JP3073053B2 - Sheet detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet detecting apparatus suitable for use in a sheet conveying apparatus for conveying a document or a sheet in a copying machine, an image reader or the like.

[0002]

2. Description of the Related Art In an apparatus for transferring and recording an original image on a sheet, such as a copying machine, a top sheet or a bottom sheet of a plurality of sheets placed on a sheet feed tray is taken out one by one and skewed. It is necessary to feed the paper to the image transfer position in a state where there is no image. In the automatic feeder, which automatically feeds the originals placed on the original tray onto the platen of the copier sequentially, the originals are taken out of the tray one by one and copied without skew. Must be fed onto the machine platen.

Therefore, in such a sheet feeding apparatus that takes out and feeds sheets (hereinafter referred to as documents) one by one, the leading or trailing end of the sheet is fed to a predetermined position, or the sheet is discharged. A number of optical sheet detecting devices for detecting that the sheet has been touched are provided at necessary portions.

This sheet detecting device comprises a light emitting element and a light receiving element. The light emitting element emits light, and the reflected light or transmitted light of the light applied to the sheet is received by the light receiving element. It is common to be configured to detect.

However, in such a sheet detecting device, since the initial sensitivity of the light receiving element and the light emitting element vary, the voltage applied to the light emitting element (light emission control signal) is usually used.
Alternatively, the output control voltage (light receiving control signal) of the light receiving element is manually adjusted by a variable resistor or the like so that the output voltage (light receiving output) of the light receiving element falls within an allowable range.

[0006]

However, even if the initial sensitivity of the light emitting element or the light receiving element is manually adjusted, the sensitivity gradually increases due to aging, or the light emitting surface or the light receiving surface is contaminated by paper dust or the like. Change rapidly,
The presence or absence of a sheet cannot be accurately detected. For this reason, in the past, the maintenance staff had to be periodically inspected for the sensitivity, and the work and management for that were extremely troublesome. In addition, there is a problem that the sensitivity is increased more than necessary, and as a result, the life of the element is shortened.

An object of the present invention is to provide a sheet detecting apparatus which can automatically adjust the sensitivities of a light emitting element and a light receiving element within an allowable range and further extend the life of these elements. To provide.

[0008]

In order to achieve the above object, the present invention comprises a light-emitting element and a light-receiving element, and the light-emitting element emits light, and reflected light or transmitted light of light applied to a sheet is received by the light-receiving element. In a sheet detecting device that receives light and detects the presence or absence of a sheet based on the amount of received light, the light emitting element emits light at an amount of light corresponding to an initial setting voltage, and an output voltage based on the amount of light when the light receiving element receives light and a sheet empty state. The output voltage is compared with a reference voltage after it is determined that there is no paper, and when the output voltage is out of the allowable range of the reference voltage, the initial setting voltage is set so as to fall within the allowable range. Then, the adjusted initial setting voltage is stored in place of the previous initial setting voltage, and the light emitting element is caused to emit light based on the stored initial setting voltage to detect the presence or absence of a sheet. It was.

The adjustment of the initial setting voltage based on the comparison between the output voltage and the paper-out threshold voltage and the comparison between the output voltage and the reference voltage is performed when the power is turned on, after a predetermined number of sheets have passed, and after a predetermined time has elapsed. Also, it is performed periodically at any time after the elapse of an arbitrary period by maintenance personnel.

[0010]

In the above configuration, the output voltage of the light emitting element is automatically adjusted periodically at a predetermined time, such as when the power is turned on, so that the light receiving output of the light receiving element is within an allowable range. Becomes unnecessary until the life of the element is almost exhausted. Therefore, the maintenance work interval is greatly lengthened, and the work cost for that is reduced. In addition, the device can be used until immediately before the device has to be replaced, thereby substantially extending the life of the device. Further, since the presence or absence of paper is determined based on the automatically adjusted output voltage, paper jams and the like can be properly handled.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a two-sided automatic document feeder will be described in detail below.

