JP2021021625A - Liquid level detector - Google Patents

Abstract

To provide a liquid level detector which can detect a liquid level with good accuracy by properly processing a received signal corresponding to a liquid level detection ultrasonic wave.SOLUTION: A transmission/reception unit transmits a liquid level detection ultrasonic wave into liquid on the basis of a drive signal generated on the basis of a drive parameter. The transmission/reception unit further receives an ultrasonic wave propagated via the liquid. A signal processing unit performs signal processing using a signal processing parameter, on a liquid level reflected signal. A physical quantity acquisition unit acquires a specific physical quantity different from a physical quantity that represents the liquid level reflected wave (S120). A parameter control unit controls at least of the drive parameter and the signal processing parameter in accordance with the specific physical quantity acquired by the physical quantity acquisition unit (S130).SELECTED DRAWING: Figure 8

Description

The present disclosure relates to a technique for detecting the position of a liquid surface.

Patent Document 1 below discloses a liquid level detection device that detects the position of the liquid level (hereinafter, referred to as "liquid level") in a tank for storing a liquid. In this liquid level detection device, a liquid level detection ultrasonic wave, which is an ultrasonic wave for liquid level detection, is transmitted from an ultrasonic oscillating element provided at the bottom of the tank. When the ultrasonic oscillating element receives the liquid level reflected wave reflected on the liquid surface by the transmitted liquid level detection ultrasonic wave, it outputs a received signal corresponding to the liquid level reflected wave. The liquid level detection device detects the liquid level by performing predetermined signal processing on the received signal.

Japanese Unexamined Patent Publication No. 2005-106548

However, as a result of detailed examination by the inventor, the following problems have been found in the configuration described in Patent Document 1 described above.
That is, in order to detect the liquid level with high accuracy, it is preferable that the signal processing of the received signal is appropriately performed. However, for example, if the liquid level detection ultrasonic wave is not output with an appropriate intensity, or if the parameters used for signal processing are not set to appropriate values according to the received signal, the received signal is processed appropriately. It may not be done.

One aspect of the present disclosure is to provide a liquid level detection device capable of accurately detecting the liquid level by appropriately processing a received signal corresponding to the liquid level detection ultrasonic wave. ..

The liquid level detection device (100) according to one aspect of the present disclosure includes a transmission / reception unit (11), a transmission drive unit (42, 62, 121), a signal processing unit (43, 63), and a liquid level calculation unit ( 41, 61, 81, S240), a physical quantity acquisition unit (41, 61, 81, S120, S310), and a parameter control unit (41, 61, 81, S130, S320).

The transmitter / receiver transmits ultrasonic waves into the liquid based on the input drive signal. When the transmission / reception unit receives the ultrasonic waves propagated through the liquid, the transmission / reception unit outputs a reception signal having a value corresponding to the intensity of the received ultrasonic waves.

The transmission drive unit transmits a liquid level detection ultrasonic wave from the transmission / reception unit by generating a drive signal based on the drive parameters. The liquid level detection ultrasonic wave is an ultrasonic wave having an intensity according to a driving parameter for detecting the liquid level which is the position of the liquid level of the liquid.

The signal processing unit performs signal processing using signal processing parameters on the liquid surface reflected signal. The liquid level reflected signal is a received signal corresponding to the liquid level reflected wave reflected by the liquid level detection ultrasonic wave on the liquid surface.
The liquid level calculation unit calculates the liquid level based on the liquid level reflection signal that has been signal-processed by the signal processing unit.

The physical quantity acquisition unit acquires a specific physical quantity. The specific physical quantity is a physical quantity that determines the intensity of the liquid level detection ultrasonic wave, or a physical quantity corresponding to the intensity of the ultrasonic wave received by the transmission / reception unit in response to the transmission of the liquid level detection ultrasonic wave. It is a physical quantity different from the physical quantity representing the surface reflected wave.

The parameter control unit controls at least one of the drive parameter and the signal processing parameter according to the specific physical quantity acquired by the physical quantity acquisition unit.
According to such a configuration, at least one of the drive parameter and the signal processing parameter is controlled according to the acquired specific physical quantity. As a result, the received signal corresponding to the liquid level detection ultrasonic wave can be appropriately signal-processed, and the liquid level can be detected with high accuracy based on the signal processing result.

Specifically, when the drive parameter is configured to be controlled according to a specific physical quantity, for example, the intensity of the liquid level detection ultrasonic wave can be adjusted appropriately by controlling the drive parameter. .. When the signal processing parameters are configured to be controlled according to a specific physical quantity, for example, the liquid surface reflected signal is appropriately controlled by controlling the signal processing parameters according to the actual level of the liquid surface reflected wave. It becomes possible to process.

It is a side sectional view of the liquid level detection device of an embodiment. It is a block diagram which shows the electrical structure of the liquid level detection apparatus of embodiment. It is explanatory drawing which shows the 1st operation example of the liquid level detection apparatus of embodiment. It is explanatory drawing which shows an example of the relationship between the burst number Nb and the peak value increase rate. It is explanatory drawing which shows an example of the relationship between the drive voltage value VD and the peak value increase rate. It is explanatory drawing which shows an example of the relationship between a burst frequency fp and a peak value Vp. It is explanatory drawing which shows the 2nd operation example of the liquid level detection apparatus of embodiment. It is a flowchart of the parameter setting process of an embodiment. It is a flowchart of the liquid level detection process of an embodiment. It is explanatory drawing which shows the 3rd operation example of the liquid level detection apparatus of embodiment.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
[1. Embodiment]
(1-1) Configuration of Liquid Level Detection Device The liquid level detection device 100 shown in FIG. 1 is mounted on a vehicle. The vehicle is equipped with a tank 200 for storing the liquid fuel 150. The liquid level detection device 100 is provided at the bottom of the tank 200 in order to detect the liquid level Lx, which is the position of the liquid level of the fuel 150 in the tank 200. The liquid level detection device 100 detects the liquid level Lx by transmitting ultrasonic waves into the fuel 150 and receiving the liquid level reflected waves which are the reflected waves reflected by the transmitted ultrasonic waves at the liquid surface.

The liquid level Lx indicates, for example, the distance from the bottom surface 200a in the tank 200 to the liquid level, that is, the height of the liquid level.
A part of the liquid level detection device 100 shown in FIG. 1 shows a side surface instead of a cross section in order to show the internal structure in an easy-to-understand manner. From a functional point of view, the liquid level detection device 100 includes roughly two functional units, specifically, a sensor unit 1 and a housing unit 2.

The sensor unit 1 is an assembly having a function of transmitting and receiving ultrasonic waves as a whole. The sensor unit 1 includes an ultrasonic oscillator 11, two internal terminals 13, an elastic body 14, a case 15, a lid 16, and two external terminals 17.

The ultrasonic oscillating element 11 is an element that transmits and receives ultrasonic waves. The ultrasonic oscillating element 11 is formed in a disk shape by a substance having a piezo effect such as PZT (lead zirconate titanate). The piezo effect is a characteristic in which the volume changes when a voltage is applied, while the voltage is generated when a force is received from the outside. Electrodes printed on almost the entire surface are provided on both sides of the ultrasonic oscillating element 11. The frequency of the ultrasonic wave transmitted from the ultrasonic oscillator 11 may be any value, and may be, for example, a frequency within a predetermined frequency band at 20 kHz or higher.

A drive signal is input to the ultrasonic oscillation element 11 from a drive circuit 42 described later. In the present embodiment, the drive signal includes, for example, a pulse voltage which is a pulse voltage. The pulse voltage is applied between the electrodes on both sides of the ultrasonic oscillating element 11 via the lead wire 3. When a pulse voltage is input, the ultrasonic oscillating element 11 oscillates ultrasonic waves by vibrating in the central axis A direction, which is the plate thickness direction, due to the above-mentioned piezo effect.

When the ultrasonic oscillating element 11 oscillates an ultrasonic wave, the ultrasonic wave is transmitted into the fuel 150 and propagates in the fuel 150. When a liquid level detection ultrasonic wave, which is an ultrasonic wave having a specified intensity for detecting the liquid level Lx, is transmitted, the liquid level detection ultrasonic wave propagates to the liquid surface and is reflected at the liquid surface. Then, the liquid surface reflected wave reflected by the liquid surface propagates in the fuel 150 to the ultrasonic oscillating element 11 and is received by the ultrasonic oscillating element 11. The specified intensity indicates a specific intensity at which the liquid level reflected wave corresponding to the ultrasonic wave transmitted from the ultrasonic oscillation element 11 can be received by the ultrasonic oscillation element 11. The ultrasonic oscillating element 11 is housed in the case 15 together with the insulating member.

