JPS6031021A - Detecting device for contained liquid - Google Patents

Abstract

PURPOSE:To improve detecting reliability, by correcting the difference in angle of total reflection at the boundary part between a liquid containing tank and a liquid with respect to light emitted from a light emitting part to whether the light is received by a light receiving part or not. CONSTITUTION:Silicone oil 2 is contained in a liquid containing tank 1. Said oil 2 is sucked by an oil pump 4 through an oil pipe 3A and stored in an oil reservoir 5. One edge of an oil applying felt 6 is immersed in the oil in the oil reservoir 5. The other edge is contacted to the surface of the upper roller of a pair of fixing rollers 7. The liquid containing tank 1 comprises a light transmitting material. A liquid detecting element 8 detects the liquid level of the oil 2. The detected result is displayed on an operating panel of a copying machine. The oil is supplied based on the display.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a device for detecting liquid in a liquid storage tank made of a light-transmitting material.

(Conventional technology) For example, in a copying machine, transfer paper that has already been transferred.

The transfer paper is fixed by passing it between a pair of fixing rollers. In this type of fixing device,
In order to achieve the offset prevention function, the surface of the fixing roller is coated with offset prevention silicone oil. This silicone oil is usually stored in a storage tank, pumped up from the tank by a suitable pump, and applied to the surface of the fixing roller via an oil-applied felt.

In such a silicone oil supply device.

If the silicone oil in the storage tank is depleted, the oil supply to the fixing roller may be interrupted, causing the transfer paper to wrap around the fixing roller.

When the wrapped transfer paper is forcibly removed, there are problems such as damaging the fixing roller and furthermore, causing the toner on the fixing roller 2 to adhere to the transfer paper.

Therefore, if the presence or absence of oil in the storage tank is detected by some means, and when this detection means detects that there is no oil, oil is replenished into the storage tank based on this detection result, the occurrence of the above-mentioned problem can be avoided. It can be prevented.

By the way, there are conventionally known devices for detecting the liquid in such a storage tank, for example, a device for detecting the amount of a liquid ironing agent in a copying machine. This detection device detects, for example, when a float with a built-in magnet moves up and down as the liquid level changes.

This is a reed switch that turns on and off.

However, in such a detection device, the float moves up and down relative to the reed switch, so if toner in the developer sticks to the movable parts, it may cause malfunction and reduce detection reliability. In addition, since the float has a built-in magnet and is configured to provide buoyancy, the float has a large shape and the detection device itself has the disadvantage of becoming bulky.

When such a float-type detection device is applied to the oil supply device described above, the detection device itself becomes bulky and there is also a risk of toner, paper powder, dust, etc. mixed into the oil. Therefore, there is a possibility that the moving parts may malfunction.

(Purpose) The present invention aims to reduce the bulk of a detection device, which completely changes the conventional general technical concept of providing a detection body for detecting the presence or absence of liquid in a storage tank in the liquid part of the storage tank. It is possible. Moreover, detection reliability can be significantly improved. The present invention aims to provide a novel contained liquid detection device.

(Structure) The structure of the present invention will be explained below based on an embodiment shown in one figure.

FIG. 1 shows a fixing device section of a copying machine which is an example of application of the present invention, and a liquid storage tank 1 in this device section contains silicone oil 2, which is an example of a liquid. There is. This silicone oil 2 is pumped up by an oil pump 4 through an oil vibrator 3A, and is pumped up into an oil reservoir 5.
It is designed to be stored in One end of the oil coated felt 6 is immersed in the oil in the oil reservoir 5, and the other end is in contact with the surface of the upper roller of the pair of fixing rollers 7. Incidentally, excess oil in the oil reservoir 5 is returned to the storage tank 1 through a return pipe 3B to be evacuated.

The liquid storage tank indicated by the reference numeral 1 is made of a light-transmitting material, as will be described later, and the liquid detection element indicated by the reference numeral 8 detects the liquid level of the oil 2, and the detection result is For example, a message is displayed on the operation panel of a copying machine, and the system detects this display and replenishes the oil.

Here, the optical detection principle of the present invention will be described below.

In FIG. 2, the liquid detection element 8 is placed in close contact with the outer wall of the storage tank 1 at a location where the presence or absence of liquid is to be detected, that is, at a location corresponding to a certain liquid level position to be detected. installed on. Liquid detection element 8
As shown in FIG. 5 (a cross-sectional view seen from the direction of arrow a in FIG. 2), a light emitting portion 8A such as a light emitting diode,
It is a 9-reflection type photodetecting element having a light receiving section 8B such as a photosensor.

For example, the storage tank 1 has a refractive index N of 1. - Made of polypropylene material that is 49% and 17%.

For example, the liquid 2 in the storage tank has a refractive index N,
Silicone oil KFg6 (product name) with a force of 1.40
is applied. Here, the refractive index No of air is 1.0
I'll leave it as that.

In the present invention, the light emitted from the light emitting part of the detection element 8 is used.

The light is totally reflected at the boundary between the storage tank 1 and the liquid 2, that is, the inner wall surface of the tank, and the presence or absence of the liquid is detected depending on whether or not this totally reflected light can be detected by the light receiving section. be. This point will be explained below, and since the sensing element 8 is configured to be brought into contact with the storage tank 1, the influence of the air layer between the two will be ignored.

Here, in FIG. 3, as a general principle, the refractive index N
When light travels from a medium with a refractive index of N2 to a medium with a refractive index of N2, the critical angle of total reflection in a medium with a refractive index of N2 is set as 03.The magnitude relationship between both refractive indexes in this case is N, It is N2.

sin θ1−N Assuming that the relationship s /s r nθ2 ” Nl holds true, total reflection is performed when θ2 is 90 degrees, so sin θ2 is a bargain of 1.

