JPH0674101B2 - Paper weight feeding detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a paper sheet weight feeding detecting device, and more specifically, in a recording device such as a copying machine or a laser beam printer, a double feeding detecting device for detecting overlapping feeding of paper sheets. Regarding

[Prior Art] Conventionally, as this type of paper sheet weight feeding detection device, a device for detecting the amount of transmitted light of the conveyed paper, or a mechanical device generated between the registration rollers when passing through the conveyed paper or the registration rollers is used. Some have been devised to detect displacement.

However, the former type that detects the amount of transmitted light of a paper sheet has the advantage of being able to detect the paper thickness without contacting the paper sheet, but when printing on both sides of the paper, the printing There is a drawback that the amount of transmitted light changes depending on the concentration of. In the case of the latter device that detects mechanical displacement between registration rollers, there is a great merit that the paper thickness can be detected almost regardless of the print density, but on the other hand, it detects subtle displacement in the registration roller. Therefore, it requires an electrically complicated circuit configuration and, in addition, requires high reliability of individual parts.

In addition, since the registration roller normally has a slight eccentricity, when detecting the displacement of the registration roller, the paper thickness signal changes following the eccentricity of the registration roller. Furthermore, at the moment when the transport paper is pinched between the registration rollers,
Overshoot and undershoot transiently occur in the paper thickness signal, which causes an error in paper thickness detection.

[Purpose] The present invention has been made in view of the above points, and is not affected by transient ripening of roller eccentricity or initial waveform of paper thickness signal. An object of the present invention is to provide a highly reliable sheet weight feeding detection device having a simple structure capable of accurately detecting the overlapped feeding of the sheet body.

[Summary of the Invention] In order to achieve such an object, the present invention provides a signal corresponding to a displacement amount of a roller pair that conveys a sheet and a displacement of the roller pair that is generated by the sheet sandwiched by the roller pair. And a thickness detecting means for outputting the above, until the roller pair makes one rotation after a lapse of time from the time when the roller pair holds the paper sheet until the influence of the transient displacement disappears. Of the output of (1), and a determination unit that determines the double feeding of the paper sheet based on the average value of the sampled output for each individual paper sheet.

Embodiments Embodiments of the present invention will be described in detail and specifically below with reference to the drawings.

1 and 2 show an example of a laser beam printer to which the present invention is applied. Here, 1 is a sheet, and the sheet 1 stored in the cassette is sent out toward the registration roller 3 via the sheet feeding roller 2 by the motor 2A rotated in accordance with a print command from an external controller (not shown), and the roller 3 After being stopped by the regulating unit B for a predetermined time, the toner is sent to the drum 4 from here at a speed matched with the rotation speed of the photosensitive drum 4 in synchronization with an external vertical synchronizing signal described later.

On the other hand, on the photosensitive drum 4, a laser beam is emitted from a laser generator 5 by a signal modulated in accordance with an image signal output from an external controller in synchronization with an external vertical synchronizing signal. It is configured so as to be guided to the exposure section A via the, where writing scanning is performed by exposure.

Thus, the electrostatic latent image formed on the photosensitive drum 4 is developed by the developing device 9 in accordance with the rotation of the drum 4, and the toner image obtained by this is transferred onto the sheet 1 by the transfer charger 10 at the transfer portion C. After passing through the transport unit 11, the fixing roller 12
The sheet 1 that has been fixed in step 1 and that has completed these steps is discharged to the tray 13. In addition, 14 is a cleaner, 15 is a primary charger, 16
Is a secondary static eliminator.

However, in this example, a non-contact type potentiometer 20 is provided in relation to the position of the registration roller 3 described above, and when the sheet 3 is sandwiched between the registration rollers 3, the expansion of the gap between them is mechanically increased by the potentiometer. 20 to be transmitted as a change. Therefore, for example, in the case of a rotary potentiometer, the position of the voltage take-out terminal can be changed by the rotation of its shaft to take out a voltage corresponding to the clearance dimension.

FIG. 3 shows an example of the double feed detection circuit according to the present invention configured to detect the overlap of the sheets 1 in response to the sheet thickness detection signal from the potentiometer 20. Intermediate tap for voltage extraction T ₂₀
When the sheet 1 is clamped by the regulation section B of the registration roller 3 and the gap between the rollers changes, it is displaced and converted into the angular displacement of the potentiometer 20 to change the resistance values of the resistors R9 and R10, and the total voltage Vcc The intermediate terminal voltage Vin corresponding to the displacement can be taken out from this tap T ₂₀ .

