JPH04106427A - Liquid level detector - Google Patents

Abstract

PURPOSE:To always enable of accurate detection on whether a liquid level in a container is above or below a specified level by forming a side wall part close to a specified level of liquid from an ultrasonic transmitting material. CONSTITUTION:An ultrasonic transmitter 55 and an ultrasonic receiver 56 are mounted on an ultrasonic transmitting mounting plate 54 provided on one side wall part of a container 51. Then, when the level of a liquid 52 in the container 51 is above a specified level, an ultrasonic wave S emitted from the transmitter 55 is reflected to the transmitter 56 with a reflector 53 being little attenuated as reflected wave S'. A controller 57 compares a signal of a high reception level with a set value to output an output with a judgment that the liquid level is above the specified level. When the liquid level is below the specified level, the reflected wave with the reflector 53 is reflected to a space above the liquid 52 being attenuated so much that it little reaches the receiver 56. Thus, a reception level is lower than the set value and the controller 57 emits an output with a judgment that the liquid level is below the specified level.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid level detection device.

[Prior art and its problems 1] Figures 5, 6, and 7 show a liquid level detection device of the first conventional example. In order to check the level L of this liquid (2), the level gauge (3) measures the predetermined liquid level L on the side wall of the container (1).

It is set up correspondingly. This is, for example, a transparent glass window, and as shown in FIG. 7, an upper limit display line (4a) and a lower limit display line (4b) are displayed as levels indicating the upper and lower limits of a predetermined distance from a predetermined level Lo.

This type of level gauge (3) is well known, but it is used to visually check the liquid level, and the position of the liquid level relative to the display lines (4a) and (4b) is measured through a transparent glass window. I'm trying to detect if it's there. However, this is done by visual inspection, and if the window is dirty or the surroundings are dark, it may be difficult to read the level L.

Figure 8 shows a second conventional example, in which the container (5) contains liquid (
6) is accommodated, and in order to measure the liquid level L, a float (7) is placed in a floating state, and rods ρ are attached above and below the float (7), which is connected to the guide member 18a. ) (8b) (fixed to a stationary part) so that it can be accurately moved up and down depending on changes in the liquid level. An electric switch (9) is connected to the upper end of the rod β. Liquid level L of liquid (6)
Due to the change in the level of the float (7), the level of the float (7) changes accordingly, and this amount of change causes the rod i to move towards the guide member [
8a) (8b) to accurately move up and down to a predetermined level L. The contacts of the electric switch (9) are opened when the voltage decreases to . This allows the container (5)
The liquid (6) inside is at a predetermined liquid level L. We are trying to detect further declines.

However, in such a device, the guide member (8a
) (8b) is fixed to a stationary part or a part of the container (not shown), but if these are deformed or corroded by the liquid (6), the rod Q may not move up and down accurately or be pulled. There are times when it stops moving. This makes it impossible to accurately detect the liquid level L0.

FIG. 9 shows a third conventional example, in which a container (lO) contains a liquid (13), and this container (lO) has a lid (
1)) is hermetically covered and therefore this lid +1
)+ and the liquid level L of the liquid (13), a closed space f121 is formed. It may be vacuumed or filled with some gas. An ultrasonic transmitter (14) and an ultrasonic receiver (15) are attached to the outer surface of the bottom wall of the container (lO) in close proximity to each other. An electrical signal for exciting the ultrasonic transmitter (14) is supplied from the liquid level measuring circuit (16). This allows the container (lO
) is emitted toward the inside of the ultrasonic wave S. This is reflected by the liquid surface level L of this liquid (13) and becomes a reflected ultrasonic wave S°, which is received by the ultrasonic receiver (15). This received signal is supplied to the liquid level measuring circuit (16). The measurement output from this circuit (16) is supplied to a liquid height comparator (17), where it is compared with a predetermined level. The liquid level measurement circuit (6) measures the time it takes to be reflected from the surface level L and return to the ultrasonic receiver (15), and this result is supplied to the liquid level comparator (17). When compared with a predetermined level or time, the predetermined liquid level L is greater than this. When it is shorter than this time, it is determined that it is at a higher level than the predetermined level Lo, and this judgment output is derived as a low level signal or a high level signal to the detection terminal (18). That's what I do.

