring 45 is interposed therebetween. In this case, the restoring force of the tension coil springs 43 and 35 and the solenoid 44 are set to the nip position A by the roller 11 and the spur 12 when the solenoid 44 is in the non-drive state.
Are set and arranged so as to be located at substantially the same height direction as the guide surface of the guide member 9.

Therefore, when a rigid paper such as a thick paper is used, the solenoid 44 is set in a non-driving state, and the paper is conveyed in a substantially horizontal state in the paper discharging direction. Contact and the like are prevented. When a sheet of paper, such as plain paper, which is not very strong, is used, the solenoid 44 is driven, whereby the plunger 44a is retracted, and the movable lever 42 moves downward against the restoring force of the tension coil spring 43. The paper discharge roller 11 and the spur 12 are displaced and the guide member 9 is moved as shown in FIG.
Is displaced obliquely downward with respect to the guide surface, and the contact between the head 3 and the sheet 5 due to the cock ring and the gap fluctuation are prevented. In this case, the displacement of the nip position is limited to two stages, but the cost is lower and the structure is simpler than the example shown in FIG. The drive of the solenoid 44 can be controlled according to the image type.

Next, still another example of the nip position changing means will be described with reference to FIG. In this example, the spindle 4
The roller 11 is rotatably supported at the tip of a movable lever 42 which is pivotally supported at 1 and the carriage 2 is displaced by a gap between the head 3 and a sheet conveying surface (a guide surface of the guide member 9). Adjustment lever 46 for adjusting
And are connected via a link mechanism.

That is, the cam portion 46a of the gap adjusting lever 46 is pivotally supported by the link member 4 pivotally supported by the support shaft 47.
The other end of the link member 48 is connected to the guide rod 1 of the carriage 2, and by rotating the gap lever 46, the carriage 2 moves up and down via the link member 48. The gap is adjusted. The other end of the link member 48 and the support shaft of the roller 11 are connected by a link member 49 so that the roller 11 is displaced by the swing of the link member 48.

Therefore, in the same figure, when the gap adjusting lever 46 is rotated in the direction indicated by the arrow, the other end of the link member 48 moves in the direction indicated by the arrow, and the gap between the head 3 and the sheet conveying surface is widened. At the same time, the movable lever 42 swings in the direction indicated by the arrow via the link member 49, the roller 11 and the spur 12 are displaced, and the nip position A is displaced to substantially the same height as the guide surface of the guide member 9.

Thus, when thick paper is used, the gap adjusting lever 46 is operated in the direction of the arrow to widen the gap, so that the nip position A can also be raised to a position close to the guide surface of the guide member 9. Since the sheet can be conveyed in a substantially horizontal direction, contact with the head due to bending can be prevented. That is, also in this case, the nip position is manually displaced in accordance with the paper type.

[0038]

As described above, according to the ink jet recording apparatus of the first aspect, the means for changing the nip position of the sheet by the sheet discharging and conveying means which feeds the sheet on which the image is recorded in the sheet discharging direction is provided. As it is equipped, it is possible to change the nip position according to the paper to be used, and it is possible to prevent contact with the head due to cockling and bending of the paper,
Image deterioration can be reduced.

According to the ink jet recording apparatus of claim 2, in the ink jet recording apparatus of claim 1,
The provision of the means for displaceably supporting the sheet discharging and conveying means and the driving means for displacing the sheet discharging and conveying means makes it possible to obtain an optimum nip position according to the type of paper and the type of image.

According to the ink jet recording apparatus of the third aspect, in the ink jet recording apparatus of the first or second aspect, the nip position of the sheet by the sheet discharging / conveying means according to the type of the designated sheet or the type of the detected sheet. Is changed, the image quality can be improved by setting the optimum nip position according to the paper type.

According to a fourth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to third aspects, the nip position of the sheet by the sheet discharging and conveying means is changed according to the type of an image to be recorded on the sheet. As a result, the image quality can be improved by setting the nip position to an optimum nip position according to the image type.

According to the ink jet recording apparatus of claim 5, in the ink jet recording apparatus of claim 1,
Since the configuration is such that the nip position of the paper by the paper discharging and conveying means is changed in conjunction with the operation member for gap adjustment, the nip position can be changed by a simple operation according to the paper thickness with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a main part of a printing mechanism of an ink jet recording apparatus according to the present invention.

FIG. 2 is an explanatory diagram for explaining a nip position changing unit of the printing mechanism unit;

FIG. 3 is an explanatory diagram of a state where a nip position of the printing mechanism is changed.

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

FIG. 5 is a flowchart illustrating an example of nip position variable control by the control unit.

FIG. 6 is a flowchart illustrating another example of nip position variable control by the control unit.

FIG. 7 is an explanatory diagram for explaining another example of the nip position changing unit of the printing mechanism unit;

FIG. 8 is an explanatory diagram for explaining still another example of the nip position changing unit of the printing mechanism unit.

FIG. 9 is an explanatory view illustrating a printing mechanism of a conventional ink jet recording apparatus.

FIG. 10 is an explanatory diagram illustrating a state when thick paper is used in the printing mechanism unit.

[Explanation of symbols]

2 ... carriage, 3 ... recording head, 5 ... paper, 6 ... paper feed roller, 7 ... conveyance roller, 8 ... pinch roller, 9 ... guide member, 11 ... roller, 12 ... spur, 13 ... paper ejection tray,
14 ... variable nip position, 16 ... movable lever, 17 ...
Stepping motor, 19: idler gear, 24: nip position table, 31: paper type designation switch, 44:
Solenoid, 46 ... Gap adjusting lever, 48, 49 ...
Link member.

Claims (5)

[Claims] 1. An ink jet recording apparatus, comprising: an image recording apparatus that records an image on a sheet using an ink jet head and feeds the sheet on which the image is recorded in a sheet discharging direction. An ink jet recording apparatus comprising means for changing a nip position of the ink jet recording apparatus. 2. An ink jet recording apparatus according to claim 1, further comprising: means for movably supporting said sheet discharging and conveying means; and driving means for displacing said sheet discharging and conveying means. Recording device. 3. The ink jet recording apparatus according to claim 1, wherein a nip position of the sheet by the sheet discharging / conveying means is changed according to a specified sheet type or a detected sheet type. Inkjet recording device. 4. The ink jet recording apparatus according to claim 1, wherein a nip position of the sheet by the sheet discharging / conveying means is changed according to a type of an image to be recorded on the sheet. Ink jet recording device. 5. The ink jet recording apparatus according to claim 1, wherein a nip position of the sheet by the sheet discharging and conveying means is changed in conjunction with an operation member for adjusting a gap.