JP2003212387A - Picture image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten time to stop reading of a detection signal from a printing medium detection means by improving a method to avoid a problem concerning turbulence of corrugation of the detection signal from the printing medium detection means. <P>SOLUTION: A sampling circuit 3 outputs a timely continuous sampling signal S2 after noise removal by a timely dispersed signal acquired by sampling a signal S1 by a specified cycle to remove high frequency noise by the detection signal S1. A signal mask circuit 5 outputs a corrected detection signal S5 to more precisely express existence of a sheet without tramping by applying masking to the signal S2 by specified short time to cause the tramping to the signal S2 immediately after the signal S2 is input and a terminal end of the sheet passes the sensor 1 and immediately after a head end of the following sheet enters the position of the sensor 1. A falling mask signal S4a and a rising mask signal S4b are input from a timer circuit 9. A circuit 5 is informed of a period of time when the tramping can be caused by the signals S4a, S4b. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a print medium detection technique in an image forming apparatus for printing an image on a supplied print medium (print paper). In the following, a printer will be taken as an example of the image forming apparatus, and a detection technique improved so as to accurately detect insertion of printing paper into the printer and ejection of printing paper from the printer will be described.

[0002]

2. Description of the Related Art As a printing paper detection mechanism in a printer, a contact sensor is used which detects the presence or absence of a printing paper by turning an electric switch ON / OFF by mechanical contact between the printing paper and a contact piece. There is something. In such a contact type sensor, for example, when the leading edge of the printing paper comes into contact with the printing paper, the switch is turned on and the detection signal rises to the “H” level (or “L”). When the trailing edge of the printing paper passes the sensor, the contact with the printing paper ends and the switch turns off and the detection signal falls to the "L" level (or rises to the "H" level). ).

In the contact type sensor as described above, at the end of the contact with the printing paper (and also at the start depending on the structure of the sensor), the contact piece vibrates for a while and the detection signal becomes "H" level. A phenomenon (rocking) (hereinafter referred to as “fluttering”) that repeatedly reciprocates between the “L” level and the “L” level may occur. This flapping problem is a phenomenon typically seen in the above-mentioned contact type sensor, but may be present in sensors having other structures.

The fluttering of the paper detection signal described above interferes with accurate detection of the printing paper. Therefore, in the conventional technique, when the end of the printing paper passes the sensor and the level of the detection signal once falls (or rises), the reading of the detection signal is stopped thereafter, and the printing paper is released from the printer. The discontinuation state continues until it is completely discharged. As a result, it is possible to avoid the influence of flapping that occurs when the trailing edge of the printing paper passes the sensor.

[0005]

In the case of a serial printer, for example, the above-described paper detection sensor is arranged in front of the print head in the paper feed path, and is used for controlling the timing at which the print paper passes in front of the print head. Used. According to the above-mentioned conventional technique, after the end of the print paper passes the paper detection sensor in front of the print head,
The reading of the detection signal of the paper detection sensor is stopped until the printing paper is ejected from the printer. This means that in the case of sequentially printing on a plurality of printing papers, waiting for the next printing paper to be taken into the printer until the printing paper before printing is ejected from the printer. Therefore, there is a problem that the waiting time from the end of printing of the previous printing paper to the start of printing of the next printing paper is long.

Accordingly, it is an object of the present invention to improve the method for avoiding the problems associated with the disturbance of the waveform of the detection signal from the print medium detection means, thereby stopping the reading of the detection signal from the print medium detection means. To save time.

Another object of the present invention is to shorten the waiting time from the completion of printing of an image on a previous print medium to the start of printing of an image on the next print medium, thereby improving the image forming apparatus. It is to improve throughput.

[0008]

An image forming apparatus according to the present invention is for printing an image on a supplied print medium, and is a print medium detecting means for detecting the presence / absence of the print medium, and the detecting means. Signal processing means for inputting a detection signal output from the means, performing correction processing on the detection signal and outputting the signal, and control means for controlling the printing operation based on the detection signal corrected by the signal processing means. And the correction process, when the input detection signal changes from a state indicating the presence of the print medium to a state indicating no or vice versa, during the predetermined dead time from the change point, the detection signal Insensitive processing for forcibly fixing the changed state at the time of the change regardless of the disturbance of the state.

