JPH02187355A - Image recording device - Google Patents

Abstract

PURPOSE:To eliminate deviation of resist and to faithfully record an image by regulating the timing of a recording operation in response to the deviation of speeds of conveying a sheet. CONSTITUTION:When image data is read from a buffer memory 8 according to a start signal, the image data is input to a shift register 30, and sequentially transferred for one line. A controller 10 sends a latch pulse to a latch 31, and holds data in the latch 31. Detecting means 11 for detecting the deviation of speeds of conveying a sheet is provided to be vertically movably in a state that the end of a semispherical columnar rod 12 is exposed in a housing 13. Variations in the driving radius R of a conveying system having a conveying belt 4 and a driving roller 5 are picked up as the vertical movements of the columnar rod 12, variations in a magnetic field due to a permanent magnet 15 disposed on the columnar rod 12 are detected by a Hall element 16, and fed to the controller 10. The controller 10 sends a heat pulse at each scanning at the timing corrected for the deviation of the speed of conveying the sheet. The heat pulse and the data from the latch 31 are sent as a calculated output through an AND gate 35 to a driving transistor 35, thereby recording it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image recording apparatus equipped with a sheet conveyance means and an image recording means, and particularly to one for performing color recording.

[Prior Art] Conventionally, there is an image recording apparatus shown in FIG. 9 that performs color recording by ejecting recording liquid from a recording head.

In this system, a sheet S is conveyed by a conveyor belt 102 that rotates in conjunction with a drive roller 101, and ink ejection ports corresponding to the image recording width are provided at corresponding positions on the conveyance path 103 of the sheet S for main scanning (horizontal scanning). ) A plurality of recording heads 104 are provided.

By the way, this device records yellow (hereinafter referred to as Y) and magenta (hereinafter referred to as M) in order to record color images.
The subtractive color mixing method attempts to reproduce all colors by mixing the three colors of , cyan (hereinafter referred to as C), but the black color obtained by mixing equal amounts of the three colors Y, M, and C is (a) Since the reflection characteristics of Y, M, and C are non-uniform, accurate black cannot be obtained and the color becomes brownish.

(b) Since recording liquids of three colors are used, the amount of recording liquid consumed increases.

(c) Color misregistration (hereinafter referred to as registration misalignment) of Y, M, and C is noticeable in thin black lines such as letters.

In order to solve this problem, black recording is corrected by adding black (hereinafter referred to as BK) to the three colors Y, M, and C.

That is, in order to record a color image, the recording head 104 configures a recording head group 105 by combining four colors of Y, M, C, and BK, and this recording head group 105 can print a color image for one line in the main scanning direction. It records pixels, and when recording the data stored in the buffer memory 106 on the conveyed sheet S, the sheet conveyance speed and the recording head 10
The recording head group 105 is controlled to perform recording at a predetermined recording timing based on conditions such as the distance between the sheets S, and the sheet S is relatively moved in the sub-scanning (vertical scanning) direction to perform color recording. Met.

[Problems to be Solved by the Invention] However, in the above conventional example, unevenness in the roundness of the drive roller 101 and the conveyor belt 102 caused by the manufacturing process
Due to thickness unevenness, etc., the driving radius R in the conveying system periodically fluctuates as shown in FIG. That is, the conveyor belt 10 rotates in conjunction with the drive roller 101.
Since the sheet S is conveyed by 2, the conveyance speed of the sheet S causes periodic fluctuations (hereinafter referred to as speed deviation) due to the above fluctuations.This is related to the problem (c) above, but Y , M, and C as a substitute for equally mixing three colors, or single-color recording of each of Y, M, and C, there are few problems, but intermediate colors with different mixing ratios of Y, M, and C In the case of color recording, the speed deviation causes a shift in the recording timing of each of Y, M, and C in the recording head group 105, resulting in registration misalignment. Therefore, in color recording including intermediate colors, the intermediate colors could not be faithfully recorded due to the above-mentioned registration deviation.

The present invention has been made to solve the problems of the prior art described above, and its purpose is to eliminate registration deviations and to perform faithful image recording.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a sheet conveyance means for conveying a sheet, and an image recording system for recording an image on the sheet conveyed by the sheet conveyance means. In the image recording apparatus, the image recording means is provided with a recording timing control means for adjusting the timing of the recording operation according to a speed deviation of sheet conveyance by the sheet conveying means.