Using this sin θ2-1, the critical angle θ3 of the medium with refractive index N (θ3:critical angle of θ)? Assuming that you are looking for
This θ3 can be derived from the following equation (1).

sinθ3 5in03N2 −　−１　・・・・・・(1) sinθ2 ■ N.

θ3. =5in'(N2/Nl) ---°-(z)
Here, the liquid storage tank 1 is made of polypropylene with a refractive index N of 1.49, and the liquid 2 is made of polypropylene with a refractive index N2.
Since it is made of silicone oil KF96 with a value of 1.40, substituting this value into equation Y (2).

A) Critical angle θ3 of total reflection when silicone oil is present regarding the part in the storage tank 1 that the detection element 8 faces
has the following value:

θ3=”” (N2/N, )=sin-' (1-
40/1.49) = 69·98°B) When silicone oil is not present in the part of the storage tank 1 that the detection element 8 faces.

That is, when air is present instead of silicone oil, the refractive index No of this air is 1, so the critical angle θ31 for total reflection in this case is the following value, assuming N2-1.

0g' = SIn (N2 /Nl) = sin (
171,49)=42.16° Here, in FIG. 4, the symbol AY is the light emitting area of the light emitting section 8A (see FIG. 5),
Symbol B) 1 Assuming that the light-receiving area of the light-receiving section 8B is the light-receiving area, total reflection can occur on the inner wall surface of the storage tank 1 made of polypropylene 17. The critical angle is θ3 when oil is present in the part indicated by the symbol 2. It takes a value of 69.98°.

, and in this case, if there is incident light at an angle greater than θ3, it will be totally reflected. In such a case, the light that passes through the wall of the storage tank 1 follows the broken line and does not reach the light receiving area B.

7- In other words, it does not reach the light receiving part 8B in FIG. 5, and the liquid detection element 8
is in the off state.

On the other hand, in the portion indicated by numeral 2, when oil is not present, that is, when an air layer is present, the critical angle θ:1 at which total reflection can occur takes a value of 42.16°.

In this case, if there is a larger incident light than θ(", it will be totally reflected. In such a case, the light that passes through the wall of the storage tank 1 will follow the solid line, and this light will pass through the light receiving area. BK transport, that is, transport to the light receiving section 8B in Fig. 5,
The liquid detection element 8 is turned on. In addition, in Figure 4,
R1 is the refracted light when oil is present, and R2 is the refracted light in the air layer when no oil is present.

In this way, with respect to the part of the liquid storage tank 1 facing the liquid detection element 8, the liquid storage tank 1 is able to detect light emitted from one light emitting part when silicone oil is not present and when silicone oil is present. The difference in the angle of total reflection at the boundary between the tank and the silicone oil can be detected using the light receiving section 8.
By relating whether or not light is detected at point B, the presence or absence of silicone oil regarding the portion 8- can be detected.

That is, the liquid level of the silicone oil 2 can be detected, and based on the detection result, silicone oil can be replenished as appropriate.

Therefore, there is no fear that the supply of silicone oil to the fixing port 7 shown in FIG. 1 will be interrupted, and problems such as the transfer paper being wrapped around the fixing roller pair 7 can be avoided.

Note that this detection device is based on the premise that the refractive index of the material of the liquid storage tank 1 is larger than the refractive index of a liquid such as silicone oil (Nr > N2), and in reality, as a light-transmitting material, Although plastic and glass have been proposed, the former plastic is more suitable in terms of moldability, handling, and weight, and the refractive index of this material is 1.4.
It is about 6 to 1.60.

On the other hand, the liquid to be detected is water (refractive index 1.33).
, silicone oil (same l.40), methylal=y-
Liquids such as ethyl alcohol (1.329) and ethyl alcohol (1.36) are suitable for single detection devices because these liquids have a smaller refractive index than plastic. I can say it.

In this way, the detection device of the present invention has a configuration in which the detection body does not come into contact with the liquid to be detected, so there is no need for the detection body to be configured liquid-tight, and it is possible to Since the structure has no movable parts, there is no risk of malfunction, and detection reliability can be further improved. Furthermore, this detection device is characterized by breaking away from the conventional technical concept of providing a slight air layer between the detection element and the object to be detected.

(Effects) According to the present invention, the size of the detection device itself can be reduced, and the reliability of detecting the presence or absence of a contained liquid can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a fixing device section of a copying machine according to an application example of the present invention, FIG. 2 is an enlarged sectional view of a detection device section for stored liquid, and FIG.
The figure is a diagram to explain the method of determining the critical angle of total reflection when light passes through media with different refractive indexes. Figure 4 explains the interaction between the presence or absence of silicone oil and the critical angle of total reflection. FIG. 5 is a cross-sectional view of the liquid sensing element. 1...Liquid storage tank, 2...Silicone oil as liquid, 8...Liquid detection element.

Claims (1)

[Claims] A liquid sensing element consisting of a light emitting part and a light receiving part is brought into contact with the outer wall of a liquid storage tank made of a light-transmitting material, and the refractive index of the liquid storage tank is larger than the refractive index of the liquid. In addition, regarding the part of the liquid storage tank where the liquid detection element faces, the difference between the liquid storage tank and the light emitted from one light emitting part when there is no liquid and when there is liquid is determined. A detection device for contained liquid that detects the presence or absence of liquid in the portion by correlating the difference in the angle of total reflection at the boundary portion with the liquid to whether or not light is detected in the light receiving portion.