JP4020064B2 - Liquid level detection device for vehicles - Google Patents

Description

  The present invention relates to a vehicular liquid level detection device that is mounted on a vehicle and detects a liquid level position of the liquid, and is suitable for use in detecting a fuel liquid level in a fuel tank installed in an automobile, for example. is there.

  2. Description of the Related Art Conventionally, in a vehicle such as an automobile, there is a vehicle liquid level detection device that detects a fuel liquid level as means for detecting the amount of liquid stored in a tank, for example, the amount of fuel. This is because a floating arm is provided on the float that floats on the surface of the fuel, the rotating arm is rotated in accordance with the change in the position of the float due to the fluctuation of the liquid level, and the change in the rotation angle is converted into, for example, a change in electrical resistance. Is common. However, such a mechanical liquid level detection device has problems such as a large physique and a limited installation location, or poor detection accuracy.

  In order to solve such a problem, instead of mechanically detecting the liquid level, for example, a method of detecting the liquid level by emitting an ultrasonic wave and receiving a reflected wave from the liquid level, that is, a non-contact type Detection methods have been proposed.

  For example, at least a transmission / reception unit of an ultrasonic oscillation element is disposed in a liquid, and a cylinder including a reflector that reflects ultrasonic waves emitted from the ultrasonic oscillation element toward the liquid surface corresponding to the ultrasonic oscillation element There exists a thing of the structure which installed the body in the liquid (for example, refer patent document 1).

  In such a liquid level detection device, the time from when the ultrasonic oscillation element emits the ultrasonic wave until the ultrasonic oscillation element receives the reflected wave of the ultrasonic wave at the liquid level, that is, the ultrasonic wave is The time required to reciprocate between the acoustic wave oscillating element and the liquid surface is measured, and the liquid surface position is detected based on the measured time.

Thereby, the physique of a liquid level detection apparatus can be reduced in size, and detection accuracy can be improved.
JP 11-153471 A

  In the above-described conventional liquid level detection device, the ultrasonic oscillation element is liquid-tightly fitted in a mounting hole formed in the bottom of the tank peripheral wall with the transmission / reception unit positioned in the tank.

  In this conventional liquid level detection device, since a part of the ultrasonic oscillation element protrudes below the outer surface of the tank, there is a possibility of being damaged by foreign matters such as stones while the vehicle is traveling.

  Therefore, as a countermeasure for this problem, it is conceivable to accommodate and fix the ultrasonic oscillation element at the bottom of the tank. Since it is difficult to fix the ultrasonic oscillating element in the tank alone, the ultrasonic oscillating element is attached to the storage case, and the storage case is fixed to the bottom of the tank, and the vibration of the ultrasonic oscillating element is controlled by the wall of the storage case. It is conceivable to propagate in the liquid via.

  In this case, in order to improve the assembly workability of the ultrasonic oscillation element to the storage case, the ultrasonic oscillation element is fixed to the storage case so that the oscillation surface of the ultrasonic oscillation element is in close contact with the wall surface of the storage case. As a specific fixing method, adhesion or the like can be considered.

  In the configuration of the countermeasure plan described above, the path through which the ultrasonic wave is propagated into the liquid is in the order of the oscillation surface of the ultrasonic oscillation element, the adhesive, the storage case wall, and the liquid.

  By the way, there exists a characteristic that the propagation energy of the ultrasonic wave in air is small compared with the propagation energy of the ultrasonic wave in the adhesive agent which is solid. Therefore, if air enters the adhesive layer filled between the oscillation surface of the ultrasonic oscillation element and the storage case wall surface, the ultrasonic energy transmitted from the ultrasonic oscillation element to the storage case wall surface is reduced, resulting in high accuracy. The liquid level may be difficult to detect.

  When the ultrasonic oscillation element is bonded and fixed to the storage case wall surface, in order to prevent air from entering the adhesive layer between the ultrasonic oscillation element and the storage case wall surface, the adhesive viscosity, temperature, There is a problem that it is necessary to manage the coating method optimally, and to manage the holding posture until the adhesive is cured after bonding, which requires a great number of man-hours and increases costs.

  The present invention has been made in view of the above points. The invention devised a method for attaching an ultrasonic oscillation element disposed in a liquid to a storage case, and can be emitted from the ultrasonic oscillation element by an easy means. It is providing the liquid level detection apparatus for vehicles which can propagate the ultrasonic wave in a liquid with high efficiency.