When the ultrasonic wave oscillating element 11 receives an ultrasonic wave, it outputs a reception signal corresponding to the received ultrasonic wave. The received signal has a voltage corresponding to the intensity of the received ultrasonic wave. The received signal is input to the receiving circuit 43 (see FIG. 2) described later.

In the following description, the "ultrasonic wave" transmitted from the ultrasonic oscillating element 11 means a liquid level detection ultrasonic wave unless otherwise specified.
The internal terminal 13 electrically connects the ultrasonic oscillating element 11 and the external terminal 17. The internal terminal 13 is formed of a metal plate. The ultrasonic oscillating element 11 and the internal terminal 13 are electrically connected by soldering. In the present embodiment, two internal terminals 13 are provided on both sides of the ultrasonic oscillating element 11 and the elastic body 14 so as to sandwich the ultrasonic oscillating element 11.

The elastic body 14 is a substantially columnar member arranged coaxially with the central axis A of the ultrasonic oscillating element 11. Of the two end faces on both sides of the elastic body 14, the first end face comes into contact with the ultrasonic oscillating element 11, and the second end face comes into contact with the lid 16. The elastic body 14 is made of an elastic material such as a flexible resin or rubber.

The case 15 is a bottomed cylindrical case having an accommodation chamber for accommodating the ultrasonic oscillating element 11, the two internal terminals 13, and the elastic body 14.
The lid 16 is a member that closes the storage chamber of the case 15. With the lid 16 locked to the case 15, the elastic body 14 is compressed by the lid 16. The elastic body 14 is designed to have a large dimension in the direction along the central axis A so that the elastic body 14 can be accommodated in the storage chamber of the case 15 in a state of being elastically deformed by being compressed by the lid 16. Therefore, the ultrasonic oscillating element 11 is fixed in the case 15 in a state of being pressed against the bottom surface of the case 15 by the elastic force of the elastic body 14. An internal terminal 13 is inserted through a hole provided in the lid 16. The tip of the internal terminal 13 projects to the outside of the storage chamber of the case 15 through the hole.

The external terminal 17 electrically connects the internal terminal 13 and the lead wire 3. The external terminal 17 is formed of a metal plate. The first end of the external terminal 17 is joined to the tip of the internal terminal 13 by welding. The second end of the external terminal 17 is crimped and connected to the lead wire 3 by crimping or the like. The external terminal 17 is fixed to the lid 16 on the outside of the storage chamber of the case 15.

Next, the housing portion 2 will be described. The housing portion 2 is an assembly that functions as a propagation path for ultrasonic waves as a whole by having a propagation path for propagating ultrasonic waves inside. As shown in FIG. 1, the housing portion 2 has a body 21, a guide pipe 22, a guide pipe 23, and a reflector 24.

The body 21 is, for example, a member made of resin. The body 21 holds and fixes the sensor unit 1, the guide pipe 22, the guide pipe 23, and the reflector 24. The guide pipe 22, the guide pipe 23, and the reflector 24 are attached to the body 21. The body 21 is fixed to the bottom surface 200a in the tank 200. The sensor unit 1 is arranged so that the central axis A of the ultrasonic oscillating element 11 is coaxial with the central axis of the guide pipe 22 and the case 15 is arranged at a predetermined distance from the inner surface of the body 21. Is attached to the body 21.

The guide pipe 22 is a metal cylinder having a substantially truncated cone shape. The guide pipe 22 is provided so that the first end of the guide pipe 22, that is, the right end in FIG. 1, faces the sensor unit 1. The guide pipe 22 has a circular cross section in a direction orthogonal to the central axis A of the guide pipe 22. The guide pipe 22 has a first path 4 inside thereof. The first path 4 is a part of the above-mentioned propagation path, and extends from the position where the ultrasonic oscillating element 11 is provided along the bottom surface 200a of the tank 200.

The first path 4 has a conical portion 26, a straight portion 27 and a stepped portion 28. The conical portion 26 is a truncated cone-shaped portion whose cross-sectional area gradually decreases as the distance from the ultrasonic oscillating element 11 increases. In other words, the diameter of the cross section of the conical portion 26 in the direction orthogonal to the central axis A decreases as the distance from the ultrasonic oscillating element 11 increases. The straight portion 27 is a straight tubular portion having a constant cross-sectional area.

The step 28 is provided at a specific reference position on the first path 4. The step portion 28 connects the conical portion 26 and the straight portion 27. The step portion 28 is a portion of the conical portion 26 whose cross-sectional area is reduced in a step-like manner at an end portion on the opposite side of the conical portion 26 from the end portion on the ultrasonic oscillating element 11 side. Due to the presence of the step portion 28, the guide pipe 22 is formed with an annular reference surface 221 coaxial with the central axis A.

The guide pipe 23 is a straight tubular metal cylinder. The guide pipe 23 is provided so that the central axis B of the guide pipe 23 is orthogonal to the central axis A and is continuous with the end portion of the guide pipe 22 on the straight portion 27 side via the body 21. The guide pipe 23 has a circular cross section in a direction orthogonal to the central axis B.

The upper end of the guide pipe 23 protrudes upward by a predetermined length from the liquid level when the specified maximum storage amount of fuel is stored in the tank 200, that is, when the liquid level Lx is the specified maximum level. Located as The term "upper" as used herein means a direction perpendicular to the bottom surface 200a of the tank 200 and away from the bottom surface 200a in the tank 200. The guide pipe 23 has a second path 5 inside. The second path 5 is another part of the above-mentioned propagation path and extends upward from the bottom of the tank 200.

Here, the state in which the vehicle is placed on the horizontal plane is referred to as a vehicle horizontal state. In the present embodiment, the tank 200 is mounted on the vehicle so that the bottom surface 200a is parallel to the horizontal plane in the vehicle horizontal state. Therefore, in the vehicle horizontal state, the liquid level of the fuel 150 is parallel to the bottom surface 200a of the tank 200. In the present embodiment, the diameter of the cross section of the second path 5 is equal to the diameter of the cross section of the straight portion 27.

The reflector 24 is a metal plate. The reflector 24 is arranged so that the central axis A of the guide pipe 22 and the central axis B of the guide pipe 23 intersect at the reflective surface 241 of the reflector 24 in a state of being held and fixed to the body 21. There is.

The reflector 24 reflects the ultrasonic waves transmitted from the ultrasonic oscillating element 11 toward the liquid surface of the fuel 150. Specifically, the reflector 24 directs ultrasonic waves incident on the reflector 24 along the central axis A of the guide pipe 22 in a direction in which the angle of incidence on the liquid surface in the vehicle horizontal state is 0 °, that is, the vehicle horizontal. It is installed so that it reflects in the direction perpendicular to the liquid surface in the state. In the present embodiment, the reflector 24 is provided so as to be inclined by 45 ° with respect to the liquid level in the horizontal state of the vehicle.

Therefore, the ultrasonic wave transmitted from the ultrasonic oscillating element 11 is propagated to the liquid surface through the first path 4, the reflection surface 241 and the second path 5, and is the ultrasonic wave reflected at the liquid surface. The wave is propagated to the ultrasonic oscillating element 11 through the second path 5, the reflecting surface 241 and the first path 4. Further, a part of the ultrasonic waves transmitted from the ultrasonic oscillating element 11 is reflected by the reference surface 221 and the reflected ultrasonic waves, which are the reflected ultrasonic waves, are received by the ultrasonic oscillating element 11.

(1-2) Electrical Configuration of Liquid Level Detection Device 100 The electrical configuration of the liquid level detection device 100 will be described with reference to FIG. As shown in FIG. 2, the liquid level detection device 100 includes a control circuit 41, a drive circuit 42, a reception circuit 43, and an ultrasonic oscillation element 11.

The control circuit 41 includes a microcomputer including a CPU 41a, a storage unit 41b, and the like. The storage unit 41b includes at least one of various semiconductor memories such as RAM, ROM, and flash memory. Further, the storage unit 41b includes a non-volatile memory in which data can be electrically rewritten. The storage unit 41b stores the parameter setting processing program of FIG. 8 and the liquid level detection processing program of FIG. 9, which will be described later.

Various functions in the control circuit 41 are realized by the CPU 41a executing a program stored in a non-transitional substantive recording medium. In this example, the storage unit 41b corresponds to a non-transitional substantive recording medium in which the program is stored. Moreover, when this program is executed, the method corresponding to the program is executed. The control circuit 41 may include one microcomputer or a plurality of microcomputers.

