JP4277761B2 - Liquid level detector - Google Patents

Description

  The present invention relates to a liquid level detecting device for detecting a liquid level position of a liquid in a tank, and is suitable for use for detecting a fuel level in a fuel tank installed in an automobile, for example.

  Conventionally, as a liquid level detecting device for detecting the liquid level of a liquid in a tank, for example, an ultrasonic oscillation element disposed in a fuel and an ultrasonic wave disposed in the fuel from an ultrasonic oscillation element And a reflection plate that reflects toward the surface, and receives the ultrasonic wave reflected by the liquid surface by an ultrasonic oscillation element via the reflection plate to calculate the liquid level (see, for example, Patent Document 1).

In the liquid level detection device described above, a cylinder having a square cross section is fixed to the bottom surface inside the fuel tank, and an ultrasonic oscillation element is superposed on one end of the cylinder toward the other end of the cylinder. A reflection plate that is attached so as to be able to emit sound waves and that reflects the ultrasonic waves that have traveled through the cylinder toward the liquid surface is provided on the other end side of the cylinder. This cylinder forms an ultrasonic wave propagation path in the liquid level detection device.
JP-A-11-153471

  In the above-described conventional liquid level detection device, the cylinder is formed so that the cross section is square and the cross section is uniform in the axial direction of the cylinder. That is, in the four wall surfaces constituting the cylindrical body, the two opposing wall surfaces are in a parallel relationship with each other.

  Ultrasound travels in the cylinder while being repeatedly reflected on each wall surface of the cylinder, but every time an ultrasonic wave is reflected on the wall surface, a part of it passes through the wall surface, etc., so the energy of the ultrasound gradually decreases. I will do it.

  In the cylindrical body in the above-described conventional liquid level detection device, that is, a cylindrical body having a uniform cross-sectional shape in almost the entire area in the axial direction, the intensity of the ultrasonic wave incident on the reflector, that is, the crossing of the cylindrical body. The sound pressure level of the ultrasonic wave per unit area on the surface is lower than the sound pressure level of the ultrasonic wave in the vicinity of the ultrasonic oscillation element.

For this reason, the sound pressure level of the ultrasonic wave reflected from the reflecting plate toward the liquid surface is lowered, and the sound pressure level of the ultrasonic wave reflected from the liquid surface is also lowered accordingly, and it is difficult to detect the liquid level with high accuracy. The present invention has been made in view of the above points, and its purpose is to devise a configuration of the propagation path from the ultrasonic oscillation element to the reflecting plate and to enter the reflecting plate. An object of the present invention is to provide a liquid level detection device capable of detecting a liquid level with high accuracy by increasing the sound pressure level of ultrasonic waves from an ultrasonic oscillation element.

  The present invention employs the following technical means to achieve the above object.

In the liquid level detection device according to the first aspect of the present invention, the ultrasonic wave oscillating element disposed at the bottom of the tank that stores the liquid, and the ultrasonic wave emitted by the ultrasonic wave oscillating element is used as the liquid level of the liquid in the tank. A reflection wall that reflects toward the surface, a cylindrical first path member that forms an ultrasonic wave propagation path between the ultrasonic oscillator and the reflection wall, and a cylindrical shape that forms an ultrasonic wave propagation path between the reflection wall and the liquid surface A liquid surface that detects the liquid surface position by emitting ultrasonic waves from the ultrasonic oscillation element and receiving a reflected wave from the liquid surface through the reflection wall by the ultrasonic oscillation element. In the detection device, the first path member is formed such that a cross-sectional area in a direction orthogonal to the axis thereof decreases as the distance from the ultrasonic oscillation element increases, and the first path member is a direction orthogonal to the axis. The cross-sectional shape of the second path portion is formed in a circular shape The material has a circular cross-sectional shape in a direction orthogonal to the axis, and the diameter dimension at the reflection wall side end of the first path member is set to be approximately equal to the diameter dimension at the reflection wall side end of the second path member. In addition, the first path member is characterized by being provided with a ring-shaped step portion formed as a surface facing the ultrasonic oscillation element .

