JPS5917439A - Detector for sheetlike matter - Google Patents

Abstract

PURPOSE:To improve the accuracy of detecting the presence of a sheet, by disposing a light emitting surface and a light receiving surface both in the same direction, while installing light reflecting devices so as to face each other with a passage in between. CONSTITUTION:A light emitting surface of a light emitting device LED1 and a light receiving surface of a light receiving device PT1 both are disposed substantially in the same direction toward a sheetlike matter passage, and a platelike or sheetlike light reflecting device AL being relatively high in a reflection factor is disposed at a position opposite to both the light emitting device LED1 and the light receiving device PT1 with the sheetlike matter passage sandwiched between them and thereby the presence of the sheetlike matter and the number of them are discriminated on the basis of a level of the signal outputted by the light receiving device PT1. Therefore, in case of such a sheet as high in light transmittability, light from the light emitting device LED1 is transmitted through the sheetlike matter, then reflected at the light reflecting device AL and again transmitted through the sheetlike matter, reaching the light receiving device PT1, so that the attenuation of light by the sheet grows large, thus the presence of the sheet is easily detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the detection of sheet-like objects, and particularly to a sheet-like object detection device that detects the presence or absence of sheet-like objects including transparent sheets and the number thereof.

For example, devices that handle such sheet-like objects, such as copying machines, printers, and facsimiles, detect the presence or absence of the sheet-like object, check whether the sheet-like object is being fed to a predetermined position, and detect the presence or absence of the sheet-like object. If there is a sheet-like object, processing continues; if there is no sheet-like object, it is necessary to display "No recording paper" or perform jam removal.

Detection of this type of sheet-like object has conventionally been performed using a photo sensor, a microsinch, an ultrasonic sensor, or the like. Among these detectors, microswitches and ultrasonic sensors are large in size and require a large amount of space; microswitches have mechanical contacts and are therefore less reliable; The electrical circuit connected to the sensor is complex and expensive. For this reason, photosensors are most commonly used. Photosensors can be used in a transmission type, in which a sheet is passed between opposing light emitting means and light receiving means, and in a reflective type, in which the light emitting means and light receiving means are oriented in the same direction and the light reflected from the sheet is detected by the light receiving means. However, with the former, it is necessary to place the light emitting means and the light receiving means separately with a sheet in between, so each of the light emitting means and the light receiving means requires a space and a mounting member for mounting. Furthermore, it is difficult to align the optical axes of the light emitting means and the light receiving means during installation, and installation is time consuming. Therefore, in applications such as copying machines that require miniaturization and cost reduction of the device, it is preferable to use a reflective photosensor.

By the way, in copying machines, for example, various types of sheets are used as recording media. Some of these sheets have low transparency, such as plain paper, and others have high transparency, such as tracing paper for second originals or transparent paper for overhead projectors. However, when detecting a sheet using a reflective photosensor, when using a transparent sheet such as tracing paper, the reflected light from the sheet is weak, so even if there is a sheet, it is determined that there is no sheet. Sometimes I end up doing it. If the signal output from the photoreceiver is amplified to increase the detection sensitivity on the photoreceiver side, it will be possible to detect ``light detection J'', that is, ``sheet present'' even for weak light. is likely to malfunction due to external light or noise generated inside the receiver.

In addition, in copying machines and the like, when static electricity is generated and overlapping sheets of paper are attracted to each other, such as in the winter when humidity is low, so-called multi-feeding, in which multiple sheets of paper are fed at once, may occur. However, in the general method of detecting the presence or absence of a sheet-like object by detecting the reflected light from the sheet-like object, the output of the light receiver changes depending on whether there is one sheet-like object or two or more sheets. Double feed cannot be detected because the signal level does not change.

The first object of the present invention is to provide a sheet-like object detection device that can detect many types of sheet-like objects including transparent sheets, and the second object is to detect the presence or absence of sheet-like objects. An object of the present invention is to provide a sheet-like object detection device capable of determining the number of sheet-like objects.

