JPH11334149A - Print position correcting method and printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress fluctuation of print position regardless of deviation or speed change of a carriage. SOLUTION: In an ink jet recording printer where a carriage mounting a print head performs scanning orthogonally to the carrying direction of recording medium, a speed detection section 42 detects speed information sequentially at the time of scanning with the carriage, and a delay circuit 46 corrects the print position dynamically in the scanning direction based on the detected speed information with reference to a table 45. According to the method, printing can be performed even in the nonconstant scanning region of the carriage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing device such as a printer and a plotter, and more particularly to a method for correcting a printing position.

[0002]

2. Description of the Related Art Conventionally, a printing apparatus such as an ink jet recording system has been known as an output apparatus for a computer or a work station.

In a printing apparatus of this type, when a carriage on which a print head is mounted is moving to the left and right, the print head is driven to discharge ink to print an image on a medium (print medium). The print timing uses a linear encoder for detecting the position of the carriage and generates the ink ejection timing from the output signal, or assuming that the carriage is operating at a constant speed, every run time. Are configured to eject ink.

[0004]

In recent years, it has been necessary to increase the operation speed of the carriage in order to respond to the demand for higher printing speed. This is because the carriage speed during printing is increased to shorten the printing time.

On the other hand, the moving speed of the carriage during printing has conventionally been required to be as stable (constant speed) as possible. This is because, when the speed of the carriage at the ink ejection timing changes or the carriage shakes due to the change, the actual ejection position on the medium varies, which causes a problem in print quality.

Therefore, as the carriage is operated at a higher speed during printing, it is necessary to increase the acceleration distance of the carriage in order to secure constant speed. Obviously, the longer the acceleration distance, the larger the size of the apparatus body.

Here, a specific description will be given of how much the print quality deteriorates due to the speed change. When printing is started during acceleration, the velocity component of the ink ejection vector in the carriage movement direction changes. As shown in FIG.
The carriage movement direction 1 with respect to the ink ejection direction 101
02, the resultant vector becomes vector 10
4 and a vector 105. As a result, the position actually printed on the medium changes (in this case, a variation d in the print position occurs). Such a phenomenon occurs due to the movement of the head and the change in the speed of the carriage.

For example, when the distance between the print head and the medium is 1 mm and the ink ejection speed is 10 m / sec, the fluctuation in the moving speed of the carriage is 0.2 mm / sec.
In the case of c, the printing position varies by about 20 μm.
This is a shift of 1/4 pixel or more in the case of 360 dpi, and causes a change in tint in the case of color printing. Also, as shown in FIG. 16, when printing ruled lines, the ruled lines may appear discontinuous.

The present invention has been made in view of such a conventional situation, and suppresses variations in the printing position even when the carriage is shaken or the speed changes (distance d in FIG. 15).
Is reduced).

More specifically, it is an object of the present invention to provide a printing method in which the color of a color image and the discontinuity of ruled lines do not occur even when printing is performed in a non-constant speed area of a carriage.

[0011]

A print position correcting method according to the present invention is a method for correcting a print position in an ink jet recording type printing apparatus in which a carriage on which a print head is mounted is scanned in a direction perpendicular to a conveying direction of a recording medium. hand,
The speed information is sequentially detected at the time of scanning of the carriage, and based on the detected speed information, the printing position in the scanning direction is dynamically corrected at the time of scanning of the carriage. Also enables printing.

According to this configuration, for example, even if printing is started while the carriage is accelerating, it is possible to obtain an image in which the color of a color image does not change and no discontinuity of ruled lines occurs. In addition, despite having the high-speed printing function, the main body configuration can minimize the size of the device portion outside the printing area.

The correction of the printing position can be performed by, for example, delaying the timing of ink ejection from the print head by a predetermined time corresponding to the speed information.

An ink-jet recording type printing apparatus according to the present invention as an apparatus for realizing the above-described printing position correction method, includes a carriage on which a print head is mounted and a scanning direction of the carriage in a direction perpendicular to the transport direction of the recording medium. Carriage driving means, printing means for driving the print head in synchronization with the amount of movement of the carriage, and printing by discharging ink droplets from the print head, speed detecting means for detecting the moving speed of the carriage, Timing change means for changing the timing for driving the print head based on the moving speed of the carriage.