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

In the liquid level detecting device for a vehicle according to claim 1 of the present invention, a tank for storing the liquid, a storage case which is disposed at the bottom of the tank and accommodates the ultrasonic oscillation element, and an ultrasonic oscillation Fixing means for pressing the ultrasonic oscillation element toward the inner surface of the storage case so that the oscillation surface of the element is in close contact with the inner surface of the storage case, and the ultrasonic wave generated by the ultrasonic oscillation element is the inner surface of the storage case A liquid level detecting device for a vehicle which detects a liquid level position by propagating a reflected wave reflected by the ultrasonic level from an opposite surface into a liquid and receiving an ultrasonic wave by an ultrasonic oscillation element. A through-hole that communicates the external space of the storage case with the inside of the storage case is formed, and when the liquid is injected into the tank, the storage case is immersed in the liquid, and the liquid passes through the through-hole to the inside of the storage case. Flows into the oscillation surface and the inner surface And the gap between the arrangement in which liquid filled.

  Since the storage case in which the ultrasonic oscillation element is stored and held is attached to the bottom of the tank, the storage case is always immersed in the liquid.

  Further, the ultrasonic oscillation element is pressed by the fixing means so that the oscillation surface is in close contact with the inner surface of the storage case. The oscillating surface and the inner surface of the storage case are macroscopically flat, but are microscopically concave and convex surfaces, respectively, so a minute gap is formed at the close contact portion between them. . When the liquid in the tank is introduced into the contact portion between the two through the through-hole provided in the storage case, the liquid enters the minute gap between the two by capillary action, and the minute gap is filled with the liquid.

  As a result, the path through which the ultrasonic wave propagates into the liquid is in the order of the oscillation surface of the ultrasonic oscillation element, the liquid, the storage case wall, and the liquid, and the ultrasonic oscillation element is fixed to the storage case via an adhesive. As described above, it is possible to reliably prevent the air from being partially mixed between the oscillation surface and the inner surface of the storage case, and hence the ultrasonic energy transmitted from the ultrasonic oscillation element to the storage case wall surface from being lowered. Therefore, it is possible to realize a liquid level detection device for a vehicle that can transmit ultrasonic waves emitted from an ultrasonic oscillation element into liquid with high efficiency by an easy means of providing a through-hole in an ultrasonic sensor contact wall of a storage case. Can do.

  In the vehicular liquid level detection device according to the second aspect of the present invention, the through hole communicates the surface and the inner surface of the storage case.

  In this case, since the through hole opens near the oscillation surface of the ultrasonic oscillation element in the storage case, the liquid in the tank is surely infiltrated into the minute gap between the oscillation surface and the inner surface of the storage case by capillary action. be able to.

  In the liquid level detecting device for a vehicle according to claim 3 of the present invention, the through hole is configured to open to the oscillation surface.

  Accordingly, the liquid in the tank can be reliably introduced into the minute gap between the oscillation surface and the inner surface of the storage case through the through hole.

  In the liquid level detecting device for a vehicle according to claim 4 of the present invention, the through hole is provided at least on the top side and the ground side of the tank.

  As a result, when the liquid is injected into the empty tank, the space around the close contact portion between the oscillation surface and the inner surface of the storage case can be reliably filled with the liquid in the storage case. The liquid can be surely filled into the minute gap between the inner surface of the case.

  In the vehicle liquid level detection device according to the fifth aspect of the present invention, the fixing means is an elastic member held in the storage case.

  Accordingly, the oscillation surface of the ultrasonic oscillation element can be brought into close contact with the inner surface of the storage case and pressed with an easy configuration.

  In the case of an elastic member, by appropriately setting the material, shape, etc., the pressing force for bringing the oscillation surface of the ultrasonic oscillation element into close contact with the inner surface of the storage case can be easily changed. Therefore, the pressing force can be easily changed as necessary.

  In the liquid level detecting device for a vehicle according to claim 6 of the present invention, the inner surface of the storage case is provided with at least three protrusions protruding toward the oscillation surface, and when the oscillation surface comes into contact with the protrusions, the oscillation surface is interposed between the oscillation surface and the inner surface. The gap is formed.

  As a result, when the ultrasonic oscillation element is assembled to the storage case, that is, when the oscillation surface of the ultrasonic oscillation element is pressed and adhered to the inner surface of the storage case, there is a protrusion corresponding to the protrusion length of the protrusion between the oscillation surface and the inner surface. A gap is formed. Therefore, the size of the gap formed between the oscillation surface and the inner surface can be set accurately.

  In the liquid level detecting device for a vehicle according to claim 7 of the present invention, a reflection wall that reflects the ultrasonic wave emitted by the ultrasonic oscillation element toward the liquid surface of the liquid, and between the ultrasonic oscillation element and the reflection wall A cylindrical body that forms an ultrasonic wave propagation path between the ultrasonic oscillation element and the reflective wall, the reflective wall is provided on one end side of the cylindrical body, and the storage case is formed of the cylindrical body. It is fixed to the other end side, and the through hole is configured to open into the internal space.