In other words, in this conventional example, the absolute value of the liquid level L is measured, but the ultrasonic waves must be passed through the liquid until it reaches the liquid level, which may cause deterioration of the liquid, such as a change in viscosity, especially if this distance is long. The time it takes for the ultrasonic wave S to reach a certain liquid level may change due to changes in the liquid level or physical properties, and in this case, even when compared with the value set in the liquid level comparator (17), the time required for the ultrasonic wave S to reach a certain liquid level may change. It is not possible to accurately detect whether it is above or below. Alternatively, if the liquid (13) contains some kind of foreign object that reflects the ultrasonic waves, the ultrasonic waves may be reflected by this and it is impossible to expect an accurate measurement of the liquid level. Figure 1O shows a liquid level detection device according to the fourth conventional example. The liquid (20) is contained in a container (19), which is also closed with a lid (27) in this conventional example. An ultrasonic transmitter (2) is placed close to the top of the lid (27).
2) and an ultrasonic receiver (23) are attached.

An electrical signal for exciting the transmitter (22) is supplied from the liquid level gauge (24), which causes the ultrasonic transmitter (22) to emit ultrasonic waves S toward the liquid level of the liquid (20). , the reflected wave S° from the liquid level is received by an ultrasonic receiver (23). This received signal is then supplied to the liquid level gauge (24), but this conventional example also uses an ultrasonic transmitter (24).
The time from when the ultrasonic wave S is emitted from 2) until it is received by the receiver (23) is measured by the liquid level gauge (24), and this measured value is compared with a predetermined value in the setting comparison circuit (25). If it is larger than this, it is judged that the liquid level is below the predetermined level, and if it is smaller than this, it is judged that it is above the predetermined level, and the judgment output is sent to the terminal (26).
Derived from.

That is, in the conventional example shown in Fig. 1O, unlike the conventional example shown in Fig. 9, the ultrasonic wave is reflected in the space (21) and the reflected wave from the liquid surface is propagated in the same space (21) and sent to the receiver (23). However, if the space (21) is a vacuum, the ultrasonic wave S cannot be propagated to the liquid level, so this conventional example cannot be applied when the space (21) is a vacuum. Can not.

1) The figure shows the 5th conventional example, and the container (30)
A liquid (31) is stored inside, and the upper part of the liquid is open, and an ultrasonic transmitter (32) and a receiver (33) are placed opposite the both side walls at a predetermined level Lo. and is mounted on a level. In this conventional example, ultrasonic waves from an ultrasonic transmitter (32) are emitted toward a receiver (33) opposite to the ultrasonic wave transmitter (32), but the liquid (31)
When the liquid level is above the predetermined level L0, the ultrasonic waves from the transmitter (32) are transmitted to the receiver (33) with less attenuation, so that the receiver (33) cannot receive the ultrasonic waves. The level is relatively high. This results in a predetermined level L. It is judged to be higher up. Also, the liquid level L of the liquid (31)
When the ultrasonic wave from the transmitter (32) is lower than a predetermined level L0, the ultrasonic wave from the transmitter (32) passes through the gas and is therefore greatly attenuated. Therefore, the level of the ultrasonic waves received by the receiver (33) becomes low.

As a result, it is determined that the liquid level L of the liquid (31) in the container (30) is below the predetermined level L0. As shown in Figure 1), when the liquid level is at a predetermined level L0, the reception level is between the relatively high value and the relatively low value.

Even in such a conventional example, the predetermined level L of the liquid (31) in the container (30). However, the transmitter (32) and receiver (33) must be accurately aligned and installed at a predetermined L0 level. If this is inaccurate, a predetermined level L. It is not possible to accurately judge whether it is below or above. Furthermore, even if the containers (30) are aligned and installed at a predetermined level, if they are made of plastic, for example, they are likely to be thermally deformed, and their relative installation positions will change due to the deformation. This makes it impossible to accurately determine whether the level of the liquid (31) in the container (30) is above or below the predetermined level L0.

[Problems to be Solved by the Invention] The present invention has been made in view of the various problems described above, and an object of the present invention is to provide a liquid level detection device that can eliminate the conventional drawbacks described above. .

[Means for Solving the Problems] The above object is to form a side wall portion of a container containing a liquid, which is close to at least a liquid level at a predetermined level, from an ultrasonic-transmissive material, and to make the outer surface of the side wall portion an ultrasonic transmitter and a receiver are attached to the container, at least one of the transmitter and the receiver is disposed on the same level as the predetermined level, and the ultrasonic wave is transmitted toward an ultrasonic reflector provided in the container. The ultrasonic wave reflected by the ultrasonic reflector from the transmitter is received by the receiver, and depending on the level of the reception level, it is determined whether the liquid level in the container is above or below the predetermined level. This is achieved by a liquid level detection device characterized in that it detects whether the liquid level is present.

