JPH02114128A - Water level detector - Google Patents

Abstract

PURPOSE:To obtain a detector with a higher reliability while requiring no adjustment by arranging a light emitting section on one of opposed side walls of a water introduction case and a light receiving section at the other thereof in such a manner as to be inclined downward. CONSTITUTION:Water in a washing tank is introduced into a water introduction case 10 made up of a light shielding material and a water level in the case 10 varies with a change in the water level within the washing tank. A light emitting element 14 comprising a light emitting diode and a light receiving element 15 comprising a photo transistor are arranged on cylindrical element holders 12 and 13 provided on opposed walls 10a and 10b of the case 10 as being inclined downward. Then, light leaving the light emitting element 14 is reflected on a water surface in the case 10 to be incident into the light receiving element 15. A control section 16 which comprises a drive circuit 17 for driving the light emitting element 14, a signal processing circuit 18 for converting an electrical signal from the light receiving element 15 into a voltage to be outputted and a rate of change detecting circuit 19 for outputting a water level detection signal detects a rate of change in an output voltage from the circuit 18 when an intensity of light received with the light receiving element 15 reaches its maximum to output a water level detection signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a water level detection device comprising a light emitting element and a light receiving element.

(Prior Art) Dishwashers and washing machines have conventionally been equipped with water level detection devices. This conventional water level detection device can be roughly divided into a float type and a water pressure type.

The float type has a float that moves up and down depending on the water level in the tank, and a lever to transmit the operation of this float to a switch, which mechanically operates the switch. There is.

In the water pressure type, an air trap is installed at the inner bottom of the tank, and a bellows is installed that operates according to the air pressure of this air trap (water pressure, that is, proportional to the water level), and the switch is operated by the operation of this bellows. .

(Problems to be Solved by the Invention) However, since all of the above-mentioned devices have mechanically movable parts and mechanical contacts, there is a risk of rust, etc. (thereby causing malfunction of each part).
It had drawbacks such as poor reliability and short service life. In addition, adjustment is required in order for the switch to operate at a predetermined water level, and in the case of a float type in particular, the float comes into direct contact with the water, so dirt can adhere to it and cause the float body to become There were problems with reliability, as the movement often slowed down.

The present invention has been made in view of the above circumstances, and its purpose is to provide a water level detection device that is highly reliable and does not require adjustment.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes a water guide case provided to introduce water in a tank, and a light emitting part on one of the opposite side walls of the water guide case, directed diagonally downward. a light-emitting element provided on the other side of the opposing side wall, and a light-receiving element having a light-receiving part oriented obliquely downward and capable of receiving light emitted from the light-emitting element and reflected on the water surface; The control section detects a predetermined water level and outputs a water level detection signal when the light receiving intensity of the light receiving element reaches the maximum.

(Function) The intensity of light emitted by the light emitting element varies depending on the output angle. The light with an emission angle of 0 degrees, that is, the light emitted from the center of the light emitting part, has the highest light intensity. The light intensity of the light emitted from areas other than the center of the light emitting part decreases as it moves away from the center.

Therefore, if the light-receiving element receives light with high light intensity, the light-receiving intensity will be high, and if it receives light with low light-intensity, the light-receiving intensity will be low.

According to the above means, the light emitted from the light emitting element is
The light is reflected on the water surface inside the water guide case and enters the light receiving element. In this case, when the height of the water surface, that is, the water level, reaches a certain water level, the reflected light of the light with the strongest output light intensity (light with an output angle of 0 degrees) enters the light receiving element, increasing the received light intensity, and otherwise At the water level, reflected light of weak output light intensity (so-called scattered light) enters the light receiving element, and the received light intensity becomes low. In other words, the intensity of the received light increases as the water level rises, and reaches its maximum at a certain water level. The control unit detects a predetermined water level and outputs a water level detection signal when the received light intensity reaches a maximum. In this case, even if the maximum light emitting intensity of the light emitting element and the light receiving sensitivity of the light receiving element vary from one water level detection device to another, the absolute value of the maximum light intensity at the light receiving element will change, but the water level at which the maximum value is indicated will remain constant. Therefore, there is no need to adjust the output of the light emitting element, etc., and a predetermined water level can always be accurately detected.

(Embodiment) The present invention is applied to a water level detection device for a dishwasher, and a first embodiment thereof will be described below with reference to FIGS. 1 to 5.

First, referring to FIG. 2, a schematic configuration of a dishwasher will be explained. 1 is a cleaning tank, 2 is a water supply valve for supplying water into the cleaning tank 1, 3 is a pump that serves as both a water injection pump and a drainage pump, and 4.5 is stored in a storage section 6 at the bottom of the cleaning tank 1. 7 is a pump motor, and 8 is a heater.