  In the liquid level detection device, the energy of the ultrasonic wave emitted from the ultrasonic oscillation element gradually attenuates due to reflection on the wall surface while traveling through the first path member.

  The cylindrical body of the conventional liquid level detection device has a uniform cross-sectional shape over almost the entire area in the axial direction. Therefore, the sound pressure level, which is an index of ultrasonic strength, that is, the pressure level generated by the action of ultrasonic waves per unit area in the cross section of the cylinder decreases as the distance from the ultrasonic oscillation element increases. In the vicinity of the reflection plate, which is the end portion on the opposite side to the acoustic wave oscillating element, the amount is considerably lowered.

  On the other hand, in the liquid level detection device according to the first aspect of the present invention, the first path member is formed such that the cross-sectional area of the cross section thereof becomes smaller as the distance from the ultrasonic oscillation element increases. In other words, the first path member is formed such that the ultrasonic propagation path tapers from the ultrasonic oscillation element toward the reflection wall.

  For this reason, the energy attenuation degree of the ultrasonic wave in which the ultrasonic wave emitted from the ultrasonic oscillation element is traveling in the first path member can be reduced as compared with the case of the cylindrical body of the conventional liquid level detection device. Therefore, the sound pressure level of the ultrasonic wave incident on the reflecting wall can be increased as compared with the conventional liquid level detection device.

  As a result, it is possible to provide a liquid level detection device capable of detecting a liquid level with high accuracy while suppressing a decrease in the sound pressure level of ultrasonic waves from the ultrasonic oscillation element incident on the reflection wall.

  In general, ultrasonic waves emitted from an ultrasonic oscillation element propagate in a conical shape with the ultrasonic oscillation element as a vertex.

  For this reason, in the conventional liquid level detection apparatus, since the cross-sectional shape of the cylinder which is the propagation path of the ultrasonic wave is square, ultrasonic energy is reduced at the four corners due to ultrasonic interference.

On the other hand, the liquid level detecting apparatus according to claim 1 of the present invention, since the cross section of the first path member has a circular shape, eliminating the energy loss due to interference of ultrasonic waves in the conventional liquid level detection apparatus described above it can. Therefore, the sound pressure level of the ultrasonic wave incident on the reflecting wall can be increased as compared with the conventional liquid level detection device.

Further, in the liquid level detecting apparatus according to claim 1 of the present invention is in the cross-sectional shape to a circular also tubular second path member forming the ultrasonic wave propagation path between the liquid level from the reflective wall.

  Thereby, ultrasonic energy loss during propagation of ultrasonic waves can be suppressed between the reflecting wall and the liquid surface.

  In general, when an ultrasonic wave travels in a liquid in a cylindrical path, if there is a portion where the cross-sectional area of the path changes suddenly (enlarges or decreases), ultrasonic energy loss occurs there.

  In the liquid level detection device, the ultrasonic wave from the ultrasonic oscillation element propagates from the first path member into the second path member through the reflection wall, or the reflected wave on the liquid level from the second path member. Propagates through the reflecting wall into the first path member.

Here, the liquid level detecting apparatus according to claim 1 of the present invention, the diameter of the reflecting wall-side end portion of the first path member is approximately equal to the diameter of the reflecting wall-side end portion of the second path member Since it is set, the cross-sectional area of the ultrasonic wave propagation path does not change at the connecting portion between the first path member and the second path member.

  Thereby, it is possible to prevent ultrasonic energy loss from occurring at the connection portion between the first path member and the second path member.

In the liquid level detecting apparatus according to claim 2 of the present invention, the second path member has a structure in which its diameter is substantially uniformly formed over the entire length.

  In this case, the second path member is a so-called circular tube having a uniform diameter. As a result, the processing and formation of the second path member can be easily performed, so that an increase in the cost of the liquid level detection device can be suppressed.