  In the above-described configuration, the ultrasonic oscillating element is not arranged to emit ultrasonic waves directly toward the liquid surface, but arranged to emit ultrasonic waves toward the reflecting wall in the tank, In addition, the light is reflected toward the liquid surface by the reflecting wall.

  As a result, even when the tank shape is complicated, for example, even when the bottom surface of the tank cannot be seen vertically from the bottom to the maximum liquid level, that is, the liquid level when the liquid storage amount in the tank is maximum, By appropriately selecting the position, the liquid level in the tank can be reliably detected from the highest liquid level to the lowest liquid level.

  In addition, since the storage case of the ultrasonic oscillation element and the reflection wall are integrally formed via the cylindrical body, the positional relationship between the ultrasonic oscillation element and the reflection wall is accurately maintained, and the liquid surface with high accuracy is obtained. A vehicle liquid level detection device capable of detection can be realized.

  In the vehicle liquid level detection device according to claim 8 of the present invention, the minimum distance between the storage case outer opening of the through hole and the inner wall of the cylindrical body facing it is formed to be equal to or greater than the diameter of the through hole. It is configured.

  In a state where the storage case for storing and holding the ultrasonic oscillation element is assembled to the cylindrical body, when the gap length between the storage case outer opening of the through hole and the inner wall of the cylindrical body facing it is small, Although liquid is introduced into the gap between the outer opening of the storage case and the inner wall of the cylinder facing it by capillary action, the surface tension action of the liquid between the outer surface of the storage case and the wall of the cylinder facing it There is a possibility that the liquid does not enter the through hole opened in the gap. That is, there is a possibility that an air layer may remain without filling the gap between the oscillation surface and the inner surface with liquid. Then, since the ultrasonic wave is transmitted from the ultrasonic oscillation element to the storage case through the air layer, in other words, the ultrasonic energy transmitted from the ultrasonic oscillation element to the storage case wall surface is reduced, so that a highly accurate liquid Surface detection becomes difficult.

  Therefore, as in the vehicle liquid level detection device according to claim 8 of the present invention, the minimum distance between the storage case outer opening of the through hole and the inner wall of the cylindrical body facing it is equal to or larger than the diameter dimension of the through hole. If it forms in this, the liquid in a cylinder can be introduce | transduced in a through-hole through the clearance gap between the surface of a storage case inner wall, and the part facing it of a cylinder. That is, the liquid in the cylinder can be introduced into the storage case. Therefore, the gap between the oscillation surface and the inner surface is filled with liquid, and ultrasonic energy is transferred from the ultrasonic oscillation element to the storage case wall surface with high efficiency, so that the ultrasonic wave emitted from the ultrasonic oscillation element is liquid with high efficiency. A liquid level detecting device for a vehicle that can propagate inside can be realized.

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

  FIG. 1 is a partial cross-sectional view of a fuel tank 2 that is a tank for storing fuel 8 as 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. Further, a two-dot chain line in FIG. 1 is the liquid level 82 when the amount of fuel stored in the fuel tank 2 is maximum, that is, when the tank is full.

  FIG. 2 is an enlarged sectional view of a portion 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.

  As shown in FIG. 1, the fuel level detecting device 1 includes a fuel tank 2 that is a tank, an ultrasonic sensor 3 that is an ultrasonic oscillation element that is housed and fixed in a housing case 4, a guide pipe 5 that is a cylinder, A reflection surface 52 that is a reflection wall that reflects the ultrasonic wave emitted from the sound wave sensor 3 toward the liquid surface 81 in the fuel tank 2, and the guide pipe 6. The guide pipe 5 is attached to the bottom surface 21 of the fuel tank 2 as shown in FIG.

  Below, the structure of the fuel liquid level detection apparatus 1 is demonstrated.

  As shown in FIG. 1, the ultrasonic sensor 3 that is an ultrasonic oscillation element is housed and fixed in a storage case 4 and is fixed to one end of a guide pipe 5 to be described later via this storage case. That is, as shown in FIG. 1, the oscillation surface 31 that emits ultrasonic waves faces the guide portion 51 that is the internal space of the guide pipe 5, that is, the ultrasonic waves emitted by the ultrasonic sensor 3 are guided by the guide pipe 5. It is fixed so as to propagate toward the other end side. When a pulsed voltage is applied to the ultrasonic sensor 3 via the lead wire 7, the oscillation surface 31 vibrates, the vibration of the oscillation surface 31 is transmitted to the bottom surface 42 of the storage case 4, and the outer surface of the storage case 4 Ultrasonic waves are emitted from the fuel 41 into the fuel 8. On the other hand, when this ultrasonic wave is reflected by the liquid surface 81 or the reflecting surface 52 and those reflected waves reach the oscillating surface 31 via the surface 41 of the storage case 4 and the oscillating surface 31 vibrates due to the pressure action thereof, it is super. The sonic sensor 3 generates a voltage, which is output to the outside through the lead wire 7 as an output signal.