[Function] In the present invention having the above configuration, for example, the speed deviation of sheet conveyance is detected by detecting the amount of variation in the driving radius of the conveyance system.

Then, by controlling the timing of the recording operation according to the detected speed deviation of sheet conveyance, it is possible to correct the relative speed deviation between the sheet and the recording means.

[Embodiment] A first embodiment of the present invention is shown in FIGS. 1 to 7, and its configuration will be explained using FIGS. 1 to 3.

1 is a sheet of paper, 2 is a registration roller that takes the timing of paper feeding and corrects the skew of the paper 1, 3 is a pressure roller that brings the paper 1 into close contact with the conveyor belt 4, and 5 is a conveyor belt. a drive roller that drives 4;
A charger is used to electrostatically attract the paper 1 to the conveyor belt 4, and 7 is a discharge tray for the discharged paper 1. 8 is a buffer memory for storing image data, and each memory 8Y, 8M, 8C, and 88K stores each color data of Y, M, C, and BK necessary to reproduce a color image. Reference numeral 9 denotes a recording head for recording image data sent from the buffer memory 8, and the recording timing between the heads is controlled by a control section 1O serving as a recording timing control means. Reference numeral 11 denotes a detection means for detecting speed deviation in sheet conveyance, and as shown in FIG. The cylindrical rod 12 is provided so as to be movable up and down in a vertical position, and a spring 14 is applied to the rear end of the cylindrical rod 12 so that the tip of the cylindrical rod 12 exposed from the housing 13 is pressed against the conveyor belt 4. ing. A permanent magnet 15 is disposed on the side of the cylindrical rod 12 within the casing 13, and a Hall element 16 is disposed at a position within the casing 13 corresponding to the permanent magnet 15.

That is, fluctuations in the driving radius R of the conveying system consisting of the conveying belt 4 and the driving roller 5 are picked up as the vertical movement of the cylindrical rod 12, and the permanent magnet 1 disposed on the cylindrical rod 12 is
5 is detected by the Hall element 16, and the detected signal is sent to the control section 10. Also,
The detection means 11 is also equipped with a position detection section 11a that optically reads a belt reference position marked on the conveyor belt 4. Reference numeral 17 denotes a single bubble jet head constituting the recording head 9, and the head 17 is formed with a conductive path 19 and an ejection port 20 for ejecting the recording ink 18. A heater 21 as a heating element that generates heat when energized is provided inside the conduction path 19 near the injection port 20. That is, as shown in FIG. 3, the recording ink 18 from the ejection port 20 to the heater 21 becomes ink droplets 23 and is ejected by the pressure of bubbles 22 generated by the heat generated by the heater 21.

Next, an example of the operation of this embodiment will be explained.

In this embodiment, there are a plurality of recording heads 9 (one in the main scanning direction).
It is composed of a bubble jet rad 17 (number of pixels for a line), but for convenience of explaining an operation example, 4000P
The following description will be made assuming that 3,360 bubble jet radars 17 necessary for recording in the transverse direction of an A4 size sheet at a resolution of I (dot per inch) are arranged in a line.

First, the paper 1 is placed at a predetermined timing by the registration roller 2.
When the paper l is fed, the paper l is brought into close contact with the conveyor belt 4 by the pressure roller 3, and then electrostatically attracted to the conveyor belt 4 by the charger 6. Then, image data is read out from the buffer memory 8 by a start signal issued from the control unit 10 to the buffer memory 8. At the same time, the image data is input to the shift register 30, and data for one line (3360 dots) is sequentially transferred. . and,
When the data for one line has been transferred, the control section 10 sends a latch pulse to the latch 31 to hold the data in the latch 31. Then, the control unit 10 sends a heat pulse for each scan at a timing that corrects the sheet conveyance speed deviation with respect to the line clock counted by an internal timer. This heat pulse and the data from the latch 31 pass through an AND circuit 35, and the calculated output from this circuit 35 is sent to a drive transistor 36 to energize the heater 21 of the bubble jet head 17 and record it. It is.

The correction of the speed deviation is carried out by the detection means 1 as shown in FIG.
The analog signal output by the A/D converter 32 is converted into a digital signal by the A/D converter 32, and this digital signal is converted into a LOOK U with appropriate correction values set in advance.
When input to the P TABLE 33 (hereinafter referred to as LUT), time correction of the signal (corresponding to Tl, T2 and T3 in FIG. 7) is performed, and the signal is sent from the latch 31 to the timing counter 34.
This is done by sending the information to and,
The timing counter 34 is reset every revolution by a signal output from the belt position detection section 11a.