The method by which the control circuit 41 achieves various functions is not limited to software, and some or all of the functions of the control circuit 41 may be realized by using one or more hardware. For example, when the above function is realized by an electronic circuit which is hardware, the electronic circuit may be realized by a digital circuit including a large number of logic circuits, an analog circuit, or a combination thereof.

The liquid level detection device 100 further includes a battery 50 and a power supply circuit 51. The battery 50 outputs a battery voltage having a predetermined voltage value VB.
A battery voltage is input to the power supply circuit 51, and a power supply voltage having a predetermined DC voltage value Vc is generated from the battery voltage and output. The power supply voltage is output to at least the drive circuit 42. The power supply circuit 51 may be configured in any way. The power supply voltage value Vc output by the power supply circuit 51 may be the same value as the battery voltage value VB, may be a value lower than the battery voltage value VB, or may be a voltage value higher than the battery voltage value VB. You may.

In the power supply circuit 51, the power supply voltage value Vc may be fixed at a constant value. The power supply circuit 51 may be configured to output the battery voltage as it is as a power supply voltage without transforming or the like.

The power supply circuit 51 may receive a power supply control signal from the control circuit 41. The power supply control signal is a signal for controlling the power supply voltage value Vc. The power supply circuit 51 configured to input the power supply control signal may be configured to generate a power supply voltage having the power supply voltage value Vc indicated by the power supply control signal.

More specifically, the power supply circuit 51 may include, for example, a plurality of regulators having different output voltage values. Then, the output voltage from one regulator indicated by the power supply control signal among the plurality of regulators may be output as the power supply voltage. Further, for example, the power supply circuit 51 may be configured to divide the voltage generated by one regulator into a plurality of different types of voltages by a plurality of voltage dividing resistors. Then, one voltage indicated by the power supply control signal may be output as the power supply voltage among the plurality of types of divided voltages.

The battery voltage is also input to other circuits in the vehicle other than the power supply circuit 51. Therefore, the battery voltage value VB may fluctuate according to the operating state of various circuits to which the battery voltage is supplied.

Further, the battery voltage may be input to the control circuit 41. In this case, the control circuit 41 may be able to detect the battery voltage value VB based on the input battery voltage.
Further, the power supply voltage generated by the power supply circuit 51 may be input to the control circuit 41. In this case, the control circuit 41 may be able to detect the power supply voltage value Vc based on the input battery voltage. Further, the control circuit 41 may be configured to operate according to the power supply voltage.

The drive circuit 42 outputs a drive signal to the ultrasonic oscillating element 11 in accordance with a drive command input from the control circuit 41, so that the ultrasonic oscillating element 11 transmits ultrasonic waves. In this embodiment, the drive signal includes a pulse voltage as described above.

In the present embodiment, the voltage value of the pulse voltage (hereinafter, referred to as “drive voltage value VD”) is a constant value, and the pulse width Tw (see FIG. 3) is also a constant value. On the other hand, the number of pulse voltages included in one drive signal and the period of the pulse voltage in one drive signal (hereinafter, referred to as "burst period Tb") can change according to a specific physical quantity as described later. The number of pulse voltages included in one drive signal is hereinafter referred to as the number of bursts Nb. The frequency corresponding to the burst period Tb, that is, the reciprocal of Tb is hereinafter referred to as "burst frequency fb".

The drive command output by the control circuit 41 includes information indicating the intensity of ultrasonic waves transmitted from the ultrasonic oscillating element 11, specifically, information indicating the above-mentioned burst number Nb and information indicating the above-mentioned burst period Tb. Is included. More specifically, the drive command includes the same number of command pulses as the number of bursts Nb, which is output in the burst period Tb.

In the liquid level detection device 100, various parameters for detecting the liquid level Lx are set. The various parameters include various drive parameters for generating a drive signal and various signal processing parameters used in signal processing in the receiving circuit 43. More specifically, the various drive parameters include the above-mentioned drive voltage value VD, the number of bursts Nb, and the burst period Tb. Various signal processing parameters include an amplification factor Ao and a detection threshold Vref0, which will be described later.

The drive voltage value VD is set to a constant value in advance in this embodiment. The control circuit 41 sets the number of bursts Nb and the burst period Tb. The control circuit 41 outputs a drive command corresponding to the set burst number Nb and burst cycle Tb, thereby outputting a drive signal having the set burst number Nb and burst cycle Tb from the drive circuit 42. As a result, ultrasonic waves having an intensity corresponding to the drive voltage value VD, the number of bursts Nb, and the burst period Tb are transmitted.

The amplification factor Ao is used in the amplifier circuit 46 described later. The detection threshold value Vref0 is used in the comparison circuit 48 described later.
The control circuit 41 is further configured to control (that is, variably set) at least one of various parameters according to a specific physical quantity, as will be described later.

As shown in FIG. 2, the drive circuit 42 of the present embodiment includes a first transistor Tr1, a second transistor Tr2, a resistor R1, and a capacitor C1. The first transistor Tr1 is, for example, an NPN type bipolar transistor. The second transistor Tr2 is, for example, a PNP type bipolar transistor.

A drive command from the control circuit 41 is input to the bases of the first transistor Tr1 and the second transistor Tr2. The collector of the first transistor is connected to the first end of the resistor R1. The power supply voltage from the power supply circuit 51 is input to the second end of the resistor R1. The emitter of the first transistor Tr1 is connected to the emitter of the second transistor Tr2 and is also connected to the first end of the capacitor C1. The second end of the capacitor C1 is connected to the ultrasonic oscillating element 11. That is, the drive signal output from the drive circuit 42 is more specifically output via the capacitor C1 in the present embodiment. The collector of the second transistor Tr2 is connected to a ground line having a ground potential.

When a drive command is input to the drive circuit 42 configured in this way, a drive signal is generated and output by turning on or off the first transistor Tr1 and the second transistor Tr2 according to the command pulse in the drive command. Will be done.

Each time a drive command is input, the drive circuit 42 outputs a drive signal according to the drive command to the ultrasonic oscillating element 11. Specifically, the pulse voltage of the burst number Nb indicated by the drive command is output to the ultrasonic oscillating element 11 at the burst period Tb indicated by the drive command. In this embodiment, the value of the pulse voltage, that is, the drive voltage value VD depends on the power supply voltage value Vc input from the power supply circuit 51 to the drive circuit 42. More specifically, in the present embodiment, the drive voltage value VD is equal to or substantially equal to the power supply voltage value Vc.

The drive signal is input to the ultrasonic oscillating element 11 via the lead wire 3, the external terminal 17, and the internal terminal 13. When a drive signal is input to the ultrasonic oscillating element 11, the ultrasonic oscillating element 11 vibrates, and ultrasonic waves are transmitted to the first path 4 via the bottom surface of the case 15.

As described above, the ultrasonic waves transmitted from the ultrasonic oscillating element 11 are reflected at the liquid surface and propagated to the ultrasonic oscillating element 11 as liquid surface reflected waves, and a part of the transmitted ultrasonic waves is a reference. It is reflected by the surface 221 and propagated to the ultrasonic oscillating element 11 as a reference surface reflected wave.

When the liquid surface reflected wave or the reference surface reflected wave is received by the ultrasonic oscillating element 11 via the bottom surface of the case 15, the ultrasonic oscillating element 11 vibrates in response to the received ultrasonic waves, thereby causing the above-mentioned above-mentioned. The received signal is output. The received signal output from the ultrasonic oscillating element 11 is input to the receiving circuit 43 via the internal terminal 13, the external terminal 17, and the lead wire 3. In the present embodiment, when the liquid surface reflected wave or the reference surface reflected wave is incident on the sensor unit 1, the bottom surface of the case 15 vibrates due to the pressure action, and the ultrasonic oscillating element 11 vibrates accordingly.

An example of the received signal is shown in FIGS. 3 and 7. FIG. 3 illustrates a received signal when the burst number Nb of the drive signal is 1, and FIG. 7 illustrates a received signal when the burst number Nb of the drive signal is 3. As shown in FIGS. 3 and 7, each time the drive signal is output, the reference surface reflection signal which is the reception signal of the reference surface reflected wave and the liquid surface reflection signal which is the reception signal of the liquid surface reflected wave are sequentially received. Will be done.

Of the received signals in FIGS. 3 and 7, the received signal generated at substantially the same timing as the drive signal corresponds to the ultrasonic wave itself oscillated by the ultrasonic oscillating element 11 by the drive signal. That is, when the ultrasonic oscillating element 11 oscillates an ultrasonic wave, the ultrasonic oscillating element 11 generates an electric signal corresponding to the ultrasonic wave oscillated by itself. The electric signal is also input to the receiving circuit 43 as a receiving signal.