  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 7 for connecting to an external electric circuit. The lead wire 7 extends out of the storage case 4 and 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 storage case 4 is formed in a substantially bottomed cylindrical shape from resin or metal. In the storage case 4, the ultrasonic sensor 3 is arranged with its oscillation surface 31 in close contact with the bottom surface 42, which is the inner surface of the storage case 4, as shown in FIG. 1. Further, as shown in FIG. 1, a plug 13 is attached to the opening end side (the right side in FIG. 1) opposite to the bottom surface 42 of the storage case 4.

  The plug 13 is formed of, for example, a resin material or the like, and its protruding portion 13 a is locked to the locking portion 45 of the storage case 4 and fixed to the storage case 4. As shown in FIG. 1, a spring 14 that is a fixing means and an elastic member is disposed between the ultrasonic sensor 3 and the plug 13.

  As the spring 14, a coil spring is used in the fuel level detecting device 1 according to one embodiment of the present invention. The spring 14 is in a compressed state when assembled into the storage case 4, and the elastic force acts in the direction indicated by the arrow in FIG. Due to this elastic force, the ultrasonic sensor 3 is pressed and adhered to the bottom surface 42 of the storage case 4.

  Further, as shown in FIG. 2, the plug 13 is provided with through holes 13b and 13c. The lead wire 7 of the ultrasonic sensor 3 is drawn out of the storage case 4 through the through hole 13c. On the other hand, the through-hole 13 b is for exhausting air accumulated in the storage case 4.

  Further, as shown in FIG. 2, the storage case 4 is provided with a through hole 43 that communicates the bottom surface 42 and the surface 41. In the fuel level detecting device 1 according to the embodiment of the present invention, the through hole 43 is formed on the top side of the fuel tank 2 in a state where the fuel level detecting device 1 is mounted on the fuel tank 2 as shown in FIG. And on the ground side. Further, as shown in FIG. 2, the through hole 43 is partially opened in the oscillation surface 31 of the ultrasonic sensor 3. Further, in a state where the storage case 4 is fixed to the guide pipe 5, the surface 53 which is the inner wall of the guide pipe 5 facing the outer opening of the storage case 4 of the through hole 43 and the outer opening of the storage case 4 of the through hole 43. A minimum distance from the surface 41 of a storage case 4, that is, a length F in FIG. 2 is set to be larger than the diameter dimension d of the through hole 43.

  In addition, the protrusion 44 of the storage case 4 is fixed to the guide pipe 5 by being locked to the locking portion 55 of the guide pipe 5.

  The guide pipe 5 that is a cylindrical body is formed of, for example, a resin material or 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 an aluminum die casting alloy. An ultrasonic sensor 3 is attached to one end side (right side in FIG. 1) of the guide pipe 5 via a storage case 4.

  Further, on the other end side (left side in FIG. 1) of the guide pipe 5, there is a reflection surface 52 that is a reflection wall that reflects the ultrasonic waves emitted from the ultrasonic sensor 3 toward the liquid surface 81 in the fuel tank 2. The guide pipe 5 and the guide pipe 5 are integrally molded. As shown in FIG. 1, the reflection surface 52 emits ultrasonic waves emitted from the ultrasonic sensor 3 and traveling along the propagation path A on the axis of the ultrasonic sensor 3 toward the liquid surface 81 and having an incident angle on the liquid surface 81. It is set to reflect in the direction of 0 °, that is, in the direction orthogonal to the liquid surface 81. That is, as shown in FIG. 1, the reflecting surface 52 is provided with an inclination of 45 ° with respect to the liquid surface. Thereby, the ultrasonic wave emitted from the oscillation surface 31 of the ultrasonic sensor 3 and traveling along the propagation path A on the axis of the ultrasonic sensor 3 is reflected by the reflection surface 52 and follows the propagation path B shown in FIG. , And is reflected by the liquid surface 81, and then enters the oscillation surface 31 along the same path as the forward path.

  Further, as shown in FIG. 1, a guide pipe 6 as an ultrasonic propagation path between the reflecting surface 52 and the liquid surface 81 is attached to the guide pipe 5. In the fuel level detecting device 1 according to one embodiment of the present invention, the guide pipe 6 is formed from a stainless steel circular pipe, and as shown in FIG. 1, for example, in the fixed hole 54 provided in the guide pipe 5. It is fixed by press-fitting or bonding. Further, as shown in FIG. 1, the front end position of the guide pipe 6 on the liquid surface 81 side is a length K higher than the liquid surface 82 when the amount of fuel 8 stored in the fuel tank 2 is maximum, that is, when the tank is full. Is set to protrude.