The third object is to provide a sheet-like object detection device that is easy to install and can be installed even in a narrow space.

In order to achieve the above object, the present invention provides a method in which the light-emitting surface of the light-emitting means and the light-receiving surface of the light-receiving means are arranged to face the sheet-like object path in substantially the same direction. A plate-shaped or sheet-shaped light reflecting means with relatively high light reflectivity is arranged at a position facing the light emitting means and the light receiving means across the passage, and the 1
- Determine the presence or absence of a sheet-like object and the number of sheet-like objects. As a result, in the case of a sheet with high light transmittance, the light emitted from the light emitting means 1 passes through the sheet, is reflected by the light reflecting means, and passes through the sheet again. The light reaches the light receiving means number 3. In this case, since attenuation of the light by the sheet-like object is small, relatively strong light reaches the light-receiving means, but the intensity is weaker than when there is no sheet-like object.

Furthermore, when the number of sheets changes, the intensity of light reaching the light receiving means changes, so the number of sheets can be determined from the intensity of the light. Furthermore, in the present invention, even when the sheet-like object is transparent paper, the light emitted from one light-emitting means and reaching the light-receiving means is transmitted twice.
Since the light passes through the sheet, the attenuation of the light by the sheet is large, making it easy to detect the presence or absence of the sheet. When the sheet-like object is plain paper, the direct reflected light from the sheet-like object also reaches the light receiving means, but in the case of plain paper for a PPC copier, for example, the light passes through the sheet and is reflected by the light reflecting means. There is also transmitted light that returns to the light receiving means, and the intensity of that transmitted light changes considerably depending on whether there is one sheet or two or more sheets. , and the number of sheets, that is, the presence or absence of double feeding. Moreover, according to the present invention, it is possible to
Since there is no need for the light emitting means and the light receiving means to face each other with a sheet in between, the light emitting means and the light receiving means can be mounted on the same surface, or the light emitting means and the light receiving means can be integrated, making installation easy. be. In particular, when the light emitting means and the light receiving means are integrated, there is no need to adjust the optical axis when attaching them to the device.

As the light reflecting means, a metal such as an aluminum plate or aluminum foil, a mirror, or the like can be used. Although a light emitting diode, a light bulb, etc. can be used as the light emitting means, it is most preferable to use a light emitting diode in terms of size and the like. A photodiode, a photo transistor, CdS, etc. can be used as the light receiving means.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1a shows a schematic configuration of one type of copying machine embodying the present invention. To explain the outline of the mechanism with reference to FIG. 1 mirror 5, 2nd mirror 6
, the lens 8, the third mirror 9, the fourth mirror 10, the magnification setting lens 25, and the slit 7. It is scan driven in the direction of AR2 and 8R3. As a result, the entire image of the document 3 is projected onto the surface of the photoreceptor tram 11, and a latent image corresponding to the image is formed. This latent image is developed by a developing device 12,
The developed toner is transferred directly below the transfer charger 13 onto the recording paper sent from the lens 1 to the roller 14 . J~Luna on the recording paper is fixed by a fixing roller 15, and the recording paper that has been fixed is sent onto a transport tray 17 by a transport roller 16. 18 is an electrostatic charger, 19
20 is a cleaning roller, and 21 is to the cleaning plate 1. The copying machine shown in FIG. 1a is of a two-stage paper feeding type in which two cassettes 22a and 22b can be attached and detached.

By selectively driving one of the paper feed rollers 23a and 23b, the recording paper in the cassette 22a or 22b is fed to the registration roller 14.

Reflective photosensors PH1 and PH2 are mounted on guide plates between paper feed rollers 23a and 23b, which serve as paths for recording paper, and registration rollers 14, respectively. Between the photosensitive drum 11 and the fixing roller 15, and between the fixing roller 15 and the paper discharge tray 17, there are reflective photosensors p)13. PI-14 and PH5 are installed.

Photo sensors PH1 and PH2 detect paper feeding error #8 when feeding paper from cassettes 22a and 22b, respectively.
Detects paper jams and double feeds.