The reception circuit 43 outputs a detection signal for calculating the liquid level Lx by performing signal processing using the above-mentioned signal processing parameters on the reception signal input from the ultrasonic oscillation element 11. The receiving circuit 43 includes an amplifier circuit 46, a detection circuit 47, and a comparison circuit 48. The received signal input to the receiving circuit 43 is input to the amplifier circuit 46 via the capacitor C2 and the resistor R2.

The amplifier circuit 46 amplifies the input received signal at a set amplification factor Ao. The amplification factor Ao may be fixed to a constant value in advance, but may be controlled by the amplification factor control signal input from the control circuit 41, that is, may be variably set.

The detection circuit 47 detects an amplified signal which is a received signal amplified by the amplifier circuit 46. This detection includes extracting a frequency component lower than the fundamental frequency component of the received signal from the received signal. The detection circuit 47 may detect the received signal by any detection method. In the present embodiment, the detection circuit 47 detects the received signal by, for example, a half-wave rectification detection method or an envelope detection method. 3 and 7 exemplify a detection signal which is a reception signal detected by the envelope detection circuit 47.

The comparison circuit 48 compares the voltage value of the detection signal output from the detection circuit 47 with the set detection threshold value Vref0, and outputs a detection signal according to the comparison result to the control circuit 41. More specifically, as illustrated in FIGS. 3 and 7, the comparison circuit 48 outputs an L level detection signal when the voltage value of the detection signal is lower than the detection threshold value Vref0, and the voltage value of the detection signal is high. When the detection threshold value is Vref0 or higher, an H level detection signal is output.

The detection threshold value Vref0 may be fixed to a constant value in advance, but may be controlled by the detection threshold value control signal input from the control circuit 41, that is, may be variably set.
The control circuit 41 basically transmits ultrasonic waves by outputting a drive command for each detection cycle T. The control circuit 41 generates a drive command corresponding to the drive timing at the drive timing for transmitting ultrasonic waves for each detection cycle T, and outputs the drive command to the drive circuit 42.

The control circuit 41 acquires a detection signal corresponding to the ultrasonic wave transmitted based on the drive command for each drive timing. Then, based on the detection signal corresponding to the liquid level reflected wave, the liquid level reflection is the time from the transmission of the ultrasonic wave from the ultrasonic oscillating element 11 to the reception of the liquid level reflected wave by the ultrasonic oscillating element 11. Time Tx (see FIGS. 3 and 7) is measured.

The control circuit 41 calculates the liquid level Lx based on the measured liquid surface reflection time Tx and the ultrasonic wave propagation velocity v. At this time, the control circuit 41 may, for example, fix the propagation velocity v to a constant value and calculate the liquid level Lx using the constant propagation velocity v.

However, the propagation speed v of the ultrasonic wave propagating through the fuel 150 may vary depending on various conditions such as the composition and temperature of the fuel 150. Therefore, in the present embodiment, the propagation velocity v of the ultrasonic wave is calculated based on the reference plane reflected wave so that the liquid level Lx can be detected accurately, and the liquid level Lx is calculated using the calculated propagation velocity v. ..

That is, in the control circuit 41, the time from when the ultrasonic wave is transmitted from the ultrasonic oscillating element 11 to when the reference surface reflected wave is received by the ultrasonic oscillating element 11 based on the detection signal corresponding to the reference surface reflected wave. The reference plane reflection time Tr (see FIGS. 3 and 7) is measured. On the other hand, the reference plane distance Lo, which is the propagation distance of ultrasonic waves from the ultrasonic oscillating element 11 to the reference plane 221 is constant and known. The control circuit 41 calculates the propagation velocity v of ultrasonic waves in the fuel 150 based on the measured reference plane reflection time Tr and the known reference plane distance Lo. The control circuit 41 calculates the liquid level Lx based on the calculated propagation velocity v and the liquid surface reflection time Tx.

The propagation velocity v is calculated by the following equation (1).
v = Lo / Tr ・ ・ ・ (1)
Then, the liquid level Lx is calculated by the following equation (2), where K is a predetermined constant.
Lx = K ・ Tx ・ v ・ ・ ・ (2)
(1-3) Parameter control function The parameter control function included in the control circuit 41 will be described. The parameter control function is a function that controls (that is, variable setting) at least one of various parameters according to a specific physical quantity.

As described above, the various parameters include a drive voltage value VD as a drive parameter, a burst number Nb and a burst period Tb, an amplification factor Ao as a signal processing parameter, and a detection threshold value Vref0.

Therefore, in the parameter control function of the present embodiment, at least one of the drive voltage value VD, the number of bursts Nb, the burst period Tb, the amplification factor Ao, and the detection threshold value Vref0 is controlled according to the specific physical quantity.

The main purpose of the parameter control function is to enable the receiving circuit 43 to appropriately process the liquid level reflected signal, which is the received signal corresponding to the liquid level reflected wave, so that the liquid level Lx can be detected accurately. To do.

For example, when the intensity of the liquid surface reflected wave is low, the level of the liquid surface reflected signal becomes low, the comparison with the detection threshold value Vref0 in the comparison circuit 48 is not performed properly, and the detection signal may not be generated properly.

Further, for example, if the intensity of the liquid surface reflected wave is too high, the received signal in the amplifier circuit 46 is not properly amplified, or the detection circuit 47 is not properly detected, so that the detection threshold value is Vref0. There is a possibility that the comparison will not be performed properly. Even if amplification and detection are performed properly, depending on the level of the detection threshold Vref0, for example, depending on the relative relationship between the detection signal level and the detection threshold Vref0, unnecessary components due to noise, for example, are reflected in the detection signal. There is a possibility that it will end up.

Therefore, the control circuit 41 executes the parameter control function, that is, controls at least one of the various parameters according to a specific physical quantity, so that the liquid level reflected signal is appropriately signal-processed by the receiving circuit 43. To do so.

Here, it will be described with reference to FIGS. 4 to 6 that the level of the liquid surface reflection signal can fluctuate according to the drive parameters.
The greater the number of bursts Nb in one drive signal, the higher the intensity of ultrasonic waves transmitted based on the drive signal. In the present embodiment, the intensity of ultrasonic waves represents, for example, the amplitude or crest value of ultrasonic waves, and the higher the intensity, the larger the amplitude or crest value.

The greater the number of bursts Nb, the higher the intensity of the transmitted ultrasonic waves. Therefore, as shown in FIG. 4, as the number of bursts Nb increases, the rate of increase of the peak value Vp (see FIG. 3) increases.

The crest value Vp may be the crest value of the reference plane reflected signal itself, but in the present embodiment, it is the crest value of the amplified signal corresponding to the reference plane reflected signal or the crest value of the detection signal. In the present embodiment, the peak value of the amplified signal and the peak value of the detected signal are the same value. When the peak value of the amplified signal and the peak value of the detected signal are different, either peak value may be used as the peak value Vp. The rate of increase of the peak value Vp in FIG. 4 means a magnification based on the peak value Vp when the number of bursts Nb is one (see FIG. 3).

Further, as shown in FIG. 5, the higher the drive voltage value VD, the higher the intensity of the ultrasonic wave, and thus the increase rate of the peak value Vp of the received signal becomes large. The rate of increase of the peak value Vp in FIG. 5 means a magnification with reference to the peak value Vp when the drive voltage value VD is a reference value (for example, 5 V).

Further, as shown in FIG. 6, the peak value Vp also fluctuates according to the burst frequency fb (= 1 / Tb) of the pulse voltage in one drive signal. As an example, FIG. 6 shows an example in which the peak value Vp is maximized when the burst frequency fb is a peak frequency of about 950 Hz. The peak value Vp decreases as the burst frequency fb deviates from the peak frequency.

Therefore, by controlling at least one drive parameter, the intensity of the transmitted ultrasonic wave can be adjusted, and the peak value Vp in the receiving circuit 43 can be adjusted.
The specific physical quantity is a physical quantity that determines the intensity of the liquid level detection ultrasonic wave, or a physical quantity corresponding to the intensity of the liquid surface reflected wave received by the ultrasonic oscillating element 11 in response to the transmission of the liquid level detection ultrasonic wave. Therefore, it is a physical quantity different from the physical quantity representing the liquid surface reflected wave.

