JPS5889543A - Optical sheet detector - Google Patents

Abstract

PURPOSE:To improve detection accuracy of a sheet, by successively providing two optical sensors in a conveying direction, sample holding output voltage of the sheet detected by the first sensor, using said voltage as the comparable reference voltage at a point of arrival time to the latter sensor and detecting the presence of the sheet. CONSTITUTION:A device is constituted in such a manner that the first and second optical sensors 15, 16 are successively arranged along a sheet conveying route 14, and comparing reference voltage corresponding to an output at a point of arrival time of a sheet 6 at the first optical sensor 15 is stored till the sheet 6 reaches the second optical sensor 16, here this comparing reference voltage is used as a threshold level to detect the presence of the sheet 6 by comparing said level with an output of the second optical sensor. In this way, optimum comparable reference voltage can be automatically set to the detected sheet 6, and misdetection can be prevented to improve detection accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical sheet detection device that can reliably detect the presence or absence of a sheet, regardless of the type of sheet.

As a sheet detection device used for jam detection in a multi-V machine, an optical sensor is used and an ax is also known. The structure of the conventional sheet detection device is shown in block diagram No. In the figure, l is an optical sensor section, 2 is a reference voltage generation section, and 3 is a comparison section that compares the output 11.EE of the optical sensor section from the reference voltage generation section 2 with a comparison standard normal pressure. It is.

The output pressure of the optical sensor section l is determined by the comparison section 3 as a comparison reference voltage and the ratio V? The presence or absence of the sheet is determined based on the comparison output. In that case, you can freely choose whether to use the sheet when the optical sensor unit/σ] output lightning pressure is higher than the comparison standard normal pressure, or whether to use the sheet when it is lower than the comparison reference voltage. can. Further, the optical sensor section 1 may include a sensor amplifier.

On the other hand, the optical sensor 1 will be referred to as a "reflective type" including a transmissive type and a reflective type (scattering type).

), what 1. The output current and voltage also change depending on the presence or absence of a sheet.

As shown in FIG. The sheet failure is detected from the fall of the output chamber IT'Vsσ1 caused by blocking the incident light G.

The reflection type optical semiconductor sensor is also composed of a light emitting diode L and a phototransistor S, as shown in the figure BG, and is connected to the sheet conveyance path. This is to detect the presence or absence of reflected light or scattered light from the sheet B during the process of passing through the phototransistor j (fE Vs a> -p rise 7-z-), which is caused by the output of the phototransistor j.

Fig. 1 σ) Optical sensor section/C-1, any type of sensor is used. The output voltage Vs of the optical sensor section is compared with a comparison reference voltage T in a comparator 3 constituted by, for example, an arithmetic intensifier, thereby determining the presence or absence of a sheet.

In the conventional optical sheet detection device described above, the comparison reference voltage of the comparison section 3 for determining the presence or absence of the sheet B was fixed.

Figure 3 A and B show the fixed comparison reference voltages ■R and 1r.
FIG. 3 is a curve diagram showing the relationship between the output voltages vs of the transmission optical sensor and the reflection type sensor with respect to the seat position to explain the relationship between the output voltages of the optical sensor section 1J. As can be seen from the figure, regardless of whether the optical sensor is a transmissive type or a reflective type, the output level when a sheet is present changes depending on the type of sheet. The output voltage Vs is determined by the contamination of the light emitting part and part of the receiver t.
t''1.G therefore decreases overall, and when the inverse G receives disturbance light, the overall G increases.To prevent detection errors due to these fluctuations, G decreases as a comparison reference voltage. vR
It is necessary to set the output voltage of the optical sensor to a level close to the intermediate level between the level when the sheet is present and the level when the sheet is not present. However, between an opaque sheet and a transparent sheet, the level of the output voltage Vs at G when the sheet is present is significantly different as shown in FIG. r-Settings
It is. For example, if the comparison reference voltage ■R'ff is set so as to detect an opaque sheet sufficiently safely, the output voltage of the optical sensor vs. the voltage difference between the presence of the sheet and the absence of the sheet is small, so the image quality is The comparison reference voltage VR will be set at a level position far away from the middle ii level of the output M\pressure s of vN, which may make it impossible to detect the transparent sheet.

An object of the present invention is to automatically set a comparison reference voltage optimal for detecting a sheet according to the type of sheet to be detected, in order to eliminate the disadvantages of the conventional apparatus as described above. This is an attempt to provide an optical sheet detection device TI# that can prevent detection errors due to dirt t1 on the scientific sensor.

