JP2002254707A - Printer and its controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printer capable of printing in high image quality even a print head is in acceleration or deceleration. SOLUTION: A controller having a delayed circuit 21 using a shift register in which a plurality of flip-flop circuits are serially connected and a timing control part 12 having a selector 22 which can supply a timing pulse Di to an input side of an appropriate flip-flop F(i) in accordance with a rotational speed of a motor is adopted. As a delayed signal D0 corresponding to the timing pulse Di inputted to the delayed circuit 21 is surely to be outputted from the last flip-flop F(n-1), missing or duplication of the pulse does not occur even if a delayed amount is changed, an appropriate delayed amount of pulse can be obtained all the time, and consequently the deterioration of print quality is prevented even during printing in acceleration or deceleration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for controlling a printing apparatus, such as a print head of a serial printer, which performs printing by reciprocating a print head, the speed of which changes during printing.

[0002]

2. Description of the Related Art Many of the current ink jet printers are so-called serial type printers which perform printing by reciprocating a print head along a shaft. In this printer, printing is performed by ejecting ink droplets from the print head when the print head is moving at a constant speed along the shaft, but the print head is accelerated or decelerated for printing at a higher speed. Sometimes printing is performed. While the print head is moving at a constant speed, the distance in the scanning direction from the ejection of ink droplets to the arrival at the printing paper is constant, whereas when the speed of the print head changes, The distance from when the ink droplet is ejected to when it reaches the printing paper changes and becomes shorter. Therefore, in order to print at a desired position during acceleration / deceleration of the print head, printing must be performed at a target position without delaying the timing at which ink droplets are ejected in synchronization with the speed control signal of the motor that drives the print head. Can not do.

FIG. 4 shows how an ink jet printer controls the rotation speed of a motor that controls the speed of a print head. When the inkjet head 3 reciprocates in the section A0 between one end P1 and the other end P2 of the carriage shaft 2, it moves at a constant speed in the central section A1, but moves in the areas A2 and P2 near the ends P1 and P2. In A3, the head 3 needs to be accelerated and decelerated. If the moving speed of the head 3 is increased, the areas A2 and A3 where acceleration and deceleration are increased, and if an area where printing can be performed by a compact printer is to be secured, printing is performed even in the areas A2 and A3 where acceleration and deceleration are performed. There is a need to do.

In the acceleration and deceleration areas A2 and A3, as shown in FIG. 5A, the area A1 is moving at a predetermined speed as shown in FIG.
The time it takes to reach the printing paper after the ink droplet is ejected is reduced. Therefore, it is necessary to delay the timing of ejecting ink droplets by an appropriate time Td.

[0005]

Therefore, a circuit for delaying the timing of ejecting ink droplets is required. However, a strobe signal from the CPU is delayed based on the data of the address decoder, and the delayed signal is stored in a memory or the like. A delay line used for outputting to another circuit can be used. This delay line is shown in FIG.
As shown in the figure, a shift register 110 in which n RS flip-flops F (n) are connected in series, and each flip-flop F (n) configuring the shift register 110
Is output to the delay signal D based on the delay select signal S0.
The multiplexer 112 includes a multiplexer 112 that selects and outputs 0 and a reset signal generator 111 that resets the state of each flip-flop F (n) by a reset signal S. Therefore, the delay line 100 having such a configuration is used.
A timing pulse train for controlling the timing at which ink droplets are ejected is placed in the flip-flop F (1) at the first stage of
By selecting the delay signal D0 output from the multiplexer 112 by the delay select signal S0 synchronized with the motor speed control signal, it is possible to obtain a delayed pulse train corresponding to a change in the speed of the print head.

By using the delay line as a means for delaying the timing pulse of printing, a control circuit capable of printing even during acceleration or deceleration of the print head can be constructed. However, when the delay line having the above configuration is used, some problems occur. First, there is a possibility that a pulse drop may occur. As shown in FIG. 7, the delay signal D0 is switched by the delay select signal S0 output during the ink ejection timing pulse Di, but the delay signal D0 is output before the delay signal D0 corresponding to the timing pulse Di is output. When the select signal S0 is output, the delay signal D0 is not output. That is, at time t1, the timing pulse Di is applied to the delay line 100.
When a delay select signal S0 for selecting a delay signal having a delay amount shorter than the time difference between time t1 and time t2 is input at time t2, a delay signal corresponding to the timing pulse Di at time t1 is input. D0 is ignored and not output. Such a phenomenon rarely occurs when the delay amount Td is equal to or less than the period (print period) T0 of the timing pulse Di, but tends to occur when the delay amount Td exceeds the print period T0. It can be said that it is difficult to control the pulse delay exceeding the print cycle.