  As a result, the ultrasonic wave emitted from the ultrasonic sensor 3 is diffused into the fuel tank 2 while being reflected by the reflecting surface 52 and traveling toward the liquid surface 81, or while being reflected by the liquid surface 81 and traveling toward the reflecting surface 52. Therefore, it is possible to prevent the reception level by the ultrasonic sensor 3 from being lowered. Further, when the liquid level 81 swings while the automobile is running, the fluctuation of the liquid level 81 in the guide pipe 6 is reduced. Accordingly, it is possible to reduce the fluctuation of the indicated value of the liquid surface 81 height H in the fuel tank 2 or the remaining amount of fuel 8 by the display unit 7.

  Next, the operation and effect of the configuration of the storage case 4 which is a feature of the fuel level detecting device 1 according to the embodiment of the present invention will be described.

  In a conventional vehicle liquid level detection device, the ultrasonic sensor 3 is bonded and fixed to the bottom surface 42 of the storage case 4. That is, an adhesive layer exists between the ultrasonic sensor 3 and the bottom surface 42 of the storage case 4.

  When the ultrasonic oscillation element is bonded and fixed to the wall surface of the storage case in the conventional liquid level detection device for vehicles, in order to prevent air from entering the adhesive layer between the ultrasonic oscillation element and the storage case wall surface, Sometimes it is necessary to optimally manage the viscosity, temperature, and application method of the adhesive, and to manage the pointing posture until the adhesive is cured after bonding, which requires a lot of man-hours and increases costs. There is a possibility of inviting.

  On the other hand, in the fuel level detecting device 1 according to the embodiment of the present invention, as shown in FIG. 2, the spring 14 is used without using an adhesive for fixing the ultrasonic sensor 3 to the storage case 4. The ultrasonic sensor 3 is pressed and fixed to the bottom surface 42 of the storage case 4 by the elastic force.

  By the way, the oscillation surface 31 of the ultrasonic sensor 3 and the bottom surface 42 of the storage case 4 are not completely flat surfaces but are minute uneven surfaces as shown in FIG. Therefore, the oscillation surface 31 and the bottom surface 42 are not completely in close contact with each other, and a minute gap C is formed between them as shown in FIG.

  Immediately after the fuel level detecting device 1 is mounted in the fuel tank 2, air enters the gap between the oscillation surface 31 and the bottom surface 42.

  When the fuel 8 is injected into the fuel tank 2, the storage case 4, the guide pipe 5, and the like are immersed in the fuel. At this time, when the fuel 8 is filled in the guide portion 51 of the guide pipe 5, the fuel 8 is introduced into the storage case 4 through the through hole 43 of the storage case 4, and reaches the contact portion between the oscillation surface 31 and the bottom surface 42. To reach. Then, the fuel 8 enters the gap C between the oscillation surface 31 and the bottom surface 42 due to the capillary phenomenon, and the gap C is completely filled with the fuel 8.

  That is, the fuel 8 is interposed in the contact portion between the oscillation surface 31 and the bottom surface 42 except for the portion where they are in solid contact, and the vibration of the ultrasonic sensor 3 is transferred to the storage case 4 via the fuel 8 without passing through air. Communicated.

  Thereby, since the vibration energy of the ultrasonic sensor 3 can be transmitted to the storage case 4 with high efficiency, the ultrasonic wave emitted from the ultrasonic sensor 3 is propagated into the fuel 8 with high efficiency while suppressing an increase in cost. A possible fuel level detection device 1 can be realized.

  Further, the through holes 43 of the storage case 4 are respectively provided on the top side and the ground side of the fuel tank 2, in other words, on the top side and the ground side of the automobile.

  Thus, when the fuel 8 is injected into the fuel tank 2, the air staying in the storage case 4 is effectively discharged from the through hole 43 to the outside of the storage case, and the gap C between the oscillation surface 31 and the bottom surface 42 is discharged. The inside can be completely filled with fuel 8.

  Further, in a state where the storage case 4 is fixed to the guide pipe 5, the surface 53 which is the inner wall of the guide pipe 5 facing the outer opening of the storage case 4 of the through hole 43 and the outer opening of the storage case 4 of the through hole 43. A minimum distance from the surface 41 of a storage case 4, that is, a length F in FIG. 2 is set to be larger than the diameter dimension d of the through hole 43.

  Here, when the length F that is the minimum distance between the surface 53 and the surface 41 of the storage case 4 that is the outer opening of the storage case 4 of the through hole 43 is small, that is, the length F is smaller than the diameter dimension d of the through hole 43. If the fuel 8 is injected into the fuel tank 2 when the fuel 8 is not filled in the gap C between the oscillation surface 31 and the bottom surface 42, a capillary phenomenon occurs between the surface 53 and the surface 41. However, the fuel 8 in this portion is pulled by the surface tension and does not enter the through hole 43. That is, it does not enter the storage case 4, so that the fuel 8 is not filled in the gap C between the oscillation surface 31 and the bottom surface 42.