Specific physical quantities are classified into, for example, type 1 physical quantities and type 2 physical quantities. The first-class physical quantity is a physical quantity indicating the magnitude of the reference plane reflection signal. The second type physical quantity is a physical quantity corresponding to the drive voltage value VD.

The first-class physical quantity includes, for example, a peak value Vp and a threshold duration Tref1 (see FIG. 3).
The threshold value duration Tref1 is a time during which the value (voltage value) of the detection signal corresponding to the reference plane reflection signal continuously becomes the reference threshold value Vref1 or more. The reference threshold value Vref1 may be set to any value. The reference threshold value Vref1 may be the same value as or different from the detection threshold value Vref0 described above. In the present embodiment, for example, the reference threshold value Vref1 and the detection threshold value Vref0 are the same values.

By acquiring the first-class physical quantity, it is possible to determine whether or not the received signal is properly signal-processed in the receiving circuit 43. For example, if the peak value Vp is out of the predetermined peak value range, or if the threshold duration Tref1 is out of the predetermined duration range, the received signal may not be properly signal-processed.

The second type physical quantity includes, for example, a drive voltage value VD, a battery voltage value VB, and a power supply voltage value Vc. For example, if the drive voltage value VD or the power supply voltage value Vc is out of the predetermined drive voltage range, ultrasonic waves of appropriate intensity may not be transmitted, which may cause the liquid level reflection signal to not reach an appropriate level. is there. In this embodiment, the power supply circuit 51 generates a power supply voltage having a constant power supply voltage value Vc from the battery voltage VB. Therefore, the fluctuation of the battery voltage value VB has little influence on the drive voltage value VD.

In the parameter control function, at least one of the various specific physical quantities described above is acquired, and at least one of the various parameters is controlled based on the acquired specific physical quantity. In this embodiment, one of various specific physical quantities is acquired.

The parameter to be controlled may be any parameter.
The parameter to be controlled may be, for example, the number of bursts Nb, which is one of the drive parameters. In this case, if the specific physical quantity to be acquired is, for example, the crest value Vp, the smaller the crest value Vp (that is, the smaller the magnitude of the reference plane reflected wave), the larger the number of bursts Nb, based on the crest value Vp. The number of bursts Nb may be controlled.

More specifically, for example, in order to determine the level of the peak value Vp, a first range lower than the first boundary value, a second range equal to or higher than the first boundary value and lower than the second boundary value, and a second range. A third range above the boundary value is set in advance. Then, when the acquired crest value Vp is included in the first range, the burst number Nb is set to N1 (N1 ≧ 3), and when the crest value Vp is included in the second range, the burst number Nb is set to N2. When the number of times (N2 <N1) is set and the peak value Vp is included in the third range, the number of bursts Nb may be set to N3 times (N3 <N2). The boundary value may be one or three or more. Further, the number of bursts Nb may be set according to the peak value Vp by a method different from the above.

Further, if the specific physical quantity to be acquired is, for example, the threshold duration Tref1, the burst number Nb may be controlled based on the threshold duration Tref1 so that the shorter the threshold duration Tref1, the larger the burst number Nb. In this case as well, a plurality of ranges may be set for the threshold duration Tref1 and the burst number Nb corresponding to the range including the threshold duration Tref1 may be set as in the above example.

If the specific physical quantity to be acquired is, for example, the drive voltage value VD or the power supply voltage value Vc, the drive voltage value VD or the power supply voltage value Vc increases as the number of bursts Nb increases as the drive voltage value VD or the power supply voltage value Vc decreases. The number of bursts Nb may be controlled based on. In this case as well, as in the above example, a plurality of ranges are set for the drive voltage value VD or the power supply voltage value Vc, and the number of bursts corresponding to the range including the drive voltage value VD or the power supply voltage value Vc. Nb may be set.

The parameter to be controlled may be, for example, a burst period Tb, which is one of the drive parameters. In this case, if the specific physical quantity to be acquired is, for example, the crest value Vp, the burst period Tb may be controlled in the direction in which the crest value Vp becomes higher as the crest value Vp is smaller.

More specifically, for example, with reference to FIG. 6, the burst period Tb is, for example, the first period corresponding to the first frequency (for example, 950 Hz) higher than the peak frequency (about 950 Hz), and the first frequency higher than the first frequency. It may be possible to control either the second cycle corresponding to two frequencies (for example, 1000 Hz) or the third cycle corresponding to a third frequency (for example, 1100 Hz) higher than the second frequency. Then, when the acquired peak value Vp is included in the first range, the burst period Tb is set to the first frequency, and when the peak value Vp is included in the second range, the burst period Tb is set to the second frequency. If the peak value Vp is included in the third range, the burst period Tb may be set to the third frequency. The burst period Tb may be set according to the peak value Vp by a method different from the above. For example, the burst period Tb may be continuously changed according to the peak value Vp.

Further, if the specific physical quantity to be acquired is, for example, the threshold duration Tref1, the burst period Tb may be controlled in the direction in which the crest value Vp becomes higher as the threshold duration Tref1 is shorter. In this case as well, as in the above example, a plurality of ranges may be set for the threshold duration Tref1 and a burst period Tb corresponding to the range including the acquired threshold duration Tref1 may be set. Good. Further, for example, the burst period Tb may be continuously changed according to the threshold duration Tref1.

Further, if the specific physical quantity to be acquired is, for example, a drive voltage value VD or a power supply voltage value Vc, the burst period Tb may be controlled in the direction in which the peak value Vp becomes higher as the drive voltage value VD or the power supply voltage value Vc is lower. .. Also in this case, as in the above example, a plurality of ranges are set for the drive voltage value VD or the power supply voltage value Vc, and the range corresponding to the acquired drive voltage value VD or the power supply voltage value Vc is included. The burst period Tb may be set. Further, for example, the burst period Tb may be continuously changed according to the drive voltage value VD or the power supply voltage value Vc.

The power supply circuit 51 may be configured so that the power supply voltage value Vc can be variably set according to the power supply control signal from the control circuit 41. In this case, the parameter to be controlled may be, for example, a drive voltage value VD which is one of the drive parameters. In this case, if the specific physical quantity to be acquired is, for example, the peak value Vp, the drive voltage value is controlled by controlling the power supply voltage value Vc based on the peak value Vp so that the smaller the peak value Vp is, the higher the drive voltage value VD is. VD may be controlled.

More specifically, for example, when the acquired peak value Vp is included in the above-mentioned first range, the drive voltage value VD is set to VD1, and when the peak value Vp is included in the second range, the drive voltage is set. When the value VD is VD2 (VD2 <VD1) and the peak value Vp is included in the third range, the drive voltage value VD may be VD3 (VD3 <VD2). The drive voltage value VD may be set according to the peak value Vp by a method different from the above.

If the specific physical quantity to be acquired is, for example, the threshold duration Tref1, the drive voltage is controlled by controlling the power supply voltage value Vc based on the threshold duration Tref1 so that the shorter the threshold duration Tref1 is, the higher the drive voltage value VD is. The value VD may be controlled. In this case as well, a plurality of ranges may be set for the threshold duration Tref1 and the drive voltage VD corresponding to the range including the threshold duration Tref1 may be set as in the above example.

If the specific physical quantity to be acquired is, for example, the drive voltage value VD or the power supply voltage value Vc, the drive voltage value VD or the power supply voltage value is increased so that the lower the drive voltage value VD or the power supply voltage value Vc is, the higher the drive voltage value VD is. The drive voltage value VD may be controlled based on Vc. In this case as well, as in the above example, a plurality of ranges are set for the drive voltage value VD or the power supply voltage value Vc, and the drive voltage corresponding to the range including the drive voltage value VD or the power supply voltage value Vc is included. The value VD may be set.

The parameter to be controlled may be, for example, an amplification factor Ao, which is one of the signal processing parameters. That is, the control circuit 41 may control the amplification factor Ao by outputting the amplification factor control signal to the amplifier circuit 46. In this case, if the specific physical quantity to be acquired is, for example, the peak value Vp, the amplification factor Ao may be controlled based on the peak value Vp so that the smaller the peak value Vp, the higher the amplification factor Ao.

More specifically, for example, when the acquired peak value Vp is included in the above-mentioned first range, the amplification factor Ao is set to A1, and when the peak value Vp is included in the second range, the amplification factor Ao is set. A2 (A2 <A1), and when the acquired peak value Vp is included in the third range, the amplification factor Ao may be A3 (A3 <A2). The amplification factor Ao may be set according to the peak value Vp by a method different from the above. For example, the amplification factor Ao may be continuously changed according to the acquired peak value Vp.