The optical sheet detection device of the present invention has first and second sheets arranged sequentially in the sheet conveying direction along the sheet conveying path, and generating outputs corresponding to the light transmittance or light reflectance G of the sheet, respectively. a second optical sensor and its first optical sensor;
7. The standard voltage for comparison according to the output of the sensor on the π sheet is reached. r A storage means for storing information until the sheet reaches the first λ optical sensor; and a comparison means for comparing, the front is detected by the first optical sensor, the position of the first optical sensor is determined by the comparison output of the comparison means, and the position of the ax sheet at the time when the ax sheet reaches the second optical sensor &S. Detect the presence or absence of sheet σ) at T2. It is characterized by this.

Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 shows an example of the arrangement of the first and second optical sensors of the present invention for an electrostatic copying machine TF.

In the same figure, a cassette containing 7 cmf sheets t′f,
r is HA roller, RI is photosensitive drum, lθ transfer opening-RA, // & ma photosensitive drum is 1 toner image and sheet 6σ)
a register roller for starting the sheet 6 by aligning the leading edges of the two; 12 is a fixing device; 13 is a paper ejection roller;
/ is the conveyance path of the sheet. Also /S and /, 7
&:t, the seventh and second optical sensors of the present invention are sequentially arranged in the sheet conveyance direction/7D indicated by the arrow along the sheet conveyance path/II, and are respectively arranged along the sheet conveyance path T. It is installed so that it can detect the sheet that is attached to it.

Kowara optical sensor/3, #: is, 2nd fil
It is the same as the conventional transmission type or reflection type optical sensor shown in A and B, and the configuration 1 and operation were explained earlier in H, so their explanation will be omitted here.

The sheet sent out from the cassette by the paper feed roller 1' is temporarily stopped by the register roller //. As a result, the sheet is re-stored at the timing when the leading edge of the sheet coincides with the leading edge of the toner image formed on the photosensitive drum 9, and the toner image is transferred onto the sheet by the &f roller lθ. Ru. σ) The sheet is fed to the fixing device /2&, where the toner image on the sheet is fixed and ejected by the ejecting roller 13. Sor
, and the like (j+) are controlled by a clock pulse G corresponding to the relative movement of the document (not shown) and the optical system.

If the sheet becomes jammed for some reason during sheet conveyance,
Failure to perform normal conveyance G1 Although it is unavoidable, continuing to operate the device when a sheet jam occurs is
This may cause problems such as damaging the photoreceptor drum 9.
Sensor i for detecting medium sheet conveyance path/l medium sheet! i
[! Is it necessary to check the presence of sheets at a predetermined timing and detect whether a sheet jam has occurred?

Depending on the shape of the sheet conveyance path, one sensor G or a plurality of sensors are disposed at one location (σ) for sheet detection. Seven optical sensors, that is, the optical sensors of the present invention (!f) are arranged on the side for sheet detection, and the first An optical system 13 is arranged. Note that the first and first optical sensors/
3. It is assumed that the transmissive type shown in FIG. 2A is used.

When copying starts, the photosensitive drum 9 rotates, and GJ receipt conveyance starts for 2 hours so that the leading edge of the sheet coincides with the leading edge of the toner image formed on the photosensitive drum 9. The operation of each member is controlled by a clock pulse G synchronized with the rotation of the sensor C1 body drum 9, with reference to the timing when the sheet B starts out due to the paper feeding roller gG. The length of the circumference of the photosensitive drum 9 is 2! For example, go
As a result, lloo pulses are generated per 7 revolutions of the photoreceptor drum, and 1 nt pulse is generated every time the sheet moves.
The register roller l
The timing at which the sheet restarts due to / is /60
The second pulse is 2t! At the timing of the r-th pulse, the photoreceptor drum 90σ) is set at lf/I' so that the leading edge of the sheet coincides with the leading edge of the toner image.
Ru.

The first optical sensor/3 is as described above? As shown, it is placed directly behind the paper feed roller L. Since there is a very low possibility that a conveyance abnormality will occur on the upstream side of the first optical sensor B, the feed roller 27'
1. The sheet is securely attached to the optical sensor/317
An example of a pulse that cannot be considered to exist in the 1 part is the lOOth pulse, and the output voltage obtained by the first optical sensor lS is sampled and held Tt'l.

For example, the hold value depends on the transmittance or reflectance of the sheet located at the position of the first optical sensor IS. This hold value is converted into the optimum comparison reference voltage G as the threshold value η and the criterion for determining the presence or absence of the sheet when the sheet is detected by the second optical sensor GJ. It is held by the storage means until the time when it is detected by the first optical sensor lB.