  On the other hand, in the fuel level detecting device 1 according to the embodiment of the present invention, the length F, which is the minimum distance between the surface 53 and the surface 41, is set larger than the diameter dimension d of the through hole 43. The fuel 8 that has entered between the surface 53 and the surface 41 can easily flow into the through-hole 43 and fill the gap 8 between the oscillation surface 31 and the bottom surface 42 with the fuel 8.

  In addition, when the fuel 8 is consumed as the operation time of the automobile elapses and the inside of the fuel tank 2 becomes almost empty, the fuel 8 is still in the guide portion 51 of the guide pipe 5 depending on the shape of the fuel tank 2. May be filled, or air may enter the guide portion 51 of the guide pipe 5. When air enters the guide portion 51 of the guide pipe 5, the fuel 8 in the gap C between the oscillation surface 31 of the ultrasonic sensor 3 and the bottom surface 42 of the storage case 4 is still in the gap C due to the action of surface tension. Retained. Further, even if air enters a part of the gap C due to vibration or the like, if the storage case 4, the guide pipe 5, etc. are immersed in the fuel after being supplied to the fuel tank 2, the gap C will be refueled. 8 is fully charged.

  Therefore, in the fuel level detecting device 1 according to the embodiment of the present invention, the fuel 8 is always filled in the gap C between the oscillation surface 31 of the ultrasonic sensor 3 and the bottom surface 42 of the storage case 4, and the ultrasonic wave is detected. The vibration energy of the sensor 3 can be transmitted to the storage case 4 with high efficiency.

  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 oscillation surface 31 is transmitted to the bottom surface 42 of the storage case 4, and ultrasonic waves are emitted from the outer surface 41 of the storage case 4 into the fuel 8. This ultrasonic wave travels along the propagation path A shown in FIG. 1 in the guide pipe 5 and enters the reflecting surface 52. Then, the light is reflected and travels along the propagation path B to reach the liquid surface 81, is reflected there, and again travels along the propagation path B and the propagation path A to enter the oscillation surface 31 of the ultrasonic sensor 3.

  The ultrasonic sensor 3 receives the reflected pulse from the liquid surface 81 and generates a voltage signal, 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 until the above-described reflected pulse is detected, and based on this, the liquid surface 81 position, that is, the liquid surface 81 height in FIG. And the remaining amount of fuel 8 in the fuel tank 2 is calculated based on the shape of the fuel tank 2 stored in advance.

  The drive circuit 93 displays a signal for displaying the liquid level 81 height H calculated by the arithmetic circuit 92 or the remaining amount of the fuel 8 on the display unit 7, 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 in the fuel tank 2 or the fuel 8 remaining amount is displayed on the display unit 10.

  In the fuel liquid level detection device 1 according to the embodiment of the present invention described above, the ultrasonic sensor 3 is used by the elastic force of the spring 14 without using an adhesive to fix the ultrasonic sensor 3 to the storage case 4. Is pressed and fixed to the bottom surface 42 of the storage case 4. Further, the storage case 4 is provided with a through hole 43 that communicates the bottom surface 42 and the surface 41, and the through hole 43 is opened to the oscillation surface 31 of the ultrasonic sensor 3.

  As a result, the fuel 8 in the fuel tank 2 is introduced into the storage case 4 through the through-hole 43, and a minute amount formed between the oscillation surface 31 of the ultrasonic sensor 3 and the bottom surface 42 of the storage case 4. Completely enters the gap C by capillary action. That is, since the gap C between the oscillation surface 31 and the bottom surface 42 is filled with the fuel 8, the vibration energy of the ultrasonic sensor 3 can be transmitted to the storage case 4 with high efficiency. Therefore, it is possible to realize the fuel level detecting device 1 that can propagate the ultrasonic wave emitted from the ultrasonic sensor 3 into the fuel 8 with high efficiency while suppressing an increase in cost.

  In the fuel level detecting device 1 according to the embodiment of the present invention described above, the through holes 43 of the storage case 4 are provided on the top side and the ground side of the fuel tank 2, in other words, on the top side and the ground side of the automobile. Each is provided.

  Thus, when the fuel 8 is injected into the fuel tank 2, the air staying in the storage case 4 is effectively discharged from the through hole 43 to the outside of the storage case, and the gap C between the oscillation surface 31 and the bottom surface 42 is discharged. The inside can be completely filled with fuel 8.