Further, if the specific physical quantity to be acquired is, for example, the threshold duration Tref1, the amplification factor Ao may be controlled based on the threshold duration Tref1 so that the shorter the threshold duration Tref1, the higher the amplification factor Ao. In this case as well, as in the above example, a plurality of ranges may be set for the threshold duration Tref1 and an amplification factor Ao corresponding to the range including the acquired threshold duration Tref1 may be set. Good. Further, for example, the amplification factor Ao may be continuously changed according to the acquired threshold value duration Tref1.

If the specific physical quantity to be acquired is, for example, a drive voltage value VD or a power supply voltage value Vc, the drive voltage value VD or the power supply voltage value Vc is such that the lower the drive voltage value VD or the power supply voltage value Vc, the higher the amplification factor Ao. The amplification factor Ao may be controlled based on the above. In this case as well, as in the above example, a plurality of ranges are set for the drive voltage value VD or the power supply voltage value Vc, and the amplification factor corresponding to the range including the drive voltage value VD or the power supply voltage value Vc. Ao may be set. Further, for example, the amplification factor Ao may be continuously changed according to the drive voltage value VD or the power supply voltage value Vc.

The parameter to be controlled may be, for example, a detection threshold value Vref0, which is one of the signal processing parameters. That is, the control circuit 41 may control the detection threshold value Vref0 by outputting the detection threshold value control signal to the comparison circuit 48. In this case, if the specific physical quantity to be acquired is, for example, the peak value Vp, the detection threshold value Vref0 may be controlled based on the peak value Vp so that the smaller the peak value Vp, the lower the detection threshold value Vref0.

More specifically, for example, when the acquired crest value Vp is included in the above-mentioned first range, the detection threshold value Vref0 is set to Vr1, and when the acquired crest value Vp is included in the second range, it is detected. When the threshold value Vref0 is Vr2 (Vr2> Vr1) and the peak value Vp is included in the third range, the detection threshold value Vref0 may be Vr3 (Vr3> Vr2). The detection threshold value Vref0 may be set according to the peak value Vp by a method different from the above. For example, the detection threshold value Vref0 may be continuously changed according to the peak value Vp.

Further, if the specific physical quantity to be acquired is, for example, the threshold value duration Tref1, the detection threshold value Vref0 may be controlled based on the acquired threshold value duration Tref1 so that the shorter the threshold value duration Tref1 is, the lower the detection threshold value Vref0 is. Also in this case, similarly to the above example, a plurality of ranges may be set for the threshold value duration Tref1 and the detection threshold value Vref0 corresponding to the range including the threshold value duration Tref1 may be set. Further, for example, the detection threshold value Vref0 may be continuously changed according to the threshold value duration Tref1.

If the specific physical quantity to be acquired is, for example, the drive voltage value VD or the power supply voltage value Vc, the acquired drive voltage value VD or the power supply is such that the lower the drive voltage value VD or the power supply voltage value Vc, the lower the increase detection threshold Vref0. The detection threshold value Vref0 may be controlled based on the voltage value Vc. In this case as well, as in the above example, a plurality of ranges are set for the drive voltage value VD or the power supply voltage value Vc, and the detection threshold value corresponding to the range including the drive voltage value VD or the power supply voltage value Vc is included. Vref0 may be set. Further, for example, the detection threshold value Vref0 may be continuously changed according to the drive voltage value VD or the power supply voltage value Vc.

Although the number of parameters to be controlled is one in this embodiment, a plurality of parameters may be controlled.
(1-4) Parameter Setting Process The parameter setting process executed by the CPU 41a in the control circuit 41 will be described with reference to FIG. The CPU 41a sets the parameter to be controlled by executing the parameter setting process shown in FIG. 8 at a predetermined parameter setting timing.

The parameter setting timing may be any timing. For example, it may be a predetermined timing after the power is turned on to the control circuit 41 and the CPU 41a is started, or it may be a timing that arrives periodically or irregularly. Further, for example, the parameter setting timing may be set immediately before the drive timing for each of the above-mentioned drive timings for detecting the liquid level Lx.

When the CPU 41a starts the parameter setting process, the liquid level detection ultrasonic wave is transmitted from the ultrasonic oscillation element 11 in S110. Each drive parameter at this time may have any value. For example, the drive parameter used when the liquid level Lx was detected immediately before may be used. Further, for example, a predetermined reference value may be used for each drive parameter.

In S120, a specific physical quantity corresponding to the ultrasonic wave transmitted in S110 is acquired. Specifically, one of the various specific physical quantities described above, which is determined as the acquisition target, is acquired. When the specific physical quantity is set to the power supply voltage Vc, the processing of S110 may be omitted.

In S130, the parameter to be controlled is set based on the specific physical quantity acquired in S120. That is, by executing the above-mentioned parameter control function, the parameter to be controlled is set to an appropriate value according to the specific physical quantity.

When the parameter to be controlled is a signal processing parameter, the parameter may be enabled in the circuit or the like by outputting the set parameter to the circuit or the like in which the parameter is used. For example, when the parameter to be controlled is the amplification factor Ao, the amplification factor of the amplification circuit 46 is set to the amplification factor Ao by transmitting the set amplification factor Ao to the amplification circuit 46 by the amplification factor control signal. May be good. Further, for example, when the parameter to be controlled is the detection threshold value Vref0, the set detection threshold value Vref0 is transmitted to the comparison circuit 48 by the detection threshold value control signal, so that the detection threshold value used in the comparison circuit 48 is set to the detection threshold value Vref0. It may be set.

(1-5) Liquid Level Detection Process Next, the liquid level detection process executed by the CPU 41a in the control circuit 41 will be described with reference to FIG. Each time the above-mentioned drive timing arrives, the CPU 41a executes the liquid level detection process using the parameters set at that time, that is, the latest parameters set in the parameter setting process.

When the liquid level detection process is started, the CPU 41a outputs a drive command based on the currently set drive parameter to the drive circuit 42 in S210. As a result, the drive circuit 42 outputs a drive signal according to the currently set drive parameter, and the ultrasonic oscillator 11 transmits a liquid level detection ultrasonic wave having an intensity corresponding to the drive parameter.

In S220, the reflected wave reception process is performed. Specifically, the reference surface reflected wave and the liquid surface reflected wave corresponding to the ultrasonic waves transmitted by the processing of S210 are sequentially received, and the reference surface reflection time Tr and the liquid surface reflection time Tx are calculated based on each. ..

In S230, the propagation velocity v of the ultrasonic wave is calculated using the above equation (1) based on the reference plane reflection time Tr calculated in S220.
In S240, the liquid level Lx is calculated using the above equation (2) based on the propagation velocity v calculated in S230 and the liquid level reflection time Tx calculated in S220.

In S250, the information indicating the liquid level Lx calculated in S240 is displayed on a display device (not shown).
In the liquid level detection process of FIG. 9, both the reference plane reflection time Tr and the liquid level reflection time Tx are measured within the same detection cycle T, and the liquid level Lx is calculated based on the measurement results. It was a premise.

On the other hand, for example, as shown in FIG. 10, both the reference surface reflection time Tr and the liquid surface reflection time Tx are not measured within the same detection cycle T, and the reference surface reflection time Tr and the liquid surface reflection time Tx are different from each other. It may be measured individually within the detection cycle T.

That is, as illustrated in FIG. 10, for example, two consecutive detection cycles T are regarded as one detection cycle group, and the first detection cycle T in the detection cycle group (hereinafter, referred to as “first detection cycle T”). Then, the reference plane reflection time Tr is measured based on the reference plane reflected wave. In the first detection cycle T, the liquid surface reflected wave is ignored and the liquid surface reflection time Tx is not measured.

Then, in the second detection cycle T (hereinafter, referred to as “second detection cycle T”) in the detection cycle group, the liquid surface reflection time Tx is measured based on the liquid surface reflected wave. Further, in the first detection cycle T or the second detection cycle T, the propagation velocity v is calculated based on the reference plane reflection time Tr measured in the first detection cycle T. In the second detection cycle T, the liquid level Lx is further calculated based on the calculated propagation velocity v and the measured liquid level reflection time Tx. In the second detection cycle T, the reference plane reflected wave is ignored and the reference plane reflection time Tr is not calculated.

Depending on the intensity of the transmitted ultrasonic waves, the reference plane reflected wave may be received in a plurality of times. FIG. 10 shows an example in which the secondary reference plane reflected wave is received after the primary reference plane reflected wave is received. In the secondary reference surface reflected wave, the primary reference surface reflected wave is reflected by the sensor unit 1 and propagates to the reference surface 221 side again, and the primary reference surface reflected wave is reflected again by the reference surface 221 and is reflected again in the sensor unit 1. It is the one that came back to.