In the liquid level detection device according to the third aspect of the present invention, the first path member and the second path member are made of a metal material.

  Since the metal material has a high reflectivity with respect to ultrasonic waves, in other words, it is difficult for ultrasonic waves to pass therethrough, if the first path member and the second path member are formed of a metal material, the ultrasonic waves are transmitted through the first path member and the second path. It is possible to suppress the energy loss of ultrasonic waves while traveling through the member to the minimum.

  Hereinafter, an example in which a liquid level detection device according to an embodiment of the present invention is applied to a fuel level detection device 1 for detecting a fuel level position in a fuel tank of an automobile will be described with reference to the drawings.

  FIG. 1 is a partial cross-sectional view of a fuel tank 2 as a tank for storing fuel 8 that is a liquid in a fuel level detecting device 1 according to an embodiment of the present invention. In FIG. 1, the vertical direction in the figure is the vertical direction of the automobile.

  2 is a cross-sectional view taken along line II-II in FIG.

  FIG. 3 is a schematic diagram for explaining an electric circuit configuration in the fuel level detecting device 1 according to the embodiment of the present invention.

  4 is a view taken along arrow IV in FIG.

  As shown in FIG. 1, the fuel level detecting device 1 includes a fuel tank 2 as a tank, an ultrasonic sensor 3 as an ultrasonic oscillation element, a guide pipe 4 as a first path member, and a reflecting plate 6 as a reflecting wall. , And a guide pipe 5 that is a second path member. The ultrasonic sensor 3, the guide pipe 4, the reflecting plate 6, and the guide pipe 5 are integrally housed and held in the body 7, and as shown in FIG. Attached to the bottom surface 21.

  Below, the structure of the fuel liquid level detection apparatus 1 by one Embodiment of this invention is demonstrated.

  As shown in FIG. 1, the ultrasonic sensor 3 that is an ultrasonic oscillation element is arranged with an oscillation surface 31 that emits ultrasonic waves facing one end side of a guide pipe 4 to be described later, facing the guide pipe 4. That is, the ultrasonic sensor 3 is fixed to a bracket 15 as shown in FIG. 1, and the bracket 15 is attached to the body 7.

  The ultrasonic sensor 3 is made of a material having a piezo effect (a characteristic that changes in volume when a voltage is applied, and generates a voltage when receiving an external force), such as PZT (lead zirconate titanate). Yes. As shown in FIG. 1, the ultrasonic sensor 3 includes a lead wire 14 for connecting to an external electric circuit. The lead wire 14 extends out of the bracket 15 and further out of the fuel tank 2. It is drawn out in an airtight manner. Further, the oscillation surface 31 of the ultrasonic sensor 3 is formed in a circular shape.

  The bracket 15 is formed in a substantially bottomed cylindrical shape from resin or metal, and the ultrasonic sensor 3 is fixed to the bottom portion 15b by, for example, adhesion. Moreover, as shown in FIG. 1, the plug 13 is fixed to the opening end side (right side of FIG. 1) of the bracket 15 by adhesion or press fitting. The plug 13 has the lead wire 14 inserted therethrough and holds it, and prevents foreign matter from entering the bracket 15. Further, the bracket 15 is directed to one end side (right side in FIG. 1) of the guide pipe 4 and the oscillation surface 31 of the ultrasonic sensor 3 is directed to the other end (left side in FIG. 1) of the guide pipe 4, that is, the ultrasonic sensor. The ultrasonic wave emitted by 3 is fixed so as to propagate in the guide pipe 4 toward the other end side (left side in FIG. 1). When a pulse voltage is applied to the ultrasonic sensor 3 via the lead wire 14, the oscillation surface 31 vibrates, the vibration of the oscillation surface 31 is transmitted to the bottom 15 b of the bracket 15, and further from the outer surface 15 a of the bracket 15. Ultrasonic waves are fired into the fuel 8. On the other hand, when this ultrasonic wave is reflected by the liquid surface 81 or the step portion 41 and those reflected waves reach the oscillating surface 31 via the surface 15a of the bracket 15, and the oscillating surface 31 vibrates by the pressure action, the ultrasonic waves are generated. The sensor 3 generates a voltage, which is output to the outside via the lead wire 14 as an output signal.