  In the fuel liquid level detection device 1 according to the embodiment of the present invention described above, the reflection surface 52 that reflects the ultrasonic wave emitted by the ultrasonic sensor 3 toward the liquid level 81, the ultrasonic sensor 3 and the reflection The guide pipe 51 which is disposed between the surface 52 and the guide portion 51 which is the internal space forms an ultrasonic wave propagation path between the ultrasonic sensor 3 and the reflection surface 52 is provided, and the reflection surface 52 is provided as the guide pipe 5. The housing case 4 is fixed to the other end side of the guide pipe 5, and the through hole 43 opens to the guide portion 51.

  As a result, when the shape of the fuel tank 2 is complicated, for example, it is not possible to see vertically from the bottom of the fuel tank 2 to the maximum liquid level 82, that is, the liquid level 82 when the liquid storage amount in the fuel tank 2 is maximum. Even in such a case, the liquid level 81 in the fuel tank 2 can be reliably detected from the highest liquid level 82 to the lowest liquid level by appropriately selecting the position of the reflecting surface 52.

  In addition, since the storage case 4 to which the ultrasonic sensor 3 is fixed and the reflection surface 52 are integrally formed via the guide pipe 5, the positional relationship between the ultrasonic sensor 3 and the reflection surface 52 is accurately maintained. Thus, the fuel level detecting device 1 that can detect the level 81 with high accuracy can be realized.

  Further, in a state where the storage case 4 is fixed to the guide pipe 5, the surface 53 which is the inner wall of the guide pipe 5 facing the outer opening of the storage case 4 of the through hole 43 and the outer opening of the storage case 4 of the through hole 43. A minimum distance from the surface 41 of a storage case 4, that is, a length F in FIG. 2 is set to be larger than the diameter dimension d of the through hole 43.

  As a result, the fuel 8 that has entered between the surface 53 and the surface 41 easily flows into the through hole 43, and the fuel 8 can be filled in the gap C between the oscillation surface 31 and the bottom surface 42.

  In FIG. 4, the fragmentary sectional view of the modification of the fuel liquid level detection apparatus 1 by one Embodiment of this invention is shown.

  In this modification, the shape of the storage case 4 is changed. That is, as shown in FIG. 4, three protrusions 46 that protrude toward the oscillation surface 31 of the ultrasonic sensor 3 are provided on the bottom surface 42 of the storage case 4. These three protrusions are arranged on the circumference concentric with the oscillation surface 31 at equiangular intervals, that is, at intervals of 120 degrees.

  When the ultrasonic sensor 3 is assembled to the storage case 4, the oscillation surface 31 comes into contact with the three protrusions 46, and there is no gap between the oscillation surface 31 of the ultrasonic sensor 3 and the bottom surface 42 of the storage case 4. As shown in FIG. 4, a gap having a length substantially equal to the height L of the protrusion 46 is formed.

  Here, the height L of the protrusion 46 is set to a dimension that allows the fuel 8 to be reliably filled between the oscillation surface 31 and the bottom surface 42 by capillary action.

  Thereby, the fuel 8 can be reliably filled between the oscillation surface 31 and the bottom surface 42, and the vibration energy of the ultrasonic sensor 3 can be transmitted to the storage case 4 with high efficiency.

  In FIG. 5, the fragmentary sectional view of the other modification in the fuel liquid level detection apparatus 1 by one Embodiment of this invention is shown.

  In another modification, the position of the through hole 43 provided in the storage case 4 is changed. That is, as shown in FIG. 5, the through-hole 43 is provided in the cylindrical wall of the storage case 4 formed in a substantially bottomed cylindrical shape, and the same as in the case of the fuel level detecting device 1 according to the embodiment of the present invention. The fuel tank 2 is provided on the top side and the ground side, in other words, on the top side and the ground side of the automobile. In this case, since the minimum distance length F between the outer peripheral surface of the storage case 4 that is the outer opening of the storage case 4 of the through hole 43 and the guide pipe 5 is set larger than the diameter dimension d of the through hole 43, The fuel 8 that has entered the outer peripheral surface of the case 4 and the guide pipe 5 can easily flow into the through-hole 43 and fill the gap 8 between the oscillation surface 31 and the bottom surface 42 with the fuel 8.

  Also with this configuration, it is possible to reliably fill the fuel 8 between the oscillation surface 31 and the bottom surface 42 and transmit the vibration energy of the ultrasonic sensor 3 to the storage case 4 with high efficiency.

  In the fuel level detecting device 1 according to the embodiment of the present invention described above, and its modified examples and other modified examples, the guide pipe 5 is formed from an aluminum die casting alloy, and the guide pipe 6 is formed from a stainless steel pipe. However, it is not necessary to limit to these materials, and they may be formed from other materials.

