JP2005140545A - Liquid level detector for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid level detector for vehicles that can precisely detect a liquid level, by enhancing the energy of ultrasonic waves propagated in a liquid at the outer periphery side of the oscillation surface of an ultrasonic oscillation element by an easy means. <P>SOLUTION: A thin section 42, whose thickness is thin is provided annularly and concentrically with an emission surface 31 of an ultrasonic sensor 3 on a wall 40 in which the ultrasonic sensor 3, is adhered and fixed. Further, an inner diameter (d) in the thin section 42 is formed to be equal to or slightly larger than a diameter D in the oscillation surface 31, thus allowing the stiffness of the wall 40 to be nearly uniform from the center section to an area near the outer periphery section, and allowing the energy of ultrasonic waves propagated in fuel 8 from the wall 40, to be at a high level at nearly the entire region in the diameter direction of a guide section 51 that is the propagation path of ultrasonic waves. Accordingly, the liquid level detector for precisely detecting a liquid surface 81 can be realized, by improving the detection signal level by the ultrasonic sensor 3 by enhancing the energy of reflection waves from the liquid surface 81. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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, an electrical resistance change 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. However, since it is difficult to fix the ultrasonic oscillation element in the tank in the state of the ultrasonic oscillation element alone, the ultrasonic oscillation element is attached to the storage case, and the storage case is fixed to the bottom of the tank so that the vibration of the ultrasonic oscillation element is suppressed. Propagating into the liquid through the wall surface of the storage case is conceivable.

  In this case, the wall surface to which the oscillation surface of the ultrasonic oscillation element of the storage case is in close contact is formed so that the entire surface is uniform. A flange or the like for attaching the storage case to another part such as a tank is provided on the outer peripheral side of the wall surface. Therefore, the rigidity of the wall surface to which the oscillation surface of the ultrasonic oscillation element is closely attached increases as it goes from the central part to the outer peripheral part. In general, the oscillation surface of the ultrasonic oscillation element is formed in a circular shape.

  When the vibration of the ultrasonic oscillation element is propagated to the wall surface of uniform thickness and the wall surface vibrates, the rigidity of the wall surface becomes higher from the central part toward the outer peripheral part. That is, it becomes the largest at the central part of the oscillation surface of the ultrasonic oscillator and becomes smaller toward the outer peripheral part. Thereby, the energy of the ultrasonic wave propagated from the wall surface into the liquid becomes maximum on the central axis of the oscillation surface, and decreases as it goes from the central axis toward the outer peripheral side.

  Therefore, the received signal level when the ultrasonic wave emitted from the ultrasonic oscillation element is reflected by the liquid surface and received by the ultrasonic oscillation element is due to the ultrasonic wave traveling on the central axis of the oscillation surface for some reason. If a situation such as attenuation or diffusion occurs, it will be significantly reduced.

  As a result, the detection signal level from the ultrasonic oscillating element is lowered, which may make it difficult to detect the liquid level with high accuracy.

  The present invention has been made in view of the above points, and its object is to devise the shape of a storage case for storing and holding the ultrasonic oscillation element, and to oscillate the ultrasonic oscillation element by an easy means. It is to provide a vehicle liquid level detection device capable of increasing the energy of ultrasonic waves propagating in the liquid on the outer peripheral side of the vehicle and capable of highly accurate liquid level detection.

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

  According to a first aspect of the present invention, there is provided a vehicular liquid level detection apparatus comprising: a tank for storing liquid; an ultrasonic oscillation element disposed at a bottom of the tank; and a storage case for accommodating and holding the ultrasonic oscillation element. The ultrasonic oscillation element is fixed with its oscillation surface in close contact with the inner surface of the wall of the storage case, and the ultrasonic wave emitted from the ultrasonic oscillation element is propagated into the liquid from the outer surface of the wall. A liquid level detection device for a vehicle that detects a liquid surface position by receiving a reflected wave reflected by a surface by an ultrasonic oscillation element, and a thin wall portion having a thin wall is annular and ultrasonically oscillated on a wall It is formed concentrically with the element, and the inner diameter of the annular thin portion is formed to be equal to or slightly larger than the diameter of the oscillation surface.

  In the conventional vehicle liquid level detection device, the wall surface of the storage case with which the oscillation surface of the ultrasonic oscillation element is in close contact is formed with a uniform thickness. For this reason, the rigidity of the wall surface increases from the central part toward the outer peripheral part. When the vibration of the ultrasonic oscillation element is propagated to the wall surface of uniform thickness and the wall surface vibrates, the amplitude of the wall surface is the center. Part, that is, the largest at the central part of the oscillation surface of the ultrasonic oscillation element, and becomes smaller toward the outer peripheral part. As a result, the energy of the ultrasonic wave propagating from the wall surface into the liquid becomes maximum on the central axis of the oscillation surface and decreases as it goes from the central axis toward the outer peripheral side. The total amount of energy is small.