The output voltage Vin taken out from the potentiometer 20 is supplied to the operational amplifier Q3 via the resistor R3 to be amplified, and further supplied to the positive input terminal side of the operational amplifier Q4. on the other hand,
Reference voltage Vr obtained from operational amplifier Q2 using a buffer circuit
By supplying e _f to the negative input terminal side of the operational amplifier Q4, the output voltage Vout expressed by the following equation (1) is output from the operational amplifier Q4.
Can be obtained.

Here, R5 and R7 are resistors that form the operational amplifier Q4 together with R6 and R8, and resistors R5 and R6 and resistors
Both R7 and R8 are equal.

Furthermore, R1 and R2 are resistors provided on the input terminal side of the positive in order to obtain an accurate reference voltage Vre _f from the operational amplifier Q2,
R4 is a resistor provided in the feedback circuit of the operational amplifier Q3, C1 is a capacitor provided between the positive input terminal of the operational amplifier Q3 and the ground, and C2 is a capacitor provided between the output side terminal of the operational amplifier Q4 and the ground.

The reference voltage Vre _f is represented by the following formula (2).

Thus through the operation amplifier Q4, converted and amplified signal voltage Vout of the output voltage Vin and the reference voltage Vre _f from the potentiometer 20 is supplied to a central processing unit (CPU) Q1.

Q1 of this CPU is, for example, CPU-μCOM87AD manufactured by NEC,
It is a central processing unit that incorporates storage devices RAM and ROM, and an AD comparator. The signal voltage Vout is input to the AD conversion analog port of the CPU Q1, where the analog signal Vout corresponding to the paper thickness signal is converted into a digital value.

Incidentally, when setting the value of such resistors R5, R7 and the reference voltage Vre _f mentioned earlier is that there is a need to consider the dynamic range and resolution of the operational amplifier and AD conversion port with the variation range of the tap voltage of the potentiometer 20 Needless to say.

Furthermore, in FIG. 3, 21 is an electrode clutch of the registration roller 3, and Q5 is a drive circuit of the electromagnetic clutch 21. Then, in Q1 of the CPU, when the paper 1 is sent out by the paper feed roller 2 and reaches the registration roller 3 described in FIG. 1, the timing is set so that the relationship between the leading edge of the image information and the leading edge of the sheet 1 is properly matched. After that, a drive signal is supplied to the drive circuit Q5, the electromagnetic clutch 21 of the registration roller 3 is turned on, the registration roller 3 is rotated, and the sheet 1 is sent to the photosensitive drum 4.

FIGS. 4 (A) to 4 (D) show timings for detecting and determining such paper feeding and double feeding of the fed papers 1 and processing operation timing. First, FIG. 4 (A) is shown. At the timing T _A , the clutch of the paper feed roller 2 is turned on at the timing shown in the figure, and the rotation of the roller 2 causes the sheet 1 to reach the regulation portion B of the registration roller 3. The regulation portion B temporarily stops the leading edge of the paper 1. The clutch is kept in the released state, and the clutch of the registration roller 3 is turned on at the time T _B as shown in FIG.

Thus, the rotation of the registration roller 3 causes the paper 1 to be fed while being sandwiched between the rollers. When the paper 1 is sandwiched between the rollers, the registration roller 3 is displaced, and the displacement is caused by the potentiometer. 20
Is taken out as a change of the tap voltage Vin, and is appropriately amplified by the amplifier circuit shown in FIG. 3, and then sent to the CPU Q1 as a paper thickness signal Vout as shown in FIG. 4 (C).

However, in the waveform signal of the paper thickness signal Vout, an overshoot amount, that is, an undershoot Su is seen at the initial stage of the fall, but such an overshoot amount Su is the registration roller 3
In general, the registration roller is held by a spring so that the two rollers are in contact with each other. Therefore, when the sheet 1 is inserted between the rollers, the spring force is applied to the registration roller. Such a transient displacement occurs.

Therefore, if the registration roller 3 is driven, the paper thickness signal
If sampling is started to capture Vout as data, the data obtained during that sampling period will have more errors.

In the present invention, in order to prevent such an error from being mixed, the time t _u until the influence of the above-mentioned undershoot Su disappears is measured by previously investigating the characteristics relating to overshoot when the registration roller 3 is displaced. Then, as shown in FIG. 4 (D), sampling is started from time T _{C, which is} a time t _u after the clutch-on time T _B of the registration roller 3, and at time T _D , as shown in FIG. ), The double feeding is determined.