FIG. 1 is a cross-sectional view showing an embodiment of an automatic two-sided document feeding apparatus to which the present invention is applied. A feeding unit 3 for feeding, a feeding unit 4 for feeding a document fed one by one to a predetermined position on a platen P, a document after image processing is discharged, and the platen P is turned upside down again. It comprises a reversing / discharging section 5 for guiding in the direction of a predetermined position, and a discharge tray 6 for stacking the discharged documents.

The paper feed section 3 comprises a pickup roller 7, a document holder 35, an empty sensor 8, a separation roller 9, a separation pad 36 and a registration sensor 10, and a motor M1 as a power source for the pickup roller 7 and the separation roller 9. Documents placed on the paper feed tray 2 are picked up from the lower side by the pickup roller 7 several times, and have a large loop margin in which only the lowermost document is separated by the separation roller 9 and the separation pad 36. Is sent out to the space 11. Here, the outer guide plate 12
The document which has changed its direction along the line reaches the nip point between the registration roller 14 and the pinch roller 15 of the transport unit 4 via the straight guide unit 13.

The conveying section 4 stretches the resist roller 14 and the pinch roller 15, a wide conveying belt 16, a driving roller 17 and a driven roller 18 for rotating the conveying belt 16, and the conveying belt 16 on the upper surface of the platen P. The document fed to the entrance of the registration roller 14 is rotated by the registration roller 14 while being pressed against the registration roller 14 and the pinch roller 15. Is transported in the direction of the platen P, and is transported onto the platen P by the transport belt 16 that has started rotating simultaneously with the registration roller 14.

At this time, since the optical registration sensor 10 is on until the trailing edge of the original is fed from the position of the registration sensor 10, the control unit, which will be described later, starts the rotation of the registration roller 14 and the drive roller 17 from the timing when the rotation starts. The number of pulses applied to the motor M2, which is the power source of the driving roller 17 and the registration roller 14, until the registration sensor 10 is turned off by the passage of the trailing edge of the document (specifically, the number of pulses from the encoder attached to the motor M2) Is counted, and the original size is classified into the standard original size according to the count value.

When copying is performed on one side only, the motor M2 is stopped when a pulse corresponding to the distance L0 from the position of the registration sensor 10 to the predetermined position A on the platen P is applied to the motor M2. As a result, the document is set at the predetermined position A on the platen P.

Note that the registration roller 14 is used for the conveyance belt 1.
A registration clutch G is interposed between the driving roller M6 and the driving motor M2.
The rotation of is not stopped.

Next, the reversing and discharging unit 5 includes a reversing roller 20 and driven rollers 21a and 21b pressed against the reversing roller 20, a switching claw 22 for reversing the document in the direction of the transport belt 16 with the front and back reversed, and a discharge sensor. 23, a sensor 24 for determining a stop timing at the time of reverse feeding, a discharge roller 25, and a motor M3 as a power source of the reversing roller 20;
The document conveyed in the discharge direction by the conveyance belt 16 with the end of the image processing on one side of the document is conveyed in the discharge direction by the reversing roller 20. At this time, the switching claw 22
Is discharged to the paper discharge tray 6 by the paper discharge rollers 25. However, the switching claw 22
Is switched to the reverse feeding side, it is guided toward the driven roller 18 of the transport belt 16 and is set again at a predetermined position on the platen P by reverse rotation of the transport belt 16.

On the other hand, at the time of double-sided copying, in order to arrange the discharge order of the originals, the originals are once passed over the platen P, and the originals are inverted by the reversing / ejection unit 5, and the inverted originals are moved to the predetermined position A of the platen P. To perform one-sided copying. Thereafter, the original is turned upside down by the reversing / ejection unit 5 and set again at the predetermined position A, and the remaining one side is copied. Thereafter, the switching claw 22 of the reversing / ejection unit 5 is switched to the state shown in FIG. Discharge to 6.

FIG. 2 is a block diagram showing a configuration of a control unit for controlling the conveyance of the original. This control unit is specifically configured by the microcomputer 30. The microcomputer 30 includes an empty sensor 8,
In addition to inputting the output signals of the registration sensor 10, the paper discharge sensor 23, and the sensor 24 for detecting the stop timing, the output signals from encoders (not shown) attached to the motors M1, M2, and M3. Clock pulses φ1, φ2, φ3 are input.

