JP3908189B2 - Liquid level detection device for vehicles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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.
[0002]
[Prior art]
Conventionally, as a vehicle liquid level detection device for detecting the amount of fuel, that is, a fuel level in an automobile or the like, a floating arm is provided on a float that floats on the surface of the fuel, and according to a change in the position of the float due to a change in the level of the liquid In general, a rotating arm is rotated and a change in the rotation angle is converted into a change in electrical resistance, for example. However, such a mechanical liquid level detection device has problems such as a large physique and a limited installation location, or poor detection accuracy.
[0003]
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 A liquid level detection apparatus has been proposed (see, for example, Patent Document 1).
[0004]
An ultrasonic sensor including an ultrasonic oscillation element and a cylinder is arranged at the bottom of a liquid container, and a liquid level measurement reflector and a propagation time measurement reflector are arranged on the cylinder facing the ultrasonic oscillation element. The ultrasonic wave emitted from the ultrasonic oscillation element is reflected by the liquid level measuring reflector toward the liquid level through the opening provided in the cylindrical body, and the reflected wave of the ultrasonic wave on the liquid level is On the other hand, the ultrasonic wave emitted from the ultrasonic oscillator by the propagation time measurement reflector is directly reflected toward the propagation time measurement reflector and received by the ultrasonic sensor. In this case, the liquid level measuring reflector and the propagation time measuring reflector are arranged in parallel. That is, they are arranged in a direction perpendicular to the traveling direction of the ultrasonic waves emitted from the ultrasonic sensor, in other words, in the width direction of the cylindrical body. Then, the liquid level position is calculated based on the received signal of the reflected wave from the liquid level via the reflector for measuring the liquid level and the received signal of the reflected wave from the reflector for measuring the propagation time. Thereby, the physique of a liquid level detection apparatus can be reduced in size, and detection accuracy can be improved.
[0005]
[Patent Document 1]
JP-A-11-153471 [0006]
[Problems to be solved by the invention]
In general, since an ultrasonic oscillation element included in an ultrasonic sensor is formed in a disc shape, ultrasonic waves are emitted from the ultrasonic sensor in a conical shape.
[0007]
By the way, in the liquid level detection device disclosed in the above-mentioned publication, the liquid level measurement reflector and the propagation time measurement reflector are arranged side by side in the width direction of the cylinder. Therefore, the ultrasonic wave incident on the liquid level measurement reflector and the propagation time measurement reflector does not have an axial shape. For this reason, the reception signal of the reflected wave from the liquid surface via the liquid level measurement reflector due to the occurrence of ultrasonic diffraction phenomenon, ultrasonic interference, etc. at the corner on the boundary between both reflectors In addition, the reception signal of the reflected wave from the reflector for measuring the propagation time may become unstable.
[0008]
For this reason, in the liquid level detection apparatus for vehicles using an ultrasonic sensor, there exists a possibility that favorable detection accuracy may not be obtained.
[0009]
The present invention has been made in view of the above points, and an object of the present invention is to provide a vehicle capable of obtaining good detection accuracy by devising the arrangement of the liquid level measurement reflector and the propagation time measurement reflector. It is in providing the liquid level detection apparatus.
[0010]
[Means for Solving the Problems]
The present invention employs the following technical means to achieve the above object.
[0011]
In the liquid level detecting device for a vehicle according to claim 1 of the present invention, a tank for storing the liquid, an ultrasonic oscillation element attached to the bottom of the tank, and an ultrasonic wave emitted by the ultrasonic oscillation element in the tank A reflective member that reflects the liquid so that the incident angle to the liquid surface is 0 degree, and a calibration reflective member that reflects the ultrasonic wave emitted by the ultrasonic oscillator toward the ultrasonic oscillator; In the vehicle liquid level detection device for detecting the liquid level position by receiving the reflected wave reflected by the liquid level and the reflected wave reflected by the calibration reflecting member while emitting ultrasonic waves by the ultrasonic oscillation element, The reflection member and the calibration reflection member are arranged so as to overlap in the traveling direction of the ultrasonic wave emitted by the ultrasonic oscillation element, and a part of the ultrasonic wave emitted from the ultrasonic oscillation element is one of the reflection member and the calibration reflection member. Through It has a configuration to reach the other.
[0012]
In general, when an ultrasonic wave is incident on a solid surface, a part of the ultrasonic wave is reflected and the traveling direction is changed, and a part of the ultrasonic wave propagates inside the solid and is emitted from the opposite surface to travel in the same direction as before the incident.