[Function 1: The side wall portion close to the liquid level at a predetermined level is made of an ultrasonic-transmissive material, so the ultrasonic waves from the transmitter attached to the outer surface of this side wall portion pass through this side wall portion. and is propagated inside the container.

When the liquid level in the container is above a predetermined level, at least one of the transmitter and receiver attached to the same side wall is on the same level as the predetermined level, so the ultrasonic wave emitted from the transmitter is transmitted toward an ultrasonic reflector in the container, and the reflected ultrasonic waves are received by the receiver. However, the ultrasonic waves emitted from the transmitter in the liquid or received by the receiver are Since the liquid passes through the liquid, its attenuation is small, so that a relatively high level at the receiver allows it to be determined that the liquid level is above a predetermined level.

Furthermore, if the level of the liquid in the container is below a predetermined level, the ultrasonic waves from the transmitter will be attenuated greatly as they propagate in space, and therefore the reception level of the reflected ultrasonic waves to the receiver will be relatively low. Therefore, from this level, it can be determined that the level of the liquid in the container is below a predetermined level.

Because of the above-mentioned actions, it is possible to detect whether the liquid level is above or below a predetermined level even if the space is a vacuum, and the ultrasonic receiver and transmitter are located on the side wall. Since it is attached to the outer surface of the container, it is not contaminated by liquid, and unlike the conventional mechanical type mentioned above, there is no need for guide members or moving members, so the level of liquid in the container is always accurately maintained. It is possible to judge whether the level is above or below the level of .

[Example] Hereinafter, a liquid level detection device according to an example of the present invention will be described with reference to the drawings.

First, the present invention will be explained in detail with reference to FIG. 1 and FIGS. 2A to 2C. In FIG. 1, a liquid (52) is contained in a container (5), and its liquid level is assumed to be L. Therefore, above this in the container [51] there is a space Δ
It defines a region that communicates with the atmosphere. Container (5
A mounting plate (54) made of a material capable of transmitting ultrasonic waves is provided on one side wall of the container (51) to close a hole (51a) formed in the side wall of the container (51), as shown in FIG. 2A. It is installed as follows.

An ultrasonic transmitter (55) and an ultrasonic receiver (56) are installed in close proximity to this, and lead wires led out from these are connected to a controller (57). Controller (5
7) Inside is the predetermined liquid level L. The corresponding electrical level is set. Furthermore, an ultrasonic reflector (53) is disposed inside the container (51), and although it is not explicitly stated, it is assumed that its ends are fixed to the opposing side wall portions of the container (51). . Further, it is assumed that the level of the receiver (56) is at a predetermined liquid level L0 as shown in FIG. 2A.

As shown in FIG. 2A, when the liquid level L of the liquid (52) in the container (51) is above the predetermined level L0, the ultrasonic wave S completely emitted from the ultrasonic transmitter (55) is transmitted to the reflector. (53) and is directed to a receiver (56) as a reflected ultrasonic wave S°. In this case, the ultrasonic wave S is
The ultrasonic waves S and the reflected ultrasonic waves S' reach the receiver (56) through trajectories shown in Figure A, but since these trajectories are within the liquid (52), they are hardly attenuated and reach the receiver (56). ), the reception level of this receiver (56) is relatively high. This reception level signal is sent to the controller (
57) and compared with the set value, the output terminal (58) indicates that the liquid circulation level L of the liquid (52) in the container (51) is now at the predetermined level L. It emits an output that is determined to be higher.

Next, as shown in FIG. 2B, the level L of the liquid (52) is at a predetermined level L. If the ultrasonic wave S is lower than that, the ultrasonic wave S from the ultrasonic transmitter (55) will be reflected by the reflector (53), but this reflected ultrasonic wave will be reflected into the space Δ above the liquid (52). Therefore, it is greatly attenuated.

Therefore, it almost never reaches the receiver (56). Therefore, the reception level of this receiver (56) is relatively low, and this level is supplied to the controller (57) and compared with the set value, and it is determined that it is lower than this, and the signal is sent from the terminal (58) to the container (51). output to determine that the liquid level L of the liquid (52) is below a predetermined level L.

FIG. 2C shows that the level L of the liquid (52) is a predetermined level L,
That is, when the installation level of the receiver (56) matches that of the receiver (56), but in this case, the received signal controller (56) is installed at an intermediate level of the receiving level shown in FIGS. 2A and 2B.
7). Therefore, in some cases, if it is made to match this set value, the output that determines that the liquid level L of the liquid (52) in the container (51) is exactly at the predetermined level L0 can be sent to the terminal (58). ) can also be made to emit from.