The photo sensor PH3 detects a jam near the lens 1 roller 14, the photo sensor PH4 detects the winding of recording paper on the photosensitive drum, and the photo sensor PH5 detects a jam in the fixing section and the presence or absence of paper ejection.

The vicinity of the photosensor PH1 is shown enlarged in FIG. 1b.

Referring to FIG. 1b, the photosensor PH1 is composed of a light emitting diode LEDI and a phototransistor PTI. Light emitting diode LED1 and photo1-transistor PTI are connected to spacers SPI and SF3, respectively.
It is fixed to the printed circuit board PCB by soldering. The printed circuit board PCB is fixed to the guide plate 30a with screws. The guide plate 30b has ■-4EDI, P
Aluminum foil AI- is attached to the position facing Tl. Spacers SPI and SF3 have slightly different thicknesses depending on their position, which causes LEDs 1 and PTI to be slightly tilted. This inclination means that the optical axis of LED 1 and PTI is exactly aligned with the aluminum foil AT-
Set it to match at the predetermined position above. Holes are formed in the guide plate 30a at positions facing the LED and PTI, so that when there are no special obstacles, the light emitted from the LEDI is reflected by the AL and reaches the PTI. There is. In addition, photosensor PH2,
PH3, PH4 and PH5 have the same configuration and installation as PH1.

2a and 2b schematically show the control circuit of the copying machine of FIG. 1. FIG. This will be explained with reference to FIGS. 2a and 2b. MPU+ and MPU2 are microprocessors 8751 manufactured by Intel Corporation. MPUI and MPU2 are connected to connector CNl-].

2 and CN2.

The MPUI includes a 4-bit A/D converter, 8-pin 1-
A/D converter, r10 & ROM, RAM memory card, voice synthesis chip, etc. are connected, and MPU
I is designed to control the light amount of the illumination lamp, fixing temperature control, control of various clutches, audio output control, etc. Connected to the MPU 2 are a key switch matrix 9 display unit of the operation panel, a voice recognition unit, a discrimination circuit CMP for discriminating the state of recording paper, and the like.

The specific configuration of the discrimination circuit CMP and its surroundings is shown in FIG. 2C. This will be explained with reference to FIG. 2C. The aforementioned photosensors PI-11, PI(2,
PH3, PT-(4 and PH5 are connected.○
P1 to OP8 are operational amplifiers, and in this embodiment, the amplification degrees of these operational amplifiers are set relatively high, and these are used as analog comparators. Operational amplifier○
The output terminals of P1 to OP8 are connected to inverters INI to
Through the INS, the microprocessor MPU2
ports PIO to P]7. #Sheet detection in the paper section can be performed using either photosensor PHI or PH2 depending on the selected cassette 1~.
In this embodiment, one of the signals output from PI-II and PH2 is selected by analog multiplexer AM,
It is configured to be applied to an operational amplifier. In the sheet feeding section, since it is desired to detect the presence or absence of various sheets 1 to 1 and the presence or absence of double feeding, the output terminal of the analog multiplexer AM is connected to five operational amplifiers ○P1 to ○P5, each having a different comparison level. Since it is only necessary to detect the presence or absence of double feeding at one position, the remaining photosensors PH3, PH4 and PH
The output terminals of 5 each have one operational amplifier ○P6. ○P
7 and OF8.

When the sheet does not block the optical path of each photosensor, the light emitted from the light emitting diode enters the phototransistor with almost no attenuation. That is, in that case, the conductivity of the phototransistor (PTI) becomes high and the output voltage of the photosensor becomes a relatively low level. When a sheet is present in the optical path of the photosensor, the amount of attenuation of the light emitted from the light emitting diode changes depending on the type and number of sheets, so the output voltage of the photosensor changes accordingly. . FIG. 3 shows an example of the relationship between the output voltage of the photosensor and the sheet.

