JP2017207374A - Liquid level detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid level detector capable of precisely detecting a liquid level using an ultrasonic wave.SOLUTION: A liquid level detector F includes: a propagation body 1 immersed in a liquid L; vibration generation means 2 for applying vibration to the propagation body 1; vibration detection means 2 for detecting vibration of the propagation body 1; and position detection means 3 for outputting a driving signal S1 to drive the vibration generation means 2, receiving a measurement signal S3 detected by the vibration detection means 2 measuring a propagation wave that is generated by the vibration of the vibration generation means 2, propagates through the propagation body 1 and is reflected, and detecting the position of a liquid level LS of liquid L. The propagation body 1 includes a groove 1a substantially orthogonal to a longitudinal direction, and a groove section 1d is further formed on a lower surface 1c of the groove 1a.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a liquid level detection device that detects the liquid level of a liquid in a tank using ultrasonic waves.

  The conventional liquid level detection device is a method for detecting the surface of an ultrasonic wave propagating through the ultrasonic good conductor by a change in the contact length between the ultrasonic good conductor and the liquid when a part of the ultrasonic good conductor in the gas is in the liquid. The level of the liquid was measured using the fact that the wave propagation time changes (see Patent Document 1).

Japanese Patent Laid-Open No. 4-86525

  Since the liquid level detection device using ultrasonic waves is influenced by temperature in principle, the liquid level detection device or a temperature sensor for detecting the temperature of the liquid to be measured is provided, and the temperature detected by the temperature sensor is corrected. It has been considered to detect the liquid level. However, the provision of the temperature sensor causes an increase in manufacturing cost, and it is necessary to perform measurement using the temperature sensor, which causes a problem that the detection process becomes complicated.

  Therefore, the present invention provides a liquid level detection device that can accurately detect a liquid level using ultrasonic waves, paying attention to the above-described problems.

  While transmitting the propagation body 1 immersed in the liquid L, the vibration generation means 2 for applying vibration to the propagation body 1, the vibration detection means 2 for detecting the vibration of the propagation body 1, and the drive signal S1 for driving the vibration generation means 2 are output. A position detecting means 3 for detecting a position of the liquid surface LS of the liquid L by receiving a measurement signal S3 detected by the vibration detecting means 2 when a propagating wave generated by the vibration of the vibration generating means 2 propagates and is reflected by the propagating body 1; In the liquid level detection device F having the above, the propagation body 1 includes a groove 1a substantially orthogonal to the longitudinal direction, and a groove 1d is further formed on the lower surface 1c of the groove 1a.

  Further, the groove portion 1d1 is characterized in that the end portion 1e side of the propagation body 1 is wider than the groove 1a side.

  Further, a plurality of groove portions 1d2 are provided.

  As described above, according to the present invention, it is possible to provide a liquid level detection apparatus that can achieve the intended purpose and that can accurately detect the liquid level using ultrasonic waves.

The block diagram of 1st Embodiment of this invention. The side view of the propagation body of the embodiment. The wave form diagram which shows the surface wave and internal propagation wave of the embodiment. The flowchart showing the liquid level detection process of the embodiment. (A) is a figure which shows the relationship between the propagation time of an internal propagation wave, and temperature, (b) is a figure which shows the relationship between the propagation time of a surface wave, and a liquid level position. The principal part enlarged view of the propagation body of the embodiment. The principal part enlarged view of the propagation body of 2nd Embodiment. The principal part enlarged view of the propagation body of 3rd Embodiment. The principal part enlarged view of the propagation body of another embodiment of 1st Embodiment. The front view of the propagation body of another embodiment. The side view of the propagation body of another embodiment. The side view of the propagation body of another embodiment.

  Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the liquid level detection device F according to the embodiment of the present invention includes at least a propagation body 1, vibration generation detection means 2, and position detection means 3.

  The propagation body 1 is immersed in a liquid L stored in a tank, for example, a medium such as gasoline or alcohol, as shown in FIG.

  The propagating body 1 is a material capable of satisfactorily transmitting vibrations. In this embodiment, the propagating body 1 is mainly made of a synthetic resin, particularly polyphenylene sulfide (PPS), and optionally added with additives. The shape of the propagating body 1 is a columnar body, and includes a propagation surface formed of a plane through which a surface wave W1 described later propagates. In the present embodiment, the propagating body 1 is a rod-shaped square column. The propagating body 1 is provided with a groove 1a that is partially cut out so as to be substantially orthogonal to the longitudinal direction. On the vibration generation detecting means 2 side of the groove 1a, an internal propagation wave reflecting portion 1b for reflecting an internal propagation wave described later is provided.