[0013]
For this reason, in the liquid level detecting apparatus for a vehicle according to claim 1 of the present invention, the reflecting member and the reflecting member for calibration are arranged so as to overlap in the traveling direction of the ultrasonic wave emitted by the ultrasonic oscillating element. When a part of the ultrasonic wave emitted from the light passes through one of the reflecting member and the calibration reflecting member and reaches the other, the ultrasonic wave is reflected on the other surface of the reflecting member and the calibration reflecting member, and again The light passes through one of the reflective member and the reflective member for calibration and enters the ultrasonic oscillation element.
[0014]
Thereby, regarding the liquid level detection, the shape of the ultrasonic wave incident on the reflecting member and the reflecting member for calibration can be made into a conical shape, that is, an axial target shape. Therefore, at the boundary portion between the two reflecting members in the conventional liquid level detecting device. The ultrasonic wave diffraction phenomenon and the interference of the ultrasonic waves can be prevented, and the reflected waves from the liquid surface and the constituent reflecting member can be stably received. Therefore, it is possible to realize a vehicular liquid level detection device that can obtain good detection accuracy.
[0015]
In the liquid level detecting device for a vehicle according to claim 2 of the present invention, the calibration reflecting member is arranged between the ultrasonic oscillation element and the reflecting member.
[0016]
Usually, the reflection member for calibration is arranged so as to be orthogonal to the traveling direction of the ultrasonic wave emitted by the ultrasonic oscillation element, while the reflecting member is inclined with respect to the traveling direction of the ultrasonic wave emitted by the ultrasonic oscillation element. For example, they are arranged at an angle of 45 °.
[0017]
For this reason, as for the path when the ultrasonic wave passes through the reflecting member and the calibration reflecting member, the reflecting member that is inclined with respect to the traveling direction of the ultrasonic wave is disposed perpendicular to the traveling direction of the ultrasonic wave. It becomes longer than the reflective member for calibration. When the ultrasonic wave travels through the solid, the attenuation level of the ultrasonic vibration energy increases and the received signal level of the reflected wave decreases, making it difficult to detect the liquid level with high accuracy. .
[0018]
Accordingly, if the ultrasonic wave emitted from the ultrasonic oscillation element is transmitted through the calibration reflecting member arranged perpendicularly to the traveling direction and reaches the reflecting member, the solid path through which the ultrasonic wave should be transmitted can be obtained. Since it can be shortened, it is possible to realize a vehicular liquid level detection device capable of highly accurate liquid level detection while suppressing a decrease in the received signal level of reflected waves.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
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.
[0020]
FIG. 1 is a partial cross-sectional view of a fuel tank 2 as a tank for storing a liquid fuel 5 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.
[0021]
FIG. 2 is a view taken along arrow II in FIG. In the drawings, the same components are denoted by the same reference numerals.
[0022]
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.
[0023]
As shown in FIG. 1, the fuel level detection device 1 is mainly composed of a fuel tank 2 as a tank, an ultrasonic sensor 3 as an ultrasonic oscillation element, a measurement plate 41 as a reflection member, and a reflection member for calibration. The calibration plate 42 is configured.
[0024]
Below, the structure of the fuel liquid level detection apparatus 1 is demonstrated.
[0025]
As shown in FIG. 1, an ultrasonic sensor 3 that is an ultrasonic oscillation element is fixed via a bracket 4 on a bottom surface 21 in a fuel tank 2 of an automobile that is a tank that stores liquid.
[0026]
The ultrasonic sensor 3 is made of a material having a piezo effect (a characteristic that changes its volume when a voltage is applied and generates a voltage when it receives an external force), such as PZT (lead zirconate titanate). An ultrasonic transducer (not shown) is provided. Then, a voltage is applied to the ultrasonic transducer to emit ultrasonic waves from the oscillation surface 31, and a force is applied to the ultrasonic transducer by the reflected wave of the ultrasonic wave received by the oscillation surface 31 to generate a voltage. That is, a reception signal is generated. The oscillation surface 31 is formed in a circular shape. The ultrasonic sensor 3 is connected to a lead 32 for applying a voltage to the ultrasonic transducer or outputting a voltage signal generated by receiving an ultrasonic wave from the ultrasonic transducer. . This lead wire 32 is drawn out to the outside of the fuel tank 2 in an airtight manner.
[0027]
The bracket 4 holds and fixes the ultrasonic sensor 3 and includes a measurement plate 41 that is a reflection member and a calibration plate 42 that is a reflection member for calibration.
[0028]
As shown in FIGS. 1 and 2, the measurement plate 41 and the calibration plate 42 are disposed so as to overlap in the traveling direction of the ultrasonic wave emitted from the ultrasonic sensor 3, that is, in the left-right direction in FIGS. 1 and 2.
