JPH0524264A - Printing timing correction method in serial dot printer - Google Patents

Abstract

PURPOSE:To improve the printing quality and to prevent the breakage of a printing head by a method wherein successive pulse-to-pulse time intervals for a fixed number of encode output pulses and the average value thereof are evaluated, and based on the difference between the both, a timing position of each encode output pulse is corrected. CONSTITUTION:A rising detection part 15 generates a rising pulse at the rising edge of an encode output pulse. A time interval detection part 16 measures intervals between the successive rising pulses. An average time interval detection part 17 takes the average of time intervals between rising pulses of a fixed number just before to find an average time interval as a reference. A comparing part 18 compares a time interval at every rising pulse with the average time interval. A variable delay part 19 adjusts a delay amount based on a time difference resulting from the comparison so that a time interval of successive rising pulses is equal to the average time interval. In this manner, a pulse train of a constant cycle outputted from the variable delay part 19 is used as a printing timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting the timing of dot printing in a serial dot printer. In the serial dot printer, the dot drive of the print head is performed based on the print data while the carrier having the print head moves in the row direction at a constant speed. The present invention improves the print irregularity by correcting the timing variation of dot printing.

[0002]

2. Description of the Related Art FIG. 7 shows the configuration of a conventional serial dot printer. In the figure, 1 is a motor, 2 is an encoder for speed detection, 3 and 4 are pulleys connected to the motor shaft, 5 is a belt, 6 is a carrier driven left and right by the belt 5, and 7 is mounted on the carrier. Print head, 8
Is a platen, 9 is a paper, 10 is a print control unit, 11 is a motor drive circuit, 12 is a print head drive circuit, and 13 is a print buffer.

The print control unit 10 controls the motor drive circuit 11 to start up the motor 1, the pulley 3 and the belt 5.
The carrier 6 is driven at a constant speed via the, the dot data is read from the print buffer 13 and supplied to the print head drive circuit 12. An encoder 2 for speed detection is directly connected to the shaft of the motor 1, and an encoder pulse output from the encoder 2 is supplied to a print head drive circuit 12 for dot drive of the print head (for example, in the case of a wire dot printer). Pinfire) used for timing.

By the way, the torque generated in the continuously driven motor 1 varies slightly due to the pole structure of the motor,
As shown by the solid line in FIG. 8A, a change in the periodicity appears in the rotation speed of the motor shaft. On the other hand, a pulley 3 is connected to the shaft of the motor 1, and a belt 5 is attached to the pulley 3.
The carrier 6 is driven via. Therefore, minute fluctuations caused by the rotation of the motor 1 are absorbed by the elasticity of the belt and are hardly transmitted to the print head 7 on the carrier 6. Therefore, the print head 7 can move smoothly as shown by the dotted line in FIG. FIG. 8B is an enlarged view of a part thereof.

However, since the print timing for dot-driving the print head 7 is determined based on the output pulse of the encoder directly connected to the motor 1, it changes according to the periodic fluctuation of the rotation of the motor 1.

FIG. 9 shows a conventional print timing generation process. 9 corresponds to the speed variation of FIG. 8 and FIG. 9 corresponds to the velocity fluctuation of the portion of FIG. In the figure, (a) is an encoder output pulse, and (b) is an encoder rising pulse generated from the encoder output pulse.
(C) is the pinfire timing (printing timing) of the print head.

As shown in the figure, when the motor speed increases, the print timing interval increases. That is, when the motor speed decreases, the print timing interval increases. For this reason,
The printing quality deteriorated due to the deviation of the periodicity in the position of the printed dots.

The deviation of the printing timing due to the fluctuation of the motor rotation as described above is also caused by noise, defective control system and the like, and sometimes a large periodic fluctuation may occur. If the print timing cycle becomes too large or too small, abnormal vibration or overheating may occur in the print head, resulting in damage to the print head.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to improve print quality and prevent damage to a print head by correcting a print timing deviation in a serial dot printer.

[0010]

SUMMARY OF THE INVENTION The present invention detects a deviation from an average value with respect to a time interval of encoder output pulses from a speed detecting encoder directly connected to a motor, corrects the deviation, and generates a print timing. Method and the fluctuation of the time interval of the encoder output pulse are monitored by the upper and lower limits set in advance.If the time interval of the encoder output pulse is within the upper and lower limits, the print timing is generated based on that. However, when it becomes larger than the upper limit value, it is replaced by the upper limit value to generate the print timing, and when it becomes smaller than the lower limit value, it is replaced by the lower limit value and the print timing is generated. is there.