On the other hand, the 2tl, 7' sheet sent out by the paper feed roller r is temporarily stopped by the tth register roller // which aligns the leading edge of the toner image forming the upper G edge with the leading edge of the sheet. , /1. Restarts at the timing of the 0th pulse. This restarted sheet reaches the optical sensor 4 at Φ, 2 at the rear left where the toner image on the photoreceptor drum 9 is transferred by the transfer roller θG, passes through the fixing device 12, and is transferred to the discharge roller 13. be discharged.

The second optical sensor /1 detects the second pulse σ) when the sheet restarts the position of the register roller l/3.
If it grows with the one provided at the point where it reaches the timing position, at the timing of the second pulse of 3&go, that sheet is nil *lJ? P, must reach the optical sensor/A of 2.

That is, the output of the second optical sensor/6 and the above σ)
I held the comparison, the semi-city pressure P, the comparison between the hands, the G, and the ratio M.
L, 3/,! Depending on the presence or absence of a comparative output of the timing of the second pulse, it is possible to detect whether the position G of the second optical sensor lt has reached the sheet without any abnormality and is an axe.

In that case, the previous M+4 comparison means σ) comparison reference voltage is the second
6 Scientific sensor/4G detects the transmittance or reflectance of the 27" sheet, ff, Since the inset G is set, the presence or absence of the sheet can be accurately detected regardless of the sheet glaze G.
1st and 10th) Optical sensor /3, /,
! .

It is possible to easily detect whether or not there is a sheet jam between the sheets.

FIG. 5 shows the tth optical sheet detection r! This shows an example of 71 circuits, including a non-inverting coefficient amplifier and a field-effect transistor (FET) for the gate.
/9, the sample and hold circuit has a configuration of 2+t'+ with the hold capacitor and the buffer 21. Gate FIT from pulse input terminal n via diode 23
When the iJ mark 100 ti-th pulse is not applied to /9, the downstream G of the paper feed roller is provided'f: reflection reflection box 1
The output voltage corresponding to the f sheet σ) fy emissivity obtained by the optical sensor /3 is
A 20G hold capacitor is used to hold the FET /95-, which is then input to the buffer 2/. Resistance R work.

From the appropriate setting of R2, that is, the setting of the downstream side of the transfer roller 12, the sheet is placed at a suitable threshold for detection by the second optical sensor. , pressure ■P are output from buffer 2. The comparison standard heavy pressure generated in this way is held by the capacitor G, which is a constant voltage with respect to the output voltage of the first optical sensor, until the next 100th pulse is applied to the input terminal n. It does not change.

Now, if a transmissive type is used as the first yC Gakuhanseisen/S as in this embodiment, a sheet with high light transmittance is used as the first optical fiber as shown in Fig. 6A. formula sensor/3
If the detected φ, σ) and 1-71 are used, a high threshold comparison standard η-pressure VR is used, and when a sheet with low light transmittance is detected, a low threshold comparison reference voltage ■R2 is used. is bolded by the sample-and-hold circuit and 7:
ru.

The optimal threshold values for Kowara ■R and ■R2, respectively, when detecting a transparent sheet and an opaque sheet using a transmissive type as the second optical sensor 16 as in this embodiment. level.

In addition, when a reflective type sensor is used as the first optical sensor/S, it is shown in FIG. When the comparison reference voltage ■R is at the hold edge, the sheet with high reflectance is conveyed Tt'l has a high threshold.The comparison reference voltage ■R2 of the candy is held.Stiffness value V, Vc: t, Using a reflective type RI R2 optical sensor as the optical sensor of 2, each optimum threshold value for detecting the wrinkles of a sheet with a low reflectance and a sheet with a high reflectance C,=T In addition, each of the comparison reference voltages vR and R2 can be set to their optimum values by appropriately selecting the values of the resistors R and R2 of the non-inverting coefficient multiplier.

As described above, the 100th σ) pulse causes the first
The hold comparison reference voltage ■R obtained by sampling and holding the output voltage of the optical sensor/Sσ) is used as the comparison reference voltage of the output voltage of the second optical sensor l.
T, this is leading. The sheet whose transmittance was measured by the first optical sensor f/3 will be transferred to the second optical sensor l at the timing of the 37.2nd pulse, unless there is any abnormality in the conveyance as explained above. Here, the output voltage is detected by the second optical sensor lB, and its output voltage is applied to the other input terminal of the comparator 21, and the hold comparison reference voltage R is applied at the timing of the 312th pulse. The presence or absence of the sheet is determined based on the threshold value and comparison.