Conversely, when a delay select signal S0 for selecting a delay signal having a long delay is input after a delay signal D0 corresponding to a certain timing pulse Di is output, the timing pulse Di from which the delay signal is output is input. May be output again. Therefore,
In spite of the delay, the timing pulse is output in a short cycle. Such a drop in the pulse or a shift in the amount of delay of the timing pulse leads to a shift in the position of the dot constituting the image, which causes unevenness or streak-like pattern of the image, which causes deterioration in image quality. . Controlling the output timing of the delay select signal S0 or reducing the change in the delay amount Td may prevent these phenomena. However, adding a circuit for controlling the timing of the delay select signal S0 increases the number of circuits and is not economical.
Further, if the amount of change in the delay amount Td is limited, the acceleration of the print head is limited, so that it is difficult to improve the printing speed.

Accordingly, an object of the present invention is to provide a control device capable of controlling a delay amount of a timing pulse so as not to cause a missing or a shift of a timing pulse which leads to unevenness of an image. The present invention provides a control device that can reliably and simply control the timing of printing in synchronization with a change in the speed of a carriage motor of a print head, etc., and accelerates and decelerates the print head with a large acceleration at low cost. Another object of the present invention is to provide a printing apparatus capable of printing a high-quality image in addition to a printing apparatus.

[0009]

Therefore, in the present invention, the amount of delay is determined by selecting the input to the delay element, instead of selecting the output from the delay element and determining the amount of delay. In order to prevent a pulse from being skipped or to be duplicated. That is, in the control device of the present invention having a delay circuit capable of delaying and outputting a signal for controlling printing timing, the delay circuit includes a plurality of serially connected delay elements and a signal for controlling timing. There are provided selection means for selectively supplying each input of the delay element, and means for outputting the output of the final or predetermined delay element as a signal for controlling the delayed timing. The delay element that is the output stage does not need to be final if it is determined in advance,
Hereinafter, the case where the output is performed from the last delay element will be described. The delay element may be a resistor or the like, but a flip-flop constituting a shift register is suitable as a device capable of controlling the delay amount with high accuracy.

According to the delay circuit of the present invention, a signal for controlling timing, that is, a timing pulse or a timing signal Di is input to the input of the delay element, and is output as a signal delayed from the last delay element, that is, the delay signal D0. Is done. Therefore, no pulse is extracted in the middle of the delay by the delay element, so that the input timing pulse or timing signal Di is all output, and the pulse is not dropped or output redundantly.
Therefore, as described above, even when it is necessary to control the delay amount exceeding the print cycle, the delay pulse does not fall out. In addition, even if the delay amount is largely changed, no missing or overlapping pulses occur, and the relationship between the timing pulses does not shift. Therefore, even if the amount of delay of the timing pulse is changed, it is possible to output the signal at a desired timing with high accuracy.

For this reason, in a printing apparatus having means for printing based on the delay signal output from the control device of the present invention, the selection means of the control device determines whether the relative speed between the printing means and the printing paper is relative. By selecting the supply destination of the timing pulse in synchronization with the change, it is possible to reliably output the delay signal whose delay amount has changed in response to the change in the speed of the printing unit without missing or overlapping pulses.
Therefore, with a simple and low-cost configuration without providing an extra circuit for controlling the timing of the signal for controlling the selection means, a timing signal having a delay amount corresponding to the acceleration and deceleration of the printing speed at high acceleration is provided. A printing device that can output and print high-quality images at high speed can be provided.

The change in speed in the printing means may be in the paper feed direction. However, as described above, in a serial type printing apparatus, acceleration and deceleration are repeated each time the print head reciprocates in the scanning direction. The effect of the control device according to the present invention is great, and it is possible to print an image with higher speed and stable image quality. A printing device of a serial type, in which the delay amount needs to be controlled by the control device of the present invention, is a device in which a gap is opened between the print head and the printing paper. The timing for ejecting ink droplets is controlled by a signal for controlling the timing, and when the print head is of the wire dot type, the timing for operating the wire pin is controlled by the signal for controlling the timing.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings. FIG. 1 shows an outline of a printer that performs printing while controlling a delay amount of a timing pulse according to a speed of a print head by a control device of the present invention. The printer 1 of the present embodiment includes a carriage 10 that reciprocates in the scanning direction X along the shaft 2, an inkjet head 3 that is mounted on the carriage 10 and reciprocates in the scanning direction X,
It has a motor 5 for reciprocating the carriage 10 in the scanning direction X via an appropriate mechanism such as a timing belt, and a control device 7 for controlling the entire printer including speed control of the carriage 10. The printer 1 according to the present embodiment includes the ink droplets 3a from the nozzles 3b of the head 3 not only in the area where the inkjet head 3 is moving at a constant speed but also in the area where the inkjet head 3 is being accelerated or decelerated near the left and right home positions. And print data φ sent from the host 4
1 is printed on a sheet 9.

