JPS58153956A - Detector for copy paper of image forming device - Google Patents

Abstract

PURPOSE:To prevent malfunctions due to external factors such as light and sound and to make it unnecessary to adjust the deviation of a switch position and sweep the dirt due to paper powder or the like, by detecting the passage of a copy paper by the output signal of an infrared sensor. CONSTITUTION:An infrared sensor 5 is provided in the position, to which the heat radiation energy from a copy paper 4 carried out through thermal fixing is made incident, between a fixing roller 2a and a pressing roller 2b and feeding rollers 3a and 3b in a copying machine 1. Screening plates 6a and 6b which intercept the heat radiation from the fixing roller 2a are provided between the infrared sensor 5 and the fixing roller 2a. In the output signal detecting circuit of the infrared sensor 5, the infrared sensor 5 is connected to an amplifier 10 and is connected furthermore to a level detector 11; and when the detector 11 detects a certain level or above, a copy paper detection signal 12 is outputted.

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.

2. Description of the Related Art Conventionally, the removal of copy paper from an image forming apparatus such as a copying machine, a laser printer, or a facsimile machine has been detected by contact detection using a microswitch or reed switch, or by non-contact detection using light, sound, or the like. However, in the case of contact detection using a micro switch or reed switch, etc., there is a drawback that the paper is not fed smoothly because the contact of the switch comes into contact with the paper, and paper jams are likely to occur. . Non-contact detection eliminates the drawbacks 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 element or the influence of external light.
In addition, there are other problems such as difficulty in detecting OHP (over head glossy) paper which transmits light well. 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 problems, and its purpose is to detect the removal of copy paper without contact by detecting the thermal radiation energy of copy paper that has been heated through thermal fixation. It is an object of the present invention to provide a copy sheet detection device for an image forming apparatus that can prevent occurrence of detection malfunctions due to factors.

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 copy paper that has been thermally fixed and carried out from a fixing device of an image forming apparatus. There are two types of infrared sensors: photon type and thermal type, and thermal type elements include resistance type, thermocouple type, capacitor type, and pyroelectric type. Among these, the pyroelectric type element is currently inexpensive and widely used.Hereinafter, the case where this pyroelectric type infrared detection element is used in the present invention will be explained. Other infrared sensors can be used as well.

Pyroelectric elements utilize the pyroelectric effect, which is the phenomenon in which electric charges appear on the surface of a crystal when a part of the crystal is heated.

In steady state, 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 with a shutter or the like and then irradiated, the temperature of the pyroelectric material rises slightly, the crystal lattice is distorted, and charges due to the crystal's spontaneous polarization appear for a minimal amount of time. In this way, in order to obtain a signal from the pyroelectric element, it is necessary to change the infrared rays from cutoff to irradiation rather than continuous irradiation.

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

In the first embodiment of the present invention, as shown in FIG.
An infrared sensor s-A+R is provided at a position where thermal radiation energy from the copy paper 4 that is carried out through the thermal fixing section Q is incident between the copy paper 4 and the photocopy sheets 4a, . . . , 3b. In addition, this infrared sensor 5
Shielding plates 6a and 6b are provided between the fixing roller 2a and the fixing roller 2a to block heat radiation from the fixing roller 2a. The fixing roller 2a is heated by an internal heater 7, this heating temperature is detected by a thermistor 8, and an input to the heater 7 is controlled by a control device (not shown) to keep the temperature of the fixing roller 2a constant.

Further, in the circuit for outputting a copy paper detection signal from the output signal of the infrared sensor 5, as shown in FIG. - When the output signal of the infrared sensor 5 is amplified by the amplifier 10 and the level detector 11 detects that the output of the amplifier 10 is above a certain level, the copy paper detection signal 2 is output. Further, as shown in FIG. 3, the amplifier 10 includes two operational amplifiers lQa and 10b, and the level detector 11 includes a variable resistor 11a and a comparator 11b.

Now, when the copy paper 4 is sent out by the belt 9 and passes between the fixing roller 2a and the presser roller, the copy paper 4 is 5
Roll at a temperature of about 0 to 60℃.

It is carried out from 2b. The temperature of the copy paper discharged from the fixing roller 2a changes over time as shown in FIG. 4. The copy paper 4 that has been thermally fixed is delivered to the delivery roller 3a,
3b, the thermal radiant energy of the copy paper 4 is incident on the infrared sensor 5, and a signal is output from the infrared serena 5 according to the above-mentioned principle at the minimum time at the moment when this thermal radiant energy is incident. The output signal of the infrared sensor 5 is amplified in two stages by the two operational amplifiers 10a and 10b of the amplifier 10 shown in FIGS. If the level is greater than the reference level set by the variable resistor 11a for the
A copy paper detection signal is output from 1b. Through the above-described operation, passage of copy paper is detected. Note that, as shown in FIG.
a and 3b, and are carried out onto the tray 13.

Next, the second embodiment of the present invention will be explained.
As shown in the figure, an infrared sensor 5 is provided at a position where the thermal radiation energy of the copy paper 4 carried out onto the tray 13 is incident. In this way, if copy paper is still detected after a certain period of time, for example 5 seconds, after copying is complete, an alarm will be issued indicating that copy paper has been left on the tray due to reasons such as forgetting to remove it. Can be done. In the case of this second embodiment, when the tray 13 is irradiated with sunlight, the temperature of the heat-fixed copy paper is around 60°C, and on the other hand, when the room temperature is around 25°C, sunlight is emitted for a long time. Since the temperature of the irradiated copy paper is about 35°C, if the detected temperature of the copy paper is set to about 40°C, no malfunction will occur.

Although the present invention is applied to a copying machine in the above embodiment, the present invention is not limited thereto, and can be applied to other image forming apparatuses that perform heat fixing, such as laser printers and facsimile machines.

As described above, in the present invention, the image forming apparatus is equipped with an infrared sensor that detects the thermal radiation energy of the copy paper sent out from the heat fixing device, and the output signal of this infrared sensor is used to detect the passage of the 2τ copying material. Because of this, when detecting copy paper without contact, there is no possibility of malfunctions caused by external factors such as light or sound, unlike in the past. This eliminates the need for maintenance work such as adjusting the detection element and cleaning the detection element from dirt caused by paper dust. Furthermore, a heating element for driving the infrared sensor is not required.

[Brief explanation of drawings]

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.
2 is a detailed circuit diagram of FIG. 2, FIG. 4 is a graph showing changes in temperature of copy paper, and FIG. 5 is a configuration diagram showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Copying machine, 2a... Fixing roller, 2b... Presser roller, 4... Copying paper, 5... Infrared sensor. Patent applicant: Minolta Camera Co., Ltd. Representative Konto Patent attorney: Aoyama Hajime and two other people 1st m! No. 21 Fig. 3 453- No. 4'M! Figure 5

Claims (2)

[Claims] (1) In an image forming apparatus that thermally fixes an image copied and copied onto copy paper by a heat fixing device, an infrared sensor that detects thermal radiation energy of the copy paper sent out from the heat fixing device is installed inside the image forming device. A copy paper detection device for an image forming apparatus, wherein the copy paper detection device is provided at a predetermined position of the infrared sensor and detects passage of copy paper based on an output signal of the infrared sensor. (2) The device according to claim 1, wherein the infrared sensor comprises a pyroelectric infrared detection element.