To explain with reference to FIG. 3, the output voltage of the photosensor is between voltage 0 and vl when there is no sheet, and when transparent paper such as racing paper is
If there are two sheets of transparent paper, the voltage is between V1 and ■2, if there are two sheets of transparent paper, the voltage is between v2 and ■3, and if one sheet of plain paper is present, the voltage is between v3 and V4. If there are two sheets of plain paper, it is between V4 and v5. In other words, by checking the output voltage of the photosensor, it is possible to detect the presence or absence of sheets and the number of sheets (multiple feeding).

In this embodiment, the operational amplifier ○PI of FIG. 2C.

OF2. ○F3. Non-inverting input terminals of OP4 and OF2 (
+) are divided into voltages Vl, V2 . V3. V4 and V5. Therefore, when the output voltage of photosensor PH1 is lower than V1, that is, in the state of "Shi 1~None", ○P1
~ All output voltages of OP5 are at a low level rLJ, but for example, when two sheets of transparent paper are fed double, the output voltage of the photosensor will be between ■2 and v3, so the output voltages of OPI and OF2 will be is inverted to high level "H", low level rLJ and low level rLJ are applied to baud 1-P10 and pH of microprocessor MPU2, respectively, and high level rHJ is applied to the other three ports. Ru. In addition, photosensor P) (3, PH4 and P)
Operational amplifier ○P6 connected to 15. ○P7 and OF
The potential of the non-inverting input terminal of 8 is set to 1, which is the same as OPI. Table 1 below shows the states of the ports of the microcomputer MPU2 in various states depending on the type of sheet, number of sheets, etc.

Table 1 When the MPU 2 reads the states of ports PIO to P17, ports PIO to P17 each correspond to data bits O to 7, and each of those pintos indicates the state of the port rH
Set to "1" and "0" depending on J and rLJ. That is, the microprocessor MPU2 determines the presence or absence of sheets in each section and the presence or absence of double feeding by reading the states of the ports PIO to P]7 at predetermined timing.

This embodiment is equipped with a voice synthesis circuit, so if the recording paper is not detected after a predetermined period of time or a paper jam occurs, a voice message will be displayed saying, ``A jam has occurred in the paper feed section.'''', etc., and then announces how to remove jammed paper, and the same process is also performed when double feeding occurs. If the photo sensor PH3 determines that there is a jam, the jam is near the registration roller, so before making an announcement, try reversing the negative registration roller, and if it returns to normal, the alarm will not be issued. Continue processing. Note that even when a jam is determined, if there is a paper located ahead of the jammed paper, the conveyance system is driven until the paper is ejected.

If a jam is detected near the photosensor PH5, that is, the fixing roller 15, the fixing heater RYUKO is immediately turned off to prevent ignition.

FIG. 4a shows a partial circuit configuration of another embodiment of the invention. This will be explained with reference to FIG. 4a.

In this embodiment, the operational amplifiers ○P1 to ○P
8, an A/D converter is used. The A/D converter used here has a built-in analog multiplexer, and is designed to selectively A/D convert signals applied to any of input terminals 0.1, 2.3, and 4. It has become.

Input channel switching is performed by a 3-bit input channel designation signal from a microcomputer. This A/D converter constantly repeats A/D conversion, and outputs a conversion completion signal when valid data is being output. Therefore, the microcomputer selects the photo sensor at the position where sheet detection is to be performed using the input channel designation signal, and reads the conversion data when the conversion end signal is output.

FIG. 4b shows a schematic sheet detection operation of the microcomputer shown in FIG. 4a. The operation of each step will be explained with reference also to FIG. 4b.

To match the timing of the St copy sequence,
The timing for checking each photosensor PHI, PH2, PH3, PH4, and Pl(5) is determined.

S2 Check the output level of each photosensor when there is no sheet. Based on the data obtained as a reference, the data in the look amplifier table in the memory that determines the level for determining the presence or absence of sheets and the number of sheets is calibrated. In other words, the lookup table contains standard comparison data (Vl-VO, V2-VO, V3-VO in Figure 3).
, V4-vO and v5-vO) are registered, and the value (VO) sampled in the "no sheet" state is added to the data in the lookup table. As a result, even if there is a change in any of the light emitting means, light receiving means, and light reflecting means, the data in the lookup table is updated to follow the change, so it is possible to accurately determine the presence or absence of sheets and the number of sheets. can be carried out.