The speed detecting means includes a linear encoder for detecting the movement of the carriage, a means for counting an output signal of the linear encoder, and a table for determining a print timing delay amount in accordance with the count value. Wherein the timing changing means comprises:
Based on the value of the staple corresponding to the sequentially provided count value, a means is provided for adding a delay to the timing for driving the print head. This allows
By accurately detecting the moving speed of the carriage and correcting the ink ejection timing at that time, more accurate print correction can be performed. Further, by using a table for determining the delay amount of the print timing, there is an advantage that the arithmetic processing by the MPU is not required. This table may be a general-purpose table such as a ROM or a RAM, or may be incorporated in a custom ASIC in some cases.

According to another aspect, an ink jet recording type printing apparatus according to the present invention includes a carriage on which a print head is mounted, a carriage driving means for scanning the carriage in a direction perpendicular to the direction of transport of the recording medium, and a carriage. A printing unit that drives the print head in synchronization with the movement amount of the print head and performs printing by discharging ink droplets from the print head, and a timing that changes the timing of driving the print head based on the detected moving speed of the carriage Changing means, wherein the carriage driving means has a stepping motor driven based on an acceleration table, and the timing changing means corresponds to the acceleration table of the stepping motor, and sequentially changes the timing for driving the print head. It is characterized by adding a delay. this is,
It is suitable for use in a device that does not have a linear scale for a linear encoder. With this configuration, high-speed and high-quality images can be obtained at low cost.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a printing apparatus according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the appearance of an ink jet type color plotter using the printing position correcting method of the present invention.

In FIG. 1, a plotter 1 includes a caster 2
It is fixed on a stand 2 with a. Plotter 1
Is provided with an operation unit 3 for a user to perform the operation, and various switches and the like installed on the operation unit 3 indicate a recording medium type, online / offline, a command, printing start, and the like. The recording medium inserted into the recording medium insertion slot 4 in the direction of arrow A is conveyed to the inside of the plotter 1 based on an input instruction from the operation unit 3, and a color image is recorded based on data provided from an external computer or the like. Printed on the medium. The recorded recording medium is discharged in the direction opposite to the arrow A from the discharge port at the top front of the plotter 1.

Next, referring to FIG. 2, the details of the printing function of the plotter 1, the transport path of the recording medium and the printing process will be described.

FIG. 2 is a perspective view showing a path from insertion to ejection of a recording medium by cutting out a part of FIG. In the plotter 1, a sheet-shaped recording medium (large-size cut paper) inserted from the recording-medium insertion slot 4 and a recording paper 6 (roll paper) wound in a roll and mounted inside a roll paper cover 7.
Can be printed on any of Here, the recording medium insertion port 4
A description will be given of the transport path of the cut sheet inserted from the above. Only the entrance is different for roll paper, and the other parts are the same as cut paper.

The user operates the roll paper cover 7 for the roll paper 6.
A leading end of a recording medium (for example, a large-sized cut sheet) is placed on the recording medium, and is inserted into the recording medium insertion port 4 in the direction of arrow A. The inserted recording medium passes between the roll paper cover 7 and the upper guide 8 and is conveyed to the upper portion of the printing plate 13 while being sandwiched by both the paper conveyance rollers 10a and 10b and the driving roller 12. . Here, printing is performed on the recording medium.

The plotter 1 has a carriage 17 which reciprocates in the direction of arrow B. The carriage 17 has a head holder 18. This head holder 18
Is mounted with a plurality of print heads 19 containing color inks (for example, black, cyan, magenta, and yellow inks). The carriage 17 is fixed to a belt 20 hung on a drive motor (not shown), and the belt 20 reciprocates in the direction of arrow B by forward and reverse rotation of the drive motor. When the belt 20 moves in the direction of the arrow B, the carriage 17 is guided by the guide rails 21 behind it, and reciprocates in the direction of the arrow B. Further, a linear scale sensor (FIG. 3) for detecting the position of the carriage 17 is provided on the carriage 17, and a linear scale 22 having equally spaced slits detected by the linear scale sensor 23 is provided between the belt 20. Is equipped with The slit pitch of the linear scale 22 corresponds to the printing density.
DPI (Dots PerInch). A linear encoder is configured by the linear scale 22 and the linear scale sensor 23. A home position sensor 24 for detecting the home position of the carriage 17 is provided at a predetermined position in the plotter 1.

At the time of printing, the recording medium is transported intermittently in a direction perpendicular to the arrow B. When forming an image on a recording medium, the recording medium is temporarily stopped, and while the carriage 17 is reciprocated in the direction of arrow B, an image forming area corresponding to the movement path of the print head 19 on the recording medium. Then, based on the image information input to the print head 19, ink droplets are ejected in synchronization with the output signal from the linear scale sensor 23, whereby an image of one band (band-like portion) is formed. Thereafter, the recording medium having a predetermined length is conveyed to form an image for the next band in a new image forming area. This operation is repeated a required number of times in the length direction of the recording medium. Thereby, the recording medium on which the color image is formed is
The paper is discharged according to a discharge guide 26 while being held between the discharge roller 14 and the spur 15. The spur 15 is the spur plate 1
6 rotatably supported.