  On the other hand, in the vehicle level detecting device according to the first aspect of the present invention, the rigidity on the outer peripheral side of the wall surface is lowered by providing an annular thin portion coaxially with the oscillation surface on the wall surface.

  As a result, the amplitude of the wall surface when the vibration of the ultrasonic oscillation element is propagated to the wall surface having a uniform thickness and the wall surface vibrates is the same as that in the center of the oscillation surface of the ultrasonic oscillation element. This is equivalent to the case of the vehicle liquid level detection device, and at the outer peripheral portion of the wall surface, the amplitude is larger than that in the conventional vehicle liquid level detection device. That is, the total amount of ultrasonic energy propagated from the wall surface into the liquid can be made larger than the total amount of ultrasonic energy propagated from the wall surface into the liquid in the conventional vehicle liquid level detection device.

  Therefore, the received signal level when the reflected wave reflected by the liquid surface of the ultrasonic wave emitted from the ultrasonic oscillation element is received by the ultrasonic oscillation element is higher than before, and the detection signal level emitted by the ultrasonic oscillation element is increased. Therefore, it is possible to realize a vehicular liquid level detection device capable of detecting a liquid level with high accuracy.

  In the liquid level detecting device for a vehicle according to claim 2 of the present invention, the thin portion is provided with a rib extending in the radial direction of the thin portion.

  As a result, it is possible to realize a vehicular liquid level detection device capable of highly accurate liquid level detection while ensuring sufficient strength of the wall surface to which the ultrasonic oscillation element of the storage case is attached.

  In the vehicle liquid level detection device according to the third aspect of the present invention, the entire surface of the wall opposite to the oscillation surface is a flat surface.

  In this case, the surface of the storage case that is in contact with the liquid and propagates the vibration of the ultrasonic oscillating element into the liquid is a flat surface.

  As a result, the phase of the ultrasonic wave propagating in the liquid and traveling in the liquid is matched over the entire surface, and the reflected wave reflected by the liquid surface of the ultrasonic wave emitted from the ultrasonic oscillator is stably received. Can do.

  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.

  3 is a cross-sectional view taken along line III-III in FIG.

  FIG. 4 is a graph showing the amplitude of the wall 40 of the storage case 4 in the fuel level detecting device 1 according to the embodiment of the present invention. In FIG. 4, the vertical axis represents the radial position of the wall 40, and the horizontal axis represents the vibration amplitude of the wall 40. In FIG. 4, a curve S represents the amplitude in the fuel liquid level detection device 1 according to one embodiment of the present invention, and a curve P represents the amplitude in the conventional vehicle liquid level detection device.

  FIG. 5 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 detection 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, and an ultrasonic sensor 3. A reflection surface 52 that reflects the emitted ultrasonic waves toward the liquid surface 81 in the fuel tank 2 and the guide pipe 6 are configured. 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.

  The ultrasonic sensor 3 that is an ultrasonic oscillation element is a substance having a piezo effect (a property that changes in volume when a voltage is applied, but generates a voltage when receiving an external force), such as PZT (zirconate titanate). Lead). 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 pulled out liquid-tight. Further, the oscillation surface 31 of the ultrasonic sensor 3 is formed in a circular shape.

  As shown in FIG. 1, the ultrasonic sensor 3 is housed and fixed in a storage case 4, and the storage case 4 is fixed to one end of a guide pipe 5 described later. That is, as shown in FIG. 1, the storage case 4 is fixed to one end of the guide pipe 5 with the oscillation surface 31 of the ultrasonic sensor 3 facing the guide portion 51 that is the internal space of the guide pipe 5. Thereby, when a pulse voltage is applied to the ultrasonic sensor 3 via the lead wire 7, the oscillation surface 31 of the ultrasonic sensor 3 vibrates, and the vibration of the oscillation surface 31 is transmitted to the storage case 4, and It propagates from the storage case 4 to the fuel 8 in the guide pipe 5 and travels in the guide pipe 5 toward the other end side. Then, when this ultrasonic wave reaches the liquid surface 81, it is reflected there, and the reflected wave reaches the oscillation surface 31 through the wall 40 of the storage case 4, and the oscillation surface 31 vibrates by the pressure action. Thereby, the ultrasonic sensor 3 generates a voltage, and this voltage change is output to the outside through the lead wire 7 as an output signal.

