JPH03206918A - Liquid-level detecting apparatus - Google Patents

Abstract

PURPOSE:To omit an air hose and to detect a liquid level without leakage of liquid by providing a constitution wherein the pressure of the liquid to be detected is directly applied on a semiconductor pressure detecting element. CONSTITUTION:Liqid to be detected 33 flows into an outer-package case member 11 through an opening part 9 provided in washing-tub outer-wall part 20 and a liquid introducing hole 12. The pressure of the liquid is applied on a semiconductor pressure detecting element 30. The pressure is taken out as the unbalanced voltage of a bridge circuit which is formed on the surface of the detecting element 30 and outputted to the outside as the electric signal through a terminal 14. Since the pressure of the liquid whose liquid level is to be measured is directly applied on the detecting element 30 in this way, the liquid level can be detected without using an air hose. At this time, water or washing liquid which is the liquid to be detected 33 is directly in contact with the detecting element. Therefore, appropriate surface treatment is performed for the detecting element to prevent deterioration.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a liquid level detection device for liquid such as water.

BACKGROUND ART Conventionally, as a method for detecting the level of a liquid such as water, a method of detecting the pressure at the bottom of a tank in which the liquid is stored has been commonly used. Furthermore, in recent years, semiconductor pressure sensing elements have rapidly become popular, and are increasingly being used as pressure sensing means. The specific method is
An appropriate air trap was provided at the bottom of the tank, and the pressure was transmitted from the air trap through an air hose, and this was detected by a semiconductor pressure sensing element to indirectly detect the liquid level.

Problems to be Solved by the Invention However, the first problem with such conventional methods is that an air hose is required to transmit pressure from the air trap at the bottom of the tank to the semiconductor pressure sensing element, which reduces the number of parts and assembly steps for the entire sensing system. There were issues in terms of cost and reliability, such as an increase in air hoses and the need to seal the air hose joints.

In addition, in order to solve this first problem, a method can be considered in which the semiconductor pressure sensing element is brought into direct contact with the liquid itself, the level of which is to be detected, and the pressure is directly detected without using an air hose. A second problem arises in that depending on the properties of the liquid, the semiconductor pressure sensing element may be physically or chemically degraded, resulting in poor reliability.

The present invention has been made in consideration of the above-mentioned problems, and for the first problem, it is an object of the present invention to provide a liquid level detection device that can detect the liquid level in a tank with a simple configuration and without providing an air hose. Our primary purpose is to provide this means. The second problem is addressed by providing a liquid level detection device that has high long-term reliability regardless of the properties of the liquid to be detected, and the second purpose is to provide this means. It is.

Means for Solving the Problems The first means for achieving the first objective is to have a semiconductor pressure sensing element and an exterior case member for fixing the semiconductor pressure sensing element therein, the exterior case member The liquid level detection device has a liquid level detection device having a liquid introduction hole for introducing the liquid whose liquid level is to be detected, and a gasket member provided around the liquid introduction hole to prevent leakage of the liquid.

In addition to the first means, the second means for achieving the second objective includes a diaphragm to which liquid pressure is applied to the exterior case member, and a semiconductor pressure sensing element that transmits the pressure received by the diaphragm. The liquid level detection device is configured to have a pressure transmission fluid.

In the first method, the pressure of the liquid in the tank is directly applied to the semiconductor pressure sensing element, and the air hose can be omitted and the liquid level can be detected without leakage. In addition to the effects of the first means, the second means uses a diaphragm and a pressure transmission fluid to perform long-term reliable liquid level detection without directly contacting the semiconductor pressure sensing element with the liquid to be detected. It is something that can be done.

