JP6270055B2 - Liquid level detector - Google Patents

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 apparatus that can accurately detect a liquid level using ultrasonic waves without using a temperature sensor, paying attention to the above-described problems.

In order to achieve the above object, the present invention provides a propagating body that is immersed in a liquid, a vibration generating means that applies vibration to the propagating body, a vibration detecting means that detects vibration of the propagating body, and a drive that drives the vibration generating means. Position detecting means for outputting a signal and propagating a wave generated by the vibration of the vibration generating means to propagate and reflect on the propagating body and receive a measurement signal detected by the vibration detecting means to detect the position of the liquid surface of the liquid In a liquid level detection device comprising:
An internal propagation wave that reflects the internal propagation wave generated inside the propagation body on a surface in a longitudinal direction different from the surface where the vibration generating means of the propagation body protrudes toward the outside of the propagation body With a reflective part,
It said vibration generating means generates the internal propagating wave inside the propagating body with generating a surface wave on the surface of the propagation member,
The position detecting means detects the vibration of the surface wave propagated and reflected by the surface wave and outputs the measurement signal, and the internal propagation wave propagates and reflects the internal propagated wave. Detects vibration and outputs a reference signal
The position detecting means detects the liquid level by correcting the propagation time of the surface wave obtained from the drive signal and the measurement signal based on the propagation time of the internal propagation wave obtained from the drive signal and the reference signal. It is.

  As described above, according to the present invention, it is possible to provide a liquid level detection device that can achieve the intended purpose and can accurately detect the liquid level using ultrasonic waves without using a temperature sensor.

The block diagram of 1st Embodiment of this invention. The side view of the propagation body of the embodiment. The flowchart showing the liquid level detection process of the embodiment. The wave form diagram which shows the surface wave and internal propagation wave 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.

  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 propagating body 1 is immersed in a liquid L stored in a tank (not shown), for example, a medium such as gasoline or alcohol.

  The propagating body 1 is a material that can transmit vibrations satisfactorily. 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 composed of a plane on which a surface wave W1 to be described later propagates. In this embodiment, the propagating body 1 is a quadrangular column. A notched groove 1a is provided in a part thereof. The groove 1a includes an internal propagation wave reflecting portion 1b that reflects an internal propagation wave to be described later.

  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. 4 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 nonvolatile memory or the like, and stores the relationship between the propagation time T1 of the internal propagation wave W2 and the temperature of the propagation body 1 shown in FIG.

  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

  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. The vibration generating means 2 generates a surface wave W1 on the surface of the propagating body 1 and an internal propagating wave W2 inside the propagating body 1, and the vibration detecting means 2 is a surface wave. W1 detects the vibration of the surface wave W1 propagated through the propagation body 1 and reflects it and outputs a measurement signal, and the internal propagation wave W2 propagates through the propagation body 1 and detects the vibration of the internal propagation wave W2 reflected and outputs a reference signal. The position detection means 3 is a drive signal. By detecting the liquid level LS by correcting the propagation time T2 of the surface wave W1 obtained by the drive signal S1 and the measurement signal S3 by the propagation time T1 of the internal propagation wave W2 obtained by the S1 and the reference signal S2, the temperature sensor is detected. It is possible to provide a liquid level detection device capable of accurately detecting the liquid level using ultrasonic waves without using it.

  Further, there is provided storage means 3b for storing the relationship between the propagation time T2 of the internal propagation wave W2 obtained from the drive signal S1 and the reference signal S2 and the temperature of the propagation body 1, and the position detection means 3 is stored in the storage means 3b. By correcting the propagation time T2 of the surface wave W1 based on the relationship between the propagation time T2 of the propagation wave W2 and the temperature of the propagation body 1 and detecting the liquid level, the liquid surface using ultrasonic waves with high accuracy without using a temperature sensor. A liquid level detection device capable of detection can be provided.

  Further, since the propagating body 1 is provided with the internal propagation wave reflecting portion 1b, it is possible to provide a liquid level detecting device capable of accurately detecting the liquid level using ultrasonic waves without using a temperature sensor. Furthermore, the surface wave W1 and the internal propagation wave W2 can be obtained by the same drive signal S1, the detection process is simplified, and the cost can be reduced.

  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. For example, as shown in FIG. 5B, the storage unit 3b indicates the position of the liquid level LS related to the propagation time T2 of the surface wave W1 for each predetermined temperature (for example, every 5 degrees Celsius) of the propagation body 1. Remember. 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.

  Further, in the present embodiment, the groove 1a is formed by cutting out the internal propagation wave reflection portion 1b. However, the present invention is not limited to this embodiment. A part of the propagating body 1 cut out to the bottom surface and formed into a key shape, a screw stopper, or another member fitted in the groove 1a may be used. The another member may be a resin or a metal.

  In the present 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.

  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 propagation wave 1 Propagator 1a Groove 1b Internal propagation wave reflection part 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 ,
An internal propagation wave that reflects the internal propagation wave generated inside the propagation body on a surface in a longitudinal direction different from the surface where the vibration generating means of the propagation body protrudes toward the outside of the propagation body With a reflective part,
It said vibration generating means generates the internal propagating wave inside the propagating body with generating a surface wave on the surface of the propagation member,
The position detecting means detects the vibration of the surface wave propagated and reflected by the surface wave and outputs the measurement signal, and the internal propagation wave propagates and reflects the internal propagated wave. Detects vibration and outputs a reference signal
The position detecting means detects the liquid level by correcting the propagation time of the surface wave obtained from the drive signal and the measurement signal based on the propagation time of the internal propagation wave obtained from the drive signal and the reference signal. A liquid level detection device characterized by the above. Storage means for storing a relationship between a propagation time of the internal propagation wave determined by the drive signal and the reference signal and the temperature of the propagation body is provided, and the position detection means is configured to store the internal propagation wave stored in the storage means. The liquid level detection apparatus according to claim 1, wherein the propagation time of the surface wave is corrected based on a relationship between a propagation time and a temperature of the propagation body. Storage means for storing a liquid surface position related to the propagation time of the surface wave based on the temperature of the propagation body is provided, and the position detection means propagates the surface wave based on the temperature of the propagation body stored in the storage means. The liquid level detection device according to claim 1, wherein the position of the liquid level is detected from the liquid level position related to time.

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