[0029]
The calibration plate 42 is disposed between the measurement plate 41 and the ultrasonic sensor 3 so as to be orthogonal to the traveling direction of the ultrasonic wave emitted by the ultrasonic sensor 3. Thereby, the calibration plate 42 reflects the ultrasonic wave emitted from the ultrasonic sensor 3 directly toward the ultrasonic sensor 3. A part of the ultrasonic wave emitted from the ultrasonic sensor 3 passes through the calibration plate 42 and enters the measurement plate 41.
[0030]
The measurement plate 41 directs the ultrasonic wave from the ultrasonic sensor 3 that has entered through the calibration plate 42 toward the liquid surface 51, and the incident angle to the liquid surface 51 becomes 0 degree, in other words, in FIG. As shown, the angle formed between the traveling direction of the ultrasonic wave and the liquid surface 51 is set to an angle that reflects in a direction that is 90 degrees. As a result, the ultrasonic wave emitted from the ultrasonic sensor 3 and reaching the liquid surface 51 through the measurement plate 41 is reflected by the liquid surface, and then travels along the same path as the forward travel, so that it reliably enters the ultrasonic sensor 3. Can be made.
[0031]
Further, since the measurement plate 41 and the calibration plate 42 are formed integrally with the bracket 4, the positional relationship between the measurement plate 41 and the calibration plate 42 and the ultrasonic sensor 3 can be maintained with high accuracy. The liquid level detection accuracy of the fuel level detecting device 1 can be maintained satisfactorily.
[0032]
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.
[0033]
As shown in FIG. 3, the control circuit 6 is supplied with electric power from the battery 9 via the ignition switch 8, oscillates the ultrasonic sensor 3, emits ultrasonic waves in a pulse shape, and uses the ultrasonic sensor 3. The liquid level position is calculated by processing the reception signal of the reflected wave of the ultrasonic pulse, the display unit 7 is driven based on the calculation result, and the driver displays the liquid level position so that the driver can visually recognize the liquid level position. Yes.
[0034]
For this reason, the control circuit 6 processes the reflected wave reception signal output from the pulse generation circuit 61 and the ultrasonic sensor 3 for applying a pulsed voltage signal to the ultrasonic sensor 3, and determines the liquid level position based on the processed signal. The calculation circuit 62 includes a calculation circuit 62 and a drive circuit 63 that outputs a drive signal for driving the display unit 7 based on the liquid level position signal calculated by the calculation circuit 62.
[0035]
The display unit 7 includes, for example, a pointer instrument or the like, and is installed in a combination meter (not shown) in front of the driver's seat of the automobile.
[0036]
Next, the fuel level detecting operation in the fuel level detecting device 1 according to the embodiment of the present invention will be described.
[0037]
When a pulsed voltage signal is applied by the pulse generation circuit 61 and the ultrasonic sensor 3 emits a pulsed ultrasonic wave into the fuel 5 in the fuel tank 2, this ultrasonic wave is incident on the calibration plate 42, and one of them. The part is reflected toward the ultrasonic sensor 3 by the calibration plate 42 as in the propagation path B shown in FIG. 1 and immediately received by the ultrasonic sensor 3. A part of the pulsed ultrasonic wave emitted from the ultrasonic sensor 3 passes through the calibration plate 42 and reaches the measurement plate 41.
[0038]
The ultrasonic wave incident on the measurement plate 41 is reflected by the measurement plate 41 and travels toward the liquid surface 51, and is reflected by the liquid surface 51 and travels the same path as the forward path, as in the propagation path A shown in FIG. Then, the signal is received again by the ultrasonic sensor 3.
[0039]
That is, when the ultrasonic sensor 3 emits one ultrasonic pulse, the ultrasonic sensor 3 receives the above-described two reflected pulses, that is, the reflected pulse from the liquid surface 51 and the reflected pulse from the calibration plate 42. First, a reflected pulse from the calibration plate 42 is received, and then a reflected pulse from the liquid surface 51 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 62.
[0040]
Here, the pulsed ultrasonic wave emitted from the ultrasonic sensor 3 has a conical shape, that is, an axial target shape. Further, the ultrasonic wave that passes through the calibration plate 42 and reaches the measurement plate 41 also has a conical shape, that is, an axial object shape. Therefore, the reflected pulse from the liquid surface 51 and the reflected pulse from the component plate 42 also have an axial target shape. As a result, it is possible to prevent the ultrasonic diffraction phenomenon and the interference of the ultrasonic waves at the boundary portion between the two reflecting members in the conventional liquid level detection device, so that the reflected pulse from the liquid level 51 and the reflection from the component plate 42 are achieved. Pulses can be received stably.
