JPH08197894A - Image forming apparatus - Google Patents

Abstract

PURPOSE: To provide an image forming apparatus in which an accurate image can be formed by preventing the positional deviation of the image due to the malfunction of a mechanical accuracy between a printing head and a home position sensor. CONSTITUTION: A printing timing signal from a linear sensor 3 is counted by a counter 5 to count the distance of movement of the printing head of a printer 1. Even if a home position sensor 4 detects that the head is moved to the home position, a central controller 6 inhibits a NAND gate 8 until at least one printing sheet is printed by the head, thereby preventing the resetting of the counter 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for printing on a printing paper from a print head while identifying the position of the print head by detecting a signal from a linear scale with a linear sensor.

[0002]

2. Description of the Related Art An image forming apparatus of this type is used, for example, in a plotter device or the like, and prints while moving a print head 22 in a scanning direction along a linear scale 21 as shown in FIG. When printing is performed on the paper 23 and one line is printed in the scanning direction, that is, when one band image is formed in the scanning direction as shown in FIG. 5, the linear scale 21 is moved at right angles to the scanning direction. The print sheet 23 is moved in a predetermined direction by a predetermined distance corresponding to a distance of one band, and the print head 22 is similarly moved at the moved position.
While moving in the scanning direction, the operation of printing on the print paper 23 by the print head 22 is repeated for several bands as shown in FIG. 5, so that one image is formed on the print paper 23. There is.

In order to detect that the print head 22 has returned to the initial home position after the print head 22 has printed in the scanning direction, the home position sensor 24 is set at the home position as shown in FIG. It is provided.

Further, the print head 22 is a linear scale 2.
When the print head 22 moves while printing in the scanning direction A along 1, a linear sensor (not shown) is provided near the print head 22 to detect the position of the moving print head 22. The linear sensor generates a print timing signal by reading the linear scale 21 while moving with the print head 22, and the position of the print head 22 is identified by counting the print timing signal with a counter as described later. There is.

A slit 21a is formed on the linear scale 21 as shown in FIG.
By detecting the presence or absence of 1a by the linear sensor,
The linear sensor is adapted to generate a print timing signal. The linear sensor is a linear scale 21.
In order to detect the slit 21a, a photo sensor or a magnetic sensor is used.

When a DC motor is used as the driving means for the carriage using the conventional linear scale,
Since the run-up distance for accelerating the carriage to the print area and stabilizing the moving speed becomes relatively long, the lateral width of the main body becomes large. Therefore, it is usually configured by using a stepping motor.

The print timing signal generated by detecting the slits of the linear scale 21 by the linear sensor is supplied to the counter 26 from the linear sensor 25 as shown in FIG. 7 and counted, and based on this counting result. The print area is determined by detecting the movement distance of the print head. Further, the counter 26 is initialized by the detection output signal of the home position sensor 24, and the counter 26 counts the print timing signal from the linear sensor 25 from the time of the initialization, whereby the home of the print head is counted. The moving distance from the position can be detected. The counter 26 is initialized every time the print head 22 completes its movement in the scanning direction A and returns to the home position.

[0008]

In the above-mentioned conventional image forming apparatus, as shown in FIG. 8, when the carriage 27 having the print head 22 passes through the home position and moves on the linear scale 21, the carriage 27 moves. A physical error occurs due to a mechanical precision failure between the home position sensor 27 and the home position sensor 24. As a result, as shown in FIG. 8, the line to be printed at the home position of the dotted line 28 is a solid line 29 before and after the line. It is misaligned and printed.

The occurrence of this deviation will be specifically described. The home position sensor 24 for detecting the reference position of the carriage 27 is generally a photo interrupter 24A.
Composed of. As shown in FIG. 9, the photo interrupter 24A is composed of a light emitting section 24a and a light receiving section 24b. A flag 27a is set on the carriage 27. The flag 27a moves between the light emitting unit 24a and the light receiving unit 24b by the movement of the carriage 27, and blocks the light emitted by the light emitting unit 24a and received by the light receiving unit 24b.

The photo interrupter 24A includes a light emitting section 24.
The light emitted from a is detected by the light receiving portion 24b and converted into an electric signal. The flag 27a of the carriage 27 blocks the light from the light emitting portion 24a to the light receiving portion 24b, so that the voltage value of the electric signal from the light receiving portion 24b changes. The output waveform of the light receiving section 24b at this time is shown in FIG. A point A in the drawing is a start point where the flag 27a blocks the photo interrupter 24A, and a point B is an end point where the flag 27a completely blocks the photo interrupter 24A. The point C is the detection point, that is, the reference position. A ~
The distance to B must be at least 300 μm.

However, mechanical vibration noise caused by harmonic components generated by high-speed movement when a stepping motor is used as the carriage moving means is 40 μm when driven at 20 kHz. The sensor output due to the vibration component generated during such high-speed operation is as shown in FIG. 36
When printing 0 dpi, one dot is 70 μm, so if an error of ± 60 μm occurs, an error of 1 dot or more will occur. Therefore, if the linear scale counter is cleared for each scan after the start of printing, there is a problem in that the image position shifts as shown in FIG.

The present invention has been made in view of the above,
An object of the invention is to provide an image forming apparatus capable of forming a highly accurate image by preventing displacement of an image due to noise due to mechanical vibration.

[0013]

In order to achieve the above object, the image forming apparatus of the present invention prints on a printing paper while moving the printing means in a predetermined scanning direction on the printing paper, After the completion of printing on the sheet, the printing means or the printing paper is moved in the moving direction perpendicular to the scanning direction, and the operation of printing on the printing paper while moving the printing means in the scanning direction at the moving position is repeated to form an image. An image forming apparatus for forming, comprising: position detecting means for detecting a position of the printing means in the scanning direction, reference position detecting means for detecting a reference position of the printing means in the scanning direction, and the position detecting means. Counting means for counting the moving distance of the printing means from the reference position detected by the reference position detecting means based on the detection signal of Until the minute printing, when the printing unit is moved to the reference position of the scanning direction, is summarized in that with the initialization preventing means for preventing the initializing said counting means.

The image forming apparatus of the present invention is characterized in that a stepping motor is used as the moving means of the printing means and an optical sensor is used as the reference position detecting means of the printing means.

[0015]

In the image forming apparatus of the present invention, the moving distance of the printing means from the reference position is counted based on the position detection signal from the position detection means, and the printing means prints at least one printing sheet. Up to the above, even when the printing means moves to the reference position, the counting means is prevented from being initialized.

Further, in the image forming apparatus of the present invention, since the stepping motor is used as the moving means of the printing means, the approach distance at the start of the movement of the carriage is shortened, and the reference position detecting means of the printing means is provided with the optical sensor. Use to increase resistance to mechanical vibration.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a main part of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus shown in FIG. 1 has a print head, and has a print unit 1 for ejecting ink onto the print paper by the print head to print on the print paper. The print unit 1 includes a temporary storage circuit 2 Is provided,
The temporary storage circuit 2 temporarily stores the print command from the central control unit 6 of the control unit 7, and supplies the stored print command to the print unit 1. The central control unit 6
Is composed of a microprocessor, a RAM, a ROM, etc., controls the entire operation of the apparatus, performs various image processing on image data transferred from the outside, and transfers the image data to the printing unit 1. ing.

Further, the control unit 7 includes the central control unit 6
In addition to the above, a counter 5 and a NAND gate 8 are further provided. The counter 5 counts the print timing signals from the linear sensor 3 having the same function as the linear sensor 21, and thereby detects the position of the print head of the printing unit 1 and the movement distance from the reference position which is the home position. Then, the detected position and movement distance are supplied to the central control unit 6.

The NAND gate 8 is supplied with a home position detection signal from the home position sensor 4 having the same function as the home position sensor 24 and a control signal from the central control unit 6, and the N signals of these two signals are supplied.
AND and take this NAND output signal to C of counter 5
It is adapted to be supplied to the LR inverting input terminal for initialization. As a result, the counter 5 is not initialized only by the home position detection signal of the home position sensor 4,
When the control signal is output from the central control unit 6,
The home position sensor 4 is initialized only when a home position detection signal is output.

In the counter 5, the UP / DOWN control signal from the central control unit 6 is supplied to the UP / DOWN input terminal, and the central sensor 6 prints from the linear sensor 3 in response to the UP / DOWN control signal. The timing signal can be counted up or down.

FIG. 2 is a waveform diagram showing the timing of each part of the image forming apparatus of FIG. The CLR inversion shown in FIG. 7A indicates an input signal to the CLR inversion input terminal of the counter 5, that is, an output signal of the NAND gate 8,
CLK in the figure (b) shows the print timing signal from the linear sensor 3 supplied to the CLK input of the counter 5, Q1 to Q4 in the figure (c) show the counter output signal of the counter 5, and UP. / DOWN (FORWARD / B
ACK) is the up / down counting direction of the counter 5, which indicates the moving direction of the print head of the printing unit 1, that is, the carriage, UP indicates FORWARD, that is, forward direction, and DOWN indicates BACK, that is, backward direction. The moving direction of the carriage can be controlled by the UP / DOWN signal from the central controller 6.

In the initial state, the central control unit 6 is the NAND
A control signal is output to the gate 8, and a home position detection signal is also supplied from the home position sensor 4 to the NAND gate 8, which causes NA
The output signal of the ND gate 8 causes the counter 5 to operate as shown in FIG.
It has been reset, that is, initialized, as shown in.