  A guide pipe 4 that is a cylindrical first path member that forms an ultrasonic wave propagation path between the ultrasonic sensor 3 and a reflection plate 6 that is a reflection wall, which will be described later, is formed of a metal material, and is one end side of the guide pipe 4 ( The right side in FIG. 1 is in contact with a bracket 15 that holds and fixes the ultrasonic sensor 3. In the fuel level detecting device 1 according to one embodiment of the present invention, the guide pipe 4 is made of an aluminum die casting alloy. The guide pipe 4 has a cross-sectional shape in a direction orthogonal to the axis A as shown in FIG. 2, and is formed in a circular shape, and the diameter dimension at the ultrasonic sensor 3 side end (right end in FIG. 1) is d1. The diameter dimension at the reflection plate 6 side end (left end in FIG. 1), which will be described later, is d2. Further, the guide pipe 4 is formed such that the cross-sectional area in the direction orthogonal to the axis A decreases as the distance from the ultrasonic sensor 3 increases, that is, from the right end to the left in FIG. . In other words, the guide pipe 4 is formed such that the diameter of the cross section in the direction orthogonal to the axis A decreases as the distance from the ultrasonic sensor 3 increases. That is, as shown in FIG. 1, the relationship d1> d2 is established. Further, as shown in FIG. 1, a step portion 41 is formed in the guide pipe 4. As shown in FIG. 2, the step portion 41 is formed in a ring shape and is formed as a surface facing the ultrasonic sensor 3. Accordingly, part of the ultrasonic waves emitted from the ultrasonic sensor 3 enters the stepped portion 41. This ultrasonic wave is reflected by the step portion 41, travels toward the ultrasonic sensor 3, and enters the ultrasonic sensor 3.

  Further, on the opposite side of the guide pipe 4 from the ultrasonic sensor 3 (left side in FIG. 1), there is a reflecting wall that reflects the ultrasonic wave emitted from the ultrasonic sensor 3 toward the liquid surface 81 in the fuel tank 2. The reflection plate 6 is disposed as shown in FIG. The reflector 6 is made of a metal material. In the fuel level detecting device 1 according to one embodiment of the present invention, the reflecting plate 6 is formed of an iron-based metal, for example, a stainless steel plate. As shown in FIG. 1, the reflection plate 6 reflects the ultrasonic wave emitted from the ultrasonic sensor 3 incident on the reflection surface 61 toward the liquid surface 81. That is, the reflector 6 is installed so as to reflect the ultrasonic wave traveling on the axis A of the guide pipe 4 toward the direction in which the incident angle with respect to the liquid surface 81 becomes 0 °, that is, the direction orthogonal to the liquid surface 81. Has been. That is, as shown in FIG. 1, the reflecting surface 61 is provided with an inclination of 45 ° with respect to the liquid surface.