  Further, in the fuel liquid level detection device 1 according to the embodiment of the present invention described above, the modified example and other modified examples, the guide pipe 5 and the guide pipe 6 are formed as separate parts, and both are assembled. The guide pipe 5 and the guide pipe 6 may be integrally formed as one piece.

  Further, the guide pipe 6 may be omitted in the fuel level detecting device 1 according to the embodiment of the present invention, its modified examples, and other modified examples.

  Further, in the fuel level detecting device 1 according to the embodiment of the present invention described above, and its modified examples and other modified examples, the reflecting surface 52 has a simple planar shape, but this is a concave surface, that is, an oscillation. The shape may be concave toward both the surface 31 and the liquid surface 81.

  Moreover, although embodiment described above demonstrated the case where the liquid level detection apparatus for vehicles of this invention was applied to the fuel level detection apparatus 1 of a motor vehicle, it applied to other than the fuel level detection apparatus 1 as an example. Also good. In other words, it may be used for detecting the level of other liquids mounted on the vehicle, such as engine oil, brake fluid or window washer fluid. Furthermore, you may apply in order to detect the liquid level in the tank for liquid transportation with which the vehicle for liquid transportation was equipped.

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 section expanded sectional view 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. It is a fragmentary sectional view in the modification of the fuel liquid level detection apparatus 1 by one Embodiment of this invention. It is a fragmentary sectional view of the other modification in the fuel liquid level detection apparatus 1 by one Embodiment of this invention.

Explanation of symbols

1 Fuel level detector (Vehicle level detector)
2 Fuel tank (tank)
21 Bottom (bottom)
3 Ultrasonic element (Ultrasonic oscillator)
31 Oscillating surface 4 Case 41 Surface 42 Inner surface 43 Through-hole 44 Projection portion 45 Locking portion 46 Projection 5 Guide pipe (cylindrical body)
51 Guide (internal space)
52 Reflective surface (reflective wall)
53 Surface (inner wall)
54 Fixing hole 55 Locking part 6 Guide pipe (cylindrical)
7 Lead wire 8 Fuel (liquid)
81 Liquid level 82 Maximum 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 13a Protrusion 13b Through hole 13c Through hole 14 Spring (fixing means, elastic member)
A, B Propagation path C Clearance d Diameter F Length H Liquid level height Hmax Maximum liquid level height K Length L Height

Claims (8)

A tank for storing liquid;
A storage case that is disposed at the bottom of the tank and houses an ultrasonic oscillation element therein ,
Fixing means for pressing the ultrasonic oscillation element toward the inner surface of the storage case so that the oscillation surface of the ultrasonic oscillation element is in close contact with the inner surface of the storage case;
The ultrasonic wave generated by the ultrasonic oscillation element is propagated into the liquid from the surface opposite to the inner surface of the storage case, and the reflected wave reflected by the liquid surface of the ultrasonic wave is transmitted by the ultrasonic oscillation element. A vehicle liquid level detection device that receives and detects the liquid level position,
Forming a through hole in the storage case to communicate the external space of the storage case with the interior of the storage case;
When a liquid is injected into the tank, the storage case is immersed in the liquid, and the liquid flows into the storage case through the through hole, and between the oscillation surface and the inner surface. A liquid level detecting device for a vehicle, wherein the gap is filled with liquid .   The liquid level detection device for a vehicle according to claim 1, wherein the through hole communicates the surface and the inner surface of the storage case.   The vehicular liquid level detection device according to claim 1, wherein the through hole opens in the oscillation surface.   The liquid level detection device for a vehicle according to any one of claims 1 to 3, wherein the through hole is provided at least on a top side and a ground side of the tank.   The liquid level detection device for a vehicle according to any one of claims 1 to 4, wherein the fixing means is an elastic member held in the storage case. Comprising at least three protrusions protruding toward the oscillation surface side on the inner surface of the storage case;
6. The vehicular liquid level detection device according to claim 1, wherein a gap is formed between the oscillation surface and the inner surface when the oscillation surface comes into contact with the protrusion. A reflecting wall that reflects the ultrasonic wave emitted by the ultrasonic oscillator toward the liquid surface;
A cylinder that is disposed between the ultrasonic oscillation element and the reflection wall, and whose internal space forms an ultrasonic propagation path between the ultrasonic oscillation element and the reflection wall;
The reflection wall is provided on one end side of the cylindrical body,
The storage case is fixed to the other end of the cylinder;
The liquid level detection device for a vehicle according to any one of claims 1 to 6, wherein the through hole opens into the internal space.   8. The vehicle according to claim 7, wherein a minimum distance between the outer opening of the storage case of the through hole and the inner wall of the cylindrical body facing the opening is equal to or greater than a diameter dimension of the through hole. Liquid level detection device.

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