According to the above construction, in the correction process applied to the detection signal from the detecting means, when the input detection signal changes from the state indicating the presence of the print medium to the state indicating no or vice versa, the change time point From the predetermined dead time, since it was decided to perform the dead processing for forcibly fixing the state after the change at the change time regardless of the disturbance of the state of the detection signal, the detection signal at the dead time Since the disturbance of the waveform is almost eliminated, it is possible to shorten the time for stopping the reading of the detection signal.

In a preferred embodiment of the present invention, the correction process includes a noise removal process for removing a high frequency noise component contained in the input detection signal before the dead process. In the present embodiment, for example, the detection means is provided at a predetermined position on the conveyance path of the print medium, and an electrical contact is opened / closed by physically contacting / separating with the medium passing through the predetermined position. Then, a contact sensor that generates a detection signal is used.

Further, in the above embodiment, when the detection signal from the detection means is input and the input detection signal changes from a state showing "Yes" to a state showing "No", or vice versa,
Immediately after the change time, the time length in which the state of the input detection signal is disturbed is measured, and the dead time is set based on the measured time length. The length of the dead time can be changed. Further, the length of the dead time is equal to or longer than the measured time length.

Further, in the modification of the above embodiment, the length of the dead time can be changed according to the print medium detecting means.

Further, in another modification of the above-described embodiment, the length of the dead time can be changed according to the number of times the presence / absence of a print medium is detected each time the image forming apparatus is used.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic structure of a main part of a printer as an example of an image forming apparatus according to an embodiment of the present invention.

As shown in FIG.
The print paper 16 is taken in from the paper feed tray 17 by the paper feed rollers 14 and 15, passes through the front of the print head 13 along the platen 18, and is then ejected onto the paper ejection tray 19. A contact type sheet detection sensor 1 for detecting the presence or absence of a sheet is arranged at a position in front of the print head 13 in the sheet feeding path. The paper detection signal S1 output from the paper detection sensor 1 is input to the paper detection circuit 11. In accordance with the principle of the present invention, the paper detection circuit 11 removes the fluttering portion from the paper detection signal S1 and outputs a correction detection signal S5 that more accurately represents the presence or absence of paper.

The correction detection signal S5 is input to the control circuit 12. The control circuit 12 includes the print head 13 and the paper feed roller 1.
It controls the driving of Nos. 4 and 15 and the correction detection signal S5 is used in the control. As will be described later, when printing is continuously performed on a plurality of printing sheets, the control circuit 1
2 uses the correction detection signal S5 to capture the next sheet at the position of the sheet detection sensor 1 after the trailing edge of the previous printing sheet has passed the sheet detection sensor 1 and feed it to the print head 13. , Can be started substantially immediately (almost real-time to the user). While the fluttering of the sheet detection signal S1 as described above continues, it is necessary to wait for the feeding operation, but this is only a very short time which can be said to be substantially zero for the user.

FIG. 2 is a block diagram showing the internal structure of the printing paper detection circuit 11.

In FIG. 1, a sampling circuit 3 inputs a sheet detection signal S1 output from the sheet detection sensor 1 and samples the sheet detection signal S1 at a predetermined cycle in order to remove high frequency noise from the sheet detection signal S1. , The noise-removed signal obtained by this sampling is used to generate and output the noise-removed temporally continuous sampling signal S2.

The signal mask circuit 5 uses the sampling signal S2
Is input, and immediately after the end of the printing paper passes the paper detection sensor 1 and immediately after the leading edge of the next printing paper enters the position of the paper detection sensor 1, the paper detection signal S1 (and thus the sampling signal S2 ), The sampling signal S2 is masked only for a predetermined short time period in which fluttering is expected to occur, and a correction detection signal S5 representing the presence or absence of fluttering and the presence or absence of printing paper is output more accurately. The signal mask circuit 5 receives the falling mask signal S4 from the timer circuit 9.
Input a and the rising mask signal S4b. By the falling mask signal S4a and the rising mask signal S4b,
The signal mask circuit 5 is notified of the period in which the above-mentioned fluttering is supposed to occur.