Ttr That is, when a transmission type sensor is used as the second C-type sensor/l, if there is a sheet, the output voltage vs of the sensor obtained from the output terminal decreases and the threshold value Vn The following and 1 (S, the output surface pressure of the comparator 2g will be at a high level. This is the state with the seat. Also, the 2nd cr)
When a reflective sensor is used as the optical sensor 16 and there is a sheet, the output normal pressure ■s of the sensor becomes higher than threshold 4r<VR, and the output η of the comparison a2g
The T pressure becomes a low level.

This is the state with the sheet. This allows the first and second optical sensors 1516 and 741 to check for sheet jams.

As explained above in detail, according to the present invention, the sheet C
1) The threshold value for comparing the output ffl<FF of the second optical sensor installed at the position where the presence or absence is to be detected is the transmittance of the sheet detected by the first optical sensor or Depending on the reflectance G, sheet σ) presence/absence σ
) is automatically set to the optimal η' level for determining σ),
Regardless of the type of sheet, the presence or absence of the sheet can be detected with high accuracy no matter what kind of sheet it is.

Further, since both the first and second optical semi-synthetic sensors are placed under substantially the same environment, changes in detection sensitivity due to dirt will exhibit substantially the same characteristics. Therefore, the threshold value for determining the presence or absence of a sheet by following the output voltage of the first optical sensor for sheet detection also changes, resulting in detection errors due to contamination of both optical semi-sensors. Is it possible to prevent this?

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of a conventional optical sheet detection device, Fig. 1 A and B are configuration diagrams of each transmission type and reflection type optical sensor, and Fig. 3 A and B are sheet A curve diagram showing the relationship between the output normal pressure of the transmission type sensor and the reflection type sensor with respect to the position, and the second figure is an example of the arrangement θ of the first and second optical sensors in the present invention.
)--Examples are shown in Figure 1 and Figure 5, which show an example 11 of the optical sheet detection circuit of the present invention. These are curve diagrams for explaining the relationship between the output voltage and the threshold value with respect to the seat position of the optical sensor, in which Figure A is for the case where a transmission type sensor is used, and Figure B is for the case when a reflection type sensor is used. /... Optical sensor section, semi-city pressure generation section for λ, 3...
・Comparison part, K... Light emitting diode,! ...Phototransistor, 6...Sheet, 7...Cassette, g.
...Paper feed roller, 9...Photoconductor drum, lo...Transfer o -7, //...Register roller, /2...Fuser, /3...Waste paper roller, /l ... Sheet transport path, ts... First optical sensor, /4... First optical sensor, /7... Sheet transport direction, 7g.
・Non-inverting coefficient unit, /9...'F'E'l for gate
' , , 26...Hold capacitor, 2/...
Buffer, n...Pulse input terminal, n...Diode, 2G...Comparator, L...Comparison output terminal. Figure 1 Figure 2 Figure 6 A - Sheet device procedural amendment document January 26, 1980 1. Indication of the case 1987 Patent application No. 187685 2. Name of the invention Optical sheet detection device 3. Amendment Relationship with the patent applicant (037) Olympus Optical Industry Co., Ltd. Telephone (58
1) No. 2241 (representative) 1. Correct "hold capacitor 20" on page 12, lines 19-20 of the specification to "hold capacitor 20." 2. In the first line of page 18, "corresponded to" was replaced with "corresponded to".
Correct. (2) Procedural amendment dated June 30, 19801, Indication of case 1987 Patent Application No. 1876852, Name of invention Optical sheet detection device 3, Person making the amendment Relationship to the case Patent applicant (08?) Olympus Optical Industry Co., Ltd. 1, corrects "optical sensor" in line 7, page 5 of the specification to "optical sensor using transparent sheet." 2. In the same page 7, line 19, "Restart," should be corrected to "Restart, 1." 8 In the same page, 8, line 20, "First optical system" 5 ” to “1st
``Optical sensor 15'' is corrected. 4 Must reach 1 on page 11, line 8. ”
should be corrected to "must have been reached."

Claims (1)

[Scope of Claims] 1. First and first lines sequentially arranged in the sheet conveying direction along the sheet conveying path, and generating an output corresponding to the light transmittance or light reflectance of the sheet, respectively. 2 no Tsu C5
According to the output of the corresponding sensor on the left sheet, the comparison standard normal pressure is set at least a little until the sheet reaches the first optical sensor. and a comparison means for comparing the output level of the first optical sensor using a comparison standard normal pressure such as ili', a!+, and the like as a threshold value, The comparison output of the comparison means at the time when the sheet detected by the optical sensor is scheduled to reach the second optical sensor.
Thus, the presence or absence of the sheet at the second optical sensor position G is detected T2. An optical sheet detection device characterized by: