JP2018040661A - Liquid level detector and method for manufacturing liquid level detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid level detector which utilizes ultrasonic waves and can detect a liquid level with high accuracy, and to provide a method for manufacturing a liquid level detector.SOLUTION: A liquid level detector includes: a propagation body which is immersed in a liquid; vibration generation means which gives vibration to the propagation body so as to generate surface waves on the surface of the propagation body; and position detection means which outputs a drive signal for driving the vibration generation means, propagates and reflects the surface waves generated by vibration of the vibration generation means to the propagation body, receives a measurement signal detected by the vibration detection means, and detects a position of a liquid level of the liquid. The propagation body has a contact portion 1g which is resin-molded by using a metal mold and has a plurality of surfaces in a longitudinal direction, has a first surface composed of a smooth surface that propagates the surface waves out of the plurality of surfaces, and is brought into contact with a take-out mechanism from the metal mold on one or more surfaces excluding the first surface out of the plurality of surfaces.SELECTED DRAWING: Figure 4

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.

  As disclosed in Patent Document 1, for example, a conventional liquid surface detection device using ultrasonic waves is a liquid surface detector that changes the propagation time until a surface wave traveling on the surface of a propagation body made of synthetic resin returns to the upper end of the propagation body. The surface position is measured.

JP 2014-206504 A

  When resin-molding the propagation body, an ejector pin can be used when separating the propagation body from the mold. In this case, a contact mark may be generated due to the ejector pin coming into contact with the surface of the propagating body. There is room for improvement in that the surface wave propagating on the surface of the propagating body is reflected at the location of the contact mark, and there is a concern that it may be adversely affected when the liquid level position is measured.

  Therefore, the present invention pays attention to the above-described problems, and even when a resin-molded propagation body is used, a liquid level detection device and a liquid level detection device that can accurately detect a liquid level using ultrasonic waves It aims at providing the manufacturing method of.

  Propagation body 1 immersed in liquid L, vibration generation means 2 for applying vibration to propagation body 1 and generating surface wave W1 on the surface of propagation body 1, vibration detection means 2 for detecting the vibration of propagation body 1, and vibration generation A driving signal for driving the means 2 is output, and the surface wave W1 generated by the vibration of the vibration generating means 2 propagates and is reflected by the propagating body 1, receives the measurement signal S3 detected by the vibration detecting means 2, and receives the liquid level of the liquid L Position detecting means 3 for detecting the position of the LS, and the propagation body 1 is resin-molded using the molds A and B, and a plurality of surfaces 1c, 1d, 1e. 1f, and includes a first surface 1c that is a smooth surface that propagates the surface wave W1 among the plurality of surfaces 1c, 1d, 1e, and 1f, and the first of the plurality of surfaces 1c, 1d, 1e, and 1f The contact part 1g which contacts the taking-out mechanism C from the metal mold | die A and B is provided in any one or more surfaces except 1 surface 1c.

  The vibration generating means 2 generates an internal propagation wave W2 inside the propagation body 1, and a second surface 1d different from the first surface 1c includes an internal propagation wave reflecting portion 1b that reflects the internal propagation wave W2. The surfaces 1d, 1e, and 1f provided with the contact portion 1g are used as attachment surfaces of the propagation body 1.

  The manufacturing method of the liquid level detection device F includes a propagation body 1 immersed in a liquid, vibration generating means 2 that applies vibration to the propagation body 1 and generates a surface wave W1 on the surface of the propagation body 1, and detects vibration of the propagation body 1. And a measurement signal detected by the vibration detection means 2 when the surface wave W1 generated by the vibration of the vibration generation means 2 is propagated and reflected by the propagation body 1. Position detecting means 3 that receives S3 and detects the position of the liquid level LS of the liquid L, and the propagation body 1 is formed by resin molding using the molds A and B, and then propagates the surface wave W1. The molds A and B are taken out by using a take-out mechanism C that contacts the surfaces 1d, 1e, and 1f other than the first surface 1c.

  The manufacturing method of the liquid level detection device F is characterized in that after the propagation body 1 is formed, a reflection surface (internal propagation wave reflecting portion) 1b on which the internal propagation wave W2 is reflected is formed.

  According to the present invention, it is possible to provide a liquid level detection device capable of accurately detecting a liquid level using ultrasonic waves and a method for manufacturing the liquid level detection device even when a resin-molded propagation body is used. it can.

The block diagram of 1st Embodiment of this invention. The side view of the propagation body of the embodiment. The figure which shows the propagation body of the same embodiment, a metal mold | die, and a taking-out mechanism. The figure which shows the propagation body and contact part 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 figure which shows 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.

  As shown in FIG. 2, the propagating body 1 is immersed in a liquid L stored in a tank, 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 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 (piezoelectric element 2a) side of the groove 1a, an internal propagation wave reflecting portion 1b for reflecting an internal propagation wave described later is provided.

  The propagation body 1 is created by resin molding using molds A and B as shown in FIG. The molds A and B are provided with an ejector pin (extraction mechanism) C, a gate port (not shown), and a parting line D. The heated synthetic resin is filled into the molds A and B through the closed gates of the molds A and B. After cooling and the synthetic resin is cured, the molds A and B are opened around the parting line D, and the propagating body 1 is pushed out by the ejector pins C provided on the mold B. Removed from mold B. After the propagation body 1 is resin-molded, the groove 1a is formed by cutting.