The output signal includes a motor M for rotating the separation roller 9 and the like of the sheet feeding unit 3, a motor M2 for rotating the conveyor belt 16, and a motor M3 for rotating the reversing roller 20. Applied pulses PM1 to PM
3. an ON signal RCL to the registration clutch G for transmitting the rotation of the motor M2 to the registration roller 14;
A drive signal SD or the like to a solenoid (not shown) for switching the switching claw 25 is output.

In such a double-sided document feeder, the registration sensor 10, the paper discharge sensor 23, and the sensor 24 for detecting the paper discharge timing are constituted by optical sensors. Among them, the registration sensor 10 is of a transmission type, the paper ejection sensor 23,
The sensor 24 for detecting the sheet ejection timing is constituted by a reflection type sensor. Then, the sensitivity is automatically adjusted using the microcomputer 30.

FIG. 3 is a circuit diagram showing an example of a configuration for automatically adjusting the sensitivity of the reflection type paper ejection sensor 23. The light emitted from the light emitting element 40 is emitted toward the document conveying path. When there is no original, the light is radiated to the background plate 41 on the back side of the original conveyance path. The background plate 41 is formed of a member having a reflection surface whose reflectance is lower than that of the original, and the light reflected by the background plate 41 is incident on the light receiving element 42. The light-emitting element 40 has an anode to which the power supply voltage Vcc is applied, a cathode grounded through the transistor 43 and the resistor 44, and inputs the initial sensitivity setting voltage V0 to the inverting input of the operational amplifier 45, so that the initial sensitivity setting voltage V0 A corresponding voltage is applied to emit light with a light emission luminance corresponding to V0.

On the other hand, the light receiving element 42 has an emitter grounded through a load resistor 46, and outputs an output voltage Vin corresponding to the amount of light received from the background plate 41.

The initial setting voltage V0 input to the inverting input of the operational amplifier 45 is output from the DA converter 47, and the output voltage Vin of the light receiving element 42 is input to the AD converter 48. The DA converter 47 converts the voltage information output from the CPU 30 into a corresponding voltage value and inputs the converted voltage value to the operational amplifier 45. On the other hand, the AD converter 48 converts the output voltage Vin of the light receiving element 42 into corresponding voltage information and inputs the information to the CPU 30.

At the end of assembling the product, the CPU 30 inputs predetermined voltage information for initial sensitivity setting to the DA converter 47 and sets the initial sensitivity so that the output voltage information of the AD converter 48 falls within the allowable range of the initial sensitivity. When the set voltage V0 is changed little by little and falls within the allowable range of the initial sensitivity, the voltage information input to the DA converter 47 at this time can be electrically written into the nonvolatile memory 4.
9 for use in subsequent sheet presence / absence detection.

The configuration shown in FIG. 3 is for adjusting the amount of emitted light. As shown in FIG. 4, a constant voltage is applied to the light emitting element 40 and the emitter load resistance 46 of the light receiving element 42 is applied. A field effect transistor 50 is connected in series,
The resistance value between the source and the drain of the field effect transistor 50 may be controlled by the gate control voltage V0 so that the output voltage Vin of the light receiving element 42 falls within the allowable range of the initial sensitivity.

As shown in FIG. 5, the configuration shown in FIG. 3 is combined with the configuration shown in FIG.
2 may be controlled using the operational amplifier 45 and the field-effect transistor 50.
In FIG. 5, the voltage for setting the initial sensitivity inputted to the operational amplifier 45 is V01, the field-effect transistor 50
Are shown as V02.

In each case, the sensitivity of the light emitting element and the light receiving element is adjusted by the voltage information. However, the voltage and the current can be treated equivalently if the resistance in the circuit is constant. Even if the adjustment is made, a completely equivalent effect can be obtained.