The main part of this embodiment is that, when ink droplets are ejected in synchronism with the output signal from the linear scale sensor 23, the ejection timing is delayed according to the speed of the carriage so that the printing position is reduced. The point is to make corrections.

Next, details of the correction method will be described. FIG. 3 is a control block diagram of the ink jet color plotter according to the present embodiment. Referring to FIG. 3, a process from input of image data to data transfer to the print head will be described.

The image input control unit 31 receives an input of image data from the external interface. The image input control unit 31 immediately outputs a DMA request (DMA1) to the MPU 34. The MPU 34 DMA-transfers the image data to the image memory 32 accordingly, and outputs a DMA acknowledge (ACK1) to the image input control unit 31 at the same time.

The MPU 34 transfers image data to the head control unit 33 to start printing. The head controller 33 transfers print data to a print head (not shown) based on the count value of the linear scale signal input in synchronization with the movement of the carriage, and at the same time, performs printing by giving a print pulse to the head. .

When there is no more image data in the head controller 33, the head controller 33 sends a request for image data to the MP
This is performed for U34 (DMA2). The MPU 34 DMA-transfers the image data in the image memory 32 to the head control unit 33 in accordance therewith. By the repetition, the image data is sent to the print head to perform printing. MPU34,
Via a drive control unit 36, a transport motor 37 for transporting the recording medium and a carriage motor 38 for reciprocating the carriage are controlled.

The operation of the MUP 34 is realized according to a control program stored in the program memory 35.

FIG. 4 shows hardware for realizing a printing position correction method corresponding to the head controller 33 shown in FIG. The configuration of the head control unit 33 will be described together with its operation.

The linear scale counter 41 receives a linear scale signal (LA,
LB), and the window comparator 44 calculates
Based on this count value, a WIND signal indicating the print position range is generated for each head (Wind0, 1, Windn).
2, 3). LA and LB are pulse signals of opposite phases (FIG. 5).
), The movement direction of the carriage can be determined from the mutual relationship. The linear scale counter 41 counts up or down according to the moving direction of the carriage. The linear scale counter 41 clears the count value by the carriage home position sensor 24.

There is a speed detecting unit 42 for measuring the carriage speed in real time by measuring the pulse interval of the linear scale signal. A specific configuration example of the speed detection unit 42 will be described later.

On the other hand, the synchronization generator 43 generates a synchronization signal Trig, which is a reference signal for determining ink ejection timing, based on the linear scale signal. Based on the synchronization signal Trig and the window signals WIND0 to WIND3, the AND circuit 47 generates Trg0 to Trg3. These are input to the delay generation circuit 46. By giving a time delay to these signals Trg0 to Trg3 by the table 45, He
at_Trg0 to 3 are output. These Heat_
In synchronization with Trg0 to Trg3, the head drive signal BLOCK_ENB and Heat
Is output from the data buffer 49, and Head_DATA corresponding to the image data is output.

FIG. 5 is a timing chart of the signals of the respective units described with reference to FIG. Here, the width (pulse period) of the linear scale signal (LB signal) is measured to detect the speed of the carriage. Now, when the value of this pulse cycle is N, this value is reflected in the delay of DLY0 (N) that determines the pulse ejection timing immediately after. In addition, DLY1 to DLY1 are also determined by measuring the linear scale interval immediately before output.

Note that Trg0 to Trg3 are respectively Wind
Valid and output when 0-3 are high. Heat
_Trg0 to 3 are respectively obtained by delaying Trg0 to 3 by a predetermined time.

As shown in FIG. 6, finally, Heat
BLOCK_ENB, Heat, Head, which are signals for actually driving the print head in synchronization with _Trg0 to 3
_DATA is output to the print head. BLOCK_E
NB is a signal for selecting a nozzle of the print head. He
at is a discharge pulse for driving the print head. He
ad_DATA is image data corresponding to the print nozzle.

FIG. 7 shows a specific configuration example of the speed detection unit 42. In this example, the speed detection unit 42 includes a count controller 411 that receives the linear scale signals LA and LB, and an 8-bit counter that receives the CNT_ENB signal and the CNT_CLR signal from the count controller 411 and an external fixed-speed Speed_CLK signal. 412.