  The guide pipe 5, which is a cylindrical second path member that forms an ultrasonic wave propagation path between the reflecting plate 6 and the liquid surface 81, is made of a metal material. In the fuel level detecting device 1 according to one embodiment of the present invention, the guide pipe 5 is formed of a stainless steel pipe. Further, the guide pipe 5 has a circular cross-sectional shape in a direction orthogonal to the axis B, and the diameter of the guide pipe 5 is uniformly formed over the entire length to the diameter dimension d3. The diameter d3 of the guide pipe 5 is formed to be equal to the diameter d2 at the end of the guide pipe 4 on the reflecting plate 6 side. Further, as shown in FIG. 1, a wave breaker plate 51 is attached to the tip of the guide pipe 5 on the side opposite to the reflecting plate 6. For example, when the automobile shakes during driving on a rough road, the liquid level 81 in the fuel tank 2 is also shaken to generate waves. At this time, if the wave flows into the guide pipe 5 from the opening on the upper end side of the guide pipe 5, the liquid level 81 temporarily rises, so that accurate detection of the liquid level 81 becomes difficult. 1 is installed at the tip of the guide pipe 5 to prevent the fuel 8 from flowing into the guide pipe 5 even when the automobile shakes and a wave is generated in the fuel tank 2. As a result, the liquid level 81 can be detected accurately. As shown in FIG. 4, the wave breaker plate 51 is provided with a notch 52 so that the air inside and outside the guide pipe 5 can be communicated. Therefore, even if the wave breaker plate 51 is attached, the liquid level 81 in the guide pipe 5 can sufficiently follow the fluctuation of the liquid level 81 outside the guide pipe 5. Further, as shown in FIG. 1, the front end position of the guide pipe 5 on the liquid surface 81 side is a predetermined length above the liquid surface 82 when the amount of fuel 8 stored in the fuel tank 2 is maximum, that is, when the fuel tank is full. It is set to stick out.

  The bracket 15, the guide pipe 4, the reflecting plate 6, and the guide pipe 5 that hold and fix the ultrasonic sensor 3 described above are attached to the body 7. The body 7 is formed of a resin material, for example, a resin material having excellent stability with respect to the fuel 8 in the fuel tank 2 in the fuel level detecting device 1 according to the embodiment of the present invention. The body 7 has a function of holding and fixing the above-described components to the bottom surface 21 of the fuel tank 2 while maintaining and fixing the positional relationship between the components with high accuracy. Further, when the guide pipe 4, the reflecting plate 6 and the guide pipe 5 are held and fixed to the body 7, the axis A of the guide pipe 4 and the axis B of the guide pipe 5 are arranged as shown in FIG. A positional relationship is formed so as to intersect on the six reflecting surfaces 61. In the fuel liquid level detection device 1 according to the embodiment of the present invention, a bracket 15 to which the ultrasonic sensor 3 is fixed, a guide pipe 4, a reflecting plate 6, and a guide pipe 5 are assembled to the body 7.

  Next, an electric circuit configuration of the fuel level detecting device 1 according to the embodiment of the present invention will be described with reference to FIG.

  As shown in the electric circuit configuration diagram of FIG. 3, the control circuit 9 is connected to the battery 12 via the ignition switch 11. The control circuit 9 is connected to the ultrasonic sensor 3. The control circuit 9 is connected to the display unit 10.

  The control circuit 9 is constituted by, for example, a microcomputer, and processes a reflected wave reception signal output from the pulse generation circuit 91 for applying a pulse voltage signal to the ultrasonic sensor 3 and the ultrasonic sensor 3, and based on that. An arithmetic circuit 92 for calculating the liquid level position, and a drive circuit 93 for outputting a drive signal for driving the display unit 10 based on the liquid level position signal calculated by the arithmetic circuit 92. When the ignition switch 11 is turned on and electric power is supplied from the battery 12, the control circuit 9 starts the operation of the fuel level detecting device 1.

  The display unit 10 includes, for example, a pointer instrument or a liquid crystal panel, and is installed in a combination meter (not shown) in front of the driver's seat of the automobile. The display unit 10 is driven by the drive circuit 93 of the control circuit 9 and displays the position of the liquid level 81 calculated by the arithmetic circuit 92, that is, the remaining amount of the fuel 8 in the fuel tank 2 so that the driver can visually recognize it.

  Next, the fuel level detecting operation in the fuel level detecting device 1 according to the embodiment of the present invention will be described.