FIG. 6 shows that the light emitting element 40 emits light at the light emission amount corresponding to the initial setting voltage V0 at the time of assembling the product in the configuration of FIG. 3, and the light amount reflected from the background plate 41 and received by the light receiving element 42 is within an allowable range. To see if it fits in
5 is a flowchart showing an operation procedure for adjusting the initial setting voltage V0 so as to fall within an allowable range.
After outputting the initial setting voltage V0 from the A converter 47, the output voltage Vin of the AD converter 48 and the reference voltage V0
And R (S1, S2). As a result, when Vin is larger than “VR + v” (where v is an allowable difference voltage), it is determined that the light emitting ability of the light emitting element 40 is too large and the light emitting amount is too large, or that the sensitivity of the light receiving element 42 is too high. This means that the initial setting voltage V0 output from the DA converter 47 is reduced by the step voltage e, and the lowered voltage is set as a new initial setting voltage V0 and the operational amplifier 4 again.
5 and the light emitting element 40 emits light at the new initial setting voltage V0 (S3, S4). As a result, Vin becomes "VR
+ V ", then Vin <VR
−Vin−VR−v, it means that the output of the light receiving element 42 is within the range between VR.

Conversely, if Vin <VR-v, it means that the amount of emitted light is too small.
Is increased by the step voltage e, and the increased voltage is input again to the operational amplifier 45 as a new initial setting voltage V0, and the new initial setting voltage V0
Causes the light emitting element 40 to emit light (S5, S6). As a result, Vin is larger than "VR-v" and "VR +
v ”, the output voltage of the light receiving element 42 is“ VR ±
Since the value falls within the allowable range of “v”, the initial setting voltage information input to the DA converter 47 at this time is stored in the memory 49 (S7).

As a result, the background plate 4 on which no original exists
Adjustment of the sensitivity when only 1 is completed. In actual sheet detection, the presence / absence of a sheet is detected using the initial setting voltage information stored in the memory 49 in the initial sensitivity setting operation. That is, since the reflectance of the actual document is higher than that of the background plate 41, the output voltage of the light receiving element 42 becomes higher than VR, whereby the presence or absence of the document can be detected.

However, as described above, the sensitivities of the light emitting element 40 and the light receiving element 42 change over time, and the light emitting surface and the like are clogged with paper dust, so that the sensitivity changes.

Therefore, it is necessary to adjust the sensitivity again at a predetermined time. The readjustment is performed when the power is turned on, after a predetermined number of sheets have been passed, after a certain time has elapsed, or after an arbitrary period of time by a maintenance person.

FIGS. 7 and 8 are flowcharts showing the operation procedure for adjusting the sensitivity each time the power is turned on.
The initial setting voltage information stored in the memory 49 is read, and the read information is input to the DA converter 47, and the light emitting element 40 is read.
At a light emission amount corresponding to the initial setting voltage V0 (S10, S11). Then, in this light emitting state, the output voltage Vin of the light receiving element 42 is compared with the paper-less threshold voltage VTH (where VTH> VR). If Vin ≧ VTH, it is detected that there is paper despite the absence of paper. Therefore, it is recognized that the document exists in front of the background plate 41 for some reason, the jam is cleared, and the paper jam is removed by a maintenance person or the like (S12, S13, S14).

However, if Vin ≦ VTH, the output voltage Vin of the AD converter 48 is compared with the reference voltage VR (S15). As a result, when Vin is larger than “VR + v” (where v is a tolerance voltage), the light emitting element 4
0 means that the light emission amount is too large or the sensitivity of the light receiving element 40 is too high.
Initial setting voltage V0 output from DA converter 47
Is reduced by the step voltage e (S17), and the reduced voltage is input again to the operational amplifier 45 as a new initial setting voltage V0, and the light emitting element 40 emits light at the new initial setting voltage V0. As a result, if Vin becomes smaller than “VR + v”, then it is compared whether Vin <VR−v (S1).
8) If Vin> VR-v, it means that the output of the light receiving element 42 is within the range between VR.

