JPS58153106A - Copying paper detecting device in image forming apparatus - Google Patents

Abstract

PURPOSE:To prevent erroneous operations, by providing an infrared ray sensor, which detects heat radiating energy of a heating body through a conveying path of the copying paper, and detecting the presence of the copying paper at a specified position based on the output signal of the infrared ray sensor. CONSTITUTION:The infrared ray sensor 5 is connected to a level detector 21 through an amplifier 20. When the output of the level detector 21 is detected to be a specified level or more, a copying paper detecting signal 22 is outputted. When the heat radiation of the heating body 6 is shielded by the copying paper 3, the heat radiating energy, which is inputted into the infrared ray sensor 5, is discontinuously decreased, and a signal is outputted from the infrared ray sensor 5. When the shielding of the heat radiation from the heating body 6 is stopped, a signal also outputted from the infrared ray sensor 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copy paper detection device in an image forming apparatus such as a copying machine.

Conventionally, detection of copy paper conveyed in image forming apparatuses such as copying machines, laser printers, facsimile machines, etc.
This is done by contact detection using a micro switch or reed switch, or non-contact detection using light, sound, etc. However, in the case of contact detection using microswitches, reed switches, etc., because the switch contacts come into contact with the paper, sometimes the paper cannot be fed smoothly and paper jams are likely to occur. There are drawbacks. Non-contact detection solves this drawback of contact detection, but in the case of non-contact detection using light, malfunctions are likely to occur due to dirt on the receiving/emitting surface of the receiving/emitting cable or the influence of external light. Problems such as difficulty in detecting OHP (overhead projector) paper, which transmits light well, are identified. Furthermore, in the case of non-contact detection using sound, there are problems in that malfunctions are likely to occur due to external sounds such as a ring of keys or the ringing of a telephone, or malfunctions due to diffused reflection of sound.

The present invention has been made in view of the above-mentioned problems, and its purpose is to detect, with an infrared sensor, the interruption of the heat radiation energy of the heating element by the conveyed copy paper.
It is an object of the present invention to provide a copy paper detection device for an image forming apparatus that does not cause detection malfunctions due to external factors when detecting the conveyance of copy paper in a non-contact manner.

Here, the principle of the present invention will be explained.

An object at a temperature above absolute zero emits thermal radiation energy from its surface corresponding to the object's absolute temperature. This thermal radiation propagates through space as electromagnetic waves, and the wavelengths of these electromagnetic waves are distributed from the visible light range to the infrared light range. Therefore, by detecting this thermal radiation energy, the temperature of an object can be measured from a remote location.

In the present invention, an infrared sensor based on the above-described principle is used to detect the copy paper being conveyed.

There are two types of infrared sensors: photon type and negligible type, and negligible type sensors include resistive type, thermocouple type, capacitor type, and pyroelectric type.

Among these, the pyroelectric type element is currently the cheapest and most widely used.Hereinafter, the case where this pyroelectric type infrared detection element is used in the present invention will be explained, but in the non-invention, the above-mentioned Other infrared sensors can be used as well.

The pyroelectric effect is a phenomenon in which charges appear on the surface of a crystal when a part of the crystal is heated.

Under normal conditions, this surface charge combines with ions and electrons in the atmosphere and is electrically neutralized, producing no output signal. When infrared rays are cut off by a shutter or the like, or when switching from blocking to irradiation, charges appear for a short time due to spontaneous polarization of the crystal. In this way, in order to obtain a signal from an electroless element,
Rather than continuously irradiating infrared rays, it is necessary to change from blocking to irradiating or from irradiating to blocking.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

As shown in FIG. 1, a first infrared sensor 5 is provided in the conveying path of the copy paper 3 between the photosensitive drum 2 of the copying machine 1 and the feeding loaf 4 of the copy paper 3. A heating element 6 is arranged opposite to the heat receiving surface of the infrared sensor 5 and across the conveyance path of the copy paper 3.
is provided. For example, a lamp, a resistor, a heater, or the like is used as the heating element 6. The above-mentioned infrared sensor 5 is supported at a position where its heat-receiving surface contacts the copy paper 3 being conveyed. Furthermore, a transfer charger 7 and a separation charger 8
A second infrared sensor 9 is placed below the conveyance path of the copy paper 3 which is carried out from the photoreceptor dome 2 through the ! provided. This infrared sensor 9 is connected to an eraser pump 10 for erasing the residual charge on the photosensitive drum 2 provided above the conveyance path of the copy paper 3.
It is supported at a position where thermal radiant energy of is incident. In addition, in order to thermally fix the transferred copy paper using a conveyor belt 11, a fixing loaf 12 and a presser roller 13 are used.
The copy paper is sent to a fixing machine, and after being fixed, is delivered to a tray 15 by a delivery loaf 14.