  When a pulse voltage signal is applied by the pulse generation circuit 91, when the ultrasonic sensor 3 emits a pulsed ultrasonic wave into the fuel 8 in the fuel tank 2, the oscillation surface 31 of the ultrasonic sensor 3 vibrates, The vibration of the oscillating surface 31 is transmitted to the bottom portion 15a of the bracket 15, and ultrasonic waves are emitted into the fuel 8 from the outer surface 15a of the bracket 15. Part of this ultrasonic wave travels through the guide pipe 4 and enters the stepped portion 41. Then, the light is reflected and enters the oscillation surface 31 of the ultrasonic sensor 3 again. On the other hand, part of the pulsed ultrasonic waves emitted from the ultrasonic sensor 3 into the fuel 8 travels inside the guide pipe 4 and enters the reflecting surface 61. Then, the light is reflected and travels in the guide pipe 5 toward the liquid surface 81. Further, the light is reflected by the liquid surface 81 and enters the ultrasonic sensor 3 through the same path as the forward path, that is, the guide pipe 5, the reflective surface 61, and the guide pipe 4.

  That is, when the ultrasonic sensor 3 is driven by the pulse generation circuit 91 to emit one ultrasonic pulse, the two reflected pulses, that is, the reflected pulse from the step portion 41 and the liquid level are correspondingly generated as described above. The reflected pulse from 81 is received. As is clear from FIG. 1, the propagation path length from the ultrasonic sensor 3 to the step portion 41 is shorter than the propagation path length from the ultrasonic sensor 3 to the liquid surface 81. A reflected pulse from the step portion 41 is received, and then a reflected pulse from the liquid surface 81 is received. The ultrasonic sensor 3 generates a voltage signal every time these reflected pulses are received, and this voltage signal is input to the arithmetic circuit 92.

  The arithmetic circuit 92 calculates the time from when the pulse generation circuit 91 generates the pulse voltage signal to when the two reflected pulses described above are detected.

  Here, the step portion 41 is provided at a predetermined position with respect to the ultrasonic sensor 3. That is, the distance between the step portion 41 and the ultrasonic sensor 3 is known. Therefore, the arithmetic circuit 92 determines the fuel based on the time from when the pulse generation circuit 91 generates the pulse voltage signal until the reflected pulse from the step portion 41 is received and the distance between the step portion 41 and the ultrasonic sensor 3. 8 is used to calculate the propagation speed of the ultrasonic pulse. Next, based on the propagation speed of the ultrasonic pulse in the fuel 8 calculated in this way and the time from when the pulse generation circuit 91 generates a pulse voltage signal until the reflection pulse from the liquid surface 81 is received. The liquid level 81 position, that is, the liquid level 81 height H in FIG. 1 is calculated, and the remaining amount of fuel 8 in the fuel tank 2 is calculated based on the fuel tank 2 shape stored in advance.

  The drive circuit 93 displays a signal for displaying the liquid level 81 height H or the remaining amount of fuel 8 calculated by the arithmetic circuit 92 on the display unit 10, for example, a pointer shaft (not shown). The drive signal for rotating to the angle corresponding to 8 remaining amount is output. Thereby, the liquid level 81 height H or the fuel 8 remaining amount in the fuel tank 2 is displayed on the display unit 10.

  Next, the structure of the guide pipe 4 and its operation and effects, which are the features of the fuel level detecting device 1 according to the embodiment of the present invention, will be described.

  In the fuel level detecting device 1 according to the embodiment of the present invention, the guide pipe 4 is formed of a metal material, that is, an aluminum die-cast material, and the cross section in the direction orthogonal to the axis A, that is, the cross section is circular, The diameter of each was formed so as to decrease as the distance from the ultrasonic sensor 3 increased. In other words, the guide pipe 4 is formed such that the ultrasonic propagation path tapers from the ultrasonic sensor 3 toward the reflection plate 6.