On the other hand, if Vin <VR−v, it means that the amount of emitted light is too small.
Is increased by the step voltage e (S19), and the increased voltage is input again to the operational amplifier 45 as a new initial setting voltage V0, and the light emitting element 40 is turned on with the new initial setting voltage V0. Flash. As a result, V
If in becomes larger than "VR-v", the limit voltage VHL indicating the maximum limit voltage of V0 is compared with the currently output initial setting voltage V0 (S21, S22), and V0
If> VHL, it is impossible to increase the light emission amount of the light emitting element 40 any more. Therefore, an alarm signal is output and a maintenance person is instructed to check for paper dust jam or the like (S23). If the alarm signal is generated due to paper dust jam, the sensitivity adjustment is performed again by turning on the power after removing the paper dust. Note that VHL is a value limited by an allowable current value of the light emitting element 40 and the like.

However, if V0 <VHL, that is, if the limit voltage has not been reached, the process returns to step S15. As a result, the output voltage Vin of the light receiving element 42 becomes VR
If the voltage falls within the allowable range of ± v, the initial set voltage information input to the DA converter 47 at this time is stored in the memory 4.
9 (S20).

The light emitting element 40 or the light receiving element 4
If the sensitivity of No. 2 is further deteriorated due to aging, the output voltage Vin of the light receiving element 42 may not be within the allowable range of VR ± v even if the paper dust is removed and the threshold voltage VHL is exceeded. .

To cope with such a case, the limit voltage VHL is set to VHL0, VHL1, VHL every time the paper dust is cleaned.
2 ……….
If the value does not fall within the allowable range even if it is raised to HLL, an instruction to replace the element is issued.

FIGS. 9 to 11 show the procedure for this. Each time the paper dust is cleaned, the maintenance person is prompted to input that the paper dust has been cleaned (S38) and stored in the memory 49. The paper dust cleaning count NC is updated (S39). After the paper dust cleaning, the power is turned on again to start the operation of FIG. 7. When the operation reaches step S19 of FIG. 7, the process proceeds to step S30 of FIG. , And then select a limit voltage VHLn (n = 1, 2, 3,...) Corresponding to the number of times of paper dust cleaning (S)
31). As shown in FIG. 10, the limit voltage VHLn is obtained by adding the coefficients a, a to the voltage V0 set in the initial sensitivity setting mode.
are calculated by multiplying b, c... and stored in the memory 49 in advance.

The threshold voltage VHLn selected at this time is
(N = 1, 2, 3,...) And the currently output set voltage V
0 (S32, S33), and if VHLn <V0, the flow returns to step S15 in FIG. 7 to perform the subsequent processing. However, if VHLn> V0, VHLn is compared with the final limit voltage VHLL (S34). If VHLn ≧ VHLL, no further improvement in sensitivity can be expected, and it is indicated that the element itself should be replaced. An alarm is output (S37). However, if VHLn ≧ VHLL, the limit voltage can be further increased, and a paper dust cleaning alarm is output (S36).

As described above, the sensitivity of the light emitting element 40 and the light receiving element 42 is gradually increased until immediately before the end of the service life, so that the sensitivity is not excessively increased, and the light emitting element 40 and the light receiving element 42 are completely deteriorated. Until that time, the presence or absence of the sheet can be accurately detected. As a result, the life of the element itself can be improved, and the maintenance management can be extremely simplified.

By the way, if the amount of light emitted from the light emitting element 40 or the sensitivity of the light receiving element 42 is reduced due to the adhesion of paper dust or the like, and if the amount of light emitted from the light emitting element 40 is increased to compensate for this, the paper When the powder is removed, the background plate 41
There is a possibility that the output voltage Vin of the light receiving element due to the reflected light from the light exceeds the paperless threshold value VTH. In such a case, a serious operation failure in which the paper absence state is erroneously detected as "paper present" is caused.

Therefore, the output voltage Vin of the light receiving element due to the reflected light from the background plate 41 is VT with respect to the initial setting voltage V0 for controlling the light emission amount of the light emitting element 40 in a state where the paper dust is not stained.
VLMT that gives a light emission amount not exceeding H is set, and V0>
When the VLMT is reached, an alarm requesting maintenance work such as paper dust removal is output. After the paper dust is cleaned, the maintenance staff resets the initial settings and resets the VLMT. In this way, the VLMT is set for each paper dust cleaning, and the final limit voltage V
Upon reaching HLL, an instruction is given to replace the element.