Then, according to the operation of the carriage carrying the print head, a print timing signal is output from the linear sensor 3 as shown in FIG. 2 (b) and supplied to the CLK of the counter 5, and the counter 5 outputs the print timing signal. 2 and the output signals Q1 to Q4 of the counter 5 are
It changes as shown in (c). Further, the central control unit 6
The position and the moving distance of the print head are identified based on the output signal of the counter 5, and the UP / DOWN signal is output, thereby controlling the moving direction of the carriage.

In this way, from the start of printing and the scanning of the first line, that is, the first band, from the second scanning onward, the print head finishes printing one sheet of printing paper at the center. The control unit 6 does not output a control signal to the NAND gate 8, thereby invalidating the home position detection signal from the home position sensor 4 and not resetting the counter 5 as shown in FIG.

Next, the operation of this embodiment will be described with reference to the flow chart shown in FIG. (3) In FIG. 3, first, initial setting is performed and the counter 5 is reset (steps S11 and S12). Then, it is checked whether or not the image data is externally supplied to the central control unit 6 (step S13), and if there is no image data, the process waits until the image data is supplied (step S14). When the image data is supplied, printing is started, and a print timing signal is supplied to the counter 5 from the linear sensor 3 that moves together with the print head that operates in the printing operation, and the counter 5 starts the counting operation. (Step S15).

After the first scan is completed, the print head returns to the home position in the second and subsequent scans, this operation is detected by the home position sensor 4, and the home position detection signal from the home position sensor 4 is sent to the NAND gate 8 , The NAND gate 8 inhibits the home position detection signal from the home position sensor 4 by the reset prohibition control signal from the central control unit 6, thereby preventing the counter 5 from being reset ( Step S16).
That is, after the second scan, the reset signal to the counter 5 is invalidated, so that the counter 5 is not reset and printing is continued.

When the printing of one sheet of printing paper is completed (step S17), the central control unit 6 releases the reset prohibition control signal to the NAND gate 8 and thereby the home position detection signal from the home position sensor 4. Is effectively supplied as a reset signal for the counter 5 (step S18). Then, in this state, when the home position is detected by the home position sensor 4 (step S19), a home position detection signal is output from the home position sensor 4, and this signal passes through the NAND gate 8 and the home position sensor 4 Is supplied to the counter 5, the counter 5 is reset (step S12), and the above-described operation is repeated thereafter.

As described above, even if the print head returns to the home position, the counter 5 is not reset until the printing of one sheet of printing paper is completed, so that all printing is performed with the first home position as a reference. Is performed based on the print timing signal from the linear sensor 3, so that the deviation of the print line on the print paper can be prevented.

[0029]

As described above, according to the present invention,
The moving distance of the printing means from the reference position is counted based on the position detection signal from the position detection means, and the printing means moves to the reference position until the printing means prints at least one sheet of printing paper. Even in such a case, since the counting means is prevented from being initialized, it is possible to appropriately prevent the deviation of the print line on the print paper and print a high-quality image.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a main part of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a waveform chart showing the timing of each part of the image forming apparatus of FIG.

FIG. 3 is a flowchart showing the operation of the image forming apparatus of FIG.

FIG. 4 is an explanatory diagram of a print head position detection operation.

FIG. 5 is an explanatory diagram of an image forming operation of the print head.

FIG. 6 is a partially enlarged view of a linear scale.

FIG. 7 is a block diagram showing a configuration of a conventional print timing signal generation unit.

FIG. 8 is an explanatory diagram showing a deviation of print lines.

FIG. 9 is a diagram showing a configuration of a photo interrupter.

FIG. 10 is an ideal sensor output waveform diagram.

FIG. 11 is a sensor output waveform diagram that is affected by actual vibration of the carriage.

[Explanation of symbols]

 1 Printing Section 2 Temporary Storage Circuit 3 Linear Sensor 4 Home Position Sensor 5 Counter 6 Central Control Section 7 Control Section 8 NAND Gate

Claims (2)

[Claims] 1. A printing means or a printing paper in a moving direction perpendicular to the scanning direction after printing on the printing paper while moving the printing means in the predetermined scanning direction on the printing paper and after the printing in the scanning direction is completed. An image forming apparatus that forms an image by repeating the operation of moving a printing unit on the printing paper while moving the printing unit in the scanning direction at the moving position, and changing the position of the printing unit in the scanning direction. Position detecting means for detecting, reference position detecting means for detecting a reference position of the printing means in the scanning direction, and from the reference position detected by the reference position detecting means based on a detection signal from the position detecting means Counting means for counting the moving distance of the printing means, and the printing means is the reference in the scanning direction until the printing means prints at least one printing sheet. Even when moved to the location, an image forming apparatus characterized by having a initializing preventing means for preventing the initializing said counting means. 2. The image forming apparatus according to claim 1, wherein a stepping motor is used as the moving means of the printing means, and an optical sensor is used as the reference position detecting means of the printing means.