The principle of the present invention will be described with reference to FIG. Figure 1
A is an explanatory view of the first method of the present invention, 15 is a rising edge detection unit of the encoder output pulse, 16 is a time interval detection unit, 17 is an average time interval detection unit, 18 is a comparison unit, 19 is a variable delay It is a department.

The rising edge detection section 15 generates a rising edge pulse at the rising edge of the encoder output pulse, and supplies it to the time interval detection section 16 and the variable delay section 19. The time interval detector 16 measures intervals between successive rising pulses, and the average time interval detector 17 averages each time interval between a fixed number of immediately preceding rising pulses to obtain a reference average time interval, It is supplied to the comparison unit 18. The comparison unit 18 compares the time interval of each rising pulse with the average time interval, and sends the time difference of the comparison result to the variable delay unit 19 so that the time interval of successive rising pulses becomes equal to the average time interval. Adjust the delay amount. In this way, the pulse train having a constant cycle output from the variable delay unit 19 is used as the print timing.

Next, FIG. 1B is an explanatory view of the second method of the present invention, in which 15 is an encoder output pulse rise detection section, 16 is a time interval detection section, 20 is an upper limit comparison section, and 21 is a lower limit comparison. 22 is an upper limit pulse generator, 23 is a lower limit pulse generator, and 24 is a multiplexer.

The rising edge detector 15 produces a rising edge pulse from the encoder output pulse and applies it to the time interval detector 16 and the multiplexer 24. Time interval detector 16
Detects the time interval of successive rising pulses and
Is applied to one input of each of the upper limit comparison unit 20 and the lower limit comparison unit 21.

Each of the upper limit comparing section 20 and the lower limit comparing section 21
Is input to each of the time interval upper limit value T_UAnd the lower limit value T
_LAnd the upper limit comparison unit 20 determines that T> T_U,under
The limit comparison unit 21 is T <T_LTo detect. These comparison parts 2
From the output of 0,21, T> T _U, T_U≧ T ≧ T_L, T <
T_LEach state of can be separated.

The upper limit pulse generator 22 generates an upper limit pulse at a timing position corresponding to the upper limit value T _U , and the lower limit pulse generator 23 generates a lower limit pulse at a timing position corresponding to the lower limit value T _L.

A rising pulse, an upper limit pulse, and a lower limit pulse of the encoder output pulse are input to the multiplexer 24, and these are selected based on the combination of the output values of the upper limit comparison unit 20 and the lower limit comparison unit 21.

That is, when T> T _U , the upper limit comparison unit 2
Only the output of 0 becomes '1' and the multiplexer 24 selects the upper limit pulse. When T _U ≧ T ≧ T _L , the outputs of both the upper limit comparison unit 20 and the lower limit comparison unit 21 are “0”.
Therefore, the multiplexer 24 selects the rising pulse from the encoder output pulse. When T < _TL , only the output of the lower limit comparison unit 21 becomes "1" and the lower limit pulse is selected by the multiplexer 24.

The pulse selected by the multiplexer 24 in this manner is used to set the printing timing.

[0020]

In the first method of the present invention shown in FIG. 1A,
By averaging the time intervals of the encoder output pulses that fluctuate cyclically depending on the fluctuations in the motor rotation speed, the center speed corresponding to the moving speed of the print head carrier is obtained. Correct the timing of the sequential encoder output pulses based on this average time interval (center speed),
Printing timing without deviation is generated.

FIG. 2A is an operation timing chart in the method of FIG. 1A. In the figure, (a) is an encoder output pulse, (b) is a rising pulse detected from the encoder output pulse, and (c) is a generated print timing.
The print timing is generated when the rising pulse is delayed by an amount td−Δt obtained by subtracting the timing error Δt from the constant delay amount td.

The timing error Δt is the amount of difference between the time interval between each rising pulse and the immediately preceding rising pulse and the average time interval. Δt = detection time interval−average time interval The average time interval is an average of the time intervals of the encoder output pulses detected in a period (n ≧ 2) that is n times the fluctuation cycle of the motor rotation speed. It can be a moving average up to the rising pulse or up to the current rising pulse.

The timing delay amount td-Δt becomes smaller when the detection time interval is larger than the average time interval and becomes large when the detection time interval is larger than the average time interval, whereby the timing fluctuation is corrected.

Next, in the second method of the present invention shown in FIG. 1B, the upper limit value T _U and the lower limit value T _L for monitoring the time interval of the encoder output pulse are set as fixed values, The print timing is generated by suppressing the fluctuation range of the timing position of the encoder output pulse within the range of T _U and T _L. The monitoring range of the time interval by T _U and T _L is updated every time the print timing is generated.