For this reason, the control device 7 of the present embodiment
Decodes the print data and control commands sent from the printer, outputs a control signal φ2 for the inkjet head 3, and outputs a timing pulse Di for discharging ink droplets.
And a motor 5 for controlling the speed at which the head 3 moves in the scanning direction according to the control signal φ2.
A motor control unit 11 capable of controlling the rotation speed of the
3 or a timing pulse Di generated from a pulse generator provided in the printing apparatus, etc., is converted into a pulse train D0 having a delay amount corresponding to the rotation speed of the motor 5, and is supplied to the ink jet head 3 so that the ink droplet 3a is appropriately converted. And a timing control unit 12 for discharging at a timing.

FIG. 2 shows the timing control section 12 of the present embodiment in more detail. The timing control unit 12 outputs a delay circuit 21 using a shift register in which n flip-flops F (0) to F (n−1) are connected in series, and a timing pulse Di supplied to the timing control unit 12. Based on a control signal φ3 of the motor 5 from the motor control unit 11, a predetermined flip-flop F (i) (i is 0 to n−1)
Selector 2 that can select and supply the input side of
2 is provided. The input D of each flip-flop F (i) of the delay circuit 21 is connected to the preceding flip-flop F (i).
-1) is supplied from an OR gate 23 which takes a logical sum of a signal from the output Q and a signal from the selector 22;
When the timing signal Di is not supplied from the selector 22, the signal output from the preceding flip-flop F (i-1) is latched and output at the next clock (CLK). The input of the first flip-flop F (0) is the signal Di from the selector 22 and the flip-flop F (0).
A signal for clearing (0), for example, a logical sum with "0" for one bit, and a flip-flop F if there is no signal Di from the selector 22
(0) is cleared and propagates to the flip-flop F (i) at the subsequent stage. Further, the output of the last-stage flip-flop F (n-1) is the output of the timing control unit 12, and the delay signal D0 in which the timing pulse Di is delayed by a predetermined time is output.

Therefore, in the delay circuit 21 of this embodiment, each flip-flop F (i) is connected to the timing pulse Di.
Is delayed by one clock. When the selector 22 selects the flip-flop F (i) that supplies the timing pulse Di according to the motor rotation speed by the motor control signal φ3, the selector 22 selects the flip-flop F (i) according to the motor rotation speed. 1
A delayed signal D0 delayed by n clocks from the clock can be output. Further, the signal Di from the selector 22 is applied to the output of the flip-flop F (n−1) of the last stage.
By inserting a gate that takes the logical sum of the above, it is possible to output a delayed signal D0 delayed by n clocks from 0 clock.

FIG. 3 is a timing chart showing the manner in which the timing pulse Di is output as a delay signal D0 delayed by a desired time by the timing control section 12 of the present embodiment. In the timing control unit 12 of the present example, for example, the signal Di input at the time t11 is output from the selector 22 by the selector 22 on the input side of the flip-flop F (n−5).
Supplied to the R gate 23, and after shifting or transmitting five flip-flops, the last flip-flop F
(N-1) is output as a delay signal D0. Also,
The signal Di input at time t13 is supplied by the selector 22 to the OR gate 23 on the input side of the flip-flop F (n-3), and after being shifted by the three flip-flops, is output as the delay signal D0.

As described above, the timing control unit 12 of this embodiment
At time t1 when the timing signal Di is input
1 to the flip-flop F supplied by the selector 22
(I) is selected and supplied to the flip-flop. Thereafter, the supplied signal is transmitted from the selected flip-flop F (i) to the subsequent flip-flop according to the shift pulse (clock signal CLK), and from the final flip-flop F (n-1). Is output. Therefore, the input timing signal Di
Is always output from the last flip-flop F (n-1) as the delay signal D0. Therefore, the selector 22 is switched by the motor control signal φ3 at any timing after the time t11 when the timing signal Di is input, and the timing pulse Di is not lost even if the delay amount Td1 is changed to the delay amount Td2. . Therefore, control of the delay time exceeding the print cycle T0 can be performed reliably and easily.

However, the flip-flop F at the subsequent stage
(I), the selector 22 outputs the next timing signal D from the selector 22 at the same timing as latching a certain timing signal Di output from the preceding flip-flop F (i-1).
When i is supplied, the timing signal Di is lost. However, such a case is limited to the case where the delay amount is changed so that the delay signals match, so it is not a circuit problem, and the software is used to select the delay amount so that the delay signals do not match. Alternatively, it is necessary to adjust the motor control method.