FIG. 10 is a timing chart of signals of each part of the speed detecting section 42. Count controller 4
11 detects the rising of the linear scale signal LA and outputs a CNT_CLR signal. This CNT_CLR
The signal is input to the CLR terminal of the 8-bit counter 412. The count controller 411 also outputs the linear scale signal L from the rising of the linear scale signal LA.
CNT_E for detecting time until rise of B
Outputs the NB signal.

That is, the speed detecting section 41 uses the CNT
By counting the number of Speed_CLKs of a fixed period input during the High period of the _ENB signal,
The carriage speed immediately before the Trig signal can be detected. It can be easily understood that the greater the value v of the output SP_DT of the 8-bit counter 412, the lower the speed.

FIG. 8 shows a specific configuration of the table 45 shown in FIG. The substance of the table 45 is a memory, and can be realized by an SRAM, a PROM, a FLASH memory, or the like. In other words, the count value SP_DT is used as an address, and the corresponding delay data is written in advance in the storage location corresponding to the address, thereby obtaining the count value SP_DT.
_DT and the delay data DLY_DT can have a one-to-one correspondence.

FIG. 9 shows a configuration example of the delay circuit 46 shown in FIG. The delay circuit 46 includes an 8-bit counter 461 and a differentiating circuit (D flip-flop 462 and AND gate 463). When the Trg signal is input to the delay circuit 46, the 8-bit counter loads the delay data DLY_DT,
The down-counting of the DLY-CLK signal at a predetermined constant cycle is started. Thereafter, when the count value reaches 0, the counter 461 outputs RC (ripple carry). At this time, at the same time as the counter 461 stops counting, the rising edge of RC is output as a Heat_Trg pulse 467. Thus, the output timing of Heat_Trg can be uniquely determined by DLY_DT. As DLY_DT is larger, RC
It can be easily understood that the time until the output of the signal becomes longer and the delay amount until the output of the Heat_Trg becomes larger than the Trg signal.

In the above embodiment, the printing timing is determined depending on the linear scale signal. However, a printing apparatus having a simpler configuration may not have a linear scale. In this case, a similar effect can be obtained by using a two-phase pulse motor (stepping motor) as the carriage motor and inputting the drive pulses as LA and LB. The excitation method can also be applied to two-phase excitation, 1-2-phase excitation, and microstep.

FIG. 11 shows the embodiment. FIG.
FIG. 4 is a drive configuration diagram of the stepping motor, and the excitation pattern is output from the MPU 34. The motor driver 36 supplies a drive current to the carriage motor 38 according to the excitation pattern.

FIG. 12 shows a typical excitation pattern. In addition, there are various excitation patterns such as micro-step driving, but they are not shown. In any case, since the rotation angle for one step is accurate due to the characteristics of the stepping motor, the moving distance of the carriage also corresponds to the step. Therefore, by counting the steps, the movement amount of the carriage, the position of the carriage, and the ejection timing of the print head can be calculated.

Further, since the speed of the carriage can be predicted in advance by the driving table of the pulse motor, a configuration in which the data of the delay 45 is written from the MPU 34 in real time is also possible.

FIG. 13 shows an example of the configuration of a head controller 33 'in another embodiment employing such a method of determining delay data. The feature of this embodiment is shown in FIG.
In this configuration, the speed detection unit 42 and the table 45 are deleted, and the circuit scale is reduced. A register 130 is provided instead of the delay circuit 46 shown in FIG. The A / B phase counter 41 has the same configuration and function as the linear scale counter 41 of FIG.

When it is not necessary to correct the printing position (printing timing) at every printing timing of one dot, for example, when the ejection is started from a place where the speed difference from the target speed is relatively small, the correction is performed at a fixed interval. , For example, 1
Even if the correction is performed every 0 to 30 dots, there is a case where the result is not inferior. In such a case, the timing of the change may be several milliseconds to several tens of milliseconds.
DLY_DT can be written from 34 directly into the register 130.

In the acceleration curve of the stepping motor shown in FIG. 14, the DLY_DT corresponding to each position of the carriage at a predetermined position (distance from the home position) Ln, Ln + 1, Ln + 2,. When the MPU 34 writes the data into the register 130, the print position can be corrected. The timing of Ln is determined in synchronization with the output timing of the excitation pattern.
DLY_DATA can be directly output from the PU.

Although the preferred embodiment of the present invention has been described above, various modifications and changes are possible. For example,
In the embodiment of FIG. 13, it is assumed that a linear scale is not used. However, a linear scale signal may be used as an input to the counter 41 and the synchronization generator 43.