[0041]
The arithmetic circuit 62 calculates a time from when the pulse generation circuit 61 generates a pulse voltage signal to when a reflected pulse is detected. Here, the arithmetic circuit 62 calculates the propagation speed of the ultrasonic pulse in the fuel 5 based on the reflected pulse from the calibration plate 42 received first, and receives the calculated propagation speed and the reflected pulse from the liquid surface 51. Based on the time until the liquid level, the liquid level 51 position, that is, the liquid level height H in FIG. 1 is calculated.
[0042]
The drive circuit 63 rotates a signal for displaying the liquid level height H calculated by the arithmetic circuit 62 on the display unit 7, for example, a pointer shaft (not shown) to an angle corresponding to the liquid level height H. The drive signal is output. Thereby, the liquid level 51 position in the fuel tank 2 is displayed on the display unit 7.
[0043]
In the fuel level detecting device 1 according to the embodiment of the present invention described above, the measurement plate 41 and the calibration plate 42 are arranged so as to overlap in the traveling direction of the ultrasonic wave emitted by the ultrasonic sensor 3, and the ultrasonic sensor 3. A part of the ultrasonic wave emitted from the laser beam passes through the measurement plate 41 and reaches the calibration plate 42.
[0044]
As a result, the shape of the ultrasonic wave incident on the measurement plate 41 and the calibration plate 42 can be conical, that is, the shape of an axis, so that the ultrasonic wave is diffracted at the boundary between the two reflecting members in the conventional liquid level detection device. Phenomenon and interference of ultrasonic waves can be prevented. Therefore, since the ultrasonic sensor 3 can stably receive the reflected wave from the liquid surface 51 and the reflected wave from the calibration plate 42, the vehicle liquid level detection device 1 that can obtain good detection accuracy is realized. can do.
[0045]
In the fuel level detecting device 1 according to the embodiment of the present invention described above, the calibration plate 42 and the measurement plate 41 are sequentially arranged from the ultrasonic sensor 3 side in the traveling direction of the ultrasonic wave emitted by the ultrasonic sensor 3. Although arranged, the measurement plate 41 and the calibration plate 42 may be arranged in this order from the ultrasonic sensor 3 side.
[0046]
Moreover, in the fuel level detecting device 1 according to the embodiment of the present invention described above, the measurement plate 41 and the calibration plate 42 are integrally formed with the bracket 4, but these may be separate parts.
[0047]
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 transport attached to the vehicle which transports various liquids.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view of a fuel level detecting device 1 according to an embodiment of the present invention.
FIG. 2 is a view taken along arrow II in FIG.
FIG. 3 is a schematic diagram for explaining an electric circuit configuration in the fuel liquid level detection device 1 according to the embodiment of the present invention.
[Explanation of symbols]
1 Fuel level detector (Vehicle level detector)
2 Fuel tank (tank)
21 Bottom (bottom)
3 Ultrasonic sensor (Ultrasonic oscillator)
31 Oscillating surface 32 Lead wire 4 Bracket 41 Measurement plate (reflective member)
42 Calibration plate (Reflective member for calibration)
5 Fuel (liquid)
51 Liquid Level 6 Control Circuit 61 Pulse Generation Circuit 62 Arithmetic Circuit 63 Drive Circuit 7 Display Unit 8 Ignition Switch 9 Battery A, B Propagation Path H Liquid Level Height

Claims (2)

A tank for storing liquid;
An ultrasonic oscillation element attached to the bottom of the tank;
A reflection member that reflects the ultrasonic wave emitted by the ultrasonic oscillation element toward the liquid surface of the liquid in the tank and the incident angle to the liquid surface is 0 degree;
A calibration reflecting member that reflects the ultrasonic wave emitted by the ultrasonic oscillation element toward the ultrasonic oscillation element;
In the vehicle liquid level detection device for detecting the liquid level position by emitting an ultrasonic wave from the ultrasonic oscillation element and receiving a reflected wave reflected by the liquid level and a reflected wave reflected by the calibration reflecting member,
The reflection member and the calibration reflection member are arranged so as to overlap in the traveling direction of the ultrasonic wave emitted by the ultrasonic oscillation element,
A liquid level detection apparatus for a vehicle, wherein a part of ultrasonic waves emitted from the ultrasonic oscillation element passes through one of the reflection member and the reflection member for calibration and reaches the other. The liquid level detection device for a vehicle according to claim 1, wherein the calibration reflection member is disposed between the ultrasonic oscillation element and the reflection member.

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