Similarly, since the delay signal D0 corresponding to the timing pulse Di input to the delay circuit 21 is output only from the last flip-flop D0, the delay signal D0 corresponding to a certain timing pulse Di overlaps. There is no possibility of being output. Therefore, the control circuit 7 including the timing control unit 12 of the present example can reliably obtain the delay signal D0 delayed by a predetermined amount without dropout or duplication of the pulse without being influenced by the timing of switching the delay amount. it can. Therefore, the motor control signal φ3
There is no need to provide a circuit for adjusting the timing of supplying the delay, and control for switching the delay amount can be realized with a simple circuit configuration. Further, the pulse width at the time of switching the delay amount is not limited as long as the delay signal is not output at the same timing. Even if acceleration / deceleration of the carriage motor 5 is performed at a high acceleration, the pulse width is desired. Delay signal D so that ink droplets are ejected at the timing
0 can be output. Therefore, by employing the control circuit 7 of the present embodiment, a printing pulse having an appropriate delay amount can always be obtained at an appropriate timing even when the delay amount is changed. ,
A low-cost printer 1 capable of high-speed printing can be provided.

The delay element may be a resistor, a transistor switch, or the like. Of course, a shift register in which a plurality of flip-flops are connected in series like the delay circuit 21 of the present embodiment has the simplest configuration and high accuracy. It is excellent in that the amount of delay can be controlled. In the above description, the present invention has been described based on an ink jet printer. However, even in a dot impact printer that projects a wire pin from a print head and prints on paper, the wire is controlled according to the moving speed of the print head. Therefore, it is possible to provide a low-cost printer capable of high-speed printing with the same configuration as described above.
Furthermore, although a serial type printer is described as an example of the printing apparatus, the present invention can be applied to a facsimile or a copier. In addition to the serial printer in which the print head reciprocates, even in a line printer, there is an area where the paper feeding speed is accelerated and decelerated, and when printing is performed in that area, the present invention is applied to print at higher speed. It is possible to do.

[0022]

As described above, in the control device of the present invention, when the timing signal for controlling the ink droplet or the wire pin is delayed by using the shift register,
A delay amount is controlled by selecting a position for supplying or inputting a timing signal to a flip-flop which is a delay element constituting a shift register, so that a delayed signal is output from the final flip-flop.
Therefore, the timing pulse for printing is always output from the last flip-flop, so that the timing pulse is not lost or output redundantly. For this reason, by employing the control device of the present invention, it is possible to provide a printing device capable of high-speed printing without deteriorating the print quality even if the delay amount of the timing pulse is changed according to the acceleration / deceleration of the motor. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a printer according to the present invention.

FIG. 2 is a diagram illustrating a schematic configuration of a timing control unit of the present example.

FIG. 3 is a timing chart illustrating how a timing pulse is delayed by the timing control unit of the present example.

FIG. 4 is a diagram showing an outline of printing by an inkjet head according to acceleration / deceleration of a motor.

FIG. 5 is a diagram illustrating a state in which the distance at which ink droplets ejected from an inkjet head lands on paper changes when the rotation speed of a motor changes.

FIG. 6 is a diagram illustrating an example in which a delay line is used as a delay circuit of a printer.

FIG. 7 is a timing chart showing how a pulse drop occurs by the delay circuit shown in FIG. 6;

[Explanation of symbols]

 Reference Signs List 1 printer 2 shaft 3 print head 3a ink drop 5 motor 9 paper 11 motor control unit 12 timing control unit 21 delay circuit 22 selector 23 OR gate CLK clock signal (shift pulse) F (i) flip-flop

Claims (6)

[Claims] 1. A control device having a delay circuit capable of delaying and outputting a signal for controlling a timing for printing, the delay circuit comprising: a plurality of delay elements connected in series;
Selecting means for selectively supplying the signal for controlling the timing to each input of the delay element, and means for outputting a final or predetermined output of the delay element as a signal for controlling the delayed timing Control device. 2. The control device according to claim 1, wherein the delay element is a flip-flop constituting a shift register. 3. The control device according to claim 1, further comprising: a unit that performs printing based on a signal that controls the delayed timing of printing, wherein the selecting unit includes the printing unit and printing paper. A printing apparatus for selecting a supply destination of a signal for controlling the timing in synchronization with a change in relative speed of the printing apparatus. 4. The printing apparatus according to claim 3, wherein the printing unit is a print head that reciprocates in a scanning direction, and the selecting unit selects a supply destination of a signal for controlling the timing according to a speed of the print head. Printing device. 5. The printing apparatus according to claim 4, wherein the print head is of an ink jet type, and the timing control signal controls a timing at which ink droplets are ejected. 6. The printing apparatus according to claim 4, wherein the print head is of a wire dot type, and the signal for controlling the timing controls timing for operating a wire pin.