The edge detection circuit 7 detects the falling edge and the rising edge of the correction detection signal S5 by monitoring the correction detection signal S5 output from the signal mask circuit 5, and detects the falling edge detection signal respectively. It outputs S3a and a rising edge detection signal S3b. Correction detection signal S
The trailing edge and the rising edge of 5 appear when the end of the printing paper passes the paper detection sensor 1 and when the leading edge of the next printing paper enters the position of the paper detection sensor 1, respectively. Therefore, the edge detection circuit 7 outputs the falling edge detection signal S3a at the time when the end of the print paper passes the paper detection sensor 1, and when the leading edge of the next print paper enters the position of the paper detection sensor 1. The rising edge detection signal S3b is output at.

The timer circuit 9 uses the falling edge detection signal S3a and the rising edge detection signal S3b from the edge detection circuit 7 as triggers, respectively, and continues for a predetermined short time length in which it is assumed that the above-mentioned fluttering is occurring. The falling mask signal S4a and the rising mask signal S4b are output to the signal mask circuit 5 as described above.

FIGS. 3 and 4 are timing charts showing input / output signal waveforms of respective parts of the printing paper detection circuit 11 shown in FIG.

In FIGS. 3 and 4, the reference numeral (a) indicates the sheet detection signal S1 output from the sheet detection sensor 1. Among the waveforms of the paper detection signal S1, those shown as whiskers are high-frequency electrical noise that sometimes intrudes from the surrounding electric circuits, and the response of the electric circuit when the paper detection signal S1 rises and falls. It is high-frequency electrical noise or the like due to "chattering" caused by the characteristics. In addition to the fluttering that has already been explained, such high-frequency noise interferes with the accurate detection of the printing paper.

In the code (a), for example, the time
T₁As before, the printing paper is placed at the position of the paper detection sensor 1.
When present, the paper detection signal S1 indicates "H" level and continues.
Kick The end of the printing paper is at the position of the paper detection sensor 1.
Time T when exiting₁(That is, the paper detection signal S1
At the time of falling), the above-mentioned "chatter" is added to the paper detection signal S1.
High frequency electrical noise is generated by the ring. Paper inspection
Output sensor 1 is at time T ₁From above high frequency electrical noise
Time T when_TwoAnd then for a while (to the user
Mechanically, though only for a very short time
It vibrates (swings), which causes the paper detection signal S1 to go "H" level.
Repeated round trips between the bell and "L" level
A so-called “flapping” phenomenon occurs. In reference numeral (a), paper
The high-frequency power generated above when the detection signal S1 rises
Time T when the atmospheric noise subsides_FourFrom the rise of the paper detection signal S1.
The high-frequency electrical noise generated during the falling is reduced.
Round time T₇In the meantime, this flapping occurs
ing. The cycle of this flap is illustrated like a beard.
Significantly longer than high-frequency noise (a)
Is clear from.

The paper detection signal S1 shown by the reference numeral (a) is supplied from the paper detection sensor 1 to the sampling circuit 3 as described above.
Entered in. The sampling circuit 3 samples the sheet detection signal S1 with a sampling period that is sufficiently short so as not to substantially affect the detection of the presence or absence of the printing sheet and that is sufficiently longer than the period of the high frequency noise described above.
Then, the sampling circuit 3 processes the temporally discrete signals obtained by the sampling in such a manner as to change the level when a plurality of temporally adjacent signals continuously match in level several times. By doing so, the above-mentioned high-frequency electrical noise is removed, and the processing results are connected so as to be temporally continuous, so that a sampling signal S2 that does not contain electrical noise is output, as indicated by symbol (b). .

In other words, in the sampling of the sheet detection signal S1, when the sheet detection signal S1 of the same level (“L” level or “H” level) is continuously sampled a predetermined number of times (for example, 4 times) or more. Indicates that the high-frequency electrical noise has not occurred and the level of the sheet detection signal S1 has been settled down. Therefore, the sampling signal S2 of the same level (L level / “H” level) as sampled above. On the contrary, when the number of sampling times of the sheet detection signal S1 of the same level is less than the predetermined number (4 times), it is determined that the high frequency electric noise is generated. The sampling signal S2 of the level before sampling the level is output.
The sampling signal S2 includes the time T ₄ to the time T described above.
_{Since the} fluttering phenomenon as shown up to ₇ remains as it is, such a sampling signal S2 is input to the signal mask circuit 5.