Figures 3 and 4 show an oil rotary vacuum pump equipped with a liquid level detection device according to an embodiment of the present invention. A motor (62) is installed adjacent to the container (6I), and a discharge port (63) and an intake port (
64) is formed in a known manner.

In addition, a liquid level detection device (80) according to the present invention is attached to one side wall of the oil container (61), and its details are shown in FIG. (61
a) is formed, and a mounting plate (65) made of an ultrasonic transparent material is sealed with a seal ring (69) interposed therebetween, and is fixed to the side wall of the container (61). (79) is fitted. The mounting plate (65) is equipped with an ultrasonic transmitter (66) and an ultrasonic receiver (67) as described above.
) is attached inside the container (61) so as to face the mounting plate (65), and an ultrasonic reflecting plate (78) (not shown) is mounted on the opposite side wall of the container (61). Fixed. An ultrasonic transmitter (66) is connected to the controller (68).
An electric signal is supplied to excite the receiver (6
7) is configured to supply a received output generated by receiving reflected ultrasound to a controller (68). Oil Q is contained in the container (61), but a vacuum space is formed above this. It is clear that the above-mentioned functions and effects can also be obtained in the container (61) containing such liquid Q. In particular, in this embodiment, the space formed above the liquid Q is a vacuum, but the fourth In the conventional example, the liquid level could not be detected in such a case, but according to this embodiment, the liquid level can be detected without the same problem.

Although the embodiments of the present invention have been described above, the present invention is of course not limited thereto and can be modified in various ways. For example, in the embodiments described above, the receiver was placed at a level above the transmitter, and this level was used as the predetermined liquid level, but these were reversed, that is, the transmitter was placed at the upper level, The receiver may also be located at a lower level. In this case, the level of the upper transmitter may be set to a predetermined liquid level. Alternatively, the receiver and transmitter may be mounted on the same level. In this case, of course, the levels of these receivers and transmitters may be set to a predetermined liquid level.

Although the specific configurations of the receiver and transmitter were not described in detail in the above embodiments, they were made of a piezoelectric material, and electrodes were attached to both sides of the material as a film or thin film. It may be something.

Further, in the above embodiments, a part of the container is made of a material that is transparent to ultrasonic waves, but the entire container may be made of such a material.

[Effects of the Invention] As described above, according to the liquid level detection device of the present invention, it is possible to always accurately detect whether the liquid level in the container is above or below a predetermined level; Even if the space above the liquid level is a vacuum, it is possible to detect the height of the level.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a container equipped with a liquid level detection device for explaining the present invention in detail, and Figs. 2A, 2B, and 2C are partially enlarged cross-sections for explaining the operation of Fig. 1. Figure, 3rd
The figure is a side view of an oil rotary vacuum pump equipped with a liquid level detection device according to an embodiment of the present invention, FIG. 4 is an enlarged sectional view of the main part of the same embodiment, and FIG. 5 is a liquid level detection device of the first conventional example. 6 is a side view of the same, FIG. 7 is an enlarged sectional view of a level gauge in the same device, and FIG. 8 is a schematic sectional view of a container equipped with a second conventional liquid level detection device. Schematic sectional view, Figure 9 is the third
FIG. 10 is a schematic cross-sectional view shown together with an electric circuit of a container equipped with a liquid level detection device according to a conventional example, and FIG.
The figure is a schematic cross-sectional view of a container equipped with a fifth conventional liquid level detection device. In the figure, (53) (78)・-・・・・・・・・・・(541
(65)・・・・・・・・・・・・f551 (661
・・・Self・・・・・・(561[67)・・・・・・
・・・・・・Reflection board mounting Plate Ultrasonic transmitter Ultrasonic receiver Agent Yasuo Iisaka 1st figure 3rd figure 2A figure 5 figure 6 figure 7rlR

Claims (2)

[Claims] (1) In a container containing a liquid, at least a side wall portion close to the liquid surface at a predetermined level is formed of an ultrasonic transparent material, and an ultrasonic transmitter and receiver are attached to the outer surface of the side wall portion, At least one of the transmitter and the receiver is disposed on the same level as the predetermined level, and the ultrasonic wave from the transmitter is transmitted toward the ultrasonic reflector provided in the container. The receiver receives reflected ultrasonic waves by the receiver, and detects whether the level of the liquid in the container is above or below the predetermined level based on the level of the reception level. Liquid level detection device. (2) Claim (2) wherein at least one of the receiver and the transmitter is formed of a film or thin film made of a piezoelectric material.
1) The liquid level detection device according to item 1).