FIGS. 12 and 13 show the procedure for this. When the power is turned on and the process reaches step S19 in FIG. 7, the process proceeds to step S50 in FIG. 12, and V0 and VLM are set.
Compare with T. If V0 <VLMT, the process returns to step S15 in FIG. 7 to perform the subsequent processing. However, V0> VL
If it is MT, the final limit voltage VHLL is compared with V0,
(S52, 53) If V0 <VHLL, recovery of the sensitivity can be expected by cleaning the paper dust, so that an alarm for instructing paper dust cleaning is output (S54). If V0>, the limit of the element has been reached, and an alarm instructing replacement of the element itself is output (S54).

The VLMT is set at the initial stage or after the processing for setting the sensitivity after cleaning the paper dust (FIG. 6), and as shown in FIG. 13, a coefficient a previously set to V0 set by the initial sensitivity setting is set. It is calculated by multiplication (S56). The coefficient a is a threshold voltage VTH when there is no paper and a reference voltage V when there is no paper.
It is set to a value smaller than the ratio VTH / VR to R. The set VLMT is stored in the EEPROM, and the value is not updated thereafter until the next sensitivity setting after cleaning the paper dust (S57).

[0048]

[0049]

[0050]

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a document feeding apparatus to which the present invention is applied.

FIG. 2 is a configuration diagram of a control unit.

FIG. 3 is a circuit diagram showing a first embodiment of the sheet detecting device of the present invention.

FIG. 4 is a circuit diagram showing a second embodiment of the sheet detecting apparatus according to the present invention.

FIG. 5 is a circuit diagram showing a third embodiment of the sheet detecting device of the present invention.

FIG. 6 is a flowchart showing an initial sensitivity adjustment procedure of the embodiment of FIG. 3;

FIG. 7 is a flowchart showing a sensitivity adjustment procedure performed when power is turned on in the embodiment of FIG. 3;

FIG. 8 is a flowchart showing a latter part of the flowchart of FIG. 8;

FIG. 9 is a flowchart illustrating a procedure for issuing a warning when the sensitivity adjustment has reached a limit.

FIG. 10 is a flowchart showing a procedure for inputting that the paper dust has been cleaned.

FIG. 11 is a flowchart showing a procedure for setting a limit voltage according to the number of times of paper dust cleaning.

FIG. 12 is a flowchart illustrating another example of a procedure for issuing a warning when sensitivity adjustment has reached a limit.

FIG. 13 is a flowchart showing a procedure for calculating a limit voltage used in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Automatic original supply apparatus 10 Registration sensor 23 Discharge sensor 30 Microcomputer 40 Light emitting element 41 Background plate 42 Light receiving element 45 Operational amplifier 47 DA converter 48 AD converter 49 Nonvolatile memory 50 Field effect transistor

Claims (2)

(57) [Claims] 1. A sheet detection device comprising a light-emitting element and a light-receiving element, wherein the light-emitting element emits light, and the light-receiving element receives reflected light or transmitted light of light applied to the sheet, and detects the presence or absence of the sheet based on the received light amount. In the device, the light emitting element emits light with an amount of light emission corresponding to the initial setting voltage, and an output voltage based on the amount of light when received by the light receiving element is compared with a threshold voltage without paper, and after it is determined that there is no paper, The output voltage and the reference voltage are compared, and when the output voltage is out of the allowable range of the reference voltage, the initial setting voltage is adjusted so as to fall within the allowable range. A sheet detecting device, wherein the sheet is replaced with a set voltage and stored, and a light emitting element is caused to emit light based on the stored initial set voltage to detect the presence or absence of a sheet. 2. The method according to claim 1, wherein the comparison between the output voltage and the threshold voltage without paper and the adjustment of the initial setting voltage based on the comparison between the output voltage and a reference voltage are performed when power is turned on, after a predetermined number of sheets have passed, and after a predetermined time has elapsed. 2. The sheet detection apparatus according to claim 1, wherein the detection is periodically performed at any time after an arbitrary period has elapsed by a maintenance person.