The correction detection signal S5 output from the signal mask circuit 5 has a waveform as shown by the symbol (g), which is the time T from the sampling signal S2 shown by the symbol (b).
_The portion corresponding to the flapping phenomenon as shown from ₄ to time T ₇ is removed. Since the correction detection signal S5 is input to the edge detection circuit 7, the edge detection circuit 7 causes the correction detection signal S5 to fall at the falling timing (the high-frequency electric signal generated at time T ₁ ) as shown by the symbol (c). noise is at time T ₂₎ time T _{2 'is} a time of slightly later than will fit, the falling edge detection signal S3
A is generated and output to the timer circuit 9.

[0029] _', the timer circuit 9 is activated, as indicated by reference numeral (e), time T _2, falling upon receiving the edge detection signal S3a (time T _2,)' is a time of slightly later than the time It continues to output from T ₃ to fall signal masking circuit masks the signal S4a 5 is at "H" level signal only until the time T _8. As described above, in the sampling signal S2, from time T ₄ to time T ₇ ,
A so-called “flapping” phenomenon occurs as indicated by reference numeral (b). However, the flapping phenomenon is removed by masking the sampling signal S2 in the signal mask circuit 5 by the input of the falling mask signal S4a to the signal mask circuit 5, and as a result, (the signal mask circuit 5 The correction detection signal S5 (which is the output signal from the above) continues to be at the “L” level from the time T ₂ to the time T _{9 as} indicated by the symbol (g). Here, the predetermined short time length in which it is assumed that the fluttering phenomenon has occurred refers to the period from time T ₃ to time T ₈ when the signal mask circuit 5 inputs the falling mask signal S4a. However, the time from time T ₃ to time T ₈ is
It is the time width of the forced Low fixed shown in, that is, the time when the above-described sampling signal S2 is masked. The time T _8, as is evident from the code (b), is set a little time later than the time T ₇ to the flapping phenomenon has disappeared.

Next, by transporting new printing paper,
In the "L" level was the rise of the sheet detection signal S1, also has the same electrical noise occurs, from time T ₉ whose electrical noise falls, the electrical noise generated during the fall of the sheet detection signal S1 in between times T ₁₄ to fit, fluttering described above occurs. The sampling circuit 3 outputs the sampling signal S2 containing no electrical noise by removing the electrical noise from the sheet detection signal S1 by the method described above.
However, since the fluttering phenomenon as shown between the time T ₁₁ and the time T ₁₄ remains in the sampling signal S2, such a sampling signal S2 is input to the signal mask circuit 5 (code (b )reference). The correction detection signal S5 from the signal mask circuit 5 has a waveform in which the portion corresponding to the flapping phenomenon is removed, as indicated by the symbol (g). In the edge detection circuit 7, as shown by the symbol (d), the rising timing of the correction detection signal S5 (time T
At time T _{9 'is} a time of slightly later than _9), generates and outputs a rising edge detection signal S3b to the timer circuit 9.

[0031] at the time of applying a rising edge detection signal S3b (time _{T 9} '), the timer circuit 9 restarts, as indicated by reference numeral (f), only from time _{T 10} to time _{T 15} "H Rising mask signal that is a "level signal"
The output of S4b to the signal mask circuit 5 is continued. The fluttering portion of the sampling signal S2 is removed by masking the sampling signal S2 in the signal mask circuit 5 by the input of the rising mask signal S4b to the signal mask circuit 5, and as a result, the correction detection signal S5 is obtained.
, In between the time T ₉ to time (not shown) which end of the new printing paper passes through the position of the paper detection sensor 1, to continue the "H" level (reference (g)).
Here, the predetermined short time length in which the fluttering phenomenon is assumed to occur refers to a period from time T ₁₀ to time T ₁₅ when the signal mask circuit 5 inputs the rising mask signal S4b. From this time T ₁₀ to time T
The time up to ₁₅ is the fixed High fixed time width shown in FIG. 4, that is, the time when the above-described sampling signal S2 is masked. The rising mask signal S4b
The time T ₁₅ falls, as apparent from the code (f), is set a little time later than the time T _14.

According to the above configuration, the signal mask circuit 5 has
And time T_ThreeFrom time T₈Falling trough
Clock signal S4a causes time T in sampling signal S2
_FourFrom time T₇The flapping around the mask is masked,
Also, at time T₁₀From time T ₁₅Standing up to
Clock signal S4b causes time T in sampling signal S2
₁₁From time T₁₄The flapping around the mask is masked
Be done. Therefore, the correction detection signal as shown by the symbol (g)
S5, that is, chattering, as described above
The logic level signal without any flapping is generated by the signal mask circuit 5
As an output signal from the control circuit 12 shown in FIG.
To be done.