  The storage case 4 is formed in a substantially bottomed cylindrical shape from resin or metal. As shown in FIG. 2, the ultrasonic sensor 3 is disposed in the storage case 4 such that the oscillation surface 31 is in close contact with the bottom surface 41 that is the inner surface of the wall 40 corresponding to the bottom of the substantially bottomed cylindrical storage case 4. Has been.

  Further, in the storage case 4, a thin wall portion 42 having a small thickness (a horizontal dimension in FIG. 2) is formed on the wall 40 to which the ultrasonic sensor 3 is closely fixed, as shown in FIG. 2. The thickness t2 of the thin portion 42 is formed thinner than the thickness of the wall 40, that is, the thickness t1 at the bottom 41 portion. Further, as shown in FIG. 3, the thin portion 42 is formed in an annular shape and concentric with the ultrasonic sensor 3. Further, as shown in FIG. 3, the inner diameter d of the thin portion 42 is formed to be equal to or slightly larger than the diameter D of the oscillation surface 31 of the ultrasonic sensor 3. Further, as shown in FIG. 2, the thin-walled portion 42 is formed by providing a step on the inner side of the wall 40 (on the right side in FIG. 2), and the surface 40 a that is the outer surface of the wall 40 is outside the wall 40. It is a flat surface over the entire surface. Further, as shown in FIG. 2, a plug 13 is attached to the opening end side (right side in FIG. 2) opposite to the bottom surface 41 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 oscillation surface 31 of the ultrasonic sensor 3 is pressed against the bottom surface 41 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.

  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 is made 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 (the left side in FIG. 1) of the guide pipe 5, a reflection surface 52 that reflects the ultrasonic wave emitted from the ultrasonic sensor 3 toward the liquid surface 81 in the fuel tank 2 is provided in the guide pipe 5. And is formed by integral molding. 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 so as 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, that is, the propagation path B and the propagation path A.

  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.

  With this guide pipe 6, the ultrasonic pulse emitted from the ultrasonic sensor 3 is reflected by the reflecting surface 52 and is directed toward the liquid surface 81, or is reflected by the liquid surface 81 and is directed toward the reflecting surface 52. Therefore, it is possible to prevent the ultrasonic pulse from being diffused or attenuated in the fuel tank 2 and the reception level of the ultrasonic sensor 3 from being lowered. Furthermore, when the liquid level 81 fluctuates due to vibration while the automobile is running, fluctuations in the liquid level 81 in the guide pipe 6 can be suppressed to a small level. 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 shape of the storage case 4, particularly the wall 40, which is a part to which the ultrasonic sensor 3 is attached, will be described, which is a feature of the fuel liquid level detection device 1 according to one embodiment of the present invention.

  In the conventional liquid level detection device for vehicles, the thickness of the wall 40 to which the ultrasonic sensor 3 is attached in the storage case 4 is uniform over the entire surface. Moreover, since the substantially cylindrical wall is connected to the outer peripheral part of the wall 40, the rigidity of the wall 40 becomes higher as it goes from the central part to the outer peripheral part.

  When the vibration of the ultrasonic sensor 3 is propagated to the wall 40 and the wall 40 vibrates in the thickness direction, the rigidity of the wall surface increases from the central part toward the outer peripheral part. As shown by the curve P in FIG. 4, it becomes the largest at the center portion with low rigidity, becomes smaller toward the outer periphery portion with high rigidity, and becomes the smallest at the outer periphery portion of the wall 40. The amplitude of the wall 40 corresponds to the energy of the ultrasonic wave propagating from the wall 40 into the fuel 8. Therefore, the energy of the ultrasonic wave propagating through the fuel 8 is on the central axis of the oscillation surface 31, that is, the propagation path A and It becomes maximum on the propagation path B, and decreases as it moves away from the outer peripheral side.

  Therefore, the reception signal level when the ultrasonic wave emitted from the ultrasonic sensor 3 is reflected by the liquid surface 81 and received by the ultrasonic sensor 3 is the ultrasonic wave traveling on the propagation path A and the propagation path B. If the phenomenon such as dampens or diffuses for some reason, it will drop significantly. For this reason, the detection signal level from the ultrasonic sensor 3 is lowered, and it may be difficult to detect the liquid level 81 with high accuracy.