In this way, when the reference surface reflected wave is received a plurality of times, it corresponds to the second and subsequent reference surface reflected waves depending on the relationship between the intensity of the reference surface reflected wave after the second time and the detection threshold value Vref0. It is possible that a detection signal will also be output. However, in the present embodiment, the detection signal corresponding to the primary reference plane reflected wave first received after the transmission of the ultrasonic wave is valid, and the reference plane reflection time Tr is measured based on the detection signal. Then, even if the detection signal corresponding to the second and subsequent reference plane reflected waves (that is, after the second reference plane reflected wave) is output, the detection signal is invalid.

Specifically, the control circuit 41 recognizes the first reflected wave detected after the time T1 has elapsed after the output of the drive signal as the primary reference plane reflected wave. The time T1 is a time during which the reverberation of the ultrasonic waves oscillated by the drive signal is sufficiently low or completely eliminated, and the reflected wave on the primary reference plane has not yet reached the sensor unit 1.

Further, in the second detection cycle T, the control circuit 41 liquidally detects the first reflected wave detected between the time T3 elapses after the output of the drive signal and the elapse of the second detection cycle T. Recognized as a surface reflected wave. The time T3 is, for example, a time sufficiently longer than the time T0 from the output of the drive signal to the detection of the second reference plane reflected wave. If there is a possibility that a third-order reference surface reflected wave or a higher-order reference surface reflected wave may be received, the liquid surface reflected wave is sent after the time during which the higher-order reference surface reflected wave can be received has elapsed. The time T3 may be set to detect.

The ultrasonic waves transmitted in the first detection period T need only be strong enough to receive the reference plane reflected wave satisfactorily. Therefore, in the first detection cycle T, it is not always necessary to output a drive signal corresponding to the currently set drive parameter.

On the other hand, in the second detection cycle T, by outputting the drive command corresponding to the current drive parameter as in S210 of FIG. 9, the drive circuit 42 outputs the drive signal corresponding to the drive parameter.

(1-6) Effects of the Embodiment According to the embodiment described above, the following effects are obtained.
That is, the control circuit 41 controls at least one of the drive parameter and the signal processing parameter according to the acquired specific physical quantity. As a result, the liquid level reflected signal can be appropriately signal-processed in the receiving circuit 43, and the liquid level Lx can be accurately detected based on the signal processing result.

Specifically, for example, by controlling the drive parameter according to a specific physical quantity, it is possible to make the intensity of the liquid level detection ultrasonic wave appropriate. Further, for example, by controlling the signal processing parameters according to a specific physical quantity, it becomes possible to appropriately process the liquid level reflected signal.

More specifically, in the present embodiment, at least one of the drive voltage value VD, the number of bursts Nb, the burst period Tb, the amplification factor Ao, and the detection threshold value Vref0 is set as controllable parameters.

By controlling any one or more of the drive voltage value VD, the number of bursts Nb, and the burst period Tb according to a specific physical quantity, the intensity of the liquid level detection ultrasonic wave can be made appropriate.

By controlling any one or both of the amplification factor Ao and the detection threshold value Vref0 according to the specific physical quantity, the liquid level reflected signal can be appropriately processed in the receiving circuit 43.

In addition, the specific physical quantities acquired to control the parameters include the peak value Vp and the threshold duration Tref1 as the first-class physical quantity, and the drive voltage value VD, the battery voltage value VB, and the power supply voltage as the second-class physical quantity. At least one of the values Vc is included. In this embodiment, one of these is acquired as a specific physical quantity. Therefore, the parameters can be appropriately controlled based on these specific physical quantities.

In the present embodiment, the ultrasonic oscillating element 11 corresponds to the transmission / reception unit of the present disclosure. The drive circuit 42 corresponds to the transmission drive unit of the present disclosure. The receiving circuit 43 corresponds to the signal processing unit of the present disclosure. The control circuit 41 corresponds to the liquid level calculation unit, the physical quantity acquisition unit, and the parameter control unit of the present disclosure. The battery 50 and the power supply circuit 51 correspond to the DC power supply of the present disclosure. The comparison circuit 48 corresponds to the detection signal generation circuit of the present disclosure. The burst period Tb corresponds to the specified period of the present disclosure.

[2. Other embodiments]
Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be implemented in various modifications.

(2-1) When the power supply circuit 51 is configured to output the battery voltage as the power supply voltage to the drive circuit 42 as it is, or when the battery voltage is transformed into the power supply voltage, the power supply is supplied according to the battery voltage value VB. When the voltage value Vc fluctuates, the battery voltage may be acquired as a specific physical quantity and the parameter may be controlled based on the battery voltage.

In this case, when the parameter to be controlled is, for example, the amplification factor Ao, the amplification factor Ao may be controlled based on the battery voltage value VB so that the lower the battery voltage value VB, the higher the amplification factor Ao.

Further, when the parameter to be controlled is, for example, the detection threshold value Vref0, the detection threshold value Vref0 may be controlled based on the battery voltage value VB so that the lower the battery voltage value VB, the lower the detection threshold value Vref0.

Further, when the parameter to be controlled is, for example, the number of bursts Nb, the number of bursts Nb may be controlled based on the battery voltage value VB so that the lower the battery voltage value VB, the larger the number of bursts Nb.

Further, when the parameter to be controlled is, for example, the burst period Tb, the burst period Tb may be controlled in the direction in which the lower the battery voltage value VB, the higher the peak value Vp.
(2-2) The circuit for outputting the drive signal may be configured in any way. In the above embodiment, the drive circuit 42 generates the drive signal by receiving the DC power supply voltage from the power supply circuit 51, but the drive signal may be generated by a circuit different from the above embodiment.

For example, a transformer may be used to generate a drive signal. Specifically, for example, a battery voltage is applied to the first end of the primary winding in the transformer, and the second end is connected to the ground line via a switching element. Then, the drive signal is output from the secondary winding of the transformer by turning the switching element on or off according to the drive command.

(2-3) The parameters that can be controlled based on the specific physical quantity are not limited to the above-mentioned drive voltage value VD, burst number Nb, burst period Tb, amplification factor Ao, and detection threshold Vref0. Parameters different from these may be controllable based on a specific physical quantity.

(2-4) The specific physical quantity acquired to control the parameters is not limited to the above-mentioned peak value Vp, threshold duration Tref1, drive voltage value VD, battery voltage value VB, and power supply voltage value Vc. The parameters may be controlled by acquiring specific physical quantities different from these.

(2-5) In each of the above embodiments, the liquid level detection device 100 used for detecting the liquid level of the fuel 150 in the tank 200 has been exemplified. However, the scope of application of the liquid level detection device of the present disclosure is not particularly limited. The liquid level detection device of the present disclosure may be used for liquid level detection of other liquids mounted on a vehicle, such as engine oil, brake fluid, window washer liquid, and the like. Further, for example, the liquid level detection device of the present disclosure may be used for liquid level detection in a liquid transport tank provided in a liquid transport vehicle or in a liquid container of various consumer devices other than the vehicle.

(2-6) The functions of one component in each of the above embodiments may be dispersed as a plurality of components, or the functions of the plurality of components may be integrated into one component. Further, a part of the configuration of the above embodiment may be omitted. In addition, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other embodiment.

1 ... Sensor unit, 4 ... First path, 5 ... Second path, 11 ... Ultrasonic oscillator, 41 ... Control circuit, 41a ... CPU, 41b ... Storage unit, 42 ... Drive circuit, 43 ... Reception circuit, 46 ... Amplifier circuit, 47 ... Detection circuit, 48 ... Comparison circuit, 50 ... Battery, 51 ... Power supply circuit, 100 ... Liquid level detector, 150 ... Fuel, 200 ... Tank.