  The vibration generation detection unit 2 is a vibration generation unit that applies vibration to the propagation body 1 and is a vibration detection unit that detects vibration of the propagation body 1.

  The vibration generation detection means 2 includes a piezoelectric element 2a, a transmission circuit 2b that transmits a signal for driving the piezoelectric element 2a, and a reception circuit 2c that receives a signal detected by the piezoelectric element 2a.

  The piezoelectric element 2a generates a surface wave W1 and an internal propagation wave W2 on the propagating body 1 and has no groove 1a up to the other end of the propagating body 1 in order to detect the surface wave W1 and the internal propagating wave W2. The piezoelectric element 2a is installed so as to protrude. The propagating body 1 and the piezoelectric element 2a are fixed in close contact. With this configuration, the piezoelectric element 2a applies vibration to the propagating body 1 to generate a surface wave W1 on the surface of the propagating body 1 and an internal propagation wave W2 inside the propagating body 1. Furthermore, vibration of the propagating body 1 (vibration caused by the surface wave W1 and the internal propagation wave W2) is detected and converted into a voltage. The surface wave W1 includes a Rayleigh wave, a leaky Rayleigh wave, and a transverse surface acoustic wave, and the internal propagation wave W2 includes a transverse wave.

  The transmission circuit 2b drives the piezoelectric element 2a. For example, the transmission circuit 2b includes a drive circuit and a transformer (not shown). A voltage is applied.

  The receiving circuit 2c detects a signal output from the piezoelectric element 2a and outputs a signal to the position detecting means 3, and includes, for example, an input protection circuit, an amplifier circuit, a band pass filter, a waveform shaping circuit, etc. (not shown). The vibration detected by the piezoelectric element 2a is output to the position detection means 3 as a signal.

  The vibration which arises in the propagation body 1 is demonstrated using FIG. FIG. 3 is shown schematically. In the figure, the leftmost vibration is the vibration V1 generated by the piezoelectric element 2a by the drive signal S1 output from the position detecting means 3. The second vibration from the left is the vibration V <b> 2 of the internal propagation wave W <b> 2 that has traveled through the propagation body 1 and reflected back by the internal propagation wave reflection portion 1 b of the propagation body 1. The rightmost vibration is the vibration V <b> 3 of the surface wave W <b> 1 that is transmitted through the surface of the propagating body 1, reflected at the other end of the propagating body 1, and returned. In the present embodiment, a signal output from the receiving circuit 2c due to the vibration V3 of the surface wave W1 is referred to as a measurement signal S3, and a signal output from the receiving circuit 2c due to the vibration V2 of the internal propagation wave W2 is referred to as a reference signal S2. It should be noted that the surface wave W1 has a property that the speed of the surface wave W1 traveling through the propagating body 1 is slow in the portion where the propagating body 1 is immersed in the liquid L, and the liquid surface LS of the liquid L is affected by the propagation time T2 of the surface wave W1. Can be detected.

  The propagation time T1 of the internal propagation wave W2 is the internal propagation wave W2 that is generated by the internal propagation wave W2 from the time t1 when the control unit 3a of the position detection unit 3 outputs the drive signal S1 and reflected by the vibration generation detection unit 2. The time T2 from the time t1 when the control unit 3a of the position detecting means 3 outputs the drive signal S1 to the time t2 until the time t2 at which the reference signal S2 is detected and output is received. This is the time until time t3 when receiving the measurement signal S3 generated and detected by the surface wave W1 reflected at the other end of the propagating body 1.

  The receiving circuit 2c of the vibration generation detecting means 2 outputs a measurement signal S3 obtained by detecting the vibration V3 of the surface wave W1 propagated and reflected by the surface wave W1 through the propagation body 1 to the position detecting means 3, and the internal propagation wave W2 propagates. A reference signal S2 obtained by detecting the vibration V2 of the internal propagation wave W2 propagated and reflected by the body 1 is output to the position detection means 3.

  The position detection unit 3 includes a control unit 3a composed of at least a microcomputer and a storage unit 3b. The position detection unit 3 outputs a drive signal S1 that drives and vibrates the vibration generation detection unit 2, and the surface wave W1 and the internal propagation wave W2, which are propagation waves generated by the vibration of the vibration generation detection unit 2, are propagated by the propagation body 1. The position of the liquid surface LS of the liquid L is detected by detecting the vibration of the surface wave W1 and the internal propagation wave W2 by the vibration generation detecting means 2.