Further, in the circuit for outputting a copy paper detection signal from the output signals of the infrared sensors 5 and 9, as shown in FIG. It is connected to the detector 21. The output signal of the infrared sensor 5 is amplified by the amplifier 20,
When the level detector 21 detects that the output of the amplifier 20 is partially above the level, the copy paper detection signal 22
is output. Furthermore, as shown in FIG.
0 includes two operational amplifiers 201 and 20b, and the level detector 21 includes a variable resistor 218 and a comparator 21b.

Now, the copy paper 3 taken in from the paper feed cassette 16 is conveyed by the feed roller 4, and when the copy paper 3 blocks the heat radiation of the heating element 6, the thermal radiation energy incident on the infrared sensor 5 is discontinuously reduced. At this very moment, a signal is output from the infrared sensor 5 according to the above-mentioned principle.

In addition, the infrared sensor 5 similarly detects the momentary minimum time when the copy paper 3 passes and the heat radiation of the heating element 6 is no longer blocked.
A signal is output from. The output signal of the infrared sensor 5 is amplified in two stages by the two operational amplifiers 20a and 20b of the amplifier 20 shown in FIGS. If the level is higher than the set reference level, the comparator 21b
A copy paper detection signal is output from. Through the above-described operation, entry and passage of copy paper is detected. Note that since the conveyed copy paper 3 passes in contact with the heat-receiving surface of the infrared sensor 5, dirt on the heat-receiving surface of the infrared sensor 5 due to paper dust etc. is cleaned, and a decrease in sensitivity of the infrared sensor 5 can be prevented.

Furthermore, the copy paper 3 that has been transferred is carried out from the photoreceptor drum 2, and while the copy paper 3 passes, an erase lamp 10
Thermal radiation entering the infrared sensor 9 from the infrared sensor 9 is blocked. In this case as well, in the same manner as described above, the infrared rays are detected by the above-mentioned principle at the minimum time when the copy paper 3 cuts off the heat radiation t-a of the Irene lamp 9 and at the minimum time when the copy paper 3 passes and is no longer blocked. A signal is output from the sensor 9, and a copy paper detection signal is output by the circuit shown in FIGS. 2 and 3.

The above-mentioned infrared sensor is desirably placed below the heating element as in the above embodiment in order to avoid heating due to thermal convection generated by the heating element, but it may be placed diagonally above the heating element. Furthermore, the copy paper detection device according to the present invention can not only detect the movement of copy paper as described above, but also detect the stoppage of the transport belt when placed near the transport belt, and can also detect the stoppage of the transport belt. By arranging an infrared sensor and a heating element across them, it is also possible to detect a shortage of copy paper in the paper feed cassette.

Further, although the above embodiments apply the present invention to a copying machine, the present invention is not limited thereto, and can be applied to other image forming apparatuses such as laser printers and facsimile machines.

As described above, the image forming apparatus according to the present invention includes a heating element and an infrared sensor that detects the thermal radiation energy of the heating element, which is connected to the copy paper conveyance path, and receives the output signal of the infrared sensor. Since it detects that the copy paper is in a predetermined position, there is no longer any malfunction caused by external factors such as light or sound when detecting the copy paper without contact. In addition, maintenance work such as adjusting the operating position of the detection switch and cleaning the detection element from dirt caused by paper dust or the like becomes unnecessary.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a processing device for an output signal of an infrared sensor, and FIG.
The figure is a detailed circuit diagram of FIG. 2. DESCRIPTION OF SYMBOLS 1... Copy machine, 3... Copy paper, 5, 9... Infrared sensor, 6... Heating element, 10... Irene lamp. Patent applicant Minolta Camera Co., Ltd. Representative Patent Attorney Aoyama Hogai (2)

Claims (3)

[Claims] (1) placed at a predetermined position inside the image forming apparatus;
The apparatus further includes a heating element, an infrared sensor for detecting thermal radiation energy of the heating element, and an infrared sensor for detecting the thermal radiation energy of the heating element, and a conveying path for all copy paper, and detects that the copy paper is at a predetermined position based on an output signal of the infrared sensor. Copy paper detection device for image forming apparatus featuring features. (2) The device according to claim 1, wherein the infrared sensor comprises a pyroelectric infrared detection element. (3) The apparatus according to claim 1, wherein the heat-receiving surface of the infrared sensor and the copy paper being conveyed are in contact with each other.