Thereby, the attenuation degree of the ultrasonic energy while the ultrasonic wave emitted from the ultrasonic sensor 3 travels through the guide pipe 4 to the reflecting plate 6 is made smaller than that in the case of the conventional liquid level detection device, and the guide pipe 4 The sound pressure level near the end of the reflecting plate 6 side, that is, the sound pressure level of the ultrasonic wave incident on the reflecting plate 6 can be made higher than the value in the conventional liquid level detection device. Therefore, the energy of the ultrasonic wave emitted from the ultrasonic sensor 3 can be used for liquid level detection with high efficiency.
It is possible to provide a fuel liquid level detection device 1 capable of highly accurate liquid level detection.

  Further, in the fuel level detecting device 1 according to the embodiment of the present invention, the diameter dimension d2 of the guide pipe 4 on the reflecting plate 6 side end portion is set equal to the diameter dimension d3 of the guide pipe 5 on the reflecting plate 6 side end portion. is doing.

  In this case, the ultrasonic wave from the ultrasonic sensor 3 propagates from the guide pipe 4 to the guide pipe 5 via the reflecting plate 6, or the ultrasonic wave reflected by the liquid surface 81 passes from the guide pipe 5 via the reflecting plate 6. When propagating into the guide pipe 4, there is almost no change in the cross-sectional area of the propagation path at the transition between the guide pipe 4 and the guide pipe 5. Thereby, it is possible to prevent ultrasonic energy loss from occurring at the connecting portion between the guide pipe 4 and the guide pipe 5.

  Further, in the fuel level detecting device 1 according to the embodiment of the present invention, the guide pipe 5 is formed so that its diameter dimension is uniform over the entire length.

  As a result, the guide pipe 5 can be formed from, for example, an easily available steel pipe, so that the cost of the fuel level detecting device 1 can be reduced. Further, when the shape of the fuel tank 2 is changed in accordance with the vehicle to be mounted, the height of the liquid level 82 when the fuel tank 2 is full also changes, so the length of the guide pipe 5 needs to be changed accordingly. is there. In this case, if the guide pipe 5 is formed of a steel pipe, the fuel level detecting device 1 corresponding to the fuel tank 2 having a different shape is manufactured by an extremely easy means of changing the length of the guide pipe 5. can do.

  In the fuel level detecting device 1 according to the embodiment of the present invention, the guide pipe 4 and the guide pipe 5 are made of a metal material.

  Since the metal material has a high reflectivity with respect to ultrasonic waves, in other words, it is difficult for ultrasonic waves to pass therethrough, if the guide pipe 4 and the guide pipe 5 are made of a metal material, the ultrasonic waves travel through the guide pipe 4 and the guide pipe 5. The energy loss of the ultrasonic wave during the process can be suppressed to the minimum, and the energy of the ultrasonic wave emitted from the ultrasonic sensor 3 can be used for the liquid level detection with high efficiency.

  In the fuel level detecting device 1 according to the embodiment of the present invention described above, the guide pipe 4 is formed from an aluminum die casting alloy and the guide pipe 5 is formed from a stainless steel pipe. It is not necessary to limit to, and other types of metal materials may be used. For example, the guide pipe 4 may be formed from a steel material, and the guide pipe 5 may be formed from an aluminum pipe. Furthermore, the guide pipe 4 and the guide pipe 5 may be formed of a material other than a metal material, such as a resin material or a ceramic material. What is necessary is just to be able to propagate ultrasonic waves with high efficiency.

  In the fuel level detecting device 1 according to the embodiment of the present invention described above, the bracket 15 to which the ultrasonic sensor 3 is fixed, the guide pipe 4, the reflector 6 and the guide pipe 5 are assembled to the body 7. The configuration is not limited to such a configuration. For example, the guide pipe 4, the reflecting plate 6, and the guide pipe 5 are simultaneously insert-molded when the body 7 is resin-molded, and then the ultrasonic sensor 3 is applied to the body 7. It is good also as a structure which assembles the bracket 15 to which is fixed.

