JPH0718736B2 - Equipment water level sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a water level sensor in equipment such as a dishwasher.

2. Description of the Related Art Conventionally, most of the equipment such as a dishwasher adopts a float switch system in which a float that moves up and down according to the water level in a tank and a switch that turns on and off depending on the up and down of the float are combined.

Problems to be Solved by the Invention However, in the above-mentioned conventional ones, the adherence of oil-containing sewage causes the float not to move up and down according to the water level during long-term use, and reliable water level control for a long time It couldn't be done.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a water level sensor for a device which electrically solves the problem of earth leakage and which has a simple structure and is capable of electrically detecting the water level. is there.

Means for Solving the Problems In order to achieve the above object, the present invention includes a piezoelectric vibrator connected to an AC commercial power source, and a metal plate forming the piezoelectric vibrator is provided on an inner surface of a resin case. A resin case having a vibrator is mounted inside the tank of the device.

Action In the above configuration, the vibration of the metal plate of the piezoelectric vibrator is transmitted to the resin case and the resin case also vibrates. However, since the vibration of the piezoelectric vibrator electrically changes between underwater and in the air, it is possible to know the water level by detecting this. Further, since the piezoelectric vibrator is in the resin case, the problem of electric leakage is solved with a simple configuration without using an insulating transformer or the like as a countermeasure against electric leakage.

Example An example of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, 1 is a tank of equipment such as a dishwasher, 2 is a piezoelectric vibrator, and 3 is a resin case having a piezoelectric vibrator 2.

The piezoelectric vibrator 2 is constructed by bonding a ceramic plate 4 and a metal plate 5, and the metal plate 5 is attached to the inner surface of the resin case 3 by adhesion or the like. The resin case 3 is made of, for example, polyphenylene sulfide resin and has a thickness of 0.8 mm or more. A ring-shaped groove 6 is provided on the surface having the piezoelectric vibrator 2. Resin case 3
The attachment to the tank 1 is performed by sandwiching the wall of the tank 1 with the collar 7 and the fastener 8. 9 is a sealing material,
10 indicates the water surface.

In FIG. 2, reference numeral 11 is a low-voltage power source which is a drive source of the piezoelectric vibrator 2, and one wire is connected to the AC commercial power source 12. Reference numeral 13 is an oscillation circuit of the piezoelectric vibrator 2, 14 is a load such as a pump or heater of equipment such as a dishwasher, and 15 is a switching element of the triac 16.

In the above water level sensor, when the piezoelectric vibrator 2 is driven by applying an alternating voltage, the vibration of the metal plate 5 is transmitted to the resin case 3. In this case, the vibration mode of the piezoelectric vibrator 2 changes depending on whether the surface of the resin case 3 is air or water. Therefore, the water level can be detected by detecting the change with an electric circuit. Further, the commercial AC power supply 12 is connected to the metal plate 5 of the piezoelectric vibrator 2, but since the resin case 3 is an insulator, there is no fear of electric leakage even if the resin case 3 is immersed in water. Since the resin case 3 is provided with the groove 6, the external force when the resin case 3 is attached to the tank 1 is absorbed by the groove 6, and the piezoelectric vibrator 2 is not adversely affected. Instead, it is possible to obtain a predetermined vibration mode.

Then, even if filthy water containing oil adheres to the surface of the resin case 3 due to long-term use to form a film, it cannot be detected because it is the electric water level detection by the piezoelectric vibrator 2. It has no effect on actual use.

EFFECTS OF THE INVENTION According to the present invention as apparent from the above-described embodiments, since the water level is electrically detected using the piezoelectric vibrator, reliable water level detection can be performed for a long period of time as compared with the conventional float switch method. Moreover, since the piezoelectric vibrator is insulated by the resin case, it has an excellent effect that the problem of electric leakage is solved with a simple structure without using an insulating transformer or the like.

[Brief description of drawings]

FIG. 1 is a sectional view of a water level sensor showing one embodiment of the present invention,
FIG. 2 is a circuit diagram thereof. 1 ... Tank, 2 ... Piezoelectric vibrator, 3 ... Resin case, 4 ...
… Shellac plate, 5 …… Metal plate, 12 …… AC commercial power supply.

Claims (1)

[Claims] 1. A piezoelectric vibrator connected to an AC commercial power source, a metal plate constituting the piezoelectric vibrator is attached to an inner surface of a resin case, and the resin case having the piezoelectric vibrator is installed in a tank of a device. A water level sensor for devices that are installed in the same position.