  The control unit 3a includes a CPU that performs processing executed by the control unit 3a, a RAM that functions as a main memory of the CPU, a ROM that stores various programs that cause the control unit 3a to execute predetermined processing, and the control unit 3a. And various converters that digitally convert input / output information (signals) for the CPU and analog convert for output.

  The storage means 3b is a non-volatile memory or the like, and can store various data such as a relationship between a propagation time of an internal propagation wave described later and the temperature of the propagation body 1.

  The position detection means 3 obtains the temperature of the propagation body 1 with reference to the storage means 3b based on the propagation time T1 of the internal propagation wave W2 obtained from the drive signal S1 and the reference signal S2, and is driven by the temperature of the propagation body 1. The liquid surface LS is accurately detected by correcting the propagation time T2 of the surface wave W1 obtained from the signal S1 and the measurement signal S3.

  Next, the processing operation of the position detection means 3 will be described with reference to FIGS.

  In step ST1, the position detection means 3 outputs a drive signal S1.

  In step ST2, the position detection means 3 determines whether or not the reference signal S2 is detected based on the internal propagation wave W2 generated in the propagation body 1 based on the drive signal S1. If it is determined that the reference signal S2 has been detected, the process proceeds to step ST3. When it determines with not detecting, it returns to step ST1.

  In step ST3, the position detection means 3 obtains a propagation time T1 in which the internal propagation wave W2 has propagated through the propagation body 1. In the present embodiment, the propagation time T1 is obtained as the propagation time T1 from the output of the drive signal S1 to the input of the reference signal S2. In the present embodiment, the time from when the position detection means 3 outputs the drive signal S1 until the piezoelectric element 2a vibrates, the piezoelectric element 2a detects the vibration, and the position detection means 3 detects the vibration via the receiving circuit 2c. The time to receive the signal is considered to be negligible.

  In step ST4, the position detection means 3 obtains the temperature of the propagation body 1 with reference to the storage means 3b from the propagation time T1 of the reference signal S2.

  In step ST5, the position detection means 3 determines whether or not the measurement signal S3 is detected based on the surface wave W1 generated on the surface of the propagation body 1 based on the drive signal S1. If it is determined that the measurement signal S3 has been detected, the process proceeds to step ST6. When it determines with not detecting, it returns to step ST1.

  In step ST <b> 6, the position detection unit 3 obtains a propagation time T <b> 2 when the surface wave W <b> 1 propagates through the surface of the propagation body 1.

  In step ST7, the position detecting means 3 calculates the propagation time T2 of the surface wave W1 based on the temperature of the propagating body 1 obtained in step ST4 by the correction coefficient (a, b) based on the temperature of the propagating body 1. The liquid level LS is detected based on the corrected propagation time. In addition, the formula which makes propagation time T2 a solution is represented by the following linear formula.

  T2 = ax + b

  The storage means 3b stores the relationship between the propagation time T1 of the internal propagation wave W2 and the temperature of the propagating body 1 as shown in FIG. 5 (a), and a predetermined value of the propagating body 1 as shown in FIG. 5 (b). The position of the liquid level LS related to the propagation time T2 of the surface wave W1 is stored for each temperature (for example, every 5 degrees Celsius). FIG. 5B illustrates another example of 0 degrees Celsius, 5 degrees Celsius, and 10 degrees Celsius. The position detecting means 3 detects the position of the liquid level LS by obtaining the position of the liquid level LS related to the propagation time T2 of the surface wave W1 based on the temperature of the propagating body 1 stored in the storage means 3b. Also good.

  As described above, the propagating body 1 immersed in the liquid L, the vibration generating means 2 for applying vibration to the propagating body 1, the vibration detecting means 2 for detecting the vibration of the propagating body 1, and the drive signal for driving the vibration generating means 2 are output. A position detecting means 3 for detecting a position of the liquid level LS of the liquid L by receiving a measurement signal detected by the vibration detecting means 2 when a propagation wave generated by the vibration of the vibration generating means 2 propagates and reflects the propagation body 1 and reflects. In the liquid level detection device F provided with the above, the groove 1a is formed in the propagation body 1, and the internal propagation wave reflection portion 1b is provided using the groove 1a, so that the ultrasonic wave can be accurately obtained without using a temperature sensor. It is possible to provide a liquid level detection device capable of detecting a liquid level using