The sampling time t is approximately equal to that of the registration roller 3.
Corresponds to one rotation time, and by setting the sampling time in this way, it is possible to minimize the mixing of the error in the paper thickness detection value due to the eccentricity of the registration roller 3.

Further, in setting the sampling time t in the above description, although the time T _B of the clutch-on of the registration roller 3 was based, in general, in this type of recording apparatus is the paper size according to the paper feeding cassette by the CPU Therefore, the driving time of the registration roller 3, that is, the crack-on time also changes depending on the paper size. So, based on the crack-off time,
It is also possible to start sampling at a time point preceding the turning-off time by a sampling time t and to perform sampling until the crack-off time so that the influence of the overshoot amount is not exerted.

The sampling time t is approximately equal to that of the registration roller 3.
Corresponds to the time for one rotation, and thus the registration roller 3
It is possible to minimize the error in the paper thickness detection value due to the eccentricity of the.

Thus, simultaneously with the start of sampling, the potentiometer 20 sends out the intermediate terminal voltage Vin generated according to the change in the paper thickness, and the intermediate terminal voltage Vin is fed through the double feeding detection circuit shown in FIG. The thickness signal Vout is taken in by the CPU Q1 and stored as digital data in the storage device RAM. Note that in the paper thickness analog signal Vout shown in FIG. 4 (C), the ripple generated by the eccentricity of the registration roller 3 in the output waveform is an initial excessive shoot Su.
Are shown following.

The storage device RAM stores digital data relating to the sampled paper thickness one after another, and the CPU calculates the average value of the data each time from the number of times of sampling and the added value, which is detected at present as shown in FIG. The data of the first sheet is DATA (1), the data of the second sheet is DATA (2) ...
DATA (j) is set, and the data from the (j-n + 1) th sheet to the (j) th sheet, that is, the data up to the nth previous sheet and its average value DATA (MEAN) are stored in the RAM.

Therefore, assuming that the (j + 1) th sheet has been fed,
It is assumed that the paper thickness signal is sampled l times for the paper. The sampling data is DATA (j + 1, i),
(Here, i = 1, 2, ... L), the average value DATA (j + 1) of the sampling data on the (j + 1) th sheet is expressed by the following equation (3).

Therefore, in this example, the average of the measured values of the data of n sheets is always traced back from the data of up to j sheets stored so far, but the latest n data up to the jth sheet is obtained.
The average value DATA (MEAN) of the measured values DATA (k) of the sheets (here, k = j to j−n) is obtained by the following formula.

Here, if j ≧ n, If j <n In this way, when the number j of paper feeds before the present is equal to or larger than the predetermined number n, the average value DATA (ME
AN), and when j is smaller than a predetermined value n, an average value DATA (MEAN) is calculated from the data values of j sheets and this is compared with the value DATA (j + 1) measured on the (j + 1) th sheet. In the present invention, all such arithmetic operations are performed at the sampling time t shown in FIG. 4 (D), and the double feed determination is made at time T _D.

Therefore, the “DATA” detected now is compared with the “DATA (MEAN)” stored in the RAM, and | DATA (MEAN) −DATA | = ΔDATA (6) The difference ΔDATA is larger than the allowable value ΔM. At this time, it is determined that the sheet 1 just fed is double-fed.

Here, the allowable value ΔM is set in advance in consideration of variations in the thickness of the sheet 1, the eccentricity of the registration rollers 3, the mechanical performance problems of the potentiometer 20, and the like. Then, such an allowable value ΔM is stored in the storage device ROM.

Next, the flow of the above control routine will be described with reference to FIG.

First, in step S1, the average value DATA (j + 1) of the sampling data for the sheet that has just been fed is calculated, and if the number of fed sheets j before that is 1 in step S2, it is not executed after step S2, but j If> 1, DATA (MEAN) is calculated in step S3. In this calculation, if j ≧ n, the equation (4) is used, and j <n
Then equation (5) is used.

Then, in step S4, ΔDATA is calculated according to the equation (6). In step S5, it is determined whether ΔDATA is larger than ΔM. If ΔDATA> ΔM, in step S6 (j +
1) It is determined that the second sheet is double-fed, and the process proceeds to the control routine of step S7 for performing the operation at the time of double-fed.