Embodiment FIG. 1 is a cross-sectional view of an embodiment in which the first method of the present invention is applied to a single-tub type washing machine. 1 is a washing tank, 2 is a dehydration tank, 3 is a pulsator that stirs the clothes inside the tank, 4 is a motor that provides rotational driving force to the dehydration tank 2 or the pulsator 3, and 6 is a helmet that transmits the rotational driving force of the motor 4. , 7 is a rotation transmission unit that decelerates the rotational driving force transmitted by the belt 6 and transmits it to the dehydration tank 2 or the pulsator 3. Reference numeral 8 denotes a liquid level detection device, which is provided with an opening 9 having an appropriate shape at the bottom of the washing tub 1, and is fixed from the outside of the washing tub 1 with an appropriate fixing member such as a screw so as to cover this opening R9. ing. Reference numeral 10 denotes a control unit that controls the washing machine, and performs various controls using the water level in the washing tub 1 detected by the liquid level detection device 8. Fig. 2 shows the external shape of the liquid level detection device 8, and Fig. 2 (A) shows the top view. (B) shows a plan view. 11 is an exterior case member in which a semiconductor pressure sensing element (not shown) is fixed; 12 is a liquid introduction hole through which a liquid whose liquid level is to be detected is introduced into the interior of the exterior case member 11; 14 is a terminal electrically connected to a semiconductor pressure sensing element disposed inside the outer case member 11; 15 to 18 are terminals for connecting the outer case member 11 to the washing tub; This is a mounting hole for attaching to. In the liquid level detection device 8, the gasket member 3 is in close contact with the washing tub 1, and the liquid to be measured can be introduced from the opening 9 of the washing tub 1 into the exterior case member 11 through the liquid introduction hole 12 without leaking to the outside. It is fixed with screws like this. This fixed situation will be explained based on FIG. 3. Third
The figure is a cross-sectional view taken along the line X-X'' in FIG. 2 showing the state in which the liquid level detection device 8 is attached to the washing tub 1 with screws. 20 is the outer wall of the washing tub, and 21 and 22 are Screws 23 and 24 are provided on the outer wall part 20 of the washing tub and are boss parts for attaching the liquid level detection device 8. As shown in the figure, the liquid level detection device M8 is attached to the gasket member 13 by screws 21 and 22. In this way, the liquid level detection device 8 is attached to the outer wall 20 of the washing tub without the detected liquid leaking to the outside.
It can be attached to.

Next, the configuration and operation of the liquid level detection device 8 in the detection state will be explained based on FIG. 4. FIG. 4 is a sectional view of the internal structure taken along the YY' section in FIG. 2. 30 is a semiconductor pressure sensing element, 3 is a wire for electrically connecting the bridge circuit connected to the semiconductor pressure sensing element 30 and the terminal 14, and 32 is for connecting a relative pressure measurement system for measuring the liquid level. The vent hole 33 is a liquid to be detected, which in this embodiment is water or washing liquid. Detected liquid 3
3 flows into the exterior case member l1 through the liquid introduction hole 12 from the opening 9 provided in the outer wall portion 20 of the washing tub, and the pressure thereof is applied to the semiconductor pressure sensing element 30. This pressure is taken out as an unbalanced voltage from a bridge circuit formed on the surface of the semiconductor pressure sensing element 30, and is outputted from the terminal 14 to the outside as an electrical signal.

In this way, by directly applying the pressure of the liquid whose level is to be measured to the semiconductor pressure sensing element, the liquid level can be detected without using an air hose.

In this case, since water or washing liquid, which is the liquid to be measured, comes into direct contact with the semiconductor pressure sensing element 30, the semiconductor pressure sensing element 3 is
0 has undergone appropriate surface treatment.

Next, an embodiment of the second means of the present invention will be described.

The embodiment of the second means is also applied to a single-tank washing machine in the same way as the first means, and its installation configuration etc. are also the same as the embodiment of the first means shown in FIGS. 1 and 3. . The external shape is also similar to the embodiment of the first means shown in FIG. The difference from the first embodiment is the internal structure, which is shown in FIG. The configuration and operation of the embodiment of the second means will be explained based on FIG. FIG. 5 is a cross-sectional view of the internal structure taken along YY' section in FIG. 2, similar to the embodiment of the first means. 40 is an exterior case member, and 4l is a gasket member. 42 is a semiconductor pressure sensing element; 43 is a wire that electrically connects the bridge circuit configured in the semiconductor pressure sensing element 40 and the terminal 44; 45;
46 is a vent hole for configuring a relative pressure measurement system for liquid level measurement, and 46 is a thin film-like hole that receives pressure from the liquid to be detected 33 and blocks the liquid to be detected 33 from the inside of the outer case member 40. A diaphragm made of SUS steel; reference numeral 47 indicates the detected liquid 3 received by the diaphragm 46;
This is a pressure transmission fluid for transmitting the pressure of No. 3 to the semiconductor pressure sensing element 42. In this embodiment, the liquid to be detected 33 is water or washing liquid. Furthermore, the pressure transmission fluid 47 uses silicone oil which is chemically relatively stable.