The time length in which the waveform of the paper detection signal S1 (and thus the sampling signal S2) is disturbed due to fluttering or chattering varies depending on the type of the paper detection sensor 1 and the thickness of the printing paper. However, the time for performing the masking in the signal mask circuit 5 is the time width of the falling mask signal S4a output from the timer circuit 9 to the signal mask circuit 5 (that is, the forced Low shown in FIG. 3).
Fixed time width), the time width of the rising mask signal S4b (that is, the fixed High time width shown in FIG. 4)
Can be changed freely by adjusting the setting of the timer circuit 9, so there is no problem.

The preferred embodiment of the present invention has been described above, but this is an example for explaining the present invention.
It is not intended to limit the scope of the invention to this embodiment only. The present invention can be implemented in various other forms. For example, instead of the print paper detection circuit 11 having the configuration shown in FIG. 2, the function of the print paper detection circuit 11 may be provided by software.

[0035]

As described above, according to the present invention,
By improving the method for avoiding the problem related to the disturbance of the waveform of the detection signal from the print medium detecting means, the time for stopping the reading of the detection signal from the print medium detecting means can be shortened.

Further, according to the present invention, the waiting time from the end of printing the image on the previous print medium to the start of the printing of the image on the next print medium is shortened to improve the throughput of the image forming apparatus. Can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a main part of a printer as an example of an image forming apparatus according to an embodiment of the invention.

FIG. 2 is a block diagram showing an internal configuration of a printing paper detection circuit shown in FIG.

FIG. 3 is a timing chart showing input / output signal waveforms of respective parts included in the printing paper detection circuit shown in FIG.

FIG. 4 is a timing chart showing input / output signal waveforms of respective parts included in the printing paper detection circuit shown in FIG.

[Explanation of symbols]

1 Paper detection sensor 3 Sampling circuit 5 signal mask circuit 7 Edge detection circuit 9 Timer circuit 11 Paper detection circuit 12 Control circuit 13 print head 14, 15 paper feed rollers 16 printing paper 17 Paper tray 18 Platen 19 Output tray 100 printers

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C058 AB08 AD01 AE02 AE09 GA13                       GB06 GB14 GB31 GB32 GB47                       GB53                 2C061 AS02 LL03                 3F048 AA05 AB01 BA05 BB10 BD07                       CC03 CC04 DA06 DC03

Claims (8)

[Claims] 1. An image forming apparatus for printing an image on a supplied print medium, wherein a print medium detecting unit for detecting the presence / absence of the print medium, and a detection signal output from the detecting unit are input, A signal processing unit that performs correction processing on the detection signal and outputs the signal, and a control unit that controls the printing operation based on the detection signal subjected to the correction processing by the signal processing unit are provided, and the correction processing receives the input. When the detection signal changes from the state showing the presence of the print medium to the state showing nothing or vice versa, for a predetermined dead time from the change time, regardless of the disturbance of the state of the detection signal, at the change time An image forming apparatus including a deadening process for forcibly fixing the changed state. 2. The image forming apparatus according to claim 1, wherein the correction process includes a noise removal process that removes a high frequency noise component included in the input detection signal before the insensitive process. . 3. The apparatus according to claim 1 or 2, wherein the detecting means is provided at a predetermined position on a conveyance path of the print medium, and physically contacts with the medium passing through the predetermined position. An image forming apparatus which is a contact type sensor that generates a detection signal by opening / closing an electric contact when separated. 4. The apparatus according to claim 1, wherein when a detection signal from the detection means is input and the input detection signal changes from a state indicating presence to a state indicating nothing or vice versa, the change. An image forming apparatus that measures a time length in which the state of the input detection signal is disturbed immediately after the time point and sets the dead time based on the measured time length. 5. The device according to claim 1, wherein An image forming apparatus in which the length of the dead time can be changed. 6. The image forming apparatus according to claim 1, wherein the dead time is equal to or longer than the measured time length. 7. The image forming apparatus according to claim 1, wherein the length of the dead time can be changed according to a print medium detecting unit. 8. The image forming apparatus according to claim 1, wherein the length of the dead time can be changed according to the number of times of detecting the presence / absence of a print medium performed each time the image forming apparatus is used.