  In the fuel level detecting device 1 according to the embodiment of the present invention described above, the guide pipe 4, the guide pipe 5 and the reflecting plate 6 are formed as independent parts and assembled to the body 7. However, at least any two of the guide pipe 4, the guide pipe 5, and the reflection plate 6 may be integrally formed as one component. In this case, the body 7 may be omitted and the body 7 may be fixed to the fuel tank 2 via any one of the guide pipe 4, the guide pipe 5, and the reflection plate 6.

  Further, in the fuel level detecting device 1 according to the embodiment of the present invention, the step portion 41 is provided in the guide pipe 4, but the step portion 41 may not be provided. In this case, for example, the temperature of the fuel 8 in the fuel tank 2 is detected by a temperature sensor (not shown) or the like, and thereby the ultrasonic wave propagation speed in the fuel 8 is corrected to calculate the liquid level 81 height H. Thus, the liquid surface 81 height H can be calculated with high accuracy.

  Moreover, although embodiment described above demonstrated the case where the liquid level detection apparatus of this invention was applied to the fuel level detection apparatus 1 of a motor vehicle as an example, you may apply other than the fuel level detection apparatus 1. FIG. . That is, in order to detect the liquid level in other liquids installed in the vehicle, such as engine oil, brake fluid or window washer liquid, or in the liquid transport tank provided in the liquid transport vehicle You may apply. Furthermore, the present invention may be applied to the use of liquid level detection in liquid containers of various consumer devices other than automobiles and vehicles.

1 is a partial cross-sectional view of a fuel level detecting device 1 according to an embodiment of the present invention. It is the II-II sectional view taken on the line in FIG. It is a schematic diagram explaining the electric circuit structure in the fuel liquid level detection apparatus 1 by one Embodiment of this invention. FIG. 4 is a view taken along arrow IV in FIG. 1.

Explanation of symbols

1 Fuel level detector (Liquid level detector)
2 Fuel tank (tank)
21 Bottom (bottom)
3 Ultrasonic sensor (Ultrasonic oscillator)
31 Oscillating surface 4 Guide pipe (first path member)
41 Step 5 Guide pipe (second path member)
51 Wave breaker 52 Communication hole 6 Reflector (reflective wall)
61 Reflecting surface 7 Body 8 Fuel (liquid)
81 Liquid level 82 Liquid level 9 Control circuit 91 Pulse generation circuit 92 Arithmetic circuit 93 Drive circuit 10 Display unit 11 Ignition switch 12 Battery 13 Plug 14 Lead wire 15 Bracket 15a Surface A Axis line B Axis line d1 Inner diameter d2 Inner diameter d3 Inner diameter H Liquid surface height The

Claims (3)

An ultrasonic oscillator disposed at the bottom of a tank for storing liquid;
A reflection wall that reflects the ultrasonic waves emitted by the ultrasonic oscillator toward the liquid surface of the liquid in the tank;
A cylindrical first path member that forms an ultrasonic wave propagation path between the ultrasonic oscillation element and the reflection wall;
A cylindrical second path member that forms an ultrasonic wave propagation path from the reflection wall to the liquid surface, and
A liquid level detection device that emits ultrasonic waves from the ultrasonic oscillation element and receives a reflected wave from the liquid level via the reflection wall by the ultrasonic oscillation element to detect the position of the liquid level. ,
The first path member is formed such that a cross-sectional area in a direction orthogonal to the axis thereof decreases as the distance from the ultrasonic oscillation element increases .
The first path member has a circular cross-sectional shape in a direction perpendicular to the axis thereof,
The second path member has a circular cross-sectional shape in a direction perpendicular to the axis thereof,
The diameter dimension at the reflection wall side end of the first path member is set substantially equal to the diameter dimension at the reflection wall side end of the second path member;
The liquid level detection device according to claim 1, wherein the first path member is provided with a ring-shaped step portion formed as a surface facing the ultrasonic oscillation element . The liquid level detection device according to claim 1 , wherein the second path member has a diameter dimension substantially uniform over the entire length . The liquid level detection device according to claim 1, wherein the first path member and the second path member are formed of a metal material .

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