Next, a second embodiment of the present invention is shown in FIG. 8, and the same parts as in the first embodiment will be described with the same reference numerals.

The detection means 11 in this embodiment has a fixed shaft 2 serving as a fulcrum.
4 is rotatably provided with a metal piece 25, this metal piece 25 is brought into contact with the conveyor belt 4, and furthermore, an eddy current sensor 26 is disposed above this metal piece 25.

That is, the eddy current sensor 26 detects fluctuations in the drive radius R of the conveyance system consisting of the conveyance belt 4 and the drive roller 5 due to the vertical movement of the metal piece 25, and this signal is sent to the control unit 1.
0.

Here, since the speed deviation has periodicity as shown in FIG. 4, the speed deviation is detected and measured in advance by the detection means 11, and this value is stored in the control unit 10 to control the recording timing. This is how it was done.

Therefore, for example, if the -speed deviation is detected and measured when the power is turned on, the detection means 11 does not need to be activated, and the control during recording is simplified.

The other configurations and operations are the same as those of the first embodiment, so their explanation will be omitted.

Note that although inkjet recording using a bubble jet method is used in this embodiment, inkjet recording using an on-demand method may also be used, and other methods such as a thermal transfer method or a structure in which a plurality of electrophotographic drums are arranged may also be used. .

In addition, the conveyance means is not limited to sheet conveyance using electrostatic adsorption.
Wrapping on a drum or transporting a roll paper may be used, and any detection means may be used as long as it is capable of detecting the driving radius of the transport system. It goes without saying that it can be arbitrarily selected depending on the conditions.

Furthermore, in this example, 3360
Although the bubble jet heads are driven simultaneously, it is numerically preferable to drive them separately (for example, 64 bubble jet heads each) in consideration of the power supply and the like.

[Effects of Invention 4] As explained below, in the present invention, by controlling the timing of the recording operation according to the speed deviation of sheet conveyance, it is possible to prevent registration deviation when recording an image. As a result, high quality images can be recorded.

Moreover, since there is no registration deviation, faithful colors can be reproduced even in color image recording including intermediate colors.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing a first embodiment of the present invention, Fig. 2 is a sectional view showing a detection means in this embodiment, and Fig. 3 (a
), (b), and (c) are cross-sectional views of the bubble jet head in this embodiment, FIG. 4 is a diagram showing the amount of variation in the driving radius in the conveyance system, and FIG. 5 is a block diagram showing the detection means of this embodiment. 6 is a drive circuit diagram of the recording head in this embodiment, FIG. 7 is a drive timing chart of the recording head group in this embodiment, and FIG. 8 is a detection means in a second embodiment of the present invention. The sectional view and FIG. 9 are schematic configuration diagrams showing a conventional example. Reference numeral 1...Paper (sheet) 3...Press roller 5...Drive roller 7...Paper output tray 9...Recording head lO...Control unit (recording timing control means) 11...
・Detection means 11a... Belt position detection section 12
... Cylindrical rod 13 ... Housing 14 ... Spring 15 ... Description of permanent magnet 2 ... Registration roller 4 ... Conveyor belt 6 ... Charger 8 ... Buffer memory 16 ...Hall element 17...Bubble jet head 18...Recording ink 19...Conducting path 20...
・Injection port 21...Heater (heating element) 22・
... Bubble 23 ... Ink droplet 24 ... Fixed shaft 25 ... Metal piece 26 ... Eddy current sensor 30 ... Shift register 31 ... Latch
32...A/D converter 33...LOOK
UP TABLE (LUT) 34...Timing counter 35...AND circuit 36...Drive transistor Figure 2 Figure 4 Figure 4

Claims (3)

[Claims] (1) In an image recording apparatus comprising a sheet conveying means for conveying a sheet, and an image recording means for recording an image on the sheet conveyed by the sheet conveying means, a speed deviation of the sheet conveyance by the sheet conveying means. An image recording apparatus characterized in that it is provided with a recording timing control means that adjusts the timing of a recording operation according to the timing of the recording operation. (2) The image recording apparatus according to claim 1, wherein the speed deviation of the sheet conveyance is measured in advance, and the timing of the recording operation is adjusted according to the measured value. (3) The image recording apparatus according to claim 1 or 2, further comprising a detection means for determining a speed deviation of sheet conveyance.