  On the other hand, in the fuel level detecting device 1 according to the embodiment of the present invention, the thin portion 42 having a small thickness (the horizontal dimension in FIG. 2) is provided on the wall 40 to which the ultrasonic sensor 3 is closely fixed. It is provided in an annular shape. The thin portion 42 is formed concentrically with the oscillation surface 31 of the ultrasonic sensor 3, and the inner diameter d of the thin portion 42 is formed to be equal to or slightly larger than the diameter D of the oscillation surface 31.

  By adopting the shape as described above, the rigidity of the wall 40 is substantially uniform from the central portion to the vicinity of the outer peripheral portion, and is rapidly increased near the outer peripheral portion.

  When the vibration of the ultrasonic sensor 3 is propagated to the wall 40 and the wall 40 vibrates in the thickness direction, the rigidity of the wall surface is as described above. Therefore, the amplitude of the wall 40 is the curve S in FIG. As shown in FIG. 4, the wall 40 is large in almost the entire region and is rapidly decreased in the immediate vicinity of the outer peripheral portion.

  Thereby, the energy of the ultrasonic wave propagating from the wall 40 into the fuel 8 can be set to a high level in almost the entire radial direction of the guide portion 51 that is the ultrasonic wave propagation path. Since the energy of the reflected wave can be increased, the detection level of the ultrasonic sensor 3 can be increased, and a fuel level detecting device capable of detecting the level 81 with high accuracy can be realized.

  Further, in the fuel level detecting device 1 according to the embodiment of the present invention, the thin portion 42 is formed by providing a step on the inside (right side in FIG. 2) of the wall 40 as shown in FIG. The surface 40a which is an ultrasonic transmission surface to the fuel 8 of 40 is a flat surface over the entire surface.

  Thereby, the phase of the ultrasonic wave traveling in the fuel 8 can be matched in the radial direction of the guide portion 51 which is the ultrasonic wave propagation path, so that the ultrasonic liquid level 81 emitted from the ultrasonic sensor 3 is used. The detection signal level when the reflected wave is reflected by the ultrasonic sensor 3 can be effectively increased.

  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. 5, 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 41 of the storage case 4, and ultrasonic waves are emitted into the fuel 8 from the outer surface 40 a of the storage case 4. This ultrasonic wave is reflected by the reflecting surface 52 in the middle, reaches the liquid surface 81, is reflected by the liquid surface 81, and then enters the oscillation surface 31 along the same path as the forward path.

  When the ultrasonic sensor 3 receives the reflected pulse from the liquid surface 81, it 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 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 in the fuel tank 2 or the fuel 8 remaining amount is displayed on the display unit 10.

  In the fuel level detecting device 1 according to the embodiment of the present invention described above, the thin wall portion 42 is annularly formed on the wall 40 to which the ultrasonic sensor 3 is closely fixed, and the oscillation surface of the ultrasonic sensor 3 is formed. 31 is provided concentrically. Further, the inner diameter d of the thin portion 42 is formed to be equal to or slightly larger than the diameter D of the oscillation surface 31.

  By adopting the shape as described above, the rigidity of the wall 40 is substantially uniform from the central portion to the vicinity of the outer peripheral portion without increasing from the central portion to the vicinity of the outer peripheral portion as in the case of the conventional liquid level detection device for vehicles. can do.

  Thereby, when the vibration of the ultrasonic sensor 3 is propagated to the wall 40 and the wall 40 vibrates in the thickness direction, the amplitude of the wall 40 is almost the entire area of the wall 40 as shown by the curve S in FIG. Therefore, the energy of the ultrasonic wave propagating from the wall 40 into the fuel 8 can be set to a high level in almost the entire radial direction of the guide portion 51 that is the ultrasonic wave propagation path. Therefore, by means of easily changing the thickness dimension of the wall 40, the energy of the reflected wave from the liquid surface 81 is increased to increase the detection signal level by the ultrasonic sensor 3, thereby detecting the liquid surface 81 with high accuracy. It is possible to realize a fuel liquid level detection device capable of

  Further, in the fuel level detecting device 1 according to the embodiment of the present invention, the thin portion 42 is formed by providing a step on the inside (right side in FIG. 2) of the wall 40 as shown in FIG. The surface 40a which is the ultrasonic transmission surface to the fuel 8 of 40 is made into a flat surface over the whole surface.

  Thereby, the phase of the ultrasonic wave traveling in the fuel 8 can be matched in the radial direction of the guide portion 51 which is the ultrasonic wave propagation path, so that the ultrasonic liquid level 81 emitted from the ultrasonic sensor 3 is used. The detection signal level when the reflected wave is reflected by the ultrasonic sensor 3 can be effectively increased.