Here, as the control routine at the time of double feeding, for example, the occurrence of the double feeding is first notified to the external controller, the feeding of the (j + 2) th sheet and thereafter is prohibited, and the (j + 1) th sheet is fed to the output tray. The fact that one misprint has occurred due to double feeding is stored in the external controller, and when the misprint is removed, the output of the print command can be obtained starting from the external controller. To

Further, when it is determined that the (j + 1) th sheet is double fed, (j +
2) If the first or subsequent sheets have been fed, the (j + 2) th and subsequent sheets are also discharged as a misprint, and the number of back pages of the discharged sheets is also stored in the external controller. To do so.

Note that when the power is first turned on and the first sheet is fed, there is no data measured before that, so at this time only data is collected and the determination of double-feeding of paper is made. Although there is no data, since the second and subsequent sheets have data measured before that, it is possible to discriminate the double feed. That is, the second
The double feeding may be determined by comparing the first sheet with the first sheet and comparing the average value up to the (n-1) th sheet with the nth sheet.

It is desirable that the value of n be set so as to reduce the error rate of double feed detection in consideration of variations in paper thickness value and drift due to temperature in the potentiometer and the amplifier circuit.

Furthermore, in this example, NEC's μCPM87AD was selected as the CPU, but the CPU is not limited to this, and it may be another type of CPU having an AD conversion port, and further, an AD converter and a general-purpose CPU. It goes without saying that even if it is a composite type, there is no difference in its effect.

Further, in the above description, the case where the non-contact type potentiometer is used as the double feed sensor has been described, but a conventional contact type potentiometer having high reliability may be used.

[Effect] As described above, according to the present invention, a signal corresponding to a displacement amount of a roller pair that conveys a sheet and a displacement of the roller pair that is generated by the sheet sandwiched by the roller pair is generated. The thickness detecting means for outputting and the thickness detecting means of the thickness detecting means until the roller pair makes one rotation after a lapse of time until the influence of the transient displacement disappears after the roller pair holds the paper sheet. Since the output is sampled and a determination unit that determines the double feeding of the sheet based on the average value of the sampled output for each individual sheet, the influence of the eccentricity or the transient displacement of the pair of conveyance rollers is provided. Therefore, it is possible to prevent an error from being mixed in the detection signal output from the thickness detecting means, and to accurately detect the double feeding of the paper sheets.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an outline of a laser beam printer equipped with a paper sheet weight feeding detection device of the present invention, FIG. 2 is a perspective view of the main part of the laser beam printer, and FIG. 3 is a double feeding according to the present invention. FIG. 4 is a block diagram showing an example of a detection circuit, FIGS. 4 (A) to 4 (E) are time charts showing the timing of generation of a paper thickness detection signal at the time of paper feeding, and FIG. 5 is a CPU used in the present invention. FIG. 6 is a block diagram for explaining the procedure for determining double feeding based on the data group stored in the storage device RAM, and FIG. 6 is a flowchart of the control operation by the CPU. DESCRIPTION OF SYMBOLS 1 ... Paper, 2 ... Paper feed roller, 3 ... Registration roller, 4 ... Photosensitive drum, 5 ... Laser generator, 6 ... Scanner, 7 ... Imaging lens, 8 ... Mirror, 9 ... Developer, 10 ... Charger, 11 ... Conveying part, 12 ... Fixing roller, 13 ... Tray, 14 ... Cleaner, 15 ... Primary charger, 16 ... Secondary charge eliminator, 20 ... Potentiometer, 21 ... Electromagnetic crack, A ... Exposure part, B ... Regular part, C ... transfer unit, R1 to R10 ... resistance, T ₂₀ ... tap, Q1 ... CPU, Q2~Q3 ... op, Q4 ... differential amplifier, C1, C2 ... capacitor, Q5 ... driving circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Zenmoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kaoru Seto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (56) References JP-A-59-200387 (JP, A) JP-B-52-36044 (JP, B2)

Claims (1)

[Claims] 1. A roller pair for conveying a paper sheet, a thickness detecting means for outputting a signal corresponding to a displacement amount of the roller pair generated by the paper sheet held by the roller pair, and the roller pair. The output of the thickness detecting means is sampled until the roller pair makes one rotation after the time from when the effect of the transient displacement disappears after the paper sheet is held by the individual paper sheet. A sheet weight feeding detection device, comprising: a discriminating unit that discriminates the double feeding of the sheet based on the average value of the sampled outputs.