Claims (16)

An ultrasonic wave is transmitted into a liquid based on an input drive signal, and when an ultrasonic wave propagated through the liquid is received, a reception signal having a value corresponding to the intensity of the received ultrasonic wave is output. The transmitter / receiver (11) configured as
A transmission drive unit configured to transmit a liquid level detection ultrasonic wave from the transmission / reception unit by generating the drive signal based on the drive parameter, and the liquid level detection ultrasonic wave is the liquid level of the liquid. The transmission drive unit (42), which is an ultrasonic wave having an intensity corresponding to the drive parameter for detecting the liquid level at the position of
A signal processing unit configured to perform signal processing using signal processing parameters on the liquid level reflected signal, which is the received signal corresponding to the liquid level reflected wave reflected by the liquid level detection ultrasonic waves. (43) and
A liquid level calculation unit (41, S240) configured to calculate the liquid level based on the liquid level reflection signal for which the signal processing has been performed by the signal processing unit.
A physical quantity that determines the intensity of the liquid level detection ultrasonic waves, or a physical quantity that corresponds to the intensity of the ultrasonic waves received by the transmission / reception unit in response to the transmission of the liquid level detection ultrasonic waves. A physical quantity acquisition unit (41, S120) configured to acquire a specific physical quantity, which is a physical quantity different from the physical quantity representing the surface reflected wave, and
A parameter control unit (41, S130) configured to control at least one of the drive parameter and the signal processing parameter according to the specific physical quantity acquired by the physical quantity acquisition unit.
A liquid level detector equipped with. The liquid level detection device according to claim 1.
further,
Propagation paths (4,5) through which the liquid level detection ultrasonic waves and the liquid level reflected waves are propagated, and
A reference plane provided at a reference position on the transmission / reception unit side of the liquid surface in the propagation path so that a part of ultrasonic waves transmitted from the transmission / reception unit is reflected and received by the transmission / reception unit. Reference plane (221) configured in
With
The specific physical quantity includes a type 1 physical quantity indicating the magnitude of the reference surface reflected signal, which is the received signal corresponding to the reference surface reflected wave reflected by the liquid level detection ultrasonic wave on the reference surface.
Liquid level detector. The liquid level detection device according to claim 2.
The first-class physical quantity is a liquid level detection device including the peak value of the reference plane reflection signal. The liquid level detection device according to claim 2.
The signal processing unit includes a detection circuit (47) configured to detect the reference plane reflected signal.
The first-class physical quantity includes a time during which the value of the detection signal, which is the reference plane reflection signal detected by the detection circuit, continuously becomes equal to or higher than the reference threshold value.
Liquid level detector. The liquid level detection device according to claim 1.
The drive signal includes at least one pulse voltage having a specified period.
The specific physical quantity includes a type 2 physical quantity corresponding to the voltage value of the pulse voltage included in the at least one pulse voltage in the drive signal for transmitting the liquid level detection ultrasonic wave from the transmission / reception unit.
Liquid level detector. The liquid level detection device according to claim 5.
The transmission drive unit (42) receives a DC power supply voltage from the DC power supply (50, 51), and the drive signal includes the at least one pulse voltage having a voltage value corresponding to the input power supply voltage value. Is configured to generate
The type 2 physical quantity includes the value of the power supply voltage or the voltage value of the pulse voltage.
Liquid level detector. The liquid level detection device according to any one of claims 2 to 4.
The drive signal includes at least one pulse voltage having a specified period.
The drive parameter includes a first drive parameter indicating the voltage value of the pulse voltage.
The transmission drive unit is configured to generate the drive signal including the at least one pulse voltage having the voltage value indicated by the first drive parameter.
The parameter control unit sets the first drive parameter based on the first-class physical quantity so that the smaller the magnitude of the reference plane reflected signal indicated by the first-class physical quantity, the larger the voltage value of the pulse voltage. Is configured to control
Liquid level detector. The liquid level detection device according to any one of claims 2 to 4.
The drive signal includes at least one pulse voltage having a specified period.
The drive parameter includes a second drive parameter indicating the number of pulse voltages in the drive signal.
The transmission drive unit is configured to generate the drive signal including the number of pulse voltages indicated by the second drive parameter.
The parameter control unit sets the second drive parameter based on the first-class physical quantity so that the smaller the magnitude of the reference plane reflected signal indicated by the first-class physical quantity, the larger the number of the pulse voltages. Configured to control,
Liquid level detector. The liquid level detection device according to any one of claims 2 to 4.
The drive signal includes at least one pulse voltage having a specified period.
The drive parameter includes a third drive parameter indicating the specified period.
The transmission drive unit is configured to generate the drive signal including the at least one pulse voltage of the specified period indicated by the third drive parameter.
The parameter control unit is configured to control the third drive parameter based on the magnitude of the reference plane reflection signal indicated by the first-class physical quantity.
Liquid level detector. The liquid level detection device according to any one of claims 2 to 4.
The signal processing unit includes an amplifier circuit (46) configured to amplify the received signal based on the amplification factor.
The liquid level calculation unit is configured to calculate the liquid level based on the liquid level reflection signal amplified by the amplifier circuit.
The signal processing parameter includes a first signal processing parameter indicating the amplification factor.
The parameter control unit controls the first signal processing parameter based on the first-class physical quantity so that the smaller the magnitude of the reference plane reflected signal indicated by the first-class physical quantity is, the higher the amplification factor is. Is configured to
Liquid level detector. The liquid level detecting device according to any one of claims 2 to 4 and 10.
The signal processing unit
An amplifier circuit (46) configured to amplify the received signal based on the amplification factor, and
A detection circuit (47) configured to detect the received signal amplified by the amplifier circuit, and a detection circuit (47).
A detection signal generation circuit (48) configured to generate a detection signal indicating a period equal to or longer than the detection threshold value in the received signal detected by the detection circuit.
With
The liquid level calculation unit is configured to calculate the liquid level based on the detection signal corresponding to the liquid level reflection signal.
The signal processing parameter includes a second signal processing parameter indicating the detection threshold.
The parameter control unit controls the second signal processing parameter based on the first-class physical quantity so that the smaller the magnitude of the reference plane reflected signal indicated by the first-class physical quantity is, the lower the detection threshold is. Is configured to
Liquid level detector. The liquid level detection device according to any one of claims 2 to 4, and 7 to 11.
The reference plane reflected wave is
The primary reference plane reflected wave reflected by the reference plane by the liquid level detection ultrasonic wave transmitted from the transmitter / receiver, and
When the primary reference surface reflected wave is received by the transmission / reception unit, the reflected wave reflected by the transmission / reception unit is reflected again by the reference surface, and the secondary reference surface reflected wave.
Including
The first-class physical quantity indicates the magnitude of the reference plane reflected signal corresponding to the primary reference plane reflected wave.
Liquid level detector. The liquid level detection device according to claim 6.
The drive signal includes the at least one pulse voltage having a specified period.
The drive parameter includes a second drive parameter indicating the number of the pulse voltages contained in the at least one pulse voltage.
The transmission drive unit is configured to generate the drive signal including the number of pulse voltages indicated by the second drive parameter.
The parameter control unit (41, S130) has the second drive parameter so that the smaller the value of the power supply voltage or the voltage value of the pulse voltage indicated by the second type physical quantity, the larger the number of the pulse voltages. Is configured to be controlled based on the type 2 physical quantity.
Liquid level detector. The liquid level detection device according to claim 6.
The drive signal includes the at least one pulse voltage having a specified period.
The drive parameter includes a third drive parameter indicating the specified period.
The transmission drive unit is configured to generate the drive signal including the at least one pulse voltage of the specified period indicated by the third drive parameter.
The parameter control unit (41, S130) is configured to control the third drive parameter based on the value of the power supply voltage or the voltage value of the pulse voltage indicated by the second type physical quantity.
Liquid level detector. The liquid level detection device according to claim 5 or 6.
The signal processing unit includes an amplifier circuit configured to amplify the received signal based on the amplification factor.
The liquid level calculation unit (41) is configured to calculate the liquid level based on the liquid level reflection signal amplified by the amplifier circuit.
The signal processing parameter includes a first signal processing parameter indicating the amplification factor.
The parameter control unit (41, S130) sets the first signal processing parameter so that the smaller the value of the power supply voltage or the voltage value of the pulse voltage indicated by the second type physical quantity, the higher the amplification factor. It is configured to control based on the type 2 physical quantity.
Liquid level detector. The liquid level detection device according to claim 5 or 6.
The signal processing unit
An amplifier circuit (46) configured to amplify the received signal based on the amplification factor, and
A detection circuit (47) configured to detect the received signal amplified by the amplifier circuit, and a detection circuit (47).
A detection signal generation circuit (48) configured to generate a detection signal indicating a period equal to or longer than the detection threshold value in the received signal detected by the detection circuit.
With
The liquid level calculation unit (41) is configured to calculate the liquid level based on the detection signal corresponding to the liquid level reflection signal.
The signal processing parameter includes a second signal processing parameter indicating the detection threshold.
The parameter control unit (41, S130) sets the second signal processing parameter so that the smaller the value of the power supply voltage or the voltage value of the pulse voltage indicated by the second type physical quantity, the lower the detection threshold value. It is configured to control based on the type 2 physical quantity.
Liquid level detector.