  In the fuel liquid level detection device 1 according to the embodiment of the present invention described above, the thickness dimension t2 of the thin wall portion 42 is set so that the amplitude of the wall 40 is uniform over almost the entire area of the wall 40. What is necessary is just to set suitably.

  In FIG. 6, the fragmentary sectional view of the modification of the fuel liquid level detection apparatus 1 by one Embodiment of this invention is shown. 6 corresponds to a cross-sectional view taken along line III-III in FIG.

  7 is a cross-sectional view taken along line VII-VII in FIG.

  In this modification, four ribs 43 are provided radially on the thin portion 42 of the storage case 4 as shown in FIG. By providing the rib 43, the strength of the thin portion 42 can be improved.

  In this case, the amplitude of the wall 40 is uniform over almost the entire area of the wall 40, and the thickness dimension t3 and the height dimension W, which are the shapes of the ribs 43, and the ribs 43 so that sufficient strength of the thin wall portion 42 can be secured. And the thickness dimension t2 of the thin portion 42 may be set as appropriate.

  In FIG. 8, 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 the fuel level detecting device 1 according to the embodiment of the present invention, the thickness t2 of the thin portion 42 is uniformly formed.

  On the other hand, in another modified example, the thickness t2 of the thin portion 42 is changed. That is, as shown in FIG. 8, the thickness t <b> 2 of the thin portion 42 is gradually reduced from the inner peripheral side to the outer peripheral side of the wall 40.

  As a result, an abrupt change in thickness at the boundary portion between the inner surface 41 of the wall 40 and the thin portion 42 is alleviated, and stress concentration in this portion is alleviated, while the ultrasonic wave propagating from the wall 40 into the fuel 8 is reduced. The energy is made uniform and high in almost the entire radial direction of the guide 51 that is the propagation path of the ultrasonic wave, and the energy of the reflected wave from the liquid surface 81 is increased to increase the detection signal level by the ultrasonic sensor 3. Thus, it is possible to realize a fuel liquid level detection device capable of detecting the liquid level 81 with high accuracy.

  In the fuel liquid level detection device 1 according to the embodiment of the present invention described above, and its modifications and other modifications, the elastic force of the spring 14 is used to fix the ultrasonic sensor 3 to the storage case 4. However, the present invention is not limited to this, and the ultrasonic sensor 3 may be fixed to the storage case 4 by other methods. For example, an adhesive may be used.

  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 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.

  Moreover, 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 storage case 4 and the guide pipe 5 are formed as separate parts, and both are assembled. However, the storage case 4 and the guide pipe 5 may be integrally formed as one component. For example, you may form by integral molding with a resin material.

  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 in the fuel liquid level detection device 1 according to one embodiment of the present invention may be omitted.

  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 the III-III sectional view taken on the line in FIG. It is a graph showing the amplitude of the wall 40 of the storage case 4 in the fuel liquid level detection apparatus 1 by one Embodiment of this invention. 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 of the modification of the fuel liquid level detection apparatus 1 by one Embodiment of this invention. It is the VII-VII sectional view taken on the line in FIG. 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 Oscillation surface 4 Case 40 Wall 40a Surface (outer surface)
41 Inner surface 42 Thin portion 43 Rib 44 Projection portion 45 Locking portion 5 Guide pipe 51 Guide portion 52 Reflecting surface 54 Fixing hole 55 Locking portion 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 A, B Propagation path d Inner diameter D Diameter H Liquid level height Hmax Maximum liquid level height K Length P, S Curve t1, t2 Thickness dimension t3 Thickness dimension W Height dimension

Claims (3)

A tank for storing liquid;
An ultrasonic oscillator disposed at the bottom of the tank;
A storage case for storing and holding the ultrasonic oscillation element;
The ultrasonic oscillating element is fixed with its oscillating surface being in close contact with the inner surface of the wall of the storage case, and the ultrasonic wave generated by the ultrasonic oscillating element is propagated from the outer wall surface into the liquid. A vehicle liquid level detection device that receives the reflected wave reflected by the liquid level by the ultrasonic oscillation element and detects the liquid level position,
The wall is formed with a thin-walled portion having a thin wall thickness and concentric with the ultrasonic oscillation element, and an inner diameter of the annular thin-walled portion is formed to be equal to or slightly larger than the diameter of the oscillation surface. A liquid level detecting device for a vehicle.   The liquid level detection device for a vehicle according to claim 1, wherein the thin portion is provided with a rib extending in a radial direction of the thin portion.   3. The vehicular liquid level detection device according to claim 1, wherein the surface of the wall opposite to the oscillation surface is entirely flat. 4.

Images