  The propagation surface (first surface) 1c is a surface that is formed smoothly by the mold A and faces the surface (second surface) 1d provided with the internal propagation wave reflection portion 1b. When the propagation body 1 is resin-molded, the ejector pin C is disposed so as to be in contact with one or more surfaces other than the propagation surface 1c. That is, the ejector pin C can be disposed so as to be in contact with the surface 1d, or can be disposed so as to be in contact with the other surfaces 1e and 1f between the propagation surface 1c and the surface 1d. Moreover, it can also arrange | position so that the surface 1d, 1e, and 1f may touch several surfaces. When the propagating body 1 is separated from the mold, contact portions 1g and 1g1 are formed on the surface in contact with the ejector pin C as shown in FIG. In this case, the contact portion 1g remains as a circular surface recessed in the surface 1d. Note that the contact portion 1g may be a protruding circular surface, and remains as a stepped circular surface on the surface 1d.

  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. In this case, the vibration generation detecting means 2 is provided in the vicinity of the end of the propagation surface 1c so that vibration is easily transmitted to the propagation surface 1c in order to form a surface wave to be described later.

  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. 5 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 stores a relationship between a propagation time T1 of an internal propagation wave W2 to be 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. 7A, and the predetermined propagating body 1 as shown in FIG. 7B. 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. 7B 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.

  By providing the contact portions 1g, 1g1 on any one or more of the surfaces 1d, 1e, 1f other than the propagation surface 1c for propagating the surface wave W1 of the propagating body 1, the surface wave W1 is contacted with the contact portions 1g, 1g1. Since the propagation time of the surface wave W1 propagating through the propagation surface 1c can be measured correctly, it is possible to provide a liquid level detection device capable of detecting the liquid level with high accuracy.

In addition, by using the surface provided with the contact portions 1g and 1g1 as a mounting surface to a mounting portion (not shown) provided in the tank of the propagating body, an obstruction factor for the propagation of the surface wave W1 to the propagation surface 1c is different. Since the amplitude of the surface wave W1 propagating through the propagation surface 1c is difficult to attenuate, it is possible to provide a liquid level detection device capable of detecting the liquid level with high accuracy.
Further, when the propagation body 1 is resin-molded, the propagation surface 1c is formed by providing a gate port or a parting line D for injecting resin on a surface provided with the contact portion 1g, that is, a surface other than the propagation surface 1c. Smooth by mold. For this reason, since processing such as cutting and polishing of the propagation surface 1c for generating a surface wave suitable for measurement is not required, it is advantageous in terms of cost and quality universality.

  It should be noted that the present invention is not limited to the above-described embodiment, and various modifications (including deletion of components) can be made without departing from the spirit of the invention. In the above-described embodiment (FIG. 3), the contact portions 1g and 1g1 are expressed as circles. However, the contact portions 1g and 1g1 are not limited to the contact with the round ejector pins. The same effect can be expected even if a corresponding shape is used.

  In the above-described embodiment, the groove 1a is formed by cutting. However, when the propagation body 1 is resin-molded, the same effect can be expected even if the groove 1a is formed using a mold at the same time.

  In the above-described embodiment, the groove 1a is formed by cutting out the internal propagation wave reflection portion 1b. However, the present invention is not limited to the above-described 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 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.

  Further, 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, as shown in FIG. The cross-sectional shape in the direction perpendicular to the direction may be a D-shaped cylindrical shape or the like. Moreover, polygonal prism shapes, such as the triangular prism shape shown to FIG.8 (b), (c), may be sufficient. Moreover, although not shown in figure, the polygon more than a pentagon may be sufficient. Furthermore, it does not need to be a regular polygon, and may be an optimum shape for attaching the propagation body 1.

  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.

A Mold B Mold C Ejector pin (Removal mechanism)
D Parting line 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 reflector (reflection surface)
1c Propagation surface (first surface)
1d surface (second surface)
1e surface 1f surface 1g contact portion 1g1 contact portion 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 (4)

A propagator immersed in a liquid;
Vibration generating means for applying vibration to the propagating body and generating surface waves on the surface of the propagating body;
Vibration detecting means for detecting vibration of the propagating body;
The liquid signal of the liquid is received by outputting a driving signal for driving the vibration generating means and receiving the measurement signal detected by the vibration detecting means by the surface wave generated by the vibration of the vibration generating means propagating and reflecting the propagation body. Position detecting means for detecting the position of the surface;
A liquid level detection device comprising:
The propagation body is resin-molded using a mold and has a plurality of surfaces in the longitudinal direction,
Of the plurality of surfaces, comprising a first surface consisting of a smooth surface for propagating the surface wave,
Of the plurality of surfaces, any one or more surfaces excluding the first surface,
A liquid level detection device comprising a contact portion that comes into contact with a take-out mechanism from the mold. The vibration generating means generates an internal propagation wave inside the propagating body,
The second surface different from the first surface includes an internal propagation wave reflection unit that reflects the internal propagation wave, and
The liquid level detection device according to claim 1, wherein the surface including the contact portion is an attachment surface of the propagation body. A propagator immersed in a liquid;
Vibration generating means for applying vibration to the propagating body and generating surface waves on the surface of the propagating body;
Vibration detecting means for detecting vibration of the propagating body;
The liquid signal of the liquid is received by outputting a driving signal for driving the vibration generating means and receiving the measurement signal detected by the vibration detecting means by the surface wave generated by the vibration of the vibration generating means propagating and reflecting the propagation body. Position detecting means for detecting the position of the surface;
A method of manufacturing a liquid level detection device comprising:
After the propagation body is resin-molded using a mold,
A method for manufacturing a liquid level detection device, wherein the liquid level detection device is extracted from the mold using an extraction mechanism that contacts a surface other than the first surface that propagates the surface wave. The method of manufacturing a liquid level detection device according to claim 3, wherein a reflection surface that reflects internal propagation waves is formed after the propagation body is formed.

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