Now, 9 is a water level detection device, which will be described with reference to FIG. Reference numeral 10 denotes a water guide case made of a light-shielding material, which has a communication pipe section 10a at the bottom that communicates with the storage section 6 of the cleaning tank 1, and an upper section that allows ventilation and can block light. The shielding plates 11 are arranged alternately. Therefore, the water in the cleaning tank 1 is introduced into the water guide case 10, and the water level in the water guide case 10 changes according to the change in the water level in the cleaning tank 1. Reference numerals 12 and 13 designate cylindrical element holders formed on the opposing side walls 10a and 10b of this water guide case 10, and these are each formed diagonally downward. Reference numeral 14 denotes a light emitting element made of, for example, a light emitting diode, which is disposed on the element holder 12 so that its light emitting part 14a faces diagonally downward. Reference numeral 15 denotes a light-receiving element made of, for example, a phototransistor, which is disposed on the element holder 13 so that its light-receiving portion 15a faces diagonally downward. The light emitted from the light emitting element 14 is reflected on the water surface within the water guiding case 10 and enters the light receiving element 15. Now, light emitting element 1
FIG. 3 shows the relationship between the output angle and output light intensity of No. 4, and FIG. 4 shows different output angles. As shown in Fig. 4(a), when the emission angle is 0 degrees,
As can be seen from FIG. 3, the intensity of the emitted light becomes the highest. Therefore, if this emitted light at an angle of 0 degrees is incident on the light receiving element 15, the light receiving intensity at the light receiving element 15 will also be maximum. On the other hand, as shown in Fig. 4 (b) and (C), if the emission angle deviates from 0 degrees (angle α or β degree), it is so-called scattered light, as can be seen from Fig. 3. The intensity of light emitted in that direction also becomes weaker. Therefore, when the emitted light at this shifted angle enters the light receiving element 15, the received light intensity also decreases.

Therefore, when the light receiving element 15 receives the emitted light with the strongest emitted light intensity, it is when the water level reaches the water level P shown in FIG.
The intensity of the light that it receives will be lower.

This relationship is shown in FIG. As can be understood from FIG. 5, the intensity of light received by the light receiving element 15 is
Even if there are variations in the maximum output intensity and the light receiving sensitivity of the light emitting element 15, the absolute value will vary, but it will always show the maximum value at the water level P.

Reference numeral 16 denotes a control unit, which includes a drive circuit 17 that drives the light emitting element 14 and a signal processing circuit 18 that converts an electric signal (current) generated according to the light receiving sensitivity of the light receiving element 15 into a voltage and outputs the voltage. Then, when the rate of change of the output voltage from the signal processing circuit 18 is detected and the detected value becomes approximately ±0 (in other words, when the light receiving intensity of the light receiving element 15 reaches the maximum), the water level detection signal Ss is output. and a rate-of-change detection circuit 19 that outputs. As can be seen from the above description, the water level detection signal Ss is output when the water level in the water guide case 10 reaches a predetermined water level P.

Note that in this dishwasher, the water level detection signal Ss
Based on this, the water supply operation by the water supply valve 2 is stopped and controlled.

According to this embodiment with the above configuration, the light emitting element 14
1 is reflected on the water surface inside the water guide case 10, the reflected light is received by the light receiving element 15, and a predetermined water level is detected based on the received light intensity. The water level can be detected with a configuration that does not require mechanical contacts. As a result, there is no rust, the operation is highly reliable, accurate water level detection is possible, and the service life is long. is also longer. In addition, considering that the received light intensity is maximum at a certain water level P, the water level detection signal Ss is output at the time when the maximum value occurs.
Even if there are variations in the light-receiving sensitivity of the light-emitting element 14, there is no need to adjust the output of the light-emitting element 14, the light-receiving sensitivity of the light-receiving element 15, etc. by 2J.

Furthermore, since each element 14.15 does not come into direct contact with water, there is no risk of it getting dirty, and even if it gets dirty, the water level at which the maximum received light intensity occurs remains unchanged, so the predetermined water level is always maintained at iF, &TE. can be detected. In the above embodiment, one water level P is detected, but as shown in FIG. Light receiving element 15.
16.17 are provided above and below, and each light receiving element 15, 16.17
The water level at which the received light intensity is the maximum is the detected water level Pa, Pb,
It may also be Pc. Furthermore, in the above embodiments, the present invention is applied to a water level detection device for a dishwasher, but is not limited thereto, and can also be applied to a water level detection device for a washing machine.

In addition, the present invention is not limited to the above embodiments, and can be implemented with various modifications without departing from the scope of the invention.

[Effects of the Invention] As is clear from the above description, the present invention includes a water guiding case provided to introduce water in the tank, and a light emitting part extending diagonally downward on one of the opposite side walls of the water guiding case. a light-emitting element provided so as to be directed toward the other side; a light-receiving element having a light-receiving section provided on the other side wall facing diagonally downward and capable of receiving light emitted from the light-emitting element and reflected on the water surface; It is equipped with a control section that detects a predetermined water level and outputs a water level detection signal when the light receiving intensity of the light receiving element reaches the maximum, thereby increasing the reliability of operation. At the same time, the service life can be extended, and various adjustments are not required.
This provides an excellent effect in that a predetermined water level can always be accurately detected.

[Brief explanation of drawings]

1 to 5 show a first embodiment of the present invention, FIG. 1 is a schematic diagram of a water level detection device, FIG. 2 is a schematic diagram of a dishwasher, and FIG. 3 is a diagram showing the emission angle and FIG. 4(a) is a diagram showing the relationship with the emitted light intensity. (b) and (c) are diagrams showing the relationship between the water level and the emission angle and the light receiving angle, respectively, and FIG. 5 is a diagram showing the relationship between the received light intensity and the water level change. FIG. 6 is a schematic diagram of the main parts of a second embodiment of the present invention. In the figure, 1 is a cleaning tank, 2 is a water supply valve, 6 is a water storage section, 9 is a water level detection device, 10 is a water guide case, 14 is a light emitting element, 15,
16 and 17 are light receiving elements. Applicant: Toshiba Corporation

Claims (1)

[Claims] 1. A water guide case provided to introduce water in the tank, a light emitting element provided on one of the opposite side walls of the water guide case so that the light emitting part is directed diagonally downward, and a light emitting element provided on the other side of the opposite side wall. A light-receiving element having a light-receiving part oriented diagonally downward and capable of receiving light emitted from the light-emitting element and reflected on the water surface; A water level detection device comprising a control section that detects the water level and outputs a water level detection signal.