[0051]

According to the present invention, even when printing is performed during non-constant-speed scanning of the carriage, it is possible to obtain an image in which the color of the color image does not change and the ruled line does not have discontinuous points. As a result, high-speed printing becomes possible.

In spite of performing high-speed printing, the size of the main body can minimize the device portion outside the printing area.

[0053]

[Brief description of the drawings]

FIG. 1 is an external view of an ink jet color plotter as an example of a printing apparatus using a print correction method of the present invention.

FIG. 2 is a perspective view showing a printing function part of the apparatus of FIG.

FIG. 3 is a control block diagram of the apparatus of FIG. 1;

FIG. 4 is a block diagram showing a hardware configuration for realizing a print position correction method corresponding to the head control unit 33 shown in FIG. 3;

FIG. 5 is a timing chart of signals of respective units described in FIG.

FIG. 6 is a timing chart of signals of other parts described in FIG.

FIG. 7 is a block diagram showing a specific configuration example of a speed detection unit 42 shown in FIG.

FIG. 8 is a block diagram illustrating a specific configuration example of a table 45 illustrated in FIG. 4;

FIG. 9 is a block diagram showing a configuration example of a delay circuit shown in FIG. 4;

FIG. 10 is a timing chart of signals of each unit of the speed detection unit 42.

FIG. 11 is a drive configuration diagram of a stepping motor that can be used in the embodiment of the present invention.

FIG. 12 is a waveform diagram showing a typical excitation pattern of a stepping motor.

FIG. 13 is a block diagram illustrating a configuration example of a head control unit 33 ′ according to a second embodiment that employs another method of determining delay data.

FIG. 14 is a graph showing an acceleration curve of a stepping motor.

FIG. 15 is an explanatory diagram for explaining a conventional problem.

FIG. 16 is an explanatory diagram for explaining a conventional problem.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Plotter, 2 ... Stand, 3 ... Operation part, 4 ... Medium insertion opening, 5 ... Dust cover, 6 ... Roll paper, 7 ... Roll paper cover, 8 ... Upper guide, 10a, 10b ... Paper transport roller, 12 ... Drive roller, 13: printing plate, 14: discharge roller, 15: spur, 17: carriage, 18: head holder, 19: print head, 20: belt, 21: guide rail, 22: linear scale, 23: linear scale sensor 24 home position sensor 26 discharge guide 31 image input unit 32 image memory 33 head control unit 34 MPU 35 program memory 3
6: drive control unit, 37: transport motor, 38: carriage motor, 41: linear scale counter, 42: speed detection unit, 43: synchronization generation unit, 44: window comparator, 45: table, 46: delay circuit.

Claims (5)

[Claims] 1. A printing position correcting method for an ink jet recording type printing apparatus in which a carriage equipped with a print head is scanned in a direction orthogonal to a conveying direction of a recording medium, wherein speed information is sequentially detected during scanning of the carriage. Based on the detected speed information, the printing position in the scanning direction is dynamically corrected at the time of scanning of the carriage, thereby enabling the printing to be performed even in the non-constant speed scanning area of the carriage. Correction method. 2. The print position correction method according to claim 1, wherein the print position is corrected by delaying the timing of ink ejection from a print head by a predetermined time corresponding to the speed information. 3. A printing apparatus of an ink jet recording system, comprising: a carriage on which a print head is mounted; a carriage driving means for scanning the carriage in a direction orthogonal to a conveying direction of a recording medium; Printing means for printing by driving the print head and ejecting ink droplets from the print head, speed detecting means for detecting the moving speed of the carriage, and controlling the print head based on the detected moving speed of the carriage. And a timing changing means for changing a driving timing. 4. The speed detecting means includes: a linear encoder for detecting a movement of a carriage; a means for counting an output signal of the linear encoder; and a delay amount of print timing corresponding to the count value. The timing change means is configured to add a delay to a timing for driving a print head based on a value of the table corresponding to the sequentially provided count value. Printing device. 5. An ink jet recording type printing apparatus, comprising: a carriage on which a print head is mounted; carriage driving means for scanning the carriage in a direction perpendicular to the direction of transport of the recording medium; Printing means for printing by driving the print head and ejecting ink droplets from the print head, and timing changing means for changing the timing for driving the print head based on the detected moving speed of the carriage. Wherein the carriage driving means has a stepping motor driven based on an acceleration table, and the timing changing means corresponds to the acceleration table of the stepping motor and sequentially adds a delay to the timing of driving the print head. A printing device characterized by the above-mentioned.