FIG. 2B is an operation timing chart of the method of FIG. 1A. In the figure, (a) is the encoder output pulse,
(B) shows the rising pulse, (c) shows the upper limit value T _U and the lower limit value T _L of the time interval, and (d) shows the generated print timing.

T_UAnd T_LIs for generating the print timing.
And the time interval of the next rising pulse (T_i)
Compared to T_i> T_UThen T_U, T_U≧ T ≧ T_LNa
Et T _i, T_i<T_LThen T_LPrint at each position of
Imming is generated.

In this way, the print timing is generated by correcting the time interval of each rising pulse between T _U and T _L.

[0028]

FIG. 3 shows the configuration of an embodiment according to the first method of the present invention. In the figure, 1 is a motor, 2 is an encoder, 15 is a rise detection unit, 25 is a time interval counter, 26 is a buffer, 27 is an average calculation unit, 28 is an average time interval register,
Reference numeral 29 is a comparison unit, 30 is a delay amount calculation unit, and 31 is a delay counter.

FIG. 4 is an operation timing chart of the embodiment shown in FIG. 3. The configuration of the embodiment of FIG. 3 will be described below with reference to FIG. The rotation of the motor 1 causes the encoder 2 to generate the encoder output pulse of FIG. 4A, and the rising edge detector 15 generates the rising edge pulse of FIG. 4B. The time interval counter 25 continuously counts clocks, outputs the count value at that time at each rising pulse of the encoder output, resets, and restarts clock counting. This count value represents the time interval of the rising pulse, is read for each rising pulse, and is sequentially stored in the buffer 26.

The average calculator 27 reads out the n pieces of data stored in the buffer 26 at the timing shown in FIG. 4D and averages them, and stores the resulting data in the average time interval register 28.

The comparison unit 29 takes the difference between the immediately preceding time interval and the average time interval, and calculates the error Δ at the timing of FIG. 4 (e).
Output t. The delay amount calculation unit 30 subtracts the error Δt from the fixed value td to obtain the delay amount (td−Δt), and loads it into the delay counter 31.

The delay counter 31 is loaded (td
The clock is subtracted and counted from −Δt), and at the timing when it reaches 0, the print timing is generated as shown in FIG.

FIG. 5 shows the configuration of an embodiment according to the second method of the present invention. In the figure, 32 is D. FF, 33 is a register, 34 is an AND gate, 35 is a hammer clock generation timer, 36 is an inverter, 37 is a lower limit value register, 3
8 is an upper limit register, 39 and 40 are comparators, 41 to 43 are JK. FF, 44 to 46 are D.I. FF, 4
Reference numeral 7 is a rise detection circuit, 48 is a fall detection circuit, 49 to 51 are AND gates, 52 is a NOR gate, 53 to 55 are OR gates, EPS is an encoder output pulse,
UPP is a lower limit pulse based on the lower limit value, DWP is an upper limit pulse based on the upper limit value, and HMCLK is a hammer clock.

FIG. 6 is an operation timing chart of the embodiment shown in FIG. The configuration of the embodiment of FIG. 5 will be described below with reference to FIG. The register 33 is set to "1" by the CPU when the operation starts, and the HMCLK generation function is enabled. The lower limit value T _L and the upper limit value T _U are set in the lower limit value register 37 and the upper limit value register 38 by the CPU. D. The value "1" of the register 33 is read into the FF 32 for each EPS of FIG. 6 (a). In the AND gate 1, the output of the inverter 36 is "1", that is, in FIG.
When HMCLK of (i) is “0”, D.I. If the output of the FF 32 is "1", a signal that becomes "1" is output as shown in FIG. 6 (b). When this signal is "0", the hammer clock generation timer 35 is reset, and when the signal becomes "1", the counting operation of the high-speed internal clock (not shown) is started. The count output of this timer is based on the generated HMCLK
The signal is changed to "0" by being fed back via 6, and is incremented by 1 every clock until the timer is reset, and is used as data for time scanning. The comparator 39 changes from "0" to "1" when the count output of the timer 35 exceeds T _L.

JK. The FF 41 outputs the signal shown in FIG. 6C according to the output states of the comparators 39 and 40. The rising detection circuit 47 and the falling detection circuit 48 are
From the rising and falling of the signal respectively, (d) of FIG.
The UPP and DWP shown in (e) are generated. UPP and D
Since WP corresponds to the lower limit value T _L and the upper limit value T _U , respectively, it is called a lower limit pulse and an upper limit pulse here.