Next, the propagation body 1 that is a feature of the present invention will be described.
As shown in FIG. 6, the propagating body 1 has a groove 1d on a surface 1c facing the internal propagation wave reflecting portion 1b. In this case, the groove portion 1d is formed in a slit shape in which a part of the lower surface 1c of the groove 1a is cut out, and is formed narrower than the gap of the groove 1a.
Therefore, even if the groove 1a is exposed from the liquid level LS by reducing the fuel in the tank by providing the groove 1d on the lower surface 1c of the groove 1a facing the internal propagation wave reflecting portion 1b, the surface tension The liquid L that is to remain in the groove 1a can be easily derived using capillary action or gravity, and the state in which the liquid L remains in the groove 1a can be suppressed. For this reason, it can prevent that detection accuracy falls by the leaky wave which propagates in the liquid L collected in the groove | channel 1a.

  Further, as shown in FIG. 7 as the second embodiment, the groove 1d1 opens wider on the end 1e side of the propagating body than the internal propagation wave reflection portion 1b side, or as shown in FIG. 8 as the third embodiment. Thus, by providing a plurality of groove portions 1d2, it can be expected that the liquid L can be led out more smoothly from the groove 1a and the liquid L is less likely to remain.

  Note that the present invention is not limited to the above-described embodiment, and various modifications (including deletion of constituent elements) can be made without departing from the spirit of the invention. In the above-described embodiment, the case where the groove portion 1d reaches the end portion 1e of the propagating body 1 is illustrated. However, as illustrated in FIG. 9, the groove portion 1d3 extends from the substantially center of the surface 1c of the propagating body 1 toward the front surface. Even if the groove 1d4 has a shape that does not reach the end 1e from the approximate center of the surface 1c toward the side surface of the propagating body 1 as shown in FIG. I can expect.

  In the above-described embodiment, the liquid level of liquid fuel such as gasoline or alcohol is detected. However, the liquid level is not limited to liquid fuel such as gasoline or alcohol, and other liquids such as water are detected. It is also possible to do. Moreover, a use is not limited to vehicles, such as a vehicle, It can utilize for a wide use.

  In addition, the shape of the propagating body 1 is not limited to a quadrangular prism, and may be any plane as long as the surface wave W1 can propagate. For example, a cross-sectional shape perpendicular to the longitudinal direction of the propagating body 1 However, it may be D-shaped or the like.

  In the above-described embodiment, the case where the internal propagation wave reflecting portion 1b and the surface 1c are substantially parallel is illustrated. However, as shown in FIG. 11, the inclined surface 1c1 that is inclined so that the center side of the propagating body 1 is lowered, As shown in FIG. 12, by providing the inclined surface 1c2 that is inclined so that the front side of the propagation body 1 is lowered, it can be expected that the action of discharging the liquid remaining in the groove 1a in a desired direction is enhanced.

  The present invention relates to a liquid level detection device, and in particular, can be used for a liquid level detection device that detects a liquid level using ultrasonic waves.

F Liquid level detection device L Liquid LS Liquid level S1 Drive signal S2 Reference signal (internal propagation wave W2)
S3 Measurement signal (surface wave W1)
T1 propagation time (internal propagation wave W2)
T2 Propagation time (surface wave W1)
V1 vibration V2 vibration (internal propagation wave)
V3 vibration (surface wave)
W1 Surface wave W2 Internal propagating wave 1 Propagating body 1a Groove 1b Internal propagating wave reflecting portion 1c surface (surface facing the propagating wave reflecting portion)
1c1 plane (surface facing the propagating wave reflector)
1c2 plane (surface facing the propagating wave reflector)
1d Groove 1d1 Groove 1d2 Groove 1d3 Groove 1d4 Groove 1e End 2 Vibration generation detection means (vibration generation means, vibration detection means)
2a Piezoelectric element 2b Transmission circuit 2c Reception circuit 3 Position detection means 3a Control unit 3b Storage means

Claims (3)

A propagating body immersed in a liquid; vibration generating means for applying vibration to the propagating body; vibration detecting means for detecting vibration of the propagating body; a drive signal for driving the vibration generating means; In a liquid level detection apparatus, comprising: a position detection means for detecting a position of the liquid level of the liquid by receiving a measurement signal that is propagated and reflected by the propagation body and reflected by the propagation body and received by the vibration detection means ,
The liquid level detecting device, wherein the propagation body includes a groove substantially orthogonal to the longitudinal direction, and a groove is further formed on a lower surface of the groove.   2. The liquid level detection device according to claim 1, wherein the groove portion is wider at an end portion side of the propagating body than at the groove side. The liquid level detection device according to claim 1, wherein a plurality of the groove portions are provided.

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