When pressure is applied to the diaphragm 46, the pressure transmission fluid 4
A compressive force acts on the diaphragm 46, but by using a fluid such as silicone oil, the diaphragm 46 is actually compressed.
The liquid level detection device has a level that does not cause deformation, and can be made into a liquid level detection device that has good mechanical durability over repeated use. Furthermore, if the pressure transmission fluid 47 has a large coefficient of thermal expansion,
causing deformation in the diaphragm 46 due to temperature changes,
Due to the disturbance pressure generated inside the exterior case member 40, the liquid level detection output becomes temperature dependent, but if it is about the same as silicone oil, there will be no problem in terms of accuracy in actual use.

The pressure of the liquid to be detected 33 is applied to the diaphragm 46 through the opening 9 provided in the outer wall 20 of the washing tub, and this pressure is applied to the semiconductor pressure sensing element 4 by the pressure transmission fluid 47.
2. In the semiconductor pressure sensing element 42, similarly to the embodiment of the first means, the pressure is converted into an unbalanced voltage of the bridge circuit formed on the surface, and outputted from the terminal 44 to the outside as an electric signal.

In this way, the liquid level can be detected without using an air hose, similar to the embodiment of the first means. Furthermore, the liquid level can be detected without direct contact between the liquid to be detected and the semiconductor pressure sensing element.

In this embodiment, the diaphragm is made of SUS steel, but it may be made of any flexible member such as rubber. Although silicone oil was used as the pressure transmission fluid, any fluid may be used as long as it is chemically stable, has a small coefficient of thermal expansion, and has a small rate of change in volume due to pressure.

As described above, since this embodiment uses the indirect detection method using the pressure transmission fluid and the diaphragm, it is possible to provide a liquid level detection device with high long-term reliability regardless of the properties of the liquid to be detected.

Effects of the Invention As explained above, in the first means, the pressure of the liquid to be detected is directly applied to the semiconductor pressure sensing element, thereby eliminating the need for an air hose and reducing the overall detection system, which was the first problem. It is possible to solve problems in terms of cost and reliability, such as an increase in the number of parts and assembly man-hours, and measures to seal the joints of air hoses. Furthermore, by providing the gasket member on the exterior case member, liquid level detection without liquid leakage can be performed with simple precautions.

In addition to the effects of the first means, the second means eliminates the need for direct contact of the liquid to be detected with the semiconductor pressure sensing element by providing the diaphragm and the pressure transmission fluid, which solves the second problem. It is possible to prevent deterioration of the semiconductor pressure sensing element due to direct exposure to the liquid to be detected, and it is possible to perform liquid level detection with high long-term reliability, and also to detect the liquid level of corrosive liquid.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an embodiment in which the first means of the present invention is applied to a single-tub washing machine, Fig. 2 shows the external shape of a liquid level detection device in the same means, and Fig. 2 (A) shows its top surface. , the same figure (B) is a side view, FIG. 3 is a cross-sectional view taken along line xx' in FIG. 2,
FIG. 4 is a sectional view taken along YY' line in FIG. 2, and FIG. 5 is a sectional view similar to FIG. 4, showing the second means of the present invention. DESCRIPTION OF SYMBOLS 1... Washing tub, 8... Liquid level detection device, 11... Exterior case member, 12... Liquid introduction hole, 13... Gasket member, 30... Semiconductor pressure sensing element, 40...・
・Exterior case member, 41... gasket member, 42・
...Semiconductor pressure sensing element, 46...Diaphragm, 4
7...Pressure transmission fluid.

Claims (2)

[Claims] (1) It has a semiconductor pressure sensing element and an exterior case member that fixes the semiconductor pressure sensing element inside, and the exterior case member has a liquid introduction hole for introducing the liquid whose liquid level is to be detected, and the liquid introduction hole. A liquid level detection device including a gasket member provided around a hole to prevent leakage of the liquid. (2) The liquid level detection device according to claim 1, wherein the exterior case member includes a diaphragm to which liquid pressure is applied, and a pressure transmission fluid that transmits the pressure received by the diaphragm to the semiconductor pressure detection element.