The AND gate 49 sets "1" when the EPS is input while the signal is "1", that is, when the time interval T between the EPS and the immediately preceding EPS is T _U ≥T ≥T _L. Output and OR gates 53 and 54
To generate the first pulse of HMCLK of FIG. 6 (i). That is, in the AND gate 49, the signal is T
_It serves as a time window for detecting T between _U and _TL .

On the other hand, AND gate 49 and AND gate 5
1 detects T when T> T _U and T <T _L , respectively. At this time, the time windows used to detect T in the AND gates 50 and 51 are the signals shown in (f) and (h) of FIG.

When T <T _U , EPS occurs before UPP, so JK. The output of the FF 42 is "0", the DWP is "0", and the output of the NOR gate 52 is "1". As a result, D. "1" is set in the FF 45 at the timing of EPS, and the signal rises to "1". The signal remains "1" until DWP occurs, and when UPP is input to the AND gate 50 during this period, the output becomes "1" and the HMCLK signal is output via the OR gates 53 and 54.
Is output as. This is the second pulse in (i) of FIG. The third pulse of (i) is an example in the case of T _U ≧ T ≧ T _L similar to the first pulse.

Next, when T> T _U , the EPS is DWP.
Will be entered after. D. The FF 44 outputs "1" from the inverted output to the D.P. Input to FF46, D. FF4
The output signal of 6 becomes "1". After that, when DWP is input, a pulse output is generated from the AND gate 51 and O
The fourth HMCLK of (i) in FIG. 6 is generated from the R gate 54. At this time, the T
The output of the AND gate 51 prevents the occurrence of the same operation as in the case of < _TL . The FF42 is set to "1" and the output of the NOR gate 52 is set to "0". As a result, D. The FF 45 reads "0" by the subsequent ESP, holds the output signal at "0", and prohibits the operation of the AND gate 50. JK. FF42 is the same E
Since it is returned to "0" by PS, normal operation is performed for the next EPS.

The generated HMCLK is sent to the inverter 36
It is fed back to the input of the AND gate 34 via the, and the hammer clock generation timer 35 is reset, and T _L and T _U are reset.

JK. The FF 43 is set to “1” in each case of T> T _U and T <T _L , and turns on the NG flag indicating an abnormality.

[0042]

According to the present invention, it is possible to reduce the influence of the print timing due to the speed variation of the motor,
Highly accurate printing without print misalignment is possible. In addition, the print head is prevented from being damaged by suppressing the print drive in the cycle that is out of the standard of the drive cycle of the print head,
The cost can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an operation timing chart of the present invention.

FIG. 3 is a configuration diagram of an embodiment according to the first method of the present invention.

FIG. 4 is an operation timing chart of the embodiment according to the first method of the present invention.

FIG. 5 is a configuration diagram of an embodiment according to a second method of the present invention.

FIG. 6 is an operation timing chart of the embodiment according to the second method of the present invention.

FIG. 7 is a configuration diagram of a conventional serial dot printer.

FIG. 8 is a drive characteristic diagram of a motor and a carrier in a conventional printer.

FIG. 9 is an explanatory diagram of a print timing generation process of a conventional printer.

[Explanation of symbols]

15 Rise detector 16 time interval detector 17 Average time interval detector 18 Comparison Department 19 Variable delay unit 20 Upper limit comparison section 21 Lower limit comparison section 22 Upper limit pulse generator 23 Lower limit pulse generator 24 multiplexer

Claims (2)

[Claims] 1. A print head carrier is driven by a motor coupled via a belt, and the print head is driven based on a pulse output from a speed detection encoder directly connected to a rotation shaft of the motor. In a serial dot printer that generates a print timing, the time interval between successive pulses of a fixed number of encoder output pulses is measured, the average value of each measured time interval is calculated, and then the average of the time interval is calculated. A print timing correction method for a serial dot printer, which corrects a timing position of each encoder output pulse based on a difference between a value and a sequential time interval of the encoder output pulse to generate a print timing. 2. A print head carrier is driven by a motor coupled via a belt, and the print head is driven based on a pulse output from a speed detection encoder directly connected to a rotation shaft of the motor. In a serial dot printer that generates a print timing to be set, a fixed upper limit value and a lower limit value are set in advance for the cycle of the encoder output pulse, and the sequential time intervals of the encoder output pulse are measured,
The time interval is compared with the upper limit value and the lower limit value, respectively, and when the time interval is between the upper limit value and the lower limit value, print timing is generated based on the encoder output pulse. When it is larger than the value, the print timing is generated at the position of the upper limit value, and when the time interval is smaller than the lower limit value, the print timing is generated at the position of the lower limit value. Print timing correction method for serial dot printers.