83 Determine whether it is time to check the paper feed section, that is, the position of PH1 or PH2.

84 Determine whether it is time to check with PH3.

85 Determine whether it is time to check with PH4.

86 Determine whether it is time to check with PH5.

S7: In accordance with the specification of the paper feed cassette, the signal of the photo sensor PH1 or PH2 is specified as the input signal of the A/D converter.

S8: Designate the signal of photosensor PH3 as the input signal of the A/D converter.

S15 The signal of the photosensor PH4 is designated as the input signal of the A/D converter.

S9: Designate the signal of the photosensor PH5 as the input signal of the A/D converter.

S10 Wait for the conversion end signal to be output.

Sll Converted data from the A/D converter is stored in a predetermined register register according to the specified photosensor.

S12 As shown in Table 1 above, the output signal level of the photosensor changes depending on the presence or absence of sheets and the number of sheets, so the digital data obtained in step Sll is
Compare the data in the lookup table to determine which one it applies to.

S13 The result determined in step S12 is jam,
Check for abnormalities such as double feeding.

S14 Diagnosis is performed and predetermined processing is performed depending on the type of abnormality.

According to this embodiment, the comparison data is constantly updated by detecting the initial light amount after the voltage is turned on, so even if the emitted light amount fluctuates or the light emitting diode, phototransistor, and reflection means become dirty, the sheet detection will be performed. There will be no wrong judgment. In addition, in this embodiment, by increasing the resolution of the A/D converter and subdividing the data in the lookup table, it is possible to accurately determine the presence or absence of sheets and the number of sheets, even for even more types of sheets with different transmittances. It can be determined.

As described above, according to the present invention, the presence or absence and number of sheet-like objects including transparent sheets can be detected.

[Brief explanation of drawings]

FIG. 1a is a side view showing the configuration of one type of copying machine implementing the present invention, FIG. 1b is an enlarged sectional view showing the vicinity of PH1 in FIG. 1a, and FIGS. 2a and 2b are the views shown in FIG. 1a. FIG. 2c is a block diagram showing the configuration of the discrimination circuit CMP of FIG. 2b, and FIG. It is a graph showing the relationship. FIG. 4a is a block diagram of an electric circuit of another embodiment of the present invention;
FIG. 4b is a flowchart showing the operation of the microcomputer shown in FIG. 4a. 1: Contact glass 2: Holding plate 3: Original 4: Illumination light 5: First mirror 6: Second mirror 7: Slit 8, 25: Lens 9: Third mirror
10: Fourth mirror 11: Photosensitive drum 12: Developing device 13: Transfer charger 14 Ni registration roller 15: Fixing roller 16: Conveyance roller 17: Paper ejection tray 18: Charger 19: Discharge charger 30a, 30b: Paper guide LEDI : Light emitting diode (light emitting means) PTI: Phototransistor (light receiving means) AL Ni-Aluminum foil (light reflecting means) SPI, SP2 spacer CMP: Discrimination circuit (level discrimination means) Patent applicant Ricoh Co., Ltd.

Claims (1)

[Claims] (]) Light-emitting means that emits light toward the path of the sheet-like object; Light-receiving means disposed near the light-emitting means with its light-receiving surface facing substantially the same direction as the light-emitting means. A sheet-like object, comprising: a light reflecting means disposed at a position facing the light-emitting means across a path of the sheet-like object; and a level discriminating means for discriminating three or more levels of signals output from the light-receiving means; Detection device. (2) The level determination means includes an analog comparator;
A sheet-like object detection device according to claim (1). (3) The sheet-like object detection device according to claim 1 or 2, wherein the light reflecting means is a metal plate. (4) The light reflecting means is a mirror.
The sheet-like object detection device according to item 1) or item (2).